JPH09112704A - Oil seal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a clearance between a seal lip and a shaft even if the shaft causes large eccentricity, provide excellent sealing performance, prevent contact force of a bumper to the shaft from becoming too large, and provide excellent durability performance. SOLUTION: As for an oil seal in which a bellows like flexible section 2 is provided on an inner peripheral side of an outer peripheral mounting section 1 and a bumper 3 and a seal lip 4 are provided on an inner peripheral side of the flexible section 2, the shape of a cross section of the flexible section 2 is substantially formed into a W-shape, and it has the length by which the flexible section 2 on a pull-out side is extended sufficiently when a shaft 5 causes large eccentricity and reduces the degree of pulling out from a compression side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil seal which is a kind of a sealing device.

[0002]

2. Description of the Related Art As shown in FIG. 3, an oil seal (dust seal) for dust used in steering of an automobile or the like is conventionally integrally formed with a bellows-shaped flexible portion 2 on an inner peripheral side of an outer peripheral mounting portion 1. Then, the bumper 3 is integrally formed on the inner peripheral side of the flexible portion 2, and one end side (upper side in the figure) of the bumper 3 in the axial direction is
A seal lip 4 that slidably comes into close contact with the shaft 5 is integrally formed.

However, in the above-mentioned conventional oil seal, the cross-sectional shape of the flexible portion 2 is substantially v-shaped,
Due to its short length, there are the following problems.

That is, as shown in FIG. 3, when the shaft 5 is largely eccentric, the bumper 3 and the seal lip 4 move axially (arrow x) in a part of the circumference, and the shaft 5 moves.
With a large inclination to the shaft 5 of the seal lip 4.
4 (B) because the contact state with respect to
As shown in FIG. 3, there is a problem that a gap 6 is generated in a part of the circumference between the seal lip 4 and the shaft 5, and a leak is generated from the gap 6. Further, at a position displaced by approximately 180 degrees with respect to the position where the gap 6 is generated, the contact force of the bumper 3 with respect to the shaft 5 becomes excessively large, which causes a problem that the bumper 3 is worn early.

[0005]

In view of the above points, the present invention provides excellent sealing performance without causing a gap between the seal lip and the shaft even when the shaft is largely eccentric. An object of the present invention is to provide an oil seal capable of exhibiting excellent durability performance without the contact force of the bumper on the shaft becoming too large.

[0006]

In order to achieve the above object, an oil seal of the present invention is provided with a bellows-shaped flexible portion on the inner peripheral side of an outer peripheral mounting portion and a bumper on the inner peripheral side of the flexible portion. Further, in the oil seal provided with the seal lip, the flexible portion has a substantially w-shaped cross-section.

[0007]

When the flexible portion has a substantially w-shaped cross section like the oil seal of the present invention having the above-mentioned structure, when the shaft is largely eccentric, the flexible portion on the pulling side is sufficiently formed. Since it has a length to be extended and the tension from the compression side is reduced, the bumper and the seal lip are hard to move in the axial direction. Therefore, since the contact state of the seal lip with respect to the shaft does not change significantly, it is possible to prevent a gap from being generated between the seal lip and the shaft and prevent the contact force of the bumper against the shaft from becoming too large. It becomes possible.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Changing the cross-sectional shape of a flexible portion from a substantially v-shape to a substantially w-shape can be rephrased as changing a single bellows to a double bellow due to the difference in shape. From the general theory, it can be said that the length is increased. The direction of w may be either the axial direction.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a half-cut cross section of an oil seal according to this embodiment. This oil seal is for steering that prevents muddy water from entering the vehicle from the engine room (outside the vehicle). It is used as a dust seal.

A bellows-shaped flexible portion (also referred to as a bellows portion) 2 is integrally formed on the inner peripheral side of an annular outer peripheral mounting portion 1 formed of a rubber-like elastic material (polymer material) such as rubber or resin. An annular bumper 3 is integrally formed on the inner peripheral side of the flexible portion 2, and an annular seal lip (on the upper side in the figure) of the bumper 3 in the axial direction slidably closes to the shaft 5 ( A first seal lip or a main lip) 4 is integrally formed, and a garter spring 7 is fitted into an annular mounting groove 4a provided on the outer peripheral surface of the seal lip 4, and one end side in the axial direction of the seal lip 4 That is, on the tip side, an annular second seal lip 8 slidably in contact with the shaft 5 is integrally molded, a shape-retaining ring 9 is embedded in the bumper 3, and the semi-section shape of the flexible portion 2 is substantially w. It is shaped like a letter.

