Toroidal continous variable transmission

The toroidal continuous variable transmission is constructed so that the thrust-directional position of the toroidal speed change unit is determined by a component manufactured with high dimensional precision. The output disks, because they are supported on the casing through radial bearings, can change their thrust-directional positions with respect to the casing. The power rollers that are supported on the support shafts secured to the trunnions cannot perform the swinging motion and therefore can form a reference for determining the thrust-directional position with respect to the casing. The power rollers whose support shafts are eccentric shafts rotatably supported on the trunnions can perform the oscillatory motion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a toroidal continuous variable 
transmission for vehicles and more particularly to a toroidal continuous 
variable transmission of a double cavity type having two toroidal speed 
change units mounted on the same shaft. 
2. Description of the Prior Art 
The toroidal continuous variable transmission generally has a toroidal 
speed change unit that comprises an input disk, an output disk disposed 
opposite the input disk and power rollers in frictional contact with these 
disks and which transmits the rotation of the input disk to the output 
disk while continuously changing the rotation speed of the input disk by 
changing a tilt angle of the power rollers. When the above toroidal 
continuous variable transmission is to be applied to vehicles, general 
practice is to use a double cavity type toroidal continuous variable 
transmission having the above-mentioned two toroidal speed change units 
arranged on the same shaft. 
An example of conventional double cavity type toroidal continuous variable 
transmission is illustrated in FIG. 5 and 6 (see Japanese Patent 
Publication No. 96901/1995). This toroidal continuous variable 
transmission has a toroidal speed change unit 1 and a second toroidal 
speed change unit 2. The first toroidal speed change unit 1 includes an 
input disk 4 mounted on a main shaft 3 through a ball spline 12; an output 
disk 5 disposed opposite the input disk 4 and rotatably mounted on the 
main shaft 3; and tiltable power rollers 6 for transmitting torque from 
the input disk 4 to the output disk 5. The second toroidal continuous 
variable transmission includes an input disk 7 mounted on the main shaft 3 
through a ball spline 28; an output disk 8 disposed opposite the input 
disk 7 and rotatably mounted on the main shaft 3; and tiltable power 
rollers 9 for transmitting torque from the input disk 7 to the output disk 
8. 
The power rollers 6 are rotatably supported on trunnions 33 through support 
shafts 34, and the power rollers 9 are rotatably supported on trunnions 37 
through rotating shafts 38. Each trunnion 33, 37 has a tilt axis 11, and 
can move in the direction of the tilt axis 11 and rotate about the tilt 
axis 11. 
The input disk 4 and the input disk 7 are connected to the main shaft 3 
through the ball splines 12, 28 and thus can be slid in the thrust 
direction of the main shaft 3 and rotated integrally with the main shaft 
3. The power is transferred from the input shaft 13 through a loading cam 
18 to the input disk 4, from which it is further transferred to the input 
disk 7 through the main shaft 3 with which the input disk 4 rotates 
together. At this time, when the power is transferred from the loading cam 
18 to the input disk 4, a thrust force corresponding to the torque being 
transferred is generated in the thrust direction by the cam roller 61. 
The powers transferred to the input disks 4, 7 are conveyed through the 
power rollers 6 to the output disk 5 and through the power rollers 9 to 
the output disk 8, respectively. The output disks 5, 8 are coupled at 
their backs by an output shaft 22 engaged with the main shaft 3, so that 
the powers transferred to the output disks 5, 8 are taken out from the 
output shaft 22. Because the output disks 5, 8 are supported rotatable on 
a casing 25 by angular ball bearings 62, which support radial and thrust 
loads through the output shaft 22 that couples the output disks 5, 8 so 
that they rotate together, they cannot be moved in the thrust direction. 
Hence, as the thrust force is generated, the positions relative to the 
casing 25 of the output disk 5 and the output disk 8 in the thrust 
direction are determined first, the positions of the power rollers 6 and 
the power rollers 9 are determined next, and then the positions of the 
input disks 4, 7 in the thrust direction are determined. 
In the toroidal speed change units 1, 2, the thrust force generated by the 
loading cam 18 presses the input disks 4, 7 and the output disks 5, 8 
strongly against the power rollers 6, 9. The power transfer from the input 
disks 4, 7 to the output disks 5, 8 is carried out by the thrust force and 
by the shearing force of oil between the disks 4, 5, 7, 8 and the power 
rollers 6, 9. Because the input disks 4, 7 and the output disks 5, 8 are 
elastically deformed by the thrust force, the positions in the thrust 
direction of the power rollers, 6, 9, the input disks 4, 7 and the output 
disks 5, 8 change according to the thrust force (i.e., the torque being 
transmitted). 
