JP2008095593A - Control unit of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control unit of an internal combustion engine capable of leaning ignition timing for promptly avoiding knocking even when fuel properties are varied. <P>SOLUTION: The internal combustion engine comprises a combustion chamber 18 in which a mixture of at least two sorts of fuel of different properties and air can be burned, an ignition plug 45 for igniting the mixture, a knock detection means 63 for detecting knocking and an air-fuel ratio detection means 61 for detecting an air-fuel ratio and is characterized in that the ECU 51 is provided with an ignition timing leaning means for updating limit ignition timing causing knocking, which varies according to the air-fuel ratio, based on a learning value to a retard side when knocking is detected and with an ignition timing control means for controlling ignition timing by the ignition plug 45 based on the limit ignition timing causing knocking updated by the ignition timing leaning means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that can use at least two types of fuels having different properties.

  2. Description of the Related Art Conventionally, internal combustion engines that are operated using a plurality of types of fuels having different properties are known. For example, there are internal combustion engines that can be operated using gasoline fuel mixed with different components such as alcohol as fuel. Here, in general, gasoline fuel and alcohol fuel are known to have high evaporability, but their fuel properties do not completely match. In such an internal combustion engine, in any case of combustion with only gasoline fuel, combustion when alcohol fuel is mixed with gasoline fuel, and combustion with only alcohol fuel, accurate ignition timing according to the engine operating condition If it is not ignited, knocking will occur. And, in the internal combustion engine that burns using the fuel having at least two different properties as described above, the fuel properties are different as described above, and therefore the ignition timing is set according to any fuel property. When the fuel is changed to a fuel having a different fuel property, the ignition timing is not matched, and as a result, knocking may occur or the engine output may be reduced. For this reason, in the conventional internal combustion engine, the ignition timing is gradually retarded or advanced according to the learning value (update width) according to whether or not knocking (knock vibration) is detected from the knock detection means, and converged to the optimum value. Some have suppressed the occurrence of excessive knocking.

  As such a control device for an internal combustion engine, for example, the learning control device described in Patent Document 1 increases the learning value when changing to a fuel having a different fuel property, thereby making the ignition timing early. This converges to an optimum value, thereby minimizing the occurrence of knocking and a decrease in output.

JP 2003-184615 A

  However, in the learning control device for an internal combustion engine described in Patent Document 1 described above, for example, when alcohol fuel is added to gasoline fuel, the alcohol fuel has a high octane number and is unlikely to knock. While trying to learn on the advance side, the alcohol fuel contains a lot of oxygen, so the air-fuel ratio deviates greatly to the lean side.For this reason, the fuel injection amount is increased by feedback control, and the air-fuel ratio is increased. Need to be controlled stoichiometrically. Here, in practice, the limit ignition timing at which knocking occurs (knock generation limit ignition timing) fluctuates from the lean side to the retard side when the air-fuel ratio is controlled from the lean side to the stoichiometric side. Even when learning of the optimal ignition timing as described above is executed during the transition period from lean to stoichiometric control, the optimal ignition timing at the target air-fuel ratio cannot be learned early. By learning while the fuel ratio is shifted, knocking at the target air-fuel ratio cannot be properly avoided, and the number of times of knocking until the learning is completed may increase.

  Therefore, an object of the present invention is to provide a control device for an internal combustion engine that can learn an ignition timing at which knocking can be avoided at an early stage even when the fuel property is changed.

  In order to achieve the above object, a control apparatus for an internal combustion engine according to a first aspect of the present invention ignites a combustion chamber in which a mixture of fuel and air having different properties can be combusted, and the mixture. An ignition plug, knock detection means for detecting knocking of the internal combustion engine, air / fuel ratio detection means for detecting the air / fuel ratio of the internal combustion engine, and when knocking is detected by the knock detection means, depending on the air / fuel ratio Ignition timing learning means for updating the changing knock generation limit ignition timing to the retard side based on the learned value, and the ignition timing by the spark plug based on the knock generation limit ignition timing updated by the ignition timing learning means And ignition timing control means for controlling.

  In the control apparatus for an internal combustion engine according to the second aspect of the present invention, based on the knocking intensity when knocking is detected by the knock detection means, the amount of unburned fuel in the combustion chamber, and the timing at which the unburned fuel self-ignites. And a learning value setting means for setting the learning value in accordance with the knocking model.

  In a control apparatus for an internal combustion engine according to a third aspect of the present invention, crank angle detection means for detecting a crank angle of the internal combustion engine, and a determination value in which the unburned fuel amount is preset when the air-fuel mixture is ignited. A predicted knock generation limit ignition timing prediction means for predicting a predicted knock generation limit ignition timing based on a knock determination crank angle and a self-ignition crank angle at which the unburned fuel self-ignites when the air-fuel mixture is ignited; And the learning value setting means sets the learning value based on a retard amount of the predicted knock generation limit ignition timing with respect to an actual knock generation ignition timing when knocking is detected by the knock detection means. Features.

  In the control apparatus for an internal combustion engine according to the fourth aspect of the invention, the predicted knock generation limit ignition timing prediction means includes the knock determination corresponding to the ignition timing with reference to the actual knock determination crank angle corresponding to the actual knock generation ignition timing. The crank angle is updated, the self-ignition crank angle corresponding to the ignition timing is updated with reference to the actual self-ignition crank angle corresponding to the actual knock generation ignition timing, and the updated knock determination crank angle and self-ignition crank angle are updated. Is set to the predicted knock generation limit ignition timing.

  In the control apparatus for an internal combustion engine according to the fifth aspect of the present invention, the curve data indicating the knock generation limit ignition timing that changes according to the air-fuel ratio, the linear data indicating the knock determination crank angle corresponding to the ignition timing, and the ignition timing are used. The storage unit stores linear data indicating the corresponding self-ignition crank angle, and the ignition timing learning unit is configured to generate curve data indicating the knock occurrence limit ignition timing stored in the storage unit based on the learned value. The predicted knock occurrence limit ignition timing is updated by offsetting, and the predicted knock occurrence limit ignition timing prediction means uses the straight line data indicating the knock determination crank angle stored in the storage unit according to the actual knock determination crank angle. The linear data indicating the self-ignition crank angle stored in the storage unit and offset on the previous point The predicted knock occurrence limit ignition timing based on the intersection of the linear data indicating the knock determination crank angle and the linear data indicating the self-ignition crank angle offset to a point corresponding to the actual self-ignition crank angle. It is characterized by predicting.

  In the control apparatus for an internal combustion engine according to the sixth aspect of the present invention, an intake port and an exhaust port communicating with the combustion chamber, an intake valve and an exhaust valve capable of opening and closing the intake port and the exhaust port, the intake valve and the The ignition timing learning means comprises variable valve means capable of opening and closing the intake port and the exhaust port using an exhaust valve and capable of changing the opening and closing timing, and load adjusting means for adjusting the load of the internal combustion engine. When updating the knock occurrence limit ignition timing, the variable valve means eliminates the overlap of the valve opening periods of the intake valve and the exhaust valve, and the load adjustment means preloads the load of the internal combustion engine. It is characterized by adjusting to a predetermined value or less.

