Patent Publication Number: US-2009236488-A1

Title: Power seat slide apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2008-076242, filed on Mar. 24, 2008, the entire contents of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a power seat slide apparatus applied to a seat for a vehicle. 
     BACKGROUND 
     A known power seat slide apparatus, which slides an upper rail relative to a lower rail in a longitudinal direction of a vehicle by rotating a screw shaft by means of a rotation of a motor, is disclosed in JPH6-19396Y2. According to the power seat slide apparatus disclosed in JPH6-19396Y2, a stopper is provided at each of front and rear portions of the screw shaft, and a moving distance of the upper rail, that is, a moving distance of the seat in a longitudinal direction thereof is restricted by contacting the stopper and a reduction gear portion. 
     Notwithstanding, according to the construction of the power seat slide apparatus disclosed in JPH6-19396Y2, because stoppers are required to be provided at the front and rear portions of the screw shaft, respectively, in order to restrict the moving distance of the seat, drawbacks arise that manufacturing cost is increased and a large degree of design change is required when a distance (referred as stroke) between the stopper is needed to be changed. 
     A need thus exists for a power seat slide apparatus which is not susceptible to the drawback mentioned above. 
     SUMMARY OF THE INVENTION 
     In light of the foregoing the present invention provides a power seat slide apparatus, which includes a lower rail adapted to be provided at a vehicle floor, an upper rail slidably supported by the lower rail for retaining a vehicle seat, the upper rail having a pair of walls formed on right and left sides thereof, a lead screw member rotatably supported by the upper rail and extending in a sliding direction of the upper rail, a lead screw nut member provided at the lower rail and threadedly engaged with the lead screw member (for rotatably moving thereon in an axial direction), an output rotation member provided at the upper rail and rotationally connected to the lead screw member, a gearbox rotatably supporting the output rotation member, a drive unit transmitting a rotational drive force to the lead screw member via the output rotation member supported by the gearbox, and a pair of cut-and-bent-away portions, each cut-and-bent-away portion being formed on each of the walls of the upper rail and being arranged at positions to face the lead screw nut member and to contact the lead screw nut member at stroke ends of the upper rail in a front-rear direction thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a seat for a vehicle; 
         FIG. 2  is a lateral view of the seat for the vehicle having a power seat slide apparatus according to embodiments of the present invention; 
         FIG. 3  is a cross-sectional view of the power seat slide apparatus when cross-sectioning in a longitudinal direction of an upper rail and a lower rail according to the embodiment of the present invention; 
         FIG. 4  is a cross-sectional view taken on line  4 - 4  in  FIG. 2 ; 
         FIG. 5  is an exploded perspective view of the power seat slide apparatus according to a first embodiment of the present invention; 
         FIG. 6  is a partially enlarged view of a cut-and-bent-away portion of the upper rail according to the first embodiment of the present invention; 
         FIG. 7  is a partially enlarged view of a modified example of a cut-and-bent-away portion of the upper rail according to the first embodiment of the present invention; 
         FIG. 8  is a partially enlarged view of a cut-and-bent-away portion of the upper rail according to a second embodiment of the present invention; and 
         FIG. 9  is an exploded perspective view of a power seat slide apparatus according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will be explained with reference to illustrations of drawing figures as follows. 
     According to the embodiments of the present invention, directions, such as right, left, front, rear, upward and downward, or the like, correspond to orientations of an occupant seating on a seat for a vehicle. As shown in  FIG. 1 , a seat  10  for a vehicle is mounted on a vehicle floor  11 . The seat  10  for the vehicle includes a power seat slide apparatus  12 . The seat  10  for the vehicle includes a seat cushion  13  forming a seat surface and a seatback  14  forming a seatback surface. The seatback  14  is attached to a rear portion of the seat cushion  13  to be rotatable relative to the seat cushion  13  in a front-rear direction of the vehicle and to be fixedly retained at predetermined adjustable angular positions. 
     As shown in  FIGS. 2 and 5 , the power seat slide apparatus  12  includes a lower rail  21 , an upper rail  22 , a lead screw member  23 , a lead screw nut member  24 , and a drive unit  25 . 
