JP2007192108A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately estimate a temperature of an intake valve of an internal combustion engine having both a port injector and a cylinder injector, in an air-fuel ratio control device for an internal combustion engine. <P>SOLUTION: An injection sharing ratio α between the port injector 20 and the cylinder injector 23 is acquired (a step 103). Based on the injection sharing ratio α, a cylinder gas temperature Tc is calculated (a step 104). Based on the cylinder gas temperature Tc, a combustion gas receiving heat quantity Qb of the intake valve received from combustion gas is calculated (a step 110). Based on a total receiving heat quantity acquired from the combustion gas receiving heat quantity Qb or the like, an intake valve temperature Tv is updated (a step 111). Based on the intake valve temperature Tv, a quantity of fuel evaporating from the intake valve and a quantity of fuel remaining in the intake valve are calculated (a step 112), and then based on the quantities, a quantity of fuel to be injected from the port injector 20 and the cylinder injector 23 are calculated (a step 113). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine, and more particularly to an air-fuel ratio control apparatus for an internal combustion engine having a function of estimating the temperature of an intake valve.

  In an internal combustion engine equipped with a port injector that injects fuel into the intake port, part of the fuel injected from the port injector once adheres to the outside of the intake valve and the rest mixes with fresh air. It is sucked into the cylinder as it is. The fuel adhering to the outside of the intake valve gradually evaporates into the intake port and flows into the cylinder with a delay. When the internal combustion engine is in a steady state, the amount of fuel adhering to the intake valve is balanced at a constant value, and the amount of fuel flowing into the cylinder becomes equal to the amount of injected fuel.

  However, when the internal combustion engine is in a transient operation state, the amount of fuel adhering to the intake valve varies. While this increase / decrease occurs, there is a deviation between the amount of fuel flowing into the cylinder and the amount of fuel injected. Therefore, in the transient operation state, in order to control the amount of fuel sucked into the cylinder with high accuracy, it is required to estimate the evaporation amount of the fuel adhering to the intake valve. Since the fuel evaporation amount from the intake valve depends on the intake valve temperature, in order to accurately estimate the fuel evaporation amount from the intake valve, it is required to estimate the intake valve temperature with high accuracy.

  Japanese Patent Application Laid-Open No. 11-14507 discloses an apparatus for calculating the intake valve temperature based on the combustion gas temperature calculated by the combustion system model. However, this publication does not disclose any specific method for calculating the intake valve temperature based on the combustion gas temperature.

Japanese Patent Laid-Open No. 11-14507 JP-A-8-177556 JP 2000-257467 A JP 11-270399 A

  By the way, there is known an internal combustion engine that includes both a port injector and an in-cylinder injector that injects fuel into a cylinder and can supply fuel from both injectors. According to such an internal combustion engine, the ratio (injection ratio) between the fuel injection amount from the port injector and the fuel injection amount from the in-cylinder injector is between 100: 0 and 0: 100 depending on the operating conditions. Can be changed. For this reason, it is possible to combine the advantages of both the port injection type internal combustion engine and the direct injection type internal combustion engine.

  Since the in-cylinder combustion state differs between the port injection internal combustion engine and the in-cylinder direct injection internal combustion engine, the temperature of the gas in the cylinder also differs. Therefore, the in-cylinder gas temperature in the internal combustion engine having both the port injector and the in-cylinder injector is different from the port injection type internal combustion engine and the in-cylinder direct injection type internal combustion engine, and also varies depending on the injection ratio. .

  In the conventional air-fuel ratio control apparatus, the above situation in the internal combustion engine having both the port injector and the in-cylinder injector is not taken into consideration, and therefore the intake valve temperature can be estimated with sufficient accuracy. could not. As a result, particularly in a transient operation state of the internal combustion engine, the air-fuel ratio in the cylinder may not be controlled with sufficient accuracy.

  The present invention has been made in order to solve the above-described problems, and in an internal combustion engine having both a port injector and an in-cylinder injector, an internal combustion engine capable of accurately estimating the temperature of the intake valve. An object is to provide an air-fuel ratio control device.

In order to achieve the above object, a first invention is an air-fuel ratio control apparatus for an internal combustion engine,
A port injector for injecting fuel into the intake port of the internal combustion engine;
An in-cylinder injector for injecting fuel into the cylinder of the internal combustion engine;
An injection ratio acquisition means for acquiring an injection ratio that is a ratio of a fuel injection amount from the port injector and a fuel injection amount from the in-cylinder injector;
An intake valve temperature estimating means for estimating the temperature of the intake valve of the internal combustion engine based on the injection ratio;
It is characterized by providing.

The second invention is the first invention, wherein
The intake valve temperature estimation means includes combustion gas heat reception amount calculation means for calculating a combustion gas heat reception amount received by the intake valve from combustion gas in a cylinder based on the injection ratio, and based on the combustion gas heat reception amount Then, the temperature of the intake valve is estimated.

The third invention is the second invention, wherein
The combustion gas heat receiving amount calculating means includes in-cylinder gas temperature calculating means for calculating the temperature of the in-cylinder gas based on the injection ratio, and calculating the combustion gas heat receiving amount based on the in-cylinder gas temperature. It is characterized by.

Moreover, 4th invention is set in 3rd invention,
The in-cylinder gas temperature calculating means includes
In-cylinder gas temperature calculation means for port injection that calculates the in-cylinder gas temperature when it is assumed that the engine is operated only by fuel injection from the port injector, as in-cylinder gas temperature during port injection,
In-cylinder in-cylinder gas temperature calculating means for calculating in-cylinder gas temperature as in-cylinder injection in-cylinder gas temperature when it is assumed that the engine is operated only by fuel injection from the in-cylinder injector;
Based on the injection ratio, the port injection cylinder temperature and the cylinder injection cylinder temperature, the injection ratio weaving means for calculating the cylinder gas temperature incorporating the effect of the injection ratio;
It is characterized by including.

The fifth invention is the third or fourth invention, wherein
The in-cylinder gas temperature calculation means includes ignition timing weaving means for weaving the influence of the ignition timing on the in-cylinder gas temperature into the in-cylinder gas temperature calculation value.

According to a sixth invention, in any one of the second to fifth inventions,
A flowing gas heat receiving amount calculating means for calculating a flowing gas heat receiving amount received from the flowing gas flowing around the intake valve;
A total heat receiving amount calculating means for calculating a total heat receiving amount received by the intake valve based on the combustion gas heat receiving amount and the flowing gas heat receiving amount;
A temperature change amount calculating means for calculating a temperature change amount of the intake valve based on the total heat receiving amount;
An initial temperature estimating means for estimating an initial temperature of the intake valve;
Further comprising
The intake valve temperature estimation means estimates the temperature of the intake valve based on the initial temperature and the temperature change amount.

