JP2005221019A - Oil seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil seal 1 capable of stabilizing the thickness of an oil film which is formed and the amount of leakage as the angle formed between a seal lip 2 and an axis 4 does not change siginificantly even if a cocking phenomenon occurs with the member to be slid such as the axis 4. <P>SOLUTION: In an oil seal 1 coming into tight contact with the objective member for free sliding such as the axis 4 at the lip end 3 of the seal lip 2, the lip end 3 comprises an R surface 7 between an oil side slope 5 and an atmosphere side slope 6. The R surface 7 continuously comprises an oil-side R surface 8 where the radius curvature r<SB>1</SB>of cross section is relatively small and an atmosphere-side R surface 9 where the radius of the curvature r<SB>2</SB>of a cross section is relatively large. The oil seal 1 comes into tight contact with the objective member for free sliding by both the oil-side R surface 8 and the atmosphere-side side R surface 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an oil seal which is a kind of sealing device. The oil seal of the present invention is suitable for use as an oil seal that needs to control the amount of leakage, such as a valve stem seal.

  Conventionally, as shown in FIG. 4, an oil having a seal lip 2 made of rubber-like elastic material and slidably in close contact with a peripheral surface of a shaft (valve stem) 4 at a lip end 3 of the seal lip 2. A seal (valve stem seal) 1 is known (see, for example, Patent Document 1). As shown in an enlarged view in FIG. 5, the lip end 3 is located between an oil-side slope portion 5 and an atmosphere-side slope portion 6. Has a round surface portion 7 having an arcuate cross section. The boundary between the oil-side inclined surface portion 5 and the rounded surface portion 7 is a point a in the figure, and both 5 and 7 are continuously connected at the point a. Further, the boundary between the rounded surface portion 7 and the atmosphere-side inclined surface portion 6 is a point b in the figure, and both 6 and 7 are continuously connected at the point b.

However, in this prior art, as shown in the figure, the rounded surface portion 7 is formed by one rounded surface (arc) having a predetermined radius of curvature r _0, and thus has the following disadvantages.

That is, when the shaft 4 is inserted into the inner peripheral side of the oil seal 1, the lip end 3 of the seal lip 2 is slidably in close contact with the peripheral surface of the shaft 4 at both the rounded surface portion 7 and the atmospheric side inclined surface portion 6. To do. Accordingly, when the cocking phenomenon (swinging phenomenon) occurs in the shaft 4 during the reciprocating motion of the shaft 4, the angle θ ₀ formed by the atmosphere-side inclined surface portion 6 and the peripheral surface of the shaft 4 changes greatly. The oil film thickness formed between them changes, which causes the amount of leakage to change. Especially for valve stem seals, the difference in oil film thickness in the reciprocating process of the shaft 4 is the amount of leakage, and the oil film thickness is determined by the angle between the seal lip 2 and the shaft 4 in the design characteristics. It is very important to keep the oil film thickness and the above angle constant to keep the amount constant.

JP 2003-83014 A

  In view of the above points, the present invention does not greatly change the angle between the seal lip and the shaft even if a cocking phenomenon occurs in a sliding member such as a shaft, and the oil film thickness and the amount of leakage formed. An object of the present invention is to provide an oil seal that can stabilize water.

  In order to achieve the above object, the oil seal of the present invention is an oil seal that is slidably in close contact with a mating member such as a shaft at the lip end of the seal lip. The rounded surface portion has an oil-side rounded surface with a relatively small cross-sectional radius of curvature and an atmospheric side rounded surface with a relatively large cross-sectional radius of curvature. The oil-side round surface and the atmosphere-side round surface are slidably in close contact with the mating member.

  In the oil seal of the present invention having the above-described configuration, the lip end of the seal lip is not in close contact with the peripheral surface of the shaft at both the round surface portion and the atmosphere-side inclined surface portion as in the prior art, but only at the round surface portion. It is in close contact with the peripheral surface of the shaft, and is in close contact with the peripheral surface of the shaft on both the oil side round surface and the atmosphere side round surface provided on this round surface portion. In this case, the angle formed between the atmosphere-side round surface and the shaft circumferential surface is determined by the angle formed between the tangent line of the atmosphere-side round surface and the shaft circumferential surface at the intersection of the two. Therefore, when the cocking phenomenon occurs on the shaft, the intersection of the two is displaced, and accordingly, the tangent also changes its position and is angularly displaced. Therefore, this angular displacement causes the atmosphere-side round surface and the peripheral surface of the shaft to form. The angle is kept almost constant. Therefore, according to the present invention, even if a cocking phenomenon occurs on the shaft, the angle formed between the atmosphere-side round surface and the peripheral surface of the shaft is kept substantially constant. Stable and leak rate is stable.

