Note: Descriptions are shown in the official language in which they were submitted.
2~~~so~
93-rTRN-536
EAT 0152 PUS
COMPOUND VEHICULAR TRANSMISSION
Technical Field
The present invention relates to a compound
change gear transmission having an improved auxiliary
section including an auxiliary countershaft gear
assembly having clutched auxiliary countershaft drive
gears. The transmission also includes a synchronized
input splitter or a two-speed master clutch input
splitter.
Background Art
Compound change gear transmissions of the type
having one or more auxiliary sections connected in
series with a main transmission section are well known
in the prior art. Briefly, by utilizing main and
auxiliary transmission sections connected in series,
assuming proper sizing of the ratio steps, the total of
available transmission ratios is equal to the product of
the main section ratios and the auxiliary section
ratios. By way of example, at least in theory, a
compound change gear transmission including a four (4)
speed main section connected in series with a three (3)
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speed auxiliary section will provide twelve available
gear ratios (4 x 3 = 12).
Auxiliary transmission sections are of three
general types: range type, splitter type or combined
range and splitter type.
In compound transmissions having a range type
auxiliary section, the ratio step or steps may be
greater than, equal to, or less than the total ratio
coverage of the main transmission section. The main
section is then shifted progressively through its ratios
in each range. Examples of compound transmissions
having range type auxiliary sections may be seen by
reference to U.S. Patent Nos. 3,105,395; 2,637,222 and
2,637,221.
In compound transmissions having a splitter
type auxiliary section, the ratio steps of the splitter
auxiliary section are less than the ratio steps of the
main transmission section. In these transmissions each
~ main section ratio is split, or subdivided, by the
splitter section. Examples of compound change gear
transmissions having splitter type auxiliary sections
may be seen by reference to U.S. Patent Nos. 4,290,515;
3,799,002; 4,440,037 and 4,527,447_
In a combined range and splitter type
auxiliary section, or sections, both range and splitter
type ratios are provided. This allows the main section
to be progressively shifted through available ratios
divided into at least two ranges while also allowing the
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main section ratios to be split in at least one of the
ranges.
Examples of a compound transmission having
a single combined range/splitter type auxiliary
section may be seen by reference to U.S. Patent Nos.
3,283,613; 3,648,546. A single combined range/splitter type
auxiliary section may also be seen by reference to
publication Small Scale Print No. 016-AD; FullerTM
Transmissions; Models RT-14613, RTO-14613, RTOO-14613,
published March 1981 by Eaton Corporation, assignee of the
present invention. Another example is the "Ecosplit"T°' model
of transmission sold by Zahnradfabrik Friedrichshafen
Aktiengeseushaft of Friedrichshafen, Federal Republic of
Germany, which utilizes- a separate splitter auxiliary
section located in front of the main transmission section
and a separate range auxiliary section located behind the
main transmission section.
It should be noted that the terms main and
auxiliary sections are relative. Thus, if the
designations for the main and auxiliary sections are
reversed, the type of auxiliary section (either range or
splitter) will also be reversed. In other words, given
what is conventionally considered a four-speed main
section with a two-speed range type auxiliary section,
if the normally designated auxiliary section is
considered the main section, the normally designated
main section would be considered a four-speed splitter
type auxiliary section. By generally accepted
transmission industry convention, and as used in
describing the present invention, the main transmission
CA 02153608 1999-12-07
-4-
section of a compound transmission is that section which
contains the greater number (or equal number) of forward
speed ratios, which allows selection of a neutral
position, which contains the reverse ratios) and/or
which is shifted (in manual or semiautomatic
transmissions) by manipulation of a shift bar, shift
rail, shift shaft, o:r shift finger assembly. Typically
the auxiliary section is shifted via a master/slave
valve/cylinder arrangement; or the like.
A conventional auxiliary transmission section,
such as that dlisclosed in U.S. Patent No. 4,754,665,
includes a mainshaft assembly and an auxiliary
countershaft assembly. The mainshaft assembly typically
includes an auxiliary section input shaft which
cooperates with an 'output shaft. The auxiliary
transmission section includes three gear layers,
combined range and splitter gearing and four distinct
selectable auxiliary section ratios.
Disclosure of he Invention
The present invention~provides a compound change
gear transmission which provides a desired number of gear
ratios utilizing fewez~ gears than traditional transmissions.
The present invention also provides a compound change gear
transmission including' a selectively clutchable countershaft
to establish selectable torque flow paths between a main
transmission section input shaft and an auxiliary transmission
section output shaft. Further, the present invention provides
CA 02153608 1999-12-07
-5-
a compound change gear transmission which includes an
auxiliary transmission section having an auxiliary
countershaft assembly for providing selectable inputs through
the auxiliary countershaft to drive an output shaft. The
present invention also provides a compound change gear
transmission which includes an auxiliary transmission section
having selectively clutchable drive gear for driving an
auxiliary countershaft so as to reduce spin back speed of a
main shaft. Still further, the present invention provides a
compound change gear transmission having a synchronized
splitter to bring an auxiliary section countershaft into
synchronous speed with a main section countershaft. The
present invention also provides a compound change gear
transmission having a two-speed master clutch splitter to
bring an auxiliary section countershaft into synchronous speed
with a main section countershaft.
