JP5790558B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine configured to be able to use a mixed fuel of gasoline and alcohol and having a plurality of cylinders.

  In recent years, the use of alcohol with low emissions such as CO (carbon monoxide) and HC (hydrocarbon) as fuel for internal combustion engines has attracted attention, and in addition to gasoline, gasoline and alcohol are mixed in any proportion. Attention has been focused on an internal combustion engine (engine) for flex fuel that can also use an alcohol-mixed fuel (see, for example, Patent Document 1).

  A vehicle equipped with such an engine is generally called an FFV (Flexible Fuel Vehicle), and uses an alcohol-mixed fuel to improve exhaust emission and reduce fossil fuel consumption. It is possible to improve performance.

  In addition, gasoline used in the engine as described above is composed of multiple components and includes a low boiling point component, so that it has a characteristic of excellent vaporization characteristics at low temperatures. On the other hand, since alcohol is a single component, its boiling point is determined and its boiling point is high (in the case of ethanol, about 78 ° C.). Thereby, the mixed fuel with a high alcohol concentration has a feature that it is extremely difficult to vaporize at a temperature lower than the boiling point of the alcohol.

  The engine disclosed in Patent Document 1 has a plurality of cylinders, and is configured such that mixed fuel is injected into an intake port provided in each cylinder. In this engine, preheat treatment using a heater is performed when starting the engine under conditions where the mixed fuel is less likely to vaporize. Specifically, at the time of starting the engine, when the alcohol concentration of the mixed fuel injected into the intake port is higher than a predetermined concentration and the temperature of the cooling water for cooling the engine is lower than the predetermined temperature, A preheating process using a heater is performed to preheat the wall surface of the intake port before fuel injection, thereby promoting vaporization of the mixed fuel injected into the intake port.

JP 2011-163158 A

  However, the injection timing of the mixed fuel at the start of the engine is uniform (same) in all cylinders. For this reason, since the intake stroke time in each cylinder is shortened by increasing the engine speed after the engine is started, there is a cylinder in which the intake stroke ends during the injection of the mixed fuel. As a result, in each cylinder of the engine, combustion may be insufficient or misfire may occur due to insufficient supply of mixed fuel. For this reason, there is a problem that it is difficult to perform stable combustion in a cylinder in which the intake stroke time is shortened due to the increase in rotation after the engine is started.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to perform stable combustion in a cylinder in which the intake stroke time is shortened due to the rotation increase after the start of the internal combustion engine. A fuel injection control device for an internal combustion engine is provided.

  As means for solving the above problems, a fuel injection control device for an internal combustion engine according to the present invention is configured as follows.

That is, a fuel injection control device for an internal combustion engine according to the present invention is configured to be able to use a mixed fuel of gasoline and alcohol, and has an internal combustion engine having a plurality of cylinders, and combustion of each cylinder of the internal combustion engine An intake passage communicating with the chamber, and at the start of the internal combustion engine, it is determined whether or not the alcohol concentration of the mixed fuel is higher than a predetermined alcohol concentration, and the temperature of the cooling water for cooling the internal combustion engine is Based on the result of determining whether or not the temperature is lower than a predetermined coolant temperature, a mode for delaying the timing of injecting the mixed fuel to each cylinder of the internal combustion engine, and the mode for all the cylinders of the internal combustion engine It is premised on a configuration that switches between modes in which the mixed fuel is injected at a uniform timing. The fuel injection control device for an internal combustion engine according to the present invention is such that when the internal combustion engine is started, the alcohol concentration of the mixed fuel is higher than a predetermined alcohol concentration, and the cooling water temperature of the internal combustion engine is a predetermined cooling water temperature. If it is determined that the negative pressure in the intake passage is equal to or higher than a predetermined value in a mode in which the timing of injecting the mixed fuel to each cylinder of the internal combustion engine is delayed, If it is determined that the negative pressure in the intake passage is not greater than or equal to a predetermined value, the injection of the mixed fuel is prohibited, and the mixed fuel is determined in accordance with the rotational speed after the internal combustion engine is started. This is characterized in that the mixed fuel is injected at an earlier timing of the injection start.

