JP2018168974A - Oil seal and bearing with seal - Google Patents

Abstract

[Problem] To achieve low torque and required sealing performance through fluid lubrication at an oil temperature within a specified range. [Solution] A plurality of protrusions 11 formed on a seal lip 10 of a seal member 1 create a fluid lubrication state between the seal lip 10 and the seal sliding surface of a mating member. The position of the sliding contact area of the protrusions 11 changes according to the elastic deformation of the seal lip 10 based on a change in oil temperature. The protrusions 11 are shaped so that their circumferential length increases toward one side that changes the position of the sliding contact area based on an increase in oil temperature. The circumferential length of the protrusions 11 changes so that the thickness of the oil film can be maintained within a certain range at an oil temperature within a specified range. The certain range is set so that a fluid lubrication state can be maintained and the gap between the surface portion 13 and the seal sliding surface between circumferentially adjacent protrusions 11 can be maintained at a certain level or less. [Selected Figure] Figure 1

Description

  The present invention relates to an oil seal used to prevent foreign matters in lubricating oil from entering the internal space of the apparatus, and a bearing with a seal including the oil seal.

  For example, foreign substances such as gear wear powder are mixed in transmissions mounted on vehicles such as automobiles and various construction machines. By adopting a sealed bearing having an oil seal as a rolling bearing that rotatably supports the rotation shaft of the transmission, foreign matter intrusion into the internal space of the bearing is prevented and early damage of the bearing is prevented.

  As such an oil seal, one having a seal member having a seal lip formed of a rubber material and a counterpart member that rotates relative to the seal member in the circumferential direction is used. The mating member is, for example, a race ring, a slinger, or the like, and has a seal sliding surface for slidingly contacting the seal lip. Even if there is an eccentricity between the seal member and the mating member, a tightening allowance is set between the seal lip and the seal sliding surface of the mating member so that the seal lip can sufficiently follow the seal sliding surface. It is common to do. When the seal member and the mating member are arranged in a predetermined manner, the seal lip presses the seal sliding surface of the mating member due to the tightening allowance. For this reason, at the time of relative rotation between the seal member and the mating member, drag resistance (seal torque) of the seal lip that comes into sliding contact with the seal sliding surface is generated. Moreover, the friction of the sliding contact causes a temperature rise. As the temperature rises, an adsorption action due to a pressure difference between the internal space and the outside is caused, and the friction increases.

  On the other hand, it has been proposed that a fluid lubrication state is established between the seal lip and the seal sliding surface of the mating member (Patent Document 1). The seal member disclosed in Patent Document 1 has a seal lip formed with a large number of protrusions arranged at predetermined intervals in the circumferential direction. The protrusion forms a wedge-shaped gap with the seal sliding surface of the mating member. When the mating member rotates at a predetermined speed or more relative to the seal member, the lubricating oil is dragged into the wedge-shaped gap, and the formation of an oil film is promoted by the wedge effect. Make sliding contact with seal sliding surface in fluid lubrication. For this reason, the seal lip and the seal sliding surface are completely separated.

  Here, the fluid lubrication state refers to a state in which a fluid film of lubricating oil is formed between two surfaces by a hydrodynamic principle, and a direct contact between friction surfaces is not generated. When the minimum oil film thickness between the two surfaces is larger than the root mean square roughness, generally three times or more, it can be regarded as a fluid lubrication state. When fluid lubrication occurs between the seal lip and the seal sliding surface of the mating member, the sliding resistance becomes almost zero, so the seal torque can be greatly reduced, which is impossible with conventional oil seals. It can be used at high peripheral speeds. Further, by setting the height of the protrusions, it is possible to prevent foreign matters having a particle size of a predetermined size or more from passing through the gaps between the protrusions, thereby preventing entry into the internal space of the apparatus.

International Publication No. WO2016 / 143786

  The thickness of the oil film formed by the wedge effect between the seal lip protrusion and the seal sliding surface of the mating member depends on the oil temperature. Since the viscosity of the lubricating oil becomes low at high temperatures, the oil film becomes thin. Since the viscosity of the lubricating oil increases at a low temperature, the oil film becomes thick. When the oil film becomes too thin, fluid lubrication is not realized, and there is a concern that the protrusion and the seal sliding surface are in direct contact with each other and the seal torque is increased. On the other hand, if the oil film becomes too thick, the gap between the surface portion of the seal lip adjacent to the circumferentially adjacent projection and the seal sliding surface becomes too large, and there is a concern that foreign matter cannot be prevented from entering. .

  In view of the above-described background, the problem to be solved by the present invention is an oil seal in which a plurality of protrusions formed on a seal lip of a seal member can be in a fluid lubrication state between the seal lip and a counterpart member. An object of the present invention is to realize a low torque property by fluid lubrication and a required sealing property at an oil temperature within a predetermined range.

  In order to achieve the above object, the present invention includes a seal member having a seal lip formed of a rubber material, and a counterpart member that rotates relative to the seal member in the circumferential direction, and is formed on the counterpart member. A tightening margin is set between the seal sliding surface and the seal lip, and the seal lip has a plurality of protrusions in sliding contact with the seal sliding surface in a fluid lubrication state at predetermined intervals in the circumferential direction. In the oil seal in which the position of the sliding contact region on the projection sandwiching the seal sliding surface and the oil film changes according to the elastic deformation of the seal lip based on a change in oil temperature, the projection is The circumferential length of the projection increases toward one side where the position of the sliding contact area changes based on an increase in oil temperature. The circumferential length of the protrusion is the oil film at an oil temperature within a predetermined range. Within a certain range of thickness The minimum value of the certain range is set so as to maintain the fluid lubrication state, and the maximum value of the certain range is adjacent to the circumferential direction of the seal lips. A configuration was adopted in which the gap between the surface portion between the protrusions and the seal sliding surface was set to be kept below a certain level.

