JPH0247609B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drum brake, and more particularly to a drum brake equipped with an automatic adjustment mechanism that automatically adjusts the clearance of a brake shoe.

Generally, when the lining attached to the brake shoe of a drum brake wears out, the stroke of the brake pedal increases and braking performance deteriorates, so an automatic adjustment mechanism is required to keep the clearance constant.

An example of the structure of a drum brake equipped with a conventional automatic adjustment mechanism is shown in FIGS. 1 and 2.

The example shown in Figure 1 is a drum brake that uses a latch-type automatic adjustment mechanism.
A lever 4 which is rotated around a shaft 3 is provided on a leading shoe 2 which is interlocked with the lever 2, and a toothed portion 4a is formed on the free end side of the lever 4, and this toothed portion 4a is engaged with a latch 5. The lever 4 is rotated in accordance with the wear of the lining, and the engagement position between the tooth portion 4a and the latch 5 is changed, so that a constant clearance can always be obtained.

However, if such a structure is adopted, a sufficient margin shown by symbol A is required between the lever 4 and the other axle hub in order for the lever 4 to operate. If the diameter is large, layout becomes extremely difficult.

The example shown in Figure 2 is a drum brake that uses a strut screw type automatic adjustment mechanism.
A strut 6 disposed between a leading shoe (not shown) and a trailing shoe 8 is configured as an assembly of a screw shaft and a nut, and an adjustment gear 7 is fixed to this screw shaft, so that when the lining is worn out, The length of the strut 6 is increased by rotating the adjustment gear using an adjustment lever (not shown) to change the screwing position with the nut, thereby automatically adjusting the clearance.

If such a structure is adopted, it will be difficult to implement it if there is not enough margin in the dimension B between the wheel cylinder 1 and the mating axle hub.

In order to solve the above-mentioned conventional drawbacks, a toothed element is provided on a strut made of plate material suspended horizontally between a pair of brake shoes, and a bell crank that can rotate in the axle direction is supported on this strut. A drum brake equipped with an automatic adjustment mechanism in which teeth formed on the bell crank are meshed with a toothed element has been introduced in Japanese Patent Publications No. 51-12782 and No. 57-43771. However, in these examples, the strut is made up of two members, or has a structure in which a separate toothed stud is fixed, and a special part is required to support the bellcrank on the strut. However, the disadvantage is that the number of parts increases and the space required is also large.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional brake system, and provides a drum brake equipped with an automatic adjustment mechanism that has a simple structure, requires a small mounting space, and can be installed in a small space. The purpose is to

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

3 and 4 illustrate the first embodiment of the present invention. In the figures, the reference numeral 10 is a leading shoe, 11 is a trailing shoe, and a lining 12 is fixed to each. .

One end of each of the leading shoe 10 and the trailing shoe 11 is connected to a return spring 1.
4 and 15 apply a restoring force to the wheel cylinder 13.

On the other hand, the other ends of the leading shoe 10 and the trailing shoe 11 are in contact with the anchor 21.

Leading shoe 10 wheel cylinder 1
A latch 16 made of a plate material is fixed at a position closer to the third side by welding, rivets, press fitting, or other mechanical means.

Further, one end of a parking lever 18 is rotatably supported on the trailing shoe 11 via a shaft 17, and a spring 19 is provided on the free end side of the parking lever 18.
Parking cable 2 given a restoring force by
0 is concatenated.

On the other hand, what is indicated by the reference numeral 22 is a strut made of a plate material that also serves as an adjuster lever, and as shown in FIG. This meshes with the straight toothed portion 16a to prevent slippage. Incidentally, the tooth portion 16a of the latch 16 may be formed in an arc shape like the tooth portion 22c of the strut 22, and in that case, a cutter for machining can be used in common. Furthermore, when the material of the latch 16 is made softer than that of the strut 22, if the teeth 22c are formed only on the strut 22, the teeth 22c of the strut will bite into the latch when the parking lever 18 is operated, thereby preventing slippage. In particular, the latch 16 does not need to be provided with teeth.

The other end of the strut 22 is in contact with the edge of the parking lever 18 via an arcuate portion 22a.

Note that the center of the arc of the toothed portion 22c of the strut is located at a position eccentric from the contact point of the arcuate portion 22a with the parking lever 18, and when the strut 22 rotates, the engagement position with the latch changes, and the position between the contact point and the engagement position changes. The distance increases gradually.

Further, the strut 22 has an L-shaped bent portion 22b extending obliquely upward in FIG.

An adjustment spring 23 is stretched between the strut 22 near the parking lever 18 side and the leading shoe 10.

Therefore, the strut 10 is always attracted to the leading shoe 10 side, and the strut 2
One end of 2 is given the habit of rotating clockwise in FIG. 4 about the arcuate portion 22a.

The operation of this embodiment configured as above will be explained.

