JPH11230207A - Back plate structure of drum brake for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a structure for back plate of a drum brake that prevents looseness in the connection between the back plate body and a dust cover or impairment in durability thereof caused overtight connection even when the back plate and dust cover expand at a different coefficient of thermal expansion caused by braking heat at a high temperature, and also prevents reduction of sealing performance between the back plate and the dust cover affected by braking heat. SOLUTION: A plurality of locking holes 30, 31 are formed a metal back plate body 25 and a dust cover 26. A circular diaphragm of rubber with a rectangle section is held between the metal back plate body 25 and the dust cover 26. A plurality of locking projections 27a, 27b are formed on both side of the diaphragm 27. The projections 27a, 27b are engaged with the locking holes 30, 31 to connected the back plate body 25 to the dust cover 26 through the diaphragm 27. A gap between the back plate body 25 and the dust cover 26 is sealed with the diaphragm 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back plate of a drum brake used for various traveling vehicles such as automobiles and motorcycles, and more particularly, to a metal back plate body and a synthetic resin made up of the back plate. And a dust cover coupling structure.

[0002]

2. Description of the Related Art In a drum brake used in an automobile or the like, a brake shoe which is in sliding contact with a brake drum is fixed inside a back plate fixed to a knuckle of a vehicle body. As a prior art formed by combining a dust cover superposed on the outer periphery of the outer surface of the back plate main body, for example, Japanese Patent Publication No.
There is one disclosed in Japanese Patent Publication No. 1262662.

[0003] In these back plates, a high-rigidity metal material that can withstand the load during braking is used for the back plate body, and a synthetic resin material for the purpose of weight reduction is used for the dust cover. In the former back plate,
The back plate body and the dust cover are each provided with a flange along the center axis direction of the back plate, and the back plate body and the dust cover are formed in a U-shaped cross section, and both flanges are press-fitted inside and outside. Thereby, the back plate body and the dust cover are integrally connected.

In the latter back plate, a plurality of engagement holes are provided in the back plate main body, a plurality of engagement protrusions and an annular seal ridge are provided in proximity to the dust cover, and the engagement of the dust cover is performed. The projection is engaged and fixed to the engagement hole of the back plate main body, and the back plate main body and the dust cover are integrally connected, and the sealing projection of the dust cover is fixed by the engagement and fixing of the engagement projection and the engagement hole. By pressing against the outer surface of the back plate main body, the gap between the back plate main body and the dust cover is sealed by a seal ridge.

[0005]

In such a back plate of a drum brake, the sliding contact between the brake shoe and the brake drum during braking is performed inside the back plate covered by the brake drum. However, the back plate expands due to high braking heat, but the metal back plate body and the synthetic resin dust cover have different coefficients of thermal expansion. On the contrary, there is a risk that the press-fitting is severe and the durability is impaired, and in the case of the latter, stress concentrates on the engaging portion between the engaging projection and the engaging hole under the influence of the braking heat as in the former, There is a possibility that the pressing force of the seal ridge is weakened and the sealing performance is reduced.

Accordingly, the present invention solves the above-mentioned problem by using a metal material and a synthetic resin material having different coefficients of thermal expansion for the back plate body and the dust cover, while avoiding the influence of high-temperature braking heat as much as possible. It is an object of the present invention to provide a back plate structure of a vehicle drum brake for the purpose of doing so.

[0007]

According to the above-mentioned object, according to the first aspect of the present invention, a drum brake for a vehicle is formed by laminating a dust cover made of a synthetic resin on an outer peripheral surface of a metal back plate body. In the back plate structure, a rubber annular diaphragm is sandwiched between the back plate main body and the dust cover, a plurality of locking projections are formed on both side surfaces of the diaphragm, and the back plate main body and the dust cover are formed. And a plurality of locking holes are formed in each of the holes, and the locking projections are engaged with the locking holes to integrally connect the back plate body and the dust cover via a diaphragm.

