DIY hydraulic pump repair

Repair of hydraulic pumps is often necessary when problems arise with this special technique. Often, such a situation does not require the intervention of qualified specialists, and if you have a little certain knowledge, you can fix it with your own hands.

It is suggested to get acquainted with the most common malfunctions and ways to eliminate them from the article.

The operation of any hydraulic pump is based on the principle of suction and discharge of liquid.

Main structural elements:

A liquid moves between them, which, when the pressure chamber is filled, begins to press on the piston, displacing it, imparting movement to the working tool.

Basic operating parameters of all types of hydraulic pumps:

• Engine speed, measured in rpm.
• Working pressure in the cylinder, in bar.
• The volume of the working fluid, in cm³ / rev or the amount of fluid displaced by the pump during one revolution of the motor shaft.

The main types of equipment:

• Manual hydraulic hydraulic pump... This is the simplest unit operating on the principle of liquid displacement.

When the handle is pressed, the piston moves upward, which creates a suction force and, through the KO2 valve, liquid enters the chamber, which is displaced when the handle is raised.

The advantages of such units:

1. low performance compared to drive units.

• Radial piston. They are able to develop pressure up to 100 bar, have a long period of operation. Radial piston pumps can be of two types:

1. rotary. In such devices, the piston group is placed inside the rotor, from its rotation the piston makes reciprocating movements, alternately joining the holes for draining the liquid through the spools;

Rotary radial piston pump device

1. with eccentric shaft. Its difference is the location of the piston group inside the stator; such pumps distribute liquid through the valves.

1. high reliability;
2. work is done with high pressure, which increases productivity;
3. creates a minimum noise level during operation.

1. high pulsation rate during liquid supply:
2. large mass.

• Axial piston. This is the most common type of equipment.

Depending on the location of the axis of rotation of the engine, there may be:

The advantages of such pumps:

1. high efficiency;
2. high performance.

1. high price.

• Gear pumps refer to rotary equipment... The hydraulic part of the structure consists of two rotating gears, their teeth, upon contact, displace liquid from the cylinder. Gear pumps can be:

1. with external gear;
2. with internal gearing, in which the gears are located inside the housing.

The photo shows the types of gear pumps.

Gear units are used in systems where the operating pressure does not exceed 20 MPa. They are most commonly used in agricultural and construction equipment, lubrication systems and mobile hydraulics.

• Simple construction.
• Small size.
• Light weight.

• Low efficiency, up to 85%.
• Small turns.
• Short service life.

Advice: To increase the service life of the hydraulic pump, it is necessary to strictly follow the requirements of the operating instructions.

Almost all breakdowns that occur during the operation of hydraulic pumps are the result of such factors as:

• Failure to comply with the rules of equipment management and neglect during its maintenance:

1. untimely replacement of oil and filters;
2. elimination of leaks in the hydraulic system.

• Errors in the selection of hydraulic fluid or oil.
• The use of accessories that do not correspond to the operating mode of the pump.
• Incorrect hardware setup.

The table provides a list of the most common malfunctions and how to fix them:

Clearance in the control rod.

The bearing seat pins are broken.

The channel between the control spool and the piston is dirty.

Seizure received on the surface of the piston impedes its smooth movement

Check and repair, if necessary, the hydraulic pump

The resistance of the hydraulic line between the remote elements of the pressure compensator and the control panel has increased.

Low control pressure

Adjust equipment control pressure

The drive shaft splines are worn out.

Piston shoes or pistons themselves are worn or damaged

Bearings worn out too much

Pressure compensator incorrectly aligned.

The spool of the control mechanism has broken.

The control spool springs are damaged or broken.

Seizure has formed on the spool or bore.

The control cylinder springs are damaged or broken.

Malfunctions of elements in the circuit of the remote pressure compensator

The minimum working volume of the equipment is set too high.

The supporting surfaces of the hydraulic pump cradle and the saddle of the support bearings are worn out or damaged

Check and, if necessary, repair the hydraulic pump

The channel from the output channel to the control spool is dirty

There is a low level of working composition in the tank.

Low pressure at the inlet to the hydraulic pump.

Worn or damaged interface surfaces between the cylinder block and the distributor.

Poor heat exchanger cooling. Inspect the heat exchanger, rinse and clean the cooling surfaces.

