JPH0234507Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement of a wheel cylinder for a drum brake.

[Prior Art] As shown in FIG. 8, generally, a drum brake 1 is provided with wheel cylinders 4A and 4B for a pair of brake shoes 3 and 3 that are pivotally mounted inside a brake drum 2. , the brake shoes 3, 3 are expanded and narrowed by the pistons 5, 6 of the wheel cylinders 4A, 4B.

As shown in FIG. 9, the wheel cylinder 4A includes a cylinder body 7.
A pair of pistons 5, 6 are fitted into the pistons 5, 6, and the outer ends 5a, 6a of each piston 5, 6 are connected to the brake shoes 3, 3, and the pistons 5,
6 between the inner ends 5b, 6b of each piston 5, 6
Disc-shaped cup members 8, 8 facing each other are provided,
Each of the cup members 8, 8 is biased outwardly by a positioning spring 10 via filling blocks 9, 9, which improve the ability of the cup members 8, 8 to fit in and release air. It is now held in place.

In addition, 14 indicates the cylinder body 7 and the pistons 5 and 6.
The boot member 14 has an outer peripheral part 14a fitted into a boot groove 7a formed in the cylinder body 7, and an inner peripheral part 14b which seals between the outer ends of the pistons 5 and 6. It is fitted into boot grooves 5d and 6d formed in 5a and 6a.

In addition, the wheel cylinder 4B shown in FIG.
is a type that uses ring-shaped cup members 11, 11, and the cup members 1 are inserted into cup grooves 5c, 6c formed at the inner ends 5b, 6b of each piston 5, 6.
1 and 11, and the respective cup members 11 and 11 are fitted together.
are held in a state where they are urged outward by springs 10 via filling blocks 12, 12, respectively.

By the way, the conventional wheel cylinder 4A,
4B, for both types, the pistons 5 and 6 are generally manufactured by cutting, but even if they are manufactured by forging or sintering, it is necessary to post-process the boot grooves 5d and 6d. In the type using the cup member 11, the cup grooves 5c, 6c
It also required post-processing, which caused high costs.

Furthermore, a boot groove 5 is provided in one of the pistons 5 and 6.
Since there are d and 6d, there is directionality when assembling.
It was time consuming to assemble.

Furthermore, since filling blocks 9, 9 and springs 10, 10 are required for the cup members 8, 11, the number of parts is large, and assembly is time-consuming, resulting in high costs.

[Purpose of the invention] The present invention was made to solve the above-mentioned conventional problems. It eliminates the need for post-processing such as boot grooves on the piston, and also eliminates the directionality of the piston, making it easier to process and assemble. The purpose of this is to contribute to cost reduction by eliminating the hassle of etc.

[Structure of the invention] Therefore, the present invention includes a cylinder body into which a piston is fitted, the inner and outer ends of the piston are formed in the shape of a symmetrical straight shaft with a small diameter, and the inner end shaft part includes: A cup member that fits into the cylinder body is fitted, and a boot member that seals between the cylinder body and the piston is fitted to the outer end shaft portion.

[Effects of the invention] According to the invention, the piston is formed with an inner end shaft portion and an outer end shaft portion, a cup member is fitted and supported on the inner end shaft portion, and a boot member is provided on the outer end shaft portion. Since the piston is fitted with a piston, there is no need for post-processing such as boot grooves and cup grooves on the piston, and costs can be reduced. Further, since the piston can be formed with symmetrical inner and outer end shaft portions, manufacturing is easy, and there is no directionality when assembling the cup member and the boot member, so that the labor of assembling can be saved.

Furthermore, since filling blocks and springs are no longer required while maintaining the same performance as before, the number of parts can be reduced, assembly is easier, and costs can be reduced.

[Embodiment] Fig. 1 shows an embodiment of a wheel cylinder 17A of a type using a dish-shaped cup member 16, which is equipped with a horizontally long cylinder body 18, into which a pair of pistons 19 and 20 are fitted. ing.

Each piston 19, 20 has an outer end shaft portion 19a in the form of a small diameter straight shaft, which is bilaterally symmetrical on both the outer end side and the inner end side.
20a and the inner end shaft portions 19b, 20b.

Inner end shaft portion 19b of each piston 19, 20,
Disc-shaped cup members 16, 16 are fitted into the respective portions 20b.

The cup member 16 is constructed by integrally molding a cup portion 16a that fits into the cylinder body 18 and a protrusion portion 16b that protrudes inward from the cup portion 16a and acts as a filling block.
The fitting hole 16c on the 6a side is connected to the inner end shaft portions 19b, 20b.
By fitting with its elastic force, it is integrally supported.

The outer end shaft portion 19a of each of the pistons 19, 20,
The inner peripheral part 21b of the boot member 21, the outer peripheral part 21a of which is fitted into the boot groove 18a formed in the cylinder body 18, is fitted into the inner peripheral part 20a.

