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Title:
A METHOD OF CONTROLLING A FUEL INJECTION SYSTEM AND A DEVICE THEREOF
Document Type and Number:
WIPO Patent Application WO/2015/024747
Kind Code:
A1
Abstract:
The present invention relates to a method and an ECU for controlling a gravity-fed electronic fuel injection system (200) for an internal combustion engine (628). The method includes the steps of determining engine speed and load requirements, ascertaining current phase in a four stroke cycle of combustion of the internal combustion engine (628), and positioning a start point and a stop point of a fuel injection in any of the four strokes of the internal combustion engine (628) based on the engine speed and load requirements, and the current stroke of the four stroke cycle.

Inventors:
REDDEMREDDY PRAMOD (IN)
PRADEEP RAMACHANDRA (IN)
ANANTHA PRASHANTH (DE)
Application Number:
PCT/EP2014/066333
Publication Date:
February 26, 2015
Filing Date:
July 30, 2014
Export Citation:
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Assignee:
BOSCH GMBH ROBERT (DE)
ROBERT BOSCH ENG & BUSINESS SOLUTIONS LTD (IN)
International Classes:
F02D41/20; F02D41/00; F02D41/14; F02M37/00; F02M51/02; F02M69/00
Domestic Patent References:
WO2002063155A12002-08-15
Foreign References:
US20070113829A12007-05-24
DE102008001044A12009-10-15
US20030192511A12003-10-16
DE102009046091A12011-08-18
DE19639172A11998-04-02
DE10014553A12001-10-04
EP1803916A12007-07-04
DE19844910A12000-04-06
US20070039593A12007-02-22
EP1775452A22007-04-18
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Claims:
WE CLAIM:

1. A method for controlling a gravity-fed electronic fuel injection system (200) for an internal combustion engine (628), comprising: determining at least one engine parameter of the internal combustion engine (628); ascertaining current phase in a four stroke cycle of the internal combustion engine (628); said method characterized by the step of: positioning a start point and a stop point of a fuel injection in any of the four strokes of the internal combustion engine (628) based on at least one engine parameter and the current stroke of the four stroke cycle.

2. The method in accordance with claim 1, wherein the start point is positioned at the beginning of inlet stroke of the internal combustion engine (628).

3. The method in accordance with claim 1, wherein the fuel injection duration overlaps at least partially with a suction stroke of the engine (628).

4. The method according to claim 1, comprises the step of controlling operating frequency of at least one fuel injector (206) based on at least one engine parameter.

5. An Electronic Control Unit (ECU) (208) for controlling a gravity-fed electronic fuel injection system (200) of an internal combustion engine (628), comprising: means (208) for determining at least one engine parameter of the internal combustion engine (628); means (208) for ascertaining current phase in a four stroke cycle of combustion of the internal combustion engine (628); and means (208) for positioning a start point and a stop point of a fuel injection in any of the strokes of said internal combustion engine (628), wherein the position of the start and the stop point of the fuel injection is done based on the at least one engine parameter and the current stroke of the cycle.

Description:
COMPLETE SPECIFICATION

TITLE

A METHOD OF CONTROLLING A FUEL INJECTION SYSTEM AND A DEVICE THEREOF

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 a 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 for controlling a gravity-fed electronic fuel injection system for an internal combustion engine is provided. The method includes the steps of determining at least one engine parameter of the internal combustion engine, ascertaining current phase in a four stroke cycle of the internal combustion engine, said method characterized by the step of positioning a start point and a stop point of a fuel injection in any of the four strokes of the internal combustion engine based on at least one engine parameter and the current stroke of the four stroke cycle.

In another aspect of the present invention, an Electronic Control Unit (ECU) for controlling a gravity-fed electronic fuel injection system of an internal combustion engine is provided. The ECU includes means for determining at least one engine parameter of the internal combustion engine, means for ascertaining current phase in a four stroke cycle of combustion of the internal combustion engine, and means for positioning a start point and a stop point of a fuel injection in any of the strokes of said internal combustion engine, wherein the position of the start and the stop point of the fuel injection is done based on the at least one engine parameter and the current stroke of the cycle.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 is a flow chart illustrating a method of controlling a fuel injection system for an internal combustion engine in accordance with an embodiment of the present invention;

Figure 2 illustrates a gravity-fed Electronic Fuel Injection (EFI) system utilized to achieve the method of controlling fuel injection system in accordance with an embodiment of the present invention;

Figure 3 is a graph illustrating variations of fuel injection duration over four stroke cycles in an internal combustion engine in accordance with an embodiment of the present invention;

Figure 4 is a graph illustrating variations of fuel injection timings and fuel injection duration over four stroke cycles with respect to pressure at an intake manifold in accordance with an embodiment of the present invention;

Figure 5 is a graph illustrating variation of operating frequency of a fuel injector with respect to rotational speed of an internal combustion engine in accordance with an embodiment of the present invention; and Figure 6 illustrates an Electronic Control Unit (ECU) for controlling a fuel injection system for an internal combustion engine in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS:

Figure 1 is a flow chart illustrating a method 100 for controlling a fuel injection system for an internal combustion engine in accordance with an embodiment of the present invention.

