JP5113126B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus that suitably controls ignition timing in an internal combustion engine having a variable valve.

  In an internal combustion engine for automobiles in recent years, an internal combustion engine having a variable valve mechanism in which a valve timing or a valve lift amount is variable in intake valves and exhaust valves tends to be generalized. The variable valve mechanism has been improved in technology from the viewpoint of increasing the degree of freedom of control, expanding the operation range, and improving responsiveness.

  In particular, a variable valve mechanism that can continuously variably control the valve lift amount has been developed, and the amount of air drawn into the cylinder by the lift continuously variable valve mechanism is controlled by an intake valve instead of the throttle valve. Therefore, an internal combustion engine that realizes a reduction in pump loss and a mirror cycle has been developed. In a control device for an internal combustion engine equipped with such a variable valve mechanism, the amount of intake air flowing through the intake pipe is detected or estimated by an air flow sensor or a pressure sensor provided in the intake pipe. Efficiency is calculated, and the control amount of the ignition timing is calculated based on the charging efficiency.

  According to the cited document 1, when the actual valve timing is deviated from the basic valve timing, a technique for suitably correcting the ignition timing in accordance with the deviation is disclosed. In the technique disclosed in the cited document 1, when the valve timing shifts to the retard side, in the low load range, the combustion rate increases with a decrease in the internal EGR amount (EGR: Exhaust Gas Recirculation). To cope with this, the ignition timing is corrected to the retard side, and in the high load range, the ignition timing is corrected to the advance side to cope with a decrease in the combustion speed accompanying a decrease in the actual compression ratio.

  On the other hand, when the valve timing shifts to the advance side, the ignition timing is corrected to the advance side to cope with the decrease in the combustion speed accompanying the increase in the internal EGR amount in the low load region, and in the high load region. Corrects the ignition timing to the retard side in order to cope with an increase in the combustion speed accompanying an increase in the actual compression ratio.

  According to the cited document 2, a technique for suitably suppressing the divergence of the knock learning amount due to the response delay of the variable valve mechanism is disclosed. When the actual valve timing deviates from the basic valve timing, the frequency of knock occurrence changes. If the learning of the knock control amount is performed according to the presence or absence of the occurrence of knock when the variable valve is deviated, the learning value of the knock control amount includes the influence due to the deviation of the variable valve, causing erroneous learning and knock control. It will diverge. In the technique disclosed in the cited document 2, the basic ignition timing set based on the operating state is canceled with the knock control amount updated according to the presence or absence of the occurrence of knock, and the steady tendency of the knock control amount. In the knock control device for an internal combustion engine that corrects by the knock learning amount updated as described above, the update of the knock learning amount is prohibited when the response delay of the variable valve is greater than or equal to a preset value.

Japanese Patent Laid-Open No. 9-209895 JP 2006-125285 A

  However, in a state where the atmospheric pressure decreases, such as in a high altitude condition, the internal EGR amount that changes based on the valve timing is also affected by the state of the atmospheric pressure. The correction cannot be performed accurately. In addition, since the change in the actual compression ratio when the valve timing deviates to the advance side or the retard side also varies depending on the valve operation angle, in a variable valve with variable valve operation angle, only the valve timing deviation Therefore, the change in the actual compression ratio cannot be taken into consideration. Further, in the configuration for calculating the ignition timing control amount based on the rotational speed, the load, and the valve timing, when considering the above-described effect of the high altitude correction that reduces the atmospheric pressure, at least the rotational speed, the load, the valve timing, and the large Since a multidimensional map with the atmospheric pressure as an axis is required, there is a problem that the map mounted on the ECU becomes large and the memory capacity increases.

  In the configuration in which the basic ignition timing set based on the driving operation point is corrected with a knock control amount that is updated or learned according to the presence or absence of the occurrence of knocking, the driving operation point is changed when the octane number of the fuel is changed. Since it is necessary to update or learn the knock control amount every time it changes, the responsiveness of the knock control deteriorates. If the configuration is such that the update of the knock learning amount is prohibited when the actual valve timing deviates from the basic valve timing, the frequency of the knock learning process decreases and the knock control accuracy deteriorates in an internal combustion engine that frequently uses variable valves. There was a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine having a variable valve whose valve operating angle is variable in consideration of the effect of changes in atmospheric pressure. In a control apparatus, an internal combustion engine control apparatus capable of accurately controlling the ignition timing of fuel without increasing the memory capacity is provided. Further, in an internal combustion engine including a variable valve and a knock detection sensor (knock detection means). Another object of the present invention is to provide a control device for an internal combustion engine that can accurately control the ignition timing of the fuel by accurately estimating the octane number of the fuel in consideration of the knocking behavior that changes according to the operating state of the variable valve.

  In order to solve the above problems, a control apparatus for an internal combustion engine according to the present invention includes a rotation speed detection means for detecting a rotation speed, an intake absolute pressure detection means for detecting an absolute pressure in an intake pipe, an absolute air pressure or an absolute exhaust gas. An internal combustion engine comprising: an absolute pressure measuring unit that measures pressure; a variable valve mechanism that varies a valve operation amount of at least one of an intake valve and an exhaust valve; and a valve operation amount detection unit that detects the valve operation amount And the charging efficiency of the inflow air into the cylinder based on at least the rotational speed, the intake absolute pressure, the atmospheric absolute pressure or the exhaust absolute pressure, and the valve operation amount. An internal EGR amount of the cylinder is calculated based on the charging efficiency calculating means for calculating, at least the rotational speed, the intake absolute pressure, the atmospheric absolute pressure or the exhaust absolute pressure, and the valve operation amount. Internal EGR amount calculation means for calculating, at least the rotational speed, the charging efficiency, the internal EGR amount, the effective compression ratio calculated from the variable valve operating amount, and the anti-fuel of the fuel supplied into the cylinder And an ignition timing calculating means for calculating the ignition timing based on the knock property index.

  According to the present invention, the charging efficiency and the internal EGR amount are calculated based on at least the rotation speed, the absolute intake pressure, the atmospheric absolute pressure or the exhaust absolute pressure, and the variable valve operation amount, and at least the rotation speed, Since the ignition timing is calculated based on the charging efficiency, the internal EGR amount, the effective compression ratio calculated from the variable valve operating amount, and the anti-knock property index of the fuel supplied into each cylinder, Accurate ignition timing even when a variable valve equipped with a variable valve mechanism (intake valve and / or exhaust valve) transitions, high altitude conditions where the atmospheric absolute pressure decreases, or when the fuel anti-knock index changes You can calculate well.

  More preferably, the control device for an internal combustion engine according to the present invention further includes knock detection means for detecting occurrence of knock in the internal combustion engine, and the control device is configured to perform the ignition based on a detection result of the knock detection means. A timing correction amount is calculated, and the ignition timing correction means for correcting the ignition timing with the ignition timing correction amount, the rotation speed, the charging efficiency, the ignition timing correction amount, and the ignition timing. Basically, an anti-knock property index correcting means for correcting the anti-knock property index is provided.

  According to the present invention, the ignition timing correction amount for correcting the knock is calculated based on the detection result of the knock detection means, and the ignition timing is corrected by the ignition timing correction amount. Further, the antiknock property index is corrected based on the rotation speed, the charging efficiency, the ignition timing correction amount, and the ignition timing. The corrected estimated anti-knock index is appropriately reflected in the ignition timing calculation results at different driving operation points, so it is necessary to perform a knock correction on the ignition timing calculation results again when the driving operation point changes. Absent.

  In addition, the knock control accuracy can be improved and the responsiveness of the knock control can be improved as compared with the method in which the ignition timing correction operation by the knock detection is sequentially performed on the ignition timing calculation result. Since the influence of the operating state of the variable valve on the knock is accurately corrected, the cause of the knock can be almost integrated into the difference between the estimated anti-knock property index and the true anti-knock property index. As described above, by providing the ignition timing correcting means based on the operating state of the variable valve, it is possible to accurately estimate the anti-knock property index even in an internal combustion engine that frequently uses the variable valve.

  In the control apparatus for an internal combustion engine according to the present invention, the charging efficiency calculation means calculates an intake air relative pressure that calculates an intake air relative pressure that is a ratio of the intake air absolute pressure and the atmospheric absolute pressure or the exhaust absolute pressure. Means, a charging efficiency reference value calculating means for calculating a charging efficiency reference value based on at least the rotational speed, the intake relative pressure, and the variable valve operating amount, and an atmospheric absolute reference pressure under a preset reference atmospheric pressure condition And a charging efficiency correction amount calculating means for calculating the correction amount of the charging efficiency based on the ratio of the atmospheric absolute pressure or the exhaust absolute pressure, and the charging efficiency reference value and the charging efficiency correction amount The filling efficiency is calculated by the product.

