Tau hydraulic machine diagram and principle of operation. Hydraulic pumps (nsh pumps)

Separate hydraulic system (design, description and principle of operation)

The hydraulic system serves to transform and transmit the energy of the tractor engine to various executive units for the purpose of:

• control of mounted machine
• control of a trailed machine through hydraulic cylinders installed on it
• driving the working parts of mounted or trailed machines through the hydraulic power take-off system of the tractor
• performing automatic coupling with mounted and trailed machines
• changes and automatic support of the selected tillage depth
• adjusting the vertical reaction of the soil to the tractor propulsion, performing auxiliary operations on servicing the tractor (changing the base, changing the track, raising the frame, etc.)

Currently, a separate-aggregate type hydraulic system is widely used.

Unified separate hydraulic mounted tractor system(Fig. 10.3) includes:

• pump with drive and activation mechanism
• oil tank
• filter
• steel pipelines
• spool-type distributor with control mechanism
• elastic sleeves
• shut-off and quick connect couplings
• main hydraulic cylinder

• as well as - flow fittings, retarding valve and sealing devices

The hydraulic systems of some tractors have a hydraulic adhesion weight increaser with a hydraulic accumulator, a power regulator or a system for automatic control of tillage depth (SARG), and a hydraulic power take-off system (HPS).

The hydraulic system is designed in such a way as to ensure the widest possible operation of the executive link - a double-acting hydraulic cylinder (or several hydraulic cylinders with independent control).

A hydraulic cylinder can have four main states: movement of the piston in one direction, movement of the piston in the other direction, fixation of the piston by blocking the oil inlet and outlet of the hydraulic cylinder, the possibility of free movement of the piston in both directions from external force by connecting both cavities of the hydraulic cylinder to each other and with drain line. The distributor, which receives a flow of oil under pressure from the pump, provides one of four options for the operation of the hydraulic cylinder. In this case, the distributor has one spool with axial movement to one of four positions.

To protect the hydraulic system from excessive pressure increases, the distributor is equipped with a safety valve adjusted to a pressure of no higher than 20.5 MPa.

The hydraulic pump is the most critical element of the hydraulic system. The efficiency of the hydraulic drive largely depends on it. The most widespread are gear pumps of the NSh type, one or two sections. In heavy agricultural and industrial tractors, axial piston pumps of both adjustable and unregulated types are also used.

The pump takes oil through the suction line from the tank, the capacity of which should be 0.5 - 0.8 minute pump output. Oil purification is carried out using a strainer or a filter with a replaceable filter element, which ensures the removal of foreign particles with a size of 25 microns for fluid supplied from gear pumps and mechanically controlled distributors, and from 10 microns for piston pumps and electro-hydraulic distributors/

Let's consider specific typical designs of hydraulic system components.

Hydraulic pumps (nsh pumps)

Each pump model has a specific alphanumeric designation that characterizes its technical data.

So the designation is deciphered as follows:

NS- gear pump

32 the volume of working fluids in cm3 displaced from the pump per shaft revolution (theoretical flow);

U- unified design;

3 - performance group characterizing the nominal pump discharge pressure: 2 - 14 MPa; 3 - 16 MPa; 4 - 20 MPa;

L- left direction of rotation of the pump drive. If the pump is in the right direction of rotation, then there is no corresponding letter in the designation.

Let's consider the design of a gear hydraulic pump and its drive.

On tractors MTZ 100, MTZ 102, a pump NSh 32-3 of right rotation is used (Fig. 10.4). Oil is pumped into the pump using the drive 2 and driven 3 gears located between the bearing 1 and clamp 5 races and plates 4. The bearing race 1 serves a single support for the gear journals. Pressure ring 5 under oil pressure in the cuff cavity (not shown in the figure, located in the area of ​​the discharge hole) is pressed against the outer surface of the gear teeth, providing the required gap between the teeth and the sealing surface of the race.

The plates 4, under oil pressure in the cavity of the end seals 16 and 14, are pressed against the gears 2 and 3, compacting them along the side surfaces in the high-pressure zone. The shaft of the drive gear 2 in the housing is sealed with two cuffs 19. The centering of the drive shaft of gear 2 relative to the mounting collar of the housing is ensured by a sleeve 20. The housing connector with the cover is sealed using a rubber O-ring.

Rice. 10.4 Oil pump NSh-32-3

1 - bearing race; 2 - drive gear; 3 - driven gear; 4 - plate; 5 - clamping clip; 6.10 - ball bearings; 7 - shaft; 8 - gear; 9 - body; 11 - fork; 12 - control roller; 13 - intermediate gear; 14 - cuff; 15 - washer; 16 - cuff; 17 - bearing cup; 18 - hairpin; 19 - cuff; 20 - centering sleeve

The pump is secured with four studs 18 on the housing 9 of the hydraulic units through a glass 17, in which it is centered by the housing seating belt. The splined shank of drive gear 2 of the pump fits into the internal splines of shaft 7, mounted on bearings 6 and 10.

When the engine is running, rotation through the independent PTO drive gears and intermediate gear 13 is transmitted to gear 8 (in the on position), which through the splines transmits rotation to shaft 7 and drive gear 2.

Gear 8 is moved by a manual control mechanism through a roller 12 with a fork 11 attached to it and can be fixed by the control handle in two positions: the drive is on, when gear 8 is out of mesh with gear 13. Switching on or off depending on the need for a hydraulic drive during MTA operation

Distributors

Distributors of the tractor mounted hydraulic system are used to distribute the flow of working fluid between consumers, to automatically switch the system to idle mode (bypassing the working fluid into the tank) during periods when all consumers are turned off, and to limit the pressure in the hydraulic system during overloads.

On agricultural tractors, monoblock three-spool, four-position distributors with manual control are most widely used. On industrial tractors, monoblock one, two or three spool and usually three-position distributors with manual and remote control are used.

Tractor distributors have an alphanumeric type designation P80 3/1-222, P80 3/2-222, P160 3/1-222- Here the letter P means distributor; first two digits of the letter maximum performance pump, l/min, with which the distributor can operate; other numbers and letters - constructive option distributor.

A typical three-spool four-position valve is shown in Fig. 10.5

In housing 1 with channels 2, spool valves 3, bypass 7 and safety valve 11 are installed. Two covers are screwed to the housing. In the top cover 4 there are hinged handles for controlling the spools. The bottom cover 10 has a cavity for draining oil into the tank. Oil from the pump is supplied to the distributor through a pipeline. From the distributor, oil can flow through six pipelines into the piston and rod cavities of hydraulic cylinders.
The bypass valve 11 is connected by a channel 6 with the cavity above the bypass valve. If the pressure in the system increases excessively, valve 1 opens and connects this cavity with the drain cavity.
The operating diagram of the distributor under various operating modes is shown in Fig. 10.6
If the implement is in the transport position and the spool is installed in the neutral position (Fig. 10.6a), then the oil flows through the calibrated hole 2 of the bypass valve 4 into the outlet channel 9 and then into the drain cavity 6 and the oil tank. Due to the throttling effect of the calibrated hole 2, the bypass valve moves away from the seat 5 and the oil flows parallel to the main flow through the valve into the drain cavity.

Rice. 10.5 Three-spool, four-position valve

The lower cavity of the hydraulic cylinder 1 communicates through a pipeline with channel 8 of the distributor, and the upper cavity with channel 7. As can be seen from the diagram, the annular belts of the spool block both channels, locking the oil in the hydraulic cylinder. When the spool is installed in the floating position (Fig. 10.6.b), the oil coming from the pump is drained into the tank through the bypass valve and outlet channel 9. Both cavities of the hydraulic cylinder communicate with the drain cavity of the distributor. The mounted implement is lowered under the influence of weight and its working parts are deepened (under the influence of a deepening moment). The depth of penetration is limited by the position of the implement's support wheel. By doing technological process the spool remains in a floating position and the support wheels of the implement can freely follow the topography of the field.
The lifting of the implement into the transport position occurs when the spool is set to the “lift” position (Fig. 10.6.c). In this case, the spool closes the outlet channel 9 and at the same time opens the access of oil from the discharge channel 3 to channel 8, which communicates with the lower cavity of the hydraulic cylinder 1.

Rice. 10.6 Diagram of operation of the distributor of a separate-unit mounted system in the following positions:
A – neutral; b – floating; c – rise; g – lowering

When the implement is forcibly lowered (Fig. 10.6.d), the bypass valve is closed; oil enters the upper cavity of the hydraulic cylinder from discharge channel 3, and oil is displaced from the lower cavity of the hydraulic cylinder and enters the tank. Forced lowering is used when operating tractors with hole diggers, bulldozers and some other special machines.
By manually setting the spool to the neutral position, you can fix the hydraulic cylinder piston in any intermediate position.
In specified positions (floating, neutral, etc.), the spool is held by a ball retainer 12 (see Fig. 10.5). Moreover, this device provides for automatic return of the spool from the “raising” and “lowering” positions to the neutral position. The spool can only be moved from the floating position to the neutral position manually.

A hydraulic cylinder (reciprocating displacement hydraulic motor) is used to drive tractor linkage mechanisms different types as an external hydraulic cylinder. Remote hydraulic cylinders, unlike the main ones, have quick-detachable connecting devices that facilitate their installation and dismantling.

For separate-unit hydraulic systems, hydraulic cylinders can be of three designs, designated by numbers 2, 3 and 4, which corresponds to a nominal fluid pressure of 14.16 and 20 MPa, respectively.
In the designation of a hydraulic cylinder, the letter C is the cylinder, and the numbers next to the letter are the internal diameter of the cylinder, mm. A single standard range of hydraulic cylinders covers six brands: Ts55, Ts75, Ts80, Ts100, Ts125 and Ts140
Depending on the design, the designs of hydraulic cylinders differ from each other.
In version 2, the hydraulic cylinder (Fig. 10.7) has a body that can be disassembled into three main parts: cylinder 9, rear cover 2 and front cover 23. All parts are tightened with four long pins or bolts. Covers 2 and 23, rod 8 and piston 6 are sealed with rubber rings 3,5,7,10 and 16. To prevent dirt from entering the hydraulic cylinder, a “cleaner” 13 is installed, consisting of a package of steel washers. To regulate the magnitude of the working stroke of the piston 6, a movable stop 15 and a hydromechanical valve 18 are used, which blocks the oil outlet from the cylinder and causes an increase in pressure in the system and an automatic return of the spool to the neutral position.

