TITLE

A METHOD OF CONTROLLING A FUEL INJECTION SYSTEM OF AN INTERNAL COMBUSTION ENGINE WHOSE FUEL

INJECTOR IS FED BY GRAVITY

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:

FIELD OF INVENTION:

The present invention relates to a method of controlling fuel injection system for an internal combustion engine. More particularly, the present invention relates to a method of controlling gasoline fuel injection system.

BACKGROUND OF THE INVENTION:

Generally, spark ignited engines are supplied with fuel through variety of means. One of the most economic modes of fuel injection is Electronic Fuel Injection (EFI) system.

The EFI system currently includes a fuel tank, a fuel pump, an Electronic Control Unit (ECU) and a fuel injector that can operate between for example, 0 to 100 Hz with respect to the engine speed.

Generally, EFI systems include the pump to create the pressure required to achieve appropriate atomization at the fuel injector. The atomization is important because it ensures proper mixture of fuel with the air. Hence, the fuel injector is required to ensure complete combustion in the internal combustion engine. However, it may be perceived that for smaller engines, such high pressure pump may not be required.

SUMMARY OF THE INVENTION:

In one aspect of the present invention, a method of controlling a gravity-fed fuel injection system is provided. The method includes the step of operating at least one fuel injector at a predetermined frequency, characterized in that, the frequency of operation of the at least one fuel injector is independent of engine speed. In one embodiment of the present invention, the frequency of operation for the at least one fuel injector is a constant. While operating the at least one fuel injector at the predetermined frequency, the step comprises fixing ON and OFF duration for each operation of the at least one fuel injector. In an embodiment, the method further includes the steps of determining number of pulses that are required for fuel injection for a single four stroke cycle of the internal combustion engine, and operating the at least one fuel injector with the determined number of pulses within the single four stroke cycle.

In another aspect of the present invention, an Electronic Control Unit (ECU) for a gravity-fed fuel injection system is provided. The ECU is adapted for operating the at least one fuel injector at a predetermined frequency, characterized in that, the frequency of operation of the at least one fuel injection is independent of the engine speed. The ECU is further adapted for determining number of pulses of fuel injection for a single four stroke cycle of the internal combustion engine and for operating the at least one fuel injector with the determined number of pulses within the single four stroke cycle.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 illustrates a gravity fed electronic fuel injection system in accordance with an embodiment of the present invention;

Figure 2 is a graph illustrating operating frequency of at least one fuel injector in accordance with an embodiment of the present invention;

Figure 3 is a flowchart illustrating a method of controlling a gravity fed fuel injection system in accordance with an embodiment of the present invention; and

Figure 4 is a block diagram illustrating an Electronic Control Unit (ECU) for controlling a gravity fed fuel injection system in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE DRAWINGS:

Figure 1 illustrates a gravity fed fuel injection system 100 in accordance with an embodiment of the present invention.

The fuel injection system 100 includes a fuel reservoir 102, a connecting pipe 104, a fuel injector 106 and an Electronic Control Unit (ECU) 108. It may be noted that, unlike most electronic fuel injection systems, the fuel injection system 100 does not include any pump to pressurize the fuel that is to be supplied to the fuel injector 106. The fuel injector 106 is adapted to meter, atomize and provide a fine spray of the fuel at a combustion cylinder of the internal combustion engine. Some of the parameters of the fuel injector 106 that are controlled by the ECU 108, in accordance with various embodiments of the present invention include operating frequency of the fuel injector 106, fuel injection timing, number of pulses per fuel injection window, and duty cycle of the fuel injector 106. For example, the duty cycle may refer to proposition of ON or opening duration of the fuel injector 106 and OFF or closed duration. In the same example, the duty cycle may be represented in percentage.

Figure 2 is a graph 200 illustrating operating frequency of the fuel injector 106 in accordance with an embodiment of the present invention.

The graph 200 includes a Y-axis 204 representing volts (V) and an X-axis 206 represents time (t) in seconds.

Duration taken for ON and OFF event combined to form one cycle or pulse of fuel injection is represented as %'. The cycles per unit time or hertz (Hz), derived as "l/ti". provides operating frequency of the fuel injector 106. In other words, the operating frequency may refer to possible number of fuel injection events per second. In accordance with the various embodiments of the present invention, the operating frequency of the fuel injector 106 is kept constant and predetermined irrespective of any change in engine speed. If the operating frequency of the fuel injector 106 is 100Hz, then time taken for 'single fuel injection event' is 10 millisecond (ms). It may be noted that, the operating frequency of the fuel injector 106 is fixed or programmed in the ECU 108 that controls the operation of the fuel injector 106. In one or more exemplary embodiments, the operating frequency of the fuel injector 106 is greater than speed of the internal combustion engine. In a four stroke cycle (shown as I, II, and III in figure 2); fuel injection windows (210, 212, and 214) represent duration of fuel injection in respective four stroke cycles. For illustration, a single four stroke cycle may include two complete rotations of crank shaft (not shown in the figure) attached to the internal combustion engine. In each of the fuel injection windows (210, 212, and 214), the number of pulses (208) are varied. For example, in a first fuel injection window 210, the number of pulses (208) is four, in a second fuel injection window 212, the number of pulses (208) is three, and in a third fuel injection window 214, the number of pulses (208) is five.

