JP2016118111A - Control device of internal combustion engine - Google Patents

Abstract

An object of the present invention is to adopt a control configuration that adjusts at least one of a fuel injection amount and an intake air amount so that a calculated crank angle period approaches a target crank angle period during lean combustion operation. Provided is a control device for an internal combustion engine that suppresses at least one of an increase in NOx emission and an increase in torque fluctuation even under a situation where the relationship between the crank angle period and the air-fuel ratio is changing with respect to the relationship To do. A calculated SA-CA10 is calculated using a crank angle sensor 42 and an in-cylinder pressure sensor 30. The fuel injection amount feedback control is executed so that the calculated SA-CA10 approaches the target SA-CA10 during the lean combustion operation. Under the situation where the feedback control is performed, when the air-fuel ratio detected by the air-fuel ratio sensor 32 is out of the air-fuel ratio range R1, the target SA-CA10 is corrected and the air-fuel ratio is out of the air-fuel ratio range R1. Suppress. [Selection] Figure 4

Description

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

  Conventionally, for example, Patent Document 1 discloses a control device for an internal combustion engine that performs a lean combustion operation. In this conventional control device, in order to enable lean combustion while reducing exhaust emission, the actual crank angle when the predetermined combustion mass ratio is reached is detected, and the detected crank angle is compared with the target crank angle. Based on the above, the fuel supply amount will be adjusted.

JP-A-9-317522 JP 2011-050661 A JP 2005-201163 A

  Since the ignition timing is not considered only by using the crank angle when the predetermined combustion mass ratio is reached as a parameter used for controlling the fuel injection amount as in the control method of Patent Document 1 described above, the above parameter is used. Thus, the air-fuel ratio during the lean combustion operation cannot be appropriately represented. On the other hand, in order to control the air-fuel ratio in the lean combustion operation region, the crank angle period from the ignition timing to the predetermined combustion mass ratio is used as a parameter, and the calculated crank angle period, which is the calculated value of the parameter, is the target value. It is conceivable to employ a method of adjusting at least one of the fuel injection amount and the intake air amount so as to approach a certain target crank angle period. There is a correlation between the crank angle period defined in this way and the air-fuel ratio.

  However, the adjustment of the fuel injection amount by the above method does not directly control the air-fuel ratio. More specifically, even if the actual crank angle period is controlled to the same target crank angle period, the air-fuel ratio is not always controlled to the same value. The reason is as follows. That is, bringing the actual crank angle period closer to the target crank angle period by adjusting the fuel injection amount or the like corresponds to bringing actual combustion closer to the target combustion. The target crank angle period is determined for the reference combustion condition. The standard combustion conditions referred to here are conditions for combustion performed when parameters related to combustion such as the tumble ratio and the properties of the fuel used are values as designed. When the combustion condition changes due to various combustion variation factors (for example, tumble flow variation or fuel property variation) with respect to the standard combustion condition, the correspondence relationship between the crank angle period and the air-fuel ratio is the standard. Deviation from the relationship under combustion conditions. As a result, even if the combustion is appropriately controlled by the adjustment, the air-fuel ratio may deviate from the target air-fuel ratio. In addition, changes in the characteristics of the sensor used to calculate the crank angle period, or individual differences between the sensors themselves, change the relationship between the crank angle period and the air-fuel ratio from the relationship under the reference combustion conditions. It becomes a factor.

  Even when the actual crank angle period is controlled to match the target crank angle period by the adjustment, if the correspondence between the crank angle period and the air-fuel ratio is shifted, the air-fuel ratio is reduced. It will deviate from the originally intended value. If the air-fuel ratio shifts to the rich side during lean combustion operation, there is a concern about an increase in NOx emissions. Conversely, if the air-fuel ratio shifts to the lean side, there is a concern about an increase in torque fluctuation.

  The present invention has been made to solve the above-described problems, and at least one of the fuel injection amount and the intake air amount is set so that the calculated crank angle period approaches the target crank angle period during the lean combustion operation. When the control configuration to be adjusted is adopted, even if the relationship between the crank angle period and the air-fuel ratio is changing with respect to the relationship under the reference combustion condition, the increase in the NOx emission amount and the torque fluctuation It is an object of the present invention to provide a control device for an internal combustion engine that can suppress at least one of the increases.

  An internal combustion engine control apparatus according to a first aspect of the present invention is an internal combustion engine control apparatus that performs a lean combustion operation at an air-fuel ratio larger than a stoichiometric air-fuel ratio, and includes an air-fuel ratio detection means, a crank angle detection means, , A combustion mass ratio calculating means, a first crank angle obtaining means, an adjusting means, and a changing means. The air-fuel ratio detection means detects the air-fuel ratio of the exhaust gas. The crank angle detection means detects the crank angle. The combustion mass ratio calculation means calculates the combustion mass ratio. The first crank angle acquisition means acquires the first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio. The adjusting means is configured to adjust the fuel injection amount and the fuel injection amount so that a calculated crank angle period that is a calculated value of a crank angle period from an ignition timing to the first crank angle approaches a target crank angle period that is a target value of the crank angle period. Adjustment of at least one of the intake air amounts is performed. When the air fuel ratio detected by the air fuel ratio detecting means is out of the air fuel ratio range including the target air fuel ratio under the situation where the adjustment by the adjusting means is performed during the lean combustion operation, The adjustment by the adjusting means is changed so that the air-fuel ratio is suppressed from deviating from the air-fuel ratio range.

  The changing unit may suppress the air-fuel ratio from deviating from the air-fuel ratio range by correcting the target crank angle period when the air-fuel ratio deviates from the air-fuel ratio range.

  The changing means increases the target crank angle period when the air-fuel ratio deviates from the air-fuel ratio range to the rich side, and when the air-fuel ratio deviates from the air-fuel ratio range to the lean side. It is preferable to reduce the crank angle period.

  The changing means may be configured to suppress the air-fuel ratio from deviating from the air-fuel ratio range by limiting the adjustment by the adjusting means when the air-fuel ratio deviates from the air-fuel ratio range.

  When the air-fuel ratio deviates from the air-fuel ratio range to the rich side, the changing unit is configured to obtain an absolute value of at least one of the fuel injection amount and the intake air amount used when the calculated crank angle period is reduced. When the adjustment is limited by reducing the upper limit of the value and the air-fuel ratio deviates from the air-fuel ratio range to the lean side, the fuel injection amount and intake air amount used when the calculated crank angle period is increased It is preferable to limit the adjustment by reducing the upper limit of the absolute value of at least one of the correction amounts.

  A control device for an internal combustion engine according to a second aspect of the present invention is a control device for an internal combustion engine that performs a lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio, comprising NOx concentration detection means, crank angle detection means, , A combustion mass ratio calculating means, a first crank angle obtaining means, an adjusting means, and a changing means. The NOx concentration detecting means detects the NOx concentration of the exhaust gas. The crank angle detection means detects the crank angle. The combustion mass ratio calculation means calculates the combustion mass ratio. The first crank angle acquisition means acquires the first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio. The adjusting means is configured to adjust the fuel injection amount and the fuel injection amount so that a calculated crank angle period that is a calculated value of a crank angle period from an ignition timing to the first crank angle approaches a target crank angle period that is a target value of the crank angle period. Adjustment of at least one of the intake air amounts is performed. The changing means is an exhaust gas in which the NOx concentration detected by the NOx concentration detecting means is discharged under combustion at the target air-fuel ratio under the situation where the adjustment by the adjusting means is performed during lean combustion operation. The adjustment by the adjusting means is changed so that the NOx concentration of the exhaust gas is suppressed from becoming higher than the predetermined value when the predetermined value is higher than the NOx concentration of the gas.

  The changing means preferably increases the target crank angle period when the NOx concentration of the exhaust gas is higher than the predetermined value.

  The changing means is configured to set an absolute value of a correction amount of at least one of a fuel injection amount and an intake air amount used when the calculated crank angle period is reduced when the NOx concentration of the exhaust gas is higher than the predetermined value. It is preferable to reduce the upper limit.

  An internal combustion engine control apparatus according to a third aspect of the present invention is an internal combustion engine control apparatus that performs a lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio, and includes an air-fuel ratio detection means, a crank angle detection means, , A combustion mass ratio calculating means, a first crank angle obtaining means, an adjusting means, and a first prohibiting means. The air-fuel ratio detection means detects the air-fuel ratio of the exhaust gas. The crank angle detection means detects the crank angle. The combustion mass ratio calculation means calculates the combustion mass ratio. The first crank angle acquisition means acquires the first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio. The adjusting means is configured to adjust the fuel injection amount and the fuel injection amount so that a calculated crank angle period that is a calculated value of a crank angle period from an ignition timing to the first crank angle approaches a target crank angle period that is a target value of the crank angle period. Adjustment of at least one of the intake air amounts is performed. The first prohibiting means is a case where the air-fuel ratio detected by the air-fuel ratio detecting means deviates from an air-fuel ratio range including the target air-fuel ratio in a situation where the adjustment by the adjusting means is performed during lean combustion operation. In addition, lean combustion operation is prohibited.

  An internal combustion engine control apparatus according to a fourth aspect of the present invention is an internal combustion engine control apparatus that performs a lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio, and includes an air-fuel ratio detection means, a crank angle detection means, , A combustion mass ratio calculating means, a first crank angle obtaining means, an adjusting means, and a second prohibiting means. The air-fuel ratio detection means detects the air-fuel ratio of the exhaust gas. The crank angle detection means detects the crank angle. The combustion mass ratio calculation means calculates the combustion mass ratio. The first crank angle acquisition means acquires the first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio. The adjusting means is configured to adjust the fuel injection amount and the fuel injection amount so that a calculated crank angle period that is a calculated value of a crank angle period from an ignition timing to the first crank angle approaches a target crank angle period that is a target value of the crank angle period. Adjustment of at least one of the intake air amounts is performed. The second prohibiting unit is configured in a case where the air-fuel ratio detected by the air-fuel ratio detecting unit deviates from an air-fuel ratio range including the target air-fuel ratio in a situation where the adjustment by the adjusting unit is being performed during lean combustion operation. In addition, the adjustment by the adjusting means is prohibited.

  An internal combustion engine control apparatus according to a fifth aspect of the present invention is an internal combustion engine control apparatus that performs a lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio, comprising NOx concentration detection means, crank angle detection means, , A combustion mass ratio calculating means, a first crank angle obtaining means, an adjusting means, and a first prohibiting means. The NOx concentration detecting means detects the NOx concentration of the exhaust gas. The crank angle detection means detects the crank angle. The combustion mass ratio calculation means calculates the combustion mass ratio. The first crank angle acquisition means acquires the first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio. The adjusting means is configured to adjust the fuel injection amount and the fuel injection amount so that a calculated crank angle period that is a calculated value of a crank angle period from an ignition timing to the first crank angle approaches a target crank angle period that is a target value of the crank angle period. Adjustment of at least one of the intake air amounts is performed. The first prohibiting means is configured such that the NOx concentration detected by the NOx concentration detecting means is discharged under combustion at the target air-fuel ratio in a situation where the adjustment by the adjusting means is performed during lean combustion operation. When the exhaust gas is higher than a predetermined value higher than the NOx concentration of the exhaust gas, the lean combustion operation is prohibited.

  An internal combustion engine control apparatus according to a sixth aspect of the present invention is an internal combustion engine control apparatus that performs a lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio, and includes a NOx concentration detection means, a crank angle detection means, , A combustion mass ratio calculating means, a first crank angle obtaining means, an adjusting means, and a second prohibiting means. The NOx concentration detecting means detects the NOx concentration of the exhaust gas. The crank angle detection means detects the crank angle. The combustion mass ratio calculation means calculates the combustion mass ratio. The first crank angle acquisition means acquires the first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio. The adjusting means is configured to adjust the fuel injection amount and the fuel injection amount so that a calculated crank angle period that is a calculated value of a crank angle period from an ignition timing to the first crank angle approaches a target crank angle period that is a target value of the crank angle period. Adjustment of at least one of the intake air amounts is performed. The second prohibiting means is configured such that the NOx concentration detected by the NOx concentration detecting means is discharged under combustion at the target air-fuel ratio in a situation where the adjustment by the adjusting means is performed during lean combustion operation. The adjustment by the adjusting means is prohibited when the NOx concentration of the exhaust gas is higher than a predetermined value.

