JP7828230B2 - sealing device - Google Patents

Description

The present invention relates to a sealing device.

A sealing device is provided between a rotating shaft and a part of the housing that supports the shaft to prevent fluids such as lubricating oil from leaking to the outside. The sealing device has a fixed part that is attached to the housing and a lip that extends from the fixed part and is capable of elastic deformation. Patent Document 1 discloses such a sealing device.

Japanese Patent Application Laid-Open No. 2019-210998

The lip of the sealing device has a lip tip that slides against the outer surface of the rotating shaft. Particularly when the shaft rotates at high speeds, the lip tip can become burned or wear abnormally, causing the lubricating oil that is being sealed to seep out from between the lip tip and the shaft, resulting in a leak. While this type of lubricating oil leakage is slight, if it continues, the amount of leakage gradually increases, and can result in a large amount of leakage.

The present disclosure therefore aims to provide a sealing device that can prevent large amounts of fluid from leaking.

(1) The sealing device disclosed herein is a sealing device that is mounted in an annular space formed between a shaft and a housing and prevents liquid from leaking from one axial side to the other axial side, and includes: a fixed portion fixed to the housing; a first lip that extends from the fixed portion toward the shaft and has a first lip tip portion that contacts the outer peripheral surface of the shaft; a second lip that extends from the fixed portion toward the shaft and has a second lip tip portion that is located on the other axial side of the first lip tip portion; and a third lip that extends from the fixed portion toward the shaft and has a third lip tip portion that is located on the other axial side of the second lip tip portion, the third lip tip portion not contacting the outer peripheral surface of the shaft, and a recess that is recessed radially outward is provided between the second lip and the third lip.

With this sealing device, even if liquid passes through the tip of the first lip, the liquid can be contained in the space formed between the first lip and the second lip. Furthermore, even if the liquid passes through the tip of the second lip, the recess between the second lip and the third lip makes it difficult for the liquid to flow beyond the third lip to the other axial direction.
The third lip tip is spaced apart from the outer circumferential surface of the shaft. Therefore, while liquid that has passed through the second lip tip may adhere to the second lip due to, for example, surface tension, it is less likely to adhere to the third lip than to the second lip. Therefore, the liquid is less likely to flow over the third lip to the other axial direction.
As a result, it is possible to prevent a large amount of fluid from leaking.

(2) Preferably, the second lip has a second protrusion or second groove on its inner circumference that guides the liquid toward one side in the axial direction as the shaft rotates. With this configuration, even if the liquid passes through the tip of the second lip and remains in the recess, it is possible to return the liquid to one side in the axial direction.

(3) Preferably, the first lip has a first protrusion or first groove on its inner circumference that guides the liquid toward one side in the axial direction as the shaft rotates. With this configuration, even if the liquid passes through the tip of the first lip and remains in the space between the first lip and the second lip, it is possible to return the liquid to one side in the axial direction.

(4) Preferably, in the sealing device described in any one of (1) to (3), the first lip tip portion contacts the outer peripheral surface of the shaft with a crushed margin, and the second lip tip portion contacts the outer peripheral surface of the shaft with a crushed margin, or the crushed margin on the outer peripheral surface of the shaft is zero, or the second lip tip portion is not in contact with the outer peripheral surface of the shaft. According to this configuration, when the crushed margin of the second lip tip portion is zero or the second lip tip portion is not in contact with the shaft, it is particularly possible to suppress an increase in rotational resistance of the shaft due to the second lip tip portion. The third lip tip portion is not in contact with the outer peripheral surface of the shaft, and does not generate rotational resistance of the shaft. In particular, if the crushed margin of the second lip tip portion is zero, it is possible to make it difficult for liquid in the space between the first lip and the second lip to flow to the other axial direction.

(5) Preferably, in the sealing device described in any one of (1) to (4), the fixing portion has a metal ring and a rubber covering portion that covers at least the inner periphery of the metal ring, and the second lip and the third lip each extend from the common covering portion. This configuration makes it easier to determine the radial positions of the second lip tip portion and the third lip tip portion relative to the outer periphery of the shaft.

(6) Preferably, in the sealing device described in (5) above, the third lip is located on one axial side of the side surface on the other axial side of the covering portion. According to this configuration, the third lip does not protrude beyond the covering portion on the other axial side. This prevents the sealing device from interfering with other components.

