Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
1999-07-26
2001-06-05
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S301000, C123S305000
Reexamination Certificate
active
06240894
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 invention is concerned with a control system for the cylinder injection type internal combustion engine which is capable of ensuring a significant reduction of harmful components contained in the exhaust gas of the engine with high efficiency while realizing improved combustion performance or drivability of the engine.
2. Description of Related Art
In general, with the spark ignition type internal combustion engine in which fuel is injected into an intake manifold for charging a uniform gas mixture into engine cylinders, a relatively high output power or torque can be generated. However, the internal combustion engine (hereinafter also referred to simply as the engine) of this type suffers a problem that the output torque thereof changes rather remarkably in dependence on the air-fuel ratio (hereinafter also referred to simply as the A/F ratio), providing thus difficulty in carrying out the control of output torque generated by the engine.
In the conventional intake manifold injection type engine (indirect fuel injection type engine) known heretofore, the air-fuel ratio can remain substantially constant, whereby the relation between an opening degree of a throttle valve and the output torque of the engine can be determined substantially definitely. For this reason, the combustion parameters such as the ignition timing and others have been determined or set definitely in dependence on the intake air flow rate (hereinafter also referred to as the intake air quantity).
By contrast, in the case of the cylinder injection type internal combustion engine, the output torque of the engine changes in dependence on the air-fuel ratio even for a same opening degree of the throttle valve. Accordingly, there arises the necessity of setting the combustion parameters such as the ignition timing and the fuel injection timing among others to optimal values in dependence on the engine load, the air-fuel ratio and others by controlling appropriately the throttle valve opening degree and the air-fuel ratio.
For having better understanding of the principle underlying the present invention, technical background thereof will be described below in some detail.
FIG. 23
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. 23
, an engine
1
constituting a 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 flow fed to the engine
1
as indicated by an arrow is installed at an upstream location of the intake pipe la. Further installed within the intake pipe
1
a
is a throttle valve
3
for regulating or adjusting 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 of 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
to serve for detecting an actual air-fuel (A/F) ratio F prevailing within the exhaust pipe
1
b
. Parenthetically, this air-fuel ratio may change within a range of e.g. 10 to 50.
A throttle valve actuator which serves as the intake air quantity regulating means
7
for adjusting or regulating the throttle valve opening degree &thgr; is provided in association with the throttle valve
3
. The throttle valve actuator
7
may be comprised of, for example, a stepping motor for operating rotatively 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 an ignition timing.
An ignition coil
10
realized in the form of a transformer having primary and secondary windings. The high voltage for ignition is generated across the secondary winding of the ignition coil
10
upon every interruption of the primary current flowing through the primary winding. 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 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 determining arithmetically control parameters for various actuators employed for the combustion control of the engine
1
on the basis of information detected by various sensors (i.e., information concerning the operation state of the engine
1
) to thereby issue driving signals indicative of the control parameters to the relevant actuators.
As the control parameter signals, 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 swirl control signal B for the swirl valve actuator (swirl rate regulating means)
19
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 consideration, an accelerator pedal stroke sensor
15
is provided in association with the accelerator pedal (not shown).
The crank angle signal CA and the accelerator pedal depression stroke signal &agr; are inputted to the ECU
12
similarly to the other sensor signals.
As additional sensors, there are provided an intake pressure sensor for detecting the intake air pressure within the intake pipe of the engine
1
, an intake-air temperature sensor for detecting the temperature of the intake air and a cooling water temperature sensor for detecting the temperature of the cooling water of the engine among others, although they are not shown in the figure. Parenthetically, the intake pressure sensor also functions as an atmospheric pressure sensor when the engine
1
is stopped.
Additionally, an ISC actuator for controlling the opening degree of an ISC (Idle Speed Control) valve provided in association with a bypass passage of the intake pipe
1
a
is provided as another actuator (not shown) for the combustion control of the engine
1
.
The crank angle sensor
14
outp
Enoki Keiichi
Ohuchi Hirofumi
Dolinar Andrew M.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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