Patent ID: 9096203
Filing Date: 2015-08-04
Classification: B60T

Abstract:
1. A brake master cylinder comprising a cylinder body connected to a booster, first and second pistons to reciprocate in the cylinder body, and a Hall sensor installed at an outside of the cylinder body, to sense operation of the pistons, for control of activation of brake lamps, further comprising: a coupling shaft formed at an end of the second piston facing the first piston; and a magnet ring assembly installed at the coupling shaft such that the magnet ring assembly faces the Hall sensor, wherein the magnet ring assembly comprises: a bushing centrally formed with a fitting hole extending in a longitudinal direction of the bushing such that the coupling shaft is fitted in the fitting hole; and a ring-shaped magnet fitted around an outer surface of the bushing, to exert magnetic force on the Hall sensor, wherein the bushing comprises a cylindrical fitting portion centrally formed with the fitting hole and formed with at least one vent hole extending in the longitudinal direction of the bushing to exhaust air existing between the bushing and the second piston.