Wheel bearing device

Abstract

A wheel bearing device includes a wheel bearing supported by a knuckle; a hub ring having a boss portion; a second constant-velocity joint; and a first constant-velocity joint. The second constant-velocity joint includes an outer ring rotatably supported by the wheel bearing, and an inner ring coupled to the boss portion of the hub ring. The first constant-velocity joint includes an outer ring coupled to the outer race of the second constant-velocity joint, and an inner ring coupled to a drive shaft. The knuckle supports a pair of camber angle-adjusting linear motion actuators, and a pair of toe angle-adjusting linear motion actuators.

Claims

1. A wheel bearing device comprising: a wheel body of a wheel of a vehicle; a wheel bearing to be supported by a knuckle of the vehicle; a hub ring including a disk portion coupled to the wheel body, and a boss portion disposed on a center axis of the disk portion; a first constant-velocity joint and a second constant-velocity joint mounted between opposed portions of the boss portion and a drive shaft; a pair of camber angle-adjusting linear motion actuators configured to press upper and lower portions of an inboard side surface of the disk portion, respectively, so as to adjust a camber angle of the wheel; and a pair of toe angle-adjusting linear motion actuators configured to press, respectively, front and rear portions, in a vehicle travel direction in which the vehicle travels, of the inboard side surface of the disk portion so as to adjust a toe angle of the wheel, wherein each of the first and second constant-velocity joints comprises a fixed constant-velocity joint including: an outer ring having a spherical inner surface having track grooves; an inner ring having a spherical outer surface having track grooves; a cage disposed between the spherical inner surface of the outer ring and the spherical outer surface of the inner ring; and balls retained by the cage so as to each roll along a respective one of the track grooves in the spherical inner surface of the outer ring and a respective one of the track grooves in the spherical outer surface of the inner ring, wherein the inner ring of the first constant-velocity joint is to be coupled to the drive shaft, and the outer ring of the first constant-velocity joint is coupled to the outer ring of the second constant-velocity joint, wherein the outer ring of the second constant-velocity joint is rotatably supported by the wheel bearing, and the inner ring of the second constant-velocity joint is coupled to the boss portion of the hub ring, and wherein the pair of camber angle-adjusting linear motion actuators, and the pair of toe angle-adjusting linear motion actuators are to be supported by the knuckle.

2. The wheel bearing device according to claim 1, further comprising: a raceway ring having an opposed surface opposed to the inboard side surface of the disk portion of the hub ring, and configured to receive axial loads of the camber angle-adjusting linear motion actuators, and axial loads of the toe angle-adjusting linear motion actuators, wherein the raceway ring has a first circular raceway groove in the opposed surface of the raceway ring, and the disk portion of the hub ring has a second circular raceway groove in a portion of the inboard side surface of the disk portion opposed to the opposed surface of the raceway ring, and wherein each of the first and second circular raceway grooves has a center on a center axis of the hub ring; and balls disposed between the first and second circular raceway grooves so as to rotatably support the raceway ring.

3. The wheel bearing device according to claim 2, further comprising a spherical seat plate having a convex spherical surface on an outer periphery of the spherical seat plate, and coupled to an open end surface of the outer ring of the second constant-velocity joint, wherein the disk portion of the hub ring has a concave spherical surface configured to guide the convex spherical surface of the spherical seat plate while kept in contact with the convex spherical surface.

4. The wheel bearing device according to claim 3, wherein each of the camber angle-adjusting linear motion actuators, and the toe angle-adjusting linear motion actuators comprises an electric ball screw assembly including: an electric motor; and a ball screw including a nut, balls, and a threaded shaft threadedly engaged with the nut through the balls of the ball screw, the ball screw being configured to be driven by the electric motor, and wherein the electric ball screw assemblies are each configured such that when the nut is driven by the electric motor, the threaded shaft is axially moved so as to apply an axial load to the disk portion of the hub ring.

5. The wheel bearing device according to claim 2, wherein each of the camber angle-adjusting linear motion actuators, and the toe angle-adjusting linear motion actuators comprises an electric ball screw assembly including: an electric motor; and a ball screw including a nut, balls, and a threaded shaft threadedly engaged with the nut through the balls of the ball screw, the ball screw being configured to be driven by the electric motor, and wherein the electric ball screw assemblies are each configured such that when the nut is driven by the electric motor, the threaded shaft is axially moved so as to apply an axial load to the disk portion of the hub ring.

