JP2010163906A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device for internal combustion engine, capable of performing feedback control of air-fuel ratio, even in cold starting, while suppressing the occurrence of error and the probability of increase in cost by calculating cylinder internal pressure. <P>SOLUTION: The air-fuel ratio control device for an internal combustion engine includes: a crank angle sensor 6 which detects rotational angular velocity of the internal combustion engine; an engine water temperature sensor 10 which detects cooling water temperature of the internal combustion engine; a virtual cylinder internal pressure calculation means which calculates virtual cylinder internal pressure of the internal combustion engine based on the rotational angular velocity and the cooling water temperature; an air-fuel ratio calculation means which calculates air-fuel ratio of the internal combustion engine based on the virtual cylinder internal pressure; and a fuel injection quantity calculation means which calculates fuel injection quantity based on the air-fuel ratio. Since air-fuel ratio control is performed by calculating the virtual cylinder internal pressure from the rotational angular velocity and the cooling water temperature, the feedback control of air-fuel ratio can be performed even in cold starting while suppressing the occurrence of error and the probability of increase in cost. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine.

  In the fuel injection control at the time of cold start, it is difficult to perform feedback control using the air-fuel ratio. Under these circumstances, fuel injection control during cold start must balance drivability, emissions, and fuel consumption while taking into account individual variations in the engine and changes over time. In many cases, the control is prioritized.

  FIG. 1 is a diagram illustrating a conventional general air-fuel ratio behavior at the time of starting. In FIG. 1, the horizontal axis indicates time, and the vertical axis indicates an air fuel ratio (AFR: Air Fuel Ratio). Also, the solid line in the figure represents the ideal starting air-fuel ratio, and the dotted line represents the starting air-fuel ratio during conventional cold start.

  As shown in FIG. 1, at the time of cold start, it is far from the ideal state, and it takes a long time to reach 15.5 which is the target air-fuel ratio. That is, at the time of cold start, since control is given priority to drivability, fuel consumption and emission are not optimized. This is because at the time of cold start, the AFR sensor is inactive and it is difficult to perform feedback control.

  Patent Document 1 discloses a technique for estimating an estimated exhaust gas state parameter using a neural network configured with the exhaust gas state parameter as a teacher signal, and controlling the air-fuel ratio according to the properties of the fuel. Patent Document 2 discloses a technique for determining an air-fuel ratio from a simple linear model and a neural network model based on an ion current or combustion pressure in a cylinder.

JP 2007-303351 A JP 2005-23863 A

  However, in the above technique, when the air-fuel ratio behavior is modeled, the flow of gas in the exhaust pipe is simplified, so that an error may occur. Further, since the air-fuel ratio behavior is expressed by a statistical model, it is necessary to frequently learn. Furthermore, an air-fuel ratio sensor or an ion current sensor is added to use an output signal of the air-fuel ratio sensor or ion current sensor as a teacher signal. This may cause an increase in cost. That is, the air-fuel ratio control at the time of cold start has a problem that there is a risk of generating errors and increasing costs.

  In view of the above problems, the present invention provides an internal combustion engine capable of suppressing the occurrence of errors and the possibility of increasing costs and calculating the air-fuel ratio feedback control by calculating the in-cylinder pressure even during cold start. An object of the present invention is to provide an air-fuel ratio control device.

  The present invention provides pressure detection means for detecting an intake pipe internal pressure of an internal combustion engine, rotation angular speed detection means for detecting a rotation angular speed of the internal combustion engine, temperature detection means for detecting a coolant temperature of the internal combustion engine, and the rotation In-cylinder pressure calculating means for calculating the in-cylinder pressure of the internal combustion engine based on the rotational angular velocity detected by the angular velocity detecting means; the intake pipe pressure detected by the pressure detecting means; the rotational angular velocity; and the temperature detection A virtual in-cylinder pressure calculating means for calculating a virtual in-cylinder pressure of the internal combustion engine based on the cooling water temperature detected by the means and the in-cylinder pressure calculated by the in-cylinder pressure calculating means; An air-fuel ratio calculating means for calculating an air-fuel ratio of the internal combustion engine based on the pressure and the virtual in-cylinder pressure calculated by the virtual in-cylinder pressure calculating means; and Based on the air-fuel ratio calculated Ri is an air-fuel ratio control apparatus for an internal combustion engine, characterized by comprising: a fuel injection amount calculating means for calculating a fuel injection amount, the. According to the present invention, even during cold start, by calculating the in-cylinder pressure, it is possible to suppress the occurrence of errors and the possibility of cost increase, and to perform feedback control of the air-fuel ratio.

