Drive apparatus for power seats

An apparatus for driving a power seat in an automotive vehicle includes a worm threadedly engaged with a worm wheel accommodated in a housing and receiving driving power, a plug supporting one end of the worm, a screw threadedly engaged with the housing for supporting the plug in the housing bore, a damper provided in the bore so as to face one side of the plug, and a spacer offering little frictional resistance interposed between the damper and the one side of the plug. The plug is moved up and down relative to the housing by turning the screw, thereby aligning the central axes of the worm wheel and worm, the spacer reducing the frictional resistance working against the plug so that the latter is capable of being slid smoothly and with fine precision.

BACKGROUND OF THE INVENTION 
This invention relates to improvements in an apparatus for driving a power 
seat in automotive vehicles or the like. 
As shown in FIG. 1, a common mechanism for applying power to a seat of an 
automotive vehicle to move the seat comprises a motor 2 fixedly secured to 
a lower bracket 1 on the vehicle body, a power seat drive apparatus 3 
fixedly secured to the lower bracket 1, a screw rod 4 coupled to the drive 
apparatus 3, and a nut member 6 fixedly secured to an upper bracket 5 
slidably engaged with the lower bracket 1 and supporting a seat cushion. 
Turning the screw rod 4 causes the nut member 6 to slide along the screw 
rod 4, thereby moving the upper bracket 5 back and forth relative to the 
lower bracket 1. 
A prior-art example of the drive apparatus 3 used in the above-described 
mechanism is illustrated in FIG. 2. The drive apparatus 3 includes a worm 
8 fixedly secured to the output shaft of the motor 2, a worm wheel 7 
threadedly engaged with the worm 8, a housing 9 having a bore 10, and a 
plug 11 fitted in the bore 10 and having a groove 12 formed in one end 
thereof. One end portion of the worm 8 is supported in the bore 10 of 
housing 9, and the other end of the worm 8 is supported by the plug 11. A 
screw 13 threadedly engaged with the housing 9 has an end portion of 
enlarged diameter received in the groove 12, thereby retaining the plug 11 
in the bore 10 of housing 9. A damper 14 consisting of e.g. polyurethane 
is disposed in the bore 10 in abutting contact with one side of the plug 
11. The opening of the housing 9 is covered by a cover 15. 
The worm wheel 7 and worm 8 are aligned by turning the screw 13 so that the 
plug 11 supporting one end of the worm 8 will move relative to the housing 
9. It should be noted that the end of the worm 8 is coupled to the motor 2 
(FIG. 1) so that the rotational torque of the motor 2 is transmitted to 
the screw rod 4 through the worm wheel 7 and worm 8. 
The alignment of the worm wheel 7 and worm 8 is extremely important for the 
sake of preventing the occurrence of noise during the operation of the 
power seat. After the drive apparatus 3 is assembled, the alignment is 
performed by turning the screw 13 to move the plug 11 up and down in the 
bore 10 of the housing 9. With the conventional arrangement, however, the 
plug 11 does not slide well on the damper 14 so that moving the plug 11 
causes the damper 14 to drag behind it. When the damper 14 returns to its 
original state during operation of the power seat, therefore, the 
relationship between the central axes of the worm wheel 7 and worm 8 
undergoes a shift and an abnormal noise is produced. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a power seat drive 
apparatus in which the relationship between the central axes of the worm 
and worm wheel can be finely adjusted. 
Another object of the present invention is to provide a power seat drive 
apparatus in which the relationship between the central axes of the worm 
and worm wheel can be finely adjusted in a short period of time. 
According to the present invention, the foregoing objects are attained by 
providing an apparatus for driving a power seat, comprising a housing 
having a bore, a worm wheel accommodated in the housing for receiving a 
driving force, a worm accommodated in the housing and threadedly engaged 
with the worm wheel, a plug provided in the bore for supporting one end of 
the worm, a screw threadedly engaged with the housing and supporting the 
plug in the bore, a damper provided in the bore so as to face one side of 
the plug, and a spacer interposed between the damper and the one side of 
the plug. 
Thus, the spacer does not allow the plug to come into direct contact with 
the damper and offers little sliding resistance to the plug when the 
latter is moved for adjustment. This enables the alignment of the central 
axes of the worm and worm wheel to be finely adjusted by turning the 
screw. 
Other features and advantages of the present invention will be apparent 
from the following description taken in conjunction with the accompanying 
drawings, in which like reference characters designate the same or similar 
parts throughout the figures thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of a power seat drive apparatus in accordance with the 
present invention will now be described with reference to FIGS. 3 and 4. 
Portions similar to those shown in FIGS. 1 and 2 are designated by like 
reference characters and need not be described again. 
As shown in FIGS. 3 and 4, the worm 8 has one end supported in the housing 
9 and its other end supported by the plug 11. As in FIG. 2, the plug 11 
has the groove 12 in which the enlarged diameter portion at the lower end 
of the screw 13 is received. The screw 13 is threadedly engaged with the 
housing 9. Turning the screw 13 moves the plug 11 up and down relative to 
the housing 9 as viewed in FIG. 4. 
According to a characterizing feature of the invention, a spacer 16 is 
interposed between the damper 14 and the plug 11. The spacer 16 consists 
of a material which offers little frictional resistance, such as a 
synthetic resin sheet of Teflon or the like or a metal plate. Numeral 15 
denotes the cover. The worm wheel 7 threadedly engaged with the worm 8 is 
supported in the housing 9 through the use of bearings 17. 
When the plug 11 is moved up and down by turning the screw 13 to align the 
central axes of the worm wheel 7 and worm 8, the spacer 16 reduces the 
frictional resistance working against the plug 11 so that the latter is 
capable of being slid smoothly and with fine precision. The plug 11 is in 
contact with the inner wall surface of the bore 10 in housing 9 in terms 
of the width direction of the plug so that the latter is prevented from 
rotating within the bore 10. The shapes of the spacer 16 and damper 14 are 
not limited to those shown in the drawings. If desired, a round spacer and 
damper can be employed. 
Thus, the spacer 16 prevents the plug 11 from directly contacting the 
damper 14 and allows the plug 11 to be slid smoothly. The plug 11 
therefore will respond correctly to movement of the screw 13 so that the 
plug 11 will travel by an amount corresponding to screw movement. This 
facilitates the adjusting operation for aligning the central axes of the 
worm wheel 7 and worm 8 and enables the adjustment to be performed in a 
shorter period of time. Since these advantages are obtained merely by 
providing the spacer and without greatly modifying the conventional 
arrangement, the manufacturing process is the same as before. This makes 
it possible to obtain the above advantages in an economical manner. 
As many apparently widely different embodiments of the present invention 
can be made without departing from the spirit and scope thereof, it is to 
be understood that the invention is not limited to the specific 
embodiments thereof except as defined in the appended claims.