According to the fuel injection control device for an internal combustion engine having such a configuration, the mixed fuel is injected by accelerating the injection start timing of the mixed fuel in accordance with the rotation speed after the start of the internal combustion engine. In a cylinder where the intake stroke time is shortened due to the increase in rotation after the start (after the first explosion), it is possible to secure the time for injecting the mixed fuel by the amount that the mixed fuel injection start timing is advanced. An amount of mixed fuel can be secured. As a result, it is possible to avoid a case where combustion is insufficient or a misfire occurs due to insufficient supply of mixed fuel in a cylinder in which the intake stroke time is shortened due to an increase in rotation after the start of the internal combustion engine (after the first explosion). Therefore, stable combustion can be performed. Further, it is possible to suppress the injection of useless mixed fuel into the intake passage until a negative pressure (a negative pressure at which the mixed fuel is easily vaporized) that can start the internal combustion engine is formed in the intake passage. Therefore, it is possible to suppress deterioration of exhaust emission.

  As specific configurations of the present invention, the following plural ones are listed.

  In the fuel injection control apparatus for an internal combustion engine according to the present invention, preferably, the fuel injection control apparatus further includes an intake passage communicating with a combustion chamber of each cylinder of the internal combustion engine, and the injection start timing of the mixed fuel is advanced so that the mixed fuel is supplied. Prior to injection, it is determined whether or not the negative pressure in the intake passage is greater than or equal to a predetermined value. If it is determined that the negative pressure in the intake passage is greater than or equal to a predetermined value, the mixing is performed. The fuel is injected into the intake passage. If comprised in this way, after the negative pressure which can start an internal combustion engine is formed in an intake passage, mixed fuel will be injected in an intake passage, Therefore A more stable combustion can be performed. .

  In the fuel injection control device for an internal combustion engine according to the present invention, preferably, when it is determined that the negative pressure in the intake passage is equal to or higher than a predetermined value, the magnitude of the rotational speed after the internal combustion engine is started is determined. Accordingly, the start timing of the injection of the mixed fuel is advanced, and an amount of the mixed fuel determined based on the coolant temperature at the start of the internal combustion engine and the alcohol concentration of the mixed fuel is injected into the intake passage. It is characterized by that. With this configuration, in the cylinder in which the intake stroke time is shortened due to the increase in rotation after the start of the internal combustion engine (after the first explosion), the time for injecting the mixed fuel is ensured by the advancement of the mixed fuel injection start timing. can do. As a result, it is possible to reliably supply an injection amount of the mixed fuel determined based on the cooling water temperature at the start of the internal combustion engine and the alcohol concentration of the mixed fuel to the combustion chamber of the internal combustion engine. It can be performed.

  According to the fuel injection control device for an internal combustion engine according to the present invention, stable combustion can be performed in a cylinder in which the intake stroke time is shortened due to the rotation increase after the internal combustion engine is started.

1 is a schematic configuration diagram schematically illustrating an example of an engine (flexible fuel internal combustion engine) to which the present invention is applied. It is a schematic block diagram which shows only 1 cylinder of the engine of FIG. It is a block diagram which shows the control system of an engine. It is a flowchart which shows an example of the fuel-injection control at the time of the engine start which ECU performs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a flexible fuel internal combustion engine (hereinafter also referred to as an engine) to which the present invention is applied will be described.

-Engine-
1 and 2 are diagrams showing a schematic configuration of an engine to which the present invention is applied. FIG. 2 shows only the configuration of one cylinder of the engine.

  As shown in FIG. 1, the engine 1 is a port injection type four-cylinder engine mounted on an FFV (Flexible Fuel Vehicle). Further, as shown in FIG. 2, a piston 3 that reciprocates in the vertical direction is provided in the cylinder block 2 that constitutes each cylinder # 0, # 1, # 2, and # 3. The piston 3 is connected to the crankshaft 5 via a connecting rod 4, and the reciprocating motion of the piston 3 is converted into rotation of the crankshaft 5 by the connecting rod 4.

  A signal rotor 6 is attached to the crankshaft 5. A plurality of teeth (projections) 6a are provided on the outer peripheral surface of the signal rotor 6 at equal angles (in this example, 10 ° CA (crank angle)). Further, the signal rotor 6 has a missing tooth portion 6b in which two teeth 6a are missing.

  A crank position sensor 31 that detects a crank angle is disposed near the side of the signal rotor 6. The crank position sensor 31 is, for example, an electromagnetic pickup, and generates a pulse signal (voltage pulse) corresponding to the teeth 6a of the signal rotor 6 when the crankshaft 5 rotates.

  The cylinder block 2 of the engine 1 is provided with a water temperature sensor 32 that detects the water temperature (cooling water temperature) of the engine cooling water. A cylinder head 7 is provided at the upper end of the cylinder block 2, and a combustion chamber 8 is formed between the cylinder head 7 and the piston 3. A spark plug 9 is disposed in the combustion chamber 8 of the engine 1. The ignition timing of the spark plug 9 is adjusted by the igniter 10. The igniter 10 is controlled by an ECU (Electronic Control Unit) 200.

