JP2015132237A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To curb degradation of fuel efficiency and NOx discharge efficiency when an air-fuel ratio is switched in an internal combustion engine capable of switching the air-fuel ratio for operation thereof between two target air-fuel ratios.SOLUTION: A virtual air-fuel ratio is switched from a first air-fuel ratio to a second air-fuel ratio upon a satisfaction of a condition for switching an operation mode from operation with the first air-fuel ratio as a target air-fuel ratio to the operation with the second air-fuel ratio as the target air-fuel ratio. After the virtual air-fuel ratio is switched, the target air-fuel ratio is: maintained at the first air-fuel ratio until an estimated air volume reaches an intermediary air volume capable of achieving required torque with a third air-fuel ratio; and switched to the third air-fuel ratio when the estimated air volume reaches the intermediary air volume. Then, after the target air-fuel ratio is switched to the third air-fuel ratio, the target air-fuel ratio is fixed at the second air-fuel ratio when a difference between the target air volume and the estimated air volume becomes not more than a threshold with the target air-fuel ratio continuously changed in a range from the third air-fuel ratio to the second air-fuel ratio on the basis of the estimated air volume and the required torque.

Description

  The present invention relates to a control device that integrally controls an air amount, a fuel supply amount, and an ignition timing of an internal combustion engine configured to be able to switch an air-fuel ratio used for operation between at least two target air-fuel ratios.

  Japanese Patent Application Laid-Open No. 2007-231849 discloses a technique (hereinafter, prior art) relating to air-fuel ratio switching control in an internal combustion engine capable of switching the operating air-fuel ratio of the internal combustion engine between a lean air-fuel ratio and a stoichiometric air-fuel ratio. Yes. According to the above prior art, when the air-fuel ratio is switched from the lean air-fuel ratio to the stoichiometric air-fuel ratio, the number of operating cylinders that minimizes the amount of change in the intake air amount when the torque is maintained is selected, and Reduced cylinder stoichiometric operation using cylinders corresponding to the number of cylinders is executed. Then, when the reduced cylinder stoichiometric operation is executed, if the torque step corresponding to the change amount of the intake air amount is larger than a predetermined value, the intake air amount is changed to maintain the torque and the intake air amount is changed. The torque step resulting from the actual response delay is eliminated by retarding the ignition timing.

JP 2007-231849 A JP-A-6-264786

  However, the retard of the ignition timing is accompanied by the possibility of a reduction in fuel consumption. In particular, since the lean limit of a lean burn engine in recent years has become large, the difference in required air amount between the stoichiometric air fuel ratio and the lean air fuel ratio has become very large. Therefore, if the above prior art is applied to such a lean burn engine to suppress the torque step due to the difference in the air amount at the ignition timing, it is necessary to continue the state in which the ignition timing is significantly retarded for a long time. May occur, and there is a risk that deterioration of fuel efficiency and influence on the catalyst cannot be overlooked.

  If the air-fuel ratio is gradually changed so as not to generate a torque step when the air-fuel ratio is switched, the air-fuel ratio can be switched without performing ignition retard control. However, if the air-fuel ratio is gradually changed from the stoichiometric air-fuel ratio to the lean air-fuel ratio, an increase in the NOx emission amount becomes a problem. That is, the NOx emission amount tends to decrease as the emission amount reaches a peak at a weak lean air-fuel ratio of about 16 and then shifts to lean. For this reason, if the air-fuel ratio is gradually changed from the stoichiometric air-fuel ratio to the lean air-fuel ratio, the time for passing through the air-fuel ratio region where the amount of NOx emission is large becomes long, and deterioration of exhaust performance becomes a problem.

  The present invention has been made in view of the above-described problems. In an internal combustion engine configured to be able to switch an air-fuel ratio used for operation between at least two target air-fuel ratios, the air-fuel ratio is switched while suppressing fluctuations in torque. At the same time, an object is to suppress the deterioration of fuel efficiency and exhaust performance at the time of switching.

  The present invention can be applied to the configuration of a control device for an internal combustion engine. The outline of the control apparatus for an internal combustion engine according to the present invention will be described below. However, as will be apparent from the contents of the present invention described below, the present invention can be applied to the procedure of the control method of the internal combustion engine, and can also be applied to an algorithm of a program executed by the control device. .

The control apparatus for an internal combustion engine according to the present invention operates from a first air-fuel ratio and a third air-fuel ratio that is leaner than the first air-fuel ratio and leaner than the air-fuel ratio at which the NOx emission amount relative to the air-fuel ratio becomes maximum. Further, the operation with the lean second air-fuel ratio can be selected, and the air amount control means for controlling the air amount, the air-fuel ratio control means for controlling the air-fuel ratio, and the ignition timing so as to achieve the required torque. An internal combustion engine control device for operating an ignition timing control means for controlling,
When the condition for switching the operation mode from the operation with the first air-fuel ratio to the operation with the second air-fuel ratio is satisfied, the air amount control means is configured such that the air amount is the required torque under the second air-fuel ratio. Controlling the first actuator for changing the air amount so as to achieve the air amount,
The air-fuel ratio control means estimates an estimated air amount from an operation amount of the first actuator when the condition is satisfied, and the estimated air amount achieves the required torque under the third air-fuel ratio. The air-fuel ratio is maintained at the first air-fuel ratio until the intermediate air amount to reach the first air-fuel ratio, and in response to the estimated air amount reaching the intermediate air amount, the air-fuel ratio is changed from the first air-fuel ratio to the first air-fuel ratio. After stepwise switching to the third air-fuel ratio and switching from the first air-fuel ratio to the third air-fuel ratio, the third air-fuel ratio is changed from the third air-fuel ratio to the third air-fuel ratio based on the estimated air amount and the required torque. Controlling the second actuator for changing the fuel supply amount so as to continuously change the air-fuel ratio within a range up to two air-fuel ratios;
The ignition timing control means controls the third actuator that changes the ignition timing so that the torque estimated from the operation amount of the first actuator becomes the required torque.

  More specifically, the first actuator includes, for example, a variable valve timing mechanism that changes valve timings of a throttle and an intake valve. If the turbocharger is provided with a supercharging characteristic variable actuator that changes its supercharging characteristic, specifically, a variable nozzle, a wastegate valve, or the like, these can also be included in the first actuator. Specifically, the second actuator is an injector that injects fuel, and includes, for example, a port injector that injects fuel into the intake port and an in-cylinder injector that directly injects fuel into the cylinder. Specifically, the third actuator is an ignition device. The control device according to the present invention integrally controls the air amount, fuel supply amount, and ignition timing of the internal combustion engine by cooperative operation of these three types of actuators.

  The control device according to the present invention can be realized by a computer. More specifically, the control device according to the present invention is configured by a computer including a memory storing a program describing processing for realizing various functions and a processor that reads and executes the program from the memory. Can do. The functions of the control device according to the present invention include a required torque receiving function, a target air-fuel ratio switching function, a target air as functions for determining the target air amount and target air-fuel ratio used for the cooperative operation of the three types of actuators. An amount calculation function and a parameter value change function are included.

  According to the required torque receiving function, the required torque for the internal combustion engine is received. The required torque is calculated based on a signal responsive to the accelerator pedal opening operated by the driver. When the driver requests the internal combustion engine to decelerate, a required torque that decreases according to the speed at which the driver closes the accelerator pedal is obtained. When the driver requests acceleration from the internal combustion engine, a required torque that increases according to the speed at which the driver opens the accelerator pedal is obtained.

  According to the target air amount calculation function, the target air amount for achieving the required torque is calculated backward from the required torque. In the calculation of the target air amount, a parameter that gives the conversion efficiency of the air amount into torque is used. The parameter value is variable and is changed by the parameter value changing function. According to the parameter value changing function, the parameter value is changed in the direction of increasing the air amount in response to satisfying the condition for switching the operation mode from the operation with the first air-fuel ratio to the operation with the second air-fuel ratio. .

  As the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the torque generated at the same air amount decreases. Therefore, the parameter corresponding to the air-fuel ratio corresponds to a parameter that gives the conversion efficiency of the air amount into torque. The parameter value changing function can use a parameter corresponding to the air-fuel ratio as a parameter that gives the conversion efficiency of the air amount into torque. According to the parameter value changing function, the parameter value is changed from a value corresponding to the first air-fuel ratio to a value corresponding to the first air-fuel ratio in response to satisfying the condition for switching the operation mode from the operation using the first air-fuel ratio to the operation using the second air-fuel ratio. It is changed to a value corresponding to 2 air-fuel ratio. If the value of the required torque is the same, the target air amount decreases as the parameter corresponding to the air-fuel ratio is richer, and the target air amount increases as the parameter is leaner.

  According to the target air-fuel ratio switching function, the target air-fuel ratio is changed from the first air-fuel ratio to the third air-fuel ratio between the first air-fuel ratio and the second air-fuel ratio after the parameter value is changed to increase the air amount. After that, the third air-fuel ratio is switched to the second air-fuel ratio. That is, the target air-fuel ratio is not directly switched from the first air-fuel ratio to the second air-fuel ratio, but is switched from the third air-fuel ratio to the second air-fuel ratio after a temporary switch to the intermediate third air-fuel ratio. . Note that the intermediate air-fuel ratio here means an air-fuel ratio that is leaner than the first air-fuel ratio and richer than the second air-fuel ratio, and the median value of the first air-fuel ratio and the second air-fuel ratio is It is not limited. Specifically, the third air-fuel ratio is set to a value of the air-fuel ratio that is leaner than the air-fuel ratio at which the NOx emission amount exhausted from the cylinder becomes maximum.

