Patent Application
20110097027
(a) Field of the Invention
The present invention relates to an outer ring for a wheel bearing. More particularly, the present invention relates to an outer ring for a wheel bearing, which can attain optimal structural strength by applying dimensions within an allowable threshold range to a supporting end, extending end, ring groove, and step surface of the outer ring and thereby prolonging a theory service life of the bearing.
(b) Description of the Related Art
Generally, a wheel bearing is a device that is connected between a suspension system and driving system of a vehicle to support the load of the vehicle and effectively rotates wheels. The wheel bearing is assembled between a hub and a knuckle to form a wheel bearing assembly.
The following will describe a typical wheel bearing assembly to which an outer ring for a wheel bearing according to a related art with reference to
As shown in
As shown in
Therefore, in a state where the hub 10 is splined to the spindle 7, the hub 10 is coupled to the wheel (not shown) of the vehicle by a flange 9 formed on an outer diameter surface thereof to transfer the torque of the driving shaft 3 to the wheel of the vehicle.
Hereinafter, In
The following will describe the typical wheel bearing assembly shown in
A lubricant is filled in a space defined between the outer and inner rings 33 and 31 and seal members 39 are installed between first ends of the inner and outer rings 33 and 31 and between second ends of the inner and outer rings 33 and 31 to prevent foreign substances from coming into the space and to prevent the lubricant filled in the space from leaking to an external side.
In order for the outer ring 33 of the bearing 30 to be fitted to the knuckle 20, the knuckle 20 is provided with the inner diameter portion 21 formed on a front end thereof. The inner diameter portion 21 is provided at an outer front end thereof with a protruding portion 23 for preventing the outer ring 33 of the bearing 30 from being separated outward in an axial direction. The inner diameter portion 21 is further provided at an inside thereof with an groove portion 25 in which a snap ring 41 for preventing the outer ring 33 of the bearing from being separated inward in the axial direction is installed.
In addition, the hub 10 includes a hub body 10a. The seating portion 11 to which the inner ring 31 of the bearing 30 is fitted is formed on an outer diameter surface of the inner side of the hub body 10a. The flange 9 extends along the outer diameter surface in a diameter direction of the hub body 10a and is connected to the wheel by a hub bolt B. Here, the hub body 10a is provided at an outer end portion thereof with a cap installing end 13 on which a hub cap (not shown) is installed. The hub body 10a is further provided at the inner diameter surface thereof with a spline S1 to which the spindle 7 is splined.
The following will describe an assembling process of the typical wheel bearing assembly 1. First, the bearing 30 is pressed into the inner diameter portion 21 of the knuckle 20 in a direction from the inner side to the outer side until the bearing 30 can be disposed on the protruding portion 23 and the snap ring 41 is inserted into the groove portion 25 formed on the knuckle 20 to assemble the bearing 30 on the knuckle 20.
After assembling the bearing on the knuckle 20, the hub 10 is pressed toward the inner ring 31 of the bearing 30 from the outer side to the inner side until the inner ring 31 is completely fitted to the seating portion 11 of the hub 10.
At this point, the spline S1 formed on the inner diameter surface of the hub body 10a is engaged with the spline S1 formed on the outer diameter surface of the spindle 7.
In this state, a spindle nut 45 is screw-coupled to a screw portion of the spindle 7 exposed to the inside of the cap installing end 13 to connect the wheel bearing assembly 1 to the spindle 7. At this point, an outer end 5b of an joint housing 5a of the constant velocity joint 5 axially supports the inner ring 31 of the bearing 30, and in this connection state, an inner gap of the bearing 30 is adjusted by tightening torque of the spindle nut 45.
There are a variety of factors that determines the service life of the bearing 30. Among the factors, the inner gap of the bearing 30 is the most important factor determining the service life of the bearing 30. That is, it is very important to accurately adjust the inner gap when mounting the bearing 30.
Meanwhile, the typical wheel bearing assembly 1 shown in
As described above, the typical wheel bearing assembly 1 is configured such that, since the inner bent front end 47 of the hub 10 that is orbital-formed has predetermined strength, the inner gap of the bearing 30 is not highly affected by coupling torque of the spindle nut 45.