In the conventional toroidal continuous variable transmission, the power 
rollers 6, 9 are supported on the trunnions 33, 37, as shown in FIG. 5, by 
the support shafts (eccentric shafts) 34, 38 offset from the power roller 
rotating centers in the direction of the tilt axes 11 so that the power 
rollers 6, 9 can oscillate about the eccentric shafts to absorb positional 
changes in the thrust direction. That is, the support shafts 34 and the 
support shafts 38 both have the axes of their ends offset from each other, 
with one end rotatably supported on the trunnions 33, 37 and the other end 
rotatably supporting the power rollers 6, 9. The power rollers 6, 9 
supported on the support shafts 34, 38 can perform an swinging motion. The 
oscillating motion of the power rollers 6, 9 can absorb positional changes 
of each disk in the thrust direction. 
With the conventional toroidal continuous variable transmission, however, 
to support the both output disks in the predetermined thrust-directional 
position relative to the casing requires a high dimensional precision for 
the casing, which makes it necessary to perform shim adjustment during 
assembly, resulting in raising the cost. The casing is made of aluminum 
for reducing the weight while the input disks, the output disks and the 
output shaft are made of steel. Because these components are made of 
different materials and have greatly differing thermal expansion 
coefficients, the conventional toroidal continuous variable transmission, 
which determines the positions of the toroidal speed change units in the 
thrust direction using the casing having a large thermal expansion 
coefficient, produces plays in the thrust direction due to temperature 
variations, giving rise to problems that the portions with plays will be 
worn or the trunnions and the disks with small clearances therebetween 
will interfere with each other. 
SUMMARY OF THE INVENTION 
The object of this invention is to solve the above-mentioned problems and 
to provide a toroidal continuous variable transmission, which determines 
the thrust-directional positions of the first and second toroidal speed 
change units by using the portions having high dimensional precision to 
enable secure and highly precise positioning in the thrust direction even 
when the dimensional precision of the casing is low and to prevent plays 
from being produced due to thermal expansion coefficient differences as 
the temperature varies. 
The present invention relates to a toroidal continuous variable 
transmission which comprises: a first input disk and a second input disk, 
both rotatable together with a main shaft and axially movable; an input 
shaft for transferring power to the first input disk through a loading 
cam; a first output disk disposed opposite the first input disk and 
rotatable relative to the main shaft; a pair of first power rollers for 
continuously changing the speed of rotation of the first input disk 
according to changes in a tilt angle with respect to the first input disk 
and the first output disk and transferring the speed-changed rotation to 
the first output disk; a first support shaft for rotatably supporting at 
one end thereof each of the first power rollers; a pair of first 
trunnions, each mounted to the other end of the first support shaft, the 
first trunnion being adapted to be displaced in the tilt axis direction 
from a neutral position and to tilt about the tilt axis; a second output 
disk disposed opposite the second input disk and rotatable relative to the 
main shaft; a pair of second power rollers for continuously changing the 
speed of rotation of the second input disk according to changes in a tilt 
angle with respect to the second input disk and the second output disk and 
transferring the speed-changed rotation to the second output disk; a 
second support shaft for rotatably supporting at one end thereof each of 
the second power rollers; a pair of second trunnions, each mounted to the 
other end of the second support shaft, the second trunnion being adapted 
to be displaced in the tilt axis direction from a neutral position and to 
tilt about the tilt axis; and an output shaft connected with the first 
output disk and the second output disk, the first and second output disks 
being disposed adjacent to each other; wherein the first output disk and 
the second output disk are supported on a casing between the output disks 
through radial bearings, axes of both ends of the first support shaft and 
of the second support shaft are offset from each other, one of the first 
and second support shafts is secured nonpivotable to the trunnion, and the 
other support shaft is mounted pivotable to the trunnion. 
In the toroidal continuous variable transmission of the above construction, 
the first and second output disks are supported on walls of a casing 
between the output disks through radial bearings, axes of both ends of one 
of the first and second support shafts are offset from each other, the 
support shaft whose axis is not off-centered is secured nonpivotable to 
the trunnion, and the support shaft whose axis is off-centered is mounted 
pivotable to the trunnion. 
