JPH0722504Y2 - Drum brake with automatic shoe clearance adjuster - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a drum brake having an automatic shoe clearance adjusting device.

2. Description of the Related Art An arcuate brake shoe that has a plate-shaped shoe web and is movably disposed on a backing plate, and one surface of the shoe web that is rotatable about an axis An adjusting member having a large number of engaging teeth formed substantially along an arc centered on the center, and fixed to the brake shoe so as to be engageable with the engaging teeth of the adjusting member, and the adjusting member has only one direction. A plurality of latching teeth that allow rotation of the brake shoe, and the shoe gap is automatically adjusted by rotating the adjustment member in the one direction when the brake shoe moves to the outer peripheral side. A drum brake equipped with an automatic shoe clearance adjusting device has been considered. For example, it is the one described in Japanese Utility Model Laid-Open No. 62-4645 which was filed by the applicant of the present invention and published.

In the drum brake provided with the automatic shoe clearance adjusting device, the engaging teeth engaged with the engaging teeth of the adjusting member are fixed to the inner peripheral surface of the shoe rim of the brake shoe, thereby providing the engaging teeth. Compared with the conventional case in which the latch member is rotatably attached to the brake shoe, there are advantages that the number of parts and the number of assembly work steps are reduced, and the drum brake is provided at a lower cost as a whole.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, even a drum brake equipped with such a shoe clearance automatic adjusting device still has a problem to be solved. That is, the radius of curvature of an arc centered on the uniaxial center on which the engaging teeth of the adjusting member are formed and the radius of curvature of the shoe rim inner peripheral surface on which the hooking teeth are formed are usually significantly different. Since it is difficult to secure a sufficient number of meshing engagement teeth with the latching teeth of the shoe rim, it is relatively difficult to rotate the adjusting member in a direction in which the rotation is blocked when the parking brake is operated. When a large force is applied, the engaging teeth and the retaining teeth may be deformed or damaged.

On the other hand, for example, as described in Japanese Utility Model Application Laid-Open No. 1-80940 filed by the applicant of the present application, a large number of engaging teeth are provided on the surface of the adjusting member opposite to one surface of the shoe web. By providing a large number of latching teeth that can be engaged with the engaging teeth at positions corresponding to the engaging teeth on one surface of the shoe web, the latching member provided with the engaging teeth can be rotated around the brake shoe. It is possible to reduce the number of parts and the number of assembling steps as compared with the conventional case in which the engaging teeth and the latching teeth can be suitably secured, and the engaging teeth and the latching teeth can be secured. It is thought that the strength can be improved, but there is still room for improvement even in this case. That is, in order to securely engage the engaging teeth and the hooking teeth, it is necessary to attach an urging means such as a leaf spring for urging the adjusting member to one side of the shoe web to the brake shoe. If the members constituting the biasing means can be provided integrally with a conventional member without separately providing them, the number of parts of the drum brake and the number of assembling steps can be further reduced.

The present invention has been made in view of the above circumstances, and its purpose is to provide a drum provided with an automatic shoe clearance adjusting device of the type described in Japanese Patent Application No. 1-80940. In the brake, the number of parts and the number of assembling work can be further reduced without separately providing the urging means.

Means for Solving the Problems In order to achieve the above object, the present invention has arcuate brake shoes having a plate-shaped shoe web and arranged on a backing plate, and the shoe web and the backing plate. And a shoe hold down device for movably supporting the brake shoe on the backing plate, and one surface of the shoe web rotatably provided around one axis and facing the one surface of the shoe web. An adjusting member having a large number of engaging teeth formed substantially along an arc centered on the axis of the adjusting member, and a position corresponding to the engaging teeth of the adjusting member on one surface of the shoe web. A large number of latching teeth, which are fixed substantially along an arc centered on one axis and allow the adjusting member to rotate in only one direction based on the engagement with the engaging teeth, and the adjusting member. Shu An urging means for urging the engaging teeth and the latching teeth to engage with each other on one surface side of the web, and the adjusting member is rotated in the one direction when the brake shoe is moved to the outer peripheral side. In a drum brake provided with a shoe gap automatic adjusting device of a type in which the shoe gap is automatically adjusted by being actuated, the urging means is provided integrally with a member constituting the shoe holddown device. .

