JPH0221457B2 - - Google Patents

Description

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

A pair of first brake shoes and a second brake shoe, each forming an arc shape and disposed on the bucking plate so as to be able to spread from each other, and pressed against the inner circumferential surface of the rotating drum, and the second brake shoe. an adjusting member that is rotatably attached to the user and has engaging teeth formed substantially along an arc centered on the rotation center; and the second brake that is engageable with the engaging teeth of the adjusting member. a latch tooth provided on the shoe and determining the rotational position of the adjustment member; a spring for causing the engagement teeth and the latch tooth of the adjustment member to engage with each other; and the first brake shoe and 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 amount of separation when the second brake shoes are expanded exceeds a predetermined amount, the rotational position of the adjustment member is changed so that the pair of brake shoes are separated from the rotating drum. A type of drum brake in which the operating time is automatically adjusted has been proposed. For example, this is described in Japanese Patent Publication No. 43-21822.

However, in this type of drum brake, the latch tooth is usually rotatably provided on the second brake shoe; On the other hand, the adjustment member is in the form of a longitudinal plate, and one end of the adjustment member is in the form of a longitudinal plate. Since the adjustment member is normally provided so as to be rotatable approximately along the radial direction of the second brake shoe, the rotational position of the adjustment member changes as the operating distance is adjusted. It will be changed to the inner circumference side,
It is difficult to avoid that the free end of the adjustment member protrudes relatively largely from the inner circumferential edge of the second brake shoe, and this may cause the adjustment member to interfere with other members when adjusting the operation time, and also cause the adjustment to be difficult. There was a problem in that the installation space for the members in the radial direction of the second brake shoe was increased as a whole.

Against this background, the present invention reduces the number of parts and assembly man-hours, prevents the adjustment member from interfering with other members, and reduces the installation space of the adjustment member in the radial direction of the second brake shoe. This was done with the purpose of providing a drum brake that is equipped with an automatic adjustment function, and its gist is that the above-mentioned types of operation intervals that can be used with an automatic adjustment function are In the drum brake, the latch tooth is fixed to a portion of the second brake shoe located approximately on the axis of the strut member, and the adjustment member is rotated approximately along the circumferential direction of the second brake shoe. The adjusting member is movably disposed in a direction in which the engaging teeth and the latching teeth of the adjusting member are disengaged when the first brake shoe and the second brake shoe are expanded. The center of rotation is movable relative to the second brake shoe.

In this way, the latch teeth are fixed to the second brake shoes, and when the pair of brake shoes are expanded, the engagement teeth of the adjustment member and the latch teeth are disengaged. The center of rotation of the adjusting member is in the second direction.
By being movable with respect to the brake shoe, at least the pin for rotatably attaching the latch teeth and the number of man-hours for assembling the pin are reduced, thereby reducing the product price. In this case, if the latch teeth are formed integrally with the second brake shoe, the number of parts and the number of assembly steps can be further reduced.

Moreover, the latch teeth are provided at a portion of the second brake shoe that is located approximately on the axis of the strut member, and the adjustment member is arranged to be rotatable approximately along the circumferential direction of the second brake shoe. As a result, the rotational position of the adjusting member is changed approximately along the circumferential direction of the second brake shoe as the operating time is adjusted. The second brake shoe of the adjustment member can be prevented from protruding largely from the inner peripheral edge, and can suitably prevent the adjustment member from interfering with other members during adjustment between operations. This allows the installation space in the radial direction to be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below 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 engaged with the notches formed at opposite positions of the shew webs 32 and 34, respectively.
The inoperative position of the brake shoes 16, 18 is maintained.

A parking brake lever 46 connected to a parking brake cable 44 is rotatably attached to one brake shoe 16 by a pin 48 . 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 cutout 42 of the strut member 38 is provided with an inward protrusion 56, and the arm portion 58 of the adjustment member 52 is inserted into the cutout 42 together with the show web 34.
By engaging with the arm part 58 and the brake shoe 16, the arm part 58 and the brake shoe 16 are prevented from coming closer than a certain distance, and by engaging the arm part 58 and the protrusion 56, the strut member 38 and When the shoe web 34 is relatively separated from the brake shoe web 34, the adjustment member 52 can be rotated substantially along the circumferential direction of the brake shoe 18. In other words, the brake shoe 16 and the adjustment member 52 are operatively connected by the strut member 38. Here, a predetermined clearance A is provided between the protrusion 56 and the arm portion 58, which approximately corresponds to the minimum operating clearance of the brake shoes 16 and 18.
When changing the rotational position of the adjusting member 52, the brake shoes 16, 18 are prevented from dragging.

