Note: Descriptions are shown in the official language in which they were submitted.
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Description
Planetary Transmission
Technical Field
This invention relates generally to a
planetary transmission, and more particularly to a
multi-speed planetary transmission for a vehicle.
Background Art
Power shift transmissions are known in the
earthmoving and trucking vehicle industries which offer
a large number of gear ratios by utilizing a plurality
of serially interconnected planetary gear sets and a
plurality of clutches and brakes for effecting the
individual gear steps. Some of these transmissions
have a two speed front section followed by a
multi-speed range section for providing four or more
forward speeds and at least one speed in reverse.
Exemplifying the art in this area are: U.S. Patent
No. 2,221,393 issued November 12, 1940 to
W. L. Carnegie; U.S. Patent No. 2,978,928 issued
April 11, 1961 to R. M. Tuck, et al; U.S. Patent No.
3,410,157 issued November 12, 1968 to W. G. Livezey;
U.S. Patent No. 3,996,817 issued December 14, 1976 to
J.E. Winzeler; U.S. Patent No. 4,090,415 issued May 23,
1978 to J. M. Gorrell, et al; and U.S. Patent No.
4,205,563 issued June 3, 1980 to J. M. Gorrell.
One of the disadvantages of these
transmissions is that they do not provide enough speeds
in the normal tillage range, if the transmission is
used in a farm vehicle. Not only are close steps
desired in the intermediate speed range, but also a
wide speed range or wide overall speed ratio is
preferred.
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Another problem with those prior transmissions
having a dual speed front section or front planetary
splitter unit is that their constructions do not favor
their use as energy dissipators during power shifting
of the gears. For example, many front sections have
utilized one interleaved disc type brake assembly for
selectively holding the sun gear of a single planetary
set stationary and providing a speed other than unity,
and one interleaved disc type clutch assembly for
selectively coupling the sun gear and the planet
carrier together and affording a direct drive speed.
But such construction is undesirable because the sun
gear operates at relatively high speed, low torque
conditions so that the energy levels that must be
absorbed by the brake and/or clutch become excessive
and require an uneconomical construction. Furthermore,
when certain ones of the clutch and/or brakes in the
associated range section are engaged, such as in
neutral, then the relative speeds of the planet gear
elements or sun gear in the front section become so
high that their service lives are appreciably reduced.
Another factor is that the construction of a
stationary disc type brake assembly does not favor the
radial distribution of lubricating fluid therethrough
for cooling and energy dissipation purposes to the same
degree as a rotating disc type clutch assembly.
Accordingly, what is desired is a simple
two-speed front section of a power shift transmission
having a disc-type coupling construction which is
associated with a relatively high torque member and
which will aid in the distribution of cooling fluid
therethrough. In this way the cost of construction can
be minimized, and yet the compact couplings that are
utilized can still absorb the appreciable amounts of
energy resulting from a gear shift. Along with this is
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the need to effectively combine the front section with
a rear range section to give a plurality of closely
spaced gear speeds in the tillage range, and the need
to provide relatively low relative speeds between the
interleaved disc and plate members of the various
clutches and brakes in the transmission.
The present invention is directed to
overcoming one or more of the problems as set forth
above.
Disclosure Of The Invention
In one aspect of the invention a planetary
transmission includes a front section having a rotating
housing and a planetary gear set having a ring gear, a
sun gear, and a planet carrier, with the ring gear
serving as the input and the rotating housing serving
as the output. Advantageously, means are provided for
holding the sun gear stationary, first clutch means are
provided for connecting the planet carrier to the
rotating housing, and second clutch means are provided
for connecting the ring gear to the rotating housing.
In another aspect of the invention the
aforementioned front section is operatively connected
to a rear section having a plurality of planetary sets
and a plurality of coupling means to provide a
multiplicity of speeds with relatively closely spaced
ratios in the intermediate range. Such construction is
particularly adaptable to a wheel tractor for
agricultural tillage purposes.
Since the sun gear element of the planetary
gear set of the front section of the transmission is
continually grounded or held stationary, the relative
speeds of the elements and the energy dissipation
capabilities of the two rotating clutches can be more
effectively determined. Furthermore, except when in
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neutral, whenever the associated engine is operating
both the ring gear and the rotating housing will be
rotating to effectively aid in the distribution of
lubricating and cooling fluid through the clutches of
the front section.
Brief Description Of The Drawings
Fig. 1 is a diagrammatic, side elevational
view of one embodiment of the planetary transmission of
the present invention and showing the planetary
elements on only one side of the rotational axis for
simplicity.