  An oil pan 11 for storing lubricating oil is provided below the cylinder block 2 of the engine 1. The lubricating oil stored in the oil pan 11 is pumped up by an oil pump (not shown) through an oil strainer (not shown) that removes foreign matters when the engine 1 is operated. Then, the pumped lubricating oil is supplied to various parts of the engine such as the piston 3, the crankshaft 5, and the connecting rod 4, and is used for lubricating and cooling the respective parts. Then, the lubricating oil supplied in this way is used for lubricating and cooling each part of the engine, and then returned to the oil pan 11 until it is pumped up again by an oil pump (not shown). Stored inside.

  An intake passage 12 and an exhaust passage 13 are connected (communication) to the combustion chamber 8 of the engine 1. A part of the intake passage 12 is formed by an intake port 12a and an intake manifold 12b. The intake passage 12 is provided with a surge tank 12c. A part of the exhaust passage 13 is formed by an exhaust port 13a and an exhaust manifold 13b.

  In the intake passage 12 of the engine 1, an air cleaner 14 that filters intake air, a hot-wire air flow meter 33 that measures the amount of intake air in the intake passage 12, an intake air temperature sensor 34 (built in the air flow meter 33), A throttle valve 15 and the like for adjusting the intake air amount are arranged. The throttle valve 15 is provided on the upstream side of the surge tank 12 c (upstream side of the intake flow) and is driven by the throttle motor 16. The opening degree of the throttle valve 15 is detected by a throttle opening degree sensor 35. The throttle opening of the throttle valve 15 is driven and controlled by the ECU 200.

A three-way catalyst 17 is disposed in the exhaust passage 13 of the engine 1. In the three-way catalyst 17, oxidation of CO and HC and reduction of NOx in the exhaust gas exhausted from the combustion chamber 8 to the exhaust passage 13 is performed, and these are made harmless CO ₂ , H ₂ O, and N ₂ . Thus, the exhaust gas is purified.

An air-fuel ratio (A / F) sensor 37 is disposed in the exhaust passage 13 upstream of the three-way catalyst 17 (upstream of the exhaust flow). The air-fuel ratio (A / F) sensor 37 is a sensor that exhibits linear characteristics with respect to the air-fuel ratio. An O ₂ sensor 38 is disposed in the exhaust passage 13 on the downstream side of the three-way catalyst 17. The O ₂ sensor 38 generates an electromotive force according to the oxygen concentration in the exhaust gas. When the output is higher than a voltage (comparison voltage) corresponding to the theoretical air-fuel ratio, the O ₂ sensor 38 determines that the output is rich and conversely compares it. When the output is lower than the voltage, it is judged as lean.

  An intake valve 18 is provided between the intake passage 12 and the combustion chamber 8, and the intake passage 12 and the combustion chamber 8 are communicated or blocked by opening and closing the intake valve 18. Further, an exhaust valve 19 is provided between the exhaust passage 13 and the combustion chamber 8, and the exhaust passage 13 and the combustion chamber 8 are communicated or blocked by opening and closing the exhaust valve 19. The opening / closing drive of the intake valve 18 and the exhaust valve 19 is performed by each rotation of the intake camshaft 20 and the exhaust camshaft 21 to which the rotation of the crankshaft 5 is transmitted via a timing chain or the like.

  In the vicinity of the intake camshaft 20, a cam position sensor 39 is provided that generates a pulse signal when the piston 3 of a specific cylinder (for example, cylinder # 0) reaches the compression top dead center (TDC). . The cam position sensor 39 is, for example, an electromagnetic pickup and is disposed so as to face one tooth (not shown) on the outer peripheral surface of the rotor provided integrally with the intake camshaft 20. When the shaft 20 rotates, a pulse signal (voltage pulse) is output. Since the intake camshaft 20 (and the exhaust camshaft 21) rotates at a rotational speed that is 1/2 that of the crankshaft 5, the cam position sensor 39 becomes 1 each time the crankshaft 5 rotates twice (720 ° rotation). Two pulse signals are generated.

