Wheel bearing assembly with brake rotor

To prevent vibrations and uneven wear of a brake resulting from runout of the brake rotor, a reliable wheel bearing assembly with a brake rotor is proposed which needs no troublesome runout adjustment at a car assembling factory. The assembly includes an outer member having two raceways on its inner circumferential surface, an inner member having raceways each provided opposite a respective one of the two raceways, and rolling elements arranged in two rows between the outer and inner members. One of the outer and inner members is provided with a wheel mounting flange, and the brake rotor is mounted to the wheel mounting flange. The runout variation of a side of the brake rotor is maintained within a standard value with a fixed-side member as a datum.

BACKGROUND OF THE INVENTION
 This invention relates to an automotive wheel bearing assembly with a brake
 rotor.
 Among automotive wheel bearing assemblies, there are ones for driving
 wheels and ones for non-driving wheels. As an example, a wheel bearing
 assembly for a driving wheel is shown in FIG. 12. It comprises an outer
 member 3 having two raceways 3a, 3b on its inner circumferential surface,
 an inner member 1 having raceways 1a, 1b opposite the raceways 3a, 3b, and
 rolling elements 8 disposed between the outer member 3 and the inner
 member 1 in two rows. The inner member 1 has a wheel-mounting flange 2.
 Also, in this example, the inner member 1 has a hole 9 for receiving a
 drive shaft in its inner circumferential surface. Of two raceways 1a, 1b
 on the inner member 1, the outer raceway 1a is formed directly on the
 outer circumferential surface of the inner member 1, while the inner
 raceway 1b is formed on a separate inner ring.
 When wheel bearing assemblies are delivered to an assembling factory of a
 car manufacturer from a wheel bearing manufacturer, a brake rotor 20,
 which has been delivered as a separate part, is fixed by bolts 18 to the
 side 2a of the wheel-mounting flange 2 at the car assembling factory. But
 if after assembling there is a runout on the side 21 of the brake rotor
 20, with the increasing speed of cars, brake judder may occur during
 braking from high speeds, or brakes may be worn unevenly. With a certain
 state of runout, brake vibrations may occur even at low speeds.
 Heretofore, in order to prevent such runout of the side 21 of the brake
 rotor 20, when the brake rotor (which has been delivered as a separate
 part) is mounted to the wheel mounting flange 2 of a wheel bearing
 assembly delivered from a wheel bearing manufacturer at a car assembling
 factory, adjustment of phase between the runout of the wheel mounting
 flange 2 and the runout of the side 21 of the brake rotor 20 was
 necessary. Such a method is rather troublesome and poor in workability.
 Also, at a car assembling factory, due to aesthetic reasons,
 rust-preventive coating is usually applied to the surface of the brake
 rotor. If a coating is applied to the brake rotor, runout tends to grow
 due to uneven thickness of the coating.
 An object of this invention is to prevent vibrations and uneven wear of a
 brake resulting from runout of the brake rotor caused by an increase in
 the car speed, and to provide a reliable wheel bearing assembly with a
 brake rotor which needs no troublesome runout adjustment at a car
 assembling factory.
 SUMMARY OF THE INVENTION
 According to this invention, there is provided a wheel bearing assembly
 with a brake rotor comprising an outer member having two raceways on inner
 circumferential surface thereof, an inner member having two raceways each
 provided opposite the two raceways on the outer member, and rolling
 elements arranged in two rows between the outer member and the inner
 member. One of the outer member and the inner member is provided with a
 wheel mounting flange, and the brake rotor is mounted to the wheel
 mounting flange. The runout variation of a side of the brake rotor is
 restricted within a predetermined value when measured while rotating the
 one member with the other of the outer member and the inner member as a
 reference.
 Such a wheel bearing assembly is highly reliable and can be assembled at a
 car assembling factory. This eliminates the runout problem, and adjustment
 of runout at the assembling factory is not necessary any more. Restricting
 the runout to 50 .mu.m or under brings good results. 30 .mu.m or under is
 more preferable.
 Forming raceways directly on the outer member and the inner member is
 advantageous because the number of parts required is less.
 The present invention is applicable to both wheel bearing assemblies for a
 driving wheel and those for a non-driving wheel.
 The restriction of runout is carried out before assembling the wheel
 bearing assembly. A brake rotor is mounted on one of the inner member or
 the outer member formed with a wheel mounting flange, and the one of these
 two is rotated while using the other as a datum.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 An automotive wheel bearing assembly comprises, as shown in FIG. 1, an
 outer member 3 having two raceways 3a, 3b on its inner circumferential
 surface, an inner member 1 having raceways 1a, 1b opposite the raceways
 3a, 3b, and rolling elements 8 disposed between the outer member 3 and the
 inner member 1 in two rows. The inner member 1 has a wheel-mounting flange
 2. A brake rotor 20 is fastened to the side 2a of the wheel mounting
 flange 2 by bolts 18. Specifically, there are assemblies for a driving
 wheel, in which the drive shaft of a constant velocity joint is mounted,
 as shown in FIGS. 1 through 7, and assemblies for a non-driving wheel, in
 which no drive shaft is mounted, as shown in FIGS. 8 through 10.
