JP2024074167A - Oil seal - Google Patents

Abstract

To provide an oil seal that can appropriately restrain entry of a foreign body from the outside while reducing wear of a lip tip of a side lip.SOLUTION: Because a lip tip 32a protruding to an outer peripheral side from a side lip 32 fitted to an outer peripheral surface 54 of a shaft 18 is brought into sliding contact with an inner peripheral surface of a cylindrical oil seal outer ring 34 formed integrally with a seal lip 44 and fitted into a through hole 14, a change in surface pressure of the lip tip 32a caused by axial backlash of the shaft 18 is restrained, and an increase in size of the lip tip 32a in a radial direction can be restrained. As a result, wear of the lip tip 32a of the side lip 32 can be reduced while entry of a foreign body is appropriately prevented.SELECTED DRAWING: Figure 1

Description

The present invention relates to a structure for preventing foreign matter from entering an oil seal.

Oil seals that are installed in the gap between a rotating body and a non-rotating body to prevent the intrusion of foreign matter from the outside are well known. The oil seal described in Patent Document 1 is one such example. However, when foreign matter such as muddy water is applied from the outside and the temperature around the oil seal is lowered, causing the surrounding pressure to decrease, the oil seal deforms and a gap is formed between the oil seal and the rotating body, allowing foreign matter to intrude through the gap. To solve this problem, Patent Document 1 brings the lip tip of the side lip formed on the oil seal into close contact with the end face of the slinger (deflector in this specification).

JP 2012-57729 A

In the oil seal of Patent Document 1, in order to ensure the surface pressure of the lip tip of the side lip even if the contact position of the lip tip of the side lip changes in the axial direction due to axial backlash of the rotor, it is necessary to increase the diameter of the side lip to ensure elasticity. On the other hand, increasing the diameter of the side lip increases the sliding speed between the lip tip of the side lip and the slinger. As a result, there is a risk that the lip tip of the side lip will wear out early.

The present invention was made against the background of the above circumstances, and its purpose is to provide an oil seal that can reduce wear on the lip tip of the side lip while adequately preventing the intrusion of foreign matter from the outside.

The gist of the present invention is that (a) an oil seal having a seal lip provided in a gap between the inner circumferential surface of a hole formed in a non-rotating body and the outer circumferential surface of a rotating body inserted into the hole, and slidably and closely contacting the outer circumferential surface of the rotating body, (b) a ring-shaped side lip provided separately from the seal lip and fitted to the outer circumferential surface of the rotating body, (c) the side lip has a lip tip that protrudes to the outer circumferential side, and (d) the lip tip is slidably and closely contacting the inner circumferential surface of the hole or the inner circumferential surface of a cylindrical oil seal outer ring that is integrally molded with the seal lip and fits into the hole.

According to the present invention, the lip tip protruding from the side lip fitted to the outer peripheral surface of the rotating body is slidably and closely contacted with the inner peripheral surface of the hole or the inner peripheral surface of a cylindrical oil seal outer ring that is integrally molded with the seal lip and fits into the hole, thereby suppressing changes in the surface pressure of the lip tip due to axial play of the rotating body and suppressing enlargement of the lip tip in the radial direction. As a result, wear of the lip tip of the side lip can be reduced while appropriately preventing the intrusion of foreign matter.

1 is a cross-sectional view of an oil seal to which the present invention is applied. 2A to 2C are diagrams illustrating a process from an oil seal of a conventional structure to the oil seal of FIG. 1 . FIG. 4 is a cross-sectional view of an oil seal according to another embodiment of the present invention.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that in the following embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately.

Figure 1 is a cross-sectional view of an oil seal 10 to which the present invention is applied. The oil seal 10 is provided to prevent the outflow of oil filled in the internal space sealed by the housing 12, which is a non-rotating body, and to prevent the intrusion of foreign matter from the outside of the housing 12. In Figure 1, the left side of the drawing of the housing 12 corresponds to the outside, and the space on the right side of the drawing of the housing 12 corresponds to the internal space. The oil seal 10 is provided so as to close the gap between the inner peripheral surface 16 of the through hole 14 formed in the housing 12 and the outer peripheral surface 20 of the drive shaft 18 (hereinafter, shaft 18), which is a rotating body. The housing 12 corresponds to the non-rotating body of the present invention, the through hole 14 corresponds to the hole of the present invention, and the shaft 18 corresponds to the rotating body of the present invention.

The shaft 18 is inserted into the through hole 14 of the housing 12 and is supported rotatably about the rotation axis CL via a bearing (not shown). The portion of the shaft 18 that is inserted into the through hole 14 is formed in a stepped shape, and the shaft diameter is made smaller than the inner diameter of the through hole 14. Therefore, a gap is formed between the inner peripheral surface 16 of the through hole 14 and the outer peripheral surface 20 of the shaft 18. An annular oil seal 10 is provided to seal this gap. The specific structure of the oil seal 10 will be described later.

