Fault analysis and elimination of gear oil 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. Dongfanghong-75 Tractor and Dongfanghong-60, 70T bulldozer mechanism uses CB46 gear pump. Dongfanghong-802/802K tractors and Dongfanghong-802KT bulldozers use CBN-E450 or CBTI-E550 gear pumps, which have high flow and reliability. The following failures are likely to occur during its use. 1. Oil pump internal parts wear Internal parts of the oil pump will 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 wear of the oil pump housing is mainly the wear of the floating shaft sleeve hole (the normal clearance of the gear shaft and shaft sleeve is 0.09-0.175mm, and 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, rubber seal aging unloading rubber seal aging deterioration, loss of elasticity, the high pressure oil chamber and low pressure oil chamber lost the seal isolation effect, will produce high pressure oil chamber pressure to low pressure oil chamber, called " "Endoleak", which reduces the working pressure and flow of the oil pump. CB46 gear pump, its normal working pressure is 100 ~ 110kg/cm2, normal oil delivery is 46L/min, the standard unloading sheet rubber seal is 5743. The self-tightening oil seal is a skeletal type oil seal of PG254210. Its damage or age failure, 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, and enters through the return oil pipe. The fuel tank produces a lot of air bubbles in the 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. Insufficient oil supply or no oil pressure in the oil pump: The working device rises slowly and trembles or cannot be lifted during lifting; there are air bubbles in the oil tank or tubing; the hydraulic system emits a “beep, squeak” sound when lifting; the tractor just starts working The device can be upgraded. After working for a period of time, if the oil temperature rises, the lifting can be slow or cannot be improved; when the load is light, the lifting can be performed, and when the load is heavy, it cannot be increased. Causes of failure: (1) The hydraulic oil level of the hydraulic tank is too low; (2) The hydraulic oil is not used according to the season; (3) The oil inlet pipe is seriously blocked by the dirt; (4) The oil pump drive gear oil seal is damaged, and the air enters the hydraulic system; (5 ) The “O” seals of the oil pump inlet and outlet ports or elbow joints are damaged. The fastening bolts of the elbow joints or the nuts of the inlet and outlet pipes are not tightened and the air enters the hydraulic system. (6) The internal leakage of the oil pump and the 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 bushings is very poor; (8) The inner parts of the oil pump are incorrectly assembled; Spinning "oil pump, causing damage to the skeleton oil seal; (10) dirty hydraulic oil. Remedy: (1) According to the season to add or replace the oil with the required grade to the specified oil surface. Remove the foreign matter inside the tubing, tighten the bolts or nuts at the joint; (2) replace the aging or damaged skeleton oil seal or "O"-shaped seal apron; (3) replace the worn gear oil pump or oil pump sleeve, when the wear is slight Smooth the end face on the 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 sleeve to install; (4) The unloading plate and the sealing ring must be installed in the oil inlet cavity, and the two sleeves can maintain the balance. The unloading seal ring shall have a preload of 0.5mm; (5) The elasticity of the guide wire shall be able to simultaneously twist the upper and lower bushings in the direction of rotation of the driven gear by a slight angle, so that the two shafts of the master and driven gears The processing plane of the sleeve fits tightly; (6) The relief groove on the sleeve must be installed on the side of the low pressure chamber to eliminate the harmful dead volume when the gear meshes; (7) Before pressing in the self-tightening oil seal, The surface is coated with a layer of lubricating oil, but also pay attention to the edge of the oil blocking the front cover, can not be installed reverse; (8) "right-handed" pump can not be installed on the "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 housing and rotate the meshing gear by hand; (10) Before installing the oil pump cover without tightening the bolt, check the clearance between the pump cover and the pump body. Between 0.6mm, if the gap is too small, replace the big seal and pressure relief. After the hydraulic oil pump is installed, it should be flexible and non-stuck. Author: Jidong Agricultural Machinery Bureau, Heilongjiang Province

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