Abstract:
The invention relates to a longitudinal seat adjustment device comprising an upper rail and a lower rail. The upper rail sits in the lower rail. Between the two rails a spindle is fixedly connected to the lower rail. Drivable on said spindle is a transmission, which can be retained in a specific manner by means of slotted bridges in the case of a crash.

Description:
PRIORITY INFORMATION  
       [0001]     This application is a continuation of co-pending Ser. No. 10/471,226 filed Jan. 20, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to a longitudinal seat adjustment device.  
         [0003]     Longitudinal seat adjustments generally have a lower rail fixed to a chassis, inside which lower rail and upper rail, to which the seat is attached, can be propelled by motor. A spindle fixed by its respective ends to the lower rail sits inside the upper rail, on which spindle a transmission fixedly coupled to the upper rail is arranged in axially movable fashion. The seat, which is located on the two upper rails arranged parallel to one another, can be propelled via a motor device that sits between the rails.  
         [0004]     Examples of devices for the purpose of longitudinal seat adjustments have been disclosed in DE 36 40 197 A1, DE 42 08 948 C2, DE 196 42 655 C2, DE 198 15 283 A1, DE 198 44 817 A1, DE 199 44 690 A1, and WO 95/16 585. There is a need for a compact longitudinal seat adjusting device in which only a few components are needed and that can without difficulty accommodate the forces that occur especially in the case of a crash, and in particular for a transmission that to transforms the rotational motion of the drive motor into a translational motion.  
         [0005]     A further goal of the present invention is for the space occupied by the longitudinal seat adjusting device to be relatively small, preferably only 15 mm in width. Moreover, the permissible protrusion of the upper rail is likewise not to be too great, at most some 15 mm. Finally, the device according to the invention is to satisfy a strength requirement in both directions, which is for example 25000 N.  
         [0006]     Finally, the device according to the invention is to be relatively rapidly adjustable, that is, for example at between 15 and 25 mm/s over a relatively long adjustment range of for example 300 mm.  
       SUMMARY OF THE INVENTION  
       [0007]     In a preferred embodiment of the invention, the rotational motion of the motor is transformed to the translational motion via a flexible shaft, a worm, a spindle, and a spindle nut.  
         [0008]     In order to reduce noise it is recommended that the spindle preferably be aligned exactly parallel to the upper rail and lower rail.  
         [0009]     In another development of the invention, at least one of the wall parts of the upper rail is provided with a notch through which a flexible shaft coupled to a drive motor is guided.  
         [0010]     In a further development of the invention, side walls of the upper rail are formed as slotted bridges and pressed into the interior of the upper rail, the transmission housing being able to be braced against these slotted bridges.  
         [0011]     The transmission housing preferably includes two housing shells made of plastic, which are connected to one another by ultrasonic welding. The housing, which is connected by ultrasonic welding of the two housing halves, is advantageously designed only for compressive loading.  
         [0012]     A clamping holding of the transmission is achieved according to the invention by metal stirrups bent into an L shape oppositely worked into a recess of the upper rail, between which stirrups the transmission housing is slipped with wall tapers.  
         [0013]     The spindle nut and the above-mentioned thrust ring, which can brace itself in walls of the upper rail in the case of a crash, are preferably formed integrally or in one piece. Both are preferably made of metal.  
         [0014]     In another development, a worm seam is coaxially applied to the spindle nut by plastic injection.  
         [0015]     The longitudinal seat adjustment functions as follows. The transmission is built into a U-shaped seat rail. This seat rail is comprised of a lower rail and an upper rail, as referred to above. The lower rail is connected to the body of the vehicle, while the upper rail is connected to the vehicle seat. The transmission housing is fixated on the upper rail via two lugs and is preferably secured with a dowel pin. The spindle nut itself is connected to the lower rail via two screws. The seat is adjusted via the translational motion of the spindle/spindle nut pair. Two rails and thus two transmissions (one left and one right) are required for the adjustment of one seat.  