Hydraulic motors are expensive products, therefore, correct operation and timely elimination of minor violations in the first hours of operation will save the hydraulic motor without bringing it to a critical state.

Nevertheless, during the operation of the equipment, some malfunctions may occur, which lead to repair of a hydraulic motor.

Below are the most common malfunctions repair of the hydraulic motor, ways to detect and fix them.

Fault type:

A) Slow speed of rotation of the drive mechanism.

Possible reason:

1. Wear of parts of the distribution unit of the hydraulic motor, parts of the piston group or destruction of the seal;
2. The formation of scoring on the surface of parts involved in the transmission of torque;
3. Increased pressure in the drain line.

Troubleshooting Methods:

• 1. AND 2. Feel the motor body temperature compared to normal and check the fluid flow rate in the drain line (leakage from the motor body). If noticeable deviations from the usual state are detected, disassemble the hydraulic motor and visually check the condition of the parts, as well as change the dimensions of the parts of the distribution unit and the piston group, check the integrity of the seals. If necessary, replace the hydraulic motor or replace only the seals.
• 3. Change the pressure in the drain line. If the pressure is exceeded, disassemble the drain pipeline, check its permeability, find the cause of the increased resistance.

Fault type:

B) Uneven rotation of the motor shaft at low speeds.

Possible reason:

1. Increased wear of parts of the distribution unit, piston group or destruction of seals;
2. The formation of scoring on the surface of the eccentric shaft and connecting rods in single-stroke motors or on parts of the piston group involved in the transmission of torque in multi-stroke motors.

Troubleshooting Methods:

1.and 2. Check the flow rate in the drain line.If a visible flow ripple is detected, disassemble the motor and inspect the parts of the distribution unit, the shaft eccentric and parts of the piston group of the motor. If necessary, replace the motor or only the seals.

Fault type:

C) Lack of rotation of the hydraulic motor shaft.

Possible reason:

1. Violations in the supply fluid line to the hydraulic motor;
2. Destruction of parts of the hydraulic motor distribution unit.

Troubleshooting Methods:

• Measure the pressure at the inlet to the hydraulic motor. If a noticeable decrease in pressure is detected, check the condition of the pump and other elements of the hydraulic system, as well as the integrity of the discharge pipeline. Eliminate the cause of the pressure drop.
• Check the flow rate in the drain line. If leaks are large, replace the hydraulic motor.

Fault type:

Possible reason:

1. Weakening of the fastening elements of pipelines;
2. Shaft journal or cuff wear, as well as increased pressure in the motor housing;
3. Destruction of seals or cracks in body parts.

Troubleshooting Methods:

• 1. Visually determine the location of the leak. Check the fastening of the piping elements.
• 2. Determine the flow rate in the drain line or the pressure in the motor housing. If the pressure is more than 0.5 kg / cm 2, disassemble the hydraulic motor and establish the cause of the increased pressure.
• 3. Replace seals or hydraulic motor.

Fault type:

E) Increased noise of mechanical origin.

Possible reason:

1. Excessive play in the articulation of the piston and connecting rod in one-way hydraulic motors or destruction of parts of the piston group.
2. Wear of shaft bearings, their destruction, or failure of bearings in the piston group of multi-way hydraulic motors.
3. Insufficient pressure in the return line for multi-port motors.

Troubleshooting Methods:

• 1.and 2. Using the auditory tube, listen to the operation of the hydraulic motor and, if knocks and impacts are detected, stop the motor and disassemble it in order to inspect the parts. Replace the bearings, otherwise replace the motor.
• 3. Measure the pressure in the drain line of the hydraulic motor. If the pressure is below normal, check the integrity of the pipeline and, if necessary, replace, establish other reasons for the pressure drop.

At the first stage of repair, equipment diagnostics is carried out, the identified malfunctions are assessed, the reasons for their occurrence. Elimination options, risks and costs are identified. After agreeing on the price, terms and types of work with the customer, repair and technical work is carried out:

• troubleshooting of products includes disassembly, identification of the reasons for failure, cleaning of parts;
• replacement of components: pumping unit, cradle, rotary plate, bearings ...;
• replacement of worn-out parts and assemblies: distributors, bushings, regulator, shaft, seals, rubber seals;
• elimination of dirt, wear and tear and its traces;
• restoration of the tightness of the locking elements;
• adjusting valve regulators;

The assembly is carried out using the necessary materials and equipment for reliable sealing, grinding of units and parts. Further tests are carried out using a specialized stand. The technical indicators are checked for compliance, the restored units are pumped.