  Specifically, in the target air-fuel ratio switching function, the target air amount is estimated until the estimated air amount estimated from the operation amount of the first actuator reaches an intermediate air amount that can achieve the required torque under the third air-fuel ratio. In response to the first function of maintaining the fuel ratio at the first air-fuel ratio and the estimated air amount reaching the intermediate air amount, the target air-fuel ratio is switched stepwise from the first air-fuel ratio to the third air-fuel ratio in a stepwise manner. After the function and the target air-fuel ratio are switched from the first air-fuel ratio to the third air-fuel ratio, the target air-fuel ratio is set within the range from the third air-fuel ratio to the second air-fuel ratio based on the estimated air amount and the required torque. The target air-fuel ratio that was changed based on the estimated air amount and the required torque in response to the third function that is continuously changed and the difference between the target air amount and the estimated air amount being equal to or less than the threshold value And a fourth function of fixing the air-fuel ratio to the second air-fuel ratio.

  In particular, according to the third function, for example, after the target air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the torque that can be achieved by the estimated air amount at a predetermined ignition timing is the required torque. Thus, the target air-fuel ratio is continuously changed from the third air-fuel ratio to the second air-fuel ratio.

  Further, according to the third function, after the target air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the NOx emission amount from the cylinder at a predetermined ignition timing is calculated based on the target air-fuel ratio. The target air-fuel ratio is continuously changed within the range from the third air-fuel ratio to the second air-fuel ratio so that the calculated NOx emission amount does not exceed a predetermined allowable limit.

  The control device according to the present invention cooperatively operates three types of actuators based on the target air amount and the target air-fuel ratio determined by the above processing. The functions of the control device according to the present invention include a first actuator control function, a second actuator control function, and a third actuator control function as functions for cooperative operation based on the target air amount and the target air-fuel ratio. included.

  According to the first actuator control function, the operation amount of the first actuator is determined based on the target air amount. Then, the first actuator is operated according to the determined operation amount. The actual air amount changes so as to follow the target air amount by operating the first actuator. In particular, when the internal combustion engine is a supercharged engine provided with a supercharger and the first actuator includes a supercharging characteristic variable actuator that changes the supercharging characteristic of the supercharger, the operation from the first air-fuel ratio is started. The target intake pipe pressure calculated from the target air amount at the time when the target air-fuel ratio is switched to the second air-fuel ratio in response to satisfying the condition for switching the operation mode to the operation with two air-fuel ratios is the supercharging region Is estimated based on the required torque. When it is estimated that the target intake pipe pressure reaches the supercharging region, the supercharging characteristic actuator is operated, and the supercharging pressure of the supercharger is increased.

  According to the second actuator control function, the fuel supply amount is determined based on the target air-fuel ratio. Then, the second actuator is operated according to the determined fuel supply amount.

  According to the third actuator control function, the ignition timing for achieving the required torque is determined based on the torque estimated from the operation amount of the first actuator and the target air-fuel ratio and the required torque. Then, the third actuator is operated according to the determined ignition timing. The actual air amount can be estimated from the operation amount of the first actuator, and the torque can be estimated from the estimated air amount and the target air-fuel ratio. The operation of the third actuator is performed so that the excess of the estimated torque with respect to the required torque is corrected by the ignition timing.

  According to the control device of the present invention, when the condition for switching from the operation at the first air-fuel ratio to the operation at the second air-fuel ratio is satisfied, the air amount is increased while the air-fuel ratio is changed to the first air-fuel ratio. Maintained. As a result, the torque achievable with the air amount and the air-fuel ratio becomes excessive than the required torque, and the ignition timing is retarded so as to compensate for the excess. The air-fuel ratio is maintained at the first air-fuel ratio until the estimated air amount estimated from the operation amount of the actuator reaches the intermediate air amount that can achieve the required torque under the third air-fuel ratio, and the estimated air amount is intermediate In response to reaching the air amount, the target air-fuel ratio is switched stepwise from the first air-fuel ratio to the third air-fuel ratio. As a result, it is possible to change the actual air-fuel ratio by jumping over a part of the air-fuel ratio region where the amount of NOx exhausted from the cylinder is large, so that it is possible to suppress the NOx emission when switching the air-fuel ratio. Become.

  After the air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the control apparatus according to the present invention is within the range from the third air-fuel ratio to the second air-fuel ratio based on the estimated air amount and the required torque. Thus, the target air-fuel ratio is continuously changed. As a result, the ignition delay amount can be reduced rather than changing the air-fuel ratio stepwise from the third air-fuel ratio to the second air-fuel ratio. Therefore, the first air-fuel ratio to the third air-fuel ratio can be reduced. In combination with the step-like change, the NOx emission amount can be suppressed and the deterioration of fuel consumption performance can be suppressed.

  In particular, according to the function of the control device according to the present invention, the parameter that gives the conversion efficiency of the air amount to torque used for the calculation of the target air amount is changed in the direction in which the air amount increases, Is maintained at the first air-fuel ratio. As a result, the torque achievable with the target air amount and the target air-fuel ratio becomes excessive beyond the required torque, and the ignition timing is retarded so as to compensate for the excess. The target air-fuel ratio is maintained at the first air-fuel ratio until the estimated air amount estimated from the operation amount of the first actuator reaches an intermediate air amount that can achieve the required torque under the third air-fuel ratio. In response to the amount reaching the intermediate air amount, the target air-fuel ratio is switched stepwise from the first air-fuel ratio to the third air-fuel ratio. As a result, it is possible to change the actual air-fuel ratio by jumping over a part of the air-fuel ratio region where the amount of NOx exhausted from the cylinder is large, so that it is possible to suppress the NOx emission when switching the air-fuel ratio. Become.

  After switching the target air-fuel ratio from the first air-fuel ratio to the third air-fuel ratio, the control device according to the present invention provides a range from the third air-fuel ratio to the second air-fuel ratio based on the estimated air amount and the required torque. The target air-fuel ratio is continuously changed within. As a result, the ignition delay amount can be reduced rather than changing the target air-fuel ratio stepwise from the third air-fuel ratio to the second air-fuel ratio. In combination with the stepwise change to the air-fuel ratio, it is possible to suppress the NOx emission amount and suppress the deterioration of the fuel consumption performance.

  In particular, according to the third function, for example, after the target air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the torque that can be achieved by the estimated air amount under the predetermined ignition timing becomes the required torque. In addition, the target air-fuel ratio is continuously changed within the range from the third air-fuel ratio to the second air-fuel ratio. Thereby, it is possible to further suppress the retard amount of the ignition timing.

  Further, according to the third function, after the target air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the NOx emission amount from the cylinder at a predetermined ignition timing is calculated based on the target air-fuel ratio. The target air-fuel ratio can be continuously changed within the range from the third air-fuel ratio to the second air-fuel ratio so that the calculated NOx emission amount does not exceed a predetermined allowable limit. As a result, the air-fuel ratio can be switched while the NOx emission amount does not exceed a predetermined allowable limit.

  When the internal combustion engine is a supercharged engine including a supercharger and the first actuator includes a supercharging characteristic variable actuator that changes the supercharging characteristic of the supercharger, the supercharging during the air-fuel ratio switching is performed. Since the supercharging characteristic actuator is operated so that the supercharging of the machine changes in an increasing direction, the air responsiveness can be improved and the time required for switching the air-fuel ratio can be shortened. Also, when the supercharging characteristic actuator is a wastegate valve, the back pressure increases by closing the wastegate valve, so the internal EGR rate during air-fuel ratio switching is increased to further reduce NOx emissions. Can do.

It is a block diagram which shows the logic of the control apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the logic of the switching of the operation mode of the control apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the image of the map used in order to determine a target air fuel ratio from a request torque and the present air amount. It is a figure which shows the relationship of the NOx discharge amount with respect to an air fuel ratio. It is a flowchart which shows the logic of the target air fuel ratio switching of the control apparatus which concerns on Embodiment 1 of this invention. It is a time chart which shows the image of the control result in the supercharging area | region by the control apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the image of the map used in order to determine a target air fuel ratio from NOx discharge | emission amount. It is a figure which shows the setting of the driving | operation area | region employ | adopted with the control apparatus which concerns on Embodiment 1 of this invention.

[Embodiment 1]
Embodiment 1 of the present invention will be described below with reference to the drawings.

  An internal combustion engine (hereinafter referred to as an engine) to be controlled in the present embodiment is a spark ignition type 4-cycle reciprocating engine and a turbo engine to which a turbocharger is attached. In addition, this engine is a so-called lean burn engine, and as an engine operation mode, a stoichiometric mode (first operation mode) in which operation is performed with a theoretical air-fuel ratio and a lean mode in which operation is performed with an air-fuel ratio leaner than the theoretical air-fuel ratio. (Second operation mode) can be selected.

  An ECU (Electrical Control Unit) mounted on the vehicle controls the operation of the engine by operating various actuators provided in the engine. The actuator operated by the ECU includes a throttle that is a first actuator that changes the air amount, a variable valve timing mechanism (hereinafter referred to as VVT), an injector that is a second actuator that supplies fuel into the cylinder, and an air-fuel mixture in the cylinder. Includes an ignition device which is a third actuator for igniting the motor. VVT is provided for the intake valve, and the injector is provided for the intake port. The ECU operates these actuators to control the operation of the engine. The engine control by the ECU includes switching of the operation mode from the stoichiometric mode to the lean mode, or from the lean mode to the stoichiometric mode.

