JP2007040266A - Intake air amount estimation device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intake air amount estimation device for an internal combustion engine capable of accurately estimating the intake air amount regardless of the temperature state of the internal combustion engine (that is, engine temperature) in an internal combustion engine capable of changing the on-off valve characteristics of the intake valve. .
A basic in-cylinder charged air amount Mcb, which is an in-cylinder charged air amount when the engine temperature is a specific temperature, is estimated, and the basic in-cylinder charged air amount Mcb is calculated from the engine temperature (or engine cooling water temperature Tw). ), Engine speed Ne, intake valve opening / closing timing Vt, intake pipe pressure Pme when the exhaust valve closes, intake valve operating angle Sa or lift amount, and in-cylinder filling Provided is an intake air amount estimation device for an internal combustion engine for obtaining an air amount Mc.
[Selection] Figure 9

Description

  The present invention relates to an intake air amount estimation device for an 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, the intake air flow rate that passes through the intake valve used to calculate the cylinder air charge amount is calculated by a linear function with the intake pipe pressure as a variable. This linear function changes for each engine operating state, and the proportionality coefficient and constant for specifying the linear function are adapted and mapped for each engine speed and each valve timing (that is, every valve overlap period). ing.

JP 2001-41095 A

  However, at the time of mapping (that is, creation of the map), the proportional coefficient and constant are adapted to the internal combustion engine when the engine temperature is a specific temperature after warming up. When the engine is cold, it is not possible to calculate an accurate intake flow rate that passes through the intake valve even if a linear function specified based on the engine operating state at that time is used. May not be calculated.

  In order to correct such an error caused by the difference in engine temperature, a correction coefficient determined based on the engine coolant temperature correlated with the engine temperature in the cylinder charge air amount calculated based on the linear function. The method of multiplying can be considered. However, in practice, if the valve timing, intake pipe pressure, etc. are different, the amount of burnt gas that flows back into the intake port differs, so the effect of the difference in engine temperature on the in-cylinder charged air amount also differs. In some cases, sufficient correction cannot be performed by multiplying the in-cylinder charged air amount calculated based on the linear function by a correction coefficient determined based only on the cooling water temperature.

  That is, the burnt gas that has flowed back into the intake port radiates heat and contracts there, but the effect of this phenomenon on the amount of charged air in the cylinder depends on the amount of burnt gas that flows back in addition to the engine temperature. Different. For this reason, if the valve timing, the pressure in the intake pipe, etc. are different and the amount of burnt gas flowing back into the intake port is different, the effect on the in-cylinder charged air amount will be different even if the difference in engine temperature is the same. . Therefore, there is a case where sufficient correction cannot be performed even if the cylinder charge air amount calculated based on the linear function is simply multiplied by a correction coefficient determined based only on the engine coolant temperature. .

  Further, the difference in engine temperature also affects the temperature of the intake air, which is also a cause of errors caused by the difference in engine temperature as described above. Although the temperature change of the air suck | inhaled here arises by heat transfer with an intake port wall surface etc., it turns out that the heat transfer rate is dependent on an intake flow velocity. The actual heat transfer is greatly influenced by the intake air flow velocity. For this reason, as a method of performing more appropriate correction, it is conceivable to change the correction coefficient for multiplying the cylinder air charge amount calculated based on the linear function in accordance with the engine speed.

  However, for example, in an internal combustion engine in which the operating angle (or lift amount) of the intake valve can be changed, the intake air flow rate is different even at the same engine speed and the same cylinder air charge amount. And heat transfer may vary. For this reason, even when the correction coefficient for multiplying the in-cylinder charged air amount calculated based on the linear function is simply changed according to the engine speed, more appropriate correction cannot be performed. There is.

  The present invention has been made in view of the above points, and the object thereof is an internal combustion engine that can change the on-off valve characteristics of the intake valve, regardless of the temperature state of the internal combustion engine (that is, the engine temperature). An object of the present invention is to provide an intake air amount estimation device for an internal combustion engine that can accurately estimate an intake air amount. In the present application, the “open / close valve characteristic” means at least one of an operating angle, a lift amount, and an open / close timing.

  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.

  According to the first aspect of the present invention, the basic in-cylinder charged air amount, which is the in-cylinder charged air amount when the engine temperature is a specific temperature, is estimated, and the basic in-cylinder charged air amount is determined as the engine temperature and the engine speed. Provided is an intake air amount estimation device for an internal combustion engine that calculates a cylinder charge air amount by performing correction based on the number, the opening / closing timing of the intake valve, and the pressure in the intake pipe when the exhaust valve closes.

  In the case of first estimating the basic cylinder filling air amount, which is the cylinder filling air amount when the engine temperature is a specific temperature, and correcting the basic cylinder filling air amount to obtain the actual cylinder filling air amount, If the opening / closing timing of the intake valve can be changed, there may be a case where the cylinder charge air amount with sufficient accuracy cannot be obtained even if correction is performed based only on the engine temperature and the engine speed. This is presumably because, when the opening / closing timing of the intake valve can be changed, the amount of gas flowing back from the cylinder into the intake port varies depending on the opening / closing timing of the intake valve.

  On the other hand, in the first aspect of the invention, as described above, the basic cylinder charge air amount is particularly large in addition to the engine temperature and the engine speed, as well as the amount of gas flowing backward from the cylinder into the intake port. Correction is also made based on the opening / closing timing of the intake valve that has an influence and the pressure in the intake pipe when the exhaust valve is closed. Therefore, in this way, in the internal combustion engine that can change the opening / closing timing of the intake valve, the intake air amount can be accurately estimated regardless of the temperature state of the internal combustion engine (that is, the engine temperature).

  According to the second aspect of the present invention, the basic cylinder charge air amount, which is the cylinder charge air amount when the engine temperature is the specific temperature, is estimated, and the basic cylinder charge air amount is determined as the engine temperature and the engine rotation. Provided is an intake air amount estimation device for an internal combustion engine that calculates the amount of air charged in a cylinder by correcting based on the number, the pressure in the intake pipe when the exhaust valve closes, and the operating angle or lift amount of the intake valve .

  In the case of first estimating the basic cylinder filling air amount, which is the cylinder filling air amount when the engine temperature is a specific temperature, and correcting the basic cylinder filling air amount to obtain the actual cylinder filling air amount, When the operating angle or lift amount of the intake valve can be changed, there may be a case where the cylinder charge air amount with sufficient accuracy cannot be obtained even if correction is performed based only on the engine temperature or the engine speed. This is considered to be caused by the fact that the flow rate of intake air varies depending on the change in the working angle or lift amount in addition to the change in the amount of backflow gas described above by changing the working angle or lift amount of the intake valve. It is done.

  On the other hand, in the invention according to claim 2, as described above, the basic cylinder charge air amount includes not only the engine temperature and the engine speed, but also the intake pipe internal pressure when the exhaust valve closes and the intake valve pressure. Correction is also made based on the operating angle or the lift amount. Therefore, in this way, in an internal combustion engine that can change the operating angle or lift amount of the intake valve, the intake air amount can be accurately estimated regardless of the temperature state of the internal combustion engine (that is, the engine temperature). Become.

  According to a third aspect of the present invention, the basic cylinder charge air amount, which is the cylinder charge air amount when the engine temperature is a specific temperature, is estimated, and the basic cylinder charge air amount is determined as the engine temperature and the engine speed. The intake air amount of the internal combustion engine, which is corrected based on the number, the opening / closing timing of the intake valve, the pressure in the intake pipe when the exhaust valve closes, and the operating angle or lift amount of the intake valve An air amount estimation device is provided.

  In the third aspect of the invention, when the opening / closing timing of the intake valve can be changed and the working angle or lift amount of the intake valve can be changed, the difference in the amount of backflow gas and the difference in the intake flow velocity are taken into consideration. The basic in-cylinder charged air amount is corrected to obtain the in-cylinder charged air amount. Therefore, according to the third aspect of the invention, in the internal combustion engine in which the opening / closing timing of the intake valve can be changed and the working angle or lift amount of the intake valve can be changed, the internal combustion engine temperature state (that is, the engine temperature) is changed. Regardless, the intake air amount can be accurately estimated.

