JPS603402Y2 - Seal structure of piston cylinder in disc brake - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved seal structure in a floating piston cylinder for operating a disc brake.

Generally, the seal structure of this type of piston cylinder is
As shown in the figure, an annular seal groove 7' is formed on the inner surface of the cylinder 1', and an annular seal ring 8' having a rectangular cross section is inserted into the seal groove 7' so as to be in contact with the outer peripheral surface of the piston 3'. The structure is such that the cylinder 1' is compressed with an appropriate interference in the radial direction, and the seal groove 7'
Since the seal ring 8' is inserted under compression, the groove width is made slightly wider than the width of the seal ring 8' in order to release the expansion of the seal ring 8' in the width direction due to this compression. The bottom wall 7c' of the piston 3
In order to prevent the seal ring 8' from following the piston 3' and sliding against the seal groove 7' when the seal ring 8' receives an external force or displacement from the brake pad side, the seal ring 8'
In order to improve the sealing action of ' on the hydraulic fluid level side of the cylinder 7', it is formed to be deep on the pad side, that is, on the front wall 7a' side, and shallower on the hydraulic fluid side, that is, on the rear wall 7b' side. The front wall 7a' of the seal groove 7' is deformed at the contact portion with the piston 3' so that the seal ring retains a restoring force due to its elasticity in order to return the piston 3' to its original position when pressure is removed. A chamfered portion 7e' was formed to allow this.

However, in the above seal structure, when the brake is activated, that is, when pressure is applied to the piston 3', the amount of deformation of the seal ring 8' due to the movement of the piston is the slope of the chamfered portion 7e' of the seal groove 7'. As a result, the amount of elastic deformation of the seal ring 8' becomes smaller than the amount of movement of the piston, and as a result, even if the pressure is removed from the piston 3', the piston 3' does not return sufficiently, and the disk Drag occurs between the brake pad and the brake pad, leading to premature wear of the pad and abnormal heating of the disc, resulting in changes in braking effectiveness, an increase in running resistance, and a decrease in vehicle fuel consumption.

Therefore, as described above, in order to increase the amount of deformation of the seal ring 8', the width of the chamfered portion 7e' of the seal groove 7' may be increased without changing the angle of inclination 2, or the width of the chamfered portion 7e' of the seal groove 7' may be increased. However, in the former case, the height of the front wall 7a' of the seal groove 7' is small, that is, the bottom of the seal groove 7' becomes shallow, and the seal ring 8' When installing, it becomes unstable to determine the position.
Although the latter can eliminate the drawbacks of the former, unless the restoring force of the seal ring 8' is set to a large value, the seal ring 8' will deform and the piston 3' will collapse into the seal ring 8' before reaching the slope of the chamfered portion 7e'. Since the seal ring 8' slides against the seal ring 8', the interference of the seal ring 8' must be increased, which increases the sliding resistance and deteriorates the braking effect at the initial stage of braking. It had drawbacks such as:

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, and also to improve the piston cylinder of a disc brake, which can increase the amount of deformation of the seal ring and increase the amount of return of the piston without changing the width of the chamfered portion of the seal groove. The purpose is to provide a seal structure.

Hereinafter, the illustrated embodiment embodying the present invention will be described in detail. As shown in FIG. The front end (left end in the figure) of the piston 3 faces one end surface of the disk 2 and has a pad 4 attached thereto.

A pad 5 facing the other end surface of the disk 2 is attached to one end 2 of the cylinder 1, and the cylinder 1 and the piston 3 are connected to each other by hydraulic fluid W such as hydraulic pressure that is pumped into the cylinder 1. is moved relative to each pad 4.
, 5 are configured to press both end surfaces of the disk 2.

A boot 6 is installed between the front end of the piston 3 and the cylinder 1 by conventional means to allow relative movement between the piston 3 and the cylinder 1 and to seal the sliding surfaces thereof.

An annular seal groove 7 is formed in the inner peripheral surface of the cylinder 1, and as shown in FIG. 2, the seal groove 7 is composed of a front wall 7a, a rear wall 7b, and a bottom wall 7c. The bottom wall 7c is formed to become gradually deeper from the rear wall 7b to the front wall 7a, and a desired angle is formed between the front wall 7a and the bottom wall 7c, that is, at the connected corner. slanted wall 7
d is formed.

An annular seal ring 8 inserted into the seal groove 7 is made of an elastic body, and has a front wall 7a and a rear wall 7b of the seal groove 7.
, a front surface, a rear surface, and an outer circumferential surface corresponding to the bottom wall 7c, respectively, and an inner circumferential surface corresponding to the outer circumferential surface of the piston 3 form a substantially rectangular cross section, and the seal groove 7 is formed at one corner of the outer circumference. A slanted portion 8a corresponding to the slanted wall 7d is formed,
Moreover, the thickness in the axial direction is formed to be narrower than the groove width of the seal groove 7, and the thickness in the radial direction is formed to be larger than the depth of the seal groove 7.

As shown in FIG. 3, the seal ring 8 is compressed and inserted between the inside of the seal groove 7 and the outer circumferential surface of the piston 3 with a predetermined interference, and is inserted into the front wall 7a of the seal groove 7.
The slanted portion 8a is formed on the slanted wall 7d of the seal groove 7, and the outer circumferential surface is formed on the bottom of the seal groove 7 so as to have a desired gap E with respect to the rear wall 7b and to seal the gap between the slanted portion 8a and the rear wall 7b. The inner peripheral surface of the wall 7c is pressed against the outer peripheral surface of the piston 3.

