JP4941413B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine capable of adjusting an EGR amount.

  Conventionally, EGR that recirculates exhaust gas into a cylinder has been used as means for reducing pump loss of an internal combustion engine. If more EGR can be introduced into the cylinder, the effect of reducing pump loss can be increased. However, on the other hand, when a large amount of EGR is introduced, there is also a problem that the combustion stability of the internal combustion engine deteriorates. In the technique described in Japanese Patent Laid-Open No. 2005-315140, the cause of this problem is considered to be because the air-fuel ratio of the air-fuel mixture is disturbed due to the increase or decrease of the EGR amount, and by taking a solution based on such recognition, Realization of mass introduction of EGR gas.

In the technique described in Japanese Patent Application Laid-Open No. 2005-315140, the throttle opening and the EGR valve opening are controlled in coordination with changes in the required torque. More specifically, when a decrease in the required torque is detected, the EGR valve is opened within the combustion limit of the internal combustion engine while maintaining the throttle opening. If the required torque cannot be achieved even if the EGR valve opening is raised to the full combustion limit, the throttle opening is lowered. On the other hand, when an increase in the required torque is detected, the throttle opening is raised while maintaining the EGR valve opening. If the required torque cannot be realized even when the throttle opening is fully opened, the EGR valve opening is lowered.
JP-A-2005-315140

  However, it is not only EGR that determines the combustion stability of an internal combustion engine. The stability of combustion also depends on the ignition timing and air-fuel ratio. In other words, the stability of combustion is determined by the combined relationship between the intake air amount, the ignition timing, the air-fuel ratio, and the EGR amount. Even if only focusing on the EGR amount, the accuracy of torque realization by the introduction of EGR Deterioration is inevitable.

  In the technique described in JP-A-2005-315140, only the so-called external EGR introduced into the cylinder through the recirculation passage from the exhaust system to the intake system is considered. Also included is internal EGR that occurs due to the overlap between the valve opening periods of the valve and the exhaust valve. In the case of an internal combustion engine that can adjust the overlap, it is desirable to consider the internal EGR as well. In addition, since there is a difference in the responsiveness of the EGR amount with respect to the operation of the actuator between the external EGR and the internal EGR, the responsiveness of each EGR is also considered in order to prevent deterioration of combustion stability due to the introduction of EGR more reliably. Is desirable.

  The present invention has been made to solve the above-described problems, and controls an internal combustion engine that can reliably realize the torque required for the internal combustion engine by preventing the deterioration of combustion due to the introduction of EGR. An object is to provide an apparatus.

In order to achieve the above object, the first invention includes an actuator for adjusting the intake air amount, an actuator for adjusting the ignition timing, an actuator for adjusting the fuel supply amount, and an actuator for adjusting the EGR amount. In a control device for an internal combustion engine,
Target value setting means for setting each target value of torque, efficiency, air-fuel ratio and EGR rate of the internal combustion engine independently of each other based on various functions required for the internal combustion engine;
Realization priority in accordance with a predetermined realization priority with the torque target value as the highest priority so that the relationship among the torque target value, efficiency target value, air-fuel ratio target value, and EGR rate target value falls within the combustion limit of the internal combustion engine. A correction means for correcting a target value with a low realization priority based on a higher target value,
Control amount calculation means for calculating the control amount of each actuator based on the torque target value, the efficiency target value, the air-fuel ratio target value, and the EGR rate target value processed by the correction means;
It is characterized by having.

According to a second invention, in the first invention,
The correction means is a means for correcting each target value by guarding each target value with the respective upper limit value and / or lower limit value. The correction priority order is referred to a higher target value. It is characterized by changing the upper limit value and / or the lower limit value of a low target value.

According to a third invention, in the first or second invention,
The correction means corrects either the efficiency target value or the air-fuel ratio target value on the basis of the torque target value and either the efficiency target value or the air-fuel ratio target value, and further, the torque target value and the post-correction The EGR target value is corrected based on the efficiency target value and the air-fuel ratio target value.

