JP4254605B2 - Engine ignition timing control device - Google Patents

Description

  The present invention relates to an ignition timing control device for an engine (internal combustion engine).

Paying attention to the fact that there are two fuels on the market, high octane fuel (octane number 98) and low octane fuel (octane number 91), when the fuel cap is opened, first set the base ignition timing for high octane fuel. If knocking occurs, it is determined that the fuel is a high-octane fuel, and if knocking does not occur, it is determined that the fuel is a low-octane fuel. When it is determined that the fuel is used, the operation is continued as it is, and when it is determined that the fuel is a low octane fuel, the operation is switched to the base ignition timing for the low octane fuel (see Patent Document 1).
Japanese Patent Laid-Open No. 5-280454

  By the way, in the overseas market, there are markets where various octane number fuels are used and the octane number is not known in advance. In the case where the technology disclosed in Patent Document 1 is applied to the fuel sold in such a market and the base ignition timing for the low octane fuel is set, the local octane number of the fuel is determined for the low octane fuel. Knock occurs when the octane number of the fuel used for matching the base ignition timing is smaller.

  In this case, in the technique of Patent Document 1 as well, the knock control by the knock sensor is performed as in the prior art. Therefore, when the knock sensor detects that the knock has occurred, the base ignition timing is stepped by the first predetermined value. After that, the base ignition timing is gradually advanced by the second predetermined value, and then the knock sensor detects that the knock has occurred again by the advance of the ignition timing in this operation. Then, the above operation is repeated.

  Thus, even if knocking occurs when the octane number of the local fuel is smaller than the octane number of the fuel used for matching the base ignition timing for the low-octane fuel, according to the technique of Patent Document 1, in order to avoid knocking The ignition timing delay and the subsequent advance operation are repeated, and knocking can be avoided by this operation. However, fuel consumption deteriorates and output decreases due to the ignition timing delay for avoiding knocking. In order to avoid such fuel consumption deterioration and output decrease, a base ignition timing calculation map is prepared for each of a plurality of different octane numbers from the maximum octane number to the minimum octane number. The ROM capacity for storing the map for calculating the base ignition timing becomes large.

  The above octane number is a parameter correlated with knock when gasoline is used as fuel, and in the case of a mixed fuel of gasoline and alcohol, the alcohol concentration in the mixed fuel is a knock correlation parameter. There is a market in the overseas market that the alcohol concentration in the mixed fuel is not known in advance. The technology of Patent Document 1 is applied to the mixed fuel sold in such a market as it is, and the alcohol concentration in the mixed fuel is high. When the base ignition timing for mixed fuel is set, and the alcohol concentration of the mixed fuel in the field is higher than the alcohol concentration of the mixed fuel used for matching the base ignition timing for the mixed fuel with high alcohol concentration Knocks. On the other hand, if the ignition timing delay operation and the subsequent advance operation to avoid knocking by the knock sensor are executed, the fuel consumption deteriorates and the output decreases. In order to avoid this, a map for calculating the base ignition timing is used. Is provided for each of a plurality of different alcohol concentrations from the lowest alcohol concentration to the highest alcohol concentration, the ROM capacity for storing the base ignition timing calculation map for each alcohol concentration increases.

  On the other hand, the compression ratio is also a knock correlation parameter. When using a fuel whose octane number is determined in advance, the compression ratio is determined by the engine specification, so the base ignition timing is matched so that knock does not occur at the compression ratio determined by the engine specification. . However, knocking occurs when the actual compression ratio becomes higher than the compression ratio of the engine specification for some reason. At this time, if the delay of the ignition timing for avoiding the knock and the subsequent advance operation are repeated based on the knock sensor, the fuel consumption deteriorates and the output decreases.

  Thus, since the fuel used and the combustion gas state in the combustion chamber are the main factors affecting the knock, the octane number and alcohol concentration are the knock correlation parameters for fuel, and the compression ratio is the knock correlation for the combustion gas state in the combustion chamber. It can be considered that these two types of knock correlation parameter estimation values are separately introduced as parameters.

  However, when knocking occurs due to a change in the fuel used, the knock detection result is reflected in the estimated value of the knock correlation parameter related to the combustion gas state in the combustion chamber. Thus, a new error occurs, and the deviation between the estimated value of the knock correlation parameter related to the fuel and the actual value of the knock correlation parameter related to the fuel is not eliminated. On the other hand, when knocking occurs due to an increase in the compression ratio due to manufacturing variations or deposits in the combustion chamber, if the knock detection result is reflected in the estimated value of the knock correlation parameter for the fuel, Since there is no change, a new error occurs in the estimated value of the knock correlation parameter for the fuel, and the estimated value of the knock correlation parameter for the combustion gas state in the combustion chamber and the actual state of the knock correlation parameter for the combustion gas state in the combustion chamber The deviation from the value is not eliminated.

  Thus, when two parameters are introduced, it is necessary to select one of the parameters under appropriate conditions.

  Therefore, the present invention feeds back the knock detection result by the knock sensor to the knock correlation parameter instead of the ignition timing, introduces two types of knock correlation parameters, and selects one of the parameters according to the condition, so as in the conventional apparatus. In addition, there is provided an apparatus capable of avoiding knock by a method that does not repeat the ignition timing retardation and the subsequent advance operation for avoiding knock and accurately calculating the estimated values of the two types of knock correlation parameters. The purpose is to do.

The present invention detects whether or not knock has actually occurred in the combustion chamber and has estimated values of a knock correlation parameter related to fuel and a knock correlation parameter related to a combustion gas state in the combustion chamber. One of the knock correlation parameters is selected, and an estimated value of the knock correlation parameter on the selected side is calculated based on the knock detection result .

An ignition timing is calculated based on the calculated knock correlation parameter estimated value, and a spark ignition is performed at this ignition timing. Specifically, the knock generation timing (θknk) in the combustion chamber is predicted based on the knock correlation parameter estimation value for the fuel, the combustion mass ratio (BRknk) at the knock generation timing is calculated, and the calculated knock generation timing The unburned fuel amount (MUB) is calculated based on the combustion mass ratio (BRknk) and the fuel amount (QINJ) in the engine, and the pressure increase amount (DP) due to combustion chamber knock based on the unburned fuel amount (MUB) The basic ignition timing (MBTCAL) corresponding to the operating conditions is calculated, and a value obtained by correcting the basic ignition timing (MBTCAL) to the retard side based on the pressure increase amount (DP) due to the knocking of the combustion chamber is calculated. The knock limit ignition timing (KNOCKcal) is set , and the spark ignition is performed at the knock limit ignition timing (KNOCKcal).

Alternatively, the knock generation time (θknk) in the combustion chamber is predicted based on the knock correlation parameter estimate for the fuel, the combustion mass ratio (BRknk) at the knock generation time (θknk) is calculated, and the calculated knock generation The unburned fuel amount (MUB) is calculated based on the combustion mass ratio (BRknk) and the fuel amount (QINJ) at the time, and the pressure increase amount due to knocking of the combustion chamber (DP) based on the unburned fuel amount (MUB) ), A basic ignition timing (MBTCAL) corresponding to the operating conditions is calculated, and the basic ignition timing (MBTCAL) is corrected to the retard side based on the pressure increase (DP) due to the knocking of the combustion chamber. It was set as the knocking limit ignition timing (KNOCKcal), based on the knock correlation parameter estimates for the combustion gas state in the combustion chamber The volume (V0) at the combustion start timing of the combustion chamber is calculated, the combustion period (BURN) from the start of combustion to a predetermined crank angle is calculated based on the volume (V0) at the start of combustion, and this combustion period (BURN) When the basic ignition timing (MBTCAL) from which MBT is obtained is calculated and the knock correlation parameter related to the combustion gas state in the combustion chamber is selected from the two types of knock correlation parameters, the knock limit ignition timing (KNOCKcal) Among the basic ignition timings (MBTCAL), the spark ignition is performed at the retarded ignition timing.

  According to the present invention, corresponding to the fact that the fuel used and the combustion gas state in the combustion chamber are the main factors affecting the knock, according to the present invention, the knock correlation parameter related to the fuel and the combustion in the combustion chamber Introduce each estimated value of knock correlation parameter related to gas state, and calculate the estimated value of knock correlation parameter related to fuel and the estimated value of knock correlation parameter related to combustion gas state in the combustion chamber according to the conditions. When knocking occurs due to the change, the estimated value of the knock correlation parameter for the fuel is calculated, and when knocking occurs due to manufacturing variations or deposits in the combustion chamber, it relates to the combustion gas state in the combustion chamber. Since the estimated value of the knock correlation parameter is calculated, any of the different types of knock correlation parameters It can also be calculated accurately estimate the data.

Further, an estimated value of the knock correlation parameter is calculated based on the knock detection result (the knock detection result is fed back to the knock correlation parameter), and an ignition timing is calculated based on the calculated knock correlation parameter estimated value. Spark ignition with. Specifically, the knock generation timing in the combustion chamber is predicted based on the knock correlation parameter estimated value, the knock limit ignition timing is calculated based on the knock generation timing, spark ignition is performed at the knock limit ignition timing , or predicts the knocking occurrence timing in the combustion chamber on the basis of the knock correlation parameter estimates for the fuel to calculate the knock limit ignition timing based on the knock occurrence timing, knocking correlation parameters related combustion gas state in the combustion chamber The volume at the combustion start timing of the combustion chamber is calculated based on the estimated value, the combustion period from the start of combustion to a predetermined crank angle is calculated based on the volume at the start of combustion, and MBT is obtained based on the combustion period. The basic ignition timing is calculated, and the knock correlation parameter related to the combustion gas state in the combustion chamber among the two types of knock correlation parameters. When a meter is selected, spark ignition is performed at the retarded ignition timing of the knock limit ignition timing and the basic ignition timing, so that the octane number of the fuel and the alcohol concentration in the mixed fuel can be known in advance. Even when using fuel that is sold in a non-market, the ignition timing delay angle and the subsequent advance angle to avoid knock, as in the conventional device that feeds back the knock detection result to the ignition timing, regardless of the operating conditions. Is not repeated. For this reason, since the knock limit ignition timing can be followed even during a transition such as acceleration or deceleration, fuel consumption deterioration and output reduction can be prevented.

  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. The injection amount is determined, and 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 “exhaust”) 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.

  In this case, in the general knock control, when the knock sensor detects that the knock has occurred, the base ignition timing is greatly retarded stepwise by the first predetermined value, and thereafter the base ignition timing is set to the second value. The operation is gradually advanced by a predetermined value, and the above operation is repeated when it is detected again by the knock sensor by the advance of the ignition timing in this operation. In this embodiment, the knock operation is repeated. The result of knock detection by the sensor 47 (knock detection means) is fed back to the estimated value OCTEST of the fuel octane number (knock correlation parameter) instead of the ignition timing, thereby retarding the ignition timing for avoiding knock as in the conventional device. And avoiding knocking in a way that does not repeat the following advance angle operation. That is, the estimated octane number OCTEST is calculated based on the knock detection result by the knock sensor 47, and the self-ignition timing θknk (knock occurrence time) in the combustion chamber 5 is predicted based on the estimated octane number OCTEST. Knock limit ignition timing KNOCKcal is calculated based on the timing θknk. When knocking occurs, the knock limit ignition timing KNOCKcal has a value retarded from the basic ignition timing MBTCAL, and spark ignition is performed using the knock limit ignition timing KNOCKcal as the ignition timing.

  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. Steps 391 to 396 will be described later.

  In steps 1 and 2, basic ignition timings MBTcal [degBTDC], MBTCALI [degBTDC], and 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 can be 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). Steps 401 to 404 will be described later.

  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 ], Dead ignition time DEADTIME [μsec] is read.

  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 time of closing the intake valve is known because it is determined by the command signal from the engine controller 31 to the intake VTC mechanism 27. 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, in practice, 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 15, 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 16, 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.

  Finally, in step 17, 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)
Here, the ignition dead time DEADTIME is set to 200 μsec. Equation (10) is for calculating the ignition dead time equivalent crank angle IGNDEAD that is the crank angle corresponding to the ignition dead time DEADTIME from the engine speed NRPM.

  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. Steps 411 to 416 in FIG. 10 will be described later.

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. Therefore, 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 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 time. 2 is calculated. Effective compression ratio Ec 2 is also a dimensionless value like the effective compression ratio Ec of the above equation (12). As shown in the following equation, the volume VTDC at the compression top dead center of the combustion chamber 5 is the volume of the combustion chamber 5 at the intake valve closing timing. 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. Steps 421 to 424 will be described later.

