Wheel bearing device

Abstract

To provide a wheel bearing device capable of achieving both of low friction in straight running of a vehicle and high rigidity in turning the vehicle.SOLUTION: A wheel bearing device 1 includes: an outer ring 2 having double row outer raceway surfaces 2c, 2d on an inner periphery; a hub ring 3 having an inner raceway surface 3c at an outer side opposed to the outer raceway surface 2d at an outer side; an inner ring 4 having an inner raceway surface 4a at an inner side opposed to the outer raceway surface 2c at an inner side; an inner-side ball train 5 and an outer-side ball train 6 having a plurality of balls 7 rollably housed between both raceway surfaces of the outer ring 2, the hub ring 3 and the inner ring 4; and a plug 11 press-fitted to a groove portion 3j of the hub ring 3 to elastically deform the hub ring 3, so as to reduce a groove curvature radius on a contact position of the balls 7 in turning the vehicle, of the inner raceway surface 3c at the outer side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] One of the performance requirements for wheel bearing devices is bearing rigidity, which contributes to driving stability. In order to increase bearing rigidity, a certain level of high preload, i.e., a large negative clearance in the bearing, is necessary. However, increasing the preload increases the contact surface pressure between the rolling elements and the raceway surface, which not only increases the rolling friction of the bearing, which affects vehicle fuel efficiency, but also reduces the bearing life if the preload is excessive. For this reason, technologies have been proposed that attempt to achieve both of these contradictory characteristics.

[0003] For example, Patent Document 1 discloses a wheel bearing device having an inner raceway surface formed in an arc shape with multiple radii of curvature, a so-called compound groove curvature, so as to provide a high preload in response to changes in the contact angle of the rolling elements when the vehicle turns.

[0004] Furthermore, Patent Document 2 discloses a wheel bearing device that is made more rigid by making the outer raceway surface, which is subjected to a high load when the vehicle turns, larger in diameter than the inner raceway surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-9895 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-345439 Summary of the Invention [Problem to be solved by the invention]

[0006] However, according to Patent Document 1, the inner raceway surface having a compound groove curvature is formed by cutting or the like, making it difficult to process, measure, and guarantee the accuracy in mass production. Also, according to Patent Document 2, the number of rolling elements on the outer side increases, making it difficult to reduce friction.

[0007] An object of the present invention is to provide a wheel bearing device that can achieve both low friction when the vehicle is traveling straight and high rigidity when the vehicle is cornering. [Means for solving the problem]

[0008] The bearing device for a wheel of the present invention is a bearing device for a wheel comprising: an outer member having a double-row outer raceway surface on its inner circumference; an inner member having a double-row inner raceway surface opposing the double-row outer raceway surface; and a double-row rolling row having a plurality of rolling elements accommodated in a rollable manner between the raceway surfaces of the outer member and the inner member, characterized in that it comprises a plug that is pressed into the inner peripheral surface of the inner member to elastically deform the inner member and change the radius of curvature of the groove at a position on the inner raceway where the rolling elements contact when the vehicle turns, to a smaller diameter; or that is pressed into the outer peripheral surface of the outer member to elastically deform the outer member and change the radius of curvature of the groove at a position on the outer raceway where the rolling elements contact when the vehicle turns, to a smaller diameter. [Effects of the Invention]

[0009] According to the present invention, the plug can be used to accurately form the desired raceway surface with a compound groove curvature, thereby achieving both low friction when the vehicle is traveling straight and high rigidity when the vehicle is cornering. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a wheel bearing device according to an embodiment; [Figure 2] FIG. 2 is a partially enlarged view of FIG. [Figure 3] FIG. 10 is a cross-sectional view of a wheel bearing device according to a first modified example. [Figure 4]FIG. 10 is a cross-sectional view of a wheel support bearing device according to a second modified example. [Figure 5] FIG. 10 is a cross-sectional view of a wheel bearing device according to a third modification. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Overall configuration of wheel bearing device] The overall configuration of the wheel support bearing device 1 will be described using Figure 1. In the following description, the inner side refers to the vehicle body side of the wheel support bearing device 1 when attached to the vehicle body, and the outer side refers to the wheel side of the wheel support bearing device 1 when attached to the vehicle body. The axial direction refers to the direction along the rotation axis R of the wheel support bearing device 1. The axially outer side refers to the direction away from the annular space S along the rotation axis R, and the axially inner side refers to the direction approaching the annular space S along the rotation axis R. Therefore, in the inner-side ball row 5, the axially outer side is the inner side, and the axially inner side is the outer side. In the outer-side ball row 6, the axially outer side is the outer side, and the axially inner side is the inner side. The radially outer side refers to the direction away from the rotation axis R, and the radially inner side refers to the direction approaching the rotation axis R.