  In the above configuration, the in-cylinder pressure calculating means includes temperature calculating means for calculating an in-cylinder gas temperature of the internal combustion engine based on the in-cylinder pressure, and the virtual in-cylinder pressure calculating means includes the intake pipe pressure, The virtual cylinder pressure can be calculated based on the rotational angular velocity, the cooling water temperature, the cylinder gas temperature calculated by the temperature calculation means, and the cylinder pressure.

  In the above configuration, the in-cylinder pressure calculating means includes temperature calculating means for calculating an in-cylinder gas temperature of the internal combustion engine based on the in-cylinder pressure, and the temperature calculating means is detected by the pressure detecting means. Mass calculating means for calculating the mass of the gas sucked into the cylinder of the internal combustion engine based on the intake pipe internal pressure, and the temperature calculating means includes the mass calculated by the mass calculating means and the in-cylinder pressure. The in-cylinder gas temperature is calculated based on the virtual in-cylinder pressure calculating means based on the rotational angular velocity, the cooling water temperature, the in-cylinder gas temperature calculated by the temperature calculating means, and the in-cylinder pressure. The virtual cylinder pressure can be calculated.

  The above configuration further includes a crank angle detection unit that detects a crank angle of the internal combustion engine, and the mass calculation unit calculates the mass according to the crank angle detected by the crank angle detection unit. can do.

  In the above configuration, the mass calculation unit may calculate the mass based on the intake pipe pressure detected by the pressure detection unit when the crank angle is at a valve closing timing.

  In the above configuration, the in-cylinder pressure calculating means calculates the in-cylinder pressure based on the rotation angular velocity at the time when the crank angle is detected and the crank angle, and calculates the temperature according to the crank angle. The means may be configured to calculate the in-cylinder gas temperature based on the mass and the in-cylinder pressure according to the crank angle.

  In the above configuration, the first case where the crank angle detected by the crank angle detecting means is at a first angle that is a predetermined angle and the second angle that is at a second angle that is different from the first angle. In accordance with each of the two cases, the in-cylinder pressure calculating means is based on the rotational angular velocity in each of the first case and the second case, and each of the first angle and the second angle, Each of the first in-cylinder pressure and the second in-cylinder pressure that is an in-cylinder pressure of the internal combustion engine in each of the first case and the second case is calculated, and the temperature calculation means includes the mass, In-cylinder gas temperature of the internal combustion engine in each of the first case and the second case based on each of the first in-cylinder pressure and the second in-cylinder pressure calculated by the in-cylinder pressure calculating means. The first in-cylinder gas And the air-fuel ratio calculating means calculate the virtual cylinder pressure, the first cylinder pressure calculated by the cylinder pressure calculating means, and the second cylinder pressure. In addition, the air-fuel ratio can be calculated based on the first in-cylinder gas temperature and the second in-cylinder gas temperature calculated by the temperature calculation unit.

  According to the present invention, it is possible to provide an air-fuel ratio control device for an internal combustion engine capable of feedback control of an air-fuel ratio by calculating the in-cylinder pressure even at the time of cold start.

FIG. 1 is a diagram illustrating the air-fuel ratio behavior at the start. FIG. 2 is a schematic view illustrating an engine to which the air-fuel ratio control apparatus for an internal combustion engine according to the first embodiment is applied. FIG. 3 is a flowchart illustrating the operation of the air-fuel ratio control apparatus for the internal combustion engine according to the first embodiment. FIG. 4 is a diagram illustrating the relationship between the air-fuel ratio AFR and the specific heat ratio κ (pressure gradient).

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

  FIG. 2 is a schematic view illustrating an engine (internal combustion engine) to which the internal combustion engine air-fuel ratio control apparatus 1 according to the first embodiment is applied.