However, in the typical wheel bearing assembly 1, due to the constitution of the protruding portion 23 formed on the outer-front end of the inner diameter portion 21 of the knuckle 20 and the structural characteristics of the outer ring 33 of the bearing 30, the bearing 30 is first assembled on the knuckle 20 and is then the hub 10 is assembled on the bearing 20. Therefore, there is still a drawback that the raceways 33a and 31a of the bearing 30 are damaged by the management of the fitting apparatus in the course of assembling of the hub 10 on the bearing 30. Furthermore, the orbital forming process must be preformed after the knuckle 20, hub 10, and bearing 30 are all assembled with each other. Therefore, it is inconvenient to perform the orbital forming process.
In addition, the outer ring 33 applied to the above-described typical bearing assembly 1 is affected by turning force Fc (i.e., a lateral direction load) that is generated when the vehicle is making a turn. The turning force Fc acts in the axial direction of the wheel bearing assembly 1 and is transferred from the hub 10 to the outer ring 33 through the rolling elements 35 of the bearing 30.
The turning force Fc transferred to the outer ring 33 is further transferred to the knuckle 20 through the snap ring 41 that is an inner supporting point of the outer ring 33.
At this point, since the outer ring 33 does not has an outer supporting point for the knuckle 20, the outer ring 33 is deformed based on a center of the snap ring 41 that is the inner supporting point at a section S where the load F by the turning force Fc is transferred.
The deformed section S of the outer ring 33 by the turning force Fc is relatively long ranging from a contact center between the outer rolling element 35 of the bearing 30 to the inner front end of the outer ring 33. That is, the deformation of the outer ring 33 becomes larger even under equal turning force Fc.
Therefore, creep may occur between the outer ring 33 and the knuckle 20. This may cause the abnormal noise.
In order to solve the above-described drawbacks, i.e., the assembling drawback of the typical wheel bearing assembly 1 and the drawback caused by the turning force Fc, as shown in
The new wheel bearing assembly is disclosed in Korean Patent Application No. 10-206-0052175 (Jun. 9, 2006) by an application of this application. The basic structures of the knuckle 2, hub 10, and bearing 30 of the new wheel bearing assembly are identical to those of the typical wheel bearing assembly 1 but the assembling structure between the knuckle 20, bearing 30, and outer ring 33 of the new wheel bearing assembly is improved compared with the typical wheel bearing assembly 1.
That is, in the new wheel bearing assembly, the bearing 30 has a supporting end 51 that protrudes in a diameter direction along an outer diameter surface 34 on an outer end portion of the outer ring 33 to support the outer ring 33 in the fitting direction against the outer front end of the knuckle 20 and a ring groove 53 in which the snap ring 41 is installed and which is formed along an outer diameter surface 34 on a side of an inner portion of the outer ring 33 to support the outer ring 33 in a direction opposite to the fitting direction against the inner front end of the knuckle 20. Instead, the protruding portion 23 and the groove portion 25 that are formed on the knuckle 20 of the typical wheel bearing assembly for the same performance are omitted in the new wheel bearing assembly.
The constitution of the new wheel bearing assembly 1 will be described in more detail in “DETAILED DESCRIPTION OF THE EMBODIMENTS.”
Meanwhile, according to the new wheel bearing assembly 1, when the inner ring 31 of the bearing 30 is supported by orbital-forming the inner front end of the hub 10, the orbital forming is performed in a state where the bearing 30 is first assembled on the hub 10, after which the assembly of the hub 10 and the bearing 30 can be assembled on the knuckle 20 in a direction from an outer side to an inner side.
As described above, as the bearing 30 is first assembled on the hub 10 before assembled on the knuckle 20, it becomes easy to manage the fitting apparatus and thus the problem that the raceways 33a and 31a of the bearing 30 are damaged by the fitting load when the bearing 30 is fitted to the hub 10 can be solved. In addition, since the orbital forming is performed before the bearing 30 is assembled on the knuckle 20, the workability can be improved.
