Abstract:
A vehicle seat is provided including a seat frame having a sitting surface frame and a backrest frame, wherein the backrest frame has a left backrest longitudinal strut and a right backrest longitudinal strut as well as a lower cross strut and an upper cross strut, the right and left backrest longitudinal struts being pivotably arranged on the lower cross strut in such a way that the backrest frame is helically deformable.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of German Patent Application No. 102012109710.0 filed Oct. 11, 2012, the contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a vehicle seat. 
     BACKGROUND OF THE INVENTION 
     Seats of this type are known in a large number of different configurations. The sitting surface frame and the backrest frame of the seat frame may differ in their upholstery. Such known seats are adjustable in terms of their seat contour and backrest contour, but are generally not sufficiently adapted to the ergonomics of a user, meaning that comfort is accordingly restricted and the user&#39;s back is not adequately supported by the backrest frame in each position, which can sometimes lead to back complaints. 
     A vehicle seat is thus known from, for example, DE 4405397 C1, of which the backrest frame is subdivided into a plurality of subsegments which are pivotable with respect to one another about a vertical axis of rotation. 
     A vehicle seat fitted with a backrest frame which is movable in this manner does make it possible to improve access for users to actuation members behind the seat and, by means of the user&#39;s upper body rotating with respect to the centre of the vehicle, to achieve simpler passage in a two-door motor vehicle, even for back-seat passengers, without obliging those sitting at the front to vacate the vehicle. 
     However, this movable backrest frame is not optimally adapted to human ergonomics so that the user of such a vehicle seat may therefore in some circumstances not experience the required seating comfort but rather may even have to put up with back complaints owing to the use of such a vehicle seat. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention addresses the object of providing a vehicle seat which is better adapted to the ergonomics of the human back, in particular during rotational movements of the back, and thus at the same time provides enhanced seating comfort to any person using this vehicle seat. 
     This object is achieved by the features of claim  1 . Advantageous embodiments of the invention are found in the dependent claims. 
     The inventive idea is that with a vehicle seat comprising a seat frame having a sitting surface frame and a backrest frame, said backrest frame has a left backrest longitudinal strut and a right backrest longitudinal strut and a lower cross strut and an upper cross strut, the right and left backrest longitudinal struts being pivotably arranged on the lower cross strut against a resistance in such a way that the backrest frame is helically deformable. This configuration allows a person sitting in such a vehicle seat according to the invention who is rotating his or her back or upper body to the left or right while resting via his back on the backrest frame, which is generally upholstered, the backrest frame is always in contact with the back of the user, who thus rests thereon in a relieving manner. The backrest frame rotates when this occurs, in such a way that the right and left backrest longitudinal struts pivot differently, said longitudinal struts remaining connected by the upper cross strut and the entire backrest frame thereby being helically deformed. The left and right backrest longitudinal struts may pivot during this process in such a way that, on the one hand, the two struts pivot backwards, albeit at different angles, in the vehicle seat longitudinal direction. On the other hand, it is also conceivable for the left or right backrest longitudinal strut to pivot forwards in the vehicle longitudinal direction and for the other backrest longitudinal strut to pivot backwards in the vehicle longitudinal direction. Since, in each case, this pivoting takes place against a resistance, the backrest longitudinal frame of the vehicle seat according to the invention supports the user as he rotates his back or upper body into its starting position, since the resistance makes it possible to accumulate a restoring force which is removed during rotation into the starting position. It is thus also ensured that even during rotation into the starting position, the entire backrest frame contacts and relieves the entire surface area of the back of the user as he rotates, since said backrest frame supports the rotational movement by removing the restoring force. 
     According to a first further inventive idea, the backrest frame additionally has a central backrest longitudinal strut which is attached pivotably about a substantially horizontal axis to the lower cross strut, the right and left backrest longitudinal struts being arranged at least in the region of their upper ends outside a fictious surface element formed by a 360° rotation of the central backrest longitudinal strut. Owing to this inventive embodiment of the backrest frame of a seat frame of a vehicle seat, deformation of the backrest frame is optimally adapted to human ergonomics, in particular during rotational movements of the back or upper body of a vehicle seat user. The individual elements of the backrest frame are in this case associated with individual elements of the human back and virtually identically reproduce the movement thereof during rotation of a user&#39;s back or upper body. The central backrest longitudinal strut is thus comparable to the human spine, whereas the lower and upper cross struts represent the human hip and shoulder axles respectively. The left and right backrest longitudinal strut can be compared to the muscular and ligamentous apparatus of the human back. 
