JP6288409B2 - Sealing device - Google Patents

Description

  The present invention relates to a sealing device.

  For example, a rotating part such as a crankshaft of an automobile is generally provided with a shaft surface sliding type oil seal (sealing device) in order to prevent leakage of lubricating oil. This type of oil seal is formed by forming a lip by vulcanizing and bonding rubber to a metal ring and incorporating a spring into the lip. The shaft is appropriately held by a lip pressed against the raceway surface by the elastic force of the spring, thereby sealing the oil.

  For example, the following Patent Document 1 discloses an oil seal in which a lip formed on an inner periphery of a seal body is pressed against an outer peripheral surface of a rotating member by a tightening force of a spring attached to the outer periphery of the seal body. Coating with a heat-shrinkable tube that allows the expansion and contraction of the film.

Japanese Utility Model Publication No. 3-172 JP-A-9-79274

The contact surface (lip sliding surface) of the lip with respect to the shaft is fluid lubricated with oil, and the lip is brought into contact with the atmosphere side and the sealing liquid side with a predetermined surface pressure distribution. Further, the tightness of the lip can be maintained satisfactorily, and the oil sealing performance can be obtained.
However, if the high-speed rotation state continues in a state where the lip sliding surface is depleted of oil (non-lubricated state), lip sag and lip wear due to sliding heat generation proceed rapidly. As a result, the tightness of the lip may be reduced and seal leakage may occur. Although the lip is pressed by a spring in order to prevent a decrease in the tension force, when the lip wears, the spring diameter changes and the spring contracts. For this reason, the restraining force of the spring before wear cannot be obtained, and the reduction of the tightening force cannot be avoided.

  On the other hand, when the initial value of the spring restraining force is increased, the squeezing force of the lip is increased. However, the torque is increased and it is difficult to obtain an appropriate surface pressure distribution. Further, Patent Document 2 discloses an attempt to reduce lip wear by a technique that does not use a spring. However, even with the technique disclosed in Patent Document 2, there is a problem in that the lip tightening force is reduced. Has not yet been resolved.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sealing device that can maintain a surface pressure distribution of a lip sliding surface over a long period of time and can suppress a decrease in lip tension.

In order to achieve the above-mentioned object, the invention according to claim 1 includes an outer member (27) having a raceway surface (26) on an inner periphery, and an annular gap (28) coaxially with the outer member with respect to the outer member. ) Between the inner member (29) and the inner member (29) having a raceway surface (30) on the outer periphery thereof, the raceway of the inner member. A seal body (2) having an annular lip (15) that contacts the surface with a predetermined surface pressure and slides against the raceway surface of the inner member, and elastically tightens the lip surrounding the lip. an annular elastic member (3), mounted so as to surround the outer periphery of the lip, and contracted by heat, seen including a heat shrinkable member that can be pressed in a direction of reducing the diameter of the lip (4) by its contraction force, The heat shrink member is the elastic member. Provided on the outer peripheral side, a sealing device.

The invention according to claim 2 is the sealing device according to claim 1, wherein the heat shrinkable member is attached to the seal body in a form before shrinkage .

According to a third aspect of the present invention, the elastic member includes a cylindrical coil spring (3), the lip is formed in an annular shape along the circumferential direction on the outer peripheral surface thereof, and the coil spring is fitted therein. The heat shrink member has a semi-cylindrical shape (23) formed so as to cover the outer peripheral surface of the elastic member exposed from the spring groove. The sealing device according to claim 1 or 2 , comprising a heat shrinkable tube (4).

According to a fourth aspect of the present invention, the seal body includes an outer ring (7) that is fitted into the gap so that an outer peripheral surface thereof is in contact with the raceway surface of the outer member, and the lip includes the outer lip. It is integrally connected to the outer ring via a lip root portion (16) so as to be disposed in the inner region of the ring, and the thickness t of the lip root portion and the thickness of the heat-shrinkable member. Sa is the sealing device according to any one of claims 1 to 3 , which satisfies a relational expression: a <t <2a.

