JP2009085123A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine, promptly making engine rotating speed close to reference engine rotating speed at starting. <P>SOLUTION: The control device calculates feedback correcting amount (FB correcting amount) to an ignition timing so as to make the engine rotating speed close to the reference rotating speed. On the other hand, the control device estimates an in-cylinder air amount at the time of closing a suction valve opening, and estimates an air/fuel ratio according to estimated in-cylinder air amount. The control device corrects the calculated FB correction amount so as to decrease torque indicated in figure as the estimated air/fuel ratio is an air/fuel ratio on a rich side. The control device corrects the ignition timing only by the corrected FB correction amount. Even when the actual air/fuel ratio becomes the air/fuel ratio on the rich side as compared with the estimated air/fuel ratio because actual in-cylinder air amount is smaller than the estimated in-cylinder air amount, therefore, the torque indicated in the figure is prevented from becoming excessive. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus for changing an ignition timing based on an engine rotation speed when starting an internal combustion engine.

  Generally, as fuel supplied to an internal combustion engine, there are light fuel that is relatively easy to atomize (light side) and heavy fuel that is relatively difficult to atomize (heavy side). Exists.

  In the initial start period after the start operation for starting the internal combustion engine, the amount of fuel provided for combustion in the combustion chamber increases as the injected fuel is more easily atomized. Therefore, when light fuel is injected, a larger amount of fuel is actually combusted than when heavy fuel is injected. Therefore, the torque generated by the pressure of the gas in the combustion chamber is the output of the internal combustion engine. The indicated torque Tq, which is the torque for rotationally driving the shaft, increases.

  Therefore, when fuel on the lighter side than the assumed fuel is injected, the engine speed NE rises excessively during the initial startup period. On the other hand, when fuel heavier than the assumed fuel is injected, the indicated torque Tq may become excessively small, and the internal combustion engine may not be started quickly.

Accordingly, one of the conventional control devices for an internal combustion engine is to set the ignition timing SA so that the indicated torque Tq is reduced when the engine speed NE is higher than a predetermined reference engine speed NEref in the initial start period. Illustrated when the feedback correction amount ΔSA corresponding to the rotational speed difference ΔNE, which is the difference between the speed NE and the reference engine rotational speed NEref, is corrected to the retard side while the engine rotational speed NE is lower than the reference engine rotational speed NEref. The ignition timing SA is corrected to the advance side by a feedback correction amount ΔSA corresponding to the rotational speed difference ΔNE so that the torque Tq is increased (see, for example, Patent Document 1).
JP 2004-19571 A

  Thus, when the engine speed NE is higher than the reference engine speed NEref, the indicated torque Tq is reduced. On the other hand, when the engine speed NE is lower than the reference engine speed NEref, the indicated torque Tq is increased. The Therefore, the engine rotation speed NE can be brought close to the reference engine rotation speed NEref. As a result, the occurrence of blow-up can be prevented and the internal combustion engine can be started quickly.

  By the way, in the initial startup period, the fuel injection amount, which is the amount of fuel injected to be supplied to the combustion chamber, is set so that the air-fuel ratio of the mixed gas formed in the combustion chamber matches the predetermined target air-fuel ratio. It is considered suitable to do. Therefore, it is desirable to set the fuel injection amount in accordance with the in-cylinder air amount that is the amount of air introduced into the combustion chamber when the intake valve closes (intake valve close time).

  On the other hand, for example, in an internal combustion engine configured to inject fuel into an intake passage (intake port) upstream of the intake valve, fuel is injected before the intake valve is closed. Therefore, in such an internal combustion engine, the in-cylinder air amount at the time when the intake valve closes (at the time when the intake valve closes) at the time before the intake valve closes (when the fuel injection amount is determined) is estimated. The fuel injection amount is determined based on the estimated in-cylinder air amount.

  However, in the initial start period, the engine speed and the flow rate of the air flowing into the combustion chamber change relatively greatly during the period from the fuel injection amount determination time to the intake valve closing time. As a result, the amount of air flowing into the combustion chamber between the fuel injection amount determination time and the intake valve closing time also changes relatively large. Accordingly, the in-cylinder air amount at the intake valve closing time estimated at the time of determining the fuel injection amount and the in-cylinder air amount actually determined at the intake valve closing time may be relatively different. . In this case, the actual air-fuel ratio is relatively different from the target air-fuel ratio.

  By the way, the feedback correction amount ΔSA is calculated based on the rotational speed difference ΔNE and a coefficient adapted in a state where the actual air-fuel ratio matches the target air-fuel ratio. Therefore, if the actual air-fuel ratio is relatively different from the target air-fuel ratio in the initial start period, the engine speed is corrected even if the ignition timing SA is corrected by the feedback correction amount ΔSA determined based on the speed difference ΔNE. There is a problem that NE cannot be brought close to the reference engine speed NEref quickly.

  The present invention has been made to address the above-described problems, and one of its purposes is to provide a control device for an internal combustion engine that can quickly bring the engine rotation speed close to the reference engine rotation speed at the time of starting. It is to provide.

In order to achieve this object, a control device for an internal combustion engine according to the present invention includes:
An intake valve that can be switched between a communication state in which a combustion chamber and an intake passage for introducing air into the combustion chamber communicate with each other, and a shut-off state in which the combustion chamber and the intake passage are blocked;
By switching the intake valve state from the shut-off state to the communication state by driving the intake valve at the time of opening the intake valve, which is a time point before the compression top dead center, The intake valve is switched from the communication state to the shut-off state by driving the intake valve at the time before the intake valve is closed before the intake valve is opened. An intake valve drive mechanism configured in
Ignition means for generating a spark in the combustion chamber;
Fuel injection means for supplying the fuel to the combustion chamber by injecting fuel;
With
A mixed gas containing the air and the fuel is formed in the combustion chamber, and the formed mixed gas is ignited by a spark generated by the ignition means and burned in the combustion chamber, thereby rotating the output shaft. The present invention is applied to an internal combustion engine configured as described above.

Furthermore, the control device for an internal combustion engine according to the present invention provides:
Rotational speed acquisition means for acquiring an engine rotational speed that is the rotational speed of the output shaft;
The engine rotation speed is set to a reference engine rotation speed set based on the rotation angle of the output shaft from the time of the first explosion when the combustion first occurs in the initial start period after the start operation for starting the internal combustion engine. An ignition timing that is a timing at which the ignition means generates a spark based on the calculated feedback correction amount and calculates a feedback correction amount based on the acquired engine rotation speed and the reference engine rotation speed so as to approach each other Ignition timing correction means for correcting
The intake valve based on a physical quantity that has been determined up to a predetermined estimated time after the intake valve closing time and is closed until the intake valve closing time and that affects the amount of air introduced into the combustion chamber. An in-cylinder air amount that is the amount of air introduced into the combustion chamber at the valve closing time is estimated, and the estimated in-cylinder air amount and a fuel injection amount that is the amount of injected fuel are And an air-fuel ratio estimating means for estimating the air-fuel ratio of the mixed gas formed in the combustion chamber.

  In addition, the ignition timing correction means converts the indicated torque, which is a torque generated by the pressure of the gas in the combustion chamber and is intended to rotationally drive the output shaft, to the air side on which the estimated air-fuel ratio is rich. The calculated feedback correction amount is corrected based on the estimated air-fuel ratio so as to decrease as the fuel ratio increases, and the ignition timing is corrected by the corrected feedback correction amount.

  The engine rotation speed may be the rotation speed of the output shaft of the internal combustion engine acquired at a certain time point, or the average value of the rotation speeds of the output shaft of the internal combustion engine acquired at a plurality of time points. May be. The engine rotation speed may be represented by a parameter that represents the rotation speed of the output shaft of the internal combustion engine. This parameter is, for example, the time (elapsed time) that has elapsed since the time when the cylinder where the combustion of the mixed gas first occurred reached the compression top dead center in the combustion cycle where the combustion occurs (the time when the first explosion occurred). . In this case, it can be said that “high engine speed” corresponds to “short elapsed time”.

  According to this, during the initial startup period, the feedback correction amount is determined based on the acquired engine rotation speed and the reference engine rotation speed so that the engine rotation speed matches the reference engine rotation speed, and the determined feedback The ignition timing is corrected based on the correction amount. Then, the mixed gas is ignited at the corrected ignition timing. Thereby, the engine rotation speed can be brought close to the reference engine rotation speed. As a result, the occurrence of blow-up can be prevented and the internal combustion engine can be started quickly.

  By the way, in the initial start period, the fuel injection amount is set so that the air-fuel ratio becomes an air-fuel ratio leaner than the maximum output air-fuel ratio that maximizes the indicated torque. Therefore, when the air-fuel ratio changes to the rich side, the indicated torque increases.

