JP5381790B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more specifically, an air inverse model is used to determine a target throttle opening, and torque control and air-fuel ratio control are performed using an air model to predict in-cylinder intake air amount. It is related with the control apparatus to perform.

  The operation of the internal combustion engine is controlled through operations of a plurality of actuators such as a throttle, an ignition device, and a fuel injection device. In order to accurately control the operation of the internal combustion engine, it is necessary to be able to accurately calculate an operation amount for obtaining a desired result, and it is also necessary to be able to accurately predict a result generated by operating the actuator. The former model is used for the inverse model of the dynamic model that models the dynamic characteristics of the internal combustion engine, and the forward model is used for the former purpose. For example, in the invention of the fuel injection device disclosed in Japanese Patent Application Laid-Open No. 2004-108216, both a dynamic model and its inverse model are used. In the present invention, the inverse model of the dynamic model is used to calculate the pumping timing of the regulating valve for setting the fuel pressure to the target value, and the dynamic model is used to predict the fuel pressure realized by the calculated pumping timing. ing.

  As an internal combustion engine dynamic model, for example, an air model disclosed in Japanese Patent Application Laid-Open No. 2007-239484 is also known. The air model is a model of the response of the in-cylinder intake air amount to the operation of the throttle, and can be composed of a throttle model, an intake pipe model, and an intake valve model. The throttle model is a calculation model in which the relationship between the throttle opening and the amount of air passing through the throttle is expressed by a mathematical expression. The intake pipe model is a calculation model that expresses the relationship between the amount of air passing through the throttle, the amount of intake air in the cylinder, and the intake pipe pressure using mathematical formulas. The intake valve model is a calculation model in which the relationship between the intake pipe pressure and the in-cylinder intake air amount is expressed by a mathematical expression. By using such an air model, it is possible to accurately predict the in-cylinder intake air amount that can be realized by operating the throttle. If the in-cylinder intake air amount can be predicted, the fuel injection amount necessary for realizing the target air-fuel ratio can be accurately calculated. Therefore, by using the air model as described above, the control accuracy of the air-fuel ratio control can be improved. .

  In addition, regarding torque control of an internal combustion engine, it is also known to use an inverse model of an air model for calculating the throttle opening. The air inverse model calculates the air model in the reverse direction. In the calculation of the throttle opening using the air inverse model, first, the target cylinder intake air amount is determined from the target torque. Then, the target cylinder intake air amount is converted into the target intake pipe pressure by an inverse model of the intake valve model. Next, the target value of the throttle passage air amount is calculated from the target intake pipe pressure by the inverse model of the intake pipe model. Finally, the throttle opening required to achieve the target throttle passing air amount is calculated using an inverse model of the throttle model. If such an air inverse model is used, the throttle opening required to achieve the target torque can be accurately calculated. That is, by using an air inverse model for calculation of the throttle opening, it is possible to increase the control accuracy of torque control.

  In the dynamic model of the internal combustion engine as described above and vice versa, the problem is how to reduce the model error with the actual phenomenon in the internal combustion engine. For this reason, in the invention disclosed in Japanese Patent Application Laid-Open No. 2004-108216, the difference between the measured value of the fuel pressure and the predicted fuel pressure based on the dynamic model is calculated, and the dynamic model and The parameter (coefficient) of each model formula of the inverse model is sequentially adjusted and updated.

  In the invention disclosed in Japanese Patent Application Laid-Open No. 2007-239484, the flow coefficient of the throttle model is corrected by a coefficient defined as a function of the output value of the air flow meter (hereinafter referred to as a calibration coefficient). The calibration coefficient is a coefficient for making the throttle passage air amount calculated by the throttle model coincide with the actual throttle passage air amount, and the update is sequentially performed using the output value of the air flow meter.

