Brake booster for preventing unwanted reaction disc deformation

摘要

An improvement of a reaction transmitting mechanism for a booster is disclosed. A forward end face of a tubular portion of a valve body which abuts against a reaction disc is provided with an uneven surface. This presents a resistance to an elastic deformation of the reaction disc when a brake booster is actuated. Accordingly, an enhanced hysteresis, which represents a difference in the output between when depressing and releasing a brake pedal, is provided without increasing the hardness of the reaction disc.