JP2011157844A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide excellent startability even if the concentration of alcohol in fuel is high in a port injection flexible fuel internal combustion engine. <P>SOLUTION: When the concentration of alcohol is low (including 0%), a start fuel injection period (the amount of fuel injected in starting) is short, and fuel injection is completed in a first injection cylinder in starting an engine before an intake valve is closed, fuel injection is performed from the first injection cylinder. On the other hand, when the concentration of alcohol is high and the start fuel injection period is remarkably long, the fuel injection cannot be completed in the first injection cylinder in starting the engine before the intake valve is closed. Therefore, in this case, the fuel injection is performed from the next cylinder. By such injection control, it is possible to ensure startability suitable for the high concentration of alcohol. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine capable of using a fuel containing alcohol.

  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. In addition to gasoline, gasoline and alcohol are mixed in any proportion. Attention has been focused on flex-fuel internal combustion engines that can also use such alcohol-containing fuels. A vehicle equipped with such an internal combustion engine is generally called a flexible fuel vehicle (FFV). By using alcohol fuel, environmental performance such as improvement of exhaust emission and reduction of fossil fuel consumption is achieved. Improvements can be made.

  However, alcohol fuel has characteristics such that it is less volatile than gasoline fuel and hardly vaporizes at low temperatures. Therefore, in the flex fuel internal combustion engine mounted on the FFV, the fuel injection amount at the start is corrected according to the alcohol concentration (see, for example, Patent Document 1).

JP 05-340286 A

  By the way, in the flexible fuel internal combustion engine, when the alcohol concentration of the fuel becomes high, the fuel injection amount at startup (required injection amount) increases remarkably. In this way, when the fuel injection amount at the time of starting is remarkably increased, in the port-injection type flexible fuel internal combustion engine, the fuel injection is not completed until the intake valve closes of the first injection cylinder at the time of starting. Since it is carried over to the next cycle of the injection cylinder), the engine cannot be started properly. Further, the amount of fuel in the next cycle of the cylinder in which the fuel has been carried over becomes excessive (rich), and the emission may deteriorate.

  The present invention has been made in consideration of such circumstances, and in a port-injection type flexible fuel internal combustion engine, even when the alcohol concentration of the fuel is high, good startability can be obtained. An object of the present invention is to realize accurate fuel injection control.

  The present invention provides an intake port and an exhaust port that communicate with each combustion chamber of a plurality of cylinders, an intake valve and an exhaust valve that open and close the intake port and the exhaust port, respectively, and is provided for each cylinder. Applied to an internal combustion engine (flexible fuel internal combustion engine) having a fuel injection valve capable of injecting alcohol-containing fuel in the passage, and the higher the concentration of alcohol contained in the fuel, the more the start is injected into the intake port or the intake passage In the fuel injection control device for increasing the fuel injection amount during start-up, the fuel injection at the start fuel injection amount set based on the alcohol concentration of the fuel cannot be completed by the closing of the intake valve of the first injection cylinder at the time of engine start In this case, it is a technical feature that the fuel injection is performed from the next cylinder.

  As a specific configuration of the present invention, a start-time fuel injection period (start-time fuel injection time) is set from the alcohol concentration, and based on the start-time fuel injection period and the intake valve closing timing, A configuration in which it is determined whether or not fuel injection can be completed before the intake valve is closed can be mentioned.

  In the present invention, the alcohol concentration is low (including 0%), the fuel injection amount at the start is small (the fuel injection period at the start is short), and the first injection cylinder at the start of the engine (the first injection cylinder at the start) If the fuel injection can be completed before the intake valve is closed in the cylinder in which the intake stroke is reached, the fuel injection is performed from the first injection cylinder.

  On the other hand, when the alcohol concentration is high and the fuel injection amount at the start is remarkably large (when the fuel injection period at the start is remarkably long), the fuel is injected before the intake valve is closed in the first injection cylinder at the start of the engine. Cannot complete injection. In this case, fuel injection is performed from the cylinder next to the first cylinder. Here, since the intake valve opening timing of the next cylinder is on the rear side (retarding side) with respect to the first cylinder, fuel injection is not performed until the intake valve closes even if the start-up fuel injection period is long. It becomes possible to complete. That is, since it becomes possible to supply the amount of fuel necessary for ignition for the next cylinder, the ignition performance is good and the engine is reliably started. Further, by such injection control, unburned fuel can be suppressed and carry-over of fuel to the next cycle can be eliminated, so that deterioration of emissions can be suppressed.