     As shown in  FIG. 5 , the lower rails  21 ,  21  correspond to a pair of rail members extended longitudinally in the front-rear direction of the vehicle and arranged in parallel to each other. One of the lower rails  21  is positioned at the right side of the seat  10  and the other lower rail  21  is positioned at the left side of the seat  10 . Each of the lower rail  21 , as shown in  FIG. 4 , includes a bottom wall  21   a , a pair of walls  21   b ,  21   b  which extend upward from right and left end portions of the bottom wall  21   a , respectively, and flange walls  21   c  formed by bending a top end of each of the walls  21   b  inwardly and by further bending the top end downwardly. The lower rail  21  is configured to have approximately a U-shaped cross-section having an opening portion  21   d  opening upward between the flange walls  21   c ,  21   c . The lower rail  21  is fixedly provided on the vehicle floor  11 . The lower rail  21  is fixed on the vehicle floor  11  by means of a fastening member, for example, a bolt at the front and rear portions thereof. 
     The upper rails  22 ,  22  as shown in  FIG. 5 , correspond to a pair of rail members extended longitudinally in the front-rear direction of the vehicle and arranged in parallel to each other. One of the upper rail  22  is positioned at the right side of the seat  10  and the other upper rail  22  is positioned at the left side of the seat  10 . As shown in  FIG. 4 , the upper rail  22  includes a top wall  22   a , a pair of walls  22   b ,  22   b  which extend downward from right and left end portions of the top wall  22   a , respectively, and flange walls  22   c ,  22   c  formed by bending a bottom end of each of the walls  22   b  outwardly and by further bending the bottom end upwardly. Each of the upper rail  22  is configured to have approximately inversed U-shaped cross-section having an opening portion  22   d  opening downward between the flange walls  22   c ,  22   c . As shown in  FIG. 5 , plural bending slots  94  having a predetermined slot width and configured in approximately U-shape are formed on each of the walls  22   b ,  22   b  so as to face predetermined positions, respectively. In those circumstances, the predetermined positions are defined as positions which are determined by stroke end positions of the seat which are particular to a type of vehicle on which the seat is assembled. The number of bending slots  94  differs depending on the number of types of vehicles to which the seat is provided. Plural tongue portions  95  are formed within the bending slots  94 . The tongue portions  95  positioned so as to correspond to the stroke ends of the seat for a particular type of vehicle are bent by a predetermined angle towards the opening portion  22   d  of the upper rail  22  after assembling the seat  10  to the vehicle to form cut-and-bent-away portions  60 ,  61 ,  62 ,  63 , which are cut and bent away from the walls  22   b ,  22   b . The cut-and-bent-away portions  60 ,  61 ,  62 ,  63  serve as stopper portions for restricting a stroke (a distance between the cut-and-bent-away portions provided at the front portion and the rear portion of the upper rail  22 ) of the seat. When the upper rail  22  moves rearward, that is, when the seat moves rearward, the cut-and-bent-away portions  60 ,  62  each provided at front portions of the walls  22   b ,  22   b , respectively, come in contact with the lead screw nut member  24  to restrict the stroke of the seat. Further, when the upper rail  22  moves forward, the cut-and-bent-away portions  61 ,  63  each provided at rear portions of the walls  22   b ,  22   b , respectively come in contact with the lead screw nut member  24  to restrict the stroke of the seat. According to the embodiments explained above, cut-and-bent-away portions  60 ,  61 ,  62 ,  63  are formed after assembling the seat  10  to the vehicle, however, the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  may be formed before assembling the seat  10  to the vehicle in accordance with the type of vehicle. 
     Detailed structure of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  will be explained hereinbelow. As shown in  FIG. 6 , the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  are formed by bending corresponding bending portions  60   a ,  61   a ,  62   a ,  63   a , respectively, by a predetermined angle towards the inside of the opening portion  22   d  opening downward of the upper rail  22 . The bending portions  60   a ,  61   a ,  62   a ,  63   a  serve as bases of the corresponding tongue portions  95  at which a cross-sectional dimension changes from a cross-sectional dimension of an adjacent portion of the upper rail  22 . End portions  60   b ,  61   b ,  62   b ,  63   b  of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  are positioned lower than a reference horizontal surface which crosses a center of a rotational shaft of the lead screw member  23 . On the other hand, the bending portions  60   a ,  61   a ,  62   a ,  63   a  serving as supporting points for bending the tongue portions  95  are positioned higher than the reference horizontal surface which crosses the center of the rotational shaft of the lead screw member  23 . The upper rail  22  is slidably supported by the lower rail  21  via rollers. In those circumstances, the bending portions  60   a ,  61   a ,  62 ,  63   a  of the respective cut-and-bent-away portions  60 ,  61 ,  62 ,  63  are positioned higher than the top ends of the flange walls  21   c ,  21   c  positioned at the right and left sides of the lower rail  21 . The seat cushion  13  for the vehicle seat  10  is fixed on the upper rail  22  via a retaining bracket  27  (see  FIG. 2 ). 
