Abstract:
A reliable brake rotor and wheel bearing assembly are proposed which make unnecessary adjustment of runout of brake rotor at the customer&#39;s factory. For runout of each of the mounting surface and back of the brake rotor itself, and runout of the side of the wheel mounting flange of the inner member to which is mounted the brake rotor, the maximum difference between the peaks of crests and troughs in each period of surface runout is restricted within a standard value, and the brake rotor is mounted to the wheel mounting flange, thereby eliminating the necessity of mounting of the brake rotor and adjustment of runout after mounting at the customer&#39;s factory to provide a reliable automotive wheel bearing assembly.

Description:
This is a divisional application of U.S. patent application Ser. No. 09/657,094, filed Sep. 7, 2000, now U.S. Pat. No. 6,575,637. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to an automotive brake rotor and a wheel bearing assembly. 
   Various kinds of wheel bearing assemblies are known including ones for driving wheels and ones for non-driving wheels.  FIG. 26  shows a wheel bearing assembly for a driving wheel. It comprises an outer member  3  having two raceways  3   a,    3   b  formed on its inner peripheral surface, an inner member  1  having two raceways  1   a,    1   b  opposite the respective raceways  3   a,    3   b,  and rolling elements or balls  8  disposed between the raceways  3   a,    3   b  on the outer member  3  and the raceways  1   a,    1   b  on the inner member  1  in two rows. The inner member  1  has a flange  2  adapted to be secured to a wheel and is formed with a splined bore  9  into which is inserted a drive shaft. 
   A brake rotor  5  is positioned by bolts  18  to the outer side  2   a  of the flange  2  and secured between the outer side  2   a  and the wheel hub by bolts  7 . Any runout of the brake rotor  5  can cause vibrations or squeal during braking, or uneven wear of the brake rotor and/or brake pad. 
   Brake rotors and wheel bearings are usually delivered to a car manufacturer, who assemble them together. It has been an ordinary practice to adjust to minimize runout of the brake rotor  5  when or after assembling the rotor and the wheel bearing, by e.g. adjusting the angular position of the mounting bolts  7 . But such work is troublesome and inefficient. 
   An object of the invention is to provide a brake rotor and a wheel bearing assembly that are reliable and need no runout adjustment at a car manufacturer. 
   SUMMARY OF THE INVENTION 
   According to the invention, a brake rotor is provided which is mounted to a rotary member of a wheel bearing assembly for rotatably supporting a wheel on a vehicle body by means of double-row rolling elements. The maximum runout variation of a mounting surface on the side of the brake rotor abutting the rotary member is restricted within a predetermined value. 
   By restricting the maximum runout variation of the mounting surface on the side of the brake rotor abutting the rotary member within a predetermined value, runout of the brake rotor mounted to the rotary member is suppressed low within a desired range and troublesome runout adjustment after assembling has become unnecessary. 
   By restricting the maximum runout variation of a back side of the mounting surface to which a wheel hub is mounted within a predetermined value, it is possible to suppress the runout of the brake rotor. 
   By restricting it to 50 μm or less, the brake rotor will be reliable and will not require any runout adjustment after assembly. 
   By restricting the runout variation per cycle of the mounting surface or its back side within a predetermined value, it is possible to smoothen the runout of the brake rotor. 
   According to the invention, the runout variation per cycle of the mounting surface should be restricted to 30 μm or less. 
   According to the invention, the maximum difference between the peak values of crests or the maximum difference between the peak values of troughs in each runout cycle of the mounting surface or its back side should be restricted within a predetermined value. Thereby it is possible to suppress the runout of the brake rotor to a lower value. The predetermined value should be not more than 30 μm. 
   According to the invention, it is preferable that the frequency per rotation of runout of the mounting surface be a multiple of the number of wheel mounting bolts or the number of the mounting bolts be a multiple of the frequency. Thereby it is possible to make uniform the deformation of the brake rotor due to tightening force applied to the mounting bolt and suppress the runout of the brake rotor resulting from the deformation of the brake rotor. 
   According to the invention, there is provided a wheel bearing assembly comprising an outer member having two raceways on its inner surface, an inner member having two raceways on its outer surface, opposite to the respective raceways on the outer member, and two rows of rolling elements mounted between the opposed raceways, wherein a wheel mounting flange is formed on one of the outer member and the inner member, wherein one side of the wheel mounting flange is a mounting surface for a brake rotor, characterized in that the maximum runout variation of the brake rotor mounting surface is restricted within a predetermined value. 
