Note: Descriptions are shown in the official language in which they were submitted.
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DRIVEN PULLEY FOR A CONTINUOUSLY VARIABLE TRANSMISSION
CROSS REFERENCE TO PRIOR APPLICATION
The present case claims the benefits of U.S. patent application No. 62/771,828
filed 27 Nov. 2018.
The entire contents of this prior patent application are hereby incorporated
by reference.
TECHNICAL FIELD
The technical field relates generally to continuously variable transmissions
(CVTs).
BACKGROUND
CVTs are commonly used on a wide range of vehicles, such as small cars or
trucks, snowmobiles,
golf carts, scooters, etc. They generally include a driving pulley
mechanically connected to a motor,
a driven pulley mechanically connected to wheels or a track, often through
another mechanical
device such as a gearbox, and a trapezoidal drivebelt transmitting torque
between the driving pulley
and the driven pulley. A CVT automatically changes the ratio as required by
load and speed
conditions, providing a high torque under high loads at low speeds and yet
controlling the rotation
speed of the motor as the vehicle accelerates. A CVT may be used with all
kinds of motors, such
as internal combustion engines or electric motors, to name just a few.
The sides of the drivebelt are, on each pulley, gripped between opposite
conical walls of two
coaxially mounted sheaves. One sheave is referred to as the fixed sheave and
is mounted to one
end of a support shaft. This other sheave is referred to as the movable sheave
and is free to move
along the support shaft with reference to the fixed sheave, for instance by
means of bushings or the
like. The relative axial position of the sheaves changes the winding diameter
of the drivebelt on
each pulley.
At a low vehicle speed, the winding diameter of the drivebelt at the driving
pulley is minimal and
the winding diameter at the driven pulley is maximal. This is referred to as
the minimum ratio since
there is the minimum number of rotations or fraction of rotation of the driven
pulley for each full
rotation of the driving pulley.
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Generally, when the rotation speed of the driving pulley increases, its
movable sheave moves closer
to the fixed sheave thereof under the effect of a control mechanism, for
instance a centrifugal
mechanism. This constrains the drivebelt to wind on a larger diameter at the
driving pulley. The
drivebelt then exerts a radial force on the sheaves of the driven pulley in
addition to the tangential
driving force by which the torque received from the motor is transmitted. This
radial force urges
the movable sheave of the driven pulley away from the fixed sheave thereof,
thereby constraining
the drivebelt to wind on a smaller diameter at the driven pulley. The radial
force is counterbalanced
at least in part by a return force, for instance a return force generated by a
spring inside the driven
pulley and/or by another biasing mechanism. It may also be counterbalanced by
a force generated
by the axial reaction of the torque applied by the drivebelt on the driven
pulley, which force results
from the presence of a cam system and/or another biasing mechanism provided to
move the
movable sheave towards the fixed sheave as the torque increases. A cam system
generally includes
a plurality of ramp surfaces on which respective followers can be engaged. The
followers can be,
for instance, sliding buttons or rollers. The set of ramp surfaces or the set
of followers is mounted
to the movable sheave. The other set can be mounted to the support shaft of
the driven pulley. The
closing effect of the cam system on the drivebelt tension is then somewhat
proportional to the
torque received from the motor.
Generally, at the maximum vehicle speed, the ratio is maximum as there is the
maximum number
of rotations or fraction of rotation of the driven pulley for each full
rotation of the driving pulley.
Then, when the vehicle speed decreases, the rotation speed of the driving
pulley eventually
decreases as well since the rotation speed of the motor will decrease at one
point. Ultimately, this
causes a decrease of the winding diameter at the driving pulley and a decrease
of the radial force
exerted by the drivebelt on the sheaves of the driven pulley. The driven
pulley is then allowed to
have a larger winding diameter as its biasing mechanism, for instance a
spring, moves the movable
sheave closer to the fixed sheave.
Some CVTs are provided with a reversible driven pulley. A reversible driven
pulley is not limited
to only provide control in a forward mode and operates in a similar fashion to
one that is not, with
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the exception that the transmission ratio can be controlled during motor
braking when the vehicle
travels in a forward direction, or be controlled when the vehicle accelerates
in a backward direction
and the direction of the torque received from the motor is changed. These
instances are generically
referred to as the motor braking mode and the reverse mode, respectively.