A fourth invention is any one of the first to third inventions,
The actuator for adjusting the EGR amount includes an external EGR actuator for adjusting the external EGR amount and an internal EGR actuator for adjusting the internal EGR amount.
further,
When the EGR rate target value changes, the response speed of the external EGR amount with respect to the change in the control amount of the external EGR actuator and the response speed of the internal EGR amount with respect to the change in the control amount of the internal EGR actuator EGR rate transient correction means for calculating the time change of the realizable range and correcting the EGR rate target value so as to be within the realizable range is provided.

A fifth invention is the fourth invention,
The EGR rate transient correction means includes an external EGR model that expresses a response of the external EGR amount to a change in the control amount of the external EGR actuator by a mathematical formula, and a response of the internal EGR amount to a change in the control amount of the internal EGR actuator. A time change of an EGR rate that is expected when the external EGR actuator and the internal EGR actuator are actually operated is calculated using the external EGR model and the internal EGR model, The obtained expected EGR rate is set as an upper limit value or a lower limit value of the realizable range.

  According to the first aspect of the invention, the torque target value has the highest priority among the various set target values, and the EGR rate target value includes the efficiency target value and the air-fuel ratio target value together with the relationship between the torque target value and the internal combustion engine. Modified to be within engine combustion limits. By calculating the control amount of each actuator based on each target value thus corrected, and controlling each actuator accordingly, the target torque can be reliably realized without destabilizing the combustion. it can. Further, with respect to the efficiency target value, the air-fuel ratio target value, and the EGR rate target value, the target value having a high realization priority is corrected by correcting the target value having a low realization priority based on the target value having a higher realization priority. It can be realized with higher accuracy.

  According to the second invention, in order to correct each target value, an upper limit value and / or a lower limit value of each target value is set, each target value is compared with its upper limit value and / or lower limit value, It is only necessary to select one of the target value and the upper limit value or the lower limit value based on the comparison result. Further, a map having a target value having a higher realization priority as a parameter can be used for setting the upper limit value and / or the lower limit value. According to this invention, the calculation required for the correction process can be simplified, and the calculation load of the control device can be suppressed.

  According to the third aspect of the invention, the target value of efficiency and air-fuel ratio can be realized as much as possible by suppressing the influence of EGR on the combustion state of the internal combustion engine. Further, a target value having a higher realization priority among efficiency and air-fuel ratio can be realized with higher accuracy.

  According to the fourth aspect of the invention, the EGR rate target value is corrected so as to be within the feasible range determined from the response speeds of the external EGR amount and the internal EGR amount. The control amounts of the external EGR actuator that adjusts the external EGR amount and the internal EGR actuator that adjusts the internal EGR amount are calculated based on the target value of the realizable EGR rate thus corrected, and each actuator is controlled accordingly. As a result, even during a transition in which the EGR rate is changing, the combustion of the internal combustion engine can be stabilized and the target torque can be reliably realized.

  According to the fifth aspect of the present invention, the transient value of the EGR rate can be accurately predicted by using the mathematical model, and the accurate predicted EGR rate is set to the upper limit value or the lower limit value of the realizable range, thereby providing the EGR rate. Realization of the torque target value during the rate transition can be made more reliable.

  FIG. 1 is a block diagram showing a configuration of a control device for an internal combustion engine as an embodiment of the present invention. Hereinafter, the configuration of the control device of the present embodiment will be described with reference to FIG.

  The internal combustion engine according to the present embodiment is a spark ignition type internal combustion engine capable of adjusting both the external EGR amount and the internal EGR amount, and includes a throttle, a valve timing variable device, a valve as an actuator for controlling the operation thereof. A lift amount variable device, an external EGR device (consisting of an EGR passage and an EGR valve), an ignition device, and a fuel supply device are provided. In order to control these actuators, the control device shown in FIG. 1 includes a throttle control unit 60, a VVT control unit 62, a VL control unit 64, an external EGR control unit 66, an ignition timing control unit 68, A fuel supply control unit 70 is provided. These control units 60, 62, 64, 66, 68 and 70 operate the actuators in charge according to the control amounts calculated from various information input to the control device.

  Information input to the control device includes the intake air flow rate measured by the air flow meter, the engine speed measured by the crank angle sensor, the water temperature measured by the water temperature sensor, the oil temperature measured by the oil temperature sensor, etc. Information about the operating state of the internal combustion engine is included.

