JP2011001856A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an engine by using alcohol concentration of fuel injected from a fuel injection valve even in a period when an alcohol concentration detection value of the fuel detected by an alcohol concentration sensor is different from the alcohol concentration of the fuel injected from the fuel injection valve.SOLUTION: In this control device, the alcohol concentration detection value is different from the alcohol concentration of the fuel injected from the fuel injection valve 21 for a while after the alcohol concentration detection value of the alcohol concentration sensor 37 is varied after fuel supply, but an air-fuel ratio F/B (feedback) correction amount is varied in accordance with the variation when the alcohol concentration of the fuel injected from the fuel injection valve 21 is varied after the alcohol concentration detection value is varied, and alcohol concentration for control (alcohol concentration of the fuel injected from the fuel injection valve 21) is updated in accordance with the presence or the absence of the variation in the alcohol concentration detection value and the air-fuel ratio F/B correction amount, and thus, the alcohol concentration for control can be accurately calculated.

Description

  The present invention relates to a control device for an internal combustion engine comprising an alcohol concentration sensor for detecting the alcohol concentration of fuel supplied from a fuel tank to a fuel injection valve, and an exhaust gas sensor for detecting an air-fuel ratio or rich / lean of exhaust gas. It is.

In recent years, demands for automobiles equipped with engines (internal combustion engines) that can use gasoline, alcohol, and mixed fuels of both as fuels have increased due to social demands such as reducing CO ₂ emissions and using alternative fuels for oil. is doing. In such an automobile, when fuel with a different alcohol concentration from the previous time is supplied to the fuel tank, the alcohol concentration of the fuel in the fuel tank changes. Since the stoichiometric air-fuel ratio differs between gasoline and alcohol, if the alcohol concentration of the fuel changes, the stoichiometric air-fuel ratio of the fuel also changes. Therefore, it is necessary to change the fuel injection amount (actual air-fuel ratio) according to the alcohol concentration of the fuel. There is.

  Therefore, as described in Patent Document 1 (Patent No. 3006304), in a system including an alcohol concentration sensor that detects the alcohol concentration of fuel and an air-fuel ratio sensor that detects the air-fuel ratio of exhaust gas, The fuel injection amount is corrected in accordance with the alcohol concentration detection value detected by the alcohol concentration sensor, and the air-fuel ratio feedback correction amount (the fuel injection amount correction amount is set so that the air-fuel ratio detected by the air-fuel ratio sensor matches the target air-fuel ratio. ) Is calculated, and the air-fuel ratio feedback correction amount is increased when it is determined at the time of fuel replacement based on the change rate of the alcohol concentration detection value.

Japanese Patent No. 3006304

  By the way, the alcohol concentration sensor is disposed in the middle of the fuel passage from the fuel tank to the fuel injection valve or in the fuel tank. Therefore, when the alcohol concentration of the fuel in the fuel tank changes due to refueling, the fuel after refueling is alcohol. Even if the alcohol concentration detection value of the alcohol concentration sensor changes after reaching the concentration sensor, after that, the fuel before the refueling remaining in the fuel passage from the alcohol concentration sensor to the fuel injection valve is not consumed. The alcohol concentration of the fuel injected from the fuel does not change. For this reason, the alcohol concentration detection value of the alcohol concentration sensor and the alcohol concentration of the fuel injected from the fuel injection valve differed for a while after the alcohol concentration detection value of the alcohol concentration sensor changed after fuel supply. It becomes a state.

  However, since the technique of Patent Document 1 does not have a function of determining the alcohol concentration of fuel injected from the fuel injection valve, the alcohol concentration detection value of the alcohol concentration sensor and the alcohol concentration of fuel injected from the fuel injection valve. In the period different from the above, there is a disadvantage that the fuel injection amount, the ignition timing, etc. cannot be corrected according to the alcohol concentration of the fuel injected from the fuel injection valve.

  Therefore, the problem to be solved by the present invention is to use the alcohol concentration of the fuel injected from the fuel injection valve even during a period in which the alcohol concentration detection value of the alcohol concentration sensor and the alcohol concentration of the fuel injected from the fuel injection valve are different. It is an object of the present invention to provide a control device for an internal combustion engine that can control the internal combustion engine.

