JP2015218704A - Internal combustion engine control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control unit capable of appropriately setting the ignition timing of a spark ignition internal combustion engine.SOLUTION: A period from an ignition period FA to a heat-generation-rate maximum period dQpeakA in which a heat generation rate reaches a maximum is specified as a first-half combustion period in an air-fuel mixture combustion period. A reference value of the first-half combustion period is specified as a reference first-half combustion period. Furthermore, an actual first-half combustion period is calculated as an actual first-half combustion period. If a deviation between the reference first-half combustion period and the actual first-half combustion period falls within a predetermined range, the ignition timing of an ignition plug is corrected to reduce the deviation. If the deviation exceeds a predetermined amount, it is determined a failure occurs.

Description

  The present invention relates to a control device for an internal combustion engine. In particular, the present invention relates to control of ignition timing in a spark ignition type internal combustion engine.

  Conventionally, in a spark ignition type internal combustion engine, ignition timing control of a spark plug has been performed in order to increase combustion efficiency. In Patent Document 1, a 50% combustion point at the time of MBT (Minimum advance for the Best Torque) is set according to the heat loss rate (a crank angle position at which the combustion ratio is 50% when the ignition timing is MBT). It is disclosed that the ignition timing is corrected according to the difference between the 50% combustion point at the time of MBT and the actual 50% combustion point.

JP 2008-25406 A

  By the way, the 50% combustion point fluctuates under the influence of various operating conditions such as an air-fuel ratio. For this reason, in order to accurately determine the 50% combustion point, it is necessary to detect various operating conditions with high accuracy and reflect these operating conditions. Therefore, it is preferable to set the 50% combustion point during MBT as a value reflecting not only the heat loss rate but also various operating conditions.

  However, when the sensor for detecting the operating condition has deteriorated over time, the detection accuracy of the operating condition cannot be sufficiently obtained, and the accuracy of the 50% combustion point obtained by reflecting the operating condition is deteriorated. there is a possibility. For this reason, if the ignition timing is corrected based on the 50% combustion point, there is a possibility that an appropriate ignition timing cannot be obtained.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a control device for an internal combustion engine capable of optimizing the ignition timing in a spark ignition type internal combustion engine. .

-Solution principle of the invention-
The inventor of the present invention has a novel finding that the first half combustion period, which is a period from when the air-fuel mixture is ignited until the heat generation rate is maximized, is not affected by the operating conditions of the internal combustion engine such as the air-fuel ratio. Obtained.

  The solution principle of the present invention is based on this new knowledge, and when the reference period of the first combustion period that is not affected by the operating conditions deviates from the actual first combustion period, the ignition timing is set so as to reduce this difference. Is to correct.

-Solution-
Specifically, the present invention is premised on a spark ignition type internal combustion engine control device. For the control device for the internal combustion engine, a period from the ignition timing of the air-fuel mixture to the maximum heat generation rate is defined as the first half combustion period. Further, the reference value of the first half combustion period is set as the reference first half combustion period, and the sensed actual first half combustion period is obtained as the actual first half combustion period. And it is set as the structure which correct | amends the ignition timing of a spark plug so that the gap between the said reference | standard first half combustion period and the said actual first half combustion period may be made small.

  As described above, the inventor of the present invention has found as a new finding that the first half combustion period is not affected by the operating conditions of the internal combustion engine such as the air-fuel ratio. Therefore, the reference first half combustion period is set as a reference value (ideal value) for the first half combustion period, and the spark plug is set so as to reduce the difference between the reference first half combustion period and the actually measured first half combustion period. If the ignition timing is corrected, the ignition timing can be appropriately corrected without being affected by the influence of the operating conditions (the influence of fluctuations in the operating conditions) or the aging of the sensor that detects these operating conditions.

  Further, it is assumed that the first half combustion period is greatly affected by the disturbance in the cylinder. In other words, it is assumed that the stronger the turbulence in the cylinder, the faster the flame propagation and the shorter the first half combustion period. The turbulence in the cylinder changes in accordance with the state quantity of the in-cylinder gas, in particular, the in-cylinder volume. That is, the larger the cylinder volume at the maximum heat generation rate (the closer the piston is to the bottom dead center in the combustion stroke), the weaker the turbulence in the cylinder. And if the disturbance in a cylinder becomes weak, flame propagation will become slow and the first half combustion period will become long. For this reason, when the maximum heat release rate timing is on the retard side with respect to the timing at which the piston reaches compression top dead center (TDC), the maximum heat release rate is on the retard side and the cylinder volume increases. The turbulence in the cylinder becomes weaker and the first half combustion period becomes longer. On the other hand, the turbulence in the cylinder becomes stronger as the maximum heat generation rate is on the advance side and the in-cylinder volume is smaller, the flame propagation becomes rapid, and the first half combustion period is shortened. As described above, the in-cylinder volume at the time when the heat generation rate is maximum is a parameter correlated with the disturbance in the cylinder. For this reason, it is preferable to calculate the reference first half combustion period based on the in-cylinder volume (the in-cylinder gas state quantity) at the maximum heat release rate. As a result, it is possible to calculate the reference first half combustion period that reflects the influence of the turbulence in the cylinder, the calculation accuracy of the reference first half combustion period is sufficiently ensured, and the ignition timing corrected using this reference first half combustion period is It will be appropriate.