  According to the control apparatus for an internal combustion engine of the present invention, the ignition timing learning means for updating the knock generation limit ignition timing that changes according to the air-fuel ratio to the retard side based on the learning value, and the ignition timing learning means are updated. Since the ignition timing control means for controlling the ignition timing by the spark plug based on the knock generation limit ignition timing is provided, it is possible to learn the ignition timing at which knocking can be avoided early even if the fuel property is changed.

  Embodiments of an internal combustion engine control apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a schematic configuration diagram showing an engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. FIG. 2 is an ECU of the engine to which the control device for an internal combustion engine according to the embodiment of the present invention is applied. FIG. 3 is a flowchart for explaining ignition timing learning control after refueling in an engine to which the control device for an internal combustion engine according to the embodiment of the present invention is applied. FIG. 4 is an internal combustion engine according to the embodiment of the present invention. FIG. 5 is a graph showing an example of a relationship between an air-fuel ratio and a knock generation limit ignition timing in an engine to which the engine control device is applied, and FIG. 5 is a knock in the engine to which the internal combustion engine control device according to the embodiment of the present invention is applied. FIG. 6 is a schematic diagram illustrating a model. FIG. 6 is a graph illustrating an example of a relationship between a crank angle and a fuel combustion ratio in an engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. 7 is a graph showing an example of the relationship between the ignition timing and the knock determination crank angle and ignition crank angle in the engine control apparatus of the internal combustion engine according to an embodiment of the present invention.

  In the control apparatus for an internal combustion engine of the present embodiment, as shown in FIG. 1, an engine 10 as an internal combustion engine is an internal combustion engine that is operated using at least two types of fuels having different properties. It can be operated using alcohol fuel and gasoline fuel as fuel.

  The engine 10 is a multi-cylinder in-cylinder injection type, and a cylinder head 12 is fastened on a cylinder block 11. A plurality of cylinder bores 13 formed in the cylinder block 11 can move pistons 14 up and down. It is mated. A crankcase 15 is fastened to the lower part of the cylinder block 11, and a crankshaft 16 is rotatably supported in the crankcase 15. Each piston 14 is connected to the crankshaft 16 via a connecting rod 17. Has been.

  The combustion chamber 18 is constituted by the wall surface of the cylinder bore 13 in the cylinder block 11, the lower surface of the cylinder head 12, and the top surface of the piston 14, and the combustion chamber 18 has a high central portion at the upper portion (lower surface of the cylinder head 12). It has a pent roof shape that is slanted. The combustion chamber 18 is capable of burning a mixture of alcohol fuel, gasoline fuel, and air, and an intake port 19 and an exhaust port 20 are formed facing the upper portion of the combustion chamber 18, that is, the lower surface of the cylinder head 12. The lower ends of the intake valve 21 and the exhaust valve 22 are positioned with respect to the intake port 19 and the exhaust port 20, respectively. The intake valve 21 and the exhaust valve 22 are supported by the cylinder head 12 so as to be movable in the axial direction, and are urged and supported in a direction (upward in FIG. 1) for closing the intake port 19 and the exhaust port 20. ing. An intake camshaft 23 and an exhaust camshaft 24 are rotatably supported on the cylinder head 12, and the intake cam 25 and the exhaust cam 26 are in contact with upper ends of the intake valve 21 and the exhaust valve 22.

  Although not shown, an endless timing chain is wound around the crankshaft sprocket fixed to the crankshaft 16 and the camshaft shaft sprockets fixed to the intake camshaft 23 and the exhaust camshaft 24, respectively. The crankshaft 16, the intake camshaft 23, and the exhaust camshaft 24 can be interlocked.

  Accordingly, when the intake camshaft 23 and the exhaust camshaft 24 rotate in synchronization with the crankshaft 16, the intake cam 25 and the exhaust cam 26 move up and down the intake valve 21 and the exhaust valve 22 at a predetermined timing. 19 and the exhaust port 20 can be opened and closed so that the intake port 19 and the combustion chamber 18 can communicate with the combustion chamber 18 and the exhaust port 20, respectively. In this case, the intake camshaft 23 and the exhaust camshaft 24 are set to rotate once (360 degrees) while the crankshaft 16 rotates twice (720 degrees). Therefore, the engine 10 executes the four strokes of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke while the crankshaft 16 rotates twice. At this time, the intake camshaft 23 and the exhaust camshaft 24 are set to one. It will rotate.

  Further, the valve mechanism of the engine 10 is a variable valve timing-intelligent (VVT) mechanism 27 or 28 that controls the intake valve 21 and the exhaust valve 22 at an optimal opening / closing timing according to the operating state. It has become. The intake / exhaust variable valve mechanisms 27, 28 as variable valve means are configured by providing VVT controllers 29, 30 at the shaft ends of the intake camshaft 23 and the exhaust camshaft 24. 32, the phase of the camshafts 23 and 24 with respect to the cam sprocket is changed by causing the hydraulic pressure from 32 to act on the advance chamber and retard chamber (not shown) of the VVT controllers 29 and 30, and the opening / closing timing of the intake valve 21 and the exhaust valve 22 Can be advanced or retarded. In this case, the intake / exhaust variable valve operating mechanisms 27, 28 advance or retard the opening / closing timing while keeping the operating angle (opening period) of the intake valve 21 and the exhaust valve 22 constant. In addition, the intake camshaft 23 and the exhaust camshaft 24 are provided with cam position sensors 33 and 34 for detecting the rotational phase thereof.

  A surge tank 36 is connected to the intake port 19 via an intake manifold 35, and an intake pipe 37 is connected to the surge tank 36. An air cleaner 38 is attached to an air intake port of the intake pipe 37. . An electronic throttle device 40 as a load adjusting means having a throttle valve 39 is provided downstream of the air cleaner 38 in the air flow direction. The cylinder head 12 is provided with an injector (fuel injection valve) 41 that directly injects fuel into the combustion chamber 18, and the injector 41 is located on the intake port 19 side and is inclined at a predetermined angle in the vertical direction. Are arranged. An injector 41 attached to each cylinder is connected to a delivery pipe 42, and a high pressure fuel pump (fuel pump) 44 is connected to the delivery pipe 42 via a high pressure fuel supply pipe 43. Further, the cylinder head 12 is provided with a spark plug 45 that is located above the combustion chamber 18 and ignites the air-fuel mixture.

  On the other hand, an exhaust pipe 47 is connected to the exhaust port 20 via an exhaust manifold 46. The exhaust pipe 47 is a three-way element that purifies harmful substances such as HC, CO, and NOx contained in the exhaust gas. Catalysts 48 and 49 are mounted. Further, the engine 10 is provided with a starter motor 50 that performs cranking. When an unillustrated pinion gear meshes with the ring gear when the engine is started, the rotational force is transmitted from the pinion gear to the ring gear to rotate the crankshaft 16. Can do.