  Therefore, if the feedback correction amount is corrected so as to reduce the indicated torque as the air-fuel ratio is richer, as in the above configuration, the actual in-cylinder air amount is larger than the planned in-cylinder air amount. As a result, the illustrated torque can be prevented from becoming excessive even if the actual air-fuel ratio becomes richer than the planned air-fuel ratio. Furthermore, even if the actual in-cylinder air amount becomes larger than the planned in-cylinder air amount, the indicated torque is too small even if the actual air-fuel ratio becomes leaner than the planned air-fuel ratio. Can be avoided. As a result, even if the actual air-fuel ratio is different from the planned air-fuel ratio, the engine speed can be quickly brought close to the reference engine speed.

  In this case, it is preferable that the air-fuel ratio estimation means is configured to detect the physical quantity at the time when the intake valve is closed and to estimate the in-cylinder air quantity based on the detected physical quantity.

  The air-fuel ratio estimation means acquires an intake time from the intake valve opening time to the intake valve close time, and corrects the estimated air-fuel ratio to a rich side as the acquired intake time becomes longer. It is suitable to be configured.

  During the period in which the state of the intake valve is maintained in the communication state, air flows from the intake passage to the combustion chamber. Thereby, vaporization of the fuel adhering to the wall surface forming the intake passage or the wall surface forming the combustion chamber is promoted. Further, the diffusion of fuel in the mixed gas formed in the combustion chamber proceeds. Accordingly, the longer the intake time during which the intake valve is maintained in the communication state, the higher the proportion of fuel vaporized out of the fuel adhering to the wall surface forming the intake passage or the wall surface forming the combustion chamber, The distribution of the fuel in the mixed gas is brought close to a uniform distribution. As a result, the amount of fuel actually burned in the combustion chamber increases. That is, the actual air-fuel ratio (actual air-fuel ratio) of the mixed gas used for combustion becomes a richer air-fuel ratio.

  Therefore, if the air-fuel ratio is corrected to the rich side as the intake time becomes longer as in the above configuration, the air-fuel ratio that is the basis for correcting the feedback correction amount can be brought close to the actual air-fuel ratio. As a result, the ignition timing can be set at an appropriate timing according to the actual air-fuel ratio, and the engine speed can be made closer to the reference engine speed more quickly.

  In this case, the air-fuel ratio estimating means acquires the compression time from the intake valve closing time to a predetermined reference time near the compression top dead center, and the estimated air-fuel ratio is made richer as the acquired compression time becomes longer. It is preferred to be configured to correct to the side.

  In the period from the intake valve closing time to a predetermined reference time near the compression top dead center, the mixed gas in the combustion chamber is compressed. Thereby, since the temperature of mixed gas becomes high, vaporization of the fuel adhering to the wall surface which forms a combustion chamber is accelerated | stimulated. Further, the pre-reaction of fuel in the mixed gas (preliminary reaction such as decomposition of fuel molecules) is promoted. Therefore, as the compression time from the intake valve closing time to the reference time becomes longer, the proportion of fuel vaporized out of the fuel adhering to the wall surface forming the combustion chamber increases, and of the fuel in the mixed gas The proportion of fuel that has been pre-reacted is increased. As a result, the amount of fuel actually burned increases. That is, the actual air-fuel ratio (actual air-fuel ratio) of the mixed gas used for combustion becomes a richer air-fuel ratio.

  Therefore, if the air-fuel ratio is corrected to the rich side as the compression time becomes longer as in the above configuration, the air-fuel ratio that is the basis for correcting the feedback correction amount can be brought closer to the actual air-fuel ratio. As a result, the ignition timing can be set at an appropriate timing according to the actual air-fuel ratio, and the engine speed can be made closer to the reference engine speed more quickly.

<First Embodiment>
Hereinafter, embodiments of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a system in which this control device is applied to a spark ignition type multi-cylinder (four-cylinder) internal combustion engine. Although FIG. 1 shows only a cross section of one cylinder, the other cylinders have the same configuration.

  The internal combustion engine 10 is configured to be operated by a four-cycle operation method. In the 4-cycle operation system, the intake stroke from the exhaust top dead center TDC1 to the intake bottom dead center BDC1, the compression stroke from the intake bottom dead center BDC1 to the compression top dead center TDC2, and the compression top dead center TDC2 to the expansion bottom dead center BDC2 This is an operation method in which each cylinder repeats a combustion cycle consisting of four strokes of an expansion stroke and an expansion stroke from an expansion bottom dead center BDC2 to an exhaust top dead center TDC1. The internal combustion engine 10 is configured such that the phases of the combustion cycles of the four cylinders differ by a magnitude corresponding to one stroke (180 ° at a crank angle described later).

  The internal combustion engine 10 includes a cylinder block portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and fuel and air to the cylinder block portion 20. An intake system 40 for supplying (introducing) the mixed gas to be included, and an exhaust system 50 for releasing the exhaust gas from the cylinder block unit 20 to the outside are included.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24 as an output shaft. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 is driven to rotate. The cylinder 21, the head of the piston 22 and the cylinder head part 30 form a combustion chamber 25.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32, a variable intake timing device 33 constituting an intake valve driving mechanism for driving the intake valve 32, an exhaust port 34 communicating with the combustion chamber 25, an exhaust A valve 35, an exhaust camshaft 36 for driving the exhaust valve 35, an ignition plug 37, an igniter 38 including an ignition coil for generating a high voltage applied to the ignition plug 37, and an injector 39 as a fuel injection means are provided. The spark plug 37 and the igniter 38 constitute ignition means for igniting the mixed gas formed in the combustion chamber 25 by generating a spark in the combustion chamber 25.

  In the intake valve 32, the combustion chamber 25 and the intake passage communicate with each other (the intake valve 32 is open), and the combustion chamber 25 and the intake passage are blocked (the intake valve 32 is closed). It is configured to be switchable to a shut-off state.

  The variable intake timing device 33 includes an intake camshaft. The variable intake timing device 33 switches the state of the intake valve 32 from the shut-off state to the communication state by driving the intake valve 32 at the intake valve opening time Tvo that is a time before the compression top dead center TDC2. The valve 32 is opened), and the intake valve 32 is driven at the intake valve closing time Tvc that is before the compression top dead center TDC2 and after the intake valve opening time Tvo. Thus, the state of the intake valve 32 is switched from the communication state to the shut-off state (the intake valve 32 is closed). The variable intake timing device 33 is configured to continuously change the camshaft phase angle φ, which is the phase angle of the intake camshaft, when driven by an actuator 33a.

  The injector 39 is connected to a fuel tank (not shown). The fuel in the fuel tank is supplied to the injector 39. The injector 39 supplies fuel into the combustion chamber 25 by injecting the supplied fuel into the intake port 31 in response to the instruction signal.

  The intake system 40 includes a plurality of independent passages communicating with the intake ports 31 of the respective cylinders, and an intake manifold 41 that forms a collecting portion that collects these passages on the upstream side, and an end portion on the collecting portion side of the intake manifold 41 Is connected to the surge tank 42, one end is connected to the surge tank 42, and the intake port 43, the intake manifold 41 and the surge tank 42 form an intake passage, and the other end of the intake duct 43 is downstream (the surge tank 42 ), An air filter 44 and a throttle valve 45 disposed in the intake duct 43 in order.

  The throttle valve 45 is rotatably supported by the intake duct 43. The throttle valve 45 is driven (controlled) by a throttle valve actuator 45a, thereby adjusting the opening (throttle valve opening TA) to adjust the passage sectional area of the intake duct 43.

  The exhaust system 50 includes a plurality of independent passages communicating with the exhaust ports 34 of the respective cylinders, and an exhaust manifold 51 that forms a collecting portion that collects these passages on the downstream side, and an end portion on the collecting portion side of the exhaust manifold 51. And an exhaust pipe 52 that forms an exhaust passage together with the exhaust port 34 and the exhaust manifold 51, and a three-way catalyst device 53 disposed in the exhaust pipe 52.

  On the other hand, this system includes a hot-wire air flow meter 61, an intake air temperature sensor 62, an intake air pressure sensor 63, a throttle position sensor 64, a cam position sensor 65, a crank position sensor 66 constituting a rotational speed acquisition means, and an accelerator opening sensor 67. , A surge tank pressure sensor 68, a coolant temperature sensor 69, and an electric control device 70 are provided.

The air flow meter 61 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The air flow meter 61 detects the flow rate of air passing through the intake duct 43 (that is, the intake flow rate) and outputs a signal representing the intake flow rate Ga.
The intake air temperature sensor 62 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The intake air temperature sensor 62 detects the temperature of the air upstream of the throttle valve 45 (ie, the intake air temperature) and outputs a signal representing the intake air temperature Ta.
The intake pressure sensor 63 is disposed in the intake duct 43 between the air filter 44 and the throttle valve 45. The intake pressure sensor 63 detects the pressure of the air upstream of the throttle valve 45 (that is, the intake pressure) and outputs a signal representing the intake pressure Pa.

