U.S. patent application number 09/886122 was filed with the patent office on 2001-11-29 for toroidal type continuously variable transmission.
This patent application is currently assigned to NSK LTD.. Invention is credited to Fujinami, Makoto, Fukushima, Hiroshi, Goto, Nobuo, Higuchi, Seiji, Imanishi, Takashi, Itoh, Hiroyuki, Kato, Hiroshi, Mitamura, Nobuaki.
Application Number | 20010046921 09/886122 |
Document ID | / |
Family ID | 34577305 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010046921 |
Kind Code |
A1 |
Imanishi, Takashi ; et
al. |
November 29, 2001 |
Toroidal type continuously variable transmission
Abstract
A toroidal type continuously variable transmission, includes: at
least one pair of disks concentrically disposed on each other and
rotatably supported independent from each other; a trunnion
swingable about a pivot shaft; a displacement shaft including a
support shaft portion and a pivot shaft portion that are parallel
and eccentric to each other, the support shaft portion rotatably
supported to the circular hole of the trunnion through a radial
bearing, the pivot shaft portion being protruded from an inner
surface of the middle portion of said trunnion; a power roller
nipped between the concave surfaces of the pair of disks while
being rotatably supported on an outer circumferential surface of
the pivot shaft portion; and a thrust bearings located between the
power roller and the inner surface of the middle portion of the
trunnions. An eccentric quantity of the displacement shaft being a
distance between the support shaft portion and the pivot shaft
portion is within a range from 5 mm to 15 mm.
Inventors: |
Imanishi, Takashi;
(Kanagawa, JP) ; Goto, Nobuo; (Kanagawa, JP)
; Fujinami, Makoto; (Kanagawa, JP) ; Kato,
Hiroshi; (Kanagawa, JP) ; Mitamura, Nobuaki;
(Kanagawa, JP) ; Itoh, Hiroyuki; (Kanagawa,
JP) ; Higuchi, Seiji; (Kanagawa, JP) ;
Fukushima, Hiroshi; (Kanagawa, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN,
MACPEAK & SEAS, PLLC
2100 Pennsylvania Avenue, NW
Washington
DC
20037-3213
US
|
Assignee: |
NSK LTD.
|
Family ID: |
34577305 |
Appl. No.: |
09/886122 |
Filed: |
June 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09886122 |
Jun 22, 2001 |
|
|
|
09344380 |
Jun 25, 1999 |
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Current U.S.
Class: |
476/40 ;
476/42 |
Current CPC
Class: |
F16H 15/38 20130101 |
Class at
Publication: |
476/40 ;
476/42 |
International
Class: |
F16H 015/38 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 1999 |
JP |
P. HEI. 11-3646 |
Claims
What is claimed is:
1. A toroidal type continuously variable transmission, comprising:
at least one pair of disks, each one surface in the axial direction
of which has a concave surface being arcuate in cross section, said
disks concentrically disposed on each other and rotatably supported
independent from each other in a state that said concave surfaces
are opposed to each other; a trunnion swingable about a pivot shaft
situated at a torsional relation with respect to a center axis of
said pair of disks, said trunnion having a circular hole formed in
a direction perpendicular to the axial direction of the pivot shaft
at a middle portion thereof; a displacement shaft including a
support shaft portion and a pivot shaft portion that are parallel
and eccentric to each other, said support shaft portion rotatably
supported to the inner surface of said circular hole through a
radial bearing, said pivot shaft portion being protruded from an
inner surface of the middle portion of said trunnion; a power
roller having an arcuate convex surface on the peripheral surface
thereof, said power roller nipped between said concave surfaces of
said pair of disks while being rotatably supported on an outer
circumferential surface of said pivot shaft portion; and a thrust
bearings located between said power roller and the inner surface of
the middle portion of said trunnions, wherein an eccentric quantity
of said displacement shaft being a distance between said support
shaft portion and said pivot shaft portion is within a range from 5
mm to 15 mm.
2. A toroidal type continuously variable transmission according to
claim 1, wherein said power roller is rotatably supported on the
outer circumferential surface of said pivot shaft portion through a
radial needle roller bearing, and a portion of the outer
circumferential surface of said pivot shaft portion contactable
with the rolling surfaces of needle rollers of said radial needle
roller bearing has a smoothed surface having a surface roughness of
0.2 .mu.mRa or less, and formed by superfinishing.
3. A toroidal type continuously variable transmission according to
claim 1, wherein said displacement shafts are made of steel, the
outer peripheral surface of at least said pivot shaft portion of
said displacement shaft is formed with a carbonitriding layer
containing 0.8 to 1.5 wt % of carbon and 0.05 to 0.5 wt % of
nitrogen, and at least the outer peripheral surface is quenched and
tempered after the carbonitriding process thereof.
4. A toroidal type continuously variable transmission according to
claim 1, wherein said power roller is rotatably supported through a
radial needle roller bearing with a retainer and a plurality of
needle rollers, said needle rollers are crowned at both end
portions in the axial direction thereof, and a crowning quantity of
said needle roller is 0.15 to 0.65% of the outer diameter of the
center portion of said needle roller in the axial direction thereof
at a position closer to the center portion side of said needle
roller from an end face thereof by 5 to 15% of the axial length of
said needle roller.
5. A toroidal type continuously variable transmission, comprising:
at least one pair of disks, each one surface in the axial direction
of which has a concave surface being arcuate in cross section, said
disks concentrically disposed on each other and rotatably supported
independent from each other in a state that said concave surfaces
are opposed to each other; a trunnion swingable about a pivot shaft
situated at a torsional relation with respect to a center axis of
said pair of disks, said trunnion having a circular hole formed in
a direction perpendicular to the axial direction of the pivot shaft
at a middle portion thereof; a displacement shaft including a
support shaft portion and a pivot shaft portion that are parallel
and eccentric to each other, said support shaft portion rotatably
supported to the inner surface of said circular hole through a
radial bearing, said pivot shaft portion being protruded from an
inner surface of the middle portion of said trunnion; a power
roller having an arcuate convex surface on the peripheral surface
thereof, said power roller nipped between said concave surfaces of
said pair of disks while being rotatably supported on an outer
circumferential surface of said pivot shaft portion through a
radial needle roller bearing; and a thrust bearings located between
said power roller and the inner surface of the middle portion of
said trunnions, wherein a portion of the outer circumferential
surface of said pivot shaft portion contactable with the rolling
surfaces of said needle rollers of said radial needle roller
bearing has a smoothed surface having a surface roughness of 0.2
.mu.mRa or less, and formed by superfinishing.
6. A toroidal type continuously variable transmission according to
claim 5, wherein said displacement shafts are made of steel, the
outer peripheral surface of at least said pivot shaft portion of
said displacement shaft is formed with a carbonitriding layer
containing 0.8 to 1.5 wt % of carbon and 0.05 to 0.5 wt % of
nitrogen, and at least the outer peripheral surface is quenched and
tempered after the carbonitriding process thereof.
7. A toroidal type continuously variable transmission according to
claim 5, wherein an eccentric quantity of said displacement shaft
being a distance between said support shaft portion and said pivot
shaft portion is within a range from 5 mm to 15 mm.
8. A toroidal type continuously variable transmission according to
claim 5, wherein said power roller is rotatably supported through a
radial needle roller bearing with a retainer and a plurality of
needle rollers, said needle rollers are crowned at both end
portions in the axial direction thereof, and a crowning quantity of
said needle roller is 0.15 to 0.65% of the outer diameter of the
center portion of said needle roller in the axial direction thereof
at a position closer to the center portion side of said needle
roller from an end face thereof by 5 to 15% of the axial length of
said needle roller.
9. A toroidal type continuously variable transmission, comprising:
at least one pair of disks, each one surface in the axial direction
of which has a concave surface being arcuate in cross section, said
disks concentrically disposed on each other and rotatably supported
independent from each other in a state that said concave surfaces
are opposed to each other; a trunnion swingable about a pivot shaft
situated at a torsional relation with respect to a center axis of
said pair of disks, said trunnion having a circular hole formed in
a direction perpendicular to the axial direction of the pivot shaft
at a middle portion thereof; a displacement shaft including a
support shaft portion and a pivot shaft portion that are parallel
and eccentric to each other, said support shaft portion rotatably
supported to the inner surface of said circular hole through a
radial bearing, said pivot shaft portion being protruded from an
inner surface of the middle portion of said trunnion; a power
roller having an arcuate convex surface on the peripheral surface
thereof, said power roller nipped between said concave surfaces of
said pair of disks while being rotatably supported on an outer
circumferential surface of said pivot shaft portion through a
radial needle roller bearing; and a thrust bearings located between
said power roller and the inner surface of the middle portion of
said trunnions, wherein said displacement shafts are made of steel,
the outer peripheral surface of at least said pivot shaft portion
of said displacement shaft is formed with a carbonitriding layer
containing 0.8 to 1.5 wt % of carbon and 0.05 to 0.5 wt % of
nitrogen, and at least the outer peripheral surface is quenched and
tempered after the carbonitriding process thereof.
10. A toroidal type continuously variable transmission according to
claim 9, wherein a portion of the outer circumferential surface of
said pivot shaft portion contactable with the rolling surfaces of
needle rollers of said radial needle roller bearing has a smoothed
surface having a surface roughness of 0.2 .mu.mRa or less, and
formed by superfinishing.
11. A toroidal type continuously variable transmission according to
claim 9, wherein an eccentric quantity of said displacement shaft
being a distance between said support shaft portion and said pivot
shaft portion is within a range from 5 mm to 15 mm.
12. A toroidal type continuously variable transmission according to
claim 9, wherein said radial needle roller bearing includes a
retainer and a plurality of needle rollers, said needle rollers are
crowned at both end portions in the axial direction thereof, and a
crowning quantity of said needle roller is 0.15 to 0.65% of the
outer diameter of the center portion of said needle roller in the
axial direction thereof at a position closer to the center portion
side of said needle roller from an end face thereof by 5 to 15% of
the axial length of said needle roller.
13. A toroidal type continuously variable transmission, comprising:
first and second disks concentrically disposed on each other and
rotatably supported about a mutual central axis, said first and
second disks respectively having arcuate concave surfaces, which
are opposed to each other; trunnions swingable about a pivot shaft
situated at a torsional relation which does not intersect with the
central axis and is a position perpendicular to the central axis; a
displacement shaft disposed on a middle portion of said trunnion
and supported in such a manner as to project from an inner surface
of said trunnion; and a power roller disposed on an inner surface
side of said trunnion and nipped between said first and second
disks in such a manner as to be rotatably supported on the
periphery of said displacement shaft through a radial bearing; the
peripheral surface of said power roller having an arcuate convex
surface contactable with said concave surfaces of said first and
second disks, wherein said radial bearing is a radial needle roller
bearing with a retainer and a plurality of needle rollers, said
needle rollers are crowned at both end portions in the axial
direction thereof, and a crowning quantity of said needle roller is
0.15 to 0.65% of the outer diameter of the center portion of said
needle roller in the axial direction thereof at a position closer
to the center portion side of said needle roller from an end face
thereof by 5 to 15% of the axial length of said needle roller.
14. A toroidal type continuously variable transmission according to
claim 13, wherein said displacement shaft includes a support shaft
portion and a pivot shaft portion being arranged to be parallel to
each other and eccentric to each other, and an eccentric quantity
of each said displacement shaft being a distance between said
support shaft portion and said pivot shaft portion is within a
range from 5 mm to 15 mm.
15. A toroidal type continuously variable transmission according to
claim 14, wherein said power rollers are rotatably supported around
the periphery of said pivot shaft portion through said radial
needle roller bearing, and wherein a portion of the outer
circumferential surface of said pivot shaft portion contactable
with the rolling surfaces of said needle rollers of said radial
needle roller bearing has a smoothed surface having a surface
roughness of 0.2 .mu.mRa or less, and formed by superfinishing.
16. A toroidal type continuously variable transmission according to
claim 14, wherein said power rollers are rotatably supported around
the periphery of said pivot shaft portion through said radial
needle roller bearing, said displacement shafts are made of steel,
the outer peripheral surface of at least said pivot shaft portion
of said displacement shaft is formed with a carbonitriding layer
containing 0.8 to 1.5 wt % of carbon and 0.05 to 0.5 wt % of
nitrogen, and at least the outer peripheral surface is quenched and
tempered after the carbonitriding process thereof.
