Integral abs and traction control having an electric modulator

Abstract

An integrated anti-lock braking (ABS)/traction control (TC) braking system is provided which includes a controller cognizant of a rotational condition of a wheel, a master cylinder, an actuator with a bore, the bore having a first fluid connection with a master cylinder and space therefrom a second fluid connection with a brake, a first normally open solenoid valve for isolating the master cylinder from the wheel brake when the controller places the system in an ABS or TC mode, and a hollow primary piston mounted within the bore along first, second and third spaced sealed peripheries having a first port connecting the interior of the primary piston with its exterior between the first and second sealed peripheries and communicating with the second fluid connection of the bore. The primary piston also has a second port fluidly connecting an end of the primary piston most adjacent to the bore first fluid connection with the interior of the primary piston and the primary piston having a check valve mounted within the second port and the primary piston has a third sealed periphery generally adjacent the bore first fluid connection. A secondary piston is mounted within the primary piston movable in a direction towards the bore first fluid connection to pressurize the brake and movable in an opposite direction to release the pressure within the brake, the secondary piston has an extreme position with respect to the primary piston wherein the secondary piston opens the check valve and further movement of the secondary piston causes the pistons to move in unison pressurizing the wheel brake. A reversible motor connected with a gear train, drive screw and nut moves the secondary piston in response to signal give by the controller.