Further, in the new wheel bearing assembly 1, although the turning force Fc generated when the vehicle is making a turn is transferred from the hub 10 to the outer ring 33 through the rolling elements 35 of the bearing 30 and acts as the load F, the load F is transferred to the knuckle 20 as the supporting end 51 formed on the outer end portion of the outer ring 33 becomes the supporting point for the outer front end of the knuckle 20.
Therefore, the deformed section of the outer ring 33 by the turning force Fc moves from the contact center between the outer rolling element 35 of the bearing 30 to the outer front end of the knuckle 20 and thus the deformed section S of the outer ring 33 is reduced. In addition, the deformation of the outer ring 33 by the turning force Fc is also reduced and thus the creep and the abnormal noise caused by the creep can be suppressed.
As described above, the new wheel bearing assembly is designed such that the supporting end 51 formed on an outer side of the outer ring 33 of the bearing 30 and the ring groove 53 in which the snap ring 41 is installed and which is formed inside the outer ring 33 are constituted to change the assembling process. Therefore, the raceway damage problem of the bearing 30 is solved and the workability for the orbital forming process is improved. Further, there is an effect that the deforming section of the outer ring 33 is shifted outward and thus the deformation of the outer ring 33 is reduced.
However, although the new wheel bearing assembly has the above effects, the outer ring 33 has poor theory foundation for a dimension thereof when designing the supporting end 51 and the ring groove 53, it is difficult for the outer ring 33 to have optimal structural strength. Therefore, there is a need to establish theory foundation for a dimension of the supporting end 51 and ring groove 53 of the outer ring 33 within an allowable threshold range.
In addition, according to the new wheel bearing assembly 1, since the protruding portion 23 that has been formed on the knuckle 20 of the typical wheel bearing assembly is omitted, a gap between the inner surface of the flange 9 formed on the hub 10 and the outer front end of the outer ring 33 of the bearing 30 is widened. However, since the installing space for the seal member installed on the bearing 30 is not effectively attained, the space usability of the outer ring 33 is low. Further, since the outer ring 33 is designed such that a diameter of a portion from the ring groove 53 to the inner end portion in a direction where the snap ring 41 is installed is identical to the overall diameter of the outer ring 33, the snap-ring 41 must be greatly deformed to be inserted into the ring groove 53.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
Embodiments have been made in an effort to provide an outer ring for a wheel bearing having advantages of attaining optimal structural strength and thus prolonging a service life of the bearing by establishing theory foundation for dimensions of a supporting end formed on an outer side of an outer diameter surface of the outer ring and a ring groove in which the snap ring is installed which is formed on an inner side of the outer diameter surface and applying optimal dimensions within an allowable threshold range to the supporting end and the ring groove.
Embodiments also provide an outer ring for a wheel bearing having an advantage of improving space usability of the outer ring by attaining an installing space of a seal member installed on the bearing through an extending end formed on an outer front end surface of the outer ring and improving an assembling property of a snap ring by making a portion of the outer ring from a ring groove to an inner front end as a step surface whose diameter is less than an overall diameter of the outer ring.
One embodiment provides an outer ring for a wheel bearing, including a supporting end that is formed on an outer side of an outer diameter surface of the outer ring and supported by an outer end of a knuckle; and a ring groove that is formed on an inner side of the outer ring and supported by an inner end of the knuckle and in which a snap ring is fitted, wherein the supporting end is dimensioned having a thickness of 1 mm or more at which the supporting end has a stress distribution within yield strength of the outer ring and a height above a section where maximum stress is applied to the supporting end under a cornering load condition less than 3 G.
When the thickness of the supporting end is 3 mm or more, the supporting end is dimensioned having a height of 1.65 mm or more.
In addition, a connecting portion between the supporting end and the outer diameter surface of the outer ring may be formed in a curved surface. At this point, the curved surface may be formed at two or more portions between the supporting end and the outer diameter surface of the outer ring.
