JP2008075563A - Method and device for calculating intake air quantity for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for calculating intake air quantity capable of accurately calculating intake air quantity introduced into the combustion chamber during engine suction stroke by using a fluid model. <P>SOLUTION: The fluid model relating to intake air is constructed. Intake air calculation value calculated by introducing predetermined operation parameter into the fluid model is corrected by being approximated to actual intake air quantity when the internal combustion engine is operated under a condition corresponding to the predetermined operation parameter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an intake air amount calculation device for an internal combustion engine that calculates the amount of intake air introduced into a combustion chamber of the internal combustion engine, and a calculation method thereof.

  A map showing the relationship between the amount of intake air introduced into the combustion chamber of the internal combustion engine and the valve timing VT of the internal combustion engine, the engine speed Ne, and the throttle opening is obtained in advance by experiments and the like. A technique of storing in a memory is known (for example, see Patent Document 1).

  By incorporating a map obtained by experiments in advance into the intake air amount calculation device, the current intake air amount of the internal combustion engine can be easily determined from the valve timing VT, the engine speed Ne, and the throttle opening of the internal combustion engine. It was possible to ask.

JP 2001-41095 A

  By the way, in order to obtain in advance an experiment or the like a map showing the relationship between the intake air amount, the valve timing VT of the internal combustion engine, the engine speed Ne, and the throttle opening, it is necessary to acquire all data on the map points. Therefore, the amount of work required for data acquisition is enormous.

  In an internal combustion engine having a variable valve lift amount, a map showing the relationship between the intake air amount and the valve timing VT, the engine speed Ne, the throttle opening, and the valve lift amount is obtained in advance by experiments or the like. With the increase in the number of map dimensions, it has been necessary to acquire an enormous number of map data.

  Therefore, in order to reduce the amount of work required to create the map, a fluid model that represents the relationship between the operating parameters of the internal combustion engine and the amount of intake air in the combustion chamber is used, and predetermined operating parameters are introduced into the fluid model to A method of obtaining the air amount by calculation is conceivable. However, there is a problem that sufficient accuracy cannot be obtained for the calculated amount of intake air, and the calculated amount of air cannot be used as it is for fuel control.

  The present invention is an intake air amount calculation device for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine, and is calculated by constructing a fluid model relating to intake air and introducing predetermined operating parameters into the fluid model. The correction means corrects the intake air amount calculation value so as to approximate the actual intake air amount when the internal combustion engine is operated in a state corresponding to the predetermined operating parameter, and the correction means includes the internal combustion engine Calculate the intake air amount calculated based on the fluid model under the valve timing conditions where the intake valve is open and the exhaust valve is not open. The reference correction factor used to correct the air volume is calculated based on the fluid model under other valve timing conditions. It is characterized by using the correction of the intake air amount calculated values.

  According to this feature, the amount of work required to calculate the correction coefficient used when correcting the calculated intake air amount to the actual intake air amount can be greatly reduced, and the calculated intake air amount can be sufficiently reduced. Accuracy can be obtained.

  In the intake air amount calculation device according to the present invention, it is preferable that the reference correction coefficient is a value that differs for each engine speed of the internal combustion engine.

  The present invention is an intake air amount calculation device for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine, and is calculated by constructing a fluid model relating to intake air and introducing predetermined operating parameters into the fluid model. Compensating means for correcting the calculated intake air amount so as to approximate the actual intake air amount when the internal combustion engine is operated in a state according to the predetermined operating parameter, and the correcting means includes the intake air amount By substituting the valve timing of the internal combustion engine at the current time into a function indicating the relationship between the correction coefficient used to correct the calculated value and the valve timing of the internal combustion engine, the current correction coefficient is obtained, and the current correction coefficient is used. And correcting the calculated intake air amount at the present time.

  According to this feature, it is possible to accurately obtain the correction coefficient corresponding to the valve timing during operation of the internal combustion engine, and it is possible to obtain sufficient accuracy for the calculated intake air amount.

In the intake air amount calculation device of the present invention, it is preferable that the function indicating the relationship between the correction coefficient and the valve timing of the internal combustion engine is a quadratic function expressed in the form of (Equation 1).
α = a · VT ² + b · VT + c (Formula 1)
α indicates a correction coefficient, VT indicates a valve timing, and a, b, and c indicate constants.

  In the intake air amount calculation device of the present invention, it is preferable that the constants a, b, and c in (Equation 1) are different values for each engine speed of the internal combustion engine.

