JP2009144552A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately acquire the changes of fuel property, by excluding the influence of an abnormality in a fuel supply device. <P>SOLUTION: A control device (electronic control unit 1) for an internal combustion engine having a fuel property determination means determining the changes of the fuel property of fuel F supplied into a combustion chamber CC, based on detection values of an exhaust sensor 83 detecting an oxygen amount in exhaust gas or an air excess ratio. The fuel property determination means determines whether a deviation between an actual air-fuel ratio and a target air-fuel ratio is caused by the changes of the fuel property or an abnormality of a fuel supply device 50. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that can be operated with fuels having different fuel properties.

  In recent years, in the automobile industry, various efforts have been made to cope with changes in the environment surrounding automobiles. For example, in the field of internal combustion engines, efforts have been made for so-called multi-fuel internal combustion engines that can be operated even with fuels having different fuel properties. A vehicle equipped with this kind of multi-fuel internal combustion engine is generally called a flexible fuel vehicle (FFV). For example, any of gasoline fuel, alcohol fuel, or a mixed fuel thereof is used. However, it is known to improve the environmental performance such as the suppression of the consumption of fossil fuels such as gasoline fuel, which can be operated and the limits of reserves continue to be sought. For example, the following Patent Document 1 discloses a multi-fuel internal combustion engine that is operated using an alcohol mixed fuel composed of gasoline fuel and alcohol fuel.

Here, this type of multi-fuel internal combustion engine can be operated even with the use of fuels having different fuel properties as described above. Therefore, if the air-fuel ratio control corresponding to the fuel properties is not executed, it is satisfactory. Output performance and emission performance cannot be obtained. Therefore, when the fuel property of the fuel changes, it is necessary to grasp the changed fuel property in order to perform appropriate air-fuel ratio control corresponding to the new fuel property. For example, Patent Document 2 below discloses an internal combustion engine that obtains an estimated value of an actual air-fuel ratio based on an actual indicated torque and a reference air-fuel ratio indicated torque, and determines a fuel property of the fuel used based on the estimated value of the actual air-fuel ratio. An engine control apparatus is disclosed. The estimated value of the actual air-fuel ratio may be calculated from the detection value of an exhaust sensor such as an O ₂ sensor provided in the exhaust passage.

JP-A-2-305335 JP 2005-120886 A

  Incidentally, in general, in the technical field of air-fuel ratio control, a detected value (hereinafter referred to as “detected actual air-fuel ratio”) or an estimated value (hereinafter referred to as “estimated actual air-fuel ratio”) and a target air-fuel ratio in the actual air-fuel ratio control. If there is a difference between them, the target fuel injection amount is increased or decreased so that the actual air-fuel ratio converges to the target air-fuel ratio. That is, when air-fuel ratio control is performed, the fuel corresponding to the target fuel injection amount for converging the actual air-fuel ratio to the target air-fuel ratio based on the comparison result between the detected actual air-fuel ratio or the estimated actual air-fuel ratio and the target air-fuel ratio. An injection amount correction value is obtained. At that time, if the fuel injection amount correction value is equal to or greater than a predetermined value, it can be determined that the fuel supplied into the combustion chamber has been switched to a fuel property different from the previous one.

  However, when an abnormality occurs in a fuel supply device (so-called fuel supply system) composed of various components from the fuel tank to the fuel injection valve, an actual fuel injection amount (hereinafter referred to as “actual fuel injection amount”). ) Will deviate from the target fuel injection amount, and if the fuel injection amount correction value set at that time is equal to or greater than the above-mentioned predetermined value, the fuel property has not changed but the fuel It may be determined that the property has changed. For example, when the fuel injection valve is clogged, the actual fuel injection amount becomes smaller than the target fuel injection amount, so that the fuel injection amount is increased toward the target air-fuel ratio to control the actual air-fuel ratio. A correction value is set. In this case, if there is a shortage of the actual fuel injection amount with respect to the target fuel injection amount, a large fuel injection amount correction value is set. There is a risk that it will be judged as “change in properties”. In addition, when the valve body of the fuel injection valve has failed to close, the actual fuel injection amount becomes larger than the target fuel injection amount, so that the reduction side is required to control the actual air fuel ratio to the target air fuel ratio. The fuel injection amount correction value is set to (5). In this case, if the surplus of the actual fuel injection amount with respect to the target fuel injection amount is large, a large fuel injection amount correction value is set. There is a risk that it will be judged as “change in properties”.

  Therefore, the present invention provides an internal combustion engine control device that can improve the disadvantages of the conventional example, and can accurately detect changes in fuel properties by eliminating the influence of abnormality of the fuel supply device. For that purpose.

  In order to achieve the above object, according to the first aspect of the present invention, the change in the fuel property of the fuel supplied to the combustion chamber is determined based on the detection value of the exhaust sensor that detects the amount of oxygen in the exhaust gas and the excess air ratio. In the control apparatus for an internal combustion engine provided with the fuel property determination means, the detected values detected by the exhaust sensor when the internal combustion engine is cold and warm are compared, and the difference between the actual air-fuel ratio and the target air-fuel ratio is detected. The fuel property determining means is configured to determine whether it is due to a change in fuel property or due to an abnormality in the fuel supply device.

  For example, as in the invention described in claim 2, the fuel property determining means determines that the fuel property has changed if the detected value in the cold state differs from the detected value in the warm state, and the detected values are the same. If there is, the fuel supply device is determined to be abnormal.

