Created on:2021-07-09 10:04

Combine hydraulic failure - drive system failure and brake system failure

Combine hydraulic failure - drive system failure and brake system failure

1、 Drive system fault

(1) Unable to walk

A 1075 combine was disassembled for inspection due to oil leakage from the gasket of hydraulic driven variable displacement pump (the gasket between feed pump and variable displacement pump). When the gasket was replaced, the pipe between the driven gears in the oil supply pump fell out, and the driver mistakenly put the pipe into the oil suction pipe of the oil supply pump, resulting in huge losses.

Fault phenomenon: after maintenance, the harvester can only move forward, not backward, and then it can't move forward.

Fault analysis: the tube between the driven gears in the oil supply pump is made of aluminum material, which is cut and gnawed by the high-speed rotating gear of the oil supply pump in the oil suction pipe, so that the whole hydraulic drive system is filled with aluminum particles. In the hydraulic drive system, aluminum terminals will block the oil way check valve, shuttle valve and high pressure safety valve, and will seriously wear the cylinder block and plunger of variable displacement pump and quantitative motor. In this fault, the hydraulic oil circuit in the forward direction was damaged first, and then in the backward direction. As a result, the harvester could only move forward but not backward at first; In the end, neither forward nor backward.

For parts with strict technical requirements, don't dismantle them by yourself. Instead, ask special technicians to handle them. At least, handle them carefully according to the parts book, so as not to cause major accidents.

(2) Failure caused by improper adjustment of plunger position of servo hydraulic cylinder

When the combine driver replaced the O-ring of the servo hydraulic cylinder plunger, he forgot to mark on the servo hydraulic cylinder plunger during disassembly. After changing the sealing ring, he installed and adjusted the servo hydraulic cylinder plunger himself. Because the plunger position is not adjusted correctly, the swash plate has an angle, which can not meet the technical requirements of the variable displacement pump and affects the service life.

The correct adjustment method is as follows.

① Remove the variable displacement pump and disassemble it correctly until you see the thrust plate on the swash plate. At this time, the swash plate should have no inclination angle.

② Measure the distance between the thrust plate and the upper side of the pump shell on two opposite points of the thrust plate on the swash plate with a sounding gauge. The maximum center position deviation of swash plate is 0.03mm.

③ Rotate the hydraulic cylinder plunger and adjust it inward or outward until it is correct.

④ After adjusting the swash plate, install the clamping seat and fix the plunger of servo hydraulic cylinder. Note: before removing the plunger of servo hydraulic cylinder, mark the plunger of servo hydraulic cylinder.

2、 Brake system failure

(1) System overview

Jl1000 series combine adopts hydraulic system as shown in Figure C for walking brake. The system is mainly composed of brake pump, brake cylinder, oil cup and connecting pipeline. The braking system is an important part of the combine, and its working condition directly affects the performance and driving safety of the combine.

The braking system works with the help of the hydraulic pressure generated by the pedal force of human. The brake pump is the key component in the system, and its structure is shown in Figure D. The upper chamber is the oil storage chamber, and the lower chamber is the working chamber. The communication and isolation of the upper and lower chambers are controlled by the plate valve assembly (including plate valve body 2, plate valve 3 and tower spring 4). When the pedal 13 is depressed, the plunger 9 moves to the right under the action of the pedal lever, and the spring 10 is compressed; At the same time, the plate valve 3 closes the plate valve assembly under the action of the tower spring 4, so the upper and lower cavities are isolated; The plunger 9 continues to move to the right, and the hydraulic pressure is generated in the working chamber. The working chamber is connected with the brake cylinder through pipeline, and the piston of the brake cylinder moves outward under the action of hydraulic pressure to realize braking. When the pedal is released, the plunger 9 is reset under the action of the spring 10; At the same time, the plate valve 3 opens, the upper and lower cavities communicate, and the hydraulic pressure is eliminated; The oil storage chamber supplies oil to the working chamber to make the working chamber full of oil all the time.

CD.jpg

The brake pump has two parallel column Plugs 9, which are respectively controlled by two pedals 13. When the two pedals are connected by the connecting plate, the two pedals act at the same time to realize the simultaneous braking of the left and right wheels. Under this working condition, the pressure of the two working chambers is balanced by the balance valve (to make the pressure of the two working chambers equal). The balance valve is composed of steel ball 8, spring 7 and plug 6. The two balance valves are set under the plunger 9. When the connecting plate is opened, a pedal can be operated independently to make the corresponding side in the working state and realize the independent braking of the left and right wheels. At this time, the balance valve acts as a check valve.

(2) Common faults of hydraulic braking system

① The possible reasons and solutions are as follows: A. if there is no hydraulic oil or lack of hydraulic oil, add hydraulic oil to the oil filling cup and exhaust; b. The hydraulic oil contains mechanical impurities, so the hydraulic oil should be replaced; c. If there is oil leakage at the sealing parts of brake pump, brake cylinder and pipe joint, the loose parts shall be tightened or the damaged sealing parts shall be replaced and the air shall be discharged; d. If the seal of the plate valve is not tight or stuck, or the sealing surface of the plate valve is damaged, the sealing surface should be reground or the plate valve assembly should be replaced; c. If the tower spring overlaps, the tower spring should be corrected or replaced.

② The pedal does not return. This is because spring 10 is deformed or broken. The spring should be replaced.

③ When both sides brake at the same time, it is normal, and when one side brake, it is out of order. This is because the sealing of the balance valve is not tight. The specific reasons are as follows: A. There are mechanical impurities at the sealing ring belt, which should be cleaned up; b. When the brake pump plunger 9 contacts with the steel ball 8 in the non working state, the adjusting bolt 12 should be screwed out to separate it. If the right brake fails, check the left balance valve, otherwise it will be the opposite.

④ The brake is weak, because there is air in the system, the air should be removed. By the way, domestic or imported brake hydraulic oil is generally used in the brake system. If there is a lack of brake oil for a while, 20 × turbine oil can also be used, and its filtering accuracy is 25um.

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