  The present invention is an intake air amount calculation method for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine, which is calculated by constructing a fluid model related to intake air and introducing predetermined operating parameters into the fluid model. The calculated intake air amount is corrected so as to approximate the actual intake air amount when the internal combustion engine is operated in a state corresponding to the predetermined operating parameter, and the correction is performed when the intake valve of the internal combustion engine is in the open state. The intake air amount calculation value calculated based on the fluid model under the valve timing condition where the period during which the exhaust valve is in the open state does not overlap is corrected to the actual intake air amount under the valve timing condition. The reference correction coefficient used when calculating the intake air amount calculated based on the fluid model under other valve timing conditions It is characterized by using a correction.

  In the intake air amount calculation method of the present invention, it is preferable that the reference correction coefficient is a value that differs for each engine speed of the internal combustion engine.

  The present invention is an intake air amount calculation method for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine, which is calculated by constructing a fluid model related to intake air and introducing predetermined operating parameters into the fluid model. The calculated intake air amount is corrected so as to approximate the actual intake air amount when the internal combustion engine is operated in a state corresponding to the predetermined operating parameter, and the correction corrects the calculated intake air amount. Is calculated by substituting the valve timing of the internal combustion engine at the current time into a function indicating the relationship between the correction coefficient used for the control and the valve timing of the internal combustion engine, and using the current correction coefficient, The quantity calculation value is corrected.

In the intake air amount calculation method of the present invention, it is preferable that the function indicating the relationship between the correction coefficient and the valve timing of the internal combustion engine is a quadratic function expressed in the form of (Equation 1).
α = a · VT ² + b · VT + c (Formula 1)
α indicates a correction coefficient, VT indicates a valve timing, and a, b, and c indicate constants.

  In the intake air amount calculation method of the present invention, the constants a, b, and c in (Equation 1) are preferably different values for each engine speed of the internal combustion engine.

  According to the present invention, the amount of work required for map creation can be reduced, and sufficient accuracy can be obtained for the calculated intake air amount.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an intake air amount calculation device according to the present invention and an engine 10 as an internal combustion engine. The intake air amount calculation device according to the present invention includes a control device 30, an air flow meter 40, a throttle sensor 42, an intake air temperature sensor 44, an intake side cam angle sensor 46, and a crank angle sensor 48. Each of these sensors 40 to 48 is connected to the control device 30.

  An engine 10 as an internal combustion engine is provided with a piston 14 movably up and down in a cylinder 12. The upper side of the piston 14 is a combustion chamber 16. An intake passage 18 a and an exhaust passage 20 a communicate with the combustion chamber 16. In the vicinity of the communication portion between the intake passage 18a and the exhaust passage 20a and the combustion chamber 16, an open / close intake valve 18b and an exhaust valve 20b are provided. The intake valve 18b and the exhaust valve 20b are driven by the rotation of an intake camshaft and an exhaust camshaft (not shown). The intake camshaft and the exhaust camshaft are connected to a crankshaft (not shown). A throttle valve 24, a surge tank 22, and an injector 50 are provided in the intake passage 18a of the internal combustion engine. The throttle valve 24 is opened and closed in conjunction with the accelerator operation, and is connected to the control device 30. The surge tank 22 smoothes air pulsations. The injector 50 is a device that injects fuel for combustion, and is connected to the control device 30.

  An air flow meter 40 is provided on the upstream side of the throttle valve 24. A throttle sensor 42 is provided in the vicinity of the throttle valve 24. An intake cam angle sensor 46 is provided in the vicinity of the intake camshaft. A crank angle sensor 48 is provided in the vicinity of the crankshaft. The air flow meter 40 detects the amount of air mt flowing through the throttle valve 24. The throttle sensor 42 detects the opening degree of the throttle valve 24. The intake side cam angle sensor 46 detects the intake side cam angle. The opening / closing timing (hereinafter referred to as VT) of the intake valve 18b corresponding to the intake side cam angle and the valve lift amount are obtained in advance by experiments or the like, and the data is stored in the control device 30. The control device 30 takes in the detected value of the intake side cam angle sensor 46 and detects the VT and the valve lift amount corresponding to the detected value. The data may be stored in a memory or the like of a device different from the control device 30 and can be variously changed. The crank angle sensor 48 detects the crank angle and the rotational speed of the crankshaft.

  In the present embodiment, the single-cylinder engine 10 is described as an example. However, the present invention is not limited to this, and an engine including a plurality of cylinders may be used, and various modifications can be made. is there.

  The control device 30 calculates the intake air amount introduced into the combustion chamber 16 of the engine 10 in the intake process of the engine 10, and calculates the intake air amount calculated by the calculator 32 as the actual intake air. A correction unit 34 that corrects the amount to approximate the amount of fuel, an injector that determines the fuel amount from the calculated intake air amount corrected by the correction unit 34 and the target air-fuel ratio, and injects the determined fuel amount The fuel injection amount control unit 36 sends a command to 50. In the present embodiment, the fuel injection amount control unit 36 is incorporated in the control device 30. However, the intake air amount calculation device according to the present invention includes the calculation unit 32, the correction unit 34, and each sensor. 40 to 48, the fuel injection amount control unit 36 may be incorporated in a device different from the control device 30, and can be variously changed.