  Here, as in the invention of claim 3, the fuel property judging means is warm if the engine temperature of the internal combustion engine is higher than the boiling point of the highest boiling point fuel that can be used in the internal combustion engine. It is desirable to be configured to judge.

  Further, as in the invention described in claim 4, the fuel property judging means judges that the engine is cold when the engine temperature of the internal combustion engine is lower than the lowest boiling point of the fuel that can be used in the internal combustion engine. It is desirable to make it so.

  The control device for an internal combustion engine according to the present invention compares the detected value of the exhaust sensor in the cold state and the detected value of the exhaust sensor in the warm state, and determines that the change in the fuel property if each detected value is different, If the detected values are the same, it is determined that the fuel supply apparatus is abnormal. For this reason, the control device for the internal combustion engine can accurately grasp the change in the fuel property by eliminating the influence due to the abnormality of the fuel supply device.

  Embodiments of an internal combustion engine control apparatus according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

  A first embodiment of a control device for an internal combustion engine according to the present invention will be described with reference to FIGS. In the following, the control device will be described in detail while explaining an example of an internal combustion engine to be applied.

  The internal combustion engine exemplified here can be operated even when using fuels having different fuel properties such as hydrocarbon fuels such as gasoline fuel, alcohol fuels (ethanol, methanol, butanol, etc.) or alcohol mixed fuels. This is a multi-fuel internal combustion engine mounted on a so-called flexible fuel vehicle. The alcohol mixed fuel is a mixed fuel of an alcohol fuel and at least one fuel having a different fuel property, and here, it is assumed that it is mixed with a hydrocarbon fuel (for example, gasoline fuel). In this alcohol-mixed fuel, the fuel properties change according to the fuel mixing ratio of the reference fuel.

  The internal combustion engine is one in which various control operations such as combustion control are executed by an electronic control unit (ECU) 1 shown in FIG. That is, the control device for the internal combustion engine is constituted by the electronic control device 1. The electronic control unit 1 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores a predetermined control program and the like, and a RAM (Random Access) that temporarily stores the calculation result of the CPU. Memory) and a backup RAM for storing information prepared in advance.

  First, the configuration of the internal combustion engine exemplified here will be described with reference to FIG. Although only one cylinder is shown in FIG. 1, the present invention is not limited to this, and can be applied to a multi-cylinder multifuel internal combustion engine. In the first embodiment, description will be made assuming that a plurality of cylinders are provided.

  The internal combustion engine includes a cylinder head 11, a cylinder block 12, and a piston 13 that form a combustion chamber CC. Here, the cylinder head 11 and the cylinder block 12 are fastened with bolts or the like via the head gasket 14 shown in FIG. 1, and the recess 11a on the lower surface of the cylinder head 11 and the cylinder bore 12a of the cylinder block 12 formed thereby. The piston 13 is disposed so as to be capable of reciprocating in the space. And the combustion chamber CC mentioned above is comprised by the space enclosed by the wall surface of the recessed part 11a of the cylinder head 11, the wall surface of the cylinder bore 12a, and the top surface 13a of the piston 13. FIG.

  This internal combustion engine sends air and fuel into the combustion chamber CC in accordance with operating conditions such as engine speed and engine load, and executes combustion control in accordance with the operating conditions. The air is sucked from the outside through the intake passage 21 and the intake port 11b of the cylinder head 11 shown in FIG. On the other hand, the fuel is supplied using the fuel supply device 50 shown in FIG.

  First, the air supply path will be described.

  On the intake passage 21 of the internal combustion engine, an air cleaner 22 for removing foreign matters such as dust contained in air introduced from the outside, and an intake air amount detection means 23 for detecting the intake air amount GA from the outside are provided. It has been. As the intake air amount detection means 23, an air amount detection sensor such as an air flow meter that directly detects the intake air amount GA, an intake pipe pressure sensor that detects the pressure in the intake passage 21 (ie, intake pressure), and the like are conceivable. . When the latter intake pipe pressure sensor is used, the intake air amount GA is obtained indirectly from the intake pressure and the engine speed NE. In this internal combustion engine, the detection signal of the intake air amount detection means 23 is sent to the electronic control unit 1, and the electronic control unit 1 calculates the intake air amount GA, the engine load KL, and the like based on the detection signal. The engine speed NE can be grasped from the detection signal of the crank angle sensor 16 that detects the rotation angle of the crankshaft 15.

  A throttle valve 24 capable of adjusting the flow rate of the air flowing into the combustion chamber CC and a throttle valve for opening and closing the throttle valve 24 on the intake passage 21 downstream of the intake air amount detection means 23. And an actuator 25. In the electronic control unit 1 of the first embodiment, the throttle valve actuator 25 is driven and controlled according to the operating conditions, and the throttle valve that adjusts the valve opening angle of the throttle valve 24 so that the valve opening degree according to the operating conditions is obtained. Control means are provided. Here, the throttle valve actuator 25 and the throttle valve control means constitute a throttle valve opening control means. Further, this internal combustion engine is provided with a throttle opening sensor 26 that detects the valve opening of the throttle valve 24 and transmits the detection signal to the electronic control unit 1.

  On the other hand, one end of the intake port 11b opens into the combustion chamber CC, and an intake valve 31 for opening and closing the opening is disposed at the opening portion. The number of openings may be one or more, and an intake valve 31 is provided for each opening. Therefore, in this internal combustion engine, air is sucked into the combustion chamber CC from the intake port 11b by opening the intake valve 31 and closed to the combustion chamber CC by closing the intake valve 31. Air inflow is blocked.