  The information input to the control device includes requests regarding various functions of the internal combustion engine. The functions of the internal combustion engine include drivability, exhaust gas, fuel consumption, noise, vibration, and the like. A host control device (not shown) that controls the entire drive device of the vehicle expresses the requests related to these functions as three physical quantities of torque, efficiency, and air-fuel ratio, and supplies them to the control device. That is, a torque request, an efficiency request, and an air-fuel ratio request are input to the control device. The efficiency here means the conversion efficiency of thermal energy that can be converted into torque to torque, and is a dimensionless parameter that is set based on the ignition timing being MBT. For example, when it is desired to use thermal energy for raising the temperature of exhaust gas for catalyst warm-up, the efficiency requirement value is set to a value smaller than the reference value of 1. Each request is not limited to one. For example, the torque request includes a torque required for vehicle control such as VSC (Vehicle Stability Control system) and TRC (Traction Control System) in addition to a shaft torque request including a request from the driver.

  The calculation for obtaining the control amount of each actuator from various information input to the control device is performed by a plurality of calculation elements 2, 4, 6, 8, 10, 12, 20, 30, 36, 40 constituting the control device. Done. Hereinafter, functions of the respective calculation elements 2, 4, 6, 8, 10, 12, 20, 30, 36, and 40 and a signal flow between the calculation elements will be described.

  The control device includes a target torque setting unit 2 that sets a target value of torque of the internal combustion engine, a target efficiency setting unit 4 that sets a target value of efficiency, a target EGR rate setting unit 6 that sets a target value of an EGR rate, and A target A / F setting unit 10 for setting a target value of an air-fuel ratio (hereinafter referred to as A / F) is provided. Among these, the target torque setting unit 2, the target efficiency setting unit 4, and the target A / F setting unit 10 aggregate a plurality of request values input from the host controller and adjust to a single value. Output as target value of internal combustion engine. Arbitration here is an operation of obtaining one numerical value from a plurality of numerical values in accordance with a predetermined calculation rule. Calculation rules include, for example, maximum value selection, minimum value selection, averaging, or superposition. The plurality of calculation rules may be appropriately combined. On the other hand, the target EGR rate setting unit 6 sets the target EGR rate using a plurality of parameters indicating the operating state of the internal combustion engine, for example, a map with the engine speed and load as axes.

  The control amount of each actuator is calculated based on the target torque, target efficiency, target EGR rate, and target air-fuel ratio set by the target value setting units 2, 4, 6, and 10. However, the control device does not use these target values as they are for calculating the control amount. Each target value set by the target value setting units 2, 4, 6, and 10 does not take into account the feasible range of the internal combustion engine. For this reason, depending on the relationship between the magnitudes of the target values output from the target value setting units 2, 4, 6, and 10, the combustion limit of the internal combustion engine may be exceeded and the internal combustion engine may not be operated properly. Therefore, the control device corrects each target value based on the mutual relationship by the correction unit 20 so that the internal combustion engine can be properly operated. The correction unit 20 corrects the target efficiency, the target EGR rate, and the target air-fuel ratio. The correction is performed by performing a guard process on the upper limit value and / or the lower limit value. Since the function of the correction unit 20 is a main part of the present embodiment, this will be described in detail later.

  The calculation of the control amount of each actuator will be described. The target intake air amount of the internal combustion engine is used to calculate the control amounts of the throttle, the valve timing variable device, the valve lift amount variable device, and the external EGR device. The throttle is an actuator that adjusts the intake air amount. The variable valve timing device and the variable valve lift amount device are internal EGR actuators that adjust the internal EGR amount. The external EGR device is an external EGR actuator that adjusts the external EGR amount.

  As a means for calculating the target intake air amount, the control device is provided with a target intake air amount calculation unit 30. More specifically, the target intake air amount calculation unit 30 includes a target torque correction unit 32 and a torque-air amount conversion unit 34.

