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Title:
ACTIVE TOE ANGLE ADJUSTMENT MECHANISM FOR VEHICLE WHEELS
Document Type and Number:
WIPO Patent Application WO/2013/104427
Kind Code:
A1
Abstract:
The present invention resides in a wheel end assembly with means for adjusting a toe angle of a vehicle wheel that is mounted to a wheel carrier (130) via a non-driven wheel bearing (150). The wheel carrier itself is mounted to a suspension member (110) of the vehicle via a stub shaft (120). Specifically, the stub shaft comprises a first section (121) that is rotationally mounted to the vehicle suspension via a first bearing arrangement (161, 162) having a first bearing axis (175). The stub shaft further has a second section (122) that supports a sleeve part (132) of the wheel carrier via a second bearing arrangement (171, 172), which has a second bearing axis (175). The assembly further comprises drive means (180, 185) for rotating the stub shaft (120) about an axis of rotation, defined by the first bearing axis (165). According to the invention, the first bearing axis is offset at an angle (α) relative to the second bearing axis. Therefore, when the stub shaft (120) is rotated relative to the wheel carrier (130), the wheel carrier is caused to move in a wobbling motion between a first position and a second position, in which the vehicle wheel has a corresponding first toe angle and a second toe angle. The first and second toe angles delimit a toe angle adjustment range. Thus, the toe angle of the vehicle wheel may be set to a predetermined value within the adjustment range by rotating the stub shaft (120) to a predetermined angular position.

Inventors:
VERHULST, Laurens (Kelvinbaan 16, MT Nieuwegein, NL-3439, NL)
DORRESTIJN, Igor (Kelvinbaan 16, MT Nieuwegein, NL-3439, NL)
Application Number:
EP2012/050518
Publication Date:
July 18, 2013
Filing Date:
January 13, 2012
Export Citation:
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Assignee:
AKTIEBOLAGET SKF (S- Göteborg, 415 50, SE)
VERHULST, Laurens (Kelvinbaan 16, MT Nieuwegein, NL-3439, NL)
DORRESTIJN, Igor (Kelvinbaan 16, MT Nieuwegein, NL-3439, NL)
International Classes:
B60G7/00; B62D17/00
Domestic Patent References:
WO2001074647A1
WO1998016418A1
Foreign References:
US20050051988A1
EP2019023A1
Attorney, Agent or Firm:
BURÖ, Peter et al. (SKF B.V, P.O. Box 2350, DT Nieuwegein, NL-3430, NL)
Download PDF:
Claims:
Claims

1. A wheel end assembly of a vehicle with means for actively adjusting a toe- angle of a non-driven vehicle wheel, the assembly (100, 200, 300) comprising:

• a wheel carrier (130, 230, 330) for supporting the vehicle wheel via a wheel bearing (150, 250, 350),

• a stub shaft (120, 220, 320) for supporting a sleeve part (132, 232, 332) the wheel carrier, whereby a first section (121 , 221 , 321 ) of the stub shaft is rotationally mounted to a suspension member (1 10, 210, 310) of the vehicle via a first bearing arrangement (161 , 162, 261 ,262, 361 ,362) which has a first bearing axis (165, 265, 365) that defines a rotation axis of the stub shaft, and

• drive means (185, 190) for rotating the stub shaft about the first bearing axis,

characterized in that

the stub shaft has a second section (122, 222, 322) that is rotationally supported relative to the wheel carrier via a second bearing arrangement (171 , 172, 271 ,272, 371 ,372), and in that

the second bearing arrangement has a second bearing axis (175, 275, 375) that is offset at an angle (a) relative to the first bearing axis, such that rotation of the stub shaft relative to the wheel carrier causes the wheel carrier to move in a wobbling motion between a first position and a second position, in which the vehicle wheel has a corresponding first toe angle and a corresponding second toe angle, the first and second toe angles thereby delimiting a toe angle adjustment range within which the toe angle of the vehicle wheel is actively adjustable by rotating the stub shaft to a predetermined angular position.