  An intake port 12a of the intake passage 12 is provided with an injector (fuel injection valve) 22 that can inject fuel that is a mixture of alcohol and gasoline alone or in combination. The injector 22 is provided for each cylinder # 0 to # 3 (see FIG. 1). These injectors 22, 22 are connected to a common delivery pipe 101. The delivery pipe 101 is supplied with fuel stored in a fuel tank 104 of a fuel supply system 100, which will be described later, so that fuel is injected from the injector 22 into the intake port 12a. This injected fuel (for example, a mixed fuel of alcohol and gasoline) is mixed with intake air to be mixed into the combustion chamber 8 of the engine 1. The air-fuel mixture (fuel + air) introduced into the combustion chamber 8 is ignited by the spark plug 9 to burn and explode. Due to combustion and explosion of the air-fuel mixture in the combustion chamber 8, the piston 3 reciprocates and the crankshaft 5 rotates.

  The operation state of the engine 1 is controlled by the ECU 200.

  As shown in FIG. 1, a fuel supply system 100 includes a delivery pipe 101 connected in common to the injectors 22... 22 of each cylinder # 0 to # 3, a fuel supply pipe 102 connected to the delivery pipe 101, a fuel. A pump (for example, an electric pump) 103 and a fuel tank 104 are provided. By driving the fuel pump 103, the fuel stored in the fuel tank 104 is supplied via the fuel supply pipe 102 to the delivery pipe 101. Can be supplied. The fuel is supplied to the injectors 22 of the cylinders # 0 to # 3 by the fuel supply system 100 having such a configuration.

  Note that the engine 1 of this example is configured to be able to use alcohol and gasoline as fuels individually or in combination, so that fuel having a predetermined alcohol concentration is stored in the fuel tank 104. The This fuel may be 100% gasoline, a mixed fuel in which alcohol such as methanol or ethanol is contained in gasoline, or 100% alcohol.

  Further, the fuel supply pipe 102 of the fuel supply system 100 is provided with an alcohol concentration sensor 105 that detects the alcohol concentration of the fuel. In this example, a known capacitance type sensor that detects the alcohol concentration of the fuel based on the dielectric constant of the fuel is used as the alcohol concentration sensor 105. However, the present invention is not limited to this, for example, the refractive index of the fuel. An alcohol concentration sensor using another detection principle such as an optical alcohol concentration sensor 105 that detects the alcohol concentration based on the above may be applied.

  In the fuel supply system 100 configured as described above, the driving of the fuel pump 103 is controlled by the ECU 200. The output signal of the alcohol concentration sensor 105 is input to the ECU 200.

-ECU-
As shown in FIG. 3, the ECU 200 includes a CPU 201, a ROM 202, a RAM 203, a backup RAM 204, and the like.

  The ROM 202 stores in advance various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 201 executes various arithmetic processes based on various control programs and maps stored in the ROM 202. The RAM 203 is a memory that temporarily stores calculation results of the CPU 201, data input from each sensor, and the backup RAM 204 is a nonvolatile memory that stores data to be saved when the engine 1 is stopped, for example. Memory.

  The CPU 201, the ROM 202, the RAM 203, and the backup RAM 204 are connected to each other via the bus 207, and are connected to the input interface 205 and the output interface 206.

The input interface 205 includes a crank position sensor 31, a water temperature sensor 32, an air flow meter 33, an intake air temperature sensor 34, a throttle opening sensor 35, an accelerator opening sensor 36 that outputs a detection signal corresponding to the depression amount of the accelerator pedal, an empty Various sensors such as an air-fuel ratio (A / F) sensor 37, an O ₂ sensor 38, a cam position sensor 39, and an alcohol concentration sensor 105 are connected.

  In addition, the ignition switch 40 is connected to the input interface 205, and when the ignition switch 40 is turned on, cranking of the engine 1 by a starter motor (not shown) is started.

  To the output interface 206, the injector 22, the igniter 10 of the spark plug 9, the throttle motor 16 of the throttle valve 15, the fuel pump 103 of the fuel supply system 100, and the like are connected.

  The ECU 200 controls the drive of the injector 22 (fuel injection control), the ignition timing control of the spark plug 9 (normal ignition timing control), and the throttle motor 16 of the throttle valve 15 based on the detection signals of the various sensors. Various controls of the engine 1 are executed including the drive control and air-fuel ratio feedback control. In addition, the ECU 200 executes start-up fuel injection control when the engine 1 described later is started. By the program executed by the ECU 200 described above, a start-time fuel injection control device when the engine 1 is started is realized.

-Fuel injection control at start-
Next, a basic flow of start-up fuel injection control according to this embodiment will be described with reference to the flowchart of FIG.