  The turbulence in the cylinder also changes depending on the engine speed. That is, the lower the engine speed, the lower the flow rate of air flowing into the cylinder from the intake system, and the turbulence in the cylinder becomes weaker. And if the disturbance in a cylinder becomes weak, flame propagation will become slow and the first half combustion period will become long. Conversely, the higher the engine speed, the higher the flow rate of air flowing from the intake system into the cylinder, and the more turbulent the cylinder is. And if the disturbance in a cylinder becomes strong, flame propagation will become rapid and the first half combustion period will become short. As described above, the engine speed is also a parameter correlated with the disturbance in the cylinder. For this reason, it is preferable to calculate the reference first half combustion period by multiplying a correction coefficient based on the engine speed (for example, an exponential function of the engine speed). As a result, it is possible to calculate the reference first half combustion period that further reflects the influence of the turbulence in the cylinder, the accuracy of the reference first half combustion period is sufficiently secured, and the ignition timing corrected using this reference first half combustion period. Is appropriate.

  As an example of the correction coefficient based on the engine rotation speed, it is preferable to use an exponential function of the engine rotation speed with a value corresponding to the tumble ratio as an index. Since the tumble ratio has a great influence on the turbulence in the cylinder as well as the engine rotation speed, the correction coefficient based on the engine rotation speed is an exponential function of the engine rotation speed with a value corresponding to the tumble ratio as an index. Accordingly, it is possible to calculate the reference first combustion period that further reflects the influence of the disturbance in the cylinder.

  Further, it is preferable to determine that a failure has occurred when the actual first half combustion period is longer than the reference first half combustion period and the difference between them is equal to or greater than a preset failure determination value.

  Thus, if the difference between the reference first half combustion period and the actual first half combustion period is large, there is some failure in the internal combustion engine, and even if the ignition timing is corrected, it is assumed that proper combustion cannot be obtained. Judgment will be made. As a result, useless ignition timing correction control is not executed.

  Specifically, as the means for obtaining the actual first half combustion period and the reference first half combustion period, the actual first half combustion period is determined from the ignition timing obtained from the ignition timing obtained from an output signal of an in-cylinder pressure sensor for sensing in-cylinder pressure. Calculate as the period up to the maximum time. Further, the reference first half combustion period is obtained as a period calculated based on the state quantity of the in-cylinder gas at the maximum time of the heat generation rate obtained from the output signal of the in-cylinder pressure sensor.

  In the present invention, the ignition timing of the spark plug is corrected so as to reduce the difference between the reference first half combustion period and the actual first half combustion period. Thereby, it becomes possible to correct | amend ignition timing appropriately, without considering the influence of the operating condition of an internal combustion engine.

It is a figure which shows schematic structure of the engine and intake / exhaust system which concern on embodiment. It is a block diagram which shows the control system of an engine. It is a figure which shows an example of a heat release rate waveform. It is a heat release rate waveform obtained in each engine operating state in which only the load rate is different from each other, and is a diagram in which each heat release rate waveform in which the ignition timing is adjusted so that the heat release rate maximum timing dQpeakA coincides with each other is displayed. is there. It is a heat generation rate waveform obtained in each engine operating state in which only the EGR rate is different from each other, and is a diagram in which each heat generation rate waveform in which the ignition timing is adjusted so that the maximum heat generation rate timing dQpeakA coincides with each other is displayed. is there. It is a heat release rate waveform obtained in each engine operating state in which only the air-fuel ratio is different from each other, and is a diagram in which each heat release rate waveform in which the ignition timing is adjusted so that the maximum heat generation rate dQpeakA coincides with each other is displayed. is there. It is a heat generation rate waveform obtained in each engine operating state in which only the oil water temperature is different from each other, and is a diagram in which each heat generation rate waveform in which the ignition timing is adjusted so that the maximum heat generation rate dQpeakA coincides with each other is displayed. is there. It is the figure which displayed in piles the heat release rate waveform obtained in each engine operation state from which only ignition timing SA mutually differs. Each heat generation rate waveform obtained in each engine operating state in which only the engine speed Ne is different from each other, and each heat generation rate waveform in which the ignition timing is adjusted so that the maximum heat generation rate timing dQpeakA coincides with each other is displayed in an overlapping manner. FIG. It is a figure which shows the result of having verified the relationship between the prediction first half combustion period calculated by Formula (1) with respect to a certain engine, and the measurement first half combustion period measured in the actual machine. It is a figure which shows the result of having verified the relationship between the prediction first half combustion period calculated by Formula (1) with respect to another engine, and the measurement first half combustion period measured in the actual machine. It is a flowchart figure which shows the procedure of ignition timing correction | amendment control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a gasoline engine for automobiles (spark ignition type internal combustion engine) will be described.

  FIG. 1 is a schematic configuration diagram showing an example of an engine 1 to which the present invention is applied.

  The engine 1 in this example is a multi-cylinder gasoline engine, and includes a piston 1b that forms a combustion chamber 1a and a crankshaft 15 that is an output shaft. The piston 1b is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1b is converted into the rotational motion of the crankshaft 15 by the connecting rod 16.

