JPH0720427Y2 - Drum brake with automatic shoe clearance adjustment - 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 mechanism.

2. Description of the Related Art A pair of brake shoes having arcuate and plate-shaped shoe webs, and one of the pair of brake shoes are rotatably provided, and the pair of brake shoes are rotated based on a parking brake operation force. A parking lever that expands the brake shoes relative to each other, an adjusting member that is rotatably provided on one of the brake shoes and that is rotated with the rotation of the parking lever, and one of the brake shoes and the adjusting member. And a tension coil spring that urges the adjustment member in a rotation direction opposite to the parking operation direction of the parking lever.
There is known a drum brake equipped with a shoe gap automatic adjustment mechanism of a type that automatically adjusts the shoe gap based on the rotation of the adjusting member. Those described in Japanese Utility Model Laid-Open No. 62-81737, which was previously filed and published by the present applicant, are such examples.

Further, in a kind of drum brake having such a shoe gap automatic adjusting mechanism, at least a part of the coil portion of the tension coil spring is located on the plate surface of the shoe web of the one brake shoe when not braking. At the same time, when the parking brake is braked, the coil portion of the tension coil spring is pressed against the plate surface of the shoe web while being extended with the rotation of the adjusting member and is positioned on the plate surface of the shoe web of the coil portion. There is a structure in which a part of the portion is configured to be moved to the inner peripheral side of the inner peripheral edge of the shoe web.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the drum brake including the shoe clearance automatic adjusting mechanism configured as described above, for example, the coil portion of the tension coil spring is pressed against the plate surface of the shoe web during braking of the parking brake. While being stretched and a part of the portion of the coil portion located on the plate surface of the shoe web is moved to the inner peripheral side from the inner peripheral edge of the shoe web, a portion of the coil portion is The coil portion and the corner portion on the inner peripheral side of the shoe web may be strongly rubbed with each other by being pressed against the plate surface and coming off from the inner peripheral edge of the shoe web, and a relatively large rubbing noise may be generated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coil portion of a tension coil spring in a drum brake including the automatic shoe clearance adjusting mechanism configured as described above. And to prevent or suppress the friction noise between the inner peripheral corners of the shoe web.

Means for Solving the Problems To achieve the above object, the present invention provides a pair of brake shoes having arcuate and plate-shaped shoe webs, and one of the pair of brake shoes is rotatably provided. , A parking lever that expands the two brake shoes relative to each other by being rotated by the parking brake operation force, and one of the brake shoes that is rotatably provided, and rotates with the rotation of the parking lever. And an adjustment member that has a coil portion and is stretched between one of the brake shoes and the adjustment member, and urges the adjustment member in a rotation direction opposite to the brake operation direction of the parking lever. At the time of non-braking, at least a part of the coil portion is located on the plate surface of the shoe web of the one brake shoe and the parking brake is provided. During braking, the coil portion is stretched while being pressed by the plate surface of the shoe web in accordance with the rotation of the adjusting member, and a part of the portion of the coil portion located on the plate surface of the shoe web is the shoe web. In a drum brake equipped with a tension coil spring that is moved to the inner peripheral side of the inner peripheral edge of, and a shoe gap automatic adjustment mechanism that automatically adjusts the shoe gap based on the rotation of the adjustment member, The portion of the coil portion of the tension coil spring that is moved toward the inner peripheral side of the inner peripheral edge of the shoe web of the one brake shoe during extension due to the parking brake braking is the plate of the shoe web during extension. By forming with a diameter smaller than the part located on the surface,
It is characterized in that a predetermined gap is formed between a portion of the coil portion which is moved toward the inner peripheral side from the inner peripheral edge of the shoe web when the parking brake is braked and the plate surface of the shoe web.

