Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
2002-03-08
2003-10-28
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S428000, C029S558000, C476S073000
Reexamination Certificate
active
06637107
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of fabricating a variator disc mounted in a toroidal continuously variable transmission.
BACKGROUND ART
FIG. 5
schematically shows a variator for use in a full toroidal continuously variable transmission as one type of the toroidal continuously variable transmission mounted in vehicles and the like. The variator
10
includes an input shaft
13
driven into rotation by a vehicular power source
12
. The input shaft
13
carries an input disc
15
on respective places near opposite ends thereof. The input disc
15
is formed with a spline hole
15
a
at its center, the spline hole formed with plural lines of spline grooves. The input disc
15
has the spline hole
15
a
meshed with a spline shaft
13
a
of the input shaft
13
so that the input disc is rotated in unison with the input shaft
13
as permitted of a minor movement axially of the input shaft
13
. The reason for permitting the movement of the input disc
15
is to apply a required load to an end of the variator
10
by, for example, biasing the right-hand input disc
15
toward the left-hand input disc
15
, as seen in the figure, by means of a hydraulic cylinder
17
connected with a hydraulic power source
16
. The input disc
15
is formed with a concave race
15
b
on one side surface thereof.
An output portion
18
of the variator
10
is relatively rotatably carried on an axially central portion of the input shaft
13
. The output portion
18
includes an output member
19
and a pair of output discs
20
integrally rotatably carried on the output member
19
. The output disc
20
is formed with a concave race
20
b
on one side surface thereof in face-to-face relation with the race
15
b
of the input disc
15
. The output member
19
is formed with a sprocket gear
19
a
on its periphery, the sprocket gear meshed with a power transmission chain
23
. Three disc-like rollers
21
are interposed between the race
15
b
of the input disc
15
and the race
20
b
of the output disc
20
in face-to-face relation. The rollers
21
are in rolling contact with the races
15
,
20
b
, as arranged with equal circumferential spacing. Each of the rollers
21
is rotatably carried by a carriage
22
, which is adapted to adjust a position of the roller
21
relative to the races
15
b
,
20
b.
Thus, the variator
10
is configured as a so-called double cavity type which includes a pair of sets, each of which consists of the input disc
15
, output disc
20
and rollers
21
. The variator is arranged such that the input discs
15
transmit torque to the output discs
20
via the six rollers
21
. The variator is adapted to vary the speed of rotation (transmission gear ratio) of the output discs
20
by adjusting the positions of the six rollers
21
by means of the carriages
22
(See the two-dot chain line in FIG.
5
).
The input disc
15
is formed from, for example, a bearing steel. The input disc is generally fabricated by the steps of heat treating a blank for hardening, the blank formed with the spline hole
15
a
and the concave race
15
b
by machining; and then finishing the race
15
b
by machining or grinding using an inside periphery (surface of minimum inside diameter) of the spline hole
15
a
as a working reference.
In the variator
10
, the individual rollers
21
must evenly contact the races
15
b
,
20
b
of the discs
15
,
20
at high contact pressure in order to ensure the torque transmission between the input discs
15
and the output discs
20
.
However, it is difficult to finish the race
15
b
of the conventional input disc
15
with high precisions because in the process for finishing the race
15
b
after the heat treatment, tooth flanks of the spline hole
15
a
, which are used as the working reference, suffer heat-treatment deformation. In addition, assembly precisions of the input disc
15
with respect to the input shaft
13
depend upon the precisions of fitting the spline hole
15
a
of the input disc
15
on the spline shaft
13
a
of the input shaft
13
. Hence, the working precisions or the heat-treatment deformation of the spline hole
15
a
and such will result in a problem such as an inclined axis of the race
15
b
relative to the axis of the input shaft
13
or the like. Thus, the assembly precisions of these elements are decreased. Accordingly, there occurs misalignment between a center of the curvature of the race
15
b
of the input disc
15
and that of the race
20
b
of the output disc
20
, thus resulting in the following problems. That is, a particular roller
21
is subjected to such a high contact pressure that the roller
21
and the race
15
b
are decreased in durability. Otherwise, a particular roller
21
is subjected to a decreased contact pressure, so that the torque transmission becomes unstable. Furthermore, there occurs a so-called uneven contact in which a contact surface between the spline hole
15
a
and the spline shaft
13
a
is limited to a particular area. This also results the decreased durability of these elements.
As a solution to these problems, it may be contemplated to precisely finish the tooth flanks of the spline hole
15
a
by electrical discharge machining after the heat treatment. Unfortunately, however, this approach has another problem of low productivity and high fabrication costs.
It is an object of the invention to provide a method of fabricating a variator disc which favorably ensures the precisions of the race with respect to the input shaft and which features high productivity and low fabrication costs.
It is another object of the invention to provide a method of fabricating a variator disc which provides the high-precision finishing of the spline hole.
DISCLOSURE OF THE INVENTION
In accordance with one aspect of the invention, a method of fabricating a variator disc for use in a variator of a toroidal continuously variable transmission, the disc having a concave race on a side surface thereof for rolling movement of rollers and including a spline hole centrally thereof to be meshed with a spline shaft of an input shaft, the method comprises the steps of: forming a concave race with a machining allowance on a side surface of an annular material; forming the spline hole through a blank formed with the race; heat treating the blank for hardening the same; and in a state where the disc is retained by the input shaft, the spline shaft of which is meshed with the spline hole of the disc after the heat treatment of the blank, finishing an outer periphery of the disc using the input shaft as a working reference, and then finishing the race using the resulting outer periphery as a working reference (claim
1
).
According to the method of fabricating the variator disc, the precisions of the race with respect to the input shaft are favorably accomplished because the outer periphery of the disc finished using the input shaft as the working reference is used as the working reference for finishing the race. Therefore, the individual rollers are allowed to evenly contact the race such that the durability of the race and rollers is ensured and that the stable torque transmission is carried out. Furthermore, the method accomplishes higher productivity and lower fabrication costs than a case where the spline hole is finished by electrical discharge machining.
In accordance with another aspect of the invention, a method of fabricating a variator disc for use in a variator of a toroidal continuously variable transmission, the disc having a concave race on a side surface thereof and including a spline hole centrally thereof to be meshed with a spline shaft of an input shaft, the method comprises the steps of: forming a concave race with a machining allowance on a side surface of an annular material: forming the spline hole through a blank formed with the race; heat treating the blank for hardening the same; and in a state where the disc is retained by the input shaft, the spline shaft of which is meshed with the spline hole of the disc after the heat treatment of the blank, finishing the race u
Hasuda Yasuhiko
Hiraoka Daiji
Misada Yasuharu
Ono Yoshihiro
Yasuhara Shinji
Cuda Rosenbaum I
Koyo Seiko Co. Ltd.
Smith , Gambrell & Russell, LLP
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