JPH03144129A - Automatic adjuster mechanism of drum brake - Google Patents

Abstract

PURPOSE:To facilitate brake adjustment from the back side of a back plate by providing an eccentric cam on one surface side of a base, by rotatably inserting its axis part into a through hole of the back plate and by having one end of an adjust link rotatably supported by an eccentric pin of the eccentric cam. CONSTITUTION:When a lock nut 8 fastened to an eccentric cam 7 projecting to the back side of a back plate 1 is loosened and the eccentric cam 7 is rotated in the B direction using a tool, a link lever 11a is rotated in the C direction. Then, the distance between an engagement part 11b of an adjust strut 12 and a support pin 10 of shoes 2 and 3 gets larger, and a gap between the shoes 2 and 3, and a brake drum gets smaller. When the lock nut 8 is tightened in this state, an automatic adjust mechanism is made in the normal use state. When abrasion is advanced and the gap between the shoes and the drum gets larger, operating of a parking brake 14 turns a ratchet wheel 13 of the adjust strut 12 by one tooth, the entire length of the adjust strut 12 is prolonged and automatic adjustment is effected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in an auto-adjuster mechanism for a drum brake, and in particular, it is possible to easily adjust the gap between a brake drum and a brake shoe from the back side of a back plate. The present invention relates to an auto-adjuster mechanism for a drum brake that enlarges the gap between the brake drum and brake shoes from the back side of a back plate so that the brake drum can be easily removed when the brake drum is removed.

[Conventional technology]

An example of a conventional drum brake auto-adjuster mechanism is the ``Toyota Corona Repair Manual''.

Published by Toyota Motor Corporation in December 1986.

The one described on pages 11-50 to 51 is known.

This conventional drum brake auto-adjuster mechanism is
When operating the parking brake, the adjustment lever rotates the adjustment wheel in one direction, extending the entire length of the auto-adjuster mechanism, and automatically adjusting the gap between the brake shoes and the brake drum.

(Problem to be Solved by the Invention) However, in such a conventional drum brake auto-adjuster mechanism, in order to reduce the distance between the brake shoes when removing the brake drum, it is necessary to adjust the adjustment hole on the back plate. The total length of the auto-adjuster mechanism was reduced by inserting two tools such as screwdrivers, using one tool to remove the adjustment lever from the adjustment wheel, and using the other tool to rotate the adjustment wheel in the opposite direction. The problem was that it was bad.

This invention was made by focusing on these conventional problems, and it is possible to easily adjust the gap between the brake drum and the brake shoes, and also to increase the gap between the brake drum and the brake shoes from the back side of the back plate. The object of the present invention is to provide an auto-adjuster mechanism for a drum brake that allows the brake drum to be easily removed.

[Means for Solving the Problems] Accordingly, the drum brake auto-adjuster mechanism according to the present invention has an automatic adjuster mechanism for a drum brake that is arranged between one end side of a pair of brake shoes facing the inner circumferential surface of a brake drum disposed on the front side of a back plate. The drum brake auto-adjuster mechanism is equipped with an adjustment strut whose entire length is extended by an adjustment lever that is linked to the operation of either the service brake or the parking brake when the gap between the brake drum and the brake shoes becomes large. An eccentric cam having an eccentric pin portion on one side of the substrate and a shaft portion with a threaded portion formed at the tip on the other side is provided on the substrate, and the shaft portion of the eccentric cam is connected to the other end of the brake shoe. In the through hole formed in the anchor and back plate that engage from the side,
Rotatably insert the eccentric pin part and the board so that it is on the front side of the back plate and the threaded part is on the back side of the back plate, screw the lock nut onto the threaded part, and attach the adjuster to the eccentric pin part of the eccentric cam. One end of the link is rotatably supported, and the other end of the adjust link is rotatably supported by a support pin provided on one brake shoe, and the end of the adjust strut is attached to a part of the link lever of the adjust link. It is characterized by being configured so that they are engaged with each other.

(Function) When the lock nut screwed into the threaded part of the shaft of the eccentric cam protruding from the back side of the back plate is loosened, the eccentric cam can be rotated using a tool such as a screwdriver.

When the eccentric cam is rotated in one direction, the eccentric cam is rotated in one direction, and the lever of the adjustment link is rotated in one direction, and the opposite ends of the brake shoe are connected via the adjustment strut. The distance between the brake drum and the brake shoe becomes smaller.

Also, when the eccentric cam is rotated in the opposite direction, the eccentric cam rotates in the opposite direction, and a portion of the lever of the adjustment link rotates in the opposite direction, reducing the distance between the opposing ends of the brake shoes. The air gap between the brake drum and brake shoes becomes larger and the brake drum can be easily removed.