17. A toroidal type continuously variable transmission according to
claim 1, wherein a maximum diameter each of said disks is 80 to 200
mm, a maximum diameter of said power roller is 50 to 120 mm, a
diameter of said support shaft portion is 10 to 40 mm, a diameter
of said pivot shaft portion is 10 to 40 mm, a distance in the axial
direction of said displacement shaft between a joint portion of
said support shaft portion and said pivot shaft portion, and an
intermediate position of said radial needle roller bearing is 10 to
40 mm, and torque to be input into the toroidal type continuously
variable transmission is 3 to 70 kg.multidot.m.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a toroidal type
continuously variable transmission which may be used as a
transmission unit constituting a vehicular transmission or may be
assembled as transmissions into various types of industrial
machines.
[0003] 2. Description of the Related Art
[0004] Study on the application of a toroidal type continuously
variable transmission (as shown in FIGS. 1 and 2 ) into a vehicular
transmission progresses. An example of the toroidal type
continuously variable transmission is disclosed in Japanese Utility
Model Unexamined Publication Sho.62-71465.
[0005] In a conventional toroidal type continuously variable
transmission shown in FIGS. 1 and 2, an input-side disk 2 is
concentrically supported to an input shaft 1. An output shaft 3 is
also disposed concentrically with an input shaft 1. An output-side
disk 4 is fastened to the inner end of the output shaft 3. In the
inside of a casing in which the toroidal type continuously variable
transmission is stored, there are located a pair of trunnions 6, 6
at an intermediate position of the both disks 2, 4 along the axial
direction thereof. The trunnions 6, 6 are swingable about their
respective pivot shafts 5, 5 respectively disposed at position
along an imaginary plane that is perpendicular to an imaginary line
connecting the respective axes of the input and output shafts 1 and
3, and distanced from the intersection of the imaginary plane and
imaginary line, as shown in FIG. 1. This physical relation is
hereinafter referred to as "torsional relation".
[0006] Each of the trunnions 6, 6 located distant from the center
axis of the input-side disk 2 and the output-side disk 4 is
concentrically provided with each of the pivot shafts 5, 5 on the
outer side surfaces of the two end portions thereof. The base end
portions of displacement shafts 7, 7 are respectively supported in
the central portions of the trunnions 6, 6 and if the trunnions 6,
6 are swung about the pivot shafts 5, 5 respectively, the
inclination angles of the displacement shafts 7, 7 can be adjusted
freely. On the peripheries of the two displacement shafts 7, 7
supported on the two trunnions 6, 6, there are rotatably supported
a plurality of power rollers 8, 8 respectively. The power rollers
8, 8 are respectively interposed between the inner surfaces 2a and
4a, opposed to each other, of the input-side disk 2 and the
output-side disk 4. The inner surfaces 2a and 4a are formed as
concave surfaces which can be obtained by rotating an arc having
the pivot shaft 5 as a center thereof. And, the peripheral surfaces
8a, 8a of the power rollers 8, 8, which are formed as
spherical-shaped convex surfaces are respectively in contact with
the inner surfaces 2a and 4a.
[0007] Between the input shaft 1 and input-side disk 2, there is
interposed a pressure device 9 of a loading cam type, while the
input-side disk 2 is elastically pressed toward the output-side
disk 4 by the pressure device 9. The pressure device 9 is composed
of a cam plate 10 rotatable together with the input shaft 1, and a
plurality of (for example, four pieces of) rollers 12, 12 which are
respectively rollably held by a retainer 11.
[0008] On one side surface (in FIGS. 1 and 2, on the left side
surface) of the cam plate 10, there is formed a drive-side cam face
13 being a curved surface which extends over the circumferential
direction of the cam plate 10. And, on the outer surface (in FIGS.
1 and 2, on the right side surface) of the input-side disk 2, there
is also formed a driven-side cam face 14 having a similar shape.
The plurality of rollers 12, 12 are each rotatably supported about
their respective shafts which extend in the radial direction with
respect to the center of the input shaft 1.
[0009] The above-structured toroidal type continuously variable
transmission operates in the following way. When the cam plate 10
is rotated with the rotation of the input shaft 1, the drive-side
cam face 13 presses the plurality of rollers 12, 12 against the
driven-side cam face 14 formed on the outer surface of the
input-side disk 2. As a result of this, the input-side disk 2 is
pressed against the plurality of power rollers 8, 8 and, at the
same time the drive-side and driven-side cam faces 13 and 14 are
pressed against the plurality of rollers 12, 12, so that the
input-side disk 2 is rotated. The rotation of the input-side disk 2
is transmitted through the plurality of power rollers 8, 8 to the
output-side disk 4, so that the output shaft 3 fastened to the
output-side disk 4 is rotated.
[0010] Next, a description will be given of a case of changing of a
rotational speed ratio (speed change ratio) of the input and output
shafts 1 and 3. At first, when decelerating the rotational speed
between the input shaft 1 and the output shaft 3, the trunnions 6,
6 are swung about the pivot shafts 5, 5 in a predetermined
direction, respectively. Then, the displacement shafts 7, 7 are
respectively inclined so that the peripheral surfaces 8a, 8a of the
power rollers 8, 8, as shown in FIG. 1, can be respectively
contacted with a near-center portion on the inner surface 2a of the
input-side disk 2 and with a near-outer-periphery portion on the
inner surface 4a of the output-side disk 4.
[0011] Also, on the other hand, when accelerating the rotational
speed between the input and output shafts 1 and 3, the trunnions 6,
6 are respectively swung about the pivot shafts 5, 5 in the
opposite direction to the predetermined direction. Then, the
displacement shafts 7, 7 are respectively inclined so that the
peripheral surfaces 8a, 8a of the power rollers 8, 8, as shown in
FIG. 2, can be respectively contacted with a near-outer-periphery
portion on the inner surface 2a of the input-side disk 2 and a
near-center portion on the inner surface 4a of the output-side disk
4. When the inclination angles of the displacement shafts 7, 7 are
set in the middle of the inclination angles shown in FIGS. 1 and 2,
then there can be at obtained an intermediate transmission ratio
between the input and output shafts 1 and 3.
[0012] A specific example of the toroidal type continuously
variable transmission is shown in FIGS. 3 and 4. This transmission
is disclosed in Japanese Utility Model Unexamined Publication No.
Hei. 1-173552, recorded in a microfilm. As shown, an input-side
disk 2 and an output-side disk 4 are rotatably supported around a
cylindrical input shaft 15 with the aid of needle roller bearings
16, 16 inserted therebetween. A cam plate 10 is spline engaged with
the outer peripheral surface of the end portion (in FIG. 3, the
left end portion) of the input shaft 15 and is prevented, by a
flange portion 17, from moving in a direction away from the
input-side disk 2. Further the cam plate 10 and rollers 12, 12
constitute a pressure device 9 of a loading cam type. The pressure
device 9, in accordance with the rotation of the input shaft 15,
rotates the input-side disk 2 while it is pressing against the
input-side disk 2 toward the output-side disk 4. An output gear 18
is coupled to the output-side disk 4 by means of keys 19, 19 so
that the output-side disk 4 and the output gear 18 are
synchronously rotated.
[0013] A pair of trunnions 6, 6, in particular, their respective
two end portions thereof are supported on a pair of support plates
20, 20 in such a manner that they can be swung and can be displaced
in the axial direction (in FIG. 3, in the front and back direction,
or in FIG. 4, the horizontal directions) thereof. And, two
displacement shafts 7, 7 are respectively supported in circular
holes 21, 21 which are respectively formed in the middle portions
of the pair of trunnions 6, 6. The two displacement shafts 7, 7
respectively include support shaft portions 22, 22 and pivot shaft
portions 23, 23 which are extend in parallel to each other but are
eccentric to each other. The support shaft portions 22, 22 are
rotatably supported inside the circular holes 21, 21 through radial
needle roller bearings 24, 24, respectively. Also, power rollers 8,
8 are rotatably supported in the peripheries of the pivotal support
portions 23, 23 through another radial needle roller bearings 25,
25, respectively.
[0014] As shown in FIGS. 5 and 6 in detail, each of the radial
needle roller bearings 25, 25 is constructed with a plurality of
needle rollers 45, 45 and cage-like window type retainers 53 for
holding rollably those needle rollers 45, 45. In this case, the
outer circumferential surface of the pivot shaft portion 23 serves
as a cylindrical inner raceway 54 of the radial needle roller
bearing 25, and the inner circumferential surface of the power
roller 8 serves as the outer raceway 55 of the radial needle roller
bearing 25.
[0015] The pair of the displacement shafts 7, 7 are respectively
disposed on 180 deg.-separated opposite sides with respect to the
input shaft 15. Also, a direction, in which the pivot shaft
portions 23, 23 of the displacement shafts 7, 7 are eccentric to
the support shaft portions 22, 22, is set as the same direction
with respect to the rotation direction of the input- and
output-side disks 2 and 4. Also, the eccentric direction is set
almost at right angles to the direction in which the input shaft 15
is disposed. Therefore, the power rollers 8, 8 are supported in
such a manner that they can be somewhat displaced in the disposing
direction of the input shaft 15. As a result, even when, due to
accumulation of the dimensional tolerance of the components parts,
the input- and output-side disks 2 and 4 are displaced from the
trunnions 6, 6 in the axial direction of the input shaft 15 (in
FIG. 3, the horizontal direction, or in FIG. 4, front-back
direction) to some degree, adequate contact of the inner surface 2a
and the inner surface 4a of the disks 2 and 4 with the peripheral
surfaces 8a of the power rollers 8 is secured. Further, when the
component parts are deformed by large loads imparted thereto in a
transmission state of the rotational force, and as a result of the
deformation, even if the power rollers 8, 8 are likely to displace
in the axial direction of the input shaft 15, this displacement of
the power rollers 8, 8 may be absorbed without applying excessive
force to the component parts.
[0016] Also, between the outer surfaces of the power rollers 8, 8
and the inner surfaces of the middle portions of the trunnions 6,
6, there are interposed thrust ball bearings 26, 26 and thrust
needle roller bearings 27 are disposed in this order from the outer
surfaces of the power rollers 8. The thrust ball bearing 26, 26 are
respectively used to allow the power rollers 8, 8 to rotate while
supporting the load applied to the power rollers 8, 8 in the thrust
direction. The thrust ball bearings 26, 26 are respectively
composed of a plurality of balls 56, 56 annular-shaped retainers
57, 57 for rollably holding the balls 56, 56 therein, and
annular-shaped outer races 28, 28. The inner raceways of the thrust
ball bearings 26, 26 are respectively formed on the outer surfaces
of the power rollers 8, 8, whereas the outer raceways thereof are
respectively formed on the inner surfaces of the outer races 28,
28.
[0017] Each of the thrust needle roller bearings 27, 27 is composed
of a race 58, a retainer 59 and needle rollers 60, 60. The race 58
and retainer 59 are combined together in such a manner that they
can be somewhat displaced in the rotation direction. The thrust
needle roller bearings 27, 27 interpose the races 58, 58 between
the inner surfaces of the trunnions 6, 6 and the outer surfaces of
the outer races 28, 28 in a state that the races 58, 58 are
contacted with the inner surfaces of the trunnions 6, 6. The thrust
needle roller bearings 27, 27 allow the pivot shaft portions 23, 23
and the races 28, 28 to rotate about the support shaft portions 22,
22 while receiving a thrust load applied to the outer races 28,
28.
[0018] Drive rods 29, 29 are respectively coupled to one end
portions (left end in FIG. 4) of the trunnions 6, 6. And, drive
pistons 30, 30 are respectively firmly coupled to the outer surface
of the middle position of the drive rods 29, 29. The drive pistons
30, 30 are oil-tightly disposed within drive cylinders 31, 31. An
amount of displacement of each of the trunnions 6, 6, which is
caused by supplying oil into and discharging it from each of the
drive cylinders 31, 31 is detected by a precess cam (not shown)
fixed to the other end portions of the trunnions 6, 6.
[0019] A lubricating-oil supplying device as shown in FIG. 7 is
provided in the insides of the drive rod 29, the trunnion 6 and the
displacement shaft 7. The lubricating-oil supplying device feeds a
sufficient amount of lubricating oil into the bearings 25 and 26 in
order to secure the durability of the radial needle roller bearing
25 and the thrust ball bearing 26. The lubricating-oil supplying
device is composed of a feeding-side oil-supply passage 42 provided
in the insides of the drive rod 29 and the trunnion 6,
oil-feedholes 43, 43 formed in the outer race 28 of the thrust ball
bearing 26, and a receiving-side oil-supply passage 44 provided in
the inside of the pivot shaft portion 23, which constitutes the
first half of the displacement shaft 7. When the toroidal type
continuously variable transmission is in operation, the
lubricating-oil supplying device feeds lubricating oil into the
feeding-side oil-supply passage 42 with the aid of a pump (not
shown) assembled into the transmission, to thereby lubricate the
bearings 25 and 26.