The seventh invention is the sixth invention, wherein
A vaporization heat amount calculating means for calculating a vaporization heat amount taken away from the intake valve when the fuel adhering to the intake valve is vaporized;
The total heat receiving amount calculation means is characterized in that a value obtained by subtracting the vaporization heat amount from a heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount is used as the total heat receiving amount.

The eighth invention is the sixth invention, wherein
The intake valve further comprises a contact surface heat receiving amount calculating means for calculating a contact surface heat receiving amount received by transmission from the valve seat,
The total heat receiving amount calculation means is characterized in that a value obtained by adding the contact surface heat receiving amount to a heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount is used as the total heat receiving amount.

According to a ninth invention, in any of the sixth to eighth inventions,
The flowing gas heat receiving amount calculating means includes:
Intake gas heat receiving amount calculating means for calculating an intake gas heat receiving amount generated due to the intake gas flowing from the intake port into the cylinder;
Blow-back heat reception amount calculation means for calculating a blow-back heat reception amount generated due to the blow-back gas flowing backward from the cylinder to the intake port;
A final heat receiving amount calculating means for calculating the flowing gas heat receiving amount based on the intake gas heat receiving amount and the blow back heat receiving amount;
It is characterized by including.

According to a tenth invention, in any one of the first to ninth inventions,
A fuel injection amount for setting the air-fuel ratio in the cylinder to the target air-fuel ratio by estimating the behavior of the fuel adhering to the intake valve based on the temperature of the intake valve estimated by the intake valve temperature estimating means An injection amount calculating means for calculating

  According to the first invention, the temperature of the intake valve of the internal combustion engine can be estimated based on the injection ratio that is the ratio between the fuel injection amount from the port injector and the fuel injection amount from the in-cylinder injector. In an internal combustion engine having both a port injector and an in-cylinder injector, the injection ratio affects the intake valve temperature. According to the first aspect, since the influence of the injection ratio can be taken into consideration, the temperature of the intake valve can be estimated with high accuracy.

  According to the second invention, it is possible to calculate the amount of combustion gas heat received by the intake valve from the combustion gas in the cylinder based on the injection ratio. The injection ratio particularly affects the amount of combustion gas received among various amounts of heat received by the intake valve. According to the second aspect of the invention, the influence of the injection ratio can be accurately reflected in the amount of heat received by the combustion gas, and as a result, the intake valve temperature can be calculated with higher accuracy.

  According to the third aspect, the in-cylinder gas temperature can be calculated based on the injection ratio, and the combustion gas heat receiving amount can be calculated based on the in-cylinder gas temperature. For this reason, when calculating the amount of heat received from the combustion gas, the influence of the injection ratio on the in-cylinder gas temperature can be accurately reflected. Therefore, the intake valve temperature can be calculated with higher accuracy.

  According to the fourth aspect of the invention, the in-cylinder gas temperature at the time of port injection when it is assumed that the engine is operated only by port injection, and the in-cylinder at the time of in-cylinder injection when it is assumed that the engine is operated only by in-cylinder injection The gas temperature can be calculated, and the in-cylinder gas temperature can be calculated based on the calculated value and the injection ratio. Therefore, it is possible to calculate the in-cylinder gas temperature by accurately incorporating the influence of the injection ratio.

  According to the fifth aspect, the influence of the ignition timing on the in-cylinder gas temperature can be factored into the calculated in-cylinder gas temperature. For this reason, the influence by the change of the ignition timing can be taken into consideration, and the in-cylinder gas temperature can be calculated with higher accuracy.

  According to the sixth aspect of the invention, it is possible to calculate the amount of flowing gas heat received by the intake valve from the flowing gas flowing therearound, and calculate the total amount of heat received based on the amount of flowing gas received and the amount of combustion gas received. be able to. Therefore, according to the sixth aspect, the influence of the flowing gas can be accurately reflected in the intake valve temperature, and the intake valve temperature can be estimated with higher accuracy.

  According to the seventh aspect, the influence of the heat of vaporization generated when the fuel adhering to the intake valve is vaporized can be reflected in the temperature of the intake valve.

  According to the eighth aspect of the invention, the influence of the contact surface heat received by the intake valve from the valve seat can also be reflected in the temperature of the intake valve.

  According to the ninth aspect of the invention, the intake gas heat receiving amount due to the intake gas flowing from the intake port into the cylinder and the blow back heat receiving amount due to the blow back from the cylinder are distinguished and calculated, A flowing gas heat receiving amount can be calculated. For this reason, according to the ninth aspect, the amount of flowing gas heat can be calculated with high accuracy, and as a result, the temperature of the intake valve can be estimated with higher accuracy.

  According to the tenth aspect, by estimating the behavior of the fuel adhering to the intake valve based on the estimated intake valve temperature, the fuel injection amount for making the in-cylinder air-fuel ratio the target air-fuel ratio can be accurately determined. Can be calculated. For this reason, the air-fuel ratio in the cylinder can be controlled with high accuracy even in a warm-up process or a transient operation state.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system according to the first embodiment of the present invention includes an internal combustion engine 10. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10.

  An air flow meter 16 for detecting an intake air amount Ga is disposed in the intake passage 12. A throttle valve 18 is disposed downstream of the air flow meter 16. Further, a port injector 20 for injecting fuel into the intake port is disposed further downstream of the throttle valve 18. Further, the internal combustion engine 10 is provided with an in-cylinder injector 23 for injecting fuel directly into the in-cylinder 22.

  The internal combustion engine 10 includes an intake valve 24 for controlling a conduction state between the intake passage 12 and the cylinder 22. A variable valve mechanism 26 is connected to the intake valve 24 as a drive source. The variable valve mechanism 26 can open and close the intake valve 24 while appropriately changing the valve opening timing, the operating angle, and the lift amount.

  An exhaust valve 28 is disposed between the cylinder 22 and the exhaust passage 14. A variable valve mechanism 30 is connected to the exhaust valve 28 as a drive source. The variable valve mechanism 30 can open and close the exhaust valve 28 while appropriately changing the valve opening timing, the operating angle, and the lift amount.