   By restricting the maximum variation of runout of the brake rotor mounting surface of the wheel mounting flange within a predetermined value, it is possible to suppress runout of the brake rotor without carrying out troublesome runout adjustment after assembling. 
   According to the invention, the predetermined value should be 50 μm and preferably 30 μm. 
   By restricting the runout variation per cycle of the brake rotor mounting surface within a predetermined value, it is possible to smoothen the runout of the braking surface of the brake rotor. 
   By restricting the maximum difference between the peak values of crests or the maximum difference between the peak values of troughs in each cycle of runout of the brake rotor mounting surface within a predetermined value, it is possible to suppress the runout of the braking surface of the brake rotor. 
   It is preferable that the frequency per rotation of runout of the brake rotor mounting surface be a multiple of the number of wheel mounting bolts or the number,of the wheel mounting bolts be a multiple of the frequency. Thereby it is possible to make uniform the deformation of the brake rotor due to tightening force applied to the mounting bolt and suppress the runout of the brake rotor resulting from the deformation of the brake rotor. 
   Also, in the arrangement in which the brake rotor mounting surface is the outer side of the wheel mounting flange, by inclining this side outwardly toward the tip of the wheel mounting flange, when the brake rotor and the wheel hub are superposed and tightened by wheel mounting bolts, the wheel mounting flange is resiliently deformed, so that the outer peripheral portion of the brake rotor mounting surface is pressed hard against the brake rotor. Thus, the brake rotor is stably supported by the outer peripheral portion. In this case too, by also restricting the maximum runout variation of the brake rotor mounting surface within a predetermined value, it is possible to suppress runout of the braking surface during rotation of the brake rotor. 
   The inclination angle of the brake rotor mounting surface is preferably 20° or less. If this angle is greater than needed, even if the wheel mounting flange is resiliently deformed, the inner peripheral portion of the brake rotor may become out of contact with the brake rotor mounting surface, so that the mounting of the brake rotor becomes unstable. The upper limit of the inclination angle that will not become unstable is determined at 20°. 
   By setting the degree of flatness and circumferential flatness of the outer peripheral portion of the brake rotor mounting surface at 30 μm or less, it is possible to suppress runout of the braking surface during rotation of the brake rotor pressed hard against the outer peripheral portion. 
   As shown in  FIG. 25A , the circumferential flatness is measured as described below. The wheel mounting flange  2  is rotated with the probe of a measuring device such as a dial gauge  22  in contact with the outer peripheral portion of the side  2   a,  which is the brake rotor mounting surface of the wheel mounting flange  2 .  FIG. 25B  is a graph showing undulation picked up by the probe of the dial gauge. The circumferential flatness is the minimum distance δ between two parallel lines L 1  and L 2  between which the undulation is contained. 
   The wheel mounting flange may be formed integrally with the outer member or the inner member. 
   By mounting the above-mentioned brake rotor with less runout on the brake rotor mounting surface, the runout of the braking surface of the brake rotor during rotation can be suppressed. 
   According to the present invention, there is also provided a wheel bearing assembly comprising an outer member having two raceways on its inner surface, an inner member having two raceways on its outer surface so as to be opposite to the two raceways on the outer member, and two rows of rolling elements mounted between the opposed raceways, a wheel mounting flange being formed on the inner member, characterised in that a brake rotor is integrally formed on the wheel mounting flange. 
   By forming a brake rotor integrally with the wheel mounting flange, the mounting of the brake rotor and runout adjustment after assembly can be eliminated. 
   By restricting the maximum runout of the braking surface of the brake rotor below a predetermined value, the runout of the braking surface of the brake rotor during rotation can be suppressed without the need of troublesome runout adjustment by the customer. 
   The predetermined value should be 100 μm or preferably 50 μm. 
   If the wheel mounting flange is mounted on the inner member, a drive shaft may be mounted in the inner member, or the inner member may be formed integrally with an outer coupling of a constant-velocity joint. 
   The inner member may comprise a first inner member having an outboard raceway and a second inner member having an inboard raceway, and the second inner member may be an outer coupling or spindle of a constant-velocity joint. 
   By inseparably coupling the first and second inner members together by deformation, no nuts are needed and a smaller number of parts, smaller weight and smaller axial length of the assembly are achieved. 
