JPH032027Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an improvement of a drum brake with automatic shoe clearance adjustment.

Prior Art A pair of brake shoes that are expandably provided on a bucking plate, a wheel cylinder that is provided on the bucking plate between one end of each brake shoe, and a star wheel are provided on both brake shoes. A strut spans between the brake shoes and supports the brake shoes from the inner circumferential side in notches formed at both ends, and extends as the star wheel rotates in one direction, and the brake shoes a return spring that constantly biases the brake shoe in a diameter-reducing direction; a parking brake lever that is rotatably attached by a pin that protrudes at one end into a through hole formed in one of the brake shoes; and the star wheel. an adjusting member having a pawl portion at one end that engages with the outer teeth of the strut, and the other end being rotatably provided on the one brake shoe by the pin while the intermediate portion is inserted into the notch of the strut. A drum brake with automatic shoe clearance adjustment is known.

In such drum brakes, the shoe gap is usually adjusted by rotating an adjusting member not only when braking by the wheel cylinders but also when operating the parking brake. However, the pin protruding from the parking brake lever is usually fitted into the through hole of the brake shoe with a predetermined play, and the adjusting member is usually inserted into the parking brake lever with the brake shoe in between. Since the adjusting member is attached to the protruding end of the pin at a position opposite to the parking brake lever, the pin falls down when the parking brake lever is rotated, and due to the falling of the pin, the adjustment member cannot be rotated accurately. As a result, there were cases where the shoe gap could not be adjusted accurately.

For this reason, the above-mentioned problem has conventionally been solved by providing a parking brake lever on one brake shoe and an adjustment member on the other brake shoe.

Problems to be Solved by the Invention However, in this case, a pin etc. for rotatably attaching the adjustment member to the other brake shoe is usually required, which increases the number of parts and increases the number of parts. However, there has been a problem in that the number of man-hours required for attaching the adjustment member increases.

Means for Solving the Problems The present invention was developed against the background of the above-mentioned circumstances, and its gist is that the backing plate is provided in an expandable manner, and that the A pair of brake shoes each having a through hole formed therein, a wheel cylinder provided on the bucking plate between each end of the brake shoes, and a star wheel, which is bridged between the two brake shoes. , a strut that supports the brake shoes from the inner circumferential side in notches formed at both ends and expands as the star wheel rotates in one direction; a return spring for biasing; a parking brake lever rotatably attached to one of the brake shoes in the through hole; and a pawl portion at one end that engages with outer peripheral teeth of the star wheel; is inserted into the notch of the strut, and an adjustment member rotatably provided at the other end of the brake shoe, when the brake shoe is expanded or contracted by the wheel cylinder. When the adjustment member is rotated in one direction, the claw portion of the adjustment member passes over the outer teeth of the star wheel, and the star wheel is rotated in the one direction during subsequent diameter reduction or expansion. In the drum brake with an automatic shoe gap adjustment type, a protrusion is integrally molded on the other end of the adjustment member, and the protrusion is fitted into the through hole formed in the other brake shoe, while the return spring One end of the adjustment member is hooked onto the adjustment member.

Operation and Effects of the Invention With this method, after the protrusion of the adjustment member is simply fitted into the through hole conventionally formed in the other brake shoe, the protrusion of the adjustment member is By simply inserting the adjusting member into the notch of the strut together with the brake shoe, the adjustment member can be rotated around the protrusion and easily attached to the other brake shoe while the protrusion is prevented from coming out of the through hole. On the other hand, by hooking one end of a return spring to the adjustment member, the adjustment member is urged in a predetermined rotational direction by the urging force of the return spring. As a result, when the adjustment member is installed on a brake shoe separate from the parking brake lever, there is no need for a pin etc. to rotatably attach the adjustment member to the brake shoe, reducing the number of parts compared to conventional methods. Also, the number of man-hours required for installing the adjustment member can be reduced.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing the main parts of a drum brake with automatic shoe gap adjustment to which the present invention is applied, in which a pair of brake shoes 12 and 14 are mounted on a bucking plate 10 and their shoe webs 16 and 18 are connected to each other.
They are supported so as to be expandable with respect to each other by shew hold down devices 20 and 22. One end of each of the brake shoes 12, 14 facing each other is engaged with both ends of a wheel cylinder 24 fixed on the bucking plate 10, and the other end of each of the brake shoes 12, 14 is engaged with both ends of a wheel cylinder 24 fixed on the bucking plate 10. are brought into contact with both sides of the anchor 26 fixed on the bucking plate 10, respectively. A strut device 28 is spanned between the two shew webs 16 and 18 at one end of each of them. This strut device 28 constitutes the strut of this embodiment.