Rice. 10.7 Hydraulic cylinder:
1 - yoke; 2 - back cover; 3,5,7,10,16 – rubber sealing rings; 4 - ring; 6 – piston; 8 - rod; 9 - cylinder; 11 - bolt; 12 – washer; 13 – “guillemot”; 14 – wing nut; 15 – emphasis; 17-valve guide; 18 – hydromechanical valve; 19 – valve seat; 20 – retarding valve fitting; 21 – retarding valve washer; 23 – front cover, 24 – nut; 25 – connecting tube; 26 – bolt; 27 – fitting; 28 – rod nut
Smooth lowering of the mounted machine is ensured by installing a retarding valve at the outlet of the hydraulic cylinder, consisting of a fitting 20 and a floating washer 21 with a calibrated hole.

In version 3, the hydraulic cylinder body consists of two main parts: the cylinder body glass is screwed to the bottom cover, and the top cover is secured with four short bolts to a flange welded to the top of the glass. There is no hydromechanical valve on the cylinder.

Hydraulic lines

Hydraulic lines of separate-unit hydraulic systems have great length and include pipelines, hoses (high pressure hoses), connecting and burst couplings with shut-off valves and seals. According to their purpose, hydraulic lines are divided into suction, pressure, drain, drain and control lines.

Metal pipelines of pressure hydraulic lines are made from seamless steel pipes designed for pressure up to 32 MPa with an internal diameter of 10,12,14,16,20,24 and 30 mm. Their tips are a nipple welded to a pipe with a pre-fitted union nut or a welded hollow head for a special hollow bolt with metal sealing gaskets.

Pipelines are bent on a special machine, which eliminates the formation of folds and flattening at the bending points.

Hoses (high pressure hoses) used to connect hydraulic units that have mutual movement.

A flexible rubber-metal hose consists of a rubber chamber, a cotton or nylon braid, a metal braid, a second layer of nylon braid, an outer rubber layer and a top layer (bandage). Oil-resistant rubber is used in the sleeves.

If necessary, the hoses are connected to each other using feed-through fittings.

Connecting and breaking couplings(Fig. 10.8) are used to connect remote hydraulic cylinders and are inserted at the points of connection (disconnection) of the hoses.

It consists of two coupling halves 1 and 8 (Fig. 10.8a) inserted into each other and tightened by a threaded connection using a union nut 6. The seal is carried out with a rubber ring 7. Two balls 5 are pressed against each other to form an annular channel through which the oil. When coupling halves 1 and 8 are disconnected, balls 5 are pressed against the seats of the coupling halves under the action of springs, locking their outlet holes and preventing oil from leaking out. Along with threaded ones, quick-connect couplings are used, in which the coupling halves are fixed to each other with a ball lock.

Breakaway coupling it is usually installed on a trailed hydraulic implement between the hoses supplying oil to the remote hydraulic cylinder and serves as a safety device in case of sudden unintended uncoupling of the implement or when the tractor leaves the uncoupled implement, but with hoses attached to the tractor.

Rice. 10.8 Couplings:
a - connecting; b – explosive

A breakaway coupling (Fig. 10.8.b) is in many ways similar to a connecting coupling, but instead threaded connection has a ball lock. In the event of an axial force at the junction of the coupling halves of more than 200...250 N, the locking balls 9 come out of the annular groove of the coupling half 10 and, acting on the locking sleeve 11, force it to move to the right, compressing the spring 13. The coupling halves are disconnected, eliminating rupture of the hoses and oil leakage.

Tanks and filters

Tanks of hydraulic mounted systems of tractors serve as a reservoir for working fluid - oil.
The volume of the tank depends on the number of consumers and the features and is 0.5...0.8 minute volumetric flow of the pump (pumps).
The oil is filtered by a full-flow filter with a replaceable filter element and a bypass valve that bypasses the oil past the filter in case of heavy pollution and increasing the pressure to 0.25...0.35 MPa.

We will sell the entire range

Reproduction of materials is permitted only with an active link to the website site - spare parts for tractors, gear pumps (NSh)

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru//

Posted on http://www.allbest.ru//

1.Hydraulic system

The most common control systems of the first group are hydraulic. In this case, the driver puts less effort into moving the handles than with mechanical control, resulting in reduced driver fatigue. Structurally, it is easier to solve the wiring of control systems using hydraulic pipelines and hoses. An example would be outrigger control. Combined system allows the use of lever-articulated transmissions before the hydraulic distributor comes into operation. In this case, the hydraulic distributors are placed in a separate block with the handles located in a place convenient for work.

The electro-hydraulic system has the following advantages: low forces on control devices, the possibility of remote control, high efficiency, low weight and low metal consumption due to a small number of wires. The disadvantage of this system is that when the mechanisms suddenly start and stop, significant dynamic loads arise. Electro-hydraulic control with proportional valves eliminates this disadvantage. For electrically driven machines, an electrical control system is used.

The drive control equipment is a system of devices consisting of engagement clutches, brakes, hydraulic valves, and hydraulic distributors.

With a hydraulic control system for the working bodies of machines and their elements, all operations (lifting, lowering) are provided with the help of pumps, hydraulic valves (control mechanisms), power actuating hydraulic cylinders, shut-off and safety valves and devices.

The hydraulic control system includes elements of a drive mechanism consisting of one or more hydraulic pumps installed either directly on the engine of the base machine and receiving drive from it, or on a special power take-off gearbox, also driven from the engine of the base machine; elements of the control mechanism, consisting of a system of switchgear devices (one or more hydraulic valves), installed, as a rule, in the driver’s cabin and designed to turn on and off certain actuators and a hydraulic servo system; elements of actuators and devices consisting of hydraulic cylinders or hydraulic motors; elements of auxiliary devices, consisting of a tank for working fluid, main filters, pipelines, locking devices(hydraulic valves, valves, plugs, etc.).

Schematic diagram of the hydraulic system. From the tank, the working fluid flows through the suction pipeline to a gear or vane or other pump, which, as a result of a drive obtained directly from the engine of the base machine or a special gearbox, supplies it through the pipeline under pressure to switchgear(hydraulic distributor) and then also under pressure into one or another cavity of the executive hydraulic cylinder connected to one or another working part of the machine. When the working fluid is directed into one or another cavity of the actuating hydraulic cylinder, its rod, and with it the system of levers, activates the working or other part of the machine, raising or lowering it or moving it in one direction or the other.

In a hydraulic drive of machines, the rotational movement of the engine shaft is converted into the rotational movement of the pump shaft, and the rotation of the latter is converted into the translational movement of the piston of the power hydraulic cylinder and is then transmitted through the hydraulic cylinder rod to the executive working elements.

From the hydraulic tank, the working fluid flows through the suction pipeline to the pump, which pumps it through the pressure line to the pump cavity of the hydraulic distributor. After this, the operation of the hydraulic drive depends on the position in which the handle and the hydraulic valve spool associated with it are placed.

The hydraulic distributor consists of a housing located in the axial hole of the spool housing and the handle.

The axial hole of the hydraulic distributor housing is equipped with special branch cavities. The cavity connects the hydraulic distributor to the pump, the cavities supply the working fluid to the hydraulic cylinder, and the drain cavities connect the hydraulic distributor to the hydraulic tank.

In position I, the spool belts block the access of the working fluid from the cavity to the cavities k, and also drain from them through the cavities and. In the case under consideration, the working fluid located in the hydraulic cylinder is locked and the controlled element of the working equipment is stationary (in a neutral position). Subsequently, the working fluid, flowing from the pump to the hydraulic distributor, increases the pressure in the pressure hydraulic line and, overcoming the resistance of the spring of the overflow valve 11, built into the hydraulic distributor through the channels, is drained back into the hydraulic tank.

In position II, when the spool is in the lower part of the axial bore of the hydraulic spool, the cavity is connected to the cavity of the hydraulic cylinder, and the cavity of the hydraulic cylinder is connected to the cavity. Then the hydraulic cylinder piston will move to the upper position.

In position III, when spool 6 is in the upper part of the axial bore of the hydraulic spool, the direction of supply of the working fluid drain will be reversed, and accordingly the hydraulic cylinder piston will move in the opposite direction.

When the spool b is in a completely lowered position (position IV), the cavity is isolated from both cavities and the hydraulic cylinder, which at this time are connected to the drain cavities. Thus, when exposed to an external load from the working equipment, the piston (and therefore the rod) of the hydraulic cylinder moves, freely pumping the working fluid contained in it from one cavity to another. This position is called "floating". It is used when moving working machines, when a machine, such as a bulldozer or scraper, transports the collected soil without burying the working body into the ground.

In hydraulic drives, mineral oils are used as the working fluid, which are selected depending on the operating conditions of the hydraulic system (summer or winter period, climatic features and etc.).

2.Maintenance

In modern road construction machines, the hydraulic drive operates at high pressures, reaching up to 20-40 MPa. At the same time, during operation, the temperature of the working fluids of hydraulic systems ranges from -60 to +100 °C. Therefore, to ensure the necessary performance, working fluids must meet basic requirements: viscosity should change as little as possible with temperature fluctuations from -50 to + 50 ° C and there should be as little mechanical impurities as possible (since this leads to blockage of oil-conducting paths) and aggressive substances; working fluids should not cause swelling of rubber products (oil seals, gaskets, etc.).

Hydraulic drives are divided into two types based on their operating principle - hydrostatic and hydrodynamic.

A hydrostatic drive consists of a pump as a driving link, receiving movement from the engine shaft or some intermediate shaft (power take-off shaft, etc.). The pump, taking working fluid from the hydraulic tank, supplies it through a pipeline to the hydraulic distributor and then through the hydraulic distributor to the executive (working) element of the machine. The working fluid, having worked in a closed hydraulic drive system, enters the hydraulic tank and then, under the action of the pump, is directed to the hydraulic distributor, etc.

The hydrodynamic drive consists of a pump wheel as a driving link, receiving movement from the engine shaft or some intermediate shaft (power take-off shaft, etc.), which, taking working fluid from the hydraulic tank, supplies it to the turbine wheel, filling it and causing it to rotate , and with it the executive (working) body of the machine or some other element of the machine, for example, running wheels. The working fluid, having worked in a closed hydrodynamic drive system, enters the hydraulic tank and then, under the action of the pump wheel, is directed to the turbine wheel, etc.

A hydrodynamic transmission with two blade wheels (pump and turbine) is called a fluid coupling, and with three or more (pump, reactor and turbine) it is called a torque converter.

In road construction machines, the hydrostatic system is predominantly used to drive working parts. This system provides the possibility of using and servicing a relatively large number of posts, rigid connection with the executive (working) bodies, easy and quick reversal of the executive (working) bodies, independent arrangement of control elements from other elements and hydraulic drive devices, simple and easy control of the hydraulic distributor levers.