  A signal rotor 17 having a plurality of protrusions 17a, 17a,... Is attached to the crankshaft 15 on the outer peripheral surface. A crank position sensor 36 is disposed in the vicinity of the signal rotor 17.

  A spark plug 3 is disposed in the combustion chamber 1 a of the engine 1. The ignition timing of the spark plug 3 is adjusted by the igniter 4. The igniter 4 is controlled by an ECU (electronic control unit) 100 described later. A water temperature sensor 31 that detects the cooling water temperature is disposed in the cylinder block 1 c of the engine 1.

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 a of the engine 1. An intake valve 13 is provided between the intake passage 11 and the combustion chamber 1a, and an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1a.

  In the intake passage 11, an air cleaner 7, an air flow meter 32, an intake air temperature sensor 33, an electronically controlled throttle valve 5 and the like are arranged. The throttle valve 5 is driven by a throttle motor 6. The opening degree of the throttle valve 5 is detected by a throttle position sensor 37. In the exhaust passage 12, an A / F sensor 35, a three-way catalyst 8, and the like are arranged.

  The intake passage 11 and the exhaust passage 12 are connected by an EGR passage 21. The EGR passage 21 lowers the combustion temperature by returning a part of the exhaust gas discharged to the exhaust passage 12 to the intake passage 11 and supplying it again to the combustion chamber 1a, thereby reducing the amount of NOx generated. is there. The EGR passage 21 is provided with an EGR cooler 22 and an EGR valve 23. The opening degree of the EGR valve 23 is controlled by the ECU 100.

  An injector (fuel injection valve) 2 that injects fuel toward the combustion chamber 1 a is attached to the intake passage 11. The fuel injected from the injector 2 is mixed with intake air to be mixed into the combustion chamber 1a of the engine 1. The air-fuel mixture introduced into the combustion chamber 1a is ignited and combusted / expanded with the ignition of the spark plug 3. The piston 1b reciprocates by the combustion / expansion of the air-fuel mixture in the combustion chamber 1a, and the crankshaft 15 rotates.

  The cylinder head is provided with an in-cylinder pressure sensor 39 for detecting the in-cylinder combustion pressure. The in-cylinder pressure sensor 39 is provided for each cylinder.

-ECU-
The ECU 100 includes a CPU 101, a ROM 102, a RAM 103, and a backup RAM 104 as shown in FIG.

  The ROM 102 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 101 executes arithmetic processing based on various control programs and maps stored in the ROM 102. The RAM 103 is a memory that temporarily stores calculation results of the CPU 101, data input from each sensor, and the like. The backup RAM 104 is a non-volatile memory that stores data to be saved when the engine 1 is stopped. is there. These ROM 102, CPU 101, RAM 103, and backup RAM 104 are connected to each other via a bus 107, and are connected to an external input circuit 105 and an external output circuit 106.

  The external input circuit 105 includes a water temperature sensor 31, an air flow meter 32, an intake air temperature sensor 33, an intake air pressure sensor 34, an A / F sensor 35, a crank position sensor 36, a throttle position sensor 37, a fuel pressure sensor 38, and an in-cylinder pressure sensor. Various sensors such as 39 are connected. The external output circuit 106 is connected to the injector 2, the igniter 4 of the spark plug 3, the throttle motor 6 of the throttle valve 5, the EGR valve 23, and the like.

  The ECU 100 executes various controls of the engine 1 including drive control (fuel injection control) of the injector 2 and drive control of the throttle motor 6 of the throttle valve 5 based on the outputs of the various sensors described above. Further, the ECU 100 executes ignition timing correction control for the spark plug 3 described later.

-Heat release rate waveform-
FIG. 3 shows an example of a heat generation rate (heat generation amount per unit rotation angle of the crankshaft 15) waveform when the air-fuel mixture burns in the combustion chamber 1a.

  The timing SA in FIG. 3 is an ignition timing. The ignition timing SA is a timing at which the spark plug 3 is ignited, that is, a timing at which spark discharge is performed between the electrodes of the spark plug 3. Timing FA in the figure is the ignition timing. This ignition time FA is a time when the air-fuel mixture is ignited by the spark discharge and an initial flame nucleus is formed. For this reason, τ in the figure is the ignition delay period.

  In the figure, dQpeakA is the maximum heat generation rate. This heat generation rate maximum timing dQpeakA is the timing at which the heat generation rate becomes maximum with the growth of the flame kernel in the combustion period of the mixture (the heat generation rate is in the period from the ignition timing SA to the combustion end timing EA). (Maximum timing).

Further, a in the figure, which is a period from the ignition timing FA to the maximum heat release rate timing dQpeakA, is referred to as the first half combustion period. Also, c in the figure, which is a period from the maximum heat release rate timing dQpeakA to the combustion end timing EA, is referred to as the second half combustion period. Q1 in the figure is the heat generation amount in the first half combustion period a, and Q2 is the heat generation amount in the second half combustion period c. The heat generation amount (total heat generation amount Q _all ) generated during the entire combustion period is expressed as the sum of the heat generation amount Q1 and the heat generation amount Q2.