  In step 41, the initial combustion period BURN1 calculated in step 171 in FIG. 10, the main combustion period BURN2 calculated in step 191 in FIG. 12, and the ignition timing dead time equivalent crank calculated in step 17 in FIG. The angle IGNDEAD, the reference crank angle θPMAX calculated in step 16 of FIG. 5 is read.

  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 intake valve exhaust timing VTCOL [deg] is calculated from the intake valve opening timing IVO and the exhaust valve closing timing EVC by the following equation.

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. Moreover, 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 blowback inert gas flow rate MRESOLtmp1 during the 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 during the overlap.

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 blown back inert gas flow rate (MRESOLtmp1, MRESOLtmp2) during the overlap is determined. 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 these, is also 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, the calculation of the knock limit ignition timing KNOCKcal 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, If the total number of moles n of all the gases is known, it indicates that 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 the first 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 from FIG. 31, and the unburned fuel amount is calculated from the combustion mass ratio BRknk at the time of self-ignition and the fuel amount QINJ by the following formula. MUB can be determined. 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, the initial combustion period, and the main combustion period are divided into three, and the characteristics of each period are approximated by a straight line.

  In this case, the characteristics shown in FIG. 31 do not change even if the engine load or the rotational speed is different. Therefore, if the engine specifications are determined, the characteristics are uniquely determined.

  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,
Thus, 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, calculation of the knock limit ignition timing KNOCKcal will be described in detail with reference to the following flowchart.

  32 and 33 (subroutine of step 2 in FIG. 2) are for calculating the knock limit ignition timing KNOCKcal, and are executed when the crank angle reaches a predetermined timing (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] and the internal inert gas amount MRES [g], the fuel amount QINJ [g] calculated in steps 52 and 53 in FIG. 14, and the step 171 in FIG. In addition to the initial combustion period BURN1 [deg] calculated in step 1, the main combustion period BURN2 [deg] calculated in step 191 in FIG. 12, the basic ignition timing MBTCAL [degBTDC] calculated in step 43 in FIG. , The ignition dead time equivalent value IGNDEAD [deg] calculated in step 17 of FIG. 5, the collector internal temperature TCOL [K] detected by the temperature sensor 43, the exhaust gas temperature TEXH [K] detected by the temperature sensor 45, A collector internal pressure PCOL [Pa] detected by the pressure sensor 44 is read. The fuel amount QINJ [g] may be obtained in proportion to the fuel injection pulse width TI [ms].

  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 knock magnitude estimated value KIC. WIDRY is the cylinder fresh air amount and MASSZ is the internal inert gas amount.

  In step 203, a value obtained by adding the basic ignition timing MBTcal [degBTDC] and the ignition dead time equivalent crank angle IGNDEAD [deg] (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 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 is calculated. This instantaneous compression ratio εθ is a 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 becomes the following linear expression.

Combustion delay period;
BR = 0 (61)
Initial combustion period;
BR = SS1 × (Θ + MBTCAL−IGNEAD) (62)
Main combustion period;
BR = 0.02 + SS2 × (Θ + MBTCAL-IGNDEAD-BURN1)
... (63)
However, SS1: 0.02 / BURN1,
SS2: 0.58 / BURN2,
Accordingly, the combustion mass ratio is calculated by the equation (61) when the calculated crank angle Θ is in the combustion delay period, by the equation (62) when in the initial combustion period, and by the equation (63) when in the main combustion period.

  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, a combustion mass ratio BRknk at the time of self-ignition is calculated. 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. Therefore, this pressure increase is obtained by a calculation formula.

  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 knock strength estimated value KIC, that is, the knock strength estimated value KIC is calculated by the following equation.

KIC = KIC0 × KN (76)
Here, the rotational speed correction coefficient KN is for reflecting the difference in the knock strength estimation value because the driver feels pressure vibration due to knock more strongly when the engine rotational speed NRPM is lower than when the rotational speed is high. is there. 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.

  In step 230, the knock retard amount KNRT [deg] is calculated by the following equation.

KNRT = KIC-trace knock strength (77)
Here, the trace knock intensity of the equation (77) is a knock intensity when a light knock occurs as is well known. The trace knock intensity is obtained by searching a table having the contents shown in FIG. 37 from the engine speed NRPM.

  In step 231, the value obtained by subtracting the knock retard amount KNRT from the basic ignition timing MBTCAL is set as the knock limit ignition timing KNOCKcal, that is, the knock limit ignition timing KNOCKcal [degBTDC] is calculated by the following equation.

KNOCKcal = MBTCAL-KNRT (78)
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 232 in FIG. 33, and after the knock retard amount KNRT = 0, the operation in step 231 is executed.

  After that, the process waits until the crank angle reaches the basic ignition timing MBTCAL of the next combustion cycle, and the processes of FIGS. 32 and 33 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.

  Next, the calculation of the estimated octane number OCTEST and the compression ratio estimated value CMPEST of the fuel during operation will be described with reference to the flow of FIG. Since the estimation of the octane number and the compression ratio is performed while detecting whether or not knocking has occurred based on the signal from the knock sensor 47, the flow in FIG. 38 is executed immediately after ignition for each cylinder and for each ignition. Here, in order to execute for each cylinder and for each ignition, it may be executed at a timing when a predetermined crank angle has elapsed from the input of a reference position signal (for each cylinder) generated by a signal from the crank angle sensor (33, 34). . Here, a case of a four-cylinder engine will be described. Of course, the present invention is not limited to a 4-cylinder engine, but can be applied to a 6-cylinder, 8-cylinder, 12-cylinder engine, or the like.

  In FIG. 38, in step 261, the cylinder number counter value (initially set to zero at the start) ktcnt is incremented by one. The cylinder number counter value ktcnt is for measuring the number of ignited cylinders.

  In step 262, the knock sensor 47 is used to check whether or not knocking has occurred for each cylinder. 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 knocking has occurred in the cylinder that was ignited at that time, and the routine proceeds to step 263. The cylinder number of the detected cylinder is stored in the memory. The four-cylinder engine has four memories, and the knock detection cylinder is, for example, No. If 1 cylinder, 1 is stored.

  In step 264, the knock counter value knkcnt (initially set to zero at start-up) is incremented by one. The knock counter value knkcnt is for measuring the number of cylinders in which knocking has occurred among all the cylinders. In the first embodiment, there is one knock sensor 47, and it is detected by this one knock sensor 47 whether or not knock has occurred for each cylinder. However, a knock sensor may be provided for each cylinder. It doesn't matter.

  In step 265, the cylinder number counter value ktcnt is compared with the number of cylinders (4 for a four-cylinder engine). If the cylinder counter value ktcnt does not reach the number of cylinders, the current process is terminated.

  The operation of steps 261 to 265 is repeated every time the next reference position signal is input. When the estimated octane number OCTEST is too larger than the actual octane number, knocking occurs in two or more cylinders. At this time, since the cylinder counter value ktcnt is equal to the number of cylinders and the knock counter value knkcnt is 2 or more in steps 265 and 266, the estimated octane number OCTEST estimated to be too large from the occurrence of knocking is changed to the actual octane number. Therefore, the process proceeds to step 267, where the octane number estimated value OCTEST is decreased 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,
In step 268, the octane number estimated value update flag (initially set to zero at start-up) = 1 is set in order to indicate that the estimated octane number has been updated by equation (79).

  On the other hand, even if there is no error from the actual octane number in the estimated octane number, knocking may occur. In the knock detection cylinder, what is the cause (possible causes are manufacturing variations and deposits in the combustion chamber 5). Etc.) The compression ratio is considered to be higher than the remaining cylinders. In addition, such a situation often occurs only for one of all cylinders. Therefore, when knocking occurs in only one cylinder among all the cylinders (that is, when the cylinder counter value ktcnt is equal to the number of cylinders and the knock counter value knkcnt is 1), the cause of the knocking is the estimated octane number. It is determined that the compression ratio is higher than the preset compression ratio ε (see equation (3) above) only in the knock detection cylinder, and the estimated compression ratio of the knock detection cylinder is In order to match the planned compression ratio ε with the actual compression ratio that has deviated, the process proceeds from step 265, 266 to step 269, where the compression ratio estimated value CMPESTi of the knock detection cylinder is increased by the first predetermined value const23. That is, the compression ratio estimated value CMPESTi of the knock detection cylinder is updated by the following equation.

CMPESTi (new) = CMPESTi (old) + const23 (80)
Where CMPESTi (new): estimated compression ratio after update,
CMPESTi (old): estimated compression ratio before update,
const23: update amount to the side to be increased,
Here, the initial value of the estimated compression ratio of the knock detection cylinder is a preset compression ratio ε (a constant value).

  In a multi-cylinder engine, any cylinder can increase from a preset compression ratio ε, so it is necessary to know the cylinder with the increased compression ratio, and a cylinder-specific compression ratio estimated value CMPESTi (i is the cylinder number) is introduced. For a 4-cylinder engine, the estimated compression ratio for each cylinder is No. The estimated compression ratio of one cylinder is CMPEST1, No. The estimated compression ratio of the two cylinders is CMPEST2, No. The estimated compression ratio of the three cylinders is CMPEST3, No. The estimated compression ratio of the four cylinders is CMPEST4. As described above, the knock detection cylinder is No. When there is one cylinder, No. Only the compression ratio estimated value CMPEST1 of one cylinder is updated to the increasing side by the above equation (80). Remaining No. 2, No. 3, no. The compression ratio estimation values CMPEST <b> 2 to CMPEST <b> 4 of the three cylinders No. 4 are as they are, that is, preset ε.

  In step 270, the compression ratio estimated value update flag (initially set to zero at start-up) = 1 is set to indicate that the compression ratio estimated value has been updated by the above equation (80), and in step 271 the knock detection cylinder (compression ratio is The cylinder number of the increasing cylinder) is stored in the memory i and saved. The reason why it is necessary to store the cylinder number of the cylinder whose compression ratio is increasing is as follows. That is, if the compression ratio is different, the above-described initial combustion period BURN1 is different, and if the initial combustion period is different, the basic ignition timing MBTCAL needs to be changed. In that case, since the ignition timing control must be performed separately for the cylinder whose compression ratio is increasing and the remaining cylinders which do not increase the compression ratio and remain at the initial setting, the compression ratio is determined in the ignition timing control for each cylinder. This is because an increasing cylinder number is required.

  In step 272, one combustion cycle for all the cylinders is completed, so that the counter values ktcnt and nkcnt are reset to prepare for the next combustion cycle, and in step 263, all the memories storing the knock detection cylinder are cleared.

  If no knock is detected, the routine proceeds from step 262 to step 273, where the octane number estimated value update flag is checked. If the octane number estimated value update flag = 0, the current process is terminated.

  When the octane number estimated value update flag = 1, knocking has occurred, so the octane number estimated value OCTEST is updated to be smaller. The knock limit ignition period calculated based on the updated octane number estimated value is greater than the basic ignition timing. Be retarded. In this case, if the ignition timing is kept at a retarded angle, the fuel efficiency will deteriorate, so after avoiding knocking, it is necessary to return the ignition timing to the basic ignition timing at which the fuel efficiency is optimal. In order to avoid knocking, the estimated octane number OCTEST is updated to a smaller side and then the estimated octane number OCTEST is returned to the larger side at a predetermined cycle.

  Therefore, when the estimated octane number OCTEST is updated to a smaller side (when the estimated octane number update flag = 1), the routine proceeds from step 273 to step 274, and the ignition timing minimum value calculated in step 3 of FIG. PADV [degBTDC] is compared with basic ignition timing MBTCAL [degBTDC] calculated in step 1 of FIG. Immediately after the octane number estimated value update flag = 1, the ignition timing minimum value PADV does not coincide with the basic ignition timing MBTCAL. That is, it is determined that the estimated octane number OCTEST and the actual octane number do not coincide with each other, and as a result, the ignition timing is retarded to avoid knocking, and the routine proceeds from step 274 to step 275 where the counter value count and the predetermined value const04 are determined. And compare. 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 275, the process proceeds to step 276 and the counter value count is incremented by one. That is, the counter value count is incremented by 1 every time the flow of FIG. 38 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 275 to step 277, 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 (81)
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 278.

  When the operation of step 277 is repeated many times, the ignition timing minimum value PADV coincides with the basic ignition timing MBTCAL. At this time, the routine proceeds from step 273, 274 to step 279, where the estimated octane number update flag = 0. This is to prepare for the next knock.

