Abstract:
An automotive power seat sliding device comprises first and second lower rails secured to a vehicle floor; first and second upper rails slidably and respectively engaged with the first and second lower rails and supporting thereon a seat; a cross beam member having both ends secured to the first and second upper rails respectively, so that the first and second upper rails slide on and along the first and second lower rails like a single unit; a drive shaft extending along the first upper rail and having a spiral groove formed therearound; a nut member secured to the first lower rail and operatively engaged with the drive shaft; an electric power unit supported by the cross beam member for rotating the drive shaft about an axis thereof; a supporting member connected to the first upper rail for rotatably supporting one end portion of the drive shaft; and a protector bracket secured to the first upper rail and having a recessed structure into which the other end of the drive shaft is received without contacting the recessed structure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to seat sliding devices of motor vehicles, and more particularly to the seat sliding device of a power type which can slide the seat to a desired position with an electric power. More specifically, the present invention is concerned with the power seat sliding device which can exhibit a satisfied durability against big shock applied thereto due to a vehicle collision or the like. 
     2. Description of the Prior Art 
     Hitherto, various power seat sliding devices have been proposed and put into practical use particularly in the field of motor vehicles. For providing the devices with a satisfied durability against a big shock applied thereto due to a vehicle collision or the like, various measures have been hitherto taken. 
     One of conventional power seat sliding devices having a certain durability against such shock is shown in Japanese Patent First Provisional Publication 6-336130. The power seat sliding device of this publication comprises generally a pair of lower rails fixed to a vehicle floor, a pair of upper rails slidably engaged with the lower rails and supporting thereon a seat, a drive shaft rotatably held by one of the upper rails and having a spiral groove formed therearound, an electric motor carried by the upper rails for driving the drive shaft, and a nut member fixed to one of the lower rails and operatively engage with the drive shaft. 
     Thus, when the electric motor is energized to rotate the drive shaft in one or other direction, the upper rails and thus the seat are moved forward or rearward on the lower rails to a desired position. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an automotive power seat sliding device, which can exhibit a satisfied durability against a big shock applied thereto due to a vehicle collision or the like. 
     According to the present invention, there is provided an automotive power seat sliding device, which comprises first and second lower rails adapted to be secured to a floor of a vehicle; first and second upper rail slidably and respectively engaged with the first and second lower rails and adapted to support thereon a seat; a cross beam member having both ends secured to the first and second upper rails respectively, so that the first and second upper rails slide on and along the first and second lower rails like a single unit; at least one drive shaft extending along the first upper rail and having a spiral groove formed therearound; a nut member secured to the first lower rail and operatively engaged with the drive shaft; an electric power unit supported by the cross beam member for rotating the drive shaft about an axis thereof; a supporting member connected to the first upper rail for rotatably supporting one end portion of the drive shaft; and a protector bracket secured to the first upper rail and having a recessed structure into which the other end of the drive shaft is received without contacting the recessed structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a perspective view of an automotive power seat sliding device which is a first embodiment of the present invention; 
     FIG. 2 is an illustration taken from the direction of the arrow “A” of FIG. 1; 
     FIG. 3 is plan view of a part of the power seat sliding device of the first embodiment, showing a protector bracket for a drive shaft; 
     FIG. 4 is a side view of the part of the power seat sliding device, showing the protector bracket for the drive shaft; 
     FIG. 5 is a view similar to FIG. 3, but showing a condition wherein the drive shaft is permitted to swing without contacting the protector bracket; 
     FIG. 6 is a view similar to FIG. 4, but showing a condition wherein the drive shaft is permitted to swing without contacting the protector bracket; 
     FIG. 7 is a view similar to FIG. 3, but showing a condition wherein the drive shaft is engaged with the protector bracket thereby to suppress undesired separation of the upper rail from the lower tail; 
     FIG. 8 is a view similar to FIG. 4, but showing a condition wherein the drive shaft is engaged with the protector bracket thereby to suppress undesired separation of the upper rail from the lower tail; 
     FIG. 9 is a view similar to FIG. 3, but showing a second embodiment of the present invention; 
     FIG. 10 is a view similar to FIG. 4, but showing the second embodiment; 
     FIG. 11 is a view similar to FIG. 9, but showing a condition wherein in the second embodiment a drive shaft is engaged with a protector bracket thereby to suppress undesired separation of the upper rail from the lower tail; 
     FIG. 12 is a view similar to FIG. 12, but showing a condition wherein in the second embodiment the drive shaft is engaged with the protector bracket thereby to suppress undesired separation of the upper rail from the lower tail; 
     FIG. 13 is view similar to FIG. 9, but showing a condition wherein in the second embodiment the drive shaft is permitted to swing without contacting the protector bracket; and 
     FIG. 14 is a view similar to FIG. 10, but showing a condition wherein the drive shaft is permitted to swing without contacting the protector bracket. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring to FIGS. 1 to  4 , particularly FIG. 1 of the drawings, there is shown an automotive power seat sliding device  100  which is a first embodiment of the present invention. 