  When the seal lip of the seal member and the seal sliding surface of the mating member are in sliding contact with each other in a fluid lubricated state, each protrusion of the seal lip has a sliding contact region that sandwiches the oil sliding film with the seal sliding surface. The wedge effect between the sliding contact area on the projection and the seal sliding surface of the mating member promotes the formation of the oil film, and the projection and the seal sliding surface are completely separated. Generally, in fluid lubrication between two surfaces, there is a correspondence between the surface pressure and the thickness of the oil film. That is, the lower the surface pressure, the thicker the oil film, and the higher the surface pressure, the thinner the oil film. There is also a correspondence between the position of the sliding contact area on the protrusion and the oil temperature. That is, when the oil temperature rises, the temperature of the seal lip that comes into contact with the lubricating oil over a wide range also rises, so that the rubber-made seal lip expands thermally. Since the oil film side resists this thermal expansion, the seal lip is elastically deformed to bend more. When the raised oil temperature falls, the seal lip returns to the shape before the oil temperature rises. With such elastic deformation of the seal lip, the attitude of the protrusion with respect to the seal sliding surface changes. In order to enable fluid lubrication even during this change, the protrusion is formed so that the position of the sliding contact region changes according to the elastic deformation of the seal lip based on the oil temperature change. That is, when the oil temperature rises, the position of the sliding contact area changes to one side corresponding to the elastic deformation of the seal lip, and when the raised temperature falls, the position changes to the other side opposite to the one side. Considering the correspondence between the above-mentioned surface pressure and the oil film thickness, and the correspondence between the position of the sliding contact area and the oil temperature, the position of the protrusion changes toward one side where the position of the sliding contact area changes based on the oil temperature rise. If a protrusion shape with a longer direction length is adopted, the position of the sliding contact area on the protrusion moves to a position where the circumferential length of the protrusion is longer as the oil temperature rises, and the surface in the sliding contact area Since the pressure is reduced, the oil film is likely to be formed thick, and as the oil temperature decreases, the position of the sliding contact area on the protrusion moves to a position where the circumferential length of the protrusion is shorter, Since the surface pressure increases, the oil film is easily formed thin. By utilizing the oil film thickness fluctuation suppressing action based on the circumferential length change of the protrusion, the oil film thickness between the sliding contact area on the protrusion and the seal sliding surface is within a certain range at an oil temperature within a predetermined range. Can be maintained. Here, if the minimum value in the certain range is set so that the fluid lubrication state can be maintained, low torque characteristics due to fluid lubrication can be realized at an oil temperature within the predetermined range. In addition, if the maximum value of the certain range is set so that the gap between the surface portion between the protrusions adjacent in the circumferential direction and the seal sliding surface can be kept below a certain level, the oil temperature within the predetermined range can be reduced. The required sealing performance can be realized.

  Ideally, it is preferable that the oil film thickness can be maintained at a constant value even if the oil temperature changes, but this can be achieved by changing the lubricating oil viscosity when the oil temperature changes or by reducing the oil film thickness. On the other hand, it is required that the oil film thickness variation suppressing action due to the change in the circumferential length of the protrusion is always balanced. In practice, fluctuations in oil film thickness can be tolerated to some extent, so parameters affecting surface pressure, lubricating oil viscosity, gaps, such as protrusion height, allowable oil temperature range, type of lubricating oil used, seal In consideration of the surface roughness property of the sliding surface, the tightening force based on the tightening margin of the seal lip, and the like, an appropriate protrusion shape may be determined so that the oil film thickness falls within the above-mentioned predetermined range.

  For example, the height of the protrusion may be the same in the entire range in which the thickness of the oil film within the certain range can be maintained. If the oil film thickness is not taken into consideration, the size of the gap between the surface portion of the seal lip between the adjacent protrusions in the circumferential direction and the seal sliding surface of the mating member Determined by height. If the heights of the protrusions are made the same in the entire range capable of maintaining a certain range of oil film thickness, it becomes easy to keep the gap below a certain level.

  If the oil film thickness becomes excessive even if the circumferential length of the protrusion is changed to suppress fluctuations in the oil film thickness, the gap between the surface between the protrusion and the seal sliding surface becomes excessive. The required sealing performance cannot be realized. For example, in a transmission used in a cold region, the viscosity of the lubricating oil particularly increases at the start of operation, and therefore, it may not be possible to cope with only the change in the circumferential length of the protrusion.

  As a suitable example in such a case, the protrusion has a height changing portion that becomes lower toward the other side opposite to the one side and becomes shorter in the circumferential direction, and the height changing portion has an oil temperature change. It is mentioned that it is arranged on the other side of the range that becomes the sliding contact area based on the above. When the oil temperature changes, the position of the sliding contact area on the protrusion changes to the other side opposite to the one side. Of the protrusions, the portion located on the other side in the range to be the sliding contact region becomes the sliding contact region at the lowest temperature. That is, the height changing portion becomes a sliding contact region in the lowest temperature region within the allowable oil temperature range. If the height change part is a shape that is lower toward the other side that changes the slidable contact area when the oil temperature drops and becomes shorter in the circumferential direction, the aforementioned gap is enlarged by shortening the circumferential length (increasing the surface pressure). In addition, the above-mentioned gap can be narrowed by reducing the height thereof, so that an excessive gap can be prevented.

  The shape of the sliding contact region on the protrusion in the cross section along the circumferential direction may be any shape that can realize fluid lubrication by the wedge effect.

  For example, the slidable contact area on the protrusion has an arc shape in a cross section along the circumferential direction, and the radius of curvature of the arc shape is set larger toward the one side.

  As another example, the slidable contact area on the protrusion is rectangular in cross section along the circumferential direction, and the circumferential length of the bottom of the rectangular shape is set longer toward the one side. It is mentioned.

  As another example, the sliding contact area on the protrusion has a shape having an inclined side in a cross section along the circumferential direction, and the circumferential length of the inclined side is set longer toward the one side. It is mentioned.

  The circumferential length of the protrusion may change gradually (continuously) toward one side on the protrusion, or may change stepwise (stepwise).