  According to a fourth and fifth aspect of the invention, in the first or third aspect of the invention, the in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient. When the temperature is lower than the specific temperature, the correction coefficient increases as the intake valve opening / closing timing is advanced.

  When the engine temperature is lower than the specific temperature, the degree of contraction of the backflow gas described above is greater than when the engine temperature is the specific temperature. Further, as the opening / closing timing of the intake valve is advanced, the amount of the backflow gas described above tends to increase, and therefore the influence of the difference in engine temperature increases. For this reason, the estimation accuracy of the intake air amount can be improved by using the inventions according to claims 4 and 5.

  According to a sixth aspect of the present invention, in the invention according to any one of the second, third and fifth aspects, the in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient. When the temperature is lower than the specific temperature, the correction coefficient decreases as the operating angle or lift amount of the intake valve increases.

  When the engine temperature is lower than the specific temperature, the degree of expansion of the sucked air is smaller than when the engine temperature is the specific temperature. In addition, as the operating angle or lift amount of the intake valve increases, the intake flow rate described above tends to increase. As the intake flow rate increases, the amount of heat transfer to the intake air decreases, resulting in a decrease in the intake air. Since the temperature change tends to be small, the influence of the difference in the engine temperature is small. For this reason, the estimation accuracy of the intake air amount can be improved by performing the invention according to the sixth aspect.

According to a seventh aspect of the invention, in the invention according to any one of the first to sixth aspects, the in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient, and the correction coefficient is determined by the engine. The higher the temperature, the smaller.
The higher the engine temperature, the smaller the degree of contraction of the backflow gas described above, and the greater the degree of expansion of the sucked air. For this reason, according to the seventh aspect of the present invention, it is possible to improve the estimation accuracy of the intake air amount.

  In the invention according to claim 8, in the invention according to any one of claims 1 to 7, the cylinder air charge amount is obtained by multiplying the basic cylinder air charge amount by a correction coefficient, and the engine temperature is When the temperature is lower than the specific temperature, the correction coefficient decreases as the engine speed increases.

  When the engine temperature is lower than the specific temperature, the degree of expansion of the sucked air is smaller than when the engine temperature is the specific temperature. In addition, the higher the engine speed, the higher the intake flow rate described above, and the higher the intake flow rate, the smaller the amount of heat transfer to the intake air and the smaller the temperature change of the intake air. Since there is a tendency, the influence of the difference in the engine temperature is small. For this reason, the estimation accuracy of the intake air amount can be improved by using the invention according to the eighth aspect.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient, and the engine temperature is When the temperature is lower than the specific temperature, the correction coefficient decreases as the pressure in the intake pipe when the exhaust valve closes increases.

  When the engine temperature is lower than the specific temperature, the degree of contraction of the backflow gas described above is greater than when the engine temperature is the specific temperature. Further, the larger the intake pipe pressure when the exhaust valve is closed, the smaller the amount of the backflow gas described above tends to be, and therefore the influence of the difference in the engine temperature becomes smaller. For this reason, the estimation accuracy of the intake air amount can be improved by using the invention according to the ninth aspect.

  According to a tenth aspect of the present invention, a basic cylinder charge air amount, which is an in-cylinder charge air amount when the engine temperature is a specific temperature, is estimated, and the basic cylinder charge air amount is multiplied by a correction coefficient to generate a cylinder. An intake air amount estimation apparatus for an internal combustion engine for determining an internal charge air amount, wherein the correction coefficient includes a first correction coefficient determined based on an engine temperature and an engine speed, an engine temperature, and an intake valve opening / closing timing. The second correction coefficient determined based on the engine temperature, the third correction coefficient determined based on the engine temperature and the intake pipe pressure when the exhaust valve closes, and the engine temperature and the operating angle or lift amount of the intake valve An intake air amount estimation device for an internal combustion engine, which is a product of at least two correction coefficients of a fourth correction coefficient determined based on the first correction coefficient or one of the second to fourth correction coefficients. provide.

  According to the tenth aspect of the present invention, when the on-off valve characteristics of the intake valve can be changed, the basic cylinder is considered in consideration of the difference in the amount of the backflow gas and the difference in the intake flow velocity according to necessity or situation. The in-cylinder air amount can be obtained by correcting the in-cylinder air amount. Therefore, according to the invention as set forth in claim 10, in an internal combustion engine that can change the on-off valve characteristics of the intake valve, it is possible to accurately estimate the intake air amount regardless of the temperature state of the internal combustion engine (that is, the engine temperature). It becomes.

  In the invention described in claim 10, the first to fourth correction coefficients are individually determined. In this way, for example, when each correction coefficient is obtained from a map or function, the number of arguments in the map or the number of variables in the function can be reduced, so that the matching man-hour can be reduced. The control load during control execution can be reduced. Furthermore, since the influence of the parameters (that is, the intake valve opening / closing timing or the intake pipe pressure when the exhaust valve closes) corresponding to each correction coefficient can be selectively considered, Application to various situations is facilitated, and the cylinder interior charge air amount can be obtained by appropriately correcting the basic cylinder fill air amount in more various situations.

  According to an eleventh aspect of the present invention, a basic cylinder charge air amount, which is an in-cylinder charge air amount when the engine temperature is a specific temperature, is estimated, and the basic cylinder charge air amount is multiplied by a correction coefficient to generate a cylinder. An intake air amount estimation device for an internal combustion engine for obtaining an internal charge air amount, wherein the correction coefficient includes engine temperature, engine speed, intake valve opening / closing timing, and intake pipe internal pressure when the exhaust valve is closed Is a backflow gas correction coefficient that corrects for errors caused by differences in engine temperature and differences in the amount of gas that flows back from the cylinder into the intake port. The product of a backflow gas correction coefficient and an intake air correction coefficient that is determined based on the engine temperature and the engine speed and corrects errors caused by the difference in engine temperature and the difference in intake flow velocity. , Intake air volume estimation of internal combustion engine To provide a device.

  According to the eleventh aspect of the present invention, in the case where the opening / closing timing of the intake valve can be changed, the basic cylinder is considered in consideration of the difference in the amount of the backflow gas and the difference in the intake flow velocity in accordance with the actual phenomenon. The in-cylinder charged air amount is corrected to obtain the in-cylinder charged air amount. Therefore, according to the invention described in claim 11, in the internal combustion engine that can change the opening / closing timing of the intake valve, the intake air amount can be accurately estimated regardless of the temperature state of the internal combustion engine (that is, the engine temperature). It becomes possible.

  In the invention as set forth in claim 11, the backflow gas correction coefficient and the intake air correction coefficient are individually determined. In this way, the influence related to the amount of the backflow gas and the influence related to the intake air flow velocity can be selectively taken into consideration, so that it can be easily applied to a wider variety of situations. The in-cylinder charged air amount can be obtained by appropriately correcting the basic in-cylinder charged air amount.

  According to a twelfth aspect of the present invention, a basic in-cylinder charged air amount that is an in-cylinder charged air amount when the engine temperature is a specific temperature is estimated, and the basic in-cylinder charged air amount is multiplied by a correction coefficient to generate a cylinder. An intake air amount estimation device for an internal combustion engine for determining an internal charge air amount, wherein the correction coefficient includes the engine temperature, the engine speed, the intake pipe internal pressure when the exhaust valve is closed, and the intake valve working angle. Alternatively, a correction coefficient that is determined based on the lift amount and a reverse flow gas correction coefficient that corrects for an error caused by a difference in engine temperature and a difference in the amount of gas flowing back from the cylinder into the intake port, and an engine temperature And a correction coefficient determined based on the engine speed and the intake valve operating angle or lift amount, and an intake air correction coefficient that corrects for errors caused by differences in engine temperature and intake flow velocity. Or one of them Is the product of the correction coefficient, to provide an intake air quantity estimation apparatus for an internal combustion engine.