2. The assembly according to claim 1 , wherein the offset angle (a) between the first and second bearing axes is less than 5.0 degrees.

3. The assembly according to claim 1 or 2, wherein the offset angle (a) is less than 3.0 degrees.

4. The assembly according to any preceding claim, wherein the offset angle (a) is less than 1 .5 degrees. 5. The assembly according to any preceding claim, wherein the first toe angle corresponding to the first position of the wheel carrier (130, 230, 330) is a toe-out angle and the second toe angle corresponding to the second position of the wheel carrier is a toe-in angle. 6. The assembly according to any preceding claim, wherein the assembly further comprises a brake calliper device (140, 240, 340) attached to a mounting part (135, 335) of the wheel carrier (130, 230, 330).

7. The assembly according to claim 6, wherein the wheel carrier further comprises a longitudinal extension (138, 338) that serves as a brake force reaction arm.

8. The assembly according to claim 7, wherein the longitudinal extension (138, 338) is connected to the vehicle suspension in manner that allows for the wobbling movement of the wheel carrier relative to the suspension.

9. The assembly according to any preceding claim, wherein the sleeve part (332) of the wheel carrier has a hardened surface that serves as an inner raceway for rolling elements of the wheel bearing (350).

10. The assembly according to any of claims 1 to 8, wherein a cylindrical outer surface of the sleeve part (132, 232) serves as a seat for an inner ring (155) of the wheel bearing (150, 250). 1 1 . The assembly according to any preceding claim, wherein the first section (121 , 221 ) of the stub shaft is axially spaced from the second section (122, 222).

12. The assembly according to any of claims 1 to 10, wherein the stub shaft (320) is hollow, the first section (321 ) of the stub shaft being constituted by an outer cylindrical surface of the of the stub shaft and the second section (322) of the stub shaft being constituted by an angled cylindrical bore of the stub shaft.

13. The assembly according to any preceding claim, wherein the sleeve part (132, 332) of the wheel carrier has a straight cylindrical bore.

14. The assembly according to any of claims 1 to 12, wherein the wheel carrier has an angled cylindrical bore.

15. The assembly according to any preceding claim, wherein the drive means for rotating the stub shaft comprises a worm gear (185) that engages a ring gear (190) coupled to the stub shaft.

Description:
ACTIVE TOE ANGLE ADJUSTMENT MECHANISM FOR VEHICLE WHEELS

FIELD OF THE INVENTION

The present invention relates to a wheel end assembly comprising means for adjusting the toe angle of a non-driven vehicle wheel.

BACKGROUND TO THE INVENTION

Varying the toe angle of the rear wheels on an automotive vehicle during operation of the vehicle can improve both handling and manoeuvrability. During braking, deceleration and acceleration, for example, a toe-in position of the rear wheels results in better vehicle dynamics. During cornering, vehicle dynamics may be optimised when the outer cornering rear wheel is initially in a toe-out position and changes to a toe-in position at a certain lateral force. Furthermore, an optimized rear wheel alignment has a positive impact on fuel economy, by minimizing the drag and spin on the rear tires.

Several solutions for active toe angle adjustment have been proposed. For example, US 2005/051988 discloses a multilink suspension system in which a wheel carrier is attached to the vehicle body by a number of arms or links. One link is actively adjustable in length by means of a motorized screw mechanism, whereby length adjustment changes the toe angle of the vehicle wheel.

Many vehicles, however, have a more simple, twist beam rear suspension design. A solution for active toe angle adjustment in a vehicle with this type of rear suspension is disclosed in EP2019023. In this solution, the wheel carrier is connected in a rigid manner to an axle frame of the vehicle. The wheel carrier is acted on by a linear actuator, which distorts part of the wheel carrier. This distortion leads to rotation of a stub axle of the wheel carrier about a vertical axis, thereby effecting an adjustment of toe angle.

