Wheel bearing device

Abstract

To provide a wheel bearing device which can lower a torque of the wheel bearing device while suppressing the occurrence of raceway surface exfoliation.SOLUTION: A wheel bearing device 1 comprises: an outer ring 2 having outside raceway surfaces 2c, 2d on an internal periphery; an inner member having inside raceway surfaces 3c, 4a; ball rows 5, 6 accommodated between the raceway surfaces of the outer ring 2 and the inner member; an inner-side seal member 10 and an outer-side seal member 20 for closing open ends of an annular space 15 which is formed of the outer ring 2 and the inner member; a first grease G1 applied in the annular space 15; and a second grease G2 applied in a space surrounded by the inner-side seal member 10 and the outer-side seal member 20 and by a hub ring 3. A dynamic viscosity of a second base oil contained in the second grease G2 is lower than that of a first base oil contained in the first grease G1. The dynamic viscosity of the first base oil is 20 to 65 mm2 / s(40°C), and the dynamic viscosity of the second base oil is 10 to 35 mm2 / s(40°C).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a wheel bearing device. [Background technology]

[0002] Conventionally, wheel bearing devices that rotatably support wheels in suspension systems for automobiles and the like are known. In a wheel bearing device, two rows of rolling elements are rotatably housed between the outer raceway surface of an outer member and the inner raceway surface of an inner member. The wheel bearing device is also provided with a sealing device that closes the open end of the annular space formed by the outer and inner members, preventing the entry of foreign matter such as mud and water. Grease is applied to the annular space between the outer and inner members and to the sealing device.

[0003] In recent years, with the tightening of energy regulations, there has been a demand for lower torque in wheel bearing devices in order to improve the fuel efficiency or electric energy consumption of automobiles. As an example of a wheel bearing device that improves low torque performance, Patent Document 1 discloses a wheel bearing device in which a grease with a reduced kinematic viscosity of the base oil is applied to the annular space between the outer member and the inner member. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6268642 [Overview of the project] [Problems that the invention aims to solve]

[0005] As mentioned above, when the kinematic viscosity of the base oil of the grease applied to the annular space of a wheel bearing device is reduced, if the kinematic viscosity of the base oil is reduced too much, for example, the oil film thickness between the raceway surface and the rolling element will decrease, which may cause raceway surface delamination and shorten the lifespan of the wheel bearing device. Therefore, there is a limit to how low the kinematic viscosity of the base oil can be reduced.

[0006] On the other hand, the grease applied inside the sealing device is generally the same type of grease used in the annular space of a wheel bearing device. However, since there is no need to worry about raceway delamination in the sealing device, it is possible to use a grease with an even lower kinematic viscosity of the base oil.

[0007] Therefore, the present invention provides a wheel bearing device that can further reduce torque while suppressing the occurrence of raceway surface delamination by using a grease in the sealing device that has a lower kinematic viscosity of the base oil than the grease applied in the annular space. [Means for solving the problem]

[0008] Specifically, the wheel bearing device comprises an outer member having double rows of outer raceway surfaces on its inner circumference, an inner member having double rows of inner raceway surfaces facing the double rows of outer raceway surfaces, double rows of rolling elements rotatably housed between the raceway surfaces of the outer member and the inner member, a sealing device that closes the open end of the annular space formed by the outer member and the inner member, a first grease applied to the annular space, and a second grease applied to the sealing device, wherein the kinematic viscosity of the second base oil contained in the second grease is smaller than the kinematic viscosity of the first base oil contained in the first grease, and the kinematic viscosity of the first base oil contained in the first grease at 40°C is 20-65 mmHg. 2 The kinematic viscosity of the second base oil contained in the second grease at 40°C is 10-35 mm² / s, and the kinematic viscosity of the second base oil contained in the second grease is 10-35 mm². 2 It is / s. [Effects of the Invention]

[0009] According to the present invention, the frictional resistance of the seal sliding part of the sealing device can be reduced, and while suppressing the occurrence of raceway surface delamination, it is possible to further reduce the torque of the wheel bearing device. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side cross-sectional view showing a wheel bearing device. [Figure 2] It is a side cross-sectional view showing the inner side seal member. [Figure 3] It is a side cross-sectional view showing the outer side seal member.

