Powered seat slide device

A powered seat slide device including at least one pair of guide rails for slidably supporting a seat such that the position of the seat relative to a floor is adjusted frontwardly and rearwardly, comprises a drive motor causing a relative sliding movement of one of the guide rails to the other, through a driving mechanism employing a gear box fixed to the one of the rails to serve as a reduction gear transmitting rotation torque from the motor to a screw-threaded shaft which is fixed onto the one of rails and engaged with a nut member rigidly mounted on the other rail for rotation relative to the screw-threaded shaft, while reducing a motor speed and increasing torque created by the motor, a motor mounting bracket formed integral with the gear box, for directly connecting the motor to the gear box, and an opening provided in the side wall of the one of rails, for avoiding the interference between the motor assembly and the guide rails.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a powered seat slide device, such as a 
motor-driven seat slide device for an automotive vehicle, and specifically 
to a powered seat slide device employing at least one pair of guide rails, 
namely an upper slidable guide rail firmly secured to the bottom surface 
of the automobile seat and a lower stationary guide rail rigidly mounted 
on the floor panel of the vehicle body, which is capable of electrically 
adjusting the position of the automobile seat assembly in a direction 
generally parallel to the longitudinal direction of the vehicle body. 
2. Description of the Prior Art 
A conventional automotive powered seat slide device employs a 
telescopically extendable guide rail structure for each side of the seat 
assembly. The telescopically extendable guide rail structure is usually 
interposed between the seat cushion and the floor panel of the vehicle. 
Referring now to FIGS. 1 and 2, there is shown a conventional powered seat 
slide device for automotive vehicles. The telescopically extendable guide 
rail structure is comprised of an upper slidable guide rail 1 firmly 
secured to a respective side portion of the base plate of the seat and a 
lower stationary guide rail rigidly mounted on the floor panel. The 
powered seat slide device also includes a guide rail driving mechanism 
being comprised of a drive motor 2, such as a DC motor, and a gear box 8 
including a worm 9 having a driven connection with a drive shaft 2b of the 
motor and a worm wheel having external threads meshed with the worm 9. As 
seen in FIG. 2, the drive motor 2 is firmly secured to the side wall 
section 1a of the upper slidable guide rail 1 by means of fasteners, for 
example a fastening bolt 4 utilized with a well-type self-locking nut 3, a 
board anchor, a blind rivet or the like. Reference numeral 5 designates a 
circular opening 5 for directly fitting the nut 3. The gear box 8 serves 
as a reduction gear for reducing revolution of the output shaft 2b of the 
motor 2 and increasing rotation torque created therethrough. The worm 
wheel is rigidly formed integral with a screw-threaded shaft 7 rotatably 
supported by the upper guide rail 1 through bearings at both ends thereof. 
Reference numeral 6 is a cut-out 6 formed at the inner side wall section 
1a of the upper slidable guide rail 1, for introducing a cylindrical hub 
section formed integral with the a main motor casing 2a of the motor 2 
thereinto. The output shaft 2b of the motor is rotatably supported by the 
above noted cylindrical hub section of the motor and outwardly extended 
The output shaft 2b has a driving connection with an input shaft 9a of the 
worm 9. Generally, the output shaft 2b is directly connected to the input 
shaft 9a as shown in FIG. 2. Alternatively, the output shaft 2b could be 
connected through a rigid coupling to the input shaft 9a, as disclosed in 
Japanese Patent First Publication Tokkai (Showa) 63-34252. In order to 
insure smooth torque transmission from the output shaft 2b of the motor to 
the input shaft 9a of the worm, the two shafts 2b and 9a are precisely 
aligned with each other. 
