DUTSON BRIAN (GB)
WO1998036191A1 | 1998-08-20 | |||
WO2003062670A1 | 2003-07-31 | |||
WO2003062670A1 | 2003-07-31 | |||
WO2002079675A1 | 2002-10-10 | |||
WO2003062675A1 | 2003-07-31 |
EP1439325A2 | 2004-07-21 | |||
US4735430A | 1988-04-05 | |||
US1817159A | 1931-08-04 | |||
DE10338271A1 | 2005-03-17 | |||
GB380485A | 1932-09-16 |
CLAIMS
1. A variator comprising a pair of races mounted for rotation about a common axis and
having respective shaped faces which together define an annular cavity containing at least
one roller which runs upon the shaped faces of the races to transfer drive from one race to the other, the roller having a roller axis and being mounted upon a carrier through bearings
which permit the roller to spin about its axis and also to precess relative to the carrier to
change the inclination of the roller axis to the common axis and so to enable changes in variator ratio, the variator further comprising a sun and a ring which are concentric with and
mounted for rotation about the common axis, the carrier engaging with the sun and the ring
so that relative rotation of the sun and ring causes a tilting motion of the carrier and a
consequent change in the inclination of the roller axis, the variator further comprising a
mechanism for controlling rotation of the sun and ring, the mechanism comprising a planet
which is mounted in the annular cavity and which operatively engages with the sun and the ring, an actuator which is operatively coupled to the planet, and an arrangement for
controlling rotation of the planet independently of its engagement with the sun and the ring.
2. A variator as claimed in claim 1 in which the arrangement for controlling rotation of the
planet serves to prevent the planet from rotating.
3. A variator as claimed in claim 1 in which the actuator is arranged to move the planet
along a circumferential direction of travel about the common axis.
4. A variator as claimed in claim 3 in which the arrangement for controlling rotation of the
planet is adapted to prevent the planet from rotating and to accommodate some movement
of the planet along a direction transverse to its travel direction.
5. A variator as claimed in claim 4 in which the arrangement for controlling rotation of the
planet comprises a tongue slidably received in a slot.
6. A variator as claimed in any preceding claim in which the actuator is a linear actuator.
7. A variator as claimed in claim 4 in which the actuator comprises a hydraulic piston and
cylinder arrangement.
8. A variator as claimed in claim 4 in which the actuator comprises a pair of pistons in
respective cylinders.
9. A variator as claimed in any of claims 6 to 8 in which the actuator is coupled to the planet
through complementary sliding parts which accommodate some movement of the planet in
a direction transverse to the actuator's direction of travel while transmitting the actuator force to the planet and preventing the planet from rotating.
10. A variator as claimed in any preceding claim in which the sun, ring and planet are
toothed and form an epicyclic gear set.
11. A variator as claimed in any preceding claim which is torque controlled.
12. A variator as claimed in any preceding claim in which the ring comprises an annular
outer part and at least one radially extending limb leading to an inner hub part.
13. A variator as claimed in claim 12 in which the hub part is journalled about the common
axis, to mount the ring.
14. A variator as claimed in claim 13 in which the planet is operatively coupled to the ring
through a control member which extends radially outwardly from the hub part of the ring.
15. A variator as claimed in claim 14 in which the control member has a toothed outer part
which meshes with a toothed outer part of the planet.
16. A variator comprising a pair of races mounted for rotation about a common axis and
having respective shaped faces which together define an annular cavity containing at least
one roller which runs upon the shaped faces of the races to transfer drive from one race to the other, the roller having a roller axis and being mounted upon a carrier through bearings
which permit the roller to spin about its axis and also to precess relative to the carrier to
change the inclination of the roller axis to the common axis and so to enable changes in variator ratio, the variator further comprising a sun and a ring which are concentric with and
mounted for rotation about the common axis, the carrier engaging with the sun and the ring so that relative rotation of the sun and ring causes a tilting motion of the carrier and a
consequent change in the inclination of the roller axis, the variator further comprising a
mechanism for controlling rotation of the sun and ring, the mechanism comprising a planet
which is mounted in the annular cavity and which operatively engages with the sun and the
ring, and an actuator which is operatively coupled to the planet to move it along a circumferential direction about the common axis, the planet being mounted in a manner
which prevents it from rotating.
