Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2001-04-16
2003-04-22
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C702S010000
Reexamination Certificate
active
06553330
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-206926, filed Jul. 7, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a measuring method for obtaining, for example, the tilting center of a power roller for a toroidal type continuously variable transmission.
FIG. 13
shows a variator that constitutes a principal part of a double-cavity half-toroidal type continuously variable transmission
10
. The transmission
10
comprises an input disc
12
and an output disc
13
, which constitute a first cavity
11
, and an input disc
12
and an output disc
13
, which constitute a second cavity
14
. A pair of power rollers
15
are provided between the input and output discs
12
and
13
of the first cavity
11
. The outer peripheral surface of each power roller
15
is in contact with the respective traction surfaces T of the input and output discs
12
and
13
. A pair of power rollers
15
are also provided between the input and output discs
12
and
13
of the second cavity
14
.
Each power roller
15
is rotatably mounted on a trunnion
17
by means of a power roller bearing
16
. The trunnion
17
is rockable around a trunnion shaft
18
. The input discs
12
are rotatable integrally with an input shaft
20
. The input shaft
20
is connected to a drive shaft
21
that is rotated by means of a drive source, such as an engine. The paired output discs
13
are connected to each other by means of a connecting member
22
. An output gear
23
is provided on the connecting member
22
. A loading cam mechanism
25
is located at the back of the input disc
12
of the first cavity
11
. The rotation of the drive shaft
21
is transmitted to the input disc
12
by means of the loading cam mechanism
25
. The rotation of each input disc
12
is transmitted to its corresponding output disc
13
through the power rollers
15
. As the output discs
13
rotate, the output gear
23
rotates.
As shown in
FIG. 7
, each substantially hemispherical power roller
15
has toroidal surfaces
30
that touch the respective traction surfaces T of the input and output discs
12
and
13
and a reference surface
31
that extends at right angles to a central axis Q of the roller
15
. Curvature centers O
L
and O
R
of the toroidal surfaces
30
, which are situated bisymmetrically with respect to the central axis Q in a cross section of the power roller
15
along the central axis Q, are kept at a distance D from the central axis Q and a distance A from the reference surface
31
each. Each toroidal surface
30
is a convex surface with the curvature radius r. The toroidal surfaces
30
touch the respective traction surfaces T of the input and output discs
12
and
13
in a tiltable manner. Each traction surface T is a concave toroidal surface with a curvature radius Rt. In
FIG. 7
, O
D
designates the curvature center of the traction surface T.
If the curvature center O
D
Of the traction surfaces T of the discs
12
and
13
is deviated from the tilting center of each power roller
15
, slipping is caused at contact portions between the power roller
15
and the discs
12
and
13
. This slipping lowers the torque transmission efficiency, and rolling fatigue that is attributable to heating shortens the life of the variator. If the deviation between the respective positions of the curvature center O
D
and the tilting center of the power roller
15
is great, a contact ellipse along which the roller
15
and the discs
12
and
13
are in contact is deviated from the boundaries of the effective traction surfaces. In this case, excessive pressure acts on the boundaries between a part of the contact ellipse and the effective traction surfaces, thereby drastically shortening the rolling fatigue life. Thus, the aforesaid positional deviation also exerts a bad influence upon an appropriate pressure at the rolling contact portions between the power roller
15
and the discs
12
and
13
.
For these reasons, it is to be desired that the power rollers
15
should be rotated synchronously and that the tilting center of each power roller
15
and the curvature center O
D
of the traction surfaces of the discs
12
and
13
should be made coincident while this transmission is driven. To attain this, the curvature radius of the toroidal surfaces
30
of the power roller
15
and the tilting center of the roller
15
must be accurately obtained so that the discs
12
and
13
and the roller
15
can be positioned accurately.
Thereupon, the toroidal surfaces
30
of each power roller
15
are measured. A shape measurer of the straight-moving type and a three-dimensional measurer are known measuring devices for the power rollers
15
. An alternative measuring device is developed and described in Jpn. Pat. Appln. KOKOKU Publication No. 59-44561. This device comprises a rotatable spindle, a micrometer attached to the spindle, a probe to be in contact with a curved surface of a workpiece, etc. In this measuring device, the probe is kept in contact with the workpiece to measure the distance of separation of the workpiece surface from a predetermined circle or circular arc. This measuring device can obtain the curvature radius r of the toroidal surfaces
30
, distance
2
D between the curvature centers O
L
and O
R
, distance A from the reference surface
31
to the curvature centers O
L
and O
R
, deviation of shape from an imaginary toroidal surface obtained by approximation to a representative circle with the curvature radius r, tilting center of each power roller
15
, etc.
Since each toroidal surface
30
has a narrow measurable region, it is subjected to representative circle approximation by computation based on measured values, its radius, curved surface shape error (distance of separation from the predetermined circle or circular arc), etc. are obtained, and the tilting center is obtained from those values. If each toroidal surface
30
that has a slight shape error &Dgr;r, such as deformation or waviness, which is caused when the power roller
15
is worked, is subjected to representative approximation, as shown in
FIG. 8
, therefore, there is a deviation or error between the curvature center O
L
of a normal shape E-F-G and a curvature center O
L
′ of an actual shape E-F-G′. In consequence, an estimated position of the tilting center of the power roller
15
is inevitably subject to an error after the roller
15
and the discs
12
and
13
are assembled.
According to a known curved surface measuring method described in Jpn. Pat. Appln. KOKAI Publication No. 8-285506, the curvature radius and curvature center of a concave surface are measured by means of a plurality of reference spheres with different diameters and a cramping member. However, this method serves only to measure concave surfaces and cannot be applied to the measurement of convex surfaces such as toroidal surfaces of power rollers.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a measuring method for a power roller, capable of easily measuring various data, such as the tilting center of a power roller for a toroidal type continuously variable transmission, with reduced errors.
In order to achieve the above object, according to the present invention, there is provided a measuring method for a power roller for a toroidal type continuously variable transmission, the power roller having a reference surface extending at right angles to the central axis thereof and toroidal surface in contact with traction surfaces of discs, the measuring method comprising: a process for obtaining an intersection between a first circular arc traced around a measuring point on the toroidal surface on one side by the extreme end of a segment with a length equal to the curvature radius of the traction surfaces and a second circular arc traced around a measuring point on the toroidal surface on the other side by the ex
Ikeda Hiroyuki
Kamamura Yuko
Barlow John
Christensen O'Connor Johnson & Kindness PLLC
Lau Tung S
NSK Ltd.
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