  As shown in FIG. 2, the engine to which the air-fuel ratio control apparatus 1 for an internal combustion engine according to the first embodiment is applied includes an engine body 4 and an ECU (Electric Control Unit) 2.

The engine body 4 is provided with an intake pipe 8, an exhaust pipe 18, and a spark plug 12. The cylinders 4b of the engine body 4, the crank angle sensor 6 for detecting the crank angle θ of the crankshaft 4a (crank angle detecting means), and the engine coolant temperature sensor 10 for detecting the cooling water temperature T _w of the engine (temperature detecting means) Is provided. The crank angle sensor 6 can detect the rotational angular velocity ω. That is, the crank angle sensor 6 functions as a rotational angular velocity detection unit and a crank angle detection unit.

The intake pipe 8, a pressure sensor 8a (pressure detection means) for detecting an intake pipe pressure P _m in the intake pipe 8, the fuel injection valves 14 and the throttle valve 16 is provided.

The crank angle θ and the angular velocity ω detected by the crank angle sensor 6 and the intake pipe pressure P _m detected by the pressure sensor 8a are transmitted to the ECU 2. The ECU 2 also controls the spark plug 12, the fuel injection valve 14 and the throttle valve 16.

  In this embodiment, the ECU 2 corresponds to a mass calculating means, an in-cylinder pressure calculating means, a virtual in-cylinder pressure calculating means, a temperature calculating means, and a fuel injection amount calculating means.

  Next, the operation of the air-fuel ratio control apparatus 1 for an internal combustion engine according to the first embodiment will be described with reference to the drawings. FIG. 3 is a flowchart illustrating the operation of the air-fuel ratio control apparatus 1 for the internal combustion engine according to the first embodiment.

  As shown in FIG. 3, first, the ECU 2 determines whether the ignition of the internal combustion engine is activated (step S10). In the case of Yes, the ECU 2 acquires the rotational angular velocity ω detected by the crank angle sensor 6 (step S11). In No, it returns to step S10.

  After step S11, the ECU 2 acquires the crank angle θ detected by the crank angle sensor 6 (step S12).

After step S12, the ECU 2 determines whether or not the crank angle θ detected by the crank angle sensor 6 is the crank angle θ _ivc at the valve closing timing (step S13). For yes, ECU 2 obtains the intake pipe pressure _{P m} detected by the pressure sensor 8a (step S14). If No in step S13, the process returns to step S12.

After step S13, the ECU 2 calculates the mass m _{cyl of} the gas sucked into the cylinder 4b from the intake pipe 8 using the following equation (1) based on the intake pipe pressure P _m detected by the pressure sensor 8a. (Step S15).

m _cyl = αP _m + β (1)
(Α, β: constant)

That is, the ECU 2 calculates the mass m _cyl based on the intake pipe pressure P _m detected by the pressure sensor 8a in accordance with the crank angle θ detected by the crank angle sensor 6. In step S15, the ECU 2 calculates the mass m _cyl based on the intake pipe pressure P _m detected by the pressure sensor 8a when the crank angle θ is at the valve closing timing.

  After step S15, the ECU 2 acquires the crank angle θ detected by the crank angle sensor 6 (step S16). After step S16, the ECU 2 determines whether the crank angle θ is a first angle that is a predetermined angle (step S17). In step S17, the first angle is 90 deg. btdc (btdc: before top dead center).

In the case of Yes (first case), the ECU 2 determines that the crank angle θ (here 90 deg. Btdc) and the crank angle is θ = 90 deg. In-cylinder volume V ₉₀ of cylinder 4b in the case of btdc, θ = 90 deg. Based on the rotational angular velocity _{omega ivc} when a rotational angular velocity omega _90, and theta = theta _ivc when a BTDC, using the following equation (2), theta = 90deg. cylinder pressure _{P 90} is calculated (first cylinder pressure) in the case of BTDC (step S18).

_{P 90 = {f 1 (θ} ) -f 2 (θ) ω 90 -f 3 (θ) ω 90 2 -f 4 (θ) ω 90 (ω 90 -ω ivc) / (90-θ ivc)} / V ₉₀ (2)

Here, f ₁ (θ), f ₂ (θ), f ₃ (θ), and f ₄ (θ) are functions of θ determined by engine design. If No in step S17, the process returns to step S16.