  In the system of this embodiment, as described above, the intake valve 24 and the exhaust valve 28 are driven by the variable valve mechanisms 26 and 30, respectively, but the mechanism for driving them is not limited to this. Absent. That is, in the system of the present embodiment, the intake valve 24 and the exhaust valve 28 may be driven by a normal cam mechanism.

  The internal combustion engine 10 is equipped with a rotation angle sensor 32 for detecting the engine speed Ne, a water temperature sensor 34 for detecting the cooling water temperature Tw, and an intake pressure sensor 36 for detecting the intake pipe pressure Pm. Yes. The system of this embodiment includes an ECU (Electronic Control Unit) 40. The ECU 40 is supplied with outputs from various sensors including the air flow meter 16 and the rotation angle sensor 32. The ECU 40 can control various actuators including the port injector 20, the in-cylinder injector 23, and the variable valve mechanisms 26 and 30 based on the sensor outputs.

  In such an internal combustion engine 10, fuel can be supplied to each cylinder from one or both of the port injector 20 and the in-cylinder injector 23 in accordance with operating conditions. In the following description, the ratio between the fuel injection amount from the port injector 20 (hereinafter referred to as “port injection amount”) and the fuel injection amount from the in-cylinder injector 23 (hereinafter referred to as “in-cylinder injection amount”). Is represented by a spraying ratio α. The injection ratio α is a ratio of the port injection amount when the total injection amount is 1. That is, the ratio between the port injection amount and the in-cylinder injection amount is represented by α: (1−α).

  The ECU 40 stores a map that defines the relationship between the operating conditions represented by the air-fuel ratio A / F, the engine speed Ne, the load KL, and the like, and the optimal injection ratio α under the operating conditions. Yes. The ECU 40 determines the injection division rate α according to the map, and calculates the port injection amount and the in-cylinder injection amount based on the injection division rate α.

[Intake Valve Temperature Estimation Method in Embodiment 1]
During operation of the internal combustion engine 10, part of the fuel injected from the port injector 20 adheres to the outside of the intake valve 24. The fuel adhering to the outside of the intake valve 24 gradually evaporates into the intake port and flows into the cylinder 22 with a delay. When the internal combustion engine 10 is in a steady operation state, the amount of fuel newly adhering to the intake valve 24 and the amount of fuel evaporating from the intake valve 24 are balanced, and the amount of fuel flowing into the cylinder 22 is determined by the port injector. 20 equal to the amount of fuel injected.

  However, when the internal combustion engine is in a warm-up process or in a transient operation state, the amount of fuel adhering to the intake valve 24 increases or decreases. For this reason, a deviation occurs between the amount of fuel flowing into the cylinder 22 and the amount of fuel injected from the port injector 20. Therefore, in order to accurately control the air-fuel ratio in the cylinder 22, it is required to accurately grasp the amount of fuel flowing into the cylinder 22 in consideration of the behavior of the fuel adhering to the intake valve 24. The

  In order to accurately estimate the behavior of the fuel adhering to the intake valve 24, that is, the ratio between the amount of fuel evaporated from the intake valve 24 and the amount of fuel remaining in the intake valve 24, the temperature of the intake valve 24 is accurately estimated. It is necessary to. In view of this, the system of the present embodiment estimates the temperature of the intake valve 24 by the method described below.

  2A and 2B are diagrams for explaining the principle by which the system of the present embodiment calculates the temperature Tv of the intake valve 24. FIG. More specifically, FIG. 2 (A) is a diagram for explaining the thermal environment of the intake valve 24 during valve closing. FIG. 2B is a view for explaining the thermal environment of the intake valve during valve opening.

  Symbols Qb, Qs, and Qf shown in FIG. 2A indicate the combustion gas heat reception amount, the contact surface heat reception amount, and the fuel vaporization heat amount, respectively. The combustion gas heat reception amount Qb is the amount of heat given from the combustion gas in the cylinder 22 to the intake valve 24. The contact surface heat receiving amount Qs is the amount of heat transferred to the intake valve 24 from the mechanical contact surface with the valve seat. Further, the fuel vaporization heat quantity Qf is a heat quantity taken away when the fuel adhering to the intake valve 24 is vaporized. As shown in FIG. 2A, during the closing of the intake valve 24, the above-described three types of heat are mainly transferred between the intake valve 24 and its surroundings.

  Symbols Qgin and Qgback shown in FIG. 2B indicate the intake gas heat reception amount and the blowback heat reception amount that are generated when the intake valve 24 is opened. The intake gas heat receiving amount Qgin is the amount of heat transferred between the fresh air flowing into the cylinder 22 from the intake port and the intake valve 24. On the other hand, the blowback heat reception amount Qgback is a heat reception amount generated due to the blowback gas flowing backward from the cylinder 22 to the intake port while the intake valve 24 is opened. As shown in FIG. 2B, during the opening of the intake valve 24, these two types of heat are mainly transferred between the intake valve 24 and its surroundings. Hereinafter, these heat reception amounts are collectively referred to as “fluid gas heat reception amount”.

  The temperature of the intake valve 24 rises by absorbing heat from the surrounding environment, and falls by releasing heat to the surrounding environment. For this reason, if the initial temperature of the intake valve 24 is known, it is possible to estimate the temperature of the intake valve 24 by detecting the total amount of heat received thereafter. And in order to perform the estimation with high accuracy, it is effective to detect the five types of heat amounts described above with high accuracy. In particular, since the flowing gas heat receiving amounts Qgin and Qgback shown in FIG. 2B vary greatly depending on the operating state of the internal combustion engine 10, the values are accurate to estimate the intake valve temperature Tv with high accuracy. It is important to ask for.

  Therefore, in the present embodiment, based on the operating state of the internal combustion engine 10, three types of heat receiving amounts Qb, Qs, Qf shown in FIG. 2A and flowing gas heat receiving amounts Qgin, Qgback shown in FIG. Are calculated separately, and the total amount of heat received by the intake valve 24 is accurately calculated by integrating them. Then, the intake valve temperature Tv is accurately estimated based on the total amount of heat received thus calculated.

  In the internal combustion engine 10, when other operating conditions are the same, the case where the operation is performed by the fuel injection only from the in-cylinder injector 23 is the case where the operation is performed by the fuel injection only from the port injector 20. The gas temperature in the cylinder 22 is lowered. One reason for this is that in the case of in-cylinder direct injection, the in-cylinder air is efficiently cooled by the latent heat of vaporization of the fuel acting directly on the inside of the cylinder. Another reason for this is that the direct cylinder injection operation has higher thermal efficiency than the port injection operation, and heat is converted into work (engine output) at a higher rate. It is because the rise of the is suppressed.