  According to the present invention, the intake relative pressure, which is the ratio of the intake absolute pressure and the atmospheric absolute pressure or the exhaust absolute pressure, is calculated, and the charging efficiency reference is based on at least the rotational speed, the intake relative pressure, and the variable valve operation amount. A value is calculated, and a charging efficiency correction amount at a high altitude condition is calculated based on a ratio between the atmospheric absolute pressure and the atmospheric absolute reference pressure, and the product of the charging efficiency reference value and the charging efficiency correction amount is calculated at a high altitude condition. Can be calculated. As a result, the charging efficiency can be calculated with high precision even when the variable valve is in transition or in high altitude conditions where the atmospheric absolute pressure decreases.

  More preferably, in the control device for an internal combustion engine according to the present invention, the internal EGR amount calculation means calculates an intake air relative pressure which is a ratio of the intake air absolute pressure and the atmospheric absolute pressure or the exhaust absolute pressure. Intake relative pressure calculation means for calculating, means for calculating an internal EGR amount reference value based on at least the rotational speed, the intake relative pressure, and the variable valve operation amount, and absolute atmospheric pressure under a preset reference atmospheric pressure condition An internal EGR amount correction amount calculating means for calculating a correction amount of the internal EGR amount based on a ratio between a reference pressure and the atmospheric absolute pressure or the exhaust absolute pressure, and the internal EGR amount reference value, The internal EGR amount is calculated by a product with the internal EGR correction amount.

  According to the present invention, the intake relative pressure, which is the ratio between the intake absolute pressure and the atmospheric absolute pressure or the exhaust absolute pressure, is calculated, and the internal EGR amount reference is based on at least the rotational speed, the intake relative pressure, and the variable valve operation amount. A value is calculated, an EGR amount correction amount under high altitude conditions is calculated based on a ratio between the atmospheric absolute pressure and the atmospheric absolute reference pressure, and a high altitude is calculated by multiplying the internal EGR amount reference value and the EGR amount correction amount. The amount of internal EGR can be calculated under conditions. Therefore, the internal EGR amount can be calculated with high accuracy even when the variable valve is in transition or at high altitude where the atmospheric absolute pressure decreases.

  More preferably, in the control device for an internal combustion engine according to the present invention, the charging efficiency reference value calculation means includes at least the rotational speed, the intake relative pressure, the lift amount of the intake valve, and the intake valve. The charging efficiency reference value under the reference atmospheric pressure condition is calculated by a polynomial having the opening timing of the exhaust gas and the closing timing of the exhaust valve as input parameters.

  According to the present invention, at least the rotation speed, the intake relative pressure, the valve operation amount (that is, the intake valve lift angle, which is the intake valve operating angle, the intake valve opening timing, and the exhaust valve closing timing). And the charging efficiency reference value under the reference atmospheric pressure condition is calculated using a polynomial having the input parameters as input parameters. Therefore, the filling efficiency reference value can be accurately calculated in consideration of the complex causal relationship that each input parameter gives to the filling efficiency reference value. Further, the memory capacity can be greatly reduced by replacing a large-scale map with a polynomial.

  More preferably, in the control device for an internal combustion engine according to the present invention, the internal EGR amount reference value calculation means includes at least the rotational speed, the intake relative pressure, the lift amount of the intake valve, and the intake air. The internal EGR amount reference value under the reference atmospheric pressure condition is calculated by a polynomial having the valve opening timing and the exhaust valve closing timing as input parameters.

  According to the present invention, at least the rotational speed, the intake relative pressure, the valve operation amount (the intake valve lift amount, which is the intake valve operating angle, the intake valve opening timing, and the exhaust valve closing timing), The internal EGR amount reference value under the reference atmospheric pressure condition is calculated using a polynomial having the input parameter as a parameter. Therefore, the internal EGR amount reference value can be accurately calculated in consideration of the complex causal relationship that each input parameter gives to the internal EGR amount reference value. Further, the memory capacity can be greatly reduced by replacing a large-scale map with a polynomial. As described above, the intake valve lift amount, which is the intake valve operating angle, the intake valve opening timing, and the exhaust valve closing timing are used as the valve operation amount as preconditions. This is because when the timing is variable and the lift timing of the exhaust valve is variable, the dependency on the charging efficiency and the internal EGR amount is high.

  More preferably, the control device for an internal combustion engine according to the present invention includes an internal EGR rate means for calculating an internal EGR rate based on at least the charging efficiency and the internal EGR amount, and the ignition timing calculating means includes: The ignition timing is calculated by a polynomial having at least the rotational speed, the charging efficiency, the internal EGR rate, the effective compression ratio, and the antiknock property index as input parameters.

  According to the present invention, an internal EGR rate is calculated based on at least the charging efficiency and the internal EGR amount, and at least the rotational speed, the charging efficiency, the internal EGR rate, the effective compression ratio, and the anti-knock property index. The ignition timing is calculated by a polynomial having as an input parameter. Therefore, the ignition timing can be accurately calculated in consideration of the complex causal relationship that each input parameter gives to the ignition timing. Further, the memory capacity can be greatly reduced by replacing a large-scale map with a polynomial.

  More preferably, the control device for an internal combustion engine according to the present invention includes a steady operating point ignition timing unit that calculates a steady operating point ignition timing based on the rotation speed and the charging efficiency. A first ignition timing calculation means for calculating a first ignition timing based on at least the rotational speed, the charging efficiency, the EGR rate, the effective compression ratio, and the antiknock property index; A steady operating point EGR rate calculating means for calculating a steady operating point EGR rate based on the rotational speed and the charging efficiency, and a means for calculating a steady operating point effective compression ratio based on the rotating speed and the charging efficiency. A second ignition based on at least the rotational speed, the charging efficiency, the steady operating point EGR rate, the steady operating point effective compression ratio, and the steady operating point anti-knock index. Second ignition timing calculation means for calculating a period, and the ignition timing calculation means adds a difference between the first ignition timing and the second ignition timing to the steady operating point ignition timing. Thus, the ignition timing is calculated.

  According to the present invention, the ignition timing at a steady operating point is calculated based on the rotational speed and the charging efficiency, and at least the rotational speed, the charging efficiency, the current EGR rate, and the current effective compression ratio are calculated. The first ignition timing is calculated based on the rotational speed and the charging efficiency, the steady operating point EGR rate is calculated, and the steady operating point effective compression ratio is calculated based on the rotational speed and the charging efficiency. And calculating a second ignition timing based on at least the rotational speed, the charging efficiency, the steady operating point EGR rate, and the steady operating point effective compression ratio, and calculating the first ignition timing and the second ignition timing. Since the ignition timing can be calculated by adding the difference from the ignition timing to the steady operating point ignition timing, when the current value of the input parameter of the ignition timing is on the steady operating point, of Fire timing is output without correction. On the other hand, when there is a difference between the current value of the variable valve that occurs during a transition and the steady target operating point, the ignition timing is corrected. With such a configuration, the ignition timing can always be set to the optimum point, so that the fuel consumption and output can be optimized.

  More preferably, in the control device for an internal combustion engine according to the present invention, the anti-knock property index is an octane number of the fuel supplied into the cylinder. According to the present invention, the octane number of the fuel is used as the antiknock property index. As a result, even when the octane number of the fuel changes, the ignition timing can be set robustly at the knock limit point, so that fuel efficiency and output can be optimized.

  As another aspect, the antiknock property index is more preferably a cetane number of fuel supplied into the cylinder. According to the present invention, the cetane number of the fuel is used as the antiknock property index. As a result, even when the cetane number of the fuel changes, the ignition timing can be set robustly at the knock limit point, so that the fuel consumption and output can be optimized.

  As another aspect, it is more preferable that the fuel supplied into the cylinder is a mixed fuel in which a plurality of types of fuel are mixed, and the anti-knock property index is a mixing ratio of the mixed fuel. . According to the present invention, a fuel mixing ratio is used as the anti-knock property index. This makes it possible to set the ignition timing robustly at the knock limit point even when the mixture ratio is changed when using a mixed fuel in which multiple fuels with known anti-knock index are used. , Fuel economy and output can be optimized.

  In addition, an error factor resulting from at least one of deterioration with time, individual variation, and environmental change of the internal combustion engine may be used as the anti-knock property index. Thus, even when the influence of the error factor is changed, the ignition timing can be set robustly at the knock limit point, so that the fuel consumption and output can be optimized.