After step S18, ECU 2 is the gas constant R, the mass _{m cyl} calculated in step S15, and based on the first cylinder pressure _{P 90} calculated in step S18, using the equation (3), the crank angle θ = 90 deg. calculating the in-cylinder gas temperature _{T 90} of the cylinders 4b (first cylinder gas temperature) in the case of BTDC (step S19).

T ₉₀ = P ₉₀ V ₉₀ / m _cyl R (3)

  After step S19, the ECU 2 acquires the crank angle θ detected by the crank angle sensor 6 (step S20). After step S20, the ECU 2 determines whether the crank angle θ is a second angle that is a predetermined angle (step S21). The second angle is a predetermined angle different from the first angle. In step S21, the second angle is, for example, 45 deg. btdc.

In the case of Yes, the ECU 2 determines that the crank angle θ (here 45 deg. Btdc) and the crank angle is θ = 45 deg. In-cylinder volume V ₄₅ of cylinder 4b in the case of btdc, θ = ₄₅ deg. Based on the rotational angular velocities ω ₄₅ and ω ₉₀ in the case of btdc, θ = 45 deg. In-cylinder pressure P ₄₅ (second in-cylinder pressure) in the case of btdc is calculated (step S22).

P ₄₅ = {f ₁ (θ) −f ₂ (θ) ω ₄₅ −f ₃ (θ) ω ₄₅ ² −f ₄ (θ) ω ₄₅ (ω ₄₅ −ω ₉₀ ) / 45} / V ₄₅ ... (4)

As shown in steps S18 and S22, the ECU 2 calculates the in-cylinder pressure according to the crank angle θ based on the rotational angular velocity ω and the crank angle θ at the time when the crank angle θ is detected. If No in step S21, the process returns to step S20.

After step S22, the ECU 2 determines that the crank angle is θ = 45 deg. Using the equation (5) based on the gas constant R, the mass m _cyl , and the second in-cylinder pressure P ₄₅ calculated in step S22. In-cylinder gas temperature T ₄₅ (second in-cylinder gas temperature) of cylinder 4b in the case of btdc is calculated (step S23).

T ₄₅ = P ₄₅ V ₄₅ / m _cyl R (5)

As shown in steps S19 and S23, the ECU 2 calculates the in-cylinder gas temperature based on the mass and the in-cylinder pressure according to the crank angle θ.

After step S23, ECU 2 obtains the cooling water temperature _{T w} of the engine detected by the engine coolant temperature sensor 10 (step S24). After step S24, ECU 2 is the rotational angular velocity omega, the first cylinder gas temperature _{T 90} and the second cylinder gas temperature _{T 45,} and based on the coolant temperature _{T w} which is detected by the engine coolant temperature sensor 10, the next ( 6) Using the equation, the crank angle θ is 90 deg. btdc to 45 deg. heat loss during changes BTDC (cooling loss) to calculate the _{Q w} (step S25).

Q _w = (0.4 + 0.17ω ^0.62 ) {(T ₄₅ + T ₉₀ ) / 2−T _w } (6)

After step S25, the ECU 2, the second cylinder pressure _{P 45} calculated in step S22, the heat loss _{Q w} calculated in step S25, based on the cylinder volume _{V 90} and _{V 45,} the following equation (7) The virtual in-cylinder pressure P ₄₅ a is calculated using (Step S26).

P ₄₅ a = P ₄₅ + 2Q _w / (V ₉₀ −V ₄₅ ) (7)

The virtual in-cylinder pressure is a crank angle θ of 90 deg. btdc to 45 deg. This is the in-cylinder pressure when there is no heat loss in the gas in the cylinder 4b during the change to btdc. That is, the ECU 2 determines the virtual in-cylinder pressure P based on the rotation angular velocity ω, the coolant temperature T _w , the first in-cylinder gas temperature T _90, the second in-cylinder gas temperature T ₄₅ , and the second in-cylinder pressure P _{45. 45a} is calculated. As shown in the formulas (3) and (5), the in-cylinder temperature is based on the mass m _cyl , and as shown in the formula (1), the mass is based on the intake pipe pressure P _m . That is, the ECU 2 calculates the virtual cylinder pressure P ₄₅ a based on the intake pipe pressure P _m , the rotational angular velocity ω, the coolant temperature T _w , and the second cylinder pressure P ₄₅ .

