JP4605041B2 - Intake air amount estimation device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake air amount estimation device for an internal combustion engine.

  The intake system of the internal combustion engine is divided into elements such as a throttle valve, an intake pipe, an intake valve, etc., and each element is modeled and expressed by a mathematical formula to obtain the intake air amount (cylinder charged air amount) of the engine by calculation. An intake air amount estimation device for an internal combustion engine using a so-called air model is known.

  In the intake air amount estimation device using such an air model, for example, as will be described later, it is possible to calculate the in-cylinder charged air amount only by the engine speed and the throttle valve opening in addition to the atmospheric pressure and the atmospheric temperature. It becomes. In addition, since the cylinder air charge amount can be calculated by calculation using a model formula, it is possible to calculate the intake air amount with good responsiveness even during transient operation where the change rate of the throttle valve opening or the like is large. .

  In such an intake air amount estimation device using an air model, the cylinder intake charge amount is calculated based on a calculation formula that models the intake system. Therefore, if there is an error in modeling the intake system, an accurate cylinder There is a problem that the amount of the inner charge air cannot be calculated.

  Even if the actual intake system is accurately modeled in the initial state, for example, when the operating characteristics and flow characteristics of a throttle valve, intake valve, etc. gradually change over a long period of time There is. Even in the initial state, the characteristics of the throttle valve vary within the tolerance, and may not always exactly match the model. Therefore, in order to calculate the accurate cylinder air charge amount by the model calculation formula, for example, an actual measurement value of a certain operation parameter is compared with the value of this operation parameter calculated by the model calculation formula during engine operation, etc. Therefore, it is necessary to correct the error of the model calculation formula.

  Therefore, the intake air amount estimation device described in Patent Document 1 includes model correction means for correcting the intake valve model calculation formula for calculating the in-cylinder intake air flow rate based on the intake pipe pressure. In particular, in the apparatus described in Patent Document 1, an intake pipe that calculates an estimated value of the intake pipe pressure using an actually measured value of the intake pipe pressure during operation and a cylinder intake air flow rate calculated by an intake valve model calculation formula. Based on the deviation from the estimated value of the intake pipe pressure calculated by the model calculation formula, the intake valve model calculation formula is modified so that the estimated value of the intake pipe pressure matches the actual measured value of the intake pipe pressure. Yes.

  That is, assuming that there is no model error in the intake pipe model calculation formula, the deviation between the measured value of the intake pipe pressure and the intake pipe pressure calculated by the intake pipe model calculation formula is the actual in-cylinder intake air flow rate and the intake pipe pressure. This represents an error from the in-cylinder intake air flow rate calculated by the valve model calculation formula, and the model error in the intake valve model is corrected by correcting the intake valve model calculation formula based on such deviation. As a result, the correction of the model error in the intake valve model is accurately performed in accordance with the actual intake system, and the accuracy of estimation of the in-cylinder charged air amount performed by the entire air model can be improved.

JP 2004-263571 A JP 2005-155535 A Japanese Patent Laid-Open No. 2004- 211590 International Publication No. 2003/033897 Pamphlet

  Incidentally, as described above, in the apparatus described in Patent Document 1, the measured value of the intake pipe pressure during operation and the in-cylinder intake air flow rate calculated by the intake valve model calculation formula are used to calculate the intake pipe model calculation formula. The intake valve model calculation formula is corrected based on the deviation from the calculated estimated value of the intake pipe pressure.

  Here, the estimated value of the intake pipe pressure calculated by the intake pipe model calculation formula is calculated using the in-cylinder intake air flow rate calculated by the intake valve model calculation formula a predetermined time ago. Therefore, while the actual measured value of the intake pipe pressure is a value corresponding to the current in-cylinder intake air flow rate, the estimated value of the intake pipe pressure calculated by the intake pipe model calculation formula is calculated by the intake valve model calculation formula. The value corresponds to the past in-cylinder intake air flow rate. Therefore, the intake valve model calculation formula can be corrected relatively accurately by the above method when the internal combustion engine is in steady operation, but the intake valve model calculation formula is accurately corrected when the internal combustion engine is in transient operation. Can not be corrected.

  Therefore, an object of the present invention is to provide an intake air amount estimation device for an internal combustion engine that can appropriately correct the model expression of an element model constituting an air model even when the engine operation is a transient operation. There is to do.

In order to solve the above-mentioned problem, in the first invention, an estimated value of the cylinder intake air flow rate calculated by an intake valve model calculation formula for calculating an estimated value of the cylinder intake air flow rate using the intake pipe pressure is used. In the intake air amount estimation device for an internal combustion engine for calculating the in-cylinder charged air amount, an intake pipe pressure estimating means for calculating an estimated value of the intake pipe pressure by an intake pipe model calculation formula using the in-cylinder intake air flow rate, and an actual An intake pipe internal pressure detection means for detecting the intake pipe internal pressure, and an estimated value of the intake pipe internal pressure calculated by the intake pipe internal pressure estimation means and the intake pipe internal pressure detection means when the internal combustion engine is performing a transient operation. Correction means for correcting the intake valve model calculation formula based on the detected actual intake pipe pressure, and the intake valve model calculation formula includes a map determined for each engine operating region. The correction means includes an actual intake pipe pressure when the engine operating state enters a specific engine operating region and an actual intake pipe pressure when the engine operating state leaves the specific engine operating region. And the estimated value of the intake pipe pressure when the engine operating state enters the specific engine operating region and the estimated value of the intake pipe pressure when the engine operating state leaves the specific engine operating region The intake valve model calculation formula is corrected by correcting the map value corresponding to the specific engine operating region based on the deviation between the two.
According to the first aspect of the present invention, the actual value of the energy of the gas flowing out from the intake pipe portion until the engine operation state enters the specific engine operation region and then leaves, and the intake valve model of such gas energy. The calculated value is compared with a value calculated using a calculation formula, and the map value is corrected so that these values match. Thus, by comparing the total amount of gas energy flowing out from the intake pipe portion while the engine operating state is in a specific engine operating region, that is, between the integrated values of the energy outflow amount per unit time during such period By comparing these, the map value corresponding to this specific engine operating region can be accurately corrected even when the internal combustion engine is performing transient operation.

  In a second invention, in the first invention, the intake pipe pressure detecting means detects an average value of an actual intake pipe pressure per cycle as an actual intake pipe pressure.

  According to the present invention, a map value corresponding to a specific engine operation region can be appropriately corrected, and thereby, an element model that constitutes an air model even when the internal combustion engine is performing transient operation. The model formula can be corrected appropriately.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The engine body 1 schematically shown in FIG. 1 represents a direct injection spark ignition type internal combustion engine. However, the present invention may be applied to another spark ignition internal combustion engine such as a port injection type spark ignition internal combustion engine or a compression self-ignition internal combustion engine.

  As shown in FIG. 1, in the embodiment of the present invention, the engine body 1 includes a cylinder block 2, a piston 3 that reciprocates within the cylinder block 2, and a cylinder head 4 fixed on the cylinder block 2. . A combustion chamber 5 is formed between the piston 3 and the cylinder head 4. In the cylinder head 4, an intake valve 6, an intake port 7, an exhaust valve 8, and an exhaust port 9 are arranged for each cylinder. Further, as shown in FIG. 1, a spark plug 10 is disposed at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is disposed around the inner wall surface of the cylinder head 4. Further, a cavity 12 extending from the lower side of the fuel injection valve 11 to the lower side of the spark plug 10 is formed on the top surface of the piston 3. Further, the cylinder head 4 is provided with an intake valve control device 13 capable of continuously changing the phase angle and the valve lift amount of the intake valve 6.

  The intake port 7 of each cylinder is connected to a surge tank 15 via an intake branch pipe 14, and the surge tank 15 is connected to an air cleaner 17 via an intake pipe 16. A throttle valve 19 driven by a step motor 18 is disposed in the intake pipe 16. On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust pipe 20, and the exhaust pipe 20 is connected to a casing 22 containing an exhaust purification catalyst 21. In the following description, portions of the intake branch pipe 14, the surge tank 15, the intake pipe 16 and the like from the throttle valve 19 to the intake valve 6 are referred to as an intake pipe portion 23.

  The electronic control unit (ECU) 31 comprises a digital computer, and is connected to each other via a bidirectional bus 32, a RAM (random access memory) 33, a ROM (read only memory) 34, a CPU (microprocessor) 35, an input. A port 36 and an output port 37 are provided. The surge tank 13 is provided with an intake pipe pressure sensor 40 for detecting the pressure of air (intake gas) in the intake pipe portion 23, and the intake pipe pressure sensor 40 is proportional to the pressure in the intake pipe portion 23. The output voltage is generated, and this output voltage is input to the input port 36 via the corresponding AD converter 38.

  The intake pipe 16 upstream of the throttle valve 19 is provided with an air flow meter 41 for detecting the flow rate of intake air flowing through the intake pipe 16, and the configuration of the air flow meter 41 in this embodiment will be described later. To do. Further, an intake air temperature sensor 42 for detecting the intake air temperature and an atmospheric pressure sensor 43 for detecting the atmospheric pressure are provided in the vicinity of the air cleaner 17. The throttle valve 19 is provided with a throttle valve opening sensor 44 that detects the opening of the throttle valve 19, and the throttle valve opening sensor 44 generates an output signal corresponding to the throttle valve opening. These air flow meter 41, intake air temperature sensor 42, atmospheric pressure sensor 43 and throttle valve opening sensor 44 output signals corresponding to intake air flow rate (mass flow rate), intake air temperature (atmospheric temperature), atmospheric pressure and throttle valve opening, respectively. This output signal is input to the input port 36 via the corresponding AD converter 38.

  A load sensor 46 that generates an output voltage proportional to the amount of depression of the accelerator pedal 45 is connected to the accelerator pedal 45, and the output voltage of the load sensor 46 is input to the input port 36 via the corresponding AD converter 38. The The crank angle sensor 47 generates an output pulse every time the crankshaft rotates 15 degrees, for example, and this output pulse is input to the input port 36. The CPU 35 calculates the engine speed from the output pulse of the crank angle sensor 45.

  On the other hand, the output port 37 is connected to the spark plug 10, the fuel injection valve 11, the intake valve control device 13, and the step motor 18 via a corresponding drive circuit 39.

  FIG. 2 is a schematic perspective view of an air flow meter 41 used in the present embodiment, and FIG. 3 is an enlarged perspective view of a heat ray measuring unit of the air flow meter 41 shown in FIG. In the present embodiment, the air flow meter 41 is a hot-wire flow meter, and as shown in FIG. 2, the air flow meter 41 is bypassed by a bypass passage that bypasses a part of the air flowing in the intake pipe 16 and the bypass passage. It has a hot-wire measuring unit 41a that measures the mass flow rate of the intake air, and a signal processing unit 41b that outputs a voltage corresponding to the measured mass flow rate. As shown in FIG. 3, the hot wire measuring unit 41a includes an intake air temperature measurement resistor 41a1 made of platinum heat wire, a support unit 41a2 that holds the intake air temperature measurement resistor 41a1 connected to the signal processing unit 41b, and a heating resistor. (Bobbin portion) 41a3 and a support portion 41a4 for connecting and holding the heating resistor 41a3 to the signal processing portion 41b. The signal processing unit 41b has a bridge circuit composed of an intake air temperature measurement resistor 41a1 and a heating resistor 41a3, and a temperature difference between the intake air temperature measurement resistor 41a1 and the heating resistor 41a3 is always constant by this bridge circuit. The power supplied to the heating resistor 41a3 is adjusted so that the power is maintained, and the supplied power is converted into a voltage and output. The relationship between the output voltage Vg of the air flow meter 41 and the flow rate of air passing through the intake pipe 16 in which the air flow meter 41 is disposed (hereinafter referred to as “air flow passage air flow rate”) is as shown in FIG.

