JP2013155614A - Control device of turbocharged engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance predicting accuracy of an intake air quantity into cylinders especially during transition operation in a control device controlling a turbocharged engine based on a predicted value of the intake air quantity into the cylinders.SOLUTION: A predicted value mcpvlv of a compressor flowing rate and a corrected value of the same is calculated from a predicted value eta0 of a throttle opening using a physical model of a turbocharged engine. A predicted value of the compressor flowing rate is calculated from a measured value TA of the throttle opening using the physical model and the compressor flowing rate estimated value is delay processed using the responding model of a flow rate sensor in calculation of the corrected value. A compressor flowing rate estimating value mcpvlv is corrected using the difference of the measured value of the intake air flowing rate by the flowing rate sensor and the delay processed compressor flowing rate estimated value mcpcrtsm as a correcting value. The predicted value epicfwd of a boost pressure is calculated from the corrected compressor flowing rate predicted value mcpfwd, and the predicted value of an intake air quantity into cylinders is calculated based on the boost pressure predicted value epicfwdd and the throttle opening predicted value eta0.

Description

  The present invention relates to a supercharged engine control device, and more particularly to a control device that controls a supercharged engine based on a predicted value of in-cylinder intake air amount.

  Today's automobile engines use electronically controlled throttles. In an engine equipped with an electronically controlled throttle, the target throttle opening is determined based on the accelerator operation amount of the driver, and the throttle is operated according to the target throttle opening. At this time, the determined target throttle opening degree is not immediately given to the throttle, but can be given to the throttle after being delayed by a certain time. Such arithmetic processing is called throttle delay control. According to the throttle delay control, the actual throttle opening changes with the delay time with respect to the change in the target throttle opening, so the future throttle opening is predicted from the target throttle opening by the delay time. can do. The ability to predict the future throttle opening is useful for improving the control accuracy of the air-fuel ratio for a port injection engine that injects fuel into the intake port and an engine that uses both port injection and in-cylinder direct injection. The in-cylinder intake air amount is determined when the intake valve is closed. In the case of an engine that performs port injection, the fuel injection start timing comes before the intake valve closes. Therefore, in order to accurately calculate the fuel injection amount necessary for realizing the target air-fuel ratio, it is necessary to predict the in-cylinder intake air amount determined in the future at the start of fuel injection. According to the throttle delay control, the throttle opening at the time when the intake valve is closed in the future can be predicted from the target throttle opening. Therefore, the in-cylinder intake air amount can be predicted based on the predicted throttle opening. it can.

  In the calculation of the in-cylinder intake air amount based on the predicted throttle opening, a physical model that physically models the behavior of air in the intake passage is used. In the case of a naturally aspirated engine, the physical model for calculating the in-cylinder intake air amount can be composed of a throttle model, an intake pipe model, and an intake valve model. The throttle model is a model for calculating the flow rate of air passing through the throttle. Specifically, an orifice flow rate equation based on a flow path area and a flow coefficient determined by the differential pressure before and after the throttle and the throttle opening is used as the throttle model. The intake pipe model is a model constructed based on a conservation law regarding air in the intake pipe. Specifically, the energy conservation law formula and the flow rate conservation law formula are used as the intake pipe model. The intake valve model is an experiment-based model in which the relationship between the intake valve flow rate and the intake pipe pressure is examined. Based on empirical rules obtained through experiments, in the intake valve model, the relationship between the intake valve flow rate and the intake pipe pressure is approximated by one or more straight lines.

  In the calculation using the above physical model, how to eliminate the influence of the modeling error is important in ensuring the prediction accuracy of the in-cylinder intake air amount. As an example of a method for improving the prediction accuracy of the in-cylinder intake air amount based on the physical model, a method disclosed in Japanese Patent No. 3760757 can be cited. According to the method disclosed in this publication, the first intake pipe pressure after a predetermined time has elapsed from the present time is calculated based on the throttle flow rate calculated based on the throttle opening, and the first intake pipe pressure is calculated based on the output of the air flow meter. 2 The intake pipe pressure is calculated. Further, an air flow meter output including a time delay is calculated by inputting the current throttle flow rate into the air flow meter model, and an intake pipe pressure having the same response as the second intake pipe pressure is calculated based on the air flow meter output. A predicted pressure is calculated by subtracting the response intake pipe pressure from the sum of the first intake pipe pressure and the second intake pipe pressure, and an estimated value of the intake valve flow rate is calculated based on the predicted pressure. The estimated value of the intake valve flow rate calculated by this method coincides with the output of the air flow meter during steady operation. That is, according to the method disclosed in the above publication, the prediction accuracy of the in-cylinder intake air amount is improved by compensating the modeling error during steady operation.

