Note: Descriptions are shown in the official language in which they were submitted.
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AUTO~OTIVE TRANSMISSION WITH CONTINUOUSLY
VARIABL~ SPEED MECHANIS~
Description
The present invention relates to a power transmission
5 which incorporates a continuously variable speed mechanism.
In general, automotive vehicles have used manual or automatic
transmissions for changing the drive ratio between the
engine output shaft and the drive wheels. The transmission
is "shifted" or changed in finite steps from start-up,
10 when a high-torque, low-speed drive is provided, up to
highway speeds, where a high-speed, low-to que drive is
provided. Shifting is accomplished by the driver dicplacing
a shift lever to change the ratio in a manual transmission,
or in an automatic transmission by the controlled release
and engagement of friction elements. Because such shifting
is in step functions, the most efficient operation (fuel
consumption, engine efficiency, and so forth) can only be
approximated with a transmission which changes gears in
discrete steps. It is thus desirable to provide a con-
tinuously variable transmission (CVT) where the gearratio is varied in a regular, continuous manner, as the
vehicle is started and accelerated to driving speeds.
The use of such a CVT employing variable-pitch pulleys
in machine tools and similar variable speed systems has been
known for some time. Recently considerable work has been
directed to the improvement of such a continuously variable
trans~ission to provide a practical component for an auto-
motive drive train. One example of such a CVT is described
and shown in U. S. Patent No. 4,0g4,203 -- Van Deursen et al.
T~is arrangement empioys a steel belt to transfer drive
between the relativeiy movable sheaves of a primary and
secondary pulley. By controlling tne sheave displacement --
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and thus the effective diameter -- of each pulley, a con-
siderable range of speed variation is attained in a con-
tinuous manner, without the step function change previously
noted in connection with manual and automatic transmissions.
Even with recent advances, such CVT transmissions for auto-
motive use have still been difficult to manufacture, and
imposed weight and volume requirements not unlike those of
other transmissions.
According to the present invention there is
provided a transmission adapted to be driven by a prime
mover, the transmission including a first shaft, a hydro-
dynamic device including a fluid coupling having turbine
and impeller elements with a torsional damper coupling the
turbine element to the first shaft. The impeller is adapted
for connection to the prime mover, and a lock-up clutch is
engageable to drivingly connect the impeller and turbine
elements for rotation together. A gear pump is connected
to be driven when the first shaft is driven and to provide
fluid under pressure for operating the lock-up clutch. A
continuously variable speed mechanism is provided which has
an input pulley mounted for rotation on the first shaft,
an output pulley and a belt intercoupling the pulleys. Each
of the pulleys includes a pair of sheaves, one sheave of
each pair being fixed with respect to lateral movement and
the other sheave in the same pair being movable laterally
relative to the one sheave. A planetary forward-reverse
gear set is connected to the first shaft, and a clutch and
brake is operatively associated with the planetary gear set
to regulate the direction of rota-tion of the input pulley.
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A second shaft is connec-ted to the output pulley with a
first gear supported on the second shaft, a third shaft
spaced from the second shaft, a second gear mounted on
the third shaft in meshing engagement with the first
gear, and a third gear mounted on the third shaft for
rotation therewith. A differential mechanism is provided
which includes an input ring gear connected to be driven
by the third gear and adapted to drive a pair of axle
shafts so that the axle shafts are driven through a four-
axis drive train by the prime mover.
The invention allows the provision oE a continuously
variable transmission suitable for automotive use which is
simple to manufacture, of a practical size, and with a
correspondingly reduced weight, while all the drive and
control components are mounted on four axes, to reduce
total width and allow installation in a small volume.
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The invention will be more clearly understood from
the following description which is given by way of example
only with reference to the accompanying drawings, in which:
Figure 1 is a simplified diagram of a continuously
variable transmission constructed in accordance with this
invention;
Figures 2 and 3 together represent a cross-section of
the transmission shown more generally in Figure l; and
Figure 4 is a representation of the displacements
between the axes of the transmission components shown in
Figures 1, 2 and 3.
