U.S. patent application number 14/783210 was filed with the patent office on 2016-02-18 for method of manufacturing cvt belt.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Masatake SHIMIZU, Akira TAKASHIMA. Invention is credited to Masatake SHIMIZU, Akira TAKASHIMA.
Application Number | 20160045948 14/783210 |
Document ID | / |
Family ID | 51689069 |
Filed Date | 2016-02-18 |
United States Patent
Application |
20160045948 |
Kind Code |
A1 |
SHIMIZU; Masatake ; et
al. |
February 18, 2016 |
METHOD OF MANUFACTURING CVT BELT
Abstract
In order to restrain the length of an endless metal ring from
dispersing, a method of manufacturing a CVT belt has a first-stage
stretching step of extending a circumferential length of an endless
metal belt by widening distances among rollers. The method includes
a measuring step of measuring a spring-back amount of the endless
metal belt in the first-stage stretching step. The method includes
a calculating step of calculating a predicted spring-back amount
that is predicted from the measured spring-back amount. The method
also includes a second-stage stretching step of stretching the
endless metal belt to process the endless metal belt into a
predetermined circumferential length by further widening the
distances among the rollers based on the predicted spring-back
amount.
Inventors: |
SHIMIZU; Masatake;
(Toyota-shi, JP) ; TAKASHIMA; Akira; (Toyota-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHIMIZU; Masatake
TAKASHIMA; Akira |
Toyota-shi
Toyota-shi |
|
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
51689069 |
Appl. No.: |
14/783210 |
Filed: |
April 8, 2013 |
PCT Filed: |
April 8, 2013 |
PCT NO: |
PCT/JP13/60637 |
371 Date: |
October 8, 2015 |
Current U.S.
Class: |
72/13.5 |
Current CPC
Class: |
F16G 5/16 20130101; B21D
53/14 20130101; F16G 1/20 20130101 |
International
Class: |
B21D 53/14 20060101
B21D053/14 |
Claims
1. A method of manufacturing a CVT belt in which an endless metal
belt is retained from inside by at least two rollers and is
processed to have a predetermined circumferential length by
widening a gap between the rollers, the method comprising: a
first-stage stretching step of stretching the endless metal belt to
extend a circumferential length of the endless metal belt by
widening a distance between the rollers; a spring-back measuring
step of measuring a spring-back amount of the endless metal belt in
the first-stage stretching step; a calculating step of calculating
a predicted spring-back amount from the measured spring-back
amount, the predicted spring-back amount being predicted to result
in a second-stage stretching step; and the second-stage stretching
step of stretching the endless metal belt and processing the
endless metal belt to have the predetermined circumferential length
by further widening the distance between the rollers based on the
predicted spring-back amount.
2. The method of manufacturing the CVT belt according to claim 1,
further comprising: a material length measuring step of measuring a
material circumferential length before stretching the endless metal
belt prior to the first-stage stretching step, wherein the endless
metal belt is stretched, in the first-stage stretching step, to be
processed such that a first-stage stretch length of a stretching
process to which the endless metal belt is subjected becomes
approximately 90 percent of a target process circumferential length
that is obtained by subtracting the material circumferential length
from a target circumferential length of the endless metal belt.
3. The method of manufacturing the CVT belt according to claim 1,
wherein the rollers include at least a first roller and a second
roller, the second roller includes a moving mechanism designed to
move the second roller toward and away from the first roller, and
an urging mechanism designed to urge the second roller in a moving
direction of the second roller, and the spring-back amount of the
endless metal belt is measured with a certain load applied to the
second roller by the urging mechanism, in the spring-back measuring
step.
4. The method of manufacturing the CVT belt according to claim 2,
wherein the rollers include at least a first roller and a second
roller, the second roller includes a moving mechanism designed to
move the second roller toward and away from the first roller, and
an urging mechanism designed to urge the second roller in a moving
direction of the second roller, and the spring-back amount of the
endless metal belt is measured with a certain load applied to the
second roller by the urging mechanism, in the spring-back measuring
step.