 The brake rotor-carrying wheel bearing assembly shown in FIG. 1 is a wheel
 bearing assembly for a driving wheel, and constitutes a first embodiment
 of this invention. The inner member 1 is formed with a hole 9 having
 splines on its inner circumferential surface adapted to engage a drive
 shaft. Of the two raceways 1a, 1b of the inner member 1, the outer raceway
 1a (with respect to the outer side of the vehicle) is formed directly on
 the outer circumferential surface of the inner member, while the inner
 raceway 1b (with respect to the inner side, i.e., central axis, of the
 vehicle) is formed on a separate inner ring 15 which is fitted on a
 shoulder at one end of a hub wheel 14.
 The hub wheel 14 of the inner member 1 of FIG. 1 is integrally formed with
 a wheel mounting flange 2 having an outer side on which is formed a wheel
 pilot 10 at its center. The wheel mounting flange 2 is formed with bolt
 holes 11 for wheel-fixing hub bolts 7. The brake rotor 20 is adapted to be
 fixed to an outer mounting surface 2a by bolts 18. The two raceways 3a, 3b
 are formed directly on the inner circumferential surface of the outer
 member 3. Further, the outer member 3 has an integral flange 4 having a
 bolt hole 12 and is adapted to be fixed to the car body. Seal members 19
 for sealing the interior of the bearing are pressed into the member 3 at
 both ends. In this embodiment of FIG. 1, the surface runout of the outer
 surface 21 of the brake rotor 20 is restricted (i.e., maintained) within a
 standard value, which is preferably 50 .mu.m or less, more preferably 30
 .mu.m or less.
 The wheel bearing assembly with a brake rotor shown in FIG. 2 is a wheel
 bearing assembly for a driving wheel and constitutes a second embodiment
 of this invention. The separate inner ring 15 in the first embodiment is
 structured to be pressed onto the wheel axle of a constant velocity joint.
 The wheel bearing assembly with a brake rotor shown in FIG. 3 is a wheel
 bearing assembly for a driving wheel, and is a third embodiment of this
 invention. In this example, the inner member 1 is integral with an outer
 ring of a constant velocity joint. Two raceways 1a, 1b are formed directly
 on the outer circumferential surface of the inner member 1. Also, a wheel
 pilot 10 and a wheel mounting flange 2 are integrally formed on the outer
 side of the inner member 1. On the other hand, two raceways 3a, 3b are
 directly formed on the inner circumferential surface of the outer member
 3. Also, the outer member has on its outer surface a knuckle-mounting
 flange, i.e., a flange 4 having bolt holes 12 and adapted to be fixed to
 the car body.
 In the embodiment of FIG. 3, a brake rotor 20 is fixed to the outer
 mounting surface 2a of the flange 2 by bolts 18. The runout of the outer
 surface 21 of the brake rotor 20 is maintained within a standard value
 which is preferably 50 .mu.m or under as in the first embodiment. For the
 subsequent embodiments too, the runout of the outer surface 21 of the
 brake rotor 20 is maintained within a standard value, which is, as in the
 first and second embodiments, desirably 50 .mu.m or under, and more
 preferably 30 .mu.m or under.
 The wheel bearing assembly with a brake rotor shown in FIG. 4 is also a
 wheel bearing assembly for a traction wheel and is a fourth embodiment of
 this invention. The two raceways 1a, 1b of the inner member 1 are formed
 on two separate inner rings 15. The inner member 1 has a wheel mounting
 flange 2 having an outer mounting surface 2a to which is fixed a brake
 rotor 20 by bolts 18. Like the wheel bearing assemblies shown in FIGS. 1
 through 3, the outer member 3 is one having two raceways 3a, 3b formed on
 its inner circumferential surface.
 The wheel bearing assembly with a brake rotor shown in FIG. 5 is also a
 wheel bearing assembly for a driving wheel, and is a fifth embodiment of
 this invention. Like the one shown in FIG. 4, the inner member 1 shown in
 FIG. 5, which is mounted on the drive shaft, has its two raceways 1a, 1b
 formed on two separate inner rings 15. Also, the outer member 3 comprises
 a housing 16 formed with a flange 4 having bolt holes 12 and adapted to be
 fixed to the car body, and an outer ring 17 formed with two raceways 3a,
 3b.
 Next, the wheel bearing assembly with a brake rotor shown in FIG. 6 is a
 wheel bearing assembly for a driving wheel, and is a sixth embodiment of
 this invention. In this embodiment, a brake rotor 20 is fixed to the inner
 side (an inner mounting surface) of the wheel mounting flange 2.
 As in this sixth embodiment, the brake rotor 20 can be mounted to the inner
 side of the wheel mounting flange 2. Therefore, because the inner side
 surface of the wheel mounting flange 2 is not a wheel mounting surface,
 the mounting surface 22 of the brake rotor 20 is, as shown in FIG. 7,
 formed in a shape having a step 23 so that the outer circumferential
 surface of the wheel mounting flange 2 of the inner member 1 serves as a
 brake pilot.
