JP2009293774A - Sealing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing device which can reduce the influence of negative pressure by a simple constitution. <P>SOLUTION: The sealing device 1 seals an annular clearance between a shaft 300 and a housing 400 with a shaft hole into which the shaft 300 is inserted while the shaft 300 and the housing 400 reciprocate relatively in an axial direction. The device 1 has a first sealing part 10 with the first tubular part 10a which is fitted and fixed on the inner circumferential face 401 of the housing 400 and the first seal lip 10b which is extended toward an oil room side O and the shaft side 300 from an atmosphere side A of the first tubular part 10a and contacts the outer circumferential face 301 of the shaft 300 slidably and a second sealing part 20 with the second tubular part 20a which is fitted and fixed on the outer circumferential face of the shaft side 300 in the first tubular part 10a and the second seal lip 20b which is extended toward the open air side A and the shaft side 300 from the oil room side O of the second tubular part 20a and contacts the outer circumferential face 301 of the shaft 300 slidably in the oil room side O than the first sealing lip 10b slidably. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sealing device that seals an annular gap between a shaft that reciprocates relative to each other in an axial direction and a housing that has a shaft hole into which the shaft is inserted.

  As this type of sealing device, a sealing device 100 used for a hydraulic cylinder in a power steering device of an automobile as shown in FIGS. 3 and 4 is known. FIG. 3 is a schematic cross-sectional view of the power steering apparatus. FIG. 4 is a schematic cross-sectional view of a sealing device according to the prior art.

  The sealing device 100 is used in a hydraulic cylinder 400 having the rack shaft 300 as a piston rod in the power steering device 200, and an annular gap between the outer peripheral surface 301 of the rack shaft 300 and the inner peripheral surface 401 of the hydraulic cylinder 400. To seal.

  As shown in FIG. 4, the sealing device 100 includes an annular seal body 101 fitted to an inner peripheral surface 401 of a hydraulic cylinder 400 as a housing, and a seal that slidably contacts the outer peripheral surface 301 of the rack shaft 300. And a lip 102.

  The seal body 101 includes a reinforcing ring 101a made of metal and a rubber-like elastic body 101b that is integrally baked and fixed to the reinforcing ring 101a. The reinforcing ring 101a includes a cylindrical portion 101c and a flange portion 101d extending inward in the radial direction from the atmosphere side A end of the cylindrical portion 101c.

  Part of the rubber-like elastic body 101b extends from the vicinity of the tip of the flange portion 101d of the reinforcing ring 101a to the oil chamber side O (sealing target region side) to form a seal lip 102.

  A spring 103 is attached to the outer periphery of the seal lip 102 to increase the pressing force against the rack shaft 300. A backup ring 104 is mounted on the inner periphery of the seal body 101 and between the root of the seal lip 102 and the front end of the flange portion 101d of the reinforcing ring 101a, and receives a high pressure from the hydraulic side O. The deformation of the seal lip 102 is suppressed, and early wear and heat generation of the seal lip 102 are prevented.

  In the sealing device 100 configured as described above, in a state where the pressure on the oil chamber side O is higher than the pressure on the atmosphere side A, the seal lip 102 is formed on the outer peripheral surface of the rack shaft 300 by the oil pressure acting from the oil chamber side O. The ring-shaped clearance between the rack shaft 300 and the hydraulic cylinder 400 can be satisfactorily sealed.

  In addition, as another structure of a sealing device, there exists what was disclosed by patent document 1, for example.

  However, when the steering direction of the power steering apparatus 200 is switched, the pressure on the hydraulic side O may be lower than the pressure on the atmosphere side A (generation of negative pressure). In such a case, the seal lip 102 may be lifted from the outer peripheral surface 301 of the rack shaft 300 due to a pressure difference, and the seal lip 102 and the rack shaft 300 may be in a non-contact state.

