Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2001-01-31
2002-06-25
Hirsch, Paul J. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C060S602000, C060S605200
Reexamination Certificate
active
06408834
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to systems for controlling EGR flow and/or turbocharger swallowing capacity/efficiency, and more specifically to systems for providing such control as a function of commanded charge flow and EGR fraction.
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 10
includes an internal combustion engine
12
having an intake manifold
14
fluidly coupled to a compressor
18
of a turbocharger 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 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 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 would accordingly be 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.
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Brackney Lary J.
Dollmeyer Thomas A.
He Chuan
Miller Paul R.
Barnes & Thornburg
Cummins Inc.
Hirsch Paul J.
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