U.S. patent application number 12/159688 was filed with the patent office on 2009-03-26 for continuously variable gear transmission.
This patent application is currently assigned to Fallbrook Technologies Inc.. Invention is credited to Anders Kolstrup.
Application Number | 20090082169 12/159688 |
Document ID | / |
Family ID | 36293541 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090082169 |
Kind Code |
A1 |
Kolstrup; Anders |
March 26, 2009 |
CONTINUOUSLY VARIABLE GEAR TRANSMISSION
Abstract
A continuously variable gear is described having an input shaft
(1), a plurality of traction balls (2) distributed radially around
the axis, each traction ball (2) is mounted on an axle (3) passing
there through, the axles (3) are tiltable in the radial grooves (4)
in the housing (5) and support plate (6), To control the position
of the traction bails (2), the axles are guided in curved slots
(13) of turnable iris plate (7). To control the axial placement of
the traction balls (2), there is a rotatable input disc (8)
positioned adjacent to the traction balls (2), a rotatable output
disc (9) positioned adjacent to the traction balls (2) opposite the
input disc (8), and a pre-spanning ring around the traction balls
(2) such that each of the traction balls (2) is making three-point
contact with the input disc (8), the output disc (9) and the
pre-spanning ring (11), the contact surface of the pre-spanning
ring (11) having a specific curvature larger than the radius of the
traction balls (2).
Inventors: |
Kolstrup; Anders; (Valby,
DK) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Fallbrook Technologies Inc.
San Diego
CA
|
Family ID: |
36293541 |
Appl. No.: |
12/159688 |
Filed: |
December 18, 2006 |
PCT Filed: |
December 18, 2006 |
PCT NO: |
PCT/IB06/54911 |
371 Date: |
June 30, 2008 |
Current U.S.
Class: |
476/38 |
Current CPC
Class: |
Y10T 477/619 20150115;
F16H 15/28 20130101; F16H 15/40 20130101 |
Class at
Publication: |
476/38 |
International
Class: |
F16H 15/26 20060101
F16H015/26 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 30, 2005 |
EP |
05028709.3 |
Claims
1-14. (canceled)
15. An apparatus for facilitating control of the ratio of a
continuously variable transmission (CVT), the apparatus comprising:
a first member having a first plurality of radial grooves; a second
member having a second plurality of radial grooves; wherein the
first and second pluralities of radial grooves are arranged
angularly about an axis; and wherein the first and second members
are configured for rotation relative to one another such that
during operation of the CVT the first plurality of radial grooves
can be angularly misaligned relative to the second plurality of
grooves.
16. The apparatus of claim 15, wherein the first member comprises a
stationary member.
17. The apparatus of claim 16, wherein the second member comprises
a support plate configured for rotation relative to the first
member.
18. The apparatus of claim 15, wherein the first member comprises a
housing member.
19. The apparatus of claim 18, wherein the second member comprises
a support plate.
20. The apparatus of claim 19, further comprising an actuator
housing and an actuator arm, the actuator housing coupled to the
support plate, and the actuator arm coupled to a mechanism for
tilting a plurality of traction balls of a CVT.
21. A method for facilitating control of the ratio of a
continuously variable transmission (CVT), the method comprising:
providing a plurality of traction balls; providing each traction
ball with a ball axle about which the traction ball rotates;
providing a first plurality of grooves for engaging a first end of
the ball axles; providing a second plurality of grooves for
engaging a second end of the ball axles; and arranging the first
and second plurality of grooves relative to one another such that
during operation of the CVT the first plurality of grooves can be
misaligned relative to the second plurality of grooves.
22. The method of claim 21, wherein the first and second plurality
of grooves comprise radial grooves.
23. The method of claim 21, wherein first plurality of grooves is
part of a housing.
24. The method of claim 23, wherein the second pluraliy of grooves
is part of a support plate.
25. The method of claim 24, further comprising providing an
actuator housing and an actuator arm, the actuator housing being
coupled to the support plate, and the actuator arm being coupled to
a mechanism for tilting the plurality of traction balls.
26. A method of controlling the ratio of a continuously variable
transmission, the method comprising: providing a plurality of
traction balls; providing a first plurality of radial grooves for
engaging a first end of each of the ball axles; providing a second
plurality of radial grooves for engaging a second end of each of
the ball axles; and providing a second plurality of radial grooves
for engaging a second end of the ball axles; and rotating the first
and second plurality of radial grooves relative to one another.
