The control system and functions of Hitachi excavator hydraulic pump controller are shown in Figure 5-2 and Figure 5-3. According to the stroke of the joystick, the displacement of the hydraulic pump is controlled to reduce the neutral loss and fine control loss. The half-flow mode of the stick that is automatically set in the working mode provides a fine control function. Cut-off function, cut-off function cancellation and 2-level overflow function together provide a guarantee for reducing overflow loss and increasing excavation power.
1. Flow control function
When the joystick is in the neutral position, the electric signal is sent to the hydraulic pump controller through the oil pressure switch of the pilot control valve. After processing, the microcomputer in the controller sends the driving signal to the hydraulic pump system to make the hydraulic pump displacement Control to the minimum, reduce the power loss when the control valve is in the neutral position. When the joystick is pulled, the oil pressure switch sends the electric signal of the corresponding flow command to the hydraulic pump controller according to the stroke of the joystick, and the microcomputer in the controller processes the corresponding drive signal to the hydraulic pump system to obtain the corresponding Hydraulic pump displacement, fine control performance is improved and power loss is reduced.
2. Cut-off (CO) function
When the load increases during work, the outlet pressure of the hydraulic pump rises. When the pressure is close to the overflow pressure, the oil pressure sensor at the outlet sends a corresponding electrical signal to the controller. After processing by the microcomputer in the controller, the corresponding drive signal is sent to the hydraulic pump system, and the cut-off (CO) valve performs the cut-off function to reduce the displacement of the hydraulic pump and reduce the overflow loss.
3. Cut-off (CO) cancellation function
The opening or canceling of the cut-off function is automatically determined by the maximum power switch, the walking joystick and the rotary lock switch or one of the three switches. When the maximum power switch is in the on position (the work mode switch must be in [HO] or [GO]), the walking lever is in the operating position, and the rotary lock switch is in the on position, their signal current is sent to the hydraulic pump controller After processing by the microcomputer, the corresponding drive signal is sent to the hydraulic pump system, the cut-off (CO) cancels the solenoid valve energization, and the cut-off function is cancelled. Even if the load increases during work and the outlet pressure of the hydraulic pump rises and approaches the overflow pressure, the displacement of the hydraulic pump will not decrease. This not only guarantees the flow rate, but also prevents speed reduction.
Four, stick half flow control function
When the work mode switch is at [F.0] or [L.0], the work mode switch on the monitor panel will send an electrical signal to the hydraulic pump controller. The processed drive signal is sent to the arm half-flow solenoid valve to stop the operation of the "arm-high speed" operating valve of the four-way reversing valve in the main operating valve. At this time, the arm cylinder only supplies oil with a single pump, which improves Precision control and finishing operations. This action is limited to the simultaneous action of the boom and the stick. When the stick is extended and the bucket is operated at the same time, the half-flow control function does not work.
Five, 2-level overflow control function
When the maximum power switch is pushed to the open position (only when the working mode switch is in [HO] or [GO], or the walking joystick is in the operating position, or the rotary lock switch is in the open position, their electrical signals are sent to the hydraulic Pump controller. The processed drive signal is input into a 2-stage overflow. CO cancels the solenoid valve. At this time, the solenoid valve opens, the cut-off function is cancelled, and the pilot pressure oil from the pilot pump flows into the main overflow valve, increasing its overflow pressure to 32.5MPa 34MPa, increase digging power and walking force.
6. Control function when TVC standby switch is on
If the controller or sensor is abnormal, the direct current flows from the battery to the torque control valve. At this time, the displacement of the hydraulic pump is controlled according to the pressure at the outlet of the hydraulic pump. Use this function to control the drive torque of the hydraulic pump.
Seven, rotation and rotation brake control function
When the rotary lock switch is in the OFF position, the rotary brake acts for nearly 4 seconds after the rotary joystick is placed in the neutral position. When the swing lever is operated, the swing brake is released and the turntable can rotate freely.
When the swing lock switch is in the ON position, the turntable is braked by the swing brake. Even if the joystick is operated, the swing brake will not be eliminated, so the turntable cannot be rotated to prevent hydraulic drift after stopping the rotation.
When the hydraulic pump controller is abnormal and the swing brake function is abnormal, the swing lock backup switch cancels the swing brake and performs a swing operation. Table 5-2 shows the rotation lock backup switch, the rotation lock switch and the rotation brake operation table.
Table 5-2 Rotary lock switch and rotary brake operation table
Rotary locking backup switch ON (when the controller is abnormal) OFF (when the controller is normal)
Rotary lock switch ON OFF ON OFF
Swing brake Brake release Brake release When the swing lock switch is turned to the ON position, the cut-off (CO) function is cancelled. In this case, if the hydraulic system of the working device is in an overflow state, the temperature of the hydraulic oil rises rapidly to reduce the warm-up time.