6. The wheel bearing device according to claim 1, further comprising a spherical seat plate having a convex spherical surface on an outer periphery of the spherical seat plate, and coupled to an open end surface of the outer ring of the second constant-velocity joint, wherein the disk portion of the hub ring has a concave spherical surface configured to guide the convex spherical surface of the spherical seat plate while kept in contact with the convex spherical surface.

7. The wheel bearing device according to claim 6, wherein each of the camber angle-adjusting linear motion actuators, and the toe angle-adjusting linear motion actuators comprises an electric ball screw assembly including: an electric motor; and a ball screw including a nut, balls, and a threaded shaft threadedly engaged with the nut through the balls of the ball screw, the ball screw being configured to be driven by the electric motor, and wherein the electric ball screw assemblies are each configured such that when the nut is driven by the electric motor, the threaded shaft is axially moved so as to apply an axial load to the disk portion of the hub ring.

8. The wheel bearing device according to claim 1, wherein each of the camber angle-adjusting linear motion actuators, and the toe angle-adjusting linear motion actuators comprises an electric ball screw assembly including: an electric motor; and a ball screw including a nut, balls, and a threaded shaft threadedly engaged with the nut through the balls of the ball screw, the ball screw being configured to be driven by the electric motor, and wherein the electric ball screw assemblies are each configured such that when the nut is driven by the electric motor, the threaded shaft is axially moved so as to apply an axial load to the disk portion of the hub ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a front view of a wheel bearing device embodying the present invention.

(2) FIG. 2 is a vertical sectional view of the wheel bearing device of FIG. 1.

(3) FIG. 3 is a vertical sectional view of each linear motion actuator of FIG. 2.

(4) FIG. 4 is a sectional view of the wheel bearing device with some parts thereof disassembled.

(5) FIG. 5 is a schematic front view illustrating the negative camber state of wheels.

(6) FIG. 6 is a schematic front view illustrating the positive camber state of the wheels.

(7) FIG. 7 is a schematic front view illustrating the toe-out state of the wheels.

(8) FIG. 8 is a schematic front view illustrating the toe-in state of the wheels.

DETAILED DESCRIPTION OF THE INVENTION

(9) A wheel bearing device embodying the present invention is now described with reference to the drawings. As illustrated in FIG. 1, upper and lower arms 3 and 4 are connected to a knuckle 2 supporting a front wheel 1 as a drive wheel, and couple the knuckle 2 to the vehicle body.

(10) As illustrated in FIG. 2, a hub ring 6 is mounted to the wheel body 5 of the front wheel 1, and includes a disk portion 7; a tubular boss portion 8 disposed at the central portion of the disk portion 7 on its inboard side surface; and a pilot portion 10 disposed on the outboard side surface of the disk portion 7, and press-fitted in a central hole 9 in the wheel body 5.

(11) The term inboard means closer to the center of the vehicle with the hub ring 6 mounted to the wheel body 5, whereas the term outboard means remoter from the center of the vehicle.

(12) A first constant-velocity joint 12 and a second constant-velocity joint 22 are mounted between the hub ring 6 and a drive shaft 11 for driving the front wheel 1.

(13) As illustrated in FIG. 4, the first constant-velocity joint 12 comprises a fixed, constant-velocity ball joint including an outer ring 13 having a spherical inner surface 14; an inner ring 15 disposed inwardly of the spherical inner surface 14, and having an spherical outer surface 16; a cage 17 mounted between the spherical inner surface 14 of the outer ring 13 and the spherical outer surface 16 of the inner ring 15; and balls 19 received in respective pockets 18 in the cage 17 that are circumferentially equidistantly spaced apart from each other such that the balls 19 are capable of rolling along track grooves 20 in the spherical inner surface 14 of the outer race 13 and track grooves 21 in the spherical outer surface 16 of the inner ring 15. In this constant-velocity ball joint, the curvature center of the track grooves 20 of the outer race 13, and the curvature center of the track grooves 21 of the inner race 15 are equidistantly offset from the center of the joint in the right and left directions so that, even when the axes of the outer and inner rings 13 and 15 form an angle, the constant-velocity ball joint can transmit rotation at a constant velocity.

