JPH0135001Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a drum brake having an automatic shoe gap adjustment function, and more particularly to a drum brake that can stably provide the automatic shoe gap adjustment function.

PRIOR ART A pair of brake shoes provided so as to be able to approach and separate from each other, a flat plate-like strut having U-shaped notches formed at both ends and stretched between the pair of brake shoes, and the brake shoe. an adjustment lever that is rotatably attached to one of the brake shoes and engages with one of the notches; and an adjustment lever that is attached to the one brake shoe and engages with an engagement tooth formed at the tip of the adjustment lever. By doing so, an adjustment lever is provided which is rotatably attached to the other brake shoe and which is rotatably attached to the notch. Conventionally, drum brakes have been provided that include a parking lever that engages with the other brake lever, and a spring that has one end hooked to the strut and always biases the strut toward the other brake shoe.

In such drum brakes, if the amount of separation between a pair of brake shoes during braking exceeds a predetermined amount due to wear of the friction material, etc., the spring always closes the other brake shoe. The adjustment lever is rotated in the direction of reducing the shoe gap by engagement with the strut which is biased to the side, and the shoe gap is automatically adjusted by changing its rotational position. In addition, when the parking lever engaged with the other notch of the strut is rotated, the strut is moved toward one brake shoe side against the biasing force of the spring, and the parking lever is rotated. While pressing the brake shoe against the rotating drum, the reaction force acts to also press the other brake shoe against the rotating drum.

Problems to be Solved by the Invention However, in such conventional drum brakes, the above-mentioned strut is always biased toward the other brake shoe side by a spring, so the strut is subject to the torsion of the spring. When a rotational moment due to a force or the like is applied, the adjustment lever engaged in one notch comes into contact with the side wall of the notch, and the adjustment lever and one brake shoe are pressed. It was hot. As a result, rotation of the adjustment lever with respect to the brake shoe is inhibited, and there is a possibility that the automatic adjustment function of the shoe gap may not be properly performed.

Means for Solving the Problems The present invention was devised to solve the above problems, and its gist is that, as mentioned above, the rotational position of the adjuster lever is in the position where it is engaged with the strut. In drum brakes in which the shoe clearance of the brake shoe is automatically adjusted by changing the The reason is that it has also been made larger.

Effects of operation and design If this is done, even if a rotational moment is applied to the strut due to the torsional force of the spring, etc.
The other notch, which has a smaller gap within the notch, is brought into contact first with the parking lever that is engaged in that notch, and the parking lever, which has a larger gap in the notch, is engaged with the parking lever first. The strainer is not brought into contact with the notch due to its rotational moment. Therefore, the possibility that the rotation of the adjustment lever with respect to one of the brake shoes will be impaired is eliminated, and the automatic shoe gap adjustment function can be stably performed. Moreover, in the present invention, it is only necessary to make the gap in one notch of the strut larger than the gap in the other notch, so the width dimension of those notches or the adjustment lever that is engaged in those notches can be adjusted. This has the advantage that the conventional device can be used almost as is, with only slight changes to the plate thickness of the parking lever.

Note that there is a risk that the operation of the parking lever will be affected by the other notch coming into contact with the parking lever, but the parking lever does not require delicate operation like the adjustment lever, so it was originally Since it is designed to operate with a large amount of force, its operation will not be hindered.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

In FIG. 1, reference numerals 10 and 12 are a pair of brake shoes mounted on a packing plate 18 by shoe hold down springs 14 and 16 so as to be able to approach and separate from each other. In addition, the other end is brought into contact with the anchor block 22. The brake shoes 10 and 12 are wheel cylinders 20
When brake fluid pressure is supplied to the rims, the pistons (not shown) push them away from each other, and the friction materials 28, 30 fixed to the outer surfaces of the rims 24, 26 are pressed against a rotating drum (not shown). ing. This provides a braking effect.

