JPH074454A - Automatic clearance regulating device of drum brake - Google Patents

Abstract

PURPOSE:To provide an automatic clearance regulating device of a drum brake which generates no pinching function to a regulating lever, and can improve the durability. CONSTITUTION:In an automatic clearance regulating device of a drum brake to regulate the clearance of shoes automatically, a regulating lever 20 has a holding hole 23 to penetrate a holding shaft 24, a relief larger than the rotating scope of the regulating lever 20 is formed to the holding hole 23, and the regulating lever 20 is composed to slide in the direction a piston is projected, when a high load is applied and a regulating gear 14 is made unrotatable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for automatically adjusting a clearance of a drum brake in which an automatic shoe clearance adjusting mechanism is mounted on a wheel cylinder.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, the actual fair 1-35.
No. 003 is disclosed. This device has an overtravel spring stretched by hooking hooking portions at both ends on a bracket fixed to a wheel cylinder body of a drum brake, and hooking on one hooking portion of the overtravel spring. In addition, it is equipped with an adjuster lever connected to the piston via a link, and the bracket is premised on an automatic gap adjusting device that swings the adjuster lever according to the stroke of the piston to rotate the adjuster gear and screw out the task skewer. A guide mechanism for guiding the movement of the adjuster lever in the piston stroke direction is separately provided between the adjuster lever and the adjuster lever to eliminate the prying action of the overtravel spring hooking portion on the bracket, thereby providing a clearance adjusting device. It has the advantage that the durability of can be improved.

[0003]

The conventional automatic gap adjusting device described above has the following problems.

<B> By providing the guide mechanism separately, the twisting action on the bracket by the hooking portion of the overtravel spring can be eliminated, but the twisting action occurs due to the relative movement of the adjuster lever and the bracket. . Therefore, the guide mechanism, instead of the bracket, is unevenly worn or crushed, resulting in the durability of the automatic gap adjusting device remaining low.

<B> In addition to the guide mechanism, a bracket or 2
Since it requires two springs (overtravel spring and return spring), the structure is complicated, the number of constituent parts is large, and the assembly is complicated.

<C> Since a part of the adjuster lever is cut out to provide the guide mechanism, the strength of the adjuster lever is reduced.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to prevent the occurrence of prying action and automatically adjust the clearance of a drum brake having excellent durability. To provide a device.

[0008]

SUMMARY OF THE INVENTION The present invention is rotatably supported by a wheel cylinder body of a drum brake via a support shaft, and one arm extending toward the opening side of the wheel cylinder is integrated with an adjusting nut of the wheel cylinder. A substantially L-shaped adjustment lever that engages with the adjustment tooth of the adjustment lever, a connecting member that extends between the other arm of the adjustment lever and the piston of the wheel cylinder, and a tension member that extends between the wheel cylinder body and the adjustment lever. On the other hand, an adjustment spring for urging the arm in the anti-adjustment direction is provided, and the adjustment lever is rotated as the piston is projected, and the adjustment teeth are rotated by the rotation of the adjustment lever, and the adjustment bolt screwed to the adjustment nut is screwed. In a device for automatically adjusting the clearance of a drum brake which automatically adjusts the shoe clearance, the adjusting lever has a supporting hole through which a spindle is inserted, and And wherein the the supporting hole to the formation of a larger relief than the range of rotation of the adjusting lever so as to permit the sliding of the adjusting lever in the direction out a clearance automatic adjustment device of the drum brake.

[0009]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings.

<B> Wheel cylinder

1 to 3 show an example of an automatic clearance adjusting device for a drum brake. In FIG. 1 and FIG. 2, a wheel cylinder 10 is a one-opening type cylinder having a cylinder hole 11. A piston 12 is slidably inserted in the cylinder hole 11, and a bottomed hole 13 of the piston 12 has an adjusting tooth. 1
An adjusting nut 15 in which 4 is integrally fixed is rotatably fitted, and the adjusting nut 1 further includes an engaging groove 16 for supporting one brake shoe (not shown).
7 is screwed.

<B> Adjustment lever

The adjusting lever 20 is a wheel cylinder 10.
A lever having a substantially L-shape having one arm 21 extending toward the opening side of the (piston 12) and the other arm 22 extending in a direction orthogonal to the one arm 21, and a stepped bolt 2 near the center thereof.
4 is formed with a support hole 23 through which a stepped bolt 24 is inserted.
It is rotatably supported by the body of the wheel cylinder 10 via. The one arm 21 of the adjusting lever 20 is formed with an engaging claw 25 that engages with the adjusting tooth 14 at the front end of the adjusting nut 15 and gives the adjusting nut 15 rotation in only one direction. The support hole 23 is formed in an oval shape (diaper shape) with a different diameter so that the opening width gradually increases from the small diameter portion 23a on the right side to the large diameter portion 23b on the left side in FIG. Support hole 23
The shape and the forming position of are not limited to this, and the point is that when the adjustment lever 20 slides in the protruding direction of the piston 12, it collides with the stepped bolt 24 so that the stepped bolt 24 and the adjustment lever 20 are separated. The relief may be formed so that the prying action does not occur. The adjusting lever 20 receives the spring force of an adjusting spring 40, which will be described later, and abuts the small-diameter portion 23a of the support hole 23 against the peripheral surface of the stepped bolt 24, so that the adjusting lever 20 is supported without rattling.

