The so-called automatic cruise means that the driver can realize the automatic driving function of the excavator without operating the walking pedal under certain circumstances. This function comes from the constant speed cruise control of the automobile system. The difference between wheel excavator and vehicle control is that the walking of wheel excavator is a full hydraulic transmission system, so it is necessary to reform the hydraulic circuit and add corresponding control points to facilitate the control system to realize this function.
The walking pedal of wheel excavator is a pilot valve with position sensor. When the pedal moves, the controller detects the pedal displacement through the pedal displacement sensor to control the engine speed. At the same time, the secondary pressure of the travel pedal controls the travel spool of the main valve through the forward or backward solenoid valve, opens the travel main oil circuit, supplies oil to the travel motor, the motor drives the gearbox, and the gearbox drives the front and rear axles through the transmission shaft to complete the travel.
According to the hydraulic working principle of walking control, in order to realize automatic cruise, we must start from the main oil circuit or pilot oil circuit, so as to meet the requirement that the walking pedal does not operate in a specific environment, and the oil supply of the walking motor can still be realized. Due to the high pressure and large flow of the main oil circuit, it is difficult to select the device, so we can only start from the pilot oil circuit. Add a two position three-way solenoid valve on the oil circuit behind the walking pedal to meet the corresponding functions.
After adding the cruise solenoid valve, during normal travel, the pilot oil controls the travel motor through the normally energized oil passage of the cruise solenoid valve and the forward or backward solenoid valve at the rear. After the cruise solenoid valve is powered on, the pilot oil will be directly from the pilot pump to port P1 and the forward or backward solenoid valve behind it to control the travel motor. At this time, the walking pedal does not work, so the automatic cruise is realized.