A friction-roller speed changer has three intermediate rollers (12a, 12b, 12c). Two rollers (12a, 12b) of which act as a wedge roller and can be moved into the narrower area of an annular space (10) by the transmission of power, wherein during power transmission from the input side in the normal state to the output side. The other intermediate roller (12a or 12b), which does not act as the wedge roller, moves into the wider area of the annular space (10) against the elastic force of the spring (14) whereby transmission efficiency for bidirectional rotation is maintained while preventing backflow of power.

FIELD OF THE INVENTION 
This invention relates to improvements to a friction-roller-type speed 
changer that is installed in various kinds of machinery and is used for 
decelerating or accelerating a rotating force from a drive unit, such as 
an electric motor, while transmitting it to a driven unit, and in the case 
that the power for the drive unit is not necessary, it improves the 
efficiency of the machinery by preventing the drive unit from being a 
load. 
BACKGROUND OF THE INVENTION 
A friction-roller-type speed changer generates less noise than a gear-type 
speed changer, such as one which uses planetary gears, even when operating 
at high speeds. The use of this kind of friction-roller-type speed changer 
in a bicycle which uses auxiliary power from an electric motor to reduce 
the amount of force required for stepping on the pedals has been disclosed 
in Japanese Patent Publication Tokukai Hei No. 7-95744. 
FIG. 1 is a block diagram of an auxiliary-powered drive apparatus for a 
bicycle etc. To drive the load 1, such as gears or the like of the 
bicycle, a first input unit 2, which is the input of human power from the 
pedals, etc., and a second input unit 3, which is from an electric motor, 
are arranged in parallel. The second input unit 3 has higher speed but 
lower torque when compared with the first input unit 2, and in the stage 
that follows it, there is a decelerator 4, which reduces the speed and 
increases the torque of the power that is input from the second input unit 
3. The input unit 3 uses a sensor (not shown in the figure) to detect tile 
drive force that is applied from the first input unit and to generate a 
drive force that corresponds to that drive force, so that even if the 
force applied to the first input unit 2 is small, it is possible to drive 
the load 1. In other words, a driving torque T.sub.2, that corresponds to 
the driving torque T.sub.1 generated by the first input unit 2, is 
generated by the second input unit 3 and decelerator 4. Moreover, both of 
these driving torques, T.sub.1 and T.sub.2, are combined in a combination 
unit 5, and the total torque T.sub.3 (if losses due to friction are 
ignored, T.sub.3 =T.sub.1 +T.sub.2) drives the load 1. 
In the example of an auxiliarily powered bycicle, when forcibly pressing 
the pedal regardless of whether going down a gradual slope or driving with 
a strong following wind, the torque T.sub.1 applied to the first input 
unit 2 may be larger than the total torque T.sub.3 required for driving 
the load (T.sub.1 &gt;T.sub.3). In this case, of the torque T.sub.1 that is 
applied to the first input unit 2, the amount (T.sub.1 -T.sub.3) that 
exceeds the torque T.sub.3 required to drive the load 1 is transmitted 
back to the second input unit 3 from the combination unit 5 by way of the 
decelerator 4 as shown in FIG. 2 This then rotates the rotor of the 
electric motor which makes up the second input unit 3. As a result, the 
driving torque T.sub.1 that is applied to the first input unit 2 is not 
efficiently used for driving the load 1, and the force required to 
generate the driving torque T.sub.1 by the first input unit 2 (for example 
the force required to press the pedal) becomes uselessly larger. 
Conventionally, to solve this kind of problem, a single-direction clutch is 
placed between the decelerator 4 and the combination unit 5, so that power 
is transmitted only in the direction of the combination unit 5 from the 
decelerator 4. On the other hand, by changing the decelerator 4 from a 
normal fiction-roller type to a wedge-roller type, it is possible to omit 
the single-direction clutch as disclosed in Japanese Patent Publication 
Tokukai Hei No. 9-061329. FIG. 3 shows a construction of this kind of 
friction-roller speed changer -of the wedge-roller type. 
This friction-roller speed changer of the wedge-roller type comprises a 
center roller 7, whose outer surface is a first cylindrical surface 6, aid 
an outer ring 9 whose inner surface is a second cylindrical surface 8, and 
which is located around the center roller 7 to rotate freely with respect 
to the center roller 7. The center roller 7 is fixed to one end of a first 
rotating shaft so that it is concentric with the first rotating shaft, and 
the end of a second rotating shaft is coupled with and fixed to the outer 
ring 9 so that it is concentric with the outer ring 9. 
In the annular space 10 between the first cylindrical surface 6 and the 
second cylindrical surface 8, there are three shafts 11a, 11b which are 
located so as to be parallel with the center roller 7 and outer ring 9, 
and these shafts 11a, 11b rotatably support intermediate rollers 12a, 12b, 
12c. The outer peripheral surface of each of these intermediate rollers 
12a, 12b, 12c is a third cylindrical surface 13 where each third 
cylindrical surface 13 comes in contact with the first and second 
cylindrical surfaces 6 and 8. Moreover, by making the center of the center 
roller 7 and the center of the outer ring 9 eccentric with each other, the 
width of the annular space 10 is uneven in the circumferential direction. 
Of the three intermediate rollers, 12a, 12b, 12c, the intermediate roller 
12a is a wedge roller that is supported so that it freely move a little hi 
the circumferential direction in the annular space 10, and through the use 
of a spring 14, that is pressure or biasing means, the wedge-roller or 
intermediate roller 12a is elastically pressed in the direction to the 
narrow width portion of the annular space 10. 
When transmitting a rotational force using a friction-roller-type speed 
changer that is constructed as described above, if the center roller 7 is 
rotated in the clockwise direction as indicated by the arrow ".alpha." in 
FIG. 3, the wedge roller or intermediate roller 12a rotates in the 
counterclockwise direction as indicated by the arrow ".beta." with shaft 
11a as the center, and the outer ring 9 also rotates in the 
counterclockwise direction as indicated by the arrow ".gamma.". 
Here, the intermediate roller 12a rotates as shown by the arrow ".beta.", 
and both the center roller 7 and the outer ring 9, which hold the 
intermediate roller 12a therebetween, rotate in opposite directions, 
".alpha." and ".gamma.", and as a result the entire intermediate roller 
12a has a tendency to move in the clockwise direction of FIG. 3 as 
indicated by the arrow ".gamma.". In other words, the intermediate roller 
12a receives a force in the direction of arrow ".gamma." from the center 
roller 7 which rotates in the direction of arrow ".alpha.", and the 
intermediate roller 12a per se rotates in the direction of arrow ".beta.", 
and by so doing, the intermediate roller 12a receives a force in the 
direction for arrow ".gamma." from the reaction received from the point of 
contact with the second cylindrical surface 8 that is formed on the inner 
peripheral surface of the outer ring 9. 
As a result, as the center roller 7 rotates, the intermediate roller 12a 
tends to move toward the narrow width area of the annular space 10. Also, 
the third cylindrical surface 13 that is formed on the outer peripheral 
silence of this intermediate roller 12a strongly presses against the first 
cylindrical surface 6 which is formed around the outer peripheral surface 
of the center roller 7, and the second cylindrical surface 8 which is 
formed around the inner peripheral surface of the outer ring 9. As a 
result, the contact pressure at the radially inner contact point 15, where 
the third cylindrical surface 13 comes in contact with the first 
cylindrical surface 6, and at the radially outer contact point 16, where 
the third cylindrical surface 13 comes in contact with the second 
cylindrical surface 8, becomes greater. 