The positive properties of the hydrostatic system, in particular, ensuring the rigidity of the connection with the elements of the executive (working) bodies of machines (due to the incompressibility of liquids), make it possible to forcibly move and hold the working bodies of machines and equipment (for example, to bury the cutting elements of the working bodies into the ground and hold them in the required position) position). At the same time, the system has a number of disadvantages: small movement of mechanisms and elements of executive (working) bodies; low translational speeds of movement of elements of working bodies (no more than 0.2 m/s); the need to use special working fluids for operation, which, depending on climatic conditions (summer, winter), have to be frequently changed in the system; labor intensity and complexity of setting up, configuring, and maintaining the system.

The main equipment used to operate hydraulic systems and hydraulic drives includes pumps, hydraulic valves, valves, and pressure regulators. hydraulic drive gear pump

Pumps used in hydraulic drives of road construction machines are divided into axial piston, gear and vane.

Gear and blade types are most widely used. However, axial piston pumps, which have the ability to create the highest pressures in hydraulic systems (taking into account modern trends in the development of hydraulic drives aimed at increasing pressure in the hydraulic systems of machines), are becoming widespread.

A gear pump consists of two mating gears located in a housing. When these gears rotate, the working fluid captured (suctioned) from the chamber through the spaces (between the gear teeth, as well as between the gear teeth and the pump body) is directed into the discharge cavity and then under pressure into the pipelines. The drive gear shaft protruding from the pump housing has a spline, through which the pump is connected to the power take-off shaft or the gearbox shaft. Gear pumps are reversible, meaning these pumps can operate both as pumps and as hydraulic motors.

A vane (vane) pump consists of a stator housed in a housing with an internal surface in a shape close to an ellipse. The rotating blades slide along this surface, moving in the cavities of the rotor. The pump rotor, mounted on a splined shaft, rotates together with vanes between two liners. Each of the liners has four holes (windows), evenly spaced around the circumference, of which two diametrically opposite ones are connected to the suction channels in the pump body, and the other two are connected to the discharge channels. During the rotation of the pump rotor, the vane blades, under the influence of centrifugal force and pressure of the working fluid, moving in the grooves, are pressed against the inner surface of the stator. When the rotor rotates, the space (volume) between the adjacent pair of vane blades, as well as the rotor and stator, due to the elliptical shape of the inner surface of the stator, changes, as a result of which when the above space (volume) increases, the working fluid is sucked in, and when the space (volume) decreases - injection. Consequently, during one revolution of the pump shaft, the suction and discharge process occurs twice, which is why vane pumps are called double-acting pumps. The opposite arrangement of the suction chambers (inlet 6) and discharge chambers (drain hole) helps to balance the pressure of the working fluid on the rotor, freeing the pump axles from unilateral radial loads.

Posted on Allbest.ru

...

Similar documents

Pumps are hydraulic machines designed to move liquids. Operating principle of pumps. Centrifugal pumps. Positive displacement pumps. Installation of vertical pumps. Pump testing. Pump Applications various designs. Vane pumps.

abstract, added 09/15/2008


Schematic diagram and composition of the hydraulic system of the conveyor drive of the canal digger. Calculation and selection of hydraulic motor, pump, pipeline. Selection of safety valve, filter and pressure gauge. Calculation of hydraulic transmission efficiency, determination of the thermal balance of the system.

course work, added 04/30/2013


Applications of vane pumps for pumping liquids - from chemicals to liquefied gases. Single-stage and multi-stage pumps. Organizing the installation of the pump and monitoring its quality. Pump maintenance and repair. Compliance with safety regulations.

course work, added 12/07/2016


Using sucker rod pumps to lift oil to the surface. Technical diagram pumping machine Installations of submersible electric centrifugal, screw, diaphragm electric pumps. System of periodic and continuous gas lift production.

course work, added 05/11/2011


Development of the mining and processing industries, purpose and use of mining machines. Technical description vibrating screen, possible failures, methods and means of eliminating them, maintenance, required number of spare parts.

course work, added 03/21/2010


Technical specifications rotary pumps. The purpose and operating principle of cantilever pumps, their design features. Determination of the optimal operating zone of a centrifugal pump, changes in productivity pumping station, supply through a pipeline.

course work, added 11/23/2011


Range and operating conditions of centrifugal blade machines (fans, blowers and compressors). Purpose of the diffuser and bypass channel. Euler's equation for the impeller. The performance, power and teamwork of a centrifugal machine.

presentation, added 08/07/2013


Types of cooling systems and the principle of their operation, design and operation of liquid system devices. Checking the level and density of the liquid, filling the system, adjusting the tension of the pump drive belt. Basic system malfunctions and maintenance.

abstract, added 11/02/2009


Operating principle, device, diagram of a vortex pump, its characteristics. Vortex pump impeller. Movement of liquid in flow channels. Dry suction ability. Pressure and characteristics of vortex pumps. Hydraulic radial force.

presentation, added 10/14/2013


Analysis of hydraulic drive operation. Preliminary and refined calculation of the hydraulic system. Selection of pump, hydraulic cylinder, pipeline. Calculation of a safety valve, spool valve. Study of the stability of the hydrocopier system.

HYDRAULIC DRIVE

DRIVE TYPES

To transfer mechanical energy from the internal combustion engine to the actuators of the working equipment, a hydraulic drive (hydraulic drive) is used, in which the mechanical energy at the input is converted into hydraulic energy, and then on exiting again into the mechanical, driving the mechanisms of the working equipment. Hydraulic energy is transmitted by a fluid (usually mineral oil), which serves as the working fluid of the hydraulic drive and is called the working fluid.

Depending on the type of transmission used, the hydraulic drive is divided into volumetric and hydrodynamic.

In a volumetric hydraulic drive Volumetric hydraulic transmission is used. In it, energy is transferred by static pressure (potential energy) of the working fluid, which is created by a positive displacement pump and is realized in a hydraulic motor of the same type, for example in a hydraulic cylinder.

In a volumetric hydraulic drive, a volumetric pump serves as a converter of mechanical energy at the input to the hydraulic transmission. Displacement of liquid from the working chambers of the pump and filling of the suction chambers with it occurs as a result of a decrease or increase in the geometric volume of these chambers, hermetically separated from each other. The work of displacement and suction is performed by the working body of the pump - a plunger, piston, plate, gear, depending on the type of pump . The reverse energy converter in the volumetric hydraulic transmission is a hydraulic motor, the working stroke of which is carried out as a result of an increase in the volume of the working chambers under the influence of liquid entering them under pressure.

Energy converters in a hydraulic drive (pumps and an engine are called hydraulic machines. The operation of a hydraulic machine is based on a change in the volume of the working chambers as a result of the supply of mechanical energy (pump) or as a result of the supply of hydraulic energy by a flow of working fluid under pressure (engine).

Energy is transmitted through pipelines, including flexible hoses, to any location on the machine. This feature of the hydraulic drive is called remoteness. Using a hydraulic drive, it is possible to drive several actuator motors from one pump or a group of pumps, and it is possible to switch on the motors independently.

The principle of operation of the hydraulic drive is based on the use of two main properties of the working fluid of the hydraulic transmission - the working fluid. The first property is that the liquid is an elastic body and is practically incompressible; second, in a closed volume of liquid, a change in pressure at each point is transmitted to other points without change. Let's consider the operation of a hydraulic drive using the example of a hydraulic jack (Fig. 56). The volumetric hydraulic drive includes a pump, tank and hydraulic motor. The volumetric pump is formed by a cylinder /, a plunger 2 s earring 3 and handle 4. The progressive hydraulic motor includes a cylinder 7 and a plunger 6. These components are connected by pipelines called hydraulic lines. The hydraulic lines are equipped with reverse

Rice. 56. Hydraulic jack:

/, 7 - cylinders, 2, 6 - plunger, 3 - earring, 4 - handle, 5 - tank, 8 - hydraulic line, 9 - valve, 10, 11 - valves

valves 10 And //. Valve 10 allows liquid to pass only in the direction away from the cylinder cavity 1 to the cylinder cavity 7, and the valve 11 - from tank 5 to cylinder /. The cavity of the cylinder 7 is connected by an additional hydraulic line to the tank 5. A shut-off valve is installed in this hydraulic line 9, which closes this line when the pump is running.

By swinging the handle 4 plunger 2 reciprocating motion is reported. When moving upward, the plunger sucks working fluid from the tank 5 through the valve // ​​into the cylinder cavity /. The liquid fills the cylinder cavity under the influence of atmospheric pressure and the liquid is in the tank. When entering downward, liquid from the cylinder cavity / is forced into the cylinder cavity 7 through the valve 10. Due to incompressibility, the volume of liquid displaced from the cylinder cavity completely enters the cylinder cavity 7 and raises the plunger to a certain height.

Plunger stroke 2 the downward stroke of the pump is working, and the upward stroke is idle; the hydraulic line connecting the tank to the pump is called suction; the hydraulic line connecting the pump to the hydraulic motor is called pressure. Multiple valves act as flow distributors and ensure continuity of pump operation.

Plunger 6 When the pump is running, it moves only in one direction - up. In order for the plunger 6 lower down (under

influence of external load or gravity), it is necessary to open the valve and release liquid from the cavity of the cylinder 7 into the tank.

Let's look at the main technical characteristics of the pump. When the pump plunger moves from one extreme position to another, the volume of the cylinder 1 change the value equal toVi = Fi* Si, where Fi and Si - respectively, the area and stroke of the plunger. This volume determines theoretical presentation pump in one stroke and is called working volume a. In pumps where the input link does not reciprocate, but performs continuous rotational motion, the displacement is called the flow rate per shaft revolution. The working volume is measured in dm 3, l, cm 3.

The product of the working volume and the number of working strokes or revolutions of the pump shaft input per unit of time - theoretical pump flow Q , measured in l/min, determines the speed of the actuators.

The liquid, enclosed in a closed volume between the plungers of the pump and the actuator cylinder, at rest acts on their working areas with the same pressure. This pressure also acts on the walls of cylinders and pipelines. It depends on the magnitude of the external load. Fluid pressure or working pressure hydraulic drive, is called the force per unit of the working surface of the plungers, cylinder walls and pipelines, etc. Exceeding the pressure above the working one, for which the parts and mechanisms of the hydraulic drive are designed, leads to their premature wear and can cause rupture of pipelines and other breakdowns.

Since the fluid pressure is transmitted uniformly in all directions and the forces are balanced by this pressure, then, provided that the friction of the plungers and their seals is neglected, the working pressure Pi == pF- i; Pg == pFs, where p is the working pressure.

This ratio inverse proportionality represents the gear ratio of a hydraulic drive with translational hydraulic machines. It is similar to the gear ratio of a simple lever. Indeed, if to the long end of the handle 4 apply force R, then with this lever you can overcome the force P, which is so many times greater d R[, how many times is the short arm of the lever less than the long one, and the path S 1 is so much less than the path S2, how many times the short arm of the lever is less than the long one. This leverage is also represented in the form of inverse proportionality.