  Here, as the intake valve 31, for example, there is a valve that is driven to open and close in accordance with the rotation of an intake camshaft (not shown) and the elastic force of an elastic member (string spring). In this type of intake valve 31, by interposing a power transmission mechanism such as a chain or a sprocket between the intake side camshaft and the crankshaft 15, the intake side camshaft is interlocked with the rotation of the crankshaft 15, Open / close drive is performed at a preset opening / closing timing. In the internal combustion engine illustrated here, the intake valve 31 that is driven to open and close in synchronization with the rotation of the crankshaft 15 can be applied.

  However, the internal combustion engine may be provided with a variable valve mechanism such as a so-called variable valve timing and lift mechanism that can change the opening / closing timing and lift amount of the intake valve 31, and thereby the opening / closing timing of the intake valve 31. And the lift amount can be changed to a suitable one according to the operating conditions. Furthermore, in this internal combustion engine, a so-called electromagnetically driven valve that opens and closes the intake valve 31 using electromagnetic force may be used in order to obtain the same effect as the variable valve mechanism.

  Next, the fuel supply device 50 will be described.

  As this fuel supply device 50, the fuel in one fuel tank is injected into the intake port 11b and / or into the combustion chamber CC, and the fuel having different fuel properties stored in a plurality of fuel tanks is mixed into the fuel mixing device. It can be considered that the mixture is mixed in the intake port 11b and / or injected into the combustion chamber CC. In this embodiment, a port injection type in which the fuel F stored in one fuel tank 41 is injected into the intake port 11b and led to the combustion chamber CC together with the intake air is shown as a representative example.

  Specifically, the fuel supply device 50 distributes the fuel F in the fuel passage 51 to each cylinder, and a feed pump 52 as a fuel pump that sucks the fuel F from the fuel tank 41 and sends it to the fuel passage 51. A fuel delivery pipe 53 and a fuel injection valve (fuel injection means) 54 for each cylinder that injects fuel F supplied from the fuel delivery pipe 53 into each intake port 11b.

The fuel supply device 50 controls the fuel injection control means of the electronic control device 1 to drive and control the feed pump 52 and the fuel injection valve 54 according to the operating conditions, and thereby the target fuel injection amount Q _tgt corresponding to the operating conditions. The fuel F is injected under fuel injection conditions such as fuel injection timing and fuel injection period. For example, the fuel injection control means causes the fuel F to be sucked up from the fuel tank 41 by the feed pump 52 and causes the fuel injection valve 54 to perform injection under the fuel injection conditions corresponding to the operating conditions.

The fuel F supplied to the intake port 11b in this way is supplied into the combustion chamber CC together with the opening of the intake valve 31, while being mixed with the air described above in the intake port 11b. Here, the target fuel injection amount Q _{tgt of the} fuel F _fed into the combustion chamber CC and the intake air amount GA of air are determined by the air-fuel ratio control means of the electronic control unit 1 according to the target air-fuel ratio corresponding to the operating conditions. The air-fuel ratio control unit of the first embodiment executes air-fuel ratio control to the target air-fuel ratio by adjusting the fuel injection amount of the fuel F. In the first embodiment, air-fuel ratio control is performed so that the main operation of the internal combustion engine is stoichiometric operation.

Specifically, the air-fuel ratio control means first performs the air-fuel ratio control to the target air-fuel ratio, and the engine rotation obtained by the intake air amount GA obtained by the intake air amount detection means 23 and the crank angle sensor 16. Based on the number NE, the basic fuel injection amount Q _bs is calculated using the following equation (1). Here, “K1” in Equation 1 is a preset constant. This basic fuel injection amount Q _bs is a value obtained so that the air-fuel ratio of the air-fuel mixture in the combustion chamber CC becomes the stoichiometric air-fuel ratio, for example, if stoichiometric operation is the operating condition.

Q _bs = K1 × GA / NE (1)

This air-fuel ratio control means is necessary for various control with respect to the basic fuel injection amount Q _bs and the main air-fuel ratio feedback correction coefficient FAF, the air-fuel ratio learning value KGi (i = 1, 2, 3,...). The target fuel injection amount Q _tgt is calculated in consideration of the correction coefficient K2, and an instruction is given to the fuel injection valve 54 to execute fuel injection at the target fuel injection amount Q _tgt . That is, in the air-fuel ratio control of the first embodiment, the basic fuel injection amount Q is calculated using the main air-fuel ratio feedback correction coefficient FAF, the air-fuel ratio learning value KGi (i = 1, 2, 3,...) And the correction coefficient K2. _By correcting _bs , the target fuel injection amount Q _tgt for controlling the actual air-fuel ratio to the target air-fuel ratio is obtained and fuel injection is performed. The target fuel injection amount Q _tgt is obtained using, for example, the following formula 2.

Q _tgt = Q _bs × FAF × KGi × K2 (2)

In the first embodiment, “FAF × KGi × K2” in Expression 2 is the fuel injection amount correction value Q _cor (Q _cor = FAF × KGi × K2). The fuel injection amount correction value Q _cor converges the actual air-fuel ratio (actual air-fuel ratio) to the target air-fuel ratio when there is a difference between the detected actual air-fuel ratio or the estimated actual air-fuel ratio and the target air-fuel ratio. This is the correction value for the fuel injection amount. The fuel injection amount correction value Q _cor shown here is exemplified as multiplying the basic fuel injection amount Q _bs, it may be one to be added to the basic fuel injection amount Q _bs.