  The predetermined combustion mass ratio is preferably 10%.

  According to the present invention, in the case where a control configuration is adopted in which at least one of the fuel injection amount and the intake air amount is adjusted so that the calculated crank angle period approaches the target crank angle period during the lean combustion operation, the reference combustion is performed. Even in a situation where the relationship between the crank angle period and the air-fuel ratio changes with respect to the condition, at least one of an increase in NOx emission and an increase in torque fluctuation can be suppressed.

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 figure showing the relationship between each of NOx density | concentration, a fuel consumption, torque fluctuation, and SA-CA10, and an air fuel ratio (A / F). It is a block diagram for demonstrating the outline | summary of the air fuel ratio control (lean limit control) which ECU performs in Embodiment 1 of this invention during a lean combustion driving | operation. It is a figure showing the setting of the update amount of the correction amount of target SA-CA10 used in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a block diagram for demonstrating the outline | summary of the air fuel ratio control (lean limit control) which ECU performs in lean combustion operation in Embodiment 2 of this invention. It is a figure showing the setting of the update amount of the correction amount of the upper and lower limit value about the FB correction amount used in Embodiment 2 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a block diagram for demonstrating the outline | summary of the air fuel ratio control which ECU in Embodiment 3 of this invention performs. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a block diagram for demonstrating the outline | summary of the air fuel ratio control (lean limit control) which ECU performs in lean combustion operation in Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 5 of this invention. It is a figure showing the setting of the update amount of the correction amount of target SA-CA10 used in Embodiment 5 of this invention. It is a figure showing the setting of the update amount of the correction amount of the upper limit value about the FB correction amount used in Embodiment 6 of the present invention.

Embodiment 1 FIG.
[System configuration of the first embodiment]
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. Further, an in-cylinder pressure sensor 30 for detecting the in-cylinder pressure is incorporated in each cylinder.

  An air-fuel ratio sensor 32 for detecting the air-fuel ratio of the exhaust gas is disposed in the exhaust passage 18. The air-fuel ratio sensor 32 outputs a signal that changes linearly with respect to the air-fuel ratio before combustion of the exhaust gas. Various catalysts for purifying exhaust gas are disposed in the exhaust passage 18 on the downstream side of the air-fuel ratio sensor 32. Here, as an example, a three-way catalyst 34 and an NSR catalyst (occlusion reduction type NOx catalyst) 36 are provided in order from the upstream side of the exhaust gas. Note that an SCR catalyst (selective reduction type NOx catalyst) may be provided in place of or along with the NSR catalyst 36 for purifying NOx during the lean combustion operation.

  Furthermore, the system of the present embodiment includes an ECU (Electronic Control Unit) 40. The ECU 40 includes at least 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 included in the internal combustion engine 10. In addition to the in-cylinder pressure sensor 30 and the air-fuel ratio sensor 32 described above, the ECU 40 measures the crank angle sensor 42 for acquiring the rotational position of the crankshaft and the engine rotational speed, and the intake air amount. Various sensors for acquiring an engine operating state such as an air flow meter 44 for the purpose are included. The sensor includes an accelerator position sensor 46 for detecting the amount of depression (accelerator opening) of an accelerator pedal of a vehicle on which the internal combustion engine 10 is mounted. 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. 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. 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 has a function of calculating the value of the cylinder volume determined by the position of the crank angle according to the crank angle.

ただし、上記（１）式において、Ｐは筒内圧力、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（０％燃焼点ＣＡ０）であり、θ_ｍａｘは燃焼終了点（１００％燃焼点ＣＡ１００）である。 [Control of Embodiment 1]
(Ignition timing and combustion mass ratio)
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-cycle pressure data (in-cylinder pressure waveform) synchronized with the crank angle (CA) can be acquired in each cycle of the internal combustion engine 10. it can. Using the obtained in-cylinder pressure data and the first law of thermodynamics, the in-cylinder heat generation amount Q at an arbitrary crank angle θ can be calculated according to the following equations (1) and (2). The combustion mass ratio (hereinafter referred to as “MFB”) at an arbitrary crank angle θ can be calculated according to the following equation (3) using the calculated in-cylinder heating value Q. In addition, the crank angle (hereinafter referred to as “CAα”) when the MFB is a predetermined ratio α (%) can be acquired by using the equation (3).

In the above equation (1), P is the in-cylinder pressure, 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 (0% combustion point CA0), and θ _max is the combustion end point (100% combustion point CA100).

  Here, a typical crank angle CAα will be described with reference to FIG. Combustion in the cylinder starts with a delay in ignition after the air-fuel mixture is ignited at the ignition timing. The starting point of this combustion, 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. Further, the crank angle CA50 when the MFB is 50% corresponds to the combustion gravity center position.

(Lean limit control using SA-CA10)
FIG. 3 is a diagram showing the relationship between the NOx concentration, fuel consumption, torque fluctuation, and SA-CA10 and the air-fuel ratio (A / F). FIG. 3 shows various characteristics in the lean air-fuel ratio region leaner than the stoichiometric air-fuel ratio. More specifically, this lean air-fuel ratio region is a region on the lean side of the air-fuel ratio of about 16 where the NOx concentration shows a peak. As a fuel efficiency technique for an internal combustion engine, a lean combustion operation performed at an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio is effective. As shown in FIGS. 3A and 3B, the leaner the air-fuel ratio, the better the fuel consumption and the lower the NOx concentration of the exhaust gas. However, if the air-fuel ratio is made too lean, combustion deteriorates and fuel efficiency deteriorates. On the other hand, the torque fluctuation gradually increases as the air-fuel ratio becomes lean, as shown in FIG. 3C, and rapidly increases when the air-fuel ratio exceeds a certain value and becomes lean. The torque fluctuation here is a fluctuation value with respect to a time-series torque value. Hereinafter, the air-fuel ratio at the lean combustion limit of the air-fuel mixture, more specifically, the air-fuel ratio when the torque fluctuation value reaches the threshold value that becomes the limit from the viewpoint of drivability of the internal combustion engine 10 is referred to as “lean limit”.

  3A to 3C, in order to realize low fuel consumption and low NOx emission, the state of the internal combustion engine 10 is monitored, and the air-fuel ratio is as lean as possible within a range in which drivability does not deteriorate. It is preferable to control the air-fuel ratio in the vicinity of the lean limit. Hereinafter, such air-fuel ratio control is referred to as “lean limit control”. In the present embodiment, as such lean limit control, feedback control of the fuel injection amount using the crank angle period (SA-CA10) from the ignition timing (SA) to CA10 which is the 10% combustion point (hereinafter simply referred to as “lean limit control”). “SA-CA10 feedback control”) is performed for each cylinder. Note that the SA-CA10 feedback control is not necessarily executed for each cylinder. That is, 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, You may correct | amend the fuel injection amount of all the cylinders so that calculation SA-CA10 based on the cylinder pressure obtained from a cylinder pressure sensor may approach target SA-CA10.

  Here, an advantage of using SA-CA10 as a parameter of the lean limit control of the present embodiment will be described. SA-CA10 is a parameter representing ignition delay. As shown in FIG. 3D, SA-CA10 has a high correlation with the air-fuel ratio, and maintains a good linearity with respect to the air-fuel ratio even near the lean limit. For this reason, the use of SA-CA10 facilitates feedback control of the air-fuel ratio in the vicinity of the lean limit. More specifically, as shown in FIG. 3D, in the air-fuel ratio region leaner than the stoichiometric air-fuel ratio, there is a relationship that SA-CA10 increases as the air-fuel ratio becomes leaner.

  Further, it can be said that SA-CA10 is more representative of the lean limit than the air-fuel ratio itself for the following reason. That is, the air-fuel ratio that becomes the lean limit changes depending on the operating conditions (for example, the engine water temperature is high or low), but the SA-CA10 is less likely to change depending on the operating conditions than the air-fuel ratio. In other words, since the air-fuel ratio that becomes the lean limit largely depends on the ignition factor of the air-fuel mixture, it can be said that the SA-CA10 that represents the ignition delay is less affected by the operating conditions than the air-fuel ratio itself. However, since the time per crank angle changes when the engine speed changes, the target SA-CA10 that is the target value of SA-CA10 is preferably set according to the engine speed. More preferably, since SA-CA10 also changes depending on the air filling rate (KL) in the cylinder, the target SA-CA10 is set according to the air filling rate instead of or together with the engine rotation speed. And good.

  Next, as a combustion point (first crank angle when MFB becomes a predetermined combustion mass ratio) used to specify a crank angle period as an index of lean limit control of the present embodiment with respect to the ignition timing, CA10 The reason why is preferable compared to other combustion points will be described. The first crank angle is not limited to CA10, and any other combustion point can be used. Even when other arbitrary combustion points are used, the obtained crank angle period basically has the advantages of high correlation with the above-described air-fuel ratio and high representativeness of the lean limit. It can be said that. However, 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 gas 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. In order to eliminate the influence of such disturbance, the configuration in which the crank angle period is corrected in accordance with the above parameters increases the number of man-hours for adaptation. On the other hand, when the combustion point in the initial combustion period (CA0-CA10) is used, the obtained crank angle period is not easily influenced by the above parameters, and the influence of the factors affecting the ignition appears well. It becomes. As a result, controllability is improved. On the other hand, the combustion start point (CA0) and the combustion end point (CA100) are likely to have errors due to the influence of noise superimposed on the output signal from the in-cylinder pressure sensor 30 acquired by the ECU 40. The influence of this noise decreases as the distance from the combustion start point (CA0) or combustion end point (CA100) increases. Therefore, in consideration of noise resistance and reduction in the number of man-hours, it can be said that CA10 is the most excellent as the first crank angle as used in the present embodiment.

(Outline of air-fuel ratio control during lean combustion operation in the first embodiment)
FIG. 4 is a block diagram for explaining the outline of air-fuel ratio control (lean limit control) performed by the ECU 40 during the lean combustion operation in the first embodiment of the present invention. SA-CA10 feedback control, which is control equivalent to lean limit control of the present embodiment, is to adjust the fuel injection amount so that “calculated SA-CA10” approaches “target SA-CA10”. The calculated SA-CA10 here is a crank angle period from the ignition timing to CA10 obtained from the analysis result of the in-cylinder pressure data obtained using the in-cylinder pressure sensor (CPS) 30 and the crank angle sensor 42. It is a calculated value. The target SA-CA10 is a value associated with a predetermined target air-fuel ratio (A / F) near the lean limit under the reference combustion condition. The standard combustion conditions referred to here are conditions for combustion performed when parameters related to combustion such as the tumble ratio and the properties of the fuel used are values as designed.

  More specifically, the configuration of the air-fuel ratio control executed by the ECU 40 can be expressed as shown in FIG. This control configuration includes a combustion mode determination unit 50, a target A / F switching unit 52, a target A / F calculation unit 54 for lean combustion, a basic injection amount calculation unit 56, a target SA-CA10 setting unit 58, and a SA-CA10 calculation. Unit 60, subtraction unit 62, FB correction amount calculation unit 64 of SA-CA10, upper and lower limit guard unit 66 of FB correction amount, addition unit 68, update amount calculation unit 70 of correction amount of target SA-CA10, addition unit 72, And an adder 74.

  The combustion mode determination unit 50 determines the combustion mode corresponding to the current engine operation region based on the engine torque and the engine rotation speed (NE). The target combustion modes are stoichiometric combustion mode in which the in-cylinder air-fuel ratio is controlled to the stoichiometric air-fuel ratio, and lean combustion in which the in-cylinder air-fuel ratio is controlled to an air-fuel ratio larger than the stoichiometric air-fuel ratio (fuel lean). Mode. In the present embodiment, as an example, the lean combustion mode is selected in a low / medium load and low / medium rotation operation region, and the stoichiometric combustion mode is an operation region on a higher load / high rotation side than the operation region in which the lean combustion mode is used. Shall be selected. The engine torque used here corresponds to, for example, target torque or actual torque. The target torque can be calculated based on the accelerator opening. The actual torque can be calculated as a torque estimated to be realized under the current air filling rate and the target air-fuel ratio on the assumption that the optimum ignition timing is used.

