A Cat excavator suddenly moves slowly during operation. Check the monitoring item records on the excavator instrument panel on site
When viewing the service manual, the historical fault code displays "69:581-06" " , indicating that the current of the proportional reducing valve of the power shift pressure of the pump controller is higher than the normal value. It is suspected that the proportional reducing valve is short circuited to the ground. The voltage of the connecting terminal of the proportional reducing valve is actually measured, and there is no obvious fault in the circuit. After searching, it is found that the circuit of the proportional reducing valve, and the clip of the harness is fixed at the bottom next to the hydraulic pump. Due to long-time action friction and high temperature, it is in the braid The short circuit caused by serious aging and melting of the partial line shall be handled again, and the binding fault shall be solved.
Summary: the Carter proportional reducing solenoid valve converts the electrical signal of the controller into the hydraulic signal of the hydraulic oil pump. The hydraulic signal (power shift pressure) is used to adjust the output of the hydraulic oil pump. The controller changes the current (PWM signal) to the solenoid coil , the solenoid adjusts the power shift pressure. The controller changes the current to the solenoid according to the selected power mode and engine speed.
The computer controller of Carter excavator will adjust the current of the solenoid coil driving the proportional reducing valve according to the position of the engine speed knob, the actual speed of the engine, the delivery pressure of the pump and the pressure of the power shift circuit. The machine will speed up the operation speed when it is light, slow down the operation speed when it is heavy load and increase the working force. This is the principle of proportional control of excavator, so When repairing Carter excavator, attention should be paid to the coordinated operation of electric control and hydraulic control. In order to better repair and maintain the excavator, it is recommended to hand it over to professional maintenance personnel to maximize the capacity of the excavator.
