Through the joint control of Hitachi excavator hydraulic pump and engine, a high level of power and fuel economy can be achieved. The change in engine speed causes the engine speed sensor and throttle control knob output signal to control the current to change accordingly. The hydraulic pump controller measures the output signal and sends the result to the torsion control valve (TvC valve) as a signal to control the flow of the hydraulic pump. In this way, the engine torque and the hydraulic pump drive torque can be optimally matched: the joint control function of the hydraulic pump and the engine is shown in Figure 2-33 and Figure 2-34.
1. The control function of working mode selection and power setting selection
Combination of 4-level working mode (HO: heavy-duty working mode; C.0: general: operating mode; F.0: finishing operating mode; L0: hoisting working mode) and 3-level power setting (H, S, L) Use, can realize the driving torque of the hydraulic pump according to the nature of the work, reduce the fuel consumption and use the engine more effectively: In general, the working mode is used as the basic method when used in conjunction with the power setting, and the power setting can be based on The choice of working mode depends on the specific situation: the performance comparison of different combinations of 4-level working mode and 3-level power setting is shown in Figure 2-37.
2. Power half maximum control function
When the working mode is set to (HO) or (C.0), press the power maximum switch of the joystick handle h of the working device, no matter which working mode and power setting is selected, the system will change to HO] and [H, cut off (CO) function is cancelled, and when the pressure is near the overflow pressure value, the flow rate increases, the pressure of the main relief valve increases from 32.5MPa to 34MPa, and the maximum digging power is increased to give the maximum production capacity. Even if the maximum power switch is continuously pressed, the maximum power function will be automatically canceled after 8.5s, and the system will return to the state before the switch was pressed.When the working mode switch is at (F.0 or (L0, this function will not work .
3. Automatic deceleration control function
(1) The automatic deceleration switch is in the on position.
①The throttle control knob is set at a position higher than 1500r/min. All the joysticks are in the neutral position. The hydraulic pump controller receives the neutral position signal and sends an automatic deceleration signal to the engine throttle controller. After receiving this signal, the throttle controller sends a drive signal to the governor motor.The governor motor returns the fuel injection pump speed control lever to the first deceleration position and maintains it for approximately 4s.At this time, the engine speed decreases from the knob position Around 100r/min
② After the joystick is in the neutral position for 4s, the drive signal is sent from the engine throttle controller to the governor motor again.The governor lever is pulled back from the first deceleration position and maintained at the second deceleration position.At this time, the engine speed is close to 1400/min under deceleration conditions
Operate any joystick, the hydraulic pump excavator receives this signal, and cancels the automatic deceleration signal to the engine throttle controller. At this time, the engine oil wide controller sends a drive signal to the governor motor to return the governor lever to the original set position (2) When the automatic deceleration switch is in the stopped position, the engine speed can be set to The desired value, even if all joysticks are in the neutral position, the engine speed will not reduce the engine speed reduction, reducing fuel consumption and noise.
4. Travel speed conversion control function
(1) When the travel speed switch is H (high speed), the travel speed solenoid valve is turned on, the pilot pressure oil enters the travel hydraulic motor regulator control valve, so that the motor swash plate tilt angle becomes smaller, the system is in a high-speed travel state.
(2) The speed of the engine throttle control knob is set to less than 1400r/min. When the travel speed switch travels in the Lo (low speed) position, even if the switch is switched to the H (high speed) position, the travel is still at low speed. When the switch is in the H (high speed) position, the driving speed is automatically converted to Io (low speed)
(3) The automatic conversion between H and Lo is based on the hydraulic pump outlet pressure. When the driving speed switch is driving at the Hi position, if the excavator is going uphill and the pressure of the walking hydraulic system is higher than 31MPa for more than 1s, the driving speed solenoid valve is closed (not energized) and the driving speed is switched to Lo. The excavator continues to drive at L (the driving speed switch is still at the H position).If driving on flat ground or downhill again, and the system pressure is less than 2MPa for more than 1s, the solenoid valve is opened (powered on), and the speed is switched to high speed again .