  In the present invention, the fuel injection start timing in the starting process may be variably set according to the alcohol concentration. When the fuel injection start timing is variably set in accordance with the alcohol concentration in this way, it becomes possible to stabilize the port wet state (the state where the fuel adheres to the intake port leading to the combustion chamber) regardless of the alcohol concentration. .

  In the present invention, the fuel injection start timing in the engine starting process may be set so that the port wet state of each cylinder becomes uniform. Specifically, for example, the fuel injection start timing with respect to the intake valve opening timing is made the same for all the cylinders, and the port wet state of each cylinder is made uniform. If such injection control is performed, good startability can be obtained.

  According to the present invention, when the fuel injection of the starting fuel injection amount set from the alcohol concentration cannot be completed by the closing of the intake valve of the first injection cylinder at the time of starting the engine, the fuel injection is performed from the next cylinder. Therefore, even if the alcohol concentration of the fuel is high, good startability can be ensured.

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 structure of the control system of an engine. It is a flowchart which shows an example of the start time fuel injection control which ECU performs. It is a figure which shows the fuel-injection timing and the injection period of the fuel injection control at the time of start-up with a low alcohol concentration. It is a figure which shows the fuel-injection timing and the injection period of the fuel injection control at the time of start in alcohol high concentration. It is explanatory drawing of the problem in case the fuel injection of the request | requirement fuel injection amount at the time of start is not completed by intake valve closing.

  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.

  The engine 1 is a port injection type four-cylinder engine mounted on an FFV, and a piston 1c that reciprocates vertically in a cylinder block 1a constituting each cylinder # 0, # 1, # 2, # 3. Is provided. The piston 1c is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1c is converted into rotation of the crankshaft 15 by the connecting rod 16.

  A signal rotor 17 is attached to the crankshaft 15. A plurality of teeth (protrusions) 17a are provided on the outer peripheral surface of the signal rotor 17 at equal angles (in this example, 10 ° CA (crank excessive)). Further, the signal rotor 17 has a missing tooth portion 17b in which two teeth 17a are missing.

  A crank position sensor 31 that detects a crank angle is disposed near the side of the signal rotor 17. The crank position sensor 31 is an electromagnetic pickup, for example, and generates a pulsed signal (voltage pulse) corresponding to the teeth 17a of the signal rotor 17 when the crankshaft 15 rotates.

  The cylinder block 1a 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 1b is provided at the upper end of the cylinder block 1a, and a combustion chamber 1d is formed between the cylinder head 1b and the piston 1c. A spark plug 3 is disposed in the combustion chamber 1 d of the engine 1. The ignition timing of the spark plug 3 is adjusted by the igniter 4. The igniter 4 is controlled by an ECU (Electronic Control Unit) 200.

  An oil pan 18 for storing lubricating oil is provided below the cylinder block 1 a of the engine 1. Lubricating oil stored in the oil pan 18 is pumped up by an oil pump (not shown) through an oil strainer that removes foreign matters during operation of the engine 1, and the engine such as the piston 1 c, crankshaft 15, connecting rod 16, etc. It is supplied to each part and used for lubrication and cooling of each part. The lubricating oil supplied in this way is used for lubrication and cooling of each part of the engine, then returned to the oil pan 18 and stored in the oil pan 18 until it is pumped up by the oil pump 19 again. The

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 d of the engine 1. A part of the intake passage 11 is formed by an intake port 11a and an intake manifold 11b. A surge tank 11 c is provided in the intake passage 11. A part of the exhaust passage 12 is formed by an exhaust port 12a and an exhaust manifold 12b.

  In the intake passage 11 of the engine 1, an air cleaner 7 that filters the intake air, a hot-wire air flow meter 33, an intake air temperature sensor 34 (built in the air flow meter 33), a throttle valve 5 for adjusting the intake air amount of the engine 1, etc. Is arranged. The throttle valve 5 is provided on the upstream side of the surge tank 11 c (upstream side of the intake flow) and is driven by the throttle motor 6. The opening degree of the throttle valve 5 is detected by a throttle opening degree sensor 35. The throttle opening of the throttle valve 5 is driven and controlled by the ECU 200.