In the previously noted conventional powered seat slide devices, the two 
shafts 2b and 9a can be precisely aligned with each other only under a 
particular condition wherein the plane defined by the ceiling wall section 
1b of the upper slidable guide rail 1 is precisely formed perpendicularly 
to the plane defined by the side wall section 1a through a precise 
machining, such as a bending process with an extremely high machining 
accuracy. Supposing that the machining accuracy in the bending process is 
less than a predetermined criterion, the angle sandwiched between the side 
wall section 1a and the ceiling wall section 1b is offset from a right 
angle (90.degree.). Thus, the two shafts 9a and 2b could be misaligned 
with each other. As a result, smooth and high torque transmission is 
prevented and consequently noise occurs at the connecting portion between 
the two shafts 9a and 2b, when the machining accuracy in the upper guide 
rail 1 is low. Furthermore, since the drive motor 2 is directly connected 
to the side wall section 1a of the upper guide rail 1 having a relatively 
low rigidity, the guide rail 1 experiences resonance through the direct 
connection with the upper guide rail 1, because the guide rail 1 must 
receive reaction force created due to moment of inertia of the rotor 
enclosed in the motor 2, during rotation of the motor. Under this 
condition, a noise level generated during operation of the driving 
mechanism is increased with great energy loss and as a result an exciting 
current value of the motor 2 is also increased, since the drive motor is 
susceptible to such resonance. As appreciated from the above, the motor 
employed in the conventional powered seat slide device has an increased 
tendency to become overloaded due to the above resonance created between 
the motor 2 and the upper guide rail 1 or the driving mechanism including 
the screw-threaded member 7 and the gear box 8. This results in a 
relatively low durability of the device. Furthermore, since the main motor 
casing 2a is directly connected to the side wall section 1a of the upper 
guide rail 1, but not to gear box 8, the alignment matching between the 
two shafts 2b and 9a is determined only by an installation accuracy in a 
relative position of the main motor casing 2a to the upper guide rail 1. 
Assuming that the installation accuracy is low, the previously noted 
resonance may occur between the motor and the driving mechanism, thereby 
resulting in a low rotation torque transmission efficiency. 
SUMMARY OF THE INVENTION 
It is, therefore, in view of the above disadvantages, an object of the 
present invention to provide a powered seat slide device employing at 
least one telescopically extendable guide rail unit, a drive motor and a 
gear box, which can provide a smooth and high torque transmission from the 
output shaft of the drive motor to an input shaft of the gear box, 
irrespective of a machining accuracy in either one guide rail of the rail 
unit for rigidly mounting the gear box thereon, or an installation 
accuracy in a relative position of the motor body to the above one guide 
rail. 
It is another object of the invention to provide a powered seat slide 
device employing a drive motor, a gear box, and a pair of guide rails 
being comprised of an upper slidable guide rail and a lower stationary 
guide rail, which can reliably prevent the motor from being overloaded 
during operation of the device, while avoiding resonance created between 
the motor and a driving mechanism for causing a sliding movement of the 
slidable guide rail relative to the stationary guide rail. 
It is a further object of the invention to provide a powered seat slide 
device which can provide a high durability of the device. 
In order to accomplish the aforementioned and other objects, a powered seat 
slide device including at least one pair of guide rails for slidably 
supporting a seat such that the position of the seat relative to a floor 
is adjusted frontwardly and rearwardly, comprises a driving mechanism 
having a driven connection with a drive motor, for causing a relative 
sliding movement of one of the guide rails to the other, the driving 
mechanism including a screw-threaded member rotatably supported on either 
one of the guide rails, a nut member engaged with the screw-threaded 
member and rigidly mounted on the other of the rails for rotation relative 
to the screw-threaded member, and a gear box fixed to the one of the rails 
to serve as a reduction gear transmitting rotation torque from the motor 
to the screw-threaded member, while reducing a motor speed and increasing 
the torque created by the motor, a motor mounting member formed integral 
with the gear box, for directly connecting the motor to the gear box, and 
an opening provided in the side wall of the one of the rails, for avoiding 
the interference between the motor assembly and the one of the guide 
rails. The motor mounting member includes a pair of brackets formed 
integral with the gear box in such a manner as to extend in the 
longitudinal direction of the one of the rails, the brackets are 
symmetrically arranged with each other in respect to an axis of input 
shaft of the gear box. 
