Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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_escription
Gear Train Having an Internal Gear Mechanism
Technical Field
This invention relates generally to a gear
train having an internal gear mechanism, and more
particularly to a gear train for a continuously
variable transmission unit to expand the useful range
10 thereofO
Background Art
The present invention is particularly useful
in a plurality of embodiments of continuously variable
transmission units of ~he type disclosed in U.S~ Patent
No. 4,152,94~ issued May 8, 1979 to Yves Kemper and
assigned to the Vadetec Corporation of Troy, Michigan.
Such continuously variable transmission units,
hereafter referred to as CVT units, are of the traction
drive type and offer considerable promise for vehicular
use .
In the general type of CVT unit referred to in
the above-designated patent three working bodies
operate to transmit torque to a rotatable output member
at a continuously variable output/input speed ratio
throughout a preselected range. The working bodies are
represented by a first body having a pair of axially
movable internal traction surfaces of revolution about
a central axis, a second body having a pair of external
cone-like traction surfaces oE revolution about an
inclined axis intersecting the central axis, and a
third body journalled for rotation about the central
axis and carrying the second body such that rotational
torque applied to the third body causes the nutational
movement of the inclined axis. If the Eirst body is
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held stationary as a reaction and the third body is
driven as an input member~ the second body can have a
nutating pinion gear coupled thereto which serves as
~he output to a gear train~ Axial movement oE the
first body with respect to the cone-like traction
surfaces of the second body results in modifying the
speed ratio to the output desired. The technical
performance and operating parameters of these
transmissions are described in an American Society of
Mechanical Engineers Article entitled "Performance of a
Nutating Traction Drive" by PO Elu and Y. Kemper of
August 18~21g 1980 and iden~ified as Paper No.
80-C2/DET~63.
The physical characteristics of many of these
CVT units are such that relatively high efficiencies
are obtained through a relatively narrow range of speed
ratios. But, by linking an output gear train to two of
the three bodies the range of speed ratios of the CVT
unit can be broadened while maintaining rela~ively high
efficiencies. One prior output gear train adapted to
broaden the speed range is illustrated in Fig~ Nos. 1
and 7 of aforementioned U.S. Patent No. 4,152,946 and
embodies a set of three conical convex gears or
external bevel gears having a common apex for
connecting the second and third working bodies to an
output shaft having one of the bevel gears thereon.
Unfortunately, that set of external bevel gears
exhibits a considerable gear tooth friction loss which
decreases the overall efficiency of the CVT unit.
Moreover, the set of external bevel gears is crowded so
that the amount of space left for the support bearings
for these gears is minimal. Stili further, it is a
relatively complex matter to adjus~ the axial
positioning of the external bevel gears with respect to
one another.
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Accordingly, it would be advantageous -to
provide an improved gear train for use with a CVT unit
of the aforementioned type which would broaden the
speed range thereof, which would be of high efficiency
such as by exhibiting an efficient gear tooth mesh,
which would be relatively compact and yet have
sufficient space for the supporting bearings, and which
would be simple and economical in construction.
The present invention is directed to a gear
train overcoming one or more of the problems as set
forth above.
Disclosure of the Invention
In one aspect of the present invention a gear
train is provided for a body rotatable about a central
axis, a first pinion gear rotatably mounted on the body
on an inclined axis, and a second pinion gear rotatably
mounted on the central axis. Advantageously, the gear
train includes an internal gear mechanism rotatably
mounted on the body on a nutating axis for transferring
torque between the body, the first pinion gear and the
second pinion gear.
In another aspect of the present invention a
gear train is provided for a body rotatable about a
central axis, a first pinion gear rotatably mounted on
the body on an inclined axis intersecting the central
axis, and a second pinion gear rotatably mounted on the
central axis, with the gear train including an internal
gear mechanism having an internally tapered gear
rotatably mounted on the body with the first and second
pinion gears being intermeshingly engaged with the
internally tapered gear.
In another aspect of the present invention a
gear train is provided for a body rotatable about a
central axis, a first pinion gear rotatably mounted on
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the body on an inclined axis intersecting the central
axis, and a second pinion gear rotatably mounted on the
central axis, with the gear train including an internal
gear mechanism having first and second internal gears
rotatabl~ mounted on the body as a unit such that the
first internal gear is connected to the first pini.on
gear and the second internal gear is connected to the
second pinion gear.
