JPS627869Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a drum brake equipped with an automatic operating gap adjustment function.

A pair of expandable bucking plates that are pressed against the inner circumferential surface of the rotating drum in order to automatically adjust the increase in the operating gap due to the rotation of the brake shoe that occurs with the use of drum brakes. and a first brake shoe and a second brake shoe, and an adjustment having engagement teeth rotatably attached to the second brake shoe and formed substantially along an arc centered on the rotation center. a member, a latch tooth that is provided on the second brake shoe so as to be engageable with an engagement tooth of the adjustment member and determines a rotational position of the adjustment member; a strut member disposed between the first brake shoe and the adjusting member to prevent the first brake shoe from approaching the adjustment member less than a certain distance; and when the separation amount when the second brake shoe is expanded exceeds a predetermined certain amount, the rotational position of the adjustment member is changed, thereby adjusting the drum brake whose operating gap is adjusted. Proposed. For example, Tokuko Sho 43-21822
This is what is described in the No. Publication.

However, according to such drum brakes,
Since it is composed of a large number of parts and requires a large number of assembly man-hours, it has the disadvantage of increasing the product price.

The present invention has been made for the purpose of providing a drum brake equipped with an automatic operating clearance adjustment function that requires a small number of parts and assemblies. a plate having a free end inclined with respect to a tangent to the circular arc, the tooth being fixed to the second brake shoe with the free end engaged with the adjustment member; The elastic member allows rotation of the adjustment member in the direction of extension of the adjustment member, but prevents rotation in the opposite direction.

In this way, the latch tooth, which was previously rotatably attached to the second brake shoe, is fixed, so that at least the pin for rotatably attaching the latch tooth and the associated assembly labor are eliminated, and since the latch tooth is made of an elastic plate material, it can be manufactured extremely easily, and the product price can be significantly reduced.

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

1 and 2, a wheel cylinder 12 and an anchor block 14 are fixed on a bucking plate 10, and a pair of arc-shaped brake shoes 16,
18 are expandably mounted on the bucking plate 10 by shew hold-down devices 20 and 22, respectively. Brake shoe 16, 18
These include friction materials 24 and 26 that are in sliding contact with the inner circumferential surface of a rotating drum (not shown), band-shaped rims 28 and 30 to which the friction materials 24 and 26 are fixed, and rims 28 and 30 that are integrally formed inside the rims 28 and 30. A return spring 36 is stretched between the brake shoes 32 and 34, and the brake shoes 16 and 18 move toward each other. energized. Bifurcated notches 40 and 42 cut in the longitudinal direction at both ends of the strut member 38 are respectively engaged with the notches formed at opposite positions of the show webs 32 and 34, and the brake shaft The inoperative position of the levers 16, 18 is maintained.

A packing brake lever 46 connected to a packing brake cable 44 is rotatably attached to one brake shoe 16 by a pin 48, and the packing brake lever 46 is attached to the shoe web 32 and the strut member 38. Furthermore, a connecting spring 50 is tensioned between the show web 32 and the strut member 38, so that the strut member 3
8 is urged toward the shew web 32 side.

The other brake shoe 18 has the brake shoe 16, 18 when the brake shoe 16, 18 is expanded by the wheel cylinder 12.
An adjustment member 52 whose rotational position is changed when the separation amount of the adjustment member 18 exceeds a predetermined certain amount is rotatably attached by a pin 54. That is, the notch 42 of the strut member 38 is provided with an inward protrusion 56, and when the arm portion 58 of the adjustment member 52 is engaged with the notch 42 together with the show web 34, the arm portion 58 and the brake shaft are connected. The adjustment member 52 is prevented from approaching the shoe web 16 by a certain distance or less, and the arm portion 58 and the protrusion 56 are engaged, so that when the strut member 38 and the show web 34 are relatively separated, the adjustment member 52 is prevented from coming closer than a certain distance. It is designed to be rotated. In other words, the brake shoe 16 and the adjustment member 52 are operatively connected by the strut member 38. Here, the protrusion 56 and the arm portion 5
A predetermined clearance A ₀ is provided between the brake shoes 16 and 8, which is substantially opposite to the minimum operating clearance of the brake shoes 16 and 18. Scratching is prevented.

The adjusting member 52 has engaging teeth 60 that substantially follow a circular arc centered on the rotation center, and a latch tooth 6 that engages with the engaging teeth 60 to prevent the adjusting member 52 from rotating.
2 is fixed to the inner peripheral surface of the rim 30.
As shown in FIGS. 3 and 4, the latch tooth 62 has a proximal end 64 that engages with a claw 66 formed by cutting and raising a portion of the rim 30, and The free end 68 is the bucking plate 1
It is formed of a longitudinal spring plate material that is bent toward the inner circumferential side of 0 to be engaged with the engagement teeth 60 at an angle of α to the tangent B of the circular arc A on which the engagement teeth 60 are connected. has been done. The engagement hole 70 formed in the middle part of the latch tooth 62 is connected to the rim 30.
The latching teeth 62 are fitted into and positioned by the engaging protrusions 72 provided on the latching teeth 60 and are positioned by the elastic force of the latching teeth 62 themselves against the engaging teeth 60 and the claw portions 66.
is fixed to the rim 30, and the free end 68 of the adjustment member 52 is allowed to rotate in the extension direction (counterclockwise direction in FIG. 4), but is prevented from rotating in the opposite direction. It is. Therefore, when the arm portion 58 is pulled toward the brake shoe 16 by the strut member 38 when the brake shoes 16 and 18 are expanded, the adjustment member 52 resists the elastic force of the latching member 62 and moves to the first position. Although the arm portion 58 is rotated counterclockwise in the figure, even if the arm portion 58 is pushed toward the brake shoe 18 by the strut member 38, the engaging tooth 60 of the adjusting member 52 engages with the latch tooth 62. 1, the adjustment member 52 cannot rotate clockwise in FIG.

