JP2008255907A - Fuel injection control device for cylinder injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit adhesion of fuel on a cylinder inner wall surface irrespective of alcohol concentration, in an engine capable of divided injection of alcohol mixed fuel. <P>SOLUTION: Ethanol mixed gasoline to be fuel is dividedly injected from an injector when a cylinder injection engine injecting fuel directly into a cylinder by the injector is operated with homogeneous combustion. Number of times of divided injection is increased according to ethanol concentration of the ethanol mixed gasoline in order to keep one fuel injection period Te during divided injection within predetermined period Tk when ethanol concentration of ethanol mixed gasoline is not less than a predetermined value α. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an in-cylinder injection engine that directly injects fuel into a cylinder, and more particularly to fuel injection control in the case of using a fuel containing alcohol such as ethanol-mixed gasoline.

  An in-cylinder injection type gasoline engine can be operated by homogeneous combustion, and fuel is injected from an injector in an intake stroke, thereby generating a uniform mixture of fuel and air. Since the fuel is directly injected into the cylinder, the fuel adhesion to the inner wall surface of the cylinder increases due to the increase in the fuel injection amount. In order to prevent the engine oil from being diluted due to an increase in the fuel adhesion amount, for example, fuel injection is divided into multiple injections (for example, refer to Patent Document 1).

On the other hand, alcohol-mixed fuel such as ethanol-mixed gasoline is also supplied to FFV (Flexible Fuel Vehicle) automobiles, etc. However, alcohol-mixed fuel has fuel properties such as vaporization characteristics and calorific value compared to pure gasoline that does not contain alcohol. Different. Further, the fuel property changes depending on the alcohol concentration, and the theoretical air-fuel ratio value decreases as the alcohol concentration increases. In order to perform fuel injection control in accordance with the alcohol concentration, for example, the air-fuel ratio is corrected according to the alcohol concentration, and the fuel injection amount is adjusted (see, for example, Patent Document 2).
JP 2004-52660 A JP-A-5-05446

  When an alcohol mixed fuel is used, it is necessary to increase the fuel injection amount from the time of using gasoline due to the difference in the theoretical air-fuel ratio. Even if the engine is operated by split injection of fuel, the fuel injection period of one fuel injection becomes longer as the fuel injection amount increases. As a result, the spray length from the injector is increased and the amount of fuel reaching the wall surface is increased, and the engine oil is diluted by the increase in the fuel adhesion amount.

  The fuel injection control device of the present invention is a fuel injection control device for an engine attached to an automobile such as an FFV that can use alcohol mixed fuel as fuel. Here, the alcohol-mixed fuel refers to a fuel obtained by mixing alcohol with a fuel such as gasoline. The alcohol mixed fuel includes not only a mixed fuel containing alcohol at a predetermined ratio but also a fuel not containing alcohol (alcohol concentration 0%) or a fuel containing only alcohol (alcohol 100%). To do.

  The fuel injection control device of the present invention includes an alcohol concentration detection means for detecting the alcohol concentration of the alcohol mixed fuel, and a fuel injection timing adjustment means for controlling the fuel injection device for directly injecting the alcohol mixed fuel into the cylinder of the spark ignition engine. With. The fuel injection timing adjusting means can divide and inject the alcohol-mixed fuel within the intake stroke according to the fuel injection amount corresponding to the alcohol concentration and the engine operating state (load, engine speed, etc.).

  When fuel with various alcohol concentrations is replenished in the fuel tank, the alcohol concentration of the fuel to be injected changes during use, and the fuel injection amount also changes accordingly. The fuel injection timing adjusting means of the present invention adjusts the number of times of fuel injection so that one fuel injection period falls within a predetermined period in order to suppress the amount of fuel adhering to the cylinder inner wall surface. Here, in the case of split injection, the single fuel injection period corresponds to a fuel injection period from the start to the end of fuel injection in each fuel injection. In the case of fuel injection only once without split injection, this corresponds to the injection period. In addition, the predetermined period is to suppress the fuel adhesion to the cylinder inner wall surface regardless of the alcohol concentration, that is, the fuel adhesion amount to the cylinder inner wall surface increases even if the fuel injection amount increases as the alcohol concentration changes. This represents a period during which fuel injection can be substantially suppressed. The predetermined period is determined according to the injection characteristics of the fuel injection device, the injection direction, the fuel pressure, the shape of the fuel chamber of the engine, and the like. For example, it may be determined as a period in which no substantial increase in fuel adhesion appears compared to when pure gasoline fuel is used.