When the seal lip 102 and the rack shaft 300 are not in contact with each other, gas is sucked from the high-pressure atmosphere side A into the low-pressure oil chamber side O, and more than the sealing device 100 through the shaft hole of the housing, the air bypass 302 and the like. The inner space of the bellows 500 located on the atmosphere side A is in a negative pressure state with respect to the outside of the bellows, that is, the outside of the apparatus. As a result, the bellows 500 may be deformed (collapsed) to cause interference with a mating member such as the rack shaft 300. In the worst case, the bellows 500 may be damaged.

  As such a negative pressure countermeasure, for example, Patent Document 2 discloses a technique in which a lip portion is added to the base side of the seal lip to prevent the seal lip from reversing when negative pressure occurs. Yes. Patent Document 3 discloses a structure in which a ring member is arranged on the outer peripheral side of the seal lip, and the seal member prevents the seal lip from being lifted by pressing the seal lip from the outside when negative pressure is generated. Has been.

However, these technologies make the shape and configuration of the seal lip special, so that the moldability and assembly of the seal lip are poor, and there is an abrupt change such as when instantaneously changing to a negative pressure state. There are cases where it is not possible to adequately cope with decompression.
Utility model registration No. 2505438 JP 2000-329237 A JP 2000-337519 A

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a sealing device that can reduce the influence of negative pressure generation with a simple configuration.

In order to achieve the above object, a sealing device according to the present invention comprises:
A sealing device for sealing an annular gap between a shaft that reciprocally moves relative to each other in an axial direction and a housing having a shaft hole into which the shaft is inserted,
A first tubular portion fitted and fixed to the surface of one of the two members;
A first seal lip extending from the anti-sealing target region side of the first cylindrical portion toward the sealing target region side and the other member side, and slidably contacting the surface of the other member;
A first seal portion having
A second cylindrical part fitted and fixed to the peripheral surface of the other member side in the first cylindrical part;
The second cylindrical portion extends from the sealing target region side toward the anti-sealing target region side and the other member side, and slides on the surface of the other member on the sealing target region side of the first seal lip. A second seal lip that freely contacts;
A second seal portion having
It is characterized by providing.

  According to this configuration, when the sealing target region side becomes negative with respect to the anti-sealing target region side, the second seal lip comes into closer contact with the surface of the other member due to the pressure difference. Therefore, it is possible to prevent the sealing target region and the anti-sealing target region from communicating with each other due to the generation of negative pressure.

  Moreover, a 1st seal part and a 2nd seal part can be integrated by fitting each cylindrical part. Therefore, it is easy to assemble, and since the seal lip or the like is not made into a special shape, it is excellent in formability.

The space between the first seal portion and the second seal portion communicates with the sealing target region side, and when the pressure on the sealing target region side fluctuates, the first seal portion and the second seal It is good to provide the communicating hole which produces a temporary pressure difference between the space between the parts and the area to be sealed.

  As a result, the occurrence of pressure accumulation in the space between the first seal portion and the second seal portion is suppressed, and the first seal lip is directly affected by the pressure fluctuation on the sealing target region side. It is suppressed.

  It is preferable that the communication hole is formed by providing a groove on a fitting surface between the first cylindrical portion and the second cylindrical portion.

  Thereby, a communicating hole can be formed with a simple configuration.

  It is good to provide the valve part which closes the said communicating hole, when the pressure of the sealing object area | region side becomes lower than the pressure of the anti-sealing object area | region side.

  Thereby, the influence of the pressure fluctuation | variation by the side of the sealing object area | region with respect to a 1st seal lip can be relieve | moderated more effectively.

  As described above, according to the present invention, the influence of the negative pressure generation can be reduced with a simple configuration.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

(Example 1)
With reference to FIG. 1, the sealing apparatus which concerns on Example 1 of this invention is demonstrated. FIG. 1 is a schematic cross-sectional view of a sealing device according to the present embodiment.

