JPH0638187Y2 - Drum break - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a drum brake.

[Conventional technology]

As a conventional drum brake that facilitates the replacement work of the brake shoes, for example, the actual development of Sho 56-54335.
Some are disclosed in the issue. In other words, the outer edge of the parking lever is brought into contact with the bolt protruding from the backing plate that is screwed to regulate the normal brake release position of the parking lever. The lever return position is retracted, and the diameter of the pair of brake shoes is reduced. Thus, even a brake drum that has been stepped due to braking can be removed without interfering with the brake shoes. As a result, the replacement work of the brake shoes becomes efficient.

[Problems to be solved by the invention]

However, in such a conventional drum brake,
Since the parking lever repeatedly hits the bolt projecting on the backing plate, the bolt is likely to tilt, and this tilt not only causes the parking release position of the parking lever to change, but also causes the parking lever to engage with the bolt. In order to prevent this tilting, it is necessary to increase the plate thickness of the backing plate or weld nuts or the like to reinforce the backing plate, and a dedicated bolt is a separate member. The structure becomes complicated in combination with that required as. In addition, measures must be taken to prevent water from seeping through the screw holes where the bolts engage.

[Means and Actions for Solving Problems]

The present invention has been made in view of the above-mentioned conventional problems, and its configuration is a disk-shaped backing plate,
A pair of brake shoes arranged facing each other, a return spring for reducing the diameter of both brake shoes, and a side of the web of one brake shoe opposite to the backing plate, pivotally supported by a support shaft, and an outer edge. In a drum brake having a parking lever whose part is in contact with the rim of one of the brake shoes and the braking release position of which is regulated, and struts connecting the parking lever and the other brake shoe, the rim of one brake shoe is provided. The inner contact surface and the outer contact surface, which are connected via a step in the radial direction, are positioned with the outer contact surface positioned farther from the backing plate than the inner contact surface. It is formed so as to be adjacent in the axial direction, and an opening is formed at a position corresponding to the parking lever of the backing plate, and when normal braking is released, Outer edge is a drum brake which is adapted to abut against the inner abutment surface.

Then, the normal braking release position of the parking lever is
The outer edge portion contacts the inner contact surface and is regulated. At the time of replacing the brake shoe, a tool is inserted through the opening of the backing plate, the tip of the parking lever is moved in the axial direction of the support shaft, and the engagement with the inner contact surface of the parking lever is released. As a result, the parking lever is further returned by the action of the return spring, the outer edge portion contacts the outer contact surface, and the diameters of both brake shoes are reduced according to the step difference between both contact surfaces. As a result, it becomes easy to remove the brake drum that has been subjected to stepwise wear.

〔Example〕

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

1 to 4 show a first embodiment in which the present invention is applied to an LT (leading trailing) type drum brake. In the figure, reference numeral 1 indicates a backing plate, and a pair of brake shoes 2 and 3 are arranged to face each other. Both brake shoes 2 and 3 have a shoe hold down device 17
It is supported by the backing plate 1 by a and 17b, one end of which is locked by a pair of pistons 4a and 4b of the wheel cylinder 4 fixedly mounted on the backing plate 1, and the other end is
It is supported by an anchor 5 fixed to the plate 1.
6 is an anchor spring, both brake shoes 2,
3 has an effect of holding the anchor 5 in place. Reference numeral 7 is a return spring stretched between the brake shoes 2 and 3 for urging the diameter reduction of the shoes 2 and 3. 8 is a parking lever, which is swingably supported by a support shaft 9 on the side opposite to the backing plate 1 of the web 3a of the one brake shoe 3 and is connected to the front end of the parking cable.
By the operation of 10, the backing plate 1 is swung on the same plane. Reference numeral 11 denotes a parking cable guide, which is formed integrally with the shoe retainer 12 that suppresses the lifting of both brake shoes 2 and 3, and is integrated with the anchor 5.