After step S26, the ECU 2 uses the following equation (8) to determine the crank angle θ based on the first in-cylinder pressure P ₉₀ , the in-cylinder volumes V ₄₅ and V ₉₀ , and the virtual in-cylinder pressure P ₄₅ a. 90 deg. btdc to 45 deg. While changing to btdc, a virtual polytropic index m ′ when there is no heat loss in the gas in the cylinder 4b is calculated (step S27).

m ′ = − V ₄₅ (P ₉₀ −P ₄₅ a) / {P ₄₅ a (V ₉₀ −V ₄₅ )} (8)

After step S27, the ECU 2 calculates an air-fuel ratio AFR of the in-cylinder gas in the cylinder 4b using the following equation (9) based on the virtual polytropic index m ′ calculated in step S27 (step S28).

AFR = (m′−0.32) / (1.4−m ′) (9)

Here, the relationship between the air-fuel ratio AFR and the virtual polytropic index m ′ will be described.

FIG. 4 is a diagram illustrating the relationship between the air-fuel ratio AFR and the specific heat ratio κ (pressure gradient). As shown in FIG. 4, there is a certain relationship between AFR and pressure gradient. Further, as shown in the above equation (8), there is also a certain relationship between the virtual polytropic index m ′ and the pressure gradient. Therefore, the ECU 2 can calculate the air-fuel ratio AFR using the above equation (9). In other words, the ECU 2 is based on the first cylinder pressure P ₉₀ , the second cylinder pressure P ₄₅ , the first cylinder gas temperature T ₉₀ , the second cylinder gas temperature T ₄₅ , and the virtual cylinder pressure P ₄₅ a. Then, the air-fuel ratio AFR is calculated.

After step S28, the ECU 2 performs the following based on the air-fuel ratio AFR, the target air-fuel ratio AFR _t (≈15.5, see FIG. 1) calculated in step S28, and the fuel injection amount reference value (pre-adapted value) τ ₀ ( The fuel injection amount of the next cylinder is calculated using equation (10) (step S29). In other words, the ECU 2 calculates the fuel injection amount τ of the next cylinder based on the air-fuel ratio AFR calculated in step S28.

τ = τ ₀ (AFR−AFR _t ) / AFR _t (10)

That is, the ECU 2 takes into account the deviation from the ideal starting air-fuel ratio as shown in FIG. 1, and the fuel injection amount of the next cylinder that brings the air-fuel ratio at the cold start closer to the ideal starting air-fuel ratio. τ is calculated. After step S29, the operation of the air-fuel ratio control apparatus for the internal combustion engine according to the first embodiment ends.

According to Example 1, ECU 2 is the rotational angular velocity omega, and on the basis of the cooling water temperature _{T w,} and calculates the virtual cylinder pressure _{P 45} a (step S26). Further, the ECU 2 calculates the air-fuel ratio AFR based on the virtual in-cylinder pressure P ₄₅ a (step S28), and calculates the fuel injection amount τ of the next cylinder based on the air-fuel ratio AFR (step S29). That is, the air-fuel ratio control apparatus according to the first embodiment, since the are based on physical phenomena such rotational angular velocity ω and the cooling water temperature T _w, even if AFR sensor is inactive during cold starting, the feedback of the air-fuel ratio Control can be performed. Therefore, drivability, fuel consumption, and emission can be optimized even during cold start.

Moreover, since it is based on physical phenomena such rotational angular velocity ω and the cooling water temperature T _w, often without using additional sensors, it is possible to suppress the cost of the air-fuel ratio control system. Also, errors due to simplifying the gas flow are less likely to occur. Furthermore, since a statistical model is not used, the frequency of learning can be made relatively low.

As parameters used for calculating the virtual in-cylinder pressure P ₄₅ a, parameters having a correlation with T _w , such as oil temperature and total fuel injection amount, can be used in addition to the cooling water temperature T _w .