According to another aspect of the invention, a powered seat slide device 
including at least one pair of guide rails for slidably supporting a seat 
such that the position of the seat relative to a floor is adjusted 
frontwardly and rearwardly, comprises a driving mechanism having a driven 
connection with a drive motor, for causing a relative sliding movement of 
one of the guide rails to the other, the driving mechanism including a 
screw-threaded member rotatably supported on either one of the guide 
rails, a nut member engaged with the screw-threaded member and rigidly 
mounted on the other of the rails for rotation relative to the 
screw-threaded member, and a gear box fixed to the one of the rails to 
serve as a reduction gear transmitting rotation torque from the motor to 
the screw-threaded member, while reducing a motor speed and increasing the 
torque created by the motor, a motor mounting bracket formed integral with 
the gear box, for directly connecting the motor to the gear box, a motor 
mounting flange formed integral with a motor casing of the motor, for 
rigidly mounting the motor on the motor mounting bracket, the motor 
mounting flange including at least two axially extending cylindrical 
hollow legs through which the motor is secured onto the motor mounting 
bracket, the cylindrical hollow legs are symmetrically arranged with each 
other in respect to the axis of the output shaft of the motor, and an 
opening provided in the side wall of the one of the rails, for avoiding 
the interference between the motor assembly and the one of the guide 
rails. The gear box has a higher rigidity than the one of the rails. The 
gear box may include a first cylindrical hub section coaxially arranged 
with the axis of the input shaft of the gear box, while rotatably 
enclosing the input shaft of the gear box, and the motor mounting flange 
may include a second cylindrical hub section coaxially arranged with the 
axis of the output shaft of the motor, while rotatably enclosing the 
output shaft of the motor. The outer periphery of the first cylindrical 
hub section is press-fitted into the inner periphery of the second 
cylindrical hub section, so as to assure a rigid connection between the 
motor assembly and the gear box.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, particularly to FIG. 7, there is shown an 
automobile powered seat slide device 20 through which a relative position 
of an automobile seat 10a to the floor panel 10 of the vehicle body is 
electrically adjustable. The powered seat slide device 20 comprises a pair 
of telescopically extendable guide rail units 20a respectively provided on 
both sides of the bottom surface of the seat 10a and in addition extending 
frontwardly and rearwardly of the seat. Each guide rail unit 20a is 
comprised of a lower stationary guide rail 21 rigidly mounted on the floor 
panel 10 of the vehicle body by means of fastening bolts and an upper 
slidable guide rail 22 firmly secured onto the side portion of the bottom 
surface of the seat by means of fasteners, such as fastening bolts, rivets 
or the like, in a manner so as to reliably support the seat and also 
slidable in relation to the lower stationary guide rail 21. As seen in 
FIG. 7, each guide rail unit 20a is secured through front and rear 
brackets 12 and 13 onto the floor panel 10 of the vehicle body. 
Referring now to FIGS. 3 and 4, a reversed hat shaped, lower stationary 
guide rail 21 includes a bottom wall section 23 and a pair of side wall 
sections 24 having a bended portion at the upper end thereof. On the other 
hand, the upper slidable guide rail 22 includes a ceiling wall section 25 
and a pair of side wall sections 26 in such a manner as to slidably 
enclose the upper bended portion of the lower stationary guide rail 21. 
With the above noted rail arrangement, an aperture 20b is defined between 
the lower and upper rails 21 and 22. As shown in FIG. 3, a driving 
mechanism 30 is provided in the aperture 20b, so as to provide a relative 
sliding movement of the upper guide rail 22 relative to the lower guide 
rail 21. The driving mechanism 30 for the guide rail is comprised of a 
screw-threaded shaft 31 extending in a longitudinal direction of the guide 
rail and a nut member 32 engaged with the screw-threaded shaft 31. As seen 
in FIG. 4, the nut member 32 is fixed onto the bottom wall section 23 of 
the lower stationary guide rail 21 by means of bolts in such a manner as 
to prevent both rotational movement and sliding movement of the nut member 
32 in respect to the lower guide rail 21. As shown in FIGS. 3 and 4, the 
driving mechanism 30 includes a gear box 40 accommodated in a chamber 20c 
defined in a slightly raised front end of the ceiling wall section 25 of 
the upper guide rail 22, a worm 50 operably accommodated in a lateral bore 
44 defined in the gear box 40, and a pair of bearing members 52 disposed 
at both ends of the lateral bore 44 in order to rotatably support an input 
shaft 51 of the worm 50. As best shown in FIG. 6, the gear box 40 is 
rigidly mounted on the ceiling wall section 25 of the upper guide rail 22 
through a pair of brackets 47, such that the brackets 47 sandwich front 
and rear ends of the gear box 40. The brackets 47 are fixed onto the 
ceiling wall section 25 by means of fastening bolts 48. The gear box 40 
serves as a reduction gear for transmitting torque created by a drive 
motor 80, such as an electrically powered drive motor, to the 
screw-threaded shaft 31, while reducing revolution of the output shaft 82 
of the motor 80 and increasing the created torque. The driving mechanism 
30 is driven by the motor 80. 
