JP4151605B2 - Engine knock control device - Google Patents

Description

  The present invention relates to a knock control device for an engine (internal combustion engine).

A knock sensor that detects the frequency of 6 to 8 kHz generated by engine knocking is provided in the engine body, and the ignition timing is retarded according to the knock intensity detected by the knock sensor to control to the optimum ignition timing. (See Patent Document 1).
JP-A-8-338295

  By the way, in order to avoid knocking in the past, the knocking limit ignition timing, strictly speaking, the trace knock point is obtained by experiment and transferred to the knock limit ignition timing map using the engine load and the rotational speed as parameters. Strictly speaking, environmental conditions (temperature, pressure and humidity) and the octane number of the fuel used are not constant, so after adjusting the conditions and correcting their sensitivity, a map of the knock limit ignition timing is created. is the current situation.

  However, such a method for knocking requires a long man-hours and a period of time required for making a map of the knock limit ignition timing, thereby prolonging the development time. Moreover, not all information such as environmental conditions and the octane number of the fuel can be included in the map of the knock limit ignition timing. For this reason, knocking does not necessarily occur, so a knock sensor is provided as in Patent Document 1 described above.

  Recently, a variable valve mechanism that can variably control the valve lift of the intake valve has appeared, and in an engine having such a variable valve mechanism, the combustion state in the combustion chamber is more determined by a command value given to the variable valve mechanism. Are very different. In order to cope with such an engine by the above method, there is no choice but to prepare a plurality of knock limit ignition timing maps according to the command value given to the variable valve mechanism, and this will further prolong the development time.

  By the way, FIG. 29 shows the pressure history in the combustion chamber at the time of knock occurrence, and when the average pressure is removed from the high-frequency component, it can be seen that the pressure in the combustion chamber rises at a stroke at the self-ignition timing θknk.

  Therefore, first basic ignition timing calculating means for calculating the basic ignition timing from which MBT is obtained as the first basic ignition timing MBTCAL, knock limit ignition timing setting means for setting the knock limit ignition timing KNOCKcal, and these first basic ignition timings. In an engine knock control device including spark ignition means that performs spark ignition at a retarded value of either MBTCAL or knock limit ignition timing KNOCKcal, the reciprocal of the time until the fuel in the combustion chamber reaches self-ignition The timing θknk at which the fuel in the combustion chamber self-ignites is estimated based on the characteristics representing the distribution, and at the autoignition timing θknk based on the characteristics of the combustion mass ratio when igniting and burning at the first basic ignition timing MBTCAL. The combustion mass ratio BRknk is calculated, and the combustion mass ratio BRknk at the calculated auto-ignition timing And the fuel amount QINJ, the unburned fuel amount MUB is calculated, the pressure increase amount DP due to the knock in the combustion chamber is calculated based on the unburned fuel amount MUB, and the pressure increase amount DP due to the knock in the combustion chamber is calculated. By calculating the first knock strength estimated value KIC based on this, it is possible to detect the knock strength without using a sensor, and the calculated first knock strength estimated value KIC is the trace knock strength (slice level). ) If this is the case, a predetermined knock retard amount KNRT is calculated, and an ignition timing retarded by the knock retard amount KNRT from the first basic ignition timing MBTCAL is set as the knock limit ignition timing KNOCKcal. A proposal was made to reduce the number of man-hours and time required for creating the ignition timing map.

  However, there were points to be improved thereafter. This is because if the ignition is performed at the knock limit ignition timing KNOCKcal and burned, the combustion speed changes by the amount of the retarded ignition timing as compared with the case where the ignition is performed at the first basic ignition timing MBTCAL. If the combustion speed changes, the characteristics of the combustion mass ratio will change. That is, the characteristics of the combustion mass ratio differ between the case where ignition is performed at the knock limit ignition timing KNOCKcal and combustion is performed and the case where ignition is performed at the first basic ignition timing MBTCAL. That is, when igniting and burning at the knock limit ignition timing KNOCKcal, the combustion mass ratio BRknk at the self-ignition timing θknk is set based on the characteristics of the combustion mass ratio when igniting and burning at the knock limit ignition timing KNOCKcal. Must be calculated. For this reason, even when igniting and burning at the knock limit ignition timing KNOCKcal, the combustion mass ratio BRknk at the self-ignition timing θknk is calculated based on the characteristics of the combustion mass ratio when igniting and burning at the first basic ignition timing MBTCAL. If calculated, an error occurs in the calculation of the combustion mass ratio BRknk at the self-ignition timing θknk, and as a result, the calculation accuracy of the first knock magnitude estimated value KIC decreases.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an apparatus in which no error occurs in the calculation of the knock strength estimation value even when ignition is performed at an ignition timing retarded from the first basic ignition timing. And

The present invention includes a first basic ignition timing calculation means for calculating a basic ignition timing obtained based on a predetermined combustion period as a first basic ignition timing, a knock limit ignition timing setting means for setting a knock limit ignition timing, In a knock control device for an engine comprising spark ignition means for performing spark ignition at a retarded value of either the first basic ignition timing or the knock limit ignition timing, combustion occurs when ignition is performed at the first basic ignition timing estimates the timing at which fuel of the chamber is self-ignited, and calculates a first knock intensity estimate based on ignition timing which is the calculated, compares the first knock intensity estimate and the slice level, the more the result of the comparison 1 knock intensity estimate sets the first basic ignition timing as the knocking limit ignition timing as in the case is less than the slice level, the comparison result from the first knock intensity estimate A predetermined knock retard amount is calculated when the slice level is equal to or higher than the slice level, and from the start of combustion to the predetermined crank angle when ignited and burned at an ignition timing retarded by the knock retard amount from the first basic ignition timing. A combustion period is calculated, a basic ignition timing obtained based on the combustion period is calculated as a second basic ignition timing, and ignition is performed at an ignition timing retarded by the knock retard amount from the second basic ignition timing. And calculating the knock magnitude as a second knock magnitude estimate value, and when the second knock magnitude estimate value coincides with the slice level, an ignition timing retarded by the knock retard amount from the second basic ignition timing is calculated. is set as the knocking limit ignition timing, a second knock intensity estimate the second knock intensity estimation value does not match with the slice level than the slice level In the case of a threshold, the calculated knock retard amount is updated to a larger value by a predetermined value, and ignition is performed at the ignition timing retarded by the updated knock retard amount from the first basic ignition timing to burn. The combustion period from the start of combustion to the predetermined crank angle is calculated as the updated combustion period, and the basic ignition timing obtained based on the updated combustion period is calculated as the updated second basic ignition timing. The knock intensity in the case of ignition and combustion at the ignition timing retarded by the updated knock retard amount from the second basic ignition timing is calculated as the updated second knock intensity estimated value. The comparison between the second knock strength estimated value and the slice level is repeated, and when the updated second knock strength estimated value matches the slice level by this repetition, the updated second knock strength estimated value matches the slice level. The ignition timing retarded by the updated knock retard amount from the basic ignition timing is set as the knock limit ignition timing, and the second knock strength estimated value does not match the slice level, and the second knock strength estimated value is less than the slice level. If it is smaller, the calculated knock retard amount is updated to a smaller value by a predetermined value, and ignition is performed at the ignition timing retarded by the updated knock retard amount from the first basic ignition timing to burn. The combustion period from the start of combustion to the predetermined crank angle is calculated as the updated combustion period, and the basic ignition timing obtained based on the updated combustion period is calculated as the updated second basic ignition timing. Renewed second knock intensity when knocking and igniting at the ignition timing retarded by the updated knock retard amount from the subsequent second basic ignition timing It is calculated as a constant value, and this updated second knock strength estimated value is repeatedly compared with the slice level, and when the updated second knock strength estimated value matches the slice level by this repetition, the updated An ignition timing retarded by an updated knock retard amount from the second basic ignition timing is set as a knock limit ignition timing .

  According to the present invention, the combustion mass ratio at the self-ignition timing is calculated based on the characteristics of the combustion mass ratio when igniting and burning at the first basic ignition timing, and the combustion at the calculated auto-ignition timing is calculated. A first knock strength estimated value is calculated based on the mass ratio and the fuel amount, and the combustion mass ratio characteristic is retarded by the knock retard amount from the second basic ignition timing based on the combustion period. Ignition that is reset to the combustion mass ratio characteristic when igniting at the timing and burned, and retarded by the knock retard amount from the second basic ignition timing using the characteristics of the combustion mass ratio after the resetting The knock intensity when igniting and burning at the timing is calculated as the second knock intensity estimate.

The present invention also provides a laminar combustion speed calculation means for calculating a laminar combustion speed that is a combustion speed in a laminar flow state of the combustion gas, and a combustion gas volume equivalent volume that calculates a volume corresponding to the combustion gas volume in the combustion chamber. A calculation means, a combustion mass ratio calculation means for calculating the combustion mass ratio of the gas combusted in the combustion chamber up to a predetermined crank angle, and a reaction probability indicating the ease of combustion of the combustion gas under a predetermined operating condition And a first combustion period for calculating a combustion period from the start of combustion to a predetermined crank angle as a first combustion period based on the laminar combustion velocity, the combustion gas volume equivalent volume, the combustion mass ratio, and the reaction probability. a calculation unit, a first basic ignition timing calculating means for calculating a basic ignition timing obtained on the basis of the first combustion period as the first basic ignition timing, a knock limit to set the knock limit ignition timing In a knock control device for an engine, comprising: a spark timing setting means; and a spark ignition means that performs spark ignition at a retarded value of any of the first basic ignition timing and the knock limit ignition timing. Estimate when the fuel in the combustion chamber self-ignites based on the characteristics representing the reciprocal distribution of the time until self-ignition, and based on the characteristics of the combustion mass ratio when igniting and burning at the basic ignition timing A combustion mass ratio at the self-ignition timing is calculated, and an unburned fuel amount or an unburned fuel ratio is calculated based on the calculated combustion mass ratio and fuel amount at the self-ignition timing. A pressure increase amount due to knock in the combustion chamber is calculated based on the fuel ratio, a first knock strength estimated value is calculated based on the pressure increase amount due to knock in the combustion chamber, and the first knock strength estimation is calculated. And comparing the slice level, the first knock intensity estimation value from the comparison result of setting the first basic ignition timing is less than the slice level as a knock limit ignition timing as it is, the knock strength estimate from the comparison result A predetermined knock retard amount is calculated when the slice level is equal to or higher than the slice level, and a predetermined crank is determined from the start of combustion when it is assumed that ignition is performed at an ignition timing retarded by the knock retard amount from the first basic ignition timing MBTCAL. The combustion period up to the corner is calculated as the second combustion period, the basic ignition timing obtained based on the second combustion period is calculated as the second basic ignition timing, and the characteristics of the combustion mass ratio are calculated based on the second combustion period. Of combustion mass ratio when ignition is performed at an ignition timing retarded by the knock retard amount from the second basic ignition timing Knock intensity estimation when it is assumed that ignition is performed at an ignition timing retarded by the knock retard amount from the second basic ignition timing using the characteristics of the combustion mass ratio after the reset. A value calculated as a second knock magnitude estimated value, and when the second knock magnitude estimated value matches the slice level, an ignition timing retarded by the knock retard amount from the second basic ignition timing is calculated as the knock limit ignition. When the second knock strength estimated value is not equal to the slice level and the second knock strength estimated value is larger than the slice level, the calculated knock retard amount is updated to be increased by a predetermined value. When the ignition timing is assumed to be ignited at the ignition timing retarded by the updated knock retard amount from the first basic ignition timing, The combustion period up to the crank angle is calculated as the updated second combustion period, and the basic ignition timing obtained based on the updated second combustion period is calculated as the updated second basic ignition timing. Combustion mass ratio when igniting and burning at the ignition timing that is retarded by the updated knock retard amount from the updated second basic ignition timing based on the second combustion period Using the characteristics of the combustion mass ratio after resetting, the ignition is performed at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing. Then, the knock magnitude when assumed to be updated is calculated as the updated second knock magnitude estimated value, and this updated second knock magnitude estimated value is repeatedly compared with the slice level. 2 When the estimated knock intensity matches the slice level, the ignition timing delayed by the updated knock retard amount from the updated second basic ignition timing is used as the knock limit ignition timing, and the second knock intensity estimated value Is not equal to the slice level and the second knock strength estimated value is smaller than the slice level, the calculated knock retard amount is updated to a value that is reduced by a predetermined value, and after the update from the first basic ignition timing. The combustion period from the start of combustion to the predetermined crank angle when it is assumed that the engine is ignited at the ignition timing retarded by the amount of knock retard is calculated as the updated second combustion period, and the updated second combustion is performed. The basic ignition timing obtained based on the period is calculated as the updated second basic ignition timing, and the characteristics of the combustion mass ratio are calculated based on the updated second combustion period. It is reset to the characteristic of the combustion mass ratio when igniting and burning at the ignition timing retarded by the updated knock retard amount from the second basic ignition timing, and the reset combustion mass ratio The updated second knock strength estimated value when the knock strength is assumed to be ignited and burned at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing using the characteristics. And the comparison between the updated second knock strength estimated value and the slice level is repeated, and when this updated second knock strength estimated value matches the slice level, the updated second knock strength estimated value matches the slice level. (2) The ignition timing retarded by the updated knock retard amount from the basic ignition timing is set as the knock limit ignition timing .

According to the present invention, the first basic ignition timing calculating means for calculating the basic ignition timing obtained based on the predetermined combustion period as the first basic ignition timing, the knock limit ignition timing setting means for setting the knock limit ignition timing, In a knock control device for an engine comprising spark ignition means for performing spark ignition at a retarded value out of any of these first basic ignition timing and knock limit ignition timing, when ignition is performed at the first basic ignition timing The time when the fuel in the combustion chamber self-ignites is estimated, the first knock strength estimated value is calculated based on the calculated self-ignition timing, the first knock strength estimated value is compared with the slice level, and the comparison result first knock intensity estimate sets the first basic ignition timing as the knocking limit ignition timing as in the case is less than the slice level than, the first knock intensity from the comparison result A predetermined knock retard amount is calculated when the constant value is equal to or higher than the slice level, and a predetermined crank angle is calculated from the start of combustion when ignition is performed at an ignition timing retarded by the knock retard amount from the first basic ignition timing. The basic ignition timing obtained based on this combustion period is calculated as the second basic ignition timing, and ignition is performed at an ignition timing retarded by the knock retard amount from the second basic ignition timing. Ignition that is calculated as a second knock strength estimated value when it burns and is retarded by the knock retard amount from the second basic ignition timing when the second knock strength estimated value matches the slice level set the timing as knocking limit ignition timing, the second knock intensity estimate second knock intensity estimation value does not match with the slice level slice level If larger, the calculated knock retard amount is updated to a value that increases by a predetermined value, and ignition is performed at the ignition timing retarded by the updated knock retard amount from the first basic ignition timing to burn. The combustion period from the start of combustion to the predetermined crank angle is calculated as the updated combustion period, and the basic ignition timing obtained based on the updated combustion period is calculated as the updated second basic ignition timing, The knock intensity in the case of ignition and combustion at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is calculated as the updated second knock intensity estimated value. When the updated second knock strength estimated value matches the slice level by repeating the comparison between the second knock strength estimated value and the slice level. The ignition timing retarded by the updated knock retard amount from the second basic ignition timing is set as the knock limit ignition timing, and the second knock strength estimated value does not match the slice level and the second knock strength estimated value is If it is smaller than the slice level, the calculated knock retard amount is updated to a value that decreases by a predetermined value, and ignition is performed at an ignition timing that is retarded by the updated knock retard amount from the first basic ignition timing. The combustion period from the start of combustion to the predetermined crank angle in the case of combustion is calculated as the updated combustion period, and the basic ignition timing obtained based on the updated combustion period is calculated as the updated second basic ignition timing. Then, the knocking intensity when the ignition is burned at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is updated. It is calculated as an intensity estimated value, and the comparison of the updated second knock intensity estimated value with the slice level is repeated, and when the updated second knock intensity estimated value matches the slice level by this repetition, the update is performed. Since the ignition timing retarded by the updated knock retard amount from the second basic ignition timing is set as the knock limit ignition timing, the combustion is performed at the ignition timing retarded by the knock retard amount from the second basic ignition timing. Even if it is made, it can calculate a 2nd knock intensity | strength estimated value accurately (a knock intensity | strength estimation will become accurate).

  According to the present invention, the combustion mass ratio at the self-ignition timing is calculated based on the characteristics of the combustion mass ratio when igniting and burning at the first basic ignition timing, and the combustion at the calculated auto-ignition timing is calculated. A first knock strength estimated value is calculated based on the mass ratio and the fuel amount, and the combustion mass ratio characteristic is retarded by the knock retard amount from the second basic ignition timing based on the combustion period. Ignition that is reset to the combustion mass ratio characteristic when igniting at the timing and burned, and retarded by the knock retard amount from the second basic ignition timing using the characteristics of the combustion mass ratio after the resetting Since the knock intensity when igniting and burning at the timing is calculated as the second knock intensity estimated value, the characteristic of the combustion mass ratio after resetting is retarded by the knock retard amount from the second basic ignition timing. It will match the actual combustion mass proportion of characteristics when burning by ignition with the ignition timing.

Further, according to the present invention, the laminar flow rate calculation means for calculating the laminar flow rate which is the combustion rate in the laminar state of the combustion gas, and the combustion gas volume for calculating the volume corresponding to the combustion gas volume in the combustion chamber Equivalent volume calculation means, combustion mass ratio calculation means for calculating the combustion mass ratio of gas combusted in the combustion chamber up to a predetermined crank angle, and reaction probability indicating the ease of combustion of combustion gas under predetermined operating conditions And a reaction probability calculating means for calculating a combustion period from the start of combustion to a predetermined crank angle as a first combustion period based on these laminar combustion velocity, combustion gas volume equivalent volume, combustion mass ratio, and reaction probability. notch of setting the combustion period calculation means, and the first basic ignition timing calculating means for calculating a basic ignition timing obtained on the basis of the first combustion period as the first basic ignition timing, the knocking limit ignition timing In a knock control device for an engine, comprising: a limit ignition timing setting means; and a spark ignition means for performing spark ignition at a retarded value of any of these first basic ignition timing and knock limit ignition timing. Based on the characteristic representing the distribution of the reciprocal of the time until the self-ignition, the time when the fuel in the combustion chamber self-ignites is estimated, and the characteristic of the combustion mass ratio when igniting and burning at the first basic ignition timing The combustion mass ratio at the self-ignition timing is calculated based on the calculated combustion mass ratio and the fuel amount at the self-ignition timing, and an unburned fuel amount is calculated based on the unburned fuel amount. It calculates a pressure increase amount due to calculate a first knock intensity estimation value based on the pressure increase amount due to the knock of the combustion chamber, the first knock intensity estimate and the slice level (trace knock Degrees) are compared, the comparison first knock intensity estimation value from the result of the first basic ignition timing is less than the slice level as it is set as the knocking limit ignition timing, a knock strength estimate from the comparison result slice When the level is equal to or higher than the level , a predetermined knock retard amount is calculated, and a combustion period when it is assumed that ignition is performed at an ignition timing retarded by the knock retard amount from the first basic ignition timing is the second combustion period. The second basic ignition timing obtained based on the second combustion period is calculated, and the characteristics of the combustion mass ratio are calculated based on the second combustion period by the knock retard amount from the second basic ignition timing. The characteristic is reset to the combustion mass ratio when ignited and burned at the retarded ignition timing, and the second basic ignition timing is set using the characteristics of the combustion mass ratio after the reset. A knock magnitude estimated value calculated when the ignition timing is retarded by a retard retard amount and burned is calculated as a second knock magnitude estimated value, and the second knock magnitude estimated value matches the slice level . An ignition timing that is retarded by a knock retard amount from the second basic ignition timing is set as a knock limit ignition timing , and the second knock strength estimated value does not match the slice level, and the second knock strength estimated value is sliced. If it is greater than the level, the calculated knock retard amount is updated to a value that increases by a predetermined value, and ignition is performed at an ignition timing retarded by the updated knock retard amount from the first basic ignition timing to burn. In this case, the combustion period from the start of combustion to the predetermined crank angle is calculated as the updated second combustion period. Based on this updated second combustion period, The basic ignition timing obtained in this way is calculated as the updated second basic ignition timing, and the characteristic of the combustion mass ratio is updated after the update from the updated second basic ignition timing based on the updated second combustion period. To the characteristic of the combustion mass ratio in the case of igniting and burning at the ignition timing retarded by the knock retard amount, and using the characteristic of the combustion mass ratio after this resetting, the updated second basic The knock intensity when the ignition is assumed to be ignited and burned at the ignition timing retarded by the updated knock retard amount from the ignition timing is calculated as the updated second knock intensity estimated value, and the updated second knock intensity is calculated. The comparison of the intensity estimated value and the slice level is repeated, and when the updated second knock intensity estimated value coincides with the slice level by this repetition, the updated value is updated from the updated second basic ignition timing. The ignition timing retarded by the amount of the retard is set as the knock limit ignition timing, and when the second knock strength estimated value does not match the slice level and the second knock strength estimated value is smaller than the slice level, the above calculation is performed. The knock retard amount is updated to a smaller value by a predetermined value, and a predetermined crank is applied from the start of combustion when it is assumed that ignition is performed at an ignition timing retarded from the first basic ignition timing by the updated knock retard amount. The combustion period up to the corner is calculated as the updated second combustion period, the basic ignition timing obtained based on the updated second combustion period is calculated as the updated second basic ignition timing, and the updated Based on the second combustion period, the combustion mass ratio is ignited at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing. Re-set to the characteristics of the combustion mass ratio in the case of firing, and retarded by the updated knock retard amount from the updated second basic ignition timing using the characteristics of the combustion mass ratio after the resetting The knock strength when assuming that it is ignited and burned at the ignition timing is calculated as the updated second knock strength estimated value, and the updated second knock strength estimated value is repeatedly compared with the slice level, When the updated second knock intensity estimated value coincides with the slice level by this repetition, the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is set as the knock limit ignition timing, respectively. If the second knock strength estimated value does not match the slice level and the second knock strength estimated value is larger than the slice level, the knock retard amount is set to a predetermined value. The combustion period from the start of combustion to the predetermined crank angle is updated when it is assumed that ignition is performed at an ignition timing retarded by the updated knock retard amount from the first basic ignition timing. Calculated as the second combustion period after that, the basic ignition timing obtained based on the second combustion period after the update is calculated as the second basic ignition timing after the update, and based on the second combustion period after the update Resetting the characteristics of the combustion mass ratio to the characteristics of the combustion mass ratio when igniting and burning at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing, Using the characteristics of the combustion mass ratio after resetting, the knock intensity when it is assumed that ignition is performed at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is performed. update Is calculated as the second knock strength estimated value, and the updated second knock strength estimated value is repeatedly compared with the slice level. By this repetition, the updated second knock strength estimated value matches the slice level. In this case, the ignition timing that is retarded by the updated knock retard amount from the updated second basic ignition timing is set as the knock limit ignition timing, and the second knock intensity estimated value does not match the slice level. If the estimated knock magnitude is smaller than the slice level, the knock retard amount is updated to a value that decreases by a predetermined value, and ignition is performed at an ignition timing that is retarded by the updated knock retard amount from the first basic ignition timing. And calculating the combustion period from the start of combustion to the predetermined crank angle as the second combustion period after the update, and the second combustion period after the update. The basic ignition timing obtained on the basis of the second basic ignition timing is calculated as the updated second basic ignition timing, and the characteristics of the combustion mass ratio are calculated from the updated second basic ignition timing based on the updated second combustion period. Reset to the characteristics of the combustion mass ratio when igniting and burning at the ignition timing retarded by the updated knock retard amount, and using the characteristics of the combustion mass ratio after this resetting, The knock intensity when the ignition is assumed to be ignited and burned at the ignition timing retarded by the updated knock retard amount from the second basic ignition timing is calculated as the updated second knock intensity estimated value. The comparison between the second knock intensity estimated value and the slice level is repeated, and when the updated second knock intensity estimated value matches the slice level by this repetition, it is updated from the updated second basic ignition timing. Since respectively set the ignition timing obtained by knocking retard amount by retarding the knock limit ignition timing, the ignition characteristics of the mass fraction burned after reconfiguration in ignition timing is retarded by the knock retard amount from the second basic ignition timing Therefore, even if the combustion is performed at the ignition timing retarded by the knock retard amount from the second basic ignition timing, the second knock intensity estimation is performed. The value can be calculated with high accuracy (the estimation of the knock intensity is accurate).