According to the present invention, a compound change gear
transmission includes an intermediate shaft disposed between
transmission input and output shafts with main countershafts
and auxiliary countershafts disposed parallel thereto. A
torque input splitter gear is coaxial with and rotatable
relative to the input shaft. A second splitter gear coaxial
with the input and intermediate shafts is mounted for
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rotational engagement with the input and intermediate
shafts. A plurality of intermediate shaft drive gears
are mounted rotatably on the intermediate shaft and a
plurality of main countershaft gears are fixed for
rotation with the main countershaft. The splitter gear
and intermediate shaft drive gears are selectively
clutchable and in continuous meshing engagement with the
main countershaft gears. An intermediate shaft output
gear is fixed for rotation with the intermediate shaft
and an output shaft range gear is coaxial with and
rotatable relative to the output shaft.
A two-way synchronizer coupling is fixed for.
rotation with the output shaft and operable for coupling
the intermediate shaft output gear and also for coupling
the output shaft splitter gear to the output shaft. The
transmission also includes an auxiliary countershaft
assembly comprising an auxiliary countershaft, a first
auxiliary countershaft gear fixed for rotation on the
auxiliary countershaft and constantly meshed with the
output shaft splitter gear, and a second auxiliary
countershaft gear selectively engageable with the
auxiliary countershaft and constantly meshed with the
intermediate shaft output gear. A clutch assembly fixed
for rotation on the auxiliary countershaft has a
position for selectively coupling the auxiliary
countershaft to the main countershaft.
The advantages accruing to the present
invention are numerous. For example, a two-speed master
clutch input splitter provides smoother starting and
enables a power shift every other shift. Furthermore,
the two-speed master clutch (e.g. a hydraulic wet
clutch) provides protection from damaging operation due
to a dry sump, since loss of lube pump and oil lube
CA 02153608 1999-12-07
pressure disengages the clutch. Another advantage of
the present inveni~ion is the reduced size and weight of
the transmission which results from the reduction in the
number of gears necessary to achieve a desired number of
available geaar ratios. A reduced number of gears also
allows a shorter, lighter transmission case which
further reduces the weight of the transmission.
The: abov~s and other features
and advantages of the present invention will be readily
appreciated by one of ordinary skill in this art from
the following detailed description of the best mode for
carrying out the invention when taken in connection with
the accompanying drawings.
~i~ef Description Of The Drawings
FIGURE 1 is a schematic illustration of a
prior art compound transmission section having a multi-
speed main transmission section connected in series with
an auxiliary transmission section;
FIGURE 2a is a schematic illustration of a
first embodiment of a compound transmission having
fourteen forward. speeds including an auxiliary
countershaft assembly constructed in accordance with the
present invention;
FIGURE 2b is a torque flow diagram
illustrating the plurality of torque flow paths through
the compound transmission of FIGURE 2a;
FIGURE as is a schematic illustration of the
shift pattern for the transmission of FIGURE 2a;
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FIGURE 3b illustrates which gear clutches of
FIGURE 2a are engaged for each position of the shift
pattern of FIGURE 3a;
FIGURE 4a is a schematic illustration of a
second embodiment of a compound transmission having ten
forward speeds including a two-speed master clutch
splitter constructed in accordance with the present
invention;
FIGURE 4b is a torque flow diagram
illustrating the plurality of torque flow paths through
the compound transmission of FIGURE 4a;
FIGURE 5a is a schematic illustration of the
shift pattern for the transmission of FIGURE 4a;
FIGURE 5b illustrates which of the gear
clutches of FIGURE 4a are engaged for each position of
the shift pattern of FIGURE 5a;
FIGURE 6a is a schematic illustration of a
third embodiment of a compound transmission having
sixteen forward speeds constructed in accordance with
the present invention;
FIGURE 6b is a torque flow diagram
illustrating the plurality of torque flow paths through
the compound transmission of FIGURE 6a;
FIGURE 7a is a schematic illustration of the
shift pattern for the transmission of FIGURE 6a;
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FIGURE 7b illustrates which of the gear
clutches of FIGURE 6a are engaged for each position of
the shift pattern of FIGURE 7a;
FIGURE 8a is a schematic illustration of a
fourth embodiment of a compound transmission having
twelve forward speeds constructed in accordance with the
present invention;
FIGURE 8b is a torque flow diagram
illustrating the plurality of torque flow paths through
the compound transmission of FIGURE 8a;
FIGURE 9a is a schematic illustration of the
shift pattern for the transmission of FIGURE 8a; and
FIGURE 9b illustrates which of the gear
clutches of FIGURE 8a are engaged for each position of
the shift pattern of FIGURE 9a.
Best Mode For Carr,~g Out The Invention
The following terminology will be used in the
description of the present invention for convenience
only and thus, will not be limiting. The words
"upwardly", "downwardly", "rightwardly", and
"leftwardly" will designate directions in the drawings
to which reference is made. The words "forward" and
"rearward" will refer respectively to the front and rear
ends of a transmission as conventionally mounted in a
vehicle, corresponding respectively to the left and
right sides of the prior.art main transmission section
illustrated in Figure 1.
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The term "compound transmission" is used to
designate a change speed or change gear transmission
having a main transmission section and an auxiliary
transmission section connected in series whereby the
selected gear reduction (or multiplication) in the main
transmission section may be compounded by further
selected gear reduction (or multiplication) in the
auxiliary transmission section. The term "upshift" as
used herein shall mean the speed gear ratio is changed
from a lower value to a higher value. The term
"downshift" as used herein shall mean the shifting from
a higher speed gear ratio to a lower speed gear ratio.
The terms "low speed gear" or "low gear" as used herein
shall designate a gear ratio utilized for relatively
lower forward speed operation in a transmission, i.e. a
set of gears having~a higher ratio of reduction of
output shaft speed relative to the speed of the input
shaft. "Synchronizing clutch assembly" and words of
similar import shall designate a clutch assembly
utilized to non-rotatably couple a selected gear to a
shaft by means of a positive clutch. Attempted
engagement of the positive clutch is prevented until the
members of the clutch are at substantially similar
rotation speeds. The synchronized clutch assembly
includes relatively large capacity friction means
associated with the clutch members which are sufficient,
upon initiation of a clutch engagement, to cause the
clutch members and all members rotating therewith to
rotate at a substantially synchronous speed.
Figure 1 schematically illustrates a well
known, commercially successful compound transmission,
indicated generally by reference numeral 10, having
eighteen forward speeds. Transmission 10 includes a
main transmission section, indicated generally by
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reference numeral 12, connected in series with an
auxiliary transmission section, indicated generally by
reference numeral 14. Typically, transmission 10 is
housed in a single housing and includes an input shaft
16 driven by an engine E through a selectively
disengaged, normally engaged master friction clutch C.
Master friction clutch C includes an input or driving
section 18 connected to the engine crankshaft 20, and a
driven portion 22 rotatably fixed to a transmission
input shaft 16.
With continuing reference to Figure 1, within
main transmission section 12, input shaft 16 carries an
input gear 24 for simultaneously driving a plurality of
substantially identical main section countershaft
assemblies 26 and 26A at substantially identical
rotational speeds. In the transmission illustrated, two
(2) substantially identical main section countershaft
assemblies are provided on diametrically opposite sides
of a mainshaft 28 which is generally coaxially aligned
with input shaft 16. Each of the main section
countershaft assemblies 26 and 26A includes a main
section countershaft 30 supported by bearings 32 and 34
in housing H, only a portion of which is schematically
illustrated.
Each of the main section countershafts 30 is
provided with an identical grouping of main section
countershaft gears 38, 40, 42, 44, 46 and 48, fixed for
rotation therewith. A plurality of main section drive
gears (mainshaft gears) 50, 52, 54, 56 and 58 surround
mainshaft 28 and are selectively clutchable, one at a
time, to mainshaft 28 for rotation therewith via sliding
jaw clutch collars 60, 62 and 64 as is well known in the
art. Clutch collar 60 may also be utilized to clutch
EAT 0152 PUS -12-
input gear 24 to mainshaft 28 to provide a direct drive
relationship between input shaft 16 and mainshaft 28.
Preferably, each of the main section mainshaft gears
encircles mainshaft 28 and is in continuous meshing
engagement with, and floatingly supported by an
associated countershaft gear group.
Typically, sliding jaw clutch collars 60, 62
and 64 are axially positioned by means of shift forks
(not illustrated) associated with a shift bar housing
l0 assembly (not illustrated) as is well known in the art.
Sliding jaw clutch collars 60, 62 and 64 are of the well
known non-synchronized double acting jaw clutch type=
Sliding jaw clutches collars 60, 62 and 64 define three-
position clutches which may be positioned in a centered,
non-engaged position as illustrated, in a fully
rightwardly engaged position, or in a fully leftwardly
engaged position.
With continuing reference to Figure 1, main
section mainshaft gear 58 functions as a reverse gear
which is in continuous meshing engagement with
'countershaft gears 48 by means of conventional
intermediate idler gears 49. It should also be noted
that while main transmission section 12 provides five
selectable forward speed ratios, the lowest forward
speed ratio is often of such a high gear reduction as to
be considered a low or "creeper" gear which is utilized
only for starting of a vehicle under severe conditions.
A creeper gear transmits torque through main
transmission section 12 when drive gear 56 is drivingly
coupled to mainshaft 28 by sliding jaw clutch 64. The
creeper gear is usually not utilized in the higher
transmission range and/or is not typically split in the
lower transmission range.
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Auxiliary transmission section 14 includes two
substantially identical auxiliary countershaft
assemblies 68 and 68A, each having an auxiliary
countershaft 70 supported by bearings 72 and 74 mounted
in housing H. Each auxiliary countershaft 70 supports
three auxiliary section countershaft gears 76, 78 and 80
fixed for rotation therewith. Auxiliary countershaft
gears 76 are constantly in mesh with auxiliary section
splitter gear 82 which is selectively coupled to
mainshaft 28 via sliding jaw clutch collar 90.
