JP6020690B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine suitable as a device for controlling an internal combustion engine having an in-cylinder pressure sensor.

  Patent Document 1 discloses a combustion control device for an internal combustion engine including an in-cylinder pressure sensor. This conventional combustion control device uses the in-cylinder pressure sensor and the crank angle sensor to calculate the combustion mass ratio data in synchronization with the crank angle, and based on this data, calculates the actual combustion start point and the combustion centroid point. calculate. In addition, when the difference obtained by subtracting the actual combustion start point from the combustion center of gravity exceeds the upper limit value, the combustion control device determines that the combustion has deteriorated and improves the combustion such as an increase in the fuel injection amount. It is going to give the treatment of. In Patent Document 1, as an example, an appropriate value between 10 and 30 percent is used as the actual combustion start point, which is the crank angle when combustion is actually started in the cylinder. As the combustion center of gravity, for example, an appropriate value between 40 and 60 percent is used as the combustion mass ratio.

  Patent Document 2 discloses a technique for estimating a heat generation rate in a cylinder using a Wiebe function. In this estimation method, in order to estimate the heat generation rate, the average in-cylinder pressure and the average in-cylinder temperature in a specific period, the volumetric efficiency of the intake air, the engine rotation speed, the fuel injection amount, the fuel injection pressure, and the EGR rate are operated. Used as a parameter.

JP 2008-069713 A JP 2011-106334 A

  The waveform of the measurement data of the combustion mass ratio varies depending on the combustion state (specifically, whether or not good combustion has been performed) or the environment (for example, temperature environment) surrounding the internal combustion engine. Therefore, if the actual measurement data of the combustion mass ratio can be properly analyzed on the actual machine, the change in the combustion state or the environment can be grasped, and the engine control as a countermeasure against the change can be appropriately performed.

  Here, the crank angle when the combustion mass ratio becomes a specific ratio is referred to as a “specific ratio combustion point”. The method described in Patent Document 1 is to grasp the combustion state by comparing the difference between measured values of two specific ratio combustion points, that is, the actual combustion start point and the combustion center of gravity point, with a determination value (upper limit value). However, the mode of change in the measured data of the combustion mass ratio varies depending on the cause of each change. For this reason, there are cases where the cause of the change in the waveform of the actual measurement data cannot be accurately specified only by using the actual measurement values of the two specific ratio combustion points as described above.

  Comparing the reference data with a larger number of measured data than the two specified ratio combustion points if the combustion mass ratio data that should be used as a reference when evaluating the measured data of the combustion mass ratio on the actual machine is provided. By doing so, it is considered that changes in combustion state or environment can be grasped more accurately. Here, according to the method described in Patent Document 2, the heat generation rate can be estimated using the Wiebe function. Combustion mass ratio data can be generated from the heat release rate data estimated in this way, and techniques for this are also known.

  Therefore, it is conceivable to use the combustion mass ratio data generated by the above method as reference data. However, as described above, the operation using the Wiebe function requires many operating condition parameters. For this reason, this method has a high calculation load. In addition, it is difficult to formulate combustion itself, and it is also difficult to extract all factors that affect combustion. For this reason, it can be said that this method is difficult to ensure the accuracy of the generated combustion mass ratio data. Therefore, this method is not suitable for mounting on an internal combustion engine.

  The present invention has been made to solve the above-described problems. In an internal combustion engine in which engine control based on a specific ratio combustion point is performed, reference data for a combustion mass ratio is generated easily and accurately, and the reference An object of the present invention is to provide a control device for an internal combustion engine capable of performing engine control as a countermeasure in accordance with a mode of change in measured data of combustion mass ratio based on data.

  An internal combustion engine control apparatus according to the present invention is an internal combustion engine control apparatus that controls an internal combustion engine that includes one or more actuators used for engine control, and includes an in-cylinder pressure sensor, a crank angle sensor, and a combustion mass ratio. A calculation unit, a combustion point calculation unit, a first control unit, a second control unit, and a third control unit are provided. The in-cylinder pressure sensor detects the in-cylinder pressure. The crank angle sensor detects a crank angle. The combustion mass ratio calculation means calculates actual measurement data of the combustion mass ratio synchronized with the crank angle based on the in-cylinder pressure detected by the in-cylinder pressure sensor and the crank angle detected by the crank angle sensor. The combustion point calculation means calculates an actual measurement value of the specific ratio combustion point that is a crank angle when the combustion mass ratio becomes the specific ratio based on the actual measurement data of the combustion mass ratio. The first control means is based on the first specific ratio combustion point which is a crank angle when the combustion mass ratio becomes the first specific ratio or the first parameter defined based on the first specific ratio combustion point. A first engine control is performed to control any one or more of the one or more actuators such that the first specific ratio combustion point or the first parameter becomes a target value. The second control means is based on the second specific ratio combustion point which is a crank angle when the combustion mass ratio becomes the second specific ratio or the second parameter defined based on the second specific ratio combustion point. Second engine control is executed to control any one or more of the one or more actuators such that the second specific ratio combustion point or the second parameter becomes a target value. The third control means selects one or more of the one or more actuators based on the degree of correlation between the measured data of the combustion mass ratio and the reference data of the combustion mass ratio based on the operating conditions of the internal combustion engine. The third engine control to be controlled is executed. The reference data of the combustion mass ratio in the crank angle period from at least the 10% combustion point to the 90% combustion point in the combustion period is based on the first target value and the second target value. Generated by at least one of the insertions. The first target value is either the target value of the first specific ratio combustion point or the first specific ratio combustion point specified from the target value of the first parameter. The second target value is either the target value of the second specific ratio combustion point or the second specific ratio combustion point specified from the target value of the second parameter. When the first crank angle period, which is the crank angle period before the combustion period, is included in the reference data for the combustion mass ratio, the reference data for the combustion mass ratio in the first crank angle period has a combustion mass ratio of zero. Percent data. When the second crank angle period, which is a crank angle period after the combustion period, is included in the reference data of the combustion mass ratio, the reference data of the combustion mass ratio in the second crank angle period has a combustion mass ratio of 100. Percent data.

  The first specific ratio combustion point and the second specific ratio combustion point are preferably specific ratio combustion points within the crank angle period from a 10% combustion point to a 90% combustion point.

  The third engine control is engine warm-up control for raising the temperature of the internal combustion engine, and includes a combustion angle before a third specific ratio combustion point when the combustion mass ratio is a third specific ratio. Combustion in the latter period, which is a crank angle period including the combustion period after the third specified ratio combustion point, in which the degree of correlation between the measured data of the combustion mass ratio in the first period, which is the period, and the reference data is greater than or equal to the first determination value It may be executed when the degree of correlation between the mass ratio actual measurement data and the reference data is lower than the second determination value.

  The third engine control is misfire suppression control that suppresses the occurrence of misfire, and is a crank angle period that includes a combustion period before the third specific ratio combustion point when the combustion mass ratio is the third specific ratio. Combustion mass in the latter period, which is a crank angle period including a combustion period after the third specified ratio combustion point, and the degree of correlation between the actual measurement data and the reference data of the combustion mass ratio in a certain earlier period is lower than the third determination value It may be executed when the degree of correlation between the ratio measurement data and the reference data is lower than the fourth determination value.

  The correlation index value indicating the degree of correlation is preferably calculated using a cross-correlation function.

  According to the present invention, the first engine control based on the first parameter defined based on the first specific rate combustion point or the first specific rate combustion point, and the second specific rate combustion point or the second specific rate combustion In the internal combustion engine in which the second engine control based on the second parameter defined based on the point is executed, the combustion mass ratio in the crank angle period from at least the 10% combustion point to the 90% combustion point in the combustion period Is generated by at least one of linear interpolation and linear extrapolation based on the first target value and the second target value. The first target value is either the target value of the first specific ratio combustion point or the first specific ratio combustion point specified from the target value of the first parameter, and the second target value is the second specific ratio combustion point Either the target value of the point or the second specific ratio combustion point specified from the target value of the second parameter. According to such a generation method, it is possible to easily and accurately generate the reference data of the combustion mass ratio while capturing the characteristics of the waveform of the combustion mass ratio data. According to the present invention, the third engine control based on the degree of correlation between the reference data generated in this way and the actual measurement data is executed. As a result, it becomes possible to perform engine control as a countermeasure in accordance with the mode of change in the actual measurement data of the combustion mass ratio based on the reference data.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a figure showing the ignition timing and the waveform of a combustion mass ratio. It is a block diagram for demonstrating the outline | summary of two types of feedback control using CA10 and CA50 which ECU performs. It is a figure showing the relationship between an air fuel ratio and SA-CA10. It is a figure for demonstrating the production method of the reference data of MFB in Embodiment 1 of this invention. It is the figure which represented typically an example of the waveform of the measurement data of MFB in which the deviation with respect to the waveform of a reference data produced because the cooling loss was excessive. It is the figure which represented typically an example of the waveform of the measurement data of MFB in which the deviation with respect to the waveform of a reference data produced a half misfire or the occurrence of misfire as a factor. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the example which evaluates the degree of correlation of the MFB data in three specific ratio combustion points, and determines the change of the measured data of MFB caused by excessive cooling loss.