     The lead screw member  23  is positioned between the lower rail  21  and the upper rail  22  which are provided on the right and left sides so that an axial center of the lead screw member  23  extends in the front-rear direction of the vehicle. As shown in  FIGS. 3 and 5 , the lead screw nut member  24 , which is fixed to the bottom surface  21   a  of the lower rail  21  by means of a bolt  28 , is threadedly engaged onto the lead screw member  23 . Front and rear portions of the lead screw member  23  are supported by the upper rail  22  so as to rotate. In other words, the lead screw member  23  is configured to rotate, however, is configured not to move in an axial direction relative to the upper rail  22 . Upon the rotation of the lead screw member  23  by the lead screw nut member  24 , the upper rail  22  slides on the lower rail  21  in the front-rear directions together with the lead screw member  23 . In those circumstances, the lead screw nut member  24  is positioned between the cut-and-bent-away portions  60 ,  62  and the cut-and-bent-away portions  61 ,  63  in the front-rear directions of the vehicle. When the upper rail  22  slides in a rearward direction on the lower rail  21 , a front surface  24   a  of the lead screw nut member  24  which is fixed to the lower rail  21  comes in contact with rear side lateral surface portions  60   c ,  62   c  of the cut-and-bent-away portions  60 ,  62 , respectively, to restrict the stroke of the upper rail  22  in the backward direction. Likewise, when the upper rail  22  slides in a forward direction on the lower rail  21 , a rear surface  24   b  of the lead screw nut member  24  comes in contact with front side lateral surface portions  61   c ,  63   c  of the cut-and-bent-away portions  61 ,  63 , respectively, to restrict the stroke of the upper rail  22  in the forward direction. 
     Hereinafter, a support structure of the lead screw member  23  relative to the upper rail  22  and a particular structure of the drive unit  25  will be explained. As shown in  FIGS. 3 and 5 , a front end retaining bracket  31  is fastened to a front end portion of the upper rail  22  by means of a bolt  32  and a nut  39 . A rear end retaining bracket  33  is fastened to a rear end portion of the upper rail  22  by means of a bolt  34  and a nut  47 . 
     The front end retaining bracket  31  shaped in a plate form includes a positioning projection  36  at a rear end portion thereof as shown in  FIG. 3 . In a state where the positioning projection  36  is fitted into a positioning hole  22   b  formed on the upper rail  22 , the front end retaining bracket  31  is fixed to the upper rail  22  for positioning. 
     As shown in  FIG. 3 , a supporting portion  32   b  is provided at the bolt  32  to project downward. A supporting hole  32   c  whose diameter is slightly larger than that of the lead screw member  23  is formed on the supporting portion  32   b . The lead screw member  23  is penetratingly positioned in the supporting hole  32   c  via a bearing member  7 . Bearing nuts  43 ,  44  are provided at the both sides of the supporting portion  32   b , respectively, in an axial direction of the lead screw member  23 . The first bearing nut  43  is threadedly engaged with an incomplete thread screw portion  23   m , or no-thread portion of the lead screw member  23  to be fixed. The second bearing nut member  44  is threadedly engaged with a reverse thread screw portion  23   c  of the lead screw member  23  to be fastened. The bearing member  7  includes a bushing  77  and a plane washer  78  which are made from a metal member or a resin member which is highly slidable. With the foregoing construction, the lead screw member  23  and the first and second bearing nuts  43 ,  44  which are fixed to the lead screw member  23  are supported by the front end retaining bracket  31  via the bearing member  7  in a radial direction and a thrust direction so as to rotate and not to displace in an axial direction of the lead screw member  23 . 
