JP2017066867A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device which can stabilize the combustion state of an internal combustion engine in course of warming-up and improve exhaust emission performance.SOLUTION: A fuel injection control device comprises: an ignition plug 10 which is disposed with an electrode protruded in a combustion chamber 7 and is adjusted in its ignition timing by an ECU 3; an injector 11 for injecting fuel into the combustion chamber 7; an engine rotation speed sensor 26 which outputs, from rotation of a crankshaft 9 of an engine 2, an engine rotation speed pulse signal of a pulse number proportional to the rotation speed of the crankshaft 9; and the ECU 3 which, in course of warming-up, determines the fuel property of fuel supplied to the engine 2 based on the engine rotation speed and the integrated value of an ignition number, causes to perform split injections, and controls an air-fuel ratio according to the fuel property.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection control device.

  In an internal combustion engine, at the time of cold start, the fuel is not sufficiently vaporized due to the fuel properties of the fuel supplied to the internal combustion engine and the ambient temperature of the internal combustion engine, and the fuel cannot be burned sufficiently, so HC (hydrocarbon) There is a problem that exhaust smoke is generated due to the generation of black smoke.

  Patent Document 1 proposes that a fuel property is determined based on a change in engine speed of the internal combustion engine after the internal combustion engine is started, and a fuel injection amount is corrected based on the determined fuel property.

Japanese Patent Laid-Open No. 03-26841

  However, Patent Document 1 describes that the fuel injection amount is corrected based on the determination result of the fuel property, but since a specific correction method is not described, the combustion state is deteriorated during warm-up. Can not be prevented.

  Therefore, an object of the present invention is to provide a fuel injection control device that can stabilize the combustion state of an internal combustion engine that is warming up and that can improve exhaust emission performance.

  One aspect of the invention of a fuel injection control device that solves the above problem is a fuel injection control device that controls injection of fuel supplied to an internal combustion engine having an in-cylinder injection mechanism. A fuel property is determined, split injection is performed, and a control unit that controls the air-fuel ratio according to the fuel property is provided.

  As described above, according to the present invention, it is possible to stabilize the combustion state of the internal combustion engine that is warming up, and to improve the exhaust emission performance.

FIG. 1 is a conceptual block diagram of a fuel injection control apparatus according to an embodiment of the present invention. FIG. 2 is a time chart showing an engine speed and an integrated number of times of ignition at the start of an engine equipped with a fuel injection control device according to an embodiment of the present invention. FIG. 2 (b) is the case of heavy gasoline. FIG. 3 is a timing chart showing the fuel injection timing in the fuel injection control of the fuel injection control device according to the embodiment of the present invention. FIG. 4 is a graph showing the relationship between the air-fuel ratio of the engine and the soot emission when the split injection control and the fuel injection control of the fuel injection control device according to one embodiment of the present invention are combined. FIG. 5 is a flowchart showing the procedure of start-up combustion stabilization processing of the fuel injection control apparatus according to the embodiment of the present invention.

  Hereinafter, a fuel injection control device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  In FIG. 1, a vehicle 1 equipped with a fuel injection control device according to an embodiment of the present invention includes an internal combustion engine type engine 2 and an ECU (Electronic Control Unit) 3 as a control unit.

  The engine 2 is formed with a cylinder 5 as a cylinder. The cylinder 5 houses a piston 6 that can reciprocate up and down in the cylinder 5. A combustion chamber 7 is provided in the upper part of the cylinder 5.

  The engine 2 is a so-called four-cycle gasoline engine that performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston 6 reciprocates in the cylinder 5.

  In addition, the piston 6 is connected to the crankshaft 9 via a connecting rod 8. The connecting rod 8 converts the reciprocating motion of the piston 6 into the rotational motion of the crankshaft 9.

  The combustion chamber 7 is provided with a spark plug 10 and an injector 11. The spark plug 10 is disposed in a state in which an electrode protrudes into the combustion chamber 7, and its ignition timing is adjusted by the ECU 3. The ECU 3 is configured to count an ignition number integrated value obtained by integrating the number of ignitions by the spark plug 10 after an ignition switch (not shown) is turned on and cranking of the engine 2 is started.