Embodiment 1 FIG.
A first embodiment of the present invention will be described with reference to FIGS.

[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes a spark ignition type internal combustion engine 10. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  The intake port of the intake passage 16 is provided with an intake valve 20 that opens and closes the intake port, and the exhaust port of the exhaust passage 18 is provided with an exhaust valve 22 that opens and closes the exhaust port. The intake passage 16 is provided with an electronically controlled throttle valve 24. Each cylinder of the internal combustion engine 10 has a fuel injection valve 26 for directly injecting fuel into the combustion chamber 14 (inside the cylinder), and an ignition device 28 for igniting the air-fuel mixture (only the ignition plug is shown). , Each provided. Furthermore, an in-cylinder pressure sensor 30 for detecting the in-cylinder pressure is incorporated in each cylinder.

  Furthermore, the system of the present embodiment includes, as a control device for controlling the internal combustion engine 10, an ECU (Electronic Control Unit) 40, a drive circuit (not shown) for driving the following various actuators, and the following various sensors. I have. The ECU 40 includes an input / output interface, a memory, and an arithmetic processing unit (CPU). The input / output interface is provided to take in sensor signals from various sensors attached to the internal combustion engine 10 or a vehicle on which the internal combustion engine 10 is mounted, and to output operation signals to various actuators for controlling the internal combustion engine 10. Yes. The memory stores various control programs and maps for controlling the internal combustion engine 10. The CPU reads out and executes a control program or the like from the memory, and generates operation signals for various actuators based on the acquired sensor signals.

  In addition to the in-cylinder pressure sensor 30 described above, the ECU 40 receives signals from a crank angle sensor 42 disposed near the crankshaft (not shown) and an air flow meter 44 disposed near the inlet of the intake passage 16. Various sensors for acquiring the engine operating state such as are included.

  The actuator from which the ECU 40 outputs an operation signal includes various actuators for controlling the engine operation such as the throttle valve 24, the fuel injection valve 26, and the ignition device 28 described above. Further, the ECU 40 has a function of acquiring an output signal of the in-cylinder pressure sensor 30 by performing AD conversion in synchronization with the crank angle. Thereby, the in-cylinder pressure at an arbitrary crank angle timing can be detected within a range allowed by the AD conversion resolution. Further, the ECU 40 stores a map that defines the relationship between the crank angle and the in-cylinder volume, and can calculate the in-cylinder volume corresponding to the crank angle with reference to such a map.

ただし、上記（１）式において、Ｖは筒内容積、κは筒内ガスの比熱比である。また、上記（３）式において、θ_ｍｉｎは燃焼開始点であり、θ_ｍａｘは燃焼終了点である。 [Combustion control in Embodiment 1]
(Calculation of MFB actual measurement data using an in-cylinder pressure sensor)
FIG. 2 is a diagram showing the ignition timing and the combustion mass ratio waveform. According to the system of the present embodiment including the in-cylinder pressure sensor 30 and the crank angle sensor 42, in each cycle of the internal combustion engine 10, the measured data of the in-cylinder pressure P in synchronization with the crank angle (more specifically, the predetermined crank angle A set of in-cylinder pressures P calculated as each value) can be acquired. Using the obtained measured data of the in-cylinder pressure P and the first law of thermodynamics, the amount of heat generation Q in the cylinder at an arbitrary crank angle θ is calculated according to the following equations (1) and (2). Can do. Then, using the actually measured data of the heat generation amount Q in the cylinder (a set of heat generation amounts Q calculated as a value for each predetermined crank angle), the combustion mass ratio at an arbitrary crank angle θ (hereinafter, “ Can be calculated according to the following equation (3). Then, by executing the MFB calculation process for each predetermined crank angle, it is possible to calculate MFB actual measurement data (a set of actual MFB) in synchronization with the crank angle. The measured data of MFB is calculated in the combustion period and a predetermined crank angle period before and after the combustion period (here, as an example, the crank angle period from the closing timing IVC of the intake valve 20 to the opening timing EVO of the exhaust valve 22).

In the above formula (1), V is the in-cylinder volume, and κ is the specific heat ratio of the in-cylinder gas. In the above equation (3), θ _min is the combustion start point, and θ _max is the combustion end point.

According to the measured data of MFB calculated by the above method, the crank angle (hereinafter referred to as “specific ratio combustion point” and indicated by “CAα”) when MFB becomes a specific ratio α (%) is shown. Can be acquired. More specifically, when the specific ratio combustion point CAα is acquired, the value of the specific ratio α may be successfully included in the MFB actual measurement data, but this value is not included. The specific ratio combustion point CAα can be calculated by interpolating based on the measured data located on both sides of the specific ratio α. Hereinafter, in the present specification, CAα obtained by using MFB actual measurement data is referred to as “actual measurement CAα”. Here, a typical specific ratio combustion point CAα will be described with reference to FIG. In-cylinder combustion starts with a delay in ignition after the air-fuel mixture is ignited at the ignition timing SA. The starting point of this combustion (θ _min in the above equation (3)), that is, the crank angle when the MFB rises is referred to as CA0. The crank angle period (CA0-CA10) from CA0 to MFB when the MFB is 10% corresponds to the initial combustion period, and the crank angle period from CA10 to the crank angle CA90 when the MFB is 90% ( CA10-CA90) corresponds to the main combustion period. In the present embodiment, the crank angle CA50 when the MFB is 50% is used as the combustion gravity center point. The crank angle CA100 when the MFB is 100% corresponds to the combustion end point (θ _max in the above equation (3)) at which the heat generation amount Q reaches the maximum value. The combustion period is specified as a crank angle period from CA0 to CA100.

(Engine control using CAα)
FIG. 3 is a block diagram for explaining an outline of two types of feedback control using CA10 and CA50 executed by the ECU 40. The engine control performed by the ECU 40 includes control using a specific ratio combustion point CAα. Here, as an example of engine control using the specific ratio combustion point CAα, two types of feedback control using CA10 and CA50 will be described. In the present embodiment, these controls are executed during a lean burn operation performed at an air / fuel ratio larger than the stoichiometric air / fuel ratio (fuel lean).

1. Feedback control of fuel injection amount using SA-CA10 In this feedback control, CA10, which is a 10% combustion point, is not used as a direct target value, but is used as follows. That is, in this specification, the crank angle period from the ignition timing SA to CA10 is referred to as “SA-CA10”. More specifically, SA-CA10 that is a difference obtained by subtracting the ignition timing SA from the measured CA10 is referred to as “measured SA-CA10”. In the present embodiment, the ignition timing SA used for the calculation of the actual measurement SA-CA10 is the final target ignition timing (the ignition timing of the next cycle) after being adjusted by feedback control of the ignition timing using the CA50 described later. Is used).

  FIG. 4 is a diagram showing the relationship between the air-fuel ratio and SA-CA10. This relationship is in the lean air-fuel ratio region on the lean side with respect to the stoichiometric air-fuel ratio, and has the same operating conditions (more specifically, engine operating conditions in which the intake air amount and the engine speed are the same). It is a thing. SA-CA10 is a parameter representing ignition delay, and there is a certain correlation between SA-CA10 and the air-fuel ratio. More specifically, as shown in FIG. 4, in the lean air-fuel ratio region, there is a relationship that SA-CA10 increases as the air-fuel ratio becomes leaner. Therefore, the target SA-CA10 corresponding to the desired target air-fuel ratio can be obtained by using this relationship. In addition, in the present embodiment, during the lean burn operation, feedback control for adjusting the fuel injection amount so that the measured SA-CA10 approaches the target SA-CA10 (hereinafter simply referred to as “SA-CA10 feedback control”). I am trying to do it.