  The throttle position sensor 64 detects the opening degree of the throttle valve 45 (throttle valve opening degree) and outputs a signal representing the throttle valve opening degree TA.

  The cam position sensor 65 outputs a signal (G2 signal) having a pulse generated only three times while the intake camshaft rotates by 360 ° (that is, the crankshaft 24 rotates by 720 °). . The three pulses include a first pulse, a second pulse that occurs when the intake camshaft rotates 90 ° after the first pulse occurs (ie, the crankshaft 24 rotates 180 °), and And a third pulse generated when the intake camshaft rotates by 90 ° after the second pulse is generated. That is, when the intake camshaft rotates by 180 ° after the third pulse is generated, the first pulse is generated again.

  The crank position sensor 66 outputs a signal having a narrow pulse generated every time the crankshaft 24 rotates 10 ° and a wide pulse generated every time the crankshaft 24 rotates 360 °. This signal is used to obtain the required rotation time T30, which is the time that elapses while the crankshaft 24 rotates 30 °, and the engine speed NE that indicates the number of times the crankshaft 24 rotates 360 ° per minute. Used for. In this example, the engine rotational speed NE is calculated based on the time elapsed from the time point 180 degrees before the current time to the current time at the crank angle.

The accelerator opening sensor 67 detects the amount of operation of the accelerator pedal 81 operated by the driver, and outputs a signal representing the amount of operation of the accelerator pedal (accelerator pedal operation amount) Accp.
The surge tank internal pressure sensor 68 detects the gas pressure (surge tank internal pressure) in the surge tank 42 and outputs a signal representing the surge tank internal pressure Ps.
The cooling water temperature sensor 69 detects the temperature of the cooling water circulating in the side wall of the cylinder 21 (cooling water temperature), and outputs a signal representing the cooling water temperature Tw.

  The electrical control device 70 is connected to each other by a bus 71, a ROM 72 that stores data such as programs, tables (lookup tables, maps), constants, and the like that are stored in advance so as to hold data to be executed by the CPU 71. A RAM 73 that temporarily holds data according to the data, a backup RAM 74 that stores data while the internal combustion engine 10 is operating, and a backup RAM 74 and AD that holds the stored data while the operation of the internal combustion engine 10 is stopped A microcomputer including an interface 75 including a converter. The interface 75 is connected to the sensors 61 to 69, supplies signals from the sensors 61 to 69 to the CPU 71, and according to instructions from the CPU 71, the actuator 33a, the igniter 38, the injector 39, and the throttle valve of the variable intake timing device 33. A drive signal (instruction signal) is sent to the actuator 45a.

<Overview of operation>
Next, an outline of the operation of the control device for an internal combustion engine configured as described above will be described by focusing on the operation for one cylinder (specific cylinder).

  As shown in FIG. 2, during the initial start period after the start operation for starting the internal combustion engine 10, the control device sets the crank angle of the specific cylinder to an angle 90 degrees before the exhaust top dead center TDC1. Then, based on the surge tank internal pressure Ps detected at the time Tc1 and the engine speed NE calculated at the time Tc1, the time when the intake valve 32 of the specific cylinder is closed (the intake valve closed). At the valve timing), the cylinder air amount that is the amount of air introduced into the combustion chamber 25 of the specific cylinder at Tvc is estimated as the first cylinder air amount KL1.

  Further, the control device estimates the first in-cylinder air amount KL1 so that the air-fuel ratio of the mixed gas formed in the combustion chamber 25 of the specific cylinder matches the target air-fuel ratio (in this example, the theoretical air-fuel ratio). Based on the above, the fuel injection amount fi, which is the amount of fuel injected by the injector 39 of the specific cylinder, is determined. And a control apparatus injects a fuel with the injector 39 of a specific cylinder in the fuel-injection period Tinj according to the determined fuel-injection quantity fi.

  Thereafter, when the predetermined intake valve opening time Tvo near the exhaust top dead center TDC1 is reached, the variable intake timing device 33 opens the intake valve 32 by driving the intake valve 32 of the specific cylinder. As a result, a mixed gas composed of air and fuel is introduced into the combustion chamber 25 of the specific cylinder. Then, when the predetermined intake valve closing time Tvc near the intake bottom dead center BDC1, the variable intake timing device 33 drives the intake valve 32 of the specific cylinder to close the intake valve 32.

  Furthermore, the control device determines the intake valve closing time based on the surge tank internal pressure Ps detected at the intake valve closing time Tvc and the engine speed NE calculated at the intake valve closing time Tvc. The in-cylinder air amount that is the amount of air introduced into the combustion chamber 25 of the specific cylinder at Tvc is estimated as the second in-cylinder air amount KL2. In addition, the control device controls the in-cylinder fuel amount fc that is the amount of fuel introduced into the combustion chamber 25 of the specific cylinder at the intake valve closing time Tvc based on the fuel injection amount fi determined at the time Tc1. And the air-fuel ratio AbyF of the mixed gas formed in the combustion chamber 25 of the specific cylinder is estimated based on the estimated second cylinder air amount KL2 and the estimated cylinder fuel amount fc.

  Further, the control device sets a rotational speed difference ΔNE (= NEref) which is a difference between a reference engine rotational speed NEref set in advance according to the rotational angle of the crankshaft 24 from the time of the first explosion and the calculated engine rotational speed NE. -NE) to determine the feedback correction amount ΔSA.

In addition, the control device corrects and corrects the feedback correction amount ΔSA determined based on the estimated air-fuel ratio AbyF so that the indicated torque decreases as the estimated air-fuel ratio AbyF becomes richer. The ignition timing SA is corrected by the feedback correction amount ΔSA. Here, the indicated torque is a torque generated by the pressure of the gas in the combustion chamber 25 and is a torque for rotationally driving the crankshaft 24.
When the corrected ignition timing SA is reached, the control device generates a spark by the spark plug 37 of the specific cylinder. Thereby, the mixed gas in the combustion chamber 25 of a specific cylinder burns.

  Thus, according to this control device, the feedback correction amount ΔSA is corrected so that the indicated torque is reduced as the air-fuel ratio AbyF estimated at the intake valve closing time Tvc is the richer air-fuel ratio. As a result, even if the actual air-fuel ratio is different from the planned air-fuel ratio (target air-fuel ratio), the engine speed NE can be quickly brought close to the reference engine speed NEref.

<Details of operation>
Next, the actual operation of the electric control device 70 will be described with reference to FIGS.
First, a driver who desires to start the operation of the internal combustion engine 10 switches the ignition switch IS from the off state to the on state in order to start the internal combustion engine 10 (a start operation for starting the internal combustion engine 10 is performed). Do). Thus, the CPU 71 sends a drive signal to the starter motor in order to rotate the crankshaft 24 (start cranking) by a starter motor (not shown). As a result, cranking is started.

(Start initial control execution judgment)
The CPU 71 reaches the time point Tc1 (fuel injection amount determination time point) Tc1 that is 90 degrees earlier than the exhaust top dead center TDC1 in the crank angle of the start initial control execution determination routine shown by the flowchart in FIG. It is executed every time (that is, every time the crank angle changes by 180 °).

  Accordingly, at a predetermined timing, the CPU 71 starts processing from step 300 and proceeds to step 305 to read the accelerator pedal operation amount Accp (load of the engine 10) detected by the accelerator opening sensor 67. Next, the CPU 71 proceeds to step 310 to determine whether or not the accelerator pedal operation amount Accp read in step 305 is “0”.

  At this time, since the driver is not operating the accelerator pedal 81, the accelerator pedal operation amount Accp is “0”. Accordingly, the CPU 71 determines “Yes” in step 310 and proceeds to step 315 to determine whether or not the combustion occurrence frequency k is smaller than a predetermined threshold frequency kth (“50” in this example).

  Here, the number of combustion occurrences k is an integer representing the number of times an arbitrary cylinder has reached the exhaust stroke from the time of the first explosion when the combustion of the mixed gas first occurs in the initial startup period to the present time. That is, it can be said that the number of combustion occurrences k represents the rotation angle of the crankshaft 24 from the time of the first explosion occurrence. Note that the combustion occurrence count k is set to “0” when the ignition switch IS is switched from the off state to the on state.

  Therefore, at this time, the number of combustion occurrences k is smaller than the threshold number kth. Accordingly, the CPU 71 determines “Yes” in step 315, proceeds to step 320, and sets the value of the start initial control execution flag Xs to “1”.