  Further, in the control device for an internal combustion engine according to the present invention, the anti-knock property index correcting means is a polynomial equation having the rotational speed, the charging efficiency, and the anti-knock property index as explanatory variables, and the ignition timing as an objective variable. More preferably, the antiknock property index is corrected by a first derivative related to the antiknock property index.

  According to the present invention, the antiknock property is obtained by a first derivative of the polynomial with the rotational speed, the charging efficiency, and the antiknock property index as explanatory variables, and the ignition timing as an objective variable, with respect to the antiknock property index. Since the index is corrected, it is possible to increase the accuracy and speed of antiknock index estimation.

  Further, the control device for an internal combustion engine according to the present invention includes a torque calculation means for calculating a torque based on the rotational speed, the charging efficiency, and the anti-knock property index, and an anti-knock by the torque ratio calculation means. Estimate the ratio of the reference torque calculated using the anti-knock property index of the reference fuel as the performance index and the estimated torque calculated using the estimated anti-knock performance index as the anti-knock property index Torque ratio calculating means for calculating as a torque ratio, and control for calculating a control amount for calculating a control amount of a throttle valve or a variable valve based on the estimated torque ratio, the rotation speed, and a target torque More preferably, a quantity calculation means is provided.

  According to the present invention, at least the rotational speed, the charging efficiency, and the reference torque calculated based on the anti-knock performance index in the fuel as the reference condition, at least the rotational speed, the charging efficiency, and the current estimated anti-knock performance Calculate the torque ratio with the estimated torque calculated based on the index, and control the throttle valve or variable valve based on the torque ratio between the reference torque and the estimated torque, the rotational speed, and the target torque. Is calculated. By adopting such a configuration, it is possible to appropriately calculate the throttle valve target control amount and the variable valve target control amount that realize the target indicated torque in consideration of changes in the indicated torque when the antiknock index changes. Can do.

  Further, in the control device for an internal combustion engine according to the present invention, the torque calculation means calculates the torque by a polynomial having at least the rotational speed, the charging efficiency, and the antiknock property index as input parameters. It is more preferable.

  According to the present invention, torque is calculated by a polynomial having at least the rotational speed, the charging efficiency, and the antiknock index as input parameters. The torque can be accurately calculated in consideration of the complex causal relationship that each input parameter gives to the torque. Further, the memory capacity can be greatly reduced by replacing a large-scale map with a polynomial.

  According to the present invention, in consideration of the effect of changes in atmospheric pressure, in a control device for an internal combustion engine having a variable valve whose valve operating angle is variable, the fuel ignition timing can be accurately adjusted without increasing the memory capacity. Can be controlled. In addition, in an internal combustion engine equipped with a variable valve and knock detection means, it is possible to more accurately estimate the fuel ignition timing by accurately estimating the octane number of the fuel in consideration of the knock behavior that changes according to the operating state of the variable valve. It can be controlled well.

The figure explaining the whole structure of embodiment of this invention. The figure explaining the change of the overlap period of an intake valve and an exhaust valve, and the change of an intake valve closing time (IVC: Intake Valve Close) at the time of changing the phase of an intake valve continuously. The figure explaining the change of the overlap period of an intake valve and an exhaust valve when the phase of an exhaust valve is changed continuously. The figure explaining the valve lift pattern of the variable valve mechanism which can change the operating angle of a valve, a lift, and a phase simultaneously. The figure explaining the relationship between the overlap period in low-altitude conditions and high-altitude conditions, and the amount of internal EGR obtained in a state where the rotation speed and the intake pressure are kept constant. The figure explaining the relationship between IVC and an effective compression ratio of the variable valve mechanism which can change the operating angle of a valve, a lift amount, and a phase simultaneously. The figure explaining the influence which an EGR rate and an effective compression ratio have on ignition timing when a rotation speed and charging efficiency are made constant. The figure explaining the relationship between the octane number and ignition timing when the rotational speed and the charging efficiency are constant, and the relationship between the octane number and the ignition delay period under the same temperature and pressure conditions. The figure explaining the means which controls ignition timing according to the state and octane number of a variable valve in an internal combustion engine carrying a variable valve. The figure explaining the polynomial which comprises the filling efficiency calculating means and the internal EGR amount calculating means in FIG. The figure explaining the control block which comprises the ignition timing calculating means in FIG. The figure explaining the control block of the steady operating point EGR rate calculating means in FIG. The figure explaining the polynomial which comprises the 1st and 2nd ignition timing calculating means in FIG. The figure explaining the output result of the ignition timing calculating means in the transitional state of the internal combustion engine in this embodiment. The figure explaining the ignition timing correction control means using a knock detection sensor. The figure explaining the knock phenomenon and its detection principle. The figure explaining the relationship between the knock detection sensor detection signal obtained by performing a predetermined frequency band pass filter process, and the ignition retard correction amount. The figure explaining the knock correction | amendment means in FIG. Diagram explaining the relationship between ignition timing and octane number at different rotational speeds and charging efficiency operating points The figure explaining the polynomial which comprises the K value calculating means in FIG. The figure explaining the output result of the ignition timing calculating means in the case of performing octane number estimation and knock correction in the transient state of the internal combustion engine immediately after the octane number of the supplied fuel changes. The figure explaining the means which calculates the controlled variable of the throttle valve and variable valve which implement | achieve a target indicated torque by the indicated torque calculated based on the reference | standard octane number and the present octane number. The figure explaining the polynomial which comprises the torque calculation means shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram for explaining the overall configuration of an embodiment of the present invention. The system of this embodiment includes an internal combustion engine 1. The internal combustion engine 1 communicates with an intake passage and an exhaust passage. An air flow sensor and an intake air temperature sensor 2 are assembled in the intake passage.

  A throttle valve 3 is provided downstream of the air flow sensor 2. The throttle valve 3 is an electronically controlled throttle valve that can control the throttle opening independently of the accelerator pedal stroke. An intake manifold 4 communicates with the throttle valve 3 downstream. The intake manifold 4 is assembled with an intake pipe pressure sensor 5 that detects the absolute pressure in the intake pipe. A tumble control valve 6 for controlling the flow of the air-fuel mixture in the combustion chamber is provided in the intake pipe.

  Further, a fuel injection valve 7 for injecting fuel into the intake port is disposed downstream of the intake manifold 4. The internal combustion engine 1 is provided with an intake valve (intake valve) 8. The intake valve 8 continuously receives an intake valve timing (valve opening / closing timing) and a lift amount (valve operating angle) as valve operation amounts. An intake variable valve mechanism 8A that is variable is provided. Further, the variable valve mechanism detects the valve timing (opening timing and closing timing of the intake valve) as a phase and detects the maximum lift amount of the intake valve 8 during the opening / closing period of the valve as an operating angle. A valve operation amount detection sensor (valve operation amount detection means) 9 is assembled.

  Further, the internal combustion engine 1 is provided with an exhaust valve 10. The exhaust valve (exhaust valve) 10 is provided with an exhaust variable valve mechanism 10A that can vary the exhaust valve timing (exhaust valve opening timing and closing timing), and detects the opening / closing timing of the exhaust valve 10 as a valve operation amount. An exhaust valve operation amount detection sensor (valve operation amount detection means) 11 is assembled. By using these sensors 9 and 11, it is possible to detect a valve operation amount of a variable valve described later. In this embodiment, the valve operation amount includes at least the lift amount of the intake valve, the opening timing (valve opening timing), and the closing timing of the exhaust valve (valve closing timing), but is attached to the intake valve and the exhaust valve. Depending on the characteristics of the variable valve mechanism, the parameter to be detected differs, and it means at least the controlled amount (parameter) of the variable valve that contributes to the charging efficiency and the internal EGR amount.

A spark plug 12 having an electrode portion exposed in the cylinder is assembled to the cylinder head portion. Further, a knock detection sensor 13 for detecting the occurrence of knock is assembled to the cylinder. A crank angle sensor 14 is assembled to the crankshaft. The rotational speed of the internal combustion engine 1 can be detected based on the output signal from the crank angle sensor 14. An O ₂ sensor 15 is assembled in the exhaust passage.

  The system of this embodiment is provided with an external EGR pipe 16 for returning a part of exhaust gas to the intake pipe and an external EGR valve 17 for controlling the external EGR flow rate. During partial load operation, pump loss and nitrogen oxide emission can be reduced by opening the external EGR valve 17 and performing EGR.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 18 as shown in FIG. The ECU 18 is connected with the various sensors described above. The ECU 18 calculates control signals to actuators such as the throttle valve 3, the fuel injection valve 7, the intake valve 8 with a variable valve mechanism, and the exhaust valve 10 with a variable valve mechanism based on detection signals from the various sensors. The actuator is controlled by a control signal from. Further, the operating state of the internal combustion engine 1 is detected based on the signals input from the various sensors described above, and the ignition timing is controlled at the timing (ignition timing) calculated by the ECU 18 according to the operating state. In response, the spark plug 12 ignites.