The adjustment member 52 has engagement teeth 60 that approximately follow an arc centered on the rotation center.
A latching tooth 62 that engages with and prevents rotation of the adjustment member 52 is integrally formed on a bulge 63 located approximately on the axis of the strut member 38 on the inner circumferential surface of the rim 30. Therefore, in this embodiment, the brake shoe 16 corresponds to the first brake shoe, and the brake shoe 18 corresponds to the second brake shoe. As shown in FIG. 3, the pin 54 attached to the adjustment member 52 so as to form the center of rotation of the adjustment member 52 provides a predetermined play in the large diameter through hole 64 provided in the shew web 34. The pin 5 is also passed through the pin 5.
4 and the shew web 34 is an engaging tooth 6.
0 and the latch teeth 62 engage with each other.
A spring 66 is stretched on the bucking plate 10 side. 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 is moved between the through hole 64 and the pin 54.
Due to the play between the engaging teeth 60 and the latch teeth 62, the engaging teeth 60 and the latch teeth 62 are first moved in the direction in which they are disengaged, and the engagement is disengaged. rotation is allowed. On the contrary, strut member 3
When the arm portion 58 is pushed toward the brake shoe 18 by the lever 8, the adjusting member 52 is moved according to the biasing force of the spring 66, and the engaging tooth 60 and the latch tooth 62 are brought into engagement. Adjustment member 5
2 in the clockwise direction in FIG. 1 is prevented.

Therefore, in the drum brake configured as described above, when not braking, the brake shoes 16 and 18, which approach each other according to the biasing force of the return spring 36, are adjusted by the adjustment member, as shown in FIG. 52 arm portion 58 and show web 32
and is supported by a strut member 38 which engages the inner peripheral surface of the rotating drum to form an operating gap therebetween.

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, the strut member 38 and the brake shoe 18 are kept in contact with the brake shoe 16 by the connecting spring 50. are relatively spaced apart and the play A
disappears. Normally, in this condition, brake shoe 1
6 and 18 are pressed against the inner peripheral surface of the rotating drum.

When the brake shoes 16, 18 are expanded, if the distance between the brake shoes 16, 18 exceeds a predetermined constant value due to wear of the friction materials 24, 26, the strut member 38 As the amount of movement of the brake shoe 18 increases,
The rotation center of the adjustment member 52 is moved to disengage the engagement teeth 60 and the latching teeth 62, and at the same time the adjustment member 52 is rotated counterclockwise in FIG.
The engaging tooth 60 and the latch tooth 62 are meshed again with a one-pitch deviation. For this reason, the adjustment member 5
The rotational position of the arm 58 is shifted by 1 pitch.
moves toward the brake shoe 16, 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. , brake shoe 16, 18
The operating gap is automatically adjusted to a smaller value. Here, the predetermined constant value is the sum of the play gap A and the distance that the arm portion 58 moves to disengage the engagement teeth 60 from the latching teeth 62. corresponds to

In addition, the brake shoe 16 of the strut member 38
When the adjustment member 52 is rotated in the direction of disengaging the engagement tooth 60 and the latch tooth 62 as it moves to the side, a rotational moment is applied to the adjustment member 52 according to the biasing force of the spring 66. occurs, so the engaging tooth 6
0 and the latch teeth 62 are disengaged, and the adjusting member 5
2 is rotated, in order to ensure that the engaging tooth 60 and the latch tooth 62 are reliably engaged with each other at a rotation position shifted by one pitch of the engaging tooth 60, the latch tooth 60 must be rotated. The engagement teeth 60 are arranged on a circular arc that becomes larger in diameter as it moves toward the rotation prevention direction (clockwise direction in FIG. 1) by the teeth 62.
It is desirable to form a

According to this embodiment, the latch teeth 62 are integrally formed on the inner circumferential surface of the rim 30, so there is no need for a pin or a latch member for rotatably attaching the latch teeth 62. Therefore, the number of parts and assembly man-hours are reduced. Therefore, drum brakes can be manufactured at low cost.

Further, according to this embodiment, the latch teeth 62 are provided on the inner circumferential surface of the rim 30 at a portion located approximately on the axis of the strut member 38,
is disposed so as to be rotatable approximately along the circumferential direction of the brake shoe 18, so that the rotational position of the adjustment member 52 changes along the circumferential direction of the brake shoe 18 as the operating time is adjusted.
As in the conventional case where the adjusting member is rotatably disposed approximately along the radial direction of the second brake shoe, the free end of the adjusting member 52 is changed substantially along the circumferential direction of the second brake shoe. It is possible to avoid the side from protruding largely from the inner peripheral edge of the brake shoe 18. As a result, it is possible to suitably prevent the adjustment member 52 from interfering with other members when adjusting the operating time, and the installation space for the adjustment member 52 in the radial direction of the brake shoe 18 is smaller than in the past. It is reduced.