(14) The second constant-velocity joint 22 also comprises, as with the first constant-velocity joint 12, a fixed, constant-velocity ball joint, and includes an outer ring 23 having a spherical inner surface 24; an inner ring 25 disposed inwardly of the spherical inner surface 24, and having an spherical outer surface 26; a cage 27 mounted between the spherical inner surface 24 of the outer ring 23 and the spherical outer surface 26 of the inner ring 25; and balls 29 received in respective pockets 28 in the cage 27 that are circumferentially equidistantly spaced apart from each other such that the balls 29 are capable of rolling along track grooves 30 in the spherical inner surface 24 of the outer race 23 and track grooves 31 in the spherical outer surface 26 of the inner ring 25.

(15) The inner ring 15 of the first constant-velocity joint 12 is fitted to one end of the drive shaft 11 through serrations so as to be rotationally fixed to the drive shaft 11.

(16) As illustrated in FIG. 2, the outer ring 13 of the first constant-velocity joint 12 is arranged coaxially with, and coupled to, the outer ring 23 of the second constant-velocity joint 22 with the closed end of the outer ring 13 opposed to the closed end of the outer ring 23. Specifically, the outer ring 13 of the first constant-velocity joint 12 has, on the closed end thereof, a stem 32 with serration teeth 34 that is fitted into a stem inserting hole 33 with serration teeth 34 that is formed in the closed end of the outer ring 23 of the second constant-velocity joint 22 such that the outer rings 13 and 23 are coupled together so as to be rotationally fixed relative to each other due to meshing engagement between the serration teeth 34 of the stem 32 and the serration teeth 34 of the stem inserting hole 33. A bolt 35 with a washer is inserted from the open end of the outer ring 23 of the second constant-velocity joint 22, screwed into a threaded hole 36 formed in the stem 32 to extend along its center axis, and tightened, to couple the outer rings 13 and 23 to each other.

(17) A boot 37 is mounted to the drive shaft 11 and the outer ring 13 of the first constant-velocity joint 12 so as to close the end opening of the outer ring 13, thereby preventing the grease contained in the outer ring 13 from leaking out, and also preventing foreign matter from entering the outer ring 13.

(18) As illustrated in FIG. 4, the outer ring 23 of the second constant-velocity joint 22 is rotatably supported by a wheel bearing 38 supported by the knuckle 2. The wheel bearing 38 includes a bearing outer race 39 having a flange 39a on its outer periphery that is screwed to the knuckle 2; and balls 41 capable of rolling along double-row raceway grooves 40 formed in the inner periphery of the bearing outer race 39. The wheel bearing 38 further includes a bearing inner race, 43 fitted on, and fixed to, a bearing support surface 42 formed on the closed end of the outer ring 23 of the second constant-velocity joint 22. The outer ring 23 is supported by the wheel bearing 38 with the balls 40 in the respective rows received in, so as to be capable of rolling along, a raceway groove 44 in the outer periphery of the bearing inner race 43, and a raceway groove 44 in the outer periphery of the outer ring 23 near its open end.

(19) Both open ends of the bearing outer race 39 are sealed by seal members 45 mounted, respectively, between the bearing outer race 39 and the outer ring 23 of the second constant-velocity joint 22, and between the bearing outer race 39 and the bearing inner race 43, so that the grease contained in the bearing outer race 39 is prevented from leaking out, and also foreign matter is prevented from entering the bearing outer race 39.

(20) The inner ring 25 of the second constant-velocity joint 22 is brought into abutment with the end surface of the boss portion 8 of the hub ring 6, and coupled to the boss portion 8. More specifically, a bolt 47 is inserted through the boss portion 8 from the outboard side of the hub ring 6, threadedly engaged in a threaded hole 46 formed in the inner ring 25 to extend along its center axis, and tightened, to fix the inner ring 25 in position.

(21) As illustrated in FIG. 2, an aligning mechanism 48 is disposed between the opposed portions of the hub ring 6 and the outer ring 23 of the second constant-velocity joint 22 so as to prevent an unbalanced load from being applied to the balls 29 of the second constant-velocity joint 22 from the hub ring 6.