The process of modifying the structure of a conventional oil seal 100 (see FIG. 2) to obtain the oil seal 10 of this embodiment will be described below with reference to FIG. 2. In FIG. 2, the lower half of the structure relative to the rotation axis CL is omitted. The shaft 18 and the housing 12 are given the same reference numerals as in FIG. 1.

The oil seal 100 of type A (end face abutting side lip structure) shown in the upper left of Figure 2 corresponds to a conventional structure. The oil seal 100 comprises a seal body 102 and a deflector 104. The seal body 102 is composed of a metal ring 106 formed with an L-shaped cross section, and a main seal 110 made of an elastic member integrally molded with the metal ring 106. The main seal 110 integrally comprises an outer periphery seal portion 112 located on the outer periphery of the metal ring 106, a seal lip 116 that is in close contact with the outer periphery of the shaft 18 so as to be able to slide, a dust lip 118, and a side lip 120.

The deflector 104 is provided to prevent foreign matter such as muddy water from entering from the outside. The deflector 104 is formed in a double cylindrical shape with a bottom. The inner circumference of the deflector 104 is fixed to the shaft 18 by press-fitting or the like. When the shaft 18 rotates, the surface of the deflector 104, which rotates integrally with the shaft 18, perpendicular to the rotation axis CL and the lip tip of the side lip 120 slide against each other.

In the oil seal 100, when the side lip 120 is pushed in the direction of the rotation axis CL by the axial play of the shaft 18, the lip tip of the side lip 120 is pushed in the axial direction and moves radially outward with respect to the rotation axis CL, so that it becomes necessary to enlarge the deflector 104 in the radial direction to overcome this. Also, even if the position where the lip tip of the side lip 120 comes into close contact with the deflector 104 changes due to the axial play of the shaft 18, in order to ensure the surface pressure of the lip tip of the side lip 120, it is necessary to enlarge the diameter of the side lip 120 to ensure elasticity. Furthermore, grease 122 is applied to the inner peripheral side of the side lip 120, but when the deflector 104 rotates, it becomes difficult to retain the grease 122 due to the effect of centrifugal force.

To solve this problem, in the oil seal 130 of embodiment B (side lip cylindrical) in the upper right of Figure 2, the sliding contact position of the lip tip of the side lip 138 is changed to the outer cylindrical portion 134 of the deflector 132. In detail, in the oil seal 130 of embodiment B, the outer cylindrical portion 134 located on the outer periphery of the deflector 132 is positioned on the inner periphery side of the through hole 14 formed in the housing 12. In addition, the side lip 138 formed on the seal body 131 is made to slide against the inner periphery of the outer cylindrical portion 134.

Because of this configuration, the side lip 138 is not pushed by the deflector 132 regardless of the axial play of the shaft 18, so deformation of the side lip 138 is suppressed and the ability to follow the axial play of the shaft 18 is improved. On the other hand, the seal tip contact angle θ (see FIG. 2) between the outer cylindrical portion 134 and the side lip 138 becomes obtuse. On the other hand, when the space sealed by the seal lip 136 and the side lip 138 formed in the seal body 131 is cooled, the space is decompressed and the side lip 138 is deformed so as to be drawn toward the inside of the space. At that time, a gap is formed between the lip tip of the side lip 138 and the outer cylindrical portion 134, which causes a problem that foreign matter (such as muddy water) from the outside is easily sucked in through the gap.

To solve this problem, in the oil seal 150 of embodiment C (side lip rotating shaft structure) shown in the lower left of Figure 2, the side lip 154 formed on the seal body 152 constituting the oil seal 150 is in sliding contact with the outer circumferential surface of the inner cylindrical portion 158 located on the inner circumferential side of the deflector 156. With this configuration, even when the space sealed by the seal lip 153 and side lip 154 formed on the seal body 152 is cooled and decompressed, causing the seal body 152 to deform, a gap is unlikely to form between the side lip 154 and the inner cylindrical portion 158. However, when the shaft 18 is assembled, the lip tip of the side lip 154 is easily turned over, which causes problems with the assembly of the oil seal 150.

To solve this problem, in the embodiment D (side lip fixed cylinder structure) shown in the lower right of FIG. 2, the seal body 172 and the side lip 174 constituting the oil seal 170 are separate. The inner periphery of the side lip 174 is fitted to the shaft 18. Also, the lip tip of the side lip 174 is in sliding contact with the inner periphery surface of the cylindrical portion 12a formed in the housing 12 (i.e., the inner periphery surface 16 of the through hole 14). By configuring the seal body 172 and the side lip 174 as separate bodies in this way, the side lip 174 is hardly affected by the reduced pressure in the internal space of the housing 12. Also, the lip tip of the side lip 174 is prevented from turning over when the shaft 18 is assembled. Therefore, the oil seal 170 of embodiment D solves all of the problems such as the inhalation of foreign matter due to the reduced pressure in the internal space of the housing 12, the deformation of the side lip 174 due to the axial play of the shaft 18, and the ease of assembly.

The oil seal 10 shown in FIG. 1 has a structure in which the deflector 176 has been eliminated while maintaining the effects of the oil seal 170 in FIG. 2. The structure of the oil seal 10 in FIG. 1 will be described below.

The oil seal 10 is composed of a seal body 30 and a side lip 32, which are constructed separately. The seal body 30 is composed of an oil seal outer ring 34 (hereinafter, seal outer ring 34) made of a metallic material, and a main seal 36. The seal outer ring 34 and the main seal 36 are molded as a single unit.

The seal outer ring 34 includes a cylindrical portion 38, an inner disk portion 40 extending from the cylindrical portion 38 toward the inner periphery, and an outer disk portion 42 extending from the cylindrical portion 38 toward the outer periphery. The cylindrical portion 38 is fixed by being pressed into the inner periphery 16 of the through hole 14 of the housing 12. The inner disk portion 40 extends toward the inner periphery from the end of the cylindrical portion 38 located on the inner space side of the housing 12 (on the right side of the drawing) in the direction of the rotation axis CL of the shaft 18. The inner disk portion 40 is formed at a position overlapping with the through hole 14 of the housing 12 when viewed in the radial direction based on the rotation axis CL. The main seal 36 is connected to the inner periphery end of the inner disk portion 40. The outer disk portion 42 is formed at the end of the cylindrical portion 38 located on the opposite side of the inner disk portion 40 in the direction of the rotation axis CL, and extends toward the outer periphery from the gap in the direction of the rotation axis CL formed between the shaft 18 and the cylindrical portion 12a of the housing 12.

The main seal 36 is an annular member made of an elastic material such as fluororubber. The main seal 36 is integrally equipped with a seal lip 44 that is slidably in close contact (sliding contact) with the outer circumferential surface of the shaft 18, a dust lip 46, and a connecting seal part 48 that is connected to the inner disk part 40. The seal lip 44 is provided to prevent oil from leaking from the internal space of the housing 12, and its inner circumferential part is in sliding contact with the outer circumferential surface 20 of the shaft 18. A garter spring 50 is attached to the outer circumferential part of the seal lip 44. The dust lip 46 extends toward the inner circumferential side, and its tip is in sliding contact with the outer circumferential surface 20 of the shaft 18. The dust lip 46 also prevents the intrusion of foreign matter from the outside. The connecting seal part 48 is located on the outer circumferential side of the part where the dust lip 46 is formed, and its outer circumferential end is connected to the inner circumferential end of the inner disk part 40.

The side lip 32 is formed in a generally V-shaped annular cross section, and has a lip tip 32a that protrudes radially outward from the outer periphery, i.e., the rotation axis CL. The inner periphery of the side lip 32 is fitted to the outer periphery 54 of the shaft 18 by press-fitting or the like. The outer periphery of the side lip 32 is covered by the seal outer ring 34, and the lip tip 32a that protrudes radially outward from the outer periphery of the side lip 32 (i.e., the radially outward from the rotation axis CL) is in close (sliding) contact with the inner periphery 56 of the cylindrical portion 38 that constitutes the seal outer ring 34.

The oil seal 10 constructed as described above provides the effects described below. First, the seal body 30 (seal body 30 and seal outer ring 34) and the side lip 32 are provided separately, so that even if the internal space of the housing 12 is depressurized, the side lip 32 is not affected, and deformation of the side lip 32 is suppressed. As a result, deformation of the side lip 32 prevents foreign matter from entering the internal space of the housing 12 from the outside.

In addition, since the lip tip 32a of the side lip 32 is in sliding contact with the inner peripheral surface 56 of the cylindrical portion 38 of the seal outer ring 34 that fits into the through hole 14 of the housing 12, even if the relative position (sliding position) between the lip tip 32a of the side lip 32 and the seal outer ring 34 in the direction of the rotation axis CL changes due to axial play, the side lip 32 is hardly deformed. Therefore, the change in the surface pressure with which the lip tip 32a of the side lip 32 presses the inner peripheral surface 56 of the cylindrical portion 38 is suppressed. In addition, since the radial dimension of the lip tip 32a of the side lip 32 based on the rotation axis CL can be made small, wear between the lip tip 32a and the cylindrical portion 38 is reduced. In addition, since the side lip 32 is fitted to the shaft 18 side, the side lip 32 is prevented from turning over when the shaft 18 is assembled.

In addition, in the oil seal 10, grease 52 that lubricates the sliding contact between the lip tip 32a of the side lip 32 and the inner circumferential surface 56 of the cylindrical portion 38 is applied to the area indicated by diagonal lines in FIG. 1, i.e., the inner circumferential side of the cylindrical portion 38 of the seal outer ring 34. When grease 52 is applied to this area, the grease 52 is not affected by centrifugal force, improving the retention of the grease 52.

In addition, by forming an outer disk portion 42 that extends from the cylindrical portion 38 of the outer seal ring 34 to the outer periphery, a complex labyrinth structure is formed in the oil seal 10. In this way, the outer seal ring 34 also serves as a deflector that prevents foreign matter from entering, making it possible to eliminate the need for a deflector.

As described above, according to this embodiment, the lip tip 32a protruding outward from the side lip 32 fitted to the outer circumferential surface 54 of the shaft 18 is integrally molded with the seal lip 44 and is in sliding contact with the inner circumferential surface 56 of the cylindrical seal outer ring 34 that fits into the through hole 14. This suppresses changes in the surface pressure of the lip tip 32a due to axial play of the shaft 18 and suppresses radial enlargement of the lip tip 32a. As a result, wear of the lip tip 32a of the side lip 32 can be reduced while appropriately preventing the intrusion of foreign matter.

Next, another embodiment of the present invention will be described. In the following description, parts common to the previous embodiment will be given the same reference numerals and will not be described.

Figure 3 is a cross-sectional view of an oil seal 200 corresponding to another embodiment of the present invention. Comparing the oil seal 200 with the oil seal 10 of the first embodiment described above, it differs in that it is provided with two side lips 204, 206.

The oil seal 200 is composed of a seal body 202 and two side lips 204, 206. The seal body 202 is basically the same as the seal body 30 of the first embodiment described above, so a detailed description will be omitted.

The side lips 204 and 206 are arranged side by side in the direction of the rotation axis CL of the shaft 18. The side lips 204 and 206 are both fitted to the outer peripheral surface 212 of the shaft 18 by press fitting or the like. In addition, the lip tips 204a, 206a extending outward from the outer peripheral side of the side lips 204 and 206 are respectively brought into sliding contact with the cylindrical portion 210 of the oil seal outer ring 208 constituting the seal body 202.

The oil seal 200 configured as above can achieve the same effect as the oil seal 10 of the above-mentioned embodiment. In addition, the oil seal 200 has two side lips 204, 206, which further enhances the effect of preventing the intrusion of foreign matter from the outside. Therefore, in areas where the road conditions are poor and muddy water is likely to be splashed up while driving, or in cases where the side lips 204, 206 are subject to severe wear, by providing two or more side lips 204, 206 as in the oil seal 200, these problems can be dealt with appropriately.

The above describes in detail an embodiment of the present invention based on the drawings, but the present invention can also be applied in other aspects.

For example, in the above embodiment, the lip tip 32a of the side lip 32 is in sliding contact with the inner peripheral surface 56 of the cylindrical portion 38 of the seal outer ring, but as shown in embodiment D of FIG. 2, the tip of the side lip may be in sliding contact with the inner peripheral surface 16 of the through hole 14 formed in the housing 12. Similarly, for the oil seal 200, the lip tips 204a, 206a of the side lips 204, 206 may be in sliding contact with the inner peripheral surface 16 of the through hole 14, respectively.

In addition, in the above-described embodiment, the oil seal 200 has two side lips 204, 206 arranged side by side in the direction of the rotation axis CL, but the number of side lips is not limited to two. In other words, three or more side lips may be arranged, and the number of side lips can be changed as appropriate depending on the driving environment.

Note that the above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

10, 200: Oil seal 12: Housing (non-rotating body) 14: Through hole (hole) 18: Drive shaft (rotating body) 32, 204, 206: Side lip 32a: Lip tip 34: Oil seal outer ring 38: Cylindrical part 44: Seal lip

Claims (1)

1. An oil seal having a seal lip that is provided in a gap between an inner peripheral surface of a hole formed in a non-rotating body and an outer peripheral surface of a rotating body inserted into the hole, the seal lip being in slidable contact with the outer peripheral surface of the rotating body,
a ring-shaped side lip provided separately from the seal lip and fitted to an outer circumferential surface of the rotating body;
The side lip has a lip tip that protrudes toward the outer periphery,
an oil seal having a lip tip that is slidably brought into close contact with an inner circumferential surface of the hole or an inner circumferential surface of a cylindrical oil seal outer ring that is integrally molded with the seal lip and fits into the hole.

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