Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
1999-07-26
2001-01-23
Kwon, John (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S295000
Reexamination Certificate
active
06176227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a control system for an internal combustion engine of cylinder injection type (also known as the direct fuel injection type engine) in which fuel is directly injected into engine cylinders to undergo combustion therein through spark ignition. More specifically, the present invention is concerned with a control system for the cylinder injection type internal combustion engine which is capable of decreasing harmful components such as nitrogen oxides NO
x
contained in the exhaust gas of the engine with high reliability by controlling an exhaust gas recirculation quantity (also referred to as the EGR quantity for short) with high accuracy.
2. Description of Related Art
Heretofore, the spark ignition type (or indirect fuel injection type) internal combustion engine in which fuel is injected into an intake manifold for charging a uniform air-fuel gas mixture into engine cylinders has been well known in the art. In the internal combustion engine (hereinafter also referred to simply as the engine) of this type, an air-fuel ratio sensor is provided in an exhaust pipe with a view to controlling the air-fuel ratio (also referred to simply as the A/F ratio) so that it assumes a stoichiometric air-fuel ratio (14.7). To this end, a feedback control is adopted.
By way of example, in a conventional control system for an internal combustion engine such as described in Japanese Unexamined Patent Application Publication No. 101645/1986 (JP-A-61-101645), such a technique is adopted that error or deviation of the detected air-fuel ratio from a desired value is corrected by employing a pair of air-fuel ratio sensors.
Further, in another conventional control system for an internal combustion engine such as described in Japanese Unexamined Patent Application Publication No. 75327/1988 (JP-A-63-75327), the air-fuel ratio feedback quantity is corrected upon acceleration/deceleration of the engine by storing acceleration/deceleration quantity data in combination with air-fuel ratio feedback quantity data in the form of table or map for every region where the air-fuel ratio feedback quantity is to be corrected.
In general, with the conventional internal combustion engines such as mentioned above, a relatively high output power or torque can be generated. However, the engine of this type suffers a problem that the output torque thereof changes rather remarkably as a function of the air-fuel ratio, involving thus difficulty in carrying out the control of the output torque generated by the engine.
Such being the circumstances, there has been developed a control system for a cylinder injection type engine in which fuel is directly injected into the cylinder for burning the fuel in a predetermined region within the cylinder.
By way of example, in a conventional control system for an cylinder injection type internal combustion engine such as described in Japanese Unexamined Patent Application Publication No. 312433/1996 (JP-A-8-312433), such a control scheme is adopted according to which a desired engine torque is arithmetically determined on the basis of engine operation state, and then various control quantities such as desired air-fuel ratio, desired fuel injection timing, ignition timing, EGR quantity, and so forth are determined on the basis of the desired engine torque.
For having better understanding of the principle underlying the present invention, technical background thereof will be described below in some detail.
FIG. 8
is a schematic diagram showing generally an arrangement of a conventional control system for a cylinder injection type internal combustion engine known heretofore.
Referring to
FIG. 8
, an engine
1
constituting an intrinsically major part of the internal combustion engine system is provided with an intake pipe
1
a
for introducing the intake air into the engine
1
and an exhaust pipe
1
b
for discharging the exhaust gas resulting from the combustion of the air-fuel mixture.
An air flow sensor
2
for detecting a flow rate or quantity Qa of the intake air fed to the engine
1
as indicated by an arrow is installed at an upstream location in the intake pipe
1
a
. Further installed within the intake pipe
1
a
is a throttle valve
3
for adjusting or regulating the intake air flow rate or quantity Qa, and a throttle position sensor
4
for detecting an opening degree &thgr; of the throttle valve
3
is provided in association with the throttle valve
3
.
Installed at a downstream location in the intake pipe
1
a
, i.e., at a location immediately preceding to the engine
1
is a surge tank
5
. On the other hand, an air-fuel ratio sensor
6
which may be constituted by a linear type O
2
-sensor is provided in the exhaust pipe
1
b
for detecting an actual air-fuel (A/F) ratio F of the exhaust gas, which ratio generally lies within a range of e.g. “10” to “50”.
A throttle valve actuator
7
(serving as an intake air quantity regulating means) is provided in association with the throttle valve.
3
for adjusting or regulating the throttle valve opening degree &thgr;. The throttle valve actuator
7
may be comprised of, for example, a stepping or stepper motor for driving rotatively and stepwise the throttle valve
3
to thereby regulate the rate or quantity Qa of the intake air flowing through the intake pipe
1
a.
Installed within each of the cylinders of the engine
1
is a spark plug
8
at which electric spark discharge takes place for igniting the air-fuel mixture within the combustion chamber of the cylinder. To this end, a distributor
9
is provided for supplying a high voltage distributively to the individual spark plugs
8
in synchronism with ignition timing.
Further provided is an ignition coil
10
which is realized in the form of a transformer having primary and secondary windings. A high voltage for the spark ignition is induced in the secondary winding of the ignition coil
10
whenever a primary current flowing through the primary winding is interrupted. The high voltage is then supplied to the distributor
9
. Provided in association with the ignition coil
10
is an ignitor
11
which is constituted by a power transistor for interrupting the current flowing through the primary winding of the ignition coil
10
in conformance with the ignition timing for the individual engine cylinders.
The spark plug
8
, the distributor
9
, the ignition coil
10
and the ignitor
11
cooperate to constitute an ignition system or means for igniting the air-fuel mixture within the individual cylinders of the engine
1
.
An ECU (Electronic Control Unit)
12
which is in charge of controlling the engine system as a whole includes a microcomputer for arithmetically determining control quantities for various actuators which are installed for the purpose of controlling combustion of in the engine
1
on the basis of information detected by various types of sensors (i.e., information concerning the operation state of the engine
1
), to thereby issue driving signals indicative of the control quantities to the relevant actuators.
As the signals indicative of the various types of control quantities, there may be mentioned an intake-air flow control signal A for the throttle valve actuator
7
, an ignition signal G for the ignitor
11
(ignition system), a fuel injection signal J for the fuel injection valve (i.e., injector)
13
, an EGR (Exhaust Gas Recirculation) control signal E for an EGR regulating valve
17
, and a purge control signal P for a purge regulating valve
26
among others.
The fuel injector
13
is mounted internally of each cylinder of the engine
1
for injecting the fuel directly into the combustion chamber defined within the cylinder. A crank angle sensor
14
for generating a crank angle signal CA is installed in association with a crank shaft which is driven rotatively by the engine
1
.
For detecting a depression stroke &agr; of an accelerator pedal manipulated by an operator or driver of a motor vehicle or the like equipped with the engine system now under consid
Enoki Keiichi
Ohuchi Hirofumi
Kwon John
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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