As also illustrated in Figure 1, auxiliary
countershaft gears 78 are constantly in mesh with, and
support, auxiliary section splitter/range gear 84 which
is selectively coupled to output shaft 86 via
synchronizing clutch-assembly 92. Output shaft 86 is
coaxial with mainshaft 28. Auxiliary section
countershaft gears 80 are constantly in mesh with, and
support, auxiliary section range gear 88 which is
selectively engageable with output shaft 86 via two
position synchronizing clutch assembly 92. Accordingly,
auxiliary section countershaft gears 76 and splitter
gear 82 define a first gear layer. Similarly, auxiliary
section countershaft gears 78 and splitter/range gear 84
define a second gear layer, while auxiliary section
countershaft gears 80 and range gear 88 define a third
gear layer. Thus, the illustrated combined splitter and
range type auxiliary transmission section 14 includes
three (3) gear layers or groups.
Sliding two position jaw clutch collar 90 is
utilized to selectively couple either splitter gear 82,
or splitter/range gear 84, to mainshaft 28. Similarly,
two position synchronizing clutch assembly 92 is
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utilized to selectively couple splitter/range gear 84,
or range gear 88, to output shaft 86.
Referring now to Figures 2a, 4a, 6a and 8a,
each figure schematically illustrates a compound
transmission 10A, 108, 1DC, and 10D, respectively
including an auxiliary transmission section 14A, 14B,
14C and 14D, respectively, constructed in accordance
with the present invention. Compound transmissions l0A-
lOD comprise main transmission sections 12A, 12B, 12C
and, 12D, respectively, which are similar in
construction and operation to main transmission section
12 described above in reference to prior art
transmission 10.
Transmission sections 12A-12D each have a
different number of intermediate mainshaft gears and
corresponding countershaft gears as hereinafter
described and illustrated in the drawings. In main
transmission sections 12A-12D, the main countershafts
are selectively engageable to the auxiliary section
countershafts for driving auxiliary transmission
sections 14A-14D and reducing the number of gears
required for a desired number of speed ratios as
described below. Immediately following, and by way of
example, is a detailed description of the transmission
of Figure 2a. The description can easily be applied to
the transmissions illustrated in Figures 4a, 6a and 8a
since primed reference numerals (xx',xx ") correspond in
position and function to the unprimed reference numerals
of Figure 2a.
With continuing reference to Figure 2a,
multiple ratio transmission l0A is a fourteen forward
speed,. four-reverse speed, compound manually operated
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transmission wherein a main transmission section 12A is
connected. in series to an auxiliary transmission section
14A. The main transmission section 12A includes a two-
speed input splitter section; whereas, auxiliary section
14A includes a four speed splitter/range section.
Typically, transmission l0A is housed within a single
housing (not shown) and includes an input shaft 122
driven by an engine (not shown), such as a diesel engine
or the like.
Within main transmission section 12A, input
shaft 122 drives a synchronizing clutch assembly 126.
Synchronizing clutch assembly 126 is actuated by an
actuator 128 such as a three-position piston, or the
like, and has a first position (corresponding to
engagement of synchronizer S1) for engaging a first
(torque) input splitter gear 132 to input shaft 122, a
second position (corresponding to engagement of
synchronizer S2) for engaging a second input splitter
gear 134 to input shaft 122, and a third position (as
illustrated) wherein first and second splitter gears
132,134 are drivingly disconnected from input shaft 122.
The input splitter section thus defines a first
synchronizer S1 and second synchronizer S2 which are
mutually exclusively engageable to couple first input
splitter gear 132 or second input splitter gear 134 to
input shaft 122. Alternatively, a two-speed master
clutch splitter may be utilized as illustrated in Figure
4a and described in greater detail below.
With continuing reference to Figure 2a, torque
input splitter gear 132 and second input splitter gear
134 simultaneously drive a pair of substantially similar
main section countershaft assemblies 138 and 138A at
substantially similar rotation speeds. In the
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transmission illustrated, main section countershaft
assemblies 138,138A are located on diametrically
opposite sides of an intermediate shaft 140 which is
generally coaxially aligned with input shaft 122 and
output shaft 124. Each of the main section countershaft
assemblies 138,138A includes a main section countershaft
142 supported by bearings (not shown). A substantially
similar grouping of main section countershaft gears
144,146,148,150, and 152 are coupled to each main
section countershaft 142 for rotation therewith.
As also illustrated in Figure 2a, main section
drive gears 154,156, and 158 surround intermediate shaft
140 and are selectively clutchable, one at a time, to
intermediate shaft 140 for rotation therewith by sliding
jaw clutches 160 and 162 as is well known in the prior
art. Sliding jaw clutch 160 may also be utilized to
couple second splitter gear 134 directly to intermediate
shaft 140 to provide a direct driving relationship
therebetween. Of course, with synchronizer S2 engaged,
second splitter gear 134 will rotate with input shaft
122 and drive main section countershaft gears 146. With
synchronizer S1 engaged, first splitter gear 132 will
rotate with input shaft 122 and drive main section
countershaft gears 144.
Main section drive gears 154,156 are in
continuous meshing engagement with, and floatingly
supported by, the associated main section countershaft
gears 148,150, respectively. Main section intermediate
shaft gear 158 is the reverse gear which is in
continuous meshing engagement with main section
countershaft gear 152 by means of conventional
intermediate idler gears 164.
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Main section sliding jaw clutch collars 160
and 162 are axially positioned by shift forks 166 and
168, respectively, and are typically manually controlled
by means of a shift lever or the like, as is well known
from the prior art. Sliding jaw clutch collars 160 and
162 are of the well known nonsynchronizing type of
double acting jaw clutch.
The manually controlled main section 12A
defines six clutches (including two synchronizing clutch
assemblies) S1,S2,J1,J2,J3 and JR. The synchronizers
S1,S2 are mutually exclusively engageable to drivingly
couple either of the two input splitter gears 132,134 to
input shaft 122. Clutches J1,J2,J3, and JR are mutually
exclusively engageable to drivingly couple intermediate
shaft 140 to input splitter gear 134, main section drive
gears 154,156, or reverse drive gear 158, respectively.
The combined splitter/range auxiliary section
14A includes two substantially similar auxiliary
countershaft assemblies 170 and 170A. Each countershaft
.assembly 170,170A includes an auxiliary countershaft 172
which is supported by bearings within a housing (not
shown). Each auxiliary countershaft 172 supports two
auxiliary section countershaft gears 174,176. Auxiliary
section countershaft gears 174 are coupled to an
auxiliary countershaft 172 for rotation therewith.
Auxiliary section countershaft gears 176 are selectively
engageable to auxiliary countershaft 172 and are in
continuous meshing engagement with intermediate shaft
output gear 178 so as to provide support thereto.
Similarly, auxiliary countershaft gears 174 are
constantly in mesh with auxiliary section range gear 180
and provide support thereto. Auxiliary section range
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gear 180 is selectively engageable to an output shaft
124 via two position synchronizing clutch assembly 186.
With continuing reference to Figure 2a, a
sliding jaw clutch collar 184 is positioned by an
actuator 188, such as a two-position piston or the like.
Control means 192 is responsive to gear shift position
and controls actuator 188 accordingly to engage clutch
J4, clutch J5, or maintain an intermediate position as
illustrated. Clutch J4 is utilized to selectively
couple main section countershafts 142 to auxiliary
section countershafts 172; whereas, clutch J5 is
utilized to selectively couple auxiliary section drive
gears 176 to auxiliary section countershafts 172. By
providing clutchable auxiliary section drive gears 176,
intermediate shaft 140 is decoupled from output shaft
124 for those gear ratios where the torque flow path
includes main countershaft 142 and auxiliary
countershaft 172, such as gears 7 and 8. Thus,
intermediate shaft 140 and its associated components are
not drivingly rotated unnecessarily when they are not
being utilized to transmit torque through transmission
10A. The resulting reduction in spin back speed of
intermediate shaft 140 facilitates smoother, faster
shifts .
As also illustrated in Figure 2a, a two
position synchronizing clutch assembly 186 is utilized
to selectively couple a range gear 180 to output shaft
124. Synchronizing clutch assembly 186 defines two
mutually exclusive engageable range torque flow paths H
and L which are operative to couple gears 178 and 180,
respectively, to output shaft 124. For example, in high
range H, synchronizing clutch assembly 186 couples
intermediate shaft output gear 178 to output shaft 124.
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In low range L, synchronizing clutch assembly 186
couples range gear 180 to output shaft 124. Thus, in
low range L, torque is transmitted to auxiliary
countershafts 172 either through intermediate shaft 140,
intermediate shaft output gear 178 and auxiliary drive
gears 176 (via engaged clutch J5); or through main
countershafts 142 and main countershaft drive gears 152
(via engaged clutch J4). Actuator 190 is a two position
fluid actuated piston for effecting selection of the
desired torque flow path, H or L, via two position
synchronizing clutch assembly 186.
Figure 2b is a torque flow diagram
illustrating the plurality of torque flow paths through
the compound transmission of Figure 2a. Torque is
transmitted either along a first axis which is coaxial
with input shaft 122, intermediate shaft 140, and output
shaft 124, or along a pair of second axes which are
coaxial with main section countershafts 142 and
auxiliary section countershafts 172. A downward step in
the torque flow diagram indicates that torque flow has
been transferred from components coaxial with the first
axis to components coaxial with the second axes.
Similarly, an upward step in the torque flow diagram
indicates that torque flow has been transferred from
components coaxial with the second axes to components
coaxial with the first axis.
For example, when gear three is selected,
synchronizer S2, and clutches J2 and J5 are engaged.
Torque is transferred along input shaft 122 (coaxial
with the first axis) through clutch S2 and through gears
134,146 (in constant meshing engagement) to main section
countershafts 142 (coaxial with the second axes).