  The calculation unit 32 takes in signals from the sensors 40 to 48 and calculates the intake air amount introduced into the combustion chamber 16 in the intake process of the engine 10 based on the signals. First, the intake air amount is calculated. The principle that is the premise of the calculation will be described.

  First, the relationship between the amount of air mt flowing through the throttle valve 24 and the intake air pressure Pm in the surge tank 22 can be expressed by the following equation (1).

・・・（１）
ここで、Ｃｄｔはスロットル弁２４の流量係数、Ａｔはスロットル弁の開口面積、Ｐａは大気圧力、Ｔａは大気温度である。

... (1)
Here, Cdt is the flow coefficient of the throttle valve 24, At is the opening area of the throttle valve, Pa is the atmospheric pressure, and Ta is the atmospheric temperature.

  The air flow meter 40 detects mt. Cdt and At corresponding to the throttle opening are obtained in advance by experiments or the like. The opening degree of the throttle valve 24 is detected by the throttle sensor 42, and Cdt and At corresponding to the detected throttle opening degree are detected. The data of Cdt and At corresponding to the throttle opening may be stored in the calculation unit 32, or may be stored in a device other than the calculation unit 32, and various changes are possible. Of course there is. The atmospheric pressure Pa and the atmospheric temperature Ta are detected by an atmospheric pressure gauge and an atmospheric temperature sensor (not shown).

  Next, a fluid model relating to the intake air introduced into the combustion chamber 16 will be described.

M is the total mass of air and burned gas existing in the combustion chamber 16, and mc is the amount of intake air per unit time introduced into the combustion chamber 16 from the intake valve 18b during one intake step of the engine 10. During the intake process, the period during which the intake valve is open overlaps with the period during which the exhaust valve is open, so that per unit time introduced in the form of backflow from the exhaust valve 20 b into the combustion chamber 16. Assuming that the amount of burned gas is me, the amount of change per hour of the total mass M of the air and burned gas present in the combustion chamber 16 is expressed by the following equation (2) based on the law of conservation of mass be able to.
dM / dt = mc + me (2)

The equation of state for the air and burned gas existing in the combustion chamber 16 is expressed by the following equation (3), where Pc is the pressure in the combustion chamber 16, Tc is the temperature, Vc is the volume, and Rc is the gas constant. Can be expressed as:
Pc · Vc = M · Rc · Tc (3)

  From the above formula (3), it can be expressed as M = Pc · Vc / Rc · Tc. If this is substituted into the above formula (2) and rearranged, it can be expressed as the following formula (4).

・・・（４）

... (4)

  On the other hand, assuming that the constant heat of the air and the burned gas existing in the combustion chamber 16 is Cvc, the thermal energy of the air and the combustion gas existing in the combustion chamber 16 is “M · Cvc · Tc”. Also, assuming that the constant-pressure specific heat of the intake air introduced into the combustion chamber 16 during one intake step of the engine 10 is Cpm and the temperature is Tm, the heat energy per unit time of the intake air is “mc · Cpm · Tm ”. If the constant pressure specific heat of the burned gas introduced into the combustion chamber 16 is Cpe and the temperature is Te, the thermal energy per unit time of the burned gas is “me · Cpe · Te”. . Further, the heat energy per time applied to the combustion chamber 16 by the work of the piston 14 is Pc · dVc / dt, and the heat energy per time flowing into the combustion chamber 16 from the outside through the cylinder 12 wall surface is represented by Q. The value of Q is set in advance by a test or the like. Then, the change amount d (M · Cvc · Tc) / dt of the thermal energy M · Cvc · Tc of the air and combustion gas existing in the combustion chamber 16 per time is based on the following thermal energy conservation law. It can be expressed as equation (5).

・・・（５）
上記式（３）からＭ＝Ｐｃ・Ｖｃ／Ｒｃ・Ｔｃと表すことができ、これを上記式（５）に代入すると、次の式（６）のように表すことができる。

... (5)
From the above equation (3), it can be expressed as M = Pc · Vc / Rc · Tc, and when this is substituted into the above equation (5), it can be expressed as the following equation (6).