17. A variator substantially as herein described with reference to, and as illustrated in, accompanying figures 1 to 9 or accompanying figures 10 and 11. |
DESCRIPTION VARIATOR
The present invention relates to rolling-traction variators of the type in which drive is
transmitted from one race to another by one or more rollers whose orientation is variable in accordance with changes in variator drive ratio. More particularly, the invention is
concerned with a novel mechanism for control of roller orientation in such a variator.
The word "variator" is used herein to refer to a device which transmits rotary drive at a
continuously variable ratio. Variators are particularly, but by no means exclusively,
applicable in motor vehicle transmissions.
The best known form of rolling-traction type variator uses at least two co-axially mounted
races having opposed faces which are shaped so that the races together define an
approximately toroidal space. At least one roller is positioned in the space between the races
and runs upon their shaped faces to transmit drive from one to the other. Changes in the
inclination of the roller are associated with changes in the relative speeds of the races, and
hence in the drive ratio provided by the variator.
The changes in roller inclination associated with changes in drive ratio will be referred to herein as "precession" to distinguish from other rotary motions of the roller, such as its
rotation about its own axis.
Some mechanism is needed to control roller inclination, and the prior art contains numerous
examples. Typically such mechanisms do not act by directly applying a torque to the roller's
mountings. Instead, the roller is mounted in such a manner that displacing it causes it to
steer itself, due to the forces exerted on it by the races, to a new inclination. The steering
effect arises because the roller seeks a position in which its own axis coincides with the common axis of the variator races, since in any other condition the motion of the roller is
non-parallel to that of the races in the area where they engage with each other. The control
mechanism serves to regulate the roller's displacement.
Examples of such mechanisms are found in many of the applicant's prior published patent
cases including PCT/GB03/00259 (WO 03/062670). In most, the displacement needed to cause the roller to steer itself is along the circumferential direction (about the common axis
of the variator races) and, by allowing the rollers to precess about an axis which is inclined to the radial plane, a relationship is established between roller displacement and roller
inclination. An actuator is provided for urging the roller along the circumferential direction
and so influencing (1) its displacement, and (2) the variator ratio.
Such mechanisms lend themselves to "torque control" of the variator. The concept is known
in the art, but will be briefly explained. More conventional "ratio controlled" transmissions
are constructed such that they receive some form of input indicating a required drive ratio,
and then adjust themselves to provide it. That is, the drive ratio is directly set. By contrast, in a torque controlled transmission it is torque which is directly set. Changes in ratio result
from application of the torque to inertias at the input and output, and the variator
automatically accommodates such changes. The sum of the torques acting on the variator
races will be referred to herein as the reaction torque, since it is the torque which must be
reacted to the variator's mountings. The reaction torque is referred to the rollers, and so through their associated actuator(s) to the variator casing. Hence by setting the actuator
force, the reaction torque itself is directly set, since (neglecting roller acceleration) the forces
exerted on each roller by the actuator and the races must be equal and opposite. Control over the transmission is exercised by controlling actuator force - and hence reaction torque
- not variator ratio.
The most widely adopted control mechanism uses a respective hydraulic piston/cylinder type actuator for each roller, the piston being coupled through a piston rod to a carriage carrying
the roller. However, a quite different type of mechanism is described herein, in which the
variator has a sun and a ring and the roller carrier engages with both. Relative rotation of
the sun and ring causes a tilting motion of the carrier, and hence causes the roller to steer
itself to a new orientation. In this type of arrangement, driving the sun is problematic. Some
coupling needs to be made to the sun for this purpose and in principle this could be made along an axial direction - e.g. through some sleeve extending along the variator's shaft - or
along a radial direction - e.g. through an arm extending through the toroidal cavity. The
former option creates design difficulties. The latter is problematic because the arm would
foul the rollers and/or their carriers as they move back and forth.
In accordance with a first aspect of the present invention, there is a variator comprising a
pair of races mounted for rotation about a common axis and having respective shaped faces which together define an annular cavity containing at least one roller which runs upon the
shaped faces of the races to transfer drive from one race to the other, the roller having a roller axis and being mounted upon a carrier through bearings which permit the roller to spin
about its axis and also to precess relative to the carrier to change the inclination of the roller
axis to the common axis and so to enable changes in variator ratio, the variator further comprising a sun and a ring which are concentric with and mounted for rotation about the
common axis, the carrier engaging with the sun and the ring so that relative rotation of the
sun and ring causes a tilting motion of the carrier and a consequent change in the inclination
of the roller axis, the variator further comprising a mechanism for controlling rotation of the
sun and ring, the mechanism comprising a planet which is mounted in the annular cavity and
which operatively engages with the sun and the ring, an actuator which is operatively coupled to the planet, and an arrangement for controlling rotation of the planet
independently of its engagement with the sun and the ring.