  The number of divided injections (including one) is determined in consideration of the characteristics of the fuel injection device (for example, the minimum amount of fuel that can be injected at one time, fuel pressure), the intake stroke period, and the like. Further, each fuel injection period at the time of divided injection is determined by the fuel pressure or the like, and is set to the same period, for example. Further, the interval between adjacent fuel injections (the period from the previous fuel injection end timing to the start of the next fuel injection) is also determined by the characteristics of the fuel injection device. As the total amount of fuel injection increases according to the alcohol concentration, the amount of fuel injection per time also increases and the time of one fuel injection becomes longer.

  The fuel injection timing adjusting means keeps one fuel injection period short by changing the number of fuel injections. For example, when the fuel injection period exceeds a predetermined period as the fuel injection amount increases according to the alcohol concentration, the fuel injection timing adjustment means increases the number of fuel injections so far, and performs one fuel injection. Keep the period within a predetermined period. Further, if the alcohol concentration decreases with time, the number of fuel injections may be reduced. By dividing the number of times of fuel injection in this way, a homogeneous air-fuel mixture is formed while suppressing an increase in fuel adhesion to the cylinder inner wall surface regardless of changes in alcohol concentration.

  In order to easily set the change in the number of fuel injections, the number of fuel injections is adjusted in accordance with the increase in alcohol concentration, based on the number of fuel injections when using pure gasoline fuel or when using alcohol-mixed fuel with a relatively low alcohol concentration. It is desirable to increase For example, the fuel injection timing adjusting means may increase the number of times of fuel injection according to the alcohol concentration when the fuel injection period is an alcohol concentration equal to or higher than a predetermined concentration value exceeding a predetermined period. The predetermined concentration value is determined as, for example, a low concentration value at which the total fuel injection amount does not substantially change from that of pure gasoline fuel.

  When the number of fuel injections is increased, if the end timing of the last fuel injection in the split injection reaches near the end of the intake stroke, the vaporization period and mixture formation period of the injected fuel become shorter, and the homogeneity of the mixture becomes unstable become. Therefore, it is preferable that the fuel injection timing adjusting means determine whether or not the alcohol concentration is equal to or lower than a predetermined limit concentration. Here, the limit concentration is the limit at which all of the divided injections according to the number of fuel injections according to the alcohol concentration are completed before the injection end limit time (for example, the time when the piston is located at the bottom dead center), which is the limit for generating a homogeneous mixture. Indicates the value. When it is determined that all fuel injections can be completed, the divided injections may be performed according to the number of fuel injections according to the alcohol concentration.

  When it is determined that all fuel injections cannot be completed before the limit injection time, that is, the alcohol concentration exceeds the limit concentration, fuel injection is performed without increasing the fuel injection period. The fuel pressure of the device should be increased. That is, it is preferable to increase the fuel injection amount to be injected in one fuel injection period by increasing the fuel pressure of the fuel injection device. The fuel injection timing adjusting means performs all the divided injections before the limit injection timing. Alternatively, the fuel injection timing adjusting means performs a part of fuel injection that can be completed before the injection end limit time in the intake stroke and ensures the remaining fuel injection to form a stratified mixture in order to ensure the stability of combustion. It is desirable to carry out in the compression stroke.