Description
TECHNICAL FIELD
[0001] The invention relates to an art of processing a CVT belt to
a predetermined length by subjecting the CVT belt to a stretching
process in consideration of spring-back, in a method of
manufacturing the CVT belt.
BACKGROUND ART
[0002] There are roughly two types of transmissions, namely, a
manual transmission and an automatic transmission as devices for
taking out an output from an engine in accordance with a running
state of a vehicle. The automatic transmission may adopt a system
that is referred to as a continuously variable transmission in
which the speed ratio can be steplessly controlled to the output
side of the engine. In recent years, the number of vehicles
adopting this continuously variable transmission has been
increasing due to technological innovation. The continuously
variable transmission is provided with an input shaft and an output
shaft that are arranged parallel to each other, and an input pulley
and an output pulley that are separately attached to the input
shaft and the output shaft respectively, as is referred to as a
belt-type continuously variable transmission. Each of this input
pulley and this output pulley is configured as a combination of a
fixed sheave and a movable sheave. A V-shaped groove is formed
between the fixed sheave and the movable sheave.
[0003] A laminated hoop that is hung on the input pulley and the
output pulley is configured as a laminated hoop consisting of a
multitude of belt elements and an annular metal body. Each of the
belt elements is formed substantially in the shape of a trapezoid,
and is arranged such that legs of the trapezoid are in contact with
the fixed sheave and the movable sheave respectively. Then, the
laminated hoop is configured to be arranged between a neck portion
extended from an upper base side of the trapezoid and the upper
base.
[0004] In Patent Document 1, there is disclosed an art regarding a
device and a method of adjusting the circumferential length of an
endless metal ring. The endless metal ring (an endless metal belt)
is hung on a plurality of rollers. While the plurality of the
rollers are rotated, the endless metal ring is extensively
stretched to be plastically deformed. In this manner, the device of
adjusting the circumferential length of the endless metal ring
adjusts the circumferential length of the endless metal ring to a
target circumferential length. This device includes circumferential
length measuring means for measuring the circumferential length of
the endless metal ring whose circumferential length has not been
adjusted yet. Besides, the device includes adjusting means for
adjusting the circumferential length of the endless metal ring to
the target circumferential length by enlarging the clearances among
the rollers such that the circumferential length of the endless
metal ring at the time of adjustment of the circumferential length
becomes longer than the target circumferential length by a
contraction amount resulting from elastic deformation of the
endless metal ring whose circumferential length has been adjusted,
based on the measured circumferential length. As a result, the
endless metal ring having a predetermined length can be
obtained.
[0005] In Patent Document 2, there is disclosed an art regarding a
device and a method of manufacturing a metal ring. The method of
manufacturing the metal ring includes a rolling step, a process
circumferential length calculating step, and a stretching step. In
the rolling step, the metal ring is rolled until the board
thickness of the metal ring (an endless metal belt) becomes equal
to a target board thickness. In the process circumferential length
calculating step, a process circumferential length of the metal
ring that is needed to plastically deform the metal ring from a
measured circumferential length to a target circumferential length
is calculated based on a correlation between a ductility factor of
the metal ring and a stretch ratio of the metal ring. In the
stretching step, the metal ring is stretched to the process
circumferential length. By this manufacturing method, the
dispersion of the circumferential length of the processed metal
ring is reduced.
RELATED TECHNICAL DOCUMENTS
Patent Documents
[0006] Patent Document 1: Japanese Patent Application Publication
No. 2004-243358 (JP 2004-243358 A)
[0007] Patent Document 2: Japanese Patent Application Publication
No. 2007-290014 (JP 2007-290014 A)
SUMMARY OF THE INVENTION
Problem to Be Solved by the Invention
[0008] However, when the CVT belt is assembled through the use of
the art disclosed in Patent Document 1 or Patent Document 2, the
following problem is considered to arise.
