Fault analysis and elimination of gear pump

The gear oil pump is an important component that lifts the low-pressure oil in the tank to the high-pressure oil that can perform work by rolling and meshing a pair of involute gears with the same parameters and structures. It is a power device that converts the mechanical energy of the engine into hydraulic energy. The following failures are likely to occur during its use.

1, oil pump internal parts wear

Internal wear of the internal parts of the pump can cause internal leakage. Among them, the leakage area between the floating sleeve and the gear end face is large, which is the main part of the internal leakage. This part of the leakage accounted for about 50% to 70% of total leakage. The volumetric efficiency of gear pumps with worn-in leakage is reduced, and the pump output power is much lower than the input power. All of its losses are converted into heat energy, which can cause the oil pump to overheat. If the bonding plane is pressed tightly, there will be a small amount of movement of the floating bushes during operation to cause wear. As a result, the farm implements can be lifted slowly or cannot be lifted. Such a floating bushing must be replaced or repaired.

2, the oil pump casing wear

Mainly the wear of the floating bushing holes (the normal clearance of the gear shaft and bushing is 0.09 to 0.175mm, the maximum must not exceed 0.20mm). The gear work is affected by the pressure oil. The gear tip is close to the oil pump housing and wears the low pressure chamber part of the pump body. Another type of wear is the circumferential wear of the working face in the housing. This wear is mainly caused by the incomplete addition of oil, so it is necessary to add oil without impurities.

3, oil seal wear, plastic seal aging

The rubber seal of the unloading sheet deteriorates in quality, loses its elasticity, loses its sealing and isolation effect on the high pressure oil chamber and the low pressure oil chamber, and generates oil pressure of the high pressure oil chamber to the low pressure oil chamber, which is called “endoleak”, which reduces the oil pump. Work pressure and flow. When the skeleton type oil seal is damaged or lost, the air is sucked into the oil pump from the gap between the oil seal and the spindle journal, or from the joint between the oil inlet port plate and the oil pump housing. After the oil return pipe enters the fuel tank, a lot of air bubbles are generated in the fuel tank. . It will cause the oil in the tank to decrease, and the oil in the oil sump in the engine will increase, which will cause the farm tool to increase slowly or not. Oil seals must be replaced to rule this out.

4, lack of oil pump oil supply or no oil pressure

Phenomenon: The working device is slow to increase, shakes when it rises or cannot be lifted; there are air bubbles in the fuel tank or tubing; when the lift is raised, the hydraulic system emits a “bang and bang” sound; the working device can be raised when the lift is started, and the oil temperature rises after working for a period of time. The increase is slow or cannot be improved; it can be increased at light loads and cannot be increased at heavy loads.

cause of issue:

(1) The oil level in the hydraulic tank is too low;

(2) The hydraulic oil was not used according to the season;

(3) The inlet pipe is seriously blocked by dirt;

(4) The oil pump drive gear oil seal is damaged and the air enters the hydraulic system;

(5) The “O”-shaped sealing ring of the oil pump inlet and outlet joints or elbow joints is damaged, the fastening bolts of the elbow joints or the nuts of the inlet and outlet oil pipes are not tightened, and the air enters the hydraulic system;

(6) Internal leakage of the oil pump, aging of the sealing ring;

(7) The end surface of the oil pump or the main and driven gear bushings is worn or scratched, and the unevenness of the end surfaces of the two shaft sleeves is excessive;

(8) Internal leakage caused by incorrect assembly of internal parts of the oil pump;

(9) "Left swivel" installed "right-handed" oil pump, causing damage to the skeleton oil seal;

(10) Dirty hydraulic oil.

Method of exclusion:

(1) According to the season add or replace the oil that meets the required grade to the specified oil level. Take out the foreign matter in the tubing and tighten the bolt or nut at the joint;

(2) Replace aging or damaged skeleton oil seals or "O" seal aprons;

(3) Replace the worn gear oil pump or oil pump bushing. When the wear is slight, smooth the end surface on the flat plate. The tolerance of unevenness is 0.03mm; the end of the upper sleeve is lower than the upper plane of the pump body (normal value is lower than 2.5-2.6mm). If it is out of tolerance, 0.1-0.2mm copper plate should be added in the lower sleeve to compensate, and when it is installed, Should be put on the rear axle sleeve to install;

(4) The unloading plate and the seal ring must be installed in the oil inlet cavity. The two shaft sleeves can maintain the balance. The unloading seal ring should have a preload of 0.5mm;

(5) The guide wire elasticity should be able to twist the upper and lower bushings at the same time towards the rotation direction of the driven gear by a small angle, so that the machining planes of the two bushings of the main and driven gears can be closely fitted.

(6) The unloading groove on the sleeve must be installed on the side of the low pressure chamber to eliminate harmful dead volume when the gear meshes;

(7) Before pressing into the self-tightening oil seal, a layer of lubricating oil shall be applied to the surface of the self-tightening oil seal, and the edge of the oil blocking oil shall be directed toward the front cover.

(8) The "right-handed" pump cannot be mounted on a "left-handed" machine, otherwise it will damage the skeleton seal;

(9) Before installing the pump cover, pour a small amount of oil into the pump casing and rotate the meshing gear by hand;

(10) Before installing the oil pump cover without tightening the bolt, check that the clearance between the pump cover and the pump body is between 0.3 and 0.6 mm. If the clearance is too small, replace the big seal ring and the pressure relief part. After the hydraulic oil pump is installed, it should be flexible and non-stuck.