(7) Preferably, in the sealing device described in (5) or (6), the second lip tip portion is located radially inward of the portion of the covering portion of the fixing portion that is connected to the first lip. According to this configuration, a space recessed toward the other axial direction is formed between the portion of the covering portion that is connected to the first lip and the second lip tip portion. When liquid passes through the first lip tip portion and is present in this recessed space, the liquid is less likely to flow toward the other axial direction.

The sealing device disclosed herein is capable of preventing large amounts of fluid from leaking even if fluid seeps out between the first lip and the shaft.

FIG. 1 is a cross-sectional view of a sealing device according to a first embodiment. FIG. 2 is an explanatory diagram showing a cross section of the sealing device and a part of the inner peripheral side. FIG. 3 is a cross-sectional view showing another embodiment (second embodiment) of the sealing device. FIG. 4 is a cross-sectional view showing still another embodiment (third embodiment) of the sealing device. FIG. 5 is an enlarged view illustrating the functions of the second lip and the third lip. FIG. 6 is an enlarged view illustrating the functions of the second lip and the third lip. FIG. 7 is an enlarged view showing a comparative example.

[Regarding the first embodiment]
Fig. 1 is a cross-sectional view of a sealing device according to a first embodiment. Fig. 1 shows a shaft 7 as viewed from the side. Fig. 1 is a cross-sectional view taken along a plane including a center line C of the shaft 7. The sealing device 10 is mounted in an annular space S formed between the shaft 7 and a part of a housing 8.

The shaft 7 is cylindrical and rotatably supported by bearings (not shown) provided in the housing 8. The shaft 7 rotates around a center line C. The center line C of the shaft 7 coincides with the center line of the sealing device 10. The sealing device 10 is used in, for example, motors and transmissions, but can also be used in other equipment.

The directions of the sealing device 10 of the present disclosure will be defined below. The direction along the center line C and the direction parallel to the center line C are defined as the axial direction. The direction perpendicular to the center line C is defined as the radial direction. The direction along a circle centered on the center line C is defined as the circumferential direction.
In the annular space S, the right side in Fig. 1 is one axial side (first axial side), and the left side in Fig. 1 is the other axial side (second axial side). In this embodiment, lubricating oil is present on the one axial side of the sealing device 10. The other axial side of the sealing device 10 is the atmosphere side. In the following description, the one axial side is referred to as the "sealed fluid side," and the other axial side is referred to as the "atmosphere side."

The sealing device 10 prevents lubricating oil on the sealed fluid side from leaking to the atmosphere in the annular space S. To this end, the sealing device 10 includes a fixed portion 14, a first lip 11, a second lip 12, and a third lip 13. Note that the liquid that the sealing device 10 prevents from leaking may be something other than lubricating oil.

The fixed portion 14 is an annular portion fixed to the housing 8. In the embodiment shown in FIG. 1, the fixed portion 14 has a first metal ring 21, a first rubber covering portion 23 that covers the first metal ring 21, a second metal ring 22, and a second rubber covering portion 24 that covers the second metal ring 22. The first metal ring 21, the first covering portion 23, and the first lip 11 form a single first seal 26. The second metal ring 22, the second covering portion 24, the second lip 12, and the third lip 13 form a single second seal 27. The first seal 26 and the second seal 27 are combined to form a single sealing device 10.

The cylindrical outer periphery 21a of the first metal ring 21 fits into the housing 8 via the outer periphery 23b of the first covering portion 23, and the first seal 26 is fixed to the housing 8. The cylindrical outer periphery 22b of the second metal ring 22 fits into the housing 8, and the second seal 27 is fixed to the housing 8. The first covering portion 23, the second covering portion 24, the first lip 11, the second lip 12, and the third lip 13 are made of an elastic material such as rubber.

The first lip 11 is annular. The first lip 11 is provided on the fixed portion 14, extending from the inner circumferential portion 23a of the first covering portion 23 toward the shaft 7. The first lip 11 has a first lip tip portion 16 that contacts the outer circumferential surface 7a of the shaft 7 with a crushed margin. An annular spring 30 is provided on the outer circumferential side of the first lip tip portion 16. The spring 30 presses the first lip tip portion 16 against the shaft 7 with its elastic restoring force. The first lip 11 has a lip base portion 15 that connects the inner circumferential portion 23a of the first covering portion 23 and the first lip tip portion 16.

