U.S. patent number RE39,647 [Application Number 10/233,481] was granted by the patent office on 2007-05-22 for disk for toroidal type continuously variable transmission.
This patent grant is currently assigned to NSK Ltd.. Invention is credited to Nobuo Gotou, Takashi Imanishi, Kiyoshi Okubo, Akira Tsubouchi.
United States Patent |
RE39,647 |
Okubo , et al. |
May 22, 2007 |
Disk for toroidal type continuously variable transmission
Abstract
The disk has a traction surface having a concave-arc-shaped
cross section which is interposed between a small diameter end
portion and a large diameter end portion. In the central portion of
the end face of the disk on the small diameter end portion side,
there is formed a through hole which extends through the disk up to
the large diameter end portion side end face of the disk, while the
inner peripheral surface of the through hole is used as an inside
diameter surface of the disk. Here, when, among metal flows
existing in the disk, a metal flow, which has such a positional
relationship with respect to the surface of the disk that an angle
.theta. formed between a metal flow on the traction surface side
and the tangent of the traction surface is smaller than or equal to
30 degrees, is defined as a "metal flow along the disk surface",
the disk is structured such that the "metal flow along the disk
surface" exists at least in the traction surface.
Inventors: |
Okubo; Kiyoshi (Maebashi,
JP), Tsubouchi; Akira (Maebashi, JP),
Imanishi; Takashi (Fujisawa, JP), Gotou; Nobuo
(Fujisawa, JP) |
Assignee: |
NSK Ltd. (Tokyo,
JP)
|
Family
ID: |
18472408 |
Appl.
No.: |
10/233,481 |
Filed: |
September 4, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
09220763 |
Dec 28, 1998 |
06113514 |
Sep 5, 2000 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Dec 26, 1997 [JP] |
|
|
9-361151 |
|
Current U.S.
Class: |
476/40;
29/893.34; 476/73; 72/360 |
Current CPC
Class: |
B21K
1/28 (20130101); F16H 15/38 (20130101); Y10T
29/49474 (20150115) |
Current International
Class: |
F16H
15/38 (20060101); B21D 22/06 (20060101) |
Field of
Search: |
;476/40,42,73 ;29/893.34
;72/360 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Joyce; William C.
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A disk for use in a toroidal type continuously variable
transmission which comprises an input disk and an output disk each
including a traction surface of a concave-arc-shaped cross section
interposed between a small diameter end portion and a large
diameter end portion and disposed concentrically with each other
with their respective traction surfaces opposed to each other, and
a power roller frictionally engageable with the respective traction
surfaces of the input disk and the output disk to thereby transmit
power, wherein said disk is used as one of the input disk and the
output disk, and said disk comprising metal flows existing along a
part of all surfaces of said disk at least including the traction
surface, wherein said metal flows have such a positional
relationship with respect to the surface of said disk that an angle
.theta. formed between said metal flow existing along the surface
and a tangent of the surface is .Iadd.greater than or equal to 2
degrees and .Iaddend.smaller than or equal to 30 degrees.
2. A disk for use in a toroidal type continuously variable
transmission according to claim 1, wherein said metal flows along
the surface exist along the traction surface in a range of an angle
.alpha. of at least 45 degrees or more in a peripheral direction of
the traction surface, where the angle .alpha. is an angle formed by
the traction surface with respect to a horizontal line passing
through a center of a radius of the traction surface and parallel
to an axis of the disk in a cross section of the disk.
3. A disk for use in a toroidal type continuously variable
transmission according to claim 1, wherein said all surfaces of
said disk has an inside diameter surface, and said metal flows
exist along said inside diameter surface in a distance of h which
is a distance from an end surface on the small diameter end
portion, and if a length of said disk in an axial direction thereof
is expressed as A, the following relationship is achieved:
h.gtoreq.1/3 A.
4. A disk for use in a toroidal type continuously variable
transmission which comprises an input disk and an output disk each
including a traction surface of a concave-arc-shaped cross section
interposed between a small diameter end portion and a large
diameter end portion and disposed concentrically with each other
with their respective traction surfaces opposed to each other, and
a power roller .[.fictionally.]. .Iadd.frictionally
.Iaddend.engageable with the respective traction surfaces of the
input disk and the output disk to thereby transmit power, wherein
said disk is used as one of the input disk and the output disk, and
said disk comprising high-density non metallic inclusions, wherein
a small radius of a contact ellipse between the traction surface
and the power roller is expressed as b when the power roller is set
horizontal so as to be parallel an axis of said disk, and said
high-density nonmetallic inclusions do not exist in an area which
is distant at least by 1.5 b or shorter in a depth direction from
the traction surface.
5. A disk for use in a toroidal type continuously variable
transmission .[.which comprises an input disk and an output disk
each including a traction surface of a concave-arc-shaped cross
section interposed between a small diameter end portion and a large
diameter end portion and disposed concentrically with each other
with their respective traction surfaces opposed to each other, and
a power roller frictionally engageable with the respective traction
surfaces of the input disk and the output disk to thereby transmit
power, wherein said disk is used as one of the input disk and the
output disk, and.]. .Iadd.according to claim 3, wherein
.Iaddend.said disk .[.comprising.]. .Iadd.comprises
.Iaddend.high-density non metallic inclusions and wherein said
high-density non metallic inclusions do not exist in an area in a
range of .Iadd.the distance .Iaddend.h .[.which is a distance from
an end surface on the small diameter end portion, and if a length
of said disk in an axial direction thereof is expressed as A, the
following relationship is achieved: h.ltoreq.1/3 A.]. .
6. A method for manufacturing a disk for use in a toroidal type
continuously variable transmission which comprises an input disk
and an output disk each including a traction surface of a
concave-arc-shaped cross section interposed between a small
diameter end portion and a large diameter end portion and disposed
concentrically with each other with their respective traction
surfaces opposed to each other, and a power roller frictionally
engageable with the respective traction surfaces of the input disk
and the output disk to thereby transmit power, wherein said disk is
used as one of the input disk and the output disk, said
manufacturing method comprising the steps of: preparing a first
cylindrical-shaped material with metal flows existing on cross
sections of said first material and extending along an axial
direction thereof; preparing a first upper mold comprising: a plane
portion perpendicular to an axis of the first material; a circular
projecting portion being projected from the plane portion, having a
diameter smaller than a diameter of the first material and being
concentrical with the first material; and a curve molding surface
connecting the plane portion and the circular projecting portion;
preparing a first lower mold comprising: a plane portion
perpendicular to the axis of the first material; and a recessed
portion formed in the plane portion, being concentrical with the
first material so that the first material being fitted into the
recessed portion; swaging the first material in the axial direction
thereof with the first upper mold and the first lower mold so as to
obtain a second material; preparing a second lower mold comprising:
a plane portion perpendicular to an axis of the second material; a
projecting portion being projected from a center of the plane
portion and being concentrical with the second material; and an
inclined portion located outside of the plane portion and inclined
obliquely and upwardly; preparing a second upper mold comprising: a
plane portion perpendicular to the axis of the second material; and
a first middle mold projected concentrically with the second
material and being formed in a substantially conical shaped;
molding the second material in an axial direction thereof with the
second upper mold and the second lower mold so as to obtain a third
material; preparing a third lower mold comprising: a large diameter
end portion molding surface perpendicular to an axis of the third
material for molding the large diameter end portion of the disk; a
projecting portion being projected from a center of the large
diameter end portion molding surface and being concentrical with
the third material; and an outer mold for regulating a diameter the
large diameter end portion of the disk; preparing a third upper
mold comprising: a small diameter end portion molding surface
perpendicular to the axis of the third material for molding the
small diameter end portion of the disk; a traction surface molding
surface located outside of the small diameter end portion molding
surface for molding the traction surface of the concave-arc-shaped
cross section; and a second middle mold located at a center of the
small diameter end portion molding surface and being concentrical
with the third material for molding a part of an inside diameter
surface of the disk; and molding the third material in an axial
direction thereof with the third upper mold and the third lower
mold so as to obtain a fourth material from which a raw disk to
finish the disk is obtained.
7. A method for manufacturing a disk for use in a toroidal type
continuously variable transmission which comprises an input disk
and an output disk each including a traction surface of a
concave-arc-shaped cross section interposed between a small
diameter end portion and a large diameter end portion and disposed
concentrically with each other with their respective traction
surfaces opposed to each other, and a power roller frictionally
engageable with the respective traction surfaces of the input disk
and the output disk to thereby transmit power, wherein said disk is
used as one of the input disk and the output disk, said
manufacturing method comprising the steps of: preparing a first
cylindrical-shaped material with metal flows existing on cross
sections of said first material and extending along an axial
direction thereof; preparing a first upper mold comprising: a plane
portion perpendicular to an axis of the first material; and a
recessed portion formed in a center of the plane portion, a lower
end portion of the first material being fitted into the recessed
portion; preparing a first upper mold comprising: a flat surface
perpendicular to the axis of the first material; a tapered recessed
portion located outside of the flat surface, the tapered recessed
portion decreasing in diameter in an upward direction and being
concentrical with the recessed portion of the first lower mold;
swaging the first material in the axial direction thereof with the
first upper mold and the first lower mold so as to obtain a second
material; preparing a second lower mold comprising: a large
diameter end portion molding surface perpendicular to an axis of
the second material for molding the large diameter end portion of
the disk; a recessed portion formed at a center of the large
diameter end portion molding surface and being concentrical with
the second material, a lower end portion of the second material
being fitted into the recessed portion; and an outer portion
located outside of the large diameter end portion molding surface,
being concentrical with the second material and having a diameter
for regulating a diameter of the large diameter end portion;
preparing an outer mold comprising: a small diameter end portion
molding surface perpendicular to the axis of the second material
for molding the small diameter end portion of the disk; a traction
surface molding surface located outside of the small diameter end
portion molding surface for molding the traction surface of the
concave-arc-shaped cross section; and a second upper mold located
at a center of the small diameter end portion molding surface and
having a cylindrical shape, the second upper mold having a tapered
recessed portion decreasing in diameter in an upward direction and
having a diameter larger than a diameter of the second material,
and a flat surface formed at a bottom of the tapered recessed
portion and having a diameter larger than an area of nonmetallic
inclusions existing at a center of an upper end of the second
material; molding the second material in an axial direction thereof
with the outer mold and the second lower mold so as to obtain a
third material from which a raw disk to finish the disk is
obtained.
