Note: Descriptions are shown in the official language in which they were submitted.
CA 02263788 1999-03-1~
IMPROVEMENTS IN ~ullJE SHIFT TRANSMISSIONS
This is a divisional of Canadian Patent
Application Serial No. 2,031, 021 filed November 28,
S 1990.
Back~rGund of the Invention
Power shift transmissions are well known in the
art. Some power shift transmissions provide shuttle
shift capability which permits the vehicle to change
direction of operation without requiring the movement of
the gearshift lever through each intermediate gear ratio.
To accomplish this operation, these known types of
shuttle shift transmissions will typically include torque
converters. In such transmissions utilizing torque
converters for shuttle shifting at high or even moderate
speeds, a high energy load is placed on the clutches.
Some power shift transmissions are
characterized in that they do not require a different
gearshift lever position for each gear ratio which may be
selected. While such transmissions have simplified
operator control, such transmissions do have drawbacks
and lack certain desirable features. For example, these
transmissions provide automatic speed ratio matching with
no means permitting an operator to intervene manually in
the automatic speed ratio matching process.
The operation or response of the transmission
clutches vary from one transmission to another, or in a
given transmission over a period of time. The present
invention alleviates some of these problems and, in
addition, provides new methods by which an operator may
effect the shuttle shifting process.
Summary of the Invention
An object of the invention is to provide
novel methods of controlling vehicle deceleration
during shuttle shifting to thereby reduce the energy
CA 02263788 1999-03-1
input to the clutches.
According to the invention in one aspect there is
provided a method of controlling vehicle deceleration
during shuttle shifting of a power shift transmission
having clutches for selectively interconnecting an input
drive shaft, an output drive shaft, and a plurality of
gears rotatably housed in said transmission in driving
relationship with said input and output drive shafts such
that a selective engagement of said clutches will effect
a varying of the speed of operation of said output shaft
for a given speed of operation of said input shaft, said
gears being arranged in preselected gear ratios from low
speed to a high speed, the method comprising:
disconnecting said transmission from said input shaft;
locking said transmission to prevent rotation of said
gears; and modulating at least one of said clutches to
decelerate the speed of movement of said vehicle to a
desired speed of operation by dissipating the inertial
energy of said vehicle through said at least one clutch.
Preferablysaid clutches include an initial clutch
set having a plurality of clutches therein for
selectively connecting said input drive shaft in driving
relationship with a first plurality of shafts and a
corresponding set of drivingly engaged first gears and.a
final clutch set having a plurality of clutches therein
for selectively connecting a second plurality of shafts
and a corresponding set of drivingly engaged second gears
in driving relationship with said output shaft for
driving the vehicle, said disconnecting step including
CA 02263788 1999-03-1~
the step of: releasing all clutches in said initial
clutch set to disconnect said input drive shaft from said
first plurality of shafts.
other aspects of the invention and its mode
of operation will ~ecome apparent upon consideration
of the following description and the accompanying
drawings.
Brief Description of the Drawings
Fig. 1 is a schematic diagram of a shuttle
shift transmission control system of the prior art;
Fig. 2 illustrates the shift pattern for a
gearshift lever;
Fig. 3 is a schematic planar development of
the three-dimensional transmission shown in Figs- 4-9.
Fig. 4 is a schematic plotting of the
transmission layout showing the locations of the shaft
centers, corresponding to lines 4-4 of Fig. 3;
Fig. 5 is a schematic plotting of the
locations and relationships of the primary drive gear
set corresponding to lines 5-5 of Fig. 3;
Fig. 6 is a schematic plotting of the
locations and relationships of the fixed gears mounted
on the first, second and third jack shafts
corresponding to lines 6-6 of Fig. 3;
Fig. 7 is a schematic plotting of the
locations and relationships of the intermediate gear
set mounted on the first, second and third jack shafts
corresponding to lines 7-7 of Fig. 3;
Fig. 8 is a schematic plotting of the
locations and relationships of the transfer gears
30 corresponding to lines 8-8 of Fig. 3;
Fig. 9 is a schematic plotting of the
CA 02263788 1999-03-1~
locations and relationships of the final drive gear
set corresponding to lines 9-9 of Fig. 3;
Fig. 10 illustrates a gearshift pattern
according to one aspect of the present invention;
Fig. 11 is a flow diagram of a program
executed by the microprocessor of Fig. 1 to preselect
a gear;
Fig. 12 is a flow diagram illustrating a
method of preselection of a forward to reverse gear
ratio prior to starting a vehicle;
Fig. 13 is a subroutine for the preselection
of a forward to reverse gear ratio;
Figs. 14a and 14b illustrate routines for
selecting reverse and forward gears, respectively,
using the ratio developed by the subroutine of Fig.
13;
Fig. 15 is a flow diagram illustrating a
first method of controlling vehicle deceleration
during the shifting of gears;
Fig. 16 is a flow diagram illustrating a
second method of controlling vehicle deceleration
during the shifting of gears;
Fig. 17 is a flow diagram illustrating a
third method of controlling vehicle deceleration
during the shifting of gears;
Fig. 18 is a flow diagram illustrating a
first method of calibrating clutches;
Fig. 19 is a flow diagram illustrating a
second method of calibrating clutches.
Figs. 2Oa and 2Ob are flow diagrams
illustrating methods for manually overriding the
automatic ratio matching feature for a power shift
transmission, the method of Fig. 20b resulting in a
temporary override for a specific interval of time.
CA 02263788 1999-03-1
-4(a)
Detailed Description of the Invention
Fiqs. 1-9 illustrate a power shift
transmission system of the prior art. As shown in
Fig. 1, the power shift transmission control system
includes a microprocessor 1, a display 2 on an
operator's control panel 2', a plurality of gearshift
swi~ches 4 which are selectively actuated by manually
CA 02263788 1999-03-1~
moving a gearshift lever 6, and a plurality of
transmission clutches 8 associated with a transmission
10 which transmits power from a rotating power input
shaft 15 to a power output or vehicle drive shaft 20.
An engine 7 unidirectionally rotates shaft 15 and a
sensor 9 senses rotation of shaft 15 to provide output
signals indicating the speed of engine 7. A sensor 5
senses rotation of shaft 20 to provide output signals
representing vehicle speed. An operator-actuated
clutch pedal 3 controls a potentiometer 3' and the
output signal from the potentiometer is applied to
microprocessor 1 to develop modulating signals which
are applied to a final set of clutches in transmission
10. The clutch pedal 3 also actuates a clutch pedal
switch CPSW when the pedal is depressed to its limit
of travel. The control system is admirably suited for
controlling the transmission of a tractor but it will
be obvious from the following description that it may
also be used to control the transmissions of other
vehicles or machines.
The gearshift switches 4 are Hall-effect
switches or similar devices which are actuated by a
magnet or magnets carried on the gearshift lever 6.
Microprocessor 1 periodically samples the clutch pedal
switch, the output of potentiometer 3', the switches
4, and the outputs of the speed sensors 5 and 9, and
in response to the sensed conditions controls
transmission clutches 8 to ~'select gears", i.e. select
the direction and rate of rotation of output shaft 20
relative to input shaft 15.
Fig. 2 is a plan view of the path over which
the gearshift lever 6 may be manually moved to
selectively actuate the gearshift switches 4. The
lever 6 is shown in the neutral position N. In this
position the microprocessor controls the transmission
clutches 8 so that no power is transmitted from input
CA 02263788 1999-03-1~
shaft 15 to output shaft 20. The microprocessor also
controls the display 2 so that the letter N is
displayed, indicating to the operator that the
transmission is in neutral.
The gearshift lever 6 may be moved forwardly
(upwardly in Fig. 2) from the neutral position to a
forward position F. When the microprocessor senses
that the gearshift lever is the forward position it
energizes clutches 8 so that rotation of the power
input shaft is transmitted to the output shaft in one
of eighteen different forward speed ratios. The
manner in which this is accomplished will be evident
from the description of transmission 10 set forth
below. At the same time, the microprocessor sends
signals to display 2 so that it displays the letter F
and a numeric value between one and eighteen. The
display thus indicates to the operator that his
transmission is in a forward gear, and further
indicates which gear.
