Development Of Center Valve Type Brake Master Cylinder

Central Valve (hereinafter referred to "CV") type Brake Master Cylinder is designed for automobile equipped with Anti-Block System (hereinafter referred to '"ABS"). At the very beginning, CV Master Cylinder was mainly installed on high-end cars. From middle of 1990's on, some local mid-end cars begin to be equipped with ABS, but there exists big gap between Chinese car industry as well as relevant parts and international advanced. So CV master cylinder has not been put into product yet round China before 2000.Common design of brake master cylinder has a hole. At released position, the hole connects working chamber to brake fluid reservoir so as to provide brake fluid. At brake position, pushrod moves forward together with piston, till seal cup passed the hole, high pressure built up in the working chamber. Each pressure building needs seal cup passing the hole, it will reduce seal cup's working life.Sealing of CV master cylinder features totally different with that of common master cylinder, a valve unit, consisting of a central valve spring inside of piston, a central valve, valve body and a spring seat against the piston. At released position, the central valve always keeps open, working chamber connecting to supply chamber. At brake position, pushrod against the piston moves forward, the central valve moves backward relatively to the piston and valve body by force of the central valve spring, thus central valve is closed, so hydraulic pressure is built up in the working chamber. Under the influence of ABS, the said hydraulic pressure is regulated according to signal from wheel speed sensor to prevent a wheel is blocked.Compared with common design, CV master cylinder features good fluid thoroughness, smoothness and reliability, thus owns longer working life. Owing to its complicated manufacturing process, so central valve is more expensive.