-Ignition timing correction control-
Next, ignition timing correction control, which is a feature of the present embodiment, will be described. First, the outline of this ignition timing correction control will be described. The ignition timing correction control of the present embodiment uses the reference value of the first half combustion period a that is the period from the ignition timing FA of the air-fuel mixture in the combustion chamber 1a to the maximum heat generation rate dQpeakA at which the heat generation rate is maximum. It is defined as the combustion period. This reference first half combustion period corresponds to, for example, the first half combustion period a when it is assumed that ideal combustion is performed in the combustion chamber 1a. The reference first half combustion period is calculated by an arithmetic expression (expression (1) described later) stored in the ECU 100. The reference first half combustion period may be obtained in advance by experiments or simulations and stored in the ECU 100.

  Further, the period from the ignition timing FA to the maximum heat generation rate dQpeakA when the air-fuel mixture is actually burned in the combustion chamber 1a is obtained as the actual first half combustion period. The actual first half combustion period is calculated based on an output signal from the in-cylinder pressure sensor 39, for example.

  Then, the ignition timing of the spark plug 3 is corrected so as to reduce the difference according to the difference between the reference first half combustion period and the actual first half combustion period.

  Further, when the actual first half combustion period is longer than the reference first half combustion period and the difference between them is equal to or greater than a preset failure judgment value, it is judged that a failure has occurred.

  Before describing the specific ignition timing correction control, the reason for using the first half combustion period in the ignition timing correction control will be described.

  As described above, the first half combustion period is a period from the ignition timing FA to the maximum heat generation rate dQpeakA. And the said reference | standard first half combustion period [CA] is prescribed | regulated using the following formula | equation (1).

V _{@ dQpeak} is an in-cylinder volume [L] as a state quantity of in-cylinder gas at the maximum heat generation rate dQpeakA, and is hereinafter referred to as a maximum heat generation rate in-cylinder volume. Ne is an engine speed (engine speed).

  This expression (1) is an expression that is established on the condition that the opening and closing timings of the intake and exhaust valves are fixed. Further, the equation (1) is established without being affected by operating conditions such as load factor, EGR rate, air-fuel ratio, and oil water temperature. That is, Expression (1) is established based on the fact that the reference first half combustion period is not affected by the operating conditions (load factor, EGR rate, air-fuel ratio, oil / water temperature). For this reason, when the reference first half combustion period is calculated by this equation (1), the influence of fluctuations in the operating conditions (load factor, EGR rate, air-fuel ratio, oil / water temperature) and the sensor for detecting these operating conditions The reference first combustion period is determined as a value that is not affected by aging deterioration, that is, a value that does not need to consider these effects. That is, the reference first half combustion period calculated by the equation (1) is obtained as a value that is highly robust against fluctuations in the operating conditions.

  The reason why the reference first half combustion period can be calculated by this equation (1) will be described below.

  Each of FIGS. 4 to 7 is a heat generation rate waveform obtained in different engine operating states, and the heat generation rate waveforms obtained by adjusting the ignition timing SA so that the maximum heat generation rate timing dQpeakA coincides with each other. It is displayed. FIG. 4 shows the heat generation rate waveforms obtained in each engine operating state in which only the load factor is different from each other. FIG. 5 shows the heat generation rate waveforms obtained in each engine operating state in which only the EGR rate is different from each other. FIG. 6 shows the heat generation rate waveform obtained in each engine operating state in which only the air-fuel ratio is different from each other. FIG. 7 shows the heat generation rate waveforms obtained when only the oil and water temperatures are different from each other as in the course of engine warm-up operation.

  As shown in FIGS. 4 to 7, the first half combustion period “a” is maintained constant regardless of any of the load factor, EGR rate, air-fuel ratio, and oil / water temperature. That is, it can be seen that the first half combustion period a is not affected by the load factor, EGR rate, air-fuel ratio, and oil water temperature.

  On the other hand, FIG. 8 shows the heat release rate waveform obtained in each engine operating state in which only the ignition timing SA is different from each other. As can be seen from FIG. 8, the first half combustion period a becomes longer as the ignition timing SA is retarded.

  FIG. 9 is a heat generation rate waveform obtained in each engine operating state in which only the engine rotational speed Ne is different from each other, and each heat generation in which the ignition timing SA is adjusted so that the maximum heat generation rate dQpeakA coincides with each other. The rate waveform is superimposed and displayed. Since the crank rotation angle [CA] per unit time [ms] increases as the engine speed Ne increases, the first half combustion period a should be longer (longer on the crank angle axis). In the case shown in FIG. 9, even if the engine speed Ne is different, the first half combustion period a is hardly changed. This is considered to be due to the fact that the higher the engine rotation speed Ne, the shorter the first half combustion period a. In other words, the higher the engine speed Ne, the longer the first combustion period a due to the larger crank rotation angle per unit time, and the shorter the first combustion period a due to “other factors”. Can be assumed.

  Thus, it can be seen that the first half combustion period a is affected by the ignition timing SA and the engine speed Ne.

  As a factor that the first half combustion period a is affected by the ignition timing SA and the engine rotational speed Ne, it is conceivable that the ignition timing SA and the engine rotational speed Ne affect the turbulence in the cylinder.

