CPCD5AⅡZ type forklift travel braking system is composed of vacuum pump, vacuum tank, vacuum booster, brake master cylinder, brake cylinder, wheel brake and brake pedal, etc. The brake type is vacuum booster, hydraulic drive, internal expansion Front brake. Common faults are as follows.
1. No brake effect when stepping on the brake pedal
Possible causes: No oil in the brake master cylinder; oil leakage in the brake system pipeline; oil leakage caused by the rupture or wear of the master cylinder; the master cylinder piston apron is damaged, swollen or worn too much; the master cylinder piston apron is installed reversely ; The oil leakage of the cylinder piston or the damage of the half shaft oil seal causes oil pollution in the brake drum, which causes the brake drum and friction lining to fail; the brake shoe friction lining wears too much, causing the rivet to be exposed or loose.
2. There is elastic resistance when stepping on the brake pedal, the braking force is insufficient
Possible reasons: there is air in the brake system; insufficient brake fluid in the master cylinder; damaged or dirty oil return valve of the supercharger; the brake fluid cannot build up enough pressure, even if the brake pedal is pressed to the end, it will not brake ; The gap between the brake drum and the friction lining is too large; the brake shoes are loose, etc.; the brake shoes are not installed properly, and the brake gap is not adjusted properly.
3. The brake pedal has rebound force and the braking effect is poor
When stepping on the brake pedal, you should listen to the "boo" sound of the vacuum supercharger for air intake. If the oil is discharged or the oil is weak, the oil path from the master pump to the vacuum booster is blocked, or the master pump is not working properly, otherwise the booster itself is faulty.
Possible cause: The pipeline is not open. You can remove the low-pressure oil pipe from the master pump to the supercharger and blow it with compressed air. If it fails to blow, the pipeline is blocked; otherwise, the master pump is not working well. The poor performance of the master pump is that the oil discharge pressure is low (standard is 3MPA, which can be measured with a pressure gauge), the master cylinder cup and apron swell; the oil outlet valve does not work well, or there is no gap between the master cylinder push rod and the piston, Block the oil return hole, so that the brake fluid cannot return to the oil storage chamber; the supercharger controls the swell of the cylinder, and the piston cannot return quickly when the brake pedal is relaxed. When the brake pedal is continuously pressed, the pedal does not return The position gradually rises, and it feels very hard when stepped on; the oil inlet of the booster control cylinder is blocked, and the atmospheric valve cannot be opened when the brake pedal is stepped on, so it does not have a boosting effect; the intake valve sealing ring swells or leaks Gas, the brake pedal position will become higher at this time, and it feels very hard when stepping on the four-wheel drag of the forklift when walking.
4. Braking delay, the brake drum becomes hot after long time walking
Possible causes: The turbocharger mechanism is stuck and the brake stroke is not adjusted properly; the brake master cylinder return hole is blocked (covered by a swollen leather cup or blocked by dirt in the brake fluid), causing the oil return to fail Smooth braking of the wheel; dirty brake fluid and slow oil return; the master cylinder swells. After the brake pedal is relaxed, the cup cannot return quickly; the control valve seal swells, causing the air valve to close The air chamber in the tympanic membrane of the power cylinder is delayed, and the tympanic membrane cannot be quickly returned. The copper tube between the brake master cylinder and the supercharger is deformed or clamped, which makes the oil return speed slow, resulting in brake drag.
5. Braking is not smooth
Possible causes: The brake drum is out of round, the gap between the brake drum and the brake shoe is abnormal; the brake shoe adjustment is abnormal.
6. Depressing the brake pedal is very laborious.
Possible causes: the sump of the master cylinder or the piston apron of the master cylinder swells; the copper tube between the master cylinder and the supercharger is deformed or pinched, making the inner hole smaller and the oil flow is not smooth; The copper tube is deformed, resulting in a smaller pore size and poor oil flow; controlling the swell of the cylinder apron; the brake fluid is deteriorated and is too viscous to make it poor in fluidity.
7. Brake deviation
Possible reasons: the braking force of the left and right wheels is not balanced, so that the forklift is biased to one side (when braking on the side, you must check which side of the brake gap or cylinder condition; when the brake is running irregularly, suddenly Left and right, if braking first to the left and then to the right, you should first check the condition of the left wheel brake, otherwise check the right wheel); or the brake shoe friction plate or brake drum is oily.
8. Oil leakage (including external leakage and internal leakage)
As long as there is an oil leak in the master cylinder, sub-cylinder, booster and pipeline, the braking efficiency will be reduced or the braking will be completely invalid.
Possible causes: The oil leakage of the master cylinder and the sub-cylinder is mostly due to the use of the leather cup and the apron for too long. The leakage is caused by wear; if the brake pedal is felt very light, it is generally the master cylinder wear. Oil leakage; poor sealing of the piston cup, apron or piston push rod apron of the supercharger booster cylinder and the control valve cup will cause oil leakage; the brake shoes are too thin or the brake gap is too large, step on hard When the brake pedal is braked, the cylinder of the cylinder is often turned to cause oil leakage.
9. Excessive brake oil consumption
Possible cause: oil leakage in the pipeline; the brake spool in the transmission shift control valve leaks into the transmission. At this time, the smell of brake oil can be heard from the transmission oil inspection hole. Check it to confirm Whether the brake oil is leaking; the sealing of the piston cup, apron or piston push rod apron of the vacuum booster booster cylinder and the control valve cup will cause excessive consumption of brake oil and open the booster afterburner air chamber The brake oil will leak out when it is serious, and it will leak into the engine oil pan through the vacuum pump lubricating oil pipe in serious cases. The engine oil is diluted or sucked into the cylinder and burned.
10. Vacuum booster failure
This kind of fault can be judged from whether the supercharger is inhaled or not and the brake oil pressure at the brake cylinder is detected.
Possible cause: The supercharger is working normally, the oil pressure at the brake cylinder should reach 11~13MPa (can be detected by a pressure gauge), if the pressure is lower than this value, the supercharger is faulty; remove the vacuum tube of the supercharger Block the pipe mouth with your hand and start the engine for a moment. If there is no suction or little suction, the vacuum tank and the vacuum tube have leaks, or the vacuum pump is not working properly. The working condition of the vacuum pump can be checked with a vacuum meter. The normal vacuum value should be -0.08-0.085MPa, below this value, the vacuum pump is faulty. After inspection, the vacuum pump, vacuum tank, and vacuum tube are normal, and the supercharger is still not working. , Located in the bottom of the car, the working environment is bad, this fault often occurs), or the air valve cannot be opened, so that the atmosphere cannot enter the afterburner.
