Patent Publication Number: US-9839962-B2

Title: Processing method for brake rotor-equipped wheel bearing devices

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. application Ser. No. 13/030,711, filed Feb. 18, 2011, which is a divisional of U.S. application Ser. No. 11/494,591, filed Jul. 28, 2006, now U.S. Pat. No. 7,913,374, the entireties of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a processing method for brake rotor-equipped wheel bearing devices, and more particularly it relates to a method for cutting the pad slide surfaces of a brake rotor. 
     2. Brief Description of the Prior Art 
     Wheel bearing devices for automobiles are used for driving wheels and non-driving wheels. At any rate, in wheel bearing devices, the surface runout of the brake surfaces, i.e., the pad slide surfaces, during rotation of the brake rotor, becomes a cause of brake shudder during braking, so that high processing accuracy and high dimensional accuracy are required of the parts of the wheel bearing device. Even if the processing accuracy is increased, however, not only does the processing errors on the parts accumulate during assembly of the wheel bearing device, but also assembling errors are produced, thus making it impossible to suppress the surface runout of the pad slide surfaces of the brake rotor. 
     To eliminate such drawbacks, there has already been proposed a cutting method (U.S. Pat. No. 6,247,219) wherein a brake rotor-equipped wheel bearing device, assembled in a mounted state, is mounted on a cutting machine and, with the brake rotor-equipped wheel bearing device supported in a mounted state, the pad slide surfaces are cut while rotating the brake rotor. 
     According to the above-mentioned conventional method, since the pad slide surfaces of the brake rotor are cut with the brake rotor-equipped wheel bearing device put in a mounted state, the accumulated errors produced by the accumulation of the processing errors of the parts, the strains produced during fixing of the brake rotor, and the like are eliminated by cutting. For this reason, the brake rotor-equipped wheel bearing device is restored to its cutting-completed state by assembling the processed brake-equipped wheel bearing device to an actual car. The surface runout of the pad slide surfaces during rotation of the brake rotor is very small, making it possible to rotate the brake rotor with high accuracy. 
     The conventional processing method for cutting the pad slide surfaces of the brake rotor of a brake rotor-equipped wheel bearing device put in a mounted state is a processing method intended to suppress the surface runout of the pad slide surfaces during rotation of the brake rotor, so as to prevent the occurrence of vibrations during braking. Of the outer and inner members relatively rotating through rolling elements, the outer member is fixed, and in this state the pad slide surfaces of the brake rotor assembled to the inner member are cut. The deformation of the rolling element contact surface during cutting load application causes the runout in the bearing rotation axis and the processing axis, resulting in the corresponding degradation of the surface runout accuracy. Referring to  FIG. 9 , the inner member  6  is rotated with the outer member  2  of a brake rotor-equipped wheel bearing device  1  being held by a chuck device  4 , and the pad slide surfaces  8   a  and  8   b  of a brake rotor  8  are lathed with the reference surface defined by the flange surface  2   a  of the outer member  2 . For this reason, the accuracies (axial runout, rigidity, etc.) of the bearing itself influence the processed brake rotor accuracy. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a method capable of cutting the pad slide surfaces of the brake rotor of a brake rotor-equipped wheel bearing device efficiently with higher accuracy. 
     One aspect of the invention resides in providing a method for cutting the pad slide surfaces of the brake rotor of a brake rotor-equipped wheel bearing device which comprises an outer member having a car body attaching flange in the outer periphery and two rows of raceways in the inner periphery, an inner member consisting of a hub ring having a wheel attaching flange in the outer periphery and an inner ring disposed in the small diameter section of the hub ring, two rows of rolling elements interposed between the raceways of the outer and inner members for relatively rotatably supporting the two members, and a brake rotor fixed to the wheel attaching flange of the hub ring, the method being characterized by comprising the steps of lathing, with the hub ring present singly, the wheel pilot end surface of the hub ring with the reference provided by the inner ring abutment surface of the hub ring, assembling the outer and inner members and the rolling elements together, fixing the brake rotor to the hub ring of the inner member, and lathing the pad slide surfaces of the brake rotor with the reference provided by the wheel pilot end surface of the hub ring. 
     When the pilot end surface of the hub ring is lathed, the reference is defined by the inner ring abutment surface of the hub ring or the raceway of the hub ring. As for a chuck position in lathing the pad slide surfaces of the brake rotor of the hub ring with the reference provided by the wheel pilot end surface of the hub ring, mention may be made of the wheel pilot outer diameter of the hub ring, the wheel pilot inner diameter of the hub ring, the serration hole inner diameter of the hub ring, and the hat section outer diameter of the brake rotor. 