  As shown in FIG. 3, in SA-CA10 feedback control, target SA-CA10 is set according to engine operating conditions (more specifically, target air-fuel ratio, engine speed, and intake air amount). The measured SA-CA10 is calculated for each cycle in each cylinder. In addition, in SA-CA10 feedback control, PI control is used as an example in order to adjust the fuel injection amount so that there is no difference between the target SA-CA10 and the measured SA-CA10. In this PI control, using the difference between the target SA-CA10 and the measured SA-CA10 and a predetermined PI gain (proportional term gain and integral term gain), fuel injection according to the difference and the magnitude of the integrated value is performed. A correction amount of the amount is calculated. The correction amount calculated for each cylinder is reflected in the basic fuel injection amount of the target cylinder. As a result, the fuel injection amount supplied to the next cycle in the cylinder is adjusted (corrected) by the SA-CA10 feedback control.

  According to the SA-CA10 feedback control, in the cylinder in which the measured SA-CA10 smaller than the target SA-CA10 is obtained, the fuel injection used in the next cycle in order to make the measured SA-CA10 larger by leaning the air-fuel ratio. Correction is performed to reduce the amount. On the contrary, in the cylinder in which the measured SA-CA10 larger than the target SA-CA10 is obtained, the fuel injection amount used in the next cycle is increased in order to reduce the measured SA-CA10 by enriching the air-fuel ratio. Correction is performed.

  According to the SA-CA10 feedback control, the air-fuel ratio can be controlled to a target value (target air-fuel ratio) during lean burn operation by using a parameter highly correlated with the air-fuel ratio, SA-CA10. Become. For this reason, the air-fuel ratio can be controlled in the vicinity of the lean limit by setting the target SA-CA10 to a value corresponding to the air-fuel ratio in the vicinity of the lean combustion limit. Thereby, low fuel consumption and low NOx emission can be realized.

2. Ignition Timing Feedback Control Using CA50 The optimal ignition timing (so-called MBT (Minimum Advance for the Best Torque) ignition timing) changes according to the air-fuel ratio. For this reason, when the air-fuel ratio changes by the SA-CA10 feedback control, the MBT ignition timing changes. On the other hand, the CA50 when the MBT ignition timing is obtained does not substantially change with respect to the air-fuel ratio in the lean air-fuel ratio region. Accordingly, the lean burn operation is not affected by the above-described change in the air-fuel ratio by correcting the ignition timing so that the difference between the measured CA50 and the target CA50 is eliminated by setting the CA50 when the MBT ignition timing is obtained as the target CA50. It can be said that the ignition timing at that time can be adjusted to the MBT ignition timing. Therefore, in the present embodiment, during the lean burn operation, SA-CA10 feedback control and feedback control for adjusting the ignition timing so that the measured CA50 approaches the target CA50 (hereinafter simply referred to as “CA50 feedback control”). To do.

  As shown in FIG. 3, in the CA50 feedback control, the target CA50 for setting the ignition timing to the MBT ignition timing depends on the engine operating conditions (more specifically, the target air-fuel ratio, engine rotational speed, and intake air amount). It is set with the value. Note that the CA50 feedback control here is not necessarily limited to control to obtain the MBT ignition timing. That is, the CA50 feedback control can also be used when a certain ignition timing other than the MBT ignition timing is set as a target value as in so-called retarded combustion. In such a case, for example, the target CA50 may be set so as to change according to the target ignition efficiency (an index value indicating the degree of deviation of the target value from the MBT ignition timing) in addition to the engine operating conditions. .

  The measured CA50 is calculated for each cycle in each cylinder. In addition, in the CA50 feedback control, PI control is used as an example in order to correct the ignition timing with respect to the basic ignition timing so that there is no difference between the target CA50 and the measured CA50. The basic ignition timing is stored in advance in the ECU 40 as a value corresponding to the engine operating conditions (mainly, the intake air amount and the engine speed). In this PI control, the difference between the target CA50 and the measured CA50 and a predetermined PI gain (proportional term gain and integral term gain) are used, and the ignition timing is corrected according to the difference and the integrated value of the difference. A quantity is calculated. The correction amount calculated for each cylinder is reflected in the basic ignition timing of the target cylinder. As a result, the ignition timing (target ignition timing) used in the next cycle in the cylinder is adjusted (corrected) by the CA50 feedback control.

  The value of the air-fuel ratio at the lean combustion limit changes under the influence of the ignition timing. More specifically, for example, when the ignition timing is retarded with respect to the MBT ignition timing, the value of the air-fuel ratio at the lean combustion limit is on the rich side as compared to when controlled at the MBT ignition timing. Moving. When SA-CA10 feedback control is executed without considering the above-described influence of the ignition timing on the value of the air-fuel ratio at the lean combustion limit, when the air-fuel ratio fluctuates to a lean side value by SA-CA10 feedback control, There is concern about misfires. Therefore, in this embodiment, as a preferred embodiment of the SA-CA10 feedback control, the combustion cycle in which the CA50 feedback control is sufficiently converged (that is, the ignition timing is sufficiently close to the MBT ignition timing). Only SA-CA10 feedback control is performed. And in order to ensure suitably the implementation frequency of the said SA-CA10 feedback control when performing SA-CA10 feedback control in such a mode, in this embodiment, the response speed of CA50 feedback control is SA-CA10 feedback control. I try to increase the response speed. Such setting of the response speed can be realized, for example, by making the PI gain used in the CA50 feedback control larger than the PI gain used in the SA-CA10 feedback control.

  Note that SA-CA10 feedback control and CA50 feedback control are executed for each cylinder in the manner described above. The internal combustion engine 10 of the present embodiment includes the in-cylinder pressure sensor 30 in each cylinder. For example, if the internal combustion engine has a configuration in which only one representative cylinder includes the in-cylinder pressure sensor, a single in-cylinder pressure is provided. Feedback control of the fuel injection amount and ignition timing of all the cylinders may be performed using the measured SA-CA10 and the measured CA50 based on the in-cylinder pressure obtained from the sensor.

[Evaluation of measured MFB data using reference data and countermeasures according to the evaluation results]
(Necessity for evaluation of measured data of MFB)
The waveform of the measured data of MFB varies depending on the combustion state (specifically, whether or not good combustion has been performed) or the environment (for example, temperature environment) surrounding the internal combustion engine 10. Therefore, if the actual measurement data of MFB can be properly analyzed on the actual machine, it is possible to grasp the change in the combustion state or the environment, and it is possible to appropriately perform the engine control as a countermeasure against the change. If the reference data to be used as a reference in the analysis is provided, it can be said that the change can be grasped more appropriately. That is, if the combustion is good (normal), the MFB actual measurement data has a high correlation with the reference data. However, when there is a change in the combustion state or the environment, the actual measurement data deviates from the reference data. Therefore, if the degree of correlation between the actual measurement data and the reference data can be evaluated, a change in the combustion state or the like can be grasped.

  Therefore, in the present embodiment, in order to accurately perform the analysis of the actual measurement data as described above on the actual machine, the MFB reference data to be used as a reference is generated on the actual machine. In addition, it is desirable that the reference data used for the evaluation of the MFB actual measurement data has a small calculation load and can be generated easily and accurately. In addition, the waveform of the MFB actual measurement data changes according to the engine operating conditions (mainly, the intake air amount, the engine speed, and the air-fuel ratio) even under a good combustion state. Therefore, the reference data needs to be able to reflect the change in the MFB waveform according to the engine operating conditions.

(Overview of MFB standard data creation method)
FIG. 5 is a diagram for explaining a method for creating MFB reference data according to Embodiment 1 of the present invention. FIG. 5 represents an xy plane (hereinafter referred to as “MFB-θ plane”) in which the crank angle θ is an x-coordinate value and the combustion mass ratio MFB is a y-coordinate value.

  As already described with reference to FIG. 3, the target CA50, which is the target value of the CA50 feedback control, is determined as a value corresponding to the engine operating conditions (target air-fuel ratio, engine rotation speed, and intake air amount). Similarly, the target SA-CA10 that is the target value of the SA-CA10 feedback control is also determined as a value according to the engine operating conditions. The indicated value (target ignition timing) of the ignition timing SA in each combustion cycle is reflected in the CA50 feedback control based on the basic ignition timing according to the engine operating conditions in the lean burn operation in which the CA50 feedback control is executed. It is determined as the value after. CA10 can be calculated from the target SA-CA10 thus calculated and the target ignition timing. However, since the CA 10 itself is not a direct control target value of the SA-CA 10 feedback control, the CA 10 is hereinafter referred to as “specific CA 10”. Note that the target SA-CA10 and the target CA50 are set assuming that the internal combustion engine 10 is used in a standard temperature environment (for example, 20 ° C.).

