Fault analysis and troubleshooting of gear oil pump

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. The internal parts of oil pump are worn, which 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. The wear of oil pump housing is mainly the wear of floating shaft sleeve hole (the normal clearance between gear shaft and shaft sleeve is 0.09 ~ 0.175 mm, and the maximum is not more than 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. When the oil seal is worn, the rubber seal of the unloading piece is aged and deteriorated, and loses its elasticity, thus losing the sealing and isolation function for the high-pressure oil chamber and the low-pressure oil chamber, resulting in the oil pressure of the high-pressure oil chamber flowing to the low-pressure oil chamber, which is called "internal leakage", which reduces the working pressure and flow 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 of oil pump or no oil pressure 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 makes "pump" sound when lifting; when the tractor is just started, the working device can be lifted, and after the oil temperature rises for a period of time, the lifting is slow or unable to be lifted; it can be lifted under light load, but not under heavy load The causes of the failure are: (1) the oil level of the hydraulic oil tank is too low; (2) The hydraulic oil was not used according to the season; (3) the oil inlet pipe was seriously blocked by dirt; (4) the oil seal of the driving gear of the oil pump was damaged, and the air entered the hydraulic system; (5) the oil inlet and outlet joints of the oil pump or the "O" ring of the elbow joint were damaged; the fastening bolts or nuts of the oil inlet and outlet pipes of the bent joint were not tightened, and the air entered the hydraulic system; (6) the oil pump leaked and the sealing ring was aged; (7) the end face of the oil pump or the main and main oil pump were damaged The end face of driven gear shaft sleeve is worn or scratched, and the unevenness of the two shaft sleeve end faces is out of tolerance; (8) the internal parts of the oil pump are assembled incorrectly, resulting in internal leakage; (9) the "left-hand" oil pump is installed with the "right-hand rotation" oil pump, which causes the frame oil seal to be damaged; and (10) the hydraulic oil is too dirty.

Troubleshooting methods: (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 the 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 the upper shaft sleeve is lower than the upper plane of the pump body (the normal value is less than 2.5 ~ 2.6mm). If it is out of tolerance, 0.1 ~ 0.2mm copper plate should be added to the lower shaft sleeve to compensate, and it should be installed on the rear shaft sleeve during installation; (4) the unloading piece and sealing ring must be installed in the oil inlet chamber, so that the two shaft sleeves can keep balance. The sealing ring of the unloading plate should have a preload of 0.5mm; (5) the elastic force of the guide 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 as to make the machining planes of the driving and driven gear two shaft sleeves closely fit; (6) the unloading groove on the shaft sleeve must be installed on the side of the low-pressure cavity to eliminate the harmful dead volume during gear meshing; (7) before pressing the self tightening oil seal Before installing the pump cover, a small amount of oil must be poured into the pump housing and the meshing gear should be turned by hand; (10) before installing the oil pump cover, the clearance between the pump cover and the pump body should be checked 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.