JP2011001848A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in an internal combustion engine using fuel containing alcohol, wherein when the temperature of an intake port, an intake valve or a combustion chamber exceeds a boiling-point temperature of alcohol, adhering alcohol component in fuel suddenly evaporates to cause over-rich state of air-fuel mixture, resulting in worsening of emission.SOLUTION: The internal combustion engine using fuel containing alcohol includes: a temperature computing means for computing an intake valve shade part temperature tin; and a control parameter changing means for changing an intake valve shade part temperature increment correction coefficient kin which is a coefficient of increment of fuel injection amount with reference to the intake valve shade part temperature tin. When it is diagnosed that the intake valve shade part temperature tin based on a variation ΔA/F of an air-fuel ratio correlation value detected by an air-fuel ratio correlation value detecting means is above the boiling-point temperature of alcohol, the intake valve shade part temperature increment correction coefficient kin is set smaller to reduce an increment of the fuel injection amount TAU.

Description

  The present invention relates to a control device for an internal combustion engine that uses a fuel containing alcohol.

  In order to save petroleum resources, a mixed fuel in which alcohol such as methanol or ethanol is mixed with gasoline at a certain ratio is used as a fuel for an internal combustion engine for automobiles.

  Alcohol has a very low evaporation characteristic in a low temperature range compared to gasoline, but has a characteristic of evaporating rapidly when the boiling point temperature is exceeded. In the mixed fuel containing alcohol, a part of the alcohol injected from the fuel injection valve leaks from the gap between the piston and the cylinder to the crankcase side without being vaporized and mixed into the engine oil. In such a case, alcohol in the engine oil evaporates as the oil temperature rises, and is returned to the intake system together with blow-by gas. On the other hand, as the oil temperature rises, the evaporation rate of alcohol in the engine oil increases rapidly as it approaches the boiling point temperature of the alcohol. As a result, when the air-fuel ratio of the air-fuel mixture becomes rich, there is a possibility that it deviates from the exhaust purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system, and harmful components in the exhaust gas increase. On the other hand, the conventional feedback control is applied to control the air-fuel ratio so as to absorb the increased amount of the air-fuel ratio deviation by lowering the lower limit value of the feedback correction range (for example, Patent Documents 1 to 3). 3).

Japanese Patent No. 2860719 (Patent Document 1)
Japanese Laid-Open Patent Publication No. 61-53429 (Patent Document 2)
Japanese Laid-Open Patent Publication No. 7-27004 (Patent Document 3)
The above prior art relates to the evaporation of alcohol in engine oil. On the other hand, when fuel containing alcohol is injected from the fuel injection valve, the fuel adhered to the port wall surface, the intake valve, the combustion chamber, etc. Changes in combustion due to air-fuel ratio roughness (fluctuation) due to the degree of evaporation of the alcohol component contained in the air and the mixing of the alcohol component itself mixed with the intake air, or deterioration of exhaust emission becomes a problem. In general, as a technology related to an internal combustion engine that uses gasoline as a fuel, there is a technology that suppresses rough air-fuel ratio by low temperature increase correction at low engine temperature or transient increase correction at transient time. However, when the operation of the internal combustion engine is continued and the fuel containing alcohol becomes higher than the boiling point temperature of the alcohol as the intake system temperature rises, the alcohol component of the mixed fuel adhering to the intake system, the alcohol component of the mixed fuel and the intake air The alcohol component that is mixed and mixed evaporates rapidly. As a result, in the control in which the low temperature increase correction and the transient increase correction are performed gradually (slowly) as the engine temperature rises in the same manner as a gasoline engine despite the use of a mixed fuel containing alcohol, the respective increase corrections are performed. Is not performed with good response, the fuel mixture tends to be over-rich. In the case of various fuels including various fuels as components, such as gasoline, the temperature window in which the fuel easily evaporates is widely distributed from the low temperature region to the high temperature region because there are many fuel components. As a result, even when the change of each increase correction or the learning correction is gradually performed over a wide temperature range, a response delay or the like hardly occurs. On the other hand, in a fuel with a high ratio of a single fuel such as alcohol, the temperature window is relatively narrow, and the peak value of the evaporation characteristic rises steeply. As a result, when a fuel with a high ratio of a single fuel such as alcohol is used, the control timing is likely to deviate from the engine temperature at which the alcohol actually evaporates if the increase correction is performed in the same manner as various fuels such as gasoline. As a result, when each of the increase corrections cannot be performed with good response, the air-fuel ratio becomes over-rich due to the evaporation of alcohol. As a result, it becomes easier to deviate from the exhaust purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system. As a result, there is a possibility that harmful components in the exhaust gas may increase. Therefore, it is necessary to devise a technique for increasing the purification capacity of the aftertreatment device that performs exhaust purification.

  Also, as in the technique disclosed in Patent Document 3, if an attempt is made to absorb the expansion of the air-fuel ratio deviation by lowering the lower limit value of the feedback correction range, the time required to complete the feedback correction becomes longer, and the feedback Since harmful components in the exhaust gas may increase before the correction is completed, it is necessary to devise measures such as increasing the purification capacity of the aftertreatment device that performs exhaust purification. Also, if the lower limit value of the feedback correction range is lowered, the correction value is difficult to converge and feedback correction may not be completed.

  In view of the above problems, an object of the present invention is to provide a control device for an internal combustion engine that can correct an air-fuel ratio shift due to temperature with good responsiveness when using a fuel with a high ratio of a single fuel. There is a thing.

  The present invention has been made to address the above problems. Specifically, it is a control device for an internal combustion engine that uses a fuel containing a predetermined fuel component, the fuel injection means for injecting fuel into the internal combustion engine, and the engine operating temperature correlation value of the internal combustion engine as the air-fuel ratio. Temperature calculation means obtained by calculation regardless of the control means, control means for controlling the command value of the control parameter of the internal combustion engine with reference to the engine operating temperature correlation value obtained by the temperature calculation means, and discharge from the internal combustion engine An air-fuel ratio correlation value detecting means for detecting the air-fuel ratio correlation value of the exhaust gas, and the engine operating temperature correlation value based on the air-fuel ratio correlation value detected by the air-fuel ratio correlation value detecting means A diagnosis means for diagnosing whether or not the temperature is near a predetermined temperature that is near the boiling point of the engine, and when the engine operating temperature correlation value is diagnosed to be equal to or higher than the predetermined temperature Is control parameter changing means for changing to the command value of the control parameter when the engine operating temperature correlation value is equal to or higher than the predetermined temperature regardless of the engine operating temperature correlation value calculated by the temperature calculating means. And comprising.