     Another aspect of this invention resides in a method for cutting the pad slide surfaces of the brake rotor of a brake rotor-equipped wheel bearing device which comprises an outer member having a car body attaching flange in the outer periphery and two rows of raceways in the inner periphery, an inner member consisting of a hub ring having a wheel attaching flange in the outer periphery and an inner ring disposed in the small diameter section of the hub ring, two rows of rolling elements interposed between the raceways of the outer and inner members for relatively rotatably supporting the two members, and a brake rotor fixed to the wheel attaching flange of the hub ring, the method being characterized by comprising the steps of grinding, with the hub ring present singly, the hub ring outer peripheral surface with the reference provided by the wheel pilot end surface of the hub ring, assembling the outer and inner members and the rolling elements together, fixing the brake rotor to the hub ring of the inner member, and lathing the pad slide surfaces of the brake rotor with the reference provided by the wheel pilot end surface of the hub ring. 
     Still another aspect of this invention resides in providing a method for cutting the pad slide surfaces of the brake rotor of a brake rotor-equipped wheel bearing device which comprises an outer member having a car body attaching flange in the outer periphery and two rows of raceways in the inner periphery, an inner member consisting of (a) a hub ring having a wheel attaching flange in the outer periphery, one row of raceways and a small diameter section and (b) an inner ring disposed in the small diameter section of the hub ring and having one row of raceways, two rows of rolling elements interposed between the raceways of the outer and inner members for relatively rotatably supporting the two members, and a brake rotor fixed to the wheel attaching flange of the hub ring, the method being characterized by comprising the steps of lathing the wheel pilot end surface of the hub ring by chucking the knuckle pilot outer diameter of the outer member with the wheel bearing device put in its assembled state, and lathing the pad slide surfaces of the brake rotor with the reference provided by the wheel pilot end surface of the hub ring. 
     As for the chuck position in lathing the pad slide surfaces of the brake rotor with the reference provided by the wheel pilot end surface of the hub ring, mention may be made of the wheel pilot inner or outer diameter of the hub ring, the serration inner diameter of the hub ring, and the hat section outer diameter of the brake rotor. 
     Further, the wheel pilot end surface of the hub ring and the flange surface of the car body attaching flange of the outer member may be clamped together, and so may the wheel pilot end surface of the hub ring and the inboard-side end surface of the outer member. 
     By lathing the pad slide surfaces of the brake rotor with the reference provided by the wheel pilot end surface of the hub ring, it becomes possible to attain a high accuracy processing which suppresses the surface runout of the pad slide surfaces of the brake rotor without restraining the outer member. To give a concrete example, the surface runout of the pad slide surfaces of the brake rotor can be made not more than 30 μm. Therefore, according to this invention, since the rotation runout of the pad slide surfaces of the brake rotor can be minimized, it is possible to improve the rotation accuracy of the brake rotor put in its mounted state and suppress the occurrence of the brake shudder during braking. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view for explaining a first step in a first embodiment of this invention; 
         FIG. 2  is a longitudinal sectional view for explaining a second step in the first embodiment of this invention; 
         FIG. 3  is a longitudinal sectional view of a wheel bearing device; 
         FIG. 4  is a longitudinal sectional view of a brake rotor-equipped wheel bearing device; 
         FIG. 5  is a longitudinal sectional view, similar to  FIG. 2 , showing a modification of the second step; 
         FIG. 6  is a longitudinal sectional view, similar to  FIG. 2 , showing a modification of the second step; 
         FIG. 7  is a longitudinal sectional view, similar to  FIG. 2 , showing a modification of the second step; 
         FIG. 8  is a longitudinal sectional view, similar to  FIG. 1 , for explaining a second embodiment of this invention; 
         FIG. 9  is a longitudinal sectional view showing the prior art; 
         FIG. 10  is a longitudinal sectional view for explaining a first step in a third embodiment of this invention; 
         FIG. 11  is a longitudinal sectional view for explaining a second step in the third embodiment of this invention; 
         FIG. 12  is a longitudinal sectional view similar to  FIG. 11 , showing a modification of the second step; 
         FIG. 13  is a longitudinal sectional view similar to  FIG. 11 , showing a modification of the second step; 
         FIG. 14  is a longitudinal sectional view similar to  FIG. 11 , showing a modification of the second step; 
         FIG. 15  is a longitudinal sectional view similar to  FIG. 11 , showing a modification of the second step; and 
         FIG. 16  is a longitudinal sectional view similar to  FIG. 11 , showing a modification of the second step. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Prior to the explanation of the processing method, a description will be given of a brake rotor-equipped bearing device which is the subject of processing. 