Based on the results of the check, additional refinement can be made or a report can be drawn up, which is provided to the client along with the repaired hydraulic pump.

Our advantage is the ability to repair any type of imported hydraulic pumps: radial and axial piston, gear, gerotor, manual and blade. All work is carried out on site, which can significantly save time and money.

We can order the repair of hydraulic pumps of various brands: Caterpillar, DAEWOO, Denison Hydraulics, EATON, Hitachi, Kawasaki, KAYABA, Komatsu, Linde, NACHI, Parker, Rexroth Bosch, Sauer Danfoss, TOSHIBA, VICKERS, etc.

Repair of hydraulic pumps is often necessary when problems arise with this special technique. Often, such a situation does not require the intervention of qualified specialists, and if you have a little certain knowledge, you can fix it with your own hands.

It is suggested to get acquainted with the most common malfunctions and ways to eliminate them from the article.

The operation of any hydraulic pump is based on the principle of suction and discharge of liquid.

Main structural elements:

A liquid moves between them, which, when the pressure chamber is filled, begins to press on the piston, displacing it, imparting movement to the working tool.

Basic operating parameters of all types of hydraulic pumps:

• Engine speed, measured in rpm.
• Working pressure in the cylinder, in bar.
• The volume of the working fluid, in cm³ / rev or the amount of fluid displaced by the pump during one revolution of the motor shaft.

The main types of equipment:

• Manual hydraulic hydraulic pump ... This is the simplest unit operating on the principle of liquid displacement.

When the handle is pressed, the piston moves upward, which creates a suction force and, through the KO2 valve, liquid enters the chamber, which is displaced when the handle is raised.

The advantages of such units:

1. relative simplicity of design, which facilitates repair if necessary;
2. reliability;
3. low price.

1. low performance compared to drive units.

• Radial piston. They are able to develop pressure up to 100 bar, have a long period of operation. Radial piston pumps can be of two types:

1. rotary. In such devices, the piston group is placed inside the rotor, from its rotation the piston makes reciprocating movements, alternately joining the holes for draining the liquid through the spools;

1. with eccentric shaft. Its difference is the location of the piston group inside the stator; such pumps distribute liquid through the valves.

1. high reliability;
2. work is done with high pressure, which increases productivity;
3. creates a minimum noise level during operation.

1. high pulsation rate during liquid supply:
2. large mass.

• Axial piston. This is the most common type of equipment.

Depending on the location of the axis of rotation of the engine, there may be:

The advantages of such pumps:

1. high efficiency;
2. high performance.

1. high price.

• Gear pumps refer to rotary equipment ... The hydraulic part of the structure consists of two rotating gears, their teeth, upon contact, displace liquid from the cylinder. Gear pumps can be:

1. with external gear;
2. with internal gearing, in which the gears are located inside the housing.

The photo shows the types of gear pumps.

Gear units are used in systems where the operating pressure does not exceed 20 MPa. They are most commonly used in agricultural and construction equipment, lubrication systems and mobile hydraulics.

• Simple construction.
• Small size.
• Light weight.

• Low efficiency, up to 85%.
• Small turns.
• Short service life.

Advice: To increase the service life of the hydraulic pump, it is necessary to strictly follow the requirements of the operating instructions.

Almost all breakdowns that occur during the operation of hydraulic pumps are the result of such factors as:

• Failure to comply with the rules of equipment management and neglect during its maintenance:

1. untimely replacement of oil and filters;
2. elimination of leaks in the hydraulic system.

• Errors in the selection of hydraulic fluid or oil.
• The use of accessories that do not correspond to the operating mode of the pump.
• Incorrect hardware setup.

The table provides a list of the most common malfunctions and how to fix them:

Clearance in the control rod.

The bearing seat pins are broken.

The channel between the control spool and the piston is dirty.

Seizure received on the surface of the piston impedes its smooth movement

Check and repair, if necessary, the hydraulic pump

The resistance of the hydraulic line between the remote elements of the pressure compensator and the control panel has increased.