That is, assuming that the seal lip 4 is integrally formed on one end side in the axial direction of the bumper 3 as a direction, the other end side in the axial direction from the outer peripheral mounting portion 1 (upper and lower sides in the drawing).
The flexible portion 2 starts toward the first flexible portion 2 and the flexible portion 2 extends toward the other end side in the axial direction, the first tapered portion 2a, the first bent portion 2b, and one end side in the axial direction. Second taper part 2
c, the second bent portion 2d, the third tapered portion 2e extending again toward the other axial end, the third bent portion 2f, and the fourth tapered portion 2g extending again toward the one axial end in this order. The bumper 3 is integrally provided, and the bumper 3 is integrally formed on one end side in the axial direction of the fourth tapered portion 2g.

The second seal lip 8 is the seal lip 4
Of the base end side cylindrical portion 8a provided continuously to the tip end portion of the above, a tapered taper portion 8b provided continuously to the base end side cylindrical portion 8a, and provided continuously to the taper portion 8b. And a sliding portion 8d for the unique shaft 5 having a substantially triangular cross-section, and the inner diameter of the seal lip 4 in the free state. It is set smaller than the inner diameter dimension, and as shown in the drawing, it is thin and long as a whole, and is shaped so that the tightening margin for the shaft 5 does not become too large. The shape-retaining ring 9 is formed of a rigid material such as metal into a substantially rectangular cross section, and the outer peripheral surface of the shape-retaining ring 9 is exposed to the bumper 3. A reinforcing ring 10 made of a rigid material such as metal is embedded in the outer peripheral mounting portion 1.

In the oil seal having the above structure, since the flexible portion 2 has a substantially w-shaped cross section, when the shaft 5 is largely eccentric, the flexible portion 2 on the pulling side is sufficiently formed. The bumper 3 and the seal lip 4 are difficult to move in the axial direction because they have a length to be extended and the tension from the compression side is reduced. Therefore, since the contact state of the seal lip 4 with the shaft 5 does not change significantly, it is possible to prevent a gap from being generated between the seal lip 4 and the shaft 5, thereby improving the sealing performance. You can FIG. 2 shows, as a result of an experiment, that the seal lip 4 becomes difficult to move in the axial direction, and the oil seal according to the example is shown by a “□” plot on the graph. The “◯” plot is the oil seal according to the first comparative example in which the cross-sectional shape of the flexible portion 2 shown in FIG. 5 is substantially v-shaped, and the “Δ” plot is the flexible portion 2 shown in FIG. 6. Is an oil seal according to a second comparative example having a substantially u-shaped cross section. The "axial distance of the lip tip" on the vertical axis of the graph means the distance x in FIG.

Further, in the oil seal having the above-mentioned structure, for the same reason, it is possible to prevent the contact force of the bumper 3 with respect to the shaft 5 from becoming excessively large, thereby suppressing the early wear of the bumper 3. The durability performance can be improved.

[0016]

The present invention has the following effects.

That is, in the oil seal of the present invention having the above structure, since the flexible portion has a substantially w-shaped cross section, when the shaft is largely eccentric, the flexible portion on the pulling side is The bumper and the seal lip do not easily move in the axial direction because they have a sufficiently extended length and the tension from the compression side is reduced. Therefore, since the contact state of the seal lip with the shaft does not change significantly, it is possible to prevent a gap from being generated between the seal lip and the shaft, thereby improving the sealing performance. Further, for the same reason, it is possible to prevent the contact force of the bumper with respect to the shaft from becoming too large, and thus it is possible to suppress early wear of the bumper and improve the durability performance.

[Brief description of the drawings]

FIG. 1 is a half cutaway view of an oil seal according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the shaft eccentricity and the axial distance of the seal lip tip.

FIG. 3 is a cross-sectional view showing an operating state of an oil seal according to a conventional example.

4A is an enlarged view of part A in FIG. 3, and FIG. 4B is an enlarged view of part B in FIG.

FIG. 5 is a half-cut sectional view of an oil seal according to a first comparative example.

FIG. 6 is a half cutaway view of an oil seal according to a second comparative example.

[Explanation of symbols]

 1 Outer peripheral mounting portion 2 Flexible portion 2a, 2c, 2e, 2g Tapered portion 2b, 2d, 2f Bent portion 3 Bumper 4 Seal lip 4a Mounting groove 5 Shaft 6 Gap 7 Garter spring 8 Second seal lip 8a Base side cylinder Part 8b Tapered part 8c Tip side cylindrical part 8d Sliding part 9 Shape retention ring 10 Reinforcement ring

Claims (1)

[Claims] 1. A bellows-shaped flexible part (2) is provided on the inner peripheral side of the outer peripheral mounting part (1), and a bumper (3) and a seal lip (4) are provided on the inner peripheral side of the flexible part (2). In the oil seal provided with, the flexible part (2) has a substantially w-shaped cross section.