     As shown in  FIG. 3 , the rear end retaining bracket  33  bent to have an L-shaped configuration in cross-section is integrally attached to the upper rail  22  by means of the bolt  34  and the nut  47 . A penetration hole  48  to which the lead screw member  23  is inserted is formed on a perpendicular portion  33   a  of the rear end retaining bracket  33 . A bushing  79  having a recessed configuration in cross-section is provided at the penetration hole  48 . A rear end shaft portion of the lead screw member  23  is rotatably supported by the bushing  79 . Accordingly, the rotation of the lead screw member  23  which is threadedly engaged with the lead screw nut member  24  is supported by two points, that is, each of the bushings  77 ,  79  are arranged at the front portion and the rear portion of the lead screw member  23 , respectively. 
     A front end portion of the front end retaining bracket  31  is bent upward approximately in a perpendicular direction at the end portion of the upper rail  22 , and an end (top end) of a bent portion  31   b  is further bent forward and orthogonally in approximately a horizontal direction to form a horizontal retaining portion  31   c  which extends in an approximately horizontal direction. A gear box  51  is fixed to a bottom surface of the horizontal retaining portion  31   c  by means of a fastening member, for example, a bolt. The gear box  51  includes a housing  52 . As shown in  FIG. 3 , a worm wheel  53 , serving as an output rotation member, is supported by the housing  52  so as to rotate about an axial line common to the lead screw member  23 . A spline hole  53   a  is formed at a rotational center portion of the worm wheel  53 , and a spline engagement portion  23   r  formed on a front end portion of the lead screw member  23  is spline-engaged with the spline hole  53   a . A worm shaft  54  having a worm which is geared with the worm wheel  53  is supported by the housing  52  so as to rotate about an axial line which is orthogonal to an axial line of the worm wheel  53 , that is, to rotate about a horizontal axial line which is orthogonal to a front-rear direction of the vehicle. The worm wheel  53  and the worm shaft  54  configure a reduction gear mechanism. 
     As shown in  FIG. 5 , a rotation transmitting shaft  55  which extends in a right and left direction of the vehicle is arranged between the gear boxes  51 ,  51  provided at the front end retaining brackets  31 ,  31  on the right and left sides, respectively. A first end of the rotation transmitting shaft  55  is connected to the worm shaft  54  supported by the gear box  51  on the left side and a second end of the rotation transmitting shaft  55  is connected to the worm shaft  54  supported by the gear box  51  on the right side. An output shaft of a motor  57  mounted on one of the gear boxes  51 ,  51  is rotationally connected to the rotation transmitting shaft  55  via a gear mechanism. Thus, the rotation of the motor  57  is transmitted to the worm shafts  54 ,  54  provided on the right and left sides via the rotation transmitting shaft  55 . 
     The motor  57 , the rotation transmitting shaft  55 , and the reduction gear mechanism including worm wheel  53  and the worm shaft  54  configure the drive unit  25 . 
     An operation of the power seat slide apparatus  12  according to the embodiment will be explained hereinbelow. When moving the vehicle seat  10  in the front-rear direction for adjustment, for example, the motor  57  is activated in a normal direction or a reverse direction by operating a switch arranged in the vicinity of the vehicle seat  10  either for moving the vehicle seat  10  forward or for moving the vehicle seat  10  rearward. Accordingly, the rotation transmitting shaft  55  is driven to rotate in the normal direction or in the reverse direction, and the rotation of the rotation transmitting shaft  55  is transmitted to the worm shafts  54 ,  54  connected to the both ends of the rotation transmitting shaft  55 , respectively, in the gear box  51 . According to the foregoing construction, the worm wheel  53  serving as the output rotation member is rotated in response to the rotation of the worm shaft  54  and the rotation of the worm wheel  53  is transmitted to the lead screw member  23  via the spline engagement portion  23   b . In consequence, the lead screw member  23  is rotated at reduced speed by the rotation of the rotation transmitting shaft  55  by the motor  57  via the reduction gear mechanism including the worm shaft  54  and the worm wheel  53 . 
     Because the lead screw nut member  24  which is fixed to the lower rail  21  is threadedly engaged with the lead screw member  23 , the lead screw member  23  moves in the axial direction relative to the lead screw nut member  24  while rotating. Thus, the upper rail  22  moves either forward or rearward via the front end retaining bracket  31  and the rear end retaining bracket  33  which rotatably support the lead screw member  23  to adjust the position of the vehicle seat  10 . 
