JP4758866B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a flexible fuel vehicle, that is, an internal combustion engine for a vehicle that can be operated with gasoline fuel, ethanol fuel, or a mixed fuel of gasoline and ethanol. The present invention relates to a control device.

  In a flexible fuel vehicle (hereinafter referred to as “FFV”), as described in Patent Document 1 below, an air-fuel ratio correction of a fuel injection amount that is usually calculated according to a deviation between a detected air-fuel ratio and a target air-fuel ratio Based on the coefficient, the fuel property (alcohol concentration) is detected.

That is, in the technique disclosed in Patent Document 1, when it is detected that fuel has been supplied, the exhaust value when the limit value (limiter) of the air-fuel ratio correction coefficient is canceled and the fuel injection amount is temporarily increased or decreased. The properties of the fuel are estimated based on the behavior of the air-fuel ratio.
JP 2003-120363 A

  In the above-described prior art, since the limit value of the air-fuel ratio correction coefficient is released immediately after refueling, it is released even when the fuel properties are not changed even though the fuel has been refueled. When the air-fuel ratio correction coefficient changes greatly due to the influence of the above, there is a disadvantage that the stability of the air-fuel ratio control is lowered.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that solves the above-described problems and learns the alcohol concentration while ensuring the stability of air-fuel ratio control.

In order to solve the above-mentioned object, according to claim 1, an air-fuel ratio detecting means for detecting an air-fuel ratio in the exhaust gas, and a fuel injection amount in accordance with a deviation between the detected air-fuel ratio and the target air-fuel ratio. An air-fuel ratio correction coefficient calculating means for calculating the air-fuel ratio correction coefficient, an alcohol concentration learning means for learning the alcohol concentration contained in the fuel based on the calculated air-fuel ratio correction coefficient, and an upper limit value of the air-fuel ratio correction coefficient Upper and lower limit value setting means for setting the lower limit value, upper and lower limit value changing means for changing the upper limit value and the lower limit value when the alcohol concentration learning means learns, and the center of the upper limit value and the lower limit value In the control device for an internal combustion engine comprising a central value calculation means for calculating a value, the upper and lower limit value changing means calculates the upper limit value and the lower limit value when the air-fuel ratio correction coefficient reaches the upper limit value. Each of the first predetermined While increasing correction only when said air-fuel ratio correction coefficient reaches the lower limit, the upper limit value and the lower limit value only decreases the corrected second predetermined value, respectively, the air-fuel ratio correction coefficient is less than the upper limit If the upper limit value is greater than the first basic value and the air-fuel ratio correction coefficient is less than or equal to the center value, the upper limit value and the lower limit value are respectively set to a third predetermined value. When the lower limit value is smaller than a second basic value set smaller than the first basic value and the air-fuel ratio correction coefficient is equal to or greater than the central value, The lower limit value is increased and corrected by a fourth predetermined value.

In the control apparatus for an internal combustion engine according to claim 2, wherein the upper and lower limit value setting means, the maximum limit value indicating the value of the maximum possible change the upper limit value in an increasing direction, in the decreasing direction of the lower limit value and sets a modifiable minimum limit value, and configured as to change the minimum limit and the maximum limit in accordance with the alcohol concentration calculated by the learning of the alcohol concentration learning means.

In the control apparatus for an internal combustion engine according to claim 3, wherein the upper and lower limit value changing means, according to the alcohol concentration previous value before the alcohol concentration learning means starts learning, the maximum limit and the minimum limit value It was constructed as to change the.

In claim 1, the upper limit value and the lower limit value of the air-fuel ratio correction coefficient of the fuel injection amount calculated according to the deviation between the detected air-fuel ratio and the target air-fuel ratio are reached, and the air-fuel ratio correction coefficient reaches the upper limit value . When the air-fuel ratio correction coefficient reaches the lower limit value, the upper limit value and the lower limit value are each corrected to decrease by the second predetermined value. Further, when the air-fuel ratio correction coefficient is not more than the upper limit value and not less than the lower limit value, the upper limit value and the lower limit value are determined when the upper limit value is larger than the first basic value and the air-fuel ratio correction coefficient is not more than the center value. When the lower limit value is smaller than the second basic value set smaller than the first basic value and the air-fuel ratio correction coefficient is equal to or greater than the center value, the upper limit value and the lower limit value are respectively corrected to decrease by the third predetermined value. Each value is corrected to be increased by a fourth predetermined value. If there is no change in the fuel properties during refueling, even if the air-fuel ratio correction coefficient changes greatly due to the influence of disturbance, the change is suppressed by the limit value, so even when learning the alcohol concentration, the air-fuel ratio control Can be ensured. In addition, since the change width of the air-fuel ratio correction coefficient itself is not changed, the maximum value of the deviation of the air-fuel ratio correction coefficient does not change, so that the stability of the air-fuel ratio control can be further ensured.