JP 2004-108216 A JP 2007-239484 A JP 2002-227682 A JP-A-10-274082 JP 2009-174328 A

  Torque control using the air inverse model can be performed in one controller together with air-fuel ratio control using the air model. In this case, since the output value of the air inverse model becomes the input value of the air model, the output value of the air model should be the same as the input value of the air inverse model. However, since the air model is calibrated with the output value of the air flow meter as described above, the output value of the air model (predicted in-cylinder intake air amount) and the input value of the air inverse model (target in-cylinder intake air amount) Does not necessarily match. Calibration of the air model is performed to correct the model error included in the air model, so if there is a gap between the predicted in-cylinder intake air amount and the target in-cylinder intake air amount, that is the air inverse model. And the model error is included in the air model.

  In order to improve the control accuracy of torque control and air-fuel ratio control of the internal combustion engine, model errors included in the air inverse model and the air model are eliminated so that the predicted in-cylinder intake air amount matches the target in-cylinder intake air amount. There is a need. As a method for that purpose, for example, application of the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2004-108216 is conceivable. That is, this is a method of calculating the difference between the target in-cylinder intake air amount and the predicted in-cylinder intake air amount, and correcting each model formula of the air inverse model and the air model based on the difference.

  However, the air model is calibrated in parallel with the output value of the air flow meter. Therefore, the correction effect based on the difference between the target in-cylinder intake air amount and the predicted in-cylinder intake air amount and the calibration effect based on the output value of the air flow meter cancel each other, and the target in-cylinder intake air amount There is a possibility that the difference between the estimated intake air amount in the cylinder does not become small. Therefore, the method disclosed in Japanese Patent Application Laid-Open No. 2004-108216 is not necessarily appropriate as a method for eliminating the model error in a control system including an air model and an air inverse model.

  The present invention has been made in view of the above-described problems, and an object thereof is to improve the control accuracy of torque control and air-fuel ratio control performed using an air model and an air inverse model.

In order to achieve the above object, the present invention
Used in an internal combustion engine having a throttle provided in an intake passage, an air flow meter arranged upstream thereof, an injector for injecting fuel into an intake port or a combustion chamber, and an air-fuel ratio sensor provided in an exhaust passage, In a control device that operates the throttle and the injector so as to realize a target torque and a target air-fuel ratio, respectively.
Target in-cylinder intake air amount determination means for converting the target torque into a target in-cylinder intake air amount;
A reverse air model in which a relationship between a change in throttle opening and a change in in-cylinder intake air amount is modeled by an inverse model, and a target for realizing the target in-cylinder intake air amount using the reverse air model; Target throttle opening calculating means for calculating the throttle opening;
Throttle operating means for operating the throttle according to the target throttle opening;
A cylinder that has an air model in which a relationship between a change in throttle opening and a change in in-cylinder intake air amount is modeled by a forward model, and predicts the in-cylinder intake air amount that is realized by operating the throttle using the air model Means for predicting the amount of intake air,
Air model calibration means for successively adjusting and updating the calibration coefficient of the air model using the output value of the air flow meter;
Air inverse model coefficient correction means for correcting a coefficient of the air inverse model based on a comparison result comparing the target cylinder intake air amount and the predicted cylinder intake air amount;
Target fuel injection amount calculating means for calculating a target fuel injection amount for realizing the target air-fuel ratio based on the predicted in-cylinder intake air amount and the actual air-fuel ratio actually measured by the air-fuel ratio sensor;
Injector operating means for operating the injector according to the target fuel injection amount;
Air model coefficient correction means for reflecting the correction result in the coefficient of the air model after correcting the coefficient of the air inverse model when the magnitude of the difference between the target air-fuel ratio and the actual air-fuel ratio is equal to or greater than a predetermined threshold; ,
It is characterized by having.