  According to this, the engine operation temperature correlation value based on the air-fuel ratio correlation value detected by the air-fuel ratio correlation value detection means is determined by the diagnostic means separately from the engine operation temperature correlation value acquired from the temperature calculation means. A diagnosis is made as to whether or not the temperature is equal to or higher than a predetermined temperature that is near the boiling point of the fuel component. Here, the engine operating temperature correlation value acquired by the temperature calculation means is, for example, the temperature in the intake system of the internal combustion engine such as the intake port, the intake valve, or the combustion chamber, or the cooling water temperature correlated to these temperatures. is there. By diagnosing whether the engine operating temperature correlation value based on the air-fuel ratio correlation value is equal to or higher than a predetermined temperature, whether or not the predetermined fuel component has reached the boiling point temperature is caused by evaporation of the predetermined fuel component More accurate diagnosis can be made from fluctuations in the air-fuel ratio. Further, when it is diagnosed that the engine operating temperature correlation value is equal to or higher than the predetermined temperature, the engine operating temperature correlation value is less than the predetermined temperature regardless of the engine operating temperature correlation value calculated by the temperature calculating means. In this case, the command value of the control parameter in the control unit is changed to the control parameter of the control unit when the temperature is equal to or higher than a predetermined temperature. As a result, the predetermined fuel component adhering to the intake port, the intake valve, the combustion chamber, etc. in the process of increasing the engine operating temperature of the internal combustion engine, or the predetermined fuel component mixed and mixed with the intake air It is possible to prevent the air-fuel ratio from becoming over-rich due to a change in evaporation characteristics. In addition, since the internal combustion engine is controlled by a control parameter that matches the evaporation of a predetermined fuel component, the amount of increase in the air-fuel ratio deviation is reduced by lowering the lower limit value of the feedback correction range. The time required to converge the fuel ratio is shortened, and the feedback correction coefficient does not become difficult to converge. As a result, an increase in harmful components in the exhaust gas due to deviation from an air purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system is suppressed, and the purification ability of the aftertreatment device that purifies the exhaust gas is increased. Is no longer needed.

  Preferably, the control parameter changing means controls the control means when the diagnosis means diagnoses that the engine operating temperature correlation value obtained by the temperature calculation means is equal to or higher than a predetermined temperature. Instead of the engine operating temperature correlation value referred to when the engine operating temperature correlation value is changed to the command value of the control parameter corresponding to the corrected engine operating temperature correlation value obtained by correcting the engine operating temperature correlation value to the predetermined temperature. It may be a thing.

  According to this, apart from the engine operating temperature correlation value acquired from the temperature calculating means, the engine operating temperature or its correlation value is equal to or higher than a predetermined temperature based on the air-fuel ratio correlation value detected by the air-fuel ratio correlation value detecting means. When the diagnosis means diagnoses that it is, the operation temperature or its correlation value is corrected to a predetermined temperature, and control is performed by the control means based on the corrected engine operation temperature or its correlation value. As a result, the control is performed according to the command value of the control parameter suitable for the evaporation of the predetermined fuel component, which is caused by a rapid change in the evaporation characteristic of the fuel in the process of increasing the engine operating temperature of the internal combustion engine. It is suppressed that the air-fuel ratio becomes overrich. As a result, an increase in harmful components in the exhaust gas due to deviation from an air purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system is suppressed, and the purification ability of the aftertreatment device that purifies the exhaust gas is increased. Is no longer needed.

  Preferably, when the engine operating temperature correlation value calculated by the temperature calculating means is equal to or higher than the predetermined temperature, the control parameter changing means is configured to calculate the temperature regardless of the diagnosis result of the diagnostic means. The command value of the control parameter of the internal combustion engine may be controlled with reference to the engine operating temperature correlation value obtained by the means.

  According to this, when the engine operating temperature correlation value calculated by the temperature calculating means becomes equal to or higher than a predetermined temperature, the corrected engine operating temperature correlation value is corrected to the predetermined temperature. Instead, it is changed to the command value of the control parameter corresponding to the engine operating temperature correlation value calculated by the temperature calculating means. As a result, when the engine operating temperature further rises from the vicinity of the boiling point temperature of the predetermined fuel component, control is performed according to the operation temperature calculated by the temperature calculating means or the command value of the control parameter corresponding to the correlation value. Is called. As a result, even when the engine operating temperature further rises from the vicinity of the boiling point temperature of the predetermined fuel component, the control is performed without deviating from the air-fuel ratio that can be purified by exhaust gas, so the increase in harmful components in the exhaust gas is suppressed. There is no need to devise such as increasing the purification capacity of the aftertreatment device for exhaust purification.

  Preferably, the temperature calculation means includes cooling water temperature acquisition means for acquiring a cooling water temperature of the internal combustion engine, and intake air amount acquisition means for acquiring an intake air amount taken in from an intake passage of the internal combustion engine. The temperature calculation means acquires a starting cooling water temperature that is a cooling water temperature at the start of the internal combustion engine by the cooling water temperature acquisition means, and uses the intake air amount acquired by the intake air amount acquisition means as the internal combustion engine. The integrated intake air amount may be obtained by integrating from the starting time, and the temperature of the internal combustion engine or a correlation value thereof may be obtained by calculation based on the integrated intake air amount and the starting cooling water temperature.

  According to this, the engine operating temperature correlation value of the internal combustion engine is estimated from the cooling water temperature at the start and the integrated intake air amount from the start. The temperature of the internal combustion engine at the time of starting is estimated as the cooling water temperature at the time of starting, and by adding an increase in the temperature of the internal combustion engine estimated from the accumulated intake air amount after the starting to this, the engine of the current internal combustion engine An operating temperature correlation value is estimated.

  Preferably, the control means increases the fuel injection amount injected by the fuel injection means when the internal combustion engine is started and / or warmed up according to the engine operation temperature correlation value obtained by the temperature calculation means. The fuel injection amount increasing means may be configured.

  According to this, since the engine operating temperature of the internal combustion engine is low at the start of the internal combustion engine and / or during warm-up, the fuel injection amount is increased in order to improve startability at start-up and stabilize the rotational speed during warm-up. Is called. In the situation where the fuel injection amount is increased in this way, when the temperature of the internal combustion engine becomes equal to or higher than the boiling point temperature of the predetermined fuel component, the intake port and the intake valve are in the process of increasing the engine operating temperature of the internal combustion engine. And the predetermined fuel component adhering to the combustion chamber, etc., or the predetermined fuel component mixed with the predetermined fuel component of the fuel and the intake air, the air-fuel ratio is exceeded due to a sudden change in evaporation characteristics. Become rich. As a result, there is a possibility that harmful components in the exhaust gas deviate from the exhaust purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system, so that the engine operating temperature of the internal combustion engine becomes the boiling point temperature of the predetermined fuel component. In the above case, by reducing the increased fuel injection amount, over-richness is suppressed as compared with the case where control is performed to increase the same fuel as the first fuel under the same conditions. As a result, the increase in harmful components in the exhaust gas due to deviation from the air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system is suppressed, and the purification ability of the aftertreatment device that purifies exhaust gas is increased. Is no longer needed.