Torque then flows through gears 148 to gear 154 and
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clutch J2 to intermediate shaft 140 (again coaxial with
the first axis). Torque is then transferred through
gear 178 to gears 176 and to auxiliary countershafts 172
(again coaxial with the second axes) via clutch J5.
Finally, torque is transferred through gears 174 to gear
180 and then to output shaft 124 via synchronizing
clutch assembly 186 (again coaxial with the first axis).
This results in a gear ratio (input shaft speed divided
by output shaft speed) of 11.80.
The speed ratios represented on the torque
f low paths for each of forward and reverse speeds are
illustrative and provide only one example of
implementation. In this particular implementation,
assumptions were made to provide equal steps between
speed ratios in the main transmission section between
the second splitter gear and auxiliary countershaft
input. This provides a lowest overall transmission
speed ratio of about 20:1 and a highest overall
transmission speed ratio of about 0.8:1. Given these
assumptions, the ratios as illustrated in Figure 2b are
obtainable. The torque flow paths for the remaining
gears, as well as the torque flow paths illustrated in
Figures 4a, 6a, and 8a, may be interpreted in an
analogous manner.
Within main transmission section 12A of Figure
2a, the number of teeth on torque input splitter gear
132 is represented by parenthetical reference letter A.
Similarly, the number of teeth on second splitter gear
134 is represented by parenthetical reference letter B.
Likewise, the number of teeth on each of main section
countershaft gears 144 is represented by parenthetical
reference letter D and the number of teeth on each of
main section countershaft gears 146 is represented by
21~36~~
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parenthetical reference letter E. Within auxiliary
section 14A, the number of teeth on range gear 180 is
represented by parenthetical reference letter C and the
number of teeth on auxiliary countershaft gears 174 is
represented by parenthetical reference letter F.
With continuing reference to Figure 2a,
various- gear ratios between meshing gears are
illustrated with a decimal numeral followed by an arrow
indicating the direction of torque flow corresponding to
l0 that gearing ratio. The gearing ratio is determined by
dividing the number of teeth on the driven gear by the
number of teeth on the driving gear. If the torque
f lows in the direction opposite that indicated by the
arrow, the gearing ratio is the reciprocal of that
shown. For example, when synchronizing clutch assembly
S1 is engaged, torque flows from input shaft 122 to
input splitter gear 132 and to main countershaft gear
144. Since this corresponds to the direction of the
arrow indicating a gear ratio of 0.78, that gear ratio
represents the number of teeth D on the driven gear 144
divided by the number of teeth A on the driving gear
132.
Compound transmissions may be designed to have
variable ratio steps or approximately equal ratio steps.
Compound transmissions having equal ratio steps, such as
those implementations of the present invention
illustrated in Figures 2a-8a, may be referred to by the
average ratio step. For example, a 28% transmission
would have ratio steps of 28%, i.e. any gear N divided
by the next higher (numerically) gear N+1 is
approximately equal to 1.28. The ratio steps are only
approximately equal due to constraints in designing and
manufacturing gears with the appropriate number of teeth
2153~Q8
EAT 0152 PUS -22-
to be used in various combinations to establish exactly
equal ratio steps. Thus, the ratio steps are within
about 10% of the ideal design value, i . e. rc -. io steps
between about 25% and 31% are obtainable using standard
gear tooling.
For compound transmissions having input
gearing ratios less than unity (overdrive input ratios),
such as those illustrated in Figures 2a (0.78) and 4a
(0.74) , the average transmission ratio step is generally
indicated by the product of the ratios defined by A/D
and E/B. For the compound transmission of Figure 2a,
the average ratio step (1.28) is equal to A/D (1.28)
multiplied by E/B (1.00). The product of the ratios
defined by C/F and E/B is then generally equal to the
average transmission ratio step (A/D ~ E/B) raised to
the 2N power, where N is equal to the total number of
forward speed ratios available on the intermediate
shaft. For example, for the 28% transmission
illustrated in Figure 2a, A/D ~ 1.28, E/B ~ 1.00, and
C/F ~ 4.39. There are three (3) forward speed ratios
available on the intermediate shaft 140 (N=3), so (E/B
~ C/F) ~ (1.28)2, or 4.44.
As illustrated in Figures 2a and 2b, the
multiple ratio transmission l0A provides fourteen
forward speeds utilizing 23 gears. Prior art
transmissions have required 29 gears to achieve fourteen
speeds since those transmissions do not couple a main
countershaft to an auxiliary countershaft. The shift
pattern for shifting fourteen forward speed transmission
l0A of the present invention is illustrated in Figure
3a. Locations of the shift lever depicted in Figure 3a
correspond to engagement of the clutches indicated in
Figure'3b.
21~3~~8
EAT 0152 PUS -23-
Referring now to Figure 3a, a first master
control having two selectable positions, defined by a
two position lever (labeled DIR and OD), splits shifts
for each position of the shift pattern. A second master
control having two selectable positions allows operator
selection of either one of the two range ratios. The
range is selected by a two position button RF. Range
shifting associated with each position of the shift
pattern is illustrated with high range indicated by the
upper half of the circle, and low range being indicated
by the lower half of the circle. For example, to select
gear nine, the shift lever is placed in the lower left
position of the shift pattern, the range shift button RF
is raised to select high range, and the splitter button
is in the DIR position. To shift the transmission from
gear nine to gear ten, the splitter button is moved from
the DIR position to the OD position.