  FIG. 39 shows how the ignition timing, the counter value count, and the octane number estimated value OCTEST move when knocking occurs because the estimated octane number is too larger than the actual octane number. Shown in the model. As shown in the figure, when knock is detected in a plurality of cylinders by the knock sensor 47 at the timing t01, it is determined that the estimated octane number OCTEST is larger than the actual octane number, and the estimated octane number OCTEST is stepped by the first predetermined value const03. Is made smaller. 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 in a plurality of cylinders at the timing of t03 thereafter, 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.

  Further, the knock detection cylinder compression ratio estimated value CMPESTi calculated in step 269 of FIG. 38 is used in FIGS. 2, 5, 10, and 13 for calculation of basic ignition timing and ignition timing control.

  Referring to FIG. 5, in steps 401 to 404 in FIG. 5, the volume of the combustion chamber 5 at the intake valve closing timing for a cylinder whose compression ratio is larger than the set value ε (hereinafter referred to as “compression ratio increasing cylinder”). Is a part to calculate.

  Here, the volume at the intake valve closing timing of the combustion chamber 5 for the cylinder with an increased compression ratio is defined as “VIVCi” and distinguished from VIVC, which is the volume at the intake valve closing timing of the combustion chamber 5 for cylinders other than the cylinder with the increased compression ratio. In addition, the clearance volume for the cylinders other than the compression ratio increasing cylinders is also referred to as “Vci” and “VIVCi” with respect to the clearance volume for the compression ratio increasing cylinders and the volume at the intake valve closing timing of the combustion chamber 5 for the compression ratio increasing cylinders. It is distinguished from VIVC which is the volume at the intake valve closing timing of the combustion chamber 5 for cylinders other than a certain Vc and compression ratio increasing cylinder.

Specifically, the compression ratio estimated value update flag is checked in step 401 of FIG. When the compression ratio estimated value update flag = 1, it is determined that there is a cylinder with an increased compression ratio, and the routine proceeds to step 402 in FIG. 5, and the compression ratio estimated value CMPESTi of the cylinder with an increased compression ratio obtained at step 269 in FIG. Then, using this estimated compression ratio CMPESTi, in step 403 of FIG. 5, the clearance volume Vci [m ³ ] of the compression ratio increasing cylinder is calculated by the following equation.

Vci = (π / 4) D ² · Hx / (CMPESTi−1) (82)
Where CMPEST: estimated compression ratio,
D: cylinder bore diameter [m],
Hx: difference between the maximum value and the minimum value of the distance from the TDC of the piston pin 76
[M],
Here, equation (82) replaces equation (3) above. The compression ratio ε in the equation (3) is a preset value (constant value), whereas the compression ratio increasing cylinder adopts the compression ratio estimated value CMPESTi (CMPESTi> ε) instead of this ε. It is.

  Using the clearance volume Vci of the cylinder with increased compression ratio obtained in this way, in step 404 of FIG. 5, the volume VIVCi at the closing timing of the intake valve of the combustion chamber 5 for the cylinder with increased compression ratio is calculated by the following equation.

VIVCi = Vci + (π / 4) D ² · Hivc (83)
D: cylinder bore diameter [m],
Hivc: TDC of piston pin 76 when intake valve is closed
Distance from [m],
The expression (83) is the same as the expression (2).

  Next, steps 411 to 414, 415, and 416 in FIG. 10 are portions for calculating the volume at the combustion start timing of the combustion chamber 5 and the initial combustion period for the compression ratio increasing cylinder. Also here, the volume at the combustion start timing of the combustion chamber 5 for the compression ratio increasing cylinder is “V0i”, and the initial combustion period for the compression ratio increasing cylinder is “BURN1i”. A distinction is made from V0, which is the volume at the start of combustion, and BURN1, which is the initial combustion period for cylinders other than the cylinder with increased compression ratio.

Specifically, the compression ratio estimated value update flag is viewed at step 411 in FIG. When the compression ratio estimated value update flag = 1, it is determined that there is a cylinder with increased compression ratio, the process proceeds to step 412 in FIG. 10, and the compression ratio estimated value CMPESTi of the cylinder with increased compression ratio obtained in step 269 in FIG. Using this compression ratio estimated value CMPESTi, the clearance volume Vci [m ³ ] of the compression ratio increasing cylinder is calculated by the above equation (82) in step 413 of FIG. In step 414 of FIG. 10, this gap volume Vci is used to calculate the volume V0i at the combustion start timing (MBTCYCL) of the combustion chamber 5 for the compression ratio increasing cylinder by the following equation.

V0i = Vci + (π / 4) D ² · Hmbtcycl (84)
Where D: cylinder bore diameter [m]
Hmbtcycl: Piston pin at the start of combustion (MBTCYCL)
Distance from 76 TDCs [m],
Further, the compression ratio estimated value update flag is also checked in step 415 of FIG. When the compression ratio estimated value update flag = 1, the routine proceeds to step 416 in FIG. 10, and the initial combustion period BURN1i [deg] of the cylinder with increased compression ratio is calculated by the following equation.

BURN1i = {(NRPM × 6) × BR1 × V0i}
/ (RPROBA × AF1 × FLAME1) (85)
However, AF1: Reaction area (fixed value) of flame kernel [m ² ],
Next, steps 421 to 425 in FIG. 13 are portions for calculating the combustion period and the basic ignition timing for the compression ratio increasing cylinder. Also here, the combustion period for the cylinder with an increased compression ratio and the basic ignition timing for the cylinder with the increased compression ratio are “BURNi” and “MBTCALI”, which are the combustion periods for the cylinders other than the cylinder with the increased compression ratio and other than the BURN and the cylinder with the increased compression ratio. This is distinguished from MBTCAL, which is the basic ignition timing for the cylinders.

  Specifically, the compression ratio estimated value update flag is checked in step 421 in FIG. When the compression ratio estimated value update flag = 1, the routine proceeds to step 422 in FIG. 13 and the initial combustion period BURN1i of the cylinder with increased compression ratio obtained at step 416 in FIG. 10 is read and this compression ratio estimated value CMPESTi is used. In step 423, the sum of the initial combustion period BURN1i and the main combustion period BURN2 of the cylinder with increased compression ratio is calculated as the combustion period BURNi [deg] of the cylinder with increased compression ratio.

  In step 424 of FIG. 13, the basic ignition timing MBTCALI [degBTDC] is calculated by the following equation using the combustion period BURNi of the cylinder with increased compression ratio.

MBTCALI = BURNi−θPMAX + IGNDEAD (86)
Next, steps 391 to 393 in FIG. 2 are portions for calculating the ignition timing minimum value and the ignition timing command value for the compression ratio increasing cylinder. Here, the ignition timing minimum value for the compression ratio increasing cylinder and the ignition timing command value for the compression ratio increasing cylinder are “PADVi” and “QADVi”, and PADV which is the ignition timing minimum value for the cylinders other than the compression ratio increasing cylinder. A distinction is made from QADV, which is the ignition timing command value for cylinders other than the cylinder with increased compression ratio.

  Specifically, the compression ratio estimated value update flag is checked at step 391 in FIG. When the compression ratio estimated value update flag = 1, the routine proceeds to step 392, where the basic ignition timing MBTCALI [degBTDC] and the knock limit ignition timing KNOCKcal [degBTDC] of the cylinder with increased compression ratio calculated at step 424 in FIG. 2, that is, the value on the retard side is selected as the ignition timing minimum value PADVi for the compression ratio increasing cylinder, and further, in step 393 of FIG. Set as command value QADVi [degBTDC]. After completion of engine warm-up, there is no correction due to water temperature or the like, so the ignition timing command value QADVi becomes equal to the ignition timing minimum value PADVi.

  In step 394 of FIG. 2, it is checked whether or not the cylinder number of the ignition cylinder matches the cylinder number of the memory i obtained in step 271 of FIG. When the cylinder number of the ignition cylinder matches the cylinder number of the memory i, the routine proceeds to step 395 in FIG. 2, and the ignition timing command value QADVi of the cylinder with increased compression ratio is transferred to the ignition register.

  On the other hand, since the cylinder number of the ignition cylinder does not match the cylinder number of the memory i for the cylinders other than the compression ratio increasing cylinder, the process proceeds from step 394 in FIG. 2 to step 396 in FIG. 2, and the ignition timing command value QADV is set in the ignition register. Transfer.

  In this way, ignition control is performed using two types of basic ignition timings (MBTCALI, which is a basic ignition timing for a cylinder with an increased compression ratio, and MBTCAL, which is a basic ignition timing for cylinders other than the cylinder with an increased compression ratio).

  Here, the effect of this embodiment (1st Embodiment) is demonstrated.

According to the first embodiment (the invention described in claims 1 and 2 ), the first factor corresponding to the fact that the fuel used and the state of the combustion gas in the combustion chamber 5 are the main influences on knocking. According to the embodiment (the invention described in claims 1 to 8), the estimated octane number OCTEST (estimated value of the knock correlation parameter for fuel) and the estimated compression ratio CMPESTi (estimated knock correlation parameter for the combustion gas state in the combustion chamber) Value) is switched according to the conditions, that is, when knocking occurs due to the change in the fuel to be used, the estimated octane number OCTEST is calculated (see steps 263 to 266 and 267 in FIG. 38). When knocking occurs due to adhesion of deposits in the combustion chamber 5, the compression ratio estimated value CMPESTi of the cylinder with increased compression ratio is calculated (FIG. 38). Steps 263 to 266 and 269), it is possible to accurately calculate any estimated value (octane number estimated value OCTEST and compression ratio estimated value CMPESTi) of different types of knock correlation parameters.

Further, according to the first embodiment (the invention described in claims 1 and 2 ), when gasoline is used as fuel, the knock detection result by the knock sensor 47 is fed back to the octane number of the fuel instead of the ignition timing ( (See FIG. 38). That is, as shown at the bottom of FIG. 39, the estimated octane value OCTEST decreases stepwise by the first predetermined value const03 when it is detected that knocking has occurred, and thereafter, the second predetermined value const05 is incremented by one. It gradually increases at a predetermined cycle. This movement is just the same as the movement of the ignition timing retard amount in the knock control of the conventional device.

Thus, according to the first embodiment (the inventions described in claims 1 and 2 ), the octane number estimated value OCTEST (estimated value of the knock correlation parameter related to fuel) is calculated based on the knock detection result by the knock sensor 47. (Refer to steps 262, 267, and 277 in FIG. 38) The ignition timing is calculated based on the estimated octane value OCTEST, and spark ignition is performed at the calculated ignition timing. Specifically, based on the estimated octane value OCTEST. The self-ignition timing θknk (knock generation timing) in the combustion chamber 5 is predicted (see steps 206 to 210 in FIG. 32 and step 218 in FIG. 33), and the knock limit ignition timing KNOCKcal is calculated based on the self-ignition timing θknk. (See steps 219 to 231 in FIG. 33), and sparks are generated at the knock limit ignition timing KNOCKcal. Since a fire is performed (see steps 3, 4 and 5 in FIG. 2), or based on the octane number estimated value OCTEST (estimated value of knock correlation parameter regarding fuel), knock limit ignition timing KNOCKcal is calculated (steps 206- FIG. 32). 210, step 218 in FIG. 33, and steps 219 to 231 in FIG. 33), the compression ratio estimated value COMPESTi (the estimated value of the knock correlation parameter relating to the combustion gas state in the combustion chamber), and the basic ignition timing MBTCALI obtained to obtain the MBT. When calculating (see steps 411, 412 to 414, 416 in FIG. 10 and steps 421 to 424 in FIG. 13) and selecting the compression ratio estimated value CMPESTi, the delay time of the knock limit ignition timing KNOCKcal and the basic ignition timing MBTCALI is selected. Spark ignition is performed at the ignition timing on the corner side (step in FIG. 2). 391 to 396), or based on the estimated octane number OCTEST (estimated value of knock correlation parameter relating to fuel), the self-ignition timing θknk (knock occurrence timing) in the combustion chamber is predicted (step of FIG. 32). 206 to 210, see step 218 in FIG. 33), knock limit ignition timing KNOCKcal is calculated based on this self-ignition timing θknk (see steps 219 to 231 in FIG. 33), and compression ratio estimated value CMPESTi (combustion gas in combustion chamber) The volume V0i at the combustion start time of the combustion chamber 5 is calculated based on the estimated value of the knock correlation parameter regarding the state (see steps 411 to 414 in FIG. 10), and predetermined from the start of combustion based on the volume V0i at the start of combustion. The combustion period BURNi up to the crank angle is calculated (step 41 in FIG. 10). 5, 416, refer to steps 421 to 423 in FIG. 13), the basic ignition timing MBTCALI for which MBT is obtained is calculated based on this combustion period BURNi (see step 424 in FIG. 13), and the compression ratio estimated value CMPESTi is selected. In addition, since the spark ignition is performed at the retarded ignition timing among the knock limit ignition timing KNOCKcal and the basic ignition timing MTCALi (see steps 391 to 394 and 396 in FIG. 2), the market in which the octane number of the fuel cannot be known in advance In the case of using the fuel sold on the market, the retard of the ignition timing for avoiding the knock and the subsequent advance as in the conventional device that feeds back the knock detection result by the knock sensor 47 to the ignition timing regardless of the driving state. The corner operation is not repeated. For this reason, since the knock limit ignition timing can be followed even during a transition such as acceleration or deceleration, fuel consumption deterioration and output reduction can be prevented.

