JPH032015Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a shun hold down device used in a drum brake.

PRIOR TECHNOLOGY A notch is disposed on a bucking plate, and has an arc-shaped notch that opens toward the inner circumferential side in the middle part in the longitudinal direction, and an engagement hole is formed at a position on the outer circumferential side of the notch. Drum brakes are known that include a pair of brake shoes, each having a different shoe web. Such drum brakes usually include a shew-hold down pin whose one end is swingably attached to the bucking plate and whose middle portion is inserted through the notch of the shew web, and other parts of the shew-hold down pin. A shew hold down device is provided which has a coil spring interposed between the end side and the shew web in a state where a predetermined preload is applied and the shew hold down pin is inserted therethrough, With this hold-down device,
The brake shoes are supported on the bucking plate in a mutually expandable manner. A rotary drum is disposed on the outer circumferential side of the pair of brake shoes with a predetermined gap from each outer circumferential surface thereof.

The above-mentioned coil spring is usually sandwiched between a pair of cups in the axial direction, and is interposed between the other end of the shoe hold down pin and the shoe web, and is mounted on a rotating drum on the outer periphery of the brake shoe. If the brake shoe is pushed out in the outer circumferential direction when the brake shoe is not installed, the shoe hold down pin will largely protrude from the opening of the notch, causing the cup and coil spring to fall off the shoe web. It was hot.

For this reason, conventionally, an engaging pawl that protrudes toward the bucking plate is provided on the outer peripheral edge of the cup on the side that comes into contact with the show web, and the engaging pawl is inserted into the engaging hole of the show web. Based on the engagement between the engagement hole and the engagement claw,
Preventing the shoot-hold down pin from popping out from the opening of the notch and preventing the cup and coil spring from falling off from the shoot web.

However, in this case, in order to provide the above-mentioned engaging claws on the cup on the shew web side, the molding process of the cup increases, and a sufficient material yield cannot be obtained. This was a factor that hindered cost reduction.

Means for Solving the Problems The present invention has been made against the background of the above-mentioned circumstances, and its gist is to provide a shunhold down device for a drum brake as described above. an engagement portion inserted into the engagement hole at one end of the coil spring on the show web side, and preventing relative movement of the coil spring in the inner circumferential direction of the show web beyond a certain limit based on engagement with the engagement hole; The goal is to include the following in one piece.

Operation and Effects of the Invention With this structure, the engaging portion integrally provided at one end of the coil spring is inserted into the engaging hole formed at a position on the outer circumferential side of the notch, thereby engaging the engaging portion. Based on the engagement between the hole and the engaging part, relative movement of the coil spring in the inner circumferential direction of the shoe web is prevented beyond a certain limit, so even if a rotating drum is not installed on the outer circumferential side of the brake shoe, Even if the brake shoe is pushed relatively far toward the outer periphery, the shoe hold down pin can be prevented from popping out of the notch opening, and the cup and coil spring can be prevented from falling off the shoe web. Furthermore, the engaging portion can be easily formed by bending one end of the wire that constitutes the coil spring, and there is no need to form a conventional engaging pawl on the cup. As a result, the drum brake can be provided at a lower cost as a whole.

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

FIG. 2 is a diagram showing an example of a drum brake equipped with a shoe hold-down device to which the present invention is applied, in which a pair of brake shoes 16 having shoe webs 12 and 14, respectively, are mounted on the bucking plate 10. 18 is the hold down device 2
0 and 22 so that they can expand with respect to each other. One end of each of the shew webs 12 and 14 that are close to each other is brought into contact with a side surface of an anchor pin 24 fixed on the bucking plate 10, and the shew webs 12 and
The other end portions of the brake shoes 14 are connected to both ends of a connecting member 28 which is extended as the adjustment wheel 26 rotates to push the brake shoes 16 and 18 toward the outer periphery to adjust the shoe gap, and a spring (not shown). They are respectively engaged according to the biasing force.

Shoe web 12 of one brake shoe 16
A parking brake lever 32 having one end connected to a parking cable 30 is rotatably attached to the other end by a pin 34 near the end on the bucking plate 10 side and the anchor pin 24 side. A strut 36 spans between the intermediate portion of the parking brake lever 32 and the shoe web 14 of the brake shoe 18. When the parking cable 30 is pulled in and the parking brake lever 32 is rotated counterclockwise in FIG. 2, both brake shoes 16 and 18 are spread apart by the strut 36 and pin 34 to perform braking. However, since such parking brake operation is well known and not necessarily necessary for understanding the present invention, a detailed explanation thereof will be omitted. The brake shoes 16, 18 are fixed by constantly urging the ends of the brake shoes 16, 18 on the side opposite to the connecting member 28 in the direction of contacting the side surfaces of the anchor pin 24, respectively. It is a return spring that reduces the diameter of.

Next, the above-mentioned shew hold down devices 20, 22
will be explained in detail. Note that since each of the hold-down devices 20 and 22 is configured in the same way, the following explanation will be given only for one of the hold-down devices 20.

As shown in FIGS. 1 and 2, the show hold down device 20 includes a semicircular and plate-shaped head 4.
2 and a shaft portion 44 whose intermediate portion is bent in a direction away from the axis.
and a pair of cups 50 having a disk shape as a whole,
51 and a coil spring 52. The shoe hold down pin 46 is swingably attached to a through hole 54 formed in the bucking plate 10 at the end opposite to the head 42, and is prevented from coming off. An intermediate portion of the hold-down pin 46 is inserted into a notch 56 formed in the longitudinal center of the shew web 12 so as to open toward the inner circumference.
On the head 42 side of the hold down pin 46,
The cup 50 is installed in such a manner that it is prevented from coming off, and the coil spring 52 is installed between the cup 50 and the cup 51 that is in contact with the show web 12, so that the coil spring 52 is perpendicular to the axis of the cups 50, 51. A predetermined preload is applied and inserted in a state in which relative movement in each direction is almost prevented and in a state in which the shuhold down pin 46 is inserted inside.