In sources of mechanical energy, hydraulic drive, engine internal combustion and electric motors, the output link is a rotating shaft, from which one or more hydraulic pumps are driven, which also have a rotating shaft as an input link. The rotary hydraulic drive (Fig. 57) includes, for example, a pump and motor of the same design.

The pump consists of a stationary housing (stator), a rotating rotor 3, in longitudinal grooves 4 which slide gates 5 and 6. ( The rotor is shifted relative to the stator axis (to the left in the figure), therefore, when rotating, its outer surface either approaches or moves away from the inner surface of the housing. The gates 5, rotating together with the rotor and sliding along the walls of the stator, simultaneously move into the grooves or move out of the grooves of the rotor. If you rotate the rotor in the direction indicated by the arrow, then between its wall, the housing wall and the gate 5 a continuously expanding crescent-shaped cavity is formedAi, into which the working fluid will be sucked from tank 1. CavityBiat this time it will continuously decrease in volume and the liquid in it will be forced out of the pump body through the tap 8 and feed to the motor.

In the valve position shown in the figure 8 liquid will fill the cavity Ai and apply pressure on the gate 11, forcing it along with the rotor 10 turn clockwise. From cavity 5.2 liquid through the tap 8 will be forced into the tank. With further rotation of the rotor 3 pump ta- __________

Fig. 57, Rotary hydraulic drive:

1 - tank, 2, 13 - housings, 3, 10 - rotors. 4 - groove, 5, 6, 9, II - gates, 7 - valve, 8 - tap, A i, Bi- pump cavities, A i, B i - motor cavities

what kind of work will the gate do? 6 pump and gate 9 motor, and the process of rotation of the rotor will proceed continuously.

In order to rotate the motor rotor in the opposite direction, you need to switch the tap 8. Then the cavity B1 the pump will communicate with the cavity B2 motor and into this cavity the working fluid will flow under pressure, and from the cavity Lz the liquid will drain into the tank. If the motor is overloaded, its rotor will stop while the pump will continue to supply liquid. As a result, the pressure in the cavity of the pump, hydraulic motor and pressure pipeline will increase until safety valve 7 opens, releasing liquid into the tank and thereby protecting the hydraulic transmission from damage.

Rotational motion is transmitted in the same way as in a belt drive. In the latter, mechanical energy is transmitted through a belt, in hydraulic transmission - by the flow of working fluid. In a belt drive, the number of revolutions of the driving and driven pulleys is inversely proportional to the ratio of their radii. With the same amount of passing fluid, the rotation speed of the pump and motor rotors is inversely proportional to their working volumes. These relationships are valid in the absence of volumetric losses in transmissions.

The power transmitted through a belt drive can be increased by increasing the width of the belt while keeping the rotation speed constant. Obviously, in hydraulic transmission this can be achieved (at constant pressure) by increasing the working volume of the pump by, for example, expanding the housing and rotor with plates.

For a hydraulic drive that includes a drive pump and a hydraulic motor on an actuator, the overall efficiency is the ratio of the power removed from the hydraulic motor shaft to the power supplied to the pump shaft.

The hydraulic drive of loaders includes components inherent in any hydraulic drive: a pump, hydraulic motors and devices for controlling the flow and protecting the hydraulic system from overloads.

Rice. 58. Block diagram of the hydraulic drive:

1, 2, 3, 4. 5. 6 - hydraulic lines; ICE - internal combustion engine, N - pump, B - tank, P - safety valve, M - pressure gauge, R- distributor;

D1, D2, D3 - hydraulic motors. N - supplied energy, N 1, N 2, N 3 - energy consumed

rice. Figure 58 shows a typical block diagram of a hydraulic drive. ut yes internal combustion engine ICE energy goes to the pump N can be expended through hydraulic motors D1, D2 and D3 a drive of the working mechanisms of the machine. The working fluid enters the pump from the tank B via suction hydraulic line 1 and supplied through a pressure hydraulic line 2 to the distributor R, in front of which a safety valve is installed P. Distributor R connected to each hydraulic motor by executive hydraulic lines 4, 5 And 6. A pressure gauge is installed in the pressure line M to control pressure in the hydraulic system.

When the hydraulic motors are turned off, the working fluid of the hydraulic drive - liquid - is pumped over by a pump N from the tank B to distributor R 0 back to tank B. The suction, pressure and drain lines form a circulation circuit. Coming from ICE energy is spent to overcome mechanical and hydraulic losses in the circulation circuit. This energy is mainly used to heat the fluid and hydraulic system.

The hydraulic motor is activated by the distributor R, at the same time, it performs the functions of regulating the flow both in terms of flow rate (at the moment of switching on) and in the direction of fluid movement (reversal) to the engines. Reversible hydraulic motors are connected to the distributor by two executive lines, which in turn are connected alternately to the pressure line 2 or drain 3 circulation circuit lines depending on the required direction of engine movement.

During operation of the hydraulic motor, the circulation circuit turns on the engine and its executive hydraulic lines; when stopped, for example, when the hydraulic cylinder rod approaches the extreme position, the circulation circuit is interrupted and a state of overload of the hydraulic system occurs, since the pump N continues to receive energy from the engine ICE. In this case, the pressure will begin to increase sharply and as a result, the engine will either stop ICE, or one of the hydraulic system mechanisms fails, for example, a hydraulic line breaks 2. To prevent this from happening, a safety valve is installed on the pressure hydraulic line. P and pressure gauge M. The valve is adjusted to a pressure higher than the operating pressure, usually 10-15%. When this pressure is reached, the valve is activated and connects

pressure hydraulic line 2 with drain 3, restoring the fluid circulation circle.

In some cases, to reduce the speed of the hydraulic motor, a throttle is installed in one executive line, limiting the supply of fluid to the motor at a given pressure. If the pump performance turns out to be greater than the specified value, the valve releases part of the liquid to be drained into the tank. Pressure gauge M designed to control pressure in the hydraulic system.

Hydraulic systems of machines usually include additional devices: controllable check valves (hydraulic locks), rotating joints (hydraulic joints), filters; distributors with o built-in safety and check valves. Loaders use power steering, which also belongs to the hydraulic drive, but has its own characteristic features of design and operation.

In hydrodynamic drive hydrodynamic transmission is used, in which energy is also transferred by a liquid, but the main importance is not the pressure (pressure energy), but the speed of movement of this liquid in its circle of circulation, i.e. kinetic energy.

In a hydromechanical transmission, the clutch and gearbox are eliminated, and the vehicle’s driving mode is changed without disconnecting the transmission from the engine by changing its rotation speed, which made it possible to reduce the number of controls.

Rice. 59. Hydrodynamic transmission:

1 - axis, 2, 16 - shafts, .3 - coupling, 4, 5, 9 - wheels. 6 - ring gear, 7 - flywheel, 8 - oil indicator, 10, 22, 23 - gears, II, 14- T op mosa. 12, I3 - blockgears, 15 - drum, 17 - lid, 18 - distributor, 19 - screw, 20 - n aco With 21 - filter, 24 - crankcase

The hydrodynamic transmission (Fig. 59) contains a torque converter located in one crankcase and two planetary gears. The torque converter is designed to change the torque on the output shaft, replacing the clutch and gearbox, and planetary gears are used to change the direction of movement of the machine, replacing the reverse mechanism.

The torque converter consists of a pump 9, turbine 5 and reactor 4 wheels The pump wheel is connected to the flywheel 7 of the engine, the turbine wheel is connected to the shaft 2, reactor wheel via overrunning clutch 3 connected to the axis / mounted on the crankcase 24. Planetary block gear 13 fixed on the output shaft 16 and interacts on one side with the satellite gears of the block gear 12, s the other is the brake drum sun gear 15. Block gear 12 freely mounted on the crankcase shaft, meshes with the block gear pinions 13, and the outer surface forms a brake pulley interacting with the brake 11. Pump wheel 9 contains gear 10, which is connected to the gear through the wheel 22 hydraulic pump 20.

The pump, turbine and reactor wheels are made with blades located at an angle to the plane of rotation.

Band brakes are actuated by hydraulic cylinders using a distributor 18, which is controlled by a handle on the control panel. When moving forward, the drum brakes 15, at the rear - block 12. Pump 20 Designed to pump oil to the torque converter, planetary gears and brake control cylinders.

When the engine is running, the oil between the blades of the pump wheel, under the action of centrifugal forces, is pressed to the periphery of the wheel and directed to the blades of the turbine wheel, and then towards the stationary blades of the reactor wheel.

At low engine speeds, the oil rotates the reactor wheel, while the turbine wheel remains stationary. As the speed increases, the overrunning clutch 3 jams on the shaft and the turbine wheel begins to rotate, transmitting engine torque through planetary gears to the output shaft 16. The direction of rotation of this shaft depends on which brake is applied. As the engine speed increases, the torque on the shaft 16 decreases and the rotation speed increases. Between input shaft 16 and the drive axle is equipped with a single-stage gearbox with a gear ratio of 0.869.

Under operating conditions, monitor the oil level and its cleanliness. Filter 21

washed systematically. Frequent clogging indicates the need to change the oil.

WORKING FLUIDS

The working fluid of hydraulic systems is considered as component hydraulic drive, since it serves as the working fluid of the hydraulic transmission. At the same time, the working fluid cools the hydraulic system, lubricates rubbing parts and protects parts from corrosion. Therefore, the performance, service life and reliability of the hydraulic drive depend on the properties of the fluid.

Loaders are working on outdoors in various regions of the country. In the cold season, the machine and working fluid can be cooled to -55 ° C, and in some areas of the Middle Asia In summer, during operation, the liquid heats up to 80 °C. On average, the fluid should ensure the hydraulic drive operates within those temperatures from -40 to +50 "C. The liquid must have long term service, be neutral to the materials used in the hydraulic drive, especially rubber seals, and also have good heat capacity and at the same time thermal conductivity in order to cool the hydraulic system.

Mineral oils are used as working fluids. However, there are no oils that are suitable for all operating conditions at the same time. Therefore, depending on their properties, oils are selected for specific operating conditions (climatic zone in which the machine is used and time of year).

The reliability and durability of the hydraulic system largely depend on correct selection working fluid, as well as on the stability of properties.