[0009] The method of manufacturing the CVT belt disclosed in each
of Patent Document 1 and Patent Document 2 is a single process. For
this reason, the endless metal belt used for a CVT belt having a
desired length may not be obtained due to the creation of
spring-back after the process. A plurality of layers of endless
metal belts used for the CVT belt are laminated on one another to
be assembled with the CVT belt. Thus, each of the endless metal
belts that is arranged on an outer peripheral side needs to be
formed longer than a corresponding one of the endless metal belts
that is arranged on an inner peripheral side thereof, by a
thickness of the endless metal belt that is arranged on the inner
peripheral side. If the circumferential lengths of these endless
metal belts on the inner peripheral side and the outer peripheral
side are inappropriate so that there is a gap created therebetween
or that the endless metal belts are too tightly laminated on each
other, an influence may be exerted not only on the assemblage but
also on the life of the CVT belt. Consequently, each of the endless
metal belts is desired to have a circumferential length that is as
close as possible to a target circumferential length.
[0010] Then, despite the fact that each of the endless metal belts
is manufactured even in consideration of the internal stress
thereof, the endless metal belts are inevitably different in board
thickness, board width and material component from one another,
although the differences are slight. As a result, it has been
empirically known that the spring-back amounts are also different
from one another. Therefore, it has been confirmed through an
experiment conducted by the applicant that each actual product does
not turn out to have a desired length even when it is processed to
the desired length while making a prediction through the use of a
spring-back ratio measured in advance as disclosed in Patent
Document 1 and Patent Document 2.
[0011] Thus, in order to solve this problem, it is an object of the
invention to provide a method of manufacturing a CVT belt that
makes it possible to restrain the length of an endless metal belt
from dispersing.
Means for Solving the Problem
[0012] In order to solve the foregoing object, a method of
manufacturing a CVT belt according to one aspect of the invention
has the following features.
[0013] (1) In the method of manufacturing the CVT belt, an endless
metal belt is retained from inside by a plurality of rollers, and
is processed into a predetermined circumferential length by
widening gaps among the rollers. This method of manufacturing the
CVT belt has a first-stage stretching step, a spring-back measuring
step, a calculating step, and a second-stage stretching step. In
the first-stage stretching step, the endless metal belt is
stretched to extend a circumferential length thereof by widening
distances among the rollers. In the spring-back measuring step, a
spring-back amount of the endless metal belt in the first-stage
stretching step is measured. In the calculating step, a predicted
spring-back amount that is predicted to result in the second-stage
stretching step is calculated from the measured spring-back amount.
In the second-stage stretching step, the endless metal belt is
stretched and processed into the predetermined circumferential
length by further widening the distances among the rollers based on
the predicted spring-back amount.
[0014] In accordance with the aforementioned aspect (1), the
spring-back amount of the endless metal belt is measured from a
result of the first-stage stretching step, the predicted
spring-back amount is calculated from the measured value, and the
endless metal belt is formed by the second-stage stretching step.
That is, the spring-back amount of the endless metal belt itself
that is to be processed is measured, and the endless metal belt is
processed into the predetermined length based on this measured
spring-back amount by the second-stage stretching step. Therefore,
even when the material, the board thickness, or the board width
differs, the dispersion of the circumferential length of the
endless metal belt can be minimized.
[0015] (2) In the method of manufacturing the CVT belt described in
(1), it is preferable that a material length measuring step of
measuring a material circumferential length before stretching the
endless metal belt prior to the first-stage stretching step be
provided, and that the endless metal belt be stretched to be
processed such that a first-stage stretch length of a stretching
process to which the endless metal belt is subjected becomes
approximately 90 percent of a target process circumferential length
that is obtained by subtracting the material circumferential length
from a target circumferential length of the endless metal belt, in
the first-stage stretching step.