  CA50 is the crank angle when the MFB is 50%, and CA10 is the crank angle when the MFB is 10%. Therefore, if the value of the target CA50 and the value of the specific CA10 are determined, the point A and the point B where the target CA50 and the specific CA10 are located on the MFB-θ plane shown in FIG. In order to evaluate the degree of correlation of the MFB actual measurement data, the reference data must have data that is paired with each data of the actual measurement data that is acquired for each predetermined crank angle. is there.

  For this purpose, in the present embodiment, linear interpolation and linear extrapolation are performed based on the two points A and B, and the MFB reference within the crank angle period from the combustion start point CA0 to the combustion end point CA100 is used. It was decided to generate data. The reference data for the crank angle period before CA0 is generated as data with an MFB of 0%, and the reference data for the crank angle period after CA100 is generated as data with an MFB of 100%. It was made to be. In this embodiment, the MFB reference data is generated in this way. The waveform through which the generated reference data passes is a waveform as shown by a broken line in FIG.

ただし、上記（４）式において、θはクランク角度である。τ_θは、相関の度合いの評価対象の２つの波形（本実施形態では、ＭＦＢの基準データと実測データの波形）についてのクランク角軸方向における相対的なずれを表す変数である。関数ｆ_ａ〜ｂ（θ）は、所定クランク角度毎に存在する離散値の集合であるＭＦＢの基準データに相当する。関数ｇ_ａ〜ｂ（τ_θ−θ）は、同様に離散値の集合であるＭＦＢの実測データに相当する。より具体的には、（ａ〜ｂ）は、これらの関数ｆ_ａ〜ｂ（θ）およびｇ_ａ〜ｂ（τ_θ−θ）がそれぞれ定義されたクランク角軸上の区間を示している。当該区間（ａ〜ｂ）は、ＭＦＢの基準データおよび実測データの中で相互相関係数Ｒの算出の対象となる（換言すると、相関の度合いの評価対象となる）基準データおよび実測データが存在するクランク角期間（以下、「計算期間α」と称する）に相当する。本実施形態で用いられる計算期間αの具体例である前期α１および後期α２については後述する。なお、筒内圧の実測データに基づいて算出したＭＦＢの実測データの中に、エンジン制御に用いる特定割合燃焼点ＣＡα（本実施形態では、ＣＡ１０とＣＡ５０）の実測値が含まれていない場合には、当該実測値を近隣の実測データの内挿によって求めるとともに、これと対となる基準データ側の値も求めたうえで、相関の度合いの評価対象にこれらの一対の値を含めてもよい。 (Evaluation of degree of correlation of MFB data using cross-correlation function)
In this embodiment, in order to evaluate the measured data of MFB, “correlation index value I _R ” indicating the degree of correlation between the MFB reference data and the measured data is obtained. Preferred Method of calculation of the correlation index value I _R, in the present embodiment, the cross-correlation function is used. Calculation of the cross-correlation coefficient R using the cross-correlation function is performed using the following equation (4).

However, in the above equation (4), θ is a crank angle. τ _θ is a variable representing a relative shift in the crank angle axis direction with respect to two waveforms (in this embodiment, MFB reference data and measured data waveforms) to be evaluated for the degree of correlation. The function f a- _b (θ) corresponds to MFB reference data, which is a set of discrete values existing at each predetermined crank angle. Similarly, the functions g a to _b (τ _θ −θ) correspond to measured data of MFB that is a set of discrete values. More specifically, (ab) shows a section on the crank angle axis in which these functions f _ab (θ) and g _ab (τ _θ −θ) are defined. The section (a to b) includes reference data and actual measurement data that are targets of calculation of the cross-correlation coefficient R (in other words, target of evaluation of the degree of correlation) in the MFB reference data and actual measurement data. Corresponds to a crank angle period (hereinafter referred to as “calculation period α”). The first period α1 and the second period α2, which are specific examples of the calculation period α used in the present embodiment, will be described later. In the case where the actual measurement value of the specific ratio combustion point CAα (CA10 and CA50 in this embodiment) used for engine control is not included in the actual measurement data of MFB calculated based on the actual measurement data of in-cylinder pressure. In addition to obtaining the actual measurement values by interpolating neighboring actual measurement data, and obtaining the values on the reference data side paired therewith, the pair of values may be included in the evaluation target of the degree of correlation.

Performing the convolution operation using the equation (4) means that the entire waveform of the measured data of MFB within the calculation period (α) is maintained while the waveform of the reference data is fixed by changing the variable τ _θ within a predetermined range. This is accompanied by an operation of continuously calculating the cross-correlation coefficient R while gradually moving in the crank angle direction (the horizontal axis direction of the waveform of the MFB reference data shown in FIG. 5). The maximum value R _max of the cross-correlation coefficient R in the process of this calculation corresponds to the cross-correlation coefficient R when the two waveforms are closest to each other as a whole. Can be expressed as: Correlation index value I _R used in this embodiment, the maximum value R _max not itself, is a value obtained by performing the predetermined normalization processing with respect to the cross-correlation coefficient R. The normalization process here is a process defined such that R _max indicates 1 when two waveforms (waveforms of reference data and measured data) completely match, and such a process itself is publicly known. Therefore, detailed description thereof is omitted here.

Correlation index value I _R calculated by the processing described above, 1 if the two waveforms coincide completely (maximum), and the degree of correlation of the two waveforms approaches zero as low. In the case where the correlation index value I _R indicates a negative value, the two waveforms there is a negative correlation, if the correlation index value I _R, which becomes the two waveforms are completely reversed -1 Indicates. Therefore, based on the correlation index value I _R obtained as described above, it is possible to grasp the degree of correlation between the reference data and the measured data of MFB. Note that the use of the cross-correlation function in the present embodiment is to compare the actually measured data with reference data (that is, ideal MFB data) for the same type of data called MFB data. Therefore, it can be said that the cross-correlation function used here is substantially an autocorrelation function.

In the present embodiment, as described above, although we decided to use the maximum value of the cross-correlation coefficient R value obtained by normalizing the correlation index value I _R, "correlation index value" in the present invention, predetermined The maximum value R _max of the cross-correlation coefficient R without the normalization process may be used. However, the correlation index value (that is, the maximum value R _max ) without the normalization process does not simply increase as the degree of correlation increases, but instead of the magnitude of the maximum value R _max and the level of correlation. There is the following relationship between them. That is, as the maximum value R _max increases, the degree of correlation increases, and when the maximum value R _max reaches a certain value X, the degree of correlation becomes the highest (that is, the two waveforms match completely). ). When the maximum value R _max increases from the value X, the degree of correlation decreases as the maximum value R _max increases. Therefore, when the maximum value R _max itself without normalization processing is used as the “correlation index value”, whether or not the “correlation index value” is less than the “determination value” is determined by the following process. It can be carried out. That is, when the maximum value R _max is out of the predetermined range centered on the value X, it can be determined that “the correlation index value is less than the determination value”, and conversely, the maximum value R _max is the predetermined value. When it falls within the range, it can be determined that “correlation index value is greater than or equal to determination value”.

(Engine control as a countermeasure according to the evaluation result of MFB data)
In the present embodiment, the reference data generated by the above method is used to evaluate the degree of correlation between the measured MFB data and the reference data for each combustion cycle in each cylinder. Hereinafter, with reference to FIG. 6 and FIG. 7, an aspect of change in actually measured data shown as an example in the present embodiment will be described.

  FIG. 6 is a diagram schematically illustrating an example of a waveform of measured MFB data in which a deviation from the waveform of the reference data occurs due to excessive cooling loss. When the internal combustion engine 10 is operated at an extremely low temperature, such as immediately after starting in a cold region, the cooling loss is excessive compared to when operating in a standard temperature environment. As shown in the example shown in FIG. 6, this influence appears remarkably with actually measured data in the second half period of combustion (CA50-CA100). More specifically, the above-mentioned influence may appear in the first half period of combustion (CA0-CA50). However, the impact is more pronounced in the second half than in the first half. For this reason, the degree of correlation of the actual measurement data with respect to the reference data is lower in the second half period than in the first half period. Further, how the above-described influence appears in the second half period is not necessarily after the data around the measured CA50 as in the example shown in FIG. 6, but after a little later data (for example, data around the measured CA80). Sometimes.