1 is a schematic view of an internal combustion engine to which a fuel supply device of the present invention is applied. 3 is a flowchart showing a post-startup fuel injection control routine executed by the ECU of the first embodiment of the present invention. It is a relationship figure showing the relationship between the cooling water temperature which concerns on embodiment of this invention, and an ethanol correction coefficient. It is a relationship figure showing the relationship between the cooling water temperature which concerns on embodiment of this invention, ethanol concentration, and fuel increase amount. It is a relationship figure showing the relationship between the cooling water temperature which concerns on embodiment of this invention, and an acceleration / deceleration increase correction coefficient. It is a relationship figure showing the relationship between the cooling water temperature which concerns on embodiment of this invention, and an acceleration increase correction coefficient. It is a relationship figure showing the relationship between the cooling water temperature which concerns on embodiment of this invention, the integrating | accumulating intake air amount, and the intake valve umbrella part temperature. It is a relationship figure showing the relationship between the intake valve umbrella part temperature which concerns on embodiment of this invention, and an intake valve umbrella part temperature increase correction coefficient. It is the flowchart which showed the flag setting routine which ECU of embodiment of this invention performs. FIG. 5 is a relational diagram showing the relationship between the amount of change in the air-fuel ratio correlation value and the engine load when the intake valve umbrella temperature exceeds the boiling point temperature of ethanol during steady operation of the internal combustion engine according to the embodiment of the present invention. FIG. 5 is a relationship diagram showing a relationship between an engine load and a variation amount of an air-fuel ratio correlation value when an intake valve umbrella temperature exceeds a boiling point temperature of ethanol during acceleration operation of the internal combustion engine according to the embodiment of the present invention. It is a relationship figure showing the relationship between the acceleration which concerns on embodiment of this invention, and the fluctuation amount correction coefficient of the air fuel ratio correlation value of the fluctuation amount of an air fuel ratio correlation value. FIG. 6 is a relationship diagram showing the relationship between the amount of change in the air-fuel ratio correlation value and the engine load when the intake valve umbrella temperature exceeds the boiling point temperature of ethanol during the deceleration operation of the internal combustion engine according to the embodiment of the present invention. It is a relationship figure showing the relationship between the deceleration which concerns on embodiment of this invention, and the fluctuation amount correction coefficient of the air fuel ratio correlation value of an air fuel ratio.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the first embodiment.

  FIG. 1 shows a first internal combustion engine control apparatus (hereinafter also referred to as “first apparatus”) according to an embodiment of the present invention using a spark ignition type, a multi-cylinder, a port injection, and a predetermined fuel component. 1 shows a schematic configuration of a system applied to fuel (here, fuel using ethanol and gasoline) and an internal combustion engine.

  An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the internal combustion engine 11, and an air flow meter 14 (intake air amount acquisition means) for detecting the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 (fuel) for injecting fuel, which will be described later, in the vicinity of the intake port of the intake manifold 20 of each cylinder. Injection means) is attached. A spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 22.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) (air-fuel ratio correlation value detecting means) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying exhaust gas is provided on the downstream side of the gas sensor 24.

  Further, the cylinder block of the engine 11 includes a coolant temperature sensor 26 (cooling water temperature acquisition means) that detects the coolant temperature, and a crank angle sensor 28 that outputs a pulse signal each time the crankshaft 27 of the engine 11 rotates by a predetermined crank angle. Is attached. Based on the output signal of the crank angle sensor 28, the crank angle and the engine speed are detected. Further, the intake air temperature is detected by the intake air temperature sensor 42.

  As the fuel for the engine 11, alcohol such as ethanol or methanol, or a fuel in which alcohol and gasoline are mixed can be used, and fuel containing these alcohols is supplied to the engine 11. The fuel discharged from the fuel pump 31 is sent to the delivery pipe 33 through the fuel pipe 32 and is distributed from the delivery pipe 33 to the fuel injection valve 21 of each cylinder. A filter 34 and a pressure regulator 35 are connected in the vicinity of the fuel pump 31 in the fuel pipe 32, and the discharge pressure of the fuel pump 31 is adjusted to a predetermined pressure by the pressure regulator 35. Is returned to the fuel tank 30 by the fuel return pipe 36.

  Further, the delivery pipe 33 is provided with an alcohol concentration sensor 37 that detects the alcohol concentration (ethanol concentration in this case) of the fuel.

Outputs of the various sensors described above are input to a control circuit (hereinafter referred to as “ECU”) 29. The ECU 29 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 21 according to the engine operating state. The auxiliary fuel injection amount of the injection nozzle 19 and the ignition timing of the spark plug 22 are controlled.
<Outline of control by the first device>
Next, the operation of the first device configured as described above will be described separately.

  The ECU 29 repeatedly executes the fuel injection control routine shown in FIG. 2 every elapse of a predetermined time.

  First, in step 205, the ECU 29 acquires the starting coolant temperature THWS from the coolant temperature sensor 26. The cooling water temperature THWS at the start is acquired in advance at the start of the internal combustion engine.

  Next, the ECU 29 proceeds to step 210 and acquires the coolant temperature THW from the coolant temperature sensor 26.

  Next, the ECU 29 proceeds to step 215 and acquires the in-cylinder intake air amount Mc. The in-cylinder intake air amount Mc is the amount (weight) of air that has flowed into the fuel injection cylinder during the current intake stroke of the fuel injection cylinder. The in-cylinder intake air amount Mc is determined based on the mass flow rate GA acquired from the air flow meter 14 and the engine rotational speed NE.

  Next, the ECU 29 proceeds to step 220 to obtain the basic fuel injection amount Fbase by dividing the in-cylinder intake air amount Mc obtained in step 215 by the target air-fuel ratio Abfref. The target air-fuel ratio Abfref is individually set according to the operating state such as at the time of start-up and steady operation, and is set to, for example, the stoichiometric air-fuel ratio in this embodiment. Therefore, the basic fuel injection amount Fbase is a fuel injection amount for making the air-fuel ratio of the air-fuel mixture supplied to the fuel injection cylinder coincide with the stoichiometric air-fuel ratio.

  Next, the ECU 29 proceeds to step 225 and acquires the ethanol concentration E from the alcohol concentration sensor 37.

  Next, the ECU 29 proceeds to step 230, and the ECU 29 proceeds to step 230 to obtain an ethanol correction coefficient ke of the basic fuel injection amount Fbase according to the ethanol concentration E. In general, the higher the ethanol concentration E, the richer the stoichiometric air-fuel ratio of the air-fuel mixture. Therefore, it is necessary to decrease the fuel injection amount TAU as the alcohol concentration increases. Therefore, the map of the ethanol correction coefficient ke of the basic fuel injection amount Fbase shown in FIG. 4 is set so that the ethanol correction coefficient ke is increased and the fuel injection amount TAU is increased as the ethanol concentration E is increased.

  Next, the ECU 29 proceeds to step 235 to obtain the fuel increase amount fwl according to the coolant temperature THW. The fuel increase amount fwl is calculated according to the coolant temperature THW and the ethanol concentration E of the fuel with reference to the map of the fuel increase amount fwl shown in FIG. In general, above the boiling point temperature of ethanol (about 78 ° C.), the higher the alcohol cooling water temperature THW, the more easily the fuel containing ethanol becomes more volatile than the fuel consisting only of gasoline. On the other hand, above the boiling point temperature of ethanol (about 78 ° C.), the higher the alcohol concentration E of the fuel, the more easily the fuel containing ethanol becomes more volatile than the fuel consisting only of gasoline, so the fuel injection amount TAU is reduced. Therefore, the map of the fuel increase amount fwl of the fuel injection shown in FIG. 3 is set so that the fuel increase amount fwl becomes smaller as the cooling water temperature THW is lower and the ethanol concentration E is higher and the fuel injection amount TAU is decreased. ing.