Low control pressure

Adjust equipment control pressure

The drive shaft splines are worn out.

Piston shoes or pistons themselves are worn or damaged

Bearings worn out too much

Pressure compensator incorrectly aligned.

The spool of the control mechanism has broken.

The control spool springs are damaged or broken.

Seizure has formed on the spool or bore.

The control cylinder springs are damaged or broken.

Malfunctions of elements in the circuit of the remote pressure compensator

The minimum working volume of the equipment is set too high.

The supporting surfaces of the hydraulic pump cradle and the saddle of the support bearings are worn out or damaged

Check and, if necessary, repair the hydraulic pump

The channel from the output channel to the control spool is dirty

There is a low level of working composition in the tank.

Low pressure at the inlet to the hydraulic pump.

Worn or damaged interface surfaces between the cylinder block and the distributor.

Poor heat exchanger cooling. Inspect the heat exchanger, rinse and clean the cooling surfaces.

We are ready to offer you not only professional repair of hydraulic motors and hydraulic pumps, but also, which is no less important, their preliminary diagnostics directly on the equipment. Very often, the problem of low efficiency of equipment operation is not associated with the operation of these units, but with their incorrect setup and adjustment.

Experienced field crews will not only be able to diagnose and configure the equipment on the spot, but also, in the event of a malfunction in the hydraulic motors and pumps themselves, dismantle them for repairs in a service center. You will not only save money, but also time.

The service department of the Tradition-K Company carries out routine and overhaul repairs of axial piston hydraulic pumps and hydraulic motors of the following models (series) and manufacturers:

• series 310, 410, 313, 303 produced by PSM-Hydraulics;
• pumps NP , hydraulic motors MP production Hydrosila ;
• pumps K3V, K5V, NV and hydraulic motors M5XM2X production KAWASAKI ;
• pumps A7V, A8VO A10VO, A11VO and hydraulic motors A2F , A6VM production REXROTH ;
• pumps HPV production HITACHI ;
• and many other leading global manufacturers.

We make repairs hydraulic pumps and hydraulic motors planetary type, radial piston motors , vane pumps and motors used in hydraulic systems of machines and mechanisms in various industries and construction.

During the repair, a complete defect identification of the product is carried out and a cost estimate is drawn up, which describes the detected defects and malfunctions, indicates the types and amount of work required to repair the product and a list of spare parts used in the repair. The repair is carried out by highly qualified specialists with extensive experience in the repair of hydraulic equipment and using special tools.

Depending on the type of hydraulic motor, hydraulic pump and the degree of wear of the component units, repair options will be proposed based on the results of the troubleshooting:

• replacement of seals;
• grinding and lapping of working surfaces;
• replacement of bearings;
• replacement of pumping units;
• restoration of fit sizes for bearings and oil seals;
• restoration (manufacturing) of the case;
• restoration or replacement of the regulator.

In case of economic inexpediency of repair, we are ready to offer you a large selection of both new and refurbished hydraulic units.

Thanks to well-established channels for the supply of spare parts, the parts and assemblies required for repair are supplied directly from the factories - manufacturers of the product received for repair.

Upon completion of the repair work, all 100% of the products are tested on a specially equipped hydraulic stand. During the tests, readings of the technical parameters of the product are taken and a conclusion is made about how well the repair was performed. At the end of the tests, a decision is made whether it is possible to give the product to the customer or whether it is necessary to modify it and re-test it.

Upon completion of repairs and testing, the product is warranted for six months.

At the first stage of repair, equipment diagnostics is carried out, the identified malfunctions are assessed, the reasons for their occurrence. Elimination options, risks and costs are identified. After agreeing on the price, terms and types of work with the customer, repair and technical work is carried out:

• troubleshooting of products includes disassembly, identification of the reasons for failure, cleaning of parts;
• replacement of components: pumping unit, cradle, rotary plate, bearings ...;
• replacement of worn-out parts and assemblies: distributors, bushings, regulator, shaft, seals, rubber seals;
• elimination of dirt, wear and tear and its traces;
• restoration of the tightness of the locking elements;
• adjusting valve regulators;

The assembly is carried out using the necessary materials and equipment for reliable sealing, grinding of units and parts. Further tests are carried out using a specialized stand. The technical indicators are checked for compliance, the restored units are pumped.

