JPH0628372U - Duo servo type drum brake - Google Patents

Abstract

(57) [Abstract] [Purpose] A shoe hold down pin is inserted into a notch provided in the shoe web and opening to the inner peripheral side, and a shoe hold is provided between the tip of the shoe hold down pin and the shoe web. In a duo-servo type drum brake provided with a pre-loaded down spring, the shoe hold down device is prevented from coming off the shoe web without significantly increasing its cost. [Structure] When the brake shoe 14 moves to an allowable limit position toward the outer peripheral side due to swinging, the shoe holddown pin 46 moves inside the brake shoe 14 to the extent that the shoe holddown device 18 is disengaged from the shoe web 12 due to external force or vibration. Inclined to the circumferential side is the curved portion of the shaft portion 42 of the shoe hold down pin 46 and the backing plate 10.
This is prevented based on the contact with the tip of the engaging projection 58 formed by cutting and raising a part of the.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a duo servo type drum brake, and more particularly to a technique for preventing the shoe hold down device from coming off from a brake shoe.

[0002]

[Prior art]

 A pair of brake shoes each having an arcuate shape and disposed on the backing plate, each having a shoe web formed with a notch opening toward the inner peripheral side in the longitudinal middle portion, and an axial shape, A shoe hold down pin that is swingably attached to the backing plate at one end and has a longitudinal middle portion inserted through a notch in the shoe web, and the other end protruding from the shoe web of the shoe hold down pin. And a shoe holddown device that is provided between the shoe web and the shoe web in a preloaded state, and that supports the brake shoes on the backing plate in a state in which they can expand each other. Duo servo type drum brakes are known. In such a duo-servo type drum brake, opposite ends of a pair of brake shoes are brought into contact with a side surface of an anchor pin fixed on a backing plate by a biasing force of a spring, and the other ends of both brake shoes are By being connected to each other by the connecting member, both brake shoes are provided so as to be swingable around the anchor pin side as a fulcrum, and the rotation is provided with a predetermined gap on the outer peripheral side of both brake shoes. Braking is performed by pressing both brake shoes against the inner surface of the drum.

[0003]

[Problems to be solved by the device]

 By the way, before the rotary drum is installed on the outer peripheral side of the brake shoe as described above, swinging around the anchor pin side of the brake shoe is not regulated by the rotary drum, and the brake shoe is compared. Since one of the brake shoes moves comparatively largely to the outer peripheral side due to the swing, the shoe hold down device provided on the brake shoe is provided by the external force or vibration. If the shoe hold-down pin of the shoe hold-down device pops out beyond the inner edge of the shoe web by a certain amount due to the shoe hold-down pin tilting toward the inner periphery of the brake shoe, the shoe hold-down pin will be attached to the inner periphery of the brake shoe. While falling to the side, the shoe hold down spring fell off the shoe web Mau fear there is.

Therefore, for example, as described in Japanese Utility Model Laid-Open No. 63-74535, which was previously filed by the applicant of the present invention, a shoe hold down spring composed of a compression coil spring has a pair of cups. When sandwiched between the shoe web and the shoe web, it extends from the outer peripheral edge of the cup on the side that contacts the shoe web to the outer circumferential side when it is preloaded between the head of the shoe hold down pin and the shoe web. By providing an engaging claw at the tip and providing an engaging hole in the portion located on the outer peripheral side of the notch of the shoe web and inserting the engaging claw into the engaging hole of the shoe web, It has been proposed to prevent disengagement of the shoe holddown device from the shoe web based on engagement with the engagement holes.

However, in this case, since the engaging claws are provided on the outer peripheral edge of the cup on the side contacting the shoe web, a common one cannot be used as the pair of cups and the material of the cup having the engaging claws. It was difficult to obtain a sufficient yield, and this had the drawback of increasing the cost of the shoe hold down device and thus the duo servo type drum brake.

On the other hand, for example, as described in Japanese Utility Model Laid-Open No. 63-64940 filed by the applicant of the present application, one end of a compression coil spring as a shoe hold down spring is disclosed. If the projections for preventing the shoe hold-down device from coming off the shoe web based on the contact with the shoe webs are formed integrally with the shoe webs of the pair of brake shoes, respectively, the above-mentioned Japanese Utility Model Application Laid-Open No. 63-74535. In this case, it is considered that all the drawbacks will be eliminated, but in this case as well, the protrusions formed on the shoe webs of the pair of brake shoes must both be formed so as to protrude to the side opposite to the backing plate of the shoe webs. Therefore, the pair of brake shoes cannot be shared, and the cost of the duo servo type drum brake is relatively high. There was a drawback.

