Abstract:
A gear step ( 1 ) for an actuator in a motor vehicle, in particular for a vehicle seat, comprises a housing ( 3 ) provided with a drive ( 1 ) mounted thereon in such a way that it is rotatable around an axis (A), and a driven output ( 21 ) rotatable about a second axis (B) differing from the axes (A). The drive ( 11 ) is used for receiving the driven output ( 21 ) by way of at least one rolling body ( 31 ), so that the axes (A, B) are parallelly offset by an eccentricity (E) and the driven output is driven by rotating the thus obtained rolling eccentricity, wherein the driven output ( 21 ) carries out a tumbling rolling movement on the housing ( 3 ) by way of a friction oscillating gear ( 33, 35 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a continuation of International Application PCT/EP2006/008102, which was filed Aug. 17, 2006. The entire disclosure of International Application PCT/EP2006/008102, which was filed Aug. 17, 2006, is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a gear stage of an actuator for a vehicle, especially one for a vehicle seat, comprising a housing, a drive mounted on the housing so that it can rotate about a first axis, and a driven output rotatable about a second axis different from the first axis. 
         [0003]    DE 197 09 852 C2 discloses a gear stage of the type described immediately above, in which a worm on a motor shaft serves as a drive and meshes in a worm gear on the driven output. This gear stage is an integral part of an actuator, in which the worm gear then drives a mechanism for the adjustment of a vehicle seat. Through suitable thread leads on the worm and the worm gear, the gear stage gears down the high motor speed to a lower input speed of the mechanism. 
       BRIEF SUMMARY OF SOME ASPECTS OF THE INVENTION 
       [0004]    An object of the present invention is to improve a gear stage of the type mentioned above. According to one aspect of the present invention, this object is achieved by a gear stage for an actuator for a vehicle, with the gear stage comprising a housing, a drive mounted to the housing for being rotated relative to the housing about a first axis, a driven output and at least one separately formed rolling element. The drive supports the driven output by way of at least the rolling element, to at least partially form a rolling eccentric. The driven output is for rotating relative to the housing about a second axis that is different from the first axis, the second axis is parallel to the first axis, and the second axis is offset from the first axis by an eccentricity. The rolling eccentric rotates in response the drive being rotated about the first axis. The driven output performs, by way of a friction gear tumbler mechanism and in response to rotation of the rolling eccentric, a rolling movement on the housing. 
         [0005]    The transmission ratio is increased, compared to the known gear stage, in that the drive, by way of the at least one separately formed rolling element, supports the driven output with the axes offset parallel by the eccentricity and drives it as the rolling eccentric, thus formed, rotates, the driven output performing a rolling movement, especially a tumbling, rolling movement on the housing by way of the friction gear tumbler mechanism. At the same time, the efficiency is also significantly improved, so that the overall efficiency of an actuator, for example, in which the inventive gear stage is preferably used, is likewise improved, which affords a reduction in the weight and the overall space taken up by the requisite components. The driven output is seen to be “supported” by the drive in as much as the driven output can also be partially supported on the housing. 
         [0006]    The rolling movement of the driven output is generally a rotational movement with a superimposed tumbling movement, although the tumbling, rolling movement can be compensated for, especially in the case of a small eccentricity, for example, by play between the driven output and the output-side mechanism to be driven (load-bearing mechanism) or the like, or through suitable elasticity of these parts. In the case of larger eccentricities, a further component, which forms the actual driven output of the gear stage and performs a rotational movement with a superimposed tumbling movement relative to the stressed driven output, but performs a pure rotational movement relative to the drive, can also be connected to the output side of the stressed driven output. 
         [0007]    The rolling eccentric between the drive and the driven output to a certain extent contributes to the overall transmission ratio. By preferably forming a groove for the preferably spherical rolling element on one of the two components, making it possible to set different rolling radii through the use of inclined side walls, for example, improvements compared to a simple rolling of the rolling element are achieved both on the drive and on the driven output. 
