Sealing device

Abstract

A sealing device is positioned between an inner member and an outer member that rotate relative to each other. The sealing device comprises a seal lip that slideably contacts the outer circumferential surface of the inner member and seals a liquid inside an interior space of the outer member. The seal lip has a liquid-side inclined surface, an air-side inclined surface, and a lip edge that extends in the circumferential direction at the boundary between the liquid-side inclined surface and the air-side inclined surface. A plurality of spiral ribs are formed on the air-side inclined surface contacting the outer circumferential surface of the inner member, the plurality of spiral ribs inclining in relation to the lip edge and extending in a spiral shape. Each spiral rib has straight-line sections having side walls parallel to each other, and a boat-bottom-shaped section that curves so as to be wider than the side walls, the straight-line sections extending from the lip edge, and the boat-bottom-shaped section being positioned farther from the lip edge than the straight-line sections. The height of each straight-line section in relation to the air-side inclined surface is 5-37 µm, inclusive.

Description

[Technical field]

[0001] The present invention relates to a sealing device disposed between relatively rotating inner and outer members. [Background technology]

[0002] A sealing device disposed between an inner member and an outer member that rotate relative to one another has a seal lip with a plurality of spiral ribs formed on its atmospheric side. This type of sealing device is used to seal liquid (e.g., lubricant) disposed in the internal space of the outer member, and the spiral ribs act to return the liquid that has leaked to the atmospheric side back to the internal space as the inner member and the outer member rotate relative to one another (pumping action). This prevents most liquid from leaking to the atmospheric side.

[0003] More specifically, the helical rib is angled relative to the lip edge of the sealing lip to provide a pumping action upon rotation of the inner member in one direction relative to the outer member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3278349 Summary of the Invention

[0005] In the case where the inner member is bidirectionally rotatable relative to the outer member, it is desirable for the sealing device to be able to suppress leakage of liquid to the atmosphere when the inner member rotates in a direction opposite to the normal direction of rotation relative to the outer member. For example, a drive shaft, transmission shaft, or axle of an automobile can rotate in two directions. In particular, the rotating shaft of a drive motor of an electric or hybrid automobile rotates at high speed.

[0006] Therefore, the present invention provides a sealing device that can suppress leakage of liquid to the atmosphere side when the inner member rotates at high speed in the reverse direction relative to the outer member.

[0007] A sealing device according to an aspect of the present invention is disposed between an inner member and an outer member which rotate relative to each other, and seals a gap between the inner member and the outer member, and includes an attachment portion attached to the outer member, and a seal lip disposed inside a hole of the outer member, slidably contacting an outer peripheral surface of the inner member, separating an internal space of the outer member from an atmosphere side, and sealing a liquid in the internal space. The seal lip has a liquid-side inclined surface disposed on the internal space side, an atmosphere-side inclined surface disposed on the atmosphere side, and a lip edge extending in the circumferential direction at a boundary between the liquid-side inclined surface and the atmosphere-side inclined surface. The liquid-side inclined surface is inclined so as to move away from the inner member as it moves away from the lip edge. The atmosphere-side inclined surface is inclined so as to move away from the inner member as it moves away from the lip edge. A plurality of spiral ribs are formed on the atmosphere-side inclined surface which contact the outer peripheral surface of the inner member, and the plurality of spiral ribs extend in a spiral manner at an incline with respect to the lip edge. Each spiral rib has a straight portion having parallel side walls and a boat-bottom shaped portion that is wider and curved than the side walls, the straight portion extending from the lip edge, and the boat-bottom shaped portion being disposed farther from the lip edge than the straight portion. The height of each straight portion relative to the atmosphere-side inclined surface is 5 μm or more and 37 μm or less.

[0008] In this embodiment, since the height of the straight portion of each spiral rib is 5 μm or more, each spiral rib exerts a pumping effect when the inner member rotates in the forward direction relative to the outer member, while the height of the straight portion of each spiral rib is 37 μm or less, leakage of liquid to the atmosphere side can be suppressed even when the inner member rotates at high speed in the reverse direction relative to the outer member. [Brief description of the drawings]

[0009] [Figure 1] 1 is a partial cross-sectional view showing a sealing device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a development view of an inner circumferential surface of a seal lip of the sealing device according to the embodiment of the present invention. [Diagram 3] 3 is a cross-sectional view of the seal lip corresponding to line III-III in FIG. 2. [Figure 4] 13 is a graph showing the results of preventing liquid leakage for each sample of the sealing device in an experiment in which a rotating shaft was rotated in a direction opposite to the normal rotation direction. [Diagram 5] FIG. 11 is a development view of an inner circumferential surface of a seal lip of a sealing device according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Various embodiments of the present invention will now be described with reference to the accompanying drawings, in which the drawings are not necessarily drawn to scale, and some features may be exaggerated or omitted.