  Preferably, the protrusion has a shape that gradually increases in the circumferential direction toward the one side. In this way, the change in the surface pressure due to the change in the circumferential length of the protrusion becomes continuous, so that the thickness of the oil film can be easily maintained within a certain range according to the change in the oil temperature.

  In the case of a typical bearing to which an oil seal is applied, the required sealing performance is generally aimed at not adversely affecting the bearing life.

  Considering application to a bearing, for example, the height of the protrusion is preferably 0.01 mm or more and less than 0.10 mm. In this way, molding of the seal lip is not difficult, and fluid lubrication between the seal lip and the seal sliding surface can be realized by a wedge effect between the protrusion and the seal sliding surface, which adversely affects the bearing life. Such foreign matter can be effectively prevented from entering the bearing internal space.

  The bearing with a seal provided with the oil seal according to the present invention, wherein the seal member separates the bearing internal space from the outside, while preventing foreign matter from entering the internal space of the bearing with the seal member, The bearing torque is reduced by a significant reduction in the seal torque. For this reason, this bearing with a seal | sticker is suitable for the use which supports the rotating shaft of the transmission of a motor vehicle.

  The present invention provides an oil seal capable of fluid lubrication between a seal lip and a mating member with a plurality of protrusions formed on the seal lip of the seal member by adopting the above configuration. At low temperature, low torque due to fluid lubrication and required sealing performance can be realized.

The front view which shows the seal lip of the seal member which concerns on 1st embodiment of this invention in a natural state Sectional drawing which shows the oil seal and bearing with seal which concern on 1st embodiment. Partial sectional view showing when the seal lip and the seal sliding surface of the first embodiment are in a fluid lubrication state Partial expanded sectional view which shows the cross section of the IV-IV line of FIG. FIG. 4 is a graph showing the relationship between the curvature radius of the protrusion and the minimum oil film thickness. Partial sectional view showing when the oil temperature rises from the state of FIG. Partial expanded sectional view which shows the cross section of the VII-VII line of FIG. The fragmentary sectional view which shows the fluid lubrication state of the seal lip which concerns on 2nd embodiment of this invention at the time of the lowest temperature The front view which shows the seal lip which concerns on 3rd embodiment of this invention in a natural state Partial expanded sectional view which shows the cross section of the XX line of FIG. The front view which shows the seal lip which concerns on 4th embodiment of this invention in a natural state Partial expanded sectional view which shows the cross section of the XII-XII line | wire of FIG. Sectional drawing which shows an example of a transmission provided with the bearing with a seal concerning this invention

  Hereinafter, a first embodiment according to the present invention will be described with reference to the accompanying drawings. The first embodiment is an example of a bearing with a seal including an oil seal. As shown in FIG. 2, the oil seal includes a seal member 1 and a counterpart member 2 that rotates relative to the seal member 1 in the circumferential direction.

  The bearing with seal includes a mating member 2 formed of an inner ring, an outer ring 4 that forms an annular bearing inner space 3 between the mating member 2, and a predetermined number interposed between the raceway of the mating member 2 and the raceway of the outer ring 4. The rolling element 5 is provided.

  The seal member 1 separates between the bearing internal space 3 and the outside (bearing periphery).

  The mating member 2 is attached to a rotating shaft (not shown) and rotates integrally with the rotating shaft. The rotating shaft is provided as a rotating portion of a vehicle transmission, a differential, a constant velocity joint, a propeller shaft, a turbocharger, a machine tool, a wind power generator, or a wheel bearing, for example. The outer ring 4 is attached to a member (not shown) that applies a load from the rotating shaft, such as a housing and a gear. This bearing with seal supports a rotating shaft rotatably.

  Lubricating oil is supplied to the sealed bearing from the outside by appropriate means such as splashing or an oil bath. On the outside side with the seal member 1 as a boundary, there are foreign matters according to the mounting destination of the bearing, such as gear wear powder, clutch wear powder, and fine crushed stone. Such powdery foreign matter can reach the vicinity of the bearing with seal by the flow of lubricating oil or atmosphere. The seal member 1 prevents foreign matter from entering the bearing internal space 3 from the outside.

  Hereinafter, the direction along the central axis (not shown) of the seal member 1 is referred to as “axial direction”. The axial direction corresponds to the left-right direction in FIG. A direction perpendicular to the axial direction is referred to as a “radial direction”. The radial direction corresponds to the vertical direction in FIG. The circumferential direction around the central axis is referred to as “circumferential direction”. The central axis of the mating member 2 is set coaxially with the central axis of the seal member 1 by design.

  A seal groove 6 is formed at an inner peripheral end of the outer ring 4. On the outer periphery of the mating member 2, a seal sliding surface 7 is formed along the circumferential direction. The seal member 1 is attached to the outer ring 4 by press-fitting the outer peripheral edge of the seal member 1 into the seal groove 6. During operation of the bearing with seal, the counterpart member 2 rotates relative to the seal member 1, and the gap between the seal member 1 and the counterpart member 2 is lubricated with lubricating oil.

  The seal sliding surface 7 has a cylindrical surface shape. The maximum height roughness Rz of the seal sliding surface 7 is 2.5 μm or less (preferably less than 1 μm). Here, the maximum height roughness Rz refers to the maximum height roughness defined in JIS standard B0601: 2013.

  The seal member 1 includes an annular cored bar 8 formed of a metal plate and a rubber material 9 attached to the cored bar 8. The entire sealing member 1 is composed of a core metal 8 and a rubber material 9. The cored bar 8 is in the shape of an annular plate that continues around the entire circumference. The material of the cored bar 8 is made of a metal having higher rigidity than that of the rubber material 9. For example, a steel plate can be cited as a material for the cored bar 8 suitable for press working. The rubber material 9 is vulcanized and bonded to the core metal 8. The type of the rubber material 9 is not particularly limited, and examples thereof include nitrile rubber and fluorine rubber.