  The start time fuel injection control according to the present embodiment is started when the ignition switch 40 (see FIG. 3) is turned ON by the operator. That is, in step ST1, it is determined whether or not the ignition switch 40 is in an ON state. If the ignition switch 40 is not in an ON state (negative determination: No), in step ST1, the ignition switch 40 is in an ON state ( This process is repeated until a positive determination is made. Further, when it is determined in step ST1 that the ignition switch 40 is in the ON state (positive determination: Yes), the process proceeds to step ST2.

  In step ST2, it is determined whether or not the alcohol concentration of the mixed fuel is higher than a predetermined concentration. In this step ST2, whether or not the alcohol concentration detected by the alcohol concentration sensor 105 (see FIG. 2) provided in the fuel supply pipe 102 of the fuel supply system 100 is higher than a predetermined concentration (whether the alcohol concentration is high). No) is determined. If it is determined in step ST2 that the alcohol concentration of the mixed fuel is higher than the predetermined concentration (high alcohol concentration) (Yes determination: Yes), the process proceeds to step ST3.

  In step ST3, it is determined whether or not the cooling water temperature for cooling the engine 1 is lower than a predetermined cooling water temperature (temperature). In step ST3, it is determined whether or not the engine coolant temperature detected by the coolant temperature sensor 32 (see FIG. 2) disposed in the cylinder block 2 of the engine 1 is lower than a predetermined coolant temperature. If it is determined in step ST3 that the cooling water temperature for cooling the engine 1 is lower than the predetermined cooling water temperature (temperature) (during low temperature start) (Yes determination: Yes), the process is performed in step ST4. Proceed.

  In step ST4, the high alcohol concentration and low temperature start fuel injection control switching flag is turned on. As a result, the ECU 200 starts the start-time fuel injection control in a mode in which the timing of injecting the mixed fuel to each cylinder # 0, # 1, # 2, # 3 of the engine 1 is delayed.

  Here, in fuel injection control at the time of starting a general FFV engine, the mixed fuel is injected before a negative pressure is formed in the intake passage 12 (intake port 12a or intake manifold 12b). That is, since the mixed fuel with high alcohol concentration in the FFV has poor vaporization characteristics, when the engine 1 is started, a negative pressure is formed in the intake passage 12 to promote the vaporization of the mixed fuel, and the intake valve 18 is opened. It is important to reduce the amount adhering to the wall surface of the intake port 12a due to fuel injection in the meantime. Therefore, in the mode in which the timing for injecting the mixed fuel is delayed, the fuel injection start timing is delayed (retarded) as the fuel injection control at the start of the engine 1 compared to the general fuel injection control at the start. Thus, after the negative pressure is formed in the intake passage 12 (the intake port 12a or the intake manifold 12b), the mixed fuel is controlled to be injected. In the present embodiment, after the start of the engine 1 (after the first explosion), if the intake stroke time becomes shorter as the engine speed increases, the amount of fuel mixture required for combustion is reduced. In order to ensure, control is performed so that the timing is advanced (advanced) from the state where the fuel injection timing is delayed. The control for accelerating the fuel injection timing will be described later.

  Further, when it is determined in step ST2 that the alcohol concentration of the mixed fuel is equal to or lower than the predetermined concentration (No determination: No), or in step ST3, the cooling water temperature for cooling the engine 1 is equal to or higher than the predetermined cooling water temperature (temperature). If it is determined (No determination: No), it is determined that the alcohol concentration is low or not at the time of low temperature start, and the process proceeds to step ST5. In step ST5, the high alcohol concentration and low temperature start fuel injection control switching flag is turned off. As a result, fuel injection control at start-up is performed in a mode in which the mixed fuel is injected into all cylinders # 0, # 1, # 2, and # 3 of the engine 1 at a uniform timing. A mode for injecting mixed fuel to all cylinders at a uniform timing will be described later.

  In step ST6, the required injection amount at start-up is determined from the coolant temperature of the engine 1 and the alcohol concentration detection value. In step ST6, referring to a predetermined map stored in the ROM 202, the alcohol concentration detected in step ST2, the cooling water temperature detected in step ST3, the intake air amount measured by the air flow meter 33, and the like. Is calculated (determined) based on a numerical value (parameter) such as atmospheric pressure calculated from Then, the process proceeds to step ST7.

  In step ST7, it is determined whether or not the starter motor is in an ON state (whether or not it is driven). In step ST7, it is determined whether or not the ignition switch 40 is turned on by the operator and cranking of the engine 1 is started by the starter motor. If it is determined in step ST7 that the starter motor is not in the ON state (negative determination: No), the process returns to step ST6. In Step ST7, when it is determined that the starter motor is in the ON state (Yes determination: Yes), the process proceeds to Step ST8.