  Next, the ECU 29 proceeds to step 240 and obtains an acceleration increase correction coefficient fmw according to the coolant temperature THW. The acceleration increase correction coefficient fmw is calculated according to the coolant temperature THW using the map of the acceleration increase correction coefficient fmw shown in FIG. In general, the basic fuel injection amount Fbase is increased in order to obtain a required torque during acceleration, but as the cooling water temperature THW is lower (that is, the fuel temperature is lower), the amount of fuel adhering to the port wall surface and the like increases. The air-fuel ratio becomes lean. Therefore, at the time of acceleration, it is necessary to increase the fuel injection amount TAU as the coolant temperature THW is lower. On the other hand, the basic fuel injection amount Fbase is reduced at the time of deceleration, but the fuel injected at the time of acceleration or steady operation still adheres to the wall surface of the port, etc. As the fuel evaporates, the air-fuel ratio becomes rich. In general, the lower the coolant temperature THW, the more fuel is adhering to the port wall surface and the like. Therefore, during deceleration, it is necessary to decrease the fuel injection amount TAU as the coolant temperature THW decreases. Accordingly, in the map of the acceleration increase correction coefficient fmw shown in FIG. 5, the ECU 29 increases the acceleration increase correction coefficient fmw and increases the fuel injection amount TAU as the cooling water temperature THW decreases during acceleration. On the other hand, the ECU 29 is set to reduce the fuel injection amount TAU by decreasing the acceleration increase correction coefficient fmw (negative value at the time of deceleration) as the coolant temperature THW becomes lower at the time of deceleration.

  Next, the ECU 29 proceeds to step 245, that is, the acceleration of the fuel injection amount TAU in accordance with the acceleration Δkl (that is, the change in the engine load (more accurately, the load factor that is the filling factor, which correlates with the indicated torque) per unit time). An increase correction coefficient kfmw is acquired. The acceleration increase correction coefficient kfmw is a coefficient that is multiplied by the acceleration increase correction coefficient fmw calculated in step 240 of FIG. 4 to correct the fuel injection amount TAU. At the time of acceleration or deceleration, the intake pressure changes by changing the throttle opening. Since the fuel vaporization speed varies depending on the intake pressure, the greater the acceleration during acceleration, the higher the intake pressure and the slower the fuel vaporization speed. As a result, the amount of fuel vaporization decreases, so the air-fuel ratio becomes lean. On the other hand, the greater the deceleration during deceleration, the lower the intake pressure and the faster the fuel vaporization speed. Therefore, the amount of fuel vaporization increases and the air-fuel ratio becomes rich. Therefore, as shown in the map of the acceleration increase correction coefficient kfmw corresponding to the acceleration Δkl shown in FIG. 6, the ECU 29 increases the acceleration increase correction coefficient kfmw as the acceleration increases during acceleration (Δkl is a positive value). The injection amount TAU is increased to prevent the air-fuel ratio of the air-fuel mixture from becoming lean. On the other hand, at the time of deceleration (Δkl is a negative value), the ECU 29 sets the acceleration increase correction coefficient kfmw to be larger as the deceleration increases. As a result, the acceleration increase correction coefficient fmw (a negative value during deceleration) acquired in step 245 of FIG. 2 is multiplied by the acceleration increase correction coefficient kfmw, which is a larger value as the deceleration increases, and fuel injection is performed. The quantity TAU is reduced.

  Next, the ECU 29 takes in the integrated intake air amount TGa after the internal combustion engine 11 is started in step 250. The integrated intake air amount TGa is acquired by integrating the intake air amount Ga passing through the intake path detected by the air flow meter 14.

  Next, the ECU 29 obtains an intake valve umbrella temperature tin (engine operation temperature correlation value) in step 255. The intake valve umbrella part temperature tin is estimated according to the start-up coolant temperature THWS and the post-startup integrated intake air amount TGa using the map of the intake valve umbrella part temperature tin shown in FIG. Operation). The intake valve umbrella temperature tin at the start is estimated as equivalent to the start-up cooling water temperature THWS. Further, the intake valve umbrella temperature tin is estimated as the intake valve umbrella temperature tin increases due to the amount of heat generated in the combustion chamber as the integrated intake air amount TGa increases. Therefore, as shown in the map of the intake valve umbrella temperature tin shown in FIG. 7, the ECU 29 increases the intake valve umbrella temperature tin as the starting coolant temperature THWS increases, and the intake valve umbrella increases as the integrated intake air amount TGa increases. The part temperature tin is estimated to be high.

  Next, the ECU 29 proceeds to step 260 and determines whether or not the intake valve umbrella temperature tin is equal to or higher than 78 ° C. (the boiling point of the predetermined fuel component, the predetermined temperature). If the ECU 29 determines “Yes” in step 260, the ECU 29 proceeds to step 265. As a result, when the intake valve umbrella temperature tin further rises from a temperature in the vicinity of 78 ° C., an intake valve umbrella temperature increase correction coefficient kin described later is obtained with reference to the intake valve umbrella temperature tin. As a result, even when the intake valve umbrella temperature tin rises further from the vicinity of the boiling point of ethanol, control is performed without deviating from the exhaust purifiable air-fuel ratio, thereby suppressing an increase in harmful components in the exhaust gas. Can do. On the other hand, if the ECU 29 determines “No” in step 260, the process proceeds to step 280.

  Next, in step 265, the ECU 29 obtains an intake valve umbrella temperature increase correction coefficient kin. The intake valve umbrella temperature increase correction coefficient kin is calculated according to the intake valve umbrella temperature tin and the ethanol concentration E using the map of the intake valve umbrella temperature increase correction coefficient kin shown in FIG. Ethanol has a characteristic that almost 100% evaporates at about 78 ° C. (boiling point temperature of ethanol). As a result, when the intake valve umbrella temperature tin exceeds the boiling point temperature of ethanol (78 ° C.), the fuel adhering to the intake port, the intake valve, the combustion chamber, etc., the ethanol component of the adhering mixed fuel, Almost all ethanol components of the mixed and mixed fuel are evaporated. As a result, the air-fuel mixture becomes over-rich. Therefore, when the intake valve umbrella temperature is lower than the boiling point temperature of ethanol or above the boiling point of ethanol, the fuel injection amount TAU is changed by setting a different intake valve umbrella temperature increase correction coefficient kin. Need to be done. As shown in the time variation of the intake valve umbrella temperature increase correction coefficient kin and the intake valve umbrella temperature increase correction coefficient kin in FIG. 8B, the ECU 29 determines that the intake valve umbrella temperature is at a certain temperature near 78 ° C. The umbrella part temperature increase correction coefficient kin is changed. Specifically, when the intake valve umbrella temperature tin is less than a certain temperature near 78 ° C., the ECU 29 keeps the intake valve umbrella temperature increase correction coefficient kin at 1.0. On the other hand, when the intake valve umbrella temperature tin is equal to or higher than a certain temperature in the vicinity of 78 ° C., the ECU 29 sets the intake valve umbrella temperature increase correction coefficient kin smaller as the ethanol concentration E is higher. As a result, by reducing the increase amount of the fuel injection amount TAU, the mixture is prevented from becoming over-rich compared to the case where control is performed to correct each fuel increase amount of the same fuel as the gasoline engine under the same conditions. be able to. In addition, since it is controlled by a control parameter that matches the evaporation of ethanol, the air-fuel ratio can be converged by reducing the lower limit value of the feedback correction range as compared with the case where an increase in the air-fuel ratio deviation is absorbed. Is shortened. As a result, an increase in harmful components in the exhaust gas due to deviation from an air purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system is suppressed, and the purification ability of the aftertreatment device that purifies the exhaust gas is increased. Is no longer needed.

