Patent ID: 7591214

Claim:
A driving motor controlling device of a construction machine, comprising: a driving motor which is connected to a pump and a tank through a swivel joint; and a motor control valve which switches a state for connecting the pump and the tank to the driving motor such that the driving motor is controlled to a stop state, a normal rotation state, or a reverse rotation state; wherein the motor control valve has a neutral position for the stop state, a normal rotation position for the normal rotation state, and a reverse rotation position for the reverse rotation state, and is switched to the neutral position, the normal rotation position, or the reverse rotation position, based on a command from a control device manipulated by a operator and a pressure of an inflow side of hydraulic oil into the driving motor; wherein the driving motor controlling device further comprises: a remote control valve which is the control device for generating a pilot pressure; a first pilot chamber which is provided in the motor control valve and on which the pilot pressure for switching and operating the motor control valve acts; a pilot pressure control valve which switches a connection state between the remote control valve and the first pilot chamber and has a discharge position for connecting the first pilot chamber to the tank and a feed position for connecting the remote control valve to the first pilot chamber; a spring which is disposed at one side of the pilot pressure control valve to bias the pilot pressure control valve toward the discharge position; a second pilot chamber which is disposed at the other side of the pilot pressure control valve and on which the pressure of the inflow side acts such that the pilot pressure control valve is biased toward the feed position; and a starting passage which connects the remote control valve to the first pilot chamber through the motor control valve, and wherein the remote control valve is connected to the first pilot chamber though the starting passage until the pilot pressure control valve is switched to the feed position, and the starting passage is blocked by the motor control valve when the pilot pressure control valve is switched to the feed position.