The first lip tip portion 16 has a first inclined surface 31 that expands in diameter toward the sealed fluid side and a second inclined surface 32 that expands in diameter toward the atmosphere side. The lip base portion 15 has a third inclined surface 33 that extends from the second inclined surface 32. The intersection of the first inclined surface 31 and the second inclined surface 32 forms the lip tip 16a of the first lip tip portion 16. The lip tip 16a contacts the outer peripheral surface 7a of the shaft 7, creating the crushed margin at the lip tip 16a.

Figure 2 is an explanatory diagram showing a cross section of the sealing device 10 and a portion of its inner circumferential side. The first lip 11 has a first ridge 38 on its inner periphery that guides the lubricating oil L toward the sealed fluid side as the shaft 7 rotates. The first ridge 38 is provided on the inner periphery of the first lip 11, excluding the lip tip 16a and the first inclined surface 31. In the embodiment shown in Figure 2, the first ridge 38 is formed on the second inclined surface 32 (excluding the lip tip 16a), the third inclined surface 33, and the inner circumferential surface 23c of the first covering portion 23. The function of the first ridge 38 will be explained later.

The second lip 12 will be described with reference to Figures 1 and 2. The second lip 12 is annular. The second lip 12 is provided on the fixed portion 14, extending from the inner circumferential portion 24a of the second covering portion 24 toward the shaft 7. The second lip 12 has a second lip tip portion 17 located closer to the atmosphere than the first lip tip portion 16. The second lip tip portion 17 has a fourth inclined surface 34 that widens in diameter toward the sealed fluid side, and a fifth inclined surface 35 that widens in diameter toward the atmosphere side.

The intersection of the fourth inclined surface 34 and the fifth inclined surface 35 forms the lip tip 17a of the second lip tip portion 17. The lip tip 17a is close to the outer peripheral surface 7a of the shaft 7. The second lip tip portion 17 (lip tip 17a) can contact the outer peripheral surface 7a of the shaft 7. However, the compression of the second lip tip portion 17 on the outer peripheral surface 7a of the shaft 7 is smaller than the compression of the first lip tip portion 16 on the outer peripheral surface 7a of the shaft 7. Specifically, in this embodiment, the compression of the second lip tip portion 17 on the outer peripheral surface 7a of the shaft 7 is zero. Note that while this compression is zero, it may be a small positive value before the sealing device 10 begins to be used. After some time has passed since the shaft 7 began to rotate, the lip tip 17a may wear down and the compression may become zero.

Alternatively, the compression allowance of the second lip tip portion 17 on the outer peripheral surface 7a of the shaft 7 may be a negative value. In other words, the second lip tip portion 17 may not contact the outer peripheral surface 7a of the shaft 7, and a gap may be formed between the lip tip 17a and the outer peripheral surface 7a of the shaft 7. However, it is preferable that a very small gap (a gap of less than 1 millimeter in the radial direction) be formed between the lip tip 17a and the outer peripheral surface 7a of the shaft 7.

The second lip tip portion 17 is located radially inward of the first covering portion 23 (inner circumferential portion 23a) to which the first lip 11 is connected. With this configuration, a recessed space K3 toward the atmosphere is formed between the first covering portion 23 (inner circumferential portion 23a) and the second lip tip portion 17.

The second lip 12 has a second ridge 39 on its inner circumference that guides lubricating oil to the sealed fluid side as the shaft 7 rotates. As shown in Figure 2, the second ridge 39 is provided on the fifth inclined surface 35 on the inner circumference side of the second lip 12. The second ridge 39 is provided in the range from the lip tip 17a to the recess 19. The function of the second ridge 39 will be explained later.

The third lip 13 is annular. The third lip 13 is provided on the fixed portion 14, extending from the inner circumferential portion 24a of the second covering portion 24 toward the shaft 7. The third lip 13 has a third lip tip portion 18 that is located closer to the atmosphere than the second lip tip portion 17. The third lip tip portion 18 has a sixth inclined surface 36 that widens in diameter toward the sealed fluid side, and a seventh inclined surface 37 that widens in diameter toward the atmosphere side.