  In addition, in the above, the numbers in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

According to the first aspect of the present invention, the heat contraction member can be contracted using the sliding heat generation of the lip, and the lip can be pressed in the direction of reducing the diameter. Since the lip is pressed from the outside by this pressing force, the surface pressure of the lip sliding surface can be increased, and the surface pressure distribution can be re-formed. As a result, the surface pressure distribution of the lip sliding surface can be maintained over a long period of time, and a decrease in the lip tightening force can be suppressed.
Further, the tension force of the lip can be expressed by an elastic member that can naturally obtain a restraining force. On the other hand, when the lip wears and the restraining force of the elastic member decreases, the heat shrinkable member can be used as a supplementary member that suppresses the decrease in the tightening force. That is, it is possible to satisfactorily suppress a reduction in the lip tightening force by a heat contraction force generated by a mechanism different from the restraining force of the elastic member.

According to the second aspect of the present invention, since the allowance for expansion until the heat-shrinkable member is completely contracted can be increased, it is possible to suppress a decrease in the tension force of the lip over a longer period .

According to the invention described in claim 3 , since the heat-shrinkable member is a semi-cylindrical heat-shrinkable tube, when the heat-shrinkable tube is heat-shrinked, a shrinkage force can be generated from any part of the heat-shrinkable tube toward the center thereof. it can. Then, these contracting forces are combined, and a pressing force can be applied in a direction perpendicular to the raceway surface of the inner member. That is, since the contraction force can be efficiently collected and synthesized in the center direction of the heat contraction tube, the loss when the contraction force is applied to the lip can be reduced.

Further, since the coil spring is covered with the lip and the heat shrinkable tube, even when a liquid containing a component that corrodes the coil spring is put on the sealing liquid side of the gap, the coil spring is protected from the liquid. Can do.
According to the invention described in claim 4 , while designing the lip root portion and the heat shrinkable member under the condition satisfying the relational expression: a <t <2a, the heat shrinkable member is prevented from interfering with the outer ring. The effect of heat shrinkage of the heat shrinkable member can be sufficiently obtained.

FIG. 1 is a perspective view of an oil seal showing an embodiment of the present invention, showing an assembled state and a disassembled state. FIG. 2 is a diagram illustrating a usage state of the oil seal of FIG. FIG. 3 is a diagram showing the state of the lip in the initial stage (before wear) and after wear. FIG. 4 is a graph showing changes in the surface pressure distribution of the lip sliding surface.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view of an oil seal 1 showing an embodiment of the present invention, showing an assembled state and a disassembled state. In FIG. 1, a part of the ring-shaped oil seal 1 is cut out to clarify the cross-sectional structure of the oil seal 1.
An oil seal 1 as an example of a sealing device of the present invention includes a seal body 2, a coil spring 3 as an example of an elastic member of the present invention, and a heat shrinkable tube 4 as an example of a heat shrinkable member of the present invention. . The seal body 2, the coil spring 3, and the heat shrinkable tube 4 are each formed in a ring shape. The oil seal 1 is assembled by fitting a coil spring 3 and a heat-shrinkable tube 4 into the seal body 2.

  The seal body 2 includes a rubber member 5 and a metal reinforcing ring 6 embedded in the rubber member 5. The seal body 2 is formed, for example, by forming a reinforcing ring 6 by pressing a metal plate such as SPCC (Steel Plate Cold Commercial) and vulcanizing and bonding a rubber material to the reinforcing ring 6. be able to. As a usable rubber material, for example, NBR (nitrile rubber), HNBR (hydrogenated nitrile rubber), ACM (acrylic rubber), VMQ (silicon rubber), FKM (fluoro rubber) and the like are suitable.