  According to the twelfth aspect of the present invention, when the operating angle or the lift amount of the intake valve can be changed, the above-described difference in the amount of backflow gas and the difference in the intake flow velocity are taken into account in accordance with the actual phenomenon. The basic in-cylinder charged air amount is corrected to obtain the in-cylinder charged air amount. Therefore, according to the twelfth aspect of the present invention, in the internal combustion engine that can change the operating angle or lift amount of the intake valve, the intake air amount is accurately estimated regardless of the temperature state of the internal combustion engine (that is, the engine temperature). It becomes possible to do.

  Further, in the invention described in claim 12, as in the invention described in claim 11, the backflow gas correction coefficient and the intake air correction coefficient are individually determined. In this case, as in the case of the invention described in claim 11, since the influence related to the amount of the backflow gas and the influence related to the intake flow velocity can be selectively taken into consideration, more various situations are possible. Therefore, it is possible to obtain the in-cylinder charged air amount by appropriately correcting the basic in-cylinder charged air amount in more various situations.

  According to a thirteenth aspect of the present invention, a basic cylinder charge air amount that is an in-cylinder charge air amount when the engine temperature is a specific temperature is estimated, and the basic cylinder charge air amount is multiplied by a correction coefficient to generate a cylinder. An intake air amount estimation device for an internal combustion engine for obtaining an internal charge air amount, wherein the correction coefficient includes engine temperature, engine speed, intake valve opening / closing timing, and intake pipe internal pressure when the exhaust valve is closed And a correction coefficient that is determined based on the working angle or lift amount of the intake valve and corrects for an error caused by a difference in engine temperature and a difference in the amount of gas flowing back from the cylinder into the intake port. A correction coefficient that is determined based on the gas correction coefficient, engine temperature, engine speed, intake valve operating angle or lift amount, and corrects errors caused by differences in engine temperature and intake flow velocity. The intake air correction coefficient While the either of the inner or the product of the correction coefficient, to provide an intake air quantity estimation apparatus for an internal combustion engine.

  According to the invention of claim 13, when the opening / closing timing of the intake valve can be changed and the operating angle or lift amount of the intake valve can be changed, the amount of the backflow gas described above in accordance with the actual phenomenon can be further increased. The basic in-cylinder charged air amount is corrected in consideration of the difference and the difference in the intake flow velocity, and the in-cylinder charged air amount is obtained. Therefore, according to the invention described in claim 13, in the internal combustion engine that can change the opening / closing timing of the intake valve and can change the operating angle or lift amount of the intake valve, the internal combustion engine is brought into a temperature state (that is, the engine temperature). Regardless, the intake air amount can be accurately estimated.

  In the invention as set forth in claim 13, as in the inventions according to claims 11 and 12, the backflow gas correction coefficient and the intake air correction coefficient are individually determined. In this way, as in the case of the inventions described in claims 11 and 12, the influence related to the amount of the backflow gas and the influence related to the intake flow velocity can be selectively taken into consideration, so that a wider variety can be obtained. Therefore, it is possible to easily correct the basic in-cylinder charged air amount and obtain the in-cylinder charged air amount in more various situations.

  The invention described in each claim has a common effect that, in an internal combustion engine that can change the on-off valve characteristics of the intake valve, the intake air amount can be accurately estimated regardless of the temperature state of the internal combustion engine (that is, the engine temperature). Play.

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 also 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.

  As shown in FIG. 1, the cylinder block 2 is provided with a cooling water temperature sensor 27 for detecting the engine cooling water temperature. 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 valve 6 is provided with a valve timing changing mechanism 23 for changing the opening / closing timing of the valve. The intake valve 6 is also provided with a working angle changing mechanism 25 that changes the working angle of the valve. In the present embodiment, when the operating angle of the intake valve 6 is changed, the lift amount of the intake valve 6 is also changed at the same time. More specifically, when the operating angle of the intake valve 6 is increased, the lift amount of the intake valve 6 is increased, and when the operating angle of the intake valve 6 is decreased, the lift amount of the intake valve 6 is decreased. In this sense, in this embodiment, it can be said that the operating angle changing mechanism 25 is a lift amount changing mechanism. However, in the following, in order to simplify the description, description will be made using the working angle.

  In the modification of the present embodiment, only the operating angle or only the lift amount may be changed. In the modification of the present embodiment, the intake valve 6 may be provided with only one of the valve timing changing mechanism 23 and the operating angle changing mechanism 25.

  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. Further, the output voltage of the cooling water temperature sensor 27 described above is also 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 valve timing changing mechanism 23 and the operating angle changing mechanism 25 are 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, 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, and a map is created in advance, and the map is searched for and obtained as necessary. When the valve timing changing mechanism 23 and the operating angle changing mechanism 25 are provided for the intake valve 6 as in the configuration shown in FIG. It is also determined based on the opening / closing timing (that is, the amount of advance or retard from the reference opening / closing timing) and the operating angle.

  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 the 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 the intake air at the time t + Δt. 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) at time t + Δt. 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. The in-cylinder charged air amount Mc at an arbitrary time t is calculated by multiplying mc by the time ΔT _{180 °} .

  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).

  When the intake air amount model M20 is used, the in-cylinder intake air flow rate mc is calculated by a linear function with the intake pipe pressure Pm as a variable as described above, and the in-cylinder intake air flow rate mc is calculated in the cylinder. It is converted into a filling air amount Mc. Here, the values of the adaptation parameters a and b used for this linear function are usually values adapted to the internal combustion engine when the engine temperature is a specific temperature after warm-up. In other words, when the maps of the adaptation parameters a and b are created, the adaptation is usually performed for the internal combustion engine in the case where the engine temperature is a specific temperature after warming up. For this reason, for example, when the engine is cold, such as immediately after the engine is started, the accurate in-cylinder intake air flow rate mc cannot be calculated even if the adaptation parameters a and b specified based on the engine speed at that time are used. As a result, the in-cylinder charged air amount Mc may not be accurately calculated.

  In order to correct such an error caused by the difference in engine temperature, for example, the cylinder charge air amount calculated based on a linear function using the adaptation parameters a and b is correlated with the engine temperature or the engine temperature. A method of multiplying a correction coefficient determined based on a certain engine coolant temperature is conceivable. However, in reality, if the valve timing, the intake pipe pressure, etc. are different, the amount of burnt gas flowing back into the intake port 7 is different, so the effect of the difference in engine temperature on the in-cylinder charged air amount is also different. In some cases, sufficient correction cannot be performed by multiplying the in-cylinder charged air amount calculated based on the linear function by a correction coefficient determined based only on the engine temperature or the engine coolant temperature.

  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.

  As described above, the burnt gas that has flowed back into the intake port 7 radiates heat and contracts there. The effect of this phenomenon on the in-cylinder charged air amount is that of the burned gas that flows back in addition to the engine temperature. It depends on the amount. For this reason, if the valve timing, the pressure in the intake pipe, etc. are different and the amount of burnt gas flowing back into the intake port 7 is different, the effect on the in-cylinder charged air amount is different even if the difference in engine temperature is the same. Become. Therefore, sufficient correction cannot be performed even if the in-cylinder charged air amount calculated based on the linear function is simply multiplied by a correction coefficient determined based only on the engine temperature or the engine coolant temperature. There is a case.

  Further, the difference in engine temperature also affects the temperature of the intake air, which is also a cause of errors caused by the difference in engine temperature as described above. Although the temperature change of the air suck | inhaled here arises by heat transfer with an intake port wall surface etc., it turns out that the heat transfer rate is proportional to an intake air flow velocity. In addition, the actual heat transfer amount is greatly affected by the intake air flow rate, and the heat transfer amount tends to decrease as the intake air flow rate increases (as a result, the higher the intake air flow rate, the smaller the temperature change of the intake air). Tend). For this reason, as a method of performing more appropriate correction, it is conceivable to change the correction coefficient for multiplying the cylinder air charge amount calculated based on the linear function in accordance with the engine speed.