If the ECU 29 determines “Yes” in step 265, the ECU 29 proceeds to step 265 and calculates the fuel injection amount TAU. The fuel injection amount TAU is calculated based on the following equation.
TAU = (Fbase * ke + fwl * kefwl * kin) * (1 + fmw * kfmw * kin)
Next, the ECU 29 proceeds to step 275, and instructs the fuel injection valve 21 to open so that the fuel injection amount TAU is injected from the fuel injection valve 21 provided for the fuel injection cylinder. Next, the ECU 29 proceeds to step 295 and once ends this routine.

  On the other hand, if the ECU 29 determines “No” in step 260, the ECU 29 proceeds to step 280 and determines whether or not the intake valve umbrella temperature determination flag Xtin is “1”. When the intake valve umbrella temperature determination flag Xtin is “1”, the ECU 29 determines that the intake valve umbrella temperature tin is lower than the boiling point temperature of ethanol. If the ECU 29 determines in step 280 that the intake valve umbrella temperature determination flag Xtin is “1”, the intake valve umbrella temperature tin estimated in step 255 in FIG. 2 remains unchanged. The ECU 29 proceeds to step 265. On the other hand, when the ECU 29 determines that the intake valve umbrella temperature determination flag Xtin is not “1” (that is, the intake valve umbrella temperature determination flag Xtin is “O”), the intake valve umbrella temperature tin is 78 ° C. The ECU 29 proceeds to step 265 and obtains the intake valve umbrella temperature increase correction coefficient kin. Next, the ECU 29 proceeds to step 270 and calculates the final fuel injection amount TAU. Next, the ECU 29 proceeds to step 275, and instructs the fuel injection valve 21 to open so that fuel is injected from the fuel injection valve 21 provided for the fuel injection cylinder by the fuel injection amount TAU. Next, the ECU 29 proceeds to step 295 and once ends this routine.

  Further, the ECU 29 is configured to repeatedly execute the flag setting routine shown in FIG. 9 every elapse of a predetermined time. Therefore, the ECU 29 starts the process from step 900 when the predetermined timing is reached, and proceeds to step 910.

  In step 910, the ECU 29 determines whether or not the internal combustion engine is in a steady operation state. The steady operation state includes a case where the engine 11 is started or warmed up. If the ECU 29 determines “Yes” in step 910, the ECU 29 proceeds to step 911 and takes in the variation ΔA / F (air-fuel ratio correlation value) of the air-fuel ratio correlation value during steady operation. As shown in FIG. 10 showing the time transition of the air-fuel ratio, the fluctuation amount ΔA / F of the air-fuel ratio correlation value is calculated as the difference between the air-fuel ratio output from the exhaust gas sensor and the target air-fuel ratio abfref.

Next, the ECU 20 proceeds to step 912 and determines whether or not the intake valve umbrella temperature determination flag Xtin is “1” (that is, whether or not the intake valve umbrella temperature tin is lower than the boiling point temperature of ethanol). . If the ECU 29 determines “Yes” in step 912, the ECU 29 proceeds to step 913.
The ECU 29 proceeds to step 913 and determines whether or not the fluctuation amount ΔA / F of the air-fuel ratio correlation value is larger than the first predetermined value α. If the ECU 29 determines “Yes” in step 913, the ECU 29 proceeds to step 914 and sets the intake valve umbrella temperature determination flag Xtin to “0”. That is, the ECU 29 determines that the intake valve umbrella temperature tin is the boiling point temperature (78 ° C.) of ethanol. Next, the ECU 29 proceeds to step 995 and once ends this routine.

  On the other hand, if the ECU 29 determines “No” in step 913, the ECU 29 proceeds to step 915 and sets the intake valve umbrella temperature determination flag Xtin to “1”. That is, the ECU 29 determines that the intake valve umbrella temperature tin is lower than the boiling point temperature of ethanol. Next, the ECU 29 proceeds to step 995 and once ends this routine.

  According to this, as shown in FIG. 8B, when the intake valve umbrella temperature tin is estimated based on the starting coolant temperature THWS and the integrated intake air amount TGa, the operation in the high rotation region is frequently used. In the situation where the actual increase in the intake valve umbrella temperature tin is fast (dotted line in FIG. 8B), the change in the intake valve umbrella temperature increase correction coefficient kin may be delayed and the air-fuel ratio may shift. is there. On the other hand, in the situation where the actual increase of the intake valve umbrella temperature tin, such as being left idle, is slow (dotted line in FIG. 8B), the change in the intake valve umbrella temperature increase correction coefficient kin is accelerated, resulting in emptying. The fuel ratio may shift. On the other hand, when the fluctuation amount ΔA / F of the air-fuel ratio correlation value is larger than the first predetermined value α during steady operation, the ECU 29 sets the intake valve umbrella temperature tin to the boiling point temperature (78 ° C.) of ethanol. Set to. As a result, as indicated by the arrow in FIG. 8B, the intake valve umbrella temperature increase correction coefficient kin is set to a more accurate value. As a result, it is possible to suppress the air-fuel mixture from becoming over-rich as compared with the case where the control is performed to correct each increase in the same fuel as in the gasoline engine under the same conditions. As a result, it is possible to suppress an increase in harmful components in the exhaust gas due to deviation from the exhaust purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system.

  Next, the intake valve umbrella temperature determination based on the variation ΔA / F of the air-fuel ratio correlation value during acceleration will be described.

  When the ECU 29 determines “No” in step 910, the process proceeds to step 920 to determine whether or not acceleration operation is being performed.

  If the ECU 29 determines “Yes” in step 920, the process proceeds to step 921 to acquire the variation ΔA / F of the air-fuel ratio correlation value during acceleration. As shown in FIG. 13, when the intake valve umbrella temperature reaches 78 ° C. when the acceleration changes by Δkl, the evaporation ratio of the ethanol component in the fuel rapidly increases, so that the air-fuel ratio feedback control is temporarily performed. The air-fuel ratio of the air-fuel mixture suddenly becomes rich. Accordingly, when the variation ΔA / F of the air-fuel ratio correlation value is larger than the second predetermined value β, it is determined that the intake valve umbrella temperature has reached 78 ° C., and the intake valve umbrella temperature is set to 78 ° C. .

