JP4241560B2 - 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, and more particularly to an intake air amount estimation device that calculates an intake air amount of an internal combustion engine by a calculation formula that models an intake system of the internal combustion engine.

  The intake system of an 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, and the models are related using pressure, temperature, flow rate, etc. There is known an intake air amount estimation device for an internal combustion engine using a so-called air model that calculates an intake air amount (in-cylinder charged air amount) of an engine by calculation.

  In an intake air amount estimation device using such an air model, it is usually possible to calculate the in-cylinder charged air amount only by the engine speed and the throttle valve opening, in addition to atmospheric pressure and atmospheric temperature. An example of an apparatus that performs this kind of intake air amount estimation is disclosed in Patent Document 1, for example.

  In the apparatus of Patent Document 1, the engine intake system is divided into each element of a throttle valve, an intake pipe including a surge tank, and an intake valve, and these elements are represented by a simulation model, and the pressure of the intake air flow in each model The temperature and flow rate are calculated using physical laws such as energy conservation law and mass conservation law. The cylinder air charge amount is calculated based on the intake air flow rate that passes through the intake valve calculated as described above.

  In the device of Patent Document 1, when the intake valve is closed (that is, when the intake valve is closed), the cylinder pressure becomes equal to the intake pipe pressure (surge tank pressure) due to the intake air filled in the cylinder. Assuming that, the in-cylinder charged air amount (that is, the in-cylinder charged air amount when the intake valve is closed) is obtained as a value proportional to the intake pipe pressure when the intake valve is closed.

JP 2001-41095 A JP 2002-201998 A

  However, when the amount of air charged in the cylinder is obtained as described above, conventionally, the influence of the gas flowing backward from the cylinder into the intake port, in particular, while the intake valve closes the intake valve, In this case, since the influence of volume change is not taken into account, the calculation accuracy may not be sufficient. That is, in actual engine operation, the intake valve may close after the intake bottom dead center. In this case, the gas in the cylinder flows backward from the cylinder into the intake port after the intake bottom dead center. It will be. The gas flowing back into the intake port in this way remains in the intake port after the intake valve is closed until the next intake valve is opened (that is, when the intake valve is opened), and the next intake valve is opened. At the time of the valve, it is sucked into the cylinder together with fresh air (air newly sucked from outside the engine), but in the transitional time when the throttle valve is opened and closed, the intake valve is closed from the time of closing the intake valve to the next intake valve. Until the valve is opened, the volume of the backflowed gas changes with the pressure change in the intake pipe. Since the amount of air actually sucked changes due to this influence, the accuracy of calculation of the in-cylinder charged air amount tends to be greatly reduced during the transition as compared to during steady operation.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an intake air amount estimation device for an internal combustion engine that can more accurately calculate the intake air amount of the internal combustion engine in a transient state accompanied by a change in the intake pipe pressure. Is to provide.

  The present invention provides an intake air amount estimating device for an internal combustion engine described in each claim as a means for solving the above-mentioned problems.

  The first invention estimates the intake pipe internal pressure when the intake valve closes in the next cycle, estimates the basic cylinder charge air amount of the next cycle based on at least the intake pipe internal pressure, The change in the intake pipe pressure from the time when the intake valve is closed in the current cycle to the time when the intake valve is opened in the next cycle is estimated, and the basic cylinder charge air amount in the next cycle is calculated based on the change in the intake pipe pressure. Provided is an intake air amount estimation device for an internal combustion engine, which corrects and obtains an in-cylinder charged air amount of the next cycle.

  In the first aspect of the invention, the pressure change in the intake pipe is estimated, and correction based on the pressure change is performed to obtain the in-cylinder charged air amount. By doing so, it becomes possible to consider the influence of the volume change accompanying the pressure change in the intake pipe due to the gas flowing back from the cylinder into the intake port on the intake air amount. However, the intake air amount of the internal combustion engine can be calculated more accurately.

  In the second aspect of the invention, in the first aspect of the invention, the correction of the basic in-cylinder charged air amount is performed when the engine speed, the opening / closing timing of at least one of the intake valve and the exhaust valve, and when the intake valve is closed in the previous cycle. A correction coefficient is obtained based on the ratio between the intake pipe internal pressure and the intake pipe internal pressure when the intake valve is opened in the next cycle, and the correction coefficient is multiplied by the basic cylinder air charge amount.

  In the third aspect of the invention, in the first aspect of the invention, the correction of the basic in-cylinder charged air amount is performed when the engine speed, the opening / closing timing of at least one of the intake valve and the exhaust valve, and when the intake valve of the previous cycle is closed. The correction amount is obtained based on the intake pipe internal pressure and the intake pipe internal pressure when the intake valve is opened in the next cycle, and the correction amount is added to the basic cylinder charge air amount.

  According to the second and third inventions, the correction of the basic cylinder charge air amount is performed in a relatively simple manner. Thereby, the calculation accuracy of the intake air amount of the internal combustion engine at the time of a transition accompanied by a change in the intake pipe pressure can be improved by a simple method.

  In the fourth aspect of the invention, in the first aspect of the invention, the correction of the basic cylinder air charge amount is performed by the gas flowing backward from the cylinder into the intake port from the time when the intake valve of the previous cycle is closed to the opening of the intake valve of the next cycle. Included in the volume change portion is a first correction amount that changes the volume in accordance with the pressure change in the intake pipe until the valve time, and corrects the effect of the burnt gas being replaced with air in the volume change portion. A second correction amount that corrects an influence due to a change in the temperature of the air that is in contact, and a third correction that corrects an influence due to the ratio of the burnt gas in the gas flowing back from the cylinder into the intake port depending on the pressure in the intake pipe The correction amount is estimated separately, and the correction amount is added to the basic cylinder air charge amount.