  In order to form a stratified mixture in the compression stroke, it is necessary to make the period from the end timing of the last fuel injection to the ignition timing at least longer than the period necessary for stratified mixture formation. This period changes according to the shape of the combustion chamber (piston surface), fuel pressure, fuel injection amount per unit time, and the like. On the other hand, the ignition timing is shifted to the advance side and the retard side according to the engine operating state. Therefore, the fuel injection timing adjusting means is based on the ignition timing that changes according to the engine operating state, and the period from the last fuel injection end timing to the ignition timing in the compression stroke is at least longer than the period necessary for the formation of the stratified mixture. Thus, it is desirable to adjust the fuel injection timing of the compression stroke.

  The in-cylinder injection engine of the present invention characterized as an engine ignites a fuel injection device that directly injects alcohol-mixed fuel into the cylinder, and a homogeneous mixture of air and alcohol-mixed fuel sucked into the cylinder, And a spark plug for burning. The fuel injection device can perform split injection of alcohol-mixed fuel in the intake stroke according to the fuel injection amount according to the alcohol concentration and the engine operating state, and a single fuel injection period suppresses the amount of fuel adhering to the cylinder inner wall surface. The alcohol-mixed fuel is injected while changing the number of fuel injections according to the alcohol concentration so as to be within a predetermined period.

  ADVANTAGE OF THE INVENTION According to this invention, in the engine which can carry out the division injection of alcohol mixed fuel, fuel adhesion to a cylinder inner wall surface can be suppressed irrespective of alcohol concentration.

  Below, with reference to drawings, the direct injection engine which is an embodiment of the present invention is explained.

  FIG. 1 is a diagram showing a schematic configuration of an entire fuel injection control system including a direct injection engine according to the first embodiment.

  The in-cylinder injection type multi-cylinder engine 10 is mounted on an automobile (not shown) such as an FFV (Flexible Fuel Vehicle), and one cylinder is shown in FIG. The air sucked into the intake pipe 14 through the air cleaner 12 is supplied to the intake port 14A of the intake pipe 14 via the electronically controlled throttle valve 16 and is sucked into the cylinder 13 of the engine body.

  The high-pressure injector 18 is attached to the cylinder head 15 so as to directly inject fuel into the cylinder 13 and injects fuel into the cylinder 13 containing intake air. A spark plug 19 attached near the top of the cylinder head 15 ignites and burns a mixture of fuel and intake air. The combustion gas is discharged from the exhaust port 26 </ b> A of the exhaust pipe 26.

  The piston 24 connected to the crankshaft 20 via the connecting rod 22 reciprocates in the cylinder 13 in accordance with the intake-exhaust cycle. On the other hand, an intake / exhaust valve (not shown) that lifts in accordance with the rotation of the camshaft (not shown) opens and closes the intake port 14A and the exhaust port 26A in accordance with the rotation of the crankshaft 20, thereby causing the piston 24 to move. At the same time, air is sucked and exhausted.

  The in-cylinder injection engine 10 can perform stratified combustion as well as homogeneous combustion. Here, the operation by homogeneous combustion is normally performed at the time of partial load, high speed, and high load. In the intake stroke, the air flowing into the cylinder 13 from the intake port 14A flows as a vortex, and fuel is injected into the air flowing from the injector 18. As a result, a homogeneous mixture in which air and fuel are uniformly mixed is formed. Then, the air-fuel mixture is ignited by the spark plug 19 and combustion occurs. As will be described later, here, split injection is performed in which the fuel is injected in a plurality of times.

The combustion gas is sent to the catalytic converter 28 through the exhaust pipe 26 and purified by the catalytic action of the three-way catalyst. The purified exhaust gas is sent to an exhaust pipe (not shown) and is circulated to the intake pipe 14 through the EGR valve 30 and the EGR pipe line 32. The O ₂ sensor 40 detects the oxygen concentration of the exhaust gas.

  On the other hand, when performing operation by stratified charge combustion according to a predetermined condition, the injector 18 injects fuel in the latter half of the compression stroke. A recess is formed in the upper surface 24A of the piston 24, and the injected fuel flows along the recess. As a result, a stratified mixture (stratified mixture) is generated, and an air-fuel mixture having a fuel concentration close to the theoretical air-fuel ratio is generated around the spark plug 19, and a lean air-fuel mixture is generated around it. Stratified combustion occurs when the stratified mixture is ignited by the spark plug 19.