Japanese Patent No. 3760757 JP2011-163301 JP 2010-242893 A

  The method of predicting the in-cylinder intake air amount using the physical model can be applied not only to a naturally aspirated engine but also to a turbocharged engine equipped with a turbocharger or a mechanical supercharger. However, the assumption regarding the upstream pressure of the throttle is greatly different between the supercharged engine and the naturally aspirated engine. In the case of a naturally aspirated engine, the throttle upstream pressure can be regarded as approximately equal to the atmospheric pressure. However, in the case of a supercharged engine, the throttle upstream pressure varies depending on the rotational speed of the compressor and the throttle opening. The estimation of the intake valve flow rate requires calculation of the throttle flow rate, and the throttle upstream pressure is used for calculation of the throttle flow rate. FIG. 2 is a graph showing the relationship between the pressure ratio “Pm / Pic” of the throttle downstream pressure to the throttle upstream pressure and the throttle flow rate “mt”. As shown in this figure, the sensitivity of the change in the throttle flow rate “mt” when the throttle opening changes from “TA1” to “TA2” depends on the pressure ratio “Pm / Pic”. For this reason, if the accuracy of the throttle upstream pressure used in the calculation is low, the calculation accuracy of the throttle flow rate is low, and the prediction accuracy of the in-cylinder intake air amount is also low. Therefore, in applying the method for predicting the in-cylinder intake air amount using the physical model to the supercharged engine, highly accurate information on the throttle upstream pressure, that is, the supercharging pressure is required.

  If the above-mentioned physical model is used, the future boost pressure can be predicted from the predicted throttle opening. If the supercharging pressure when the intake valve is closed can be predicted, the predicted value of the in-cylinder intake air amount can be obtained from the predicted value and the predicted throttle opening. However, the calculation based on the physical model may include modeling errors due to various factors such as adaptation error when creating the physical model, manufacturing variations of engine components, environmental changes and aging changes, and hysteresis errors of the actuator. Therefore, when calculating the predicted value of the cylinder intake air amount from the predicted value of the supercharging pressure based on the physical model, it is between the predicted value of the cylinder intake air amount and the actual value (actual value when the intake valve is closed). May cause errors due to modeling errors.

  The present invention has been made in view of the above-described problems, and provides a control device for a supercharged engine that can improve the accuracy of predicting the amount of intake air in a cylinder, particularly the amount of intake air in a cylinder during transient operation. With the goal.

  In order to achieve the above object, a supercharged engine control apparatus according to the present invention is configured to perform the following operations.

  According to one form of this invention, this control apparatus acquires the predicted value of the throttle opening in the time of predetermined time ahead from the present time. Then, the predicted value of the compressor flow rate is calculated from the predicted value of the throttle opening using the physical model of the supercharged engine. In parallel with this, the control device acquires a measured value of the intake air flow rate by the flow rate sensor, acquires a measured value of the throttle opening amount by the throttle opening sensor, and uses the physical model to determine the throttle opening amount. An estimated value of the compressor flow rate is calculated from the measured value, and the estimated value of the compressor flow rate is delayed using a response model of the flow rate sensor.

  The response model of the flow sensor models the response delay with respect to the actual value of the measured value of the intake flow rate by the flow sensor. Therefore, the value obtained by delaying the compressor flow rate calculated by the physical model with the response model of the flow rate sensor should theoretically match the measured value of the intake flow rate by the flow rate sensor. If there is a difference between the measured value of the intake flow rate and the estimated value obtained by delaying the compressor flow rate, it can be said that the flow rate error is caused by the modeling error of the physical model.

  The control device calculates a difference between the measured value of the intake air flow rate and the estimated value obtained by delaying the compressor flow rate, and corrects the predicted value of the compressor flow rate using the difference as a correction amount. Thereby, the influence of the modeling error of the physical model included in the predicted value of the compressor flow rate is compensated. The control device calculates a predicted value of the boost pressure from the predicted value of the compressor flow rate compensated for the influence of the modeling error in this way, and based on the predicted value of the boost pressure and the predicted value of the throttle opening. Calculate the predicted value of in-cylinder intake air amount.

  According to the present control device, in the control device that predicts the in-cylinder intake air amount of the supercharged engine and controls the supercharged engine based on the predicted value, the in-cylinder intake air amount, particularly in-cylinder intake during transient operation The prediction accuracy of the air amount can be increased.