In other words, considering the case where the maximum heat generation rate dQpeakA is on the retard side of TDC, the ignition timing FA and the maximum heat generation rate dQpeakA also shift to the retard side as the ignition timing SA shifts to the retard side. The in-cylinder volume at the maximum heat generation rate dQpeakA (in-cylinder volume V _@dQpeak at the maximum heat generation rate) is increased, and the turbulence in the cylinder is weakened. And if the disturbance in a cylinder becomes weak, flame propagation will become slow and the first half combustion period a will become long. Conversely, as the ignition timing SA shifts to the advance side, the ignition timing FA and the maximum heat generation rate dQpeakA also shift to the advance side, and the in-cylinder volume V _@dQpeak at the maximum heat generation rate decreases and Disturbances become stronger. Thereby, flame propagation becomes rapid and the first half combustion period a becomes short.

  Further, the lower the engine speed Ne, the lower the flow rate of air flowing into the cylinder from the intake system, and the turbulence in the cylinder becomes weaker. And if the disturbance in a cylinder becomes weak, flame propagation will become slow and the first half combustion period a will become long. On the contrary, the higher the engine speed Ne, the higher the flow velocity of the air flowing into the cylinder from the intake system, and the turbulence in the cylinder becomes stronger. And if the disturbance in a cylinder becomes strong, flame propagation will become rapid and the first half combustion period a will become short. The above-mentioned “other factors (factors that shorten the first half combustion period a)” is that the flame propagation is rapid due to the fact that the higher the engine speed Ne, the stronger the turbulence in the cylinder. .

The inventor of the present invention derived the formula (1) based on this new knowledge. In this equation (1), the in-cylinder volume, particularly the maximum in-cylinder volume V _{@ dQpeak} , is used as a variable as the in-cylinder gas state quantity correlated with the ignition timing SA that is the controlled variable. Yes. That is, as described above, as the ignition timing SA shifts to the retard side, the maximum heat generation rate timing dQpeakA also shifts to the retard side, and the in-cylinder volume V _@dQpeak increases, which is correlated with the ignition timing SA. The in-cylinder volume V _@dQpeak is used as a variable as the state quantity of the in-cylinder gas.

Specifically describing each coefficient in Equation (1), C and α are obtained by identification based on experiments and the like. Further, β is a value corresponding to the tumble ratio in the cylinder, and is given as a larger value as the tumble ratio is larger. Note that β may be set by identification based on experiments or the like. These coefficients can also be identified with respect to changes in the opening / closing timings of the intake and exhaust valves. As described above, the expression (1) is multiplied by the exponential function (correction coefficient) of the engine rotational speed Ne based on the in-cylinder volume V _@dQpeak at the maximum heat generation rate and with the value β corresponding to the tumble ratio as an exponent. Thus, the reference first half combustion period is calculated.

  FIG. 10 and FIG. 11 show the results of verifying the relationship between the predicted first half combustion period as the reference first half combustion period calculated by Expression (1) and the measured first half combustion period measured in the actual machine for different engines. It is a graph which shows. The engine used for this verification has an ideal combustion with no deposits attached to the in-cylinder and intake / exhaust valves, and has the same compression ratio as the design, and there is no reduction in spark plug capacity. It has become a thing. That is, the relationship between the predicted first half combustion period and the measured first half combustion period is verified using an engine that has not changed over time. In FIG. 10, the engine speed Ne increases in the order of “◯”, “Δ”, “□”, “◇”, “×”, “+”, “▽”. For example, “◯” is 800 rpm, “Δ” is 1000 rpm, “□” is 1200 rpm, “◇” is 1600 rpm, “×” is 2400 rpm, “+” is 3200 rpm, and “▽” is 3600 rpm. In FIG. 11, the engine speed Ne increases in the order of “◯”, “×”, “+”, “Δ”, and “□”. For example, “◯” is 800 rpm, “×” is 1200 rpm, “+” is 2400 rpm, “Δ” is 3600 rpm, and “□” is 4800 rpm.

  As can be seen from FIGS. 10 and 11, the predicted first half combustion period substantially coincides with the measured first half combustion period, and it is understood that the reference first half combustion period is calculated with high accuracy by the equation (1).

As described above, the reference first half combustion period is not affected by the load factor, air-fuel ratio, EGR rate, and oil / water temperature, and is based on the maximum heat _release rate in-cylinder volume V _{@ dQpeak} and the engine speed Ne. Can be prescribed. These maximum in-cylinder volume V _@dQpeak and engine speed Ne are parameters that correlate with the turbulence in the cylinder as described above. In other words, the load factor, the air-fuel ratio, the EGR rate, and the oil / water temperature are assumed to have no influence on the reference first half combustion period because there is almost no correlation with the disturbance in the cylinder. Then, without considering these load factor, air-fuel ratio, EGR rate, and oil / water temperature, the maximum heat _release rate cylinder volume V _@dQpeak and the engine speed Ne, which are parameters correlated with the turbulence in the cylinder, are obtained. Because the reference first half combustion period can be defined on the basis of this, when the operating conditions such as the load factor, the air-fuel ratio, the EGR rate, and the oil / water temperature change, or because the sensor that detects these operating conditions has deteriorated over time. Even if the detected operating conditions include errors or the operating conditions fluctuate due to aging of the actuator that adjusts these operating conditions, the reference first half combustion period is the maximum heat release rate in-cylinder volume. It is obtained uniformly from V _{@ dQpeak} and engine speed Ne. For this reason, when the reference first half combustion period is calculated by the equation (1), it is not necessary to consider the influence of fluctuations in the operating conditions and the aging deterioration of the sensor that detects these operating conditions. A combustion period is required. That is, the reference first half combustion period calculated by the equation (1) is obtained as a value that is highly robust against fluctuations in the operating conditions.

