JPH018749Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automatic braking gap adjustment device for a drum brake.

[Conventional technology]

A conventional drum brake equipped with this type of braking gap automatic adjustment device is shown in Fig. 4, which is a leading/trailing brake equipped with a hydraulic actuation mechanism and a mechanical actuation mechanism as a parking brake. With a type drum brake, a leading side brake shoe 2 and a trailing side brake shoe 3 are supported on the back plate 1 by a shoe hold down pin 4 and a shoe hold spring 5, respectively, and face each other. The ends of both brake shoes 2 and 3 on the fulcrum side (the ends of the lower side omitted in the figure) abut against an anchor (not shown) fixed to the back plate 1, the other expansion side end 2a,
3a is brought into contact with the respective ends of two pistons 7, 8 inserted from both ends of a double-ended cylinder type wheel cylinder 6 fixed to the back plate 1, and both brake shoes 2, 3 are expanded. A return spring 9 is stretched between the open end portions 2a and 3a, and a master cylinder (not shown) is inserted into a hydraulic pressure chamber 10 defined between both pistons 7 and 8 of the wheel cylinder 6. By introducing the generated pressure fluid and pushing the pistons 7 and 8, the brake shoes 2 and 3 are expanded against the elastic force of the return spring 9, and the brake shoes are expanded. 2,
Hydraulic braking is achieved by sliding brake linings 2b and 3b provided on the outer periphery of the wheels 3 on the inner periphery of a brake drum (not shown) that rotates together with the wheel.

Further, a first strut member 11 is provided between the expansion side ends 2a and 3a of both brake shoes 2 and 3.
and the second strut member 12 are connected to the adjustment gear 1.
A strut 15, which is connected to the first strut member 11 by rotatably fitting the adjusting bolt 14 with the bolt 3 attached thereto, and by rotatably screwing the adjuster bolt 14 to the second strut member 12, is adjacent to the wheel cylinder 6. The strut 15 is
One end 15a thereof is fitted into a fitting recess 2d formed in the shew web 2c on the end 2a side of the leading side brake shoe 2, and the shew web 2c is held in place from both sides, and the other end 15b is also engaged. Similarly, the fitting recess 3d formed in the shoe web 3c of the trailing side brake shoe 3 is engaged to allow movement of the strut 15 in the axial direction, and rotation of the first strut member 11 and the second strut member 12 is performed. They are arranged to regulate each movement.

Further, in the trailing side brake shoe 3, the input lever 16 of the parking brake has a support shaft 17 whose one end 16a is provided on the shoe web 3c of the expansion side end 3a of the brake shoe 3.
The input lever 16 is rotatably arranged on the back plate 1 side surface of the show web 3c.
The point of action 16b is connected to the fitting recess 3 of the shew web 3c.
The input lever 16 is engaged with the end 15b of the strut 15 fitted to the end 15b of the strut 15, and the input lever 16 is rotated by pulling a brake wire (not shown) that is locked to the end of the input lever 16 on the force side. At point 16b, the strut 15 is mechanically pushed in the direction of the leading brake shoe 2 to move the leading brake shoe 2 in the outer circumferential direction, and the trailing brake shoe connected by the support shaft 17 is also moved. The brake shoes 3 are expanded by moving toward the outer circumference, and the brake linings 2b, 3b of both brake shoes 2, 3 are rubbed against a brake drum (not shown) that rotates together with the wheels, thereby applying a parking brake. The braking action is performed by

and the leading side brake shoe 2.
In the vicinity of the fitting recess 2d of the shew web 2c, there is a first arm 18b having a feed pawl 18a formed at its tip that engages with the adjustment gear 13, and a second arm 18b that comes into contact with the end 15a of the strut 15 to restrict rotation. An adjustment lever 18 having an arm 18c formed in a substantially V-shape rotates around a support shaft 18d on the surface of the show web 2c on the side opposite to the back plate, using a point on the proximal end side of the arms 18b and 18c as a fulcrum. The adjustment lever 18 is supported by the shew web 2c that supports the adjustment lever 18.
It is biased to rotate clockwise in FIG. 4 by the adjuster spring 19 stretched therebetween, and in the normal state, it is rotated clockwise by the second arm 18c in contact with the end 15a of the strut 15. It is arranged so that its rotation is restricted. Note that 20 is an axle shaft insertion hole formed in the center of the back plate 1, and arrow A is the direction of rotation of a brake drum (not shown) when the vehicle is moving forward.