  By the way, in the control device for the internal combustion engine, the combustion chamber 5 is filled when the intake valve 6 is closed in order to set the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 5 of the internal combustion engine to the target air-fuel ratio. The amount of air (hereinafter referred to as “cylinder charged air amount Mc”) is estimated, and the fuel injection valve 11 is set so that the air-fuel ratio of the air-fuel mixture becomes the target air-fuel ratio based on the estimated cylinder charged air amount Mc. Defines the amount of fuel injected into the combustion chamber 5 (or intake passage) of the internal combustion engine (hereinafter referred to as “fuel injection amount”). Therefore, in order to accurately set the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber 5 of the internal combustion engine to the target air-fuel ratio, it is necessary to accurately estimate the cylinder charge air amount Mc.

  Usually, the in-cylinder charged air amount Mc is estimated from a large number of sensors such as an air flow meter and a large number of maps using output values from these sensors as arguments. However, when the in-cylinder charged air amount Mc is estimated using the map in this way, in order to make the estimated value of the in-cylinder charged air amount Mc more accurate, the number of necessary maps and their arguments are required. The number of will increase. If the number of maps increases in this way, the ROM of the ECU for storing the maps must have a large storage capacity, which increases the manufacturing cost of the control device for the internal combustion engine. Furthermore, in order to create each map, a calibration operation must be performed for each type of internal combustion engine in which the map is used, but the number of measurement points in this calibration operation increases according to the number of maps and the number of arguments thereof. If the number of maps and the number of arguments increase, the number of man-hours for fitting work will increase.

  In view of this, a control device for an internal combustion engine that calculates the in-cylinder charged air amount Mc by numerical calculation using various models without using a map has been studied. In such a control apparatus, the number of necessary maps is reduced as much as possible by using a lot of numerical calculations. This greatly reduces the number of man-hours for performing the fitting work, but also the in-cylinder charged air amount Mc Can be calculated accurately. Among such control devices, one proposed by the applicant of the present application is a control device equipped with the air model shown in FIG. The illustrated air model is the simplest model applied to an internal combustion engine, and this air model will be described below.

  As shown in FIG. 5, the air model includes a throttle model M10, an intake pipe model M20, and an intake valve model M30. The throttle model M10 includes an opening (throttle valve opening) θt of the throttle valve 19 detected by the throttle valve opening sensor 44 and an atmospheric pressure (or an intake pipe) around the internal combustion engine detected by the atmospheric pressure sensor 43. 16) Pa, the air temperature around the internal combustion engine detected by the intake air temperature sensor 42 (or the temperature of air sucked into the intake pipe 16) Ta, and an intake pipe model M20 described later. By calculating the calculated pressure in the intake pipe portion 23 (hereinafter referred to as “intake pipe pressure”) Pm, and substituting the values of these input parameters into the model formula of the throttle model M10 described later, A flow rate of air passing through the throttle valve 19 per unit time (hereinafter referred to as “estimated value mt of the air flow rate through the throttle”) is calculated. The estimated value mt of the throttle passage air flow rate calculated in the throttle model M10 is input to the intake pipe model M20.

  The intake pipe model M20 includes an estimated value mt of the throttle passage air flow rate calculated in the throttle model M10 and a flow rate of air flowing into the combustion chamber 5 per unit time described below (hereinafter referred to as “in-cylinder intake”). The definition of the in-cylinder intake air flow rate mc will be described in detail in the description of the intake valve model M30), and the values of these input parameters are described later. By substituting into the model equation of M20, the pressure of the air present in the intake pipe portion 23 (hereinafter referred to as “intake pipe pressure Pm”) and the temperature of the air present in the intake pipe portion 23 (hereinafter referred to as “intake air”). (Referred to as “in-pipe temperature Tm”). The intake pipe pressure Pm and the intake pipe temperature Tm calculated in the intake pipe model M20 are both input to the intake valve model M30, and the intake pipe pressure Pm is also input to the throttle model M10.

  In addition to the intake pipe pressure Pm and the intake pipe temperature Tm calculated in the intake pipe model M20, an atmospheric temperature Ta is input to the intake valve model M30, and the values of these input parameters are set in the intake valve model M30 described later. By substituting into the model equation, the cylinder intake air flow rate mc is calculated. The calculated in-cylinder intake air flow rate mc is converted into the in-cylinder charged air amount Mc, and the fuel injection amount from the fuel injection valve is determined based on the in-cylinder charged air amount Mc. The in-cylinder intake air flow rate mc calculated in the intake valve model M30 is input to the intake pipe model M20.

  As can be seen from FIG. 5, in the air model, the parameter value calculated in one model is used as an input value to another model. Therefore, in the entire air model, the actually input value is the throttle valve opening θt, There are only three parameters of the atmospheric pressure Pa and the atmospheric temperature Ta, and the cylinder charge air amount Mc is calculated from these three parameters.

Next, each model M10 to M30 of the air model will be described.
In the throttle model M10, an estimated value mt of the throttle passage air flow rate is calculated from the atmospheric pressure Pa, the atmospheric temperature Ta, the intake air pressure Pm, and the throttle valve opening θt based on the following equation (1). Here, μt in the equation (1) is a flow coefficient in the throttle valve, which is a function of the throttle valve opening θt, and is thus determined from a map as shown in FIG. Further, At indicates the opening cross-sectional area of the throttle valve, which is a function of the throttle valve opening θt, and is determined from a map as shown in FIG. Note that μt · At obtained by collecting the flow coefficient μt and the opening cross-sectional area At may be obtained from one throttle map from the throttle valve opening θt. R is a constant related to the gas constant, and is actually a value obtained by dividing the gas constant by the mass Mlmol of gas (air) per mol.

Φ (Pm / Pa) is a function shown in the following formula (2), and κ in the formula (2) is a specific heat ratio (a constant value). Since this function Φ (Pm / Pa) can be expressed in a graph as shown in FIG. 8, such a graph is stored as a map in the ROM 34 of the ECU 31 and is actually calculated using the equation (2). Alternatively, the value of Φ (Pm / Pa) may be obtained from the map.

  Expressions (1) and (2) of the throttle model M10 are such that the gas pressure upstream of the throttle valve 19 is the atmospheric pressure Pa, the gas temperature upstream of the throttle valve 19 is the atmospheric temperature Ta, and the gas downstream of the throttle valve 19 is Applying the law of conservation of mass, the law of conservation of energy and the law of conservation of momentum to the model of the throttle valve 19 as shown in FIG. , And by using the Mayer relation.

In the intake pipe model M20, the intake pipe pressure Pm and the intake pipe temperature Tm are calculated from the estimated value mt of the throttle passage air flow rate, the in-cylinder intake air flow rate mc, and the atmospheric temperature Ta based on the following formulas (3) and (4). Is calculated. Vm in the equations (3) and (4) is a constant equal to the volume of the intake branch pipe 14, the surge tank 15, the intake pipe 16 and the like (intake pipe portion 23) from the throttle valve 19 to the intake valve 6. is there.

Here, the intake pipe model M20 will be described with reference to FIG. When the total gas amount (total air amount) in the intake pipe portion 23 is M, the temporal change in the total gas amount M is the flow rate of the gas flowing into the intake pipe portion, that is, the estimated value mt of the air flow rate through the throttle, and the intake air Since it is equal to the difference between the flow rate of the gas flowing out from the pipe portion, that is, the in-cylinder intake air flow rate mc, the following equation (5) is obtained according to the law of conservation of mass, and the gas state in this equation (5) and the intake pipe portion 23 Equation (3) is obtained from the equation (Pm · Vm = M · R · Tm).

Further, the temporal change amount of the gas energy M · Cv · Tm in the intake pipe portion 23 is equal to the difference between the energy of the gas flowing into the intake pipe portion 23 and the energy of the gas flowing out of the intake pipe portion 23. Therefore, when the temperature of the gas flowing into the intake pipe portion 23 is the atmospheric temperature Ta and the temperature of the gas flowing out from the intake pipe portion 23 is the intake pipe temperature Tm, the following equation (6) is obtained from the energy conservation law. Equation (4) is obtained from Equation (6) and the gas equation of state.

In the intake valve model M30, the in-cylinder intake air flow rate mc is calculated from the intake pipe internal pressure Pm, the intake pipe internal temperature Tm, and the atmospheric temperature Ta based on the following equation (7). In the equation (7), a and b are intake valves in the case of an internal combustion engine having a variable valve mechanism that can change the phase angle (valve timing) and operating angle of the intake valve 6 from the engine speed Ne. 6 is a value determined from the phase angle and the working angle.

  The above-described intake valve model M30 will be described with reference to FIG. In general, the in-cylinder charged air amount Mc, which is the amount of air charged in the combustion chamber 5 when the intake valve 6 is closed, is determined when the intake valve 6 is closed (when the intake valve is closed). This is proportional to the pressure in the combustion chamber 5 when the intake valve 6 is closed. Further, the pressure in the combustion chamber 5 when the intake valve 6 is closed can be regarded as being equal to the pressure of the gas upstream of the intake valve 6, that is, the intake pipe pressure Pm. Therefore, the cylinder charge air amount Mc can be approximated as being proportional to the intake pipe pressure Pm.

  Here, the average air flow rate flowing out of the intake pipe portion 23 per a certain time (for example, a crank angle of 720 °), or the intake pipe portion 23 per a certain time (for example, a crank angle of 720 °). If the cylinder intake air flow rate mc (described in detail below) is obtained by dividing the amount of air sucked into the combustion chambers 5 of all cylinders by the predetermined time, the cylinder charge air amount Mc becomes the intake pipe pressure Pm. Therefore, it is considered that the in-cylinder intake air flow rate mc is also proportional to the intake pipe pressure Pm. From this, the above formula (7) is obtained based on the theory and empirical rules. The value a in the equation (7) is a proportional coefficient, and the value b is a value representing the burned gas remaining in the combustion chamber 5 (the amount of burned gas remaining in the combustion chamber 5 when the exhaust valve 8 is closed). Is divided by a time ΔT180 ° described later). In actual operation, the intake pipe temperature Tm may change greatly during transient operation, and Ta / Tm derived based on theory and empirical rule is multiplied as a correction for this.