A three-way catalyst 8 is disposed in the exhaust passage 12 of the engine 1. In the three-way catalyst 8, oxidation of CO and HC and reduction of NOx in the exhaust gas exhausted from the combustion chamber 1d to the exhaust passage 12 is performed, and these are made harmless CO ₂ , H ₂ O, and N ₂ . In this way, the exhaust gas is purified.

An air-fuel ratio (A / F) sensor 37 is disposed in the exhaust passage 12 upstream of the three-way catalyst 8 (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 12 on the downstream side of the three-way catalyst 8. 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 13 is provided between the intake passage 11 and the combustion chamber 1d. By opening and closing the intake valve 13, the intake passage 11 and the combustion chamber 1d are communicated or blocked. Further, an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1d. By opening and closing the exhaust valve 14, the exhaust passage 12 and the combustion chamber 1d are communicated or blocked. The opening / closing drive of the intake valve 13 and the exhaust valve 14 is performed by each rotation of the intake camshaft 21 and the exhaust camshaft 22 to which the rotation of the crankshaft 15 is transmitted via a timing chain or the like.

  A cam position sensor 39 that generates a pulse-like signal when the piston 1c of a specific cylinder (for example, cylinder # 0) reaches the compression top dead center (TDC) is provided in the vicinity of the intake camshaft 21. . 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 21. When the shaft 21 rotates, a pulse signal (voltage pulse) is output. Since the intake camshaft 21 (and the exhaust camshaft 22) rotates at a half speed of the crankshaft 15, the cam position sensor 39 becomes 1 each time the crankshaft 15 rotates twice (720 ° rotation). Two pulse signals are generated.

  In the intake port 11a of the intake passage 11, an injector (fuel injection valve) 2 capable of injecting fuel that is a mixture of alcohol and gasoline alone or mixed is disposed. The injector 2 is provided for each cylinder # 0 to # 3. These injectors 2... 2 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 2 into the intake port 11a. This injected fuel (for example, a mixed fuel of alcohol and gasoline) is mixed with intake air to be mixed into the combustion chamber 1d of the engine 1. The air-fuel mixture (fuel + air) introduced into the combustion chamber 1d is ignited by the spark plug 3 and combusted / exploded. The piston 1c reciprocates due to combustion / explosion of the air-fuel mixture in the combustion chamber 1d, and the crankshaft 15 rotates.

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

  The fuel supply system 100 includes a delivery pipe 101 commonly connected to the injectors 2... 2 of the cylinders # 0 to # 3, a fuel supply pipe 102 connected to the delivery pipe 101, and a fuel pump (for example, an electric pump) 103. The fuel tank 104 and the like are provided, and by driving the fuel pump 103, the fuel stored in the fuel tank 104 can be supplied to the delivery pipe 101 via the fuel supply pipe 102. Then, fuel is supplied to the injectors 2 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 so that alcohol and gasoline can be used alone or in combination as fuel, so that fuel having a predetermined alcohol concentration is stored in the fuel tank 104. 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 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. An ignition switch 40 is connected to the input interface 205. 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 2, the igniter 4 of the spark plug 3, the throttle motor 6 of the throttle valve 5, the fuel pump 103 of the fuel supply system 100, and the like are connected.

  The ECU 200 controls the drive of the injector 2 (fuel injection control), the ignition timing control of the spark plug 3 (normal ignition timing control), the throttle motor 6 of the throttle valve 5 based on the detection signals of the various sensors described above. Various controls of the engine 1 are executed including the drive control and air-fuel ratio feedback control. Further, the ECU 200 executes the following “cylinder discrimination process” and “startup fuel injection control”.

  The fuel injection control device of the present invention is realized by the program executed by the ECU 200 described above.

-Cylinder discrimination processing-
First, in the signal rotor 17 used for detecting the crank angle applied to this example, as shown in FIG. 2, each tooth 17a is formed at every 10 ° CA, and 34 teeth 17a lacking two are provided. have. When the toothless portion 17b of the signal rotor 17 passes in the vicinity of the crank position sensor (electromagnetic pickup) 31, the generation interval of the voltage pulse becomes long. The rotation phase (crank position) of the crankshaft 15 can be detected by the output of a signal (missing tooth signal) corresponding to the missing tooth portion 17b of the signal rotor 17, and the time when each cylinder is located at the top dead center. Can be recognized. The output signal (missing tooth signal) of the crank position sensor 31 corresponding to the missing tooth portion 17b of the signal rotor 17 is a signal for judging the top dead center position for cylinder discrimination, that is, the “top dead center position judging signal”. It has become.