Embodiments for Carrying out the Invention

[0011] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

[0012] [Wheel Bearing Device] The wheel bearing device 1 shown in FIG. 1 is an embodiment of the wheel bearing device according to the present invention, and rotatably supports a wheel in a suspension device of a vehicle such as an automobile. The wheel bearing device 1 includes an outer ring 2 which is an outer member, a hub ring 3 and an inner ring 4 which are inner members, two rows of inner side ball rows 5 and outer side ball rows 6 which are rolling element rows, an inner side seal member 10, and an outer side seal member 20.

[0013] [[ID=-- --]]ID=22 Here, the inner side refers to the vehicle body side of the wheel bearing device 1 when attached to the vehicle body, and the outer side refers to the wheel side of the wheel bearing device 1 when attached to the vehicle body. Also, the axial direction refers to the direction along the rotation axis of the wheel bearing device 1.

[0014] An inner side opening 2a into which the inner side seal member 10 can be fitted is formed at the inner side end of the outer ring 2. An outer side opening 2b into which the outer side seal member 20 can be fitted is formed at the outer side end of the outer ring 2.

[0015] When the inner side seal member 10 is fitted into the inner side opening 2a, the inner side opening end of the annular space 15 formed by the outer ring 2 and the inner member is blocked. When the outer side seal member 20 is fitted into the outer side opening 2b, the outer side opening end of the annular space 15 is blocked.

[0016] The inner seal member 10 and the outer seal member 20 are sealing devices that close the open ends of the annular space 15 formed by the outer ring 2, which is an outer member, and the inner member. Thus, by closing the inner and outer open ends of the annular space 15 with the inner seal member 10 and the outer seal member 20, a sealing function is exerted to suppress the intrusion of foreign matters such as muddy water into the wheel bearing device 1.

[0017] On the inner peripheral surface of the outer ring 2, an inner outer raceway surface 2c and an outer outer raceway surface 2d are formed. On the outer peripheral surface 2o of the outer ring 2, a vehicle body mounting flange 2e for mounting the outer ring 2 to a vehicle body side member (knuckle) is integrally formed. The vehicle body mounting flange 2e is provided with bolt holes 2f through which fastening members for fastening the vehicle body side member and the outer ring 2 are inserted.

[0018] On the inner side end portion of the outer peripheral surface 3o of the hub ring 3, a small diameter step portion 3a having a smaller diameter than the outer side end portion is formed. On the outer side end portion of the hub ring 3, a wheel mounting flange 3b for mounting a wheel is integrally formed. The wheel mounting flange 3b is provided with bolt holes 3f into which hub bolts are press-fitted.

[0019] On the outer peripheral surface 3o of the hub ring 3, an outer inner raceway surface 3c is provided so as to face the outer outer raceway surface 2d on the outer side of the outer ring 2. Further, in the hub ring 3, a lip sliding surface 3d with which the outer seal member 20 slides is formed on the base side of the wheel mounting flange 3b.

[0020] An inner ring 4 is provided on the small diameter step portion 3a of the hub ring 3. On the outer peripheral surface of the inner ring 4, an inner inner raceway surface 4a is provided so as to face the inner outer raceway surface 2c on the inner side of the outer ring 2.

[0021] The inner ball row 5 and the outer ball row 6, which are rolling elements, are composed of multiple balls 7, which are rolling elements, held by a cage 8. The inner ball row 5 is rotatably sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner outer raceway surface 2c of the outer ring 2. The outer ball row 6 is rotatably sandwiched between the inner raceway surface 3c of the hub ring 3 and the outer outer raceway surface 2d of the outer ring 2.

[0022] A first grease G1 is applied to the interior of the annular space 15. The first grease G1 is applied mainly between the inner ball row 5 and the inner raceway surface 4a and the outer raceway surface 2c, and between the outer ball row 6 and the inner raceway surface 3c and the outer raceway surface 2d.

