Hybrid construction machine

A hybrid construction machine that performs regeneration using a working oil discharged from an actuator, comprising:

• a regenerative hydraulic motor rotated by the working oil discharged from the actuator;
• a power generator connected to the hydraulic motor;
• a control valve provided in a flow passage that connects the actuator to the hydraulic motor, an opening of which is controlled by a pilot pressure led to a pilot chamber thereof;
• and
• a solenoid pilot control valve that leads a pressure on an upstream side of the control valve to the pilot chamber of the control valve as the pilot pressure,
• wherein the control valve comprises:
• a main spool that is incorporated to be free to slide into a valve main body such that one end thereof faces the pilot chamber and switches an inflow port and an outflow port between a blocked state and a communicating state;
• and
• a biasing member that is housed in a spring chamber faced by the other end of the main spool and biases the main spool against the pilot pressure of the pilot chamber, and
• a pressure receiving area of the main spool for receiving the pilot pressure of the pilot chamber is equal to an area obtained by subtracting a pressure receiving area of the main spool for receiving a pressure of the outflow port in a direction for moving the main spool against the biasing force of the biasing member from a pressure receiving area of the main spool for receiving a pressure of the outflow port in a direction for moving the main spool against the pilot pressure of the pilot chamber.