The ECU 34 including a CPU, a ROM, and a RAM controls the operation of the engine 10, and together with a crank position sensor 36, an intake air temperature sensor 37, a throttle valve position sensor 38, and an intake pipe pressure sensor 39, an O ₂ sensor 40, an accelerator opening degree. Signals from sensors such as the sensor 41 and the water temperature sensor 42 are detected. Further, the ECU 34 outputs a control signal to the injector 18, spark plug 19, throttle valve 14, EGR valve 30, etc., based on parameter information such as the detected accelerator opening, the rotational speed and rotational position of the crankshaft 20. In addition to the fuel injection timing and ignition timing, the fuel injection amount, the intake air amount, the EGR rate, and the like are adjusted. Here, the combustion operation based on the stoichiometric air-fuel ratio (stoichiometric value) is performed, and the fuel injection amount and the like are adjusted based on the detected oxygen concentration.

  As shown in FIG. 2, the fuel stored in the fuel tank 44 is sucked up by the low-pressure pump 46 attached to the fuel tank 44 and sent to the high-pressure pump 48. The sucked fuel is pressurized to the target injection pressure (fuel pressure) by the high pressure pump 48 and supplied to the injector 18 through the fuel distribution pipe 50. A low pressure regulator 53 is provided in the fuel tank 44, and a high pressure regulator (not shown) is provided in the high pressure pump 48, and each adjusts the fuel pressure.

  The fuel tank 44 is replenished with fuel such as ethanol-containing ethanol-containing gasoline, ethanol 100% neat ethanol, or pure gasoline not containing ethanol. A capacitance type ethanol concentration sensor 52 provided in the fuel distribution pipe 50 detects the ethanol concentration (0% to 100%) of the fuel injected into the cylinder based on the dielectric constant of ethanol. The fuel pressure sensor 51 detects the fuel pressure in the fuel distribution pipe 50.

  FIG. 3 is a flowchart of a fuel injection control process executed by the ECU 34. Here, a fuel injection control process during operation by homogeneous combustion is shown. FIG. 4 is a timing chart of fuel injection, and the fuel injection timing is represented by the crank angle. The fuel injection control process is executed at predetermined time intervals as an interrupt process for the main process.

  In step S101, the ethanol concentration sensor 52 detects the ethanol concentration (%). Since the fuel tank 44 is supplemented with ethanol-mixed gasoline, neat ethanol, or pure gasoline not containing ethanol as described above, the ethanol concentration of the fuel depends on the type of fuel to be supplemented and the degree of mixing. It changes from time to time. Unlike gasoline, the calorific value and vaporization characteristics of ethanol are lower than those of gasoline (in the case of pure ethanol, the theoretical air-fuel ratio is about 9). It is necessary to increase the fuel injection amount as the ethanol concentration increases. In step S102, it is determined whether the ethanol concentration is equal to or greater than a predetermined value α.

  In step S102, when it is determined that the ethanol concentration is lower than the predetermined value α, that is, the ethanol concentration is low and close to the fuel property of pure gasoline, the process proceeds to step S103, and split injection when pure gasoline is used is executed. The number of divided injections, the fuel injection timing, etc. are set. As described above, in the operation by homogeneous combustion, fuel split injection is executed, and when the ethanol concentration is lower than the predetermined value α, split injection is performed with the number of fuel injections being three.

  FIG. 4 shows the timing of divided injection. Each fuel injection period Tg in the divided injection is the same, and one fuel injection period Tg is determined so as to prevent fuel from adhering to the wall surface of the cylinder 13. The fuel injection period Tg varies according to the injection characteristics such as the fuel pressure of the injector 18. Further, the fuel injection interval (time interval from the end of one fuel injection to the start of the next fuel injection) Th is determined according to the injection characteristics of the injector 18 and the like. Here, the fuel injection period Tg and the fuel injection interval Th are both set to the same period and interval.