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

  FIG. 1 is a schematic diagram for explaining the system of the present invention.

  The air is stored in the intake collector 2 and then introduced into the combustion chamber 5 of each cylinder via the intake manifold 3. Fuel (gasoline) is injected and supplied from a fuel injector 21 arranged in the intake port 4 of each cylinder. The fuel injected into the air is vaporized and mixed with the air to form a gas (air mixture) and flows into the combustion chamber 5. This air-fuel mixture is confined in the combustion chamber 5 when the intake valve 15 is closed, and is compressed by the rise of the piston 6.

  In order to ignite this compressed air-fuel mixture with a high-pressure spark, an ignition device 11 of an electronic power distribution system is provided in which an ignition coil with a built-in power transistor is arranged in each cylinder. That is, the ignition device 11 includes an ignition coil 13 that stores electrical energy from the battery, a power transistor that energizes and shuts off the primary side of the ignition coil 13, and a primary current of the ignition coil 13 that is provided on the ceiling of the combustion chamber 5. It includes a spark plug 14 that receives a high voltage generated on the secondary side of the ignition coil 13 due to interruption of the spark coil 13 and performs spark discharge.

  When a spark is blown off by the spark plug 14 slightly before the compression top dead center and the compressed mixture is ignited, the flame spreads and then explosively burns, and the gas pressure by this combustion works to push down the piston 6. This work is taken out as the rotational force of the crankshaft 7. The combusted gas (exhaust gas) is discharged into the exhaust passage 8 when the exhaust valve 16 is opened.

A three-way catalyst 9 is provided in the exhaust passage 8. When the air-fuel ratio of the exhaust gas is in a narrow range (window) centered on the stoichiometric air-fuel ratio, the three-way catalyst 9 can efficiently remove harmful three components such as HC, CO, and NOx contained in the exhaust gas simultaneously. Since the air-fuel ratio is the ratio of the intake air amount and the fuel amount, the intake air amount introduced into the combustion chamber 5 per one cycle of the engine (crank angle 720 ° section in a four-cycle engine) and the fuel injector 21 The engine controller 31 uses the intake air flow rate signal from the air flow meter 32 and the fuel from the fuel injector 21 based on the signals from the crank angle sensors (33, 34) so that the ratio to the fuel injection amount becomes the stoichiometric air-fuel ratio. While determining the injection amount, the air-fuel ratio is feedback controlled based on a signal from an O ₂ sensor 35 provided upstream of the three-way catalyst 9.

  A so-called electronically controlled throttle 22 in which a throttle valve 23 is driven by a throttle motor 24 is provided upstream of the intake collector 2. Since the torque required by the driver appears in the amount of depression of the accelerator pedal 41 (accelerator opening), the engine controller 31 determines a target torque based on a signal from the accelerator sensor 42, and a target air for realizing this target torque. The amount is determined, and the opening degree of the throttle valve 23 is controlled via the throttle motor 24 so as to obtain this target air amount.

  Cam sprockets and crank sprockets are attached to the front portions of the intake valve camshaft 25, the exhaust valve camshaft 26, and the crankshaft 7, respectively, and a timing chain (not shown) is hung around these sprockets so that the camshaft 25 and 26 are driven by the crankshaft 7 of the engine, and are interposed between the cam sprocket and the intake valve camshaft 25 to continuously adjust the phase of the intake valve cam with a constant operating angle. A variable intake valve timing control mechanism (hereinafter referred to as “intake VTC mechanism”) 27 that can be controlled, and a cam sprocket and an exhaust valve camshaft 26 are interposed between the camshaft 26 and the exhaust valve cam. Variable exhaust valve timing control mechanism (hereinafter referred to as “exhaust”) that can control the phase continuously. Provided with that.) 28 and TC mechanism ". When the opening / closing timing of the intake valve 15 and the opening / closing timing of the exhaust valve 16 are changed, the amount of the inert gas remaining in the combustion chamber 5 changes. As the amount of the inert gas in the combustion chamber 5 increases, the pumping loss decreases and the fuel consumption improves. Therefore, the target intake valve closing timing and the target exhaust gas indicate how much inert gas should remain in the combustion chamber 5 depending on the operating conditions. The valve closing timing is determined in advance, and the engine controller 31 determines the target intake valve closing timing and the target exhaust valve closing timing from the operating conditions (engine load and rotation speed) at that time, so that these target values can be obtained. The intake valve closing timing and the exhaust valve closing timing are controlled via the actuators of the intake VTC mechanism 27 and the exhaust VTC mechanism 28.

  An intake air temperature signal from the intake air temperature sensor 43, an intake air pressure signal from the intake air pressure sensor 44, an exhaust gas temperature signal from the exhaust air temperature sensor 45, and an exhaust gas pressure signal from the exhaust air pressure sensor 46 are output from the water temperature sensor 37. The engine controller 31 that is input together with the coolant temperature signal controls the ignition timing that is the primary current cutoff timing of the spark plug 14 via the power transistor 13.

  In this case, the ignition timing when knock does not occur is the basic ignition timing MBTCAL according to the operating conditions. However, knocking may occur in the combustion chamber 5 in a high load low rotation speed region of the engine. If this occurs, the durability of the engine decreases, so the engine controller 31 performs knock control by ignition timing control.

  FIG. 2 is a flowchart showing the overall flow of ignition timing control. This flow shows a flow of operations, not a flow executed at regular intervals.

  In steps 1 and 2, the basic ignition timing MBTCAL [degBTDC] and the knock limit ignition timing KNOCKcal [degBTDC] are calculated.

  Here, the calculation of the basic ignition timing MBTCAL will be described first. First, the ignition timing control based on the combustion analysis will be outlined (the basic concept is described in Japanese Patent Laid-Open No. 2003-148236).

  As shown in FIG. 3, the crank angle at which the combustion pressure of the air-fuel mixture reaches the maximum value Pmax when the air-fuel mixture is ignited with MBT (minimum advance angle value at which maximum torque is obtained) is defined as a reference crank angle θPMAX [degATDC]. The reference crank angle θPMAX is substantially constant regardless of the combustion method, and is generally in the range of 12 to 15 degrees after compression top dead center, and at most 10 to 20 degrees after compression top dead center.

  FIG. 4 shows changes in the combustion mass ratio BR (combustion gas mass ratio) obtained by the combustion analysis in the combustion chamber in the spark ignition engine. The combustion mass ratio BR representing the ratio of the combustion mass to the fuel supplied to the combustion chamber is 0% at the time of ignition, and reaches 100% by complete combustion. Experiments have confirmed that the combustion mass ratio at the reference crank angle θPMAX is constant and about 60%.

  The combustion period corresponding to the change allowance until the combustion mass ratio BR reaches about 60% corresponding to the reference crank angle θPMAX from 0% is a period in which there is almost no change in both the combustion mass ratio and the combustion pressure immediately after the start of combustion. It is divided into an initial combustion period and a main combustion period in which the combustion mass ratio and the combustion pressure increase rapidly. The initial combustion period is a stage from the start of combustion until flame nuclei are formed, and the flame nuclei are formed when the combustion mass ratio changes from 0% to 2% to 10%. During this initial combustion period, the rate of increase in combustion pressure and combustion temperature is small, and the initial combustion period is long with respect to changes in the combustion mass ratio. The length of the initial combustion period is susceptible to changes in temperature and pressure in the combustion chamber.

  On the other hand, in the main combustion period, the flame propagates from the flame kernel to the outside, and the flame speed (that is, the combustion speed) increases rapidly. Therefore, the change in the combustion mass ratio during the main combustion period is larger than the change in the combustion mass ratio during the initial combustion period.

  In the engine controller 31, the period until the combustion mass ratio reaches 2% (changes) is set as the initial combustion period BURN1 [deg], and the period from the end of the initial combustion period BURN1 to the reference crank angle θPMAX (combustion chamber volume ratio) In other words, the main combustion period BURN2 [deg] is distinguished from 2% to about 60%. Then, a combustion period BURN [deg] that is the sum of the initial combustion period BURN1 and the main combustion period BURN2 is calculated, a reference crank angle θPMAX [degATDC] is subtracted from the combustion period BURN, and an ignition dead time equivalent crank described later is further calculated. The crank angle position to which the angle IGNDEAD [deg] is added is set as the basic ignition timing MBTCAL [degBTDC], which is the ignition timing at which MBT is obtained.

  The pressure and temperature in the combustion chamber 5 during the initial combustion period in which flame nuclei are formed are almost equivalent to the pressure and temperature at the time of ignition, but the ignition timing is calculated from this, but accurate ignition is performed from the beginning. The time cannot be set. Therefore, as shown in FIG. 13, the previous value of the basic ignition timing is calculated as the previous combustion start timing MBTCYCL [degBTDC] (step 44), and this value is used to calculate the initial combustion period as shown in FIG. (Step 162), the calculation of the initial combustion period is cyclically repeated to obtain a highly accurate result without time delay.

  Next, the calculation of the basic ignition timing MBTCAL executed by the engine controller 31 will be described in detail with reference to the following flowchart.

  FIG. 5 is for calculating various physical quantities necessary for calculating the ignition timing, and is executed at regular time intervals (for example, every 10 msec).

  First, in step 11, the intake valve closing timing IVC [degBTDC], the collector internal temperature TCOL [K] detected by the temperature sensor 43, the collector internal pressure PCOL [Pa] detected by the pressure sensor 44, and the temperature sensor 45 are detected. Exhaust temperature TEXH [K], internal inert gas rate MRESFR [%], cooling water temperature TWK [K] detected by temperature sensor 37, target equivalent ratio TFBYA, engine rotational speed NRPM [rpm] detected by crank angle sensor ].

  Here, the crank angle sensor includes a position sensor 33 for detecting the position of the crankshaft 7 and a phase sensor 34 for detecting the position of the intake camshaft 25, and is based on signals from these two sensors 33 and 34. The engine speed NRPM [rpm] is calculated.

  The intake valve closing timing IVC is known from the command value given to the intake VTC mechanism 27. Alternatively, the actual intake valve closing timing may be detected by the phase sensor 34.

  The internal inert gas ratio MRESFR is a value obtained by dividing the amount of inert gas remaining in the combustion chamber by the total amount of gas in the combustion chamber, and the calculation thereof will be described later. The ignition dead time DEADTIME is a constant value.

  The target equivalent ratio TFBYA is calculated in a fuel injection amount calculation flow (not shown). The target equivalent ratio TFBYA is an unnamed number, and is a value represented by the following expression when the theoretical air-fuel ratio is 14.7.

TFBYA = 14.7 / target air-fuel ratio (1)
For example, from equation (1), when the target air-fuel ratio is the stoichiometric air-fuel ratio, TFBYA = 1.0, and when the target air-fuel ratio is a lean value such as 22.0, TFBYA is a positive value less than 1.0. is there.

In step 12, the volume of the combustion chamber 5 at the intake valve closing timing IVC (that is, the volume at the compression start timing) VIVC [m ³ ] is calculated. The volume VIVC of the combustion chamber 5 when the intake valve is closed is determined by the stroke position of the piston 6. The stroke position of the piston 6 is determined by the crank angle position of the engine.

  Referring to FIG. 6, consider a case where the rotation center 72 of the crankshaft 71 of the engine is offset from the center axis 73 of the cylinder. Assume that the connecting rod 74, the joint point 75 between the connecting rod 74 and the crankshaft 71, and the piston pin 76 that connects the connecting rod 74 and the piston are in the relationship shown in the figure. At this time, the volume VIVC of the combustion chamber 5 at the closing timing of the intake valve can be expressed by the following equations (2) to (6).

VIVC = f1 (θivc) = Vc + (π / 4) D ² · Hivc (2)
Vc = (π / 4) D ² · Hx / (ε−1) (3)
^{Hivc = {(CND + ST 2} /2) - (CRoff-PISoff) 2} 1/2
− {(ST / 2) · cos (θivc + θoff)}
+ (CND ² −X ² ) ^1/2 (4)
X = (ST / 2) · sin (θivc + θoff) −CRoff + PISoff (5)
θoff = arcsin {(CRoff−PISoff) / (CND · (ST / 2))} (6)
Where Vc: gap volume [m ³ ],
ε: compression ratio,
D: cylinder bore diameter [m],
ST: Full piston stroke [m],
Hivc: Piston pin 76 at the intake valve closing timing
Distance from TDC [m],
Hx: The maximum and minimum values of the distance from the TDC of the piston pin 76
Difference [m],
CND: length of connecting rod 74 [m],
CRoff: Offset distance of the nodal point 75 from the cylinder center axis 73
[M],
PISoff: From the center axis 73 of the crankshaft rotation center 72
Offset distance [m],
θivc: Intake valve closing timing crank angle [degATDC],
θoff: Piston pin 76 and crankshaft rotation center 72 are connected
Angle [deg] between the line and the vertical line in TDC,
X: horizontal distance [m] between the nodal point 75 and the piston pin 76,
As described above, the crank angle θivc at the intake valve closing timing is determined by the command signal from the engine controller 31 to the intake VTC mechanism 27 and thus is known. By substituting the crank angle θivc (= IVC) at this time into the equations (2) to (6), the volume VIVC of the combustion chamber 5 at the closing timing of the intake valve can be calculated. Therefore, practically, the volume VIVC of the combustion chamber 5 at the intake valve closing timing is set by a table using the intake valve closing timing IVC as a parameter. When the intake VTC mechanism 27 is not provided, a constant value can be given.

  In step 13, the temperature (that is, the compression start timing temperature) TINI [K] of the combustion chamber 5 at the intake valve closing timing IVC is calculated. The temperature of the gas flowing into the combustion chamber 5 is a temperature of a gas in which the fresh air flowing into the combustion chamber 5 and the inert gas remaining in the combustion chamber 5 are mixed. The temperature of the fresh air flowing into the combustion chamber 5 is Since the temperature of the inert gas equal to the fresh air temperature TCOL in the intake collector 2 and remaining in the combustion chamber 5 can be approximated by the exhaust temperature TEXH in the vicinity of the exhaust port, the temperature of the combustion chamber 5 at the intake valve closing timing IVC. TINI is the following from the fresh air temperature TCOL in the intake collector 2, the exhaust gas temperature TEXH, and the internal inert gas ratio MRESFR that is the ratio of the inert gas remaining in the combustion chamber 5 at the timing when the intake valve closing timing IVC is reached. It can be obtained by an expression.

TINI = TEXH × MRESFR + TCOL × (1−MRESFR) (7)
In step 14, the pressure (that is, compression start timing pressure) PINI [Pa] at the intake valve closing timing IVC of the combustion chamber 5 is calculated. That is, the collector internal pressure PCOL at the timing when the intake valve closing timing IVC is reached is taken in as the pressure PINI at the intake valve closing timing IVC.

  In step 15, a reaction probability RPROBA [%] representing the flammability of the air-fuel mixture in the combustion chamber 5 is calculated. The reaction probability RPROBA is a dimensionless value and depends on the three parameters of the residual inert gas ratio MRESFR, the cooling water temperature TWK [K], and the target equivalent ratio TFBYA, and can be expressed by the following equation.

RPROBA = f3 (MRESFR, TWK, TFBYA) (8)
More specifically, the maximum value of the reaction probability obtained by the combination of the three parameters MRESFR, TWK, and TFBYA is set to 100%, the relationship between these parameters and the reaction probability RPROBA is experimentally obtained, and the obtained reaction probability RPROBA is obtained. Are stored in advance in the memory of the engine controller 31 as a table corresponding to the parameters. In step 14, the reaction probability RPROBA is obtained by searching this table according to the parameters.

  Specifically, a table of water temperature correction coefficients having characteristics as shown in FIG. 7 according to the cooling water temperature TWK, a table of internal inert gas rate correction coefficients (not shown) set similarly, and a target equivalent ratio A table of equivalence ratio correction coefficients having characteristics as shown in FIG. 8 according to TFBYA is stored in the memory in advance. The maximum value of each correction coefficient is 1.0, and the reaction probability RPROBA is calculated by multiplying the product of the three types of correction coefficients by the maximum value of 100% of the reaction probability.

  Explaining each table, the water temperature correction coefficient shown in FIG. 7 becomes larger as the cooling water temperature TWK is higher, and becomes 1.0 when the cooling water temperature TWK is 80 ° C. or higher. The equivalence ratio correction coefficient shown in FIG. 8 is the maximum value of 1.0 when the target equivalence ratio TFBYA is 1.0, that is, the stoichiometric air-fuel ratio. The ratio correction factor decreases. Although the internal inert gas rate correction coefficient is not shown, it is 1.0 when the internal inert gas rate MRESFR is zero.

  In step 15, a reference crank angle θPMAX [degATDC] is calculated. As described above, the reference crank angle θPMAX does not fluctuate very much, but it still tends to advance as the engine speed NRPM increases. Therefore, the reference crank angle θPMAX can be expressed by the following equation as a function of the engine speed NRPM. it can.

θPMAX = f4 (NRPM) (9)
Specifically, the reference crank angle θPMAX is obtained by searching a table of characteristics shown in FIG. 9 stored in advance in the memory of the engine controller 31 from the engine speed NRPM. In order to facilitate calculation, the reference crank angle θPMAX can be regarded as constant.

FIG. 10 is for calculating the initial combustion period BURN1 [deg], and FIG. 12 is for calculating the main combustion period BURN2 [deg], which is executed at regular intervals (for example, every 10 msec). 10 and 12 are executed following FIG.
Either of FIGS. 10 and 12 may be executed first.

First, referring to FIG. 10, in step 161, the previous combustion start timing MBTCYCL [degBTDC], the volume VIVC [m ³ ] at the intake valve closing timing of the combustion chamber 5 calculated in step 12 of FIG. 5, and the step of FIG. The temperature TINI [K] at the intake valve closing timing of the combustion chamber 5 calculated in 13, the pressure PINI [Pa] at the intake valve closing timing of the combustion chamber 5 calculated in Step 14 of FIG. 5, and the engine speed NRPM [Rpm], the reaction probability RPROBA [%] calculated in step 15 of FIG. 5 is read.

  Here, the previous combustion start timing MBTCYCL is a value one cycle before [degBTDC] of the basic ignition timing MBTCAL, and the calculation thereof will be described later with reference to FIG.

In step 162, the volume V0 [m ³ ] at the combustion start timing of the combustion chamber 5 is calculated. As described above, the ignition timing (combustion start timing) here is not the basic ignition timing MBTCAL calculated in the current cycle but a value one cycle before the basic ignition timing. That is, the volume V0 at the combustion start timing of the combustion chamber 5 is calculated from MBTCYCL, which is a value one cycle before the basic ignition timing, by the following equation.

V0 = f6 (MBTCYCL) (11)
Specifically, the volume V0 of MBTCYCL in the combustion chamber 5 is calculated from the stroke position of the piston 6 at the previous combustion start timing MBTCYCL and the bore diameter of the combustion chamber 5. In step 12 of FIG. 5, the volume VIVC of the combustion chamber 5 at the intake valve closing timing IVC is obtained by searching a table of intake valve closing timing volumes using the intake valve closing timing as a parameter. Here, MBTCYCL is set as a parameter. The volume V0 of the combustion chamber 5 at the previous combustion start time MBTCYCL may be obtained by searching the table of the previous combustion start time volume.

  In step 163, an effective compression ratio Ec at the combustion start timing is calculated. The effective compression ratio Ec is a dimensionless value, and is a value obtained by dividing the volume V0 of the combustion chamber 5 at the combustion start timing by the volume VIVC of the combustion chamber 5 at the intake valve closing timing, as shown in the following equation.

Ec = f7 (V0, VIVC)
= V0 / VIVC (12)
In step 164, the temperature increase rate TCOMP in the combustion chamber 5 from the intake valve closing timing IVC to the combustion start timing is calculated based on the effective compression ratio Ec as shown in the following equation.

TCOMP = f8 (Ec) = Ec ^ (κ−1) (13)
Where κ: specific heat ratio,
Equation (13) is an equation for the rate of temperature rise of the adiabatic compressed gas. Note that “^” on the right side of the equation (13) represents power calculation. This symbol is also used in the formula described later.

  κ is a value obtained by dividing the constant pressure specific heat of the gas adiabatically compressed by the constant volume specific heat. If the gas adiabatically compressed is air, κ = 1.4, and this value may be used simply. However, the calculation accuracy can be further improved by experimentally determining the value of κ for the air-fuel mixture.

  FIG. 11 illustrates equation (13). Therefore, it is possible to obtain the temperature increase rate TCOMP by storing a table of such characteristics in advance in the memory of the engine controller 31 and searching the table based on the effective compression ratio Ec.

In step 165, the temperature T0 [K] at the combustion start timing of the combustion chamber 5 is multiplied by the temperature TINI at the intake valve closing timing of the combustion chamber 5 by the temperature increase rate TCOMP, that is, T0 = TINI × TCOMP (14)
It is calculated by the following formula.

  Steps 166 and 167 are the same as steps 164 and 165. That is, at step 166, the pressure increase rate PCOMP in the combustion chamber 5 from the intake valve closing timing IVC to the combustion start timing is calculated based on the effective compression ratio Ec as shown in the following equation.

PCOMP = f9 (Ec) = Ec ^ κ (41)
Where κ: specific heat ratio,
The equation (41) is also an equation for the rate of increase in pressure of gas that is adiabatically compressed in the same manner as the equation (13). “^” On the right side of the equation (41) represents power calculation as in the equation (13).

  κ is the same as the value used in the above equation (13). If the gas to be adiabatically compressed is air, κ = 1.4, and this value may be used simply. However, the calculation accuracy can be further improved by obtaining the value of κ from the composition and temperature of the air-fuel mixture.

  It is also possible to obtain a pressure increase rate PCOMP by storing a table having the same characteristics as in FIG. 11 in advance in the memory of the engine controller 31 and searching the table based on the effective compression ratio Ec.

In step 167, the pressure P0 [Pa] at the combustion start timing of the combustion chamber 5 is multiplied by the pressure PINI at the intake valve closing timing of the combustion chamber 5 by the pressure increase rate PCOMP, that is, P0 = PINI × PCOMP (42)
It is calculated by the following formula.

  In step 168, the laminar combustion speed SL1 [m / sec] in the initial combustion period is calculated by the following equation (known).

SL1 = f10 (T0, P0)
= SLstd × (T0 / Tstd) ^2.18 × (P0 / Pstd) ^−0.16 (15)
Where Tstd: reference temperature [K],
Pstd: Reference pressure [Pa]
SLstd: Reference laminar combustion at reference temperature Tstd and reference pressure Pstd
Speed [m / sec],
T0: temperature [K] at the combustion start timing of the combustion chamber 5;
P0: pressure [Pa] at the combustion start timing of the combustion chamber 5;
The laminar combustion velocity (laminar flame velocity) is the flame propagation velocity in the absence of gas flow, and is independent of the compression velocity in the combustion chamber 5 and the intake air flow velocity in the combustion chamber 5. 5 is known to be a function of the temperature and pressure of 5, so that the laminar combustion speed in the initial combustion period is a function of the combustion start temperature T0 and the combustion start pressure P0, and as described later, the main combustion period. Is a function of compression top dead center temperature TTDC and compression top dead center pressure PTDC. This is because the laminar combustion speed generally varies depending on the engine load, the inert gas ratio in the combustion chamber 5, the intake valve closing timing, the specific heat ratio, and the intake air temperature. Since it is a factor that affects T and pressure P, it is assumed that the laminar combustion speed can be finally defined by the temperature T and pressure P in the combustion chamber 5.