A gear train desirabl.y includes an internal
gear mechanism having either one internal gear or a
juxtaposed pair of internal gears which are rotatably
mounted on an input body of a CVT unit on a nutating
axis. Preferably, straight tapered internal gear teeth
are used which are intermeshed with straight spur gear
teeth of a first pinion gear associated with the
inclined working body of the CVT unit and straight spur
gear teeth of a second or output pinion gear. This
results in a relatively compact gear train having a
particularly efficient gear tooth intermesh construc-
tion, and yet serves the primary function of extendingthe speed ratio range of the associated CVT unit over
that of a single working body output connection, for
example.
Brief Description of the Drawin~3s
Fig. 1 is a diagrammatic, longitudinal
sectional view of a CVT unit incorporating a gear train
and illustrating one embodiment of the presen~
invention;
Fig. 2 is a diagrammatic and substantially
enlarged longitudinal sectional view of the gear train
portion of E'ig. 1 to better illustrate details thereof;
and
Fig. 3 is a diagrammatic, longitudinal
sectional vi.ew oE a second internal gear mechanism for
the gear train illustrating another embodiment of the
present invention.
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Bes~ Mode for Carryin~ Out the Invention
Referring initially to Fig. 1, a CVT unit 10
of the nutating traction drive type includes a gear
train designated generally by the reference numeral 12
at the right side thereof when viewing the drawing
which is constructed in accordance with the present
invention. The longitudinal cross-sectional view
illustrated includes a plane containing a primary
central axis 14, a secondary inclined axis 16 and a
third nutating axis 18.
The CVT unit 10 includes a frame or housing 20
including a left end portion 22 supporting a bearing
assembly 24 and a right end portion 26 supporting a
first bearing assembly 28 and a second bearing assembly
30. The first of three working bodies of the CVT unit
includes a crank-like alpha body 32 which is journalled
in the bearing assemblies 24,30 for rotation about the
central axis 14. In the instant embodiment the alpha
body or input body 32 is powerably rotated by its
connection to a conventional engine or motor driven
power train, not shown, at an input gear 33. However,
the alpha body may be driven at the opposite end
thereof equally well. The second working body includes
a nutatable beta body identified generally by the
reference numeral 34 supported by a pair of end bearin~
assemblies 36,38 within the alpha body 32 for rotation
about the inclined axis 16 which intersects the central
axis at an intersecting point 40. The third working
body includes an omega body iden~ified generally by the
re~erence numeral 42 which is concentric with and
axially movable with respect to the central axis for
varying the speed ratio of the CVT unit.
More particularly, the nutatable beta body 34
includes a pair of oppositely convergent conical or
cone-like members 44,46 supported for a preselected
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degree of both axial and rotational movement relative
to a nutating shaft 48. For this purpose, a first pair
oE cylindrical sleeve hearing members 50 are secured tG
the shaft for freely carrying lhe distal or small ends
of the conical members~ and a second pair of
cylindrical sleeve bearing members 52 freely carry the
proximal or large ends of the conical members on the
shaft. A ball and ramp mechanism 54 is located
generally centrally of the shai-t and includes first and
second annular collar members 56,58 which
arenonrotatably connected to the shaft by a spline
connection 60. Each of the co:Llars has a plurality of
appropriately ramped pockets 62 defined therein which
face a corresponding plurality of similarly ramped
pockets 64 defined in the end face of each of the
conical members. A force transmitting ball 66 is
received within each of the facing pockets 62,64 and
resilient spring means 68 disposed between the collars
continually biases the collars apart and generally
axially away from the intersect point 40 centrally oE
the shaft 48.
The omega body 42 includes a pair of axially
adjustable traction rings 70,72 defining interior omega
rolling surfaces 74,76 which are surfaces of revolution
about the central axis 14. These omega rolling
surfaces may be crowned in cross section but generally
have a relatively constant radius. The traction rings
are nonrotatably connected to the housing 20 and are
symmetrically movable toward and away from each other
along the central axis by a suitable adjustment
mechanism 78. In the instant embodiment the adjustment
mechanism includes a plurality of parallel adjustment
rods 80 having left and right hand threads 82,84 on the
opposite end~ thereof which are screwthreadably
received in the traction rinys. Each of the rods is
freely supported in a bearing block 85 for rota~ion
relative to the housing 20. An input pinion gear 86
secured to each rod is intermeshingly engaged with a
controlling ring gear 88, so that with rotation of the
controlling ring gear about the central axis in one
direction the traction rings will be urged toward one
another to the central posi~ions illustrated in phantom
outline. When the controlling ring gear is rotated in
the opposite direction the traction rings will be moved
away from one another to the solid line positions
illustrated in Fig. 1.