  On the other hand, if it is determined in step S102 that the ethanol concentration is greater than or equal to the predetermined value α, the number of divided injections is determined in accordance with the fuel injection amount based on the ethanol concentration in step S104. Then, the fuel injection period and the fuel injection start timing in one fuel injection are determined according to the determined number of fuel injections and the amount of fuel injection. In order to make each fuel injection period constant, a fuel amount obtained by dividing the total amount of fuel injection by the number of fuel injections is determined as one fuel injection period.

  In FIG. 4, the injection timing when the number of divided injections is not changed with respect to the fuel injection amount of a predetermined ethanol concentration (≧ α) and set to the same number of times as that of pure gasoline (= 3 times) is indicated by a broken line. ing. In general, the amount of fuel adhering to the wall surface of the cylinder 13 is influenced not only by the fuel pressure but also by the fuel injection period. The longer the fuel injection period, the greater the amount of fuel adhering. In the fuel injection period T'e, the amount of fuel attached to the wall surface of the cylinder 13 is increased compared to the period Tg.

  In the present embodiment, the number of divided injections is determined so that one fuel injection period falls within a predetermined period (hereinafter, represented by reference sign Tk) regardless of the ethanol concentration. The predetermined period Tk changes according to the injection characteristics of the injector 18, the shape of the combustion chamber, and the like, and is defined as a limit period for preventing an increase in the amount of fuel diluted with engine oil by suppressing the fuel adhesion amount. As shown in FIG. 4, the fuel injection timing when the number of divided injections is set to 4 is shown. One fuel injection period Te is shorter than the predetermined period Tk. The fuel injection period Te is set so as to exceed the shortest injection period determined by the performance of the injector 18, that is, the limit injection period.

  In the ROM of the ECU 34, the number of times of addition to the reference number of fuel injections (here, 3 times) when using ethanol-mixed gasoline having a concentration lower than the predetermined concentration value α, that is, the reference number of fuel injections. The number of injections to be increased is stored according to the ethanol concentration. In FIG. 4, the number of injections is increased by one with respect to the reference number of fuel injections.

  In step S105, the end timing of the last fuel injection in the split injection, that is, the split injection end timing Kf is calculated based on the intake stroke period according to the engine speed, the set fuel injection period Te, and the fuel injection interval Th. However, the injection start timing in the first fuel injection during the divided injection is constant regardless of the ethanol concentration, and the fuel injection interval Th does not change with the ethanol concentration. In step S106, it is determined whether the calculated divided injection end timing Kf is before the timing corresponding to the bottom dead center position of the piston 24, that is, whether all the divided injections are completed within the intake stroke period. The At the alcohol concentration (limit concentration) at which the divided injection end timing Kf is before the bottom dead center, fuel can be injected within the intake stroke. When the fuel injection timing is delayed, the time until atomization of the injected fuel and formation of the air-fuel mixture is shortened, and the homogeneity of the air-fuel mixture deteriorates. Here, the injection end limit time Kf is set to a time according to the bottom dead center.

  If it is determined in step S106 that the divided injection end timing is before the injection end limit timing Kf, the process proceeds to step S107, the number of times of fuel injection obtained in step S102 is set, and one fuel injection period, A fuel injection interval is set. The injector 18 divides and injects fuel according to the set number of fuel injections, fuel injection period, and fuel injection interval.

  On the other hand, when the divided injection end timing exceeds the injection end limit timing Kf in step S106, the process proceeds to step S108. In step S108, the fuel pressure of the injector 18 at each fuel injection is increased by a predetermined amount so that all fuel injections are completed before the injection end limit time Kf. As a result, the amount of fuel injected in one fuel injection increases, and the divided injection is performed with the number of injections that is less by the number of times of fuel injection exceeding the injection end limit timing Kf. However, the fuel pressure is corrected as long as the fuel adhesion does not increase.