[0023] In the wheel bearing device 1, a double-row angular contact ball bearing is formed by an outer ring 2, a hub ring 3 and an inner ring 4, an inner ball row 5, and an outer ball row 6. The wheel bearing device 1 may also be composed of a double-row tapered roller bearing.

[0024] [Inner side sealing member] As shown in Figure 2, the inner sealing member 10 includes a core metal 11, an elastic member 12, and a slinger 13. The core metal 11 is made of, for example, a steel plate and has a cylindrical fitting portion 11a that is fitted to the inner diameter of the inner opening 2a of the outer ring 2, and an annular side plate portion 11b that extends inward from the outer end of the fitting portion 11a.

[0025] The elastic member 12 is made of, for example, synthetic rubber and is fixed to the core metal 11 by vulcanization bonding. The elastic member 12 has a base portion 121 that is vulcanized and bonded to the core metal 11, and a grease lip 122, a first side lip 123, and a second side lip 124 that extend from the base portion 121 and are each formed in an annular shape. The grease lip 122, the first side lip 123, and the second side lip 124 are sealing lips of the elastic member 12.

[0026] The grease lip 122 is positioned on the innermost side of the seal lip of the elastic member 12 and extends from the base 121 toward the inner and outer sides. The first side lip 123 is positioned on the outermost side of the seal lip of the elastic member 12 and extends from the base 121 toward the outer and inner sides. The second side lip 124 is positioned further inward than the first side lip 123 and further outward than the grease lip 122, and extends from the base 121 toward the outer and inner sides.

[0027] The slinger 13 is made of, for example, a steel plate and has a cylindrical fitting portion 13a that is fitted to the inner end of the inner ring 4, and an annular side plate portion 13b that extends from the inner end of the fitting portion 13a toward the outer diameter.

[0028] The grease lip 122 of the elastic member 12 is in slidable contact with the fitting portion 13a of the slinger 13. The first side lip 123 and the second side lip 124 of the elastic member 12 are in slidable contact with the side plate portion 13b of the slinger 13. The surface of the fitting portion 13a facing the grease lip 122, and the surface of the side plate portion 13b facing the first side lip 123 and the second side lip 124 are sliding surfaces into which the seal lip of the elastic member 12 slidably contacts. Furthermore, the space formed by the seal lip of the elastic member 12 and the sliding surface of the slinger 13 is the internal space of the inner side seal member 10.

[0029] The inner sealing member 10 is coated with a second grease G2. Specifically, the second grease G2 is applied, for example, between the grease lip 122 and the fitting portion 13a of the slinger 13, and between the first side lip 123 and the second side lip 124 and the side plate portion 13b of the slinger 13. In other words, the second grease G2 is applied within the internal space of the inner sealing member 10.

[0030] [Outer side sealing member] As shown in Figure 3, the outer sealing member 20 has a core metal 21 and an elastic member 22. The core metal 21 is made of, for example, a steel plate and is cylindrical in shape, and is fitted to the outer opening 2b of the outer ring 2.

[0031] The elastic member 22 is made of, for example, synthetic rubber and is fixed to the core metal 21 by vulcanization bonding. The elastic member 22 has a base portion 221 that is vulcanized and bonded to the core metal 21, and a grease lip 222, a first side lip 223, and a second side lip 224 that extend from the base portion 221 and are each formed in an annular shape. The grease lip 222, the first side lip 223, and the second side lip 224 are sealing lips of the elastic member 22.

[0032] The grease lip 222 is located on the innermost side of the seal lip of the elastic member 22 and extends inward from the base 221. The first side lip 223 is located on the outermost side of the seal lip of the elastic member 22 and extends inward from the base 221. The second side lip 224 is located on the innermost side of the seal lip of the elastic member 223 and on the outermost side of the grease lip 222 and extends inward from the base 221.

[0033] The grease lip 222, the first side lip 223, and the second side lip 224 of the elastic member 22 are in slidable contact with the lip sliding surface 3d of the hub wheel 3. The lip sliding surface 3d is the sliding surface into which the seal lip of the elastic member 22 slidably contacts. The space formed by the seal lip of the elastic member 22 and the lip sliding surface 3d of the hub wheel 3 is the internal space of the outer side seal member 20.

