Created on:2021-06-28 11:48

Take e514 combine as an example to diagnose and repair.

Combine hydraulic failure

Take e514 combine as an example to diagnose and repair.

(1) Heavy steering

First check the tire pressure and mechanical parts, normal; It was found that there was emulsification when checking the oil, and the steering was still heavy after changing the oil. It was suspected that there was a problem with the low-pressure oil pipe; After careful inspection, there is a pinnose hole on the low-pressure rubber pipe from the oil tank to the gear pump, which makes the gear pump empty, the hydraulic steering fails, and turns into manual steering, which makes it feel heavy. After replacing the low-pressure rubber pipe, the fault was eliminated.

(2) Header cannot be raised

The newly overhauled e514 combine can't be raised again after the header is raised and then lowered. Other hydraulic systems are normal. The fault should be in the hydraulic system of the header, because it began to rise and could not rise again after falling. It was suspected that the fault was in the gear pump. After decomposition and inspection, it was found that the rubber oil stop ring was broken and the metal retaining ring was extruded and deformed. Further observation and analysis showed that the integral shaft of the pump was reversed, and the oil return hole aligned with the low-pressure chamber was turned into the high-pressure chamber, so that the high-pressure oil entered the low-pressure space. When the header was raised, the high-pressure oil squeezed out the rubber oil stop ring and flowed into the low-pressure chamber of another hydraulic pump, which became the "supply pump", and then the header could not be raised. After replacing the rubber oil stop ring, metal retaining ring and refitting the integral shaft sleeve, the fault was eliminated.

Combine hydraulic failure

(1) Failure analysis of Don River combine

In less than half a year, a Don River harvester suddenly lost its driving ability, and other systems worked normally. First, check the oil, but no abnormality is found; Check the oil circuit between the oil tank and the make-up pump again, and the incoming oil is smooth without leakage. Start the engine and check the supply pump to ensure it works normally; When checking the variable displacement pump, do not pump oil. When the variable displacement pump was removed from the vehicle, it was found that the oil filling hole was blocked by iron slag, and the fault was eliminated after removal.

(2) Three failure cases of Yenisei combine harvester

① After working for a wheat harvest, the harvester shows weak driving ability in both forward and backward directions. First, check the oil, no abnormality; There is no oil leakage in the low pressure oil circuit; The variable displacement pump and motor are normal; Open the fuel tank cap to observe, the fuel return is not smooth during driving, and the filter is blocked. The filter was replaced and the fault was eliminated.

② In autumn harvest operation, the oil temperature of hydraulic drive system rises rapidly after working for a period of time. Then the walking speed slows down until it can't walk. The standby car can travel a certain distance after it is slightly cold. After inspection, the cooler and oil return safety valve are normal. Finally, after dismantling the variable displacement pump, it was found that the oil distribution plate and liner plate (bearing plate) had been seriously worn, resulting in the decrease of volumetric efficiency of the system, the internal leakage of high pressure oil, and the rapid rise of oil temperature due to throttling. In addition, due to the poor viscosity and temperature of the used hydraulic oil, the viscosity decreases when the temperature is high, which also aggravates the internal leakage. After the replacement of relevant parts and qualified hydraulic oil, the fault was eliminated.

③ The transmission shaft of the harvester was replaced because the spline of the transmission shaft of the variable displacement pump was worn. After the new axle was replaced, the locomotive could not run. The problems were not solved by checking and adjusting the relevant valve bodies, and it was found that the servo system could not be adjusted normally on the vehicle, that is, when the upper nut of the servo valve was loosened and the adjusting screw was screwed in and out, the outer arm of the servo valve did not move. Then loosen the plugs on both sides of the servo valve and on the end face of the motor, and try to see the oil pressure (because there is no testing equipment, this method is simple and intuitive to judge), and it is found that the external injection pressure of the hydraulic oil is high. Release the motor safety valve and pull the outer arm of the servo valve to and fro, and no oil can be seen, but the return oil cooling pipeline vibrates rhythmically. This shows that the oil make-up system is normal, and most of the pressure oil leaks through the variable system, resulting in no high-pressure oil output. The variable displacement pump was disassembled and the transmission shaft was checked with dial indicator on the lathe. It was found that the shaft was seriously bent. Troubleshooting after replacing the shaft.

Combine hydraulic failure

This paper introduces the common faults of hydraulic system of 3080 combine.