[0011] As shown in Fig. 1, a sealing device 1 according to an embodiment of the present invention is disposed between a stationary housing (outer member) 2 and a rotating shaft (inner member) 4, and seals the gap between the housing 2 and the rotating shaft 4. A shaft hole 2A is formed in the housing 2, and the rotating shaft 4 is disposed in the shaft hole 2A. A liquid, i.e., oil as a lubricant, is disposed in the internal space of the housing 2. The rotating shaft 4 is cylindrical, the shaft hole 2A has a circular cross section, and the sealing device 1 is annular, although only the left half of them is shown in Fig. 1.

[0012] The rotating shaft 4 is, for example, a drive shaft, a transmission shaft or an axle of a motor vehicle.

[0013] The sealing device 1 has an outer cylindrical portion 10, a connecting portion 12, and an inner cylindrical portion 14. The outer cylindrical portion 10 is a mounting portion that is attached to the housing 2. In the illustrated example, the outer cylindrical portion 10 is fitted (i.e., pressed) into the axial hole 2A by an interference fit method. However, other mounting methods may be used. The connecting portion 12 is disposed closer to the atmosphere than the outer cylindrical portion 10, and connects the outer cylindrical portion 10 and the inner cylindrical portion 14.

[0014] The sealing device 1 is a composite structure having an elastic ring 16 and a rigid ring 18. The elastic ring 16 is made of an elastic material, such as an elastomer. The rigid ring 18 is made of a rigid material, such as a metal, and reinforces the elastic ring 16. The rigid ring 18 has a substantially L-shaped cross-sectional shape. The rigid ring 18 is embedded in the elastic ring 16 and is in close contact with the elastic ring 16. Specifically, the rigid ring 18 is provided across the outer cylindrical portion 10 and the connecting portion 12.

[0015] The inner cylindrical portion 14 is made of only an elastic material, and a seal lip 20 and a dust lip 22 are formed on the inner cylindrical portion 14. The seal lip 20 and the dust lip 22 are disposed inside the axial hole 2A of the housing 2, and are in slidable contact with the outer circumferential surface of the rotating shaft 4.

[0016] The seal lip 20 separates the internal space of the housing 2 from the atmosphere side, and seals the liquid in the internal space. That is, the seal lip 20 plays a role in preventing the outflow of the lubricant.

[0017] The dust lip 22 is disposed closer to the atmosphere than the seal lip 20, and serves to prevent foreign matter (including water (including muddy water or salt water) and dust) from flowing into the internal space from the atmosphere side. The dust lip 22 is an inclined annular plate, and extends obliquely from its base toward the atmosphere side and radially inward.

[0018] The seal lip 20 is a protrusion formed on the inner circumferential surface of the inner cylindrical portion 14, and has a liquid-side inclined surface 24 arranged on the internal space side, an atmosphere-side inclined surface 26 arranged on the atmosphere side, and a lip edge 28 that extends in the circumferential direction at the boundary between the liquid-side inclined surface 24 and the atmosphere-side inclined surface 26. The liquid-side inclined surface 24 has the shape of a side surface of a truncated cone, and is inclined so as to move away from the rotation axis 4 the further it moves away from the lip edge 28. The atmosphere-side inclined surface 26 also has the shape of a side surface of a truncated cone, and is inclined so as to move away from the rotation axis 4 the further it moves away from the lip edge 28.

[0019] A garter spring 30 that compresses the seal lip 20 radially inward is wound around the outer circumferential surface of the inner cylindrical portion 14. However, the garter spring 30 is not necessarily essential.

[0020] A plurality of spiral ribs 32 are formed on the atmosphere-side inclined surface 26. These spiral ribs 32 extend helically and inclined with respect to the lip edge 28. The spiral ribs 32 are arranged at equal angular intervals from one another in the circumferential direction.