  Here, the cylinder intake air flow rate mc will be described with reference to FIG. 12 when the internal combustion engine has four cylinders. In FIG. 12, the horizontal axis represents the rotation angle of the crankshaft, and the vertical axis represents the flow rate of air actually flowing from the intake pipe portion 23 into the combustion chamber 5 per unit time. As shown in FIG. 12, in the four-cylinder internal combustion engine, the intake valve 6 is opened in the order of, for example, the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder, and the intake valve 6 corresponding to each cylinder is opened. Air flows from the intake pipe portion 23 into the combustion chamber 5 of each cylinder according to the valve opening amount. For example, the displacement of the flow rate of air flowing into the combustion chamber 5 of each cylinder from the intake pipe portion 23 is as shown by a broken line in FIG. The flow rate of the air flowing into is as shown by the solid line in FIG. Further, for example, the in-cylinder charged air amount Mc to the first cylinder is as shown by hatching in FIG.

  On the other hand, the in-cylinder intake air flow rate mc is obtained by averaging the flow rate of the air flowing into the combustion chambers 5 of all the cylinders from the intake pipe portion 23 shown by the solid line, and is indicated by a one-dot chain line in the drawing. In the cylinder intake air flow rate mc indicated by the one-dot chain line, in the case of four cylinders, the crankshaft is 180 ° (that is, the angle 720 ° at which the crankshaft rotates during one cycle in the four-stroke internal combustion engine) The in-cylinder charged air amount Mc is obtained by multiplying the time ΔT180 ° required for rotation by an angle divided by the number. Therefore, the cylinder intake air amount Mc is calculated by multiplying the cylinder intake air flow rate mc calculated by the intake valve model M30 by ΔT180 ° (Mc = mc · ΔT180 °). More specifically, in consideration of the fact that the in-cylinder charged air amount Mc is proportional to the pressure when the intake valve is closed, the in-cylinder intake air flow rate mc when the intake valve is closed is multiplied by ΔT180 °. The filling air amount Mc.

Next, a description will be given of a case where the air model is mounted on a control device for an internal combustion engine and the in-cylinder charged air amount Mc is actually calculated. The in-cylinder charged air amount Mc is expressed by solving the above equations (1), (3), (4), and (7) using an air model. In this case, in order to be processed by the ECU 31, these equations need to be discretized. When the formula (1), the formula (3), the formula (4), and the formula (7) are discretized using the time t and the calculation interval Δt, the following formulas (8), (9), and (10) are respectively obtained. And Equation (11) is obtained. The intake pipe internal temperature Tm (t + Δt) is calculated by equation (12) from Pm / Tm (t + Δt) and Pm (t + Δt) calculated by equations (9) and (10), respectively.

  In the air model implemented in this manner, the estimated value mt (t) of the throttle passage air flow rate at time t calculated by the equation (8) of the throttle model M10 and the equation (11) of the intake valve model M30 are calculated. The in-cylinder intake air flow rate mc (t) at time t is substituted into the equations (9) and (10) of the intake pipe model M20, whereby the intake pipe pressure Pm (t + Δt) and the intake pipe temperature at time t + Δt are calculated. Tm (t + Δt) is calculated. Next, the calculated Pm (t + Δt) and Tm (t + Δt) are substituted into the equations (8) and (11) of the throttle model M10 and the intake valve model M30, thereby estimating the throttle passing air flow rate at time t + Δt. mt (t + Δt) and in-cylinder intake air flow rate mc (t + Δt) are calculated. Then, by repeating such calculation, the cylinder intake air flow rate mc at any time t is calculated from the throttle valve opening θt, the atmospheric pressure Pa, and the atmospheric temperature Ta, and the calculated cylinder intake air flow rate is calculated. By multiplying mc by the time ΔT180 °, the in-cylinder charged air amount Mc at an arbitrary time t is calculated.

  At the time of starting the internal combustion engine, that is, at time t = 0, the intake pipe pressure Pm is equal to the atmospheric pressure (Pm (0) = Pa), and the intake pipe temperature Tm is equal to the atmospheric temperature (Tm (0)). = Ta), the calculation in each of the models M10 to M30 is started.

  In the air model, the atmospheric temperature Ta and the atmospheric pressure Pa are assumed to be constant. However, the air model may be a value that changes with time, for example, a value detected at time t by an intake air temperature sensor for detecting the atmospheric temperature. Is the atmospheric temperature Ta (t), and the value detected at time t by the atmospheric pressure sensor for detecting the atmospheric pressure is the atmospheric pressure Pa (t), the above equations (8), (10), and (11) May be substituted into.

  Incidentally, as described above, in the apparatus shown in FIG. 5, the in-cylinder charged intake amount is calculated by sequential calculation from the start of the engine, using a model formula that inputs only the throttle valve opening θt, the atmospheric temperature Ta, and the atmospheric pressure Pa. . For this reason, if there is a modeling error in each element model of the air model, the calculated in-cylinder charged intake air amount becomes inaccurate and the fuel injection amount cannot be accurately calculated.

  On the other hand, considering each element model of the air model (the throttle model M10, the intake pipe model M20, and the intake valve model M30), even if there is no error in the modeling itself, changes in characteristics due to use and variations due to manufacturing tolerances There may be a modeling error due to the above. Therefore, the in-cylinder intake air amount obtained from the air model is compared with the intake air amount obtained from the air flow meter or the intake pipe pressure, and the intake air amount calculated from the model formula matches the actually measured value obtained from the air flow meter or the like. As has been done to fix.

  However, such a conventional correction method is to uniformly correct the entire air model that is a set of each element model, but in reality, the error generated in each model is not uniform, and each model is not uniform. Every one is different. For this reason, it is not possible to correct the model accurately with the method of uniformly correcting the whole.For example, if the in-cylinder charged intake air amount is corrected so as to match the actually measured value when the internal combustion engine is in steady operation, When the internal combustion engine is performing a transient operation, the calculated value of the intake pressure may be far from the actual measurement value, resulting in a large error in the in-cylinder charged intake amount during the transient operation. .

  Therefore, in this embodiment, although the model is corrected based on the actual measurement value, the entire air model (M10 to M30) is not uniformly corrected, but correction according to each element model is performed separately.

  Here, among the element models included in the air model, the throttle model M10 and the intake valve model M30 are likely to vary due to manufacturing / assembly tolerances and characteristic changes (changes in flow coefficient, etc.) due to use. On the other hand, the intake pipe model M20 is a relatively simple model in which only the volume is a problem, and the characteristic change due to variation and use hardly occurs. There is no need to modify this model. Therefore, in this embodiment, the model formulas of the throttle model M10 and the intake valve model M30, which are likely to cause modeling errors, are individually corrected based on the actual measurement values during engine operation.

  Hereinafter, the model correction method of this embodiment will be described. In the present embodiment, the current actual airflow passing air flow rate, throttle valve opening, and intake pipe pressure are measured by the airflow meter 41, throttle valve opening sensor 44, and intake pressure sensor 40, respectively, and these values are used. A correction operation is performed on the throttle model M10, the intake valve model M30, etc. independently of the calculation of the in-cylinder charged intake air amount in FIG.

  First, the correction operation of the throttle model M10 will be described. FIG. 13 is a block diagram illustrating a correction operation of the throttle model M10. As shown in FIG. 13, an air flow meter model M40 is used when the throttle model is corrected. The air flow meter model M40 receives a throttle passage air flow rate calculated by the throttle model M10 (hereinafter referred to as "estimated value of the throttle passage air flow rate") mt, and the value of the input parameter is described later. By substituting into the model equation of model M40, the air flow meter 61 outputs when the flow rate of air actually passing through the throttle valve 19 (hereinafter referred to as “actual throttle passage air flow rate”) is this value. A wax output value is calculated.

  That is, the actual output of the air flow meter 41 is relative to the actual air flow passing air flow rate (the air flow passing air flow rate and the throttle passing air flow rate are considered to be substantially the same, and will be described below as the throttle passing air flow rate). There is a response delay based on the inherent response characteristics, and therefore, the value does not correspond to only the actual throttle passage air flow rate at that time. The air flow meter model M40 is a model simulating this response characteristic. When the air flow through the throttle valve 19 is estimated by the estimated value mt of the air flow through the throttle valve after taking into account the response delay of the air flow meter 41, the air flow meter model M40 is an air flow meter model M40. An output value (hereinafter referred to as “expected output value”) that the meter 41 will output is calculated.

  Here, the air flow meter model M40 will be specifically described. In the air flow meter 41, as described above, the power supplied to the heating resistor 41a3 is adjusted so that the temperature difference between the intake temperature measuring resistor 41a1 and the heating resistor (bobbin portion) 41a3 is always kept constant. The airflow passage air flow rate is calculated based on the supplied power. Here, since the supplied power indicates the amount of heat released from the bobbin portion 41a3 and the support portion 41a4 to the air passing through the intake pipe 16, the air flow meter 41 is based on the amount of heat released from the bobbin portion 41a3 and the support portion 41a4. In other words, the airflow passing air flow rate is calculated.

  More specifically, the bobbin portion 41a3 is formed by winding a platinum hot wire around a cylindrical ceramic bobbin and coating the outer periphery thereof with glass. For this reason, heat dissipation from the platinum heat wire to the surrounding air is delayed due to the glass layer interposed between the platinum heat wire and the surrounding air. Therefore, even when the flow rate of the air passing through the intake pipe 16 suddenly increases, the amount of heat released from the bobbin portion 41a3 per unit time (hereinafter simply referred to as “heat dissipation amount”) is not immediately available. It does not increase, but increases with some delay. In other words, the amount of heat released from the bobbin portion 41a3 has a response delay with respect to the actual airflow passing air flow rate. The same applies to the amount of heat released from the support portion 41a4. The amount of heat released from the support portion 41a4 has a response delay with respect to the actual airflow passing air flow rate.

It is known that this response delay can be approximated to a first-order delay, and the response delay of the heat radiation amount of the bobbin portion 41a3 is expressed by the following equation (13). Here, ω _b in the equation (13) is a heat dissipation amount of the bobbin portion 41a3 converted from the output value of the air flow meter 41, that is, a heat dissipation amount actually radiated from the platinum hot wire of the bobbin portion 41a3 as a result of the heat dissipation delay (hereinafter referred to as “heat dissipation amount”). , Referred to as “delayed heat release amount”). W _b in the equation (13) is a heat dissipation amount compensated for the response delay, that is, a heat dissipation amount radiated from the platinum heat wire of the bobbin portion 41a3 when it is assumed that no heat dissipation delay occurs (hereinafter referred to as “complete heat dissipation amount”). Designated). That is, the complete heat radiation amount W _b is equal to the heat radiation amount when the internal combustion engine is in steady operation, and is basically a function of only the flow rate of air passing through the intake pipe 16 near the air flow meter 41. Since the flow rate of air passing through the intake pipe 16 near the air flow meter 41 is substantially equal to the flow rate of air passing through the throttle, the complete heat radiation amount W _b can be considered as a function of the flow rate of air passing through the throttle. relationship between the true heat radiation amount W _b from can be expressed as in FIG. 14. Further, τ _b in the equation (13) is a time constant of a first-order lag in heat radiation from the bobbin portion 41a3, and a calculation method thereof will be described later.

Similarly, the response delay of the heat radiation amount of the support portion 41a4 is expressed by Expression (14). The complete heat dissipation amount W _b from the support portion 41a4 can also be considered as a function of the throttle passage air flow rate, and the relationship between the throttle passage air flow rate and the complete heat release amount W _s from the support portion 41a4 can be expressed as shown in FIG. it can. Further, τ _s in the equation (14) is a time constant of a first-order lag in heat dissipation from the support portion 41a4.