     As shown in FIG. 1, the automotive power seat sliding device  100  comprises generally two lower rails  1  which are fixed to a vehicle floor and two upper rails  3  which are slidably engaged with the lower rails  1  and supports thereon a seat proper (not shown). Although not shown in the drawing, one end of a seat belt is fixed to a rear end portion of one of the upper rails  3 . 
     Each lower rail  1  has front and rear ends mounted on front and rear mounting brackets  5  which are bolted to the vehicle floor. 
     As is understood from FIG. 2, each lower rail  1  comprises a longitudinally extending flat base portion  7 , two side wall portions  9  which are integral with and extend longitudinally along side edges of the flat base portion  7 , and two thin outer guide portions  11  which extend toward each other from upper ends of the respective side wall portions  9 . Inward edges of the outer guide portions  11  are bent inwardly, that is, toward the flat base portion  7 . Thus, between the bent edges of the outer guide portions  11 , there is defined a longitudinally extending slot  17 . 
     For rotatably supporting thereon the corresponding upper rail  3 , a plurality of cylindrical rollers  13  are rotatably put on the flat base portion  7  of the lower rail  1 . That is, each roller  13  is arranged to run longitudinally on and along the flat base portion  7 . 
     As is seen from FIG. 1, the side wall portions  9  of each lower rail  1  are each formed with a plurality of lock openings  15 . It is however to be noted that these lock openings  15  are necessary only when the seat sliding device  100  is designed as a manual type, as will become apparent hereinafter. 
     Referring back to FIG. 2, each upper rail  3  is constructed of two rail members which are connected to each other in a back-to-back back connecting manner. The upper rail  3  comprises a vertical wall portion  19  which extends longitudinally in and along the slot  17  of the corresponding lower rail  1 , and two thin inner guide portions  21  which are put in the lower rail  1  and extend in opposed directions from a lower end of the vertical wall portion  19 . Outward edges of the inner guide portions  21  are bent upward, that is, toward the respective outer guide portions  11  of the lower rail  1 . 
     As is seen from FIG. 2, due to provision of the inwardly bent edges of the outer guide portions  11  and the upwardly bent edges of the inner guide portions  21 , there are defined two longitudinally extending spaces (no numeral) for receiving therein ball bearings  25 . More specifically, the ball bearings  25  are located at front and rear end portions of the longitudinally extending spaces. For placing the ball bearings in such locations, retainers (not shown) are fixed to the inner guide portions  21  of the upper rail  3 . The cylindrical rollers  13  put on the flat base portion  7  of the lower rail  1  rotatably support thereon the respectively inner guide portions  21  of the upper rail  3 . More specifically, the cylindrical rollers  13  are located at front and rear end portions of the flat base portion  7 . For placing the rollers  13  at such locations, retainers (not shown) are fixed to the lower rail  1 . 
     Referring back to FIG. 1, there are arranged at inner sides of the upper rails  3  two drive shafts  27  (only one is shown) each extending longitudinally along the upper rail  3 . As will become apparent as the description proceeds, these two drive shafts  27  are supported by the upper rails  3  and driven in one and other directions by a single electric motor  29  supported by the upper rails  3 . 
     As shown in FIG. 1, each upper rail  3  has at its front end a transmission case  31 . Each case  31  rotatably supports a front end portion of the corresponding drive shaft  27 . The case  31  installs therein a transmission mechanism which includes two mutually engaged bevel gears. 
     As is seen from FIGS. 1 and 2, each drive shaft  27  has a nut member  35  operatively engaged therewith. As is seen from FIG. 2, each nut member  35  is secured to a bracket  33  extending from the lower rail  1 . Thus, when the drive shaft  27  is rotated in one direction, the same is forced to move longitudinally forward or rearward relative to the fixed nut member  35  thereby to move the upper rails  3  and thus the seat (not shown) in the same direction relative to the fixed lower rails  1 . 
     As is shown in FIG. 1, a cross beam member  43  has both ends bolted to the front ends of the upper rails  3  and has the transmission cases  31  fixed thereto by means of bolts  45 . One of the bevel gears in each case  31  is connected to the front end of the corresponding drive shaft  27 . 
     An elongate transmission shaft  47  transversely extends between the transmission cases  31 , which has ends each being connected to the other bevel gear in the corresponding case  31 . An electric motor  29  is fixed to a lower surface of the cross beam member  43  to drive the transmission shaft  47 . 
     Thus, when, upon energization of the electric motor  29 , the transmission shaft  47  is rotated in one direction, the rotation is transmitted to both the drive shafts  27  through the respective transmission mechanisms in the transmission cases  31 . Thus, the upper rails  3 , that is, the seat (not shown) on the upper rails  3  is moved forward or rearward relative to the fixed lower rails  1 . 
     In the first embodiment  100 , the following measures are further employed. 