  FIG. 2 is a diagram for explaining a change in the overlap period of the intake valve and the exhaust valve and a change in the intake valve closing timing (IVC: Intake Valve Close) when the phase of the intake valve is continuously changed. is there.

  As the phase of the intake valve is changed to the advance side by the variable valve mechanism, the overlap period with the exhaust valve increases. In an internal combustion engine having a variable valve (an intake valve or an exhaust valve with a variable valve mechanism), the variable valve is controlled so that the overlap period occurs under a partial load condition, and exhaust gas in the exhaust pipe is temporarily taken into the intake pipe. Internal EGR is generated by blowing back. As the internal EGR amount increases, pump loss under partial load conditions can be reduced, and the combustion gas temperature can be reduced, so that nitrogen oxides in the exhaust gas can be reduced. In the internal EGR control by varying the intake valve phase, the IVC also changes uniquely with the overlap period.

  FIG. 3 is a diagram for explaining a change in the overlap period between the intake valve and the exhaust valve when the phase of the exhaust valve is continuously changed. As the phase of the exhaust valve is changed to the retard side, the overlap period with the intake valve increases. As described above, even in an internal combustion engine provided with a variable valve of an exhaust phase variable type, internal EGR can be increased, and pump loss and nitrogen oxides under partial load conditions can be reduced. In the internal EGR control by varying the exhaust valve phase, IVC is fixed and only the overlap period is changed. In combination with the intake phase variable valve, the IVC and the overlap period can be controlled independently.

  FIG. 4 is a diagram for explaining a valve lift pattern of a variable valve mechanism capable of simultaneously changing the valve operating angle, lift, and phase. In an internal combustion engine that controls the charging efficiency of air flowing into the cylinder mainly using a conventional throttle valve, the negative pressure is generated by restricting the upstream pressure of the intake valve with the throttle valve, so the fuel consumption deteriorates due to pump loss. Is a problem.

  If the intake air amount can be controlled by the opening / closing timing of the intake valve without reducing the upstream pressure of the intake valve, the deterioration of fuel consumption due to the pump loss can be suppressed. In the variable valve shown in FIG. 4, an intake valve opening timing (IVO) is obtained by combining a lift variable mechanism that continuously varies the valve lift amount of the intake valve and a phase variable mechanism that continuously varies the phase. ) Is fixed, and the intake valve closing timing (IVC) is changed.

  By providing such a variable valve mechanism, it is possible to realize an internal combustion engine that mainly controls the charging efficiency of the air flowing into the cylinder by using the variable valve. In this variable lift mechanism, the maximum lift amount of the valve within the valve operating angle increases as the valve operating angle increases, and has the relationship shown in the lower part of FIG. When the required torque is small, the lift amount can be reduced, and at the same time, the valve closing timing (IVC) can be advanced (advanced) to reduce the intake amount. At this time, since the valve closing timing (IVC) is advanced, the piston compression amount can be made relatively small as compared with the piston expansion amount. It is characterized by an improvement effect.

  FIG. 5 is a diagram for explaining the relationship between the overlap period and the internal EGR amount under the low altitude condition and the high altitude condition obtained in a state where the rotation speed and the intake pressure are kept constant. The internal EGR amount here is a value obtained by dividing the mass of burned gas remaining in the cylinder by the mass of air in a standard state corresponding to the stroke volume.

  As shown in FIG. 5, the internal EGR amount can be divided into a part caused by blowback determined according to the overlap period and a part determined according to the clearance volume part of the exhaust valve closing timing (EVC). Further, the internal EGR amount is affected by the relationship between the exhaust pressure and the intake pressure. Specifically, when the exhaust pressure drops under high altitude conditions under conditions where there is overlap, the amount of internal EGR is greatly reduced due to the reduction in the amount of burnt gas blown back from the exhaust pipe into the cylinder. To do. On the other hand, under the condition where there is no overlap, even if the exhaust pressure is reduced, the amount of decrease in the internal EGR amount is limited to the portion caused by the clearance volume, so the amount of decrease is relatively small.

  Therefore, in an internal combustion engine equipped with a variable valve, in order to accurately estimate the amount of internal EGR including high altitude conditions, it is necessary to consider not only the overlap period but also the effects of intake pressure and atmospheric pressure (or exhaust pressure). There is. Further, since the internal EGR amount has a great influence on the combustion process that is important in determining the optimal ignition timing, it is necessary to perform ignition timing control in consideration of the internal EGR amount in an internal combustion engine equipped with a variable valve.

  FIG. 6 is a diagram for explaining the relationship between the IVC and the effective compression ratio of the variable valve mechanism that can change the valve operating angle, the lift amount, and the phase at the same time. If the IVC is advanced (advanced) or delayed (retarded) significantly from the bottom dead center (BDC), the substantial amount of piston compression decreases. If the effective compression ratio is defined by the ratio of the cylinder volume at the top dead center (TDC) and the cylinder volume at the IVC, the geometry obtained from the ratio of the cylinder volume at the TDC and the cylinder volume at the BDC. The effective compression ratio decreases in both the case where the BDC is accelerated and the case where the delay is delayed as compared with the scientific compression ratio.

  After the IVC, the gas sucked into the cylinder generally undergoes an adiabatic process due to the piston compression action, so that the IVC timing significantly affects the ultimate pressure and ultimate temperature during TDC. Since the pressure and temperature at the time of TDC have a great influence on the combustion process that is important in determining the optimal ignition timing, it is necessary to perform ignition timing control in consideration of IVC in an internal combustion engine equipped with a variable valve.

  FIG. 7 is a diagram for explaining the influence of the EGR rate and the effective compression ratio on the ignition timing when the rotational speed and the charging efficiency are constant. Since the combustion speed decreases as the EGR rate increases, the optimal ignition timing (MBT: Minimum spark for Best Torque) for maximizing the torque changes to the advance side. Therefore, in the control device for the internal combustion engine, it is necessary to perform advance correction control of the ignition timing in accordance with the EGR rate. Further, as the effective compression ratio increases, the ultimate pressure and temperature at the time of TDC increase, and the frequency of knock generation increases. In a control apparatus for an internal combustion engine, it is necessary to perform ignition retardation correction control for avoiding knocking in accordance with an increase in effective compression ratio under relatively high load conditions.

  FIG. 8 is a diagram for explaining the relationship between the octane number and the ignition delay period under the same temperature and pressure conditions, and the relationship between the octane number and the ignition timing when the rotation speed and the charging efficiency are constant. The self-ignition delay period is a delay period from when a homogeneous mixture of fuel and air starts to react at a predetermined pressure and temperature, until the pressure and temperature rise instantaneously with a sudden exothermic reaction. Point to.

  In an internal combustion engine using a spark ignition operation, combustion progresses as the air-fuel mixture ignited from the spark plug propagates through the entire combustion chamber. At this time, the pressure and temperature of the unburned gas are increased by the compression of the piston and the compressed gas from the burned gas and the heat transfer from the wall surface high temperature portion, so that the self-ignition reaction proceeds simultaneously. Knocking can be avoided by setting the ignition timing to the retard side from the MBT so that combustion by flame propagation is completed during the self-ignition delay period. As the flame speed increases and the load condition becomes lower, the flame propagation period increases and the self-ignition delay period decreases. Therefore, knocking is likely to occur, and it is necessary to set the ignition timing to a more retarded side. With high-octane fuel, knocking is unlikely to occur because the self-ignition delay period increases. Therefore, as the octane number increases, the ignition timing can be set to the advance side, and can be brought close to the MBT point, so that the full-open torque can be improved at a low rotational speed and the fuel consumption rate can be reduced. Since the octane number of the fuel differs depending on the supplied fuel, it is necessary to perform correction control of the ignition timing according to the octane number.

  FIG. 9 is a diagram for explaining means for controlling the ignition timing in accordance with the state of the variable valve and the octane number in an internal combustion engine equipped with variable valves (intake valve and exhaust valve). The intake relative pressure, which is the ratio of the intake absolute pressure and the atmospheric absolute pressure (exhaust absolute pressure), is calculated and used to calculate the charging efficiency. The intake absolute pressure can be detected by the intake pipe pressure sensor 5, and the atmospheric absolute pressure can be detected by an exhaust pipe pressure sensor (not shown in FIG. 1) of the internal combustion engine. In the charging efficiency calculation means of block 91, the rotational speed, the intake relative pressure (intake absolute pressure / atmospheric absolute pressure), the variable valve operation amount (intake valve operating angle (equivalent to the lift amount of the intake valve lift amount)) and the intake valve Using the opening timing IVO and the exhaust valve closing timing EVC) as input parameters, the charging efficiency corresponding to the standard atmospheric pressure (filling efficiency reference value) is calculated.