  By the way, the vehicle is equipped with an electronic control unit (ECU) 51 that is configured around a microcomputer and can control each part of the engine 10, and the ECU 51 can control the injector 41, the spark plug 45, and the like. Yes. That is, an air flow sensor 52 and an intake air temperature sensor 53 are mounted on the upstream side of the air flow direction of the intake pipe 37, and an intake pressure sensor 54 is provided in the surge tank 36, and the measured intake air amount and intake air temperature are measured. The intake pressure (intake pipe negative pressure) is output to the ECU 51. The electronic throttle device 40 is provided with a throttle position sensor 55, which outputs the current throttle opening to the ECU 51. The accelerator position sensor 56 outputs the current accelerator opening to the ECU 51. Further, a crank angle sensor 57 serving as a crank angle detecting means for detecting the crank angle of the engine 10 outputs the detected crank angle of each cylinder to the ECU 51, and the ECU 51 performs an intake stroke in each cylinder based on the detected crank angle. In addition to determining the compression stroke, the expansion stroke, and the exhaust stroke, the engine speed is calculated. Here, the engine speed corresponds to the rotational speed of the crankshaft 16 in other words. If the rotational speed of the crankshaft 16 increases, the rotational speed of the crankshaft 16, that is, the engine rotational speed of the engine 10 also increases. Get higher.

  The cylinder block 11 is provided with a water temperature sensor 58 that detects the engine cooling water temperature, and outputs the detected engine cooling water temperature to the ECU 51. Further, the cylinder head 12 is provided with an in-cylinder pressure sensor 59 as in-cylinder pressure detecting means for detecting the pressure in the combustion chamber 18, that is, in-cylinder pressure, and outputs the detected in-cylinder pressure to the ECU 51. . The in-cylinder pressure sensor 59 detects the in-cylinder pressure based on, for example, a detection element whose resistance value changes according to the applied pressure, and outputs the detection result to the ECU 51. The in-cylinder pressure sensor 59 may be another type of sensor as long as it can detect the in-cylinder pressure.

  The delivery pipe 42 communicating with each injector 41 is provided with a fuel pressure sensor 60 that detects the fuel pressure, and outputs the detected fuel pressure to the ECU 51. On the other hand, the exhaust pipe 47 has an A / F sensor 61 as an air-fuel ratio detecting means for detecting the air-fuel ratio of the engine 10 upstream of the three-way catalyst 48 in the exhaust gas flow direction, and an oxygen sensor 62 downstream of the exhaust gas flow direction. Is provided. The A / F sensor 61 detects the exhaust gas air-fuel ratio of the exhaust gas before being introduced into the three-way catalyst 48, outputs the detected air-fuel ratio to the ECU 51, and the oxygen sensor 62 is discharged from the three-way catalyst 48. Thereafter, the oxygen concentration of the exhaust gas is detected, and the detected oxygen concentration is output to the ECU 51. The air-fuel ratio (estimated air-fuel ratio) detected by the A / F sensor 61 is used for feedback control of the air-fuel ratio (theoretical air-fuel ratio) of the mixed gas composed of intake air and fuel. That is, the A / F sensor 61 detects the exhaust air-fuel ratio from the rich region to the lean region from the oxygen concentration in the exhaust gas and the unburned gas concentration, and feeds back this to the ECU 51 to correct the fuel injection amount. Thus, the combustion can be controlled to an optimum combustion state that matches the operating state. An oxygen sensor or the like may be used instead of the A / F sensor 61 as the air-fuel ratio detection means.

  Further, the ECU 51 is electrically connected with a knock sensor 63 as knock detection means for detecting knocking of the engine 10 and a fuel amount sensor 64 for detecting the amount of fuel in the fuel tank. The knock sensor 63 detects the occurrence of knocking in the engine 10 based on, for example, a piezoelectric element whose voltage changes due to vibration of the cylinder block 11 and outputs the detection result to the ECU 51. The knock sensor 63 may be another type of sensor as long as it can detect the occurrence of knocking.

  Therefore, the ECU 51 drives the high-pressure fuel pump 44 based on the detected fuel pressure so that the fuel pressure becomes a predetermined pressure, and also detects the detected intake air amount, intake air temperature, intake pressure, throttle opening, accelerator opening. The fuel injection amount (fuel injection time), the injection timing, the ignition timing, etc. are determined based on the engine operating state such as the engine speed and the engine coolant temperature, and the injector 41 and the spark plug 45 are driven to perform the fuel injection and ignition. Execute. Further, the ECU 51 feeds back the detected oxygen concentration of the exhaust gas to correct the fuel injection amount so that the air-fuel ratio becomes stoichiometric (theoretical air-fuel ratio).

  The ECU 51 can control the intake / exhaust variable valve mechanisms 27 and 28 based on the engine operating state. That is, when the temperature is low, the engine is started, the engine is idle, or the load is light, the exhaust gas blows back to the intake port 19 or the combustion chamber 18 by eliminating the overlap between the exhaust valve 22 closing timing and the intake valve 21 opening timing. Reduce the amount to enable stable combustion and improved fuel efficiency. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valve 21 is advanced, thereby reducing the amount of intake air that blows back to the intake port 19 and improving the volume efficiency. At the time of high load and high rotation, the closing timing of the intake valve 21 is retarded in accordance with the rotation speed, so that the timing is adjusted to the inertial force of the intake air and the volume efficiency is improved.

  Here, in such an engine 10, the occurrence of knocking is prevented in any of combustion with only gasoline fuel, combustion with alcohol fuel mixed with gasoline fuel, and combustion with only alcohol fuel. In order to obtain a high output, it is necessary to ignite the air-fuel mixture at an accurate ignition timing according to the engine operating state. And in the engine 10 which burns using the fuel with at least two kinds of different properties as described above, if the ignition timing is set according to any fuel property, the fuel is changed to a fuel having a different fuel property. At this time, the ignition timing is not suitable, and as a result, knocking may occur or the engine output may decrease. Therefore, when the fuel property is changed, it is important for the ignition timing to converge to the optimal ignition timing at an early stage in order to suppress the occurrence of excessive knocking and improve the output.

  By the way, for example, when alcohol fuel is added to gasoline fuel, the alcohol fuel has a high octane number and is difficult to knock, so it tries to learn the ignition timing on the advance side, but the alcohol fuel contains a lot of oxygen. For this reason, the air-fuel ratio is greatly deviated to the lean side. For this reason, it is necessary to increase the fuel injection amount by feedback control and control the air-fuel ratio to stoichiometric. Here, in actuality, when the air-fuel ratio is controlled from lean to stoichiometric, the knock generation limit ignition timing fluctuates in accordance with this, so in the transition period when the air-fuel ratio is controlled from lean to stoichiometric. Even if learning of the optimal ignition timing as described above is performed, the optimal ignition timing at the target air-fuel ratio cannot be learned at an early stage. There is a risk that knocking at the air-fuel ratio cannot be properly avoided, and the number of knocks until the learning is completed may increase. Here, the knock generation limit ignition timing is the limit ignition timing at which knocking occurs, and if ignition is performed on the advance side with respect to the knock generation limit ignition timing, knocking occurs, while ignition occurs on the retard side. If knocked, no knocking will occur. However, if the ignition timing is retarded too much, sufficient output may not be ensured. For this reason, in order to ensure an appropriate output while avoiding knocking, it is necessary to ignite near the knock generation limit ignition timing to the extent that knocking does not occur.