[0020] In the thus constructed toroidal type continuously variable
transmission, a rotation of the input shaft 15 is transmitted to
the input-side disk 2 through the pressure device 9. A rotation of
the input-side disk 2 is transmitted through the pair of power
rollers 8, 8 to the output-side disk 4, and a rotation of the
output-side disk 4 is output from the output gear 18. To change the
rotational speed change ratio between the input shaft 15 and the
output gear 18, the pair of drive pistons 30, 30 are displaced in
the opposite directions to each other. In accordance with the
displacement of the drive pistons 30, 30, the pair of trunnions 6,
6 displace in the opposite directions, so that the lower power
roller 8 disposed in the downside of FIG. 4 displaces to the right,
while at the same time the upper power roller 8 disposed in the
upside of FIG. 4 displaces to the left. Accordingly, the direction
of forces in the tangential direction which act on contact
positions where the peripheral surfaces 8a, 8a of the power rollers
8, 8 are in contact with the inner surface 2a of the input-side
disk 2 and the inner surface 4a of the output-side disk 4, is
changed. In accordance with the changing of the direction of the
forces, the trunnions 6, 6 are swung about the pivot shafts 5, 5
which are supported by the support plates 20, 20 in the opposite
directions to each other. As a result, as shown in FIGS. 1 and 2,
the contact positions where the peripheral surfaces 8a, 8a of the
power rollers 8, 8 are in contact with the inner surface 2a and the
inner surface 4a of the input- and output-side disks 2 and 4 are
shifted, whereby the rotational speed change ratio between the
input shaft 15 and the output gear 18 is changed. The control of
the rotational speed change ratio to a desired value is conducted
in a manner that the amounts of the displacements of the trunnions
6, 6 in the axial directions of the pivot shafts 5, 5, which are
detected by the precess cam, is adjusted by adjusting the amounts
of the pressurized oil charged to and discharged from the drive
cylinders 31, 31.
[0021] When the rotational force is transmitted between the input
shaft 15 and the output gear 18, based on the elastic deformation
of the component parts, the power rollers 8, 8 are displaced in the
axial direction of the input shaft 15. As a result, the
displacement shafts 7, 7 which pivotally support the power rollers
8 are slightly turned about the support shaft portions 22,
respectively. Due to the turning of the displacement shafts 7, 7,
the outer surfaces of the outer races 28, 28 of the thrust ball
bearings 26, 26 are displaced relative to the inner surfaces of the
trunnions 6, 6. A force required for the relative displacement is
small because the thrust needle roller bearings 27 are present
between the outer surfaces of the races 28, 28 and the inner
surfaces of the trunnions 6, 6. This fact implies that a force to
change an inclination angle of each of the displacement shafts 7, 7
is small.
[0022] Turning now to FIGS. 8 and 9, there are shown toroidal type
continuously variable transmissions increased in their
transmissible torque. As shown, a couple of input disks 2A and 2B
and a couple of output disks 4, 4 are arranged side by side around
an input shaft 15a in the power transmission direction. In either
structure (FIGS. 8 and 9), an output gear 18a is disposed in a
middle portion of the input shaft 15a to be rotatably supported
around the input shaft 15a. The output disks 4, 4 are
spline-engaged to both ends of a cylindrical sleeve 32 provided in
the central portion of the output gear 18a. Needle roller bearings
16, 16 are respectively provided between the inner circumferential
surfaces of the output disks 4, 4 and the outer circumferential
surface of the input shaft 15a. With provision of the needle roller
bearings 16, the output disks 4, 4 are supported around the input
shaft 15a so as to be rotatable about the input shaft 15a and
movable in the axial direction of the input shaft 15a. The input
disks 2A and 2B are supported at both ends of the input shaft 15a
while being rotatable together with the input shaft 15a. The input
shaft 15a is rotatable driven by a drive shaft 33 through the
pressure device 9 of the loading cam type. There is provided a
radial bearing 34, such as a sliding bearing or a needle roller
bearing, is disposed between the outer circumferential surface of
the tip end (right end of in FIGS. 8 and 9) of the drive shaft 33
and the inner circumferential surface of the base end (left end in
FIGS. 8 and 9) of the input shaft 15a. Therefore, the drive shaft
33 and the input shaft 15a are concentrically combined with each
other such that those shafts are slightly movable in the rotational
direction.
[0023] The rear surface of input-side disk 2A (located on the right
side in FIGS. 8 and 9) is thrust against a loading nut 35 directly
(in the structure shown in FIG. 9) or with a coned disk spring 36
having large resilience being interposed therebetween (in the
structure shown in FIG. 8), to thereby substantially prevent the
displacement of the input-side disk 2A in the axial directions
(horizontal directions in FIGS. 8 and 9) of the input shaft 15a. On
the other hand, the input-side disk 2B facing the cam plate 10 is
supported to be movable in the axial direction of the input shaft
15a with the aid of a ball spline 37. A coned disk spring 38 and a
thrust needle roller bearing 39 are serially disposed between the
rear surface (right-side surface in FIGS. 8 and 9) of the
input-side disk 2B and the front surface (right-side surface in
FIGS. 8 and 9) of the cam plate 10. The coned disk spring 38
functions so as to impart pre-load to contact portions where the
inner surfaces 2a of the input-side disks 2A and 2B and the inner
surface 4a of the output-side disk 4 are in contact with the
peripheral surfaces 8a, 8a of the power rollers 8, 8. The thrust
needle roller bearing 39 allows the input-side disk 2B to rotate
relative to the cam plate 10 when the pressure device 9
operates.
[0024] In the structure of FIG. 8, the output gear 18a is rotatably
supported while the axial displacement thereof being prevented, on
a partitioning wall 40 provided inside of the housing, by a pair of
ball bearings 41, 41 of the angular type. In the structure of FIG.
9, the output gear 18a is axially displaceable. In the toroidal
type continuously variable transmission of the double cavity type
in which the couple of input-side disks 2A and 2B and the couple of
output-side disks 4, 4 are arranged side by side in the power
transmission direction, as shown in FIGS. 8 and 9, one of the
input-side disks 2A and 2B, which faces the cam plate 10 or both of
them is or are axially movable with respect to the input shaft 15a
by means of the ball spline 37, 37a. The reason for this is that
the transmission structure is designed so as to allow the
input-side disks 2A and 2B to displace in the axial directions of
the input shaft 15a, while securing the synchronous rotations of
the input-side disks 2A and 2B, based on the elastic deformation of
the related component parts due to operations of the pressure
device 9.
[0025] The ball spline 37 and ball spline 37a include
inner-diameter ball-spline grooves 62 formed in the inner
circumferential surfaces of the input-side disks 2A and 2B,
outer-diameter ball-spline grooves 63 formed in the outer
circumferential surfaces of the intermediate portion of the input
shaft 15a, and a plurality of balls 64, 64 rollably provided
between the inner-diameter ball-spline grooves 62 and the
outer-diameter ball-spline grooves 63. As for the ball spline 37
for supporting the input-side disk 2B located closer to the
pressure device 9, a stopper ring 66 is retained in a stopper
groove 65 formed in a portion of the inner circumferential surface
of the input-side disk 2B, which is closer to the inner surface 2a
thereof, to thereby limit the balls 64, 64 in displacing toward the
inner surface 2a of the input-side disk 2B. Further, it prevents
the balls 64, 64 from slipping off from between the inner-diameter
ball-spline grooves 62 and the outer-diameter ball-spline grooves
63. As for the ball spline 37a for supporting the input-side disk
2A located apart from the pressure device 9 in the transmission
structure of FIG. 8, a stopper ring 66a is retained in a stopper
groove 65a formed in the outer circumferential surface (a portion
thereof closer to the left end in FIG. 8) of the input shaft 15a,
to thereby limiting the balls 64, 64 in displacing toward the inner
surface 2a of the input-side disk 2A.
[0026] In the known or proposed toroidal type continuously variable
transmission, less consideration is given to the eccentric
quantities of the displacement shafts 7, 7 for supporting
respectively the power rollers 8, 8 on the inner surfaces of the
intermediate portions of the trunnions 6, 6. The support shaft
portion 22, 22 and the pivot shaft portion 23, 23 are parallel to
each other, but the former is eccentric from the latter, viz.,
their centers are not coincident with each other (FIGS. 13, 24 and
25). Little qualitative consideration has been made on an eccentric
quantity L.sub.7 present between the support shaft portion and the
pivot shaft portion 23, 23. The study by inventor(s) on the
toroidal type continuously variable transmission showed the
following fact: To extract desired performances of the toroidal
type continuously variable transmission, it is essential to place
the eccentric quantity L.sub.7 within a proper range of eccentric
quantity values. This fact will be described by use a case where
the toroidal type continuously variable transmission of the double
cavity type as shown in FIG. 10 is in a maximum deceleration state
where trouble occurrence is most frequent.
[0027] When the eccentric quantity L.sub.7 is excessively small,
the speed change ratio of the toroidal type continuously variable
transmission shifts from a desired speed change ratio for the
following reason. To absorb the dimensional tolerance of the
component parts and the elastic deformations of those parts during
the power transmission, the pivot shaft portion 23 constituting
each displacement shafts 7 revolves around the support shaft
portion 22. For example, at the time of the transmission of power,
a thrust load that is generated by the pressure device 9 thrusts
the output-side disk 4. The output-side disk 4 is elastically
displaced from a position (dot chain line in FIG. 11) to another
position (solid line in FIG. 11), and the input-side disk 2B is
displaced toward the output-side disk 4 (right side in FIG. 11). In
accordance with the displacement, the power roller 8 held between
the inner surface 2a of the input-side disk 2B and the inner
surface 4a of the output-side disk 4 moves in the axial direction
(referred to as an x-direction, for ease of explanation) of the
input shaft 15a. With the movement, the trunnion 6, the
displacement shaft 7 and the power roller 8 changes from their
disposition of FIG. 12A to another disposition of FIG. 12B. The
change of the disposition of those components results from the
revolution of the pivot shaft portion 23 with respect to the
support shaft portion 22. Therefore, the pivot shaft portion 23 and
the power roller 8 move also in the axial direction (referred to as
a y-direction, for ease of explanation) of the pivot shafts 5, 5
which pivotally supports the trunnion 6 as well as in the
x-direction, as shown in FIGS. 13A and 13B.
[0028] The movement of the pivot shaft portion 23 and the power
roller 8 in the y-direction, as seen from the above description, is
the same as the operation of them in a case where the trunnions 6
are displaced in the axial direction of the pivot shafts 5, 5 by
moving forward and backward the drive rods 29 (see FIG. 4) to
change an inclination angle of the power roller 8 for the purpose
of changing the rotational speed change ratio of the input-side
disk 2B and the output-side disk 4. Accordingly, when the power
roller 8 displaces in the x-direction, on the basis of the
displacement in the y-direction which is simultaneously applied,
the power roller 8 is displaced by a distance corresponding to the
displacement in the y-direction caused by the revolution, although
the trunnion 6 per se does not displace in the y-direction. When a
degree of speed change (speed change quantity), which is caused by
such a displacement of the power roller is small, no problem
arises. When it is too much large, the speed change ratio cannot be
controlled as desired.
[0029] To control the speed change ratio of the toroidal type
continuously variable transmission, a controller decides a target
speed change ratio based on a signal representative of
throttle-valve position, engine speed, or running speed; an
instruction signal indicative of the target speed change ratio is
applied to a related electric motor; and controls the switching of
a hydraulic-pressure control valve, and thus operates the drive
pistons 30 (FIG. 4). And, the contact positions where the
peripheral surfaces 8a of the power rollers 8 are in contact with
the inner surface 2a of the input-side disk 2 (2A, 2B) and the
inner surface 4a of the output-side disk 4 are shifted to other
positions, so as to change the inclination angles of the power
rollers 8. However, where a quantity y8 of a displacement of the
power roller 8 in the y-direction, caused by the revolution motion,
is increased, another action not caused by the signals stated above
exists in addition to the action for the changing of the speed
change ratio, which is caused by the drive pistons 30, 30.
Therefore, the toroidal type continuously variable transmission
changes its speed change ratio. Further, an actual speed change
ratio is greatly deviated from the target one, and the toroidal
type continuously variable transmission operates in a region out of
an optimum region of its characteristic where the fuel consumption
by the engine is efficient and the output power of the engine is
high. This situation should be avoided.
