JPH0322584Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Industrial Application Field The present invention relates to a drum brake for a vehicle, in particular, to a back plate and a brake shoe web disposed on the inner surface of the back plate. A mounting pin is passed through the pin hole provided, and the outer end head of the mounting pin is engaged with the edge of the pin hole on the outer surface of the back plate, and the inner end of the mounting pin is inserted between the inner end of the mounting pin and the web. The present invention relates to a dustproof cover that is provided with a spring that presses the brake shoe against the inner surface of the back plate, and that is attached to the outer surface of the back plate to cover an opening of a brake drum that cooperates with the brake shoe.

(2) Prior art In this type of drum brake, water enters the inner surface of the back plate through the gap between the pin hole of the back plate and the outer head of the installation pin, so it is necessary to seal the gap. .

Therefore, conventionally, a rubber seal ring is interposed between the outer head of the installation pin and the outer peripheral edge of the pin hole (see Japanese Utility Model Application No. 59-6638).

(3) Problems to be solved by the invention Some drum brakes use a leaf spring bent into a U-shape as the spring. Upon engagement with the end, the spring is compressed and the installation pin is rotated to align the inner end with the pin hole of the spring. If the seal ring is arranged as described above in such a drum brake, the tension force around the installation pin acts on the seal ring in a compressed state as the installation pin rotates, so the seal ring may be damaged. There is a problem that the durability of the seal ring is reduced, and when the seal ring is replaced, the mounting pin must be removed, resulting in poor workability.

Furthermore, during braking, the above-mentioned installation pin may follow the movement of the brake shoe via the spring, and may oscillate to some extent within the range of play between the pin hole of the back plate, and as a result of this oscillation, the above-mentioned seal There is a risk that the ring will be strongly compressed and its durability will be impaired, resulting in further deterioration of the sealing function.

An object of the present invention is to provide the drum brake that can solve all of the above problems.

B. Structure of the invention (1) Means for solving the problem In order to achieve the above object, the invention provides a back plate and a brake shoe web disposed on the inner surface of the back plate. a mounting pin is passed through the pin hole, the outer end head of the mounting pin is engaged with the pin hole mouth edge of the outer surface of the back plate, and between the inner end of the mounting pin and the web, A drum brake for a vehicle, wherein a spring is interposed to press the brake shoe against the inner surface of the back plate, and a dustproof cover is attached to the outer surface of the back plate to cover an opening of a brake drum that cooperates with the brake shoe. , the dustproof cover is provided with an overhanging portion facing the end face of the outer end head of the installation pin, and has a recessed portion for receiving the outer end head of the installation pin, and the open end of the recessed portion extends over its entire circumference. It is characterized in that an elastic sealing member that is in close contact with the outer surface of the back plate is detachably held in the projecting portion.

(2) Effect Even if the installation pin rotates during assembly or swings slightly following the brake shoe during braking, the opening end of the recess of the sealing member remains unaffected by these movements. is always in close contact with the outer surface of the back plate over its entire circumference, and can perform the desired sealing function, and no large external force is applied to the sealing member even when the mounting pin rotates or swings as described above. .

Further, when replacing the seal member, the installation pin can be kept in the set state, and there is no need to take the trouble to remove it.

(3) Embodiment The illustrated example shows a two-leading shoe drum brake for a vehicle, and in FIGS. 1 and 2, a pair of upper and lower wheel cylinders 2 ₁ , 2 ₂ are attached to the inner surface of a back plate 1 fixed to the vehicle body. A pair of left and right brake shoes 3 ₁ and 3 ₂ are respectively arranged point-symmetrically around the center of the back plate 1. The brake drum 4 surrounds the brake shoes 3 ₁ and 3 ₂ and rotates together with the wheels in the direction of arrow A in FIG.

The wheel cylinders 2 ₁ and 2 ₂ each include a cylinder body 5 having an opening at one end, and a piston 7 that is slidably fitted into the cylinder body 5 to define a hydraulic chamber 6. It is fixed to the back plate 1 with bolts (not shown). An anchor 8 is attached to the opposite side of the opening of the cylinder body 5. Engagement grooves 9 and 10 are formed at the outer ends of the piston 7 and the anchor 8, respectively.
One end portion of the corresponding web 11 ₁ , 11 ₂ of the brake shoes 3 ₁ , 3 ₂ is engaged with the brake shoe 10 . The engagement is maintained between the webs 11 ₁ , 11 ₂ of both brake shoes 3 ₁ , 3 ₂ , and both brake shoes 3 ₁ , 3 ₂
return springs 12 ₁ , 12 ₂ that urge the
is tensioned, and the engagement prevents relative rotation between the cylinder body 5 and the piston 7.