27. The method of claim 26, further comprising providing an input
disc in contact with the plurality of balls, and wherein a
clockwise rotation of the input disc and a clockwise rotation of
the second plurality of grooves results in the ball axles being
tilted in a first direction in the radial grooves.
28. The method of claim 27, wherein a counterclockwise rotation of
the second plurality of grooves results in the ball axles being
tilted in a second direction in the radial grooves.
29. The method of claim 26, wherein providing a second plurality of
radial grooves comprises providing a support plate comprising a
plurality of radial grooves.
30.-35. (canceled)
36. A continuously variable transmission (CVT) comprising: a
plurality of traction balls angularly arrayed about a shaft, each
traction ball provided with a ball axle about which the ball
rotates; an input disc in contact with the traction balls; an
output disc in contact with the traction balls; a prespanning ring
in contact with the balls; wherein the input and output discs
contact the balls at a position that is radially inward relative to
the position where the prespanning ring contacts the balls; and
wherein the prespanning ring is configured to translate axially
when the ball axles are tilted.
37. A continuously variable transmission (CVT) comprising: a shaft;
a plurality of traction balls arrayed angularly about a
longitudinal axis of the shaft; a plurality of tiltable ball axles,
each ball axle corresponding to a traction ball; a first plurality
of radial grooves engaging a first end of the balls axles; a second
plurality of radial grooves engaging a second end of the ball
axles; and wherein the first plurality of radial grooves is
configured for rotation relative to the second plurality of radial
grooves such that rotation of the first plurality of radial grooves
causes the ball axles to tilt in the first and second pluralities
of radial grooves.
38. The CVT of claim 37, wherein the first plurality of grooves are
formed in a support plate.
39. The CVT of claim 38, wherein the second plurality of grooves is
stationary and the support plate is configured to have minor
rotational play about its ideal aligned position.
40. The CVT of claim 37, further comprising an input disc, an
output disc, and a prespanning ring, wherein the input disc, output
disc, and prespanning ring each contacts the plurality of traction
balls.
Description
TECHNICAL FIELD
[0001] The present invention relates to a continuously variable
gear transmission of the kind set forth in the preamble of claim
1.
BACKGROUND ART
[0002] In continuously variable gear transmissions of this kind it
is known to provide an axial force generator in the form of a
spring to ensure the necessary contact pressure between the
surfaces of the input and output discs and the traction balls. A
continuously variable gear transmission of this kind is e.g. known
from U.S. Pat. No. 2,469,653, in which the tension of the spring
for providing the necessary contact pressure can be adjusted by
means of a nut.
DISCLOSURE OF THE INVENTION
[0003] It is the object of the present invention to provide a
variable gear transmission of the kind referred to above, in which
the torque transfer is improved under varying loads and during fast
change of transmission ratio, and having an efficient, simple and
compact design compared to the prior art. This object is achieved
with a continuously variable gear transmission of said kind, which
according to the present invention also comprises the features set
forth in the characterising part of claim 1. With this arrangement,
the forces from the pre-spanning ring, having a curvature with a
radius larger than the radius of the traction balls and a pre-span,
will provide the necessary normal forces in the contact points when
the transmission is running with a constant ratio, in which
situation the traction balls and the pre-spanning ring will have
contact where the pre-spanning ring has its largest inner diameter.
When the gear transmission ratio is increased by tilting the ball
axes, the output shaft has to accelerate the driven unit and
therefore a higher transfer torque is necessary. The inertia of the
driven unit often has a size so that the acceleration torque is
larger than the transferred torque when the gear is not in the
transient phase.
[0004] The fast tilt of the traction ball axes will make the
pre-spanning ring move axially in the same direction as the ball
surface. When the pre-spanning ring moves axially, the normal force
will change because of the changed inner diameter at the contact
point. When the transmission ratio stops changing, the pre-spanning
ring will move back to its normal position with contact point at
the largest inner diameter with a speed related to the operating
speed.
[0005] The exact curvature of the inner surface of the pre-spanning
ring can be designed to match the requirements of the specific
usage, e.g. a smaller radius will mean an ability to accelerate
units with greater inertia.
[0006] The continuously variable gear transmission may further be
provided with an axial force generator which will increase the
normal forces on the traction balls when the torque requirements
rise, and decrease the forces when the torque requirements
fall.