・・・（６）
ここで、燃焼室１６内に存在する空気及び既燃ガスの比熱比（定圧比熱／定積比熱）をκｃとすると、Ｃｖｃ＝Ｒｃ／（κｃ−１）となる。また、燃焼室１６内に導入される吸入空気の比熱比をκｍとし、気体定数をＲｍとすると、Ｃｐｍ＝κｍ・Ｒｍ／（κｍ−１）となる。また、燃焼室１６内に導入される既燃ガスの比熱比をκｅとし、気体定数をＲｅとすると、Ｃｐｅ＝κｅ・Ｒｅ／（κｅ−１）となる。これらを式（６）に代入して整理すると、次の式（７）のように表すことができる。

... (6)
Here, when the specific heat ratio (constant pressure specific heat / constant volume specific heat) of air and burned gas existing in the combustion chamber 16 is κc, Cvc = Rc / (κc−1). Further, when the specific heat ratio of the intake air introduced into the combustion chamber 16 is κm and the gas constant is Rm, Cpm = κm · Rm / (κm−1). Further, if the specific heat ratio of the burned gas introduced into the combustion chamber 16 is κe and the gas constant is Re, Cpe = κe · Re / (κe−1). If these are substituted into Expression (6) and rearranged, they can be expressed as the following Expression (7).

・・・（７）
ここで、κｃ、κｍ、κｅの値については、空気と同じとみなしてκｃ＝κｍ＝κｅ＝１．４としても良い。また、燃焼室１６内に導入される吸入空気の比熱比κｍの値は１．４とし、既燃ガスの比熱比κｅは一般的な一定値１．３３とし、燃焼室１６内に存在する空気及び既燃ガスの比熱比κｃは、空気と既燃ガスとの質量比から計算して求めることとしても良い。

... (7)
Here, the values of κc, κm, and κe may be regarded as the same as air, and κc = κm = κe = 1.4. Also, the value of the specific heat ratio κm of the intake air introduced into the combustion chamber 16 is 1.4, the specific heat ratio κe of the burned gas is a general constant value 1.33, and the air existing in the combustion chamber 16 The specific heat ratio κc of the burned gas may be calculated from the mass ratio of air and burned gas.

  The intake air amount mc can be expressed by the following equation (8).

・・・（８）
ここで、Ｃｄｍは吸気バルブ１８ｂの流量係数、Ａｍは吸気バルブ１８ｂの開口面積である。吸気側カム角度に対応するＣｄｍ及びＡｍは予め実験等によって求められている。吸気側カム角度センサ４６によって吸気側カム角度が検出され、該検出された吸気側カム角度に対応するＣｄｍ及びＡｍが検出される。上記吸気側カム角度に対応するＣｄｍ及びＡｍのデータは、演算部３２が記憶していても良いし、演算部３２とは別の他の装置が記憶していても良く、種々の変更が可能であることは勿論である。同様にして、既燃ガス量ｍｅは、次の式（９）で表すことができる。

... (8)
Here, Cdm is a flow coefficient of the intake valve 18b, and Am is an opening area of the intake valve 18b. Cdm and Am corresponding to the intake side cam angle are obtained in advance through experiments or the like. The intake-side cam angle is detected by the intake-side cam angle sensor 46, and Cdm and Am corresponding to the detected intake-side cam angle are detected. The Cdm and Am data corresponding to the intake side cam angle may be stored in the calculation unit 32, or may be stored in another device other than the calculation unit 32, and various changes are possible. Of course. Similarly, the burnt gas amount me can be expressed by the following equation (9).

・・・（９）
ここで、Ｃｄｅは排気バルブ２０ｂの流量係数、Ａｅは排気バルブ２０ｂの開口面積である。排気側カム角度に対応するＣｄｅ及びＡｅは予め実験等によって求められている。排気側カム角度センサによって排気側カム角度が検出され、該検出された排気側カム角度に対応するＣｄｅ及びＡｅが検出される。上記排気側カム角度に対応するＣｄｅ及びＡｅのデータは、演算部３２が記憶していても良いし、演算部３２とは別の他の装置が記憶していても良く、種々の変更が可能であることは勿論である。

... (9)
Here, Cde is a flow coefficient of the exhaust valve 20b, and Ae is an opening area of the exhaust valve 20b. Cde and Ae corresponding to the exhaust side cam angle are obtained in advance by experiments or the like. The exhaust cam angle is detected by the exhaust cam angle sensor, and Cde and Ae corresponding to the detected exhaust cam angle are detected. The Cde and Ae data corresponding to the exhaust side cam angle may be stored in the calculation unit 32, or may be stored in another device other than the calculation unit 32, and various changes are possible. Of course.

  The above equations (4), (7), (8), and (9) are equations representing a fluid model relating to the intake air introduced into the combustion chamber 16, and the calculation unit 32 calculates 1 of the engine 10 from the above equation (1). By calculating the intake air pressure Pm at each time point during one intake step and introducing the Pm into the model equation, the calculated intake air amount mc at each time point can be determined. Hereinafter, the calculation process of the intake air amount mc calculation value in the calculation unit 32 will be described in detail.

