Abstract:
The seat depth adjustable motor vehicle seat comprises a first seat part, a second seat part and a longitudinal adjustment device interposed between the first seat part and the second seat part and allowing for displacement movement in a first seat direction of the first seat part relative to the second seat part. The seat further comprises a toothed rack connected to the second seat part and extending substantially in the first seat direction. A primary gear meshes with the toothed rack. A secondary gear is in rotating communication with the primary gear. A toothed bar extends substantially in a second seat direction and engages the secondary gear. A third seat part is slidably disposed in the second seat direction and is connected to the toothed bar.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Application No. DE 10 2007 060 926.6, filed Dec. 14, 2007, which is hereby incorporated by reference in its entirety as part of the present disclosure. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a seat depth adjustable motor vehicle seat as set forth in the preamble of patent claim  1 . Such a motor vehicle seat is known from DE 19 628 381 A1. Further, there is known from DE 698 27 303 T2 a vehicle seat the seat depth of which is adjustable, a second seat part thereof, which is a front seat part, being adjustable relative to a first, rear seat part by means of an electric motor. On the vehicle seat previously known from DE 199 13 503 A1, which can be positioned different distances apart by means of an adjustment device. A similar vehicle seat is also shown in DE 199 55 296 C1. 
     A problem with the seat depth adjustment devices of the seat part is that the padding must somehow follow or be compensated on the one side, meaning it must conform to the length variations; on the other side however, the cover of the padding must also be configured accordingly. The padding should have the same quality everywhere, irrespective of the seat depth adjustment. Additionally, it is desired that the least possible crinkles occur in the cover and that there are as few gaps as possible, be they covered or not. 
     In view of the vehicle seat of the type mentioned herein above, it is the object of the invention to further develop the previously known vehicle seat in such a manner that the seat part be adjustable in the direction so as to allow for a more favorable configuration of the padding, in particular also of the cover, than before. 
     SUMMARY OF THE INVENTION 
     In view of the seat depth adjustable motor vehicle seat of the type mentioned herein above, the solution to this object is that a toothed rack extending substantially in the first seat direction is connected to the second seat part, that there is provided a primary gear meshing with the toothed rack, that there is provided a secondary gear in rotating communication with the primary gear, that there is provided a toothed bar extending substantially in a second seat direction and engaging the secondary gear and that there is provided a third seat part that is slidably disposed in the second seat direction and that is connected to the toothed bar. 
     On this motor vehicle seat, the motor drive responsible and provided for longitudinal adjustment between the first seat part and the second seat part is indirectly used at the same time for the drive between the second seat part and a third seat part. This is achieved by the fact that there are provided a primary gear and a toothed rack cooperating therewith, which are being moved with respect to each other by the longitudinal adjustment. Accordingly, the linear movement is converted back into a movement of rotation. This movement of rotation is then advantageously transmitted to the secondary gear which meshes the toothed rod which is associated with the third seat part and which moves together with the third seat part or it directly drives the third seat part. 
     As a result, all the seat parts are driven in synchronism. Two seat parts are moved with only one motor drive of the longitudinal adjustment. The first seat part moves relative to the second seat part and the third seat part additionally moves with respect to the first or the second seat part. In all, the seat part is divided into three or possibly even more seat parts. As a result, it becomes easier to bridge the gap and to adapt the cover fabric, e.g., to let it conform to the change. 
     It is preferred that the third seat part forms a seat front edge. In another preferred developed embodiment, the axis of the primary gear is connected to the second seat part, thus moving together therewith. In an alternative, the primary gear is framed on either side between toothed rack and toothed rod and is engaged. In this case, the gear follows half of the movement of the second seat part relative to the first one. This movement can be used to directly drive the third seat part or to provide a secondary gear having a desired tooth ratio with respect to the primary gear and meshes the toothed bar. In the last case, the third seat part can travel a longer distance than in the first case. 