[0030] In the conventional technique, it is considered that the
preferable way to suppress the y-directional movement of the power
roller 8, which is produced when the power roller 8 is moved in the
x-direction is to secure the eccentric quantity L.sub.7 of the
support shaft portions 22, 22 from the pivot shaft portions 23, 23
as large as possible. Further, it is recognized that where the
eccentric quantity L.sub.7 is excessively large, a cross sectional
area of the joint portion where the support shaft portions 22, 22
and the pivot shafts portions 23, 23 are jointed together is small,
and as a result, a stress generated in the joint portion is great
and in this condition it is very difficult to secure a satisfactory
durability of the displacement shafts 7, 7. Therefore, the designer
considers that the eccentric quantity L.sub.7 has certain values of
the upper limit, and they determine the eccentric quantity L.sub.7
on the basis of the best balance between the securing of the
durability of the displacement shaft and the suppressing of the
y-directional component.
[0031] As described above, the conventional design of the eccentric
quantity L.sub.7 between the support shaft portions 22, 22 and the
pivot shaft portions 23, 23 constituting the displacement shafts 7,
7 is not based on definite rules constructed in consideration with
the performance on the speed-ratio change of the toroidal type
continuously variable transmission. The inventor(s) discovered that
there is a specific correlation between the eccentric quantity
L.sub.7 and the speed-ration change performance of the toroidal
type continuously variable transmission, and that the eccentric
quantity L.sub.7 with a specific range, provides a satisfactory
speed-ratio change performance.
[0032] Further, in designing the conventional toroidal type
continuously variable transmission, any special consideration has
been given to the surface natures of the displacement shafts 7
which are used for supporting the power rollers 8, 8 on the
trunnions 6, 6 in rotatable and displaceable fashion. Therefore, a
satisfactory durability of the transmission is not always
guaranteed where the transmission is used under hard conditions.
The reason for this will be described with reference to FIGS. 14
through 17. When the toroidal type continuously variable
transmission is in operation, the power roller 8 is strongly
compressed between the input-side disk 2 and the output-side disk 4
as shown in FIG. 14. Accordingly, the center hole of the power
roller 8 is deformed to be elliptical as exaggeratedly illustrated
in FIG. 15. In this state, the pivot shaft portion 23 of the
displacement shaft 7 is strongly thrust in the directions in which
the input-side disk 2 and the output-side disk 4 are arranged.
[0033] When the power roller 8 is strongly compressed between the
input-side disk 2 and the output-side disk 4, a large force thrusts
the power roller 8 outwardly in the radial directions of the
input-side disk 2 and the output-side disk 4 when viewed in cross
section, since the peripheral surfaces 8a of the power roller 8 is
engaged with the inner surface 2a of the input-side disk 2 and the
inner surface 4a of the output-side disk 4. Due to the thrust
forces, the trunnion 6 supporting the power roller 8 on its inner
surface is elastically deformed from the configuration shown in
FIG. 16A to the configuration shown in FIG. 16B. Since the support
shaft portion 22 of the displacement shaft 7 is somewhat offset
from the center of the trunnion 6, the displacement shaft 7 is
inclined by the elastic deformation of the trunnion 6. The
inclination of the displacement shaft 7 leads to partial contact of
the outer circumferential surface of the pivot shaft portion 23 of
the displacement shaft 7 with the needle rollers 45, 45
constituting the radial needle roller bearing 25. More
particularly, as shown by oblique lattices in FIG. 17, rolling
surfaces of the needle rollers 45, 45 are strongly pressed against
the outer circumferential surface of the pivot shaft portion
23.
[0034] The partial contact by the elastic deformation of the power
roller 8 and the partial contact by the inclination of the
displacement shaft 7 are summed, so that load regions as indicated
by oblique lattices in FIG. 18 appear in the pivot shaft portions
23. In those load regions, large area pressure is applied from the
rolling surfaces of the needle rollers 45, 45 to the outer
circumferential surfaces of the pivot shaft portions 23. The
surface roughness of the rolling surface (the inner and outer
raceway portions being in contact with the rolling surfaces of the
needle rollers 45, 45) of a general radial needle roller bearing,
used in a high speed region of 10,000 rpm or higher, is about 0.4
.mu.mRa. However, since the rolling surfaces of the needle rollers
45, 45 are strongly contacted with the outer circumference surface
of the pivot shaft portion 23 in the above load regions, an oil
film is hard to be formed on the contact portions when the surface
roughness of the outer circumference surface is about 0.4
.mu.mRa.
[0035] In the portions on which large area pressure exerts, a large
amount heat is generated according to the operation of the toroidal
type continuously variable transmission. Those portions are also
located close to traction portions where the peripheral surfaces 8a
of the power roller 8 are in contact with the inner surface 2a of
the input-side disk 2 and the inner surface 4a of the output-side
disk 4. Elevation of temperature caused by the heat generated in
the traction portions is great. Accordingly, the heat-resistance of
those portions receiving the large area pressure needs to be
secured for securing a satisfactory durability of the displacement
shaft 7.
[0036] In addition, in the conventional toroidal type continuously
variable transmission, the radial needle roller bearings 25 which
rotatably support the power rollers 8 around the pivot shaft
portions 23 of the displacement shafts 7, respectively, are not
always satisfactory in their durability. The reason for this will
be described hereunder.
[0037] Where the toroidal type continuously variable transmission
is used for a transmission unit of a motor vehicle, an automotive
power that is output from the engine to the input shafts 15, 15a is
transmitted to the output-side disk 4, through the input-side disk
2, 2A, 2B and the power rollers 8, 8. The toroidal type
continuously variable transmission may be considered in the form of
the radial needle roller bearings 25, which support the power
rollers 8, 8 around the pivot shaft portions 23, respectively. In
this case, it is operated in an outer race rotating mode in which
the power roller 8 having the outer raceway 55 revolves. A load
applied to the thus radial needle roller bearing 25 is a radial
component of a force, that is, a traction force, applied to the
traction portions of the power roller 8 supported by the radial
needle roller bearing 25, viz., the contact portions where the
inner surfaces 2a of the input disks 2A and 2B and the inner
surface 4a of the output-side disk 4 are in contact with the
peripheral surfaces 8a of the power rollers 8.
[0038] The radial load applied to the radial needle roller bearing
25 varies depending on the output power (in particular torque) of
the engine and a changing state of the speed change ratio of the
toroidal type continuously variable transmission. In the case of a
normal aspiration engine of the displacement volume of 2,000 to
3,000 cc, the radial load is approximately 500 to 700 kgf (5000 to
700N) under the condition that the toroidal type continuously
variable transmission is in a maximum deceleration state and a
maximum torque input state. In the case of the natural aspiration
engine of 800 cc to 1500 cc in displacement volume, it is
approximately 200 to 400 kgf (2000 to 4000N) under the same
condition as above.
[0039] The radial needle roller bearing 25 is capable of
sufficiently enduring such a radial load if it is under a general
load loading condition. However, the power roller 8, which
functions as the outer race of the radial needle roller bearing 25,
is repeatedly elastically deformed due to loads from the inner
surface 2a of the input-side disk 2, 2A, 2B and the inner surface
4a of the output-side disk 4. Therefore, an excessive area pressure
acts on a part of the rolling contact surface, and the durability
of the power roller 8 is possibly lost. This will be described with
reference to FIGS. 19 to 22.
[0040] When the toroidal type continuously variable transmission is
in operation, loads indicated by an arrow a in FIGS. 19 to 20 are
imparted to two opposed positions on each of the power rollers 8, 8
from the inner surface 2a of the input-side disk 2, 2A, 2B and the
inner surface 4a of the output-side disk 4. As seen from FIGS. 19
to 20, those loads are directed toward the positions on the power
rollers 8, 8 closer to the trunnions 6, 6. When the loads directed
to the arrow a are increased in value, the inside diameters of the
power rollers 8, 8 are elastically deformed as exaggeratedly shown
in FIG. 21, the outer raceway 55 is deformed to be elliptical in
cross section as exaggeratedly illustrated in FIG. 22. In this
case, the amount of deformation of the outer raceway 55 is not
caused in the axial direction of the radial needle roller bearing
25 and increases in quantity toward the trunnions 6, 6 with respect
to the radial direction thereof. At a specific portion in the
circumferential direction of the outer raceway 55, the elastic
deformation inwardly in the radial direction thereof is conducted
two times during one turn of each power roller 8.
[0041] As the result of the elastic deformation of the outer
raceway 55, the distance between the inner raceway 54 and the outer
raceway 55 of the radial needle roller bearing 25 becomes narrower
at two opposite positions in the radial direction where it faces
the inner surface 2a of the input-side disk 2, 2A, 2B and the inner
surface 4a of the output-side disk 4, and it is close to the
trunnion 6. At those positions, the needle rollers 45, 45 of the
radial needle roller bearing 25 are forcibly compressed between the
inner raceway 54 and the outer raceway 55. As a result, an
excessive area pressure, which is due to an edge load, is applied
to parts of the inner raceway 54 and the outer raceway 55, which
face the ends of the needle rollers 45, 45 (when axially viewed)
The excessive area pressure causes early flaking-off on those
portions.
[0042] When the portions are damaged by such pressure-flaking,
sound and vibration generated at the radial needle roller bearing
25 become large. As a result, sounds and vibrations generated by
not only the toroidal type continuously variable transmission
having the radial needle roller bearings assembled thereinto but
also the transmission unit having the toroidal type continuously
variable transmission, are increased. This adversely affects the
drive feeling of the vehicle having the transmission unit. Further,
when flakes separated from the traces enter into the traction
portion transmitting the automotive power, the area pressure
excessively increases thereat. This possibly causes the damages
such as the flaking in the early stage in the inner surface 2a of
the input-side disk 2, 2A, 2B and the inner surface 4a of the
output-side disk 4, and the peripheral surfaces 8a, 8a of the power
rollers 8, 8, which form the traction portion. Moreover, the
strainer and the filters may be clogged with the flakes thus
caused. This results in reduction of the discharge amount of the
pump for supplying the lubricating oil, poor lubricating, and
reduction of lifetime of other parts.
SUMMARY OF THE INVENTION
[0043] Accordingly, a first object of the present invention is to
provide a toroidal type continuously variable transmission in which
the eccentric quantity between the support shaft portion and pivot
shaft portion is optimized in value and hence good speed-ration
change performance is ensured.
[0044] Further, a second object of the present invention is to
provide a toroidal type continuously variable transmission with
pivot shaft portions, which is high in durability and reliability
by making it easy to form an oil film on the contact portions where
the outer circumferential surfaces of the pivot shaft portions are
contacted with the rolling surfaces of the needle rollers, and by
increasing the durability of the displacement shaft including the
pivot shaft portion through the improvement of the heat resistance
of the outer circumferential surfaces of the pivot shaft
portions.
[0045] Accordingly, an object of the present invention is to
provide an input disk unit of a toroidal type continuously variable
transmission which succeeds in solving the problems arising from
the radial load of the radial needle roller bearings.
[0046] According to the first aspect of the present invention,
there is provided a toroidal type continuously variable
transmission, including: at least one pair of disks, each one
surface in the axial direction of which has a concave surface being
arcuate in cross section, the disks concentrically disposed on each
other and rotatably supported independent from each other in a
state that the concave surfaces are opposed to each other; a
trunnion swingable about a pivot shaft situated at a torsional
relation with respect to a center axis of the pair of disks, the
trunnion having a circular hole formed in a direction perpendicular
to the axial direction of the pivot shaft at a middle portion
thereof; a displacement shaft including a support shaft portion and
a pivot shaft portion that are parallel and eccentric to each
other, the support shaft portion rotatably supported to the inner
surface of the circular hole through a radial bearing, the pivot
shaft portion being protruded from an inner surface of the middle
portion of the trunnion; a power roller having an arcuate convex
surface on the peripheral surface thereof, the power roller nipped
between the concave surfaces of the pair of disks while being
rotatably supported on an outer circumferential surface of the
pivot shaft portion; and a thrust bearings located between the
power roller and the inner surface of the middle portion of the
trunnions, wherein an eccentric quantity of the displacement shaft
being a distance between the support shaft portion and the pivot
shaft portion is within a range from 5 mm to 15 mm.
[0047] The toroidal type continuously variable transmission, like
the conventional one, transmits a rotational force between the
input-side disk and the output-side disk, and changes a rotational
speed ratio of the input-side disk and the output-side disk by
changing the inclination angle of the trunnion.