Delayed heat radiation amounts ω _b and ω _s from the bobbin portion 41a3 and the support portion 41a4 are calculated by the equations (13) and (14). In the air flow meter 41, the output voltage changes according to the amount of heat radiated from the bobbin portion 41a3 and the support portion 41a4 as a result of the heat radiation delay, that is, the amount of delayed heat radiation, so the equations (13) and (14) The output value (expected output value) AFMmt that the airflow meter 41 will output is calculated based on the sum of the delayed heat radiation amount calculated by (ω _b + ω _s ). In the present embodiment, the relationship between the sum of the delayed heat dissipation amount (ω _b + ω _s ) in the air flow meter 41 and the expected output value AFMmt of the air flow meter 41 is obtained in advance experimentally or by calculation, and a map as shown in FIG. This is stored in the ROM 34 of the ECU 31. Then, the expected output value AFMmt of the air flow meter 41 is calculated using the map based on the sum of delayed heat dissipation ω _b + ω _s calculated from the equations (13) and (14). The calculation of the expected output value AFMmt of the air flow meter 41 based on the sum of delayed heat dissipation ω _b + ω _s using the above map can be expressed as the following equation (15).

The primary delay time constant τ _b of the bobbin portion 41a3 is calculated by the following equation (16), and the primary delay time constant τ _s of the support portion 41a4 is calculated by the following equation (17). In Expression (16) and Expression (17), u is an air flow rate per unit cross-sectional area in the flow path in the detection unit of the air flow meter 41, that is, in the bypass passage of the air flow meter 41. The air flow rate u per unit sectional area is calculated based on the output value AFM of the air flow meter 41 by a map or by a predetermined calculation formula. K _b , k _s , m _b , and m _s are constants obtained in advance by experiment or calculation, k _b and m _b are constants for the bobbin portion 41a3, and k _s and m _s are constants for the support portion 41a4. Respectively. Since the degree of response delay differs between the bobbin portion 41a3 and the support portion 41a4, a calculation for calculating an expected output value from the air flow rate through the throttle by setting the time constant by separating the bobbin portion 41a3 and the support portion 41a4. The accuracy is to be improved.

Next, a case where the airflow meter model M40 is mounted on the control device of the internal combustion engine, and the expected output value AFMmt of the airflow meter 41 is calculated from the estimated value mt of the throttle passage air flow rate actually calculated by the throttle model M10. explain. The expected output value AFMmt of the air flow meter 41 is expressed by solving the above equations (13) and (14) using the air flow meter model M40. In this case, in order to be processed by the ECU 31, these equations need to be discretized. When the equations (13) and (14) are discretized using the time t and the calculation interval Δt, the following equations (18) and (19) are obtained, respectively.

In the air flow meter model M40 mounted in this way, the delayed heat release amount ω _b (t) from the bobbin portion 41a3 at the time t, the delayed heat release amount ω _s (t) from the support portion 41a4, and the formula of the throttle model M10 ( 8) The estimated value mt (t) of the throttle passage air flow rate at time t calculated in 8) is substituted into the equations (18) and (19), whereby the delayed heat release amount ω _b (from the bobbin portion 41a3 at time t + Δt. t + Δt) and the delayed heat radiation amount ω _s (t + Δt) from the support portion 41a4 are calculated. Then, the predicted output value AFMmt (t + Δt) of the air flow meter 41 at time t + Δt is calculated by the equation (15) using these delayed heat radiation amounts ω _b (t + Δt) and ω _s (t + Δt).

  Returning again to the correction operation of the throttle model, in the present embodiment, the current intake pipe pressure Pm and the throttle valve opening θt (and the atmospheric pressure Pa, measured with the intake pressure sensor 40 and the throttle valve opening sensor 44). The throttle model so that the estimated value mt of the throttle passage air flow calculated by the throttle model M10 (FIG. 5) using the atmospheric temperature Ta) matches the current throttle passage air flow calculated from the output of the air flow meter 41. (1) is corrected.

  That is, in FIG. 13, when the estimated value mt of the throttle passage air flow rate calculated by the equation (1) of the throttle model M10 using the actual measurement value Pm and the throttle valve opening θt is input to the air flow meter model M40, It is converted into an expected output value AFMmt of the air flow meter 41 when it is assumed that the throttle-passing air flow rate is the estimated value mt of the throttle-passing air flow rate.

  Therefore, when the modeling error is not included in the throttle model M10, that is, when the actual throttle passing air flow rate matches the estimated value mt of the throttle passing air flow rate calculated by the throttle model M10, The output value AFM of the air flow meter 41 and the expected output value AFMmt of the air flow meter model M40 should match. If they do not match, the actual throttle passing air flow rate and the estimated value mt of the throttle passing air flow rate are obtained. Therefore, it is considered that there is a modeling error in the throttle model M10.

  Therefore, when the output value AFM and the predicted output value AFMmt do not match, the predicted output value AFMmt is the output value (actual value) AFM of the air flow meter 41 in order to compensate for the modeling error occurring in the throttle model M10. It is necessary to correct the calculation formula of the throttle model M10 so that

上記式（２０）のパラメータのうち流量係数μｔは製品毎のばらつきや使用による特性変化の影響を受けやすい。したがって、本実施形態では、スロットルモデルＭ１０の式（２０）により算出されたスロットル通過空気流量の推定値ｍｔをエアフロメータモデルＭ４０の式（１３）および式（１４）に代入して算出された予想出力値ＡＦＭｍｔがエアフロメータ４１の出力値ＡＦＭに一致するように流量係数μｔの値を修正することとしている。これにより、スロットルモデルＭ１０が修正され、スロットルモデルＭ１０を用いた計算結果をエアフロメータ４１の出力値と一致させることができるようになり、よってスロットルモデルＭ１０によって算出されたスロットル通過空気流量の推定値ｍｔを実際のスロットル通過空気流量に一致させることができるようになる。なお、当然ながらスロットルモデルＭ１０の上記修正結果は図５筒内充填吸気量Ｍｃの計算にも同時に反映され、筒内充填吸気量Ｍｃの推定精度が向上するようになる。 Here, in the present embodiment, as described above, the following formula (20) is used as the calculation formula of the throttle model M10.

Among the parameters of the above equation (20), the flow coefficient μt is easily affected by variations among products and characteristic changes due to use. Therefore, in this embodiment, the estimated value mt of the air flow rate through the throttle calculated by the equation (20) of the throttle model M10 is substituted into the equations (13) and (14) of the air flow meter model M40, and the prediction calculated The value of the flow coefficient μt is corrected so that the output value AFMmt matches the output value AFM of the air flow meter 41. As a result, the throttle model M10 is corrected, and the calculation result using the throttle model M10 can be made to coincide with the output value of the air flow meter 41. Therefore, the estimated value of the throttle passage air flow rate calculated by the throttle model M10. It becomes possible to make mt equal to the actual throttle passage air flow rate. Of course, the correction result of the throttle model M10 is also reflected in the calculation of the in-cylinder charged intake air amount Mc in FIG. 5, so that the estimation accuracy of the in-cylinder charged intake air amount Mc is improved.

As a method for correcting the value of the flow coefficient μt, for example, the following equation (21) is conceivable. Note that μt ′ in the equation (21) is a corrected flow coefficient.

  However, if the value of the flow coefficient μt is corrected by the equation (21), it can be appropriately corrected when the internal combustion engine is in steady operation, but it should be appropriately corrected when the internal combustion engine is in transient operation. I can't. This will be briefly described below with reference to FIG.

FIG. 16 is a time chart of the throttle valve opening θt and the values of various parameters relating to the air flow rate. In the figure, time t ₀ shows when the throttle valve opening θt becomes θt _0, and time t ₁ shows when the throttle valve opening θt becomes θt ₁ . Further, FIG. 16 shows that the actual throttle passage air flow rate (solid line in FIG. 16) and the estimated value mt (dot chain line in FIG. 16) of the throttle passage air flow rate calculated by the throttle model M10 are before time t _0. The time chart is shown in the case where the values are substantially the same after time t ₀ . That is, FIG. 16 shows an estimated value of the air flow rate through the throttle calculated by the throttle model M10 because an error has occurred in the value of the flow coefficient μt before the time t ₀ , that is, when the throttle valve opening θt is smaller than θt _0. When mt has deviated from the actual air flow rate through the throttle and after time t ₀ , that is, when the throttle valve opening θt is greater than or equal to θt ₀ , there is almost no error in the value of the flow coefficient μt. The time chart in the case where the estimated value mt of the calculated throttle passage air flow rate substantially matches the actual throttle passage air flow rate is shown.

  As described above, since the air flow meter 41 has a response delay based on a heat release delay, when the actual flow rate of air passing through the throttle changes as shown in FIG. 16, the output value AFM (see FIG. 16 is a delay with respect to the actual throttle passage air flow rate. In particular, considering that the output value AFM of the air flow meter 41 can be approximated with a first-order lag with respect to the actual throttle passage air flow rate, the current output value AFM of the air flow meter 41 is only the current actual throttle passage air flow rate. It does not change according to the above, but also changes according to the past actual throttle passage air flow history.

  Further, as described above, in the air flow meter model M40, since the response delay based on the heat release delay of the air flow meter 41 is taken into consideration, as shown in FIG. The expected output value AFMmt calculated by the air flow meter model M40 is also delayed with respect to the estimated value mt of the throttle passage air flow rate calculated by the throttle model M10.

For this reason, as shown in FIG. 16, the estimated value mt of the throttle passage air flow rate calculated by the throttle model M10 after time t ₀ substantially coincides with the actual throttle passage air flow rate. After t ₀ , the output value AFM of the air flow meter 41 and the expected output value AFMmt calculated by the air flow meter model M40 do not match. Therefore, for example, if the flow coefficient μt of the throttle model M10 is to be corrected by the equation (21) using the output value AFM and the predicted output value AFMmt, the flow coefficient μt has no error after time t _0. Therefore, the flow coefficient μt is corrected.

Alternatively, as a method for correcting the value of the flow coefficient μt, for example, the following equation (22) is conceivable. Thus, by using the integration, it is possible to suppress the influence of noise existing in the output value AFM of the air flow meter 41.

  However, even when the value of the flow coefficient μt is corrected by the equation (22), it can be appropriately corrected when the internal combustion engine is in steady operation, but when the internal combustion engine is in transient operation. It cannot be corrected properly. This will be briefly described below.

  Here, the map of the flow coefficient μt is divided into certain engine operation regions, and the map value of the flow coefficient μt is set for each engine operation region. Specifically, the map of the flow coefficient μt is obtained by dividing the throttle valve opening θt into a plurality of map areas as shown in FIG. 17, and one flow coefficient μt map for each map area of the throttle valve opening θt. Value is set. Therefore, when the flow coefficient μt is corrected, the value of the flow coefficient μt corresponding to the map area is corrected for each map area of the throttle valve opening θt.

