Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2002-09-27
2003-04-22
Mohanty, Bibhu (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S492000, C701S105000, C701S115000
Reexamination Certificate
active
06550457
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electronic fuel injection control apparatus for controlling a quantity of fuel injected from an injector into an internal combustion engine for driving a vehicle.
BACKGROUND OF THE INVENTION
When an injector(an electromagnetic fuel injection valve), which is mounted on an intake pipe of an engine for example, is used as means for supplying fuel to an internal combustion engine, an injection quantity of the fuel from the injector is controlled by an electronic fuel injection control apparatus (EFI).
Since the injection quantity of the fuel from the injector is required to be determined such that an air-fuel ratio of a mixture supplied to the engine is kept within a predetermined range, it is necessary to estimate an amount of intake air which is sucked into a cylinder during an intake stroke when the fuel injection quantity is determined.
As a method for estimating the amount of intake air which is sucked into the cylinder during the intake stroke of a four-cycle internal combustion engine, a speed-density system has been widely adopted. In the speed-density system which comprises an intake pressure sensor for detecting a pressure at a downstream side of a throttle valve within the intake pipe as an intake pipe pressure (a negative pressure) and speed detecting means for detecting a rotational speed of the engine, the intake air amount is estimated from the intake pipe pressure detected by the intake pressure sensor, the rotational speed of the engine, and an volumetric efficiency of the engine, then the fuel injection quantity to be required is arithmetically operated for obtaining a predetermined air-fuel ratio based on the intake air amount.
The injector opens its valve when a drive current is provided thereto, and injects the fuel provided from a fuel pump into the intake pipe. Generally, a pressure of fuel provided to an injector is kept constantly by a pressure regulator, so that the injection quantity of the fuel from the injector is determined in accordance with a time (a fuel injection time) during which the injector valve is opened. Therefore, in the electronic fuel injection control apparatus, the fuel injection quantity is arithmetically operated as a fuel injection time, then the injector is driven so that the fuel is injected over the arithmetical operation period of time for fuel injection.
FIG. 12
, which relates to a four-cycle single cylinder internal combustion engine, shows a change in an intake pipe pressure and a change in an opening degree of the throttle valve relative to a time t when the engine is accelerated, and also shows a change in a fuel injection command signal provided to the injector relative to a time t. In
FIG. 12
, each of A
1
to A
4
denotes a period of time during which the engine is on the intake stroke, and Vi
1
to Vi
4
respectively denote fuel injection command signals provided to an injector drive circuit at a timing ti
1
to ti
4
of starting the fuel injection during the intake strokes A
1
to A
4
. Width of the injection command signal corresponds to a fuel injection time. The injector drive circuit supplies the drive current to the injector as long as the injection command signals are provided, and then allows the fuel to be injected from the injector.
An actual injector opens its valve to start the fuel injection when the drive current exceeds a predetermined valve opening current value, so that a time width of the injection command signal is not exactly equal to the fuel injection time. However, in this specification, the time width of the injection command signal is taken as the fuel injection time, for the sake of simplicity.
As shown in
FIG. 12A
, an intake pipe pressure of the four-cycle single cylinder internal combustion engine significantly decreases during the intake stroke, and the intake pipe pressure becomes a minimum at the end of the intake stroke. In an example shown in
FIG. 12A
, respective minimum values of pressures within the intake pipe during the intake strokes A
1
to A
4
are P
1
to P
4
, respectively.
In the example shown in
FIG. 12
, an operation for accelerating the engine is conducted immediately before starting an intake stroke A
3
, wherein an opening degree of the throttle valve is increased. At a state before conducting the accelerating operation, the opening degree of the throttle valve is kept substantially constant. In this case, minimum values of the intake pipe pressure are substantially constant as represented by P
1
and P
2
, provided that a load does not change. On the contrary, when the accelerating operation is conducted and the opening degree of the throttle valve increases, the intake air amount also increases. Therefore, a minimum value of the intake pipe pressure becomes higher with increase in the opening degree of the throttle valve, as represented by P
3
and P
4
.
FIG. 13
, which relates to the four-cycle single cylinder internal combustion engine, shows changes in an intake pipe pressure and in an opening degree of the throttle valve relative to a time t when the engine is decelerated, and also shows a change in a fuel injection command signal provided to the injector relative to a time t. In
FIG. 13
, each of A
1
to A
4
denotes a period of time during which the engine is on the intake stroke. And Vi
1
to Vi
4
respectively denote fuel injection command signals provided to the injector drive circuit at a timing ti
1
to ti
4
of starting the fuel injection during the intake strokes A
1
to A
4
.
In an example shown in
FIG. 13
, an operation for decelerating the engine is conducted immediately after completing an intake stroke A
2
, wherein an opening degree of the throttle valve is decreased. At a state before conducting the decelerating operation, the opening degree of the throttle valve is kept substantially constant. In this case, minimum values of the intake pipe pressure are substantially constant, provided that a load does not change. However, when the decelerating operation is conducted and the opening degree of the throttle valve decreases, the intake air amount also decreases. Therefore, a minimum value of the intake pipe pressure becomes lower with decrease in the opening degree of the throttle valve, as represented by P
3
, P
4
, and P
5
(an absolute value of the negative pressure will become larger).
In an speed-density type of EFI internal combustion engine, a basic injection time for injecting fuel at each intake stroke is arithmetically operated based on an intake air amount, which has been estimated from an intake pipe pressure and a rotational speed detected during the previous intake stroke, and various control conditions. In a single cylinder internal combustion engine or in a multi-cylinder internal combustion engine which has an intake pipe mounted on each cylinder, wherein an intake pipe pressure has a minimum value, the minimum value detected during the previous intake stroke is used as a value of the intake pipe pressure to be used for estimating the intake air amount.
In an example shown in
FIG. 12
for example, a basic injection time for injecting fuel at an intake stroke A
2
is arithmetically operated from an intake air amount which has been estimated from a minimum value P
1
of an intake pipe pressure and a rotational speed detected during an intake stroke A
1
. Similarly, basic injection times for injecting fuel at intake strokes A
3
and A
4
(injection times at a steady operation) respectively are arithmetically operated from respective intake air amounts which have been estimated from minimum values P
2
and P
3
of pressures within an intake pipe and respective rotational speeds detected during intake strokes A
2
and A
3
. The same is true of an example shown in FIG.
13
.
When an opening degree of the throttle valve is maintained substantially constant or when an opening degree of the throttle valve is gradually changed, a difference between an intake air amount during the previous intake stroke which has been used for arithmetically operating the basic inject
Kishibata Kazuyoshi
Kitagawa Yuichi
Sato Hiroyasu
Kokusan Denki Co. Ltd.
Mohanty Bibhu
Pearne & Gordon LLP
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