With this configuration, the portion of the coil portion of the tension coil spring that is moved toward the inner peripheral side of the inner peripheral edge of the shoe web of the one brake shoe when the coil portion is extended due to the parking brake braking is effective. Abbreviated) is formed with a diameter smaller than the portion located on the plate surface of the shoe web even when it is stretched, so that when the braking is not applied between the moving portion of the coil portion and the plate surface of the shoe web. Since a predetermined gap is formed, when the coil portion of the tension coil spring is stretched while being pressed against the plate surface of the shoe web during parking brake braking, contact between the moving portion of the coil portion and the inner peripheral edge portion of the shoe web Can be avoided to prevent generation of rubbing noise between the coil part and the inner peripheral side corner part of the shoe web, or even if the moving part of the coil part is Minute, the inner peripheral edge of the shoe web comes into contact with each other, and even if a rubbing noise is generated when the moving part of the coil part comes off the inner peripheral corner of the shoe web, the contact pressure can be reduced compared to the conventional case. The amount of rubbing noise can be suppressed.

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. A pair of brake shoes 12 and 14 are arranged on a backing plate 10 so as to face each other. It is set up. These brake shoes
12,14 is a plate-shaped shoe rim 16 bent in an arc shape,
A shoe web 18 that is arcuate and plate-shaped, is provided so as to project on the inner peripheral surface of the shoe rim 16 and is positioned substantially parallel to the plate surface of the backing plate 10, and the lining 19 fixed to the outer peripheral surface of the shoe rim 16. The shoe webs 18 are supported by shoe shoe down devices 20, 22 so that they can be expanded. Brake shoes 12,1
The opposite end portions of the shoe webs 18 of 4 are respectively brought into contact with the side surfaces of the anchors 24 fixed on the backing plate 10, and the other end portions of the shoe webs 18 of the brake shoes 12, 14 are backing plates. It is engaged with both ends of a wheel cylinder 26 fixed on the wheel 10. Then, the brake shoes 12 and 14 are extruded toward the outer peripheral side by the wheel cylinder 26 and pressed against the inner peripheral surface of the rotating drum (not shown), whereby the braking by the service brake is performed.

A parking lever 28 is rotatably attached to a plate surface of the shoe web 18 of the brake shoe 12 on the backing plate 10 side by a pin 30 at one end thereof, and a parking lever is attached to the other end of the parking lever 28. cable
32 are connected. A strut device is provided between the longitudinal middle portion of the parking lever 28 and the shoe web 18 of the brake shoe 12 and the shoe web 18 of the brake shoe 14.
34 is bridged, and the brake shoes 12 and 14 are supported from the inner peripheral side by the strut device 34. As a result, when the parking lever 28 is rotated in the parking brake operating direction (counterclockwise direction in FIG. 1) by the parking cable 32, the brake shoes 12 and 14 are pushed outward by the pin 30 and the strut device 34, respectively. Then, the parking brake is applied. The strut device 34 is provided with a star wheel 36 at an intermediate portion in the longitudinal direction, and is extended with the rotation of the star wheel 36 in one direction to change the return positions of the brake shoes 12, 14 to the outer peripheral side. Incidentally, 38 is a return spring.

An adjusting member 40 is rotatably attached to a plate surface of the shoe web 18 of the brake shoe 12 on the backing plate 10 side by a pin 30 common to the parking lever 28. The adjusting member 40 includes the star wheel at the claw portion 42.
The parking lever 28 is engaged with the outer peripheral teeth of the parking lever 36, and is engaged with an engaging protrusion (not shown) provided at one end of the strut device 34 at an engaging hole (not shown). It is designed to be rotated together with the brake shoes 12,1.
When the amount of rotation of the adjusting member 40 in the counterclockwise direction in FIG. 1 exceeds a predetermined amount due to wear of the lining 19 of 4, the claw portion 42 rides over one outer peripheral tooth of the star wheel 36. When the parking brake operating force is released, the adjusting member 40 moves in the clockwise direction in FIG. 1 according to the urging force of the tension coil spring 44 stretched between the shoe web 18 of the brake shoe 12 and the adjusting member 40. As the claw portion 42 rotates the star wheel 36 in the one direction to extend the strut device 34, the clearance between the brake shoes 12, 14 and the rotating drum (the shoe) is increased. The gap) is adjusted automatically.