One of the main indicators by which they select and evaluate

oils, this is the viscosity. Viscosity characterizes the ability of a working fluid to resist shear deformation; measured in centistokes (cSt) at a given temperature (usually 50 °C) and in conventional units - degrees Engler, which are determined using a viscometer and express the ratio of the time a liquid of a given volume (200 cm 3) flows through a calibrated hole to the time the same volume flows water. The ability of a hydraulic drive to operate at low and low temperatures primarily depends on viscosity. high temperatures. As the machine operates, the viscosity of the working fluid decreases and its lubricating properties deteriorate, which shortens the service life of the hydraulic drive.

During oxidation, resinous deposits fall out of the oil, forming a thin hard coating on the working surfaces of parts that are destructive to rubber seals and filter elements. The intensity of oil oxidation increases sharply with increasing temperature, so you should not allow an increase pace oil temperature above 70 °C.

Typically, working fluids are completely replaced in spring and autumn.

If all-season oil is used, it must be replaced after 300-1000 hours of hydraulic drive operation, depending on the type (the replacement period is indicated in the instructions), but at least once a year. In this case, the system is flushed with kerosene at idle speed. The frequency of replacement depends on the brand of liquid, the operating mode of the system volume and the tank in relation to the pump supply. The larger the system capacity, the less frequently the oil needs to be changed.

The durability of the hydraulic system is affected by the presence of mechanical impurities in the oil, therefore filters are included in the hydraulic system purification of oil from mechanical impurities, as well as magnetic plugs.

The basis for choosing oil for the hydraulic system is the temperature of the limit of use of this fluid, depending on the type of hydraulic drive pump. The lower temperature limit of use is determined not by the pour point of working fluids, but by the pumpability limit of the pump, taking into account losses in the suction hydraulic line. for gear pumps, this limit is a viscosity of 3000-5000 cSt, which corresponds to the pumpability limit during short-term (start-up) operation. The lower temperature limit of stable operation is determined by filling the working chamber of the pump, at which the volumetric efficiency reaches its greatest value, which approximately for gear pumps corresponds to a viscosity of 1250-1400 cSt.

The upper temperature limit for the use of the working fluid is determined by the lowest viscosity value, taking into account its heating during operation. Exceeding this limit causes an increase in volumetric losses, as well as sticking of the surfaces of mating friction pairs, their intense local heating and wear due to deterioration of the lubricating properties of the oil.

The basis for the use of a particular type of oil is the recommendation of the manufacturer of the hydraulic drive machine.

Before adding or changing oil, check the neutrality of the mixed oils. The appearance of flakes, sedimentation and foaming indicate that mixing is unacceptable. In this case, the old oil must be drained and the system flushed.

When filling the system, measures are taken to ensure the purity of the oil being poured. To do this, check the serviceability of the filling filters, the cleanliness of the funnel and the filling container.

HYDRAULIC MACHINES

In a volumetric hydraulic drive, hydraulic machines are used: pumps, pump motors and hydraulic motors, the operation of which is based on alternately filling the working chamber with working fluid and displacing it from the working chamber.

Pumps convert the mechanical energy supplied to them from the engine into the energy of fluid flow. Rotational motion is imparted to the pump input shaft. Their input parameter is the shaft rotation speed, and the output parameter is the fluid supply. The liquid moves in the pump due to its displacement from the working chambers by pistons, gates (blades), gear teeth, etc. In this case, the working chamber is a closed space, which during operation alternately communicates with either the suction hydraulic line or the pressure line.

In hydraulic motors, the energy of the working fluid flow is converted back into mechanical energy at the output link (hydraulic motor shaft), which also performs rotational motion. Based on the nature of the movement of the output link, a distinction is made between rotary motion engines - hydraulic motors and translational motion engines - hydraulic cylinders.

Hydraulic motors and pumps are divided according to the possibility of regulation, the possibility of changing the direction of rotation, according to the design of the working chamber and other design features.

Some designs of pumps (hydraulic motors) can perform the functions of a hydraulic motor (pump); they are called pump-motors.

Loaders use unregulated (non-reversible) pumps of various designs: gear, vane, axial piston. Adjustable hydraulic motors (pumps) have a variable volume of working chambers.

A gear pump (Fig. 60) consists of a pair of interlocking gears, placed in a housing that tightly encloses them, having channels on the input and output sides of the mesh. Pumps with external spur gears are the simplest and are characterized by operational reliability, small overall dimensions and weight, compactness and other positive qualities. Maximum pressure of gear pumps 16-20 MPa, flow up to 1000 l/min, rotation speed up to 4000 rpm, service life

Rice. 60. Scheme of operation of a gear pump

on average 5000 hours.

During rotation, the gear fluid contained in the cavity of the teeth is transferred from the suction chamber along the periphery of the housing to the discharge chamber and further into pressure hydraulic line. This occurs due to the fact that when the gears rotate, the teeth drive more fluid than can fit in the space vacated by the meshing teeth . The difference in volumes described by these two pairs of teeth is the amount of liquid that is displaced into the discharge cavity. As it approaches the discharge chamber, the fluid pressure increases, as shown by the arrows. In hydraulic systems, pumps NSh-32, NSh-46, NSh-67K are used, their modifications are NSh-32U and NSh-46U.

The NS pump (Fig. 61) contains 12 master and slave 11 gears and bushings 6. The housing is closed with a cover 5, screwed on 1. Between the body 12 and cover 5 is sealed with an O-ring 8. The drive gear is made as one piece ts splined shaft, which is sealed with a cuff 4, installation of cover 5 in the bore using support 3 and spring 2 rings The front bushings 6 are placed in the bores of the cover 5 and sealed with rubber rings. They can move along their axes. The pump's discharge cavity is connected by a channel to the space between the ends of the said bushings and the cover. Under fluid pressure, the front bushings together with the gears are pressed against the rear which, in turn, are pressed against the body 12, providing automatic sealing of the ends of the bushings and gears.

In the pump discharge cavity near the elbow 13 the pressure on the ends of the bushings is many times greater than on the opposite side. At the same time, the pressure on the ends of the covers from the body tends to press the bushings against cover 5. Together, this can cause the bushings to skew towards the suction cavity, one-sided wear of the bushings and increased oil leaks. In order to reduce the uneven loading of the bushings, part of the area of ​​the ends of the bushings is covered with a relief plate 7, sealed along the contour with a rubber ring. This ring is tightly clamped between the ends of the body and the cover, and as a result, relative equality of forces acting on the bushings is created.

The bushings wear out as the pump operates, and the distance between the ends and the cover increases. In this case, the ring of the relief plate 7 expands, maintaining the necessary seal between the cover and the bushings. The tightness of this ring determines the reliable and long work pump

Rice. 61. NSh gear pump:

/ - screw, 2, 3, 8 - rings. 4 - cuff, 5 - cover, 6 - gear bushing, 7 - plate, 9 - cotter pin, 10, II - gears, 12 - frame, 13 - square

During assembly, a gap of 0.1-0.15 mm is left between the mating bushings. After assemblies this gap is forced. To do this, the bushings are unfolded and fixed with spring pins, which are installed in the holes of the bushings.

NSh pumps produce right and left rotation. On the pump body, the direction of rotation of the drive shaft is indicated by an arrow. For a left-hand rotation pump (as viewed from the cover side), the drive shaft rotates counterclockwise, and the suction side is on the right. A right-hand rotation pump differs from a left-hand rotation pump in the direction of rotation of the drive gear and its location.

When replacing a pump, if the new and replaced pumps differ in the direction of rotation, the direction of inlet and outlet of fluid into the pump must not be changed. The pump suction pipe (large diameter) must always be connected to the tank. Otherwise, the drive gear seal will be under high pressure and will be disabled.

If necessary, the left-hand rotation pump can be converted into a right-hand rotation pump. In order to assemble a right-hand rotation pump (Fig. 62, A, b), it is necessary to remove the cover, remove the front bushings / from the body, 2 complete with spring cotter pins 4, rotate 180° and reinstall. In this case, the line of junction of the bushings will be rotated, as shown in Fig. 62. Then the driving and driven gears are swapped and their pins are inserted into the previous bushings. The front bushings are rearranged in the same way as the rear ones. After this, install unloading plate 7 (see Fig. 61) with an o-ring in the same place 8, a then the roofs are previously rotated 180°.

Pumps NSh-32 and NSh-46 are unified in design; their rods differ only in tooth length, which determines the working volume of the pumps.

NShU pumps (index U means “unified”) differ from NSh pumps in the following features. Instead of unloading plate and ring 8 a solid rubber plate is installed 12 (Fig. (Sandwiched between the cover 3 and body 1. At the point where the bushing journals pass through the plate 12 holes are made into which sealing rings are installed 13 with thin steel washers adjacent to the lid. Arc-shaped channels are made on the ends of the bushings adjacent to the gears 14. Guide spring pins 9 (see Fig. 61) are removed, and on the suction side a segment-shaped rubber seal is inserted into the housing bore 15 (see Fig. 63) and aluminum liner 16.

Rice. 62. Assembly of NSh pump bushings:

a - left rotation, b - right rotation; I, 2- bushings, 3 - well, 4 - cotter pin, 5 - body

Rice. 63. NShU gear pump:

/ - frame, 3, 4 - gears, 9 - cover 5, 6 - bushings, 7, 9, 13 - rings, 8 - cuff, 10 - bolt, // - washer, 12 - plates 14 - bushing channels, 15 - compaction 16 - inserts; A - space under the pump cover

When the NShU pump operates, oil from the discharge chamber enters the space above the front bushings and tends to press these bushings against the ends of the gears. At the same time, oil pressure acts on the bushing from the side of the teeth, entering the arc-shaped channels 14v As a result of the action of pressure on the gear bushings, the operating time of the pump is under a certain force directed from the cover into the depths of the pump housing. This design ensures automatic preloading and, consequently, end wear of gears and bushings and affects the sealing properties of the plate 12. Rubber seal 15 necessary to ensure that oil from the space above the bushings does not penetrate into the suction cavity.

A number of loader models use NSh-67K and HUJ -100K (Fig. 64). These pumps consist of a housing/cover 2, clamp 7 and bearing 5 races, driven 3 and leading 4 gears, centering sleeves, seals and fasteners.

Rice. 64. Hydraulic pump NSh-67K(NSH-100K):

/ - frame, 2 - lid, 3, 4- gears, 5, 7, - cages, 6. 11, 14, 15 - cuffs, 8 - bolt, 9 - washer, 10 - ring, 12 - plate,I3 - platics

Bearing race 5 is made in the form of a half-cylinder with four bearing seats, in which the driven 3 and presenter 4 gears. The clamping ring 7 provides a radial seal; it rests on the gear journals with its supporting surfaces. The collar also serves as a radial seal. 13, in which creates a force to press the holder against the gear teeth. Support plate 12 designed to bridge the gap between the body and the clamping holder. The clamping ring 7 compensates for the radial gap between its own sealing surface and the gear teeth as the supporting surfaces wear out.