     If a person sitting in such a vehicle seat according to the invention now rotates his/her back or upper body while resting via his/her back on the backrest frame, which is generally upholstered, the person&#39;s shoulder axle rotates with respect to their hip axle, the muscular and ligamentous apparatus being rotated helically or torsionally together with the spine. In the same manner, the right, left and central backrest longitudinal struts of the vehicle seat according to the invention rotate helically or torsionally with respect to one another, while remaining connected by the upper and lower cross struts. This ergonomic configuration of the backrest longitudinal strut not only improves comfort for the vehicle seat user but rather, owing to the constant and reliable contacting of his/her back with the, generally upholstered, backrest frame, also prevents back complaints, even during rotational movements of the back, because the backrest frame is able to absorb stresses, which consequently do not have to be borne by the user&#39;s ligamentous and muscular apparatus. 
     According to a further inventive idea, the upper cross strut is divided in two, into a first cross strut part arranged between the left backrest longitudinal strut and the central backrest longitudinal strut and a cross strut part arranged between the right backrest longitudinal strut and the central backrest longitudinal strut. This embodiment of the invention means that the vehicle seat according to the invention is even better adapted to human ergonomics since, just like the shoulder axle of a person, the upper cross strut is no longer a rigid axle. 
     In order for the vehicle seat according to the invention to reproduce even more closely the ergonomics of the shoulder, it has proved to be advantageous for, preferably in an articulated manner, the first cross strut part to be held in receiving portions on the left backrest longitudinal strut and the central backrest longitudinal strut, and the second cross strut part to be held in receiving portions on the right backrest longitudinal strut and the central backrest longitudinal strut. In this case, the mobility of the entire upper region of the backrest frame basically corresponds to the mobility of the human shoulder region, meaning that back movements, in particular rotational and torsional movements of the back, are able to be supported particularly well by the seat according to the invention, and this in turn enhances seating comfort and minimises the likelihood of back complaints. 
     In order for the various sitting positions that may be adopted by users of the vehicle seat to be accommodated with respect to the backrest inclination, it has proved to be helpful for the lower cross strut to be pivotable with respect to the sitting surface frame about a horizontal axis which extends substantially perpendicular to the seat longitudinal direction. 
     To facilitate helical or torsional rotation, the lower cross strut has a central region, on which the central backrest longitudinal strut is arranged, and two regions which are angled therefrom in the seat longitudinal direction about an angle and on which the left backrest longitudinal strut and the right backrest longitudinal strut are arranged 
     In order to produce helical rotations of the backrest frame which are as realistic as possible and, at the same time, to achieve adequate support in the side region for a user of the vehicle seat according to the invention, it has proved preferable for this angle to be 45°. 
     In principle it is indeed possible for the left and right backrest longitudinal struts to be rigidly fixed to the lower cross strut, the helical rotation then being produced by resilient properties of the left and right backrest longitudinal struts over their longitudinal extension. However, it is advantageous for the left backrest longitudinal strut to be arranged on one angled region so as to be pivotable about an axis and for the right backrest longitudinal strut to be arranged on the other angled region so as to be pivotable about another axis. 
     To achieve a sitting position which is as comfortable and pleasant as possible, the central backrest longitudinal strut is constructed in a substantially planar manner as a longitudinal component. In this manner, the pressure exerted by the back of a vehicle seat user onto the backrest frame is able to be dissipated over a large area by the central backrest longitudinal strut, without pressure points in the back region of the user from small surface regions acting on the user&#39;s back, potentially through an upholstery of the backrest frame. 
     For the same reasons, the embodiment aims for the left backrest longitudinal strut to be substantially planar, the upper end thereof being angled about an angle with respect to the lower end, and for the right backrest longitudinal strut to be substantially planar, the upper end thereof being angled about the same angle with respect to the lower end. 
     The choice of materials for the backrest longitudinal strut and the cross struts is wide, although metal or plastics material are generally chosen since, in terms of their dimensional stability and resilience, these materials have already been tested in many automotive engineering fields and can be adapted to the most diverse of requirements, while still meeting the most stringent of safety requirements and standards. 
     The lower the cross strut can, on the one hand, be constructed, as an integral component of the sitting surface frame, in one piece therewith or with a part thereof. 