By configuring the braking gap automatic adjustment device as described above, the brake linings 2b, 3b
When the brake shoes 2, which are expanded by the pistons 7, 8 of the wheel cylinder 6 when a hydraulic braking operation is performed,
3 is expanded by a predetermined amount or more, and both brake shoes 2 and 3 are expanded by a predetermined amount or more, the moving distance of the leading side brake shoe 2 in the outer circumferential direction also becomes a predetermined distance or more, and the end of the strut 15 15a is the engagement recess 2d of the shew web 2c.
By moving away from the strut 15, the adjustment lever 18, whose rotation was restricted by the end 15a of the strut 15, is allowed to rotate, and the adjustment lever 18 is moved by the elastic force of the adjustment spring 19. Rotate clockwise in Fig. 4, and
The adjustment gear 13 is rotated by the feed pawl 18a formed on the arm 18b in the direction in which the adjustment bolt 14 to which the adjustment gear 13 is attached is screwed out from the second strut member 12, and the adjustment gear 13 is rotated from the second strut member 12. By screwing out the strut bolt 14, the entire length of the strut 15 is extended, and the return positions of both brake shoes 2, 3 are changed to the outer circumferential side to automatically adjust to a predetermined braking gap.

After this adjustment of the braking gap is completed, when the braking by hydraulic pressure is released and both brake shoes 2 and 3 move inward, the second arm 18c comes into contact with the end 15a of the strut 15 again. The adjustment lever 18 is rotated counterclockwise in FIG. 4, and the feed pawl 18a formed on the first arm 18b of the adjustment lever 18
Pass over only one tooth of the adjusting gear 1.
3 and meshes at a new meshing position to complete the automatic adjustment of the braking gap.

[Problems to be Solved by the Invention] Therefore, in the above-mentioned conventional automatic braking gap adjustment device for drum brakes, the adjustment lever 18 rotatably supported on the leading side brake shoe 2 is adjusted by adjusting its feed. Since the pawl 18a is biased by the adjustment spring 19 so as to rotate the adjustment gear 13 in the direction of extension of the strut 15, the adjustment lever 18 is used to hook both ends of the adjustment spring 19.
Also, due to an error in the position of the locking hole drilled in the shew web 2, or variations in the spring strength of the adjuster spring 19, which is a coil spring, the biasing force of the adjuster lever 18 may be reduced. There was a problem that it took time to adjust the strength to the designed strength.

The present invention was developed in view of the above points, and it reduces the number of parts that make up the automatic braking gap adjustment device, has a simple structure and is easy to assemble, and has a stable and appropriate spring strength. The object of the present invention is to provide an automatic braking gap adjustment device for a drum brake that can provide a precise braking gap adjustment effect.

(Means for Solving the Problems) As a means for solving the above problems, the present invention provides that one end of a pair of brake shoes slidably supported on a back plate is brought into contact with an anchor to serve as a fulcrum, and the other end is used as a fulcrum. The ends of the strut are disposed so as to be expandable by a brake shoe expansion device, both ends of the strut are brought into contact with a shoe web near the brake shoe expansion device, and an adjustment gear of the strut is rotatably provided on the shoe web. In an automatic braking gap adjustment device for drum brakes, the braking gap is automatically adjusted by rotating the adjuster lever, extending the strut, and changing the return position of both brake shoes outward. The structure includes a first arm having a feed claw at its tip that engages with an adjustment gear, a second arm that contacts the end of the strut to restrict rotation, and a spring leg extending from the first arm. In addition, the spring leg portion is disposed in elastic engagement with the brake show web so as to rotate the feed pawl in the direction of engagement with the adjustment gear and the adjustment gear in the direction of strut extension. There is.

[Effect]

By integrally forming the spring leg part on the adjustment lever in this way, there is no variation in the biasing force of the adjustment lever for each product, and
A separate adjusting spring is not required, making assembly work easier.

〔Example〕

An embodiment in which the present invention is applied to a leading/trailing type drum brake will be described below with reference to FIGS. 1 to 3.

In this embodiment, instead of the adjustment lever and adjustment spring in the conventional automatic braking gap adjustment device for drum brakes shown in FIG. 4, an adjustment lever with integrally formed spring legs is used. Components that are the same as those of the conventional automatic braking gap adjustment device for a drum brake shown in FIG. 4 are given the same reference numerals, and detailed explanation thereof will be omitted.

A leading side brake shoe 2 and a trailing side brake shoe 3 are installed inside the back plate 1.
are elastically supported by a shoe hold down pin 4 and a shoe hold spring 5, respectively, and the ends of both brake shoes 2 and 3 on the fulcrum side (the lower omitted end in FIG. 1) are The ends 2a, 3a on the other expanding side contact an anchor (not shown)
are brought into contact with the respective ends of the pistons 7 and 8 of the wheel cylinder 6, and a return spring 9 is stretched between the expansion side ends 2a and 3a of both brake shoes 2 and 3, Pressure fluid generated in a master cylinder (not shown) is introduced into a hydraulic pressure chamber 10 defined between both pistons 7 and 8 of the wheel cylinder 6 to expand both the brake shoes 2 and 3. , braking is performed by hydraulic pressure.

Further, between the expansion side ends 2a and 3a of both brake shoes 2 and 3, the first strut member 11 and the second strut member 12 are connected to the adjustment gear 13.
A strut 15 connected by an adjusting bolt 14 with a
5 has its one end 15a fitted into the fitting recess 2d of the leading side brake shoe 2, and locks the shoe web 2c so as to sandwich it from both sides, and the other end 15b is similarly attached to the trailing side brake shoe 2. The strut 15 is disposed so as to be engaged with the fitting recess 3d of the shoe 3, allowing the strut 15 to move in the axial direction, and restricting rotation.

A parking brake input lever 16 is rotatably disposed on the trailing side brake shoe 3 by a support shaft 17, and the operating point 16b of the input lever 16 is connected to the end 15b of the strut 15. The strut 15 is rotated so as to be mechanically pushed in the direction of the leading side brake shoe 2 by pulling the brake wire (not shown), and the leading side brake shoe 2 is rotated in the outer circumferential direction. At the same time, the trailing side brake shoe 3 connected by the support shaft 17 is moved in the outer circumferential direction and expanded to perform a braking action by the parking brake.

and the leading side brake shoe 2.
In the vicinity of the fitting recess 2d of the shew web 2c, there is a first arm 30b having a feed pawl 30a formed at its tip that engages with the adjustment gear 13, and a second arm 30b that comes into contact with the end 15a of the strut 15 to restrict rotation. An adjustment lever 30 has an arm 30c formed in a substantially V-shape, and a spring leg 31 extending from the proximal end of the first arm 30b toward the back plate is integrally formed with the arm 30c. It is rotatably supported by a support shaft 32 on the surface of the show web 2c on the side opposite to the back plate, with one point on the base end side as a fulcrum.

The spring leg portion 31 extending from the base end of the first arm 30b forms a loop portion 31a on the base end side to provide elastic force, and the tip side from the loop portion 31a is A locking step portion 31b is inclined toward the first arm 30b side on which the claw 30a is formed, and protrudes toward the first arm 30b side at its tip.
is bent, and when the adjustment lever 30 is supported on the shoe web 2c of the brake shoe 2 by the support shaft 31 so that the feed pawl 30a meshes with the adjustment gear 13, the spring leg portion 31 is bent. The distal end side elastically engages with the engagement side 2e formed linearly in the vicinity of the fitting recess 2d of the shew web 2c, thereby urging the adjustment lever 30 clockwise in FIG. The portion 32b is located closer to the back plate 1 than the engaging side 2e, and the feed pawl 30a is biased in the direction of meshing with the adjustment gear 13.