[0016] In accordance with the aforementioned aspect (2), the
stretching process is carried out such that the first-stage stretch
length of the endless metal belt in the first-stage stretching
step, namely, the length by which the endless metal belt is
extended in the first-stage stretching step becomes approximately
90% of the target process circumferential length that is obtained
by subtracting the material circumferential length from the target
circumferential length. This contributes toward reducing the
dispersion of the circumferential length of the processed endless
metal belt. As a result, it is possible to contribute toward
prolonging the life of the CVT belt.
[0017] (3) In the method of manufacturing the CVT belt described in
(1) or (2), it is preferable that the plurality of the rollers
include at least a first roller and a second roller, that the
second roller have moving means moving toward and away from the
first roller, and urging means for urging the second roller in a
moving direction thereof, and that the spring-back amount of the
endless metal belt be measured with a certain load applied to the
second roller by the urging means, in the spring-back measuring
step.
[0018] In accordance with the aforementioned aspect (3), a certain
load is applied to the second roller by the urging means in
measuring the spring-back amount of the endless metal belt, so the
endless metal belt is stretched on the first roller and the second
roller without slackening. Therefore, the spring-back amount can be
accurately measured. This makes it possible to contribute toward
reducing the dispersion of the circumferential length of the
processed endless metal belt. As a result, it is possible to
contribute toward prolonging the life of the CVT belt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is an illustrative view of an endless metal belt
length adjusting mechanism according to an embodiment of the
invention.
[0020] FIG. 2 is a time chart regarding an operation cycle of an
adjusting device according to the present embodiment of the
invention.
[0021] FIG. 3 is a flowchart regarding the processing of a material
ring according to the present embodiment of the invention.
[0022] FIG. 4 shows a correlation diagram regarding a spring-back
amount according to the present embodiment of the invention.
[0023] FIG. 5 is a perspective view of a CVT belt according to the
present embodiment of the invention.
[0024] FIG. 6 is an exploded perspective view of the CVT belt
according to the present embodiment of the invention.
[0025] FIG. 7 is a graph prepared for comparison, with a
first-stage stretch ratio being 90%.
[0026] FIG. 8 is a graph prepared for comparison, with the
first-stage stretch ratio being 60%.
[0027] FIG. 9 is a graph prepared for comparison, with the
first-stage stretch ratio being 40%.
MODE FOR CARRYING OUT THE INVENTION
[0028] First of all, the embodiment of the invention will be
described using the drawings serving as a reference. Incidentally,
the details of the drawings used herein are simplified for the
convenience of illustration.
[0029] FIG. 1 shows an illustrative view of an endless metal belt
length adjusting mechanism according to the present embodiment of
the invention. FIG. 1 is intended only to illustrate the concept of
an adjusting device 10. Therefore, this drawing is simplified. The
adjusting device 10 includes two rollers, namely, a driving roller
20 and a driven roller 30. A material ring 11 is hung on the
driving roller 20 and the driven roller 30. The material ring 11
means an endless metal belt 110 whose circumferential length has
not been adjusted yet. The driving roller 20 includes a rotational
driving mechanism (not shown), and is configured to rotate with a
predetermined torque. The driven roller 30 is configured to rotate
following the driving roller 20, with the material ring 11 hung on
the driving roller 20 and the driven roller 30. Besides, the driven
roller 30 includes a moving mechanism (not shown) that is designed
to move toward and away from the driving roller 20.
[0030] Besides, an inter-roller distance between the driving roller
20 and the driven roller 30 is measured by a sensor 50 (not shown).
A magnetic measuring instrument is employed as this sensor 50.
However, other types of sensors may also be employed as long as the
inter-roller distance between the driving roller 20 and the driven
roller 30 can be accurately measured. By measuring the inter-roller
distance between the driving roller 20 and the driven roller 30, a
length of the material ring 11 is calculated from a diameter of the
driving roller 20 and a diameter of the driven roller 30. As shown
in FIG. 4, which will be described later, endless metal belts 110
whose circumferential lengths are different from one another
(material rings 11 whose circumferential lengths have been
adjusted) are formed in a superimposed manner on laminated hoops
104. The circumferential lengths of the endless metal belts 110 are
so set as to increase by a thickness of the endless metal belts 110
in the sequence in which the endless metal belts 110 are
superimposed on one another in an outward direction. In the present
embodiment of the invention, each of the laminated hoops 104 is
formed by superimposing a plurality of layers of the endless metal
belts 110 on one another.