Next, another embodiment of the present invention will be described. In the following description, parts common to those in the above-mentioned embodiments are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 4, a through hole 68 is formed at the center of rotation of the adjustment member 52, and an annular projection 70 is formed at the opening edge of the through hole 68 on the shew web 34 side by burring. The annular protrusion 70 is fitted into the through hole 64 with an appropriate clearance, and one end of the spring 66 is locked in the through hole 68 from the backing plate 10 side, and the other end is locked in the shew web 34. has been done.

According to this embodiment, since the pin 54 for attaching the adjustment member 52 is not required, there is an advantage that the number of parts and the number of assembly steps are further reduced.

In FIGS. 5 and 6, the latch tooth 62 is a member separate from the rim 30, and is a substantially fan-shaped latch made of a wear-resistant material such as hardened steel, carburized steel, or nitrided steel. The latch member 72 is provided with a rectangular engagement protrusion 74 that protrudes in the opposite direction to the latch teeth 62 and is fixed to the brake shoe 18 . That is, the rim 30 has a notch 7 that is approximately the same size as the engaging protrusion 74 of the hooking member 72.
6 is formed and the engaging protrusion 74 is fitted into the notch 76, and the hooking member 72 is held in the thickness direction by the claw portion 78 cut and raised when forming the notch 76 and the show web 34. It is being held between.

According to this embodiment, since the latch teeth 62 are formed on the sealing member 72 made of wear-resistant material, the engagement teeth 62
The wear due to engagement with the locking member 72 is significantly reduced, and even if it wears out, only the locking member 72 needs to be replaced. In addition, the hanging member 72
To attach the brake shoe 18 to the brake shoe 18, it is only necessary to fit it into the notch 76, so the assembly work is extremely easy, and since only the latching member 72 needs to be made of wear-resistant metal, the brake shoe 18 can be made inexpensive.

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

For example, by erecting a pin in the shew web 34 and forming a large diameter hole in the adjustment member 52 into which the pin is inserted or a long hole substantially parallel to the strut member 38, the adjustment member 52 can be attached to the shew web 34. It may also be attached rotatably.

Further, the arm portion 58 of the adjustment member 52 and one end of the strut member 38 are pivotally connected, and the show web 32
and the other end of the strut member 38 may be connected with a predetermined clearance A. In short, it is sufficient that the shew web 32 and the arm portion 58 are operatively connected with a predetermined clearance A.

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

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment of the present invention with the rotating drum removed. FIG. 2 is a cross-sectional view taken from the side of FIG. 1. FIG. 3 is a partial sectional view showing a main part of the embodiment shown in FIG. FIG. 4 is a diagram corresponding to FIG. 3 showing another embodiment of the present invention. FIG. 5 is a front view showing the main parts of another embodiment of the present invention.
FIG. 6 is a sectional view taken from the side in FIG. 5. 10: Bucking plate, 16: Brake shoe (first brake shoe), 18: Brake shoe (second brake shoe), 38: Strut member, 52: Adjustment member, 60: Engaging tooth, 62: Latch tooth, 66: Spring.

Claims (1)

[Scope of Claims] 1. A pair of first and second brake shoes each forming an arc shape and disposed on a bucking plate so as to be able to expand with respect to each other, and pressed against the inner circumferential surface of a rotating drum. an adjusting member rotatably attached to the second brake shoe and having engaging teeth formed substantially along an arc centered on the rotation center; and an adjusting member that engages with the engaging teeth of the adjusting member. a latch tooth that is removably provided on the second brake shoe and determines a rotational position of the adjustment member; a spring that causes the engagement tooth of the adjustment member and the latch tooth to engage with each other;
a strut member disposed between the first brake shoe and the adjustment member to prevent them from coming closer than a certain distance and operatively connect the first brake shoe and the adjustment member; The rotational position of the adjustment member is changed via the strut member when the separation amount when the first brake shoe and the second brake shoe are expanded exceeds a predetermined certain amount. By being
In a drum brake of the type in which the operating distance of the pair of brake shoes with respect to the rotating drum is automatically adjusted, the latch tooth is provided at a portion of the second brake shoe that is located approximately on the axis of the strut member. is fixedly installed, and the adjusting member is rotatably arranged substantially along the circumferential direction of the second brake shoe;
The center of rotation of the adjustment member is aligned in the direction in which the engagement teeth of the adjustment member and the latching teeth are disengaged when the first brake shoe and the second brake shoe are expanded. A drum brake with an automatic adjustment function, characterized by being movable relative to the second brake shoe.