Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2001-10-29
2003-05-13
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C073S114220, C123S478000
Reexamination Certificate
active
06561164
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to internal combustion engines having electric-actuated fuel injectors that inject fuel into combustion chambers of the engine. More particularly it relates to a system and method that uses several variables, including injector control pressure and the duration of an injector-actuation signal applied to the fuel injectors, in a process that calculates, by a mathematical formula, the quantity of fuel injected by a fuel injector during an injection, and that calibrates each fuel injector by adjustment of the formula.
BACKGROUND OF THE INVENTION
A known electronic engine control system comprises a processor-based engine controller that processes various data to develop fueling data for the engine. The fueling data represents a quantity of fuel that is to be introduced into the engine for combustion. That control system also includes an injector control module, or injector driver module, for operating fuel injectors that inject fuel into the engine in quantities corresponding to the fueling data. The fueling data is supplied to the injector control module from the engine controller, and the injector control module has its own processor for processing the supplied data to develop proper data for causing the fuel injectors to inject fuel in quantities corresponding to the fueling data calculated by the engine controller. For any one or more of various reasons that need not be discussed here, the injector control module may also make certain adjustments to the supplied data when the engine control strategy and/or injector calibration make it appropriate to do so.
The injector control module also comprises injector drivers each of which delivers an electric current signal to an electric actuator of the respective fuel injector. A fuel injector may have one or more electric actuators depending on its particular construction. The signal that is applied to a fuel injector to cause an injection of fuel is commonly referred to generically as a pulse width modulated signal. In the case of a fuel injector that has a single actuator, the actuating signal is a true pulse whose width sets the amount of time of an injection, and hence essentially determines the quantity of fuel that the fuel injector injects into the corresponding engine cylinder in consequence of that applied pulse. In the known engine controller that is being referred to, it is the injector control module that calculates the pulse width by processing the fueling data supplied to it by the engine controller.
The particular nature of the electric actuation of any particular fuel injector depends on the particular construction of the fuel injector. There is the single actuator type mentioned above. Another type of fuel injector, one for a compression-ignition internal combustion engine, comprises an intensifier piston for creating a high-pressure injection of fuel directly into an associated engine cylinder. The intensifier piston comprises a head of given end area exposed to a control fluid, oil for example, in a control chamber, and a plunger, or rod, of smaller end area exposed to liquid fuel in an injection chamber. The electric actuator comprises a spool valve that uses two electric actuators, i.e. solenoid coils, to control the introduction of pressurized control fluid into the control chamber and the draining of control fluid from the control chamber.
When an electric signal for initiating a fuel injection is applied to one of the two electric actuators for the spool valve, control fluid is introduced under pressure through one portion of the spool valve into the control chamber to downstroke the intensifier piston and cause fuel in the injection chamber to be injected under pressure from a nozzle of the fuel injector into an associated engine cylinder. The intensifier piston amplifies the pressure of the control fluid by a factor equal to the ratio of the head end area to the plunger end area to cause the amplified pressure to be applied to liquid fuel in the injection chamber. As a result, fuel is injected into a combustion chamber at a pressure substantially greater than the pressure of the control fluid.
When an electric signal for terminating the fuel injection is applied to the other electric actuator, the spool valve operates to terminate the downstroke of the intensifier piston and instead allow control fluid to drain from the control chamber through another portion of the spool valve so that the intensifier piston can then upstroke to re-charge the injection chamber with liquid fuel in preparation for the next injection.
Examples of fuel injectors having valves like those just described appear in U.S. Pat. Nos. 3,837,324; 5,460,329; 5,479,901; and 5,597,118.
Where a single electric actuator controls a fuel injector valve, the beginning of an electric pulse applied to the actuator initiates an injection, and the injection terminates when the pulse ends. The injection time is therefore set by the width, i.e. time duration, of the actual electric pulse applied to the injector actuator.
Commonly assigned U.S. Pat. No. 6,029,628 is an example of a fuel injector comprising two electric actuators that operate respective valve mechanisms. A supply valve mechanism is controlled by an electric supply valve actuator for selectively controlling flow of control fluid through a supply passage for downstroking an intensifier piston. A drain valve mechanism is controlled by an electric drain valve actuator for selectively controlling flow of control fluid through a drain passage. Each valve actuator is selectively operable independent of the other to selectively operate the respective valve mechanism independent of the other. Actuation of the supply valve mechanism while the drain valve mechanism is not being actuated initiates an injection, and the injection terminates when the drain valve mechanism is actuated.
The use of two electric signals, each applied to a respective one of the two actuators, to set the duration of a fuel injection is like that described previously for the fuel injector that has two actuators for operating a spool valve because the difference between the times at which the two actuators are actuated, rather than the time duration of an actual electric pulse, controls the duration of an injection. But the two signals in effect define a pulse width for operating the fuel injector that is equivalent to the pulse width of a single pulse signal that determines the injection time of a fuel injector that has only a single electric actuator. Hence, reference to pulse width in a generic context should be understood to include an actual pulse width of a single signal or an equivalent pulse width resulting from the use of one signal to initiate an injection and another signal to terminate the injection.
The known engine controller also contains one or more look-up tables that its processor uses to calculate the desired fueling data, which is then processed to calculate the widths of electric pulses that operate the fuel injectors. The look-up tables are derived from actual testing of fuel injectors. Fuel injectors are mapped for various combinations of values for injector control pressure and actuating signal pulse width. Each combination of values defines a corresponding value for desired fueling data. A sufficient number of combinations are needed to cover the relevant ranges of the variables, but the available size of the look-up tables ultimately determines how many combinations can actually be stored in memory of the controller.
While increasing look-up table size, and hence the number of combinations that can be stored, will endow the tables with a higher degree of resolution that may be desirable for increased fueling accuracy, the increased size of the electronic storage medium that is required to contain the stored data increases the cost of the controller. A greater amount of mapping is also required in order to obtain the greater amount of data.
A lesser number of stored combinations may decrease the resolution, and hence decrease fueling accuracy. T
Calfa Jeffrey P.
International Engine Intellectual Property Company LLC
Lukasik Susan L.
Moulis Thomas N.
Sullivan Dennis Kelly
LandOfFree
System and method for calibrating fuel injectors in an... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for calibrating fuel injectors in an..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for calibrating fuel injectors in an... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3030717