Basic function
The pilot valve controls the stroke, direction and main control valve of the spool. The basic function of the pilot valve is supplied to the main control valve valve core to the main control valve valve core through the basic function of the primary valve, the base function of the primary valve, and supplies the output pressure (secondary pressure) of the pilot valve to the main control valve valve.
In order to make this function correctly, the pilot valve has the following functions.
1 The oil port P supplies oil from the hydraulic pump.
2 Exhaust port The pressure of the oil port is sent to the end of the control valve space 3 3 The oil tank oil port T controls the output pressure described above.
4 spool connection of the oil port to the oil port or fuel tank oil port 5 lead valve control output pressure, including a spring acting on the spool
2. Main components
The function of the modern excavator function spool is the oil pressure supplied by the hydraulic pump in the oil port P, and the conversion oil path is to determine if the oil pressure of the oil port P can output to the port, or the spool output can determine the pressure output.
A spring acting on the spool to determine the output pressure.
The spring deviation changes, the push rod is inserted and slides in the plug.
The displacement of the push rod is changed by the cam and the adjustment nut, and the displacement is controlled by the pedal, and the pedal can be tilted in any direction to any direction.
The spring acts on the valve housing and the spring seat and as much as possible to return the push rod to the zero-emission position to ensure that it is reset to the intermediate position.
The operator feels the correct sense of control through the spring reaction.
3. Operation
(1) The force of the pedal in the intermediate position spring determines that the output pressure of the pilot valve is not applied to the spool. Therefore, the spool is pushed to the position of the oil port. Because the output oil port is only connected to the tank oil port T, the output oil port pressure and the fuel tank pressure becomes equal
(2) Pedal in tilt position
When the push rod is pushed down, the spool moves down, then the oil port P is connected to the oil port, and the oil flow supplied from the pump produces oil pressure.
When the pressure of the oil port is equal to equal to the spring force set by the inclined pedal, the pressure is balanced with the spring force. If the pressure of the oil port is increased above the set pressure, the oil port P is disconnected from the oil port, while the port T is connected to the oil port. If the pressure of the oil port is reduced
Small to the set pressure, the oil port P is connected to the oil port, and the port T is disconnected from the oil port.
In this way, the secondary pressure always maintains a stable value. Moreover, the pedal tilt exceeds an angle, and the upper end of the spool is inserted into the bottom of the push rod, and the output pressure is connected to the oil port P.