     An example of a wheel bearing device for driving wheels is shown in  FIG. 3 , and a brake rotor-equipped wheel bearing device in which the wheel bearing device is integrated with the brake rotor is shown in  FIG. 4 . This wheel bearing device has as main components an outer member  10  corresponding to a bearing outer ring, an inner member  20  corresponding to a bearing inner ring, and two rows of rolling elements  36  interposed between the outer and inner members  10  and  20 . 
     The outer member  10  is provided in its outer periphery with a flange or car body attaching flange  12 , for fixing to a car body, such as a knuckle, and is formed in its inner periphery with two raceways  14 . The portion of the outer member  10  indicated by the reference character  16  is a pilot section to be inserted in an attachment hole formed in the knuckle or the like; herein the portion is referred to as the knuckle pilot. 
     The inner member  20  consists of a hub ring  20 A and an inner ring  20 B. The hub ring  20 A is formed with a wheel pilot  22  at its outboard end appearing in the left-hand side of  FIG. 3 , and with a small diameter section  24  at its inboard end on the opposite side. The hub ring  20 A is centrally formed with an axially extending spline (or serration, thereinafter the same) hole  26 . The outer periphery of the outboard end of the hub rig  20 A is provided with a flange for attaching a wheel, i.e., a wheel attaching flange  28 . The wheel attaching flange  28  has a plurality of hub bolts  30  attached thereto. The intermediate outer periphery of the hub ring  20 A is formed with a raceway  32 . 
     The inner ring  20 B is disposed on the small diameter section  24  of the hub ring  20 A as by a tight fit, with the end surface of the inner ring  20 B being abutted against its surface  25  radially rising from the small diameter section  24 . In this sense, the surface  25  will be called the inner ring abutment surface. The outer periphery of the inner ring  20 B is formed with a raceway  34 . The respective raceways  32  and  34  of the hub ring  20 A and inner ring  20 B correspond to the two raceways  14  of the outer member  10 . And, two rows of rolling elements  36  are rollably interposed between the raceway  14  of the outer member  10  and the raceways  32  and  34  of the inner member  20  (the hub ring  20 A and inner ring  20 B), supporting the outer and inner members  10  and  20  for their relative rotation. 
     In addition, seals  38  are mounted in the opposite ends between the opposed surfaces of the outer and inner members  10  and  20 . The seals  38  prevent foreign matter from entering the bearing, and also prevent leakage of the grease filled in the bearing. 
     In the wheel bearing device constructed in the manner described above, in assembling it to an actual car, the car body attaching flange  12  of the outer member  10  is attached to the car body. Further, the spline shaft disposed in the outer joint member of the constant velocity joint is inserted in the spline hole  26  in the hub ring  20 A. A nut is put in screw engagement with a threaded shaft formed at the front end of the spline shaft to effect tightening with standard torque, axially pressing the hub ring  20 A and inner ring  20 B, thereby preloading the bearing. Further, a brake rotor  40  and a wheel (not shown) are attached to the hub bolts  30  of the wheel attaching flange  28  and wheel nuts (not shown) are tightened. The wheel is centered by the wheel pilot  22 , and so is the brake rotor  40  by a brake pilot  21 . 
     Next, a description will be given of the method for processing the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  in the brake rotor-equipped wheel bearing device. The processing method in the first embodiment consists of a first step and a second step. In the first step, with the hub ring  20 A present singly, the end surface  23  of the wheel pilot  22  of the hub ring  20 A is lathed with the reference provided by the inner ring abutment surface  25 . In the second step, with the bearing put in its assembled state, after the brake rotor is attached, the outer diameter of the wheel pilot  22  of the hub ring  20 A is chucked, and the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  are lathed with the reference provided by the wheel pilot end surface  23 . 
     The first step will be described with reference to  FIG. 1 . The hub ring  20 A constituting the inner member  20  of the wheel bearing device is held at the small diameter section  24  by a chuck device  42 . At this time, the chuck device  42  is abutted against the inner ring abutment surface  25 . The spline shaft of a work carry  46  is inserted in the spline hole  26  in the hub ring  20 A, and the work carry  46  is rotated as indicated by an arrow, thus imparting a torque so that the hub ring  20 A will rotate around the rotation center of the wheel bearing device. And, a turning tool  44  is fed as indicated by an arrow in white to lathe the end surface  23  of the wheel pilot  22  with the reference provided by the inner ring abutment surface  25 . Irrespective of dimensional errors or assembly errors in each member, this processing makes it possible to control the axial runout of the end surface  23  of the wheel pilot  22  to a sufficiently small value during rotation of the wheel bearing device. 