The rubber member 5 integrally forms an outer ring 7 and an inner ring 9 provided in an inner region of the outer ring 7 so that an annular groove 8 is formed between the inner peripheral surface of the outer ring 7. Including.
The outer ring 7 is formed in a substantially L shape in sectional view having a flange portion 10 extending radially inward from a peripheral edge on one axial end side. The flange portion 10 forms the bottom of the groove 8 between the inner peripheral surface of the outer ring 7 and the inner ring 9. The oil seal 1 is attached to an object to be sealed (for example, the rotating portion 25 shown in FIG. 2) so that the flange portion 10 is on the outside. Therefore, in the oil seal 1 attached to the object to be sealed, the surface (sealing liquid side surface) in contact with the inner sealing liquid is opened by the groove 8 and the surface in contact with the outer atmosphere (atmospheric side surface) is the flange portion. 10 is occluded. In the following, the open side of the groove 8 (the side where the flange portion 10 is not formed) is referred to as “sealing liquid side”, and the opposite side of the sealing liquid side (the side where the flange portion 10 is formed) is referred to as “atmosphere side”. explain.

On the outer peripheral surface of the outer ring 7, chamfered portions 11 and 12 are formed at both ends in the axial direction. The chamfered portions 11 and 12 are formed over the entire circumference of the outer peripheral surface of the outer ring 7. The chamfered portions 11 and 12 facilitate the attachment of the oil seal 1 to the object to be sealed.
On the other hand, the inner peripheral surface of the outer ring 7 includes a tapered surface 13 that gently slopes radially outward from the flange portion 10 toward the open end of the groove 8. In this embodiment, the tapered surface 13 is formed between the flange portion 10 and a depth position slightly closer to the closed end side than the open end of the groove 8. As a result, the thickness of the outer ring 7 is reduced on the open end side of the groove 8, so that the distance between the outer ring 7 and the inner ring 9 (width of the groove 8) is widened. Therefore, workability at the time of attaching two members such as the coil spring 3 and the heat shrinkable tube 4 to the seal body 2 via the groove 8 can be improved. The inner peripheral surface of the outer ring 7 may be a tapered surface 13 in the entire section from the flange portion 10 to the open end of the groove 8.

Further, a shallow groove 14 is formed on the atmospheric side surface of the outer ring 7 (the surface of the flange portion 10) over the entire circumference.
The inner ring 9 includes a lip 15 formed over the entire circumference of the inner ring 9 and a lip root portion 16 that supports the lip 15 so as to be able to expand and contract by bending elasticity. That is, when a force in the direction toward the radially outer side or the inner side is applied to the lip 15, a bending stress is applied to the lip root portion 16 by the force and the lip root portion 16 is deformed, and the lip 15 is expanded in diameter by the deformation. Or reduce the diameter.

The lip 15 is formed so that a radially inner portion (opposite side of the outer ring 7) of the seal body 2 selectively protrudes radially inward. Specifically, the inner portion of the lip 15 is formed in a wedge shape in cross section, and the axis 18 of the seal body 2 is provided on each of the sealing liquid side and the atmosphere side with respect to the protruding tip (lip tip 17). It has a pair of surface inclined with respect to.
The pair of surfaces are a lip sealing liquid side surface 19 and a lip atmosphere side surface 20, respectively, and are asymmetric with respect to the symmetry axis 21 passing through the lip tip 17 in a cross-sectional view. More specifically, the lip sealing liquid side surface 19 is asymmetric by tilting at a larger angle with respect to the axis 18 of the seal body 2 than the lip atmosphere side surface 20. For example, the angle θ ₁ of the lip sealing liquid side surface 19 with respect to the axis 18 is 0 ° to 90 °, while the angle θ ₂ of the lip atmosphere side surface 20 is 0 ° to 90 °. Moreover, the angle θ ₃ of the lip tip 17 formed by the lip sealing liquid side surface 19 and the lip atmosphere side surface 20 intersecting is, for example, 90 ° to 180 °.

  On the other hand, a spring groove 22 is formed in a radially outer portion of the lip 15 facing the outer ring 7 with the groove 8 interposed therebetween. The spring groove 22 is formed in a semicircular shape in sectional view over the entire circumference of the outer peripheral surface of the lip 15, and the inner diameter thereof is substantially the same as the outer diameter of the coil spring 3. Further, in this embodiment, the position of the spring groove 22 is shifted to the atmosphere side from the lip tip 17. This deviation is formed by offsetting the center of the spring groove 22 to the atmosphere side with respect to the lip tip 17.