As the contact pressure at both the inner and outer contact points 15 and 
16 of the wedge roller or intermediate roller 12a becomes greater, at 
least one of the center roller 7 and outer ring 9, that are respectively 
pressed by the third cylindrical surface formed around the outer 
peripheral surface of the intermediate roller 12a, is displaced a little, 
due to an installation gap or to elastic deformation, in the respective 
radial direction. 
As a result, the contact pressure becomes higher at two radially inner 
contact points 15 where the third cylindrical surfaces 13 that are formed 
around the outer peripheral surfaces of the remaining intermediate rollers 
12b, 12c come in contact with the first cylindrical surface 6, and at two 
radially outer contact points 16 where these third cylindrical surfaces 13 
come in contact with the second cylindrical surface 8. 
The force which moves the intermediate roller 12a, which functions as a 
wedge roller, in the direction of the narrow width area of the annular 
space 10 varies according to the size of the torque that is transmitted 
from the center roller 7 to the outer ring 9. Moreover, as this force 
becomes large, the contact pressure at the radially inner and outer 
contact points 15 and 16 becomes greater. Therefore, the transmission 
efficiency of the fiction-roller-type speed changer is maintained by 
automatically selecting a contact pressure that corresponds to the 
transmission torque. 
The above was an example of using the friction-roller-type speed changer as 
a decelerator, where the center roller 7 was taken to be the input side 
and the outer ring 9 was taken to be the output side. Conversely, if the 
friction-roller-type speed changer is used as an accelerator by taking the 
outer ring 9 to be the input side and the center roller 7 to be the output 
side, except that the direction of rotation is opposite, the other action 
is the same, and it is possible to transmit power between the outer ring 9 
and the center roller 7, while at the same time maintaining the 
transmission efficiency of the friction-roller-speed changer by 
automatically selecting a contact pressure that corresponds to the 
transmitted torque. 
If the members on the output side rotate at a higher speed than the speed 
which corresponds to the members on the input side, the intermediate 
roller 12a which functions as a wedge roller, tends to move in the 
direction to the wide portion in tile annular space 10, and the contact 
pressure at the radially inner contact points 15 and radially outer 
contact points 16 is lost, and transmission of power between the center 
roller 7 and the outer ring 9 is broken. 
In other words, when the friction-roller speed changer is used as a 
decelerator, if the outer ring 9 rotates in the direction of arrow 
".gamma." in FIG. 3 while the center roller 7 is stopped, the intermediate 
roller 12a tends to move in the direction to the wide area in the annular 
space 10 against the elastic force of the spring 14. When the 
friction-roller speed changer is used as an accelerator as well, if the 
center roller 7 rotates in the direction opposite to the arrow ".alpha." 
in FIG. 3 while the outer ring 9 is stopped, the intermediate roller 12a 
tends to move in the direction to the wide area in the annular space 10 
against the elastic force of the spring 14. 
In the case of a wedge-roller type friction-roller speed changer when the 
output member rotates at a higher speed than the speed that corresponds to 
the input member, power transmission between the center roller 7 and outer 
ring 9 is broken off. Therefore, in the drive system shown in FIGS. 1 and 
2, even if the single-direction clutch between the decelerator 4 and the 
combination unit 5 is omitted, it is possible to prevent the drive force 
that is applied to the first input unit 2 due to the existence of the 
electric motor or second input unit 3 from becoming uselessly large. 
As in the case of an auxiliary-powered bicycle, if the construction is such 
that the direction of the driving force applied to the load 1 is set, then 
by using the friction-roller speed changer of the wedge-roller type as 
shown in FIG. 3 as a decelerator 4, it is possible to both reduce cost by 
omitting the single-direction clutch and to maintain the transmission 
efficiency by optimizing the contact pressure. On the other hand, if the 
direction of the driving force to be applied to the load 1 is not set, 
then the friction-roller speed changer as shown in FIG. 3 cannot be used. 
In other words, with the friction-roller speed changer shown in FIG. 3, if 
the direction of rotation of the transmitted power is reversed, then the 
intermediate roller 12a, which functions as a wedge roller, tends to move 
in the direction to the wide area in the annular space 10, and the contact 
pressure at the radially inner contact points 15 and the radially outer 
contact points 16 is lost, and power is not transmitted between the center 
roller 7 and the outer ring 9. For example, the friction-roller speed 
changer of FIG. 3 cannot be used in a device that is driven by stepping on 
a pedal, such as in an amusement park ride or a pedal boat, or where it is 
possible to turn the pedals in both directions. 
In this kind of situation, a friction-roller speed changer is used that is 
constructed as shown in FIG. 4, where there are three intermediate rollers 
12a, 12b and 12c, of which the intermediate rollers 12a and 12b function 
as wedge rollers. FIG. 4 shows the friction-roller speed changer that is 
disclosed on U.S. Pat. No. 4,709,589. In this second example of a 
friction-roller speed changer, two intermediate rollers 12a, 12b of the 
three intermediate rollers 12a, 12b, 12c are supported so that they can 
each move a little in the circumferential direction of the annular space 
10, and act as wedge rollers. 
Moreover, these two intermediate rollers 12a, 12b, which act as wedge 
rollers, are elastically pressed toward the narrow width area of the 
annular space 10 by springs 14, respectively, in substantially opposite 
circumferential directions (move toward each other). With the construction 
of this second example, regardless of the direction of the relative 
rotation of the center roller 7 and outer ring 9, one of the two 
intermediate rollers 12a, 12b, which act as wedge rollers, is wedged into 
the narrow width area of the annular space 10, and maintains the contact 
pressure at the radially inner contact points 15 and radially outer 
contact points 16. Therefore, regardless of the direction of rotation of 
the transmitted power, it is possible to maintain the transmission 
efficiency by optimizing the contact pressure. 
In the case of a friction-roller speed changer, as shown in FIG. 4, that is 
capable of maintaining the transmission efficiency regardless of the 
direction of rotation of the transmitted power, if the driving torque that 
T.sub.1 that is applied by the first input unit 2 is greater than the 
torque T.sub.3 that is required to drive the load 1 (T.sub.1 &gt;T.sub.3) as 
shown in FIG. 4 as described above, then the force required to generate 
the driving torque T.sub.1 at the first input unit 2 becomes uselessly 
greater. In other words, in the case of the friction-roller speed changer 
shown in FIG. 4, regardless of the relative direction of rotation between 
the center roller 7 and the outer ring 9, power is constantly transmitted 
between the center roller 7 and the outer ring 9. Accordingly, if the 
driving torque T.sub.1 that is applied at the first input unit 2 is 
greater than the torque T.sub.3 required to drive the load 1, the electric 
motor, which makes up the second input unit 3, in addition to the load 1 
must be driven by the power applied from the first input unit 2 through 
human power. As a result, the force that must be applied at the first 
input unit 2 becomes uselessly larger, and this is undesirable. 
In the friction-roller speed changer having a single intermediate roller 
12a as the wedge roller as shown in FIG. 3, when the rotational force is 
added in a reversed direction from the side of load 1, it is impossible to 
separate the load 1 from the second input unit 3 (FIGS. 1 and 2). For 
example, when moving back the auxiliarily powered bicycle, the outer ring 
9 (FIG. 3), that is the decelerator 4, tends to be rotated in a clockwise 
direction in FIG. 3 (opposite direction to the arrow .gamma. in FIG. 3) by 
the rear wheel l of the bicycle, that is load, by means of a chain and 
crank shaft. 