As shown in FIGS. 2 and 3, in the upper wheel cylinder ₂₁ , a hydraulic pressure introduction port 13 communicating with the hydraulic chamber 6 opens on the outer side of the back plate 1, and a master cylinder (not shown) is connected to the port 13. An extending introduction pipe 14 is connected. In addition, a hydraulic communication port 15 that communicates with the hydraulic chamber 6 and a hydraulic pressure introduction port 13 that opens on the outer side of the back plate ₁ of the lower wheel cylinder 22 are connected to the communication pipe 1.
6 , and its hydraulic pressure introduction port 13 communicates with the hydraulic chamber 6 .

As shown in Figures 3 and 4, the back plate 1
A dustproof cover 17 is attached to the outer surface of the cover 17 so as to protrude further radially outward than the outer peripheral edge thereof. The tips of both bent edges 1a and 17a of the back plate 1 and dustproof cover 17 are loosely fitted into both annular grooves 4a and 4b formed on the end surface of the brake drum 4, respectively, thereby forming a labyrinth around the back plate 1. Therefore, the intrusion of dust and the like into the inner surface of the back plate 1 is suppressed.

Brake shoe 3 ₁ for back plate 1,
The installation structure of _3.2 is as follows.

As shown in FIGS. 1, 2, and 4, the web 11 of the back plate 1 and each brake shoe 3 ₁ , 3 _2
1 , 11 ₂ and each web 11 ₁ , 11 _{2 ,} and the installation pin 20 is passed through pin holes 19 ₁ to 19 ₄ formed in the U-shaped spring 18 made of a leaf spring superposed on each web 11 1 , 11 2 ,
The outer end head 20a of the installation pin 20 engages with the edge of the pin hole 191 on the outer surface of the back plate 1, and the inner end 20b of the spring ₁₈ engages with the opening edge of the pin hole 191 on the outer surface of the back plate 1.
Pin hole 19 on the side ₄ Engages with the mouth edge. In this state,
The spring 18 is compressed, and the brake shoes 3 ₁ and 3 ₂ are pressed against the inner surface of the back plate 1 by its elastic force.

The inner end 20b of the installation pin 20 is connected to its shaft 20
Correspondingly, the pin hole ₁₉₄ on the brake drum 4 side of the spring 8 has a pair of locking protrusions p through which both the locking protrusions p can be inserted. It is equipped with a notch c. When installing the brake shoes 3 ₁ , 3 ₂ , the spring 18 is compressed and the installation pin 20 is rotated so that both the locking protrusions P and both the notches C are offset, respectively.

In this staggered state, both locking protrusions p engage with locking grooves 18a formed in the spring 18 in parallel to the direction in which they are arranged, thereby locking the installation pin 20 against rotation.

In the above configuration, when braking, the master cylinder is operated and its output oil pressure is supplied to the oil pressure chamber 6 of the upper wheel cylinder 2 ₁ , and the oil pressure is transferred to the lower wheel cylinder 2 ₂ via the connecting pipe 16 .
These oil pressures cause the pistons 7 of each wheel cylinder 2 ₁ , 2 ₂ to advance outward, expand the corresponding brake shoes 3 ₁ , 3 ₂ , and press them against the inner peripheral surface of the brake drum 4. This allows a braking force to be applied to the brake drum 4 and therefore to the wheels.

The present invention provides the following seal structure around the outer end head 20a of the installation pin 20 in this type of drum brake.

The dustproof cover 17 integrally has a projecting portion 1 facing the outer end head 20a of each installation pin 20.
7b is provided, and a notch 21 with a narrowed mouth is formed in the overhanging portion 17b.

The elastic sealing member 22 is made of an elastic material such as rubber, and includes a main body 22a having a recess h on the end face for receiving the outer head 20a of the installation pin 20, and a notch 21 that is integrally protruded from the main body 22a. It includes a constricted portion 22b that engages with the constricted portion 22b, and a retaining portion 22c that is integrally connected to the constricted portion 22b and overlaps the notch 21.