.Iadd.8. A disk for use in a toroidal type continuously variable
transmission which comprises an input disk and an output disk each
including a traction surface of a concave-arc-shaped cross section
interposed between a small diameter end portion and a large
diameter end portion and disposed concentrically with each other
with their respective traction surfaces opposed to each other, and
a power roller rollingly engageable with the respective traction
surfaces of the input disk and the output disk to thereby transmit
power, wherein said disk is used as one of the input disk and the
output disk, and said disk comprising metal flows existing along a
surface of said disk including at least of part of the traction
surface, wherein said metal flows have such a positional
relationship with respect to the surface of said disk that an angle
.theta. formed between each of said metal flows existing along the
surface and a tangent of the surface is greater than or equal to 2
degrees and smaller than or equal to 30 degrees..Iaddend.
.Iadd.9. A disk for use in a toroidal type continuously variable
transmission according to claim 8, wherein said metal flows along
the surface exist along the traction surface in a range of an angle
.alpha. of at least 45 degrees or more in a peripheral direction of
the traction surface, where the angle .alpha. is an angle formed by
the traction surface with respect to a horizontal line passing
through a center of a radius of the traction surface and parallel
to an axis of the disk in a cross section of the disk..Iaddend.
.Iadd.10. A disk for use in a toroidal type continuously variable
transmission according to claim 8, wherein said surface of said
disk further includes an inside diameter surface, and said metal
flows exist along said inside diameter surface in a distance of at
least h which is a distance starting at an end surface of the small
diameter end portion and extending towards an end surface of the
large diameter end portion, and if a length of said disk in a axial
direction thereof is expressed as A, the following relationship is
achieved: h=A/3..Iaddend.
.Iadd.11. A disk for use in a toroidal type continuously variable
transmission which comprises an input disk and an output disk each
including a traction surface of a concave-arc-shaped cross section
interposed between a small diameter end portion and a large
diameter end portion and disposed concentrically with each other
with their respective traction surfaces opposed to each other, and
a power roller rollingly engageable with the respective traction
surfaces of the input disk and the output disk to thereby transmit
power, wherein said disk is used as one of the input disk and the
output disk, and said disk comprising high-density non metallic
inclusions, wherein a small radius of a contact ellipse between the
traction surface and the power roller is expressed as b when the
power roller is set so as to be parallel an axis of said disk, and
said high-density nonmetallic inclusions do not exist in an area
which is distant at least by 1.5 b or shorter in a depth direction
from the traction surface..Iaddend.
.Iadd.12. A disk for use in a toroidal type continuously variable
transmission which comprises an input disk and an output disk each
including a traction surface of a concave-arc-shaped cross section
interposed between a small diameter end portion and a large
diameter end portion and disposed concentrically with each other
with their respective traction surfaces opposed to each other, and
a power roller rollingly engageable with the respective traction
surfaces of the input disk and the output disk to thereby transmit
power, wherein said disk is used as one of the input disk and the
output disk, and said disk comprising metal flows existing along a
surface of said disk including at least of part of the traction
surface, wherein said metal flows have such a positional
relationship with respect to the surface of said disk that an angle
.theta. formed between each of said metal flows existing along the
surface and a tangent of the surface is smaller than or equal to 30
degrees, and wherein said metal flows along the surface exist along
the traction surface at least in a range of an angle .alpha. of at
least 45 degrees or more in a peripheral direction of the traction
surface, where the angle .alpha. is an angle formed by the traction
surface with respect to a horizontal line passing through a center
of a radius of the traction surface and parallel to an axis of the
disk in a cross section of the disk, and said angle .theta. varies
for said metal flows exist along the traction surface at least in
said range of said angle .alpha...Iaddend.
.Iadd.13. A disk for use in a toroidal type continuously variable
transmission according to claim 12, wherein said surface of said
disk further includes an inside diameter surface, and said metal
flows exist along said inside diameter surface in a distance of at
least h which is a distance starting at an end surface of the small
diameter end portion and extending towards an end surface of the
large diameter end portion, and if a length of said disk in a axial
direction thereof is expressed as A, the following relationship is
achieved: h=A/3..Iaddend.
.Iadd.14. A disk for use in a toroidal type continuously variable
transmission according to claim 12, wherein said angle .theta. is
greater than or equal to 2 degrees and smaller than or equal to 30
degrees..Iaddend.
.Iadd.15. A disk for use in a toroidal type continuously variable
transmission according to claim 14, wherein said angle .theta. is
greater than or equal to 5 degrees and smaller than or equal to 20
degrees..Iaddend.
.Iadd.16. A disk for use in a toroidal type continuously variable
transmission which comprises an input disk and an output disk each
including a traction surface of a concave-arc-shaped cross section
interposed between a small diameter end portion and a large
diameter end portion and disposed concentrically with each other
with their respective traction surfaces opposed to each other, and
a power roller rollingly engageable with the respective traction
surfaces of the input disk and the output disk to thereby transmit
power, wherein said disk is used as one of the input disk and the
output disk, and said disk comprising metal flows existing along at
least a part of the traction surface of said disk, wherein said
metal flows have such a positional relationship with respect to the
surface of said disk that an angle .theta. formed between each of
said metal flows existing along the surface and a tangent of the
surface is greater than or equal to 2 degrees and smaller than or
equal to 30 degrees..Iaddend.
.Iadd.17. A disk for use in a toroidal type continuously variable
transmission according to claim 15, wherein said angle .theta. is
greater than or equal to 5 degrees and smaller than or equal to 20
degrees..Iaddend.
.Iadd.18. A disk for use in a toroidal type continuously variable
transmission according to claim 10, wherein said disk comprises
high-density non metallic inclusions, and said high-density non
metallic inclusions do not exist in an area along said inside
diameter surface at least in a range of the distance h..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk for use in a toroidal type
continuously variable transmission which can be used in vehicles,
various kinds of industrial machines, and the like.
2. Description of the Related Art
A toroidal type continuously variable transmission comprises, for
example, as shown in FIG. 15, input and output disks a and b which
are disposed concentrically with each other, and a power roller c
which is interposed between the respective traction surfaces f and
i of the input and output disks a and b1.
In the input disk a, between the small diameter end portion d and
large diameter portion e thereof, there is formed a traction
surface f the cross section of which provides a concave-arc shape
and, in the output disk b1, similarly, between the small diameter
end portion g and large diameter portion h thereof, there is formed
a traction surface i the cross section of which provides a
concave-arc shape. On the side of the input disk a that is distant
from the power roller c, there is concentrically disposed a loading
cam through a plurality of engaging rollers (both of which are not
shown), so that, due to the oil pressure that is supplied between
the loading cam and input disk a, a driving force proportional to a
torque can be applied toward the input disk a.
The power roller c is a device which can be frictionally engaged
with the respective traction surfaces f and i of the input and
output disks a and b1 to thereby transmit power; and, the power
roller c is supported by a trunnion j in such a manner that it can
be inclined in the diameter direction of the input and output disks
a and b1. And, if the trunnion j is operated by a drive mechanism
(not shown) to thereby change the contact positions of the power
roller c in the diameter direction thereof with respect to the
input and output disks a and b1, then a rotation speed ratio
between the input and output disks a and b1, that is, a speed
change ratio can be varied continuously.
By the way, the toroidal type continuously variable transmission is
required to transmit a higher torque and, for this reason, the
input and output disks, a, b1 and power roller c receive very large
repeated bending stress and repeated shearing stress when compared
with ordinary mechanical parts (such as ordinary gears and
bearings); and, in the input and output disks a and b1, especially,
as shown by fine hatchings in FIG. 17, the traction surfaces f, i,
small diameter end portions d, g, and inside diameter surfaces at
the small diameter end portion side d (g) receive large repeated
bending stress and repeated shearing stress. Therefore, when
manufacturing the input and output disks a and b1, it is necessary
to use such highly durable material that can resist such repeated
bending stress and repeated shearing stress.
Conventionally, to manufacture the input and output disks a and b1,
for example, as shown in FIG. 12, cylindrical-shaped material
(carburized steel or the like) having a length equal to the axial
length of the input and output disks a and b1 is shaved or cut to
thereby produce such a final shape as shown in FIG. 16.
However, in the conventional method for manufacturing the input and
output disks a and b1, the yield of the material is poor and it
takes long time to cut or shave the material, with the result that
the production costs of the input and output disks a and b1 are
soaring.
Also, because a metal flow (the flow of structure) k is arranged
along the axial direction of the disk, in the traction surfaces f
and i with which the power roller c is frictionally engaged with a
large pressure, the metal flow k comes to an end and, actually,
does not extend along the traction surfaces f and i. As a result of
this, not only the material is easy to peel off in the portions of
the traction surfaces f and i with which the power roller c is
frictionally engaged, but also an impact crack or a fatigue crack
is easy to occur in the input and output disks a and b starting at
the broken portions of the metal flow k, thereby providing an
obstacle to the long lives of the input and output disks a and
b1.
SUMMARY OF THE INVENTION
The present invention aims at eliminating the drawbacks found in
the disks used in the conventional toroidal type continuously
variable transmission. Accordingly, it is an object of the
invention to provide a disk for use in a toroidal type continuously
variable transmission which not only can reduce the production cost
thereof but also can realize a long life.
By the way, in the center of the cylindrical-shaped material and in
the neighboring portion of such center (that is, in FIGS. 12 and
16, 0.3 D portions: where, D designates the diameter of the
cylindrical-shaped material), nonmetallic inclusions, which have a
great influence on the fatigue breaking strength of the disk, are
high in density (see FIG. 13) and, therefore, it is desired that
the nonmetallic inclusions are not present in the heavy bending
stress areas of the disk (for example, the inside diameter surface
of the small diameter end portions and the like) and in the areas
of the traction surfaces that receive the heaviest shearing
stress.