  Next, the routine proceeds to step 922, where the ECU 29 acquires the variation correction coefficient Δkl2 of the air-fuel ratio correlation value according to the acceleration Δkl. As the acceleration Δkl increases, the fuel increase correction amount is increased by the acceleration increase correction coefficient kfmw. However, the variation in the final fuel injection amount TAU increases by performing this acceleration correction and other fuel injection amount TAU corrections. End up. Therefore, in consideration of the variation of the air-fuel ratio as the acceleration Δkl increases, the determination is performed on the value corrected so that the fluctuation amount ΔA / F of the air-fuel ratio correlation value increases. As a result, as shown in the map of the variation correction coefficient Δkl2 of the air-fuel ratio correlation value in FIG. 12, the variation correction coefficient Δkl2 of the air-fuel ratio correlation value is increased as the acceleration Δkl increases. The fluctuation amount ΔA / F of the air-fuel ratio correlation value is largely corrected by multiplying the fluctuation amount ΔA / F of the air-fuel ratio correlation value by the fluctuation amount correction coefficient Δkl2 of the air-fuel ratio correlation value. As a result, it is possible to determine whether or not the intake valve umbrella temperature has exceeded 78 ° C. without being affected by an increase in variation in air-fuel ratio due to an increase in acceleration Δkl.

  Next, the routine proceeds to step 923, where the ECU 29 corrects the fluctuation amount ΔA / F of the air-fuel ratio correlation value by multiplying the fluctuation amount ΔA / F of the air-fuel ratio correlation value by the fluctuation amount correction coefficient Δkl2 of the air-fuel ratio correlation value.

  Next, the ECU 29 proceeds to step 924 to determine whether or not the intake valve umbrella temperature determination flag Xtin is “1” (that is, whether or not the intake valve umbrella temperature tin is less than the boiling point temperature of ethanol). If the ECU 29 determines “Yes” in step 924, the ECU 29 proceeds to step 925.

  Next, the ECU 29 determines in step 925 whether or not the variation ΔA / F of the air-fuel ratio correlation value after the correction in step 923 is larger than the second predetermined value β. If the ECU 29 determines “Yes” in step 925, it is determined that the intake valve umbrella temperature tin has reached 78 ° C., and the process proceeds to step 926 where the intake valve umbrella temperature determination flag Xtin is set to “0”. . Next, the ECU 29 proceeds to step 995 and once ends this routine.

  On the other hand, if the ECU 29 determines “No” in step 925, it is determined that the intake valve umbrella temperature tin has not reached 78 ° C. Next, the ECU 29 proceeds to step 927 and sets the intake valve umbrella temperature determination flag Xtin to “1”. Next, the ECU 29 proceeds to step 995 and once ends this routine.

  According to this, as shown in FIG. 8B, when the intake valve umbrella temperature tin is estimated based on the starting coolant temperature THWS and the integrated intake air amount TGa, the operation in the high rotation region is frequently used. In the situation where the actual increase in the intake valve umbrella temperature tin is fast (dotted line in FIG. 8B), the change in the intake valve umbrella temperature increase correction coefficient kin may be delayed and the air-fuel ratio may shift. is there. On the other hand, in the situation where the actual increase of the intake valve umbrella temperature tin, such as being left idle, is slow (dotted line in FIG. 8B), the change in the intake valve umbrella temperature increase correction coefficient kin is accelerated. The fuel ratio may shift. On the other hand, when the acceleration changes by Δkl during acceleration, if the fluctuation amount ΔA / F of the air-fuel ratio correlation value is larger than the second predetermined value β, the intake valve umbrella temperature Xtin is set to the boiling point temperature of ethanol. Set to (78 ° C). Further, by correcting the fluctuation amount ΔA / F of the air-fuel ratio correlation value to a larger value as the acceleration Δkl is larger, it is possible to eliminate the influence of an increase in air-fuel ratio variation due to an increase in the acceleration Δkl. Thus, as indicated by the arrow in FIG. 8B, the intake valve umbrella temperature increase correction coefficient kin in step 265 of FIG. 2 is set to a more accurate value. As a result, it is possible to suppress the air-fuel mixture from becoming over-rich as compared with the case where the control is performed to correct each increase in the same fuel as in the gasoline engine under the same conditions. As a result, it is possible to suppress deterioration of engine drivability and suppress deterioration of fuel consumption and emission.

  Next, the intake valve umbrella temperature determination based on the variation ΔA / F of the air-fuel ratio correlation value during deceleration will be described.

  The ECU 29 determines “No” in step 910, then proceeds to step 920, determines “No”, and then proceeds to step 931.

  In step 931, the ECU 29 obtains the fluctuation amount ΔA / F of the air-fuel ratio correlation value during acceleration. As shown in FIG. 13, when the intake valve umbrella temperature reaches 78 ° C. when the deceleration changes by Δkl, the air-fuel ratio feedback control is temporarily performed for over-riching due to evaporation of the ethanol component in the ethanol mixed fuel. Therefore, the ECU 29 excessively decreases the basic fuel injection amount Fbase, and the air-fuel ratio of the air-fuel mixture increases rapidly. As a result, a fluctuation amount ΔA / F of the air-fuel ratio correlation value is generated. Accordingly, the ECU 29 determines that the intake valve umbrella temperature has reached 78 ° C. when the fluctuation amount ΔA / F of the air-fuel ratio correlation value is larger than a third predetermined value γ described later, and determines the intake valve umbrella temperature. Set to 78 ° C.

  Next, the routine proceeds to step 932, where the ECU 29 obtains the variation correction coefficient Δkl3 of the air-fuel ratio correlation value according to the deceleration Δkl. As the deceleration Δkl increases, the fuel increase correction amount is reduced by the acceleration increase correction coefficient kfmw. However, the variation in the final fuel injection amount TAU increases by performing this acceleration correction and other fuel injection amount TAU corrections. End up. Therefore, it is necessary to correct the variation ΔA / F of the air-fuel ratio correlation value so as to increase as the deceleration Δkl increases. As a result, as shown in the map of the variation correction coefficient Δkl3 of the air-fuel ratio correlation value in FIG. 14, the variation correction coefficient Δkl3 of the air-fuel ratio correlation value is increased as the deceleration Δkl increases. The variation amount ΔA / F of the air-fuel ratio correlation value is largely corrected by multiplying the variation amount ΔA / F of the air-fuel ratio correlation value by the variation amount correction coefficient Δkl3 of the air-fuel ratio correlation value. As a result, it is possible to determine whether or not the intake valve umbrella temperature tin has exceeded 78 ° C. without being affected by an increase in variation in the air-fuel ratio due to an increase in the deceleration Δkl.

  Next, the routine proceeds to step 933, where the ECU 29 corrects the fluctuation amount ΔA / F of the air-fuel ratio correlation value by multiplying the fluctuation amount ΔA / F of the air-fuel ratio correlation value by the fluctuation amount correction coefficient Δkl3 of the air-fuel ratio correlation value.

  Next, the ECU 29 proceeds to step 934 to determine whether or not the intake valve umbrella temperature determination flag Xtin is “1” (that is, whether or not the intake valve umbrella temperature tin is lower than the boiling point temperature of ethanol). If the ECU 29 determines “Yes” in step 934 (that is, the intake valve umbrella temperature tin is less than the boiling point temperature of ethanol), the ECU 29 proceeds to step 935.