The expanded brake shoes 10, 12 are reduced in diameter by a return spring 32 stretched between them, and stopped by a strut 34 at a non-operating position. The strut 34 has U-shaped notches 3 at both ends, as shown in FIG.
The brake shoes 10, 12
Shew webs 40, 42 of the. In addition, the strut 34 is connected to the brake shoe 12.
It is always biased toward the brake shoe 12 by a spring 44 stretched between the brake shoe 12 and the brake shoe 12, so that when the brake shoe 12 is pushed to the left in FIG. It's summery.

The brake shoe web 42 of the brake shoe 12 has
A parking lever 46 is rotatably attached by a pin 48. This parking lever 4
6 is connected at its free end to the parking brake cable 50 and is engaged in the notch 38 of the strut 34 as shown in FIG. 2 near the pin 48, so that the parking brake cable 50 By being tightened, it rotates counterclockwise in FIG. 1, pressing the brake shoe 10 against the rotating drum via the strut 34, and as a reaction, also pressing the brake shoe 12 against the rotating drum. Also, a spring 5 stretched between the brake shoe 12
2, the parking lever 46 is always held in a pivoted position in which it abuts the rim 26 of the brake shoe 12, as shown in FIG.

On the other hand, the shoe web 40 of the brake shoe 10
A longitudinal adjustment lever 54 is rotatably attached to one end thereof by a pin 56. The adjustment lever 54 is a plate-like member, and the notch 3 of the strut 34 is located in the middle part.
6 is engaged. Further, an engagement hole 58 is formed in the intermediate portion of the adjustment lever 54, and is engaged with a protrusion 60 provided at one end of the strut 34 in this engagement hole 58 with a certain amount of play. Inner peripheral surface of engagement hole 58 and protrusion 6
0 (see Figure 2) is the appropriate shoe clearance between the brake shoe 10 and the rotating drum and the appropriate shoe clearance between the brake shoe 12 and the rotating drum when the brake is not applied. When the amount of separation between the brake shoes 10 and 12 exceeds the gap A when the brake is applied, the protrusion 60 of the strut 34 enters the engagement hole 58 of the adjustment lever 54. The adjustment lever 54 is rotated clockwise in FIG. 1 by contacting the circumferential surface.

Further, a plurality of engagement teeth 62 are provided at the free end of the adjuster lever 54 along an arc centered on the pin 56.
is formed, and the shew web 40 is connected by the pin 64.
Adjustment strap 6 rotatably attached to
It is meshed with 6. asia stretch 66
is always biased by a torsion coil spring 68 in the direction of engagement with the engagement tooth 62 of the adjustment lever 54, and the first
Rotation in the counterclockwise direction in the figure is prevented, but rotation in the clockwise direction is allowed by resisting the biasing force of the torsion coil spring 68 and getting over the engagement teeth 62. Then, when the brake shoes 10 and 12 are separated during braking, the amount of separation between the brake shoes 10 and 12 exceeds the gap A due to wear of the friction materials 28 and 30, and the adjustment lever 54 rotates clockwise due to engagement with the strut 34. When the engagement position between the engagement teeth 62 of the adjuster lever 54 and the adjuster strap 66 is moved by one pitch, the rotational position of the adjuster lever 54 is changed by that one pitch. When the brake shoes 10 and 12 are brought closer to each other as the brakes are released, the adjustment lever 54 held at the new rotational position comes into contact with the strut 34, thereby causing the brake shoes 10 and 12 to move closer together. The non-operating position is slightly spaced apart compared to before the brake operation, and the shoe gap between the brake shoes 10, 12 and the rotating drum is adjusted to an appropriate shoe gap corresponding to the gap A. The rotation of the adjustment lever 54 in the clockwise direction in FIG.
The rotation is in the direction of reducing the shoe gap.

Here, the strut 34 is normally biased toward the brake shoe 12 by a spring 44 stretched between it and the brake shoe 12, but as described above, tensile stress is applied to the spring 34. If so, the strut 34 to which one end of the spring 34 is latched may be subjected to a rotational moment, for example as indicated by the arrow in FIG. For this reason,
In conventional drum brakes, strut 3
4 rotates as shown by the dashed line in FIG.
4 and the show web 40 and pressed against them, the rotation of the adjustment lever 54 around the pin 56 was inhibited, and there was a risk that the above-mentioned automatic adjustment function of the show gap could not be performed normally. .