  In order to solve the above problems, an invention according to claim 1 is directed to an alcohol concentration sensor that detects an alcohol concentration of fuel supplied from a fuel tank to a fuel injection valve, and an exhaust gas that detects an air-fuel ratio or rich / lean of exhaust gas. In a control device for an internal combustion engine including a gas sensor, based on an alcohol concentration detection value detected by an alcohol concentration sensor and a control state of air-fuel ratio feedback control executed based on an output of an exhaust gas sensor, from a fuel injection valve A control alcohol concentration calculation means for calculating the alcohol concentration of the injected fuel as the alcohol concentration used for control of the internal combustion engine (hereinafter referred to as “control alcohol concentration”) is provided.

  For a while after the alcohol concentration detection value of the alcohol concentration sensor changes after fuel supply, the alcohol concentration detection value of the alcohol concentration sensor is different from the alcohol concentration of the fuel injected from the fuel injection valve. However, when the alcohol concentration of the fuel injected from the fuel injection valve changes, the control state of the air-fuel ratio feedback control (for example, the air-fuel ratio feedback correction amount, the air-fuel ratio deviation amount, the target air-fuel ratio and the actual air-fuel ratio Therefore, the control alcohol concentration (the alcohol concentration of the fuel injected from the fuel injection valve) is calculated using the alcohol concentration detection value of the alcohol concentration sensor and the control state of the air-fuel ratio feedback control. be able to. Thus, even when the alcohol concentration detection value of the alcohol concentration sensor and the alcohol concentration of the fuel injected from the fuel injection valve are different, the fuel injection is performed using the control alcohol concentration that is the alcohol concentration of the fuel injected from the fuel injection valve. The internal combustion engine can be appropriately controlled by correcting the amount, ignition timing, and the like. In addition, there is an advantage that the calculation accuracy of the control alcohol concentration can be improved by using information on both the alcohol concentration detection value and the control state of the air-fuel ratio feedback control.

  In this case, as in claim 2, the control alcohol concentration is set according to the presence or absence of the change in the alcohol concentration detection value and the fuel injection amount correction amount (hereinafter referred to as “air-fuel ratio feedback correction amount”) by air-fuel ratio feedback control. You may make it update. When the alcohol concentration of the fuel injected from the fuel injection valve changes after the alcohol concentration detection value of the alcohol concentration sensor changes, the air-fuel ratio feedback correction amount changes accordingly. If the control alcohol concentration is updated according to the air-fuel ratio feedback correction amount, the control alcohol concentration (the alcohol concentration of the fuel injected from the fuel injection valve) can be obtained with high accuracy.

  Specifically, as in claim 3, when the air-fuel ratio feedback correction amount exceeds a predetermined value after the alcohol concentration detection value has changed, the control alcohol concentration is allowed to be updated or the update speed is increased. May be. In this manner, when the air-fuel ratio feedback correction amount exceeds a predetermined value (a predetermined value on the rich side or a predetermined value on the lean side) after the alcohol concentration detection value of the alcohol concentration sensor changes, the fuel injection valve injects the fuel injection valve. It can be determined that the alcohol concentration of the fuel to be changed has changed the air-fuel ratio feedback correction amount, and the update of the control alcohol concentration can be permitted or the update speed can be increased.

  Further, as described in claim 4, after starting the process of permitting the update of the control alcohol concentration or increasing the update speed, the correction amount of the fuel injection amount and the air-fuel ratio feedback correction amount according to the detected alcohol concentration value, When the values almost coincide, the process of permitting the update of the control alcohol concentration or increasing the update speed may be terminated. In this way, when the fuel injection amount correction amount corresponding to the alcohol concentration detection value and the air-fuel ratio feedback correction amount substantially coincide with each other (for example, when the deviation between the two becomes a predetermined value or less), the alcohol concentration sensor. It is determined that the detected alcohol concentration value and the control alcohol concentration (alcohol concentration of the fuel injected from the fuel injection valve) substantially coincide with each other, and the update of the control alcohol concentration is permitted or the update speed is set. The speeding up process can be terminated.