  In the above equation (15), the reference temperature Tstd, the reference pressure Pstd, and the reference laminar combustion speed SLstd are values determined in advance by experiments.

Under a pressure of 2 bar or more, which is a normal pressure in the combustion chamber 5, the pressure term (P0 / Pstd) ^−0.16 in the equation (15) becomes a small value. Accordingly, it is also possible to define the reference laminar combustion speed SLstd only by the reference temperature Tstd with the pressure term (P0 / Pstd) ^−0.16 being a constant value.

  Accordingly, when the reference temperature Tstd is 550 [K], the reference laminar combustion rate SLstd is 1.0 [m / sec], and the pressure term is 0.7, the temperature T0 and the laminar combustion rate at the combustion start timing The relationship with SL1 can be approximately defined by the following equation.

SL1 = f11 (T0)
= 1.0 × 0.7 × (T0 / 550) ^2.18 (16)
In step 169, the gas flow turbulence intensity ST1 in the initial combustion period is calculated. The turbulence intensity ST1 of the gas flow is a dimensionless value, and depends on the flow rate of fresh air flowing into the combustion chamber 5 and the penetration of injected fuel from the fuel injector 21.

  The flow rate of fresh air flowing into the combustion chamber 5 depends on the shape of the intake passage, the operating state of the intake valve 15, and the shape of the intake port 4 where the intake valve 15 is provided. The penetration of the injected fuel depends on the injection pressure of the fuel injector 21, the fuel injection period, and the combustion injection timing.

  Finally, the turbulence strength ST1 of the gas flow during the initial combustion period can be expressed by the following equation as a function of the engine speed NRPM.

ST1 = f12 (NRPM) = C1 × NRPM (17)
Where C1: constant,
It is also possible to obtain the turbulence intensity ST1 from a table using the rotational speed NRPM as a parameter.

  In step 170, the gas combustion speed FLAME1 [m / sec] in the initial combustion period is calculated from the laminar combustion speed S1 and the turbulence intensity ST1 by the following equation.

FLAME1 = SL1 × ST1 (18)
If there is gas turbulence in the combustion chamber 5, the gas combustion speed changes. Equation (18) takes into account the contribution (influence) to the combustion speed associated with this gas turbulence.

  In step 171, the initial combustion period BURN1 [deg] is calculated by the following equation.

BURN1 = {(NRPM × 6) × BR1 × V0}
/ (RPROBA × AF1 × FLAME1) (19)
However, AF1: Reaction area (fixed value) of flame kernel [m ² ],
The equation (19) and the equation (22) to be described later are derived from the following basic equation that the combustion period is obtained by dividing the mass of the combustion gas by the combustion speed. The equations (19) and (22) The numerator and denominator on the right-hand side do not immediately indicate the mass of combustion gas or the burning rate.

Combustion period [sec] = total mass in cylinder [g] / (unburned gas density [g / m ³ ]
× Flame surface area [m ² ] × Flame speed [m / sec])
... (Supplement 1)
Since the unburned gas density in the right side denominator of (Supplement 1) is a value obtained by dividing the unburned gas mass [g] by the unburned gas volume [m ³ ], the charging efficiency ITAC corresponding to the mass as in the conventional device. It cannot be said that the unburned gas density can be calculated accurately with the function of only. Therefore, experimental formulas shown in the above formula (19) and formula (22) to be described later are obtained for the first time by introducing a predetermined approximation to the formula (complement 1) while checking the experimental results.

  Here, BR1 on the right side of the equation (19) is a change amount of the combustion mass ratio from the combustion start timing to the end timing of the initial combustion period BURN1, and here BR1 = 2% is set. (NRPM × 6) on the right side of the equation (19) is a process for converting the unit from rpm to crank angle (deg). The reaction area AF1 of the flame kernel is set experimentally.

  Further, it can be assumed that the combustion chamber volume does not change during the initial combustion period. Therefore, when calculating the initial combustion period BURN1, the combustion chamber volume V0 at the start of combustion, which is the first combustion chamber volume, is employed.

Next, the flow of FIG. 12 is followed. In step 181, similarly to step 161 of FIG. 10, the volume VIVC [m ³ ] at the intake valve closing timing of the combustion chamber 5 calculated in step 12 of FIG. The temperature TINI [K] at the intake valve closing timing of the combustion chamber 5 calculated in step 13 of FIG. 5, the pressure PINI [Pa] at the intake valve closing timing of the combustion chamber 5 calculated in step 14 of FIG. The speed NRPM [rpm], the reaction probability RPROBA [%] calculated in step 15 of FIG. 5 is read, and the cylinder fresh air amount MACYL [g], the target equivalent ratio TFBYA, the internal inert gas amount MRES [g], The external inert gas amount MEGR [g] is read.

  Here, although an external EGR device is not shown in FIG. 1, as far as FIG. 12 is concerned, an explanation will be given on the premise of an engine equipped with an external EGR device. In this case, the external inert gas amount MEGR may be calculated using, for example, a known method (see Japanese Patent Laid-Open No. 10-141150). It should be noted that when an engine that does not include an external EGR device as in the present embodiment shown in FIG. 1 is used, it is sufficient to handle the external inert gas amount MEGR = 0. The calculation of the cylinder fresh air amount MACYL and the internal inert gas amount MRES will be described later with reference to FIG.

Steps 182 and 183 are the same as steps 163 and 164 in FIG. That is, in step 182, the effective compression ratio Ec at the compression top dead center. 2 is calculated. Effective compression ratio Ec 2 is also a dimensionless value like the effective compression ratio Ec of the above equation (12). The value divided by VIVC.

Ec 2 = f13 (VTDC, VIVC) = VTDC / VIVC
... (43)
In equation (43), the volume VTDC at the compression top dead center of the combustion chamber 5 is constant regardless of the operating conditions, and may be stored in the memory of the engine controller 31 in advance.

In step 183, the temperature increase rate TCOMP due to adiabatic compression in the combustion chamber 5 during the period from the intake valve closing timing IVC to the compression top dead center. 2 is an effective compression ratio Ec as shown in the following equation: 2 is calculated.

TCOMP 2 = f14 (Ec 2)
= Ec 2 ^ (κ-1) (44)
Where κ: specific heat ratio,
A table having the same characteristics as in FIG. 11 is stored in advance in the memory of the engine controller 31 and the effective compression ratio Ec. By searching the table from 2, the temperature rise rate TCOMP 2 can also be obtained.

  In step 184, the total gas mass MGAS [g] in the combustion chamber 5 is calculated from the cylinder fresh air amount MACYL, the target equivalent ratio TFBYA, the internal inert gas amount MRES, and the external inert gas amount MEGR by the following equation.

MGAS = MACYL × (1 + TFBYA / 14.7) + MRES + MEGR
... (45)
“1” in parentheses on the right side of the equation (45) is a fresh air, and “TFBYA / 14.7” is a fuel.

  In step 185, the total gas mass MGAS of the combustion chamber 5, the cylinder fresh air amount MACYL, and the target equivalent ratio TFBYA are used to calculate the temperature increase amount (combustion increase temperature) TBURN [K] due to the combustion of the air-fuel mixture using the following equation. .

TBURN = {MACYL × (TFBYA / 14.7) × BRk × Q}
/ (Cv × MGAS) (46)
Where Q is the constant calorific value of the fuel,
BRk: Combustion mass ratio of fuel in cylinder,
Cv: constant volume specific heat,
The numerator on the right side of the equation (46) means the total heat generated by the fuel in the cylinder [J], and the denominator means the temperature increase rate per unit generated heat [J / K]. That is, the equation (46) is an approximate equation applied to the thermodynamic formula.

  Here, the combustion mass ratio BRk of the in-cylinder fuel is adapted in advance through experiments or the like. For example, 60% / 2 = 30% is set. In this embodiment, since the combustion mass ratio BR reaches about 60% as the combustion period, the intermediate 30% is set as BRk.

  Since the constant calorific value Q of fuel varies depending on the type of fuel, it is obtained in advance by experiments or the like according to the type of fuel. The constant volume specific heat Cv is a value of 2 to 3, and the representative value is adapted beforehand by an experiment or the like. However, the calculation accuracy can be further improved by obtaining the value of the constant volume specific heat Cv from the composition and temperature of the air-fuel mixture.

In step 186, the temperature TTDC [K] at the compression top dead center of the combustion chamber 5 is changed from the temperature TINI at the intake valve closing timing of the combustion chamber 5 to the temperature increase rate TCOMP to the compression top dead center. Multiply by 2 and add the combustion rise temperature TBURN to the multiplication value, that is, the following equation is used.

TTDC = TINI × TCOMP 2 + TBURN
... (47)
In step 187, the temperature TTDC and the volume VTDC at the compression top dead center of the combustion chamber 5 and the pressure PINI, the volume VIVC and the temperature TINI at the closing timing of the intake valve of the combustion chamber 5 are The pressure PTDC [K] is calculated.

PTDC = PINI × VIVC × TTDC / (VTDC × TINI)
... (48)
Equation (48) is obtained using the equation of state. That is, the following equation of state is established using the pressure, volume and temperature (PINI, VIVC, TINI) at the intake valve closing timing.

PINI x VIVC = n · R · TINI (Supplement 2)
Where n is the number of moles
R: gas constant,
Since the volume is almost equal in the vicinity of the compression top dead center, the following equation of state is established using the pressure, volume and temperature (PTDC, VTDC, TTDC) at the compression top dead center.

PTDC × VTDC = n · R · TTDC (Supplement 3)
When n · R is eliminated from both (complement 3) and (complement 2) and PTPT is solved, the above equation (48) is obtained.

  In step 188, similarly to step 168 of FIG. 10, a laminar combustion speed SL2 [m / sec] in the main combustion period is calculated by the following equation (known).

SL2 = f15 (TTDC, PTDC)
= SLstd × (TTDC / Tstd) ^2.18 × (PTDC / Pstd) ^−0.16
... (49)
Where Tstd: reference temperature [K],
Pstd: Reference pressure [Pa]
SLstd: reference laminar burning velocity at reference temperature Tstd and reference pressure Pstd
[M / sec],
TTDC: temperature [K] at the compression top dead center of the combustion chamber 5;
PTDC: pressure [Pa] at the compression top dead center of the combustion chamber 5
The explanation of the equation (49) is the same as the equation (16). That is, the reference temperature Tstd, the reference pressure Pstd, and the reference laminar combustion speed SLstd in the equation (49) are values determined in advance by experiments. Under a pressure of 2 bar or more, which is a normal pressure in the combustion chamber 5, the pressure term (PTDC / Pstd) ^−0.16 in the equation (49) becomes a small value. Accordingly, it is also possible to define the reference laminar combustion speed SLstd only by the reference temperature Tstd with the pressure term (PTDC / Pstd) ^−0.16 being a constant value. Therefore, when the reference temperature Tstd is 550 [K], the reference laminar combustion speed SLstd is 1.0 [m / sec], and the pressure term is 0.7, the temperature TTDC at the compression top dead center and the laminar combustion The relationship with the speed SL2 can be approximately defined by the following equation.

SL2 = f16 (TTDC)
= 1.0 × 0.7 × (TTDC / 550) ^2.18
... (50)
In step 189, the turbulence intensity ST2 of the gas flow during the main combustion period is calculated. The turbulence intensity ST2 of the gas flow can be expressed by the following equation as a function of the engine speed NRPM, similarly to the turbulence intensity ST1 of the gas flow during the initial combustion period.

ST2 = f17 (NRPM) = C2 × NRPM (20)
Where C2 is a constant,
It is also possible to obtain the turbulence intensity ST2 from a table using the rotation speed as a parameter.

  In step 190, from the laminar combustion speed SL2 [m / sec] and the turbulence intensity ST2 of the gas flow in the main combustion period, the combustion speed FLAME2 [m / sec] in the main combustion period is calculated by the following equation.

FLAME2 = SL2 × ST2 (21)
However, SL2: Laminar burning velocity [m / sec],
Equation (21) considers the contribution to the combustion speed associated with gas turbulence, as in Equation (18).

  In step 191, the main combustion period BURN2 [deg] is calculated by the following equation similar to the equation (19).

BURN2 = {(NRPM × 6) × (BR2 × VTDC)}
/ (RPROBA × AF2 × FLAME2) (22)
However, AF2: reaction area [m ² ] of the flame kernel,
Here, BR2 on the right side of the equation (22) is a change amount of the combustion mass ratio from the start timing to the end timing of the main combustion period. Since the combustion mass ratio BR becomes 2% at the end of the initial combustion period, and then the main combustion period starts and the combustion mass ratio BR reaches 60% and the main combustion period ends, BR2 = 60 % -2% = 58% is set. AF2 is an average reaction area in the growth process of the flame kernel, and is set to a fixed value experimentally determined in advance, like AF1 in the equation (19).

  During the main combustion period, the combustion chamber volume changes with the compression top dead center interposed therebetween. That is, it can be considered that the compression top dead center position exists at the approximate center between the start timing of the main combustion period and the end timing of the main combustion period. In addition, the combustion chamber volume does not change much in the vicinity of the compression top dead center even if the crank angle changes. Therefore, the combustion chamber volume in the main combustion period is represented by the combustion chamber volume VTDC at the compression top dead center.

  FIG. 13 is for calculating the basic ignition timing MBTCAL [degBTDC], and is executed at regular intervals (for example, every 10 msec). This is executed following the flow that is executed later in FIGS.

  In step 41, the initial combustion period BURN1 [deg] calculated in step 171 of FIG. 10, the main combustion period BURN2 [deg] calculated in step 191 of FIG. 12, and calculated in step 16 of FIG. The reference crank angle θPMAX [degATDC] and the ignition timing dead time equivalent crank angle IGNDEAD [deg] are read.

  The calculation of the above-mentioned ignition dead time equivalent crank angle IGNDEAD will be described with reference to the flow of FIG. 51 (refer to Japanese Patent Application No. 2003-109040 for details). The flow in FIG. 51 is executed after the combustion periods BURN1 and BURN2 shown in the flow in FIGS. 10 and 12 are calculated and before the flow in FIG. 13 is executed.

  Here, the ignition dead time DEADTIME [μsec] is first calculated, and the ignition dead time DEADTIME is converted into a crank angle. The dead ignition time DEADTIME is a delay time from when the ignition command is received until when combustion actually starts in the combustion chamber 5. There are three factors that influence the ignition dead time, namely, the pressure and temperature of the combustion chamber 5 and the air-fuel ratio of the air-fuel mixture, and the influence of these factors on the ignition dead time is calculated as independent of each other.

51, in step 411, the basic ignition timing MBTCAL [degBTDC] calculated in step 43 of FIG. 13, the volume VIVC [m ³ ] at the intake valve closing timing of the combustion chamber 5 calculated in step 12 of FIG. The temperature TINI [K] at the intake valve closing timing of the combustion chamber 5 calculated in step 13 of FIG. 5, the pressure PINI [Pa] at the intake valve closing timing of the combustion chamber 5 calculated in step 14 of FIG. The target equivalent ratio TFBYA and the engine speed NRPM [rpm] are read.

  In steps 412 to 415, the effective compression ratio Ec (= V0 / VIVC) at the combustion start timing is calculated in the same manner as steps 162 to 167 in FIG. 10, and the temperature of the combustion chamber 5 at the combustion start timing is calculated using the compression ratio Ec. T0 and the pressure P0 at the combustion start timing of the combustion chamber 5 are calculated.

T0 = TINI × Ec ^ (κ−1) (10-1)
P0 = PINI × Ec ^ κ (10-2)
Where κ: specific heat ratio,
In step 416, an ignition dead time basic value DEADTIME0 [μsec] is calculated by the following equation as a function of the pressure P0 at the combustion start timing of the combustion chamber 5.

DEADTIME0 = f21 (P0) (10-3)
For example, the ignition dead time basic value DEADTIME0 may be obtained by searching a table having the contents shown in FIG. 44 from the pressure P0 at the combustion start timing of the combustion chamber 5. The ignition dead time basic value DEADTIME0 is a value when the theoretical air-fuel ratio is set and the temperature at the combustion start timing of the combustion chamber 5 is the reference temperature, and becomes larger as the pressure P0 is higher as shown in FIG. The reason for the increased ignition dead time at high pressure is that the air-fuel mixture is less likely to vaporize at high pressure.

  Steps 417 to 419 are parts for calculating two correction coefficients for the ignition dead time. That is, when the temperature at the combustion start timing of the combustion chamber 5 falls below the reference temperature, or when the air-fuel ratio of the air-fuel mixture deviates from the stoichiometric air-fuel ratio, the ignition dead time basic value DEADTIME0 does not match the actual value, the temperature correction coefficient Kdtmt An excess air ratio correction coefficient Kdtmlmb is introduced.

  First, at step 417, a temperature correction coefficient Kdtmt of the ignition dead time is calculated by the following equation as a function of the temperature T0 at the combustion start timing of the combustion chamber 5.

Kdtmt = f22 (T0) (10-4)
For example, the temperature correction coefficient Kdtmt may be obtained by searching a table having the contents shown in FIG. 45 from the temperature T0 at the combustion start timing of the combustion chamber 5. As shown in FIG. 45, the temperature correction coefficient Kdtmt is 1.0 when the temperature is equal to or higher than the reference temperature, and increases as the temperature becomes lower than the reference temperature. That is, as the temperature T0 is lower, the ignition dead time becomes longer.

  In step 418, the reciprocal of the target equivalent ratio TFBYA is determined as the target excess air ratio TLAMBDA, that is, the target excess air ratio TLAMBDA is obtained by the following equation.

TLAMBDA = 1 / TFBYA (10-5)
In step 419, the excess air ratio correction coefficient Kdtmlmb for the ignition dead time is calculated by the following equation as a function of the target excess air ratio TLAMBDA.

Kdtmlmb = f23 (TLAMBDA) (10-6)
For example, the excess air ratio correction coefficient Kdtmlmb may be obtained by searching a table having the contents shown in FIG. 46 from the target excess air ratio TLAMBDA. As shown in FIG. 46, the excess air ratio correction coefficient Kdtmlmb is a minimum value of 1.0 when the target excess air ratio TLAMBDA is 1 (that is, at the stoichiometric air-fuel ratio), and is a value that is larger or larger than this. That is, the ignition dead time becomes longer even when the air-fuel ratio deviates from the stoichiometric air-fuel ratio to the rich side or to the lean side.

  In step 420, the ignition dead time DEADTIME [μsec] is calculated by correcting the ignition dead time basic value DEADTIME0 with two correction coefficients Kdtmt and Kdtmlmb.

DEADTIME = DEADTIME0 × Kdtmt × Kdtmlmb
... (10-7)
Here, the pressure P0 is corrected to the basic value (DEADTIME0) by the temperature T0 and the air-fuel ratio (TLAMBDA). However, the present invention is not limited to this, and the pressure P0 and the empty value are determined based on the temperature T0. It may be corrected by the fuel ratio (TLAMBDA) or may be corrected by the temperature T0 and the pressure P0 based on the air / fuel ratio (TLAMBDA). In addition, the factors affecting the ignition dead time are not limited to this, and there are charging efficiency and inert gas rate (internal inert gas rate MRES and external inert gas rate). Thus, the ignition dead time can be calculated. However, it is not always necessary to consider all five factors, and the ignition dead time may be calculated using at least one factor as a parameter.

  Finally, in step 421, the ignition dead time equivalent crank angle IGNDEAD [deg] is calculated. The ignition dead time equivalent crank angle IGNDEAD is a crank angle section from the timing at which the engine controller 31 outputs a signal for cutting off the primary current of the ignition coil 13 until the ignition plug 14 actually ignites, and can be expressed by the following equation. .

IGNDEAD = f5 (DEADTIME, NRPM) (10-8)
The expression (10-8) is for calculating the ignition dead time equivalent crank angle IGNDEAD, which is the crank angle corresponding to the ignition dead time DEADTIME, from the engine speed NRPM.

  Returning to FIG. 13, in step 42, the sum of the initial combustion period BURN1 and the main combustion period BURN2 is calculated as the combustion period BURN [deg].

  In step 43, the basic ignition timing MBTCAL [degBTDC] is calculated by the following equation.

MBTCAL = BURN−θPMAX + IGNDEAD (23)
In step 44, the value obtained by subtracting the ignition dead time equivalent crank angle IGNDEAD from the basic ignition timing MBTCAL is calculated as the previous combustion start timing MBTCYCL [degBTDC].

  Assuming that the basic ignition timing MBTCAL calculated in step 43 is used as the ignition timing command value for the current cycle, the previous combustion start timing MBTCYCL calculated in step 44 is calculated until the ignition timing for the next cycle is reached. Used in step 162.

  FIG. 14 is for calculating the internal inert gas ratio MRESFR in the combustion chamber 5 and is executed at regular intervals (for example, every 10 msec). This flow is executed prior to the flow of FIG.

  In step 51, the output of the air flow meter 32 and the target equivalent ratio TFBYA are read. In step 52, based on the output of the air flow meter 32, a new air amount (cylinder fresh air amount) MACYL flowing into the combustion chamber 5 is calculated. As a method for calculating the cylinder fresh air amount MACYL, a known method may be used (see JP 2001-50091 A).

  In step 53, an internal inert gas amount MRES in the combustion chamber 5 is calculated. The calculation of the internal inert gas amount MRES will be described with reference to the flow of FIG.

  In FIG. 15 (subroutine of step 53 in FIG. 14), in step 61, an inert gas amount MRESCYL at the exhaust valve closing timing EVC in the combustion chamber 5 is calculated. The calculation of the inert gas amount MRESCYL will be further described with reference to the flowchart of FIG.

  In FIG. 16 (subroutine of step 61 in FIG. 15), in step 71, the exhaust valve closing timing EVC [degBTDC], the exhaust temperature TEXH [K] detected by the temperature sensor 45, the exhaust pressure PEXH [kPa] detected by the pressure sensor 46 ].

  Here, just as the intake valve closing timing IVC is known from the command value given to the intake VTC mechanism 27, the exhaust valve closing timing EVC is also known from the command value given to the exhaust VTC mechanism 28.

  In step 72, the volume VEVC of the combustion chamber 5 at the exhaust valve closing timing EVC is calculated. This may be obtained by searching a table using the exhaust valve closing timing as a parameter, similarly to the volume VIVC at the intake valve closing timing IVC. That is, when the exhaust valve VTC mechanism 28 is provided, the volume VEVC at the exhaust valve closing timing EVC of the combustion chamber 5 may be obtained by searching the table shown in FIG. 23 from the exhaust valve closing timing EVC. When the exhaust VTC mechanism 28 is not provided, a constant value can be given.

  Although not shown, when a mechanism for changing the compression ratio is provided, the combustion chamber volume VEVC at the exhaust valve closing timing corresponding to the amount of change in the compression ratio is obtained from the table. When a mechanism for changing the compression ratio in addition to the exhaust VTC mechanism 28 is provided, the combustion chamber volume at the exhaust valve closing timing is obtained by searching a map corresponding to the exhaust valve closing timing and the compression ratio change amount.