     The second step will be described with reference to  FIG. 2 . The brake rotor  40  is attached ( FIG. 4 ) to the hub ring  20 A of the wheel bearing device ( FIG. 3 ) having passed through the first step. The thus constructed brake rotor-equipped wheel bearing device, as shown in  FIG. 2 , is held at the outer diameter of the wheel pilot  22  by the chuck device  48   a . At this time, the chuck device  48   a  is abutted against the end surface  23  of the wheel pilot  22 . In this state, the spline shaft of the work carry  52  is inserted in the spline hole  26 , and the inner member  20  is rotated while feeding the turning tools  50   a  and  50   b  as shown in double-dot dash lines, thereby lathing the pad slide surfaces  40   a  and  40   b  of the brake rotor  40 . 
     According to this embodiment, it is possible to secure the end surface  23  of the wheel pilot  22  whose axial surface runout accuracy is made very small with respect to the rotation of the wheel bearing device in the first step, and in the second step, with this used as the reference, the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  are lathed, thereby making it possible to minimize the axial surface runout of the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  with respect to the rotation of the wheel bearing device. 
     Further, strains which are produced when the brake rotor  40  is fixed to the wheel attaching flange  28  are removed. Further, in the conventional system, since the slide pad surfaces  40   a  and  40   b  of the brake rotor  40  are cut by fixing the outer member  10 , runout is produced in the bearing rotation axis and in the processing axis due to deformation of the rolling element contact surface when a cutting load is applied, resulting in a phenomenon in which the surface runout accuracy is degraded by an amount corresponding thereto. In this embodiment, however, since the outer member  10  is not restrained when the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  are processed, runout is hardly produced in the bearing rotation axis and the processing axis, so that they can be processed with corresponding accuracy. 
     Referring to the first step, it has been stated that when the end surface  23  of the wheel pilot  22  of the hub ring  20 A which provides the reference is lathed, the inner ring abutment surface  25  is used as the reference. However, the end surface  23  of the wheel pilot  22  may be lathed with the reference provided by the inner ring abutment surface  25 . 
     Further, when the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  are lathed in the second step, the hub ring  20 A is held at the outer diameter of the wheel pilot  22  by the chuck device  48   a ; as for the chuck position of the hub ring  20 A at this time, however, besides the outer diameter of the wheel pilot  22  as shown in  FIG. 2 , mention may be made of the inner diameter of the wheel pilot  22  ( FIG. 5 ), the inner diameter of the serration hole  26  ( FIG. 6 ), and the hat section outer diameter of the brake rotor  40  ( FIG. 7 ). More specifically, in  FIG. 5 , the inner diameter is chucked with the chuck device  48   b  abutted against the wheel pilot end surface  23 . In  FIG. 6 , with the chuck device  48   c  abutted against the wheel pilot end surface  23 , the inner diameter of the serration hole  26  in the hub ring  20 A is chucked by the chuck device  48   d . In  FIG. 7 , with the chuck device  48   c  abutted against the wheel pilot end surface  23 , the hat section outer diameter is chucked by the chuck device  48   e.    
     The second embodiment is such that, as shown in  FIG. 8 , with the hub ring  20 A present singly, the outer peripheral surface of the hub ring  20 A is ground with the reference provided by the end surface  23  of the wheel pilot  22 . In this case, the end surface of the wheel pilot  22  is supported by the chuck device  54 , and use is made of a formed grinding stone  56  having a contour corresponding to the outer peripheral surface of the hub ring  20 A including at least the raceway  32 , inner ring abutment surface  25 , and small diameter sections  24 . 
     In addition, the wheel bearing device has been described so far by taking as an example one for driving wheels formed with the spline hole  26  in the inner member  20  (hub ring  20 A); however, the wheel bearing device may be such that it is used for non-driving wheels and such that the hub ring  20 A is solid. 
     Next, the third embodiment of this invention will be described with reference to  FIGS. 10 through 16 . It consists of a first step and a second step. In the first step, the end surface  23  of the wheel pilot  22  of the hub ring  20 A is lathed in a bearing ASSY state ( FIG. 10 ), and in the second step, the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  are lathed ( FIG. 11 ). 