In this case, the intermediate roller 12a tends to move toward the narrower 
area of the annular space 10 to transmit the rotational force to the 
center roller 7 from the outer ring 9. Consequently, when moving back the 
auxiliarily powered bicycle, the electric motor, that is the second input 
unit 3, must be rotated, and by that amount, the force required to move 
back the bicycle is larger. 
U.S. Pat. No. 4,481,842 discloses a structure to shut off the power 
transmission when the torque that is to be transmitted through the 
friction-roller speed changer is at a predetermined value or more. 
However, in this structure, if the torque is below the predetermined valve, 
the power is transmitted even when it is not desired. On the contrary, 
when the torque is the predetermined value or more, the power transmission 
is shut off even when the power transmission is required. Therefore, the 
structure does not make sense in solving the problems as mentioned above. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a friction-roller speed 
changer to solve this problem. 
Another object of the present invention is to provide a friction-roller 
speed changer with transmission efficiency improved while preventing the 
useless application of resistance. 
Another object of the present invention is to provide a friction-roller 
speed changer wherein whether power transmission is carried out or not is 
freely selected.

DETAILED DESCRIPTION OF THE INVENTION 
The friction-roller speed changer of this invention in one feature is 
similar in construction to the second example of a friction-roller speed 
changer as shown FIG. 4, in that it comprises a first rotating shaft, a 
center roller which is attached to the end of the first rotating shad so 
that it is concentric with the first rotating shaft, and whose outer 
peripheral surface forms a first cylindrical surface, an outer ring whose 
inner peripheral surface forms a second cylindrical surface and which is 
provided around the center roller to freely rotate with respect to the 
center roller, a second rotating shaft provided concentric with the outer 
ring and having one end portion securely connected to the outer ring, at 
least three shafts that are arranged inside the annular space between the 
first cylindrical surface and second cylindrical surface so as to be 
parallel with the first rotating shaft, and at least three intermediate 
rollers which are rotatably supported by these three shafts, respectively, 
and whose outer peripheral surfaces each form a third cylindrical surface. 
Also, by making the center of the first rotating shaft eccentric with the 
center of the second rotating shaft and outer ring, the width of the 
annular space becomes unequal in the circumferential direction to provide 
narrower and wider areas in the annular space. 
Moreover, two of the at least three intermediate rollers care supported so 
that they can be displaced a little in the circumferential direction of 
the annular space and act as wedge rollers, and a pressure means is used 
in order to elastically press these two intermediate rollers, which act as 
wedge rollers, toward the narrower width area of the annular space in 
opposite directions from each other in the substantially circumferential 
direction. 
Particularly in the friction-roller speed changer of this invention, there 
is a selective pressure means for pressing one of the two intermediate 
rollers which act as wedge rollers, in the direction of the wider area of 
the annular space against the elastic force of the pressure means. Through 
this selective pressure means, one of the two intermediate rollers or 
wedge rollers, is pressed toward the wider area of the annular space. 
In the friction-roller speed changer of this invention constructed as 
described above, only the intermediate roller that acts as a wedge roller 
when transmitting the rotating drive force that is applied at the input 
side in the normal state, is elastically pressed in the direction to the 
narrower width area of the annular space by an elastic member. The 
intermediate roller that does not act as a wedge roller when transmitting 
the rotating drive force that is applied at the input side in the normal 
state, is pressed in the direction to the wider area of the annular space 
against the force of an elastic member by a selective pressure means. 
Therefore, the rpm of the input side becomes less than the rpm which 
corresponds to the rpm of the output side, and even if there is a tendency 
for a backflow of power from the output side to the input side, the 
contact pressure between the intermediate rollers and the first thru third 
cylindrical surfaces does not increase, making it possible to prevent 
backflow of power from tile driven unit or output side to the drive unit 
or input side. 
Now, FIGS. 5 thru 10 show a first example of the embodiments of this 
invention. The friction-roller speed changer 17 of this invention is 
equipped with a housing 18. This housing 18 is attached to the frame etc. 
(not shown in the figures) and covers the center roller 7, which is 
integrally fixed to the end of the rotating drive shaft 20 of the electric 
motor 19 of the second input unit so that it is concentric with this 
rotating drive shaft 20. The rotating drive shaft 20 corresponds to the 
first rotating shaft or second rotating shaft in the present 
specification. The housing 18 comprises a main body 21 that is cylindrical 
with a bottom, and a cover 22 that covers the opening on the base end of 
the main body 21. The center roller 7 is inserted into the housing 18 
through a hole 23 that is formed just off center from the center of the 
cover 22. Moreover, a bearing 24 is located between the inner peripheral 
surface of this hole 23 and the outer peripheral surface of the base end 
portion of the center roller 7. 
Provided at a portion on the inside of the housing 18 and surrounding the 
center roller 7 are three shafts 11a, 11b, which are arranged in parallel 
with the center roller 7. In other words, one end of each of these shafts 
11a, 11b (top end in FIGS. 5 and 8) is supported by the cover 22, and the 
other end (bottom end in FIGS. 5 and 4) is supported by a connection plate 
25. Of these three shafts 11a, 11b, the shaft 11b, as shown in the FIG. 5, 
is fixed so that it does not move by pressure fitting or without play with 
both ends thereof inserted in holes 26 that are formed in the cover 22 and 
connection plate 25. Therefore, this shaft 11b does not move in the 
circumferential or radial direction inside the housing 18. 
The remaining two shafts 11a are supported by the cover 22 and connection 
plate 25 so that the both ends thereof can freely move a little in the 
circumferential and radial directions inside the housing 18. Therefore, as 
shown in FIG. 8, in the parts of the cover 22 and connection plate 25 that 
are in alignment with both ends of the shafts 11a, there are support holes 
27 that are round with an inner diameter larger than the outer diameter of 
the both ends of the shafts 11a, or that are long in the circumferential 
direction of the cover 22 and connection plate 25, and both ends of the 
shafts 11a loosely fit into these support holes 27. Also, these shafts 
11a, 11b support rotatably the intermediate rollers, 12a, 12b, 12c. 
The intermediate rollers 12a, 12b, 12c are supported so that they do not 
move in the axial direction with respect to the shafts 11a, 11b which 
rotatably support them. Therefore, the intermediate rollers 12a, 12b, 12c 
are fixed around the shafts 11a, 11b, so that these intermediate rollers 
12a, 12b, 12c rotate freely with the shafts 11a, 11b, or the shafts 11a, 
11b are made stationary, and instead the intermediate rollers 12a, 12b, 
12c are supported around the shafts 11a, 11b so that they rotate freely by 
way of deep groove-shaped ball bearings as shown in FIG. 5. 
Part of the connection plate 25 is joined to protrusions located on part of 
the inside surface of the cover 22 (bottom surface in FIG. 5 on the side 
where the intermediate rollers 12a, 12b, 12c are installed) at a location 
separated the intermediate rollers 12a, 12b, 12c. (The protrusions are 
disclosed in U.S. Pat. No. 4,709,589 and so are not shown in the figure.) 
