| 摘要 |
In an electric motor-driven booster, a sharp change of reaction force to an operation of a brake pedal is reduced to improve the brake pedal operation feeling. An operation of the brake pedal causes an input rod 34 and an input piston 32 to advance, and an electric motor 40 is driven according to the movement of the input piston 32 to propel a primary piston 10 through a ball-screw mechanism 41, thereby generating a desired brake hydraulic pressure in a master cylinder 2. At this time, the input piston 32 receives the hydraulic pressure in the master cylinder 2 to feed back a part of reaction force during braking to the brake pedal. When the brake pedal is further depressed after the output of the electric motor 40 has reached a maximum output and the primary piston 10 has stopped, a lock nut 74 abuts against a movable spring retainer 78 and compresses a reaction force spring 79, thereby applying a reaction force to compensate for a reduction in the rate of increase in the reaction force due to the stop of the primary piston 10. |
