JPH0130671Y2 - - Google Patents

Description

[Detailed description of the invention] Technical field This invention relates to a drum brake, and in particular, to a drum brake equipped with a device that automatically adjusts the shoe operating gap between the brake shoe and the brake drum. .

Prior Art A type of drum brake has a strut spanning between a pair of brake shoes. There is a brake shoe that automatically adjusts the operating gap of the brake shoe by extending the brake shoe according to the amount of wear on the brake shoe. The strut is an engaging portion in which one end of opposite sides of the first and second rod-shaped members branches into two, and the engaging portion is engaged with each of the pair of brake shoes. , having a star wheel in the middle part and the second
The first and second members are connected to each other by a connecting member that is fitted in the member so as to be relatively rotatable and is screwed onto the first member at the other end. When the connecting member is rotated by the adjuster, the first member screwed into the connecting member is pushed out by the screw action and the strut is extended, thereby pushing the pair of brake shoes in the direction of action. The shoe operating gap is adjusted.

Problems to be Solved by the Invention By the way, in such drum brakes, the engaging portions, which are bifurcated at both ends, are designed to sandwich the webs of a pair of brake shoes. is engaged with, but
In this case, a slight gap is created between the engaging part of the strut and the shew web, causing the strut to wobble around the axis, and based on this wobbling, the adjustment of the shew operating gap cannot be performed accurately. A problem arose. When trying to extend the strut by rotating the star wheel, the first
A co-rotation phenomenon occurs in which the member rotates together with the connecting member within the range allowed by the above-mentioned wobbling, and the amount of extension of the strut does not correspond accurately to the amount of rotation of the star wheel.

Means for Solving the Problems The present invention has been made to solve such problems, and its gist is that each of the rod-shaped first and second members on opposite sides The end portions are bifurcated engaging portions, and these engaging portions are engaged with the first and second brake shoes in a state where they are sandwiched, respectively, and a star wheel is provided in the intermediate portion. , the first member and the second member are connected to each other by a connecting member that is relatively rotatably fitted to the second member at one end side and screwed to the first member at the other end side. and a return spring stretched between the pair of brake shoes in the vicinity of the strut, and the connecting member and the first member are screwed together as the star wheel rotates in one direction. In a drum brake of a type in which the shoe operating gap between the pair of brake shoes and the brake drum is adjusted by extending the strut by changing the amount, the part of the return spring is
The first member is configured such that the first member cannot rotate relative to the first brake shoe around the axis when the star wheel rotates in one direction.
This is due to the fact that it is pressed elastically against a part of the member.

Operation and Effects of the Invention By doing this, by elastically pressing a part of the return spring against a part of the first member, the first member is moved to the first brake seat when the star wheel rotates in the one direction. Since it is prevented from rotating relative to the user around the axis, there is a gap between the engaging part of the first member and the first brake shoe in the direction in which the engaging part sandwiches the first brake shoe. Even if the first member is rotated in the shoe operation gap adjustment direction, the first member can be prevented from being rotated together with the star wheel and the connecting member. As a result, the strut can be accurately extended by an amount corresponding to the amount of rotation of the star wheel.
The shoe operating gap can be adjusted with high precision.

Embodiments Hereinafter, embodiments 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 arcuate brake shoes, each end of which is connected to an anchor 1 fixed on a bucking plate 14.
6, and each other end opposite to the one end is also brought into contact with the bucking plate 14.
Each is engaged with a piston 20 of a wheel cylinder 18 fixed above. These pair of brake shoes 10, 12 are pushed apart from each other by the piston 20 and pressed against a brake drum (not shown).

A return spring 22 is stretched between the pair of brake shoes 10, 12, so that the pair of brake shoes 10, 12 are returned to the non-operating position when the brakes are released. Also, a strut 24 is installed between the brake shoes 10 and 12.
The strut 24 is used to define the return amount (shoe operating gap) of the brake shoes 10, 12. A parking lever 26 and an adjustment lever 28 are rotatably attached to one brake shoe 12 by a common pin 30. When the end of the parking lever 26 opposite to the pin 30 is pulled to the right in FIG. It acts to press the brake drums 10 and 12 against the brake drum. The adjustment lever 28 also rotates when the parking lever 26 is rotated, and when the amount of rotation exceeds a certain amount, the star wheel 3 of the strut 24 rotates.
2 is rotated to extend the strut 24. Note that the adjustment lever 28 is biased clockwise in the figure by a spring 34. Further, the spring 34 also acts to press the tooth feeding portion 37 of the adjuster lever 28 against the star wheel 32.

As shown in detail in FIGS. 2 and 3, the strut 24 includes a rod-shaped first member 36 and a second member 38, and a connecting member 40 that connects them.
It is composed of. The first member 36 and the second member
Each opposite end of the member 38 is provided with flat engaging portions 46, 48 which engage the webs 42, 44 of the brake shoes 10, 12 as shown in FIGS. 2 and 4. A notch is formed into which the end edge is inserted, and it is bifurcated. These engaging portions 46 and 48 are formed in cutout portions 5 formed in the webs 42 and 44 so as to sandwich the webs 42 and 44.
0,52. Connecting member 40
has a star wheel 32 in the middle part, and one end side is a shaft-like part 54 having a circular cross section, and the shaft-like part 54 is fitted into the fitting hole of the second member 38 so as to be relatively rotatable. . On the other hand, the other end has a male threaded portion 56.
is formed, and this male threaded portion 56 is screwed into the female threaded hole of the first member 36. That is, when a rotational operation force is applied to the star wheel 32 and the connecting member 40 is rotated, the strut 24 is moved to the first position.
The member 36 is pushed out by the screw action, increasing its overall length.