In the control apparatus for an internal combustion engine according to claim 2, since it is configured as to change the maximum limit and the minimum limit value in accordance with the alcohol concentration learned value, in addition to the effects mentioned above, the stability of the air-fuel ratio control Can be secured even better. The maximum deviation of the air-fuel ratio correction coefficient when the alcohol concentration learning is determined by the deviation of the alcohol concentration is changed by refueling, the limit values be relocated in accordance with the alcohol concentration, to suppress the change of unnecessary limits And the stability of the air-fuel ratio control can be further ensured. Therefore, it is possible to optimally achieve both alcohol concentration learning and air-fuel ratio control.

In the control apparatus for an internal combustion engine according to claim 3, according to the alcohol concentration previous value before starting the alcohol concentration learning, since it is configured as to change the maximum limit and a minimum limit value, to the effects mentioned above In addition, the stability of the air-fuel ratio control can be further ensured. That is, the maximum limit and the minimum limit value of the air-fuel ratio correction coefficient is determined by the alcohol concentration, but the limit the alcohol concentration before starting the alcohol concentration learning, i.e., by be relocated in accordance with the alcohol concentration of the previous Therefore, an unnecessary change in the limit value can be suppressed, and the stability of the air-fuel ratio control can be further ensured. Therefore, it is possible to optimally achieve both alcohol concentration learning and air-fuel ratio control.

  The best mode for carrying out the control apparatus for an internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing an overall control apparatus for an internal combustion engine according to an embodiment of the present invention.

  In FIG. 1, reference numeral 10 indicates a four-cylinder (cylinder) four-cycle internal combustion engine (only one cylinder is shown; hereinafter referred to as “engine”) mounted on an FFV (not shown). In the engine 10, the air (intake air) drawn from the air cleaner 12 and passing through the intake pipe 14 is adjusted in flow rate by the throttle valve 16 and flows through the intake manifold 18, and two intake valves (only one is shown) 20 are opened. When it is done, it flows into the combustion chamber.

  The throttle valve 16 is mechanically disconnected from an accelerator pedal (not shown) disposed on the floor surface of the FFV driver's seat, connected to a DC motor (actuator) 22, and driven by the DC motor 22 to open and close. . Thus, the opening degree of the throttle valve 16 is controlled by a DBW (Drive By Wire) method.

  A main injector 24 is disposed near the intake port in front of the intake valve 20. Fuel that is stored in the main fuel tank 26 and pumped up by the main fuel pump 28 disposed inside the main fuel tank 26 is pumped to the main injector 24 via the main fuel supply pipe 30.

  As the fuel stored in the main fuel tank 26, a mixed fuel of gasoline and ethanol (ethyl alcohol), specifically, a mixed fuel (E22) of 78% gasoline and 22% ethanol (E22) is ethanol of 0% gasoline and 100% ethanol. Alcohol fuel up to fuel (E100) is scheduled. Incidentally, the alcohol fuel has a stoichiometric air / fuel ratio that is richer than that of gasoline, and the deviation increases as the alcohol concentration increases.

  A sub-injector 32 is disposed upstream of the main injector 24 in the vicinity of the intake port. The sub fuel stored in the sub fuel tank 34 and pumped up by the sub fuel pump 36 is pumped to the sub injector 32 through the sub fuel supply pipe 38. As the sub fuel, gasoline fuel, E22 or the like is used.