         [0008]    The friction gear tumbler mechanism, which in the case of a smaller eccentricity produces a slight tumbling relative movement between the driven output and the housing, makes a prime contribution to the overall transmission ratio. A rolling point, which preferably occurs between a hoop of the driven output and a guide in the housing, serves as the instantaneous pole for the tumbling, rolling movement of the driven output. Upon rotation of the drive, a force, preferably built up through a wedging of the drive, the rolling element and the driven output, exerts the driving moment on the driven output at the rolling point. Free turning of the drive once it has completed its driving rotation dissipates this force again and protects the components. 
         [0009]    Favorable geometric ratios ensure definite, calculable relative movements. Two rolling elements tensioned against one another serve to prevent any idle travel at the beginning of the drive rotation, and the gear stage becomes self-locking. The inventive gear stage is preferably combined with electronically commutated motors and self-locking mechanisms with eccentric epicyclic gearing. 
         [0010]    In a preferred embodiment, at least one of the transmission elements (the housing, the drive and/or the driven output), and preferably all of these transmission elements, are composed of a plastic-metal composite material. The metal parts contained therein ensure a high load-bearing capacity, while the plastic areas permit complex geometries, cost-effective manufacture, a lower weight and very good damping characteristics in the non-load absorbing areas. The metal parts are preferably made by machining from thin sheets of high-strength metal of approximately constant material thickness, which avoids expensive remachining. 
         [0011]    Other aspects and advantages of the present invention will become apparent from the following. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention will be explained in more detail below with reference to two exemplary embodiments shown in the drawings, in which: 
           [0013]      FIG. 1  shows an axial section through the first exemplary embodiment along the line I-I in  FIG. 2 , 
           [0014]      FIG. 2  shows a radial section through the first exemplary embodiment along the line II-II in  FIG. 1 , 
           [0015]      FIG. 3  shows a section corresponding to  FIG. 1  through a first applied use of the invention, 
           [0016]      FIG. 4  shows a section corresponding to  FIG. 1  through a second applied use of the invention, 
           [0017]      FIG. 5  shows an axial section through the second exemplary embodiment along the line V-V in  FIG. 6 , and 
           [0018]      FIG. 6  shows a radial section through the second exemplary embodiment along the line VI-VI in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0019]    In the first exemplary embodiment a gear stage  1  has an approximately cylindrically symmetrical housing  3  with a central first axis A. A housing collar  5  is formed radially inside on the housing  3  concentrically with the first axis A. Radially outside, the housing  3  has a housing cover  7 , which is formed separately from a housing body  9  and is securely connected to the housing body  9  when assembling the gear stage  1 . A drive  11  is likewise supported on the housing  3  concentrically with the first axis A. The drive  11  has a hollow cylindrical drive tube  13  inserted through the housing collar  5  concentrically with the first axis A, with a drive flange  15  protruding radially outwards at the end face and a drive bearing ring  17  formed thereon concentrically with the first axis A and overlapping the housing collar  5 . A roller bearing  19 , for example a ball bearing or preferably a needle bearing, is arranged between the inside of the drive bearing ring  17  and the outside of the housing collar  5 . The roller bearing  19  directly supports (with little friction) the drive  11  in a radial direction. 
         [0020]    A driven output  21  is cylindrically symmetrical about a second axis B, which is arranged parallel to the first axis A offset by an eccentricity E of preferably less than 0.5 mm, for example 0.2 mm. The driven output  21  has a hollow cylindrical driven output tube  23  concentric with the second axis B and inserted into the drive tube  13 , a driven output disk  25  protruding radially outwards at the end face, and a driven output bearing ring  27  formed thereon concentrically with the second axis B and overlapping the drive bearing ring  17 . On the inside of the driven output bearing ring  27  facing the drive bearing ring  17 , the driven output  21  has an annular, peripheral V-shaped groove, abbreviated as groove  29 . The side walls of the groove  29  preferably run obliquely to the second axis B, for example at 60° to the second axis B. A single ball  31  is arranged at a point on the periphery between the outside of the drive  11  (i.e. the outside of the drive bearing ring  17 ) and the groove  29 , with the groove  29  partially receiving the ball  31 . 