Referring now to the nonmetallic inclusions, it is known that the
strength of material with respect to repeated bending stress is
greatly influenced by the size of the defect thereof at which the
breaking of the material can start. For example, in a book titled
"Effects of small defects and nonmetallic inclusions" (Written by
Yukitaka Murakami, published by Yokendo Ltd.), there is stated as
follows: that is,
The fatigue limit of material when repeated bending is applied to
the material can be expressed by the following equation;
.sigma..function. ##EQU00001## where K: 1.43 (when a defect is
present on the surface of the material); K: 1.41 (when a defect is
present in such a manner as to be in contact of the material
surface) K: 1.56 (when a defect is present in the interior of the
material) .SIGMA..sub.w: fatigue limit Hv: hardness of material
(relating to the strength of the matrix of the material), and,
(area).sup.1/2: a square root of a projection area obtained when a
defect or a crack is projected in the greatest main stress
direction (an amount representing the dimension of a defect or a
crack).
Therefore, for a mechanical part which is used under severe
conditions such as the toroidal type continuously variable
transmission (that is, under such severe conditions, the mechanical
part receives not only great repeated bending stress but also great
repeated shearing stress), it is desirable to use material in which
a defect providing a starting point of the breaking of the material
has been controlled.
Generally, it is known that the main defect cause of steel
requiring high strength is an oxide-related nonmetallic inclusions.
As a method for controlling such oxide-related nonmetallic
inclusions, there are known the JIS method (JIS-G-0555), the ASTM
method (ASTM-E45) and the like. Also, for bearing material
requiring especially high cleanliness, there are known a method
which, for example, as disclosed in Japanese Patent Publication No.
Hei. 3-294435, melts material again using an electron beam melting
method to float large-sized oxide-related nonmetallic inclusions of
the material to thereby control the cleanliness of the material,
and an extreme statistical method disclosed in the above-cited book
"Effects of small defects and nonmetallic inclusions" (Written by
Yukitaka Murakami, published by Yokendo Ltd.) (that is, a method in
which the greatest diameter of oxide-related nonmetallic inclusions
per unit area S.sub.0 is investigated from several test pieces and,
after then, the thus investigated result is processed
statistically, thereby predicting the greatest diameter of
oxide-related nonmetallic inclusions in an area S required).
For a ball-and-roller bearing, a gear and the like, using the
above-mentioned cleanliness controlling methods, the steel
cleanliness is controlled so that they are able to perform their
expected functions. However, in the disks and power roller which
constitute the toroidal type continuously variable transmission,
the absolute values of the stress applied thereto (in particular,
the contact surface pressure thereof is of the order of 4.0 GPa and
the bending stress thereof is 90 kgf/mm.sup.2) are large when
compared with the ball-and-roller bearing, a gear and the like to
which normal repeated stress is applied. Besides, not only the
repeated bending stress and repeated shearing stress are applied
simultaneously to the disks and power roller but also the volume
thereof receiving such stress is large. For these reasons, in the
toroidal type continuously variable transmission, it is difficult
to obtain sufficient strength using the above-mentioned nonmetallic
inclusions control method. That is, there is desired new means
which can cope with the influence of the nonmetallic
inclusions.
In attaining the above object, according to the invention, there is
provided a disk for use in a toroidal type continuously variable
transmission which comprises input and output disks each including
a traction surface of a concave-arc-shaped cross section interposed
between a small diameter end portion and a large diameter end
portion and disposed concentrically with each other with their
respective traction surfaces opposed to each other, and a power
roller frictionally engageable with the respective traction
surfaces of the input and output disks to thereby transmit power.
The disk is used as one of the input disk and the output disk, and
has metal flows. Under the finished state of the disk after all
necessary finishing operations are executed, the metal flows of the
disk which has the following positional relationship with respect
to the surface of the disk is defined as "metal flows along the
disk surface", that is, an angle .theta. formed between the metal
flow on the surface side and the tangent of the surface is smaller
than or equal to 30 degrees, preferably, smaller than or equal to
20 degrees. The disk is structured such that the metal flows along
the disk surface exist along a part of all surfaces including the
traction surface.
Here, when the angle .theta. of a metal flow with respect to the
tangent of the surface of the disk, especially, the traction
surface exceeds 30 degrees, then the metal flow becomes equivalent
to an end flow (that is, a metal flow which does not extend along
the disk surface), which not only causes the material to peel off
but also incurs the bending fatigue thereof or the like to thereby
cause the disk to break (that is, the crack life of the disk is
shortened).
Also, although it is desirable that the lower limit value of the
angle .theta. may be infinitely approximate to 0, (.theta.=0), as
can be seen from the relationship between a state of the material
after forged (shown by a two-dot chained line) and a state of the
material after completion of working (shown by a solid line) in
FIGS. 5 and 9, for example, in the case of the traction surface 4
and inside diameter surface 2, the margin between them varies, with
the result that the angles of metal flows 6 intersecting with the
traction surface 4 and inside diameter 2 after worked vary from the
angles thereof after forged. For example, if a special attention is
paid to one metal flow 6 after forged, then it is clear that it
does not intersect with above-mentioned respective surfaces at a
constant angle but the intersecting angles of the present metal
flow 6 is changed between a state of the material after forged and
a state of the material after completion of working. And, the
intersecting angle .theta. of the metal flow with respect to the
respective surfaces used in the present application, that is, the
angle .theta. of the metal flow having an influence on the peel-off
and bending fatigue of the material is defined that it does not
mean the state of the material after forged but means the state of
the material after worked, namely, the practically usable state of
the material.
Therefore, it may be sufficient that the metal flow 6 after forged
shows a state which, when the working is completed, is believed to
be able to provide the range of the angle .theta. defined in the
present application by means of a given margin. However, although a
product having the angle .theta. equal to 0 or infinitely
approximate to 0 is the most desirable from the viewpoint of the
performance of the disk, it is also desirable to reduce the margin
as much as possible. Also, in order to avoid the variations in the
margin, or in order to remove the margin at right angles or at
other angles with respect to the surfaces, that is, due to the
working need, if the angle .theta. is obtained extremely severely,
then poor working or similar inconveniences can occur, that is, the
yield of the products can be degraded, with the result that the
manufacturing cost of the disk is caused to rise.
Since the present invention has an object to provide a disk which
not only can improve the performance thereof but also can reduce
the manufacturing cost thereof and a method for manufacturing the
same disk, there is employed .theta.=2-30 degrees, preferably,
.theta.=5-20 degrees. In particular, the lower limit of the angle
.theta. is defined mainly from the viewpoint of the improvement in
both of the performance and yield, whereas the lower limit thereof
is defined, as described above, mainly from the viewpoint of the
improvements in the peel-off and bending fatigue.
The foregoing description is the definition of the metal flow
existing along the disk surface.
(i) Also, the "metal flow along the disk surface", preferably, may
exist not only on the above-mentioned traction surface but also on
the portion of the inside diameter surface of the disk that extends
axially from the small diameter end face of the disk at least in
the range of 1/3 A where the length of the disk in the axial
direction thereof is expressed as A.
In this manner, the "metal flow along the disk surface" is formed
in such a manner as to exist also on the inside diameter surface of
the disk axially from the small diameter end face of the disk at
least in the range of 1/3 A. The reason for this is as follows:
that is, since a peripheral groove for a snap ring as shown in FIG.
17 and the like are formed in the inside diameter surface, the
inside diameter surface is a portion which can be affected severely
by the bending stress or the like; and, therefore, up to the area
of 1/3 A of the disk, it is necessary to dispose the metal flow
along the disk surface in the range of .theta. angle according to
the invention.
(ii) In this case, if the "metal flow existing along the disk
surface" is formed in such a manner as to exist also in the end
face of the disk on the small diameter end portion side thereof,
then the bending fatigue and the concentration of the stress
applied to the peripheral groove can be relieved, thereby being
able to extend the life of the disk still further.
(iii) Further, referring to FIG. 14, preferably, the "metal flow
existing along the disk surface" may exist along the traction
surface in the peripheral direction thereof in the range of an
angle .alpha. of 45 degrees or more, preferably, 48 degrees or
more, where the angle .alpha. is an angle which is formed by the
traction surface with respect to a horizontal line (a line
extending in parallel to the axis of the disk) passing through the
center of radius O.
In this case, the area that receives the severest bending stress
and the like in the traction surface (see the fine hatching
portions shown in FIG. 17) can be covered by the "metal flow
existing along the disk surface", which makes it possible to
prevent the breakage of the disk caused by the bending stress and
the like.
(iv) Further, the toroidal type continuously variable transmission
disk according to the invention is manufactured by forging (which
will be described later) using a mold. In this case, referring to
FIGS. 10 and 15, where the small radius of a contact ellipse
between the traction surface and power roller is expressed as b
when the power roller is set horizontal (that is, parallel to the
axis of the disk), that is, when a speed change ratio is 1:1,
preferably, nonmetallic inclusions having a high density may exist
in an area which is distant by 1.5 b or longer in the depth
direction from the traction surface. Hereupon, "high density" is
defined by the number of nonmetallic inclusions of 10 .mu.m or
larger as shown in FIG. 13. "High density area" is such an area of
0.3 D portion in FIG. 13.
The reason for the above is as follows: that is, the area that
receives the severest shearing stress in the traction surface is an
area which exists within 1.5 b in the depth direction from the
traction surface and, therefore, if no nonmetallic inclusions are
present in this area, then the life of the disk cannot be
influenced at all (see FIG. 11).
(v) Also, as described above, since the portion of the inside
diameter surface that extends axially in the range of 1/3 A from
the end face on the small diameter end portion side is a portion
which can be affected severely by the bending stress or the like
due to the formation of the peripheral groove for the snap ring and
the like, preferably, no nonmetallic inclusions may be present in
1/3 A range portion of the present inside diameter surface.
By the way, FIGS. 18A to 18D and 19A to 19D respectively show
methods respectively for manufacturing a disk for a toroidal type
continuously variable transmission, which are disclosed in Japanese
Patent Publication No. Hei. 9-126289. These disk manufacturing
methods can be used to manufacture only the disk that includes a
metal flow of .theta.=0 degree among the disks according to the
present invention, but they are not able to manufacture the
remaining disks including metal flows of other angles than
.theta.=0 degree. In brief, in the above-disclosed manufacturing
methods, there are found some problems to be solved.