During the motor braking
.. mode, the torque is no longer coming from the motor to the wheels or track
of the vehicle, but in
the opposite direction. In the reverse mode, the vehicle accelerates backwards
by changing the
direction of the torque received from the motor delivered at the CVT, as
aforesaid. Various
arrangements can be used to change the direction of the torque and bring the
CVT in the reverse
mode. For instance, if the vehicle is driven by an electric motor, the
electric motor can be a
bidirectional motor. In the case of an internal combustion engine, it is also
possible to change the
direction of rotation using an electric controller capable of selecting in
which direction the engine
rotates. Another possible approach is to use a gearbox capable of selectively
reversing the direction
of its output torque, which output torque is then delivered to the CVT.
A reversible driven pulley includes a second set of ramp surfaces and
sometimes a second set of
followers if the first set of followers is not designed to be used with the
second set of ramp surfaces.
The first set of ramp surfaces is used when the torque received from the motor
is in one direction
(forward mode), and the second set of ramp surfaces is used during a motor
braking mode or when
the torque received from the motor is in the opposite direction (reverse
mode).
It is worth mentioning that there is possibly a motor braking mode when the
vehicle travels in a
backward direction. However, given the fact that most vehicles travel
backwards only on very short
distances, such mode is rarely considered in the design of a driven pulley.
Nevertheless, a designer
may choose to design a driven pulley with such mode.
It is generally desirable that the maximum ratio of a CVT be as high as
possible. The minimum
winding diameter at the driven pulley is one of the limiting factors. The
presence of various parts
between the bottom of the belt-receiving groove and the support shaft is an
obstacle to a more
compact design. Yet, some configurations can be very difficult or sometimes
even impossible to
achieve if the available space around the CVT cannot be increased.
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Overall, there is still room for further improvements in this area of
technology.
SUMMARY
In one aspect, there is provided a driven pulley for use in a continuously
variable transmission
having a drivebelt, the driven pulley being coaxially mountable around a
support shaft and
including: a fixed sheave having opposite front and rear sides, the front side
of the fixed sheave
being provided with a conical wall; a movable sheave coaxial with the fixed
sheave and having
opposite front and rear sides, the front side of the movable sheave being
provided with a conical
wall facing the conical wall of the fixed sheave to form a drivebelt-receiving
groove; a support
coaxial with the two sheaves, the support being at a fixed axial distance from
the fixed sheave and
facing the rear side of the movable sheave; at least two axisymmetric first
cam surfaces provided
on one among the rear side of the movable sheave and the support; a set of
first cam followers
provided on the other one among the second side of the movable sheave and the
support, each first
cam follower being engageable with a respective one of the first cam surfaces;
a biasing element
provided between the movable sheave and the support; first means for providing
a direct torque-
transmitting engagement between the sheaves while allowing a relative axial
motion between them,
the first means being located within an annular space between the support
shaft and a bottom of
the belt-receiving groove; second means for pivotally connecting the fixed
sheave on the support
shaft; third means for pivotally and slidably connecting the movable sheave on
the support shaft;
and fourth means for rigidly connecting the support to the support shaft.
In another aspect, there is provided a driven pulley, as shown, described
and/or suggested herein.
In another aspect, there is provided a method of manufacturing a driven
pulley, as shown, described
and/or suggested herein.
In another aspect, there is provided a CVT including a driven pulley, as
shown, described and/or
suggested herein.
More details on the various aspects, features and advantages of the proposed
concept can be found
in the following detailed description and the appended figures.