  Next, the ECU 29 determines in step 935 whether or not the variation ΔA / F of the air-fuel ratio correlation value after the correction in step 933 is larger than the third predetermined value γ. If the ECU 29 determines “Yes” in step 935, it is determined that the intake valve umbrella temperature tin has reached 78 ° C., and the process proceeds to step 936 to set the intake valve umbrella temperature determination flag Xtin to “0”. . Next, the ECU 29 proceeds to step 995 and once ends this routine.

  On the other hand, if the ECU 29 determines “No” in step 935, it is determined that the intake valve umbrella temperature tin has not reached 78 ° C. Next, the ECU 29 proceeds to step 937 and sets the intake valve umbrella temperature determination flag Xtin to “1”. Next, the ECU 29 proceeds to step 995 and once ends this routine.

According to this, as shown in FIG. 8B, when the intake valve umbrella temperature tin is estimated based on the starting coolant temperature THWS and the integrated intake air amount TGa, the operation in the high rotation region is frequently used. In the situation where the actual increase in the intake valve umbrella temperature tin is fast (dotted line in FIG. 8B), the change in the intake valve umbrella temperature increase correction coefficient kin may be delayed and the air-fuel ratio may shift. is there. On the other hand, in the situation where the actual increase of the intake valve umbrella temperature tin, such as being left idle, is slow (dotted line in FIG. 8B), the change in the intake valve umbrella temperature increase correction coefficient kin is accelerated. The fuel ratio may shift. On the other hand, when the deceleration changes by Δkl during deceleration, if the fluctuation amount ΔA / F of the air-fuel ratio correlation value is larger than the third predetermined value γ, the intake valve umbrella temperature Xtin is set to 78 ° C. Set. Further, by correcting the fluctuation amount ΔA / F of the air-fuel ratio correlation value to a larger value as the deceleration Δkl is larger, it is possible to eliminate the influence of the increase in variation in the air-fuel ratio due to the increase in the deceleration Δkl. As a result, the intake valve umbrella temperature tin is estimated more accurately. As a result, as shown by the arrow in FIG. 8B, the intake valve umbrella temperature increase correction coefficient kin is set to a more accurate value. As a result, it is possible to suppress the air-fuel mixture from becoming over-rich as compared with the case where the control is performed to correct each increase in the same fuel as in the gasoline engine under the same conditions. As a result, it is possible to suppress deterioration of engine drivability and suppress deterioration of fuel consumption and emission.
Thus, this control device
A control device for an internal combustion engine using a fuel containing a predetermined fuel component,
Fuel injection means (fuel injection valve 21) for injecting fuel into the internal combustion engine;
Temperature calculating means (steps 205, 250, 255, etc. in FIG. 2) for calculating an engine operating temperature correlation value (intake valve umbrella temperature tin) of the internal combustion engine;
Control the command values (fuel increase amount fwl, intake valve umbrella portion increase correction coefficient kin, acceleration increase correction coefficient fmw, etc.) of the internal combustion engine with reference to the engine operating temperature correlation value obtained by the temperature calculation means Control means (steps 235, 240, step 265, etc. in FIG. 2),
Air-fuel ratio correlation value detecting means (exhaust gas sensor 24, steps 911, 921 and 931 in FIG. 9) for detecting the air-fuel ratio correlation value of the exhaust gas discharged from the internal combustion engine;
The engine operating temperature correlation value based on the air-fuel ratio correlation value (variation amount ΔA / F of the air-fuel ratio correlation value) detected by the air-fuel ratio correlation value detecting means is the boiling point of the predetermined fuel component (boiling point temperature of ethanol) : Diagnostic means (steps 913, 925, and 935 in FIG. 9) for diagnosing whether or not the temperature is equal to or higher than a predetermined temperature that is a temperature in the vicinity of 78 ° C.)
When the diagnostic means determines that the engine operating temperature correlation value is equal to or higher than the predetermined temperature, the engine operating temperature correlation is independent of the engine operating temperature correlation value calculated by the temperature calculating means. Control parameter changing means (steps 260, 280 and 285 in FIG. 2, 914 and 915 in FIG. 9) for changing to a command value of the control parameter when the value is equal to or higher than the predetermined temperature;
Is provided.
The increase of harmful components in the exhaust gas is suppressed, and it is not necessary to devise such as improving the purification ability of the aftertreatment device that performs exhaust purification.

Further, the control parameter changing means includes
When the diagnostic means diagnoses that the engine operating temperature correlation value is equal to or higher than a predetermined temperature, the engine operating temperature correlation value is used instead of the engine operating temperature correlation value referred to when the control means performs control. The value is changed to the command value of the control parameter corresponding to the corrected engine operating temperature correlation value obtained by correcting the value to the predetermined temperature (steps 260, 280 and 285 in FIG. 2, 914 and 915 in FIG. 9, etc.) .

Further, when the engine operating temperature correlation value calculated by the temperature calculating means is equal to or higher than the predetermined temperature, the control parameter changing means is controlled by the temperature calculating means regardless of the diagnosis result of the diagnostic means. The command value of the control parameter of the internal combustion engine is controlled with reference to the obtained engine operating temperature correlation value (steps 260 and 265 in FIG. 2).
The temperature calculation means includes
Cooling water temperature acquisition means (cooling water temperature sensor 26, steps 205 and 210 in FIG. 2) for acquiring the cooling water temperature of the internal combustion engine;
Intake air amount acquisition means (air flow meter 14, step 215 and step 250 in FIG. 2) for acquiring the intake air amount sucked from the intake passage of the internal combustion engine,
The temperature calculating means includes
The cooling water temperature acquisition means acquires a starting cooling water temperature that is a cooling water temperature when starting the internal combustion engine (cooling water temperature sensor 26, step 205 in FIG. 2),
An integrated intake air amount is acquired by integrating the intake air amount acquired by the intake air amount acquisition means from the start of the internal combustion engine (air flow meter 14, step 250 in FIG. 2, etc.),
Based on the integrated intake air amount and the starting coolant temperature, the temperature of the internal combustion engine and its correlation value are obtained by calculation (step 255 in FIG. 2).

The control means includes
Fuel injection amount increasing means (FIG. 2) for increasing the fuel injection amount injected by the fuel injection means at the time of starting and / or warming up the internal combustion engine according to the engine operating temperature correlation value obtained by the temperature calculating means. Steps 235, 240, and 245).