In this toroidal continuous variable transmission, the output disk is 
mounted unrotatable to a cylindrical portion of the output shaft and the 
cylindrical portion of the output shaft is supported on the casing through 
the radial bearings. 
Alternatively, in this toroidal continuous variable transmission, the 
output shaft is mounted unrotatable to a cylindrical portion of the output 
disk and the cylindrical portion of the output disk is supported on the 
casing through the radial bearings. 
Because the toroidal continuous variable transmission is constructed as 
described above, power is transferred from the input shaft through the 
loading cam to the first input disk. At the same time, the rotation of the 
first input disk is also transferred to the second input disk through the 
main shaft. When the power is transferred from the loading cam to the 
first input disk, a thrust force of a magnitude corresponding to the 
torque being transferred is generated by the action of the cam roller. The 
power transferred to the first input disk is conveyed through the first 
power rollers to the first output disk. At the same time, the power 
transferred to the second input disk is conveyed to the second output disk 
through the second power rollers. The power is further transferred from 
these output disks to the output shaft that couples together the rear 
portions of the output disks. 
The thrust force produced by the action of the loading cam elastically 
deforms the first input disk, the first output disk, the second input disk 
and the second output disk. Here, the axes of both ends of the first and 
second support shafts are offset from each other or made eccentric; one of 
these support shafts is mounted unrotatable or unpivotable to one of the 
trunnions; and the other support shaft is mounted pivotable to the other 
trunnion. For example, the first support shaft is mounted unrotatable or 
unpivotable to the first trunnion and the second support shaft is mounted 
pivotable to the second trunnion. In this case, the first power rollers 
cannot perform the swing motion relative to the first trunnions. However, 
the first output disk and the second output disk are supported on the 
casing through the radial bearings that support only radial loads and the 
second power rollers are supported swingable on the second trunnions, so 
that the toroidal continuous variable transmission can absorb changes in 
the thrust-directional position caused by deformations of these disks. 
Further, when the axes of both ends of one of the first and second support 
shafts are offset from each other or made eccentric and the off-centered 
support shaft is mounted pivotable to one of the trunnions, for example, 
when the axes of both ends of the first support shaft are not offset from 
each other and the axes of both ends of only the second support shaft are 
offset, the first power rollers cannot perform swinging motion relative to 
the first trunnions. However, because the first and second output disks 
are supported on the casing through radial bearings that support only 
radial loads and because the second power rollers are mounted swingable to 
the second trunnions, this toroidal continuous variable transmission can 
absorb changes in the thrust-directional position of the speed change 
units caused by deformations of these disks. 
Furthermore, because the first and second output disks are supported on the 
casing directly or through the output shaft by the radial bearings that 
support only radial loads and the first power rollers cannot perform 
swinging motion, the thrust-directional positions of the first input disk 
and the first output disk with respect to the casing are first determined 
in such a way that the centers of the toroidal surfaces of these disks 
coincide with the tilt axes of the first trunnions, followed by the 
thrust-directional positions of the output shaft, the second output disk, 
the second power rollers and the second input disk being determined 
successively in that order. As explained above, the positions in the 
thrust direction of the input disks and the output disks forming the 
toroidal speed change units are determined by the power rollers as a 
reference which have high dimensional precision. 
In this toroidal continuous variable transmission constructed as described 
above, because the thrust-directional positions of the input disks and the 
output disks forming the toroidal speed change units are determined by one 
of the pairs of power rollers which have high dimensional precision, there 
is no need to increase the machining precision of a part of the casing 
where the bearings are mounted, as is required by the conventional 
transmission, thus obviating the selection of shims during assembly and 
lowering the cost. 
When the casing is made of aluminum for lighter weight, the difference in 
thermal expansion coefficient between the casing and the steel input disk, 
output disk or output shaft unavoidably causes excess plays between these 
components in the conventional toroidal continuous variable transmissions. 
With the toroidal continuous variable transmission of this invention, 
however, because the thrust-directional positioning of the input disk and 
the output disk is performed with one of the pairs of power rollers which 
have high machining precision-taken as a reference, a variety of problems, 
such as unwanted plays due to temperature variations, wear caused by 
excess plays and interference between trunnions and disks having too small 
clearances therebetween, are all eliminated, assuring reliable performance 
.

DETAILED DESCRIPTION OF THE EMBODIMENT 
Embodiments of the toroidal continuous variable transmission according to 
this invention will be described according to the accompanying drawings. 