  According to a fifth aspect, in the fourth aspect, the first correction amount includes the amount of change in the volume of the backflow gas accompanying the change in pressure in the intake pipe, the pressure in the intake pipe when the intake valve is opened in the next cycle, and the previous cycle. Is estimated using the burnt gas ratio in the backflow gas corresponding to the pressure in the intake pipe when the intake valve is open, and the second correction amount is determined by the volume change amount of the backflow gas and the intake valve of the next cycle. Estimated using the pressure in the intake pipe when the valve is opened, the ratio of burned gas in the backflow gas corresponding to the pressure in the intake pipe when the intake valve is opened in the previous cycle, and the average temperature of the backflow gas, 3 correction amounts are the amount of change in the volume of the backflow gas, the pressure in the intake pipe when the intake valve is opened in the next cycle, and the burnt amount in the backflow gas corresponding to the pressure in the intake pipe when the intake valve is opened in the previous cycle. Corresponds to the gas ratio and intake pipe pressure when the intake valve is opened in the next cycle That is estimated by using the burnt gas ratio of the reverse flow gas.

  In the fourth and fifth inventions, the first to third correction amounts are estimated separately. By doing so, it becomes easy to apply to various situations, and it is possible to improve the calculation accuracy of the intake air amount of the internal combustion engine at the time of transition accompanied by a change in the intake pipe pressure in more diverse situations.

  The invention described in each claim has a common effect that the intake air amount of the internal combustion engine can be calculated with higher accuracy during a transient time accompanied by a change in the intake pipe pressure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or similar components are denoted by common reference numerals.

  FIG. 1 is a schematic view showing an example in which the intake air amount estimation device for an internal combustion engine of the present invention is applied to a direct injection spark ignition internal combustion engine. The present invention may be applied to other spark ignition internal combustion engines and compression ignition internal combustion engines.

  As shown in FIG. 1, 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. The cylinder head 4 is provided with an intake valve 6, an intake port 7, an exhaust valve 8, and an exhaust port 9 for each cylinder. The intake valve 6 is provided with a variable valve timing mechanism 23 that changes the opening / closing timing of the valve. 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. 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. Note that F in FIG. 1 indicates the fuel injected into the combustion chamber 5.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a downstream intake pipe 13, and the surge tank 14 is connected to an air cleaner 16 via an upstream intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed in the intake pipe 15. On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected to an exhaust purification device 20.

  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.

  A throttle opening sensor 43 for detecting the opening of the throttle valve 18 and an atmospheric pressure sensor for detecting the pressure of the atmosphere around the internal combustion engine or the pressure of the air taken into the intake pipe 15 (intake pressure). 44 and an atmospheric temperature sensor 45 for detecting the temperature of the atmosphere around the internal combustion engine or the temperature of the air taken into the intake pipe 15 (intake air temperature), and the output voltage of these sensors corresponds to the corresponding AD. The signal is input to the input port 36 via the converter 38.

  A load sensor 47 that generates an output voltage proportional to the amount of depression of the accelerator pedal 46 is connected to the accelerator pedal 46, and the output voltage of the load sensor 47 is input to the input port 36 via the corresponding AD converter 38. For example, the crank angle sensor 48 generates an output pulse every time the crankshaft rotates 30 degrees, and the 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 48. On the other hand, the output port 37 is connected to the spark plug 10, the fuel injection valve 11, the step motor 17 and the like via a corresponding drive circuit 39. The variable valve timing mechanism 23 is also controlled by an electronic control unit (ECU) 31.

  By the way, in recent years, an intake system of an internal combustion engine is modeled and an intake air amount (cylinder charged air amount) of the engine is calculated by applying an energy conservation law, a mass conservation side, a state equation, and the like to the models. An intake air amount estimation device for an internal combustion engine is known. In such an intake air amount estimation device, for example, a throttle model, an intake pipe model, an intake valve model, etc. are constructed for the intake system of the internal combustion engine, and by using these models, the throttle valve opening, the atmospheric pressure, In addition, the amount of air filled in the cylinder is obtained from the atmospheric temperature and the like. In the internal combustion engine provided with such an intake air amount estimation device, various controls are performed based on the in-cylinder charged air amount thus obtained.

  Also in the present embodiment, the intake air amount is estimated using a model in the configuration as shown in FIG. 1, and control based on the value is performed. Prior to the description, the case where the intake air amount model M20, which is a premise part of the intake air amount estimating device of the present embodiment, is used will be described first.

  FIG. 2 is a diagram showing an intake air amount model M20. As shown in FIG. 2, the intake air amount model M20 includes a throttle model M21, an intake pipe model M22, and an intake valve model M23. The throttle model M21 includes a throttle valve opening (throttle valve opening) θt detected by a throttle opening sensor, an atmospheric pressure Pa around the internal combustion engine detected by an atmospheric pressure sensor, and an atmospheric temperature sensor. The atmospheric temperature Ta around the internal combustion engine and the pressure (intake pipe pressure) Pm in the intake pipe from the throttle valve to the intake valve calculated in the intake pipe model M22, which will be described later, are input. Is substituted into a model equation of a throttle model M21, which will be described later, to calculate the flow rate of air passing through the throttle valve per unit time (throttle valve passing air flow rate) mt. The throttle valve passage air flow rate mt calculated in the throttle model M21 is input to the intake pipe model M22.

  The intake pipe model M22 includes a throttle valve passing air flow rate mt calculated in the throttle model M21 and a flow rate of air flowing into the combustion chamber per unit time described in detail below (hereinafter referred to as “cylinder intake air flow rate mc”). Note that the definition of the in-cylinder intake air flow rate mc will be described in detail in the intake valve model M23), and the values of these input parameters are substituted into the model expression of the intake pipe model M22 described later. Thus, the intake pipe pressure Pm and the temperature in the intake pipe from the throttle valve to the intake valve (intake pipe temperature) Tm are calculated. The intake pipe pressure Pm and the intake pipe temperature Tm calculated in the intake pipe model M22 are both input to the intake valve model M23, and the intake pipe pressure Pm is also input to the throttle model M21.

  In addition to the intake pipe pressure Pm and the intake pipe temperature Tm calculated in the intake pipe model M22, the air temperature Ta is input to the intake valve model M23, and these values are substituted into a model formula of the intake valve model M23 described later. Thus, the in-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 M23 is input to the intake pipe model M22.

  As can be seen from FIG. 2, in the intake air amount model M20, a parameter value calculated in one model is used as an input value to another model. Therefore, when the intake air amount model M20 is used, the in-cylinder charged air amount Mc can be calculated from the atmospheric pressure Pa, the atmospheric temperature Ta, the throttle valve opening θt, and the engine speed.