Figure 1 depicts in simplified form the transmission
10 of this invention. The transmission 10 includes a
hydrodynamic device 14, a forward reverse planetary mechanism
24, a belt and pulley mechanism 53, a reduction gear section
63, and a differential mechanism 74.
A vehicle engine, for example, drives input or drive
shaft 11. Drive shaft 11 is connected to an impeller 12
of a hydrodynamic device 14, shown as a fluid coupling
which also has a turbine 16. The turbine is coupled
through a torsional damper 18 to a first shaft 20, aligned
along a first axis referenced A. A lock-up clutch 22 is
positioned to lock the impeller to the turbine and shaft 20
with minimal losses when this clutch is actuated.
A forward-reverse planetary gear set 24 includes a
sun gear 26, a pair of planet gears 28,30 and a ring gear
32. The planet or pinion gears 28,30 mesh with each other,
with the ~irst pinion 28 also meshing with sun gear 26, and
the outer pinion 30 in the mesh with ring gear 32. The
pinion gears are supported on the carrier arms 34,36, of a
carrier output element 38. A clutch 40 is connected
between sun gear 26 and ring gear 32. A band brake mechanism
42 is coupled between ring gear 32 and ground. It is thus
apparent that engagement of clutch 40 effectively locks up
the sun gear to the ring gear, and provides a 1:1 ratio
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drive between shaft 20 and the output member 38 which is
tied to another shaft 44. Release of clutch 40 and en-
gagement of the band brake 42 grounds ring gear 32, to
effect a reverse rotation of the shaft 44 with respect
to the input angular displacement of shaft 20.
Belt-and-pulley mechanism 53 includes a shaft 44
connected to a movable sheave of an input or first pulley
assembly 48, which also includes a movable sheave 50.
It will become apparent from the subsequent explanation
10 that the sheaves 46,50 of the first pulley assembly 48
are mounted for common rotation about axis A, but in a
lateral sense, sheave 46 is fixed with respect to lateral
movement whereas sheave 50 is movable along the direction
of axis A. Hence the terms "fixed" and "movable" as applied
to the sheave portions of each pulley assembly described
herein, and in the appended claims, refer to lateral
movement along an axis such as axis A and not to rotational
or other conventional displacement. A fluid chamber 52
is defined behind movable sheave 50 as shown in a general
manner, so that the admission of fluid under pressure into
this chamber will displace movable sheave 50 to the right
as shown in the drawing, and removal of fluid from the
chamber will allow the sheave to be displaced to the left.
A belt 54 provides a driving connection between first
pulley 48 and a second or output pulley 56, which includes
a fixed sheave 58 and a movable sheave 60. A fluid chamber
52 is defined adjacent movable sheave 60 to afford dis-
placement of this sheave to the left and right along axis B.
Thus the controlled displacement of adjustable sheave 50
in the first pulley 48, and a concomitant displacement
in an opposite sense of the other movable sheave 60 in the
output pulley 56, effects a change in the drive ratio be-
tween shaft 20 and shaft 64, coupled to fixed sheave 58,
in a well known manner. A more complete disclosure of
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such an arrangement is described in U. S. Patent No.
4,143,558 which issued March 13, 1979, and thus an ex-
tensive showing and description of the movable pulley
arrangements in such a drive system will not be given
herein.
Reduction gear section 63 includes a first gear 66
affixed to one end of shaft 64, which is aligned along
axis B. A second gear 68 is in mesh with gear 66 and is
connected to a third shaft 70, aligned on third axis
designated C. A third gear 72 is also connected to third
shaft 70.
Differential mechanism 74 includes a ring gear 76
meshing with third gear 72 on shaft 70. The differential
also includes pinion gears 80 mounted on a center pin 79,
in turn mounted in a case on carrier 78, and a pair of
output or side gears 82,84 meshing with gears 80 and
connected respectively to individual axle shafts 86 and 88,
aligned on a fourth axis designated D. Thus when input
energy from any suitable prime mover is applied over
input shaft 11, the output or axle shafts 86,88 are driven
in a manner apparent from this brief explanation. A more
detailed explanation of this structure and its operation
will now be set out.