  When the combustion mode determination unit 50 determines that the combustion mode to be used in the current operation region is the stoichiometric combustion mode, the target A / F switching unit 52 selects the theoretical air / fuel ratio as the target air / fuel ratio. On the other hand, when the combustion mode determination unit 50 determines that the combustion mode to be used in the current operation region is the lean combustion mode, the target A / F switching unit 52 determines that the lean combustion target A / F calculation unit 54 The value to be calculated is selected as the target air-fuel ratio. Although illustration in FIG. 4 is omitted, when the stoichiometric air-fuel ratio is selected as the target air-fuel ratio, known feedback control, that is, the air-fuel ratio detected by the air-fuel ratio sensor 32 is the target air-fuel ratio. Feedback control of the fuel injection amount is performed so that the fuel ratio becomes the stoichiometric air-fuel ratio.

  The target A / F calculation unit 54 at the time of lean combustion determines a target air-fuel ratio in the operation region using the lean combustion mode based on the air filling rate (KL) and the engine speed (NE). Since this target air-fuel ratio is set in consideration of the NOx concentration and torque fluctuation, it becomes a value within an air-fuel ratio range R1 (a value near the center of the air-fuel ratio range R1) described later with reference to FIG. Instead of the air filling rate, engine torque (target torque or actual torque, etc.) may be used.

  The basic injection amount calculation unit 56 calculates a basic injection amount that is a basic fuel injection amount necessary to realize the target air-fuel ratio output from the target A / F switching unit 52 under the current intake air amount. . A value common to all cylinders is used for this basic injection amount.

  Target SA-CA10 setting unit 58 sets target SA-CA10 based on the air filling rate and the engine speed. The ECU 40 stores a map (not shown) that predetermines the target SA-CA10 based on the relationship between the air filling rate and the engine rotation speed. Here, the target SA-CA10 is referred to with reference to such a map. Is set. More specifically, as shown in FIG. 3D, there is a correlation between the air-fuel ratio and SA-CA10. Here, based on the air filling ratio used in the target A / F calculation unit 54 and the engine rotation speed, the correlation between the air-fuel ratio when the combustion is performed under the standard combustion conditions and the SA-CA10 is used. A target SA-CA10 corresponding to the target air-fuel ratio is set as a value based on the air filling rate and the engine speed. With such a method, the target SA-CA10 is associated with the target air-fuel ratio during the lean combustion operation.

  The SA-CA10 calculation unit 60 calculates the calculated SA-CA10 using the ignition timing (SA) and the analysis result of the in-cylinder pressure detected by the in-cylinder pressure sensor (CPS) 30. Calculation SA-CA10 is calculated for each cycle in each cylinder. The subtractor 62 calculates a difference ΔSA-CA10 between the final target SA-CA10 after passing through an adder 74 described later and the calculated SA-CA10. Here, the difference ΔSA−CA10 is a value obtained by subtracting the target SA−CA10 from the calculated SA−CA10. The difference ΔSA−CA10 is calculated for each cylinder.

  The FB correction amount calculation unit 64 calculates an FB correction amount that is a correction amount of the fuel injection amount for setting the difference ΔSA−CA10 to zero. For example, PI control is used for calculating the FB correction amount. Specifically, the FB correction amount calculation unit 64 uses the difference ΔSA−CA10 and a predetermined PI gain (proportional term gain and integral term gain) according to the difference ΔSA−CA10 and the magnitude of the integrated value. The correction amount of the fuel injection amount is calculated as the FB correction amount. The FB correction amount is calculated for each cylinder.

  The upper / lower limit guard unit 66 performs the FB correction calculated by the FB correction amount calculation unit 64 so that the final FB correction amount to be added to the basic injection amount in the addition unit 68 is a value within a predetermined range. Limit the amount as needed. This predetermined range is defined by an upper limit value and a lower limit value that the upper / lower limit guard unit 66 has. That is, the FB correction amount calculated by the FB correction amount calculation unit 64 is not necessarily added as it is to the basic injection amount, and an FB correction amount outside the predetermined range is input to the upper / lower limit guard unit 66. In this case, the FB correction amount limited to a value equal to the upper limit value or the lower limit value is finally output from the upper / lower limit guard unit 66 to the adding unit 68.

  The final FB correction amount that has passed through the upper / lower limit guard unit 66 is added to the basic injection amount in the adding unit 68, whereby the final fuel injection amount to be injected by the fuel injection valve 26 is determined. By performing such fuel injection amount correction processing for each cylinder, correction of the fuel injection amount for bringing the calculated SA-CA10 closer to the target SA-CA10 is reflected in the fuel injection amount of the target cylinder. . Thereby, the fuel injection amount supplied to each cylinder of the internal combustion engine 10 is adjusted (corrected) by the SA-CA10 feedback control.

  According to the SA-CA10 feedback control described above, by controlling the calculated SA-CA10 so as to approach the target SA-CA10 associated with the target air-fuel ratio, the air-fuel ratio is controlled near the lean limit during the lean combustion operation. can do. As described above, there is a correlation between SA-CA10 and the air-fuel ratio, but SA-CA10 feedback control does not directly control the air-fuel ratio. More specifically, even if the actual SA-CA10 is controlled to the same target SA-CA10, the air-fuel ratio is not always controlled to the same value. The reason is as follows. That is, bringing the actual SA-CA10 closer to the target SA-CA10 by adjusting the fuel injection amount is equivalent to bringing the actual combustion closer to the target combustion. If combustion changes due to various combustion variation factors (for example, variation in tumble flow or variation in properties of fuel used) with respect to the reference combustion condition in which the target SA-CA10 is associated with the air-fuel ratio, SA- Deviation occurs in the correspondence between CA10 and the air-fuel ratio. For example, when the tumble flow changes with respect to the tumble flow under the standard combustion condition and the combustion deteriorates, the fuel injection amount is adjusted by the SA-CA10 feedback control so that the actual combustion approaches the target combustion. As a result, even if the combustion becomes equivalent, the air-fuel ratio becomes a different value. Thus, even if the combustion is appropriately controlled by the SA-CA10 feedback control, the air-fuel ratio may deviate from the target air-fuel ratio. Further, the characteristic change of the in-cylinder pressure sensor 30 used for the calculation of SA-CA10, or the individual difference of the in-cylinder pressure sensor 30 itself, etc., also relates to the relationship between the SA-CA10 and the air-fuel ratio under the reference combustion conditions that are associated with each other. It becomes a factor to change from the relationship.

  Even when the actual SA-CA10 is controlled so as to match the target SA-CA10 by the SA-CA10 feedback control, if the correspondence between the SA-CA10 and the air-fuel ratio is shifted, The fuel ratio will deviate from the originally intended value. If the air-fuel ratio shifts to the rich side during the lean combustion operation, the NOx concentration increases from FIG. Conversely, if the air-fuel ratio shifts to the lean side, there is a concern about an increase in torque fluctuation. Therefore, during lean combustion operation, a high air-fuel ratio controllability that can suitably achieve both NOx emission suppression and torque fluctuation reduction is required.

  Therefore, in the present embodiment, the relationship between the SA-CA10 and the air-fuel ratio changes with respect to the relationship under the associated reference combustion condition in a situation where SA-CA10 feedback control is performed during the lean combustion operation. In order to allow both NOx emission suppression and torque fluctuation reduction to be suitably achieved even under such circumstances, the following control is performed. That is, when the air-fuel ratio detected by the air-fuel ratio (A / F) sensor 32 deviates from the air-fuel ratio range R1 including the target air-fuel ratio during the lean combustion operation during the execution of the SA-CA10 feedback control, the air-fuel ratio. The target SA-CA10 is corrected so that the deviation from the air-fuel ratio range R1 is suppressed. Note that the “air-fuel ratio detected by the air-fuel ratio sensor 32” used in such processing may be the one using the output value of the air-fuel ratio sensor 32 as it is, or converting the output value into an air-fuel ratio. It may be the value after Further, since the air-fuel ratio used for such processing is to detect the air-fuel ratio of the gas subjected to combustion in the cylinder, the exhaust gas to be detected is arranged at the most upstream position as the air-fuel ratio sensor 32 does. It is desirable that the catalyst be upstream of the catalyst (three-way catalyst 34 in the case of the internal combustion engine 10). The same applies to the detection of the NOx concentration in the fifth embodiment described later.

  In order to correct the target SA-CA10, the control configuration illustrated in FIG. 4 includes an update amount calculation unit 70, an addition unit 72, and an addition unit 74. According to this control configuration, the update amount calculation unit 70 calculates the update amount of the correction amount of the target SA-CA10, and the calculated update amount is added to the previous value of the correction amount by the addition unit 72. The previous value here is a value used in the previous cycle of the same cylinder. The correction amount of the target SA-CA10 output from the adding unit 72 is added to the target SA-CA10 set by the target SA-CA10 setting unit 58 in the adding unit 74. Hereinafter, specific correction processing of the target SA-CA10 will be described with reference to FIG.

  FIG. 5 is a diagram showing the setting of the update amount of the correction amount of the target SA-CA10 used in the first embodiment of the present invention. FIG. 5 shows the relationship in the lean air-fuel ratio region leaner than the theoretical air-fuel ratio. The NOx concentration and torque fluctuation in the lean air-fuel ratio region have already been described with reference to FIGS. 3 (A) and 3 (C), but are schematically shown in FIG. That is, if the air-fuel ratio is leaner than a certain level, the NOx concentration of the exhaust gas does not change much with respect to the change in the air-fuel ratio, while if the air-fuel ratio becomes richer than a certain level, the NOx concentration becomes less than the air-fuel ratio. The more it becomes richer, the bigger it becomes. The torque fluctuation has a tendency opposite to that of the NOx concentration, and rapidly increases as the air-fuel ratio approaches the lean limit. From this relationship, an air-fuel ratio range R1 in which the NOx concentration is not more than a predetermined value and the torque fluctuation is not more than a predetermined value is obtained. As described above, the air-fuel ratio range R1 is an air-fuel ratio range in which the NOx concentration and the torque fluctuation are within allowable levels during the lean combustion operation.

  According to the setting shown in FIG. 5, when the air-fuel ratio is within the air-fuel ratio range R1, the update amount of the correction amount of the target SA-CA10 is set to zero. Accordingly, in this case, since the correction amount of the target SA-CA10 is not updated from the previous value, the final target SA-CA10 input to the subtracting unit 62 is not changed from the previous value.

  On the other hand, according to the above setting, when the air-fuel ratio deviates from the air-fuel ratio range R1 to the rich side, a positive update amount is calculated. As a result, the target SA-CA10 is corrected so as to increase. When the target SA-CA10 increases, the fuel injection amount is decreased so that the calculated SA-CA10 approaches the increased target SA-CA10. That is, increasing the target SA-CA10 means that the fuel injection amount is corrected to the decreasing side and the air-fuel ratio is corrected to the lean side. More specifically, the positive update amount is increased as the deviation amount of the air-fuel ratio on the rich side with respect to the lower limit (rich side boundary) of the air-fuel ratio range R1 is increased. As a result, the target SA-CA10 is corrected so as to increase as the shift amount on the rich side increases. For this reason, the larger the deviation amount, the stronger the lean correction of the air-fuel ratio is promoted, and therefore the air-fuel ratio is more positively suppressed from shifting to the rich side than the air-fuel ratio range R1. .

  Further, according to the above setting, when the air-fuel ratio deviates from the air-fuel ratio range R1 to the lean side, a negative update amount is calculated. As a result, the target SA-CA10 is corrected to be small. When the target SA-CA10 decreases, the fuel injection amount is increased so that the calculated SA-CA10 approaches the reduced target SA-CA10. That is, reducing the target SA-CA10 means that the fuel injection amount is corrected to the increase side and the air-fuel ratio is corrected to the rich side. More specifically, as the deviation amount of the air-fuel ratio on the lean side with respect to the upper limit (lean side boundary) of the air-fuel ratio range R1 is larger, the negative update amount is increased on the negative side. As a result, the target SA-CA10 is corrected so as to decrease as the deviation amount on the lean side increases. For this reason, as the deviation amount is larger, rich correction of the air-fuel ratio is more strongly urged, so that the air-fuel ratio shifts more leanly to the lean side than the air-fuel ratio range R1 is more positively suppressed. .