  Here, in a four-cycle engine, for example, as shown in FIG. 5, two rotations (720 ° CA) of the crankshaft that rotates in accordance with the raising and lowering of the piston is one cycle of the engine cycle. Located at the top dead center twice per cycle. For this reason, it is impossible to determine which of the two dead centers is at the top dead center only by the output signal (missing tooth signal) of the crank position sensor 31 as described above. That is, cylinder discrimination cannot be performed. Therefore, in this example, the cylinder discrimination is enabled by combining the output signal (voltage pulse) of the cam position sensor 39 with the output signal (missing tooth signal) of the crank position sensor 31. The cylinder discrimination will be described below.

  First, as described above, the crank position sensor 31 outputs the missing tooth signal once (two times in one cycle of the engine cycle) while the crankshaft 15 makes one rotation (360 ° CA). In this example, the crank position sensor 31 outputs a missing tooth signal at 210 ° CA before top dead center of the cylinder # 0 and the cylinder # 2.

  Further, as described above, the cam position sensor 39 outputs a voltage pulse once during the rotation of the crankshaft 15 twice (once in one cycle of the engine cycle). In this example, the cam position sensor 39 outputs a voltage pulse when the cylinder # 0 is located at the compression top dead center and the cylinder # 2 is located at the exhaust top dead center.

  With this configuration, if the cam position sensor 39 generates a voltage pulse when the crank position sensor 31 outputs a missing tooth signal, the cylinder # 0 is positioned at the compression top dead center and the cylinder # 2 is exhausted. It will be located at the dead center. When the crank position sensor 31 outputs a missing tooth signal and the cam position sensor 39 does not generate a voltage pulse, the cylinder # 0 is located at the exhaust top dead center and the cylinder # 2 is located at the compression top dead center. Will do. The voltage pulse generated by the cam position sensor 39 in this way is a signal for performing cylinder discrimination, that is, a “cylinder discrimination signal”.

  Thus, based on the missing tooth signal of the crank position sensor 31 (first detection of the top dead center position determination signal) and the presence or absence of the generation of the cylinder determination signal (voltage pulse) of the cam position sensor 39 corresponding to the detection. Thus, cylinder discrimination (crank angle determination) can be performed during one revolution of the crankshaft 15 at the latest. Such cylinder discrimination makes it possible to recognize the piston position of each cylinder at the time of engine start, operation after start, etc., and to perform engine operation control such as precise fuel injection control and ignition timing control. it can.

-Fuel injection control at start-
Next, start time fuel injection control executed by the ECU 200 will be described.

  In this example, it is possible to execute start-up fuel injection control at a low alcohol concentration (including the case of 100% gasoline fuel) and start-up fuel injection control at a high alcohol concentration. A basic flow of the start-up fuel injection control will be described with reference to the flowchart of FIG. The control routine of FIG.

  The starting fuel injection control in this example is started when the ignition switch 40 is turned on (IG-ON). When start-up fuel injection control is started, the cooling water temperature of the engine 1 is read from the output signal of the water temperature sensor 32 and the alcohol concentration of the fuel is read from the output signal of the alcohol concentration sensor 105 in step ST101.

  Next, in step ST102, the required start fuel injection amount (hereinafter sometimes referred to as start time fuel injection) Q is calculated using the coolant temperature and alcohol concentration read in step ST101 with reference to a predetermined map. The start time fuel injection period τ is calculated from the calculated start time required fuel injection amount Q and the injection characteristics (injection amount per unit time, etc.) of the injector 2.

  Regarding the map used for calculating the required fuel injection amount Q at the time of starting, it is necessary to increase the fuel injection amount at the time of starting as the coolant temperature is lower, and it is necessary to increase the fuel injection amount at the time of starting as the alcohol concentration is higher. In consideration of a certain point, the required fuel injection amount at start-up is obtained by experiment / simulation calculation using the cooling water temperature and alcohol concentration as parameters, and a value that is adapted based on the result is mapped. This map is stored in the ROM 202 of the ECU 200.