         [0016]     The principal function of the transmission includes transforming the rotational motion into a translational motion. The rotational motion is transmitted to the transmission by a motor and the adapted flexible shaft via a square integrated into the transmission worm. The spindle is driven via the injection-coated worm gear with a well-defined transmission ratio. The transformation to translational motion is effected via the spindle/spindle nut pair. A trapezoidal thread is available to both parts.  
         [0017]     The transmission according to the invention is distinguished in particular by the fact that it can withstand very high forces in the case of a crash. The housing of the transmission is not itself capable of withstanding the forces in the case of a frontal crash. Such forces are around 24000 N. In the transmission according to the invention, the housing of the transmission is destroyed in the case of a crash and the thrust ring, which is preferably made of metal, can push against the contact surfaces of the upper rail on both sides.  
         [0018]     The parts upper rail, thrust ring, spindle, spindle nut and lower rail in the longitudinal seat adjustment device according to the invention are situated in the force transmission path in the case of a crash and can advantageously withstand the crash forces.  
         [0019]     The longitudinal seat adjustment device according to the invention is distinguished by the free positionability of the transmission on the rail, the integral forming of the thrust ring/spindle nut, a rotating nut, and a rotating spindle. Moreover, a larger travel distance results with the device according to the invention under the same installation conditions.  
         [0020]     Moreover, the device according to the invention, or the transmission implemented therein, is distinguished by the following features.  
         [0021]     The geared adjustment drive is composed of only four or five components. The gearing parts of the worm transmission are directly supported in a plastic cage. Separate support components can be dispensed with. The cage constituents are connected and fixated by ultrasonic welding via an individual lowering path with an eye to lash-free functioning of the gearing parts. The flexible shaft attachment is an integral constituent of the fixation of the transmission to the seat rail. The flexible shaft attachment provides a coaxial fixation of the rotating flexible shaft to the drive worm and is preferably fastened to the plastic cage via a bayonet connection with snap closure.  
         [0022]     The transmission cage is connected to the seat rail in a lash-free but elastic manner via slotted bridges and rimmed holes in sheet metal and can be individually adapted in the assembly process. The spindle nut is simultaneously the worm gear and the thrust ring. The integrated thrust ring relieves the plastic transmission of crash forces in the case of a crash. The thrust ring here braces itself by projection on notches made in the seat rail.  
         [0023]     The threaded spindle can be removed subsequently for purposes of assembly and repair.  
         [0024]     These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  is a perspective illustration of a lower rail with a spindle installed and a transmission sitting on the spindle;  
         [0026]      FIG. 2  is a perspective illustration of the rail of  FIG. 1 ;  
         [0027]      FIG. 3  illustrates the transmission held in the upper rail;  
         [0028]      FIG. 4  is an end-on view of the arrangement depicted in  FIG. 2  and  FIG. 3  in end-on view,  
         [0029]      FIG. 5  illustrates for one embodiment dimensional information on the travel distance of the upper rail relative to the lower rail in mm;  
         [0030]      FIG. 6  is a detail view of the end stop overlap;  
         [0031]      FIG. 7  illustrates the seat rail section in the transmission region;  
         [0032]      FIG. 8  illustrates the upper rail with opened housing;  
         [0033]      FIG. 9  is illustrates fastening of the transmission to the lower rail;  
         [0034]      FIG. 10  illustrates an assembly sequence for the device according to the invention;  
         [0035]      FIG. 11  illustrates the region of the transmission on an enlarged scale;  
         [0036]      FIG. 12  illustrates the transmission in an exploded view;  
         [0037]      FIG. 13  illustrates the flexible shaft adapter; and  
         [0038]      FIGS. 14A and 14B  present detail views to explain the accommodation of crash forces with the device according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]      FIG. 1  illustrates a spindle  14  that sits inside a lower rail with an O-shaped cross section, which is fixed to the chassis of a vehicle via mounting screws  12  at either end. The spindle  14  is fixedly arranged in a lower rail  10  at both its ends via an end stop  18 . The connection between the spindle  14  and the lower rail  10  can be effected in arbitrary fashion. In the exemplary embodiment depicted, the spindle  14  is fastened to the bottom of the lower rail  10  via its end stops  18  with mounting rivets  16 . The device includes an adjustment nut  20  and a stop nut  22 . A transmission  30  is propellably arranged on the spindle and is driven by a flexible shaft  50 . When the flexible shaft  50  rotates, the transmission moves to the left or right on the spindle  14 , depending on the direction the flexible shaft  50  turns.  