The method 100 includes a plurality of steps to control the fuel injection system for the internal combustion engine. For instance, the fuel injection system explained in reference to the present embodiment can be a gasoline fuel injection system.

The method 100 is initiated in step 102. In step 104, one or more engine parameters are determined. The engine parameters may include engine speed, torque demand and load requirements. During operation of the internal combustion engine, the engine speed and load may be varying continuously. Hence, based on the engine speed and load requirements, fuel injection is controlled. In step 106, current phase of a four stroke cycle is ascertained. The phase of the four stroke cycle at that point in time can be identified using variety of techniques. One method is to know the current position of a piston within a cylinder of the internal combustion engine. For example, the position of the piston is identified using a unit that includes a crank wheel with missing tooth, and an inductive or capacitive sensor. Such techniques may be known to person skilled in the art and hence the explanation on their working is forfeited.

In step 108, fuel injection duration is varied in accordance with the current phase of the four stroke cycle and the engine speed and load requirements. In general, it may be known to have fuel injection in the four stroke cycle timed during suction or inlet stroke of the four stroke cycle. However, in order to achieve optimal power output and to meet variety of engine speed and load requirements, adjustment to fuel injection duration may be necessary. In the present invention, the duration of fuel injection may be varied continuously over a period of time to meet the engine speed and load requirements. Further, the position of start and stop of fuel injection duration is also varied across different phases (suction, compression, ignition and exhaust) of the four stroke cycle.

Thus the invention provides complete flexibility to vary the start time of the fuel injection, to vary the stop time of the fuel injection. According to the invention, these two fuel injection timings are positioned anywhere in the four strokes of the cycle. The injection duration is also varied depending upon the engine parameters.

In this document, fuel injection timing refers to either start time of the fuel injection or stop time of the fuel injection or both.

In step 110, operating frequency of at least one fuel injector is varied based on engine speed. In an exemplary embodiment, the operating frequency of the fuel injector is varied with respect to increase in the engine speed.

The above explanation of fuel injection strategy may be adapted to any four stroke internal combustion engine. One of the advantages of the above explained method may be to achieve proper fuel atomization and flow rate without usage of a fuel injection pump in circuit of the Electronic Fuel Injection (EFI) System.

Figure 2 illustrates a gravity-fed Electronic Fuel Injection (EFI) system 200 utilized to achieve the method of controlling fuel injection system in accordance with an embodiment of the present invention.

In an embodiment of the present invention, the fuel injection system 200 includes a fuel reservoir 202, a fuel supply line 204, a fuel injector 206, and an Electronic Control Unit (ECU) 208. For illustration, one fuel injector 206 is provided. However, number of fuel injectors can be present. Further, the fuel injector 206 can be present at different orientations and locations. The fuel injector 206, in an embodiment, is positioned at intake manifold (not shown in figure) of the internal combustion engine. In another embodiment, the fuel injector 206 can be positioned at cylinder body (not shown in figure) of the internal combustion engine, such as in Gasoline Direct Ignition (GDI) technique. Such different positioning of the fuel injector 206 may be known to person skilled in the art and explanation for the same is forfeited. It may be noted that the fuel injection system 200 does not include a fuel injection pump to create the required pressure of fuel that is to be injected in the internal combustion engine. The fuel is gravity-fed from the fuel reservoir 202 to the fuel injector 206.

In an exemplary embodiment, the fuel injector 206 is capable of accurate metering and atomization of the fuel. The fuel injector 206 may also act as a positive displacement pump for pressurizing the fuel.

Figure 3 is a graph illustrating variation of fuel injection duration over four stroke cycles in the internal combustion engine in accordance with an embodiment of the present invention.

A graph 300 is provided for illustrating variation of fuel injection duration over different cycles. Axis 302 refers to duration of fuel injection. For example, at a particular point in time, the angle of crank is related to time or duration in the four stroke cycle. Hatched areas 304, 306, and 308 represent different fuel injection timings and fuel injection durations adapted in the four stroke cycles. In an embodiment, based on the engine speed and load requirements, the fuel injection duration is varied. For example, during high speed and high load conditions, such as when a vehicle is driven uphill, the fuel injection duration is increased.

In an embodiment, as shown in the hatched area 304, the fuel injection may happen at the beginning of suction or inlet stroke. The pressure drop that occurs at an intake manifold (not shown in the figure) of the internal combustion engine can be used to the advantage of fuel injection right at the start of the inlet stroke in the four stroke cycle. In the same embodiment, the fuel injection duration (duration between the start and stop points of fuel injection) overlaps at least partially with a suction stroke of the engine.

Figure 4 is a graph 400 illustrating variations of fuel injection timings and fuel injection duration over four stroke cycles in relation to pressure at an intake manifold in accordance with an embodiment of the present invention.