In the first embodiment, as shown in FIGS. 5, 10, 12, and 13, laminar combustion velocities SL1 and SL2, combustion gas volume equivalent volume (V0, VTDC), combustion mass ratio (BR1, BR2) The combustion period from the start of combustion to the predetermined crank angle (BURN1, BURN2) is calculated based on the reaction probability RPROBA, and the basic ignition timing MBTCAL is calculated based on the combustion period (BURN1, BURN2). Instead of calculating the basic ignition timing MBTCAL, a base ignition timing map may be provided. In this case, the knock limit ignition timing calculation means is a pressure increase amount estimation means for estimating the pressure increase amount DP due to the knock of the combustion chamber 5 based on the self-ignition timing θknk (knock generation timing) and the operating conditions (see FIG. 33). Steps 219 to 226), knock strength estimated value calculating means for calculating the knock strength estimated value KIC based on the pressure increase DP (see steps 227 to 229 in FIG. 33), and the knock strength estimated value KIC. The knock retard amount calculating means for calculating the knock retard amount KNRT (see step 230 in FIG. 33) and a value obtained by correcting the basic ignition timing MBTCAL to the retard side by the knock retard amount KNRT is set as the knock limit ignition timing KNOCKcal. A knock limit ignition timing setting means (see step 231 in FIG. 33). Invention) according to claim 1, 2, even if the give in the map base ignition timing as the basic ignition timing, it is not necessary to provide a map of the base ignition timing for each of a plurality of different octane number from the maximum octane number to the minimum octane number This prevents the ROM capacity from increasing.

According to the first embodiment (the inventions described in claims 1 and 2 ), the knock correlation parameter relating to the fuel is the octane number of the fuel. Therefore, when gasoline is used as the fuel, the octane number of the fuel can be accurately estimated.

According to the first embodiment (the invention according to claim 9 ), the condition for selecting one of the two types of knock correlation parameters is the knock counter value knkcnt (of the cylinder in which knocking has occurred among all the cylinders). (See step 266 of FIG. 38), in the case of a multi-cylinder engine having a plurality of cylinders, which knock correlation parameter causes the knock, that is, the cause of the knock is the octane number of the fuel. Whether it is based on (a knock correlation parameter related to fuel) or a compression ratio (a knock correlation parameter related to a combustion gas state in the combustion chamber) can be accurately determined.

According to the first embodiment (the invention described in claim 11 ), when the knock counter value knkcnt (the number of cylinders in which knocking has occurred) is 1 (single), the compression ratio (the knock correlation relating to the combustion gas state in the combustion chamber) Parameter (see steps 266 and 269 in FIG. 38), in the case of a multi-cylinder engine having a plurality of cylinders, the compression ratio estimation value CMPESTi for each cylinder (estimation value of the knock correlation parameter relating to the combustion gas state in the combustion chamber) ) Can be calculated.

According to the first embodiment (the invention described in claim 19 ), the laminar combustion velocity (SL1, SL2), which is the combustion velocity in the laminar flow state of the combustion gas, is calculated and corresponds to the combustion gas volume in the combustion chamber. The volume (V0, VTDC) to be calculated is calculated, the combustion mass ratio (BR1, BR2) of the gas combusted in the combustion chamber up to a predetermined crank angle is calculated, and the combustion gas is easily burned under predetermined operating conditions. The reaction probability RPROBA is calculated, and predetermined from the start of combustion based on the laminar combustion velocity (SL1, SL2), the combustion gas volume equivalent volume (V0, VTDC), the combustion mass ratio (BR1, BR2), and the reaction probability RPROBA. The combustion period (BURN1, BURN2) to the crank angle is calculated, and the basic ignition timing MBTCAL from which MBT is obtained is calculated based on the combustion period (BURN1, BURN2). At the same time, the combustion period is divided into an initial combustion period BURN1 and a main combustion period BURN2 (see step 1, FIG. 5, FIG. 10, FIG. 12, FIG. 13 in FIG. 2), and the compression ratio estimation of the cylinder with an increased compression ratio is performed. Based on the value CMPESTi, the volume V0i at the start timing of the combustion chamber is calculated (see steps 413 and 414 in FIG. 10), and the volume V0 at the combustion start timing of this combustion chamber is set as the volume corresponding to the combustion gas volume in the combustion chamber. Is used to calculate the initial combustion period BURN1 of the cylinder with an increased compression ratio (see step 416 in FIG. 10), which is caused by manufacturing variations and deposits adhering to the combustion chamber 5 when using a fuel having a predetermined octane number. Even when there is a cylinder whose actual compression ratio is higher than the compression ratio of the engine specification, the knock detection result is ignited regardless of the operating state. It is never repeated and the operation of the retard and advance to subsequent ignition timing for knock avoidance as in the conventional apparatus is fed back to the year. For this reason, since the knock limit ignition timing can be followed even during a transition such as acceleration or deceleration, fuel consumption deterioration and output reduction can be prevented.

According to the first embodiment (the invention described in claim 20 ), the intake valve closing timing is based on the volume VIVC of the combustion chamber 5 at the intake valve closing timing and the volume V0 at the combustion start timing as shown in FIG. The effective compression ratio Ec from IVC to the combustion start timing is calculated (see step 163 in FIG. 10), and the temperature TINI at the intake valve closing timing of the combustion chamber 5 and the effective compression ratio Ec at the combustion start timing of the combustion chamber 5 are calculated. The temperature T0 is calculated from the pressure PINI at the intake valve closing timing of the combustion chamber 5 and the effective compression ratio Ec, respectively, and the pressure P0 at the combustion start timing of the combustion chamber 5 is calculated (see steps 164 to 167 in FIG. 10). A laminar combustion speed SL1 used for calculating the initial combustion period BURN1 is calculated based on the temperature T0 and the pressure P0 at the combustion start timing of the chamber 5 (see step 168 in FIG. 10). In addition, since the volume VIVCi of the combustion chamber 5 at the closing timing of the intake valve of the compression ratio increasing cylinder is calculated based on the compression ratio estimated value CMPESTi of the compression ratio increasing cylinder (see steps 403 and 404 in FIG. 5), the octane number is calculated in advance. In the case of using a fuel having a fixed compression ratio, even when a cylinder is produced in which the actual compression ratio is higher than the expected compression ratio due to manufacturing variations or deposits in the combustion chamber 5, the compression ratio The volume VIVC at the closing timing of the intake valve of the combustion chamber 5 for the increased cylinder can be accurately calculated.

  The flow of FIGS. 40 and 42 is the second embodiment, FIG. 40 replaces FIG. 32 of the first embodiment, and FIG. 42 replaces FIG. 38 of the first embodiment. 40, the same step number is assigned to the same part as FIG. 32, and the same step number is assigned to the same part as FIG. 38 in FIG. FIG. 33 is a flow common to the first and second embodiments.

  A mixed fuel of gasoline and alcohol (alcohol-containing fuel) may be used. In this case, when the base ignition timing is set, the alcohol concentration in the mixed fuel is checked, and the base ignition timing is matched so that knocking does not occur when the mixed fuel having the checked alcohol concentration is used.

  However, for example, in the overseas market, when the alcohol concentration in the mixed fuel is different from the mixed fuel used for matching the base ignition timing, for example, when the alcohol concentration in the mixed fuel is lower than the alcohol concentration of the mixed fuel used for matching, knocking occurs. If the ignition timing delay and the subsequent advance operation are repeated, even if knocking can be avoided due to the ignition timing retardation, fuel consumption deteriorates and output decreases.

  The second embodiment is applied when a mixed fuel of alcohol and gasoline is used as a fuel to be used. One of two types of knock correlation parameters is selected according to conditions, and the knock correlation parameter on the selected side is selected. Is calculated based on the knock detection result by the knock sensor 47, and the self-ignition timing θknk (knock) in the combustion chamber 5 is calculated based on the alcohol concentration estimated value ALTEST. Occurrence timing) and the knock limit ignition timing KNOCKcal is calculated based on the self-ignition timing θknk.

  The difference from the first embodiment will be mainly described. In FIG. 40, steps 281 to 283 are parts for calculating 1 / τ for the mixed fuel of the alcohol concentration estimated value ALCEST. If a map of 1 / τ is provided for each of a plurality of different alcohol concentrations from the lowest alcohol concentration to the highest alcohol concentration, the ROM capacity becomes too large, and therefore, 1 for the fuel with the lowest alcohol concentration (for example, 0%). Only the map of / τ and the map of 1 / τ for the fuel with the highest alcohol concentration (for example, 85%), and the alcohol concentration between the lowest alcohol concentration and the highest alcohol concentration (alcohol concentration estimated value) 1 / τ for the mixed fuel of (ALCEST) is calculated by interpolating between 1 / τ for the fuel having the alcohol concentration of 0% and 1 / τ for the fuel having the alcohol concentration of 85%.

  More specifically, in steps 281 and 282, the first time is obtained by searching the maps having the contents shown in FIGS. 41A and 41B from the compression start temperature TC0 and the compression start pressure PC0, respectively. / Τ, 1 / τ for a mixed fuel with an alcohol concentration of 85% is calculated. Each 1 / τ is a value that increases as the temperature and pressure increase as shown in FIGS. 41A and 41B. Further, if the temperature and pressure are the same, 1 / τ in the mixed fuel having the alcohol concentration of 0% tends to be larger than 1 / τ in the mixed fuel having the alcohol concentration of 85%. Therefore, in step 283, 1 / τ in the mixed fuel of the alcohol concentration estimated value ALCEST is calculated by the following equation (interpolation calculation equation).

1 / τEST = 1 / τ85 + (85-ALCTEST)
× (1 / τ0−1 / τ85) / (85-0)
... (Supplement 18)
However, 1 / τEST: 1 / τ in the mixed fuel of the alcohol concentration estimated value ALCEST,
1 / τ0: 1 / τ with a mixed fuel with an alcohol concentration of 0%,
1 / τ85: 1 / τ with a mixed fuel with an alcohol concentration of 85%,
Here, the calculation of the alcohol concentration estimated value ALCEST will be described later.

  In step 209, 1 / τ of the alcohol concentration estimated value ALCEST in the mixed fuel is added to the integrated value SUM.

  Next, when the cylinder number counter value ktcnt is equal to the number of cylinders and the knock counter value knkcnt is 2 or more in steps 265 and 266 in FIG. It is determined that the alcohol concentration estimated value ALCEST is lower than the actual alcohol concentration due to the change of the mixed fuel, and the process proceeds from Steps 265 and 266 to Step 291 to increase the alcohol concentration estimated value ALLCEST by the first predetermined value const13. That is, the alcohol concentration estimated value ALEST is updated by the following equation.

ALLCEST (new) = ALCEST (old) + const13 (87)
However, ALCEST (new): Estimated alcohol concentration after update,
ALCEST (old): Estimated alcohol concentration before update,
const13: update amount to the higher side,
In step 292 of FIG. 42, the alcohol concentration estimated value update flag (initially set to zero at start-up) = 1 is set to indicate that the alcohol concentration estimated value is updated by the equation (87).

  If no knock is detected, the process proceeds from step 262 to step 293, and the alcohol concentration estimated value update flag is checked. If the alcohol concentration estimated value update flag = 0, the current process is terminated.