[0021] FIG. 2 is a development view of the inner circumferential surface of the seal lip 20. As shown in FIG. 2, each spiral rib 32 has a straight portion 34 and a boat-bottom shaped portion 36 that is wider and curved than the side wall 34a of the straight portion 34. The straight portion 34 is a portion called a "parallel thread projection" in Patent Document 1, extends linearly, and has side portions 34a that are parallel to each other. The boat-bottom shaped portion 36 is a portion called a "boat-bottom thread projection" in Patent Document 1, and has a boat-bottom shape. That is, the width of the boat-bottom shaped portion 36 gradually increases from one end along the longitudinal direction of the boat-bottom shaped portion 36, and gradually decreases from the center portion to the other end. In each spiral rib 32, the straight portion 34 and the boat-bottom shaped portion 36 are arranged in series, the straight portion 34 extends from the lip edge 28, and the boat-bottom shaped portion 36 is arranged farther from the lip edge 28 (toward the atmosphere) than the straight portion 34.

[0022] Each spiral rib 32 contacts the outer peripheral surface of the rotating shaft 4. Fig. 3 shows a state in which the seal lip 20 including the spiral rib 32 contacts the outer peripheral surface of the rotating shaft 4. As shown in Fig. 3, the lip edge 28 and the spiral rib 32 are elastically deformed by contacting the outer peripheral surface of the rotating shaft 4. The amount of deformation of the lip edge 28 is called the interference IN.

[0023] The straight portion 34 of the spiral rib 32 close to the lip edge 28 has a uniform height H relative to the atmosphere-side inclined surface 26 over the longitudinal direction of the spiral rib 32 when not elastically deformed (shown by a virtual line). However, the portion of the straight portion 34 close to the lip edge 28 is elastically deformed by contacting the outer circumferential surface of the rotating shaft 4. In reality, the deformation amount (tightening margin IN) of the lip edge 28 is much larger than the height H of the straight portion 34, but the height H is shown exaggerated in FIG. 3.

[0024] On the other hand, the boat-bottom shaped portion 36 away from the lip edge 28 does not contact the outer circumferential surface of the rotating shaft 4. However, if the straight portion 34 wears, the boat-bottom shaped portion 36 may come into contact with the outer circumferential surface of the rotating shaft 4. The height H of the straight portion 34 mentioned above means the height of the straight portion 34 in the initial state after the manufacturing of the sealing device 1.

[0025] The inclination direction of each spiral rib 32 is adapted to the rotation of the rotating shaft 4 in the first direction R1 in Fig. 2. In other words, when the rotating shaft 4 rotates in the first direction (forward direction, i.e., the normal rotation direction of the rotating shaft 4) R1, each spiral rib 32 exerts a pumping action to return the liquid from the atmosphere side to the internal space.

[0026] However, when the rotating shaft 4 rotates in the second direction (reverse direction) R2 in Fig. 2, the contact state of the seal lip 20 with the rotating shaft 4 becomes unstable due to the spiral rib 32, and liquid may leak from the internal space to the atmosphere. Such leakage is understood to be caused by a slight deformation of the seal lip 20 including the spiral rib 32 or a decrease in the tension of the seal lip 20 against the rotating shaft 4. The higher the rotation speed of the rotating shaft 4 in the second direction R2, the more likely the liquid leakage is to occur. It is preferable to be able to suppress the liquid from leaking to the atmosphere even when the rotating shaft 4 rotates at high speed in the second direction R2.

[0027] Therefore, the applicant conducted an experiment to investigate the performance of the helical rib 32 using a plurality of sample sealing devices 1 in which the height H of the straight portion 34 of the helical rib 32 was different.

[0028] In the samples used in the experiment, the height H was 14 μm, 25 μm, 37 μm, and 48 μm. The material of the elastic ring 16 of the sample was FKM (fluororubber). The diameter of the rotating shaft 4 in contact with the seal lip 20 was 65 mm.

[0029] The liquid stored in the internal space is low-viscosity automatic transmission fluid (ATF). The liquid was poured into the internal space up to the height of the central axis of the rotating shaft 4 (the part below the central axis of the rotating shaft 4 was immersed in the liquid).

[0030] In the experiment, the rotating shaft 4 was rotated in both the first direction R1 and the second direction R2, and it was determined whether or not the liquid leaked to the atmosphere. Specifically, if the liquid was visible beyond the dust lip 22, it was determined that the liquid had leaked to the atmosphere. The distance from the lip edge 28 of the seal lip 20 to the dust lip 22 was 6 mm in the no-load state.