  The main air-fuel ratio feedback correction coefficient FAF in the above equation 2 is a learning value used for control (fuel injection amount feedback correction control) for converging the actual air-fuel ratio of the air-fuel mixture in the combustion chamber CC to the target air-fuel ratio. Therefore, it can also be said to be a main air-fuel ratio feedback learning convergence value. As the main air-fuel ratio feedback correction coefficient FAF, “1.0” is set as a value corresponding to the theoretical air-fuel ratio. For example, when the stoichiometric operation is used as the operating condition, the main air-fuel ratio is converged to the theoretical air-fuel ratio. A fuel ratio feedback correction coefficient FAF is obtained.

The main air-fuel ratio feedback correction coefficient FAF is calculated by an air-fuel ratio control means of the electronic control unit 1 in accordance with a detection value from an exhaust sensor 83 described later. For example, if the air-fuel ratio control means is in the stoichiometric operation mode and the detection value from the exhaust sensor 83 indicates a lean air-fuel ratio or a rich air-fuel ratio, a value “1. The main air-fuel ratio feedback correction coefficient FAF is increased or decreased around “0”. In other words, this air-fuel ratio control means, if the detected actual air-fuel ratio calculated from the detection value of the exhaust sensor 83 or the estimated actual air-fuel ratio is rich (over-rich) with respect to the stoichiometric air-fuel ratio, the main air-fuel ratio. Reduction correction control of the target fuel injection amount Q _tgt is performed by reducing the feedback correction coefficient FAF from “1.0”, and the detected actual air fuel ratio or the estimated actual air fuel ratio is leaner than the stoichiometric air fuel ratio. If so, the main air-fuel ratio feedback correction coefficient FAF is increased from “1.0” to perform the increase correction control of the target fuel injection amount Q _tgt .

The air-fuel ratio learning value KGi in the above equation 2 is a learning value used for feedback correction control of the fuel injection amount, like the main air-fuel ratio feedback correction coefficient FAF. For example, the air-fuel ratio learning value KGi is the average value of the main air-fuel ratio feedback correction coefficient FAF when the stoichiometric operation is used (hereinafter referred to as “average main air-fuel ratio feedback correction coefficient”) FAF _AV . Is a value that is increased or decreased around the reference value “1.0” based on the average main air-fuel ratio feedback correction coefficient FAF _AV so as to converge within a predetermined range including “1.0”. The air-fuel ratio control means increases the air-fuel ratio learning value KGi and increases the average main air-fuel ratio feedback correction coefficient FAF _AV when the stoichiometric operation is in progress. If the air-fuel ratio feedback correction coefficient FAF _AV is outside the predetermined range, the air-fuel ratio learning value KGi is decreased. That is, the air-fuel ratio control means, by increasing or decreasing the air-fuel ratio learned value KGi based on the average main air-fuel ratio feedback correction coefficient FAF _AV, the average main air-fuel ratio feedback correction coefficient FAF _AV is converged within a predetermined range of the Thus, learning of the air-fuel ratio learning value KGi is completed. The learned air-fuel ratio value KGi learned in this way is a value corresponding to the deviation of the air-fuel ratio from the appropriate value.

  Here, the subscript “i” of the air-fuel ratio learning value KGi corresponds to the air-fuel ratio learning region i (i = 1, 2, 3,...). That is, in the first embodiment, for example, a plurality of air-fuel ratio learning regions i are set in correspondence with the operating region, that is, the engine load KL (intake air amount GA) and the engine speed NE for each predetermined range. The air-fuel ratio learning value KGi is set for each air-fuel ratio learning region i. In the first embodiment, a different value is set for each air-fuel ratio learning region i for the air-fuel ratio learning value KGi.

  The correction coefficient K2 in the above equation 2 is a value required in various controls such as fuel increase control during warm-up operation and fuel F increase control or decrease control during acceleration / deceleration.

  As described above, the internal combustion engine according to the first embodiment enables operation with various fuels F having different fuel properties. For this reason, the driver does not always supply the alcohol mixed fuel having the same fuel mixing ratio as the current fuel tank because the alcohol mixed fuel is stored in the fuel tank 41 at the present time. There is also the possibility of refueling or gasoline fuel. In the first place, alcohol blended fuel provided at a fueling facility is not always available with the same fuel blend ratio. Furthermore, although the main component of gasoline fuel provided at a fueling facility is gasoline fuel depending on the country or region, it may be provided as alcohol mixed fuel in which alcohol fuel is mixed with the gasoline fuel.

  For this reason, the fuel F in the fuel tank 41 may be composed mainly of gasoline fuel (that is, highly evaporative fuel with a high fuel mixing ratio of gasoline fuel), or alcohol fuel. In some cases (that is, a low-evaporation fuel with a high fuel mixing ratio of alcohol fuel). That is, the fuel F having the same fuel properties as that before refueling is not always stored in the fuel tank 41 after refueling. The stoichiometric air-fuel ratio (in other words, stoichiometric point) differs between fuels having different fuel properties, and there is an optimum air-fuel ratio corresponding to the operating conditions for each fuel property. Yes. The optimal air-fuel ratio is, for example, an air-fuel ratio that can exhibit good output performance under operating conditions that emphasize output performance, and an air-fuel ratio that can exhibit good emission performance under operating conditions that perform emission performance. That is.