  In step 73, the gas constant REX of the inert gas in the combustion chamber 5 is obtained by searching the table shown in FIG. 24 from the target equivalent ratio TFBYA. As shown in FIG. 24, the gas constant REX of the inert gas is the smallest when the target equivalent ratio TFBYA is 1.0, that is, the stoichiometric air-fuel ratio, and becomes larger whether it is larger or smaller.

  In step 74, the temperature TEVC of the combustion chamber 5 at the exhaust valve closing timing EVC is estimated based on the exhaust temperature TEXH. For simplicity, the exhaust temperature TEXH may be set as TEVC as it is. Note that the temperature TEVC of the combustion chamber 5 at the closing timing of the exhaust valve changes depending on the amount of heat corresponding to the fuel injection amount of the injector 21. Therefore, if such characteristics are taken into consideration, the calculation accuracy of TEVC is improved.

  In step 75, the pressure PEVC at the exhaust valve closing timing EVC of the combustion chamber 5 is calculated based on the exhaust pressure PEXH. Simply, the exhaust pressure PEXH may be set to PEVC.

  In step 76, from the volume VEVC at the exhaust valve closing timing EVC of the combustion chamber 5, the temperature TEVC at the exhaust valve closing timing EVC, the pressure PEVC at the exhaust valve closing timing EVC, and the inert gas gas constant REX, the exhaust valve of the combustion chamber 5 is obtained. The inert gas amount MRESCYL at the closing timing EVC is calculated by the following equation.

MRESCYL = (PEVC × VEVC) / (REX × TEVC) (24)
When the calculation of the inert gas amount MRESCYL at the exhaust valve closing timing EVC of the combustion chamber 5 is completed in this way, the processing returns to FIG. 15, and in step 62, the overlap of the intake and exhaust valves 15 and 16 (“O / L” in the figure). The amount of inactive gas MRESOL during the overlap is calculated, which is the amount of inert gas that is blown back from the exhaust side to the intake side.

  The calculation of the inert gas amount MRESOL will be described with reference to the flowchart of FIG.

  In FIG. 17 (subroutine of step 62 in FIG. 15), in step 81, the intake valve opening timing IVO [degBTDC], the exhaust valve closing timing EVC [degBTDC], and the exhaust valve of the combustion chamber 5 calculated in step 74 of FIG. The temperature TEVC at the closing timing EVC is read.

  Here, since the intake valve opening timing IVO is a timing earlier than the intake valve closing timing IVC by the opening angle of the intake valve 15, the opening angle of the intake valve 15 (which is known in advance) from the intake valve closing timing IVC. Can be sought.

  In step 82, the overlap amount VTCOL [deg] of the intake and exhaust valves is calculated from the following equation from the intake valve opening timing IVO and the exhaust valve closing timing EVC.

VTCOL = IVO + EVC (25)
For example, the intake valve opening timing IVO is at the intake top dead center position when the intake VTC mechanism 27 actuator is not energized, and the intake valve opening timing is advanced from the intake top dead center when the intake VTC mechanism 27 actuator is energized. The exhaust valve closing timing EVC is at the exhaust top dead center when the exhaust VTC mechanism 28 actuator is not energized, and the exhaust valve closing timing EVC is at the exhaust top dead center when the exhaust valve VTC mechanism 28 actuator is energized. In the case of more advanced characteristics, the sum of IVO and EVC becomes the overlap amount VTCOL of the intake and exhaust valves.

  In step 83, the accumulated effective area ASUMOL during the overlap is calculated by searching the table shown in FIG. 25 from the overlap amount VTCOL of the intake and exhaust valves. As shown in FIG. 25, the integrated effective area ASUMOL during the overlap is a value that increases as the overlap amount VTCOL of the intake and exhaust valves increases.

  Here, FIG. 26 is an explanatory diagram of the integrated effective area ASUMOL during the overlap of the intake and exhaust valves, where the horizontal axis indicates the crank angle, and the vertical axis indicates the respective opening areas of the intake valve 12 and the exhaust valve 15. Yes. The effective opening area at any time during the overlap is the smaller of the exhaust valve opening area and the intake valve opening area. The integrated effective area ASUMOL in the entire period during the overlap is an integral value (hatched portion in the figure) during the period in which the intake valve 15 and the exhaust valve 16 are open.

  By calculating the accumulated effective area ASUMOL during the overlap in this way, the overlap amount between the intake valve 15 and the exhaust valve 16 can be approximated as one orifice (outflow hole), and the state of the exhaust system and The gas flow rate passing through the virtual orifice can be simply calculated from the state of the intake system.

  In step 84, the specific heat ratio SHEATR of the inert gas remaining in the combustion chamber 5 is obtained by searching the map shown in FIG. 27 from the target equivalent ratio TFBYA and the temperature TEVC at the exhaust valve closing timing EVC of the combustion chamber 5. calculate. As shown in FIG. 27, the specific heat ratio SHEATR of the inert gas remaining in the combustion chamber is the smallest when the target equivalent ratio TFBYA is in the vicinity of 1.0, and it is larger or smaller than that. Further, under the condition where the target equivalent ratio TFBYA is constant, the temperature TEVC at the exhaust valve closing timing EVC of the combustion chamber 5 becomes smaller as the temperature becomes higher.

  In step 85, a supercharging determination flag TBCRG and a choke determination flag CHOKE are set. The setting of the supercharging determination flag TBCRG and the choke determination flag CHOKE will be described with reference to the flowchart of FIG.

  In FIG. 18 (subroutine of step 85 in FIG. 17), in step 101, the intake pressure PIN detected by the intake pressure sensor 44 and the pressure PEVC at the exhaust valve closing timing EVC of the combustion chamber 5 calculated in step 75 of FIG. Is read.

  In step 102, an intake exhaust pressure ratio PINBYEX is calculated from the intake pressure PIN and the pressure PEVC at the exhaust valve closing timing EVC of the combustion chamber 5 by the following equation.

PINBYEX = PIN / PEVC (26)
This intake / exhaust pressure ratio PINBYEX is an unknown number, and 1 is compared with this in step 103. When the intake / exhaust pressure ratio PINBYEX is 1 or less, it is determined that there is no supercharging, and the routine proceeds to step 104 where the supercharging determination flag TBCRG (initially set to zero) = 0.

  If the intake / exhaust pressure ratio PINBYEX is greater than 1, it is determined that there is supercharging, and the routine proceeds to step 105 where the supercharging determination flag TBCRG = 1.

  In Step 106, the specific heat ratio MIXAIRSHR of the mixture is obtained by searching the table shown in FIG. 28 from the target equivalent ratio TFBYA read in Step 51 of FIG. Replace with SHEATR. As shown in FIG. 28, the specific heat ratio MIXAIRSHR of the air-fuel mixture is a value that increases as the target equivalent ratio TFBYA decreases.

  In steps 106 and 107, the specific heat ratio SHEATR of the inert gas is replaced with the specific heat ratio MIXAIRSHR of the air-fuel mixture in consideration of supercharging such as turbocharging or inertial supercharging. That is, during supercharging, the gas flow during the overlap of the intake / exhaust valve is directed (blows through) from the intake system to the exhaust system. In this case, the specific heat ratio of the gas passing through the virtual orifice is the specific heat of the inert gas. By changing the ratio to the specific heat ratio of the air-fuel mixture, the amount of gas blown through is accurately estimated, and the amount of internal inert gas is accurately calculated.

  In Step 108, based on the specific heat ratio SHEATR of the inert gas calculated in Step 84 of FIG. 17 or Steps 106 and 107 of FIG. 18, the minimum and maximum choke determination thresholds SLCHOKE and SLCHOKEH are calculated by the following equations. To do.

SLCHOKER = {2 / (SHEATR + 1)}
^ {SHEATR / (SHEATR-1)} (27a)
SLCHOKEH = {− 2 / (SHEATR + 1)}
^ {-SHEATR / (SHEATR-1)} (27b)
These choke determination threshold values SLCHOKE and SLCHOKEH calculate the limit value for choking.

  If it is difficult to calculate each power of (27a) right side and (27b) right side in step 108, the calculation results of equations (27a) and (27b) are used as the minimum choke determination threshold value SLCHOKEL table and maximum choke determination. The threshold value SLCHOKEH table may be stored in advance in the memory of the engine controller 31 and obtained by searching the table from the specific heat ratio SHEATR of the inert gas.

  In step 109, it is determined whether or not the intake / exhaust pressure ratio PINBYEX is within the range of not less than the minimum choke determination threshold value SLCHOKEEL and not more than the maximum choke determination threshold value SLCHOKEH, that is, not in the choke state. If the intake / exhaust pressure ratio PINBYEX is within the range, it is determined that there is no choke, and the routine proceeds to step 110 where the choke determination flag CHOKE (initially set to zero) = 0.

  If the intake / exhaust pressure ratio P1NBYEX is not within the range, it is determined that choke is present, and the routine proceeds to step 111 where the choke determination flag CHOKE = 1.

  When the setting of the supercharging determination flag and the choke determination flag is thus completed, the process returns to FIG. 17 and the following four cases are performed in steps 86 to 88.

<1> When supercharging determination flag TBCRG = 0 and choke determination flag CHOKE = 0 <2> When supercharging determination flag TBCRG = 0 and choke determination flag CHOKE = 0 <3> Supercharging determination flag TBCRG = 0 and choke When determination flag CHOKE = 1 <4> When supercharging determination flag TBCRG = 1 and choke determination flag CHOKE = 0 When the above <1>, the routine proceeds to step 89 and overlaps when there is no supercharging and no choke If the average blown back inert gas flow rate MRESOLtmp1 is <2>, the process proceeds to step 90, and the blown back inert gas flow rate MRESOLtmp2 during the overlap when there is no supercharging and choke is present is step 91 when <3>. Go on to overlap when there is supercharging and no choke The average blowback inert gas flow rate MRESOLtmp3 in the case of <4> is advanced to step 92 to calculate the blowback inert gas flow rate MRESOLtmp4 with supercharging and with choke, respectively. Move to active gas flow rate MRESOLtmp.

Here, calculation of the inert gas flow rate MRESOLtmp1 during the overlap when there is no supercharging and no choke will be described with reference to the flow of FIG. 19. In step 121 of FIG. 19 (subroutine of step 89 in FIG. 17), step 73 in FIG. , 75, the gas constant REX of the inert gas, and the pressure PEVC when the exhaust valve of the combustion chamber 5 is closed are read.

  In step 122, based on the gas constant REX of the inert gas and the temperature TEVC at the exhaust valve closing timing of the combustion chamber 5 read in step 81 of FIG. 17, a density term MRSOLD used in a gas flow rate calculation formula described later. Is calculated by the following equation.

MRSOLD = SQRT {1 / (REX × TEVC)} (28)
Here, “SQRT” on the right side of equation (28) is a function that calculates the square root of the value in the parenthesis on the right.

  If the square root of the density term MRSOLD is difficult to calculate, the calculation result of equation (28) is stored in advance in the memory of the engine controller 31 as a map, and the gas constant REX and the temperature of the combustion chamber 5 at the exhaust valve closing timing are stored. You may obtain | require by searching the map from TEVC.

  In step 123, based on the specific heat ratio SHEATR of the inert gas calculated in step 84 of FIG. 17 and the intake / exhaust pressure ratio PINBYEX calculated in step 102 of FIG. The pressure difference term MRSOLP used is calculated by the following equation.

MRSOLP = SQRT [SHEATR / (SHEATR-1)
× {PTNBYEX ^ (2 / SHEATR)
-PTNBYEX ^ ((SHEATR + 1) / SHEATR)}] (29)
In step 124, from the density term MRSOLD, the pressure difference term MRSOLP, and the pressure PEVC at the exhaust valve closing timing of the combustion chamber 5, the blow-back inert gas flow rate MRESOLtmp1 during overlap without supercharging and without choke is expressed by the following equation. In step 125, the calculated value is transferred to the blown back inert gas flow rate MRESOLtmp.

MRESOLtmp1 = 1.4 × PEVC × MRSOLD × MRSOLP (30)
Next, the calculation of the blown back inert gas flow rate when there is no supercharging and when there is a choke will be described with reference to the flow of FIG. 20. In FIG. 20 (subroutine of step 90 of FIG. 17), in steps 131 and 132, steps 121 and 122 of FIG. In the same manner as described above, the gas constant REX of the inert gas and the pressure PEVC at the time of closing the exhaust valve of the combustion chamber 5 are read, and the density term MRSOLD is calculated from the above equation (28).

  In step 133, the choke pressure difference term MRSOLPC is calculated by the following equation based on the specific heat ratio SHEATR of the inert gas calculated in step 84 of FIG.

MRSOLPC = SQRT [SHEATR × {2 / (SHEATR + 1)} ^ {(SHEATR + 1) / [SHEATR-1)}] (31)
If it is difficult to calculate the power and square root of equation (31), the calculation result of equation (31) is stored in advance in the memory of the engine controller 31 as a table of choke pressure difference term MRSOLPC. Alternatively, it may be obtained by searching the table from the specific heat ratio SHEATR of the inert gas.

  In step 134, from the density term MRSOLD, the choke pressure difference term MRSOLPC, and the pressure PEVC when the combustion chamber 5 is closed, the inert gas flow rate MRESOLtmp2 blown back during overlap without supercharging and with choke is calculated. In step 135, the calculated value is transferred to the blown back inert gas flow rate MRESOLtmp.

MRESOLtmp2 = PEVC × MRSOLD × MRSOLPC (32)
Next, calculation of the blowback gas flow rate with supercharging and without choke will be described with reference to the flow of FIG. 21. In FIG. 21 (subroutine of step 91 in FIG. 17), in step 141, the intake pressure PIN detected by the intake pressure sensor 44 is explained. Is read.

  In step 142, the supercharging pressure difference term MRSOLPT is calculated from the specific heat ratio SHEATR of the inert gas calculated in steps 106 and 107 in FIG. 18 and the intake / exhaust pressure ratio PINBYEX calculated in step 102 in FIG. 18. Is calculated by the following equation.

MRSOLPT = SQRT [SHEATR / (SHEATR-1)
× {PINBYEX ^ (-2 / SHEATR)
-PINBYEX ^ (-(SHEATR + 1) / SHEATR)}] (33)
If the power calculation and the square root calculation of Expression (33) are difficult, the calculation result of Expression (33) is stored in advance in the memory of the engine controller 31 as a map of the supercharging pressure difference term MRSOLPT, You may obtain | require by searching the map from the specific heat ratio SHEATR of an inert gas, and the intake-exhaust pressure ratio PINBYEX.

  In step 143, based on the pressure difference term at the time of supercharging MRSOLPT and the intake pressure PIN, the inactive gas flow rate MRESOLtmp3 during the overlap with supercharging and without choke is calculated by the following equation, and the calculated value is calculated in step 143. At 144, the flow returns to the blown back inert gas flow rate MRESOLtmp.

MRESOLtmp3 = −0.152 × PIN × MRSOLPT (34)
Here, by setting the blown back inert gas flow rate MRESOLtmp3 in the equation (34) to a negative value, the gas flow rate of the air-fuel mixture blown from the intake system to the exhaust system during the overlap can be expressed.

Next, the calculation of the flow rate of the inert gas blown back during overlap with supercharging and with choke will be described with reference to the flow of FIG. 22. In FIG. 22 (subroutine of step 92 in FIG. 17), in steps 151 and 152, the step of FIG. Similarly to 141, the intake pressure PIN detected by the intake pressure sensor 44 is read, and the choke pressure difference term MRSOLPC is calculated by the aforementioned equation (31) as in step 132 of FIG.

  In step 153, based on the choke pressure difference term MRSOLPC and the intake pressure PIN, the overlap blow-back gas flow rate MRESOLtmp4 with supercharging and with choke is calculated by the following equation, and the calculated value is exceeded in step 154. Transfer to blown inert gas flow rate MRESOLtmp during lap.

MRESOLtmp4 = −0.108 × PIN × MRSOLPC (35)
Here, the blown back inert gas flow rate MRESOLtmp4 of the equation (35) can also represent a gas flow rate of the air-fuel mixture blown from the intake side to the exhaust side during the overlap, similarly to MRESOLtmp3.

  In this way, when the calculation of the blown back inert gas flow rate MRESOLtmp during the overlap divided according to the combination of the presence or absence of supercharging and the presence or absence of choke is completed, the process returns to FIG. From the inert gas flow rate MRESOLtmp and the integrated effective area ASUMOL during the overlap period, the blown back inert gas amount MRESOL during the overlap is calculated by the following equation.

MRESOL = (MRESOLtmP × ASUMOL × 60)
/ (NRPM × 360) (36)
When the calculation of the blown back inert gas amount MRESSOL is completed in this way, the process returns to FIG. 15, and in step 63, the inert gas amount MRESCYL at the exhaust valve closing timing EVC in the combustion chamber 5 and the blowback during overlap are returned. The internal inert gas amount MRES is calculated by adding the gas amount MRESOL, that is, the following equation.

MRES = MRESCYL + MRESSOL (37)
As described above, the flow rate of the inert gas blown back during overlap (MRESOLtmp3, MRESOLtmp4) becomes negative when there is supercharging, and therefore, the amount of blown inert gas MRESOL during overlap of the above equation (36) also becomes negative. According to the equation (37), the internal inert gas amount is reduced by the amount of the blown back inert gas amount MRESOL during the overlap.

  When the calculation of the internal inert gas amount MRES is completed in this way, the flow returns to FIG. 14. In step 54, using this internal inert gas amount MRES and the target equivalent ratio TFBYA, the internal inert gas rate MRESFR is calculated by the following equation. (Ratio of the amount of internal inert gas to the total amount of gas in the combustion chamber 5) is calculated.

MRESFR = MRES
/{MRES+MACYL×(1+TFBYA/14.7)} (38)
This completes the calculation of the internal inert gas ratio MRESFR.

  As described above, according to the present embodiment, the internal inert gas amount MRES is configured by the inert gas amount MRESCYL when the exhaust valve of the combustion chamber 5 is closed and the blowback gas amount MRESOL during the overlap of the intake and exhaust valves. In this case, the temperature TEV and pressure PEVC at the closing timing of the exhaust valve in the combustion chamber 5 are calculated (steps 74 and 75 in FIG. 16), and these temperature TEVC, pressure PEVC and inert gas are calculated. Since the inert gas amount MRESCYL at the exhaust valve closing timing of the combustion chamber 5 is calculated from the state constant (Equation (24) above) based on the gas constant REX (see step 76 of FIG. 16), Even during transient operation in which the amount of state (PEVC, VEVC, TEVC) inside the combustion chamber 5 changes every moment, the combustion chamber 5 can be accurately obtained regardless of the operating conditions. The inert gas amount MRESCYL in the exhaust valve closing timing can be calculated (estimated).

  In addition, based on the temperature TEVC and pressure PEVC of the combustion chamber 5 when the exhaust valve is closed, the gas constant REX and specific heat ratio SHEATR of the inert gas, and the intake pressure PIN, the blow-back inert gas flow rate (MRESOLtmp1, MRESOLtmp2) during the overlap is calculated. This was calculated (see FIGS. 19 and 20), and this gas flow rate was multiplied by the integrated effective area ASUMOL during the overlap to calculate the amount of blown back gas MRESOL during the overlap (see step 93 in FIG. 17). Therefore, the overlapped blow-back gas amount MRESOL can be calculated (estimated) with high accuracy.

  As described above, if both the inert gas amount MRESCYL and the overlapped blow-back gas amount MRESSOL in the combustion chamber 5 at the closing timing of the exhaust valve can be calculated (estimated) with high accuracy, the internal inert gas amount MRES, which is the sum of them, can also be accurately calculated. The internal inert gas ratio MRESFR calculated based on the internal inert gas amount MRES that can be estimated with high accuracy can be calculated (estimated). By making use of the temperature TINI at the intake valve closing timing IVC (see step 13 in FIG. 5), the temperature TINI at the intake valve closing timing IVC in the combustion chamber 5 can be accurately calculated. In addition, the engine can be appropriately controlled by making use of the internal inert gas amount MRES that can be accurately estimated for the fuel injection amount, valve opening / closing timing (overlap amount), and the like. .

  Further, since the gas constant REX of the inert gas and the specific heat ratio SHEATR of the inert gas are values corresponding to the target equivalent ratio TFBYA (see FIGS. 24 and 27), the operation is performed at an air-fuel ratio that deviates from the theoretical air-fuel ratio. (E.g. during lean operation where the air / fuel ratio is leaner than the stoichiometric air / fuel ratio, in order to stabilize the engine's originally unstable state, such as during cold start, the engine is on the rich side of the stoichiometric air / fuel ratio. Immediately after starting the engine operating at the air-fuel ratio, since the same large output is required, the exhaust valve closing timing of the combustion chamber 5 is also applied during full load operation where the air-fuel ratio is richer than the stoichiometric air-fuel ratio. Inert gas amount MRESCYL, overlapped blow-back gas amount MRESSOL, total internal inert gas amount MRES, and internal inert gas ratio MRESFR based on this are accurately calculated. It can be.

  Further, since the accumulated effective area ASUMOL during the overlap period is defined as the area of the virtual orifice, and it is assumed that the exhaust gas blows through the virtual orifice from the combustion chamber 5 to the intake system, the amount of the blown back inert gas amount MRESOL during the overlap is assumed. Calculation is simplified.

  This completes the description of the calculation of the internal inert gas ratio MRESFR in the combustion chamber 5, and next, knock control will be described.

  Here, the concept of the newly created knock control will be described first. FIG. 29 shows the pressure history in the combustion chamber 5 when knocking occurs. When the average pressure from which the high frequency component is removed is redrawn, it can be seen that the pressure in the combustion chamber 5 increases at a stretch at the self-ignition timing θknk (knock generation timing). The pressure increase due to the knock is considered to occur as a result of the unburned air-fuel mixture in the combustion chamber 5 burning at an equal volume, and the pressure increase dP is calculated by a thermodynamic calculation formula as follows.

  Assuming that all the unburned gas of the unburned fuel amount MUB burns by equal volume combustion, the calorific value Q is given by the following equation from thermodynamics.

Q = CF # × MUB (Supplement 4)
Where CF #: lower heating value of fuel,
On the other hand, the gas temperature in the combustion chamber 5 rises due to the calorific value Q. Therefore, if this temperature rise is ΔT, the following equation is established.

Q = Cv × M × ΔT (Supplement 5)
Where M is the mass of all gases in the combustion chamber 5,
Cv: constant volume specific heat of burned gas,
If both equations of (Supplement 4) and (Supplement 5) are equal, and solving for the temperature rise ΔT, the following equation is obtained.

ΔT = (CF # × MUB) / (Cv × M) (Supplement 6)
Differentiate both sides of the gas equation of state PV = nRT (however, V is constant because of constant volume change).

V × dP = dn × R × T + n × R × dT (Supplement 7)
Here, since the change in the number of moles n is small in a state where knocking occurs, the following equation is obtained with dn = 0 on the right side of Equation (7).

dP = (n × R / V) × dT (Supplement 8)
If the temperature rise dT (= ΔT) is eliminated from both equations (Auxiliary 8) and (Auxiliary 6) and the pressure rise dP is arranged, the following equation is finally obtained.

dP = n * R * CF # * MUB / (V * Cv * M) (Supplement 9)
That is, (Supplement 9) is obtained by calculating the unburned fuel amount MUB, the volume V of the combustion chamber 5 at the time of self-ignition, the constant volume specific heat Cv of the burned gas, the mass M of all the gases in the combustion chamber 5, and the combustion chamber 5 If the total number of moles n of all the gases is known, the pressure increase dP can be obtained by a calculation formula.

