Patent Application
20080106041
The present invention relates to a seal structure of rotation member having a seal lip which is fixed to one of a rotatable member and a fixed member and is in relatively slidable contact with the other member.
There has been known a seal structure of rotation member having a seal lip which is fixed to one of a rotatable member and a fixed member and is in relatively slidable contact with the other member. Such a seal structure has a function to prevent invasion of water and dust into a bearing unit and to prevent leakage of grease from a bearing unit when the seal structure is mounted at both sides of a rolling element of a roll bearing unit.
Grease is applied where a seal lip is in relatively slidable contact so as to make both of them contact smoothly and slidably.
The following patent document 1 describes such a structure that a slinger which is mounted on a bearing unit and is fixed to a rotatable member and a seal lip which is fixed to a fixed member and slidable contacts with the slinger are combined. It also discloses that a part to which the tip end of the seal lip slidably contacts is a smooth surface to ensure sealing ability.
In these days, many attempts to improve the fuel consumption of automobiles have been done and the reduction of rotary torque for the bearing parts of axle has been expected.
The above-mentioned grease applied to the slidably contact surface of the slinger and the seal lip has comparatively high base oil kinematic viscosity like 70 to 75 mm2/sec at 40 degrees centigrade (40° C.) considering the sealing ability. Application of such a grease keeps the sealing ability and makes smooth slidable contact. However, the torque caused by the viscosity resistance of grease cannot be ignored, thereby failing to meet the requirement of improving the fuel consumption.
When the part to which the tip end of the seal lip is in slidable contact is a smooth surface as mentioned in the patent document 1, the sealing ability is secured, however, the friction resistance is enlarged to increase the rotary torque.
When the surface of the tip end of the seal lip is transcribed with a mold with a concave-convex treatment and is surface-finished with a sandblast or a sandpaper to make rough surface, it is assumed that the friction resistance at the part to which a slinger slidably contacts is reduced, thereby being effective for reducing the torque.
However, when the surface of the tip end is roughened with a mold with a concave-convex treatment, the concave-convex surface of the mold is worn after several moldings and the concave-convex surface of the product (seal lip) is disappeared, thereby losing the effect of torque reduction. As to the method of making rough surface with a sandblast or a sandpaper, the quality is varied because the treatment surface is an elastic material such as rubber, thereby causing variation in the quality and productivity problems.
The present invention is proposed in order to solve the above-mentioned problems and the present invention is characterized of a seal structure of a rotation member which keeps the sealing ability of a seal member and makes able to reduce the torque.
According to the first aspect of the present invention, a seal structure of rotation member having a seal lip which is fixed to one of a rotatable member and a fixed member and relatively slidable contacts with the other member is characterized in that a surface to which the seal lip slidably contacts is applied with grease having basic oil kinematic viscosity of 10 to 60 mm2/sec at 40° C. and that plural concavo-convex dimples are formed on the surface to which the seal lip slidably contacts.
According to the second aspect of the present invention, a seal structure of rotation member having a seal lip which is fixed to one of a rotatable member and a fixed member and has relatively slidable contact with the other is characterized in that a surface to which the seal lip slidable contacts is applied with grease having basic oil kinematic viscosity of 10 to 30 mm2/sec at 40° C.
According to the third aspect of the present invention, the seal structure of rotation member described in the second aspect is characterized in that plural concavo-convex dimples are formed on the surface to which the seal lip slidably contacts.
According to the fourth aspect of the present invention, the seal structure of rotation member described in the first and third aspects is characterized in that the surface roughness Ra of the surface to which the seal lip slidably contacts is 0.5 to 1.5 μm.
According to the fifth aspect of the present invention, the seal structure of rotation member described in any one of the first, third or fourth aspect is characterized in that the dimple is formed by way of collision method of minute rigid particles.
According to the sixth aspect of the present invention, the seal structure of rotation member described in any of above aspects is characterized in that the rotatable member and the fixed member constitute a bearing unit.
According to the seventh aspect of the present invention, the seal structure of rotation member described in the sixth aspect is characterized in that the other member is a rotatable member with a metal slinger and the seal lip relatively slidable contacts with the metal slinger.
According to the first aspect of the seal structure of a rotation member of the present invention, grease with basic oil kinematic viscosity of 10 to 60 mm2/sec at 40° C. is applied on the surface to which the seal lip is in slidably contact, thereby enabling to reduce the rotary torque while keeping the sealing ability. Further, the surface to which the seal lip slidably contacts is formed with plural concave-convex surface dimples, so that the grease is kept in the concave-convex parts. The oil film of grease is not destroyed even when the pressure caused by the seal lip is acted on the surface to which the seal lip is in slidable contact, so that the torque can be remarkably reduced while further keeping the sealing ability by the multiple effect of such grease with the above basic oil kinematic viscosity.