  Therefore, the air-fuel ratio control means sets the target air-fuel ratio according to the fuel properties so that the optimum air-fuel ratio is obtained. In the first embodiment, the air-fuel ratio control means performs the air-fuel ratio feedback correction control according to the above-described equation 2, so that the optimum target air-fuel ratio according to the fuel property of the fuel F supplied into the combustion chamber CC at that time Will be set. At the time of the setting, the learning value (main air / fuel ratio feedback correction coefficient FAF and air / fuel ratio learning value KGi) is updated. For example, when the fuel F is switched to a new fuel property, the learning value is updated as that corresponding to the new fuel property. Therefore, in that case, the air-fuel ratio control is subsequently executed on the assumption that the fuel F having the new fuel property is used.

  The air-fuel mixture in the combustion chamber CC that is air-fuel ratio controlled in this way is burned by the ignition operation of the spark plug 61 when the ignition timing according to the operating conditions is reached. The in-cylinder gas (combustion gas) after being burned is discharged from the combustion chamber CC to the exhaust port 11c shown in FIG. 1 and discharged to the atmosphere through the exhaust passage 81.

  An exhaust valve 71 that opens and closes an opening between the exhaust port 11c and the combustion chamber CC is disposed. The number of openings may be one or more, and the exhaust valve 71 described above is provided for each opening. Accordingly, in this internal combustion engine, combustion gas is discharged from the combustion chamber CC to the exhaust port 11c by opening the exhaust valve 71, and closing the exhaust valve 71 to the combustion gas exhaust port 11c. Is blocked.

  Here, as the exhaust valve 71, as in the intake valve 31 described above, a valve with a power transmission mechanism, a valve with a variable valve mechanism such as a so-called variable valve timing & lift mechanism, or a so-called electromagnetically driven valve is used. Can be applied.

Further, an exhaust purification device 82 is disposed on the exhaust passage 81 to purify harmful components in the exhaust gas. Further, on the exhaust passage 81 of the first embodiment, an exhaust sensor 83 is disposed on the upstream side (combustion chamber CC side) of the exhaust purification device 82. The exhaust sensor 83 is a sensor for obtaining information when calculating or estimating the actual air-fuel ratio of the air-fuel mixture in the combustion chamber CC. For example, as the exhaust sensor 83, an O ₂ sensor that detects the amount of oxygen in the exhaust gas or an A / F sensor (broadband λ sensor) that detects the excess air ratio (λ value) in the exhaust gas can be used. .

Incidentally, whether or not the fuel F supplied to the combustion chamber CC has been switched to a new fuel property can be executed based on the detection value of the exhaust sensor 83. In other words, the presence or absence of switching of the fuel property can be determined from the magnitude of the fuel injection amount correction value Q _cor = FAF × KGi × K2. This is because when the fuel F is switched, the actual air-fuel ratio greatly deviates from the target air-fuel ratio by the difference in fuel properties. The deviation is indicated by the detection of the exhaust sensor 83. This is because the value (fuel injection amount correction value Q _cor ). Therefore, when the fuel injection amount correction value Q _cor becomes large (when the absolute value of the fuel injection amount correction value Q _cor exceeds the predetermined value α), it is possible to determine “change in fuel property”. Become. The predetermined value α is obtained from an experiment or simulation to obtain a fuel injection amount correction value Q _cor when the fuel is switched between the fuels F having various fuel properties, and the fuel injection amount correction for each of the fuels F is corrected. The value Q _cor may be set. Here, the electronic control unit 1 of the first embodiment is provided with a fuel property determination unit that performs determination regarding a change in the fuel property of the fuel F. Therefore, the air-fuel ratio control means is such that the updated learning value (main air-fuel ratio feedback correction coefficient FAF or air-fuel ratio learning value KGi) is made to correspond to the new fuel property based on the determination result of the fuel property determination means. Can be identified.

However, when an abnormality occurs in the fuel supply device 50 (for example, the fuel injection valve 54 is clogged or the needle valve is defective), the actual fuel injection amount is deviated from the target fuel injection amount Q _tgt , and the actual The fuel ratio will show a different value with respect to the target air-fuel ratio. Therefore, in such a case, a new fuel injection amount correction value Q _cor is calculated by the air-fuel ratio feedback correction control described above. Since the absolute value of the new fuel injection amount correction value Q _cor increases as the deviation between the actual fuel injection amount and the target fuel injection amount Q _tgt increases, the absolute value of the new fuel injection amount correction value Q _cor may exceed the predetermined value α described above. is there. When the absolute value of the new fuel injection amount correction value Q _cor exceeds the predetermined value α, the air-fuel ratio control means erroneously determines that the fuel property has changed even though the fuel property has not changed. As a result, the learning value is updated as a new fuel property.

Thus, in the first embodiment, the deviation of the actual air-fuel ratio with respect to the target air-fuel ratio when the absolute value of the fuel injection amount correction value Q _cor exceeds the predetermined value α is due to the change in fuel properties. Or whether it is caused by an abnormality of the fuel supply device 50 (fuel supply system).

  The fuel property determination means of the first embodiment obtains the detected value of the exhaust sensor 83 when the internal combustion engine is cold and warm, and compares these values so that the difference between the actual air-fuel ratio and the target air-fuel ratio is reduced. It is determined whether it is caused by a change in fuel properties or an abnormality in the fuel supply device 50 (fuel supply system).