Fig. 2 is a chart showing the various clutches
and brakes which must be engaged to obtain the ten
forward and one reverse speeds of the transmission
illustrated in Fig. 1, along with the total speed ratio
reduction for each speed and the step ratios between
each speed.
Fig. 3 is a graph illustrating the
transmission input horsepower as a percentage of the
maximum versus the transmission output speed as a
percentage of the maximum for the transmission
illustrated in Fig. 1.
Fig. 4 is a diagrammatic, side elevational
sectionalized view of the front section of the
planetary transmission shown in Fig. 1, and
illustrating portions thereof in greater detail.
Best Mode For Carrying Out The Invention
Referring to Fig. 1, a vehicle planetary
transmission 10 is schematically illustrated on one
side of a rotational axis 12 which includes an
engine-driven input shaft 14 and a tubular output shaft
16 connected to a conventional mechanism, not shown,
for powerably rotating the ground-engaging members of
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the vehicle. Six interconnected planetary gear sets or
epicyclic gear trains 18,20,22,24,26 and 28 are
rotatably supported concentrically along the axis
within a surrounding and generally tubular transmission
housing 30. Three clutch means or disc type clutch
assemblies 32,34 and 36 and five brake means or disc
type brake assemblies 38,40,42,44 and 46 are serially
arranged along the length of the transmission for
cooperating with and selectively coupling certain
elements of the planetary gear sets and providing ten
forward speeds and one reverse speed as is generally
indicated by the speed chart of Fig. 2.
The planetary transmission 10 has a front
section or splitter speed unit 48 of particularly
advantageous construction, and a rear section or range
unit 50 associated therewith. The front section
includes the first planetary gear set 18 and the first
and second clutch means 32,34, and basically serves to
provide an underdrive mode and a direct drive mode of
operation. The rear section includes the remaining
planetary gear sets 20,22,24,26 and 28, the third
clutch means 36, and the five brake means 38,40,42,44
and 46 and provides a plurality of speed reduction
ratios as well as at least one reverse speed.
As is best shown in Fig. 4, the front section
48 includes a rotating housing 52 which is supported by
a pair of axially spaced ball bearing assemblies 54,56
indirectly to the transmission housing 30 through
intermediate stationary members or flanged sleeves 58
and 60 respectively. The first planetary gear set 18
has first ring gear, sun gear and planet carrier
elements 62,64 and 66 of the type wherein a plurality
of similar planet gear elements 68 are rotatably
mounted on the carrier element and are in intermeshing
engagement with the teeth on the ring and sun gear
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elements. The carrier element 66 is made up of a
central body part 66' and a generally encircling
externally toothed ring 66" releasably connected
thereto by a spline and retaining ring lock 67. Such
construction permits more convenient machining of the
elements 66',66" while also contributing to compactness
and the accommodation thereof to alignment with the
associated elements of the front section.
Advantageously, holding means 69 are provided
for continually holding the sun gear element 64
stationary as a reaction member. In the instant
example this means includes a tubular extension 70
integral with the sun gear element which is releasably
connected to the stationary member 58 by a spline 71
for assembly and disassembly purposes. Thus both the
sun gear 64 and the planet carrier element 66 have a
preselected degree of floatability or self-alignment
capability. The carrier element 66 is at least in part
located axially by a thrust bearing assembly 72
encircling the tubular extension 70 and contacting the
end of the stationary member 58. An engine-driven
input gear 73 is splined to the front end of the input
shaft 14, and the ring gear element 62 is splined to
the rear end of the input shaft. A third ball bearing
assembly 74 rotatably supports the ring gear element in
the rotating housing 52, and thus indirectly supports
the input shaft. A radially inwardly open annular
chamber 75 is defined between the carrier body part 66'
and the ring gear element 62, and lubricating fluid
directed to this chamber tends to urge the carrier
element to the left when viewing the drawing against
the thrust bearing assembly solely by the action of the
centrifugal head. Fluid in this chamber is also
directed to the planet gear bearings 77 and to the
clutch means 32134 for cooling purposes.
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The planetary transmission 10 desirably
includes an elongate power take off (PT0) shaft 76
which can be releasably connected to the input shaft 14
by splines 78. The engine driven PTo shaft can extend
along the rotational axis 12 and out the rear portion
of the transmission for driving auxiliary equipment and
for convenient removal.
