A yc35-6 machine, a: operates the stick. After the pilot valve handle is reset, the stick continues to operate for a certain distance. b: Or the stick automatically moves to the end after the machine is started.
Analysis: when the operation is stopped and the pilot valve handle is in the middle position, the reversing valve core should also be in the middle position (at this time, the pilot oil ports at both ends of the valve core are connected with the oil tank). If the valve core is offset from the middle position, the oil cylinder will act. Obviously, the above fault is caused by the stick reversing valve core unable to return to the middle position (or not reset in time).
Failure of the reversing valve element to return to the neutral position will cause the above B fault.
If the reversing valve element is not reset in time, the above a fault will be caused.
(d) the failure of the reversing valve element to return to the neutral position is affected by the following three aspects:
1) The valve element is stuck. Pollutants and iron filings jam the valve element.
2) When the operation is stopped, the pilot pressure oil at the first end of the reversing valve element is not drained. This is mostly due to the blockage of the damping hole of the pilot unidirectional throttle valve element at the pilot oil port at one end of the reversing valve element.
3) After startup, the pilot pressure oil at the end of the reversing valve element is automatically connected. This is because the pilot spool is stuck open., To judge whether the reversing valve core is stuck, the pilot pressure oil at the - end of the reversing valve core is not drained, or the pilot valve is faulty, the left control box can be lifted before starting up. If the fault is eliminated, the pilot valve core is stuck; Otherwise, the reversing valve element is stuck or the pilot pressure oil at one end of the reversing valve element is not drained.
(the reversing valve element is not reset in time due to the following two aspects:
1) The pilot pressure oil at one end of the reversing valve element releases slowly. It may be that the damping hole of the pilot unidirectional throttle valve element at the pilot oil port of the reversing valve element end is blocked; It may be that the stick pilot spool resets slowly.
First, check whether the pilot oil ports at both ends of the stick change-over valve are equipped with pilot one-way throttle valves. If yes, remove the one-way throttle valves for cleaning, unblock the damping holes or cancel the throttle valve core. If the fault still exists or the pilot one-way throttle valve is not installed, replace the two pilot hoses of the adjacent swing change-over valve and the stick change-over valve. If the stick action fault is eliminated, it indicates that there is a problem with the stick pilot valve, If the fault still exists, it means that the pilot control is OK, and the rest is that there is a problem with the stick reversing valve element.
2) Movement resistance of reversing valve spool and spring return force.
Remove the stick reversing valve core, and check whether the valve core can slide freely and whether the valve core return spring is broken (if the spring is broken, the connection between the valve core and the spring seat is loose).
