JP2002295544A - Back plate structure of drum brake for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the rigidity and the abrasion resistance of a ledge face with a simple structure, and manufacture a back plate body which is light in weight and not expensive. SOLUTION: A dust shield 36 is formed with a thinner plate than a back plate body projecting toward a brake drum 2a direction and inserted with clearance in labyrinth shape with a circular edge part 2d of the brake drum 2a at an outer periphery of the back plate body housing brake shoes 23, 24, which expand and contract freely. The ledge face 36c supporting rims 23b, 24b of the brake shoes 23, 24 is integrally formed to the dust shield 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back plate structure of a drum brake used for a traveling vehicle such as an automobile or a motorcycle, and more particularly, to a structure for holding a brake shoe housed in a back plate body.

[0002]

2. Description of the Related Art In a drum brake for a vehicle, a dust shield is fixed to an outer peripheral portion of a back plate body which accommodates a brake shoe so as to be able to expand and contract by spot welding or the like. Water and dust are prevented from entering the drum brake by loosely fitting in a labyrinth shape with the part. A plurality of ledge surfaces project from the back plate body toward the inside of the back plate, and the rims of the brake shoes are supported on these ledge surfaces to guide the expansion and contraction movement of the brake shoes.

[0003] A relatively thin metal plate such as a steel plate is used for the back plate body and the dust shield. The ledge surface of the back plate body wears due to repeated sliding contact with the rim of the brake shoe. Since a ledge surface which may be depressed and which requires relatively high precision must be formed separately from press forming performed on the back plate body itself, a technique disclosed in Japanese Patent Application Laid-Open No. 9-25969 is proposed. Have been.

This drum brake comprises a back plate main body and a dust shield, and a dust cover on the outer peripheral side of the dust shield for preventing dust from entering the inside of the back plate. The back plate main body and the dust shield are formed by casting. And the base of the ledge surface is raised on the back plate body, the dust cover is formed of a separate thin metal plate, the ledge surface is formed on the dust cover, and the dust cover is attached to the back plate. The main body and the dust shield are stuffed during casting, so that the base of the ledge surface of the back plate main body is covered with the ledge surface of the dust cover.

[0005]

In the back plate body and the dust shield which are cast and formed, a portion which does not receive much load from the brake shoe is formed thin, and a portion which receives a large load such as a ledge surface is formed thick. It has the advantage that it can be formed into meat, but in the case of cast molding, a certain thickness is also required for the thin-walled part, and the weight increases only as compared to the one manufactured by pressing a metal plate such as a steel plate. Alternatively, since an expensive casting mold and many casting steps are required, production is troublesome and costly.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a back plate structure of a vehicle drum brake which can improve the rigidity and abrasion resistance of a ledge surface with a simple structure and can be manufactured at a low cost and light weight. It is an object.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a back plate body for accommodating a brake shoe so as to be able to expand and contract, and a protrusion protruding from an outer peripheral portion of the back plate body toward a brake drum. In a back plate structure of a vehicle drum brake provided with an annular edge portion and a dust shield loosely fitted in a labyrinth, the dust shield is formed to be thicker than the back plate body, and the brake shoe is attached to the dust shield. A ridge surface for supporting the rim is formed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a drum-in-disk brake will be described below with reference to the drawings. The drum-in disc brake 1 includes a disc brake 10 on the outer periphery of a drum-in disc rotor 2 that rotates integrally with a wheel (not shown), and a drum brake 2 on the inner periphery.
0 is disposed, the disc brake 10 is used as a main brake, and the drum brake 20 is used as a parking brake.

In the drum-in-disk rotor 2, a disk rotor 2b for a disk brake is integrally formed around the opening of a brake drum 2a for a drum brake, and a bottom plate 2c of the brake drum 2a is connected to a flange 3a of the hub unit 3. 3a between the wheel and the wheel 4
The hub unit 3 and the wheel 4
And the wheels together with the wheels. At the opening of the brake drum 2a, an annular edge 2d composed of a circumferential groove and two inner and outer circumferential projections is formed, and a dust shield 36 of the back plate 21 described later is formed in a labyrinth in the annular edge 2d. To be loosely fitted.

The hub unit 3 has the above-mentioned flange 3a and the bottom plate 2c of the brake drum 2a bolted to the wheel 4, and the small-diameter shaft portion 3b on the distal end side is supported by the knuckle 5 via the bearing 6, and has a base end. The large-diameter shaft portion 3c on the side is fitted and attached to the bottom plate 2c of the brake drum 2a and the wheel 4.