First clutch means 32, when engaged, directly
couples the first planet carrier element 66 to the
rotating housing 52. Alternatively, but in a similar
manner, second clutch means 34 directly couples the
first ring gear element 62 to the rotating housing. In
the embodiment illustrated each of these clutch means
includes a hydraulically engaged annular actuating
piston 80 which is retracted by a plurality of
compression springs 82. Pressurized fluid can be
selectively delivered to the respective actuating
chamber 84 defined between the rotating housing and
piston on one side thereof, and counterbalancing fluid
under basically only centrifugal pressure is supplied
to a balancing chamber 86 on the opposite side thereof
to promote more rapid disengagement of the piston upon
release of pressure to the actuating chamber. In
general, lubricating fluid is directed to the left
balance chamber 86 when viewing Fig. 4 along the path
designated by the flow arrows identified by the letter
A, and to the right balance chamber 86 along the path
illustrated by the flow arrows identified by the letter
B.
The third clutch means 36 shown in Fig. 1 only
schematically is of similar construction to the clutch
means 32,34 illustrated in Fig. 4, and the five brake
means 38,40,42,44 and 46 are preferably hydraulically
engaged and spring engaged also. It is to be
appreciated that while the remaining clutch means and
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brake means are not illustrated in detail, they are
preferably of the disc type having a plurality of
interleaved discs and plates which are axially
slideable toward engagement by the respective actuating
pistons as is known to those skilled in the power shift
transmission art.
Referring now to Fig. 1 and the construction
of the rear section 50, the second planetary set 20 can
be noted to include second ring gear, sun gear and
planet carrier elements 88,90 and 92 and a plurality of
similar planet gear elements 94. The second sun
element 90 is connected to an elongate, tubular
intermediate shaft 95 for joint rotation with the
rotating housing 52 forming the output of the front
section 48, as is an annular plate member 96. The
- third clutch means 36, when engaged, directly couples
the annular plate member and planet carrier element
together.
The third planetary set 22 includes third ring
gear, sun gear and planet carrier elements 98,100 and
102 and a plurality of planet gear elements 104. As is
schematically illustrated in Fig. 1, the third ring
element 98 is connected for joint rotation with the
second carrier element 92. Also, the third sun gear
100 is connected for joint rotation with the
intermediate shaft 95.
The fourth planetary gear set 24 includes
fourth ring gear, sun gear and planet carrier elements
106,108 and 110 and a plurality of planet gear elements
112. The fourth planet carrier 110 is preferably
integrally connected to the third planet carrier 102
and is directly releasably connected to the output
shaft 16 through splines or the like, not shown. The
fourth sun gear 108 is releasably coupled to the
intermediate shaft 95 for joint rotation.
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I.ikewise, the fifth planetary gear set 26 has
fifth ring gear, sun gear and planet carrier elements
114,116 and 118 and a plurality of planet gear elements
120. An intermediate annular plate 122 effectively
connects the fifth sun gear 116 and fourth ring gear
106 for joint rotation.
Lastly, the sixth planetary gear set 28 has
sixth ring gear, sun gear and planet carrier elements
124,126 and 128 and a double or compound set of planet
gear elements 130,132, with the planet gears 130
intermeshing with the ring gear 124 and the planet
gears 132 intermeshing with the sun gear 126. The
adjacent sun gears 116 and 126 are preferably
integrally connected to each other, and the adjacent
planet carriers 118 and 128 are preferably integrally
connected to each other to affect manufacturing
economy. The unitized planet carrier 118,128 is
releasably and non-rotatably connected to the output
shaft 16.
With such construction each of the ring gear
elements 88,98,106,114 and 124 is selectively held
stationary to provide the desired reaction element by
the actuation of the respective first to fifth brake
means 38,40,42,44 and 46 respectively.
Industrial A~plicability
The planetary transmission 10 has been
installed in an agricultural, wheeled vehicle and has
been found to be operationally very effective. In the
first forward gear the first clutch means 32 is engaged
in the front section 48 to provide an underdrive mode
of operation at a speed reduction with respect to the
input shaft 14 of about 1.4. Simultaneously, the last
or fifth brake means 46 is engaged in the rear section
50 to hold the ring gear 124 fixed to the encircling
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housing 30 and to provide a speed reduction with
respect to the intermediate shaft 95 and the input
fourth sun gear 108 of about 7.5. Thus, the fourth and
sixth planetary sets 24 and 28 cooperate in the rear
section along multiple power paths with the planet
carrier torques being additive to drive the output
shaft 16 in first gear so as to provide a ground speed,
for example, of about 3.2 kph (2 mph).
A shift to second gear from first gear is
accomplished by disengaging the first clutch means 32
and engaging the second clutch means 34. This results
in the direct coupling of the input ring gear 62 to the
output rotating housing 52 for a direct drive mode in
the front section 48. Reference is made to the speed
chart of Fig. 2, wherein it can be noted that the fifth
brake means 46 remains engaged.
