What is the structure and working principle of TVC valve of Komatsu excavator?
TVC valve is controlled by balancing the spring force after the oil discharge pressure PP1 and PP2 of the main pump and the output pressure PC2 of TVC valve.
When the load of the main pump is small (when the change-over switch is turned on in L state), due to the low oil discharge pressure PP1 and PP2 of the main pump. Therefore, spool 2 is pushed to the lower end by spring 1. As a result, the discharge pressure PC of the control pump becomes the same as the output pressure pT2 of the TVC valve. At this time, the output pressure pT2 of TVC valve becomes the maximum, and the servo valve increases the inclination angle of plunger pump and the flow is also the maximum.
When the load of the main pump is large (when the change-over switch is turned on in the s state), due to the increase of the oil discharge pressure of the main pump PP1 and PP2, the piston is pushed outward, and the slide valve 2 moves upward. Because the oil in the cut holes a and B on the slide valve is throttled, the openings of hole B and C (discharge hole) become larger. Therefore, at this time, the output pressure pT2 of TVC valve decreases, and the servo valve reduces the inclination angle of plunger pump and the flow.
When the change-over switch is turned on in the L state, the solenoid valve 7 is powered on, and the shaft 6 pushes the piston 5 upward to improve the effect of spring 1.
When the solenoid valve circuit on TVC valve fails, the machine will lose the function of fine adjustment and have no automatic function during operation. When the solenoid valve circuit fails, what will affect the work of the excavator. 7. How does the electronic control olss automatic deceleration system work?
When the control lever of the operating mechanism is in the middle position, it can automatically reduce the engine speed. When the operating mechanism starts to work, that is, when the control lever is pulled to the working position, the engine speed can be automatically accelerated to the speed of the original throttle working position without moving the throttle handle.
Turn the automatic deceleration switch to on. When the operating mechanism and the connecting rod of the traveling mechanism are not moved (in the middle position), a signal is sent from the microcomputer of the control box to start the solenoid valve, the hydraulic cylinder extends, and the engine speed will be reduced to 1150r / min after 4S. At this time, the position of the throttle handle remains unchanged. If the operating mechanism starts to work, the solenoid valve will be closed immediately, the hydraulic lever and governor lever will automatically reset to the original handle position, and the speed will automatically return to the original speed.
Understand the working principle of TVC valve of Komatsu excavator, and better inspect and repair Komatsu excavator after failure