The strut device 28 includes the first strut member 3
0 and a second strut member 32 and a member 36 having a star wheel 34. A female threaded hole (not shown) is formed in the first strut member 30, and a male threaded portion of a male threaded member 36 is screwed into the female threaded hole. On the other hand, a fitting hole (not shown) is formed in the second strut member 32, and a shaft portion that holds the star wheel 34 of the male threaded member 36 and projects on the opposite side from the male threaded portion is inserted into the fitting hole. They are fitted so that they can rotate relative to each other with a predetermined rotational resistance applied. Strut device 28
, that is, both strut members 30, 32
As shown in FIG. 2, at each end opposite to the side connected by the male threaded member 36, there is a notch 3 cut out from each tip to a predetermined depth.
8 and 40 are formed, and a shoe web 18 of the brake shoe 14 and a parking brake lever 44, which will be described later, are respectively fitted into the cutout 38, and a shoe web 16 and a parking brake lever 44 of the brake shoe 12 are fitted into the cutout 40, respectively. The intermediate portions of adjustment members 46, which will be described later, are respectively fitted. As a result, both brake shoes 12 and 14 are mutually supported from the inner circumferential side by the strut device 28, and by rotating the star wheel 34 in one direction, the male threaded member 36
The second strut member 32 and the first strut member 30 are moved relative to each other in a direction away from each other, so that the strut device 28 is extended.

In one brake shoe 14, a pin 42 protruding from one end is fitted into a through hole (not shown) formed at the end of the shoe web 18 on the wheel cylinder 24 side in a state where it is prevented from coming off. The parking brake lever 4 has a parking cable (not shown) connected to its other end.
4 is rotatably attached.

An adjustment member 46 is rotatably provided at the end of the other brake shoe 12 on the wheel cylinder 24 side. The adjustment member 46 has a generally L-shaped plate shape as a whole, and a claw portion 48 formed at one end thereof is engaged with the outer circumferential teeth of the star wheel 34, and a third end portion is formed at the other end. As shown in FIG. 3, a cylindrical projection 50 is integrally protruded by burring. Then, the protrusion 50 is fitted into the through hole 52 formed in the shoe web 16 of the brake shoe 12 at a position symmetrical to the through hole of the brake shoe 14 with the wheel cylinder 24 in between. 46
is attached to the brake shoe 12 so as to be rotatable about the axis of the protrusion 50. The brake shoes 12 and 14 are usually molded in substantially the same shape, and the through hole 52 of the brake shoe 12 has been previously formed. Further, in a portion of the adjustment member 46 located slightly on the claw portion 48 side from the protrusion 50, a show web 16 is provided.
A projection 54 is formed by being bent at a predetermined distance from
is installed. This return spring 56
As a result, the adjustment member 46 is constantly rotated in the counterclockwise direction in FIG. Brake shoe 1 is energized and
One end side of each of 2 and 14 is constantly biased in the diameter reduction direction. In addition, 58 is the brake shoe 12, 14
This is a return spring that constantly biases each other end side in the diametrical direction.

In the drum brake configured as described above, when the parking brake lever 44 is rotated clockwise in FIG. 1 by the parking cable, the strut device 28 is moved to the left in the figure and the brake shoe 12 is pushed out to the outer circumferential side, and the pin 42 is rotated clockwise in the figure using the bottom of the notch 38 formed in the first strut member 30 as a fulcrum, thereby pushing the brake shoe 14 to the outer circumferential side. As a result, both brake shoes 12 and 14 are pressed against a rotating drum (not shown). At this time, as the strut device 28 moves to the left in FIG.
2, the shoe gap adjustment operation is not performed.

On the other hand, during braking with the service brake, when the brake shoes 12 and 14 are expanded by the wheel cylinder 24, the adjustment member 46 directs the strut device 28 toward the brake shoe 14 according to the biasing force of the return spring 56. Once upon a time (1st
It is rotated counterclockwise in the figure while being pushed (rightward in the figure). The amount of rotation of the adjustment member 46 increases as the amount of wear on the brake shoes 12, 14 increases, and when the amount of wear on the brake shoes 12, 14 exceeds a predetermined limit, the amount of rotation of the adjustment member 46 increases. , 14, the claw portion 4 of the adjusting member 46
8 rides over one outer peripheral tooth of the star wheel 34, and when the brake shoes 12 and 14 are subsequently expanded by the wheel cylinder 24, the star wheel 3
4 is rotated by a predetermined amount in the one direction, the strut device 28 is expanded. The shapes of the outer peripheral teeth of the star wheel 34 and the claw portions 48 of the adjusting member 46 are formed in this manner in advance. As a result, the brake shoe 1
The return positions of brake shoes 2 and 14 are updated in the outer circumferential direction, and the gap (shoe gap) between brake shoes 12 and 14 and the rotating drum is automatically adjusted.