By controlling the planet's rotation independently of its engagement with the sun and the
ring, the planet can be used to control movement of both the sun and the ring. The planet
can also move along with the sun and ring, and as a result problems of fouling at the rollers
etc. by the planet can be avoided.
Whilst it is necessary in some way to control rotation of the planet independently of its
engagement with the sun and the ring, this should not be taken to imply that a mechanism
must be provided for rotating the planet. In a preferred embodiment, the arrangement serves
simply to prevent the planet from rotating. In such embodiments, the actuator is preferably
arranged to move the planet along a circumferential direction of travel, about the common
axis. It is this circumferential movement of the planet which produces the relative rotation
of the sun and the ring needed to control tilting of the carrier and hence variator ratio.
The path of movement of the planet is typically an arc of a circle about the common axis.
In preferred embodiments the arrangement for controlling rotation of the planet comprises
for example a tongue slidably received in a slot. In this way some movement of the planet
transverse to its direction of travel can be accommodated.
The actuator itself is preferably a linear actuator, still more preferably a hydraulic piston and
cylinder arrangement. The most preferred embodiments comprise a pair of pistons in
respect of cylinders.
Coupling between the planet and the actuator may be made through complimentary sliding
parts which accommodate some movement of the planet in a direction transverse to the
actuator's direction of travel while transmitting the actuator force to the planet and preventing the planet from rotating.
It is particularly preferred that the sun, ring and planet are toothed to form an epicyclic gear
set.
The present invention is well adapted to use in a torque controlled variator. This can be achieved simply by directly controlling the force applied by the actuator to the planet, which
in turn directly controls the reaction torque of the variator.
Preferably the ring comprises an annular outer part and at least one radially extending limb
leading to an inner hub part. The hub part may be journalled about the common axis, to
mount the ring.
It is particularly preferred that the planet is operatively coupled to the ring through a control member which extends radially outwardly from the hub part of the ring. By transmitting the
torque required to control rotation of the ring to its hub part, which can be supported through its bearing, problems of distortion of the outer part of the ring can be avoided.
Preferably in such an embodiment the control member has a toothed outer part which
meshes with a toothed outer part of the planet.
In accordance with a second aspect of the present invention, there is a variator comprising
a pair of races mounted for rotation about a common axis and having respective shaped faces which together define an annular cavity containing at least one roller which runs upon
the shaped faces of the races to transfer drive from one race to the other, the roller having
a roller axis and being mounted upon a carrier through bearings which permit the roller to
spin about its axis and also to precess relative to the carrier to change the inclination of the
roller axis to the common axis and so to enable changes in variator ratio, the variator further comprising a sun and a ring which are concentric with and mounted for rotation about the
common axis, the carrier engaging with the sun and the ring so that relative rotation of the
sun and ring causes a tilting motion of the carrier and a consequent change in the inclination
of the roller axis, the variator further comprising a mechanism for controlling rotation of the
sun and ring, the mechanism comprising a planet which is mounted in the annular cavity and
which operatively engages with the sun and the ring, and an actuator which is operatively coupled to the planet to move it along a circumferential direction about the common axis,
the planet being mounted in a manner which prevents it from rotating.
In accordance with a third aspect of the present invention, there is a variator comprising two
races mounted for rotation about a common axis and having shaped, opposed faces defining an annular space containing at least one roller which runs upon the races to transfer drive
between them, the roller being mounted on a carrier such that its inclination to the common
axis is variable to enable changes in variator drive ratio, the variator further comprising
rotatably mounted sun and ring parts with which the carrier engages so that relative rotation of the sun and ring causes a tipping motion of the carrier and a consequent change in roller
inclination, and a planet which engages with both the sun and the ring to control their
positions, the rotational position of the planet being controlled independently of its
engagement with the sun and the ring.