  The altitude correction is performed by multiplying the filling efficiency (filling efficiency reference value) equivalent to the standard atmospheric pressure by the filling efficiency correction amount that is the ratio of the atmospheric absolute pressure to the standard atmospheric pressure (atmospheric absolute pressure / standard absolute pressure). (Calculate filling efficiency). With such a configuration, even when the variable valve mechanism is operated under high altitude conditions where the atmospheric pressure decreases, the charging efficiency can be calculated with high accuracy.

  In the internal EGR amount calculation means of the block 92, the rotation speed, the intake relative pressure, the variable valve operation amount (the intake valve operating angle (equivalent to the lift amount of the intake valve), the intake valve opening timing IVO and the exhaust valve closing timing) EVC) is used as an input parameter to calculate the internal EGR amount equivalent to the standard atmospheric pressure (internal EGR amount reference value). By multiplying the internal EGR amount equivalent to the standard atmospheric pressure (internal EGR amount reference value) by the EGR amount correction amount, which is the ratio of atmospheric absolute pressure to standard atmospheric pressure (atmospheric absolute pressure / standard absolute pressure), the high altitude correction is performed. Perform (calculate internal EGR amount).

  With such a configuration, the internal EGR amount can be calculated with high accuracy even when the variable valve is operated under high altitude conditions where the atmospheric pressure decreases. In the present embodiment, the standard atmospheric pressure is used. However, if the filling efficiency can be corrected under high altitude conditions, the absolute atmospheric pressure under the preset standard atmospheric pressure conditions can be used instead of the standard atmospheric pressure. A reference pressure may be used.

  The internal EGR rate calculation means of block 93 calculates the internal EGR rate (the ratio of internal EGR gas in the gas flowing into the cylinder) based on the charging efficiency and internal EGR amount calculated in blocks 91 and 92. . In this configuration, even when the variable valve is operated under a high altitude condition where the atmospheric pressure decreases, it is possible to consider changes in charging efficiency and internal EGR rate, which are important parameters for the ignition timing calculation, in the ignition timing calculation. .

  In the effective compression ratio calculation means of block 94, the effective compression ratio is based on the variable valve operation amount (the intake valve operating angle (equivalent to the lift amount of the intake valve lift), the intake valve opening timing IVO and the exhaust valve closing timing EVC). Is calculated.

  The ignition timing calculation means in block 95 uses the rotational speed, charging efficiency, EGR rate, effective compression ratio, and octane number of fuel supplied into the cylinder (which is one of the anti-knock characteristics indexes) as input parameters. Calculate. In the present embodiment, the EGR rate and the effective compression ratio are used as intermediate parameters, so that the influence of the variable valve on the ignition timing is considered. With this configuration, the ignition timing can be calculated accurately without increasing the ignition timing calculation parameter even when the degree of freedom of control of the variable valve is increased or when the environment changes such as high altitude conditions. Is possible.

  FIG. 10 is a view for explaining polynomials constituting the charging efficiency calculating means and the internal EGR amount calculating means in FIG. As explanatory variables, the rotational speed is set to x1, the intake relative pressure is set to x2, the intake operating angle is set to x3, IVO is set to x4, and EVC is set to x5. Set the filling efficiency or internal EGR amount as the target variable. The coefficient A multiplied by each term is a partial regression coefficient, and a value is set for each objective variable. The partial regression coefficient numbers 2 to 5 in the group 101 are affected by the rotational speed on the charging efficiency or the internal EGR amount, and the partial regression coefficient numbers 6 to 9 in the group 102 are based on the intake relative pressure on the charging efficiency or the internal EGR amount. In the group 103, the partial regression coefficient numbers 16 to 19 have an influence of the intake operating angle on the charging efficiency or the internal EGR amount. In the group 104, the partial regression coefficient numbers 36 to 39 have the IVO based on the charging efficiency or the internal EGR amount. Further, the partial regression coefficient numbers 71 to 74 of the group 105 are required to determine the effect of EVC on the charging efficiency or the internal EGR amount, respectively. Further, partial regression coefficient numbers 10 to 15 in the group 102 are affected by the interaction term of the rotational speed and the intake relative pressure, and partial regression coefficients 21 to 35 in the group 103 are the rotational speed, the intake relative pressure, and the intake operation angle. The partial regression coefficients 40 to 70 in the group 104 are affected by the interaction term between the rotational speed, the intake relative pressure, the intake operating angle, and the IVO, and the partial regression coefficient 75 to For 126, the influence of the interaction term of the rotational speed, the intake relative pressure, the intake operating angle, and IVO and EVC is obtained. From the sum of these terms and a plurality of data of filling efficiency (or internal EGR amount) obtained in advance by experiment etc., each value of the partial regression coefficient is calculated, and a polynomial is created (set). By substituting the explanatory variables, the filling efficiency (or internal EGR amount) can be calculated.

  By setting higher-order terms and interaction terms in the polynomial in this way, the charging efficiency and the internal EGR amount can be accurately calculated in consideration of the complex causal relationship that each input parameter gives to the charging efficiency and the internal EGR amount. Can do. Further, the memory capacity can be greatly reduced by replacing a large-scale map with a polynomial. In the system of the present embodiment, a quinary quartic polynomial is used as a means for calculating the filling efficiency and the internal EGR amount, but the present invention is not limited to this. That is, the order and the number of dimensions may be changed according to the relationship between the required accuracy and the allowable value of the calculation load. Other parameters representing the rotational speed, load, and variable valve state quantity may be used as explanatory variables. By appropriately excluding higher-order terms and interaction terms that do not contribute to accuracy improvement from the polynomial by the stepwise method or the like, the relationship between the accuracy of the polynomial and the computation load can be improved. Since the charging efficiency and internal EGR amount are affected by the pulsation effect and inertia effect of the intake pipe and exhaust pipe flow, the order of 5th order or higher may be required for the rotational speed. The accuracy can be improved by trimming the output result of the polynomial using a map or a table.

  FIG. 11 is a diagram for explaining a control block constituting the ignition timing calculation means in FIG. The steady operating point ignition timing calculating means of block 111 calculates the ignition timing at the steady operating point using the rotational speed and the charging efficiency as input parameters. In the system of this embodiment, various parameters such as variable valve positions (positions of intake valves and exhaust valves) are assigned to the rotational speed and the charging efficiency.

  In the steady operating point ignition timing calculation means, the optimum ignition timing acquired on the steady operating point of various parameters determined by the combination of the rotational speed and the charging efficiency is stored in a two-dimensional map with the rotational speed and the charging efficiency as two axes. Has been. The variable valves ((intake valves and exhaust valves) are controlled with the above steady target operating point as the target value. However, during transients where the rotational speed and charging efficiency change suddenly, In some cases, the current value may be far from the current value, and the optimum ignition timing changes because the EGR rate and the effective compression ratio take different values even at the same rotational speed and the charging efficiency operating point. In order to consider the minutes, the following correction is performed in the system of the present embodiment.

  That is, the first ignition timing calculation means of block 112 calculates the first ignition timing based on the current values of the rotational speed, charging efficiency, EGR rate, octane number, and effective compression ratio. Next, the steady operating point EGR rate calculating means of the block 113 calculates an EGR rate corresponding to the steady operating point based on the current value of the rotational speed and the charging efficiency. On the other hand, the steady operating point effective compression ratio calculating means of block 114 calculates an effective compression ratio corresponding to the steady operating point based on the current value of the rotational speed and the charging efficiency. The second ignition timing calculation means of block 115 calculates the second ignition timing based on the rotational speed, the charging efficiency, the EGR rate corresponding to the steady operating point, the effective compression ratio equivalent to the steady operating point, and the steady operating point octane number. To do.

  Here, the steady operation point means an operation point when the operation point characterized by the rotational speed and the load is in a steady state, and the steady operation point ignition timing is defined for each of the steady operation points. It is the set ignition timing, and the steady operating point EGR rate is the EGR rate when the intake pipe pressure and the variable valve state are determined for each steady operating point and these are under the target state. The steady operating point execution compression ratio is the effective compression ratio when the variable valve state is determined for each of the above steady operating points and is under the target state. The octane number is an octane number that is premised on setting the steady operating point ignition timing.

