Brake control system for vehicles

Claim 1

A brake control system for vehicles comprising fluid braking means, a microprocessor having input brake control means and output fluid brake application means, the output fluid brake application means comprising means responsive to a digital signal characteristic of a desired fluid braking pressure, wherein the brake application means comprises improved fluid pressure regulating means comprising; (a) fluid pressure chamber means for developing and maintaining a regulated braking fluid pressure, (b) valve means having a spool selectively operable axially to select brake application, release and lap positions for selectively governing fluid pressure in the braking means and in the fluid pressure chamber, (c) digital linear actuating means comprising a stepping motor having axially operable shaft means coaxially connected to one end of the spool of the valve means and responsive to the digital signal to actuate the spool axially alternately to application and release brake control positions, (d) control means including the valve means and a piston carrying the stepping motor operable responsive to changes of fluid pressure in the chamber for maintaining output pressure to the fluid braking means in accordance with the characteristics of the digital signal, and (e) the piston being biased by a metering spring to permit expansion of the pressure chamber volume in accordance with an increase of fluid pressure within the fluid pressure chamber corresponding to the output pressure.