     In a case where the switch for moving the vehicle seat  10  forward or for moving the vehicle seat  10  backward is continuingly operated, the lead screw member  23  continuously rotates so that the upper rail  22  continuously moves in the forward direction or the rearward direction relative to the lower rail  21 . In those circumstances, the cut-and-bent-away portions  60 ,  62 ,  61 ,  63  formed on each of the walls  22   b ,  22   b  of the upper rail  22  which function as a pair on the right side and left side by bending the corresponding tongue portions by a predetermined angle towards the inside of the opening portion  22   d  which opens downward of the upper rail  22 . In consequence, the rear surface  24   b  of the lead screw nut member  24  fixed to the lower rail  21  and the lateral surfaces  61   c ,  63   c  of the cut-and-bent-away portions  61 ,  63  contact each other when the upper rail  22  moves in the forward direction to restrict the stroke. Further, the front surface  24   a  of the lead screw nut member  24  and the lateral surfaces  60   c ,  62   c  of the cut-and-bent-away portions  60 ,  62  contact each other when the upper rail  22  moves in the rearward direction to restrict the stroke. 
     With the construction of the power seat slide apparatus  12  of the embodiment, the stroke of the upper rail is restricted by machining the upper rail  22  to form the bending slots  94  and by bending the corresponding tongue portions to form the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 , whereas additional separate parts serving as stoppers are required to be provided at the lead screw member in the known conventional apparatuses. Thus, the manufacturing cost is reduced according to the power seat slide apparatus  12  of the embodiment. 
     Further, according to the first embodiment, the bending portions  60   a ,  61   a ,  62   a ,  63   a  of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  of the upper rail  22  are positioned at a higher level than the top ends of the flange walls  21   c ,  21   c  of the lower rails  21 ,  21  provided at the right and left sides as a pair. Accordingly, a workspace for forming each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  after assembling the vehicle seat  10  is ensured. Thus, in case of assembling the vehicle seat  10  to various types of vehicles, the plural bending slots  94  are provided on the walls  22   b ,  22   b  of the upper rail  22  in advance, and the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  positioned appropriate for a particular type of the vehicle are formed by bending the corresponding tongue portions after assembling the vehicle seat  10 . In consequence, parts of the upper rail  22  for various types of vehicles are standardized to reduce manufacturing costs. 
     According to the first embodiment, the positions of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  are determined so that the end portions  60   b ,  61   b ,  62   b ,  63   b  are arranged to be at the lower level than the horizontal surface which crosses the rotational axis of the lead screw member  23  and the bending portions  60   a ,  61   a ,  62   a ,  63   a  are arranged to be at the higher level than the horizontal surface which crosses the rotational axis of the lead screw member  23 . Thus, because each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  extends to overlap the rotational center of the lead screw member  23 , in a case where each of lateral surfaces  60   c ,  61   c ,  62   c ,  63   c  of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  comes in contact with either the front surface  24   a  or the rear surface  24   b  of the lead screw nut member  24 , the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  receive the load of the lead screw member  23  without inclining. In other words, the load applied to the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  via the lead screw member  23  is effectively received with less force. Accordingly, a considerable level of load by the motor rotation is stably received, the lead screw member  23  stops safely without damages due to the flexural load, or the like, thereby improving reliability. 
     According to the first embodiment, the plural bending slots  94  having a predetermined width and formed in approximately U-shape are formed on the pair of walls  22   b ,  22   b  of the upper rail  22  so as to face each other. However, the configuration of the bending slots  94  is not limited. For example, the bending slots  94  are formed approximately in an inverted U-shape. In those circumstance, for example as shown in  FIG. 7 , each of cut-and-bent-away portions  70 ,  71 ,  72 ,  73  formed by each of bending slots is bent by a predetermined angle towards an inside of an opening portion  76   d  which opens downward of an upper rail  76  at bending portions  70   a ,  71   a ,  72   a ,  73   a . The bending portions  70   a ,  71   a ,  72   a ,  73   a  serve as bases of the corresponding tongue portion  95  at which a cross-sectional dimension changes from a cross-sectional dimension of an adjacent portion of the upper rail  22 . In consequence, each of the end portions  70   b ,  71   b ,  72   b ,  73   b  of each of the cut-and-bent-away portions  70 ,  71 ,  72 ,  73  of the upper rail  76  is arranged at the higher level than the top ends of respective flange walls  21   c ,  21   c  of the lower rail  21 . Further, the end portions  70   b ,  71   b ,  72   b ,  73   b  of each of the cut-and-bent-away portions  70 ,  71 ,  72 ,  73  are positioned higher than a reference horizontal surface which crosses a center of the rotational shaft of the lead screw member  23 . On the other hand, bending portions  70   a ,  71   a ,  72   a ,  73   a  are positioned higher than the reference horizontal surface which crosses the center of the rotational shaft of the lead screw member  23 . According to this construction, the advantages similar to the first embodiment can be attained. 