In particular, referring at first to the conventional disk
manufacturing method shown in FIGS. 18A to 18D, cylindrical-shaped
material (carburized steel or the like) n with its metal flows m
extending on the outer peripheral surface of the material along the
axial direction thereof is concentrically held by and between an
upper mold o and a lower mold p, and the material n is then molded
by a given amount (see FIG. 18B). Here, the upper mold o includes a
small diameter end portion molding surface s for molding the small
diameter end portion r of a disk q and a traction surface molding
surface u for molding the traction surface t having a
concave-arc-shaped cross section of the disk q, whereas the lower
mold p includes a large diameter end portion molding surface w for
molding the large diameter end portion v of the disk q. And, the
upper mold o and lower mold p are moved further closely to each
other to thereby pressure forge the material n in the axial
direction thereof several times, so that not only the small
diameter end portion r and large diameter end portion v are
respectively molded in the upper and lower end portions of the
material n respectively, but also the traction surface t is molded
between the small diameter end portion r and large diameter end
portion v.
Next, as shown in FIG. 18C, the upper mold o and lower mold p are
moved most closely to each other to thereby pressure forge the
material n into the final shape of the disk q and, after then, not
only the thus forged and molded final shape is ground or finished
but also the inside diameter surface portion thereof is cut to
thereby produce the inside diameter surface x of the disk q1,
thereby completing the final product of the disk q1 that is shown
in FIG. 18D.
However, in the present conventional manufacturing method, since
the cylindrical-shaped material n is forged up to the final shape
of the disk q1 using one kind of upper and lower molds o and p, the
contact time between the upper and lower molds o, p and the
material n is long, which makes it easy for the upper and lower
molds o and p to be influenced by heat which is generated in the
molding or forging operation. As a result of this, there is raised
an inconvenience that the surface hardness of the upper and lower
molds o and p can be lowered and the lives of the upper and lower
molds o and p can be thereby shortened.
Also, in the final stage of the above molding operation, because
the space between the upper and lower molds o and p is filled with
the material n in a tightly closed state, the thicknesses of the
corner portions of the upper and lower molds o and p can be easily
reduced or burrs are easy to occur in the present corner portions.
Besides, if trying to improve the shape of disk q1 by force, then
an excessive molding load must be applied to the upper and lower
molds o and p, with the result that the upper and lower molds o and
p can be broken.
Further, in the step to be executed after the material is
mold-forged, the forged material is finished by grinding.
Therefore, the grinding margin must be minimized in order to
shorten the working time necessary for the grinding operation as
much as possible. As a result of this, it is necessary to reduce
the degree of abrasion in the upper and lower molds o and p during
the forging operation, so that the lives of the upper and lower
molds o and p can be inconveniently shortened.
In addition, since the upper and lower molds o and p are not
structured such that they hold the cylindrical-shaped material n
within their interior portions, the cylindrical-shaped material n
is easy to shift from the centers of the upper and lower molds o
and p, which results in the worsened working precision.
Thus, in order to eliminate the above-mentioned inconveniences
found in the conventional disk manufacturing method, the present
inventors have developed a conventionally unknown new disk
manufacturing method as follows: that is, this disk manufacturing
method is suitable for manufacturing a disk according to the
invention and, especially, in addition to the disk according to the
invention, the present method is ideal for manufacturing a disk
which includes the before-mentioned respective means (i) and
(iii).
In particular, the present disk manufacturing method comprises: a
first step in which cylindrical-shaped material with its metal
flows existing on the outer peripheral surface thereof and
extending along the axial direction of the material is swaged using
a first forging mold; a second step in which the swaged material is
molded using a second forging mold to thereby form a portion of the
inside diameter surface of the disk in the central portion of the
upper end face of the material, and the shape of the molding
surface of the second forging mold is transferred to the present
inside diameter surface portion; and a third step in which the
material obtained in the second step is molded using a third
forging mold to thereby form a small diameter end portion, a
traction surface and a large diameter end portion, the inside
diameter surface portion molded in the second step is pushed
further to such an extent as allows a residual wall to be left
between the back surface of the large diameter end portion and the
present inside diameter surface portion, and further a burr is
formed on the outside diameter surface of the present large
diameter end portion, wherein, after the burr and residual wall of
the mold forged product obtained through the respective steps are
removed, the mold forged product is ground to thereby form a disk
having its final shape, and the thus ground disk is heat treated
and is finished.
In the present disk manufacturing method, since the mold forging
operation is carried out in three steps using three kinds of molds,
the contact time between the mold and material can be shortened,
which makes it possible to reduce the heat influence on the molds
during the molding operation. As a result of this, the mold surface
hardness can be maintained in a good level to thereby be able to
improve the lives of the molds used.
Also, if the amount of swaging of the cylindrical-shaped material
is increased in the first step, then it is possible to reduce the
molding amounts not only in the second step but also in the third
step in which a high molding load is required in order to obtain a
shape approximate to the final shape of the product. As a result of
this, the working burden of the forging mold in the second and
third steps can be relieved so that the lives of the molds can be
extended.
Further, the increased swaging amount of the cylindrical-shaped
material in the first step can reduce not only the degree of
push-in of the inside diameter surface portion of the forging mold
in the second step but also the degree of further push-in of the
forging mold inside diameter portion molded in the second step.
This makes is possible to enhance greatly the life of the portion
of the material of the forging mold that can be most influenced by
heat.
Still further, since the mold forging operation is carried out in
three steps using three kinds of molds, the flow of the material
during the forging operation can be set freely. This means that a
shape matched to the final shape of the product can be set in the
previous steps (that is, in the first and second steps), thereby
being able to provide a well-balanced mold forged product.
Yet further, because the disk is obtained by grinding the mold
forged product, even if the forged product before ground is a rough
forged product (for example, a hot-forged product), the present
disk manufacturing method is sufficiently able to deal with such
forged product; and, because there is little need to pay attention
to the abrasion of the molds (that is, because, even if the molds
wear to some degree, they can still be used), the costs of the
molds can be reduced in the long run.
In addition, due to the fact that, in the third step, the burr is
produced on the outside diameter surface of the large diameter end
portion at the time when the molding operation is completed,
tightly closed forging is avoided to thereby be able to prevent an
unnecessary molding load from increasing. This makes it possible to
improve the lives of the molds.
By the way, if the height H1 of the central portion of the material
after it is swaged in the first step is set in the range of 80-120%
of the height 2 of the material when the forged product is
completed in the third step, then the enhanced lives of the molds
in the second and third steps can be achieved effectively.
Also, in the above-mentioned first to third steps, by disposing
positioning means which is capable of centering or positioning the
respective forging molds with respect to the material, the material
can be positioned accurately and positively in the molding center
of the forging molds in each step. Thanks to this, the material can
be always molded at the correct position to thereby be able to
provide a high-precision mold forged product. That is, there can be
provided a forged product in which a metal flow existing along the
surface of the disk according to the present invention can be
obtained by a post-machining operation.
Next, description will be given below of the conventional disk
manufacturing method which is shown in FIGS. 19A to 19D. This is a
method in which part of the inside diameter surface x of a disk q2
is molded when the material is forged by molds. That is, at first,
as shown in FIG. 19B, the upper end portion of the
cylindrical-shaped material n is drawn to thereby set the diameter
of the present upper end portion smaller than the diameter of the
small diameter end portion r and, next, the cylindrical-shaped
material n is concentrically held by and between an upper mold y
and a lower mold z and is then molded by a given amount (see FIG.
19C). The upper mold y includes a small diameter end portion
molding surface s for molding the small diameter end portion r of
the disk q2, a traction surface molding surface u for molding a
traction surface t having a concave-arc shaped cross section, and a
projection a1 which is provided in the central portion of the small
diameter end portion molding surface s for molding a portion of the
inside diameter surface x of the disk q2 from the small diameter
end portion r side. On the other hand, the lower mold z includes a
large diameter end portion molding surface w for molding the large
diameter end portion v, and a projection a2 which is provided in
the central portion of the large diameter end portion molding
surface w for molding a portion of the inside diameter surface x of
the disk q2 from the large diameter end portion v side.
Next, the upper and lower molds y and z are moved to approach each
other further and the material n is forged several times in the
axial direction thereof, whereby not only the small diameter end
portion r and large diameter end portion v are molded respectively
in the upper and lower end portions of the material n but also the
traction surface t is molded between the small diameter end portion
r and large diameter end portion v; and, then an operation to mold
the inside diameter surface x by the projections a1 and a2 is
started.
Next, as shown in FIG. 19D, the upper and lower molds y and z are
moved further to approach each other most closely and the material
n is mold-forged into the final shape of the disk q2. In this
forging operation, the inside diameter surface x is held in a state
where the residual wall a3 thereof is still left. After then, the
residual wall a3 of the inside diameter surface x is removed by
cutting or by grinding to thereby complete the inside diameter
surface x and, at the same time, the material n is further ground,
which completes the final product of the disk q2.
In the above-mentioned conventional disk manufacturing method,
there occurs a phenomenon in which the end points of the metal
flows m appearing in the upper and lower ends of the
cylindrical-shaped material n in FIG. 19B are pulled into the
interior of the cylindrical-shaped material n in FIG. 19C; and, as
a result of this, the metal flows exist along the surface shape of
the disk q2 (.theta.=0 degree) ranging from the traction surface t
to the small diameter end portion r and the portion of the inside
diameter surface x that is located on the small diameter end
portion r side thereof.
However, in the step shown in FIG. 19C, it is very difficult to
mold the cylindrical-shaped material n in such a manner that the
end points of the metal flows m are pulled into the interior of the
cylindrical-shaped material n and, therefore, in most cases, the
end points of the metal flows m are left somewhere on the upper and
lower end faces of the material n. As a result of this, it is
difficult to allow the metal flows having the angle of .theta.=0
degree to exist positively along the surface of the disk q2.
Also, there is a high possibility that high-density nonmetallic
inclusions existing in the neighboring portion of the central
portion of the cylindrical-shaped material n can be left in the
portion to which the bending stress is applied severely, that is, a
portion ranging from the small diameter end face of the disk q2
axially to the portion of the inside diameter surface that extends
in the 1/3 A range thereof, which has an ill effect on the life of
the disk.
Thus, in order to eliminate the inconveniences found in the
above-mentioned conventional disk manufacturing method, the present
inventors have developed a conventionally unknown new disk
manufacturing method as follows: that is, this disk manufacturing
method is suitable for manufacturing a disk according to the
invention and, especially, in addition to the disk according to the
invention, the present method is ideal for manufacturing a disk
which includes all of the before-mentioned means (i) to (v).