Here, the start initial control execution flag Xs is a flag indicating whether or not feedback control (starting initial control) for correcting the ignition timing SA based on the engine speed NE is executed, and the value thereof is “1”. If it is, start initial control is executed, and “0” indicates that start initial control is not executed. As will be described later, the value of the start initial control execution flag Xs is set to “0” when the accelerator pedal operation amount Accp is greater than “0” and / or when the combustion occurrence count k is equal to or greater than the threshold count kth. Set (see step 325).
Then, the CPU 71 proceeds to step 399 to end the present routine tentatively.

(Combustion start judgment)
Further, the CPU 71 executes the combustion start determination routine shown by the flowchart in FIG. 4 following the start initial control execution determination routine of FIG.

  Therefore, when the execution of the start initial control execution determination routine is completed, the CPU 71 starts the process from step 400 and proceeds to step 405 to determine whether or not the value of the combustion start flag Xb is “0”.

  Here, the combustion start flag Xb is a flag indicating whether or not combustion of the mixed gas has occurred in any of the cylinders from the cranking start time to the present time, and its value is “1”. If it exists, “0” indicates that it did not occur. As will be described later, the value of the combustion start flag Xb is set to “1” when the required rotation time T30 is shorter than the predetermined threshold time α in this routine (see step 420), and the ignition switch IS is turned on. Set to “0” when switched from off to on.

  Accordingly, since the value of the combustion start flag Xb is “0” at this time, the CPU 71 determines “Yes” in step 405 and proceeds to step 410, separately based on the signal from the crank position sensor 66. The calculated required rotation time T30 is read.

  Next, the CPU 71 proceeds to step 415 to determine whether or not the required rotation time T30 read in step 410 is shorter than the threshold time α. Here, the threshold time α is set to a time slightly shorter than the minimum value of the required rotation time T30 when it is assumed that combustion does not occur during cranking.

  At this time, no combustion of the mixed gas has occurred. Accordingly, since the required rotation time T30 is longer than the threshold time α, the CPU 71 makes a “No” determination at step 415 to directly proceed to step 499 to end the present routine tentatively.

(Calculation of the number of combustion occurrences)
In addition, the CPU 71 executes the combustion occurrence number calculation routine shown by the flowchart in FIG. 5 following the combustion start determination routine in FIG.

  Accordingly, when the execution of the combustion start determination routine ends, the CPU 71 starts the process from step 500 and proceeds to step 505 to determine whether or not the value of the start initial control execution flag Xs is “1”.

  At this time, since the value of the start initial control execution flag Xs is “1”, the CPU 71 determines “Yes” in step 505, proceeds to step 510, and the value of the combustion start flag Xb is “1”. It is determined whether or not there is.

  At this time, no combustion of the mixed gas occurs in any cylinder. Accordingly, since the value of the combustion start flag Xb is “0”, the CPU 71 makes a “No” determination at step 510 to directly proceed to step 599 to end the present routine tentatively.

(First cylinder air amount estimation)
Further, the CPU 71 estimates the in-cylinder air amount at the intake valve closing time Tvc that comes next to the cylinder (n-th cylinder) that has reached the fuel injection amount determination time Tc1 at the current time. The first in-cylinder air amount estimation routine shown by the above is executed following the combustion occurrence number calculation routine of FIG.

  Here, the value n is an integer representing that the nth cylinder is the cylinder that has reached the fuel injection amount determination time Tc1 at the present time. The value n is set by the CPU 71 executing a cylinder discrimination routine (not shown) for discriminating the cylinder. For the sake of convenience, in this specification, the first cylinder, the second cylinder, the third cylinder, and the first cylinder are arranged in ascending order of the period from the start of cranking to the first fuel injection amount determination time Tc1. This is called a 4-cylinder.

  Accordingly, when the execution of the combustion occurrence number calculation routine is completed, the CPU 71 starts the process from step 600 and proceeds to step 605 to determine whether or not the value of the start initial control execution flag Xs is “1”.

  At this time, since the value of the start initial control execution flag Xs is “1”, the CPU 71 determines “Yes” in step 605 and proceeds to step 610 to detect the surge detected by the surge tank pressure sensor 68. The tank pressure Ps is read.

  Next, the CPU 71 proceeds to step 615 and reads the engine speed NE separately calculated based on the signal from the crank position sensor 66. Then, the CPU 71 proceeds to step 620, and the camshaft phase, which is the phase angle of the intake camshaft of the variable intake timing device 33, separately calculated based on the signal from the cam position sensor 65 and the signal from the crank position sensor 66. Read angle φ.

  Next, the CPU 71 proceeds to step 625 to read the table MapC that defines the relationship between the engine rotational speed NE and the camshaft phase angle φ and the coefficient C, the engine rotational speed NE read in step 615 and the step 620. The coefficient C is determined based on the camshaft phase angle φ. Here, the coefficient C is a proportional coefficient.

  In the following description, a table represented as MapX (a, b) means a table that defines the relationship between the variable a, the variable b, and the value X. Further, obtaining the value X based on the table MapX (a, b) means obtaining (determining) the value X based on the current variable a and the current variable b and the table MapX (a, b). It means that. Note that there may be one variable or three or more variables.

  Further, in step 625, the CPU 71 determines a value D based on the table MapD (NE, φ). Here, the value D is a value reflecting the amount of burned gas remaining in the combustion chamber 25.

  Then, the CPU 71 proceeds to step 630, and the value determined in step 625 to the value C · Ps obtained by multiplying the coefficient C determined in step 625 by the surge tank internal pressure Ps read in step 610. The in-cylinder inflow air flow rate mc is set to a value C · Ps + D to which D is added. Here, the in-cylinder inflow air flow rate mc is a flow rate of air flowing into the combustion chamber 25 of the nth cylinder.

  Next, the CPU 71 proceeds to step 635 to determine the intake time Tint based on the table MapTint (NE, φ). Here, the intake time Tint is the time from when the intake valve 32 of the nth cylinder is opened until the intake valve 32 of the nth cylinder is closed (that is, when the intake valve 32 of the nth cylinder is opened). This is an estimated value of the time during which air is substantially introduced into the combustion chamber 25 of the nth cylinder by maintaining the state of

Thereafter, the CPU 71 proceeds to step 640 to multiply the in-cylinder inflow air flow rate mc set in step 630 by the intake time Tint determined in step 635 and mc · Tint into the first in-cylinder air amount. Set KL1. Here, the first in-cylinder air amount KL1 is the amount of air introduced into the combustion chamber 25 of the nth cylinder at the time Tvc when the intake valve 32 of the nth cylinder is closed (at the time of intake valve closing) Tvc. Is an estimated value.
Then, the CPU 71 proceeds to step 699 to end the present routine tentatively.

(Fuel injection amount determination)
In addition, the CPU 71 executes the fuel injection amount determination routine shown by the flowchart in FIG. 7 following the first in-cylinder air amount estimation routine of FIG.

  Therefore, when the execution of the first in-cylinder air amount estimation routine is completed, the CPU 71 starts the process from step 700 and proceeds to step 705, and the engine speed NE calculated separately based on the signal from the crank position sensor 66. Is read.

  Next, the CPU 71 proceeds to step 710 to determine whether or not the value of the start initial control execution flag Xs is “1”. At this time, since the value of the start initial control execution flag Xs is “1”, the CPU 71 determines “Yes” in Step 710 and proceeds to Step 715, and the value of the combustion start flag Xb is “1”. It is determined whether or not there is.

  At this time, no combustion of the mixed gas occurs in any cylinder. Accordingly, since the value of the combustion start flag Xb is “0”, the CPU 71 makes a “No” determination at step 715 to proceed to step 720 to reach the nth cylinder (currently the fuel injection amount determination time Tc1). The fuel injection amount fi (n) of the cylinder) is set to the pre-combustion fuel injection amount fi0. Here, the pre-combustion fuel injection amount fi0 is preset to a predetermined value. The pre-combustion fuel injection amount fi0 may be a value set so as to increase as the cooling water temperature Tw decreases.

Next, the CPU 71 proceeds to step 725 and sends an instruction signal corresponding to the fuel injection amount fi (n) of the nth cylinder set in step 720 to the injector 39 of the nth cylinder. Thus, the injector 39 of the nth cylinder injects fuel by the fuel injection amount fi (n) in the fuel injection period Tinj corresponding to the determined fuel injection amount fi (n) of the nth cylinder.
Then, the CPU 71 proceeds to step 799 to end this routine once.

