Hydraulic fluid supply device and electric actuator

1. A hydraulic fluid supply device, comprising:

an adjustable-speed motor;

a variable-volume pump which is driven by the adjustable-speed motor and ejects hydraulic fluid;

an electric motor control unit which controls the adjustable-speed motor so as to achieve an intended rotation speed; and

a pump control unit which controls the variable-volume pump so that an ejection volume of the variable-volume pump decreases with an increase in an ejection pressure of the variable-volume pump,

wherein the pump control unit includes:

an operation member that is moved by a pressure of hydraulic fluid ejected from the variable-volume pump, and that increases/decreases the ejection volume of the variable-volume pump;

an elastic member that biases the operation member in a direction against the pressure of hydraulic fluid acting on the operation member; and

a pressure control unit provided between the variable-volume pump and the operation member,

wherein the pressure control unit is switched to a first switch position so as to block a connection to a passage communicating the variable-volume pump with the operation member, or a second switch position so as to communicate the variable-volume pump with the operation member, and

wherein the pressure control unit is held in the first switch position when the ejection pressure of the variable-volume pump is lower than the predetermined pressure and switched to the second switch position when the ejection pressure of the variable-volume pump reaches the predetermined pressure.

2. The hydraulic fluid supply device, according to claim 1 , wherein the pump control unit controls the variable-volume pump so that the ejection volume of the variable-volume pump decreases proportionally to an increase in the ejection pressure of the variable-volume pump.

3. An electric actuator, comprising:

a hydraulic fluid supply device as defined in claim 2 ; and

an actuator actuated in response to input of hydraulic fluid from the variable-volume pump.

4. An electric actuator, comprising:

a hydraulic fluid supply device as defined in claim 1 ; and

an actuator actuated in response to input of hydraulic fluid from the variable-volume pump.

5. The electric actuator according to claim 4 , for driving a rudder face of a wing of an airplane.

6. A hydraulic fluid supply device, comprising:

an adjustable-speed motor;

a variable-volume pump which is driven by the adjustable-speed motor and ejects hydraulic fluid;

an electric motor control unit which controls the adjustable-speed motor so as to achieve an intended rotation speed; and

a pump control unit which controls the variable-volume pump so that the ejection volume of the variable-volume pump equals a first ejection volume while the ejection pressure of the variable-volume pump is lower than a predetermined pressure, and that the ejection volume of the variable-volume pump equals a second ejection volume when the ejection pressure of the variable-volume pump reaches the predetermined pressure, the second ejection volume being smaller than the first ejection volume, wherein

the pump control unit includes:

an operation member which is moved by a pressure of hydraulic fluid ejected from the variable-volume pump, and which increases/decreases the ejection volume of the variable-volume pump;

an elastic member which biases the operation member in a direction against the pressure of hydraulic fluid acting on the operation member; and

a switch valve provided between the variable-volume pump and the operation member, which valve is switched to a first switch position so as to block a connection to a passage communicating the variable-volume pump with the operation member, or a second switch position so as to communicate the variable-volume pump with the operation member,

the switch valve being held in the first switch position when the ejection pressure of the variable-volume pump is lower than the predetermined pressure and switched to the second switch position when the ejection pressure of the variable-volume pump reaches the predetermined pressure.

7. An electric actuator, comprising:

a hydraulic fluid supply device as defined in claim 6 ; and

an actuator actuated in response to input of hydraulic fluid from the variable-volume pump.

8. A hydraulic fluid supply device, comprising:

adjustable-speed motor;

a variable-volume pump which is driven by the adjustable-speed motor and ejects hydraulic fluid;

an electric motor control unit which controls the adjustable-speed motor so as to achieve an intended rotation speed; and

a pump control unit which controls the variable-volume pump so that the ejection volume of the variable-volume pump equals a first ejection volume until a predetermined period elapses from a point when the rotation speed of the adjustable-speed motor becomes substantially constant,

and that the ejection volume of the variable-volume pump equals a second ejection volume upon elapse of the predetermined period from the point when the rotation speed of the adjustable-speed motor becomes substantially constant, wherein

the pump control unit includes:

an operation member which is moved by a pressure of hydraulic fluid ejected from the variable-volume pump, and which increases/decreases the ejection volume of the variable-volume pump;

an elastic member which biases the operation member in a direction against the pressure of hydraulic fluid acting on the operation member; and

a switch valve provided between the variable-volume pump and the operation member, which valve is switched to a first switch position so as to block a connection to a passage communicating the variable-volume pump with the operation member, or a second switch position so as to communicate the variable-volume pump with the operation member, the switch valve being held in the first switch position until the predetermined period elapses from the point when the rotation speed of the adjustable-speed motor becomes substantially constant and switched to the second switch position upon elapse of the predetermined period from the point when the rotation speed of the adjustable-speed motor becomes substantially constant.

9. An electric actuator, comprising:

a hydraulic fluid supply device as defined in claim 8 ; and

an actuator actuated in response to input of hydraulic fluid from the variable-volume pump.