Abstract:
A seat slide apparatus includes an upper rail smoothly slidable relative to a lower rail without using any balls. A part of the convex portion of the lower rail made of lightweight metal alloy material contacts the flange portions of the steel-made upper rail with an elastic spring force.

Description:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 11-359208 filed on Dec. 17, 1999, the entire content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     This invention generally relates to a vehicle seat apparatus. More particularly, the present invention pertains to a seat slide apparatus for a vehicle having a combination of steel and light metal rails. 
     BACKGROUND OF THE INVENTION 
     Known vehicle seat slide apparatus are basically composed of a lower rail fixed to the vehicle floor, an upper rail which holds the seat to slidably move the seat in the vehicle longitudinal direction relative to the lower rail, and a lock mechanism for effecting engagement and disengagement of the lower and upper rails for adjusting the seat position. The seat slide apparatus should be light in weight and the sliding resistance of the upper rails relative to the lower rail should be relatively small. For this reason, the rails are made from lightweight metal alloy such as by aluminum alloy extrusion forming, and rollers or balls are positioned between the sliding surfaces of the rails to reduce frictional resistance. 
     However, an undesirably large number of components is required to produce these types of seat sliding apparatus because balls or rollers are required as well as a mechanism for supporting the balls or rollers. In addition, the shape of the rail must be relatively accurately dimensioned, especially at the ball or roller holding portion. However, it is difficult to maintain desired dimensions within a tolerance range using an extrusion forming method. 
     One proposal for addressing some of the disadvantages and drawbacks associated with the construction of known seat sliding apparatus is described in Japanese Utility Model Published Application No. Hei 6(1994)-74465. This seat slide apparatus is composed of a lower rail made of steel, an upper rail comprised of a sliding portion made of aluminum alloy and a seat support portion made of steel, and a lock mechanism engageable with a hole in the lower rail and supported on the seat support portion. The lower portion of the sliding member of this apparatus possesses an H-shaped cross-section having sufficient wall thickness. The apparatus is designed to prevent excessive play of both rails and smoothly slide the upper rail relative to the lower rail by contacting parts of both the upper portions and the outer surface of the vertical portions of the H-shaped part with the inner wall surface of the hollow portion of the lower rail. 
     So long as the dimensions of the two rails are kept within a small dimensional tolerance, this construction of the seat sliding apparatus reduces the number of components, such as the balls or rollers, without causing sticking during the sliding movement of the upper rail relative to the lower rail due to the contact between the different materials such as steel material and aluminum alloy material, However, this construction of the seat sliding apparatus requires high accuracy forming for the rails. Even a slight deviation from the tolerance causes an excessive play between both rails, thus increasing the sliding resistance. 
     In light of the foregoing, a need exists for a seat sliding apparatus that is not as susceptible to the disadvantages and drawbacks identified above. 
     A need exists for a seat slide apparatus which utilizes a different technological solution to produce an improved seat slide apparatus. 
     SUMMARY OF THE INVENTION 
     According to the present invention, the seat slide apparatus is designed so that a portion of the steel upper rail contacts the inner wall of the hollow portion of the lower rail by using a spring force. It is preferable to provide a surface portion having indented and projecting portions (grooves and ridges) on the inner wall of the hollow portion of the lower rail. A portion of the upper rail is elastically in contact with the surface portion having the projections. 
     The dimensional tolerance range of the upper rail and the lower rail can be wider by utilizing the elastic characteristics of the upper rail and without causing excessive play of the upper rail during sliding motion relative to the lower rail. In addition, the sliding resistance is kept constant and the assembly work is easier to carry out. 
     Thus, according to one aspect of the invention, a seat slide apparatus includes a lower rail made from light metal alloy materials having a pair of side portions upwardly extending from both ends of the base portion, with each surface of the inner wall of the side portion having a projection portion. An upper rail made from steel material has flange portions upwardly extending from both ends of a horizontal bottom portion, and each flange portion elastically contacts the projection portions. 
     According to another aspect of the invention, a vehicle seat slide apparatus includes a lower rail, an upper rail and a lock mechanism. The lower rail is adapted to be secured to the floor of the vehicle and includes a base portion and a pair of side portions. Each of the side portions extends upwardly from one end of the base portion and possesses an inwardly inclined portion. A plurality of projections extend from the inner wall surface of each inclined portion. The upper rail includes a horizontal bottom portion and a pair of flange portions extending upwardly from ends of the horizontal bottom portion. Each flange portion faces one of the inclined portions of the side portion of the lower rail, and each of the flange portions of the upper rail is in contact with the projections of one of the inclined portions. The lock mechanism is engageable with a portion of the lower rail and the upper rail to fix the position of the upper rail with respect to the lower rail. 