  When a V-type engine is used and an air-fuel ratio sensor is provided for each bank, the update amount of the correction amount of the target SA-CA10 is determined by the output of the air-fuel ratio sensor of each bank. It is better to calculate for each bank accordingly. When the target SA-CA10 is corrected by such a method, the target SA-CA10 that is finally compared with the calculated SA-CA10 also has a different value for each bank.

(Specific processing in Embodiment 1)
FIG. 6 is a flowchart showing a control routine executed by the ECU 40 in order to realize the air-fuel ratio control during the lean combustion operation according to the first embodiment of the present invention. Note that this routine is repeatedly executed for each cycle at a predetermined timing after the end of combustion in each cylinder.

  In the routine shown in FIG. 6, the ECU 40 first executes the process of step 100. The process of step 100 is a process of the combustion mode determination unit 50, and determines whether or not the lean combustion operation is being performed. If it is determined in step 100 that the lean combustion operation is not being performed, the ECU 40 immediately ends the processing in the current processing cycle.

  On the other hand, when it is determined that the lean combustion operation is being performed, the ECU 40 proceeds to step 102. The process of step 102 is a process of the target A / F switching unit 52, and calculates the target air-fuel ratio used for the lean combustion operation. Next, the ECU 40 proceeds to step 104. The process of step 104 is a process of the target A / F calculation unit 54 and the basic injection amount calculation unit 56. In step 104, the calculated value obtained by the processing in step 102 is selected as the target air-fuel ratio for combustion in the next cycle, and the basic injection amount is calculated based on the target air-fuel ratio and the intake air amount.

  Next, the ECU 40 proceeds to step 106. The process of step 106 is a process of the target SA-CA10 setting unit 58, and sets the target SA-CA10 according to the air filling rate and the engine speed. The ECU 40 stores a map (not shown) in which the target SA-CA10 is determined in advance based on the relationship between the air filling rate and the engine speed. In step 106, the target SA-CA10 is set with reference to such a map.

  Next, the ECU 40 proceeds to step 108. The process of step 108 is a process of the update amount calculation unit 70, and calculates the update amount of the correction amount of the target SA-CA10. As shown in FIG. 5, the ECU 40 stores a map in which the relationship between the update amount and the air-fuel ratio is determined in advance. In step 108, the update amount is calculated with reference to such a map. More specifically, the air-fuel ratio used when referring to this map is lower than the instantaneous value of the air-fuel ratio detected by the air-fuel ratio sensor 32, for example, as a countermeasure against noise superimposed on the sensor output. It is preferable to use a value after smoothing processing using a filter or the like. Further, when the air-fuel ratio deviates from the air-fuel ratio range R1, the positive or negative update amount is not calculated immediately, but is positive or negative on the condition that the air-fuel ratio deviates from the air-fuel ratio range R1 for a predetermined time. It is better to calculate a negative update amount. It is preferable to take measures similar to these in Embodiments 2 to 8 described later.

  Next, the ECU 40 proceeds to step 110. The process of step 110 is a process of the adding unit 72, and the correction amount of the target SA-CA10 used in the current processing cycle is obtained by adding the update amount of the correction amount of the target SA-CA10 to the previous value of the correction amount. Is to be calculated. As described above, when the air-fuel ratio is within the air-fuel ratio range R1, the update amount is set to zero, so the correction amount is not substantially updated. On the other hand, when the air-fuel ratio deviates from the air-fuel ratio range R1 to the rich side or the lean side, a positive or negative update amount is calculated, so that the correction amount is updated in the current processing cycle.

  Next, the ECU 40 proceeds to step 112. The process of step 112 is a process of the adding unit 74, and the correction amount of the target SA-CA10 after passing through the adding unit 72 is added to the target SA-CA10 set by the target SA-CA10 setting unit 58. To calculate the final target SA-CA10.

  Next, the ECU 40 proceeds to step 114 and uses the in-cylinder pressure sensor 30 and the crank angle sensor 42 to acquire in-cylinder pressure data measured during combustion in the current cycle. Next, the ECU 40 proceeds to step 116. The process of step 116 is a process of the SA-CA10 calculation unit 60, and calculates the calculated SA-CA10. More specifically, as the ignition timing used for calculating the calculated SA-CA10, for example, the target ignition timing used in the current cycle can be used. The 10% combustion point CA10 can be acquired by using the analysis result (MFB waveform) of the in-cylinder pressure data.

  Next, the ECU 40 proceeds to step 118. The process of step 116 is a process of the subtracting unit 62 and calculates the difference ΔSA−CA10. Next, the ECU 40 proceeds to step 120. The process of step 120 is a process of the FB correction amount calculation unit 64, and calculates an FB correction amount that is a correction amount of the fuel injection amount for making the difference ΔSA−CA10 zero. Specifically, when the calculated SA-CA10 is larger than the target SA-CA10 (that is, when the difference ΔSA-CA10 is a positive value), the air-fuel ratio is shifted to the lean side from the target air-fuel ratio. Therefore, a positive FB correction amount (that is, an FB correction amount for correcting the fuel injection amount to the increasing side and correcting the air-fuel ratio to the rich side) is calculated. Conversely, when the calculated SA-CA10 is smaller than the target SA-CA10 (that is, when the difference ΔSA-CA10 is a negative value), the air-fuel ratio is shifted to the rich side from the target air-fuel ratio. Therefore, a negative FB correction amount (that is, an FB correction amount for correcting the fuel injection amount to the decreasing side and correcting the air-fuel ratio to the lean side) is calculated. When the calculated SA-CA10 is equal to the target SA-CA10, the FB correction amount becomes zero.

  Next, the ECU 40 proceeds to step 122. The process of step 122 is a process of the upper / lower limit guard unit 66, and acquires the final FB correction amount. The final FB correction amount is basically the FB correction amount calculated by the processing of step 120, but the FB correction amount is a value exceeding the upper limit value or the lower limit value of the upper / lower limit guard unit 66. Is equal to the upper limit value or the lower limit value.

  Next, the ECU 40 proceeds to step 124. The process of step 124 is a process of the adding unit 68, and adds the final FB correction amount acquired in step 122 to the basic injection amount calculated in step 104. The final fuel injection amount calculated by this processing is used in the next cycle.

  According to the routine shown in FIG. 6 described above, the fuel injection amount feedback control is executed so that the calculated SA-CA10 approaches the target SA-CA10. As described above, SA-CA10 has linearity with respect to the air-fuel ratio even near the lean limit. Unlike the method of the present embodiment, when the fuel injection amount is adjusted so that the first crank angle becomes a certain target value using only the first crank angle when the predetermined combustion mass ratio is obtained. Has the following problems. That is, when the ignition timing changes, the first crank angle when a predetermined combustion mass ratio is obtained changes accordingly. On the other hand, even if the ignition timing changes, the crank angle period from the ignition timing to the first crank angle hardly changes. Therefore, by using the crank angle period (SA-CA10 in the present embodiment) as an index for adjusting the fuel injection amount, the influence of the ignition timing is eliminated as compared with the case where only the first crank angle is used. Thus, the correlation with the air-fuel ratio can be properly grasped.

  In addition, according to the above routine, when the air-fuel ratio deviates from the air-fuel ratio range R1 during the execution of the SA-CA10 feedback control, the target SA-CA10 is corrected. More specifically, when the air-fuel ratio deviates from the air-fuel ratio range R1 to the rich side, the target SA-CA10 is increased to promote lean correction of the air-fuel ratio, while the air-fuel ratio falls from the air-fuel ratio range R1. When the value deviates to the lean side, the target SA-CA10 is reduced in order to promote rich correction of the air-fuel ratio. Thus, even when the calculated SA-CA10 is appropriately controlled in the vicinity of the target SA-CA10, the relationship between the SA-CA10 and the air-fuel ratio is changed due to factors such as changes in combustion conditions. Thus, it is possible to prevent the air-fuel ratio from deviating from the air-fuel ratio range R1 near the target air-fuel ratio. That is, by monitoring the air-fuel ratio using the air-fuel ratio sensor 32, it becomes possible to cope with changes in the air-fuel ratio that cannot be noticed only by executing the SA-CA10 feedback control. In addition, since the air-fuel ratio detected by the air-fuel ratio sensor 32 is given to the SA-CA10 feedback control, the combustion targeted for actual combustion while the air-fuel ratio is reliably kept within the air-fuel ratio range R1. SA-CA10 feedback control can be executed so as to be close to. Further, the limit of NOx emission and the limit of torque fluctuation can be managed by the air-fuel ratio. According to the control of the present embodiment described above, the SA-CA10 and the air-fuel ratio with respect to the relationship under the reference combustion conditions with which the association is performed in the situation where the SA-CA10 feedback control is performed during the lean combustion operation. Even in a situation where the relationship between and NOx changes, it is possible to suitably achieve both NOx emission suppression and torque fluctuation reduction.

  Moreover, since the method of this embodiment corrects the target value itself of SA-CA10 feedback control, the control is rational compared with the methods of other Embodiments 2 to 4. And according to this method, since it becomes clear what value it is going to control SA-CA10, it can be said that the expansibility and expandability of control are high.

  By the way, in Embodiment 1 described above, when the air-fuel ratio deviates from the air-fuel ratio range R1 to the rich side, the target SA-CA10 is increased, and when the air-fuel ratio deviates from the air-fuel ratio range R1 to the lean side. Is to reduce the target SA-CA10. However, the correction of the target crank angle period in the present invention is not necessarily performed when the air-fuel ratio deviates from the air-fuel ratio range to either the rich side or the lean side, and the air-fuel ratio is not limited to the rich side and the lean side. It may be implemented only when one of the above is deviated.

  In the first embodiment described above, CA10 is the “first crank angle” according to the present invention, calculated SA-CA10 is the “calculated crank angle period” according to the present invention, and target SA-CA10 is the “target crank angle” according to the present invention. In the “crank angle period”, the air-fuel ratio range R1 corresponds to the “air-fuel ratio range” in the present invention. Further, the ECU 40 detects the air-fuel ratio using the air-fuel ratio sensor 32 to realize the “air-fuel ratio detecting means” in the present invention. The ECU 40 detects the crank angle using the crank angle sensor 42, thereby The “crank angle detection means” in the present invention is realized, and the combustion mass ratio (MFB) is calculated using the in-cylinder pressure data during the combustion period acquired by the ECU 40 using the in-cylinder pressure sensor 30 and the crank angle sensor 42. Thus, the “combustion mass ratio calculation means” in the present invention is realized, and the “first crank angle acquisition means” in the present invention is realized by the ECU 40 using the calculation result of the combustion mass ratio to acquire CA10. The ECU 40 executes the processing of the above steps 118 to 124, whereby the “adjustment means” in the present invention. Is achieved and, then, ECU 40 is "changing means" is realized in the first aspect of the present invention by executing the process of step 108-112.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.

[Control of Embodiment 2]
(Outline of air-fuel ratio control during lean combustion operation in Embodiment 2)
The present embodiment is different from the first embodiment in that the control configuration shown in FIG. 7 is used instead of the control configuration shown in FIG. 4 when controlling the internal combustion engine 10 described above. The control according to the present embodiment performs fuel injection when the air-fuel ratio detected by the air-fuel ratio sensor 32 deviates from the air-fuel ratio range R1 under the condition where SA-CA10 feedback control is performed during the lean combustion operation. The control range of the FB correction amount is limited by correcting the upper and lower limit values of the amount of FB correction amount, thereby suppressing the air-fuel ratio from deviating from the air-fuel ratio range R1.

  FIG. 7 is a block diagram for explaining an outline of air-fuel ratio control (lean limit control) performed by the ECU 40 during the lean combustion operation in the second embodiment of the present invention. In the control configuration shown in FIG. 7, instead of the update amount calculation unit 70, the addition unit 72, and the addition unit 74 described above, an update amount calculation unit 76 for correction amounts of upper and lower limit values and addition units 78, 80, 82, and 84 The control configuration is the same as that shown in FIG. 4 except that it is provided.