  In general, in a system that performs air-fuel ratio feedback control, the air-fuel ratio variation due to system differences or changes over time is learned by learning the air-fuel ratio feedback correction amount (correction amount of fuel injection amount by air-fuel ratio feedback control) in a predetermined cycle. However, if the air-fuel ratio feedback correction amount is changed when the air-fuel ratio feedback correction amount is changed due to a change in the alcohol concentration of the fuel injected from the fuel injection valve, the individual difference of the system, change with time, etc. The air-fuel ratio feedback correction amount including the influence of the change in the alcohol concentration of the fuel is learned in addition to the air-fuel ratio variation due to the air-fuel ratio.

  Therefore, as in claim 5, there may be provided a learning prohibiting means for prohibiting learning of the air-fuel ratio feedback correction amount during a period in which the update of the control alcohol concentration is permitted or the update speed is increased. In this way, the period during which the control alcohol concentration is allowed to be updated or the update speed is increased, that is, the alcohol concentration of the fuel injected from the fuel injection valve changes and the air-fuel ratio feedback correction amount exceeds the predetermined value. During this period, the air-fuel ratio feedback correction amount is determined to include the influence of the change in the alcohol concentration of the fuel in addition to the air-fuel ratio variation due to system differences or changes over time, and learning of the air-fuel ratio feedback correction amount is prohibited. And a decrease in learning accuracy can be prevented.

  According to a sixth aspect of the present invention, there is provided fuel refueling determination means for determining whether or not fuel has been supplied to the fuel tank, and after the fuel refueling determination means has determined that fuel has been supplied, the alcohol concentration detection value When the air-fuel ratio feedback correction amount exceeds a predetermined value after the change, the update of the control alcohol concentration may be permitted or the update speed may be increased. In this way, after confirming that the fuel has been refueled, when the air-fuel ratio feedback correction amount exceeds the predetermined value after the alcohol concentration detection value of the alcohol concentration sensor changes, the fuel injection valve injects the fuel. Therefore, it is possible to permit the update of the control alcohol concentration or to increase the update speed.

FIG. 1 is a diagram showing a schematic configuration of an engine control system in one embodiment of the present invention. FIG. 2 is a flowchart for explaining the flow of processing of the fuel correction amount calculation routine. FIG. 3 is a diagram conceptually illustrating an example of a map of the fuel correction amount.

Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects 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, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11, and a fuel injection valve that injects fuel toward the intake port in the vicinity of the intake port of the intake manifold 20 of each cylinder. 21 is attached. An ignition 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 the ignition plug 22 of each cylinder.

  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.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a knock sensor 29 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 28 that outputs a pulse signal every time the crankshaft 27 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 27. Based on the output signal of the crank angle sensor 28, the crank angle and engine The rotation speed is detected.

  The engine 11 can use any of a plurality of types of fuel having different fuel properties, for example, gasoline, alcohol such as ethanol or methanol, and alcohol mixed fuel obtained by mixing alcohol with gasoline. In addition, any one of alcohol and alcohol mixed fuel is selected and refueled in the fuel tank 30. A fuel pump 31 that pumps up fuel is provided in the fuel tank 30. 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 fuel 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 regulated to a predetermined pressure by the pressure regulator 35, and surplus fuel exceeding that pressure The minute amount is returned into the fuel tank 30 by the fuel return pipe 36.

  An alcohol concentration sensor 37 that detects the alcohol concentration of the fuel supplied to the engine 11 is attached to a predetermined position of the fuel passage (fuel pipe 32 or delivery pipe 33) from the fuel tank 30 to the fuel injection valve 21. Yes. The location where the alcohol concentration sensor 37 is attached is not limited to the fuel passage, and may be in the fuel tank 30. The alcohol concentration sensor 37 may use any configuration of alcohol concentration sensor. For example, a capacitance-type alcohol concentration that detects the alcohol concentration by measuring the capacitance according to the relative dielectric constant of the fuel. A sensor or an optical (transmission type) alcohol concentration sensor that measures the amount of light transmitted through the fuel (transmittance) to detect the alcohol concentration may be used.

  The outputs of the various sensors described above are input to a control circuit (hereinafter referred to as “ECU”) 38. The ECU 38 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 21 according to the engine operating state and the like. The ignition timing of the spark plug 22 is controlled.