There is still room for improvement however. SUMMARY OF THE INVENTION

The present invention resides in a wheel end assembly as specified in claim 1 . The assembly comprises a wheel carrier, which supports a vehicle wheel via a non-driven wheel bearing. The wheel carrier itself is mounted to a suspension member of the vehicle via a stub shaft. Specifically, the stub shaft comprises a first section that is rotationally mounted to the vehicle suspension via a first bearing having a first bearing axis. The stub shaft further has a second section that supports a sleeve part of the wheel carrier via a second bearing, which has a second bearing axis. The assembly further comprises drive means for rotating the stub shaft about an axis of rotation, defined by the first bearing axis. According to the invention, the first bearing axis is offset at an angle relative to the second bearing axis. Therefore, when the stub shaft is rotated relative to the wheel carrier, the wheel carrier is caused to move in a wobbling motion between a first position and a second position, in which the vehicle wheel respectively has a first toe angle and a second toe angle. The first and second toe angles delimit a toe angle adjustment range. Thus, the toe angle of the vehicle wheel may be set to a predetermined value within the adjustment range by rotating the stub shaft through a predetermined angle. The magnitude of the toe angle adjustment range depends on the offset angle between the first and second bearing axes. Specifically, the magnitude is equal to twice the offset angle. The offset angle is preferably 5 degrees or less. In this range, movement of the wheel carrier may be used also for steering of the vehicle wheel. When only slight toe angle adjustment is required, the offset angle is preferably 3 degrees or less, more preferably 1 degree or less.

In the first position, the wheel carrier may be arranged relative to the vehicle suspension such that the first toe angle is a toe-out angle. In the second position, the second toe angle of the vehicle wheel is suitably a toe-in angle. Therefore, if the stub shaft has an angular position of zero degrees in the first position of the wheel carrier, a desired toe-in angle, a toe-neutral angle or a toe-out angle (within the adjustment range) may be set by rotating the stub shaft to an appropriate angle of between 0 and 180 degrees. According to the invention, the second section of the stub shaft, which supports the wheel carrier, revolves in a conical fashion about a wobble point at which the first and second bearing axes intersect. Consequently, a camber angle of the vehicle wheel also changes when the wheel carrier is at an intermediate position between the first and second positions. The first and second positions of the wheel carrier represent the two positions where, at a distance from the wobble point, the first and second bearing axes lie at the same height above the road, and where wheel camber angle is zero. Therefore, in a preferred embodiment, the wheel carrier is arranged such that in the first and second positions, the wheel has a first toe angle and a second toe angle which are advantageous for common driving conditions. For example, the first toe angle may be - 1 .0 ° , which is generally beneficial at relatively low vehicle speeds. The second toe angle may be +1.0 ° , which is generally beneficial at relatively higher vehicle speeds. The advantage of this embodiment is that wheel carrier is most often in the first and second positions, at which the corresponding camber angle of the vehicle wheel is zero degrees. The change in camber at intermediate positions is very slight, however, and the wheel carrier may temporarily operate at an intermediate position without adverse effects.

In an advantageous further development of the invention, the wheel carrier further comprises a mounting part, and the assembly further comprises a brake calliper device attached to the mounting part. Consequently, movement of the wheel carrier results in a corresponding movement of the brake calliper device, meaning that brake pads of the brake calliper remain in alignment with e.g. a brake disc mounted to the wheel bearing. Accelerated brake pad wear is therefore avoided.

In the same plane as the mounting part, the wheel carrier preferably has a longitudinal extension. Suitably, the longitudinal extension has a mounting hole or slot for attachment to the vehicle chassis via a sliding pin or some other attachment means which allows for the movement of the wheel carrier relative to the chassis. The longitudinal extension acts as a brake force reaction arm, which prevents the wheel carrier rotating under braking and also prevents excessive reaction forces being exerted on the second bearing. Furthermore, the attachment of the longitudinal extension to the chassis prevents the wheel carrier from rotating when the stub shaft is rotated.

