JPH0130672Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an automatic gap adjustment device for a cam type drum brake.

A mechanical drum brake that uses a cam mechanism as a means for expanding the brake shoe is used as a braking device for two-wheeled vehicles. This type of drum brake, which is equipped with an anchor adjuster type automatic gap adjustment device, transmits the movement of a cam, brake shoe, etc. during braking operation to the anchor via an adjuster lever, and gradually extends the anchor. This structure automatically adjusts the shoe gap within a certain range.

Therefore, in this type of automatic gap adjustment device,
In general, as adjustment progresses, the adjuster lever is likely to fail to return due to rusting, etc., which in turn causes failure to return to the cam, brake shoe, etc. that connects the adjuster lever, causing the brake shoe to drag against the drum. There was a problem.

The present invention aims to provide an automatic gap adjustment device that does not have the above-mentioned problems in a cam type drum brake, and the present invention will be specifically explained below with reference to illustrated embodiments.

A pair of brake shoes 2 and 3 are arranged facing each other on the bucking plate 1, and an anchor 4 fixed to the bucking plate 1 is sandwiched between one end of the brake shoes 2 and 3, and the other end A cam 5 rotatably supported by the bucking plate 1 is sandwiched between the parts. The cam 5 rotates when the brake shoe 6 is pulled, and the other end portions of the brake shoes 2 and 3 are spread apart and brought into pressure contact with a drum (not shown), thereby producing a braking force. 7 and 8 are shoe return springs, respectively. The above configuration is substantially the same as a conventional cam-type leading-trailing type brake.

The configuration of the anchor 4 will be explained. As shown in FIG. 2, a cylindrical adjuster case 9 is fixed to the backing plate 1, and an adjuster nut 11, which has an adjuster gear 10 with teeth 10a formed on the outer edge fixed to one end thereof, is rotated into the adjuster case 9. It is movably inserted loosely, and a snap spring 12 is attached to the other end. Therefore, the adjuster nut 11 is restrained from moving in the axial direction with respect to the adjuster case 9 by the snap spring 12 and the adjuster gear 10. A pair of adjuster screws 13 and 14 are screwed together with reverse threads on both sides inside the adjuster nut 11, and each adjuster screw 13 and 14 is connected to a forked portion 13a and 14a at its outer end, respectively. One end of the web of the brake shoes 2 and 3 is received and their relative rotation is restrained.

In this embodiment, when the brake is released, the adjuster gear 10
This shows a negative-type automatic gap adjustment device that automatically adjusts the shoe gap by rotating the screw. In Fig. 2, the right adjuster screw 13 has a right-hand screw, and the left adjuster screw 14 are left-handed threaded screws into the adjuster nuts 11, and the tooth portions 10a of the adjuster gear 10 have a tooth shape that enables clockwise feeding when viewed from the right by swinging the adjuster lever 15, which will be described later. has been given.

15 is an adjuster lever, and as shown in FIG.
6, the cam 5 is rotatably attached to the shaft, and one end engages with the gear teeth 10a of the adjuster gear so as to be able to feed in only one direction. 5b, and is brought into contact from the outside with a pin 17 which is fixed as a protrusion on the other end of the web of one brake shoe 2. 18 is the pin 17 of the adjuster lever 15.
This is a return spring that is a return means that provides a habit of coming into contact with the object.

The reason why the adjuster lever 15 is engaged with the shaft attachment point 16 by the notch 15a is to avoid unnecessary excessive force acting on the adjuster lever 15 during braking and give priority to the braking action.

Next, the effect will be explained. When the brake lever 6 is pulled to rotate the cam 5 and the other ends of the brake shoes 2 and 3 are expanded, the adjuster lever 15 is moved as one brake shoe 2 moves.
swings around the pivot point 16.

If the brake shoe 2 has wear that exceeds the normal shoe clearance, the adjuster lever 15
The other end passes one tooth past the adjuster gear 10 and engages with the next tooth. When the brake is released, both brake shoes 2 and 3 are released by the shoe return springs 7 and 8.
The diameter is reduced by the action of the adjuster lever 1.
5 returns to its original position by the action of the return spring 18, and rotates the adjuster nut 11, which is integral with the adjuster gear 10. As a result, both adjuster screws 13 and 14 are respectively screwed outward to expand one end of both brake shoes 2 and 3, and the shoe gap is automatically adjusted to the regular shoe gap. Even if the adjuster nut 11 is stuck due to rusting or the like and the adjuster lever 15 cannot be returned to its original position, the action of the shoe return springs 7 and 8 not only prevents the brake shoe 3 but also the brake shoe 3. The brake shoe 2 also returns to its original position independently of the adjuster lever 15.

By the way, as shown in FIG. 4, an elongated hole 15'b having a side edge substantially parallel to the working surfaces 5a and 5b of the cam 5 when not in operation is formed in the adjuster lever 15'.
A pin 17, which is a protrusion fixed to the brake shoe 2, is inserted into the elongated hole 15'b, and the movement of the other end of the brake shoe 2 due to the rotation of the cam 5 is caused to swing to the adjuster lever 15'. In addition to transmitting it as movement,
The return of the lever 15' is performed integrally with the brake shoe 2, and the function as a return means is performed through the elongated hole 15'.
It can be given in b.

As explained above, since the present invention has the above structure, a return force acts on the adjuster lever at a large lever ratio L/l with the shaft attachment point as a fulcrum, making it difficult for the lever to return incorrectly. The operation as an automatic adjustment device becomes stable, and the brake shoe returns to a non-braking state by the action of the shoe return spring, and the adjuster lever returns individually by the biasing force of the return spring, so the adjuster nut adjusts. Even if the brake shoe and cam are stuck to the star case due to rust, the brake shoe and cam will surely return to their original positions, no dragging phenomenon will occur, and the reliability of the brake device will be improved.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a cam type drum brake equipped with an automatic gap adjustment device according to the present invention, Fig. 2 is a sectional view showing an enlarged anchor, and Fig. 3 is an A of Fig. 1.
- A sectional view and FIG. 4 are explanatory diagrams showing other structural examples of the adjuster lever. 1: Bucking plate, 2, 3: Brake shoe, 4: Anchor, 5: Cam, 7, 8: Shoe return spring, 9: Adjuster case, 1
0: Adjuster star gear, 10a: Teeth, 11: Adjuster nut, 13, 14: Adjuster star screw, 13a, 14a: Forked part, 15, 15': Adjuster star lever, 16: Pin (shaft attachment point), 17:
Pin (projection), 18: Return spring.

Claims (1)

[Scope of utility model registration request] A pair of brake shoes biased to reduce their diameter by a shoe return spring are arranged facing each other on the bucking plate, and an anchor fixed to the bucking plate is sandwiched between one end of the brake shoes. In the cam type drum brake, a cam rotatably supported by a bucking plate is sandwiched between the anchor and the other end thereof, and both brake shoes are expanded by the rotation of the cam. An adjuster case fixed to a plate, an adjuster nut inserted into the adjuster case so as to be rotatable and restrained from moving in the axial direction, and with an adjuster gear formed at one end, and a reverse thread on both sides of the adjuster nut. It consists of a pair of adjuster screws that are screwed together and whose outer ends are engaged with one end of the brake shoe in a relatively unrotatable manner, and whose one end is pivotably supported on a bucking plate. and a return mechanism whose one end engages with the adjuster gear so that it can be fed in only one direction, and whose other end abuts and engages with the protrusion at the other end of one brake shoe from the outside, and which provides the corresponding engagement behavior. An automatic gap adjustment device characterized by having an adjuster lever with a spring attached to the other end.