If the inner peripheral part 21b of the boot member 21 is set to have a long shape in the axial direction as shown in the figure, the outer end shaft part 1
9a, 20a, and as shown in FIG. This eliminates the need to form boot grooves in the pistons 19 and 20 as in the conventional case.

With the above configuration, the pistons 19, 2
0, outer end shaft portions 19a, 20a and inner end shaft portion 19b,
20b, and there is no need to provide a boot groove or a cup groove, the pistons 19, 20 can be manufactured by forging or sintering alone, and there is no need for post-processing. ,20b,1
Since 9a and 20a are symmetrical, there is no directionality during assembly.

Furthermore, the cup portion 16a of the cup member 16 is fitted into the cylinder body 18, and the fitting hole 16c is fitted into the inner end shaft portions 19b, 20b, thereby functioning to hold the cup portion 16a so that it does not fall down.

Therefore, the protrusion 16b functions as a conventional filling block, and the fitting hole 16c functions as a conventional spring, so that the same performance as the conventional one can be maintained.

FIG. 2 shows an embodiment of a wheel cylinder 14B of a type using a ring-shaped cup member 23, and parts having the same structure and function as those in the embodiment of FIG.

In this embodiment, a ring-shaped cup member 23 is attached to the inner end shaft portion 19b, 20b of each piston 19, 20.
are fitted, and the inner end shaft portions 19b, 20b
Each cup member 23,
23 is held so that it does not fall.

In addition to the cover member 25a with a collar shown in FIG. 3a, the cover member 25b without a collar shown in FIG. 3b, the ring-shaped cover member 25c shown in FIG. 3c, and the cover member 25c shown in FIG. 3d. It may be a cover member 25d with a ring-shaped notch.

On the other hand, as shown in FIG.
It is also possible to form a boot groove in the inner circumferential portion 21b of the boot member 21 by fitting cover members 25b, 25c, 25d similar to those described above to the front portions of the outer end shaft portions 19a, 20a of the boot member 21. can. With this configuration, as shown in FIG.
The brake shoe 3 is brought into contact with the boot member 21.
There is no need to press the inner circumferential portion 21b.

Further, as shown in FIGS. 6a, b, and c, straight-shaped shoe grooves 19d and 20d that engage with the brake shoes 3 and 3 are formed in the outer end shaft portions 19a and 20a of the pistons 19 and 20. You can also. In order to eliminate the directionality, the inner end shaft portion 19b,
It is preferable to form dummy shoe grooves 19d' and 20d' also in 20b to make them symmetrical. In this case, the shoe groove 1
Protrusions 16d and 16d are formed to engage with 9d' and 20d'. Note that the shoe grooves 19d and 20d are the sixth
It may also be in the shape of a cross, as shown in Figure d.

In addition, as shown in FIG. 7, the pistons 19, 2
It is also possible to adopt a configuration in which a rotating ring member 26 with a shoe groove is fitted to the outer end shaft portions 19a, 20a of the rotor.

In each of the above embodiments, the pair of pistons 19 and 20 that expand and narrow the pair of brake shoes 3 and 3 are used.
Although we have taken as an example a so-called double-effect type drum brake, which is equipped with a single-effect drum brake, it goes without saying that it can also be applied to a so-called single-effect type drum brake, in which one piston operates one brake shoe. .

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a type of wheel cylinder using a dish-shaped cup member according to the present invention, Fig. 2 is a sectional view of a type of wheel cylinder using a ring-shaped cup member, and Figs. 3 a to d are various covers. 4 and 5 are cross-sectional views of essential parts of a wheel cylinder showing a modified example, FIG. 6 a is a side view of the shoe grooved piston, and FIG. 6 b is a front view of FIG. 6 a. , FIG. 6c is a sectional view of the cup member, FIG. 6d is a front view of a shoe grooved piston showing a modified example, and FIG.
The figure is a sectional view of the main part of the piston fitted with the shoe grooved ring member, and Figure 8 is a front view of the drum brake.
FIG. 9 is a sectional view of a wheel cylinder using a conventional dish-shaped cup member, and FIG. 10 is a sectional view of a wheel cylinder using a ring-shaped cup member. 16, 23...Cup member, 16a, 23a...
...Cup part, 16b, 23b...Protrusion part, 16c
... Fitting hole, 17A, 17B ... Wheel cylinder, 18 ... Cylinder body, 19, 20 ... Piston, 19a, 20a ... Outer end shaft portion, 19b, 2
0b...Inner end shaft portion, 21...Boot member, 25...
...Cover member, 26...Ring member.

Claims (1)

[Scope of utility model registration request] It has a cylinder body into which a piston is fitted, the inner and outer ends of the piston are formed in the shape of a symmetrical small-diameter straight shaft, and a cup member that fits into the cylinder body is fitted into the inner end shaft part. A drum brake wheel cylinder, further comprising a boot member fitted to the outer end shaft portion to seal between the cylinder body and the piston.