 In the mounting surface 22 of the brake rotor 20, only holes 24 for bolts
 18 for fixing the brake rotor 20 are formed, and cutouts 25 are formed to
 prevent the hub bolts 7 from interfering with the mounting surface 22. By
 forming the cutouts 25 in the mounting surface 22 of the brake rotor 20,
 when nuts are tightened onto the hub bolts 7, even if the wheel is
 deformed axially, the brake rotor 20 will not be affected at all. Thus it
 is possible to further reduce the runout of the brake rotor 20.
 As in the sixth embodiment, mounting the brake rotor 20 to the inner side
 of the wheel mounting flange is applicable to the other embodiments too.
 Next, the wheel bearing assembly with a brake rotor shown in FIG. 8 is a
 wheel bearing assembly for a non-driving wheel, and is a seventh
 embodiment of this invention. Of the two raceways 1a, 1b of the inner
 member 1, the outer raceway 1a is formed directly on its outer surface,
 while the, inner raceway 1b is formed on a separate inner ring 15 mounted
 on its inner end. The inner member 1 is integrally formed with a wheel
 mounting flange 2. To the outer mounting surface 2a of the wheel mounting
 flange 2, a brake rotor 20 is fixed by bolts 18. Also, the outer member 3
 has two raceways 3a, 3b formed directly on its inner circumferential
 surface, and has on the outer circumferential surface a flange 4 having
 bolt holes 12 for fixing to the car body. A threaded portion 30 is formed
 on the inner side of the inner member 1. By tightening with a nut 31, the
 inner ring 15 is fixed to give the bearing a preload and a bearing
 rigidity. Further, the inner side is sealed by a hub cap 32.
 The wheel bearing assembly with a brake rotor shown in FIG. 9 is a wheel
 bearing assembly for a non-driving wheel, and is an eighth embodiment of
 this invention. It has a wheel mounting flange 2 on the outer member 3,
 and has two raceways 3a, 3b directly formed on the inner surface of the
 outer member 3. Inside the outer member 3, an inner member 1 (comprising
 inner rings 15) having raceways 1a, 1b on the outer surface is provided.
 In this embodiment, a brake rotor 20 is fixed to the outer mounting
 surface 2a of the wheel mounting flange 2 of the outer member 3.
 The wheel bearing assembly with a brake rotor shown in FIG. 10 is a ninth
 embodiment of this invention. This wheel bearing assembly has its outer
 member 3 formed by pressing a separate outer ring 17 having two rows of
 raceways 3a, 3b on the inner circumferential surface into an outer ring
 having a wheel mounting flange 2. An inner member 1 (inner rings 15)
 formed with raceways 1a, 1b on its outer surface is provided inside the
 outer member 3 through rolling elements 8. In this embodiment of FIG. 10,
 a brake rotor 20 is fixed to the outer mounting surface 2a of the wheel
 mounting flange 2 of the outer member 3 by bolts 18. In the eighth and
 ninth embodiments, the runout of the outer surface 21 of the brake rotor
 20 is maintained within a standard value, which is, like the previous
 embodiments, preferably 50 .mu.m or less, more preferably 30 .mu.m or
 less.
 In the wheel bearing assembly of each of the above embodiments, the seal is
 shown by numeral 19, and other like parts are denoted by like numerals.
 Also, while in each of the above embodiments, the brake rotor 20 and the
 separate wheel mounting flange are fixed to each other by bolts, the brake
 rotor 20 and the wheel mounting flange 2 may be integrally formed.
 Next, a way to maintain the runout of the outer surface 21 of the brake
 rotor 20 is described.
 In a wheel bearing assembly with a brake rotor assembled, the surface
 runout of the outer surface 21 of the brake rotor 20 can be maintained
 within a standard value. This is possible by fixing the outer member 3 to
 a measuring table 5 as shown in FIG. 1, rotating the inner member 1 by a
 full turn with the outer member 3 fixed as a datum, and measuring the
 axial runout variation of the outer surface 21 of the brake rotor 20 fixed
 to the outer mounting surface 2a of the wheel mounting flange 2 by use of
 a dial gauge 6 pressed against the outer surface 21 of the brake rotor 20.
 The standard value of runout is preferably 50 .mu.m or under. Since the
 runout variation of the outer surface 21 of the brake rotor 20 is greater
 at the outer side, the runout variation is controlled at a portion near
 the outer circumference.
 As described above, in the wheel bearing assembly with a brake rotor
 according to this invention, when shipped from a wheel bearing
 manufacturer, the runout variation of the side of the brake rotor is
 maintained within a standard value beforehand with the fixed-side member
 as a reference. Therefore, it is reliable, and no troublesome brake rotor
 runout adjustment is necessary at the car assembling factory.
 Also, only the surface of the brake rotor may be coated after the runout
 variation of the side face of the brake rotor has been maintained. There
 is no need to dismount the brake rotor from the wheel bearing assembly
 with the brake rotor for coating for rust prevention. Thus it is possible
 to suppress errors in runout variation caused by dismounting of the rotor.