In this way, the biasing means for biasing the adjusting member to one side of the shoe web of the brake shoe to engage the engaging tooth of the adjusting member and the latching tooth of the shoe web with each other is provided. ,
Since it is provided integrally with a member that constitutes the shoe hold-down device provided between the shoe web and the backing plate, compared to the case where the member that constitutes such biasing means is provided separately, the drum It is possible to further reduce the number of brake parts and the number of assembly work steps.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing an essential part of a drum brake equipped with an automatic shoe clearance adjusting device to which the present invention is applied. On a backing plate 10, a pair of arcuate brake shoes 12 and 14 are provided. They are supported by the shoe hold down devices 16 and 18 so as to be capable of expanding relative to each other at an intermediate portion in the longitudinal direction. The brake shoes 12 and 14 are plate-shaped shoe rims 20 and 22 that are bent in an arc shape, and plate-shaped shoes that project from the inner peripheral surfaces of the shoe rims 20 and 22 and are positioned substantially parallel to the backing plate 10. The shoe fold down devices 16 and 1 are configured to have webs 24 and 26 and linings 28 and 30 fixed to the outer peripheral surfaces of the shoe rims 20 and 22, respectively.
Numeral 8 is composed of shoe hold down pins 32 and 34 slidably projected on the backing plate 10 and U-shaped leaf springs, and is arranged on the side opposite to the backing plate 10 side of the shoe webs 24 and 26. Shoe Hold Down Spring 38,4
0 and, respectively, the shoe web 24,
The shoe hold down springs 38, 40 are preloaded between the heads of the shoe hold down pins 32, 34 and the shoe webs 24, 26, which pass through the shoe 26 and the shoe hold down springs 38, 40, respectively. Shoe web 2
The opposite ends of 4, 26 are respectively brought into contact with the side surfaces of the anchors 42 fixed on the backing plate 10, and the other ends of the shoe webs 24, 26 are fixed on the backing plate 10. The two ends of the wheel cylinder 4 are engaged with each other. Incidentally, 46 is a shoe return spring. In such a drum brake, the brake shoes 12 and 14 are pushed toward the outer peripheral side against the biasing force of the shoe return spring 46 by the wheel cylinder 44 and are pressed against the inner peripheral surface of the rotating drum (not shown). The rotation of the rotary drum is suppressed, and braking by the service brake is performed.

On one side of the shoe web 24 of the brake shoe 12, a parking brake lever 50 having a long plate shape and having a parking cable 48 connected at one end is pinned at the other end.
It is rotatably attached by 52. As shown in FIGS. 1 and 2, on one surface 53 of the other brake shoe 14 opposite to the backing plate 10 side of the shoe web 26, as shown in FIGS.
The adjustment member 54 is
The engagement with the shoe web 26 allows rotation in one direction (clockwise direction in FIG. 1) but prevents rotation in the opposite direction. That is, on the other end side of the adjusting member 54 and on the surface opposite to the one surface 53 of the shoe web 26, a large number of engaging teeth 58 are formed substantially along an arc centered on the axial center of the pin 56. Is formed and the shoe web 26
A large number of retaining teeth 60 are formed at positions corresponding to the engaging teeth 58 on the one surface 53 substantially along an arc centered on the axial center of the pin 56. On the other hand, the shoe hold down spring 40 of the shoe hold down device 18 on the side of the brake shoe 14 has a pair of facing portions 62 and 64 facing each other, as shown in FIG.
A connecting portion 66 that connects the facing portions 62 and 64 to each other, and a connecting portion 66 that extends for a predetermined distance from the end of one facing portion 64 that abuts the one surface 53 of the shoe web 26 to the other facing portion 62 side and at the tip thereof. An extension 68 extending a predetermined distance in a direction away from
With the extension portion 68, the other end side (engaging tooth 58 side) of the adjusting member 54 is provided on one surface of the shoe web 22 by the extending portion 68.
As the engaging teeth 58 of the adjusting member 54 and the latching teeth 60 of the shoe web 26 are pressed against 53 by a predetermined pressing force, the adjusting member 54 is rotated clockwise in FIG. Movement is allowed but rotation in the counterclockwise direction is blocked. The shapes of the engaging teeth 48 and the latching teeth 50 are previously determined as such. Therefore, in the present embodiment, the shoe hold down spring 40 corresponds to the member constituting the shoe hold down device in the claim, and
The extending portion 68 corresponds to the urging means.

As shown in FIG. 1, between the brake shoes 12 and 14, the shoe web 24 and the parking brake shoe 50, and the shoe web 26 and the adjusting member 4 are respectively provided in notches (not shown) formed at both ends. The strut 70 is bridged in a sandwiched state, and when not braking, the bottom surface of one notch of the strut 70 and the side end surface of the shoe web 24 abut, and the bottom surface of the other notch of the strut 70 and the adjusting member. Due to the contact with the side end surface of 54, the diameter reduction of the brake shoes 12, 14 beyond a certain limit due to the urging force of the shoe return spring 46 is prevented. When the parking cable 48 is pulled in and the parking brake lever 50 is rotated counterclockwise in FIG. 1, the strut 70 is pushed toward the brake shoe 14 side, and the brake shoe 14 is moved through the adjusting member 54 and the like. Is pushed toward the outer peripheral side and pressed against the inner peripheral surface of the rotary drum, and the brake shoe 12 is pushed toward the outer peripheral side via the pin 52 and pressed against the inner peripheral surface of the rotary drum, whereby braking by the parking brake is performed. Done. At this time, a relatively large force acts on the engaging teeth 58 of the adjusting member 54 and the engaging teeth 60 of the shoe web 26 in accordance with the parking brake operating force. Since a large number of meshing with 60 is secured, the engaging teeth 58
Also, the latching teeth 60 are preferably prevented from being deformed or damaged.