  FIG. 1 is a block diagram showing the logic of the ECU according to the present embodiment. The ECU includes an engine controller 100 and a powertrain manager 200. The engine controller 100 is a control device that directly controls the engine, and corresponds to the control device according to the present invention. The powertrain manager 200 is a control device that performs integrated control of the entire drive system including an engine, an electronically controlled automatic transmission, and vehicle control devices such as VSC and TRC. The engine controller 100 is configured to control the operation of the engine based on a signal received from the powertrain manager 200. The engine controller 100 and the powertrain manager 200 are both realized by software. Specifically, the functions of the engine controller 100 and the powertrain manager 200 are realized in the ECU by reading a program stored in the memory and executing the program by the processor.

  In the block showing the powertrain manager 200 in FIG. 1, among the various functions provided in the powertrain manager 200, some of the functions related to engine control are represented by blocks. An arithmetic unit is assigned to each of these blocks. Programs corresponding to the respective blocks are prepared in the ECU, and the functions of the respective arithmetic units are realized in the ECU by being executed by the processor.

  The arithmetic unit 202 calculates the requested first torque and transmits it to the engine controller 100. In the figure, the required first torque is indicated as “TQ1r”. The first torque is a kind of torque that does not have high responsiveness required for the engine and that may be realized in the near future if not immediately. The requested first torque is a requested value of the first torque that the powertrain manager 200 requests for the engine, and corresponds to the requested torque in the present invention. A signal output in response to the opening of the accelerator pedal is input to the arithmetic unit 202 from an accelerator position sensor (not shown). The required first torque is calculated based on the signal. The requested first torque is a shaft torque.

  The arithmetic unit 204 calculates the requested second torque and transmits it to the engine controller 100. In the figure, the required second torque is indicated as “TQ2r”. The second torque is a type of torque that has higher urgency or priority than the first torque and requires high responsiveness to the engine, that is, a type of torque that is required to be realized immediately. The responsiveness mentioned here means responsiveness when the torque is temporarily reduced. The requested second torque is a requested value of the second torque that the powertrain manager 200 requests from the engine. The required second torque calculated by the arithmetic unit 204 is required for the shift control of the electronically controlled automatic transmission, the torque required for the traction control, and the side slip prevention control. Torque required from the vehicle control system, such as torque, is included. The first torque is a torque required for the engine constantly or over a long period of time, whereas the second torque is a torque required for the engine suddenly or for a short period of time. For this reason, the arithmetic unit 204 outputs an effective value corresponding to the magnitude of the torque to be realized only when an event that actually requires such torque occurs, and while such an event does not occur Outputs an invalid value. The invalid value is set to a value larger than the maximum shaft torque that can be output by the engine.

  The arithmetic unit 206 calculates the gear ratio of the automatic transmission and transmits a signal for instructing the gear ratio to a transmission controller (not shown). The transmission controller is realized as one function of the ECU, like the powertrain manager 200 and the engine controller 100. A flag signal is input from the engine controller 100 to the arithmetic unit 206. In the figure, the flag signal is described as “FLG”. The flag signal is a signal indicating that the operation mode is being switched. While the flag signal is on, the arithmetic unit 206 fixes the gear ratio of the automatic transmission.

  The arithmetic unit 208 transmits to the engine controller 100 a stop signal instructing to stop the operation mode switching in response to the predetermined condition being satisfied. In the figure, the stop signal is described as “Stop”. The predetermined condition is that a request to greatly change the operating state of the engine is issued from the powertrain manager 200.

  Next, the configuration of the engine controller 100 will be described. Interfaces 101, 102, 103, and 104 are set between the engine controller 100 and the powertrain manager 200. The interface 101 corresponds to the required torque receiving means in the present invention, and the required first torque is transferred at the interface 101. In the interface 102, a stop signal is transferred. The interface 103 exchanges flag signals. Then, the requested second torque is transferred at the interface 104.

  In the block showing the engine controller 100 in FIG. 1, among the various functions provided in the engine controller 100, three types of actuators, that is, the throttle 2 and VVT 8 as the first actuator, the injector 4 as the second actuator, and The functions related to the cooperative operation of the ignition device 6 that is the third actuator are represented by blocks. An arithmetic unit is assigned to each of these blocks. Programs corresponding to the respective blocks are prepared in the ECU, and the functions of the respective arithmetic units are realized in the ECU by being executed by the processor.

  The engine controller 100 is roughly composed of three large arithmetic units 120, 140, and 160. The large arithmetic unit 120 calculates values of various control parameters for the engine. The control parameters include target values for various control amounts for the engine. Further, the target values include those calculated based on the request value transmitted from the powertrain manager 200 and those calculated inside the large arithmetic unit 120 based on the information related to the operating state of the engine. . The required value is a control amount value that is unilaterally requested from the powertrain manager 200 without considering the engine state, whereas the target value is set based on a feasible range determined by the engine state. Is the value of the controlled variable. More specifically, the large arithmetic unit 120 includes four arithmetic units 122, 124, 126, and 128.

  The arithmetic unit 122 calculates a target air-fuel ratio, a virtual air-fuel ratio, a switching target efficiency, and a switching target second torque as control parameters for the engine. In the figure, the target air-fuel ratio is expressed as “AFt”, the virtual air-fuel ratio is expressed as “AFh”, the target efficiency for switching is expressed as “ηtc”, and the target second torque for switching is expressed as “TQ2c”. Has been. The target air-fuel ratio is a target value of the air-fuel ratio realized in the engine, and is used for calculating the fuel injection amount. On the other hand, the virtual air-fuel ratio is a parameter that gives a conversion efficiency of torque into an air amount, and is used for calculating a target air amount. The target efficiency for switching is a target value of the ignition timing efficiency for switching the operation mode, and is used for calculating the target air amount. The ignition timing efficiency means the ratio of the torque that is actually output with respect to the torque that can be output when the ignition timing is the optimal ignition timing, and is 1 that is the maximum value when the ignition timing is the optimal ignition timing. The optimum ignition timing basically means MBT (Minimum Advance for Best Torque), and when the trace knock ignition timing is set, it is more retarded of the MBT and the trace knock ignition timing. It means a certain ignition timing. The target second torque for switching is a target value of the second torque for switching the operation mode, and is used for switching calculation of ignition timing efficiency when the operation mode is switched. The operation mode is switched by a combination of these control parameter values calculated by the arithmetic unit 122. The relationship between the content of processing performed in the arithmetic unit 122 and switching of the operation mode will be described in detail later.

  In addition to the requested first torque, the requested second torque, and the stop signal given from the powertrain manager 200, various information related to the engine operating state such as the engine speed is input to the arithmetic unit 122. Of these, the requested first torque is used as information used to determine the timing for switching the operation mode. The requested second torque and the stop signal are used as information for determining whether switching of the operation mode is permitted or prohibited. When the stop signal is input and when the request second torque having an effective value is input, the arithmetic unit 122 does not execute the process related to the switching of the operation mode. Further, the arithmetic unit 122 transmits the above-described flag signal to the powertrain manager 200 during the switching of the operation mode, that is, while the calculation process for switching the operation mode is being executed.

  The arithmetic unit 124 uses, as a control parameter for the engine, the first torque among the torques required to maintain the current engine operating state or to realize a predetermined operating state. Calculate the classified torque. Here, the torque calculated by the arithmetic unit 124 is referred to as other first torque. In the figure, the other first torque is indicated as “TQ1etc”. The arithmetic unit 124 outputs a valid value only when such torque is actually needed, and calculates an invalid value while such torque is not needed.

  The arithmetic unit 126 uses, as a control parameter for the engine, a second torque out of the torque required to maintain the current engine operating state or to realize a predetermined operating state. Calculate the classified torque. Here, the torque calculated by the arithmetic unit 126 is referred to as other second torque. In the figure, the other second torque is described as “TQ2etc”. The arithmetic unit 126 outputs a valid value only when such torque is actually needed, and calculates an invalid value while such torque is not needed.

  The arithmetic unit 128 calculates the ignition timing efficiency required to maintain the current engine operating state or to realize a predetermined operating state as a control parameter for the engine. Here, the ignition timing efficiency calculated by the arithmetic unit 128 is referred to as other efficiency. In the figure, other efficiency is indicated as “ηetc”. The other efficiency includes the ignition timing efficiency necessary for warming up the exhaust gas purification catalyst when the engine is started. The lower the ignition timing efficiency, the less energy that is converted into torque from the energy generated by the combustion of the fuel, and that much energy is discharged along with the exhaust gas into the exhaust passage to warm up the exhaust purification catalyst. Will be used. While it is not necessary to realize such efficiency, the efficiency value output from the arithmetic unit 128 is held at 1 which is the maximum value.

  From the large arithmetic unit 120 configured as described above, the required first torque, other first torque, target air-fuel ratio, virtual air-fuel ratio, switching target efficiency, other efficiency, required second torque, switching target second Torque and other second torque are output. These control parameters are input to the large arithmetic unit 140. The requested first torque and the requested second torque provided from the powertrain manager 200 are shaft torques, but the large arithmetic unit 120 converts them into the indicated torque. Conversion of the required torque to the indicated torque is performed by adding or subtracting the friction torque, the accessory driving torque, and the pump loss to the required torque. Note that the torque such as the switching target second torque calculated within the large arithmetic unit 120 is calculated as the indicated torque.

  Next, the large arithmetic unit 140 will be described. As described above, various engine control parameters are sent from the large arithmetic unit 120. Of these, the requested first torque and the other first torque are requests for control amounts belonging to the same category, and cannot be established at the same time. Similarly, the requested second torque, the other second torque, and the switching target second torque are requests for control amounts belonging to the same category and cannot be established at the same time. Similarly, the target efficiency for switching and the other efficiency are requests for control amounts belonging to the same category, and cannot be established at the same time. For this reason, a process called arbitration is required for each control amount category. Arbitration here is calculation processing for obtaining one numerical value from a plurality of numerical values, such as maximum value selection, minimum value selection, averaging, or superposition, for example, and appropriately combining a plurality of types of calculation processing It can also be. In order to carry out such arbitration for each control amount category, the large arithmetic unit 140 includes three arithmetic units 142, 144, and 146.