   By forming a dimension-controlled negative axial clearance between the rolling elements and the raceways, it is possible to provide a wheel bearing assembly high in rigidity, and in a state assembled in a vehicle body, while the vehicle is turned, it is possible to prevent the member on the side having the wheel mounting flange from inclining toward the member on the fixed side to eliminate uneven contact between the brake rotor mounted to the wheel mounting flange and the brake pads, thus preventing uneven wear of both of them. Thus, coupled with the effect by restricting the maximum variation of runout of the brake rotor mounting surface within a predetermined value, it is possible to suppress runout of the braking surface during rotation of the brake rotor. 
   At least one of the two raceways on the inner member may be formed on a separate raceway member fixed to the inner member. This facilitates control of the axial clearance between the rolling elements and the raceways. 
   By inseparably coupling the inner member and the separate raceway member together by plastic deformation, no nuts are needed and a smaller number of parts, smaller weight and smaller axial length of the assembly are achieved. 
   According to this invention, there is provided a wheel bearing assembly wherein one of the outer member and the inner member that carries the wheel mounting flange is rotatable and the other is nonrotatable and wherein the outer member and inner member defines an annular space therebetween in which are disposed rolling elements. The wheel bearing assembly further comprises a slinger fixed to the one of the outer and inner members, seal members for sealing both sides of the annular space, an encoder having multiple magnetic poles and fixed to the slinger, a sensor for sensing fluctuations in the magnetic flux produced by the encoder when the encoder rotates and for producing a signal indicative of the revolving speed of the encoder, and a rotational speed detector for receiving the signal and for calculating the revolving speed of the one member based on the signal. 
   In comparison with the arrangement in which a rotational speed detector is separately provided, a compact and light-weight assembly is provided with a greater freedom of design. 
   According to this invention, there is also provided a wheel bearing assembly wherein the wheel mounting flange is fastened to a brake rotor by bolts inserted through bolt holes formed in the flange, the wheel bearing assembly further comprising arrangements for preventing the bolts from turning in the respective bolt holes. 
   This reduces the surface pressure between serrations formed at the neck of the bolt and the inner wall of the bolt hole and thus prevents strains from producing on the side of the flange on which the brake rotor is mounted. 
   The arrangement for preventing the bolts from turning may comprise a bolt head having a noncircular cross-section, and a protrusion formed on the wheel mounting flange near each of the bolt holes and engaging the head to prevent the each bolt from turning in the bolt hole. 
   The noncircular head may have a flat side face formed thereon, or have a knurled surface, or an oval cross-section. 
   The protrusions may be pressed against the respective heads by plastic deformation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a vertical sectional view showing a brake rotor of a first embodiment; 
       FIG. 2  is a vertical sectional view showing a wheel bearing assembly of a first embodiment on which is mounted the brake rotor of  FIG. 1 ; 
       FIG. 3  is a vertical sectional view showing how the runout of a mounting surface of the brake rotor of  FIG. 1  was measured; 
       FIG. 4  is a graph showing the measuring results of runout of  FIG. 3 ; 
       FIG. 5  is a vertical sectional view showing how runout of a side of the wheel mounting flange was measured; 
       FIG. 6  is a vertical sectional view showing a modified measuring method; 
       FIG. 7  is a graph showing the measuring results of runout of  FIG. 5 ; 
       FIG. 8  is a graph showing the measuring results of runout when the brake rotor of  FIG. 1  was mounted to the wheel bearing assembly of  FIG. 2 ; 
       FIG. 9  is a vertical sectional view showing a wheel bearing assembly of a second embodiment; 
       FIGS. 10A ,  10 B are partial enlarged sectional views showing a method of measuring an axial clearance of the wheel bearing assembly of  FIG. 9 ; 
       FIG. 11  is a vertical sectional view showing the wheel bearing assembly of a third embodiment; 
       FIG. 12  is a vertical sectional view showing a wheel hub fastened to the wheel bearing assembly of  FIG. 11 ; 
       FIG. 13  is a vertical sectional view showing a wheel bearing assembly of a fourth embodiment; 
       FIG. 14A  is an enlarged sectional view of the rotation speed detector of the assembly of  FIG. 13 ; 
       FIG. 14B  is a perspective view of the encorder used in the rotation speed detector; 
       FIG. 15  is a vertical sectional view of the wheel bearing assembly of a fifth embodiment; 
       FIG. 16A  is a partially cutaway perspective view of the wheel mounting bolt at its head portion; 
       FIG. 16B  is a front view thereof; 
       FIGS. 17A  to  19 A are similar views to  FIG. 16A  of modified embodiments of the wheel mounting bolt at their head portion; 
       FIGS. 17B  to  19 B are front views thereof; 
       FIG. 20A  is a similar view of another modified embodiment of the wheel mounting bolt before plastic deformation of the protrusion; 
       FIG. 20B  is a similar view of the same after plastic deformation of the protrusion; 
       FIG. 21  is a vertical sectional view showing a sixth embodiment; 
       FIG. 22  is a similar view showing a seventh embodiment; 
       FIG. 23  is a similar view showing an eighth embodiment; 
       FIG. 24  is a similar view showing a ninth embodiment; 
       FIG. 25A  is a perspective view showing how circumferential flatness of a wheel mounting flange was measured; 
       FIG. 25B  is a graph for explaining how the circumferential flatness is obtained from the measuring results; and 
       FIG. 26  is a vertical sectional view showing a conventional wheel bearing assembly. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The embodiments are described with reference to  FIGS. 1-25 . 