  In this case, the self-ignition timing of the combustion chamber 5 can be obtained using a known method. In the known method, the temperature and pressure in the combustion chamber 5 are calculated for each unit crank angle, 1 / τ with respect to the temperature and pressure is obtained from FIG. 30A or 30B, and the value obtained by integrating 1 / τ is 1. Is set to the self-ignition timing θknk. Here, τ in FIG. 30A or 30B is the time until the fuel in the combustion chamber 5 reaches self-ignition. When the self-ignition timing θknk is obtained, the volume Vknk at the self-ignition time of the combustion chamber 5 is mechanically obtained from the self-ignition timing θknk.

  In this embodiment, when gasoline is used as the fuel, the octane number estimated value OCTEST of this fuel is calculated, and it is necessary to calculate 1 / τ for the fuel of this octane number estimated value OCTEST. For this reason, the fuel with the estimated octane number OCTEST is 1 / τ based on the octane number 100 (maximum octane number) shown in FIG. 30A and 1 / τ based on the octane number 80 (minimum octane number) fuel shown in FIG. 30B. 1 / τ is calculated (described later).

  On the other hand, if the self-ignition timing θknk is known, the combustion mass ratio BRknk at the time of self-ignition can be obtained using the characteristics of the combustion mass ratio shown in FIG. 31, and from the combustion mass ratio BRknk at the time of self-ignition and the fuel amount QINJ The unburned fuel amount MUB can be obtained by the following calculation formula. That is, since BRknk is already combusted in the fuel amount QINJ, the remaining 1-BRknk is not combusted yet.

MUB = QINJ × (1-BRknk) (Supplement 10)
However, in FIG. 31, in order to simplify the calculation, the combustion start delay period (IGNEADref1), the initial combustion period (BURN1ref1), and the main combustion period (BURN2ref1) are divided into three, and the characteristics of each period are approximated by a straight line.

  In this case, the characteristics of the combustion mass ratio shown in FIG. 31 do not change even if the engine load or rotational speed is different unless the fuel used is changed. It is not necessary to adapt every difference in conditions.

  Next, the constant volume specific heat Cv of burned gas can also be calculated by a thermodynamic calculation formula as follows. That is, since the definition of the constant pressure specific heat Cp is Cp = (∂E / ∂T) p, when this equation is integrated, the following equation is obtained.

∫dE = Cp × ∫dT (Supplement 11)
∴E = Cp × T (Supplement 12)
From the formula (Supplement 12), the constant pressure specific heat Cp is given by the following formula.

Cp = E / T (Supplement 13)
On the other hand, Cp−Cv = R is established when the pressure is constant and the ideal gas is changed. Therefore, when the constant pressure specific heat Cp is eliminated from this equation and (Equation 13) and the constant volume specific heat Cv is arranged, the following equation is finally obtained. .

Cv = E / TR (Supplement 14)
E: Enthalpy,
T: Average temperature at the time of self-ignition in the combustion chamber 5,
The mass M of all gases in the combustion chamber 5 of the above (Supplement 9) can be calculated by the following equation.

M = MRES + MACYL + QINJ (Supplement 15)
Where MRES: amount of internal inert gas,
MACYL: Cylinder fresh air volume,
QINJ: Fuel amount,
In this way, the unburned fuel amount MUB, the constant volume specific heat Cv of the burned gas, and the mass M of all the gases in the combustion chamber 5 are also calculated by the formulas of (Supplement 10), (Supplement 14), and (Supplement 15), respectively. It can be seen that it can be obtained. The remaining unknowns are the total number of moles n of all the gases in the combustion chamber 5 of the above (Supplement 9), the enthalpy E of the (Supplement 14) and the average temperature T (= TE) at the self-ignition timing in the combustion chamber 5. It is.

  Here, the total number of moles n of all the gases in the combustion chamber 5 and the number of moles of each component gas can be obtained by calculation using the basic equation of combustion, and the moles of each component gas. Using the number and the empirical formula, the enthalpy E of the formula (Supplement 14) can be calculated. The average temperature TE at the self-ignition timing in the combustion chamber 5 can also be obtained by calculation using a thermodynamic equation.

  In this way, the pressure increase dP due to knocking is configured so that it can be obtained almost by calculation formula without relying on a table or map, thereby greatly reducing the man-hours and time required for creating a table or map. Can be reduced.

  After that, the pressure increase dP obtained in this way is related to the knock, and this dP is converted into a knock strength estimated value.

  Next, the calculation of the first knock magnitude estimated value KIC will be described in detail with reference to the following flowchart.

  32 and 33 are used to calculate the first knock magnitude estimated value KIC, which is executed when the crank angle reaches a predetermined time (for example, MBTCAL). In the following description, there is a part where the physical quantity already obtained in the above-described flow is obtained in duplicate.

  32, in step 201, the cylinder fresh air amount MACYL [g], the internal inert gas amount MRES [g], the fuel amount QINJ [g], the first basic ignition timing calculated in steps 52 and 53 in FIG. MBTCAL1 [degBTDC], first ignition dead time equivalent crank angle IGNDEADref1 [deg], collector internal temperature TCOL [K] detected by the temperature sensor 43, exhaust temperature TEXH [K] detected by the temperature sensor 45, pressure sensor 44 The pressure in the collector PCOL [Pa] detected by is read. The fuel amount QINJ [g] may be obtained in proportion to the fuel injection pulse width TI [ms].

  Here, the flow in FIGS. 32 and 33 is configured as a subroutine of step 307 in FIGS. 39 and 40, which will be described later. Therefore, the crank angle equivalent to the ignition dead time is the first ignition dead time equivalent crank angle “IGNEADref1 The basic ignition timing is “MBTCAL1” which is the first basic ignition timing, the ignition dead time equivalent value IGNDEAD calculated in step 421 in FIG. 51, and the basic ignition timing MBTCAL calculated in step 43 in FIG. Not. However, the physical meaning does not change.

  In step 202, the cylinder fresh air amount MACYL [g] is moved to WIDRY [g], and the internal inert gas amount MRES [g] is moved to MASSZ [g]. These WIDRY and MASSZ are introduced for use only in calculating the first knock magnitude estimated value KIC1, etc., WIDRY is the cylinder fresh air amount, and MASSZ is the internal inert gas amount.

  In step 203, a value obtained by subtracting the first ignition dead time equivalent crank angle IGNDEADref1 [deg] from the first basic ignition timing MBTCAL1 [degBTDC] (that is, the crank angle at the start of combustion) is set to the crank angle θ [degBTDC].

  In step 204, the compression start temperature TC0 [K] of the combustion chamber 5 is calculated by the following equation.

TC0 = {(WIDRY + QINJ) × TCOL + MASSZ × TEXH}
/ (WIDRY + QINJ + MASSZ) (60)
Here, the specific heat of the inert gas and fresh air is made equal to simplify the equation.

  In step 205, the compression start pressure PC0 [Pa] of the combustion chamber 5 is calculated. For this purpose, the collector internal pressure PCOL at the intake valve closing timing IVC detected by the pressure sensor 44 may be set to PC0.

  Steps 206 to 208 are parts for calculating 1 / τ of the estimated octane number OCTEST for the fuel. If a 1 / τ map is provided for each of a plurality of different octane numbers from the maximum octane number to the minimum octane number, the ROM capacity becomes too large. Therefore, here, the 1 / τ map for the fuel having the maximum octane number (for example, 100) and the minimum octane number Only 1 / τ map for (for example, 80) fuels, and 1 / τ for fuels with an octane number (octane number estimated value OCTEST) between the maximum octane number and the minimum octane number are the fuels of those octane number 100 fuels. It is calculated by interpolating between 1 / τ and 1 / τ for fuel with an octane number of 80.

  Specifically, in steps 206 and 207, by searching the maps having the contents shown in FIGS. 30A and 30B from the compression start temperature TC0 and the compression start pressure PC0, 1 / τ and octane number 80 for the fuel having the octane number 100 are obtained. 1 / τ is calculated for each fuel. Each 1 / τ is a value that increases as the temperature and pressure increase as shown in FIGS. 30A and 30B. Further, if the temperature and pressure are the same, 1 / τ for the fuel with an octane number of 100 tends to be greater than 1 / τ for the fuel with an octane number of 80. Therefore, in step 208, 1 / τ in the fuel of the estimated octane number OCTEST is calculated by the following equation (interpolation calculation equation).

1 / τEST = 1 / τ80 + (OCTEST-80)
× (1 / τ100-1 / τ80) / (100-80)
... (Supplement 17)
Where 1 / τEST: 1 / τ in the fuel of the estimated octane number OCTEST
1 / τ100: 1 / τ with 100-octane fuel
1 / τ80: 1 / τ with fuel of octane number 80
Here, calculation of the estimated octane value OCTEST will be described later with reference to FIG.

  In step 209, 1 / τ of the estimated octane number OCTEST with fuel is added to the SUM. SUM represents an integrated value of 1 / τ. The initial value of the integrated value SUM is zero.

  In step 209, 1 / τ of the estimated octane number OCTEST with fuel is added to the SUM. SUM represents an integrated value of 1 / τ. The initial value of the integrated value SUM is zero.

  In step 210, the integrated value SUM is compared with 1. When the integrated value SUM is less than 1, it is not the timing of self-ignition, so the routine proceeds to step 211 where the current crank angle θ is compared with the predetermined value const01. Here, a crank angle position (for example, 90 degATDC) at which knocking after ignition no longer occurs is set as the predetermined value const01. When the current crank angle θ does not exceed the predetermined value const01, the routine proceeds to step 212, and the crank angle is advanced by a predetermined angle const02 (for example, 1 deg).

  In step 213, the instantaneous compression ratio εθ in the combustion chamber 5 at the current crank angle θ is calculated. This instantaneous compression ratio εθ is the reciprocal of the value obtained by dividing the clearance volume Vc of the combustion chamber 5 by the volume of the combustion chamber 5 at the current crank angle θ. Since the volume of the combustion chamber 5 at the current crank angle θ is determined by the stroke position of the piston 6, that is, the crank angle of the engine, a table with the crank angle θ as a parameter is created in advance and this table is searched from the current crank angle θ. What is necessary is just to ask for.

  In step 214, the combustion mass ratio BR at the current crank angle θ is calculated. For this purpose, first, a crank angle Θ [degATDC] for obtaining a combustion mass ratio is calculated from the current crank angle θ.

  In this case, the crank angle Θ as a variable is a value obtained by taking the compression top dead center TDC as a reference zero and adding the retard side to the plus and the advance side minus to the crank angle Θ [degATDC]. When used, the combustion mass ratio BR is expressed by the following primary expression using the first basic ignition timing MBTCAL1, the first ignition dead time equivalent crank angle IGNDEADref1, the first initial combustion period BURN1ref1 and the first main combustion period BURN2ref1 described later. .

First combustion delay period;
BR = 0 (61)
First initial combustion period;
BR = SS1 × (Θ + MBTCAL1-IGNEADrefref1)
... (62)
First main combustion period;
BR = 0.02 + SS2 × (Θ + MBTCAL1-IGNDEADref1
-BURN1ref1)
... (63)
However, SS1: 0.02 / BURN1ref1,
SS2: 0.58 / BURN2ref1,
Since the setting (initial setting) of the combustion mass ratio BR described here is the content of step 308 in FIGS. 39 and 40 described later, the first initial combustion period is “BURN1ref1”, and the first main combustion period is “BURN2ref1”. The first ignition dead time equivalent crank angle is “IGNEADref1”, the first basic ignition timing is “MBTCAL1”, BURN1 calculated in step 171 of FIG. 10, and BURN2 calculated in step 191 of FIG. The ignition dead time equivalent value IGNDEAD calculated in step 421 in FIG. 51 and the basic ignition timing MBTCAL calculated in step 191 in FIG. However, the physical meaning does not change.

  Therefore, when the calculated crank angle Θ is in the first combustion delay period, the combustion is performed by the expression (61), when it is in the first initial combustion period, by the expression (62), and when in the first main combustion period, the combustion is performed by the expression (63). Calculate mass percentage.

  In steps 215 and 216, an average temperature TC [K] and an average pressure PC [Pa] when the fuel in the combustion chamber 5 burns are calculated by the following equations.

TC = TC0 × εθ ^ 0 ・ 35
+ CF # × QINJ × BR / (MASSZ + WIDRY + QINJ)
... (64)
PC = PC0 × εθ ^ 1.35 × TC / TC0 / εθ ^ 0.35 (65)
Where εθ is the instantaneous compression ratio,
CF #: Lower heating value of fuel,
The equations (64) and (65) are equations when it is assumed that the gas is adiabatically compressed in the combustion chamber 5 and combusted with a constant volume change. That is, the first term on the right side of equation (64) is the temperature after adiabatic compression, PC0 × εθ ^ 1.35 on the right side of equation (65) is the pressure after adiabatic compression, and the second term on the right side of equation (64). TC / TC0 / εθ ^ 0.35 on the right side of Equation (65) represents the rate of pressure increase due to combustion at constant volume change, where the term is the temperature rise due to combustion at constant volume change.

  In step 217, the temperature Tub of the unburned mixture in the combustion chamber 5 is calculated by the following equation.

Tub = TC0 × εθ ^ 0 · 35 × (PC / PC0 / εθ ^ 1.35)
^ (0.35 / 1.35) (66)
The equation (66) is an equation when it is assumed that the gas is adiabatically compressed in the combustion chamber 5 and is burned by a reversible adiabatic change, unlike the equation (64). That is, TC0 × εθ ^ 0.35 on the right side of equation (66) represents the temperature after adiabatic compression, and (PC / PC0 / εθ ^ 1.35) ^ (0.35 / 1.35) on the right side of equation (66). Represents the rate of temperature rise due to combustion in a reversible adiabatic change.

  It is assumed that the pressure of the unburned mixture is equal to the average pressure PC in the above equation (65).

  Here, the difference between the average temperature TC of the equation (64) and the temperature Tub of the unburned mixture of the equation (66) is as follows. That is, the average temperature TC in the equation (64) is a temperature when it is assumed that the heat generated in the combustion chamber 5 raises the temperature of all the gases in the combustion chamber 5. On the other hand, the unburned gas mixture temperature Tub of the equation (66) is in a state where the gas is separated into the burned gas and the unburned gas in the combustion chamber 5, and the heat generated in the combustion chamber 5. Is a temperature when it is assumed that only the burned gas is heated. Then, a sudden pressure increase occurs due to self-ignition of the unburned mixture, and knocking occurs.

  Thereafter, the process returns to Step 206. In Steps 206 and 207, instead of the initial combustion start temperature TC0 and the combustion start pressure PC0, the unburned mixture temperature Tub obtained in Steps 216 and 217 is changed. By searching maps containing the contents of FIG. 30A and FIG. 30B from the unburned mixture pressure (= PC), 1 / τ for an octane number 100 fuel and 1 / τ for an octane number 80 fuel are calculated. In step 208, 1 / τ in the fuel of the estimated octane number OCTEST is calculated based on these two 1 / τ using the above-mentioned (Supplement 17), and 1 / τ in the fuel of the calculated octane number estimated value OCTEST is calculated. In step 209, τ is integrated into the integrated value SUM. Then, the summed SUM and 1 are compared in step 210, and the current crank angle θ and the predetermined value const01 are compared in step 211. When the integrated value SUM is less than 1 and the crank angle θ does not exceed the predetermined value const02, the operations of steps 212 to 217 are performed to calculate the combustion chamber average pressure PC and the unburned mixture temperature Tub, and the step is again performed. The operations 206 to 217 are repeated.

  Thus, every time the crank angle θ is advanced by the predetermined value const02, the combustion chamber average pressure PC and the unburned mixture temperature Tub are recalculated to calculate 1 / τ in the fuel of the estimated octane number OCTEST, and this is used as the integrated value SUM. By integrating, the integrated value SUM in step 209 gradually increases toward 1.

  When the integrated value SUM eventually becomes 1 or more, it is determined that the self-ignition timing (knock occurrence time) has come, and the routine proceeds from step 210 to step 218 in FIG. 33, and the crank angle θ at that time is shifted to the self-ignition timing θknk.

  In step 219 of FIG. 33, the combustion mass ratio BRknk at the time of self-ignition is calculated using the characteristics of the initial combustion mass ratio BR shown in FIG. This is because when the auto-ignition timing θknk is in the initial combustion period, the auto-ignition timing θknk is converted into the crank angle Θ based on the compression top dead center TDC, and the converted crank angle Θ is expressed by the above equation (62). In addition, when the self-ignition timing θknk is in the main combustion period, the self-ignition timing θknk is converted into the crank angle Θ based on the compression top dead center TDC, and the converted crank angle Θ is converted into the above (63) It can be obtained by assigning each to the formula.

  In step 220, an average temperature TE at the time of self-ignition of the combustion chamber 5 at θknk is calculated. This may be obtained by calculating the average temperature TC of the combustion chamber 5 obtained by substituting 1.0 into the combustion mass ratio BR on the right side of the equation (64) as the self-ignition average temperature TE of the combustion chamber 5.

  In step 221, the volume Vknk of the combustion chamber 5 at the self-ignition timing θknk is calculated. Since the volume Vknk of the combustion chamber 5 at the self-ignition timing θknk is determined by the stroke position of the piston 6, that is, the crank angle of the engine, similarly to the volume at the current crank angle θ of the combustion chamber 5, a table using the crank angle θ as a parameter. May be obtained by searching this table from θknk during self-ignition.

  In step 222, the unburned fuel amount MUB [g] at the time of self-ignition is calculated from the fuel amount QINJ [g] and the combustion mass ratio BRknk at the time of self-ignition by the following equation.

MUB = QINJ × (1-BRknk) (67)
The expression (67) is the above (complement 10) itself.

  In step 223, the total gas mole number MLALL is calculated. This will be described with reference to the flowchart of FIG.

  34 (subroutine of step 223 in FIG. 33), in step 241, the internal inert gas amount MASSZ [g], the cylinder fresh air amount WIDRY [g], and the fuel amount QINJ [g] calculated in step 202 of FIG. In step 242, the internal inert gas ratio RTOEGR in the combustion chamber 5 is calculated by the following equation.

RTOEGR = MASSZ / (MASSZ + WIDRY + QINJ) (68)
In step 243, the number of moles of each gas component when all the fuel in the combustion chamber 5 is burned (that is, BR = 1) is calculated. However, the gas components are limited to O ₂ , N ₂ , CO ₂ , CO, and H ₂ O other than the fuel. Further, the fuel composition of gasoline is approximated by C ₇ H ₁₄ .

First, the number of moles WEDRY [mol] of the total exhaust gas generated after the fuel amount QINJ [g] is combusted and the respective gas components such as O ₂ , N ₂ , CO ₂ , CO, and H ₂ O in the exhaust gas The number of moles of XEO2 [mol], XEN2 [mol], XECO2 [mol], XECO [mol], and XEH2O [mol] is calculated as follows.

Total exhaust gas; WEDRY = MIDRY # × WlDRY-QlNJ
/ (B # × AC # + A # × AH) × (A # / 4) (69.1)
Oxygen; XEO2 = {MIDRY # × WlDRY × 0.21-QINJ
/ (B # × AC # + A # × AH) × (B # + A # / 4)}
/ WEDRY (69.2)
Carbon dioxide; XECO2 = {QINJ / (B # × AC # + A # × AH #) × B #}
/ WEDRY (69.3)
Carbon monoxide; XECO = 0 (69.4)
Nitrogen: XEN2 = 1-XEO2-XECO2-XECO (69.5)
Water; XEH2O = {MIDRY # × WIDRY × 15/745
+ QINJ / (B # × AC # + A # × AH #)
× A # / 2} / WEDRY (69.6)
However, MIDRY #: Number of moles of fresh gas per gram
AH #: molar mass of hydrogen,
AC #: molar mass of carbon,
A #, B #: constant,
Here, since the composition of gasoline is approximated by C ₇ H ₁₄ , the constant A # is 14 and the constant B # is 7.

  Next, the number of moles of each gas component at the initial stage of the combustion cycle WGAS [mol], WEGR [mol], WO2 [mol], WN2 [mol], WCO2 [mol], WCO [mol], WH2O [mol] Calculate as follows.

Fuel: WGAS = QINJ / (B # × AC # + A # × AH #)
... (70.1)
Inert gas; WEGR = MIDRY # × WIDRY × RTOEGR (70.2)
Oxygen: WO2 = MIDRY # × WIDRY × 0.21 + WEGR × XEO2
... (70.3)
Nitrogen; WN2 = MIDRY # × WIDRY × 0.89 + WEGR × XEN2
... (70.4)
Carbon dioxide; WCO2 = WEGR × XECO2 (70.5)
Carbon monoxide; WCO = WEGR × XECO (70.6)
Water; WH2O = MIDRY # × WIDRY × 15/745
+ WEGR × XEH2O (70.7)
Next, the number of moles MGLAS [mol], MLO2 [mol], MLN2 [mol], MLCO2 [mol], MLCO [mol], MLH2O [mol] of each gas component when all are combusted (that is, BR = 1). Calculate as follows.

Fuel; MLGAS = WGAS-QINJ / (B # × AC # + A # × AH #)
... (71.1)
Oxygen; MLO2 = WO2- (B # + A # / 4) × QlNJ
/ (B # × AC # + A # × AH #) (71.2)
Nitrogen; MLN2 = WN2 (71.3)
Carbon dioxide; MLCO2 = WCO2 + B # × QINJ
/ (B # × AC # + A # × AH #) (71.4)
Carbon monoxide; MLCO = WCO (71.5)
Water; MLH2O = WH2O + A # / 2 × QINJ
/ (B # × AC # + A # × AH #) (71.6)
This completes the calculation of the number of moles of each gas component when all the fuel in the combustion chamber 5 has been burned (that is, BR = 1), and thus the process proceeds to step 244 to calculate the sum of the number of moles of each gas component. As the total number of gas moles MLALL when all of the fuel is burned, that is, the total number of gas moles MLALL is calculated by the following equation.

MLALL = MLGAS + MLO2 + MLN2 + MLCO2 + MLCO + MLH2O
... (71.7)
When the calculation of the total gas mole number MLALL is completed in this way, the process returns to step 224 in FIG. 33 to calculate the gas enthalpy (enthalpy of self-ignited fuel gas) E [cal / mol]. The calculation of the gas enthalpy will be described with reference to the flow of FIG. 35 (subroutine of step 224 in FIG. 33), in step 251, the self-ignition average temperature TE of the combustion chamber 5 calculated in step 220 of FIG. 33, and each gas calculated in steps 243 and 244 of FIG. The number of moles of components MLGAS, MLO2, MLN2, MLCO2, MLCO, MLH2O, and the total number of moles of gas MLALL are read.

In step 252, enthalpy EO2, EN2, ECO2, ECO, EH2O of each gas component is calculated from the average temperature TE during self-ignition. What is necessary is just to calculate the enthalpy of each gas component using the following Mizutani empirical formula (refer to internal combustion engine vol.11 No.125p79).
(1) When TE <1200K E = A0 # + 1000 × (A1 # × (TE / 1000)
+ A2 # / 2 × (TE / 1000) ^ 2
+ A3 # / 3 × (TE / 1000) ^ 3
+ A4 # / 4 × (TE / 1000) ^ 4
+ A5 # / 5 × (TE / 1000) ^ 5) + HDL # (72.1)
(2) When TE> 1200K E = B0 # + 1000 × (B1 # × (TE / 1000)
+ B2 # × LN (TE / 1000)
-B3 # / (TE / 1000)
-B4 # / 2 / (TE / 1000) ^ 2
-B5 # / 3 / (TE / 1000) ^ 3) + HDL # (72.2)
However, A0 # to A5 #, B0 to B5 #, and HDL # are adapted values obtained by experiments,
In step 253, the enthalpy EG of the fuel is calculated by the following equation.