(22) The aligning mechanism 48 includes a spherical seat plate 49 screwed to the open end surface of the outer ring 23. The spherical seat plate 49 has a convex spherical surface 50 on its outer periphery that is kept in contact with a concave spherical surface 51 formed on the disk portion 7 of the hub ring 6 such that, when the hub ring 6 and the inner ring 25 rotate with their axes forming an angle, the concave spherical surface 51 of the hub ring 6 is guided by the convex spherical surface 50 of the spherical seat plate 49 while kept in contact with the convex spherical surface 50, and the convex spherical surface 50 receives an unbalanced load from the hub ring 6, thereby preventing an unbalanced load from being applied to the balls 29.

(23) A raceway ring 52 is disposed at a position opposed to the radially outer portion of the disk portion 7 on its inboard side. Circular raceway grooves 53 and 54 each having a center on the center axis of the hub ring 6 are formed in the opposed surfaces of the raceway ring 52 and the disk portion 7, respectively. Balls 55 are disposed between the raceway grooves 53 and 54 such that the raceway ring 52 and the hub ring 6 are rotatable relative to each other.

(24) As illustrated in FIGS. 5 and 6, the knuckle 2 supports a pair of upper and lower camber angle-adjusting linear motion actuators 56 configured to adjust the camber angle of the drive wheel 1 (which is a front wheel 1) by pressing the upper and lower portions of the inboard side surface of the raceway ring 52, respectively. As illustrated in FIGS. 7 and 8, the knuckle 2 also supports a pair of toe angle-adjusting linear motion actuators 57 configured to adjust the toe angle of the front wheel 1 by pressing, respectively, the front and rear portions, in the vehicle travel direction, of the inboard side surface of the raceway ring 52.

(25) In the embodiment, each of the camber angle-adjusting linear motion actuators 56 and the toe angle-adjusting linear motion actuators 57 comprises an electric ball screw assembly 60 (shown in FIG. 3) constituted by an electric motor 61, and a ball screw 62 configured to be driven by the electric motor 61.

(26) The electric motor 61 comprises a motor case 63 screwed to the knuckle 2; a stator 64 supported by the inner diameter surface of the motor case 63; and a rotor 65 mounted inside of the stator 64. The ball screw 62 comprises a nut 66 mounted inside of the rotor 65 of the electric motor 61; balls 67; and a threaded shaft 68 including a spherical presser 69 at its distal end, and threadedly engaged with the nut 66 through the balls 67. The ball screw 62 is configured such that when the nut 66 is rotated by the electric motor 61, and the threaded shaft 68 is axially moved, the presser 69 at the distal end of the threaded shaft 68 presses the raceway ring 52.

(27) In order to smoothly move the threaded shaft 68 toward the raceway ring 52, the threaded shaft 68 is biased toward the raceway ring 52 by an elastic member 70.

(28) As illustrated in FIG. 2, a seal member 58 is mounted between the outer peripheral portions of the opposed surfaces of the raceway ring 52 and the disk portion 7 of the hub ring 6, thereby preventing grease from leaking out. A boot 59 closes the space between the raceway ring 52 and the bearing outer race 39, thereby preventing the leakage of grease, and the entry of foreign matter.

(29) The above-described wheel bearing device according to the embodiment is used for each of the front wheels (drive wheels 1), and in order to adjust the camber angle of each front wheel, one of the pair of camber angle-adjusting linear motion actuators 56 (shown in FIG. 1) is activated. For example, when the lower one of the camber angle-adjusting linear motion actuators 56 is activated to move its threaded shaft 68 toward the raceway ring 52, the threaded shaft 68 presses the lower portion of the raceway ring 52 so that, as illustrated in FIG. 5, the front wheel 1 is inclined to form a negative camber angle, at which the shown ground contact point P of the tire surface of the front wheel is located outwardly of the shown center axis L of the front wheel.

(30) On the other hand, when the upper one of the camber angle-adjusting linear motion actuators 56 (shown in FIG. 1) is activated to move its threaded shaft 68 toward the raceway ring 52, the threaded shaft 68 presses the upper portion of the raceway ring 52 so that, as illustrated in FIG. 6, the front wheel 1 is inclined to form a positive camber angle, at which the shown ground contact point P of the tire surface is located inwardly of the shown center axis L.

