disc brake caliper

Disc Brake Pad Support Arrangements Swing Yoke Type Brake Caliper

This disc brake caliper is a single cylinder unit and is of light weight. The caliper unit uses a rigid yoke of steel pressing, a cylinder assembly, two pads and a carrier bracket bolted to the suspension hub carrier. A tongue and groove joint rigidly secure the cylinder to one side of the yoke frame while the yoke itself pivots at one end on it supporting carrier bracket. The disc is mounted on the transmission drive shaft hub which it is mounted provides the drive to the disc. The lining pads are supported on either side of the disc in the yoke frame (Fig. 28.28).

Fig. 28.28. Swing yoke type brake caliper

During operation of the foot brake, hydraulic pressure pushes the piston and inboard pad against their adjacent disc face. At the same time, the hydraulic reaction moves the cylinder in the opposite direction so that the outboard pad and cylinder body are bridged. Then the yoke pivots, forcing the outboard pad against the disc face opposite to that of the inboard pad.

As the pads wear the yoke moves through an arc about its pivot. The lining pads are tapered in shape to compensate for this tilt. The operating clearance between the pads and disc is maintained roughly constant by the inherent distortional stretch and retraction of the pressure seals as the hydraulic pressure is increased and reduced respectively.

Sliding Yoke Type Brake Caliper

In this type of caliper unit the cylinder body is rigidly fixed to the suspension hub carrier. The yoke slides between parallel grooves formed in the cylinder casting (Fig. 28.29).

Application of the foot brake causes hydraulic pressure to push the pistons apart. The direct piston forces the direct pad against the disc whereas the indirect piston forces the yoke to slide in the cylinder in the opposite direction until the indirect pad contacts the outstanding disc face. Further increase in pressure provides an equal but opposing force which sandwiches the disc > between the friction pads.

Fig. 28.30. Slide pin type brake caliper

Sliding Pin Type Brake Caliper.

This type of disc brake caliper unit incorporates a disc, a carrier bracket, a cylinder caliper bridges, piston and seals, friction pads and a pair of support guide pins (Fig. 28.30). The carrier bracket is bolted onto the suspension hub carrier. It supports the cylinder caliper bridge and absorbs the brake torque reaction. The cylinder caliper bridge is mounted on a pair of guide pins that slide in holes in the carrier bracket. The guide pins only support and guide the bride. These are sealed against dirt and moisture by dust covers. The frictional drag of the pads is absorbed by the carrier bracket.

The application of the foot brake generates hydraulic pressure that pushes the piston and cylinder apart. The inboard pad moves up to the inner disc face. In contrast, the cylinder and bridge react in the opposite direction until the outboard pad touches the outside disc face. Further increase of hydraulic pressure imposes equal but opposing forces against the disc faces via the pads.

Similar to all other types of caliper units, in slide pin type also, the brake calipers pad to disc free clearance is provided by the pressure seals. The pressure seals are fitted inside recesses in the cylinder wall. They grip the piston when hydraulic pressure forces the piston outwards, getting distorted in the process. When the foot brake is released the pressure is withdrawn from the piston crown and the strain energy of the elastic rubber pulls back the piston so that the pressure seal is restored to its original shape.

Sliding Cylinder Body Type Brake Caliper

This type of brake caliper unit uses a carrier bracket bolted to the suspension hub carrier and a single piston cylinder bridge caliper. The caliper straddles the disc and slides laterally on guide keys located in wedge-shaped grooves formed in the carrier bracket (Fig. 28.31).

The hydraulic pressure, generated due to the application of the foot brake, pushes the piston along with the direct acting pad onto the inside disc face. The cylinder body caliper bridge is pushed in the opposite direction, so that it reacts and slides in its guide groove at right angles to the disc. This causes the indirect pad to contact the outside disc face, equalizing the forces acting on both sides of the disc.

Fig. 28.31. Slide cylinder body type brake caliper.

A pad to disc face working clearance is provided as in the other units by the retraction of the pressure seal, after the hydraulic pressure collapses. Anti-rattle springs are incorporated alongside each of the two-edge-shaped grooves to avoid vibration and noise caused by the relative movements between the bridge caliper and carrier bracket sliding joint