[0031] Although not shown in the drawing, the driving roller 20 and
the driven roller 30 are crowned. By rotating the driving roller
20, the material rings 11 also rotate accordingly along an
elliptical trajectory. The material rings 11 are designed not to
lose synchronism due to crowning. Then, the driven roller 30 moves
away from the driving roller 20, so the material rings 11 are
extended to predetermined circumferential lengths respectively.
After the material rings 11 are processed into the endless metal
belts 110 of predetermined lengths, the plurality of the endless
metal belts 110 are laminated on one another to be assembled as the
CVT belt 100.
[0032] Besides, the driven roller 30 is fitted with a weight 35
that serves as urging means for urging the driven roller 30 in a
moving direction thereof. The driven roller 30 is structured such
that a predetermined load is always applied, in the moving
direction of the driven roller 30, to each of the material rings 11
that are hung on the driving roller 20 and the driven roller 30.
That is, the driven roller 30 is structured to be moved by a moving
mechanism (not shown) that is provided separately, while being
always pulled by the weight 35.
[0033] FIG. 2 shows a time chart regarding an operation cycle of
the adjusting device 10. FIG. 3 shows a flowchart regarding the
processing of each of the material rings 11. The time chart shown
in FIG. 2 is expressed as a graph with the axis of ordinate
representing circumferential length and with the axis of abscissa
representing time. The operation of the adjusting device 10 will be
described using FIGS. 2 and 3.
[0034] First of all in S1, a material circumferential length of the
material ring 11 is confirmed. In circumferential length
measurement m1, a material circumferential length L1 is calculated
based on data of the sensor 50 (not shown). Then, a stretching
process of the material ring 11 is carried out in a first-stage
stretching step p1 in S2. In the first-stage stretching step p1,
the material ring 11 is stretched to a first-stage stretch
circumferential length L2. The first-stage stretch circumferential
length L2 is set such that a distance of the stretching process,
namely, a moving distance of the driven roller 30 becomes 90
percent of a target circumferential length L5 from a result
measured through circumferential length measurement m1.
[0035] After having moved by the first-stage stretch
circumferential length L2, the driven roller 30 is retained for a
predetermined time while a certain force is applied to the driven
roller 30 by the moving mechanism thereof in a traveling direction
thereof, in a first retaining step c1. By nulling the driving force
of the driven roller 30 afterward, spring-back occurs in the
material ring 11, and the driven roller 30 moves toward the driving
roller 20 side. In this case, the weight 35 is connected to the
driven roller 30. Therefore, the driven roller 30 stops with a
certain tensile force held applied to the material ring 11, and the
circumferential length of the material ring 11 shortens by a
spring-back amount Sb1 and becomes equal to a first-stage
post-stretch circumferential length L3.
[0036] In S3, a measuring step m3 is carried out to measure the
spring-back amount Sb1 resulting from the first-stage stretching
process. As described previously, the circumferential length of the
material ring 11 is calculated from the distance between the
driving roller 20 and the driven roller 30. Then in S4, a predicted
spring-back amount Sb2 that results when a second-stage stretching
process is carried out is calculated referring to the measured
spring-back amount Sb1. The predicted spring-back amount Sb2 is
calculated based on a correlating equation that is obtained in
advance. FIG. 4 shows a correlation diagram regarding the
spring-back amount Sb1. The axis of ordinate represents the
second-stage spring-back amount, and the axis of abscissa
represents the first-stage spring-back amount. The material ring 11
is stretched in advance to carry out an actual measurement. A
result of this actual measurement is plotted, and the correlating
equation using a determination coefficient is obtained. The
predicted spring-back amount Sb2 is calculated with the aid of this
spring-back amount correlating equation that is obtained in
advance.
