Fluid pressure pump motor

1. A fluid pressure pump motor comprising:

a fluid pressure pump that is configured to supply a hydraulic fluid to a fluid pressure actuator;

a fluid pressure motor that is configured to be rotationally driven by the hydraulic fluid reflowing from the fluid pressure actuator;

a supply/discharge passage where both a hydraulic fluid pumped in to the fluid pressure pump and a hydraulic fluid discharged from the fluid pressure motor flow; and

a variable valve provided in the supply/discharge passage and capable of controlling a fluid path area of the supply/discharge passage,

wherein the variable valve reduces the fluid path area of the supply/discharge passage for simultaneously actuating the fluid pressure pump and the fluid pressure motor to be smaller than the fluid path area for actuating only one of the fluid pressure pump and the fluid pressure motor.

2. The fluid pressure pump motor according to claim 1 , further comprising an electric motor that is configured to generate regenerative electric power by rotating the fluid pressure motor and rotationally drive the fluid pressure pump using regenerative electric power.

3. The fluid pressure pump motor according to claim 1 , wherein the fluid pressure pump is a variable capacity pump, and

the variable valve is configured to control the fluid path area of the supply/discharge passage depending on a pump-in capacity of the fluid pressure pump.

4. The fluid pressure pump motor according to claim 1 , wherein the fluid pressure pump is a fixed capacity pump, and

the variable valve is configured to control the fluid path area of the supply/discharge passage depending on a rotational number of the fluid pressure pump.

5. The fluid pressure pump motor according to claim 1 , wherein the fluid pressure pump motor is applied to a hybrid type construction machine in which the fluid pressure actuator is driven by a hydraulic fluid pumped out from a main fluid pressure pump driven by a motor,

the fluid pressure motor is configured to be rotationally driven by a hydraulic fluid discharged from the fluid pressure actuator, and

the fluid pressure pump is configured to assist the main fluid pressure pump to drive the fluid pressure actuator using the pumped-out hydraulic fluid.

6. The fluid pressure pump motor according to claim 1 , wherein the variable valve is a rotary valve which is buried in a wall surface of the supply/discharge passage to maximize the fluid path area of the supply/discharge passage, and

the variable valve protrudes toward an inner side of the supply/discharge passage and reduce the fluid path area of the supply/discharge passage as the variable valve is pivoted with respect to a rotational shaft.

7. The fluid pressure pump motor according to claim 1 , wherein the variable valve is a gate valve having:

a gate buried in a wall surface of the supply/discharge passage to maximize the fluid path area of the supply/discharge passage and movable along a radial direction of the supply/discharge passage, and

a shaft screwed to the gate to advance or retreat the gate with respect to the supply/discharge passage as the shaft is rotated.

8. The fluid pressure pump motor according to claim 1 , wherein the variable valve is a butterfly valve provided in the supply/discharge passage and pivoted with respect to a valve stem to control the fluid path area of the supply/discharge passage.

9. The fluid pressure pump motor according to claim 1 , wherein the variable valve is a spool valve having:

a spool buried in a wall surface of the supply/discharge passage to maximize the fluid path area of the supply/discharge passage and movable along a radial direction of the supply/discharge passage;

a back pressure chamber that biases the spool toward an inner side of the supply/discharge passage by virtue of the supplied hydraulic oil; and

a return spring that biases the spool toward the back pressure chamber.