Here, when the fuel property of the fuel F changes, the evaporation characteristic changes (the gasoline fuel has better evaporation property than the alcohol fuel or the alcohol-mixed fuel), so the intake port of the fuel F according to the fuel property The adhesion amount to 11b etc. increases / decreases. The amount of fuel F adhering to the intake port 11b and the like is almost none at the time of warming-up after the warm-up operation, regardless of the fuel property of the fuel F. Resulting in. In other words, when the difference between the actual air-fuel ratio and the target air-fuel ratio is caused by a change in the fuel property of the fuel F, the actual air-fuel ratio is less than the target air-fuel ratio due to the fuel F adhering to the intake port 11b or the like when cold. Therefore, the detected value of the exhaust sensor 83 shows a value different from that at the warm time. Therefore, the fuel property determining means can determine “a change in fuel property” if the detected value of the exhaust sensor 83 in the cold state is different from the detected value of the exhaust sensor 83 in the warm state. More specifically, the adhesion of the fuel F to the intake port 11b or the like causes a difference between the cold fuel injection amount correction value Q1 _cor and the warm fuel injection amount correction value Q2 _cor as shown in FIG. Cause it to occur. For this reason, if there is a difference between the cold fuel injection amount correction value Q1 _cor and the warm fuel injection amount correction value Q2 _cor , the fuel property determination means of the first embodiment will "Change in properties".

FIG. 2 shows that the fuel injection amount correction value Q1 _cor , during the cold time and during the warm time when the fuel property of the fuel F changes (here, the fuel oil is switched from gasoline fuel to alcohol fuel with poor evaporation characteristics). Q2 _cor is expressed. The breakdown of each of the fuel injection amount correction values Q1 _cor and Q2 _cor is common regardless of the engine coolant temperature as the engine temperature (that is, whether it is cold or warm). Some change depending on the engine coolant temperature (that is, depending on whether it is cold or warm). First, as common things regardless of the engine coolant temperature, the fuel injection amount correction value Qe _cor resulting from the variation inherent in the internal combustion engine (that is, variation in intake air amount and fuel injection amount) and the fuel property of the fuel F There is a fuel injection amount correction value Qs _cor resulting from a deviation of the stoichiometric point accompanying the change. Also, the fuel injection amount correction value Qf _cor resulting from the amount of fuel F adhering to the intake port 11b and the like described above changes depending on the engine coolant temperature. The engine temperature may be not only the engine cooling water temperature but also the oil temperature of the lubricating oil.

On the other hand, when an abnormality occurs in the fuel supply device 50, the same abnormal phenomenon appears regardless of the engine coolant temperature (that is, whether it is cold or warm), so that the detection by the exhaust sensor 83 occurs. The value shows the same value between the cold time and the warm time. Therefore, the fuel property determination means can determine that the fuel supply system is abnormal if the detected value of the exhaust sensor 83 in the cold state and the detected value of the exhaust sensor 83 in the warm state show the same value. More specifically, as shown in FIG. 3, if there is no difference between the fuel injection amount correction value Q1 _cor during the cold time and the fuel injection amount correction value Q2 _cor during the warm time, System ”is determined.

FIG. 3 shows the fuel injection amount correction values Q1 _cor and Q2 _cor during the cold time and the warm time when the fuel supply device 50 is abnormal. The breakdowns of the respective fuel injection amount correction values Q1 _cor and Q2 _cor are the same regardless of the engine coolant temperature (that is, regardless of whether the engine is cold or warm). There are a fuel injection amount correction value Qe _cor resulting from engine-specific component variations and a fuel injection amount correction value Qi _cor associated with an abnormality in the fuel supply device 50.

  Hereinafter, the operation of the control apparatus for an internal combustion engine according to the first embodiment will be described with reference to the flowchart of FIG.

  First, the fuel property determination means of the electronic control device 1 of the first embodiment determines whether or not the first fuel property determination execution condition is satisfied (step ST1). The first fuel property determination execution condition is a condition necessary for execution of the first fuel property determination performed when the internal combustion engine is cold, and when the internal combustion engine is in a stable operating state. I mean. Here, the stable operating state of the internal combustion engine is a state in which the fluctuation of the intake air amount GA (engine load KL) is small and the injection characteristic of the fuel injection valve 54 is not greatly changed. The fuel property determination means determines that the engine is cold when the engine coolant temperature detected by the water temperature sensor 17 shown in FIG. 1 is lower than a predetermined temperature (for example, the engine coolant temperature before the warm-up operation starts). Further, the fuel property determination means does not have a large variation in the multiplication value (NE × KL) of the engine speed NE detected by the crank angle sensor 16 and the engine load KL derived by the intake air amount detection means 23, for example. Sometimes it is determined that the internal combustion engine is in a stable operating state.

  When it is determined in step ST1 that the first fuel property determination execution condition is not satisfied, the fuel property determination means repeats step ST1 at all times or every predetermined time until the first fuel property determination execution condition is satisfied.

On the other hand, when it is determined in step ST1 that the first fuel property determination execution condition is satisfied, the fuel property determination means determines the cold fuel injection amount correction value Q1 from the main air-fuel ratio feedback correction coefficient FAF and the like described above. _cor is obtained (step ST2). The cold fuel injection amount correction value Q1 _cor is calculated for air-fuel ratio control by the air-fuel ratio control means. Therefore, in step ST2, the cold fuel injection amount correction value Q1 _cor calculated by the air-fuel ratio control means may be read so as not to overlap the same calculation processing.

  Subsequently, the fuel property determination means determines whether or not the second fuel property determination execution condition is satisfied (step ST3). The second fuel property determination execution condition is a condition necessary for execution of the second fuel property determination performed when the internal combustion engine is warm, and when the internal combustion engine is in a stable operating state. I mean. The fuel property determining means determines that the engine is warm when the engine coolant temperature detected by the water temperature sensor 17 is higher than a predetermined temperature (for example, the engine coolant temperature after the warm-up operation is completed). Further, this fuel property determination means determines whether or not the internal combustion engine is in a stable operating state based on the engine speed NE and the engine load KL, for example, as in the cold state.

