High performance anti-lock brake system for original equipment and after-market applications

Claim 1

An anti-lock brake system for a vehicle comprising: a master cylinder having a master cylinder piston mounted for reciprocal movement therein; actuating means for moving the master cylinder piston when an operator of the vehicle operates a vehicle brake actuating device; a wheel cylinder having a wheel cylinder piston which is mounted for reciprocal movement therein; a rotatable brake element connected for rotation with a wheel of the vehicle; a non-rotatable brake element interposed between the wheel cylinder piston and the rotatable brake element; a hydraulic link comprising a volume of constrained working fluid interposed between the master cylinder piston and the wheel cylinder piston so as to hydraulically link movement of the master cylinder piston with movement of the wheel cylinder piston, whereby when the vehicle operator operates the vehicle brake actuating device in order to slow down the vehicle, the movement of the master cylinder piston causes a corresponding movement of the wheel cylinder piston which urges the non-rotatable brake member to frictionally engage the rotatable brake member, thereby slowing down the vehicle; valve means provided in the hydraulic link for controlling a condition of fluid communication between the master cylinder and the wheel cylinder, wherein the valve means is controllable to selectively provide either one of a first condition which allows two way fluid communication between the master cylinder and the wheel cylinder and a second condition which allows exclusive one way fluid communication from the wheel cylinder to the master cylinder, wherein, an upstream portion of the hydraulic link is defined between the master cylinder piston and the valve means and a downstream portion of the hydraulic link is defined between the wheel cylinder piston and the valve means, and wherein the downstream portion of the hydraulic link defines an internal volume within which the working fluid is substantially constrained when the movement of the wheel cylinder piston has urged the non-rotatable brake member into frictional engagement with the rotatable brake member; piezoelectric means, comprising at least one piezoelectric element to which a voltage potential is applied, for increasing and decreasing the internal volume of the downstream portion of the hydraulic link in response to changes in a magnitude of the voltage potential applied to the piezoelectric element; wheel speed sensing means for producing a wheel speed signal indicative of a rotational speed of the wheel; and a controller electrically connected to the valve means, the piezoelectric means, and the wheel speed sensing means; wherein the controller comprises: skid determining means for determining the existence of an incipient wheel skid condition at the vehicle wheel on the basis of at least the wheel speed signal; normal braking mode control means, operative when the incipient wheel skid condition does not exist, for controlling the valve means to provide the first condition of fluid communication between the master cylinder and the wheel cylinder; cut-off means, responsive to the determined existence of the incipient wheel skid condition, for controlling the valve means to provide the second condition of fluid communication between the master cylinder and the wheel cylinder; piezoelectric element contracting means, operative after the second condition of fluid communication has been established, for controlling the magnitude of the voltage potential applied to the piezoelectric element so as to cause the piezoelectric element to contract, thereby increasing the internal volume of the downstream portion and reducing a hydraulic pressure in the wheel cylinder to alleviate the incipient wheel skid condition; means for sensing an alleviation of the incipient wheel skid condition, on the basis of at least the wheel speed signal; piezoelectric element expanding means, responsive to the sensed alleviation of the incipient wheel skid condition, for controlling the voltage potential applied to the piezoelectric element so as to cause the piezoelectric element to expand, thereby decreasing the internal volume of the downstream portion and increasing the hydraulic pressure in the wheel cylinder; monitoring means for monitoring the voltage potential applied to the piezoelectric element by the piezoelectric element expanding means; and normal braking resume means for controlling the valve means to provide the first condition of fluid communication between the upstream portion and the downstream portion of the hydraulic link when the voltage potential applied to the piezoelectric element by the piezoelectric element expanding means has reached a predetermined voltage potential, wherein the valve means and the piezoelectric means are provided within a module attached to a portion of the vehicle in such a manner that the piezoelectric means is located within an auxiliary chamber of the module downstream of the valve means, wherein the upstream portion comprises a first brake line section, the downstream portion comprises a second brake line section, wherein the second brake line section comprises a flexible brake line, and wherein the module is interposed between the first brake line section and the second brake line section.