〔Example〕 Embodiments of the present invention will be described below with reference to the drawings.

As an example, a description will be given of a leading-trailing type drum brake that automatically adjusts the gap between the brake drum and the brake shoes when the parking brake is operated.

First, to explain the configuration, in Fig. 2, the back plate l fixed to the axle housing (not shown)
A brake drum (not shown) that rotates in the A direction when moving forward with respect to the back plate 1 is arranged on the front side of the back plate 1, and a leading shoe 2 and a trailing shoe 3 are arranged opposite to the inner peripheral surface of this brake drum. Ru. A wheel cylinder 4 is arranged between the ends of the two shoes 2.3 on one side (upper part of the figure), and the diameters of the two shoes 2, 3 are reduced by a return spring (not shown). , the shoes 2.3 are biased in a direction that separates the two shoes 2.3 from the brake drum.

In FIGS. 1 and 2, the other ends of the shoes 2 and 3 on the opposite side from the wheel cylinder 4 (lower part in FIG. 2) are connected to anchors 6 fixed to the back plate l via the retainer plate 5. engaged.

This back plate 1. Through holes 1a, 5a and 6a are formed in the retainer plate 5 and the anchor 6, respectively.

Also, the eccentric cam 7 is made up of a substrate 7a, an eccentric pin portion 7b fixed to one surface of the substrate 7a, and a shaft portion 7d fixed to the other surface of the substrate 7a and having a threaded portion 7c at its tip.
is formed, and the eccentric pin portion 7b of the eccentric cam 7 is connected to the shaft portion 7.
It is eccentric with respect to d.

The shaft portion 7d of the eccentric cam 7 is connected to the through hole 1a formed in the back plate 1, retainer plate 5, and anchor 6.
, 5a and 6a, the base plate 7a and the eccentric pin part 7b of the eccentric cam 7 are located on the front side of the anchor 6, which is the front side of the back plate 1, and the threaded part 7c of the eccentric cam 7 is , protrudes from the back side of the back plate 1. After the lock nut 8 is screwed into this threaded portion 7C and the eccentric cam 7 is rotated, the eccentric cam 7 can be fixed at an appropriate position.

Note that the end face of the tip of the threaded portion 7C of the eccentric cam 7 has a (-) groove (-) for rotating the eccentric cam 7 with a driver.
Alternatively, it may be a (+) groove. ) 7e is formed to rotate the eccentric cam 7 from the back side of the back plate 1.

In FIG. 2, a support pin 10 is fixed to one end of the leading shoe 2 that engages with the wheel cylinder 4, and one end of an adjustment link 11 is rotatably attached to the support pin 10. This adjustment link 11 extends downward along the leading shoe 2, and the other end of the adjustment link 11 is rotatably attached to the eccentric pin portion 7b of the eccentric cam 7. Also, adjust link 11
A short link lever part 11a is attached to the end of the support pin 10 side.
is formed, and the engaging portion 11b of this link lever part 11a
One end of the adjustment strut 12 (leading shoe 2 side) is engaged with the adjustment strut 12, and the other end of the adjustment strut 12 is engaged with a retaining portion 3a formed at the end of the trailing shoe 3 on the wheel cylinder 4 side. There is.

The adjustment strut 12 has a ratchet wheel 13 that engages an adjustment lever portion 14a of the parking brake lever 14.

Next, the operation of the above embodiment will be explained.

1 and 2, the lock nut 8 screwed onto the threaded portion 7c at the tip of the shaft portion 7d of the eccentric cam 7 protruding from the back side of the back plate 1 is loosened, and a (- ) When a screwdriver as a tool is inserted into the groove 7e and rotated counterclockwise, for example, the eccentric cam 7 rotates in the direction B. As a result, the adjustment link 11 rotates about the support pin 10, and the link lever portion 11a of the adjustment link 11 rotates in the C direction, thereby connecting the engagement portion 11b of the adjustment strut 12 and the shoes 2, 3. The distance from the support pin 10 increases. For this reason, leading shoe 2
The distance between the shoe 2.3 and the trailing shoe 3 becomes larger, and the gap between the shoe 2.3 and the brake drum becomes smaller. If the lock nut 8 is tightened in this state, the auto-adjust mechanism will be in its normal operating state.