Specific embodiments of the present invention will now de described, by way of example only, with reference to the accompanying drawings, in which:-
Figure 1 is a section in an axial plane through a first variator embodying the present
invention, showing only half of the variator, to one side of its axis;
Figure 2 is a view of the same variator along an axial direction, one of the variator's races
being omitted to reveal interior parts. This drawing also omits the mechanism used to drive the sun and ring;
Figure 3 is a perspective illustration of the same variator, again omitting one of the races but including the mechanism used to drive the sun and ring;
Figure 4 shows a carrier part;
Figure 5 shows an exploded assembly comprising the carrier part and a bearing race;
Figure 6 shows an exploded assembly comprising a variator roller and associated bearing
parts;
Figure 7 shows an assembly comprising the carrier, roller and bearing;
Figures 8 and 9 both show a roller assembly and its associated sun and ring, viewed along an axial direction,
Figure 10 is a perspective view of a second variator embodying the present invention, in
which one of the variator races and a control member are omitted to reveal interior parts;
and
Figure 11 corresponds to Figure 10 but includes the control member.
The general construction of the present variator 10 can be appreciated from Figures 1 to 3.
It is of toroidal-race, twin cavity type, having an inner race 12 whose semi-toroidally
recessed surfaces 14, 16 respectfully face toward similarly shaped surfaces 18, 20 of outer
races 22, 24 to define approximately toroidal cavities 26, 28. The races are mounted for rotation about a common axis 30 defined by a main shaft 32. The outer races 22, 24 are
splined to the shaft and so rotate along with it. The inner race is mounted upon a rotary
bearing 34 and so is rotatable relative to the shaft. It carries on its outer periphery a rotor
36, through which rotary drive is transferred to/ from the inner race.
Each cavity 26, 28 contains a set of rollers 38, 40. In the present embodiment there are three
rollers per cavity. The rollers run upon the recessed surfaces 14, 16, 18, 20 of the races and so serve to transfer drive between them. The inclination of roller 38 to the common axis 30
is represented in Figure 1 by the angle I. Precession of the rollers changes roller inclination
I and accordingly, since it results in a change of the relative lengths of the circular paths
traced upon the respective races by each of the rollers, changes the relative speeds of the
inner and outer races 12, 22, 24. Hence drive is transferred between the main shaft 32 and
the rotor 36 at a continuously variable ratio.
To provide traction between the rollers and the races, they must be biased toward each other. This is typically achieved using a hydraulic or mechanical "end load" arrangement to
urge one race axially toward its fellows. The end load arrangement is not shown herein, but examples can be found in international patent application PCT/GB02/01551, Torotrak
(Development) Ltd, publication no. WO02/079675. The rollers and races do not make contact with each other, but instead are constantly separated by a thin film of traction fluid,
maintained by ejecting fluid onto them. Again, the means used to supply the traction fluid is not directly relevant for present purposes and is not shown herein, but suitable
arrangements can be found in Torotrak (Development) Ltd's international patent application
PCT/GB03/00281, published under no. WO03/062675.
Each roller 38, 40 is carried upon a respective carrier 42, 44. Both cavities 26, 28 contain
a respective sun 46, 48 and a respective ring 50, 52. The suns and the rings are co-axial with
and rotatable about the common axis 30. The sun is radially inboard of the ring. Between
themselves each sun/ring pair defines an annulus in which the carriers 42, 44 are mounted by engagement with the sun and ring. In the present embodiment the suns, rings and carriers
are toothed in the manner of gear wheels so that together they form what is in effect an
epicyclic gear arrangement. The ring's teeth are internal and it forms an annular gear wheel.
The teeth need not be continuous around the entire inner circumference of the ring, since
the range of motion of the ring is limited. Likewise the carriers do not require a complete circular outer periphery since they move only through a limited angular range. Hence the
carriers 42, 44 are each formed with a radially inner part-circular portion 54 coupled to a
radially outer part-circular portion 56 through a limb 58 (see Figure 4 in particular). This
formation of the carriers allows them to fit into the available space without fouling other
parts such as the rollers themselves.
The suns 46, 48 in the two cavities 26, 28 are coupled to each other through a sleeve 60 passing through the inner race 12, so that they rotate together. Note that the inner race 12
is consequently journalled upon the sleeve, rather than directly on the main shaft 32. The
sleeve 60 is itself journalled on the main shaft 32 by virtue of two bearings 62, 64 in the
respective cavities 26, 28. Each of the rings 50, 52 is coupled through radially extending
limbs 66, 68 to a respective hub 70, 72 and in this way is rotatably mounted, through a
respective bearing 74, 76, upon the sleeve 60. The limbs 66, 68 are shaped and positioned
to avoid fouling the rollers etc. within the cavities.
Each roller 38, 40 is mounted upon its carrier 42, 44 through a bearing arrangement which
allows the roller two degrees of freedom : (1) the roller is able to rotate about its own axis
and (2) the roller is able to precess, to change its inclination and hence the variator ratio.
