Brake system

Abstract

When an electrical fluid pressure generator fails and a wheel cylinder is operated by brake fluid pressure generated by a master cylinder, if a first fluid pressure system leading to a rear fluid chamber of the electrical fluid pressure generator fails and is opened to the atmosphere, braking is performed by brake fluid pressure of a second fluid pressure system transmitted from the master cylinder through a front fluid chamber of the electrical fluid pressure generator to a wheel cylinder. At this time, a front supply port, which communicates through a front second cup seal facing rearward with the rear fluid chamber opened to the atmosphere due to the failure, does not communicate with the master cylinder but with a reservoir. Therefore, it is possible to prevent leakage of the brake fluid pressure generated by the master cylinder through the front supply port, the front second cup seal and the rear fluid chamber, thereby ensuring braking by the second fluid pressure system leading to the front fluid chamber of the electrical fluid pressure generator.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present invention claims priority under 35 USC § 119 based on Japanese patent application No. 2006-270556, filed on Oct. 2, 2006. The subject matter of this priority document is incorporated by reference herein.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a brake system having a master cylinder for generating brake fluid pressure based on a brake operation of a driver, and an electrically controlled fluid pressure generator (herein after “electrical fluid pressure generator”) for generating brake fluid pressure by an electrically controllable actuator.[0004]2. Description of the Related Art[0005]Japanese Patent Application Laid-open No. 2003-137084 discloses a brake system of the type referred to as a brake by wire (BBW) brake system, which converts a brake operation of a driver into an electrical signal used to operate an electrical fluid pressure generator, and operates a wheel cyl...

AI Technical Summary

Benefits of technology

[0013]According to the first aspect of the invention, when the electrical fluid pressure generator fails and the wheel cylinder is operated by the brake fluid pressure generated by the master cylinder, if a first fluid pressure system leading to the rear fluid chamber of the electrical fluid pressure generator fails and is opened to the atmosphere, braking is performed by brake fluid pressure of the second fluid pressure system transmitted from the master cylinder through the front fluid chamber of the electrical fluid pressure generator to the wheel cylinder. At this time, the front supply port, which communicates through the front second cup seal facing rearward with the rear fluid chamber opened to the atmosphere due to the failure, does not communicate with the master cylinder but with the reservoir. Therefore, it is possible to prevent leakage of the brake fluid pressure generated by the master cylinder through the front supply port, the front second cup seal and the rear fluid chamber, thereby ensuring braking by the second fluid pressure system leading to the front fluid chamber of the electrical fluid pressure generator.

[0015]According to the second aspect of this invention, when the electrical fluid pressure generator fails and the wheel cylinder is operated by the brake fluid pressure generated by the master cylinder, if the first fluid pressure system leading to the rear fluid chamber of the electrical fluid pressure generator fails and is opened to the atmosphere, braking is performed by the brake fluid pressure of the second fluid pressure system transmitted from the master cylinder through the front fluid chamber of the electrical fluid pressure generator to the wheel cylinder. At this time, the front third cup seal facing forward is arranged between the front supply port communicating with the master cylinder and the rear fluid chamber opened to the atmosphere due to the failure. Therefore, the front third cup seal prevents leakage of the brake fluid pressure generated by the master cylinder from the front supply port through the rear fluid chamber, thereby ensuring braking by the second fluid pressure system leading to the front fluid chamber of the electrical fluid pressure generator.

[0017]According to the third aspect of the present invention, because the ABS for decreasing, maintaining and increasing the brake fluid pressure transmitted to the wheel cylinder is arranged between the electrical fluid pressure generator and the wheel cylinder, locking of a wheel upon braking can be suppressed and a braking distance can be reduced.

[0019]According to the fourth aspect of this invention, because the shutoff valve closing at least during operation of the ABS is arranged between the master cylinder and the electrical fluid pressure generator, it thereby prevents hydraulic pressure change due to the operation of the ABS from being transmitted as a kickback to the master cylinder.

Problems solved by technology

Therefore, there is a possibility that the second fluid pressure system leading to the front fluid chamber 139B might fail at the same time.

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