[0034] The outer sealing member 20 is coated with a second grease G2. Specifically, the second grease G2 is applied, for example, between the grease lip 222, the first side lip 223, and the second side lip 224 of the elastic member 22 and the lip sliding surface 3d of the hub wheel 3. In other words, the second grease G2 is applied within the internal space of the outer sealing member 20.

[0035] [First grease and second grease] The first grease G1 contains a first base oil and a first thickener. As the first base oil, for example, a base oil consisting of mineral oil and synthetic hydrocarbon oil can be used. Alternatively, as the first base oil, a base oil consisting solely of synthetic hydrocarbon oil, i.e., a base oil containing 100% synthetic hydrocarbon oil, can be used. As the synthetic hydrocarbon oil of the first base oil, for example, poly-α-olefin or polybutene can be used. From the viewpoint of low torque properties, it is preferable to use poly-α-olefin as the synthetic hydrocarbon oil.

[0036] When a base oil consisting solely of synthetic hydrocarbon oil is used as the first base oil, it has advantages such as being less affected by temperature and reducing the rotational torque at the coated area, compared to when a base oil consisting of mineral oil and synthetic hydrocarbon oil is used.

[0037] The first base oil has a kinematic viscosity of 20-65 mmHg at 40°C. 2 The value is / s. The kinematic viscosity of the first base oil at 40°C can be measured in accordance with JIS K 2220 23.

[0038] As the first thickener, for example, a urea compound, which is an organic compound having a urea group, or a lithium complex, which is a soap produced by reacting lithium hydroxide with a fatty acid and a dibasic acid, can be used. As the urea compound, for example, a diurea compound having two urea groups can be used.

[0039] The first grease G1 may contain additives such as antioxidants, anti-wear agents, and rust inhibitors. For example, an amine antioxidant can be used as the antioxidant. For example, an amine phosphate can be used as the anti-wear agent. For example, an amine compound can be used as the rust inhibitor. The first grease G1 may contain other additives as appropriate.

[0040] The second grease G2 contains a second base oil and a second thickener. As the second base oil, for example, a base oil consisting of mineral oil and synthetic hydrocarbon oil can be used. Alternatively, as the second base oil, a base oil consisting solely of synthetic hydrocarbon oil, i.e., a base oil containing 100% synthetic hydrocarbon oil, can be used. As the synthetic hydrocarbon oil for the second base oil, for example, poly-α-olefin or polybutene can be used. From the viewpoint of low torque properties, it is preferable to use poly-α-olefin as the synthetic hydrocarbon oil.

[0041] When a base oil consisting solely of synthetic hydrocarbon oil is used as the second base oil, it has advantages such as being less affected by temperature and reducing the rotational torque at the coated area, compared to when a base oil consisting of mineral oil and synthetic hydrocarbon oil is used.

[0042] The second base oil has a kinematic viscosity of 10-35 mm at 40°C. 2 The value is / s. The kinematic viscosity of the second base oil at 40°C can be measured in accordance with JIS K 2220 23.

[0043] As the second thickener, for example, a urea compound, which is an organic compound having a urea group, or a lithium complex, which is a soap produced by reacting lithium hydroxide with a fatty acid and a dibasic acid, can be used. As the urea compound, for example, a diurea compound having two urea groups can be used.

[0044] The second grease G2 may contain additives such as antioxidants, anti-wear agents, and rust inhibitors. For example, amine antioxidants can be used as antioxidants. For example, amine phosphates can be used as anti-wear agents. For example, amine compounds can be used as rust inhibitors. The second grease G2 may contain other additives as appropriate.

[0045] The components of the first base oil, first thickener, and additives in the first grease G1 may be the same as those of the second base oil, second thickener, and additives in the second grease G2. However, some or all of the components of the first base oil, first thickener, and additives in the first grease G1 may be different from those of the second base oil, second thickener, and additives in the second grease G2.