As described above, the “stable operation state of the internal combustion engine” is included as the first fuel property determination execution condition and the second fuel property determination execution condition, if the internal combustion engine is not in a stable operation state. This is because the fuel injection amount correction value Qe _cor due to inherent variation (variation in intake air amount and fuel injection amount) may be different between the cold time and the warm time. This is to prevent the calculation accuracy of the fuel injection amount correction values Q1 _cor and Q2 _cor from being lowered.

  When it is determined in step ST3 that the second fuel property determination execution condition is not satisfied, the fuel property determination unit repeats step ST3 at all times or every predetermined time until the second fuel property determination execution condition is satisfied.

On the other hand, when it is determined in step ST3 that the second fuel property determination execution condition is satisfied, the fuel property determination means obtains the fuel injection amount correction value Q2 _cor during the warm time in the same manner as during the cold time ( Step ST4). The air-fuel ratio control means also calculates the fuel injection amount correction value Q2 _cor during the warm period for air-fuel ratio control. Accordingly, in step ST4, the warm fuel injection amount correction value Q2 _cor calculated by the air-fuel ratio control means may be read so that the same calculation processing is not repeated.

After obtaining the cold fuel injection amount correction value Q1 _cor and the warm fuel injection amount correction value Q2 _cor in this way, the fuel property determination means performs the respective fuel injection amount correction values Q1 _cor and Q2 _cor. It is determined whether or not the absolute values of both are larger than the aforementioned predetermined value α (step ST5). That is, in this step ST5, it is determined whether or not there is a possibility that the fuel property of the fuel F supplied into the combustion chamber CC has changed.

In step ST5, it is determined that at least one of the absolute value of the cold fuel injection amount correction value Q1 _{cor and} the absolute value of the warm fuel injection amount correction value Q2 _cor is equal to or less than the predetermined value α. In this case, the fuel property determination means determines that there is no change in the fuel property of the fuel F supplied into the combustion chamber CC, and ends this calculation process.

If it is determined in step ST5 that the absolute value of the cold fuel injection amount correction value Q1 _{cor and} the absolute value of the warm fuel injection amount correction value Q2 _cor are both greater than the predetermined value α, The fuel property determination means determines whether or not the cold fuel injection amount correction value Q1 _cor matches the warm fuel injection amount correction value Q2 _cor (step ST6).

When it is determined in step ST6 that the cold fuel injection amount correction value Q1 _cor and the warm fuel injection amount correction value Q2 _cor do not match, the fuel property determination means determines whether the combustion chamber CC It is determined that the fuel F supplied inside is “change in fuel properties” (step ST7). Then, the air-fuel ratio control means of the first embodiment is the learning value (the main air-fuel ratio feedback correction coefficient FAF and the air-fuel ratio learning value KGi) when the fuel injection amount correction value Q2 _cor at the time of _warming is calculated. Is updated to correspond to a new fuel property (step ST8).

On the other hand, if it is determined in step ST6 that the cold fuel injection amount correction value Q1 _cor and the warm fuel injection amount correction value Q2 _cor match, the fuel property determination means System abnormality "is determined (step ST9).

As described above, the control device for the internal combustion engine of the first embodiment compares the fuel injection amount correction values Q1 _cor and Q2 _cor for the cold time and the warm time (that is, each of the cold time and the warm time). By comparing the difference between the actual air-fuel ratio and the target air-fuel ratio, the deviation of the actual air-fuel ratio from the target air-fuel ratio when the absolute value of the fuel injection amount correction value Q _cor exceeds the predetermined value α It can be clarified whether it is caused by a change in properties or an abnormality of the fuel supply device 50 (fuel supply system). Therefore, the control device for the internal combustion engine can accurately grasp the change in the fuel property by eliminating the influence due to the abnormality of the fuel supply device 50.

  By the way, it is preferable that the arithmetic processing from step ST1 to ST9 is configured to be executed at least once after the ignition signal is switched from off to on, for example. This is because the fuel property of the fuel F is highly likely to change due to refueling after the ignition is turned off.

In the present embodiment 1, the "fuel supply system abnormality" when the fuel injection amount correction value Q2 _cor at between fuel injection amount correction value Q1 _cor and temperature during the cold completely match determination It is configured to make it. However, in this case, even a slight calculation error of the fuel injection amount correction values Q1 _cor and Q2 _cor is not taken into consideration, and there is a possibility that even if the fuel supply system is abnormal, it is determined that the fuel property change has occurred. is there. Therefore, here, if the difference between the cold fuel injection amount correction value Q1 _cor and the warm fuel injection amount correction value Q2 _cor is within a predetermined range, it is determined that the fuel supply system is abnormal. You may comprise as follows.

  A second embodiment of the control apparatus for an internal combustion engine according to the present invention will be described. The control device for the internal combustion engine according to the second embodiment is prepared as a function of the electronic control device 1 as in the first embodiment. Moreover, the same thing as Example 1 is illustrated also about the internal combustion engine which is an application object of this control apparatus.