According to a second aspect of the present invention, there is provided a back plate structure for a vehicle drum brake, wherein a dust cover made of synthetic resin is superposed on an outer peripheral surface of a metal back plate body. A rubber annular diaphragm is interposed between the dust cover and the dust cover, a plurality of locking projections are formed on both side surfaces of the diaphragm, and a plurality of locking holes are respectively formed in the back plate body and the dust cover. The back plate body and the dust cover are integrally connected with each other by engaging the locking projection with the locking hole, and the center axis of the diaphragm is positioned at least radially inward of the locking projection of the diaphragm. An annular sealing ridge extending in the direction of the diaphragm from the thickness of the diaphragm. The elastic contact.

According to these inventions, the back plate body and the dust cover are connected via the annular diaphragm, and the back plate body and the dust cover are not in direct contact with each other. Expansion at a rate does not affect the other. Also,
Between the back plate body and the dust cover, which are separated by the annular diaphragm, a seal ridge provided on the annular diaphragm itself or the diaphragm elastically contacts and seals the opposing surfaces of the back plate body and the dust cover.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a first embodiment of the present invention. A drum brake 1 has a pair of brake shoes 3 and 4 opposed to each other inside a back plate 2 fixed to a knuckle of a vehicle body. A wheel cylinder 5 is provided between one end of the shoes 3 and 4, and an anchor 6 is provided between the other ends of the shoes. The brake shoes 3 and 4 are used for turning the hydraulic pressure of the wheel cylinder 5 or rotating the parking lever 7. The inner plate is an inwardly expanding drum brake that expands with the anchor 6 as a fulcrum. The back plate 2 is provided with a brake drum 8 that rotates integrally with an axle not shown.
The linings 3a and 4a of the brake shoes 3 and 4 are brought into sliding contact with the inner peripheral surface of the brake drum 8 to perform a braking action.

Shoe return springs 9, 10 are stretched between the brake shoes 3, 4 near the inside of the wheel cylinder 5 and near the outside of the anchor 6, so that both brake shoes 3, 4 are constantly reduced in diameter. An adjuster 11 is provided inside the shoe return spring 9 on the wheel cylinder side, and a brake set between the linings 3a, 4a and the inner peripheral surface of the brake drum 8 is provided. The gap C1 is always kept constant.

The wheel cylinder 5 is a cylinder body 1
A pair of pistons 14, 14 are inserted into the second cylinder hole 13, and a hydraulic pressure generated by a separate hydraulic master cylinder (not shown) is supplied to a hydraulic chamber 15 between the pistons 14, 14. , 14 are pushed toward both ends of the cylinder hole 13 so that both brake shoes 3, 4 are operated.

The parking lever 7 has a base end pivotally supported by a support shaft 16 on a web 3b of the brake shoe 3 between the back plate 2 and one of the brake shoes 3 so as to be parallel to the back plate 2 and the web 3b. It is arranged in. One end of a wire cable 17 is connected to the tip of the parking lever 7, and a lever return spring 18 is connected to the wire cable 17.
One end is wound around the parking lever 7 and the other end is wound around the anchor 6, and the parking lever 7 is always outside the back plate around the support shaft 16 by the elastic force of the lever return spring 18. The rearward limit is restricted by the contact between the stopper 7a at the tip of the parking lever and the rim 3c of the brake shoe 3.

The other end of the wire cable 17 is connected to a service brake operator near the driver's seat, and when the driver operates the service brake operator, the wire cable 17 compresses the lever return spring 18 while FIG. The parking lever 7 is pulled leftward, and the parking lever 7 rotates in the back plate inward direction (clockwise direction in FIG. 2) about the support shaft 16 as a fulcrum.
The rotation of the parking lever 7 is controlled by the first
Acting as a force for pushing the second strut members 19 and 20 leftward in FIG. 2, pushing the other brake shoe 4 outward with the anchor 6 as a fulcrum, and moving the lining 4 a to the inner peripheral surface of the brake drum 2. To make sliding contact.