  In step ST8, after the cranking of the engine 1 is started by the starter motor, the number of teeth 6a (the number of teeth) of the signal rotor 6 attached to the crankshaft 5 is counted up, so that all cylinders # 0, # The number of intake strokes of 1, # 2, and # 3 is calculated. Then, the process proceeds to step ST9.

  In step ST9, the estimated negative pressure of the intake passage 12 (intake port 12a or intake manifold 12b) corresponding to the number of intake strokes calculated in step ST8 is calculated. In step ST9, the intake passage 12 is based on the number of intake strokes calculated in step ST8, the exhaust amount of the engine 1, and the numerical values (parameters) such as the volume of the intake passage 12 (intake port 12a or intake manifold 12b). The estimated negative pressure (estimated intake passage negative pressure) is calculated. Then, the process proceeds to step ST10.

  In step ST10, the cylinders # 0, # 1, # 2, and # 3 of the engine 1 are determined (determined) based on detection signals from the crank position sensor 31 and the cam position sensor 39 and the like. Then, the process proceeds to step ST11.

  Here, in the present embodiment, in step ST11, it is determined whether or not the estimated intake passage negative pressure calculated in step ST9 is a predetermined value or more (whether or not it is a predetermined negative pressure or more). The predetermined negative pressure indicates the magnitude (absolute value) of the negative pressure at which the mixed fuel injected into the intake passage 12 (intake port 12a) is easily vaporized in step ST12 described later. If it is determined in step ST11 that the estimated intake passage negative pressure is not greater than or equal to the predetermined value (smaller than the predetermined value) (negative determination: No), the current negative pressure in the intake passage 12 is determined. Then, it is determined that the mixed fuel is difficult to vaporize, and the process returns to step ST8. In Step ST11, when it is determined that the estimated intake passage negative pressure is equal to or higher than the predetermined value (Yes: Yes), the mixed fuel is gas if the current negative pressure in the intake passage 12 is large. It is determined that it is easy to convert, and the process proceeds to step ST12.

  Next, in the present embodiment, the injection of the mixed fuel is started in step ST12. In this step ST12, the mixed fuel is injected at a timing determined for each cylinder # 0, # 1, # 2, # 3 according to the coolant temperature detected by the water temperature sensor 32 and the number of times of the mixed fuel injection. Start. Here, generally, after the engine 1 is started (after the first explosion), the number of revolutions of the engine 1 increases as the number of injections of the mixed fuel increases, so that each cylinder # 0, # 1 , # 2, # 3, the intake stroke time is shortened, so that there is a cylinder in which the intake stroke ends during the injection of the mixed fuel. Therefore, in step ST12, a predetermined map stored in advance in the ROM 202 (a map set so that the mixed fuel injection start timing is variable for each cylinder in accordance with the cooling water temperature and the number of times of fuel injection). The mixed fuel is injected with reference to FIG. As a result, the mixed fuel injection is performed for each cylinder # 0, # 1, # 2, # 3 in which the intake stroke time is shortened according to the increase (magnitude) of the rotational speed after the engine 1 is started (after the first explosion). The start timing is advanced (advanced), and the mixed fuel is injected into the intake passage 12. The injection amount of the mixed fuel is an amount determined based on the cooling water temperature and the alcohol concentration. As a result, if the engine speed is increased and the intake stroke time is shortened after the engine 1 is started (after the first explosion), the necessary amount of the mixed fuel is ensured by increasing the timing of starting the mixed fuel injection. It becomes possible to do. Then, the process proceeds to step ST13.

  In step ST13, it is determined whether or not the engine speed is equal to or greater than a predetermined value. And in step ST13, when an engine speed is not more than predetermined value (negative determination: No), a process is returned to step ST12. In step ST13, if the engine speed is greater than or equal to a predetermined value (Yes determination: Yes), the process proceeds to step ST14.

  In step ST14, by switching to the fuel injection timing after the engine 1 is started, the control for accelerating the fuel injection start timing is ended.

  Further, when it is determined in step ST2 that the alcohol concentration of the mixed fuel is equal to or lower than the predetermined concentration (No determination: No), or in step ST3, the temperature of the cooling water for cooling the engine 1 is the predetermined cooling water temperature. When it is determined that the temperature is equal to or higher than (temperature) (negative determination: No), it is determined that the alcohol concentration is low or not at the time of low temperature start, and the process proceeds to step ST5. In step ST5, the high alcohol concentration and low temperature start fuel injection control switching flag is turned off. As a result, fuel injection control at start-up is performed in a mode in which the mixed fuel is injected into all cylinders # 0, # 1, # 2, and # 3 of the engine 1 at a uniform timing. Then, the process proceeds to step ST15.