  Specifically, being unaffected by the load factor means that the robustness against the prediction error of the intake air amount, the fluctuation of the intake air amount for each cycle, and the intake air amount measurement error due to the deterioration of the air flow meter 32 is high. It turns out that. Further, the fact that the air-fuel ratio is not affected is due to an air-fuel ratio measurement error due to deterioration of the A / F sensor 35, fluctuations in the intake air amount for each cycle, and fuel adhering to the inner wall surface of the intake passage 11. This means that the robustness against changes in the amount of fuel introduced into the cylinder is high. In addition, being not affected by the EGR rate means that it is robust against fluctuations in the amount of EGR gas introduced due to deposit adhesion on the EGR valve 23, changes over time in the internal EGR quantity, fluctuations in the EGR quantity for each cycle, and the like. Is expensive. Also, being not affected by the oil / water temperature means that the water temperature detection error due to the deterioration of the water temperature sensor 31 and the robustness against the oil temperature detection error due to the deterioration of the oil temperature sensor are high.

  Further, since it is not necessary to consider the load factor, the air-fuel ratio, the EGR rate, and the oil / water temperature in calculating the reference first half combustion period, the number of steps for determining the reference first half combustion period can be reduced.

  Hereinafter, the ignition timing correction control will be specifically described. FIG. 12 is a flowchart showing the procedure of ignition timing correction control. This flowchart is executed in the ECU 100 for each combustion cycle of each cylinder. That is, the ECU 100 constitutes a control device for an internal combustion engine in the present invention.

  First, in step ST1, in-cylinder combustion pressure is measured for a cylinder in which a combustion stroke is performed. In this measurement, the ECU 100 receives an output signal from the in-cylinder pressure sensor 39, and information on the in-cylinder combustion pressure corresponding to the output signal is accumulated in the RAM 103.

  In step ST2, it is determined whether or not the measurement of the in-cylinder combustion pressure is completed. In this ignition timing correction control, if the ignition timing FA and the maximum heat generation rate dQpeakA are acquired, the reference first combustion period and the actual first combustion period can be calculated. When the occurrence rate maximum time dQpeakA is acquired, it is determined that the measurement of the in-cylinder combustion pressure is completed.

  Specifically, in the present embodiment, the ignition timing FA is a timing (crank angle) at which the heat generation rate reaches 1 [J / CA] after the ignition timing SA (after the ignition command signal is output to the spark plug 3). Position). That is, the ignition timing FA is defined as the time when the heat generation rate reaches 1 [J / CA] based on the output signal of the in-cylinder pressure sensor 39. This value is not limited to this, and can be set as appropriate. For example, a timing when the heat generation rate exceeds 0 [J / CA] after the ignition timing SA may be set as the ignition timing FA. Further, the timing at which the heat generation amount after the ignition timing SA reaches a predetermined ratio (for example, 5%) with respect to the total heat generation amount may be set as the ignition timing FA.

  Further, the maximum heat generation rate dQpeakA is defined as a timing (crank angle position) at which the heat generation rate has changed from rising to lowering, so that the heat generation rate obtained based on the output signal of the in-cylinder pressure sensor 39 is When turning from ascending to descending, it is determined that the time is defined as the maximum heat release rate timing dQpeakA and the measurement of the in-cylinder combustion pressure is completed.

  If the measurement of the in-cylinder combustion pressure is not completed and a NO determination is made in step ST2, the routine returns and the measurement of the in-cylinder combustion pressure is continued.

  When the measurement of the in-cylinder combustion pressure is completed and YES is determined in step ST2, the process proceeds to step ST3, where the ignition timing FA and the maximum heat generation rate dQpeakA are based on the accumulated information on the in-cylinder combustion pressure. Is calculated. That is, as described above, the crank angle position at the time when the heat generation rate reaches a predetermined value is calculated as the ignition timing FA, and the crank angle position at the time when the heat generation rate turns from rising to lowering is calculated as the maximum heat generation rate. Calculated as time dQpeakA.

  Then, it moves to step ST4 and calculates the actual first half combustion period. The calculation of the first half combustion period is performed by subtracting the crank angle position of the ignition timing FA from the crank angle position of the maximum heat release rate timing dQpeakA.

In step ST5, the reference first half combustion period is calculated. The calculation of the reference first half combustion period is performed using the equation (1). That is, the maximum heat generation rate in-cylinder volume V _@dQpeak , which is the in-cylinder volume at the maximum heat generation rate dQpeakA calculated based on the accumulated in-cylinder combustion pressure information, and the engine speed Ne, By substituting into the equation (1), the reference first half combustion period is calculated. At this time, the in-cylinder volume V _@dQpeak at the maximum heat generation rate is geometrically determined by the crank angle position (piston position) of the maximum heat generation rate dQpeakA.