  The in-cylinder gas temperature in the internal combustion engine 10 approaches the value when operating only by port injection as the injection ratio α increases. That is, the in-cylinder gas temperature becomes high. On the contrary, the in-cylinder gas temperature in the internal combustion engine 10 approaches the value when operating only by in-cylinder direct injection as the injection ratio α is smaller. That is, the in-cylinder gas temperature is lowered. If the in-cylinder gas temperature is different, the combustion gas heat receiving amount Qb and the like are also different, so the intake valve temperature Tv is also different.

  Thus, in the internal combustion engine 10 provided with both the port injector 20 and the in-cylinder injector 23, the intake valve temperature Tv also depends on the injection ratio α. Therefore, in the present embodiment, the intake valve temperature Tv is estimated with higher accuracy by taking into account the influence of the injection ratio α.

[Specific Processing in Embodiment 1]
FIG. 3 is a flowchart of a routine executed in the present embodiment in order to realize the above function. The routine shown in FIG. 3 is started when the internal combustion engine 10 starts. Here, first, the coolant temperature Tw at that time is set as the initial value of the intake valve temperature Tv (step 101). When the internal combustion engine 10 is stopped for a sufficiently long time, the intake valve temperature Tv converges to the temperature of the internal combustion engine 10, that is, the cooling water temperature Tw. For this reason, when the internal combustion engine 10 is started, the process of step 101 can be performed to accurately estimate the intake valve temperature Tv.

  Next, various parameters representing the current state of the internal combustion engine 10 are measured (step 102). Specifically, in addition to the intake air amount Ga, the engine speed Ne, the engine load KL, and the air-fuel ratio A / F, the state of the variable valve mechanism 26 (the valve opening timing VT of the intake valve 24, the lift amount) VL and working angle Vθ) are detected. As the air-fuel ratio A / F, a target air-fuel ratio value set by the ECU 40 or an exhaust air-fuel ratio value detected by an air-fuel ratio sensor (not shown) arranged in the exhaust passage 14 can be used. .

  Subsequent to the process of step 102, the value of the ejection ratio α is acquired (step 103). As described above, the ECU 40 stores a map that defines the relationship between the operating conditions such as the air-fuel ratio A / F, the engine speed Ne, the load KL, and the injection ratio α. Here, by comparing the map with the operating condition detected in step 102, the injection division ratio α is acquired.

  Next, the temperature (representative temperature) Tc of the gas in the cylinder 22 is calculated by the method described below (step 104). The in-cylinder gas temperature Tc is used as a basis for obtaining the combustion gas heat receiving amount Qb and the like as will be described later.

In the present embodiment, first, the in-cylinder gas temperature Tc1 during port injection and the in-cylinder gas temperature Tc2 during cylinder injection are calculated. Here, the in-cylinder gas temperature Tc1 at the time of port injection is an in-cylinder gas temperature when it is assumed that the engine is operated only by fuel injection from the port injector 20, and the in-cylinder gas temperature Tc2 at the time of in-cylinder injection is This is the in-cylinder gas temperature when it is assumed that the engine is operated only by fuel injection from the inner injector 23. In the present embodiment, the in-cylinder gas temperature Tc1 during port injection and the in-cylinder gas temperature Tc2 during in-cylinder injection are respectively calculated by the following arithmetic expressions.
Tc1 = K1 * A / F + K2 * Ne + K3 * KL + K4 * Ga (1)
Tc2 = K5 * A / F + K6 * Ne + K7 * KL + K8 * Ga (2)

  In the above equations (1) and (2), A / F is the air-fuel ratio, Ne is the engine speed, Ga is the intake air amount, and K1 to K8 are predetermined coefficients.

  The values of the coefficients K1 to K8 are determined in advance for each combustion mode of the internal combustion engine 10, and these values are stored in the ECU 40. Here, the combustion mode of the internal combustion engine 10 will be described. The internal combustion engine 10 of the present embodiment switches from the stoichiometric air-fuel ratio (or rich air-fuel ratio) to an extremely lean air-fuel ratio by switching to the four combustion modes of stoichiometric combustion mode, homogeneous lean combustion mode, weak stratified combustion mode, and stratified combustion mode. It is possible to operate at a wide air-fuel ratio up to the fuel ratio.

  In the stoichiometric combustion mode, an operation is performed by combustion of an air-fuel mixture in which the entire cylinder is uniformly made to have a stoichiometric air-fuel ratio (or rich air-fuel ratio). At this time, the fuel is injected from one or both of the port injector 20 and the in-cylinder injector 23.

  In the homogeneous lean combustion mode, an operation is performed by combustion of an air-fuel mixture in which the entire cylinder is uniformly made to have a lean air-fuel ratio. In this homogeneous lean combustion mode, a lean air-fuel mixture can be stably burned by the effect of swirl or tumble formed in the cylinder.

  In the weak stratified combustion mode, the fuel injected from the port injector 20 or the fuel injected from the in-cylinder injector 23 during the intake stroke forms a lean and homogeneous air-fuel mixture throughout the cylinder, and also during the compression stroke. By injecting fuel from the in-cylinder injector 23, a rich air-fuel mixture of the stoichiometric air-fuel ratio is locally formed in the vicinity of the spark plug. According to this weakly stratified combustion mode, the entire cylinder can be operated at a leaner air-fuel ratio than in the homogeneous lean combustion mode.

  In the stratified combustion mode, after inhaling air into the cylinder, fuel is injected from the in-cylinder injector 23 during the compression stroke, so that a rich air-fuel mixture of the stoichiometric air-fuel ratio is locally formed in the vicinity of the spark plug. At the same time, an air layer is formed around it. According to this stratified combustion mode, it is possible to perform operation at a leaner air-fuel ratio as a whole in the cylinder than in the weak stratified combustion mode.

  In the ECU 40, the values of the coefficients K1 to K8 adapted for each combustion mode are stored in advance. As described above, when the other operating conditions are the same, the in-cylinder gas temperature Tc1 during port injection is higher than the in-cylinder gas temperature Tc2 during cylinder injection. For this reason, when A / F, Ne, KL, and Ga are the same, the values of the coefficients K1 to K8 are set so that Tc1 is calculated to be larger than Tc2.

