The travel speed selection valve is shown in Figure 5-35. The variable servo piston 1 is connected to the valve disc 6 through the connecting rod 5, so when the servo piston 1 is moved, the inclination angle of the cylinder 7 is changed by the valve disc 6, resulting in a change in the displacement of the hydraulic motor, and finally the walking speed Variety. .
When the low-speed or medium-speed walking mode is selected, the pump valve controller (PVC) does not send an electronic control signal to the walking (high-speed-low speed) solenoid valve. Therefore, the pilot pressure oil that changes the speed cannot flow from the port SH to the variable servo The piston 1, so that the spool 3 is held downward by the spring 2, so that the pressure oil P from the motor oil port flows into the oil chambers B and C.
Since the area of the oil chamber C receiving pressure oil is larger than that of the oil chamber B, the variable servo piston 1 moves upward to increase the inclination of the swash plate to the maximum. At this time, the stroke of the motor plunger increases, that is, the displacement of the walking motor increases, and the walking The motor rotates at a low speed,
has thus achieved low and medium speed walking. In the low-speed walking mode, the flow rate of the hydraulic pump is reduced by about 40%. Therefore,
Excavator walking hydraulic motor runs at low speed.
When you need to choose high-speed walking mode at light load, the pump valve controller (PVC) sends an electronic control signal to the walking (high-speed to low-speed) solenoid valve, so the pilot pressure oil that changes speed flows from the oil port SH into the oil chamber C. Move the spool 3 upward. Then, the pressure oil in the oil chamber C is discharged through the inner passage of the valve core 3. Since the pressure oil P from the motor oil port flows into the oil chamber B, the servo piston 1 moves downward, reducing the inclination angle of the cylinder 7, the stroke of the motor plunger is reduced, and the traveling motor rotates at a higher speed, achieving high speed Walking way.
When the walking load is large, PVC stops sending control signals to the proportional solenoid valve, so the inclination angle of the cylinder increases and the walking speed is reduced to reduce the walking load.