The lip root portion 16 may be a thin-walled portion that can support the lip 15 so as to be freely contractible and expandable by bending elasticity, and is generally formed with a thickness t of 0.1 mm or more.
In this embodiment, the reinforcing ring 6 is selectively embedded in the outer ring 7 in the rubber member 5, and is formed in a substantially L shape in the same sectional view as the outer ring 7.
The coil spring 3 is formed in a cylindrical shape having an outer diameter substantially the same as the inner diameter of the spring groove 22 of the lip 15. The type of the coil spring 3 is not particularly limited, and a general one can be used. In this embodiment, the coil spring 3 is cited as an example of an elastic member capable of elastically tightening the lip 15. However, for example, a rubber tube or the like may be used instead of the coil spring 3.

  The heat-shrinkable tube 4 is formed using a rubber material that shrinks when heated. There are various types of rubber materials of this type, but it is preferable to select a rubber material that starts to shrink at a temperature equal to or higher than the heat resistant limit temperature of the rubber material constituting the lip 15. In other words, it is preferable to select a rubber material that does not thermally shrink within the range of the heat-resistant safety temperature of the rubber material constituting the lip 15 (the temperature at which wear or melting does not occur even when the lip 15 is continuously used). As an example satisfying the above condition, for example, when the lip 15 is formed of NBR (heat-resistant limit temperature: about 120 ° C.), an NBR heat-shrink rubber is selected, and the lip 15 is made of fluoro rubber (heat-resistant limit). Teflon (registered trademark) heat-shrinkable rubber is selected.

  The heat-shrinkable tube 4 is made of the rubber material described above, and extends to the outer side in the axial direction from the semi-cylindrical portion 23 opened toward the inner side in the radial direction of the heat-shrinkable tube 4 and from the peripheral edge on one axial side of the semi-cylindrical portion 23 The flange portion 24 is integrally formed. The inner diameter of the semicylindrical portion 23 is substantially the same as the outer diameter of the coil spring 3. In this embodiment, the heat-shrinkable tube 4 has a semi-cylindrical portion 23 and a flange portion 24 formed with a uniform thickness a. The thickness a preferably satisfies the relational expression: a <t <2a with the thickness t of the lip root portion 16.

  In order to assemble the oil seal 1 using the seal body 2, the coil spring 3, and the heat shrinkable tube 4, for example, first, the coil spring 3 is connected to the spring groove 22 of the lip 15 via the groove 8 of the seal body 2. Fit into. Next, the heat-shrinkable tube 4 is aligned with the groove 8 of the seal body 2 so that the flange portion 24 is on the back side, and the coil spring 3 exposed from the spring groove 22 is overlapped so that the lip root portion 16 and the flange portion 24 overlap. The semi-cylindrical part 23 is fitted. Thereby, the oil seal 1 is assembled. In this assembled state, the flange portion 24 is supported by the lip root portion 16 of the oil seal 1, and the spring groove 22 of the lip 15 and the semi-cylindrical portion 23 of the heat shrinkable tube 4 are combined to be closed from the outside. A cylindrical space is formed, and the coil spring 3 is accommodated in the cylindrical space. That is, the coil spring 3 is completely protected by the lip 15 and the heat-shrinkable tube 4 by covering the inner half of the oil seal 1 in the radial direction with the lip 15 and the outer half of the radial direction with the heat-shrinkable tube 4. Yes. It is preferable that the heat shrinkable tube 4 is not heated and is not subjected to any heat history until the oil seal 1 is attached to the object to be sealed. It may be slightly shrunk to improve the adhesion.

FIG. 2 is a diagram illustrating a usage state of the oil seal 1 of FIG. FIG. 3 is a diagram showing the state of the lip 15 in the initial stage (before wear) and after wear. FIG. 4 is a graph showing changes in the surface pressure distribution of the lip sliding surface 31.
The oil seal 1 described with reference to FIG. 1 is mainly used in, for example, rotating parts of automobile engines, transmissions, etc., but is not limited thereto, construction machines, machine tools, aircrafts, ships, rail vehicles, agricultural machines, petroleum It can be used for machines in all fields such as chemical plants, nuclear power plants, and home appliances.