Next, the reaction force from the other brake shoe 4 is applied to the first and second strut members 19 of the adjuster 11,
Acting on the parking lever 7 through 20, the parking lever 7 rotates clockwise in FIG. 2 with the contact point A with the first strut member 19 as a fulcrum. To lining 3a
Is brought into sliding contact with the inner peripheral surface of the brake drum 2 to perform a braking action.

When the operation of the service brake operator is released, the parking lever 7 pulls the wire cable 17 rightward in FIG. It rotates outward (counterclockwise in FIG. 2) and brake shoes 3,
4 operates in the opposite direction to the above-described braking, the stopper piece 7a of the parking lever 7 abuts the rim 3c of the brake shoe 3, and each member returns to the predetermined retreat limit position shown in FIG.

The adjuster 11 includes a first strut member 19 that engages with the web 3b of one brake shoe 3 and the parking lever 7, a second strut member 20 that engages with the web 4b of the other brake shoe 4, and And an adjustment lever 22 that meshes with the adjustment bolt 21. The adjusting lever 22 is pivotally supported by a web 4b of the other brake shoe 4 by a support shaft 23, and a meshing state of the adjusting bolt 21 and the adjusting lever 22 is maintained by a spring 24 stretched between the adjusting lever 22 and the web 4b. doing.

When the linings 3a and 4a of the brake shoes 3 and 4 are worn and the braking gap C1 between the brake shoes 8 and the brake drum 8 is larger than a predetermined value, the brake shoes 3 and 4 are larger than usual. When the webs 3b and 4b of the brake shoes 3 and 4 are expanded,
By separating from the second strut members 19, 20, the adjustment lever 22 pivots on the support shaft 23 as a fulcrum to extend the adjustment bolt 21, and the first and second strut members 19, 20 are extended, so that the brake is provided. The position where the diameter of the shoes 3 and 4 is reduced is regulated outward, and the predetermined braking clearance C1 is automatically reset.

The back plate 2 includes a back plate body 25 using a metal plate such as a steel plate and a synthetic resin dust cover 26 provided on the outer periphery of the outer surface of the back plate body 25. The structure is such that they are integrally connected via an annular diaphragm 27. The back plate body 25 includes a recess 25a that occupies most of the back plate body 25, a flat plate 25b surrounding an opening edge of the recess 25a, and projects to one side around an outer peripheral edge of the flat plate 25b. Flange 25c. The components such as the brake shoes 3 and 4, the wheel cylinder 5, and the anchor 6 are disposed on the inner surfaces of the recess 25 a and the flat plate 25 b surrounded by the flange 25 c.
An axle insertion hole 28 and a plurality of vehicle body mounting holes 29 are formed in the flat portion 25b, and a plurality of locking holes 30 are formed in the flat plate portion 25b.

The dust cover 26 has an annular cover body 2 having a diameter larger than that of the flange 25c of the back plate body 25.
6a is formed on the outer peripheral edge so as to surround a flange 26b protruding to one side, and the cover main body 26a has a locking hole 31 of the same shape on the same circumference as the locking hole 30 of the back plate main body 25. And the opening 32 inside the cover main body 26a is formed with the concave portion 25 of the back plate main body 25.
It is formed to have a larger diameter than a. The diaphragm 27 is
An annular body having substantially the same diameter as the flat plate portion 25b of the back plate main body 25, the cross section of which is formed in a rectangular shape having a width in the radial direction longer than the thickness in the central axis direction. The locking projections 27a and 27b having a portion are provided in the same number as the locking holes 30 and 31 of the back plate body 25 and the dust cover 26, and the entirety including the locking projection 27a is provided.
It is integrally formed of a synthetic rubber material capable of withstanding high-temperature braking heat.