  The ignition timing is calculated by adding the difference between the first ignition timing and the second ignition timing to the ignition timing at the steady operating point. When the current value of the input parameter of the ignition timing is on the steady operating point, the ignition timing at the steady operating point is output without correction. On the other hand, when there is a difference between the current value of the variable valve that occurs during a transition and the steady target operating point, the ignition timing is corrected. With the configuration shown in FIG. 11, the ignition timing can always be set to the optimum point, so that the fuel consumption and output can be optimized.

  FIG. 12 is a diagram for explaining a control block of the steady operating point EGR rate calculating means 113 in FIG. The steady operating point intake absolute pressure calculating means of block 121 calculates the intake absolute pressure corresponding to the steady operating point based on the current value of the rotational speed and the charging efficiency. The steady operating point intake operating angle calculation means of block 122 calculates the intake operating angle corresponding to the steady operating point based on the current value of the rotational speed and the charging efficiency. The steady operating point IVO calculating means of block 123 calculates the IVO corresponding to the steady operating point based on the current value of the rotational speed and the charging efficiency. The steady operating point EVC calculating means of the block 124 calculates an EVC corresponding to the steady operating point based on the current values of the rotational speed and the charging efficiency. In block 125, steady operation is performed based on the rotational speed, the charging efficiency, the intake relative pressure corresponding to the steady operation point, the intake operation angle corresponding to the steady operation point, the IVO corresponding to the steady operation point, and the EVC corresponding to the steady operation point. The amount of internal EGR corresponding to the point is calculated. Based on the charging efficiency and the internal EGR amount corresponding to the steady operating point, an internal EGR rate corresponding to the steady operating point is calculated in block 126.

  FIG. 13 is a diagram for explaining polynomials constituting the first and second ignition timing calculation means in FIG. As explanatory variables, the rotational speed is set to x1, the charging efficiency is set to x2, the EGR rate is set to x31, the effective compression ratio is set to x32, and the octane number is set to x33. Set the ignition timing in the objective variable. The coefficients B, C, and D multiplied by each term are partial regression coefficients, and values are set for each combination of the objective variable and the explanatory variable. Numbers 2 to 5 of the partial regression coefficient B of the group 131 are affected by the rotation speed on the ignition timing, and numbers 6 to 9 of the partial regression coefficient B of the group 132 are affected by the charging efficiency on the ignition timing. The number 16-19 of the partial regression coefficient B has an effect of the EGR rate on the ignition timing, and the number 134-19 of the partial regression coefficient C has the effect of the effective compression ratio on the ignition timing. Regression coefficient D numbers 16 to 19 are required to determine the influence of the octane number on the ignition timing. Further, in the group 132, the partial regression coefficient B numbers 10 to 15 are affected by the interaction term between the rotational speed and the charging efficiency, and in the group 133, the partial regression coefficient B 20 to 35 are the rotational speed, the charging efficiency, and EGR. The effect of the interaction term with the rate is 20 to 35 of the partial regression coefficient C of the group 134, and the effect of the interaction term of the rotational speed, the charging efficiency and the effective compression ratio is the effect of the partial regression coefficient D of the group 135. For 20 to 35, the influence of the interaction term of the rotational speed, filling efficiency, and octane number is required. By calculating each partial regression coefficient value from the sum of these terms and a plurality of ignition timing data obtained beforehand through experiments, etc., a polynomial is created (set), and the explanatory variables are substituted into this polynomial. By doing so, the filling efficiency (or the amount of internal EGR) can be calculated.

  By setting the higher-order terms and the interaction terms in the polynomial in this way, the ignition timing can be accurately calculated in consideration of the complex causal relationship that each input parameter gives to the ignition timing. Further, the memory capacity can be greatly reduced by replacing a large-scale map with a polynomial. In the system of the present embodiment, a ternary quartic polynomial is used as means for calculating the ignition timing, but the present invention is not limited to this. That is, the order and the number of dimensions may be changed according to the relationship between the required accuracy and the allowable value of the calculation load. As explanatory variables, a configuration in which a polynomial in which other parameters that affect the ignition timing such as the intake air temperature, the air-fuel ratio, and the water temperature are set may be additionally used. By appropriately excluding higher-order terms and interaction terms that do not contribute to accuracy improvement from the polynomial by the stepwise method or the like, the relationship between the accuracy of the polynomial and the computation load can be improved.

  FIG. 14 is a diagram for explaining the output result of the ignition timing calculation means in the transient state of the internal combustion engine in the present embodiment. This figure shows changes in the variable valve position, EGR rate, effective compression ratio, and ignition timing when the charging efficiency is changed while the rotational speed is kept constant. The variable valve is controlled using the variable valve position at the steady operating point as a target value based on the rotational speed and the charging efficiency, but changes with a delay from the target value due to the limitation of the operating speed of the variable valve mechanism. Therefore, the EGR rate and the effective compression ratio that change under the influence of the variable valve position also change away from the value corresponding to the steady operating point. The ignition timing control amount is corrected in consideration of the EGR rate and the effective compression ratio that change due to the delay in the operation of the variable valve. That is, the difference between the ignition timing at the steady operating point (corresponding to the output A in FIG. 11) and the ignition timing at the actual operating point (corresponding to the output B in FIG. 11) is the ignition timing corresponding to the operation delay of the variable valve. It is considered as a correction amount.

  FIG. 15 is a diagram for explaining ignition timing correction control means using a knock detection sensor (knock detection means). In the knock correction means of block 151, the knock correction amount (that is, the ignition timing correction amount) and the estimated octane number based on the previous value of the ignition timing output from the ignition timing calculation means, the detected value of the knock detection sensor, the rotational speed, and the charging efficiency. Is calculated. In block 152, the ignition timing is calculated based on the rotational speed, the charging efficiency, the EGR rate, the effective compression ratio, and the estimated octane number. The ignition timing calculation means shown in block 152 may have the same configuration as the ignition timing calculation means described in FIG. The knock corrected ignition timing is calculated by adding a knock correction amount (ignition timing correction amount) to the ignition timing output from the ignition timing calculating means (correcting the ignition timing).

  In the ignition timing calculation means constituting the present embodiment, the influence of the variable valve operating state on the knock is accurately corrected, so that the factor causing the knock is almost concentrated on the difference between the estimated octane number and the true octane number. Can do. In this way, by providing the ignition timing correction means based on the operating state of the variable valve, the octane number can be estimated with high accuracy even in an internal combustion engine that frequently uses the variable valve. In addition, since the octane number estimation requires a certain calculation time, the ignition timing can be set immediately at the knock limit point when a knock is detected by separately providing means for applying the knock correction amount to the ignition timing calculation result. .

  FIG. 16 is a diagram for explaining the knock phenomenon and its detection principle. Under conditions of low rotational speed and high load, after ignition, compression action by flame propagation and piston compression, and unburned gas that has been heated to high temperature and pressure by heat transfer from the high temperature part of the wall cause self-ignition, which causes a sudden pressure rise and pressure vibration. May cause knock. In the ignition timing control of the internal combustion engine, in order to avoid the knock, the ignition timing is retarded from the MBT point to a limit point at which the knock does not occur. In the system of the present embodiment, a knock detection sensor is assembled to the cylinder block, the vibration of the cylinder block caused by the pressure vibration of the combustion gas in the cylinder is detected, and a predetermined frequency band pass filter is detected in the vibration waveform. Based on the signal information obtained by processing, it is possible to detect the presence or absence of knocking and the knock intensity.

  FIG. 17 is a diagram for explaining the relationship between the detection signal of the knock detection sensor obtained by performing the predetermined frequency band pass filter process and the ignition retardation correction amount. It is known that the knock intensity is proportional to the amplitude value of the detection signal of the knock detection sensor due to the unburned gas ratio at the self-ignition timing. As the ignition timing is set to the advance side from the knock limit point, the proportion of unburned gas at the self-ignition timing increases, so that the knock strength tends to increase. If the knock intensity is high, it is considered that the ignition timing is set to the more advanced side, so the knock correction amount is set to a larger value (the ignition timing correction amount so that the ignition timing is set to the more retarded side). To avoid knocks.

  FIG. 18 is a diagram for explaining the knock correction means in FIG. The ignition delay calculation means in block 181 calculates the ignition timing retardation correction amount (ignition timing correction amount) based on the knock detection sensor detection signal, and immediately with respect to the ignition timing output from the ignition timing calculation means described later. Perform knock correction (ignition timing correction). The ignition timing calculation means in block 182 calculates the ignition timing based on the rotational speed, charging efficiency, EGR rate, effective compression ratio, and estimated octane number. The ignition timing calculation means of the block 182 may have the same configuration as the ignition timing calculation means described in FIG.