  The injector 11 is a so-called in-cylinder fuel injection valve that injects fuel supplied from a fuel tank (not shown) by a fuel pump into the combustion chamber 7.

  The engine 2 is provided with an intake port 12 and an exhaust port 21. The intake port 12 communicates the combustion chamber 7 with an intake passage 14a described later. The intake port 12 is provided with an intake valve 13.

  The intake valve 13 is opened and closed so as to communicate or block the intake passage 14a and the combustion chamber 7.

  An intake pipe 14 is connected to the intake port 12. An intake passage 14 a communicating with the intake port 12 is formed in the intake pipe 14. An electronically controlled throttle valve 15 is provided in the intake passage 14a. The throttle valve 15 is electrically connected to the ECU 3.

  The throttle valve 15 adjusts the intake air amount of the engine 2 by controlling the throttle opening degree according to a command signal from the ECU 3.

  On the other hand, the exhaust port 21 is provided with an exhaust valve 22. The exhaust valve 22 is opened and closed so as to communicate or block an exhaust passage 24a described later and the combustion chamber 7.

  An exhaust pipe 24 is connected to the exhaust port 21. An exhaust passage 24 a communicating with the exhaust port 21 is formed in the exhaust pipe 24. An air-fuel ratio sensor 25 is provided in the exhaust passage 24a.

  The engine 2 configured as described above is an ignition type engine in which an air-fuel mixture of the intake air whose flow rate is adjusted by the throttle valve 15 and the fuel injected by the injector 11 is ignited by the spark plug 10 and ignited.

  The ECU 3 includes a computer unit that includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a flash memory, an input port, and an output port.

  The ROM of the computer unit stores a program for causing the computer unit to function as the ECU 3 along with various control constants and various maps. That is, the computer unit functions as the ECU 3 when the CPU executes a program stored in the ROM.

  In addition to the air-fuel ratio sensor 25 described above, various sensors such as an engine speed sensor 26, an accelerator opening sensor 28, and a water temperature sensor 29 are connected to the input port of the ECU 3.

  The air-fuel ratio sensor 25 detects a wide range of continuous air-fuel ratio changes from the oxygen concentration in the exhaust gas of the engine 2.

  The engine speed sensor 26 outputs an engine speed pulse signal having a pulse number proportional to the speed of the crankshaft 9 from the rotation of the crankshaft 9 of the engine 2. The ECU 3 can detect the engine speed based on the engine speed pulse signal.

  The accelerator opening sensor 28 detects an accelerator opening representing an operation amount of the accelerator pedal 27. The water temperature sensor 29 detects the water temperature of the cooling water of the engine 2.

  On the other hand, various control objects such as a spark plug 10, an injector 11, and a throttle valve 15 are connected to the output port of the ECU 3.

  The ECU 3 calculates a required load of the engine 2 based on the accelerator opening detected by the accelerator opening sensor 28, and calculates a target ignition timing, a fuel injection amount, and an intake air amount of the engine 2 according to the required load. The ECU 3 controls the operation state of the engine 2 by controlling the spark plug 10, the injector 11, and the throttle valve 15 so that the calculated target ignition timing, fuel injection amount, and intake air amount are obtained.

<Fuel property judgment method>
A fuel property determination method used in the present embodiment will be described.

  In the present embodiment, the ECU 3 indicates that the engine speed detected by the engine speed sensor 26 has completely exploded since the ignition switch (not shown) is turned on and cranking of the engine 2 is started. Whether the fuel is light gasoline or heavy gasoline is determined on the basis of the above-mentioned ignition number integrated value S until the determination rotational speed N representing

  FIG. 2 is a diagram showing an engine speed and an integrated number of times of ignition at the time of starting the engine due to a difference in fuel properties of fuel supplied to the engine 2. FIG. 2 (a) is a diagram of light gasoline, FIG. ) Is for heavy gasoline.

  As shown in FIG. 2 (a), in the case of light gasoline, the number of times of ignition accumulated until the engine speed reaches the determination speed N when the engine speed starts up quickly at the start of the engine is low. It becomes smaller than the number-of-ignitions threshold value X that determines that the air-fuel mixture is difficult to ignite or the air-fuel mixture is hard to ignite.