  As described above, according to the first embodiment, when the in-cylinder injection engine 10 is operated by homogeneous combustion, ethanol mixed gasoline serving as fuel is dividedly injected from the injector 18 in the intake stroke. When the ethanol concentration of the ethanol mixed gasoline is equal to or greater than the predetermined value α, the number of fuel injections is increased according to the ethanol concentration. As a result, a single fuel injection period Te at the time of divided injection is within the predetermined period Tk, and dilution of engine oil due to fuel adhering to the wall surface can be prevented. As a result, it is possible to prevent deterioration in lubrication performance due to oil dilution and instability of stoichiometric operation due to evaporation of unburned fuel. In addition, since all the divided injections are completed before the injection end limit time Kf, a homogeneous mixture is reliably formed.

  Next, a second embodiment will be described with reference to FIGS. In the second embodiment, unlike the first embodiment, when all the divided injections cannot be completed before the bottom dead center (intake stroke period), the remaining fuel is injected in the compression stroke. Other configurations are substantially the same as those in the first embodiment.

  FIG. 5 is a flowchart of the fuel injection control process in the second embodiment. FIG. 6 is a timing chart of divided injection in the second embodiment.

  The execution of steps S201 to S206 is the same as the execution of steps S101 to S106 in FIG. That is, when the ethanol concentration is equal to or greater than the predetermined value α, the number of fuel injection divisions is increased, and the injection end timing is calculated according to the number of division injections. Then, it is determined whether or not the calculated injection end timing is an injection end limit timing Kf corresponding to the bottom dead center. When the calculated injection end time is before the injection end limit time Kf, the process proceeds to step S207, and the number of divided injections and the fuel injection time are set as they are. On the other hand, when it is determined in step S206 that the injection end timing exceeds the injection end limit timing Kf, the process proceeds to step S208, and the fuel injection timing in the compression stroke is obtained.

  In FIG. 6, the fuel injection timing based on the number of divided injections according to the ethanol concentration is shown by a broken line. When fuel is divided and injected at the determined number of divided injections (here, 4 times), the fuel injection end timing exceeds the injection end limit timing Kf (bottom dead center). In the second embodiment, fuel injection that cannot be completed within the intake stroke (fourth fuel injection in FIG. 4) is executed in the compression stroke to form a stratified mixture. The fuel injection timing is determined in the latter half of the compression stroke close to the ignition timing Ks in order to perform operation by weak stratified combustion by forming a stratified mixture.

  In step S209, the required ignition timing Ks is calculated based on parameter information such as the engine speed and the required torque. In step S210, the timing at which the obtained ignition timing Ks is shifted to the advance side by a predetermined period Lm is set as the injection end timing during the compression stroke.

  In order to cause weak stratified combustion, fuel is injected in the latter half of the compression stroke close to the ignition timing Ks. However, if the fuel is too close to the ignition timing Ks, a stratified mixture is not formed and incomplete stratified combustion occurs. For this reason, the fuel injection timing is corrected in accordance with the ignition timing Kf that changes in accordance with the operating condition so as to ensure a predetermined period Lm from the fuel injection end timing to the ignition timing necessary for the formation of the stratified mixture. The predetermined period Lm is determined according to various characteristics such as the shape of the inner surface of the cylinder 13 of the engine, the fuel pressure, and the fuel injection amount per unit time.

  In step S211, the number of divided injections obtained in step S204, the fuel injection period in the intake stroke, the fuel injection interval, and the fuel injection timing in the compression stroke are set. The injector 18 divides and injects fuel from the intake stroke to the compression stroke based on a control signal from the ECU 34.

  The number of divided injections can be arbitrarily set, and may be set according to the injection performance of the injector 18 and the like. When pure gasoline is used, fuel may be injected at one time (the number of times of fuel injection is 1), divided injection when the ethanol concentration becomes high, and the number of divided injections may be set to 2 or 3 Good. Further, one fuel injection period Te may be set to a different period for each fuel injection, and may be set so that each fuel injection period falls within a predetermined period Tk. Further, instead of obtaining the increase in the number of fuel injections directly from the ethanol concentration, the total amount of fuel injections is calculated first according to the ethanol concentration, and then the number of fuel injections is adjusted according to the ethanol concentration. Good.