  When the alcohol concentration estimated value update flag = 1, knocking has occurred, so the alcohol concentration estimated value ALCEST is updated to the higher side according to the above equation (87), and the knock limit calculated based on the updated alcohol concentration estimated value The ignition period is retarded from the basic ignition timing. In this case, if the ignition timing is kept at a retarded angle, the fuel efficiency will deteriorate, so after avoiding knocking, it is necessary to return the ignition timing to the basic ignition timing at which the fuel efficiency is optimal. In order to avoid knocking, the alcohol concentration estimated value ALCEST is updated to the higher side and then returned to the lower side in a predetermined cycle.

  For this reason, when the alcohol concentration estimated value ALCEST is updated to the higher side (when the alcohol concentration estimated value update flag = 1), the routine proceeds from step 293 to step 274, and the ignition timing calculated in step 3 of FIG. The minimum value PADV [degBTDC] is compared with the basic ignition timing MBTCAL [degBTDC] calculated in step 1 of FIG. Immediately after the alcohol concentration estimated value update flag = 1, the ignition timing minimum value PADV does not coincide with the basic ignition timing MBTCAL. In other words, it is determined that the alcohol concentration estimated value ALCEST does not match the actual alcohol concentration, and as a result, the ignition timing is retarded to avoid knocking, and the routine proceeds from step 274 to step 294 where the counter value count and the predetermined value are determined. Compare the value const14. The initial value of the counter value count is zero. Since the counter value count is initially less than the predetermined value const14 after proceeding to step 294, the process proceeds to step 276 and the counter value count is incremented by one. That is, the counter value count increases by 1 each time the flow of FIG. 42 is executed once, so that the counter value count eventually becomes equal to or greater than the predetermined value const14. At this time, the routine proceeds from step 294 to step 295, where the alcohol concentration estimated value ALCEST is lowered by the second predetermined value const15. That is, the alcohol concentration estimated value ALEST is updated by the following equation.

ALLCEST (new) = ALCEST (old) -const15 (88)
However, ALCEST (new): Estimated alcohol concentration after update,
ALCEST (old): Estimated alcohol concentration before update,
const15: update amount to the lower side,
Also, in Steps 284 and 285 in FIG. 40 and Step 294 in FIG. 42, the predetermined values const11, const12, and const14 are set to values different from those in the first embodiment. These predetermined values are matched by a preliminary experiment or the like in advance. However, the predetermined values const11 and const12 may be the same as the predetermined values const01 and const02 of the first embodiment.

  In FIG. 43, knocking occurs because the estimated alcohol concentration value is too lower than the actual alcohol concentration, that is, the ignition timing, the counter value count, and the estimated alcohol concentration value ALTEST when knocking is detected in a plurality of cylinders among all the cylinders. Shows the movement of the model. As shown in the figure, when knocking occurs in a plurality of cylinders at the timing of t11, it is determined that the alcohol concentration estimated value ALCEST is lower than the actual alcohol concentration, and the alcohol concentration estimated value ALCEST is stepwise set to the first predetermined value const13. Only get higher. As a result, if knocking does not occur, every time the counter value count reaches the predetermined value const14, the alcohol concentration estimated value ALCEST decreases by the second predetermined value const15. Then, after the ignition timing minimum value PADV coincides with MBTCAL at the timing of t12, the update of the alcohol concentration estimated value ALCEST is stopped and the value at that time is held. If knocking occurs again in a plurality of cylinders at the timing of t13 thereafter, the above operation is repeated.

  The alcohol concentration estimated value ALCEST calculated in this way is used to calculate 1 / τ for the fuel of the alcohol concentration estimated value ALEST at step 283 in FIG.

  Further, the compression ratio estimated value CMPESTi of the cylinder with increased compression ratio calculated in step 269 of FIG. 42 is used in FIGS. 2, 5, 10, and 13 common to the first and second embodiments.

According to the second embodiment, the second embodiment (the inventions according to claims 1 and 2 ) corresponds to the fact that the fuel used and the combustion gas state in the combustion chamber are the main factors affecting the knock. According to the above, the alcohol concentration estimated value ALCEST (estimated value of knock correlation parameter related to fuel) and the compression ratio estimated value CMPEST (estimated value of knock correlation parameter related to the combustion gas state in the combustion chamber) are calculated by switching according to the conditions, that is, When knocking occurs due to the change in the fuel used, the alcohol concentration estimated value ALCEST is calculated (see steps 263 to 266 and 291 in FIG. 42), and due to manufacturing variations and deposits in the combustion chamber. When knocking occurs, the compression ratio estimated value CMPESTi of the cylinder with increased compression ratio is calculated (steps 263 to 266, 2 in FIG. 42). 69), it is possible to accurately calculate any estimated values (alcohol concentration estimated value ALEST and compression ratio estimated value CMPESTi) of different types of knock correlation parameters.

Further, according to the second embodiment (the invention described in claims 1 and 2 ), in the case of a mixed fuel of gasoline and alcohol, the knock detection result obtained by the knock sensor 47 is not the ignition timing but the alcohol concentration in the mixed fuel. (See FIG. 42). That is, as shown in the lowermost part of FIG. 43, the alcohol concentration estimated value ALCEST increases stepwise by the first predetermined value const13 when the occurrence of knocking is detected, and thereafter the second predetermined value const15. It gradually becomes smaller at a predetermined cycle. This movement is just the same as the movement of the ignition timing retard amount in the knock control of the conventional device.

Thus, according to the second embodiment (the inventions described in claims 1 and 2 ), the alcohol concentration estimated value ALLCEST is calculated based on the knock detection result by the knock sensor 47 (steps 262, 291 in FIG. 42). 295), an ignition timing is calculated based on the estimated alcohol concentration value ALTEST, and spark ignition is performed at the calculated ignition timing. Specifically, the ignition timing in the combustion chamber 5 is determined based on the estimated alcohol concentration value ALTEST. The ignition timing θknk (knock occurrence timing) is predicted (see steps 281 to 283, 209, 210 in FIG. 40, step 218 in FIG. 33), and the knock limit ignition timing KNOCKcal is calculated based on the self-ignition timing θknk (see FIG. 33, steps 219 to 231), and spark ignition is performed at this knock limit ignition timing KNOCKcal (FIG. 2). (See Steps 3, 4, and 5) or based on the alcohol concentration estimated value ALEST (estimated value of the knock correlation parameter for fuel), the knock limit ignition timing KNOCKcal is calculated (steps 281 to 283, 209, 210, FIG. 40). 33, and the basic ignition timing MBTCALI from which MBT is obtained is calculated based on the compression ratio estimated value CMPESTi (the estimated value of the knock correlation parameter relating to the combustion gas state in the combustion chamber). (See steps 411, 412 to 414, 416 in FIG. 10 and steps 421 to 424 in FIG. 13) When the compression ratio estimated value CMPESTi is selected, the retard side of the knock limit ignition timing KNOCKcal and the basic ignition timing MBTCALI Spark ignition is performed at the ignition timing (see step 2 in FIG. 2). 391 to 396), or based on the alcohol concentration ALCEST (estimated value of knock correlation parameter for fuel), the auto-ignition timing θknk (knock occurrence timing) in the combustion chamber is predicted (step 281 in FIG. 40). ˜283, 209, 210 (see step 218 in FIG. 33), the knock limit ignition timing KNOCKcal is calculated based on the self-ignition timing θknk (see steps 219 to 231 in FIG. 33), and the compression ratio estimated value CMPESTi (combustion chamber) The volume V0i at the combustion start timing of the combustion chamber 5 is calculated based on the estimated value of the knock correlation parameter regarding the combustion gas state (see steps 411 to 414 in FIG. 10), and combustion is performed based on the volume V0i at the start of combustion. The combustion period BURNi from the start to the predetermined crank angle is calculated (FIG. 10). Steps 415 and 416, and Steps 421 to 423 in FIG. 13), the basic ignition timing MBTCALi at which MBT is obtained is calculated based on the combustion period BURNi (see Step 424 in FIG. 13), and the compression ratio estimated value CMPESTi is selected. At this time, the spark limit ignition timing KNOCKcal and the basic ignition timing (of the MTCALi, spark ignition is performed at the retarded ignition timing (see steps 391-394, 396 in FIG. 2), so the alcohol concentration in the mixed fuel is Even in the case of using mixed fuel sold in a market that is not known in advance, the ignition timing retardation for avoiding knock as in the conventional device that feeds back the knock detection result to the ignition timing regardless of the operating state. Subsequent advancement operations are not repeated. For this reason, since the knock limit ignition timing can be followed even in a transition as in the first embodiment, it is possible to prevent fuel consumption deterioration and output reduction.

According to the second embodiment (the inventions described in claims 1 and 2 ), the knock correlation parameter relating to the fuel is the alcohol concentration of the mixed fuel. Therefore, in the case of the mixed fuel of gasoline and alcohol, the alcohol concentration of the mixed fuel. Can be estimated accurately.

  In addition, it goes without saying that the same effects as those of the first embodiment can be obtained.

  The flow of FIGS. 44 and 47 is the third and fourth embodiments, the flow of FIG. 44 is replaced with FIG. 38 of the first embodiment, and the flow of FIG. 47 is replaced with FIG. 42 of the second embodiment. These flows show the flow after engine startup in chronological order, and are not executed at regular intervals.

  In the third embodiment, the knock detection result is set to the octane number estimated value OCTEST when it is determined that fuel is supplied to an engine using gasoline, and the knock detection result is set to the compression ratio estimated value CMPEST when it is not determined that fuel is supplied. In the fourth embodiment, when it is determined that fuel has been supplied to an engine that uses a mixed fuel of gasoline and alcohol, the knock detection result is used as the alcohol concentration estimated value ALEST when it is determined that the fuel has been supplied. When the determination is not made, the knock determination result is fed back to the compression ratio estimated value CMPEST. Here, in the first and second embodiments, it is detected in which cylinder knocking has occurred, but in the third and fourth embodiments, it is not necessary to determine the cylinder. Therefore, it is only necessary to detect whether knocking has occurred for each cylinder or whether knocking has occurred for all cylinders.

  Although the fuels used in the third and fourth embodiments are different, the calculation method of the estimated value is almost the same, so the parts common to the two embodiments will be described together, and the two embodiments will be described. The different parts will be described separately.

  44 and 47, it is checked in step 301 whether the fuel cap is opened while the ignition key is OFF. For this purpose, a sensor for detecting the opening / closing of the fueling cap is provided at the fueling port, and it is only necessary to detect whether or not the fueling cap is opened based on the output from the sensor and hold the result. When it is determined that the information indicating that the refueling cap has been opened is held while the ignition key is OFF, the flow proceeds to step 302 to indicate that refueling has been performed, and the refueling flag = 1 is set.

  In the third embodiment, 100% as an initial value is entered in the octane number estimated value OCTEST in step 302 of FIG. This is because the knock detection result is immediately reflected in the estimated octane number. That is, if the octane number of the fuel supplied is 100%, it does not knock because it matches the estimated octane number OCTEST (= 100%) entered as the initial value. However, when the octane number of the supplied fuel is smaller than 100%, the initial value entered in the estimated octane number OCTEST is too large, and knocking occurs. Therefore, every time knocking occurs, the estimated octane number OCTEST decreases by the first predetermined value const03, and when knocking does not occur, the estimated octane number OCTEST converges, that is, the convergence value of the fuel that has been refueled. It is considered to be octane number.

  Similarly, in the fourth embodiment, in step 331 of FIG. 47, 0% as an initial value is entered in the alcohol concentration estimated value ALCOTEST. This is because the knock detection result is immediately reflected in the estimated alcohol concentration value. That is, if the alcohol concentration of the supplied mixed fuel is 0%, knocking does not occur because it matches the estimated alcohol concentration value ALCSEST (= 0%) entered as the initial value. However, when the alcohol concentration of the fuel mixture supplied is higher than 0%, the initial value of 0% entered in the alcohol concentration estimated value ALCEST is too low and knocking occurs. Therefore, at this time, every time a knock occurs, the alcohol concentration estimated value ALCEST is increased by the first predetermined value const13. When the knock does not occur, the alcohol concentration estimated value ALLCEST converges, that is, the converged value is refueled. This is considered to be the alcohol concentration of the mixed fuel.