  On the other hand, as shown in FIG. 2 (b), in the case of heavy gasoline, the ignition speed integration value S until the engine speed reaches the determination speed N is slow. It becomes larger than the ignition frequency threshold value X.

  From this, the ECU 3 determines that the ignition number integrated value S from the start of cranking of the engine 2 until the engine speed detected by the engine speed sensor 26 reaches the determination speed N is greater than the ignition number threshold value X. If it is smaller, it is determined that the fuel supplied to the engine 2 is light gasoline.

  On the other hand, the ECU 3 determines that the ignition number integrated value S from when the cranking of the engine 2 is started until the engine speed detected by the engine speed sensor 26 reaches the determination speed N is equal to or greater than the ignition frequency threshold value X. It is determined that the fuel supplied to the engine 2 is heavy gasoline.

  The determination rotational speed N and the ignition frequency threshold value X are obtained in advance by experiments or the like and stored in the ROM of the ECU 3.

<Fuel injection control method according to fuel properties>
A fuel injection control method according to the fuel properties used in the present embodiment will be described.

  When the ECU 3 determines that the fuel supplied to the engine 2 is light gasoline during the cold start of the engine 2, the ECU 3 performs split injection of the fuel and makes the air-fuel ratio of the air-fuel mixture lean. In the case of light gasoline, it is easy to vaporize, so there is a margin to the combustion limit on the lean side, and black smoke countermeasures are taken by making it lean.

  On the other hand, when the ECU 3 determines that the fuel supplied to the engine 2 is heavy gasoline when the engine 2 is cold-started, the ECU 3 performs split injection of the fuel and sets the air-fuel ratio of the air-fuel mixture to stoichiometric ( Control near the theoretical air-fuel ratio). In the case of heavy gasoline, it is difficult to evaporate, so there is no allowance on the combustion limit on the lean side, and robustness is ensured without leaning. The theoretical air-fuel ratio is the ratio of the amount of air introduced per unit fuel mass of the air-fuel mixture that is theoretically the most efficient in combustion, and is generally 14.5 to 14.7.

  When the ECU 3 determines that the fuel is heavy gasoline, the heavy gasoline is less likely to be a gas mixture, so an air-fuel ratio limit threshold Z that prevents enrichment to the air-fuel ratio where soot can be generated is provided. No enrichment beyond the limit threshold Z of the air-fuel ratio is performed.

  When the engine 2 is started, the ECU 3 has a coolant temperature of the engine 2 detected by the water temperature sensor 29 that is higher than a cryogenic temperature threshold T1 indicating a very low temperature and a warming-up state threshold T2 indicating a warming-up state. If it is low, it is determined that the engine is cold starting.

  When performing the divided injection, the ECU 3 divides the intake process and the compression process into the fuel injection. Note that the fuel injection amount may be larger in the compression process than in the intake process. Thus, exhaust emission can be improved by performing split injection.

  When the split injection is performed, the ECU 3 performs different fuel injection controls in the intake process and the compression process. The fuel injection control of the fuel injection control device according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 3, for fuel injection in the intake process, the ECU 3 determines a time point at which fuel injection is started, indicated by T1 and T2 in the drawing, and performs fuel injection based on the fuel injection amount performed in the intake process. Determine the time.

  For the fuel injection in the compression process, the ECU 3 determines the time point at which the fuel injection ends, indicated by T3 and T4 in the figure, and determines the fuel injection time based on the fuel injection amount performed in the compression process.

The ECU 3 changes the timing of split injection according to the fuel properties and the state of the vehicle 1. When the ECU 3 determines that the fuel is heavy gasoline, the heavy gasoline is less likely to be mixed with light gasoline, so the timing of split injection is changed as follows.
1) The fuel injection is started at the timing T1 earlier than the fuel injection start timing T2 of the light gasoline for the injection in the intake process for the mixture formation.
2) In order to form a rich air-fuel mixture in the vicinity of the spark plug 10, the injection in the compression process ends the fuel injection at a timing T4 that is later than the fuel injection end timing T3 of the light gasoline.