  The target torque and the corrected target efficiency corrected by the correction unit 20 are input to the target torque correction unit 32. The target torque correction unit 32 divides and corrects the target torque by the corrected target efficiency, and outputs the corrected target torque to the torque-air amount conversion unit 34. If the corrected target efficiency is 1, which is the normal value, the target torque set by the target torque setting unit 2 is output to the torque-air amount conversion unit 34 as it is. On the other hand, if the corrected target efficiency is smaller than the normal value 1, the target torque is raised by division by the corrected target efficiency, and the raised corrected target torque is output to the torque-air amount conversion unit 34.

  The torque-air amount conversion unit 34 calculates the intake air amount necessary for realizing the corrected target torque using the MBT air amount map. The MBT air amount map is a map for converting the corrected target torque into the intake air amount, and describes the relationship between the torque and the intake air amount when the ignition timing is MBT. In the MBT air amount map, various operating conditions that affect the relationship between torque and intake air amount, such as engine speed, A / F, and EGR rate, are used as parameters. Among these, regarding the A / F and the EGR rate, the correction target A / F and the correction target EGR rate output from the correction unit 20 are used.

  The target intake air amount calculated by the torque-air amount conversion unit 34 is used by the intake system control amount calculation unit 36 together with the corrected target EGR rate output from the correction unit 20. The intake system control amount calculation unit 36 calculates the control amount of each actuator using an air inverse model, a VVT model, a VL model, and an external EGR model. The air inverse model is an inverse model obtained by modeling the response of the intake air amount to the operation of the throttle on the basis of fluid dynamics and the like and expressing it by a mathematical expression. The VVT model is a numerical expression of the response of the internal EGR amount to changes in the valve timing of the intake valve and the exhaust valve. The VL model expresses the response of the internal EGR amount to a change in the lift amount of the intake valve by a mathematical expression. The external EGR model is a mathematical expression of the response of the external EGR amount to the operation of the EGR valve. The intake system control amount calculation unit 36 calculates the control amount of each actuator using these models, and sets them in the corresponding control units 60, 62, 64, 66.

  Next, calculation of the control amount of the actuator related to ignition will be described. An actuator related to ignition is an ignition device, and an ignition timing (represented by a crank angle) based on TDC is used as a control amount. The control device calculates the target ignition timing in the target ignition timing calculation unit 40 and sets it in the ignition timing control unit 68.

  Torque efficiency is used for calculating the target ignition timing in the target ignition timing calculation unit 40. The torque efficiency is a ratio of the target torque to the estimated torque of the internal combustion engine, and is calculated by the torque efficiency calculation unit 12. The estimated torque is a torque that is output when the ignition timing is MBT under the expected intake air amount assumed under the current intake conditions. The estimated torque is calculated by the estimated torque calculator 8. The torque efficiency calculation unit 12 divides the target torque set by the target torque setting unit 2 by the estimated torque calculated by the estimated torque calculation unit 8, and calculates the calculation result as torque efficiency. However, the torque efficiency output from the torque efficiency calculation unit 12 is not directly input to the target ignition timing calculation unit 40, but the corrected torque efficiency corrected by the correction unit 20 is input to the target ignition timing calculation unit 40. Entered.

  More specifically, the target ignition timing calculation unit 40 includes a required ignition timing calculation unit 42, a predicted optimal ignition timing calculation unit 44, an ignition retard amount calculation unit 46, an optimal ignition timing calculation unit 48, a cold correction amount calculation unit 50, A knock correction amount calculation unit 52 and a target ignition timing setting unit 54 are included.

  The corrected torque efficiency output from the correction unit 20 is input to the required ignition timing calculation unit 42. The required ignition timing calculation unit 42 calculates the required ignition timing for realizing the corrected torque efficiency based on the expected intake air amount. A required ignition timing map is used for calculating the required ignition timing. The required ignition timing map is a map for converting the corrected torque efficiency into the ignition timing, and various operating conditions that affect the determination of the ignition timing, such as the target torque, the rotation speed, and the valve timing, are used as parameters. Further, the correction target EGR rate and the correction target A / F output from the correction unit 20 are also used as parameters. This map is designed such that when the corrected torque efficiency is 1, the required ignition timing is set to the optimal ignition timing, and the required ignition timing is set to the retard side as the corrected torque efficiency is smaller.