Moreover, a gap 29 is formed between one side surface of the connection 
plate 25 (top surface in FIG. 5) and one side surface of the intermediate 
rollers 12a, 12b, 12c (bottom surface in FIG. 5) in the area between the 
shafts 11a which support the intermediate rollers 12a, 12b that act as 
wedge rollers. This gap 29 makes it possible for a pressure lever 30 (to 
be described later) to rock freely. Also, of the protrusions not shown in 
the figure, the protrusion that is located between the pair of shafts 11a 
is placed in the radially outer portion of the annular space 10 where the 
intermediate rollers 12a, 12b, 12c are located (further outward in the 
radial direction than the shafts 11a, 11a). 
Moreover, on the inside of the housing 18, in the area that surrounds the 
intermediate rollers 12a, 12b, 12c, there is a rotatable cylindrical outer 
ring 9 that has a bottom. This outer ring 9 comprises a cylindrical 
section 31 and a circular disc plate 32 that covers the opening at one end 
(bottom end in FIG. 5) of the cylindrical section 31. The inner peripheral 
surface of the cylindrical section 31 forms a smooth second cylindrical 
surface 8 which comes in contact with a smooth third cylindrical surfaces 
13 which are formed on the outer peripheral surfaces of the intermediate 
rollers 12a, 12b, 12c. Also, the base end (the top end in FIG. 5) of an 
output shaft 33 is connected to the outer surface of the disc plate 
section 32 (the surface opposite of the space where the intermediate 
rollers 12a, 12b, 12c are located, or the lower surface in FIG. 5). This 
output shaft 33 corresponds to the second rotating shaft or first rotating 
shaft in the present application. Moreover, this output shaft 33 protrudes 
out from the housing 18 through a second through hole 34 that is formed in 
the center portion of the main body 21 of the housing 18. 
A bearing 35 is located between the outer peripheral surface at a base end 
portion of the output shaft 33 and the inner peripheral surface of the 
second through hole 34, so that the outer ring 9 and output shaft 33 are 
supported so as to rotate freely with respect to the housing 18. Also, a 
gear 36 for retrieving the power is attached around the tip half portion 
of the output shaft 33 (lower half portion in FIG. 5), in the part that 
protrudes out from the housing 18. 
The outer peripheral surfaces of the intermediate rollers 12a, 12b, 12c 
come in contact with the outer peripheral surface of the center roller 7 
and the inner peripheral surface of the outer ring 9. 
In the friction-roller speed changer of this invention, similar to the 
second example of the prior friction-roller speed changer shown in FIG. 4, 
the center of the center roller 7 is eccentric with reference to the 
centers of the output shaft 33 and outer ring 9 In other words, as 
described above, the through hole 23, through which the center roller 7 is 
inserted, is located just a little off center from the center of the 
housing 18, and the second through hole 34, through which the output shaft 
33 passes, is located in the center of the housing 18. Furthermore, the 
output shaft 33 that is supported on the inside of the second through hole 
34 is concentric with the outer ring 9. Therefore, the center roller 7 is 
eccentric with reference to the outer ring 9 and output shaft 33 by the 
amount ".epsilon." that the through hole 23 is separated from the center 
of the housing 18. Also, the dimension of the width of the annular space 
10 between the outer peripheral surface of the center roller 7 and the 
inner peripheral surface of the outer ring 9, where the intermediate 
rollers 12a, 12b, 12c are located, is unequal in the circumferential 
direction by the amount corresponding to this eccentricity ".epsilon.". 
Therefore, the intermediate rollers 12a, 12b, 12c have different outer 
diameters by the amount that the width size of the annular space 10 is 
unequal in the circumferential direction. In other words, the intermediate 
rollers 12a, 12b, which act as wedge rollers and which are located on the 
side where the center roller 7 is eccentric with respect to the outer ring 
9 (left side in FIG. 6), have the same relatively small diameter. 
On the other hand, the intermediate roller 12c, which acts as a guide 
roller and which is located on the opposite side from the center roller 7 
which is eccentric with respect to the outer ring 9 (right side in FIG. 
6), has a larger diameter than the diameters of the two intermediate 
rollers 12a, 12b, which act as wedge rollers. 
Moreover, the third cylindrical surfaces 13 which are formed around the 
outer peripheral surfaces of these three intermediate rollers 12a, 12b, 
12c, come in contact with the first cylindrical surface 6 formed around 
the outer peripheral surface of the center roller 7, and with the second 
cylindrical surface 8 formed around the inner peripheral surface of the 
outer ring 9. The speed change ratio of the friction-roller speed changer 
17 is determined from the ratio of the diameter of the first cylindrical 
surface 6 and diameter of the second cylindrical surface 8. Therefore, in 
order to obtain the required speed reduction ratio, it is possible to fit 
a sleeve around the tip end portion of the center roller 7 and to brig the 
outer peripheral surface of the sleeve in contact with the outer 
peripheral surfaces of the intermediate rollers 12a, 12b, 12c. In this 
case, the first cylindrical surface is formed by the outer peripheral 
surface of the sleeve. 
Moreover, between the two intermediate rollers 12a, 12b, which act as wedge 
rollers, and the housing 18 or connecting plate 25, there is a pressure 
means or springs 14 that elastically press or bias the two intermediate 
rollers 12a, 12b toward the narrow width area of the annular space 10, in 
opposite directions from each other in the circumferential direction 
(toward each other). 
Furthermore, in the fiction-roller speed changer 17 of this invention, 
there is a selective pressure means that presses one of the two 
intermediate rollers 12a, 12b, which act as wedge rollers, toward the wide 
area of the annular space 10 against the elastic force of the spring 14. 
In this embodiment, in order to construct this selective pressure means, 
the base end portion of a pressure lever 30 is friction fitted at the tip 
end portion of the center roller 7 in the part that sticks out from one 
side surfaces (lower surfaces in FIG. 4) of the intermediate rollers 12a, 
12b, 12c. In other words, a small-diameter section 37 that is concentric 
with the center roller 7 is formed on the tip end portion of the center 
roller 7, and a fitting cylindrical portion 38 is formed in the base end 
portion of this pressure lever 30 and fitted onto and supported by this 
small-diameter section 37 though a friction sleeve 39. Therefore, when the 
center roller 7 is rotating, the pressure lever 30 tends to rotate in the 
same direction as the center roller 7 due to a torque that is determined 
based on the friction force between the inner and outer peripheral 
surfaces of the friction sleeve 39 and the outer peripheral surface of the 
small-diameter section 37 and the inner peripheral surface of the fitting 
cylindrical portion 38. 
The pressure lever 30 freely moves in a rocking manner in the gap 29 in the 
circumferential direction of the annular space 10, so that the tip end 
portion of the pressure lever 30 abut against the shafts 11a that support 
the two intermediate rollers 12a, 12b which act as wedge roller. On the 
other hand, the elastic force of the springs 14 which presses these shafts 
11a is relatively weak, such that if the pressure lever 30 is pressing 
against either one of tie shafts 11a, the intermediate roller 12a (or 12b) 
that is supported by that shaft 11a is pressed in the direction to the 
wide area in the annular space 10. 
If rotational force is transmitted by a friction-roller speed changer 
constructed as described above, contact pressure is always maintained 
between the third cylindrical surfaces 13 which are formed around either 
one of the wedge rollers or intermediate rollers 12a (or 12b) and around 
the guide roller or intermediate roller 12c, and the first cylindrical 
surface 6 which is formed around the center roller 7, and the second 
cylindrical surface 8 which is formed around the outer ring 9. 