<C> Connecting member

The connecting member 30 has an annular portion 31 formed in the front.
Is engaged with the piston 12, and the connecting arm 32 formed rearward from the annular portion 31 is engaged with the other arm 22 of the adjusting lever 20 so that the sliding motion of the piston 12 in the protruding direction is rotated. It is being transmitted as a dynamic movement.

<D> Adjustment spring

The adjusting spring 40 is stretched between the retaining bolt 18 of the wheel cylinder 10 and the adjusting lever 20, and urges the adjusting lever 20 in the anti-adjusting direction (clockwise direction in FIG. 1) and at the same time, the one arm. The engaging claw 25 of 21 urges the adjusting tooth 14 to press. In this embodiment, the adjusting spring 40
The case where one of them is connected to a position closer to the other arm 22 side than the support portion of the adjusting lever 20 is shown.
The tension position is not limited to the position shown in the figure, as long as the adjustment lever 20 can be biased in the above-mentioned direction. In FIG. 2, reference numeral 19 is an air bleeder.

[0018]

Next, the operation of the automatic gap adjusting device will be described.

<B> Normal brake operation

When the brake is operated with the shoe clearance exceeding the set amount, the wheel cylinder 10 shown in FIGS.
The piston 12 projects from the. The connecting member 30 moves integrally with the protrusion of the piston 12, and the connecting arm 32 of the connecting member 30 pulls the other arm 22 of the adjusting lever 20. The adjusting lever 20 rotates counterclockwise around the stepped bolt 24. At this time, the adjustment lever 20 rotates by contacting the small diameter portion 23a of the support hole 23 with the stepped bolt 24.
With the rotation of the adjusting lever 20, the adjusting teeth 14 are pressed to rotate the adjusting nut 15, and the adjusting bolt 17 is screwed out to automatically adjust the shoe gap.

<B> When the adjusting teeth cannot rotate

Adjusting nut 15 by applying a hydraulic pressure above a predetermined value
When the adjustment tooth 14 of the adjustment nut 15 becomes unrotatable due to an increase in the axial force on the adjustment nut 15, the adjustment lever 20 receives a sliding force in the protruding direction of the piston 12. Support hole 2 for adjusting lever 20
Since a clearance larger than the rotation range of the adjustment lever 20 is formed in the adjustment lever 3, the adjustment lever 20 is slid in the protruding direction of the piston 12 while the adjustment spring 40 is extended, and the support hole 23 and the stepped bolt 24 are provided. Prying force does not act on the bearing of the. Further, as the piston 12 is projected, the adjusting teeth 14, the adjusting nut 15, the adjusting bolt 17, the adjusting lever 20, and the group of connecting members 30 slide substantially integrally, so that, for example, the engaging claw 25 of the adjusting lever 20 and the adjusting claw 25 are adjusted. No sliding occurs in the parts where the mutual parts are engaged, such as the engaging parts of the teeth 14 and the engaging parts of the other arm 22 of the adjusting lever 20 and the connecting arm 32 of the connecting member 30.

[0023]

Since the present invention is as described above, the following effects can be obtained.

<A> Since the support hole of the adjusting lever is formed with a clearance larger than the range of rotation of the adjusting lever, no twisting force acts on the support shaft and the adjusting lever. Therefore, neither component is worn or crushed, and the durability is improved.

<B> When the adjusting tooth of the adjusting nut cannot rotate due to a high load, the adjusting tooth,
The adjustment nut, the adjustment lever, and the connecting member group slide substantially integrally. Therefore, for example, the engaging parts of the adjusting lever and the adjusting teeth, the engaging parts of the adjusting lever and the connecting member, and the like where the mutual parts are engaged do not slide, and there is concern about wear, scraping, or deformation. There is no increase in durability.

<C> The construction can be simplified, the number of constituent parts can be reduced, and the assemblability can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of an automatic gap adjusting device according to the present invention.

FIG. 2 is a side view of the gap automatic adjustment device with a part broken away.

FIG. 3 is a plan view of the automatic gap adjusting device when the adjusting teeth cannot rotate.

[Explanation of symbols]

 10 Wheel Cylinder 11 Cylinder Hole 12 Piston 13 Bottomed Hole 14 Adjusting Tooth 15 Adjusting Nut 16 Engaging Groove 17 Adjusting Bolt 18 Locking Bolt 19 Air Breeder 20 Adjusting Lever 21 One Arm 22 Other Arm 23 Supporting Hole 23a Small Diameter 23b Large Diameter Part 24 Stepped bolt (support shaft) 30 Connecting member 31 Annular part 32 Connecting arm 40 Adjusting spring

Claims (1)

[Claims] 1. A substantially L, which is rotatably supported by a wheel cylinder body of a drum brake via a support shaft and has one arm extending toward the opening side of the wheel cylinder engaged with an adjusting tooth integral with an adjusting nut of the wheel cylinder. It is stretched between the wheel-cylinder body and the adjustment lever, and the one arm of the adjustment lever is urged in the anti-adjustment direction. A drum for automatically adjusting the shoe gap by rotating the adjusting lever with the protrusion of the piston, rotating the adjusting teeth by rotating the adjusting lever, and screwing out the adjusting bolt screwed into the adjusting nut. In the automatic brake gap adjusting device, the adjusting lever has a support hole penetrating the support shaft, and the adjusting lever slides in the protruding direction of the piston as the adjusting spring extends. Characterized in that the formation of the larger relief than the range of rotation of the adjusting lever into the support hole so as to permit, clearance automatic adjustment device of the drum brake.