Patent ID: 10507817

Abstract:
An electric motor (2) is controlled according to the stroke of an input rod (30) moved in response to an operation of a brake pedal. The rotation of the electric motor is transmitted through a belt transmission mechanism (45) to a ball-screw mechanism (38) to propel a primary piston (10), thereby generating a brake hydraulic pressure in a master cylinder (4). The belt transmission mechanism has pulleys (45A, 45B), one of which is secured to an output shaft of the electric motor. The output shaft and a nut member (39) of the ball-screw mechanism are held by bearings (42A, 42B and 42C) secured to a rear housing (3B) which is a single member. Thus, before an electric motor-driven booster (1) is assembled, the belt transmission mechanism can be subassembled to the rear housing. Therefore, a belt (46) can be adjusted for tension in the state of a subassembly.