sealing device

Abstract

To provide a sealing device capable of suppressing a large amount of leakage of a fluid.SOLUTION: A sealing device 10 is mounted on an annular space S formed between a shaft 7 and a housing 8, and prevents a liquid on one side in an axial direction from leaking to the other side in the axial direction. The sealing device 10 includes: a fixing part 14 fixed to the housing 8; a first lip 11 having a first lip tip part 16 which comes into contact by having a crush margin on an outer peripheral surface 7a of the shaft; a second lip 12 having a second lip tip part 17 positioned further on the other side in the axial direction than the first lip tip part 16; and a third lip 13 having a third lip tip part 18 positioned further on the other side in the axial direction than the second lip tip part 17. A crush margin on the outer peripheral surface 7a of the shaft of the second lip tip part 17 is smaller than the crush margin on the outer peripheral surface 7a of the shaft of the first lip tip part 16. The third lip tip part 18 comes into non-contact with the outer peripheral surface 7a of the shaft. Between the second lip 12 and the third lip 13, a recess part 19 recessed to the outside in a radial direction is provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sealing device. [Background technology]

[0002] A sealing device is provided between a rotating shaft and a part of a 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 elastically deformable. Patent Document 1 discloses such a sealing device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-210998 Summary of the Invention [Problem to be solved by the invention]

[0004] The lip of the sealing device has a lip tip that slides against the outer periphery of the rotating shaft. When the shaft rotates at high speed, the lip tip can suffer surface burns and abnormal wear, causing the lubricating oil to seep out from between the lip tip and the shaft, resulting in a leak. While this leakage is slight, if it continues, the amount of leakage gradually increases, potentially resulting in a large amount of leakage.

[0005] Therefore, an object of the present disclosure is to provide a sealing device that can suppress large amounts of fluid leakage. [Means for solving the problem]

[0006] (1) The sealing device of the present disclosure 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 extending from the fixed portion toward the shaft and having a first lip tip portion that contacts the outer peripheral surface of the shaft; a second lip extending from the fixed portion toward the shaft and having a second lip tip portion that is located on the other axial side of the first lip tip portion; and a third lip extending from the fixed portion toward the shaft and having a third lip tip portion that is located on the other axial side of the second lip tip portion, wherein the third lip tip portion does not contact 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.

[0007] 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.

[0008] (2) Preferably, the second lip has a second protrusion or a second groove on its inner periphery 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, the liquid can be returned to the one side in the axial direction.

[0009] (3) Preferably, the first lip has a first protrusion or a first groove on its inner periphery 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, the liquid can be returned to the one side in the axial direction.

[0010] (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 does not contact 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 does not contact 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 does not contact the outer peripheral surface of the shaft, and does not generate rotational resistance of the shaft due to the third lip tip portion. In particular, when 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.

[0011] (5) Preferably, in the sealing device according to any one of (1) to (4), the fixing portion has a metal ring and a rubber covering portion that covers at least an inner peripheral portion of the metal ring, and the second lip and the third lip are each provided extending from the common covering portion. With this configuration, the radial positions of the second lip tip portion and the third lip tip portion relative to the outer peripheral surface of the shaft can be easily determined.

[0012] (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. With 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.

[0013] (7) Preferably, in the sealing device described in (5) or (6), the second lip tip portion is located radially inside a portion of the covering portion of the fixing portion that is connected to the first lip. According to this configuration, a recessed space is formed on the other axial side 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 the recessed space, the liquid is less likely to flow to the other axial side. [Effects of the Invention]

[0014] According to the sealing device of the present disclosure, even if fluid seeps out between the first lip and the shaft, it is possible to prevent a large amount of fluid from leaking. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a sealing device according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing a cross section of the sealing device and a part of the inner peripheral side. [Figure 3] FIG. 3 is a cross-sectional view showing another embodiment (second embodiment) of the sealing device. [Figure 4] FIG. 4 is a cross-sectional view showing still another embodiment (third embodiment) of the sealing device. [Figure 5] FIG. 5 is an enlarged view illustrating the functions of the second lip and the third lip. [Figure 6] FIG. 6 is an enlarged view illustrating the functions of the second lip and the third lip. [Figure 7] FIG. 7 is an enlarged view showing a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0016] [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.