  FIG. 7 is a diagram schematically illustrating an example of a waveform of measured MFB data in which a deviation from the waveform of the reference data has occurred due to the occurrence of a semi-misfire or misfire. Here, the semi-misfire refers to combustion in which flame propagation stops and misfire occurs while combustion heat is generated, and a flame is not sufficiently formed. Further, complete misfire (hereinafter simply referred to as “misfire”) means that the air-fuel mixture misfires without igniting. As shown in FIG. 7, the waveform of the measured MFB data in the case of a semi-misfire has a delayed start of combustion and the rise of the MFB data as compared to the waveform of the reference data in a good combustion state to be used as a reference. It will be gentler. On the other hand, when misfire occurs, heat generation does not occur, so the measured data of MFB changes at a value of 0% MFB. Actually, even if misfire occurs, the influence of noise superimposed on the output of the in-cylinder pressure sensor 30 may appear in the waveform of the measured data of the MFB. In such a case, the waveform of the measured data of the MFB is , MFB fluctuates around 0%. As described above, the actual measurement data in the case where a semi-misfire or misfire has occurred has a low correlation with the reference data in the entire combustion period of the reference data.

  As can be seen from the comparison results between the measured MFB data and the reference data shown in FIGS. 6 and 7, just by evaluating the degree of correlation of the MFB data in the second half of the combustion period, the cause of the divergence of the measured data is the cooling loss. It can be said that it is difficult to accurately discriminate whether it is due to a half or misfire.

Therefore, in the present embodiment, in order to evaluate the degree of correlation of the MFB data in the first half period of combustion, the correlation index value I _R1 is calculated for the first half period α1, which is a calculation period including the first half period and its surroundings. It was. Furthermore, it was decided to calculate the correlation index value I _R2 to assess the degree of correlation MFB data during the second half period of combustion, the late α2 is the second half period and the calculation period including the periphery thereof as a target.

In addition, in the present embodiment, when the correlation index value I _R2 related to the latter α2 is less than the predetermined determination value I _Rth , the cooling is performed when the correlation index value I _R1 related to the first α1 is equal to or _larger than the determination value I _Rth. It was determined that the actual measurement data of MFB had changed with respect to the reference data due to the excessive loss. In this case, predetermined engine warm-up control for increasing the temperature of the internal combustion engine 10 is performed.

In the present embodiment, when the correlation index value I _R2 related to the late α2 is less than the determination value I _Rth and the correlation index value I _R1 related to the previous α1 is also less than the determination value _IRth , It was decided that the actual measurement data of MFB had changed with respect to the reference data due to misfire. In this case, predetermined misfire suppression control for suppressing the occurrence of misfire (including semi-misfire) is performed.

(Specific processing in Embodiment 1)
FIG. 8 is a flowchart showing a routine executed by ECU 40 in the first embodiment of the present invention. This routine is started at the timing when the opening timing of the exhaust valve 22 has elapsed in each cylinder during the lean burn operation, and is repeatedly executed for each combustion cycle.

  In the routine shown in FIG. 8, the ECU 40 first acquires the current engine operating conditions in step 100. The engine operating conditions here mainly correspond to the engine speed, the intake air amount, and the air-fuel ratio. The engine rotation speed is calculated using the crank angle sensor 42. The intake air amount is calculated using the air flow meter 44. The air-fuel ratio is an air-fuel ratio targeted during lean burn operation.

  Next, the ECU 40 proceeds to step 102 and acquires a target CA 50 and a specific CA 10 that are parameters for determining the waveform of the MFB reference data. More specifically, the ECU 40 acquires a target CA50 that is separately calculated for execution of CA50 feedback control. The ECU 40 also includes a target SA-CA10 that is separately calculated for execution of the SA-CA10 feedback control, and a target ignition timing that corresponds to the final indicated value of the ignition timing after the CA50 feedback control is reflected. To get. In addition, the ECU 40 calculates the specific CA10 by adding the target ignition timing to the target SA-CA10.

  Here, for example, when the air-fuel ratio changes to the lean side, the slope of the MFB waveform during the combustion period decreases. The MFB reference data needs to correspond to the change in the MFB waveform according to such engine operating conditions. Since the target CA50 is determined as a value corresponding to the engine operating condition, the influence of the engine operating condition has been factored into the target CA50. Similarly, the influence of the engine operating conditions has been factored into the target SA-CA10. Further, as described above, the target SA-CA10 and the target CA50 are set on the assumption that the internal combustion engine 10 is used in a standard temperature environment (for example, 20 ° C.). For this reason, the influence of the temperature surrounding the internal combustion engine 10 is already incorporated into the target SA-CA10 and the target CA50. The basic ignition timing that is the basis for calculating the target ignition timing is determined as a value corresponding to the engine operating conditions (intake air amount and engine speed). The change in the MBT ignition timing accompanying the change in the air-fuel ratio is dealt with by correcting the ignition timing by CA50 feedback control. For this reason, it can be said that the influence of the engine operating conditions has already been incorporated into the target ignition timing after the CA50 feedback control is reflected. Therefore, it can be said that the influence of the engine operating conditions is already incorporated into the specific CA10 that is determined depending on the target SA-CA10 and the target ignition timing. As described above, since the influence of the engine operating conditions has been incorporated into the target CA50 and the specific CA10, the reference data generated based on these has already been incorporated into the MFB waveform depending on the engine operating conditions. It can be said.

  Next, the ECU 40 proceeds to step 104. In step 104, processing for specifying two points A and B on the MFB-θ plane is performed using the target CA50 and the specific CA10 acquired in step 102.

  Next, the ECU 40 proceeds to step 106. In step 106, based on the two points A and B, MFB reference data other than the two points A and B is generated. Specifically, first, the reference data in the crank angle period from the combustion start point CA0 to the combustion end point CA100 is generated as follows. That is, the reference data of the crank angle period (CA10 to CA50) between the points A and B is generated by linear interpolation based on the two points A and B. On the other hand, the reference data of the crank angle period (CA0 to CA10 and CA50 to CA100) outside the crank angle period specified by point A and point B is linearly extrapolated based on two points A and B. Generated. Further, as described above, the reference data for the crank angle period before CA0 is generated as data with an MFB of 0%, and the reference data for the crank angle period after CA100 is 100%. Is generated as data.

  Next, the ECU 40 proceeds to step 108. In step 108, the measured data of MFB is calculated according to the above equation (3) based on the measured data of the in-cylinder pressure acquired using the in-cylinder pressure sensor 30 in the current combustion cycle.

Next, the ECU 40 proceeds to step 110. In step 110, the correlation index value I _R1 is calculated using the above equation (4) for the relevant data in the previous period α1 among the MFB reference data and the actual measurement data calculated in steps 106 and 108, respectively. The Here, as an example, the first period α1 is a crank angle period from the ignition timing SA to less than CA50.

Next, the ECU 40 proceeds to step 112. In step 112, the correlation index value I _R2 is calculated using the above equation (4) for the relevant data in the late α2 among the MFB reference data and the actual measurement data calculated in steps 106 and 108, respectively. The Here, as an example, the late α2 is a crank angle period from CA50 (including CA50) to EVO. Note that the CA 50 used to define the early α1 and the late α2 is specified using “reference data” of the MFB.

Next, the ECU 40 proceeds to step 114. In step 114, it is determined whether or not the correlation index value I _R2 related to the late α2 calculated in step 112 is less than the determination value I _Rth . The determination value I _Rth is set in advance as a value that can discriminate the deviation of the measured data from the reference data in the previous period α1 due to the semi-misfire. When the change due to the semi-misfire has occurred, the actual measurement data of the previous period α1 greatly deviates from the reference data, compared to the case where the change in the actual measurement data due to the cooling loss occurs. In addition, when a change due to misfire occurs, the actual measurement data of the previous period α1 greatly deviates from the reference data as compared with a case where a change due to half misfire occurs. Therefore, by setting the determination value _IRth as described above, for example, it is possible to identify the change factor of the actual measurement data to be processed in this routine.

If the determination in step 114 is not established (I _R2 ≧ I _Rth ), the ECU 40 immediately ends the process in the current combustion cycle. On the other hand, if the determination in step 114 is true (I _R2 <I _Rth ), that is, if it can be determined that the measured data of the MFB in the later α2 has a low degree of correlation with the reference data, the ECU 40 Proceed to 116. In step 116, it is determined whether or not the correlation index value I _R1 related to the previous period α1 calculated in step 110 is less than the determination value I _Rth .