[0012] The wheel bearing device 1 shown in Fig. 1 is a bearing device for a driven wheel that rotatably supports a wheel in the suspension of a vehicle such as an automobile. The wheel bearing device 1 has a configuration known as a third generation, and includes an outer ring 2 as an outer member, a hub ring 3 and an inner ring 4 as inner members, two rolling rows of inner ball rows 5 and outer ball rows 6, an inner seal member 9 and an outer seal member 10.

[0013] The outer ring 2 supports the hub wheel 3 and the inner ring 4. An inner side opening 2a is formed at the inner side end of the outer ring 2, into which an inner side seal member 9 can be fitted. An outer side opening 2b is formed at the outer side end of the outer ring 2, into which an outer side seal member 10 can be fitted. An inner side outer raceway surface 2c and an outer side outer raceway surface 2d are formed in the circumferential direction on the inner peripheral surface of the outer ring 2. A vehicle body mounting flange 2e is formed integrally with the outer peripheral surface of the outer ring 2, for mounting the outer ring 2 to a vehicle body member. Bolt holes 2g are formed in the vehicle body mounting flange 2e, into which fastening members (here, bolts) are inserted to fasten the vehicle body member and the outer ring 2.

[0014] The hub wheel 3 rotatably supports a vehicle wheel and brake rotor (or brake drum) (not shown). The inner end of the outer circumferential surface of the hub wheel 3 is provided with a small diameter step 3a that extends in the axial direction and changes to a small diameter. A wheel mounting flange 3b for mounting a wheel is formed integrally with the outer end of the hub wheel 3. Bolt holes 3f are formed in the wheel mounting flange 3b, into which hub bolts are press-fitted to fasten the hub wheel 3 to the wheel or brake components.

[0015] The hub wheel 3 is provided with an outer inner raceway surface 3c that faces the outer outer raceway surface 2d of the outer ring 2. A seal land 3d with which the lip of the outer seal member 10 slides is formed on the base side of the wheel mounting flange 3b of the hub wheel 3.

[0016] An inner ring 4 is provided on the small diameter step 3a of the hub ring 3. The inner ring 4 is fixed to the small diameter step 3a of the hub ring 3 by press fitting and crimping. The inner ring 4 applies preload to the inner ball row 5 and the outer ball row 6. A crimped portion 3h is formed at the inner end of the hub ring 3, where the inner end face of the inner ring 4 is crimped.

[0017] An inner raceway surface 4a is formed on the outer peripheral surface of the inner ring 4. In other words, the inner raceway surface 4a is formed by the inner ring 4 on the inner side of the hub ring 3. The inner raceway surface 4a faces the outer raceway surface 2c on the inner side of the outer ring 2. A fitting surface 4b is formed on the outer peripheral surface at the inner end of the inner ring 4, into which an inner-side seal member 9 can be fitted.

[0018] The inner ball row 5 and outer ball row 6, which are rolling rows, are formed by a plurality of balls 7, which are rolling elements, being held in a cage 8. The inner ball row 5 is rollably sandwiched between the inner raceway surface 4a of the inner ring 4 and the inner-side outer raceway surface 2c of the outer ring 2. The outer ball row 6 is rollably sandwiched between the inner raceway surface 3c of the hub ring 3 and the outer-side outer raceway surface 2d of the outer ring 2. In other words, the inner ball row 5 and the outer ball row 6 are rollably housed between the raceway surfaces of the outer member and the inner member.

[0019] In the wheel bearing device 1, the outer ring 2, the hub ring 3, the inner ring 4, the inner ball row 5, and the outer ball row 6 constitute a double-row angular contact ball bearing.