  Also in the control configuration shown in FIG. 7, the air-fuel ratio detected by the air-fuel ratio sensor 32 is used while executing the SA-CA10 feedback control, as in the control configuration shown in FIG. However, in the control configuration shown in FIG. 7, the air-fuel ratio detected by the air-fuel ratio sensor 32 is input to the update amount calculation unit 76.

  The update amount calculation unit 76 calculates the update amounts of the correction amounts of the upper limit value and the lower limit value for the FB correction amount of the fuel injection amount. The calculated update amount of the upper limit correction amount is added to the previous correction amount by the adding unit 78. The correction amount of the upper limit value output from the adding unit 78 is added to the base value of the upper limit value in the adding unit 80. Thereby, the final upper limit value is calculated. Similarly, the calculated update amount of the lower limit correction amount is added to the previous correction amount by the adding unit 82. The correction amount of the lower limit value output from the adding unit 82 is added to the base value of the lower limit value in the adding unit 84. Thereby, the final lower limit value is calculated. Hereinafter, specific correction processing of the upper and lower limit values will be described with reference to FIG.

  FIG. 8 is a diagram showing the setting of the update amount of the correction amount of the upper and lower limit values for the FB correction amount used in the second embodiment of the present invention. The relationship between the NOx concentration and torque fluctuation in the lean air-fuel ratio region shown in FIG. 8 and the air-fuel ratio is the same as that shown in FIG.

  According to the setting shown in FIG. 8, when the air-fuel ratio is within the air-fuel ratio range R1, the update amount of the correction amount of the upper and lower limit values (guard value) is set to zero. Therefore, in this case, since the upper and lower limit correction amounts are not updated from the previous value, the final upper and lower limit values input to the upper and lower limit guard unit 66 are not changed from the previous value.

  On the other hand, according to the above setting, when the air-fuel ratio deviates from the air-fuel ratio range R1, the negative update amount is calculated for the upper limit value, while the update amount of the lower limit correction amount is Zero. As a result, the upper limit value is corrected to be smaller, but the lower limit value is not updated. When the upper limit value of the FB correction amount is small, it is limited that the fuel injection amount is greatly increased. In other words, reducing the upper limit value reduces the upper limit of the absolute value of the FB correction amount used when the calculated SA-CA10 is reduced (that is, when the air-fuel ratio is made rich), and therefore the air-fuel ratio is made rich. It means not to correct too much to the side. The setting shown in FIG. 8 will be described in more detail. As the deviation amount of the air-fuel ratio on the rich side with respect to the lower limit (rich-side boundary) of the air-fuel ratio range R1 is larger, the negative update amount is increased on the minus side. The As a result, the upper limit value is corrected so as to decrease as the deviation amount on the rich side increases. For this reason, the larger the deviation amount, the more actively the deviation of the air-fuel ratio toward the rich side is suppressed.

  Further, according to the above setting, when the air-fuel ratio deviates from the air-fuel ratio range R1, the positive update amount is calculated for the lower limit value, while the update amount of the upper limit correction amount is Zero. As a result, the lower limit is corrected so as to increase (decrease on the minus side), but the upper limit is not updated. When the lower limit value of the FB correction amount is increased, it is limited to greatly reduce the fuel injection amount. In other words, increasing the lower limit value means reducing the upper limit of the absolute value of the FB correction amount used when the calculated SA-CA10 is increased (that is, when the air-fuel ratio is made lean). It means not to correct too much to the side. The setting shown in FIG. 8 will be described in more detail. The larger the deviation amount of the air-fuel ratio on the lean side with respect to the upper limit (lean side boundary) of the air-fuel ratio range R1, the larger the positive update amount. As a result, the lower limit value is corrected so as to increase as the deviation amount on the lean side increases. For this reason, the larger the deviation amount, the more actively the deviation of the air-fuel ratio toward the lean side is suppressed.

  When a V-type engine is used and an air-fuel ratio sensor is provided for each bank, the update amount of the upper / lower limit correction amount depends on the output of the air-fuel ratio sensor of each bank. It is better to calculate for each bank. When the target SA-CA10 is corrected by such a method, the target SA-CA10 that is finally compared with the calculated SA-CA10 also has a different value for each bank.

(Specific processing in Embodiment 2)
FIG. 9 is a flowchart showing a control routine executed by the ECU 40 in order to realize the air-fuel ratio control during the lean combustion operation according to the second embodiment of the present invention. In FIG. 9, the same steps as those shown in FIG. 6 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 9, the ECU 40 proceeds to step 200 after calculating the FB correction amount in step 120. The process of step 200 is a process of the update amount calculation unit 76, and calculates the update amount of the correction amount for the upper and lower limit values of the FB correction amount. The ECU 40 stores a map in which the relationship between the update amount and the air-fuel ratio is determined in advance as shown in FIG. In this step 200, the update amount is calculated with reference to such a map.

  Next, the ECU 40 proceeds to step 202. The process of step 202 is the process of the addition unit 78 and the addition unit 82, and is used in the current processing cycle by adding the update amount of each correction amount of the upper limit value and the lower limit value to the previous value of each correction amount. The correction amount of the lower limit value is calculated. As described above, the upper limit correction amount is updated only when the air-fuel ratio deviates from the air-fuel ratio range R1 on the rich side, while the lower limit correction amount is lower than the air-fuel ratio range R1. Will be updated only when it goes off to the lean side.

  Next, the ECU 40 proceeds to step 204. The process of step 204 is the process of the addition unit 80 and the addition unit 84, and the correction amount of the upper and lower limit values after passing through the addition unit 78 and the addition unit 82 is added to the base values of the upper limit value and the lower limit value, respectively. By doing so, the final upper limit value and lower limit value are respectively calculated. Next, the final fuel injection amount used in the next cycle is calculated using the FB correction amount within the range limited by the final upper and lower limit values calculated by such a method ( Steps 122 and 124).

  According to the routine shown in FIG. 9 described above, when the air-fuel ratio deviates from the air-fuel ratio range R1 during the execution of the SA-CA10 feedback control, the upper and lower limit values of the FB correction amount of the fuel injection amount are corrected. . More specifically, when the air-fuel ratio deviates from the air-fuel ratio range R1 to the rich side, the upper limit value is reduced to limit the rich correction of the air-fuel ratio, while the air-fuel ratio is lean from the air-fuel ratio range R1. If it deviates, the lower limit value is increased in order to limit the lean correction of the air-fuel ratio. Even when the control range of the FB correction amount is limited by the method of the present embodiment, the calculated SA-CA10 is appropriately controlled in the vicinity of the target SA-CA10, but the SA is caused by factors such as changes in combustion conditions. -Even under a situation where the relationship between CA10 and the air-fuel ratio is changing, it is possible to suppress the air-fuel ratio from deviating from the air-fuel ratio range R1 near the target air-fuel ratio.

  In the method of the present embodiment, the SA-CA10 feedback control itself is continued while the control range of the FB correction amount is limited. For this reason, it becomes possible to bring the target combustion closer to the target combustion by the SA-CA10 feedback control while keeping the air-fuel ratio within the range due to the above limitation. By continuing the SA-CA10 feedback control, it becomes possible to maintain the air-fuel ratio in a more appropriate air-fuel ratio range as compared with the method of the fourth embodiment (prohibition of SA-CA10 feedback) described later. Furthermore, since it is possible to maintain the air-fuel ratio in an appropriate air-fuel ratio range as compared with the case where the SA-CA10 feedback control is prohibited, it is possible to easily suppress NOx emission. For this reason, compared with the case where the SA-CA10 feedback control is prohibited, it is possible to secure a reduction in the execution frequency of the rich spike for purifying NOx, that is, the execution frequency of the lean combustion operation.

  By the way, in Embodiment 2 described above, when the air-fuel ratio deviates from the air-fuel ratio range R1 to the rich side, the upper limit value of the FB correction amount is reduced, and the air-fuel ratio deviates from the air-fuel ratio range R1 to the lean side. In some cases, the lower limit is increased. However, the correction of the upper and lower limit values of the correction amount in the present invention is not necessarily limited to that performed when the air-fuel ratio deviates from the air-fuel ratio range to either the rich side or the lean side. It may be implemented only when it is off to either one of the lean side.

  In the second embodiment described above, the “changing means” in the first aspect of the present invention is realized by the ECU 40 executing the processing of steps 200 to 204 described above.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIGS. 10 and 11 again.

[Control of Embodiment 3]
(Outline of air-fuel ratio control in Embodiment 3)
The present embodiment is different from the first embodiment in that the control configuration shown in FIG. 10 is used instead of the control configuration shown in FIG. 4 when controlling the internal combustion engine 10 described above. The control according to the present embodiment is performed when the air-fuel ratio detected by the air-fuel ratio sensor 32 deviates from the air-fuel ratio range R1 in a situation where SA-CA10 feedback control is performed during the lean combustion operation. Combustion operation is prohibited.

  FIG. 10 is a block diagram for explaining the outline of the air-fuel ratio control performed by the ECU 40 in the third embodiment of the present invention. The control configuration shown in FIG. 10 deletes the correction amount update amount calculation unit 70 and the addition units 72 and 74 of the target SA-CA 10 from the control configuration shown in FIG. 4 and replaces the target A / F switching unit 52 with it. This corresponds to the one provided with the target A / F switching unit 86.

  An air-fuel ratio detected by the air-fuel ratio sensor 32 is input to the target A / F switching unit 86. The target A / F switching unit 86 functions in the same manner as the target A / F switching unit 52 when the air-fuel ratio during the lean combustion operation is within the air-fuel ratio range R1. That is, when the combustion mode determined by the combustion mode determination unit 50 is the lean combustion mode, if the air-fuel ratio is within the air-fuel ratio range R1, the lean combustion mode as determined is finally set. select. Thereby, the lean combustion operation with SA-CA10 feedback control is executed as usual. On the other hand, even if the combustion mode corresponding to the current engine operation region is the lean combustion mode, the target A / F switching unit 86 is in the case where the air-fuel ratio is out of the air-fuel ratio range R1, Finally, the stoichiometric combustion mode is selected without selecting the lean combustion mode. As a result, the lean combustion operation is prohibited and the stoichiometric combustion operation is executed.

(Specific processing in Embodiment 3)
FIG. 11 is a flowchart showing a control routine executed by the ECU 40 in order to realize air-fuel ratio control according to Embodiment 3 of the present invention. In FIG. 11, the same steps as those shown in FIG. 6 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 9, the ECU 40 first executes the process of step 300. The process of step 300 is a process of the combustion mode determination unit 50, and determines whether or not the combustion mode corresponding to the current engine operating region is the lean combustion mode based on the engine torque and the engine speed. It is.

  If the determination in step 300 is not established, that is, if it is determined that the combustion mode corresponding to the current engine operation region is the stoichiometric combustion mode, the ECU 40 proceeds to step 302. In step 302, various processes for stoichiometric combustion operation (setting of target air-fuel ratio, calculation of basic injection amount, air-fuel ratio feedback control using air-fuel ratio sensor 32, etc.) are executed.

  On the other hand, when it is determined in step 300 that the lean combustion mode is set, the ECU 40 proceeds to step 304. The process of step 304 is a process of the target A / F switching unit 86, and determines whether or not the air-fuel ratio detected by the air-fuel ratio sensor 32 is within the air-fuel ratio range R1 (see FIG. 5). is there.

  If it is determined in step 304 that the air-fuel ratio is within the air-fuel ratio range R1, the ECU 40 finally selects the lean combustion mode, and executes a series of processes from step 102 onward. As a result, the lean combustion operation with SA-CA10 feedback control is executed.

  On the other hand, if the determination in step 304 is not satisfied, that is, if it is determined that the air-fuel ratio is out of the air-fuel ratio range R1, the ECU 40 finally selects the stoichiometric combustion mode instead of the lean combustion mode. Then, the process proceeds to Step 302. As a result, the execution of the lean combustion operation is prohibited, and the stoichiometric combustion operation is executed instead.

