The function of the accumulator is to provide sufficient oil pressure to the brake when the engine suddenly stops, the brake pump fails or the output oil pressure is insufficient, so that the forklift driver can brake and stop in an emergency. Taking a certain type of internal combustion forklift as an example, this paper expounds the working principle and troubleshooting method of energy accumulator alarm device.
1. Working principle
The structure of the accumulator alarm device is shown in the attached figure, which is mainly composed of one-way valve 1, oil chamber 2, energy storage spring 3, low-pressure alarm switch 4 and safety valve 5.
Principle of accumulator alarm device
The pressure oil output by the brake pump enters the oil chamber 2 through the check valve 1 and compresses the energy storage spring 3, so as to convert the pressure energy of the oil into the potential energy compressed by the energy storage spring 3. The function of check valve 1 is to prevent the oil from flowing back from the inlet of pressure oil.
The low pressure alarm switch 4 is a diaphragm normally closed switch. When the oil pressure in oil chamber 2 is higher than 3.9Mpa, the low pressure alarm switch will be disconnected and the alarm circuit will be cut off to stop the alarm.
In order to limit the pressure value of the accumulator within the safe range, the system is equipped with safety valve 5. When the oil pressure in oil chamber 2 exceeds the set value (13Mpa) of safety valve 5, safety valve 5 is unloaded and the discharged oil flows back to oil tank 6.
When the forklift driver depresses the brake pedal, if the brake supply oil pressure is too low, the energy storage spring 3 releases the compression potential energy and hydraulically flows the oil in the oil chamber 2 into the brake valve to provide the required oil pressure for braking.
When the forklift equipped with energy accumulator is started, the alarm is usually in the alarm state. The reason is that the oil pressure in oil chamber 2 is too low when the forklift is just started. At this time, the forklift driver should press the brake pedal to the bottom 3 ~ 5 times with his foot when the engine is started and the forklift is stopped, so as to close the brake valve. After the brake valve is closed, the oil pressure in oil chamber 2 increases, and the alarm can be automatically released.
2. Troubleshooting methods
There are usually two kinds of failure of accumulator alarm device: one is that the alarm signal of the alarm does not release, and the other is that there is no alarm all the time.
(1) The alarm signal is not released
The fault shows that after the forklift is started, press the brake pedal to the bottom with your foot for 3 ~ 5 times in the parking state, and the alarm will not be released all the time. The reasons may be the blockage of check valve, oil leakage of system, low pressure of safety valve or failure of alarm. The troubleshooting methods are as follows:
First, connect an oil pressure gauge with a measuring range of 20MPa at the outlet of pressure oil to observe the change of accumulator oil pressure.
Secondly, check whether the check valve is blocked. If the pointer of the oil pressure gauge does not change after pressing the brake pedal to the bottom for 3 ~ 5 times, it indicates that the check valve is blocked by dirt and the oil cannot enter the oil chamber. The check valve needs to be cleaned. If it is still blocked after cleaning, replace it.
Again, check the system for leaks. If the pointer of the oil pressure gauge changes slowly and does not reach 3.9Mpa after the brake pedal is pressed for 3 ~ 5 times, it may be caused by oil leakage from the accumulator housing or safety valve. It is necessary to find the oil leakage point and replace the damaged parts.
Then, check the set pressure of the safety valve. After stepping on the brake pedal for 3 ~ 5 times, if the oil pressure increases rapidly, but the pointer suddenly stops before reaching the specified pressure value (13Mpa), it indicates that the unloading pressure of the safety valve is low, that is, the safety valve has begun to drain oil before the accumulator reaches this value. At this time, it needs to be cleaned, and then its unloading pressure should be adjusted again.
Finally, check the low-voltage alarm switch. If the pressure reaches 13Mpa and still does not alarm, it indicates that the low-pressure alarm switch is damaged and needs to be replaced.
(2) The alarm has no alarm
The fault shows that after the forklift is parked for a long time, the alarm does not alarm when starting the engine for many times. The reason may be the failure of low-voltage alarm switch, alarm or related circuits. The troubleshooting methods are as follows:
First, connect an oil pressure gauge with a measuring range of 20MPa at the outlet of pressure oil, and then connect an oil drain switch. Turn on the oil drain switch and gradually release the oil in the accumulator so that the pressure value displayed on the pressure gauge is slightly lower than 3.9Mpa.
Secondly, check whether the low-voltage alarm switch is damaged. If the alarm gives an alarm after starting the engine, it indicates that the low-pressure alarm switch and alarm are in good condition, and the pressure maintaining performance of the accumulator and brake valve is in good condition. If the alarm does not give an alarm, replace the low-voltage alarm switch and check it again. If the alarm can be given after replacing the low-voltage alarm switch, it indicates that the low-voltage alarm switch is damaged. If the replaced low-voltage alarm switch still has no alarm, it indicates that the alarm circuit or alarm is faulty.
Finally, check the alarm circuit and alarm failure. Use a test lamp or a multimeter to check whether the alarm is powered on. If it is powered on, it can be determined that the alarm is faulty and should be repaired or replaced. If there is no electricity, the alarm circuit is open circuit, and the open circuit position shall be found section by section.