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BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a cross-section view of a continuously variable transmission (CVT)
incorporating an
example of a driven pulley as improved;
FIG. 2 is a semi-schematic top view illustrating the CVT of FIG. 1 installed
in a generic vehicle;
5 FIG. 3 is a first isometric view of the driven pulley in FIG. 1, the
driven pulley being at the
minimum ratio position;
FIG. 4 is a side view of the driven pulley shown in FIG. 3;
FIG. 5 is a second isometric view of the driven pulley shown in FIG. 3;
FIG. 6 is a view similar to FIG. 3 but with a cutaway section;
.. FIG. 7 is a cross-section view of the driven pulley shown in FIG. 3;
FIG. 8 is an isometric view illustrating the front side of the movable sheave
in the driven pulley
shown in FIG. 3;
FIG. 9 is an isometric view illustrating the rear side of the fixed sheave in
the driven pulley shown
in FIG. 3;
.. FIGS. 10 and 11 are enlarged isometric views of the central hub of the
fixed sheave in the driven
pulley shown in FIG. 3;
FIGS. 12 and 13 are isometric views of the fixed sheave and the support shaft
in the driven pulley
shown in FIG. 3;
FIG. 14 is an enlarged view of one of the inserts provided in the passageways
of the driven pulley
shown in FIG. 3;
FIG. 15 is an enlarged exploded view showing how an insert can be positioned
into a passageway;
FIGS. 16 and 17 are isometric views of the support in the driven pulley shown
in FIG. 3;
FIG. 18 is a side view of the driven pulley shown in FIG. 3, the driven pulley
being now at the
maximum ratio position;
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FIG. 19 is a cross-section view of the driven pulley shown in FIG. 18;
FIGS. 20 and 21 are isometric views similar to FIGS. 3 and 5 but showing a
variant of the driven
pulley as improved where the hub is made integral with the rest of the fixed
sheave;
FIG. 22 is a cross-section view of the driven pulley shown in FIGS. 20 and 21;
FIG. 23 is a cross-section view of a variant of the driven pulley as improved;
FIG. 24 is a cross-section view of another variant of the driven pulley as
improved;
FIG. 25 is a cross-section view of a CVT incorporating an example of a known
driven pulley;
FIG. 26 is a semi-schematic top view illustrating the CVT of FIG. 25 installed
in the same generic
vehicle as in FIG. 2; and
__ FIGS. 27 and 28 are cross-section views provided for dimensional
comparisons between the driven
pulleys in FIGS. 1 and 25.
DETAILED DESCRIPTION
FIG. 1 is a cross-section view of a continuously variable transmission (CVT)
100 incorporating an
example of a driven pulley 200 as improved herein. The CVT 100 also includes a
driving
pulley 102 and a trapezoidal drivebelt 104. The illustrated driving pulley 102
is only an example
provided for the sake of illustration and many other possible configurations
or arrangements exist.
The driven pulley 200 can thus be used with a different kind of driving
pulley.
The driving pulley 102 includes a fixed sheave 110 and a movable sheave 112.
The fixed
sheave 110 is so-called because, during operation, it remains at the same
axial position along a
support shaft 114 on which it is mounted. The movable sheave 112 is axially
movable along the
support shaft 114 with reference to the fixed sheave 110 and is so-called for
this reason. The
position of the movable sheave 112 is governed by a control mechanism, for
instance a centrifugal
mechanism 116 with flyweights as shown. Other kinds of control mechanisms can
be used as well,
such as an electromechanical mechanism, a hydraulic mechanism, etc.
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The support shaft 114 of the driving pulley 102 is designed to be mounted on
the output shaft of a
motor, for instance an internal-combustion engine, an electric motor or any
other suitable kind of
motor capable of generating torque. The driving pulley 102 can also be mounted
on a shaft that is
not directly located at the output of the motor.
The driving pulley 102 of FIG. 1 is designed for use with an internal-
combustion engine. In the
illustrated example, the movable sheave 112 is farther than the width of the
drivebelt 104 when the
rotation speed of the driving pulley 102 is below a certain threshold, for
instance when the engine
is at idle speed. The centrifugal mechanism 116 does not generate enough axial
force to
counterbalance a return spring 118 and this caused the distance between the
sheaves 110, 112 to
be maximum. No motive power is transmitted from the driving pulley 102 to the
drivebelt 104.
This situation can be referred to as the unclutched position. Furthermore, the
illustrated driving
pulley 102 includes a bearing arrangement 120 mounted around the support shaft
114 at the bottom
of the drivebelt-receiving groove. This bearing arrangement 120 includes one
or more bearings, for
instance ball bearings or the like, to support the interior of the drivebelt
104. When the driving
pulley 102 is in the unclutched position, the bearing arrangement 120
minimizes the forces
transmitted from the driving pulley 102 to the drivebelt 104 and the driving
pulley 102 simply
rotates at the engine idle speed.
Some implementations may use a bearing arrangement 120 having a one-way
mechanism therein.