That is, when the thickness of the supporting end is 4 mm or more, the curved surfaces may be formed at both sides of a flat inclined surface having a predetermined length, including a first curved surface having a curvature radius of 0.5 mm or more with the supporting ends and a second curved surface having a curvature radius of 1.2 mm with the outer diameter surface.
Alternatively, when the thickness of the supporting end is 4 mm or more, the curved surface may be defined by the supporting end and the outer diameter surface of the outer ring, having a curvature radius of 1.2 mm or more.
When a minimum thickness of the snap ring is 0.5 mm, the ring groove may be dimensioned having a depth of 0.5 mm or more,
The ring groove may be formed with a curvature radius of 0.1 mm or more between an inner circumference thereof and both inner surfaces.
Meanwhile, the supporting end may be dimensioned having a thickness of 3 mm or more at which the supporting end has a stress distribution within yield strength of the outer ring and a height above a section where maximum stress is applied to the supporting end under a cornering load condition less than 3 G.
At this point, the supporting end may be dimensioned having a height of 2 mm or more.
The outer ring may further include an extending end extending outward from an outer side front end surface.
The extending end may be dimensioned having a thickness less than a thickness of an outer end portion of the outer ring.
In addition, the extending end may be dimensioned having a length in an axial direction of 0.5 mm or more.
A connecting portion between the extending end and the supporting end may be formed in a curved surface having a curvature radius of 0.1 mm or more.
In addition, the outer ring may further include a step surface formed from the ring groove and an inner end portion, the step surface having an outer diameter less than an overall outer diameter of the outer ring.
A step between the outer diameter surface of the outer ring and the step surface may be dimensioned having 0.1 mm that is a minimum grinding process margin or less.
Exemplary embodiments of the present invention will hereinafter be described in detail with reference to the accompanying drawings.
In the following description of the exemplary embodiments, identical functions and elements to the related art will be assigned with same names and numerical numbers as those of the related art and the detailed description thereof will be omitted.
When describing an outer ring for a wheel bearing according to an exemplary embodiment of the present invention, as shown in
In order to establish theory foundation for a dimension of an outer ring 33 and apply a dimension within an allowable threshold range to the outer ring 33, an overall constitution of a wheel bearing assembly 1 of a first exemplary embodiment, to which a supporting end 51 formed on an outer side of the outer ring 33 and a ring groove 53 in which a snap ring 41 is installed and which is formed on at an outer side of the outer ring 33 are applied will be described with reference to
That is, as shown in
The bearing 30 includes the outer ring 33 having a raceway 33a on an inner diameter surface thereof, an inner ring 31 having a raceway 31a on an outer diameter surface thereof, the rolling elements 35 interposed and rolling between the raceways 33a and 31a of the respective outer and inner rings 33 and 31, seal members 39 that are installed between first ends of the inner and outer rings 33 and 31 and between second ends of the inner and outer rings 33 and 31 to prevent foreign substances from coming into the space and to prevent a lubricant filled in a space between the outer and inner rings 33 and 31 from leaking to an external side, and cages 37 formed along grooves (not shown) in which the rolling elements 35 are inserted and spaced apart from each other in a circumferential direction.
In the wheel bearing assembly 1 for a vehicle, the rolling elements 35 are arranged along two lines (i.e., an outer line and an inner line).
The knuckle 20 is connected to a vehicle body by a suspension (not shown). The knuckle 20 is provided at a front end thereof with an inner diameter 21 within which the outer ring 33 is inserted. The knuckle 20 is further provided at outer and inner end portions with a flat outer and inner ends 27a and 27b.
The hub 10 includes a hub body 10a and a flange 9 for coupling to a vehicle wheel.
The inner ring 31 of the bearing 30 is inserted into an inner side of the outer diameter surface of the hub body 10a. The hub body 10a is provided at an outer end portion thereof with a circular cap installing end 13 along a circumference of the outer end portion so that a hub cap can be mounted on the hub body 10a. The hub body 10a is provided at an inner diameter surface thereof with a spline S1 coupled to a spline S2 of the spindle 7.