  However, for example, in an internal combustion engine in which the operating angle (or lift amount) of the intake valve can be changed as in the present embodiment, the intake flow velocity differs even at the same engine speed and the same cylinder air charge amount. Therefore, the heat transfer rate and heat transfer amount may differ. For this reason, even when the correction coefficient for multiplying the in-cylinder charged air amount calculated based on the linear function is simply changed according to the engine speed, more appropriate correction cannot be performed. There is.

  In the present embodiment, in consideration of the above, calculation is performed using the intake air amount model M20 in consideration of the influence of the difference in the on-off valve characteristics of the intake valve on the error caused by the difference in engine temperature as described above. In the internal combustion engine capable of correcting the in-cylinder charged air amount and changing the on-off valve characteristics of the intake valve, the intake air amount can be accurately estimated regardless of the temperature state of the internal combustion engine (that is, the engine temperature). .

  Hereinafter, the correction performed in the present embodiment will be specifically described. In other words, in the present embodiment, the in-cylinder charged air amount calculated using the intake air amount model M20 is set as the basic in-cylinder charged air amount Mcb, and this value is used as the engine temperature, the engine speed Ne, and the opening / closing of the intake valve. Correction is made based on the timing Vt, the intake pipe pressure Pme when the exhaust valve closes, and the intake valve operating angle Sa, so as to obtain the in-cylinder charged air amount Mc. In this embodiment, the engine coolant temperature Tw is used as an index representing the engine temperature.

  FIG. 9 is a flowchart showing the control performed for the correction in the present embodiment. When this control starts, first, in step 101, the engine coolant temperature Tw, the engine speed Ne, the opening / closing timing Vt of the intake valve 6 and the operating angle Sa of the intake valve 6 are read. Here, the opening / closing timing Vt of the intake valve 6 is expressed by an advance angle or retardation amount from a predetermined reference opening / closing timing.

  In step 101, when the engine coolant temperature Tw, the engine speed Ne, the opening / closing timing Vt of the intake valve 6 and the operating angle Sa of the intake valve 6 are read, the process proceeds to step 103, where the exhaust valve is closed. The intake pipe pressure Pme at the time of valve operation (that is, when the exhaust valve 8 is closed) is estimated. This estimation is performed using the intake air amount model M20 described above.

  When the intake pipe pressure Pme when the exhaust valve is closed is estimated at step 103, the routine proceeds to step 105. In step 105, the engine coolant temperature Tw, the engine speed Ne read in step 101, the opening / closing timing Vt of the intake valve 6, and the operating angle Sa of the intake valve 6, and the exhaust valve closing estimated in step 103. The correction coefficient Cr is determined based on the intake pipe pressure Pme at the time.

  This correction coefficient Cr is obtained by multiplying the basic in-cylinder charged air amount Mcb calculated using the intake air amount model M20 in the subsequent step 107 and correcting the value to obtain the in-cylinder charged air amount Mc. is there. In the present embodiment, the engine coolant temperature Tw, the engine speed Ne, the opening / closing timing Vt of the intake valve 6 and the operating angle Sa of the intake valve 6 are obtained so that a correction coefficient Cr suitable for such a purpose can be obtained. A map of the correction coefficient Cr is created in advance using the intake pipe pressure Pme when the exhaust valve is closed as an argument. In step 105, the correction coefficient Cr is obtained using this map. In another embodiment, the engine coolant temperature Tw, the engine speed Ne, the opening / closing timing Vt of the intake valve 6, the operating angle Sa of the intake valve 6, and the intake pipe pressure Pme when the exhaust valve is closed A function for obtaining the correction coefficient Cr using as a variable may be set in advance, and in step 105, the correction coefficient Cr may be obtained using this function.

  10 to 15 show the correction coefficient Cr and the parameters representing the above-described operating state used as arguments (that is, the engine coolant temperature Tw, the engine speed Ne, the opening / closing timing Vt of the intake valve 6, and the action of the intake valve 6). It is an example of the figure which shows the relationship between angle Sa and the exhaust pipe internal pressure Pme at the time of exhaust valve closing.

  FIG. 10 shows the relationship between the correction coefficient Cr and the engine coolant temperature Tw. According to this figure, the higher the engine coolant temperature Tw, that is, the higher the engine temperature, the smaller the correction coefficient Cr. Here, the higher the engine temperature, the smaller the degree of contraction of the backflow gas described above, and the greater the degree of expansion of the sucked air. For this reason, the basic in-cylinder charged air amount Mcb can be corrected appropriately by having the relationship as shown in FIG. 10 between the correction coefficient Cr and the engine coolant temperature Tw, and the in-cylinder charged air amount. The estimation accuracy of Mc can be improved.

  FIG. 11 shows the correction coefficient Cr, the opening / closing timing Vt of the intake valve 6 and the exhaust valve closing time when the engine temperature is lower than the specific temperature after warm-up where the adaptation parameters a and b are adapted. The relationship with the intake pipe pressure Pme is shown. Curves Pme1, Pme2, and Pme3 in the figure show the relationship between the correction coefficient Cr and the opening / closing timing Vt of the intake valve 6 when the intake pipe pressure Pme when the exhaust valve is closed is Pme1, Pme2, and Pme3, respectively. Here, Pme1 <Pme2 <Pme3.

  According to this figure, the correction coefficient Cr tends to increase as the opening / closing timing Vt of the intake valve 6 is advanced. The correction coefficient Cr tends to decrease as the intake pipe pressure Pme when the exhaust valve is closed increases. When the engine temperature is lower than the specific temperature, the degree of contraction of the backflow gas described above is greater than when the engine temperature is the specific temperature. Further, as the opening / closing timing Vt of the intake valve 6 is advanced, the valve overlap period becomes longer and the amount of the backflow gas described above tends to increase, and therefore the influence of the difference in the engine temperature increases. On the other hand, the larger the intake pipe pressure Pme when the exhaust valve is closed, the smaller the amount of the backflow gas mentioned above, and therefore the influence of the difference in engine temperature becomes smaller. For this reason, the correction coefficient Cr, the opening / closing timing Vt of the intake valve 6 and the intake pipe pressure Pme when the exhaust valve is closed have a relationship as shown in FIG. It can correct | amend appropriately and can improve the estimation precision of the cylinder filling air amount Mc.

  FIG. 12 shows the relationship between the correction coefficient Cr, the intake pipe pressure Pme when the exhaust valve is closed, and the opening / closing timing Vt of the intake valve 6 when the engine temperature is lower than the specific temperature. Curves Vt1, Vt2, and Vt3 in the figure show the relationship between the correction coefficient Cr when the opening / closing timing Vt of the intake valve 6 is Vt1, Vt2, and Vt3, respectively, and the intake pipe pressure Pme when the exhaust valve is closed. Here, Vt1 is the most retarded timing, and gradually becomes the advanced timing in the order of Vt2 and Vt3. Note that FIG. 12 is substantially the same as FIG. 11, and the tendency shown therein is also the same as FIG. 11, so detailed description thereof is omitted here.

  FIG. 13 shows the relationship between the correction coefficient Cr, the operating angle Sa of the intake valve 6 and the engine speed Ne when the engine temperature is lower than the specific temperature. Curves Ne1, Ne2, and Ne3 in the figure show the relationship between the correction coefficient Cr and the working angle Sa of the intake valve 6 when the engine speed Ne is Ne1, Ne2, and Ne3, respectively, where Ne1 <Ne2. <Ne3.