Different kinds of devices are possible. A one-way bearing arrangement 120
allows the driving
pulley 102 to rotate at idle speed without transmitting any significant force
to the drivebelt 104, for
instance when the engine is started and the vehicle is not moving. However, it
allows torque to be
transmitted from the drivebelt 104 to the driving pulley 102, even if it is in
the unclutched position,
as soon as the outer race of the bearing arrangement 120 rotates faster than
the rest of the driving
pulley 102. This situation may occur, for instance, when the vehicle travels
down a hill and the
engine is at idle speed. The one-way bearing arrangement 120 can automatically
initiate a motor-
braking mode in such circumstance since it can force the driving pulley 102,
along with the engine,
to rotate faster. This increase in the rotation speed will eventually activate
the centrifugal
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mechanism 116 to reduce the distance between the two sheaves 110, 112 enough
to put them into
a full engagement with the lateral sides of the drivebelt 104. This capability
can be referred to as a
self-activated engine braking (SAEB). If the bearing arrangement 120 is not a
one-way bearing, or
if no bearing arrangement is present at all, then the engine braking will not
occur unless the driver
of the vehicle voluntary increases to engine speed just enough to at least
pinch the drivebelt 104
between the sheaves 110, 112. This situation can be referred to as a driver-
activated engine braking
(DAEB). A driver can activate engine braking even if the CVT has a SAEB
capability but a CVT
without a SAEB capability will not go into an engine braking mode by itself
When designing a CVT with a SAEB capability, it is generally desirable that
the driven pulley
.. includes a full-torque configuration, namely that the two sheaves of the
driven pulley be in a direct
torque-transmitting engagement. In a driven pulley that does not have a full-
torque configuration,
the fixed sheave is in a direct torque-transmitting engagement with the
support shaft of the driven
pulley and about half the torque received from the drivebelt 104 goes from the
fixed sheave directly
to the support shaft. The other half goes through the movable sheave and is
transmitted to the
support shaft by the cam system. Because a different set of cam surfaces is
engaged by the followers
during motor braking, the transition between the sets of cam surfaces creates
a relative angular
displacement of the movable sheave with reference to the support shaft of the
driven pulley. The
fixed sheave does not follow the rotation of the movable sheave when it is in
a direct torque-
transmitting engagement with the support shaft and this results in shear
forces on the drivebelt.
This is prevented in a full-torque configuration because the fixed sheave and
the movable sheave
do not pivot relative to one another.
FIG. 2 is a semi-schematic top view illustrating the CVT 100 of FIG. 1
installed in a generic
vehicle 130. This example is only for the sake of illustration and there are
numerous other possible
configurations and arrangements. The vehicle 130 includes an engine 132, and
the driving
pulley 102 of the CVT 100 is mounted at the end of an output shaft thereof The
driven pulley 200
is mounted at the end of an input shaft of a gearbox 134. This gearbox 134 is
connected to the
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driving wheels of the vehicle 130 by a driveshaft 136 and other powertrain
components. Other
configurations and arrangements are possible as well.
FIG. 3 is a first isometric view of the driven pulley 200 in FIG. 1, the
driven pulley 200 being at
the minimum ratio position. The driven pulley 200 includes a fixed sheave 210
having opposite
.. front and rear sides. FIG. 3 shows the rear side of the fixed sheave 210.
The front side of the fixed
sheave 210 includes a conical wall 212 extending on a major portion of its
radius. The driven
pulley 200 also includes a movable sheave 214 that is coaxial with the fixed
sheave 210. The
movable sheave 214 has opposite front and rear sides, the front side of the
movable sheave 214
being provided with a conical wall 216. The conical wall 216 of the movable
sheave 214 faces the
conical wall 212 of the fixed sheave 210 to form a drivebelt-receiving groove
218, as shown in
FIG. 4. FIG. 4 is a side view of the driven pulley 200 shown in FIG. 3.
FIG. 5 is a second isometric view of the driven pulley 200 shown in FIG. 3.
The driven pulley 200 also includes a radially extending support 220 coaxial
with the fixed and
movable sheaves 210, 214. This support 220 is at a fixed axial distance from
the fixed sheave 210
and faces the rear side of the movable sheave 214. In the illustrated example,
the support 220 is in
the form of a cam plate supporting a plurality of axisymmetric cam surfaces
222, 224. There are
two sets of cam surfaces 222, 224 in the illustrated example and each set
includes two cam surfaces.
Each first cam surface 222 faces a corresponding adjacent one of the second
cam surface 224. The
set of first cam surfaces 222 is provided for the forward mode and the set of
second cam
surfaces 224 is provided for the motor-braking mode. Other configurations and
arrangements are
possible. For instance, the set of second cam surfaces 224 can be omitted in
some implementations.