[0037] In S5, a second-stage stretch circumferential length L4 is
determined. The second-stage stretch circumferential length L4 is
determined from the predicted spring-back amount Sb2 thus
calculated. Then in S6, the material ring 11 is stretched for the
second time in a second-stage stretching step p2. In the
second-stage stretching step p2, the driven roller 30 is moved
based on the second-stage stretch circumferential length L4
determined in S5. When the driven roller 30 is moved to a position
corresponding to the second-stage stretch circumferential length
L4, the moving mechanism of the driven roller 30 retains the driven
roller 30 for a predetermined time while applying a certain force
to the driven roller 30 in the traveling direction thereof, in a
second retaining step c2. By nulling the driving force of the
driven roller 30 afterward, the driven roller 30 is returned toward
the driving roller 20 side by the predicted spring-back amount Sb2.
Finally in S7, the circumferential length of the material ring 11
is measured.
[0038] In this manner, the processing of the material ring 11 is
ended. FIG. 5 shows a perspective view of the CVT belt 100. FIG. 6
shows an exploded perspective view of the CVT belt 100. The CVT
belt 100 is constituted of the laminated hoops 104 that are formed
by superimposing elements 102 and the plurality of the endless
metal belts 110 on one another. The CVT belt 100 is completed by
inserting the annular laminated hoops 104 into constriction
portions 116 that are provided in the elements 102 at two locations
respectively. In this manner, after each of the material rings 11
is processed into a corresponding one of the endless metal belts
110 having a predetermined length, the plurality of the endless
metal belts 110 are superimposed on one another to form the
laminated hoops 104. The CVT belt 100 is formed by assembling the
laminated hoops 104 with the elements 102.
[0039] The CVT belt 100 is manufactured with the aforementioned
configuration according to the present embodiment of the invention.
Therefore, the operation and effect as will be described
hereinafter are achieved.
[0040] First of all, as the effect of the present embodiment of the
invention, it is possible to mention that the length of each of the
endless metal belts 110 can be restrained from dispersing. In the
method of manufacturing the CVT belt 100 according to the first
embodiment of the invention, each of the endless metal belts 110 is
retained from inside by the plurality of the rollers (the driving
roller 20 and the driven roller 30), and the endless metal belt 110
is processed into a predetermined circumferential length by
widening a gap between the driving roller 20 and the driven roller
30. This manufacturing method has the first-stage stretching step,
the spring-back measuring step, the calculating step, and the
second-stage stretching step p2. In the first-stage stretching
step, the endless metal belt 110 is stretched to extend the
circumferential length thereof by widening the distance between the
driving roller 20 and the driven roller 30. In the spring-back
measuring step, the spring-back amount Sb1 of the endless metal
belt 110 in the first-stage stretching step p1 is measured. In the
calculating step, the predicted spring-back amount Sb2 that is
predicted to result in a subsequent step is calculated from the
measured spring-back amount Sb1. In the second-stage stretching
step p2, the endless metal belt 110 is stretched to be processed
into the predetermined circumferential length by further widening
the distance between the driving roller 20 and the driven roller 30
based on the predicted spring-back amount Sb2.
[0041] The process is carried out in two stages, that is, the
first-stage stretching step p1 and the second-stage stretching step
p2. After the material ring 11 is stretched from the material
circumferential length L1 to the first-stage stretch
circumferential length L2 in the first-stage stretching step p1, it
is measured through spring-back amount measurement m2 that the
material ring 11 has reached the first-stage post-stretch
circumferential length L3 due to spring-back. Using the value of
the spring-back amount Sb1 obtained herein, the predicted
spring-back amount Sb2 is predicted, and the second-stage stretch
circumferential length L4 is determined. Then, the material ring 11
eventually reaches the target circumferential length L5. By thus
acquiring the spring-back amount Sb1 in the first-stage stretching
step p1 and calculating the predicted spring-back amount Sb2 from
the acquired result, the less dispersed target circumferential
length L5 can be obtained.