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

Air-fuel ratio control device 1
ECU 2
Engine body 4
Crankshaft 4a
Cylinder 4b
Crank angle sensor 6
Engine water temperature sensor 10
Fuel injection valve 14

Claims (7)

Pressure detecting means for detecting the pressure in the intake pipe of the internal combustion engine;
Rotational angular velocity detection means for detecting the rotational angular velocity of the internal combustion engine;
Temperature detecting means for detecting a coolant temperature of the internal combustion engine;
In-cylinder pressure calculation means for calculating an in-cylinder pressure of the internal combustion engine based on the rotation angular speed detected by the rotation angular speed detection means;
Based on the intake pipe pressure detected by the pressure detection means, the rotational angular velocity, the coolant temperature detected by the temperature detection means, and the in-cylinder pressure calculated by the in-cylinder pressure calculation means, the internal combustion engine Virtual cylinder pressure calculation means for calculating the virtual cylinder pressure of the engine;
Air-fuel ratio calculating means for calculating an air-fuel ratio of the internal combustion engine based on the in-cylinder pressure and the virtual cylinder pressure calculated by the virtual cylinder pressure calculating means;
An air-fuel ratio control apparatus for an internal combustion engine, comprising: a fuel injection amount calculation unit that calculates a fuel injection amount based on the air-fuel ratio calculated by the air-fuel ratio calculation unit. The in-cylinder pressure calculating means includes temperature calculating means for calculating an in-cylinder gas temperature of the internal combustion engine based on the in-cylinder pressure,
The virtual in-cylinder pressure calculation means is configured to generate the virtual in-cylinder pressure based on the intake pipe pressure, the rotational angular velocity, the cooling water temperature, the in-cylinder gas temperature calculated by the temperature calculation means, and the in-cylinder pressure. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein: The in-cylinder pressure calculating means includes temperature calculating means for calculating an in-cylinder gas temperature of the internal combustion engine based on the in-cylinder pressure,
The temperature calculation means includes mass calculation means for calculating the mass of gas sucked into the cylinder of the internal combustion engine based on the intake pipe pressure detected by the pressure detection means,
The temperature calculating means calculates the in-cylinder gas temperature based on the mass calculated by the mass calculating means and the in-cylinder pressure,
The virtual in-cylinder pressure calculating means calculates the virtual in-cylinder pressure based on the rotational angular velocity, the cooling water temperature, the in-cylinder gas temperature calculated by the temperature calculating means, and the in-cylinder pressure. 2. An air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein Crank angle detection means for detecting a crank angle of the internal combustion engine,
The air-fuel ratio control apparatus for an internal combustion engine according to claim 3, wherein the mass calculation means calculates the mass according to the crank angle detected by the crank angle detection means.   5. The internal combustion engine according to claim 4, wherein the mass calculating unit calculates the mass based on the intake pipe internal pressure detected by the pressure detecting unit when the crank angle is at a valve closing timing. 6. Air-fuel ratio control device. The in-cylinder pressure calculating means calculates the in-cylinder pressure according to the crank angle based on the rotation angular velocity at the time when the crank angle is detected and the crank angle.
6. The air-fuel ratio control apparatus for an internal combustion engine according to claim 4, wherein the temperature calculation means calculates the in-cylinder gas temperature based on the mass and the in-cylinder pressure according to the crank angle. . The first case where the crank angle detected by the crank angle detecting means is a first angle which is a predetermined angle, and the second case where the crank angle is a second angle which is different from the first angle. According to each
The in-cylinder pressure calculating means is configured to perform the first case and the second based on the rotation angular velocity in each of the first case and the second case, and each of the first angle and the second angle. Each of the first in-cylinder pressure and the second in-cylinder pressure, which is the in-cylinder pressure of the internal combustion engine in each of the cases,
The temperature calculating means is based on each of the first case pressure and the second in-cylinder pressure calculated by the mass and the in-cylinder pressure calculating means. Calculating each of the first in-cylinder gas temperature and the second in-cylinder gas temperature that is the in-cylinder gas temperature of the internal combustion engine in each;
The air-fuel ratio calculating means includes the virtual cylinder pressure, the first cylinder pressure and the second cylinder pressure calculated by the cylinder pressure calculating means, and the first cylinder calculated by the temperature calculating means. The air-fuel ratio control apparatus for an internal combustion engine according to claim 6, wherein the air-fuel ratio is calculated based on an internal gas temperature and the second in-cylinder gas temperature.

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