Incidentally, the engagement teeth 60 of the adjustment member 52 are connected to the latching teeth 62.
It is serrated to ensure reliable engagement.

Therefore, in the drum brake configured as described above, when the drum brake is not in operation, the brake shoes 16 and 18, which approach each other according to the biasing force of the return spring 36, are adjusted as shown in FIG. It is supported by a strut member 38 which engages the member 52 and the shew web 32 to form an operating gap between it and the inner peripheral surface of the rotating drum.

In such a state, the wheel cylinder 12
When the brake shoes 16 and 18 are expanded by being driven by the strut member 38, since the strut member 38 is brought into contact with the brake shoe 16 by the connecting spring 50, the strut member 38 and the brake shoe 18 are separated. The clearance A ₀ disappears due to the relative separation. Normally, in this condition, the brake shoe 1
6 and 18 are pressed against the inner peripheral surface of the rotating drum.

When the brake shoes 16 and 18 are expanded, the amount of separation between the brake shoes 16 and 18 increases due to wear of the friction materials 24 and 26, and the amount of movement of the strut member 38 relative to the brake shoe 18 increases. When the size increases, the protrusion 56 of the strut member 38 and the arm portion 58 of the adjusting member 52 come to engage with each other, and the adjusting member 52 rotates counterclockwise in FIG. 1 against the elastic force of the latch teeth 62. be rotated.
When the amount of separation between the brake shoes 16 and 18 further increases and exceeds a predetermined value, the engagement teeth 60 and the latch teeth 62 are disengaged, and at the same time the latch teeth 62 are disengaged. Based on the elastic force, the engaging teeth 60 and the latch teeth 62 are brought into engagement again with a one-pitch deviation. Therefore, the rotational position of the adjusting member 52 is changed by one pitch, and the arm portion 58 is moved to the brake shoe 1.
6 side, so when the operation of the wheel cylinder 12 is released and the brake shoe 16 and the arm portion 58 are brought into contact with both ends of the strut member 38 according to the biasing force of the return spring 36,
The operating gap between the brake shoes 16 and 18 is automatically adjusted to a smaller value. Here, the predetermined constant value refers to the play gap A ₀ and the arm required to rotate the adjustment member 52 in order to disengage the engagement tooth 60 from the latching tooth 62. This corresponds to the value obtained by adding the moving distance of the section 58.

In this way, according to this embodiment, since the latch tooth 62 is fixedly provided on the inner circumferential surface of the rim 30, there is no need for a pin or the like for rotatably attaching the latch tooth 62. The number of parts and assembly man-hours are reduced. Further, since the latch tooth 62 is made of a longitudinal spring plate material, the latch tooth 62 itself can be manufactured very easily. Therefore, drum brakes can be manufactured quickly and inexpensively.

Furthermore, in this embodiment, since the latch tooth 62 is fixed to the rim 30 by its elastic force,
Latch teeth 62 do not require bolts or rivets, etc.
Another advantage is that the installation work can be done extremely easily.

Although the embodiment of the present invention has been described above based on the drawings, the present invention can be applied to other aspects as well.

For example, the latch tooth 62 is positioned and fixed by a claw portion 66 and an engaging protrusion 72 provided on the shoot rim 30, but an engagement member may be fixedly provided on the shoot web 34 or the shoot rim 30, or an engagement groove may be formed. It is also possible to position and fix it by forming it, or it can be fixed with bolts or the like if the complexity of the installation work is tolerable.

Moreover, the shape of the latch tooth 62 may be formed into a linear shape or the like. In short, it is sufficient to provide a free end that is inclined with respect to a tangent to a circular arc formed by a series of engagement teeth 60.

The above-mentioned embodiment is merely one embodiment of the present invention, and the present invention may be modified in various ways without departing from its spirit.

[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. 2 and 3 are a sectional view and a sectional view, respectively, of FIG. FIG. 4 is a partial sectional view showing the main part of FIG. 1. 10: Bucking plate, 16, 18: Brake shoe, 38: Strut member, 52: Adjusting member, 60: Engagement tooth, 62: Latch tooth, 68: Free end.

Claims (1)

[Claims for Utility Model Registration] A pair of first and second brake shoes that are expandably attached to a bucking plate and pressed against the inner peripheral surface of a rotating drum; and the second brake shoe. an adjusting member rotatably attached to the adjusting member and having engaging teeth formed substantially along an arc centered on the rotation center; and the second brake shaft being engageable with the engaging teeth of the adjusting member. A latch tooth is provided on the shoe and determines the rotational position of the adjustment member, and a latch tooth is provided between the first brake shoe and the adjustment member to prevent them from approaching each other by a certain distance or less. , a strut member operatively connecting the first brake shoe and the adjustment member, wherein the distance between the first brake shoe and the second brake shoe when they are extended is a predetermined constant amount. In the drum brake, in which the operating gap between the pair of brake shoes with respect to the rotating drum is automatically adjusted by changing the rotational position of the adjusting member when the amount exceeds the amount, A plate member including a free end inclined with respect to a tangent to the circular arc, the free end being fixed to the second brake shoe in a state engaged with the adjustment member, and the direction in which the free end extends 1. A drum brake equipped with an automatic operating gap adjustment function, characterized in that the adjustment member is made of an elastic member that allows the adjustment member to rotate but prevents rotation in the opposite direction.