  According to the routine shown in FIG. 11 described above, when the air-fuel ratio deviates from the air-fuel ratio range R1 during the execution of the SA-CA10 feedback control, the lean combustion operation is prohibited and the lean combustion operation is switched to the stoichiometric combustion operation. Is switched. Since the lean combustion operation itself is not performed, it can be avoided that the air-fuel ratio shifts to the rich side or the lean side from the air-fuel ratio range R1 in the lean combustion operation region. For this reason, it is possible to suppress an increase in NOx emission amount or an increase in torque fluctuation due to such a deviation in air-fuel ratio. Further, unlike the methods of the first and second embodiments, this method cannot be performed while continuing the lean combustion operation with SA-CA10 feedback control, but the control configuration is prohibited in order to prohibit the lean combustion operation itself. It can be simplified.

  Incidentally, in the above-described third embodiment, the lean combustion operation is prohibited even when the air-fuel ratio deviates from the air-fuel ratio range R1 to either the rich side or the lean side. However, the prohibition of the lean combustion operation in the present invention may be implemented only when the air-fuel ratio deviates to one of the rich side and the lean side instead of the above.

  In the third embodiment described above, the “first prohibiting means” according to the third aspect of the present invention is realized by the ECU 40 executing the process of step 302 when the determination of step 304 is not established. Has been.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIGS.

[Control of Embodiment 4]
(Outline of air-fuel ratio control during lean combustion operation in Embodiment 4)
The present embodiment is different from the first embodiment in that the control configuration shown in FIG. 12 is used instead of the control configuration shown in FIG. 4 when controlling the internal combustion engine 10 described above. The control according to the present embodiment is performed when the air-fuel ratio detected by the air-fuel ratio sensor 32 deviates from the air-fuel ratio range R1 in a situation where the SA-CA10 feedback control is performed during the lean combustion operation. -Execution of CA10 feedback control is prohibited. In addition, the target air-fuel ratio during which SA-CA10 feedback control is prohibited is set to a richer value than the value during execution of SA-CA10 feedback control.

  FIG. 12 is a block diagram for explaining an overview of air-fuel ratio control (lean limit control) performed by the ECU 40 during the lean combustion operation in the fourth embodiment of the present invention. In the control configuration shown in FIG. 12, the correction amount update amount calculation unit 70 and the addition units 72 and 74 of the target SA-CA 10 are deleted from the control configuration shown in FIG. 4, and the target A / F calculation unit 54 is used instead. This corresponds to an A / F calculation unit 88 and an FB correction amount calculation unit 90 instead of the FB correction amount calculation unit 64.

  The air-fuel ratio detected by the air-fuel ratio sensor 32 is input to the target A / F calculation unit 88 and the FB correction amount calculation unit 90, respectively. The target A / F calculation unit 88 functions in the same manner as the target A / F calculation unit 54 when the air-fuel ratio during the lean combustion operation is within the air-fuel ratio range R1. That is, the target air-fuel ratio is determined as usual based on the air filling rate (KL) and the engine speed (NE). On the other hand, when the air-fuel ratio is out of the air-fuel ratio range R1, the target A / F calculation unit 88 sets the value used when the air-fuel ratio during the lean combustion operation is within the air-fuel ratio range R1. On the other hand, a value on the rich side by a predetermined margin within the air-fuel ratio range R1 is set as the target air-fuel ratio.

  The FB correction amount calculation unit 90 functions in the same manner as the FB correction amount calculation unit 64 when the air-fuel ratio during the lean combustion operation is within the air-fuel ratio range R1. That is, in this case, in order to perform SA-CA10 feedback control, an FB correction amount that is a fuel injection amount correction amount for making the difference ΔSA-CA10 zero is calculated as usual. On the other hand, when the air-fuel ratio is out of the air-fuel ratio range R1, the FB correction amount calculation unit 90 outputs the FB correction amount to the upper / lower limit guard unit 66 as zero. When this process is performed, the fuel injection amount is not corrected using the SA-CA 10, and the final fuel injection amount remains the basic injection amount. That is, SA-CA10 feedback control is prohibited, and the fuel injection amount is adjusted by open loop control. However, unlike Embodiment 3 described above, in this embodiment, the lean combustion operation itself is continued even when the air-fuel ratio is outside the air-fuel ratio range R1.

  Further, the air-fuel ratio range R1 used in the present embodiment may be set based on the concept described above with reference to FIG. 5, but is preferably set based on the following viewpoints. is there. That is, the variation range of the air-fuel ratio assumed during the execution of the SA-CA10 feedback control is obtained in advance in consideration of variations in various components of the internal combustion engine 10, individual differences in the in-cylinder pressure sensor 30, and the like. The air-fuel ratio range R1 is preferably set so as to correspond to the air-fuel ratio range. When the air-fuel ratio deviates from the set air-fuel ratio range R1, it is preferable to determine that the in-cylinder pressure sensor 30 is abnormal and prohibit the SA-CA10 feedback control.

(Specific processing in Embodiment 4)
FIG. 13 is a flowchart showing a control routine executed by the ECU 40 in order to realize the air-fuel ratio control during the lean combustion operation according to the fourth embodiment of the present invention. In FIG. 13, the same steps as those shown in FIG. 6 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 13, the ECU 40 proceeds to step 400 after determining that the lean combustion operation is being performed in step 100. In step 400, it is determined whether or not the air-fuel ratio detected by the air-fuel ratio sensor 32 is within the air-fuel ratio range R1 (see FIG. 5).

  When it is determined in step 400 that the air-fuel ratio is within the air-fuel ratio range R1, the ECU 40 executes a series of processes after step 102. As a result, the SA-CA10 feedback control is executed as usual.

  On the other hand, if the determination in step 400 is not satisfied, that is, if it is determined that the air-fuel ratio is outside the air-fuel ratio range R1, the ECU 40 proceeds to step 402. The process of step 402 is a process of the target A / F calculation unit 88, and a value on the rich side within the air-fuel ratio range R1 by a predetermined margin is calculated as the target air-fuel ratio with respect to the value calculated in step 102. To do. Next, the ECU 40 proceeds to step 404 and calculates the basic injection amount using the target air-fuel ratio calculated in step 402. Next, the ECU 40 proceeds to step 406. The process of step 406 is a process of the FB correction amount calculation unit 90 and calculates the FB correction amount as zero. After executing the process of step 406, the ECU 40 proceeds to step 122.

  According to the routine shown in FIG. 13 described above, when the air-fuel ratio deviates from the air-fuel ratio range R1 during execution of the SA-CA10 feedback control, the FB correction amount is set to zero, so that the SA-CA10 feedback is performed. Execution of control is prohibited. Thereby, it can be avoided that the air-fuel ratio shifts to the rich side or the lean side from the air-fuel ratio range R1 by the action of the SA-CA10 feedback control. For this reason, it is possible to suppress an increase in NOx emission amount or an increase in torque fluctuation due to such a deviation in air-fuel ratio. Unlike the first and second embodiments, this method cannot be performed while continuing SA-CA10 feedback control. However, unlike the first embodiment, the lean combustion operation is continued. . For this reason, it is possible to ensure a high frequency of lean combustion operation. Note that the prohibition of the SA-CA10 feedback control in the present embodiment can be said to correspond to the FB correction amount upper and lower limit values in the second embodiment narrowed to the limit.

  Further, according to the above routine, the target air-fuel ratio when SA-CA10 feedback control is prohibited is a predetermined margin within the air-fuel ratio range R1 with respect to the value when SA-CA10 feedback control is executed. Only set to the rich side. As a result, in a situation where feedback control that leads to control of the air-fuel ratio is not executed, lean combustion is more reliably suppressed while suppressing an increase in torque fluctuation and occurrence of misfire more reliably than when the target air-fuel ratio is not changed. You will be able to continue driving.

  By the way, in the above-described fourth embodiment, SA-CA10 feedback control is prohibited even when the air-fuel ratio deviates from the air-fuel ratio range R1 to either the rich side or the lean side. However, the prohibition of adjustment by the adjusting means in the present invention may be implemented only when the air-fuel ratio deviates to either the rich side or the lean side, instead of the above.

  In the fourth embodiment described above, the “second prohibiting means” according to the fourth aspect of the present invention is realized by the ECU 40 executing the process of step 406 when the determination of step 400 fails. Has been.

Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIGS.

[System Configuration of Embodiment 5]
FIG. 14 is a diagram for describing a system configuration of internal combustion engine 100 according to the fifth embodiment of the present invention. An internal combustion engine 100 shown in FIG. 14 includes a NOx sensor 102 for detecting the NOx concentration of the exhaust gas in the exhaust passage 18 upstream of the three-way catalyst 34 instead of the air-fuel ratio sensor 32. Except for this point, the internal combustion engine 100 is configured similarly to the internal combustion engine 10 shown in FIG. More specifically, the NOx sensor 102 used here is a known NOx sensor that also has a function of detecting the oxygen concentration of the exhaust gas, and according to the oxygen concentration of the exhaust gas, as with the air-fuel ratio sensor 32 described above. Output is also possible. For this reason, the ECU 40 can detect not only the NOx concentration but also the air-fuel ratio based on the output of the NOx sensor 102.

[Control of Embodiment 5]
(Outline of air-fuel ratio control during lean combustion operation in the fifth embodiment)
Although illustration is omitted, the control configuration of the present embodiment is basically the same as the control configuration shown in FIG. 4 in the first embodiment. However, in this control configuration, the parameter input to the update amount calculation unit 70 for the correction amount of the target SA-CA10 is the NOx concentration detected by the NOx sensor 102 instead of the air-fuel ratio detected by the air-fuel ratio sensor 32. There is a difference from the control configuration shown in FIG.

  FIG. 15 is a diagram showing the setting of the update amount of the correction amount of the target SA-CA10 used in the fifth embodiment of the present invention. In the present embodiment, the NOx concentration detected by the NOx sensor 102 is used to calculate the update amount of the correction amount of the target SA-CA10. Specifically, the predetermined value V1 shown in FIG. 15 is a value corresponding to the NOx concentration at the lower limit (rich side boundary) of the air-fuel ratio range R1 shown in FIG. 5 of the first embodiment. The predetermined value V1 is a value higher than the NOx concentration of the exhaust gas discharged under combustion at the target air-fuel ratio in the lean combustion operation. It should be noted that the “NOx concentration detected by the NOx sensor 102” used for such processing may be a value obtained by using the output value of the NOx sensor 102 as it is, or after the output value is converted into the NOx concentration. May be the value.

  There is a relationship as shown in FIG. 5 and the like between the NOx concentration and the air-fuel ratio. For this reason, the fact that the NOx concentration is larger than the predetermined value V1 corresponds to the air-fuel ratio deviating to the rich side from the air-fuel ratio when the NOx concentration becomes the predetermined value V1. According to the setting shown in FIG. 15, when the NOx concentration is equal to or lower than the predetermined value V1, that is, when it is not recognized that the air-fuel ratio shifts to the rich side from the air-fuel ratio when the NOx concentration becomes the predetermined value V1. The update amount is zero. Therefore, in this case, the final target SA-CA10 input to the subtracting unit 62 is not changed from the previous value.

  On the other hand, according to the above setting, when the NOx concentration is higher than the predetermined value V1, a positive update amount is calculated. As a result, as already described in the first embodiment, the target SA-CA10 is corrected so as to increase. As a result, the air-fuel ratio is suppressed from shifting to a richer side than the air-fuel ratio when the NOx concentration becomes the predetermined value V1. More specifically, in the example shown in FIG. 15, the update amount is increased as the NOx concentration is higher than the predetermined value V1. As a result, as described above, the target SA-CA10 is corrected so as to increase as the NOx concentration increases with respect to the predetermined value V1, that is, as the deviation amount of the air-fuel ratio to the rich side increases. For this reason, it is more positively suppressed that the air-fuel ratio shifts to the rich side from the air-fuel ratio when the NOx concentration becomes the predetermined value V1.