  Steps 303 and 304 in FIGS. 44 and 47 are portions for determining whether or not all the fuel before refueling has been consumed after refueling. The execution timing of this part is immediately after the fuel injection of each cylinder. Immediately after refueling, the fuel before refueling remains in the fuel pipe, and when all the fuel in the fuel pipe is consumed, it can be considered that the fuel has been replaced with the fuel after refueling. Therefore, the fuel consumption amount SUMQ from the start is calculated, and it is determined that the fuel has been replaced when the fuel consumption amount SUMQ matches the fuel pipe capacity. That is, in step 303 in FIGS. 44 and 47, the fuel consumption SUMQ (new) [g] (initially set to zero at the start) immediately after the end of the current injection is compared with a predetermined fuel pipe capacity [g] (constant value). To do. Since the fuel consumption SUMQ (new) is smaller than the fuel pipe capacity immediately after the start, the routine proceeds to step 304 in FIGS. 44 and 47, and the fuel consumption SUMQ (new) immediately after the end of the current injection is used in preparation for the next fuel injection. It shifts to SUMQ (old) [g] which is the fuel consumption immediately after the end of injection.

  When the next fuel injection is performed, in step 305 of FIGS. 44 and 47, the next fuel injection amount Qf [g] is added to the SUMQ (old) that is the fuel consumption immediately after the previous injection ends, and the current injection ends. SUMQ (new), which is the fuel consumption immediately after, is calculated. Here, in order to obtain the current fuel injection amount Qf, the fuel injection pulse width Ti [ms] used for the current fuel injection may be multiplied by a conversion coefficient to be converted into a fuel mass unit [g]. 44 and 47, the fuel consumption amount SUMQ (new) is again compared with the predetermined fuel pipe capacity. If the fuel consumption amount SUMQ (new) is smaller than the fuel pipe capacity, the operations of steps 304, 305, and 303 in FIGS. 44 and 47 are repeated.

  If the number of fuel injections from the start increases, the fuel consumption SUMQ (new) eventually reaches the fuel pipe capacity. At this time, it is determined that the fuel before refueling has been replaced with the fuel after refueling. 44, the process proceeds from step 303 to step 306 in FIG. 44, and the octane number estimated value OCTEST is calculated. In the fourth embodiment, the process proceeds from step 303 in FIG. 47 to step 332 in FIG.

  The calculation of the estimated octane number OCTEST in the third embodiment will be described with reference to the flowchart of FIG.

  45 (subroutine of step 306 in FIG. 44) is basically the same as FIG. 38 of the first embodiment, and therefore the same step numbers are assigned to the same parts as in FIG. In the first embodiment, whether knocking occurs in a plurality of cylinders among all cylinders based on the knock detection result for each cylinder, or is knocking occurring in only one cylinder among all cylinders? When the knock occurs in a plurality of cylinders among all the cylinders, the estimated octane number OCTEST is calculated. When the knock occurs only in one cylinder among all the cylinders, the knock occurs. Since the configuration is such that the compression ratio estimated value CMPESTi of the cylinder (that is, the compression ratio increasing cylinder) is calculated, the configuration is complicated, such as making the compression ratio estimated value a value for each cylinder or performing cylinder discrimination. In the third embodiment, immediately after refueling, it is detected whether or not knocking occurs in a state where the estimated octane number is set to 100%. When knocking occurs, the knocking detection result is immediately converted to the octane number. Since to be reflected in the value OCTEST, it has a simpler structure as the first embodiment. That is, when it is detected in step 262 that knocking has occurred in FIG. 45, the routine proceeds to step 267, where the octane number estimated value OCTEST is updated by the above formula (79) to the smaller side by the first predetermined value const03, and thereafter In steps 274 to 278, the octane number estimated value OCTEST is returned to the side where the estimated octane number OCTEST is increased by the above equation (81) at a predetermined cycle by a second predetermined value const05.

  Similarly, calculation of the alcohol concentration estimated value ALCEST in the fourth embodiment will be described with reference to the flow of FIG.

  FIG. 48 (subroutine of step 332 in FIG. 47) is basically the same as FIG. 42 of the second embodiment, and the same step numbers are assigned to the same parts as in FIG. Also in the second embodiment, whether knocking occurs in a plurality of cylinders among all cylinders based on the knock detection result for each cylinder, or is knocking occurring in only one cylinder among all cylinders? If a knock occurs in a plurality of cylinders among all the cylinders, an alcohol concentration estimated value ALLCEST is calculated. If a knock occurs in only one cylinder among all the cylinders, the knock occurs. Since the configuration is such that the compression ratio estimated value CMPESTi of the cylinder (that is, the compression ratio increasing cylinder) is calculated, the configuration is complicated, but in the fourth embodiment, the alcohol concentration estimated value is set to 0% immediately after refueling. Whether or not knocking occurs in the set state is detected, and when knocking occurs, the knocking detection result is immediately reflected in the alcohol concentration estimated value ALCEST. It has become more simple structure and form. That is, when it is detected in step 262 that knocking has occurred in FIG. 48, the routine proceeds to step 291 where the alcohol concentration estimated value ALCEST is updated by the above equation (87) to the higher side by the first predetermined value const13, and thereafter In steps 274, 294, 276, 295, and 278, the alcohol concentration estimated value ALCEST is returned to the lower side by the second predetermined value const15 by the above equation (88) at predetermined intervals.

  When the calculation of the estimated octane value OCTEST is thus completed in the third embodiment, the process returns to FIG.

  The processing timing of steps 307 to 313 in FIG. 44 is the same as the calculation timing in FIG. 45, and is executed following the calculation in FIG.

  In step 307 in FIG. 44, it is determined whether or not knocking has occurred in the subroutine in FIG. 45. In step 308 in FIG. 44, the previous octane number estimated value OCTEST (old) and the current octane number estimated value OCTEST (new) To see if they match. As described in the subroutine of FIG. 45, the estimated octane value OCTEST is decreased by the first predetermined value when knocking occurs, and is returned to the side by which the second predetermined value is increased unless knocking occurs thereafter. 44, the process proceeds from step 307 in FIG. 44 to step 309 in FIG. 44, and after the value of the current octane number estimated value OCTEST (new) is moved to the previous octane number estimated value OCTEST (old), Return to 306.

  On the other hand, after the octane number estimated value is decreased to avoid knocking, knock is not detected in step 307 of FIG. 44, and the octane number estimated value OCTEST is returned to the side of increasing by the second predetermined value. The value OCTEST (new) does not match the previous estimated octane number OCTEST (old). Therefore, at this time, after performing the operation of step 310 of FIG. 44 (the same operation as step 309 of FIG. 44) from steps 307 and 308 of FIG. 44, the process returns to step 306 of FIG. 44 and steps 306, 307, 308 of FIG. , 310 is repeated.

  Eventually, if the current octane number estimated value OCTEST (new) matches the previous octane number estimated value OCTEST (old), the process proceeds from step 308 in FIG. 44 to step 311 in FIG.

  Similarly, when the calculation of the alcohol concentration estimated value ALCEST is finished in the fourth embodiment, the process returns to step 333 in FIG.

  The processing timings of steps 333 to 336, 311, 337, and 313 in FIG. 47 are the same as the calculation timings in FIG. 48, and are executed following the calculation in FIG.

  In step 333 of FIG. 47, it is determined whether or not knocking has occurred in the subroutine of FIG. 48, and in step 334 of FIG. 47, the previous alcohol concentration estimated value ALEST (old) and the current alcohol concentration estimated value ALTEST (new ) Matches. As described in the subroutine of FIG. 48, the alcohol concentration estimated value ALCEST is increased by the first predetermined value when knocking occurs, and is returned to the lower side by the second predetermined value unless knocking occurs thereafter. Therefore, at the timing when knocking is detected, the process proceeds from step 333 in FIG. 47 to step 335 in FIG. 47, and the value of the current alcohol concentration estimated value ALEST (new) is moved to the previous alcohol concentration estimated value ALTEST (old). Then, the process returns to step 332.

  On the other hand, after the alcohol concentration estimated value is increased to avoid knocking, knock is not detected in step 333 of FIG. 47, and the alcohol concentration estimated value ALCEST is returned to the lower side by the second predetermined value. The alcohol concentration estimated value ALLCEST (new) does not match the previous alcohol concentration estimated value ALLCEST (old). Therefore, at this time, after performing the operation of step 336 of FIG. 47 (the same operation as step 335 of FIG. 47) from steps 333 and 334 of FIG. 47, the process returns to step 332 of FIG. 47 and steps 332, 333 and 334 of FIG. 336 is repeated.

  Eventually, if the current alcohol concentration estimated value ALCEST (new) and the previous alcohol concentration estimated value ALLCEST (old) coincide with each other, the process proceeds from step 334 in FIG. 47 to step 311 in FIG.

  44 and 47, the counter value count2 (initially set to zero at start-up) is incremented by one. In the third embodiment, the counter value count2 indicates the number of times the current octane number estimated value OCTEST (new) and the previous octane number estimated value OCTEST (old) coincide with each other in the third embodiment. In the fourth embodiment, the current alcohol concentration estimated value. This is for measuring the number of times that the ALLCEST (new) and the previous alcohol concentration estimated value ALECEST (old) coincide.

  In the third embodiment, the counter value count2 and the predetermined value const21 are compared in step 312 of FIG. 44, and in the fourth embodiment, the counter value count2 and the predetermined value const22 are compared in step 337 of FIG. In the third embodiment, the predetermined value const21 determines a delay until it is determined that the estimated octane number has converged. In the fourth embodiment, the predetermined value const22 determines a delay until it is determined that the estimated alcohol concentration value has converged. The predetermined value const21 is larger than the predetermined value const05, and the predetermined value const22 is larger than the predetermined value const15. The actual values of the predetermined values const21 and 22 are obtained by matching.

  In the third embodiment, since the counter value count2 is initially less than the predetermined value const21, the process returns to step 306 in FIG. 44 and the operations in steps 306 to 312 in FIG. 44 are repeated. When the counter value count2 eventually exceeds the predetermined value const21, it is determined that the estimated octane number has converged, and the process proceeds from step 312 in FIG. 44 to step 313 in FIG.

  Similarly, in the fourth embodiment, since the counter value count2 is initially less than the predetermined value const22, the process returns to step 332 in FIG. 47 and the operations in steps 332 to 336, 311 and 337 in FIG. 47 are repeated. When the counter value count2 eventually exceeds the predetermined value const22, it is determined that the alcohol concentration estimated value has converged, and the process proceeds from step 337 in FIG. 47 to step 313 in FIG.

  In step 313 of FIGS. 44 and 47, the fueling flag = 0, the fuel consumption amount SUMQ (new) = 0, and SUMQ (old) = 0 are prepared for the next fueling.

  On the other hand, if it is determined that the fuel cap has not been opened while the ignition key is OFF, that is, it has been determined that fuel has not been applied while the ignition key is OFF, the routine proceeds to step 314 from step 301 in FIGS. The value CMPEST is calculated. In the third embodiment, the calculation proceeds to step 314 in FIG. 44 even after the calculation of the estimated octane value OCTEST is completed. However, after the calculation of the estimated octane value OCTEST is completed, step 314 in FIG. 44 is performed. It may be configured to skip to step 315 in FIG. In the fourth embodiment, the process proceeds to step 314 in FIG. 47 even after the calculation of the alcohol concentration estimated value ALCEST is completed. However, after the calculation of the alcohol concentration estimated value ALLCEST is completed, the process proceeds to step 314 in FIG. It may be configured to skip to step 315 in FIG.

  The calculation of the compression ratio estimated value CMPEST in step 314 of FIGS. 44 and 47 will be described with reference to the flow of FIG.

  46 common to the third and fourth embodiments (the third embodiment is the subroutine of step 314 in FIG. 44 and the fourth embodiment is the subroutine of step 314 in FIG. 47) is the same as FIG. 45 and the same as FIG. The same step number is given to the part. That is, when it is detected in FIG. 46 that knocking has occurred, it is determined that the cause is that the compression ratio estimated value CMPEST is higher than the actual compression ratio, and the routine proceeds to step 321 where the compression ratio estimated value CMPEST is determined. Is increased by the first predetermined value const23. That is, the compression ratio estimated value CMPEST is updated by the following equation.

CMPEST (new) = CMPEST (old) + const23 (89)
Where CMPEST (new): updated compression ratio estimate,
CMPEST (old): estimated compression ratio before update,
const23: update amount to the side to be increased,
Here, the initial value of the compression ratio estimated value is ε in the above equation (3).

  Thereafter, in steps 274, 322, 276, 323, and 278 of FIG. 46, the routine proceeds to step 323 at predetermined intervals, and the compression ratio estimated value CMPEST is decreased by the second predetermined value const25. That is, the compression ratio estimated value CMPEST is updated by the following equation.