The disc brake 10 includes the disc rotor 2b, a caliper bracket 11 fixed to the knuckle 5 at one side of the disc rotor 2b, and a caliper supported by the caliper bracket 11 so as to be movable in the disc axial direction. A pair of friction pads 13, 1 arranged between the body 12 and the action portion 12 a and the reaction portion 12 b of the caliper body 12 with the disc rotor 2 b interposed therebetween.
3 is provided.

The action part 12a of the caliper body 12 includes:
A piston 15 is accommodated in a cylinder hole 14 opened to the disk rotor 2b side. When a pressure liquid is supplied from a separate hydraulic master cylinder (not shown) to a hydraulic chamber 16 at the bottom of the cylinder hole 14, the piston 15 By moving in the direction of the rotor, the friction pad 13 on the action section side is pressed against one side surface of the disk rotor 2b. Next, the caliper body 12 moves in the direction of the action portion due to the braking reaction force, and the reaction force claw 12c of the reaction portion 12b moves to the friction pad 13 on the reaction portion side.
Is pressed against the other side surface of the disk rotor 2b to perform a braking operation as a main brake.

The drum brake 20 is a duo-servo type mechanical parking brake.
A primary-side brake shoe 23 and a secondary-side brake shoe 24 formed in an arc shape are arranged opposite to each other so as to be able to expand and contract. The brake shoes 23 and 24 are provided with the above-described webs 23 a and
24a and rims 23b, 24b fixed to the outer peripheral edges of the webs 23a, 24a in a direction crossing the back plate 21.
And linings 23c, 24c attached to the outer peripheral surfaces of the rims 23b, 24b.
The intermediate portion 24a is held by the back plate 21 using a shoe hold-down pin 25 and a shoe hold-down spring 26.

One end portions 23d, 2 of the webs 23a, 24a
4d is supported by the anchor 27, and the other ends 23e and 24e are supported by the floating support 28, respectively.
At one end of the webs 23a, 24a, return springs 29a, 29a are stretched between the webs 23a, 24a and the anchor 27, and the webs 23a, 24a are stretched.
A return spring 29b is stretched between the other ends of the brake shoes 23a and 24a, and urges both brake shoes 23 and 24 in the diameter reducing direction. The brake shoes 23 and 24 are
b and 24b are respectively supported on the ledge surface 36c of the back plate 21 at three locations near the anchor 27, near the floating support 28, and at an intermediate portion thereof.

The web 24 of the secondary brake shoe 24
a, a parking operation lever 30 is rotatably supported by a support shaft 31. Connecting rods 32 are provided near one ends 23d, 24d of both webs 23a, 24a.
A return spring 33 is stretched between the connecting rod 32 and the web 24a of the secondary brake shoe 24 and the parking operation lever 30, and both brake shoes 23, 24 The expansion and contraction is performed by operating a wire cable 34 connected to the tip of the lever 30.

The back plate 21 includes a back plate body 35a for accommodating the brake shoes 23 and 24,
It is composed of a dust cover 35b for dust prevention which is continuous with the outer peripheral side of the back plate main body 35a, and a dust shield 36 attached to the inner outer peripheral side of the back plate main body 35a.

The back plate body 35a and the dust cover 35b are integrally formed by pressing a single thin steel plate. The back plate main body 35a is a disk having a knuckle 5 and a through hole 35c for the hub unit 3 formed in the center, and various components of the drum brake 20, including the brake shoes 23, 24 and the anchor 27, are provided therein. The inner peripheral side portion is bolted to the flange 5a of the knuckle 5 so that the drum brake 2
0 is attached. The dust cover 35b surrounds the outside of the brake drum 2a to prevent dust from entering the inside of the drum brake 20 covered by the brake drum 2a.
5d, the caliper body 12 of the disc brake 10
Are arranged.

A steel plate thicker than the back plate body 35a and the dust cover 35b is used for the dust shield 36. The steel plate is press-formed into an L-shaped cross section, and the inner peripheral mounting portion 36b is attached to the back plate body 35a. The main body 36a on the outer peripheral side is disposed orthogonal to the back plate main body 35a by being fused to the inner outer peripheral side of the brake drum 2a by spot welding or the like.
Is loosely fitted in a labyrinth shape by
The entry of rainwater and dust into the drum brake 20 is prevented.

The mounting portion 36b of the dust shield 36 is provided with three ledge surfaces 36c at positions corresponding to the rims 23b and 24b of the brake shoes 23 and 24, respectively. The ledge surface 36c is
b is raised in parallel to the direction of the back plate, and the brake shoe 2 extends in the radial direction of the back plate 21.
The brake shoes 23, 24 are formed by attaching the side surfaces of the back plates of the rims 23b, 24b to these ledge surfaces 36c. Supported, rim 23b,
24b slides on the ledge surface 36c to guide the expansion and contraction in and out of the back plate.