  The inventor of the present application combines such split injection control and fuel injection control, and for each fuel property of the fuel supplied to the engine 2, the relationship between the air-fuel ratio of the air-fuel mixture and the soot discharge amount is clarified through experiments. It was. FIG. 4 is a graph showing the results.

  As shown in FIG. 4, in the case of heavy gasoline, the amount of soot emission is minimized around the stoichiometric area. On the other hand, in the case of light gasoline, the amount of soot emission is minimized in the region L on the lean side of the stoichiometry. Thus, when the fuel supplied to the engine 2 is heavy gasoline, the air-fuel ratio of the air-fuel mixture is adjusted around the stoichiometric range, and when the fuel supplied to the engine 2 is light gasoline, the air-fuel ratio of the air-fuel mixture is made lean. By adjusting to the side, exhaust emission can be improved.

  A start-up combustion stabilization process performed by the fuel injection control apparatus according to the present embodiment configured as described above will be described with reference to FIG. Note that the start-up combustion stabilization process described below is started when the engine 2 is started.

  In step S1, the ECU 3 starts integrating the number of times of ignition of the spark plug 10. In step S2, the ECU 3 determines whether or not the engine speed detected by the engine speed sensor 26 is equal to or higher than the above-described determination speed N. When it is determined that the engine speed is not equal to or higher than the determination speed N, the ECU 3 repeats the process of step S2. When it is determined that the engine speed is equal to or higher than the determination speed N, the ECU 3 advances the process to step S3.

  In step S3, the ECU 3 determines whether or not the ignition number integrated value S is smaller than the ignition number threshold value X. If it is determined that the ignition count integrated value S is smaller than the ignition count threshold value X, the ECU 3 proceeds to step S4. When it is determined that the ignition count integrated value S is not smaller than the ignition count threshold value X, the ECU 3 proceeds to step S7.

  In step S4, the ECU 3 determines that the fuel supplied to the engine 2 is light gasoline.

  In step S5, the ECU 3 determines whether or not the engine coolant temperature detected by the water temperature sensor 29 is higher than the cryogenic temperature threshold T1 and lower than the warm-up state threshold T2. When it is determined that the engine coolant temperature is not higher than the cryogenic temperature threshold value T1 or lower than the warm-up state threshold value T2, the ECU 3 ends the process. If it is determined that the engine coolant temperature is higher than the cryogenic temperature threshold T1 and lower than the warm-up state threshold T2, the ECU 3 advances the process to step S6.

  In step S6, the ECU 3 performs the fuel split injection as described above, and adjusts the air-fuel ratio of the air-fuel mixture to the lean side.

  In step S7, the ECU 3 determines that the fuel supplied to the engine 2 is heavy gasoline.

  In step S8, the ECU 3 determines whether or not the engine coolant temperature detected by the water temperature sensor 29 is higher than the cryogenic temperature threshold T1 and lower than the warm-up state threshold T2. When it is determined that the engine coolant temperature is not higher than the cryogenic temperature threshold value T1 or lower than the warm-up state threshold value T2, the ECU 3 ends the process. If it is determined that the engine coolant temperature is higher than the cryogenic temperature threshold T1 and lower than the warm-up state threshold T2, the ECU 3 advances the process to step S9.

  In step S9, the ECU 3 performs the split fuel injection as described above, and adjusts the air-fuel ratio of the air-fuel mixture around the stoichiometric range.

  As described above, the above-described embodiment includes the ECU 3 that determines the fuel property of the fuel supplied to the engine 2 during the warming-up, performs split injection, and controls the air-fuel ratio according to the fuel property.

  Thereby, split injection is performed and the air-fuel ratio is controlled according to the fuel properties. For this reason, the combustion state of the engine 2 can be stabilized, and the exhaust emission performance can be improved.

  Further, the ECU 3 determines the fuel property of the fuel based on the ignition number integrated value S from when the cranking of the engine 2 is started until the engine speed detected by the engine speed sensor 26 reaches the determination speed N. judge.