  The arithmetic unit 142 is configured to adjust the first torque. The requested first torque and the other first torque are input to the arithmetic unit 142. The arithmetic unit 142 arbitrates them and outputs the arbitrated torque as the finally determined target first torque. In the figure, the finally determined target first torque is indicated as “TQ1t”. As an arbitration method in the arithmetic unit 142, minimum value selection is used. Therefore, when a valid value is not output from the arithmetic unit 124, the requested first torque given from the powertrain manager 200 is calculated as the target first torque.

  The arithmetic unit 144 is configured to adjust the ignition timing efficiency. The target efficiency for switching and other efficiency are input to the arithmetic unit 144. The arithmetic unit 144 arbitrates them and outputs the arbitrated efficiency as the finally determined target efficiency. In the figure, the finally determined target efficiency is expressed as “ηt”. As an arbitration method in the arithmetic unit 144, minimum value selection is used. From the viewpoint of fuel efficiency, it is preferable that the ignition timing efficiency is 1, which is the maximum value. Therefore, unless there is a special event, the target efficiency for switching calculated by the arithmetic unit 122 and the other efficiencies calculated by the arithmetic unit 128 are held at 1 which is the maximum value. Therefore, the target efficiency value output from the arithmetic unit 144 is basically 1, and a value smaller than 1 is selected only when some event occurs.

  The arithmetic unit 146 is configured to adjust the second torque. The requested second torque, the other second torque, and the switching target second torque are input to the arithmetic unit 146. The arithmetic unit 146 arbitrates them and outputs the arbitrated torque as the finally determined target second torque. In the figure, the finally determined target second torque is described as “TQ2t”. As an arbitration method in the arithmetic unit 146, minimum value selection is used. The second torque is basically an invalid value including the target second torque for switching, and is switched to an effective value indicating the magnitude of the torque to be realized only when a specific event occurs. Therefore, the target second torque output from the arithmetic unit 146 is basically also an invalid value, and the valid value is selected only when some event occurs.

  The large arithmetic unit 140 configured as described above outputs the target first torque, target efficiency, virtual air-fuel ratio, target air-fuel ratio, and target second torque. These control parameters are input to the large arithmetic unit 160.

  The large arithmetic unit 160 corresponds to an inverse model of the engine, and is composed of a plurality of models represented by maps and functions. The operation amount of each actuator 2, 4, 6, 8 for cooperative operation is calculated by the large arithmetic unit 160. Of the control parameters input from the large arithmetic unit 140, both the target first torque and the target second torque are treated as target values of torque for the engine. However, the target second torque has priority over the target first torque. In the large arithmetic unit 160, the target second torque is achieved when the target second torque is an effective value, and the target first torque is achieved when the target second torque is an invalid value. The amount of operation of each actuator 2, 4, 6, 8 is calculated. The operation amount is calculated so that the target air-fuel ratio and the target efficiency are achieved simultaneously with the target torque. That is, in the control device according to the present embodiment, torque, efficiency, and air-fuel ratio are used as engine control amounts, and air amount control, ignition timing control, and fuel injection amount are based on target values of these three types of control amounts. Control is implemented.

  The large arithmetic unit 160 includes a plurality of arithmetic units 162, 164, 166, 168, 170, 172, 174, 176, 178. Among these arithmetic units, those relating to air amount control are arithmetic units 162, 164, 166, 178, and those relating to ignition timing control are arithmetic units 168, 170, 172, which are related to fuel injection amount control. What is to be done is the arithmetic units 174, 176. Hereinafter, the function of each arithmetic unit will be described in order from the arithmetic unit related to the air amount control.

  The arithmetic unit 162 receives the target first torque, the target efficiency, and the virtual air-fuel ratio. The arithmetic unit 162 corresponds to the target air amount calculation means in the present invention, and uses the target efficiency and the virtual air-fuel ratio to back-calculate the target air amount for achieving the target first torque from the target first torque. In this calculation, the target efficiency and the virtual air-fuel ratio are used as parameters that give the conversion efficiency of the air amount into torque. In the present invention, the air amount is the amount of air sucked into the cylinder, and the filling efficiency or load factor obtained by making it dimensionless is within the same range of the air amount in the present invention.

  The arithmetic unit 162 first calculates an air amount control target torque by dividing the target first torque by the target efficiency. When the target efficiency is smaller than 1, the air amount control target torque is larger than the target first torque. This means that the air amount control by the actuators 2 and 8 is required to potentially output a torque larger than the target first torque. On the other hand, when the target efficiency is 1, the target first torque is directly calculated as the air amount control target torque.

  Next, the arithmetic unit 162 converts the air amount control target torque into the target air amount using the torque-air amount conversion map. The torque-air amount conversion map is a map in which torque and air amount are associated with various engine state amounts including engine speed and air-fuel ratio as keys, assuming that the ignition timing is the optimal ignition timing. is there. This map is created based on data obtained by testing the engine. The actual value or target value of the engine state quantity is used for searching the torque-air quantity conversion map. As for the air-fuel ratio, the virtual air-fuel ratio is used for map search. Therefore, in the arithmetic unit 162, the air amount necessary for realizing the target torque for air amount control under the virtual air-fuel ratio is calculated as the target air amount. In the figure, the target air amount is described as “KLt”.

  The arithmetic unit 164 reversely calculates a target intake pipe pressure that is a target value of the intake pipe pressure from the target air amount. In calculating the target intake pipe pressure, a map describing the relationship between the amount of air taken into the cylinder through the intake valve and the intake pipe pressure is used. Since the relationship between the air amount and the intake pipe pressure varies depending on the valve timing, the parameter value of the map is determined from the current valve timing in calculating the target intake pipe pressure. In the figure, the target intake pipe pressure is indicated as “Pmt”.

  The arithmetic unit 166 calculates a target throttle opening that is a target value of the throttle opening based on the target intake pipe pressure. In calculating the target throttle opening, an inverse model of the air model is used. Since the air model is a physical model that models the response characteristics of the intake pipe pressure to the operation of the throttle 2, the target throttle opening for achieving the target intake pipe pressure by using the inverse model is calculated backward from the target intake pipe pressure. can do. In the figure, the target throttle opening is indicated as “TA”. The target throttle opening calculated by the arithmetic unit 166 is converted into a signal for driving the throttle 2 and transmitted to the throttle 2 via the interface 111 of the ECU. The arithmetic units 164 and 166 correspond to the first actuator control means in the present invention.

  The arithmetic unit 178 calculates a target valve timing that is a target value of the valve timing based on the target air amount. For the calculation of the target valve timing, a map in which the air amount and the valve timing are associated with each other using the engine speed as an argument is used. The target valve timing is a displacement angle of the VVT 8 that is optimal for achieving the target air amount based on the current engine speed, and its specific value is determined by adaptation for each air amount and each engine speed. Yes. In the figure, the target valve timing is indicated as “VT”. The target valve timing calculated by the arithmetic unit 178 is converted into a signal for driving the VVT 8 and transmitted to the VVT 8 via the interface 112 of the ECU. The arithmetic unit 178 also corresponds to the first actuator control means in the present invention.

  Next, functions of the arithmetic unit related to ignition timing control will be described. The arithmetic unit 168 calculates the estimated torque based on the actual throttle opening and valve timing realized by the air amount control described above. The estimated torque in this specification means torque that can be output when the ignition timing is set to the optimal ignition timing based on the current throttle opening, valve timing, and target air-fuel ratio. First, the arithmetic unit 168 calculates an estimated air amount from the measured value of the throttle opening and the measured value of the valve timing using the forward model of the air model described above. The estimated air amount is an estimated value of the air amount actually realized by the current throttle opening degree and valve timing. Next, the estimated air amount is converted into the estimated torque using the torque-air amount conversion map. In the search of the torque-air amount conversion map, the target air-fuel ratio is used as a search key. In the figure, the estimated torque is expressed as “TQe”.

  The target second torque and the estimated torque are input to the arithmetic unit 170. The arithmetic unit 170 calculates a commanded ignition timing efficiency that is a command value of the ignition timing efficiency based on the target second torque and the estimated torque. The command ignition timing efficiency is expressed as a ratio of the target second torque to the estimated torque. However, an upper limit is set for the commanded ignition timing efficiency, and when the ratio of the target second torque to the estimated torque exceeds 1, the value of the commanded ignition timing efficiency is set to 1. In the figure, the indicated ignition timing efficiency is expressed as “ηi”.

  The arithmetic unit 172 calculates the ignition timing from the indicated ignition timing efficiency. Specifically, the optimal ignition timing is calculated based on the engine state quantity such as the engine speed, the required torque, and the air-fuel ratio, and the retard amount with respect to the optimal ignition timing is calculated from the indicated ignition timing efficiency. If the command ignition timing efficiency is 1, the retard amount is set to zero, and the retard amount is increased as the command ignition timing efficiency is smaller than one. Then, the optimum ignition timing plus the retard amount is calculated as the final ignition timing. However, the final ignition timing is limited by the retard limit guard. The retard limit is the most retarded ignition timing at which misfires are guaranteed not to occur, and the retard limit guard sets the final ignition timing so that the ignition timing is not retarded beyond the retard limit. Guarding. In calculating the optimum ignition timing, a map that associates the optimum ignition timing with various engine state quantities can be used. For calculating the retard amount, a map that associates the retard amount with the ignition timing efficiency and various engine state amounts can be used. In searching these maps, the target air-fuel ratio is used as a search key. In the figure, the ignition timing is indicated as “SA”. The ignition timing calculated by the arithmetic unit 172 is converted into a signal for driving the ignition device 6 and transmitted to the ignition device 6 via the interface 113 of the ECU. The arithmetic units 168, 170, 172 correspond to the third actuator control means in the present invention.