The ends of the gears are sealed using two plates 13, which rise by force from the pressure in the cavity sealed by the cuffs 14. The force created in the chambers of the clamping ring, sealed with cuffs 15, balances the clip 7 from the force that is transmitted from the chambers through the cuffs 14. The drive shaft is sealed using cuffs that are held in the housing by support and locking rings. The pumping element (gears assembled with cages and plates) is secured against rotation in the housing by a centering sleeve.

Ring 10 seals the connector between the body and the cover, connected to each other by bolts.

Proper operation and durability of pumps are ensured by compliance with technical operation rules.

The hydraulic system must be filled with clean oil. of proper quality and the corresponding brand, recommended for a given pump when operating in a given temperature range; Monitor the serviceability of the filters and the required oil level in the tank. In the cold season, you cannot immediately turn on the pump to the working load.

It is necessary to let the pump idle for 10-15 minutes at medium engine speed. During this time, the working fluid will warm up and the hydraulic system will be ready for operation. It is not allowed to give the pump maximum speed when warming up.

Cavitation is dangerous for the pump - local release of gases and steam from the liquid

(liquid boiling) followed by destruction of released vapor-gas bubbles, accompanied by local high-frequency hydraulic microshocks and pressure surges. Cavitation causes mechanical damage to the pump and can damage the pump. To prevent cavitation, it is necessary to eliminate the causes that can cause it: foaming of the oil in the tank, which causes a vacuum in the suction cavity of the pump, air leakage into the suction cavity of the pump through the shaft seal, clogging of the filter in the suction line of the pump, which worsens the conditions for filling its chambers, separation of air from liquid in receiving filters (as a result, the liquid in the tank is saturated with air bubbles and this mixture is sucked in by the pump), high degree rarefaction in suction line for the following reasons: high fluid velocity, high viscosity and increased liquid lift height,

The operation of the pump largely depends on the viscosity of the working fluid used. There are three operating modes depending on the viscosity Sliding mode characterized by significant volumetric losses due to internal leaks and external leaks, which decrease with increasing viscosity. In this mode, the volumetric efficiency of the pump sharply decreases, for example, for the NSh-32 pump with a viscosity of 10 cSt it is 0.74-0.8, for NPA it is 0.64-0.95. Stable operation mode characterized by stability of volumetric efficiency in a certain viscosity range, limited by the upper limit of viscosity at which the working chambers of the pump are completely filled. Feed failure mode - disruption due to insufficient filling of the working chambers.

Gear pumps are characterized by the widest range of stable operation depending on viscosity. This property of the pumps has made them effective for use on machines operating outdoors, where, depending on the time of year and day, the ambient temperature varies within significant limits.

Due to wear of gear pumps, their performance deteriorates. The pump does not develop the required operating pressure and reduces flow. In NSh pumps, due to wear of the end mating surfaces of the bushings, the tension of the sealing ring covering the unloading plate decreases. This leads to oil circulation inside the pump and a decrease in its flow. Misalignment of gears and bushings in combination has the same consequences. vertical plane due to uneven wear of the bushings on the suction side of the pump.

A vane pump (Fig. 65) is used on some models of loaders to drive power steering, and the power steering pump of a ZIL-130 car is used. Rotor 10 pump, freely sitting on the splines of shaft 7, has grooves in which the gates move 22. Stator working surface 9, attached to the body 4 The pump has an oval shape, due to which two suction and discharge cycles are provided per one revolution of the shaft. Distribution disc // in the cover cavity 12 at. is pressed by oil pressure entering the cavity from the injection zone. Oil is supplied to the suction zones from both sides of the rotor through two windows at the end of the housing.

Piston pumps and hydraulic motors are made of various types and purposes; depending on the location of the pistons in relation to the axis of the cylinder block or the axis of the shaft, they are divided into axial piston and radial piston. Both types can operate with both pumps and hydraulic motors. A piston hydraulic motor (pump), in which the piston axes are parallel to the axis of the cylinder block or make angles with it of no more than 40°, is called an axial piston. A radial piston hydraulic motor has piston axes, perpendicular to the axis cylinder block or located at an angle of no more than 45°,

Axial piston motors are made with an inclined block (Fig. 66, A), in them, movement is carried out due to the angle between the axis of the cylinder block and the axis of the output link or with an inclined washer (Fig. 66, b), when the movement of the output link is carried out due to the connection (contact) of the pistons with the flat end of the disk, inclined to the axis of the cylinder block.

Hydraulic motors with an inclined washer are usually manufactured unregulated (with a constant displacement), and hydraulic motors (pumps) with an inclined block are made unregulated or adjustable (with a variable displacement). I regulate the working volume by changing the angle of inclination of the block. When the ends of the cylinder block) washers are parallel, the pistons do not move in the cylinders and the flow to coca stops, at the greatest angle of inclination - the feed is maximum.

b) d)

Rice. 66. Piston hydraulic motors:

A -axial piston with an inclined block, b - also with an inclined washer. 9 - radial piston cam, G - Same. crank; / - block. 2 - connecting rod. 3 - piston, 4 - rotor, 5-body, 6 - washer

Radial piston hydraulic motors are cam and crank motors. In the cams (Fig. 66, V) the transmission of motion from the pistons to the output link is carried out by a cam mechanism, in crank-rod ones (Fig. 66, G) - crank mechanism.

Hydraulic cylindersAccording to their purpose, they are divided into main and auxiliary. The main hydraulic cylinders are an integral part of the actuator, its engine, and the auxiliary cylinders ensure the operation of the control, monitoring system or activate auxiliary devices.

There are single-acting cylinders - plunger and double-acting - piston (Table 4). For the first, the extension of the input link (plunger) occurs due to the pressure of the working fluid, and movement in the opposite direction is due to the force of a spring or gravity, for the second, the movement of the output link; (rod) in both directions is produced by the pressure of the working fluid.

The plunger cylinder (Fig. 67) is used to drive the load lifter. It consists of a welded body 2, plunger 3, bushings 6, nuts 8 and sealing elements, cuffs, sealing 5 and wiper rings.

Sleeve 6 serves as a guide for the plunger and at the same time limits its upward stroke. It is secured in the body with a nut 8. The cuff seals the interface between the plunger and the sleeve, and ring 5 seals the interface between the sleeve and the body. To the plunger using a pin 10 the traverse is attached. Air periodically accumulates in the cylinder. A plug is used to release it into the atmosphere. 4. The surface of the plunger has a high surface finish. To ensure that it is not damaged during operation, a wiper ring is installed to prevent dust and abrasive particles from getting into the plunger interface 3 and bushings 6; bushing 6 made of cast iron so that the steel plunger does not ride up; the cylinder is supported on the movable and stationary parts of the lift through spherical surfaces so that bending loads are eliminated.

Rice. 67, Plunger cylinder:

/ - pin, 2 - frame; 3 - plunger, 4 - cork, 5, 9 - rings, 6 - sleeve,- 7 - sealing device, 8 - screw, 10- hairpin

Oil is supplied to the cylinder through a fitting at the bottom of the housing 2. At the extreme upper position the plunger 3 the shoulder rests against the bushing 6.

Piston cylinders (Fig. 68) have a variety of designs. For example, a forklift tilt cylinder consists of a housing 12, including a sleeve and a rod bottom welded to it // with a piston 14 and O-rings 13. Piston 14 secured to the stem shank 11 with a nut 3 co cotter pin 2. The shank has a groove for an O-ring 4. At the front of the cylinder there is a cylinder head 5 with a bushing. The rod in the head has a seal in the form of a cuff 9 with thrust ring 10. The head is secured in the cylinder with a threaded cap 6 with wiper 7.

A necessary condition for the operation of a hydraulic cylinder is the sealing of the rod (plunger) at the point where it exits the cylinder body, and in a piston cylinder - sealing of the rod and piston cavities. Most designs use standard rubber rings and cuffs for sealing. Fixed sealing is carried out using rubber O-rings.

Rubber O-rings or cuffs are installed on the pistons as seals. The service life of the round ring is significantly increased if it is installed in conjunction with one (for single-sided seal) or two (for double-sided seal) rectangular Teflon rings.

The rod caps are equipped with one or two seals, as well as a wiper to clean the rod as it is retracted into the cylinder. Plastic seals at smaller overall dimensions have a significantly longer service life compared to rubber ones.

Rice. 68. Piston cylinder:

1 - plug, 2 - cotter pin, 3 - screw, 4, 10, 13 - rings.S - cylinder head, 6 - cover, 7 - wiper, 8 - oiler 9 - cuff, // - stock, 12 - body, 14 - piston

During the technical operation of hydraulic cylinders, the following basic rules should be observed. When working, do not allow dirt to get on the working surface of the rod and protect this surface from mechanical damage; even a scratch breaks the seal of the cylinder.

If the machine has been standing for a long time with the working surface of the rod open, then before work, clean the rod with a soft cloth soaked in oil or kerosene.

Failure of the seal between the piston and rod cavities while the cylinder is under significant load can result in damage to the housing or breakout of the rod cover due to rod effect,

The pressure difference produced at a given flow rate at which the valve moves to throttle the flow is determined by adjusting the spring using the nut. The more the spring is tightened, the greater the load the valve will operate. Spring is adjustable So to ensure stable lowering of the forklift without a load.

Installing a back-throttle valve ensures a constant lowering speed, but does not exclude lowering of the load and loss of liquid in the event of a sudden break in the supply hydraulic line, which is a disadvantage of the described design. The ability to regulate the lowering speed by changing the pump flow is realized yc by installing the lift cylinder valve block, which you attach directly to the cylinder.

The valve block performs four functions: it allows the entire fluid flow into the cylinder with minimal resistance and locks the fluid in the cylinder when the distributor spool is in the neutral position, and if the supply hydraulic line is damaged, it regulates the fluid flow leaving the cylinder using a controlled throttle valve, while the flow rate from the cylinder is proportional to the pump performance ; provides emergency lowering of cargo in case of failure of the hydraulic drive (hydraulic pump, pipelines) of the engine.

The valve block (Fig. 74) consists of a body 10, which houses the check valve 4 with rod 5 and spring 6, controlled valve / spring 2, fittings 3 and 9, covers, valve seats and seals. In the fitting 9 a damper nut with a calibrated hole is attached.

By turning on the distributor to lift liquid through the fitting 3 directed to the end of the valve 4, compressing the spring with pressure force, opens it and enters the cavity A cylinder. Spring force 2 valve / is pressed tightly against the seat. In the cavity B there is no pressure.