         [0021]    On its outside, i.e. the outside of the driven output bearing ring  27 , the driven output  21  has a peripheral, radially protruding hoop  33 . The hoop  33  is formed concentrically with the second axis B and—in the manner of a tongue-and-groove connection—engages in a peripheral guide  35  in the housing  3 . The channeled guide  35  is an annular groove that is concentric with first axis A. The channeled guide  35  is formed partly by the housing body  9  and partly by the housing cover  7 . In this regard, the housing body  9  and the housing cover  7  together form a face of the housing  3 /guide  35  that faces radially inwards. 
         [0022]    The side walls of the guide  35  run slightly obliquely in relation to a plane perpendicular to the first axis A, so that the hoop  33  cannot penetrate fully to the bottom of the guide  35 , but only as far as a rolling point W. The hoop  33 , i.e. the driven output  21 , and the guide  35 , i.e. the housing  3 , form a friction gear mechanism, hereinafter referred to as a friction gear tumbler mechanism. On the side radially opposite the rolling point W, the distance between the hoop  33  and the guide  35  or the driven output  21  and the housing  3  is 2×E greater than at the rolling point W. Likewise, the distance between the drive  11  and the driven output  21  at the point nearest to the rolling point W is 2×E greater than the corresponding distance on the radially opposite side. A quasi peripherally curved wedge face therefore exists both between the driven output  21  and the housing  3  and also between the driven output  21  and the drive  11 . The contact points between the housing  3 , the drive  11  and the driven output  21  lie substantially in the same plane, which runs perpendicular to the axes A and B. 
         [0023]    The outside of the drive  11 , the ball  31  and the groove  29  together form a geometry in which the ball  31  is wedged between the drive  11  and the driven output  21 , since the contact angle is smaller than the self-locking angle and therefore no sliding friction occurs at the contact points of the ball  31 , as is also known on wedging roller free-wheel clutches, for example. With the drive  11  stationary, the ball  31 —viewed in the peripheral direction of the first axis A—initially lies at the same angle as the rolling point W and hence without any radial tensioning between the drive  11  and the groove  29 . When the drive  11  is driven, on the other hand, the ball  31  also moves until the aforementioned wedging occurs. With the present geometries and materials, the ball  31  precedes the rolling point W by approximately 45° (preceding angle). 
         [0024]    In  FIG. 2  the drive  11  is driven counterclockwise, so that the ball  31  rolls on the outside of the driven output  11 , i.e. it rotates clockwise in  FIG. 2 . This leads to a relative rolling movement of the ball  31  in the groove  29  and due to the wedging leads to a considerable force F at the contact point between the ball  31  and the driven output  21 . Since the driven output  21  bears against the housing  3  at the rolling point W, i.e. the rolling point W forms an instantaneous pole, the force F generates a torque acting on the driven output  21  about the rolling point W. This leads to a tumbling, rolling movement of the driven output  21  on the housing  3 , clockwise in  FIG. 2 . If the direction of rotation of the drive  11  is reversed, the direction of rotation of the driven output  21  is likewise reversed after an idle travel of twice the preceding angle of the ball  31 . A suitable lubricant may be provided in order to increase the instantaneous coefficients of friction at the points with a higher surface unit pressure, while reducing the wear on the ball  31  or the rolling point W, for example. 
         [0025]    The gear stage  1  is of two-stage design, being embodied as a friction gear tumbler mechanism with rolling eccentric. Because of the rolling movement of the ball  31  between the drive  11  and the driven output  21 , the rolling eccentric with the ball  31  initially has a theoretical transmission ratio of approximately 2:1. The groove  29 , which provides for a smaller rolling radius towards the driven output  21  than the radius of the ball  31 , gives rise to an additional transmission component of in this case 4:1. The friction gear tumbler mechanism stage gives rise to a transmission ratio component approximately equal to the outside diameter of the driven output  21  (diameter of the housing  3  at the rolling point W) of 2×E, in this case about 125:1. Overall therefore, the rotation of the drive  11  can be geared down by several orders of magnitude. As the eccentricity E decreases, the disruptive effects diminish and the transmission ratio (or the reduction ratio) increases. In order that the transmission elements can withstand the contact forces and stresses resulting from the drive torques without being destroyed, high-strength metal materials are preferably used for this purpose. It is also feasible, however, by using high-strength plastics, to give the driven output  21  an elastic surface, for example, in order to damp vibrations and to provide significantly larger contact surfaces. 