[0017] The shaft 7 has a cylindrical shape and is rotatably supported by a bearing or the like (not shown) provided in the housing 8. The shaft 7 rotates about a center line C. The center line C of the shaft 7 and the center line of the sealing device 10 coincide with each other. The sealing device 10 is used in, for example, motors, transmissions, etc., but can also be applied to other equipment.

[0018] The directions of the sealing device 10 of the present disclosure are 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."

[0019] The sealing device 10 prevents the 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 fixing 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 other than the lubricating oil.

[0020] 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.

[0021] The cylindrical outer peripheral portion 21a of the first metal ring 21 is fitted into the housing 8 via the outer peripheral portion 23b of the first covering portion 23, and the first seal 26 is fixed to the housing 8. The cylindrical outer peripheral portion 22b of the second metal ring 22 is fitted 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.

[0022] The first lip 11 is annular. The first lip 11 is provided on the fixed portion 14, extending from the inner peripheral 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 peripheral surface 7a of the shaft 7 with a crushed margin. An annular spring 30 is provided on the outer peripheral side of the first lip tip portion 16. The spring 30 presses the first lip tip portion 16 against the shaft 7 by its elastic restoring force. The first lip 11 has a lip base portion 15 that connects the inner peripheral portion 23a of the first covering portion 23 and the first lip tip portion 16.

[0023] The first lip tip portion 16 has a first inclined surface 31 that widens in diameter toward the sealed fluid side and a second inclined surface 32 that widens 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 comes into contact with the outer peripheral surface 7a of the shaft 7, and the squeezed margin is generated at the lip tip 16a.

[0024] 2 is an explanatory diagram showing a cross section of the sealing device 10 and a portion of its inner peripheral side. The first lip 11 has a first ridge 38 on its inner peripheral surface that guides the lubricating oil L to the sealed fluid side as the shaft 7 rotates. The first ridge 38 is provided on the inner peripheral side of the first lip 11 in a range excluding the lip tip 16a and the first inclined surface 31. In the embodiment shown in FIG. 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 peripheral surface 23c of the first covering portion 23. The function of the first ridge 38 will be explained later.

[0025] 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 in the fixed portion 14, extending from the inner peripheral 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 whose diameter increases toward the sealed fluid side, and a fifth inclined surface 35 whose diameter increases toward the atmosphere side.

[0026] 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) is able to come into contact with the outer peripheral surface 7a of the shaft 7. However, the compression allowance of the second lip tip portion 17 on the outer peripheral surface 7a of the shaft 7 is smaller than the compression allowance of the first lip tip portion 16 on the outer peripheral surface 7a of the shaft 7. Specifically, in this embodiment, the compression allowance of the second lip tip portion 17 on the outer peripheral surface 7a of the shaft 7 is zero. Note that although the compression allowance is zero, it may be a small positive value before the sealing device 10 is first used, and the lip tip 17a may wear down and become zero some time after the shaft 7 starts rotating.

[0027] Alternatively, the squeeze of second lip tip portion 17 on the outer peripheral surface 7a of shaft 7 may be a negative value. In other words, second lip tip portion 17 may not contact the outer peripheral surface 7a of shaft 7, and a gap may be generated between lip tip 17a and outer peripheral surface 7a of shaft 7. However, it is preferable that a very small gap (a gap of less than 1 millimeter in the radial direction) is generated between lip tip 17a and outer peripheral surface 7a of shaft 7.

[0028] The second lip tip portion 17 is located radially inside the first covering portion 23 (inner peripheral portion 23a) connected to the first lip 11. With this configuration, a space K3 recessed toward the atmosphere is formed between the first covering portion 23 (inner peripheral portion 23a) and the second lip tip portion 17.

[0029] The second lip 12 has a second ridge 39 on its inner periphery that guides lubricating oil to the sealed fluid side as the shaft 7 rotates. As shown in FIG. 2 , the second ridge 39 is provided on the fifth inclined surface 35 on the inner periphery of the second lip 12. The second ridge 39 is provided in a range from the lip tip 17a to the recess 19. The function of the second ridge 39 will be explained later.

[0030] The third lip 13 is annular. The third lip 13 is provided on the fixed portion 14, extending from the inner peripheral 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.

[0031] 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 a manufacturing error occurs within the dimensional tolerance of the third lip 13.

[0032] A recess 19 is provided between the second lip 12 and the third lip 13. The recess 19 is a portion recessed radially outward and is a V-shaped groove that continues in the circumferential direction. The recess 19 is a portion between the fifth inclined surface 35 and the sixth inclined surface 36.