  Next, in step ST103, based on the start-time fuel injection period τ and the intake valve closing timing calculated in step ST102, whether or not fuel injection can be completed before the intake valve closing of the first injection cylinder is completed. judge. More specifically, for example, in the example of FIGS. 5 and 6, the intake valve 13 of the cylinder # 2 is opened at the crank angle “0 ° CA”, and the intake valve of the cylinder # 2 at the crank angle “240 ° CA”. 13 is closed, so whether or not the fuel injection end timing comes before the intake valve closing timing (240 ° CA) when fuel injection is started at 0 ° CA (at the time of cylinder discrimination determination) judge.

  When the determination result in step ST103 is affirmative (YES) (when fuel injection can be completed before the first injection cylinder is closed), fuel injection control at start-up with low alcohol concentration is executed. (Step ST104). On the other hand, when the determination result in step ST103 is negative (NO) (when the first injection cylinder cannot complete fuel injection before the intake valve is closed), fuel injection control at start-up with high alcohol concentration is performed. Execute (step ST105).

  Specific examples of the start-up fuel injection control at a low alcohol concentration and the start-up fuel injection control at a high alcohol concentration will be described below.

-Fuel injection control at start-up with low alcohol concentration-
The start-up fuel injection control with a low alcohol concentration will be described with reference to FIG. In FIG. 5, the crank angle (° CA) is represented with the compression top dead center (TDC) of cylinder # 0 (first cylinder) as the reference position, that is, “0 ° CA”. Further, “τa” shown in FIG. 5 is a start-up fuel injection period set (calculated) in accordance with the low concentration of alcohol by the processing of steps ST102 to ST103 of FIG. 4 described above.

  (1) When the crank position sensor 31 outputs a missing tooth signal (at 210 ° C. before the top dead center of cylinder # 0 and cylinder # 2), the cylinder (first injection cylinder) that reaches the intake stroke most recently is selected. recognize. In the example of FIG. 5, cylinder # 2 is the first injection cylinder. At the time when the crank position sensor 31 outputs the missing tooth signal, the cylinder (first injection cylinder) that reaches the intake stroke most recently may be cylinder # 0. This case will be described later.

  (2) When the alcohol concentration is low (or the gasoline fuel is 100%), the fuel injection amount Q at the start is injected, and the intake valve closing of the first injection cylinder (cylinder # 2 in the example of FIG. 5) is performed. (The fuel injection end timing is before the intake valve closing timing), so fuel injection is performed from the first injection cylinder. Specifically, as shown in FIG. 5, the cam position sensor 39 detects a voltage pulse (cylinder discrimination) when the cylinder discrimination is finalized (crank angle is finalized), that is, at the compression top dead center “0 ° CA” of the cylinder # 0. When the signal is output, fuel injection of the cylinder # 2 (fuel injection in the starting fuel injection period τa) is performed.

  (3) When the crank angle reaches 180 ° CA (when the intake valve 13 of the cylinder # 3 is opened), as shown in FIG. 5, the fuel injection of the cylinder # 3 (in the fuel injection period τa at start-up) Fuel injection).

  (4) When the crank angle reaches 360 ° CA (when the intake valve 13 of the cylinder # 0 is opened), as shown in FIG. 5, the fuel injection of the cylinder # 0 (the fuel in the starting fuel injection period τa) Injection). At the same time, the spark plug 3 of the cylinder # 2 is ignited. At this time, for cylinder # 2, fuel injection for the required fuel injection amount at the time of start is completed by the time the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite.

  (5) When the crank angle reaches 540 ° CA (when the intake valve 13 of the cylinder # 1 is opened), as shown in FIG. 5, the fuel injection of the cylinder # 1 (the fuel in the start time fuel injection period τa) Injection). At the same time, the ignition plug 3 of the cylinder # 3 is ignited. At this time, as for cylinder # 3, fuel injection corresponding to the required fuel injection amount at start-up is completed by the time the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite. Further, when the crank angle reaches 540 ° CA, the synchronous injection after the start of the cylinder # 2 is performed.