Figure 3b illustrates the engaged clutches of
Figure 2a for each combination of the shift lever, range
button RF, and splitter lever illustrated in Figure 3a.
For example, when gear six is selected, the shift lever
is in the lower right position of the shift pattern, the
range button RF is lowered to select low range, and the
splitter lever is in the OD position. As indicated by
Figure 3b, clutches S1, J1, J5, and L (synchronizing
clutch assembly 186) are engaged. As illustrated in
Figures 3a and 3b, operation of transmission l0A (Figure
2a) from the lowest speed ratio, gear one, to the
highest speed ratio, gear fourteen, requires only six
(6) movements of the shift lever.
Referring now to Figure 4a, a ten forward
speed transmission having an auxiliary section
constructed in accordance with the present invention is
CA 02153608 1999-12-07
-24-
illustrated. Multiple ratio transmission lOB utilizes
20 gears rather than the 23 gears typically employed in
comparable prior art transmissions. The embodiment of
transmission 10B illustrated in Figure 4a differs from
transmission l0A illustrated in Figure 2a in that an
optional tw~~-speed master clutch splitter C' has
replaced a master clutch (not shown) and synchronizing
clutch a.ssemrbly 12'6. An analogous construction may be
utilized in transmissions 10A, lOC, and lOD illustrated
in Figures 2a, 6a, and 8a, respectively, wherein a
synchronizin<~ clutch assembly and master clutch is
replaced by a two-speed master clutch splitter.
With continuing reference to Figure 4a, two-
speed master clutch splitter C' preferably includes at
least two selectable engaged positions for selection of
one of two selectable input ratios . Clutch C' also has
a selectable disengaged position to provide the torque
break function of a traditional master clutch. Clutch
C' includes z~ twin input or driving section 18' and 18A'
connected to an engine crankshaft 20', and corresponding
twin driven ;portions 22' and 22A' rotatably fixed to a
transmission input shaft 122'. Thus, the engagement of
first driving section 18' to first driven section 22' is
represented by clutch S1 while the engagement of second
driving section 18A' to second driven section 22A' is
represented ;by clutch S2. A greater understanding and
appreciation of the construction and operation of such
a two-speed master clutch splitter may be achieved by
reference to United States Patents Nos. 4,831,894 and
4,966,048r
As with the transmission illustrated in Figure
2a, the parenthetical reference letters shown in Figure
~1~3~~1~
EP.T 0152 PUS -25-
4a represent the number of teeth on the associated gear
or gears. Thus, in the main transmission section 12A,
the number of teeth on torque input splitter gear 132'
is represented by parenthetical reference letter A, etc.
Figure 4b illustrates the plurality of torque
flow paths through the compound transmission of Figure
4a, in addition to the engaged clutches and the
approximate ratios attained for each available gear.
The speed ratios represented on the torque flow paths
for each of forward and reverse speeds are illustrative
and provide only one example of possible
implementations. In the implementation illustrated
assumptions were made to provide equal steps between
speed ratios in the main transmission section between
the second splitter 'gear and auxiliary countershaft
input. For this implementation, the lowest ratio would
be about 11:1 and the highest ratio would be about
0.8:1. Given these assumptions, the ratios as
illustrated in Figure 4b are obtainable.
In transmission lOB, as in transmission 10A,
the average transmission ratio step is generally equal
to the product of the ratios determined by A/D and E/B.
The product of the ratios determined by C/F and E/B is
generally equal to the average transmission ratio step
raised to the 2N power, where N is equal to the total
number of forward speed ratios available on the
intermediate shaft. For example, for the transmission
illustrated in Figure 4a, A/D ~ 1.35, E/B ~ 1.00, and
C/F ~ 3.32. There are two (2) forward speed ratios
available on the intermediate shaft 140' (N=2), so (E/B
~ C/F) ~ (1.35)2'x, or 3.33.
2153fi~~
EAT 0152 PUS -26-
Figure 5a illustrates the shift pattern for
shifting the ten forward speed transmission of Figure
4a. A two position splitter lever (labeled OD and DIR)
on the side of the circle (representing the gear shift
lever) controls splitter shifts for each position of the
shift lever. A range shifting button is unnecessary
since range shifting is performed automatically when the
gear shift lever is moved either to or from the far
right positions corresponding to gears 7/8 and 9/10.
For example, moving the gear shift lever from the 5/6
position to the 7/8 position automatically shifts
synchronizing clutch assembly 186' from low range to
high range. Likewise, moving the gear shift lever from
either the 7/8 position or the 9/10 position to any
other position automatically shifts synchronizing clutch
assembly 186' from high range to low range.
Figure 5b illustrates the engaged clutches of
Figure 4a for each position of the shift pattern
illustrated in Figure 5a. As may be seen, operation of
transmission lOB from the lowest speed ratio, gear one,
to the highest speed ratio, gear ten, requires only four
(4) movements of the shift lever.
