Seat sliding device of a vehicle

A stationary rail of generally channel-shaped construction is secured to the vehicle floor so as to have an elongate opening thereof oriented to the direction of movement of a seat mounted thereover. The stationary rail has a coaxially extending main portion or section and coaxially extending guided and guiding portions or members. A movable rail connected to the seat has throughout the length thereof the same cross section as the stationary rail. The movable rail is slidably engaged with the stationary rail in such a manner that the guided and guiding portions thereof are engaged with the corresponding guided and guiding portions of the movable rail in a mutually inverted relationship, having the main portion thereof and the corresponding truck portion of the movable rail spaced. Rollers are embraced by the stationary and movable rails in such a manner that the cylindrical outer surface of each roller engages with both the main portions of the stationary and movable rails.

BACKGROUND OF THE INVENTION 
The present invention relates to a seat sliding device of a vehicle, and 
more particularly to a device of a type which uses rollers for improving 
the seat sliding characteristics thereof. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided an improved seat 
sliding device for a motor vehicle, which assures smooth sliding movement 
of the seat relative to the vehicle floor even when a heavy load is 
applied thereto. 
The seat sliding device of the invention comprises an elongate stationary 
rail having a generally channel-shaped construction and secured to the 
vehicle floor in such a manner that the axially extending opening thereof 
is oriented laterally with respect to the seat mounted thereover. The 
stationary rail has a coaxially extending truck portion and coaxially 
extending first and second guiding portions. An elongate movable rail is 
connected to the seat to move therewith. The movable rail has throughout 
the length thereof a cross section identical to that of the stationary 
rail and is slidably engaged with the stationary rail in such a manner 
that the first and second guiding portions of the stationary rail are 
engaged with the corresponding guided portions of the movable rail in a 
mutually inverted relationship, the truck portion of the stationary rail 
and the corresponding truck portion of the movable rail being spaced apart 
from one another. A plurality of rollers are embraced by the mutually 
engaged stationary and movable rails in such a manner that the cylindrical 
outer surface of each roller engages with both the truck portions of the 
stationary and movable rails.