  The sealing device 1 according to the present embodiment is used in a hydraulic cylinder having a rack shaft as a piston rod in a power steering device as shown in FIG. 3, and includes an outer peripheral surface 301 of a rack shaft 300 as a shaft and a housing. The annular gap between the hydraulic cylinder 400 and the inner peripheral surface 401 is sealed.

  As shown in FIG. 1, the sealing device 1 is roughly composed of a first seal portion 10 and a second seal portion 20.

  The first seal portion 10 includes a metal reinforcing ring 11 and a rubber-like elastic body 12 that is integrally baked and fixed to the reinforcing ring 11. The reinforcing ring 11 includes a substantially cylindrical tubular portion 11a and a flange portion 11b extending substantially radially inward from an end of the tubular portion 11a on the atmosphere side A (anti-sealing target region side). .

  A part of the rubber-like elastic body 12 is baked and fixed continuously from the inner peripheral surface of the cylindrical portion 11a to the oil chamber side O end and the outer peripheral surface so as to cover the surface of the cylindrical portion 11a of the reinforcing ring 11. Has been. The cylindrical portion 11 a of the reinforcing ring 11 and a part of the rubber-like elastic body 12 covering the surface thereof constitute the first cylindrical portion 10 a in the first seal portion 10. The first tubular portion 10 a is fitted and fixed to the inner peripheral surface 401 of the hydraulic cylinder 400.

  Another part of the rubber-like elastic body 12 extends from the vicinity of the tip of the flange portion 11b of the reinforcing ring 11 to the oil chamber side O (sealing target region side) to form a first seal lip 10b. The first seal lip 10b extends from the atmosphere side A of the first tubular portion 10a toward the oil chamber side O and the rack shaft 300, and slidably contacts the outer peripheral surface 301 of the rack shaft 300.

  A spring 13 is attached to the outer periphery of the first seal lip 10b to increase the tightening force against the rack shaft 300. Further, a backup ring 14 is mounted on the inner periphery of the first seal portion 10 and closer to the atmosphere side O than the root of the first seal lip 10b, and the deformation, early wear, and heat generation of the first seal lip 10b are suppressed. Is planned.

  The second seal portion 20 includes a metal reinforcing ring 21 and a rubber-like elastic body 22 that is integrally baked and fixed to the reinforcing ring 21. The reinforcing ring 21 includes a substantially cylindrical tubular portion 21a, and a flange portion 21b that extends substantially inward in the radial direction from the oil chamber side O end of the tubular portion 21a.

  The tubular portion 21 a of the reinforcing ring 21 is fitted and fixed to the inner peripheral surface of the first tubular portion 10 a of the first seal portion 10 as the second tubular portion 20 a of the second seal portion 20. A part of the rubber-like elastic body 22 extends from the vicinity of the tip of the flange portion 21b of the reinforcing ring 21 to the atmosphere side A to form a second seal lip 20b. The second seal lip 20b extends from the oil chamber side O of the second cylindrical portion 20a toward the atmosphere side A and the rack shaft 300 side, and slidably contacts the outer peripheral surface 301 of the rack shaft 300.

  A plurality of grooves 12a extending substantially in the axial direction are equally arranged in the circumferential direction on the inner circumferential surface of the first cylindrical portion 10a. Each groove 12a includes an oil chamber side O and a space S between the first seal portion 10 and the second seal portion 20 in a state where the first tubular portion 10a and the second tubular portion 20a are fitted. Is provided to communicate.

  The communication hole formed in this way prevents pressure accumulation from occurring in the space S, and causes a time difference between the pressure fluctuation on the oil chamber side O and the pressure fluctuation in the space S caused by the pressure fluctuation. That is, it is a small hole that causes a temporary pressure difference between the space S and the oil chamber side O when the pressure on the oil chamber side O varies. By this communication hole, it is suppressed that the pressure in the space S falls rapidly with the pressure fluctuation of the oil chamber side O, and the influence of the pressure fluctuation of the oil chamber side O with respect to the 1st seal lip 10b is relieved.