  As described above, according to the first device, when the intake valve umbrella temperature exceeds the boiling point temperature (78 ° C.) of ethanol, the ethanol component and intake air of the fuel adhering to the intake port, the intake valve, the combustion chamber, etc. All ethanol components in the mixed and mixed fuel will evaporate. In contrast, as shown in the map of the intake valve umbrella temperature increase correction coefficient kin in FIG. 8, when the intake valve umbrella temperature tin is equal to or higher than a certain temperature near the boiling point of ethanol, the ethanol concentration E is The intake valve umbrella temperature increase correction coefficient kin is changed so as to set the intake valve umbrella temperature increase correction coefficient kin smaller as the value is higher. As a result, by reducing the increase amount of the fuel injection amount TAU, it is possible to prevent the air-fuel mixture from becoming over-rich compared to the case where the control for performing the fuel increase correction of the same fuel as the gasoline engine is performed under the same conditions. be able to. As a result, an increase in harmful components in the exhaust gas due to deviation from an air purifiable air-fuel ratio that can be purified by the aftertreatment device provided in the exhaust system is suppressed, and the purification ability of the aftertreatment device that purifies the exhaust gas is increased. Is no longer needed.

  Further, as shown in FIG. 8 (b), when the intake valve umbrella temperature tin is estimated based on the starting coolant temperature THWS and the integrated intake air amount TGa, the operation in the high rotation range is frequently used. In a situation where the actual rise of the intake valve umbrella temperature tin is fast (dotted line in FIG. 8B), there is a possibility that the air-fuel ratio is shifted due to a delay in changing the intake valve umbrella temperature increase correction coefficient kin. On the other hand, in the situation where the actual increase of the intake valve umbrella temperature tin, such as being left idle, is slow (dotted line in FIG. 8B), the change in the intake valve umbrella temperature increase correction coefficient kin is accelerated. The fuel ratio may shift. On the other hand, when the fluctuation amount ΔA / F of the air-fuel ratio correlation value becomes larger than a predetermined value during steady operation, acceleration or deceleration, the post-starting coolant temperature THWS and the post-startup integrated intake air amount TGa Instead of setting the intake valve umbrella temperature increase correction coefficient kin according to the intake valve umbrella temperature tin estimated by the above, the intake valve umbrella temperature increase correction is performed assuming that the intake valve umbrella temperature tin is equal to or higher than the boiling point temperature of ethanol. Set the coefficient kin. This makes it possible to accurately determine whether or not the evaporation rate of ethanol has rapidly increased due to the intake valve umbrella temperature tin becoming equal to or higher than the boiling point temperature.

  In the embodiment of the present invention, ethanol is used as a component to be mixed with gasoline, but other alcohols such as methanol may be used, or a single fuel other than alcohol may be used. Furthermore, the present invention may be applied to a fuel having an alcohol concentration of 100%.

  In the embodiment of the present application, the fuel is supplied to the combustion chamber by the port injection method, but the fuel may be directly supplied to the combustion chamber by the direct injection method.

  Further, in the embodiment of the present application, the intake valve umbrella temperature tin as the intake system temperature is estimated or calculated based on the starting coolant temperature THWS and the integrated intake air amount TGa, but instead of this technique, the intake system temperature is simply calculated. You may estimate or calculate from the output value of temperature sensors, such as water temperature. Further, in the embodiment of the present application, whether or not the evaporation rate of a predetermined fuel component contained in the mixed fuel is rapidly increased based on the intake port umbrella temperature tin and the intake port, the intake valve, the combustion chamber, and the like. The determination may be made based on the intake port temperature, the combustion chamber temperature, the compression end temperature, and the like.

  In the embodiment of the present application, the fluctuation amount ΔA / F of the air-fuel ratio correlation value of the air-fuel ratio is calculated as the difference between the air-fuel ratio output from the exhaust gas sensor and the target air-fuel ratio abfref. Another means for detecting the fluctuation amount of the air-fuel ratio correlation value, such as calculating the fluctuation value of the air-fuel ratio and the air-fuel ratio at the previous measurement, may be employed.

Further, the predetermined fuel component may be a fuel component contained in gasoline such as ethanol or the like, and a fuel component not contained in gasoline as long as it contributes to the work of the internal combustion engine by burning. There may be. The fuel containing a predetermined fuel component may be composed of a single fuel component such as containing only ethanol, or may contain a plurality of fuel components.

DESCRIPTION OF SYMBOLS 11 ... Internal combustion engine, 12 ... Intake pipe, 16 ... Throttle valve, 19 ... Injection nozzle, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 24 ... Exhaust gas sensor, 26 ... Cooling water temperature sensor, 29 ... ECU 30 ... Fuel tank, 37 ... Alcohol concentration sensor,

Claims (5)

A control device for an internal combustion engine using a fuel containing a predetermined fuel component,
Fuel injection means for injecting fuel into the internal combustion engine;
Air-fuel ratio correlation value detecting means for detecting an air-fuel ratio correlation value of the exhaust discharged from the internal combustion engine;
A temperature calculating means for calculating an engine operating temperature correlation value of the internal combustion engine independently of the air-fuel ratio;
Control means for controlling a command value of a control parameter of the internal combustion engine with reference to the engine operating temperature correlation value obtained by the temperature calculating means;
Based on the air-fuel ratio correlation value detected by the air-fuel ratio correlation value detecting means, it is diagnosed whether or not the engine operating temperature correlation value is equal to or higher than a predetermined temperature at which the temperature near the boiling point of the predetermined fuel component is reached. Diagnostic means;
When the diagnosis means diagnoses that the engine operation temperature correlation value is equal to or higher than the predetermined temperature, the engine operation temperature correlation is irrespective of the engine operation temperature correlation value calculated by the temperature calculation means. Control parameter changing means for changing to a command value of the control parameter when the value is equal to or higher than the predetermined temperature;
A control device for an internal combustion engine, comprising: The control apparatus for an internal combustion engine according to claim 1,
The control parameter changing means includes
When the diagnosis means diagnoses that the engine operation temperature correlation value obtained by the temperature calculation means is equal to or higher than a predetermined temperature, the engine operation temperature correlation value referred to when controlling by the control means Instead, the engine operating temperature correlation value is changed to the command value of the control parameter according to the corrected engine operating temperature correlation value after correcting the predetermined temperature.
A control device for an internal combustion engine. The control device for an internal combustion engine according to claim 1 or 2,
When the engine operating temperature correlation value calculated by the temperature calculation means is equal to or higher than the predetermined temperature, the control parameter changing means is obtained by the temperature calculation means regardless of the diagnosis result of the diagnosis means. Change to the command value of the control parameter according to the engine operating temperature correlation value,
A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to any one of claims 1 to 3,
The temperature calculating means includes
Cooling water temperature acquisition means for acquiring the cooling water temperature of the internal combustion engine;
Intake air amount acquisition means for acquiring the intake air amount sucked from the intake passage of the internal combustion engine,
The temperature calculating means includes
The cooling water temperature acquisition means acquires a starting cooling water temperature that is a cooling water temperature when starting the internal combustion engine,
Acquiring an integrated intake air amount by integrating the intake air amount acquired by the intake air amount acquisition means from the start of the internal combustion engine;
The temperature of the internal combustion engine or a correlation value thereof is obtained by calculation based on the integrated intake air amount and the cooling water temperature at the time of starting.
A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to any one of claims 1 to 4,
The control means includes
The fuel injection amount increasing means increases the fuel injection amount injected by the fuel injection means at the time of starting and / or warming up the internal combustion engine according to the engine operating temperature correlation value obtained by the temperature calculating means. The
A control device for an internal combustion engine.