The intersection of the sixth inclined surface 36 and the seventh inclined surface 37 forms the lip tip 18a of the third lip tip portion 18. The lip tip 18a does not contact the outer peripheral surface 7a of the shaft 7. A gap is provided around the entire circumference between the lip tip 18a and the outer peripheral surface 7a of the shaft 7. The third lip tip portion 18 does not contact the outer peripheral surface 7a of the shaft 7 even if manufacturing errors occur within the dimensional tolerance of the third lip 13.

A recess 19 is provided between the second lip 12 and the third lip 13. The recess 19 is a V-shaped groove that extends radially outward and is continuous in the circumferential direction. The recess 19 is located between the fifth inclined surface 35 and the sixth inclined surface 36.

In the embodiment shown in FIG. 1, the fixing portion 14 includes a second metal ring 22 and a second rubber covering portion 24 that covers at least the inner circumferential portion 22a of the second metal ring 22. The second lip 12 and the third lip 13 each extend from a common second covering portion 24 (inner circumferential portion 24a). Specifically, the second lip 12 protrudes from a first portion of the inner circumferential portion 24a that is located on the sealed fluid side. The third lip 13 protrudes from a second portion of the inner circumferential portion 24a that is located on the atmosphere side.

This configuration makes it easy to determine the radial positions of the second lip tip portion 17 and the third lip tip portion 18 relative to the outer peripheral surface 7a of the shaft 7. In other words, by fixing the fixing portion 14 to the housing 8, the positional relationship between the second lip tip portion 17 and the outer peripheral surface 7a of the shaft 7 (a relationship in which the crushing allowance is zero) is appropriately set, and the third lip tip portion 18 does not come into contact with the outer peripheral surface 7a of the shaft 7.

The third lip 13 is located closer to the sealed fluid than the atmospheric-side side surface 41 of the second covering portion 24. In other words, the third lip 13 does not protrude further toward the atmosphere than the second covering portion 24.

[Functions of the first ridges 38 and the second ridges 39]
In FIG. 2, the first ridges 38 are shown schematically by lines, and the second ridges 39 are shown schematically by lines.
The first ridges 38 are provided at intervals in the circumferential direction on the inner periphery of the first lip 11. The first ridges 38 have a shape that protrudes radially inward from the second inclined surface 32.
A plurality of second ridges 39 are provided at intervals in the circumferential direction on the inner periphery of the second lip 12. The second ridges 39 have a shape that protrudes radially inward from the fifth inclined surface 35.

When the shaft 7 rotates, the air around the shaft 7 flows in the same direction as the rotation of the shaft 7. If lubricating oil L adheres to the first ridge 38, the lubricating oil L is pushed by the air flowing in the circumferential direction and guided along the first ridge 38 toward the sealed fluid, approaching the lip tip 16a (see the dotted arrow in Figure 2). As a result, the lubricating oil L adhering to the second inclined surface 32 is guided to the vicinity of the lip tip 16a.

This continuous pumping action by the first ridge 38 allows the lubricating oil L to be returned to the sealed fluid side beyond the lip tip 16a. The first ridge 38 is inclined circumferentially and axially in accordance with the rotational direction of the shaft 7 so that the lubricating oil L is guided toward the sealed fluid side by being pushed by the air flowing in the circumferential direction, as described above.

When the shaft 7 rotates, the air around the shaft 7 flows in the same direction as the rotation of the shaft 7. If lubricating oil L adheres to the second ridge 39, the lubricating oil L is pushed by the air flowing in the circumferential direction and guided along the second ridge 39 toward the sealed fluid, approaching the lip tip 17a (see the dotted arrow in Figure 2). As a result, the lubricating oil L adhering to the recess 19 and fifth inclined surface 35 is guided to the vicinity of the lip tip 17a.

This pumping action by the second ridge 39 continues, allowing the lubricating oil L to be returned to the sealed fluid side beyond the lip tip 17a. The second ridge 39 is inclined circumferentially and axially in accordance with the rotational direction of the shaft 7 so that the lubricating oil L is guided toward the sealed fluid side by being pushed by the air flowing in the circumferential direction, as described above.

In the case of the sealing device 10 shown in Figure 1, the cylindrical outer peripheral portion 22b of the second metal ring 22 overlaps radially with a portion of the cylindrical outer peripheral portion 21a of the first metal ring 21 and a portion of the first covering portion 23 sandwiched therebetween. In the first embodiment shown in Figure 1, the first seal 26 and second seal 27 are attached to the housing 8 as a single unit.

