Fault analysis and troubleshooting of gear oil pump
Date of issue:[2020-08-17] Click through rate:The gear oil pump is an important part of the oil tank which can raise the low pressure oil in the oil tank to the high pressure oil which can do work through the rolling engagement of a pair of involute gears with the same parameters and structure. It is a power device that converts the mechanical energy of the engine into hydraulic energy. The cb46 gear pump is used in Dongfanghong-75 tractor and dongfanghong-60, 70t bulldozer. The cbn-e450 or cbti-e550 gear pump is used for dongfanghong-802 / 802K tractor and dongfanghong-802k bulldozer. The pump has large flow rate and good reliability. In the process of its use, it is easy to have the following faults.
1. Wear of internal parts of oil pump
Wear of internal parts of oil pump will cause internal leakage. The leakage area between floating sleeve and gear end face is large, which is the main part of internal leakage. This part of the leakage accounts for about 50% ~ 70% of the total internal leakage. The volume efficiency of the gear pump with wear and internal leakage decreases, and the output power of the pump is much lower than the input power. Its loss is all converted into heat energy, which will cause the oil pump to overheat. If the joint plane is pressed tightly, the floating shaft sleeve will be worn due to a small amount of movement during working, which will make the agricultural tools lift slowly or can not be lifted. Such floating shaft sleeve must be replaced or repaired.
2. Wear of oil pump housing
The main reason is the wear of floating sleeve hole (the normal clearance between gear shaft and shaft sleeve is 0.09 ~ 0.175 mm, and the maximum clearance shall not exceed 0.20 mm). Under the action of pressure oil, the gear tip is close to the oil pump housing, and the low-pressure cavity part of the pump body is worn. The other kind of wear is the circumferential wear of the working surface in the shell. This kind of wear is mainly caused by the impure oil, so it is necessary to add the oil without impurities.
3. The oil seal is worn and the rubber seal is aged
The rubber oil seal of the unloading plate is aged and deteriorated, and loses its elasticity. It has lost the sealing and isolation function for the high pressure oil chamber and the low pressure oil chamber, which will cause the oil pressure of the high pressure oil chamber to flow into the low pressure oil chamber, which is called "internal leakage", which reduces the working pressure and flow rate of the oil pump. The normal working pressure of cb46 gear pump is 100 ~ 110kg / cm2, the normal oil delivery capacity is 46L / min, and the standard rubber oil seal of unloading plate is 57 × 43. The self tightening oil seal is pg25 × 42 × 10 skeleton type oil seal. If it is damaged or fails for a long time, air will be drawn into the oil pump from the gap between the oil seal and the main shaft journal or from the joint between the oil inlet connecting plate and the oil pump shell, and then enters the oil tank through the oil return pipe, resulting in a large number of bubbles in the oil tank. It will reduce the oil in the oil tank and increase the oil in the engine oil sump, which will make the agricultural tools lift slowly or not. The oil seal must be replaced to correct this problem.
4. Insufficient oil supply or no oil pressure from oil pump Phenomenon: the working device is lifted slowly, shaking or unable to lift when lifting; there are bubbles in the oil tank or oil pipe; the hydraulic system sends out "chirp, chirp" sound when lifting; the working device can be lifted when the tractor is just started, and it will be slow or unable to be lifted after the oil temperature rises for a period of time; it can be lifted under light load, but can not be lifted under heavy load.
Cause of failure:
(1) The oil level of hydraulic oil tank is too low;
(2) Hydraulic oil is not used according to season;
(3) The oil inlet pipe is seriously blocked by dirt;
(4) Oil seal of driving gear of oil pump is damaged, and air enters into hydraulic system;
(5) The "O" seal ring of oil pump inlet and outlet joint or elbow joint is damaged, the fastening bolt of elbow joint or the nut of inlet and outlet pipe is not tightened, and air enters the hydraulic system;
(6) Oil pump internal leakage, seal ring aging;
(7) The end face of the oil pump or the end face of the driving and driven gear shaft sleeve is worn or scratched, and the unevenness of the two shaft sleeve end faces is out of tolerance;
(8) Internal leakage caused by incorrect assembly of internal parts of oil pump;
(9) "Left rotation" installation of "right rotation" oil pump, resulting in damage to the framework oil seal;
(10) The hydraulic oil is too dirty.
Exclusion method:
(1) According to the season, add or change the oil of the required brand to the specified oil level. Take out the foreign matters in the oil pipe and tighten the bolts or nuts at the joint;
(2) Replace aging or damaged framework oil seal or "O" shaped sealing rubber ring;
(3) Replace the worn gear oil pump or oil pump shaft sleeve, and grind the end face on the flat plate when the wear is slight. The allowable unevenness error is 0.03mm; the end face of upper shaft sleeve is lower than the upper plane of pump body (the normal value is lower than 2.5 ~ 2.6mm). If it is out of tolerance, 0.1 ~ 0.2mm copper sheet should be added to the lower shaft sleeve to compensate. When installing, it should be installed on the rear shaft sleeve;
(4) The unloading plate and sealing ring must be installed in the oil inlet chamber to keep the balance between the two shaft sleeves. The sealing ring of unloading plate should have a preload of 0.5mm;
(5) The elastic force of the guide steel wire should be able to twist the upper and lower shaft sleeves towards the rotation direction of the driven gear at the same time, so that the processing planes of the two shaft sleeves of the driving gear and the driven gear fit closely;
(6) The unloading groove on the shaft sleeve must be installed on one side of the low pressure chamber to eliminate the harmful closed dead volume during gear meshing;
(7) Before pressing in the self tightening oil seal, a layer of lubricating oil should be applied on the surface of the self tightening oil seal, and the oil blocking edge should be oriented towards the front cover, and the installation should not be reversed;
(8) The "right-hand" pump can not be installed on the "left-hand" machine, otherwise the framework oil seal will be damaged;
(9) Before installing the pump cover, a small amount of oil must be poured into the pump shell, and the meshing gear is turned by hand;
(10) Before installing the oil pump cover and tightening the bolts, check whether the clearance between the pump cover and the pump body is between 0.3 ~ 0.6mm. If the clearance is too small, replace the large sealing ring and pressure relief parts. After the hydraulic oil pump is installed, it should rotate flexibly without jamming.
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