  According to this figure, the correction coefficient Cr tends to decrease as the operating angle Sa of the intake valve 6 increases. Further, the correction coefficient Cr tends to decrease as the engine speed Ne increases. When the engine temperature is lower than the specific temperature, the degree of expansion of the sucked air is smaller than when the engine temperature is the specific temperature. Further, the larger the operating angle of the intake valve 6, the higher the intake flow velocity described above, and the higher the intake flow velocity, the smaller the amount of heat transfer to the intake air, resulting in a change in the temperature of the intake air. Tends to be small, so the influence of the difference in engine temperature is small. Similarly, the higher the engine speed, the faster the intake air flow rate described above, so the influence of the difference in engine temperature becomes smaller. For this reason, the basic cylinder charge air amount Mcb can be corrected appropriately by having the relationship shown in FIG. 13 between the correction coefficient Cr, the operating angle Sa of the intake valve 6 and the engine speed Ne. In addition, it is possible to improve the estimation accuracy of the in-cylinder charged air amount Mc.

  FIG. 14 shows the relationship between the correction coefficient Cr, the engine speed Ne, and the opening / closing timing Vt of the intake valve 6 when the engine temperature is lower than the specific temperature. Curves Vt4, Vt5, and Vt6 in the figure show the relationship between the correction coefficient Cr and the engine speed Ne when the opening / closing timing Vt of the intake valve 6 is Vt4, Vt5, and Vt6, respectively, where Vt4 is the largest. The timing is on the retard side, and gradually becomes the timing on the advance side in the order of Vt5 and Vt6.

  According to this figure, the correction coefficient Cr tends to decrease as the engine speed Ne increases. Further, the correction coefficient Cr tends to increase as the opening / closing timing of the intake valve 6 is advanced. As described above, when the engine temperature is lower than the specific temperature, the degree of expansion of the sucked air is smaller than that when the engine temperature is the specific temperature, and the backflow gas described above is reduced. The degree of contraction increases. In addition, the higher the engine speed Ne, the higher the intake flow velocity described above, and the higher the intake flow velocity, the smaller the amount of heat transferred to the intake air and the smaller the temperature change of the intake air. Since there is a tendency, the influence of the difference in the engine temperature is small. On the other hand, as the opening / closing timing Vt of the intake valve 6 is advanced, the valve overlap period becomes longer and the amount of the backflow gas described above tends to increase. Therefore, the influence of the difference in the engine temperature increases. Therefore, the basic cylinder charge air amount Mcb can be corrected appropriately by having the relationship as shown in FIG. 14 between the correction coefficient Cr, the engine speed Ne, and the opening / closing timing Vt of the intake valve 6. In addition, it is possible to improve the estimation accuracy of the in-cylinder charged air amount Mc.

  FIG. 15 shows the relationship between the correction coefficient Cr when the engine temperature is lower than the specific temperature, the intake pipe pressure Pme when the exhaust valve is closed, and the engine speed Ne. Curves Ne4, Ne5, and Ne6 in the figure show the relationship between the correction coefficient Cr when the engine speed Ne is Ne4, Ne5, and Ne6 and the intake pipe pressure Pme when the exhaust valve is closed. Ne4 <Ne5 <Ne6.

  According to this figure, the correction coefficient Cr tends to decrease as the intake pipe pressure Pme when the exhaust valve is closed increases. Further, the correction coefficient Cr tends to decrease as the engine speed Ne increases. As described above, when the engine temperature is lower than the specific temperature, the degree of contraction of the backflow gas described above is greater than when the engine temperature is the specific temperature, and the intake air The degree of expansion is small. Further, the larger the intake pipe pressure Pme when the exhaust valve is closed, the smaller the amount of the backflow gas described above tends to be, and therefore the influence of the difference in the engine temperature becomes smaller. Furthermore, the higher the engine speed Ne, the higher the intake air flow rate described above, and the higher the intake air flow rate, the smaller the amount of heat transferred to the intake air and the smaller the temperature change of the intake air. Therefore, the influence of the difference in engine temperature is small. For this reason, the basic cylinder charge air amount Mcb is appropriately corrected by the relationship between the correction coefficient Cr, the intake pipe pressure Pme when the exhaust valve is closed, and the engine speed Ne as shown in FIG. It is possible to improve the estimation accuracy of the in-cylinder charged air amount Mc.

  When the correction coefficient Cr is determined in step 105, the process proceeds to step 107. In step 107, as described above, the correction coefficient Cr determined in step 105 is multiplied by the basic cylinder charge air amount Mcb calculated using the intake air amount model M20 (Mc = Cr · Mcb). As a result, the basic in-cylinder charged air amount Mcb is corrected, the in-cylinder charged air amount Mc is obtained, and the present control ends.

  As is apparent from the above description, in the present embodiment, the basic in-cylinder charged air amount Mcb, which is the in-cylinder charged air amount when the engine temperature is a specific temperature, is determined from the engine temperature, the engine speed Ne, the intake valve. 6 is corrected based on the opening / closing timing Vt of 6, the intake pipe pressure Pme when the exhaust valve 8 is closed, and the operating angle Sa of the intake valve 6 to obtain the in-cylinder charged air amount Mc. In this way, in the case where the opening / closing timing Vt of the intake valve 6 can be changed and the operating angle Sa of the intake valve 6 can be changed, the basic cylinder is considered in consideration of the difference in the amount of backflow gas and the difference in intake flow velocity. The in-cylinder charged air amount Mcb is obtained by correcting the inner charged air amount Mcb. As a result, when the opening / closing timing Vt of the intake valve 6 can be changed and the operating angle Sa of the intake valve 6 can be changed, the intake air amount can be accurately adjusted regardless of the temperature state of the internal combustion engine (that is, the engine temperature). It is possible to estimate.

  As described above, in the modification of the present embodiment, the intake valve 6 may be provided with only one of the valve timing changing mechanism 23 and the operating angle changing mechanism 25. Although detailed explanation will be omitted because it seems to be easily understood from the explanation so far, when only the valve timing changing mechanism 23 is provided in the intake valve 6, the engine temperature is the above specific temperature. The in-cylinder charged air amount Mcb, which is the in-cylinder charged air amount, is the engine temperature, the engine speed Ne, the intake valve opening / closing timing Vt, and the intake pipe pressure Pme when the exhaust valve 8 is closed. When the intake air valve 6 is provided with only the operating angle changing mechanism 25, the basic in-cylinder charged air amount Mcb is determined based on the engine temperature and the engine. The in-cylinder charged air amount Mc is obtained by correction based on the rotational speed Ne, the intake pipe pressure Pme when the exhaust valve 8 is closed, and the operating angle Sa of the intake valve 6.

  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 calculated using the intake air amount model M20 is set as the basic in-cylinder charged air amount Mcb, and the values are the engine temperature, the engine speed Ne, and the intake air. The in-cylinder charged air amount Mc is determined by correction based on the valve opening / closing timing Vt, the intake pipe pressure Pme when the exhaust valve closes, and the intake valve operating angle Sa. In this embodiment as well, the engine coolant temperature Tw is used as an index representing the engine temperature. Further, in the following description of the present embodiment, the description of the parts common to the above-described embodiment is omitted in principle.

  FIG. 16 is a flowchart showing the control performed for the correction in the present embodiment. When this control starts, first, at step 201, the engine coolant temperature Tw, the engine speed Ne, the opening / closing timing Vt of the intake valve 6, and the operating angle Sa of the intake valve 6 are read. In the subsequent step 203, the intake pipe pressure Pme when the exhaust valve is closed (that is, when the exhaust valve 8 is closed) is 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 pressure Pme when the exhaust valve is closed is estimated at step 203, the routine proceeds to step 205. In step 205, the first correction coefficient Cr1 is determined based on the engine coolant temperature Tw and the engine speed Ne read in step 201. The first correction coefficient Cr1 is for considering the influence of the engine speed Ne, and multiplies the basic in-cylinder charged air amount Mcb calculated by using the intake air amount model M20 in step 213 described later. Then, the value is corrected to obtain the in-cylinder charged air amount Mc.

  In the present embodiment, a map of the first correction coefficient Cr1 is created in advance using the engine coolant temperature Tw and the engine speed Ne as arguments so that the first correction coefficient Cr1 suitable for such a purpose can be obtained. In step 205, the first correction coefficient Cr1 is obtained using this map. In another embodiment, a function for obtaining the first correction coefficient Cr1 using the engine coolant temperature Tw and the engine speed Ne as variables is set in advance, and this function is used in step 205. Thus, the first correction coefficient Cr1 may be obtained.