The bearing arrangement will now be described with reference to Figures 4 through 7.
Rotation of the roller 38 about its own axis is provided for by means of a needle bearing 78
(Figure 6) received in the roller's central bore. Between the roller and the bearing is a
tolerance ring 80. By virtue of a corrugated construction, the tolerance ring provides some
compliance between the roller 38 and the bearing 78. In use the roller is subject to a large
force along its diameter by the variator races, and is deformed somewhat as a result. The
tolerance ring resiliently deforms to accommodate the roller deformation and so ensures that
the compressive force is borne principally by the roller itself, rather than being passed on to
the bearing. The inner race of the bearing is formed in two parts 82, 84 assembled around
a hub 86 (figure 5). The two race parts may for example be welded together, followed by
machining of their outer circumference to provide the regular circular surface required of
the inner bearing race. Alternatively they could be secured together by a circular band
around their circumference (not shown) which would provide the bearing surface. Circular
spigots 88 project from either side of the hub 86 and are concentric with and aligned along a precession axis 90. The spigots are received in complementary circular recesses 92 in inner
faces of the respective inner race parts 82, 84. The construction permits the inner bearing
race 82, 84, and the roller carried upon it, to precess relative to the carrier 42, 44 about precession axis 90.
It is important to note that the precession axis does not lie in a radial plane (i.e. a plane
which is perpendicular to the common axis 30 of the variator races, such as the plane of the
paper in Figure 2). Instead the precession axis is inclined to such a plane, to form what is
referred to as the castor angle. The point is best understood from Figure 4, which shows the
carrier 42, 44 along a direction perpendicular to the precession axis 90. The carrier's gear
teeth are seen to be inclined to the precession axis rather than perpendicular to it. This angle
of the gear teeth determines the castor angle between the precession axis and the radial
plane. The castor angle has an important bearing on variator function.
Figures 8 and 9 are intended to clarify the motion of the roller. In these drawings the roller
38, 40 is contained in a shroud 93, which is omitted from the other drawings for the sake of clarity.
It has already been explained that the roller has two degrees of freedom in its motion relative to its carrier. Additionally, the carrier itself has two degrees of freedom. It can (1) move
along a circumferential path (dotted line 95 in Figure 8) about the common axis 30 and (2)
carry out a tilting motion. In Figure 9 line 96 is a radial line - it passes through the common
axis 30 and through the centre point of the carrier 42, 44. Line 98 is a reference line fixed
with respect to the carrier. The angle X between these two lines is referred to herein as the
carrier's angle of tilt. Note that if the sun 46 and ring 50 were to rotate through identical angles, the result would be that the carrier would move circumferentially, but its angle of tilt
would not change, since the radius 96 and the reference line 98 would turn through identical
angles. Hence there would be no roller precession and no change of variator ratio.
However, consider what happens when the 46 and ring 50 rotate through different angles.
In Figure 8, the roller's position corresponds to a 1:1 variator ratio. The carrier's tilt angle
X is zero. In Figure 9, the sun 46 and ring 50 have both been advanced clockwise, causing
the roller to move along its path 95, but also the sun has advanced clockwise relative to the ring, causing the carrier 42 to tilt - the tilt angle X is now non-zero. The effect of this tilt of
the carrier is to produce a transient steering effect upon the roller 38, which has thus
precessed with respect to the carrier, adopting the illustrated, inclined, position and so changing the variator ratio. It should be apparent therefore that through the sun and ring
46, 48, 50, 52, control can be exercised over the variator.
Driving the sun and ring appropriately to control the variator presents a challenge, not least
due to the sun's position within the variator cavity. Figure 3 illustrates a variator provided with a suitable control arrangement embodying the present invention.
The arrangement uses a planet 100 which engages with and controls both the sun and the ring. The planet is here formed somewhat similarly to the carriers 42, 44. It has inner and
outer toothed portions to engage with the sun and ring respectively and these lie on a circular locus, but the planet does not require - and does not have - a full circular periphery,
and is shaped such that it can fit into the limited space between two carriers 42 without fouling them. The carrier's rotational position is not controlled by its engagement with the
sun or ring. In the illustrated embodiment, it is instead prevented from rotating by
engagement of a tongue 102 formed on the planet with a slot 104 formed in a control bar
106. The control bar projects laterally from a hydraulic piston 108 received in a cylinder
110. The hydraulic actuator formed by the piston and cylinder is double acting - that is, by
pressurising opposed working chambers 112, 114 it be made to exert a force in either
direction. The tongue and slot engagement of the planet with the control bar permits lateral
motion of the planet with respect to the piston, which is necessary since the planet follows
a path which is an arc of a circle.