  The calculation unit 32 starts the calculation when the intake valve 18b starts to open. Assuming that the time when the intake valve 18b starts to open is t0, the pressure Pc and temperature Tc in the combustion chamber 16 at time t0 are Pc (t0) and Tc (t0), respectively, and the pressure Pe and temperature of the burned gas at time t0. Te is defined as Pe (t0) and Te (t0), respectively. Pc (t0) and Pe (t0) are set to atmospheric pressure (Pa), and these values are given to the calculation unit 32 as initial values. Here, the value of Pe in the intake process of the engine 10 remains atmospheric pressure (Pa) and does not change. Tc (t0) and Te (t0) are detected by a temperature sensor (not shown), and these detection signals are taken into the calculation unit 32. For the detection of Tc and Te, a map using the engine speed, load, and the like as parameters is prepared in advance by experiments, and the current Tc corresponding to the current engine speed, load, etc. from the map. Te may be obtained and, of course, various modifications are possible.

  The calculation unit 32 obtains the intake air pressure Pm (t0) in the surge tank 22 at time t0 from the above equation (1), and the value of the intake air temperature Tm (t0) at time t0 based on the detection signal from the intake temperature sensor 44. Capture. Then, the calculation unit 32 substitutes Pc (t0), Pm (t0), and Tm (t0) into the model equation (8) to calculate the intake air amount mc (t0) at time t0, and The burned gas amount me (t0) at time t0 is calculated by substituting Pc (t0), Pe (t0), and Te (t0) into the model equation (9).

  Next, the calculating part 32 calculates | requires Pc (t1) and Tc (t1) in the following time t1 using the said model formula (4) (7).

  First, calculation of Pc (t1) will be described. Here, when the model equation (7) is differentiated by the Euler method, it can be expressed as the following equation (10).

・・・（１０）
ここで、上記式（１０）に含まれる燃焼室１６内の体積Ｖｃの算出方法について図２を参照しながら説明する。

... (10)
Here, a method of calculating the volume Vc in the combustion chamber 16 included in the above equation (10) will be described with reference to FIG.

FIG. 2 is a model diagram for calculating the volume Vc in the combustion chamber 16, where S is the height of the combustion chamber 16, l is the length of the connecting rod that connects the piston 14 and the crankpin, and r is the crank. The rotation radius of the shaft, θ, represents the angular velocity of the crankshaft. The height S of the combustion chamber 16 and the volume Vc of the combustion chamber 16 can be expressed by the following equations (11) and (12), respectively.
S = (l + r) − {rcos θ + √ (l ² −r ² sin ² θ)} (11)
Vc = π · (Bore / 2) ² · S + V _{at piston top} (12)
Bore in the equation (12) represents the diameter of the cylinder 12, and V _{at piston top} represents the volume in the combustion chamber 16 when the piston 14 is at compression top dead center or exhaust top dead center. Each value is preset.

  The calculation unit 32 detects the crankshaft angular velocity θ (t0) at the time t0 when the intake valve 18b starts to open and the crankshaft angular velocity θ (t1) at the next time t1 by the crank angle sensor 48, respectively. By substituting these detected values into the above equations (11) and (12), Vc (t0) at time t0 and Vc (t1) at the next time are calculated.

  Then, the calculation unit 32 calculates Vc (t0) and Vc (t1) obtained using the above formulas (11) and (12), and the above Pc (t0), mc (t0), Tm (t0), me Substituting (t0) and Te (t0) into the above equation (10), Pc (t1) is calculated.

  Next, calculation of Tc (t1) will be described. When the model formula (4) is differentiated by the Euler method in the same manner as described above, it can be expressed as the following formula (13).

・・・（１３）
演算部３２は、上記式（１３）に上記Ｐｃ（ｔ１）、Ｐｃ（ｔ０）、Ｔｃ（ｔ０）、ｍｃ（ｔ０）、ｍｅ（ｔ０）、Ｖｃ（ｔ０）を代入することによって、次の時刻ｔ１におけるＴｃ（ｔ１）を求めることができる。

... (13)
The calculation unit 32 substitutes the above Pc (t1), Pc (t0), Tc (t0), mc (t0), me (t0), and Vc (t0) into the above equation (13), so that the next time Tc (t1) at t1 can be obtained.

  Then, the calculation unit 32 obtains the intake air pressure Pm (t1) in the surge tank 22 at the next time t1 from the above equation (1), and also uses the detection signal from the intake temperature sensor 44 to determine the intake air temperature Tm (t1). , And Pc (t1) obtained from the Pm (t1) and Tm (t1) and the above equation (10) are substituted into the model equation (8), and the intake air amount mc ( t1) is calculated. At the same time, the calculation unit 32 substitutes the Pc (t1), Pe (t1), and Te (t1) into the model equation (9) to calculate the burned gas amount me (t1) at the next time t1.