  At that time, the ECU 38 makes the air-fuel ratio of the exhaust gas coincide with the target air-fuel ratio (for example, the theoretical air-fuel ratio) based on the output of the exhaust gas sensor 24 when a predetermined air-fuel ratio F / B control execution condition is satisfied. The air-fuel ratio F / B correction amount is calculated, and the air-fuel ratio F / B control for correcting the fuel injection amount of the fuel injection valve 21 using the air-fuel ratio F / B correction amount is executed. Here, “F / B” means “feedback” (hereinafter the same).

  Further, the ECU 38 learns the air-fuel ratio F / B correction amount (correction amount of the fuel injection amount by the air-fuel ratio F / B control) during the air-fuel ratio F / B control, and the learned air-fuel ratio F / B correction amount is empty. The fuel ratio learning value is stored in a rewritable nonvolatile memory (a rewritable memory that holds stored data even when the ECU 38 is powered off) such as a backup RAM (not shown) of the ECU 38.

  By the way, when fuel having a different alcohol concentration from the previous fuel is supplied to the fuel tank 30 and the alcohol concentration of the fuel in the fuel tank 30 changes, the theoretical air-fuel ratio of the fuel also changes. Therefore, fuel injection is performed according to the alcohol concentration of the fuel. The amount (actual air-fuel ratio) needs to be changed.

  However, since the alcohol concentration sensor 37 is disposed in the middle of the fuel passage from the fuel tank 30 to the fuel injection valve 21 or in the fuel tank 30, if the alcohol concentration of the fuel in the fuel tank 30 changes due to refueling, refueling Even if the subsequent fuel reaches the alcohol concentration sensor 37 and the alcohol concentration detection value of the alcohol concentration sensor 37 changes, the pre-refueling remaining in the fuel passage from the alcohol concentration sensor 37 to the fuel injection valve 21 thereafter. If the fuel is not consumed, the alcohol concentration of the fuel injected from the fuel injection valve 21 does not change. For this reason, the alcohol concentration detection value of the alcohol concentration sensor 37 and the alcohol concentration of the fuel injected from the fuel injection valve 21 for a while after the alcohol concentration detection value of the alcohol concentration sensor 37 changes after fuel supply. Will be in different states.

  Therefore, the ECU 38 executes the fuel correction amount calculation routine of FIG. 2 described later, and is injected from the fuel injection valve 21 based on the alcohol concentration detection value of the alcohol concentration sensor 37 and the air-fuel ratio F / B correction amount. The alcohol concentration of the fuel is calculated as the alcohol concentration used for control of the engine 11 (hereinafter referred to as “control alcohol concentration”), and the fuel correction amount (correction amount of the fuel injection amount) is calculated using this control alcohol concentration. .

  The alcohol concentration detection value of the alcohol concentration sensor 37 differs from the alcohol concentration of the fuel injected from the fuel injection valve 21 for a while after the alcohol concentration detection value of the alcohol concentration sensor 37 changes after fuel supply. However, if the alcohol concentration of the fuel injected from the fuel injection valve 21 changes after the alcohol concentration detection value of the alcohol concentration sensor 37 changes, the air-fuel ratio F / B correction amount changes accordingly. If the control alcohol concentration is updated in accordance with the presence or absence of the change in the alcohol concentration detection value and the air-fuel ratio F / B correction amount, the control alcohol concentration (the alcohol concentration of the fuel injected from the fuel injection valve 21) can be accurately determined. Can be sought.

  In this embodiment, the air-fuel ratio F / B correction amount exceeds a predetermined value (a predetermined value on the rich side or a predetermined value on the lean side) after it is determined that the fuel has been supplied and after the alcohol concentration detection value has changed. In some cases, it is determined that the alcohol concentration of the fuel injected from the fuel injection valve 21 has changed and the air-fuel ratio F / B correction amount has changed, and the update rate of the control alcohol concentration is increased.

  Further, after starting the process of increasing the update rate of the control alcohol concentration, the fuel correction amount (correction amount of the fuel injection amount) and the air-fuel ratio F / B correction amount (in accordance with the alcohol concentration detection value of the alcohol concentration sensor 37) When the fuel injection amount correction amount by the air-fuel ratio F / B control substantially coincides (for example, when the difference between the two becomes a predetermined value or less), the alcohol concentration detection value of the alcohol concentration sensor 37 and the control alcohol It is determined that the concentration (alcohol concentration of the fuel injected from the fuel injection valve 21) is substantially the same, and the process of increasing the update rate of the control alcohol concentration is terminated.