Next, each of the models M21 to M23 of the intake air amount model M20 will be described.
In the throttle model M21, from the atmospheric pressure Pa (kPa), the atmospheric temperature Ta (K), the intake pipe pressure Pm (kPa), and the throttle valve opening θt, the throttle valve passing air flow rate mt ( g / s) is calculated. Here, μ in the equation (1) is a flow coefficient in the throttle valve, which is a function of the throttle valve opening θt, and is determined from a map as shown in FIG. At (m ² ) represents the opening sectional area (throttle opening area) of the throttle valve and is a function of the throttle valve opening θt. Note that μ · At, which is a combination of the flow coefficient μ and the throttle opening area At, may be obtained from the throttle valve opening θt using a single map. R is a gas constant.

  Φ (Pm / Pa) is a function shown in the following formula (2), and κ in the formula (2) is a specific heat ratio (κ = Cp (isobaric specific heat) / Cv (isovolume specific heat), which is a constant value. ). Since this function Φ (Pm / Pa) can be expressed in a graph as shown in FIG. 4, such a graph is stored as a map in the ROM of the ECU, and is actually calculated using equation (2). Alternatively, the value of Φ (Pm / Pa) may be obtained from the map.

  Expressions (1) and (2) of the throttle model M21 are such that the pressure of the gas upstream of the throttle valve 18 is the atmospheric pressure Pa, the temperature of the gas upstream of the throttle valve 18 is the atmospheric temperature Ta, and the gas passing through the throttle valve 18 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 18 as shown in FIG. , And by using the Mayer relation.

In the intake pipe model M22, from the throttle valve passage air flow rate mt (g / s), the in-cylinder intake air flow rate mc (g / s), and the atmospheric temperature Ta (K), the following equations (3) and (4) are obtained. Based on this, the intake pipe pressure Pm (kPa) and the intake pipe temperature Tm (K) are calculated. Note that Vm (m ³ ) in the equations (3) and (4) is the value of the portion of the intake pipe or the like from the throttle valve including the surge tank to the intake valve (hereinafter referred to as the “intake pipe portion”) 13 ′. A constant equal to the volume.

  Here, the intake pipe model M22 will be described with reference to FIG. When the total gas amount in the intake pipe portion 13 ′ is M, the temporal change in the total gas amount M is the flow rate of the gas flowing into the intake pipe portion 13 ′, that is, the throttle valve passing air flow rate mt, and the intake pipe portion 13 ′. Is equal to the difference between the flow rate of the gas flowing out from the cylinder, that is, the in-cylinder intake air flow rate mc, and the following equation (5) is obtained from the law of conservation of mass. (3) is obtained from (R · Tm).

  In addition, the temporal change amount of the gas energy M · Cv · Tm in the intake pipe portion 13 ′ is the difference between the energy of the gas flowing into the intake pipe portion 13 ′ and the energy of the gas flowing out of the intake pipe portion 13 ′. equal. Therefore, if the temperature of the gas flowing into the intake pipe portion 13 ′ is the atmospheric temperature Ta and the temperature of the gas flowing out of the intake pipe portion 13 ′ is the intake pipe temperature Tm, the following equation (6) is obtained from the energy conservation law. From this equation (6) and the gas equation of state, equation (4) is obtained.

  In the intake valve model M23, 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 Expression (7), a and b are conforming parameters determined based on at least the engine speed NE. A map is created in advance, and the map is searched for and obtained as necessary. When the variable valve timing variable mechanism 23 is provided for the intake valve 6 as in the configuration shown in FIG. 1, the adaptation parameters a and b are the opening / closing timing of the intake valve 6 (that is, (Advance or retard angle from the reference opening / closing timing).

  The above-described intake valve model M23 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). It is proportional to the pressure in the combustion chamber 5 when the intake valve is closed. Further, the pressure in the combustion chamber 5 when the intake valve is closed can be regarded as being equal to the pressure of the gas upstream of the intake valve, that is, the intake pipe pressure Pm. Accordingly, the cylinder charge air amount Mc can be approximated as being proportional to the intake pipe pressure Pm when the intake valve is closed.

  Here, the average of the total amount of air flowing out from the intake pipe portion 13 'per unit time, or the amount of air taken into all the combustion chambers 5 from the intake pipe portion 13' per unit time is equalized. If the cylinder intake air flow rate mc (detailed below) is averaged over the intake stroke of one cylinder, the cylinder charge air amount Mc is proportional to the intake pipe pressure Pm. The flow rate mc is also considered to be proportional to the intake pipe pressure Pm. From this, the above formula (7) is obtained based on the theory and empirical rules. In the equation (7), the conforming parameter a is a proportional coefficient, and the conforming parameter b is a value related to the amount of burnt gas remaining in the combustion chamber 5 when the exhaust valve is closed. Further, in actual operation, the intake pipe temperature Tm may change greatly during a transition. Therefore, 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. 8 when the internal combustion engine has four cylinders. In FIG. 8, the horizontal axis represents the rotation angle of the crankshaft, and the vertical axis represents the amount of air actually flowing into the combustion chamber 5 from the intake pipe portion 13 'per unit time. As shown in FIG. 8, 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 into the combustion chamber 5 of each cylinder from the intake pipe portion 13 'according to the valve opening amount. The displacement of the flow rate of the air flowing into the combustion chamber 5 of each cylinder from the intake pipe portion 13 'is as shown by the broken line in FIG. 8, and the intake pipe portion 13' combining these changes into the combustion chamber 5 of all cylinders. The flow rate of the inflowing air is as shown by the solid line in FIG. Further, for example, the in-cylinder charged air amount Mc to the first cylinder corresponds to the hatched portion in FIG.

On the other hand, the in-cylinder intake air flow rate mc is obtained by averaging the amount of air flowing into the combustion chambers 5 of all the cylinders from the intake pipe portion 13 'indicated by the solid line, and is indicated by a one-dot chain line in the figure. Has been. 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 required for rotation by ΔT _{180 °} (which can be calculated from the engine speed). Therefore, the cylinder intake air amount Mc can be calculated by multiplying the cylinder intake air flow rate mc calculated by the intake valve model M23 by ΔT _{180 °} (Mc = mc · ΔT _{180 °} ).