  Next, functions of the arithmetic unit related to fuel injection amount control will be described. The arithmetic unit 174 calculates the estimated air amount from the measured value of the throttle opening and the measured value of the valve timing using the forward model of the air model. The estimated air amount calculated by the arithmetic unit 174 is preferably an air amount predicted when the intake valve closes. The amount of air in the future can be predicted from the target throttle opening, for example, by setting a delay time from the calculation of the target throttle opening to the output. In the figure, the estimated air amount is described as “KLe”.

  The arithmetic unit 176 calculates a fuel injection amount necessary for achieving the target air-fuel ratio, that is, a fuel supply amount, from the target air-fuel ratio and the estimated air amount. The calculation of the fuel injection amount is executed when the calculation timing of the fuel injection amount arrives in each cylinder. In the figure, the fuel injection amount is described as “TAU”. The fuel injection amount calculated by the arithmetic unit 176 is converted into a signal for driving the injector 4 and transmitted to the injector 4 via the interface 114 of the ECU. The arithmetic units 174 and 176 correspond to the second actuator control means in the present invention.

  The above is the outline of the logic of the ECU according to the present embodiment. Next, the arithmetic unit 122 that is a main part of the ECU according to the present embodiment will be described in detail.

  FIG. 2 is a block diagram showing the logic of the arithmetic unit 122. In the block showing the arithmetic unit 122 in FIG. 2, among the various functions provided in the arithmetic unit 122, functions related to switching of the operation mode are represented by blocks. An arithmetic unit is assigned to each of these blocks. Programs corresponding to the respective blocks are prepared in the ECU, and the functions of the respective arithmetic units are realized in the ECU by being executed by the processor.

  First, the arithmetic unit 402 will be described. The arithmetic unit 402 calculates a reference value for torque. The reference value is the torque at the boundary between the lean mode and the stoichiometric mode, and the optimum value is adapted for each engine speed from the viewpoint of fuel efficiency, exhaust gas performance, and drivability. The arithmetic unit 402 calculates a reference value suitable for the engine speed with reference to a map prepared in advance. In the figure, the reference value is written as “Ref”.

  Next, the arithmetic unit 404 will be described. The requested first torque is input to the arithmetic unit 404. Further, the reference value calculated by the arithmetic unit 402 is set for the arithmetic unit 404. The arithmetic unit 404 changes the value of the virtual air-fuel ratio used for calculating the target air amount based on the relationship between the input requested first torque and the reference value. More specifically, the arithmetic unit 404 switches the virtual air-fuel ratio from the first air-fuel ratio to the second air-fuel ratio or from the second air-fuel ratio to the first air-fuel ratio. The first air-fuel ratio is a theoretical air-fuel ratio (for example, 14.6). In the figure, the first air-fuel ratio is indicated as “AF1”. The second air-fuel ratio is an air-fuel ratio leaner than the first air-fuel ratio, and is set to a certain constant value (for example, 26.0). In the figure, the second air-fuel ratio is indicated as “AF2”. The arithmetic unit 404 corresponds to parameter value changing means in the present invention. While the requested first torque is greater than the reference value, the arithmetic unit 404 sets the virtual air-fuel ratio to the first air-fuel ratio in response to the requested first torque being greater than the reference value. When the requested first torque decreases in response to the driver's deceleration request, and eventually the requested first torque falls below the reference value, the arithmetic unit 404 responds to the decrease in the requested first torque to the reference value or less in response to the virtual air-fuel ratio. Is switched from the first air-fuel ratio to the second air-fuel ratio.

  Next, the arithmetic unit 406 will be described. The requested first torque is input to the arithmetic unit 406. The arithmetic unit 406 converts the requested first torque into an air amount using the torque-air amount conversion map. The search of the torque-air amount conversion map includes an air-fuel ratio intermediate between the first air-fuel ratio and the second air-fuel ratio, that is, an air-fuel ratio that is leaner than the first air-fuel ratio and richer than the second air-fuel ratio. Three air-fuel ratios are used. In the figure, the third air-fuel ratio is expressed as “AF3”. Therefore, the arithmetic unit 406 calculates the amount of air necessary for realizing the required first torque under the third air-fuel ratio. Hereinafter, the air amount calculated by the arithmetic unit 406 is referred to as an intermediate air amount, and is expressed as “KLi” in the drawing.

  Next, the arithmetic unit 408 will be described. The arithmetic unit 408, together with the arithmetic unit 406, constitutes the target air-fuel ratio switching means in the present invention. In the arithmetic unit 408, the first air-fuel ratio used in the stoichiometric mode and the second air-fuel ratio used in the lean mode are preset as default values for the target air-fuel ratio. Further, a third air-fuel ratio that is an intermediate air-fuel ratio is set in advance. The specific value of the third air-fuel ratio is determined by adaptation based on the relationship with the retard limit of the ignition timing and the relationship with the exhaust performance, which will be described later. In the arithmetic unit 408, the virtual air-fuel ratio determined by the arithmetic unit 404, the intermediate air amount calculated by the arithmetic unit 406, the previous step value of the target air amount calculated by the arithmetic unit 162, and the arithmetic unit 174 The previous step value of the estimated air amount is input. The arithmetic unit 408 also creates an AF conversion map for determining the air-fuel ratio necessary to achieve the required first torque under the conditions of the ignition timing corresponding to a predetermined torque efficiency and the current estimated air amount. It has been. The torque efficiency here refers to the conversion efficiency of air amount into torque. FIG. 3 shows an image of a map showing the relationship between the air amount and torque at a predetermined torque efficiency. As shown in this figure, if the torque efficiency is constant, the amount of torque that can be achieved with the same amount of air is determined by the air-fuel ratio. Therefore, the target air-fuel ratio for achieving the required first torque under a predetermined torque efficiency continuously changes to the lean side as the current estimated air amount increases.

  When the arithmetic unit 408 detects that the virtual air-fuel ratio input from the arithmetic unit 404 has been switched from the first air-fuel ratio to the second air-fuel ratio, the arithmetic unit 408 performs a comparison between the intermediate air amount and the estimated air amount. This is performed for each series of controls. Immediately after the virtual air-fuel ratio is switched from the first air-fuel ratio to the second air-fuel ratio, the estimated air amount is smaller than the intermediate air amount. Further, since the estimated torque is a value larger than the requested first torque, the commanded ignition timing efficiency becomes a value smaller than 1, and the ignition timing is retarded. When the estimated air amount eventually reaches the intermediate air amount, the arithmetic unit 408 quickly switches the target air-fuel ratio from the first air-fuel ratio to the third air-fuel ratio at that time. Immediately after the target air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the estimated air amount matches the intermediate air amount. Further, since the estimated torque is the requested first torque, the indicated ignition timing efficiency becomes 1, and the ignition timing becomes the optimal ignition timing.

  After switching the target air-fuel ratio from the first air-fuel ratio to the third air-fuel ratio, the arithmetic unit 408 switches the target air-fuel ratio to the air-fuel ratio determined by the AF conversion map. The calculation of the target air-fuel ratio using the AF conversion map is performed for each series of controls executed by the arithmetic unit 408 using the map shown in FIG. When the estimated air amount is sufficiently close to the target air amount, specifically, when the difference between the target air amount and the estimated air amount becomes equal to or smaller than a predetermined threshold value, the arithmetic unit 408 sets the target air fuel ratio to the second air fuel ratio. To fix. That is, after the virtual air-fuel ratio is switched from the first air-fuel ratio to the second air-fuel ratio, the target air-fuel ratio is temporarily switched from the first air-fuel ratio to the third air-fuel ratio, which is an intermediate air-fuel ratio, in a stepwise manner. The air-fuel ratio is continuously switched from the second air-fuel ratio. That is, after the target air-fuel ratio is instantaneously switched from the first air-fuel ratio to the third air-fuel ratio, the third air-fuel ratio is gradually changed from the third air-fuel ratio to the second air-fuel ratio so as to gradually approach the second air-fuel ratio. The air-fuel ratio is finally switched to the second air-fuel ratio through switching to the air-fuel ratio between the fuel ratio and the second air-fuel ratio. The operation mode is switched from the stoichiometric mode to the lean mode by switching the target air-fuel ratio.

  Note that the specific value of the third air-fuel ratio is determined by adaptation based on the relationship with the retard limit of the ignition timing and the relationship with the exhaust performance. FIG. 4 is a diagram showing the relationship of the NOx emission amount from the cylinder with respect to the air-fuel ratio under a predetermined ignition timing. As shown in this figure, when the air-fuel ratio is changed from the stoichiometric air-fuel ratio to the lean air-fuel ratio under the optimum ignition timing, the NOx emission amount once increases and becomes the maximum at the weak lean air-fuel ratio (for example, 16.0). Then decrease. Accordingly, if the third air-fuel ratio is set to an air-fuel ratio leaner than the weak lean air-fuel ratio (for example, 18.0), the target air-fuel ratio is changed from the first air-fuel ratio to the third air-fuel ratio, and the NOx emission amount is reduced. The air-fuel ratio region of the maximum weak lean air-fuel ratio jumps and changes. As a result, the actual air-fuel ratio can be changed while avoiding the air-fuel ratio region in which an increase in the NOx emission amount becomes a problem, so that the NOx emission amount at the time of switching the air-fuel ratio is effectively suppressed.