  The rotating part 25 of such a machine is generally arranged rotatably with a housing 27 (outer member) having a raceway surface 26 on the inner periphery and an annular gap 28 coaxially with the housing 27 with respect to the housing 27. Rotation shaft 29 (inner member). The oil seal 1 is used to prevent the lubricating oil as an example of the sealing liquid put in the gap 28 from leaking from the end of the rotating shaft 29 or the entry of dirt and dust into the gap 28 from the outside. used. Specifically, the oil seal 1 is set by being pushed into the gap 28 of the rotating portion 25 so that the sealing liquid side is the back side.

  Thereby, the outer raceway surface 26 of the gap 28 is sealed by the outer peripheral surface of the outer ring 7, and the inner raceway surface 30 is sealed by the lip 15. At this time, the lip 15 is expanded from the inside by the difference between the outer diameter of the rotating shaft 29 and the inner diameter of the oil seal 1, and is tightened from the outside by the elastic force of the coil spring 3. As a result, the lip tip 17 (see FIG. 1) selectively protruding from the lip 15 is pressed against the raceway surface 30 of the rotating shaft 29 and deformed.

On the other hand, with respect to the rotating shaft 29, the deformed lip tip 17 is pressed with a constant contact area. FIG. 3 schematically shows the pressure distribution (surface pressure distribution) by the lip tip 17, and FIG. 4 shows the surface pressure distribution in a graph.
That is, as shown by an arrow on the rotating shaft 29 in FIG. 3, in the initial state (before wear) immediately after the oil seal 1 is set on the rotating portion 25, the contact surface of the lip 15 with respect to the rotating shaft 29 (lip sliding). The surface pressure distribution of the surface 31) is asymmetric on the atmosphere side and the sealing side with respect to the symmetry axis 32 passing through the center of the oil seal 1 in the axial direction.

  As shown in FIG. 1, this asymmetric phenomenon is caused by the fact that the center of the spring groove 22 is offset to the atmosphere side with respect to the lip tip 17, so that the contact position of the lip 15 is relative to the position of the coil spring 3 (spring position). This is because it shifts to the sealing liquid side. In this embodiment, as shown in FIGS. 3 and 4, the surface pressure of the lip sliding surface 31 starts in the direction from the atmospheric end of the lip sliding surface 31 to the end of the sealing liquid side. When the contact position is defined as x, the distribution is such that x increases as it increases, and is almost the maximum at the lip 15 contact position. An oil film derived from the lubricating oil is formed on the lip sliding surface 31, and the sealing property of the lubricating oil is maintained well while the above surface pressure distribution is maintained.

  However, when the lip sliding surface 31 is depleted of lubricating oil (non-lubricated state), the rotating shaft 29 continues to rotate at a high speed, and sliding heat generation exceeding the heat resistant limit temperature of the rubber material constituting the lip 15 is prolonged. If continued for a long time, the lip 15 and the lip 15 wear rapidly, resulting in the “after-wear” state shown in FIG. As a result, as shown by the broken lines in FIGS. 3 and 4, the appropriate surface pressure distribution in the initial state is collapsed, the contact width of the lip sliding surface 31 is widened, and the surface pressure of the lip sliding surface 31 is based on the maximum value. Decreases to about half. In this state, the tension of the lip 15 is too low, and seal leakage may occur. On the other hand, the lip 15 is pressed by the coil spring 3 in order to prevent a decrease in the tension force. However, when the lip 15 is worn, the diameter of the coil spring 3 also changes and the coil spring 3 contracts. For this reason, the restraining force of the coil spring 3 in the initial state cannot be obtained, and the reduction of the tightening force cannot be avoided.