  According to the present invention, the calibration result of the air model is sequentially adjusted and updated using the output value of the air flow meter, while the target in-cylinder intake air amount is compared with the predicted in-cylinder intake air amount based on the air model. Based on this, the coefficient of the air inverse model can be corrected. If the magnitude of the difference between the target air-fuel ratio and the actual air-fuel ratio is equal to or greater than a predetermined threshold, after correcting the air inverse model coefficient, the correction result can be reflected in the air model coefficient. As a result, the model error of the inverse model and the air model is reduced, and both the accuracy of torque control and the accuracy of air-fuel ratio control are improved.

1 is a schematic view showing a configuration of an internal combustion engine according to an embodiment of the present invention. It is a block diagram which shows the structure of the control apparatus of embodiment of this invention. It is a flowchart which shows the correction | amendment procedure of the air reverse model and air model of embodiment of this invention.

  Embodiments of the present invention will be described with reference to FIGS. 1 to 3.

  First, an internal combustion engine controlled by the control device of the present embodiment will be described. FIG. 1 is a schematic diagram showing the configuration of the internal combustion engine of the present embodiment. The internal combustion engine 1 of the present embodiment is a spark ignition type four-stroke engine. The internal combustion engine 1 includes a combustion chamber 14 defined by a piston 2 and a cylinder wall surface. A spark plug 8 for igniting the fuel mixture in the combustion chamber 14 is attached to the top of the combustion chamber 14. Further, an intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14. An intake valve 4 for controlling a communication state between the intake passage 16 and the combustion chamber 14 is provided at a connection portion between the intake passage 16 and the combustion chamber 14. An exhaust valve 6 for controlling a communication state between the exhaust passage 18 and the combustion chamber 14 is provided at a connection portion between the exhaust passage 18 and the combustion chamber 14. Further, the internal combustion engine 1 of the present embodiment is a multi-cylinder engine, and the combustion chamber 14 exists for each cylinder. The intake passage 16 is formed by an intake manifold 22 connected to each cylinder, and an intake duct 20 connecting the intake manifold 22 and the intake port. An electronically controlled throttle 12 is disposed in the intake duct 20, and an air flow meter 24 is attached upstream thereof. An injector 10 is attached to each intake branch pipe of the intake manifold 22. A catalyst 26 is disposed in the exhaust passage 18 and an air-fuel ratio sensor 28 is attached upstream thereof.

  The control device of the present embodiment is realized as part of the function of the electronic control unit 30 that controls the internal combustion engine 1. The electronic control unit 30 as a control device receives various information regarding the operating state and operating conditions of the internal combustion engine 1 from various sensors provided inside and outside the internal combustion engine 1. The electronic control unit 30 operates the actuator of the internal combustion engine 1 based on the information, and controls the operation of the internal combustion engine 1 by the operation. Information input to the electronic control unit 30 includes the intake air amount measured by the air flow meter 24, the exhaust air / fuel ratio measured by the air / fuel ratio sensor 28, the engine speed, the atmospheric pressure, the atmospheric temperature, and the like. The actuator operated by the electronic control unit 30 includes the injector 10, the throttle 12, and the like.

  The electronic control unit 30 as a control device performs torque control and air-fuel ratio control of the internal combustion engine 1. The torque control of the internal combustion engine 1 is performed mainly by adjusting the cylinder intake air amount by operating the throttle 12, and the air-fuel ratio control of the internal combustion engine 1 is performed mainly by adjusting the fuel injection amount by operating the injector 10. FIG. 2 is a block diagram showing the configuration of the electronic control unit 30 when focusing on torque control and air-fuel ratio control. As shown in FIG. 2, the electronic control unit 30 includes a torque-KL conversion map 32, an air inverse model 34, an air model 36, and a model correction unit 38. The configuration shown in FIG. 2 is a configuration that is virtually realized by the CPU operating in accordance with a program stored in the memory of the electronic control unit 30.

  The torque-KL conversion map 32 in FIG. 2 is a map in which the torque and the in-cylinder intake air amount are associated using engine information such as engine speed and ignition timing as keys. The target torque set based on the torque request from the driver or the torque request from the vehicle control device is converted into a target in-cylinder intake air amount (indicated as target KL in FIG. 2) by the torque-KL conversion map 32. .