The present invention has been made in view of the above circumstances, and an object thereof is to insert a shoe hold down pin into a notch provided in the shoe web and opening to the inner peripheral side. In the duoservo type drum brake in which a shoe hold down spring is preloaded between the tip of the shoe hold down pin and the shoe web, the shoe of the shoe hold down device does not increase its cost. It is to prevent getting off the web.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the gist of the present invention resides in a duo-servo type drum brake of the type described above, which is located between the backing plate of the shoe hold down pin and the shoe web. This is because the backing plate is provided with a pin inclination restricting portion that restricts the inclination of the shoe hold-down pin toward the inner circumferential side of the shoe web beyond a certain limit based on the contact with the portion.

[0009]

[Effect of action and device]

 By doing so, for example, before the rotary drum is disposed on the outer peripheral side of the brake shoe, the brake shoe moves relatively greatly to the outer peripheral side due to its swing, and the shoe hold-down pin is arranged on the inner peripheral side of the shoe web. Even if the shoe hold-down spring pops out significantly from the inner peripheral edge of the shoe web and tends to fall off the shoe web due to tilting toward, the part of the shoe hold-down pin located between the backing plate and the shoe web. Of the shoe hold-down spring, the shoe hold-down pin can be prevented from further tilting toward the inner circumference of the shoe web due to its contact with the pin tilt restricting part provided on the backing plate. Since it can be prevented from falling off the web, the shoe hold down device From coming off blanking it can be suitably prevented.

In this case, when the compression coil spring as the shoe hold-down spring is provided between the tip portion of the shoe hold-down pin and the shoe web in a state of being sandwiched between the pair of cups, the shoe web side thereof. As in the conventional case where the engagement claw for preventing the shoe hold down device from coming off is provided on the outer peripheral edge of the cup of the cup, it is not possible to use a common pair of cups and the cup provided with the engagement claw. There is no problem that it is difficult to obtain a sufficient material yield, and a protrusion that prevents the shoe hold-down device from coming off due to contact with one end of the compression coil spring is provided with a shoe web of a pair of brake shoes. The problem that a pair of brake shoes cannot be shared as in the conventional case in which The above effect can be obtained simply by providing the backing plate with the pin inclination restricting portion, and thus there is an advantage that the cost of the duo servo type drum brake is not increased so much.

[0011]

【Example】

 An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 3 is a view showing an essential part of an example of a duoservo type drum brake to which the present invention is applied, and is used as a parking brake mechanism of a drum-in disc brake, for example. In the figure, on the backing plate 10, a pair of brake shoes 14 and 16 each having a shoe web 12 and having an arc shape as a whole are supported by shoe hold down devices 18 and 20 so as to be capable of expanding. The common brake shoes 14 and 16 are used. The opposite ends of the brake shoes 14, 16 are brought into contact with the side surfaces of the anchor pins 22 fixed on the backing plate 10, and the other ends of the brake shoes 14, 16 are Both ends of a connecting member 26 having an adjusting wheel 24 for adjusting the shoe clearance are engaged with each other according to the urging force of a spring (not shown). In FIG. 3, 28 is a parking brake lever, 30 is a strut, 32 is a parking cable, 34 is a cable guide, 36 is a shoe lifting prevention plate, and 38 and 40 are between the brake shoes 14 and 16 and the anchor pin 22. It is a shoe return spring stretched over.

A rotating drum (not shown) is disposed on the outer peripheral side of the brake shoes 14 and 16 with a predetermined gap, and the brake shoes 14 and 16 are rotated by the counterclockwise rotation of the parking brake lever 28. Braking is performed by expanding and pressing against the inner peripheral surface of the rotating drum, but the operation of such a drum brake is well known and is not always necessary for understanding the present invention. Detailed explanation is omitted. Since the connecting member 26 simply connects the other end portions of the brake shoes 14 and 16 to each other, in the state before the rotating drum is disposed on the outer peripheral side of the brake shoes 14 and 16. Can swing the brake shoes 14 and 16 relatively to the left and right in FIG. 3 with the anchor pin 22 side as a fulcrum.

Next, the shoe hold down devices 18, 20 will be described.