  The calculation unit 32 repeats the above calculation until the intake valve 18b is closed again. FIG. 3 shows an example of the calculation result. The horizontal axis represents time, and the time when the intake valve 18b is closed again is tn. The vertical axis represents the valve lift amounts of the intake valve 18b and the exhaust valve 20b during the period from when the intake valve 18b starts to open until it closes again, and the integrated value of the calculated intake air amount mc at each time point during the period. Yes. Here, the integrated value of the intake air amount mc in the predetermined period when the intake valve 18b starts to open is a negative value because the intake valve 18b is in the open state when the intake valve 18b starts to open. This is because the period in which the exhaust valve 20b is open overlaps and the residual gas in the combustion chamber 16 blows back to the intake valve 18b until the exhaust valve 20b is closed.

  However, it is difficult to ensure sufficient accuracy for the intake air amount mc calculated by the calculation unit 32, and the intake air amount mc calculated value cannot be used as it is for fuel control. Therefore, the correction unit 34 takes in the intake air amount mc calculation value at each time point during the intake process of the engine 10 calculated by the calculation unit 32, and calculates the intake air amount mc calculation value at each time point at the actual time at each time point. Correction is made to approximate the intake air amount mc.

  The correction unit 34 multiplies the intake air amount mc calculation value by a correction coefficient to obtain the intake air amount mc calculation value at each time point during the intake process of the engine 10 at an actual time point during the intake process of the engine 10. Correction to approximate the intake air amount mc is performed. Hereinafter, a method for obtaining the correction coefficient will be described.

  In a VT condition in which the period during which the intake valve 18b of the engine 10 is open and the period during which the exhaust valve 20b is open, that is, the VT most retarded condition (VT = 0), the intake air pressure Pm and the intake The relationship with the air amount mc is a substantially linear relationship as shown in FIG.

  Under such VT most retarded angle conditions, a straight line indicating the relationship between the intake air pressure Pm and the calculated intake air amount mc is approximated to a straight line indicating the relationship between the intake air pressure Pm and the actual intake air amount mc. The reference correction coefficient α1 for the calculation can be calculated by the least square method shown in the following equation (14).

minΣ (α1 · mc _calculation −mc _{actual measurement} ) ² (14)
Here, the reference correction coefficient α1 is sufficient as shown in FIG. 5 even if it is used for correction to approximate the calculated intake air amount mc to the actual intake air amount mc under other VT conditions. Accuracy can be obtained. In the present embodiment, focusing on this point, the correction unit 34 employs a configuration in which the reference correction coefficient α1 is used to correct the calculated intake air amount mc under all VT conditions. According to such a configuration, the amount of work required for calculating the correction coefficient can be significantly reduced, and sufficient accuracy can be obtained for the calculated intake air amount mc. Therefore, the corrected intake air amount mc The calculated value can be used for fuel control.

  The reference correction coefficient α1 may be obtained in advance through experiments or the like, and the value may be stored in the correction unit 34, or may be stored in a memory or the like of another device. Of course, it is possible to change.

  Further, when the rotational speed of the engine 10 changes under the engine VT most retarded angle condition, the straight line indicating the relationship between the intake air pressure Pm and the intake air amount mc shown in FIG. 4 changes, and the intake air pressure Pm and the intake air amount are changed. The error between the straight line indicating the relationship between the calculated mc value and the straight line indicating the relationship between the intake air pressure Pm and the actual intake air amount mc also changes. Then, the reference correction coefficient α1 becomes a different value for each rotation speed of the engine 10, but in the present embodiment, the value of the reference correction coefficient α1 is previously determined for each rotation speed of the engine 10 through experiments or the like. The data is stored in the correction unit 34. The data is not limited to the mode stored in the correction unit 34, but may be stored in another device, and can be variously changed.

"Another embodiment"
Another embodiment relating to the method of obtaining the correction coefficient will be described. In the present embodiment, attention is paid to the fact that the change in the correction coefficient with respect to VT can be approximated by a quadratic expression. The change of the correction coefficient with respect to VT can be expressed as the following equation (15), where α2 is the correction coefficient.
α2 = a · VT ² + b · VT + c (15)
“A”, “b”, and “c” in the equation (15) are constants, and are all different values for each rotation speed of the engine 10.

