Abstract:
A vehicle seat has a backrest with a backrest frame, attached to a seat supporting structure, that can be pivoted to a limited extent about a horizontal axis of rotation in order to permit active sitting. To permit active sitting even at high transverse acceleration forces, as occur during the operation of a motor vehicle, two bearing devices are attached to the backrest frame, and a backrest basic body is mounted on the bearing devices so that it can rotate about the horizontal axis of rotation.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
       [0001]    This invention relates to a vehicle seat with a backrest that has a backrest frame attached to a seat supporting structure and pivotable to a limited extent about a horizontal axis of rotation in order to permit active sitting. 
         [0002]    During active sitting, the lower part of the backrest is pivoted forward, as a result of which the pelvis of a person sitting on the vehicle seat is straightened up, and vice versa. German utility model document DE 90 06 316 U1 discloses a seat with two back shells which are arranged laterally and are fastened to a common transverse rail via a respective leaf spring with a coil. European patent EP 0 107 627 B1 discloses a chair with a seat and a backrest. The backrest is able to move from a straightened-up position relative to the seat into a partially tilted position. The known chair is inter alia characterized in that the backrest is formed from a row of at least three segments which are arranged one above another, are connected to one another in an articulated manner about corresponding, horizontal axes and are arranged in such a manner that, in the partially tilted position of the backrest, they form a curve with a curvature which essentially corresponds to the curvature of the curved back of a user. European patent EP 0 537 839 B1 discloses a supporting element for seats, which comprises two panel-like side bodies and a generally flexible, connecting intermediate body which extends in the manner of a bridge between the inner ends of the side bodies. The above-described seat structures are not readily suitable for use in motor vehicles. German patent DE 37 07 926 C2 discloses a vehicle seat with a backrest which, as a supporting structural element, has a molded shell with a central part and side guide parts which are integral therewith and extend away laterally forward. The molded shell is matched approximately to the back width of an average to large seat user. The side guide parts are designed such that they can be pivoted resiliently in relation to the central part and are suspended in such a manner on an essentially flexurally rigid backrest frame that, in the case of individuals who are narrower than the structurally predetermined width of the molded shell, the side guide parts move toward each other shifting the central part back. German patent DE 39 10 143 C2 discloses a motor vehicle seat with a backrest and a pair of side supports which are connected pivotably to both sides of the backrest via corresponding pivoting shafts. 
         [0003]    It is the object of the invention to provide a vehicle seat with a backrest which has a backrest frame which is attached to a seat supporting structure and can be pivoted to a limited extent about a horizontal axis of rotation in order to permit active sitting, which vehicle seat permits active sitting even in the case of high transverse acceleration forces, as occur during the operation of a motor vehicle. 
         [0004]    This object is achieved in the case of a vehicle seat with a backrest which has a backrest frame which is attached to a seat supporting structure and can be pivoted to a limited extent about a horizontal axis of rotation in order to permit active sitting. Two bearing devices are attached to the backrest frame, and a backrest basic body is mounted on the bearing devices in a manner such that it can rotate about the horizontal axis of rotation. The backrest is preferably coupled at its end facing the seat surface to the seat support structure. This makes it possible to adjust the inclination or to fold the backrest over. During operation, the backrest is fixed with respect to the coupling at the end facing the seat surface. In order to permit active sitting, the backrest can be rotated freely about the horizontal axis of rotation, which is preferably arranged level with the upper edge support of the pelvis, or can be rotated about a limited angle of rotation counter to the prestressing force of at least one spring device. This permits a frequent change of the loading of the intervertebral disks. The mounting of the backrest basic body in the backrest frame permits a stable mounting of the backrest basic body, which permits active sitting even in the case of high transverse acceleration forces, as occur during the operation of a motor vehicle. 
         [0005]    In a preferred exemplary embodiment of the vehicle seat, the two bearing devices are guided displaceably in the longitudinal direction of the backrest on a respective guide rail attached to the backrest frame. This permits a height adjustment of the horizontal axis of rotation in a simple manner. 
         [0006]    In a further preferred exemplary embodiment of the vehicle seat, the two bearing devices two further bearing devices for the backrest basic body are attached to the backrest frame and each have a rotation limiting element which is guided in an elongated hole. As a result, the angle of rotation of the backrest basic body relative to the backrest frame about the horizontal axis of rotation is limited. The backrest basic body is preferably prestressed into a central position by at least one spring device. 
         [0007]    In a further preferred exemplary embodiment of the vehicle seat, the backrest is divided in the longitudinal direction and has two backrest shells which are attached to a plurality of retaining arms which run essentially horizontally. The two backrest shells permit a uniform enclosure of the upper body and the waist of an individual sitting on the vehicle seat. 
         [0008]    In a further preferred exemplary embodiment of the vehicle seat, the retaining arms comprise a lower, an upper and a central pair of retaining arms, said central pair of retaining arms being arranged between the lower and the upper pair of retaining arms, as viewed in the longitudinal direction of the backrest. The three pairs of retaining arms permit an individual adjustment of the backrest shells without adversely affecting the stability of the mounting. 