     FIGS. 1 and 2  show a first embodiment.  FIG. 1  shows a brake rotor  5  embodying the present invention.  FIG. 2  shows a wheel bearing assembly embodying the invention with the brake rotor  5  mounted thereon. Elements identical or similar to those of  FIG. 26  are denoted by the same numerals. 
   The wheel bearing assembly of  FIG. 2  is for a driving wheel. It has an inner member  1  formed with a splined bore  9  in which is received a drive shaft. The inner member  1  is further formed with an integral wheel mounting flange  2  extending radially outwardly from its outer surface, and a wheel pilot  10  axially protruding from its outer end face. The wheel bearing assembly further includes an outer member  3  having a flange  4  formed with bolt holes  12  through which bolts are inserted to secure the outer member to a stationary part of the vehicle body. 
   A brake rotor  5  is positioned by bolts  18  with its side face  5   a  against an outer side  2   a  of the flange  2 . It is secured in position between the flange  2  of the wheel bearing assembly and a wheel hub  14  by bolts  7  inserted through bolt holes  6  and  11  formed in the rotor  5  and the flange  2 , respectively, with its back and front sides  5   a,    5   b  pressed against the outer side  2   a  of the flange  2  and the inner side of the hub  14 , respectively. The wheel mounting bolt  7  is prevented by serrations  7   a  from turning in the hole  11  formed in the wheel mounting flange  2 . 
   The inner member  1  comprises a main portion formed with a first raceway  1   a  on its outer surface, and a separate ring member  15  press-fitted on a stepped or recessed portion of the main portion and formed with a second raceway  1   b  on its outer surface. The outer member  3  has two raceways  3   a  and  3   b  directly formed on its inner surface so as to be opposite the raceways  1   a  and  1   b  on the inner member  1 . Rolling elements or balls  8  are received between the respective opposed pairs of raceways  1   a,    1   b  and  3   a,    3   b.  Seal members  19  are provided at both axial ends of the space in which the balls  8  are retained to seal this space. 
   For the material of the inner member  1  and outer member  3 , a carbon steel is used, the carbon content of which is 0.45-1.10 wt %, preferably 0.45-0.75 wt %. Its surface is treated by induction hardening, carburizing hardening or laser hardening so that the surface hardness will be about Hv 500-900. The depth of the hardened layer is about 0.7-4.0 mm at portions where the raceways  1   a,    3   a,    3   b  are formed and about 0.3-2.0 mm at other portions. 
     FIG. 3  shows how the runout of the mounting side  5   a  of the brake rotor  5  was measured. The rotor  5  was placed on a rotary table  20  with its mounting side  5   a  up and a boss  21  was received in the center hole of the rotor. The table  20  was then turned 360° and the runout was measured by use of a dial gauge  22  fixed to the boss  21 . Then, the rotor  5  was turned upside down and the runout was measured for the reverse side  5   b  in the same manner as above. Since the runout is greater at the radially outer portion of the rotor, the runout was measured at central points between the outer edge of the side  5   a  and the circle circumscribing the bolt holes  6  for more strict runout control. 
     FIG. 4  shows the runout curve of the side  5   a  thus measured. The maximum runout variation in the entire 360° interval and the maximum variation in any one-cycle interval are both 20 μm, which are smaller than the standard values determined for these parameters, i.e. 50 μm and 30 μm, respectively. The curve has a frequency of two per rotation of the rotor and thus has two crests (local maximums) and troughs (local minimums) for each 360°. As shown, the difference between the largest and smallest local maximums is 4 μm while the difference between the largest and smallest local minimums is 3 μm. These values are far smaller than 30 μm, which is a standard value determined for these parameters. 