In addition, the flange 9 extends along the outer diameter surface of the hub body 10a in a diameter direction and is integrally formed with the hub body 10a so that it can be coupled to the vehicle wheel by a hub bolt B.
At this point, an orbital-forming process where the inner end portion of the hub 10 extends and the front end of the extended inner end is bent outward in the diameter direction is used such that the bent front end 47 can support the inner end of the inner ring 31 in the axial direction and thus the inner gap of the bearing 30 can be pre-adjusted by an orbital forming apparatus that can be precisely controlled.
In the wheel bearing assembly 1 having the above-described structure, as shown in
Describing an assembling process of the wheel bearing assembly 1 to which the above-described outer ring 33 for the wheel bearing is applied, the bearing 30 is fitted to the hub 10 by pressing the bearing 30 in a direction from the inner side to the outer side of the hub 10 such that the inner ring 31 of the bearing 30 is installed in the seating portion 11 of the hub 10.
After the inner ring 31 is installed on the seating portion 11 of the hub 10, the inner side front end of the hub 10 is orbital-formed to support the inner ring 31 of the bearing 30 in an axial direction.
After assembling the bearing 30 and the hub 10, the bearing 30 assembled with the hub 10 is fitted to the inner diameter portion 21 of the knuckle 20 by pressing the bearing 30 in a direction from the outer side to the inner side such that the supporting end 51 of the outer ring 33 is supported by an outer end 27a of the knuckle 20. In a state where the outer ring 33 is completely fitted to the inner diameter portion 21, the snap ring 41 is installed in the ring groove 53 of the outer ring 33 so that the outer ring 33 can be supported by the inner end of the knuckle 20.
At this point, as the spindle 7 of the constant velocity joint 5 is inserted through the inner diameter surface of the hub 10, the spline S2 of the spindle 7 is engaged with the spline S1 formed on the inner diameter surface of the hub 10. In this state, a spindle nut 45 is coupled to a screw portion 43 of the spindle 7 exposed to an inside of the cap installing end 13 of the hub 10, thereby connecting the wheel bearing assembly 1 to the spindle 7.
As described above, as can be noted from an overall structure and assembling process of the wheel bearing assembly 1 to which the outer ring 33 of the first exemplary embodiment is applied, the drawback that the raceways 33a and 31a of the bearing 30 are damaged as in the related art can be solved by changing the assembling order by applying the supporting end 51 and the ring groove 53 that are respectively formed on the outer and inner sides of the outer diameter surface 34 of the outer ring 33 and thus the workability for the orbital forming process can be improved. In addition, the deformed portion of the outer ring 33 by turning force Fc is shifted to the outer side, the deformation of the outer ring 33 can be reduced. However, in order to prolong a theory service life by attaining optimal structural strength determined by dimensions of the supporting end 51 and ring groove 53 on the outer ring 33, optimal dimensions of the supporting end 51 and ring groove 53 within an allowable threshold range must be established.
The optimal dimensions of the supporting end 51 and ring groove 53 within the allowable threshold range and the theory foundation on the optimal dimensions are as follows:
First, in order to establish an optimal dimension (an optimal thickness T and an optimal height H) of the supporting end 51 of the outer ring 33, as shown in
As shown in
Here, since “Axle-Load/2” is applied per tire pitch, the load Fa applied becomes “(930 kgf/2)×6” (i.e., 2,790 kgf) when the gravity of 6 G acts.
Meanwhile, describing the properties of materials of the respective constituent elements of the wheel bearing assembly 1 for the test samples, as shown in
As shown in
Accordingly, the thickness T1 of the supporting end 51, which can be applied under all load conditions (less than 6 G), must be at least 3 mm. The thickness T1 of the supporting end 51, which can be applied under the load condition less than 3 G must be 1 mm or more.
The thickness T1 of the supporting end 51 may be established in proportion to a specification of the outer ring of the first exemplary embodiment.