  In the present invention, the oil side round surface having a relatively small radius of curvature and the atmospheric side round surface having a relatively large radius of curvature are continuously provided on the rounded surface portion for the following reason.

That is, in the oil seal 1 of FIG. 5 according to the above-described conventional example, the lip end 3 is slidably in close contact with the peripheral surface of the shaft 4 only by the round surface portion 7 so as to utilize the tangential angular displacement as in the present invention. If set so, the initial crushing distance of the lip end 3 with respect to the shaft 4 becomes too small. When the radius of curvature r ₀ of the rounded surface 7 is set large so that the lip end 3 is slidably in close contact with the peripheral surface of the shaft 4 only by the rounded surface portion 7, on the contrary, the lip with respect to the shaft 4 is reversed. The initial crushing edge at the end 3 becomes too large. On the other hand, when the oil-side radius surface having a relatively small radius of curvature and the air-side radius surface having a relatively large radius of curvature are continuously provided as in the present invention, the axis is formed only by the radius surface in order to use the tangent line. It is possible to realize a state of being slidably in close contact with the peripheral surface of the lip, and to set the initial crushing margin of the lip end with respect to the shaft to an appropriate size.

  The present invention has the following effects.

  That is, in the oil seal of the present invention having the above-described configuration, a round surface portion is provided at the lip end of the seal lip, and an oil side round surface having a relatively small radius of curvature and an air having a relatively large radius of curvature are provided on the rounded surface portion. A side round surface is provided, and both the oil side round surface and the atmosphere side round surface are configured to be slidably in close contact with the peripheral surface of the shaft. The angle formed by the atmosphere-side round surface and the peripheral surface of the shaft is kept substantially constant. Therefore, the oil film thickness formed between both surfaces can be stabilized, and the leakage amount can be stabilized accordingly.

  In addition, since the oil-side radius surface having a relatively small radius of curvature and the atmosphere-side radius surface having a relatively large radius of curvature are provided continuously, the initial crushing margin of the lip end relative to the shaft is set to an appropriate size. Can be set.

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

  FIG. 1 shows a cross section of a main part of an oil seal 1 according to an embodiment of the present invention. The oil seal 1 is configured as follows.

That is, the oil seal 1 (valve stem seal) is slidably in close contact with the peripheral surface of a shaft (valve stem) 4 that is a sliding counterpart at a lip end 3 of a seal lip 2 made of rubber-like elastic material. The lip end 3 is provided with a radius surface portion 7 between the oil side slope portion 5 and the atmosphere side slope portion 6, and the radius surface portion 7 has a radius of curvature r ₁ having a cross-sectional shape. A relatively small oil-side radius surface 8 and an atmosphere-side radius surface 9 having a relatively large curvature radius r _{2 in the} cross-sectional shape are continuously provided (r ₁ <r ₂ ).

The oil-side inclined surface portion 5 is formed in a cross-sectional linear shape or a gentle curved surface shape (linear shape in the figure), and forms a predetermined angle θ ₁ with the peripheral surface of the shaft 4.

The oil-side round surface 8 is formed in a circular arc shape with a relatively small radius of curvature r ₁ , and forms a predetermined angle θ ₂ with the peripheral surface of the shaft 4. The angle θ ₂ formed between the oil-side rounded surface 8 and the peripheral surface of the shaft 4 is determined by the angle formed between the tangent 8 a of the oil-side rounded surface 8 and the peripheral surface of the shaft 4 at the intersection of the both. θ ₂ is set smaller than θ ₁ . In addition, the boundary between the oil side inclined surface portion 5 and the oil side rounded surface 8 is a point c in the figure, and both 5 and 8 are continuously and smoothly connected at the point c.

The atmosphere-side round surface 9 is formed in a circular arc shape with a relatively large curvature radius r ₂ , and forms a predetermined angle θ ₃ with the peripheral surface of the shaft 4. The angle θ ₃ formed between the atmosphere-side rounded surface 9 and the peripheral surface of the shaft 4 is formed by the tangent line 9a of the atmospheric-side rounded surface 9 and the peripheral surface of the shaft 4 at the intersection (point f in FIG. 2) of both. Determined by angle. The boundary between the oil-side round surface 8 and the atmospheric-side round surface 9 is a point d in the figure, and the both 8 and 9 are continuously and smoothly connected at this point d. As a result, the circle with the radius of curvature r ₂ (virtual circle) and the circle with the radius of curvature r ₁ (virtual circle) overlap each other at one point on the circumference, so the former forms the latter circumscribed circle. .