[0048] In case of the continuously variable transmission of the
invention, the eccentric quantitie of the displacement shaft, which
supports the power roller on the trunnion is controlled to be
within a predetermined range. Therefore, the inclination angle of
the trunnion and the power roller about the pivot shafts can
exactly be adjusted in accordance with the displacement quantity of
the trunnion over the axial direction of the pivot shaft. As a
result, the rotational speed ratio of the input- and output-side
disks can be accurately adjusted as desired, to thereby improve the
speed change performances of the continuously variable
transmission.
[0049] According to the second aspect of the invention, there is
provided a toroidal type continuously variable transmission,
including: at least one pair of disks, each one surface in the
axial direction of which has a concave surface being arcuate in
cross section, the disks concentrically disposed on each other and
rotatably supported independent from each other in a state that the
concave surfaces are opposed to each other; a trunnion swingable
about a pivot shaft situated at a torsional relation with respect
to a center axis of the pair of disks, the trunnion having a
circular hole formed in a direction perpendicular to the axial
direction of the pivot shaft at a middle portion thereof; a
displacement shaft including a support shaft portion and a pivot
shaft portion that are parallel and eccentric to each other, the
support shaft portion rotatably supported to the inner surface of
the circular hole through a radial bearing, the pivot shaft portion
being protruded from an inner surface of the middle portion of the
trunnion; a power roller having an arcuate convex surface on the
peripheral surface thereof, the power roller nipped between the
concave surfaces of the pair of disks while being rotatably
supported on an outer circumferential surface of the pivot shaft
portion through a radial needle roller bearing; and a thrust
bearings located between the power roller and the inner surface of
the middle portion of the trunnions, wherein a portion of the outer
circumferential surface of the pivot shaft portion contactable with
the rolling surfaces of the needle rollers of the radial needle
roller bearing has a smoothed surface having a surface roughness of
0.2 .mu.mRa or less, and formed by superfinishing.
[0050] Further, in the toroidal type continuously variable
transmission of the invention, the displacement shafts are made of
steel, the outer peripheral surface of at least the pivot shaft
portion of the displacement shaft is formed with a carbonitriding
layer containing 0.8 to 1.5 wt % of carbon and 0.05 to 0.5 wt % of
nitrogen, and at least the outer peripheral surface is quenched and
tempered after the carbonitriding process thereof.
[0051] Further, in the continuously variable transmission, the
displacement shafts are made of steel, and a carbonitriding layer
containing 0.8 to 1.5 wt % of carbon and 0.05 to 0.5 wt % of
nitrogen is formed on a surface portion of the outer peripheral
surface of at least the drive shaft of the displacement shaft, and
following the carbonitriding process, at least the surface portion
is quenched and tempered.
[0052] The toroidal type continuously variable transmission, like
the conventional one, transmits a rotational force between the
input-side disk and the output-side disk, and changes a rotational
speed ratio of the input-side disk and the output-side disk by
changing the inclination angle of the trunnion.
[0053] In the toroidal type continuously variable transmission
according to the second aspect of the invention, an oil film is
easy to form on the contact portion where the outer peripheral
surface of the pivot shaft portion is in contact with the rolling
surfaces of the needle rollers of the radial needle roller bearing.
The oil film formed effectively prevents damages (e.g., early
flaking) of the outer peripheral surface of the pivot shaft
portions.
[0054] Since the carbonitriding layer is formed on the outer
peripheral surface of the pivot shaft portions, its heat resistance
is high enough to prevent the outer peripheral surface from
damaging such as the early flakes. Moreover, according to a third
aspect of the invention, there is provided a toroidal type
continuously variable transmission, including: first and second
disks concentrically disposed on each other and rotatably supported
about a mutual central axis, the first and second disks
respectively having arcuate concave surfaces, which are opposed to
each other; trunnions swingable about a pivot shaft situated at a
torsional relation which does not intersect with the central axis
and is a position perpendicular to the central axis; a displacement
shaft disposed on a middle portion of the trunnion and supported in
such a manner as to project from an inner surface of the trunnion;
and a power roller disposed on an inner surface side of the
trunnion and nipped between the first and second disks in such a
manner as to be rotatably supported on the periphery of the
displacement shaft through a radial bearing; the peripheral surface
of the power roller having an arcuate convex surface contactable
with the concave surfaces of the first and second disks, wherein
the radial bearing is a radial needle roller bearing with a
retainer and a plurality of needle rollers, the needle rollers are
crowned at both end portions in the axial direction thereof, and a
crowning quantity of the needle roller is 0.15 to 0.65% of the
outer diameter of the center portion of the needle roller in the
axial direction thereof at a position closer to the center portion
side of the needle roller from an end face thereof by 5 to 15 % of
the axial length of the needle roller.
[0055] The toroidal type continuously variable transmission, like
the conventional one, transmits a rotational force between the
input-side disk and the output-side disk, and changes a rotational
speed ratio of the input-side disk and the output-side disk by
changing the inclination angle of the trunnion.
[0056] In the continuously variable transmission accoding to the
third aspect of the invention, proper amounts of crowning is
applied to the needle rollers of the radial needle roller bearings,
which rotatably support the power rollers on the displacement
shafts. Therefore, the invention prevents excessive area pressure
from being applied to the component parts of the radial needle
roller bearings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] FIG. 1 is a side view schematically showing a basic
structure of a conventional toroidal type continuously variable
transmission when it is in a maximum deceleration state;
[0058] FIG. 2 is a side view schematically showing the basic
structure of the toroidal type continuously variable transmission
when it is in a maximum acceleration state;
[0059] FIG. 3 is a partial cross sectional view showing a specific
structure of a conventional first toroidal type continuously
variable transmission towards which the invention is directed;
[0060] FIG. 4 is a cross sectional view taken on line IV-IV in FIG.
3;
[0061] FIG. 5 is a cross sectional view showing a main portion of
the conventional toroidal type continuously variable transmission
in which power rollers are in a free state;
[0062] FIG. 6 is a cross sectional view taken on line XI-XI in FIG.
5;
[0063] FIG. 7 is a cross sectional view showing a main portion
incorporating a lubricating-oil supplying path thereinto;
[0064] FIG. 8 is a partial cross sectional view showing a specific
structure of a conventional second toroidal type continuously
variable transmission towards which the invention is directed;
[0065] FIG. 9 is a partial cross sectional view showing a specific
structure of a conventional third toroidal type continuously
variable transmission towards which the invention is directed;
[0066] FIG. 10 is a cross sectional view schematically showing the
toroidal type continuously variable transmission of FIG. 8 when it
is in a maximum deceleration state;
[0067] FIG. 11 is an enlarged view showing an upper-left portion of
FIG. 10;
[0068] FIG. 12A is a sectional view showing a structure including a
trunnion and a power roller when viewed in the direction of an
arrow B in FIG. 11 in a state that no power is transmitted;
[0069] FIG. 12B is a sectional view showing a structure including a
trunnion and a power roller when viewed in the direction of an
arrow B in FIG. 11 in a state that large power is transmitted;
[0070] FIGS. 13A and 13B are diagrams for explaining a displacement
of the center of rotation of the power roller in a state that large
power is transmitted;
[0071] FIG. 14 is a partial cross sectional view for explaining a
load applied to the power roller when the toroidal type
continuously variable transmission is in operation;
[0072] FIG. 15 is a cross sectional view taken on line XV-XV in
FIG. 14;
[0073] FIGS. 16A and 16B are cross sectional views showing a
deformation of the trunnion when the toroidal type continuously
variable transmission is in operation;
[0074] FIG. 17 is a cross sectional view for explaining load
regions of the pivot shaft portion caused by an inclination of the
pivot shaft;
[0075] FIG. 18 is a diagram showing load regions of the pivot shaft
portions caused by the inclination of the pivot shafts and
deformation of the power rollers;
[0076] FIG. 19 is a cross sectional view for explaining loads
applied to the power rollers when the continuously variable
transmission similar to the structure shown in the FIG. 3 is in
operation;
[0077] FIG. 20 is a cross sectional view for explaining loads
applied to the power rollers when the continuously variable
transmission similar to the structure shown in the FIG. 13 is in
operation;
[0078] FIG. 21 is a cross sectional view showing a main portion of
the conventional continuously variable transmission shown in the
FIG. 5 in a state that the power roller is deformed;
[0079] FIG. 22 is a cross sectional view taken on line XXII-XXII in
FIG. 21;
[0080] FIG. 23 is a graph showing how the revolution of the pivot
shaft according to an eccentric quantity of the displacement shaft
affects a displacement of the power roller in the axial direction
of the pivot shaft according to a first embodiment of the
invention;
[0081] FIGS. 24A and 24B are diagrams showing the displacement
shaft when viewed from the axial direction of the input-side disk
and the output-side disk, for explaining a force acting on the
displacement shaft during the power transmission;
[0082] FIG. 25 is a cross sectional view taken on line XXV-XXV in
FIG. 8;
[0083] FIG. 26A and 26B are diagrams showing two specific
displacement shafts, illustrated for the same purpose as of FIG.
24;
[0084] FIGS. 27A and 27B are views showing the relation of the
eccentric quantities with the cross sectional areas and the moment
of inertial of area of the joint portions, and the deformation
quantities of the displacement shafts in the axial direction of the
pivot shafts, relating to the two displacement shafts shown in
FIGS. 26A and 26B each having three different eccentric
quantities;
[0085] FIG. 28 is a graph showing how the elastic deformation
according to the eccentric quantity effects the displacement amount
of the displacement shaft in the axial direction of the pivot
shaft, relating to the displacement shaft shown in FIG. 26A;
[0086] FIG. 29 is a graph showing how the elastic deformation
according to the eccentric quantity effects the displacement amount
of the displacement shaft in the axial direction of the pivot
shaft, relating to the displacement shaft shown in FIG. 26B;
[0087] FIG. 30 is a diagram showing second embodiment of a toroidal
type continuously variable transmission according to the present
invention, in which a displacement shaft is viewed from the same
direction as in FIG. 4;
[0088] FIG. 31 is a cross sectional view showing a structure
including a power roller and a thrust ball bearing according to the
second embodiment;
[0089] FIG. 32 is a cross sectional view showing a main portion of
a third embodiment of the present invention, in which a power
roller is in a free state;
[0090] FIG. 33 is a cross sectional view showing the power roller
being elastically deformed according to the third embodiment;
[0091] FIG. 34 is a cross sectional view taken on line XXXIV-XXXIV
in FIG. 33;
[0092] FIG. 35 is a cross sectional view showing a needle roller of
a radial needle roller bearing;
[0093] FIG. 36 is a graph showing a relationship between a
durability of the radial needle roller bearing and a crowning
quantity, obtained in a first test; and
[0094] FIG. 37 is a graph showing a relationship between a
durability of the radial needle roller bearing and a crowning
quantity, obtained in a second test.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0095] Some preferred embodiments of a toroidal type continuously
variable transmission constructed according to the present
invention will be described with reference to the accompanying
drawings.
[First Embodiment]
[0096] The toroidal type continuously variable transmission of a
first embodiment may be characterized in that an eccentric quantity
L.sub.7 between the support shaft portion 22 and the pivot shaft
portion 23, constituting the displacement shaft 7 for supporting
the power roller 8 with respect to the trunnion 6, is selected to
be within a predetermined range of quantity values, whereby a
rotational speed ratio of the input-side disk 2 (2A, 2B) to the
output-side disk 4 is set at a desired one. The remaining structure
of the continuously variable transmission is substantially the same
as of the conventional or proposed toroidal type continuously
variable transmission, which was already described with reference
to FIGS. 3 through 8. For this reason, no further description and
illustration of the structure will be given except some portions
required for explanation of the invention. A description will be
given of the process that the inventor(s) discovered the fact that
when the eccentric quantity L.sub.7 of the support shaft portion 22
with respect to the pivot shaft portion 23 is selected to be within
a range from 5 to 15 mm, the rotational speed ratio can be set at a
desired one.