Considering now the more detailed showing of Figure ~,
pilot 11 is welded or otherwise connected to cover 90,
which in its turn is connected to impeller ]2 of fluid
coupling 14. Those skilled in the art will appreciate
that other hydrodynamic devices, such as a torque converter,
could be substituted for fluid coupling 14. ~ driveplate
assembly 92 incorporating a driveplate 96 is connected by
fastening means, shown as bolts 94, to the prime mover,
and fastened by additional nuts, studs or screws 98 to
cover 30.
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Lock-up clutch 22 includes a plurality of friction
plates 100, certain of which are affixed to member 102
of the torsional damper 18. The other clutch plates are
affixed to an extension of clutch cylinder 104, which
in turn is welded to cover 90 for rotation as input drive
plate 96 is driven. A fluid chamber 106 is coupled by
a conduit 108 to another conduit 110, in the center of
hollow shaft 112. A gear pump 114 is mounted on and
driven by shaft 112, to provide the fluid under pressure
for operating lock-up clutch 22 and the other fluid-
actuated components of the arrangement shown in Figures
2 and 3.
Turbine element 16 is coupled by plate 116 to the
damper 18, and the output side of damper 18 is connected
15 to member 118, which in turn is splined to first shaft 20
on axis A.
Shaft 20 is also splined to sun gear 26 of the
planetary gear set 24, and is likewise splined to a
forward clutch cylinder 120 which carries certain of the
20 friction discs 122 in forward clutch 40. The other clutch
plates are affixed to forward clutch hub member 124,
which in turn is welded to a ring gear support 126,
one end of which is fastened to ring gear 32 of the
forward-reverse gear set.
The carrier pin 36 is received in carrier output
element 38, which is connected by a plurality of screws
128 (only one of which is shown) to laterally fixed sheave
46 of first or input pulley 48. Sheave 46 is journalled
about axis A, and a bearing 130 is positioned between
30 sheave 46 and the adjacent portion 132 of the trans-
mission housing. Sheave 50, is connected to fixed sheave
46/133 via a ball spline (not shown) which permits
lateral movement only. In a rotational sense sheave 50
is, in effect, splined to sheave 46 for drive transmiss~on
35 puposes. These sheaves 45 and 50 of input pulley 4
rotate as an entity. The provision of fluid in the
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chamber 52 is effective to displace movable sheave 50
to the right as shown in the drawing, from its maximum
left position as illustrated, to increase the effective
diameter of the pulley arrangement as seen by the belt.
The annular wall member 134 forms the rear wall of the
fluid chamber, and a portion of this member also provides
a stop for the extremity of adjustable sheave 50.
A seal member 136 is provided between wall member 134
and a cylinder 138 to retain the fluid within charnber
52 as the movable sheave is displaced to the right
and then again to the left. Details of the metal belt
itself and the more precise details of the sheave
construction and arrangement are not shown in Figures
2 and 3, in that such arrangements are now known in
this art. For example, see United States Patent No.
4,143,558 - Van Deursen et al, entitled "Variable-V-
Belt Transmission", which issued March 13, 1979.
Second shaft 64 is mounted on the second axis,
referenced B, at the juncture of Figures 2 and 3.
Shaft 64 is journalled between a bearing 142 at the
left end, and another bearing assembly 144 at the
right end. Fixed sheave 58 is integral with shaft 64
for rotation therewith about axis B when the output
pulley assembly 56 receives angular drive over the
belt (as represented iII ~igure 1) from the input pulley
arrangement 48. In Figures 2 and 3, movable sheave 60
is connected to fixed pulley 58 by a ball spline (not
shown), as explained above in connection with sheaves
50,46 of the first pulley. A first annular member 148
has one end portion affixed in shaft 64 for rotation
therewith, and an additional outer annular member 150
is affixed to the movable pulley sheave 60 for
cooperation with member 148 and the side wall of the
pulley to define f]uid chamber 62. An orifice 1~2
in member 148 provides metered flow of fluid from
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chamber 62 into the adjacent chamber portion 154
when chamber 62 is pressurized.