  The ECU 40 switches the combustion mode based on a predetermined rule according to the operating condition of the internal combustion engine 10. When obtaining the in-cylinder gas temperature Tc1 during port injection and the in-cylinder gas temperature Tc2 during cylinder injection, first, the values of the coefficients K1 to K8 corresponding to the current combustion mode are acquired. Then, by using the coefficients K1 to K8 and the operating condition parameters acquired in the above step 102, the calculation is performed according to the above equations (1) and (2), so that the in-cylinder gas temperature Tc1 during port injection and the cylinder The in-cylinder gas temperature Tc2 during the internal injection can be calculated.

After the in-cylinder gas temperature Tc1 during port injection and the in-cylinder gas temperature Tc2 during in-cylinder injection are calculated as described above, the in-cylinder gas temperature Tc is then calculated by the following arithmetic expression.
Tc = {α * Tc1 + (1−α) * Tc2} * γ * γ1 (3)

  In the above equation (3), the term {α * Tc1 + (1−α) * Tc2} is obtained by multiplying the in-cylinder gas temperature Tc1 during port injection by the ratio α of the port injection amount and the in-cylinder during in-cylinder injection. This is a term obtained by adding the gas temperature Tc2 multiplied by the ratio (1-α) of the in-cylinder injection amount. By performing such a calculation, the influence of the injection ratio α can be accurately incorporated into the calculated value of the in-cylinder gas temperature Tc. Therefore, according to the above equation (3), it is possible to calculate the accurate in-cylinder gas temperature Tc in consideration of the influence of the injection ratio α. For this reason, in the steps described later, the combustion gas heat receiving amount Qb and the like can be calculated with extremely high accuracy.

  In the above equation (3), γ1 is an ignition timing influence coefficient, and γ is an ignition timing correction coefficient. FIG. 4A is a diagram showing the relationship between the ignition timing influence coefficient γ1 and the average air-fuel ratio A / F of the entire cylinder, and FIG. 4B shows the ignition timing correction coefficient γ and the injection ratio α. It is a figure which shows the relationship. The ECU 40 stores a map corresponding to these relationships. When the calculation of the above equation (3) is performed, the ignition timing influence coefficient γ1 and the ignition timing correction coefficient γ are acquired according to the map.

  As shown in FIG. 4A, the ignition timing influence coefficient γ1 is set to a smaller value as the average air-fuel ratio A / F becomes leaner as the combustion mode is changed. Since the optimum ignition timing varies depending on the average air-fuel ratio A / F, the system according to the present embodiment changes the ignition timing according to the average air-fuel ratio A / F. When the ignition timing changes, the combustion state changes, and the in-cylinder gas temperature Tc also changes. According to the above equation (3), by adding the ignition timing influence coefficient γ1, the influence of the ignition timing change according to the average air-fuel ratio A / F can be accurately reflected in the in-cylinder gas temperature Tc.

  As shown in FIG. 4B, the ignition timing correction coefficient γ is set to a larger value as the injection ratio α is larger, that is, as the port injection ratio is larger. In general, the optimal ignition timing differs between port injection and in-cylinder injection due to various circumstances. For example, in the case of in-cylinder injection, the in-cylinder air can be effectively cooled by the latent heat of vaporization of the fuel, and knocking is less likely to occur. be able to. For this reason, in the system according to the present embodiment, the ignition timing is changed according to the injection ratio α. According to the above equation (3), by adding the ignition timing correction coefficient γ, it is possible to accurately reflect the influence of the ignition timing change according to the injection ratio α on the in-cylinder gas temperature Tc.

  As described above, according to the above equation (3), the influence of the change of the ignition timing is accurately reflected in the in-cylinder gas temperature Tc by including the ignition timing influence coefficient γ1 and the ignition timing correction coefficient γ. Can be made. For this reason, in the present embodiment, a very accurate in-cylinder gas temperature Tc can be obtained.

  According to the routine shown in FIG. 3, following the process of step 104, it is determined whether or not the amount of blowback caused by opening the intake valve 24 is larger than the determination value α (step 105). The blowback amount can be estimated based on the state of the internal combustion engine 10, specifically, for example, based on the load KL of the internal combustion engine 10, the valve overlap amount VOL, the engine speed NE, and the like.

  FIGS. 5A to 5C are diagrams showing the relationship between the blowback amount, the load KL, the valve overlap VOL, and the engine speed NE. In the present embodiment, the ECU 40 stores a map corresponding to these relationships. In step 105, the map is referenced to estimate the amount of blow-back that is predicted to occur under the current situation, and it is further determined whether the estimated value is greater than a predetermined determination value α.

  The determination value α is a value for determining whether or not it is necessary to consider the blow back heat reception amount Qgback when obtaining the flowing gas heat reception amount. That is, it is a value for judging whether or not a large amount of blowback has occurred, and it is necessary to consider the blowback heat reception amount Qgback. Therefore, when it is recognized that the blowback amount> α is not satisfied, that is, when the blowback amount is equal to or less than the determination value α, it can be determined that it is not necessary to consider the influence of the blowback when estimating the flowing gas heat receiving amount. In this case, after calculating the intake gas heat receiving amount Qgin, the value is directly used as the flowing gas heat receiving amount (step 106). Hereinafter, the flowing gas heat receiving amount obtained here will be represented by the sign “Qg”.

  On the other hand, if it is determined in step 105 that the blowback amount> α is established, it can be determined that the influence of the blowback needs to be taken into account when obtaining the flowing gas heat receiving amount. In this case, the intake gas heat receiving amount Qgin and the blow back heat receiving amount Qgback are calculated, and the sum of these is set as the flowing gas heat receiving amount (step 107). Hereinafter, the flowing gas flow heat quantity obtained here will be denoted by the sign “Qg ′”.

(Example of calculation method for intake gas heat reception Qgin)
The intake gas heat receiving amount Qgin described above can be calculated by, for example, the following arithmetic expression.
Qgin = hgin ・ (Tin−Tv) ・ dtin
hgin = 0.0404 ・ (kg / Dv) ・ Revin ^0.868・ (Dv / liftv) ^0.275
Revin = (ρg ・ Ug ・ Dv) / μg (4)

  However, in the upper equation, hgin is a heat transfer coefficient and can be obtained by the intermediate equation. Further, Tin is the temperature of the intake gas, Tv is the intake valve temperature, and dtin is the time during which the intake gas is circulating around the intake valve 24. Tin can be substituted by the intake air temperature. As the Tv, an estimated value of the current intake valve temperature can be used. Dtin can be obtained based on the engine speed Ne, the lift amount VL of the intake valve 24, the operating angle Vθ, and the like.