Since the seal structure of this embodiment is constructed as described above, the hydraulic fluid W flowing into the cylinder 1 passes through the sliding surface between the cylinder 1 and the piston 3, as shown in FIG. The hydraulic fluid W is flowing into the gap between the rear wall 7b of the seal groove 7 and the end face of the seal ring 8, and in a state where no pressure is applied to the hydraulic fluid W, the master cylinder is moved by normal means to brake the disc brake. When pressure is applied to the hydraulic fluid W in the cylinder 1 from (not shown), the piston 3
As shown in FIG. 4, the disc 2 is moved relative to the cylinder 1 in the direction of the arrow P shown in the figure, and the disc 2 is pressed by both pads 4.degree. 5 to perform braking.

At this time, the seal ring 8 that follows the movement of the piston 3
The movement of the outer circumferential surface and the slanted portion 8a is restrained by the bottom 7c of the seal groove 7 and the slanted wall 7d, and the surface pressure against the slanted wall 7d increases, so that the piston 3 is elastically deformed. Follow and move.

Therefore, the seal ring 8 is deformed within the gap E formed between the seal ring 8 and the front wall 7a of the seal groove 7 by an amount corresponding to the amount of movement of the piston 3, while the insertion position in the seal groove 7 is fixed.

Then, when the hydraulic fluid W is depressurized to release the brake on the disk 2, the piston 3 returns to its original position (the state shown in FIG. 3) due to the restoring elasticity of the seal ring 8.

That is, when the amount of movement of the piston 3 described above is within the deformation range of the seal ring 8, the piston 3 is returned to its original position without moving relative to the seal ring 8, and the amount of movement of the piston 3 is within the deformation range of the seal ring 8. When the maximum possible deformation amount of the hydraulic fluid W exceeds the gap E, the piston 3 moves relative to the seal ring 8 by an amount obtained by subtracting the maximum possible deformation amount of the seal ring 8 from the movement amount of the piston 3. By removing the pressure, it is returned to its original position in the same manner as described above.

In this embodiment, as described above, the amount of deformation of the seal ring 8 can be allowed to follow the amount of movement of the piston 3, and thereby the amount of return of the piston 3 can be made as large as possible. However, as shown in FIG. 5, when a chamfered portion 7e is formed on the front wall 7a of the seal groove 7, the chamfered portion 7e is further formed with respect to the gap E with the front wall 7a in the above-described embodiment. Since the gap is increased, a larger amount of deformation of the seal ring 8 can be tolerated.

In this embodiment, the diagonal wall 7d is formed in the seal groove 7 at the joint between the front wall 7a and the bottom wall 7C, but instead of this, as shown in FIG. The seal ring 8 is formed obliquely with respect to the wall 7c, and a gap E is formed between the oblique front wall 7a and the front surface of the seal ring 8.
Even if the structure is configured to allow deformation within the elastic limit of , the same effects as those of the above-mentioned embodiments can be obtained.

As is clear from the above description, the present invention forms a diagonal wall between the front wall and the bottom wall of the seal groove, or forms the entire front wall as a diagonal wall with respect to the bottom wall. Unlike conventional seal structures, the seal ring to be inserted is formed with a diagonal portion corresponding to the diagonal wall, and the structure forms a desired gap to the front wall of the seal groove for sealing. , the amount of deformation within the elastic limit of the seal ring can be increased in accordance with the amount of movement of the piston without changing the chamfered part of the front wall, so the piston can be returned sufficiently and the drag of the brake can be minimized. To eliminate scuffing and the like of a seal ring, and to improve its durability.

Moreover, by configuring the present invention as described above,
There is no need to increase the tightening margin of the seal ring, the braking effect at the initial stage of braking can be smoothed, and the gap between the seal ring and the seal groove can be set very easily in accordance with the rigidity of the cylinder.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a sectional view schematically showing a cylinder of a disc brake, Fig. 2 is an enlarged sectional view of main parts showing the relationship between the seal groove and the seal ring, and Fig. 3. and Fig. 4 is an explanatory diagram showing the operating state of the main parts, Fig. 5 and Fig. 6.
The figure is an enlarged sectional view of a main part showing a separate part of the present invention, and FIG. 7 is an explanatory view showing a conventional seal structure. 1 Niji cylinder, 3: Piston, 7: Seal groove, 7a: Front wall, 7c: Bottom wall, 7d: Slanted wall, 8: Seal ring, 8
a: Oblique part.

Claims (1)

[Scope of utility model registration request] A seal structure for an automobile disc brake having a cylinder and a piston slidably inserted into the cylinder, the seal structure being provided on the inner surface of the cylinder and defined by a front wall, a rear wall and a bottom wall. an annular sealing groove having a substantially rectangular cross-section; and an elastically deformable sealing ring having a substantially rectangular cross-section defined by a front surface, a rear surface, an inner surface, and an outer surface and having a radial thickness greater than the depth of the sealing groove. The bottom wall of the seal groove is formed to become gradually deeper from the rear wall to the front wall, and a part or all of the front wall in contact with the bottom wall is inclined toward the front and inward of the cylinder. a part of the front surface of the seal ring has an inclination that substantially coincides with the V-shaped front wall of the seal groove to form a V-shape with the outer surface; The apex of the V-shaped surface of the seal ring is arranged at the apex of the V-shaped wall of the seal groove, and when pressed by the piston, the V-shaped surface of the seal ring is elastically deformed to form the V-shaped wall of the seal groove. 1. A seal structure for a piston cylinder in a disc brake, wherein the front wall and the rear wall of the seal groove engage with the letter-shaped wall and have a gap over their entire area with respect to the front and rear surfaces of the seal ring before deformation.