     Other features and advantages of the invention will become more apparent upon reviewing the appended claims and the following non restrictive description of three embodiments of the invention, given by way of example only with reference to the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 : shows a perspective illustration, in parts in the form of an assembly drawing, for a first exemplary embodiment. 
         FIG. 2 : shows a side view of a second exemplary embodiment that is built similar to the first exemplary embodiment shown in  FIG. 1 , a seat part being shown in its largest seat depth. 
         FIG. 3 : shows a view like  FIG. 3 , but now in the position of least seat depth. 
         FIG. 4 : shows a perspective illustration similar to  FIG. 1  but now for a third exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Herein after, the first and the second exemplary embodiment according to the  FIGS. 1 through 3  will be described first; these two exemplary embodiments are closely related. Then, the other embodiment will be discussed, in particular insofar as it is different from the other ones discussed previously. 
     As is known, the adjustable vehicle seat has an underframe  20 . It comprises a longitudinal adjustment device  22  with two pairs of rails that are configured ac-cording to prior art and carry front rockers  24  as well as rear rockers  26 . On the rockers  24 ,  26  there is retained a seat carrier that is substantially formed from a left side part  30  and from a right side part  32  which are hinge-linked to the rockers  24 ,  26 . These two side parts  30 ,  32  form a first seat part  33 . 
     There is further provided a cushion shell  34 . It occupies about 40 to 70% of the seat part and forms cheeks at the sides. The cushion shell  34  forms the second seat part. In its rear region the first seat part  33  has long holes  36  through which holding devices  38  extend in the assembled condition, the holding devices being provided each on the side parts  30 ,  32 . An articulated longitudinal guide is thus formed. 
     The two side parts  30 ,  32  are joined together by a front cross beam  40 . A front end of a longitudinal adjustment device  44  is retained thereon in a housing  42 . As can be seen from the  FIGS. 2 and 3 , this longitudinal adjustment device is con-figured to be a spindle drive; in this respect, the reader is referred to the applications WO 03/068551 A1, DE 103 53 245 A1, DE 1 755 740 A1, U.S. Pat. No. 6,260,922 B1, DE 10 2005 028 620 A1 and DE 198 15 283 C2. The longitudinal adjustment device  44  has a drive housing  46  that is retained in a holding device  48  which in turn is connected to the first seat part  33 . In the drive housing, a spindle nut is rotatably carried in a known way that has not been illustrated herein though, the spindle nut forms a surrounding grip around a spindle  50 . The axial position of this spindle  50  can be adjusted with respect to the drive housing  46  as this can be seen when comparing the  FIGS. 2 and 3 , where the two end positions are illustrated. 
     A toothed rack  52  is connected to the second seat part  34 ; it extends in a first seat direction  54 , see arrow. This direction lies in the same x-z plane as a second seat direction which is defined by the longitudinal axis of the spindle  50 , al-though it differs slightly, for example by 5 to 10 degrees. The angle with respect to the x-axis is greater with the first seat direction  54  than with the second seat direction. 
     A primary gear  56  engages the toothed rack  52 . This primary gear  56  is rotatable about an axis line of an axis  58 ; this axis line extends in the x-z plane and is perpendicular to the first seat direction  54 . 
     A secondary gear  60  is connected to the primary gear  56  so as to be driven jointly, in the embodiment shown, these two gears  56 ,  60  are made from one piece. The secondary gear  60  has a significantly larger diameter than the primary gear  56  so that a transmission of at least 1 to 1.5, preferably of at least 1 to 2, is achieved between the two of them. A toothed bar  62 , which is parallel to the toothed rack  52 , meshes the secondary gear  60 . The two of them, meaning the toothed bar  62  and the toothed rack  52  can move relative to each other in the first seat direction  54 . 