[0031] In the experiment with rotation in the first direction R1, the peripheral speed of the rotating shaft 4 was 50 m / s. In none of the samples did the liquid leak into the atmosphere.

[0032] Next, the experiment in the second direction R2 will be described. In Fig. 4, the minimum circumferential speed at which the liquid leaked to the atmosphere side is plotted for each sample when the rotating shaft 4 is rotated in the second direction R2. When the height H is 48 μm, the liquid leaked to the atmosphere side even at a significantly low circumferential speed. On the other hand, when the height H is 25 μm or 37 μm, the liquid leaked to the atmosphere side at a circumferential speed higher than 20 m / s. This indicates that when the height H is 25 μm or 37 μm, the liquid does not leak to the atmosphere side even when the rotating shaft 4 is rotated in the second direction R2 at a circumferential speed of 20 m / s. Since it is considered clear that the liquid does not leak to the atmosphere side when the height H is lower, even when the rotating shaft 4 is rotated in the second direction R2 at a circumferential speed of 20 m / s, the sample with a height H of 14 μm was not tested.

[0033] Therefore, it is preferable that the height H of the straight portion 34 of each spiral rib 32 relative to the atmosphere-side inclined surface 26 is 37 μm or less. By setting the height H of the straight portion 34 of each spiral rib 32 to 37 μm or less, leakage of liquid to the atmosphere side can be suppressed even when the rotating shaft 4 rotates at high speed in the second direction (reverse direction) R2 relative to the housing 2.

[0034] On the other hand, the height H of the straight portion 34 of each helical rib 32 relative to the atmosphere-side inclined surface 26 is preferably 5 μm or more. By setting the height H of the straight portion 34 of each helical rib 32 to 5 μm or more, each helical rib 32 exerts a pumping action when the rotating shaft 4 rotates in the first direction (forward direction) R1 relative to the housing 2.

[0035] Fig. 5 is a development view of the inner circumferential surface of the seal lip 20 of a sealing device according to a modified example of the embodiment. In this modified example, a plurality of spiral ribs 32 extending in different directions are provided. Specifically, although only a part of the inner circumferential surface of the seal lip 20 is shown in Fig. 5, a plurality of groups 42, each of which is made up of a plurality of spiral ribs 32, and a plurality of groups 44, each of which is made up of a plurality of spiral ribs 32, are provided on the atmosphere-side inclined surface 26, and the groups 42, 44 are arranged alternately in the circumferential direction.

[0036] In the group 42, the inclination direction of each helical rib 32 is adapted to the rotation of the rotating shaft 4 in the first direction R1. That is, when the rotating shaft 4 rotates in the first direction R1, each helical rib 32 in the group 42 exerts a pumping action to return the liquid from the atmosphere side to the internal space.

[0037] In the group 44, the inclination direction of each helical rib 32 is adapted to the rotation of the rotating shaft 4 in the second direction R2. That is, when the rotating shaft 4 rotates in the second direction R2, each helical rib 32 in the group 44 exerts a pumping action to return the liquid from the atmosphere side to the internal space.

[0038] 5, the helical ribs 32 of either group exert a pumping action regardless of the direction in which the rotating shaft 4 rotates. The present invention does not intend to exclude the modification of FIG.

[0039] However, in the above experiment on the embodiment in which all the spiral ribs 32 have the same inclination direction, when the rotating shaft 4 was rotated in the first direction R1 at a peripheral speed of 50 m / s, no liquid leaked out to the atmosphere, whereas when the rotating shaft 4 was rotated in the second direction R2 at a lower peripheral speed, the liquid leaked out to the atmosphere. In other words, when the rotating shaft 4 was rotated in the second direction R2 at a peripheral speed of 50 m / s, there was a risk of liquid leaking out to the atmosphere in the area corresponding to group 42, and when the rotating shaft 4 was rotated in the first direction R1 at a peripheral speed of 50 m / s, there was a risk of liquid leaking out to the atmosphere in the area corresponding to group 44.

[0040] Therefore, an embodiment in which all of the spiral ribs 32 have the same inclination direction is preferable to this modified example. If the rotating shaft 4 is, for example, an axle of an automobile, the rotation direction of the rotating shaft 4 differs depending on whether the axle is disposed on the left or right side. In this case, it is preferable to prepare two types of sealing devices with different inclination directions of the spiral ribs 32, and select the sealing device according to the rotation direction.