  However, after the virtual air-fuel ratio is switched from the first air-fuel ratio to the second air-fuel ratio, during the period in which the target air-fuel ratio is maintained at the first air-fuel ratio, the retard amount of the ignition timing increases as the air amount increases. It grows gradually. Therefore, it is preferable that the third air-fuel ratio is set to an optimal value by adaptation considering the retard limit of the ignition timing, fuel efficiency, and NOx emission amount.

  After the target air-fuel ratio is switched to the third air-fuel ratio, the third air-fuel ratio is continuously changed to the air-fuel ratio corresponding to the current air amount by the AF conversion map, so that the ignition timing is delayed in this period. The angular amount is suppressed and the fuel efficiency is improved. However, as shown in FIG. 4, when the ignition timing is retarded from the optimum ignition timing, the NOx emission amount decreases over the entire air-fuel ratio due to the decrease in the combustion temperature. Therefore, the AF conversion map used in the arithmetic unit 408 is an air-fuel ratio necessary for achieving the required first torque with the current estimated air amount under the condition that the torque efficiency is slightly reduced (for example, 80%). It is assumed that the map is determined. Thereby, the NOx emission amount during the period when the target air-fuel ratio is the third air-fuel ratio is suppressed.

  The above series of processing executed by the arithmetic unit 408 can be expressed by the flowchart shown in FIG. The procedure for switching the target air-fuel ratio by the arithmetic unit 408 will be described again along this flowchart. The series of processing shown in this flowchart is repeatedly executed at a predetermined calculation cycle.

  In step S1 of the flowchart, the arithmetic unit 408 determines whether or not the switching of the virtual air-fuel ratio from the first air-fuel ratio to the second air-fuel ratio has been completed. If the virtual air-fuel ratio remains the first air-fuel ratio, the processing of the arithmetic unit 408 proceeds to step S7. In step S7, the target air-fuel ratio is maintained at the first air-fuel ratio. After step S7, the processing of the arithmetic unit 408 returns to step S1 again. During this period, if the estimated torque is the value of the requested first torque, the ignition timing becomes the optimal ignition timing. If the virtual air-fuel ratio is switched to the second air-fuel ratio, the processing of the arithmetic unit 408 proceeds to step S2.

  When the virtual air-fuel ratio is switched to the second air-fuel ratio, the estimated air amount increases toward the target air amount corresponding to the second air-fuel ratio. In step S2, the arithmetic unit 408 determines whether or not the estimated air amount has reached the intermediate air amount. If the estimated air amount has not reached the intermediate air amount, the processing of the arithmetic unit 408 proceeds to step S7, and the target air-fuel ratio is maintained at the first air-fuel ratio. During this period, since the estimated torque is larger than the required first torque, the ignition timing is retarded. On the other hand, if it is determined in step S2 that the estimated air amount has reached the intermediate air amount, the processing of the arithmetic unit 408 proceeds to step S3.

  In step S3, the arithmetic unit 408 switches the target air-fuel ratio stepwise from the first air-fuel ratio to the third air-fuel ratio. As a result, the estimated air amount coincides with the intermediate air amount, and the estimated torque becomes the value of the requested first torque, so the ignition timing becomes the optimal ignition timing. After step S3, the processing of the arithmetic unit 408 proceeds to step S4. In step S4, a target air-fuel ratio for achieving the requested first torque is calculated from the AF conversion map having a predetermined torque efficiency based on the current estimated air amount. As a result, the ignition timing in this period is set to a retard timing corresponding to the torque efficiency.

  After step S4, the processing of the arithmetic unit 408 proceeds to step S5. In step S5, the arithmetic unit 408 determines whether or not the estimated air amount has reached the target air amount. As a result, if the estimated air amount has not reached the target air amount, the processing of the arithmetic unit 408 returns to step S4 again.

  The arithmetic unit 408 repeatedly executes the process of step S4 until the determination result of step S5 becomes affirmative. As a result, the target air-fuel ratio is continuously changed as the estimated air amount increases, and the ignition timing in this period is set to the retarded timing corresponding to the torque efficiency. Eventually, when the estimated air amount reaches the target air amount, the processing of the arithmetic unit 408 proceeds to step S6. In step S6, the arithmetic unit 408 fixes the target air / fuel ratio at the second air / fuel ratio. Thereby, the switching of the target air-fuel ratio from the first air-fuel ratio to the second air-fuel ratio is completed.

  In the flowchart, the arithmetic unit 408 executes the processes of steps S2 and S7, the first means of the present invention executes the processes of steps S2 and S3, and the second means of the present invention performs steps S4 and S4. The third means of the present invention is realized by executing the processes of steps S5 and S5, and the fourth means of the present invention is realized by executing the processes of steps S5 and S6.

  Returning to FIG. 2 again, finally, the arithmetic unit 410 will be described. The arithmetic unit 410 calculates the switching target second torque. As described above, the switching target second torque is input to the arithmetic unit 146 together with the requested second torque and the other second torque, and the minimum value is selected by the arithmetic unit 146. The requested second torque and the other second torque are normally invalid values, and are switched to valid values only when a specific event occurs. The same applies to the switching target second torque, and the arithmetic unit 410 normally sets the output value of the switching target second torque to an invalid value.

  The requested first torque, the target air-fuel ratio, and the virtual air-fuel ratio are input to the arithmetic unit 410. According to the logic of the arithmetic units 404 and 408, the target air-fuel ratio and the virtual air-fuel ratio match before the start of the operation mode switching process and also match after the completion of the switching process. However, there is a difference between the target air-fuel ratio and the virtual air-fuel ratio during the operation mode switching process. The arithmetic unit 410 calculates the switching target second torque having an effective value only while a deviation occurs between the target air-fuel ratio and the virtual air-fuel ratio. Here, the required first torque is used as an effective value of the switching target second torque. That is, while there is a difference between the target air-fuel ratio and the virtual air-fuel ratio, the calculation unit 410 outputs the requested first torque as the switching target second torque.

  The above is the details of the logic of the arithmetic unit 122, that is, the operation mode switching logic employed in the present embodiment. Next, control results when engine control is executed according to the above-described logic will be described with reference to the drawings.

  FIG. 6 is a time chart showing an image of a control result by the ECU according to the present embodiment.

  In FIG. 6, the first chart shows the time change of the torque. As described above, “TQ1r” is the requested first torque, “TQ2c” is the switching target second torque, and “TQe” is the estimated torque. Here, it is assumed that the requested first torque is the final target first torque, and the switching target second torque is the final target second torque. In addition to these torques, the actual torque is represented by a dotted line in the chart. However, actual torque is not measured by actual engine control. The actual torque line drawn on the chart is an image line supported by the test results.

  The second chart in FIG. 6 shows the time variation of the air amount. As described above, “KLt” is the target air amount, “KLe” is the estimated air amount, and “KLi” is the intermediate air amount. In the chart, the actual air amount is represented by a dotted line together with these air amounts. However, the actual air amount is not measured by actual engine control. The actual air volume line drawn on the chart is an image line supported by the test results.

  The third chart in FIG. 6 shows the change over time in the indicated ignition timing efficiency. As described above, “ηi” is the indicated ignition timing efficiency.

  The fourth chart in FIG. 6 shows the time change of the ignition timing. As described above, “SA” is the ignition timing. In the chart, the retard limit of the ignition timing is represented by a two-dot chain line.

  The fifth chart in FIG. 6 shows the time change of the air-fuel ratio. As described above, “AFt” is the target air-fuel ratio, and “AFh” is the virtual air-fuel ratio. “AF1” is the first air-fuel ratio, “AF2” is the second air-fuel ratio, and “AF3” is the third air-fuel ratio. The time chart of the actual air-fuel ratio is shown in the sixth chart in FIG.

  Based on FIG. 6, the control result by the target air-fuel ratio switching logic employed in the present embodiment will be described. At the time of deceleration, both the target air-fuel ratio and the virtual air-fuel ratio are maintained at the first air-fuel ratio, which is the theoretical air-fuel ratio, until the required first torque decreases to the level of the reference value represented by “Ref”. Therefore, the target air amount calculated from the requested first torque and the virtual air-fuel ratio decreases in conjunction with the decrease in the requested first torque. During this period, the target second torque for switching is set to an invalid value in response to the target air-fuel ratio and the virtual air-fuel ratio matching. If the target second torque for switching is an invalid value, the indicated ignition timing efficiency is 1, so the ignition timing is maintained at the optimal ignition timing. In the chart, the ignition timing changes according to the decrease in the required first torque. This is a change corresponding to the fact that the optimal ignition timing changes according to the engine speed and the air amount.

  When the requested first torque falls below the reference value, only the virtual air-fuel ratio is switched from the first air-fuel ratio to the second air-fuel ratio. That is, the target air-fuel ratio is maintained at the first air-fuel ratio that is the stoichiometric air-fuel ratio, while the virtual air-fuel ratio is made lean in a stepwise manner. The operation with the second air-fuel ratio that is a lean air-fuel ratio requires a larger amount of air than the amount of air required for the operation with the first air-fuel ratio that is the stoichiometric air-fuel ratio. For this reason, when the virtual air-fuel ratio used for calculation of the target air amount is switched to the second air-fuel ratio in a stepwise manner, the target air amount also increases in a stepwise manner at the time of the switching. However, since there is a response delay before the actuator operates and the air amount changes, the actual air amount and the estimated air amount that is the estimated value do not increase stepwise, but increase after the target air amount. I will do it.