  The expected optimal ignition timing calculation unit 44 calculates the optimal ignition timing under the expected intake air amount. An ignition timing map is used for calculating the optimal ignition timing. This map is a map for converting the estimated torque into the optimum ignition timing, and various operating conditions that affect the determination of the ignition timing, such as the rotational speed and the valve timing, are used as parameters. Further, the correction target EGR rate and the correction target A / F output from the correction unit 20 are also used as parameters.

  The ignition retard amount calculation unit 46 is a deviation between the optimal ignition timing based on the expected intake air amount calculated by the expected optimal ignition timing calculation unit 44 and the required ignition timing calculated by the required ignition timing calculation unit 42. ΔSA is calculated, and the calculation result is output as an ignition retardation amount. The ignition retard amount calculated here is an ignition retard amount necessary for realizing the target torque under the estimated intake air amount. When the corrected torque efficiency is 1, that is, when the estimated torque and the target torque match, the required ignition timing matches the optimal ignition timing, so that the output ignition retard amount becomes zero. On the other hand, when the torque efficiency is smaller than 1, that is, when there is a difference between the estimated torque and the target torque, an ignition delay amount is calculated to compensate for the difference by torque adjustment by retarding the ignition timing. The

  The optimum ignition timing calculation unit 48 calculates the optimum ignition timing based on the actual intake air amount of the internal combustion engine. An optimal ignition timing map is used for calculation of the optimal ignition timing here. This map is a map for converting the actual intake air amount into the optimal ignition timing, and various operating conditions that affect the determination of the ignition timing, such as the rotational speed, are used as parameters. Further, the correction target EGR rate and the correction target A / F output from the correction unit 20 are also used as parameters. The actual intake air amount of the internal combustion engine can be accurately obtained by taking into consideration the actual air flow rate measured by the air flow meter in addition to the current intake conditions such as the throttle opening.

  The target ignition timing setting unit 54 adds the ignition delay amount calculated by the ignition delay amount calculation unit 46 to the optimal ignition timing calculated by the optimal ignition timing calculation unit 48. Further, the cold correction amount output from the cold correction amount calculation unit 50 and the knock correction amount output from the knock correction amount calculation unit 52 are added. The cold correction amount calculation unit 50 reads out and outputs a retard amount corresponding to the starting temperature of the internal combustion engine from the map, and the knock correction amount calculation unit 52 calculates a retard amount for avoiding the occurrence of the knock. Output. The target ignition timing setting unit 54 sets the total value as the target ignition timing of the internal combustion engine, and sets it in the ignition timing control unit 68.

  Finally, calculation of the control amount of the actuator related to fuel supply will be described. An actuator related to fuel supply is a fuel supply device, and the drive time of the injector, that is, the fuel injection time is used as a control amount. The fuel supply device may supply fuel directly into the cylinder or may inject fuel into the intake port. The fuel injection time is calculated based on the target A / F and the intake air amount. The correction target A / F corrected by the correction unit 20 is input to the fuel supply control unit 70.

  The overall configuration and function of the control device of the present embodiment has been described above. Next, details of the correction unit 20 which is a main part of the present embodiment will be described with reference to FIGS. 2, 3 and 4 in addition to FIG.

  The correction unit 20 corrects each target value based on the mutual relationship so that the internal combustion engine can be properly operated as described above, and each target value is set to the respective upper limit value and / or lower limit value. Each target value is corrected by guarding with. According to such a correction method, it is only necessary to compare each target value with its upper and lower limit values and select either the target value and the upper limit value or the lower limit value based on the comparison result. Can be simplified, and the calculation load on the control device can be reduced.

  As shown in FIG. 1, the correction unit 20 includes an efficiency guard unit 22, an EGR rate guard unit 24, a torque efficiency guard unit 26, and an A / F guard unit 28. The efficiency guard unit 22 guards the target efficiency set by the target efficiency setting unit 4 with the upper limit efficiency and the lower limit efficiency. The EGR rate guard unit 24 guards the target EGR rate set by the target EGR rate setting unit 6 with the upper limit EGR rate and the lower limit EGR rate. The torque efficiency guard unit 26 guards the torque efficiency calculated by the torque efficiency calculation unit 12 with the upper limit efficiency and the lower limit efficiency. The upper limit efficiency and the lower limit efficiency used in the torque efficiency guard unit 26 are equal to the upper limit efficiency and the lower limit efficiency used in the efficiency guard unit 22. Then, the A / F guard unit 28 guards the target A / F set by the target A / F setting unit 10 with the upper limit A / F and the lower limit A / F.