Meanwhile, as shown in
In the stress distribution between nodes P1 and P2 on the outer diameter surface 34 of the outer ring 33, as shown in a stress graph of
Accordingly, the height H of the supporting end 51, which can be applied under all load conditions, must be 1.65 mm or more when the thickness T1 is 3 mm, preferably, 5 mm or more to attain a minimum contacting sectional area with the knuckle 20.
The height H of the supporting end 51 may be established in proportion to the specification of the outer ring of the first exemplary embodiment.
According to the first exemplary embodiment, the outer ring 33 is provided at the outer side of the outer diameter surface 34 with the supporting end 51 and thus, as shown in
That is, as can be noted from the simulation analysis result shown in
According to the simulation analysis results, as shown in
The stress values are less than 150.9 kgf/mm2 that is the yield strength of the outer ring 33. However, when the curved surface is not provided with the flat inclined surface, the curvature radius R may be 1.2 mm or more. Even when the curved surface is provided with the flat inclined surface, the curvature radius R between the inclined surface and the supporting end 51 may be 0.5 mm or more.
As shown in
At this point, a portion between an inner circumference and both inner surfaces of the ring groove 53 may be formed in the curve surface having a curvature radius of 0.1 mm or more to prevent the generation of the crack.
As described above, as the dimensions of the supporting end 51 and ring groove 53 of the outer ring are established as optimal dimensions within the allowable threshold range according to the theory foundation, the optimal structural strength of the outer ring 33 can be attained and thus the theory service life of the bearing can be prolonged.
As shown in
The outer ring of the second exemplary embodiment further includes an extending end 61 formed on an outer side front end surface thereof in addition to the supporting end 51 and the ring groove 53 of the outer ring 33 of the first exemplary embodiment. The extending end 61 allows a seal member installing space for the seal member installed on the bearing 30 to be attained and thus the space usability of the outer ring 33 can be improved.
A thickness T2 of the extending end 61 may be established to be less than a thickness of an outer end portion of the outer ring 33 and a length L of the extending end 61 may be established to be 0.5 mm or more.
In addition, the connecting portion between the extending end 61 and the supporting end 51 may be formed in a curved surface having a curvature radius of 0.1 mm or more to prevent the generation of crack.
In addition, the outer ring 33 is provided with a step surface 63 such that an inner side end portion of the outer ring 33 has a diameter less than an overall diameter of the outer ring 33 in a direction in which the snap ring 41 is installed from the ring groove 53. Therefore, the interference occurring when the bearing 30 is fitted to the inner diameter portion 21 of the knuckle 20 can be reduced and the assembling property of the snap ring 41 can be improved.
At this point, a step G between the outer diameter surface 34 of the outer ring 33 and the step surface 63 may be less than 0.1 mm that is a minimum grinding process margin. If the step G is 0.1 mm or more, the separation force of the snap ring 41 may increase.
According to the outer ring 33 for the bearing of the second exemplary embodiment, the installing space for the seal member 39 can be sufficiently attained by the extending end 61 and thus the space usability of the outer ring 33 can be improved. In addition, the assembling property of the bearing 30 and the knuckle 20 and the assembling property of the snap ring 41 can be enhanced by the step surface 63.
The outer ring for the bearing according to the present invention has the following effects.
As the optimal dimensions within the allowable threshold range are applied to the supporting end that is formed in a flange shape on an outer side end portion of the outer diameter portion of the outer ring and the ring groove in which the snap ring is installed and which is formed on the inner side of the outer diameter portion by establishing theory foundation on the dimension, the outer ring can attain the optimal structural strength and thus the theory service life of the bearing can be prolonged. Furthermore, it can be expected that the weight of the bearing can be reduced within the scope the bearing attains the sufficient structure strength.
Further, since the extending end is formed on the outer side front end surface, the installing space for the seal member can be sufficiently attained and the space usability can be improved. In addition, the lubricant filling space between the inner and outer rings can be enlarged and thus the cooling efficiency can be enhanced.
Since the step surface having a diameter less than an overall diameter of the outer ring is formed on the outer ring from the ring groove to the inner side front end, the assembling property of the snap ring can be improved and the bearing can be assembled on the inner diameter surface of the knuckle without any interference.
While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