[0020] The inner seal member 9 and the outer seal member 10 are seal members that close the open ends of the annular space S formed by the outer member and the inner member. The inner seal member 9 is attached to the inner open end of the annular space S formed between the outer ring 2 and the inner ring 4. On the other hand, the outer seal member 10 is attached to the outer open end of the annular space S formed between the outer ring 2 and the hub wheel 3.

[0021] [plug] The wheel bearing device 1 includes an annular groove 3j formed on the inner peripheral surface 3g of the outer hub ring 3 and centered on the rotation axis R; a female thread 3k formed on the inner peripheral surface 3g radially inward of the groove 3j; an annular plug 11 press-fitted into the groove 3j; and a bolt 12 threadedly engaging the female thread 3k to secure the plug 11 in the axial direction. The outer peripheral surface 11a of the plug 11, which has a predetermined interference, is press-fitted into the inner peripheral surface 3g of the hub ring 3, and the plug 11 presses the hub ring 3 radially outward, causing a portion of the inner raceway surface 3c of the outer hub ring 3 to elastically deform radially outward, resulting in the outer inner raceway surface 3c having a compound groove curvature rather than a single curvature. Note that the groove 3j, the female thread 3k, and the bolt 12 are not essential components; it is sufficient that at least the plug 11 is secured to the inner peripheral surface 3g of the hub ring 3.

[0022] The groove 3j is a groove into which the plug 11 can be press-fitted, and is composed of a cylindrical inner circumferential surface 3m whose axis is the rotation axis R, and an annular bottom surface 3n that extends radially inward from the inner end of the inner circumferential surface 3m. The inner circumferential surface 3m is preferably formed with high precision by grinding so as to have a predetermined inner diameter. The groove 3j has the bottom surface 3n, which allows the plug 11 to be accurately positioned in the axial direction.

[0023] The female thread portion 3k is a female thread for fixing the bolt 12 to the hub wheel 3, and is formed from the inner periphery of the bottom surface 3n of the groove portion 3j toward the inside in the axial direction. The bolt 12 is screwed into the female thread portion 3k, and the head of the bolt 12 presses against the plug 11 to fix it.

[0024] The plug 11 is press-fitted into the inner peripheral surface 3m of the groove 3j to elastically deform the hub wheel 3, thereby reducing the radius of curvature of the groove near the groove shoulder on the outer inner raceway 3c, where the balls 7 come into contact when the vehicle turns. The vicinity of the groove shoulder refers to the radially outer edge of the inner raceway surfaces 3c and 4a, and the radially inner edge of the outer raceway surfaces 2c and 2d. The plug 11 is an annular member with a substantially rectangular cross section, and has an outer peripheral surface 11a, an inner peripheral surface 11b, an inner side surface 11d, and an outer side surface 11c.

[0025] The outer peripheral surface 11a is a surface that fits into the inner peripheral surface 3m of the groove portion 3j and has a larger diameter than the inner peripheral surface 3m of the groove portion 3j. The inner peripheral surface 11b is formed with a larger diameter than the female thread portion 3k so as not to interfere with the bolt 12. The inner side surface 11d is a surface that abuts against the bottom surface 3n of the groove portion 3j. By press-fitting the plug 11 until the inner side surface 11d abuts against the bottom surface 3n, the plug 11 can be accurately positioned in the axial direction. The outer side surface 11c is a surface that is pressed by the bolt 12. By having the outer side surface 11c pressed and fixed by the bolt 12, it is possible to prevent the plug 11 from falling off.

[0026] By configuring the plug 11 as an annular member as in this embodiment, it is possible to arrange the plug 11 in a space-saving manner. There are no particular limitations on the shape of the plug 11, and the plug 11 may be, for example, a spherical member having a uniform outer diameter, or a tapered annular member whose outer circumferential surface widens from the axially inner side to the axially outer side.

[0027] The plug 11 is preferably made of a material harder than the hub wheel 3, which is the component to be press-fitted. Examples of such materials that can be used include hardened SUJ2, SK material, and S53C. This suppresses deformation and wear of the plug 11, enabling the outer-side inner raceway surface 3c to be deformed with precision.