In the set state, return spring 1
4, 15, 19 and adjust spring 23
The force causes the strut 22 to be pulled toward the latch 16, and the distance between the bent portion 22b and the side surface of the opening 18a is maintained at δ.

In this state, when hydraulic pressure is applied to the wheel cylinder 13 and the leading shoe 10 and trailing shoe 11 move toward the brake drum, the strut 22 moves to follow the leading shoe 10 due to the tensile force of the spring 23, and the gap δ is increased. Decrease.

When the hydraulic pressure is released, it returns to its original state.

On the other hand, as the lining wears down and the gap between the brake shoe and the brake drum increases,
Due to the movement of both shoes, the movement of the strut 22 following the leading shoe 10 is caused by the bending portion 22b.
is stopped by engagement with the side surface of the opening 18a of the parking lever, and the strut 22 and latch 16
There is a gap between us. Then, due to the tensile force of the spring 23, the strut 22 is rotated clockwise as shown by the arrow in FIG. 4 about the contact portion between the side surface of the opening 18a and the bent portion 22b.

As a result, the engagement position between the strut 22 and the latch 16 shifts, and the distance between the contact point of the strut 22 with the parking lever 18 and this engagement position increases, and the left and right brake shoes 10, 11 The gap between the brake shoe and the brake drum is automatically adjusted.

At this time, since the operating direction of the strut 22 is in the axle direction, even if the drum diameter is small and the mating hub has a large outer diameter, it can be installed in a small space.

Furthermore, since the strut also serves as an adjustment lever, no extra members are required, and no connection parts such as pins are required.

Although the latch 16 is provided as an engaging member on the free end side of the strut 22, the leading shoe 10 and the strut 22 may be directly engaged if the strength can be guaranteed.

In a second embodiment shown in FIGS. 5 and 6, the latch 16 is not fixed to the leading shoe 10, but is constructed as an assembly with a pin 24, which is formed on the leading shoe 10. After passing through the opening 10a with a gap δ, the latch 16 is attached to the leading shoe 10 by means of a spring washer 25 and a clip 26, and the latch 16 is slidable relative to the leading shoe 10. The adjuster spring 23 is stretched between the strut 22 and the head 24a of the pin 24, so that the strut 2
2 is biased so that it can rotate in a direction that increases the gap between both brake shoes 10 and 11. Note that the reference numeral 27 indicates a spring for causing the strut 22 to follow the movement of the trailing shoe 12.

The operation of this embodiment is almost the same as that of the first embodiment, or when hydraulic pressure is applied to the wheel cylinder 13, the strut 22 follows the trailing shoe 11 by the spring 27, so that the latch 16 is activated by the adjusting spring. 23 and slides, and at this time the pin 24 is pulled by the leading shoe 10.
The strut 22 is stopped by engaging the side surface of the opening 10a of the strut 22, and the strut 22 rotates.

As is clear from the above description, according to the present invention, a strut is used as an adjustment lever, one end of which is engaged with one brake shoe, and the other end is engaged with the other brake shoe without slipping. Since the struts are engaged and the spring gives the strut the ability to rotate in the direction of increasing the distance between the pair of brake shoes, a constant clearance can always be maintained even if the lining is worn.

Furthermore, since the strut is made of a single plate and also serves as an adjustment lever, no extra parts are required, and a large base is not required.

Furthermore, since the direction of rotation of the strut is in the axle direction, it can be mounted in a small space, and can be mounted even when the drum diameter is small and the mating axle hub outer diameter is large.

[Brief explanation of drawings]

Figures 1 and 2 are schematic configuration diagrams explaining different conventional structures, Figures 3 and 4 are diagrams explaining a first embodiment of the present invention, and Figure 3 is a front view, FIG. 4 is a side view of the strut, FIGS. 5 and 6 illustrate a second embodiment of the present invention, FIG. 5 is a front view, and FIG. 6 is a side view of the strut. 10... Leading shoe, 10a... Opening,
11... Trailing shoe, 12... Lining,
13... Wheel cylinder, 14, 15, 19... Return spring, 16... Latch, 16a... Teeth, 18... Parking lever, 22... Strut, 22a... Arc-shaped part, 22b... Bent part, 22c
...Tooth portion, 23...Adjustment spring, 24...Pin, 24a...Head, 25...Spring washer, 26...
Clip, 27...spring.

Claims (1)

[Claims] 1. In a drum brake equipped with a strut that is suspended horizontally between a pair of brake shoes and regulates the return position of the brake shoes, the strut is made of a single plate and One end is connected so as to be rotatable in the direction, and the other end has an arc-shaped tooth portion that engages directly with the other brake shoe or indirectly through a plate attached to the other brake shoe. The center of the circular arc of the teeth is offset from the center of rotation of the strut, and the strut is disposed between the strut and the other brake shoe with a spacing between the strut and the other brake shoe. A drum brake is characterized by having a spring attached to it to rotate it in the direction where it increases.