Abstract:
A device for adjusting the camber and/or the toe of a vehicle wheel of a motor vehicle includes a wheel carrier, which has a wheel-side carrier part and an axle-side guide part, between which rotary parts that can be rotated relative to each other are arranged, wherein at least one of the rotary parts can be adjusted in both rotational directions by means of a drive and a gear stage in order to adjust the toe and/or the camber. The gear stage for the rotary part is configured as harmonic drive gear train having a driving, elliptical drive disk, and a stationary, internally toothed ring gear.

Description:
CROSS-REFRENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2010/004375, filed Jul. 17, 2010, which designated the United States and has been published as International Publication No. WO 2011/020534 A2 and which claims the priority of German Patent Application, Serial No. 10 2009 038 423.5, filed Aug. 21, 2009, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a device for adjusting camber and/or toe of the wheels of wheel suspensions, in particular for motor vehicles. 
     A generic device for adjusting camber and/or toe of a vehicle wheel of a motor vehicle is known from DE 10 2004 049 296 A1. The device has a wheel carrier, which includes a wheel-side carrier part and an axle-side guide part. Arranged between these are rotary parts which are rotatable relative to one another, with at least one of the two rotary parts being adjustable in both rotational directions via a drive and a transmission stage for setting camber and/or toe. 
     The rotary parts arranged between the carrier part and the guide part, can be rotated as desired according to a set value input with the assistance of respectively associated drive units. The desired camber/toe setting is established in dependence on the combination of the rotation angles. This means, the wheel-side carrier part can be inclined up to several angular degrees relative to the guide part, which is immovably connected to the control arms. A prerequisite for this is, however, the provision of two separate drives which can rotate the two rotary parts independently of one another. The drive units are normally configured for high rotation speeds at small torque and gear down via a transmission stage. This results in high torque at a predefined power output. The transmission can be designed, for example, by a spur gear stage, optionally by a planetary set. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a device of a generic type which can be integrated into wheel suspensions in an especially space-saving manner, and which attains small adjustment forces and precise adjustment paths as a result of high achievable transmission ratios. 
     According to the invention, this object is solved by a device for adjusting camber and/or toe of a vehicle wheel of a motor vehicle, including a wheel carrier having a wheel-side carrier part and an axle-side guide part between which rotary parts are arranged which are rotatable relative to one another, wherein at least one of the rotary parts is adjustable in both directions of rotation via a drive and a transmission stage for adjustment of camber and/or toe, wherein the transmission stage for the rotary part is configured as harmonic drive transmission with a driving, elliptical drive disk, a gear sleeve flexibly supported on the drive disk, and a stationary internally toothed ring gear. 
     According to the present invention transmission is not a spur gear stage or a planetary set; Rather the transmission is configured for at least one of the rotary parts as harmonic drive transmission with a driving, elliptical drive disk, a gear sleeve flexibly supported on the drive disk, and a stationary, internally toothed ring gear. These types of harmonic drive transmissions are known per se from the state of the art. The driven gear sleeve has a lower number of teeth than the ring gear so that a difference in rotation angle relative to the stationary ring gear is generated in each revolution of the driving drive disk and used for the adjustment. This allows the realization of transmission ratios of for example 50 to 100 to enable a particularly smooth and precise adjustment of the rotary part while requiring only small installation space, in particular in radial extension. 
     In order to reduce the number of components, the harmonic drive transmission is comprised of few compact parts and can provide high transmission ratios in a most compact installation space. Thus, the elliptical drive disk, i.e. the wave generator, the gear sleeve flexibly supported on the latter, and the stationary internally toothed ring gear constitute only three components that are required for the transmission. The rotational moment of inertia encountered during operation is thereby very small. 
     For a compact configuration, the harmonic drive transmission, in particular the elliptical drive disk thereof, can be arranged, at least partially, radially within the rotary part. The rotary part can be configured hollow-cylindrical with an internal mounting space in which the harmonic drive transmission can be partially arranged. 