The strut 70 is constantly urged toward the brake shoe 12 by the tension coil spring 72, and is moved in the direction away from the brake shoe 14 together with the brake shoe 12 during braking by the service brake. At this time, as the linings 28, 30 of the brake shoes 12, 14 are worn, the adjusting member 54 is rotated clockwise by the end of the strut 70 in FIG. When the distance (shoe gap) between them exceeds a predetermined amount, the engaging tooth 58 of the adjusting member 54 passes over one latching tooth 60 of the shoe web 26 and the return rotational position of the adjusting member 54. Is updated in the clockwise direction in FIG. 1 by a predetermined amount, the reduced diameter positions (return positions) of the brake shoes 12, 14 are updated by a predetermined amount on the outer peripheral side, and the increased shoe gap is automatically adjusted. . When the adjusting member 54 is rotated in the shoe gap adjusting direction, the shoe hold down spring 40 may be continuously rotated together with the adjusting member 54. However, the connecting portion 66 of the shoe hold down spring 40 and the shoe rim 22 of the brake shoe 14 may be rotated. Such continuous rotation is prevented by the contact with the inner peripheral surface of the.

As described above, according to this embodiment, the biasing force of the adjusting member 54 toward the one surface 53 side of the shoe web 26 and the engaging tooth 58 of the adjusting member 54 and the engaging tooth 60 of the shoe web 26 are engaged with each other. Since the extending portion 68 as a means is integrally formed with the shoe hold down spring 40 which has been conventionally provided,
The number of parts of the drum brake and the number of man-hours for assembling can be reduced as compared with the case where the members constituting such biasing means are provided separately.

Further, according to the present embodiment, the shoe hold down spring is based on the contact between the connecting portion 66 of the shoe hold down spring 40 and the inner peripheral surface of the shoe rim 22 of the brake shoe 14.
Since it is possible to prevent the 40 from being continuously rotated together with the adjusting member 54, there is an advantage that it is not necessary to separately provide a continuous rotation preventing means.

Incidentally, in the above-mentioned embodiment, the adjusting member 54 and the latching tooth 60
Is provided on one surface 53 of the shoe web 26 opposite to the backing plate 10 side, that is, on the surface of the shoe web 26 on which the shoe hold down spring 40 is disposed. As shown in the drawing, the adjusting member 54 and the latching tooth 60 are provided on one surface 74 of the shoe web 26 on the backing plate 10 side (the surface of the shoe web 26 opposite to the side on which the shoe hold down spring 76 is disposed). Even when provided, the present invention can be applied.
In this case, for example, from the end portion of the one facing portion 62 of the shoe hold down spring 76 that does not contact the shoe web 26 and that is located on the inner peripheral side of the shoe web 26, the backing plate than the shoe web 26 is provided. An extension portion 78 is provided that extends a predetermined distance toward the 10 side and extends a predetermined distance in a direction away from the connecting portion 66 at its tip, and the extension member 78 presses the adjusting member 54 against the one surface 74 of the shoe web 26.

Further, in the above-mentioned embodiment, the case where the urging means is integrally provided to the shoe hold down spring formed of a U-shaped plate spring has been described, but it is not always necessary.
For example, it is possible to integrally provide the biasing means on the cup of the shoe holddown device having the compression coil spring and the pair of cups arranged on both sides in the axial direction thereof.

In addition, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a drum brake provided with an automatic shoe clearance adjusting device to which the present invention is applied. Second
The drawing is an enlarged view of a main part of a cross section taken along line II-II in FIG.
FIG. 3 is a view showing another example of the present invention and is a view corresponding to the main part of FIG. FIG. 4 shows IV-IV in FIG.
It is a figure which shows the principal part of a visual cross section, and is a figure corresponded to FIG. 10: Backing plate 14: Brake shoe 18: Shoe hold-down device 26: Shoe web 40,76: Shoe hold-down spring 53, 74: One side 54: Adjusting member 58: Engaging tooth 60: Latching tooth 68, 78: Extending Departure (biasing means)

Claims (1)

[Scope of utility model registration request] 1. An arc-shaped brake shoe having a plate-shaped shoe web, the arc-shaped brake shoe disposed on a backing plate, and provided between the shoe web and the backing plate.
A shoe hold down device for movably supporting the brake shoe on the backing plate, and a rotatably provided uniaxially rotatable member on one surface of the shoe web, the surface being opposite to the one surface of the shoe web. An adjusting member having a large number of engaging teeth formed substantially along an arc centered on the one axial center, and the one axial center at a position corresponding to the engaging teeth of the adjusting member on one surface of the shoe web. A large number of latching teeth, which are fixed along a circular arc as a center and allow the adjusting member to rotate only in one direction based on the engagement with the engaging teeth, the adjusting member and the shoe web. Urging means for urging the engaging teeth and the latching teeth to engage each other by moving the adjusting member to rotate in the one direction when the brake shoe moves to the outer peripheral side. The type that the shoe clearance is automatically adjusted by In drum brake equipped with an automatic shoe clearance adjustment device, drum brake equipped with an automatic shoe clearance adjustment device, characterized in that provided integrally with the urging means to the members constituting the shoe Hol de down device.