It is a block diagram which shows the cylinder intake air amount prediction model used with the control apparatus of the supercharged engine of embodiment of this invention. It is a figure which shows that the sensitivity of the change of the throttle flow rate immediately after the change of the throttle opening depends on the throttle front-rear pressure ratio.

  Embodiments of the present invention will be described with reference to the drawings.

  The supercharged engine to which the control device of the present embodiment is applied is a spark ignition type four-cycle reciprocating engine that controls torque by adjusting an air amount by a throttle. The supercharger included in the supercharged engine of the present embodiment is a turbocharger that drives a compressor disposed in an intake passage by rotation of a turbine disposed in an exhaust passage. The turbine is provided with a wastegate valve capable of actively controlling the opening degree. An intercooler is provided between the compressor and the throttle for cooling the air whose temperature has increased due to compression by the compressor. The supercharged engine of the present embodiment is also a port injection type engine that injects fuel into the intake port of each cylinder.

  The control device of the present embodiment is realized as part of the function of an ECU (Electronic Control Unit) that controls the supercharged engine. Various information and signals regarding the operating state and operating conditions of the engine are input to the ECU from various sensors such as an air flow meter and a throttle opening sensor that are flow sensors. The ECU operates various actuators such as a throttle and a waste gate valve based on the information and signals. A supercharging pressure sensor may be attached to the supercharging engine, but the signal from the supercharging pressure sensor is not used in the prediction of the in-cylinder intake air amount described below.

  The ECU as the control device has a function of predicting the in-cylinder intake air amount. In the case of a port injection type engine, it is necessary to calculate the required fuel injection amount and start fuel injection before the intake valve is closed and the in-cylinder intake air amount is determined. For this reason, at the time of calculating the fuel injection amount, it is necessary to predict the in-cylinder intake air amount determined in the future. A programmed in-cylinder intake air amount prediction model is used for prediction of the in-cylinder intake air amount by the ECU. The in-cylinder intake air amount prediction model is a physical model of air behavior in a supercharged engine, and its outline is represented by the block diagram of FIG.

  As shown in FIG. 1, the in-cylinder intake air amount prediction model used in the present embodiment is composed of four calculation blocks indicated by reference numerals 2, 4, 6, and 8. The configuration and function of each calculation block shown in FIG. 1 will be described below.

  The calculation block 2 is a calculation block for calculating a predicted value of the compressor flow rate at a future time point from a predicted value of the throttle opening. The predicted value of the throttle opening is prefetched from the target throttle opening determined based on the accelerator operation amount in throttle delay control separately performed by the ECU. In the present embodiment, it is assumed that the throttle opening at a future time is predicted from the target throttle opening by a predetermined control period from the current time.

  The calculation block 2 is one physical model, and includes a plurality of element models, that is, a turbo rotational speed model M1, a compressor model M2, an intercooler model M3, a throttle model M4, an intake pipe model M5, and an intake valve model M6. ing. Hereinafter, the contents of these element models included in the calculation block 2 will be described. However, these element models are publicly known, and since they are not characteristic points in the present invention, description of the details of each element model such as mathematical formulas and maps is omitted.

  The turbo speed model M1 is a model of the rotational behavior of the turbocharger, and the relationship that is established among the intake valve flow rate, the wastegate valve opening degree, and the turbo speed is modeled. The turbo rotational speed model M1 is configured by a map based on mathematical formulas or experimental data. In the turbo rotation speed model M1, a waste gate valve opening “wgv” estimated from an operation amount of the waste gate valve and an intake valve flow rate “mc” calculated by an intake valve model M6 described later are input. The turbo rotation speed “Ntb” is calculated from the input information.

  The compressor model M2 is a model of a turbocharger compressor, and a relationship that is established among the turbo rotation speed, the supercharging pressure, and the compressor flow rate is modeled. The compressor model M2 is configured by a map based on mathematical formulas or experimental data. In the compressor model M2, information such as a turbo speed “Ntb” calculated by the turbo speed model M1 and a supercharging pressure “Pic (epicvlv)” calculated by an intercooler model M3 described later is input. The compressor flow rate “mcp” is calculated from the input information. Note that “epicvlv” added to “Pic”, which is a code indicating the supercharging pressure, is a code for distinguishing from the supercharging pressure calculated in other calculation blocks. In the figure and in this specification, parameters other than the supercharging pressure are also given such distinguishing symbols as necessary, or the contents of the parameters only by such distinguishing symbols. It represents.