Based on the results of the check, additional refinement can be made or a report can be drawn up, which is provided to the client along with the repaired hydraulic pump.

Our advantage is the ability to repair any type of imported hydraulic pumps: radial and axial piston, gear, gerotor, manual and blade. All work is carried out on site, which can significantly save time and money.

We can order the repair of hydraulic pumps of various brands: Caterpillar, DAEWOO, Denison Hydraulics, EATON, Hitachi, Kawasaki, KAYABA, Komatsu, Linde, NACHI, Parker, Rexroth Bosch, Sauer Danfoss, TOSHIBA, VICKERS, etc.

Pump casing and casing-adjacent assemblies

Low fluid supply, difficult fluid passage, as a result of which working operations take place under additional load

We would like to draw your attention to the fact that when diagnosing hydraulic systems, one should take into account the fact that the hydraulic system consists not only of a hydraulic motor or a hydraulic pump, and when diagnosing, it is imperative to pay attention to hydraulic valves, hydraulic cylinders and hydraulic valves installed in the system. Since it is not uncommon for us to receive hydraulic pumps for repair, which, during the initial troubleshooting and installation on the stand (before the first breakdown for repair), turn out to be quite working and show their normal performance, and the problem was in the hydraulic valve or in the “stuck” valve ...

Axial piston hydraulic pump is now very widely used in various hydraulic drives. This can be explained by its many advantages over similar analogs. The axial piston hydraulic pump has smaller radial dimensions, dimensions, mass and moment of inertia of rotating masses. Also, over this hydromechanism it is much easier to carry out installation and repair. Such a hydraulic pump has the ability to operate at a higher speed.

1. Cylinder block with pistons (plungers)
2. Switchgear
3. Thrust disc
4. Connecting rods
5. Drive shaft

The pump, during its operation, when the shaft rotates, starts the rotation of the cylinder block. During the inclined arrangement of the thrust disk or the cylinder block, the pistons perform reciprocating axial movements along the entire axis of rotation of the cylinder block (except for the rotary one). At the moment when the pistons move out of the cylinders, suction occurs, when they move in, discharge.

Axial piston hydraulic pumps have working chambers... which act as cylinders, axially located relative to the rotor axis, and the pistons are displacers.

All hydraulic pumps of axial piston structures are made according to four generally accepted, different schematic diagrams:

Power Cardan Pumps... swash plate drive shaft - power cardan, which is a universal joint with two degrees of freedom. By means of connecting rods, the pistons can be connected to the disc. This arrangement allows the torque from the drive engine to be transmitted to the cylinder block through the cardan joint and the swash plate.

Double Cardan Shaft Pumps... here the angles between the axis of the intermediate shaft and the axes of the driven and driving shafts are taken as equal units and equal 1 = 2 = / 2. This scheme allows you to generate synchronous rotation of the driving and driven shafts, while the cardan is completely unloaded.

Axial piston hydraulic pumps of cardless type... here the entire cylinder block is connected to the drive shaft using piston connecting rods and washers. Note that cardan-type pumps are much easier to manufacture, have a smaller cylinder block and are more reliable in operation in comparison with cardan-type pumps.

Swashplate Piston Point Pumps... this scheme of hydraulic pumps is the simplest, since there are no cardan shafts and connecting rods. But in order for the mechanism to work as a hydraulic pump, a structure for forced extension of the pistons from the cylinders is needed in order to press them against the supporting surface of the swash plate. For example, these can be springs placed in cylinders.

Rotary axial piston pumps and hydraulic motors are widely used.

Their kinematic basis is a crank mechanism, in which the cylinders move parallel to one another, and the pistons simultaneously move with the cylinders, and at the same time move relative to the cylinders due to the rotation of the crank shaft.

As we have already seen, an axial piston hydraulic pump consists of many units and parts, like any other component of hydraulic equipment. And the operation of the system as a whole depends on the correct and well-coordinated operation of all mechanisms of the hydraulic apparatus.

So we recommend that you strongly monitor the condition of the hydraulic pump or hydraulic motor.... gradually study the technical characteristics of the unit and try to replace worn parts in time. So, for example, you should not allow depressurization, control the liquid level and pressure. But if the hydraulic pump is still broken and out of order, immediately seek help and ask for repair of the hydraulic pump.

Hydraulic pump repair, diagnostics, restoration.