Referring to the example shown in FIG. 16, when one map region of the throttle valve opening θt is θt ₀ to θt ₁ , the period during which the throttle valve opening θt is within the map region is from time t ₀ to time t It is up to ₁ . Therefore, the error rate of the value of the flow coefficient μt when the throttle valve opening θt is in this map region is expressed as the average value of the output value AFM of the air flow meter 41 from time t ₀ to time t ₁ and the air flow meter model M40. Is calculated based on the ratio with the average value of the predicted output value AFMmt calculated by the equation (22), it is considered that the error in the value of the flow coefficient μt can be compensated relatively accurately. ) To correct the value of the flow coefficient μt has been proposed. More specifically, in the equation (22), the ratio between the average value of the output value AFM of the air flow meter 41 and the average value of the expected output value AFMmt is the integrated value of the output value AFM of the air flow meter 41 and the expected output value thereof. Since it is equal to the ratio with the integrated value of AFMmt, in equation (22), the integrated value of the output value AFM of the air flow meter 41 (area S ₁ + S in FIG. 16) is added to the flow coefficient μt (θt) currently stored in the map. ₂ ) is multiplied by an integral value of the expected output value AFMmt (area S _{1 in} FIG. 16) (θt · (S ₁ + S ₂ ) / S ₁ ) to correct the flow coefficient μt (θt) The calculated value μt ′ (θt) is calculated.

However, as described above, in the example shown in FIG. 16, after the time t _0, the actual throttle passing air flow rate and the estimated value mt of the throttle passing air flow rate calculated by the throttle model M40 are substantially the same. Nevertheless, since there is a response delay in the air flow meter 41, the predicted value calculated by the integrated value (S ₁ + S ₂ ) of the output value AFM of the air flow meter 41 from time t ₀ to time t ₁ and the air flow meter model M40. The integrated value (S ₁ ) of the output value AFMmt from time t ₀ to time t ₁ does not match. For this reason, the flow coefficient μt is corrected even though there is no error in the flow coefficient μt in the map region where the throttle valve opening θt is θt ₁ to θt ₂ .

  As described above, when the value of the flow coefficient μt is corrected by the equations (21) and (22), it can be accurately corrected when the internal combustion engine is in steady operation, but the internal combustion engine is in transient operation. When it is, it cannot be corrected accurately. Accordingly, the present invention provides an intake air amount estimation device for an internal combustion engine that can accurately correct the value of the flow coefficient μt even when the internal combustion engine is in a transient operation.

FIG. 18 is a time chart of the throttle valve opening θt and the values of various parameters relating to the air flow rate, as in FIG. Hereinafter, with reference to FIG. 18, the correction of the flow coefficient μt in the map region A where the throttle valve opening degree θt is θt ₀ to θt ₁ will be considered. As shown in the equations (13) and (14), in the air flow meter model M40, it is assumed that there is a first-order lag with respect to the estimated value mt of the air flow rate through the throttle calculated by the throttle model M10. An output value AFMmt is calculated. For this reason, the expected output value AFMmt of the air flow meter model M40 is calculated based on the estimated value mt of the throttle passage air flow before a predetermined time as well as the estimated value mt of the current throttle passage air flow calculated by the throttle model M10. Will be.

For example, when the throttle valve opening θt has penetrated the map area A at time t ₀ as shown in FIG. 18, the expected output value AFMmt calculated by the air flow meter model M40 at time t ₀ after the time t ₀ after Is calculated using not only the estimated value mt of the throttle passage air flow rate calculated by the throttle model M10 but also the estimated value mt of the throttle passage air flow rate calculated by the throttle model M10 before time t ₀ . That is, the expected output value AFMmt calculated by the air flow meter model M40 is calculated based on the estimated value mt of the throttle passage air flow rate when the throttle valve opening θt is in the map region other than the map region A. .

Here, as described above, in the example shown in FIG. 18, the flow coefficient μt corresponding to the map area A where the throttle valve opening θt is θt ₀ to θt ₁ is to be corrected, and the flow coefficient μt is corrected. The ratio of the actual throttle passage air flow rate to the estimated value mt of the throttle passage air flow rate calculated by the throttle model M10 is calculated as the output value AFM of the air flow meter 41 and the expected output value AFMmt calculated by the air flow meter model M40. I am trying to calculate from the ratio. However, when the throttle valve opening degree θt is in the map area A, the expected output value AFMmt calculated by the air flow meter model M40 is affected by the estimated value mt of the throttle passage air flow rate in the map area other than the map area A. Therefore, when the throttle valve opening degree θt is in the map area A, the ratio between the output value AFM of the air flow meter 41 and the expected output value AFMmt calculated by the air flow meter model M40 is such that the throttle valve opening degree θt is in the map area A. The ratio of the actual throttle passage air flow rate to the estimated value mt of the throttle passage air flow rate in the case of the above is not shown.

Therefore, in the present embodiment, when correcting the flow coefficient μt when the throttle valve opening θt is in the map region A, the predicted output value AFMmt calculated by the air flow meter model M40 is not directly used, but the predicted output The influence of the estimated value mt of the air flow rate through the throttle valve before the throttle valve opening θt enters the map area A from the value AFMmt (when the throttle valve opening θt is smaller than θt _{0 in} the example shown in FIG. 18). The removed value (hereinafter referred to as “corrected output value”) AFMmte is used.

In the present embodiment, calculation of the corrected output value AFMmt is basically performed in the same manner as the calculation of the predicted output value AFMmt in the air flow meter model M40. That is, the delayed heat radiation amounts ω _be and ω _se of the bobbin portion 41a3 and the support portion 41a4 are calculated by the following equations (23) and (24), and the equation (25) is calculated based on the calculated delayed heat radiation amounts ω _be and ω _se. ) To calculate a corrected output value AFMmte from a map similar to the map shown in FIG. Expressions (23) and (24) are discretized as shown in the following expressions (26) and (27) using the time t and the calculation interval Δt for processing by the ECU 31.

However, unlike the calculation of the predicted output value AFMmt in the air flow meter model M40, the correction output value AFMmt is calculated for each map area. That is, when the throttle valve opening θt enters a certain map area, in the example shown in FIG. 18, when the throttle valve opening θt enters the map area A (that is, the throttle valve opening θt becomes θt ₀ ). 18), calculation of the corrected output value AFMmte in the map area is started, and when the throttle valve opening θt departs from the map area, the throttle valve opening θt is changed from the map area A in the example shown in FIG. The calculation of the corrected output value AFMmte in the map area is completed when the vehicle has left (that is, when the throttle valve opening θt becomes θt ₁ ).

  In calculating the corrected output value AFMmte, an estimated value mt of the throttle passage air flow rate calculated by the throttle model M10 before the throttle valve opening θt enters the map area A (hereinafter referred to as “the past throttle passage air flow rate”). In order to eliminate the influence of the estimated value mt ”, the value of the corrected output value AFMmte (hereinafter referred to as“ initial value ”) when the throttle valve opening θt enters the map area A is referred to as an air flow meter. The output value AFM of 41 is almost the same value.

  That is, as described above, the corrected output value AFMmte is calculated in the ECU 31 based on the discretized equations (26) and (27), but these equations (26) and (27) are other than the initial values. There is no term in which the estimated value mt of the throttle passage air flow rate (before the throttle valve opening θt enters the map area A) is affected. Conversely, as long as the initial value is set to a value that is not affected by the estimated value mt of the past throttle passage air flow rate, the influence of the estimated value mt of the past throttle passage air flow rate on the corrected output value AFMmte is reduced. It can be minimized.

  In the present embodiment, the initial value of the corrected output value AFMmte when the throttle valve opening θt enters the map area A is set to a value almost the same as the output value AFM of the air flow meter 41 at that time, so the corrected output value AFMmte Is not a value determined based on the estimated value mt of the past throttle passage air flow rate, but a value determined based on the output value AFM of the air flow meter 41 when the throttle valve opening θt enters the map area A. Therefore, the influence of the estimated value mt of the past throttle passage air flow rate is removed from the corrected output value AFMmte.

Thus, in order to calculate the subsequent corrected output value AFMmt by the equations (23) and (24) with the initial value of the corrected output value AFMmte being substantially similar to the output value AFM of the air flow meter 41, the time t ₀ it is necessary to match the actual amount of heat dissipated from the actual heat radiation amount and support section 41a4 of the bobbin portion 41a3 at time t ₀ the delay amount of heat radiation delay heat radiation amount and support section 41a4 of the bobbin portion 41a3 in. However, it is difficult to calculate the actual amount of heat radiation from the bobbin portion 41a3 and the support portion 41a4 at time t ₀ from the output value AFM of the air flow meter 41 at time t _0. That is, the total amount of actual heat radiation from the bobbin portion 41a3 and the support portion 41a4 can be obtained from the output value AFM of the air flow meter 41 by using the map shown in FIG. It is not possible to determine the actual heat dissipation from

  Therefore, in the present embodiment, an observer that can calculate the actual heat radiation amount from each of the bobbin portion 41a3 and the support portion 41a4 of the air flow meter 41 relatively accurately is used. This observer always calculates an approximate value of the actual heat radiation amount from each of the bobbin portion 41a3 and the support portion 41a4 of the air flow meter 41 regardless of the time and the map region of the throttle valve opening θt.

Specifically, the observer uses the following equation (28) and equation (29) to approximate the actual heat radiation amount from the bobbin portion 41a3 (hereinafter referred to as “approximate heat radiation amount”) ω _bo and the support portion 41a4. Approximate values of actual heat dissipation (hereinafter referred to as “approximate heat dissipation”) ω _so are respectively calculated. In the formula (28) and Equation (29), K _I is the same coefficient and integration coefficient used for integral control or the like. AFMmto is a value calculated by the following equation (30) (that is, from the map of FIG. 15) based on the sum of the approximate heat dissipation amounts ω _bo and ω _so calculated by the observer.

Therefore, in the observer, the output value AFMmto of the air flow meter 41 calculated based on the output value AFM of the air flow meter 41 and the approximate heat dissipation ω _bo and ω _so calculated by the observer (hereinafter referred to as “approximate output value”). (AFM-AFMmto) is accumulated over time. The cumulative value of the deviation between the output value AFM and the approximate output value AFMmto changes based on the error between the actual throttle passage air flow rate and the estimated value mt of the throttle passage air flow rate calculated by the throttle model M10. The absolute value of the cumulative value of the deviation increases as the absolute value of increases. Therefore, the estimated value mt of the throttle passage air flow rate calculated by the throttle model M10, adding the value obtained by multiplying the coefficient K _I to the accumulated value of the deviation between the calculated approximate output value AFMmto the output value AFM and observer Thus, an error between the actual throttle passing air flow rate and the estimated value mt of the throttle passing air flow rate calculated by the throttle model M10 can be compensated to some extent. Thus, the observer, the actual throttle-passing air flow rate substantially equal to the throttle-passing air flow rate approximate heat dissipation omega _bo based on, for omega _so is calculated, approximating the heat radiation amount calculated by the observer omega _bo, omega _so the The actual heat radiation amount from the bobbin portion 41a3 and the support portion 41a4 is almost equal.