     Preferably, the rotary part can at the same time also form the gear sleeve which is arranged between the ring gear and the drive disk of the harmonic drive transmission. In this case, the gear sleeve can be directly connected to the rotary part. The ring gear can at the same time be directly fastened to the carrier part or to the guide part, i.e. radially outside of the rotary part or the gear sleeve. 
     Particularly preferred can be the provision of a harmonic drive transmission for each of the rotary parts, with one of the transmissions being arranged on the carrier part and the second transmission being arranged on the guide part to act on the respective rotary parts, respectively. 
     A particularly favorable construction can further be realized when operating the harmonic drive transmission via an electric motor having a rotor which is supported in coaxial relationship to the elliptical drive disk of the transmission in the carrier part and/or in the guide part. This allows a particularly compact axial and radial arrangement of the entire servo drive within the wheel suspension. Preferably, the electric motor can be configured as hollow motor having a hollow space through which a cardan shaft can be guided. 
     To achieve a weight-saving construction, the drive disk and the rotor can each be arranged about a common bearing sleeve, with the stator of the electric motor being arranged in surrounding relationship to the rotor in the guide part and/or the carrier part. This also allows for example to guide a cardan shaft, which drives the wheel of the motor vehicle, through the construction up to the corresponding wheel flange. 
     A rigid and, with regard to manufacture, favorable construction is further achieved, when the bearing sleeve, which carries the rotor of the electric motor, is supported on both sides of the rotor via rolling bearings in the guide part and/or the carrier part. 
     Furthermore, the rotary parts can each be rotatably supported on an extended section of the bearing sleeve via respective rolling bearings and connected in driving relationship to the drive gear sleeve of the harmonic drive transmission, which gear sleeve is flexibly supported on the drive disk. In this way, manufacturing tolerances of the interacting functional parts can be advantageously controlled and a pre-assembled mounting unit can be created. 
     An additional coupling element can be arranged between the wheel-side carrier part and the axle-side guide part for allowing transmission of a torque, for example a braking torque, from the wheel-side carrier part to the axle-side guide part and thus to the vehicle body. The coupling element can be a metal bellows which cardanically connects the guide part to the carrier part, or a cardan joint which is arranged radially outside of the rotary parts. For space-efficient construction, the harmonic drive transmission can be arranged radially within the coupling element. Thus, for achieving a compact arrangement in radial direction, the internally toothed ring gear of the harmonic drive transmission, which interacts with the gear sleeve, can be positioned radially within cantilevers which are formed on the guide part and the carrier part and on which a cardan joint is supported which cardanically connects the guide part and the carrier part. 
     Finally, the carrier-side electric motor can be positioned within a wheel bearing which supports a wheel flange for a wheel of the motor vehicle and, optionally, a brake disk in a substantially uniform rotation plane relative to the wheel bearing to thereby attain a particularly structurally short and robust wheel bearing and arrangement of the electric motor. In terms of construction, the wheel flange can advantageously be configured in the shape of a cup and have a hub section which faces the vehicle interior and surrounds the carrier-side electric motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the following, an exemplary embodiment of the invention is explained with further details. The schematic drawing shows in: 
         FIG. 1  a schematic illustration of a wheel suspension for motor vehicles with wheel guiding elements and a multipart wheel carrier with rotatable rotary parts for adjusting the camber and the toe of the wheel; 
         FIG. 2  a sectional representation of the wheel carrier according to  FIG. 1 , cut open by a 90° angle along the rotational axis of the wheel, with two harmonic drive transmissions to actuate the rotary parts; 
         FIG. 3  a vertical longitudinal section of the wheel carrier according to  FIGS. 1 and 2 ; and 
         FIG. 4  a principle depiction of a harmonic drive transmission, according to the prior art. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a rear wheel suspension  10  for motor vehicles in a roughly schematic outline in which a wheel carrier  12  is articulated to a superstructure  18 , which is only outlined, via transverse control arms  14 ,  16  as wheel guiding elements. 