Note that a cut-out 27 is formed at the inner side wall section 26 of one 
guide rail unit 20a so as to introduce thereinto a cylindrical hub section 
83 formed integral with a main motor casing 80a of the motor 80, while 
avoiding the interference between the cylindrical hub section 83 and the 
side wall section 26 of the upper guide rail 22, and in addition a pair of 
openings 27a are formed at the inner side wall section 26 in such a manner 
as to sandwich the cut-out 27, so as to introduce thereinto a pair of 
cylindrical hollow legs 84 formed integral with a motor mounting flange 
81, while avoiding the interference between the cylindrical hollow legs 84 
and the side wall section 26. The hollow legs 84 are symmetrically 
arranged with each other in respect to the center axis of the motor output 
shaft 82 and extend in parallel with the axis of the shaft 82. The hollow 
section of each leg 84 exposes to an opening 85 bored in the flange 81 for 
introducing the male screw-threaded section of a bolt 86. The hub section 
83 is provided for rotatably supporting the output shaft 82 of the motor 
80 and coaxially arranged with the output shaft 82. The other axially 
extending section of the output shaft 82, which extends through the other 
end 80b of the motor 80 faced apart from the hub section 83, is directed 
to the gear box 40 attached to the other guide 7 rail unit 20a through a 
flexible wire 70. 
In addition to the above, the powered seat slide device according to the 
invention includes a pair of motor mounting brackets 41 formed integral 
with the gear box 40 and extending along the side walls of the brackets 47 
in a longitudinal direction of the guide rail. Each mounting bracket 41 
has a counterbore 43 fitted to the free end of the cylindrical hollow leg 
84 and a central female screw-threaded hole 42 formed in an essentially 
center of the counterbore 43. 
As shown in FIG. 4, the rear end of the screw-threaded shaft 31 is 
rotatably supported on the ceiling wall section 25 of the upper guide rail 
22 by means of a bearing member 33, while the front end of the 
screw-threaded shaft 31 is inserted through the bracket 47 into the gear 
box 40 and rigidly fitted into a center of a worm wheel 60 operably 
enclosed in the gear box 50. A pair of stoppers 34 are provided in the 
vicinity of front and rear ends of the screw-threaded shaft 31 so as to 
restrict frontward and rearward movements of the shaft 31 relative to the 
lower stationary guide rail 21. 
Referring now to FIGS. 5 and 6, the worm wheel 60 is rotatably provided in 
an internal space 46 defined in a substantially center portion of the gear 
box 40 and meshed with the worm 50. Reference numeral 45 designates a 
laterally extending cylindrical hub section which is provided for 
receiving the bearing 52 rotatably supporting the input shaft 51 of the 
worm 50 and simultaneously fitting with the cylindrical hub section 83 of 
the motor 80. The hub section 45 is coaxially arranged with the axis of 
the worm shaft 51 in such a manner as to rotatably enclose the worm shaft. 
With the above described arrangement of the powered seat slide device 20 
according to the invention, when the disassembled parts shown in FIG. 4 
are assembled to each other, the drive motor assembly is directly attached 
onto the gear box 40 having a relatively high rigidity, without 
introducing the interference between the cylindrical hub section 83 and 
the side wall section 26 of the upper guide rail 22 and the interference 
between the cylindrical hollow legs 84 and the side wall section 26. This 
reliably prevents resonance created between the drive motor and the 
driving mechanism. 
The assembling order of the powered seat slide device 20 of the preferred 
embodiment will be hereinafter described in detail with reference to FIG. 
3 or FIG. 4. 