If the determination in step 116 is not established (I _R2 <I _Rth and I _R1 ≧ I _Rth ), the ECU 40 proceeds to step 118. In this case, it is determined that the measured data of the late α2 MFB has a low degree of correlation with the reference data, but the measured data of the previous α1 MFB has a high degree of correlation with the reference data. it can. For this reason, in this case, the ECU 40 determines that the measured data of the MFB has changed due to the cooling loss, and executes engine warm-up control. Here, as an example of the engine warm-up control, the fuel injection amount is increased. More specifically, a correction amount for increasing by the engine warm-up control is added to the fuel injection amount determined by reflecting the correction by SA-CA10 feedback control. According to such control, since the air-fuel ratio is changed to the stoichiometric air-fuel ratio side by increasing the fuel injection amount under the lean burn operation, it is possible to increase the heat generation amount and promote engine warm-up. The engine warm-up control is reflected in the fuel injection amount for the next cycle of the cylinder subjected to the current determination. However, changes in the temperature environment is a factor cooling loss becomes excessive is not a unique situation to the cylinder, reflection of the control is not limited to the same cylinder, first after the current determination not to be established You may start from the cylinder in which the fuel injection amount is instructed. The engine warm-up control is continued until the determination in step 114 is not established.

On the other hand, when the determination in step 116 is satisfied (I _R2 <I _Rth and I _R1 <I _Rth ), the ECU 40 proceeds to step 120. In this case, it can be determined that the MFB actual measurement data of both the latter α2 and the first α1 have a low degree of correlation with the reference data. For this reason, in this case, the ECU 40 determines that the measured data of the MFB has changed due to a semi-misfire or misfire, and executes misfire suppression control. Here, the fuel injection amount is increased as an example of the misfire suppression control. More specifically, a correction amount for increasing by the misfire suppression control is added to the fuel injection amount determined by reflecting the correction by SA-CA10 feedback control. In this way, misfire suppression control is performed in addition to air-fuel ratio control by SA-CA10 feedback control, so that misfire can be more reliably suppressed. The misfire suppression control is reflected in the fuel injection amount for the next cycle of the cylinder subjected to the current determination. The misfire suppression control is continued until the determination in step 114 is not established.

  According to the routine processing shown in FIG. 8 described above, MFB reference data can be generated based on the target CA 50 and the specific CA 10. The target CA50 is a control target value used for CA50 feedback control, which is one of the engine controls performed by the internal combustion engine 10. The specific CA10 is a specific ratio combustion point that is determined depending on the target SA-CA10 used for SA-CA10 feedback control, which is one of engine controls, and the target ignition timing determined by CA50 feedback control. . The advantages of the MFB reference data generation method using the target CA50 and the specific CA10, which are parameters having such properties, will be described below in comparison with a known MFB data generation method.

(Advantages of MFB Reference Data Generation Method in Embodiment 1)
As an example of a known method for generating MFB data, there is a method using a Weibe function. This approach attempts to formulate combustion. However, this method has the following problems. That is, first, since the calculation amount increases, the calculation load of the ECU increases. In order to express the combustion waveform (MFB waveform) more accurately using the Wiebe function, it is necessary to appropriately set various parameters used in the Wiebe function. For this purpose, it is necessary to consider various engine operating condition parameters such as the intake air amount, engine rotation speed, air-fuel ratio and ignition timing, as well as combustion temperature and in-cylinder gas flow rate. If the combustion waveform is calculated using such many engine operating condition parameters, the mathematical formula becomes more complicated. For this reason, calculation load becomes high.

  Another problem with the known MFB data generation method is that it is difficult to ensure the accuracy of the generated MFB data. This is because it is difficult to formulate combustion itself, and it is also difficult to extract all factors that affect combustion. From the above, it cannot be said that it is suitable for mounting as compared with the method of the present embodiment having the advantages described later.

  On the other hand, the MFB reference data generation method of the present embodiment is simple for the following reasons, and more suitable as a comparison target for evaluating the degree of correlation of MFB actual measurement data. It can be said that data can be generated.

  That is, first, the value of the target CA 50 is determined for the premised engine control. Further, the specific CA10 is determined depending on the target SA-CA10 whose value is determined in the same manner as the target CA50. That is, the target CA 50 and the specific CA 10 that are parameters used as a basis for generating the reference data in the present embodiment do not need to be set in advance for generating the reference data, and also when acquired on an actual machine. Does not require complicated calculations. For this reason, it can be said that these are parameters that are easy to obtain. And based on these target CA50 and specific CA10, reference | standard data can be produced | generated by the simple calculation of linear interpolation and linear extrapolation. For this reason, the method of this embodiment can remarkably reduce the amount of calculation compared with the above-mentioned known method, and the calculation load of the ECU 40 becomes extremely low. Therefore, it can be said that this method is more suitable for implementation.

  Further, the MFB waveform has a characteristic of rising linearly during the main combustion period (from CA10 to CA90). Therefore, it can be said that the reference data can be easily acquired while appropriately capturing the characteristics of the MFB waveform by generating the reference data within the main combustion period using linear interpolation and linear extrapolation. More precisely, the combustion waveform is not bent at one point at the combustion start point CA0 and the combustion end point CA100 as schematically shown in FIG. 5 and the like, and the crank angle period from CA0 to around CA10, and In the crank angle period around CA90 to CA100, it bends while being slightly rounded (see FIG. 2). However, these crank angle periods are short from the whole combustion period, and the fact that the MFB waveform is slightly rounded in the crank angle period is from the viewpoint of comparing the degree of correlation of the MFB data. It can be said that there is no big influence. For this reason, it can be said that it is sufficient to generate reference data by linear extrapolation for these crank angle periods as in this embodiment.

  Next, the reason why it can be said that the MFB data generation method of the present embodiment can generate reference data more suitable as a comparison target for evaluating the degree of correlation of measured data of MFB. The target CA50 is a target value for CA50 feedback control as a premise. In the SA-CA10 feedback control, the fuel injection amount is controlled so that the measured SA-CA10 becomes the target SA-CA10, and the ignition timing is also controlled to the target ignition timing obtained by the CA50 feedback control. For this reason, it can be said that CA10 is indirectly controlled by executing SA-CA10 feedback control and CA50 feedback control so that it becomes a specific CA10 determined depending on the target SA-CA10 and the target ignition timing. In this respect, it can be said that the specific CA10 corresponds to an indirect control target value. From the above, when the SA-CA10 feedback control and the CA50 feedback control are being executed, the measured waveform of the MFB is generated based on the target CA50 and the specific CA10 by these controls. It can be said that the fuel injection amount and the ignition timing are controlled so as to approach.

  As described above, the target CA50 and the specific CA10 have already been factored in the influence of the engine operating conditions. Therefore, the reference data generated based on these can change the MFB waveform depending on the engine operating conditions. It has been woven. From the above, according to the method of the present embodiment, the reference engine waveform (here, SA-CA10 feedback control and CA50) is generated by directly generating the waveform of the reference data from the target CA50 and the specific CA10. It can be said that the combustion waveform targeted by feedback control (in other words, the ideal combustion waveform) can be uniquely determined based on the target CA50 and the specific CA10. In this embodiment, MFB data having such an ideal combustion waveform is used as reference data. For this reason, the method of the present embodiment can generate reference data more suitable as a comparison target for evaluating the degree of correlation of measured data of MFB, compared to the case where MFB data generated by the above-described known method is used. It becomes like this.

(Effects regarding the change factors of the MFB actual measurement data and the measures according to the specified factors)
Further, according to the processing of the above routine, the degree of correlation between the measured data of MFB and the reference data can be suitably evaluated using the reference data having the advantages described above. Then, by using the evaluation result, it is possible to specify that the cause of the change in the measured data of MFB is excessive cooling loss, or semi-misfire / misfire. More specifically, the above-described specification can be performed accurately using the characteristics of changes in measured data due to differences in factors.

  In addition, according to the processing of the above routine, it is possible to perform engine warm-up control or misfire suppression control as a countermeasure corresponding to the specified factor. That is, engine control is performed based on the degree of correlation between the MFB actual measurement data and the reference data.

  Further, when the engine warm-up control is continuously executed, the actually measured data that has deviated from the reference data as shown in FIG. 6 approaches the reference data as time passes. According to the above routine, the degree of correlation increases as a result of the divergence being resolved, so the determination in step 114 is not established, and the engine warm-up control is terminated. Since the evaluation result of the MFB data can be acquired for each combustion cycle, according to the engine warm-up control based on this evaluation result, the timing of engine warm-up completion is indirectly determined based on the engine coolant temperature. In comparison, it can be said that the time can be determined early. This leads to an improvement in fuel consumption.

[Modification of Embodiment 1]
By the way, in Embodiment 1 mentioned above, the reference | standard data of a combustion period (from CA0 to CA100) are produced | generated based on target CA50 and specific CA10. However, the two specific ratio combustion points used for generating the reference data for the combustion period are not limited to CA50 and CA10 as long as they are used for the assumed engine control, and are selected from CA0 to CA100. Any specific ratio combustion point (for example, CA90) may be used. However, as described above, the MFB waveform changes linearly in the main combustion period (from CA10 to CA90) strictly, so the two specific ratio combustion points that are the basis for generating the reference data are , CA10 to CA90 are preferably selected.