  Next, a case where the in-cylinder charged air amount Mc is actually calculated using the intake air amount model M20 will be described. The in-cylinder charged air amount Mc is obtained by solving the above equations (1), (3), (4), and (7) using the intake air amount model M20. In this case, in order to be processed by the ECU 31, these equations need to be discretized. When the equation (1), the equation (3), the equation (4), and the equation (7) are discretized using the time t and the calculation interval (discrete time) Δt, the following equations (8), (9), Equations (10) and (11) are obtained. The intake pipe internal temperature Tm (t + Δt) is calculated by Expression (12) from Pm / Tm (t + Δt) and Pm (t + Δt) calculated by Expression (9) and Expression (10), respectively.

In the intake air amount model M20 implemented in this way, the throttle valve passage air flow rate mt (t) at time t calculated by the equation (8) of the throttle model M21 and the equation (11) of the intake valve model M23. The calculated in-cylinder intake air flow rate mc (t) at time t is substituted into the equations (9) and (10) of the intake pipe model M22, whereby the intake pipe pressure Pm (t + Δt) and intake air at time t + Δt are calculated. The tube temperature 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 M21 and the intake valve model M23, thereby the throttle valve passing air flow rate mt (t 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 an arbitrary 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 ΔT _{180 °} , 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 M21 to M23 is started.

  In the intake air amount model M20, the atmospheric temperature Ta and the atmospheric pressure Pa are assumed to be constant. However, the intake air amount model M20 may be a value that changes depending on the time. For example, the atmospheric temperature sensor for detecting the atmospheric temperature at the time t. Assuming that the detected value 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 You may make it substitute to (11).

  By the way, when the intake air amount model M20 as described above is used, the influence of the gas that flows backward from the cylinder into the intake port 7, particularly the intake port while the intake valve closes the intake valve. The effect of volume change is not taken into account. For this reason, the value of the in-cylinder charged air amount calculated using the intake air amount model M20 may not be sufficiently calculated as it is.

  That is, in actual operation of the internal combustion engine, the intake valve 6 may close after the intake bottom dead center. In this case, the gas in the cylinder from the cylinder to the intake port 7 after the intake bottom dead center. Will flow backwards. The gas that has flowed back into the intake port 7 in this manner remains in the intake port 7 until the next time the intake valve 6 is opened (when the intake valve is opened), and fresh air (new air) is opened when the next intake valve is opened. The air is sucked into the cylinder together with the air sucked from outside the engine. Here, during steady operation, a substantially constant amount of backflow gas corresponding to the pressure in the intake pipe at that time is sucked every time, so that the calculation accuracy is greatly reduced by appropriately setting the adaptive parameters a and b. It is possible to avoid. However, since the volume of the backflowed gas changes with the pressure change in the intake pipe from the time when the intake valve is closed until the next time when the intake valve is opened, the volume of the backflowed gas changes during the transition time when the throttle valve 18 is opened and closed. The amount of air actually sucked in changes due to the influence, and the calculation accuracy of the in-cylinder charged air amount tends to be greatly reduced as compared with the steady operation.

  Considering in more detail the factors that cause a decrease in the calculation accuracy of the in-cylinder charged air amount at the time of transition as described above, the following three are considered. That is, the first is that the gas flowing back from the cylinder into the intake port 7 changes in volume along with the change in pressure in the intake pipe from when the intake valve is closed in the previous cycle to when the intake valve is opened in the next cycle, This is due to the fact that the burned gas was replaced with air at the volume change portion. This will be described with reference to FIG. FIG. 9 schematically shows the change of the backflow gas in the intake port 7 taking the transition time when the throttle valve 18 is open as an example. In this example, when the intake valve of the previous cycle is closed, the backflow gas is filled up to the position indicated by the dotted line A. Thereafter, the throttle valve 18 is opened to increase the pressure in the intake pipe, and the intake valve of the next cycle is opened. At the time of valve operation, the backflow gas is compressed to the position indicated by the dotted line B. A portion X sandwiched between the dotted line A and the dotted line B is the volume change portion. The volume change portion X is originally filled with the backflow gas, and this is replaced with fresh air by the change in the intake pipe pressure. However, the backflow gas contains air and burned gas. Therefore, the amount of intake air actually increases by the amount that the burned gas portion in the backflow gas is replaced with air.

  The second effect is due to the change in the temperature of the air contained in the volume change portion. This will also be described using the case shown in FIG. As described above, since air is also included in the backflow gas originally in the volume change portion X, air is replaced with air for that portion. However, the air that is replaced is fresh and the temperature is low. For this reason, even if air is replaced with air, it is replaced with high-density air as much as the temperature drop. As a result, in the case shown in FIG. 9, the amount of intake air increases. .

The third effect is due to the fact that the ratio of burned gas in the gas flowing backward from the cylinder into the intake port varies depending on the intake pipe pressure. The ratio of burned gas in the backflow gas is equal to the ratio of burned gas remaining in the cylinder, and tends to increase as the intake pipe pressure decreases. Therefore, for example, when considering the transition of opening the throttle valve 18, that is, the case where the intake pipe pressure rises, the ratio of burned gas in the gas flowing back from the cylinder into the intake port 7 in the previous cycle is It will be higher than the ratio of burnt gas in the backflow gas in the cycle. For this reason, even if the intake pipe pressure is the same value, for example, a certain pressure Pmx, the ratio of burnt gas in the backflow gas existing in the intake port 7 during steady operation with the intake pipe pressure maintained at the pressure Pmx However, when the pressure in the intake pipe changes from a lower pressure to the pressure Pmx, the ratio of burned gas in the backflow gas existing in the intake port 7 is larger. As a result, the amount of intake air decreases by the difference in the ratio of burned gas when the throttle valve 18 is opened, that is, when the intake pipe pressure increases.
In addition, since it seems that it is clear from the above description about the transition time which closes the throttle valve 18, ie, the case where the pressure in an intake pipe falls, explanation is omitted here.

