U.S. patent number RE38,615 [Application Number 09/640,366] was granted by the patent office on 2004-10-12 for system and method for decreasing ratio changing time in electronically enhanced powertrain systems.
This patent grant is currently assigned to Eaton Corporation. Invention is credited to John Dresden, III, Thomas A. Genise, Simon Hornby, Ronald K. Markyvech, Richard A. Nellums, John E. Stainton.
United States Patent |
RE38,615 |
Dresden, III , et
al. |
October 12, 2004 |
System and method for decreasing ratio changing time in
electronically enhanced powertrain systems
Abstract
A system and method for decreasing the time required to complete
a ratio change in an electronically enhanced powertrain system is
provided. The powertrain system includes a number of devices for
providing a retarding torque to engine rotation to increase the
decay rate of the engine speed during an upshift. These devices
include an engine brake and an input shaft brake. A retarding
torque is also provided by increasing engine accessory load by
controlling various engine accessories such as a cooling fan, an
air compressor, a hydraulic pump, an air conditioning compressor,
and an alternator.
Inventors: |
Dresden, III; John (Farmington
Hill, MI), Genise; Thomas A. (Dearborn, MI), Hornby;
Simon (Bolton Lancashire, GB), Markyvech; Ronald
K. (Allen Park, MI), Nellums; Richard A. (Farmington
Hills, MI), Stainton; John E. (Chorley, GB) |
Assignee: |
Eaton Corporation (Cleveland,
OH)
|
Family
ID: |
10756406 |
Appl.
No.: |
09/640,366 |
Filed: |
August 16, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
461715 |
Jun 5, 1995 |
05655407 |
Aug 12, 1997 |
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Foreign Application Priority Data
Current U.S.
Class: |
74/336R; 192/222;
477/86; 477/92 |
Current CPC
Class: |
F16H
61/0403 (20130101); B60W 10/11 (20130101); B60W
30/18 (20130101); B60W 10/06 (20130101); F16H
63/502 (20130101); F16H 59/70 (20130101); F16H
59/36 (20130101); F16H 61/21 (20130101); F16H
59/40 (20130101); Y10T 74/1926 (20150115); Y10T
477/644 (20150115); Y10T 477/6425 (20150115); F16H
59/46 (20130101); F16H 2061/0411 (20130101); F16H
59/50 (20130101) |
Current International
Class: |
F16H
61/00 (20060101); F16H 59/00 (20060101); F16D
67/00 (20060101); F16H 059/00 (); F16H 061/00 ();
F16D 067/00 (); B60K 041/02 () |
Field of
Search: |
;477/92,94,86,96,170,171,172 ;74/336R ;192/216,222 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0427000 |
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Dec 1990 |
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EP |
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0270708 |
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May 1991 |
|
EP |
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0638455 |
|
Feb 1995 |
|
EP |
|
2154235 |
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Apr 1973 |
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FR |
|
2041114 |
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Sep 1980 |
|
GB |
|
2182734 |
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May 1987 |
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GB |
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Other References
SAE Technical Paper Series, Automated Mechanical Transmission
Controls, Nov. 7-10, 1983.* .
Proc. Instn. Mechn. Engrs., vol. 199, No. D4, A New Concept of
Truck Transmission, 1985.* .
Truck, pp. 34-41, Mar. 1993.* .
Progress On the Drivetrain Electronic Systems of the Japanese
Trucks and Buses, Elichi Kato, Hino Motors, Ltd.* .
Automated Mechanical Transmission Controls, Hiroshi Yoshimura and
Atsushi Hirako, Isuzu Motors Limited, Japan.* .
Scania CAG--Computer-Aided Gearshifting, Hal Holmelius, Saab-Scania
AB Sweden.* .
Commercial Motor, UK Has To Wait For Geartronic Debut, Sep. 26-Oct.
2, 1991, p. 8.* .
Commercial Motor, Shifting With More Brains, Sep. 19-25, 1991.*
.
Powertrain Electronic--Progress On The Use and Development of the
Computer Aided Gearshift Systems, Christian Bader, Mercedes-Benz
AG, pp. 375-385.* .
Electronically Controlled Mechanical Automatic Transmission for
Heavy Duty Trucks and Buses, S. Tanaka, F. Moniyama, M. Terasawa,
& S. Innami, Hino Motors, Ltd., pp. 161-169..
|
Primary Examiner: Ho; Ha
Attorney, Agent or Firm: Hinman; Kevin M. Gordon; Howard
D.
Parent Case Text
RELATED APPLICATIONS
This application is related to copending applications U.S. Ser. No.
08/103,947, filed Aug. 10, 1993, titled CONTROL SYSTEM/METHOD FOR
ENGINE BRAKE-ASSISTED SHIFTING and U.S. Ser. No. 08/179,060, filed
Jan. 7, 1994, titled ENGINE BRAKE-ENHANCED UPSHIFT CONTROL
METHOD/SYSTEM, and assigned to the same assignee, EATON
CORPORATION, as this application.
Claims
What is claimed is:
1. A method for reducing a ratio changing time in a mechanical
powertrain system including an engine having a device operative to
retard engine rotation, the engine being coupled .Iadd.by a master
friction clutch .Iaddend.to a mechanical change gear transmission
having a plurality of gear ratio combinations and a neutral gear
state selectively engageable between a transmission input shaft and
a transmission output shaft, the system also including an
electronic control unit for receiving a plurality of input signals
indicative of an engine speed, an output shaft speed, and a neutral
gear state, the electronic control unit also being operative to
generate command signals for controlling the engine retarding
device, the method comprising: sensing the neutral gear state which
occurs after disengaging a current gear ratio and before effecting
engagement of a target gear ratio; .[.and.]. while the master
friction clutch is engaged, applying a retarding torque to the
engine while the engine speed is above a synchronous speed at which
engagement of the target gear ratio is effected so as to increase
engine deceleration and reduce ratio changing time.Iadd.; .Iaddend.
.Iadd.monitoring the closure rate at which engine speed approaches
the synchronous speed; and controlling application of the retarding
torque based on the closure rate.Iaddend..
2. The method of claim 1 wherein the transmission further includes
an input shaft brake for retarding rotation of the input shaft and
wherein applying a retarding torque comprises actuating the engine
retarding device in combination with actuating the input shaft
brake.
3. The method of claim 2 wherein the engine retarding device is an
engine compression brake.
4. The method of claim 1 wherein the transmission system further
includes a plurality of engine accessories coupled to the engine
and in communication with the electronic control unit and wherein
applying a retarding torque comprises energizing at least one of
the plurality of engine accessories to increase engine load.
5. The method of claim 4 wherein the engine accessories include a
cooling fan, an air compressor, a hydraulic pump, an air
conditioning compressor, and an alternator.
6. The method of claim 1 wherein the transmission system further
includes a plurality of engine accessories coupled to the engine
and in communication with the electronic control unit, the
transmission further includes an input shaft brake for retarding
rotation of the input shaft, and wherein applying a retarding
torque comprises actuating a combination of devices selected from
the group consisting of the plurality of engine accessories, the
engine retarding device, and the input shaft brake..[.
7. The method of claim 1 further comprising: monitoring the closure
rate at which the engine speed approaches the synchronous speed;
and controlling application of the retarding torque based on the
closure rate..].
8. The method of claim .[.7.]. .Iadd.1 .Iaddend.wherein controlling
application of the retarding torque includes increasing the
retarding torque.
9. The method of claim .[.7.]. .Iadd.1 .Iaddend.wherein monitoring
the closure rate includes determining if the engine speed is above
an engine idle reference speed.
10. A control system for reducing a ratio changing time of a
mechanical powertrain system including an engine coupled to a
mechanical change gear transmission having a plurality of gear
ratio combinations and a neutral gear state selectively engageable
between a transmission input shaft and a transmission output shaft,
the powertrain system also including an electronic control unit for
receiving a plurality of input signals indicative of an engine
speed, an output shaft speed, and a neutral gear state, the
electronic control unit also being operative to generate command
signals for controlling the engine and the transmission, the
control system comprising: means for applying a retarding torque in
response to a command from the electronic control unit, the
retarding torque being applied to the engine while the engine speed
is above a synchronous speed at which the target gear ratio is
effected so as to increase engine deceleration and reduce ratio
changing time; means for monitoring the closure rate at which the
engine speed approaches the synchronous speed; and means for
controlling application of the retarding torque based on the
closure rate.
11. The control system of claim 10 wherein the means for applying a
retarding torque comprises an input shaft brake attached to the
transmission and in communication with the electronic control unit
for retarding rotation of the input shaft.
12. The control system of claim 10 wherein the means for applying a
retarding torque comprises an engine brake.
13. The control system of claim 12 wherein the engine brake is an
engine compression brake.
14. The system of claim 10 wherein the means for applying a
retarding torque comprises a plurality of engine accessories
coupled to the engine for increasing a load on the engine so as to
retard engine rotation.
15. The system of claim 10 wherein the means for applying a
retarding torque comprises an engine cooling fan for increasing a
load on the engine so as to retard engine rotation.
16. The system of claim 15 wherein the means for applying a
retarding torque further comprises an air compressor, a hydraulic
pump, an air conditioning compressor, and an alternator, all of
which are coupled to the engine for increasing a load on the engine
so as to retard engine rotation.
17. The system of claim 10 wherein the means for monitoring the
closure rate includes means for determining if the engine speed is
above an engine idle reference speed.
18. The method of claim 1 wherein the transmission further includes
an input shaft brake for retarding rotation of the input shaft and
wherein the step of applying a retarding torque comprises actuating
the input shaft brake..Iadd.
19. A method for reducing a ratio changing time in a mechanical
powertrain system including an engine having a device operative to
retard engine rotation, the engine being coupled by a master
friction clutch to a mechanical change-gear transmission having a
plurality of gear ratio combinations and a neutral gear state
selectively engageable between a transmission input shaft and a
transmission output shaft, the system also including an electronic
control unit for receiving a plurality of input signals indicative
of an engine speed, an output shaft speed, and a neutral gear
state, the electronic control unit also being operative to generate
command signals for controlling the engine retarding device, the
method comprising: sensing the neutral gear state which occurs
after disengaging a current gear ratio and before effecting
engagement of a target gear ratio; determining a first value
indicative of one of (i) a current engine speed and (ii) an
expected engine speed; determining a second value indicative of one
of (i) a current synchronous speed for engaging said target ratio
and (ii) an expected synchronous speed for engaging said target
ratio; determining a difference between said first and second
values; and while the master friction clutch is engaged, generating
command signals to said engine retarding device for applying a
retarding torque to the engine while the engine speed is above a
synchronous speed at which engagement of the target gear ratio is
effective so as to increase engine deceleration and reduce ratio
changing time, said engine retarding device controlled in
accordance with at least one of (i) said difference and (ii) a rate
of change of said difference. .Iaddend..Iadd.
20. The method of claim 19 wherein, if said difference is less than
about 40 RPM, then the engine retarding device is not activated.
.Iaddend..Iadd.
21. The method of claim 19, wherein said engine retarding device
has a determined reaction time, and said engine retarding device is
controlled based upon said reaction time. .Iaddend..Iadd.
22. A method for reducing a ratio changing time in a mechanical
powertrain system including an engine having a device operative to
retard engine rotation, the engine being coupled by a master
friction clutch to a mechanical change-gear transmission having a
plurality of gear ratio combinations and a neutral gear state
selectively engageable between a transmission input shaft and a
transmission output shaft, the system also including an electronic
control unit for receiving a plurality of input signals indicative
of an engine speed, an output shaft speed, and a neutral gear
state, the electronic control unit also being operative to generate
command signals for controlling the engine retarding device, the
method comprising: sensing the neutral gear state which occurs
after disengaging a current gear ratio and before effecting
engagement of a target gear ratio; determining a value indicative
of an engine speed; determining a synchronous window of engine
speeds for engaging said target gear ratio; and while the master
friction clutch is engaged, generating command signals to said
engage retarding device for applying a retarding torque to the
engine while the engine speed is above a synchronous speed at which
engagement of the target gear ratio is effective so as to increase
engine deceleration and reduce ratio changing time, said engine
retarding device controlled in accordance with said value and said
synchronous window. .Iaddend..Iadd.
23. The method of claim 22 wherein said engine retarding device has
a determined reaction time, and said engine retarding device is
controlled based upon said reaction time. .Iaddend..Iadd.
24. A method for reducing a ratio changing time in a mechanical
powertrain system including an engine having a device operative to
retard engine rotation, the engine being coupled by a master
friction clutch to a mechanical change-gear transmission having a
plurality of gear ratio combinations and a neutral gear state
selectively engageable between a transmission input shaft and a
transmission output shaft, the system also including an electronic
control unit for receiving a plurality of input signals indicative
of an engine speed, an output shaft speed, and a neutral gear
state, the electronic control unit also being operative to generate
command signals for controlling the engine retarding device, the
method comprising: sensing the neutral gear state which occurs
after disengaging a current gear ratio and before effecting
engagement of a target gear ratio; determining a rate of engine
speed decay required for synchronous engagement of said target
ratio; comparing said rate to a reference value; and only if said
rate exceeds said reference value, while mater friction clutch is
engaged, applying a retarding torque to the engine while the engine
speed is above a synchronous speed at which engagement of the
target gear ratio is effective so as to increase engine
deceleration and reduce ratio changing time. .Iaddend..Iadd.
25. A method for reducing a ratio changing time in a mechanical
powertrain system including an engine having a device operative to
retard engine rotation, the engine being coupled by a master
friction clutch to a mechanical change-gear transmission having a
plurality of gear ratio combinations and a neutral gear state
selectively engageable between a transmission input shaft and a
transmission output shaft, the system also including an electronic
control unit for receiving a plurality of input signals indicative
of an engine speed, an output shaft speed, and a neutral gear
state, the electronic control unit also being operative to generate
command signals for controlling the engine retarding device, the
method comprising: determining a value indicative of a natural
engine speed decay rate; sensing the neutral gear state which
occurs after disengaging a current gear ratio and before effecting
engagement of a target gear ratio; and while the master friction
clutch is engaged, generating command signals to said engine
retarding device for applying a retarding torque to the engine
while the engine speed is above a synchronous speed at which
engagement of the target gear ratio is effective so as to increase
engine deceleration and reduce ratio changing time, said engine
retarding device controlled in accordance with said value.
.Iaddend..Iadd.
26. A method for reducing a ratio changing time in a mechanical
powertrain system including an engine having a device operative to
retard engine rotation, the engine being coupled by a master
friction clutch to a mechanical change-gear transmission having a
plurality of gear ratio combinations and a neutral gear state
selectively engageable between a transmission input shaft and a
transmission output shaft, the system also including an electronic
control unit for receiving a plurality of input signals indicative
of an engine speed, an output shaft speed, and a neutral gear
state, the electronic control unit also being operative to generate
command signals for controlling the engine retarding device, the
method comprising: sensing the neutral gear state which occurs
after disengaging a current gear ratio and before effecting
engagement of a target gear ratio; and determining if engaging said
target gear ratio involves a multiple ratio upshift; and while the
master friction clutch is engaged, generating command signals to
said engine retarding device for applying a retarding torque to the
engine while the engine speed is above a synchronous speed at which
engagement of the target gear ratio is effective so as to increase
engine deceleration and reduce ratio changing time, said engine
retarding device controlled in accordance with said determination.
.Iaddend..Iadd.
27. The method of claim 26 wherein said engine retarding device is
activated only during multiple ratio upshifts. .Iaddend.
Description
RELATED APPLICATIONS
This application is related to copending applications U.S. Ser. No.
08/103,947, filed Aug. 10, 1993, titled CONTROL SYSTEM/METHOD FOR
ENGINE BRAKE-ASSISTED SHIFTING and U.S. Ser. No. 08/179,060, filed
Jan. 7, 1994, titled ENGINE BRAKE-ENHANCED UPSHIFT CONTROL
METHOD/SYSTEM, and assigned to the same assignee, EATON
CORPORATION, as this application.
TECHNICAL FIELD
The present invention relates to a system and method for decreasing
the time required to complete a ratio change in an electronically
enhanced engine and transmission system.
BACKGROUND ART
Electronically enhanced transmission systems have been well
developed in the prior art as may be seen by reference to U.S. Pat.
Nos. 4,361,060; 4,595,986; 4,648,290; 4,722,248; and 5,050,427, the
specifications of which are hereby incorporated by reference in
their entirety. Transmission systems such as these have been
utilized to provide a variety of gear ratios to enhance the
flexibility and torque multiplication of an engine to service a
plethora of applications. The most common applications include MVMA
Class 7 and Class 8 tractor semi-trailer vehicles although other
applications, such as automobile or stationary power plant
powertrains, may also be serviced.
Art electronic control module which includes a microprocessor is
often used to control the powertrain, which includes an engine as
well as a multiple gear ratio transmission. The continuous
evolution of microprocessor technology has enabled increased
accuracy and expanded the scope of control over engine and
transmission operations. The electronic control module collects
data from various sensors and issues commands appropriate for the
current operating conditions to control the engine and
transmission. Engine control may include modulating fuel, operating
engine accessories, or managing application of an engine brake or
driveline retarder. Transmission control may include selection of
an appropriate gear ratio, including disengagement of the current
gear ratio and engagement of a new target gear ratio, or operation
of an input shaft brake.
Efficient ratio changing improves fuel economy and enhances
drivability of a vehicle. Under certain demanding situations, such
as when negotiating a steep grade with a heavily loaded vehicle,
swift ratio changes are required to prevent the vehicle from losing
momentum and missing the window of opportunity to complete the
shift entirely. Under normal driving conditions, an operator may
have to shift gears more than fifteen times before reaching highway
speeds. In these applications, inefficiency in ratio changing may
accumulate to a significant amount of wasted time. Thus, it is
desirable to reduce the time necessary to complete a ratio change
or shift.
A typical ratio change involves a number of steps. First, the
operator must interrupt the transfer of torque from the engine
through the transmission to the driveline. This may be accomplished
by disengaging a master clutch which provides a frictional coupling
between the engine and the transmission. Alternatively, a "throttle
dip" may be performed where the throttle is abruptly decreased.
Once the torque transfer has been interrupted, the current gear is
disengaged and the transmission is in a neutral state.
The next step in a typical ratio change involves selecting the
target gear ratio. This may be the next available gear ratio in the
sequence, or a number of available ratios may be skipped, depending
on the current operating conditions. Before engaging the target
gear, the transmission input shaft should rotate at a substantially
synchronous speed for the current output shaft speed and target
gear ratio. When the master clutch is engaged, the input shaft
speed may be controlled by controlling engine speed since the
engine and transmission are coupled. Engine speed may be increased
(for a downshift) or decreased (for an upshift) to realize
synchronous speed. On transmissions equipped with an input shaft
brake, the input shaft speed may be reduced by disengaging the
master clutch and applying the input shaft brake (also known as an
inertia brake or clutch brake). However, input shaft brakes with
sufficient capacity to decrease ratio changing time add cost and
complexity to the transmission system and require accurate
sequencing of events for satisfactory operation, so many
transmissions only utilize simple versions of these devices.
For transmissions without input shaft brakes, synchronous speed
will not be attained with the master clutch engaged on an upshift
until the engine speed naturally decays to synchronous. As engines
become more and more efficient, the reduction of internal
frictional losses results in a substantially lower natural engine
decay rate. This results in a correspondingly longer time to
complete a ratio change. Thus, it is desirable to increase engine
deceleration during an upshift to achieve synchronous speed shortly
after disengagement of the current gear.
A device often utilized to provide a variable retarding force to an
engine, is an engine brake. The most common engine brakes may be
either engine compression brakes or exhaust brakes. These devices
are well known in the prior art and are commonly provided on
heavy-duty vehicles. Examples of vehicular automated mechanical
transmission systems utilizing engine brakes may be seen by
reference to U.S. Pat. Nos. 4,933,850 and 5,042,327 the
specifications of which are hereby incorporated by reference in
their entirety.
Engine compression brakes are usually manually operated and provide
a variable retarding force resisting engine rotation by altering
valve timing of one, two, or three banks of cylinders. This creates
compressive force within the cylinders which resists rotation of
the crankshaft. Exhaust brakes operate in a similar fashion by
restricting exhaust flow from the engine. Exhaust brakes do not
offer the responsiveness or flexibility of engine compression
brakes although they are less expensive to employ.
Traditionally, engine brakes are utilized to assist the vehicle
service brakes by supplying a resisting torque on the driveline
when descending long grades. Manual operation of the engine brake
in these situations continues to be a desirable option. More
recently, engine brakes have been manually operated to decrease the
time required for ratio changes. For this application, manual
operation of the engine brake often results in large torque
disturbances to the vehicle driveline due to inappropriate timing
in applying and releasing the engine brake. This reduces
drivability of the vehicle and may also adversely affect the
durability of powertrain components. Furthermore, proper operation
is largely dependent upon the skill and experience of the vehicle
operator.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a
system and method for reducing the time required to complete a
ratio change, in particular, an upshift ratio change, in a manual,
semi-automatic or fully automatic transmission.
It is an additional object of the present invention to provide a
system which reduces the time required to achieve synchronous speed
by increasing a retarding force acting on engine rotation.
Another object of the present invention is to provide a system
which automates control of an engine compression brake to decrease
ratio changing time in a manual, semi-automatic or fully automatic
transmission.
A still further object of the present invention is to provide a
system which increases engine load to supply a variable retarding
force so as to improve ratio changing times in a manual,
semi-automatic or fully automatic transmission.
Yet another object of the present invention is to provide a system
which reduces driveline disturbances during an upshift by utilizing
an engine brake when a transmission neutral condition is
sensed.
In carrying out the above object and other objects and features of
the present invention, a control system is provided for reducing
the ratio changing time of a mechanical transmission system. The
transmission system includes an engine selectively coupled by a
master friction clutch to a mechanical change gear transmission.
The system also includes an electronic control unit for receiving a
plurality of input signals indicative of an engine speed, an output
shaft speed, and a neutral gear state of the transmission. The
electronic control unit also generates command signals for
controlling the engine and the transmission. The transmission
includes a plurality of gear ratio combinations, and a neutral gear
state, selectively engageable between a transmission input shaft
and a transmission output shaft. The control system utilizes a
sensor for sensing the neutral gear state which occurs after
disengaging a current gear ratio and before effecting a target gear
ratio in the transmission. The system also includes devices for
applying a retarding torque to the engine in response to a command
from the electronic control unit. The retarding torque is applied
to the engine while the engine speed is above the synchronous speed
at which the target gear ratio is effected, so as to increase
engine deceleration and reduce ratio changing time. A method is
also provided for use with the system and similar systems.
The above objects and other objects, features, and advantages of
the present invention will be readily appreciated by one of
ordinary skill in the art from the following detailed description
of the best mode for carrying out the invention when taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a powertrain system
including a mechanical transmission and an engine brake according
to the present invention;
FIG. 2a is a graphical representation of a typical upshift with a
master friction clutch engaged, unassisted by an engine brake;
FIG. 2b is a graphical representation of an attempted upshift under
demanding conditions without utilizing an engine brake;
FIG. 2c is a graphical representation of an engine brake assisted
upshift with a master friction clutch engaged according to the
present invention; and
FIG. 3 is a flow chart illustrating the method of reducing ratio
changing times according to the present invention;
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically depicts a vehicular powertrain system,
indicated generally by reference numeral 10. The system includes an
internal combustion engine 12 which is selectively coupled to the
input shaft 14 of a multiple gear change transmission 16 via a
master friction clutch 18. Engine 12 may be any of a number of
types of internal combustion engines, such as a diesel engine or a
gasoline engine. Master friction clutch 18 includes driving
elements 20 which are attached to the crankshaft 22 of engine 12,
and driven elements 24 which are attached to input shaft 14. When
master friction clutch 18 is engaged, substantially all the torque
delivered by engine 12 is transmitted through driving elements 20
and driven elements 24 to transmission 16.
Output shaft 26 of transmission 16 is adapted to engage an
appropriate driveline component (not specifically illustrated),
such as a differential, drive axle, transfer case, or the like.
Powertrain system 10 may also include a heat exchanger 28, such as
a conventional radiator, an electrically controllable cooling fan
30, and an engine brake 32. Other components may include a
hydraulic pump for power steering or other oil operated devices, an
air conditioned compressor for cab climate control, an alternator
for supplying electrical power, and an air compressor 34 and a
compressed air storage tank 36 for powering pneumatically actuated
devices or systems, such as the transmission input shaft brake 38,
or the vehicle service brakes (not specifically illustrated).
Powertrain system 10 includes a number of sensors and actuators to
effect control of the system as determined by the electronic
control unit (ECU) 40. The various sensors provide information
indicative of the current operating conditions to ECU 40 via input
means 42. ECU 40 utilizes this information in executing a
predetermined set of instructions, stored in a memory, to generate
command signals. The command signals are relayed to the various
actuators via output means 44.
Some representative sensors in communication with ECU 40 include a
crankshaft sensor 46 for indicating engine speed (ES), an input
speed sensor 48 for indicating transmission input speed (IS), and
an output shaft sensor 50 for indicating transmission output speed
(OS). Other sensors include a throttle position sensor 52 for
indicating the position of throttle pedal 54, a brake-applied
sensor 58 to indicate the state of service brake pedal 56 for
applying the vehicle service brakes, and a gear selection indicator
60 for selecting a reverse (R), neutral (N), or drive (D) gear of
transmission 16. In some applications, an additional gear selector
is provided to indicate a request for an upshift or downshift. A
manual engine brake selector 62 is provided for allowing manual
control of the engine brake under certain operating conditions, as
described below.
Powertrain system 10 also includes a number of actuators in
communication with ECU 40. The actuators receive commands from ECU
40 via output means 44. Preferably, a standard communications link,
such as the SAE J1922 or SAE J1939, is utilized for the actuators
and sensors. The actuators may also provide feedback to ECU 40 via
input means 42 to effect a closed-loop control system. Typical
actuators include a fuel controller 70 for regulating the amount of
fuel delivered to engine 12, and a clutch operator 72 for engaging
and disengaging master friction clutch 18. Commands from ECU 40 may
also be directed to actuators through other controllers. For
example, fuel controller 70 may be responsible for activating
engine brake 32 upon request by ECU 40. Transmission operator 74 is
operative to change the gear ratio of transmission 16 to achieve a
selected gear. Transmission operator 74 also provides a signal
indicative of the currently engaged gear or a neutral gear state of
transmission 16.
Any of a number of known sensor types may be utilized to provide
information related to the current operating conditions to ECU 40
without departing from the spirit or the scope of the present
invention. Similarly, known electric, hydraulic, pneumatic, and
combination actuators may be implemented to realize the present
invention. Transmission system controls and actuators of the type
described above may be appreciated in greater detail by reference
to U.S. Pat. Nos. 4,959,986; 4,576,065; and 4,445,393, the
specifications of which are hereby incorporated by reference in
their entirety.
A better understanding of the operation of the present invention
will be facilitated by reference to FIGS. 2a through 2c which are
graphical representations of various component rotational speeds
during three different upshifts.
FIG. 2a is a graphical representation of an upshift performed by
powertrain system 10 of FIG. 1 with master friction clutch 18
engaged and without utilizing engine brake 32. The upshift begins
at time t.sub.1 where the current gear is disengaged so that
transmission 16 is in a neutral gear state as indicated by
transmission operator 74 or by a comparison of transmission input
and output speeds. Also at time t.sub.1, the engine is defuelled by
fuel controller 70. Since master friction clutch 18 is still
engaged, input shaft 14 is coupled to crankshaft 22 and engine
speed (ES) is equal to input speed (IS). As illustrated, ES (and
IS) decreases until achieving synchronous with output shaft speed
(OS) at time t.sub.2 (illustrations assume a target gear ratio of
1.00). Synchronous speed is achieved when IS=OS * GR.sub.T, where
GR.sub.T is the target gear ratio.
Since engine brake 32 is not being used, the rate at which ES
decreases is the natural decay rate of the system. The natural
decay rate is a function of the rotational inertia of the rotating
engine, clutch, and transmission components. Also near time
t.sub.2, when ES is within approximately 40 RPM of synchronous,
transmission operator 74 engages the selected target gear. At time
t.sub.3, fuel is restored to engine 12 by fuel controller 70 and
the upshift has been completed.
In FIG. 2b, a graphical representation of an attempted upshift
under demanding conditions, such as when ascending a steep grade,
is shown. Similar to the event illustrated in FIG. 2a, at time
t.sub.1, transmission operator 74 disengages the current gear and
indicates a neutral gear state to ECU 40 while engine 12 is
defuelled by fuel controller 70. Without engine fueling, the
vehicle slows down rapidly, causing OS to decrease. The natural
decay rate of engine 12 is too gradual to attain synchronous before
reaching engine idle speed at time t.sub.4. Thus, the window of
opportunity to complete the desired upshift has passed and the
upshift must be aborted.
FIG. 2c is a graphical representation of an upshift performed by
powertrain system 10 with master friction clutch 18 engaged while
also utilizing engine brake 32. At time t.sub.a, the current gear
is disengaged, engine 12 is defuelled, and ES begins to decrease at
its natural decay rate. ECU 40 generates a command signal to apply
engine brake 32 when a neutral gear state is indicated by
transmission operator 74 at time t.sub.b. Engine brake 32 is
operative to increase the decay rate of ES such that synchronous
speed may be attained at time t.sub.c. The target gear is engaged
at time t.sub.c by transmission operator 74 in response to a
command signal from ECU 40. Power to engine 12 is restored at time
t.sub.d as fuel controller 70 increases the delivered fuel in
response to a command from ECU 40, thereby completing the upshift.
Of course, transmission gear disengagement and engagement could
remain under control of the vehicle operator, and still be within
the scope of the present invention. In the case of manual control
of gear engagement, at time T.sub.c fuel controller 70 would
operate to maintain ES and IS at synchronous speed until
transmission operator 74 indicated that the target gear had been
manually engaged.
As illustrated in FIG. 1, engine brake 32 is in communication with
engine brake selector 62, which provides for manual operation of
engine brake 32 when descending a long grade. Typically, the engine
brake is actuated when ES is above idle and throttle pedal 54 is
fully released. Engine brake selector 62 could also be arranged to
allow driver selection of the level of retardation to be provided
during an upshift, so that zero, one, two or three banks of
cylinders are activated when signaled by ECU 40. Engine brake
activation could also be limited to multiple ratio upshifts only,
or only when the required engine speed decay rate for an acceptable
upshift exceeds a given threshold. These techniques minimize the
wear and tear resulting from engine brake use.
As previously discussed, an engine brake may be either a
compression brake or an exhaust brake. In addition to conventional
engine brakes, the present invention controls engine accessories to
effect a modified form of engine braking. By selectively energizing
and de-energizing accessories such as cooling fan 30, air
compressor 34, or other devices (not shown) such as hydraulic
pumps, air conditioning compressors, or alternators, the load on
engine 12 may be increased or decreased, respectively, so as to
vary the engine speed decay rate. Furthermore, an input shaft brake
38 under control of ECU 40 may be applied with the master clutch
engaged to supply an additional retarding force operative to
increase the decay rate of engine 12. Of course, any combination of
the above devices, or other similar devices such as a driveline
retarder, may be used together to produce a variable retarding
force depending upon the particular system operating
conditions.
Since various engine braking devices, such as an engine compression
brake, take a significant time to respond relative to the total
time required for an upshift, these devices may be actuated prior
to sensing a neutral gear state. For example, in FIG. 2c, the
engine brake would be actuated before time t.sub.a to reduce or
eliminate the time lapse between time t.sub.a and time t.sub.b. The
exact actuation time would depend upon the response time of the
particular braking device being utilized and the details of the
arrangements to ensure that the current gear will be disengaged.
This strategy works particularly well with engines which revert to
idle fuelling when the engine brake is activated. Reverting to idle
fuelling accomplishes the throttle dip function which interrupts
torque transfer through the transmission to allow disengagement of
the current gear.
Engine brake response time is also considered in determining when
to deactivate the engine brake. The present invention deactivates
the engine brake at an appropriate time to anticipate a natural
engine speed decay rate when ES will be within the synchronous
window, i.e. within about 40 RPM of synchronous speed.
If the target speed for IS is below a reference value such as 200
RPM above engine idle speed, alternative synchronization methods
must be implemented, such as disengaging the master clutch and
actuating an input shaft brake. One situation where this occurs is
in completing a stationary shift since OS is near zero so
synchronous speed is below the engine idle reference speed.
The present invention also provides for various contingencies to
accommodate diverse operating conditions. If the engine brake
engages prior to its predicted engagement (due to a varying
response time), clutch operator 72 may disengage master friction
clutch 18 while the current gear is being disengaged so the shift
may progress acceptably. Other alternative control sequences are
initiated by ECU 40 in the event that synchronization is not being
accomplished, as in the case illustrated in FIG. 2b. For example,
engine braking may be increased by using a combination of
conventional engine braking with engine accessory loading and
application of input shaft brake 38.
Typically, input shaft brakes are utilized to decelerate the input
shaft of a transmission when the master friction clutch is
disengaged. Thus, traditional input shaft brakes are designed to
decelerate a limited rotational inertia. Therefore, utilizing input
shaft brake 38 according to the present invention may require a
high-capacity input shaft shaft brake 38 tws input shaft brake 38
to accommodate the rotational inertia generated by engine 12,
crankshaft 22, and master friction clutch 18 so that input shaft
brake 38 may be applied while master friction clutch 18 is still
engaged.
FIG. 3 is a flowchart illustrating the method of decreasing ratio
changing times according to the present invention. At step 80, the
ECU gathers information from the various sensors and actuators of
the system and obtains values for ES, IS, OS, and a limiting value
for engine braking. If an upshift has been requested by the
operator, or is indicated by the ECU, step 82 directs processing to
continue with step 84. Otherwise, the process loops back to step
80.
As also shown in FIG. 3, step 84 includes disengaging the current
gear and selecting an appropriate target gear. Once the current
gear is disengaged, the transmission is in a neutral gear state. If
ES is above an idle reference value, as determined by step 86, then
a test is performed to determine if engine speed is within the
synchronous window step 88. Otherwise, if ES is below idle speed,
alternate control strategies are initiated by step 98 which include
those contingencies discussed above. If a speed within the
synchronous window has not been attained, a retarding torque is
applied as indicated by step 94. This may include activating an
engine compression brake, increasing engine accessory load, or a
combination of these as previously discussed.
Still referring to FIG. 3, the closure rate between ES and
synchronous speed is examined at step 96. If the closure rate is
satisfactory for current operating conditions, the process
continues with step 86. Otherwise, alternate control strategies are
implemented by step 98. Once the synchronous speed window is
attained as determined by step 88, the retarding torque is removed
at step 90 and the target gear is engaged at step 92 so as to
complete the upshift.
It is understood, of course, that while the form of the invention
herein shown and described constitutes a preferred embodiment of
the invention, it is 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.
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