Likewise, it is possible to have only two cam surfaces in a given set or more
than three. Other
variants are possible as well.
The illustrated cam surfaces 222, 224 are designed to be engaged by respective
followers 230, 232
provided, in this implementation, on the rear side of the movable sheave 214.
In the illustrated
example, a pair of the two followers 230, 232 is located on a double-sided
sliding button affixed
into a corresponding clamp 234 by a fastener 236, for instance a threaded
fastener such as a bolt or
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screw. Other configurations and arrangements are possible. Among other things,
the same follower
can also be designed to engage both a first cam surface 222 and an adjacent
second cam
surface 224. The followers can be in the form of rollers. Other kinds of
followers are possible as
well. Still, the relative position of the cam surfaces 222, 224 and that of
the followers 230, 232 can
5 be inverted. The cam surfaces 222, 224 would then be provided on the rear
side of the movable
sheave 214 and the followers 230, 232 would be provided on the support 220.
Other variants are
possible as well.
It should be noted that the engine 132 in the example shown in FIG. 2 is
rotating clockwise when
viewed from the left side of the CVT 100. FIG. 4 thus shows the follower 230
engaging its
10 corresponding first cam surface 222 like when the vehicle 130
accelerates in the forward travel
direction. The opposite follower 232 will engage its corresponding second cam
surface 224 when
the vehicle 130 is in a motor-braking mode. Some motors are designed to rotate
counterclockwise,
even when moving in the forward travel direction and accordingly, the cam
surfaces 224 would be
engaged by the followers 232 when the vehicle 130 accelerates in the forward
travel direction.
FIG. 6 is a view similar to FIG. 3 but with a cutaway section.
FIG. 7 is a cross-section view of the driven pulley 200 shown in FIG. 3. FIG.
7 shows, among other
things, a support shaft 240 around which the various components of the driven
pulley 200 can be
mounted. This support shaft 240 includes a plurality of longitudinally
disposed axisymmetric
internal splines 242 to ensure a good torque-transmitting engagement with the
input shaft of the
gearbox 134 (FIG. 2), which input shaft would then have corresponding outer
splines. Still, in the
illustrated example, the support shaft 240 is inserted over the input shaft,
the right side being the
point of entry, and the driven pulley 200 is pushed over the input shaft until
it is fully seated. The
free end of the input shaft will then be located on the left-hand side of the
machined section inside
the support shaft 240 in FIG. 7. A blocking member can then be inserted
through the remaining
left end to lock the driven pulley 200 in place. Other configurations and
arrangements are possible.
Among other things, all components or at least one of the components can be
mounted directly to
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the input shaft of the gearbox 134. Still, the driven pulley 200 can be
installed on a shaft that is not
a gearbox. Other variants are possible as well.
A biasing element 250 is provided between the movable sheave 214 and the
support 220. This
biasing element 250 can be, for instance, a helical compression/torsion
spring. The biasing element
urges the movable sheave 214 towards the fixed sheave 210. Other
configurations and
arrangements are possible. For instance, the biasing element can be formed by
more than one spring
and/or by other kinds of springs. Other variants are possible as well.
The driven pulley 200 has a direct torque-transmitting engagement between the
two
sheaves 210, 214 but it is still possible for the mobile sheave 214 to move in
the axial direction
relative to the fixed sheave 210. This driven pulley 200 thus has a full-
torque configuration. The
parts creating this feature are located within a relatively small annular
space between the support
shaft 240 and a bottom of the belt-receiving groove 218. Among other things,
the cam
surfaces 222, 224 and the followers 230, 232 are located behind the rear side
of the movable sheave
214 and they do not retrieve space below the belt-receiving groove 218.
In the illustrated example, there are three elongated and axially extending
members 260 rigidly
attached to the movable sheave 214 and projecting from its front side towards
the fixed sheave 210.
The members 260 can be two or more than three in number. Each member 260
extends across the
fixed sheave 210 through a corresponding passageway 262. The members 260 can
be added parts
rigidly connected to the movable sheave 214 or, as shown, be parts made
integral with the movable
sheave 214. Other configurations and arrangements are possible as well. For
instance, one could
provide the members 260 on the fixed sheave 210 and corresponding passageways
262 on the
movable sheave 214 in some implementations.