  When the first correction coefficient Cr1 is determined in step 205, the process proceeds to step 207. In step 207, the second correction coefficient Cr2 is determined based on the engine coolant temperature Tw read in step 201 and the opening / closing timing Vt of the intake valve 6. The second correction coefficient Cr2 is for considering the influence of the opening / closing timing Vt of the intake valve 6. Like the first correction coefficient Cr1, in step 213 described later, the intake air amount model M20 is calculated. The basic in-cylinder charged air amount Mcb calculated by use is multiplied and corrected to obtain the in-cylinder charged air amount Mc.

  In the present embodiment, in order to obtain the second correction coefficient Cr2 suitable for such a purpose, the second correction coefficient Cr2 is set in advance using the engine coolant temperature Tw and the opening / closing timing Vt of the intake valve 6 as arguments. A map has been created, and in step 207, the second correction coefficient Cr2 is obtained using this map. In another embodiment, a function for obtaining the second correction coefficient Cr2 using the engine coolant temperature Tw and the opening / closing timing Vt of the intake valve 6 as variables is set in advance. The second correction coefficient Cr2 may be obtained using a function.

  When the second correction coefficient Cr2 is determined in step 207, the process proceeds to step 209. In step 209, the third correction coefficient Cr3 is determined based on the engine coolant temperature Tw read in step 201 and the intake pipe pressure Pme when the exhaust valve is closed estimated in step 203. The third correction coefficient Cr3 is for considering the influence of the intake pipe pressure Pme when the exhaust valve is closed. Similar to the first and second correction coefficients Cr1 and Cr2, step 213 described later is performed. In FIG. 5, the basic in-cylinder charged air amount Mcb calculated using the intake air amount model M20 is multiplied and corrected to obtain the in-cylinder charged air amount Mc.

  In the present embodiment, in order to obtain the third correction coefficient Cr3 suitable for such a purpose, the third correction is performed in advance with the engine coolant temperature Tw and the intake pipe pressure Pme when the exhaust valve is closed as arguments. A map of the coefficient Cr3 is created, and in step 209, the third correction coefficient Cr3 is obtained using this map. In another embodiment, a function for obtaining the third correction coefficient Cr3 using the engine coolant temperature Tw and the intake pipe pressure Pme when the exhaust valve is closed as variables is set in advance. In this case, the third correction coefficient Cr3 may be obtained using this function.

  When the third correction coefficient Cr3 is determined in step 209, the process proceeds to step 211. In step 211, the fourth correction coefficient Cr4 is determined based on the engine coolant temperature Tw read in step 201 and the operating angle Sa of the intake valve 6. The fourth correction coefficient Cr4 is for considering the influence of the operating angle Sa of the intake valve 6. Like the first, second, and third correction coefficients Cr1, Cr2, and Cr3, steps that will be described later. In step 213, the in-cylinder charged air amount Mc is calculated by multiplying the basic in-cylinder charged air amount Mcb calculated by using the intake air amount model M20 to obtain the in-cylinder charged air amount Mc.

  In the present embodiment, in order to obtain the fourth correction coefficient Cr4 suitable for such purpose, the fourth correction coefficient Cr4 is preliminarily set with the engine coolant temperature Tw and the operating angle Sa of the intake valve 6 as arguments. A map has been created, and in step 211, the fourth correction coefficient Cr4 is obtained using this map. In another embodiment, a function for obtaining the fourth correction coefficient Cr4 using the engine coolant temperature Tw and the operating angle Sa of the intake valve 6 as variables is set in advance. The fourth correction coefficient Cr4 may be obtained using a function.

  When the fourth correction coefficient Cr4 is determined in step 211, the process proceeds to step 213. In step 213, as described above, the correction coefficients Cr1, Cr2, Cr3, Cr4 determined in step 205 to step 211 are multiplied by the basic in-cylinder charged air amount Mcb calculated using the intake air amount model M20. (Mc = Cr1, Cr2, Cr3, Cr4, Mcb). As a result, the basic in-cylinder charged air amount Mcb is corrected, the in-cylinder charged air amount Mc is obtained, and the present control ends.

  As described above, in the present embodiment, the basic in-cylinder charged air amount Mcb, which is the in-cylinder charged air amount when the engine temperature is the specific temperature, is based on the engine temperature and the engine speed Ne. The first correction coefficient Cr1 that is determined, the second correction coefficient Cr2 that is determined based on the engine temperature and the opening / closing timing Vt of the intake valve 6, and the engine temperature and the intake pipe pressure Pme when the exhaust valve 8 is closed. The in-cylinder charged air amount Mc is obtained by multiplying the third correction coefficient Cr3 determined on the basis of the third correction coefficient Cr4 determined on the basis of the engine temperature and the operating angle Sa of the intake valve 6. .

  In this way, in the case where the opening / closing timing Vt of the intake valve 6 can be changed and the operating angle Sa of the intake valve 6 can be changed, the basic cylinder is considered in consideration of the difference in the amount of backflow gas and the difference in intake flow velocity. The in-cylinder charged air amount Mcb is obtained by correcting the inner charged air amount Mcb. As a result, when the opening / closing timing Vt of the intake valve 6 can be changed and the operating angle Sa of the intake valve 6 can be changed, the intake air amount can be accurately adjusted regardless of the temperature state of the internal combustion engine (that is, the engine temperature). It is possible to estimate.

  In the present embodiment, the first to fourth correction coefficients Cr1, Cr2, Cr3, and Cr4 are individually determined. In this way, when each correction coefficient Cr1, Cr2, Cr3, Cr4 is obtained from a map or a function, the number of arguments in the map or the number of variables in the function can be reduced, thereby reducing the number of man-hours for adaptation. In addition, it is possible to reduce the control load during control execution.

  Furthermore, by using the fact that the first to fourth correction coefficients Cr1, Cr2, Cr3, Cr4 are individually determined, in other embodiments, the first to fourth correction coefficients Cr1, Cr2, Cr3 are used. , Cr4, or the product of two or three correction coefficients of the first to fourth correction coefficients Cr1, Cr2, Cr3, Cr4 to the basic cylinder charge air amount Mcb. Alternatively, the in-cylinder charged air amount Mc may be obtained by multiplication.

  That is, in this case, the influence of parameters (that is, the intake valve open / close timing, the intake pipe internal pressure when the exhaust valve closes, etc.) corresponding to the respective correction factors Cr1, Cr2, Cr3, Cr4 is necessary. Alternatively, it can be selectively considered according to the situation, so that it can be easily applied to more various situations, and the basic in-cylinder charged air amount Mcb can be appropriately corrected in more various situations to obtain the in-cylinder charged air amount. Mc can be determined.

  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 calculated using the intake air amount model M20 is set as the basic in-cylinder charged air amount Mcb, and the values are the engine temperature, the engine speed Ne, and the intake air. The in-cylinder charged air amount Mc is determined by correction based on the valve opening / closing timing Vt, the intake pipe pressure Pme when the exhaust valve closes, and the intake valve operating angle Sa.

  In particular, in this embodiment, correction according to the actual phenomenon is performed. That is, there are two factors that cause an error in the in-cylinder charged air amount due to the difference in engine temperature: one related to the intake air and the other related to the gas flowing back into the intake port. In other words, regarding the intake air, the amount of heat transfer to the intake air due to the difference in heat transfer to the intake air due to the difference in engine temperature and the difference in intake flow velocity and the difference in heat transfer coefficient due to the difference in intake flow velocity. It is conceivable that the degree of expansion of the sucked air varies due to the difference in temperature of the sucked air resulting from the difference, and the amount of air filled in the cylinder varies accordingly. In addition, for the gas that flows back into the intake port, the intake timing of fresh air differs depending on the amount of gas flowing back and the degree of contraction of the backflow gas due to the difference in engine temperature. It is conceivable that the amount of air produced is different.