  (6) When the crank angle reaches 0 ° CA in the second cycle (when the intake valve 13 of the cylinder # 2 is opened), the ignition plug 3 of the cylinder # 0 is ignited as shown in FIG. At this time, as for cylinder # 0, fuel injection for the required fuel injection amount at the time of start is completed by the time the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite. Further, when the crank angle reaches 0 ° CA in the second cycle, the synchronous injection after the start of the cylinder # 3 is performed.

  (7) When the crank angle reaches 180 ° CA in the second cycle, the spark plug 3 of the cylinder # 1 is ignited as shown in FIG. At this time, for cylinder # 1, fuel injection for the required fuel injection amount at the time of start is completed by the time when the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite. Further, when the crank angle reaches 180 ° CA in the second cycle, the synchronous injection after the start of the cylinder # 0 is performed.

  (8) When the crank angle reaches 360 ° CA in the second cycle, the ignition plug 3 of the cylinder # 2 is ignited as shown in FIG.

  In the example of FIG. 5, since cylinder # 2 and cylinder # 0 are in a 360 ° phase, when the crank position sensor 31 outputs a missing tooth signal, the cylinder that reaches the intake stroke most recently (the first injection) In this case, when the cylinder # 0 reaches the exhaust top dead center (crank angle “360 ° CA”), the cam position sensor 39 detects a voltage pulse (cylinder discrimination). When the signal is not output), the fuel injection of the cylinder # 0 (the fuel injection in the starting fuel injection period τa) is performed, and then the fuel injection of each cylinder of the cylinder # 1, the cylinder # 2, and the cylinder # 3 (Fuel injection during start-up fuel injection period τa) / Ignition may be performed sequentially by the same processing as described above.

-Fuel injection control at start-up with high alcohol concentration-
First, when the alcohol concentration is high, the starting fuel injection period (starting required fuel injection amount) τb becomes significantly longer. For this reason, when the same injection control as that in the case of the low alcohol concentration is performed, as shown in FIG. 6A, the fuel injection cannot be completed before the intake valve closing of the first injection cylinder (cylinder # 2). It will be carried over to the next cycle of the cylinder. In such a situation, it is impossible to start properly. This point will be described. As shown in FIG. 7, when the fuel injection cannot be completed before the intake valve of the injection cylinder is closed (when the fuel injection end timing is later than when the intake valve is closed), the amount of fuel necessary for ignition is supplied. It is not possible to ignite (cannot start). If ignition and combustion are not possible, unburned fuel will be discharged and emissions will deteriorate. Further, if the fuel is carried over to the next cycle, the amount of fuel in the next cycle becomes excessive (rich), and the emission may deteriorate.

  In this way, when the alcohol concentration is high, when the same injection control is performed as in the case of low alcohol concentration, startability and emission are deteriorated. In the example shown in FIG. 6A, ignition is started for the first time in the second cycle of the cylinder # 2.

  In consideration of the above points, in this example, when the fuel injection of the required fuel injection amount at start-up cannot be completed by the intake valve closing of the first injection cylinder at engine start-up, the fuel in the next cylinder It is characterized by improving startability and emission by carrying out injection.

  An example of the injection control will be described with reference to FIG. In FIG. 6B as well, the crank angle (° CA) is represented with the compression top dead center (TDC) of cylinder # 0 (first cylinder) as the reference position, that is, “0 ° CA”. Further, “τb” shown in FIG. 6B and FIG. 6A is the fuel at start-up that is set (calculated) according to the high alcohol concentration by the processing of steps ST102 to ST103 in FIG. It is an injection period.

  (11) When the crank position sensor 31 outputs a missing tooth signal (at 210 ° C. before the top dead center of cylinder # 0 and cylinder # 2), the cylinder that reaches the intake stroke most recently (first injection cylinder) Recognize In the example of FIG. 6B, the cylinder # 2 is the first injection cylinder. However, when the alcohol concentration is high, the start time fuel injection period τb is long, and fuel injection of the start time fuel injection amount can be completed before the intake valve closing of the first injection cylinder (cylinder # 2). Since this is not possible, fuel injection is performed in the next cylinder without performing fuel injection in the first injection cylinder.