CMPEST (new) = CMPEST (old) −const25 (90)
Where CMPEST (new): updated compression ratio estimate,
CMPEST (old): estimated compression ratio before update,
const25: update amount to the side to be reduced,
When the calculation of the compression ratio estimated value CMPEST is thus completed, the process returns to step 315 in FIGS. 44 and 47 to check whether or not the ignition key is turned off. If the ignition key is not OFF, the operation in step 314 is repeated. If the ignition key is turned off, the processing in FIGS. 44 and 47 is terminated.

  The octane number estimated value OCTEST calculated in this way in the third embodiment is calculated in this way in the fourth embodiment to calculate 1 / τ in the fuel of the octane number estimated value OCTEST in step 208 of FIG. The alcohol concentration estimated value ALCEST is used to calculate 1 / τ for the mixed fuel of the alcohol concentration estimated value ALEST at step 283 in FIG.

Corresponding to the change of the fuel to be used by refueling, according to the third and fourth embodiments (inventions of claims 12 and 13) , one of the two types of knock correlation parameters is set. The condition for selection is whether or not it has been determined that the refueling cap has been opened while the ignition key is OFF (whether or not refueling has been determined) (FIGS. 44 and 47 for the third and fourth embodiments). Therefore, when refueling is determined, it is possible to immediately calculate the estimated value of the knock correlation parameter for the fuel (octane number estimated value OCTEST for the third embodiment, alcohol concentration estimated value ALTEST for the fourth embodiment). (See steps 301 and 306 in FIG. 44 for the third embodiment, and steps 301 and 332 in FIG. 47 for the fourth embodiment). Immediately it is possible to converge the estimated value of the knocking correlation parameters a fuel immediately after refueling by.

In other words, if it is not when refueling is determined, the compression ratio estimated value CMPEST (the estimated value of the knock correlation parameter related to the combustion gas state in the combustion chamber) may be calculated immediately (claim 14). The compression ratio estimated value CMPEST can be quickly converged when it is not when refueling is determined.

  The flow of FIGS. 49 and 50 is the fifth and sixth embodiments, the flow of FIG. 49 is replaced with FIG. 38 of the first embodiment, and the flow of FIG. 50 is replaced with FIG. 42 of the second embodiment.

  In the fifth embodiment, the knock detection result is basically fed back to the estimated octane number OCTEST. However, the octane number estimated value OCTEST is limited to a predetermined range, and when the limit is exceeded, the estimated octane number is fixed to the limit value. Instead, the value is reset to an almost intermediate value within a predetermined range, and the knock detection result at that time is fed back to the compression ratio estimated value CMPEST. In addition, the sixth embodiment basically feeds back the knock detection result to the alcohol concentration estimated value ALTEST, but gives a limit of a predetermined range to the alcohol concentration estimated value ALTEST, and if the limit is exceeded, the alcohol concentration estimated value is Instead of being fixed to the limit value, it is reset to a value approximately in the middle of the predetermined range, and the knock detection result at that time is fed back to the compression ratio estimated value CMPEST.

  If it demonstrates from 5th Embodiment, in FIG. 49, in step 341, octane number estimated value OCTEST will be calculated. This is because the cause of knocking is influenced by the compression ratio in addition to the octane number, but in the fifth embodiment, the knock detection result is first reflected in the estimated octane number including the influence due to the compression ratio. For the calculation of the estimated octane value OCTEST, the flow of FIG. 45 described in the third embodiment may be used.

  Steps 342 and 343 in FIG. 49 are parts for limiting the estimated octane number OCTEST calculated in this way to a predetermined range. The predetermined range is a range of octane number of a commercially available fuel (for example, a range of 80% to 100%). That is, the estimated octane number OCTEST cannot be beyond the range of the octane number of commercially available fuels. However, in step 341 of FIG. 49, the knock detection result including the influence due to the compression ratio is reflected in the estimated octane number, so that the estimated octane number OCTEST is influenced by the compression ratio. The range of octane numbers can be exceeded. Therefore, when the estimated octane number exceeds 100% in step 342 in FIG. 49, the process proceeds to step 344 in FIG. 49, where the estimated octane number OCTEST is reset to the intermediate value const30 within a predetermined range and the cause that knocking is less likely to occur. 49, the compression ratio estimated value CMPEST is reduced by a predetermined value const32 in step 345 of FIG. That is, the compression ratio estimated value CMPEST is updated by the following equation.

CMPEST (new) = CMPEST (old) −const32 (91)
Where CMPEST (new): updated compression ratio estimate,
CMPEST (old): estimated compression ratio before update,
const32: update amount to the side to be reduced,
49, when the estimated octane number falls below 80%, the routine proceeds to step 346 in FIG. 49, where the estimated octane number is reset to the intermediate value const30 within the predetermined range, and the cause of the knock is large. In step 347 of FIG. 49, the compression ratio estimated value CMPEST is increased by a predetermined value const31. That is, the compression ratio estimated value CMPEST is updated by the following equation.

CMPEST (new) = CMPEST (old) + const31 (92)
Where CMPEST (new): updated compression ratio estimate,
CMPEST (old): estimated compression ratio before update,
const31: update amount to the side to be increased,
The purpose of resetting the estimated octane value OCTEST to the intermediate value const30 within the predetermined range is to reset the octane number estimated value OCTEST once and reestimate the octane number. As the intermediate value const30, about 90% which is an intermediate value between the minimum 80% and the maximum 100% is adopted. The actual value of the intermediate value const30 is determined by adaptation. The initial value of the compression ratio estimated value CMPEST is ε in the above equation (3).

  Next, the sixth embodiment will be described. In FIG. 50, in step 351, an alcohol concentration estimated value ALCEST is calculated. This is because the cause of knocking is the influence of the compression ratio in addition to the alcohol concentration, but in the sixth embodiment, the knock detection result is first reflected in the alcohol concentration estimated value ALEST including the influence due to the compression ratio. It is. For the calculation of the alcohol concentration estimated value ALCEST, the flow of FIG. 48 described in the fourth embodiment may be used.

  Steps 352 and 353 in FIG. 50 are portions for limiting the alcohol concentration estimated value ALLCEST calculated in this way to a predetermined range. The predetermined range is a range of alcohol concentration of a commercially available mixed fuel (for example, a range of 0% to 85%). In other words, the alcohol concentration estimated value ALCEST cannot originally exceed the alcohol concentration range of the commercially available mixed fuel. However, in step 351 of FIG. 50, since the knock detection result is reflected in the alcohol concentration estimated value including the influence due to the compression ratio, the alcohol concentration estimated value ALCEST is commercially available under the influence of the compression ratio. The range of alcohol concentration of the mixed fuel can be exceeded. Therefore, when the estimated alcohol concentration is lower than 0% in step 352 of FIG. 50, the process proceeds to step 354 of FIG. Is determined that the compression ratio is small, and the compression ratio estimated value CMPEST is decreased by a predetermined value const32 in step 345 of FIG. That is, the compression ratio estimated value CMPEST is updated by the above equation (91).

  Further, when the estimated alcohol concentration exceeds 85% in step 353 in FIG. 50, the routine proceeds to step 355 in FIG. 50, where the estimated alcohol concentration is reset to the intermediate value const40 within a predetermined range, and the cause of knocking is the large compression ratio. In step 347 of FIG. 50, the compression ratio estimated value CMPEST is increased by a predetermined value const31. That is, the compression ratio estimated value CMPEST is updated by the above equation (92).

  The purpose of resetting the alcohol concentration estimated value ALCEST to the intermediate value const40 within the predetermined range is to reset the alcohol concentration estimated value ALEST once and to estimate the alcohol concentration again. As the intermediate value const40, an intermediate value between the minimum of 0% and the maximum of 85% is about 40% to 50%. The actual value of the intermediate value const40 is obtained by adaptation.

  The octane number estimated value OCTEST calculated in this way in the fifth embodiment is calculated in this way in the sixth embodiment to calculate 1 / τ in the fuel of the octane number estimated value OCTEST in step 208 of FIG. The alcohol concentration estimated value ALCEST is used to calculate 1 / τ for the mixed fuel of the alcohol concentration estimated value ALEST at step 283 in FIG.

According to the fifth and sixth embodiments (the invention described in claim 15) , the estimated value of the knock correlation parameter relating to the fuel (the octane number estimated value OCTEST for the fifth embodiment, the alcohol concentration estimated value ALTEST for the sixth embodiment) ) To a predetermined range (a range of 100% to 80% for the fifth embodiment, a range of 0% to 85% for the sixth embodiment), and one of two types of knock correlation parameters is selected. The condition is whether or not the estimated value of the knock correlation parameter relating to the fuel has deviated from a predetermined range (steps 342 and 343 in FIG. 49 for the fifth embodiment, and steps 352 and 353 in FIG. 50 for the sixth embodiment). Therefore, the compression ratio estimated value CMPEST (estimated value of knock correlation parameter related to the combustion gas state in the combustion chamber) is calculated. It becomes simple. That is, it is simpler than FIG. 46 showing the calculation method of the compression ratio estimated value CMPEST according to the third and fourth embodiments.

  The flow of FIGS. 51, 52, 53, and 54 is a flow common to the third, fourth, fifth, and sixth embodiments, and FIGS. 2, 5, and 5 of the first and second embodiments, respectively. 10 and 13 are replaced. 51, the same step number is assigned to the same portion as FIG. 2, the same step number is assigned to the same portion as FIG. 5 in FIG. 52, the same step number is assigned to the same portion as FIG. 54, the same steps as those in FIG.

  In the first and second embodiments, the volume (VIVC, VIVCi) at the intake valve closing timing of the combustion chamber 5 and the combustion start timing of the combustion chamber 5 are divided into cylinders with an increased compression ratio and cylinders other than the cylinder with an increased compression ratio. The volume (V0, V0i), the initial combustion period (BURN1, BURN1i), and the basic ignition timing (MBTCAL, MBTCALI) were calculated in the third, fourth, fifth, and sixth embodiments. The volume at the intake valve closing timing, the volume at the combustion start timing of the combustion chamber 5, the initial combustion period, and the basic ignition timing are calculated as values common to all the cylinders.

The difference from the first and second embodiments will be mainly described. In FIG. 52, in step 431, the gap volume Vc [m ³ ] is calculated by the following equation.

Vc = (π / 4) D ² · Hx / (CMPEST-1) (93)
Where CMPEST: estimated compression ratio,
D: cylinder bore diameter [m],
Hx: difference between the maximum value and the minimum value of the distance from the TDC of the piston pin 76
[M],
Here, the expression (93) replaces the above expression (3) of the first and second embodiments. In the first and second embodiments, the compression ratio ε in the equation (3) is assumed to be constant. In the third, fourth, fifth, and sixth embodiments, the compression ratio estimated value CMPEST as a variable value is It is a thing.

  Using the clearance volume Vc thus obtained, in step 432 of FIG. 52, the volume VIVC of the combustion chamber 5 at the intake valve closing timing is calculated by the following equation.

VIVC = Vc + (π / 4) D ² · Hivc (94)
D: cylinder bore diameter [m],
Hivc: TDC of piston pin 76 when intake valve is closed
Distance from [m],
This equation (94) is the same as the above equation (2) in the first and second embodiments.

Next, in step 441 in FIG. 53, the gap volume Vc [m ³ ] is calculated by the above equation (93), and this gap volume Vc is used, and in step 442 in FIG. 53, the combustion start timing ( The volume V0 in (MBTCYCL) is calculated.

V0 = Vc + (π / 4) D ² · Hmbtcycl (95)
Where D: cylinder bore diameter [m]
Hmbtcycl: Piston pin at the start of combustion (MBTCYCL)
Distance from 76 TDCs [m],
Next, steps 421 to 424 in FIG. 13 are omitted in FIG. 54, and steps 391 to 396 in FIG. 2 are omitted in FIG.

In the first aspect of the invention, the function of the knock correlation parameter estimated value calculating means is the steps 262, 265, 266, 267, and 269 of FIG. 38, and the function of the knock occurrence time predicting means is the steps 206, 207, and 208, 209, 210, 218 in FIG. 33, the function of the knock limit ignition timing calculating means is in steps 219 to 231 in FIG.
The function of the ignition execution means is performed by steps 2, 3, and 5 in FIG.