Fluid under pressure is supplied through a passage
162 in a member 146, through a passage 156 in the center
of shaft 140, a radial passage 158 and a channel 160
within movable sheave 60 to complete the path for fluid
transfer into chamber 62. In general the construction
of the movable sheave 60 is similar to that shown above
in connection with sheave 50 and depicted in greater
detail in the patent referenced above.
Reduction gear section 63 includes gear 66 affixed
to the left end of shaft 64, meshing with adjacent gear
68 to provide a first reduction through the transmission.
Gear 68 is splined to third shaft 70, journalled about
a central axis C, the third axis of this arrangement.
Bearings 170,172 support shaft 70 in the position in-
dicated. Also affixed to third shaft 70 is another gear
72, meshing with ring gear 76 of differential 74 which
rotates about the fourth axis, D, of this system.
Ring gear 76 is secured to a differential carrier 78,
which thus rotates with ring gear 76 and drives center
pin 79 of differential 74. Pin 79 has rotatably mounted
thereon pinion gears 80 of the differential, and the
pinion gears in turn mesh with side gears 82,84 which
are connected to drive axle shafts 86,88.
In operation, drive is supplied from the prime mover
through driveplate 96 to cover 90, which drives impeller
12. This provides drive to turbine 16, which through
torsional damper 18 drives shaft 20. Cover 90, via the
cover hub, imparts drive to shaft 112 and thus to pump
114. The pump provides fluid under pressure through
channel 110 in shaft 112, and other channels, for
energizing the various components previously described.
When the turbine approaches the speed of the impeller,
lock-up clutch 22 will be actuated in a well known manner
by admitting fluid through the channel 108,106 to engage
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the clutch discs and in e~fect lock cover 90 to the
torsional damper 18, to eliminate any losses in the fluid
coupling. Accordingly, at this time shaft 20 is being
driven from cover 90, but there is no drive over pulley
system 53 until either clutch 40 or brake 42 is engaged.
Assuming it is desired to drive the vehicle in which
the transmission is mounted in the forward direction,
fluid is admitted into the chamber adjacent clutch plates
122 of forward clutch 40, in effect locking sun gear 26
to ring gear 32, and drive is taken from planet carrier
38 to drive fixed sheave 46 of first pulley assembly 48.
Pulley assemblies 48,56 are depicted in their start-up
positions, to provide a low-speed, high-torque power
transfer between the components on first axis A and those
on second axis B. As the second pulley assembly 56 is
driven, first gear 66 on shaft 64 is also driven, and this
in turn drives gear 68, which meshes with gear 66. Gear
68, mounted on third shaft 70 on axis C, imparts drive
to this shaft which in turn rotates gear 72 which meshes
with ring gear 76. This in turn drives differential 74
to drive axle shafts 86,88.
If it is desired to reverse the direction of power
flow from the prime mover to the axle shafts 86,88, forward
clutch 40 is released, unlocking sun gear 26 from ring
gear 32. Band brake 42 is then engaged, locking ring gear
32 to the transmission housing. Drive is then taken from
sun gear 26 through planet carrier 38, to drive fixed
sheave 46 in the opposite direction than that obtained
when clutch 40 was engaged. The remainder of the system
operates in the same manner as previously described to
provide opposite rotation of axle shafts 86,88.
Figure 4 shows the spatial relationship between the
four separate axes of the system shown in Figures 1-3,
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viewed from the left hand side of a vehicle in which
the transmission of the invention is mounted. Tbe center-
line of the engine is shown along the vertical axis and
axis A is on the centerline. The distances between axis
A and the second, third and fourth axes B, C and D are
indicated in millimeters on the illustration. At the
right of the drawing, the vertical distances between
axes A and B, and between axes A and D, are also shown.
It is thus apparent by mounting the several assemblies
shown in Figures 1-3 in the manner shown, a system is
provided for incorporating a continuously variable trans-
mission on a multiple axis arrangement, with the minimum
transverse distance required for effective driving of
the output axle shafts when input rotational energy
is received from a suitable prime mover~