A through hole 58 is formed in the shew web 12 at a position on the outer peripheral side of the notch 56 and slightly on the connecting member 28 side. On the other hand, at one end of the coil spring 52 on the shew web 12 side, there is a direction substantially parallel to the axis of the coil spring 52 at a tip extending from one end of the wire constituting the coil spring 52 toward the outer circumferential direction of the coil spring 52. A protrusion 60 that protrudes a predetermined distance toward the backing plate 10 is integrally formed therein, and this protrusion 60 is inserted into the through hole 58 . Therefore, in this embodiment, the through hole 58 constitutes an engagement hole, and the protrusion 60 constitutes an engagement portion. As a result, relative movement of the coil spring 52 and the cups 50, 51 in the inner circumferential direction of the shoot web 12 beyond a certain limit is prevented based on the engagement between the protrusion 60 and the through hole 58. This certain limit is a relative movement position of the coil spring 52 that is necessary and sufficient to prevent the shew hold down pin 46 from popping out of the opening of the notch 56 and the coil spring 52 etc. from falling off the shew web 12. hand,
It is determined in relation to the diameter and formation position of the through hole 58, the depth dimension of the notch 56, etc. In addition, the first
In the figure, the through hole 58 and the protrusion 60 are shown by solid lines instead of imaginary lines for easy understanding.

As described above, according to this embodiment, the coil spring is activated based on the engagement (abutment) between the inner wall surface of the through hole 58 formed in the shew web 12 and the protrusion 60 protruding from one end of the coil spring 52. 52 and cups 50, 51 in the inner circumferential direction of the shoe web 12 beyond a certain limit, even if a rotating drum is not disposed on the outer circumferential side of the brake shoe 16 (as shown in FIG. Even if the brake shoe 16 is pushed relatively far toward the outer periphery in the state shown in FIG. Coil spring 52 and cup 5
0 and 51 are moved almost integrally with the brake shoe 16. As a result, the shoe hold down pin 46 may pop out from the opening of the notch 56, and the cups 50, 51 and the coil spring 5 may
2 from falling off the shew web 12. Moreover, the protrusion 60 can be easily formed by bending one end of the wire that constitutes the coil spring 52, and there is no need to form an engaging claw on the cup 51 as in the conventional case. Since the molding steps are further reduced and the material yield is further improved, the drum brake is provided at a lower cost overall.

Further, according to this embodiment, since the protrusion 60 is made of spring steel integrally with the coil spring 52, a relatively large force is applied to the protrusion 60 when the protrusion 60 and the through hole 58 are engaged. It has the advantage that its strength is maintained based on elastic deformation even when it is deformed.

Although the through hole 58 is formed to have a sufficiently larger diameter than the wire diameter of the protrusion 60 in the above-described embodiment, it may have a diameter slightly larger than the protrusion 60.

Further, in the above embodiment, the through hole 58 is located on the outer peripheral side of the notch 56 and slightly close to the connecting member 28.
Although it is formed at a side position, the position may be such that relative movement of the coil spring, etc. in the inner circumferential direction of the shew web by engagement with an engaging portion provided at one end of the coil spring can be prevented beyond the above-mentioned certain limit. For example, the engagement hole may be formed at another position.

Further, in the above embodiment, cups 50 and 51 having different shapes are used, but it is also possible to use cups 50 and 51 having the same shape.

Furthermore, in the above-mentioned embodiments, the present invention was applied to a dual-servo type drum brake equipped with only a parking brake mechanism, but this is not necessarily necessary. The effects of the present invention can be obtained as long as the drum brake is equipped with a shun-hold down device that is mounted with a shun-hold down pin inserted into the notch.

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

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of the main parts of FIG. FIG. 2 is a front view showing an example of a drum brake equipped with a shun hold down device to which the present invention is applied. 10: Bucking plate, 12, 14: Show web, 16, 18: Brake show, 20,
22: Shuhold down device, 46: Shuhold down pin, 52: Coil spring, 5
6: Notch, 58: Through hole, 60: Projection.

Claims (1)

[Claims for Utility Model Registration] Disposed on the bucking plate, a notch is formed in an arc shape and opens toward the inner circumferential side in the middle part in the longitudinal direction, and at a position on the outer circumferential side from the notch. A drum brake comprising a pair of brake shoes each having a shoe web in which an engagement hole is formed, one end of which is swingably attached to the bucking plate, and an intermediate portion of which is inserted into the notch of the shoe web. The shew-hold down pin is interposed with a predetermined preload applied between the other end of the shew-hold down pin and the shew web, and the shew-hold down pin is inserted therethrough. It has a coil spring,
A shoe hold-down device for supporting the brake shoes on the bucking plate in a state in which they can be expanded relative to each other, the shoe hold-down device being inserted into the engagement hole at one end of the coil spring on the shoe web side, and being inserted into the engagement hole. A shoe hold down device for a drum brake, characterized in that it integrally includes an engagement portion that prevents relative movement of the coil spring in the inner circumferential direction of the shoe web beyond a certain limit based on engagement with a matching hole.