EG = B # / AC # × ECO2 + A # / AH # × EH20 / 2
+ (B # / AC # + A # / AH # / 4) × EO2 (72.3)
In step 254, the average enthalpy E of each gas component is calculated by the following equation, the processing in FIG. 35 is terminated, and the processing returns to step 225 in FIG.

E = (MLGAS × EG + MLO2 × EO2 + MLN2 × EN2
+ MLCO2 × ECO2 + MLCO × ECO + MLH2O × EH2O)
/ MLALL (72.4)
In step 225 of FIG. 33, the constant volume specific heat Cv [J / K · g] of the burned gas is calculated by the following equation using the gas enthalpy E and the average temperature TE at the time of self-ignition of the combustion chamber 5.

Cv = E / TE-R # (73)
Where R #: universal gas constant,
Expression (73) is an expression obtained by replacing T → TE and R → R # in the above (complement 14).

  In step 226, the pressure increase due to self-ignition, that is, the pressure increase DP [Pa] due to knocking is calculated by the following equation.

DP = (WALL × MUB × R # × CF #)
/ {Cv × Vknk × (MASSZ + QINJ + WIDRY)}
... (74)
Where CF #: lower heating value of fuel,
As shown in FIG. 29, the pressure increase DP in the equation (74) is such that the pressure in the combustion chamber 5 increases stepwise due to the occurrence of knocking.

  Expression (74) is an expression obtained by replacing dP → DP, n → MLALL, R → R #, V → Vknk, M → MASSZ + WIDRY + QINJ in the above (Appendix 9).

  In step 227, the knock magnitude estimated value basic value KIC0 is calculated by the following equation.

KIC0 = correlation coefficient 1 × DP (75)
Here, the correlation coefficient 1 on the right side of equation (75) is a coefficient for representing the correlation with the knock intensity. In this case, the knock strength estimated value basic value KIC0 increases as the pressure increase DP due to knock increases.

  In step 228, a rotational speed correction coefficient KN is calculated from the engine rotational speed NRPM by searching a table having the contents shown in FIG. 36, and in step 229, this rotational speed correction coefficient KN is set to the knock magnitude estimated value basic value KIC0. The multiplied value is used as the first knock magnitude estimated value KIC, that is, the first knock magnitude estimated value KIC is calculated by the following equation.

KIC = KIC0 × KN (76)
Here, the rotational speed correction coefficient KN is for the driver to feel pressure vibration due to knock more strongly when the engine rotational speed NRPM is lower than when the rotational speed is high, so that this difference is reflected in the first knock strength estimated value. Is. That is, as shown in FIG. 36, the value of KN is 1.0 when the reference rotational speed NRPM0 is 1.0 and exceeds 1.0 in a lower rotational speed range, and conversely in a higher rotational speed range than the reference rotational speed NRPM0. The value is less than 1.0. Actual values are adapted by experiment.

  On the other hand, the integrated value SUM may not reach 1, and at this time, the current crank angle θ eventually exceeds the predetermined value const01 in step 211 of FIG. At this time, the process proceeds from step 211 in FIG. 32 to step 230 in FIG. 33, where a predetermined value is entered in the first knock magnitude estimated value KIC, and the current process is terminated.

  Next, calculation of the estimated octane number OCTEST of the fuel during operation will be described with reference to the flow of FIG. Since the estimation of the octane number is performed while detecting whether or not knocking has occurred based on the signal from the knock sensor 47, the flow in FIG. 37 is executed immediately after ignition for each ignition. Here, in order to execute each ignition, it may be executed at a timing at which a predetermined crank angle has elapsed from the input of a reference position signal generated by a signal from the crank angle sensor (33, 34).

  In FIG. 37, at step 261, the knock sensor 47 is used to check whether knock has occurred. For example, the voltage value detected by the knock sensor 47 is compared with a predetermined value, and if the voltage value exceeds the predetermined value, it is determined that knock has occurred, that is, the estimated octane number OCTEST is greater than the actual octane number. Proceeding to 262, the estimated octane value OCTEST is reduced by the first predetermined value const03. That is, the estimated octane value OCTEST is updated by the following equation.

OCTEST (new) = OCTEST (old) -const03 (79)
However, OCTEST (new): Estimated value of octane number after update,
OCTEST (old): Estimated octane value before update,
const03: update amount to the side to be reduced,
If knock is not detected, the routine proceeds from step 261 to step 263, where the ignition timing minimum value PADV [degBTDC] calculated in step 3 of FIG. 2 and the basic ignition timing MBTCAL [degBTDC] calculated in step 1 of FIG. Compare When the minimum ignition timing value PADV coincides with the basic ignition timing MBTCAL, the estimated octane number OCTEST and the actual octane number coincide with each other. Therefore, it is not necessary to change the estimated octane number, so the current process is terminated.

  On the other hand, when the ignition timing minimum value PADV does not coincide with the basic ignition timing MBTCAL, it is determined that the estimated octane number OCTEST does not coincide with the actual octane number, and as a result, the ignition timing is retarded. Then, the counter value count is compared with the predetermined value const04. The initial value of the counter value count is zero. Since the counter value count is initially less than the predetermined value const04 after proceeding to step 264, the process proceeds to step 265 and the counter value count is incremented by one. That is, the counter value count increases by 1 each time the flow of FIG. 37 is executed once, so that the counter value count eventually becomes equal to or greater than the predetermined value const04. At this time, the routine proceeds from step 264 to step 266, where the octane number estimated value OCTEST is increased by the second predetermined value const05. That is, the estimated octane value OCTEST is updated by the following equation.

OCTEST (new) = OCTEST (old) + const05 (80)
However, OCTEST (new): Estimated value of octane number after update,
OCTEST (old): Estimated octane value before update,
const05: Update amount to the side to be increased,
Since the estimated octane value OCTEST is updated every time the counter value count reaches the predetermined value const04, the counter value count is reset to zero in step 267.

  FIG. 38 shows the movement of the ignition timing, the counter value count, and the estimated octane number OCTEST. As shown in the figure, when knocking is detected by the knock sensor 47 at timing t01, it is determined that the estimated octane number OCTEST is greater than the actual octane number, and the estimated octane number OCTEST is decreased stepwise by the first predetermined value const03. The As a result, if knock does not occur, every time the counter value count reaches the predetermined value const04, the estimated octane value OCTEST increases by the second predetermined value const05. Then, after the ignition timing minimum value PADV coincides with MBTCAL at the timing of t02, the update of the octane number estimated value OCTEST is stopped and the value at that time is held. If knocking occurs again at the subsequent timing t03, the above operation is repeated.

  The octane estimated value OCTEST calculated in this way is used to calculate 1 / τ for the fuel of the octane estimated value OCTEST in step 208 of FIG.

  39 and 40 (subroutine of step 2 in FIG. 2) are for calculating the second knock limit ignition timing KNOCKcal, and are executed when the crank angle reaches a predetermined timing (for example, MBTCAL).

  39, steps 301 to 307 are portions for calculating the first basic ignition timing MBTCAL1 [degBTDC], and are basically the same as the basic ignition timing MBTCAL calculation methods shown in FIGS. 10, 12, and 13 described above. . However, in FIGS. 10 and 12 described above, the initial combustion period BURN1 is set using 2% (= BR1) which is the combustion mass ratio at the end time of the initial combustion period and the volume V0 at the combustion start time of the combustion chamber 5. (Refer to Step 171 in FIG. 10) Further, the main combustion period BURN2 using 58% (= BR2) which is the combustion mass ratio at the end timing of the main combustion period and the volume VTDC at the compression top dead center timing of the combustion chamber 5. (Refer to step 191 in FIG. 12), here, 1% (= BR1p) which is the combustion mass ratio in the intermediate period of the first initial combustion period, and 1% when the combustion mass ratio of the combustion chamber 5 is 1% Is used to determine the first initial combustion period BURN1ref1 (see step 351 of FIG. 41) and the combustion mass in the vicinity of the intermediate period of the first main combustion period. A multiplexer 31% and (= BRmb31p), to calculate a first main combustion period BURN2ref1 using the volume Vmb31p during mass fraction burned 31% of the combustion chamber (see step 371 in FIG. 42).

  As shown in the above equations (19) and (22) at the beginning of development, the combustion start time and compression top dead center time for the combustion chamber volume (V0, VTDC) are represented by the combustion mass ratio (BR1, BR2). However, the above formulas (19) and (22) are empirical formulas in the first place, and it is more average to adopt almost the intermediate period of each combustion period in subsequent experiments. Since it has been found that the value can be obtained, the values for the intermediate period are again adopted for the combustion chamber volume and the combustion mass ratio, which are values for calculating the combustion period. That is, for the first initial combustion period (also for the second initial combustion period to be described later), the combustion mass ratio is in the interval of 2% from 0%, so the time of 1%, which is exactly 1/2, is adopted. The first main combustion period (also in the second main combustion period described later) is a section where the combustion mass ratio is 58% from 2%, so that exactly 1/2 is 28%, as shown in FIG. In terms of area, the latter half is larger, so the 31% time slightly biased to the latter half is adopted. However, the timing is not limited to 31%, and may be any timing close to this.

  Specifically, in FIG. 39, in step 301 in FIG. 39, the initial combustion period BURN1, [deg] calculated in step 171 in FIG. 10, the main combustion period BURN2 [deg] calculated in step 191 in FIG. 12, and in FIG. In addition to the basic ignition timing MBTCAL [degBTDC] calculated in step 43, the ignition dead time equivalent value IGNDEAD [deg] calculated in step 421 in FIG. 51, and the reference crank angle calculated in step 16 in FIG. Read θPMAX [degATDC].

In step 302, the basic ignition timing MBTCAL is shifted to the ignition timing θign [degBTDC], and in steps 303 and 304, the volume Vmb1p [m ³ ] when the combustion mass ratio of the combustion chamber 5 is 1% and the combustion mass ratio of the combustion chamber 5 is 31%. The volume Vmb31p [m ³ ] at is calculated as a function of θign-IGNDEAD-BURN1 / 2 and θign-IGNDEAD-BURN1-BURN2 / 2 as variables by the following equation.

Vmb1p = f25 (θsign−IGNDEAD−BURN1 / 2)
... (81)
Vmb31p = f25 (θsign−IGNDEAD−BURN1
-BURN2 / 2)
... (82)
Θign-IGNDEAD-BURN1 × (1/2) as a variable on the right side of equation (81) is a crank angle [degBTDC] when the combustion mass ratio is 1%, and θign-IGNDEAD-BURN1 as a variable on the right side of equation (82) -BURN2 × (1/2) is the crank angle [degBTDC] when the combustion mass ratio is 31%, and the equations (81) and (82) are the functions of these crank angles at the respective crank angles of the combustion chamber 5. The volumes Vmb1p and Vmb31p are obtained. That is, as shown in FIG. 31, there is a relationship between the combustion mass ratio and the crank angle Θ, and the volume of the combustion chamber 5 is determined as determined in step 12 of FIG. 5 and step 162 of FIG. Since it is determined by the crank angle at that time (which is a function of the crank angle), each crank angle Θ [degATDC] when the combustion mass ratio is 1% and 31% is similar to the combustion mass ratio characteristics shown in FIG. A table having the crank angle θ as a parameter from the converted crank angle θ is obtained by converting the obtained crank angle θ into the crank angle θ [degBTDC]. By searching, the volume Vmb1p when the combustion mass ratio of the combustion chamber 5 is 1% and the volume Vmb31p when the combustion mass ratio of the combustion chamber 5 is 31% can be obtained.

  In the right side of the above equations (81) and (82), IGNDEAD, BURN1, and BURN2 are given as negative values because the unit of the ignition timing θsign on the right side of equations (81) and (82) is the same as MBTCAL. This is because it is a unit of [degBTDC]. For this reason, the crank angle in the parentheses on the right side of the equations (81) and (82) is a value on the retard side of the basic ignition timing MBTCAL.

  In step 305, the first initial combustion period BURN1ref1 is calculated using the combustion mass ratio 1% and the volume Vmb1p of the combustion chamber 5 at the combustion mass ratio 1%, the combustion mass ratio 31%, and the combustion mass ratio 31 of the combustion chamber 5 The first main combustion period BURN2ref1 is calculated using the chamber volume Vmb31p at the time of%. Here, in order to distinguish from BURN1 and BURN2 calculated by the flow of FIG. 10 and FIG. 12, “ref1” as a subscript is attached. Of these, the calculation of the first initial combustion period BURN1ref1 and the second initial combustion period BURN1ref2 to be described later is performed according to the flow of FIG. Will be described.

  First, from FIG. 41, the basic concept of the calculation method of the first or second initial combustion period here is the same as the calculation method of the initial combustion period shown in FIG. Here, the calculation method of the first initial combustion period will be representatively described.

In FIG. 41 (subroutine of step 305 in FIG. 39), in step 341, the cylinder fresh air amount MACYL [g], the internal inert gas amount MRES [g] and the fuel amount QINJ [calculated in steps 52 and 53 in FIG. g], collector internal temperature TCOL [K] detected by the temperature sensor 43, exhaust temperature TEXH [K] detected by the temperature sensor 45, collector internal pressure PCOL [Pa] detected by the pressure sensor 44, FIG. The volume VIVC [m ³ ] at the intake valve closing timing of the combustion chamber 5 calculated in step 12 and the engine rotational speed NRPM [rpm], the reaction probability RPROBA [%] calculated in step 15 of FIG. read volume Vmb1p [m ^3] of the combustion mass proportion of 1% when the combustion chamber 5 is calculated in step 303

  In step 342, an effective compression ratio Emb1p at a combustion mass ratio of 1% is calculated by the following equation.

Emb1p = Vmb1p / VIVC (83)
The operation for calculating TC and PC in steps 343 to 347 is the same as the operation for calculating TC and PC in steps 202, 204, 205, 215 and 216 in FIG. The difference is that in steps 215 and 216 of FIG. 32, εθ which is the compression ratio at the crank angle θ at that time and BR which is the combustion mass ratio at the crank angle θ at that time are used. Steps 346 and 347 in FIG. 41 use Emb1p, which is an instantaneous compression ratio when the combustion mass ratio is 1%, and BR1p, which is the combustion mass ratio when the combustion mass ratio is 1%. That is, in steps 346 and 347 of FIG. 41, the average temperature TC [K] and the average pressure PC [Pa] when the fuel in the combustion chamber 5 burns are calculated by the following equations.

TC = TC0 × Emb1p ^ 0 · 35
+ CF # × QINJ × BR1p / (MASSZ + WIDRY + QINJ)
... (84)
PC = PC0 * Emb1p ^ 1.35 * TC / TC0 / Emb1p ^ 0.35
... (85)
Where CF #: lower heating value of fuel,
The operation for calculating the first initial combustion period in steps 348 to 351 is the same as the operation for calculating the initial combustion period in steps 168 to 171 of FIG. The difference is that the laminar combustion speed SL1 is calculated using the temperature T0 and the pressure P0 at the combustion start timing of the combustion chamber 5 in step 168 in FIG. 10, whereas in step 348 in FIG. , The point where the laminar combustion speed SL1 is calculated using the temperature TC and the pressure PC obtained by the equation (85), and BR1 (= 2) which is the combustion mass ratio at the end of the initial combustion period BURN1 in step 171 of FIG. %) And V0 which is the volume of the combustion chamber 5 at the combustion start timing, the initial combustion period BURN1 is calculated, whereas in step 351 of FIG. 41, the combustion mass ratio at the intermediate timing of the first initial combustion period 1% (= BR1p) and Vmb1p which is the volume of the combustion chamber 5 when the combustion mass ratio is 1%, the first initial combustion period BURN1ref1 In terms of calculation it is. That is, in step 348, the laminar combustion speed SL1 [m / sec] in the first initial combustion period is calculated, and in step 351, the first initial combustion period BURN1ref1 [deg] is calculated by the following equations.

SL1 = SLstd × (TC / Tstd) ^2.18 × (PC / Pstd) ^−0.16 (86)
Where Tstd: reference temperature [K],
Pstd: Reference pressure [Pa]
SLstd: Reference laminar combustion at reference temperature Tstd and reference pressure Pstd
Speed [m / sec],
BURN1ref1 = {(NRPM × 6) × BR1p × Vmb1p}
/ (RPROBA × AF1 × FLAME1) (87)
However, AF1: Reaction area (fixed value) of flame kernel [m ² ],
Note that “BURN1ref1” shown in step 351 of FIG. 41 collectively indicates “BURN1ref1” that is the first initial combustion period and “BURN1ref2” that is the second initial combustion period (that is, i is 1 or 2). . The flow of FIG. 41 is used in two places, step 305 in FIG. 39 and step 321 in FIG. 40. Of these, step 305 in FIG. 39 shows the first initial combustion period BURN1ref1, and step 321 in FIG. This is because the initial combustion period BURN1ref2 is calculated.

  Next, turning to FIG. 42, the basic concept of the calculation method of the first or second main combustion period here is the same as the calculation method of the main initial combustion period shown in FIG. Here, the calculation method of the first main combustion period will be described as a representative.

In FIG. 42 (subroutine of step 305 in FIG. 39), in step 361, the cylinder fresh air amount MACYL [g], the internal inert gas amount MRES [g], and the fuel amount QINJ [ g], collector internal temperature TCOL [K] detected by the temperature sensor 43, exhaust temperature TEXH [K] detected by the temperature sensor 45, collector internal pressure PCOL [Pa] detected by the pressure sensor 44, FIG. The volume VIVC [m ³ ] at the intake valve closing timing of the combustion chamber 5 calculated in step 12 and the engine rotational speed NRPM [rpm], the reaction probability RPROBA [%] calculated in step 15 of FIG. read the volume Vmb31p [m ^3] of the combustion mass proportion of 31% when the combustion chamber 5 is calculated in step 304 No.

  In step 362, an effective compression ratio Emb31p at a combustion mass ratio of 31% is calculated by the following equation.

Emb31p = Vmb31p / VIVC (88)
The operation for calculating TC and PC in steps 363 to 367 is the same as the operation for calculating TC and PC in steps 202, 204, 205, 215 and 216 in FIG. The difference is that in steps 215 and 216 of FIG. 32, εθ which is the compression ratio at the crank angle θ at that time and BR which is the combustion mass ratio at the crank angle θ at that time are used. Steps 366 and 367 in FIG. 42 use Emb31p which is a compression ratio when the combustion mass ratio is 31% and BR31p which is the combustion mass ratio when the combustion mass ratio is 31%. That is, in steps 366 and 367 in FIG. 42, the average temperature TC [K] and the average pressure PC [Pa] when the fuel in the combustion chamber 5 burns are calculated by the following equations.

TC = TC0 × Emb31p ^ 0 ・ 35
+ CF # × QINJ × BR31p / (MASSZ + WIDRY + QINJ)
... (89)
PC = PC0 * Emb31p ^ 1.35 * TC / TC0 / Emb31p ^ 0.35
... (90)
Where CF #: lower heating value of fuel,
The operation for calculating the first main combustion period in steps 368 to 371 is the same as the operation for calculating the main combustion period in steps 188 to 191 in FIG. The difference is that the temperature TTDC and the pressure PTDC at the compression top dead center of the combustion chamber 5 are used in step 188 in FIG. 12, whereas in step 368 in FIG. 42, the above equations (89) and (90) are used. 12 using the temperature TC and the pressure PC, BR2 (= 58%) which is the combustion mass ratio at the end of the main combustion period BURN2 in step 191 of FIG. 12, and the volume at the compression top dead center of the combustion chamber 5 Whereas a certain VTDC is used, in step 371 of FIG. 42, the combustion mass ratio is 31% (= BR31p) in the vicinity of the intermediate period of the first main combustion period, and the combustion mass ratio of the combustion chamber 5 is 31%. It is a point using Vmb31p which is the volume in time. That is, in step 368, the laminar combustion speed SL2 [m / sec] in the first main combustion period is calculated, and in step 371, the first main combustion period BURN2ref1 [deg] is calculated by the following equations.

SL2 = SLstd × (TC / Tstd) ^2.18 × (PC / Pstd) ^−0.16 (91)
Where Tstd: reference temperature [K],
Pstd: Reference pressure [Pa]
SLstd: Reference laminar combustion at reference temperature Tstd and reference pressure Pstd
Speed [m / sec],
BURN2ref1 = {(NRPM × 6) × BR31p × Vmb31p}
/ (RPROBA × AF2 × FLAME1) (92)
However, AF2: Reaction area (fixed value) of flame kernel [m ² ],
Note that “BURN2ref1” shown in step 371 of FIG. 42 also collectively indicates “BURN2ref1” that is the first main combustion period and “BURN2ref2” that is the second main combustion period (that is, i is 1 or 2). . The flow of FIG. 42 is used in two places, step 305 in FIG. 39 and step 321 in FIG. 40. Of these, step 305 in FIG. 39 shows the first main combustion period BURN2ref1, and step 321 in FIG. This is because the main combustion period BURN2ref2 is calculated.

  When the calculation of the two first combustion periods BURN1ref1 and BURN2ref1 is thus completed, the process returns to step 306 in FIG. 39 to calculate the first ignition dead time equivalent crank angle IGNDEADref1 [deg]. Also here, in order to distinguish from IGNDEAD calculated by the flow of FIG. 51, “ref1” is added as a subscript. The calculation of the first ignition dead time equivalent crank angle IGNDEADref1 and the later-described second ignition dead time equivalent crank angle IGNDEADref2 will be described with reference to the flowchart of FIG.

  The flow of FIG. 43 (subroutine of step 306 in FIG. 39) is for calculating the crank angle IGNDEADref1 corresponding to the first or second dead ignition time, and the calculation method is the crank corresponding to the dead ignition time shown in FIG. It is basically the same as the method for calculating the angle IGNDEAD. Here, the calculation method of the first main combustion period will be described as a representative.

51 differs from the calculation method of the ignition dead time equivalent crank angle IGNDEAD in FIG. 51 in that the previous combustion start timing MBTCYCL is used to calculate the volume V0 at the combustion start timing of the combustion chamber 5 in FIG. 43 (see steps 411 and 412 in FIG. 51), FIG. 43 shows only the point where the ignition timing θign is used (see steps 381 and 382 in FIG. 43). Therefore, the difference will be mainly described. In step 381 in FIG. 43, the ignition timing θign [degBTDC] (= MBTCAL) obtained in step 302 in FIG. 39 and the combustion chamber 5 calculated in step 12 in FIG. The volume VIVC [m ³ ] at the intake valve closing timing, the temperature TINI [K] at the intake valve closing timing calculated in step 13 of FIG. 5, and the combustion chamber 5 calculated in step 14 of FIG. The pressure PINI [Pa] at the intake valve closing timing, the target equivalence ratio TFBYA, and the engine rotational speed NRPM [rpm] are read, and the volume V0 at the combustion start timing of the combustion chamber 5 is calculated in step 382 using the ignition timing θigng. .

  In Steps 383 to 385, the temperature T0 [K] at the combustion start timing of the combustion chamber 5 and the pressure P0 [Pa] at the combustion start timing of the combustion chamber 5 are calculated in the same manner as Steps 413 to 415 in FIG.

  Note that “IGNEADref1” shown in step 391 of FIG. 43 also collectively indicates “IGNEADref1”, which is the crank angle corresponding to the first ignition dead time, and “IGNEADref2”, which is the crank angle equivalent to the second ignition dead time (that is, i is 1 or 2). The flow of FIG. 43 is used in two places, step 306 in FIG. 39 and step 322 in FIG. 40. Among these, in step 306 in FIG. 39, the first ignition dead time equivalent crank angle IGNDEADref1 is set to step 322 in FIG. This is because the second ignition dead time equivalent crank angle IGNDEADref2 is calculated.