In particular, the present disk manufacturing method comprises: a
first step in which a cylindrical-shaped material with metal flows
existing on the outer peripheral surface thereof and extending
along the axial direction thereof is swaged using a first forging
mold and, at the same time, the upper end portion of the present
cylindrical-shaped material is drawn; and, a second step in which
the material obtained in the first step is molded using a second
forging mold to thereby form a traction surface and a large
diameter end portion and, at the same time, a portion of an inside
diameter surface is formed in the central portion of the present
material in such a manner that a residual wall is left between the
back surface of the large diameter end portion and the present
inside diameter surface portion. And, the present disk
manufacturing method is characterized in that, when forming a
portion of the inside diameter portion in the central portion of
the material in the second step, the upper end portion of the
present material is restricted by a portion of the second forging
mold to thereby prevent the present upper end portion from
increasing in diameter during the molding operation and, at the
same time, high-density nonmetallic inclusions existing in the
central portion of the present material are pushed into the lower
end side of the material to thereby expand the lower end side of
the material outwardly in the diameter direction thereof; and,
further, after the residual wall of the mold forged product
obtained through the respective steps is removed, the material is
ground to thereby mold the same into the final shape of the disk
and the thus molded disk is heat treated and finished.
In the present disk manufacturing method, it is possible to obtain
a disk (a finished product) simply and positively in which the
"metal flows existing along the disk surface" each having the angle
of .theta.=2-30 degrees exist respectively in the end face of the
disk on the small diameter end portion side thereof, the traction
surface of the disk, the outer peripheral surface of the large
diameter end portion of the disk, and the back surface of the large
diameter end portion thereof.
Also, partly because use of the mold forging operation makes it
possible to reduce the diameter of the cylindrical-shaped material,
partly because, in the second step, the upper end portion of the
present material is restricted by a portion of the second forging
mold to thereby prevent the present upper end portion from
increasing in diameter during the molding operation, and partly
because the high-density nonmetallic inclusions existing in the
central portion of the present material are pushed into the lower
end side of the material to thereby expand the lower end side of
the material outwardly in the diameter direction thereof, there can
be obtained simply and positively a disk in which the high-density
nonmetallic inclusions do not exist in the following areas: that
is, the area of the traction surface portion that receives the
severest shearing stress in the traction surface portion, that is,
the area extending in the depth direction from the traction surface
by a distance less than 1.5 b; and, the area of the disk ranging
axially from the end face of the small-diameter-end-portion side
inside diameter surface portion receiving a severe bending stress
due to formation of the peripheral groove for the snap ring up to
the 1/3 A (A is the axial length of the disk) range portion.
By the way, preferably, in the second step, a burr may be produced
on the outside diameter surface of the large diameter end portion
at the time when the molding is completed. That is, the thus
produced burr can avoid a tightly closed forging operation to
thereby prevent an unnecessary molding load from increasing, which
in turn makes it possible to enhance the lives of the molds.
Also, in the above-mentioned first and second steps, by disposing
positioning means which is capable of centering or positioning the
respective forging molds with respect to the material, the material
can be positioned accurately and positively in the molding center
of the forging molds in each step. Thanks to this, the material can
be always molded at the correct position to thereby be able to
provide a high-precision mold forged product.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is an is an explanatory view of a toroidal type continuously
variable transmission disk which is a first embodiment according to
the invention;
FIG. 2 is an explanatory view of a first step employed in a disk
manufacturing method, in particular, the left half section shows a
state of a disk material before molded, while the right half
section shows a state of a disk material after molded;
FIG. 3 is an explanatory view of a second step employed in the disk
manufacturing method, in particular, the left half section shows a
state of a disk material before molded, while the right half
section shows a state of a disk material after molded;
FIG. 4 is an explanatory view of a third step employed in the disk
manufacturing method, in particular, the left half section shows a
state of a disk material before molded, while the right half
section shows a state of a disk material after molded;
FIG. 5 is an explanatory view of an example of a final step
employed in the disk manufacturing method;
FIG. 6 is an explanatory view of a toroidal type continuously
variable transmission disk which is a second embodiment according
to the invention;
FIG. 7 is an explanatory view of a first step employed in a disk
manufacturing method, in particular, the left half section shows a
state of a disk material before molded, while the right half
section shows a state of a disk material after molded;
FIG. 8 is an explanatory view of a second step employed in the disk
manufacturing method, in particular, the left half section shows a
state of a disk material before molded, while the right half
section shows a state of a disk material after molded;
FIG. 9 is an explanatory view of an example of a final step
employed in the disk manufacturing method,
FIG. 10 is an explanatory view of the existing portion of the
high-density nonmetallic inclusions in a disk;
FIG. 11 is a graphical representation to explain the relationship
between the depth from the surface of a traction surface and the
distribution of shearing stress;
FIG. 12 is an explanatory view of the existing portion of the
high-density nonmetallic inclusions in a cylindrical-shaped
material before molded;
FIG. 13 is a graphical representation to explain the relationship
between the diameter of the cylindrical-shaped material before
molded and the number of nonmetallic inclusions;
FIG. 14 is a view to explain the meanings of .alpha. and
.theta.;
FIG. 15 is a section view to explain a toroidal type continuously
variable transmission;
FIG. 16 is an explanatory view of a conventional disk;
FIG. 17 is an explanatory view of a portion of a disk which
receives large repeated bending stress and repeated shearing
stress;
FIG. 18A-FIG. 18D are explanatory views of a conventional disk
manufacturing method; and
FIG. 19A-FIG. 19E are explanatory views of another conventional
disk manufacturing method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, description will be given below of the preferred embodiments
of a toroidal type continuously variable transmission according to
the invention with reference to the accompanying drawings In
particular, FIG. 1 is an explanatory view of the input and output
disks of a toroidal type continuously variable transmission which
are a first embodiment according to the invention; FIG. 2 is an
explanatory view of a first step employed in a disk manufacturing
method; FIG. 3 is an explanatory view of a second step employed in
the disk manufacturing method; FIG. 4 is an explanatory view of a
third step employed in the disk manufacturing method; FIG. 5 is an
explanatory view of an example of a final step employed in the disk
manufacturing method; FIG. 6 is an explanatory view of the input
and output disks of a toroidal type continuously variable
transmission which are a second embodiment according to the
invention; FIG. 7 is an explanatory view of a first step employed
in a disk manufacturing method; FIG. 8 is an explanatory view of a
second step employed in the disk manufacturing method; and, FIG. 9
is an explanatory view of an example of a final step employed in
the disk manufacturing method.
At first, description will be given below of a disk (a finished
product) which is a first embodiment according to the invention
with reference to FIG. 1. This disk 1 includes a traction surface 4
having a concave-arc-shaped cross section interposed between a
small diameter end portion 2 and a large diameter end portion 3;
and, in the central portion of the end face of the disk ion the
small diameter end portion 2 side thereof, there is formed a
through hole which extends therethrough up to the back surface of
the large diameter end portion 3, while the inner peripheral
surface of the through hole provides an inside diameter surface 5.
Here, with reference to FIGS. land 14, among the metal flows 6 that
exist in the disk 1, a metal flow 6, which has such a positional
relationship with respect to the surface of the disk 1 that the
metal flow 6 on the traction surface 4 side has an angle .theta. of
2-30 degrees, preferably, 5-20 degrees with respect to a tangent P
of the traction surface 4, is defined as a "metal flow 6 along the
disk surface".
In the disk 1, a "metal flow 6 along the disk surface" having the
angle .theta.=2-30 degrees exists in the traction surface 4; a
"metal flow 6 along the disk surface" having the angle .theta.=2-30
degrees exists in the area of the inside diameter surface 5 ranging
from the end face of the inside diameter surface 5 on the small
diameter end portion 2 side thereof to the range of 1/3 A, where
the length of the disk 1 in the axial direction thereof is
expressed as A; and, a "metal flow 6 along the disk surface" having
the angle .theta.=2-30 degrees exists in the outside diameter
surface of the large diameter end portion 3 and in a portion of the
back surface of the present large diameter end portion 3.
Also, a "metal flow 6 along the disk surface" having the angle
.theta.=2-30 degrees exists in the traction surface 4 in such a
manner that, with reference to FIG. 14, it extends along the
peripheral direction of the traction surface 4 in the range of an
angle .alpha. of 45 degrees with respect to a horizontal line
passing through the center of curvature O of the traction surface 4
(that is, a line extending in parallel to the axis of the disk 1).
By the way, a metal flow 6 having the angle .theta. of greater than
30 degrees with respect to the tangent P of the traction surface 4
becomes equivalent to an end flow (a metal flow which does not
exist along the disk surface), so that such metal flow not only
causes the material to peel off but also gives rise to the bending
fatigue to the disk and thus the rupture of the disk (the lowered
crack life).
In the thus structured disk 1, since the "metal flow 6 along the
disk surface" having the angle .theta.=2-30 degrees exists in the
traction surface with which the power roller can be frictionally
engaged with a large pressure, especially when the disk 1 is used
under a low load condition, not only the material in the engaged
portion of the traction surface 4 where it is frictionally engaged
with the power roller can be prevented from peeling off, but also
an impact crack or a fatigue crack is hard to occur in the disk 1
so that the long life of the disk 1 can be realized.
Also, because the "metal flow 6 along the disk surface" having the
angle .theta.=2-30 degrees exists in the area of the inside
diameter surface 5 ranging from the end face of the inside diameter
surface 5 on the small diameter end portion 2 side thereof to the
range of 1/3 A, within the portion of the inside diameter surface 5
that is relatively weak against the bending stress and the like due
to the formation of the peripheral groove for the snap ring, the
metal flow can be prevented from providing an end flow, which makes
it possible to realize the further longer life of the disk 1.
Further, since the "metal flow 6 along the disk surface" having the
angle .theta.=2-30 degrees exists in the traction surface 4 in the
range of an angle .alpha. of 45.degree. C., the area of the
traction surface 4 that receives the severest bending stress and
the like in the traction surface 4 (see the fine hatching portion
in FIG. 17) is covered by the "metal flow 6 along the disk
surface", thereby being able to prevent effectively the breakage of
the disk 1 caused by the bending stress and the like.
