Vehicle brake device

A vehicle brake device comprising:

• a hydraulic pressure generating portion having a driving portion which drives a master piston;
• an actuator disposed between the hydraulic pressure generating portion and a wheel cylinder for outputting a master pressure which is a hydraulic pressure in a master chamber to the wheel cylinder by adjusting the master pressure;
• and
• a controlling portion which maintains a driving force of the driving portion when a control subject pressure which is a hydraulic pressure in a control subject chamber is within a dead zone set based on a target value of the control subject pressure, wherein
• the control subject pressure varies in response to a variation of the master pressure and a pulsation is generated in the master pressure accompanying an operation of the actuator,
• the vehicle brake device further including:
• a rigidity information obtaining portion which obtains a rigidity information which relates to a rigidity of the control subject chamber, the rigidity of the control subject chamber being the pressure change of the control subject chamber required to change the unit volume of the control subject chamber;
• and
• a dead zone setting portion which sets the dead zone based on the rigidity information obtained by the rigidity information obtaining portion such that the higher the rigidity of the control subject chamber, or the higher the probability of rigidity increase of the control subject chamber, the wider the dead zone is set, wherein
• the rigidity of the control subject chamber is higher as the control subject pressure is higher,
• the actuator forms an anti-lock brake system and the rigidity information obtaining portion obtains a road surface information which 1) relates to a friction coefficient on a travelling road surface as the rigidity information and 2) is used to determine the probability of rigidity increase of the control subject chamber, and
• the dead zone setting portion sets the dead zone based on the road surface information such that the lower the friction coefficient, the wider the dead zone is set.