  The requested second torque for switching is an effective value from when the requested first torque falls below the reference value until the target air-fuel ratio and the virtual air-fuel ratio coincide again after the target air-fuel ratio deviates from the virtual air-fuel ratio. The value is the same as the first torque. On the other hand, the estimated torque calculated based on the estimated air amount and the target air-fuel ratio is obtained from the first air-fuel ratio of the virtual air-fuel ratio to the second air-fuel ratio while the target air-fuel ratio is maintained at the first air-fuel ratio. As the estimated amount of air increases due to switching, it gradually increases compared to the required first torque. As a result of the estimated torque changing with respect to the required first torque, the command ignition timing efficiency, which is the ratio of the switching target second torque to the estimated torque, monotonously decreases.

  The indicated ignition timing efficiency determines the ignition timing. The smaller the value of the commanded ignition timing efficiency, the larger the retard amount of the ignition timing with respect to the optimum ignition timing. After the virtual air-fuel ratio is switched from the first air-fuel ratio to the second air-fuel ratio, the ignition timing is monotonously retarded in response to a decrease in command ignition timing efficiency.

  Eventually, the actual air amount and the estimated air amount reach the intermediate air amount. At that time, the target air-fuel ratio is quickly switched from the first air-fuel ratio to the third air-fuel ratio. At this time, the target air-fuel ratio changes stepwise instead of continuously. As a result, the actual air-fuel ratio can be changed by jumping over the air-fuel ratio region where the NOx emission amount increases.

  When the target air-fuel ratio is switched to the third air-fuel ratio, the target air-fuel ratio is continuously switched to a value for achieving the required first torque based on the current estimated air amount and predetermined torque efficiency. The predetermined torque efficiency value is a value set from the viewpoint of suppressing the NOx emission amount. After the target air-fuel ratio is switched to the third air-fuel ratio, the estimated torque becomes larger than the required first torque as the estimated air amount is increased by an amount corresponding to a predetermined torque efficiency. As a result of the estimated torque becoming a large value with respect to the requested first torque, the command ignition efficiency, which is the ratio of the switching target second torque to the estimated torque, becomes a value smaller than 1, so that the ignition timing is equal to the command ignition timing efficiency. Delayed in response to the decrease.

  When the estimated air amount converges to the target air amount and the difference between the target air amount and the estimated air amount becomes equal to or less than the threshold value, the target air-fuel ratio is fixed to the second air-fuel ratio. This completes the switching of the operation mode from the stoichiometric mode to the lean mode. Further, in response to the coincidence between the target air-fuel ratio and the virtual air-fuel ratio, the switching target second torque is returned to an invalid value. Thereby, the command ignition efficiency is returned to 1, and the ignition timing is returned to the optimum ignition timing again.

  First, consider a case where the target air-fuel ratio is changed stepwise from the third air-fuel ratio to the second air-fuel ratio as a comparative example. During the period in which the third air-fuel ratio is maintained, the estimated torque gradually increases as compared with the requested first torque as the estimated air amount increases. As a result, the ignition timing gradually increases the retard amount in response to a decrease in the instruction ignition timing efficiency. Thus, when the retard amount of the ignition timing is increased, fuel consumption is deteriorated. In addition, a retard limit is set for the ignition timing, and retarding the ignition timing beyond the retard limit is not allowed. As a result, the torque increase due to the excess air amount cannot be sufficiently offset by the retard of the ignition timing.

  On the other hand, according to the logic employed in the present embodiment, while the target air-fuel ratio is fixed at the third air-fuel ratio, the ignition timing does not continuously increase the retard amount, By retarding the air-fuel ratio continuously, the retard amount of the ignition timing is suppressed. According to such a logic, while the target air-fuel ratio is continuously changing from the third air-fuel ratio toward the second air-fuel ratio, the NOx emission amount is suppressed and the deterioration of fuel consumption is also suppressed. .

  As described above, according to the logic employed in the present embodiment, when switching from the operation with the first air-fuel ratio to the operation with the second air-fuel ratio, the actual air is jumped over the air-fuel ratio region where the NOx emission amount increases. While changing the fuel ratio stepwise, the actual air-fuel ratio is continuously changed according to the air response. Thereby, while suppressing the fluctuation | variation of a torque and switching an air fuel ratio, the deterioration of the fuel consumption performance at the time of switching and the deterioration of NOx discharge | emission performance can be suppressed.

[Others]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be adopted.

  According to the logic employed in the present embodiment, the arithmetic unit 408 calculates the target air-fuel ratio to be used as the third air-fuel ratio using the AF conversion map, but does not exceed the allowable limit of the NOx emission amount. May be incorporated into the calculation. Hereinafter, the calculation procedure will be described with reference to FIG. FIG. 7 is a diagram showing the relationship of the NOx emission amount with respect to the air-fuel ratio. First, the arithmetic unit 408 calculates a target air-fuel ratio for achieving the required first torque based on the current estimated air amount from an AF conversion map having a predetermined torque efficiency (for example, 80%). Next, the arithmetic unit 408 calculates the NOx emission amount corresponding to the calculated target air-fuel ratio using the relationship shown in FIG. If the NOx emission amount does not exceed a predetermined allowable limit, the target air-fuel ratio calculated from the AF conversion map is used as the target air-fuel ratio in this step. On the other hand, when the NOx emission amount exceeds a predetermined allowable limit, the previous step value of the target air-fuel ratio is used as the current target air-fuel ratio. As a result, the NOx emission amount during the period in which the target air-fuel ratio is the third air-fuel ratio is suppressed below the allowable limit.

  According to the logic employed in the present embodiment, the arithmetic unit 404 switches the virtual air-fuel ratio from the first air-fuel ratio to the second air-fuel ratio in response to the request first torque falling below the reference value. Yes. However, the method for switching the virtual air-fuel ratio is not limited to this, and the third air-fuel ratio may be routed when the virtual air-fuel ratio is switched from the first air-fuel ratio to the second air-fuel ratio. More specifically, while the requested first torque is greater than the reference value, the computing unit 404 sets the virtual air / fuel ratio to the first air / fuel ratio in response to the requested first torque being greater than the reference value. To do. When the requested first torque decreases and the requested first torque falls below the reference value, the arithmetic unit 404 changes the virtual air-fuel ratio from the first air-fuel ratio to the third value in response to a decrease in the requested first torque below the reference value. Switch to air-fuel ratio. Thereafter, the arithmetic unit 404 performs a comparison between the intermediate air amount and the estimated air amount for each series of controls executed by the arithmetic unit 404. When the estimated air amount reaches the intermediate air amount, the arithmetic unit 404 quickly switches the virtual air-fuel ratio from the third air-fuel ratio to the second air-fuel ratio at that time.

  When the arithmetic unit 408 detects that the virtual air-fuel ratio input from the arithmetic unit 404 has been switched from the first air-fuel ratio to the third air-fuel ratio, the arithmetic unit 408 performs a comparison between the intermediate air amount and the estimated air amount. This is performed for each series of controls. Immediately after the virtual air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the estimated air amount is smaller than the intermediate air amount. Further, since the estimated torque is a value larger than the requested first torque, the commanded ignition timing efficiency becomes a value smaller than 1, and the ignition timing is retarded. When the estimated air amount eventually reaches the intermediate air amount, the arithmetic unit 408 quickly switches the target air-fuel ratio from the first air-fuel ratio to the third air-fuel ratio at that time. As a result, the target air-fuel ratio changes by jumping over the air-fuel ratio region of the weak lean air-fuel ratio where the NOx emission amount is maximum. As a result, the actual air-fuel ratio can be changed while avoiding the air-fuel ratio region in which an increase in the NOx emission amount becomes a problem, so that the NOx emission amount at the time of switching the air-fuel ratio is effectively suppressed.

  Further, when the estimated air amount reaches the intermediate air amount, the virtual air-fuel ratio is switched from the third air-fuel ratio to the second air-fuel ratio, and the target air-fuel ratio continuously changes to the air-fuel ratio according to the current air amount. Be made. Thereby, the air amount is changed toward the target air amount corresponding to the second air-fuel ratio while suppressing the retard amount of the ignition timing. As described above, even when the virtual air-fuel ratio is switched from the first air-fuel ratio to the second air-fuel ratio via the third air-fuel ratio when the operation mode is switched from the stoichiometric mode to the lean mode, the virtual air-fuel ratio is changed to the first air-fuel ratio. Similar to the direct switching from the fuel ratio to the second air-fuel ratio, it is possible to suppress the deterioration of the fuel consumption performance and the NOx emission performance.

  The engine to be controlled in the present embodiment is not limited to a lean burn engine with a turbocharger, but may be a lean burn engine to which no turbocharger is attached. The engine to be controlled in the present embodiment is a lean burn engine with a turbocharger, and includes a supercharging characteristic variable actuator that changes the supercharging characteristic of the turbocharger such as a waste gate valve (hereinafter referred to as WGV). If it is, the following control related to WGV may be performed.

  FIG. 8 shows the setting of the operation region in the present embodiment. The operating region is specified by the intake pipe pressure and the engine speed. In the ECU, the setting of the operation region as shown in this figure is stored as a map. The ECU executes the operation mode switching according to the map. According to this figure, the lean mode region in which the lean mode is selected is set in the low / medium rotation / low / medium load region. From this figure, it can be seen that there is a region where the lean mode is selected even in the supercharging region where the intake pipe pressure is higher than the atmospheric pressure. That is, when switching the operation mode, the operation mode may be switched from the stoichiometric mode in the supercharging region to the lean mode in the supercharging region. In this case, when the WGV is once opened, it is necessary to raise the once reduced supercharging pressure again to realize the air amount corresponding to the lean mode of the supercharging region, and the time required for switching the operation mode Will be prolonged.