     The wheel carrier  12 , which rotatably receives the wheel  20 , is subdivided into a guide part  22  which is articulated to the transverse control arms  14 ,  16 , a carrier part  24  which receives the wheel  20  via a corresponding wheel bearing, and two rotatable rotary parts  26 ,  28  are supported on the guide part  22  and the carrier part  24  with confronting end-side slanted surfaces  30 . The rotary part  26  is tiltable with its central axis  31  (compare  FIG. 3 ) in relation to the rotary part  28  which can rotate about its rotation axis  32 . A rotation of one or both rotary parts  26 ,  28  causes a tilting of the carrier part  24  relative to the guide part  22  and accordingly an adjustment of the camber and/or toe of the wheel  20  of the wheel suspension  10 . 
     The wheel load is supported in a known manner against the superstructure  18  by a support spring  34 . A telescopic shock absorber is arranged within the support spring  34 . Further, the wheel  20  is driven via a cardan shaft  38 , shown only as outline, of a drive assembly, with the cardan shaft  38  extending through the wheel carrier  12  and connected in driving relationship to the wheel  20 . 
       FIGS. 2 and 3  show the wheel carrier  12  of the wheel suspension  10  in detail. 
     The guide part  22  is articulated with a base plate  22   a  to the upper control arm  14 , to the lower control arm  16 , and to a control arm  42  not visible in  FIG. 1 , via hinges generally designated with  40 , and carries a hub part  22   b . Further, the guide part  22  has two diametrically opposed cantilevers  22   c  which horizontally protrude outwards and on which a support ring  46  is supported for limited rotation via pivot pins  44 . 
     The carrier part  24  of the wheel carrier  12  also has a base plate  24   a  and a hub part  24   b  fastened thereto. Also protruding from the base plate  24   a  are two diametrically opposed cantilevers  12   c  which, however, are offset by 90° relative to the cantilevers  22   c  and protrude inwards and which are swingably connected to the support ring  46  via two further pivot pins  44 . The cantilevers  12   c ,  22   c  jointly form with the support ring  46  a cardan joint which allows the carrier part  24  to pivot or tilt relative to the guide part  22 , but to act in circumferential direction in a form-fitting manner. 
     On its outer circumferential wall  24   ba , the hub part  24   b  of the carrier part  24  carries a dual-row ball bearing or wheel bearing  48  via which a wheel hub  50 , which is provided with a splined toothing, is rotatably supported. Fastened on the wheel hub  50  by not shown wheel bolts, is a brake disk  52  of a disk brake of the motor vehicle and the wheel  20  ( FIG. 1 ). 
     The two rotary parts  26 ,  28  are rotatably supported between the carrier part  24  and the guide part  22  of the wheel carrier  12  in coaxial relationship to the rotation axis  32 , with their abutting end-side slanted surfaces  30  (compare  FIG. 3 ) causing the tilting of the carrier part  24  in the vertical axis (camber adjustment) and/or the horizontal axis (toe adjustment) by rotating the rotary parts  26 ,  28  in the same or opposite directions. As shown in  FIG. 3 , the point of intersection  54  between the straight connecting lines of the joint axes of the pivot pins  44  with a straight connecting line of the slanted surfaces  30  lies exactly on the rotation axes  31 ,  32  of the rotary parts  26 ,  28 . 
     The rotary parts  26 ,  28  are operated by two harmonic drive transmissions  52 ,  58  via coaxially arranged electric motors  60 . 
     The harmonic drive transmissions  56 ,  58 , which are known per se from the state of the art, are now described with reference to the exploded illustration of  FIG. 4 . For sake of simplicity, the reference signs are also used on the wheel carrier  12  in the following description. 
     The harmonic drive transmissions  56 ,  58  according to  FIG. 4  include essentially a driving elliptical drive disk  62 , i.e. a so-called wave generator, a flexible rolling bearing  64  arranged about the outer circumference of the drive disk, an outputting gear sleeve  66  which is formed by a flexible steel sleeve and has outer teeth  66   a , and finally a stationary ring gear  68  which has internal teeth  68   a.    
     The drive disk  62  is inserted with the rolling bearing  64  in the flexible gear sleeve  66  so that the drive disk  62  also adopts an elliptical outer shape. 