First, as shown in FIGS. 1 and 2, the shoe holddown device 18 provided on the side of the brake shoe 14 includes a shaft portion 42 that is bent in a direction in which a longitudinal intermediate portion is separated from an axial center. A shoe hold down pin 46 having a head portion 44 provided at one end of the shaft portion 42 and protruding to the outer peripheral side, a pair of disc-shaped cups 48 and 50 as a whole, and between the cups 48 and 50. It is composed of a compression coil spring 52 as a shoe hold down spring which is sandwiched in a state in which relative movement in a direction perpendicular to the axial center of the cups 48 and 50 is almost prevented. The shoe hold down pin 46 is swingably attached to the through hole 54 formed in the backing plate 10 at the end opposite to the head portion 44 so that the shoe hold down pin 46 is prevented from coming off. The intermediate portion in the longitudinal direction is inserted through a notch 56 formed so as to open toward the inner peripheral side in the longitudinal central portion of the shoe web 12 of the brake shoe 14. The compression coil spring 52 sandwiched by the cups 48 and 50 projects from the shoe web 12 to the opposite side of the backing plate 10 and the head of the shoe hold down pin 46 through which the cups 48 and 50 and the compression coil spring 52 are inserted. It is provided between 44 and the shoe web 12 in a state where a predetermined preload is applied.

On the other hand, in the shoe holddown device 20 provided on the brake shoe 16 side, as shown in FIG. 4, the shoe holddown pin 53 is configured to have a linear shaft portion 55. The shoe hold-down device 18 is configured similarly to the shoe hold-down device 18, and is mounted between the shoe web 12 of the brake shoe 16 and the backing plate 10 in the same manner as the shoe hold-down device 18.

FIGS. 1 and 2 show the portion of the backing plate 10 near the through hole 54 to which the shoe hold down pin 46 is attached and on the inner side of the through hole 54 by a predetermined distance. As described above, the backing plate 10 is partially cut and raised to form the engaging projection 58 that projects toward the brake shoe 14 side at a substantially right angle. Further, as shown in FIG. 4, the backing plate 10 is also provided at a portion near the through hole 54 to which the shoe hold down pin 53 is attached and located at the inner side of the through hole 54 by a predetermined distance. An engaging protrusion 60 is formed on the side of the brake shoe 16 and is inclined toward the outer peripheral side of the backing plate 10 by a predetermined angle when a part of 10 is cut and raised.

The position where the engaging projection 58 is separated from the through hole 54 on the shoe hold-down pin 46 side and the protruding height are, for example, left side (outer peripheral side) as shown in FIG. 2 when the brake shoe 14 swings. When the shoe hold down device 46 moves to the allowable limit position, the shoe hold down pin 46 tilts toward the inner circumferential side of the brake shoe 14 to the extent that the shoe hold down device 18 disengages from the shoe web 12. It is predetermined in relation to the shape of the curved portion of the shoe hold down pin 46, etc. so that it can be prevented based on the contact between the curved portion of the shoe and the tip of the engaging projection 58. Further, the separation position and the height position of the tip end portion of the engaging projection 60 from the through hole 54 on the shoe hold down pin 53 side are, for example, on the right side (outer periphery) as shown in FIG. 4 when the brake shoe 16 swings. When the shoe hold down device 20 moves to the allowable limit position, the shoe hold down pin 53 tilts toward the inner peripheral side of the brake shoe 16 until the shoe hold down device 20 comes off the shoe web 12. It is predetermined so that the shaft portion 55 of 53 and the tip of the engaging projection 60 can be prevented from contacting each other. In the present embodiment, the engagement protrusions 58 and 60 respectively form the pin tilt restricting portion.

As described above, according to the present embodiment, the brake shoe 12 or 14 moves relatively largely to the outer peripheral side due to the swing before the rotary drum is arranged on the outer peripheral side of the brake shoe 12 or 14, and As the shoe hold-down pin 46 or 53 tilts toward the inner side of the brake shoe, the cups 48, 50 and the compression coil spring 52 largely protrude from the inner peripheral edge of the shoe web 12 as shown in FIGS. 2 and 4. Even if the shoe web 12 is about to fall off from the shoe web 12, the shoe hold down pin 46 is caused by the curved portion of the shoe hold down pin 46 or 53 coming into contact with the engaging projection 58 or 60 provided on the backing plate 10. Alternatively, it is possible to prevent further inclination of 53 to the inner peripheral side of the shoe web 12. Accordingly, the cups 48, 50 and the compression coil spring 52 can be prevented from falling off the shoe web 12, so that the shoe holddown devices 18, 20 are preferably prevented from coming off the shoe web 12. be able to.