   In this embodiment, the rotor is secured in position by four mounting bolts  7 . The arrows in  FIG. 4  show the positions of the wheel mounting bolts  7 , which correspond to the positions of the crests of runout of the side  2   a.  But this is not a must. Although not shown, the runout curve of the side  5   b  was almost the same as that of the side  5   a  shown in FIG.  4 . In other words, the frequency was two and the difference between the largest and smallest local maximums, the difference between the largest and smallest local minimums, and the maximum variation in any one-cycle were the same with the side  5   a.  Those were smaller than the respective standard values. 
   From  FIG. 4 , it will be apparent that the maximum variation in the entire 360° interval of the runout curve and the maximum variation in any one-cycle interval are equal to each other if the runout curve has a runout frequency of two or less as shown in FIG.  4 . The former is not equal to but larger than the latter if the runout frequency is 3 or over. 
     FIG. 5  shows how the runout of the outer side  2   a  of the flange  2  of the wheel bearing assembly was measured. The wheel bearing assembly with the rotor not mounted was mounted with the outer member  3  fixed to a bench  23  so that the inner member  1  be rotatable. In this state, the inner member  1  with the wheel mounting flange  2  was turned 360° and the runout of the side  2   a  of the flange  2  was measured by a dial gauge  22 . Since its runout, too, is greater at the radially outer portion of the flange, the runout was measured at central points between the outer edge of the flange  2  and the cicumcircle of the bolt holes  11  for more strict runout control. 
   The runout of side  2   a  may be measured with the inner side of the inner member  1  fitted and positioned in a hole  25   a  of a rotary ring  25  mounted on a measuring stand  24  as shown in  FIG. 6 , and by turning the rotary ring  25  together with the inner member  1  by one full turn. The runout was measured by means of a dial gauge  22  fixed to the measuring stand  24 . 
     FIG. 7  shows the runout curve (solid line) of the side  2   a  thus measured and a similar runout curve (dotted line) for another wheel bearing assembly as a comparative example which will be described later. Both curves have a frequency of four per rotation of the rotor and thus have four crests (local maximums) and troughs (local minimums). The maximum variation in one-cycle interval of the runout curve and the maximum variation in the entire 360° interval are 25 μm and 35 μm, respectively, which are smaller than standard values for these parameters, i.e. 30 μm and 50 μm, respectively. As shown, the difference between the largest and smallest local maximums is 10 μm while the difference between the largest and smallest local minimums is 15 μm. Thus, these values are far smaller than 30 μm, which is a standard value for these parameters. The arrows in  FIG. 7  show the positions of the wheel mounting bolts  7 , which correspond to the positions of the crests of runout of the side  2   a.    
     FIG. 8  is a graph showing the maximum runout variations when runout was measured with the brake rotor  5  having runout characteristics shown in  FIG. 7  mounted on the flange  2  of the wheel bearing assembly and when it was measured with not only the brake rotor but the wheel hub  14  mounted on the side  5   b  of the brake rotor  5 . The solid line is for the wheel bearing assembly embodying the present invention and the dotted line is for the comparative example of wheel bearing assembly. The runout was measured at outer side of the surface  5   c  of the rotor against which the brake pad is pressed. 
   As will be apparent from these results, while the maximum runout variation of the rotor alone was about 20 μm, this value jumped up to about 70 μm when the rotor was mounted to the comparative example of the wheel bearing assembly and exceeded 70 μm when the wheel hub was further mounted. In contrast, this value was suppressed to about 35 μm even when the rotor was mounted to the wheel bearing assembly of the invention and further the wheel hub was mounted. This clearly shows that with the brake rotor and the wheel bearing assembly embodying the present invention, it is possible to reduce the runout of the rotor drastically in an actual travel situation. 
   In the second to ninth embodiments which will be described below, the difference between the largest and smallest local maximums, the difference between the largest and smallest local minimums, and the maximum variation in any one-cycle interval and the maximum variation in the entire 360° interval were measured for the front and back sides  5   a,    5   b  of the rotor  5  and the side  2   a  of the flange  2 . These values, though not shown, were all smaller than the respective standard values except for the back side  5   b  of the rotor  5  in the fourth embodiment. The frequency of runout per rotation was a multiple of the number of the mounting bolts  7 . Or the latter was a multiple of the former. 