Agricultural, construction, communal and special equipment has been used for many years, and the same number of hydraulic units are used, which, with their technological characteristics, contribute to an increase in the power and stability of machines, and ensure more productive and well-coordinated work.

Among such hydraulic units, which are the most widespread and most efficiently and often used are hydraulic pumps and hydraulic motors. They are mechanisms that can convert fluid energy into mechanical energy through the output shaft. The rotation of the shaft thereby makes the entire machine work.

Today, hydraulic pumps are used on various technical devices and machines, so manufacturers produce many different types and types of pumps. And each type and type should be used strictly for its intended purpose, for a specific system or task for which they are intended.

Hydraulic pump parts... like any other mechanism, they are subject to wear and tear during their operation and subsequently require replacement. Also, the elements that have been damaged or received a defect during operation should be replaced, that is, the hydraulic pump should be repaired in a timely manner.

During operation, the hydraulic pump must be checked after some time for possible defects, and carefully monitor the condition of the hydraulic elements.It is also important to control temperature, pressure, tightness and liquid level.

If you regularly monitor the condition of your unit... and carry out preventive checks on time, the hydraulic pump will serve for a long time. In cases where the pump still fails, it is necessary to identify the cause and repair the hydraulic pump.

Remember. repair of hydraulic pumps must be carried out in workshops with specialized, modern equipment, and only by highly qualified specialists. Accordingly, only original and high-quality spare parts should be installed.

Repair begins with diagnosing and determining the cause of the problem. At this stage, the parts that need to be refurbished or replaced are identified. This could be a hydraulic pump drive, piston, bearing, or any other component.

The device of the hydraulic pump is thoroughly studied and tested on a special stand. All nodes requiring replacement or restoration are identified.

After agreeing on the list of restoration work and parts to be replaced, the price of repairing the hydraulic pump is determined. After agreeing on the cost with the customer, we proceed directly to the repair.

Troubleshooting for hydraulic pumps takes from 1 to 3 working days.

In fact, repair is reduced to replacing defective parts or restoring surfaces subject to wear (main pumping unit, distributor, piston block, base plates).

In our warehouse there is a wide assortment of necessary components for the repair of both imported and domestic hydraulic units: shafts, bearings, rings, washers, bushings, plungers, valve boxes, rubber goods, etc. ...

If necessary, missing parts can be made to order or purchased from manufacturers.

At the final stage of the repair, the hydraulic pump is assembled and checked on a test bench. In case of successful passing of the tests (all standards and regulations are observed), the tested hydraulic pump is sent to the customer.

Axial piston hydraulic pump, hydraulic motor; Schematic diagram; Principle of operation, drawings, description, characteristics.

In volumetric hydraulic drives, along with gear drives, rotary axial piston pumps and hydraulic motors are widely used. The kinematic basis of such hydraulic machines is a crank mechanism, in which the cylinders move parallel to one another, and the pistons move together with the cylinders and at the same time, due to the rotation of the crank shaft, move relative to the cylinders. Axial piston hydraulic machines (Fig. 1) are made according to two main schemes: with a swash plate and with an inclined block of cylinders.

A hydraulic machine with an inclined disk includes a cylinder block, the axis of which coincides with the axis of the drive shaft 1, and at an angle a to it is the axis of the disk 2, to which the piston rods 3 are connected 5. Below is a diagram of the operation of the hydraulic machine in pump mode. The drive shaft drives the cylinder block.

When the unit is rotated around the pump axis by 180 °, the piston makes a translational motion, pushing the liquid out of the cylinder. With a further 180 ° rotation, the piston makes a suction stroke. The cylinder block with its polished end surface adheres tightly to the carefully machined surface of the stationary valve 6, in which the semi-annular grooves are made 7. One of these grooves is connected through channels to the suction pipeline, the other to the pressure pipeline. Holes are made in the cylinder block connecting each cylinder of the block with a hydraulic valve. If a working fluid is supplied to the hydraulic machine through the channels under pressure, then, acting on the pistons, it forces them to reciprocate, and they, in turn, rotate the disk and the shaft connected to it. Thus, the axial piston hydraulic motor works.