(2nd cylinder air volume estimation)
Further, the CPU 71 estimates the in-cylinder air amount at the present time of the cylinder (m-th cylinder) that has reached the intake valve closing time Tvc every time any cylinder reaches the intake valve closing time Tvc as the estimation time. Therefore, the second in-cylinder air amount estimation routine shown by the flowchart in FIG. 8 is executed. Note that the execution of the processing of the second in-cylinder air amount estimation routine corresponds to the achievement of part of the function of the air-fuel ratio estimation means.

  Here, the value m is an integer indicating that the m-th cylinder is the cylinder that has reached the intake valve closing time Tvc at the present time. The value m is set by the CPU 71 executing a cylinder discrimination routine (not shown) for discriminating the cylinder.

  This second in-cylinder air amount estimation routine is the same as that shown in FIG. 6 except that the second in-cylinder air amount KL2 is used instead of the first in-cylinder air amount KL1 as the estimated value of the in-cylinder air amount. This routine is the same as the one-cylinder air amount estimation routine. Here, the second in-cylinder air amount KL2 is an estimated value of the amount of air introduced into the combustion chamber 25 of the m-th cylinder at the present time (intake valve closing time Tvc).

  Therefore, when the predetermined timing is reached, the CPU 71 starts the process from step 800 and executes the processes of steps 805 to 640 as in the case of executing the processes of steps 605 to 640 of the first in-cylinder air amount estimation routine of FIG. The process of step 840 is executed. In other words, the CPU 71 determines the current time based on the surge tank pressure Ps detected at the present time, the engine speed NE calculated at the current time, and the camshaft phase angle φ detected at the current time. The in-cylinder air amount that is the amount of air introduced into the combustion chamber 25 of the m-th cylinder is estimated as the second in-cylinder air amount KL2.

  The surge tank internal pressure Ps detected at the intake valve closing time Tvc and the engine speed NE calculated at the intake valve closing time Tvc are physical quantities determined by the intake valve closing time Tvc. It can be said that this is a physical quantity that affects the amount of air introduced into the combustion chamber 25.

(Air-fuel ratio estimation)
Further, the CPU 71 is configured to execute the air-fuel ratio estimation routine shown in the flowchart of FIG. 9 following the second cylinder air amount estimation routine of FIG. Note that the execution of the processing of the air-fuel ratio estimation routine corresponds to the achievement of part of the function of the air-fuel ratio estimation means.

  Therefore, when the execution of the second in-cylinder air amount estimation routine is completed, the CPU 71 starts the process from step 900 and proceeds to step 905 to determine whether or not the value of the start initial control execution flag Xs is “1”. judge.

  At this time, since the value of the start initial control execution flag Xs is “1”, the CPU 71 determines “Yes” in step 905 and proceeds to step 910, and separately based on the signal from the crank position sensor 66. The calculated engine speed NE is read. Next, the CPU 71 proceeds to step 915 and reads the cooling water temperature Tw detected by the cooling water temperature sensor 69.

  Then, the CPU 71 proceeds to step 920 to determine the fuel adhesion rate R based on the table MapR (KL2, NE, Tw). Here, the fuel adhesion rate R is the ratio of the fuel directly adhering to the intake passage forming member (the wall surface forming the intake port 31 and the intake valve 32), which is a member forming the intake passage, of the injected fuel ( Adhesion rate).

  Further, in step 920, the CPU 71 determines the fuel residual ratio P based on the table MapP (KL2, NE, Tw). Here, the fuel residual rate P is the ratio of the fuel adhering to the intake passage forming member to the fuel adhering to the intake passage forming member even after one combustion cycle (residual rate). ).

  Next, the CPU 71 proceeds to step 925, the equation shown in step 925, the fuel adhesion rate R and the fuel residual rate P determined in step 920, the m-th cylinder (the intake valve closing at the present time). Based on the fuel injection amount fi (m) of the m-th cylinder determined at the fuel injection amount determination time Tc1 and the fuel adhesion amount fw (m) of the m-th cylinder. The fuel amount fc is estimated.

  The fuel injection amounts fi (1) to fi (4) are set to “0” when the ignition switch IS is switched from the off state to the on state. The fuel adhesion amounts fw (1) to fw (4) are also set to “0” when the ignition switch IS is switched from the off state to the on state.

  Then, the CPU 71 proceeds to step 930 to determine the formula shown in step 930, the fuel adhesion rate R and the fuel residual rate P determined in step 920, and the fuel injection amount determination time Tc1 for the m-th cylinder. The fuel adhesion amount fw (m) of the m-th cylinder is updated based on the determined fuel injection amount fi (m) of the m-th cylinder and the fuel adhesion amount fw (m) of the m-th cylinder.

Next, the CPU 71 proceeds to step 935 so that the in-cylinder fuel amount estimated in step 925 is calculated from the second in-cylinder air amount KL2 estimated by the CPU 71 executing the second in-cylinder air amount estimation routine. The air-fuel ratio AbyF is set to a value KL2 / fc divided by fc. Here, the air-fuel ratio AbyF is an estimated value of the air-fuel ratio of the mixed gas formed in the combustion chamber 25 of the m-th cylinder.
Then, the CPU 71 proceeds to step 999 to end this routine once.

(Ignition timing decision)
In addition, the CPU 71 executes an ignition timing determination routine shown by a flowchart in FIG. 10 following the air-fuel ratio estimation routine in FIG.

  Accordingly, when the execution of the air-fuel ratio estimation routine ends, the CPU 71 starts the process from step 1000 and proceeds to step 1005 to determine whether or not the value of the start initial control execution flag Xs is “1”.

  At this time, since the value of the start initial control execution flag Xs is “1”, the CPU 71 determines “Yes” in Step 1005 and proceeds to Step 1010, and the value of the combustion start flag Xb is “1”. It is determined whether or not there is.

  At this time, no combustion of the mixed gas occurs in any cylinder. Therefore, since the value of the combustion start flag Xb is “0”, the CPU 71 determines “No” in step 1010 and proceeds to step 1015 to set the ignition timing SA to a predetermined predetermined pre-combustion ignition timing. Set to SA0.

  Note that the pre-combustion ignition timing SA0 is represented by BTDC. BTDC is defined for each cylinder. BTDC is the rotation angle (crank angle) of the crankshaft 24 with the compression top dead center TDC2 in each cylinder as the origin and the direction opposite to the rotation direction of the crankshaft 24 taken positively. Hereinafter, in this specification, any variable representing the ignition timing is represented by BTDC.

Next, the CPU 71 proceeds to step 1020 to send an instruction signal corresponding to the ignition timing SA set in step 1015 to the igniter 38 of the m-th cylinder (the cylinder that has reached the intake valve closing time Tvc at the present time). Is sent to. Thereby, the igniter 38 of the m-th cylinder applies a high voltage to the spark plug 37 of the m-th cylinder at the ignition timing SA. As a result, the spark plug 37 of the m-th cylinder generates a spark in the combustion chamber 25 of the m-th cylinder.
Then, the CPU 71 proceeds to step 1099 to end the present routine tentatively.

  Thereafter, when a sufficient amount of vaporized fuel is introduced into the combustion chamber 25 of a cylinder due to vaporization of the fuel adhering to the intake passage forming member, the spark plug 37 sparks in the combustion chamber 25 of the cylinder. The mixed gas burns by generating. Here, as shown in FIG. 11, the description will be continued assuming that the first combustion (first explosion) occurs in the first cylinder.

  In this case, when the crankshaft 24 is rotated by 90 ° from the time when the first cylinder reaches the compression top dead center TDC2 of the combustion cycle in which the first combustion in the first cylinder has occurred (the first explosion occurs), the CPU 71 Starts the combustion start determination routine of FIG. 4 and proceeds to step 415.

  At this time, since a relatively large indicated torque is generated due to the combustion of the mixed gas in the first cylinder, the required rotation time T30 is shorter than the threshold time α.

Accordingly, the CPU 71 determines “Yes” in step 415, proceeds to step 420, and sets the value of the combustion start flag Xb to “1”.
Then, the CPU 71 proceeds to step 499 to end this routine once.

  Further, when the CPU 71 starts processing of the combustion occurrence number calculation routine of FIG. 5 and proceeds to step 510 where it is determined whether or not the value of the combustion start flag Xb is “1”, the CPU 71 proceeds to step 510. If “Yes”, the process proceeds to step 515.

  In step 515, the CPU 71 sets the combustion occurrence count k to a value k + 1 (= 1) obtained by adding “1” to the combustion occurrence count k (= 0). Next, the CPU 71 proceeds to step 599 to end the present routine tentatively.

  In addition, when the CPU 71 starts processing of the fuel injection amount determination routine of FIG. 7 and proceeds to step 715 where it is determined whether or not the value of the combustion start flag Xb is “1”, the CPU 71 proceeds to step 715. At step 730, the process proceeds to step 730.

