VALVE UNIT FOR AN ANTI-LOCK BRAKING SYSTEM

A valve unit for an ABS system having a single hydraulic chamber configured to receive a brake fluid, with a delivery port for supplying the brake fluid to a brake caliper, and a passage to for letting the brake fluid from a master cylinder into the single hydraulic chamber is provided. A single piston, longitudinally movable within the single hydraulic chamber, has first transverse surfaces facing the delivery port and defining as a whole a first transverse area, second transverse surfaces facing away from the delivery port and defining as a whole a second transverse area greater than the first transverse area. A longitudinal cavity extends in the single piston establishing fluid communication between the first and second transverse surfaces, whereby displacement of the single piston towards the delivery port occludes the passage and increments the volume available for the brake fluid in the single hydraulic chamber.