     Further, the configuration of the bending slots formed on the walls  22   b  of the upper rail  22  is not necessarily to be symmetrically arranged. In other words, the configuration of the bending slots at the right side and the configuration of the bending slots at the left side may differ from each other. For example, the bending slots at one side may be configured in an approximately U-shape and the bending slots at the other side may be configured in an approximately inverted U-shape. In those circumstances, the configuration and the arrangements of the bending slots shaped in the approximately U-shape and the approximately inverted U-shape is similar to the cut-and-bent-away portions  60 ,  70  in  FIGS. 6 and 7 , and similar advantages and the effects can be attained. 
     A second embodiment will be explained with reference to  FIGS. 8 and 9  as follows. According to the construction of the second embodiment, each of the cut-and-bent-away portions formed on corresponding walls  86   b ,  86   b  includes an upper flap portion and a lower flap portion which are provided at an upper portion and a lower portion of each of the walls  86   b ,  86   b  formed on the right side and the left side. The differences of the second embodiment from the first embodiment will be explained hereinafter. Other constructions of the second embodiment are common to the constructions of the first embodiment. The same reference numeral is provided for the common constructions to the first embodiment and the explanations thereof will not be repeated. 
     According to the second embodiment, end portions  80   b ,  81   b ,  82   b ,  83   b ,  90   b ,  91   b ,  92   b ,  93   b  of respective cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  prior to being bent are arranged to be at a higher level than the top portions of the flange walls  21   c ,  21   c  provided at the right side and the left side of the lower rail  21 , respectively. Thus, work spaces for forming cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  are ensured even after the vehicle seat  10  is assembled. In a case where the power seat slide apparatus  12  is applied to various types of vehicles, plural bending slots  96  formed in approximately H-shape having a predetermined groove width are formed on the walls  86   b ,  86   b  of an upper rail  86  and tongue portions  97 ,  98  which are positioned so as to be compatible to a particular vehicle type are bent after assembling the vehicle seat  10 . According to the foregoing construction, parts of the upper rail  86  are standardized, thus reducing the manufacturing cost. Similar to the first embodiment, each of the cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  may be bent in advance prior to the assembling of the vehicle seat  10 . 
     After the cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  are bent, the end portions  80   b ,  82   b ,  90   b ,  92   b  are positioned higher than the reference horizontal surface which crosses the center of the rotational shaft of the lead screw member  23 . On the other hand, the end portions  81   b ,  83   b ,  91   b ,  93   b  are positioned lower than the reference horizontal surface which crosses the center of the rotational shaft of the lead screw member  23  after the cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  are bent. According to the foregoing construction, in a case where lateral surfaces  80   c ,  81   c ,  82   c ,  83   c ,  90   c ,  91   c ,  92   c ,  93   c  of respective cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  come in contact with either the front surface  24   a  or the rear surface  24   b  of the lead screw nut member  24 , the load of the rotational shaft of the lead screw member  23  is received in a well balanced manner without inclining. In other words, the load applied to the cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  via the lead screw member  23  is effectively received with less force. Accordingly, a considerable level of load by the motor rotation is stably received to safely stop the lead screw member  23 , thereby improving the reliability. 
     According to the embodiments of the present invention, the lead screw member  23  is engaged with the worm wheel  53  housed in the gear body  51  by means of a spline. However, the output rotation member which is engaged with the lead screw shaft  23  by means of the spline is not limited to a worm or a worm wheel mechanism as long as an output of the motor  57  is rotationally transmitted to the lead screw member  23 . 