[Regarding other embodiments of the sealing device 10]
3 is a cross-sectional view showing another configuration (second embodiment) of the sealing device 10. In the second embodiment, the cylindrical outer peripheral portion 22b of the second metal ring 22 does not overlap with the first metal ring 21 in the radial direction. The outer peripheral portion 22b of the second metal ring 22 extends from the annular portion 22c of the second metal ring 22 toward the atmosphere. A rubber covering portion 42 covers the outer peripheral portion 22b. The outer peripheral portion 22bc is fitted into the housing 8 via the covering portion 42.

In the second embodiment, the first seal 26 and the second seal 27 can be attached to the housing 8 separately. Alternatively, the sealing device 10 can be constructed by adding the second seal 27 to the existing first seal 26.

[Regarding still another embodiment of the sealing device 10]
4 is a cross-sectional view showing yet another embodiment (third embodiment) of the sealing device 10. In the third embodiment, the fixing portion 14 is composed of one metal ring 28 and a rubber covering portion 29 that covers the metal ring 28. The first lip 11, the second lip 12, and the third lip 13 each extend from an inner periphery 29a of the covering portion 29. In the third embodiment, the sealing device 10 can be easily handled and attached to the housing 8.

In the third embodiment, the second lip tip portion 17 is located radially inside the covering portion 29 (inner circumferential portion 29a) to which the first lip 11 is connected. A space K3 recessed toward the atmosphere is formed between the covering portion 29 (inner circumferential portion 29a) and the second lip tip portion 17.

In the second and third embodiments, the same components as in the first embodiment are designated by the same reference numerals, and descriptions of the same components will be omitted.

[Regarding the sealing device 10 of each embodiment]
The sealing device 10 of each of the first to third embodiments includes a first lip 11, a second lip 12, and a third lip 13 that extend from a fixed portion 14 that is fixed to the housing 8 toward the shaft 7. The first lip 11 has a first lip tip portion 16 that contacts the outer peripheral surface 7a of the shaft 7. The second lip 12 has a second lip tip portion 17 that is located closer to the atmosphere than the first lip tip portion 16. The third lip 13 has a third lip tip portion 18 that is located closer to the atmosphere than the second lip tip portion 17. The third lip tip portion 18 does not contact the outer peripheral surface 7a of the shaft 7. A recess 19 that is recessed radially outward is provided between the second lip 12 and the third lip 13.

With the sealing device 10 having the above configuration, even if lubricating oil present on the sealed fluid side of the sealing device 10 passes through the first lip tip portion 16, the lubricating oil can be retained in the first space K1 formed between the first lip 11 and the second lip 12. Furthermore, even if the lubricating oil passes through the second lip tip portion 17, the recess 19 between the second lip 12 and the third lip 13 makes it difficult for the lubricating oil to flow beyond the third lip 13 to the atmosphere.

Figures 5 and 6 are enlarged views explaining the function of the second lip 12 and the third lip 13. Figure 5 shows the state in which the shaft 7 is stopped from rotating (stopped state). Figure 6 shows the state in which the shaft 7 is rotating. As shown in Figure 5, lubricating oil L that passes through the second lip tip portion 17 to the atmosphere side (left side in Figure 5) is captured in the recess 19. As shown in Figure 6, when the shaft 7 rotates, the lubricating oil L in the recess moves toward the lip tip 17a of the second lip tip portion 17 due to the function of the second ridge 39. For this reason, the lubricating oil L is less likely to flow over the third lip 13 and into the atmosphere side.

Figure 7 is an enlarged view showing a comparative example. Figure 7 shows a case in which the third lip tip portion 18 contacts the outer peripheral surface 7a of the shaft 7, just like the second lip tip portion 17. In this comparative example, lubricating oil L that passes through the second lip tip portion 17 to the atmosphere side (left side in Figure 7) may be trapped between the lip tip 18a of the third lip tip portion 18 and the outer peripheral surface 7a of the shaft 7 due to surface tension. This increases the likelihood that the lubricating oil L will eventually pass over the lip tip 18a to the atmosphere side and leak out of the sealing device 10.