  Thus, the fuel property of the fuel is determined based on the ignition number integrated value S from the start of cranking until the engine speed reaches the determination speed N. For this reason, it is possible to determine the fuel property from an early stage using the information before the complete explosion of the engine, and it is possible to control the fuel injection using the determined information.

  Further, the ECU 3 adjusts the air-fuel ratio of the air-fuel mixture to the lean side when the fuel property of the fuel is light gasoline.

  Thereby, when the fuel property of the fuel is light gasoline, the air-fuel ratio of the air-fuel mixture is adjusted to the lean side. For this reason, the combustion state of the engine 2 can be stabilized, and the exhaust emission performance can be improved.

  Further, when the fuel property of the fuel is heavy gasoline, the ECU 3 adjusts the air-fuel ratio of the air-fuel mixture around the stoichiometry.

  Thereby, when the fuel property of the fuel is heavy gasoline, the air-fuel ratio of the air-fuel mixture is adjusted around the stoichiometry. For this reason, the combustion state of the engine 2 can be stabilized, and the exhaust emission performance can be improved.

  Moreover, ECU3 divides | segments into the intake process and compression process of the engine 2, and performs fuel injection, when implementing split injection.

  Thereby, the divided injection is performed by dividing into the intake process and the compression process of the engine 2. For this reason, the combustion state of the engine 2 can be stabilized, and the exhaust emission performance can be improved.

  Further, when the fuel property of the fuel is heavy gasoline, the ECU 3 starts fuel injection at a timing earlier than that of light gasoline in the intake process of the split injection engine 2.

  As a result, when the fuel property of the fuel is heavy gasoline, fuel injection is started at an earlier timing than the light gasoline in the intake process, and atomization of the heavy gasoline that is less likely to be an air-fuel mixture than the light gasoline is promoted. For this reason, the combustion state of the engine 2 can be stabilized, and the exhaust emission performance can be improved.

  Further, when the fuel property of the fuel is heavy gasoline, the ECU 3 terminates the fuel injection at a timing later than that of the light gasoline in the compression process of the engine 2 of the split injection.

  As a result, when the fuel property of the fuel is heavy gasoline, fuel injection is terminated at a later timing than the light gasoline in the compression process, and a rich air-fuel mixture is formed in the vicinity of the spark plug 10. For this reason, the ignitability of the air-fuel mixture is improved, the combustion state of the engine 2 can be stabilized, and the exhaust emission performance can be improved.

  While embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that changes may be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims.

1 Vehicle 2 Engine 3 ECU (Control Unit)
DESCRIPTION OF SYMBOLS 10 Spark plug 11 Injector 26 Engine speed sensor 29 Water temperature sensor

Claims (7)

A fuel injection control device for controlling injection of fuel supplied to an internal combustion engine having an in-cylinder injection mechanism,
A fuel injection control device comprising a control unit that determines a fuel property of the fuel during warm-up, performs split injection, and controls an air-fuel ratio according to the fuel property.   2. The fuel injection control according to claim 1, wherein the control unit determines the fuel property of the fuel based on an integrated value of the number of ignitions from the start of cranking to the time when the engine speed of the internal combustion engine reaches a determination speed. apparatus.   3. The fuel injection control device according to claim 1, wherein when the fuel property of the fuel is light fuel, the control unit adjusts the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio.   3. The fuel injection control device according to claim 1, wherein when the fuel property of the fuel is heavy fuel, the control unit adjusts the air-fuel ratio to be close to the stoichiometric air-fuel ratio.   5. The fuel injection control according to claim 1, wherein, when performing the divided injection, the control unit performs control so that fuel is injected divided into a compression process and an intake process of the internal combustion engine. 6. apparatus.   6. The fuel according to claim 5, wherein, when the fuel property of the fuel is heavy fuel, the control unit starts fuel injection at an earlier timing than the light fuel in the intake process of the internal combustion engine of the split injection. Injection control device.   6. The fuel according to claim 5, wherein when the fuel property of the fuel is heavy fuel, the control unit terminates fuel injection at a timing later than the light fuel in the compression process of the internal combustion engine of the split injection. Injection control device.

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