     When the longitudinal adjustment device  44  is driven, starting from the position shown in  FIG. 3 , the toothed rack  52  is pushed forward and thereby caused to move relative to the primary gear  56 . If one considers that the first seat part  33  is stationary, the axis  58  also remains stationary, the primary gear  56  remaining stationary as well as a result thereof. It is rotated by virtue of the movement of the second seat part. As a result, the secondary gear  60  is also rotated, which pushes the toothed bar  62  forward until the position shown in  FIG. 2  is reached. By virtue of the transmission between the primary gear  56  and the secondary gear  60 , the toothed bar  62  moves a considerably larger distance in the first seat direction  54  while the longitudinal adjustment device  44  performs its adjustment movement, in the second exemplary embodiment, it moves approximately double this distance. A third seat part  64  is connected to the toothed bar  62 . This third seat part  64  forms a front edge  66  of the seat. 
     The third exemplary embodiment shown in  FIG. 4  differs from the first exemplary embodiment shown in  FIG. 1  by the fact that the primary gear  56  is now not rotatable about an axis motion-linked to the first seat part. Instead, a toothed rod  68  is motion-linked to the first seat part, the toothed rod extending parallel to the toothed rack  52 . Between the toothed rod  68  and the toothed rack  52  there is located the primary gear  56 . In the discussed implementation, there is pro-vided, like in the first exemplary embodiment, a long hole that is formed in the second seat part  34 . A pin, which is connected to the first seat part  33  at the bottom and to the toothed rod  60  at the top, engages this long hole. In  FIG. 1 , the axis  58  is provided instead of this pin. 
     Upon actuation of the longitudinal adjustment device  44 , the toothed rod  66  and the toothed rack  52  are moved with respect to each other in the first seat direction  54 . As a result, the primary gear  56  rotates. The secondary gear  60 , which meshes the toothed bar  62  associated with the third seat part  64 , rotates along therewith at the same angular velocity. 
     The unit consisting of the primary gear  56  and the secondary gear  60  moves both relative to the toothed rod  68  and to the toothed rack  52 . There is provided a suited guide part such as a slide that is guided lengthwise by at least one of the toothed rack  52  or the toothed rod  68  or at another place in the first seat direction  54  and comprises an axis for the gear combination  56 ,  60 . 
     Through appropriate choice of the ratio between the diameter of the primary gear  56  and the secondary gear  60 , the desired gear transmission ratio or gear reduction can be achieved; it is also possible to equip both gears with the same diameter. 
     Between the discrete seat parts  33  and  34  as well as  34  and  64 , there are pro-vided suited guides known in the art, which fix the displacement movements. The already mentioned long holes  36  and the associated holding devices  38  as well as the long hole mentioned in the second seat part  34  through which ex-tends the axis  58  or a pin, belong thereto. A long hole  36  extending in the first seat direction  54  in the third seat part  64 , through which extends the axis  58 , also belongs thereto, see  FIG. 1 . 
     Between the first seat part  33  and the second seat part  34 , an actually known seat spring system (not shown) can be arranged, the seat spring system lengthening or shortening during adjustment movement between these two seat parts  33 ,  34 . 
     Preferably, the toothed rack  52  is at least 30% shorter than the toothed bar  62 . The toothed rack  52  and the toothed rod  68  are preferably built identically. The parts  52 ,  62 ,  68 ,  56  and  60  are preferably injection-molded parts, in particular made from plastic material. In a preferred embodiment, the second seat part  34  is moved forward about 32.5 mm with respect to the first seat part  33  and the third seat part is also moved forward about 32.5 mm relative to the second seat part  34  through the arrangement consisting of the toothed rack  52 , the gears  56  and  60  and the toothed bar  62 . Approximately one half of the padding extension is taken from the rear part, the other half from the front part. The longitudinal direction of the longitudinal adjustment device, meaning of the spindle  50  in particular, can differ from the actual direction of the displacement movement between the first seat part  33  and the second seat part  34  by approximately 10 degrees or also 20 degrees for example. These directions lie in the x-z plane.