Meanwhile, when the basic oil kinematic viscosity at 40° C. becomes lower than 10 mm2/sec, the fluidity of grease is increased, the grease is not kept in the concave-convex parts to be dispersed from the slidably contact surface by the rotary slidable contacting actions, thereby reducing the sealing ability and increasing the friction resistance. Further, when the basic oil kinematic viscosity at 40° C. becomes larger than 60 mm2/sec, the viscosity resistance is enlarged, so that the grease is strongly kept on the concave-convex surface and the reduction effect of torque is reduced.
According to the second aspect of the seal structure of rotation member of the present invention, grease with basic oil kinematic viscosity of 10 to 30 mm2/sec at 40° C. is applied on the surface to which the seal lip slidably contacts, thereby enabling to remarkably reduce the rotary torque while keeping the sealing ability without having a concave-convex surface on the surface to which the seal lip slidably contacts.
Meanwhile, when the basic oil kinematic viscosity at 40° C. becomes lower than 10 mm2/sec, the fluidity of grease is increased, the grease is dispersed from the slidably contact surface by the rotary sliding and contacting actions, thereby reducing the sealing ability and increasing the friction resistance. Further, when the basic oil kinematic viscosity at 40° C. becomes larger than 30 mm2/sec, the remarkable reduction effect of rotary torque is not achieved.
According to the third aspect of the seal structure of rotation member of the present invention, the surface to which the seal lip is in slidable contact is formed with plural concave-convex dimples. The grease is kept in the concave-convex parts and the oil film of the grease is not destroyed when the pressure caused by the seal lip is acted on the slidably contact surface, and the torque is reduced while further keeping the sealing ability by the multiple effect with the grease with the above-mentioned base oil kinematic viscosity.
According to the fourth aspect of the seal structure of rotation member of the present invention, the asperity Ra of the surface to which the seal lip is in slidable contact is preferably set at 0.5-1.5 μm. If it is less than 0.5 μm, the retention capacity of grease near the smooth surface is reduced and the grease loss and friction resistance increase are caused. If it is larger than 1.5 μm, the surface becomes too rough, thus deteriorating the sealing ability.
According to the fifth aspect of the seal structure of rotation member of the present invention, many dimples are formed on the slidably contact surface by way of collision method of minute rigid particles, thereby easily forming the dimples.
According to the sixth aspect of the seal structure of rotation member of the present invention, the rotatable member and the fixed member comprise a bearing unit. If the present invention is applied to the bearing unit of automobiles, the vehicle consumption is improved while keeping such sealing ability that prevents invasion of water and dust into the bearing unit and prevents leakage of grease from the bearing unit.
According to the seventh aspect of the seal structure of rotation member of the present invention, if the seal lip is designed to have relatively slidable contact with a metal slinger, the rotary torque is remarkably reduced while keeping the sealing ability like the aspects mentioned above.
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Now the preferred embodiments of the present invention are explained hereinafter referring to the drawings.
A preferred embodiment of the present invention is explained.
The reference numeral 4 is an outer wheel which is fixed to a suspension of vehicle body (not shown). Two rows of rolling elements (balls) 5 . . . are interposed between the outer wheel 4 and the inner wheel (the hub 3 and the inner wheel member 33) so as to be retained with a retainer 51. The reference numerals 6, 9 are seal members mounted in a rolling portion of the rolling elements 5 . . . in order to prevent leakage of grease (lubricant agent like grease and so on) and to prevent invasion of dirt and water from outside and they are pressed between the outer wheel 4 and the inner wheel (the hub 3 and the inner wheel member 33).
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A seal lip 8 is pressed in the corresponding position in the slinger 7. The seal lip 8 comprises a core member 80 made of stainless steel or low-carbon steel and a lip body 81 made of elastic material like rubber which is integrally formed with the core member 80. The lip body 81 includes plural lip portions 82 . . . extending like a tongue and the tip ends of the lip portions 82 . . . elastically contact with the surface of the slinger 7 accompanied with elastic deformation when the slinger 7 and the seal lip 8 are fitted in each other to consist the seal member 6. Thus constructed seal lip 8 is pressed in the circumference body (inner circumference) of the outer wheel 4.