Also, it is possible to efficiently transmit the rotational driving force 
from the center roller 7 to the outer ring 9 by way of either one of the 
intermediate rollers 12a (or 12b) and intermediate roller 12c. When doing 
this, the other intermediate roller 12b (or 12a) of the two intermediate 
rollers 12a, 12b, is moved toward the wide area of the annular space 10 by 
the pressure lever 30 which makes up the selective pressure means, and 
therefore it does not supply any rotational driving force to the outer 
ring 9 from the center roller 7. 
If, for example, the center roller rotates in the clockwise direction as 
shown by arrow ".alpha." in FIG. 9, the intermediate roller 12a which is 
supported by one of the shafts 11a (lower one in FIGS. 9 and 10), is moved 
toward the narrow area of the annular space 10, and this intermediate 
roller 12a acts as a wedge roller and efficiently transmits the rotational 
driving force from the center roller 7 to the outer rig 9. 
On the other hand, the other of the shafts 11a (upper one in the figure) is 
pressed by the pressure lever 30, so that the intermediate roller 12b, 
which is supported by this shaft 11a, is retracted toward the wide area of 
the annular space 10 as shown in FIG. 10 (A). In this state, if the speed 
that the output shaft 33 rotates the outer ring 9 becomes faster than the 
speed that the center roller 7 is trying to rotate the outer ring 9 (when 
the outer ring 9 in FIG. 10 (A) tends to relatively rotate in the 
counterclockwise direction with reference to the center roller 7), both of 
the two intermediate rollers 12a, 12b, which act as wedge rollers, are 
retracted toward the wide area of the annular space 10. In other words, in 
this state, the intermediate roller 12b, that is supported by the upper 
shaft 11a in FIGS. 9 and 10, is pressed by the pressure lever 30, and not 
only is it retracted toward the wide area of the annular space 10, but the 
intermediate roller 12a tends to be retracted toward the wide area of the 
annular space 10 by the rotational force that is applied from the outer 
ring 9. 
As a result, the contact pressure between all of the third cylindrical 
surfaces 13 which are formed around the outer peripheral surfaces of all 
of the intermediate rollers 12a, 12b, 12c, and the first and second 
cylindrical surfaces 6, 8, becomes low, and transmission of the rotational 
driving force from the outer ring 9 to the center roller 7 stops. 
Therefore, the existence of the electric motor 19 applies no resistance to 
rotating the outer ring 9 from the side of the output shaft 33. In other 
words, as shown in FIG. 7, when the driving torque T.sub.1, that is input 
from the first input unit 2, becomes larger than the torque T.sub.3, that 
is required for driving the load 1, there is a tendency for a backflow of 
rotational driving force, as shown by arrow ".theta." in the figure, from 
the first input unit 2 to the second input unit 3 where the electric motor 
19 is located. However, even in this case, if the friction-roller speed 
changer 17 of this invention is used as a decelerator 4, then the backflow 
of rotational driving force is cut off by the decelerator 4, as shown by 
the "X " mark in the figure, so that it is possible to prevent the second 
input unit 3 from resisting the driving force that is applied from the 
first input unit 2. 
On the other hand, if the center roller 7 rotates in the counterclockwise 
direction as shown by arrow ".beta." in FIG. 6, the intermediate roller 
12b, that is supported by tile upper shaft 11a in FIGS. 6, 9 and 10, moves 
toward the narrow area of the annular space 10, and this intermediate 
roller 12b, which acts a wedge roller, and efficiently transmits the 
rotational driving force from the center roller 7 to the outer ring 9. 
Here, the lower shafts 11a in FIGS. 6, 9 and 10 is biased by the pressure 
lever 30, and the intermediate roller 12a, that is supported by the lower 
shaft 11a in FIGS. 6, 9 and 10, is retracted toward the wide area of the 
annular space 10 as shown in FIG. 10 (B). In this case as well, backflow 
of rotational driving force is cut off by the decelerator 4, so that it is 
possible to prevent the second input unit 3 from resisting the driving 
force that is applied from the first input unit 2. 
In the explanation above, the friction-roller speed changer 17 was used as 
a decelerator, however, even if it is used as an accelerator, by similar 
function, it is possible to prevent the second input unit 3 from resisting 
the driving force that is applied from the first input unit 2. If the 
friction-roller speed changer 17 is used as an accelerator, the outer ring 
9 becomes the input side, and the center roller 7 becomes the output side. 
Next, FIGS. 11 and 12 show a second example of the invention. In this 
embodiment, on the part of the housing 18 that is separated in the axial 
direction from the outer rig 9, there is a pair of pressure arms 40a, 40b 
that are supported so as to move freely in the radial direction of the 
housing 18. Moreover, these pressure arms 40a, 40b are driven in the 
radial direction of the housing 18 by an actuator (not shown in the 
figures) such as a solenoid or air cylinder. A slanted surface 41 is 
formed on the tip end portions of these pressure arms 40a, 40b. Also, when 
the pressure arms 40a, 40b have been moved inward in the radial direction 
of the outer ring 9, the slanted surface 41 comes in contact with the 
outer peripheral surfaces of the shafts 11a, and this causes the wedge 
rollers or intermediate rollers 12a, 12b which are supported by the shafts 
11a to retract toward the wide area of the annular space 10. 
In this embodiment of the invention which is constructed as described 
above, the detection signal from a sensor which detects the direction of 
rotation of the center roller 7 (or outer ring 9) on the input side is 
input to a controller which controls the actuator. When power is 
transmitted from the input side, specifically center roller 7 (or outer 
ring 9) to the output side, specifically output ring 9 (or center roller 
7), the intermediate roller 12a (or 12b) that does not act as a wedge 
roller must be retraced toward tie wide area of the annular space 10, and 
therefore the pressure arm 40a (or 40b) is pushed forward in the direction 
of the shaft 11 a which supports that intermediate roller 12a (or 12b). 
The other construction and functions are the same as that of the first 
embodiment. 
The friction-roller speed changer of this invention is constructed and 
functions as described above, and makes it possible to improve the 
efficiency of auxiliary power supplied from a source such as an electric 
motor to a driven unit that rotates in both direction. 
The friction-roller speed changer of this invention in another feature also 
comprises a first rotating shaft, a center roller which is attached to the 
end of the first rotating shaft so that it is concentric with the first 
rotating shaft, and whose outer peripheral surface forms a first 
cylindrical surface, an outer ring whose inner peripheral surface forms a 
second cylindrical surface and which is provided around the center roller 
to freely rotate with respect to the center roller, a second rotating 
shaft provided concentric with the outer ring and having one end portion 
securely connected to the outer ring, a plurality of shafts that are 
arranged inside the annular space between the first cylindrical surface 
and second cylindrical surface so as to be parallel with the first 
rotating shaft, and a plurality of intermediate rollers which are 
rotatably supported by the shafts, respectively, and whose outer 
peripheral surfaces each form a third cylindrical surface. Also, by making 
the center of the first rotating shaft eccentric with the center of the 
second rotating shaft and outer ring, the width of the annular space 
becomes unequal in the circumferential direction to provide narrower and 
wider areas in the annular space. 
Moreover, at least one of the intermediate rollers is supported so as to be 
displaced a little in the circumferential direction of the annular space 
to act as a wedge roller, and a pressure means is used in order to 
elastically press the at least one intermediate roller, which acts as the 
wedge roller, toward the narrower width area of the annular space. 