  The air inverse model 34 is obtained by modeling the relationship between the change in the throttle opening and the change in the in-cylinder intake air amount using an inverse model. The electronic control unit 30 converts the target cylinder intake air amount into the throttle opening by the air inverse model 34. The throttle opening output from the air inverse model 34 is a throttle opening required to achieve the target in-cylinder intake air amount. The electronic control unit 30 operates the throttle 12 with the output value of the air inverse model 34 as the target throttle opening (indicated as target TA in FIG. 2).

  The air model 36 is obtained by modeling the relationship between the change in the throttle opening and the change in the in-cylinder intake air amount using a forward model. The electronic control unit 30 converts the target throttle opening output from the air inverse model 34 into the in-cylinder intake air amount by the air model 36. The in-cylinder intake air amount output from the air model 36 is the in-cylinder intake air amount that is predicted to be realized by the target throttle opening. The electronic control unit 30 realizes the target air-fuel ratio based on the predicted in-cylinder intake air amount (denoted as predicted actual KL in FIG. 2) by the air model 36 and the exhaust air-fuel ratio actually measured by the air-fuel ratio sensor 28. The target fuel injection amount is calculated, and the injector 10 is operated according to the target fuel injection amount.

  The model correction unit 38 is provided to improve the model accuracy of the air inverse model 34 and the air model 36. The model correction unit 38 compares the target in-cylinder intake air amount with the predicted in-cylinder intake air amount, and corrects the coefficients of the model calculation formulas of the air inverse model 34 and the air model 36 based on the comparison result. Hereinafter, in order to clarify a specific correction method, model calculation formulas constituting the air inverse model 34 and the air model 36 will be briefly described.

  It is assumed that the air model 36 of the present embodiment includes a throttle model, an intake pipe model, and an intake valve model. In addition, the air inverse model 34 of the present embodiment is composed of a throttle model inverse model, an intake pipe model inverse model, and an intake valve model inverse model.

  The throttle model is a calculation model in which the relationship between the throttle opening and the amount of air passing through the throttle is expressed by a mathematical expression. The amount of air passing through the throttle is determined by the gas pressure and temperature before and after the throttle 12 and the opening area of the throttle 12. The following formula 1 is a specific model calculation formula.

In Formula 1, _{m t} is the air flowing into the intake manifold 22 through a throttle 12 flow rate (g / sec), namely, it means throttle air flow. Ta represents atmospheric temperature, Pa represents atmospheric pressure, and _Pm represents intake manifold pressure (that is, intake pipe pressure). TA means the throttle opening. B is a collective representation of the flow coefficient and the opening area of the throttle 12, and is a function of the throttle opening TA. Φ is _a function of P _m / P _a .

The intake pipe model is a calculation model that expresses the relationship between the amount of air passing through the throttle, the amount of intake air in the cylinder, and the intake pipe pressure using mathematical formulas. The model calculation formula derived from the energy conservation law is the following formula 2, and the model calculation formula derived from the mass conservation law is the following formula 3. The flow rate of air m _c in each formula is sucked into the combustion chamber 14 from the intake manifold 22 (g / sec), namely, it means in-cylinder intake air quantity.

  The intake valve model is a calculation model in which the relationship between the intake pipe pressure and the in-cylinder intake air amount is expressed by a mathematical expression. The following formula 4 is a specific model calculation formula. In Equation 4, a and b are coefficients determined by the engine speed, and their initial values are determined by adaptation.

  The air model 36 calculates the above four model calculation formulas in the forward direction, and the air reverse model 34 calculates in the reverse direction. That is, the air model 36 and the air inverse model 34 share the same model calculation formula. However, the air model 36 has a function that the air inverse model 34 does not have. The function is a function for correcting the flow coefficient of the throttle model according to the output value of the air flow meter 24. Because of this function, the output value of the air flow meter 24 (indicated as AFM in FIG. 2) is sequentially input to the air model 36.