The seal member 6 is thus comprised of the slinger 7 and the seal lip 8. The surface of the lip portions 82 . . . which elastically contacts with the slinger 7 becomes a seal surface sliding each other accompanied with the rotation of the inner wheel (hub 3 and the inner wheel member 33), thereby preventing invasion of dirt or water into the bearing unit 1 from outside and preventing leakage of grease filled in the bearing unit 1. In the figure, three lip portions 82 are provided, however the shape of the lip portion 82 is not limited to it. In addition, the structure of the lip portion 82 is not limited in the embodiment shown in the figure. Three lip portions 82 may elastically contact with the slinger 7 as shown in
The seal structure of the present invention is characterized in that a slidable contact surface 73 of the slinger 7 and the seal lip 8 is applied with grease G having basic oil kinematic viscosity of 10 to 60 mm2/sec at 40° C. and a convexo-concave surface provided with plural dimples is formed on the slidable contact surface 73.
The grease G to be applied may be ester, synthetic hydrocarbon, mineral oil, or mixture of ester and mineral oil, however it is not limited to them.
The above value of basic oil kinematic viscosity is based on the experiment which is described hereinafter. If it is within the range from 10 to 60 mm2/sec at 40° C., the torque can be reduced while keeping the sealing ability. Further, if the grease G has the basic oil kinematic viscosity within the range from 10 to 30 mm2/sec at 40° C., remarkable torque reduction effect can be achieved without forming the dimples 73a mentioned hereinafter on the slidable contact surface 73 of the slinger 7 to the seal lip 8.
The production method of such plural dimples 73a . . . is not limited. It may be formed by shot peening such that minute rigid particles are collided or it may be formed such that the minute rigid particles formed as a steel ball having the diameter from 40 to 200 μm are sprayed to be collided at the spray speed of 100 m/sec or above.
Providing such plural dimples 73a . . . , the grease G is kept in the space formed with the dimple 73a to keep the oil film even when the pressure is applied in case of relative slidable contact at high speed with the tip end of the lip portion 82, thereby reducing the sliding resistance and resistance coefficient. Therefore, the restraining effect of heat generation can be expected as well as the torque can be reduced.
If the asperity Ra (JIS BO601-2001) of the slidable contact surface 73 of the slinger 7 in this case is 0.5 to 1.5 μm, the sealing ability is kept and the torque is reduced, thereby being most preferable.
In the above embodiment, the minute rigid particles for forming the dimples 73a . . . are steel balls, however, small balls made of other metal, glass, ceramic and so on may be used depending on the material of the surface to be processed. The material of the surface to be processed includes metal sheet of stainless steel, rolled plate (SPCC) and so on.
The seal member 9 is not specifically described above, however, if it is constructed similar to the seal member 6, the torque reduction effect and the fuel consumption improvement effect become more remarkable.
It goes without saying that the present invention can be applied not only to the bearing unit 1 shown in the figure but also to the bearing structure in which the inner wheel is fixed and the outer wheel is rotatable.
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In the embodiment 1 mentioned above, the seal member 6 is constructed such that the metal singer 7 fixed to the rotatable side and the seal lip 8 which is in relatively slidable contacted with the slinger 7 fixed to the rotatable side. However, this embodiment explains a seal structure such that the slinger 7 is not provided and the seal lip 8 itself consists a seal member 6. The common members to the embodiment 1 have the same reference numerals and their explanations are omitted here.
The seal lip 8 is pressed in the inner circumference of the outer wheel 4 being a fixed member so as to be fixed. The seal lip 8 comprises a core member 80 made of stainless steel, low-carbon steel, or the like and a lip body 81 made of elastic material like rubber which is integrally formed with the core member 80. The lip body 81 is provided with plural lip portions 82 . . . extending like a tongue. The tip ends of the lip portions 82 . . . are elastically contacted with the slidable contact surface 73 of the inner wheel member 33 accompanied with elastic deformation.
This embodiment relates to the seal structure with the seal lip 8 for a rotation member. It is characterized in that the slidable contact surface 73 of the inner wheel member 33 to which the seal lip 8 slidably contacts is applied with grease having the basic oil kinematic viscosity of 10 to 60 mm2/sec at 40° C. This embodiment is common to the embodiment 1 in that the slidable contact surface 73 is a concavo-convex surface with plural dimples and the surface asperity Ra is from 0.5 to 1.5 μm. It goes without saying that the plural dimples may be formed by colliding minute rigid particles. Further, the present invention can be applied not only to the bearing unit 1 shown in the figure but also to the bearing structure in which the inner wheel is fixed and the outer wheel is rotatable.
