JPH0514022Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention extends a strut disposed between a pair of brake shoes arranged opposite to each other on a back plate to regulate the contracted position of both brake shoes. The present invention relates to an automatic braking gap adjustment device for vehicle drum brakes.

[Conventional technology]

For example, the automatic braking gap adjustment device disclosed in Japanese Utility Model Publication No. 13783/1983 will be explained based on FIG.
A return spring 4 that biases both brake shoes 3, 3 in the direction of diameter reduction is installed between them, and both brake shoes 3, 3 are expanded and rotated by a foil cylinder 5 fixed to the back plate 2. The brake linings 3a, 3a are worn out due to repeated braking operations, and the linings 3a, 3a are worn out due to repeated braking operations.
An automatic adjustment device 6 is provided to correct the increase in the braking gap between the brake drum and the brake drum.

This braking gap automatic adjustment device 6 includes a first strut member 7 and a second strut member connected between the two brake shoes 3 via an adjuster bolt 8 screwed into the first strut member 7. A strut 10 consisting of a strut 9 is disposed, and the end of the first strut member 7 is connected to the web 3b of one brake shoe 3, and the end of the second strut member 9 is connected to the web 3b of the other brake shoe 3. The adjustment lever 12, which is rotatably supported on the web 3b of the other brake shoe 3 by a pin 11, is rotated by the operation of the adjustment spring 13. The adjustment bolt 8 engages with the adjustment lever 12 by the rotation of the adjustment lever 12.
The ratchet gear 14 is rotated to extend both strut members 7, 9 to regulate the contracted position of both brake shoes 3, 3, thereby automatically adjusting the braking gap.

[The problem that the idea aims to solve]

However, in the case of the above structure, when the ratchet gear 14 is rotated, the adjustment lever 12 rotates at an angle with respect to the web 3b.
As shown in the figure, the outer periphery of the pin 11 inserted and fixed into the adjustment lever 12 is in surface contact with the circumferential surface of the shaft hole 3c of the web 3b that pivotally supports the pin 11. This has caused a problem in that the pin 11 and the shaft hole 3c are distorted, causing uneven wear of the pin 11 and the shaft hole 3c.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an automatic braking gap adjustment device for a vehicle drum brake that eliminates twisting between the pin and the shaft hole and improves the durability of the pin and shaft hole.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a first
A strut consisting of a strut member and a second strut member connected via an adjustment bolt screwed into the first strut member is provided, and is rotatably supported by a pin on the web of the brake shoe. In the braking gap automatic adjustment device for a vehicle drum brake, the adjustment lever rotates the ratchet gear of the adjustment bolt to regulate the contracted position of both brake shoes. , a small diameter shaft part on the other end,
A tapered shaft portion is provided between the large diameter shaft portion and the small diameter shaft portion, the large diameter shaft portion is inserted into and fixed to a web of the brake shoe, and the adjustment lever has a tapered shaft portion having a diameter larger than the small diameter shaft portion. The tapered shaft has a shaft hole in which the small-diameter shaft portion is loosely inserted, and an arcuate contact surface that slides into contact with the circumferential surface of the tapered shaft portion is formed on the web-side periphery of the shaft hole. .

[Effect]

Therefore, in order to automatically adjust the braking gap, even if the adjustment lever is tilted and rotated with respect to the web of the brake shoe, the inner diameter of the shaft hole is larger than the small diameter shaft of the pin. Because of this, only the contact position between the arcuate contact surface and the pin's tapered shaft changes, and no prying occurs between the shaft hole and the pin.
This eliminates abrasion and improves durability.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2. Components that are the same as those in the prior art example are given the same reference numerals and their explanation will be omitted.

The adjustment lever 20 has a first arm 20b whose tip engages with the ratchet gear 14 of the adjustment bolt 8 and a second arm 20c which abuts the end of the second strut member 9, extending from a base plate 20a. The pin 21 fixed to the web 3b of the other brake shoe 3 is inserted into the shaft hole 2 formed in the base plate 20a.
0d, and is rotatably supported, and biased clockwise in FIG. 1 by an adjusting spring 13.

The adjustment lever 20 moves to the left in FIG. 1 due to the expansion of the brake shoes 3, 3, and the second arm 20c and the second strut member 9 are separated. The force rotates clockwise in the figure, and returns to the initial position as the brake shoes 3, 3 move in the diameter reduction direction. When the braking gap is within a predetermined amount, the tip of the first arm 20b only slides on the same tooth surface of the ratchet gear 14 and does not rotate the ratchet gear 14, but if the linings 3a, 3a wear more than a predetermined amount, the adjustment lever 20 becomes larger, the tip of the first arm 20b passes over the teeth of the ratchet gear 14 and engages with the next tooth to rotate the ratchet gear 14, thereby extending the strut 10 and causing the brake shoe 3, The reduced position of No. 3 is regulated to compensate the braking gap to an appropriate gap.