         [0040]     Referring to  FIG. 2 , an upper rail  40  is fixedly coupled to the transmission  30 . A seat, preferably a seat of a motor vehicle, is fastened to the upper rail  40 . The lower rail  10  together with the upper rail  40  and the transmission  30  are arranged parallel to one another under the seat to be adjusted. Between each such pair of rails sits a drive motor, which drives the flexible shaft  50  of each transmission  30  so that the seat can be moved toward the front or toward the rear.  
         [0041]     The seat of the transmission in the upper rail  40  is depicted on an enlarged scale in  FIG. 3 .  FIG. 7  gives a similar depiction, but viewed from the other side, with the lower rail omitted. In its upper wall part, the upper rail  40  has at its disposal a notch in which the box-shaped housing of the transmission  30  sits.  
         [0042]     The transmission  30  is clampingly held in the notch  45 . For this purpose, wall sections of the upper wall are bent inwardly by  90 ° into the notch  45  and serve as a stop lug  43 . Two of these stop lugs  43  are situated oppositely in the longitudinal direction of the upper rail  40 . The stop lugs  43  can be seen in  FIG. 8 . Moreover, the box-shaped housing of the transmission  30  sits between two parallel wall sections  46 , which extend upwardly in parallel fashion integrally from the side walls of the upper rail  40 . Thus transmission  30 , which is formed from a housing top  31  and a housing bottom  32  and is preferably made of plastic, sits between the two above-mentioned stop lugs  43  and the wall sections  46 . The wall section  46  facing toward the observer is provided with a hole through which the flexible shaft  50  intrudes into the interior of the housing of the transmission  30 .  
         [0043]     Slotted bridges  41  are pressed into the side walls of the upper rail  40 . These are wall sections that have been pressed into the interior of the upper rail  40  through slots, parallel to one another, made in the side walls of the upper rail  40 . Such slotted bridges  41  are located in pairs directly opposite one another. The slotted bridges  41  constrict the interior space of the upper rail  40  and serve (compare  FIG. 9 ) as a stop for the housing top  31  and the housing bottom  32  of the transmission  30 . A notch  42 , which lies between the respectively arranged slotted bridges  41 , are located oppositely in the two sides of the upper rail  40 . The notch  42  serves for the partial accommodation of a thrust ring  34  in a manner explained below.  
         [0044]     The flexible shaft  50  projects into the interior of the housing of the transmission  30  via a flexible shaft adapter  52 . A worm  35 , which is in engagement with a spindle nut  36 , sits in the interior of the transmission  30  at the end of the flexible shaft adapter  52 . The spindle nut  36  is provided with a worm gear. As seen  FIG. 12  in particular, a thrust ring is integrally molded onto this spindle nut with worm gear.  
         [0045]     The spindle nut, the worm gear and the thrust ring are preferably made of metal. In addition, there can also be a plain washer  37  inside the transmission  30 . The housing of the transmission  30 , comprised of the housing bottom  32  and the housing top  31 , is made of plastic and has box-shaped parts  31  a and  32   a  through which the spindle  14  is guided. The ends of the box-shaped parts  31  a and  32   a  find their stop on the above-mentioned slotted bridges  41 . When the transmission is propelled via the flexible shaft  50 , the upper rail is carried along the spindle and thus inside the lower rail  10  by the totality of the arrangement of transmission and upper rail as described.  
         [0046]     As illustrated in  FIG. 9 , the slotted bridges  11  can also be made in the bottom wall of the lower rail. The slotted bridges  11  are likewise wall sections bent or impressed toward the upper rail, which wall sections as shown in  FIG. 9 , are arranged oppositely to the mounting rivets  16  in front of the respective end stops  18 .  