   In the description of the embodiments shown in  FIGS. 9-25 , like elements are denoted by like numerals as in FIG.  2 . 
     FIG. 9  shows a second embodiment. This wheel bearing assembly is for a driving wheel and a dimension-controlled negative axial clearance is formed between the rolling elements  8  and the raceways  1   a,    1   b,    3   a,    3   b.  With the inner ring  15  pressed on the stepped portion  17  of the inner member  1  with a negative axial clearance, the inner end  17   a  of the stepped portion  17  is plastically deformed by caulking to hold the ring  15  in this state. Otherwise, this embodiment is structurally the same as the first embodiment. 
   In bearing machining steps, the negative axial clearance can be set to a desired value by controlling the pitch P 0  between the raceways  3   a,    3   b  on the outer member  3 , and the distance P 1  to the center of the outer raceway  1   a  and the distance P 2  to the center of the inner raceway  1   b  from a boundary position  17   b  of the stepped portion  17  into which the inner member  15  is pressed on the outer periphery of the inner member  1 , and by selecting them so that the relation P 0 &gt;P 1 +P 2  is established. 
   Specifically the setting and control of the negative axial clearance can be carried out in the following steps. First, as shown in  FIG. 10A , the inner ring  15  is pressed into the stepped portion  17 , the end  17   a  of which has not been plastically deformed, and stopped temporarily. In the stopped state, the outer member  3  is axially reciprocated to measure the moving stroke ΔS. 
   Next, as shown in  FIG. 10B , the inner ring  15  is pressed until the end face of the inner ring  15  abuts the boundary position  17   b  of the stepped portion  17 , and the press-in stroke C is measured. The difference (ΔS−C) between the measured values of the moving stroke ΔS and the press-in stroke C is the set axial clearance, and this value is controlled to a desired negative value. 
   The press-in stroke C can be measured by making the inner end  17   a  of the recessed portion  17  (before plastic deformation) as a reference surface and measuring the distance A from the reference surface to the inner end face of the inner ring  15  and the distance B from the reference surface to the inner end face of the inner ring after completion of pressing in FIG.  10 B and deducting B from A (C=B−A). 
   The inner member  1  is made of carbon steel and hardened to a surface hardness Hv of about 500-900 like in the first embodiment except the end  17   a  of the recessed portion  17 , which is not hardend and has a surface hardness Hv of about 200 to 300 so that this portion is ductile enough to be plastically deformable. 
     FIG. 11  shows a third embodiment. This wheel bearing assembly is also for a driving wheel and of the same structure as the first embodiment. The outer side  2   a  of the wheel mounting flange  2  to which is mounted the brake rotor  5  is formed slightly inclined by the inclination angle θ to the outer side toward the tip of the wheel mounting flange  2 . In this embodiment, the inclination angle θ is set at 10°. 
   As shown in  FIG. 12 , when the brake rotor  5  and the wheel hub  14  are superposed to the side  2   a  and fastened by wheel mounting bolts  7  and nuts  7   b  to the wheel mounting flange  2  with a predetermined tightening torque, the wheel mounting flange  2  is subjected to elastic deformation, so that the outer peripheral portion of the side  2   a,  which is the brake rotor mounting surface, is pressed hard against the brake rotor  5 . Thus, the brake rotor is stably supported by the outer peripheral portion. Coupled with the effect by restricting the maximum variation of runout of the side  2   a,  this makes it possible to suppress: runout of the braking surface  5   c  during rotation of the brake rotor  5 . 
   If the inclination angle θ is greater than necessary, even if the wheel mounting flange  2  is resiliently deformed, the inner peripheral portion of the brake rotor  5  will be out of contact with the side surface  2   a,  so that the mounting of the brake rotor becomes unstable. Thus, the inclination angle θ should preferably be not more than 20°. 
   The degree of flatness and the circumferential flatness of the outer peripheral portion of the side  2   a  of the flange  2  should be both 30 μm or less to suppress runout of the braking surface  5   c  during rotation of the brake rotor  5  which is pressed hard against the outer peripheral portion. 
     FIG. 13  shows a fourth embodiment, which is also a wheel bearing assembly for a driving wheel. It includes a seal member  19   a  for sealing the inner side of the annular space in which are housed rolling elements  8 . As shown in  FIG. 14A , the seal member  19   a  comprises a seal ring  26  mounted to the outer member  3 , which is fixed, and a slinger  27  fixed to the rotating inner member  1 . The slinger  27  comprises a cylindrical portion  27   b  pressed on the land  15   a  of the inner ring  15 , and a radial flange  27   a  extending radially outwardly from the inboard end of the cylindrical portion  27   b.    