  In order to correct the flow coefficient of the throttle model in the air model 36, a calibration coefficient defined as a function of the output value of the air flow meter is used. The calibration coefficient is a coefficient for making the throttle passage air amount calculated by the throttle model coincide with the actual throttle passage air amount, and is multiplied by the flow coefficient. Therefore, B included in Expression 1 is expressed as a product of the flow coefficient and the throttle opening area when Expression 1 is a model calculation expression of the air inverse model 34, but Expression 1 is a model calculation expression of the air model 36. Is expressed as a product of a flow coefficient, a throttle opening area, and a calibration coefficient.

  The model correction unit 38 corrects the coefficient a or the coefficient b included in the model calculation formula 4 or the coefficient B included in the model calculation formula 1 to thereby calculate the target cylinder intake air amount and the predicted cylinder intake air amount. To eliminate the difference. How to correct the coefficient to be corrected is determined in advance in relation to the magnitude of the difference and positive / negative. The model correction unit 38 corrects the air inverse model 34 and the air model 36 according to the predetermined rule.

  FIG. 3 is a flowchart showing a procedure for correcting the air inverse model 34 and the air model 36 performed by the model correction unit 38. In the first step S2, it is determined whether or not there is a difference between the target cylinder intake air amount (target KL) and the predicted cylinder intake air amount (predicted actual KL). If there is no difference, it is assumed that there is no influence by the model error, and the process of the subsequent step is skipped.

  If it is determined in step S2 that a difference has occurred, the process of step S4 is performed. In step S4, the coefficient of the air inverse model 34 is corrected based on the magnitude of the difference and its sign. However, the air model 36 is not corrected simultaneously with the air inverse model 34 in this step. This is because the air model 36 is calibrated in parallel with the model calculation formula based on the output value of the air flow meter 24. The correction based on the difference is performed only on the air inverse model 34, and only the calibration based on the output value of the air flow meter 24 is performed on the air model 36, so that the difference between the target cylinder intake air amount and the predicted cylinder intake air amount is reduced. It is possible to avoid a situation where it does not become very small.

  In the next step S6, the difference between the target air-fuel ratio and the actual air-fuel ratio actually measured by the air-fuel ratio sensor 28 is calculated, and it is determined whether or not the magnitude of the difference is greater than or equal to a predetermined threshold value. The electronic control unit 30 determines the basic fuel injection amount based on the predicted in-cylinder intake air amount and the target air-fuel ratio, and corrects the fuel injection amount so that the fed back actual air-fuel ratio approaches the target air-fuel ratio. ing. For this reason, if the calculation of the predicted in-cylinder intake air amount by the air model 36 is accurate, the difference between the target air-fuel ratio and the actual air-fuel ratio can be kept small. However, if the calculation is not accurate, the difference between the target air-fuel ratio and the actual air-fuel ratio is not easily reduced.

  If it is determined in step S6 that there is a difference greater than or equal to the threshold value between the target air-fuel ratio and the actual air-fuel ratio, the process of step S8 is performed. In step S8, the correction result of the coefficient of the air inverse model 34 performed in step S4 is also reflected in the coefficient of the air model 36. That is, only when the difference between the target air-fuel ratio and the actual air-fuel ratio does not become small, the coefficient of the air model 36 is corrected after the correction of the coefficient of the air inverse model 34. For example, when the coefficient a of the model calculation formula 4 is corrected in the air inverse model 34, the same correction is performed on the coefficient a of the model calculation formula 4 in the air model 36. As a result of such processing, it is possible to reduce the model error included in the air model 36 and increase the accuracy of calculation of the predicted in-cylinder intake air amount by the air model 36.