When the piston 108 moves, the sun 46 and ring 50 are both moved, by means of the planet 100, in the same direction. However because the sun has a smaller diameter and fewer teeth
than the ring, the sun moves through a greater angle. Hence the carriers 42, 44 are (a) moved along their circumferential path and (b) tilted, to change variator ratio.
This arrangement can be used to provide torque control. It provides the requisite relationship between the roller's circumferential position and the variator ratio. The net
torque exerted on the rollers by the races is reacted through the piston 108, so that the force
exerted by the piston is proportional to - and determines - the reaction torque.
The relationship between piston position and carrier tilt depends upon the relative sizes of
the ring and sun, and can be chosen to suit other design requirements.
One possible difficulty with the drive arrangement illustrated in Figure 3 is that the load
exerted by the planet 100 upon the ring 50 can prove to be excessive. Note in this regard
that the forces exerted upon the ring 50 by all six of the variator rollers are to be reacted
through the single planet 100. The resultant asymmetric load can cause undesirable
distortion of the ring 50. High loads can also be imposed on the sun 46, but are less
problematic since the sun is a more compact and rigid component.
In principle it would be possible to use additional planets for variator control - perhaps one per variator cavity - but this would increase constructional complexity. Instead, in the
embodiment illustrated in Figures 10 and 11, the approach is to apply the required torque to the ring 50 through its inner portion - which can be relatively rigid and directly supported
by a bearing - rather than through its less rigid outer portion. The variator seen in these
drawings has much in common with the variator of Figure 3 and the same reference
numerals will be used for components common to both. Figure 10 omits a control member
150, to reveal the parts beneath, whilst Figure 11 includes this component.
In the present embodiment the ring 50 has an integral hub 152, which is coupled to the
ring's annular outer portion through spokes 154, of which there are three in the present
embodiment. The hub 152 contains a bearing (not seen in the drawings) through which the
ring 50 is rotatably mounted upon the main shaft 32. The control arrangement for driving
the sun 46 and ring 50 once more comprises a hydraulic actuator of double acting type, having in this embodiment a pair of piston heads 156, 158 coupled through a coupling rod
160. The piston heads 156, 158 run in respective cylinders 162, 164 and the drawings show
ports 166, 168 through which hydraulic fluid - at controlled pressure - is introduced to
working chambers 170, 172 within the respective cylinders. The difference in these
pressures constitutes the main control signal used to regulate variator behavior, and is
adjusted by means of associated hydraulics. The aforementioned pressure difference
corresponds to a net force upon the coupling rod 160 and this force is transmitted to the
planet 100. As in the Figure 3 embodiment, a coupling is required between the hydraulic
actuator and the planet 100 which provides for transmission of the actuator's force and
which accommodates the curvature of the path taken by the planet 100 as it moves back and forth. This coupling is achieved in the present embodiment by means of a tongue 174 which
is rigidly coupled to the planet 100 (they are formed as a single component in the illustrated embodiment) and which extends radially to be received in a complementarily formed slot in
the coupling rod 160. By sliding along this slot slightly, the torque 174 allows the planet
100 to follow its curved path. The tongue 174 is a close fit in its slot, however, so that the coupling thus formed prevents the planet 100 from rotating.
As before a radially innermost toothed portion of the planet 100, indicated at 176 in Figure
10, meshes with the sun 46. A radially outer toothed portion 178 of the planet 100 is operationally coupled to the ring 50, but in the present embodiment (and in contrast to the
embodiment illustrated in Figure 3) it does not mesh with the ring 50. Instead, it meshes with interior gear teeth 180 of control member 150.
The control member 150 is coupled to the ring 50 to move along with it. in the present
embodiment, control member 150 has a control hub 182 which lies around the main shaft
32 and is bolted to the hub 152 of the ring 50. An arm 184 of the control member 150 extends radially from the control hub 182 and terminates in a return 186 carrying gear teeth
180, which face radially inwardly, to mesh with the planet 100 as mentioned above. Thus
movement of the planet 100 is transmitted through the control member 150 to the ring 50.
Any tendency for asymmetric distortion of the ring 50 is reduced in this embodiment, since
lateral loads are reacted through the control hub 152 to the main shaft 32.