Machine element or mechanism – Gearing – Backlash take-up
Reexamination Certificate
1999-11-12
2002-03-05
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Gearing
Backlash take-up
C074S425000, C297S330000, C297S344170
Reexamination Certificate
active
06352006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a reduction gear for use in a seat of a vehicle for reducing the rotating speed of a drive shaft connected to a prime mover and transmitting its rotary motion to an output shaft.
2. Discussion of the Related Art
Shown in
FIG. 9
is a conventionally known reduction gear
100
suited for use in a power seat of a vehicle, for example. This reduction gear
100
comprises as its basic constituent elements a worm
103
formed integrally with an inner shaft
103
a
which is coaxially connected to the end of a drive shaft
102
of a driving motor
101
, a worm wheel
104
engaged with the worm
103
, an output shaft
105
combined integrally with the worm wheel
104
which is formed concentrically around the curved outer surface of the output shaft
105
, and a casing
106
in which the worm
103
and the worm wheel
104
are fitted.
The casing
106
is provided with a tubular housing
107
accommodating the worm
103
, and a cylindrical bearing plug
108
for rotatably supporting the extreme end of the drive shaft
102
is fitted into a terminal end (right end in
FIG. 9
) of the tubular housing
107
. There is formed a shaft-supporting hole
109
in an inner end surface of the cylindrical bearing plug
108
on a common axis with the drive shaft
102
. The inner diameter of the shaft-supporting hole
109
is made slightly larger than the outer diameter of an outer shaft
103
b
of the worm
103
so that the extreme end of the worm
103
is rotatably fitted into the shaft-supporting hole
109
.
Further, a small hole is made in an end surface of the outer shaft
103
b
, and a steel ball
110
is fitted concentrically in the small hole with part of the steel ball
110
protruding outward from the small hole. On the other hand, a washer
111
is fitted at the bottom of the shaft-supporting hole
109
, and the worm
103
is allowed to rotate smoothly with the washer
111
held in contact with the steel ball
110
.
In the reduction gear
100
thus constructed, the rotary motion of the driving motor
101
is transmitted to the worm
103
, and the rotation of the worm
103
is transmitted to the worm wheel
104
, causing the worm wheel
104
to turn at a reduced rotating speed. Since the rotating speed of the worm wheel
104
is reduced, the output shaft
105
turns at a lower speed than the drive shaft
102
.
In the aforementioned conventional reduction gear
100
, variations in the length of the worm
103
are compensated by adjusting the length of thread engagement of the cylindrical bearing plug
108
and by elastic deformation of the washer
111
which is in contact with the steel ball
110
. However, the amount of elastic deformation of the washer
111
could be smaller than the amount of variations in the length of the worm
103
and, thus, the reduction gear
100
has a problem that it might not be able to fully compensate for dimensional variations of the worm
103
. It is therefore necessary to improve the accuracy of the length of the worm
103
and this would result in an increase in manufacturing cost.
Further, the length of thread engagement between the cylindrical bearing plug
108
and the tubular housing
107
is apt to vary due to vibrations or other causes. Therefore, the cylindrical bearing plug
108
could loosen in a long run, causing the steel ball
110
at the extreme end surface of the worm
103
to be separated from the washer
111
, even though the end of the outer shaft
103
b
of the worm
103
is securely supported by the cylindrical bearing plug
108
immediately after assembly. Thus, there arises a problem that the worm
103
would become shaky in its axial direction. When this has happened, it is necessary to readjust the thread engagement of the cylindrical bearing plug
108
by tightening it, which is quite inconvenient for users.
Furthermore, since three components including the cylindrical bearing plug
108
, the steel ball
110
and the washer
111
are required for rotatably supporting the extreme end of the worm
103
, the conventional reduction gear
100
entails high component costs and complex assembly operation. This poses another problem that the efficiency of assembly work is relatively low.
1. Field of the Invention
SUMMARY OF THE INVENTION
It is an object of the invention to provide a reduction gear for a vehicle seat which has overcome the aforementioned problems in the prior art.
According to an aspect of the invention, a reduction gear for a vehicle seat, comprises a worm connectable with an end of a drive shaft of a driver, a worm wheel meshed with the worm and connectable with an output shaft, and a casing for rotatably supporting the worm and the worm wheel. The casing is formed with a hollow cylindrical portion for accommodating the worm, and provided with a resilient member for urging the worm toward the drive shaft.
Other features of the present invention will be more readily understood from the following detailed description when read in conjunction with accompanying drawings.
REFERENCES:
patent: 3469469 (1969-09-01), Burger
patent: 3583253 (1971-06-01), Grimshaw et al.
patent: 3848477 (1974-11-01), Giandinoto et al.
patent: 4040307 (1977-08-01), Koster
patent: 4621933 (1986-11-01), Musso
patent: 5794480 (1998-08-01), Schöensteiner
patent: 196 31 228 (1998-02-01), None
patent: 0 871 280 (1998-10-01), None
Delta Kogyo Co. Ltd.
Fenstermacher David
Smith Patent Office
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