JPS6225549Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a brake lever support device for a drum brake having a cross-pull type brake lever. In an internally expanding drum brake equipped with an automatic adjustment device, the brake shoe is automatically expanded toward the drum as the lining wears, and the gap with the drum is always maintained at a predetermined value. However, at the same time as the lining wears, some wear also occurs on the lining sliding surface of the drum.
This wear is not necessarily uniform and usually has unevenness in the width direction. For this reason, when trying to remove the drum to replace the brake shoe, for example, due to the engagement between the drum and the lining,
There may be cases where the drum cannot be pulled out in the axial direction.
To facilitate the removal of the drum when this problem occurs, the brake lever is normally supported away from the back plate, and when the above problem occurs, the brake lever is retracted from its normal support position toward the back plate. Various brake lever support devices have been proposed in the past that increase the gap between the brake shoe and the drum and allow the drum to be removed. However, these brake lever support devices generally have the disadvantage that it is difficult to achieve both reliable support of the brake lever under normal conditions and ease of removal and reassembly when the aforementioned problem occurs. There is. As an example, a support member having a pair of elastic holding pieces bent at both ends of a band plate is elastically locked to a guide member that guides the rotation of the brake lever, and when the support member is released, the brake lever is FIG. 9 shows a brake lever support device that is retracted to increase the gap between the brake shoe and the drum. In this example, the support member that locks the support member to the guide member absorbs the impact force from the brake lever when the parking brake is released and the frictional force caused by sliding between the brake lever and the support member when the service brake is activated. Since the elastic holding piece is received in the direction of removal, there is a risk that the support member will fall off from the guide member. If the support member falls off, the gap between the brake shoe and the drum will suddenly increase, resulting in the brake pedal's stroke increasing and causing it to touch the floor, or causing the brake fluid to become insufficient and the brakes to be ineffective. There is a high possibility of causing a serious accident. On the other hand, if the holding force of the elastic holding piece is increased in order to prevent the support member from falling off, the operating force for attaching and detaching increases, and the detaching operation and
Also, it becomes a factor that makes the assembly operation difficult. Generally, the support member is located behind the brake and inside the wheel, so it is surrounded by the axle housing,
There is a vehicle suspension system, brake piping, etc., and it is normal that workability is not good, so it is necessary to not only securely attach the support member and prevent it from falling off, but also to prevent it from falling off.
It is also required that removal and reassembly operations be easy.

In other words, if the existing support members are designed to prevent them from falling off, it takes time to attach and detach them, and conversely, if the focus is placed on the ease of attaching and detaching the support members, there is a risk of them falling off. It didn't exist.

The present invention has been developed to solve the above-mentioned problems, and allows easy removal and assembly operations while reliably preventing the support member that supports the brake lever from falling off. An object of the present invention is to provide a brake lever support device for a brake drum.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
An embodiment of the present invention is shown in FIGS. 1 to 6. Brake shoes 2 and 3, which are slidably mounted on a fixed back plate 1, have their upper adjacent ends abutted against a piston of a wheel cylinder 4, and their lower adjacent ends abutted against a fixed anchor 5, respectively. The brake lever 6 loosely fits into the opening 2a of the brake shoe 2 and
It consists of an inner arm 6a that abuts on the outer end 2b of the 6b, the strut 8 is pivotally connected to the end of the strut 8 by a pin 9. One side 6c of the outer arm 6b contacts the guide surface 10a of the guide member 10 fixedly provided on the outer surface 1b of the back plate 1, and the end surface 6d contacts the back 11a of the support member 11. The support member 1
1 is integrally molded from a plate material and includes a back portion 11a and the back portion 1.
A pair of legs 11b formed by bending both sides of the back part 1a into a U-shape, and a convex part 11c extending from one end surface of the back part 11a and protruding in the direction of the legs 11b at the tip. It consists of a tongue portion 11d and a long hole-shaped hook portion 11e provided near the end of the back portion 11a on the opposite side to the tongue portion 11d.
The back portion 11a of this support member 11 is brought into surface contact with the brake lever 6, and the leg portion 11b is also brought into surface contact with the back plate 1.

Further, the tongue portion 11d is an extension of the contact surface of the support member 11 and is provided to protrude in a direction perpendicular to the operating direction of the brake lever 6.

The guide member 10 is fixed to the back plate 1 at a position that is an extension of the tongue portion 11d and away from the line of action when the brake lever is actuated.