     On the other hand, it is of course also conceivable for the lower cross strut to be arranged on the sitting surface frame as a separate component, preferably by means of angle brackets, in which said cross strut is pivotably held about the axis. 
     According to a further inventive idea of the invention, it can be provided for at least the central backrest longitudinal strut to accumulate a restoring force during pivoting, preferably a restoring force generated by a spring. This feature ensures that the backrest frame is of a stability which is not deflected out of its rest position according to a normal position at the slightest force application. Such a restoring force also ensures that rotational movement back to the normal position is supported by the backrest frame. 
     In addition to the central longitudinal strut, while pivoting out of their rest position according to a normal position, the right and left backrest longitudinal struts can of course also accumulate a restoring force, preferably a restoring force generated by a spring, as a result of which the return of the backrest frame having pivoted out of its rest position corresponding to a normal position is particularly smooth. 
     According to a standalone inventive idea, a vehicle comprising at least one above-described vehicle seat is also intended for protection. 
     Further aims, advantages, features and applications of the present invention will become apparent from the following description of an embodiment, with reference to the drawings. All of the features which are described or graphically shown form the subject matter of the present invention either per se or in any expedient combination, irrespective of the manner in which they are combined in the claims or in the dependency references thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In said drawings: 
         FIG. 1 : is a top view of an embodiment of a seat frame of a vehicle seat according to the invention in a normal position; 
         FIG. 2 : is a rear view of the seat frame in  FIG. 1 ; 
         FIG. 3 : is a side view of the seat frame in  FIG. 1 ; 
         FIG. 4 : is a perspective view of the seat frame in  FIG. 1 ; 
         FIG. 5 : is a top view of the embodiment of the seat frame in  FIG. 1  in a leftward-pivoted position; 
         FIG. 6 : is a rear view of the seat frame in  FIG. 5 ; 
         FIG. 7 : is a side view of the seat frame in  FIG. 5 ; 
         FIG. 8 : is a perspective view of the seat frame in  FIG. 5 ; 
         FIG. 9 : is a top view of the embodiment of the seat frame in  FIG. 1  in a rightward-pivoted position; 
         FIG. 10 : is a rear view of the seat frame in  FIG. 9 ; 
         FIG. 11 : is a side view of the seat frame in  FIG. 9 ; 
         FIG. 12 : is a perspective view of the seat frame in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 4  show various views of an embodiment of a seat frame  11  of a vehicle seat according to the invention in a normal position, which is assumed when the back or upper body of the vehicle seat user is not rotated. The seat frame  11  basically consists of a sitting surface frame  12  and a backrest frame  13  which is pivotably arranged thereon at an inclination. In the present embodiment, the backrest frame  13  is arranged pivotably about an axis  21  on angle brackets  29 , which are rigidly arranged on and fixed to the sitting surface frame  12 . 
     The backrest frame  13  basically consists of central, left and right backrest longitudinal struts  14 ,  15  and  16 , which are interconnected by means of a lower and an upper cross strut  17  and  18 . 
     The lower cross strut  17  is mainly formed by a central region  22  and regions  23  and  24  which are arranged thereon and angled in the vehicle longitudinal direction  20 . The regions  23  and  24  are angled about an angle  25 , which is approximately 45° in this embodiment. The central backrest longitudinal strut  14  is arranged on the central region  22  of the lower cross strut  17  so as to be pivotable about a horizontal axis  19 , whereas the left backrest longitudinal strut  15  is arranged on the angled region  23  so as to be pivotable about an axis  26  and the right backrest longitudinal strut  16  is arranged on the angled region  24  so as to be pivotable about an axis  27 . 
     The upper cross strut  18  is divided in two in this embodiment, a first cross strut part  18   a  interconnecting the central and left backrest longitudinal struts  14  and  15 , whereas a second cross strut part  18   b  interconnects the central and right backrest longitudinal struts  14  and  16 . In this arrangement, the cross strut parts  18   a  and  18   b  are, however, not rigidly fixed to the backrest longitudinal struts  14 ,  15  and  16  but are held in receiving portions  30 ,  31 ,  32  and  33  in an articulated manner. 
     Both the left and the right backrest longitudinal struts  15 ,  16  are angular in this case. The left backrest longitudinal strut  15  can thus be broken down into a lower end  15   a  and an upper end  15   b  and the right backrest longitudinal strut  16  into a lower end  16   a  and an upper end  16   b . The angles  28  between both upper and lower ends  15   a ,  16   a  and  15   b ,  16   b  are equal, yet are oriented in mirror symmetry, just like the arrangement of the left and right backrest longitudinal struts  15  and  16  on the lower cross strut  17 . 