     The gear sleeve  66  in turn is inserted in the rotationally symmetric ring gear  68 , with only several teeth of the gear sleeve  66  meshing with the ring gear  68 . Further, the gear sleeve  66  is configured with fewer teeth than the ring gear  68 . 
     When the drive disk  62  is driven about a rotation angle of 360° by the electric motor  60 , the gear sleeve  66 , which is flexibly guided via the rolling bearing  64 , rolls off in the ring gear  68 , whereby because of the lower number of teeth, the gear sleeve  66  is rotated in opposition to the driving direction of the drive disk  62  to a smaller degree relative to the stationary ring gear  68  to thereby cause the adjustment of the rotary parts  26 ,  28 . 
     The harmonic drive transmissions  56 ,  58  ( FIGS. 2 and 3 ) are arranged in coaxial relationship to the rotation axis  32  in the wheel carrier  12  and radially within the cantilevers  22   a ,  24   a  of the guide part  22  and the carrier part  24 . 
     Thus, the driving drive disk  62  of the harmonic drive transmission  56  is configured in one piece with a bearing sleeve  70  which is rotatably supported in axial direction on both sides of the stator  60   a  of the electric motor  60  via rolling bearings  72 ,  74  in the guide part  22  and in the hub part  22   b , respectively, and in the base part  22   a.    
     The flexible rolling bearing  64 , which suitably receives the gear sleeve  66 , is arranged around the elliptical outer circumference of the drive disk  62 . 
     The outputting gear sleeve  66  is formed onto the adjacent rotary part  28 , with the rotary part  28  being rotatably supported on an extended section  70   a  of the bearing sleeve  70  via an attached bearing throat  28   a  and a further rolling bearing  76 . 
     The gear sleeve  66  meshes with the ring gear  68  which is bolted to the base plate  22   a  of the guide part  22 . 
     The rotor  60   b  of the electric motor  60  is arranged directly on the bearing sleeve  70  between the two rolling bearings  72 ,  74 . 
     The arrangement of the harmonic drive transmission  58  and of the electric motor  60  in the carrier part  24  of the wheel carrier  12  is essentially a mirror image so that same reference signs are used for structurally identical parts. 
     Thus, the drive disk  62  is again formed on a bearing sleeve  80  which is rotatably supported in the carrier part  24  or base part  24   a  and an inner circumferential wall  24   bb  of the hub part  24   b  via rolling bearings  72 ,  74 . 
     The flexible gear sleeve  66  is formed directly onto the axially adjoining rotary part  26  which in turn is rotatably supported on an extended section  80   a  of the bearing sleeve  80  via an attached bearing throat  26   a  and a rolling bearing  76 . 
     The electric motor  60  is arranged in the hub part  24   b  between the two rolling bearings  72 ,  74  and has a stator  60   a  which is inserted in the hub part  24   b , while its rotor  60   b  is formed directly on the bearing sleeve  80 . As can be seen, the electric motor  60  lies advantageously essentially in a uniform rotation plane with the wheel bearing  48  which is arranged radially outside and has an inner bearing ring  48   a  positioned on a hub section  50   a  of the cup-shaped wheel hub  50 . 
     The ring gear  68  of the harmonic drive transmission  58  is tightly bolted to the base plate  24   a  of the carrier part  24 . 
     By activating the electric motors  60  in the one or other rotational direction, the rotary parts  26   28  can be rotated in the same or opposite directions by the harmonic drive transmissions  56  and/or  58  as described with reference to  FIG. 4  in such a manner that a tilting the carrier part  24  relative to the guide part  22  of the wheel carrier  12  allows adjustment of the camber and/or toe of the wheel  20  of the wheel suspension  10  in a desired manner. 
     As the harmonic drive transmissions  56 ,  58  enable the implementation of the high transmission ratio, a sensitive, smooth camber and/or toe adjustment can be attained, which in addition has only small self-aligning torques which optionally may be decelerated. 
     The electric lines leading to the electric motors  60  and their connections to a corresponding electronic control device are not shown.