This guide member 10 is formed by bending a plate material into an L-shape or a U-shape, and a guide surface 10a in contact with the brake lever 6 is provided with a hole 10b for inserting and extracting a tongue portion 11d. A notch 10c is provided at the end of the portion to be fixed. The tongue portion 11d of the support member 11 is inserted into the hole 10b of the guide member 10, and the convex portion 11c at the tip of the tongue portion 11d is inserted into the notch 10c of the guide member 10.
is locked. At this time, the tongue portion 11d is the root portion 11
f, the support member 11 receives a reaction force from the guide member 10, and the convex portion 11c receives a reaction force from the back plate 1 or the guide member 10, and deforms elastically, and this elastic force causes the leg portion 11b of the support member 11 to It is pressed and fixed onto the outer surface 1b. The plate-shaped strut 8 has a pair of wing portions 8a and 8b bent in opposite directions at the portions that abut the back plate 1 at both ends in the longitudinal direction. A toothed element 12 is fixed to the center portion of the strut 8 so as not to rotate, and a plurality of teeth are formed on the outer peripheral surface of the toothed element 12. A bell crank lever 13 is pivotally attached to the elongated hole at the end of the strut 8 opposite to the end to which the brake lever 6 is pivoted so as to be rotatable and linearly movable in the longitudinal direction of the strut 8. The first arm 13a of the bell crank lever 13 has an outer cam surface 13b and an inner cam surface 13c, and is loosely fitted into the opening 3a of the brake shoe 3 with a predetermined gap δ. The outer cam surface 13b abuts the outer end 3b of the opening 3a. The second arm 13d of the bell crank lever 13 has a plurality of teeth that mesh with the teeth of the toothed element 12 on its arcuate end surface. Toothed element 1
A low-load spring 15 is tensioned between 2 and the pin 14 and biases the bellcrank lever 13 in the direction of the toothed element 12, so that the two teeth are normally in mesh. A large-load spring 16 is stretched between the strut 8 and the brake shoe 2, and biases them toward each other. Both brake shoes 2,
Return springs 17, 18 are stretched between the outer ends 2 of the openings 2a, 3a of both brake shoes 2, 3.
The brake shoes 2 and 3 are biased so that the brake shoes b and 3b come into contact with the inner arm 6a of the brake lever 6 and the outer cam surface 13b of the first arm 13a of the bell crank lever 13, respectively.

Next, the operation of the drum brake configured as described above will be explained. First, during service braking, when the wheel cylinder 4 is operated, the brake shoes 2 and 3 are expanded against the return force of the return springs 17 and 18, and come into pressure contact with the rotating drum to brake it. When the amount of expansion of the brake shoes 2 and 3 is smaller than the predetermined gap δ, the strut 8, brake lever 6, and bell crank lever 13 work together to follow the movement of the brake shoe 2 by the large load spring 16. However, automatic adjustment is not performed. At this time, the outer arm 6b of the brake lever 6 slides to the left in FIG. 2 while being pressed against the back part 11a of the support member 11 by the force of the large load spring 16, and when the brake is released, the outer arm 6b returns to the position shown in FIG. 18, it returns to almost its original position. When the linings 2c and 3c wear out and the amount of expansion of the brake shoes 2 and 3 exceeds the predetermined gap δ, the opening 3a of the brake shoe 3 is inserted into the inner cam surface 13c of the first arm 13a of the bell crank lever 13. The inner end 3d of the bell crank lever 13 comes into contact with the bell crank lever 13.
moves to the right in FIG. 2 against the force of the small load spring 15, and the bell crank lever 13 and the toothed element 1
2, the bellcrank lever 13 rotates clockwise and then, when the brake is released, engages the toothed element 12 in its new position, keeping the effective length of the strut 8 in an increased state; Lining 2c,
3c to keep the gap with the drum constant. At this time as well, the brake lever 6 is moved to the support member 11 as in the case where the automatic adjustment described above is not performed.
The device slides on the back portion 11a of the device. Next, when the parking brake is applied, when a force is applied to the cable 7 in the direction of the arrow, the brake lever 6 uses the pin 9 as a fulcrum to press the brake shoe 2 against the drum, and then the brake lever 6 and the outer end of the opening 2a of the brake shoe 2 Return springs 17, 1 with the contact portion with 2b as a fulcrum
8 and the force of the large load spring 16
Then, move the bell crank lever 13 to the right in FIG. 2 to press the brake shoe 3 against the drum. At this time, the outer arm 6b of the brake lever 6 separates from the support member 11, and the guide surface 1 of the guide member 10
0a, and then returns to the original position when the brake is released, and the back part 1 of the support member 11
It hits 1a.