The sealing member 22 covers the outer head 20a of the mounting pin 20 received in the recess h, and the open end of the recess h is always in contact with the outer surface of the back plate 1 over its entire circumference. Because they are in close contact, even if the installation pin 20 rotates during assembly or swings slightly following the brake shoes 3 ₁ and 3 ₂ during braking,
The gap between the pin hole ₉₁ of the back plate 1 and the outer end head 20a of the installation pin 20 can always be reliably sealed by the seal member 22 without being affected by these movements.

Furthermore, the seal member 22 can be attached to and detached from the overhanging portion 17b by engaging and disengaging the constricted portion 22b of the seal member 22 with the notch 21.
2. Replacement work can be easily performed.

Another advantage is that no special member is required to hold the seal member 22.

The communication pipe 16 between the upper and lower wheel cylinders 2 ₁ and 2 ₂ is connected to the outer end head 20a of one of the installation pins 20.
It is bent into a U-shape so that it can be bypassed,
The bent portion 16a is covered with an overhanging portion 17b of the dustproof cover 17, and in order to prevent the communication pipe 16 from vibration, the bent portion 6a has an overhanging portion 17b.
An elastic tube 23 made of rubber or the like is fitted between the back plate 1 and the back plate 1.

In this way, the bent portion 1 is
Covering the connecting tube 6a can prevent the bent portion 16a from colliding with other objects, which is effective in improving the durability of the communicating tube 16.

C. Effects of the invention As described above, according to the invention, the dustproof cover is provided with a protruding part that faces the end surface of the outer end head of the installation pin, has a recessed part for receiving the outer end head of the installation pin, and has a concave part that receives the outer end head of the installation pin. An elastic seal member whose opening end is in close contact with the outer surface of the back plate over its entire circumference is removably held in the overhang, so that the installation pin does not rotate during assembly or follow the brake shoe during braking. Even if the opening end of the concave portion of the sealing member is not affected by such movement, the opening end of the recess always remains in precise contact with the outer surface of the back plate over its entire circumference, and the desired sealing function is maintained. Therefore, the gap between the pin hole of the back plate and the outer end head of the installation pin can always be reliably sealed by the seal member. Further, since no large external force is applied to the seal member due to the rotation or swinging of the installation pin, the durability of the seal member can be improved. Furthermore, since the sealing member can be easily replaced without removing the installation pin, the workability is good. Furthermore, since the sealing member is held on the protruding portion of the dustproof cover attached to the back plate, there is no need to provide a special member for holding the sealing member, which contributes to simplification of the structure and cost reduction.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a side view, FIG. 2 is a cross-sectional view taken along the line of FIG. 1, FIG. 3 is a view taken along the arrow in FIG. FIG. 1...Back plate, ₃₁ , ₃₂ ...Brake shoe, 4...Brake drum, 17...Dust cover, 18...Spring, ₁₉₁ to ₁₉₄ ...Pin hole,
20... Installation pin, 20a... Outer end head, 20b
...inner end.

Claims (1)

[Scope of utility model registration request] Pin holes 1 formed in the back plate 1 and the webs 11 1 and 11 ₂ of the brake shoes _{3 1} and 3 ₂ arranged on the inner surface of the back plate 1, respectively.
The installation pin 20 is passed through 9 ₁ and 19 ₂ , and the outer end head 20a of the installation pin 20 is engaged with the edge of the pin hole 19 1 on the outer surface of the back plate 1, and the inner end of the installation pin 20 is inserted into the pin hole 19 ₁ on the outer surface of the back plate 1. part 20b and the web 11 ₁ , 1
A spring 18 for pressing the brake shoes 3 ₁ , 3 ₂ against the inner surface of the back plate 1 is interposed between the brake drum 4 and the brake shoes 3 ₁ , 3 _{2 .} Dustproof cover 17 that covers the opening
In the drum brake for a vehicle, the dustproof cover 17 is provided with an overhanging portion 17b that faces the end surface of the outer end head 20a of the installation pin 20, and the outer end head of the installation pin 20 An elastic seal member 22 having a recess h for receiving the recess 20a, and the open end of the recess h being in close contact with the outer surface of the back plate 1 over its entire circumference.
A drum brake for a vehicle, characterized in that the above-mentioned projecting portion 17b is detachably held.