[0007] By means of the combination of the axial force generator and
the curvature of the pre-spanning ring, the transmission will
automatically adjust to the prevailing load situation.
[0008] Preferably all forces for providing the required torque are
internal and limited to the input shaft, from the axial force
generator to the input disc, the traction balls, the pre-spanning
ring, the output disc and through a thrust bearing back to the
input shaft. Thus, these forces are not transferred through the
housing.
[0009] The position of the traction balls is controlled by their
three-point contact, and the angle of the traction ball axles can
be controlled by a rotatable iris plate. The iris plate is a disc
or plate with spiral grooves, and the iris plate is shaped to fit
around the curvature of the traction balls, keeping a constant
distance to the traction balls.
[0010] The axles of the traction balls pass through the radial
grooves in the support plate and the spiral grooves in the iris
plate and when the iris plate is rotated, the axles will tilt. In
order to provide room for the tilting movement, the grooves in the
iris plate are wider than the diameter of the axles and in order to
prevent play, the axles are fitted with iris rollers having a
diameter equal to the width of the grooves in the iris plate.
Different systems for rotation of the iris plate can be envisaged,
such as e.g. using a step motor for controlling the transmission
ratio.
[0011] If the step motor or similar actuator is connected to the
support plate with the radial grooves and the support plate has a
minor rotational play, the actuator forces under rapid movement can
be minimised. This will be explained in the following.
[0012] If the axle of each traction ball is lying in a plane
through the input shaft respectively, the balls are performing a
pure rolling and the ball axles are stable.
[0013] If the radial grooves in the housing and support plate are
not perfectly aligned, the ball axle is tilted and the ball will
behave like a turning wheel on a car. Because is it axially fixed
it can only start tilting in the groove.
[0014] This reaction will continue until the ball axles hit the
stops in the grooves and the reaction time and direction will be
dependent upon the size of the misalignment and the turning
direction of the support plate relative to the rotational direction
of the input disc.
[0015] If the rotational direction of the input disc is clockwise
and the support plate is provided with a small rotation clockwise,
the front ends of the ball axles will move towards the rotational
axis of the input shaft. If the support plate is rotated counter
clockwise, the front ends of the ball axles will move away from the
rotational axis of the input shaft. Thus by controlling the
rotational position of the support plate it is possible to enforce
and support the activation of the iris plate.
[0016] If the actuator housing is connected to the support plate
and the actuator arm is connected to the iris plate, these will
always move in opposite directions, and if the support plate is
flexibly mounted with springs forcing it towards the ideal aligned
position, the actuator forces can be kept to a minimum and at the
same time providing a quick actuation.
[0017] As a simplistic alternative the supporting rotation of the
support plate can be provided by means of that part of the force
from the iris plate to the traction ball axles, which is not
directed in the radial direction of the grooves in the support
plate. This solution will only require that the turning of the iris
plate for reducing the transmission ratio is chosen in accordance
with the corresponding rotational direction of the input disc, and
naturally that the support plate is flexibly mounted with a
possibility of a small rotation.
[0018] In an alternative embodiment the continuously variable gear
transmission further comprises a disengagement mechanism, which
lets the driven unit freewheel relative to the driving unit, when
no drive of the driven unit is needed. Preferably the disengagement
mechanism is controlled by the iris plate in such a way that with
the transmission in its lowest ratio further turning of the iris
plate keeps the traction ball axles in the same position and ramps
on the iris plate transfers a force through a clutch plate to the
input disc, which consequently is disengaged from the traction
balls, thus disengaging the connection between the driving unit and
the driven unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Embodiments of the invention will be described more fully
below with reference to the drawing, in which
[0020] FIG. 1 shows a sectional view of a continuous variable
transmission according to the invention seen in the direction A-A
in FIG. 2,
[0021] FIG. 2 shows a side view of the continuously variable
transmission showing the radial grooves in the support plate,
[0022] FIG. 3 shows the iris plate with spiral grooves,
[0023] FIG. 4A shows a sectional view of the axial force
generator,
[0024] FIG. 4b shows an exploded view of the axial force
generator,