[0097] The discovered fact is valid when a toroidal type
continuously variable transmission can be used for a transmission
unit of a general motor vehicle, and when the component parts of
the continuously variable transmission have the following
dimensions:
[0098] Outside diameters of input- and output-side disks 2(2A, 2B)
and 4:80 to 200 mm
[0099] Outside diameter of power roller 8:50 to 120 mm
[0100] Outside diameter of support shaft portion 22:10 to 40 mm
[0101] Outside diameter of pivot shaft portion 23:10 to 40 mm
[0102] Support length of power roller 8 when it is supported by
pivot shaft portion 23 (=L.sub.23 in FIG. 25, to be given later):10
to 40mm
[0103] Torque to be input into toroidal type continuously variable
transmission: 3 to 70 kg.multidot.m
[0104] A first attention was paid to how the eccentric quantity
L.sub.7 affects an inclination angle of the power roller 8, which
is directly linked with the rotational speed ratio. To absorb
dimensional tolerance of the component parts and the elastic
deformations of those parts during the power transmission, the
pivot shaft portion 23 of the displacement shaft 7 revolves about
the center of the support shaft portion 22 thereof, as shown in
FIG. 13A, and the center of the pivot shaft portion 23 shifts from
a point {circumflex over (1)} to another point {circumflex over
(2)} of FIG. 13A. In this case, the center of the support shaft
portion 22 is left at a point {circumflex over (3)} of FIG. 13A. A
displacement of the pivot shaft portion 23 produced when the pivot
shaft portion 23 revolves about the support shaft portion 22 as
shown in FIG. 13A can be analyzed with reference to FIG. 13B. In
FIG. 13B, L.sub.7 is a quantity of an eccentricity of the pivot
shaft portion 23 from the support shaft portion 22; x.sub.8 is a
displacement of the power roller 8 toward the output-side disk 4;
and y.sub.8 is a displacement of the power roller 8 produced when
it is displaced toward the pivot shaft 5, which pivotally supports
the trunnion 6, in accordance with the displacing of the power
roller 8 toward the output-side disk 4. In the chart of FIG. 13B,
the following equation is established:
L.sub.7.sup.2=(L.sub.7 -y.sub.8).sup.2+x.sub.8.sup.2
[0105] Rearranging the above equation for Y.sub.8, then we have
y.sub.8.sup.2-2L.sub.7y.sub.8+x.sub.8.sup.2=0
[0106] A displacement Y.sub.8 toward the pivot shaft 5 is given
by
y.sub.8L.sub.7-(L.sub.7.sup.2-x.sub.8.sup.2)
[0107] Design and test of various toroidal type continuously
variable transmissions of small power to large power were made. The
experience shows that in the case of the toroidal type continuously
variable transmissions for motor vehicles, when it is in a maximum
deceleration state and a maximum torque input state as already
shown in FIG. 10, the displacement x.sub.8 is within approximately
1.5 to 2.5 mm as the total of the dimensional tolerance and the
elastic deformations of the component parts of the continuously
variable transmission. That is, the displacement x.sub.8 in case of
the continuously variable transmission for small power is
substantially 1.5 mm, and the displacement x8 in case of the
continuously variable transmission for large power is substantially
2.5 mm. The value of the displacement x.sub.8 is calculated from
the elastic deformation quantities of the component parts
calculated by an FEM analysis, and it was confirmed through a
measurement using an actually assembled toroidal type continuously
variable transmission. In the measurement, the outer surfaces
(opposed to the power rollers 8) of the outer races 28, 28 (FIGS. 3
to 11) of the thrust ball bearings 26, 26, were blackening, and the
toroidal type continuously variable transmission was actually
operated. The displacement x.sub.8 was confirmed from the contact
traces left on the outer surfaces, which result from their contact
with the thrust needle roller bearings 27, 27 (FIGS. 3, 4, 10 and
11).
[0108] The displacement x.sub.8 of the power roller 8 toward the
output-side disk 4 is 1.5 to 2.5 mm as just mentioned. The
quantities of the displacement y.sub.8 caused by the displacement
x.sub.8 was calculated by use of the above equation, and the result
of calculations is graphically depicted in FIG. 23. In the graph of
FIG. 23, the quantities of the displacement y.sub.8 are plotted
about three displacements x.sub.8 of 1.5 mm, 2.0 mm and 2.5 mm. As
seen from the graph, of the displacement x.sub.8 being within the
range from 1.5 mm to 2.5 mm, the displacement y.sub.8 increases
when the eccentric quantity L.sub.7 is within 7 mm, irrespective of
the values of the displacement x8. Particularly when the eccentric
quantity L.sub.7 is smaller than 5 mm, the displacement Y.sub.8 has
a large value. From this, it is seen that to reduce the
displacement y.sub.8, the eccentric quantity L.sub.7 is 5 mm or
larger, preferably 7 mm or larger.
[0109] The eccentric quantity L.sub.7 affects the rotational speed
ratio of the input-side disk 2 (2A, 2B) to the output-side disk 4,
in connection with the dimensions of an actual toroidal type
continuously variable transmission. Let us calculate the affection
of the eccentric quantity. The following preconditions for the
calculation were set up: 1) the displacement x.sub.8 of the power
roller 8 toward the output-side disk 4, based on the dimensional
tolerance of the component parts and the elastic deformations of
those parts, was 2 mm; 2) a full speed-change-ratio angle as a turn
angle of the power roller 8 between a maximum acceleration position
(FIG. 1) and a maximum deceleration position (FIG. 2) was
60.degree.; and 3) a cam lead of the precess cam was 45
mm/360.degree. in connection with the turn angle. It is general
that the turn angle (full speed-change-ratio angle) of the power
roller 8 is selected to be within 50.degree. to 70.degree.,
although it depends on the width of the speed change ratio. A test,
conducted by the company of the present patent application, showed
that a preferable cam lead ranges 40 mm/360.degree. to 60
mm/360.degree..
[0110] With the above conditions, calculation about the affection
of the eccentric quantity L.sub.7 to the speed change ratio will be
made. To calculate, it is assumed that the eccentric quantity
L.sub.7 is 3 mm. When the power roller 8 is displaced 2 mm in the
x-direction, the power roller 8 displaces 0.764 mm in the
y-direction with the revolution of the pivot shaft portion 23 about
the support shaft portion 22. In this case, a turn angle of the
trunnion 6 caused by the y-directional movement, i.e., a
speed-change-ratio angle of the power roller 8, is
(0.764/45).times.360.degree.=6.1120.degree.. When this value is
compared with 60.degree. of the full speed-change-ratio angle, then
we have 6.1120.degree./60.degree.=0.102. This figure teaches that
when the pivot shaft portion 23 revolves around the support shaft
portion 22 to displace the power roller 8 in the y-direction, the
speed-change-ratio angle of the power roller 8 changes by 10.2% of
the full speed-change-ratio angle. This figure, 10.2%, is very
large, and does not lead to the achievement of a desired speed
change ratio performance.
[0111] If the eccentric quantity L.sub.7 is 10 mm, the power roller
8 moves 0.202 mm in the y-direction under the same conditions as in
the above case. A speed-change-ratio angle of the power roller 8
according to the movement is
(0.202/45).times.360.degree.=1.616.degree.. When this value is
compared with the value of the full speed-change-ratio angle, then
1.616.degree./60.degree.=0.027. This value is much smaller than
that in the case of L.sub.7=3 mm; a deviation of the
speed-change-ratio angle is only 2.7%, and hence it leads to the
achievement of a desired speed change ratio performance. Further,
if L.sub.7=15 mm and L.sub.7=20 mm, the displacements y.sub.8 of
the power roller in the y-direction are 0.134 mm and 0.100 mm, and
changing rates of the speed-change-ratio angle are 1.8% and 1.3%.
There is no great difference between the calculation result in the
case of L.sub.7=15 mm and that in the case of L.sub.7=20 mm. This
fact teaches that increase of the eccentric quantity L.sub.7 to a
value in excess of 15 mm is insignificant in preserving the speed
change ratio performance by suppressing the displacement y.sub.8 in
the y-direction.
[0112] Although the reason why the lower limit of the eccentric
quantity L.sub.7 is set at 5 mm, preferably 7 mm is as mentioned
above, the upper limit of the eccentric quantity L.sub.7 will be
described. The support shaft portion 22 of the displacement shaft 7
is supported by the radial needle roller bearings 24 within the
annular holes 21, which is provided in the middle portion of the
trunnion 6. The displacement shaft 7 is supported on the trunnion 6
in a cantilever fashion, as shown in FIG. 24A. When the toroidal
type continuously variable transmission is in operation, a large
force in an arrow direction of .alpha. of FIGS. 24A and 25 is
applied to the power rollers 8, 8, which is rotatably supported on
the pivot shaft portion 23 of the displacement shaft 7, by means of
the radial needle roller bearing 25. That is, a force, the
direction of which is the rotational direction of the input-side
disk 2 (2A, 2B) is applied to the contact portion where the inner
surface 2a of the input-side disk 2 (2A, 2B) is in contact with the
peripheral surfaces 8a of the power roller 8. A force, the
direction of which is opposite to the rotational direction of the
output-side disk 4 (i.e., the same as the rotational direction of
the input-side disk 2) is applied to the contact portion where the
inner surface 4a of the output-side disk 4 is in contact with the
peripheral surfaces 8a of the power roller 8. This force is
applied, as shown in an arrow direction of .beta. in FIG. 24B, to
the center position in the axial direction of the radial needle
roller bearing 25 on the center axis of the pivot shaft portion 23,
so that the force acts to bend the displacement shaft 7. If the
displacement shaft 7 has a low rigidity, the displacement shaft 7
is greatly deformed, and the power roller 8 supported on the
displacement shaft 7 is easy to displace in the arrow direction of
a(substantially coincident with the y-direction).
[0113] On the other hand, a portion of the displacement shaft 7
where the rigidity is the lowest is the joint portion where the
support shaft portion 22 is jointed to the pivot shaft portion 23.
Increase of the eccentric quantity L.sub.7 between the support
shaft portion 22 and the pivot shaft portion 23 leads to reduction
of the cross sectional area of the joint portion and hence lowering
of the rigidity in the joint portion. Where the eccentric quantity
L.sub.7 is small, the cross sectional area of the joint portion
takes the shape of a perfect circle or similar to the same. As the
eccentric quantity L.sub.7 increases, the cross sectional area
becomes elliptical in shape or is shaped like a rugby ball. Thus,
with increase of the eccentric quantity L.sub.7, the cross
sectional area changes its shape from the perfect circle to the
ellipse or rugby ball. The moment of inertia of area of the joint
portion changes, so that a deformation of the displacement shaft 7,
caused by the forces having the directions of .alpha. and .beta.,
increases in its quantity. The fact that this deformation in the
.alpha. and .beta. directions is large leads to the fact that the
contact points, where the peripheral surface 8a of the power roller
8 is in contact with the inner surface 2a of the input-side disk 2
and the inner surface 4a of the output-side disk 4, are greatly
moved in the y-direction. It is desirable to reduce the quantities
of the deformation in the .alpha. and .beta. directions as small as
possible, as well as in the case of the displacement in the
y-direction based on the eccentric quantity L.sub.7.
[0114] Specific configurations and dimensions of the displacement
shaft 7 will be described. To this end, two examples of the
displacement shaft 7 are given in FIGS. 26A and 26B. The
displacement shaft shown in FIG. 26A is to be assembled into a
toroidal type continuously variable transmission for the engine of
relatively small power, and the displacement shaft shown in FIG.
26B is to be assembled into a toroidal type continuously variable
transmission for the engine of relatively large power. In FIGS. 26A
and 26B, numerals indicate the outside diameters (in mm) of
portions indicated by dimension lines. FIGS. 27A and 27B show those
two displacement shafts each having three different eccentric
quantities L.sub.7, together with specific values of the cross
sectional areas S(mm.sup.2) and the moment I of inertial of area of
the joint portions, and the deformation quantities .lambda.(mm) of
the displacement shaft 7 in the axial direction (y-direction) of
the pivot shafts.
[0115] The deformation quantity .lambda. of the displacement shaft
7 is expressed by
.lambda.=PL.sub.23.sup.3/(3EI)
[0116] In the above equation, P is a load applied to the
displacement shaft 7. The load P corresponds to an automotive power
transmitted through the power roller 8, i.e., a traction force.
L.sub.23 is a distance from a point of application to a fulcrum of
the load P, viz., the length of an arm, and corresponds the length
from the joint portion between the support shaft portion 22 and the
pivot shaft portion 23 to the center position of the radial needle
roller bearing 25 when viewed in the axial direction. E is Young's
modulus of a hard metal, e.g., bearing steel of the displacement
shaft, and is 21000 kgf/mm.sup.2. The distance L.sub.23 (from the
force application point to the fulcrum) and the force P were 25 mm
and 250 kgf for the displacement shaft 7 for the small engine power
shown in FIGS. 26A and 27A, and 30 mm and 600 kgf for the
displacement shaft 7 for the large engine power shown in FIGS. 26B
and 27B.
[0117] Under the above-mentioned preconditions, calculation was
made on the deformation quantity .lambda. of the displacement shaft
7 according to an influence of the eccentric quantity L.sub.7. FIG.