  Based on the above, in the present embodiment, the influence of the gas flowing back from the cylinder into the intake port 7, particularly, the volume in the intake port 7 while the reverse flow gas is closed. In consideration of the changing effect, the cylinder charge air amount calculated using the intake air amount model M20 is corrected, and the intake air amount of the internal combustion engine can be calculated more accurately even during a transient state accompanied by a change in the intake pipe pressure. I can do it.

  Hereinafter, the correction performed in the present embodiment will be specifically described. That is, in this embodiment, the cylinder air charge amount for the next cycle calculated using the intake air amount model M20 is set as the basic cylinder air charge amount Mcb for the next cycle, and this value is the intake valve for the previous cycle. Correction is made on the basis of a change in pressure in the intake pipe from when the valve is closed to when the intake valve is opened in the next cycle, and the in-cylinder charged air amount Mc in the next cycle is obtained.

  FIG. 10 is a flowchart showing the control performed for the correction in the present embodiment. When this control starts, first, at step 101, the engine speed and the opening / closing timing of the intake valve 6 are read. Here, the opening / closing timing of the intake valve 6 is expressed by an advance angle or retardation amount from a predetermined reference opening / closing timing.

  When the engine speed and the opening / closing timing of the intake valve 6 are read in step 101, the process proceeds to step 103, and the intake pipe pressure PmIVC (n-1) at the time of closing the intake valve in the previous cycle and the next cycle. The intake pipe pressure PmIVO (n) when the intake valve is opened is estimated. These estimations are basically performed using the intake air amount model M20 described above. Here, (n-1) means the previous cycle, and (n) means the next cycle. This also applies to other parameters used in the following description.

  If the intake pipe pressures PmIVC (n-1) and PmIVO (n) are estimated in step 103, the process proceeds to step 105. In step 105, the engine speed read in step 101 and the opening / closing timing of the intake valve 6 and the pressure ratio PmIVC (n−) determined from the intake pipe pressures PmIVC (n−1) and PmIVO (n) estimated in step 103 are obtained. 1) A correction coefficient Cm is determined based on / PmIVO (n). In the subsequent step 107, the correction coefficient Cm is multiplied by the basic cylinder charge air amount Mcb of the next cycle calculated using the intake air amount model M20 to correct the value, and the cylinder charge air of the next cycle is corrected. The amount Mc is obtained. In the present embodiment, the engine speed, the opening / closing timing, and the pressure ratio PmIVC (n−1) / PmIVO (n) are used as arguments in advance so as to obtain a correction coefficient Cm suitable for such a purpose. A map of the correction coefficient Cm is created, and in step 105, the correction coefficient Cm is obtained using this map. The correction coefficient Cm tends to increase as the engine speed decreases and as the opening / closing timing is retarded. Further, the value of the pressure ratio PmIVC (n−1) / PmIVO (n) tends to increase as the distance from 1 increases.

  In the subsequent step 107, as described above, the correction coefficient Cm determined in step 105 is multiplied by the basic cylinder charge air amount Mcb of the next cycle calculated using the intake air amount model M20. As a result, the basic in-cylinder charged air amount Mcb is corrected, the in-cylinder charged air amount Mc of the next cycle is obtained, and the present control ends.

  As described above, in the present embodiment, the pressure change in the intake pipe is estimated, and correction based on the pressure change is performed to obtain the in-cylinder charged air amount Mc. By doing so, it is possible to consider the influence of the volume change accompanying the pressure change in the intake pipe of the gas flowing back from the cylinder into the intake port 7 on the intake air amount. In this case, the intake air amount of the internal combustion engine can be calculated with higher accuracy.

  Next, another embodiment of the present invention will be described. This embodiment can be implemented with the configuration shown in FIG. Also in this embodiment, the in-cylinder charged air amount for the next cycle calculated using the intake air amount model M20 is set as the basic in-cylinder charged air amount Mcb for the next cycle, and this value is the intake valve for the previous cycle. The in-cylinder charged air amount Mc of the next cycle is obtained by correction based on the change in the intake pipe pressure from the time of closing the valve to the time of opening the intake valve of the next cycle. In the following description of the present embodiment, the description of the parts common to the above-described embodiment is omitted in principle.

  FIG. 11 is a flowchart showing the control performed for the correction in the present embodiment. When this control starts, first, in step 201, the engine speed and the opening / closing timing of the intake valve 6 are read. In the subsequent step 203, the intake pipe pressure PmIVC (n-1) when the intake valve is closed in the previous cycle and the intake pipe pressure PmIVO (n) when the intake valve is opened in the next cycle are estimated. The control executed in step 201 and step 203 is the same as the control executed in step 101 and step 103 described above.

  When the intake pipe pressures PmIVC (n-1) and PmIVO (n) are estimated in step 203, the process proceeds to step 205. In step 205, the correction amount Ca is determined based on the engine speed read in step 201 and the opening / closing timing of the intake valve 6 and the intake pipe pressures PmIVC (n-1) and PmIVO (n) estimated in step 203. Is done. This correction amount Ca is added to the basic cylinder charge air amount Mcb of the next cycle calculated using the intake air amount model M20 in the subsequent step 207 to correct the value, and the cylinder charge air of the next cycle is corrected. The amount Mc is obtained. In the present embodiment, the engine speed, the opening / closing timing, and the intake pipe internal pressure PmIVC (n-1) at the time of closing the intake valve in the previous cycle are obtained so that the correction amount Ca suitable for such purpose can be obtained. A map of the correction amount Ca is created in advance with the intake pipe pressure PmIVO (n) at the time of intake valve opening in the next cycle as an argument. In step 205, the correction amount Ca is obtained using this map.

  In the subsequent step 207, as described above, the correction amount Ca determined in step 205 is added to the basic in-cylinder charged air amount Mcb calculated using the intake air amount model M20. Thus, the basic cylinder air charge Mcb is corrected, the cylinder internal charge air quantity Mc of the next cycle is obtained, and the present control ends.

  As described above, also in the present embodiment, the pressure change in the intake pipe is estimated as in the above-described embodiment, and correction based on this is performed to obtain the in-cylinder charged air amount Mc. Therefore, according to the present embodiment, it is possible to calculate the intake air amount of the internal combustion engine with higher accuracy during a transient time accompanied by a change in the intake pipe pressure.