[0033] In the embodiment shown in FIG. 1 , the fixing portion 14 has 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.

[0034] This configuration makes it easy to determine the radial positions of second lip tip portion 17 and third lip tip portion 18 relative to the outer peripheral surface 7a of shaft 7. In other words, by fixing fixed portion 14 to housing 8, the positional relationship between second lip tip portion 17 and outer peripheral surface 7a of shaft 7 (a relationship in which the crushing allowance is zero) is appropriately set, and third lip tip portion 18 does not come into contact with outer peripheral surface 7a of shaft 7.

[0035] The third lip 13 is located closer to the sealed fluid side than the atmosphere-side side surface 41 of the second covering portion 24. In other words, the third lip 13 does not protrude further than the second covering portion 24 toward the atmosphere side.

[0036] [Function of the first ridge 38 and the second ridge 39] In FIG. 2, the first ridges 38 are shown schematically by lines, and the second ridges 39 are shown schematically by lines. A plurality of 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.

[0037] When the shaft 7 rotates, 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 ridges 38, the lubricating oil L is pushed by the air flowing in the circumferential direction and guided along the first ridges 38 toward the sealed fluid so as to approach the lip tip 16a (see the dotted arrow in FIG. 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.

[0038] The lubricating oil L can be returned to the sealed fluid side beyond the lip tip 16a by continuing the pumping action of the first ridges 38. The first ridges 38 are provided inclined with respect to the circumferential and axial directions in accordance with the rotational direction of the shaft 7 so that the lubricating oil L is guided to the sealed fluid side by being pushed by the air flowing in the circumferential direction as described above.

[0039] When the shaft 7 rotates, 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 ridges 39, the lubricating oil L is pushed by the air flowing in the circumferential direction and guided along the second ridges 39 toward the sealed fluid so as to approach the lip tip 17a (see the dotted arrow in FIG. 2). As a result, the lubricating oil L adhering to the recesses 19 and the fifth inclined surface 35 is guided to the vicinity of the lip tip 17a.

[0040] The lubricating oil L can be returned to the sealed fluid side beyond the lip tip 17a by continuing the pumping action of the second ridges 39. The second ridges 39 are provided inclined with respect to the circumferential and axial directions in accordance with the rotational direction of the shaft 7 so that the lubricating oil L is guided to the sealed fluid side by being pushed by the air flowing in the circumferential direction as described above.

[0041] 1, the cylindrical outer peripheral portion 22b of the second metal ring 22 overlaps in the radial direction with a part of the cylindrical outer peripheral portion 21a of the first metal ring 21 and a part of the first covering portion 23 sandwiched therebetween. In the first embodiment shown in FIG. 1, the first seal 26 and the second seal 27 are attached to the housing 8 as a single unit.

[0042] [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 is provided so as to extend 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.

[0043] In the second embodiment, the first seal 26 and the second seal 27 can be attached separately to the housing 8. Alternatively, the sealing device 10 can be configured by adding the second seal 27 to the existing first seal 26.

[0044] [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 extend from an inner circumferential portion 29a of the covering portion 29. In the third embodiment, the sealing device 10 can be easily handled and attached to the housing 8.

[0045] In the third embodiment, the second lip tip portion 17 is located radially inside the covering portion 29 (inner peripheral portion 29a) connected to the first lip 11. A space K3 recessed toward the atmosphere is formed between the covering portion 29 (inner peripheral portion 29a) and the second lip tip portion 17.

[0046] In each of the second and third embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and a description of the same components will be omitted.

[0047] [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.

[0048] According to the sealing device 10 having the above configuration, even if the 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 side.

[0049] 5 and 6 are enlarged views illustrating the functions of the second lip 12 and the third lip 13. FIG. 5 shows a state in which the rotation of the shaft 7 is stopped (stopped state). FIG. 6 shows a state in which the shaft 7 is rotating. As shown in FIG. 5, the lubricating oil L that passes through the second lip tip portion 17 toward the atmosphere (left side in FIG. 5) is captured in the recess 19. As shown in FIG. 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 toward the atmosphere.

[0050] Fig. 7 is an enlarged view showing a comparative example. Fig. 7 shows a case where the third lip tip portion 18 contacts the outer peripheral surface 7a of the shaft 7, similar to the second lip tip portion 17. In this comparative example, the lubricating oil L that passes through the second lip tip portion 17 to the atmosphere side (left side in Fig. 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 possibility 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.

