Maintenance of Hydraulic Fault of Ningbo Benye 404 Tractor

The following introduces the common fault causes and maintenance methods of hydraulic braking device of four-wheel tractor for the reference of tractor drivers and maintenance personnel.

First, the causes of common faults of hydraulic braking device

1. The hydraulic brake is weak or weak. This is because air is mixed in the brake pipe or brake cylinder. When the brake pedal is depressed, the hydraulic oil does not circulate smoothly in the pipeline, resulting in weak braking or weak braking.

2. The hydraulic brake cannot be completely released. Because the gap between the master cylinder push rod head and the piston is too large or too small, the brake cannot be completely released. Under normal circumstances, when the brake pedal is completely released and the brake plate and aluminum piston return, the clearance between the head of the master cylinder push rod and the piston is1~ 2 mm. If this clearance is too large, the idle stroke of the pedal will be too long, which is not convenient for operation. If the clearance is too small, it will cause the push rod to abut against the piston, so that the oil return hole of the master cylinder is covered by the edge of the rubber sealing cup, which will lead to the failure that the brake cannot be completely released.

3. The brakes are not flexible. Braking inflexibility is caused by improper adjustment of the gap between brake shoe and brake drum. Under normal circumstances, the clearance should be 0.3 ~ 0.5 mm. If the clearance is too large and the brake pedal stroke is too long, the braking time will be prolonged and the braking effect will be affected. If the gap is too small, the braking temperature will rise again, resulting in the locking failure of the brake shaft.

4. The braking of the main engine and trailer is not synchronous. Because the small four-wheeled tractor is equipped with a trailer to transport goods, the center of gravity is located at the trailer, and the trailer has large forward inertia and braking force when braking. If it is not adjusted properly, it will cause the failure that the braking of the main engine and trailer is out of sync.

Second, the inspection and diagnosis of common faults of hydraulic braking device

When there is no oil leakage in the hydraulic brake oil circuit, press the brake pedal and diagnose according to the situation.

Step on the pedal a few times, if you feel elastic, it means there is air in the oil circuit; If the pedal does not move, it means that there is other oil in the brake oil to expand the master cylinder cup; When the brake pedal is released, the master cylinder sends out a "sobbing" echo, indicating that the master cylinder cup is turned over or the ejector rod is too long, and then the spring force of the return spring of the cylinder is insufficient or the return spring is broken; If you keep stepping on the brake pedal, you still can't feel the resistance, indicating that the master cylinder is short of oil.

Three, the common fault maintenance methods of hydraulic braking device

When troubleshooting the hydraulic braking device, the hydraulic braking oil circuit should be checked first. When it is confirmed that there is no oil leakage, the following methods should be adopted for troubleshooting.

1. Drain the hydraulic oil pipeline.

Stop the engine first, tighten the joints at all parts of the pipeline, and continuously press the brake pedal until it stops.

At this time, the gas in the pipeline is squeezed into the brake cylinder installed in the wheel. Then, one person presses the brake pedal, and the other person unscrews the bleeder screw of the sub-cylinder, so that the residual gas is discharged from the bleeder hole of the sub-cylinder. Repeat the above action 1 ~ 2 times until the residual gas is completely exhausted, and then tighten the air bleed screw. In this way, the pumps are operated one after another until all the gas is discharged.

2. Adjust the gap between the brake shoe and the brake drum.

The gap between the brake shoe and the brake drum is too small, and the temperature of the brake drum rises, which is easy to cause braking delay, locking and other faults; The gap is too large, the brake pedal stroke is too long, the driver is inconvenient to operate, and the braking time is delayed, which affects the braking effect. The gap between the brake shoe and the brake drum should be adjusted to 0. 3 ~ 0.5 mm .. First, adjust the gap between the brake shoe and the brake drum to make them completely closed, then turn the brake adjusting nut in the loosening direction and turn 7 ~ 8 teeth along its cylindrical surface. When adjusting the brake with fixed brake shoe fulcrum, the eccentric shafts of the two brake shoe fulcrums can be toggled for many times, and the braking test is carried out during the adjustment until the braking effect is satisfactory.

3. Adjustment of asynchronous braking between main engine and trailer.

If the brakes of the main engine and trailer are not synchronized, they should be adjusted and tested at the same time. The specific adjustment method is as follows: firstly, remove the main engine brake connecting rod and adjust all parts of the trailer brake device until there are drag marks between the trailer wheels and the ground during braking, then connect the main engine brake connecting rod with the pedal transmission arm and adjust the connection length of the main engine brake connecting rod until all wheels and the ground have friction marks during braking, which is considered as qualified adjustment.

4. Repair of brake drum and brake shoe

If the brake drum is not round, it can be rounded on the lathe. If the inner diameter of the brake drum is larger than the outer diameter of the brake shoe, appropriate cloth gaskets can be added on both sides of the friction plate; If the inner diameter of the brake drum is smaller than the outer diameter of the brake shoe, the brake drum can rotate normally. No matter which method is adopted, the contact area between the brake drum and the brake shoe must reach more than 70%.

5. Adjustment of spring pressure of quick connector

When it is confirmed that the quick coupler is not installed, but the self-locking phenomenon occurs, the spring pressure of the two jacking balls must be adjusted so that the spring pressure of the front (oil supplier) jacking balls is less than that of the rear.

6. Eliminate the oil leakage of the sub-pump.

If the oil leakage is not caused by the damage of cylinder parts, it is likely that the distance between the center of cylinder positioning hole and the top of brake shoe is too small. When the distance is less than 2~4 mm, the depth of the top of the brake shoe can be cut off by 2 ~ 4 mm with a file. ..