         [0026]    In order to prevent the formation of non-circular surfaces when at a standstill, provision is preferably made, when no longer in use, to turn the drive  11  back by a free-turning angle (fixed default of 90°, for example, or electronically determined), in order that the ball  31  can roll back by its preceding angle and come to rest in the closest possible proximity to the rolling point W, where it no longer builds up any force F. 
         [0027]    In order to improve the contact of the ball  31  on the drive  11  during operation, thereby also improving the wedging action, i.e. in order as far as possible to avoid “slipping” at this point, in a modified embodiment there is preferably always a slight friction between the drive  11  and the ball  31 , without impeding the rotation. This slight friction may be applied, for example, by way of the normal force of a spring between the drive  11  and the ball  31  or by magnetizing one of the components. In order to reduce the idle travel of the ball  31  on reversing the direction, in a modified embodiment two balls  31  may be provided, which are held together or apart by springs. The gear stage  1  thereby also becomes self-locking. 
         [0028]    In a first applied example the inventive gear stage  1  is combined with a motor  41  to form a drive unit  43 . In this case the gear stage  1  and the motor  41  are integrated into one another by fitting multiple permanent magnets as rotor magnets  45  to the drive  11 , preferably to the drive tube  13 , so that the drive  11  becomes a rotor, and by arranging multiple stator stacks  47  in the housing  3  for contact-free interaction with the rotor magnets  45 . A control  49  provides for electronic commutation of the stator stacks  47  and hence of the motor  41 . For speed control via a feedback, an annular magnet  51  is fitted to the driven output  21 , preferably to the driven output tube  23 , and interacts with a Hall sensor  53  in the housing  3  connected to the control  49 , in order to detect the angular position of the driven output  21 . Except for the electronic components of the motor  41 , the gear stage  1  forms one coatable unit. 
         [0029]    In a second applied example the inventive gear stage  1  is combined with a mechanism  61  to form an actuator  63  in a vehicle, especially one for a vehicle seat. Such a mechanism  61  is described in the form of a seat back inclination adjuster for a vehicle seat in DE 101 44 840 A1, the entire disclosure content of which is expressly incorporated herein by reference. The mechanism  61  embodied as a self-locking eccentric epicyclic gearing has a first fitting  65 , which takes the form of an internal gear, and a second fitting  67 , which has a formed-on gear meshing with the internal gear. The first fitting  65  is firmly connected to the backrest of the vehicle seat, for example, while the second fitting  67  is connected to the seat part of the vehicle seat. A two-part (or alternatively single-part) driver  69  together with two wedge segments  71  tensioned against one another defines an eccentric, which is supported between the first fitting  65  and the second fitting  67  and on rotation produces a tumbling, rolling movement of the first fitting  65  against the second fitting  67 . 
         [0030]    For combining the gear stage  1  with the mechanism  61 , the housing  3  is fitted by way of its housing cover  7  to the first fitting  65 , while an externally profiled shaft  73  at one end meshes in an internal profile of the driven output tube  23  and at the other end in an internal profile of the driver  69 . Here some play is in each case provided between the profiles, in order to compensate for the tumbling movement of the driven output  21 . The tumbling movement could also be compensated for by other means, in particular flexible means (e.g., flexible mechanisms). 
         [0031]    The actuator  63  might also (e.g., alternatively) adjust the height and/or the inclination of the seat surface of the vehicle seat. 
         [0032]    By combining the first and second applied examples, the actuator  63  is completed by a motor  41 . 
         [0033]    Unless otherwise described below, the second exemplary embodiment is identical to the first exemplary embodiment, for which reason identical or similarly functioning components carry the same reference numerals prefixed by 100. Individual or multiple features of the first exemplary embodiment can also be embodied in combination with the features of the second exemplary embodiment and vice-versa. 