In the first embodiment described above, if the engine cooling water temperature is higher than a predetermined temperature (for example, the engine cooling water temperature after the completion of the warm-up operation), it is determined that the engine is warm. At that time, the internal combustion engine is in a stable operating state. In other words, it is determined that the second fuel property determination execution condition is met when warm. However, as described above, the evaporation characteristic of the fuel F changes along with the change in the fuel properties. Therefore, if the boiling point of the fuel F is higher than the predetermined temperature, even when it is determined that the fuel is warm, the fuel F is sent to the intake port 11b. It will stick. In other words, in the first embodiment, depending on the evaporation characteristic (specifically, boiling point) of the fuel F, the fuel resulting from the amount of the fuel F adhering to the intake port 11b or the like even when it is determined to be warm The injection amount correction value Qf _cor is generated. For this reason, at that time, the fuel injection amount correction value Q1 _cor during the cold time and the fuel injection amount correction value Q2 _cor during the warm time coincide with each other, and it may be determined that the fuel supply system is abnormal. There is sex.

  Therefore, in the second embodiment, the temperature condition (that is, a predetermined temperature for determining that the fuel is warm) is optimized to determine the second fuel property determination execution condition, and the intake port 11b and the like are optimized. The time when the fuel F adhesion is suppressed is set as the warm time.

Specifically, the predetermined temperature related to the second fuel property determination execution condition is set to a temperature higher than the boiling point of the fuel F. As a result, when it is determined that the engine coolant temperature exceeds the predetermined temperature and it is warm, it is possible to prevent the fuel F from adhering to the intake port 11b and the like, so that the fuel F to the intake port 11b and the like can be suppressed. The generation of the fuel injection amount correction value Qf _cor due to the adhesion amount can be prevented, and the calculation accuracy of the warm fuel injection amount correction value Q2 _cor can be increased. Therefore, in the second embodiment, it is possible to avoid an erroneous determination that “the fuel supply system is abnormal”.

  Actually, it is difficult to set the predetermined temperature to a temperature lower than the boiling point of the fuel F each time, although the fuel property may be changed. For this reason, the fuel F that may be used in the internal combustion engine is estimated in advance, and the boiling point of the fuel having the worst evaporation characteristics (in other words, having a high boiling point) among the various fuels F is used as a reference. Thus, the predetermined temperature related to the second fuel property determination execution condition may be set. That is, it is preferable that the predetermined temperature related to the second fuel property determination execution condition is set to an engine coolant temperature higher than the boiling point of the fuel F having the highest boiling point among the fuels F used in the internal combustion engine.

On the other hand, it is preferable that the predetermined temperature for determining the cold time related to the first fuel property determination execution condition is derived from the same idea. That is, it is preferable that the predetermined temperature related to the first fuel property determination execution condition is set to an engine cooling water temperature lower than the boiling point of the fuel F having the lowest boiling point among the fuels F used in the internal combustion engine. Thus, when the engine coolant temperature is lower than the predetermined temperature and it is determined that the engine is cold, the fuel F adheres to the intake port 11b or the like according to the fuel property of the fuel F, and the intake port 11b A fuel injection amount correction value Qf _cor resulting from the amount of fuel F adhering to the fuel can be generated. This reason, here, it is possible to enhance the computational accuracy of the fuel injection amount correction value Q1 _cor of the cold, the fuel injection amount correction value at the time between the fuel injection amount correction value Q1 _cor and temperature during cold Q2 _cor It is possible to avoid an erroneous determination that “the fuel supply system is abnormal” that occurs when

  As described above, the control device for an internal combustion engine according to the present invention is useful as a technique capable of accurately grasping the change in the fuel property by eliminating the influence due to the abnormality of the fuel supply device.

It is a figure shown about an example of the internal combustion engine used as the application object of the control apparatus of the internal combustion engine which concerns on this invention. It is a figure showing the fuel injection amount correction value at the time of the cold time and the warm time when the fuel property of the fuel is changed (switched from the highly evaporated fuel to the low evaporated fuel). It is a figure showing the fuel injection amount correction value at the time of cold and warm when abnormality occurs in the fuel supply device. 3 is a flowchart illustrating an arithmetic processing operation of the control device for an internal combustion engine according to the present invention.

Explanation of symbols

1 Electronic control device (control device for internal combustion engine)
16 Crank angle sensor 17 Water temperature sensor 23 Intake air amount detection means 41 Fuel tank 50 Fuel supply device 51 Fuel passage 52 Feed pump 53 Fuel delivery pipe 54 Fuel injection valve 83 Exhaust sensor CC Combustion chamber F Fuel

Claims (4)

In a control device for an internal combustion engine provided with a fuel property determination means for determining a change in fuel property of fuel supplied into a combustion chamber based on a detection value of an exhaust sensor that detects an oxygen amount in an exhaust gas and an excess air ratio,
The fuel property determination means compares the detected values detected by the exhaust sensor when the internal combustion engine is cold and warm, and the difference between the actual air-fuel ratio and the target air-fuel ratio is due to a change in the fuel property. A control device for an internal combustion engine, characterized in that it is determined whether there is an abnormality in a fuel supply device.   The fuel property determining means determines that the fuel property has changed if the detected value at the cold time and the detected value at the warm time are different, and determines that the fuel supply device is abnormal if the detected values are the same. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the control apparatus is configured as described above.   The fuel property determining means is configured to determine that the engine is warm when the engine temperature of the internal combustion engine is higher than the boiling point of the fuel that can be used in the internal combustion engine. Item 3. The control device for an internal combustion engine according to Item 1 or 2.   The fuel property determining means is configured to determine that the engine is cold when the engine temperature of the internal combustion engine is lower than the boiling point of the fuel that can be used in the internal combustion engine. Item 3. The control device for an internal combustion engine according to Item 1 or 2.

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