     As can be seen in  FIG. 3  in particular, the right backrest longitudinal strut  16 , when viewed from the side, covers the left backrest longitudinal strut  15  in this normal position. 
       FIGS. 5 to 8  now show the embodiment in  FIGS. 1 to 4 , the backrest frame  13  being pivoted leftward, which corresponds to a rightward rotation of the back or upper body of the person sitting in the vehicle seat. In this case, the left backrest longitudinal strut  15  is pivoted leftwards about the axis  26 , the central backrest longitudinal strut  14  about the axis  19  and the right backrest longitudinal strut  16  about the axis  27 . 
     As can be seen in  FIGS. 5 and 7  in particular, the right backrest longitudinal strut  16  has moved backwards in relation to the seat longitudinal direction  20  at both its lower end  16   a  and its upper end  16   b , whereas the left backrest longitudinal strut  15  has moved forwards in relation to the seat longitudinal direction  20  at both its lower end  15   a  and its upper end  15   b . As a result of this movement, the entire backrest frame  13  has been helically deformed, since the backrest longitudinal struts  14 ,  15  and  16  are fixed locally on the lower cross strut  17  at their pivots and are therefore locally rigid in their orientation. 
     By contrast, since it is divided in two and the two cross strut parts  18   a  and  18   b  are mounted in an articulated manner in the receiving portions  30  to  33  of the backrest longitudinal struts  14 ,  15  and  16 , the cross strut  18  is not fixed in position but can follow the movement of the backrest longitudinal struts  14 ,  15  and  16  as they pivot about the axes  19 ,  26  and  27 . 
     The figures do not explicitly show a spring-loading of the backrest longitudinal struts  14 ,  15  and  16 . However, the advantageous result of this is that the pivoted backrest longitudinal struts  14 ,  15  and  16  move into their normal position in  FIG. 1  to from their pivoted position in  FIGS. 5 to 8  or also in  FIGS. 9 to 12  in a virtually self-acting manner, without the person sitting in the vehicle seat needing to expend force to this effect. It is, however, necessary for force to be expended to bring about this pivoting from the rest position in  FIGS. 1 to 4 . This is, however, also desirable in order for an unwanted pivoting to not be triggered by even small external influences, as may occur owing to centrifugal accelerations during cornering for example. 
       FIGS. 9 to 12  now show the embodiment in  FIGS. 1 to 4 , the backrest frame  13  being pivoted rightward, which corresponds to a leftward rotation of the back or upper body of the person sitting in the vehicle seat. In this case, the left backrest longitudinal strut  15  is pivoted rightwards about the axis  26 , the central backrest longitudinal strut  14  about the axis  19  and the right backrest longitudinal strut  16  about the axis  27 . 
     As can be seen in  FIGS. 9 and 11  in particular, the left backrest longitudinal strut  15  has moved backwards in relation to the seat longitudinal direction  20  at both its lower end  15   a  and its upper end  15   b , whereas the right backrest longitudinal strut  16  has moved forwards in relation to the seat longitudinal direction  20  at both its lower end  16   a  and its upper end  16   b . As a result of this movement, the entire backrest frame  13  has been helically deformed, since the backrest longitudinal struts  14 ,  15  and  16  are fixed, with the exception of the permitted rotational movement, on the lower cross strut  17  and to this effect have set orientations. 
     LIST OF REFERENCE NUMERALS 
     
         
           11  Seat frame 
           12  Sitting surface frame 
           13  Backrest frame 
           14  Central backrest longitudinal strut 
           15  Left backrest longitudinal strut 
           15   a  Lower end of the left backrest longitudinal strut 
           15   b  Upper end of the left backrest longitudinal strut 
           16  Right backrest longitudinal strut 
           15   a  Lower end of the right backrest longitudinal strut 
           15   b  Upper end of the right backrest longitudinal strut 
           17  Lower cross strut 
           18  Upper cross strut 
           18   a  Cross strut part 
           18   b  Cross strut part 
           19  Axis 
           20  Seat longitudinal direction 
           21  Axis 
           22  Central region 
           23  Angled region 
           24  Angled region 
           25  Angle 
           26  Axis 
           27  Axis 
           28  Angle 
           29  Angle bracket 
           30  Receiving portion 
           31  Receiving portion 
           32  Receiving portion 
           33  Receiving portion