  When the calculation of the first ignition dead time equivalent crank angle IGNDEADref1 [deg] using the ignition timing θign is completed in this way, returning to FIG. 39, in step 307, the first combustion calculated in steps 305 and 306 in FIG. The first basic ignition timing MBTCAL1 [degBTDC] is calculated by the following equation using the periods BURN1ref1, BURN2ref1, and the first ignition dead time equivalent crank angle IGNDEADref1.

MBTCAL1 = BURN1ref1 + BURN2ref1-θPMAX
+ IGNDEADref1
... (93)
Here, in order to distinguish from the basic ignition timing MBTCAL calculated by the flow of FIG. 13, “1” is added as a subscript. Therefore, the equation (93) is basically the same as the equation (23).

  In step 308, using the first combustion periods BURN1ref1, BURN2ref1, the first ignition dead time equivalent crank angle IGNDEADref1, and the first basic ignition timing MBTCAL1 calculated in this way, the waveform of the combustion mass ratio BR is obtained as shown in FIG. Initial setting. That is, the above equations (61) to (63), which are equations for the combustion mass ratio in each of the first combustion delay period, the first initial combustion period, and the first main combustion period, are calculated, and the calculated expressions are stored. Keep it.

  In step 309, the knock magnitude estimated value at the first basic ignition timing MBTCAL1 is calculated as the first knock magnitude estimated value KIC. The calculation of the first knock magnitude estimated value KIC has been described above with reference to FIGS. That is, FIGS. 32 and 33 are subroutines of step 308 of FIG. Accordingly, the description of the calculation of the first knock magnitude estimated value KIC is omitted.

  In step 310, the trace knock intensity is obtained by searching a table having the contents shown in FIG. 47 from the engine speed NRPM. As is well known, the trace knock intensity is a knock intensity when a light knock occurs, and is a value that increases as the engine speed NRPM decreases as shown in FIG.

  In step 311, the first knock magnitude estimated value KIC is compared with the trace knock magnitude. When the first knock magnitude estimated value KIC is less than the trace knock magnitude, it is determined that the waveform of the combustion mass ratio BR may remain the initial setting shown in FIG. 31, and the routine proceeds to step 312 where the first basic ignition timing MBTCAL1 is knocked as it is. The limit ignition timing KNOCKcal [degBTDC] is set and the current process is terminated.

  On the other hand, when the first knock magnitude estimated value KIC is equal to or greater than the trace knock magnitude, it is determined that the initial combustion mass ratio BR waveform shown in FIG. 31 has a deviation from the actual combustion mass waveform, and the actual combustion In order to reset the combustion mass ratio waveform in accordance with the change in the mass ratio, the routine proceeds from step 311 to step 313, where the ignition timing knock retard amount KNRT [deg] is based on the difference between the first knock magnitude estimated value KIC and the trace knock magnitude. That is, the calculation is performed by the following equation and the operation proceeds to the operation shown in FIG.

KNRT = (KIC−trace knock intensity) × predetermined value (94)
Steps 314 to 327 in FIG. 40 are portions for calculating the knock magnitude estimated value when the ignition timing is retarded from the second basic ignition timing MBTCAL2 and burning as the second knock magnitude estimated value KIC2. . In FIG. 40, first, at step 314, the value of the ignition timing θign [degBTDC] (= MBTCAL1) is moved to θignz [degBTDC] representing the previous value, and the value obtained by subtracting the knock retard amount KNRT from the previous ignition timing value θignz (that is, the first value). The ignition retard θign [degBTDC] is calculated as a value retarded by the knock retard amount KNRT from the basic ignition timing MBTCAL1. This is only the first time. From the second time, the value of the ignition timing θign is transferred to θignz representing the previous value, and the value obtained by subtracting the knock retard amount KNRT from the previous ignition timing value θignz (that is, calculated in step 323 in FIG. 40). Is calculated as the ignition timing θign) from the second basic ignition timing MBTCAL2 (a value retarded by the knock retard amount KNRT).

  In step 315, the values of the first combustion periods BURN1ref1 and BURN2ref1 and the first ignition dead time equivalent crank angle IGNDEADref1 calculated in steps 305 and 306 of FIG. 39 are set as the second initial combustion period, the second main combustion period, and the second ignition period. The operation shifts to BURN1ref2z, BURN2ref2z, and IGNEADref2z representing the previous values of the crank angle corresponding to the dead time. However, this is only the first time, and from the second time, the second initial combustion period BURN1ref2, the second main combustion period BURN2ref2, and the second ignition dead time equivalent crank angle IGNDEADref2 calculated in steps 321 and 322 in FIG. Move to BURN1ref2z, BURN2ref2z, and IGNEADref2z representing values.

In step 316, the volume Vmb1p [m ³ ] at the time when the combustion mass ratio of the combustion chamber 5 is 1% is next calculated using the ignition timing θign (initially the ignition timing retarded by the knock retard amount KNRT from the first basic ignition timing MBTCAL1). Calculate by the formula. This operation is the same as the operation in step 303 in FIG.

Vmb1p = f25 (θsign−IGNEADREFref2z
-BURN1ref2 / 2)
... (95)
Steps 317 to 320 are parts for calculating the volume Vmb31p when the combustion mass ratio of the combustion chamber 5 is 31%. First, at step 317, the previous value θmb31pz [degBTDC] of the crank angle when the combustion mass ratio is 31% is calculated by the following equation.

θmb31pz = θignz-IGNEADref2z-BURN1ref2z
-BURNN2ref2 / 2
... (96)
In step 318, the difference θ2pdif [deg] between the previous value of the crank angle when the combustion mass ratio is 2% and the current value of the crank angle when the combustion mass ratio is 2% is calculated by the following equation.

θ2pdif = (θignz−IGNEADref2z−BURN1ref2z)
-([Theta] ign-IGNEADref2-BURN1ref2) (97)
In step 319, the current value θmb31p [degBTDC] of the crank angle when the combustion mass ratio is 31% is calculated by the following equation.

θmb31p = θmb31pz−θ2pdif (98)
In step 320, the volume Vmb31p [m ³ ] at a combustion mass ratio of 31% in the combustion chamber 5 is calculated from the crank angle θmb31p by the following equation. This operation is the same as the operation in step 304 in FIG.

Vmb31p = f25 (θmb31p) (99)
In steps 321 and 322, the second initial combustion period BURN1ref2 and the second main combustion period BURN2ref2 are used by using the combustion chamber volumes Vmb1p and Vmb31p obtained by the equations (95) and (99), and the first basic ignition is performed for the first time. Using the ignition timing (MBTCAL1-KNRT) retarded from the timing MBTCAL1, the temperature T0 and the pressure P0 at the combustion start timing of the combustion chamber 5 are calculated, and the second ignition dead time equivalent crank angle IGNDEADref2 is calculated. For the calculation of the second combustion periods BURN1ref2, BURN2ref2 and the second ignition dead time equivalent crank angle IGNDEADref2, the flow of FIGS. 41, 42, and 43 may be used.

  In step 323, the second basic ignition timing MBTCAL2 [2] is calculated by the following equation that is the same as the equation (93) using the second combustion periods BURN1ref2, BURN2ref2 and the second ignition dead time equivalent crank angle IGNDEADref2 calculated in this way. degBTDC] is calculated.

MBTCAL2 = BURN1ref2 + BURN2ref2-θPMAX
+ IGNDEADref2
... (100)
As a result, all of the second basic ignition timing MBTCAL2, the second initial combustion period BURN1ref2, the second main combustion period BURN2ref2, and the second ignition dead time equivalent crank angle IGNDEADref2 necessary for resetting the combustion mass waveform BR are obtained. In step 324, these values are used to reset the combustion mass waveform. That is, a primary expression of the combustion mass ratio BR in the second combustion delay period, the second initial combustion period, and the second main combustion period is calculated by the following expression similar to the above expressions (61) to (63), and the calculated expression Remember.

Second combustion delay period;
BR = 0 (101)
Second initial combustion period;
BR = SS1 × (Θ + MBTCAL2-IGNDEADref2)
... (102)
Second main combustion period;
BR = 0.02 + SS2 × (Θ + MBTCAL2-IGNDEADref2
-BURN1ref2)
... (103)
However, SS1: 0.02 / BURN1ref2,
SS2: 0.58 / BURN2ref2,
FIG. 48 shows a model of the difference between the initial combustion mass ratio waveform (see solid line) and the reset combustion mass ratio waveform (see alternate long and short dash line). When ignition is performed at an ignition timing (MBTCAL1-KNRT) retarded by a knock retard amount KNRT from the first basic ignition timing MBTCAL1, the combustion speed is higher than when ignition is performed at the first basic ignition timing MBTCAL1 and combustion is performed. Since it becomes slow, the waveform of the combustion mass ratio changes.
Therefore, the second combustion periods BURN1ref2, BURN2ref2, and second ignition waste, which are values when ignition is performed again at the ignition timing (MBTCAL1-KNRT) retarded by the knock retard amount KNRT from the first basic ignition timing MBTCAL1. The time-equivalent crank angle IGNDEADref2 and the second basic ignition timing MBTCAL2 are calculated, and the combustion mass ratio is reset from these, which is the characteristics of the one-dot chain line. According to the characteristics of this alternate long and short dash line, the change in the actual combustion mass ratio that has changed by the delay in the combustion speed accompanying the delay from the basic ignition timing can be approximated well.

  When the resetting of the combustion mass waveform is completed in this way, in step 325, the knock intensity at the ignition timing (= MBTCAL2-KNRT) retarded from the second basic ignition timing MBTCAL2 using the reset combustion mass waveform. The estimated value is calculated as the second knock strength estimated value KIC2. The second knock strength estimated value is given a subscript “2” to distinguish it from the first knock strength estimated value KIC calculated in step 309 of FIG.

  The calculation of the second knock strength estimated value KIC2 will be described with reference to the flowcharts of FIGS.

  49 and 50 (subroutine of step 325 in FIG. 40), the calculation method of the second knock strength estimated value KIC2 itself is the same as the method of calculating the first knock strength estimated value KIC shown in FIGS. Therefore, the same step numbers are assigned to the same parts as those in FIGS.

  32 and 33 are only steps 401, 402, 403, 404, and 405. That is, in step 401, the knock retard amount KNRT used in step 313 in FIG. 39 in addition to the second ignition dead time equivalent crank angle IGNDEADref2 and the second basic ignition timing MBTCAL2 calculated in steps 322 and 323 in FIG. And (MBTCAL2-KNRT) -IGNREADref2 is input to the crank angle θ in step 402. This is to calculate the second knock magnitude estimated value KIC2 from the ignition timing delayed by the knock retard amount KNRT from the second basic ignition timing MBTCAL2.

  In steps 204 to 217 and step 218 in FIG. 50, the self-ignition timing θknk is calculated in the same manner as in FIGS. 32 and 33.

  In step 403 of FIG. 50, the combustion mass ratio BRknk at the self-ignition timing θknk is calculated using the characteristics of the combustion mass ratio after resetting. The method for calculating the combustion mass ratio BRknk at the self-ignition timing θknk is the same as the operation at step 219 in FIG. That is, when the self-ignition timing θknk is in the second initial combustion period, the self-ignition timing θknk is converted into the crank angle Θ based on the compression top dead center TDC, and the converted crank angle Θ is converted into the above (102 When the self-ignition timing θknk is in the second main combustion period, the self-ignition timing θknk is converted into the crank angle Θ based on the compression top dead center TDC, and the converted crank angle Θ is It can obtain | require by substituting each to (103) Formula.

  In steps 220 to 228 and 404 in FIG. 50, the unburned fuel amount MUB is calculated using the combustion mass ratio BRknk and the fuel amount QINJ, and the pressure increase DP due to knock is calculated based on the unburned fuel amount MUB. Then, the second knock magnitude estimated value KIC2 is calculated based on the pressure increase amount DP due to the knock.

  When the calculation of the second knock magnitude estimated value KIC2 using the reset combustion mass waveform is completed in this way, the process returns to FIG. 40, and the second knock magnitude estimated value KIC2 and the trace knock magnitude are compared in step 326. To do. As a result of the comparison, when the second knock magnitude estimated value KIC2 and the trace knock magnitude match, the reset combustion mass waveform represents that the actual combustion mass waveform at the retarded ignition timing is well approximated. At this time, the routine proceeds to step 327, the value of MBTCAL2-KNRT (= θsign), which is the ignition timing at that time, is shifted to the knock limit ignition timing KNOCKcal [degBTDC], and the current processing is terminated.

  On the other hand, the fact that the second knock magnitude estimated value KIC2 and the trace knock magnitude do not coincide indicates that the combustion mass waveform for the current ignition timing does not yet coincide with the actual combustion mass waveform. Then, the second knock strength estimated value KIC2 is compared with the trace knock strength to see whether or not the knock retard amount is appropriate. When the second knock magnitude estimated value KIC2 is larger than the trace knock magnitude, it is determined that the knock retard amount KNRT calculated in step 313 in FIG. 39 is still insufficient, and the routine proceeds to step 329, where the knock retard amount KNRT is set to the first knock retard amount KNRT. Increase by a predetermined value const1. That is, the knock retard amount KNRT is updated by the following equation.

KNRT (new) = KNRT (old) + const1 (104)
Where KNRT (new): amount of knock retard after update,
KNRT (old): Knock retard amount before update,
const1: Update amount to increase side,
After updating the knock retard amount in this way, the process returns to step 314 and the operations of steps 314 to 326 are executed again. That is, in step 314, the ignition timing θign is calculated using the updated knock retard amount KNRT, and the operations in steps 315 to 323 are executed using this new ignition timing θign, which is necessary for setting the combustion mass waveform. MBTCAL2, BURN1ref2, BURN2ref2, and IGNDEADref2 are calculated, and the combustion mass waveform is reset in step 324 using these, and the second knock intensity estimation at the new ignition timing θign is performed using the waveform of the reset combustion mass ratio. The value KIC2 is calculated in step 325, and the calculated second knock magnitude estimated value KIC2 and the trace knock magnitude are compared in step 326. As a result of the comparison, if the second knock magnitude estimated value KIC2 coincides with the trace knock magnitude, the routine proceeds from step 326 to step 327, and the value of MBTCAL2-KNRT (= θsign), which is the ignition timing at that time, is set to the knock limit ignition timing KNOCKcal. To end the current process.

  If the second knock strength estimated value KIC2 still does not coincide with the trace knock strength, the routine proceeds to step 328, where it is determined whether or not the second knock strength estimated value KIC2 is greater than or equal to the trace knock strength. Is greater than or equal to the trace knock intensity, the knock retard amount KNRT is further updated to the increase side in step 329, and then the operation returns to step 314 and the operations of steps 314 to 326 are executed again. In this way, the second knock strength estimated value KIC2 eventually coincides with the trace knock strength, and the operation of step 327 is executed to end the current operation.

  On the other hand, if the second knock magnitude estimated value KIC2 is smaller than the trace knock magnitude, it is determined that the knock retard amount KNRT calculated in step 313 in FIG. 39 is too large and the routine proceeds from step 328 to step 330, where the knock retard amount KNRT Is reduced by a second predetermined value const2. That is, the knock retard amount KNRT is updated by the following equation.

KNRT (new) = KNRT (old) -const2 (105)
Where KNRT (new): amount of knock retard after update,
KNRT (old): Knock retard amount before update,
const2: update amount to the side to be reduced,
After updating the knock retard amount in this way, the process returns to step 314 and the operations of steps 314 to 326 are executed again. That is, in step 314, the ignition timing θign is calculated using the updated knock retard amount KNRT, and the operations in steps 315 to 323 are executed using this new ignition timing θign, which is necessary for setting the combustion mass waveform. MBTCAL2, BURN1ref2, BURN2ref2, and IGNDEADref2 are calculated, and the combustion mass waveform is reset in step 324 using these, and the second knock intensity estimation at the new ignition timing θign is performed using the waveform of the reset combustion mass ratio. The value KIC2 is calculated in step 325, and the calculated second knock magnitude estimated value KIC2 and the trace knock magnitude are compared in step 326. As a result of the comparison, if the second knock magnitude estimated value KIC2 coincides with the trace knock magnitude, the routine proceeds from step 326 to step 327, and the value of MBTCAL2-KNRT (= θsign), which is the ignition timing at that time, is set to the knock limit ignition timing KNOCKcal. To end the current process.

  If the second knock strength estimated value KIC2 still does not coincide with the trace knock strength, the process proceeds to step 328, and it is determined whether the second knock strength estimated value KIC2 is less than the trace knock strength or not. Is less than the trace knock intensity, the knock retard amount KNRT is further updated to the decrease side (advance side) in step 330, and then the process returns to step 314 and the operations in steps 314 to 326 are executed again. In this way, the second knock strength estimated value KIC2 eventually coincides with the trace knock strength, and the operation of step 327 is executed to end the current operation.

  Depending on how the predetermined values const1 and const2 are set, the second knock magnitude estimated value KIC2 and the trace knock magnitude do not match and the knock retard amount KNRT may not converge. The predetermined values const1 and const2 are matched by a preliminary experiment or the like. Alternatively, a predetermined allowable range is provided for the trace knock intensity, and when the second knock intensity estimated value KIC2 falls within this allowable range, it is considered that the knock retard amount KNRT has converged and the process proceeds to step 327.

  Note that the loop operation from step 314 to step 330 in FIG. 40 ends in an instant, and is not prolonged until the basic ignition timing MBTCAL of the next combustion cycle.

  Thereafter, the process waits until the crank angle reaches the basic ignition timing MBTCAL of the next combustion cycle, and the processes of FIGS. 39 and 40 are executed again. Thus, the knock limit ignition timing KNOCKcal is obtained for each combustion cycle.

  When the calculation of the knock limit ignition timing KNOCKcal is completed in this manner, the process returns to step 3 in FIG. Is selected as the ignition timing minimum value PADV, and in step 4, a value obtained by adding various corrections based on the water temperature or the like is set as an ignition timing command value QADV [degBTDC]. After completion of engine warm-up, there is no correction due to the water temperature or the like, so the ignition timing command value QADV becomes equal to the ignition timing minimum value PADV.

  The ignition timing command value QADV set in this way is transferred to the ignition register in step 5, and an ignition signal for cutting off the primary current from the engine controller 31 at the timing when the actual crank angle coincides with the ignition timing command value QADV is generated by the ignition coil 13. Is output.

  Here, the effect of this embodiment is demonstrated.

  According to the present embodiment (the invention described in claim 4), the knock limit ignition timing setting means is based on the characteristic representing the distribution of the reciprocal of the time until the fuel in the combustion chamber 5 reaches self-ignition. 5 based on the self-ignition timing estimation means (see step 218 in FIGS. 32 and 33) for estimating the self-ignition timing θknk of the fuel within 5 and the characteristics of the combustion mass ratio when igniting and burning at the basic ignition timing MBTCAL Based on the auto-ignition combustion mass ratio calculating means (see step 219 in FIG. 33) for calculating the combustion mass ratio BRknk at the auto-ignition timing θknk, and the calculated combustion mass ratio BRknk and the fuel amount QINJ at the auto-ignition timing. An unburned fuel amount calculating means for calculating the unburned fuel amount MUB (see step 222 in FIG. 33), and a pressure generated by knocking in the combustion chamber based on the unburned fuel amount MUB. A pressure increase calculation means for calculating the force increase DP (see step 226 in FIG. 33), and a first knock intensity KIC that calculates the first knock intensity estimated value KIC based on the pressure increase DP due to the knock in the combustion chamber 5 The strength estimated value calculating means (see steps 227 to 229 in FIG. 33), the comparing means (see step 311 in FIG. 39) for comparing the first knock strength estimated value KIC and the trace knock strength (slice level), and this comparison From the result, when the first knock magnitude estimated value KIC is greater than or equal to the trace knock magnitude, the knock retard quantity calculating means (see step 313 in FIG. 39) for calculating a predetermined knock retard quantity KNRT and the first basic ignition timing MBTCAL1 Assuming that ignition is performed at an ignition timing (MBTCAL1-KNRT) retarded by a knock retard amount KNRT. Second combustion period calculation means (see steps 314 to 321 in FIG. 40) for calculating a combustion period from the start of combustion to a predetermined crank angle as a second combustion period (BURN1ref2, BURN2ref2), and this second combustion period (BURN1ref2) , BURN2ref2) based on the second basic ignition timing calculating means (see step 323 in FIG. 40) for calculating the basic ignition timing at which MBT is obtained as the second basic ignition timing MBTCAL2, and the second combustion period (BURN1ref2, BURN2ref2) Based on the above, the characteristics of the combustion mass ratio are changed to the characteristics of the combustion mass ratio in the case where ignition is performed at the ignition timing (MBTCAL2-KNRT) retarded by the retard amount KNRT from the second basic ignition timing (MBTCAL2). And resetting means for resetting (steps in FIG. 324) and the characteristics of the combustion mass ratio after resetting, it is assumed that ignition is performed at an ignition timing (MBTCAL2-KNRT) retarded by a knock retard amount KNRT from the second basic ignition timing MBTCAL2. Second knock strength calculation means (see step 325 in FIG. 40) for calculating the knock strength estimate value in this case as the second knock strength estimate value KIC2, and when the second knock strength estimate value KIC2 matches the trace knock strength, (2) A knock limit ignition timing setting means (see steps 326 and 327 in FIG. 40) for setting the ignition timing (MBTCAL2-KNRT) delayed by the knock retard amount KNRT from the basic ignition timing MBTCAL2 as the knock limit ignition timing KNOCKcal. Therefore, the characteristic of the combustion mass ratio after resetting is the second basic ignition timing. This matches the characteristics of the actual combustion mass ratio when ignition is performed at the ignition timing (MBTCAL2-KNRT) retarded by the knock retard amount KNRT from MBTCAL2, and the knock retard amount from the second basic ignition timing MBTCAL2 Even when the combustion is performed at the ignition timing (MBTCAL2-KNRT) retarded by KNRT, the second knock magnitude estimated value KIC2 can be calculated with high accuracy (the estimation of the knock magnitude is accurate).

  The laminar combustion speed when ignition is performed at an ignition timing (MBTCAL2-KNRT) retarded from the second basic ignition timing MBTCAL2 is ignited at the first basic ignition timing MBTCAL1 (or MBTCAL calculated in step 43 of FIG. 13). Corresponding to the difference from the laminar combustion speed at this time, according to the present embodiment (invention of claim 5), the second combustion period calculation means calculates the second combustion period (BURN1ref2, BURN2ref2) Since it is calculated using the laminar combustion speed (SL1, SL2) different from the laminar combustion speed when igniting and burning at the first basic ignition timing MBTCAL1 (or MBTCAL calculated in step 43 of FIG. 13) (FIG. 10 step 168 and FIG. 41 step 348, FIG. 12 step 188 and FIG. 42 step 3. 8), accurately calculate the laminar combustion velocity (SL1, SL2) when igniting and burning at the ignition timing (MBTCAL2-KNRT) retarded by the knock retard amount KNRT from the second basic ignition timing MBTCAL2 it can.

  The turbulence intensity (ST1, ST2) is ignited with the ignition timing (MBTCAL2-KNRT) retarded by the knock retard amount KNRT from the second basic ignition timing MBTCAL2, and at the first basic ignition timing MBTCAL1. Accordingly, it has been confirmed by experiment that there is no difference between the first combustion period and the second combustion period calculation means according to the present embodiment (the invention according to claim 7). Corrects the laminar combustion velocity (SL1, SL2) with the turbulence intensity (ST1, ST2) (see step 350 in FIG. 41, step 370 in FIG. 42) and the turbulence intensity used by the second combustion period calculation means (see FIG. 41). ST1 and ST2) are the same as the turbulence intensity (SL1, ST2) used by the first combustion period calculation means (see step 169 in FIG. 10 and step 349 in FIG. 41, FIG. 12). Because see step 369 of step 189 and FIG. 42), the calculation of the second combustion period by the second combustion period calculation means can be reduced ROM capacity with be accurate.