[0025] FIG. 5A shows a sectional view of the pre-spanning ring and
a traction ball, in the constant ratio state,
[0026] FIG. 5B shows a sectional view of the pre-spanning ring and
a traction ball after a quick tilt of the traction balls axles
[0027] FIG. 6A shows the iris plate with modified grooves and ramps
for the alternative embodiment with disengagement mechanism,
[0028] FIG. 6B shows the iris plate of FIG. 6a in a perspective
view more clearly showing the ramps,
[0029] FIG. 7 shows the clutch plate and control pins used in the
alternative embodiment
[0030] FIG. 8 shows a sectional view of the continuously gear
transmission in accordance with the alternative embodiment with the
disengagement mechanism cut through a traction ball,
[0031] FIG. 9 shows a sectional view corresponding to FIG. 8, but
cut between the traction balls.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] FIG. 1 shows a section through a continuously variable
transmission according to an embodiment of the invention. The
transmission comprises an input shaft 1 whose rotation is to be
converted into rotation of an output shaft 10, whose one end
extends out of the gear, said output shaft 10 being axially aligned
with the input stub shaft 1. As shown in FIGS. 4A and 4B, the input
shaft 1 is connected by an axial force generator to an input disc
8. The axial force generator consists of a number of ramps 14 on
the input shaft 1, a number of ramps 15 on the input disc 8 and in
between a number of balls 16. This axial force generator provides
an axial force varying with the torque of the input shaft 1. The
slope of the ramps 14, 15 is calculated to create an axial force to
result in the needed normal force on the traction balls 2 to give
the required traction.
[0033] This axial force presses the traction balls 2 towards the
pre-spanning ring 11. When the input shaft 1 rotates the traction
balls 2, they will start spinning, and the contact point between
traction balls 2 and pre-spanning ring 11 will move to the axial
centre of the pre-spanning ring 11, where the inner diameter is
largest, as shown in FIG. 5A.
[0034] When the traction balls 2 are tilted rapidly, the
pre-spanning ring will follow axially and the contact point will
move to a point with a smaller inner diameter of the pre-spanning
ring 11, as shown in FIG. 5B, which results in a larger normal
force at the contact points of the traction balls 2.
[0035] The positions of the traction balls are defined by the three
contact points with the input disc 8, pre-spanning ring 11 and
output disc 9, and the axles are supported by the grooves in the
housing 5 and the support plate 6 shown in FIG. 2.
[0036] The iris plate 7 shown in FIG. 3 controls the angle of the
traction ball axles 3. The axles 3 of the traction balls 2
supported by the radial grooves 4 in the housing 5 and the support
plate 6 passes through the grooves 13 in the iris plate 7. When the
iris plate 7 turns, the axles 3 will tilt. In order to make it
possible for the axles 3 to pass through the grooves 13 at an
angle, the grooves 13 in the iris plate 7 are wider than the
diameter of the friction ball axles 3. To prevent play, the
friction ball axles 3 are equipped with iris rollers 17, which have
the same diameter as the grooves 13 in the iris plate.
[0037] The iris plate 18 shown in FIGS. 6A and 6B comprises grooves
19, the inner part of which maintain a constant radius, in order to
provide the minimum transmission ratio in connection with
disengagement. The disengagement is provided by means of the ramps
20 on the iris plate 18, said ramps 20 forcing the clutch plate 21
shown in FIG. 7 towards the thrust bearing 22, when the iris plate
18 is turned further onwards after reaching the minimum
transmission ratio. The thrust bearing 22 will thus push the input
disc 8 away from its engagement with the traction balls 2 whereby
the driven unit is disengaged from the driving unit. In this
situation i.e. the disengaged position of the input disc 8, the
torque on the input shaft 1 will be close to zero and thus if an
axial force generator is present, the axial force will be at a
minimum, further supporting the disengagement of the transmission.
The rotational position of the clutch plate 21 may be controlled by
means of pins 23 inserted in the housing, whereby the movement of
the clutch plate 21 is limited to an axial movement.
[0038] The FIGS. 8 and 9 show different cross-sectional views of
the transmission with the disengagement mechanism implemented. In
FIG. 8 the cross-sectional view is provided through a traction ball
1 and in FIG. 9 a cross-sectional view is provided between the
traction balls 1.
[0039] Above the invention has been described in connection with a
preferred embodiment, however, many deviations may be envisaged
without departing from the scope of the following claims, such as
having the pre-spanning ring positioned on the inside of the
traction balls 2 and the input and output discs positioned with
contact on the outside of the traction balls 2, or other possible
mechanisms for tilting the traction balls 2, etc.
* * * * *