     According to the embodiment of the present invention, the cut-and-bent-away portion  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  is formed on each of the walls  22   b ,  76   b ,  86   b  of the upper rail  22 ,  76 ,  86  at the position to face the lead screw nut member  24  and to come in contact with the lead screw nut member  24  at stroke end positions of the upper rail  22 ,  76 ,  86 . Thus, with a minimum construction of parts, that is, providing additional machining of the upper rail  22 ,  76 ,  86  to form the cut-and-bent-away portion  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93 , a stroke of the upper rail  22 ,  76 ,  86 , or the vehicle seat  10  which operates with considerable level of load is restricted, thereby reducing the manufacturing cost. 
     According to the embodiment, the lower rail  21  includes a pair of walls  21   b ,  21   b  formed on right and left sides thereof, each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  includes an end portion  60   b ,  61   b ,  62   b ,  63   b ,  70   b ,  71   b ,  72   b ,  73   b ,  80   b ,  81   b ,  82   b ,  83   b ,  90   b ,  91   b ,  92   b ,  93   b  and a bending portion  60   a ,  61   a ,  62   a ,  63   a ,  70   a ,  71   a ,  72   a ,  73   a ,  80   a ,  81   a ,  82   a ,  83   a ,  90   a ,  91   a ,  92   a ,  93   a  where the cut-and-bent-away  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  portion is bent, and wherein the bending portion  60   a ,  61   a ,  62   a ,  63   a ,  80   a ,  82   a ,  90   a ,  92   a  is positioned at a higher level than a top end of the wall of the lower rail in a state where the upper rail  22 ,  76 ,  86  and the lower rail  21  are engaged. 
     According to the embodiment of the present invention, because either the end portion  60   b ,  61   b ,  62   b ,  63   b ,  70   b ,  71   b ,  72   b ,  73   b ,  80   b ,  81   b ,  82   b ,  83   b ,  90   b ,  91   b ,  92   b ,  93   b  of each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  or the bending portion  60   a ,  61   a ,  62   a ,  63   a ,  70   a ,  71   a ,  72   a ,  73   a ,  80   a ,  81   a ,  82   a ,  83   a ,  90   a ,  91   a ,  92   a ,  93   a , where the cut-and-bet-away portion  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  is bent, of each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  is positioned higher than the top end  21   c  of the walls  21   b  functioning as a pair provided at the right side and left side of the lower rail  21  in a state where the upper rail  22 ,  76 ,  86  and the lower rail  21  are engaged, the workspaces for bending each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  are ensured even after assembling the seat  10 . Accordingly, in a case where the power seat slide apparatus  12  is mounted to various types of vehicles, the plural bending slots  94 ,  96  may be formed on the walls  22   b ,  76   b ,  86   b  of the upper rail  22 ,  76 ,  86  in advance and each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  which is positioned so as to be compatible to a particular type of the vehicle may be bent. Accordingly, the parts of the upper rail  22 ,  76 ,  86  are standardized, thereby reducing the manufacturing cost. 
     According to further aspect of the power seat slide apparatus according to the present invention, one of the end portion  60   b ,  61   b ,  62   b ,  63   b ,  70   b ,  71   b ,  72   b ,  73   b ,  80   b ,  81   b ,  82   b ,  83   b ,  90   b ,  91   b ,  92   b ,  93   b  and the bending portion  60   a ,  61   a ,  62   a ,  63   a ,  70   a ,  71   a ,  72   a ,  73   a ,  80   a ,  81   a ,  82   a ,  83   a ,  90   a ,  91   a ,  92   a ,  93   a  of each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  is arranged at positions higher than a reference horizontal surface which crosses a center of a rotational shaft of the lead screw member  23 , and the other of the end portion  60   b ,  61   b ,  62   b ,  63   b ,  70   b ,  71   b ,  72   b ,  73   b ,  80   b ,  81   b ,  82   b ,  83   b ,  90   b ,  91   b ,  92   b ,  93   b  and the bending portion  60   a ,  61   a ,  62   a ,  63   a ,  70   a ,  71   a ,  72   a ,  73   a ,  80   a ,  81   a ,  82   a ,  83   a ,  90   a ,  91   a ,  92   a ,  93   a  of each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  is arranged at positions lower than the reference horizontal surface which crosses the center of the rotational shaft of the lead screw member  23 . 