In contrast to this, as shown in Figures 5 and 6, according to the sealing device 10 of each of the first to third embodiments, the third lip tip portion 18 is spaced apart from the outer peripheral surface 7a of the shaft 7. For this reason, as shown in Figure 6, the lubricating oil L that has passed through the second lip tip portion 17 may adhere to the second lip 12 due to, for example, surface tension, but it is less likely to adhere to the third lip 18 than to the second lip 17. For this reason, the lubricating oil L is less likely to flow over the third lip 18 to the atmosphere side.
As a result, it is possible to prevent a large amount of lubricating oil from leaking.

In the sealing device 10 of each of the first to third embodiments, the crushed portion of the second lip tip portion 17 is smaller than the crushed portion of the first lip tip portion 16, making it possible to suppress an increase in rotational resistance and heat generation of the shaft 7 caused by the second lip tip portion 17. The third lip tip portion 18 does not contact the outer peripheral surface 7a of the shaft 7, so the third lip tip portion 18 does not cause rotational resistance of the shaft 7.

In the sealing device 10 of each of the first to third embodiments (see FIG. 1 , for example), as described above, the compression allowance of the second lip tip portion 17 on the outer peripheral surface 7 a of the shaft 7 is zero. Alternatively, the second lip tip portion 17 is not in contact with the outer peripheral surface 7 a of the shaft 7. This further enhances the function of the second lip tip portion 17 to suppress an increase in the rotational resistance of the shaft 7. In particular, if the compression allowance of the second lip tip portion 17 is zero, it is possible to make it difficult for the lubricating oil in the first space K1 between the first lip 11 and the second lip 12 to flow toward the atmosphere.
Alternatively, the second lip tip portion 17 may be in contact with the outer peripheral surface 7a of the shaft 7 with a squeezed margin. In this case as well, it is possible to make it difficult for the lubricating oil in the first space K1 to flow to the atmosphere side.

As explained in Figure 2, the second lip 12 has a second ridge 39 on its inner circumference that guides the lubricating oil L to the sealed fluid side as the shaft 7 rotates. As shown in Figures 5 and 6, even if the lubricating oil L in the first space K1 passes through the second lip tip portion 17 and remains in the recess 19, the rotation of the shaft 7 allows the lubricating oil L to be returned to the sealed fluid side.

Instead of the second ridge 39, a second groove may be formed on the inner circumference of the second lip 12. Even in this case, when the shaft 7 rotates, the lubricating oil is pushed by the air flowing in the circumferential direction and returned along the second groove to the sealed fluid side.

As explained with reference to Figure 2, the first lip 11 has a first ridge 38 on its inner circumference that guides the lubricating oil L toward the sealed fluid side as the shaft 7 rotates. Even if the lubricating oil present on the sealed fluid side of the sealing device 10 passes through the first lip tip portion 16 and remains in the first space K1 between the first lip 11 and the second lip 12, as the shaft 7 rotates, the lubricating oil can be returned to the sealed fluid side beyond the lip tip 16a of the first lip tip portion 16.

Instead of the first ridge 38, a first groove may be formed on the inner circumference of the first lip 11. Even in this case, when the shaft 7 rotates, the lubricating oil is pushed by the air flowing in the circumferential direction and returned along the first groove to the sealed fluid side.

In the sealing device 10 of the first embodiment (Fig. 1) and the second embodiment (Fig. 3), the fixing portion 14 has a second metal ring 22 and a rubber second covering portion 24 that covers at least the inner peripheral portion 22a of the second metal ring 22. The second lip 12 and the third lip 13 each extend from a common second covering portion 24. This configuration makes it easy to determine the radial positions of the second lip tip portion 17 and the third lip tip portion 18 relative to the outer peripheral surface 7a of the shaft 7.

In the sealing device 10 of the third embodiment (Figure 4), the fixing portion 14 has a metal ring 28 and a rubber covering portion 29 that covers at least the inner peripheral portion 28a of the metal ring 28. The second lip 12 and the third lip 13 each extend from a common covering portion 29. The first lip 11 also extends from the covering portion 29. This configuration makes it easy to determine the radial positions of the first lip tip portion 11, the second lip tip portion 17, and the third lip tip portion 18 relative to the outer peripheral surface 7a of the shaft 7.