  Next, still another embodiment of the present invention will be described. This embodiment can also be implemented by the configuration shown in FIG. Also in this embodiment, the in-cylinder charged air amount for the next cycle calculated using the intake air amount model M20 is set as the basic in-cylinder charged air amount Mcb for the next cycle, and this value is the intake valve for the previous cycle. The in-cylinder charged air amount Mc of the next cycle is obtained by correction based on the change in the intake pipe pressure from the time of closing the valve to the time of opening the intake valve of the next cycle. In particular, in this embodiment, the three effects described above as factors that reduce the calculation accuracy of the in-cylinder charged air amount at the time of transition (that is, the burnt gas is generated in the volume change portion of the backflow gas in the intake port). Effects due to air replacement, effects due to changes in the temperature of the air contained in the volume change part of the backflow gas, and effects due to the difference in the ratio of burned gas in the backflow gas depending on the pressure in the intake pipe ), A correction amount for correcting each influence is separately obtained. Note that, in the following description regarding the present embodiment as well, the description of the parts common to the other embodiments described above will be omitted in principle.

  FIG. 12 is a flowchart showing the control performed for correcting the basic in-cylinder charged air amount Mcb (that is, the in-cylinder charged air amount calculated using the intake air amount model M20) in the present embodiment. is there. When this control starts, first, at step 301, the engine speed and the opening / closing timing of the intake valve 6 are read. In the subsequent step 303, the intake pipe pressure PmIVC (n-1) when the intake valve of the previous cycle is closed and the intake pipe pressure PmIVO (n) when the intake valve of the next cycle is opened are estimated. The control performed in step 301 and step 303 is the same as the control performed in step 101 and step 103 or step 201 and step 203 described above.

  When the intake pipe pressures PmIVC (n−1) and PmIVO (n) are estimated in step 303, the process proceeds to step 305. In step 305, the burned gas ratio EGR (n-1) in the backflow gas with respect to the intake pipe pressure PmIVO (n-1) at the time of opening the intake valve in the previous cycle, and the intake air at the time of opening the intake valve in the next cycle The burned gas ratio EGR (n) in the backflow gas with respect to the pipe pressure PmIVO (n) is obtained. The ratio of burned gas in the backflow gas, that is, the ratio of burned gas remaining in the cylinder is affected by the pressure in the intake pipe as described above, but in addition to the engine speed and the opening / closing timing of the intake valve 6 to be influenced. For this reason, in the present embodiment, a map capable of obtaining the ratio of burned gas during normal operation is created in advance using the intake pipe pressure, the engine speed, and the opening / closing timing as arguments. The burned gas ratios EGR (n-1) and EGR (n) are determined based on the above. Here, the intake pipe pressure PmIVO (n−1) at the time of opening the intake valve in the previous cycle, which is necessary to obtain the burned gas ratio EGR (n−1), is obtained by using the intake air amount model M20 described above. Estimated.

  When the burned gas ratios EGR (n-1) and EGR (n) are determined in step 305, the process proceeds to step 307, where the average temperature Tp of the backflow gas is obtained. In the present embodiment, a map in which the average temperature Tp of the backflow gas is obtained from the engine speed and the burned gas ratio EGR (n-1) is created in advance, and in step 307, the average is calculated based on this map. The temperature Tp is determined.

  When the average temperature Tp is determined in step 307, the process proceeds to step 309, where the volume change amount ΔVp of the backflow gas from when the intake valve is closed in the previous cycle to when the intake valve is opened in the next cycle is obtained. It is done. This volume change amount ΔVp corresponds to the volume of the volume change portion X in the case described with reference to FIG. In the present embodiment, a map in which the volume change amount ΔVp is obtained in advance from the engine speed, the opening / closing timing of the intake valve 6, and the pressure ratio PmIVC (n−1) / PmIVO (n) is created in advance. In step 309, the volume change amount ΔVp is determined based on this map.

  When the volume change amount ΔVp is determined in step 309, the process proceeds to step 311. In step 311, the first of the three effects described above as a factor that reduces the calculation accuracy of the in-cylinder charged air amount at the time of transition, that is, the volume change portion of the backflow gas in the intake port is already present. A first correction amount Ca1 for correcting the influence of the replacement of the fuel gas with air is obtained. In the present embodiment, the map for obtaining the first correction amount Ca1 includes the volume change amount ΔVp, the intake pipe pressure PmIVO (n) when the intake valve is opened in the next cycle, and the burned gas ratio EGR ( n-1) as an argument, and in step 311, the first correction amount Ca1 is determined based on this map.

  When the first correction amount Ca1 is determined in step 311, the process proceeds to step 313. In step 313, it is included in the second effect among the three effects described above as a factor that decreases the calculation accuracy of the cylinder charge air amount during the transition, that is, the volume change portion of the backflow gas. A second correction amount Ca2 for correcting the influence of the change in the air temperature is obtained. In the present embodiment, the map for obtaining the second correction amount Ca2 includes the volume change amount ΔVp, the intake pipe pressure PmIVO (n) when the intake valve is opened in the next cycle, the average temperature Tp, and the The burned gas ratio EGR (n−1) is created in advance as an argument. In step 313, the second correction amount Ca2 is determined based on this map.

  When the second correction amount Ca2 is determined in step 313, the process proceeds to step 315. In step 315, the third effect among the three effects described above as a factor that reduces the calculation accuracy of the in-cylinder charged air amount at the time of transition, that is, the ratio of the burned gas in the backflow gas is determined in the intake pipe. A third correction amount Ca3 for correcting the influence due to different pressures is obtained. In the present embodiment, the map for obtaining the third correction amount Ca3 includes the volume change amount ΔVp, the intake pipe pressure PmIVO (n) when the intake valve is opened in the next cycle, and the burned gas ratio EGR ( n-1) and EGR (n) are created in advance, and in step 315, the third correction amount Ca3 is determined based on this map.

