Patent ID: 7690736

Claim:
A braking system for a vehicle comprising: a hydraulic system for applying braking pressure to a braking device of a wheel for the vehicle; a return fluid path, forming a part of the hydraulic system, and operatively communicated with a wheel cylinder of the braking device for circulating brake fluid from the wheel cylinder in the hydraulic system; and a liquid pump provided in the return fluid path, wherein the liquid pump comprises; a pump housing and a piston; a suction chamber formed in a cylindrical hole of the pump housing, into which the brake fluid is sucked through an inlet port formed in the pump housing; a cylindrical space formed in the pump housing, into which one end of the piston is fluid-tightly and slidably inserted to form a pump chamber, so that the suction chamber is operatively communicated with the pump chamber and the brake fluid supplied from the suction chamber into the pump chamber is pressurized; a supporting hole formed in the pump housing and coaxially arranged with the cylindrical hole and the cylindrical space, the other end of the piston being fluid-tightly and slidably inserted into the supporting hole; and a sliding ring provided at the piston and slidably in contact with an inner peripheral surface of the cylindrical hole for fluid-tightly sealing a space between an outer peripheral surface of the piston and the inner peripheral surface of the cylindrical hole of the pump housing, so that the suction chamber is formed by the pump housing, the piston, and the sliding ring, wherein the inlet port is formed in the pump housing so as to always open to the suction chamber at the inner peripheral surface of the cylindrical hole, wherein the suction chamber increases its volume when a volume of the pump chamber is decreased in accordance with a reciprocal movement of the piston, whereas the suction chamber decreases its volume when the volume of the pump chamber is increased in accordance with the reciprocal movement of the piston, and wherein an inner diameter “Dk ” of the cylindrical hole of the pump housing for forming the suction chamber is made larger than an inner diameter “Dc ” of the cylindrical space.