[0046] The kinematic viscosity of the second base oil contained in the second grease G2 is lower than that of the first base oil contained in the first grease G1 applied to the annular space 15 of the wheel bearing device 1. As a result, the second grease G2 is a lower viscosity grease than the first grease G1.

[0047] In other words, in the wheel bearing device 1, the kinematic viscosity of the first base oil in the first grease G1 and the kinematic viscosity of the second base oil in the second grease G2 are set such that the kinematic viscosity of the second base oil contained in the second grease G2 applied to the inner seal member 10 and the outer seal member 20 is smaller than the kinematic viscosity of the first base oil contained in the first grease G1 applied to the annular space 15 of the wheel bearing device 1.

[0048] Thus, in the wheel bearing device 1, since the kinematic viscosity of the second base oil is lower than that of the first base oil, the shear stress of the second grease G2 can be reduced compared to the case where the kinematic viscosity of the second base oil and the kinematic viscosity of the first base oil are set to the same magnitude. As a result, the frictional resistance of the sealing sliding parts of the inner side seal member 10 and the outer side seal member 20 can be reduced, and the rotational torque of the wheel bearing device 1 can be reduced overall.

[0049] In the inner seal member 10 and the outer seal member 20, there is no need to worry about the occurrence of raceway surface delamination. Therefore, by using a second grease G2 in the inner seal member 10 and the outer seal member 20, in which the kinematic viscosity of the second base oil is lower than that of the first base oil, it is possible to further reduce the torque of the wheel bearing device 1 while suppressing the occurrence of raceway surface delamination.

[0050] The sealing sliding portion of the inner sealing member 10 is the sliding portion of the sealing lip of the inner sealing member 10 against the slinger 13, and the sealing sliding portion of the outer sealing member 20 is the sliding portion of the sealing lip of the outer sealing member 20 against the lip sliding surface 3d.

[0051] In particular, in the wheel bearing device 1, the kinematic viscosity of the first base oil in the first grease G1 is set to 20-65 mm². 2 Set a small value such as / s (40℃) and set the kinematic viscosity of the second base oil in the second grease G2 to 10-35 mm². 2 By setting an even smaller value such as / s(40℃), it is possible to further reduce the rotational torque of the wheel bearing device 1.

[0052] The amount of the second grease G2 applied to the inner sealing member 10 and the outer sealing member 20 is 50 wt% or less of the amount of the first grease G1 applied to the annular space 15.

[0053] If a large amount of the low-viscosity second grease G2 mixes with the first grease G1 applied in the annular space 15, it will cause adverse effects such as a reduction in the lifespan of the wheel bearing device 1. Therefore, it is preferable to reduce the application amount of the second grease G2 relative to the application amount of the first grease G1. Thus, in the wheel bearing device 1, the application amount of the second grease G2 is set to 50 wt% or less relative to the application amount of the first grease G1, suppressing adverse effects such as a reduction in the lifespan of the wheel bearing device 1.

[0054] In the wheel bearing device 1, it is more preferable that the application amount of the second grease G2 applied to the inner side seal member 10 and the outer side seal member 20 is 20 wt% or less relative to the application amount of the first grease G1 applied in the annular space 15.

[0055] Note that the application amount of the second grease G2 applied to the inner side seal member 10 and the application amount of the second grease G2 applied to the outer side seal member 20 are about the same.

[0056] (First Embodiment of the First Grease and the Second Grease) In the wheel bearing device 1, an urea-based grease having a kinematic viscosity at 40°C of the first base oil of 63 mm 2 / s is used as the first grease G1 and applied in the annular space 15, and an urea-based grease having a kinematic viscosity at 40°C of the second base oil of 18 mm 2 / s can be used as the second grease G2 and applied to the inner side seal member 10 and the outer side seal member 20.

[0057] (Second Embodiment of the First Grease and the Second Grease) In the wheel bearing device 1, an urea-based grease having a kinematic viscosity at 40°C of the first base oil of 63 mm 2 / s is used as the first grease G1 and applied in the annular space 15, and an urea-based grease having a kinematic viscosity at 40°C of the second base oil of 18 mm 2A lithium complex grease with a viscosity of / s can be used as the second grease G2 and applied to the inner sealing member 10 and the outer sealing member 20.