  Then, when the third correction amount Ca3 is determined in step 315, in the subsequent step 317, the first, second, and third correction amounts Ca1, Ca2, and Ca3 determined in steps 311 313, and 315 are determined. It is added to the basic cylinder charge air amount Mcb of the next cycle calculated using the intake air amount model M20. Thus, the basic cylinder air charge Mcb is corrected, the cylinder internal charge air quantity Mc of the next cycle is obtained, and the present control ends.

  As described above, also in the present embodiment, the intake pipe pressure change is estimated and the cylinder charge air amount Mc is obtained by performing a correction based on the estimated change in the intake pipe pressure, as in the above-described embodiments. Therefore, according to the present embodiment, it is possible to calculate the intake air amount of the internal combustion engine with higher accuracy during a transient time accompanied by a change in the intake pipe pressure.

  Further, in the present embodiment, the correction amounts for correcting the three effects described above as factors that reduce the calculation accuracy of the in-cylinder charged air amount during the transition are the first, second, and third correction amounts, respectively. It is determined (estimated) separately as Ca1, Ca2, and Ca3. By doing so, it becomes easy to apply to various situations, and it is possible to improve the calculation accuracy of the intake air amount of the internal combustion engine at the time of transition accompanied by a change in the intake pipe pressure in more diverse situations. That is, for example, the control load can be reduced by reducing the number of dimensions of the map, and as a result, it becomes easy to perform the correction for a wider range of operating conditions.

  Next, still another embodiment of the present invention will be described. This embodiment can also be implemented by the configuration shown in FIG. Also in this embodiment, the in-cylinder charged air amount for the next cycle calculated using the intake air amount model M20 is set as the basic in-cylinder charged air amount Mcb for the next cycle, and this value is the intake valve for the previous cycle. The in-cylinder charged air amount Mc of the next cycle is obtained by correction based on the change in the intake pipe pressure from the time of closing the valve to the time of opening the intake valve of the next cycle. In this embodiment as well, as in the embodiment described with reference to FIG. 12, correction for correcting the three effects described above as factors that cause the calculation accuracy of the in-cylinder charged air amount to decrease during transition. The amounts are obtained separately as the first, second, and third correction amounts Ca1, Ca2, and Ca3, respectively. However, in the present embodiment, these correction amounts Ca1, Ca2, and Ca3 are obtained by calculation instead of using a map. Hereinafter, control performed for correcting the basic in-cylinder charged air amount Mcb in the present embodiment will be described. In the following description regarding the present embodiment, the description of the parts common to the above-described embodiments is omitted in principle.

  FIG. 13 is a flowchart showing the control performed for correcting the basic cylinder air charge Mcb in the present embodiment. When this control starts, first, at step 401, the engine speed and the opening / closing timing of the intake valve 6 are read. The control executed in step 401 is the same as the control executed in step 101, step 201, step 301, etc. described above.

  When the engine speed and the opening / closing timing of the intake valve 6 are read in step 401, the process proceeds to step 403, where the intake pipe pressure PmIVC (n-1) at the time of closing the intake valve in the previous cycle, The intake pipe pressure PmIVO (n) and the intake pipe temperature Tm when the intake valve is opened are estimated. These estimations are basically performed using the intake air amount model M20 described above.

  In step 403, when the intake pipe pressures PmIVC (n-1), PmIVO (n) and the temperature Tm are estimated, the process proceeds to step 405. In step 405, the burned gas ratio EGR (n-1) in the backflow gas with respect to the intake pipe pressure PmIVO (n-1) at the time of opening the intake valve in the previous cycle, and the intake air at the time of opening the intake valve in the next cycle The burned gas ratio EGR (n) in the backflow gas with respect to the pipe pressure PmIVO (n) is obtained. The control executed in step 405 is the same as the control executed in step 305 described above.

  When the burned gas ratios EGR (n-1) and EGR (n) are determined in step 405, the process proceeds to step 407, where the average temperature Tp of the backflow gas is obtained. The control executed in step 407 is the same as the control executed in step 307 described above.

  When the average temperature Tp is determined in step 407, the process proceeds to step 409, where the volume change amount ΔVp of the backflow gas from when the intake valve is closed in the previous cycle to when the intake valve is opened in the next cycle is obtained. It is done. In the present embodiment, the volume change amount ΔVp is calculated based on the following equation (13).

  Here, Vp is the volume of the backflow gas in the intake port 7 when the intake valve is closed in the previous cycle. This value is obtained on the basis of a map in which the backflow gas volume during steady operation can be obtained in advance using the engine speed and the opening / closing timing of the intake valve 6 as arguments.

  When the volume change amount ΔVp is calculated in step 409, the process proceeds to step 411. In step 411, the first effect among the three effects described above as a factor that reduces the calculation accuracy of the in-cylinder charged air amount at the time of transition, that is, the volume change portion of the backflow gas in the intake port is already detected. A first correction amount Ca1 for correcting the influence of the replacement of the fuel gas with air is obtained. In the present embodiment, the first correction amount Ca1 is calculated based on the following formula (14).

  When the first correction amount Ca1 is calculated in step 411, the process proceeds to step 413. In step 413, it is included in the second influence among the three influences described above as a factor that the calculation accuracy of the cylinder charge air amount decreases during the transition, that is, the volume change portion of the backflow gas. A second correction amount Ca2 for correcting the influence of the change in the air temperature is obtained. In the present embodiment, the second correction amount Ca2 is calculated based on the following formula (15).

  When the second correction amount Ca2 is calculated in step 413, the process proceeds to step 415. In step 415, the third effect among the three effects described above as a factor that reduces the calculation accuracy of the in-cylinder charged air amount at the time of transition, that is, the ratio of burned gas in the backflow gas is determined in the intake pipe. A third correction amount Ca3 for correcting the influence due to different pressures is obtained. In the present embodiment, the third correction amount Ca3 is calculated based on the following equation (16).

  Then, when the third correction amount Ca3 is calculated in step 415, in the subsequent step 417, the first, second, and third correction amounts Ca1, Ca2, and Ca3 calculated in steps 411, 413, and 415 are calculated. It is added to the basic cylinder charge air amount Mcb of the next cycle calculated using the intake air amount model M20. Thus, the basic cylinder air charge Mcb is corrected, the cylinder internal charge air quantity Mc of the next cycle is obtained, and the present control ends.