  In the middle equation, kg is the heat transfer coefficient of the intake gas, and Dv is the diameter of the intake valve 24. These are all known values. Further, liftv is the lift amount of the intake valve 24 and can be detected from the state of the variable valve mechanism 26 in the present embodiment. Revin is a value defined by the lower equation.

  In the lower equation, ρg is the gas density of the intake port, and Ug is the gas flow rate of the intake port. ρg and Ug can be calculated by a known method based on the temperature of the intake port, the intake air amount Ga, the intake pipe pressure Pm, and the like. Further, μg is a viscosity coefficient of the suction gas, and is a known value. Therefore, the intake gas heat receiving amount Qgin can be obtained by calculation using the above equation (4).

(Example of calculation method for blowback heat reception Qgback)
The blow back heat receiving amount Qgback can be calculated by, for example, the following arithmetic expression.
Qgback = hgback ・ (Tback−Tv) ・ dtback
hgback = 1.2 · (kg / liftv) · Revback ^0.38 · (2 · liftv / Dv) ^0.62
Revback = (ρg ・ Ug ・ liftv) / μg (5)

  However, in the upper equation, hgback is a heat transfer coefficient and can be obtained by the intermediate equation. Tback is the temperature of the blowback gas, and dtback is the time during which blowback occurs around the intake valve 24. Tback can be substituted by the in-cylinder gas temperature Tc. Further, dtback can be obtained based on the engine speed Ne, the valve opening timing VT of the intake valve 24, the lift amount VL, the working angle Vθ, and the like.

  In the middle equation, kg is the heat transfer coefficient of the blown-back gas, and Dv is the diameter of the intake valve 24. These are all known values. Further, liftv is the lift amount of the intake valve 24 and can be detected from the state of the variable valve mechanism 26 in the present embodiment. Revback is a value defined by the lower equation.

  In the lower equation, ρg is the gas density of the intake port, and Ug is the gas flow rate of the intake port. ρg and Ug can be calculated by a known method based on the temperature of the intake port, the intake air amount Ga, the intake pipe pressure Pm, and the like. Further, μg is a viscosity coefficient of the suction gas, and is a known value. For this reason, the blow-back heat receiving amount Qgback can be obtained by calculation using the above equation (5).

  The flowing gas heat receiving amount Qg to be obtained in the step 106 can be calculated by using the above equation (4). Further, the flowing gas heat receiving amount Qg ′ to be obtained in step 107 can be obtained by adding the calculation result of the above formula (4) and the calculation result of the above formula (5). In this way, the flowing gas heat receiving amount can be calculated by calculation both when the influence of blowback is not taken into account (Qg) and when the influence is taken into account (Qg ′).

(Examples of other calculation methods for fluid gas heat received Qg, Qg ')
However, the method for obtaining the flowing gas heat receiving amounts Qg and Qg ′ is not limited to the method using the arithmetic expression as described above. That is, the flowing gas heat receiving amount Qg that does not consider the influence of blowback can be mapped in advance using the engine speed Ne, the engine load KL, the valve opening timing VT of the intake valve 24, and the like as parameters. Similarly, it is possible to map the flowing gas heat receiving amount Qg ′ in consideration of the blowback effect in advance. For this reason, after these maps are stored in the ECU 40 in advance, in steps 106 and 107, the flow gas heat receiving amount Qg or Qg ′ may be obtained by referring to these maps.

(Calculation of contact surface heat reception Qs)
In the routine shown in FIG. 3, the contact surface heat receiving amount Qs is then calculated (step 108). The contact surface heat receiving amount Qs can be calculated by, for example, an arithmetic expression shown below.
Qs = hs ・ (Tvs−Tv) ・ dts
hs = 4130 · (Pm / 50000) ^0.6 (6)

  However, in the upper equation, hs is a heat transfer coefficient and can be obtained by the lower equation. Tvs is the temperature of the valve seat, and can be substituted by the cooling water temperature Tw. Dts is the time during which the intake valve 24 is seated on the valve seat, and can be calculated based on the engine speed Ne and the operating angle Vθ of the intake valve 24 here. Pm in the lower equation is the intake pipe pressure.

  The contact surface heat receiving amount Qs can be obtained by calculation using the state of the internal combustion engine 10 as a parameter by using the above equation (6). Therefore, in step 108, the contact surface heat receiving amount Qs can be accurately obtained.

  However, the method for obtaining the contact surface heat receiving amount Qs is not limited to the method using the arithmetic expression as described above. That is, the amount of heat per unit time that the intake valve 24 receives from the valve seat is a value that is almost uniquely determined with respect to the difference ΔT between the valve seat temperature and the intake valve temperature Tv. The time during which the intake valve 24 is seated on the valve seat is a function of the engine speed Ne and the operating angle Vθ of the intake valve 24. For this reason, the contact surface heat receiving amount Qs can be mapped in advance using the temperature difference ΔT, the engine speed Ne, and the operating angle Vθ as parameters. Therefore, in step 108, the contact surface heat receiving amount Qs may be obtained based on the map.

(Calculation of fuel vaporization heat quantity Qf)
Next, in the routine shown in FIG. 3, the fuel vaporization heat quantity Qf is calculated (step 109). The fuel vaporization heat quantity Qf can be calculated by, for example, an arithmetic expression shown below.
Qf = mf · {(Tv−Tf) · Cpf + Hf} · dtf (7)

  In the above equation (7), mf is the fuel evaporation amount. The fuel evaporation amount mf can be obtained based on the amount of fuel injected toward the intake valve 24 (port injection amount), the intake valve temperature Tv, the intake pipe pressure Pm, and the like. Tf is the fuel temperature, and the value can be approximated by a fixed value corresponding to the cooling water temperature at the start, for example. Cpf is the specific heat of fuel, and Hf is the latent heat of fuel vaporization. Any of these can be treated as default values. Dtf is a time to be considered as the fuel vaporization period, and can be set here as a function of the engine speed Ne.

  The fuel vaporization heat quantity Qf can be obtained by calculation using the state of the internal combustion engine 10 as a parameter by using the above equation (7). Therefore, in step 109, the fuel vaporization heat quantity Qf can be accurately obtained.

  However, the method for obtaining the fuel vaporization heat quantity Qf is not limited to the method using the arithmetic expression as described above. That is, the fuel vaporization heat quantity Qf can be mapped in advance using the port injection quantity and the intake valve temperature Tv as parameters. Therefore, in step 109, the fuel vaporization heat quantity Qf may be obtained by referring to the map.