   This bearing assembly further includes a wheel speed detector  30  comprising a multi-polarized encoder  28  mounted on the outer surface of the radial flange  27   a  of the slinger  27 , and a sensor  29  fixed to the inboard end of the outer member  3 , opposite the encoder  28  to detect any change in magnetic flux. The outboard side of the bearing annular space is also sealed by a seal member  19   b  similar to the seal member  19   a.  Otherwise, this embodiment is structurally the same as the second embodiment. 
   As shown in  FIG. 14A , the seal ring  26  comprises a metallic core ring  31  having a cylindrical portion  31   a  pressed into the outer member  3 , and a seal rubber  32  stuck on the core ring  31  to cover its one side. The seal rubber  32  has two radially inner lips  32   a,    32   b  resiliently pressed against the outer surface of the cylindrical portion  27   b  of the slinger  27  and a side lip  32   c  resiliently pressed against the inner surface of the radial flange  27   a  of the slinger to seal the annular space. 
   As shown in  FIG. 14B , the encoder  28  is a ring made of a resilient magnetizable material and magnetized so that numerous N and S poles are arranged alternately in a circumferential direction. Specifically, the encoder  28  is formed by uniformly kneading e.g. a rubber or a rubber-like synthetic resin such as polyamide, polyolefin or an ethylene polymer with a magnetic powder such as barium ferrite or rare-earth magnetic powder to obtain a composite magnetizable material, crosslinking the thus obtained material, if it is rubber, shaping into a ring, and magnetizing by an ordinary magnetizing means such as a multi-polarizing yoke. The encoder ring thus formed is bonded to the radial flange  27   a  of the slinger  27  by vulcanization or with an adhesive. Rubbers usable for the encoder include NBR (nitrile), acrylic rubber elastomers, fluororubber elastomers and silicon elastomers. Among them, acrylic rubber elastomers, fluororubber elastomers and silicon elastomers are especially preferable because they are heat-resistant and thus can minimize the influence of heat produced during braking. 
   The sensor  29 , which is fixed to the end of the outer member  3  by screws  33  (FIG.  14 A), produces a signal indicative of the number of revolutions of the inner member  1  and thus that of the wheel based on change in fluctuating magnetic flux produced by the rotating encoder  28 . The signal produced is entered into e.g. an ABS controller. The sensor  29  may be an active sensor comprising a magnetic detector element such as a magnetic resistor element whose output changes with the flow direction of the magnetic flux, and an IC (integrated circuit) having a waveform shaping circuit. 
     FIG. 15  shows a fifth embodiment, which is also a wheel bearing assembly for a driving wheel. The inner member  1  of this bearing includes two separate inner rings  15  pressed on the outer surface of the inner member  1  and each formed with a raceway  1   a,    1   b.  The outer member  3  includes a separate outer ring  16  pressed into the inner surface of the outer member and formed with raceways  3   a,    3   b.  As shown in  FIGS. 16A and 16B , each wheel mounting bolt  7  has its head  34  cut out to form a flat side  34   a.  Near the edge of the bolt hole  11 , the flange  2  is formed with a protrusion  35   a  having a flat surface to be in abutment with the flat side  34   a  of the bolt head  34  to prevent the bolt  7  from turning in the bolt hole  11 . Otherwise, this embodiment is structurally the same as the first embodiment. 
   This arrangement reduces the surface pressure between serrations  7   a  formed at the neck of the bolt  7  and the inner wall of the bolt hole  11  and thus prevents strains from producing on the side  2   a  of the flange  2  on which the brake rotor  5  is mounted. 
   A few more arrangements for achieving the same purpose are shown in  FIGS. 17-20 . In the arrangement of  FIGS. 17A and 17B , the head  34  of each bolt  7  is formed with two flat sides  34   b  and a protrusion  35   b  having two flat surfaces abuttting the two flat sides  34   b  is formed on the flange  2  around the bolt hole  11 . 
   In the arrangement of  FIGS. 18A and 18B , each bolt has a hexagonal head  34  having six sides  34   c  and received in a complementary hexagonal bore of a protrusion  35   c  formed on the flange  2  around the bolt hole  11 . 
   In the arrangement of  FIGS. 19A and 19B , each bolt has an oval head  34  received in a complementary oval bore of a protrusion  35   d  formed on the flange  2  around the bolt hole  11 . 
