Patent ID: 8157332

Claim:
A control device ( 26 ) adapted to a vehicle brake apparatus (A) equipped with: a master cylinder ( 23 ) for establishing a hydraulic brake pressure in response to an operation of a brake operation member ( 21 ); a vacuum booster ( 22 ) boosting an operation force of the brake operation member by using a vacuum supplied thereto and outputting a boosting force to the master cylinder; a wheel cylinder (WC**) applying a braking force to a wheel (W**) of a vehicle (M) upon supply of the hydraulic brake pressure from the master cylinder; a pressure differential control valve ( 41 , 51 ) provided in a hydraulic pressure passage ( 25 a , 25 b ) connecting the master cylinder and the wheel cylinder for controlling a wheel cylinder side hydraulic pressure to be higher than a master cylinder side hydraulic pressure by a controlled pressure differential amount; a hydraulic pressure pump ( 44 a , 54 a ) connected to the hydraulic pressure passage ( 25 a , 25 b ) connecting the master cylinder and the wheel cylinder for establishing a hydraulic brake pressure upon receipt of an output from an electric motor and supplying the established hydraulic brake pressure to the wheel cylinder, independently of the hydraulic brake pressure established by the master cylinder; a vacuum detecting means ( 22 f 2 ) for detecting the vacuum supplied to the vacuum booster ( 22 ); and a master cylinder pressure detecting means ( 25 a 1 ) for detecting the master cylinder pressure, the control device ( 26 ) comprising: a vacuum pressure obtaining means ( 26 a , step 104 ) obtaining the vacuum supplied to the vacuum booster by means of the vacuum detecting means; a master cylinder pressure obtaining means ( 26 b , step 102 ) for obtaining the master cylinder pressure by means of the master cylinder pressure detecting means; and a boosting control means ( 26 e , step 306 in a flowchart in FIG. 13 ) establishing a boosting pressure as an additional hydraulic brake pressure and supplying the boosting pressure to the wheel cylinder, in addition to the master cylinder pressure established in response to the operation of the brake operation member, whereby the hydraulic pressure pump and the pressure differential control valve are controlled from the time when the master cylinder pressure obtained by the master cylinder pressure obtaining means has reached a value equal to or more than a boosting limit pressure which is a master cylinder pressure corresponding to a boosting limit of the vacuum booster at the vacuum obtained by the vacuum pressure obtaining means so that the boosting pressure agrees to a target boosting pressure obtained with a target boosting gain which is smaller than a basic boosting gain corresponding to a servo-ratio of the vacuum booster for a period until the vacuum booster reaches the boosting limit.