     According to another aspect of the invention, a seat slide apparatus for a vehicle includes a lower rail adapted to be secured to the vehicle floor, an upper rail and a lock mechanism. The lower rail includes a base portion and a pair of side portions, with each of the side portions extending upwardly from one end of the base portion. The upper rail includes a horizontal bottom portion and a pair of flange portions extending upwardly from ends of the horizontal bottom portion. Each flange portion includes a surface portion facing a surface portion of the side portion. A plurality of projections extend away from either the surface portion of each side wall or the surface portion of each flange, and the other of the surface portion of each side wall and the surface portion of each flange contacts the projections. The lock mechanism is adapted to engage a portion of the lower rail and the upper rail to fix the position of the upper rail with respect to the lower rail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawing figures in which like reference numerals designate like elements and wherein: 
     FIG. 1 is a perspective view of a seat slide apparatus according to the present invention; and 
     FIG. 2 is a cross-sectional view of the seat slide apparatus shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the seat slide apparatus  1  according to the present invention includes a lower rail  3  that is adapted to be fixed to the vehicle floor through a bracket  2 , an upper rail  4  slidably disposed in the longitudinal direction relative to the lower rail  3 , and a lock mechanism  7  operated by a handle  5  and engageable with holes  6  provided on the lower rail  3 . The lock mechanism  7  is supported by the upper rail through a bracket  8 . 
     Referring to FIG. 2, the lower rail  3  is formed by extrusion of light metal alloy such as aluminum alloy and includes a pair of side portions  10  extending upwardly from both sides of a base portion  9 , an upwardly and slightly inwardly inclined portion  11  extending from each of the side portions  10 , and a tip portion  12  extending downward from the top end of each inclined portion  11 . A plurality of rollers  13  are situated on the base portion  9 . 
     The holes  6  receiving the engaging part of the lock mechanism  7  are provided on one of the side portions  10  of the lower rail  3 . The inner wall surface of the inclined portion  11  of each side portion  10  is provided with a surface region or surface portion  14  having one or more convex elements or projections. Thus, the surface portion possesses surface characteristics differing from the surface characteristics of the portion of the inner wall surface of each side portion adjoining the surface portion  14 . Generally speaking, the surface portion  14  possesses a plurality of spaced apart projections, with grooves being defined between adjacent projections. The projections or protuberances of the surface portion  14  can be, for example, knurled or grooved, or can be a somewhat wave-shaped configuration. 
     The upper rail  4  is composed of two generally L-shaped plates made from spring steel. The two generally L-shaped plates are connected to form a reverse T- shaped upper rail. The end of the horizontal bottom portion  16  of each plate extends upwardly and inwardly to form a flange portion  15  at each side of the upper rail. Both flange portions  15  are adapted to be elastically deformed inwardly or outwardly relative to the horizontal bottom portion  16 . In addition, the horizontal bottom portions  16  of the upper rail  4  are in contact with the rollers  13 . 
     A through hole  17  is provided in one of the flange portions  15  of the upper rail  4 . The tip end of the lock mechanism  7  forming an engaging part of the lock mechanism  7  extends into and is engageable with the hole  17  in the flange portion  15  and one of the holes  6  in the side portion  10  of the lower rail  3  to lock the upper and lower rails  4 ,  3  relative to one another. 
     The elastic flange portions  15  of the upper rail  4  face towards and are always in contact with the respective surface portions  14  of the lower rail  3 . It is to be understood that the surface portions  14  are not limited to the shape and configuration shown in FIG.  1 . The surface portions  14  can be in a variety of other configurations, including a surface having arc-shaped regions or reverse V-shaped regions. The surface portions  14  forming projection portions preferably contact the respective flange portions  15  along several spaced apart line contacts or several spaced apart point contacts. 
     When the lock mechanism  7  is disengaged from the holes  6  of the lower rail  3  by operating the handle  5 , the upper rail  4  is free to move relative to the lower rail  3  and the driver can thus adjust the seat to any preferable position. Rattling is prevented during sliding movement of the seat or under vehicle vibration conditions because the flange portions  15  of the upper rail  4  elastically contact the respective surface portion  14  of the lower rail  3  that is provided with the projections. In addition, the sliding movement between the steel and light weight metal alloy material avoids sticking between the two parts and also reduces the sliding resistance. Moreover, abrasion powder generated by the frictional contact of the light weight metal alloy material is able to enter the bottom of the surface of the indented regions or grooves of the surface portion  14 , thus avoiding interference with the siding surface. It is thus possible to achieve a relatively constant sliding resistance. It is also to be understood that the convex portion(s) or projections forming the surface portion  14  can also be made separately from the lower rail  3  and then subsequently fixed to the side portions  10  of the lower rail  3 . 
     The principles, preferred embodiments and modes 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.