  The seal member 1 has a seal lip 10 formed of a rubber material 9. The seal lip 10 is made of a part of a rubber material 9 extending from the edge 8 a of the core metal 8 toward the seal sliding surface 7. The edge of the cored bar 8 is the inner or outer peripheral edge of the cored bar 8 that defines the diameter of the cored bar 8 that is closer to the seal sliding surface 7.

  The seal lip 10 is a radial lip. Here, the radial lip exhibits a sealing action with a seal sliding surface along the axial direction such as the seal sliding surface 7 or a seal sliding surface with an acute angle gradient within 45 ° with respect to the axial direction. A seal lip having a radial tightening margin with respect to the seal sliding surface.

  In FIG. 2, a cross section when the seal member 1 is attached to the outer ring 4 and arranged coaxially with the counterpart member 2 is shown by a solid line, and the state before the seal member 1 is attached to the outer ring 4 (seal member 1 The outer shape in the vicinity of the seal lip 10 when viewed from the same cross section is drawn with a two-dot chain line. As shown in the figure, when the seal member 1 in the natural state is attached to the outer ring 4, the seal lip 10 is pressed against the seal sliding surface 7 by the tightening allowance δ with respect to the seal sliding surface 7. For this reason, the seal lip 10 is elastically deformed so as to bend, and generates a force (tightening force) for pressing the seal sliding surface 7 in the radial direction. The mounting error, manufacturing error, eccentricity between the mating member 2 and the outer ring 4 are absorbed by the elastic deformation of the seal lip 10.

  Although the radial lip is illustrated as the seal lip 10, it may be changed to an axial lip. The axial lip is a seal sliding surface along the radial direction or a sealing sliding lip having a sharp slope of less than 45 ° with respect to the radial direction and a sealing lip that exhibits a sealing action. It has an axial allowance in between.

  The vicinity of the seal lip 10 when the space between the seal lip 10 and the seal sliding surface 7 is in a fluid lubrication state is shown in FIG. FIG. 1 shows a state when the seal lip 10 is in a natural state when viewed in the axial direction from the bearing internal space 3 side. As shown in these figures, the seal lip 10 includes a plurality of protrusions 11 arranged at predetermined intervals in the circumferential direction, and a solid portion 12 that is continuous over the entire circumference in the circumferential direction.

  The solid portion 12 is continuous with the same cross-sectional structure on the entire circumference in the circumferential direction. The solid part 12 includes a surface part 13 extending between the protrusions 11 adjacent in the circumferential direction. Considering a cross section in which the seal lip 10 is cut along an arbitrary virtual axial plane with the central axis of the seal member 1 as one side, the seal lip 10 is located between the adjacent protrusions 11 in the circumferential direction (that is, the cross section of the protrusion 11). The portion facing the seal sliding surface 7 corresponds to the surface portion 13.

  As shown in FIG. 3, the protrusion 11 has a height H from the solid portion 12 toward the seal sliding surface 7. As shown in FIG. 1, the protrusions 11 are arranged at regular intervals in the circumferential direction, and are distributed on the seal lips 10 with an even arrangement in the circumferential direction. That is, when considered around the central axis of the seal member 1, the plurality of protrusions 11 are arranged at a constant pitch angle. The space | interval can be set to 0.2 mm or more and 3.0 mm or less (preferably 0.2 mm or more, 1.5 mm or less), for example.

  The protrusion 11 is formed in a shape having a certain length in the radial direction from the lip tip 14 of the seal lip 10 in a natural state. The lip tip 14 is a peripheral portion of the seal lip 10 that defines the diameter of the seal lip 10 (the inner diameter or the outer diameter of the seal lip 10) in a natural state. The lip tip 14 in the figure is on the inner diameter of the seal lip 10, but when the seal lip is brought into sliding contact with the seal sliding surface of the outer ring, the lip tip is on the outer diameter of the natural seal lip.

  When the seal member 1 is attached to the outer ring 4 as shown in FIG. 2, the seal lip 10 comes into contact with the seal sliding surface 7 from the protrusion 11 shown in FIG. 1 and is elastically deformed as shown in FIG. Thus, the protrusion 11 is arranged to face the seal sliding surface 7 in the radial direction. In this arrangement state, the seal lip 10 is bent from the waist 15, and the protrusion 11 is in contact with the seal sliding surface 7 at a part thereof. The waist 15 is a portion located near the edge of the core 8 of the seal lip 10 and accumulates a bending reaction force when the seal member 1 is attached.

  As shown in FIG. 4, the protrusion 11 forms a wedge-shaped gap with the seal sliding surface 7. Here, the wedge-shaped gap refers to a gap that gradually narrows in the radial direction toward the projection 11 in the circumferential direction.

  The surface of the protrusion 11 has an arc shape in a cross section along the circumferential direction. Here, the cross section along the circumferential direction refers to a cross section of the projection 11 when the projection 11 is cut by a virtual plane orthogonal to the seal sliding surface 7 and extending along the circumferential direction.

  In this cross-sectional shape, the aforementioned arc-shaped curvature radius R is, for example, 0.4 mm or more and less than 9.0 mm (preferably 0.4 mm or more and 6.0 mm or less, more preferably 0.4 mm or more, 3. 0 mm or less).

  The height H of the protrusion 11 is smaller than the radius of curvature R of the protrusion 11, for example, 0.01 mm or more and less than 0.10 mm (preferably 0.01 mm or more and 0.08 mm or less, more preferably 0.01 mm or more, 0.05 mm or less).

  As shown in FIG. 4, a gap 16 is formed between the surface portion 13 of the seal lip 10 and the seal sliding surface 7. The gap 16 communicates between the bearing internal space 3 and the outside (see FIG. 2). The gap 16 shown in FIG. 4 does not become larger than the height H of the protrusion 11 with respect to the size in the direction perpendicular to the seal sliding surface 7, but is secured at a predetermined ratio or more with respect to the height H. The That is, the seal member 1 can be in direct contact with the mating member 2 only by the plurality of protrusions 11, and cannot be in direct contact with the seal sliding surface 7 at each surface portion 13.