When the gearshift lever 6 is in the forward
position F it may be moved laterally to change forward
gears. When the gearshift lever 6 is moved to its
rightmost extent of travel in the forward position it
actuates a switch. This position is designated the
FUP position. The microprocessor 1 periodically
samples the switches 4 and, when the gearshift lever 6
is in the FUP position, the microprocessor
periodically changes the clutches 8 which are
energized so that the speed ratio between output shaft
20 and input shaft 15 increases. When the highest
forward gear t18) is reached, the microprocessor
continues to energize the clutches 8 to keep the
transmission in gear 18 even though the gearshift
lever 6 continues to actuate the FUP switch. As the
microprocessor 1 controls the transmission clutches 8
it also controls the display 2 to indicate forward
CA 02263788 1999-03-1~
gear (F) and which forward gear (1-18) the
transmission is in.
In like manner, the gearshift lever 6 may be
moved laterally to the left in the forward position to
downshift the transmission. In the forward downshift
position FDN the lever 6 actuates one of gearshift
switches 4. The microprocessor periodically
downshifts the transmission 10 by controlling clutches
8, and as the transmission is shifted downwardly the
microprocessor controls display 2 to indicate that the
transmission is in forward gear and which forward
gear. By holding the lever 6 in the forward downshift
position the operator may downshift the transmission
one gear at a time until forward gear 1 is reached.
At this time, the microprocessor continues to output
signals to the transmission clutches 8 to select
forward gear 1 even though the gearshift lever 6 is
held in the FDN position .
When the gearshift lever 6 is in the reverse
position R, it may be moved laterally to the right to
increase the reverse gear speed ratio of transmission
10, or moved laterally to the left to decrease the
reverse gear speed ratio. At each limit of travel,
designated the RUP and RDN positions respectively,
gearshift switches 4 are actuated to control the
microprocessor 1 for upshifting or downshifting the
reverse gear speed. As long as the gearshift lever is
in the reverse position the display 2 displays the
letter R to indicate reverse gear and also displays a
number between 4 and 12 indicating which reverse gear
the transmission is in. There are 9 reverse gears,
the lowest being fourth gear and the highest being
twelfth gear.
The gearshift lever 6 is biased so that if
it is in the FUP or FDN position it returns to the F
position when manual force is removed. In like
CA 02263788 1999-03-1~
manner, if the lever is in the RUP or RDN position and
force is removed, the lever returns to the R position.
In addition, the gearshift lever 6 is provided with a
lift collar (not shown). In shifting between the
forward and reverse gear positions, the collar must be
lifted. Otherwise, movement of the gearshift lever is
stopped at the neutral position.
Figs. 3-9 illustrate details of the
transmission 10. As shown in Figs. 3 and 4, the
transmission 10 includes an exterior casing 12 forming
a framework for supporting the power input shaft 15
rotatably journalled on the casing 12 at a central
location extending entirely through the transmission
10 from an engine end 16, which receives rotational
power directly from the engine 7, to a drive end 17 at
the opposing end of the transmission 10, which can be
used as a power takeoff shaft. The centers of a power
output shaft 20, a first jack shaft 21, a second jack
shaft 22, a third jack shaft 23, a fourth jack shaft
26, a fifth jack shaft 28, and the shaft 55 of a
double transfer gear are located in Fig. 4. Each of
shafts 20, 21, 22, 23, 26, 28 and 55 is journalled by
bearings rotatably supporting the respective shafts
for rotation within the casing 12. The relationships
between these various shafts and the gears mounted
thereon are described in greater detail below in
conjunction with Figs. 3 and 5-9.
Referring now to Figs. 3 and 5, it can be
seen that the power input shaft 15 is provided with a
drive pinion 18 splined thereto for rotation therewith
at the engine end 16 of the power input shaft 15. The
drive pinion 18 is drivingly engaged with a primary
drive gear set 30. More specifically, the drive
pinion 18 is directly engaged with a first drive gear
31 rotatably mounted on the first jack shaft 21 for
rotation independently of said first shaft 21. The
CA 02263788 1999-03-1~
drive pinion 18 is also directly engaged with a third
drive gear 33 rotatably mounted on the third jack
shaft 23 for rotation relative thereto. The third
drive gear 33 is meshed in engagement with a second
drive gear 32, which in turn is rotatably mounted on
the second jack shaft 22. Each of the drive gears 31,
32 and 33 is journalled by bearings mounted on their
respective jack shafts and driven by the power input
shaft 15 by virtue of direct or indirect engagement
with the drive pinion 18. Each of the drive gears 21,
22 and 23 is sized differently to provide different
speeds of rotation thereof when rotated by the drive
pinion 18.
As can be seen in Figs. 3 and 6, each of the
jack shafts 21, 22 and 23 is provided with a
corresponding fixed gear 35, 36 and 37, respectively.
The second fixed gear 36 is drivingly engaged with
both the first fixed gear 35 and the third fixed gear
37 so that the rotation of any one of the jack shafts
21, 22 and 23 will effect a simultaneous rotation of
all the other jack shafts 21, 22 and 23. Since all
the fixed gears 33, 36 and 37 are identical in size,
the first jack shaft 21, the second jack shaft 22 and
the third shaft 23 will rotate at identical speeds.
As shown in Figs. 3 and 7, the transmission
10 is also provided with an intermediate gear set 40
correspond-ing to the primary drive gear set 30 and
including a first intermediate gear 41 mounted on the
first jack shaft 21 for rotation relative thereto, a
second intermediate gear 42 rotatably mounted on the
second jack shaft 22, and a third intermediate gear 43
rotatably supported on the third jack shaft 23. The
intermediate gears 41, 42 and 43 are differently sized
to effect a different speed ratio particularly when
combined with the differently sized drive gears 31, 32
and 33 of the primary drive gear set 30, as will be
CA 02263788 1999-03-1~
--10--
described in greater detail below. The first and
third intermediate gears 41, 43 are engaged with a
transfer hub assembly 45 as will be described below,
while the second intermediate gear 42 is drivingly
engaged with the third intermediate gear 43. Like the
primary drive gear set 30, each intermediate gear 41,
42 and 43 is journalled by bearings mounted on the
corresponding jack shaft 21, 22 and 23 to permit
independent rotation therebetween.
The intermediate gear set 40 is engaged with
a transfer hub assembly 45 rotatably supported from
the casing 12 concentric with the power input shaft
15. The transfer hub assembly 45 includes a first
transfer gear 46 drivingly engaged with the first
intermediate gear 41 and a second transfer gear 47
drivingly engaged with the third intermediate gear 43.
The transfer hub assembly 45 is also provided with a
co-joined third transfer gear 48 and fourth transfer
gear 49 to transfer rotational power from the
intermediate gear set 40 to a transfer gear set 50.
Referring to Figs. 3 and 8, the third
transfer gear 48 is drivingly engaged with a reverse
transfer gear 51 fixed to a fifth jack shaft 28
rotatably supported in the casing 12. Likewise, a
high-speed transfer gear 53 is rotatably journalled on
the power output shaft 20 and is drivingly engaged
with the fourth transfer gear 49 for rotation
therewith independently of the power output shaft 20
and is drivingly engaged with the fourth transfer gear
49 for rotation therewith independently of the power
output shaft 20. A double transfer gear 55 having a
shaft-like configuration and integral gear members 55a
and 55b is rotatably supported in the casing 12. The
gear member 55a is also drivingly engaged with the
fourth transfer gear 49, while the other gear member
55b is engaged with a low-speed transfer gear 57
CA 02263788 1999-03-1~
--11--
fixedly secured for rotation with a fourth jack shaft
26 rotatably journalled in the casing 12.
As can be best seen in Figs. 3 and 9, a
final drive gear set 60 includes a high-speed final
gear 61 rigidly secured to the power output shaft 20
for rotation therewith, a low-speed final gear 62
rotatably journalled by bearings on the fourth jack
shaft 26 for rotation independently relative thereto,
and a reverse final gear 63 rotatably journalled on
the fifth jack shaft 58 for rotation relative thereto.
The final drive gear set 60 is interengaged for
simultaneous rotation such that the high-speed final
gear 61 fixed to the power output shaft 20 is
operatively intermeshed with both the low-speed final
gear 62 and the reverse final gear 63.
Referring now to Fig. 3, the transmission
includes three clutch sets 70, 75 and 80 operable to
effect rotation of the various gears rotatably mounted
on jack shafts with the corresponding shaft. The
initial clutch set 70 includes a first clutch 71
mounted on the first jack shaft 21, a second clutch 72
mounted on the second jack shaft 22 and a third clutch
73 mounted on the third jack shaft 23. Each clutch
71, 72 73 of the initial clutch set 70 is operable to
engage the corresponding drive gear 31, 32 and 33 to
effect rotation of the corresponding jack shaft 21, 22
and 23 with the corresponding drive gear 31, 32 and 33
at the speed the corresponding drive gear is rotating.