Hereinafter, the processing content of the fuel correction amount calculation routine of FIG. 2 executed by the ECU 38 will be described.
The fuel correction amount calculation routine shown in FIG. 2 is repeatedly executed at a predetermined cycle while the ECU 35 is turned on, and serves as a control alcohol concentration calculation means in the claims. When this routine is started, first, in step 101, it is determined whether or not fuel has been supplied to the fuel tank 30 depending on whether or not the fuel supply determination flag is set to “1”. The process of step 101 serves as fuel refueling determination means in the claims.

  Here, the fuel refueling determination flag monitors, for example, a detection value of a fuel level sensor (not shown) for detecting a fuel level (remaining fuel amount) in the fuel tank 30 and starts the engine (ignition switch is turned on). When the fuel level detected at the time of the engine increases more than the fuel level detected at the previous engine stop (ignition switch off), it is determined that the fuel has been refueled and the fuel refueling determination flag is set to “1”. Set. Alternatively, when the opening / closing of the fuel cap is detected by a fuel cap opening / closing switch (not shown) that detects the opening / closing of the fuel cap that closes the fuel filler opening of the fuel tank 30, it is determined that the fuel has been refueled. The determination flag may be set to “1”. Alternatively, the detection value of a fuel temperature sensor (not shown) that detects the fuel temperature in the fuel tank 30 is monitored, and it is determined that the fuel has been refueled when the fuel temperature in the fuel tank 30 rapidly decreases. Thus, the fuel supply determination flag may be set to “1”.

  If it is determined in step 101 that the fuel supply determination flag = 1 (fuel is supplied), the process proceeds to step 102, where the alcohol concentration changes depending on whether the alcohol concentration change flag is set to “1”. It is determined whether or not the alcohol concentration detection value of the sensor 37 has changed. Here, the alcohol concentration change flag is set to “1” when, for example, the alcohol concentration detection value changes by a predetermined amount or more.

  If it is determined in step 101 that the fuel supply determination flag = 1 (fuel has been supplied) and it is determined in step 102 that the alcohol concentration change flag = 1 (the alcohol concentration detection value has changed), Proceeding to step 103, the update amount of the control alcohol concentration is set to a larger value to increase the update speed when the control alcohol concentration is updated. In this case, for example, the update amount of the control alcohol concentration may be changed according to the change amount of the alcohol concentration detection value.

  On the other hand, when it is determined in step 101 that the fuel supply determination flag = 0 (no fuel is supplied), or in step 102, the alcohol concentration change flag = 0 (the alcohol concentration detection value has not changed). If it is determined, the process proceeds to step 104, where the update amount of the control alcohol concentration is set to a smaller value, and the update speed when the control alcohol concentration is updated is slowed down.

  Thereafter, the routine proceeds to step 105, where it is determined whether the air-fuel ratio F / B control execution condition is satisfied, and the air-fuel ratio F / B control execution condition is satisfied (that is, during the air-fuel ratio F / B control). If it is determined that the air / fuel ratio F / B correction amount has exceeded a predetermined value (a predetermined value on the rich side or a predetermined value on the lean side), the target air / fuel ratio (for example, the theoretical air / fuel ratio) is determined. It is determined whether the deviation of the air-fuel ratio with respect to (fuel ratio) is large.

  If it is determined in step 106 that the air-fuel ratio F / B correction amount has exceeded a predetermined value (the air-fuel ratio deviation is large), the process proceeds to step 107, and whether or not the air-fuel ratio deviation is in the rich direction. If it is determined that the air-fuel ratio deviation is in the rich direction, the process proceeds to step 108 where the control alcohol concentration is decreased by the update amount set in step 103 or 104. Update. On the other hand, if it is determined in step 107 that the air-fuel ratio shift is in the lean direction, the process proceeds to step 109 and the control alcohol concentration is increased by the update amount set in step 103 or 104. Update alcohol concentration. The initial value of the control alcohol concentration is set to, for example, the alcohol concentration detection value of the alcohol concentration sensor 37 when the alcohol concentration change flag = 0.