A strut 13 receives the inner edge of the base end of the parking lever 8 on the support shaft 9 side at the forked portion 13a at one end, and the inner edge of the brake shoe 2 at the forked portion at the other end. Are connected. This strut 13 constitutes a strut type auto adjuster, and the adjuster nut 13
c, an adjuster rod 13 having an adjuster wheel 13d
e and adjuster socket 13f. Reference numeral 14 is an L-shaped adjuster lever, one end of which is pivotally supported by the support shaft 9 on the web 3a of the brake shoe 3 and the other end of which can be fed to the adjuster wheel 13d in only one direction. And a chute toe lever spring 15 stretched between the lever 14 and the brake shoe 2 provides a turning habit in a clockwise direction.

Then, on the rim 3b of one of the brake shoes 3, a web is
The holes 16 are formed on the side farther from the backing plate 1 than 3a, as shown in FIGS. This hole 16
Is an outer edge portion protruding near the tip of the parking lever 8.
8a is the inner contact surface of the rim 3b that contacts when normal braking is released
The bottom surface of the hole 16 formed by lining 3d, which is formed at a position displaced from the central axis 3c, forms the outer contact surface 3e. That is, the inner contact surface 3c is formed between the web 3a and the hole 16, and the outer contact surface 3e is located farther from the backing plate 1 than the inner contact surface 3c. Hole 16
Can be processed at the same time when the rim 3b is punched by a press. Thus, the inner contact surface 3c and the outer contact surface 3e are connected via the step 3f formed by the plate thickness of the rim 3b so as to extend in the radial direction of the backing plate 1 and are adjacent to each other in the central axis direction. ing. In addition, an opening 18 is formed in the backing plate 1 so as to correspond to the vicinity of the tip of the parking lever 8 in the braking release state.
It is closed by a rubber plug 19.

Next, the operation will be described.

If the parking cable 10 is pulled and the parking lever 8 is operated at the time of the parking lever, one brake shoe 3 expands, and the reaction force causes the other brake shoe 2 to expand via the strut 13. In this way, both brake shoes 2 and 3 are brought into sliding contact with a brake drum (not shown), and a braking force is obtained. If the parking lever 8 is actuated when the shoe gap exceeds the regular gap, the adjuster lever 14 is pulled by the shooter lever spring 15 and swings to feed the adjuster wheel 13d one tooth to move the adjuster rod 13e. By rotating the adjuster nut 13c, the length of the strut 13 is substantially extended and the shoe gap is automatically adjusted.

When replacing the brake shoes 2 and 3, the plug 19 is removed, a tool such as a screwdriver is inserted through the opening 18, and the tip of the parking lever 8 is pushed up. As a result, the parking lever 8 slightly swings in the axial direction of the support shaft 9 due to the looseness of attachment with the support shaft 9, and the inner contact surface of the outer edge portion 8a.
The engagement with the 3c is released, and the return spring 7 and the chute lever spring 15 swing in the returning direction, so that the outer edge portion 8a enters the hole 16 and contacts the outer contact surface 3e. As a result, the diameters of both brake shoes 2 and 3 are reduced according to the radial step 3f, so that the brake drum that is subject to stepwise wear due to braking can be easily performed without rotating the adjuster wheel 13d of the auto adjuster. It can be removed. If the parking lever 8 is actuated once, the outer edge portion 8a elastically swings back in the axial direction of the support shaft 9 after the outer edge portion 8a exits from the hole 16, and after the braking is released, the outer edge portion 8a has the inner contact surface. Take the braking release position where it abuts 3c.

FIGS. 5 and 6 show the essential parts of the second embodiment of the present invention. The same parts as those of the first embodiment are designated by the same reference numerals and their description is omitted. In this embodiment, the brake shoe 3
The rim 3b is positioned on the side farther from the backing plate 1 than the web 3a, and the bulging portion 20 is processed by press molding to form a step extending in the radial direction of the backing plate 1.
The inner contact surface 3h and the outer contact surface 3i, which are connected via 3g,
They are formed so as to be adjacent to each other in the direction of the central axis, and the outer edge portion 8a of the parking lever 8 contacts the inner contact surface 3h when the normal braking is released. That is, the bulging portion 20 is formed between the web 3a and the outer contact surface 3i, and the outer contact surface 3i is located farther from the backing plate 1 than the inner contact surface 3h. .