In order to calculate the approximate heat radiation amounts ω _bo and ω _so from the estimated value mt of the throttle passage air flow rate and the output value AFM of the air flow meter 41 by mounting the observer in the control device of the internal combustion engine, the equation (28 ) And equation (29) need to be discretized. When the equations (28) and (29) are discretized using the time t and the calculation interval Δt, the following equations (31) and (32) are obtained, respectively. In addition, ΔAFMINT (t) in Expression (31) and Expression (32) is a cumulative value of AFM (t) −AFMmto (t) at time t, and is expressed by Expression (33) below.

In the observer implemented in this way, the approximate heat dissipation amounts ω _bo (t) and ω _so (t) from the bobbin portion 41a3 and the support portion 41a4 at time t, the time calculated by the equation (8) of the throttle model M10. The estimated value mt (t) of the air flow rate through the throttle at t, the output value AFM (t) of the air flow meter 41 at time t, and the approximate output value AFMmto (t) calculated by the observer at time t are expressed by Equation (31), Substituting into Equations (32) and (33), approximate heat dissipation amounts ω _bo (t + Δt) and ω _so (t + Δt) at time t + Δt are calculated. Then, based on these approximate heat dissipation amounts ω _bo (t + Δt) and ω _so (t + Δt), an approximate output value AFMmto (t + Δt) at time t + Δt is calculated by equation (30), and the approximate output value AFMmto (t + Δt) at time t + Δt. Is used for the subsequent calculation of the approximate heat dissipation ω _bo and ω _so . Then, by repeating such calculation, the approximate heat dissipation amounts ω _bo and ω _{so at} an arbitrary time t are calculated from the estimated value mt of the air flow rate through the throttle and the output value AFM of the air flow meter 41.

FIG. 19 is an enlarged time chart showing the transition of the parameter relating to the flow rate at times t _{0 to} t ₁ in FIG. As can be seen from FIG. 19, the approximate output value AFMmto (short broken line in FIG. 19) calculated by the observer is substantially the same value as the output value AFM of the air flow meter 41. As described above, in calculating the corrected output value AFMmte, when the throttle valve opening θt enters the map area A, that is, at the time t ₀ , the approximate heat dissipation amount ω _bo of the bobbin portion 41a3 and the support portion calculated by the observer are calculated. An approximate heat release amount ω _{so of} 41a4 is used. Therefore, in the calculation of the corrected output value AFMmte, the initial values of the delayed heat radiation amounts ω _be and ω _se , that is, the delayed heat radiation amounts ω _be (t ₀ ) and ω _se (t ₀ ) at the time t ₀ were calculated by the observer. Approximate heat dissipation ω _bo (t ₀ ) and ω _se (t ₀ ) at time t ₀ (ω _be (t ₀ ) = ω _bo (t ₀ ), ω _se (t ₀ ) = ω _so (t ₀ )). Therefore, fix the output value AFMmte at time t ₀ has the same value as the approximate output value AFMmto of the observer at time t _0.

Then, when the calculation of the corrected output value AFMmte, delay heat dissipation omega _BE, the initial value of omega _se, i.e. lag heat radiation amount omega _BE at time t ₀ (t _0), after ω _se (t ₀₎ is calculated, above expression (26) and lag heat radiation amount at time t ₀ after the equation (27) omega _bE (t), omega _se (t) is calculated, and delay the heat radiation amount omega _bE in these time t ₀ after the time t Based on (t) and ω _se (t), the corrected output value AFMmte (t) at time t after time t ₀ is calculated using the above equation (25). The corrected output value AFMmte calculated in this way changes as shown by a dotted line in FIG. That is, the corrected output value AFMmte is the same value as the approximate output value AFMmto calculated by the observer at time t ₀ , and thereafter gradually shifts to the expected output value AFMmt calculated by the air flow meter model M40. To do.

The corrected output value AFMmte calculated in this way is a value from which the influence of the estimated value mt of the throttle passage air flow rate before the throttle valve opening θt enters the map area A is removed as described above. . For this reason, the ratio between the output value AFM of the air flow meter 41 and the corrected output value AFMmte in the map area A is the ratio of the actual throttle passing air flow rate in the map area A and the throttle passing air flow rate calculated by the throttle model M10. This is shown relatively accurately, that is, the error rate of the flow coefficient μt of the throttle model M10 in the map area A is shown. Therefore, similarly to the above equation (22), the error rate Err is calculated by the following equation (34) based on the output value AFM of the air flow meter 41 and the corrected output value AFMmte.

That is, the error rate Err is a value obtained by integrating the output value AFM of the air flow meter 41 while the throttle valve opening θt is in a specific map region (map region A in the examples shown in FIGS. 18 and 19), that is, A value obtained by integrating the output value AFM from the time t ₀ to the time t ₁ (area S ₃ + S _{4 in} FIG. 19), the throttle valve opening θt is the specific map region (in the example shown in FIGS. 18 and 19). The value obtained by integrating the corrected output value AFMmte over the map area A), that is, the value obtained by dividing the corrected output value AFMmte by the value (area S _{3 in} FIG. 19) integrated from the time t ₀ to t ₁ . It is equal to ((S ₃ + S ₄ ) / S ₃ ). By multiplying the error rate Err calculated in this way by the map value of the flow coefficient μt in the specific map area (the map area A in the examples shown in FIGS. 18 and 19), the map value of the flow coefficient μt is obtained. Corrected accurately.

In the above embodiment, the map value of the flow coefficient μt corresponding to the map area A where the throttle valve opening θt is θt ₀ to θt ₁ has been described. However, the same applies to other map areas as well. The map value of the flow coefficient μt corresponding to the map area is corrected. Thereby, even during the transient operation of the internal combustion engine, the map value of the flow coefficient μt corresponding to each map area can be corrected accurately.

  By the way, as described above, by using the corrected output value AFMmte, the influence of the estimated value mt of the throttle passage air flow before the throttle valve opening θt enters the map area A is removed. However, the output value AFM of the air flow meter 41 is also affected by the actual throttle passage air flow rate before the throttle valve opening θt enters the map area A, and even if the corrected output value AFMmte is used as described above. The influence of the past actual throttle passage air flow rate cannot be removed from the output value AFM of the air flow meter 41. For this reason, as described above, the error rate of the flow coefficient μt of the throttle model M10 calculated based on the output value AFM and the corrected output value AFMmte of the air flow meter 41 is different from the error rate of the actual flow coefficient μt. Slightly different values.

  Therefore, in the modified example of the above embodiment, the influence of the past actual throttle passage air flow rate is removed from the output value AFM of the air flow meter 41. Hereinafter, a method for accurately calculating the error rate of the flow coefficient μt of the throttle model M10 by removing the influence of the past actual throttle passage air flow rate from the output value AFM of the air flow meter 41 will be described.

  Incidentally, in general, the response of a sensor such as the air flow meter 41 can be separated into an initial value response and a zero response. Here, the initial value response is a transition of the output value of the sensor after time t when it is assumed that the state quantity after a certain time t is zero, and the zero response is a state until a certain time t. It is a transition of the output value of the sensor after time t when it is assumed that the quantity is zero.

FIG. 20 is a diagram illustrating an initial value response curve and a zero response curve for the output value AFM of the air flow meter 41. Here, Φ ₁ indicates an initial value response curve (broken line) with respect to time 0, and the output value of the air flow meter 41 when it is assumed that the actual air flow rate through the throttle is zero after time 0. It shows the transition. Also, Φ ₂ indicates a zero response curve (one-dot chain line) with respect to time 0. When it is assumed that the actual flow rate of air passing through the throttle up to time 0 is zero, that is, from time 0, the air flow meter 41 The transition of the output value of the air flow meter 41 when the measurement is started is shown.

That is, the initial value response curve changes according to the output value of the air flow meter 41 at time 0, that is, according to the actual throttle passage air flow before time 0, while the zero response curve changes from time 0. It changes according to the actual throttle passage air flow rate at. The output value AFM (t) of the air flow meter 41 at each time t after time 0 is a value Φ ₁ (t) at the time t of the initial value response curve and a value Φ ₂ (t) at the time t of the zero response curve. (AFM (t) = Φ ₁ (t) + Φ ₂ (t)). The relationship between the output value AFM of the air flow meter 41, the value Φ _{1 at} each time of the initial value response curve, and the value Φ _{2 at} each time of the zero response curve is a reference time (see FIG. 20). In the example shown, the time 0) is established at any time.

  As described above, the zero response curve changes in accordance with the actual throttle passage air flow rate after a predetermined time. Therefore, from the zero response curve of the output value AFM of the air flow meter 41 based on the time of entry into the specific map area, The effect of the actual throttle passage air flow before entering that particular map area has been eliminated. Therefore, by obtaining such a zero response curve and comparing it with the zero response curve for the corrected output value AFMmte (more precisely, the curve corresponding to the zero response curve for the corrected output value AFMmte), as described later. The error rate of the flow coefficient μ can be accurately calculated by removing the influence of the actual throttle passage air flow before entering the specific map area.

However, since it is difficult to calculate the zero response based on the time t ₀ , in this embodiment, the initial value response curve based on the time t ₀ from the output value AFM of the air flow meter 41 at each time. The zero response is calculated by subtracting the value Φ ₁ (Φ ₂ (t) = AFM (t) −Φ ₁ (t)).

Here, a method of calculating the value Φ _{1 at} each time of the initial value response curve with the time t ₀ as a reference will be described. As described above, the value Φ _{1 at} each time of the initial value response curve indicates the transition of the output value of the air flow meter 41 when it is assumed that the actual throttle passage air flow rate is zero after time t ₀ . The estimated value mt of the air flow rate through the throttle in the above equations (13) and (14) can be obtained by setting it to zero. That is, the heat dissipation amounts ω _bi and ω _si for the initial value response curve are expressed by the following equations (35) and (36). In this case, the heat radiation amount omega _bi (t ₀₎ at time t _0, omega _si (t ₀₎ is an approximation of actual heat radiation amount at time t ₀ approximate heat radiation amount _{ω bo (t 0), ω} so ( t ₀ ) is used.

Then, based on the heat radiation amounts ω _bi and ω _si calculated by the equations (35) and (36), the value at each time of the initial value response curve from the map similar to the map shown in FIG. 15 by the equation (37). Φ ₁ is calculated. Equations (35) and (36) are discretized for use by ECU 31.

By subtracting the value Φ ₁ at each time of the initial value response curve based on the time t ₀ calculated in this way from the output value AFM of the air flow meter 41, the time t ₀ for the output value of the air flow meter 41 is obtained. A value Φ _{2 at} each time of the zero response curve with reference to is calculated.

Since the corrected output value AFMmte also uses the approximate heat dissipation ω _bo and ω _so at time t ₀ , by subtracting the value Φ ₁ at each time of the initial value response curve described above from the corrected output value AFMmte, A value at each time of the zero response curve for the corrected output value AFMmte is calculated. For this reason, in this embodiment, when calculating the error rate Err of the flow coefficient μt of the throttle model M10, the time t ₀ regarding the output value AFM of the air flow meter 41, the corrected output value AFM mte, and the output value of the air flow meter 41. Is calculated by the following equation (38) using the value Φ _{1 at} each time of the initial value response curve with reference to.