  Therefore, in the control device for the engine 10 of the present embodiment, as shown in FIG. 2, the ECU 51 has an ignition timing control unit 71 as ignition timing control means for controlling the ignition timing by the ignition plug 45, and the air-fuel ratio. By providing the ignition timing learning unit 72 as ignition timing learning means for updating the changing knock generation limit ignition timing based on the learning value, the ignition timing that can avoid knocking at an early stage is learned.

  More specifically, in the engine 10, the ECU 51 includes a learning value setting unit 73 serving as a learning value setting unit that sets a learning value, and a predicted knock generation limit ignition timing prediction unit that predicts a predicted knock generation limit ignition timing. The predicted knock occurrence limit ignition timing prediction unit 74 is provided. The learning value setting unit 73 sets a learning value based on the amount of retardation of the predicted knock generation limit ignition timing with respect to the actual knock generation ignition timing when knocking is detected by the knock sensor 63, and the ignition timing learning unit 72, when knocking is detected by the knock sensor 63, updates the knock occurrence limit ignition timing to the retard side based on this learning value. Then, the ignition timing control unit 71 controls the ignition timing by the spark plug 45 based on the knock generation limit ignition timing updated by the ignition timing learning unit 72.

  Here, the ECU 51 includes a processing unit 75, a storage unit 76, and an input / output unit 77, which are connected to each other and can exchange signals with each other. A drive circuit (not shown) that drives each part of the engine 10 and the various sensors described above are connected to the input / output unit 77, and the input / output unit 77 inputs and outputs signals to and from these sensors and the like. The storage unit 76 stores a computer program for controlling the engine 10. The storage unit 76 is a hard disk device, a magneto-optical disk device, a non-volatile memory such as a flash memory (a storage medium that can be read only such as a CD-ROM), or a RAM (Random Access Memory). A volatile memory or a combination thereof can be used.

  The processing unit 75 includes a memory (not shown) and a CPU (Central Processing Unit). The above-described ignition timing control unit 71, ignition timing learning unit 72, learning value setting unit 73, prediction knock generation limit ignition timing prediction unit. 74.

  The ignition timing learning control after refueling in the engine 10 is calculated by the processing unit 75 reading the computer program into a memory incorporated in the processing unit 75 based on the detection result by the sensor provided in each part of the vehicle. This is executed by sending a control signal according to the calculation result. At that time, the processing unit 75 appropriately stores a numerical value in the middle of the calculation in the storage unit 76, and takes out the stored numerical value and executes the calculation. When the engine 10 is controlled, it may be controlled by dedicated hardware different from the ECU 51 instead of the computer program.

  Here, the ignition timing learning control after refueling by the control device of the engine 10 of the present embodiment will be described in detail based on the flowchart of FIG. The following operations are mainly executed by the ECU 51.

  First, when the driver starts the engine 10, ignition timing learning control is started, and the ECU 51 acquires the operating state of the engine 10 from various sensors (S100). Next, the ECU 51 determines the presence or absence of refueling based on the fuel increase amount in the fuel tank during a predetermined period by the fuel amount sensor 64 (S102). If the amount of increase in fuel is greater than a preset value, ECU 51 determines that there is refueling (S102: Yes), turns on the refueling flag (S104), and determines whether the post-fueling ignition timing learning condition is satisfied. Is determined (S106). If the fuel increase amount is smaller than a preset value, it is determined that there is no refueling (S102: No), and it is determined whether or not the post-fueling ignition timing learning condition is satisfied by passing S104 (S106).

  Specifically, in determining whether or not the post-refueling ignition timing learning condition is satisfied, the ECU 51 determines whether or not the refueling flag is ON, whether combustion is stable, and fuel use after starting It is determined whether or not the amount is equal to or greater than a predetermined value. The determination of the combustion stability is performed in order to avoid learning in an unstable driving state. For example, the determination is made according to the rotational speed detected by the crank angle sensor 57 or the in-cylinder pressure detected by the in-cylinder pressure sensor 59. It is also possible to make a determination according to the elapsed time from the engine start. The determination of whether or not the amount of fuel used after the start is equal to or greater than a predetermined value is to determine whether or not the old fuel remaining in the fuel pipe has been used up. It can be determined according to the pipe volume that is present, and can also be determined according to the elapsed time since the engine start.

  When it is determined that the post-refueling ignition timing learning condition is not satisfied (S106: No), that is, the refueling flag is OFF, the combustion is not stable, or the old fuel remaining in the fuel pipe is used up. If it is determined that it is not, the process returns to S100 and the subsequent processing is repeated. When it is determined that the ignition timing learning condition after fueling is satisfied (S106: Yes), that is, when it is determined that the fueling flag is ON, the combustion is stable, and the old fuel remaining in the fuel pipe is used up. The ECU 51 adjusts the intake air amount sucked into the combustion chamber 18 by the electronic throttle device 40 as load adjusting means to adjust the load of the engine 10 to a predetermined value or less, and variable valve operating means. The intake / exhaust variable valve operating mechanisms 27, 28 eliminate the overlap of the valve opening periods of the intake valve 21 and the exhaust valve 22 (S108). If the load of the engine 10 has already been adjusted to a predetermined value or less before S108 and the overlap between the valve opening periods of the intake valve 21 and the exhaust valve 22 has been controlled to 0, this is continued.

  Here, since the alcohol fuel has a high octane number and is unlikely to cause knocking, there is a possibility that, for example, the ignition timing is learned to be relatively advanced when alcohol fuel is used. At this time, if the fuel is changed from alcohol fuel to normal gasoline fuel, the gasoline fuel has a lower octane number than alcohol fuel, so the ignition timing learned to the advance side as described above The actual knock generation limit ignition timing moves to the retard side, and as a result, large knocking may occur. However, as described above, the load of the engine 10 is adjusted to a predetermined value or less, and the overlap of the opening period of the intake valve 21 and the exhaust valve 22 is eliminated, thereby suppressing the charging efficiency of the intake air into the combustion chamber 18. At the same time, since the amount of internal EGR is suppressed and the rise in the in-cylinder temperature is suppressed, it is possible to avoid an operating state in which large knocking is likely to occur.

  Next, the ECU 51 determines whether or not knocking has occurred by the knock sensor 63 (S110). When the occurrence of knocking is detected (S110: Yes), a learning value for updating the knock generation limit ignition timing is predictedly calculated by the learning value setting unit 73 (S112), and the air-fuel ratio is set by the ignition timing learning unit 72. The knock generation limit ignition timing that changes accordingly is updated based on this learned value (S114).

4 is a graph showing an example of the relationship between the air-fuel ratio and the knock generation limit ignition timing in the engine 10, where the horizontal axis represents the air-fuel ratio (A / F) and the vertical axis represents the ignition timing (deg. BTDC). : Before Top Dead Center). In the figure, the dotted line represents an example of the curve X ₀ indicating the knock generation limit ignition timing before updating based on the learned value, and the solid line represents an example of the curve X ₁ indicating the knock generation limit ignition timing after updating. As shown in the figure, the limit ignition timing at which knocking occurs actually changes as the air-fuel ratio changes. More specifically, the knock generation limit ignition timing gradually moves from the rich side toward the stoichiometric side toward the retarded angle side, and then returns from the predetermined air-fuel ratio toward the lean side again toward the advanced side. It has the property of moving.