The graph 400 includes a first characteristic curve 402 and a second characteristic curve 404. X-Axis 410b is common for both the first and second characteristic curves 402 and 404, the X-axis represents time in seconds. Axis 410a represents pressure in Pa (pascal) or Bar and axis 412 represents voltage signal in V (Volts).

The first characteristic curve 402 displays variation of pressure at the intake manifold of the internal combustion engine over different four stroke cycles. The second characteristic curve 404 displays different fuel injection timings and fuel injection durations at different four stroke cycles (I, II, and III). A phase 406 portrays pressure drop at the intake manifold of the internal combustion engine at one of the portions of the four stroke cycle (shown as II). In an embodiment, the phase 406 may represent inlet or suction stroke in the four stroke cycle (shown as II). A portion 408 of the second characteristic curve 404 represents fuel injection duration for the four stroke cycle (II). It may be noted that the pressure drop at the intake manifold is utilized to the advantage of injecting a mixture of fuel and air. It may also be observed that, the start point 414 is positioned at the beginning of inlet stroke of the four stroke cycle (III). However, in accordance with various embodiments, the start and stop points of fuel injection can be positioned at any stroke or phase of the four stroke cycle.

Further, it may also be noted that, a start point 414 and a stop point 416 over the four stroke cycle (II) is different from the start and stop points (418 and 420) of the four stroke cycle (III). In an embodiment, during the four stroke cycle (III), there may be increased fuel requirement and the hence fuel injection duration (shown as 422) is increased. The injection duration (422) is varied by changing the start and stop points (418 and 420), when compared with the four stroke cycle (II).

Figure 5 is a graph 500 illustrating variation of operating frequency of the fuel injector 206 with respect to rotational speed of an internal combustion engine in accordance with an embodiment of the present invention.

The graph 500 includes axis 502 representing the operating frequency of the fuel injector and axis 504 representing the speed of the internal combustion engine. A characteristic curve 506 displays relation between the operating frequency of the fuel injector 206 and the speed of the internal combustion engine. It may be observed from the characteristic curve 506 that the operating frequency of the fuel injector may increase proportional to the speed of the internal combustion engine. Figure 6 illustrates the Electronic Control Unit (ECU) 208 for controlling the fuel injection system 200 for an internal combustion engine 628 in accordance with an embodiment of the present invention.

In an embodiment of the present invention, the ECU 208 is an embedded system. The ECU 208 includes a memory 602, a microprocessor 604, a bus 606, an Input and Output (I/O) port 608, and a communication interface 610.

In an embodiment, the ECU 208 is configured to control the fuel injection system 200 to meet the fuel demand of the internal combustion engine 628. More particularly, the ECU 208 controls the fuel injector 206 which acts as both the fuel injector and a positive displacement pump. In an exemplary embodiment, the ECU 208 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 and so forth. The ECU 208 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 208 has a set of predefined instructions installed in the memory 602. For example, the memory 602 can be one 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 are executed with the help of a machine such as the microprocessor 604 or a microcontroller. Hence, the ECU 208, in accordance with the present embodiment is adapted to perform the predefined instructions including the determination of engine speed and load requirements, the ascertainment of current phase in a four stroke cycle of the internal combustion engine 628, and the variation of fuel injection duration in the cycle based on at least one engine parameter including the engine speed and load requirements, and the current phase of the cycle of the internal combustion engine 628. More specifically, the start and stop points of fuel injection is varied and positioned in any of the strokes in a four stroke cycle. Further the ECU 208 is adapted to control the operating frequency of the fuel injector 206 based on the engine speed requirement.

In an embodiment, means for ascertaining current stroke of the four stroke cycle receives input from a crank shaft position sensor 618. In another embodiment, the current stroke of the four stroke cycle can be ascertained using an 'in-cylinder pressure sensor' (not shown). Readings from the pressure sensor may be compared with a look-up table (stored in the memory 602) and the current stroke of the four stroke cycle can be identified. The electronic signals or impulses from the crank shaft position sensor 618 is primarily received a the I/O port 608, processed by the microprocessor 604 in accordance with the predefined instructions stored in the memory 602 of the ECU 208.

In an embodiment of the present invention, means for varying and positioning the start and stop points of the fuel injection send electric signals through the I/O port 608 to energize a solenoid of the fuel injector 206 and de-energize the solenoid of the fuel injector 206.

It may also be observed, that unlike conventional electronic fuel injection systems, where either the start of injection is fixed or the end of the injection time is fixed with respect to the crank shaft position or piston position, the ECU 208 according to the present invention varies the starting time of the injection and stopping time of the injection and position the start and stop points anywhere in between 0 degree to 720 degrees (constituting two rotations of the crank shaft of the internal combustion engine) of the four stroke cycle.

In an embodiment, the ECU 208 takes input from an intake air pressure sensor 616, an intake air temperature sensor 614, an engine speed sensor 620, and a crank shaft position sensor 618. Intake valve 624 and exhaust valve 622 of the internal combustion engine are operated by cams 626. Further in an exemplary embodiment, the fuel injector 206 is controlled by the ECU 208 by taking inputs from the sensors.

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.