Internal-combustion engines – Combustion chamber means having fuel injection only – Having a particular relationship between injection and...
Reexamination Certificate
2000-05-23
2001-01-09
Kwon, John (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Having a particular relationship between injection and...
C123S478000, C701S104000
Reexamination Certificate
active
06170459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection control assembly for a cylinder-injected engine for controlling fuel injection based on a mean fuel pressure acting on an injector, and in particular relates to a fuel injection control assembly for a cylinder-injected engine in which reliability is improved by calculating the mean fuel pressure to a high precision and ensuring that control and calculation track changes in the fuel pressure.
2. Description of the Related Art
Cylinder-injected engines in which an injector is disposed in a combustion chamber of an engine cylinder and fuel is injected directly into the combustion chamber are well known as referenced by Japanese Patent Laid-Open No. HEI 11-62676 and Japanese Patent Laid-Open No. HEI 11-153054, etc.
For example, the fuel injection control assembly for a cylinder-injected engine disclosed in Japanese Patent Laid-Open No. HEI 11-62676 includes a mean fuel pressure computing means for calculating the mean fuel pressure from weighted means of fuel pressure detected at times other than when the injector is injecting fuel, and correcting the length of an injection pulse which is output to the injector based on the mean fuel pressure.
The fuel injection control assembly for a cylinder-injected engine disclosed in Japanese Patent Laid-Open No. HEI 11-153054 detects fuel pressure at predetermined intervals (or in synchrony with a rotational angle of the engine) at times other than when the injector is injecting fuel.
FIG. 12
is a structural diagram schematically showing a generic fuel injection control assembly for a cylinder-injected engine.
In
FIG. 12
, injectors IF are disposed in each cylinder of an engine
1
, the injectors IF injecting fuel directly into a combustion chamber in each cylinder.
Various sensors
2
for detecting running states and a fuel pressure sensor
12
are disposed in the engine
1
. The various sensors
2
include a conventional airflow sensor, throttle sensor, crank angle sensor, etc.
Running information from the various sensors
2
and fuel pressure information PF from the fuel pressure sensor
12
are input into an electronic control unit (ECU)
20
. The injectors
1
F have electromagnetic solenoids activated by an injection pulse signal J from the ECU
20
, the injectors
1
F being opened by passing current through the solenoids.
Fuel supplied to the injectors
1
F is drawn from a fuel tank
3
and adjusted to a target fuel pressure PFo in a high-pressure pipe
8
. Thus, an amount of fuel proportional to the duration of the injection pulse signal J (the injection pulse duration) is injected by the injectors
1
F.
Intake air is distributed to each cylinder of the engine
1
by means of an air supply pipe (not shown). An air filter, the airflow sensor, a throttle valve, a surge tank, and an intake manifold are disposed in the air supply pipe in that order from an upstream end.
Fuel (such as gasoline) in the fuel tank
3
is drawn into a low-pressure pump
4
driven by a motor
4
M. Low-pressure fuel discharged by the low-pressure pump
4
is supplied to a high-pressure pump
7
via a fuel filter
5
and a low-pressure pipe
6
.
A low-pressure return pipe
6
A having a low-pressure regulator
9
disposed therein branches from the low-pressure pipe
6
, returning to the fuel tank
3
.
The high-pressure fuel pump
7
is driven by the engine
1
, the rotational frequency of the high-pressure fuel pump
7
corresponding to the rotational frequency of the engine
1
.
FIG. 13
is a characteristic graph showing the relationship between engine rotational frequency Ne and the discharge cycle TP of the high-pressure pump
7
. Because the rotational frequency of the high-pressure pump
7
is proportional to the rotational frequency Ne of the engine, the discharge cycle TP of the high-pressure pump
7
is shortened as the engine rotational frequency Ne increases, as shown in FIG.
13
.
In
FIG. 12
, high-pressure fuel discharged from the high-pressure pump
7
is supplied to the injectors
1
F via the high-pressure pipe
8
. A high-pressure return pipe
8
A having a high-pressure regulator
10
disposed therein branches from the high-pressure pipe
8
, a downstream end of the high-pressure return pipe
8
A converging with the low-pressure pipe
6
and the low-pressure return pipe
6
A.
The low-pressure regulator
9
adjusts the amount of fuel returning to the fuel tank
3
from the low-pressure return pipe
6
A. The pressure of fuel supplied by the low-pressure pump
4
to the high-pressure pump
7
is adjusted to a predetermined low pressure depending on the amount of fuel returned by the low-pressure regulator
9
.
The high-pressure regulator
10
is driven by an excitation current Ri (a control signal) supplied by the ECU
20
, and adjusts the amount of fuel returned to the low-pressure return pipe
6
A, and adjusts the actual fuel pressure PF acting on the injectors
1
F to the target fuel pressure PFo.
In other words, the high-pressure regulator
10
returns fuel from the downstream side of the high-pressure fuel pump
7
to the low-pressure side by continuously changing the cross-sectional area of an opening of the high-pressure return pipe
8
A in response to the excitation current Ri.
The fuel pressure sensor
12
detects the fuel pressure PF in the high-pressure pipe
8
.
The ECU
20
not only receives fuel pressure information PF from the fuel pressure sensor
12
, but also receives information about the running state from the various sensors
2
, performing predetermined computational processes and outputting a calculated control signal to various actuators.
For example, the ECU
20
seeks the mean fuel pressure PFm from the fuel pressure PF detected by the fuel pressure sensor
12
and outputs a control signal which will make the mean fuel pressure PFm match the target fuel pressure PFo.
Next, the mean fuel pressure computing operation according to a conventional fuel injection control assembly for a cylinder-injected engine.
FIG. 14
is a timing chart showing the operation of the fuel pressure detecting process and the averaging process according to a conventional fuel injection control assembly for a cylinder-injected engine.
FIG. 14
shows changes in the injection pulse signal J and the fuel pressure PF over time. In
FIG. 14
, TC is the calculation cycle for the mean fuel pressure PFm (see dotted chain line) by the ECU
20
, and TJ is the length of the injection pulse signal J. t is the fuel pressure detection cycle of the ECU
20
, the fuel pressure PF being detected once in each cycle t.
In the waveform of the fuel pressure PF, the white circles represent detected values of fuel pressure PF used to compute the mean, and the black circles represent detected values of fuel pressure PF not used to compute the mean. Because the fuel pressure PF decreases over the time period of the injection pulse duration TJ (when fuel is being injected), the fuel pressure PF detected during this time period (black circles) is eliminated from the calculation of the mean fuel pressure PFm. Moreover, the broken line represents the changes in fuel pressure during fuel shutoff.
First, when the injectors
1
F are activated by the injection pulse signal J, fuel is injected by the injectors
1
F, and the fuel pressure PF changes as indicated by the solid line in FIG.
14
. Moreover, when the injection pulse duration TJ is zero (a fuel shutoff state), the fuel pressure PF increases in response to the discharge operation of the high-pressure fuel pump
7
as indicated by the broken line in FIG.
14
.
At that time, in the calculation of the mean fuel pressure PFm, the calculation cycle TC is set in response to the discharge cycle TP of the high-pressure pump
7
, and the mean fuel pressure PFm is only calculated from the fuel pressure (PF) detected at time periods other than the fuel injection time period (see white circles).
Consequently, when the injection pulse duration TJ is long, the number of times that fuel pressure PF is detected is insufficient, making cal
Hisato Hiromichi
Ohuchi Hirofumi
Ono Takahiko
Kwon John
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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