First of all, the gear box 40 employing the worm 50 and the worm wheel 60 
is attached through the brackets 47 to the ceiling wall section 25 of the 
upper slidable guide rail 22, by means of bolts 48. Thereafter, the drive 
motor 80 is directly mounted through the motor mounting flange 81 on the 
gear box 40, such that the cylindrical hollow legs 84 are fitted into the 
counterbores 43 and simultaneously the outer periphery of the cylindrical 
hub section 45 of the gear box 40 is fitted into the inner periphery of 
the cylindrical hub section 83 of the motor 80 and in addition the 
cylindrical end of the output shaft 82 of the motor 80 is engaged with the 
input shaft 51 of the worm 50. In order to achieve a rigid connection 
between the motor mounting flange 81 and the motor mounting bracket 41, 
the bolts 86 are screwed into the female screw-threaded holes 42. In the 
preferred embodiment, the solid input shaft 51 of the worm is press-fitted 
into the output shaft 82 of the motor so as to assuringly provide a rigid 
connection between the two shafts 51 and 82. Furthermore, the motor 
mounting brackets 41 are formed integral with the gear box 40 in such a 
manner as to extend in the longitudinal direction of the upper guide rail 
22 and in addition the frontwardly extending bracket 41 and the rearwardly 
extending bracket 41 are symmetrically arranged with each other in respect 
to the center axis of the worm shaft 51. Such a symmetrical arrangement is 
suitable to certainly receive reaction force created by rotation of the 
rotor of the motor 80. In this manner, the worm shaft 51 is rotated 
together with the drive motor shaft 82. As best seen in FIG. 6, during 
assembling, the drive motor assembly is not contact with the guide rail 
unit 20a at all, since the center cut-out 27 and the openings 27a function 
to avoid the previously noted interference between the guide rail and the 
motor assembly. 
As will be appreciated from the above, the alignment matching between the 
input shaft 51 of the worm 50 and the output shaft 82 of the motor 80 is 
affected only by the machining accuracy of the gear box 40, but not by the 
machining accuracy of the upper guide rail 22. 
As is generally known, the guide rail has a relatively low rigidity for the 
purpose of lightening of the guide rail unit, while the gear box has a 
higher rigidity than the guide rail for the purpose of smooth torque 
transmission. Assuming that offset load is applied to the seat by the 
vehicle occupant, the upper guide rail 22 is slightly deformed. Under this 
condition, if the motor assembly is attached to the upper slidable guide 
rail, there is a tendency for the two shafts 51 and 82 to be slightly 
misaligned to each other. At this time, when the power seat slide device 
is operated, noise occurs between the motor and the driving mechanism with 
a relatively great energy loss. Consequently, the motor is irregularly 
rotated, with fluctuations in the motor speed. 
In the powered seat slide device according to the invention, the motor 
assembly is directly attached to the gear box. Since the gear box having a 
relatively high rigidity is usually suitable for a precise machining, the 
gear box can be easily manufactured with a high machining accuracy. 
Through direct connection between the motor assembly and the gear box, the 
output shaft of the motor can be easily and precisely aligned with the 
input shaft of the worm. As appreciated from the above, the durability of 
the device 20 of the embodiment is enhanced due to a precise alignment 
matching between the two shafts 51 and 82, and due to a reliable rigid 
connection between the motor assembly and the gear box having a high 
rigidity. 
Referring now to FIG. 5, the output torque created by the motor 80 is 
smoothly transmitted from the output shaft 82 to the input shaft 51 of the 
worm 50. Thereafter, the rotation torque is transmitted to the 
screw-threaded shaft 31 through the worm 50 and the worm wheel 60 which 
are arranged perpendicularly to each other and meshed with each other. 
Since the nut member 32 is firmly fixed onto the lower stationary guide 
rail 21, the screw-threaded shaft 31 is moved rearwardly or frontwardly by 
means of the stationary nut member 32 in accordance with rotational 
movement of the shaft 31, with the result that the upper slidable guide 
rail 22 mounted onto the bottom of the seat is relatively moved in 
relation to the lower stationary guide rail 21. In this manner, the 
position of the seat relative to the floor panel of the vehicle body is 
reliably adjusted by means of the driving mechanism employed in the 
powered seat slide device 20. 
In the preferred embodiment, although the input shaft 51 and the output 
shaft 82 are directly connected to each other, the two shafts may be 
connected through a rigid coupling so as to achieve rigid connection 
between the two shafts 51 and 82. It is preferable that the two shafts 51 
and 82 are connected through a slider coupling, such as Oldham's coupling, 
since the Oldham's coupling permits two slightly misaligned shafts to be 
joined, while smoothly transmitting rotation torque from the output shaft 
of the motor to the input shaft of the worm. 
While the foregoing is a description of the preferred embodiments for 
carrying out the invention, it will be understood that the invention is 
not limited to the particular embodiments shown and described herein, but 
may include variations and modifications without departing from the scope 
or spirit of this invention as described by the following claims.