For example, if the ignition timing at which the occurrence of knocking is detected at the lean air-fuel ratio A is assumed to be the ignition timing a, and the curve X ₁ is a curve indicating the actual knock generation limit ignition timing, the air-fuel ratio A The knock generation limit ignition timing is the ignition timing b. At this time, if the air-fuel ratio A is controlled to the target air-fuel ratio on the stoichiometric side and ignition is performed at the ignition timing b without considering the characteristic that the knock generation limit ignition timing as described above changes according to the air-fuel ratio. The knock generation limit ignition timing at the target air-fuel ratio actually changes to the retard side to become the ignition timing c, and as a result, the retard amount of the ignition timing is insufficient, and the advance angle is advanced with the curve X ₁ as a boundary. Ignition is executed at the ignition timing within the knocking generation region which is the side region. That is, knocking frequently occurs while the air-fuel ratio A is controlled to the stoichiometric target air-fuel ratio.

However, in this embodiment, the ignition timing learning unit 72 updates the knock generation limit ignition timing, which changes according to the air-fuel ratio, to the retard side based on the learned value. That is, the ignition timing learning unit 72 offsets the curve X ₀ indicating the knock occurrence limit ignition timing before update to the curve X ₁ on the retard side according to the learning value. Then, the ignition timing control unit 71 sets an appropriate ignition timing according to the target air-fuel ratio based on the curve X ₁ indicating the offset knock generation limit ignition timing, and controls the ignition timing by the ignition plug 45. Therefore, even when the air-fuel ratio is controlled to the target air-fuel ratio, it does not pass through the knocking occurrence region, so that the ignition timing is properly learned even in the transition period in which the air-fuel ratio is controlled to the target air-fuel ratio. Thus, it is possible to learn an ignition timing at which knocking can be avoided at an early stage.

  Here, the relationship between the air-fuel ratio and the knock generation limit ignition timing shown in FIG. 4 changes according to the operating state of the engine 10. Therefore, the relationship between the air-fuel ratio and the knock generation limit ignition timing may be mapped according to each operation state of the engine 10 and stored in the storage unit 76, or approximated based on various parameters indicating the operation state. Data may be converted into an equation and stored in the storage unit 76. The ignition timing learning unit 72 reads and updates the knock generation limit ignition timing stored in the storage unit 76 according to the operating state.

  Here, the learning value for updating the knock generation limit ignition timing is the knocking intensity when knocking is detected by the learning value setting unit 73, and the combustion value in the combustion chamber 18 as schematically shown in FIG. It is set according to the amount of unburned fuel and the knocking model based on the timing at which the unburned fuel self-ignites.

  The self-ignition prediction formula representing the timing at which the unburned fuel in the combustion chamber 18 self-ignites can be modeled using, for example, the following mathematical formula (1). Here, A, B, C, and Ea are compatible values, P is the in-cylinder pressure, Tu is the in-cylinder unburned fuel temperature, and φ is the equivalence ratio. This equation (1) is a so-called Livinggood-Wu integral, and the unburned fuel in the combustion chamber 18 is self-ignited at the timing when this equation is established.

  If the unburned fuel in the combustion chamber 18 remains in the combustion chamber 18 at a predetermined amount at the self-ignition timing, knocking occurs.

  FIG. 6 is a graph showing an example of the relationship between the crank angle and the fuel combustion ratio in the engine, where the horizontal axis is the crank angle (deg. ATDC: After Top Dead Center), and the vertical axis is the fuel combustion ratio (%). Yes. As shown in FIG. 6, the amount of unburned fuel in the combustion chamber 18 changes according to the crank angle and decreases as the stroke proceeds.

  Here, at the timing when the unburned fuel in the combustion chamber 18 is self-ignited, the minimum amount of unburned fuel required for knocking is set as the TK determination value. This TK determination value is set in advance according to the engine speed, load, and the like. The crank angle at which the amount of unburned fuel becomes equal to or less than the TK determination value when the air-fuel mixture in the combustion chamber 18 is ignited at a certain ignition timing is defined as the knock determination crank angle Cb, and the timing at which the unburned fuel self-ignites. Let the crank angle be the self-ignition crank angle Cl.

FIG. 7 is a graph showing an example of the relationship between the ignition timing, the self-ignition crank angle Cl, and the knock determination crank angle Cb in the engine to which the control apparatus for an internal combustion engine according to the embodiment of the present invention is applied. As shown in the figure, the self-ignition crank angle Cl and the knock determination crank angle Cb correspond to a predetermined ignition timing and can be expressed by an approximate linear expression. That is, the self-ignition crank angle Cl and the knock determination crank angle Cb corresponding to a certain ignition timing can be uniquely calculated according to the ignition timing. In the figure, the self-ignition crank angle Cl corresponding to the ignition timing is indicated by a straight line Y (Y ₀ and Y ₁ ), and the knock determination crank angle Cb corresponding to the ignition timing is indicated by a straight line Z (Z ₀ and Z ₁ ). The self-ignition crank angle Cl and the knock determination crank angle Cb become larger as the ignition timing is retarded.

  Here, when the stroke proceeds beyond the knock determination crank angle Cb at which the amount of unburned fuel becomes equal to or less than the TK determination value, the amount of unburned fuel necessary for occurrence of knocking has not remained in the combustion chamber 18. Even when the self-ignition crank angle Cl is reached, knocking does not occur. That is, in FIG. 7, knocking does not occur in the region where the crank angle increases (upper side in the drawing) with the straight line Z as the boundary.

  On the other hand, in the stroke before the knock determination crank angle Cb, the amount of unburned fuel necessary for the occurrence of knocking remains sufficiently in the combustion chamber 18, so that knocking occurs when the self-ignition crank angle Cl is reached. Will occur. That is, knocking occurs in the ignition timing region where [knock determination crank angle Cb]> [self-ignition crank angle Cl].

  Note that the greater the amount of unburned fuel when the self-ignition crank angle Cl is reached, the greater the knocking strength. That is, as the value of [knock determination crank angle Cb] − [self-ignition crank angle Cl] increases, the amount of unburned fuel at the time when the self-ignition crank angle Cl is reached increases, so the strength of the knock increases. . That is, the value of [knock determination crank angle Cb] − [self-ignition crank angle Cl] is a value corresponding to the knocking strength, and the larger the value, the larger the knocking strength.

  The predicted knock generation limit ignition timing prediction unit 74 predicts the predicted knock generation limit ignition timing based on the knock determination crank angle Cb and the self-ignition crank angle Cl using the characteristics of the knocking model described above. The relationship between the ignition timing, the knock determination crank angle Cb, and the self-ignition crank angle Cl may be mapped according to each operation state of the engine 10 and stored in the storage unit 76, or an approximate linear expression (straight line Y, Z) may be converted into data and stored in the storage unit 76. The predicted knock generation limit ignition timing prediction unit 74 reads the knock determination crank angle Cb and the self-ignition crank angle Cl stored in the storage unit 76 according to the ignition timing, and predicts the predicted knock generation limit ignition timing.