(31) When the front one of the pairs of toe angle-adjusting linear motion actuators 57 is activated, its threaded shaft 68 presses the front portion, in the vehicle travel direction, of the raceway ring 52, thereby adjusting the toe angle of the front wheel 1 to a toe-out state, in which the front portion, in the vehicle travel direction, of the front wheel is inclined outwardly.

(32) On the other hand, when the rear one of the toe angle-adjusting linear motion actuators 57 is activated, its threaded shaft 68 presses the rear portion, in the vehicle travel direction, of the raceway ring 52, thereby adjusting the toe angle of the front wheel 1 to a toe-in state, in which the front portion, in the vehicle travel direction, of the front wheel is inclined inwardly.

(33) When the camber angle and the toe angle are adjusted as described above, the outer and inner rings 23 and 25 of the second constant-velocity joint 22 are inclined relative to each other, and rotate at a constant velocity in this inclined state, so that the rotation of the inner ring 25 is transmitted to the front wheel 1 through the hub ring 6.

(34) When each front wheel 1 forms a negative camber angle as illustrated in FIG. 5, a force causing the front wheel 1 to move inwardly in the vehicle travel direction acts on the front wheel 1. In this case, by, as illustrated in FIG. 7, adjusting the toe angle of each front wheel 1 such that the front wheel 1 is in the toe-out state, a force causing the front wheel 1 to move outwardly in the vehicle travel direction acts on the front wheel 1, thereby offsetting the force applied to the front wheel 1 due to the negative camber angle. As a result thereof, the vehicle can stably travel in a straight line.

(35) When each front wheel 1 forms a positive camber angle as illustrated in FIG. 6, a force causing the front wheel 1 to move outwardly in the vehicle travel direction acts on the front wheel 1. In this case, by, as illustrated in FIG. 8, adjusting the toe angle of each front wheel 1 such that the front wheel 1 is in the toe-in state, a force causing the front wheel 1 to move inwardly in the vehicle travel direction acts on the front wheel 1, thereby offsetting the force applied to the front wheel 1 due to the positive camber angle. As a result thereof, the vehicle can stably travel in a straight line.

(36) By, as illustrated in FIG. 2, pressing the raceway ring 52, which is supported by the hub ring 6 through the balls 55 so as to be rotatable relative to the hub ring 6, by use of the threaded shafts 68 of the camber angle-adjusting linear motion actuators 56 and the toe angle-adjusting linear motion actuators 57, it is possible to markedly reduce the rotational resistance applied to the hub ring 6, and thus to rotate the front wheel 1 in a smooth manner, compared to the arrangement in which the hub ring 6 is pressed directly by the linear motion actuators 56 and 57.

(37) In the exploded front view of FIG. 4, the hub ring 6, the spherical seat plate 49, the second constant-velocity joint 22, and the wheel bearing 38 form a single unit by screwing bolts 80 mounted to the spherical seat plate 49 into threaded holes 81 formed in the open end surface of the outer ring 23, and tightening the bolts 80, and the single unit can be mounted to, and separated from, the wheel bearing device. Therefore, the wheel bearing device can be assembled easily, and even if a part or parts of the unit are damaged, the damaged part(s) can be easily replaced with a new one(s).

(38) While the wheel bearing device supports a front wheel 1 in the embodiment, the wheel bearing device may be used to support a rear wheel.

DESCRIPTION OF REFERENCE NUMERALS

(39) 1: front wheel (vehicle wheel) 2: knuckle 5: wheel body 6: hub ring 7: disk portion 8: boss portion 11: drive shaft 12: first constant-velocity joint 13, 23: outer ring 14, 24: spherical inner surface 15, 25: inner ring 16, 26: spherical outer surface 17, 27: cage 19, 29: ball 20, 21, 30, 31: track groove 22: second constant-velocity joint 38: wheel bearing 49: spherical seat plate 50: convex spherical surface 51: concave spherical surface 52: raceway ring 53, 54: raceway groove 55: ball 56: camber angle-adjusting linear motion actuator 57: toe angle-adjusting linear motion actuator 61: electric motor 62: ball screw 66: nut 68: threaded shaft