In this case, engaging claws extending toward the outer peripheral side are provided on the outer peripheral edge of the cup on the shoe web side, and engaging holes for inserting the engaging claws are provided on the shoe web to engage the engaging claws. As in the conventional case in which the shoe holddown device is prevented from coming off due to the engagement with the hole, a cup that cannot use a common pair of cups for sandwiching the compression coil spring and has its engaging claws is provided. There is no problem that it is difficult to obtain a sufficient material yield of the above, and the protruding portion that prevents the shoe holddown device from coming off due to the contact with one end of the compression coil spring as the shoe holddown spring. There is a problem that the pair of brake shoes cannot be shared as in the conventional case in which the shoe webs of the pair of brake shoes are integrally formed. The above effect can be obtained by simply cutting and raising a part of the backing plate 10 to form the engaging projections 58 and 60, so that the cost of the duoservo type drum brake is hardly increased. There are advantages.

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can be applied to other aspects.

For example, in the above-described embodiment, the engaging projections 58 and 60 as the pin tilt restricting portions are formed by cutting and raising a part of the backing plate 10. However, this is not always necessary. Even when the pin inclination restricting portion is constituted by another member having an L shape or a block shape and is fixed at a predetermined position of the backing plate 10, the temporary effect of the present invention can be obtained.

Further, in the above-described embodiment, the engaging projections 58, 60 are provided with notches in the tip end surfaces thereof, and when the shoe hold-down pins 46, 53 are fitted in the notches, inclination above a certain limit occurs. It can also be configured to be regulated.

Further, in the above-described embodiment, the shoe hold down spring is composed of the compression coil spring 52, but it is not always necessary. For example, when it is composed of a leaf spring or a bamboo spring. Also in this case, the effect of the present invention can be obtained by providing the pin inclination regulating portion of the present invention on the backing plate.

Further, in the above embodiment, the linear shoe hold down pin 53 and the engaging projection 60 on the side of the brake shoe 16 are replaced with a shoe hold down pin 46 and an engaging projection having a curved portion similar to that on the side of the brake shoe 14. 58 may be provided, or when the rotation space of the parking brake lever 28 can be ensured, the brake shoe 16 side is replaced with the shoe hold down pin 46 and the engagement protrusion 58 on the brake shoe 14 side. Similar shoe hold down pins 53 and engagement projections 60 may be provided.

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

[Brief description of drawings]

FIG. 1 is an enlarged view of a main part of a cross section taken along line I-I in FIG.

FIG. 2 shows a state in which an inclination of a shoe hold-down pin toward an inner circumferential side of the brake shoe beyond a certain limit is prevented by an engagement projection in a state where the brake shoe moves to an outer circumferential side to an allowable limit position in FIG. It is a figure.

FIG. 3 is a diagram showing an example of a duo servo type drum brake to which the present invention is applied, and is a diagram showing a main part.

4 is an enlarged view of a main part of a cross section taken along the line IV-IV in FIG. 3 and is a view corresponding to FIG. 2.

[Explanation of sign]

 10: backing plate 12: shoe web 14, 16: brake shoe 18, 20: shoe hold down device 46, 53: shoe hold down pin 52: compression coil spring 56: notch 58, 60: engaging protrusion (pin tilt restricting portion) )

Claims (1)

[Scope of utility model registration request] 1. A pair of brake shoes, each of which has a circular arc shape and is disposed on a backing plate, and has shoe webs each having a notch opening toward an inner peripheral side in a longitudinal middle portion, and a pair of brake shoes. From the shoe web of the shoe hold down pin, the shoe hold down pin being pivotally attached to the backing plate at one end and having a longitudinal intermediate portion inserted through a notch in the shoe web; A shoe hold down spring provided in a pre-loaded state between the projecting other end and the shoe web, and a shoe hold down device for supporting the brake shoes on the backing plate in a state capable of expanding each other. A duo-servo type drum brake, the backing plate of the shoe hold down pin and The backing plate is provided with a pin inclination restricting portion for restricting an inclination of the shoe hold-down pin toward the inner peripheral side of the shoe web beyond a certain limit based on contact with a portion located between the shoe web and the shoe web. A duo servo type drum brake characterized by that.