  In block 183, the ignition timing retardation correction amount is subjected to low-pass filter processing, and then added to the previous ignition timing value calculated in block 182. The K value calculation means of block 184 calculates a proportional coefficient K value based on the rotation speed and the charging efficiency, and corrects the previous value of the estimated octane number using a multiplication value thereof.

  The proportionality coefficient K value is a value determined based on the sensitivity that the octane number gives to the ignition timing. For example, in the table or map, the proportional coefficient K value has different values depending on the rotation speed and charging efficiency. In block 185, limiters are provided for the upper limit value and the lower limit value so that the estimated octane value falls within a predetermined range, and limiter processing is performed on the estimated octane value.

  In the present embodiment, a configuration is adopted in which knock correction is immediately performed (ignition timing is corrected) based on the knock detection sensor detection signal, and at the same time, the estimated octane number is corrected (anti-knock property index is corrected). The corrected estimated octane number is also appropriately reflected in the ignition timing calculation results at different operating points, so that when the operating point changes, there is no need to perform a knock correction on the ignition timing calculation results again. Compared with a method in which knock correction operation by knock detection is sequentially performed on the ignition timing calculation result, knock control accuracy is improved and responsiveness of knock control is improved.

  FIG. 19 is a diagram for explaining the relationship between the ignition timing and the octane number at operating points of different rotational speeds and charging efficiency. The relationship between the octane number and the ignition timing in the low rotation high load condition A, the low rotation low load condition B, the high rotation high load condition C, and the high rotation low load condition D all tend to be different. The amount of change in the ignition timing is large.

  On the other hand, under the high rotation and low load condition D, no knock occurs at any octane number, so the ignition timing does not change with respect to the octane number. In the system of this embodiment, the following calculation is performed to estimate the true octane number using the relationship between the octane number and the ignition timing and the detection result of the knock detection sensor (knock detection means). That is, when the ignition timing is calculated based on the current estimated octane number and knock is detected by the knock detection sensor, the knock correction amount (ignition timing correction amount) based on the detected knock intensity (detection result) The ignition timing is corrected by adding the ignition timing calculation value (ignition timing) to the knock correction amount (ignition timing correction amount), and the corrected ignition timing is considered to be the true ignition timing.

  Assuming that the octane number that realizes the true ignition timing is the true octane number, the current estimated octane number is corrected. At this time, the octane number can be appropriately corrected by using the inverse value (proportional coefficient K value) of the first derivative related to the octane number of the ignition timing. Since the K value varies greatly depending on the rotational speed and the charging efficiency, the accuracy and speed of the octane number estimation can be increased by changing the rotational speed and the charging efficiency. In the case of the driving operation point D, the proportionality coefficient K value becomes excessive, and there is a possibility that the estimated octane number is erroneously corrected. Therefore, at the driving operation point where the K value is a predetermined value or more, K = 0 The octane number may not be substantially corrected.

  FIG. 20 is a diagram for explaining a polynomial constituting the K value calculation means in FIG. As explanatory variables, a rotational speed is set in x1, a filling efficiency is set in x2, and an octane number is set in x33. Set the first derivative of the octane number of the ignition timing as the objective variable. The coefficient D multiplied by each term is a partial regression coefficient, and can be used in common with the partial regression coefficient shown in FIG. That is, numbers 16 to 19 of the regression coefficient D are affected by the octane number on the first derivative related to the octane number of the ignition timing, and 20 to 35 of the partial regression coefficient D are the first derivative of the interaction term of the rotational speed, the charging efficiency, and the octane number. The effect on the function is calculated. By setting higher-order terms and interaction terms in the polynomial in this way, it is possible to take into account the complex causal relationship that each input parameter gives to the first derivative related to the octane number of the ignition timing, thereby improving the accuracy of the octane number estimation. And speed up.

  In the system of the present embodiment, a ternary cubic polynomial is used as means for calculating the first derivative related to the octane number of the ignition timing, but the present invention is not limited to this. That is, the order and the number of dimensions may be changed according to the relationship between the required accuracy and the allowable value of the calculation load. As an explanatory variable, a configuration in which a polynomial in which other parameters that affect the first derivative related to the octane number of the ignition timing such as the intake air temperature, the air-fuel ratio, and the water temperature are set may be additionally used. By appropriately excluding higher-order terms and interaction terms that do not contribute to accuracy improvement from the polynomial by the stepwise method or the like, the relationship between the accuracy of the polynomial and the computation load can be improved.

  In the case of the driving operation point D in FIG. 19 where the octane number does not affect the ignition timing, the proportionality coefficient K value becomes excessive, and there is a possibility that the estimated octane number is erroneously corrected. At an operation point of operation equal to or greater than a predetermined value, K = 0 may be set so that the octane number is not substantially corrected. Moreover, it is good also as a structure which uses the two-dimensional map which used the rotational speed and the filling efficiency for two axes for the K value calculation means.

  FIG. 21 is a diagram for explaining the output result of the ignition timing calculation means when performing octane number estimation and knock correction (ignition timing correction) in a transient state of the internal combustion engine immediately after the octane number of the supplied fuel changes. The figure shows the transition of the estimated octane number, knock correction amount (ignition timing correction amount), and ignition timing calculation result when the charging efficiency is changed while the rotation speed is kept constant. Immediately after the charging efficiency is increased and the knock is detected by the knock detection sensor, knock correction (ignition timing correction) based on the calculation result of the knock correction amount (ignition timing correction amount) is performed. On the other hand, the correction of the estimated octane number is started based on the knock correction amount. As the estimated octane number is corrected, the knock correction amount decreases. When the estimated octane number matches the true octane number, knock correction after the ignition timing calculation is not performed. At this stage, since the corrected true octane number is used, the ignition timing calculation is appropriately performed even when the operating point changes, and it is not necessary to perform knock correction again. Therefore, the knock control accuracy is improved and the responsiveness of the knock control is improved as compared with the method of sequentially performing the knock correction operation by the knock detection on the ignition timing calculation result.

  FIG. 22 is a diagram for explaining means for calculating the control amounts of the throttle valve and the variable valve that realize the target indicated torque based on the indicated torque calculated based on the reference octane number and the current octane number. In block 221, the indicated torque corresponding to the reference octane number is calculated based on the rotational speed, the charging efficiency, and the octane number under the reference conditions. In block 222, the indicated torque corresponding to the estimated octane number is calculated based on the rotational speed, the charging efficiency, and the current estimated octane number. The target reference indicated torque is corrected by the ratio of the indicated torque corresponding to the reference octane number and the indicated torque corresponding to the estimated octane number, and the target indicated torque is calculated. The reference octane number is the reference octane number (anti-knock property index) of the fuel, and the reference torque is a value calculated based on the reference octane number, the rotational speed, and the charging efficiency. The estimated torque is a value that is calculated based on the estimated octane number, the rotation speed, and the charging efficiency.

  The target reference indicated torque is calculated in consideration of the driver required torque, the external required torque, the mechanical loss, and the like under the reference conditions. In blocks 223 and 224, a throttle valve target control amount and / or a variable valve target control amount is calculated based on the rotational speed and the target indicated torque. With such a configuration, it is possible to appropriately calculate the throttle valve target control amount and the variable valve target control amount that realize the target indicated torque in consideration of the change in the indicated torque when the octane number changes. In the configuration of the present invention, the octane number is used as one of the input parameters for the illustrated torque calculation, but the present invention is not limited to this. The mixing ratio of a plurality of fuels having different anti-knock index and calorific value can be used as a parameter.

  FIG. 23 is a diagram for explaining a polynomial constituting the illustrated torque calculation means in FIG. As explanatory variables, a rotational speed is set in x1, a charging efficiency is set in x2, and an octane number (reference octane number or estimated octane number) is set in x33. Set the indicated torque to the objective variable. The coefficient E multiplied by each term is a partial regression coefficient. The partial regression coefficient numbers 2 to 5 have the effect of the rotational speed on the indicated torque, and the partial regression coefficient numbers 6 to 9 in the group 231 have the effect of the charging efficiency on the indicated torque. For 19, the influence of the octane number on the indicated torque is obtained. Furthermore, the partial regression coefficient numbers 10 to 15 in the group 232 are affected by the interaction term between the rotational speed and the charging efficiency, and the partial regression coefficients 20 to 35 in the group 233 are the interaction between the rotational speed, the charging efficiency and the octane number. The effect of each term is required. By setting the higher-order terms and interaction terms in the polynomial in this way, the indicated torque can be accurately calculated in consideration of the complex causal relationship that each input parameter gives to the indicated torque. Further, the memory capacity can be greatly reduced by replacing a large-scale map with a polynomial. In the system of the present embodiment, a ternary quartic polynomial is used as the means for calculating the indicated torque, but the present invention is not limited to this. That is, the order and the number of dimensions may be changed according to the relationship between the required accuracy and the allowable value of the calculation load. As explanatory variables, a configuration may be used in which a polynomial in which other parameters that affect the indicated torque such as the intake air temperature, the air-fuel ratio, and the water temperature are set is additionally used. By appropriately excluding higher-order terms and interaction terms that do not contribute to accuracy improvement from the polynomial by the stepwise method or the like, the relationship between the accuracy of the polynomial and the computation load can be improved.

