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1.故障现象我公司1台zE230E型液压挖掘机,司机将该机油门旋钮旋至Ⅳ挡及以上挡位,并将操纵手柄或行走踏板回到中位3s后,发动机转速不能自动回到怠速状态,依旧保持在设定挡位的转速,即自动怠速功能失效。但油门旋钮Ⅲ挡及以下挡位,自动怠速功能正常。2.自动怠速控制原理该挖掘机设有自动怠速功能,其控制原理如图1所示。自动怠速信号油由先导泵输出,从P_s口进入主控阀,经过所有主控阀阀芯(串联连接)。当工作装置及行走装置没有动作时,信号油从D_(r2)口回油箱,此时主控阀P_x口和P_y口压力低于0.5MPa,安装在P_x口的工作装置压力开关和P_y口、行走装置压力开关断开。
1. Symptom My company a zE230E hydraulic excavator, the driver of the throttle knob to the gear and Ⅳ gear shift above, and the joystick or walking pedal back to the median 3s, the engine speed can not automatically return to idle speed State, still remain in the set gear speed, automatic idle function failure. However, the throttle knob III gear and the following gear, automatic idle function is normal. 2. Automatic idle speed control principle The excavator with automatic idle function, the control principle shown in Figure 1. Automatic idle signal oil from the pilot pump output from the P_s port into the main control valve, after all the main control valve spool (series connection). When the working device and the traveling device do not move, the signal oil is returned from the D_ (r2) port to the fuel tank. At this time, the pressure of the pilot valve P_x port and P_y port is lower than 0.5MPa, and the pressure switch and the P_y port of the working device installed on the P_x port, Travel device pressure switch off.