  After the actual first half combustion period and the reference first half combustion period are calculated in this way, the process proceeds to step ST6, and whether or not the value obtained by subtracting the reference first half combustion period from the actual first half combustion period is equal to or less than a predetermined value A. judge. That is, it is determined whether or not the deviation of the actual first half combustion period to the positive side with respect to the reference first half combustion period is a predetermined value or less. The predetermined value A can be set to an arbitrary value, and is set in advance based on experiments and simulations.

  When the value obtained by subtracting the reference first half combustion period from the actual first half combustion period is equal to or less than the predetermined value A (when the deviation of the actual first half combustion period to the positive side with respect to the reference first half combustion period is small), YES determination is made in step ST6. And return as it is. That is, the process returns with no correction of the ignition timing required.

  On the other hand, if the value obtained by subtracting the reference first half combustion period from the actual first half combustion period exceeds the predetermined value A, and if NO is determined in step ST6, the process proceeds to step ST7, and the reference first half combustion period is changed from the actual first half combustion period. It is determined whether or not the subtracted value is less than a predetermined value B (the failure determination value). The predetermined value B is set as a value larger than the predetermined value A. That is, in step ST7, it is determined whether or not the deviation of the actual first half combustion period from the reference first half combustion period to the positive side is greater than the predetermined value A and less than the predetermined value B. The predetermined value B can be set to an arbitrary value and is set in advance based on experiments and simulations. As an example, the predetermined value A is set to 3 ° CA in terms of a crank angle, and the predetermined value B is set to 10 ° CA in terms of a crank angle. These values are not limited to this.

  When the value obtained by subtracting the reference first half combustion period from the actual first half combustion period is less than the predetermined value B (the deviation of the actual first half combustion period from the reference first half combustion period to the positive side is greater than the predetermined value A and less than the predetermined value B) If there is, the determination at step ST7 is YES and the process proceeds to step ST8.

  In this step ST8, the maximum heat generation rate dQpeakA for obtaining the optimum torque is mapped based on the value obtained by subtracting the reference first half combustion period from the actual first half combustion period (deviation between the actual first half combustion period and the reference first half combustion period). Extracted from This map is created in advance by experiments and simulations and stored in the ECU 100. That is, the relationship between the value obtained by subtracting the reference first half combustion period from the actual first half combustion period and the maximum heat generation rate dQpeakA for obtaining the optimum torque is mapped for each engine speed and stored in the ECU 100. The maximum heat generation rate dQpeakA for obtaining the optimum torque is extracted from the map. Specifically, the larger the value obtained by subtracting the reference first half combustion period from the actual first half combustion period, that is, the longer the actual first half combustion period relative to the reference first half combustion period, the higher the heat release rate maximum timing dQpeakA to the advance side. Map values to be transferred are extracted.

  In step ST9, the ignition timing is corrected so as to obtain the maximum heat release rate timing dQpeakA extracted in step ST8. That is, the more the maximum heat release rate timing dQpeakA extracted from the map is on the advance side (the larger the value obtained by subtracting the reference first half combustion period from the actual first half combustion period), the more the ignition timing shifts to the advance side. The ignition timing is corrected so as to increase the amount. In this case, the ignition timing before correction is the ignition timing set in the previous routine. Alternatively, it is an ignition timing set by a known technique (for example, an ignition timing set by performing retardation correction when knocking is detected).

  The ignition timing corrected in this way is used as the ignition timing in the next combustion stroke in the same cylinder. Moreover, you may utilize as an ignition timing in the combustion stroke of the cylinder which reaches a combustion stroke next.

  On the other hand, if the value obtained by subtracting the reference first half combustion period from the actual first half combustion period is equal to or greater than the predetermined value B, and if NO is determined in step ST7, the process proceeds to step ST10, and failure determination is performed. That is, the failure determination is performed without correcting the ignition timing, assuming that a failure has occurred in the engine 1. This failure includes a failure that affects the turbulence in the cylinder. For example, when deposits are attached to the intake valve 13 or the exhaust valve 14 (deposits are attached to the valve face), the gas tightness in the cylinder cannot be ensured in the combustion stroke, and gas escapes from the cylinder. In addition, there may be a case where good combustion cannot be performed or misfire occurs due to a reduction in the capacity of the spark plug 3.

  When the failure determination is made in this way, the MIL (warning lamp) on the meter panel in the passenger compartment is turned on to urge the driver to warn and abnormality information is written in the diagnosis provided in the ECU 100. become.

As described above, in the present embodiment, the first half combustion period is used when performing ignition timing correction control. It has been found as a new finding that the first half combustion period is not affected by the operating conditions of engine load factor, EGR rate, air-fuel ratio and oil water temperature. Then, assuming that the reference first half combustion period does not depend on any of the engine load factor, EGR rate, air-fuel ratio, and oil / water temperature, the maximum heat _release rate in-cylinder volume V _@dQpeak and engine speed Ne (more specifically, Specifically, it is calculated based on an exponential function of the engine speed Ne with the value β corresponding to the tumble ratio as an index. Then, the ignition timing correction control is performed using this first reference combustion period. For this reason, it is possible to appropriately correct the ignition timing without being affected by operating conditions such as load factor, EGR rate, air-fuel ratio, and oil water temperature, and by aging deterioration of a sensor that detects these operating conditions. In other words, by correcting the ignition timing so that the actual first half combustion period approaches the reference first half combustion period, it is possible to obtain an appropriate ignition timing adapted to the current hardware configuration change (aging).