  During operation of the bearing with seal, the mating member 2 shown in FIG. 2 rotates relative to the seal member 1. Lubricating oil supplied from the outside during the operation (the lubricating oil is indicated by a dot pattern in FIG. 4) enters the gap 16 as shown in FIGS. 3 and 4, and is indicated by an arrow A in FIG. It is dragged in the relative rotation direction and lubricates between the seal lip 10 and the counterpart member 2.

  Here, since each protrusion 11 of the seal lip 10 has an arc shape with a radius of curvature R of 0.4 mm or more and less than 9.0 mm in a cross section along the circumferential direction, the seal sliding surface 7 of the mating member 2 is provided with each protrusion. When moving in the circumferential direction with respect to 11, the lubricating oil in the gap 16 is effectively dragged between the protrusions 11 and the seal sliding surface 7 along the surfaces of the protrusions 11. At this time, the formation of the oil film is promoted by the wedge effect, and when the relative rotation speed is equal to or higher than a predetermined value, the lubrication state between each protrusion 11 and the counterpart member 2 becomes a fluid lubrication state, and the seal torque is drastically reduced. . Of course, each surface portion 13 and the seal sliding surface 7 are not in direct contact with each other during the relative rotation from the stop of the bearing with seal. Further, since the seal torque is small, frictional heat between the seal lip 10 and the counterpart member 2 is hardly generated. Furthermore, the lubricating oil supplied from the outside passes between the seal lip 10 and the seal sliding surface 7 through the gap 16, so that the frictional heat between the seal lip 10 and the seal sliding surface 7 is dissipated. Is done. Therefore, it is possible to extremely effectively suppress the temperature rise of this sealed bearing.

  As described above, when the seal lip 10 and the seal sliding surface 7 are in sliding contact with each other in a fluid lubrication state, each protrusion 11 of the seal lip 10 has a sliding contact region sandwiching the seal sliding surface 7 and the oil film. Here, the sliding contact region of the protrusion 11 pushes the oil film sandwiched between the seal sliding surface 7 to the seal sliding surface 7 side by the action of the tightening force of the seal lip 10 and reduces the pressure in the oil film based on the wedge effect. It refers to the surface portion of the projection 11 to be received. The protrusion 11 is completely lifted from the seal sliding surface 7 by the pressure received in the sliding contact area. At this time, the distance between the protrusion 11 and the seal sliding surface 7 is the shortest between one portion of the sliding contact area and the seal sliding surface 7. In addition, the oil film thickness t between the protrusion 11 and the seal sliding surface 7 is minimized at the shortest distance.

  FIG. 5 is a graph showing a numerical analysis result obtained by investigating the relationship between the oil temperature and the minimum oil film thickness when the curvature radius of the protrusion is three levels of large, medium, and small. These three levels are selected from the range of 0.2 to 1.5 mm in the radius of curvature R of the protrusions, and the heights of the protrusions are the same. CVTF is assumed as the lubricating oil. The peripheral speed of the relative rotation of the seal sliding surface 7 with respect to the seal lip 10 is assumed to be 2.51 m / s. FIG. 5 shows that the minimum oil film thickness between the sliding contact area of the protrusion and the seal sliding surface increases as the oil temperature decreases. This is presumably because the viscosity of the lubricating oil increases. Moreover, it turns out that an oil film becomes thick, so that the curvature radius of protrusion is large. This is because when the radius of curvature of the protrusion is increased, the circumferential length of the sliding contact area when the protrusion is slidably contacted with the sliding surface of the seal and elastically deformed increases, and the surface pressure acting on the sliding contact area of the protrusion (basic In addition, this is considered to be due to a decrease in the pressure of the sealing lip mentioned above and the dynamic pressure action of the wedge effect. That is, the circumferential length in the sliding contact area of the protrusion is changed according to the oil temperature. Specifically, the curvature radius in the sliding contact area of the protrusion is reduced at a low temperature, and the curvature radius of the protrusion is increased at a high temperature. It is considered that a certain oil film thickness can be maintained at all oil temperatures by increasing the oil temperature.

  In the fluid lubrication state in which the correspondence between the surface pressure and the oil temperature is recognized, when the seal lip 10 and the seal sliding surface 7 are in a thermal equilibrium state with the oil temperature, the protrusion 11 is in sliding contact as shown in FIG. In the region 17, the seal sliding surface 7 and the oil film are sandwiched. When the oil temperature rises from the state of FIG. 3, the temperature of the seal lip 10 that comes into contact with the lubricating oil in a wide range also increases, so that the rubber-made seal lip 10 thermally expands. Since the oil film side resists this thermal expansion, the seal lip 10 is elastically deformed to bend more. With this elastic deformation, the position of the protrusion 11 with respect to the seal sliding surface 7 changes, so that the position of the sliding contact area of the protrusion 11 gradually changes from the sliding contact area 17 to one side (right side in the figure, waist 15 side).

  FIG. 6 shows a state in which the seal lip 10 and the seal sliding surface 7 are in a thermal equilibrium state at an oil temperature several tens of degrees higher than the state of FIG. At this time, the protrusion 11 sandwiches the seal sliding surface 7 and the oil film in the sliding contact region 18. When the oil temperature decreases from the state shown in FIG. 6, the seal lip 10 is elastically deformed so as to gradually return to the shape shown in FIG. With this elastic deformation, the position of the protrusion 11 with respect to the seal sliding surface 7 returns, so that the position of the sliding contact area of the protrusion 11 gradually increases from the sliding contact area 18 to the other side (that is, the opposite side to the one side in the figure). (Left side, lip tip 14 side) When returning to the thermal equilibrium state shown in FIG. 3, the protrusion 11 again sandwiches the seal sliding surface 7 and the oil film in the sliding contact region 17. When the oil temperature further rises from the state of FIG. 6, the position of the sliding contact region of the protrusion 11 changes to one side (right side in the drawing) as compared to the sliding contact region 18 of FIG. When the oil temperature further decreases, the position of the slidable contact region of the protrusion 11 is merely changed to the other side (left side in the figure) as compared with the slidable contact position 17 of FIG. Thus, the protrusion 11 is formed such that the position of the sliding contact region changes according to the elastic deformation of the seal lip 10 based on the oil temperature change.

