Patent ID: 6315369
Filing Date: 2001-11-13
Classification: B60T

Abstract:
A hydraulically operated braking system for a vehicle having a wheel, including a wheel brake cylinder for braking said wheel, and a hydraulic pump operated by an electric motor to operate said wheel brake cylinder, comprising:motor control device which is connected to said electric motor and controls an electric current to be applied to said electric motor, by pulse width modulation, such that a PWM frequency at which the electric current is controlled by the pulse width modulation is set at a relatively high value higher than an upper audibility limit while the braking system is placed in a normal braking operation during which the generation of an operating noise of the braking system is not allowed, and at a relatively low value not higher than the upper audibility limit while the braking system is placed in one of (a) a slip control braking operation in which the pressure of the pressurized working fluid from said hydraulic pump to said wheel brake cylinder is controlled so as to hold a degree of slipping of said wheel within a predetermined range, (b) a vehicle stability control braking operation for improving a running stability of the vehicle, and (c) an abrupt braking operation, the generation of said operating noise being allowed in said slip control braking operation, said vehicle stability control braking operation and said abrupt braking operation.