Back plate body 25 and dust cover 2
6 accommodates the recess 25a of the back plate main body 25 in the opening 32 of the dust cover 26, and places the diaphragm 27 opposite each other while the back plate main body 25 and the flanges 25c and 26b of the dust cover 26 are concentrically positioned inside and outside. Between the flat plate portion 25b and the cover main body 26a with elastic force, and the locking projections 27a, 2
7b is engaged with the locking holes 30 and 31 to be integrally connected as the back plate 2.

The drum brake 1 in which the components such as the brake shoes 3 and 4 and the wheel cylinder 5 are disposed on the back plate 2 as described above uses the knuckle of the vehicle body by using the vehicle body mounting hole 29 of the back plate body 25. The brake drum 8 is fixed to an axle penetrating through the axle insertion hole 28 of the back plate 2. The drum brake 1 mounted on the vehicle body is covered with the brake drum 8, and the inner peripheral side of the back plate 2 in which the recessed portion 25 a of the back plate main body 25 is accommodated in the opening 32 of the dust cover 26 is sealed by the diaphragm 27. On the outer peripheral side of the plate 2, the flange 2 which is located concentrically
The labyrinth structure formed by alternately entering the openings 5c and 26b and the opening of the brake drum 8 is sealed.

As described above, the drum brake 1 according to this embodiment is
Is a back plate body 2 constituting the back plate 2
5 and the dust cover 26 are made of metal and synthetic resin having different coefficients of thermal expansion.
7 and the back plate body 2
5 and the dust cover 26 do not have a direct fitting relationship, so that the back plate body 25 and the dust cover 26
However, even when the diaphragm 27 expands at a different coefficient of thermal expansion due to the braking heat generated by the sliding contact between the brake shoes 3 and 4 and the brake drum 8, the diaphragm 27 is elastically deformed and absorbs it. The thermal expansion of the dust cover 26 does not affect the other, and the connection state between the back plate main body 25 and the dust cover 26 can be kept good for a long time.

The diaphragm 27 sandwiched between the back plate body 25 and the flat plate portion 25b of the dust cover 26 and the cover body 26a seals the inner peripheral side of the back plate 2 with an elastic force. Even if there is a gap C2 between the opening 32 and the recess 25a of the back plate main body 25, the diaphragm 27 reliably prevents dust or rainwater from entering the back plate 2. The labyrinth structure formed by the flanges 25c and 26b and the opening of the brake drum 8 seals the outer peripheral side of the back plate 2 as before. Further, in the present embodiment, the diaphragm 27
Functions as an anti-vibration material between the back plate main body 25 and the dust cover 26, and can effectively prevent brake squeal due to micro vibration of the back plate main body 25 or the dust cover 26.

FIG. 3 shows a second embodiment of the present invention. This embodiment differs from the first embodiment in the shape of the diaphragm 40 connecting the back plate body 25 and the dust cover 26. The diaphragm 40 itself is formed in a ring shape thinner than that of the first embodiment, and the same locking projections 4 as those of the first embodiment are provided on both side surfaces of the diaphragm 40.
0a, 40b are provided in the same number as the locking holes 30, 31 of the back plate body 25 and the dust cover 26, and
Annular seal ridges 40c and 40d are integrally provided on the inner peripheral side and the outer peripheral side of the diaphragm 40.

The seal ridges 40c and 40d are formed in a bifurcated cross section which extends beyond the thickness of the diaphragm 40 in the direction of the center axis of the diaphragm 40, and connect the back plate body 25 and the dust cover 26 with each other. When the diaphragm 40 is located between the flat plate portion 25b and the cover main body 26a, the inner and outer seal ridges 40c and 40d are
The flat plate portion 25b and the cover body 2 instead of the diaphragm 40
6a, and the locking projections 40a, 40b are inserted into the locking holes 30, 3 of the back plate body 25 and the dust cover 26.
By engaging with the first member 1, the seal protrusions 40 c and 40 d are bent and elastically contact the opposing surfaces of the flat plate portion 25 b and the cover main body 26 a, and the back plate main body 25 and the dust cover 26 are integrally connected as the back plate 2.