  Therefore, in this embodiment, the heat shrinkable tube 4 having the semicylindrical portion 23 that surrounds the outer periphery of the lip 15 and covers the coil spring 3 is provided. Since the heat shrinkable tube 4 starts to shrink at a temperature equal to or higher than the heat resistant limit temperature of the rubber material constituting the lip 15, the heat shrinkable tube 4 is shrunk using the amount of heat generated by sliding heating. Due to this contraction, as indicated by an arrow F in FIG. 3, contraction force is generated in the central direction from any part of the heat contraction tube 4, and these forces are combined to be perpendicular to the raceway surface 30 of the rotation shaft 29. The pressing force works.

  The pressing force presses the lip 15 from the outside over the entire circumference, so that the contact width of the lip sliding surface 31 is kept wide as shown in FIGS. Thus, the surface pressure can be increased, and it can be restored to the initial state on the basis of the maximum value. As a result, a surface pressure distribution for obtaining a pressing force equivalent to that in the initial state can be recreated. That is, even if it becomes difficult to obtain a sufficient tightening force only by the restraining force of the coil spring 3 due to wear of the lip 15 or the like, the heat shrinkage force generated by a mechanism different from the restraining force of the coil spring 3 A decrease in the tension of the lip 15 can be suppressed.

Further, as shown in FIG. 1, since the thickness t of the heat shrinkable tube 4 and the thickness a of the lip root portion 16 satisfy the relational expression: a <t <2a, the heat shrinkable tube 4 is While preventing the interference with the ring 7, it is possible to sufficiently obtain the effect due to the heat shrinkage of the heat shrinkable tube 4.
Furthermore, as shown in FIG. 1, since the coil spring 3 is completely covered with the lip 15 and the heat shrinkable tube 4, a liquid containing a component that corrodes the coil spring 3 is placed on the sealing liquid side. However, the coil spring 3 can be protected from the liquid.

As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.
For example, in the above-described embodiment, the configuration in which the coil spring 3 is sandwiched between the lip 15 and the heat-shrinkable tube 4 is taken up, but the seal body 2 has a force for urging the lip 15 radially inward. If it is, the coil spring 3 may be omitted.

  The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims.

  DESCRIPTION OF SYMBOLS 1 ... Oil seal, 2 ... Seal main body, 3 ... Coil spring, 4 ... Heat-shrinkable tube, 7 ... Outer ring, 15 ... Lip, 16 ... Lip root part, 22 ... Spring groove, 23 ... Semi-cylindrical part, 26 ... ( Raceway surface of the housing, 27 ... housing, 28 ... gap, 29 ... rotation axis, 30 ... raceway surface (of the rotation axis)

Claims (4)

The gap between the outer member having a raceway surface on the inner periphery and the inner member having a raceway surface on the outer periphery, arranged coaxially with the outer member and sandwiching an annular gap with respect to the outer member. A sealing device attached to
A seal body having an annular lip that contacts the raceway surface of the inner member at a predetermined surface pressure and slides against the raceway surface of the inner member;
An annular elastic member surrounding the lip and elastically tightening the lip;
Mounted so as to surround the outer periphery of the lip, and contracted by heat, seen including a heat shrinkable member that can be pressed in a direction of reducing the diameter of the lip by the contractile force,
The heat shrink member is a sealing device provided on the outer peripheral side of the elastic member .   The sealing device according to claim 1, wherein the heat shrink member is attached to the seal body in a form before shrink. The elastic member includes a cylindrical coil spring,
The lip is formed in an annular shape along the circumferential direction on the outer peripheral surface thereof, and has a substantially semicircular spring groove in cross-sectional view into which the coil spring is fitted.
The heat shrinkable member comprises said resilient semi-cylindrical heat-shrinkable tube formed so as to cover the outer peripheral surface of the member exposed from the spring groove sealing device as claimed in claim 1 or 2. The seal body includes an outer ring that is fitted into the gap so that an outer peripheral surface thereof is in contact with the raceway surface of the outer member,
The lip is integrally connected to the outer ring via a lip root so as to be disposed in an inner region of the outer ring,
The sealing device according to any one of claims 1 to 3 , wherein a thickness t of the lip root portion and a thickness a of the heat shrinkable member satisfy a relational expression: a <t <2a.

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