This toroidal continuous variable transmission is a double cavity type, in 
which two toroidal speed change units 1, 2 are mounted side by side on the 
main shaft 3. The toroidal speed change unit 1 comprises an input disk 4, 
an output disk 5 disposed opposite the input disk 4, and power rollers 6 
disposed between the input disk 4 and the output disk 5 and in frictional 
engagement with the toroidal surfaces of the disks 4, 5. The toroidal 
speed change unit 2, like the toroidal speed change unit 1, also comprises 
an input disk 7, an output disk 8 disposed opposite the input disk 7, and 
power rollers 9 disposed between the input disk 7 and the output disk 8 
and in frictional engagement with the toroidal surfaces of the disks 7, 8. 
Each of the toroidal speed change units 1, 2 is provided with two power 
rollers 6, 6, 9, 9. The power rollers 6, 6 and the power rollers 9, 9 are 
rotatable on their own rotating axes 10 and tiltable about tilt axes 11 
extending perpendicular to the rotating axes 10. 
The input disk 4 is mounted on one end of the main shaft 3 through a ball 
spline 12 so that it can be moved in the axial direction of the main shaft 
3 and rotate together with the main shaft 3. The power from the engine is 
supplied through a torque converter to the input shaft 13. The input shaft 
13 is arranged on the same axis of the main shaft 3. A front end portion 
14 of the input shaft 13 is fitted into a center hole 15 formed at one end 
of the main shaft 3 and supported relatively rotatable. A flange portion 
16 formed at the end of the input shaft 13 is provided with claws 17. 
Opposite the flange portion 16 is a loading cam 18 which is provided with 
claws 19 that engage with the claws 17. Through the engaged claws 17, 19 
the torque is transferred from the input shaft 13 to the loading cam 18. A 
thrust bearing 21 is installed between the loading cam 18 and the flange 
portion 20 formed at the end of the main shaft 3. 
The output disk 5 and the output disk 8 are spline-connected at their backs 
to cylindrical portions 22A provided on both sides of an output shaft 22 
so that the two output disks can be rotated together. The output shaft 22 
is a hollow shaft fitted over the main shaft 3 and has an output gear 23 
integrally formed at an intermediate part of the hollow shaft. The output 
disk 5 and the output disk 8 are supported on walls 26 of the casing 25 by 
radial bearings, i.e., roller bearings 24, which support radial loads 
through the output shaft 22. 
The other end of the main shaft 3 is rotatably supported on the casing 25 
through a bearing 27. The input disk 7 is supported on the main shaft 3 
through the ball spline 28 so that it can be moved in the axial direction 
of the main shaft 3 and rotated together with the main shaft 3. On the 
back side of the input disk 7 is installed a disc spring 29, which is 
securely mounted by tightening a nut 31 with a spacer 30 interposed 
between. The input disk 7 is urged toward the output disk 8 by the disc 
spring 29. The main shaft 3 has an axially extending oil passage 32 
therein, which constitutes a lubricating oil passage. The oil passage 32 
branches to supply a lubricating oil to the toroidal surfaces of the 
toroidal speed change units 1, 2, ball splines 12, 28, and bearings 21, 
24. 
A pair of power rollers 6 in frictional contact with the toroidal surface 
of the input disk 4 and with the toroidal surface of the output disk 5 are 
rotatably supported on support shafts 34 secured to the trunnions 33, as 
shown in FIG. 2. The support shafts 34 have the axes of their ends offset 
from each other, that is, they form eccentric shafts, with one end 35 
secured to the trunnions 33 and the other end 36 rotatably supporting the 
power rollers 6. Because the support shafts 34 are secured unrotatable or 
unpivotable to the trunnions 33, the power rollers 6 cannot be swung even 
when subjected to external forces. 
Thus, when the input disk 4 and the output disk 5 are elastically deformed, 
their displacements in the thrust direction cannot be absorbed by the 
support shafts 34. The displacement of the input disk 4 is transmitted to 
the main shaft 3 through the thrust bearing 21, causing the main shaft 3 
to move in the axial direction to absorb the displacement. Because the 
output disk 5 is supported on the wall 26 of the casing 25 by the radial 
bearing 24, when the output disk 5 is elastically deformed, it can be 
moved axially together with the output disk 8 toward the input disk 7. 
