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Excavator speed control system, how it appears difficult to start and turn off abnormal

A  Kobelco  excavator , difficulty in starting and stalling appear abnormal and other issues. Failure, its symptoms are: When the ignition key is in the ON position, the motor speed control lever back and forth constantly , and issued a ” whining ” sound ( this time, even the key to the start position ST , the engine can not be start ) , about 1min after the swing stops ; when the ignition key to the ST position when the engine starts, but does not turn off, turn the ignition key to turn off only the position OFF, and then let the working device moves about, then the ignition key to ON position , the engine can stall , but the center but still can not turn off the computer . Meanwhile, the engine is started , the excavator working device feedback signal can not speed motor ( engine speed ) control , which has always been at idling speed motors , resulting in a variety of actions excavator slow . Finally find out the speed control system is the ” grounding line ” virtual access caused.

The excavator is equipped with engine speed motors , excavators start, turn off the speed control and jobs are related with speed motors . All aircraft control systems installed in the cab by computer control .

Under normal circumstances, when the ignition key is in the ON position, the motor speed control lever will quickly swing to the pre-start position , then stop. When the ignition key to the ST position, the engine starts. As long as the ignition key to the OFF position , the engine stalled, stopped , about 4s after the computer is turned off .

After starting the engine speed with the working parts of the machine operation and improved, but also the speed and the machine switches on . Machine speed control switch into low and high speed two gear. When the switch is in a low speed position, even if the machine walking, turning or operating such action , the engine speed will not increase too obvious ; when the speed switch is in the high position , a working parts of the machine operation, the engine speed will significantly improved ; and when the work equipment does not operate , regardless of the speed control switch in a low speed or high-speed gear , the engine idle condition . These conditions are achieved through the computer .

Referring to the circuit with the fault -related control charts ( see photo ) , we learned that the aircraft’s ignition key has five locations , including warm-up position and the ACC position and the failure does not matter. According speed motor control lever constantly swing and lose speed control situation , initially believed to be from the computer to speed motors or motor speed control circuit malfunction. Therefore, the first measure of the control circuit , the results are current output ( because they do not know the current value is the number of standard , can not determine whether it is normal ) .

Ultimately, we disconnect each connected to the computer 5 plugs. When unplug and plug connection speed motor , excavator except there is no speed control and the engine does not stall , the start normally. So you can determine the speed control system is a problem , eliminating the possibility of starting a system failure . Speed ​​control circuit through a careful examination , and finally found speed motor connected with ” grounding line” circuit occurs , reconnect after excavator working back to normal.

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