On the other hand, the drum brake of the present embodiment has a gap in the width direction in the notch 36 formed at one end of the strut 34, that is, a width dimension a of the notch 36 and an ajar engaged in the notch 36. The difference (a-b) between the thickness dimension b of the strever 54 and the shew web 40 is the gap in the width direction in the notch 38 formed at the other end, that is, the notch 3
8, and the parking lever 46 and the show web 4 engaged in the notch 38 thereof.
It is set to be larger than the difference (c-d) from the plate thickness dimension d of No. 2. For this reason, spring 4
Even if a rotational moment is applied to the strut 34 due to the torsional force of the strut 34, the strut 34 will first come into contact with the parking lever 46 and the show web 42, which are engaged in the notch 38 with a small gap. The adjustment lever 54 and the shear web 40, which are engaged with the notch 36 with a large gap, will not come into contact with the notch 36 and be pressed.

Therefore, the pin 56 of the adjustment lever 54
Eliminates the risk of loss of rotation around the
The automatic shoe gap adjustment function described above can be stably performed. Moreover, the gap (a-b) is changed to the gap (c
-d) for larger notches 36, 38;
Since it is only necessary to slightly change either the width dimensions a and c of the adjuster lever 54, the parking lever 46, or the plate thickness dimensions of the shew webs 40 and 42, there is no need to increase the number of parts or make major design changes. This has the advantage that conventional equipment can be used almost as-is.

On the other hand, in this case, the side wall of the notch 38 is brought into contact with the parking lever 46 and the shew web 42, and the parking lever 46 and the shew web 42 are pressed, and the parking lever 4
However, the parking lever 46 does not require delicate operation like the adjustment lever 54.
Further, the spring 52 resists the frictional force generated between the spring 52 and the shew web 42, and the parking lever 4
6, the operation of the parking lever 46 is not hindered at all by friction with the shew web 42.

In this embodiment, an adjustment lever 54 and a show web 40 are provided in the notches 36 and 38, respectively.
Although the parking lever 46 and the show web 42 are engaged, the adjustment lever 54,
It is also possible to configure so that only the parking lever 46 is engaged. That is, FIG. 4 is a diagram showing an example of this, and in this figure, the notch 70 is adapted to be engaged only with the parking lever 46, and in this case, the gap in the width direction within the notch 70 is , is the difference (e-f) between the width dimension e of the notch 70 and the plate thickness dimension f of the parking lever 46.

Although the embodiments of the present invention have been described in detail above, these are merely illustrative, and the present invention may be implemented in various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof. Of course it is possible.

[Brief explanation of the drawing]

FIG. 1 is a front view of a drum brake according to an embodiment of the present invention with the rotating drum removed. Second
The figure is a - sectional view in FIG. 1. FIG. 3 is a - sectional view in FIG. 2. FIG. 4 is a sectional view showing the main parts of another embodiment of the present invention. 10, 12: Brake shoe, 34: Strut, 36, 38, 70: Notch, 44: Spring, 46: Parking lever, 54: Adjustment lever, 66: Adjustment strap.

Claims (1)

[Claims for Utility Model Registration] A pair of brake shoes that are provided so as to be able to approach and separate from each other, and a flat strut that has U-shaped notches formed at both ends and is stretched between the pair of brake shoes. an adjustment lever that is rotatably attached to one of the brake shoes and engages with one of the notches; and an adjustment lever that is attached to the one brake shoe and formed at the tip of the adjustment lever. An adjustment strap that prevents the adjustment lever from rotating in the direction of expanding the shoe gap by engaging with the engagement tooth, but allows rotation in the direction of reducing the shoe gap, and is rotatably attached to the other of the brake shoes. a parking lever that engages with the other one of the notches, and a spring that has one end latched onto the strut and always biases the strut toward the other brake shoe, In a drum brake of the type in which the shoe gap of the brake shoe is automatically adjusted by changing the moving position, the widthwise gap in the one notch is changed to the widthwise gap in the other notch. A drum brake that is characterized by being larger than the original.