  In the first and second embodiments, the fuel injection control is performed based on the theoretical air-fuel ratio. However, the target air-fuel ratio to be requested is set according to the driving situation and the driving situation, and the set target air-fuel ratio is set. The fuel injection amount may be controlled based on the above. Fuel injection control may be performed according to the engine operating state and the ethanol concentration.

  In this embodiment, ethanol-mixed gasoline is used, but alcohol-mixed fuel other than ethanol may be used, and the amount of increase in the fuel injection amount may be adjusted according to the type of alcohol.

It is a schematic block diagram of the whole fuel-injection control system including the cylinder injection type engine which is 1st Embodiment. It is a schematic block diagram of a fuel supply system. It is a flowchart of the fuel-injection control process performed by ECU. It is a timing chart of divided injection. It is a flowchart of the fuel-injection control process in 2nd Embodiment. It is a timing chart of the division | segmentation injection in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 In-cylinder injection type engine 13 Cylinder 14 Intake pipe 26 Exhaust pipe 18 Injector 19 Spark plug 34 ECU
52 Ethanol concentration sensor Te, Tg Single fuel injection period Kf Injection end limit timing Tk Predetermined period

Claims (7)

Alcohol concentration detection means for detecting the alcohol concentration of the alcohol mixed fuel;
A fuel injection device that directly injects alcohol-mixed fuel into a cylinder of a spark-ignition engine can be controlled, and alcohol-mixed fuel can be dividedly injected in the intake stroke according to the fuel injection amount according to the alcohol concentration and engine operating state. Fuel injection timing adjustment means,
The fuel injection control device, wherein the fuel injection timing adjustment means adjusts the number of times of fuel injection according to the alcohol concentration so that one fuel injection period falls within a predetermined period.   The fuel injection timing adjusting means increases the number of fuel injections according to the alcohol concentration when the one fuel injection period is an alcohol concentration equal to or higher than a predetermined concentration value exceeding the predetermined period. Item 4. The fuel injection control device according to Item 1.   3. The fuel injection control device according to claim 2, wherein the fuel injection timing adjusting unit performs split injection according to the number of fuel injections according to the alcohol concentration when the alcohol concentration is equal to or less than a predetermined limit concentration.   When the alcohol concentration exceeds the limit concentration, the fuel injection timing adjustment means increases the fuel pressure of the fuel injection device to increase the fuel injection amount injected in one fuel injection period, and is divided before the limit injection timing. The fuel injection control device according to claim 3, wherein all injections are performed.   When the alcohol concentration exceeds the limit concentration, the fuel injection timing adjustment means performs a part of fuel injection that can be terminated before the injection end limit timing in an intake stroke, and forms the stratified mixture with the remaining fuel injection The fuel injection control device according to claim 3, wherein the fuel injection control device is performed in a compression stroke.   The fuel injection timing adjusting means changes the ignition timing according to the engine operating state so that the period from the end timing of the last fuel injection in the compression stroke to the ignition timing is at least a period necessary for the formation of the stratified mixture. 6. The fuel injection control device according to claim 5, wherein the fuel injection timing of the compression stroke is adjusted according to the above. A fuel injection device for directly injecting alcohol-mixed fuel into the cylinder;
A spark plug that ignites and burns a homogeneous mixture of air and alcohol mixed fuel sucked into the cylinder;
The fuel injection device can perform split injection of alcohol-mixed fuel in the intake stroke according to the fuel injection amount according to the alcohol concentration and the engine operating state, and one fuel injection period can reduce the amount of fuel adhering to the cylinder inner wall surface. An in-cylinder injection engine characterized by injecting alcohol-mixed fuel while changing the number of times of fuel injection according to the alcohol concentration so as to be within a predetermined period of time.

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