  Thus, the alcohol concentration of the fuel injected from the fuel injection valve 21 when the air-fuel ratio F / B correction amount exceeds the predetermined value after it is determined that the fuel has been supplied and after the alcohol concentration detection value has changed. Is changed and the air-fuel ratio F / B correction amount is changed, and the update rate of the control alcohol concentration is increased.

  On the other hand, if it is determined in step 106 that the air-fuel ratio F / B correction amount does not exceed the predetermined value (the difference in air-fuel ratio is small), the routine proceeds to step 110, where the fuel supply determination flag = 1 and alcohol It is determined whether or not a predetermined period has elapsed since the density change flag = 1. Here, in the predetermined period, for example, the alcohol concentration of the fuel injected from the fuel injection valve 21 changes and the air-fuel ratio F / B correction amount changes from the time when the alcohol concentration detection value of the alcohol concentration sensor 37 changes. It is set to be slightly longer than the time required for the process. This predetermined period may be a fixed value set in advance, or may be changed according to the engine operating state (for example, engine speed, engine load, etc.).

  When it is determined in step 110 that a predetermined period has elapsed since the fuel supply determination flag = 1 and the alcohol concentration change flag = 1, the process proceeds to step 111, and the fuel correction amount map shown in FIG. 3 is referred to. Then, a fuel correction amount corresponding to the alcohol concentration detection value of the alcohol concentration sensor 37 is calculated, and whether or not the fuel correction amount corresponding to the alcohol concentration detection value substantially matches the air-fuel ratio F / B correction amount. Is determined by, for example, whether or not the absolute value of the deviation between them is equal to or less than a predetermined value.

  When it is determined in step 111 that the fuel correction amount corresponding to the alcohol concentration detection value and the air-fuel ratio F / B correction amount substantially coincide, the alcohol concentration detection value of the alcohol concentration sensor 37 and the control alcohol concentration It is determined that (alcohol concentration of the fuel injected from the fuel injection valve 21) is almost in agreement, the process proceeds to step 112, the fuel refueling determination flag is reset to “0”, and the alcohol concentration change flag is set. Reset to “0”. Thereby, the process for increasing the update rate of the control alcohol concentration is completed. In this case, the alcohol concentration detection value of the alcohol concentration sensor 37 may be set as the control alcohol concentration as it is.

  After calculating the control alcohol concentration as described above, the routine proceeds to step 113, where the fuel correction amount corresponding to the control alcohol concentration is calculated with reference to the fuel correction amount map shown in FIG. This fuel correction amount map is set so that the fuel correction amount increases as the alcohol concentration increases. The ECU 38 calculates the final fuel injection amount using the basic fuel injection amount according to the engine operating state, the fuel correction amount according to the control alcohol concentration, the air-fuel ratio F / B correction amount, and the like.

  In the present embodiment described above, the alcohol concentration detection value of the alcohol concentration sensor 37 and the fuel injection valve 21 are injected for a while after the alcohol concentration detection value of the alcohol concentration sensor 37 changes after fuel supply. If the alcohol concentration of the fuel injected from the fuel injection valve 21 changes after the alcohol concentration detection value of the alcohol concentration sensor 37 changes, the air-fuel ratio F / F changes accordingly. Focusing on the change in the B correction amount, the alcohol concentration for control (injected from the fuel injection valve 21) according to the presence or absence of a change in the alcohol concentration detection value of the alcohol concentration sensor 37 and the air-fuel ratio F / B correction amount. Since the fuel alcohol concentration is updated, the control alcohol concentration can be obtained with high accuracy. Thereby, even when the alcohol concentration detection value of the alcohol concentration sensor 37 and the alcohol concentration of the fuel injected from the fuel injection valve 21 are different, the control alcohol concentration which is the alcohol concentration of the fuel injected from the fuel injection valve 21 is used. Thus, the engine 11 can be appropriately controlled by correcting the fuel injection amount. In addition, there is an advantage that the calculation accuracy of the control alcohol concentration can be improved by using information on both the alcohol concentration detection value and the air-fuel ratio F / B control amount.

  In the above embodiment, when the air-fuel ratio F / B correction amount exceeds a predetermined value after it is determined that the fuel has been supplied and the alcohol concentration detection value has changed, the update rate of the control alcohol concentration is increased. Although the speed is increased, the update of the control alcohol concentration may be permitted. Further, the process of determining whether or not the fuel has been refilled is omitted, and when the air-fuel ratio F / B correction amount exceeds a predetermined value after the alcohol concentration detection value has changed, the update rate of the control alcohol concentration is increased. You may make it quick or allow an update.