As shown in FIG. 1 and FIG. 2, the tension coil spring 44 is provided with a coil portion 46 formed in a taper shape whose diameter becomes smaller toward the adjustment member 40 side and both ends of the coil portion 46. It has a pair of hook parts 48, 50 and
In a state where the coil portion 46 is located on the side opposite to the backing plate 10 side of the shoe web 18 of the brake shoe 12, the hook portion 48 is hooked to the shoe web 18 and the other hook portion 50 of the adjustment member 40 is provided. It is hooked on the hook 52. During non-braking, as shown in FIG. 2, most of the coil portion 46 is located on the plate surface 54 located on the side opposite to the backing plate 10 side of the shoe web 18, and the coil portion 46 is 46 adjustment members 40
One roll located at the end opposite to the side is brought into contact with the plate surface 54, and an adjusting member is provided between the portion other than the one roll of the coil portion 46 and the plate surface 54 of the shoe web 18. A predetermined gap is formed that increases toward the 40 side. Adjustment member 40
The latching portion 52 is located closer to the backing plate 10 than the coil portion 46, and a force to the backing plate 10 side acts on the coil portion 46 as the coil portion 46 extends during parking brake braking. However, since the gap is formed between the coil portion 46 and the plate surface 54 of the shoe web 18 during non-braking, when the coil portion 46 is expanded during parking brake braking, for example, the third As shown in the drawing, a part of the portion of the coil portion 46 located on the plate surface 54 in FIG. 2 (see FIGS. 2 and 3).
The fourth roll from the left in the figure) is moved toward the inner peripheral side of the inner peripheral edge of the shoe web 18 without contacting the inner peripheral edge of the shoe web 18.

Here, FIG. 4 is a view showing a main part of a drum brake provided with a conventional shoe clearance automatic adjusting mechanism. In FIG. 4, the same parts as those in the embodiment of the present invention are designated by the same reference numerals and detailed description thereof will be omitted. In the figure, the tension coil spring 60 is configured to have a cylindrical coil portion 62, and the entire portion of the coil portion 62 located on the plate surface 54 of the shoe web 18 is brought into contact with the plate surface 54. Has been. Therefore, when the coil portion 62 is stretched during parking brake braking, a part of the coil portion 62 of the shoe web 18 is partially moved by the pressing force exerted on the coil portion 62 to the backing plate 10 side (downward in FIG. 4). By coming off from the inner peripheral edge to the backing plate 10 side, the coil portion 62 and the inner peripheral side corner portion of the shoe web 18 may be strongly rubbed with each other to generate a relatively large rubbing noise.

On the other hand, according to the present embodiment, the tension coil spring 44
The coil portion 46 is formed in a taper shape whose diameter decreases toward the adjustment member 40 side, and the portion other than one turn of the coil portion 46 on the opposite side to the adjustment member 40 side and the plate surface 54 of the shoe web 18 are formed. By forming the predetermined gap during non-braking, even if the coil portion 46 is extended while being applied with a force in the direction of being pressed against the plate surface 54 of the shoe web 18 during parking brake braking, The contact itself between the portion (moving portion) that is moved to the inner peripheral side of the inner peripheral edge of the shoe web 18 with the extension of the coil portion 46 and the inner peripheral edge portion of the shoe web 18 is avoided, whereby the coil portions are The generation of rubbing noise between the moving portion of 46 and the inner peripheral side corner of the shoe web 18 is prevented. The effect of preventing rubbing noise between the moving portion of the coil portion 46 and the inner peripheral side corner portion of the shoe web 18 is obtained even when the coil portion 46 contracts when the adjusting member 40 returns and rotates.

Further, according to the present embodiment, a predetermined gap is formed between the plate surface 54 of the shoe web 18 and the portion of the coil portion 46 other than one turn on the side opposite to the adjusting member 40 side when the brake is not applied. As a result, it is possible to suitably suppress the coil portion 46 from being rubbed along the plate surface 54 of the shoe web 18 during braking of the parking brake, and thus it is possible to effectively suppress the rubbing sound caused by such rubbing.