(Specific processing in the fifth embodiment)
The air-fuel ratio control during the lean combustion operation according to the present embodiment can be realized by causing the ECU 40 to execute a routine process similar to the routine shown in FIG. More specifically, instead of the process of step 108, a process for calculating the update amount from the detected NOx concentration using a map in which the relationship between the update amount and the NOx concentration as shown in FIG. 15 is determined in advance. Should be done.

  According to the control of the fifth embodiment described above, when the NOx concentration becomes higher than the predetermined value V1 during the execution of the SA-CA10 feedback control, the target SA-CA10 is used to prompt the air-fuel ratio lean correction. Is increased. Thus, even when the calculated SA-CA10 is appropriately controlled in the vicinity of the target SA-CA10, the relationship between the SA-CA10 and the air-fuel ratio is changed due to factors such as changes in combustion conditions. The NOx concentration detected by the NOx sensor 102 is used to make the NOx concentration higher than the predetermined value V1 (more specifically, on the rich side from the air-fuel ratio when the NOx concentration becomes the predetermined value V1. It is possible to suppress the deviation of the air-fuel ratio). In other words, by monitoring the NOx concentration of the exhaust gas using NOx92, it becomes possible to cope with a change in the air-fuel ratio that cannot be noticed only by executing the SA-CA10 feedback control. According to the control of the present embodiment described above, the SA-CA10 and the air-fuel ratio with respect to the relationship under the reference combustion conditions with which the association is performed in the situation where the SA-CA10 feedback control is performed during the lean combustion operation. NOx emissions can be suitably suppressed even in a situation where the relationship with the above is changing.

  In order to determine whether or not the air-fuel ratio has shifted to a richer side than the air-fuel ratio when the NOx concentration reaches the predetermined value V1 during execution of the SA-CA10 feedback control, the air-fuel ratio as in the first embodiment or the like is determined. It can be said that the method of using the NOx sensor 102 as in the present embodiment is preferable to the method of using the sensor 32 for the following reason. In the case of the method using the air-fuel ratio sensor 32, the relationship between the air-fuel ratio and the NOx concentration as shown in FIG. However, the relationship between the air-fuel ratio and the NOx concentration may vary. Therefore, in order to determine whether or not the air-fuel ratio has shifted to a richer side than the air-fuel ratio when the NOx concentration reaches the predetermined value V1, it is better to directly detect the NOx concentration using the NOx sensor 102. It can be said that it is accurate.

  By the way, in the above-described fifth embodiment, during the execution of the SA-CA10 feedback control, the target SA-CA10 is corrected according to the determination result using the NOx concentration detected by the NOx sensor 102. The air-fuel ratio is prevented from shifting to a richer side than the air-fuel ratio when the NOx concentration reaches the predetermined value V1. In order to prevent the air-fuel ratio from deviating from the air-fuel ratio when the torque fluctuation becomes the allowable limit value with respect to such processing, the detected value of the air-fuel ratio as described in the first embodiment. You may make it combine the process which correct | amends target SA-CA10 according to the determination result using these. Specifically, a predetermined value corresponding to the upper limit (lean side boundary) of the air-fuel ratio range R1 is prepared, and when the detected value of the air-fuel ratio becomes larger than the predetermined value, the target SA-CA10 is set. What is necessary is just to combine the process to make small. If the NOx sensor 102 of this embodiment is used, not only the NOx concentration but also the air-fuel ratio can be detected. For this reason, the rich side and lean side processes may be performed using the NOx sensor 102. The same applies to the processing of Embodiments 6 to 8 described later. If a NOx sensor that cannot detect both NOx concentration and air-fuel ratio is used, an air-fuel ratio sensor may be used in combination.

  In the fifth embodiment described above, the predetermined value V1 corresponds to the “predetermined value” in the present invention. The ECU 40 detects the NOx concentration using the NOx sensor 102 to realize the “NOx concentration detecting means” in the present invention, and the ECU 40 performs a routine process similar to the routine shown in FIG. 6 as described above. By executing, the “changing means” in the second aspect of the present invention is realized.

Embodiment 6 FIG.
Next, Embodiment 6 of the present invention will be described with reference to FIG.

[Control of Embodiment 6]
(Outline of air-fuel ratio control during lean combustion operation in Embodiment 6)
In the present embodiment, when the internal combustion engine 100 described above is controlled, the following control configuration is adopted. That is, although illustration is omitted, the control configuration of the present embodiment is basically the same as the control configuration shown in FIG. 7 in the second embodiment. However, this control configuration includes an update amount calculation unit to which the NOx concentration detected by the NOx sensor 102 is input instead of the update amount calculation unit 76. This update amount calculation unit functions to calculate the update amount of the correction amount only for the upper limit value of the upper limit value and the lower limit value of the FB correction amount. Thus, in the present control configuration, the lower limit value is not corrected. For this reason, the addition parts 82 and 84 are not provided. Therefore, a preset base value is always used as the upper limit value.

  FIG. 16 is a diagram showing the setting of the update amount of the upper limit correction amount for the FB correction amount used in the sixth embodiment of the present invention. In the present embodiment, the NOx concentration detected by the NOx sensor 102 is used to calculate the update amount of the upper limit correction amount. Specifically, as shown in FIG. 16, when the NOx concentration is equal to or less than a predetermined value V1, the update amount is set to zero. Therefore, in this case, the final lower limit value input to the upper / lower limit guard unit 66 is not changed from the previous value.

  On the other hand, according to the above setting, when the NOx concentration is higher than the predetermined value V1, a negative update amount is calculated. As a result, as already described in the second embodiment, the upper limit value of the FB correction amount is corrected to be small. That is, the upper limit of the absolute value of the FB correction amount used when the calculated SA-CA10 is reduced (that is, when the air-fuel ratio is made rich) is reduced. As a result, the air-fuel ratio is suppressed from shifting to a richer side than the air-fuel ratio when the NOx concentration becomes the predetermined value V1. The setting shown in FIG. 16 will be described in more detail. As the NOx concentration is higher than the predetermined value V1, the negative update amount is increased on the negative side. As a result, as described above, the upper limit value is corrected to be smaller as the NOx concentration is higher than the predetermined value V1, that is, as the deviation amount of the air-fuel ratio to the rich side is larger. For this reason, it is more positively suppressed that the air-fuel ratio shifts to the rich side from the air-fuel ratio when the NOx concentration becomes the predetermined value V1.

(Specific processing in the sixth embodiment)
The air-fuel ratio control during the lean combustion operation according to the present embodiment can be realized by causing the ECU 40 to execute a routine process similar to the routine shown in FIG. More specifically, instead of the process of step 200, a process for calculating the update amount from the detected NOx concentration using a map in which the relationship between the update amount and the NOx concentration as shown in FIG. Should be done.

  According to the control of the sixth embodiment described above, when the NOx concentration becomes higher than the predetermined value V1 during the execution of the SA-CA10 feedback control, the upper limit value is set to limit the rich correction of the air-fuel ratio. It is made smaller. Thus, even when the calculated SA-CA10 is appropriately controlled in the vicinity of the target SA-CA10, the relationship between the SA-CA10 and the air-fuel ratio is changed due to factors such as changes in combustion conditions. The NOx concentration detected by the NOx sensor 102 is used to make the NOx concentration higher than the predetermined value V1 (more specifically, on the rich side from the air-fuel ratio when the NOx concentration becomes the predetermined value V1. It is possible to suppress the deviation of the air-fuel ratio).

  In the above-described sixth embodiment, the ECU 40 executes the routine process similar to the routine shown in FIG. 9 as described above, thereby realizing the “changing means” according to the second aspect of the present invention. .

Embodiment 7 FIG.
Next, a seventh embodiment of the present invention will be described.

[Control of Embodiment 7]
(Outline of air-fuel ratio control in Embodiment 7)
In the present embodiment, when the internal combustion engine 100 described above is controlled, the following control configuration is adopted. That is, although illustration is omitted, the control configuration of the present embodiment is basically the same as the control configuration shown in FIG. 10 in the third embodiment. However, this control configuration is different in that the parameter input to the target A / F switching unit 86 is the NOx concentration detected by the NOx sensor 102 instead of the air-fuel ratio detected by the air-fuel ratio sensor 32. 10 is different from the control configuration shown in FIG.

  In the present embodiment, when the target A / F switching unit 86 determines that the combustion mode corresponding to the current engine operation region is the lean combustion mode, and the NOx concentration is equal to or less than the predetermined value V1, the lean combustion mode is set. Select as is. On the other hand, even if the combustion mode corresponding to the current engine operation region is the lean combustion mode, if the NOx concentration is higher than the predetermined value V1, the target A / F switching unit 86 will eventually be The stoichiometric combustion mode is selected without selecting the lean combustion mode. As a result, the lean combustion operation is prohibited and the stoichiometric combustion operation is executed.

(Specific processing in Embodiment 7)
The air-fuel ratio control according to the present embodiment can be realized by causing the ECU 40 to execute a routine process similar to the routine shown in FIG. More specifically, instead of the process of step 304, a process for determining whether or not the NOx concentration is equal to or less than a predetermined value V1 may be performed.

  According to the control of the seventh embodiment described above, when the NOx concentration becomes higher than the predetermined value V1 during the execution of the SA-CA10 feedback control, the lean combustion operation is prohibited and the lean combustion operation is changed to the stoichiometric combustion. Switching to operation is performed. Thus, by using the NOx concentration detected by the NOx sensor 102, it is possible to prevent the air-fuel ratio from deviating to the rich side from the air-fuel ratio when the NOx concentration reaches the predetermined value V1.

  In the seventh embodiment described above, the “first prohibiting means” according to the fifth aspect of the present invention is realized by the ECU 40 executing the routine process similar to the routine shown in FIG. 11 as described above. ing.

Embodiment 8 FIG.
Next, an eighth embodiment of the present invention will be described.

[Control of Embodiment 8]
(Outline of air-fuel ratio control during lean combustion operation in Embodiment 8)
In the present embodiment, when the internal combustion engine 100 described above is controlled, the following control configuration is adopted. That is, although illustration is omitted, the control configuration of the present embodiment is basically the same as the control configuration shown in FIG. 12 in the fourth embodiment. However, in this control configuration, the parameters input to the target A / F calculation unit 88 and the FB correction amount calculation unit 90 are the NOx concentration detected by the NOx sensor 102 instead of the air-fuel ratio detected by the air-fuel ratio sensor 32. Is different from the control configuration shown in FIG.

  In the present embodiment, the target A / F calculation unit 88 determines the target air-fuel ratio as usual if the NOx concentration is equal to or less than the predetermined value V1. On the other hand, when the NOx concentration is higher than the predetermined value V1, the target A / F calculation unit 88 has the NOx concentration equal to the predetermined value V1 with respect to the value used when the NOx concentration is equal to or lower than the predetermined value V1. A value on the rich side by a predetermined margin is set as the target air-fuel ratio within a range not reaching the current air-fuel ratio.

  If the NOx concentration is equal to or less than the predetermined value V1, the FB correction amount calculation unit 90 performs FB correction, which is a fuel injection amount correction amount for setting the difference ΔSA-CA10 to zero in order to execute SA-CA10 feedback control. The amount is calculated as usual. On the other hand, when the NOx concentration is higher than the predetermined value V1, the FB correction amount calculation unit 90 outputs the FB correction amount as zero to the upper / lower limit guard unit 66. When this processing is performed, as already described in the fourth embodiment, correction of the fuel injection amount using the SA-CA10 is not performed, and therefore the SA-CA10 feedback control is prohibited. . However, the lean combustion operation itself is continued.

  Further, the predetermined value V1 used in the present embodiment may be set based on the concept described above with reference to FIG. 15, but is preferably set based on the following viewpoints. . That is, taking into account variations in various components of the internal combustion engine 10 and individual differences of the in-cylinder pressure sensor 30, the boundary on the rich side of the variation range of the air-fuel ratio assumed during the execution of the SA-CA10 feedback control is determined in advance. I ask you to. And it is good to set predetermined value V1 so that it may become NOx concentration corresponding to the air fuel ratio in the boundary of the said rich side. When the NOx concentration becomes larger than the predetermined value V1 set in this way, it is preferable to determine that the in-cylinder pressure sensor 30 is abnormal and prohibit the SA-CA10 feedback control.

