Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2000-06-28
2001-05-08
Kwon, John (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S305000
Reexamination Certificate
active
06227163
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection control system for an internal combustion engine of cylinder injection type (also called direct injection type), which system is designed to inject directly a fuel into a plurality of cylinder chambers of the engine for allowing a fuel mixture to be burnt or combusted in a lean state in response to spark ignition. More particularly, the invention is concerned with a fuel injection control system for an engine of cylinder injection type which system is so arranged as to suppress occurrence of the so-called torque shock upon changeover of combustion modes while protecting combustion performance from degradation to thereby enhance drivability of a motor vehicle equipped with the engine.
2. Description of Related Art
Heretofore, there has been well known in the art such a cylinder injection type internal combustion engine in which the fuel injectors are disposed in the individual cylinders, respectively, for injecting directly the fuel into the combustion chambers as well as the fuel injection control system therefor. By way of example, reference is to be made to Japanese Patent Application Laid-Open No. 312396/1996 (JP-A-8-312396).
In the cylinder injection type internal combustion engine, torque generated by the engine will change in dependence on the air-fuel ratio even in the state where the throttle valve is held at a same opening degree. Accordingly, it is necessary to set optimally the combustion parameters such as the ignition timing and the fuel injection timing in dependence on the engine load and the air-fuel ratio by controlling properly the opening degree of the throttle valve and hence 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. 12
is a schematic diagram showing generally an arrangement of a conventional fuel injection control system for a cylinder injection type internal combustion engine known heretofore.
Referring to
FIG. 12
, an internal combustion engine (hereinafter also referred to as the engine)
1
is equipped with an intake pipe
1
a
for introducing the intake air into the engine 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 Qa, wherein a throttle position sensor
4
for detecting the opening degree &thgr; of the throttle valve
3
is provided in association therewith.
Installed at a downstream location within the intake pipe
1
a,
e.g., 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 association with the exhaust pipe
1
b
for detecting an actual air-fuel ratio F of the exhaust gas, which ratio ordinarily lies within a range of e.g. 10 to 50.
A throttle valve actuator
7
is provided in association with the throttle valve
3
for adjusting the opening degree &thgr; thereof. This actuator
7
may be constituted, for example, by a stepping or stepper motor which is designed for stepwise driving rotationally the throttle valve
3
to thereby adjust the rate or quantity 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 is caused to take place for igniting the air-fuel mixture charged into the combustion chamber defined within the cylinder. To this end, a distributor
9
is provided for supplying a high voltage distributively to the individual spark plugs
8
in conformance with proper ignition timing.
Further installed is an ignition coil
10
which is realized in the form of a transformer having primary and secondary windings. A high voltage required 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 engine cylinders.
The spark plug
8
, the distributor
9
, the ignition coil
10
and the ignitor
11
cooperate to constitute a so-called ignition system for igniting or firing the air-fuel mixture within the individual cylinders of the engine
1
.
Each of the engine cylinders is equipped with a fuel injector
13
for injecting directly the fuel into the cylinder chamber. A crank angle sensor
14
for generating a crank angle signal CA is provided in association with the crank shaft which is driven rotationally by the engine
1
.
The crank angle sensor
14
is designed to output a pulse signal corresponding to the engine rotation number or engine speed (rpm) as the crank angle signal CA and serves also as an engine rotation sensor (or engine speed sensor), as is well known in the art. Further, the crank angle signal CA contains pulses having edges which represent the reference crank angles for the individual cylinders, respectively, wherein the reference crank angles are used for arithmetically determining various control timings for operation of the engine
1
.
An accelerator pedal (not shown) manipulated by an operator or driver is provided with an accelerator pedal position sensor
15
for detecting the accelerator pedal stroke &agr;.
An exhaust gas recirculation passage (hereinafter also referred to as the EGR passage)
16
is provided between the exhaust pipe
1
b
and the surge tank
5
for the purpose of recirculating a part of the exhaust gas into the intake pipe
1
a,
wherein a stepping-motor-driven type EGR regulating valve
17
(constituting a part of the EGR regulating means) is provided in association with the EGR passage
16
for regulating the amount or quantity of the exhaust gas recirculated to the intake pipe. This quantity is referred to as the EGR quantity.
An ECU (Electronic Control Unit)
12
which is in charge of controlling the engine system as a whole is comprised of a microcomputer for arithmetically determining control quantities or parameters for various actuators which are installed for controlling the fuel combustion in the engine
1
on the basis of information detected by various types of sensors (i.e., information concerning the operation states of the engine
1
), to thereby issue driving signals indicative of control quantities to the relevant actuators.
As the control signals, there may be mentioned an intake-air quantity control signal A for the throttle actuator
7
, an ignition timing signal G for the ignitor
11
(and hence for the ignition system), an injection pulse signal J for each of the fuel injector
13
, an EGR control signal E for the EGR regulating valve
17
and others.
As other sensors not shown in the drawings, there may be mentioned an intake air pressure sensor disposed within the intake manifold of the engine for detecting the intake air pressure of the engine
1
(also referred to as the boost pressure Pb which represents the intra-cylinder intake air quantity), a water temperature sensor for detecting the temperature of cooling water for the engine
1
and the like.
In general, the engine
1
has different types of combustion modes which include a homogeneous combustion mode in which the fuel injection is carried out during the suction stroke and a stratified combustion mode in which the fuel injection is carried out during the compression stroke.
FIG. 13
is a view for illustrating the combustion modes (or fuel injec
Enoki Keiichi
Nishiyama Ryoji
Ohuchi Hirofumi
Kwon John
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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