The principle of operation of an axial piston pump-hydraulic motor with an inclined cylinder block is as follows.The block 4 of cylinders with pistons 5 and connecting rods 9 is inclined relative to the drive disk 2 of the shaft 1 at a certain angle. The cylinder block receives rotation from the shaft through the universal joint 8. When the shaft rotates, the pistons 5 and the connecting rods 9 associated with them begin to reciprocate in the cylinders of the block, which rotates with the shaft. During one revolution of the block, each piston sucks in and discharges the working fluid. One of the slots 7 in the valve 6 is connected to the suction pipeline, the other to the pressure one. The displacement flow of an axial piston pump with an inclined block of cylinders can be adjusted by changing the angle of inclination of the axis of the block relative to the axis of the shaft within 25 °. When the cylinder block is aligned with the drive shaft, the pistons do not move and the pump displacement is zero.

The design of an unregulated axial piston hydraulic motor pump with a swash plate is shown in Fig. 2.

In the housing 4, together with the shaft 1, the cylinder block 5 rotates. The pistons 11 are supported on the swash plate 3 and thereby reciprocate. Axial pressure forces are transmitted directly to the body parts - the front cover 2 through the cradle 14 and the rear cover 8 of the body - through the piston shoes 13 and the hydraulic valve 7, which are hydrostatic bearings that successfully operate at high pressure and sliding speed.

In the axial piston pump-hydraulic motor, an end-type working fluid distribution system is used, formed by the end face 6 of the cylinder block, on the surface of which the windows 9 of the cylinders open, and by the end face of the hydraulic valve 7.

The distribution system has several functions. It is a thrust bearing that receives the sum of axial pressure forces from all cylinders; a switch for connecting the cylinders with the suction and discharge lines of the working fluid; a rotating seal separating the suction and discharge lines from one another and from the surrounding cavities. The surfaces forming the distribution system must be mutually centered, and one of them (the surface of the cylinder block) must have a little freedom of self-orientation for the formation of a lubricant layer. These functions are performed by a movable involute spline connection 12 between the cylinder block and the shaft. To prevent the joint of the distribution system from opening under the action of the centrifugal forces of the pistons, a central clamping of the block by a spring 10 is provided.

In an unregulated axial piston pump-hydraulic motor with a reversible flow and an inclined block of cylinders (Fig. 3) the axis of rotation of the cylinder block 7 is inclined to the axis of rotation of the shaft 1. The spherical heads 3 of the connecting rods 4 are embedded in the drive disc 14 of the shaft, also fixed with the help of spherical hinges 6 in pistons 13.

When the cylinder block and the shaft rotate around their axes, the pistons reciprocate relative to the cylinders. The shaft and the block rotate synchronously with the help of connecting rods, which, passing alternately through the position of maximum deviation from the axis of the piston, adjoin its skirt 5 and press on it. For this, the piston skirts are made long, and the connecting rods are equipped with body journals. The cylinder block, rotating around the central spike 8, is located in relation to the shaft at an angle of 30 ° and is pressed by a spring 12 against the camshaft disc (not shown in the figure), which is pressed against the cover 9 by the same force.

The working fluid is supplied and removed through the windows 10 and 11 in the cover 9. The pistons located in the upper part of the block make a suction stroke for the working fluid. At the same time, the lower pistons displace the liquid from the cylinders and make a discharge stroke. Lip seal 2 in the front cover of the hydraulic machine prevents oil leakage from the non-working cavity of the pump.

The loss of productivity developed by a gear pump at certain pressures is especially influenced by an increase in the end clearances between gears 1 and 4 and support bushings 3 (Fig. 52).Leakage through the end clearances is approximately 3 times greater than through the radial clearances with an equal value of these clearances, since when the gears rotate, resistance to oil flow is created along the radial clearances between the projections of the teeth and the bore in the housing; in addition, the path of oil movement along the radial clearances from the discharge cavity to the suction cavity is much greater than along the end clearances. At the same time, the rotation of the gears promotes oil leakage through the end clearances in the direction of their rotation.

Thus, increased end clearances are the main reason for reduced pump performance and oil pressure.

When disassembling the pump after long-term operation, wear of the housing 5 is usually found in the area of ​​gears 1 and 4 over the entire surface of rollers 2 and 8 and support bushings 3. Pump flanges 9 and 10 are practically not subject to wear. The contacting ends of the gears and bearing bushings are especially worn out, on the surfaces of which annular scoring, waviness, etc. are formed.