[0042] This is because the predicted spring-back amount Sb2 can be
calculated in consideration of a dispersion resulting from
individual differences among the material rings 11 or the like
since the spring-back amount Sb1 of each of the material rings 11
is measured through spring-back amount measurement m2. As a result,
the dispersion of the target circumferential length L5 can be
substantially eliminated. By thus restraining the target
circumferential length L5 of each of the endless metal belts 110
from dispersing, the degree of adhesion among the endless metal
belts 110 in the laminated hoops 104 can be enhanced. Consequently,
it is possible to contribute toward prolonging the life of the CVT
belt 100.
[0043] Besides, if it is assumed that the finished material ring 11
has the target circumferential length L5, the material ring 11 is
stretched such that the material circumferential length L1 reaches
a target of 90% of the target circumferential length L5, in the
first-stage stretching step p1. That is, there is established a
relationship: (a first-stage target circumferential length
e1)=0.9.times.(a target circumferential length e2) as shown in FIG.
2. FIG. 7 shows a graph prepared for comparison, with the
first-stage stretch ratio being 90%. FIG. 8 shows a graph prepared
for comparison, with the first-stage stretch ratio being 60%. FIG.
9 shows a graph prepared for comparison, with the first-stage
stretch ratio being 40%. The axis of ordinate represents the
second-stage spring-back amount, and the axis of abscissa
represents the first-stage spring-back amount. It is apparent from
these results that a deviation width x1 shown in FIG. 7, a
deviation width shown in FIG. 8, and a deviation width shown in
FIG. 9 are different from one another. That is, the deviation width
x1 can be narrowed by setting the first-stage stretch ratio as high
as 90%. As a result, it is possible to contribute toward reducing
the dispersion of the target circumferential length L5 into which
each of the material rings 11 is stretched.
[0044] The invention has been described above referring to the
present embodiment thereof. However, this invention should not be
limited to the embodiment thereof, but can also be carried out by
appropriately changing part of the configuration thereof without
departing from the gist of the invention. For example, although a
magnetic measuring instrument is employed to confirm the position
of the driven roller 30 in the present embodiment of the invention,
the invention does not need to be limited thereto as long as there
are other methods enabling accurate measurement of the distance
between the driving roller 20 and the driven roller 30. For
example, the employment of an optical measuring instrument or the
like is not excluded. Besides, the driven roller 30 includes the
weight 35 to apply a certain load to the driven roller 30 in a
traveling direction thereof, but the invention should not be
limited to the configuration in which the weight 35 is employed. An
urging method employing an elastic member or a pneumatic urging
method may also be adopted as long as the driven roller 30 can
thereby be urged with a certain force.
TABLE-US-00001 Description of Reference Symbols 10 ADJUSTING DEVICE
11 MATERIAL RING 20 DRIVING ROLLER 30 DRIVEN ROLLER 35 WEIGHT 50
SENSOR 100 CVT BELT 102 ELEMENT 104 HOOP 110 ENDLESS METAL BELT 116
CONSTRICTION PORTION L1 CIRCUMFERENTIAL LENGTH OF MATERIAL L2
FIRST-STAGE STRETCH CIRCUMFERENTIAL LENGTH L3 FIRST-STAGE
POST-STRETCH CIRCUMFERENTIAL LENGTH L4 SECOND-STAGE STRETCH
CIRCUMFERENTIAL LENGTH L5 TARGET CIRCUMFERENTIAL LENGTH Sb1
SPRING-BACK AMOUNT Sb2 PREDICTED SPRING-BACK AMOUNT e1 FIRST-STAGE
TARGET CIRCUMFERENTIAL LENGTH e2 TARGET CIRCUMFERENTIAL LENGTH
* * * * *