         [0034]    In the second exemplary embodiment a gear stage  101  has an approximately cylindrically symmetrical housing  103  with a central first axis A. A housing collar  105  is formed radially inside on the housing  103  concentrically with the first axis A. Radially outside, the housing  103  has a housing cover  107 , which is formed separately from a housing body  109  and is securely connected to the housing body  109  when assembling the gear stage  101 . A drive  111  is likewise supported on the housing  103  concentrically with the first axis A. The drive  111  has a hollow cylindrical drive tube  113  inserted through the housing collar  105  concentrically with the first axis A, with a drive flange  115  protruding radially outwards at the end face and a drive bearing ring  117  formed thereon concentrically with the first axis A and overlapping the housing collar  105 . A roller bearing  119 , for example a ball bearing or preferably a needle bearing, is arranged between the inside of the drive bearing ring  117  and the outside of the gear collar  105 . The roller bearing directly supports (with little friction) the drive  111  in a radial direction (in relation to the first axis A). 
         [0035]    A driven output  121  is cylindrically symmetrical about a second axis B, which is arranged parallel to the first axis A offset by an eccentricity E of preferably less than 0.5 mm, for example 0.2 mm. The driven output  121  has a hollow cylindrical driven output tube  123  concentric with the second axis B and inserted into the drive tube  113 , a driven output disk  125  protruding radially outwards at the end face, and a driven output bearing ring  127  formed thereon concentrically with the second axis B and overlapping the drive bearing ring  117 . On the inside of the driven output bearing ring  127  facing the drive bearing ring  117 , the driven output  121  has an annular, peripheral V-shaped groove  129  of curved profile. Two single balls  131  are each arranged at a point on the periphery between the outside of the drive  111  (i.e. the outside of the drive bearing ring  117 ) and the groove  129 , with the groove  129  partially receiving the balls  131 . 
         [0036]    On its outside, i.e. the outside of the driven output bearing ring  127 , the driven output  121  has a peripheral, radially protruding hoop  133 . The hoop  133  is formed on concentrically with the second axis B and—in the manner of a tongue-and-groove connection—engages in a peripheral guide  135  in the housing  103 . The channeled guide  135  is an annular groove that is concentric with first axis A. The channeled guide  135  is formed partly by the housing body  109  and partly by the housing cover  107 . In this regard, the housing body  109  and the housing cover  107  together form a face of the housing  103 /guide  135  that faces radially inwards. 
         [0037]    The side walls of the guide  135  run slightly obliquely in relation to a plane perpendicular to the first axis A, so that the hoop  133  cannot penetrate fully to the bottom of the guide  135 , but only as far as a rolling point W. The hoop  133 , i.e. the driven output  121 , and the guide  135 , i.e. the housing  103 , form a friction gear mechanism, hereinafter referred to as a friction gear tumbler mechanism. On the side radially opposite the rolling point W, the distance between the hoop  133  and the guide  135  or the driven output  121  and the housing  103  is 2×E greater than at the rolling point W. Likewise, the distance between the drive  111  and the driven output  121  at the point nearest to the rolling point W is 2×E greater than the corresponding distance on the radially opposite side. A quasi peripherally curved wedge face therefore exists both between the driven output  121  and the housing  103  and also between the driven output  121  and the drive  111 . The contact points between the housing  103 , the drive  111  and the driven output  121  lie substantially in the same plane, which runs perpendicular to the axes A and B. 
         [0038]    The outside of the drive  111 , the balls  131  and the groove  129  together form a geometry in which the balls  131  preceding the rolling point W (by a preceding angle) can be wedged between the drive  111  and the driven output  121 , since the contact angle is smaller than the self-locking angle and therefore no sliding friction occurs at the contact points of the balls  131 , as is also known on wedging roller free-wheel clutches, for example. Accordingly, the ball  131  following the rolling point W does not wedge. When the drive  111  is driven, the balls  131  roll on the outside of the driven output  111 . This leads to a relative rolling movement of the balls  131  in the groove  129  and due to the wedging of the preceding ball leads to a considerable force at the contact point between the preceding ball  131  and the driven output  121 . Since the driven output  121  bears against the housing  103  at the rolling point W, i.e. the rolling point W forms an instantaneous pole, the force generates a torque acting on the driven output  121  about the rolling point W. This leads to a tumbling, rolling movement of the driven output  121  against the housing  103 . If the direction of rotation of the drive  111  is reversed, the direction of rotation of the driven output  121  is likewise reversed after a minimal idle travel (until the other ball  131  wedges). A suitable lubricant may be provided in order to increase the instantaneous coefficients of friction at the points with a higher surface unit pressure, while reducing the wear on the balls  131  or the rolling point W, for example. If the balls  131  are compressed or held apart by springs (e.g., biased with respect to one another), the gear stage  101  becomes self-locking. 