A pair of power rollers 9, 9 frictionally engaged with the toroidal surface 
of the input disk 7 and with the toroidal surface of the output disk 8 are 
rotatably supported on the support shafts 38 that are pivotably supported 
on the trunnions 37. That is, the support shafts 38 have the axes of their 
ends offset from each other, i.e., they form eccentric shafts, with one 
end 39 pivotably supported on the trunnions 37 and the other end 40 
rotatably supporting the power rollers 9. Hence, when the input disk 7 and 
the output disk 8 are elastically deformed, the power rollers 9 supported 
on the support shafts 38 can swing to absorb the positional changes in the 
thrust direction. 
The thrust force generated by the action of the loading cam 18 elastically 
deforms the input disk 4, the output disk 5, the input disc 7 and the 
output disk 8. As described above, the support shafts 34 and the support 
shafts 38 are eccentric shafts with the axes of their ends offset from 
each other. The support shafts 34 are mounted unpivotable to the trunnions 
33 while the support shafts 38 are mounted pivotable to the trunnions 37. 
Hence, the power rollers 6 cannot swing relative to the trunnions 33. 
However, because the output disk 5 and the output disk 8 are supported on 
the casing 25 through the radial bearings 24 that support only radial 
loads and the power rollers 9 are supported swingable on the trunnions 37, 
the positional changes in the thrust direction of the disks 4, 5, 7, 8 due 
to elastic deformations are absorbed by the thrust-directional 
displacement of the main shaft 3 and by the swinging motion of the power 
rollers 9. 
Because the output disk 5 and the output disk 8 are supported on the casing 
25 through the radial bearings 24 that support only radial loads, the 
thrust-directional positions of the output disks 5, 8 relative to the 
casing 25 can change. As for the support shafts 34, because the support 
shafts 34 are secured to the trunnions 33 and the power rollers 6 
supported on the support shafts 34 cannot swing, the power rollers 6 
constitute the reference for determining the thrust-directional positions 
of the speed change units with respect to the casing 25. In other words, 
the thrust-directional positions of the input disk 4 and the output disk 5 
relative to the casing 25 are determined so that the centers of the 
toroidal surfaces of the disks 4, 5 coincide with the tilt axes 11 of the 
trunnions 33. Subsequently, the thrust-directional positions of the output 
shaft 22, the output disk 8, the power rollers 9, and the input disk 7 are 
determined in that order. The input disks 4, 7, the output disks 5, 8 and 
the output shaft 22 are generally made of steel. Where the casing 25 is 
made of an aluminum material for lighter weight, the toroidal continuous 
variable transmission of this embodiment can still perform precise 
positioning in the thrust direction of the disks 4, 5, 7, 8 without having 
to fabricate the casing 25 with high dimensional precision as required by 
the conventional toroidal continuous variable transmission. Because the 
thrust-directional positions are determined by the power rollers 6 he 
components whose manufacture precision is high t is possible to make 
accurate positioning in the thrust direction even if the casing 
dimensional precision is low, thereby preventing plays from being produced 
by thermal expansion differences when temperature changes occur. 
The trunnions 33 are supported on the casing 25 so that they are pivotable 
and axially movable. The trunnions 33 have the tilt axes 11 and can be 
moved in the axial direction of the tilt axes 11 and also pivot about the 
tilt axes 11. The tilt axes 11 of the trunnions 33 are provided with 
pistons 41 that are slidably installed in hydraulic cylinders 42 formed in 
the casing 25. In the hydraulic cylinders 42 the pistons 41 define a 
speed-increase side cylinder chamber 43B and a speed-decrease side 
cylinder chamber 43A. When an oil pressure is supplied to the 
speed-increase side cylinder chamber 43B, the transmission shifts to the 
speed-increase side. When the oil pressure is supplied to the 
speed-decrease side cylinder chamber 43A, the transmission shifts to the 
speed-decrease side. 
The trunnions 37, like the trunnions 33, are supported on the casing 25 so 
that they are pivotable and axially movable. The trunnions 37 have the 
tilt axes 11 and can be moved in the axial direction of the tilt axes 11 
and also pivot about the tilt axes 11. The tilt axes 11 of the trunnions 
37 are provided with pistons 44 that are slidably installed in hydraulic 
cylinders 45 formed in the casing 25. In the hydraulic cylinders 45 the 
pistons 44 define a speed-increase side cylinder chamber 46B and a 
speed-decrease side cylinder chamber 46A. When an oil pressure is supplied 
to the speed-increase side cylinder chamber 46B, the transmission shifts 
to the speed-increase side. When the oil pressure is supplied to the 
speed-decrease side cylinder chamber 46A, the transmission shifts to the 
speed-decrease side. 