Likewise, an intermediate clutch set 75 includes
first, second and third intermediate clutches 76, 77
and 78, respectively, mounted on the first, second,
and third jack shafts 21, 22 and 23, respectively, for
engagement with the corresponding intermediate gear
41, 42 and 43 at the speed a which the corresponding
jack shaft is being driven.
A final clutch set 80 includes a high-speed
CA 02263788 1999-03-1
-12-
final clutch 81 mounted on the power output shaft 20
and engageable to couple the high-speed transfer gear
53 to the high-speed final gear 61 when so engaged.
The final clutch set 80 also includes a low-speed
final clutch 82 mounted on the fourth jack shaft 26 to
effect a coupling, when engaged, between the low-speed
transfer gear 57 and the low-speed final gear 62.
Likewise, the final clutch set 80 also includes a
reverse final clutch 83 mounted on the fifth jack
shaft 28 for selectively coupling the reverse transfer
gear 51 to the reverse final gear 63. To attain any
given speed of rotation of the power output shaft 20
for a given speed of rotation of the power input
shaft, only one selected clutch of each clutch set 70,
75, 80 is engaged at a time. The engagement of two
clutches of any one clutch set 70, 75 and 80 will have
the effect of locking the transmission lO.
With all of the components of the
transmission 10 situated as described above,
transmission 10 can transmit a given engine speed
received by the engine end 16 of the power input shaft
15 to the output shaft 20 in twenty-seven different
speed variations with eighteen forward speeds and nine
reverse speeds. It can be seen that the drive pinion
18 constantly delivers rotational power from the
engine to the primary gear set 30 such that the first,
second, and third drive gears 31, 32 and 33 are
constantly driven with the drive pinion 18 relative to
the respective jack shaft 21, 22 and 23 on which the
gears of the primary drive gear set 30 are
respectively mounted. The engagement of one of the
clutches 71, 72 and 73 of the initial clutch set 70
effects an engagement of the corresponding drive gear
31, 32 or 33 with the respective jack shaft 21, 22 or
23 and effects rotation of the jack shafts 21, 22 and
23 at the speed at which the corresponding drive gear
CA 02263788 1999-03-1~
...
-13-
is being rotated. Since the intermeshed fixed gears
35, 36 and 37 are of identical size, rotation of any
one of the jack shafts 21, 22 and 23 will effect
rotation of all three jack shafts 21, 22 and 23 at
identically the same speed as the drive gear 31, 32
and 33 engaged by the selected clutch of the initial
clutch set 70.
The engagement of one of the clutches of the
initial clutch set 70 will effect a corresponding
rotation of the first, second, and third jack shafts
21, 22 and 23 at a selected speed corresponding to the
corresponding drive gear from the primary drive gear
set 30. A subsequent engagement of one of the
clutches 76, 77 and 78 of the intermediate clutch set
75 will effect an engagement between the corresponding
intermediate gear from the intermediate gear set 40
with the rotating jack shaft corresponding to the
selected intermediate clutch at the speed at which the
jack shafts 21, 22 and 23 are rotating. Since all of
the intermediate gears of the intermediate gear set 40
are engaged with the transfer hub assembly 45,
directly or indirectly, which in turn is engaged with
the transfer gear set 50, an engagement of one of the
clutches of the intermediate clutch set 75 will effect
a rotation of all gears of the intermediate gear set
40, the transfer hub assembly 45, all of the transfer
gears 46, 47, 48 and 4g and all of the gears in the
transfer gear set 50, as well as the corresponding
rotation of both the fourth and fifth jack shafts 26,
28 due to a fixed engagement with the corresponding
transfer gears 51, 57.
Finally, an engagement of one of the
clutches 81, 82 and 83 of the final clutch set 80 will
transfer rotational power from the corresponding
transfer gear to the corresponding final gear 61, 62
and 63 of the final drive gear set 60 to cause a
CA 02263788 1999-03-1~
rotation of the power output shaft 20 at the speed
ratio corresponding to the combination of the
respective gears engaged by the activated clutches of
the initial clutch set 80.
By way of specific example, the engagement
of the second clutch 72 of the initial clutch set 70
will couple the second drive gear 32 to the second
jack shaft 22 and effect rotation of the first,
second, and third jack shafts 21, 22 and 23 at the
speed at which the second drive gear 32 is being
rotated due to engagement with the third drive gear 33
and the driving engagement of the third drive gear 33
and the driving engagement of the third drive gear 33
with the drive pinion 18. In the example being
described, both the first and third drive gears 31, 33
rotate on the corresponding jack shaft 21, 23 without
transferring rotational power thereto. In fact, the
engagement of the second clutch 72 will result in a
rotation of both the first and third jack shafts 21
and 23 at a speed different than the speed at which
either of the corresponding first and third drive
gears 31, 33 is independently rotating.
By way of continuing the example started
above, the subsequent engagement of the first
intermediate clutch 76 drivingly couples the first
intermediate gear 41 with the rotating first jack
shaft 21 to effect a corresponding rotation of the
entire intermediate gear 41 with the rotating first
jack shaft 21 to effect a corresponding rotation of
the entire intermediate gear set 40 due to the
intermeshed engagement with the first transfer gear 46
and resultant rotation of the second transfer gear 47
co-joined therewith, which in turn independently
rotates the second and third intermediate gears 42, 43
on respective jack shafts 22 and 23. As noted with
the exemplary description above with respect to the
CA 02263788 1999-03-1~
primary drive gear set 30, the intermediate gears 42,
43 rotate independently of the jack shafts 22 and 23
without driving engagement therebetween because the
corresponding clutches 77 and 78 have not been
engaged.
As noted above, the rotation of the transfer
gears 46 and 47 cause a corresponding rotation of the
entire transfer hub assembly 45 and effect a
corresponding rotation of the entire transfer gear set
So, as well as the fourth and fifth jack shafts 26 and
28. The selected combination of the second drive gear
32 and the first intermediate gear 41 effects rotation
of the reverse transfer gear 51, the high-speed
transfer gear 53, and the low-speed transfer gear 57
at a preselected ratio. As one skilled in the art
will readily realize, the different combinations of
engagements between the primary drive gear set 30 and
the intermediate gear set 40 provide for nine
different speed ratios at which the transfer gears 51,
53 and 57 are rotated.
Continuing the example started above, a
final selection of the low-speed final clutch 82 will
couple the rotation of the fourth jack shaft 26 and
the integral low-speed transfer gear 57 to the low-
speed final gear 62. The intermeshed engagementbetween the low-speed final gear 62 and the high-speed
final gear 61 will effect a rotation of the power
output shaft 20 at the predetermined speed
corresponding to the combination of clutch engagements
described above. Since the reverse final clutch 83
remains disengaged, the reverse final gear 63 can
rotate harmlessly on the fifth jack shaft 28 due to
the engagement with the high-speed final gear 61.
If, in the example given above, the high-
speed final clutch 81 had been selected for engagementrather than the low-speed final clutch 82, the high-
CA 02263788 1999-03-1
-16-
speed final clutch 81 would have coupled the high-
speed transfer gear 53 to the high-speed final gear 61
to directly power the rotation of the power output
shaft 20. The engagement of the high-speed final
clutch 81 means that neither the low-speed final
clutch 82 nor the reverse final clutch 83 is engaged
so low-speed final gear 62 and the reverse final gear
63 can rotate harmlessly on the respective jack shafts
26 and 2 8 on which they are mounted due to engagement
with the high-speed gear 61.
The various combinations of the engagement
of gears of both the primary drive gear set 30 and the
intermediate gear set 40 provides nine possible speed
ratios for rotation of the individual gears 61, 62 and
63 of the final drive gear set 60. Accordingly, the
above-described transmission will provide nine
different low-range speeds for rotation of the power
output shaft 20 when the low-speed final clutch 82 is
engaged, as well as nine different high-range speeds
when the high-speed final clutch 81 is selected, or
nine different speeds of reverse rotation of the power
output shaft 20 if the reverse final clutch 83 is
engaged.
The torque transmitting elements of the
clutches in transmission 10 are hydraulically actuated
to transfer torque. Solenoid operated valves control
the pressure applied to the clutches and thus the
torque transferred to the output shaft 20 to move the
vehicle.
The electrical signals applied to the
solenoids for the clutches 81, 82 and 83 in the final
clutch set 80 may be modulated to incrementally vary
the pressure applied to the torque transmitting
elements. As the clutch pedal 3 is depressed, the
magnitude of the signal applied to microprocessor 1
from the potentiometer 31 varies. Using this signal,
CA 02263788 1999-03-1
-17-
the microprocessor develops a pulse width modulated
signal that is applied to the solenoid of one of the
clutches 81, 82 or 83 depending on which gear the
transmission is in. When the clutch pedal 3 is fully
depressed, it actuates the clutch pedal switch CPSW.
When microprocessor 1 senses that CPSW is actuated it
applies a signal to the solenoid of one of the
clutches 81, 82 or 83 so that no hydraulic pressure is
applied to the torque transmitting element of the~0 clutch and no torque is transmitted by the clutch.
Preselection of Gears
In accordance with one aspect of the present
invention, a gear speed may be selected any time the
gearshift lever 6 is in the neutral position. Since
the gearshift lever must be in neutral, the operator
may devote full attention to the gear selection
process without compromising safety.
Preselection of a gear speed is made
possible ~y providing for lateral movement of the
gearshift lever 6 in the neutral position as
illustrated in Fig. 10. At its leftmost or rightmost
extent of travel, designated the NDN and NUP
positions, respectively, the gearshift lever 6
actuates gearshift switches 4 to signal microprocessor
1 that it is in the NDN or NUP position.
Briefly, the operator accomplishes
preselection of gears by placing the gearshift lever
in neutral and selectively moving the gearshift lever
between the NUP, NDN and N positions to increment or
decrement the displayed gear value until it agrees
with the gear he wishes to select.
Fig. 11 is a flow diagram of a suitable
routine which may be executed by microprocessor 1 to
effect preselection of gears. The routine is entered
at step 112 when the microprocessor 1 senses that the
gearshift lever 6 is in the N position. The display 2
CA 02263788 l999-03-l~
-18-
is updated at step 114. At step 116 the program waits
for the operator to move the gearshift lever to the
NUP or NDN position. At this point the display 2 will
be displaying the letter N and a value representing
the contents of a register PSG. The register PSG is a
memory location in microprocessor 1 which stores a
value representing the gear last preselected.
Assume first that the operator wishes to
increase the preselected gear value PSG to some value
greater than the value being displayed by display 2.
He moves the gearshift lever from the N position to
the NUP position to exit step 116.
At step 122 the microprocessor tests the
gearshift switches to see if the gearshift lever is in
the NUP position. If the operator has moved the
gearshift lever to the NUP position, signifying that
he wishes to preselect a higher numbered gear than
that being displayed, the test at step 122 proves
true. The program advances to step 124 where the
value of PSG is tested. If the value is less than 18,
the test at step 124 proves false and the program
moves to step 126 where the value in the PSG register
is incremented by one and saved. At step 128 the
display is updated to display the new value in PSG.
After the display is updated, the program
waits at step 130 for a fixed interval of time, on the
order of a fraction of a second. This wait provides
time for the operator to react and move the gearshift
lever out of the NUP position as the value in the PSG
register approaches the gear speed the operator wishes
to select.
At step 132 the gearshift lever switches are
tested to determine if the operator has moved the
gearshift lever to the N position. Assuming he has
not, the test at step 132 proves false and the
subsequent test for the NUP position at step 134
CA 02263788 1999-03-1~
--19--
proves true. The program branches back to step 124 to
again test the value in the PSG register and, if it is
not 18, increment it at step 126 and display the
updated value at step 128 D
As the displayed value of the PSG register
approaches the forward gear which the operator wishes
to select, he may move the gearshift lever to the N
position in anticipation of stopping the incrementing
of the PSG register when the PSG register is at the
desired value. When he does this, the program, when
it reaches step 132, senses that the gearshift lever 6
is in the N position and waits.
The program continues to execute step 132 as
long as the operator leaves the gearshift lever in the
N position. This enables him to observe the displayed
preselected gear value and determine if it is higher,
lower, or equal to the gear he wishes to select.
Assuming first that the displayed value is lower than
the desired speed, the operator may again move the
gearshift lever to the right to the NUP routine. The
program advances from step 132 through step 134 and
back to step 124 again so that incrementing of the
value in the PSG register is resumed.
If the gearshift lever is held too long in
the NUP position, the value in the FG register will
reach a count of 18 corresponding to the highest
forward gear. When this happens, the test at step 124
proves true and the program branches directly from
step 124 to step 132 so that the steps 124, 132 and
134 are repeatedly executed as long as the gearshift
lever is held in the NUP position.
If the operator should overshoot the value
of the gear he wishes to preselect, he may reduce the
value PSG by moving the gearshift lever to the NDN
position. For example, assume that the operator
desired to preselect gear 9 but for some reason he
CA 02263788 1999-03-1
-20-
holds the gearshift lever in the NUP position too long
so that the PSG register is incremented to some value
greater than 9 before the operator returns the lever
to the N position. At this point the display 2 is
displaying the higher value and the program is
repeatedly executing step 132. When the operator
moves the gearshift lever to the NDN position the
program advances to step 134 and tests the gearshift
switches to see if the gearshift lever is in the NUP
position. Since it is not the program advances to
step 122' and tests to see if the gearshift lever is
in the NDN position. Since it is, the program moves
to step 124' where it tests the value in the PSG
register. If the value is not one (representing the
lowest forward gear) it is decremented at step 126'
and the display is updated at step 128'.
The program then waits at step 130' for a
fraction of a second to give the operator time to move
the gearshift lever to the N position if the displayed
value of PSG is the forward speed which the operator
wishes to select. At step 132' the gearshift switches
are tested to see if the gearshift lever is in the N
position. If the operator is still holding the
gearshift lever in the NDN position, the program
advances to step 134' and loops back to step 124' in
preparation for again testing the value PSG and
decrementing it if it is not one.
If necessary, the operator may again
increment the value PSG by moving the gearshift lever
to the N position and then to the NUP position. The
program moves from step 132' to step 134' and then
through step 122 to step 124. From this point the
incrementing of PSG takes place as previously
described.
It will be noted that the program steps in
right half of Fig. 11 are a mirror image of the
CA 02263788 l999-03-l~
--21--
program steps shown in the left half. The steps in
the left half are executed when the gearshift lever is
selectively moved between the NUP and N positions to
increment the value PSG and the steps in the right
half are executed as the gearshift lever is
selectively moved between the NDN and N positions to
decrement the value PSG. If the operator has
completed his preselection of a gear, he may exit the
routine by moving the gearshift lever to the F or the
R position. When the program reaches step 132 and the
gearshift lever is in the F or R position, the program
sequentially executes steps 132, 134 and 122', then
exits the routine. On the other hand, if the program
reaches step 13 21 and the gearshift lever is in the F
or R position, the program sequentially executes steps
132', 134 ' and 122 before executing step 122 1 and
exiting the routine.
The operations described above enable the
operator to preselect a single value of PSG. This
value determines both the forward gear and the reverse
gear which will be selected when the operator moves
the gearshift lever from the N position to the F or R
position. However, the value of PSG may be also used
to access a table of reverse gear values to obtain a
preselected reverse gear. Generally, if PSG is
greater than the highest reverse gear ( 12) PSG
accesses a location in the table which stores the
value 12, and if PSG is less than the lowest reverse
gear ( 4 ) PSG accesses a location in the table which
stores the value 4 . For values between 4 and 12, PSG
access a table location storing a corresponding value.
Proqrammable Forward-To-Reverse Speed Selection
Different applications for shuttle shifting
have different requirements for the forward-to-reverse
speed relationship. That is, some applications may be
best performed when the reverse speed is faster than
CA 02263788 1999-03-1
-22-
the forward speed while others may be best performed
when the forward speed is faster than the reverse
speed, and still other applications are best performed
when the speeds are equal.
In accordance with the principles of the
present invention, an operator may select any one of
several modes of operation. That is, he may program
microprocessor 1 by operation of the gearshift lever 6
to provide any one of several reverse gear speeds
relative to a forward gear speed. The relationships
are as follows:
R4 (lowest reverse gear) selected regardless
of forward gear.
Reverse gear the same speed as forward gear.
Reverse gear 1, 2 or 3 gears faster than
forward gear.
Reverse gear 1, 2 or 3 gears slower than
forward gear.
Figs. 12 and 13 illustrate a method whereby,
prior to starting the engine, an operator may select a
value representing a desired one of these forward
speed to reverse speed relationships. A ratio value
is generated and stored and subsequently used by the
microprocessor 1 so that a specific forward to reverse
speed relationship is obtained by shuttle shifting
between forward and reverse after the engine is
started. That is, during operation of the vehicle the
operator controls the selection of forward gear speed
while reverse gear speed automatically is determined
by the selected forward gear and the value RATIO which
is preselected prior to starting the engine. The
operator initiates the forward-to-reverse speed
programming mode by holding the gearshift lever in the
reverse upshift position (RUP) while turning on the
ignition key. After going through an initialization
routine at step 110, the microprocessor tests the
CA 02263788 1999-03-1
-23-
gearshift switches 4 at step 111 to see if the
gearshift lever is in the RUP position. If it is, the
program branches to step 150 where it gets RATIO and
updates the display 2.
RATI0 is a value stored in a non-volatile
memory location. It represents the relationship of
reverse gear to forward gear.
RATIO -3 -2 -1 0 +1 +2 +3 L
FG 1 R4 R4R4 R4 R4 R4 R4 R4
2 . . . . . R4 R5
3 . . . . R4 R5 R6
4 . . . R4 R5 R6 R7
. . R4 R5 R6 R7 R8
6 . R4 R5 R6 R7 R8 R9
7 R4 R5 R6 R7 R8 R9 R10
8 R5 R6 R7 R8 R9 R10 Rll
9 R6 R7 R8 R9 R10 Rll R12
R7 R8 R9 R10 R11 R12
11 R8 R9 R10 Rll R12
20 12 R9 R10 R11 R12
13
14
16
25 17
18 R9 R10 Rll R12 R12 R12 R12 R4
Forward/Reverse Speed Relationships
Table I
Table I shows the relationship of the reverse gear to
a selected forward gear for each value of RATI0. As
shown in Table I, RATI0 has one of the values -3, -
2, -1, 0, +1, +2, +3 or L. If RATIO has the value L,
the lowest reverse gear will be selected regardless of
the forward gear value. If RATI0 has the value
between -3 and +3, then RATIO is added to the selected
CA 02263788 l999-03-l~
-24-
forward gear to determine which reverse gear will be
selected. However, if the sum of the forward gear
value and RATI0 is less than 4, then the lowest
reverse gear R4 is selected, and if the sum is greater
than 12 then the reverse gear is selected as shown in
Table I.
Returning to Fig. 12, after the display is
updated at step 150 the program moves to step 152
where it waits since the operator is holding the
gearshift lever in the RUP position. This gives the
operator an opportunity to observe the displayed value
of ratio and determine if it needs modification. The
operator moves the gearshift lever to the R position
and the program advances to step 154 where it again
waits for movement of the gearshift lever. When the
operator moves the gearshift lever out of the R
position, the program advances to an Adjust Ratio
routine 156 illustrated in Fig. 13.
Assume first that the operator, at step 154
moves the gearshift lever to some position other than
an UP or DN position. When the program enters the
Adjust Ratio routine, the tests of the gearshift
switches at steps 160 and 160' prove false and the
program moves back to step 160. Steps 160 and 160
are repeatedly executed until the ignition switch is
turned off or the gearshift lever is moved to an UP or
DN position. It should be noted that the selection of
a ratio value may be accomplished using any UP and DN
gearshift lever positions. For the sake of
simplicity, the flow diagram of Fig. 13 is drawn for
the case where the RUP and RDN positions are used.
Assume now that the value of RATI0 displayed at step
150 is lower than the value the operator wishes to
select so that he moves the gearshift lever to the RUP
position to exit from step 156. In Fig. 13, the RUP
test at step 160 proves true and the program moves to
CA 02263788 1999-03-1
-25-
step 162 where it tests the value of RATIO. If ratio
is not at its maximum value, it is incremented and
saved in a non-volatile memory location at step 164
and the display updated at 166 before the program
moves to step 168.
The routine waits at step 168 for a fraction
of a second long enough for the operator to observe
the displayed value of RATI0 and move the gearshift
lever if he desires to do so. It then advances to
step 170 to test the gearshift switches to see if the
gearshift lever is in the R position. If the operator
is still holding the gearshift lever in the RUP
position the routine advances to step 172 where the
test for the RUP position proves true. The program
loops back to step 162 to test RATI0, increment and
save it if it is not at its maximum value, and display
the incremented value. This continues until the
operator moves the gearshift lever to the R position.
At step 170 the program continuously tests to see if
the gearshift lever is in the R position, and remains
at step 170 as long as the test proves true. If the
operator moves the gearshift lever from the R position
to the RDN position, the program moves from step 170
to step 172 where the test for RUP proves false. The
program advances to step 160' and since the gearshift
lever is in the RDN position step 162' is executed
where the value of RATIO is tested to see if it is at
its lowest value. Assuming it is not, RATIO is
decremented and saved at step 164' and the display
updated at step 166'. The program waits for a
fraction of a second at step 168' to permit the
operator to observe the display, and then proceeds to
step 170' where the gearshift switches are tested to
see if the gearshift lever is in the R position.
If the operator has moved the gearshift
lever to the R position, the program waits at step
CA 02263788 1999-03-1
-26-
170' until he moves the gearshift lever to another
position. If he moves the gearshift lever to the RDN
position, the program advances to step 172', where the
RDN test proves true, and loops back to step 162' to
again update the display. On the other hand, if the
operator moves the gearshift lever from the R position
to the RUP position the program moves from step 170'
to step 172' and step 160. From step 160 the program
tests RATIO and possibly updates it as previously
described.
Thus, the operator may selectively move the
gearshift lever between the R, RDN and RUP positions,
the value of RATIO being decremented while the
gearshift lever is in the RDN position and
incremented when the gearshift lever is in the RUP
position. However, as explained above, the FDN,
FUP, NUP and NDN positions may also be used for
incrementing/decrementing ratio. The flow diagram of
Fig. 13 may thus be generalized by providing UP tests
at steps 160 and 172, DN tests at steps 160' and 172',
and N, F or R tests at steps 17 0 and 1701.
If, during incrementing of RATIO it reaches
its maximum value (+3) the test at step 162 proves
true and the program jumps from step 162 to step 170,
thereby bypassing the incrementing step. In like
manner, if RATIO reaches its minimum value (L=4)
during decrementing the program jumps from step 162'
to step 170' thereby bypassing the decrementing step.
After the operator has adjusted the value of
RATIO to the desired value, he may terminate the
adjustment by turning the ignition switch off. The
operator must turn the ignition switch off and then on
again, this time not holding the gearshift lever in
the RUP position, in order to use the value of RATIO
which he has programmed into the system.
After the ignition switch is turned off and
CA 02263788 1999-03-1
-27-
then on again to the start position to start engine 7,
the microprocessor begins executing a program wherein
it samples the gearshift switches and energizes the
clutches in transmission 10 as the operator moves the
gearshift lever to actuate the switches. Each time
the gearshift lever is moved to the R position, the
microprocessor executes the subroutine shown in Fig.
14a. At step 180 the microprocessor detects from the
gearshift switches that the gearshift lever has been
moved to the R position. At step 182 a current gear
register CG is tested to see if it contains a value
greater than 12. The CG register stores the value of
the gear (forward) from which the transmission is
being shifted. If CG is equal to or greater than 12,
a previous gear register PG is set to the value 12 at
step 184. If CG has a value less than 12 then at step
186 the PG register is set equal to CG. At step 190,
PG and RATIO are used to address a table location in
memory and read the reverse gear value RG from memory.
The value stored in the memory table correspond to the
values in Table I, above, for the values of forward
gear between 1 and 12. The value of RG is then used
by the microprocessor l at step 192 to energize the
clutches in transmission lO.
Although not part of the illustrated routine
of Fig. 14a, it should be noted that upon upshifting
or downshifting in reverse, or if speed matching
occurs as subsequently described, the previous gear
register PG is cleared.
When the gearshift lever is shifted from
reverse to forward, the microprocessor detects, at
step 194 (Fig. 14b), that the lever is in the F
position. At step 195, PG is tested to see if it has
been cleard. If it has, a table is addressed at step
198 to read out the forward gear value FG and at step
199 the microprocessor uses this value of FG to
CA 02263788 1999-03-1
-28-
energize the transmission clutches.
On the other hand, if the test at step 195
shows that the PG register has not been cleared, then
FG is set equal to PG.
From the foregoing description it is seen
that the routine illustrated in-Figs. 12 and 13
enables the operator to preselect a forward-to-reverse
gear relationship value if he holds the gearshift
lever in the RUP position as he turns the ignition on.
Figs. 14a and 14b illustrate how this value is used to
modify whatever forward gear value the operator
happens to select to thereby obtain a reverse gear
value for controlling transmission lO. The selection
of reverse gear is made according to Table I.
Controlled Vehicle Deceleration
Durinq Shuttle Shiftinq
Shuttle shifting of the transmission 10 from
forward to reverse gear, or from reverse to forward
gear results in an energy load on the transmission
oil, and loading of the vehicle engine with a
consequent increase in fuel consumption. The energy
load placed on the clutches increases at a rate
proportional to the square of the vehicle speed so
that when the vehicle speed reaches about 4 MPH the
2 5 clutches in the transmission are overloaded by shuttle
shifting. Thus, larger and more expensive clutches
become necessary for shuttle shifting even at moderate
vehicle speeds. However, several methods have been
developed for controlling transmission 10 to prevent
clutch overloading and, for a given clutch sizing,
permit shuttle shifting at moderate or high vehicle
speeds without overloading the clutches.
Fig. 15 illustrates a first method which may
be used at low and moderate vehicle speeds up to about
7 or 8 miles per hour. Assume that the vehicle has
been in some forward gear and the operator moves the
CA 02263788 1999-03-1
-29-
gearshift lever 6 (Fig. 10) from the F to the R
position. At step 200, the microprocessor senses that
the gearshift lever is in the R position the program
proceeds to step 204 where the microprocessor applies
signals to the clutches in the initial and
ir~termediate clutch sets 70 and 75 (Fig. 3) to select
the lowest gear speed. At step 206 a modulating
signal is applied to the low speed clutch 82 or the
reverse clutch 83 in the final clutch set 80. The
output shaft 20 is rotating, being driven at this time
because of forward vehicle movement. Application of
the modulating signal to the clutch in the final
clutch set causes the output shaft 20 to begin driving
the transmission and this load begins slowing the
output shaft 20. The modulating signal is a pulse
width modulated current signal that is applied to the
solenoid which controls the valve that in turn
controls the pressure applied to the torque
transmitting element of the clutch.
At step 208, the speed of the output shaft
20 is sensed by sensor 5 (Fig. 1) and the
microprocessor 1 compares this speed with some
threshold value near zero. If the speed is greater
than the threshold value, the microprocessor decreases
the modulating signal at step 210 and waits for a
short interval of time at step 212 before looping back
to again execute steps 206 and 208. The decreased
modulating signal causes a higher hydraulic pressure -
to be applied to the torque transmitting element of
clutch 82.
When the speed of shaft 20 has been reduced
so that the sensed speed is less than the threshold
value, this condition is detected at step 2 08 and the
program moves to step 214 where the microprocessor 1
applies signals to the clutch sets 70, 75 and 80 to
select the desired reverse gear speed.
CA 02263788 1999-03-1
-30-
When shifting takes place from reverse to
forward gear, the microprocessor 1 executes a sequence
of steps like steps 204-214 with the exception that
the forward gear clutches are set to select the
desired forward gear at step 214.
The method just described permits shuttle
shifting of transmissions at low and moderate speeds
even without torque converters. However, this method
is not satisfactory for use when shuttle shifting at
higher speeds. An incremental increase in efficiency in
such operation can be gained in the following manner. It
has been found that, with proper clutch control, clutch
energy loads can be reduced thus allowing shuttle
shifting to take place at higher speeds while resulting in
lower oil temperatures and lower clutch energy loads.
Furthermore, by sharing the energy load between two or
more clutches, shifting may be accomplished at even
higher speeds. Also, there is a reduced engine load
and a greater economy of fuel use. To gain all of
these advantages, the transmission lO illustrated in
Fig. 3 may be controlled as illustrated in the flow
diagram of Fig. 16 when the gearshift lever 6 (Fig. 1)
is moved into either the reverse position R or the
forward position F to select a new desired gear speed.
At step 220, all of the clutches 71, 72 and
73 in the initial clutch set 70 are released thereby
disconnecting the engine 7 from the transmission.
Gearing within the transmission continues to rotate.
Next, two or more of the clutches 76, 77 and 78 in the
intermediate clutch set 75 are energized at step 222
thereby locking up the transmission and stopping
rotation of the internal transmission parts. After
the transmission has been locked up, one of the
clutches 81, 82 and 83 in the final clutch set is
modulated at step 224 to connect the transmission
gearing to the output shaft 20 thereby decelerating
the vehicle. The output speed is monitored by the
output shaft speed sensor 5 (Fig. 1). When the
CA 02263788 1999-03-1
-31-
vehicle is nearly stopped, the microprocessor outputs
signals to the clutches in the transmission 10 to
actuate the appropriate clutches to select a desired
ne~ gear speed. At step 226 the microprocessor senses
the speed and if the speed exceeds a threshold value
the microprocessor computes a new modulating signal
value at step 228 and waits a short interval at step
230. The new modulating signal is then applied to the
solenoid of the clutch in set 80 when the program
loops back to step 224. As described above with respect
to step 208, the transmission may then shift to the ,
selected gear.
Fig. 17 illustrates a further method for
controlling vehicle deceleration when shuttle
shifting. The method illustrated in Fig. 17 is
particularly suited for shuttle shifting at high
vehicle speeds. It allows shuttle shifting at maximum
vehicle speed without free wheeling and without
excessive clutch loads. The initiation of shifts is
~ased on vehicle speed hence the method automatically
adapts to variations in vehicle deceleration due to
surface conditions, grades, drawbar loads and operator
use of service brakes.
The microprocessor 1 enters the routine of
Fig. 17 when the gearshift lever 6 is in the forward
gear position F and the forward speed of the vehicle
is above about 7.5 MPH. Actually, the forward speed
of the vehicle is determined by the speed sensor 5
which senses the rate of rotation of the transmission
output shaft 20. The shaft carries a 72-tooth gear
whose rotation is magnetically sensed by the sensor 5
which produces one output pulse for each tooth sensed
on the rotating gear. Table II shows, for an
exemplary embodiment, the correlation between each
forward gear and the frequency of the output signal
from the speed sensor 5.
CA 02263788 1999-03-1
-32-
DO NOTIF FREQUENCY OF
DOWNS~IFTOUTPUT FROM
FROMSENSOR EXCEEDS
s FG=18 2802
17 2392
16 2043
1724
14 1472
13 1257
12 1067
11 911
778
9 662
8 565
7 483
6 408
408
4 408
3 408
2 408
Table II
The routine of Fig. 17 starts at step 250
where the vehicle speed, or more particularly the
output frequency of the sensor 5 is compared with a
threshold frequency value. If the sensor output
frequency is lower than the threshold value it means
that another deceleration strategy should be used.
Thus, from step 250 an exit is made from the routine
to one of the routines described above for controlling
vehicle deceleration.
If the test at step 250 shows that the
vehicle speed is high enough to invoke the high speed
deceleration routine, the program moves to step 252.
At this step, the microprocessor successively accesses
its memory which stores the values shown in column 2
CA 02263788 1999-03-1~
of Table II, and compares each accessed value with the
frequency of the output signal from sensor 5 until it
finds the lowest gear that will not overspeed the
engine. That is, it finds the highest frequency value
in the table which is still less than the frequency of
the output signal from the sensor 5. For example, if
the output from sensor 5 is a 1400 HZ signal, the
value 1257 is the highest frequency in the ta~le which
is still less than 1400. This corresponds to gear 13.
The microprocessor reads this value from the table and
sends it to the display at step 254. At step 256 the
value 13 is used to energize the clutches in
transmission 10 to select forward gear 13. Since
forward gear 13 would normally drive the shaft 20 at
only 1257 HZ or 1257X60/72 RPM but the actual rotation
of the shaft is greater, the engine becomes a load
which slows down the vehicle.
After the transmission is shifted into gear
13 at step 256, the program enters a loop comprising
steps 258 and 260. At step 258 the frequency of the
output signal from sensor 5 is compared with the
threshold frequency to see if the speed is such that
the downshift strategy is still required. If it is
not, the routine exits to another deceleration routine
as described above that is suitable for use at lower
speeds.
If the test at step 258 shows that the speed
is still greater than the threshold value the program
executes step 260. At this step the microprocessor
tests the vehicle speed as measured by the output from
sensor 5 and determines if the transmission can be
downshifted one gear. This is done by accessing the
table for gear 13 to read out frequency value 1257,
and then comparing 1257 with the output frequency as
measured by sensor 5. If sensor 5 is still producing
an output signal greater than 1257 HZ, the program
CA 02263788 1999-03-1~
loops back to again execute steps 258 and 260. At
some point the vehicle will be decelerated so that the
output signal from sensor 5 is less than 1257 HZ.
When this is determined at an execution of step 260,
the display is updated at step 262 to display gear 12
and at step 264 clutches are energized to select gear
12 so that the engine 7 again becomes a load on the
output shaft 20.
Steps 258 and 260 are again repeatedly
executed and, if the test at step 260 shows the speed
as measured by sensor 5 to be less than the value
accessed from the table, steps 262 and 264 are
executed to update the display and downshift the
transmission one gear. This continues until a test at
step 258 shows that the speed of the vehicle is low
enough to employ a low or medium speed deceleration
routine as described above. At this point an exit is
made from the routine of Fig. 17 to the new
deceleration routine.
Clutch Calibration
As explained above, solenoid operated valves
control the hydraulic pressure applied to the clutches
and thus the torque transferred by the clutches to
move the vehicle. Variations in the current applied
to the solenoids, the valve adjustments, and the
pressure required to begin to transfer torque all
result in inconsistent operation from one tractor to
the next, and variations in the operation of a given
tractor over a period of time.
According to one aspect of the present
invention, a calibration program is stored in
microprocessor 1 for calibrating the clutches in the
final clutch set 80 of transmission 10. This program
may be used on each new tractor after assembly, or as
required by service or clutch wear, to determine the
magnitude of a current which must be applied to a
CA 02263788 1999-03-1
-35-
solenoid so that the clutch controlled by the solenoid
produces a torque just sufficient to reduce engine
speed. A value representing this magnitude of current
is stored in the microprocessor or memory during the
calibration program. Subsequently, when the solenoid
is to be energized the value is read from the memory
to control the magnitude of the current applied to the
solenoid.
Fig. 18 is a flow diagram illustrating one
method of clutch calibration. During this method of
calibration, the vehicle brakes should be applied so
that the output shaft 20 (Fig. 3) of the transmission
does not rotate. This assures uniform loading
conditions during the calibration procedure. The
microprocessor 1 starts the routine at step 300 by
setting Is=IMAXl where I~ is the maximum current which
may be applied to the solenoid of the clutch being
calibrated. At step 301, a current corresponding the
value of Is is applied to the solenoid of the clutch
being calibrated. It should be remembered that the
hydraulic pressure applied to one of the clutches in
transmission 10 varies inversely with respect to the
current Is applied to the clutch solenoid. Therefor,
when Is=IMAX is applied to the clutch at step 301, the
lowest hydraulic pressure is applied to the clutch.
This pressure should be low enough such that the
clutch is not applied.
At step 302 the routine waits for an
interval of time sufficient for the engine speed to
stabilize after any loading caused by energization of
the clutches. After this interval of time has
elapsed, the calibration routine advances to step 303
where the microprocessor 1 determines the engine speed
RPM as sensed by the sensor 9 (Fig. 1). This
reference value of engine speed is saved and the
program advances to step 304 where Is is decremented
CA 02263788 l999-03-l~
-36-
and applied to the clutch being calibrated to thereby
increase the pressure to the clutch.
At step 305, the program again waits for a
sufficient interval of time for the engine speed to
stabilize after any loading caused by application of
the decremented value of Is to the clutch solenoid at
step 304. At step 306 the engine speed is again
sensed and at step 307 the new engine speed RPM1 is
compared with the reference engine speed RPM. If RPMl
is less than RPM, it means that a reliable calibration
of the clutch cannot be obtained and servicing of the
clutch and/or its controls is required. The program
branches to step 308 where the microprocessor 1 sends
signals to the display 2 to display an error code
indicating a high Is error. After the display is
energized the calibration routine ends.
If the comparison at step 307 shows that
RPM1 is not less than RPM then at step 309 Is is again
decremented and applied to the solenoid of the clutch
being calibrated. The program waits at step 310 for
the engine speed to stabilize in case the new value of
Is applied to the solenoid resulted in a loading of the
engine as a result of torque being transmitted by the
clutch. The engine speed is again sensed at step 311
and compared at step 312 with the value RPM saved at
step 303.
If the comparison at step 312 shows that
RPM1 is less than RPM, the program moves to step 313
where the value of Is generated at step 309 is compared
with a minimum permissible value IMIN If IS is not
less than IMIN the program loops back to step 309.
The loop comprising steps 309-313 is
repeatedly executed until the comparison at step 312
shows RPM to be greater than RPM1, or the test at step
313 shows that Is is less than IMIN~ If RPM is greater
than RPMl, it means that the engine has slowed as a
CA 02263788 1999-03-1
-37-
result of being loaded, and this in turn indicates
that the clutch being calibrated has transmitted
torque in response to the signal Is generated the last
time step 309 was executed. This value of Is is saved
at step 315. Subsequently, each time the clutch is to
be energized the microprocessor 1 subtracts the saved
value of Is from a fixed current value and the
difference current is applied to the clutch as a
modulating signal.
If, during execution of the loop comprising
steps 309-313, the test at step 313 proves true, it
means that the clutch cannot be calibrated without
servicing. The microprocessor 1 sends signals to
display 2 to display a low current error message on
the display at step 314.
It will be understood that Fig. 18
illustrates the routine for calibrating a single one
of the clutches 81, 82 or 83. The routine must be
executed for each clutch to be calibrated so that a
calibration value of Is is saved for each clutch.
For ease of description, steps 307 and 312
show a comparison of RPM and RPM1. However, as is
conventional in measurement systems, a small offset
value may be added to RPM before it is compared with
RPM1. Also, steps 304 and 309 show Is being
decremented by 1. It should be understood that "l"
represents an increment of current necessary to change
the pressure applied by the clutch torque transmitting
element some fixed increment such as lOpsi.
In the calibration method illustrated in
Fig. 18, the vehicle brakes are applied during the
calibration procedure to prevent vehicle movement, and
the engine speed is sensed to determine when a load is
placed on the engine as a result of the clutch
transmitting a torque. However, it is possible to
calibrate the clutches by not applying the vehicle
CA 02263788 1999-03-1
-38-
brakes during the calibration procedure, and sensing
when the vehicle begins to move. Vehicle movement may
be sensed by sensor 5 (Fig. l) which senses rotation
of the transmission output shaft 20.
Fig. 19 illustrates the method of
calibrating a clutch by sensing when the clutch
transmits sufficient torque to move the vehicle. At
step 320 Is is set equal to IMAX SO that maximum current
is applied to the solenoid of the clutch being
calibrated resulting in minimum hydraulic pressure
being applied to the torque transmitting element of
the clutch. Clutch solenoids are then energized at
step 321 so that drive power from the engine may be
transmitted to the transmission output shaft 20. This
may be any combination of clutch solenoids necessary
to select a particular gear, so long as the
combination includes the solenoid of the clutch being
calibrated. At step 322 the program waits for any
torque transmitted by the clutches to be manifested by
movement of the vehicle, or more specifically,
rotation of the transmission output shaft 20. At step
323 the microprocessor l acts with sensor 5 to sense
rotation of the shaft 20. If it is rotating at this
time it means that it is impossible to calibrate the
clutch so the program branches to step 329 where the
microprocessor sends signals to the display 2 to cause
it to display an out of range error code.
If the test at step 323 shows that output
shaft 20 is not rotating, the program decrements Is at
step 324 and applies this decremented value of Is to
the solenoid of the clutch being calibrated. This
causes an increase in the hydraulic pressure applied
to the torque transmitting element of the clutch. At
step 325 the program waits for this increased pressure
to take effect and at step 326 the output shaft
rotation is again sensed.
CA 02263788 1999-03-1
-39-
Assuming that shaft 20 is still not
rotating, the program advances to step 327 to compare
the value of Is produced at step 324 with a minimum
permissible solenoid current IM}N. If Is is not less
than IM1N the program loops back to step 324. The loop
comprising steps 324-327 is repeatedly executed and Is
is decremented on each execution until one of the
tests at step 326 or 327 proves true.