A shift from second to third gear is achieved
by returning to the underdrive mode in the front
section 48, and by engaging the third brake means 42
and disengaging the fifth brake means 46. Since the
ring gear element 106 is held stationary to the housing
30, the fourth planetary gear set 24 is thereby
actuated and a rear section speed reduction of about
3.7 is provided.
Continuing with an upshift to fourth gear, the
front section of the transmission continues in the
underdrive mode and the rear section is operated so as
to engage solely the second brake means 40. This
secures the third ring gear 98 to the housing 30 and
results in a speed reduction of about 3.1 through the
third planetary gear set 22.
In fifth gear the front section of the
transmission is returned to a direct drive mode and the
rear section is returned to the speed reduction
established in third gear. In other words, the third
brake means 42 is operated again.
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In sixth gear the front section continues in
direct drive and the rear section reverts to the speed
reduction established in fourth gear.
In seventh gear, the front section reverts to
the underdrive mode and the rear section is operated so
as to engage the first brake means 38. This results in
holding the second ring gear 88 stationary as a
reaction member, and causing the second and third
planetary gear sets 20,22 to cooperate through multiple
or split power flow paths to provide a speed reduction
of about 1.9 between the intermediate shaft 95 and the
output shaft 16.
In eighth gear the front section reverts to
direct drive and the rear section remains as in seventh
gear.
In ninth gear the front section is changed to
the underdrive mode, and the rear section is placed in
a direct drive mode. The direct drive portion is
accomplished by the engagement of the third clutch
means 36. This couples the intermediate sha~t 95, the
sun gears 90 and 100, the planet carrier 92 and the
ring gear 98 for joint rotation.
In top gear the front section is returned to
direct drive and the rear section can remain in direct
drive as in ninth gear. This can provide a vehicle
ground speed of about 32 kph (20 mph).
Reverse is achieved by placing the front
section in the underdrive mode by engagement of clutch
means 32 and by engaging the fourth brake means 44 and
holding the fifth ring gear 114 stationary. In the
rear section the fourth and fifth planetary gear sets
24,26 cooperate to provide a negative speed reduction
of about 4.3 through multiple power paths wherein the
planet carrier torques are subtracted from one
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another. A second speed reverse speed is conveniently
available, if needed, by engaging the clutch means 34
in the front section.
Looking now at the graph of Fig. 3, and the
step ratios noted between the gear speeds as is
illustrated in the last column of Fig. 2, it is to be
appreciated that the third gear through seventh gear
speeds are tightly grouped. This is advantageous in
that if the transmission 10 is used on a wheeled farm
or agricultural tractor then the speed of the vehicle
can be precisely matched to the tillage or plowing
requirements most often utilized in the 5.6 kph (3.5
mph) through 12.9 kph (8 mph? speed range, for
example. This results in greater economy of
operation. Moreover, a wide overall speed ratio is
also provided.
By incorporating an output rotating housing 52
and associated pair of clutches 32 and 34 in the front
splitter speed unit 48, along with a continually fixed
first sun gear 64, the energy dissipation associated
with each gear shift can be effectively taken in the
front section of the transmission without the speeds of
the various elements of the first planetary gear set 18
becoming excessive.
In neutral, the third clutch means 36 is
preferably engaged and the first and second clutch
means 32,34 disengaged. Hence the input shaft 14 is
disconnected from the rotating housing output of the
front section. This is advantageous in the event the
vehicle is parked for a considerable period of time the
rotating housing 52 is stationary while the input shaft
is being driven by the engine of the vehicle for
powering auxiliary equipment, not shown, by way of the
PT0 shaft 76. In such mode of operation torque on the
first sun gear 64 is substantially zero and the
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relative speeds of the elements of the first planetary
gear set 18 are low enough that the transmission can be
operated indefinitely without effecting the service
life. In contrast, prior art splitter units have
released the sun gear to freewheel along with the
planet gears at undesirably high speeds under these
circumstances.
Another feature of the front speed unit 48 is
that it provides effective PTO shaft operation along
the central axis without more than two concentric
shafts. This simplifies the construction and aids in
compactness of the speed unit.
Still further, note that the rotating housing
52 in the front section is normally rotating so that
the distribution of lubricating and cooling fluid
therethrough is encouraged through centrifugal action.
Other aspects, objects and advantages of this
invention can be obtained from a study of the drawings,
the disclosure and the appended claims.