[0028] As shown in FIG. 2, the plug 11 is press-fitted onto the inner peripheral surface 3m of the groove 3j, elastically deforming the hub wheel 3 radially outward, thereby reducing the groove curvature radius at position A (groove shoulder of the inner raceway surface 3c) on the outer inner raceway surface 3c where the ball 7 contacts during vehicle cornering. In FIG. 2, surface B shows the inner raceway surface 3c before the plug 11 is press-fitted. In this way, by reducing the groove curvature radius at position A on the inner raceway surface 3c where the ball 7 contacts during vehicle cornering, the negative clearance of the bearing is increased, i.e., the contact surface pressure between the ball 7 and the inner raceway surface 3c is increased (high preload), achieving high rigidity during vehicle cornering. The effect of the plug 11 is greatest on the outer inner raceway surface 3c, which is the raceway surface that receives the greatest load during vehicle cornering.

[0029] In FIG. 2, position C on the inner raceway surface 3c where the ball 7 contacts when the vehicle is traveling straight indicates a position where the negative clearance of the bearing is set small (low preload) for the purpose of reducing friction when the vehicle is traveling straight. The position of the plug 11 is designed so that the groove curvature radius at position C where the ball 7 contacts when the vehicle is traveling straight does not change even when the plug 11 is press-fit. In this embodiment, the inner side surface 11d of the plug 11 is located on the outer side of position A where the ball 7 contacts when the vehicle is turning. This prevents elastic deformation of the raceway surface at position C where the ball 7 contacts when the vehicle is traveling straight, but allows elastic deformation of the raceway surface at position A where the ball 7 contacts when the vehicle is turning. In other words, the inner raceway surface 3c can have a compound groove curvature. The axial position of the plug 11 is not particularly limited, as long as it is located at a position where the inner raceway surface 3c on the outer side can elastically deform to have the desired compound groove curvature.

[0030] According to the above configuration, the inner raceway surface 3c on the outer side can be made to have a compound groove curvature, which makes it possible to achieve both low friction when the vehicle travels straight and high rigidity when the vehicle turns. Furthermore, by using the plug 11, the inner raceway surface 3c having the compound groove curvature can be easily formed with the same precision as by cutting.

[0031] [Method of manufacturing wheel bearing device] In the assembly process of the wheel bearing device 1, after the outer ring 2, hub ring 3, inner ring 4, inner ball row 5, outer ball row 6, inner seal member 9, and outer seal member 10 are assembled and the crimped portion 3h is formed, that is, after the preload applied to the wheel bearing device 1 is determined, the diameter of the inner circumferential surface 3m of the groove 3j, into which the plug 11 is press-fitted, is measured. Then, a plug 11 having an outer diameter corresponding to the measured diameter of the inner circumferential surface 3m is selected and press-fitted. To do this, it is necessary to create data in advance on combinations of the outer diameter of the plug 11 and the inner diameter of the groove 3j that will result in the desired amount of deformation of the inner raceway surface 3c, and to produce plugs 11 with various outer diameters.

[0032] This allows the plug 11 to be selected with an optimum outer diameter depending on the variation in the inner diameter of the groove 3j. Therefore, the inner raceway surface 3c can be made to have a complex groove curvature with high precision. Furthermore, by measuring the inner diameter of the groove 3j after determining the preload applied to the wheel bearing device 1, precision is improved.

[0033] It is also possible to use plugs 11 with one type of outer diameter and not measure the diameter of the inner circumferential surface 3m of groove 3j. It is also possible to assemble plug 11 to hub wheel 3 alone in advance.

[0034] [Variation 1] 3 is a cross-sectional view of a wheel support bearing device 20 of Modified Example 1. The wheel support bearing device 20 of Modified Example 1 differs from the wheel support bearing device 1 described above in that it includes a groove 3q formed on an inner peripheral surface 3p on the inner side of the hub ring 3, a female thread portion 3r, a plug 21, and a bolt 22. As the other configurations are the same as those of the wheel support bearing device 1, detailed description thereof will be omitted. The groove 3q, the female thread portion 3r, the plug 21, and the bolt 22 are arranged axially symmetrically with the outer side groove 3j, the female thread portion 3k, the plug 11, and the bolt 12, and have the same structure although they are different in size.