  In step 730, the CPU 71 determines the starting initial fuel injection amount fia based on the table Mapfia (KL1, NE), and sets the fuel injection amount fi (4) of the fourth cylinder to the determined starting initial fuel injection amount fia. . Here, the table Mapfia shows that the required initial fuel injection amount fia is the target air-fuel ratio leaner than the maximum output air-fuel ratio at which the indicated torque becomes the maximum in the illustrated air-fuel ratio of the mixed gas formed in the combustion chamber 25. In this example, it is set in advance based on experimentally measured values so as to be an amount that matches the theoretical air-fuel ratio.

  Note that the processing in step 730 is executed by estimating the in-cylinder air amount at a time before the intake valve closing time Tvc (actually, the intake valve opening time Tvo) and estimating the in-cylinder air. This corresponds to the achievement of part of the function of the means for determining the fuel injection amount based on the amount and the target air-fuel ratio.

  Next, the CPU 71 proceeds to step 725 and sends an instruction signal corresponding to the fuel injection amount fi (4) of the fourth cylinder set in step 730 to the fourth cylinder (current fuel injection amount determination time Tc1). Then, the routine shown in FIG. 7 is temporarily terminated.

Then, the crankshaft 24 rotates and the third cylinder reaches the intake valve closing time Tvc. At this time, when the CPU 71 starts processing of the ignition timing determination routine of FIG. 10 and proceeds to step 1010 where it is determined whether or not the value of the combustion start flag Xb is “1”, the CPU 71 At 1010, it is determined as “Yes”, and the process proceeds to Step 1025.
In step 1025, the CPU 71 reads the engine speed NE calculated separately based on the signal from the crank position sensor 66.

  Next, the CPU 71 proceeds to step 1030 to determine the reference engine speed NEref based on the table MapNEref (k). Here, the table MapNEref shows that when the required reference engine speed NEref is obtained in an experiment using a predetermined reference fuel, the crankshaft 24 is rotated by an angle obtained by multiplying the number of combustion occurrences k by 180 ° from the initial explosion occurrence time. Is set in advance so as to coincide with the engine rotational speed NE acquired in step (1).

  Next, the CPU 71 proceeds to step 1035 to add a predetermined positive coefficient L to a value NEref-NE obtained by subtracting the engine rotational speed NE read in step 1025 from the reference engine rotational speed NEref determined in step 1030. A feedback correction amount ΔSA is set to a value L · (NEref−NE) multiplied by. Here, the coefficient L is a coefficient adapted in a state where the actual air-fuel ratio matches the target air-fuel ratio.

  Next, the CPU 71 proceeds to step 1040 to determine the air-fuel ratio compensation correction amount δ based on the table Mapδ (AbyF). Here, the table Map δ indicates that the air-fuel ratio compensation correction amount δ obtained when the air-fuel ratio AbyF matches the target air-fuel ratio (in this example, the theoretical air-fuel ratio) is “0”, and the air-fuel ratio AbyF Is greater than the target air-fuel ratio (the lean-side air-fuel ratio), the air-fuel ratio compensation correction amount δ required becomes a positive value, while the air-fuel ratio AbyF is smaller than the target air-fuel ratio (rich-side air-fuel ratio). The air-fuel ratio compensation correction amount δ that is obtained in the case of (the fuel ratio) is set in advance so as to be a negative value. Further, in the table Mapδ, as the air-fuel ratio AbyF becomes smaller (the air-fuel ratio on the rich side) becomes smaller, the required air-fuel ratio compensation correction amount δ becomes smaller (an amount for correcting the ignition timing SA to the retard side). ) In advance.

Next, the CPU 71 proceeds to step 1045 to set the feedback correction amount ΔSA to a value ΔSA + δ obtained by adding the feedback correction amount ΔSA to the air-fuel ratio compensation correction amount δ. Then, the CPU 71 proceeds to step 1050 to set (replace) the ignition timing SA to a value SA + ΔSA obtained by adding the feedback correction amount ΔSA to the ignition timing SA.
Note that the execution of the processing from step 1025 to step 1050 corresponds to the achievement of the function of the ignition timing correction means.

  Next, the CPU 71 proceeds to step 1020 and sends an instruction signal corresponding to the ignition timing SA set in step 1050 to the igniter 38 of the cylinder (third cylinder) that has reached the intake valve closing time Tvc at the present time. 10 is temporarily terminated.

  In this way, during the initial startup period, the feedback correction amount ΔSA is determined based on the acquired engine rotational speed NE so that the engine rotational speed NE matches the reference engine rotational speed NEref, and the determined feedback correction amount ΔSA is determined. Only the ignition timing SA is corrected. Then, the mixed gas is ignited at the corrected ignition timing SA. As a result, the engine speed NE can be made closer to the reference engine speed NEref. As a result, the occurrence of blow-up can be prevented and the internal combustion engine 10 can be started quickly.

  Further, the air-fuel ratio of the mixed gas formed in the combustion chamber 25 is estimated, and the feedback correction amount ΔSA is corrected so that the indicated torque Tq becomes smaller as the estimated air-fuel ratio AbyF is the richer air-fuel ratio. The

  As a result, the actual in-cylinder air amount becomes smaller than the planned in-cylinder air amount, so that the actual air-fuel ratio becomes a richer air-fuel ratio than the planned air-fuel ratio (target air-fuel ratio). Also, it is possible to avoid the illustrated torque Tq from becoming excessive. Furthermore, even if the actual air-fuel ratio becomes larger than the planned in-cylinder air amount, the actual air-fuel ratio becomes leaner than the target air-fuel ratio, the indicated torque Tq becomes too small. You can avoid that. As a result, even if the actual air-fuel ratio is different from the target air-fuel ratio, the engine speed NE can be quickly brought close to the reference engine speed NEref.

  The process for performing the start initial control is continued until the value of the start initial control execution flag Xs is changed to “0”.

  Then, with the passage of time, the process of step 515 in FIG. 5 is repeatedly executed, whereby the combustion occurrence count k is increased, and the combustion occurrence count k becomes the threshold count kth at a certain point.

  Therefore, when the CPU 71 starts processing of the start initial control execution determination routine of FIG. 3 and proceeds to step 315 at this time, the CPU 71 determines “No” in step 315 and proceeds to step 325. The CPU 71 sets the value of the start initial control execution flag Xs to “0” at step 325, and once ends this routine at step 399.

  In addition, when the CPU 71 starts processing of the combustion occurrence number calculation routine of FIG. 5 and proceeds to step 505 in which it is determined whether or not the value of the start initial control execution flag Xs is “1”, the CPU 71 In step 505, it is determined as “No”, and the process proceeds directly to step 599 to end this routine once.

  Further, when the CPU 71 starts the processing of the first in-cylinder air amount estimation routine of FIG. 6 and proceeds to step 605 for determining whether or not the value of the start initial control execution flag Xs is “1”, the CPU 71 Determines “No” in step 605 and proceeds directly to step 699 to end this routine once.

  In addition, when the CPU 71 starts processing of the fuel injection amount determination routine of FIG. 7 and proceeds to step 710 in which it is determined whether or not the value of the start initial control execution flag Xs is “1”, the CPU 71 In step 710, “No” is determined, and the process proceeds to step 735.

  The CPU 71 reads the intake air flow rate Ga detected by the air flow meter 61 in step 735. Next, the CPU 71 proceeds to step 740 to determine the normal fuel injection amount fib based on the table Mapfib (Ga, NE), and to the determined normal fuel injection amount fib, the fuel injection amount fi (n) of the nth cylinder. Set. Here, the table Mapfib is such that the obtained normal fuel injection amount fib is an amount that matches the air-fuel ratio of the mixed gas formed in the combustion chamber 25 with the target air-fuel ratio (the theoretical air-fuel ratio in this example). Further, it is preset based on experimentally measured values.

  Next, the CPU 71 proceeds to step 725 to send an instruction signal corresponding to the fuel injection amount fi (n) of the nth cylinder set in the above step 740 to the injector 39 of the nth cylinder. The routine of 7 is once ended.

  When a certain cylinder reaches the intake valve closing time Tvc, the CPU 71 starts the process of the second in-cylinder air amount estimation routine of FIG. Then, when the CPU 71 proceeds to step 805 in which it is determined whether or not the value of the start initial control execution flag Xs is “1”, it determines “No” in step 805 and directly proceeds to step 899 to execute this routine. Is temporarily terminated. That is, the CPU 71 ends this routine once without executing the process of estimating the in-cylinder air amount.

  Further, when the CPU 71 starts the processing of the air-fuel ratio estimation routine of FIG. 9 and proceeds to step 905 for determining whether or not the value of the start initial control execution flag Xs is “1”, the CPU 71 proceeds to step 905. At step 999, the routine is directly terminated.