     According to the embodiment of the present invention, each of the end portions  60   b ,  61   b ,  62   b ,  63   b ,  70   b ,  71   b ,  72   b ,  73   b ,  80   b ,  81   b ,  82   b ,  83   b ,  90   b ,  91   b ,  92   b ,  93   b  of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 , 91 ,  92 ,  93  and each of the bending portions  60   a ,  61   a ,  62   a ,  63   a ,  70   a ,  71   a ,  72   a ,  73   a ,  80   a ,  81   a ,  82   a ,  83   a ,  90   a ,  91   a ,  92   a ,  93   a  where the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  are bent are arranged to be positioned at the lower level and the upper level relative to the reference horizontal surface which crosses the rotational axis of the lead screw member  23 , respectively. Thus, because each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  is arranged to extend to overlap the rotational axis center of the lead screw member  23 , in the event that each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  comes in contact with either the front surface  24   a  or the rear surface  24   b  of the lead screw nut member  24 , each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63 ,  70 ,  71 ,  72 ,  73 ,  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  receive the load of the rotational axis of the lead screw member  23  without inclining. Accordingly, a considerable level of the load by the motor rotation is stably received, thereby stopping the lead screw member  23  safely without being damaged by the flexural load. Accordingly, the reliability of the power seat slide apparatus  12  is enhanced. 
     With the constructions according to the embodiment, the end portion  70   b ,  71   b ,  72   b ,  73   b  of the each of the cut-and-bent-away portions  70 ,  71 ,  72 ,  73  is positioned higher than the top end  21   c  of the wall  21   b  of the lower rail  21  in a state where the upper rail  76  and the lower rail  21  are engaged, and the bending portion  70   a ,  71   a ,  72   a ,  73   a  is positioned lower than the reference horizontal surface which crosses the center of the rotational shaft of the lead screw member  23 . 
     With the constructions according to the embodiment, the bending portion  60   a ,  61   a ,  62   a ,  63   a  of each of the cut-and-bent-away portions  60 ,  61 ,  62 ,  63  is positioned higher than the top end  21   c  of the wall  21   b  of the lower rail  22  in a state where the upper rail  22  and the lower rail  21  are engaged, and the end portion  60   b ,  61   b ,  62   b ,  63   b  is positioned lower than the reference horizontal surface which crosses the center of the rotational shaft of the lead screw member  23 . 
     With the constructions according to the embodiment, each of the walls  22   b ,  76   b  of the upper rail  22 ,  76  includes a bending slot  94  formed either approximately in a U-shape or approximately in an inversed U-shape and a tongue portion  95  formed within the bending slot  94 , and the bending portion  60   a ,  61   a ,  62   a ,  63   a ,  70   a ,  71   a ,  72   a ,  73   a  is formed by bending the tongue portion  95  towards an inside of an opening portion  22   d ,  76   d  opening downward of the upper rail  22 ,  76 . 
     With the constructions according to the embodiment, a pair of the cut-and-bent-away portions include first and second pairs of cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  provided at an upper portion and a lower portion of the walls of the upper rail  86 , respectively. 
     With the constructions according to the embodiment, the bending portions  80   a ,  81   a ,  82   a ,  83   a ,  90   a ,  91   a ,  92   a ,  93   a  of the cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  provided at the upper portion and the lower portion of each of the walls  86   b  of the upper rail  86  are positioned at the higher level and the lower level relative to a reference horizontal surface which crosses a center of a rotational shaft of the lead screw member  23 , respectively. 
     With the constructions according to the embodiment, the end portions  80   b ,  81   b ,  82   b ,  83   b ,  90   b ,  91   b ,  92   b ,  93   b  of the cut-and-bent-away portions  80 ,  81 ,  82 ,  83 ,  90 ,  91 ,  92 ,  93  provided at the upper portion and the lower portion of each of the walls  86   b  of the upper rail  86  are positioned at the higher level and the lower level relative to a reference horizontal surface which crosses a center of a rotational shaft of the lead screw member  23 , respectively. 
     With the constructions according to the embodiment, the power seat slide apparatus  12  further includes a bending slot  96  formed in an approximately H shape and formed on each of the walls  86   b , 86   b  of the upper rail  86 , and a tongue portion  98  formed within the bending slot  96 . The bending portion  80   a ,  81   a ,  82   a ,  83   a ,  90   a ,  91   a ,  92   a ,  93   a  is formed by bending the tongue portion towards an inside of an opening portion  86   d  opening downward of the upper rail  86 . 
     The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.