The present embodiment thus constructed has the same effects as those of the first embodiment, and also has a seal ridge 40c which extends in the inner and outer periphery of the diaphragm 40 in a bifurcated manner in the axial direction beyond the thickness of the diaphragm 40. , 40d, the diaphragm 40 can be bent in the direction of the central axis when the locking projections 40a, 40b are engaged with the locking holes 30, 31.
Assembly work can be performed very easily. Further, an annular sealing ridge 40c provided radially inward from the locking projections 40a and 40b elastically contacts and seals the opposing surfaces of the flat plate portion 25b of the back plate main body 25 and the cover main body 26a of the dust cover 26. The seal ridges 40c reliably prevent dust and rainwater entering from the gap C2 on the inner peripheral side of the back plate.

In the above-described second embodiment, the seal ridges of the diaphragm are provided on the inner peripheral side and the outer peripheral side of the locking projections. For this purpose, a seal ridge may be provided at least on the inner peripheral side of the locking projection of the diaphragm.

[0029]

As described above, the back plate structure of the vehicle drum brake according to the present invention is constructed as described above, so that the metal back plate body and the synthetic resin dust cover have different thermal expansions due to the braking heat. The rubber diaphragm elastically deforms and absorbs even if it expands at a constant rate, so the thermal expansion of the back plate body and the dust cover does not affect the other, and the connection between the back plate body and the dust cover The condition can be kept good for a long time. Further, the diaphragm functions as a vibration isolator between the back plate main body and the dust cover, and can effectively prevent brake squeal due to micro vibration of the back plate main body and the dust cover.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along the line II of FIG. 2 showing a first embodiment of the present invention;

FIG. 2 is a front view of a drum brake showing a first embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a drum brake showing a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drum brake 2 ... Back plate 3, 4 ... Brake shoe 3a, 4a ... Lining 5 ... Wheel cylinder 6 ... Anchor 7 ... Parking lever 8 ... Brake drum 11 ... Adjuster 17 ... Wire cable 25 ... Metal back plate main body 25a ... recess 25b ... flat plate 25c ... flange 26 ... synthetic resin dust cover 26a ... cover body 26b ... flange 27 ... rubber annular diaphragm 27a, 27b ... locking projection 30, 31 ... locking hole 32 ... opening 40 ... diaphragms 40a, 40b ... locking projections 40c, 40d ... seal ridges C1 ... braking gaps between the linings 3a, 4a and the brake drum 8 C2 ... openings 32 of the dust cover 26 and recesses 25a of the back plate body 25. Gap between

Claims (2)

[Claims] 1. A back plate structure for a vehicle drum brake constructed by laminating a synthetic resin dust cover on the outer periphery of an outer surface of a metal back plate main body, wherein between the back plate main body and the dust cover. A rubber annular diaphragm is sandwiched between the diaphragms, a plurality of locking projections are formed on both side surfaces of the diaphragm, and a plurality of locking holes are formed in the back plate body and the dust cover, respectively. A back plate structure for a vehicle drum brake, wherein the locking projection is engaged with a hole, and the back plate main body and the dust cover are integrally connected via a diaphragm. 2. A back plate structure for a vehicle drum brake, wherein a dust cover made of synthetic resin is superimposed on an outer peripheral surface of a metal back plate body. A rubber annular diaphragm is interposed therebetween, a plurality of locking projections are formed on both side surfaces of the diaphragm, and a plurality of locking holes are formed in the back plate body and the dust cover, respectively. The locking projection is engaged with the hole, the back plate body and the dust cover are integrally connected, and at least radially inward from the locking projection of the diaphragm in the central axis direction of the diaphragm, the thickness of the diaphragm is smaller than the thickness of the diaphragm. An annular seal ridge that extends is provided, and the seal ridge is elastically contacted with the opposing surface of the back plate body and the dust cover. Plate structure of a vehicle drum brake to be used.