Thus, in calculating the error rate of the flow coefficient μt, by using the corrected output value AFMmt, the estimated value mt of the past throttle passage air flow rate existing in the expected output value AFMmt calculated by the air flow meter model M40 is obtained. The influence is removed, that is, the component included in the expected output value AFMmt is removed from the expected output value AFMmt due to the influence of the air flow rate through the throttle before a predetermined time. Further, by subtracting the value Φ ₁ at each time of the initial value response curve from the output value AFM and the corrected output value AFMmte of the air flow meter 41, past actual throttle passage air existing in the output value AFM of the air flow meter 41 and the like. The influence of the flow rate is removed, that is, the component included in the output value AFM of the air flow meter can be removed from the output value of the air flow meter due to the influence of the air flow rate through the throttle before a predetermined time.

  For this reason, the error rate Err calculated by the above equation (38) is the actual throttle passing air flow rate when the throttle valve opening θt is within the predetermined map region and the throttle passing air flow rate calculated by the throttle model M10. Since the calculation is based on the estimated value, the error rate of the flow coefficient when the throttle valve opening degree θt is within a predetermined map region can be accurately calculated.

  Next, the correction operation of the intake valve model M30 will be described. As described above, the value a used in the equation (7) of the intake valve model M30 is a proportional coefficient, and the value b is a value representing burned gas remaining in the combustion chamber 5. These values a and b vary in accordance with the engine speed NE, the phase angle and the operating angle of the intake valve (hereinafter, the intake valve opening timing VVT will be described as an example). Therefore, the relationship between the engine speed NE and the intake valve opening timing VVT and these values a and b is calculated in advance experimentally or by calculation, as shown in FIGS. 21 (a) and 21 (b). The map is stored in the ECU 31 as well as the engine speed NE detected by the crank angle sensor 47 and the intake valve opening timing to the intake valve control device 13 when calculating the above equation (7) in the intake valve model M30. These values a and b are calculated from the above map using VVT. 21A shows a map of the value a, FIG. 21B shows a map of the value b, the x-axis in the figure is the engine speed NE, and the y-axis is the intake valve opening timing. VVT (advance angle as the y-axis increases) is shown.

  However, errors may occur in these values a and b due to changes in characteristics due to use and variations due to manufacturing tolerances as described above. As described above, when there is an error in the values a and b, it is necessary to correct the map values of the values a and b in order to compensate for the modeling error of the intake valve model M30. Here, in the present embodiment, the values a and b are determined for each engine operation region. In the example shown in FIG. 21, the values a and b are set for each map area (for example, the hatched portion in FIG. 21 represents one map area), that is, for each engine speed at regular intervals and at regular intervals. It is determined for each intake valve opening timing. Therefore, the correction of the values a and b must be performed for each map area.

Therefore, in this embodiment, the values a and b used in the equation (11) of the intake valve model M30 are corrected for each map area. In the following, as an example, the engine speed NE and the intake valve opening timing VVT are in the map region B (that is, the engine speed NE is between NE ₁ and NE ₂ and the intake valve opening timing VVT is from VVT _1. A method of correcting the map values a _ij and b _ij of the values a and b in the case of the map area between VVT ₂ will be described.

FIG. 22 is a time chart of the intake pipe pressure Pm, the engine speed NE, and the intake valve opening timing VVT during operation of the internal combustion engine. In the illustrated example, the engine speed NE at time t ₀ later has a NE ₀ or more, and the time t ₁ the engine rotational speed in the subsequent NE has become NE ₁ or more. That is, the engine speed NE has a value between NE ₀ and NE ₁ over from time t ₀ to time t _1, and the value between NE ₀ and NE ₁ in other time is not. On the other hand, the intake valve opening timing VVT is a value between VVT ₁ and VVT ₂ from time t ₀ to time t ₁ .

Therefore, the value of the engine rotational speed NE and the intake valve opening timing VVT, the time t ₀ before rather than in the map region B, at time t ₀ from time t ₀ with entering the map area B to time t ₁ Within the map area B. Then detached from the map area B at time t _1, after time t ₁ is not in the map area B. When the values of the engine speed NE and the intake valve opening timing VVT are within the map area B, that is, from time t ₀ to time t ₁ , the value a corresponding to the map area B in the intake valve model M30. _ij and _bij are used.

Here, considering the above formula (6) again, the left side of the formula (6) represents a temporal change amount of the internal energy of the gas in the intake pipe portion 23, and the right side of the formula (6) is represented by Cp · mt · Ta represents the energy of the gas flowing into the intake pipe portion 23, and Cp · mc · Tm represents the energy of the gas flowing out of the intake pipe portion 23, respectively. Here, considering the gas state equation (Pm · Vm = M · R · Tm) in the intake pipe portion 23, the left side of the equation (6) can be expressed as the following equation (39).

Therefore, the amount of change in internal energy between time t ₀ and time t ₁ can be expressed as the following equation (40). In particular, since it is detected actual intake pipe pressure Pmr by the intake pipe pressure sensor 40, by using the actual intake pipe pressure Pmr in formula (40), the actual in between the time t ₀ to time t ₁ The amount of change in internal energy can be calculated accurately. In Expression (40), Pmr (t ₀ ) represents the actual intake pipe pressure at time t ₀ , and Pmr (t ₁ ) represents the actual intake pipe pressure at time t ₁ .

On the other hand, as described above, the map value of the flow coefficient μt of the throttle model M10 is sequentially corrected with respect to the energy of the gas flowing into the intake pipe portion 23 (that is, Cp · mt · Ta on the left side of the equation (6)). Therefore, the flow coefficient μt of the throttle model M10 is an appropriate value. Therefore, when the actual intake pipe pressure Pmr detected by the intake pipe pressure sensor 40 is used as the intake pipe pressure Pm in the equation (1) of the throttle model M10, the energy of the gas flowing into the intake pipe portion 23 is accurately calculated. be able to. In particular, the energy of the gas flowing into the intake pipe portion 23 from time t ₀ to time t ₁ can be calculated by the following equation (41).

Thus, the amount of change in internal energy from time t ₀ to time t ₁ is the above equation (40), and the energy of the gas flowing into the intake pipe portion 23 from time t ₀ to time t ₁ is the above equation (40). 41), the energy of the gas flowing out from the intake pipe portion 23 from time t ₀ to time t ₁ is calculated by the following equation (42) obtained by subtracting equation (40) from equation (41). It can be calculated accurately.

Here, as described above, the energy of the gas flowing out from the intake pipe portion 23 can be expressed by Cp · mc · Tm, and the in-cylinder intake air flow rate mc (that is, calculated by the intake valve model M30 as this mc) (that is, Using equation (7), the energy of the gas flowing out from the intake pipe portion 23 from time t ₀ to time t ₁ can be expressed as the following equation (43). Since both formula (42) and formula (43) represent the energy of the gas flowing out from the intake pipe portion 23, the values calculated by these formulas should be the same.

  However, if there is an error in the model equation (7) of the intake valve model M30, the values calculated by the equations (42) and (43) do not match. In particular, in the above formula (43), when the actual intake pipe pressure Pmr detected by the intake pipe pressure sensor 40 is used as the intake pipe pressure, the formula (42) does not match the formula (43). Is considered to be a case where there is an error in the map values of the values a and b used in equation (7).

Therefore, in the present embodiment, the error rate of the cylinder intake air flow rate mc calculated by the intake valve model M30 with respect to the actual cylinder intake air flow rate (actual cylinder intake air flow rate / cylinder calculated by the intake valve model M30). The inner intake air flow rate) is α. Since the value calculated by multiplying the error rate α by the equation (43) is equal to the value calculated by the equation (42), the following equation (44) is established. When the equation (44) is solved for the error rate α, the error rate α can be expressed as the following equation (45).

The error rate α thus calculated is the in-cylinder intake calculated by the actual in-cylinder intake air flow rate and the intake valve model M30 when the engine speed NE and the intake valve opening timing VVT are in the map region B. The error rate with respect to the estimated value mc of the air flow rate is represented. In order to compensate for the error in the in-cylinder intake air flow rate, in this embodiment, the map values a _ij and b _ij corresponding to the map area B are multiplied by the error rate α to obtain new values a and b. The map values a _ij and b _ij in the map area B are set as (a _ij = α · a _ij , b _ij = α · b _ij ). In this way, by correcting the map values of the values a and b used in the equation (7) of the intake valve model M30, the estimated value mc of the in-cylinder intake air flow rate calculated by the intake valve model M30 is changed to the actual in-cylinder The value can be approximately equal to the intake air flow rate.

  As described above, in this embodiment, the engine operating state (for example, the engine speed NE and the intake valve opening timing VVT) enters the specific engine operating region (for example, the map region B) and then leaves. The actual value of the energy of the gas flowing out from the intake pipe portion 23 (that is, the value calculated using the energy conservation law of the intake pipe portion 23) and the intake valve model M30 of such gas energy are calculated. By correcting the map values of the values a and b corresponding to the specific engine operating region based on the ratio between the actual value and the value calculated using the intake valve model M30. Even when the internal combustion engine is performing transient operation, the map values of the values a and b can be corrected accurately.

  Here, the estimated value Pm of the intake pipe pressure calculated by the intake pipe model M20 is calculated using the estimated value mc of the in-cylinder intake air flow rate calculated by the intake valve model M30 a predetermined time ago. Therefore, for example, based on the deviation between the actual value of the intake pipe pressure and the estimated value of the intake pipe pressure calculated by the intake pipe model M20 using the estimated value mc of the in-cylinder intake air flow rate calculated by the intake valve model M30. If the map values of the values a and b are to be corrected, the actual measured value of the intake pipe pressure is a value corresponding to the current actual in-cylinder intake air flow rate, whereas the intake pipe model M20 calculates the intake pipe internal pressure. Since the estimated value of the pressure is a value corresponding to the estimated value mc of the in-cylinder intake air flow rate calculated by the intake valve model M30, the intake valve is relatively accurately obtained when the internal combustion engine is in steady operation. Although the model can be corrected, the intake valve model cannot be corrected accurately when the internal combustion engine is in transient operation.

  On the other hand, in the present embodiment, the intake air is discharged after the engine operating state (for example, the engine speed NE and the intake valve opening timing VVT) enters a specific engine operating region (for example, the map region B) and then leaves. The actual value of the energy of the gas flowing out from the pipe part 23 (that is, the value calculated using the energy conservation law of the intake pipe part 23) and the intake valve model M30 of the energy of such gas were calculated. The values are compared with each other, and the map values of the values a and b are corrected so that these values match. In this way, by comparing the total amount of energy of the gas flowing out from the intake pipe portion 23 while the engine operating state is in a specific engine operating region, that is, the integrated value of the energy outflow amount per unit time during that time. By comparing each other, even if the internal combustion engine is performing a transient operation, the map values of the values a and b corresponding to the specific engine operation region can be accurately corrected.

Next, the case where the error rate α is actually calculated from the estimated value mt of the air flow rate through the throttle and the actually measured value of the intake pipe pressure Pm by mounting the above equation (45) in the control device of the internal combustion engine will be described. The ECU 31 cannot calculate the integral term in the equation (45) as it is. Therefore, the integral term for the estimated value mt of the throttle passage air flow rate in the equation (45) is calculated by the following equation (46) discretized using the time t and the calculation interval Δt, and the intake pipe pressure Pm is calculated. The integral term is calculated by the following equation (47) discretized using time t and calculation interval Δt.

