Patent ID: 8220261
Filing Date: 2012-07-17
Classification: F15B

Abstract:
1. A master cylinder having at least one piston that pressurizes a hydraulic fluid when a stepping force on a brake pedal is transmitted thereto and sends the pressurized hydraulic fluid to at least a wheel cylinder, wherein: the piston includes a large diameter passage and a small diameter passage having a diameter smaller than that of the large diameter passage; and a valve body is fastened to the large diameter passage to control fluid communication between the large diameter passage and the small diameter passage, the valve body including a plunger coupling hole and a channel through which the hydraulic fluid communicates between the large diameter passage and the small diameter passage; wherein a plunger slidably passes the valve body through the plunger coupling hole and closes the channel of the valve body when the stepping force on the brake pedal is transmitted to the piston; wherein an end portion of the plunger slidably passing through the plunger coupling hole of the valve body and disposed in the small diameter passage is coupled with an elastic member, which returns the plunger to close the channel of the valve body when the stepping force on the brake pedal disappears; and wherein the end portion of the plunger is coupled to the elastic member by an elastic member guide configured to extend toward a rear end of the valve body in a longitudinal direction thereof in the small diameter passage so as to receive the elastic member thereon, the plunger coupling hole being formed through the valve body and the elastic member guide.