Construction Machine

Abstract

A construction machine is provided which is capable of detecting an operation state of an operation device even if the idle rotation speed for a prime mover is set to a low value and is capable of setting the idle rotation speed for the prime mover to a low value. A hydraulic excavator includes an operation device that generates a pilot pressure corresponding to an operation amount of an operation lever and switches a control valve with the generated pilot valve, and a controller that controls an electric motor such that the rotation speed of the electric motor becomes an idle rotation speed set in advance when a no-operation state of the operation device continues. The hydraulic excavator further includes a hydraulic pressure signal line that is connected between the discharge side of a pilot pump and a tank and in which the control valve is interposed, a fixed restrictor provided between the discharge side of the pilot pump and the control valve in the hydraulic pressure signal line, and pressure sensors that individually detect the hydraulic pressures on the upstream side and the downstream side of the fixed restrictor. The controller detects an operation state of the operation device on the basis of results of detection of the pressure sensors.

1 . A construction machine that includes a prime mover, a hydraulic pump driven by the prime mover, a hydraulic actuator, a control valve that controls flow of hydraulic fluid from the hydraulic pump to the hydraulic actuator, an operation device that generates a pilot pressure corresponding to an operation amount of an operation lever and switches the control valve with the generated pilot pressure, and a controller that controls, when a no-operation state of the operation device continues, a rotation speed of the prime mover to an idle rotation speed set in advance, the construction machine comprising:
 a pilot pump that is driven by the prime mover and whose discharge pressure is used as a source pressure of the pilot pressure;   a pilot relief valve provided on a discharge side of the pilot pump;   a hydraulic pressure signal line that is connected between the discharge side of the pilot pump and a tank and in which the control valve is interposed such that the hydraulic pressure signal line is interrupted when the control valve is switched from a neutral position;   a fixed restrictor provided between the discharge side of the pilot pump and the control valve in the hydraulic pressure signal line;   a first pressure sensor that detects a hydraulic pressure on an upstream side of the fixed restrictor; and   a second pressure sensor that detects a hydraulic pressure on a downstream side of the fixed restrictor, wherein   the controller is configured to detect an operation state of the operation device based on results of detection of the first pressure sensor and the second pressure sensor.   
     
     
         2 . The construction machine according to  claim 1 , wherein
 the controller is configured to detect an operation state of the operation device based on a differential pressure between the hydraulic pressure detected by the first pressure sensor and the hydraulic pressure detected by the second pressure sensor.   
     
     
         3 . The construction machine according to  claim 1 , wherein
 the prime mover is an electric motor.