In the illustrated example, the fixed sheave 210 is pivotally mounted directly
on the support
shaft 240 using one or more bushings 270. The bushings 270 are provided on the
interior surface
of a central hub 272 partially extending at the rear side of the fixed sheave
210. The central hub 272
is rigidly connected to the fixed sheave 210 using fasteners 274, for instance
a plurality of
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axisymmetric and axially extending screws or bolts. Other configurations and
arrangements are
possible. For instance, other kinds of fasteners can be used. Other variants
are possible as well.
FIG. 7 shows that in the illustrated example, the free end of the central hub
272 abuts against an
annular bushing 280, which is itself engaged against a rigid washer 282. The
inner rim of the
washer 282 fits snugly on the outer surface of the support shaft 240, and an
oversized annular end
portion 284 prevents it from moving out of the support shaft 240. The forces
exerted by the
drivebelt 104 on the conical wall 212 of the fixed sheave 210 will prevent it
from axially moving
along the support shaft 240 towards the opposite end. Other configurations and
arrangements are
also possible. For instance, the central hub 272 can be made integral with the
rest of the fixed
sheave 210 in some implementations. The bushings can also be replaced by other
elements, for
instance bearings or the like. Other variants are possible as well.
In the illustrated example, the movable sheave 214 is pivotally and slidably
connected directly on
the support shaft 240 using one or more bushings 290. These bushings 290 are
provided between
the support shaft 240 and the interior of an annular inner portion 292 of the
movable sheave 214.
Other configurations and arrangements are possible as well.
In the illustrated example, the support 220 on which the cam surfaces 222, 224
are provided is
rigidly mounted to the support shaft 240 using an arrangement capable at least
of establishing a
torque-transmission engagement between them. This may include serrations or
other features, such
as a key 300 as shown in FIG. 7. The support 220 is also prevented from moving
in the axial
direction using a retaining ring 302 or the like. The rigid connection is thus
achieved using two
kinds of connectors. Other configurations and arrangements are possible as
well.
FIG. 8 is an isometric view illustrating the front side of the movable sheave
214 in the driven
pulley 200 shown in FIG. 3. As can be seen, the members 260 are axisymmetric
and have a
noncircular cross section. Each member 260 has a substantially flattened U-
shaped cross-section,
with the open side facing radially outward. The inner wall of each member 260
is curved. The
shape of these members 260 is designed to provide an optimum resistance to
torque and also to the
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centrifugal forces when the driven pulley 200 rotates at high speeds. Other
configurations and
arrangements are possible.
FIG. 9 is an isometric view illustrating the rear side of the fixed sheave 210
in the driven pulley 200
shown in FIG. 3. FIG. 9 shows, among other things, the three axisymmetric
passageways 262 of
this example. Each passageway 262 provides an opening to accommodate the
corresponding
member 260. The passageways 262 are immediately adjacent to a central opening
264 and are
radially inside the conical wall 212 of the fixed sheave 210. This area can be
referred to as an inner
radial portion 266. Other configurations and arrangements are possible.
FIGS. 10 and 11 are enlarged isometric views of the central hub 272 of the
fixed sheave 210 in the
driven pulley 200 shown in FIG. 3.
FIGS. 12 and 13 are isometric views of the fixed sheave 210 and the support
shaft 240 in the driven
pulley 200 shown in FIG. 3.
Each sheave 210, 214 is generally made of a metallic material and an insert
310 made of another
material can be provided at each passageway 262 to simplify the manufacturing
process and reduce
costs, among other things. With such insert 310, the inner periphery of the
passageways 262 and
the outer surface of the members 260 do not need to be machined with a high
precision to ensure a
proper sliding engagement. One of the inserts 310 can be seen, for instance,
in FIGS. 6 and 7.
FIG. 14 is an enlarged view of one of the inserts 310 provided in a passageway
262 of the driven
pulley 200 shown in FIG. 3. Each insert 310 is designed to be individually
affixed, for instance
simply by snapping, inside each passageway 262. The illustrated example
includes two opposite
and parallel side portions 312 that are made integral with one another through
a transverse
portion 314. The insert 310 is made of a material having a lower coefficient
of friction than that of
the fixed sheave 210, for instance a plastic material having a good resistance
to wear. The
inserts 310 could be made by injection molding. In use, at least some of the
outer surface of the
members 260 will be in a sliding engagement with the inserts 310. The insert
310 can snap-fit into
the passageway 262 using side tabs 316. FIG. 15 is an enlarged exploded view
showing how an
insert 310 can be positioned into a passageway 262 in the illustrated example.