28 shows a variation of the deformation quantity .lambda. of the
displacement shaft 7 assembled into the toroidal type continuously
variable transmission for the small power engine shown in FIG. 26A
and 27A with respect to the eccentric quantity L.sub.7. FIG. 29
shows a variation of the deformation quantity .lambda. of the
displacement shaft 7 assembled into the toroidal type continuously
variable transmission for the large power engine shown in FIG. 26B
and 27B with respect to the eccentric quantity L.sub.7. As seen
from FIGS. 28 and 29, a curve representative of a variation of the
deformation quantity .lambda. of the displacement shaft 7 rises
when the eccentric quantity L.sub.7 is 12 mm or longer,
irrespective of the size of the displacement shaft 7. When the
eccentric quantity L.sub.7 is 15 mm or larger, the curve sharply
rises. From this fact, it is seen that the upper limit of the
eccentric quantity L.sub.7 is 15 mm, preferably 12 mm.
[0118] From the analysis described above, it is concluded that if
the dimensions of the toroidal type continuously variable
transmission are within the above-mentioned ones, the eccentric
quantity L.sub.7 of the pivot shaft portion 23 of the displacement
shaft 7 to the support shaft portion 22 thereof is selected to be
within a range from 5 mm to 15 mm, irrespective of the magnitude of
an automotive power (in particular torque) transmitted by the
toroidal type continuously variable transmission, or the size of
the displacement shaft 7. Thus, a variation of the speed change
ratio, which is due to the dimensional tolerance of the component
parts of the continuously variable transmission and elastic
deformations caused by thrust loads applied during the power
transmission, can be reduced to such a variation level as to create
no problem in practical use.
[0119] As seen from the foregoing description, in the toroidal type
continuously variable transmission constructed as mentioned above,
its speed change ratio can be controlled to a desired one, and
hence in a motor vehicle having the continuously variable
transmission of the invention assembled thereinto, the improvement
of running performances and efficient fuel consumption are both
achieved.
[0120] [Second Embodiment]
[0121] Turning now to FIGS. 30 to 31, there is shown a second
embodiment of the present invention. In this embodiment to be
described hereunder, the invention is directed to the improvement
of the displacement shafts 7 for rotatably supporting the power
rollers 8 on the trunnions 6 (FIGS. 1 through 7). The remaining
structure and operation of the continuously variable transmission
are substantially the same as of the conventional or proposed
toroidal type continuously variable transmission already described.
For this reason, a description and illustration of the similar
structure will be omitted or simply given, and a feature of the
invention and a portion except for the above explained will be
given.
[0122] As shown, the displacement shaft 7 includes a support shaft
portion 22 and a pivot shaft portion 23, which are parallel to each
other but the former is eccentric from the latter. A flange portion
46 is formed at a continuous portion where the support shaft
portion 22 and the pivot shaft portion 23 are continuous. The
outside diameter D.sub.47 of a base-side half part 47 of the pivot
shaft portion 23, located closer to the flange portion 46, is
larger than the outside diameter D.sub.48 of the tip-side half part
48 of the same (D.sub.47>D.sub.48). When the outside diameter
D.sub.47 of the base-side half part 47 of the pivot shaft portion
23 is increased, the following advantages are produced. The cross
section area of the continuous portion between the support shaft
portion 22 and the pivot shaft portion 23 is secured in a
satisfactory level. A bending rigidity of the continuous portion is
increased. Therefore, the displacement shaft 7 is hard to bend at
this continuous portion during the operation of the continuously
variable transmission, and the displacement shaft 7 is less
deformed when it is subject to heat treatment.
[0123] Further, in the base surface of the support shaft portion
22, i.e., its base surface located closer to the flange portion 46,
there is formed a chamfered part 49 which is chamfered at a portion
outwardly protruding from the outer peripheral surface of the
flange portion 46 of the base surface in the radial direction of
the support shaft portion 22. The chamfered part 49 prevents the
interference with the outer race 28 of the thrust ball bearing 26
which supports the power roller 8, and provides a smooth surface of
the continuous portion between the support shaft portion 22 and the
flange portion 46. The smooth surface eliminates deformation of the
displacement shaft 7 during its heat treatment. An inclination
angle .theta. of the chamfered part 49 is preferably within a range
from 10 to 45.degree..
[0124] On the other hand, there is formed a center hole 50 in the
central portion of the outer race 28 of the thrust ball bearing 26
for supporting the power roller 8, which is rotatably supported by
the displacement shaft 7 as mentioned above. The center hole 50 can
receive the flange portion 46 and the base-side half part 47 in a
fitting fashion without the rattling therebetween. The center hole
50 includes a small-diameter portion 51 for receiving the base-side
half part 47 fittingly, and a large-diameter portion 52 for
receiving the flange portion 46 fittingly. The depth D.sub.52 of
the large-diameter portion 52 is slightly larger than the thickness
T.sub.46 of the flange portion 46 (D.sub.52>T.sub.46) . With
such dimensional selection, a part of the flange portion 46 is not
protruded out of the outer surface (upper surface in FIG. 31) of
the outer race 28 when the flange portion 46 and the base part 47
are fit into the center hole 50. This is needed in order to prevent
the flange portion 46 from interfering with the thrust needle
roller bearing 27 (FIGS. 3 through 7), which is located between the
outer race 28 and the inner surface of the trunnion 6.
[0125] The power roller 8 is rotatably supported on the tip-side
half part 48 of the pivot shaft portion 23 of the thus configured
displacement shaft 7 by means of the radial needle roller bearing
25 (FIGS. 4 through 7). A portion of the outer circumferential
surface of the tip-side half part 48, that is, in the outer
circumferential surface of the pivot shaft portion 23, a rolling
surface of thereof with which the rolling surfaces of the needle
rollers 45, 45 (shown in FIGS. 3 to 7, and FIGS. 14 and 15) of the
radial needle roller bearing 25 are brought into contact is
smoothed to have a surface roughness of 0.2 .mu.mRa or less, by
superfinishing. Grinding finishing, not superfinishing, can produce
within 0.2 .mu.mRa (surface roughness); however, grinding technique
is difficult, and its cost is high. In this respect, use of the
surperfinishing is preferable. The displacement shaft 7 is made of
steel, for example, chromium-molybdenum steel (e.g., SCM 435 (JIS G
4105)) or high-carbon-chromium bearing steel (e.g., SUJ 2 (JIS
G4805)) A carbonitriding layer containing 0.8 to 1.5 wt % of carbon
and 0.05 to 0.5 wt % of nitrogen is formed on a surface portion
(actually, the entire surface of the displacement shaft 7) of the
outer peripheral surface of at least the lower part 48 of the
displacement shaft 7 made of steel. Following the carbonitriding
process, at least the surface portion (actually the entire surface
of the displacement shaft 7) is quenched and tempered, so as to
increase the hardness of the surface portion to HRc60 or
higher.
[0126] In the thus constructed toroidal type continuously variable
transmission, an oil film is easy to form on the contact portion
where the outer peripheral surface of the lower part 48 of the
pivot shaft portion 23 is in contact with the rolling surfaces of
the needle rollers 45, 45 of the radial needle roller bearing 25.
And, the formed oil film prevents damages (e.g., early flaking) of
the outer peripheral surface of the tip-side half part 48. Table 1
shows the results of an endurance test, conducted by the
inventor(s). The test was conducted to know how the surface
roughness of the outer peripheral surface of the tip-side half part
48 affects the lifetime of the outer peripheral surface thereof.
Samples 1 to 8 were tested under the same conditions which are
other than the surface roughness of the outer peripheral surface of
the tip-side half part 48; the material, carbon density, and
nitrogen density are the same as of sample 4 in Table 2 to be given
later, and surface hardness is HRc62.
1TABLE 1 Surface roughness of the outer surface of the tip-side
half super- Judge- No. part [.mu.mRa] finishing Test result ment 1
1.0 no Rolling surface/needle outer X surface flaked after 10 hr 2
0.6 no Rolling surface flaked after X 71 hr 3 0.6 no Rolling
surface/needle outer X surface flaked after 64 hr 4 0.5 no Rolling
surface flaked after X 111 hr 5 0.4 yes Rolling surface flaked
after X 209 hr 6 0.2 yes No problem after 250 hr .largecircle. 7
0.2 yes No problem after 250 hr .largecircle. 8 0.1 yes No problem
after 250 hr .largecircle.
[0127] The test results show that the outer surface of the lower
part 48 is not damaged (not suffered from early flaking, for
example) if the outer surface is superfinished to have 0.2 .mu.mRa
or less in surface roughness. The surface roughness of the surface
other than the tip-side half part 48 does not need to finish
smoothly as that of the tip-side half part 48. Approximately 1.6
.mu.mRa is satisfactory for the surface roughness of its outer
surface since the support shaft portion 22 is just supported on the
trunnion 6 so as to allow its slight pivoting displacement.
[0128] Since the carbonitriding layer is formed on the surface
portion of the outer peripheral surface of at least the tip-side
half part 48 of the pivot shaft portion 23, its heat resistance is
high enough to prevent the outer peripheral surface from suffering
from early flakes. To know how the carbon and nitrogen contents
(densities) of the carbonitriding layer formed in the surface
portion of the lower part 48 affects the lifetime of the outer
peripheral surface, an endurance test was conducted. The test
results are shown in Table 2. In testing samples 1 to 7, other
conditions than the carbon and nitrogen contents (densities) of the
carbonitriding layer formed in the outer peripheral surface of the
tip-side half part 48 were equal; the finished sample 6 in Table 1
was used.
2TABLE 2 Carbon Nitrogen Judge- No. Material density % density %
Test results ment 1 SCM420 0.78 0.21 Flakes after 171 hr X 2 SCM435
0.96 0.02 Flakes after 201 hr X 3 SCM435 0.83 0.25 No problem after
.largecircle. 250 hr 4 SCM420 1.08 0.06 No problem after
.largecircle. 250 hr 5 SUJ2 1.41 0.46 No problem after
.largecircle. 250 hr 6 SUJ2 1.00 0.00 Flakes after 163 hr X 7 SUJ2
1.53 0.32 Flakes after 142 hr X
[0129] The toroidal type continuously variable transmission thus
constructed succeeds in preventing the peripheral surfaces of the
pivot shaft portions of the displacement shafts for supporting the
power rollers to the trunnions from damaging, e.g., flaking in
early stage. Therefore, the durability and reliability of the
continuously variable transmission are improved.
[0130] [Third Embodiment]
[0131] A third embodiment of the present invention will be
described with reference to FIGS. 32 to 35. In the embodiment, the
present invention is directed to the improvement of the radial
needle roller bearings 25a for rotatably supporting the power
rollers 8 on the periphery of the pivot shaft portions 23
constituting the displacement shafts 7 in a toroidal type
continuously variable transmission. The remaining structure and
operation of the continuously variable transmission are
substantially the same as of the conventional or proposed toroidal
type continuously variable transmission already described. For this
reason, a description and illustration of the similar structure
will be omitted or simply given. The description of the embodiment
will be made placing emphasis on its feature.
[0132] Each radial needle roller bearing 25a is constructed with a
plurality of needle rollers 45a, 45a and a cage-like window type
retainer 53 for retaining rollably those needle rollers 45, 45. In
this case, the outer circumferential surface of the pivot shaft
portion 23 serves as the cylindrical inner raceway 54 of the radial
needle roller bearing 25, and the inner circumferential surface of
the power roller 8 serves as the outer raceway 55 of the radial
needle roller bearing 25.
[0133] In case of the toroidal type continuously variable
transmission, as well shown in FIG. 35, both ends of the needle
roller 45a (when viewed axially) are tapered to have crownings 68,
68. A crowning quantity .delta..sub.68 of the needle roller 45a,
viz., a distance (radially ranges) of the outer surface of the
crowning 68 from the outer circumferential surface of the needle
roller 45a (assumed by extending straight from the outer surface of
the cylindrical portion 69, which is provided in the center portion
of the needle roller 45a in the axial direction thereof), is
determined in the following way. It is assumed that the axial
length of the needle roller 45a is L.sub.45a, the outer diameter of
the cylindrical portion 69 is D.sub.69, and a distance from each
end face of the needle roller 45a to a measuring point of the
crowning quantity .delta..sub.69 is L.sub.68. Further, it is
assumed that the distance L.sub.68 to the measuring point is
selected to be 5 to 15% of the axial length L.sub.45a;
L.sub.45a=(0.05 to 0.15).times.L.sub.45a. Under this conditions,
the crowning quantity .delta..sub.68 is selected to be 0.15 to
0.65% of the outer diameter D.sub.69 of the cylindrical portion 69;
.delta..sub.68=(0.0015 to 0.0065).times.D.sub.69.