In one embodiment, the sleeve part of the wheel carrier is made of bearing steel and has a hardened surface that serves as an inner raceway for rolling elements of the wheel bearing. An advantage of this embodiment is greater radial compactness. In an alternative embodiment, the sleeve part has a cylindrical outer surface for receiving a wheel bearing unit. The advantage of this embodiment is that the wheel carrier may be made from a metal material that is lighter and cheaper than bearing steel.

In an assembly according to the invention, the stub shaft and wheel carrier may be designed in a number of ways in order to effect the wobbling motion of the wheel carrier and corresponding toe angle adjustment of the vehicle wheel.

In one example, the first and second sections of the stub shaft and the first and second bearings are axially spaced. One advantage of this is that the drive means for rotating the stub shaft may be located relatively far inboard, i.e. away from the harsh operating environment of the wheel bearing.

In a preferred embodiment, the wheel carrier has a straight cylindrical bore. This simplifies the manufacture of the wheel carrier and of the second bearing that supports the sleeve part of the wheel carrier. Suitably, the second shaft section and the second bearing axis extend in a lateral direction essentially perpendicular to a longitudinal direction of the vehicle (when the wheel carrier is in the first and second positions). The first section of the shaft and the first bearing axis then extend at the offset angle, relative to the lateral direction.

Alternatively, the first shaft section and first bearing axis may extend in the lateral direction, while the second shaft section and the second bearing axis are angled relative thereto. The wheel carrier and the second bearing then have a correspondingly angled cylindrical bore. In a still further example, the first and second bearings are radially spaced. The stub shaft is hollow and has a first shaft section in the form of an angled cylindrical bore that is rotatably supported on an angled axle by the first bearing. The second shaft section is formed by a straight cylindrical outer surface of the hollow stub shaft, on which the wheel carrier is mounted via the second bearing. The advantage of this arrangement is greater axial compactness.

In all embodiments, the first bearing and the second bearing may comprise a sliding bearing arrangement. The sliding bearing arrangement may comprise, for example, one or more polymer bushings. Other bearing types and materials are also possible.

Furthermore, the drive means for rotating the stub shaft may be executed in a number of manners. In one example, the stub shaft is provided with a ring gear that engages with a driven worm gear mounted to the chassis. In other examples, the stub shaft is chain driven or directly coupled to the output shaft of a motor.

Thus, the present invention provides a straightforward arrangement for adjusting the toe angle of a vehicle wheel. Other advantages of the present invention will become apparent from the following detailed description and accompanying drawings.

DESCRIPTION OF THE FIGURES

In the following, the invention is described with reference to the accompanying drawings, in which:

Fig. 1 , Fig. 2 and Fig. 3 respectively show a cross-section of a first embodiment, a second embodiment and a third embodiment of a wheel end assembly according to the invention, viewed from above. DETAILED DESCRIPTION

An example of a first embodiment of a wheel end assembly according to the invention is depicted in Figure 1 . The assembly 100 comprises a wheel carrier 130 mounted to a suspension member 1 10 of the vehicle via a stub shaft 120. The wheel carrier 130 has a sleeve part 132 with a cylindrical outer surface for receiving an inner ring 155 of a wheel bearing 150. Suitably, the wheel bearing has a flanged outer ring 158 for receiving a brake disc and a vehicle wheel (not shown). The assembly is configured to enable active adjustment of a toe angle of the vehicle wheel.

The stub shaft 120 has a first shaft section 121 and a second shaft section 122. The first shaft section 121 is rotationally mounted to the suspension member 1 10 by a first bearing arrangement, which in this example comprises axially spaced bushings 161 and 162. The assembly further comprises means for rotating the stub shaft. Suitably, a ring gear 190 is coupled to the first shaft section 121 at an inboard end, which ring gear is driven by a worm gear 185. Other drive mechanisms are possible. The stub shaft is therefore rotatable about a shaft axis of rotation, defined by a first axis 165 of the first bearing arrangement 161 , 162. The sleeve part 132 of the wheel carrier is supported on the second shaft section 122 via a second bearing arrangement. In the depicted example, the second bearing comprises axially spaced bushings 171 , 172 and has a second bearing axis 175. According to the invention, the second shaft section 122 and second bearing axis 175 are offset at an angle a with respect to the first shaft section 121 and the first bearing axis (shaft rotation axis) 165.