The hydraulic cylinders 42 and the hydraulic cylinders 45 communicate with 
each other through oil passages 47A, 47B. The speed-increase side cylinder 
chambers 43B of the hydraulic cylinders 42 communicate with the 
speed-increase side cylinder chambers 46B of the hydraulic cylinders 45 
through an oil passage 47B. The speed-decrease side cylinder chambers 43A 
of the hydraulic cylinders 42 communicate with the speed-decrease side 
cylinder chambers 46A of the hydraulic cylinders 45 through an oil passage 
47A. The speed-increase side cylinder chambers 43B, 46B communicate with a 
B port of a spool valve 48 through the oil passage 47B. The speed-decrease 
side cylinder chambers 43A, 46A communicate with an A port of the spool 
valve 48 through the oil passage 47A. 
In the spool valve 48 is slidably disposed a spool 49, which is held at a 
neutral position by springs 50 installed at the axial ends of the spool 
valve 48. The spool valve 48 is formed at one end with an SA port and at 
the other end with an SB port, the SA port being supplied with a pilot 
pressure through a solenoid valve 51A, the SB port with a pilot pressure 
through a solenoid valve 51B. The spool valve 48 has a PL port leading to 
a line pressure (oil pressure source), an A port leading to the 
speed-decrease side cylinder chambers 43A, 46A through the oil passage 
47A, a B port leading to the speed-increase side cylinder chambers 43B, 
46B through the oil passage 47B, and T ports leading to a reservoir R. The 
solenoid valves 51A, 51B in response to control signals output from a 
controller 52, displace the spool 49 in the axial direction. 
The tilt axis 11 of the trunnion 33 is connected at its end with a precess 
cam 53, which is engaged with one end of a lever 54 which is pivotally 
supported at the center. The other end of the lever 54 is connected to the 
potentiometer 55. The potentiometer 55 measures the axial displacement and 
tilt angle of the tilt axis 11 of the trunnion 33 to produce a synthesized 
displacement signal, and feeds it to the controller 52. This toroidal 
continuous variable transmission has a car speed sensor 56, an engine 
revolution sensor 57, a throttle opening sensor 58 and the like to send 
speed change information signals such as car speed, engine revolution and 
throttle opening to the controller 52. The controller 52, according to 
these speed change information, sends control signals to the solenoid 
valves 51A, 51B. 
Next, the operation of the toroidal continuous variable transmission will 
be explained. When the engine is started, the power of the engine is 
transferred through the torque converter to the input shaft 13, from which 
it is further transferred through the loading cam 18 to the input disk 4. 
As the input disk 4 rotates, the power rollers 6 are driven to transfer 
the rotation to the output disk 5. At the same time, the torque supplied 
to the input disk 4 is conveyed to the main shaft 3 and further to the 
input disk 7 that rotates with the main shaft 3. Then, the rotation of the 
input disk 7 is transferred through the power rollers 9 to the output disk 
8. 
Normally, the trunnions 33, 37 are at a neutral position for a certain 
transmission ratio. The neutral position is where the rotating center line 
A--A of the input disks 4, 7 and the output disks 5, 8 and the rotating 
center O of the power rollers 6, 9 intersect. The speed change is done by 
displacing the trunnions 33, 37 in the axial direction of the tilt axis 11 
from the neutral position. When, during torque transmission, the trunnions 
33, 37 are displaced in the tilt axis direction, the trunnions 33, 37 tilt 
about the tilt axes 11 in a direction and at a speed corresponding to the 
direction and amount of the displacement, changing the ratio of a radius 
described by the frictional contact point between the input disks 4, 7 and 
the power rollers 6, 9 to a radius described by the frictional contact 
point between the output disks 5, 8 and the power rollers 6, 9, thereby 
performing continuous speed change. 
The tilting of the power rollers 6, 9 is performed by the controller as 
follows. First, the controller 52 calculates actual transmission ratio 
from the synthesized displacements of the trunnions 33, 37 detected by the 
potentiometer 55, sets target displacements of the trunnions 33, 37 
according to the deviation between the target transmission ratio and the 
actual transmission ratio, and outputs control signals to the solenoid 
valves 51A, 51B. Then, oil pressures SB, SA are supplied from the solenoid 
valves 51A, 51B to the ends of the spool valve 48. 