  Therefore, in the modification of the present embodiment, when it is determined that the operation mode is switched from the stoichiometric mode of the supercharging region to the lean mode of the supercharging region from the degree of decrease in the required first torque, the WGV Control is performed to keep closing. Thereby, since air responsiveness can be improved, the time which switching of an operation mode can be shortened effectively. Further, if the WGV is closed during the switching of the operation mode, the internal EGR rate increases as a result of increasing the back pressure. Thereby, it becomes possible to effectively suppress the NOx emission amount when the operation mode is switched. The operation amount of the WGV may be the duty ratio of the solenoid that drives the WGV, instead of the opening of the WGV.

  In the embodiment, the third air-fuel ratio has been described as 18.0. However, if the air-fuel ratio is leaner than the air-fuel ratio at which the NOx emission amount becomes maximum (for example, 16.0), the exhaust performance (NOx emission amount) and the fuel consumption performance ( The optimum value may be set as appropriate in consideration of the retard amount of the ignition timing.

  Switching of the operation mode executed by the logic adopted in the present embodiment is not limited to switching from the stoichiometric mode to the lean mode during deceleration, but switching from the stoichiometric mode to the lean mode during acceleration, for example, idle operation It can also be applied to switching of operation modes during acceleration from.

  In the embodiment, the air-fuel ratio (virtual air-fuel ratio) used for calculating the target air amount can be replaced with an equivalence ratio. The equivalence ratio is also a parameter that gives the conversion efficiency of the air amount into torque and corresponds to a parameter corresponding to the air-fuel ratio. Similarly, the excess air ratio can be used as a parameter that gives the conversion efficiency of the air amount into torque.

  As the first actuator that changes the amount of air sucked into the cylinder, a variable lift amount mechanism that makes the lift amount of the intake valve variable can also be used. The variable lift mechanism can be used alone instead of the throttle, or can be used in combination with another first actuator such as a throttle or VVT. VVT may be omitted.

  A variable nozzle can also be used as the supercharging characteristic variable actuator that changes the supercharging characteristic of the turbocharger. Further, if the turbocharger is assisted by an electric motor, the electric motor can be used as a supercharging characteristic variable actuator.

  In the implementation of the present invention, the injector as the second actuator is not limited to the port injector. An in-cylinder injector that directly injects fuel into the combustion chamber may be used, or both a port injector and an in-cylinder injector may be used in combination.

  The first air fuel ratio is not limited to the stoichiometric air fuel ratio. It is also possible to set the air-fuel ratio leaner than the stoichiometric air-fuel ratio to the first air-fuel ratio and set the air-fuel ratio leaner than the first air-fuel ratio to the second air-fuel ratio.

2 throttle 4 injector 6 ignition device 8 variable valve timing mechanism 100 engine controller 101 interface 200 as required torque receiving means power train manager 162 arithmetic units 164, 166, 178 as target air amount calculating means arithmetic as first actuator control means Units 174, 176 Arithmetic units 168, 170, 172 as second actuator control means Arithmetic units 404 as third actuator control means Arithmetic units 406, 408 as parameter value changing means Arithmetic units as target air-fuel ratio switching means

Claims (10)

An operation with the first air-fuel ratio and an operation with the second air-fuel ratio that is leaner than the first air-fuel ratio and leaner than the third air-fuel ratio that is leaner than the air-fuel ratio at which the NOx emission amount with respect to the air-fuel ratio becomes maximum The air quantity control means for controlling the air quantity, the air fuel ratio control means for controlling the air fuel ratio, and the ignition timing control means for controlling the ignition timing are operated so as to be selectable and achieve the required torque. In a control device for an internal combustion engine,
When the condition for switching the operation mode from the operation with the first air-fuel ratio to the operation with the second air-fuel ratio is satisfied, the air amount control means is configured such that the air amount is the required torque under the second air-fuel ratio. Controlling the first actuator for changing the air amount so as to achieve the air amount,
The air-fuel ratio control means estimates an estimated air amount from an operation amount of the first actuator when the condition is satisfied, and the estimated air amount achieves the required torque under the third air-fuel ratio. The air-fuel ratio is maintained at the first air-fuel ratio until the intermediate air amount to reach the first air-fuel ratio, and in response to the estimated air amount reaching the intermediate air amount, the air-fuel ratio is changed from the first air-fuel ratio to the first air-fuel ratio. After stepwise switching to the third air-fuel ratio and switching from the first air-fuel ratio to the third air-fuel ratio, the third air-fuel ratio is changed from the third air-fuel ratio to the third air-fuel ratio based on the estimated air amount and the required torque. Controlling the second actuator for changing the fuel supply amount so as to continuously change the air-fuel ratio within a range up to two air-fuel ratios;
The control device for an internal combustion engine, wherein the ignition timing control means controls a third actuator that changes an ignition timing so that a torque estimated from an operation amount of the first actuator becomes the required torque. The air-fuel ratio control means includes
After the air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, the third air-fuel ratio is changed from the third air-fuel ratio so that the torque that can be achieved by the estimated air amount at the predetermined ignition timing becomes the required torque. 2. The control device for an internal combustion engine according to claim 1, wherein the control device is configured to continuously change the air-fuel ratio within a range up to the second air-fuel ratio. The air-fuel ratio control means includes
After the air amount is changed by the air amount control means, the NOx emission amount from the cylinder at a predetermined ignition timing is calculated based on the air-fuel ratio so that the calculated NOx emission amount does not exceed a predetermined allowable limit. 3. The control device for an internal combustion engine according to claim 1, wherein the control unit is configured to continuously change the air-fuel ratio within a range from the third air-fuel ratio to the second air-fuel ratio. The air amount control means includes
A target air amount calculating means for back-calculating a target air amount for achieving the required torque based on a parameter giving efficiency of conversion of the air amount into torque from the required torque;
First actuator control means for determining an operation amount of the first actuator based on the target air amount, and controlling the first actuator according to the operation amount;
The air-fuel ratio control means includes
Parameter value changing means for changing the parameter in a direction to increase the air amount in response to the condition being satisfied;
After the parameter is changed to increase the air amount, the target air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, and the target air-fuel ratio is switched from the third air-fuel ratio to the second air-fuel ratio. Means,
A second actuator control means for determining a fuel supply amount based on the target air-fuel ratio and controlling the second actuator according to the fuel supply amount;
The ignition timing control means includes
An ignition timing for achieving the required torque is determined based on the torque estimated from the operation amount of the first actuator and the target air-fuel ratio and the required torque, and the third actuator is controlled according to the ignition timing. Including third actuator control means,
The target air-fuel ratio switching means is
First means for maintaining the target air-fuel ratio at the first air-fuel ratio until the estimated air amount reaches the intermediate air amount;
Second means for stepwise switching the target air-fuel ratio from the first air-fuel ratio to the third air-fuel ratio in response to the estimated air amount reaching the intermediate air amount;
After the target air-fuel ratio is switched from the first air-fuel ratio to the third air-fuel ratio, within the range from the third air-fuel ratio to the second air-fuel ratio based on the estimated air amount and the required torque. Third means for continuously changing the target air-fuel ratio;
The control device for an internal combustion engine according to claim 1, comprising: The parameter is a parameter corresponding to the air-fuel ratio,
The parameter value changing means includes means for switching the value of the parameter from a value corresponding to the first air-fuel ratio to a value corresponding to the second air-fuel ratio in response to the condition being satisfied. 5. The control device for an internal combustion engine according to claim 4, wherein The parameter is a parameter corresponding to the air-fuel ratio,
The parameter value changing means is configured to switch the value of the parameter from a value corresponding to the first air-fuel ratio to a value corresponding to the third air-fuel ratio in response to the condition being satisfied;
Means for switching the value of the parameter from a value corresponding to the third air-fuel ratio to a value corresponding to the second air-fuel ratio in response to the estimated air amount reaching the intermediate air amount;
The control apparatus for an internal combustion engine according to claim 4, comprising: The third means includes
After switching the target air-fuel ratio from the first air-fuel ratio to the third air-fuel ratio, the third air-fuel ratio is set such that the torque that can be achieved by the estimated air amount at a predetermined ignition timing becomes the required torque. The control device for an internal combustion engine according to any one of claims 4 to 6, wherein the target air-fuel ratio is continuously changed within a range from a first air-fuel ratio to a second air-fuel ratio. The third means includes
After switching the target air-fuel ratio from the first air-fuel ratio to the third air-fuel ratio, the NOx emission amount from the cylinder at a predetermined ignition timing is calculated based on the target air-fuel ratio, and the calculated NOx emission The target air-fuel ratio is continuously changed within a range from the third air-fuel ratio to the second air-fuel ratio so that the amount does not exceed a predetermined allowable limit. The control device for an internal combustion engine according to any one of 4 to 7. The target air-fuel ratio switching means is
In response to the difference between the target air amount and the estimated air amount being equal to or less than a threshold, the target air-fuel ratio that has been changed based on the estimated air amount and the required torque is changed to the second air-fuel ratio. The control device for an internal combustion engine according to any one of claims 4 to 8, further comprising fourth means for fixing to the engine. The internal combustion engine is a supercharged engine equipped with a supercharger;
The first actuator includes a supercharging characteristic variable actuator that changes a supercharging characteristic of the supercharger,
The first actuator control means includes
In response to satisfying a condition for switching the operation mode from the operation with the first air-fuel ratio to the operation with the second air-fuel ratio, the target air at the time when the target air-fuel ratio is switched to the second air-fuel ratio. Whether or not the target intake pipe pressure calculated from the amount reaches the supercharging region is estimated based on the required torque, and the supercharging characteristic is variable when the target intake pipe pressure is estimated to reach the supercharging region. The control device for an internal combustion engine according to any one of claims 4 to 9, wherein an actuator is operated to change in a direction to increase a supercharging pressure of the supercharger.

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