With continued reference to FIG. 7, the prediction of the predicted knock occurrence limit ignition timing by the predicted knock occurrence limit ignition timing prediction unit 74 will be specifically described. Now, let the ignition timing when knocking is detected by the knock sensor 63 be the actual knock generation ignition timing A. At this time, the crank angle at which vibration due to knocking is actually detected is the actual self-ignition crank angle Cl ₀ at the actual knock generation ignition timing A, that is, the timing when the unburned fuel actually self-ignites.

The straight line Y indicating the self-ignition crank angle Cl corresponding to the predetermined ignition timing passes through the points represented by the actual knock generation ignition timing A and the actual self-ignition crank angle Cl ₀ . That is, the predicted knock generation limit ignition timing prediction unit 74 does not change the inclination of the straight line Y ₀ indicating the self-ignition crank angle Cl indicated by the dotted line in the figure, and changes the actual knock generation ignition timing A and the actual self-ignition crank angle Cl. The self-ignition crank angle Cl is updated based on the actual self-ignition crank angle Cl ₀ corresponding to the actual knock generation ignition timing A by offsetting to the straight line Y ₁ indicated by the solid line passing through the point represented by _0. .

Next, the actual knock determination crank angle Cb ₀ corresponding to the actual knock generation ignition timing A is at least the actual self-ignition crank angle Cl ₀ because knocking has actually occurred at the actual knock generation ignition timing A. It should have taken a larger value. The value of [actual knock determination crank angle Cb ₀ ] − [actual self-ignition crank angle Cl ₀ ] corresponds to the current knocking strength.

Specifically, the predicted knock generation limit ignition timing prediction unit 74 calculates the heat generation ratio according to the in-cylinder pressure detected by the in-cylinder pressure sensor 59 when knocking occurs, and calculates the fuel combustion ratio. Since the relationship between the combustion ratio and the crank angle is as shown in FIG. 6 described above, the crank angle corresponding to the amount of unburned fuel remaining when this knocking occurs is calculated. be able to. At this time, since knocking has actually occurred at the actual knock generation ignition timing A, at this combustion rate, the amount of unburned fuel in the combustion chamber 18 remains at least the TK determination value. That is, this crank angle can be predicted as the actual knock determination crank angle Cb ₀ .

Linear Z indicating the knock determination crank angle Cb corresponding to a predetermined ignition timing would pass through the point represented by the actual knock ignition timing A and the actual knocking determination crank angle Cb _0. That is, the predicted knock generation limit ignition timing prediction unit 74 does not change the slope of the straight line Z ₀ indicating the knock determination crank angle Cb indicated by the dotted line in the figure, and changes the actual knock generation ignition timing A and the actual knock determination crank angle Cb. The knock determination crank angle Cb is updated with the actual knock determination crank angle Cb ₀ corresponding to the actual knock generation ignition timing A as a reference by offsetting to the straight line Z ₁ indicated by the solid line passing through the point represented by _0. .

As described above, knocking occurs in the ignition timing region where [knock determination crank angle Cb]> [self-ignition crank angle Cl], while [knock determination crank angle Cb] <[self-ignition crank angle Cl]. No knocking occurs in the ignition timing region. That is, the ignition timing corresponding to the crank angle C ₁ (C ₁ = Cb ₁ = Cl ₁ ) where [knock determination crank angle Cb] = [self-ignition crank angle Cl] is the limit ignition timing at which knocking occurs at this time Can be predicted. That is, the predicted knocking occurrence limit ignition timing prediction unit 74, a straight line Y ₁ that is offset so as to pass the point represented by real knock ignition timing A and the actual ignition crank angle Cl _0, the actual knock ignition timing A The ignition timing at the intersection with the straight line Z ₁ offset so as to pass through the point represented by the actual knock determination crank angle Cb ₀ can be predicted as the predicted knock generation limit ignition timing B.

The learned value setting unit 73 sets a learned value based on the actual knock generation ignition timing A and the predicted knock generation limit ignition timing B predicted by the predicted knock generation limit ignition timing prediction unit 74. That is, the learning value setting unit 73 sets the retard amount of the predicted knock generation limit ignition timing B with respect to the actual knock generation ignition timing A as the learning value. The ignition timing learning unit 72 offsets the curve X ₀ indicating the knock generation limit ignition timing shown in FIG. 4 to the delay side to the curve X ₁ according to the learning value set by the learning value setting unit 73. Ignition timing control unit 71, in the offset curves X _1, controls the optimum ignition timing of the ignition plug 45 based on the knocking limit ignition timing in accordance with the target air-fuel ratio. Thus, the predicted knock generation limit ignition timing B is predicted, and the retard amount from the actual knock generation ignition timing A is set to the learning value to update the knock generation limit ignition timing. For example, from alcohol fuel to gasoline fuel Even when a large amount of knocking is likely to occur, such as when it is changed, the learning value (retard amount) from the ignition timing at which knocking has occurred can be set early, improving the convergence of learning and making it optimal quickly The ignition timing can be learned.

  Referring to FIG. 3 again, ECU 51 determines whether or not knocking has occurred by knock sensor 63 (S110). If no knocking has been detected (S110: No), refueling by learning value setting unit 73 is performed. The learning value of the knock generation limit ignition timing is updated in the advance direction with the subsequent ignition timing update width (advance amount) (S116), and the ignition timing learning unit 72 sets the knock generation limit ignition timing based on this learning value. Update (S114). Here, the ignition timing update range (advance amount) after refueling is set in advance to a value larger than the normal update range so that learning to the advance side can be completed early.

  Then, after the knock generation limit ignition timing is updated in S114, the ignition timing control unit 71 controls the ignition timing of the spark plug 45 based on the updated knock generation limit ignition timing. Thereafter, the ECU 51 determines whether or not the post-refueling ignition timing learning termination condition is satisfied (S118).

  In determining whether or not the post-refueling ignition timing learning termination condition is satisfied, specifically, the ECU 51 reduces the update range of the learning value compared to the previous update of the knock occurrence limit ignition timing, When the learning direction is reversed and knocking does not occur within a predetermined period, it is determined that the ignition timing learning termination condition after refueling is satisfied. Note that the learning direction is reversed when learning is performed on the advance side during the previous update and learning is performed on the retard side during the current update, or vice versa.

  When it is determined that the ignition timing learning termination condition after refueling is not satisfied (S118: No), the process returns to S100 and the subsequent processing is repeated. If it is determined that the post-refueling ignition timing learning termination condition is satisfied (S118: Yes), the fueling flag that was turned ON in S104 is turned OFF, and then the process returns to S100 and the subsequent processing is repeated.

  According to the control apparatus for the engine 10 according to the embodiment of the present invention described above, the combustion chamber 18 in which the mixture of fuel and air having different properties can be combusted, and the ignition plug that ignites the mixture. 45, a knock sensor 63 for detecting knocking of the engine 10, and an A / F sensor 61 for detecting the air-fuel ratio of the engine 10. When the knock sensor 63 detects knocking in the ECU 51, the air-fuel ratio is increased. An ignition timing learning unit 72 that updates the knock generation limit ignition timing that changes according to the learning value to the retard side, and ignition by the spark plug 45 based on the knock generation limit ignition timing updated by the ignition timing learning unit 72 An ignition timing control unit 71 for controlling the timing is provided.