It may be observed from the figure 2 that the operating frequency of the fuel injector 106 is kept constant and the number of pulses to open and close the injector is varied based upon the engine speed and load. In other words, tl is kept constant for the windows 210, 212 and 214.

Further, in an embodiment, it can be observed from a fuel injection event 202 that the ON and OFF durations of the fuel injection are equal. Hence, duty cycle of fuel injection may be approximately 50%. The proposition of the ON and OFF duration is represented in percentage as the duty cycle of the fuel injection. In accordance with various embodiments of the present invention, the duty cycle is kept constant. In other embodiments the duty cycle may vary depending upon the engine speed and load.

Figure 3 is a flowchart 300 illustrating a method of controlling the gravity fed electronic fuel injection system 100 in accordance with an embodiment of the present invention.

The method is initiated in step 302. In step 304, a predetermined operating frequency of the fuel injector 106 is fetched, for example, from memory of the ECU 108. The operating frequency of the fuel injector 106 is independent of the speed of the internal combustion engine. For example, even when the speed of the internal combustion varies, the operating frequency of the fuel injector 106 is kept constant. Hence, the operating frequency is independent of the speed of the internal combustion engine. Further, in an exemplary embodiment, the operating frequency of the fuel injector 106 is greater than speed of the internal combustion engine.

In step 306, the number of pulses that are required for fuel injection for a single four stroke cycle of the internal combustion engine is determined. In accordance with various embodiments of the present invention, the number of pulses of fuel injection is varied. In step 308, the fuel injector 106 with the determined number of pulses within the single four stroke cycle is operated. In step 310, ON and OFF duration for each cycle of operation of the fuel injector is fixed. In an embodiment of the present disclosure, proposition of the ON and OFF duration of the fuel injector may represent a duty cycle of fuel injection represented in percentage and is not varied.

Figure 4 is a block diagram illustrating an Electronic Control Unit (ECU) for controlling a gravity fed fuel injection system in accordance with an embodiment of the present invention.

In an embodiment of the present invention, the ECU 108 is an embedded system. The ECU 108 includes a memory 402, a microprocessor 404, a bus 406, an Input and Output (I/O) port 408, and a communication interface 410.

In an embodiment, the ECU 108 is configured to control the fuel injection system 200 to meet the fuel demand of an internal combustion engine 428. More particularly, the ECU 108 controls the fuel injector 106 which may act as both the fuel injector and a positive displacement pump. In an exemplary embodiment, the ECU 108 is adapted to control operating parameters of the fuel injection system 200 such as operating frequency, flow rate, pulses, duty cycle of fuel injection and so on and so forth. The ECU 108 may also include an oscillator (not shown in the figure) or a system clock, a Power Supply Module (PSM) (not shown in the figure), an analog signal conditioner and a digital signal conditioner.

In another embodiment, the ECU 108 has a set of predefined instructions installed in the memory 402. For example, the memory 402 can constitute one or more of Read Only Memory (ROM), Random Access Memory (RAM), Electrically Erasable and Programmable Memory (EEPROM,) and a Non-Volatile RAM. The set of predefined instructions which are stored in the memory 402 are executed with the help of a machine such as the microprocessor 404 or a microcontroller. Hence, the ECU 108, in accordance with the present embodiment is adapted to perform the predefined instructions including operation of the fuel injector 106 at a predetermined frequency, wherein the frequency of operation of the fuel injector 106 is independent of the speed of the internal combustion engine 428. In another embodiment, the ECU 108 in association with the microprocessor 404 is capable of determining number of pulses that are required for fuel injection for a single four stroke cycle of the internal combustion engine 428, and operating the fuel injector 106 with the determined number of pulses within the single four stroke cycle. In accordance with an embodiment of the present invention, output of an intake manifold pressure sensor 416, an intake manifold temperature sensor 414, an engine speed sensor 418, and a crankshaft position sensor 420 are connected to the ECU 108. In other words, the ECU 108 may take multiple inputs including pressure, temperature, engine speed, crankshaft position, load requirements, and other parameters associated with the internal combustion and control the fuel injector 106 in accordance with the set of predefined instructions including operating the fuel injector 106 at a predetermined frequency that is independent of engine speed.

It may be apparent to a person skilled in the art to realize certain minor modifications in light of the content disclosed in various embodiments of the present invention. The scope of the present invention shall be interpreted only with the claims appended herein.