  In addition, when the CPU 71 starts the processing of the ignition timing determination routine of FIG. 10 and proceeds to step 1005 for determining whether or not the value of the start initial control execution flag Xs is “1”, the CPU 71 In step 1005, the determination is “No”, and the process proceeds to step 1055.

  In step 1055, the CPU 71 reads the engine speed NE calculated separately based on the signal from the crank position sensor 66, and in step 1060, reads the intake air flow rate Ga detected by the air flow meter 61.

  Next, the CPU 71 proceeds to step 1065 to determine the normal time ignition timing SAb based on the table MapSAb (Ga, NE), and sets the ignition timing SA to the determined normal time ignition timing SAb.

  Then, the CPU 71 proceeds to step 1020 to send an instruction signal corresponding to the ignition timing SA set in step 1065 to the igniter 38 of the cylinder that has reached the intake valve closing time Tvc at the present time. Thereafter, the routine of FIG. 10 is temporarily terminated.

Next, a case where the driver operates the accelerator pedal 81 before the combustion occurrence frequency k becomes equal to or greater than the threshold frequency kth will be described.
In this case, when the CPU 71 starts the processing of the start initial control execution determination routine of FIG. 3 and proceeds to step 310, the CPU 71 determines “No” in step 310 and proceeds to step 325. The CPU 71 sets the value of the start initial control execution flag Xs to “0” at step 325, and once ends this routine at step 399.

  Then, the CPU 71 sets the fuel injection amount fi (n) of the nth cylinder to the normal fuel injection amount fib in step 740, similarly to the case where the combustion occurrence number k becomes equal to or greater than the threshold number kth. In step 1065, the ignition timing SA is set to the normal timing fire timing SAb.

  As described above, according to the first embodiment of the control apparatus for an internal combustion engine according to the present invention, even when the actual air-fuel ratio differs from the target air-fuel ratio during the initial startup period, the engine speed NE Can be quickly brought close to the reference engine speed NEref.

  In the first embodiment, the control device is configured to execute the ignition timing determination routine at the intake valve closing time Tvc. However, the ignition timing determination routine is operated at a crank angle greater than the compression top dead center TDC2. It may be configured to execute at a time point 90 degrees before. In this case, the air-fuel ratio estimation routine may also be executed at a time point that is 90 ° before the compression top dead center TDC2.

  In the first embodiment, the control device is configured to adopt the intake valve closing time Tvc as the estimated time point for estimating the second in-cylinder air amount KL2, but the intake valve closing time point Tvc is used. Adopting a time point later than the most advanced timing of the assumed ignition timing (for example, a time point 90 ° before the compression top dead center TDC2 at the crank angle) It may be configured to.

  In this case, the control device holds in the RAM 73 the surge tank internal pressure Ps detected at the intake valve closing time Tvc and the engine speed NE calculated at the intake valve close time Tvc in the RAM 73, It is preferable that the second cylinder air amount KL2 is estimated based on the pressure Ps and the engine rotational speed NE.

Second Embodiment
Next, an internal combustion engine control apparatus according to a second embodiment of the present invention will be described.
Incidentally, air flows into the combustion chamber 25 from the intake passage while the intake valve 32 is open (the state of the intake valve 32 is maintained in the communication state). Thereby, vaporization of the fuel adhering to the wall surface forming the intake passage or the wall surface forming the combustion chamber 25 is promoted. Further, the diffusion of fuel in the mixed gas formed in the combustion chamber 25 proceeds.

  Therefore, the longer the intake time Tint from the intake valve opening time Tvo to the intake valve closing time Tvc (the time during which the state of the intake valve 32 is maintained in the communication state) becomes longer, the wall surface or combustion chamber 25 that forms the intake passage. The ratio of the fuel to be vaporized out of the fuel adhering to the wall surface forming the gas becomes high, and the distribution of the fuel in the mixed gas becomes close to a uniform distribution. As a result, the amount of fuel actually burned in the combustion chamber 25 increases. That is, as shown in FIG. 12, the longer the intake time Tint, the richer the air / fuel ratio of the mixed gas used for combustion becomes a richer air / fuel ratio.

  In the period from the intake valve closing time Tvc to the compression top dead center TDC2, the mixed gas in the combustion chamber 25 is compressed. Thereby, since the temperature of mixed gas becomes high, vaporization of the fuel adhering to the wall surface which forms the combustion chamber 25 is accelerated | stimulated. Further, the pre-reaction of fuel in the mixed gas (preliminary reaction such as decomposition of fuel molecules) is promoted.

  Therefore, as the compression time Tcmp from the intake valve closing time Tvc to the compression top dead center TDC2 as the reference time becomes longer, the proportion of the fuel vaporized out of the fuel adhering to the wall surface forming the combustion chamber 25 increases. The ratio of the fuel in which the pre-reaction is completed out of the fuel in the mixed gas becomes high. As a result, the amount of fuel actually burned increases. That is, as shown in FIG. 13, as the compression time Tcmp becomes longer, the actual air-fuel ratio becomes a richer air-fuel ratio.

  Therefore, the control device according to the second embodiment corrects the estimated air-fuel ratio AbyF based on the intake time Tint and the compression time Tcmp. The control device according to the second embodiment is different from the control device according to the first embodiment only in that the air-fuel ratio AbyF is corrected. Accordingly, the following description will focus on such differences.

  The control apparatus according to the second embodiment replaces the air-fuel ratio estimation routine shown in FIG. 9 with an air-fuel ratio estimation routine in which the processing of step 935 of this routine is replaced with the processing of steps 1435 to 1455 shown in FIG. Is supposed to run.

  Therefore, when the CPU 71 starts processing of the air-fuel ratio estimation routine, the CPU 71 proceeds to step 1435 after executing the processing of step 905 to step 930. In step 1435, the CPU 71 reads the camshaft phase angle φ separately calculated based on the signal from the cam position sensor 65 and the signal from the crank position sensor 66.

  Next, the CPU 71 proceeds to step 1440 to determine the intake time Tint based on the table MapTint (NE, φ) and determine the compression time Tcmp based on the table MapTcmp (NE, φ).

  Here, the intake time Tint is the time from when the m-th cylinder intake valve 32 opens until the m-th cylinder intake valve 32 closes (that is, when the m-th cylinder intake valve 32 opens). This is an estimated value of the time during which air is substantially introduced into the combustion chamber 25 of the m-th cylinder by maintaining the current state. Further, the compression time Tcmp is the time from when the intake valve 32 of the m-th cylinder is closed until the m-th cylinder reaches the compression top dead center TDC2 (that is, the mixed gas in the combustion chamber 25 of the m-th cylinder is substantially equal). Is the estimated time).

  The table MapTint is set in advance based on experimentally measured values so that the required intake time Tint becomes shorter as the engine speed NE becomes higher. Similarly, the table MapTcmp is also set in advance based on experimentally measured values so that the required compression time Tcmp becomes shorter as the engine speed NE becomes higher.

  Then, the CPU 71 proceeds to step 1445 to determine the intake correction coefficient Aint based on the table MapAint (Tw) and to determine the compression correction coefficient Acmp based on the table MapAcmp (Tw).

  Here, in the table MapAint, the required intake correction coefficient Aint becomes smaller as the required intake correction coefficient Aint becomes a negative value and the coolant temperature Tw becomes higher (the absolute value of the intake correction coefficient Aint | Aint Is set in advance based on experimentally measured values. Similarly, in the table MapAcmp, the calculated compression correction coefficient Acmp becomes smaller as the calculated compression correction coefficient Acmp becomes a negative value and the cooling water temperature Tw becomes higher (the absolute value | Acmp of the compression correction coefficient Acmp). Is set in advance based on experimentally measured values.

  Next, the CPU 71 proceeds to step 1450, where the expression shown in step 1450, the intake time Tint and compression time Tcmp determined in step 1440, the intake correction coefficient Aint determined in step 1445, and The air-fuel ratio correction coefficient Raf is determined based on the compression correction coefficient Acmp and a predetermined basic value Raf0 larger than “1” (see FIG. 15). The basic value Raf0 is determined so that the air-fuel ratio correction coefficient Raf becomes a positive value even when the value | Aint · Tint + Acmp · Tcmp |

Then, the CPU 71 proceeds to step 1455 to set the in-cylinder fuel amount fc set in step 925 of the air-fuel ratio estimation routine to the second in-cylinder air amount KL2 set in the second in-cylinder air amount estimation routine. The air / fuel ratio AbyF is set to a value Raf · KL2 / fc obtained by multiplying the value KL2 / fc divided by the air / fuel ratio correction coefficient Raf determined in step 1450. That is, the air-fuel ratio AbyF is a value obtained by correcting the air-fuel ratio estimated based on the estimated second in-cylinder air amount KL2 and the estimated in-cylinder fuel amount fc based on the intake time Tint and the compression time Tcmp. Set to
Then, the CPU 71 proceeds to step 999 to end this routine once.