The intercooler model M3 is a physical model constructed based on a conservation law regarding air in the intercooler in the intake passage. As the intercooler model M3, specifically, an energy conservation law formula and a flow rate conservation law formula are used. In the intercooler model M3, information such as a compressor flow rate “mcp” calculated by the compressor model M2 and a throttle flow rate “mt” calculated by a throttle model M4 to be described later is input. The supercharging pressure “Pic” is calculated. In the supercharged engine, an air bypass valve is connected in the middle of the path from the compressor to the throttle. When the air bypass valve is open, air for the air bypass valve flow rate is extracted from the intercooler. In that case, the input to the intercooler may be replaced with a value obtained by subtracting the air bypass valve flow rate from the compressor flow rate m _cp .

  The throttle model M4 is a model for calculating the flow rate of air passing through the throttle. Specifically, the throttle model M4 is based on a differential pressure before and after the throttle, a flow passage area determined by the throttle opening, and a flow coefficient. The orifice flow rate formula is used. In the throttle model M4, the throttle opening prediction value “eta0” prefetched by the throttle delay control, the supercharging pressure “Pic” calculated by the intercooler model M3, and the intake pipe pressure calculated by the intake pipe model M5 described later. Information such as “Pm (epmvlv)” is input, and the throttle flow rate “mt” is calculated from the input information.

The intake pipe model M5 is a physical model constructed based on a conservation law relating to air in the intake pipe. As the intake pipe model M5, specifically, an energy conservation law equation and a flow rate conservation law equation are used. In the intake pipe model M5, information such as a throttle flow rate “mt” calculated by the throttle model M4 and an intake valve flow rate “mc” calculated by an intake valve model M6, which will be described later, is input. The pressure “Pm” is calculated. In the supercharged engine, an EGR valve is connected on the way from the throttle to the intake valve. When the EGR valve is open, EGR gas corresponding to the EGR flow rate is introduced into the intake pipe. In that case, may be replaced with a value entered was added to the EGR flow to the throttle flow rate m _t of the intake pipe.

  The intake valve model M6 is an experiment-based model that examines the relationship between the intake valve flow rate and the intake pipe pressure. Based on empirical rules obtained through experiments, in the intake valve model M6, the relationship between the intake air amount and the intake pipe pressure is approximated by a straight line. The coefficient of the linear equation is not a constant, but is a variable determined by the engine speed, the wastegate valve opening, the intake valve timing, the exhaust valve timing, and the like. In the intake valve model M6, in addition to the intake pipe pressure “Pm” calculated in the intake pipe model M5, the engine speed “NE”, the wastegate valve opening “wgv”, the valve timing of the intake valve “InVT”, the exhaust valve The valve timing “ExVT” and other information are input, and the intake valve flow rate “mc (eklvlv)” is calculated from the input information.

  The ECU extracts the compressor flow rate “mcpvlv” calculated by the compressor model M2 from the various parameters calculated by the calculation block 2. The compressor flow rate “mcpvlv” is calculated from the predicted value “eta0” of the throttle opening, and is a predicted value of the compressor flow rate at a future time by a predetermined control period. The ECU inputs the extracted compressor flow rate prediction value “mcpvlv” to the calculation block 6 described later.

  The calculation block 4 is a calculation block for calculating the estimated value of the compressor flow rate at the present time from the measured value of the throttle opening by the throttle opening sensor. The calculation block 4 is a physical model having the same configuration as the calculation block 2 described above, and includes a turbo rotation speed model M1, a compressor model M2, an intercooler model M3, a throttle model M4, an intake pipe model M5, and an intake valve model M6. It is configured. The input / output of information between these element models M1, M2, M3, M4, M5, and M6 is the same as that in the calculation block 2. However, in the calculation block 4, the measured value “TA” of the throttle opening by the throttle opening sensor is input to the throttle model M4.

  The ECU extracts the compressor flow rate “mcpcrt” calculated by the compressor model M2 from the various parameters calculated by the calculation block 4. The compressor flow rate “mcpcrt” is an estimated value of the compressor flow rate at the present time. The ECU inputs the extracted compressor flow rate estimated value “mcpcrt” to the air flow meter model M7. The air flow meter has a response delay based on an inherent response characteristic. The air flow meter model M7 is a model that simulates the response characteristics of the air flow meter, and performs delay processing corresponding to the response delay of the air flow meter on the input compressor flow rate estimation value “mcpcrt”. The ECU inputs the compressor flow rate estimated value “mcpcrtsm” delayed by the air flow meter model M 7 to the calculation block 6.

