Operation Control Circuit for Construction Machine

An operation control circuit for a construction machine, comprising:

• a pilot hydraulic fluid pressure source which is driven by an engine, and which supplies a pilot pressure hydraulic fluid to a pilot conduit at a flow rate which corresponds to an engine rotational speed;
• an operation valve which is connected to said pilot hydraulic fluid pressure source via said pilot conduit, and which controls an operation of a control valve for controlling a flow rate of working hydraulic fluid supplied from a main hydraulic fluid pressure source to an actuator by supplying the pilot pressure hydraulic fluid from said pilot hydraulic fluid pressure source to said control valve;
• a pressure adjustment valve which is provided partway along said pilot conduit, and which adjusts the pressure in said pilot conduit to a predetermined pressure;
• and
• a throttle section which is provided to connect between partway along said pilot conduit and a tank;
• wherein, when the engine rotational speed of said engine has become less than or equal to a first engine rotational speed, a pressure difference before and after said throttle section is set so that its value becomes lower than said predetermined pressure.