Next, description will be given below of a method for manufacturing
the disk 1 with reference to FIGS. 2 to 5.
(First Step)
In FIG. 2, there is shown a first step (a swaging step) employed in
the present disk manufacturing method. In particular, the left half
section of FIG. 2 shows a state before the material is swaged,
whereas the right half section of FIG. 2 shows a state after the
material is swaged. In the first step, a cylindrical material
(carburized steel or the like) W1 with metal flows 6 existing on
the outer peripheral surface of the material and extending along
the axial direction of the material is interposed between an upper
mold 11 and a lower mold 12; and, next, the upper mold 11 is moved
in the axial direction of the cylindrical-shaped material W1 to
swage the present cylindrical-shaped material W1, thereby molding
the same into a material W2 having such a shape as shown in the
right half section of FIG. 2. Here, in the first step, a swaging
ratio is set larger than an ordinary swaging ratio; and, in this
case, if the height H1 of the central portion of the material W2
after swaged is set in the range of 80-120% of the height H2 of a
material W4 which is shown in FIG. 4 and is obtained when the
forging operation is completed, then the lives of forging molds
used in second and third steps (which will be discussed later) can
be enhanced effectively.
In the plane portion 12a of the lower mold 12, there is formed a
recessed portion 13 into which the lower end portion of the
cylindrical-shaped material W1 can be fitted; that is, if the lower
end portion of the cylindrical-shaped material W1 is fitted into
the recessed portion 13, then the cylindrical-shaped material W1
can be aligned with the lower mold 12 with accuracy. Also, in the
central portion of the upper mold 11, there is provided a circular
projecting portion 14 having a diameter smaller than the diameter
of the cylindrical-shaped material W1; and, the circular projecting
portion 14, in the swaging operation, molds the central portion of
the cylindrical-shaped material W1 to thereby spread the diameter
of the material. Further, between the outer peripheral side plane
portion 11a outside of the circular projecting portion 14 of the
upper mold 11 and the circular projecting portion 14, there is
formed a curve molding surface 15 which is curved outwardly in the
diameter direction of the upper mold from the circular projecting
portion 14 in such a manner as to expand gradually and upwardly and
also which continues with the plane portion 11a of the upper mold.
The present curve molding surface 15 is capable of transferring the
curved shape to the swaged material W2.
(Second Step: Intermediate Step)
Now, FIG. 3 shows a second step employed in the present disk
manufacturing method; and, the left half section of FIG. 3 shows a
state of the material before molded, whereas the right half section
thereof shows a state of the material after molded. The function of
the second step is to give the optimum shape to the material in
order that the volume of the material can be distributed properly,
that is, in order to be able to prevent the reduced thickness and
burrs from occurring in a third step. If the shape of the material
formed in the second step is not proper, then, when the material is
molded in the third step, the burrs or the reduced thickness can be
generated on the inside diameter corners (on the upper end side) of
the material, or burrs on the outside diameter surface of the large
diameter end portion of the material (which will be discussed
later) can be reduced in the thickness thereof. Also, another
function of the second step is to give the material such a shape
which allows alignment to be achieved positively between the
material W3 and mold in the third step.
Referring firstly to upper and lower molds 21 and 22 employed in
the second step, in the central portion of the plane portion 21a of
the upper mold 21, there is projectingly disposed a middle mold 25
which has a substantially conical-shaped projection. On the other
hand, the lower mold 22 includes, in the portion thereof that is
located near the outer periphery thereof, an inclined portion 23
which is inclined obliquely upwardly, that is, outwardly in the
diameter direction of the material W2 swaged in the first step;
and, the material W2 can be aligned with the lower mold 22 where
the lower end side outer peripheral edge of the material W2 is in
contact with the inclined portion 23 of the lower mold 22. At the
then time, the lower end face of the material W2 is set in such a
manner as to float slightly from the upper end face of a projecting
portion 24 provided on the central plane portion 22a of the lower
mold 22.
And, in this state, if the upper mold 21 and middle mold 25 are
moved down integrally, then not only the middle mold 25 invades
into the upper end face central portion of the material W2 to
thereby form a recessed portion 5a which is a portion of the inside
diameter surface 5, but also the plane portion 21a of the upper
mold 21 presses against the upper end face of the material W2 to
thereby apply a molding pressure; and, due to this molding
pressure, as shown in the right half section of FIG. 3, the shapes
of the plane portion 22a, inclined portion 23 and projecting
portion 24 of the lower mold 22 are respectively transferred to the
lower end portion of the material W2, so that the material W2 is
molded into the shape of the material W3.
(Third Step)
Now, FIG. 4 shows a third step employed in the present disk
manufacturing method; and, in particular, the left half section of
FIG. 4 shows a state of the material before molded, whereas the
right half section thereof shows a state of the blank after molded.
In the third step, an upper mold 31 includes a small diameter end
portion molding surface 33 for molding the small diameter end
portion 2 of the disk 1, a traction surface molding surface 34 for
molding the traction surface 4 having a concave-arc-shaped cross
section, and a middle mold 35 which is disposed in the central
portion of the small diameter end portion molding surface 33 and is
used to mold a portion of the inside diameter surface 5 from the
small diameter end portion 2 side; and, a lower mold 32 includes a
large diameter end portion molding surface 36 for molding the large
diameter end portion 3, and a projecting portion 37 which is
disposed in the central portion of the large diameter end portion
molding surface 36 concentrically with the middle mold 35. Onto the
projecting portion 37, there can be fitted the recessed portion 26
of the material W3 to which the shape of the projecting portion 24
of the lower mold 22 was transferred in the second step. That is,
if the recessed portion 26 is fitted with the projecting portion
37, then the material W3 can be positioned in the central portion
of the lower mold 32 accurately and positively. Also, on the outer
peripheral portion of the lower mold 32, there is disposed an outer
mold 38; and, the outer mold 38 and lower mold 32 cooperate
together in forming a molding space for forming a recess-shaped
large diameter end portion.
And, in this state, if the upper mold 31 and middle mold 35 are
moved down integrally, then not only the shapes of the small
diameter end portion molding surface 33, traction surface molding
surface 34 and large diameter end portion molding surface 36 are
respectively transferred to the material W3, but also the middle
mold 35 invades into the recessed portion 5a of the material W3 to
thereby mold a recessed portion 5b, that is, a portion of the
inside diameter 5 with a residual wall 39 left between the lower
end side recessed portion and the recessed portion 5b. Thanks to
this, as shown in the right half section of FIG. 4, the material W3
is molded into a material W4 having a shape approximate to the
final shape of the disk 1. By the way, in the third step, at the
time when the molding is completed, there is formed a clearance C
between the upper mold 31 and outer mold 38 to thereby allow a burr
S to be produced on the outside diameter surface of the large
diameter end portion 3. That is, the production of the burr S can
avoid a tightly closed forging operation to thereby prevent an
unnecessary molding load from increasing, which makes it possible
to improve the lives of the molds used.
In the mold forged product W4 obtained in the above manner, in a
post-step, from a state shown by a two-dot chained line in FIG. 5,
the burr S is trimmed and removed by a press and the residual wall
39 of the inside diameter surface 5 is removed by a press; and,
after then, the whole surface of the mold forged product W4 is
ground so that it is molded into the disk 1 having the final shape
shown by a solid line in FIG. 5. And, after the disk 1 is molded in
this manner, the disk 1 is carburized or carbonitrided, that is,
the disk 1 is heat treated and further the heat treated disk 1 is
ground in such a manner as to have a required precision, before the
disk 1 is incorporated into a toroidal type continuously variable
transmission.
In the present disk manufacturing method, since the mold forging
operation is carried out in three steps using three kinds of molds,
the contact time between the molds and material is shortened to
thereby be able to reduce the heat influence on the molds in the
molding operation. As a result of this, the mold surface hardness
can be maintained in a good level, which in turn makes it possible
to improve the lives of the molds.
Also, because the swaging amount of the cylindrical-shaped material
W1 is set larger than the ordinary swaging amount in the first
step, not only in the second step but also in the third step which
requires a high molding load in order to obtain a state close to
the shape of the product, the molding amount can be reduced, with
the result that the working burdens of not only the forging molds
21 and 22 in the second step but also the forging molds 31 and 32
in the third step can be reduced, thereby being able to extend the
lives of these forging molds.
Further, since the swaging amount of the cylindrical-shaped
material W1 is set larger than the ordinary swaging amount in the
first step, the push-in degree of the middle mold 25 in the second
step as well as the push-in degree of the middle mold 35 in the
third step can be reduced, which makes it possible to enhance
greatly the tool lives of the middle molds 25 and 35 which can be
most susceptible to the heat influence of the material.
Still further, due to the fact that the material is positioned at
the molding centers of the molds accurately and positively in the
respective steps including the first to third steps, the material
can be always molded at a correct position to thereby obtain a mold
forged product of high precision.
Yet further, since the mold forging operation is carried out in
three steps using three kinds of molds, the material flow in the
forging operation can be set freely. As a result of this, if the
shape that corresponds with the final shape of the disk is set in
the pre-steps (first and second steps), then a well-balanced mold
forged product can be obtained.
In addition, because the disk 1 is obtained by grinding the mold
forged product W4, even if the forged product before it is ground
is a rough forged product (for example, a hot-forged product and
the like), the present disk manufacturing method is surely able to
deal with such forged product. Also, since it is little necessary
to pay attention to the abrasion of the molds (that is, since the
molds can be used even if they are abraded to some degree), the
costs of the molds can be reduced in the long run.
Next, description will be given below of a disk for a toroidal type
continuously variable transmission, which is a second embodiment
according to the invention.