[0058] In the wheel bearing device 1, the difference between the kinematic viscosity of the first base oil in the first grease G1 at 40°C and the kinematic viscosity of the second base oil in the second grease G2 at 40°C is 30 mm 2 It is preferable that the kinematic viscosity is less than / s. Thus, the difference between the kinematic viscosity of the first base oil at 40°C and the kinematic viscosity of the second base oil at 40°C is 30 mm. 2 By setting it to a small value less than / s, it is possible to reduce the adverse effects that occur when the second grease G2 mixes with the first grease G1.

[0059] (Third embodiment of the first and second greases) In the wheel bearing device 1, the kinematic viscosity of the first base oil at 40°C is 31 mmHg. 2 A urea-based grease with a viscosity of / s is used as the first grease G1 and applied to the annular space 15, and the kinematic viscosity of the second base oil at 40°C is 18 mm². 2 A urea-based grease with a viscosity of / s can be used as the second grease G2 and applied to the inner sealing member 10 and the outer sealing member 20.

[0060] In this embodiment, the wheel bearing device 1 is configured as a third-generation wheel bearing device 1 in which the inner raceway surface 3c is directly formed on the outer circumference of the hub ring 3. However, it is not limited to this, and may also be a second-generation structure in which a pair of inner rings 4 are press-fitted and fixed to the hub ring 3.

[0061] Although embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, but is merely illustrative. It can be implemented in various other forms without departing from the spirit of the invention, and the scope of the present invention is indicated by the claims, and further includes all modifications within the meaning and scope of equivalents as described in the claims. [Explanation of Symbols]

[0062] 1. Wheel bearing device 2 Outer ring 2c (Inner side) outer raceway surface 2d (Outer side) outer raceway surface 3 Hub wheels 3c (Outer side) Inner raceway surface 3D lip sliding surface 4. Inner Ring 4a (Inner side) Inner raceway surface 5. Inner ball row 6 Outer ball row 7 Ball 10 Inner side sealing member 13 Slinger 15. Ring space 20 Outer side sealing member 122 Grease slip (of the inner sealing component) 123 (First side lip of the inner sealing member) 124 (Second side lip of the inner sealing member) 222 Grease slip (of outer sealing member) 223 (First side lip of outer sealing member) 224 (Second side lip of outer sealing member) G1 First Grease G2 Second Grease

Claims

1. An outer member having double rows of outer raceway surfaces on its inner circumference, An inner member having double rows of inner raceway surfaces opposite to the double rows of outer raceway surfaces, A double row of rolling elements is rotatably housed between the raceway surfaces of the outer member and the inner member, A sealing device that closes the open end of the annular space formed by the outer member and the inner member, The first grease applied within the annular space, The second grease is applied to the internal space of the sealing device, A wheel bearing device comprising, The internal space of the sealing device is the space formed by the seal lip of the sealing device and the lip sliding surface of the inner member that contacts the seal lip. The first thickener contained in the first grease and the second thickener contained in the second grease are different. The kinematic viscosity of the second base oil contained in the second grease is smaller than the kinematic viscosity of the first base oil contained in the first grease. The kinematic viscosity of the first base oil contained in the first grease at 40°C is 20 to 65 mm². ２ / s, The kinematic viscosity of the second base oil contained in the second grease at 40°C is 10 to 35 mm². ２ / s, A wheel bearing device characterized in that the amount of the second grease applied is 50 wt% or less of the amount of the first grease applied.

2. The wheel bearing device according to claim 1, wherein the first base oil of the first grease and the second base oil of the second grease contain 100% synthetic hydrocarbon oil.

3. The difference between the kinematic viscosity of the first base oil at 40°C and the kinematic viscosity of the second base oil at 40°C is 30 mm. ２ A wheel bearing device according to claim 1 or claim 2, wherein the value is less than / s.

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