  When the oil temperature is within a predetermined range, the protrusion 11 has a sliding contact region within a specific range B indicated by an arrow in FIG. The height H of the protrusion 11 is constant within the specific range B. The protrusion 11 does not have a portion higher than the specific range B. The size (maximum value) of the gap 16 shown in FIG. 4 with respect to the direction perpendicular to the seal sliding surface 7 (radial direction in the example shown in the figure and the vertical direction in the figure) must take the oil film thickness t into consideration. For example, the height H of the protrusion 11 in the specific range B is determined. That is, the size of the gap 16 is the height direction of the protrusion from the sum of the height H of the protrusion 11 and the oil film thickness t (minimum oil film thickness) in the sliding contact area of the protrusion 11 in the fluid lubrication state. It is considered to be determined by subtracting the amount of elastic deformation.

  The oil film thickness t in the slidable contact region of the protrusion 11 increases as the surface pressure in the slidable contact region of the protrusion 11 decreases as shown in the numerical analysis results described above, and the surface pressure in the slidable contact region increases. The higher the thickness, the thinner. The surface pressure in the sliding contact region of the protrusion 11 is determined according to the area of the sliding contact region, and the area is determined according to the circumferential length of the protrusion 11 in the sliding contact region. Since the specific range B that can be a slidable contact area on the protrusion 11 is an arc shape in a cross section along the circumferential direction, the slidable contact area at a certain position is set based on the setting of the radius of curvature of the arc and the center of curvature. The circumferential length and height of the projection 11 can be determined.

  Therefore, as shown in FIG. 1, the protrusion 11 is formed in a shape that gradually increases in the circumferential direction toward one side (opposite the lip tip 14) in the radial direction.

  For example, FIG. 4 shows an arc shape in the slidable contact region 17 of FIG. 3, whereas FIG. 7 shows an arc shape in the slidable contact region 18 of FIG. The radius of curvature R shown in FIG. 7 is made larger than the radius of curvature R shown in FIG. 4, and the center of curvature O shown in FIG. 7 is closer to the solid portion 12 side than the position of the center of curvature O shown in FIG. By changing the position, the height H of the protrusion 11 in the cross section shown in FIG. 4 and the height H of the protrusion 11 in the cross section shown in FIG. 7 are made the same, and the protrusion 11 in the cross section shown in FIG. The circumferential length Lr of the protrusion 11 in the cross section shown in FIG. 7 can be made larger than the circumferential length Lr. Thus, the sliding contact region of the protrusion 11 has an arc shape in a cross section along the circumferential direction, and the radius of curvature R of the arc shape is directed to one side (the side opposite to the lip tip 14) shown in FIG. Is set large.

  The change in the circumferential length of the protrusion 11 shown in FIG. 1 is that the seal sliding surface 7 and the oil film are moved at an oil temperature within a predetermined range, that is, in a sliding contact region at any position within the specific range B shown in FIG. When sandwiched, the oil film thickness t (see FIGS. 4 and 7) is set to be maintained within a certain range. The change in the circumferential length of the protrusion 11 is theoretically preferably set so that the oil film thickness t can be maintained at a constant value. Actually, thermal expansion of the seal lip 10 occurs behind the change of the oil temperature, and pressure fluctuation between the bearing internal space and the outside may affect the elastic deformation of the seal lip 10, and the oil film thickness t Although it is difficult to maintain a strictly constant value, it is possible to maintain the oil film thickness t within a certain range.

  The minimum value within a certain range allowed as the oil film thickness t is set to a value that can maintain the fluid lubrication state between the protrusion 11 and the seal sliding surface 7. This minimum value can be set, for example, to a value that is larger than the root mean square roughness of the combined sliding contact area of the seal sliding surface 7 and the protrusion 11, and preferably three times or more. Here, the root mean square roughness refers to the root mean square roughness Rq defined in JIS standard B0601: 2013.

  The maximum value in a certain range allowed as the oil film thickness t is set to a value that can keep the gap 16 below a certain value. This maximum value may be determined according to a desired particle size to be prevented from passing through the gap 16. For example, the value obtained by subtracting the elastic deformation amount in the height direction of the protrusion from the sum of the height H at the sliding contact position of the protrusion 11 and the oil film thickness t at the maximum value in the certain range is less than the desired particle size. The maximum value can be set as follows.

  The oil seal and the bearing with seal are as described above, and are illustrated in FIGS. 3 and 6 when the seal lip 10 of the seal member 1 and the counterpart member 2 shown in FIG. As described above, the protrusion 11 has a sliding contact region that sandwiches the seal sliding surface 7 and the oil film in any one of the specific ranges B. When the oil temperature rises within a predetermined range, an oil film thinning action occurs due to a decrease in the viscosity of the lubricating oil. However, the position of the sliding contact region of the protrusion 11 moves to one side within the specific range B (right side in the figure, waist 15 side). As a result, the circumferential length of the protrusion 11 in the sliding contact region is increased, the surface pressure in the sliding contact region is reduced, and the oil film is easily formed thick. 7) is maintained within a certain range (preferably a constant value). On the other hand, when the temperature falls within a predetermined range, an oil film thickness increasing action occurs due to an increase in the viscosity of the lubricating oil. However, the position of the sliding contact region of the protrusion 11 is the other side in the specific range B shown in FIG. Lip tip 14 side), the circumferential length of the protrusion 11 in the sliding contact area is shortened, the surface pressure in the sliding contact area is increased, and the oil film is easily formed thinly. t (see FIGS. 4 and 7) is maintained within a certain range (preferably a constant value). As long as the oil film thickness t is within a certain range, the fluid lubrication state between the protrusion 11 and the seal sliding surface 7 is maintained, and the size of the gap 16 is maintained below a certain value. Therefore, the oil seal and the bearing with seal can realize low torque by fluid lubrication and required sealing performance at an oil temperature within a predetermined range.