         [0047]     As shown in  FIG. 9 , in the case of a crash the axial acceleration of the seat that occurs is intercepted both by the slotted bridges  11  and  41  and also by the thrust ring in cooperation with the notch in the upper rail  40 . The slotted bridges  11  and  41  are in each case arranged in pairs to ensure effective bracing of the adjustment device of the seat adjustment regardless of whether the acceleration is toward the front or the rear in the case of a crash. In addition, the thrust ring  34 , in cooperation with the notch of the upper rail, likewise works up the force that occurs upon forward or backward acceleration.  
         [0048]     As shown in  FIG. 9 , the end stops  18  are formed by U-shaped brackets. The spindle  14  protrudes through the longitudinal arms of these U-shaped brackets, retaining shackles being provided at the ends of these U-shaped brackets through which the mounting rivets  16  are guided.  
         [0049]     The device depicted in  FIG. 1  to  FIG. 3  is depicted in  FIG. 4  as an end-on cross-sectional view of the seat rail. The reference characters already explained again stand for the known parts. As shown in  FIG. 4, 4  the lower rail  10 , which is U-shaped in cross section, has inwardly reflexed wall parts. Outwardly reflexed wall parts of the upper rail  40  intrude between these inwardly bent wall parts of the lower rail  10 , as viewed from the side walls of the upper rail  40 . This ensures that upper rail  40  and lower rail  10  cannot become laterally offset. Moreover, some guidance is provided.  
         [0050]      FIG. 5  illustrates schematically the possible travel distance between the upper rail and the lower rail. In the present exemplary embodiment, 343 mm is provided as a possible travel distance.  
         [0051]      FIG. 6  illustrates in cross-sectional view, the slotted bridges made in the upper rail  40 , which markedly constrict the interior space in the U-shaped upper rail and thus serve as a stop for the transmission  30 .  
         [0052]      FIG. 10  illustrates the upper rail  40  and the lower rail  10  together with the above-described individual components in exploded view. Components discussed above are provided with the same reference characters as above.  
         [0053]     The transmission  30  is drawn in  FIG. 11  with the housing bottom  32  and the housing top  31  together with box-shaped integrally molded elements in the assembled condition. The stop lugs inwardly turned over from the upper wall of the upper rail  40  can also be seen in this depiction.  
         [0054]     Thrust ring  34  extends forth laterally from the housing of the transmission  30 .  FIG. 12 , already explained, shows the transmission in an exploded view. Here the spindle nut  36  together with the worm gear and the integrally molded thrust ring  34  can be seen clearly. The worm  35 , which is driven by the flexible shaft, engages with the worm gear  37 . The transmission is moved along the spindle  14  by this drive.  
         [0055]     The transmission is illustrated without a housing in  FIG. 13 , the worm on the flexible shaft  50  having been omitted for greater clarity. The flexible shaft  50  is guided into the housing of the transmission via the flexible shaft adapter  52 , already referred to. A bayonet connection  60  with grips  62  takes care of mounting the flexible shaft to the housing of the transmission  30  in a suitable manner. In  FIG. 16 , once again, individual depictions, each in longitudinal section, are shown in order to make clear the accommodation of crash forces. Here it should be remarked that the notch  42  or relief in the upper rails  40  in the region of the thrust ring  34  is formed such that there is no contact between the thrust ring  34  and the upper rail  40  in the normally installed condition. Only in the case of a crash does the thrust ring  34  brace itself against the housing wall of the upper rail  40 . As can be seen from  FIG. 14 , in particular from the depiction at the top right, the thrust ring  34  touches the upper rail  40  in the case of a crash with a contact surface that is segment-shaped at the left and right on the thrust ring  34 . Thus the thrust ring  34  braces itself symmetrically against the left side wall and the right side wall of the upper rail  40 .  
         [0056]     Although the present invention has been illustrated and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.