There Is No Return Spring On The Disc Brake. How Does The Brake Pad Return?
There is no return spring on the disc brake. How does the brake pad return?
Originally, the secret lies in the piston of the brake cylinder. The brake cylinder of disc brake is also called brake caliper. It is composed of piston and caliper body. The piston moves in the caliper body. One side bears the pressure of brake oil, and the other side pushes the brake pad to clamp the brake disc to generate braking force. There is a sealing ring between the piston and the caliper body, which is used to seal the brake oil. The return of the piston is completed by this sealing ring.
The section of the seal ring is not a normal circle, but a rectangle. When the car is braking, the piston presses the brake pad to the brake disc under the action of hydraulic pressure, which produces friction torque (braking force). At this time, the edge of the rectangular sealing ring will produce slight elastic deformation under the action of piston friction; When the brake is released, the pressure acting on the back of the piston disappears, and the rectangular sealing ring returns to its original state under the action of elastic force, which drives the piston back to its original position. This is the return principle of disc brake pads. Some people may say, is the deformation of this sealing ring that large? In fact, only a little bit of this deformation is enough. After the compression force between the two is released, the high-speed rotating brake disc will push the brake pad back a little. Under normal circumstances, the gap between the brake pad and the brake disc is less than 0.1mm.
The rectangular sealing ring can also adjust the brake clearance automatically. In use, the gap between the brake pad and the brake disc gradually increases due to wear. When the deformation of the piston sealing ring reaches the limit, the piston can still move forward under the action of hydraulic pressure until the brake disc is compressed; But when the brake is released, the distance that the rectangular sealing ring can make the piston return is the same, that is, the gap between the brake pad and the brake disc still maintains the standard value. This is the principle of disc brake automatic adjustment of brake clearance.
Therefore, the rectangular sealing ring in the brake caliper plays a very important role. It can not only seal the brake oil, but also make the piston return and adjust the brake clearance. Therefore, the structure of this kind of rectangular sealing ring is quite precise, and it has high requirements for its elasticity, heat resistance, geometric accuracy of cutting edge and surface finish. In practice, it is rarely damaged, and it is difficult to repair if it is damaged. Generally, the brake caliper assembly is replaced directly.