     That is, as is seen from FIG. 1, a protector bracket  37  is secured to a rear end portion of each upper rail  3  in such a manner as to cover a rear end portion of the corresponding drive shaft  27 . The protector bracket  37  is constructed of a rigid metal. 
     As is understood from FIGS. 3 and 4, the protector bracket  37  comprises a rear wall  39  which faces a rear end  27   a  of the drive shaft  27  and a surrounding wall  41  which is integral with the rear wall  39  and surrounds a rear end portion of the drive shaft  27 . 
     It is to be noted that under normal condition, the rear end  27   a  of the drive shaft  27  is slightly spaced away from the protector bracket  37 , that is to say, the rear end  27   a  is not contact with the protector bracket  37 . As is seen from FIG. 4, the rear end  27   a  of the drive shaft  27  is spaced from the rear wall  39  of the bracket  37  by the distance of “d”, and as is seen from FIG. 3, the rear end  27   a  is spaced from the surrounding wall  41  of the bracket  37  by the distance of “d1”. 
     Thus, under normal condition, each drive shaft  27  can rotate freely without contacting the corresponding protector bracket  37 . That is, as is seen from FIGS. 5 and 6, even if the drive shaft  27  is subjected to a vibration under rotation thereof as is illustrated by a phantom line, the rear end portion  27   a  of the drive shaft  27  is suppressed from contacting or engaging with the protector bracket  37 . This brings about a smoothed rotation of the drive shaft  27  inducing a smoothed forward or rearward movement of the upper rails  3  and thus the seat mounted on the rails  3 . 
     While, as is seen from FIGS. 7 and 8, if, due to a vehicle collision or the like, an abnormally large force “F” (see FIG. 8) is suddenly applied to the upper rail  3  through the seat belt (not shown), the upper rail  3  is forced to incline forward relative to the corresponding lower rail  1 . However, when the inclination of the upper rail  3  exceeds a certain level defined by the above-mentioned spaces “d” and “d1”, the protector bracket  37  secured to the upper rail  3  is brought into abutment with the rear end portion  27   a  of the drive shaft  27 . In this condition, the drive shaft  27  serves as a reinforcing means, and thus, thereafter, the inclination movement of the upper rail  3  is suppressed. Thus, undesired separation of the upper rail  3  from the lower rail  1  is assuredly prevented. 
     Referring to FIGS. 9 to  14 , there is shown an automotive power seat sliding device  200  which is a second embodiment of the present invention. 
     Since the second embodiment  200  is similar in construction to the above-mentioned first embodiment  100 , only parts and construction which are different from those of the first embodiment  100  will be described in detail in the following for simplification of the description. 
     As is seen from FIGS. 9 and 10, the protector bracket  37 ′ used in the second embodiment  200  has substantially the same shape as that  37  of the first embodiment  100 . However, in the second embodiment  200 , a circular opening  49  is formed in the rear wall  39  of the protector bracket  37 ′. The diameter of the opening  49  is smaller than the diameter of the drive shaft  27 . 
     Furthermore, in this second embodiment  200 , the rear end  27   a ′ of the drive shaft  27  is tapered. Under normal condition, the protector bracket  37 ′ and the drive shaft  27  are so arranged that the opening  49  faces the tapered rear end  27   a ′ of the drive shaft  27  keeping a certain clearance “d”, “d1” therebetween. 
     Thus, under normal condition, each drive shaft  27  can rotate freely without contacting the corresponding protector bracket  37 ′, like in the case of the first embodiment  100 . That is, as is seen from FIGS. 13 and 14, even if the drive shaft  27  is subjected to a vibration under rotation thereof as is illustrated by a phantom line, the rear end portion  27   a ′ of the drive shaft  27  is suppressed from contacting or engaging with the protector bracket  37 ′. 
     While, as is seen from FIGS. 11 and 12, if, due to a vehicle collision of the like, an abnormally large force “F” (see FIG. 12) is suddenly applied to the upper rail  3  through the seat belt (not shown), the upper rail is forced to incline forward relative to the corresponding lower rail  1 . However, when the inclination of the upper rail  3  exceeds a certain level, the protector bracket  37 ′ secured to the upper rail  3  is brought into abutment with the tapered rear end portion  27   a ′ of the drive shaft  27  and finally the circular opening  49  of the protector bracket  37 ′ receives therein the tapered end  27   a ′ of the drive shaft  27 . That is, upon this, a so-called locked condition is established between the protector bracket  37 ′ and the drive shaft  27 , and thus, thereafter, the inclination movement of the upper rail  3  is assuredly suppressed using the drive shaft  27  as a reinforcing means. Due to establishment of the locked condition, the undesired separation of the upper rail  3  from the lower rail  1  is much assuredly prevented. 
     The entire contents of Japanese Patent Application P10-361169 (filed Dec. 18, 1998) are incorporated herein by reference. 
     Although the invention has been described above with reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Various modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings.