Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2001-01-31
2002-11-12
Wolfe, Willis R. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C123S568210, C060S600000, C060S602000, C060S605200
Reexamination Certificate
active
06480782
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to systems for managing charge flow and EGR fraction in an EGR control system for an internal combustion engine, and more specifically to such systems for controllably arbitrating between commanded values of charge flow and EGR fraction and the physical capabilities of corresponding EGR and/or turbocharger control mechanisms.
BACKGROUND OF THE INVENTION
Systems for controlling EGR flow and/or turbocharger swallowing capacity are known and have been widely implemented, particularly in the heavy diesel engine industry. An example of one known system
10
for providing such control is shown in FIG.
1
and includes an internal combustion engine
12
having an intake manifold
14
fluidly coupled to a compressor
18
of a turbocharger
25
via intake conduit
16
, wherein the compressor
18
receives fresh air via intake conduit
20
. The turbocharger compressor
18
is mechanically coupled to a turbocharger turbine
24
via drive shaft
22
, wherein turbine
24
is fluidly coupled to an exhaust manifold
28
of engine
12
via exhaust conduit
30
, and is further fluidly coupled to ambient via exhaust conduit
26
. An EGR valve
32
is disposed in fluid communication with the intake conduit
16
and the exhaust conduit
30
, and a differential pressure sensor, or &Dgr;P sensor,
34
is disposed across the EGR valve
32
to sense a pressure change, or delta pressure, across valve
32
. An electronic EGR flow controller
36
has a first input receiving a signal indicative of desired EGR valve position, and has a first output electrically connected to EGR valve
32
via signal path
38
. In the system shown in
FIG. 1
, the EGR flow controller is configured to apply the EGR position signal directly to the EGR valve
32
. Controller
36
includes a second input receiving a signal indicative of a desired delta pressure value, or &Dgr;P target, and a third input electrically connected to the &Dgr;P sensor
34
via signal path
40
and receiving a signal thereat indicative of sensed delta pressure (&Dgr;P). The &Dgr;P value is subtracted from the &Dgr;P target value within the EGR flow controller
36
and a &Dgr;P error value produced thereby is applied to a proportional-integral (PI) or other known controller
44
. An output of controller
44
produces a variable geometry turbocharger signal VGT that is used to control the swallowing capacity and/or efficiency of the turbocharger
25
via any of a number of known techniques via signal path
46
. In operation, charge flow to the engine
12
, defined for the purposes of the present invention as the sum of fresh air flow into intake conduit
16
and EGR flow into intake conduit
16
, is controlled via control of the position of the EGR valve
32
and the pressure differential between the exhaust conduit
30
and intake conduit
16
.
One drawback associated with an EGR flow control system
10
of the type illustrated in
FIG. 1
is that there exists an interdependency between charge flow and EGR flow such that EGR flow and fresh air flow cannot be controlled separately. Once EGR flow is established by the EGR flow controller
36
, the resulting charge flow is defined by whatever fresh air flow is available. System
10
may therefore be optimized for NOx control or for particulate control, but generally not for both. It is accordingly desirable to provide for an EGR control system wherein EGR flow and fresh air flow may be controlled separately to therefore gain better and more consistent control over the charge flow. Such a system for achieving this goal is described in co-pending U.S. patent application Ser. No. 09/773,654, entitled SYSTEM FOR DECOUPLING EGR FLOW AND TURBOCHARGER SWALLOWING CAPACITY/EFFICIENCY CONTROL MECHANISMS, which is assigned to the assignee of the present invention and the contents of which are incorporated herein by reference.
In such a system, however, it is further desirable to provide a control strategy that arbitrates between EGR/turbocharger control commands and the corresponding capabilities of the EGR and/or turbocharger control mechanisms. In conventional EGR/turbocharger control systems, EGR/turbocharger control commands are typically( based on open-loop control techniques, and therefore do not take into account current operating states of the various EGR system and/or turbocharger actuators. As a result, the desired EGR/turbocharger control commands may request one or more of the various EGR system and/or turbocharger actuators to respond in a manner that, due to its current operational state, it cannot satisfy or should not satisfy due to potential violation of a related operational constraint. What is therefore needed is a control strategy that limits EGR/turbocharger control commands based on current EGR system and/or turbocharger operating conditions and/or based on the capabilities of the EGR system and/or turbocharger control mechanisms.
SUMMARY OF THE INVENTION
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for managing charge flow and EGR fraction in an internal combustion engine comprises a valve disposed between an exhaust manifold and an intake manifold of an internal combustion engine, means for determining a differential pressure across the valve resulting from flow of exhaust gas from the exhaust manifold to the intake manifold, a valve position sensor producing a position signal indicative of a position of the valve relative to a reference valve position, and a control circuit limiting a commanded EGR fraction value to a limited EGR fraction value as a function of the differential pressure signal and of the position signal.
In accordance with another aspect of the present invention, a system for managing charge flow and EGR fraction in an internal combustion engine comprises a turbocharger for an internal combustion engine including a compressor supplying fresh air to an intake manifold of the engine, means for determining an outlet temperature of the compressor, a limiter producing a penalty value as a function of the outlet temperature, and a control circuit limiting a commanded charge flow value to a limited charge flow value as a function of the penalty value.
In accordance with yet another aspect of the present invention, a system for managing charge flow and EGR fraction in an internal combustion engine comprises a turbocharger for an internal combustion engine including a compressor supplying fresh air to an intake manifold of the engine, a speed sensor producing a speed signal indicative of a rotational speed of the compressor, a limiter producing a penalty value as a function of the speed signal, and a control circuit limiting a commanded charge flow value to a limited charge flow value as a function of the penalty value.
In accordance with still another aspect of the present invention, a system for managing charge flow and EGR fraction in an internal combustion engine comprises a valve disposed between an exhaust manifold and an intake manifold of an internal combustion engine, means for determining a differential pressure across the valve resulting from flow of exhaust gas from the exhaust manifold to the intake manifold, a limiter producing a penalty value as a function of the differential pressure, and a control circuit limiting a commanded charge flow value to a limited charge flow value as a function of the penalty value.
In accordance with a further aspect of the present invention, a system for managing charge flow and EGR fraction in an internal combustion engine comprises a turbocharger for an internal combustion engine including a compressor supplying fresh air to an intake manifold of the engine, means for determining an outlet temperature of the compressor, a speed sensor producing a speed signal indicative of a rotational speed of the compressor, a first limiter producing a first penalty value as a function of the outlet temperature, a second limiter producing a second penalty value as a function of the sp
Brackney Larry J.
Brunemann George
Dollmeyer Thomas A.
Cummins Inc.
Wolfe Willis R.
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