Patent ID: 8341956

Claim:
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.