Thus, according to this embodiment, the brake shoes 2, 3
When replacing, the plug 19 is removed, a tool is inserted through the opening 18, and the tip of the parking lever 8 is pushed up.
As a result, the tip of the parking lever 8 moves and the engagement of the outer edge 8a with the inner contact surface 3h is released, so that the lever 8 is returned by the action of the return spring 7 and the shoot lever lever 15. Rocks to the outer edge 8a
Contacts the outer contact surface 3i. As a result, the diameters of both brake shoes 2 and 3 are reduced according to the step 3g, so
With respect to the replacement work of No. 3, the same operation as that of the first embodiment can be obtained.

The embodiment in which the present invention is applied to the LT type drum brake has been described above, but the present invention is also applicable to a DS (duo servo) type drum brake including a parking brake.

[Effect of device]

As can be understood from the above description, according to this invention, the following effects can be obtained.

(1) When the brake is released, the parking lever hits the rim of the brake shoe and does not act as an external force on the backing plate or another member between the parking lever and the brake shoe or the extension member. It does not easily change, and has excellent reliability and durability. As described above, a separate member for extending the parking lever or an extending member is not required, and the rim of the brake shoe is formed with a hole, a bulge or the like to form the inner contact surface and the outer contact surface. The structure is extremely simple because it only needs to be done.

(2) The backing plate need only be provided with an opening, and the backing plate does not require any particular reinforcement. In addition, the opening can be easily closed in a liquid-tight manner with a rubber plug,
It is easy to prevent flooding.

(3) By inserting a tool from the opening of the backing plate and pushing up the parking lever, the tip of the brake shoe can be moved to reduce the diameter of both brake shoes, making it easy and reliable to reduce the diameter of both brake shoes. Can be done.

(4) The present invention is effective when the portion of the backing plate corresponding to the adjuster wheel is covered by the wheel support member of the vehicle and the opening cannot be formed at this portion.

[Brief description of drawings]

1 to 4 show a first embodiment of the present invention, FIG. 1 is a partial sectional view, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 shows an opening of a backing plate. FIGS. 4 and 5 are partial cross-sectional views showing an enlarged main portion, FIG. 5 is a partial cross-sectional view showing an enlarged main portion of a second embodiment of the present invention, and FIG. FIG. 3 is a sectional view similar to FIG. 2 shown in an enlarged manner. 1: backing plate, 2, 3: brake shoes, 3a: web, 3b: rim, 3c, 3h: inner contact surface, 3d: lining, 3e, 3i:
Outside contact surface, 3f, 3g: step, 7: return spring, 8: parking lever, 8a: outer edge, 9: spindle, 13: strut, 16: hole,
18: opening, 19: plug, 20: bulge,

Claims (1)

[Scope of utility model registration request] 1. A pair of brake shoes arranged opposite to each other on a disc-shaped backing plate, a return spring for reducing the diameter of both brake shoes, and a web of one brake shoe on a side opposite to the backing plate. , A parking lever pivotally supported by a support shaft, the outer edge portion of which is brought into contact with the rim of one of the brake shoes, and a braking release position is regulated, and the parking lever and the other brake shoe are connected. In a drum brake having a strut, the inner abutment surface and the outer abutment surface, which are connected to the rim of one brake shoe via a step in the radial direction, and the outer abutment surface is abutted on the inner side. Located on the side farther from the backing plate than the surface and formed adjacent to each other in the direction of the central axis, and corresponding to the parking lever of the backing plate. Forming an opening in a position, during normal brake release, drum brake, characterized in that the outer edge has to be in contact with the inner contact surface.