  The correction unit 20 limits the target efficiency, the target EGR rate, the torque efficiency, and the effective range of the target A / F by the guard units 22, 24, 26, and 28, so that these relationships are within the combustion limit of the internal combustion engine. To fit in. However, if the guard values used in the guard portions 22, 24, 26, and 28 are fixed, the operating range of the internal combustion engine that can be realized becomes narrow, and it is possible to meet the demands regarding various functions of the internal combustion engine. Disappear. Therefore, the correction unit 20 makes the guard values of the guard units 22, 24, 26, and 28 variable according to the relationship between the target torque, the target efficiency, the target EGR rate, and the target A / F, as will be described below. Each target value is realized as much as possible within a range not exceeding the combustion limit.

  FIG. 2 is a block diagram showing the configuration of the correction unit 20 more specifically. As shown in this figure, the target torque and the target A / F are input to the efficiency guard unit 22 and the torque efficiency guard unit 26 as reference information. The efficiency guard unit 22 and the torque efficiency guard unit 26 set the upper limit efficiency and the lower limit efficiency based on the target torque and the target A / F. A map is used for setting the upper limit efficiency and the lower limit efficiency. In this map, in addition to the target torque and target A / F, the rotation speed and water temperature (or oil temperature) are also used as parameters.

  A target torque and target efficiency are input to the A / F guard unit 28 as reference information. The A / F guard unit 28 sets the upper limit A / F and the lower limit A / F based on the target torque and the target efficiency. A map is used for setting the upper limit A / F and the lower limit A / F. In this map, in addition to the target torque and target efficiency, the rotation speed and water temperature (or oil temperature) are also used as parameters.

  The A / F guard 28, the efficiency guard 22, and the torque efficiency guard 26 function in conjunction with each other according to the operation mode of the internal combustion engine. As operation modes of the internal combustion engine, an efficiency priority mode and an A / F priority mode are provided. In the efficiency priority mode, the realization of the target efficiency is prioritized over the target A / F, and in the A / F priority mode, the realization of the target A / F is prioritized over the target efficiency. Therefore, in the efficiency priority mode, the target efficiency guard process based on the target A / F by the efficiency guard unit 22 and the torque efficiency guard unit 26 is not performed, and the target based on the target efficiency by the A / F guard unit 28 is not performed. Only the A / F guard process is performed. On the contrary, in the A / F priority mode, the guard process for the target A / F based on the target efficiency is not performed, but only the guard process for the target efficiency based on the target A / F is performed.

  More specifically, the EGR rate guard unit 24 includes a steady guard unit 242, a transient guard unit 244, and a transient upper / lower limit value calculation unit 246. The steady guard unit 242 guards the target EGR rate with an upper limit value and a lower limit value (steady guard value) corresponding to the steady state, and the transient guard unit 244 upper limit value and lower limit corresponding to the transient state where the EGR rate is changing. The target EGR rate is guarded with a value (transient guard value). The reason why the transition guard unit 244 is provided separately from the steady guard unit 242 is that there is a response delay in the change of the EGR rate with respect to the operation of the actuator.

  The target guard, the corrected target efficiency, and the corrected target A / F are input to the steady guard unit 242 as reference information. The corrected target efficiency is the target efficiency that has passed through the efficiency guard unit 22, and the corrected target A / F is the target A / F that has passed through the A / F guard unit 28. In this embodiment, the realization of the target torque is given the highest priority, and then the realization of the target efficiency or the target A / F is prioritized. Therefore, the steady guard unit 242 sets the upper limit EGR rate and the lower limit EGR rate based on the target torque, the corrected target efficiency, and the corrected target A / F. A map is used for setting the upper limit EGR rate and the lower limit EGR rate. In this map, in addition to the target torque, the correction target efficiency, and the correction target A / F, the rotation speed and the water temperature (or oil temperature) are also used as parameters.