[0134] In the toroidal type continuously variable transmission of
the embodiment, the needle rollers 45a of radial needle roller
bearing 25a for rotatably supporting the power roller 8 to the
pivot shaft portions 23 of the displacement shafts 7 are crowned
(designated by numeral 68) with a proper crowning quantity.
Therefore, even when the power rollers 8 receives large thrust
loads during the operation of the continuously variable
transmission and are elastically deformed, and as a result, the
space width between the inner raceway 54 and the outer raceway 55
of the radial needle roller bearing 25a loses its uniformity, the
crowning of the needle rollers 45a effectively prevents excessive
area pressure from being applied to the component parts of the
radial needle roller bearing 25a.
[0135] That is, during the operation of the toroidal type
continuously variable transmission, the power roller 8 receives
large thrust forces at two positions thereon, radially opposite to
each other, from the inner surface 2a of the input-side disk 2 and
the inner surface 4a of the output-side disk 4 (shown in FIGS. 1 to
3, 8, 9, 19 and 20), and elastically deforms as exaggeratedly
illustrated in FIGS. 33 and 34. However, even if the power roller 8
is thus elastically deformed to lose the uniformity of the space
width between the inner raceway 54 and the outer raceway 55, the
ends of the needle rollers 45a do not come in contact with the
inner raceway 54 and the outer raceway 55. Accordingly, the
continuously variable transmission of the embodiment is prevented
from the early flaking caused by the edge load.
[0136] As described above, both ends of each needle roller 45a
(when viewed axially viewed) of the radial needle roller bearing
25a are properly crowned (designated as numeral 68). The crowning
prevents the occurrence of the edge loading, to thereby improve the
durability of the radial needle roller bearing 25a. When the outer
raceway 55 structured by the inner circumferential surface of the
power roller 8 is elastically deformed, the needle rollers 45a
retained by the retainers 53 somewhat change their attitude, so
that the rolling surfaces of the needle rollers 45a, 45 provide the
inner raceway 54 and the outer raceway 55. Contact of the rolling
surfaces of the needle rollers 45a, 45a with the inner raceway 54
and the outer raceway 55 is put in a proper contact state, to
thereby suppress an excessive increase of the area pressure on the
contact portions.
[0137] In this connection, when the crowning quantity
.delta..sub.68 is too small, generation of the edge load is
insufficiently suppressed. In this case, the durability of the
radial needle roller bearing 25a is insufficiently improved. On the
contrary, when it .delta..sub.68 is too large, the needle rollers
45a, 45a of the radial needle roller bearing and the power roller 8
supported by the radial needle roller bearing 25a are slanted. The
result has an opposite effect that the edge load is easy to
generate and the early flaking is easy to occur. In addition, since
the power roller 8 transmits the automotive power while rotating at
high speed in a state that the power roller 8 is slanted compared
with the normal attitude, to thereby generate large sound and
vibrations. The whole transmission with the transmission unit
containing the toroidal type continuously variable transmission
generates large sound and vibrations, and thus, this adversely
affects the drive feeling of the vehicle having the transmission
unit.
[0138] On the other hand, in the present invention, the crowning
quantity (.delta..sub.68 is controlled as described above, and
hence the generation of the edge load is not prevented, and the
power rollers 8 are not slanted during the operation of the
continuously variable transmission.
[0139] A test conducted by the inventor(s) to set the crowning
quantity .delta..sub.68 as described above will be described. High
speed endurance tests was performed by use of a motor dynamo for
two toroidal type continuously variable transmissions for small
engine power and for large engine power.
[0140] As the toroidal type continuously variable transmission for
large engine power, a double cavity type toroidal type continuously
variable transmission of which the cavity diameter D.sub.0 is 130
mm (cavity diameter D.sub.0=distance between the pivot shafts 5, 5
provided at both ends of the trunnions 6, 6, FIG. 4) was used. The
operating conditions in the test were: the number of revolutions
each of the input-side disks 2A and 2B was 4000 rpm; input torque
was 300 Nm; and the speed change ratio was 0.5 (the number of
revolutions of the output-side disk 4 was 1/2 of that of the input
disks). Dimensions of the radial needle roller bearing 25a were:
the diameter of an inscribed circle of each needle roller 45a was
25 mm; the diameter of a circumscribed circle was 33 mm (outside
diameter of the cylindrical portion 59 of the needle roller 45a was
4 mm); and the axial length L.sub.45a of the needle roller 45a was
16.8 mm.
[0141] Under the conditions the above-mentioned, a test for
confirming the durability of the radial needle roller bearing 25a
was conducted while varying the crowning quantity .delta..sub.68 of
the needle rollers 45 (that is, using the crowning quantity
.delta..sub.68 as a parameter), and thus, proper crowning
quantities .delta..sub.68 could be obtained from the test. In
advance of high speed endurance test, an elastic deformation
quantity of the power roller 8 wad calculated on the basis of the
values of the load applied from the input- disk 2 and output-side
disk 4 to the power roller 8 during the operation of the
continuously variable transmission, by an FEM process. The
deformation quantity obtained was considered into the crowning
quantity .delta..sub.68. A target time for the high speed endurance
test was set at 200 hours. The value of 200 hours may be used as a
reference value for endurance for the lifetime of the transmission
unit of the vehicular transmission.
[0142] The test results are shown in Table 3 and FIG. 36.
3TABLE 3 Crowning quantity .delta..sub.68 at a position distance 2
mm Test from the end of the No. needle roller Test results A No
crowning The rolling surface of the needle roller & the inner
race flake after 32 and 45 hours, respectively. B 0.002 mm The
rolling surface of the needle roller & the inner race flake
after 78 and 96 hours, respectively. C 0.004 mm The rolling surface
of the needle roller & the inner race flake after 164 and 135
hours, respectively. D 0.006 mm Test was over 200 hours and
terminated after 250 hours, and no flake. The test was conducted
two times. E 0.015 mm Test was over 200 hours and terminated after
250 hours, and no flake. The test was conducted two times. F 0.026
mm Test was over 200 hours and terminated after 250 hours, and no
flake. The test was conducted two times. G 0.028 mm The rolling
surface of the needle roller & the inner race flake after 189
and 172 hours, respectively. H 0.035 mm The rolling surface of the
needle roller & the inner race flake after 62 and 39 hours,
respectively. Levels of sound and vibration were large.
[0143] The toroidal type continuously variable transmission being
the small single cavity type of which the cavity diameter D.sub.0
is 104 mm was subjected to the high speed endurance test. The
operating conditions in the test were: the number of revolutions of
the input-side disk 2 was 4000 rpm; input torque was 60 Nm; and the
speed change ratio was 0.5. Dimensions of the radial needle roller
bearing 25a were: the diameter of an inscribed circle of each
needle roller 45a was 16 mm; the diameter of a circumscribed circle
was 20mm (outside diameter of the cylindrical portion 69 of the
needle roller 45a was 2 mm); and the axial length L.sub.45a was
13.8 mm.
[0144] The test results are shown in Table 4 and FIG. 37.
4TABLE 4 Crowning quantity .delta..sub.68 at a position distance
1.5 mm Test from the end of the No. needle roller Test results A No
crowning The rolling surface of the needle roller & the inner
race flake after 21 and 16 hours, respectively. B 0.002 mm The
rolling surface of the needle roller & the inner race flake
after 92 and 129 hours, respectively. C 0.003 mm Test was over 200
hours and terminated after 250 hours, and no flake. The test was
conducted two times. D 0.007 mm Test was over 200 hours and
terminated after 250 hours, and no flake. The test was conducted
two times. E 0.013 mm Test was over 200 hours and terminated after
250 hours, and no flake. The test was conducted two times. F 0.015
mm The rolling surface of the needle roller & the inner race
flake after 148 and 117 hours, respectively. G 0.022 mm The rolling
surface of the needle roller & the inner race flake after 85
and 68 hours, respectively. Levels of sound and vibration were
large.
[0145] As seen from the test results, when the outside diameter of
the cylindrical portion 69 of the needle roller 45a is 4 mm, a
target durability is secured in a condition that the crowning
quantity .delta..sub.68 is within the range from 0.006 mm to 0.026
mm. When it is 2 mm, the target durability is secured in a
condition that the crowning quantity .delta..sub.68 is within 0.003
mm to 0.013 mm. In those cases, to secure a satisfactory
durability, the crowning quantity .delta..sub.68 must be 0.15% to
0.65% of the outside diameter D.sub.69 of the cylindrical portion
69 of the needle roller 45a. The crowning quantity .delta..sub.68
was measured at a position closer to the center of the needle
roller 45a (axially viewed) by 5 to 15% of the axial length
L.sub.45a of the needle roller 45a, measured from the end face
thereof. In the actual endurance test, the measuring point was
distanced 2 mm (11.9%) from the end face of the needle roller when
the axial length L.sub.45a is 16.8 mm (outside diameter=4 mm). It
was distanced 1.5 mm (10.9%) from the end face of the needle roller
when the axial length L.sub.45a is 13.8 mm (outside diameter=2 mm).
In sample E where the axial length L.sub.45a is 16.8 mm (outside
diameter=4 mm), the crowning quantity was 0.011 mm (0.275%) at a
position distanced 2.5 mm (14.9%) from the end face. The crowning
quantity was also 0.023 mm (0.58%) at a position distanced 0.9 mm
(5.4%) from the end face. Those figures satisfy the conditions set
forth in claim. In sample D where the axial length L.sub.45a is
13.8 mm, the crowning quantity was 0.005 mm (0.25%) at a position
distanced 2.0 mm (14.5%) from the end face. The crowning quantity
was also 0.010 mm (0.5%) at a position distanced 0.7 mm (5.1%) from
the end face. The conditions set forth in claim are satisfied in
those figures.
[0146] When an initial radial gap of the radial needle roller
bearing 25a is set to be large, a slant of the power roller 8 to
the pivot shaft portion 23 of the displacement shaft 7 is large, to
thereby cause unpleasant sound and vibrations during the operation
of the toroidal type continuously variable transmission. Further,
due to a variation and the reversal of the torque to be transmitted
by the continuously variable transmission (reversal : switching of
the driving state to and from an engine braking state), the power
roller 8 is repeatedly biased to one side (when viewed in the
radial direction) by a distance corresponding to the radial gap.
This results in increasing an unresponsive zone (where the speed
change is not conducted even if a speed change signal is input),
and this phenomenon causes a disadvantage in the speed change
control.
[0147] For this reason, it is preferable that the actual radial
gap, while somewhat considering the deformation quantity of the
power rollers 8, is somewhat larger than a gap recommended for the
radial needle roller bearing constructed with the needle rollers
45a, 45a and the retainer 53 (cage and roller), written in a
catalog of those component parts. In a case that the outside
diameter (diameter of the inner raceway 54) of the pivot shaft
portion 23 of the displacement shaft 7 is 15 to 30 mm and the
inside diameter (diameter of the outer raceway 55) of the power
roller 8 is 20 to 40 mm, a preferable radial gap in the initial
stage (the power roller 8 being free) is approximately 0.020 to
0.055 mm in diameter. For this values, the recommended gap
according to catalog are approximately 0.08 to 0.035 mm.
[0148] To prevent the early flaking, it is preferable that the
surface roughness of the contact portions in contact with the
rolling surfaces of the needle rollers 45a is set to be good. The
catalog recommends that the surface roughness Rmax of the outer
peripheral surface (inner raceway 54) of the pivot shaft portion 23
of the displacement shaft 7 is 1.6S, and the surface roughness Rmax
of the inner peripheral surface (outer race 54) of the power roller
8 is 3.2S. It is preferable that those actual surface roughness are
set to be somewhat smaller than the recommended ones (smoother).
The surface hardness of the inner raceway 54 and the outer raceway
55 is set to be substantially equal to that of the rolling surfaces
of the needle rollers 45a, 45a, set at HRc60 or higher as
recommended in the catalog.
[0149] With thus structured and operated toroidal type continuously
variable transmission, the invention can provide an excellent
durability thereof, and thus, promote the practical use of the
toroidal type continuously variable transmission.
[0150] The present disclosure relates to the subject matter
contained in Japanese patent application Nos. Hei. 10-6791 filed on
Jan. 16, 1998, Hei. 10-11661 filed on Jan. 23 and Hei. 11-3646
filed on Jan. 11, 1999 which are expressly incorporated herein by
reference in its entirety.
[0151] While only certain embodiments of the invenoin have been
specifically described herein, it will apparent that numerous
modifications may be made thereto without departing from the spirit
and scope of the invention.
* * * * *