Rice. 74. Valve block:

1,4 - valves, 2, 6 - springs. 3,9 - fittings. 5 - rod, 7 - lock nut; 8 - cap, 10 - frame

In the neutral position of the distributor spool, the pressure of the liquid in the cylinder and the force of the valve spring 4 pressed tightly to the saddle; also pressed to its seat by a valve / spring 2, eliminating fluid leakage from the cylinder. By switching the distributor to lower, the pressure hydraulic line from the pump is connected to the cavity B and through the throttle washer with drain IN, and the cavity D communicates with the drain. The higher the pump performance, the greater the pressure created in the cavity B, as the pressure drop across the throttle plate increases. Fluid pressure causes the valve / to move to the left, communicating with the cavity And with cavity D, and the liquid is transferred through the annular gap into the tank.

When the valve moves, spring compression and pressure in the cavity increase IN, since the hydraulic resistance is drain

the line increases with increasing flow proportionally to the opened valve, and the pressure in the cavity is balanced B. The valve movement will also decrease and the valve will move to the right under the action of the spring 2 and pressure in the cavity IN, partially blocking the annular gap. If at the same time we reduce the pump flow and thereby the pressure in front of the damper nut, then the pressure in the cavity B will also decrease and, with the force of spring 2, the valve will move to the right, partially blocking the annular gap.

Smooth and reliable operation of the controlled valve is ensured by the selection of the spring 2, valve diameter 1 and the angle of its conical part, the volume of the cavity and the diameter of the calibrated hole in the damper nut. In this regard, any change in the controlled valve is unacceptable, since it can lead to disruption of its proper operation, for example, to the occurrence of self-oscillations, which is accompanied by impacts of the valve on the seat and noise.

If the drive fails, the emergency lowering of the lift is carried out in the following sequence: the distributor handle is set to the neutral position, the protective cap is removed 8; rod 5 is kept from turning by inserting a screwdriver into the slot and unscrewing locknut 7; rod 5 is turned with a screwdriver counterclockwise by 3-4 turns (counting the turns along the slot); The distributor handle is set to the “descent” position and the load lifter is lowered. If the load lifter does not lower, then set the distributor handle to the neutral position and additionally unscrew rod 5.

After lowering, the rod must be returned to its original position by rotating clockwise and the lock nut and protective cap must be replaced.

If, when the distributor handle is set to the neutral position, the load drops under the influence of gravity, this indicates incomplete closing of the valves. The reasons may be: leakage at the interface between the seats and the conical surfaces due to the ingress of solid particles; jamming of one of the valves as a result of solid particles entering the gap between the body and the valves; the controlled valve does not rest against the seat due to clogging of the calibrated hole in the damper nut (liquid in the cavity B turns out to be locked).

If, when moving the handle to the “descent” position, the forklift does not c repents, this indicates that the calibrated hole is clogged.

To ensure safety when changing the tilt of the forklift, an adjustable throttle with a check valve is installed in the hydraulic lines to the tilt cylinders. The latter is installed in the hydraulic line to the piston cavity of the tilt cylinder.

A throttle with a check valve (Fig. - 75) consists of a housing. which houses valve 7, spring 6, nut 5, plunger with seal 2, screw 4 and a locknut. When the forklift is tilted back, the liquid passes into the cylinder through the check valve 7; during the reverse stroke, the liquid from the cylinder cavity is forced out to drain through the annular gap between the side hole of the housing and the plunger cones and the inclined hole in the housing. By rotating the nut, a gap is established that ensures a safe speed for tilting the forklift forward.

Forklifts typically use two separate pumps to drive the power steering implement. If one pump is used to supply consumers, a flow divider is installed in the hydraulic system. It is designed to divide the fluid flow into the drive of the working equipment and into the hydraulic booster, while a constant speed of rotation of the wheels must be ensured at different pump flows.

The flow divider (Fig. 76) has a housing 1 with a hollow plunger 5, safety valve 4, spring 2, cork 3 and fitting 7. A diaphragm is fixed in the plunger 6 s hole. From the pump, liquid enters the cavity A and through the hole in the diaphragm into the cavity B to the hydraulic booster (or hydraulic steering). The diameter of the hole in the diaphragm is chosen so that the cavity B 15 l/min flows at low engine speeds. As the pump performance increases, the pressure in the cavity A increases, plunger 5 rises, compressing the spring 2, and through the side holes in the plunger, part of the liquid flow enters the distributor. At the same time, the fluid flow into the cavity increases B, the pressure in it increases and excess fluid passes through the safety valve 4 goes into the cavity IN and then into the tank. Plunger movement 5 and valve operation 4 ensure constant fluid flow to power the hydraulic booster.

Rice. 75. Throttle with check valve:

/ - housing, 2 - seal, 3 - plunger,

4, 5 - screw, 6 - spring, 7 - valve

Rice. 76. Flow divider:

/ - frame. 2 - spring. 3 - cork, 4 - valve, 5 - plunger, 6 - diaphragm, 7 - fitting; A, B, C, D - cavities

In other divider designs, an adjustable throttle is installed instead of a diaphragm with a hole.

By turning the valve handle, the siphon is connected to the atmosphere, preventing liquid from flowing out of the tank under the influence of gravity.

If the valve is opened and the pump starts, the liquid will foam, the pump will operate noisily and will not develop pressure in the hydraulic system. Therefore, you should always check the closure of the valve before starting work, before starting the engine.

A shut-off valve is installed in the hydraulic system of the loader to disconnect the pressure gauge. To measure the pressure, you need to unscrew the tap one or two turns; after measuring, turn off the distributor and turn on the tap. Working with the pressure gauge constantly on is not allowed.

HYDRAULIC TANK, FILTERS, PIPELINES

Hydraulic tankdesigned to accommodate and cool the working fluid of the hydraulic system. Its volume, depending on the pump flow and the volume of the hydraulic cylinders, is equal to 1-3 minute pump flow. The hydraulic tank includes a filler neck with a strainer and a valve connecting its cavity to the atmosphere, a liquid level indicator, and a drain plug. The tank reservoir is welded, with a transverse partition. The suction and drain tubes in the form of siphons are placed on different sides of the partition, which allows you to dismantle the hydraulic lines suitable for the hydraulic tank without draining the liquid. 10-15% of the tank volume is usually occupied by air.

Filtersserve to clean the working fluid in the hydraulic system.

Filters are built into the tank or installed separately. The filter in the filler neck of the hydraulic tank ensures cleaning during refueling. He made of wire mesh; its filtering qualities are characterized by the cell size in the light and the cross-sectional area of ​​the cells per unit surface area. In some cases they use mesh filters with 2-3 layers of filter mesh, which increases cleaning efficiency.

A drain filter with a bypass valve is installed on the drain hydraulic line of domestic loaders (Fig. 77). The filter consists of a housing 6 with lid 10 and fitting 1, in which filter elements are placed on tube 5 4 with felt rings 7 at the ends, tightened with a nut 16. The housing is fixed on top of the tube 14 bypass valve. Ball 13 pressed by a spring /5, which is held in the tube using brackets 17, 18. The filter is installed on the return hydraulic line from the power steering.

The liquid enters the outer side of the filter elements and, passing through the cells of the elements and through the slot in tube 5, enters the central channel connected to the drain hydraulic line. By As the hydraulic system operates, the filter elements become dirty, the filter resistance increases, when the pressure reaches 0.4 MPa, the bypass valve opens and the liquid is drained into the tank unpurified. The passage of liquid through the valve is accompanied by a specific noise, which indicates the need to clean the filter. Cleaning is done by partially disassembling the filter and washing the filter elements. Installing a filter on the drain from the hydraulic booster, operating at lower pressure, does not cause pressure loss in the hydraulic system of the working equipment.

On Balkankar loaders, the filter is installed in the suction hydraulic line (suction filter) and is placed in the hydraulic tank. The suction filter (Fig. 78) contains a housing /,

Rice. 77. Drain filter with bypass valve:

/ - union, 2, 7, 11, 12 - rings, 3 - pin, 4 - filter element, 5 - a tube, 6 - frame, 8 - cap. 9, 15 - springs, 10 - lid, 13 - ball. 14 - body, valves, 16 - screw, 17, I8 - staples

Rice. 78. Suction filter:

/ - frame, 2 - spring, 3 - lid, 4 filter element, 5 - valve

between the covers 3 which the filter element is placed 4. The covers and the element are pressed against the body by a spring 2. The filter element is made of brass mesh, which has 6400 holes per 1 cm2, which ensures a cleaning accuracy of 0.07 mm. If the mesh is clogged, the liquid is sucked in by the hydraulic pump through the bypass valve. 5. The setting of the bypass valve made at the factory should not be violated during operation - this can cause backwater on the drain if the filter is installed on the drain hydraulic line, or cavitation of the hydraulic pump if the filter is installed in the suction line.

PipelinesThe hydraulic drive is made of steel pipes, high and low pressure hoses (suction hydraulic line). Sleeves are used to connect parts of hydraulic systems that move relative to each other.

For installation of parts of pipelines, connections with an internal cone are used (Fig. 79, a). The tightness of the connection is ensured by tight contact of the surface of the steel ball nipple with the conical surface of the fitting / using a nut 2. The nipple is butt welded to the pipe.

Rice. 79. Pipe connections:

a - with an inner ring, b - with a flared ring, c - with a cutting ring;

1 - union, 2 - screw, 3, 5 - nipples, 4 - pipe, 6 - cutting ring

Pipes of small diameter (6.8 mm) are connected with a flaring (Fig. 79, b) or with a cutting ring (Fig. 79, b) V). In the first case, the pipe 4 it is pressed against the fitting by a conical nipple 5 with the help of a nut, in the second - the seal is made by the sharp edge of the ring when screwing the union nut.

When installing hoses, they must not be bent at the embedment site or twisted along their longitudinal axis. It is necessary to provide a length reserve to reduce the length of the hose under pressure. The hoses must not touch the moving parts of the machine.

HYDRAULIC DIAGRAMS FOR LOADER

Schematic hydraulic diagrams show the design of hydraulic systems using graphic symbols (Table 5),

Let's consider a typical hydraulic diagram loader 4045Р (Fig. 80). It includes two independent hydraulic systems with a common tank 1. The tank is equipped with a filling filter 2 with a ventilation valve-prompter, and the suction hydraulic line coming from the tank has a jet break valve 3. Two hydraulic pumps are driven from a common shaft, small 5 - for driving the hydraulic booster and large 4 - for driving working equipment. From the large pump, fluid is supplied to a monoblock distributor, which includes a relief valve and three spools: one to control the lift cylinder, one to control the tilt cylinder, and the third to operate additional attachments. From the spool 6 the fluid is directed through one hydraulic line to the block 12 valves and into the cavity of the lift cylinder, and through another parallel to the control cavity of the valve block and into the drain line through the throttle 13.