This embodiment is constructed as described above. In the parking drum brake 20, when the wire cable 34 is pulled and the parking operation lever 30 is turned, the connecting rod 32 is moved to the left in FIG. And the primary side brake shoe 23 is moved to the web 23a.
Of the brake drum 2a is pressed against the inner peripheral surface of the brake drum 2a.

Next, when the pulling of the wire cable 34 is continued and the parking operation lever 30 is further rotated, the secondary brake shoe 24 is moved by the above-described reaction to the web 24a.
Of the brake drum 2a is pressed against the inner peripheral surface of the brake drum 2a.

From such a state, the brake drum 2a
For example, when a rotational force in the direction of arrow A acts on the brake drum 2a, the two brake shoes 23 and 24 rotate together in the same direction, and one end 24d of the web 24a of the secondary brake shoe 24 is moved. By contacting the anchor 27, the rotation of the brake shoes 23 and 24 is regulated. As a result, a braking torque is generated between the linings 23c and 24c and the inner peripheral surface of the brake drum 2a, and the braking torque is transmitted from the one end 24d to the anchor 27 through the web 4a of the secondary brake shoe 24.

Further, in the drum brake 20 of the present embodiment employing the duo-servo type, the self-energizing action generated in the primary brake shoe 23 is transmitted through the floating support 28 to the secondary brake shoe 24.
And act as a self-energizing force to brake the brake drum 2a with a large servo force.

For this reason, a large load is also applied to the ledge surface 36c on which the rims 23b and 24b of the brake shoes 23 and 24 slide, but the ledge surface 36c of the embodiment is used.
Are formed integrally with the dust shield 36 made of a steel plate thicker than the back plate 21, so that the rigidity and wear resistance of the ledge surface 36c are improved.

As a result, compared to the conventional product in which the ledge surface is provided on the back plate body made of a thin steel plate, wear and depression on the surface of the ledge surface can be prevented well, and a stable braking force can be maintained well for a long period of time. Furthermore, since it is not necessary to separately perform press forming of the back plate itself and press forming of the ledge surface, productivity can be improved.

Also, compared to the prior art in which the back plate body and the dust shield are cast-molded, an expensive casting mold and many casting steps can be omitted, and the production can be performed at low cost. In addition, the back plate 21 does not require the wall thickness as in the prior art casting, occupies a large area as the back plate 21, and the back plate main body 35a and the dust cover 35b, which do not apply much load, are formed of a single thin steel plate. Thus, the weight of the drum brake 20 can be reduced.

Although the above embodiment has been described with reference to a drum-in-disk brake combined with a disk brake and a mechanical parking brake of a duo-servo type, the present invention is not limited to this. It is also applicable to.

[0028]

As described above, according to the back plate structure of the vehicle drum brake of the present invention, the rigidity and wear resistance of the ledge surface are improved. Therefore, compared to the conventional product in which the ledge surface is provided on the thin metal back plate main body, wear and depression of the ledge surface can be prevented well, and a stable braking force can be maintained well for a long time. Since it is not necessary to separately perform the press forming of itself and the press forming of the ledge surface, productivity can be improved.

Further, compared to the prior art in which the back plate body and the dust shield are cast and formed, an expensive casting mold and many casting steps can be omitted, and the production can be performed at low cost. In addition, the thickness of the back plate is not required as in the case of the prior art, and the back plate occupies a large area as the back plate and is formed of a thin metal plate. it can.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along the line II of FIG. 3;

FIG. 2 is an enlarged sectional view of a main part of a drum-in-disc brake showing one embodiment of the present invention.

FIG. 3 is a front view of a drum-in-disk brake showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drum-in-disc brake, 2 ... Drum-in-disc rotor, 2a ... Brake drum, 2d ... Annular edge part,
20: drum brake, 21: back plate, 23,
24: brake shoe, 23b, 24b: rim, 35a
... Back plate body, 35b ... Dust cover, 36 ...
Dust shield, 36a: Body part of dust shield 36, 36c: Ledge surface

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J058 AA03 AA07 AA13 AA17 AA24 AA28 AA33 AA37 AA90 BA27 BA62 BA68 CA22 DC02 DC22 FA01

Claims (1)

[Claims] 1. A back plate body for accommodating a brake shoe so as to be expandable and contractable, and a dust shield protruding from an outer peripheral portion of the back plate body toward a brake drum and loosely fitting into an annular edge of the brake drum in a labyrinth manner. In the back plate structure of the vehicle drum brake provided, the dust shield is formed to be thicker than the back plate body, and a ledge surface for supporting the rim of the brake shoe is formed on the dust shield. Back plate structure of vehicle drum brake.