  Further, since the oil seal and the bearing with seal are the same in the entire range (specific range B) in which the height H of the protrusion 11 can maintain the oil film thickness t within a certain range, the oil film thickness in the certain range. The size of the gap 16 can be determined based on the maximum value of the thickness t and the desired sealability (foreign particle size), and the gap 16 can be easily kept below a certain level.

  Further, as shown in FIG. 1, the oil seal and the bearing with seal have a shape in which the protrusion 11 gradually increases in the circumferential direction toward one side (the side opposite to the lip tip 14). The surface pressure change due to the change in length becomes continuous, and the oil film thickness t (see FIGS. 4 and 7) can be easily maintained in a certain range according to the oil temperature change.

  Further, in the oil seal and the bearing with seal, since the height H of the protrusion 11 (see FIGS. 4 and 7) is 0.01 mm or more, the wedge effect is effectively obtained under the general use conditions of the bearing. 1 can be generated, and when the seal lip 10 shown in FIG. 1 is manufactured with a mold, the protrusion 11 can be formed reliably, and the height H of the protrusion 11 (FIG. 4). ) (See FIG. 7) is less than 0.10 mm (preferably 0.08 mm or less, more preferably 0.05 mm or less). ) Can be effectively prevented.

  In addition, if the particle size of the foreign matter contained in the lubricating oil in the bearing internal space 3 is 50 μm or less, the life ratio of the rolling bearing (ratio of the actual life to the calculated life) is a value that can sufficiently withstand practical use in the transmission of an automobile. (For example, about 7 to 10 times). In the oil seal and the bearing with seal, the height H of the protrusion 11 (see FIGS. 4 and 7) is 0.01 mm or more and less than 0.10 mm (preferably 0.01 mm or more and 0.08 mm or less, more preferably 0). .01 mm or more and 0.05 mm or less), which is particularly suitable for securing the sealing performance of the bearing in practical use in an automobile transmission.

  A second embodiment according to the present invention will be described with reference to FIG. In the following, only the differences from the first embodiment will be described, and the corresponding components with the first embodiment will be used with the same names.

  As shown in FIG. 8, the protrusion end 22 located on the other side of the protrusion 20 (the left side in the figure, the lip tip 21 side) is in the vicinity of the lip tip 21 and is the lowest of the protrusions 20, It has no substantial height. The protrusion 20 has a height changing portion 23 that gradually decreases toward the other side (left side in the figure). The height changing portion 23 is arranged on the other side of the protrusion 20 in a range that becomes a sliding contact region based on the oil temperature change. That is, the height changing portion 23 becomes a sliding contact region in a continuous region (lowest temperature region) including the lowest temperature in the allowable oil temperature range. The height change portion 23 and the protrusion end 22 are continuously lowered from the height change portion 23 toward the other side (left side in the figure), but this interval does not become a sliding contact area.

  The height changing portion 23 has a shape that gradually decreases in the circumferential direction toward the other side (left side in the drawing). Since the circumferential direction length change in the height changing portion 23 is different only in the method of setting the radius of curvature and the center of curvature as in the first embodiment, the illustration and explanation thereof is omitted.

  In the second embodiment, since the height changing portion 23 that becomes a sliding contact region in the lowest temperature region is a shape that decreases toward the other side (left side in the drawing) and shortens in the circumferential direction, The expansion of the gap described above can be suppressed by shortening the circumferential length of the protrusion 20, and the gap described above can be narrowed by reducing the height, thereby preventing an excessive gap.

  8 shows an example in which a part of the protrusion 20 is the height changing portion 23, but the entire range allowed as a sliding contact area in the protrusion 20 is lower toward the other side and shorter in the circumferential direction. It is also possible to change to a shape.

  In the first embodiment and the second embodiment described above, the slidable contact region on the protrusion is formed in an arc shape in a cross section along the circumferential direction, but is changed to another protrusion shape that can realize fluid lubrication by the wedge effect. Is also possible.

  A third embodiment as an example thereof will be described with reference to FIGS. FIG. 9 shows the natural state in the vicinity of the protrusion 30 as in FIG. 1, and the upper side in the figure corresponds to one side (the side opposite to the lip tip 31). FIG. 10 shows a cross section along the circumferential direction of the sliding contact area on the protrusion 30. The oil film is not shown.

  As shown in FIG. 10, the slidable contact area on the protrusion 30 is rectangular in cross section along the circumferential direction. As shown in FIG. 9, the circumferential length Lrb of the base 32 in the rectangular shape is gradually set longer toward one side (upper side in the figure). Thereby, the circumferential direction length change of the protrusion 30 is implement | achieved.

  A fourth embodiment will be described with reference to FIGS. The fourth embodiment shows a modification example to yet another projection shape. FIG. 11 shows the natural state in the vicinity of the protrusion 40 as in FIG. 1, and the upper side in the figure corresponds to one side (the side opposite to the lip tip 41). FIG. 12 shows a cross section along the circumferential direction of the sliding contact area on the protrusion 40. The oil film is not shown.

  As shown in FIG. 12, the slidable contact area on the protrusion 40 has a shape having an inclined side 42 in a cross section along the circumferential direction. The inclined side 42 has a gradient gradually approaching the seal sliding surface 7 in the relative rotation direction A. The circumferential length and height of the bottom side 43 extending in the circumferential direction from the inclined side 42 are constant at any position on the protrusion 40 in FIG. As shown in FIG. 11, the circumferential length Lrt of the inclined side 42 in the cross-sectional shape is gradually set longer toward one side (upper side in the figure). Thereby, the circumferential direction length change of the protrusion 40 is implement | achieved.