As shown in FIG. 6, the present disk (finished product) 51 includes
a small diameter end portion 2, a large diameter end portion 3, and
a traction surface 4 which is interposed between the small diameter
end portion 2 and large diameter end portion 3 and has a
concave-arc shaped cross section; and, in the central portion of
the end face of the disk on the small diameter end portion 2 side
thereof, there is formed a through hole which extends through the
disk 51 up to the back surface of the large diameter end portion 3,
while the inner peripheral surface of the through hole is used as
an inside diameter surface 5 of the disk. Here, with reference to
FIGS. 6 and 14, among the metal flows 6 that exist in the disk 51,
a metal flow 6, which has such a positional relationship with
respect to the surface of the disk 51 that the metal flow 6 on the
traction surface 4 side has an angle .theta. of 2-30 degrees,
preferably, 5-20 degrees with respect to a tangent P of the
traction surface 4, is defined as a "metal flow 6 along the disk
surface". In the disk 51, "metal flow 6 along the disk surface"
each having the angle .theta.=2-30 degrees exist continuously in
the end face of the disk 51 on the small diameter end portion 2
side thereof, in the traction surface 4, in the outside diameter
surface of the large diameter end portion 3, and in the back
surface of the large diameter end portion 3; and, a "metal flow 6
along the disk surface" having the angle .theta.=2-30 degrees
exists in the area of the inside diameter surface 5 ranging from
the end face of the inside diameter surface 5 on the small diameter
end portion 2 side thereof to the range of 1/3 A, where the length
of the disk 51 in the axial direction thereof is expressed as
A.
By the way, a metal flow 6 having the angle .theta. of greater than
30 degrees with respect to the tangent P of the traction surface 4
becomes equivalent to an end flow (a metal flow which does not
exist along the disk surface), so that such metal flow not only
causes the material to peel off but also gives rise to the bending
fatigue of the disk and thus the rupture of the disk (the lowered
crack life).
Also, in the present disk 51, with further reference to FIGS. 10
and 15, when the power roller is set horizontal (that is, parallel
to the axis of the disk), that is, where the small radius of the
contact ellipse between the traction surface and power roller is
expressed as b when a speed change ratio is 1:1, a nonmetallic
inclusions 52 of high density exists in an area which is distant by
1.5 b or longer in the depth direction from the traction surface.
Further, no nonmetallic inclusions are present in an area which
exists within the range of 1/3 A (A is the length of the disk 51 in
the axial direction thereof) from the end face of the inside
diameter surface 5 on the small diameter end portion 2 side
thereof.
In the thus structured disk 51, since the "metal flows 6 along the
disk surface" each having the angle .theta.=2-30 degrees exist
continuously in the traction surface 4 with which the power roller
can be frictionally engaged with a large pressure, especially when
the disk 51 is used under a high load condition, not only the
material in the engaged portion of the traction surface 4 where it
is frictionally engaged with the power roller can be prevented from
peeling off, but also an impact crack or a fatigue crack is hard to
occur in the disk 51 so that the long life of the disk 51 can be
realized.
Also, because the "metal flow 6 along the disk surface" having the
angle .theta.=2-30 degrees exists in the area of the inside
diameter surface 5 ranging from the end face of the inside diameter
surface 5 on the small diameter end portion 2 side thereof to the
range of 1/3 A, within the portion of the inside diameter surface 5
that is relatively weak against the bending stress and the like due
to the formation of the peripheral groove for the snap ring, the
metal flow can be prevented from providing an end flow, and, at the
same time, since the "metal flow 6 along the disk surface" having
the angle .theta.=2-30 degrees exists in the end face of the disk
51 on the small diameter end portion 2 side thereof as well, the
bending fatigue as well as the concentration of the stress on the
peripheral groove can be relieved, which makes it possible to
extend the life of the disk 51 further.
Further, the nonmetallic inclusions 52 of high density are absent
not only in the area of the traction surface 4 that extends within
the range of 1.5 b in the depth direction from the traction surface
and receives the severest shearing stress in the traction surface,
but also in the portion of the inside diameter surface 5 that
extends axially within the range of 1/3 A from the small diameter
end portion side end face of the inside diameter surface that can
be affected severely by the bending stress or the like due to the
formation of the peripheral groove for the snap ring and the like.
This can avoid the ill effects of the nonmetallic inclusions on the
life of the disk 51.
Next, description will be given below of a method for manufacturing
the disk 51 with reference to FIGS. 7 to 9.
(First step: Swaging step)
Now, FIG. 7 shows a first step (a swaging step) employed in the
present disk manufacturing method; and, in particular, the left
half section of FIG. 7 shows a state of a material before swaged,
whereas the right half section of FIG. 7 shows a state thereof
after swaged. In the first step, a cylindrical material (carburized
steel or the like) W11 with metal flows 6 existing on the outer
peripheral surface of the material and extending along the axial
direction of the material is interposed between an upper mold 51
and a lower mold 152; and, next, the upper mold 51 is moved in the
axial direction of the cylindrical-shaped material W11 to swage the
present cylindrical-shaped material W11, thereby molding the same
into a material W12 having such a shape as shown in the right half
section of FIG. 7.
In the plane portion 152a of the lower mold 152, there is formed a
recessed portion 53 into which the lower end portion of the
cylindrical-shaped material W11 can be fitted; that is, if the
lower end portion of the cylindrical-shaped material W11 is fitted
into the recessed portion 53, then the cylindrical-shaped material
W11 can be aligned with the lower mold 152 accurately and
positively.
On the other hand, in the central portion of the upper mold 51,
there is formed a tapered recessed portion 51a which decreases in
diameter in the upward direction thereof in such a manner as to be
concentric with the recessed portion 53 of the lower mode 152,
while the bottom surface of the present tapered recessed portion
51a is formed as a flat surface 54. And, the peripheral edge (a
boundary portion between the outer peripheral surface and upper end
face of the cylindrical-shaped material W11) of the upper end face
of the cylindrical-shaped material W11 is in contact with the
slanting portion 55 of the tapered recessed portion 51a. Thanks to
this, when the upper mold 51 is moved down, the upper mold 51
restricts the upper end portion of the cylindrical-shaped material
W11 to thereby be able to not only align the cylindrical-shaped
material W11 with the upper mold 51 accurately and positively but
also transfer the shape of the slanting portion 55.
(Second step)
Now, FIG. 8 shows a second step employed in the present disk
manufacturing method; and, in particular, the left half section of
FIG. 8 shows a state of the material before molded, whereas the
right half section of FIG. 8 shows a state thereof after molded. In
the second step, the material W12 swaged in the first step is
interposed between a lower mold 62 and an upper mold 61 mounted on
an outer mold 65 and the upper mold 61 is moved in the axial
direction of the material W12 to thereby mold the material W12 into
a material W13 which has such a shape approximate to the final
shape of the disk 51 as shown in the right half section of FIG.
8.
The lower mold 62 includes a large diameter end portion molding
surface 63 for molding the large diameter end portion 3 of the disk
51 and, in the central portion of the large diameter end portion
molding surface 63, there is a recessed portion 64 into which a
projecting portion 56 (to which the shape of the recessed portion
53 of the lower mold 52 was transferred in the first step) can be
fitted. That is, if the projecting portion 56 of the material W12
is fitted into the recessed portion 64 of the lower mold 62, then
the material W12 is prevented from playing with respect to the
lower mold 62 so that the alignment of the material W12 with the
lower mold 62 can be achieved accurately and positively.
The outer mold 65 includes a small diameter end portion molding
surface 66 for molding the small diameter end portion 2 of the disk
51 and a traction surface molding surface 67 for molding the
traction surface 4; and, in the central portion of the small
diameter end portion molding surface 66, there is projectingly
provided the upper mold 61 having a cylindrical shape.
In the lower end face of the upper mold 61, there is formed a
shallow tapered recessed portion 68 which reduces gradually in
diameter as it goes upwardly. The bottom surface of the tapered
recessed portion 68 is formed as a flat surface 69 and the diameter
of the flat surface 69 is set larger than the area diameter of
nonmetallic inclusions 52 of high density which exist in the
central portion of the upper end face of the material W12 swaged in
the first step. Also, since the outer peripheral surface of the
upper end portion of the material W12 is in contact with the
slanting portion 70 of the tapered recessed portion 68, the
alignment of the material W12 with the upper mold 61 can be
achieved accurately and positively. Therefore, the inside diameter
D2 of the slanting portion 70 of the tapered recessed portion 68,
in particular, the inside diameter D2 of the contact position of
the slanting portion 70 with the material W12 is larger than the
diameter D1 of the upper end face of the material W12.
And, in this state, if the outer mold 65 and upper mold 61 are
moved down integrally, then not only the shapes of the small
diameter end portion molding surface 66, traction surface molding
surface 67 and large diameter end portion molding surface 63 are
respectively transferred to the material W12, but also the upper
mold 61 invades into the central portion of the material W12 to
thereby mold a recessed portion 5d, that is, a portion of the
inside diameter 5 with a residual wall 71 left between the recessed
portion 64 and the present recessed portion 5d. Thanks to this, as
shown in the right half section of FIG. 8, the material W12 is
molded into a material W13 having a shape approximate to the final
shape of the disk 51. By the way, in the second step, at the time
when the molding is completed, there is formed a clearance C
between the lower mold 62 and outer mold 65 to thereby allow a burr
S to be produced on the outside diameter surface of the large
diameter end portion 3. That is, the production of the burr S can
avoid a tightly closed forging operation to thereby prevent an
unnecessary molding load from increasing, which makes it possible
to improve the lives of the molds used.
Also, when the upper mold 61 invades into the central portion of
the material W12, not only the tapered recessed portion 68 of the
upper mold 61 restricts the upper end portion of the material W12
to thereby prevent the present upper end portion from increasing in
diameter during molding, but also the nonmetallic inclusions 52 of
high density existing in the central portion of the material W12
are pushed into the lower end side of the material W12 to thereby
expand the present lower end side outwardly in the diameter
direction of the material W12.
In the mold forged product W13 obtained in the above manner, in a
post-step, from a state shown by a two-dot chained line in FIG. 9,
the burr S is trimmed and removed by a press and the residual wall
71 of the inside diameter surface 5 is removed by a press; and,
after then, the whole surface of the mold forged product W13 is
ground so that it is molded into the disk 51 having the final shape
shown by a solid line in FIG. 9. And, after the disk 51 is molded
in this manner, the disk 51 is carburized or carbonitrided, that
is, the disk 51 is heat treated and further the heat treated disk
51 is ground in such a manner as to have a required precision,
before the disk 51 is incorporated into a toroidal type
continuously variable transmission.