(Specific processing in the eighth embodiment)
The air-fuel ratio control during the lean combustion operation according to the present embodiment can be realized by causing the ECU 40 to execute a routine process similar to the routine shown in FIG. More specifically, instead of the process of step 400, a process of determining whether or not the NOx concentration is equal to or less than a predetermined value V1 may be performed. Further, instead of the process of step 402, the target air-fuel ratio used when the NOx concentration is higher than the predetermined value V1 may be calculated by the above-described method.

  According to the control of the eighth embodiment described above, when the NOx concentration becomes higher than the predetermined value V1 during the execution of the SA-CA10 feedback control, the execution of the SA-CA10 feedback control is prohibited. Thereby, it can be avoided that the NOx concentration shifts to the rich side from the air-fuel ratio when the NOx concentration becomes the predetermined value V1 due to the action of the SA-CA10 feedback control.

  In the above-described eighth embodiment, the “second prohibiting means” in the sixth aspect of the present invention is realized by the ECU 40 executing the routine processing similar to the routine shown in FIG. 13 as described above. ing.

Other embodiments.
By the way, in Embodiment 1-8 mentioned above, in lean limit control using SA-CA10, adjusting fuel injection quantity using feedback control so that calculation SA-CA10 approaches target SA-CA10. It is said. However, in the present invention, the adjustment target for causing the calculated crank angle period to approach the target crank angle period may be the intake air amount instead of the fuel injection amount. Furthermore, both the fuel injection amount and the intake air amount may be the objects of the adjustment. Specifically, in the case of adjustment of the intake air amount, if the calculated SA-CA10 is larger than the target SA-CA10, the intake air amount is reduced to make a rich correction of the air-fuel ratio. When the calculated SA-CA10 is smaller than the target SA-CA10, the intake air amount is increased in order to correct the air-fuel ratio lean. The adjustment of the intake air amount here is preferably performed using, for example, a known intake variable valve mechanism that can control the amount of air sucked into the cylinder for each cycle.

  In addition, when the SA-CA10 feedback control prohibition process, the FB correction amount upper / lower limit correction process, or the target SA-CA10 correction process is performed in Embodiments 2 to 4 or 6 to 8, In such a manner, the normal process without any of these processes may be restored. That is, for example, when the air-fuel ratio detected by the air-fuel ratio sensor 32 continues to be within the air-fuel ratio range R1 for a predetermined time, the return to the normal processing may be permitted. Further, for example, the return may be permitted at the start of the trip of the vehicle after the trip in which the air-fuel ratio detected by the air-fuel ratio sensor 32 falls within the air-fuel ratio range R1. Further, for example, after it is determined that the air-fuel ratio detected by the air-fuel ratio sensor 32 is within the air-fuel ratio range R1, the lean combustion operation is interrupted by performing the fuel cut or stoichiometric combustion operation, and then the lean combustion is performed again. Return may be permitted when starting operation.

  In addition, the correction process of the target SA-CA10 in the first embodiment and the correction process of the upper and lower limit values of the FB correction amount in the second embodiment may be executed in combination as appropriate, which uses the NOx sensor 102. The same applies to the relationship between the fifth embodiment and the sixth embodiment. Furthermore, the processes of the first to fourth embodiments (the same applies to the processes of the fifth to eighth embodiments) may be combined in the following manner, for example. That is, the air-fuel ratio is changed from the air-fuel ratio range R1 even though the target SA-CA10 correction process in the first or fifth embodiment or the upper and lower limit values of the FB correction amount in the second or sixth embodiment is performed. When the deviating state continues for a predetermined time or more, or after the air-fuel ratio once falls within the air-fuel ratio range R1 by performing the target SA-CA10 correction process or the upper / lower limit correction process, the air-fuel ratio becomes the air-fuel ratio. When it is out of the range R1, the lean combustion operation prohibiting process or the SA-CA10 feedback control prohibiting process may be performed.

  In the first to eighth embodiments described above, in order to calculate the combustion mass ratio (MFB), the analysis result of the in-cylinder pressure data acquired using the in-cylinder pressure sensor 30 and the crank angle sensor 42 is used. Yes. However, the calculation of the combustion mass ratio in the present invention is not necessarily limited to using the in-cylinder pressure data. That is, the fuel mass ratio may be calculated by, for example, detecting an ion current generated by combustion with an ion sensor and using the detected ion current, or measuring an in-cylinder temperature. If possible, it may be calculated using a history of in-cylinder temperature.

10, 100 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 32 Air-fuel ratio sensor 34 Three-way catalyst 36 NSR catalyst (occlusion reduction) Type NOx catalyst)
40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Air flow meter 46 Accelerator position sensor 50 Combustion mode determination unit 52, 86 Target A / F switching unit 54, 88 Target A / F calculation unit 56 Basic injection amount calculation unit 58 Target SA-CA10 setting unit 60 SA- CA10 calculation unit 62 Subtraction unit 64, 90 FB correction amount calculation unit 66 Upper / lower limit guard units 68, 72, 74, 78, 80, 82, 84 Addition unit 70, 76 Update amount calculation unit 102 NOx sensor

Claims (13)

A control device for an internal combustion engine that performs lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
Air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas;
Crank angle detecting means for detecting the crank angle;
A combustion mass ratio calculating means for calculating a combustion mass ratio;
First crank angle acquisition means for acquiring a first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
The fuel injection amount and the intake air amount are set so that the calculated crank angle period, which is the calculated value of the crank angle period from the ignition timing to the first crank angle, approaches the target crank angle period, which is the target value of the crank angle period. An adjusting means for adjusting at least one of them,
In a situation where the adjustment by the adjustment means is performed during lean combustion operation, when the air-fuel ratio detected by the air-fuel ratio detection means is out of the air-fuel ratio range including the target air-fuel ratio, the air-fuel ratio is Changing means for changing the adjustment by the adjusting means so as to suppress the deviation from the air-fuel ratio range;
A control device for an internal combustion engine, comprising:   2. The change unit according to claim 1, wherein when the air-fuel ratio is out of the air-fuel ratio range, the change means suppresses the air-fuel ratio from being out of the air-fuel ratio range by correcting the target crank angle period. The internal combustion engine control device described.   The changing means increases the target crank angle period when the air-fuel ratio deviates from the air-fuel ratio range to the rich side, and when the air-fuel ratio deviates from the air-fuel ratio range to the lean side. The control apparatus for an internal combustion engine according to claim 2, wherein the crank angle period is reduced.   The change means suppresses the air-fuel ratio from deviating from the air-fuel ratio range by limiting the adjustment by the adjusting means when the air-fuel ratio deviates from the air-fuel ratio range. The control apparatus of the internal combustion engine described in 1.   When the air-fuel ratio deviates from the air-fuel ratio range to the rich side, the changing unit is configured to obtain an absolute value of at least one of the fuel injection amount and the intake air amount used when the calculated crank angle period is reduced. When the adjustment is limited by reducing the upper limit of the value and the air-fuel ratio deviates from the air-fuel ratio range to the lean side, the fuel injection amount and intake air amount used when the calculated crank angle period is increased 5. The control apparatus for an internal combustion engine according to claim 4, wherein the adjustment is limited by reducing an upper limit of an absolute value of at least one of the correction amounts. A control device for an internal combustion engine that performs lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
NOx concentration detection means for detecting the NOx concentration of exhaust gas;
Crank angle detecting means for detecting the crank angle;
A combustion mass ratio calculating means for calculating a combustion mass ratio;
First crank angle acquisition means for acquiring a first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
The fuel injection amount and the intake air amount are set so that the calculated crank angle period, which is the calculated value of the crank angle period from the ignition timing to the first crank angle, approaches the target crank angle period, which is the target value of the crank angle period. An adjusting means for adjusting at least one of them,
In a situation where the adjustment by the adjustment means is performed during lean combustion operation, the NOx concentration detected by the NOx concentration detection means is the NOx concentration of the exhaust gas discharged under combustion at the target air-fuel ratio. Changing means for changing the adjustment by the adjusting means so that the NOx concentration of the exhaust gas is suppressed from becoming higher than the predetermined value when higher than a predetermined value higher than the predetermined value;
A control device for an internal combustion engine, comprising:   The control device for an internal combustion engine according to claim 6, wherein the change unit increases the target crank angle period when the NOx concentration of the exhaust gas is higher than the predetermined value.   The changing means is configured to set an absolute value of a correction amount of at least one of a fuel injection amount and an intake air amount used when the calculated crank angle period is reduced when the NOx concentration of the exhaust gas is higher than the predetermined value. The control apparatus for an internal combustion engine according to claim 6, wherein the upper limit is reduced. A control device for an internal combustion engine that performs lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
Air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas;
Crank angle detecting means for detecting the crank angle;
A combustion mass ratio calculating means for calculating a combustion mass ratio;
First crank angle acquisition means for acquiring a first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
The fuel injection amount and the intake air amount are set so that the calculated crank angle period, which is the calculated value of the crank angle period from the ignition timing to the first crank angle, approaches the target crank angle period, which is the target value of the crank angle period. An adjusting means for adjusting at least one of them,
When the adjustment by the adjustment means is being performed during the lean combustion operation, when the air-fuel ratio detected by the air-fuel ratio detection means is out of the air-fuel ratio range including the target air-fuel ratio, the lean combustion operation is performed. A first prohibiting means to prohibit;
A control device for an internal combustion engine, comprising: A control device for an internal combustion engine that performs lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
Air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas;
Crank angle detecting means for detecting the crank angle;
A combustion mass ratio calculating means for calculating a combustion mass ratio;
First crank angle acquisition means for acquiring a first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
The fuel injection amount and the intake air amount are set so that the calculated crank angle period, which is the calculated value of the crank angle period from the ignition timing to the first crank angle, approaches the target crank angle period, which is the target value of the crank angle period. An adjusting means for adjusting at least one of them,
In a situation where the adjustment by the adjustment means is performed during lean combustion operation, when the air-fuel ratio detected by the air-fuel ratio detection means is out of the air-fuel ratio range including the target air-fuel ratio, the adjustment means A second prohibiting means for prohibiting the adjustment;
A control device for an internal combustion engine, comprising: A control device for an internal combustion engine that performs lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
NOx concentration detection means for detecting the NOx concentration of exhaust gas;
Crank angle detecting means for detecting the crank angle;
A combustion mass ratio calculating means for calculating a combustion mass ratio;
First crank angle acquisition means for acquiring a first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
The fuel injection amount and the intake air amount are set so that the calculated crank angle period, which is the calculated value of the crank angle period from the ignition timing to the first crank angle, approaches the target crank angle period, which is the target value of the crank angle period. An adjusting means for adjusting at least one of them,
In a situation where the adjustment by the adjustment means is performed during lean combustion operation, the NOx concentration detected by the NOx concentration detection means is the NOx concentration of the exhaust gas discharged under combustion at the target air-fuel ratio. First prohibiting means for prohibiting lean combustion operation when higher than a predetermined value higher than,
A control device for an internal combustion engine, comprising: A control device for an internal combustion engine that performs lean combustion operation at an air-fuel ratio larger than the stoichiometric air-fuel ratio,
NOx concentration detection means for detecting the NOx concentration of exhaust gas;
Crank angle detecting means for detecting the crank angle;
A combustion mass ratio calculating means for calculating a combustion mass ratio;
First crank angle acquisition means for acquiring a first crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
The fuel injection amount and the intake air amount are set so that the calculated crank angle period, which is the calculated value of the crank angle period from the ignition timing to the first crank angle, approaches the target crank angle period, which is the target value of the crank angle period. An adjusting means for adjusting at least one of them,
In a situation where the adjustment by the adjustment means is performed during lean combustion operation, the NOx concentration detected by the NOx concentration detection means is the NOx concentration of the exhaust gas discharged under combustion at the target air-fuel ratio. A second prohibiting means for prohibiting the adjustment by the adjusting means when the predetermined value is higher than a predetermined value;
A control device for an internal combustion engine, comprising:   The control apparatus for an internal combustion engine according to any one of claims 1 to 12, wherein the predetermined combustion mass ratio is 10%.

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