In the second aspect of the invention, the function of the knock correlation parameter estimated value calculating means is the steps 262, 265, 266, 267, and 269 of FIG. 38, and the function of the knock occurrence time predicting means is the steps 206, 207, and 208, 209, 210, 218 in FIG. 33, the function of the knock limit ignition timing calculating means is in steps 219 to 231 in FIG. 33, and the function of the combustion start volume calculating means is in steps 411 to 414 in FIG. The functions of the calculation means are steps 415 and 416 in FIG. 10 and steps 421 to 423 in FIG. 13, the function of the basic ignition timing calculation means is in step 424 in FIG. 13, and the function of the ignition execution means is steps 391 to 394 in FIG. 396, respectively.

The engine control system figure of one Embodiment. The flowchart for demonstrating the ignition timing control of 1st, 2nd embodiment. 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 the physical quantity of 1st, 2nd embodiment. 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 the initial combustion period of 1st, 2nd embodiment. The characteristic figure of a temperature rise rate. The flowchart for demonstrating calculation of the main combustion period. The flowchart for demonstrating calculation of the basic ignition timing of 1st, 2nd embodiment. 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 the knock limit ignition timing of 1st, 3rd, 5th embodiment. The flowchart for demonstrating calculation of the knock limit ignition timing of 1st, 2nd, 3rd, 4th, 5th, 6th embodiment. 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. Trace knock strength characteristic chart. The flowchart for demonstrating calculation of an octane number estimated value and a compression ratio 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 the knock limit ignition timing of 2nd, 4th, 6th embodiment. FIG. 5 is a characteristic diagram of 1 / τ for a mixed fuel having an alcohol concentration of 0% according to the second embodiment. The characteristic diagram of 1 / τ in the mixed fuel with the alcohol concentration of 85% of the second embodiment. The flowchart for demonstrating calculation of the alcohol concentration estimated value and compression ratio estimated value of 2nd Embodiment. The wave form diagram which shows the motion of the alcohol concentration estimated value at the time of knock detection of 2nd Embodiment. The flowchart for demonstrating calculation of the octane number estimated value and compression ratio estimated value of 3rd Embodiment. The flowchart for demonstrating calculation of the octane number estimated value of 3rd, 5th embodiment. 10 is a flowchart for explaining calculation of a reduction ratio estimated value according to the third and fourth embodiments. The flowchart for demonstrating calculation of the octane number estimated value and compression ratio estimated value of 4th Embodiment. The flowchart for demonstrating calculation of the alcohol concentration estimated value of 4th, 6th embodiment. The flowchart for demonstrating calculation of the octane number estimated value and compression ratio estimated value of 5th Embodiment. The flowchart for demonstrating calculation of the octane number estimated value and compression ratio estimated value of 6th Embodiment. The flowchart for demonstrating the ignition timing control of 3rd, 4th, 5th, 6th embodiment. 10 is a flowchart for explaining calculation of physical quantities according to third, fourth, fifth, and sixth embodiments. The flowchart for demonstrating calculation of the initial stage combustion period of 3rd, 4th, 5th, 6th embodiment. The flowchart for demonstrating calculation of the basic ignition timing of 3rd, 4th, 5th, 6th embodiment.

Explanation of symbols

1 Engine 5 Combustion chamber 11 Ignition device (spark ignition means)
21 Fuel Injector 31 Engine Controller 47 Knock Sensor (Knock Strength Detection Means)

Claims (20)

Knock detecting means for detecting whether or not knock actually occurs in the combustion chamber;
When gasoline is used as fuel, the octane number of the fuel, or when gasoline and alcohol are mixed, the alcohol concentration in the mixed fuel is the knock correlation parameter for fuel, and the compression ratio is the knock correlation parameter for the combustion gas state in the combustion chamber. Each of the knock correlation parameters related to the fuel and the knock correlation parameters related to the combustion gas state in the combustion chamber, and one of the two types of knock correlation parameters is selected according to the condition, and the selected side Knock correlation parameter estimated value calculating means for calculating an estimated value of the knock correlation parameter based on the knock detection result;
Knock generation timing prediction means for predicting the knock generation timing in the combustion chamber based on the knock correlation parameter estimate for the fuel;
A combustion mass ratio calculation means at the time of knock generation for calculating a combustion mass ratio at the knock generation time;
An unburned fuel amount calculating means for calculating an unburned fuel amount based on the combustion mass ratio and the fuel amount at the calculated knock generation time;
A pressure increase amount estimating means for estimating a pressure increase amount due to knocking of the combustion chamber based on the unburned fuel amount;
Basic ignition timing calculating means for calculating basic ignition timing according to operating conditions;
Knock limit ignition timing setting means for setting, as a knock limit ignition timing, a value obtained by correcting the basic ignition timing to the retard side based on the amount of pressure increase due to the knock of the combustion chamber;
Ignition timing control apparatus for an engine, wherein the obtaining Bei an ignition execution means for performing the spark ignition at the knocking limit ignition timing. Knock detecting means for detecting whether or not knock actually occurs in the combustion chamber;
When gasoline is used as fuel, the octane number of the fuel, or when gasoline and alcohol are mixed, the alcohol concentration in the mixed fuel is the knock correlation parameter for fuel, and the compression ratio is the knock correlation parameter for the combustion gas state in the combustion chamber. The knock correlation parameter related to these fuels and the knock correlation parameter related to the combustion gas state in the combustion chamber are estimated, and one of the two types of knock correlation parameters is selected according to the conditions, and the knock correlation on the selected side is selected. Knock correlation parameter estimated value calculating means for calculating an estimated value of a parameter based on the knock detection result;
Knock generation timing prediction means for predicting the knock generation timing in the combustion chamber based on the knock correlation parameter estimate for the fuel;
A combustion mass ratio calculation means at the time of knock generation for calculating a combustion mass ratio at the knock generation time;
An unburned fuel amount calculating means for calculating an unburned fuel amount based on the combustion mass ratio and the fuel amount at the calculated knock generation time;
A pressure increase amount estimating means for estimating a pressure increase amount due to knocking of the combustion chamber based on the unburned fuel amount;
Basic ignition timing calculating means for calculating basic ignition timing according to operating conditions;
Knock limit ignition timing setting means for setting, as a knock limit ignition timing, a value obtained by correcting the basic ignition timing to the retard side based on the amount of pressure increase due to the knock of the combustion chamber;
Combustion start volume calculating means for calculating a volume at the combustion start timing of the combustion chamber based on a knock correlation parameter estimated value related to a combustion gas state in the combustion chamber;
Combustion period calculation means for calculating a combustion period from the start of combustion to a predetermined crank angle based on the volume at the start of combustion;
Basic ignition timing calculating means for calculating a basic ignition timing for obtaining MBT based on the combustion period;
When the knock correlation parameter related to the combustion gas state in the combustion chamber is selected from the two types of knock correlation parameters, ignition is performed with spark ignition at the retarded ignition timing of the knock limit ignition timing and the basic ignition timing. ignition timing control apparatus for an engine, wherein the benzalkonium a execution means. A knock generation volume calculating means for calculating a volume at the knock generation timing of the combustion chamber based on the knock generation timing;
3. The engine ignition timing control device according to claim 1, wherein the pressure increase amount due to the combustion chamber knock is estimated also based on the volume of the combustion chamber at the knock generation timing . A fuel gas specific heat estimating means for estimating the specific heat of the fuel gas in the combustion chamber;
3. The engine ignition timing control device according to claim 1, wherein the pressure increase due to knocking of the combustion chamber is estimated based on the specific heat of the fuel gas in the combustion chamber . The fuel gas specific heat estimation means is
Fuel gas enthalpy calculating means for calculating the enthalpy of the fuel gas by a calculation formula;
Means for calculating the average temperature at the time of knock occurrence, which calculates the average temperature of the combustion chamber at the time of occurrence of the knock by a calculation formula;
Fuel gas specific heat calculating means for calculating the specific heat of the fuel gas based on the enthalpy of the fuel gas and the average temperature at the time of knock generation;
To consist of an ignition timing control device for an engine according to claim 4, characterized in. A total gas mole number calculating means for calculating the mole number of all the gases in the combustion chamber;
3. The engine ignition timing control device according to claim 1, wherein the pressure increase amount due to knocking of the combustion chamber is estimated based on the number of moles of all gases in the combustion chamber . A total gas mass calculating means for calculating the mass of all gases in the combustion chamber;
3. The engine ignition timing control device according to claim 1, wherein the pressure increase amount due to knocking of the combustion chamber is estimated based on the masses of all gases in the combustion chamber . Knock generation volume calculation means for calculating the volume of the combustion chamber at the knock generation timing based on the knock generation timing;
Fuel gas specific heat estimation means for estimating the specific heat of the fuel gas in the combustion chamber;
A total gas mole number calculating means for calculating the mole number of all the gases in the combustion chamber;
A total gas mass calculating means for calculating the mass of all gases in the combustion chamber;
With
The value obtained by multiplying the amount of unburned fuel in the combustion chamber by the number of moles of all the gases in the combustion chamber is the volume of the combustion chamber at the time of knock generation, the specific heat of the fuel gas, and the total gas in the combustion chamber. The engine ignition timing control device according to claim 1 or 2, wherein the pressure increase amount due to knocking of the combustion chamber is estimated by a calculation formula that divides by a value obtained by multiplying by mass . A plurality of cylinders, the two types of knock above conditions for selecting one of the correlation parameters claim 1 or 2, characterized in that the number of cylinders knocking out of all the cylinders has occurred An ignition timing control device for an engine as described in 1. 10. The engine ignition timing control apparatus according to claim 9 , wherein a knock correlation parameter related to the fuel is selected when the number of cylinders in which the knock has occurred is plural . 10. The engine ignition timing control apparatus according to claim 9 , wherein a knock correlation parameter relating to a combustion gas state in the combustion chamber is selected when the number of cylinders in which the knock has occurred is singular . Ignition timing control device for an engine according to claim 1 or 2, wherein the condition for selecting one is whether or not to determine the lubrication of said two knock correlation parameters. The engine ignition timing control apparatus according to claim 12, wherein a knock correlation parameter related to the fuel is selected when the fuel supply is determined . The engine ignition timing control apparatus according to claim 12 , wherein a knock correlation parameter related to a combustion gas state in the combustion chamber is selected when the fuel supply is not determined .   The estimated value of the knock correlation parameter related to the fuel has a predetermined range limitation, and the condition for selecting one of the two types of knock correlation parameters is that the estimated value of the knock correlation parameter related to the fuel is The engine ignition timing control apparatus according to claim 1 or 2, wherein the engine ignition timing control apparatus according to claim 1 or 2 is whether or not a predetermined range is exceeded.   16. The engine ignition timing control device according to claim 15, wherein a knock correlation parameter related to a combustion gas state in the combustion chamber is selected when an estimated value of the knock correlation parameter related to the fuel is out of a predetermined range. .   The engine ignition timing control device according to claim 16, wherein the estimated value of the knock correlation parameter relating to the fuel is reset to an intermediate value within the predetermined range.   16. The engine ignition timing control device according to claim 15, wherein the knock correlation parameter related to the fuel is selected when the estimated value of the knock correlation parameter related to the fuel does not deviate from a predetermined range.   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 combustion period calculating means for calculating a combustion period from the start of combustion to a predetermined crank angle based on these laminar combustion speed, combustion gas volume equivalent volume, combustion mass ratio and reaction probability;
  Basic ignition timing calculation means for calculating a basic ignition timing for obtaining MBT based on the combustion period;
  With
  Dividing the combustion period into an initial combustion period and a main combustion period;
  Combustion start volume calculating means for calculating a volume at the combustion start timing of the combustion chamber based on a knock correlation parameter estimated value related to a combustion gas state in the combustion chamber;
  Initial combustion period calculating means for calculating the initial combustion period using the volume at the combustion start timing of the combustion chamber as a volume corresponding to the combustion gas volume in the combustion chamber;
  The engine ignition timing control device according to claim 1, further comprising:   Calculate the effective compression ratio from the intake valve closing timing to the combustion starting timing based on the volume at the intake valve closing timing of the combustion chamber and the volume at the combustion starting timing,
  From the temperature of the combustion chamber intake valve close timing and this effective compression ratio, the temperature at the combustion start timing of the combustion chamber, and from the pressure of the combustion chamber intake valve close timing and this effective compression ratio, the pressure at the combustion start timing of the combustion chamber. Respectively,
  When calculating the laminar combustion speed used for calculation of the initial combustion period based on the temperature and pressure at the combustion start timing of these combustion chambers,
  20. The engine ignition timing control device according to claim 19, wherein a volume of the combustion chamber at an intake valve closing timing is calculated based on the estimated compression ratio.