[0051] 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 toward the atmosphere. As a result, it is possible to prevent a large amount of lubricating oil from leaking.

[0052] According to 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, so it is possible to suppress an increase in rotational resistance and heat generation of the shaft 7 due to the second lip tip portion 17. The third lip tip portion 18 is not in contact with the outer peripheral surface 7a of the shaft 7, so that the third lip tip portion 18 does not generate rotational resistance of the shaft 7.

[0053] In the sealing device 10 of each of the first to third embodiments (see, for example, FIG. 1 ), as described above, the compression allowance of the second lip tip portion 17 on the outer peripheral surface 7a of the shaft 7 is zero. Alternatively, the second lip tip portion 17 is not in contact with the outer peripheral surface 7a 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 toward the atmosphere.

[0054] As explained with reference to Fig. 2, the second lip 12 has a second ridge 39 on its inner periphery that guides the lubricating oil L to the sealed fluid side as the shaft 7 rotates. As shown in Figs. 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 makes it possible to return the lubricating oil L to the sealed fluid side.

[0055] Instead of the second ridge 39, a second groove may be formed on the inner periphery of the second lip 12. In this case as well, when the shaft 7 rotates, the lubricating oil is pushed by the air flowing in the circumferential direction and returned to the sealed fluid side along the second groove.

[0056] 2, 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. 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, the rotation of the shaft 7 makes it possible to return the lubricating oil to the sealed fluid side beyond the lip tip 16a of the first lip tip portion 16.

[0057] Instead of the first ridges 38, first grooves may be formed on the inner periphery of the first lip 11. In this case as well, when the shaft 7 rotates, the lubricating oil is pushed by the air flowing in the circumferential direction and returned along the first grooves to the sealed fluid side.

[0058] 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 second covering portion 24 made of rubber that covers at least the inner peripheral portion 22a of the second metal ring 22. The second lip 12 and the third lip 13 are each provided extending from the common second covering portion 24. With this configuration, 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 can be easily determined.

[0059] In a sealing device 10 of a third embodiment (FIG. 4), the fixing portion 14 has a metal ring 28 and a rubber covering portion 29 that covers at least an 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. With this configuration, 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 can be easily determined.

[0060] 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 side (to the right in FIGS. 1 and 3) than the atmosphere-side side surface 41 of the second covering portion 24. In the sealing device 10 of the third embodiment (FIG. 4), the third lip 13 is located closer to the sealed fluid side (to the right in FIG. 4) than the atmosphere-side side surface 41 of the covering portion 29. 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 members.

[0061] In the sealing device 10 of each of the first to third embodiments, the second lip tip portion 17 is located radially inside a portion of the second covered portion 24 (covered portion 29) that is connected to the first lip 11. Therefore, a space K3 that is recessed toward the atmosphere is formed between the portion of the second covered portion 24 (covered portion 29) that is connected to the first lip 11 and the second lip tip portion 17. For example, in Fig. 1, when 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.

[0062] As described above, according to the sealing device 10 of each of the above-described 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.

[0063] 〔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.

[0064] The above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and includes all modifications within the scope equivalent to the configurations described in the claims. [Explanation of symbols]

[0065] 7 axes 7a Outer surface 8. Housing 10 Sealing device 11 First Lip 12 Second Lip 13 Third Lip 14 Fixed part 16 First lip tip 17 Second lip tip 18 Third lip tip 19 Recess 21 First metal ring 22 Second metal ring 23 First covering part 24 Second covering part 28 Metal ring 29 Covering part 38 First ridge 39 Second ridge 41 Side S Annular Space

Claims

1. 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.

2. The sealing device according to claim 1 , wherein the second lip has, on an inner periphery thereof, a second protrusion or a second groove portion that guides the liquid toward one axial side as the shaft rotates.

3. 3. The sealing device according to claim 1, wherein the first lip has, on an inner periphery thereof, a first protrusion or a first groove portion that guides the liquid toward one axial side as the shaft rotates.

4. 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.

5. 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.

6. The sealing device according to claim 5 , wherein the third lip is located on one axial side of the side surface of the covering portion on the other axial side.

7. The sealing device according to claim 5 , wherein the second lip tip portion is located radially inside a portion of the covering portion of the fixing portion to which the first lip is connected.

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