[0041] Although the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the scope of the invention as set forth in the appended claims. Such changes, modifications and alterations are intended to be embraced within the scope of the invention.

[0042] For example, in the above embodiment, the sealing device 1 is disposed between a stationary housing (outer member) 2 and a rotating shaft (inner member) 4, but it may also be disposed between a rotating outer member and a stationary inner member. [Explanation of symbols]

[0043] 1 Sealing device 2 Housing (outer member) 4 Rotating shaft (inner part) 10 Outer cylindrical part (mounting part) 12 Connecting part 14 Inner cylindrical part 20 Seal Lip 22 Dust Trip 24 Liquid side slope 26 Atmospheric side slope 28 Lip Edge 32 Spiral Rib 34 Straight section 34a side wall 36 Bottom shape part

Claims

1. A sealing device disposed between an inner member that rotates in a first direction and a second direction opposite to the first direction relative to an outer member and the outer member, the sealing device sealing a gap between the inner member and the outer member, a mounting portion attached to the outer member; a seal lip that is disposed inside the hole of the outer member, slidably contacts the outer peripheral surface of the inner member, separates the inner space of the outer member from the atmosphere side, and seals the liquid in the inner space; Equipped with the seal lip has a liquid-side inclined surface disposed on the internal space side, an atmosphere-side inclined surface disposed on the atmosphere side, and a lip edge located on a boundary between the liquid-side inclined surface and the atmosphere-side inclined surface and extending in a circumferential direction, The liquid side inclined surface is inclined so as to move away from the inner member as it moves away from the lip edge, the atmosphere side inclined surface is inclined so as to move away from the inner member as it moves away from the lip edge, a plurality of spiral ribs are formed on the atmosphere side inclined surface in contact with the outer circumferential surface of the inner member, the plurality of spiral ribs extending in a spiral manner inclined with respect to the lip edge so as to accommodate rotation of the inner member in the first direction; each helical rib has a straight portion having parallel side walls and a boat-shaped portion that is wider and curved than the side walls, the straight portion extending from the lip edge, and the boat-shaped portion being disposed farther from the lip edge than the straight portion; The height of each of the straight portions with respect to the atmosphere-side inclined surface is 5 μm or more and 37 μm or less. A sealing device characterized by:

2. the plurality of spiral ribs are inclined relative to the lip edge in the second direction of the inner member toward the atmosphere side. The sealing device according to claim 1 .

3. a first plurality of groups of the plurality of helical ribs and a second plurality of groups of a plurality of other helical ribs; the plurality of other spiral ribs are formed on the atmosphere side inclined surface and contact the outer circumferential surface of the inner member, the plurality of other spiral ribs extend in a spiral manner inclined with respect to the lip edge so as to conform to the rotation of the inner member in the second direction; each of the plurality of other spiral ribs has a straight portion having side walls parallel to each other and a boat-shaped portion that is wider and curved than the side walls, the straight portion extending from the lip edge, and the boat-shaped portion being disposed farther from the lip edge than the straight portion; A height of the straight portion of each of the other spiral ribs relative to the air-side inclined surface is 5 μm or more and 37 μm or less, the plurality of other helical ribs of the plurality of second groups are inclined in the first direction of the inner member toward the atmosphere side relative to the lip edge to accommodate rotation of the inner member in the second direction. The sealing device according to claim 2 .

4. The first groups and the second groups are alternately arranged in a circumferential direction. The sealing device according to claim 3.

5. The straight portion is adapted to be in contact with an outer circumferential surface of the inner member and elastically deformed. The sealing device according to claim 1 .

6. The boat-bottom shaped portion is configured not to come into contact with an outer circumferential surface of the inner member. The sealing device according to claim 5.

7. In the spiral rib, the straight portion and the boat bottom shaped portion are arranged in series. The sealing device according to claim 1 .

8. The width of the boat-bottom shaped portion gradually increases from one end along the longitudinal direction of the boat-bottom shaped portion and gradually decreases from the central portion to the other end. The sealing device according to claim 1 .

9. The height of each of the straight portions with respect to the air-side inclined surface is 5 μm or more and 25 μm or less. The sealing device according to claim 1 .

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