Particularly, the intermediate roller acting as the wedge roller, or the 
shaft for supporting the intermediate roller is made of a magnetic 
material or permanent magnet, and a solenoid is supported and fixed to 
face the intermediate roller or the shaft. The intermediate or wedge 
roller can be displaced toward the wider area of the annular space 
depending on whether the solenoid is turned on or off. 
Accordingly, only the intermediate roller which is a wedge roller upon 
transmitting the rotational drive force added at the input side in the 
normal state is elastically pressed toward the narrower area of the 
annular space only when the rotational drive force is input from the input 
side in the normal state. 
Consequently, except when the rotational drive force normally added at the 
input side in the normal state is transmitted, no rotational force is 
transmitted between the center roller and the outer ring. 
Now, FIGS. 13 thru 19 show another example of the embodiments of this 
invention. The friction-roller speed changer 17 of this invention is 
equipped with a housing 18 which is made off a non-magnetic material such 
as aluminium alloy. This housing 18 is attached to the frame etc. (not 
shown in the figures) and covers the center roller 7, which is integrally 
fixed to the end of the rotating drive shaft 20 of the electric motor 19 
of the second input unit so that it is concentric with this rotating drive 
shaft shaft 20. The rotating drive shaft 20 corresponds to the first 
rotating shaft or second rotating shaft in the present specifications. The 
housing 18 comprises a main body 21 that is cylindrical with a bottom, and 
a cover 22 that covers the opening on the base end of the main body 21. 
The center roller 7 is inserted into the housing 18 through a hole 23 that 
is formed almost at the center of the cover 22. Moreover, a bearing 24 is 
located between the inner peripheral surface of this hole 23 and the outer 
peripheral surface of the base end portion of the center roller 7. 
Provided at a portion on the inside of the housing 18 and surrounding the 
center roller 7 are three shafts 11a, 11b, which are arranged in parallel 
with the center roller 7. In other words, one end of each of these shafts 
11a, 11b (top end in FIGS. 13 and 16) is supported by the cover 22, and 
the other end (bottom end in FIGS. 13 and 16) is supported by a connection 
plate 25. Of these three shafts 11a, 11b, the two shafts 11b are fixed so 
as not to move by pressure fitting or without play with both ends thereof 
inserted in holes 26 that are formed in the cover 22 and connection plate 
25. Therefore, the two shafts 11b do not move in the circumferential or 
radial direction inside the housing 18. 
The remaining single shaft 11a is supported by the cover 22 and connection 
plate 25 so that the both ends thereof can freely move a lite in the 
circumferential and radial directions inside the housing 18. Therefore, as 
shown in FIGS. 14 to 16, in the parts of the cover 22 and connection plate 
25 that are in alignment with both ends of the shafts 11a, there are 
support holes 27 that are round with an inner diameter larger than the 
outer diameter of the both ends of the shafts 11a, or that are long in the 
circumferential direction of the cover 22 and connection plate 25, and 
both ends of the shafts 11a loosely fit into these support holes 27. Also, 
these shafts 11a, 11b support rotatably the intermediate rollers, 12a, 
12b, 12c. 
Incidentally, part of the connection plate 25 is joined to protrusions 128 
located on part of the inside surface of the cover 22 (left surface in 
FIG. 13 on the side where the intermediate rollers 12a, 12b, 12c are 
installed) at a location separated the intermediate rollers 12a, 12b, 12c. 
Moreover, on the inside of the housing 18, in the area that surrounds the 
intermediate rollers 12a, 12b, 12c, there is a rotatable cylindrical outer 
ring 9 that has a bottom. This outer ring 9 comprises a cylindrical 
section 129 and a circular disc plate 130 that covers the opening at one 
end (bottom end in FIGS. 13, 16) of the cylindrical section 129. The inner 
peripheral surface of the cylindrical section 129 forms a smooth second 
cylindrical surface 8 which comes in contact with a smooth third 
cylindrical surfaces 13 which are formed on the outer peripheral surfaces 
of the intermediate rollers 12a, 12b, 12c. Also, the base end (the top end 
in FIGS. 13, 16) of an output shaft 131 is connected to the outer surface 
of the disc plate section 130 (the surface opposite of the space where the 
intermediate rollers 12a, 12b, 12c are located, or the lower surface in 
FIGS. 13, 16). This output shaft 131 corresponds to the second rotating 
shaft or first rotating shaft in the present application. Moreover, this 
output shaft 131 protrudes out from the housing 18 through a second 
through hole 132 that is formed in the center portion of the main body. 21 
of the housing 18. 
A bearing 133 is located between the outer peripheral surface at a base end 
portion of the output shaft 131 and the inner peripheral surface of the 
second through hole 132, so that the outer ring 9 and output shaft 131 are 
supported so as to rotate freely with respect to the housing 18. 
The outer peripheral surfaces of the intermediate rollers 12a, 12b, 12c 
come in contact with the outer peripheral surface of the center roller 7 
and the inner peripheral surface of the outer ring 9. 
In the friction-roller speed changer of this invention, similar to the 
examples of the prior art friction-roller speed changer shown in FIGS. 3, 
4, the center of the center roller 7 is eccentric with reference to the 
centers of the output shaft 131 and outer ring 9. In other words, as 
described above, the through hole 23, through which the center roller 7 is 
inserted, is located almost at the center of the housing 18, and the 
second through hole 132, through which the output shaft 131 passes, is a 
little separated from the center of the housing 18. Accordingly, the 
thickness of the peripheral wall of housing 18 is uneven in the 
circumferential direction. Furthermore, the output shaft 131 that is 
supported on the inside of the second through hole 132 is concentric with 
the outer ring 9. Therefore, the center roller 7 is eccentric with 
reference to the outer ring 9 and output shaft 131 by the amount 
".epsilon." (FIGS. 13, 16) that the through hole 132 is separated from the 
center of the housing 18. Also, the dimension of the width of the annular 
space 10 between the outer peripheral surface of the center roller 7 and 
the inner peripheral surface of the outer ring 9, where the intermediate 
rollers 12a, 12b, 12c are located, is unequal in the circumferential 
direction by the amount corresponding to this eccentricity " .epsilon.". 
Therefore, the intermediate rollers 12a, 12b, 12c have different outer 
diameters by the amount that the width size of the annular space 10 is 
unequal in the circumferential direction. In other words, the two 
intermediate rollers 12a, 12b, which are located on the side where the 
center roller 7 is eccentric with respect to the outer ring 9 (lower side 
in FIGS. 14, 16), have the same relatively small diameter. 
On the other hand, the intermediate roller 12c, which is located on the 
opposite side from the center roller 7 which is eccentric with respect to 
the outer ring 9 (upper side in FIGS. 13, 14, 16), has a larger diameter 
than the diameters of the two intermediate rollers 12a, 12b. 
