Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-12-22
2001-07-10
Kwon, John (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S478000, C701S105000
Reexamination Certificate
active
06257205
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a system for controlling a fuel injector for an internal combustion engine including a controller in communication with a current driver connected to the injector.
BACKGROUND ART
An internal combustion engine includes an engine block defining a plurality of cylinders, with an injector located at each cylinder. Fuel injectors are fed by one or more, high or low pressure pumps, as is well known in the art of fuel injection systems. The use of the electronically controlled fuel injector has become widespread. This type of fuel injector is in communication with the engine controller, and the engine controller generates a command signal to demand the initiation of the injection event. In response to the command signal, a current driver connected to an injector supplies current. Because fuel injection control strategies are complex, sometimes a sensing element is used to provide a signal indicative of the injector current during fuel injection.
A control circuit monitors the current detected by the sensing element, and controls the current driver in accordance with the injection strategy. Monitoring the current through the sensing element allows, for example, detection of the current inflection that occurs as the injector opens. Further, for example, monitoring the injector current allows the use of an injection control strategy in which a full current drive is used to open the injector, but then a pulse width modulated drive signal is used to maintain the injector in the open state. Although the full strength drive signal is needed to open the injector, the pulse width modulated signal through the bulk of the injection event has is been found to reduce power dissipation.
Many times, different injectors require slightly different control strategies in order to provide acceptable performance. For example, the inflection in the injector current that is known to indicate that the injector has opened may have different characteristics for different injectors. For example, voltage levels near the inflection point may vary from injector to injector, and particularly from manufacturer to manufacturer. Further, for example, due to the construction of the injector, different injectors may require different duty cycles for the pulse width modulated portion of the injector drive signal. In an existing fuel injection control systems and drive circuits, changing an injector means that the drive circuitry hardware must be modified so as to be suitable for the characteristics of the new injector. Further, aside from current detection, existing control systems do not have much functionality besides direct current sensing.
For the foregoing reasons, there is a need for a system for controlling a fuel injector that may be made to accommodate different injectors having different performance characteristics with less difficulty than the systems and drive circuits existing today, and that has added functionality compared to the existing systems.
DISCLOSURE OF INVENTION
It is, therefore, an object of the present invention to provide a system for controlling a fuel injector including programmable control logic configured to provide a threshold signal indicative of a threshold current for the injector with the control logic being programmable to allow selection of the threshold current for the particular injector.
It is another object of the present invention to provide a system for controlling a fuel injector including comparator and logic circuits, and control logic configured to receive and process control signals from the logic circuit to determine an injection timing signal.
In carrying out at least one of the above objects, a system for controlling a fuel injector in accordance with an injection control strategy for an internal combustion engine is provided. The engine includes a controller in communication with a current driver connected to the injector. The controller commands injection by generating a command signal. The current driver is connected to a sensing element that provides an injector signal indicative of the injector current. The system comprises programmable control logic and a comparator circuit. The programmable control logic is configured to provide a threshold signal indicative of a threshold current for the injector. The control logic is programmable to allow selection of the threshold current. The comparator circuit includes a comparator that receives and compares the injector signal to the threshold signal. The comparator provides an output signal based on the comparison to allow the injector to be controlled based on the comparison.
In a preferred embodiment, the system further comprises a digital-to-analog converter receiving a plurality of digital signals from the controller. The controller includes the programmable control logic for determining the plurality of digital signals. The converter has an analog output for providing the threshold signal as an analog voltage.
In some embodiments, the comparator circuit includes a detection portion for detecting an inflection in the injector current. The programmable control logic provides a first threshold signal indicative of an upper characteristic threshold current for the injector and a second threshold signal indicative of a lower characteristic threshold current for the injector. The detection portion comprises a first comparator and a second comparator. The first comparator receives and compares the injector signal to the first threshold signal, and provides an output based on the comparison. The second comparator receives and compares the injector signal to the second threshold signal, and provides an output based on the comparison.
In some embodiments, the comparator circuit includes a modulation portion for modulating the injector current. The programmable control logic provides an upper limit threshold signal indicative of an upper limit threshold current for the injector and a lower limit threshold signal indicative of a lower limit threshold current for the injector. The modulation portion comprises a first comparator and a second comparator. The first comparator receives and compares the injector signal to the upper limit threshold signal, and provides an output based on the comparison. The second comparator receives and compares the injector signal to the lower limit threshold signal, and provides an output based on the comparison.
Further, in carrying out at least one of the above objects, an internal combustion engine including a fuel injector and an engine controller for controlling the engine is provided. The engine controller controls the fuel injector in accordance with an injection control strategy. The controller is in communication with a current driver connected to the injector, and the controller commands injection by generating a command signal. The current driver is connected to a sensing element that provides an injector signal indicative of the injector current. The engine further comprises programmable control logic and a comparator circuit. The control logic is configured to provide a threshold signal indicative of a threshold current for the injector. The control logic is programmable to allow selection of the threshold current. The comparator circuit includes a comparator that receives and compares the injector signal to the threshold signal and provides an output signal based on the comparison to allow the injector to be controlled based on the comparison.
Further, in carrying out at least one of the above objects, a method for controlling a fuel injector in accordance with an injection control strategy for an internal combustion engine is provided. The method comprises selecting a threshold current for the injector, and programming control logic to provide a threshold signal indicative of the threshold current for the injector. The control logic is programmable to allow selection of the threshold current. The method further comprises comparing the injector signal to the threshold signal, and controlling the injector based on the comparison.
Further
Calvas George Tom
McCarthy Robert J.
Ford Global Technologies Inc.
Kwon John
Stec Jennifer
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