Other configurations
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and arrangements are possible as well. Among other things, the inserts 310 can
have a shape
different from the one shown and described. The inserts 310 could be made of
another material or
materials, and other manufacturing methods are possible. The inserts 310 can
nevertheless be
omitted entirely in some implementations. Other variants are possible as well.
FIGS. 16 and 17 are isometric views of the support 220 in the driven pulley
200 shown in FIG. 3.
FIG. 18 is a side view of the driven pulley 200 shown in FIG. 3, the driven
pulley 200 being now
at the maximum ratio position. This is, for instance, the position at the
maximum speed of the
vehicle. FIG. 19 is a cross-section view of the driven pulley 200 shown in
FIG. 18.
FIGS. 20 and 21 are isometric views similar to FIGS. 3 and 5 but showing a
variant of the driven
pulley 200 as improved where the central hub is made integral with the rest of
the fixed sheave 210.
FIG. 22 is a cross-section view of the driven pulley 200 shown in FIGS. 20 and
21.
FIG. 23 is a cross-section view of a variant of the driven pulley 200 as
improved. In FIG. 23, the
fixed sheave 210 is supported on the support shaft 240 using two bearings 320,
322. The
bearing 320 is a thrust bearing. Variants are possible as well.
FIG. 24 is a cross-section view of another variant of the driven pulley 200 as
improved. In FIG. 24,
each axially extending member 260 has a circular cross-section, namely
elongated rods. These rods
are also parts added to the movable sheave 214. They can be inserted in
corresponding holes by
interference. Other kinds of attachments are possible as well.
FIG. 25 is a cross-section view of a CVT 400 incorporating an example of a
known driven pulley.
This CVT 400 includes a driving pulley 402, a drivebelt 404 and a driven
pulley 406.
FIG. 26 is a semi-schematic top view illustrating the CVT of FIG. 25 installed
in the same generic
vehicle as in FIG. 2. As can be seen, the improved driven pulley 200 requires
less space at the left
thereof than that of the driven pulley 406. This space saving using the
improved driven pulley 200
can be important in some vehicle designs.
FIGS. 27 and 28 are cross-section views provided for dimensional comparisons
between the driven
pulleys 406, 200 in FIGS. 1 and 25. As can be seen, although they have an
identical outer diameter,
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the range of winding diameters on the improved driven pulley 200 is increased
by the distance A
compared to that of the known driven pulley 406. The width of the parts
extending beyond the left
side of the fixed sheave is also notably smaller, the distance C being only a
fraction of the
distance B.
5 The present detailed description and the appended figures are meant to be
exemplary only, and a
skilled person will recognize that many changes can be made while still
remaining within the
proposed concept. Among other things, and unless otherwise explicitly
specified, none of the
elements, characteristics or features, or any combination thereof, should be
interpreted as being
necessarily essential simply because of their presence in one or more examples
described, shown
10 and/or suggested herein.
REFERENCE NUMERALS
100 continuously variable transmission (CVT)
102 driving pulley
104 drivebelt
15 110 fixed sheave (of driving pulley)
112 movable sheave (of driving pulley)
114 support shaft (of driving pulley)
116 centrifugal mechanism (of driving pulley)
118 return spring (of driving pulley)
120 bearing arrangement
130 generic vehicle
132 engine
134 gearbox
136 driveshaft
200 driven pulley
210 fixed sheave
212 conical wall (of fixed sheave)
214 movable sheave
216 conical wall (of movable sheave)
218 drivebelt-receiving groove
220 first support
222 first cam surface
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16
224 second cam surface
230 first follower
232 second cam follower
234 clamp
236 fastener
240 support shaft
242 internal splines
250 biasing element
260 axially extending member
262 passageway (in the fixed sheave)
264 central opening (of fixed sheave)
266 inner radial portion (of fixed sheave)
270 bushing (for fixed sheave)
272 hub
274 fastener
280 annular bushing
282 washer
284 oversized annular end portion
290 bushing (of movable sheave)
292 annular inner portion (of movable sheave)
300 key
302 retaining ring
310 insert
312 side portion (of insert)
314 transverse portion (of insert)
316 side tab (of insert)
320 bearing
322 bearing
400 continuously variable transmission (CVT)
402 driving pulley (of CVT 400)
404 drivebelt (of CVT 400)
406 driven pulley (of CVT 400)