The wheel carrier 130 is further connected to the vehicle chassis in a manner that does not allow the wheel carrier to rotate, which will be explained in more detail below. When the stub shaft 120 is rotated, the second shaft section 122 rotates in a conical manner about a point 180, where the second bearing axis 175 intersects the shaft rotation axis 165. Therefore, rotation of the stub shaft relative to the wheel carrier causes the wheel carrier 130 to wobble about the point 180. The wobbling motion of the wheel carrier causes a change in the toe angle of vehicle wheel, which is variable within an adjustment range determined by the offset angle a between the shaft rotation axis 165 and the second bearing axis 175. Specifically, the magnitude of the adjustment range is equal to 2a.

The position of the wheel carrier 130 is adjustable between two extremes, which will be defined as a first position and a second position. In Figure 1 , the wheel carrier is depicted in the first position, at which the first and second bearing axes 165, 175 lie at the same height above the road, along the length of each axis. In the first position, the stub shaft 120 and wheel carrier 130 in this example are arranged such that the vehicle wheel has a toe angle of -1.0 ° (i.e. a toe out angle). Let us assume that the offset angle a is 1.0 degrees. Rotation of the stub shaft causes the second shaft section 122 to rotate in a conical motion about the point 180, which makes the wheel carrier 130 and vehicle wheel move in a toe-in direction, indicated by arrow 195. When the stub shaft has rotated through 180 degrees, the second position of the wheel carrier is reached. In the second position, the vehicle wheel has a toe angle of +1.0 (i.e. a toe-in angle). In the second position, the first and second bearing axes again lie in the same horizontal plane. Therefore, by rotating the stub shaft to a predetermined angular position, a toe angle of between - 1 .0 ° and + 1 .0 ° can be set.

In an advantageous development of the invention, the wheel end assembly further comprises a brake calliper device mounted to the wheel carrier. Thus, brake pads of the device remain in alignment with the brake disk (not shown) mounted to the wheel bearing 150, regardless of the toe angle of the vehicle wheel. As a result, the brake pads are not subject to increased wear or drag. The wheel carrier 130 suitably comprises a mounting part 135 for the brake calliper device 140 (shown schematically in Figure 1 ). In the same plane as the mounting part 135, the wheel carrier further comprises an extension 138 with a mounting hole 139. The wheel carrier is further connected to the vehicle suspension via this mounting hole, in a manner which allows for the movement of the wheel carrier. A sliding pin connection or other suitable connection may be used. The further connection prevents rotation of the wheel carrier when the stub shaft is rotated or when the brake is applied.

The extension 138 is also configured to act as a brake force reaction arm. During braking, a reaction force is exerted on the second bearing arrangement 171 , 172. To reduce the reaction force on this bearing arrangement, the mounting hole is suitably located at a distance from the axial centreline of the wheel carrier. For a typical car wheel end assembly, the distance is preferably greater than 50 mm. In the embodiment of Figure 1 , the offset angle a is realised in that the second shaft section 122 extends in a lateral direction essentially perpendicular to the longitudinal direction of the vehicle, while the first shaft section 121 is offset from the lateral. An advantage of this embodiment is that the sleeve part 132 of the wheel carrier may have a straight cylindrical bore. The bushings 171 , 172 of the second bearing arrangement may then also have a straight cylindrical bore. Other designs of the wheel carrier and stub shaft are also possible.