Moreover, the third cylindrical surfaces 13 which are formed around the 
outer peripheral surfaces of these three intermediate rollers 12a, 12b, 
12c, come in contact with the first cylindrical surface 6 formed around 
the outer peripheral surface of the center roller 7, and with the second 
cylindrical surface 8 formed around the inner peripheral surface of the 
outer ring 9. The speed change ratio of the friction-roller speed changer 
17 is determined from the ratio of tie diameter of the first cylindrical 
surface 6 and diameter of the second cylindrical surface 8. Therefore, in 
order to obtain the required speed reduction ratio, it is possible to fit 
a sleeve around the tip end portion of the center roller 7 and to bring 
the outer peripheral surface of the sleeve in contact with the outer 
peripheral surfaces of the intermediate rollers 12a, 12b, 12c. In this 
case, the first cylindrical surface is formed by the outer peripheral 
surface of the sleeve. 
Moreover, the intermediate roller 12a rotatable supported around the shaft 
11a acts as wedge rollers. Accordingly, there is a pressure means or 
springs 14 provided between the shaft 11a with the intermediate roller 12a 
and the connection plate 25 as shown in FIGS. 14, 16, 17. The spring 14 
that is a compression spring, elastically press or bias the wedge roller 
12a toward tile narrow width area of the annular space 10 through the 
pressing piece 134 and the shaft. 11a. 
In the friction-roller speed changer 17 of this invention, the shaft 11a 
for supporting the wedge roller or intermediate roller 12a is made of a 
magnetic material such as steel. And, the cover 22 has a portion formed 
with a support hole 135 which is opened on the inner peripheral surface of 
the support hole 27 on the side of the wider width area of the annular 
space 10. Supported in the support hole 135 is a solenoid 136 the tip end 
face of which (left lower end face of FIG. 15) faces the outer peripheral 
surface at the end of the shaft 11a. When the solenoid 136 is turned on, 
the magnetic attractive force of the larger than the elastic force of the 
spring 14 is exerted between the solenoid 136 and the shaft 11a. 
Thus, the spring 14 set in the connection plate 25 is aligned with the 
solenoid 136 set in the cover 22, so that the displacement direction of 
the intermediate roller 12a supported by the shaft 11a can be freely 
selected. Specifically, when the solenoid 136 is not turned on, the shaft 
11a and intermediate roller 12a are elastically biased by the elastic 
force of the spring 14 toward the narrower area of the annular space 10, 
while when the solenoid 136 is turned on, the shaft 11a and intermediate 
roller 12a are biased toward the wider area of the annular space 10. 
By transmitting rotational force by the friction roller speed changer 
constructed as mentioned above, the contact pressure can be secured 
between the first cylindrical surface 6 around the center roller 7 and the 
third cylindrical surfaces 13 around the wedge or intermediate roller 12a 
and around the two guide or intermediate rollers 12b, 12c and between the 
second cylindrical surface 8 inside the outer ring 9 and the third 
cylindrical surfaces 13 around the wedge or intermediate roller 12a and 
around the two guide or intermediate rollers 12b, 12c. The rotational 
drive force can be efficiently transmitted from the center roller 7 to the 
outer ring 9 through the three intermediate rollers 12a, 12b, 12c. This 
transmitting operation of the rotational drive force is similar to, that 
of the example of FIG. 3. 
Upon transmitting the rotational drive force applied through the center 
roller 7, normally on the input side, to the friction-roller speed changer 
17 of this invention, the wedge or intermediate roller 12a is elastically 
pressed toward the narrower areas of the annular space 10 only when tie 
rotational drive force is input from the center roller 7. For example, in 
the present embodiment, the electric power to the solenoid 136 is 
controlled under the condition as shown in the flow chart of FIG. 18. 
First, in the case where the electric motor 19 is turned on, and the 
solenoid 136 is turned off when the rotational drive force produced by the 
electric motor 19 is transmitted from the center roller 7 to the outer 
ring 9 through the intermediate rollers 12a, 12b, 12c. As a result, the 
rotational drive force is efficiently transmitted from the center roller 7 
to the outer ring 9, which is similar to the example of FIG. 3. 
On the other hand, in the case where the electric motor 19 is not turned 
on, and there is no need of the rotational drive force taken out, the 
solenoid 136 is turned on, so that tie shaft 11a and the intermediate 
roller 12a are displaced toward the wider area of the annular space 10 as 
shown in FIG. 19. Consequently, the contact pressure is lost between the 
first cylindrical surface 6 around the center roller 7 and the third 
cylindrical surfaces 13 around the wedge or intermediate roller 12a and 
around the two guide or intermediate rollers 12b, 12c and between the 
second cylindrical surface 8 inside the outer ring 9 and the third 
cylindrical surfaces 13 around the wedge or intermediate roller 12a and 
around the two guide or intermediate rollers 12b, 12c. In this state, the 
rotational drive force is not transmitted to the center roller 7, and the 
existence of the electric motor 19 is not a resistance against the 
rotation of theouter ring 9. Accordingly, for example, the auxiliarily 
powered bicycle can be easily moved back. 
FIG. 20 shows another example of the embodiments of this invention, where 
the tip end face of the solenoid 136 is separated from the outer 
peripheral surface of the shaft 11a of the magnetic material when the 
solenoid 136 is turned on, which is different from the example of FIG. 17. 
Specifically, in this example, when the solenoid 136 is turned on to 
attract the shaft 11a against the elastic force of the spring 14, the 
outer peripheral surface of the shaft 11a comes into contact with the 
inner peripheral surface of the support holes 27 before the tip end face 
of the solenoid 136 comes into contact with the outer peripheral surface 
of the shaft 11a. Accordingly, when the solenoid 136 is turned off, the 
tip end face of the solenoid 136 is easily separated from the outer 
peripheral surface of the shaft 11a, and the shaft 11a is hardly 
magnetized. The other elements of structure and operation are 
substantially the same as those of FIG. 17. 
FIGS. 21 to 23 show another example of the embodiments of the present 
invention, where the present invention is applied to the conventional 
structure as shown in FIG. 4, specifically having two intermediate rollers 
12a, 12b as wedge rollers for sufficient transmission efficiency in either 
rotational direction of drive force to be transmitted. Accordingly, the 
solenoids 136a, 136b are provided in alignment with the springs 14 to 
elastically press the shafts 11a with intermediate rollers 12a, 12b in 
circumferentially opposite directions. The solenoids 136a, 136b are set in 
a similar manner as in the example of FIGS. 13 and 19. 
In the present embodiment, the electric power to the solenoid 136a, 136b is 
controlled under the condition as shown in the flow chart of FIG. 23. 
First, in the case where the electric motor 19 (FIG. 13) is turned on to 
rotate the center roller 7, and when the rotational drive force produced 
by the electric motor 19 is transmitted from the center roller 7 to the 
outer ring 9 either one of the solenoids 136a, 136b is turned on and the 
other turned off corresponding to the rotational direction (see 
.alpha..sub.1 and .alpha..sub.2 in FIG. 22). As a result, the rotational 
drive force is efficiently transmitted from the center roller 7 to the 
outer ring 9, which is similar to the example of FIG. 4. 
On the other hand, in the case where the electric motor 19 is not turned 
on, and there is no need of the rotational drive force taken out, the 
solenoid 136a, 136b are turned on, so that the shafts 11a and the 
intermediate rollers 12a are displaced toward the wider area of the 
annular space 10, so that they are separated from each other. 
Consequently, the contact pressure is lost between the first cylindrical 
surface 6 around the center roller 7 and the third cylindrical surfaces 13 
around the three intermediate rollers 12a, 12b, 12c and between the second 
cylindrical surface 8 inside the outer ring 9 and the third cylindrical 
surfaces 13 around the three intermediate rollers 12a, 12b, 12c. In this 
state, the rotational drive force of the outer ring 9 is not transmitted 
to the center roller 7, and the existence of the electric motor 119 is not 
a resistance against the rotation of the outer ring 9. 