When the test at step 326 indicates that
shaft 20 is rotating, the last value of Is produced at
step 324 is saved in memory at step 328 and the
program ends. This value of Is may subsequently be
used to control the magnitude of the current applied
to the clutch.
If the program should execute the loop
comprising steps 324-327 SO many times that Is is
decremented to a value less than IM~N the c~utch cannot be
ca~ibrated Step 327 detects that Is is less
than IMIN and the program moves to step 329 where an
out of range error code is sent to display 2 before
the program ends.
Manual Override of Automatic Ratio Matchinq
The prior art transmission control system
shown in Fig. 1 employs an automatic ratio matching
feature to reduce clutch slippage when shifting gears,
or to prevent start-up in a high gear which could
overload the clutches. In addition, the automatic
ratio matching feature permits direct shifting from -
one gear to another without shifting through all of
the intermediate gears.
In Fig. 1 the microprocessor 1 invokes a
ratio matching routine when the gearshift lever 6 is
moved to the neutral position or when the clutch pedal
3 is depressed. The microprocessor 1 computes a speed
ratio based on the rates of rotation of input shaft 15
and output shaft 20 as sensed by the sensors 9 and 5,
CA 02263788 1999-03-1
-40-
respectively, and energizes the display 2 to indicate
the optimum gear for the computed ratio. The
computation is repeated and the display updated as
long as pedal 3 is depressed or the gearshift lever 6
is in the neutral position. When the pedal 3 is
released and the gearshift lever 6 is moved to the
forward or the reverse position, the microprocessor 1
sends signals to the clutches 8 to select the gear
corresponding to the gear displayed on the display 2.
While the automatic ratio matching feature
is admirably suited for its intended purpose, it does
remove some control of the transmission 10 from the
operator. Fig. 20a is a flow diagram illustrating a
method for manually overriding the automatic ratio
matching feature of the system of Fig. 1. The
microprocessor 1 invokes the routine of Fig. 2Oa when
it senses, at step 400, that the clutch pedal 3 has
been depressed to actuate the clutch pedal switch
CPSW, or the gearshift lever is in the neutral
position N. At step 401, the microprocessor updates
the display 2 and sets a timer. At steps 402 and 404,
the microprocessor determines from the gearshift
switches 4 whether the gearshift lever 6 is in one of
the upshift or downshift positions. Assume for the
moment that it is not. The program checks the timer
at step 406 to see if .1 second has elapsed since the
timer was set at step 401. The program loops back and
repeats steps 402, 404 and 406 until the .1 second
interval expires. This gives the operator time to
operate the gearshift lever if he wishes.
When the .1 second interval expires, the
program advances to step 408 to calculate the ratio
between the rate of rotation of output shaft 20 and
input shaft 15. This ratio defines the gear which
will be selected when the gearshift lever 6 is moved
out of the neutral position or the clutch pedal 3 is
CA 02263788 l999-03-l~
-41-
released. At step 410 the display 2 is updated to
display the gear value.
At step 412, the microprocessor tests the
gearshift switches 4 and the clutch pedal switch CPSW.
If the clutch pedal is still depressed and the
gearshift lever is still in the neutral position, the
program loops back to step 402 to repeat the
operations just described.
Should the operator release the clutch pedal
and shift the gearshift lever out of neutral,
automatic ratio matching is effective. At step 412 an
exit is made from the routine to set the clutches to
the gear corresponding to the gear last displayed at
step 410.
In accordance with the invention, the steps
402 and 404 are provided to permit the operator to
override the automatic ratio matching operation. The
override may take place any time after the routine is
entered but before the clutch pedal is released and
the gearshift lever is moved out of neutral. The
override is effected when the operator moves the
gearshift lever to an upshift or a downshift position.
If the gearshift lever is moved to an upshift position
an exit is made from the routine at step 402 to an
upshift routine and if it is moved to a downshift
position an exit is made from the routine at step 404
to a downshift routine.
The manual override method illustrated in
Fig. 20a is permanent in that automatic ratio matching
will not occur again until the next time the gearshift
lever 6 is shifted to the neutral position or the
clutch pedal 3 is depressed. Fig. 2Ob illustrates a
manual override method which is temporary in that the
automatic ratio matching starts again if the gearshift
lever remains in neutral or the clutch pedal remains
depressed for a specific interval of time.
CA 02263788 1999-03-1
-42-
The routine of Fig. 20b is entered at step
420 when the microprocessor senses that the operator
has depressed the clutch pedal or shifted the
gearshift lever into neutral. At step 422 the display
is updated and a .l second timer is reset. Tests are
then made at steps 424 and 426 to see if the gearshift
lever has been shifted to an upshift or a downshift
position. Assuming for a moment that the gearshift
lever has not been moved to an upshift or a downshift
position, the program advances to step 428 and tests
the .1 second timer to see if it has timed out. If it
has not, the program branches back to step 424 to
repeat the loop comprising steps 424, 426 and 428
until the .1 second interval has elapsed.
At the end of the .1 second interval the
microprocessor tests a l second timer at step 430 to
see if it is running. This timer is set as
subsequently explained and for the moment assume that
it is not running. The program proceeds to step 432
to calculate a ratio as explained previously with
respect to step 408 of fig. 20a. At step 434 the
calculated ratio value is used to update the display,
thereby indicating to the operator the gear which will
be selected when he moves the gearshift lever out of
neutral or releases the clutch pedal.
At step 436 the clutch pedal switch and
gearshift lever switches are tested and, if the
operator has not released the clutch pedal or has not
shifted out of neutral, the program branches back to
step 422 to repeat the sequence of operations just
described. If the operator should move the gearshift
lever out of neutral, or release the clutch pedal, the
program exits the routine at step 436 and proceeds to
complete the automatic ratio matching by setting the
clutches in the transmission to select the gear
corresponding to the gear value last displayed at step
. .,
CA 02263788 1999-03-1
434.
Assume now that while the microprocessor is
still executing the loop extending from step 424 to
step 436, the operator moves the gearshift lever to
the upshift or downshift position. If he moves it to
the upshift position the program branches to step 440
to increment the gear selection value being displayed
on the display 2, and if he moves it to the downshift
position the program branches to step 442 to decrement
the displayed gear selection value. After step 440 or
442 ls executed, the microprocessor updates the
display at step 444 and sets a timer at step 446.
The timer set at step 446 is the timer which
is tested at step 430. When the timer is set, it runs
for one second. During this one second interval the
test at step 430 will prove true and the
microprocessor will skip steps 432 and 434 thus
bypassing the calculation and display of the automatic
ratio matching gear.
After step 446 is executed, the program
proceeds to step 436 to see if the clutch pedal is
released and the gearshift lever has been shifted out
of neutral. If it has, then the program exits the
routine at step 436 and proceeds to select the gear
corresponding to the gear value displayed at step 444.
To summarize the operations in fig. 20b, if
the routine is entered and, during execution of the
routine, the gearshift lever is not shifted to one of
the upshift or downshift positions, normal automatic
ratio matching occurs when the test at step 436 shows
that the gearshift lever is not in neutral and the
clutch pedal is released.
On the other hand, if the operator moves the
gearshift lever to a downshift or upshift position he
may increment or decrement the displayed gear value.
He may increment or decrement by more than one by
CA 02263788 1999-03-1
-44-
holding the gearshift lever in the upshift or
downshift position. He may even increment or
decrement the displayed gear value, shift the
gearshift lever to neutral, and then shift it back to
one of the upshift or downshift positions so long as
he does not leave the gearshift lever in neutral long
enough for the one-second timer to time out. If he
should permit the timer to time out, steps 432 and 434
would no longer be bypassed and the automatic ratio
lo matching would again be in effect. Even at this point
he may again override the automatic ratio matching
feature by again moving the gearshift lever to the
upshift or downshift position. When step 436 detects
that the gearshift lever is not in neutral and the
clutch pedal is not depressed, the transmission is
shifted into the gear whose value was last displayed
at step 434 or 444. the value displayed at step 434
is used if the gearshift lever has not been moved to
the upshift or downshift position while the routine
was being executed, or if more than one second has
elapsed since the gearshift lever was last in the
upshift or downshift position. The value displayed at
step 444 is used only if the clutch pedal is released
and the gearshift lever is shifted out of neutral
within one second of the time the value is first
displayed.