The atmosphere-side inclined surface portion 6 is formed in a cross-sectional linear shape or a gentle curved surface shape (linear shape in the figure), and forms a predetermined angle θ ₄ with the peripheral surface of the shaft 4. θ ₄ is set larger than θ ₃ . Further, the boundary between the atmosphere-side rounded surface 9 and the atmosphere-side slope 6 is a point e on the drawing, and both 6, 9 are connected continuously and smoothly at the point e.

  The oil seal 1 is slidably in close contact with the peripheral surface of the shaft 4 on both the oil side round surface 8 and the atmospheric side round surface 9.

In the oil seal 1 having the above-described configuration, the lip end 3 of the seal lip 2 is not in close contact with the peripheral surface of the shaft 4 at both the rounded surface portion 7 and the atmospheric side slope portion 6 as in the prior art, but only on the rounded surface portion 7. In close contact with the peripheral surface of the shaft 4, both the oil side round surface 8 and the atmosphere side round surface 9 provided on the round surface portion 7 are in close contact with the peripheral surface of the shaft 4. As described above, the angle θ ₃ formed by the atmosphere-side rounded surface 9 and the peripheral surface of the shaft 4 is equal to the tangent line 9a of the atmospheric-side rounded surface 9 and the circumference of the shaft 4 at the intersection (point f in FIG. 2) of both. It is determined by the angle formed with the surface. Therefore, as shown in an enlarged view in FIG. 2, when a cocking phenomenon occurs in the shaft 4 that is displaced from the one-dot chain line to the two-dot chain line in the drawing, the intersection of the atmosphere-side round surface 9 and the peripheral surface of the shaft 4 is The point f is displaced from the upper point f to the point g, and accordingly, the tangent line 8a also changes its position from the one-dot chain line to the two-dot chain line in the figure and is angularly displaced. At this time, the angle formed between the atmosphere-side round surface 9 and the peripheral surface of the shaft 4 is θ ₃ ′ in the drawing, and this θ ₃ ′ is substantially equal to θ ₃ . Therefore, according to the present invention, as long as the oil seal 1 is slidably in close contact with the peripheral surface of the shaft 4 on both the oil-side radius surface 8 and the atmosphere-side radius surface 9, a cocking phenomenon occurs on the shaft 4. However, since the angle formed between the atmosphere-side rounded surface 9 and the peripheral surface of the shaft 4 is kept substantially constant, the oil film thickness formed between the both 4 and 9 can be stabilized. Accordingly, the leakage amount can be stabilized.

Further, since the oil-side radius surface 8 having a relatively small radius of curvature r _{1 and} the air-side radius surface 9 having a relatively large radius of curvature r ₂ are continuously provided, the lip end with respect to the shaft 4 as described above. 3 can be set to an appropriate size.

The oil seal 1 according to the above embodiment has a lip end 3 formed by _two arcs having different curvatures r ₁ and r ₂ , and the on-axis oil side angle θ ₂ and the on-axis atmosphere side angle θ ₃ are 2. It is set by the kind of curvature, and the oil side angle θ ₂ and the atmospheric side angle θ ₃ on the shaft are determined by two types of rounds, thereby changing the wear and the change in the contact posture of the shaft 4 (cocking and eccentricity) ) Can be improved.

The oil seal 1 according to the above embodiment can be variously modified in the technical scope of the present invention. For example, in the above embodiment, the relationship between the curvature radii r ₁ and r ₂ is r ₂ <2r ₁ as illustrated.
However, this relationship is opposite, as shown in FIG.
r ₂ > 2r ₁
It may be.

Sectional drawing of the principal part of the oil seal which concerns on the Example of this invention 1 is an enlarged view of the main part of FIG. Sectional drawing of the principal part of the oil seal which concerns on the other Example of this invention. Half cut sectional view of oil seal according to conventional example The main part enlarged sectional view of the oil seal

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oil seal 2 Seal lip 3 Lip end 4 Axis 5 Oil side slope part 6 Atmosphere side slope part 7 Round surface part 8 Oil side round surface 8a, 9a Tangent 9 Atmosphere side round surface

Claims (1)

In the oil seal (1) slidably in close contact with the mating member such as the shaft (4) at the lip end (3) of the seal lip (2),
The lip end (3) has a rounded surface portion (7) between the oil-side slope portion (5) and the atmosphere-side slope portion (6),
The rounded surface portion (7) includes an oil-side rounded surface (8) having a relatively small curvature radius (r ₁ ) in a cross-sectional shape and an air-side rounded surface (9) having a relatively large sectional curvature radius (r ₂ ). And continuously
An oil seal characterized by being slidably in close contact with the mating member on both the oil side round surface (8) and the atmospheric side round surface (9).

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