BRIEF DESCRIPTION OF THE INVENTION 
Prior to describing the invention, a conventional seat sliding device will 
be outlined with reference to FIG. 1 in order to clarify the invention. 
Referring to FIG. 1, a sectioned view of a conventional seat sliding device 
is provided. Although not shown, a seat is mounted on the device and 
achieves its sliding movement relative to a vehicle floor (not shown) on 
which the device is arranged. The device comprises generally an elongate 
stationary rail 10 having a C-shaped cross section, as shown. The rail 10 
is secured to the vehicle floor and is arranged so as to have the elongate 
opening 10a thereof oriented laterally with respect to the seat. An 
elongate movable rail 12 is axially movably received in the stationary 
rail 10. For improving the sliding, the movable rail 12 is provided at its 
upper and lower sides with sliding blocks 14 and 16, made of, for example, 
plastics, which are slidably engaged with the curved inside surfaces 10b 
and 10c of the stationary rail 10. The movable rail 12 is formed with 
openings 12a through which headed bolts 18 pass. An annular spacer 20 is 
mounted on each bolt 18. A nut 22 and a washer 24 are engaged with the 
threaded portion of each bolt 18 in order to fasten a bracket 26 to the 
bolt 18 and thus to the movable rail 12. The bracket 26 is secured at its 
upper portion to the frame construction of the seat, so that the movement 
of the seat is carried out by sliding the movable rail 12 along the 
stationary rail 10. Because the bracket 26 is not coaxial with the 
stationary and movable rails 10 and 12, the rails are loaded in an off 
axial manner. 
However, this seat sliding device has suffered from the drawback that 
substantially all of the weight of the seat assembly is supported by only 
the lower section of the device, that is to say, by the curved inside 
surface 10c of the stationary rail 10 and the sliding block 16 of the 
movable rail 12. The increase in weight of the seat assembly by a seat 
occupant sitting thereon therefore tends to deform the sliding block 16, 
thereby disabling the smooth sliding of the movable rail 12 relative to 
the stationary rail 10. Furthermore, it has been revealed that long use of 
the device causes a considerable wearing-out of the block 16, which also 
induces non-smooth sliding of the movable rail 12. 
To eliminate the above-mentioned drawback is an essential object of the 
present invention. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 2 to 5, there is shown a seat sliding device according 
to the present invention, which is free of the above-mentioned drawback. A 
seat 44 (FIG. 5) is mounted on the device to achieve its sliding movement 
relative to the vehicle floor F on which the device is arranged. The 
device comprises an elongate stationary rail 28 having a generally 
channel-shaped construction and connected to the vehicle floor F. As will 
be described in detail hereinafter, an elongate movable rail 38 having the 
same cross section as the stationary rail 28 is longitudinally slidably 
engaged with the stationary rail 28 through rollers 40 and 42. As in the 
prior art, the device of the invention is loaded in an off axial manner, 
as can be seen in FIG. 5. 
The stationary rail 28 comprises, as is seen from FIG. 3, a vertical flat 
portion 28b, an upper horizontal flat portion 28c with a downwardly bent 
end 28d, a lower horizontal flat portion 28e, and a curled portion 28f 
extending from the lower flat portion 28e, all these portions extending 
along the axis of the rail 28. As is clearly visible in the drawing, 
curled portion 28f recurves at least three-quarters (270.degree.) around a 
longitudinal axis passing through its center of curvature. As can also be 
seen from the drawing, the portions 28b, 28c and 28d are arranged to 
constitute a channel, and the bent end 28d extends inward of the channel 
to form a guiding groove 28g at one side of the channel. The curled 
portion 28f projects outward to form a guiding portion. As is seen from 
FIG. 2, the stationary rail 28 is connected at its longitudinal ends, by 
bolts 30 and 32, to supporting brackets 34 and 36 secured to the vehicle 
floor F. The rail 28 is arranged to have the elongate opening 28a thereof 
oriented laterally with respect to the seat mounted thereover. 
The curled portion 28f together with lower flat portion 28e comprise a 
guided member. The channel comprised of portions 28c, 28d, and part of 28b 
comprises a guiding portion. The rest of 28b comprises a main section. 
Axially slidably engaged with the stationary rail 28 is an elongate movable 
rail 38 which has, throughout the length thereof, a cross section 
identical to that of the stationary rail 28. Thus, portions of the movable 
rail 38 corresponding to those of the stationary rail 28 are designated by 
affixing the same letter to the numeral 38, in the drawings. As is 
understood from the drawings, the movable rail 38 is slidably engaged with 
the stationary rail 28 having the at least 270.degree. curled portion 38f 
thereof received in the guiding groove 28g of the stationary rail 28, and 
having the guiding groove 38g thereof, defined by portions 38b, 38c, and 
38d, thereof receiving the curled portion 28f of the stationary rail 28. 
It can be seen in the drawing that curled portion 28f substantially fills 
guiding groove 38g, and that the same is true of curled portion 38f with 
respect to guiding groove 28g. Thus, the guided members substantially fill 
the guiding members. That is to say, the movable and stationary rails 38 
and 28 have cross sections which are identical and which permit one to be 
interlocked with the other in a mutually inverted configuration. Curled 
portions 28 f and 38f preferably contact the respective guiding portions 
of the channels at two points, viz., 28b, 38b and 28d, 38d. This minimizes 
frictional interaction while at the same time providing minimal clearance. 
A suitable bracket is secured to the movable rail 38 to connect the 
movable rail 38 with the seat. 
Two rollers 40 and 42 are embraced by the stationary and movable rails 28 
and 38 in such a manner that the cylindrical outer surface of each roller 
engages with or runs on the flat portions 28e and 38e of each nail, 
respectively. In other words, the rollers 40 and 42 are disposed within a 
longitudinal channel seen end-on in FIG. 3. In the described embodiment, 
this channel is substantially rectangular. The channel is formed on the 
sides by the opposed interior faces of the main sections of the rails, and 
top and bottom by the opposed interior faces of the guided members. 
Although not shown in the drawings, another seat sliding device having 
identical construction to the above-mentioned device is arranged beside 
the mentioned one for achieving stable sliding movement of the seat. 
With the above-stated construction of the invention, it will be appreciated 
that the axial movement of the movable rail 38 induces rolling of the 
rollers 40 and 42 on the flat truck portions 28e and 38e of the stationary 
and movable rails 28 and 38, which permits smooth sliding movement of the 
seat. During the movement of the movable rail 38, the curled portion 38f 
and the groove portion 38g thereof are positively guided by the associated 
guiding portions 28g and 28f of the stationary rail 28, preventing 
disengagement of the movable rail 38 from the stationary rail 28. Of 
course, the rollers 40 and 42 are of rigid material of sufficient 
stiffness that it can support the weights of both the seat assembly and 
the occupant to be seated thereon. As the movable and stationary rails may 
be produced simply by cutting off lengths of the same stock, mass 
production may be facilitated and invisible costs reduced.