By configuring the braking gap automatic adjustment device as described above, when braking is performed by hydraulic pressure operation, the adjustment lever 30 is moved toward the spring leg portion 31 as both brake shoes 2 and 3 are expanded. Due to the elastic force, it rotates clockwise in Figure 1, but
If the braking gap is within a predetermined range, the adjusting gear 13 is not rotated by simply moving the feed pawl 30a of the adjusting lever 30 between the two meshing teeth on both sides, and the braking gap is adjusted. I won't do it, but
When the brake linings 2b, 3b are worn and the braking gap exceeds a predetermined value, both brake shoes 2, 3
Since the expansion distance increases, the amount of rotation of the adjustment lever 30 increases, and the feed pawl 30a of the adjustment lever 30, which rotates clockwise, rotationally drives the adjustment gear 13.

When the adjustment gear 13 is rotationally driven, the adjustment bolt 14 is attached to the second strut member 1.
The strut 15 is rotated in the direction in which it screws out from the strut 2 to extend the entire length of the strut 15, and the return position of both brake shoes 2 and 3 is changed to the outer circumferential side, thereby adjusting the braking gap to a predetermined amount.

After this adjustment of the braking gap is completed, when the brake by hydraulic operation is released and both brake shoes 2 and 3 move inward, the second arm 30c comes into contact with the end 15a of the strut 15 again. The adjustment lever 30 is rotated counterclockwise in FIG. 1 against the elastic force of the spring leg 31, and the feed pawl 30a of the adjustment lever 30 passes over only one tooth of the adjustment gear 13. , meshes with the adjustment gear 13 at a new meshing position to complete automatic adjustment of the braking gap.

[Effect of idea]

As explained above, in the automatic braking gap adjustment device for a drum brake according to the present invention, the adjustment lever is elastically engaged with the brake shoe, the feed pawl of the first arm is engaged with the adjustment gear, and the adjustment gear is strutted. Since the spring legs that bias the adjustment lever to rotate in the extension direction are integrally formed, the biasing force of the adjustment lever is stabilized and it is effectively prevented from floating, and the adjustment spring This has the advantage that the number of parts can be reduced and assembly work can be made easier.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a plan view showing the main parts of a drum brake that employs the automatic braking gap adjustment device according to the present invention, and FIG. 1 is a cross-sectional view, FIG. 3 is a perspective view of an adjustment lever, and FIG. 4 is a plan view showing a drum brake equipped with a conventional braking gap automatic adjustment device. DESCRIPTION OF SYMBOLS 1... Back plate, 2... Leading side brake shoe, 3... Trailing side brake shoe, 2a, 3a... Expansion side end, 2c, 3c... Shoe web, 11... First strut member, 12...
Second strut member, 13... Adjustment gear, 1
4... Adjustment bolt, 15... Strut, 30
...Adjust lever, 30a...Feed claw, 30b...
First arm, 30c...Second arm, 31...Spring leg portion, 31a...Loop portion, 31b...Locking stepped portion.

Claims (1)

[Scope of utility model registration request] One end of a pair of brake shoes slidably supported on a back plate is in contact with an anchor to serve as a fulcrum, and the other end is arranged so as to be expandable by a brake shoe expansion device, and the brake shoe can be expanded. Both ends of the strut are brought into contact with a shoe web near the device, and the adjustment gear of this strut is rotated by an adjustment lever rotatably provided on the shoe web to extend the strut and move the return positions of both brake shoes outward. In the drum brake automatic braking gap adjustment device that automatically adjusts the braking gap by changing the braking gap, the adjustment lever includes a first arm having a feed pawl that engages with an adjustment gear at its tip, and an end of the strut. A second arm that contacts and restricts rotation and a spring leg extending from the first arm are integrally formed, and
The drum brake is characterized in that the spring leg portion is disposed in resilient engagement with the brake shoe web so as to rotate the feed pawl in the direction of engagement with the adjustment gear and the adjustment gear in the direction of strut extension. Brake gap automatic adjustment device.