Thus, to effect a relative speed change, beta
rolling surfaces 90,92 defined respectively on the
conical members 44,46 make engagement with the omega
rolling ~urfaces 74,76 of the traction rings 70,72
along symmetrically spaced apart points along the
central axis. When the omega body 42 is restrained
against movement about its axis the relative speed
relationship of the rotating alpha body 32 and the
nutating shaft 48 is related to ~he internal radius of
the omega rolling surfaces 70~72 and the external
radius of the beta rolling surfaces 90,92 in contact
with the traction rings 70,72. The ball and ramp
mechanism 54 serves to continually bias the conical
members away from each other along the inclined axis
and into preselected load bearing engagement with the
traction rings. The operation of the CVT unit 10 so
far described is similar structurally and functionally
to the general disclosure of U~S. Patent No. 4,152,946
mentioned above and to the disclosure of U.S. Patent
No. 4,280,369 issued July 28, 1981 to Harvey N. Pouliot
relating to a ball and ramp mechanism Eor a CVT unit of
the type i]lustrated in Fig. 1, the full contents of
which are incorporated by reference into the instant
speciEication.
Turning now to the gear train 12 shown best in
Fig. 2, it can be noted to include a f:irst pinion gear
94 connected for joint rotation with the nutating shaft
48. Thus, the first pinion gear is indirectly
rotatably mounted on the alpha body 32 on the inclined
axis 16. A second pinion gear 96 integrally connected
to an output shaft 48 is rotatably mounted in the
housing 20 in the bearing assembly 28 along the central
axis 140 In accordance with the present .invention an
internal gear means or an internal gear mechanism 100
is provided for transferring torque between the alpha
body 32, the first pinion gear 94 and the second pinion
gear 96, with the internal gear means being rotatably
mounted on the alpha body on the nutating axis 18.
The internal gear mechanism 100 includes an
annular supporting hub 102 having an internal
cylindrical bore 104 and a retaining ring groove 106
defined in the bore. A cylindrical bearing seat 108 is
defined by the alpha body 32 concentric with the
nutating axis 18, and a pair of oppvsed tapered roller
bearing assemblies 110 are disposed on the seat. A
retaining cap 112 defining an annular shoulder 114 is
releasably secured to the alpha body by one or more
screwthreaded fasteners or bolts 116 such that the
roller bearing assemblies are positively clamped in
place against an cpposite annular shoulder 118 formed
in the alpha body. A thrust absorbing ring 120 is
received in the groove 106 and serves to retain the
outer races of the bearing assemblies in a proper
centralized location with the hub.
The internal gear mechanism 100 further
includes first and second internal gears 122 and 124
releasably secured to the opposite outer end faces of
the hub by a plurality of fasteners or bolts 126
~5 arranged peripherally around the hub. Each of the
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internal gears 122,124 has a plurality of internal gear
teeth 128,130 which are preferably arranged in two
cones or in a common cone and thus are tapered. I
prefer that straight gear teeth be used, and by the
term "straight" it is meant that the gear teeth are
aligned with a plane through the axis of rotation
thereof. This permits the teeth 132,134 of the irst
and second pinion gears 94,96 to be straight spur c3ear
teeth for simplicity of construction and for minimizing
thrust forces within the gear train
Industrial Ap~licability
In a first mode of operation o the CVT unit
10 corresponding to the wide positioning of the
15 traction rings 70,72 shown in Fig. 1, the output shaft
98 is rotated at minimum torque and at maximum speed
conditions. For example~ with the traction rings being
held stationary and the alpha body 32 being rotated by
a conventional power means, not shown, at 1 rpm in a
counterclockwise (CCW) direction when viewing the
drawing from the right along central axis 14, the
internal gear mechanism 100 can be rotated at about
0.05 rpm in the clockwise ~CW) direction in addition to
its nutating motion, the beta body 34 can be rotated at
about 1.0 rpm in the clockwise (CW) direction in
addition to its nutating motion, and the output shaft
at about 1.33 rpm in the clockwise (CW) direction.
In a second mode of operation of the CVT unit
10 corresponding to the juxtaposed positioning of the
traction rings 70,72 as shown in phantom lines in Fig.
1, the output shat 98 is rota-ted at maximum torque and
at minimum speed conditions. With the traction rings
again being held stationary and the alpha body 32 being
rotated at 1 rpm in a counterclockwise (CCW) direction,
the internal gear mechanism 100 can be rotated at about
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0.42 rpm in the counterclockwise (CCW) dixection, the
beta body 34 can be rotated at about 0.11 rpm in the
clockwise ~CW) direction, and the output shaft 98 at
about 0 30 rpm in the clockwise direction.
