JPS623548Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealing structure for a piston sliding portion, particularly to a sealing structure for a piston sliding portion of a vehicle disc brake.

In general, sealing of the piston sliding joint is necessary to ensure good and smooth sliding of the piston.
Particularly in vehicle disc brakes, sealing is essential because the device is susceptible to muddy water and the like.

Fig. 1 shows a conventional example of a sealing structure for such a piston sliding part, in which an inner circumferential groove 3' formed at the opening of the cylinder 2' of the cylinder body 1' and a sealing structure at the tip of the piston 5' are used. A boot 6' is installed in between to seal the sliding portion from the outside air.

By the way, even with such a sealing structure, with a disc brake, there is a risk that the bellows part 6c' of the boot 6' may be damaged by flying stones etc. and the seal may be released. In addition, it is also being considered to provide a double seal. For example, an inner peripheral lip that snaps into engagement with the outer periphery of the piston is formed on the swollen end portion that is assembled to the cylinder body side that accommodates the piston of a disc brake.

However, simply such a configuration has the following problems. That is, when assembling the piston into the cylinder, it is often necessary to at least assemble the boot to the cylinder body side beforehand, especially when the assembly part on the cylinder body side is of the inner circumferential groove type. In such a case, as the piston is pushed in, the air in the cylinder may be compressed, causing the piston to return, which poses a problem in that it will interfere with the work of assembling other members.

To prevent this, the shape of the inner lip formed on the boot for double sealing must be highly flexible so that the compressed air inside the cylinder can escape to the outer periphery. It turns out.

The present invention has been developed to solve these difficulties, and allows the compressed air inside the cylinder to escape to the outside without being particularly restricted by the shape of the inner circumferential lip.

The sealing structure of the piston sliding portion according to the present invention, which has been developed to achieve this purpose, is characterized by a cylinder body, a piston that is slidably accommodated in the cylinder of the cylinder body, and In the sealing structure of the piston sliding portion, which includes an elastic boot extending from the inner circumferential groove of the cylinder opening to the tip of the piston, the piston has a stepped small diameter portion on the tip side and a bottom side. The stepped small diameter portion is formed at a position that generally opposes the inner circumferential groove of the cylinder body when the piston is pushed into the cylinder inner bottom, and the stepped small diameter portion is formed at a position that generally faces the inner circumferential groove of the cylinder body when the piston is pushed to the inner bottom of the cylinder. The inner circumferential surface of the swollen end that fits into the circumferential groove has a
A sealing inner circumferential lip is formed which circumferentially contacts the outer circumferential surface of the large diameter portion of the piston, but has a radial dimension spaced apart from the outer circumferential surface of the stepped small diameter portion. It's where you are.

Hereinafter, the present invention will be explained based on the drawings.

In FIG. 2, 1 is a cylinder body, 2 is a cylinder, 3 is a large-diameter inner circumferential groove formed at the cylinder opening of cylinder body 1, and 4 is cylinder body 1.
This is a circumferential groove formed slightly inside the cylinder opening.

5 is a piston slidably fitted to the cylinder 2;
In this embodiment, it is formed as a hollow piston that opens toward the tip (the end on the cylinder opening side), and a stepped small diameter portion 5a is formed on the outer periphery of the tip.

The piston 5 is arranged so that, when the piston 5 is pushed to the bottom of the cylinder 2, the stepped small diameter portion 5a at the tip comes to a position facing at least the inner circumferential groove of the cylinder opening of the cylinder body.

Reference numeral 6 denotes a boot having an expandable bellows portion 6c, one of which has a swollen end 6a that fits into the inner circumferential groove 3 of the cylinder opening of the cylinder body 1, and the other swollen end 6b that fits into the stepped portion of the piston 5. It is provided so as to be tightly secured to the small diameter portion 5a.

The boot 6 is installed between the cylinder body 1 and the piston 5 as described above, thereby sealing the sliding surface of the cylinder 2 and the piston 5 from the outside air, and also seals the sliding surface of the cylinder 2 and the piston 5 from the outside air. An inner peripheral lip 6d formed on the swollen end 6a of the piston 5 is provided so as to make a double seal by snapping onto the large diameter portion of the piston 5.

In this embodiment, when the piston 5 is pushed into the cylinder 2, the stepped small diameter portion 5a of the piston 5 is provided so as to face the inner circumferential groove 6a of the cylinder opening. At this time, the inner circumferential lip 6d of one of the swollen ends 6a of the boot is disengaged from the piston 5, so that when the piston is assembled, the boot 5
Even with the cylinder 2 attached, the problems associated with compressing the sealing air in the cylinder 2 do not occur.

That is, in the final stage of assembly, the elastic engagement between the inner circumferential lip 6d and the piston 5 can be released, so that compressed air is not trapped.
Therefore, there are no restrictions on the shape of the inner circumferential lip 6d to prevent the containment of compressed air.

The reference numeral 7 designates a boot ring for securely assembling one swollen end 6a of the boot 6 into the inner circumferential groove 3, and is, for example, an annular elastic ring having a spring force in the outer radial direction. Further, 8 is a sealing member fitted into the inner circumferential groove 4, forming a liquid-tight seal on the sliding surface.

As mentioned above, the sealing structure of the piston sliding portion according to the present invention is extremely effective in ensuring the sealing performance of boots such as disc brakes, which are likely to be damaged by flying stones. Furthermore, the practical benefits are extremely great, as there is virtually no restriction on the shape of the inner lip to obtain the double sealing property.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a piston sliding portion sealing structure showing a comparative example, and FIG. 2 is a partial sectional view of a piston sliding portion sealing structure showing an embodiment of the present invention. 1, 1'... Cylinder body, 2, 2'... Cylinder, 3, 3'... Inner circumferential groove, 4, 4'... Inner circumferential groove,
5, 5'... Piston, 5a, 5a'... Tip stepped small diameter part, 6, 6'... Boot, 6a, 6b, 6a',
6b'...Bullet end part, 6c, 6c'... Bellows part, 6d...
...Inner lip, 7, 7'...Boot ring, 8,
8'... Seal member.

Claims (1)

[Scope of utility model registration request] A seal for a piston sliding part that includes a cylinder body, a piston that is slidably accommodated in the cylinder of the cylinder body, and an elastic boot that extends from the inner circumferential groove of the cylinder opening of the cylinder body to the tip of the piston. In the locking structure, the piston has a stepped small diameter portion on the tip side and a large diameter portion on the bottom side, and the stepped small diameter portion is formed in the cylinder when the piston is pushed to the inner bottom of the cylinder. The boot is formed at a position generally facing the inner circumferential groove of the body, and the inner circumferential surface of the swollen end portion of the boot that fits into the inner circumferential groove of the cylinder body is provided with a circumferential resilient force on the outer circumferential surface of the large diameter portion of the piston. 1. A sealing structure for a piston sliding portion, characterized in that an inner peripheral lip for sealing is formed with a radial dimension spaced apart from an outer peripheral surface of the stepped small diameter portion.