The operating hydraulic lines of spool 7 are connected in parallel to the tilt cylinders of the forklift: one with the piston cavities, the other with the rod cavities. Throttles are installed at the entrance to the cavities. The third spool is a reserve one. 1

When the distributor is in the neutral position, liquid from the pump is supplied to each distributor spool and through open channel in the spools it drains into the tank. If the spool is moved to one or another working position, then the drain channel is locked and through another channel that opens, the liquid enters the executive hydraulic line, and the opposite hydraulic line communicates with drain

In the “Lift” position of the lift cylinder spool, the liquid passes into the cylinder cavity through the check valve of the valve block and lifts the forklift. In the indicated and neutral positions of the spool, reverse flow of fluid is excluded, i.e., the forklift cannot lower. In the spool position " Ha lowering" the pressure line from the pump communicates with the drain through the throttle and at the same time enters the control cavity of the valve block. At low engine speeds, the pressure in the cavity of a small controlled valve will open slightly, the flow from the cylinder cavity will be small and the speed of lowering the load will be limited.

To increase the lowering speed, it is necessary to increase the engine speed, the pressure in front of the throttle will increase, controlled, the valve will open by a larger amount and the flow from the cylinder cavity will increase.

Throttles are installed in the hydraulic lines to the cavities of the tilt cylinders, which limit the tilt speed of the forklift.

The hydraulic system of the Balkankar loaders (Fig. 81) uses

Rice. 80. Hydraulic diagram of the loader 4045Р:

I -tank, 2 -filter, 3 - valve, 4, 5 - hydraulic pumps, 6, 7 - spools. 8 - tap, 9 - pressure gauge 10, II - cylinders, 12 - valve block, 13 - throttle, 14, - filter, 15 - hydraulic booster

one pump. The working fluid comes to the pump from the tank / through the filter 2 s bypass valve and is supplied to the flow divider, which directs part of the fluid to the hydraulic steering wheel 17, and the rest of the flow - to the sectional distributor // containing four spools and safety valve 5. From the spool 9 k lift cylinder cavity 13 via check valve 12 there is only one hydraulic line. When rising, the entire fluid flow will be directed into the cylinder cavity, and when lowering, the flow rate is limited by the flow area of ​​the throttle. Also via check valve ,

Rice. 81. Hydraulic system of the Balkankar loader: I

1 - tank, 2- filter. 3 - pump, 4, 5, 10, It, 15 - valves, 6-9 - spools, 11 - distributor. 13, 14, 16 - cylinders, 16 - flow divider, 17 - hydraulic steering wheel

Oil is directed to the rod end of the tilt cylinders, allowing the forklift to slowly tilt forward for safety.

Spools b and 7 are designed for attachments. The fluid pressure in the actuating hydraulic cylinders of the attachments is regulated by a separate safety valve.

How the hydraulic system works. The system contains 4 basic elements and many other elements designed for specific purposes. Here is a description of these 4 basic elements.

• Liquid reservoir. This is a tank or other vessel that contains the liquid that powers the system.
• Liquid circuit. These are pipes through which fluid passes from one element of the system to another.
• Hydraulic pump. This device pumps fluid through a circuit, creating energy to produce work.
• Hydraulic motor or cylinder. This element produces "movement" by receiving energy from the pump.
  • Auxiliary elements that control or regulate fluid, such as valves that remove excess fluid, regulators, accumulators, pressure switches, pressure meters.

Determine the type of energy source needed for your system. This can be an electric motor, an internal combustion engine, steam, wind or water power. The most important requirement is availability and the ability to produce sufficient torque.

Study simple, everyday hydraulic systems to better understand the principle. The hydraulic lift allows the average person to lift more than 20 tons. Power steering in a car reduces the amount of force required to turn the steering wheel, and hydraulic wood splitter allows you to split the hardest wood.

Create a blueprint for your hydraulic system using the required parameters. Determine what power source you are going to use to create the pressure, as well as the type of control valves, pump type, and piping. You need to choose a method to deliver energy to accomplish the task for which you are creating a hydraulic system, such as lifting a heavy load or splitting wood.

Determine the amount of work the system must do to properly size the components. A large capacity system will require a large volume pump. Volume is calculated in liters per minute, and pressure in kilograms per square centimeter. All this also applies to the hydraulic motor or cylinder that will drive the device. For example, a cylinder used in forklifts. It requires "X" liters of oil at "Y" pressure to lift "___" kilograms by "___" meters.

Select a suitable fluid container. A steel or plastic tank with sealed hose clamps will do. Remember that the tank is not under pressure while the system is running, but you will need a valve in case excess fluid flows back into the tank.

Select the appropriate material to create the outline. Reinforced rubber hoses with O-rings will be the simplest solution, but high-strength steel pipes are much stronger and require less repair.

Select the appropriate valve system. A simple fluid valve suitable for your system pressure will work as a control valve, but for more complex operations you will need a spool valve to control unsteady flow as well as change the direction of flow in the system.

Select pump type and capacity. There are two types of hydraulic pumps. The first is the “Generator,” which pushes fluid through two or more meshed gears in a sealed casing. The second is "roller" - using several cylindrical rollers around the camera in a sealed casing. Each has its own advantages and disadvantages, so choose the one that suits you best.

Connect a suitable motor to the pump. The pumps can be operated by direct drive, via reduction gear, chain, belts and sprocket. The choice depends on the purpose of the device.

A hydraulic system is a device designed to convert small forces into large ones by using a fluid to transmit energy. There are many varieties of nodes operating according to this principle. The popularity of systems of this type is explained primarily by their high efficiency, reliability and relative simplicity of design.

Scope of use

This type of system is widely used:

1. In industry. Very often, hydraulics are an element of the design of metal-cutting machines, equipment intended for transporting products, loading/unloading them, etc.
2. In the aerospace industry. Similar systems are used in various types of controls and chassis.
3. In agriculture. It is through hydraulics that the attachments of tractors and bulldozers are usually controlled.
4. In the field of cargo transportation. Cars are often equipped with hydraulic
5. In a ship, in this case, it is used in steering and is included in the design of turbines.

Operating principle

Any hydraulic system operates on the principle of a conventional fluid lever. Supplied inside such a unit working environment(in most cases, oil) creates the same pressure at all its points. This means that by applying a small force on a small area, you can withstand a significant load on a large one.

Next, we will consider the principle of operation of such a device using the example of such a unit as a hydraulic one. The design of the latter is quite simple. Its circuit includes several filled with liquid, and auxiliary). All these elements are connected to each other by tubes. When the driver presses the pedal, the piston in the master cylinder moves. As a result, the liquid begins to move through the tubes and enters the auxiliary cylinders located next to the wheels. After this, the braking is applied.

Design of industrial systems

The hydraulic brake of a car - the design, as you can see, is quite simple. Industrial machines and mechanisms use more complex liquid devices. Their design may be different (depending on the scope of application). However circuit diagram industrial hydraulic system is always the same. Typically it includes the following elements:

1. Liquid reservoir with neck and fan.
2. Coarse filter. This element is designed to remove various types of mechanical impurities from the liquid entering the system.
3. Pump.
4. Control system.
5. Working cylinder.
6. Two fine filters (on the supply and return lines).
7. Distribution valve. This structural element is designed to direct fluid to the cylinder or back to the tank.
8. Check and safety valves.

Hydraulic system operation industrial equipment also based on the fluid lever principle. Under the influence of gravity, the oil in such a system enters the pump. It is then directed to the control valve and then to the cylinder piston, creating pressure. The pump in such systems is not designed to suck in liquid, but only to move its volume. That is, the pressure is created not as a result of its work, but under the load from the piston. Below is a schematic diagram of the hydraulic system.

Advantages and disadvantages of hydraulic systems

The advantages of units operating on this principle include:

• The ability to move large-sized and weighted loads with maximum precision.
• Virtually unlimited speed range.
• Smooth operation.
• Reliability and long service life. All components of such equipment can be easily protected from overloads by installing simple pressure relief valves.
• Economical in operation and small in size.

In addition to the advantages, hydraulic industrial systems, of course, and certain disadvantages. These include:

• Increased risk of fire during operation. Most fluids used in hydraulic systems are flammable.
• Sensitivity of equipment to contamination.
• The possibility of oil leaks, and therefore the need to eliminate them.

Hydraulic system calculation

When designing such devices, many of the most important factors are taken into account. various factors. These include, for example, the kinematic fluid, its density, the length of pipelines, rod diameters, etc.

The main goals of performing calculations for a device such as a hydraulic system are most often to determine:

• Pump characteristics.
• The stroke values ​​of the rods.
• Working pressure.
• Hydraulic characteristics of lines, other elements and the entire system as a whole.

The hydraulic system is calculated using various arithmetic formulas. For example, pressure losses in pipelines are determined as follows:

1. The estimated length of the highways is divided by their diameter.
2. The product of the density of the liquid used and the square of the average flow rate is divided by two.
3. Multiply the resulting values.
4. Multiply the result by the travel loss coefficient.

The formula itself looks like this:

• ∆p i = λ x l i(p) : d x pV 2: 2.

In general, in this case, the calculation of losses in highways is carried out approximately according to the same principle as in such simple designs like hydraulic heating systems. Other formulas are used to determine pump characteristics, piston stroke, etc.

Types of hydraulic systems

All such devices are divided into two main groups: open and closed type. The schematic diagram of the hydraulic system we considered above belongs to the first type. Low and medium power devices usually have an open design. More complex closed-type systems use a hydraulic motor instead of a cylinder. The liquid enters it from the pump and then returns to the main line.

How the repair is carried out

Since the hydraulic system in machines and mechanisms plays a significant role, its maintenance is often entrusted to highly qualified specialists from companies engaged in this particular type of activity. Such companies usually provide a full range of services related to the repair of special equipment and hydraulics.

Of course, these companies have all the equipment necessary to carry out such work. Hydraulic system repairs are usually performed on site. Before carrying it out, in most cases, various kinds of diagnostic measures must be carried out. For this purpose, companies involved in hydraulic maintenance use special installations. Employees of such companies also usually bring the components necessary to fix problems with them.

Pneumatic systems

In addition to hydraulic ones, pneumatic devices can be used to drive components of various types of mechanisms. They work on approximately the same principle. However, in this case, the energy of compressed air, not water, is converted into mechanical energy. Both hydraulic and pneumatic systems cope with their task quite effectively.

The advantage of devices of the second type is, first of all, the absence of the need to return the working fluid back to the compressor. The advantage of hydraulic systems compared to pneumatic ones is that the environment in them does not overheat or overcool, and therefore, there is no need to include any additional components or parts in the circuit.