Referring now to Figure 6a, a multiple ratio
transmission lOC having sixteen forward speeds utilizing
23 gears is shown. Prior art transmissions have
required 29 gears to achieve sixteen speeds since they
do not couple main countershafts to auxiliary
countershafts. The various torque flow paths, engaged
clutches, and approximate ratios of transmission lOC are
illustrated in Figure 6b. Since this compound
transmission has an underdrive input gearing ratio
(1.21), the average transmission ratio step is generally
indicated by the product of the ratios defined by D/A
2i53~0~
EAT 0152 PUS -27-
and E/B. Thus, the average ratio step (1.21) is equal
to D/A (1.21) multiplied by E/B (1.00). The product of
the ratios defined by C/F and E/B is then generally
equal to the average transmission ratio step (D/A ~ E/B)
raised to the 2N power, where N is equal to the total
number of forward speed ratios available on the
intermediate shaft. Thus, in this case, D/A ~ 1.21, E/B
1.00, and C/F ~ 3.13. There are three (3) forward
speed ratios available on the intermediate shaft 140"
(N=3), so (E/B ~ C/F) ~ (1.21)2'x, or 3.13.
With continuing reference to Figure 6a,
although it is possible to utilize auxiliary
countershaft drive gears 176" which are selectively
engageable to auxiliary countershafts 172", in this
embodiment, drive gears 176" are fixed to auxiliary
countershafts 172". This is possible due to the lower
gear ratio (1.46) between output shaft range gear 178"
and drive gears 176" as compared to the analogous gear
ratios for the transmissions of Figure 2a (1.64), Figure
4a ( 1. 83 ) , and Figure 8a ( 1. 64 ) . Thus, the spin back
speed of intermediate shaft 140" is less significant in
the transmission illustrated in Figure 6a such that
clutchable auxiliary countershaft drive gears are not
required.
The shift pattern for shifting transmission
lOC of Figure 6a is illustrated in Figure 7a. Figure 7b
illustrates the engaged clutches corresponding to each
shift lever position illustrated in Figure 7a. As with
the transmission illustrated in Figure 2a, a two
position splitter lever (labeled DIR and OD) splits
shifts for each position of the shift pattern. A two
position range shift button RF is utilized to select
high range (corresponding to the upper half of the
21~360~
EAT 0152 PUS -28-
circles) or low range (corresponding to the lower half
of the circles).
As illustrated in Figures 7a and 7b, operation
of transmission lOC from the lowest speed ratio, gear
one, to the highest speed ratio, gear sixteen, requires
only seven (7) movements of the shift lever. The speed
ratios represented on the torque flow paths of Figure 7b
for each of the forward and reverse speeds are
illustrative and represent only one possible
implementation. In the implementation illustrated
assumptions were made to provide equal steps between
speed ratios in the main transmission section between
the second splitter gear and auxiliary countershaft
input. For this implementation, the lowest overall
transmission speed ratio would be about 12:1 and the
highest overall transmission speed ratio would be about
0.7:1. Given these assumptions, the ratios as
illustrated in Figure 6b are readily obtainable.
Referring now to Figure 8a, a multiple ratio
transmission lOD having twelve forward speeds utilizing
20 gears is illustrated. Comparable prior art
transmissions required 23 gears to achieve twelve speeds
without the use of coupling the main countershafts to
the auxiliary countershafts. As with the transmission
illustrated in Figure 6a, this compound transmission
has an underdrive input gearing ratio (1.28).
Therefore, the average transmission ratio step is
generally indicated by the product of the ratios defined
by D/A and E/B. Thus, the average ratio step (1.28) is
equal to D/A (1.28) multiplied by E/B (1.00). The
product of the ratios defined by C/F and E/B is then
generally equal to the average transmission ratio step
(D/A ~~E/B) raised to the 2N power, where N is equal to
EAT 0152 PUS -29-
the total number of forward speed ratios available on
the intermediate shaft. Thus, in this case, D/A ~ 1.28,
E/B ~ 1.00, and C/F ~ 2.68. There are two (2) forward
speed ratios available on the intermediate shaft 140"
(N=2) , so (E/B ~ C/F) ... (1.28)2'x, or 2.68.
A torque flow diagram for the transmission of
Figure 8a is shown in Figure 8b. The shift pattern for
shifting the twelve forward speed transmission of Figure
8a is illustrated in Figure 9a with locations of the
shift lever corresponding to the engagement of clutches
as illustrated in Figure 9b. Transmission lOD utilizes
a splitter lever and a range shift button RF to select
a desired gear. Thus, operation of transmission lOD
from the lowest speed ratio (about 9:1), corresponding
to gear one, to the highest speed ratio (about 0.6:1),
corresponding to gear twelve, requires only five (5)
movements of the shift lever.
It is understood, of course, that while the
forms of the invention herein shown and described
constitute the preferred embodiments of the present
invention, they are not intended to illustrate all
possible forms thereof. It will also be understood that
the words used are descriptive rather than limiting, and
that various changes may be made without departing from
the spirit or scope of the invention as claimed below.