[0035] The plug 21 is press-fitted into the groove 3q, elastically deforming the hub ring 3 and the inner ring 4 radially outward, thereby reducing the groove curvature radius at the position on the inner raceway surface 4a on the inner side where the balls 7 come into contact when the vehicle turns (the groove shoulder of the inner raceway surface 4a). This increases the contact surface pressure between the balls 7 and the shoulder of the inner raceway surface 4a (high preload), achieving high rigidity when the vehicle turns.

[0036] The position of the plug 21 is designed so that press-fitting the plug 21 does not change the groove curvature radius at the position where the ball 7 contacts when the vehicle is traveling straight. In this embodiment, the outer side surface 21c of the plug 21 is located on the inner side of the position where the ball 7 contacts when the vehicle is turning. This prevents elastic deformation of the raceway surface at the position where the ball 7 contacts when the vehicle is traveling straight, but allows elastic deformation of the raceway surface at the position where the ball 7 contacts when the vehicle is turning. In other words, the inner raceway surface 4a can be made to have the desired compound groove curvature. There are no particular limitations on the axial position of the plug 21, as long as it is located at a position where the inner raceway surface 4a can be elastically deformed to have the compound groove curvature.

[0037] According to the above configuration, the inner raceway surface 4a on the inner side can be made to have a compound groove curvature, which makes it possible to achieve both low friction when the vehicle travels straight and high rigidity when the vehicle turns. Furthermore, by using the plug 21, the inner raceway surface 4a having the compound groove curvature can be easily formed with the same precision as by cutting.

[0038] In the assembly process of the wheel bearing device 20, after the outer ring 2, hub ring 3, inner ring 4, inner ball row 5, outer ball row 6, inner seal member 9, and outer seal member 10 are assembled and the crimped portion 3h is formed, that is, after the preload applied to the wheel bearing device 20 is determined, the inner diameter of groove 3q, which is the surface into which the plug 21 is press-fitted, is measured. Then, the plug 21 having an outer diameter corresponding to the measured value of the inner diameter of groove 3q is selected and press-fitted. This makes it possible to obtain the same functions and effects as when the plug 11 described above is used.

[0039] [Variation 2] 4 is a cross-sectional view of a wheel support bearing device 30 of modified example 2. The wheel support bearing device 30 is a bearing device for a driving wheel. The wheel support bearing device 30 of modified example 2 differs from the wheel support bearing device 1 described above in that the hub wheel 31 has a through-hole portion 3s that can be spline-fitted with the constant velocity universal joint 90, and the nut 32 that secures the hub wheel 31 to the constant velocity universal joint 90 also secures the plug 11. As the other configurations are the same as those of the wheel support bearing device 1, detailed description thereof will be omitted.

[0040] Therefore, the wheel bearing device 30 for a driving wheel can also achieve the same functions and effects as the wheel bearing device 1 described above.

[0041] [Variation 3] 5 is a cross-sectional view of a wheel support bearing device 40 of Modified Example 3. The wheel support bearing device 40 of Modified Example 3 differs from the wheel support bearing device 30 of Modified Example 2 in that it is provided with an enlarged diameter step 3t formed on the outer peripheral surface of the outer side of the outer ring 2 and extending in the axial direction, and a plug 41 press-fitted into the step 3t; other configurations are the same as those of the wheel support bearing device 30, and therefore detailed description thereof will be omitted.

[0042] The plug 41 is press-fitted into the step 3t to elastically deform the outer ring 2 radially inward, thereby reducing the groove curvature radius at the position on the outer raceway 2d on the outer side where the balls 7 come into contact when the vehicle turns (the groove shoulder of the outer raceway 2d). This increases the contact surface pressure between the balls 7 and the shoulder of the outer raceway 2d (high preload), achieving high rigidity when the vehicle turns.

[0043] The position of the plug 41 is designed so that press-fitting the plug 41 does not change the groove curvature radius at the position where the ball 7 contacts when the vehicle is traveling straight. In this embodiment, the outer side surface 41c of the plug 41 is located on the inner side of the position where the ball 7 contacts when the vehicle is turning. This prevents elastic deformation of the raceway surface at the position where the ball 7 contacts when the vehicle is traveling straight, but allows elastic deformation of the raceway surface at the position where the ball 7 contacts when the vehicle is turning. In other words, the outer raceway surface 2d can have a desired compound groove curvature. There are no particular limitations on the axial position of the plug 41, as long as it is located at a position where the outer raceway surface 2d can be elastically deformed to have the compound groove curvature.