  In step ST15, the required injection amount at start-up is determined from the coolant temperature of the engine 1 and the alcohol concentration detection value. In step ST15, referring to a predetermined map stored in the ROM 202, the alcohol concentration detected in step ST2, the cooling water temperature detected in step ST3, the intake air amount measured by the air flow meter 33, and the like. Based on the numerical value (parameter) such as the atmospheric pressure calculated from the above, the required fuel injection amount at start is calculated (determined). Thereafter, the process proceeds to step ST16.

  In step ST16, it is determined whether or not the starter motor is in an ON state (whether or not it has been driven). In step ST16, it is determined whether or not the ignition switch 40 is turned on by the operator and cranking of the engine 1 is started by the starter motor. If it is determined in step ST16 that the starter motor is not in the ON state (negative determination: No), the process returns to step ST15. If it is determined in step ST16 that the starter motor is in the ON state (positive determination: Yes), the process proceeds to step ST17.

  In step ST17, based on the detection timing of the toothless portion 6b of the signal rotor 6 before the cylinder is determined, the cylinders # 0, # 1, # 2, and # 3 are mixed with the cylinders that can be estimated (estimated) as the intake stroke. Start fuel injection. Thereafter, the cylinders # 0, # 1, # 2, and # 3 are determined (determined). Then, the process proceeds to step ST18.

  In step ST18, after the cylinder is determined, injection of the mixed fuel is started at a uniform timing for all the cylinders. Then, the process proceeds to step ST19.

  In step ST19, it is determined whether or not the engine speed is equal to or greater than a predetermined value. And in step ST19, when an engine speed is not more than predetermined value (negative determination: No), a process is returned to step ST18. In step ST19, if the engine speed is greater than or equal to a predetermined value (Yes determination: Yes), the process proceeds to step ST20.

  In step ST20, by switching to the fuel injection timing after the engine 1 is started, the control for injecting the mixed fuel at the same timing for all the cylinders is completed.

  As described above, in the present embodiment, as described above, the mixed fuel is injected by accelerating the injection start timing of the mixed fuel in accordance with the rotation speed after the engine 1 is started (after the first explosion). . As a result, in the cylinder in which the intake stroke time is shortened due to the increase in rotation after the engine 1 is started (after the first explosion), it is possible to secure the time for injecting the mixed fuel by the amount that the mixed fuel injection start timing is advanced. Therefore, the amount of mixed fuel necessary for combustion can be ensured. As a result, it is possible to avoid a case where combustion becomes insufficient or a misfire occurs due to insufficient supply of mixed fuel in a cylinder in which the intake stroke time is shortened due to an increase in rotation after the engine 1 is started (after the first explosion). Therefore, stable combustion can be performed.

  In the present embodiment, as described above, it is determined whether or not the negative pressure in the intake passage 12 is equal to or higher than a predetermined value prior to injecting the mixed fuel by accelerating the injection start timing of the mixed fuel. However, when it is determined that the negative pressure in the intake passage 12 is not equal to or higher than the predetermined value (smaller than the predetermined value), the injection of the mixed fuel is prohibited. Thus, useless mixed fuel is injected into the intake passage 12 until a negative pressure capable of starting the engine 1 (a negative pressure at which the mixed fuel easily vaporizes) is formed in the intake passage 12. Therefore, the exhaust emission can be prevented from deteriorating.

  In the present embodiment, as described above, it is determined whether or not the negative pressure in the intake passage 12 is equal to or higher than a predetermined value prior to injecting the mixed fuel by accelerating the injection start timing of the mixed fuel. If it is determined that the negative pressure in the intake passage 12 is greater than or equal to a predetermined value (step ST11), the mixed fuel is injected into the intake passage 12 (step ST12). Thereby, after the negative pressure capable of starting the engine 1 is formed in the intake passage 12, the mixed fuel is injected into the intake passage 12, so that more stable combustion can be performed.

