Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-02-02
2001-05-22
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S494000, C361S154000
Reexamination Certificate
active
06234150
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection control device which feeds the fuel in an amount corresponding to the operation conditions into an internal combustion engine by controlling the fuel pressure injected from an injector and the time for opening the valve body of the injector. In particular, the invention relates to a fuel injection control device which does not wastefully consume the electric power and makes it possible to sufficiently expand the dynamic range in which the amount of fuel is controlled by shortening the time for opening and closing the valve body of the injector.
2. Prior Art
In the fuel injection control device for direct cylinder injection-type internal combustion engines for vehicles, in general, the fuel having a large pressure is injected from the injector since the fuel must be injected into a cylinder in which the pressure is elevated during the compression stroke.
In the fuel injection control device of this type, therefore, it is desired to drive the injector depending upon the fuel pressure since the effect of fuel pressure upon the valve body that opens and closes the injector is no longer negligible.
In the fuel injection control device of the direct cylinder injection type, further, strict limitation is imposed on the timing for injecting the fuel and a wide dynamic range is required for controlling the amount of fuel.
In order to expand the dynamic range for controlling the amount of fuel while shortening the operation time for opening and closing the valve body of the injector, therefore, there can be contrived a method of changing the operation time for opening the valve by not only variably setting the fuel pressure but also variably setting the over-excitation period in the initial operation for opening the valve body depending upon the fuel pressure.
A device which controls the over-excitation period at the time of opening the valve depending upon the fuel pressure and controls the holding current after the valve body has moved up to the fully opened position, has been concretely disclosed in the prior art (Japanese Patent Application No. 112014/1999) filed by the present applicant.
That is, in variably setting the over-excitation period depending upon the fuel pressure, when the fuel pressure is high, the time for opening the valve body is minimized by setting an over-excitation period for flowing a relatively large exciting current required for opening the valve body of the injector.
When the fuel pressure is low, the over-excitation period for opening the valve is set to a required shortest period to suppress an excess of exciting current at the time of opening the valve. At the time of closing the valve, the valve is closed during the period in which the holding current is flowing after the over-excitation period.
This makes it possible to maintain a maximum fuel control amount during the high fuel pressure and to set a minimum fuel control amount to a small value during the low fuel pressure, expanding the dynamic range for controlling the amount of fuel inclusive of varying the fuel pressure.
Here, the valve body of the injector receives not only the resilient force of the spring but also the reaction (force in the direction for closing the valve) that varies depending upon the fuel pressure. In order to maintain the valve opened overcoming the reaction due to the high fuel pressure, therefore, the holding current is set to a value for producing a sufficiently large suction force compatible with the reaction corresponding to a high fuel pressure.
When the fuel pressure is low, however, a small reaction acts upon the valve body of the injector. Therefore, the holding current that is set to cope with the high fuel pressure, becomes too great.
In a state where the holding current is too great, when the valve body is closed from a state where the holding current is flowing, the operation for closing the valve starts from the over-excited state. Despite the exciting current is shut off, therefore, an extended period of time is required until the residual magnetic flux (force for maintaining the valve opened) of the electromagnetic coil extinguishes, making it difficult to quickly close the valve.
The above-mentioned prior art will now be concretely described with reference to
FIGS. 3
to
5
.
FIG. 3
is a functional block diagram illustrating a fuel injection control device which variably sets the over-excitation period depending upon the fuel pressure.
In
FIG. 3
, an injection control means
1
comprises an ECU (electronic control unit) which constitutes a main body of the fuel injection control device.
The injection control means
1
includes an injector
2
, various sensors
3
and a fuel pressure regulator means
4
, and controls the injector
2
depending upon the operation conditions to inject the fuel in a proper amount.
The injector
2
has a valve body opened and closed by an electromagnetic coil and a spring, and injects the fuel of a predetermined amount into an internal combustion engine being controlled by the injection control means
1
.
The valve body of the injector
2
, the electromagnetic coil for opening the valve body and the spring for closing the valve body will be described later with reference to FIG.
4
.
When not energized, the valve body of the injector
2
is closed by the urging force of the spring. When a current is supplied to the electromagnetic coil, the valve body of the injector
2
is opened overcoming the urging force of the spring.
As described above, further, the valve body of the injector
2
receives the reaction in the direction of closing the valve due to the fuel pressure.
Various sensors
3
include, for example, an intake air amount sensor for detecting the amount Qa of the air taken in by the internal combustion engine, a rotational speed sensor for detecting the rotational speed Ne of the engine, and a fuel pressure sensor for detecting the pressure Pf of the fuel injected from the injector
2
. The sensors
3
detect the operation conditions of the internal combustion engine and send signals to the injection control means
1
.
The fuel pressure regulator means
4
adjusts the pressure Pf of the fuel that is to be injected from the injector
2
.
An injector drive means
5
excites the electromagnetic coil to open the valve body of the injector
2
. Here, the injector drive means
5
is included in the injection control means
1
. The injector drive means
5
, however, may be provided on the outer side of the injection control means
1
.
The injection control means
1
further includes a fuel pressure control unit
11
, an exciting current control unit
12
, an injection timer
13
, an over-excitation timer
14
, an over-excitation period control unit, and a holding current control unit
16
.
The fuel pressure control unit
11
in the injection control means
1
operates a target fuel pressure based on the operation conditions and controls the fuel pressure regulator means
4
depending on the target fuel pressure. Then, the fuel pressure regulator means
4
feeds a required fuel pressure Pf that complies with the operation conditions to the injector
2
.
The exciting current control unit
12
controls the injection timer
13
and the over-excitation timer
14
depending upon the operation conditions and the fuel pressure Pf, controls the exciting current i fed to the electromagnetic coil and the excitation time through the injector drive means
5
, and controls the time for opening the valve of the injector
2
.
The injection timer
13
produces an injection pulse J corresponding to the time for opening the valve body of the injector
2
.
The over-excitation timer
14
produces an over-excitation pulse E corresponding to the over-excitation period in the initial period of time for opening the valve body.
The over-excitation period control means
15
variably sets the setpoint value of the over-excitation timer
14
depending on the fuel pressure Pf, and adjusts the over-excitation period for feeding a large over-exciting cu
Mitsubishi Denki & Kabushiki Kaisha
Solis Erick
Sughrue Mion Zinn Macpeak & Seas, PLLC
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