  In the present embodiment, based on the above, the correction coefficient related to the intake air and the correction coefficient related to the backflow gas are separately determined, and more accurate correction is performed in accordance with the actual phenomenon. In this embodiment as well, the engine coolant temperature Tw is used as an index representing the engine temperature. Also, in the following description of the present embodiment, the description of the parts common to the other embodiments described above is omitted in principle.

  FIG. 17 is a flowchart showing the control performed for the correction in the present embodiment. When this control starts, first, at step 301, the engine coolant temperature Tw, the engine speed Ne, the opening / closing timing Vt of the intake valve 6 and the operating angle Sa of the intake valve 6 are read. In the subsequent step 303, the intake pipe pressure Pme when the exhaust valve is closed (that is, when the exhaust valve 8 is closed) is 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 pressure Pme when the exhaust valve is closed is estimated in step 303, the process proceeds to step 305. In step 305, the intake flow velocity Qa is estimated based on the engine speed Ne read in step 301 and the operating angle Sa of the intake valve 6. In this embodiment, a map of the intake flow velocity Qa is created in advance with the engine speed Ne and the operating angle Sa of the intake valve 6 as arguments, and in step 305, the intake flow velocity Qa is obtained using this map. . In another embodiment, a function for obtaining the intake air flow rate Qa using the engine speed Ne and the operating angle Sa of the intake valve 6 as variables is set in advance, and this function is used in step 305. The intake flow velocity Qa may be obtained.

  When the intake flow velocity Qa is estimated in step 305, the process proceeds to step 307. In step 307, the engine speed Ne read in step 301, the opening / closing timing Vt of the intake valve 6, the operating angle Sa of the intake valve 6, and the intake pipe pressure Pme at the time of closing the exhaust valve estimated in step 303 are determined. Based on the above, the amount Vg of gas flowing backward from the cylinder into the intake port is estimated. In the present embodiment, the reverse flow gas amount Vg is preliminarily set using the engine speed Ne, the opening / closing timing Vt of the intake valve 6, the operating angle Sa of the intake valve 6, and the intake pipe pressure Pme when the exhaust valve is closed as arguments. A map is created, and in step 307, the backflow gas amount Vg is obtained using this map. In another embodiment, the backflow gas amount using the engine speed Ne, the opening / closing timing Vt of the intake valve 6, the operating angle Sa of the intake valve 6, and the intake pipe pressure Pme when the exhaust valve is closed as variables. A function for obtaining Vg may be set in advance, and in step 307, the backflow gas amount Vg may be obtained using this function.

  When the backflow gas amount Vg is estimated in step 307, the process proceeds to step 309. In step 309, the intake air correction coefficient Cra is determined based on the engine coolant temperature Tw read in step 301 and the intake flow velocity Qa estimated in step 305. The intake air correction coefficient Cra corrects an error caused by a difference in engine temperature and a difference in intake flow velocity. The basic cylinder calculated by using the intake air amount model M20 in step 313 described later is used. This is for multiplying the inner charge air amount Mcb and correcting the value to obtain the in-cylinder charge air amount Mc.

  In the present embodiment, a map of the intake air correction coefficient Cra is created in advance using the engine coolant temperature Tw and the intake air flow rate Qa as arguments so that the intake air correction coefficient Cra suitable for such purposes can be obtained. In step 309, the intake air correction coefficient Cra is obtained using this map. In another embodiment, a function for obtaining the intake air correction coefficient Cra using the engine coolant temperature Tw and the intake flow velocity Qa as variables is set in advance, and in step 309, this function is used for intake. The air correction coefficient Cra may be obtained.

  When the intake air correction coefficient Cra is determined in step 309, the process proceeds to step 311. In step 311, the engine coolant temperature Tw and the engine speed Ne read in step 301, the intake pipe pressure Pme when the exhaust valve is closed estimated in step 303, and the backflow gas amount estimated in step 307. Based on Vg, the backflow gas correction coefficient Crg is determined. The backflow gas correction coefficient Crg is used to correct an error caused by a difference in engine temperature and a backflow gas amount. Like the intake air correction coefficient Cra, in step 313 described later, the intake air is corrected. This is for multiplying the basic in-cylinder charged air amount Mcb calculated using the quantity model M20 and correcting the value to obtain the in-cylinder charged air amount Mc.

  In the present embodiment, the engine coolant temperature Tw, the engine speed Ne, the intake pipe pressure Pme when the exhaust valve is closed, and the backflow gas so as to obtain the backflow gas correction coefficient Crg suitable for such purposes. A map of the backflow gas correction coefficient Crg is created in advance using the amount Vg as an argument, and in step 311, the backflow gas correction coefficient Crg is obtained using this map. In another embodiment, in order to obtain the backflow gas correction coefficient Crg using the engine coolant temperature Tw, the engine speed Ne, the intake pipe pressure Pme when the exhaust valve is closed, and the backflow gas amount Vg as variables. This function may be set in advance, and in step 311, the backflow gas correction coefficient Crg may be obtained using this function.

  When the backflow gas correction coefficient Crg is determined in step 311, the process proceeds to step 313. In step 313, as described above, the basic in-cylinder calculated by using the intake air amount model M20, the intake air amount correction coefficient Cra determined in step 309 and the backflow gas correction coefficient Crg determined in step 311. The charged air amount Mcb is multiplied (Mc = Cra · Crg · Mcb). As a result, the basic in-cylinder charged air amount Mcb is corrected, the in-cylinder charged air amount Mc is obtained, and the present control ends.

  As described above, in the present embodiment, the engine temperature, the engine speed Ne, and the intake air with respect to the basic in-cylinder charged air amount Mcb that is the in-cylinder charged air amount when the engine temperature is the specific temperature. This is a correction coefficient determined based on the opening / closing timing Vt of the valve 6, the intake pipe pressure Pme when the exhaust valve 8 is closed, and the operating angle Sa of the intake valve 6. Is determined based on the backflow gas correction coefficient Crg for correcting an error caused by the difference in the amount of gas Vg flowing back in, the engine temperature, the engine speed Ne, and the operating angle Sa of the intake valve 6. An in-cylinder charged air amount Mc is obtained by multiplying an intake air correction coefficient Cra that corrects an error caused by a difference in engine temperature and an intake flow velocity Qa.

  In this way, in the case where the opening / closing timing Vt of the intake valve 6 can be changed and the operating angle Sa of the intake valve 6 can be changed, the difference in the amount of the backflow gas and the intake flow velocity described above more in line with the actual phenomenon. The basic in-cylinder charged air amount Mcb is corrected in consideration of the difference, and the in-cylinder charged air amount Mc is obtained. As a result, when the opening / closing timing Vt of the intake valve 6 can be changed and the operating angle Sa of the intake valve 6 can be changed, the intake air amount can be accurately adjusted regardless of the temperature state of the internal combustion engine (that is, the engine temperature). It is possible to estimate.

  In the present embodiment, the backflow gas correction coefficient Crg and the intake air correction coefficient Cra are individually determined. In other embodiments using this fact, the in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount Mcb by only one of the backflow gas correction coefficient Crg and the intake air correction coefficient Cra. Mc may be obtained. In this case, among the effects of the difference in engine temperature on the amount of charged air in the cylinder, those related to the backflow gas (more specifically, the effects related to the amount of the backflow gas) and those related to the sucked air (more specifically) Can be selectively taken into account, which makes it easier to apply to a variety of situations, and appropriately corrects the basic cylinder charge air amount in a variety of situations. The in-cylinder charged air amount can be obtained.