         [0009]    In a further preferred exemplary embodiment of the vehicle seat, on the retaining arms of the lower and of the upper pair of retaining arms, a respective supporting arm is guided displaceably in the longitudinal direction of the retaining arms. This permits a displacement of the bearing shells transversely with respect to one another. 
         [0010]    In a further preferred exemplary embodiment of the vehicle seat, a respective fastening element is coupled to the ends of the supporting arms of the lower and of the upper pair of retaining arms. The coupling points of the fastening elements define essentially vertically running axes of rotation about which the bearing shells can be rotated for adjustment purposes. This permits an individual adjustment of the bearing shells. 
         [0011]    In a further preferred exemplary embodiment of the vehicle seat, in the retaining arms of the central pair of retaining arms, a respective guide shoe, to which a lever arm is coupled, is guided displaceably in the longitudinal direction of the retaining arms. The guide shoes permit displacement of the bearing shells transversely with respect to one another. 
         [0012]    In a further preferred exemplary embodiment of the vehicle seat, a respective fastening element is coupled to the ends of the lever arms. This permits a defined rotation of the bearing shells about the vertically running axes of rotation. 
         [0013]    In a further preferred exemplary embodiment of the vehicle seat, the retaining arms of a pair of retaining arms are arranged at an obtuse angle with respect to one another. The pairs of retaining arms are preferably each connected fixedly to the backrest basic body. 
         [0014]    Further advantages, features and details of the invention emerge from the description below, in which various exemplary embodiments are described in detail with reference to the drawing. The features mentioned in the claims and in the description may each be essential to the invention on their own or in any desired combination. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  shows a perspective illustration of a vehicle seat according to the invention from the side; 
           [0016]      FIG. 2  shows the vehicle seat of  FIG. 1  from the front; 
           [0017]      FIG. 3  shows the vehicle seat of  FIG. 1  obliquely from the front; 
           [0018]      FIG. 4  shows a perspective illustration of the internal construction of a vehicle seat according to the invention obliquely from the front; 
           [0019]      FIG. 5  shows the internal construction of  FIG. 4  from the front; and 
           [0020]      FIG. 6  shows the internal construction of  FIGS. 4 and 5  obliquely from above. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    In  FIGS. 1 to 3 , a vehicle seat  1  according to the invention is illustrated perspectively in various views. The vehicle seat  1  has a backrest  2  and a seat surface  3 . The backrest  2  comprises a backrest frame  5  which is attached pivotably about an axis of rotation  7  to a seat supporting structure  9  to which the vehicle seat surface  3  is also attached. The backrest  2  is divided into two backrest shells  11 ,  12  which are attached to the backrest frame  5 . In addition, a head restraint  13  is fastened to the backrest frame  5 . 
         [0022]    In  FIG. 1 , a double arrow  14  indicates that the backrest shells  11 ,  12  are displaceable in the longitudinal direction of the backrest frame  5 . A displacement of the backrest shells  11 ,  12  in the direction of the double arrow  14  serves to match the backrests  2  to the shape of a vehicle occupant. It is furthermore indicated in  FIG. 1  that the backrest shells  11 ,  12  can be pivoted to a limited extent about an axis of rotation  15 , as indicated by a double arrow  16 . Pivoting of the backrest shells  11 ,  12  about the axis of rotation  15  preferably takes place counter to the prestressing force of at least one spring device (not illustrated). 
         [0023]    It is indicated in  FIG. 2  that the backrest shells  11 ,  12  can furthermore be rotated about two axes of rotation  18 ,  19 . The corresponding movement of the backrest shells  11 ,  12  about the axes of rotation  18 ,  19  is indicated by double arrows  21 ,  22 . 
         [0024]    In  FIG. 3 , it is indicated by a double arrow  24  that the two backrest shells  11 ,  12  are also attached to the backrest frame  5  in a manner such that they can be displaced transversely with respect to each other. The movement of the backrest shells  11 ,  12  in the direction of the double arrow  24  takes place, like the movement of the backrest shells  11 ,  12  in the direction of the double arrows  20 ,  21  (see  FIG. 2 ), for adjustment purposes. 
         [0025]    In  FIGS. 4 to 6 , the internal construction of the vehicle seat  1 , which is illustrated in simplified form in  FIGS. 1 to 3 , is illustrated perspectively in various views. For clarity reasons, only part of the backrest frame  5  is illustrated schematically in  FIG. 4 . The backrest frame  5  may be of closed or open design, for example may be of U-shaped design. Four guide rails  31 ,  32 ,  33 ,  34  are fastened to the backrest frame  5 . The guide rails  31  to  34  are arranged essentially in the longitudinal direction of the backrest. The two guide rails  31 ,  32  are arranged on two opposite sides in the lower half of the backrest and form a lower pair of guide rails. The two guide rails  33 ,  34  are arranged on two opposite sides in the upper half of the backrest and form an upper pair of guide rails. 
         [0026]    A respective bearing bracket  36 ,  37  is guided in a manner such that it can be displaced in the longitudinal direction on the guide rails  31 ,  32 . A bearing bracket  36 ,  37  together with a bearing support  38 ,  39  in each case forms a bearing device for a backrest basic body. The bearing supports  38 ,  39  are fastened to the backrest basic body  40 . The fastening takes place preferably releasably, for example by means of screw connections. The bearing devices formed in each case by a bearing bracket  36 ,  37  and a bearing support  38 ,  39  permit the backrest basic body  40  to rotate about an axis of rotation  41 . A rotational movement of the backrest basic body  40  about the axis of rotation  41  is indicated by an arrow  42 . Of course, the rotation of the backrest basic body  40  can take place in both directions of rotation about the axis of rotation  41 . 
         [0027]    A respective bearing bracket  44 ,  45  is guided displaceably in the longitudinal direction on the guide rails  33 ,  34 . A respective guide element protrudes inward from the free end of the bearing brackets  44 ,  45 . In the case of the bearing bracket  44 , it can be seen that the guide element is formed by a screw bolt  46  which is fastened by one end to the bearing bracket  44 . The screw bolt  46  may be screwed, for example, into a correspondingly designed threaded hole in the bearing bracket  44 . A screw head is provided at the other end of the screw bolt  46 . The screw bolt  46  extends through an elongated hole  48  which is left free in a bearing support  49 . The bearing support  49  and a bearing support  50 , which is designed analogously in a mirror-inverted manner, are fastened to the backrest basic body  40 . The angle of rotation during rotation of the backrest basic body  40  about the axis of rotation  41  is limited by the elongated holes in the bearing supports  49 ,  50 . 
         [0028]    In addition to the bearing supports  38 ,  39 ,  49 ,  50 , six retaining arms  51  to  56  are fastened to the backrest basic body  40 . The retaining arms  51  to  56  are arranged in pairs horizontally and at an obtuse angle of approximately 160 degrees with respect to one another. The retaining arms  51 ,  52  form a lower pair of retaining arms. The retaining arms  53 ,  54  form an upper pair of retaining arms. A central pair of retaining arms formed by the retaining arms  55 ,  56  is arranged between the pairs of retaining arms  51 ,  52  and  53 ,  54 . The retaining arms  51  to  56  are arranged in such a manner that they butt in pairs against one another in the region of a center axis  58 . They are fastened to the backrest basic body  40  in the region of the point of abutment. 
         [0029]    In the retaining arms  51  to  54 , a respective end of a supporting arm  61  to  64  is guided displaceably in the longitudinal direction of the retaining arms. A respective fastening element  71  to  74  is coupled to the free ends of the supporting arms  61  to  64 . The fastening elements  71  to  74  serve to fasten bearing shells (not illustrated in  FIG. 4 ). 
         [0030]    In the retaining arms  55 ,  56 , a respective guide shoe  81 ,  82  is guided displaceably in the longitudinal direction of the retaining arms. A respective end of a lever arm  83 ,  84  is coupled to the guide shoes  81 ,  82 . A respective fastening element  85 ,  86  is coupled to the other end of the lever arms  83 ,  84 . 
         [0031]    The fastening elements  71 ,  73 ,  85  serve to fasten a first backrest shell. The fastening elements  72 ,  74 ,  86  serve to fasten a second backrest shell. Displacement of the guide shoes  81 ,  82  in the retaining arms  55 ,  56  makes it possible to rotate the backrest shells, as indicated on the left side in  FIG. 4  by an arrow  91 . A prerequisite for such a rotation of the backrest shells is that the supporting arms  61  to  64  retain their position relative to the assigned retaining arms  51  to  54 . 
         [0032]    In  FIG. 5 , it is indicated by arrows  101  to  104  that the backrest basic body  40  with the retaining arms  51  to  56  fastened thereto is displaceable vertically. Such a displacement, which, of course, can take place in both directions, can in particular adjust the height of the horizontal axis of rotation ( 41  in  FIG. 4 ). 
         [0033]    The pivoting of the backrest shells about vertical axes of rotation  108 ,  109  is explained below with reference to  FIG. 6 . A respective motor  87 ;  88 ;  89  with an associated gear device is arranged below the connecting points of the pairs of retaining arms  51 ,  52 ;  55 ,  56 ;  53 ,  54 . A respective motor shaft which is assigned to a retaining arm can be rotated about the central axis  58  by the motors  87  to  89 . The rotational movement of the motor shaft is transmitted with the aid of bevel gears and spindles to the supporting arms  61  to  64  or the guide shoes  81 ,  82 . 
         [0034]    For example, rotation of the motor shaft assigned to the motor  88  in the direction of an arrow  111  leads to the guide shoes  81 ,  82  being displaced outward in the retaining arms  55 ,  56 , as indicated by arrows  114 ,  115 . This movement in turn leads to the fastening elements  85 ,  86  with the backrest shells fastened thereto rotating in the direction of arrows  118 ,  119 . These movements in turn lead to the fastening elements  71  to  74  rotating together with the backrest shells fastened thereto about the axes of rotation  108 ,  109 , as indicated by arrows  121  to  124 .