  As a configuration for forming such a communication hole, various configurations are conceivable, such as providing a groove in the second cylindrical portion 20a, or providing a groove on each fitting surface of the cylindrical portion. From this point of view, a configuration in which a groove is formed in the rubber-like elastic body 22 of the first cylindrical portion 10a as in the present embodiment is preferable.

  In the sealing device 1 configured as described above, the outer peripheral surface of the first cylindrical portion 10 a is in close contact with the inner peripheral surface 401 of the hydraulic cylinder 400 by fitting and fixing, and the first seal lip 10 b is mainly the rack shaft 300. By slidably contacting the outer peripheral surface 301, the annular gap between the rack shaft 300 and the hydraulic cylinder 400 can be satisfactorily sealed.

  When the pressure on the oil chamber side O is higher than the pressure on the atmosphere side A, the pressure in the space S communicating with the oil chamber side O is also higher than the pressure on the atmosphere side A and receives the pressure in the space S. The first seal lip 10 b and the second seal lip 20 b are in close contact with the outer peripheral surface 301 of the rack shaft 300.

When the pressure on the oil chamber side O is instantaneously higher than the pressure in the space S due to pressure fluctuation, the second seal lip 20b is instantaneously lifted from the outer peripheral surface 301 of the rack shaft 300. However, since the first seal lip 10b is kept in close contact with the rack shaft 300, the sealed state by the sealing device 1 is maintained.

  When the pressure on the oil chamber side O changes instantaneously and becomes lower than the pressure on the atmosphere side A, the pressure in the space S communicating with the oil chamber side O through the communication hole is finally Although the pressure is the same as the pressure on the oil chamber side O, the moment when the pressure on the oil chamber side O fluctuates temporarily becomes higher than the pressure on the oil chamber side O. That is, a temporary pressure difference is generated between the space S and the oil chamber side O. Therefore, the second seal lip 20b is in a state of being in close contact with the rack shaft 300 under pressure in the space S.

  Further, the first seal lip 10b is maintained in a contact state with the rack shaft 300 because the influence of the instantaneous pressure fluctuation on the oil chamber side O is alleviated by the communication hole and the space S. In other words, it is possible to suppress a situation in which the first seal lip 10 b is lifted from the outer peripheral surface 301 of the rack shaft 300 due to an instantaneous change in the pressure on the oil chamber side O.

  Moreover, since the sealing device 1 according to the present embodiment is configured to integrate the first seal portion 10 and the second seal portion 20 by fitting the respective cylindrical portions, assembly work is easy. . Further, the communication hole for preventing pressure accumulation and reducing pressure fluctuation can be easily formed by providing a groove on the fitting surface of the first seal portion 10 and the second seal portion 20.

  Furthermore, the fitting portion between the first seal portion 10 and the second seal portion 20 is configured to fit the cylindrical portions of the metal reinforcing ring through a rubber-like elastic body, A good adhesion state can be formed by absorbing dimensional errors and variations in fitting force.

(Example 2)
With reference to FIG. 2, the sealing device 1a which concerns on Example 2 of this invention is demonstrated. FIG. 2 is a schematic cross-sectional view of the sealing device 1a according to the present embodiment, where (a) shows a normal operation and (b) shows a momentary change to a negative pressure state.

  Hereinafter, matters that are not particularly described are the same as those in the first embodiment, and the same components are denoted by the same reference numerals, description thereof is omitted, and only different points will be described.

  In the sealing device 1 according to the first embodiment, the atmosphere side O and the space S are always in communication with each other through the communication hole. Therefore, depending on the magnitude of the pressure fluctuation, the effect of reducing the pressure fluctuation due to the communication hole cannot be obtained, and the first seal lip 10b may be affected by the pressure fluctuation on the oil chamber side O.