The parking lever 26 attached to the brake shoe 12 together with the shoe web 44 is engaged with the engagement portion 48 of the second member 38.
The turning force of the parking lever 26 is applied to the strut 24.
is transmitted to the brake shoe 10 via the brake shoe 10, and the brake shoe 10 is moved in the direction of application. Note that the other brake shoe 12 is moved by the reaction force. The second member 38 is provided with a projection 58 for connecting the strut 24 and the adjustment lever 28, and this projection 58 connects the adjustment lever 28.
The strut 2 is engaged with the through hole 60 of the strut 2.
4 is moved to the right in the figure, the adjustment lever 28 is rotated.
The adjustment lever 28 has a tooth feeding portion 37, which is pressed against the star wheel 32 according to the biasing force of the spring 34. The tooth feed portion 37 is pressed against the outer peripheral surface of the engaging teeth formed on the outer periphery of the star wheel 32, but normally it does not engage with the engaging teeth and the adjuster lever 28 remains constant. When the star wheel 32 is rotated more than a certain amount, it engages with an adjacent engaging tooth, and when the brake is released, the star wheel 32 is rotated by one engaging tooth.

The return spring 22 is connected to the strut 2
4, and a coiled portion 66 wound around the strut 24. One straight part 62
is one surface (the upper surface in FIG. 3) of the flat engaging portion 46 of the first member 36 and a portion located on one side of the shew web 42 (the packing plate 14 side in FIG. 3). The part located on the opposite side) is pressed elastically against the
As a result, the engaging portion 46 and the first member 36 are restrained from rotating relative to the shew web 42 around the axis.

In the drum brake configured as described above, when the brake shoes 10 and 12 are worn out due to repeated braking, the brake shoes 1
The gap between 0, 12 and the brake drum, ie the shoe operating gap, increases. Brake shoe 1
As the operating gaps of 0 and 12 increase, the amount of rotation of the parking lever 26, the amount of movement of the strut 24, and the amount of rotation of the adjustment lever 28 increase, respectively, when the parking brake is applied. When the amount of rotation of the adjuster lever 28 increases, its tooth feed portion 37 passes over the engagement tooth of the star wheel 32 and comes to engage with the next engagement tooth, causing the star wheel 32 to rotate when the brake is released. At this time, the engaging portion 46 of the first member 36 and the shew web 4
If there is a gap, or play, between the two, the first member 36 will rotate around the axis together with the connecting member 40 by the amount allowed for the play, and the first member 36 will become a star wheel. It is no longer pushed out by an amount commensurate with the rotation amount of 32. In other words, the shoe operating gap cannot be adjusted accurately. However, in the above device, the first member 3
6 is in a restrained state by the return spring 22, that is, in a non-rotatable state,
When the star wheel 32 is rotated, the first member 36 is accurately pushed out by a corresponding amount. Therefore, in the above device, if the brake shoes 10, 12 are worn and the shoe operating gap increases, the shoe operating gap is appropriately adjusted by the increased amount.

Moreover, the above device prevents the rotation of the first member 36 by skillfully utilizing a part of the return spring 22 originally provided in the drum brake, and is different from the conventional drum brake. It has the advantage that there is no need to add any special parts.

Although the embodiments of the present invention have been described in detail above, the present invention can be implemented in other embodiments.

For example, in the above embodiment, a part of the return spring is pressed against the engaging part of the first member, but a pressing part separate from the engaging part is provided in the first member, and the return spring is pressed against the engaging part of the first member. It is also possible to press part of the spring against it.

Furthermore, the present invention can be implemented with various modifications based on the knowledge of those skilled in the art, such as being generally applicable to drum brakes in which the return spring is located near the strut. 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 brake drum removed, and Figs. 2 and 3 are sectional views and front views of main parts showing the strut and its surroundings in Fig. 1, respectively. It is a diagram. FIG. 4 is a perspective view of essential parts showing the engaged state of the strut and shoe in FIGS. 1 to 3. FIG. 10, 12: Brake shoe, 22: Return spring, 24: Strut, 32: Star wheel, 36: First member, 38: Second member, 4
0: Connecting member, 46, 48: Engaging portion, 54: Shaft portion, 56: Male thread portion.

Claims (1)

[Claims for Utility Model Registration] Each opposite end of a first member and a second member having a rod shape is an engaging portion bifurcated into two,
The engaging part is engaged with the first and second brake shoes in a state where they are sandwiched therebetween, and has a star wheel in the middle part, and is fitted to the second member at one end so as to be relatively rotatable. A strut in which the first member and the second member are connected to each other by a connecting member screwed into the first member at the other end thereof, and the pair of brake shoes are connected in the vicinity of the strut. and a return spring tensioned between the struts, and as the star wheel rotates in one direction, the amount of threaded engagement between the connecting member and the first member is changed to extend the strut. In a drum brake of a type in which a shoe operating gap between a pair of brake shoes and a brake drum is adjusted, a part of the return spring is connected to the first member when the star wheel rotates in one direction. A drum brake characterized in that the first member is elastically pressed against a part of the first member so as to be prevented from rotating relative to the first brake shoe around an axis.