  As described above, also in the present embodiment, the intake pipe pressure change is estimated and the cylinder charge air amount Mc is obtained by performing a correction based on the estimated change in the intake pipe pressure, as in the above-described embodiments. Therefore, according to the present embodiment, it is possible to calculate the intake air amount of the internal combustion engine with higher accuracy during a transient time accompanied by a change in the intake pipe pressure.

  Also in the present embodiment, the correction amounts for correcting the three effects described above as factors that cause the calculation accuracy of the in-cylinder charged air amount to decrease during the transition are the first, second, and third correction amounts, respectively. It is determined (estimated) separately as Ca1, Ca2, and Ca3. Therefore, according to the present embodiment, the correction can be easily applied to more various situations, and the calculation accuracy of the intake air amount of the internal combustion engine at the time of transition accompanied by the change in the intake pipe pressure in the more diverse situations can be improved. be able to. Further, in the present embodiment, the first, second, and third correction amounts Ca1, Ca2, Ca3, and the like are obtained by calculation instead of a map. Thereby, the number of maps can be reduced as compared with the embodiment described with reference to FIG.

  In each of the above-described embodiments, the cylinder intake air amount mc is obtained from the cylinder intake air amount Mc finally obtained after correction, and the value is input to the intake pipe model M22. The calculation in the intake air amount model M20 may be performed.

  Further, in each of the above-described embodiments, the variable valve timing mechanism 23 is provided only in the intake valve 6, but the present invention is not limited to this, and both the intake valve 6 and the exhaust valve 8, or The present invention can also be applied to a case where only the exhaust valve 8 is provided with a variable valve timing mechanism.

FIG. 1 is a schematic view showing an example in which the intake air amount estimation device for an internal combustion engine of the present invention is applied to a direct injection spark ignition type internal combustion engine. FIG. 2 is a diagram illustrating an intake air amount model. FIG. 3 is a diagram showing the relationship between the throttle valve opening and the flow coefficient. FIG. 4 is a diagram illustrating the function Φ (Pm / Pa). FIG. 5 is a diagram showing a basic concept of the throttle model. FIG. 6 is a diagram showing a basic concept of the intake pipe model. FIG. 7 is a diagram showing a basic concept of the intake valve model. FIG. 8 is a diagram relating to the definition of the cylinder charge air amount and the cylinder intake air flow rate. FIG. 9 is a diagram for explaining the change in the backflow gas in the intake port, taking as an example a transient time when the throttle valve opens. FIG. 10 is a flowchart showing control executed in an embodiment of the present invention. FIG. 11 is a flowchart showing the control performed in another embodiment of the present invention. FIG. 12 is a flowchart showing control executed in still another embodiment of the present invention. FIG. 13 is a flowchart showing control executed in still another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 5 Combustion chamber 6 Intake valve 7 Intake port 8 Exhaust valve 9 Exhaust port 11 Fuel injection valve 13 Intake pipe 18 Throttle valve

Claims (5)

  Estimate the intake pipe pressure when the intake valve closes in the next cycle, estimate the basic cylinder charge air amount of the next cycle based on at least the intake pipe pressure, and close the intake valve closure of the previous cycle The change in the intake pipe pressure from the valve timing to the opening of the intake valve in the next cycle is estimated, the basic cylinder charge air amount in the next cycle is corrected based on the intake pipe pressure change, and the next cycle An intake air amount estimation device for an internal combustion engine for obtaining an in-cylinder charged air amount of a cycle.   The correction of the basic cylinder charge air amount includes the engine speed, the opening / closing timing of at least one of the intake valve and the exhaust valve, the intake pipe pressure when the intake valve of the previous cycle is closed, and the intake valve opening of the next cycle 2. An intake air amount estimation device for an internal combustion engine according to claim 1, wherein a correction coefficient is obtained based on a ratio to the intake pipe pressure at the time, and the correction coefficient is multiplied by the basic cylinder charge air amount. .   The correction of the basic cylinder charge air amount includes the engine speed, the opening / closing timing of at least one of the intake valve and the exhaust valve, the intake pipe pressure when the intake valve is closed in the previous cycle, and the intake valve opening of the next cycle. 2. The intake air amount estimation device for an internal combustion engine according to claim 1, wherein a correction amount is obtained based on an intake pipe pressure at the time of valve, and the correction amount is added to the basic cylinder charge air amount. The correction of the basic cylinder charge air amount is as follows.
The gas flowing back from the cylinder into the intake port changes in volume along with the change in pressure in the intake pipe from when the intake valve is closed in the previous cycle to when the intake valve is opened in the next cycle. A first correction amount for correcting the influence of the gas being replaced with air;
A second correction amount for correcting an influence caused by a change in the temperature of the air contained in the volume change portion;
Estimating separately the third correction amount for correcting the influence of the ratio of burned gas in the gas flowing backward from the cylinder into the intake port depending on the pressure in the intake pipe,
The intake air amount estimation device for an internal combustion engine according to claim 1, wherein the correction amount is added to the basic cylinder charge air amount. The first correction amount is set to the volume change amount of the backflow gas accompanying the change in the intake pipe pressure, the intake pipe pressure when the intake valve is opened in the next cycle, and the intake pipe pressure when the intake valve is opened in the previous cycle. Estimated using the ratio of burned gas in the corresponding backflow gas,
The second correction amount includes a volume change amount of the backflow gas, an intake pipe pressure when the intake valve is opened in the next cycle, and an intake pipe pressure corresponding to the intake pipe pressure when the intake valve is opened in the previous cycle. Estimated using the burnt gas ratio and the average temperature of the backflow gas,
The third correction amount includes the amount of change in the volume of the backflow gas, the pressure in the intake pipe at the time of opening the intake valve in the next cycle, and the pressure in the backflow gas corresponding to the pressure in the intake pipe at the time of opening the intake valve in the previous cycle. The intake air amount estimation of the internal combustion engine according to claim 4, wherein the estimation is made using a burnt gas ratio and a burnt gas ratio in the backflow gas corresponding to the pressure in the intake pipe when the intake valve is opened in the next cycle. apparatus.

Images