  Therefore, the knock generation limit ignition timing that changes according to the air-fuel ratio is updated to the retard side based on the learned value, and the ignition timing is controlled based on the updated knock generation limit ignition timing, so the air-fuel ratio is Even in the transition period in which the target air-fuel ratio is controlled, the ignition timing can be properly learned, so that it is possible to learn the ignition timing that can avoid knocking at an early stage even if the fuel property is changed. Moreover, since the optimal ignition timing can be learned early, an appropriate output can be secured early.

  Furthermore, according to the control apparatus for the engine 10 according to the embodiment of the present invention described above, the knocking strength when the knocking is detected by the knock sensor 63, the amount of unburned fuel in the combustion chamber 18, and the unburned fuel. A learning value setting unit 73 that sets a learning value according to a knocking model based on the timing at which the fuel self-ignites is provided. Therefore, the ignition timing learning unit 72 updates the knock generation limit ignition timing according to the learning value set every time knocking occurs based on the knocking strength and the knocking model at the time of occurrence of knocking. The ignition timing can be quickly retarded to an appropriate ignition timing at which knocking does not occur, the convergence to the optimal ignition timing is improved, and the optimal ignition timing can be learned early.

  Furthermore, according to the control apparatus for the engine 10 according to the embodiment of the present invention described above, the crank angle sensor 57 for detecting the crank angle of the engine 10 and the amount of unburned fuel when the air-fuel mixture is ignited in advance. Prediction knock generation limit for predicting the predicted knock generation limit ignition timing based on the knock determination crank angle Cb that is less than the set determination value and the self-ignition crank angle Cl at which the unburned fuel self-ignites when the mixture is ignited The learning value setting unit 73 sets a learning value based on the amount of retardation of the predicted knock generation limit ignition timing with respect to the actual knock generation ignition timing when knocking is detected by the knock sensor 63. To do. Therefore, the predicted knock generation limit ignition timing is predicted based on the knock determination crank angle Cb and the self-ignition crank angle Cl, and the delay amount of the predicted knock generation limit ignition timing with respect to the actual knock generation ignition timing is set as a learning value. Therefore, for example, even when large knocking is likely to occur, for example, when alcohol fuel is changed to gasoline fuel, the optimal learning value according to the predicted knock generation limit ignition timing can be set early, as a result, Convergence to the optimal ignition timing can be further improved and the occurrence of knocking can be effectively suppressed.

Furthermore, according to the control apparatus for engine 10 according to the embodiment of the present invention described above, the predicted knock generation limit ignition timing prediction unit 74 uses the actual knock determination crank angle Cb ₀ corresponding to the actual knock generation ignition timing as a reference. The knock determination crank angle Cb corresponding to the ignition timing is updated, and the self-ignition crank angle Cl corresponding to the ignition timing is updated based on the actual self-ignition crank angle Cl ₀ corresponding to the actual knock generation ignition timing. The ignition timing at which the knock determination crank angle Cb is equal to the self-ignition crank angle Cl is set as the predicted knock generation limit ignition timing. Therefore, by updating the knock determination crank angle Cb and the self-ignition crank angle Cl with reference to the actual knock determination crank angle Cb ₀ and the actual self-ignition crank angle Cl ₀ , [knock determination crank angle Cb] = [self-ignition crank angle It can be predicted that the ignition timing corresponding to the crank angle C ₁ that becomes Cl] is the knock generation limit ignition timing. As a result, it is possible to easily calculate the retard amount of the predicted knock occurrence limit ignition timing with respect to the actual knock occurrence ignition timing, and by setting this retard amount to the learned value, the learned value is set to the predicted knock occurrence limit ignition timing. It can be a value according to For this reason, an optimal learning value can be set at an early stage of learning of the ignition timing.

Furthermore, according to the control apparatus for the engine 10 according to the embodiment of the present invention described above, the curve X indicating the knock generation limit ignition timing that changes according to the air-fuel ratio, and the self-ignition crank angle Cl corresponding to the ignition timing are obtained. The storage unit 76 stores a straight line Y indicating the knock determination crank angle Cb corresponding to the ignition timing, and the ignition timing learning unit 72 includes a curve X indicating the knock generation limit ignition timing stored in the storage unit 76. Is updated based on the learning value to update the knock generation limit ignition timing, and the predicted knock generation limit ignition timing prediction unit 74 uses the straight line Y indicating the self-ignition crank angle Cl stored in the storage unit 76 real knock determination linear Z indicating the knock determination crank angle Cb stored in the storage unit 76 together with the offset ignition crank angle Cl ₀ to response was the point Offset on points corresponding to the rank angle Cb _0, predicts a predicted knocking occurrence limit ignition timing based on the intersection of the straight line Z showing a straight line Y and the knock determination crank angle Cb indicating the self-ignition crank angle Cl which is the offset To do. Therefore, the calculation amount in the ECU 51 can be reduced, and as a result, the post-refueling ignition timing learning control can be executed at high speed.

  Furthermore, according to the control apparatus for the engine 10 according to the embodiment of the present invention described above, the intake port 19 and the exhaust port 20 that communicate with the combustion chamber 18, and the intake valve that can freely open and close the intake port 19 and the exhaust port 20 are provided. 21 and the exhaust valve 22, the intake port 19 and the exhaust port 20 can be opened and closed using the intake valve 21 and the exhaust valve 22, and the intake and exhaust variable valve mechanisms 27 and 28 that can change the opening and closing timing, and the engine 10 And the electronic throttle device 40 for adjusting the load of the intake and exhaust when the ignition timing learning unit 72 updates the knock generation limit ignition timing. The overlap in the valve opening period is eliminated, and the electronic throttle device 40 adjusts the load of the engine 10 to a predetermined value or less that is set in advance. Therefore, the load of the engine 10 is adjusted to a predetermined value or less, and the overlap of the opening periods of the intake valve 21 and the exhaust valve 22 is eliminated, thereby suppressing the charging efficiency of the intake air into the combustion chamber 18 and the internal EGR amount. Is suppressed and an increase in the in-cylinder temperature is suppressed, so that it is possible to avoid an operating state in which large knocking is likely to occur. As a result, in the subsequent ignition timing learning, more accurate ignition timing learning can be executed while avoiding the occurrence of large knocking.

  In addition, the control apparatus of the engine 10 which concerns on the Example of this invention mentioned above is not limited to the Example mentioned above, A various change is possible in the range described in the claim. In the above description, the control device for an internal combustion engine of the present invention is applied to a cylinder injection type multi-cylinder engine. However, the present invention is not limited to this type of engine, but can be applied to an in-line or V-type engine. Even when applied to a port injection type internal combustion engine, the same effects can be obtained. In the above description, the internal combustion engine that can be operated using alcohol fuel and gasoline fuel as at least two types of fuels having different properties has been described. However, the present invention is not limited to this. For example, hydrocarbon fuel and hydrogen It may be an internal combustion engine that can use both gases as fuel.

  In the above description, the learning value is described as being set according to the knocking strength and the knocking model when knocking is detected by the learning value setting unit 73. However, the learning value is set in advance according to the driving state. You may make it use.