Next, when trying to remove the drum for shoe replacement etc., the unevenness of the drum and the linings 2c and 3c.
If the drum cannot be removed due to engagement with the screwdriver, attach the tip of the screwdriver to the support member 11 as shown in FIG.
When the shaft is applied to the outside arm 6b of the brake lever 6 and a force is applied to the handle in the direction of the arrow, the support member 11 is pulled out from the guide member 10 by the lever action, and the brake lever 6 is released. The force of the large load spring 16 and return springs 17 and 18 causes the cable 7 to rotate clockwise in FIG. 2 by the amount of slack in the cable 7. At this time, the brake shoes 2 and 3 move inward due to the reverse action of the parking brake described above, and the unevenness of the drum and the linings 2c and 3c
This disengages the drum, making it possible to remove the drum. Furthermore, if necessary, it is also possible to disconnect the cable 7 and the brake lever 6 to further increase the amount of retraction of the brake lever 6.

Next, the effects of the present invention in this embodiment will be explained. First, the support member is not mounted on the guide member, but is inserted between the guide member and the back plate to reduce the sliding friction between the brake lever and the support member during service braking, and the brake lever when releasing the parking brake. By making the leg portion receive the impact force instead of the tongue portion, that is, the elastic deformation portion, the support member is prevented from falling off and the above-mentioned no-brake accident is prevented.

Furthermore, by providing a hook for removal on the support member, it can be removed using a general tool such as a screwdriver.
The support member can be removed with a small force and with an extremely simple operation. In addition, by supporting the brake lever with one hand and inserting the tongue of the support member into the hole of the guide member with the other hand and pushing firmly,
Reassembly is also easy.

As described above, according to the present invention, it is possible to achieve both the reliability of attachment and the ease of attachment and detachment of the brake lever support member, which has been difficult in the past.

FIG. 7 shows another embodiment of the present invention. The support member 111 is integrally molded from synthetic resin or the like and is attached to the back 1.
11a, leg portion 111b, convex portion 111c, tongue portion 11
1d and a hook portion 111e. According to this embodiment, by using a low friction material such as Teflon as the material of the support member, it is possible to reduce the sliding frictional resistance against the brake lever and improve the return of the shoe. FIG. 8 shows still another embodiment of the present invention. The support member 211 includes a back portion 211a, leg portions 211b, a protruding hook portion 211e, and a convex portion 211 at one end, which are integrally molded from synthetic resin or the like.
c, and a plate tongue portion 211d whose opposite end is cast into the back portion 211a. According to this embodiment, a strong device is realized which reduces the sliding resistance of the brake lever and is made of a plate tongue having strong elastic force.

As a result, it is possible to reliably prevent the support member from falling off.
In addition, it can be easily attached and detached with a simple operation.

Further, since the sliding surfaces of the brake lever and the support member are always in surface contact except during operation, it is possible to reliably prevent foreign matter such as mud from adhering to the sliding surfaces.

Therefore, there is no need to worry about the gap between the brake shoe and the drum changing unexpectedly and causing malfunction.

It is clear that the support member according to the present invention can be easily constructed using a suitable elastic material such as wire in addition to the three embodiments described above. Also,
In either case, it is possible to use either a hole or a protrusion as the hook portion of the support member.

[Brief explanation of the drawing]

1 to 6 show an embodiment of the present invention. Fig. 1 is a plan view of the drum brake, Fig. 2 is a cross-sectional view of Fig. 1, Fig. 3 is a cross-sectional view of Fig. 2, Fig. 4 is a perspective view of the guide member, and Fig. 5 is a support member. FIG. 6 is a perspective view of the main part of the drum brake showing the detachment operation of the support member. FIG. 7 is a perspective view of a support member showing another embodiment of the present invention, and FIG. 8 is a perspective view of a support member showing still another embodiment of the present invention. FIG. 9 is a perspective view of essential parts of a conventional drum brake. 1...back plate, 1b...outer surface, 2,
3... Brake shoe, 6... Brake lever,
6a...Inner arm, 6b...Outer arm, 7...Cable, 8...Strut, 10...Guide member, 10
b... hole, 11, 111, 211... support member,
11a, 111a, 211a...back, 11b,
111b, 211b...leg, 11d, 111
d, 211d...tongue.

Claims (1)

[Scope of Claim for Utility Model Registration] A drum brake that has a pair of brake shoes mounted on a back plate so as to be able to expand and a brake lever that expands the brake shoes, at a position away from the back plate. a support member having a back portion that makes surface contact with the brake lever at the bottom and legs that make surface contact with the back plate, and a surface that stands up from the outer surface of the back plate that is out of the line of action of the brake lever; a guide member having a hole for insertion of the tongue on its surface, and an elastic tongue extending integrally from the support member on one side of the support member in a direction perpendicular to a plane including the operating locus of the brake lever; A brake lever support device for a drum brake, further comprising: a hook portion for locking a tool on the other side of the support member, and configured such that the tongue piece can be inserted into and landed on the guide member.