  In the above embodiment, the control alcohol concentration is calculated based on the alcohol concentration detection value and the air-fuel ratio F / B correction amount. However, the control of the alcohol concentration detection value and other air-fuel ratio F / B control is performed. The control alcohol concentration may be calculated based on the state (air-fuel ratio deviation amount, ratio of target air-fuel ratio to actual air-fuel ratio, etc.).

  In the above embodiment, the fuel injection amount is corrected according to the control alcohol concentration. However, other engine control parameters (ignition timing, throttle opening, EGR amount, valve timing) are adjusted according to the control alcohol concentration. Etc.) may be corrected.

  In the present invention, the control alcohol concentration is allowed to be updated or the update speed is increased, that is, the alcohol concentration of the fuel injected from the fuel injection valve 21 is changed so that the air-fuel ratio F / B correction amount is predetermined. In the period exceeding the value, it is determined that the air-fuel ratio F / B correction amount includes the influence of the change in the alcohol concentration of the fuel in addition to the variation in the air-fuel ratio due to the individual difference of the system and the change over time. The learning of the correction amount may be prohibited to prevent the learning accuracy from being lowered.

  In addition, the present invention is not limited to the intake port injection type engine as shown in FIG. 1, but includes an in-cylinder injection type engine, and both an intake port injection fuel injection valve and an in-cylinder injection fuel injection valve. It can also be applied to dual-injection engines.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 30 ... Fuel tank, 31 ... Fuel pump, 32 ... Fuel piping, 33 ... Delivery pipe, 37 ... Alcohol concentration sensor, 38 ... ECU (control alcohol concentration calculation means, learning prohibition means, fuel supply determination means)

Claims (6)

In an internal combustion engine control device comprising an alcohol concentration sensor for detecting an alcohol concentration of fuel supplied from a fuel tank to a fuel injection valve, and an exhaust gas sensor for detecting an air-fuel ratio or rich / lean of exhaust gas,
Based on the alcohol concentration detection value detected by the alcohol concentration sensor and the control state of air-fuel ratio feedback control executed based on the output of the exhaust gas sensor, the alcohol concentration of the fuel injected from the fuel injection valve is determined as an internal combustion engine. A control device for an internal combustion engine, comprising control alcohol concentration calculation means for calculating an alcohol concentration used for engine control (hereinafter referred to as "control alcohol concentration").   The control alcohol concentration calculation means is configured to control the alcohol according to the presence or absence of a change in the alcohol concentration detection value and a fuel injection amount correction amount (hereinafter referred to as “air-fuel ratio feedback correction amount”) based on the air-fuel ratio feedback control. 2. The control apparatus for an internal combustion engine according to claim 1, further comprising means for updating the concentration.   The control alcohol concentration calculation means is a means for permitting the update of the control alcohol concentration or increasing the update speed when the air-fuel ratio feedback correction amount exceeds a predetermined value after the alcohol concentration detection value has changed. The control apparatus for an internal combustion engine according to claim 2, comprising:   The control alcohol concentration calculation means starts the process of permitting the update of the control alcohol concentration or increasing the update speed, and then corrects the fuel injection amount correction amount according to the alcohol concentration detection value and the air-fuel ratio feedback. 4. The control apparatus for an internal combustion engine according to claim 3, further comprising means for permitting the update of the control alcohol concentration or ending the process of increasing the update speed when the correction amount substantially matches.   5. The internal combustion engine according to claim 3, further comprising a learning prohibiting unit that prohibits learning of the air-fuel ratio feedback correction amount during a period in which the update of the control alcohol concentration is permitted or the update speed is increased. Engine control device. A fuel refueling determination means for determining whether fuel has been refueled in the fuel tank;
The control alcohol concentration calculating means is configured to detect when the air-fuel ratio feedback correction amount exceeds a predetermined value after the fuel supply determining means determines that the fuel has been supplied and after the alcohol concentration detection value has changed. 6. The control apparatus for an internal combustion engine according to claim 2, further comprising means for permitting renewal of the control alcohol concentration or increasing a renewal speed.

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