  As mentioned above, although embodiment of this invention has been explained in full detail using drawing, a concrete structure is not limited to this embodiment, Even if there is a design change in the range which does not deviate from the gist of the present invention. These are included in the present invention.

  For example, in this embodiment, the octane number of the fuel supplied into the cylinder is used as the anti-knock property index. For example, the anti-knock property index includes the cetane number of the fuel supplied into the cylinder and a plurality of types. If it is an index that can evaluate anti-knock properties (ease of occurrence of combustion in the combustion chamber of the engine) such as a mixture ratio of the mixed fuel in the mixed fuel mixed with the above fuel, it is particularly limited. It is not a thing.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Air flow sensor and intake air temperature sensor 3 Throttle valve 4 Intake manifold 5 Intake pipe pressure sensor 6 Tumble control valve 7 Fuel injection valve 8 Intake valve (variable valve)
8A Intake variable valve mechanism 9 Valve lift sensor and valve timing sensor 10 Exhaust valve (variable valve)
10A Exhaust variable valve mechanism 11 Valve timing sensor 12 Spark plug 13 Knock detection sensor 14 Crank angle sensor 15 O ₂ sensor 16 External EGR pipe 17 External EGR valve 18 ECU (Electronic Control Unit)

Claims (13)

Rotational speed detecting means for detecting rotational speed, intake absolute pressure detecting means for detecting absolute pressure in the intake pipe, absolute pressure measuring means for measuring atmospheric absolute pressure or exhaust absolute pressure, and at least one of an intake valve and an exhaust valve A control apparatus for an internal combustion engine, comprising: a variable valve mechanism that makes the valve operation amount variable; a valve operation amount detection unit that detects the valve operation amount; and a knock detection unit that detects a knock occurrence ;
Charging efficiency calculating means for calculating the charging efficiency of the inflowing air into the cylinder based on at least the rotational speed, the intake absolute pressure, the atmospheric absolute pressure or the exhaust absolute pressure, and the valve operation amount; ,
An internal EGR amount calculating means for calculating an internal EGR amount of the cylinder based on at least the rotational speed, the intake absolute pressure, the atmospheric absolute pressure or the exhaust absolute pressure, and the valve operation amount;
Ignition timing based on at least the rotational speed, the charging efficiency, the internal EGR amount, the effective compression ratio calculated from the valve operation amount, and the anti-knock property index of the fuel supplied into the cylinder Ignition timing calculation means for calculating
Ignition timing correction means for calculating a correction amount of the ignition timing based on a detection result of the knock detection means, and correcting the ignition timing by the ignition timing correction amount;
An internal combustion engine comprising: an anti-knock property index correcting means for correcting the anti-knock property index based on the rotation speed, the charging efficiency, the ignition timing correction amount, and the ignition timing. Engine control device. The charging efficiency calculating means includes an intake relative pressure calculating means for calculating an intake relative pressure which is a ratio of the intake absolute pressure and the atmospheric absolute pressure or the exhaust absolute pressure;
Wherein at least the rotational speed and the intake relative pressure based on the valve operation amount, and the charging efficiency reference value calculating means for calculating a charging efficiency reference value,
Charging efficiency correction amount calculating means for calculating a correction amount of the charging efficiency based on a ratio between the atmospheric absolute reference pressure in a preset reference atmospheric pressure condition and the atmospheric absolute pressure or the exhaust absolute pressure, and
Wherein the product of charging efficiency reference value and the charging efficiency correction amount control apparatus for an internal combustion engine according to claim 1, characterized in that computing the charging efficiency. The internal EGR amount calculating means includes an intake relative pressure calculating means for calculating an intake relative pressure that is a ratio of the intake absolute pressure and the atmospheric absolute pressure or the exhaust absolute pressure;
An internal EGR amount reference value calculating means for calculating an internal EGR amount reference value based on at least the rotational speed, the intake relative pressure, and the valve operation amount;
An internal EGR amount correction amount calculation means for calculating a correction amount of the internal EGR amount based on a ratio between the atmospheric absolute reference pressure in a preset reference atmospheric pressure condition and the atmospheric absolute pressure or the exhaust absolute pressure. Prepared,
And the internal EGR amount reference value, the product of the internal EGR correction amount control apparatus for an internal combustion engine according to claim 1, characterized in that computing the internal EGR amount. The charging efficiency reference value calculating means has at least the rotational speed, the intake relative pressure, the lift amount of the intake valve, the opening timing of the intake valve, and the closing timing of the exhaust valve as input parameters. The control device for an internal combustion engine according to claim 2 , wherein the charging efficiency reference value under the reference atmospheric pressure condition is calculated by a polynomial that The internal EGR amount reference value calculation means inputs at least the rotational speed, the intake relative pressure, the lift amount of the intake valve, the opening timing of the intake valve, and the closing timing of the exhaust valve. The control apparatus for an internal combustion engine according to claim 3 , wherein the internal EGR amount reference value under the reference atmospheric pressure condition is calculated by a polynomial expressed as follows. An internal EGR rate means for calculating an internal EGR rate based on at least the charging efficiency and the internal EGR amount;
The ignition timing calculating means calculates the ignition timing by a polynomial having at least the rotational speed, the charging efficiency, the internal EGR rate, the effective compression ratio, and the anti-knock property index as input parameters. The control device for an internal combustion engine according to any one of claims 1 to 5 . The ignition timing calculating means includes
Steady operating point ignition timing means for calculating a steady operating point ignition timing based on the rotational speed and the charging efficiency;
At least the rotational speed and the charging efficiency, and the internal EGR rate, and the effective compression ratio, and the anti-knock index, based on a first ignition timing calculation means for calculating a first ignition timing,
Steady operating point EGR rate calculating means for calculating a steady operating point EGR rate based on the rotation speed and the charging efficiency;
A steady operating point effective compression ratio calculating means for calculating a steady operating point effective compression ratio based on the rotation speed and the charging efficiency;
Based on at least the rotational speed, the charging efficiency, the steady operating point EGR rate, the steady operating point effective compression ratio, and the anti-knock index for setting the steady operating point ignition timing , Second ignition timing calculation means for calculating the second ignition timing,
The ignition timing calculating means calculates the ignition timing by adding a difference between the first ignition timing and the second ignition timing to the steady operating point ignition timing. The control apparatus of the internal combustion engine in any one of 1-6 . The control device for an internal combustion engine according to any one of claims 1 to 7 , wherein the anti-knock property index is an octane number of fuel supplied into the cylinder. The control device for an internal combustion engine according to any one of claims 1 to 7 , wherein the anti-knock property index is a cetane number of fuel supplied into the cylinder. Fuel supplied to the cylinder is a mixed fuel in which a plurality of types of fuel are mixed, the antiknock property index, any claim 1-7, characterized in that the mixing ratio of the mixed fuel A control device for an internal combustion engine according to claim 1. The anti-knock property index correcting means uses the first derivative related to the anti-knock property index of a polynomial having the rotational speed, the charging efficiency and the anti-knock property index as explanatory variables, and the ignition timing as an objective variable. The control device for an internal combustion engine according to any one of claims 1 to 10 , wherein the antiknock property index is corrected. Torque calculating means for calculating torque based on the rotation speed, the charging efficiency, and the anti-knock property index;
The torque ratio calculating means calculates the reference torque calculated using the anti-knock index of the reference fuel as the anti-knock index and the estimated anti-knock index as the anti-knock index. Torque ratio calculating means for calculating the ratio of the estimated torque and the estimated torque ratio as the estimated torque ratio;
And the estimated torque ratio, and the rotational speed, and the target torque, based on, claims, characterized in that it comprises a control amount calculation means for calculating a control amount for calculating a control amount of the control amount or variable valve of the throttle valve Item 12. The control device for an internal combustion engine according to any one of Items 1 to 11 . The internal combustion engine according to claim 12 , wherein the torque calculation means calculates the torque by a polynomial having at least the rotation speed, the charging efficiency, and the antiknock property index as input parameters. Control device.

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