Patent ID: 7758132
Filing Date: 2010-07-20
Classification: B60T

Abstract:
1. A braking hydraulic circuit that controls linear reduction of a front/rear wheel braking liquid pressure and solves a difference in gradient of the front/rear wheel braking liquid pressure in a vehicle, the braking hydraulic circuit comprising: a liquid pressure supply line that supplies a liquid pressure from a master cylinder to wheel cylinders of wheels upon braking according to an operation of a brake pedal by a driver and at normal braking with no application of an ABS (Antilock Brake System); supply path control valves that are normal open type solenoid valves and are provided on said liquid pressure supply line to control a flow of a hydraulic pressure to be supplied from the master cylinder to the wheel cylinders of the wheels; a liquid pressure return line that is formed to control liquid pressures to be discharged from the wheel cylinders at a time of pressure reduction control with the an application of the ABS; return path control valves that are normal close type solenoid valves and are provided on said liquid pressure return line to form a two-system liquid pressure flow that separately passes liquid pressures to be discharged from the wheel cylinders and then unifies the liquid pressures, such that a difference in pressure intensification gradient is eliminated according to a difference in generation time of a braking pressure between the front/rear wheels at the time of the pressure reduction control; a TCS liquid pressure supply line that shares the liquid pressure supply line and supplies the liquid pressure of the master cylinder to the wheel cylinders through a high pressure switching valve, a motor, and a suction pump at the a time of implementation of a TCS (Traction Control System) to control tire-slipping with no operation of the brake pedal; and a controller that controls the valves provided on the hydraulic circuit, the motor, and the suction pump based on wheel speed information measured by a wheel speed sensor at the time of normal braking, the ABS pressure reduction control, or the implementation of the TCS, wherein the liquid pressure return line comprises: wheel cylinder liquid pressure return lines that extend from the wheel cylinder of the front left wheel and the wheel cylinder of the rear right wheel, and have unidirectional check valves, respectively; a unified liquid pressure return line that is formed by unifying said wheel cylinder liquid pressure return lines; a connection liquid pressure return line that is connected between said unified liquid pressure return line and a suction pump, and has a unidirectional check valve, and to which an accumulator that temporarily stores the liquid pressure is connected; and a discharge liquid pressure return line that is connected to the liquid pressure supply lines connected to the master cylinder to return the liquid pressure pumped from said suction pump to the master cylinder, and wherein front wheel and rear wheel return path control valves are provided in said wheel cylinder liquid pressure return lines, respectively, to open/close the wheel cylinder liquid pressure return lines, and a unified return path control valve is provided on the connection liquid pressure return line connected to said unified liquid pressure return line.