In the above description, the predicted knock occurrence limit ignition timing prediction unit 74 has been described as predicting the predicted knock occurrence limit ignition timing using the crank angle, but it may be simply predicted using time. Good. In the above description, the predicted knock generation limit ignition timing prediction unit 74 calculates the ignition timing corresponding to the crank angle C ₁ where [knock determination crank angle Cb] = [self-ignition crank angle Cl] as the predicted knock generation limit ignition. Although it has been described that the timing is predicted, knocking does not occur in the ignition timing region where [knock determination crank angle Cb] <[self-ignition crank angle Cl], so [knock determination crank angle Cb] = [self-ignition crank] The ignition timing corresponding to the crank angle satisfying [knock determination crank angle Cb] <[self-ignition crank angle Cl] by giving a slight margin to the crank angle C ₁ corresponding to the angle Cl] is also set as the predicted knock generation limit ignition timing. Good.

  In the above description, the crank angle corresponding to the amount of unburned fuel remaining when knocking occurs according to the in-cylinder pressure detected by the in-cylinder pressure sensor 59 is calculated. It may be stored in the storage unit 76 as a mathematical model based on various parameters and calculated based on this mathematical model. In this case, since it is not necessary to provide the in-cylinder pressure sensor 59, the configuration can be simplified, and the manufacturing cost can be reduced. The air-fuel ratio at the time of occurrence of knocking detected by the A / F sensor 61 may be calculated in consideration of the time until the exhaust gas discharged from the combustion chamber 18 contacts the A / F sensor 61. In this case, more accurate ignition timing learning is possible.

  As described above, the control apparatus for an internal combustion engine according to the present invention learns the ignition timing at which knocking can be avoided at an early stage, and is suitable for use in various internal combustion engines.

1 is a schematic configuration diagram illustrating an engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. 1 is a block diagram illustrating an ECU of an engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. It is a flowchart explaining ignition timing learning control after refueling in an engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. It is a graph showing an example of the relationship between the air fuel ratio and knock generation limit ignition timing in the engine to which the control device for an internal combustion engine according to the embodiment of the present invention is applied. It is a mimetic diagram explaining the knocking model in the engine to which the control device of the internal-combustion engine concerning the example of the present invention was applied. It is a graph showing an example of the relationship between the crank angle in an engine to which the control apparatus of the internal combustion engine which concerns on the Example of this invention was applied, and a combustion ratio. It is a graph showing an example of the relationship between the ignition timing in the engine to which the control apparatus of the internal combustion engine which concerns on the Example of this invention was applied, a knock determination crank angle, and a self-ignition crank angle.

Explanation of symbols

10 Engine (Internal combustion engine)
14 Piston 16 Crankshaft 18 Combustion chamber 19 Intake port 20 Exhaust port 21 Intake valve 22 Exhaust valve 27 Intake variable valve mechanism (variable valve means)
28 Exhaust variable valve mechanism (variable valve mechanism)
40 Electronic throttle device (load adjustment means)
41 Injector 45 Spark plug 51 ECU
57 Crank angle sensor (crank angle detection means)
61 A / F sensor (air-fuel ratio detection means)
63 Knock sensor (knock detection means)
71 Ignition timing control unit (ignition timing control means)
72 Ignition timing learning unit (ignition timing learning means)
73 Learning value setting unit (learning value setting means)
74 Predictive knock generation limit ignition timing prediction section (Predictive knock generation limit ignition timing prediction means)
75 processing unit 76 storage unit

Claims (6)

A combustion chamber capable of combusting a mixture of fuel and air having at least two different properties; and
A spark plug for igniting the air-fuel mixture;
Knock detecting means for detecting knocking of the internal combustion engine;
Air-fuel ratio detection means for detecting the air-fuel ratio of the internal combustion engine;
An ignition timing learning means for updating a knock occurrence limit ignition timing that changes according to the air-fuel ratio to a retard side based on a learned value when knocking is detected by the knock detection means;
Ignition timing control means for controlling the ignition timing by the spark plug based on the knock generation limit ignition timing updated by the ignition timing learning means,
Control device for internal combustion engine. Learning that sets the learning value according to the knocking intensity when knocking is detected by the knock detection means, and the knocking model based on the amount of unburned fuel in the combustion chamber and the timing at which the unburned fuel self-ignites. It comprises a value setting means,
The control apparatus for an internal combustion engine according to claim 1. Crank angle detecting means for detecting a crank angle of the internal combustion engine;
A knock determination crank angle at which the amount of unburned fuel becomes equal to or less than a predetermined determination value when the mixture is ignited, and a self-ignition crank angle at which the unburned fuel self-ignites when the mixture is ignited A predicted knock generation limit ignition timing prediction means for predicting a predicted knock generation limit ignition timing based on
The learning value setting means sets the learning value based on a retard amount of the predicted knock generation limit ignition timing with respect to an actual knock generation ignition timing when knocking is detected by the knock detection means. ,
The control apparatus for an internal combustion engine according to claim 2. The predicted knock generation limit ignition timing prediction means updates the knock determination crank angle corresponding to the ignition timing with reference to the actual knock determination crank angle corresponding to the actual knock generation ignition timing, and corresponds to the actual knock generation ignition timing The self-ignition crank angle corresponding to the ignition timing is updated using the actual self-ignition crank angle as a reference, and an ignition timing at which the updated knock determination crank angle is equal to the self-ignition crank angle is determined as the predicted knock generation limit ignition timing. It is characterized by
The control device for an internal combustion engine according to claim 3. Curve data indicating a knock generation limit ignition timing that changes according to the air-fuel ratio, linear data indicating the knock determination crank angle corresponding to the ignition timing, and linear data indicating the self-ignition crank angle corresponding to the ignition timing are stored. A storage unit,
The ignition timing learning means updates the knock generation limit ignition timing by offsetting the curve data indicating the knock generation limit ignition timing stored in the storage unit based on the learning value,
The predicted knock occurrence limit ignition timing prediction means offsets linear data indicating the knock determination crank angle stored in the storage unit onto a point corresponding to the actual knock determination crank angle and is stored in the storage unit. The linear data indicating the self-ignition crank angle is offset on a point corresponding to the actual self-ignition crank angle, and the linear data indicating the knock determination crank angle and the linear data indicating the self-ignition crank angle are offset. Predicting the predicted knock occurrence limit ignition timing based on the intersection point,
The control device for an internal combustion engine according to claim 4. An intake port and an exhaust port communicating with the combustion chamber;
An intake valve and an exhaust valve that can freely open and close the intake port and the exhaust port;
Variable valve operating means capable of opening and closing the intake port and the exhaust port using the intake valve and the exhaust valve and capable of changing the opening and closing timing;
Load adjusting means for adjusting the load of the internal combustion engine,
When the ignition timing learning means updates the knock occurrence limit ignition timing,
The variable valve means eliminates the overlap of the valve opening period of the intake valve and the exhaust valve,
The load adjusting means adjusts the load of the internal combustion engine to a predetermined value or less set in advance.
The control device for an internal combustion engine according to any one of claims 1 to 5.

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