  FIG. 3 shows the relationship between the target torque and the EGR rate that can be realized under the target torque. The realizable EGR rate is an EGR rate that can be finally realized when all the actuators related to EGR are used. In this figure, efficiency and A / F are constant. In the aforementioned map, the feasible EGR rate shown in FIG. 3 is set as the upper limit value (steady guard value) in the steady state of the target EGR rate.

  The target EGR rate subjected to guard processing by the steady guard unit 242 is subsequently subjected to guard processing by the transient guard unit 244 as well. The upper and lower limit values (transient guard values) used in the transient guard unit 244 are calculated by the transient upper and lower limit value calculation unit 246.

  The transient upper / lower limit calculation unit 246 includes a VVT model and a VL model, which are internal EGR models, and an external EGR model. By using the VVT model and the VL model, it is possible to calculate the response speed of the internal EGR amount with respect to the change in each control amount of the valve timing variable device and the valve lift amount variable device when the target EGR rate changes. Also, by using the external EGR model, it is possible to calculate the response speed of the external EGR amount with respect to the change in the control amount of the external EGR device when the target EGR rate changes. If these response speeds are known, it is possible to calculate the time change of the EGR rate that is expected when the variable valve timing device, the variable valve lift amount device, and the external EGR device are actually operated.

  FIG. 4 shows a calculation example of the time change of the EGR rate using a model. In this example, the actual EGR rate change expected when the target EGR rate is increased from α to β at the current time and the valve timing variable device and the external EGR device are operated accordingly is calculated. . The operation of the EGR rate by the variable valve timing device is characterized in that although the response speed of the EGR rate is fast, the range of the EGR rate that can be operated is narrow. On the other hand, the operation of the EGR rate by the variable valve timing device is characterized in that the range of the EGR rate that can be operated is wide although the response speed is slow. As a result, in the transient state, the realizable EGR rate changes with time as shown in FIG. The transient upper and lower limit value calculation unit 246 sets the feasible EGR rate shown in FIG. 4 as the upper limit value (transient guard value) in the transient state of the target EGR rate.

  As described above, according to the control apparatus of the present embodiment, the target torque is given the highest priority among the target values set based on various functions required for the internal combustion engine, and the target EGR rate is determined based on the target efficiency and These relations including the target torque as well as the target air-fuel ratio are corrected so as to be within the combustion limit of the internal combustion engine. By calculating the control amount of each actuator based on each target value thus corrected and controlling each actuator accordingly, the target torque can be reliably realized without destabilizing combustion. Also, with regard to target efficiency, target air-fuel ratio, and target EGR rate, target values with higher realization priority have higher accuracy by correcting target values with lower realization priority based on target values with higher realization priority. Can be realized.

  Furthermore, according to the control apparatus of the present embodiment, the target EGR rate is corrected in the transient guard unit 244 so that it falls within the feasible range determined from the respective response speeds of the external EGR amount and the internal EGR amount. By calculating the control amounts of the variable valve timing device, the variable valve lift amount device, and the external EGR device based on the realizable target EGR rate thus corrected, the EGR rate is obtained by controlling each actuator accordingly. Even during the changing transition, the combustion of the internal combustion engine can be stabilized and the target torque can be reliably realized.

  In the present embodiment, the target torque setting unit 2, the target efficiency setting unit 4, the target EGR rate setting unit 6, and the target A / F setting unit 10 correspond to “target value setting means” of the present invention. The correction unit 20 corresponds to the “correction unit” of the present invention, and in particular, the transient guard unit 244 and the transient upper / lower limit value calculation unit 246 correspond to the “EGR rate transient correction unit” of the present invention. The target intake air amount calculation unit 30, the intake system control amount calculation unit 36, and the target ignition timing calculation unit 40 correspond to “control amount calculation means” of the present invention.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above embodiment, the target EGR rate is calculated inside the control device. However, the target EGR rate may be input as a required value from the host control device in the same manner as the target torque, target efficiency, and target A / F. Further, in the above embodiment, the target efficiency and the target priority for realizing the target A / F are set higher than the target EGR rate, but the target priority for realizing the target EGR rate may be set higher. Alternatively, the priority for realizing the target EGR rate can be increased according to the operation mode of the internal combustion engine.