  In the first embodiment described above, reference data for the entire combustion period from CA0 to CA100 is generated using linear interpolation and linear extrapolation based on the target CA50 and specific CA10. However, as described above, the MFB waveform in the crank angle period from CA0 to CA10 and the crank angle period from CA90 to CA100 is strictly rounded slightly. Therefore, the reference data of at least one of these crank angle periods is generated in such a manner that a rounded waveform is reproduced using, for example, a quadratic function without using linear interpolation or linear extrapolation. It may be.

  In the first embodiment described above, both linear interpolation and linear extrapolation are used for generating the MFB reference data during the combustion period. However, either one of linear interpolation and linear extrapolation is used depending on the positions of the two specific ratio combustion points that are the basis for generating the reference data. For example, when the reference data is generated for the entire combustion period based on CA0 and CA100, only linear interpolation is used. In addition, in reality, it is considered that the possibility of being selected is low, but if two reference data corresponding to two adjacent measured data in the combustion period are selected as the two specific ratio combustion points. Only linear extrapolation will be used.

  In the first embodiment described above, the target CA 50 and the specific CA 10 are used as the basis for generating the reference data. However, depending on the two specific ratio combustion points used for the assumed engine control, both may be control target values, or both may be specific ratio combustion points determined depending on the control target value, that is, It may be an indirect control target value.

  In the first embodiment described above, a cross-correlation function is used to calculate a correlation index value indicating the degree of correlation between MFB actual measurement data and reference data. However, the “degree of correlation between the actual measurement data of the combustion mass ratio and the reference data” in the present invention is not necessarily calculated using a cross-correlation function. That is, the “degree of correlation” is, for example, a value obtained by summing the square of the difference between the measured data of the MFB and the reference data at the same crank angle for a predetermined calculation period (so-called residual square). Sum). In the case of the residual sum of squares, the higher the degree of correlation, the smaller the value.

  Here, the use of the cross-correlation function is superior to the residual sum of squares in the following points. That is, in the MFB actual measurement data waveform, a slight deviation from the reference data waveform may occur between combustion cycles due to combustion variations. According to the residual sum of squares, even if such a deviation in the waveform of the actually measured data occurs, it is calculated as a value of a certain magnitude. That is, the residual sum of squares reacts sensitively to small deviations in measured data caused by combustion variations. For this reason, it may be difficult to accurately detect the above-described combustion state or environmental change as distinguished from such combustion variations.

On the other hand, to calculate the cross-correlation function, as described above, the entire waveform of the MFB actual measurement data within the calculation period α is fixed in the crank angle direction (MFB shown in FIG. 5 while the waveform of the reference data is fixed. Operation of continuously calculating the cross-correlation coefficient R while moving little by little (in the horizontal axis direction of the waveform of the reference data). Then, the maximum value of the values obtained after normalizing the cross-correlation coefficient R obtained in the course of this operation is the correlation index value I _R in the calculation target of the combustion cycle. For this reason, the shape of the MFB data itself is the same as the reference data, but the cross-correlation function is used even if the measured data slightly deviates from the reference data in the crank angle direction due to combustion variations. According if, moved reference data and the correlation index value I _R in balanced state of almost correlation is to be calculated measurement data. For this reason, the use of the cross-correlation function is less susceptible to the effects of combustion variations than the use of the residual sum of squares. Therefore, the characteristics of changes in the waveform of measured data due to changes in the combustion state or environment are more characteristic. It can be said that it can be detected with high accuracy.

In the first embodiment described above, the determination value I _Rth common to the correlation index value I _R1 related to the previous period and the correlation index value I _R2 related to the latter period is used in the process of specifying the change factor of the measured data of the MFB. . However, the determination value used in the above process may not be common, it may be used separate determination value in the correlation index value I _R2 regarding late correlation index values I _R1 related year. Therefore, the “first determination value” and the “second determination value” in the present invention may be the same value or different values. Similarly, the “third determination value” and the “fourth determination value” may be either the same value or different values. This also applies to the relationship between the “first determination value” and the “third determination value” and the relationship between the “second determination value” and the “fourth determination value”.

In the present invention, the “degree of correlation between the actual measurement data of the combustion mass ratio and the reference data” is obtained by using a method such as the above-described cross-correlation function or the residual sum of squares to obtain a waveform of three or more consecutive data. It is preferable to be evaluated as a target. However, the “correlation degree” determination method for capturing the change in the waveform of the actual measurement data caused by excessive cooling loss may be, for example, the following method described with reference to FIG. FIG. 9 is a diagram for describing an example in which the degree of correlation of MFB data at three specific ratio combustion points is evaluated to determine a change in measured data of MFB due to excessive cooling loss. . CA80 is used together with CA10 and CA50 used in the above-described two feedback controls as the three specific ratio combustion points used for this determination. In order to evaluate the degree of correlation between the actual measurement data and the reference data on the second half of combustion, a straight line L passing through two points P1 and P2 of the reference data at CA50 and CA80 on the MFB-θ plane, and CA50 And the straight line L ′ passing through the two points P1 ′ and P2 ′ of the actual measurement data at CA80 is calculated. Further, in order to evaluate the degree of correlation between the actual measurement data and the reference data in the first half of combustion, the distance D between the reference data point P3 and the actual measurement data point P3 ′ at CA10 is calculated. Then, by determining whether or not the distance D is less than or equal to a predetermined value, the degree of correlation between the measured data of the MFB and the reference data on the first half of combustion (corresponding to “first term” in the present invention) is the first. It is determined whether it is 1 or more. Further, by determining whether or not the amount of change in the slope of the straight line L ′ with respect to the slope of the straight line L is greater than or equal to a predetermined value, the actual measurement of MFB on the latter half of combustion (corresponding to “late stage” in the present invention). It is determined whether or not the degree of correlation between the data and the reference data is lower than the second determination value. When it is determined that the distance D is equal to or less than the predetermined value and the amount of change regarding the straight lines L and L ′ is equal to or greater than the predetermined value, the actual measurement data caused by excessive cooling loss is determined. It is determined that a change has occurred, and engine warm-up control is executed.

  In Embodiment 1 described above, the evaluation result of the degree of correlation of the MFB data is used to determine the cause of the change in the MFB actual measurement data between the excessive cooling loss and the semi-misfire / misfire. Then, engine control (engine warm-up control or misfire suppression control) is performed as a countermeasure according to the determination result. However, a specific example of engine control based on the degree of correlation of MFB data in the present invention is not limited to the above. In other words, any method other than the above-described example may be used as long as it grasps the change in the measured data of the MFB to grasp the change in the combustion state or the environment and is a countermeasure against the change.

  In the first embodiment described above, the increase in the fuel injection amount has been described as an example of the engine warm-up control. However, “engine warm-up control” in the present invention is not limited to the above example. That is, for example, when a mechanism capable of varying the circulating flow rate of the engine cooling water is provided, or when the pump for circulating the engine cooling water is an electric type, the engine warm-up control is performed by the engine cooling water. The control may be to reduce the circulation flow rate.

  In the first embodiment described above, the increase in the fuel injection amount has been described as an example of the misfire suppression control. However, the “misfire suppression control” in the present invention is not limited to the above example. For example, when an ignition device capable of adjusting the ignition energy is provided, the control for increasing the ignition energy may be used.

In the first embodiment described above, the crank angle period (calculation period α) for which the correlation index values I _R1 and I _R2 are calculated is divided into the first period α1 and the second period α2 with the CA50 of the reference data as a boundary. It is said. However, the “early period” and “late period” in the present invention are not limited to those corresponding to the first half period and the second half period of the combustion divided with the CA50 as a boundary. In other words, if the boundary between the “early period” and the “late period” is within a range where the cause of the change in the measured data of the MFB can be separated between the excessive cooling loss and the semi-misfire / misfire, other than CA50 It may be an arbitrary third specific ratio combustion point. In the first embodiment, the ignition timing SA is used as the start point of the first period α1, and the opening timing EVO of the exhaust valve 22 is used as the end point of the second period α2. In the present invention, the starting point of the “pre-term” is not limited to the ignition timing SA, but may be any time after the closing timing IVC of the intake valve 20. On the other hand, the end point of the “late stage” in the present invention is not limited to EVO, and if the crank angle timing at which combustion can be reliably determined in consideration of combustion variation or the like is obtained in advance, The end point of “late stage” may be such crank angle timing. Further, the “early period” in the present invention may not include the crank angle period before the combustion period, and similarly, the “late period” does not include the crank angle period after the combustion period. It does not have to be.