As can be seen clearly from the above description, in the present
disk manufacturing method, it is possible to obtain the disk 51
(finished product) simply and positively in which "metal flows 6
along the disk surface" each having the angle .theta.=2-30 degrees
exist in the end face of the disk 51 on the small diameter end
portion 2 side thereof, in the traction surface 4, in the outside
diameter surface of the large diameter end portion 3, and in the
back surface of the large diameter end portion 3.
Also, not only since use of the mold forging method can reduce the
diameter of the cylindrical-shaped material W11 in the first step,
but also since, in the second step, the tapered recessed portion 68
of the upper mold 61 restricts the upper end portion of the
material W12 to thereby prevent the present upper end portion from
increasing in diameter during molding and also the nonmetallic
inclusions 52 of high density existing in the central portion of
the material W12 are pushed into the lower end side of the material
W12 to thereby expand the present lower end side outwardly in the
diameter direction of the material W12, there can be obtained the
disk 51 simply and positively in which the nonmetallic inclusions
52 of high density are absent not only in the area of the traction
surface 4 that extends within the range of 1.5 b in the depth
direction from the traction surface and receives the severest
shearing stress in the traction surface, but also in the portion of
the inside diameter surface 5 that extends axially within the range
of 1/3 A from the small diameter end portion side end face of the
inside diameter surface that can be affected severely by the
bending stress or the like due to the formation of the peripheral
groove for the snap ring and the like.
Now, Table 1 shows the results of a disk durability test in which,
when it is assumed that a load is 5 tons and a load position is the
groove bottom of the traction surface, the respective disks are
tested in the durability thereof by changing the angle .alpha. (see
FIG. 14). Here, the angle .alpha. is an angle formed between the
traction surface 4 and a horizontal line passing through the center
of curvature O (that is, a line extending in parallel to the axis
of a disk).
In Table 1, disks No. 1 to No. 6 are respectively embodiments
according to the invention. In particular, in each of the disks No.
1 to No. 4, the "metal flow 6 along the disk surface" having the
angle .theta.=2-30 degrees exists in the traction surface thereof.
Also, among these disks, in the No. 1 and No. 2 disks, the angle is
set such that .alpha.<45 degrees and, in the No. 3 and No. 4
disks, the angle is set such that .alpha..gtoreq.45 degrees. And,
as the No. 5 and No. 6 disks, there were used disks in which the
"metal flows 6 along the disk surface" having the angle
.theta.=2-30 degrees exist continuously in the traction surface
thereof. On the other hand, as the No. 7 and No. 8 disks, there
were used conventional disks which were manufactured by cutting.
Except for the above-mentioned conditions, the same test conditions
(such as size, material, load condition and the like) were set for
all the disks in the present disk durability test.
By the way, the angle was adjusted to .theta.=2-30 degrees by
previously checking a metal flow after forged and by adjusting the
margin. In particular, a metal flow having the angle .theta.
smaller than or equal to the angle .alpha. is assumed as a metal
flow along the disk surface which satisfies the .theta. range
according to the invention; and, a metal flow having the angle
.theta. larger than the angle .alpha. is assumed as a metal flow
which has an angle out of the .theta. range according to the
invention. That is, the disks were observed for breakage under the
above conditions. The forged disks were manufactured by using the
above-mentioned two manufacturing methods properly.
TABLE-US-00001 TABLE 1 No. .alpha.[deg.] Test Result Judgment 1
Embodiment 27 Broken in 123 hrs. .DELTA. 2 Embodiment 37 Broken in
194 hrs. .DELTA. 3 Embodiment 48 Vibrated in 289 hrs. .smallcircle.
Crack in traction surface 4 Embodiment 50 Vibrated in 272 hrs.
.smallcircle. Crack in traction surface 5 Embodiment -- Nothing
wrong in 350 hrs. .circleincircle. 6 Embodiment -- Nothing wrong in
350 hrs. .circleincircle. 7 Conventional -- Broken in 97 hrs. X
Example 8 Conventional -- Broken in 63 hrs. X Example
Load: approx. 5 ton Load position: Groove bottom
As can be seen clearly from Table 1, the disks (No. 1 to No. 6)
according to the invention are greatly enhanced in the durability
of the traction surface thereof when compared with the conventional
disks (No. 7 and No. 8).
Also, among the disks according to the invention, the disks having
.alpha..gtoreq.45 degrees (No. 3 and No. 4) are enhanced in
durability when compared with the disks having .alpha.<45
degrees; and, in the disks (No. 5 and No. 6) in which the "metal
flows 6 along the disk surface" having the angle .theta.=2-30
degrees exist continuously in the traction surface thereof, even
after 350 hours have passed, there was found nothing wrong on the
traction surface thereof, that is, it can well be said that they
have the greatest durability.
By the way, although the present durability test was finished in
350 hrs., in the disks having .theta..apprxeq.0 degree and
.theta..apprxeq.2 degrees, it is believed that nothing wrong can be
found even after the passage of 350 hrs. and thus it can be
expected that these disks are almost equivalent to the disks No. 5
and No. 6 in performance.
Now, Table 2 shows the results of a second disk durability test in
which the depth of a disk ranging from the traction surface thereof
to the area of the high-density nonmetallic inclusions (0.3 D
portion: see FIGS. 10 and 12) is caused to vary. By the way, in
Table 2, b designates the small radius of the contact ellipse
between the traction surface and power roller when a speed change
ratio is 1:1 (see FIG. 15).
In Table 2, disks No. 1 to No. 8 are all embodiments according to
the invention and, for each of the disks, there was used a disk in
which the "metal flow 6 along the disk surface" having the angle
.theta.=2-30 degrees exists in the traction surface thereof. The
present durability test was conducted for all disks under the same
conditions, except that the depth of a disk ranging from the
traction surface thereof to the area of the high-density
nonmetallic inclusions varies in the respective disks.
TABLE-US-00002 TABLE 2 Depth of 0.3 D portion from No. surface Test
Result Judgment 1 0 Traction surface peels .DELTA. off in 170 hrs.
2 0.25 b Traction surface peels .DELTA. off in 173 hrs. 3 0.60 b
Traction surface peels .smallcircle. off in 212 hrs. 4 0.90 b
Traction surface peels .smallcircle. off in 208 hrs. 5 1.25 b
Traction surface peels .smallcircle. off in 239 hrs. 6 1.6 b
Nothing wrong in 250 hrs. .circleincircle. 7 2.55 b Nothing wrong
in 250 hrs. .circleincircle. 8 4.5 b Nothing wrong in 250 hrs.
.circleincircle. b: Small radius of contact ellipse between
traction surface and power roller when speed change ratio is
1:1
As can be clearly understood from Table 2, as the depth of the 0.3
D portion from the traction surface to the high-density nonmetallic
inclusions area increases, the durability of the traction surface
is enhanced and, especially, the depth is larger than or equal to
1.5 b, nothing wrong is found even after 250 hrs. have passed,
which shows that the traction surface having the depth larger than
or equal to 1.5 b is most excellent in durability.
Now, Table 3 shows the results of a third durability test conducted
on disks which are different from each other in the existing area
of the high-density nonmetallic inclusions of the disk inside
diameter surface, in particular, on the durability of the inside
diameter surfaces of the disks on their respective small diameter
end portion sides. Here, A expresses the axial length of the disk
(that is, the length of the disk in the axial direction thereof),
and B expresses the axial length of the inside diameter surface
from the end face of the inside diameter surface on the small
diameter end portion side thereof.
In Table 3, No. 3 to No. 8 test pieces are disks which were
manufactured according to the embodiments of the invention. In the
present durability test, as the embodiments of the invention, there
were used disks in each of which the "metal flow 6 along the disk
surface" having the angle .theta.=2-30 degrees exists in the inside
diameter surface thereof in the range from the small diameter end
portion side end face of the inside diameter surface to the axial
depth of (B/A).times.100% where the axial length of the disk is
expressed as A. Also, as No. 1 and No. 2 disks, there were used
conventional disks which were manufactured by cutting. That is, in
the present durability test, all disks were tested under the same
conditions, except that the disks differ from each other in the
existing area of the high-density nonmetallic inclusions of the
disk inside diameter surface. By the way, in the disks No. 3 to No.
8, the relationship between the nonmetallic inclusions and their
respective existing area (B/A).times.100% were adjusted by
adjusting the margins of the respective disks when they were
manufactured. In this case as well, as the test disks, there were
properly used forged disks which were manufactured according to the
above-mentioned two manufacturing methods.
TABLE-US-00003 TABLE 3 (B/A) .times. Working 100 Judg- No. Method
[%] Test Result ment 1 Conventional Cutting -- Inside diameter
portion X Example on small diameter side was broken in 68 hrs. 2
Conventional Cutting -- Inside diameter portion X Example on small
diameter side was broken in 59 hrs. 3 Embodiment Forging 15 Inside
diameter portion .DELTA. on small diameter side was broken 171 hrs.
4 Embodiment Forging 22 Inside diameter portion .smallcircle. on
small diameter side was broken 211 hrs. 5 Embodiment Forging 34 No
problem after .circleincircle. passage of 250 hrs. 6 Embodiment
Forging 41 No problem after .circleincircle. passage on 250 hrs. 7
Conventional Forging 53 No problem after .circleincircle. Example
passage of 250 hrs. 8 Conventional Forging 51 No problem after
.circleincircle. Example passage of 250 hrs.
As can be seen obviously from Table 3, the disks (No. 3 to No. 8)
according to the invention are greatly improved in the durability
of the inside diameter surface on the small diameter end portion
side thereof when compared with the conventional disks (No. 1 and
No. 2).
Also, out of the disks according to the invention, in the disks in
which the high-density nonmetallic inclusions exist in the inside
diameter surface over the ((B/A).times.100%) area of more than 33%,
nothing wrong was found in the small diameter end portion side
inside diameter surface thereof even after the passage of 250 hrs.,
which shows that these disks are most excellent in durability.
As can be clearly understood from the foregoing description
according to the invention, there can be provided a toroidal type
continuously variable transmission disk which not only permits the
reduction of the production cost thereof but also can extend the
life thereof.
Although the invention has been described in its preferred form
with a certain degree of particularity, it is understood that the
present disclosure of the preferred form can be changed in the
details of construction and in the combination and arrangement of
parts without departing from the spirit and the scope of the
invention as hereinafter claimed.
* * * * *