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The embodiment 2 mentioned above shows the seal structure in which the slinger is not provided and the seal lip 8 itself consists a seal member 6. In this embodiment 3, the seal lip 8 is similarly constructed and the surface to which the seal lip 8 slidably contacts is different. The common members to the embodiments 1 and 2 have the same reference numerals and their explanations are omitted here.
In this embodiment, the seal lip 8 is pressed in the inner circumference of the outer wheel 4 being a fixed member so as to be fixed, like the embodiment 2. The seal lip 8 comprises a core member 80 made of stainless steel, low-carbon steel, or the like and a lip body 81 made of elastic material like rubber and so on which is integrally formed with the core member 80 so as to cover the core member 80. The lip body 81 is provided with plural lip portions 82 . . . extending like a tongue. The tip end of the lip portions 82 . . . elastically contacts with the side wall (the slidable contact surface 73) of a circumferencial groove formed on the inner wheel member 33 accompanied with elastic deformation.
This embodiment relates to the seal structure of rotation member provided with the seal lip 8 which slidably contacts with the side wall of the circumferential groove 33a. It is characterized in that the slidable contact surface 73 to which the seal lip 8 slidably contacts is applied with grease having the basic oil kinematic viscosity of 10 to 60 mm2/sec at 40° C. This embodiment is common to the embodiment 1 in that the slidable contact surface 73 is a concavo-convex surface with plural dimples and the asperity Ra is from 0.5 to 1.5 μm. It goes without saying that the plural dimples may be formed by colliding minute rigid particles. Further, the present invention can be applied not only to the bearing unit 1 shown in the figure but also to the bearing structure in which the inner wheel is fixed and the outer wheel is rotatable.
5 pieces of seal member with surface process comprised of a slinger and a seal lip were prepared, the slinger being made of SUS430 and being dimple processed such that steel balls having the diameter from 40 to 200 μm were sprayed to be collided to the slidably contact surface to the seal lip at the spray speed of 100 m/sec or above so as to have the asperity Ra of 0.85 μm, and the seal lip being molded with NBR. Further 5 pieces of seal member without surface process comprised of a slinger without dimple process and a seal lip were prepared. Grease having basic oil kinematic viscosity of 15.3 to 74.7 mm2/sec was applied on each seal member. 10 kinds of samples were prepared as shown in
It has been found that, as mentioned above, if the slinger is not surface treated, when grease with basic oil kinematic viscosity of 15.3 mm2/sec is applied thereon, the torque can be reduced at about 35% of the current product (without surface treatment, basic oil kinematic viscosity of grease: 74.7 mm2/sec). Further, when the basic oil kinematic viscosity is 25.5 mm2/sec, the torque can be reduced at about 30%. When the basic oil kinematic viscosity is 30.5 mm2/sec, the torque can be reduced at about 20%. However, in this case, it can be the that the torque is remarkably reduced when the slinger is surface treated.
On the other hand, it has been found that, providing surface treatment, when the basic oil kinematic viscosity is 48.1 mm2/sec, the torque can be reduced at about 25% of the current product; when the basic oil kinematic viscosity is 30.5 mm2/sec, the torque can be reduced at about 40%; when the basic oil kinematic viscosity is 25.5 mm2/sec, the torque can be reduced at about 40%; and further when the basic oil kinematic viscosity is 15.3 mm2/sec, the torque can be reduced at about 45%. Using the existing grease (basic oil kinematic viscosity: 74.7 mm2/sec), if the slinger is provided with surface treatment, the torque can be reduced at about 20%, however, it is not remarkably effective comparing with other experimental data.
Therefore, if the slinger is surface treated, it is effective to have basic oil kinematic viscosity of 10 to 60 mm2/sec.
From the above experimental data, it has been found that the torque can be reduced by applying a grease having lower basic oil kinematic viscosity than a current grease (basic oil kinematic viscosity: 74.7 mm2/sec). Further when the slidably contact surface is provided with surface treatment, in addition to the effect of grease, the torque can be more remarkably reduced.
Further, it has been found that the torque can be effectively reduced at the basic oil kinematic viscosity of 10 to 30 mm2/sec if the slinger is not surface treated, and at the basic oil kinematic viscosity of 10 to 60 mm2/sec if the slinger is surface treated.
The above mentioned basic oil kinematic viscosity shows that of grease at 40° C.
The present invention is applied to a seal structure of rotation member having a seal lip which is fixed to one of a rotatable member and a fixed member and has slidable contact with the other member.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-364677 | Dec 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/23144 | 12/16/2005 | WO | 00 | 1/9/2008 |