  In the present embodiment, as described above, when it is determined that the negative pressure in the intake passage 12 is equal to or higher than the predetermined value (Yes in Step ST11: Yes), the rotation speed after the engine 1 is started is increased. Accordingly, the injection start timing of the mixed fuel is advanced, and an amount of the mixed fuel determined based on the coolant temperature at the start of the engine 1 and the alcohol concentration of the mixed fuel is injected into the intake passage 12 (step) ST12). As a result, in the cylinders # 0, # 1, # 2, and # 3 in which the intake stroke time is shortened due to the rotation increase after the engine 1 is started (after the first explosion), the mixed fuel is started earlier by the timing of the injection start. The time for injecting fuel can be secured. As a result, the injection amount of the mixed fuel determined based on the cooling water temperature at the start of the engine 1 and the alcohol concentration of the mixed fuel can be reliably supplied to the combustion chamber 8 of the engine 1, so that it is more stable. Combustion can be performed.

-Other embodiments-
In the above embodiment, the alcohol concentration sensor is provided in the fuel supply system to detect the alcohol concentration, but the present invention is not limited to this. For example, the alcohol concentration may be estimated based on the exhaust air / fuel ratio obtained from the output signal of the air / fuel ratio (A / F) sensor.

  Moreover, although the example which applied this invention to the fuel-injection control of a 4-cylinder flexible fuel internal combustion engine was shown in the said embodiment, this invention is not limited to this. For example, the present invention can be applied to a fuel injection control device of a flexible fuel internal combustion engine having an arbitrary number of cylinders such as 6 cylinders and 8 cylinders. Further, the engine type (series type, V type, horizontally opposed type, etc.) is not particularly limited.

  Moreover, although the example which calculates the magnitude | size of atmospheric pressure from the intake air amount etc. which were measured with the airflow meter was shown in the said embodiment, this invention is not limited to this. For example, atmospheric pressure may be measured using a pressure sensor such as a vacuum sensor.

  Moreover, in the said embodiment, although the example of the vehicle which uses only a flexible fuel internal combustion engine as a drive source was shown, this invention is not limited to this. For example, the present invention can be applied to a hybrid vehicle using a flexible internal combustion engine and an electric motor as drive sources.

  INDUSTRIAL APPLICABILITY The present invention can be used for a fuel injection control device for an internal combustion engine. More specifically, the present invention is configured to be able to use a mixed fuel of gasoline and alcohol and has a plurality of cylinders. It can be used for a control device.

1 engine (internal combustion engine)
8 Combustion chamber 12 Intake passage # 0, # 1, # 2, # 3 cylinder

Claims (3)

It is configured to be able to use a mixed fuel of gasoline and alcohol, and includes an internal combustion engine having a plurality of cylinders, and an intake passage communicating with a combustion chamber of each cylinder of the internal combustion engine ,
At the start of the internal combustion engine, it is determined whether or not the alcohol concentration of the mixed fuel is higher than a predetermined alcohol concentration, and whether or not the temperature of cooling water for cooling the internal combustion engine is lower than a predetermined cooling water temperature A mode in which the timing of injecting the mixed fuel into each cylinder of the internal combustion engine is delayed based on the result of the determination, and a mode in which the mixed fuel is injected into all cylinders of the internal combustion engine at a uniform timing In an internal combustion engine fuel injection control device that switches between
When it is determined that the alcohol concentration of the mixed fuel is higher than a predetermined alcohol concentration and the cooling water temperature of the internal combustion engine is lower than a predetermined cooling water temperature when the internal combustion engine is started, the internal combustion engine In a mode in which the timing of injecting the mixed fuel to each of the cylinders is delayed, it is determined whether or not the negative pressure in the intake passage is greater than or equal to a predetermined value, and the negative pressure in the intake passage is greater than or equal to a predetermined value If it is determined that the fuel injection is not, the injection of the mixed fuel is prohibited , and the mixed fuel is injected by accelerating the injection start timing of the mixed fuel in accordance with the rotation speed after starting the internal combustion engine. A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1 ,
Prior to injecting the mixed fuel by accelerating the injection start timing of the mixed fuel, it is determined whether or not the negative pressure in the intake passage is greater than or equal to a predetermined value, and the negative pressure in the intake passage is reduced. A fuel injection control device for an internal combustion engine, wherein the fuel mixture is injected into the intake passage when it is determined that the value is equal to or greater than a predetermined value. The fuel injection control device for an internal combustion engine according to claim 2 ,
When it is determined that the negative pressure in the intake passage is greater than or equal to a predetermined value, the injection start timing of the mixed fuel is advanced according to the magnitude of the number of revolutions after starting the internal combustion engine, and the internal combustion engine A fuel injection control device for an internal combustion engine, wherein an injection amount of a mixed fuel determined based on a cooling water temperature at the time of starting the engine and an alcohol concentration of the mixed fuel is injected into the intake passage.

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