[0044] According to the above configuration, the outer raceway surface 2d on the outer side can be made to have a compound groove curvature, which makes it possible to achieve both low friction when the vehicle travels straight and high rigidity when the vehicle turns. Furthermore, by using the plug 41, the outer raceway surface 2d having the compound groove curvature can be easily formed with the same precision as by cutting.

[0045] In the assembly process of the wheel bearing device 40, the plug 41 is attached to the outer ring 2 alone in advance. At this time, the outer diameter of the step 3t may be measured, and a plug 41 having an inner diameter corresponding to the measurement value may be selected and press-fitted. This makes it possible to select a plug 41 with an optimal inner diameter depending on variations in the outer diameter of the step 3t. This allows the outer raceway surface 2d to have a complex groove curvature with high precision.

[0046] Depending on the position of the vehicle body mounting flange 2e, it is also possible to press a plug into the outer peripheral surface on the inner side of the hub wheel 3, 31. In this case, the plug reduces the groove curvature radius at the position on the inner side outer raceway surface 2c where the balls come into contact when the vehicle turns (groove shoulder portion of the outer raceway surface 2c).

[0047] The above-mentioned wheel bearing devices 1, 20, 30, 40 have been described as wheel bearing devices with a third-generation inner ring rotation structure in which the inner raceway surfaces 3c of the rolling elements are formed directly on the outer periphery of the hub ring 3, 31, but are not limited to this and may, for example, be a second-generation (2.5th generation) inner ring rotation structure in which a pair of inner rings are press-fitted into the hub ring, or a first-generation structure consisting of an outer ring and an inner ring. Also, the above-mentioned wheel bearing devices 1, 20 for driven wheels may be a third-generation outer ring rotation structure or a second-generation (2.5th generation) structure.

[0048] The above-described embodiment merely illustrates a typical form of the present invention, and various modifications can be made without departing from the gist of the present invention. For example, the wheel bearing device may include at least one of the plugs described above. Furthermore, if the wheel bearing device includes multiple plugs, there are no limitations on the combination of plugs. Furthermore, if possible, a step portion may be used instead of a groove portion, and a groove portion may be used instead of a step portion. [Explanation of symbols]

[0049] 1 Wheel bearing device 2 Outer ring (outer member) 2c, 2d outer raceway surface 3 Hub ring (inner part) 3c, 4a Inner raceway surface 4 Inner ring (inner part) 5 Inner ball row (rolling row) 6 Outer ball row (rolling row) 7 Balls (rolling elements)

Claims

1. an outer member having a double-row outer raceway surface on its inner periphery; an inner member having a double-row inner raceway surface facing the double-row outer raceway surface; a double row of rolling elements having a plurality of rolling elements rollably accommodated between the raceway surfaces of the outer member and the inner member, a plug that is press-fitted into an inner peripheral surface of the inner member to elastically deform the inner member and thereby reduce the radius of curvature of the groove at a position on the inner raceway with which the rolling elements contact when the vehicle turns, or that is press-fitted into an outer peripheral surface of the outer member to elastically deform the outer member and thereby reduce the radius of curvature of the groove at a position on the outer raceway with which the rolling elements contact when the vehicle turns.

2. 2. The wheel bearing device according to claim 1, wherein the plug is made of a material harder than either the inner member or the outer member into which it is press-fitted.

3. 3. The wheel bearing device according to claim 1, wherein the inner member or the outer member has a groove or a step into which the plug can be press-fitted.

4. 3. The wheel bearing device according to claim 1, wherein the plug is press-fitted into the inner circumferential surface of the outer side of the inner member to elastically deform the inner member, thereby changing the radius of curvature of the groove on the inner raceway surface on the outer side at a position with which the rolling elements come into contact when the vehicle turns.

5. 3. The wheel bearing device according to claim 1, wherein the plug is an annular member.

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