(Calculation of combustion gas heat received Qb)
In the routine shown in FIG. 3, next, the combustion gas heat receiving amount Qb is calculated (step 110). The combustion gas heat receiving amount Qb can be calculated by, for example, an arithmetic expression shown below.
Qb = hb ・ (Tc−Tv) ・ dtb
hb = 0.013 · Dc ^−0.2 · Pc ^0.8 · Uc ^0.8 · Tc ^−0.53 (8)

  However, in the upper equation, hb is a heat transfer coefficient and can be obtained by the lower equation. In the upper and lower equations, Tc is the in-cylinder gas temperature described above. In the upper equation, dtb is the time during which the temperature of the combustion gas acts on the intake valve 24, and can be calculated based on the engine speed Ne here.

  In the lower equation, Dc is the cylinder diameter and can be treated as a predetermined value. Pc is the in-cylinder pressure, and can be measured by, for example, an in-cylinder pressure sensor. Uc is the gas flow velocity in the cylinder 22 and can be estimated by a known method based on the operating state of the internal combustion engine 10.

  In this step 110, using the in-cylinder gas temperature Tc calculated in the above step 104, the combustion gas heat receiving amount Qb is calculated according to the above equation (8). As described above, the in-cylinder gas temperature Tc used here is a value calculated accurately in consideration of the influence of the injection ratio α. Therefore, according to the processing in step 110, it is possible to obtain an accurate combustion gas heat receiving amount Qb that takes into consideration the influence of the injection ratio α.

  However, the method for obtaining the combustion gas heat receiving amount Qb is not limited to the method using the arithmetic expression including the in-cylinder gas temperature Tc as described above. That is, the combustion gas heat receiving amount Qb is preliminarily mapped by using the operating conditions such as the engine speed Ne, the engine load KL, the valve opening timing VT of the intake valve 24, the fuel injection amount, and the injection ratio α as parameters. It is possible to make it. Therefore, in step 110, the combustion gas heat receiving amount Qb may be obtained with reference to the map.

(Renewal of intake valve temperature Tv)
When the above process is completed, an update process for the intake valve temperature Tv is then performed (step 111). Specifically, first, the total heat receiving amount (Qg or Qg ′ + Qs−Qf + Qb) of the intake valve 24 is calculated based on all the heat receiving amounts obtained in the current processing cycle. Next, the total amount of heat received is divided by the specific heat of the intake valve 24 (assumed to be known), thereby calculating a temperature change ΔTv generated during the current processing cycle. Finally, by adding ΔTv to the current intake valve temperature Tv, the intake valve temperature Tv is updated to the latest value.

(Calculation of fuel injection amount and execution of fuel injection)
Once the latest intake valve temperature Tv is obtained as described above, the amount of fuel evaporated from the intake valve 24 and the amount of fuel remaining in the intake valve 24 in the current operation cycle is next based on the intake valve temperature Tv. Are calculated (step 112). This calculation process can be performed using, for example, a known fuel behavior model represented by the adhesion rate / residual rate.

  When the fuel amount evaporated from the intake valve 24 and the fuel amount remaining in the intake valve 24 are calculated, the fuel amount to be injected from the port injector 20 and the in-cylinder injector 23 is then calculated based on those values. (Step 113). Specifically, first, the amount of fuel that needs to be supplied to the cylinder 22 in order to make the air-fuel ratio realized in the cylinder 22 the target air-fuel ratio is calculated. Next, the amount of fuel that needs to be injected from the port injector 20 and the in-cylinder injector 23 to realize the calculated supplied fuel amount is the amount of fuel that evaporates from the intake valve 24 and the fuel that remains in the intake valve 24 After calculating the amount, it is calculated based on a known method. When the port injection amount and the in-cylinder injection amount are calculated in this way, a process of injecting the calculated amounts of fuel from the port injector 20 and the in-cylinder injector 23 is executed (step 114).

  As described above, according to the routine shown in FIG. 3, the amount of heat received that affects the intake valve temperature Tv includes the flow gas received amount Qg or Qg ′, the contact surface received heat amount Qs, the fuel vaporized heat amount Qf, and the combustion gas received amount. It can be divided into heat quantity Qb and estimated individually.

  In particular, the combustion gas heat receiving amount Qb that is easily affected by the injection division rate α can be estimated with high accuracy by reflecting the current injection division rate α.

  According to such an updating method, various phenomena occurring in the internal combustion engine 10 and further the influence of the injection ratio α can be finely reflected in the intake valve temperature Tv, and the estimation accuracy can be sufficiently increased. Can do. For this reason, according to the system of the present embodiment, the intake valve temperature Tv can be estimated with extremely high accuracy.

  Further, in the present embodiment, the flowing gas heat receiving amount Qg or Qg ′ can be estimated by further distinguishing between the case where the influence of the blowback should be considered and the case where it is not necessary to consider. Finally, the intake valve temperature Tv can be updated by integrating the amounts of heat received.

  Then, according to the routine shown in FIG. 3, the amount of fuel evaporated from the intake valve 24 and the amount of fuel remaining in the intake valve 24 are extremely reduced by using the intake valve temperature Tv estimated with such extremely high accuracy. It can be obtained with high accuracy. For this reason, even when the internal combustion engine 10 is in a warm-up process or in a transient operation state, the amount of fuel flowing into the cylinder 22 can be accurately calculated. Therefore, the air-fuel ratio in the cylinder 22 can be accurately controlled even in the warm-up process or the transient operation state.

  By the way, in the first embodiment described above, in estimating the intake valve temperature Tv, in addition to the flowing gas heat reception amount Qg or Qg ′ and the combustion gas heat reception amount Qb, the contact surface heat reception amount Qs and the fuel vaporization heat amount Qf are calculated. However, the estimation method is not limited to this. That is, the influence of the contact surface heat reception amount Qs and the fuel vaporization heat amount Qf on the intake valve temperature Tv is smaller than the influence of the flowing gas heat reception amount Qg or Qg ′ and the combustion gas heat reception amount Qb. May be estimated without considering the contact surface heat reception amount Qs and the fuel vaporization heat amount Qf.

  In the first embodiment described above, the ECU 40 executes the process of step 103, so that the “spout distribution rate acquisition means” in the first invention executes the processes of steps 104, 110 and 111. As a result, the “intake valve temperature estimating means” in the first invention executes the processing of steps 104 and 110, so that the “combustion gas heat receiving amount calculating means” in the second invention executes the processing of step 104. By doing so, the “in-cylinder gas temperature calculating means” in the third aspect of the invention is realized.