  Therefore, in the sealing device 1a according to the present embodiment, when the oil chamber side O is instantaneously changed to a negative pressure state in order to reduce the influence of pressure fluctuation on the first seal lip 10b more reliably, the communication hole The valve part which can be closed is provided.

  The valve portion is configured by a lip 12 b provided on the inner periphery of the first cylindrical portion 10 a of the first seal portion 10. In the lip 12b, a part of the rubber-like elastic body 12 baked and fixed to the inner peripheral surface of the cylindrical portion 11a of the reinforcing ring 11 is formed from the vicinity of the opening portion on the space S side of the communication hole, and the second seal portion. It is formed so as to extend substantially in the axial direction toward the oil chamber side O on the axial center side with respect to the cylindrical portion 20a.

  During normal operation, there is a gap between the outer peripheral surface of the lip 12b and the inner peripheral surface of the second cylindrical portion 20a, and the oil chamber side O and the space S are in communication.

When the oil chamber side O instantaneously changes to a negative pressure state, the lip 12b is moved to the opening portion side (oil chamber side O) of the communication hole due to an instantaneous pressure difference generated between the oil chamber side O and the space S. The diameter is increased and deformed so as to be sucked, and is brought into close contact with the inner peripheral surface of the second cylindrical portion 20a, and the communication hole is closed.

  Thereby, the rapid fall of the pressure in the space S is suppressed, and a pressure difference can be formed between the oil chamber side O and the space S more reliably. Therefore, it is possible to more effectively mitigate the influence of the pressure fluctuation on the oil chamber side O with respect to the first seal lip 10b.

  In the above description, the case where the present embodiment is a sealing device used for a hydraulic cylinder of a power steering device has been described as an example. However, the present application is also applied to other sealing devices used in applications that generate a pressure difference. It goes without saying that the invention can be applied. Further, it goes without saying that the present invention can be suitably applied even when the sealing device is configured to be fitted and fixed to the shaft instead of the housing.

FIG. 1 is a schematic cross-sectional view of the sealing device according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the sealing device according to the second embodiment. FIG. 3 is a schematic cross-sectional view of the power steering apparatus. FIG. 4 is a schematic cross-sectional view of a sealing device according to the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sealing device 10 1st seal | sticker part 10a 1st cylindrical part 10b 1st seal lip 11 Reinforcement ring 11a Cylindrical part 11b Flange part 12 Rubber-like elastic body 12a Groove 13 Spring 14 Backup ring 20 Second seal part 20a 2nd cylinder 20b Second seal lip 21 Reinforcement ring 21a Tubular portion 21b Flange portion 22 Rubber elastic body 300 Rack shaft 400 Cylinder

Claims (4)

A sealing device for sealing an annular gap between a shaft that reciprocally moves relative to each other in an axial direction and a housing having a shaft hole into which the shaft is inserted,
A first tubular portion fitted and fixed to the surface of one of the two members;
A first seal lip extending from the anti-sealing target region side of the first cylindrical portion toward the sealing target region side and the other member side, and slidably contacting the surface of the other member;
A first seal portion having
A second cylindrical part fitted and fixed to the peripheral surface of the other member side in the first cylindrical part;
The second cylindrical portion extends from the sealing target region side toward the anti-sealing target region side and the other member side, and slides on the surface of the other member on the sealing target region side of the first seal lip. A second seal lip that freely contacts;
A second seal portion having
A sealing device comprising:   The space between the first seal portion and the second seal portion communicates with the sealing target region side, and when the pressure on the sealing target region side fluctuates, the first seal portion and the second seal The sealing device according to claim 1, further comprising a communication hole that generates a temporary pressure difference between the space between the first portion and the space to be sealed.   The sealing device according to claim 2, wherein the communication hole is formed by providing a groove on a fitting surface between the first cylindrical portion and the second cylindrical portion.   The sealing device according to claim 2, further comprising a valve portion that closes the communication hole when the pressure on the sealing target region side becomes lower than the pressure on the anti-sealing target region side.

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