In the embodiment described above, the contact between the moving portion of the coil portion 46 and the inner peripheral edge portion of the shoe web 18 is configured to be avoided during parking brake braking, but this is not always necessary. They may come into contact. That is, even if the moving portion of the coil portion comes into contact with the inner peripheral edge portion of the shoe web and a rubbing noise is generated when the moving portion of the coil portion comes off the inner peripheral side corner portion of the shoe web, the contact pressure is Since the noise is reduced as compared with the conventional one, it is possible to preferably suppress the magnitude of the rubbing noise.

Further, in the above-described embodiment, the coil portion 46 of the tension coil spring 44 is formed in a tapered shape such that the entire length in the longitudinal direction becomes smaller toward the adjustment member 40 side. A portion of the coil portion 46 other than one turn on the side opposite to the adjustment member 40 side may be formed in a cylindrical shape having a smaller diameter than the one turn. In short, the portion of the shoe web that is moved to the inner peripheral side of the inner peripheral edge of the shoe web during extension due to parking brake braking has a smaller diameter than the portion that is located on the plate surface of the shoe web during extension. If it is formed as described above, the effect of the present invention can be obtained.

Further, in the above-mentioned embodiment, even when the entire coil portion 46 is positioned on the plate surface 54 of the shoe web 18 during non-braking, the coil portion 46 is positioned during braking of the parking brake.
The effect of the present invention can be obtained when 46 is extended while being pressed by the plate surface 54 and a part of the coil portion 46 is moved to the inner peripheral side of the inner peripheral edge of the shoe web 18.

Further, in the above-mentioned embodiment, the leading trailing type drum brake has been described, but the present invention can be applied to a dual two-leading type drum brake having a shoe clearance automatic adjusting mechanism similar to the above-mentioned embodiment. Of course.

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

[Brief description of drawings]

FIG. 1 is a view showing an example of a drum brake provided with an automatic shoe clearance adjusting mechanism to which the present invention is applied, and is a front view showing a main part. FIG. 2 is an enlarged view of a main part of a cross section taken along line II-II of FIG. FIG. 3 is a view showing a state in which the tension coil spring is extended along with the rotation of the adjusting member in FIG. FIG. 4 is a view showing a main part of a drum brake provided with a conventional automatic shoe clearance adjusting mechanism, and is a view corresponding to FIG. 12,14: Brake shoe 18: Shoe web 28: Parking lever 40: Adjusting member 44: Tensile coil spring 46: Coil part 54: Plate surface

Claims (1)

[Scope of utility model registration request] 1. A pair of brake shoes having arcuate and plate-shaped shoe webs, and one of the pair of brake shoes is rotatably provided and is rotated by a parking brake operating force. A parking lever that expands a pair of brake shoes relative to each other, an adjustment member that is rotatably provided on the one brake shoe and that is rotated with the rotation of the parking lever, and a coil portion. The tension member is stretched between one brake shoe and the adjusting member to urge the adjusting member in a rotation direction opposite to the braking operation direction of the parking lever, and at least a part of the coil portion when not braking. The coil portion is located on the plate surface of the shoe web of the one brake shoe, and when the parking brake is braked, the coil portion is rotated by the rotation of the adjusting member. A tension coil spring that is stretched while being pressed by the plate surface of the coil web, and a part of the portion of the coil portion located on the plate surface of the shoe web is moved to the inner peripheral side from the inner peripheral edge of the shoe web. A drum brake provided with a shoe gap automatic adjusting mechanism of automatically adjusting the shoe gap based on the rotation of the adjusting member, wherein the coil portion of the tension coil spring is extended when the parking brake is extended. By forming the portion of the one brake shoe that is moved toward the inner peripheral side of the inner peripheral edge of the shoe web with a diameter smaller than the portion that is located on the plate surface of the shoe web even during the extension,
A predetermined gap is formed between a portion of the coil portion that is moved toward an inner peripheral side of an inner peripheral edge of the shoe web during braking of the parking brake and a plate surface of the shoe web during non-braking. Drum brake with automatic shoe clearance adjustment mechanism.