   In the arrangement of  FIGS. 20A and 20B , the bolt head  34  has a knurled side  36 . An annular protrusion  35   e  is formed on the flange  2  around the bolt hole  11  and pressed against the knurled surface  36  by plastically deforming it by forging. Since the bolt is positively prevented from turning by this arrangement, the serrations on the neck are not necessary and thus are omitted. 
     FIG. 21  shows the sixth embodiment, which is for a driving wheel. The brake rotor  5  is mounted to the inner side  2   b  of the flange  2  and only the hub  14  is mounted to its outer side  2   a.  Otherwise, this embodiment is structurally identical to the first embodiment. 
     FIG. 22  shows the seventh embodiment, which is also for a driving wheel. In this embodiment, the inner member  1  is integral with an outer coupling of a constant-velocity joint  13 . The raceways  1   a,    1   b  of the inner member  1  are formed directly on the outer surface of the outer coupling of the joint  13 . Otherwise, this embodiment is structurally identical to the first embodiment. 
     FIG. 23  shows the eighth embodiment, which is for a non-driving wheel. Like the wheel bearing assemblies described above for a driving wheel, the bearing assembly of this embodiment has an inner member  1  formed with an integral wheel mounting flange  2  extending radially outwardly from its outer surface, and a wheel pilot  10  axially protruding from its outer end face. The brake rotor  5  is secured in position between the outer side  2   a  of the flange  2  and the wheel hub  14  by the mounting bolts  7 . The wheel bearing assembly further includes an outer member  3  having a flange  4  formed with bolt holes  12  through which bolts are inserted to secure the outer member to a stationary part of; the vehicle body. 
   The inner member  1  comprises a main portion formed with a first raceway  1   a  on its outer surface and a separate ring member  15  formed with a second raceway  1   b  on its outer surface. The outer member  3  has two raceways  3   a  and  3   b  formed on its inner surface so as to be opposite to the raceways  1   a  and  1   b.    
     FIG. 24  shows the ninth embodiment, which is also for a non-driving wheel but differs from the eighth embodiment in that the flange  2  is integral with the outer member  3  and the inner member  1  is comprised of two inner rings  15 . Like the eighth embodiment, the rotor  5  is secured to the outer side  2   a  of the flange  2 . 
   The outer member  3  is formed with raceways  3   a,    3   b  directly on its inner periphery and the inner rings  15  (forming the inner member  1 ) formed with raceways  1   a,    1   b  are mounted inside of the outer member  3  through rolling members  8 . 
   The wheel bearing assembly of this embodiment is fastened with the inner member  1  mounted on a stationary axle. In order to measure the runout of the side  2   a  of the wheel mounting flange  2  as shown in  FIG. 5 , the inner member  1  was fixed on a reference shaft, and the outer member  3  formed with the wheel mounting flange  2  was turned by one full turn, and the runout of the side  2   a  of the flange  2  was measured by use of a dial gauge  22 . 
   A tenth embodiment is a wheel bearing assembly for a driving wheel. It comprises an inner member  1  having a first inner member and a second inner member which is an outer coupling of a constant-velocity joint. The first inner member is formed with a wheel mounting flange  2  with which the brake rotor  5  is integrally formed. The first inner member is formed with a splined hole  9  in its inner periphery. The second inner member  1   d  has a cylindrical portion fitted in the splined hole  9  of the first inner member. By deforming the end of the cylindrical portion, the first and second inner members are inseperably coupled together. 
   The outboard raceway, is formed on a separate inner ring pressed on the cylindrical portion of the first inner member and the inboard raceway is formed directly on the second inner member. Otherwise, this embodiment is the same as the first embodiment. The maximum runout variation of the rotor braking surface  5   c  is restricted to not more than 50 μm. 
   Also, with the wheel bearing assembly according to this invention, since the maximum variation of runout of the brake rotor mounting surface of the wheel mounting flange provided on one of the inner and outer members is restricted within a predetermined value, and a dimension-controlled negative axial clearance is formed between the plurality of rows of rolling elements and raceways to increase rigidity of the wheel bearing assembly, or the brake rotor mounting surface is made as an outer side of the wheel mounting flange, and this outer side is inclined to the outer side toward the tip side of the wheel mounting flange so that the brake rotor is supported by the outer peripheral portion of this side with good stability, it is possible to suppress runout of the braking surfaces during rotation of the brake rotor.