The pin 21 has a large diameter shaft portion 21a at one end, a small diameter shaft portion 21b at the other end, and a tapered shaft portion 21c between the large diameter shaft portion 21a and the small diameter shaft portion 21b. The web 3b of the other brake shoe 3 is inserted through and fixed to the shaft portion 21a.

The shaft hole 20d formed in the substrate 20a of the adjustment lever 20 is formed to have a larger diameter than the small diameter shaft portion 21b, and the small diameter shaft portion 21b is loosely inserted into the shaft hole 20d. For example, by pressing from the web 3b side to the opposite web 3b side, the web side periphery of the shaft hole 20d is curved, and the web side periphery of the shaft hole 20d slides into contact with the circumferential surface of the tapered shaft portion 21c. An arcuate contact surface 20e is formed.

Therefore, the adjustment lever 20, in which the small-diameter shaft portion 21b of the pin 21 is loosely inserted into the shaft hole 20d, has its arcuate contact surface 20e in contact with the circumferential surface of the tapered shaft portion 21c of the pin 21, and is separated from the web 3b. The first arm 20b is installed so that there is almost no sliding resistance with the web 3b during rotation, and when the tip of the first arm 20b passes over the teeth of the ratchet gear 14 and engages with the next tooth, the adjuster Even if the lever 20 tilts and rotates with respect to the web 3b, the inner diameter of the shaft hole 20d does not match the pin 21.
Since it is formed to have a larger diameter than the small diameter shaft portion 21b of the pin 21, a prying occurs between the shaft hole 20d and the pin 21 simply by changing the contact position between the arcuate contact surface 20e and the tapered shaft portion 21c of the pin 21. This eliminates wear and tear and improves durability.

[Effect of idea]

As described above, in this invention, an adjustment lever rotatably supported by a pin is arranged between a pair of brake shoes arranged opposite to each other on a back plate, and regulates the contracted position of both brake shoes. In an automatic braking gap adjustment device for a vehicle drum brake that rotates a ratchet gear of a strut, the pin has a large diameter shaft portion at one end, a small diameter shaft portion at the other end, and a shaft portion between the large diameter shaft portion and the small diameter shaft portion. The adjustment lever has a tapered shaft portion between them, and the large diameter shaft portion is inserted into and fixed to the web of the brake shoe, and the adjustment lever is formed to have a larger diameter than the small diameter shaft portion so that the small diameter shaft portion is loosely inserted. and an arc-shaped contact surface that slides on the circumferential surface of the tapered shaft portion is formed on the web-side periphery of the shaft hole, so that the adjustment lever can be rotated while tilting when rotating the ratchet gear. When the pin tilts and rotates with respect to the shaft hole as the pin moves, no prying occurs between the pin and the shaft hole, and durability can be improved.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the present invention. Figure 1 is a front view of a drum brake, Figure 2 is a cross-sectional view of Figure 1, and Figure 3 is a front view of a conventional example. FIG. 4 is a cross-sectional view of FIG. 3. 2... Back plate, 3... Brake shoe, 3b... Web, 6... Braking gap automatic adjustment device, 7... First strut member, 8... Adjustment bolt, 9... Second strut member, 10...
Strut, 14... Ratchet gear, 20...
Adjustment lever, 20d...Shaft hole, 20e...
Arc-shaped contact surface, 21...pin, 21a...large diameter shaft section, 21b...small diameter shaft section, 21c...tapered shaft section.

Claims (1)

[Scope of utility model registration request] A strut consisting of a first strut member and a second strut member connected via an adjustment bolt screwed into the first strut member is disposed between a pair of brake shoes disposed opposite to each other on the back plate. Braking of a drum brake for a vehicle in which the ratchet gear of the adjustment bolt is rotated by an adjustment lever rotatably supported by a pin on the web of the brake shoe to regulate the reduced position of both brake shoes. In the automatic gap adjustment device, the pin has a large-diameter shaft portion at one end, a small-diameter shaft portion at the other end, and a tapered shaft portion between the large-diameter shaft portion and the small-diameter shaft portion, and The adjusting lever has a shaft hole that is formed to have a larger diameter than the small diameter shaft portion and into which the small diameter shaft portion is loosely inserted, and the adjustment lever has a shaft hole that is formed to have a larger diameter than the small diameter shaft portion and is loosely inserted into the web of the brake shoe. 1. An automatic braking gap adjustment device for a vehicle drum brake, characterized in that an arcuate contact surface is formed on a side peripheral edge to make sliding contact with the circumferential surface of the tapered shaft portion.