  The above embodiment is an example in which the present invention is applied to an internal combustion engine having a valve timing variable device and a valve lift amount variable device. However, the present invention is also applied to an internal combustion engine having only one internal EGR actuator. Is possible. Further, the present invention can be applied to an internal combustion engine having only an external EGR actuator without an internal EGR actuator, and conversely, can be applied to an internal combustion engine having only an internal EGR actuator without an external EGR actuator. It is.

It is a block diagram which shows the structure of the control apparatus of the internal combustion engine as embodiment of this invention. It is a block diagram which shows the structure of the correction part of the control apparatus shown in FIG. It is a figure for demonstrating the setting of the steady guard value of an EGR rate. It is a figure for demonstrating the setting of the transient guard value of an EGR rate.

Explanation of symbols

2 Target torque setting unit 4 Target efficiency setting unit 6 Target EGR rate setting unit 8 Estimated torque calculation unit 10 Target A / F setting unit 12 Torque efficiency calculation unit 20 Correction unit 22 Efficiency guard unit 24 EGR rate guard unit 242 Steady guard unit 244 Transient guard section 246 Transient upper / lower limit calculation section 26 Torque efficiency guard section 28 A / F guard section 30 Target intake air amount calculation section 36 Intake system control amount calculation section 40 Target ignition timing calculation section 60 Throttle control section 62 VVT control section 64 VL control unit 66 External EGR control unit 68 Ignition timing control unit 70 Fuel supply control unit

Claims (5)

In a control device for an internal combustion engine, comprising an actuator for adjusting an intake air amount, an actuator for adjusting an ignition timing, an actuator for adjusting a fuel supply amount, and an actuator for adjusting an EGR amount,
Target value setting means for setting each target value of torque, efficiency, air-fuel ratio and EGR rate of the internal combustion engine independently of each other based on various functions required for the internal combustion engine;
Realization priority in accordance with a predetermined realization priority with the torque target value as the highest priority so that the relationship among the torque target value, efficiency target value, air-fuel ratio target value, and EGR rate target value falls within the combustion limit of the internal combustion engine. A correction means for correcting a target value with a low realization priority based on a higher target value,
Control amount calculation means for calculating the control amount of each actuator based on the torque target value, the efficiency target value, the air-fuel ratio target value, and the EGR rate target value processed by the correction means;
A control device for an internal combustion engine, comprising:   The correction means is a means for correcting each target value by guarding each target value with the respective upper limit value and / or lower limit value. The correction priority order is referred to a higher target value. 2. The control apparatus for an internal combustion engine according to claim 1, wherein an upper limit value and / or a lower limit value of a target value having a low value is changed.   The correction means corrects either the efficiency target value or the air-fuel ratio target value on the basis of the torque target value and either the efficiency target value or the air-fuel ratio target value, and further, the torque target value and the post-correction 3. The control device for an internal combustion engine according to claim 1, wherein the EGR target value is corrected based on the efficiency target value and the air-fuel ratio target value. The actuator for adjusting the EGR amount includes an external EGR actuator for adjusting the external EGR amount and an internal EGR actuator for adjusting the internal EGR amount.
further,
When the EGR rate target value changes, the response speed of the external EGR amount with respect to the change in the control amount of the external EGR actuator and the response speed of the internal EGR amount with respect to the change in the control amount of the internal EGR actuator The internal combustion engine according to any one of claims 1 to 3, further comprising EGR rate transient correction means for calculating a time change of the realizable range and correcting the EGR rate target value so as to be within the realizable range. Engine control device.   The EGR rate transient correction means includes an external EGR model that expresses a response of the external EGR amount to a change in the control amount of the external EGR actuator by a mathematical formula, and a response of the internal EGR amount to a change in the control amount of the internal EGR actuator. A time change of an EGR rate that is expected when the external EGR actuator and the internal EGR actuator are actually operated is calculated using the external EGR model and the internal EGR model, 5. The control apparatus for an internal combustion engine according to claim 4, wherein the obtained expected EGR rate is set as an upper limit value or a lower limit value of a realizable range.

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