Here, FIG. 4 shows an example of a conventional shoe gap automatic adjustment type drum brake. In the following description, the same parts as in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the figure, the adjustment member 70 has a longitudinal plate shape, and the end opposite to the claw portion 72 is connected to the show web 1.
It is rotatably attached to a pin 74 protruding from 6. A protrusion 76 that protrudes toward the end of the brake shoe 12 on the wheel cylinder 24 side is provided at the intermediate portion of the adjustment member 70, and this protrusion 76 is fitted into the notch 40. Between the intermediate part of the adjustment member 70 and the part of the shew web 16 located on the anchor 26 side, there is a
A spring 78 is tensioned to constantly bias the adjustment member 70 clockwise in the figure, and the return spring ring 56 is attached to both brake shoes 1.
It is installed between 2 and 14. In this case as well, when the brake shoes 12, 14 are expanded by the wheel cylinder 24, the adjustment member 70 moves the strut device 28 to the right in FIG. Based on the fact that it is pushed and rotated clockwise in the figure, the shoe gap is adjusted in substantially the same manner as in the case described above. However, in such a conventional drum brake with automatic shoe gap adjustment, the pin 74 is required, and it is also necessary to separately form a through hole in the shoe web 16 for protruding the pin 74. In addition, since it is usually desirable to arrange the return spring 56 on the outer circumferential side of the bucking plate 10 due to space considerations,
A separate spring 78 as described above is required. For this reason, the number of parts is relatively large, and the work of attaching the adjustment member 70 requires a relatively large number of man-hours.

On the other hand, according to this embodiment, the through hole 52 conventionally formed in the brake shoe 12 has a
After simply fitting the protrusion 50 integrally protruding into the adjusting member 46, the intermediate portion of the adjusting member 46 is simply fitted into the notch 40 of the strut device 28, and the adjusting member 46 is then fitted to the brake shoe 12. The adjustment member 46 can be easily attached to the adjustment member 46 by simply hooking one end of the return spring 56 similar to the conventional one to the protrusion 54 of the adjustment member 46.
Since a rotational force is applied to a predetermined rotational direction,
It is no longer necessary to separately provide through holes in the pin 74, spring 78, and brake shoe 12 as in the conventional case, and the number of parts and adjustment member 46 are reduced.
The installation work time is reduced.

In the above-mentioned embodiment, the protrusion 50 is formed into a cylindrical shape by burring, but it is not necessarily necessary to do so. For example, it may be formed into a cylindrical shape with a bottom by drawing, or it may be formed into a semi-cylindrical shape. It may be cut up into a shape.

Further, in the above-mentioned embodiment, a so-called positive type is shown in which the shoe gap is automatically adjusted when the brake shoes 12 and 14 are expanded. The shape and the engagement position between the claw portion 48 and the star wheel 34 are appropriately determined, and the male threaded member 36
If the thread direction of the male threaded portion is formed in the opposite direction to that of the above-described embodiment, it is also possible to obtain a negative-type shoe gap automatic adjustment type drum brake.

Further, in the above-mentioned embodiments, a leading-trailing type drum brake has been described, but it goes without saying that the present invention can also be applied to other drum brakes, such as a dual-leading type drum brake.

In addition, various changes may be made to the present invention without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a front view showing the main parts of an automatic shoe gap adjustment type drum brake to which the present invention is applied.
FIG. 2 is a cross-sectional view showing the main parts of FIG. 1. FIG. 3 is an enlarged view showing a main part of a cross section taken along the line - in FIG. 1. FIG. 4 is a diagram showing the main parts of a conventional shoe gap automatic adjustment type drum brake,
2 is a diagram corresponding to FIG. 1. 10...Backing plate, 12, 14...
Brake shoe, 24...Wheel cylinder, 2
8... Strut device, 34... Star wheel, 38, 40... Notch, 44... Parking brake lever, 46... Adjustment member, 48... Claw portion, 50... Protrusion, 52... Through hole, 56 ...Return spring.

Claims (1)

[Claims for Utility Model Registration] A pair of brake shoes that are expandably provided on a bucking plate and have through holes formed at one end of each pair facing each other; It has a wheel cylinder provided on the bucking plate and a star wheel, which spans between the brake shoes, and supports the brake shoes from the inner circumferential side in notches formed at both ends. a strut that expands as the star wheel rotates in one direction; a return spring that constantly biases the brake shoe in a radially contracting direction; and a return spring that is rotatably attached to one of the brake shoes in the through hole. a parking brake lever, and a pawl portion at one end that engages with the outer peripheral tooth of the star wheel,
an adjustment member rotatably provided at the other end of the brake shoe with the intermediate portion inserted into the notch of the strut, and when the brake shoe is expanded by the wheel cylinder or When the adjustment member is rotated in one direction during diameter reduction, the claw portion of the adjustment member passes over the outer teeth of the star wheel, and the star wheel is rotated in the one direction during subsequent diameter reduction or expansion. In the drum brake with automatic shoe gap adjustment of the type in which the brake shoe is rotated to A shoe gap automatic adjustment type drum brake, characterized in that one end of a return spring is hooked to the adjustment member.