  Further, in this embodiment, if the ignition timing FA and the maximum heat generation rate dQpeakA are obtained without creating the entire heat generation rate waveform, the reference first half combustion period and the actual first half combustion period can be calculated. Therefore, it is possible to optimize the ignition timing. For this reason, the ignition timing correction control can be simplified.

  Furthermore, in the present embodiment, when the difference between the reference first half combustion period and the actual first half combustion period is large, some kind of failure has occurred in the engine 1, and even if the ignition timing is corrected, proper combustion cannot be obtained. Therefore, the failure determination is performed. As a result, useless ignition timing correction control is not executed.

-Other embodiments-
In the embodiment described above, the case where the present invention is applied to a gasoline engine for automobiles has been described. The present invention is not limited to this, and can also be applied to spark ignition engines other than those for automobiles. Moreover, it is not specifically limited to a gasoline engine, For example, it is applicable also to a gas engine.

  In the above-described embodiment, the in-cylinder volume is cited as the state quantity of the in-cylinder gas at the time when the heat generation rate is the maximum. However, in other state quantities that define the turbulence in the cylinder (which affects the turbulence in the cylinder). There may be.

  In the above embodiment, when the value obtained by subtracting the reference first half combustion period from the actual first half combustion period is equal to or less than the predetermined value A, the ignition timing is not corrected. The present invention is not limited to this, and when the value obtained by subtracting the reference first half combustion period from the actual first half combustion period is a negative value (when the actual first half combustion period is shorter than the reference first half combustion period), the value is set to that value. Accordingly, the ignition timing may be corrected to the retard side.

  In the above embodiment, the reference first half combustion period is calculated as not depending on any of the engine load factor, EGR rate, air-fuel ratio, and oil water temperature. However, it depends on at least one of these operating conditions. You may make it calculate as what does not exist.

Moreover, in the said embodiment, the reference | standard first half combustion period was calculated using Formula (1). The present invention is not limited to this, and a map for extracting the reference first half combustion period from the maximum heat generation rate in-cylinder volume V _@dQpeak and the engine speed Ne is stored in the ECU 100, and the reference first half combustion period is determined from this map. You may make it extract.

  According to the present invention, since it is possible to optimize the ignition timing in a spark ignition type internal combustion engine, the invention can be applied to an internal combustion engine for automobiles, for example.

1 engine (internal combustion engine)
3 Spark plugs
39 In-cylinder pressure sensor 100 ECU
FA Mixture ignition timing a First half combustion period dQpeakA Maximum heat generation rate V _@dQpeak Maximum heat generation rate cylinder volume Ne ^β Correction factor based on engine speed V _@dQpeak ^α Maximum heat generation rate Based on maximum cylinder volume Correction factor

Claims (7)

In the control device for the spark ignition internal combustion engine,
The period from the ignition timing of the air-fuel mixture to the maximum heat generation rate that maximizes the heat generation rate is defined as the first half combustion period,
The reference value of the first half combustion period is used as the first reference combustion period, and the sensed actual first half combustion period is obtained as the first half combustion period.
A control apparatus for an internal combustion engine, wherein the ignition timing of a spark plug is corrected so as to reduce a difference between the reference first half combustion period and the actual first half combustion period. The control apparatus for an internal combustion engine according to claim 1,
The control apparatus for an internal combustion engine, characterized in that the reference first half combustion period is calculated based on a state quantity of in-cylinder gas at a heat release rate maximum timing. The control apparatus for an internal combustion engine according to claim 2,
The control device for an internal combustion engine, wherein the in-cylinder gas state quantity is an in-cylinder volume. The control device for an internal combustion engine according to claim 2 or 3,
The control apparatus for an internal combustion engine, wherein the reference first combustion period is calculated by multiplying a correction coefficient based on an engine rotational speed. The control apparatus for an internal combustion engine according to claim 4,
The control device for an internal combustion engine, wherein the correction coefficient based on the engine rotational speed is an exponential function of the engine rotational speed with a value corresponding to the tumble ratio as an index. In the control device for an internal combustion engine according to any one of claims 1 to 5,
An internal combustion engine characterized by determining that a failure has occurred when the actual first half combustion period is longer than the reference first half combustion period and the difference between them is equal to or greater than a preset failure determination value. Control device. In the control device for an internal combustion engine according to any one of claims 2 to 5,
The first half combustion period is a period from the ignition timing obtained from the output signal of the in-cylinder pressure sensor that senses the in-cylinder pressure to the maximum heat generation rate,
The control apparatus for an internal combustion engine, characterized in that the reference first half combustion period is a period calculated based on a state quantity of in-cylinder gas at the maximum heat release rate obtained from an output signal of the in-cylinder pressure sensor. .

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