What is the structure and working principle of TVC valve of Komatsu excavator?
The TVC valve is controlled by balancing the spring force of the spring after the discharge pressures Pp1, Pp2 of the main pump and the output pressure Pc2 of the TVC valve.
When the load of the main pump is small (when the changeover switch is turned on in the L state), the discharge pressures Pp1 and Pp2 of the main pump are low. Therefore, the slide valve 2 is pushed to the lower end by the 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 the TVC valve becomes maximum, the servo valve makes the plunger pump tilt angle larger, and the flow rate is also maximum.
When the main pump load is large (when the switch is turned on in the S state), due to the increase in the main pump discharge pressures Pp1 and Pp2, the piston is pushed outside and the spool 2 moves upward, due to the cutouts a and b The oil is throttled, and the openings of holes b and c (drain holes) become larger. Therefore, at this time, the output pressure Pt2 of the TVC valve drops, the servo valve makes the plunger pump tilt angle smaller, and the flow rate also becomes smaller accordingly.
When the change-over switch is turned on in the L state, the solenoid valve 7 is turned on, and the shaft 6 pushes the piston 5 upward to achieve the effect of improving the spring 1.
When the solenoid valve circuit on the TVC valve fails, the machine will lose the fine-tuning effect during operation, and there is no automatic function. When the solenoid valve line fails, the excavator's work will be affected. 7. How does the electronically controlled OLSS automatic deceleration system work?
When the operating mechanism joystick is in the middle position, it can automatically reduce the engine speed, and when the operating mechanism starts working, that is, when the joystick is moved to the working position, the engine speed can be automatically accelerated to the working position of the crude oil door without moving the throttle handle. Speed.
Turn the automatic deceleration switch to ON. When the operating mechanism and walking mechanism linkage are not moved (in the middle position), a signal is sent from the control box microcomputer to start the solenoid valve, the hydraulic cylinder is extended, and the engine speed will be reduced to 4s after 4s. At 1150r / min, the position of the throttle handle remains unchanged. If the operating mechanism starts to work, the solenoid valve is immediately closed, the hydraulic lever and the governor lever are automatically reset to the original handle position, and the speed is automatically restored to the original speed.
