NANO

BRAKE SYSTEM 497 BRAKES AUTO INCREMENTAL BRAKE General: For the drum brakes to function correctly, the brake shoes must remain close to the drumwithout touching it. If they get too far away from the drum (as the shoes wear down, for instance), the piston will require more fluid to travel that distance, and this will increase the pedal travel. So to avoid this excess travel, drum brakes are having an automatic adjuster which ensures that, the gap between brake shoes and brake drum remains constant. This gap is the distance traveled by the brake shoe, when it comes in contact with the brake drum. Auto adjuster comprises of the strut assembly, adjuster screw sub assembly and the rocker. The pawl is attached in the strut assembly by spring force and with offset leaf spring, engages with the adjustment nut. It provides optimal adjustment value of approximately 0.02 mm for every brake adjustment. Working: (a) Driving (non – braking) Mode: The shoe return springs, upper and lower, pulls both brake shoes together, away from brake drum. This results in forcing the adjuster screw sub assembly and the brake adjuster nut against the strut assembly so that the rocker located between them can not move. (b) Brake applied mode: When the service brakes are applied, the wheel cylinder pistons forces brake shoes against the brake drum. This causes the adjuster bolt spring to pull the adjuster screw sub assembly and the adjuster nut away from the strut assembly, thus generating a gap in which the rocker is free to move. Rocker movement under leaf spring force causes pawl to push tooth of adjuster nut. This results into rotation of adjuster nut which expands adjuster screw sub assembly. This restores gap between shoes and drum, thereby maintaining it.