  Changes in the circumferential length of the protrusions can change the circumferential length in the surface area that contributes to the wedge effect that affects the surface pressure, i.e., the surface area that forms a wedge-shaped gap with the seal sliding surface. Thus, the surface pressure can be effectively increased or decreased. As long as the protrusions are symmetrical in the circumferential direction as exemplified in the first to third embodiments, the low torque performance and the sealing performance described above are equivalent regardless of the direction in which the lubricating oil is dragged by the relative rotation. Is more advantageous than the circumferentially asymmetric protrusions as exemplified in the fourth embodiment. Instead, in the case of a symmetric protrusion in the circumferential direction, the surface area on the protrusion forming the wedge-shaped gap is limited to about half of the circumferential length of the protrusion, whereas the protrusion has the same circumferential length. In the case of the projection shape of the fourth embodiment (see FIG. 12), the most part of the circumferential length of the projection 40 is the inclined side 42, and the wedge-shaped gap can be formed relatively long in the circumferential direction. This is advantageous in that the pressure can be increased or decreased relatively.

  An example in which the bearing with seal corresponding to any of the above-described embodiments supports the rotating shaft of the transmission of an automobile is shown in FIG. The illustrated transmission is a multi-stage transmission in which the gear ratio is changed stepwise, and the above-described embodiment is used as the bearing 100 with a seal that rotatably supports the rotation shaft (for example, the input shaft S1 and the output shaft S2). It has one that falls under either. The illustrated transmission includes an input shaft S1 to which engine rotation is input, an output shaft S2 provided in parallel with the input shaft S1, and a plurality of gear trains G1 to G4 that transmit the rotation from the input shaft S1 to the output shaft S2. Each of the gear trains G1 to G4 and a clutch (not shown) incorporated between the input shaft S1 or the output shaft S2, and the gear trains G1 to G4 used by selectively engaging the clutches. This changes the speed ratio of the rotation transmitted from the input shaft S1 to the output shaft S2. The rotation of the output shaft S2 is output to the output gear G5, and the rotation of the output gear G5 is transmitted to a differential gear or the like. Each of the input shaft S1 and the output shaft S2 is rotatably supported by a bearing 100 with a seal. The transmission was splashed or injected by splashing of lubricating oil (for example, transmission oil) accompanying rotation of the gear or by injection of lubricating oil from a nozzle provided inside the housing H. Lubricating oil is applied to the side surface of each bearing 100 with seal.

  In the above-described embodiment, the inner ring rotating type bearing has been described as an example. However, the present invention is applied to an outer ring rotating type bearing (a bearing in which the seal member is fixed to the inner ring and the counterpart member is on the outer ring side). It is also possible.

  Further, in the above-described embodiment, the description has been given by taking as an example a type of bearing that uses balls as rolling elements, but the present invention may be applied to a type of bearing that uses cylindrical rollers or tapered rollers as rolling elements. Good.

  Moreover, although the above-mentioned embodiment demonstrated the example which provided the sealing member in the both sides of the bearing internal space, you may make it provide a sealing member only in the one side of a bearing internal space.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. Accordingly, the scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Seal member 2 Opposite member 3 Bearing inner space 4 Outer ring 5 Rolling body 7 Seal sliding surface 8 Metal core 9 Rubber material 10 Seal lip 11, 20, 30, 40 Protrusion 12 Solid part 13 Surface part 16 Gap 17, 17 Sliding Contact area 23 Height change part 32 Bottom side 42 Inclined side 100 Sealed bearing S1 Input shaft (rotating shaft)
S2 Output shaft (rotary shaft)

Claims (10)

A seal member having a seal lip formed of a rubber material, and a mating member that rotates relative to the seal member in the circumferential direction;
A tightening margin is set between the seal sliding surface formed on the mating member and the seal lip,
The seal lip has a plurality of protrusions in sliding contact with the seal sliding surface in a fluid lubricated state at predetermined intervals in the circumferential direction,
In the oil seal in which the position of the sliding contact region of the protrusion sandwiching the seal sliding surface and the oil film changes according to the elastic deformation of the seal lip based on an oil temperature change,
The protrusion has a shape in which the circumferential length increases toward one side that changes the position of the sliding contact region based on an increase in oil temperature, and the circumferential length of the protrusion is an oil within a predetermined range. It changes so that the thickness of the oil film can be maintained within a certain range at a temperature, and the minimum value of the certain range is set to maintain the fluid lubrication state, and the maximum value of the certain range is An oil seal characterized by being set so that a gap between a surface portion between the circumferentially adjacent projections of the seal lip and the seal sliding surface can be kept below a certain level.   The oil seal according to claim 1, wherein the height of the protrusion is the same in the entire range in which the thickness of the oil film within the certain range can be maintained.   The protrusion has a height changing portion that becomes lower toward the other side opposite to the one side and becomes shorter in the circumferential direction, and the height changing portion is a range that becomes the sliding contact region based on an oil temperature change. The oil seal according to claim 1, wherein the oil seal is disposed on the most other side.   The slidable contact region on the protrusion has an arc shape in a cross section along the circumferential direction, and the radius of curvature of the arc shape is set to be larger toward the one side. Oil seal as described in the section.   The said sliding contact area | region on the said protrusion is rectangular shape in the cross section along the circumferential direction, The circumferential direction length of the said rectangular base is set long toward the said one side. The oil seal according to any one of the above.   The slidable contact region on the protrusion has a shape having an inclined side in a cross section along a circumferential direction, and a circumferential length of the inclined side is set longer toward the one side. 4. The oil seal according to any one of 3 above.   The oil seal according to any one of claims 1 to 5, wherein the protrusion has a shape that gradually increases in the circumferential direction toward the one side.   The oil seal according to any one of claims 1 to 7, wherein a height of the protrusion is 0.01 mm or more and less than 0.10 mm.   A bearing with a seal, comprising the oil seal according to any one of claims 1 to 8, wherein the seal member separates the bearing internal space from the outside.   The bearing with a seal according to claim 9 which supports a rotating shaft of an automobile transmission.

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