  FIG. 6 is a graph representing Equation (15), where the horizontal axis represents VT and the vertical axis represents the correction coefficient α2. The correction unit 34 stores in advance the function represented by the equation (15), substitutes the VT of the engine 10 at a certain point in the intake process of the engine 10 to obtain a correction coefficient at the certain point, and performs the correction. The calculated value of the intake air amount mc at a certain time is corrected using the coefficient.

  According to this configuration, the correction coefficient α2 at each time point corresponding to the VT of the engine 10 at each time point during the intake process of the engine 10 can be accurately obtained, and the correction coefficient α2 is corrected using the correction coefficient α2. Sufficient accuracy can be obtained for the calculated intake air amount mc at each time point.

  In the present embodiment, the quadratic function represented by Expression (15) is obtained in advance for each rotation speed of the engine 10 through experiments or the like, and these data are stored in the correction unit 34. However, the present invention is not limited to this. Of course, various changes can be made. For example, the data may be stored in a memory or the like of a device other than the correction unit 34.

  As described above, the intake air amount mc calculation value corrected by the correction unit 34 is sent to the fuel injection amount control unit 36, and the fuel injection amount control unit 36 sets the corrected intake air amount mc calculation value in advance. The amount of fuel to be injected is determined from the target air-fuel ratio, and a command is sent to the injector 50 to inject the determined amount of fuel.

  When the calculation and correction of the intake air amount mc calculation value at each time point during one intake process of the engine 10 is completed and the engine enters the next intake process, the calculation unit 32 and the correction unit 34 of the control device 30 perform the above operations. Similarly, calculation and correction of the intake air amount mc calculation value at each time point during the intake process of the next engine 10 are performed. Hereinafter, calculation and correction of the intake air amount mc calculation value are repeatedly performed for each intake process of the engine 10.

  In the present embodiment, the description has focused on an example in which the intake air pressure mc at each time point is obtained by introducing the intake pressure Pm at each time point during one intake process of the engine 10 into the fluid model. Of course, various modifications are possible without being limited thereto. For example, a map showing the relationship between the suction pressure Pm and the intake air amount mc calculation value by a bench test or the like is created in advance, the map is stored in the arithmetic unit 32 or another device, and the map is used. An aspect may be employed in which the intake air amount mc calculation value at each time point corresponding to the suction pressure Pm at each time point in one intake process of the engine 10 is obtained.

  In addition, a certain amount of operation data of the engine 10 is accumulated under a steady state of the engine in which the time change of the engine speed, VT, and throttle opening is below a certain value, and the accumulated operation data and the fluid The map showing the relationship between the suction pressure Pm and the intake air amount mc calculation value may be automatically created from the model, and various changes can be made without departing from the scope of the present invention.

  Next, intake air amount calculation control executed by the control device 30 will be described. FIG. 7 is a flowchart illustrating an example of intake air amount calculation control executed by the control device 30.

  In the intake air amount calculation control, first, in step S101, it is determined whether or not the intake valve 18b of the engine 10 is open. If it is determined that the intake valve 18b is open, the process proceeds to the next step S102. move on. When it is determined that the intake valve 18b is not open, intake air amount calculation control is not performed. As a method of determining whether or not the intake valve 18b is in the open state, for example, it can be determined by a detection signal from the intake side cam angle sensor 46, but is not limited thereto, and various changes can be made. Of course, for example, a determination may be made based on the detection signal of the crank angle sensor 48.

  In step S102, as described above, the calculation unit 32 of the control device 30 calculates the calculated intake air amount mc at a certain point in time during one intake process of the engine 10, and proceeds to the next step S103.

  In step S103, as described above, the correction unit 34 of the control device 30 approximates the intake air amount mc calculated at a certain time during one intake process of the engine 10 to the actual intake air amount mc at the certain time. When this correction is completed, the execution of this routine is terminated. The corrected intake air amount mc calculation value is sent to the fuel injection amount control unit 36 as described above and used for fuel control. Thereafter, the above control routine is repeated in the intake process of the engine 10, and the calculation and correction of the intake air amount mc calculated at each time point during the intake process of the engine 10 is performed.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

1 is a configuration diagram showing an intake air amount calculation device and an engine 10 according to the present invention. It is a model figure for calculation of the volume Vc in the combustion chamber 16 which concerns on this invention. It is a figure which shows an example of the calculation result of the intake air amount mc calculation value which concerns on this invention. It is a figure which shows the relationship between the intake air pressure Pm and the intake air amount mc on the VT most retarded angle conditions which concern on this invention. It is a figure which shows the accuracy at the time of using the reference | standard correction coefficient (alpha) 1 based on this invention for correction | amendment of the intake air amount mc calculation value on other VT conditions. It is a figure which shows the change of correction coefficient (alpha) 2 with respect to VT which concerns on this invention. It is a flowchart explaining the intake air amount calculation control performed by the arithmetic unit 30 according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Engine, 12 Cylinder, 14 Piston, 16 Combustion chamber, 18a Intake passage, 18b Intake valve, 20a Exhaust passage, 20b Exhaust valve, 22 Surge tank, 24 Throttle valve, 30 Control device, 32 Calculation part, 34 Correction part, 36 Fuel injection amount control unit, 40 air flow meter, 42 throttle sensor, 44 intake temperature sensor, 46 intake side cam angle sensor, 48 crank angle sensor.