  On the other hand, if the magnitude of the difference between the target air-fuel ratio and the actual air-fuel ratio is smaller than the threshold value, the process of step S8 is skipped. That is, the correction of the coefficient of the air model 36 reflecting the correction result of the coefficient of the air inverse model 34 is not performed. If the coefficient of the air model 36 is also corrected following the air inverse model 34, further reduction of the model error can be expected. However, by correcting the coefficient of the air model 36, there is no possibility that the difference between the target air-fuel ratio and the actual air-fuel ratio will temporarily increase until the calibration based on the output value of the air flow meter 24 works. Not exclusively. In the present embodiment, if the calculation accuracy of the target predicted cylinder intake air amount has already been secured, priority is given to maintaining the current state, and correction of the coefficient of the air model 36, which is unnecessary and urgent processing, is performed. It has been decided not to.

  As described above, according to the control device of the present embodiment, the calibration coefficient of the air model 36 is sequentially adjusted and updated using the output value of the air flow meter 24, while the target cylinder intake air amount and the air model 36 are updated. The coefficient of the air inverse model 34 can be corrected based on the comparison result obtained by comparing the predicted in-cylinder intake air amount. If the magnitude of the difference between the target air-fuel ratio and the actual air-fuel ratio actually measured by the air-fuel ratio sensor 29 exceeds a predetermined threshold, after correcting the coefficient of the air inverse model 34, the correction result is stored in the air model 36. It can be reflected in the coefficient. As a result, the model errors of the air inverse model 34 and the air model 36 are reduced, and both the accuracy of torque control and the accuracy of air-fuel ratio control are improved.

  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 model calculation formulas 1, 2, 3, and 4 of the air inverse model 34 and the air model 36 are examples of formulas that can be taken, and a stricter formula can be used as the model calculation formula. A simplified formula can also be used as a model calculation formula.

1 Internal combustion engine 10 Injector 12 Throttle 14 Combustion chamber 16 Intake passage 18 Exhaust passage 24 Air flow meter 28 Air-fuel ratio sensor 30 Electronic control unit 32 Torque-KL conversion map 34 Air inverse model 36 Air model 38 Model correction unit

Claims (1)

Used in an internal combustion engine having a throttle provided in an intake passage, an air flow meter arranged upstream thereof, an injector for injecting fuel into an intake port or a combustion chamber, and an air-fuel ratio sensor provided in an exhaust passage, In a control device that operates the throttle and the injector so as to realize a target torque and a target air-fuel ratio, respectively.
Target in-cylinder intake air amount determination means for converting the target torque into a target in-cylinder intake air amount;
A reverse air model in which a relationship between a change in throttle opening and a change in in-cylinder intake air amount is modeled by an inverse model, and a target for realizing the target in-cylinder intake air amount using the reverse air model; Target throttle opening calculating means for calculating the throttle opening;
Throttle operating means for operating the throttle according to the target throttle opening;
A cylinder that has an air model in which a relationship between a change in throttle opening and a change in in-cylinder intake air amount is modeled by a forward model, and predicts the in-cylinder intake air amount that is realized by operating the throttle using the air model Means for predicting the amount of intake air,
Air model calibration means for sequentially adjusting and updating the calibration coefficient of the air model using the intake air amount actually measured by the air flow meter;
Air inverse model coefficient correction means for correcting a coefficient of the air inverse model based on a comparison result comparing the target cylinder intake air amount and the predicted cylinder intake air amount;
Target fuel injection amount calculating means for calculating a target fuel injection amount for realizing the target air-fuel ratio based on the predicted in-cylinder intake air amount and the actual air-fuel ratio actually measured by the air-fuel ratio sensor;
Injector operating means for operating the injector according to the target fuel injection amount;
Air model coefficient correction means for reflecting the correction result in the coefficient of the air model after correcting the coefficient of the air inverse model when the magnitude of the difference between the target air-fuel ratio and the actual air-fuel ratio is equal to or greater than a predetermined threshold; ,
A control device for an internal combustion engine, comprising:

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