Then, regarding the integral term for the estimated value mt of the throttle passing air flow rate, the estimated value mt (t) of the throttle passing air flow rate at time t is substituted into the equation (46), whereby the throttle passing air flow rate at time t is An integral term value mtint (t) for the estimated value mt is calculated. As for the integral term for the intake pipe internal pressure Pm, the intake pipe internal pressure Pm (t) at time t is substituted into the equation (47), whereby the integral term value hint (t) for the intake pipe internal pressure Pm at time t is obtained. ) Is calculated. In calculating any integral term, when the engine speed NE and the intake valve opening timing VVT enter the target map region, that is, the estimated value mt (t ₀ ) of the throttle passage air flow at time t ₀ . Further, the above equations (46) and (47) are calculated using the intake pipe pressure Pm (t ₀ ) as an initial value.

Then, the calculation of the error rate α by the equation (45) is performed after the engine speed NE and the intake valve opening timing VVT have departed from the target map area, that is, after the time t ₁ . Since it is the throttle-passing air flow rate estimate mt (t ₀₎ an initial value at time t ₀ for formula (46), the value of the integral term for the estimated value mt of the throttle passage air flow rate at time t ₁ mtint ( t ₁ ) represents the integral value of mt from time t ₀ to time t ₁ , and the initial value for equation (47) is the intake pipe pressure Pm (t ₀ ) at time t ₀ . the value of the integral term for the intake pipe pressure Pm at time t ₁ hint (t ₁₎ represents an integral value of a · Pm + b from time t ₀ to time t _1. Therefore, the error rate α in the map area is calculated by the following equation (48).

  By the way, in the above description, the error rate α is calculated by the equation (45) using the intake pipe pressure actually measured by the intake pipe pressure sensor 40. However, the actual pressure in the intake pipe portion 23 greatly fluctuates due to the intake pulsation, and the intake pipe pressure actually measured by the intake pipe pressure sensor 40 also fluctuates greatly as shown by the solid line in FIG. On the other hand, in the intake pipe model M20 and the intake valve model M30 described above, the pressure pulsation generated in the intake pipe portion 23 is ignored and one cycle of the actual pressure in the intake pipe portion 23 (in this embodiment, the crank angle is 720 °). ) Is used as the intake pipe pressure Pm (hereinafter referred to as “average value between cycles”). Further, the output of the intake pipe pressure sensor 40 often includes noise.

Therefore, when the error rate α is calculated directly using the intake pipe pressures Pm (t ₀ ) and Pm (t ₁ ) at time t ₀ and time t ₁ measured by the intake pipe pressure sensor 40, that is, the engine speed NE. When the error rate α is calculated directly using the intake pipe pressure Pmr actually measured by the intake pipe pressure sensor 40 when the intake valve opening timing VVT enters or leaves a certain map area, the error rate α is calculated. The error rate α may become inaccurate.

  Therefore, in the present embodiment, as described above, the intake pipe pressure Pm actually measured by the intake pipe pressure sensor 40 is not directly used to calculate the error rate α, and the intake pipe pressure measured by the intake pipe pressure sensor 40 is not calculated. The error rate α is calculated using the average value between cycles (broken line in FIG. 23). That is, the average value of the intake pipe pressure measured by the intake pipe pressure sensor 40 in the cycle including the time when the engine speed NE and the intake valve opening timing VVT enter a certain map region is calculated as the intake air at the time of entering the map. Using the mean value between the cycles of the intake pipe pressure actually measured by the intake pipe pressure sensor 40 in the cycle including the time when the pipe pressure is deviated from the map area as the pipe pressure Pmr, the above formula is used. The error rate α is calculated from (45).

  As described above, by using the average value between the cycles of the intake pipe pressure detected by the intake pipe pressure sensor 40 as the intake pipe pressure Pmr used in the expression (45), the intake pipe pressure Pmr input to the expression (45) is obtained. Similarly to the intake pipe pressure Pm used in the intake pipe model M20 and the intake valve model M30, the value excludes the influence of pressure pulsation generated in the intake pipe portion 23. Thus, the error rate α can be calculated. Further, it is possible to suppress the influence of noise included in the output of the intake pipe pressure sensor 40 in calculating the error rate α.

  Next, a modified example of the above embodiment will be described. In the above embodiment, after calculating the error rate α, the value a and the value b are multiplied by the error rate α, and both map values a and b are corrected at the same rate. However, there are cases where the error of only the value a is large or the error of only the value b is large, as well as a case where an error of the same degree is not necessarily generated in both the map values of the value a and the value b. Therefore, in order to correct the map value of the value a and the value b accurately, it is necessary to correct the value a and the value b separately without correcting the value a and the value b at the same rate.

Therefore, in this modification, the value a and the value b are separately corrected based on the error rate α calculated as described above. In this modified example, first, when the engine speed NE and the intake valve opening timing VVT are in a certain map region, the error rate α is calculated based on the above equation (45), and the error rate α is calculated. An average value Pmave of the intake pipe pressure Pm during an integration period, that is, a period in which the engine speed NE and the intake valve opening timing VVT are in the map region is calculated. For convenience, the error rate and the average value of the intake pipe pressure calculated in this way are α ₁ and Pm ₁ , respectively. Thereafter, when the engine speed NE and the intake valve opening timing VVT are again in the map region, the error rate α and the average value Pmave of the intake pipe pressure are calculated as described above. For convenience, the error rate and the average value of the intake pipe pressure calculated in this way are α ₂ and Pm ₂ , respectively.

  FIG. 24 is a diagram showing the relationship between the intake pipe pressure Pm and the cylinder intake air flow rate mc when the engine speed NE and the intake valve opening timing VVT are in the map region. The relationship between the in-cylinder intake air flow rate mc and the intake pipe pressure Pm calculated by the intake valve model M30 before the map values of the values a and b are corrected is, for example, the relationship indicated by the solid line in FIG. ing.

Here, α ₁ (a · Pm ₁ + b) calculated using the error rate α ₁ calculated as described above and the intake pipe pressure Pm ₁ is the actual cylinder when the intake pipe pressure is Pm _1. The internal intake air flow rate is accurately represented, and α ₂ (a · Pm ₂ + b) calculated using the error rate α ₂ and the intake pipe pressure Pm ₂ is an actual value when the intake pipe pressure is Pm _2. This accurately represents the in-cylinder intake air flow rate. From this, a straight line (broken line in FIG. 24) passing through the two points of the point (Pm ₁ , α ₁ (a · Pm ₁ + b)) and the point (Pm ₂ , α ₂ (a · Pm ₂ + b)) is It is considered that the relationship between the intake pipe pressure and the actual in-cylinder intake air flow rate is expressed relatively accurately.

  Therefore, by correcting the map values of the values a and b, the relationship between the intake pipe pressure Pm and the in-cylinder intake air flow rate mc calculated by the intake valve model M30 is a straight line passing through the above two points, so that the intake air The estimated value mc of the in-cylinder intake air flow rate calculated by the valve model M30 can be set to a value substantially equal to the actual in-cylinder intake air flow rate.

Therefore, in the present embodiment, the map values of the values a and b are corrected by the following equations (49) and (50) by using the error rates α ₁ and α ₂ and the intake pipe pressures Pm ₁ and Pm ₂ described above. I am going to do that. In equations (49) and (50), value a ′ and value b ′ indicate the map values after correction.

  By correcting the map values of the values a and b in this manner, the cylinder intake air flow rate mc calculated by the intake valve model M30 using the map values of the corrected values a ′ and b ′ is the actual cylinder. The value is almost equal to the internal milk air flow rate. Therefore, according to this modified example, the map values of the value a and the value b can be corrected separately, whereby the map values of the value a and the value b can be corrected accurately.

It is a figure which shows the whole internal combustion engine carrying the intake air amount estimation apparatus of this invention. It is a schematic perspective view of the air flow meter shown in FIG. It is an expansion perspective view of the heat ray measuring part of the air flow meter shown in FIG. It is a figure which shows the relationship between the output voltage of an airflow meter, and an airflow passage air flow rate. It is a block diagram of an air model. It is a figure which shows the relationship between a throttle-valve opening degree and a flow coefficient. It is a figure which shows the relationship between a throttle-valve opening degree and opening cross-sectional area. It is a figure which shows function (PHI) (Pm / Pa). It is a figure which shows the basic concept of a throttle model. It is a figure which shows the basic concept of an intake pipe model. It is a figure which shows the basic concept of an intake valve model. It is a figure regarding the definition of the cylinder filling gas amount and the cylinder intake gas amount. It is a figure which shows correction operation of a throttle model. It is a figure which shows the relationship between a throttle passage air flow rate and complete heat dissipation. It is a figure which shows the relationship between the sum of delayed heat dissipation, and the estimated output value of an airflow meter. It is a time chart with the value of various parameters regarding a throttle valve opening and an air flow rate. It is a map of the flow coefficient determined based on the throttle valve opening. It is a time chart with the value of various parameters regarding a throttle valve opening and an air flow rate. It is the figure which expanded a part of FIG. It is a figure for demonstrating an initial value response and a zero response. It is a figure which shows the map of the values a and b defined based on the engine speed and the intake valve opening timing. 4 is a time chart of intake pipe pressure, engine speed, and intake valve opening timing. It is a time chart of the pressure in an intake pipe. It is the figure which showed the relationship between the pressure in an intake pipe and the in-cylinder intake air flow rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine main body 5 Combustion chamber 6 Intake valve 7 Intake port 8 Exhaust valve 11 Fuel injection valve 14 Intake branch pipe 15 Surge tank 16 Intake pipe 19 Throttle valve 23 Intake pipe part

Claims (2)

The intake air of the internal combustion engine that calculates the cylinder charge air amount using the estimated value of the cylinder intake air flow rate calculated by the intake valve model calculation formula that calculates the estimated value of the cylinder intake air flow rate using the intake pipe internal pressure In the quantity estimation device,
An intake pipe pressure estimating means for calculating an estimated value of the intake pipe pressure by an intake pipe model calculation formula using a cylinder intake air flow rate;
Intake pipe pressure detection means for detecting the actual intake pipe pressure,
When the internal combustion engine is in a transient operation, the intake air pressure is calculated based on the estimated value of the intake pipe pressure calculated by the intake pipe pressure estimation means and the actual intake pipe pressure detected by the intake pipe pressure detection means. Correction means for correcting the valve model calculation formula,
The intake valve model calculation formula uses a map value determined for each engine operating region,
The correction means includes a deviation between an actual intake pipe pressure when the engine operating state enters a specific engine operating region and an actual intake pipe pressure when the engine operating state leaves the specific engine operating region. Between the estimated value of the intake pipe pressure when the engine operating state enters the specific engine operating region and the estimated value of the intake pipe pressure when the engine operating state leaves the specific engine operating region An intake air amount estimation device for an internal combustion engine that corrects an intake valve model calculation formula by correcting a map value corresponding to the specific engine operation region based on the above.   The intake air amount estimation device for an internal combustion engine according to claim 1, wherein the intake pipe pressure detection means detects an average value of an actual intake pipe pressure per cycle as an actual intake pipe pressure.

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