  In the first embodiment described above, the example in which the degree of correlation of the MFB data is evaluated using the cross-correlation function for each cylinder has been described. However, the evaluation of the degree of correlation of the MFB data is performed using any representative cylinder. It may be executed as a target. Then, engine control based on the degree of MFB correlation in the representative cylinder may be performed for all cylinders.

  Moreover, in Embodiment 1 mentioned above, the example which adjusts a fuel injection amount by SA-CA10 feedback control was demonstrated. However, the adjustment target of the SA-CA10 feedback control used for the combustion control during the lean burn operation is not limited to the fuel injection amount, but may be the intake air amount or the ignition energy. If the fuel injection amount or the intake air amount is an adjustment target, this feedback control can be positioned as air-fuel ratio control. Further, the specific ratio combustion point CAα used for the feedback control is not necessarily limited to CA10, and may be another combustion point. However, regarding application to this feedback control, it can be said that CA10 is superior to other combustion points for the following reason. That is, when the combustion point in the main combustion period (CA10-CA90) after CA10 is used, the obtained crank angle period is a parameter (EGR rate, intake air temperature and intake temperature) that affects combustion when the flame spreads. Greatly affected by the tumble ratio). That is, the crank angle period obtained in this case is not purely focused on the air-fuel ratio, and is weak against disturbance. As described above, the combustion points around the combustion start point CA0 and the combustion end point CA100 are likely to cause errors due to the influence of noise superimposed on the output signal from the in-cylinder pressure sensor 30. The influence of this noise decreases as the distance from the combustion start point CA0 and the combustion end point CA100 increases toward the center of the combustion period. Considering these points, it can be said that CA10 is the most excellent.

In the first embodiment described above, the degree of correlation of the MFB data is evaluated based on the correlation index values I _R1 and I _R2 during lean burn operation involving the implementation of SA-CA10 feedback control and CA50 feedback control. It is said. However, on the premise that the “first engine control” and the “second engine control” in the present invention are performed, the evaluation is not limited to the lean burn operation but is performed, for example, during the theoretical air-fuel ratio combustion operation. It may be.

In the first embodiment described above, the “burning mass ratio calculating means” in the present invention is realized by the ECU 40 executing the process of step 108, and the MFB calculated by the ECU 40 according to the above equation (3). By calculating the specific ratio combustion point CAα such as CA10 based on the actually measured data, the “combustion point calculating means” in the present invention is realized, and the ECU 40 executes SA-CA10 feedback control in the present invention. The “first control means” is realized, and the ECU 40 executes the CA50 feedback control, whereby the “second control means” in the present invention is realized, and the ECU 40 responds to the determination results of steps 114 and 116. In the present invention, the process of step 118 or 120 is executed. "Third controlling device" is realized. Further, the fuel injection valve 26 and the ignition device 28 are the “one or more actuators” in the present invention, the CA 10 is the “first specific ratio combustion point” in the present invention, and the SA-CA 10 is the “first parameter” in the present invention. Further, SA-CA10 feedback control is the “first engine control” in the present invention, CA50 is the “second specific ratio combustion point” in the present invention, and CA50 feedback control is the “second engine control” in the present invention. The warm-up control and the misfire suppression control are “third engine control” in the present invention, and the specific CA 10 is “first specific ratio combustion point specified from the“ first target value ”and“ target value of the first parameter ”in the present invention. In addition, the target CA50 is changed from the ignition timing SA to the “second target value” and “target value of the second specific ratio combustion point” in the present invention. The "first crank angle period" at the crank angle period invention to, and crank angle period from the CA100 to EVO to the "second crank angle period" in the present invention, and corresponds respectively. Further, the CA50 in the reference data is the “third specific ratio combustion point” in the present invention, and the first period α1 is the “first period that is the crank angle period including the combustion period before the third specific ratio combustion point” in the present invention. The latter period α2 corresponds to “a second period that is a crank angle period including a combustion period after the third specified ratio combustion point” in the present invention. The determination value I _Rth corresponds to each of the “first to fourth determination values” in the present invention. Although different from the first embodiment, if a parameter defined based on CA50 (for example, SA-CA50) is used, the SA-CA50 is used as the “second parameter” in the present invention. If the target CA10 is set in the CA10 itself, the target CA10 corresponds to the “target value of the first specific ratio combustion point” in the present invention. For example, the SA-CA50 itself has the target SA- If CA50 is set, the specific CA50 specified from the target SA-CA50 corresponds to the “second specific ratio combustion point specified from the target value of the second parameter” in the present invention.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Intake valve 22 Exhaust valve 24 Throttle valve 26 Fuel injection valve 28 Ignition device 30 In-cylinder pressure sensor 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Air flow meter

Claims (5)

A control device for an internal combustion engine that controls an internal combustion engine including one or more actuators used for engine control,
An in-cylinder pressure sensor for detecting the in-cylinder pressure;
A crank angle sensor for detecting the crank angle;
Combustion mass ratio calculation means for calculating actual measurement data of the combustion mass ratio synchronized with the crank angle based on the in-cylinder pressure detected by the in-cylinder pressure sensor and the crank angle detected by the crank angle sensor;
Combustion point calculation means for calculating an actual measurement value of a specific ratio combustion point that is a crank angle when the combustion mass ratio becomes a specific ratio based on the actual measurement data of the combustion mass ratio;
Based on the first specific ratio combustion point which is the crank angle when the combustion mass ratio becomes the first specific ratio or the first parameter defined based on the first specific ratio combustion point, the first specific ratio combustion point Alternatively, first control means for executing first engine control for controlling any one or more of the one or more actuators so that the first parameter becomes a target value;
Based on the second specific ratio combustion point which is the crank angle when the combustion mass ratio becomes the second specific ratio or the second parameter defined based on the second specific ratio combustion point, the second specific ratio combustion point Alternatively, second control means for executing second engine control for controlling any one or more of the one or more actuators so that the second parameter becomes a target value;
Third engine control that controls one or more of the one or more actuators based on the degree of correlation between the measured data of the combustion mass ratio and the reference data of the combustion mass ratio based on the operating conditions of the internal combustion engine Third control means for executing
With
The reference data of the combustion mass ratio in the crank angle period from at least the 10% combustion point to the 90% combustion point in the combustion period is based on the first target value and the second target value. Generated by at least one of the insertions,
The first target value is either the target value of the first specific ratio combustion point or the first specific ratio combustion point specified from the target value of the first parameter,
The second target value is either the target value of the second specific ratio combustion point or the second specific ratio combustion point specified from the target value of the second parameter,
When the first crank angle period, which is the crank angle period before the combustion period, is included in the reference data for the combustion mass ratio, the reference data for the combustion mass ratio in the first crank angle period has a combustion mass ratio of zero. As percentage data,
When the second crank angle period, which is a crank angle period after the combustion period, is included in the reference data of the combustion mass ratio, the reference data of the combustion mass ratio in the second crank angle period has a combustion mass ratio of 100. A control apparatus for an internal combustion engine, characterized in that the data is percentage data.   The first specific ratio combustion point and the second specific ratio combustion point are specific ratio combustion points within the crank angle period from a 10% combustion point to a 90% combustion point. Control device for internal combustion engine.   The third engine control is engine warm-up control for raising the temperature of the internal combustion engine, and includes a combustion angle before a third specific ratio combustion point when the combustion mass ratio is a third specific ratio. Combustion in the latter period, which is a crank angle period including the combustion period after the third specified ratio combustion point, in which the degree of correlation between the measured data of the combustion mass ratio in the first period, which is the period, and the reference data is greater than or equal to the first determination value 3. The control device for an internal combustion engine according to claim 1, wherein the control device is executed when the degree of correlation between the measured data of the mass ratio and the reference data is lower than the second determination value. 4.   The third engine control is misfire suppression control that suppresses the occurrence of misfire, and is a crank angle period that includes a combustion period before the third specific ratio combustion point when the combustion mass ratio is the third specific ratio. Combustion mass in the latter period, which is a crank angle period including a combustion period after the third specified ratio combustion point, and the degree of correlation between the actual measurement data and the reference data of the combustion mass ratio in a certain earlier period is lower than the third determination value The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the control device is executed when the degree of correlation between the ratio measurement data and the reference data is lower than a fourth determination value.   5. The control apparatus for an internal combustion engine according to claim 1, wherein the correlation index value indicating the degree of correlation is calculated using a cross-correlation function.

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