(1) Automatic deceleration of walking

① When there is no leakage in the external oil pipe, joint and hydraulic cylinder, it may be due to the oil seal (8) on the check valve × 1.9) the oil seal should be replaced in case of internal leakage of distributor due to damage. There are three caps on the outside of the distributor, and the one-way valve cap of the walking CVT system is on the driver's side; Downward is the one-way valve cover which controls the lifting of the reel; The other on the outside is the one-way valve cap which controls the lifting of header. Remove the CVT check valve cap with a wrench; Take out the spring and spring seat, and then clamp out the check valve with pliers to replace the oil seal. Be careful not to lose the ball (5 / 16 ") between check valve and rotary valve.

② Another possible reason is that there is a gap between the cone of the check valve and the cone of the distributor body. After the check valve is installed into the valve body, strike the check valve inward with a hammer. Then clamp the check valve with pliers and rotate it clockwise and counterclockwise for 2 turns respectively. Finally, pull out the check valve and check the cone surface of the check valve. If there is polishing mark in the middle of the cone surface, it indicates that the indirect contact between the check valve and the valve body is good and will not cause leakage.

③ The oil leakage of hydraulic cylinder head (as31666) is also a possible cause of automatic deceleration. The oil leakage of hydraulic cylinder head may be caused by oil seal (4) × ten × 5) It's caused by damage. The method of replacing the oil seal is: first adjust to the lowest speed position of CVT (so that the oil in the hydraulic cylinder will not splash out and hurt people), and then remove the hydraulic cylinder head from the hydraulic cylinder of CVT intermediate plate. At this time, you can see that there is a retaining ring on the end face of the hydraulic cylinder head contacting with the intermediate plate. Use the retaining ring pliers to remove the retaining ring and take out the spacer, then you can see the damaged oil seal. Pick out the oil seal with a small hook or needle and replace it with a new one. Pay attention to the oil seal groove surface should be installed outward.

(2) Automatic lowering of reel

① It may be that the oil seal (8x 1.9) of the check valve of the distributor control reel is damaged. The replacement method of the oil seal is the same as that of the walking CVT check valve, because the structure of the three-way check valve on the distributor is the same.

② It may also be caused by damage to the reel oil seal. There are three oil seals in the hydraulic cylinder of the reel, which are dust ring, oil seal (uhs28) and O-ring (43.7) from the outside to the inside × 2.65)。 The oil seal replacement method is: retract the plunger of the hydraulic cylinder of the reel to the lowest position, and then remove the hydraulic cylinder from the arm of the reel. It can be seen that there is an inner guide sleeve at the plunger, and its end face has a slot; Remove the guide sleeve by turning it anticlockwise with a screwdriver, then take out the plunger and replace the three oil seals.

(3) Automatic lowering of header

① It may be due to the check valve oil seal (8) that the distributor controls the header lifting × 1.9) damage. The replacement method is the same as the oil seal of CVT check valve.

② It is also possible that the header hydraulic cylinder leaks oil. It is common to leak oil from the plunger. The maintenance method is as follows. First retract the plunger of the hydraulic cylinder to the lowest position, and then place the removed hydraulic cylinder on the vise. Remove the guide sleeve with a pipe wrench and replace the oil seal. From the outside to the inside, there are oil seal, dust ring (D35) and O-ring (41) × 5) and Y-ring (D35).

(4) Pay more attention in use and maintenance to prevent faults

① When disassembling the walking belt (d34099), use a crowbar to move the middle plate of CVT, and do not take the hydraulic cylinder head as the fulcrum, otherwise the oil needle of the hydraulic cylinder head will be easily bent. When the hydraulic cylinder head rotates with the hydraulic cylinder, the oil seal (4 × ten × 5) It will be damaged quickly and cause oil leakage of hydraulic cylinder head.

② The crop straw wrapped on the hydraulic cylinder head must be cleaned in time, otherwise the bearing seal ring is easy to be damaged. At the same time, it is easy to bend the oil needle of the hydraulic cylinder and damage the oil seal (4) × ten × 5) , causing oil leakage of the hydraulic cylinder head.

③ After the oil seal of hydraulic cylinder is replaced, clean the hydraulic cylinder with clean hydraulic oil before installation.

④ The hydraulic oil must be changed after the first 100 hours of operation of the hydraulic system, and the hydraulic oil filter must be changed at the same time. After that, the hydraulic oil must be changed every two years or after 500 hours of operation. N68 advanced antiwear hydraulic oil shall be used. It should be pointed out that clean hydraulic oil is the basis to ensure the reliability of the hydraulic system.

⑤ When changing the hydraulic oil, the hydraulic oil in the hydraulic cylinder must be drained, because the position of the hydraulic cylinder is very low. There are many residual impurities, and it is difficult to circulate to the hydraulic oil filter. If the oil is only discharged from the hydraulic tank, the oil in the hydraulic cylinder will not be discharged. The oil mixed with impurities can easily damage the hydraulic cylinder and oil seal.

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