     The first step will be described with reference to  FIG. 10 . The outer diameter of the knuckle pilot  16  of the outer member  10  of the wheel bearing device is held by the chuck device  42 . And, the serration shaft of the work carry  46  is inserted in the serration hole  26  in the hub ring  20 A, and the work carry  46  is rotated as indicated by an arrow, thus imparting a torque so that the hub ring  20 A will rotate around the rotation center of the wheel bearing device. And, the turning tool  44  is fed as indicated by an arrow in white to lathe the end surface  23  of the wheel pilot  22 . Irrespective of dimensional errors or assembly errors in each member, this processing makes it possible to control the axial runout of the end surface  23  of the wheel pilot  22  to a sufficiently small value during rotation of the wheel bearing device. 
     The second step will be described with reference to  FIG. 11 . The brake rotor  40  is attached to the hub ring  20 A of the wheel bearing device having passed through the first step and is fixed in position by tightening the nuts  31 . The thus constructed brake rotor-equipped wheel bearing device, as shown in  FIG. 11 , is held at the inner diameter of the wheel pilot  22  by the chuck device  48   a . At this time, the chuck device  48   a  is abutted against the end surface  23  of the wheel pilot  22 . In this state, the serration shaft of the work carry  46  is inserted in the serration hole  26 , and the inner member  20  is rotated while feeding the turning tools  50   a  and  50   b  as shown in double-dot dash lines, thereby lathing the pad slide surfaces  40   a  and  40   b  of the brake rotor  40 . 
     According to this embodiment, it is possible to secure the end surface  23  of the wheel pilot  22  whose axial surface runout accuracy is made very small with respect to the rotation of the wheel bearing device in the first step, and in the second step, with this used as the reference, the pad slide surfaces  40   a  and  40   b  are lathed, thereby making it possible to minimize the axial surface runout of the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  with respect to the rotation of the wheel bearing device. 
     Further, strains which are produced when the brake rotor  40  is fixed to the wheel attaching flange  28  are removed. Further, in the conventional system, since the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  are cut by fixing the outer member  10 , runout is produced in the bearing rotation axis and in the processing axis due to deformation of the rolling element contact surface when a cutting load is applied, resulting in a phenomenon in which the surface runout accuracy is degraded by an amount corresponding thereto. In this embodiment, however, since the outer member  10  is not restrained when the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  are processed, runout is hardly produced in the bearing rotation axis and the processing axis, so that they can be processed with corresponding accuracy. 
     As for the chuck position of the hub ring  20 A in lathing the pad slide surfaces  40   a  and  40   b  of the brake rotor  40  in the second step, besides the inner diameter of the wheel pilot  22  as described above with reference to  FIG. 11 , the outer diameter of the wheel pilot  22  may be chucked by a chuck device  48   a ′, as shown in  FIG. 12 . Alternatively, arrangements as shown in  FIGS. 13 and 14  may be employed. In the modification shown in  FIG. 13 , with the chuck device  48   b  abutted against the wheel pilot end surface  23 , the inner diameter of the serration hole  26  in the hub ring  20 A is chucked by the chuck device  48   c . In the modification shown in  FIG. 14 , with the chuck device  48   b  abutted against the wheel pilot end surface  23 , the hat section outer diameter of the brake rotor  40  is chucked by the chuck device  48   d.    
     Further, as shown in  FIGS. 15 and 16 , the clamping may be such that the wheel pilot end surface  23  of the hub ring  20 A and the outer member  10  are clamped from axially opposite sides. In each case, the radial movement of the outer member  10  is not restrained, a fact which eliminates the drawbacks of the accuracies (axial runout, rigidity, etc.) of the bearing itself influencing the brake rotor accuracy after processing. In the case of  FIG. 15 , one rotatable chuck device  48   e  holds the outer diameter of the wheel pilot  22  of the hub ring  20 A while abutting against the wheel pilot end surface  23 . The other stationary chuck device  54   a  is abutted against the flange surface  13  of the car body attaching flange  12  of the outer member  10 . In the case of  FIG. 16 , the rotatable chuck device  48   e  holds the outer diameter of the wheel pilot  22  of the hub ring  20 A while abutting against the wheel pilot end surface  23 , and the stationary chuck device  54   b  is abutted against the inboard-side end surface  18  of the outer member  10 . 
     In addition, the wheel bearing device has been described so far by taking as an example one for driving wheels, formed with the serration hole  26  in the inner member  20  (hub ring  20 A); however, the wheel bearing device may be such that it is used for non-driving wheels and such that the hub ring  20 A is solid. The chucking of the hub ring in this case may be similar to the chucking described with reference to  FIG. 15 or 16 . Alternatively, projections may be provided in some places, for example, 3 or 4 places, on the circumference of the wheel pilot inner diameter section of the hub ring in the forging process. Alternatively, a notch may be formed in the wheel pilot end surface, so that a tool may be hooked thereon for turning.