When the oil pressures SB and SA supplied to the spool valve 48 have a 
relation of SA&lt;SB, the spool 49 shifts toward left in FIG. 2 to connect 
the oil passage 47B to a pressure source through the PL port and the oil 
passage 47A to the reservoir R through the T port, causing the pressure 
Pup of the oil passage 47B to become higher than the pressure Pdown of the 
oil passage 47A (Pup&gt;Pdown). As a result, the pressure difference between 
the cylinder chambers 43A and 43B causes the trunnion 33 on the right side 
of the toroidal speed change unit 1 in FIG. 2 to move down and the 
trunnion 33 on the left side to move up. 
Similarly, the trunnion 37 on the right side of the toroidal speed change 
unit 2 moves down and the trunnion 37 on the left side moves up. As the 
trunnions are displaced vertically in this way, the trunnions 33, 33 and 
the trunnions 37, 37 tilt about the tilt axes 11, initiating the speed 
change sequence for increasing the speed. The controller 52 performs a 
feedback control to make the actual transmission ratio approach the target 
transmission ratio. As the actual transmission ratio approaches the target 
transmission ratio, the target displacement of each trunnion 33, 33, 37, 
37 comes close to zero. When the actual transmission ratio agrees the 
target transmission ratio, the target displacements of the trunnions 33, 
33, 37, 37 become zero, returning the power rollers 6, 9 to the neutral 
position, finishing the speed change sequence. 
Next, by referring to FIG. 3, another embodiment of the toroidal continuous 
variable transmission of this invention will be described. This embodiment 
differs from the first embodiment of FIG. 1 in the structure of the back 
of the output disks 5, 8, the structure of the output shaft 22, and the 
structure for supporting the output disks 5, 8 on the wall 26 of casing 
25. In other respects, constructions are similar to the first embodiment. 
The identical parts are given like reference numerals and explanation will 
center on these differing structures. 
The output disk 5 and the output disk 8 each have cylindrical portions 59, 
59 extending axially from their back. An output gear 60 as the output 
shaft bridges the both cylindrical portions 59, 59 and engages them so 
that it can rotate together with the cylindrical portions 59, 59. The 
output disk 5 and the output disk 8 are directly supported on the walls 26 
of the casing 25 through the radial bearings 24 that support only radial 
loads. 
Next, by referring to FIG. 4, still another embodiment of the toroidal 
continuous variable transmission will be explained. This embodiment shown 
in FIG. 4 differs from the first embodiment of FIG. 2 in the structure of 
support shafts 34, 34 and the mounting structure on the trunnions 33, 33. 
In other respects, constructions are similar to those shown in FIG. 1 and 
2. The identical parts are given like reference numerals and explanation 
will center on these differing structures. 
The support shafts 34, 34 are formed straight without offsetting the axes 
of their ends 35, 36. One end 35, 35 of the support shafts 34, 34 is 
mounted unpivotable or unrotatable on the trunnions 33, 33, and the other 
end 36, 36 of the support shafts 34, 34 rotatably supports the power 
rollers 6, 6. Because the power rollers 6,6 are positioned relative to the 
casing 25, they cannot swing with respect to the trunnions 33, 33. On the 
other hand, the support shafts 38, 38 are eccentric shafts with the axes 
of their ends 39, 40 offset from each other. One end 39, 39 of the support 
shafts 38, 38 is pivotably supported on the trunnions 37, 37, as in the 
conventional transmission, while the other end 40, 40 of the support 
shafts 38, 38 rotatably supports the power rollers 9, 9. That is, because 
the power rollers 9, 9 are swingably supported on the trunnions 37, 37, 
the toroidal continuous variable transmission of this embodiment can 
absorb changes in the thrust-directional position caused by deformations 
of the disks 4, 5, 7, 8. 
While, in the embodiment of FIG. 4, the one end 35, 35 of the support 
shafts 34, 34 is mounted unpivotable on the trunnions 33, 33, because the 
axes of both ends 35, 36 of the support shafts 34, 34 are not offset, they 
can be pivotably mounted on the trunnions 33, 33. 
Although, in the above embodiments, only the power rollers 9, 9 are shown 
to perform the swinging motion with the power rollers 6, 6 not performing 
the swinging action, it is possible to set only the power rollers 6, 6 to 
perform the swinging motion and the power rollers 9, 9 not to oscillate.