  Specifically, as shown in FIG. 6 (b), the cam position sensor 39 detects a voltage pulse at the time when cylinder discrimination is confirmed (crank angle is confirmed), that is, at the compression top dead center “0 ° CA” of cylinder # 0. When the (cylinder discrimination signal) is output, fuel injection of the cylinder # 3, which is the next cylinder of the cylinder # 2, is performed (fuel injection in the starting fuel injection period τb). In this way, by performing fuel injection in the next cylinder # 3, fuel injection of the starting fuel injection amount can be completed before the intake valve is closed.

  In this example, when the crank position sensor 31 outputs the missing tooth signal, the cylinder (first injection cylinder) that reaches the intake stroke most recently may be cylinder # 0. This case will be described later. .

  (12) When the crank angle reaches 180 ° CA, fuel injection of the cylinder # 0 (fuel injection in the starting fuel injection period τb) is performed as shown in FIG. 6B. In the fuel injection of the cylinder # 0, the fuel injection start timing (“α” shown in FIG. 6B) with respect to the intake valve opening timing is the same as that of the cylinder # 3.

  (13) When the crank angle reaches 360 ° CA, fuel injection of the cylinder # 1 (fuel injection in the starting fuel injection period τb) is performed as shown in FIG. 6B. In the fuel injection of the cylinder # 1, the fuel injection start timing (“α” shown in FIG. 6B) with respect to the intake valve opening timing is the same as that of the cylinder # 3.

  (14) When the crank angle reaches 540 ° CA, the fuel injection of the cylinder # 2 is performed as shown in FIG. In the fuel injection of the cylinder # 2, the fuel injection start timing (“α” shown in FIG. 6B) with respect to the intake valve opening timing is the same as that of the cylinder # 3. When the crank angle reaches 540 ° CA, the spark plug 3 of the cylinder # 3 is ignited. At this time, as for cylinder # 3, fuel injection corresponding to the required fuel injection amount at start-up is completed by the time the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite.

  (15) When the crank angle reaches 0 ° CA in the second cycle, the spark plug 3 of the cylinder # 0 is ignited. At this time, as for cylinder # 0, fuel injection for the required fuel injection amount at the time of start is completed by the time the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite. Further, when the crank angle reaches 0 ° CA in the second cycle, the synchronous injection after the start of the cylinder # 3 is performed.

  (16) When the crank angle reaches 180 ° CA in the second cycle, the spark plug 3 of the cylinder # 1 is ignited. At this time, for cylinder # 1, fuel injection for the required fuel injection amount at the time of start is completed by the time when the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite. Further, when the crank angle reaches 180 ° CA in the second cycle, the synchronous injection after the start of the cylinder # 0 is performed.

  (17) When the crank angle reaches 360 ° CA in the second cycle, the spark plug 3 of the cylinder # 2 is ignited. At this time, for cylinder # 2, fuel injection for the required fuel injection amount at the time of start is completed by the time the intake valve is closed, and the fuel amount necessary for ignition is supplied. Make sure to ignite. Further, when the crank angle reaches 360 ° CA in the second cycle, the synchronous injection after the start of the cylinder # 1 is performed.

  (18) When the crank angle reaches 540 ° CA in the second cycle, the ignition plug 3 of the cylinder # 3 is ignited, and at the same time, the synchronous injection after the start of the cylinder # 2 is performed.

  In the example of FIG. 6B, the cylinder # 2 and the cylinder # 0 are in a 360 ° phase, and therefore, when the crank position sensor 31 outputs a missing tooth signal, the cylinder that first approaches the intake stroke (first In this case, when the cylinder # 0 reaches the exhaust top dead center (crank angle “360 ° CA”) (the cam position sensor 39 generates a voltage pulse ( When the cylinder discrimination signal is not output), the fuel injection of the cylinder # 1 which is the next cylinder of the cylinder # 0 (the fuel injection in the start time fuel injection period τb shown in FIG. 6B) is performed, and thereafter In addition, the fuel injection (fuel injection in the starting fuel injection period τb) and ignition of the cylinders # 2, # 3, and # 0 may be sequentially performed by the same process as described above. .