         [0039]    The gear stage  101  is of two-stage design, being embodied as a friction gear tumbler mechanism with rolling eccentric. Because of the rolling movement of the balls  131  between the drive  111  and the driven output  121 , the rolling eccentric with the balls  131  initially has a theoretical transmission ratio of approximately 2:1. The groove  129 , which provides for a smaller rolling radius towards the driven output  121  than the radius of the balls  131 , gives rise to an additional transmission component of in this case 4:1. The friction gear tumbler mechanism stage gives rise to a transmission ratio component approximately equal to the outside diameter of the driven output  121  (diameter of the housing  103  at the rolling point W) of 2×E, in this case about 125:1. Overall therefore, the rotation of the drive  111  can be geared down by several orders of magnitude. As the eccentricity E decreases the disruptive effects diminish and the transmission ratio (or the reduction ratio) increases. 
         [0040]    At least one of the transmission elements: the housing  103 , the drive  111  and the driven output  121 , and preferably all of these, are composed of a plastic-metal composite material. The metal parts contained therein allow the transmission elements to withstand the contact forces and stresses resulting from the drive torques without being destroyed. Manufacturing from thin sheets of high-strength metal (preferably steel) is preferred, since deep drawing, punching and stamping or the like afford the necessary precision and surface quality without additional remachining. Heat treatment serves to improve the strength characteristics. The associated metal parts are molded into preferably high-strength plastics and thereby joined together. The plastic areas permit complex geometries and cost-effective manufacture in the non-load bearing areas, a lower weight and very good damping characteristics, and hence an improved noise behavior, and if necessary a flexible surface for vibration damping and significantly larger contact areas. Unless otherwise specified, the metal parts in the second exemplary embodiment have an at least approximately constant material thickness, while the plastic areas occupy the remaining space of the corresponding transmission elements. 
         [0041]    In the second exemplary embodiment the housing  103  has a metal part  103   m . The metal part  103   m  forms/extends from the housing collar  105 , across the housing body,  109  to the guide  135 , where the metal part  103   m  bears against the hoop  133 . Otherwise, the housing body  109  is formed by a plastic area  103   k  of the housing  103 . The housing cover  107  assigned to the housing  103  has a metal part  107   m . The metal part  107   m  extends up to the guide  135 , to bear against the hoop  133 . The remainder of the housing  103  is in the form of a plastic area  107   k . The respective plastic areas  103   k  and  107   k  are ultrasonically welded together to join the housing  103  and the housing cover  107 . 
         [0042]    The drive  111  has a first metal part  111   m  and a second metal part  111   n . The first metal part  111   m  forms/extends from the drive tube  113  via the drive flange  115  to the side of the drive bearing ring  117  facing the roller bearing  119 . The second metal part  111   n  is arranged on the side of the drive bearing ring  117  facing the balls  131 . The remainder of the drive  111  is in the form of a plastic area  111   k  that is in the drive bearing ring  117 . 
         [0043]    The driven output  121  has a first metal part  121   m  and a second metal part  121   n . The first metal part  121   m  is part of the driven output bearing ring  127 , and is arranged on the side facing the housing  103  and the housing cover  107 , where the first metal part  121   m  extends over/partially forms the hoop  133 . The second metal part  121   n  is part of the driven output bearing ring  127  on the side facing the balls  131 . The plastic area  121   k  of the driven output  121  extends from the inside of the driven output bearing ring  127  over the entire driven output disk  125  and the entire driven output tube  123 . 
         [0044]    Like the first exemplary embodiment, the gear stage  101  may be combined with a motor to form a drive unit and/or with a mechanism to form an actuator, for adjusting the inclination of a backrest of a vehicle seat, for example. 
         [0045]    It will be understood by those skilled in the art that while the present invention has been discussed above with reference to exemplary embodiments, various additions, modifications and changes can be made thereto without departing from the spirit and scope of the invention as set forth in the following claims.