Rice. 52. Gear pump

Overhaul of the pump associated with the restoration of the housing and replacement of gears, it is advisable to carry out only in well-organized repair facilities. However, even in this case, during repairs, they usually do not restore the worn inner surface of the housing, since the radial clearance on the side of the discharge hole after replacing worn gears and bearings is almost equal to the clearance of the new pump, and the clearance increased due to the pump on the side of the suction hole will not provide significantly affect the normal operation of the pump.

Repair of pump gears depends on the nature of their wear. Wear of the ends of the teeth is eliminated by grinding while observing the parallelism of the planes of the ends and their perpendicularity to the axis of the gear wheel within 0.015 mm. Gear wheels with a worn out tooth profile are replaced with new ones.

Usually gears are made of 45 steel or 40X steel, hardened by heating with high frequency currents. Newly manufactured or restored gears must meet the following technical conditions: face runout of gears - no more than 0.01 mm; non-parallelism of ends - no more than 0.015 mm; runout of the outer surface relative to the hole - 0.015-0.02 mm; taper and ovality along the outer surface - no more than 0.02 mm.

Gear shafts worn out in the bearing seats are replaced with new ones, less often they are restored. The rollers are made of steel 20X, cemented to a depth of 1.2 mm and hardened to a hardness of HRC 60-62. The necks of the rollers, which are the rolling surfaces of the needles, are carefully ground and roughened to Ra = 0.10 μm.

The backup rolls of the needle bearings are rebuilt or replaced with new ones. When restoring support bushings, their worn ends are ground to eliminate traces of wear. After grinding the ends, it is necessary to restore the grooves for the passage of oil between the teeth. The bore holes of the support bushings are ground to the diameter required for the installation of the closest standard needle bearing, taking into account the diameter of the journal of the remanufactured or replaced roller.

To ensure normal operation of the pump gears, the support sleeves are ground in pairs in one size, while the parallelism of the ends should be within 0.01 mm. The beating of the outer cylindrical surface of the bushing relative to the axis of its hole is allowed up to 0.01 mm, and the beating of the ends relative to the axis of the hole at the largest diameter should be no more than 0.01 mm. Compliance with these conditions guarantees the absence of pinching of the gears with small end clearances.

After restoration or replacement of gears and bearing bushings, their total width is determined. Taking this size into account, one of the ends of the body is ground so that the length of the bore in the body (size A, Fig. 52) is 0.06-0.08 mm larger than the overall width of the gear and two support sleeves.When grinding the body, the non-parallelism of its ends must be ensured within the range of 0.01-0.02 mm. The uniformity and size of the provided end clearance between the gears and the ends of the bushings is the main criterion for the quality of pump repair. In some cases, the required end clearance can be provided with foil spacers that are installed between the ends of the body and the flanges. However, this method of adjustment is not reliable enough and is recommended only in some cases before the next scheduled repair.

For normal operation of the pump, it is necessary that the end face of the collar of the sleeve 6 (see Fig. 52) over the entire surface adjoins the packing follower 7. When repairing the packing follower, grind it flat until traces of wear are removed. The end of the collar of the sleeve is also ground, maintaining the perpendicularity of the end to the axis of the hole of the sleeve; butt runout should not exceed 0.01 mm.

Before assembly, all parts of the pump to be repaired must be rinsed in kerosene and lubricated with a thin layer of mineral oil, and the needle bearings must be rinsed in gasoline and lubricated with grease. The planes of the body, covers and bushings must be free of nicks and scratches. The pump assembly must be carried out in such a way that the worn-out inner surface of the housing is on the side of the suction port, i.e. on the left, when viewed from the side of the drive shaft, and the drainage channels on the bushings are brought out in the same direction.

In order to avoid clamping and misalignment of shafts and gears, the screws for fastening the flanges must be tightened alternately and to failure, while the ease of rotation of the rollers is checked by hand.

The repaired pump is tested on a special bench to determine the capacity and volumetric efficiency (efficiency).

The volumetric efficiency is the ratio of the pump's performance at a certain pressure to its own productivity without pressure. It characterizes the quality of the pump repair. The more precisely and with smaller gaps the mating parts are made, the less internal leaks in the pump and the greater the value of the volumetric efficiency.