  As described above, according to the fuel injection control at the start of this example, the fuel alcohol concentration is high, and the fuel injection of the start fuel injection amount set based on the high alcohol concentration is performed at the time of engine start. When the first injection cylinder (for example, cylinder # 2) cannot be completed before the intake valve is closed, fuel injection (first injection for starting) is performed in the next cylinder (for example, cylinder # 3). With respect to the next cylinder, it becomes possible to supply a fuel amount necessary for ignition, and good ignitability can be obtained. Thereby, even if the alcohol concentration is high, appropriate startability can be obtained. Further, unburned fuel can be suppressed, and carry-over of fuel to the next cycle can be eliminated, so that deterioration of emissions can be suppressed. Therefore, the start-up fuel injection control in this example can achieve both startability and emission.

  In addition, in the example of FIG. 6B, the fuel injection start timing with respect to the intake valve opening timing (crank angle period α shown in FIG. 6B) is set in all the cylinders # 3, # 0, # 1, and # 2. Since they are the same, the port wet state of each cylinder # 0 to # 3 (the state where fuel adheres to the intake port 11a leading to the combustion chamber 1d) can be made uniform, thereby obtaining good startability. it can.

  Here, in the example of FIG. 6B, the fuel injection start timing in the starting process may be variably set according to the alcohol concentration. In this case, for example, as the alcohol concentration is higher, the fuel injection start timing at the time of starting is set to a crank angle that is more forward (more advanced) than the intake valve opening timing. Even when the fuel injection start timing is variably set according to the alcohol concentration in this way, the fuel injection start timing with respect to the intake valve opening timing is the same in all the cylinders # 3, # 0, # 1, and # 2. As above, the port wet state of each cylinder # 0 to # 3 may be made uniform.

-Other embodiments-
In the above example, the alcohol concentration sensor 105 is provided in the fuel supply system 100, 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 37.

  In the above example, the cylinder discrimination (crank angle determination) is performed from the output signals of the crank position sensor 31 and the cam position sensor 39, but the cylinder discrimination (crank angle determination) may be performed by other known means. Good.

  In the above example, the present invention is applied to the fuel injection control of a 4-cylinder flexible fuel internal combustion engine. However, the present invention is not limited to this example. The present invention can be applied to fuel injection control of a flexible fuel internal combustion engine. Further, the engine type (separate type such as series type, V type, and horizontally opposed type) is not particularly limited.

  In the above example, an example of a vehicle using only a flexible fuel internal combustion engine as a drive source has been described. However, the present invention can also be applied to a hybrid vehicle using a flexible fuel internal combustion engine and an electric motor as drive sources. In the case of a hybrid vehicle, for example, when there is an engine start request, the start time fuel injection control as shown in FIG. 4 may be executed.

  The present invention can be used for fuel injection control of a flexible fuel internal combustion engine capable of using a fuel containing alcohol, and more specifically, can be used for fuel injection control at the time of engine start.

1 Engine # 0 to # 3 Cylinder 1d Combustion chamber 2 Injector (fuel injection valve)
DESCRIPTION OF SYMBOLS 3 Spark plug 11 Intake passage 11a Intake port 12 Exhaust passage 13 Intake valve 14 Exhaust valve 31 Crank position sensor 39 Cam position sensor 100 Fuel supply system 105 Alcohol concentration sensor 200 ECU

Claims (4)

An intake port and an exhaust port communicating with each combustion chamber of a plurality of cylinders, an intake valve and an exhaust valve for opening and closing the intake port and the exhaust port, respectively, are provided for each cylinder, and alcohol is provided in the intake port or the intake passage. Fuel injection control applied to an internal combustion engine having a fuel injection valve capable of injecting contained fuel and increasing the fuel injection amount at start-up that is injected into the intake port or intake passage as the concentration of alcohol contained in the fuel is higher In the device
If the fuel injection of the starting fuel injection amount set based on the alcohol concentration of the fuel cannot be completed by the intake valve closing of the first injection cylinder at the time of starting the engine, the fuel injection is performed from the next cylinder A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1,
Whether or not fuel injection can be completed before the intake valve closing of the first injection cylinder based on the fuel injection period at the start and the intake valve closing timing based on the alcohol concentration of the fuel A fuel injection control device for an internal combustion engine, characterized in that The fuel injection control device for an internal combustion engine according to claim 1 or 2,
A fuel injection control device for an internal combustion engine, wherein the fuel injection start timing in the engine starting process is variably set according to the alcohol concentration. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3,
A fuel injection control device for an internal combustion engine, wherein a fuel injection start timing in an engine start process is set so that a port wet state of each cylinder is uniform.

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