Patent ID: 6851760

Claim:
A method for driving an electric motor of a recirculating type hydraulic pressure modulator disposed in a hydraulic pressure conduit connecting a master cylinder and a wheel cylinder for modulating a pressure difference between a hydraulic pressure in the wheel cylinder and a hydraulic pressure outputted from the master cylinder, the recirculating type hydraulic pressure modulator comprising an auxiliary reservoir, a normally open type valve disposed between the master cylinder and the wheel cylinder, a normally closed type valve disposed between the wheel cylinder and the auxiliary reservoir, and a hydraulic pump driven by the electric motor for recirculating hydraulic fluid discharged from the wheel cylinder through the normally closed valve and stored within the auxiliary reservoir to the hydraulic pressure conduit, the method comprising: detecting a pressure inputted to a vacuum type booster from a negative pressure source; comparing the detected pressure with a predetermined threshold pressure value; judging whether or not a brake pedal is under operation; driving the electric motor so that when the detected pressure is greater than the predetermined threshold pressure value and when the brake pedal is under operation the hydraulic pump recirculates to the hydraulic pressure conduit only hydraulic fluid within the auxiliary reservoir that has come from the wheel cylinder through the normally closed type valve; judging whether or not the brake pedal is released; and terminating the driving of the electric motor when the brake pedal is released.