Claims (10)

An intake air amount calculation device for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine,
The intake air amount calculation value calculated by introducing a predetermined operation parameter into the fluid model representing the relationship between the operation parameter of the internal combustion engine and the intake air amount in the combustion chamber is a state corresponding to the predetermined operation parameter. And a correction means for correcting so as to approximate the actual intake air amount when the internal combustion engine is operated.
The correction means calculates an intake air amount calculation value calculated based on the fluid model under a valve timing condition in which the period during which the intake valve of the internal combustion engine is open and the period during which the exhaust valve is open do not overlap. The reference correction coefficient used when correcting the actual intake air amount under the valve timing condition is used for correcting the calculated intake air amount calculated based on the fluid model under other valve timing conditions. An intake air amount calculation device characterized by the above. The intake air amount calculating device according to claim 1,
The intake air amount calculation device according to claim 1, wherein the reference correction coefficient is a value that differs for each engine speed of the internal combustion engine. An intake air amount calculation device for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine,
The intake air amount calculation value calculated by introducing a predetermined operation parameter into the fluid model representing the relationship between the operation parameter of the internal combustion engine and the intake air amount in the combustion chamber is a state corresponding to the predetermined operation parameter. And a correction means for correcting so as to approximate the actual intake air amount when the internal combustion engine is operated.
The correction means substitutes a valve timing of the internal combustion engine at a current time into a function indicating a relationship between a correction coefficient used for correcting a calculated intake air amount and a valve timing of the internal combustion engine, and corrects the current correction coefficient And calculating the intake air amount calculation value at the present time using the correction coefficient at the current time. The intake air amount calculation device according to claim 3,
An intake air amount calculation apparatus characterized in that a function indicating a relationship between the correction coefficient and the valve timing of the internal combustion engine is a quadratic function expressed in the form of (Equation 1).
α = a · VT ² + b · VT + c (Formula 1)
α is the correction factor,
VT is the valve timing,
a, b, and c are constants. The intake air amount calculation device according to claim 4,
The constants a, b, and c in (Equation 1) are different values for each engine speed of the internal combustion engine. An intake air amount calculation method for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine,
The intake air amount calculation value calculated by introducing a predetermined operation parameter into the fluid model representing the relationship between the operation parameter of the internal combustion engine and the intake air amount in the combustion chamber is a state corresponding to the predetermined operation parameter. Thus, the correction is made to approximate the actual intake air amount when the internal combustion engine is operated, and the correction is based on the period when the intake valve of the internal combustion engine is open and the period when the exhaust valve is open. The reference correction coefficient used in correcting the calculated intake air amount calculated based on the fluid model under the non-overlapping valve timing condition to the actual intake air amount under the valve timing condition is used as another valve timing. Used to correct the calculated intake air amount calculated based on the fluid model under the above conditions. Method. The intake air amount calculation method according to claim 6,
The intake air amount calculation method according to claim 1, wherein the reference correction coefficient is a different value for each engine speed of the internal combustion engine. An intake air amount calculation method for obtaining an intake air amount introduced into a combustion chamber of an internal combustion engine,
The intake air amount calculation value calculated by introducing a predetermined operation parameter into the fluid model representing the relationship between the operation parameter of the internal combustion engine and the intake air amount in the combustion chamber is a state corresponding to the predetermined operation parameter. Is corrected to approximate the actual intake air amount when the internal combustion engine is operated, and the correction is performed between the correction coefficient used for correcting the calculated intake air amount and the valve timing of the internal combustion engine. An intake valve characterized by substituting a valve timing of the internal combustion engine at a current time into a function indicating a relationship to obtain a correction coefficient at a current time, and correcting the calculated intake air amount at the current time using the correction coefficient at the current time Air quantity calculation method. An intake air amount calculation method according to claim 8,
The intake air amount calculation method, wherein the function indicating the relationship between the correction coefficient and the valve timing of the internal combustion engine is a quadratic function expressed in the form of (Equation 1).
α = a · VT ² + b · VT + c (Formula 1)
α is the correction factor,
VT is the valve timing,
a, b, and c are constants. An intake air amount calculation method according to claim 9,
The constants a, b, and c in (Equation 1) are different values for each engine speed of the internal combustion engine.

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