S The above designated extremes of the speed
ratio range of the CVI~ unit 10 and gear train 12 is
based upon a ratio change of the ex~ernal beta rolling
surfaces 44,46 divided by the interior omega rolling
~urfaces 74,76 between about 0O5 and 0.9, and the
number of the gear teeth 132,1~8,130,134 to be
respe~tively 21,40,40 and 18 for a 7/6 ratio.
It can thus be appreciated that the CVT unit
10, and particularly the disposition of the traction
rings 70,72 along the central axis 14 is effective to
cause the conical members 44,46 to rotate the nutating
shaft 48 and to change the angular velocity of the
first pinion gear 94 relative to the alpha body 32
through a preselected range~ Moreoever, this range can
be modified by proper selection of the rolling
diameters involved. The construction parameters of the
gear train 12 used therewith can also be modified to
change the overall characteristics applied to the
output shaft 98.
If desired, the gear train 12 can be modified
such that the first and second pinion gears 94,96 are
external straight bevel gears, and the first and second
internal gears 122,124 are internal straight bevel
gears having a common apex at the intersection point
40. ~ still further modification would be to make the
gear teeth of all four of these bevel gears spiral
bevel gear teeth. The nutating axis 18 need not be in
a common plane with the central axis 14 and the
inclined axis 16 in all of the embodiments, but still
would be generall~ intermediate or between them when
viewing the common plane at a right angle.
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A second embodiment of the present invention
is illustrated in Fig 3 which e~ploys an in~ernal gear
mechanism 136 having but a single internally tapered
gear 138. In Fig. 3 componen~s similar in function to
those described with respect to the ~irst embodiment
are identified by the same reference numbers.
In the gear train 12 of Fig. 3 the reaction of
the beta rolling surface 92 against the rolling surface
76 of the traction ring 72 as the alpha body 32 is
lo rotated causes the nutating shaft 48 and first pinion
gear 94 to be driven as descrihed above with respect to
the ~irst embodimentO However, the output torque is
transferred from the first pinion gear 94 to the second
pinion gear 96 solely through a plurality of preferably
straight, internally tapered gear tee~h 140. A rolling
bearing assembly 142 is pressed into an internal
cylindrical seat 144 formed within the alpha body and
has an internal cylindrical surface 146 concentric with
the nutatin~ axis ]8 for receiving a corresponding
external cylindrical surface 148 formed on the internal
gear. Thus, in the second embodiment the internal gear
138 is externally supported for rotation within the
alpha body, whereas in the first embodiment the
internal gear mechanism 100 is internally supported by
the rolling bearing assemblies 110 on the alpha body.
The construction of the internal gear
mechanism 136 is not only simple and economical, but
also is of narrow width for compactness along the
central axis 14. Ebr example, note that the pinion
30 gears 94,96 of ~ig. 3 are located generally in a common
nutating plane 150 normal to the nutating axis 18 and
passing centrally through the bearing assembly 142. In
contrast, the corresponding pinion gears 94,96 of Fig.
2 are spaced axially apart. While I prefer that the
pinion gears of Fig. 3 be substantially similar
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cylindrical spur gears with straight teeth, I
contemplate that minor modifications can be made to one
or both of them such as by tapering them or crowning
them to better match the teeth of the internally
tapered gear 138. The pinion gears 94~96 can be of
unequal diameter and can have unequal numbers of teeth,
in which event I contemplate reorienting the nutating
axis 18 to either an offset state so ~hat it does not
pass through the intersecting point 40 and/or to a
position not angularly bisecting the angle between the
central and inclined axes 14,16. Preferably, the three
axes 14, 16 and 18 should be maintained in a common
plane, with the nutating axis being generally
intermediate the other two axesO
From the foregoing it can be appreciated that
the gear train 1~ and internal gear mechanisms 100 and
136 of the present invention are simple and rugged in
construction, are axially and radially compact, are of
a construction sufficient for spacious installation o~
the adequately sized supporting bearings, and are of a
relatively high efficiency because an internal-external
gear tooth mesh has comparatively lower gear tooth
friction losses than an external-external gear tooth
mesh. Since the first and second pinion gears
preferably have straight gear teeth, the axial
adjustment problems associated with conical or bevel
gear interfaces are eliminated. Yet all of these
advantages are accomplished while providing the same
range broadening and ratio characteristics of other
prior art gear trains associated with CVT units of the
nutating traction drive type.
Other aspects, objects and advantages will
become apparent from a study of the specification,
drawings and appended claims.
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