  According to this embodiment (the invention described in claim 8), the first and second combustion periods are divided into a plurality (two of the initial combustion period and the main combustion period) according to the change in the combustion mass ratio. Therefore, it is possible to cope with an actual phenomenon in which the combustion speed (that is, the combustion mass ratio) changes greatly between the early stage and the late stage of combustion.

  According to the present embodiment (the invention described in claim 9), when the second combustion period calculation means calculates the second combustion period (BURN1ref2, BURN2ref2), the combustion chamber 5 is in an intermediate period of the combustion period. Since the volume (Vmb1p, Vmb31p) and the combustion mass ratio (BR1p, BR31p) in the intermediate period of the combustion period of the combustion chamber 5 are used (see step 351 in FIG. 41 and step 371 in FIG. 42), the second combustion period The calculation accuracy of (BURN1ref2, BURN2ref2) is increased, and the accuracy of resetting the characteristics of the combustion mass ratio is also improved.

  According to the present embodiment (the invention described in claim 10), an ignition signal is output to an ignition device (spark ignition means) including an ignition coil 13 and an ignition plug 14 and the like, and then the ignition plug 14 causes the inside of the combustion chamber 5 to flow. The crank angle (IGNEADref2) corresponding to the ignition dead time, which is the crank angle interval until ignition is performed, is a parameter relating to combustion (pressure P0 at the combustion start timing of the combustion chamber 5, temperature T0 at the combustion start timing of the combustion chamber 5, and air-fuel ratio). The ignition dead time equivalent crank angle calculating means is calculated according to the target excess air ratio TLAMBDA (see FIG. 43), and the resetting means is based on the ignition dead time equivalent crank angle (IGNEADref2). (See steps 322 to 324 in FIG. 40), the parameters related to combustion change. , The characteristics of the combustion mass proportion can be accurately set again.

  In the embodiment, the case where the pressure increase amount DP due to knock in the combustion chamber is calculated based on the unburned fuel amount MUB has been described. However, the pressure increase amount DP due to knock in the combustion chamber is calculated based on the unburned fuel ratio. However, it does not matter (the invention according to claims 3 and 4).

  In the embodiment, a laminar combustion speed (SL1, SL2) which is a combustion speed in a laminar flow state of combustion gas, a combustion gas volume equivalent volume (V0, VTDC) which is a volume corresponding to the combustion gas volume in the combustion chamber, a predetermined value From the start of combustion based on the combustion mass ratio (BR1, BR2) of the gas combusted in the combustion chamber up to the crank angle and the reaction probability (RPROBA) indicating the ease of combustion of the combustion gas under predetermined operating conditions. First combustion period calculation means for calculating a first combustion period (BURN1, BURN2) up to the corner, and a basic ignition timing (MBTCAL) at which MBT is obtained based on the first combustion period (BURN1, BURN2) The first basic ignition timing calculation means for calculating the ignition timing has been described. However, the present invention is not limited to this, and the MB is calculated by other known calculation methods. The present invention can be applied to the basic ignition timing obtained and calculates the first basic ignition timing of (claim 1).

  In the embodiment, as shown in FIGS. 39 and 40, the first combustion periods BURN1ref1, BURN2ref1, the first ignition dead time equivalent crank angle IGNDEADref1, and the first basic ignition timing MBTCAL1 are calculated (see steps 305 to 307 in FIG. 39). Based on these, the characteristics of the combustion mass ratio are initially set (see step 308 in FIG. 39), and the case where the ignition timing is retarded with reference to the basic ignition timing MBTCAL1 has been described. The combustion mass ratio characteristics are initially set based on the combustion periods BURN1 and BURN2 shown in FIG. 5, the crank angle IGNDEAD corresponding to the ignition dead time shown in FIG. 51, and the basic ignition timing MBTCAL shown in FIG. The ignition timing is retarded based on the basic ignition timing MBTCAL shown in May be configured to so that (claim 4).

  In the embodiment, the second combustion period calculation means uses a laminar combustion speed (SL1, SL2) different from the laminar combustion speed when the second combustion period is ignited and combusted at the first basic ignition timing MBTCAL. As described in the case of calculation (see step 348 in FIG. 41 and step 368 in FIG. 42), the second combustion period calculation means ignites and combusts the second combustion period at the first basic ignition timing MBTCAL1. It can also be calculated using the same laminar burning velocity (SL1, SL2) as the laminar burning velocity (the invention according to claim 6). According to this, the calculation load can be reduced.

  In the embodiment, the case where the estimated octane number is calculated has been described. However, the present invention is not limited to this, and the present invention is applicable to a case where the estimated octane number is not calculated. Furthermore, it is applicable to those using a mixed fuel of gasoline and alcohol.

  In the first aspect of the present invention, the function of the self-ignition timing estimation means is the step 218 of FIGS. 32 and 33, and the function of the first knock strength estimated value calculation means is the steps 227 to 229 of FIG. The function is step 311 in FIG. 39, the function of the knock retard amount calculating means is in step 313 in FIG. 39, the function of the combustion period calculating means is in steps 314 to 321 in FIG. 40, and the function of the second basic ignition timing calculating means is 40, the function of the second knock strength estimated value calculation means is performed by step 325 of FIG. 40, and the function of the knock limit ignition timing setting means is performed by steps 326 and 327 of FIG.

  In the invention described in claim 4, the function of the laminar combustion velocity calculating means is the same as that of step 168 of FIG. 10 and step 188 of FIG. 12, and the function of the combustion gas volume equivalent volume calculating means is that of steps 162 and FIG. In step 182, the function of the combustion mass ratio calculation means is in step 171 in FIG. 10 and step 191 in FIG. 12, the function of the reaction probability calculation means is in step 15 in FIG. 5, and the function of the first combustion period calculation means is in FIG. In step 171 of FIG. 12 and step 191 of FIG. 12 (or step 305 of FIG. 39), the function of the first basic ignition timing calculation means is the function of the self-ignition timing estimation means by step 43 of FIG. 13 (or step 307 of FIG. 39). The function is based on step 218 in FIGS. 32 and 33, and the function of the self-ignition combustion mass ratio calculating means is the step in FIG. 19, the function of the unburned fuel amount calculating means is according to step 222 of FIG. 33, the function of the pressure increase amount calculating means is according to step 226 of FIG. 33, and the function of the first knock strength estimated value calculating means is step 227 of FIG. ˜229, the function of the comparison means is according to step 311 of FIG. 39, the function of the knock retard amount calculation means is according to step 313 of FIG. 39, and the function of the second combustion period calculation means is according to steps 314 to 321 of FIG. 2 The function of the basic ignition timing calculating means is based on step 323 in FIG. 40, the function of the resetting means is based on step 324 in FIG. 40, and the function of the second knock intensity estimated value calculating means is based on step 325 in FIG. The function of the setting means is performed by steps 326 and 327 in FIG.

The engine control system figure of one Embodiment. The flowchart for demonstrating ignition timing control. The pressure change figure of a combustion chamber. The characteristic view explaining the change of a combustion mass ratio. The flowchart for demonstrating calculation of a physical quantity. Diagram explaining the positional relationship between the crankshaft of the engine and the connecting rod. The characteristic diagram of a water temperature correction coefficient. The characteristic view of an equivalence ratio correction coefficient. The characteristic figure of a standard crank angle. The flowchart for demonstrating calculation of an initial combustion period. The characteristic figure of a temperature rise rate. The flowchart for demonstrating calculation of the main combustion period. The flowchart for demonstrating calculation of basic ignition timing. The flowchart for demonstrating calculation of an internal inert gas rate. The flowchart for demonstrating calculation of an internal inert gas amount. The flowchart for demonstrating calculation of the amount of inert gas at the time of EVC. The flowchart for demonstrating calculation of the amount of inert gas blown back during overlap. The flowchart for demonstrating the setting of a supercharging determination flag and a choke determination flag. The flowchart for demonstrating calculation of the inactive gas flow rate during the overlap when there is no supercharging and there is no choke. The flowchart for demonstrating the calculation of the inactive gas flow rate during the overlap at the time of supercharging without a choke. The flowchart for demonstrating the calculation of the inactive gas flow rate during the overlap at the time of supercharging and no choke. The flowchart for demonstrating calculation of the inactive gas flow rate during the overlap at the time of supercharging and a choke. The characteristic figure of the combustion chamber volume in the exhaust valve closing timing. The characteristic figure of the gas constant of an inert gas. The characteristic figure of the integrated effective area during overlap. Explanatory drawing of the integrated effective area during overlap. The characteristic figure of the specific heat ratio of an inert gas. The characteristic figure of the specific heat ratio of air-fuel | gaseous mixture. The characteristic view which shows the pressure history in the combustion chamber at the time of knock generation. The characteristic diagram of 1 / τ for fuel with an octane number of 100. The characteristic diagram of 1 / τ with fuel of octane number 80. The characteristic view which shows the change of the combustion mass ratio at the time of approximating with a straight line. The flowchart for demonstrating calculation of a 1st knock magnitude estimated value. The flowchart for demonstrating calculation of a 1st knock magnitude estimated value. The flowchart for demonstrating calculation of a total gas mole number. The flowchart for demonstrating calculation of gas enthalpy. The characteristic diagram of a rotational speed correction coefficient. The flowchart for demonstrating calculation of an octane number estimated value. The wave form diagram which shows the motion of the octane number estimated value at the time of knock detection. The flowchart for demonstrating calculation of a knock limit ignition timing. The flowchart for demonstrating calculation of a knock limit ignition timing. The flowchart for demonstrating calculation of the 1st or 2nd initial stage combustion period. The flowchart for demonstrating calculation of the 1st or 2nd main combustion period. The flowchart for demonstrating calculation of the 1st or 2nd ignition dead time equivalent crank angle. The characteristic figure of ignition dead time basic value. The characteristic figure of a temperature correction coefficient. The characteristic diagram of an excess air ratio correction coefficient. Trace knock strength characteristic chart. The characteristic view which shows the reset of a combustion mass ratio. The flowchart for demonstrating calculation of a 2nd knock magnitude estimated value. The flowchart for demonstrating calculation of a 2nd knock magnitude estimated value. The flowchart for demonstrating calculation of an ignition dead time equivalent crank angle.

Explanation of symbols

1 Engine 5 Combustion chamber 11 Ignition device (spark ignition means)
21 Fuel injector 31 Engine controller

Claims (15)

First basic ignition timing calculating means for calculating a basic ignition timing obtained based on a predetermined combustion period as a first basic ignition timing;
Knock limit ignition timing setting means for setting the knock limit ignition timing;
In a knock control device for an engine comprising spark ignition means for performing spark ignition at a retarded value of either the first basic ignition timing or the knock limit ignition timing,
The knock limit ignition timing setting means,
Self-ignition timing estimating means for estimating a timing at which the fuel in the combustion chamber self-ignites when ignited at the first basic ignition timing;
First knock intensity estimated value calculating means for calculating a first knock intensity estimated value based on the calculated self-ignition timing;
A comparison means for comparing the first knock strength estimated value with the slice level;
A knock limit ignition timing setting means for setting the first basic ignition timing as the knock limit ignition timing as it is when the first knock magnitude estimated value is less than the slice level from the comparison result;
Knock retard amount calculating means for calculating a predetermined knock retard amount if the first knock intensity estimates from the comparison result is a slice level or higher,
Combustion period calculating means for calculating a combustion period from the start of combustion to a predetermined crank angle when igniting and burning at an ignition timing retarded by this knock retard amount from the first basic ignition timing;
A second basic ignition timing calculating means for calculating a basic ignition timing obtained based on the combustion period as a second basic ignition timing;
Second knock intensity estimated value calculating means for calculating, as a second knock intensity estimated value, a knock intensity when igniting and burning at an ignition timing delayed by the knock retard amount from the second basic ignition timing;
Knock limit ignition timing setting means for setting, as a knock limit ignition timing, an ignition timing retarded by the knock retard amount from the second basic ignition timing when the second knock intensity estimated value matches the slice level ;
If the second knock strength estimate does not match the slice level and the second knock strength estimate is greater than the slice level,
Update the calculated knock retard amount to a side that increases by a predetermined value,
A combustion period from the start of combustion to a predetermined crank angle in the case of ignition and combustion at an ignition timing retarded by the updated knock retard amount from the first basic ignition timing is calculated as an updated combustion period;
The basic ignition timing obtained based on the updated combustion period is calculated as the updated second basic ignition timing,
Calculating the knock intensity when igniting and burning at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing as the updated second knock intensity estimated value;
The updated second knock strength estimated value is compared with the slice level.
When the updated second knock intensity estimated value coincides with the slice level by this repetition, the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is the knock limit ignition. As time
If the second knock strength estimate does not match the slice level and the second knock strength estimate is smaller than the slice level,
Update the calculated knock retard amount to a smaller value by a predetermined value,
A combustion period from the start of combustion to a predetermined crank angle in the case of ignition and combustion at an ignition timing retarded by the updated knock retard amount from the first basic ignition timing is calculated as an updated combustion period;
The basic ignition timing obtained based on the updated combustion period is calculated as the updated second basic ignition timing,
Calculating the knock intensity when igniting and burning at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing as the updated second knock intensity estimated value;
The updated second knock strength estimated value is compared with the slice level.
When the updated second knock intensity estimated value coincides with the slice level by this repetition, the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is the knock limit ignition. An engine knock control device comprising: knock limit ignition timing setting means for setting each as a timing . The first knock strength estimated value calculation means calculates a combustion mass ratio at the self-ignition timing based on a characteristic of a combustion mass ratio when igniting and burning at the first basic ignition timing. A calculating means, and a knock intensity estimated value calculating means for calculating a first knock intensity estimated value based on the calculated combustion mass ratio and fuel amount at the self-ignition timing,
The second knock intensity estimated value calculating means is configured to ignite and burn when the combustion mass ratio characteristic is retarded by the knock retard amount from the second basic ignition timing based on the combustion period. Using the resetting means for resetting to the characteristics of the combustion mass ratio and the characteristics of the combustion mass ratio after the resetting, ignition is performed at an ignition timing retarded by the knock retard amount from the second basic ignition timing. 2. The engine knock control apparatus according to claim 1, further comprising knock intensity estimated value calculating means for calculating a knock intensity for combustion as a second knock intensity estimated value. The self-ignition timing estimation means estimates the time when the fuel in the combustion chamber self-ignites based on the characteristics representing the distribution of the reciprocal of the time until the fuel in the combustion chamber reaches self-ignition,
The first knock strength estimated value calculation means calculates a combustion mass ratio at the self-ignition timing based on a characteristic of a combustion mass ratio when igniting and burning at the first basic ignition timing. An unburned fuel amount calculating means for calculating an unburned fuel amount or an unburned fuel ratio based on the calculated combustion mass ratio and fuel amount at the calculated self-ignition timing, and the unburned fuel amount or unburned fuel. A pressure increase amount calculating means for calculating a pressure increase amount due to knock in the combustion chamber based on the ratio; and a knock strength estimated value calculating means for calculating a first knock strength estimated value based on the pressure increase amount due to the knock in the combustion chamber; Consists of
The second knock intensity estimated value calculating means is configured to ignite and burn when the combustion mass ratio characteristic is retarded by the knock retard amount from the second basic ignition timing based on the combustion period. Using the resetting means for resetting to the characteristics of the combustion mass ratio and the characteristics of the combustion mass ratio after the resetting, ignition is performed at an ignition timing retarded by the knock retard amount from the second basic ignition timing. 2. The engine knock control apparatus according to claim 1, further comprising knock intensity estimated value calculating means for calculating a knock intensity for combustion as a second knock intensity estimated value. Laminar combustion speed calculating means for calculating a laminar combustion speed that is a combustion speed in a laminar state of the combustion gas;
A combustion gas volume equivalent volume calculating means for calculating a volume corresponding to the combustion gas volume in the combustion chamber;
Combustion mass ratio calculating means for calculating the combustion mass ratio of the gas combusted in the combustion chamber by a predetermined crank angle;
Reaction probability calculation means for calculating a reaction probability indicating the ease of combustion of combustion gas under a predetermined operating condition;
A first combustion period calculating means for calculating a combustion period from the start of combustion to a predetermined crank angle as a first combustion period based on these laminar combustion speed, combustion gas volume equivalent volume, combustion mass ratio and reaction probability;
First basic ignition timing calculation means for calculating a basic ignition timing obtained based on the first combustion period as a first basic ignition timing;
Knock limit ignition timing setting means for setting the knock limit ignition timing;
In a knock control device for an engine comprising spark ignition means for performing spark ignition at a retarded value of either the first basic ignition timing or the knock limit ignition timing,
The knock limit ignition timing setting means,
Self-ignition timing estimation means for estimating the time when the fuel in the combustion chamber self-ignites based on the characteristics representing the distribution of the reciprocal of the time until the fuel in the combustion chamber reaches self-ignition,
A self-ignition combustion mass ratio calculating means for calculating a combustion mass ratio at the self-ignition timing based on a characteristic of a combustion mass ratio when igniting and burning at the first basic ignition timing;
An unburned fuel amount calculating means for calculating an unburned fuel amount or an unburned fuel ratio based on the burned mass ratio and the fuel amount at the calculated self-ignition timing;
A pressure increase amount calculating means for calculating a pressure increase amount due to knocking in the combustion chamber based on the unburned fuel amount or the unburned fuel ratio;
First knock intensity estimated value calculating means for calculating a first knock intensity estimated value based on the amount of pressure increase due to knock in the combustion chamber;
A comparison means for comparing the first knock strength estimated value with the slice level;
A knock limit ignition timing setting means for setting the first basic ignition timing as the knock limit ignition timing as it is when the first knock magnitude estimated value is less than the slice level from the comparison result;
Knock retard amount calculating means for calculating a predetermined knock retard amount if the first knock intensity estimates from the comparison result is a slice level or higher,
A second combustion period in which a combustion period from the start of combustion to a predetermined crank angle is calculated as a second combustion period when it is assumed that combustion is performed at an ignition timing retarded by this knock retard amount from the first basic ignition timing. A calculation means;
Second basic ignition timing calculation means for calculating a basic ignition timing obtained based on the second combustion period as a second basic ignition timing;
Based on the second combustion period, the characteristic of the combustion mass ratio is reset to the characteristic of the combustion mass ratio when igniting and burning at an ignition timing retarded by the knock retard amount from the second basic ignition timing. Resetting means,
Using the characteristics of the combustion mass ratio after the resetting, the knock intensity when the ignition is assumed to be ignited and burned at the ignition timing retarded by the knock retard amount from the second basic ignition timing is calculated as the second knock intensity estimated value. Second knock strength estimated value calculating means for calculating as
Knock limit ignition timing setting means for setting, as a knock limit ignition timing, an ignition timing retarded by the knock retard amount from the second basic ignition timing when the second knock intensity estimated value matches the slice level ;
If the second knock strength estimate does not match the slice level and the second knock strength estimate is greater than the slice level,
Update the calculated knock retard amount to a side that increases by a predetermined value,
The combustion period from the start of combustion to the predetermined crank angle when assuming that the ignition is performed at the ignition timing retarded by the updated knock retard amount from the first basic ignition timing is the updated second combustion period. Calculate
The basic ignition timing obtained based on the updated second combustion period is calculated as the updated second basic ignition timing,
In the case of igniting and burning at the ignition timing that is retarded by the updated knock retard amount from the updated second basic ignition timing based on the updated second combustion period. Reset to combustion mass ratio characteristics,
Using the characteristics of the combustion mass ratio after resetting, the knock intensity when it is assumed that ignition is performed at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is performed. Calculate as the updated second knock strength estimate,
The updated second knock strength estimated value is compared with the slice level.
When the updated second knock intensity estimated value coincides with the slice level by this repetition, the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is the knock limit ignition. As time
If the second knock strength estimate does not match the slice level and the second knock strength estimate is smaller than the slice level,
Update the calculated knock retard amount to a smaller value by a predetermined value,
The combustion period from the start of combustion to the predetermined crank angle when assuming that the ignition is performed at the ignition timing retarded by the updated knock retard amount from the first basic ignition timing is the updated second combustion period. Calculate
The basic ignition timing obtained based on the updated second combustion period is calculated as the updated second basic ignition timing,
In the case where the combustion mass ratio characteristic is ignited at an ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing based on the updated second combustion period. Reset to combustion mass ratio characteristics,
Using the characteristics of the combustion mass ratio after resetting, the knock intensity when it is assumed that ignition is performed at the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is performed. Calculate as the updated second knock strength estimate,
The updated second knock strength estimated value is compared with the slice level.
When the updated second knock intensity estimated value coincides with the slice level by this repetition, the ignition timing retarded by the updated knock retard amount from the updated second basic ignition timing is the knock limit ignition. An engine knock control device comprising knock limit ignition timing setting means for setting each as a timing .   The second combustion period calculating means calculates the second combustion period by using a laminar combustion speed different from the laminar combustion speed when igniting and burning at the first basic ignition timing. The engine knock control apparatus according to claim 4. The second combustion period calculating means calculates the second combustion period by using the same laminar combustion speed as the laminar combustion speed when igniting and burning at the first basic ignition timing. The engine knock control apparatus according to claim 4 . The first and second combustion period calculating means correct the laminar combustion speed with the turbulence intensity,
The engine knock control apparatus according to claim 5 or 6, wherein the turbulence intensity used by the second combustion period calculation means is the same as the turbulence intensity used by the first combustion period calculation means.   5. The engine knock control device according to claim 4, wherein the first and second combustion periods are divided into a plurality of periods according to a change in the combustion mass ratio.   When calculating the second combustion period, the second combustion period calculation means uses a volume of the combustion chamber at an intermediate period of the combustion period and a combustion mass ratio of the combustion chamber at an intermediate period of the combustion period. The engine knock control apparatus according to claim 4.   Corresponding to the ignition dead time corresponding to the combustion dead time corresponding to the crank angle section that is the crank angle section from when the ignition signal is output to the spark ignition means until ignition is performed in the combustion chamber by the spark ignition means 5. The engine knock control apparatus according to claim 4, further comprising a crank angle calculation unit, wherein the resetting unit resets the combustion mass ratio characteristic even based on the crank angle corresponding to the dead ignition time.   11. The parameter relating to combustion is at least one of an air-fuel ratio, a pressure at the combustion start timing of the combustion chamber, a temperature at the combustion start timing of the combustion chamber, a charging efficiency, and an inert gas ratio. Engine knock control device. 5. The engine knock control apparatus according to claim 1, wherein the predetermined knock retard amount is a value based on a difference between the first knock strength estimated value and the slice level. 6. A self-ignition volume calculating means for calculating the volume of the combustion chamber at the self-ignition time based on the self-ignition time;
5. The engine knock control apparatus according to claim 4, wherein the amount of pressure increase due to the knock is calculated based on the volume of the combustion chamber at the time of self-ignition.   A fuel gas specific heat estimating means for estimating a specific heat of the self-ignited fuel gas in the combustion chamber is provided, and a pressure increase amount due to the knock is calculated based on a specific heat of the self-ignited fuel gas in the combustion chamber. The engine knock control apparatus according to claim 4.   The fuel gas specific heat calculating means includes a fuel gas enthalpy calculating means for calculating the enthalpy of the fuel gas to be ignited by a calculation formula, and an average temperature at the time of self-ignition for calculating an average temperature of the combustion chamber at the self-ignition timing by the calculation formula. The fuel gas specific heat calculating means for calculating the specific heat of the fuel gas that self-ignites based on the enthalpy of the fuel gas and the average temperature at the self-ignition timing. Engine knock control device.