In general, construction machines, such as hydraulic excavators, incorporate a speed input device (e.g. an engine control dial) that is used to direct speed of an engine (diesel engine). An operator operates the speed input device to thereby set a target speed for the engine. In such a construction machine, control (auto idle control) is performed so as to set the engine speed to a value (idle speed) smaller than the speed directed by the speed input device when a predetermined period of time elapses after all of operating devices (control levers) that direct operation of a hydraulic actuator (a driven member) are held in neutral positions. Reduction in fuel consumption (hereinafter may be referred to as fuel efficiency) or noise, for example, is thereby achieved.
A known technique relating to the construction machine that performs the auto idle control is intended to prevent, for example, black smoke from occurring or fuel efficiency from being reduced. Such a problem arises from a difference in response between the engine speed and a capacity of a hydraulic pump (a tilting angle) involved when the two are to be increased (see, for example, Patent Document 1). To achieve the foregoing object, the abovementioned technique makes small the engine speed and the capacity of the hydraulic pump during the auto idle control and, when the auto idle state is thereafter restored to a normal operating state, brings back the engine speed and, after the lapse of a predetermined period of time, brings back the capacity of the hydraulic pump.
USPTO Backgrounds
USPTO Backgrounds