  As a result, the air-fuel ratio AbyF that serves as a basis for correcting the feedback correction amount ΔSA can be brought close to the actual air-fuel ratio. As a result, the ignition timing SA can be set at an appropriate timing according to the actual air-fuel ratio, and the engine speed NE can be made closer to the reference engine speed NEref more quickly.

  In the second embodiment, the control device is configured to determine both the intake time Tint and the compression time Tcmp based on the engine rotational speed NE calculated at the intake valve closing time Tvc. The intake time Tint is determined based on the engine rotational speed NE calculated at the intake valve closing time Tvc, and the compression time Tcmp is determined based on the engine rotational speed NE calculated at the compression top dead center TDC2. It may be configured as follows. In this case, the control device is preferably configured to execute the air-fuel ratio estimation routine and the ignition timing determination routine at the compression top dead center TDC2.

  In the second embodiment, the control device is configured to correct the air-fuel ratio AbyF based on both the intake time Tint and the compression time Tcmp. However, one of the intake time Tint and the compression time Tcmp is used. The air-fuel ratio AbyF may be corrected based on the above.

  In addition, this invention is not limited to said each embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, in each of the above embodiments, the control device is configured to estimate the second in-cylinder air amount KL2 based on the engine rotational speed NE calculated at the intake valve closing time Tvc. The second in-cylinder air amount KL2 is estimated based on the average value of the engine speed NE calculated at the valve closing time Tvc and the engine speed NE calculated at the intake valve opening time Tvo. It may be configured.

  Further, in each of the above embodiments, the control device is configured to estimate the second in-cylinder air amount KL2 based on the surge tank internal pressure Ps, but based on the intake flow rate Ga detected by the air flow meter 61. The second in-cylinder air amount KL2 may be estimated. In addition, the control device applies a parameter determined at the intake valve closing time Tvc to an air model in which the behavior of air in the intake passage is described in accordance with physical laws such as an energy conservation law, a momentum conservation law, and a mass conservation law. Thus, the second in-cylinder air amount KL2 may be estimated. This air model is a well-known model disclosed in Japanese Patent Application Laid-Open Nos. 2003-184613 and 2001-41095.

  In addition, in each of the embodiments described above, the control device sets the feedback correction amount ΔSA before correction based on the air-fuel ratio AbyF to the rotational speed difference ΔNE (= NEref) that is the difference between the engine rotational speed NE and the reference engine rotational speed NEref. −NE) is set to an amount L · (NEref−NE) (see step 1035 in FIG. 10), but the amount is proportional to the value obtained by differentiating the rotational speed difference ΔNE or the rotational speed difference ΔNE. May be set to an amount proportional to the integrated value. Further, the control device sets the feedback correction amount ΔSA before correction based on the air-fuel ratio AbyF to an amount proportional to the rotational speed difference ΔNE, an amount proportional to a value obtained by differentiating the rotational speed difference ΔNE, and a rotational speed difference ΔNE. May be set to the sum of all the quantities proportional to the integrated value, or may be set to the sum of any two of these three quantities.

  Further, in each of the above embodiments, when the air-fuel ratio AbyF becomes richer than the maximum output air-fuel ratio, the air-fuel ratio AbyF becomes smaller (becomes the rich-side air-fuel ratio) instead of the table Mapδ. It may be configured to use a table that is set so that the required correction amount δ for air-fuel ratio compensation increases (is an amount that corrects the ignition timing SA to the more advanced side).

1 is a schematic configuration diagram of a system in which a control device according to a first embodiment of the present invention is applied to a spark ignition internal combustion engine. 2 is a time chart conceptually showing the operation of the control device shown in FIG. 1 for a specific cylinder. It is the flowchart which showed the program for determining whether it is a program which CPU shown in FIG. 1 performs a starting initial control. 2 is a flowchart showing a program executed by the CPU shown in FIG. 1 for determining whether or not the first combustion has occurred after cranking has started. 2 is a flowchart showing a program executed by the CPU shown in FIG. 1 for calculating the number of times an arbitrary cylinder has reached an exhaust stroke from the time of the first explosion to the present time. 2 is a flowchart showing a program executed by the CPU shown in FIG. 1 for estimating a first in-cylinder air amount. 2 is a flowchart showing a program executed by a CPU shown in FIG. 1 for determining a fuel injection amount. 3 is a flowchart showing a program executed by the CPU shown in FIG. 1 for estimating a second in-cylinder air amount. FIG. 3 is a flowchart showing a program executed by the CPU shown in FIG. 1 for estimating an air-fuel ratio. 2 is a flowchart showing a program executed by a CPU shown in FIG. 1 for determining an ignition timing. 4 is a time chart showing the timing for determining the fuel injection amount and ignition timing for each cylinder. It is the graph which showed the change of the real air fuel ratio with respect to intake time. It is the graph which showed the change of the real air fuel ratio with respect to compression time. It is a flowchart showing the process performed in addition to the process shown in FIG. 9, in order that the control apparatus which concerns on 2nd Embodiment of this invention estimates an air fuel ratio. It is the graph which showed notionally the relationship between intake time and compression time, and an air fuel ratio correction coefficient.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 21 ... Cylinder, 22 ... Piston, 24 ... Crankshaft, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 33 ... Variable intake timing device, 37 ... Spark plug, 38 ... Igniter, 39 ... Injector, 42 ... Surge tank, 66 ... Crank position sensor, 68 ... Surge tank pressure sensor, 71 ... CPU.

Claims (4)

An intake valve that can be switched between a communication state in which a combustion chamber and an intake passage for introducing air into the combustion chamber communicate with each other, and a shut-off state in which the combustion chamber and the intake passage are blocked;
By switching the intake valve state from the shut-off state to the communication state by driving the intake valve at the time of opening the intake valve, which is a time point before the compression top dead center, The intake valve is switched from the communication state to the shut-off state by driving the intake valve at the time before the intake valve is closed before the intake valve is opened. An intake valve drive mechanism configured in
Ignition means for generating a spark in the combustion chamber;
Fuel injection means for supplying the fuel to the combustion chamber by injecting fuel;
With
A mixed gas containing the air and the fuel is formed in the combustion chamber, and the formed mixed gas is ignited by a spark generated by the ignition means and burned in the combustion chamber, thereby rotating the output shaft. Applied to an internal combustion engine configured to
Rotational speed acquisition means for acquiring an engine rotational speed that is the rotational speed of the output shaft;
The engine rotation speed is set to a reference engine rotation speed set based on the rotation angle of the output shaft from the time of the first explosion when the combustion first occurs in the initial start period after the start operation for starting the internal combustion engine. An ignition timing that is a timing at which the ignition means generates a spark based on the calculated feedback correction amount and calculates a feedback correction amount based on the acquired engine rotation speed and the reference engine rotation speed so as to approach each other Ignition timing correction means for correcting
An internal combustion engine control device comprising:
The intake valve based on a physical quantity that has been determined up to a predetermined estimated time after the intake valve closing time and is closed until the intake valve closing time and that affects the amount of air introduced into the combustion chamber. An in-cylinder air amount that is the amount of air introduced into the combustion chamber at the valve closing time is estimated, and the estimated in-cylinder air amount and a fuel injection amount that is the amount of injected fuel are An air-fuel ratio estimating means for estimating the air-fuel ratio of the mixed gas formed in the combustion chamber based on,
The ignition timing correction means is a torque generated by the pressure of gas in the combustion chamber and is a torque to rotate the output shaft. The estimated air-fuel ratio is the rich-side air-fuel ratio. A control device for an internal combustion engine configured to correct the calculated feedback correction amount based on the estimated air-fuel ratio and to correct the ignition timing by the corrected feedback correction amount so as to be made smaller. The control apparatus for an internal combustion engine according to claim 1,
The control apparatus for an internal combustion engine, wherein the air-fuel ratio estimation means is configured to detect the physical quantity when the intake valve is closed and to estimate the in-cylinder air quantity based on the detected physical quantity. The control apparatus for an internal combustion engine according to claim 1 or 2,
The air-fuel ratio estimation means is configured to acquire an intake time from the intake valve opening time to the intake valve close time and correct the estimated air-fuel ratio to a rich side as the acquired intake time becomes longer. Control device for an internal combustion engine. The control apparatus for an internal combustion engine according to any one of claims 1 to 3,
The air-fuel ratio estimating means acquires a compression time from the intake valve closing time to a predetermined reference time near the compression top dead center, and corrects the estimated air-fuel ratio to the rich side as the acquired compression time becomes longer. A control device for an internal combustion engine configured to

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