If you continue to use the brake in this condition, the lining attached to the shoe 2.3 and the inner surface of the brake drum will wear out, and the gap between the brake drum and the shoe 2.3 will become larger, causing the problem when you operate the parking brake. , the adjustment lever part 14a of the parking brake lever 14 rotates the ratchet wheel 13 of the adjustment strut 12 by one tooth, and the entire length of the adjustment strut 12 is extended, thereby increasing the gap between the brake drum and the shoes 2 and 3. becomes smaller and automatically adjusts the air gap.

Further, if the shaft portion 7d of the eccentric cam 7 is rotated in the right direction with the lock nut 8 loosened, the eccentric cam 7 will rotate in the opposite direction B, and the link lever portion 11a of the adjustment link 11 will be rotated.
rotates in the counter-C direction, and the gap between the leading shoe 2 and the trailing shoe 3 becomes smaller. This increases the gap between the brake drum and the shoe 2.3, allowing the brake drum to be easily removed.

In the embodiment described above, the eccentric cam 7 having the base plate 7a, the eccentric pin part 7b, the threaded part 7c, and the shaft part 7d having the (-) groove 7e may be formed by fixing each part as separate parts and integrating them. Of course, it may be formed integrally in advance.

Moreover, although the case where the adjustment link 11 is provided on the leading shoe 2 side is illustrated, it may be provided on the trailing shoe 3 side.

Furthermore, although the example is applied to a leading-trailing type drum brake that automatically adjusts the parking brake when operating the parking brake, the present invention is applicable to a two-leading type or duo-servo type drum brake. The present invention is applicable to an auto-adjuster mechanism having an adjustment strand that operates when the service brake is released or when the service brake is operated or released.

〔Effect of the invention〕

As explained above, according to the drum brake auto-adjuster mechanism according to the present invention, in the drum brake auto-adjuster mechanism equipped with an adjustment strut, the eccentric pin portion is provided on one side of the substrate, and the eccentric pin portion is provided on the other side of the substrate. An eccentric cam having a shaft portion with a threaded portion formed at the tip is provided, and the shaft portion of the eccentric cam is inserted into a through hole formed in an anchor and a back plate that engages with the other end of the brake shoe, and an eccentric pin portion is inserted into the through hole formed in the back plate. Insert the circuit board rotatably so that the board is on the front side of the back plate and the threaded part is on the back side of the back plate, screw the lock nut onto the threaded part, and attach one end of the adjustment link to the eccentric pin part of the eccentric cam. At the same time, the other end of the adjustment link is rotatably supported by a support pin provided on one brake shoe, and the end of the adjustment strut is engaged with the link lever part of the adjustment link. Because of this structure, the gap between the brake drum and brake shoes can be easily adjusted from the back side of the back plate, and the gap can be enlarged to easily remove the brake drum. Even if the sliding surface of the surface becomes worn and the brake shoe becomes jammed, the effect is that the brake drum can be easily removed.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view taken along the I-T line in FIG. 2 showing essential parts of an embodiment of an auto-adjuster mechanism for a drum brake according to the present invention, and FIG. 2 is a front view showing the entire drum brake. . 1... Back plate, la, 6a... Through hole, 2
...Leading shoe (brake shoe), 3...
・Trailing shoe (brake shoe), 6... Anchor, 7... Eccentric cam, 7a... Board, 7b...
・Eccentric pin part, 7c...Threaded part, 7d...Shaft part, 7
e...(-) groove, 8...lock nut, 10...
Support pin, 11 Adjustment link, lla... Link lever part, 12... Adjustment strut, 14...
・Parking brake lever 14a... Part of the adjustment lever (adjustment lever).

Claims (1)

[Claims] When a gap between the brake drum and the brake shoe becomes large between opposing ends of a pair of brake shoes facing the inner peripheral surface of the brake drum disposed on the front side of the back plate. In an auto-adjuster mechanism for a drum brake equipped with an adjustment strut whose entire length is extended by an adjustment lever linked to the operation of either the service brake or the parking brake, the drum brake has an eccentric pin portion on one side of the substrate and the other side has an eccentric pin portion. An eccentric cam having a shaft portion with a threaded portion formed at the tip on the surface side, and the shaft portion of the eccentric cam is connected to an anchor with which the other end side of the brake shoe engages and a through hole formed in the back plate. , the eccentric pin part and the board are rotatably inserted so that they are located on the front side of the back plate and the threaded part is located on the back side of the back plate, and a lock nut is screwed into the threaded part, One end of an adjustment link is rotatably supported on the eccentric pin portion of the eccentric cam, and the other end of the adjustment link is rotatably supported on a support pin provided on one side of the brake shoe. An auto-adjuster mechanism for a drum brake, characterized in that the end of the adjusting strut is engaged with a link lever portion of a link.