FIG. 24 shows another example of the embodiments of the present invention, 
where the solenoid 136 to displace the shaft 11a against the elastic force 
of the spring 14 is provided in the support hole 135a which is formed 
through the cover 22 and in parallel with the center roller 7. By this 
construction, the power supply leads for the solenoid 136 are not taken 
out of the electric motor 19 with the friction-roller speed changer, which 
has the cover 22 provided adjacent the electric motor 19. In addition, in 
this structure of FIG. 24 where the stator of the motor 19 can be 
positioned closer to the solenoid 136, the wiring for power control to the 
stator and associated solenoid 136 can be simplified. The other elements 
of structure and operation are substantially the same as those of FIG. 13. 
In the examples as mentioned above, as the solenoid is turned on, the 
intermediate rollers as wedge rollers are moved together with their shafts 
toward the wider area of the annular space 10. On the contrary, it is 
possible, as the solenoid is turned of to make the intermediate rollers as 
wedge rollers moved together with their shafts toward the wider area of 
the annular space 10 based on the elastic force of the spring which is 
weak comparing with the attractive force of the solenoid. In this case, 
the solenoid elastically presses the intermediate or wedge rollers toward 
the narrower area of the annular space 10. 
In addition, it is possible to make the wedge or intermediate rollers of a 
magnetic material such as steel, so that the solenoid facing the outer 
peripheral surface of the center roller can be turned on so as to move the 
intermediate roller(s) toward the wider or narrower area of the annular 
space. In this construction, the both ends of the shaft supporting the 
intermediate roller can elastically pressed with a spring, so that the 
intermediate roller is elastically moved toward the narrow (or wide) area 
of the annular space. Accordingly, the balance of the forces between the 
shaft and the intermediate roller becomes good in the circumferential 
direction of the annular space. 
FIG. 25 show another example of the embodiments of the present invention, 
where a pair of support holes 135b, 135c extend in opposite directions 
with reference to the circumferential direction in the annular space, with 
the support hole 27 therebetween. The both ends of shaft 11a of the wedge 
roller or intermediate roller are loosely engaged with the support hole 
27. The solenoids 136c, 136d are provided in the support holes 135b, 135c, 
respectively, so that the tip end face of the solenoids 136c, 136d faces 
the outer peripheral surface at the end of the shaft 11a. This example 
does not equipped with the spring to press the shaft 11a toward the 
narrower area of the annular space as in the previous examples. 
In the present example having the pair of solenoids 136c, 136d, depending 
on whether the rotational force is transmitted between the center roller 7 
and the outer ring, either one of the solenoids 136c, 136d is turned on, 
and the other turned off. Specifically, when transmitting the rotational 
force from the center roller 7 to the outer ring, the solenoid 136c (left 
lower one in FIG. 25) is turned on and the solenoid 136d (right upper one 
in FIG. 25) is turned off. As a result, the shaft 11a with the 
intermediate roller is displaced toward the narrower area of the annular 
space. In this state, the solenoid 136c functions as a pressure means to 
elastically press the wedge or intermediate roller toward the narrower 
area of the annular space, and the rotational drive force is transmitted 
efficiently from the center roller 7 to the outer ring as in the structure 
of FIG. 3. 
On the other hand, when there is no need of transmitting the rotational 
drive force from the center roller 7 to the outer ring, the solenoid 136d 
is turned on and the solenoid 136c is turned off. As a result, the shaft 
11a with the intermediate roller is displaced toward the wider area of the 
annular space. In this state, the rotational drive force is not 
transmitted to the center roller 7, and the existence of the electric 
motor connected to tie center roller 7 is not a resistance against the 
rotation of the outer ring. 
The pair of solenoids provided for each of the shafts for supporting the 
intermediate or wedge roller can be applied to the structure of FIGS. 21 
to 23 where two intermediate rollers are used as wedge rollers. In 
addition, the intermediate or wedge roller is made of a magnetic material 
such as steel, and the intermediate roller can be moved in a 
circumferential direction of the annular space, based on the power control 
to the pair of solenoids opposed to each other with respect to the outer 
peripheral surface of the center ring. 
FIG. 26 show another example of the embodiments of the present invention, 
where the shaft 11a for supporting the intermediate or wedge roller 12a is 
axially magnetized (left and right directions in FIG. 26), and the tip end 
face (lower end face in FIG. 26) of the solenoid 136 faces the outer 
peripheral surface of the shaft 11a at one end thereof (right end in FIG. 
26). Based on the change in power supply directions to the solenoid 136, 
the tip end face of the solenoid 136 becomes either S-pole or N-pole. In 
this example, the spring to press the shaft 11a toward the narrower area 
of the annular space is not provided. 
Incidentally, the solenoid 136 can be arbitrarily provided either in the 
narrower area or in the wider area of the annular space with reference to 
the shaft 11a, which is a design matter depending o installation space 
etc. The direction of the power supply, to the solenoid 136 depends on 
whether the rotational force is transmitted between the center roller and 
the outer ring or not, which in turn depends on the side where the 
solenoid 136 is provided. 
With the present example, the power supply to the solenoid 136 is changed 
in direction and the magnetic polarity on the tip end face of die solenoid 
136 is changed depending on whether the rotational force is transmitted 
between the center roller and the outer ring. The following explanation is 
made on the example of the solenoid 136 with S-pole on its end face 
provided in the wider area of the annular space 10 with reference to the 
shaft 11a. 
When transmitting the rotational drive force from the center roller to the 
outer ring, the tip end face is magnetized in the S-pole. As a result, 
based on the magnetic repulsive force between the like poles, the shaft 
11a with the intermediate roller 12a is displaced toward the narrower area 
of the annular space 10. In this state, the rotational drive force can be 
transmitted efficiently from the center roller to the outer ring as in the 
case of FIG. 4. The solenoid 136 functions as a pressure means to 
elastically press the wedge or intermediate roller 12a toward the narrower 
area of the annular space. 
On the other hand, when there is no need of transmitting the rotational 
drive force from the center roller to the outer ring, the tip end face is 
magnetized in the N-pole. As a result, based on the magnetic attractive 
force between the unlike poles, the shaft 11a with the intermediate roller 
12a is displaced toward the wider area of the annular space 10. In this 
state, the rotational drive force is not transmitted to the center roller. 
In this example, the spring is omitted and only the single solenoid is 
provided to displace the shaft 11a with the intermediate roller in either 
circumferential direction of the annular space, which provides a compact 
and light-weighted structure. 
When the solenoid is placed on the narrower area of the annular space, the 
direction of magnetization is reversed with respect to whether or not the 
transmission of rotational drive force is required, but the similar 
function and effects are obtained. Accordingly, the present invention 
provide a compact and light structure. 
The present invention is described on the examples using three shafts each 
with an intermediate roller, but the friction roller speed change of the 
wedge roller type can be composed of a plurality of shafts each with an 
intermediate roller, specifically e.g. of two intermediate rollers or of 
four intermediate rollers. The two intermediate rollers, when adopted, are 
placed slightly on the narrower area side of the annular space, not on the 
diametrically opposite positions, with respect to the circumferential 
direction of the center roller. When two wedge rollers are adopted, three 
or more intermediate rollers are required.