Patent ID: 8500213

Claim:
An electrically actuated booster comprising: a master cylinder that generates a brake fluid pressure; an input member that moves forward and backward in response to an operation of a brake pedal; an assist member arranged to be movable relative to said input member; an electrically-operated actuator that causes said assist member to move forward and backward by applying a thrust to said assist member; and a controller that controls said electrically-operated actuator, wherein said controller controls said electrically-operated actuator based on the operation of the brake pedal, and a boosted brake fluid pressure is generated in said master cylinder by the thrust applied to said assist member, said electrically actuated booster further comprising: either a relative displacement detector that detects a relative displacement between said input member and said assist member or an assist displacement detector that detects a displacement of said assist member, wherein said controller includes a target displacement setting unit that sets a target displacement that makes variable relative displacement relationship between said input member and said assist member based on an operation amount of the brake pedal, and a control unit that controls said electrically-operated actuator so that the relative displacement relationship between said input member and said assist member becomes equal to said target displacement on a basis of a signal from said relative displacement detector or said assist displacement detector, and wherein urging means is provided between said input member and said assist member to urge said input member relative to said assist member toward a neutral position of relative displacement therebetween.