An example of a second embodiment of a wheel end assembly 200 according to the invention is shown in Figure 2. In this example, the first shaft section 221 extends in the lateral direction and is supported relative to the suspension member 220 by axially spaced bushings 261 , 262 of the first bearing arrangement, which have a straight cylindrical bore. The first bearing axis 265 and shaft axis of rotation therefore also extend in the lateral direction. The offset angle a between the first bearing axis 265 and the second bearing axis 275 of the second bearing arrangement 271 , 272 is achieved in that the second shaft section 222 is angled relative to the lateral direction. Correspondingly, the sleeve part 232 of the wheel carrier 230 and the axially spaced bushings 271 , 272 have an angled bore. As before, rotation of the stub shaft 220 causes the wheel carrier to wobble about the intersection point 280, which changes the toe angle of the vehicle wheel. In this example, the offset angle a is 1.5 degrees and the toe angle of the vehicle wheel is adjustable between -1 .0 degrees and + 2.0 degrees by rotating to stub shaft to a predetermined angular position. In the first and second embodiments, the first and second sections of the stub shaft and the first and second bearing arrangements are axially spaced from each other. In a third embodiment, an example of which is depicted in Figure 3, the stub shaft is executed as a hollow shaft, whereby the first and second shaft sections and the first and second bearing arrangements are radially spaced.

The first section 321 of the hollow stub shaft 320 is formed by an angled bore 321 of the stub shaft. The suspension member of the vehicle in this example of a wheel end assembly 300 is formed by an angled axle 310 that extends through the first shaft section 321 . The first shaft section is rotationally supported on the angled axle 310 by the first bearing arrangement, which again comprises axially spaced bushings 361 , 362. The bushings have an angled bore, such that the second bearing axis and the shaft axis of rotation 365 extend at an angle from the lateral direction. The second section of the stub shaft 320 is formed by a cylindrical outer surface 322 of the stub shaft. The second shaft section 322 is rotationally supported relative to the sleeve part 332 of the wheel carrier 330 by the second bearing arrangement comprising axially spaced bushings 371 , 372. The wheel carrier 330 and the bushings 371 , 372 have a cylindrical bore, and the second bearing axis 375 extends in the lateral direction. The second bearing axis 375 intersects the first bearing axis 365 at the point 380, which in accordance with the invention is a wobble point that causes the wheel carrier to move from the first position to the second position when the stub shaft is rotated through 180 degrees. In this example, the offset angle a is 2.0 degrees and the toe angle of the vehicle wheel is adjustable between - 2.0 degrees and + 2.0 degrees.

Furthermore, the wheel carrier in this example comprises a hardened surface that serves as an inner raceway for first and second rows of rolling elements of the wheel bearing 350. This allows for greater radial compactness. The sleeve part 332 is therefore made of a bearing-grade steel. Preferably, the longitudinal extension 338 and the mounting part 335 of the wheel carrier are made of a different metal material, such as aluminium or mild steel, and are joined to the sleeve part 332 by means of welding, a screw connection or other suitable joint.

A number of aspects/embodiments of the invention have been described. It is to be understood that each aspect/embodiment may be combined with any other aspect/embodiment. Moreover the invention is not restricted to the described embodiments, but may be varied within the scope of the accompanying patent claims. Reference numerals

100,200,300 wheel end assembly

110, 210, 310 suspension member

120,220,320 stub shaft

121, 221, 321 1 st section of stub shaft

122, 222, 322 2 nd section of stub shaft

130, 230, 330 wheel carrier

132, 232, 332 sleeve part of wheel carrier

135,335 mounting part of wheel carrier for brake calliper device

138, 338 extension (brake force reaction arm)

139 mounting hole

140240, 340 brake calliper device

150,250,350 wheel bearing

155 inner ring of wheel bearing

158 flanged outer ring of wheel bearing

161, 162 first bearing arrangement

261 , 262 first bearing arrangement

361 , 362 first bearing arrangement

165,265,365 first bearing axis

171, 172 second bearing arrangement

271,272 second bearing arrangement

371, 372 second bearing arrangement

175,275,375 second bearing axis

180,280,380 wobble point

185 worm gear

190 ring gear

195 arrow indicating toe-in direction

a offset angle between first and second bearing axes