In the sealing device 10 of the first embodiment (Fig. 1) and the second embodiment (Fig. 3), the third lip 13 is located closer to the sealed fluid than the atmosphere-side side surface 41 of the second covering portion 24 (to the right in Figs. 1 and 3). In the sealing device 10 of the third embodiment (Fig. 4), the third lip 13 is located closer to the sealed fluid than the atmosphere-side side surface 41 of the covering portion 29 (to the right in Fig. 4). With this configuration, the third lip 13 does not protrude further toward the atmosphere than the second covering portion 24 (covering portion 29). This prevents the sealing device 10 from interfering with other components.

In the sealing device 10 of each of the first to third embodiments, the second lip tip portion 17 is located radially inward of the portion of the second covering portion 24 (covering portion 29) that is connected to the first lip 11. As a result, a space K3 recessed toward the atmosphere is formed between the portion of the second covering portion 24 (covering portion 29) that is connected to the first lip 11 and the second lip tip portion 17. For example, in FIG. 1, if lubricating oil on the sealed fluid side of the sealing device 10 passes through the first lip tip portion 16 and is present in the recessed space K3 of the first space K1, the lubricating oil is unlikely to flow toward the atmosphere.

As described above, with the sealing device 10 of each of the above embodiments, even if lubricating oil seeps out between the first lip 11 and the shaft 7, it is possible to prevent a large amount of lubricating oil from leaking.

〔others〕
A third ridge similar to the second ridge 39 may be provided on the inner periphery of the third lip 13. The third ridge is provided on at least one of the sixth inclined surface 36 and the seventh inclined surface 37. In this case, when the shaft 7 rotates, the lubricating oil present on the inner periphery of the third lip 13 is pushed by the air flowing in the circumferential direction and returned to the sealed fluid side along the third ridge. Note that a third groove may be provided instead of such a third ridge.

The above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is indicated by the claims, not by the above-described embodiments, and includes all modifications that are equivalent to the configurations described in the claims.

7 Shaft 7a Outer circumferential surface 8 Housing 10 Sealing device 11 First lip 12 Second lip 13 Third lip 14 Fixing portion 16 First lip tip portion 17 Second lip tip portion 18 Third lip tip portion 19 Recess 21 First metal ring 22 Second metal ring 23 First covering portion 24 Second covering portion 28 Metal ring 29 Covering portion 38 First ridge 39 Second ridge 41 Side surface S Annular space

Claims (7)

A sealing device that is installed in an annular space formed between a shaft and a housing and prevents liquid from leaking from one axial side to the other axial side,
a fixing portion fixed to the housing;
a first lip extending from an inner peripheral portion of the fixing portion toward the shaft and one axial direction , the first lip having a first lip tip portion contacting an outer peripheral surface of the shaft;
a second lip extending from the fixed portion toward the shaft and one axial side and having a second lip tip portion positioned on the other axial side of the first lip tip portion;
a third lip extending from the fixed portion toward the shaft and having a third lip tip portion positioned on the other axial side of the second lip tip portion;
Equipped with
the third lip tip portion is not in contact with the outer circumferential surface of the shaft,
A recess recessed radially outward is provided between the second lip and the third lip,
the second lip tip portion is located radially inside the inner circumferential portion of the fixing portion to which the first lip is connected, and a space recessed toward the other axial side is provided between the inner circumferential portion and the second lip tip portion.
Sealing device. The sealing device described in claim 1, wherein the second lip has a second protrusion or second groove on its inner circumference that guides the liquid to one axial side as the shaft rotates. A sealing device as described in claim 1 or claim 2, wherein the first lip has a first protrusion or a first groove on its inner circumference that guides the liquid to one axial side as the shaft rotates. the first lip tip portion contacts the outer peripheral surface of the shaft with a crushed margin,
3. The sealing device according to claim 1, wherein the second lip tip portion is in contact with the outer peripheral surface of the shaft with a crushing allowance, has zero crushing allowance on the outer peripheral surface of the shaft, or is not in contact with the outer peripheral surface of the shaft. the fixing portion has a metal ring and a rubber covering portion that covers at least an inner periphery of the metal ring,
The sealing device according to claim 1 or 2, wherein the second lip and the third lip are respectively provided extending from the common covering portion. The sealing device described in claim 5, wherein the third lip is located axially on one side of the side surface on the other axial side of the covering portion. The sealing device described in claim 5, wherein the second lip tip portion is located radially inward of the portion of the covering portion of the fixed portion to which the first lip is connected.