In addition to the predicted compressor flow rate “mcpvlv” calculated in the calculation block 2 and the estimated compressor flow rate value “mcpcrtsm” after delay processing, the calculation block 6 receives the measured value “egaafm” of the intake flow rate by the air flow meter. The The compressor flow rate “mcpcrtsm” after the delay processing should theoretically match the measured value “egaafm” of the intake flow rate by the air flow meter. However, in reality, there is a flow rate error due to the modeling error of the physical model used in the calculation block 4 between the compressor flow rate “mcpcrtsm” after the delay process and the intake flow rate measurement value “egaafm”. To do. Therefore, the ECU calculates a difference between the measured intake flow rate “egaafm” and the estimated compressor flow rate “mcpcrtsm” in the calculation block 6. Then, by adding the above difference as a correction amount to the predicted compressor flow rate “mcpvlv”, the influence of the modeling error of the physical model included in the predicted compressor flow rate “mcpvlv” is compensated. The corrected compressor flow rate predicted value “mcpfwd” is expressed by the following equation (1).

  Since the measured value “TA” of the throttle opening and the predicted value “eta0” are equal during steady operation, the predicted compressor flow rate “mcpvlv” and the estimated compressor flow rate “mcpcrt” calculated using the same configuration model Matches. Further, since the influence of the response delay of the air flow meter is eliminated during steady operation, the compressor flow rate predicted value “mcpvlv” matches the compressor flow rate estimated value “mcpcrtsm” after the delay process. As a result, as can be seen from the equation (1), the corrected compressor flow rate predicted value “mcpfwd” after correction and the intake flow rate measured value “egaafm” by the air flow meter can be matched during steady operation. As a result, it is possible to prevent the predicted compressor flow rate from greatly deviating from the actual value even during transient operation, and the robustness against modeling errors in the in-cylinder intake air amount prediction can be improved.

  The ECU inputs the corrected compressor flow rate predicted value “mcpfwd” calculated in the calculation block 6 to the calculation block 8. The calculation block 8 is a calculation block for calculating the intake valve flow rate from the corrected compressor flow rate predicted value and the predicted throttle opening value. The calculation block 6 is a sub model that constitutes a part of the physical model of the calculation block 2, and includes an intercooler model M3, a throttle model M4, an intake pipe model M5, and an intake valve model M6. Input / output of information between these element models M3, M4, M5 and M6 is the same as that in the calculation block 2. However, in the calculation block 8, the corrected compressor flow rate predicted value “mcpfwd” is input to the intercooler model M 3, and the boost pressure predicted value “epicfwd” calculated from the compressor flow rate predicted value “mcpfwd” and the throttle opening prediction are calculated. The value “eta0” is input to the throttle model M4. In the calculation block 8, the intake valve flow rate “eklfwd” is calculated based on the predicted boost pressure value “epicfwd” and the predicted throttle opening value “eta0”. The intake valve flow rate “eklfwd” is a predicted value of the intake valve flow rate at a future time point for a predetermined control period. When the calculation timing of the fuel injection amount arrives, the ECU calculates the in-cylinder intake air amount that is predicted when the intake valve is closed based on the intake valve flow rate predicted value “eklfwd”. Then, the required fuel injection amount is calculated using the predicted value of the cylinder intake air amount and the target air-fuel ratio.

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 element models used in the above-described embodiments may be integrated into a single model. Further, the present invention is applicable not only to a port injection type engine but also to an engine capable of using both port injection and in-cylinder direct injection. Further, the present invention can be applied not only to a turbocharger but also to a supercharged engine equipped with a mechanical supercharger.

2, 4, 6, 8 Calculation block M1 Turbo speed model M2 Compressor model M3 Intercooler model M4 Throttle model M5 Intake manifold model M6 Intake valve model M7 Air flow meter model

Claims (1)

In the control device for predicting the cylinder intake air amount of the supercharged engine and controlling the supercharged engine based on the predicted value,
Means for obtaining a predicted value of the throttle opening at a predetermined time ahead of the current time;
Means for calculating a predicted value of the compressor flow rate from the predicted value of the throttle opening using a physical model of the supercharged engine;
Means for obtaining a measured value of the intake flow rate by the flow sensor;
Means for obtaining a measured value of the throttle opening by the throttle opening sensor;
Means for calculating an estimated value of the compressor flow rate from the measured value of the throttle opening using the physical model;
Means for delaying the estimated value of the compressor flow rate using a response model of the flow sensor;
Means for calculating a difference between the measured value of the intake flow rate and the delay-processed estimated value of the compressor flow rate, and correcting the predicted value of the compressor flow rate using the difference as a correction amount;
The predicted value of the boost pressure is calculated from the corrected predicted value of the compressor flow, and the predicted value of the cylinder intake air amount is calculated based on the predicted value of the boost pressure and the predicted value of the throttle opening. Means to
A supercharged engine control device.

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