  In the first embodiment described above, the ECU 40 executes the calculation of the above equation (1) in the process of step 104, whereby the “port injection cylinder gas temperature calculation means” in the fourth invention is By executing the calculation of the above expression (2) in the process of step 104, the “in-cylinder injection cylinder temperature calculation means” in the fourth invention performs the calculation of the above expression (3) in the process of step 104. When executed, the “split rate weaving means” in the fourth invention and the “ignition timing weaving means” in the fifth invention are realized.

  In the first embodiment described above, the ECU 40 executes the process of step 101, so that the “initial temperature estimation means” in the sixth aspect of the invention executes the process of step 106 or 107. The “fluid gas heat receiving amount calculating means” in the sixth aspect of the invention realizes the “total heat receiving amount calculating means” and the “temperature change amount calculating means” in the sixth aspect of the invention by executing the processing of step 111 described above. ing.

  Furthermore, in the first embodiment described above, the ECU 40 executes the process of step 109, so that the “vaporization heat amount calculating means” in the seventh aspect of the invention executes the process of step 108, thereby executing the eighth step. The “contact surface heat reception amount calculation means” in the invention calculates the intake gas heat reception amount Qgin in step 106, so that the “intake gas heat reception amount calculation means” in the ninth invention calculates the blow back heat reception amount Qgback in step 107. Thus, the “blow-back heat receiving amount calculating means” in the ninth invention calculates the flowing gas heat receiving amount Qg or Qg ′ in step 106 or 107, thereby “final heat receiving amount calculating means” in the ninth invention. However, by executing the processing of steps 112 and 113, the “injection amount calculating means” There are realized respectively.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the method in which the system of Embodiment 1 of this invention calculates intake valve temperature Tv. It is a flowchart of the routine performed in Embodiment 1 of the present invention. (A) is a diagram showing the relationship between the ignition timing influence coefficient γ1 and the average air-fuel ratio A / F of the entire cylinder, and (B) shows the relationship between the ignition timing correction coefficient γ and the injection ratio α. FIG. It is the figure which showed the relationship between the amount of blowbacks, load KL, valve overlap VOL, and engine speed NE.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 20 Port injector 23 In-cylinder injector 24 Intake valve 26, 30 Variable valve mechanism 28 Exhaust valve 40 ECU (Electronic Control Unit)

Claims (10)

A port injector for injecting fuel into the intake port of the internal combustion engine;
An in-cylinder injector for injecting fuel into the cylinder of the internal combustion engine;
An injection ratio acquisition means for acquiring an injection ratio that is a ratio of a fuel injection amount from the port injector and a fuel injection amount from the in-cylinder injector;
An intake valve temperature estimating means for estimating the temperature of the intake valve of the internal combustion engine based on the injection ratio;
An air-fuel ratio control apparatus for an internal combustion engine, comprising:   The intake valve temperature estimation means includes combustion gas heat reception amount calculation means for calculating a combustion gas heat reception amount received by the intake valve from combustion gas in a cylinder based on the injection ratio, and based on the combustion gas heat reception amount 2. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein the temperature of the intake valve is estimated.   The combustion gas heat receiving amount calculating means includes in-cylinder gas temperature calculating means for calculating the temperature of the in-cylinder gas based on the injection ratio, and calculating the combustion gas heat receiving amount based on the in-cylinder gas temperature. 3. An air-fuel ratio control apparatus for an internal combustion engine according to claim 2, wherein The in-cylinder gas temperature calculating means includes
In-cylinder gas temperature calculation means for port injection that calculates the in-cylinder gas temperature when it is assumed that the engine is operated only by fuel injection from the port injector, as in-cylinder gas temperature during port injection,
In-cylinder in-cylinder gas temperature calculating means for calculating in-cylinder gas temperature as in-cylinder injection in-cylinder gas temperature when it is assumed that the engine is operated only by fuel injection from the in-cylinder injector;
Based on the injection ratio, the port injection cylinder temperature and the cylinder injection cylinder temperature, the injection ratio weaving means for calculating the cylinder gas temperature incorporating the effect of the injection ratio;
The air-fuel ratio control apparatus for an internal combustion engine according to claim 3, comprising:   5. The internal combustion engine engine according to claim 3, wherein the in-cylinder gas temperature calculating means includes ignition timing weaving means for weaving the influence of the ignition timing on the in-cylinder gas temperature into the in-cylinder gas temperature calculation value. Fuel ratio control device. A flowing gas heat receiving amount calculating means for calculating a flowing gas heat receiving amount received from the flowing gas flowing around the intake valve;
A total heat receiving amount calculating means for calculating a total heat receiving amount received by the intake valve based on the combustion gas heat receiving amount and the flowing gas heat receiving amount;
A temperature change amount calculating means for calculating a temperature change amount of the intake valve based on the total heat receiving amount;
An initial temperature estimating means for estimating an initial temperature of the intake valve;
Further comprising
The internal combustion engine according to any one of claims 2 to 5, wherein the intake valve temperature estimation means estimates the temperature of the intake valve based on the initial temperature and the temperature change amount. Air-fuel ratio control device. A vaporization heat amount calculating means for calculating a vaporization heat amount taken away from the intake valve when the fuel adhering to the intake valve is vaporized;
7. The total heat receiving amount calculating means, wherein the total heat receiving amount is a value obtained by subtracting the vaporization heat amount from a heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount. An air-fuel ratio control apparatus for an internal combustion engine. The intake valve further comprises a contact surface heat receiving amount calculating means for calculating a contact surface heat receiving amount received by transmission from the valve seat,
The total heat receiving amount calculation means uses the value obtained by adding the contact surface heat receiving amount to the heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount as the total heat receiving amount. The air-fuel ratio control apparatus for an internal combustion engine according to claim 6. The flowing gas heat receiving amount calculating means includes:
Intake gas heat receiving amount calculating means for calculating an intake gas heat receiving amount generated due to the intake gas flowing from the intake port into the cylinder;
Blow-back heat reception amount calculation means for calculating a blow-back heat reception amount generated due to the blow-back gas flowing backward from the cylinder to the intake port;
A final heat receiving amount calculating means for calculating the flowing gas heat receiving amount based on the intake gas heat receiving amount and the blow back heat receiving amount;
The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 6 to 8, characterized by comprising:   A fuel injection amount for setting the air-fuel ratio in the cylinder to the target air-fuel ratio by estimating the behavior of the fuel adhering to the intake valve based on the temperature of the intake valve estimated by the intake valve temperature estimating means The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 9, further comprising injection amount calculation means for calculating

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