  In the modification of the present embodiment, only one of the valve timing changing mechanism 23 and the operating angle changing mechanism 25 may be provided in the intake valve 6. Although it will be easily understood from the above description, a detailed description is omitted. However, when only the valve timing changing mechanism 23 is provided in the intake valve 6, the backflow gas correction coefficient Crg is set to The intake air correction coefficient Cra is determined based on the temperature, the engine speed Ne, the opening / closing timing Vt of the intake valve 6, and the intake pipe pressure Pme when the exhaust valve 8 is closed. It is determined based on the engine speed Ne. On the other hand, when the intake valve 6 is provided with only the operating angle changing mechanism 25, the backflow gas correction coefficient Crg is calculated based on the engine temperature, the engine speed Ne, and the intake pipe when the exhaust valve 8 is closed. The intake air correction coefficient Cra is determined based on the pressure Pme and the operating angle Sa amount of the intake valve 6, and the intake air correction coefficient Cra is determined based on the engine temperature, the engine speed Ne, and the operating angle Sa of the intake valve 6. .

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 flowchart showing the control performed in one embodiment of the present invention. FIG. 10 is a diagram showing the relationship between the correction coefficient Cr and the engine coolant temperature Tw. FIG. 11 shows the relationship between the correction coefficient Cr, the intake valve opening / closing timing Vt, and the intake pipe pressure Pme when the exhaust valve is closed when the engine temperature is lower than the specific temperature at which the adaptation parameters a and b are adapted. FIG. FIG. 12 is a diagram showing the relationship between the correction coefficient Cr, the intake pipe pressure Pme when the exhaust valve is closed, and the intake valve opening / closing timing Vt when the engine temperature is lower than the specific temperature. FIG. 13 is a diagram showing the relationship between the correction coefficient Cr, the intake valve operating angle Sa, and the engine speed Ne when the engine temperature is lower than the specific temperature. FIG. 14 is a diagram showing the relationship between the correction coefficient Cr, the engine speed Ne, and the intake valve opening / closing timing Vt when the engine temperature is lower than the specific temperature. FIG. 15 shows the relationship between the correction coefficient Cr, the intake pipe pressure Pme when the exhaust valve is closed, and the engine speed Ne when the engine temperature is lower than the specific temperature. FIG. 16 is a flowchart showing the control executed in another embodiment of the present invention. FIG. 17 is a flowchart showing the control performed 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 23 Valve timing change mechanism 25 Operating angle (lift amount) change mechanism 27 Cooling water temperature sensor

Claims (13)

  A basic cylinder charge air amount, which is the cylinder charge air amount when the engine temperature is a specific temperature, is estimated, and the basic cylinder charge air amount is calculated from the engine temperature, the engine speed, the intake valve opening / closing timing, An intake air amount estimation device for an internal combustion engine that obtains an in-cylinder charged air amount by correcting based on an intake pipe pressure when the exhaust valve is closed.   Estimate the basic cylinder charge air amount, which is the cylinder charge air amount when the engine temperature is a specific temperature, and close the basic cylinder charge air amount based on the engine temperature, the engine speed, and the exhaust valve. An intake air amount estimation device for an internal combustion engine that obtains an in-cylinder charged air amount by performing correction based on the intake pipe pressure at the time and the operating angle or lift amount of the intake valve.   A basic cylinder charge air amount, which is the cylinder charge air amount when the engine temperature is a specific temperature, is estimated, and the basic cylinder charge air amount is calculated from the engine temperature, the engine speed, the intake valve opening / closing timing, An intake air amount estimation device for an internal combustion engine that obtains an in-cylinder charged air amount by correcting based on an intake pipe pressure when the exhaust valve is closed and an operating angle or lift amount of the intake valve.   The in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient. When the engine temperature is lower than the specific temperature, the opening / closing timing of the intake valve is advanced. 2. The intake air amount estimation device for an internal combustion engine according to claim 1, wherein the correction coefficient increases as the value increases.   The in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient. When the engine temperature is lower than the specific temperature, the opening / closing timing of the intake valve is advanced. 4. The intake air amount estimation device for an internal combustion engine according to claim 3, wherein the correction coefficient increases as the value increases.   The in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient. When the engine temperature is lower than the specific temperature, the larger the operating angle or lift amount of the intake valve, The intake air amount estimation device for an internal combustion engine according to any one of claims 2, 3, and 5, wherein the correction coefficient is reduced.   The in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient, and the correction coefficient decreases as the engine temperature increases. The intake air amount estimation device for an internal combustion engine according to one item.   The in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient. When the engine temperature is lower than the specific temperature, the correction coefficient decreases as the engine speed increases. The intake air amount estimation device for an internal combustion engine according to any one of claims 1 to 7, wherein the intake air amount estimation device is configured as follows.   The in-cylinder charged air amount is obtained by multiplying the basic in-cylinder charged air amount by a correction coefficient, and when the engine temperature is lower than the specific temperature, the intake pipe internal pressure when the exhaust valve is closed The intake air amount estimation device for an internal combustion engine according to any one of claims 1 to 8, wherein the correction coefficient decreases as the value increases.   An internal combustion engine for estimating an in-cylinder charged air amount, which is an in-cylinder charged air amount when the engine temperature is a specific temperature, and determining the in-cylinder charged air amount by multiplying the basic in-cylinder charged air amount by a correction coefficient. In the intake air amount estimation device, the correction coefficient is determined based on the engine temperature and the engine speed, and the second correction coefficient determined based on the engine temperature and the opening / closing timing of the intake valve. A third correction coefficient determined based on the engine temperature and the pressure in the intake pipe when the exhaust valve closes, and a fourth correction coefficient determined based on the engine temperature and the operating angle or lift amount of the intake valve An intake air amount estimation device for an internal combustion engine, which is a product of at least two correction coefficients of the above or any one of the second to fourth correction coefficients. An internal combustion engine for estimating an in-cylinder charged air amount, which is an in-cylinder charged air amount when the engine temperature is a specific temperature, and multiplying the basic in-cylinder charged air amount by a correction coefficient to obtain an in-cylinder charged air amount. An intake air amount estimation device,
The correction coefficient is a correction coefficient determined based on the engine temperature, engine speed, intake valve opening / closing timing, and intake pipe pressure when the exhaust valve is closed. A backflow gas correction coefficient for correcting an error caused by a difference in the amount of gas flowing back into the intake port, or a correction determined based on the backflow gas correction coefficient, the engine temperature, and the engine speed An intake air amount estimation device for an internal combustion engine, which is a product of an intake air correction coefficient that corrects an error caused by a difference in engine temperature and an intake air flow rate. An internal combustion engine for estimating an in-cylinder charged air amount, which is an in-cylinder charged air amount when the engine temperature is a specific temperature, and multiplying the basic in-cylinder charged air amount by a correction coefficient to obtain an in-cylinder charged air amount. An intake air amount estimation device,
The correction coefficient is a correction coefficient that is determined based on the engine temperature, the engine speed, the pressure in the intake pipe when the exhaust valve closes, and the operating angle or lift amount of the intake valve. Based on the backflow gas correction coefficient that corrects for errors caused by the difference in the amount of gas flowing back from the cylinder into the intake port, the engine temperature, the engine speed, and the intake valve operating angle or lift amount Or an intake air correction coefficient that corrects an error caused by a difference in engine temperature and a difference in intake flow velocity, or a product of these correction coefficients. An intake air amount estimation device for an internal combustion engine. An internal combustion engine for estimating an in-cylinder charged air amount, which is an in-cylinder charged air amount when the engine temperature is a specific temperature, and multiplying the basic in-cylinder charged air amount by a correction coefficient to obtain an in-cylinder charged air amount. An intake air amount estimation device,
The correction coefficient is a correction coefficient determined based on the engine temperature, the engine speed, the intake valve opening / closing timing, the intake pipe pressure when the exhaust valve closes, and the intake valve operating angle or lift amount. Backflow gas correction coefficient that corrects for errors caused by the difference in engine temperature and the amount of gas that flows back from the cylinder into the intake port, engine temperature, engine speed, and intake valve action A correction coefficient that is determined based on the angle or the lift amount, and is one of the intake air correction coefficients that correct errors caused by a difference in engine temperature and a difference in intake flow velocity, or these An intake air amount estimation device for an internal combustion engine, which is a product of correction coefficients.

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