  The main injector 24 and the sub injector 32 are electrically connected to an ECU (Electronic Control Unit) 40 through a drive circuit (not shown), and a drive signal indicating valve opening time is transmitted from the ECU 40 through the drive circuit. When supplied, the valve is opened, and fuel corresponding to the valve opening time is injected into the intake port. The injected fuel mixes with the air that flows in to form an air-fuel mixture (pre-air mixture), and flows into the combustion chamber when the intake valve 20 is opened. The sub fuel is used only when the engine 10 is started.

  A spark plug 44 is disposed in the combustion chamber. The spark plug 44 is connected to an ignition device (not shown) made of an igniter or the like. When an ignition signal is supplied from the ECU 40, the ignition device generates a spark discharge between the electrodes of the spark plug 44. The mixture is thereby ignited and burned, driving the piston 46 downward.

  A crankshaft (not shown in the figure) 50 is connected to the piston 46 and converts the vertical motion of the piston 46 into rotational motion inside the crankcase 48 below the cylinder block that encloses the piston 46. Is shown). The lower part of the crankcase 48 constitutes an oil pan that receives oil (lubricating oil).

  Exhaust gas (exhaust gas) generated by combustion flows to the exhaust pipe 54 through the exhaust port 52 when two exhaust valves (not shown) are opened. A catalyst device 56 (consisting of a two-bed three-way catalyst) is disposed in the exhaust pipe 54. When the catalyst device 56 is in an active state, the exhaust gas is released into the atmosphere outside the engine after removing harmful components such as HC, CO, and NOx.

  The space above the liquid level of the main fuel tank 26 and the sub fuel tank 34 is connected to a canister 62 via charge passages 58 and 60, and the canister 62 is disposed on the intake pipe 14 via a purge passage 64. Connected downstream. The purge passage 64 is provided with a purge control valve 64a composed of an electromagnetic valve, and opens the purge passage 64 when excited.

  In the configuration described above, the fuel vapor evaporated from the main fuel tank 26 and the sub fuel tank 34 flows to the canister 62 through the charge passages 58 and 60 and is adsorbed by the adsorbent 62a accommodated therein. When the purge control valve 64a is excited inside the canister 62, a negative pressure is applied from the intake pipe 14, and the adsorbed fuel vapor is taken in through the purge passage 64 together with fresh air introduced from the atmosphere opening hole 62b. Purged into the system.

  A PCV (Positive Crankcase Ventilation) hole is formed in the upper part of the crankcase 48 and is connected to the downstream side of the position where the throttle valve 16 is disposed in the intake pipe 14 by a reflux passage 68. The recirculation passage 68 is provided with a check valve 68a, and the alcohol vapor mixed in the oil in the crankcase pushes the check valve 68a open when the pressure exceeds a predetermined pressure, and is purged through the recirculation passage 68 as blow-by gas to the intake system. The

  The cylinder head above the cylinder block is provided with a valve operating mechanism 70 that is operated by hydraulic pressure, and changes the valve timing and lift amount of the intake valve 20 between two characteristics, high and low.

  A crank angle sensor 72 is disposed in the vicinity of the crankshaft of the engine 10, and a cylinder discrimination signal based on the rotation of the pulsar plate 50 described above, and a TDC signal indicating a TDC (top dead center) of each cylinder or a crank angle in the vicinity thereof. And a crank angle signal obtained by subdividing the TDC signal.

  An air flow meter 74 having a temperature detecting element is disposed in the vicinity of the air cleaner 12 and outputs a signal corresponding to the amount of air (intake air) Q taken from the air cleaner 12 and the intake air temperature TA.

  A MAP sensor 76 is disposed downstream of the throttle valve 16 in the intake pipe 14 and outputs a signal indicating the intake pipe pressure PBA in absolute pressure. A throttle opening sensor 78 is disposed in the throttle valve 16. A signal corresponding to the position (throttle opening) TH is output.

  A water temperature sensor 80 is disposed in a cooling water passage (not shown) of the engine 10 to output a signal corresponding to the engine cooling water temperature TW, and a knock sensor 82 is disposed in the cylinder block, so that vibrations generated in the engine 10 are detected. A corresponding signal is output.

A wide area air-fuel ratio sensor 84 is disposed upstream of the catalyst device 56 in the exhaust system, and outputs a signal corresponding to the oxygen concentration in the exhaust gas in a wide range from the stoichiometric air-fuel ratio to rich or lean. Based on the output of the wide area air-fuel ratio sensor 84, the detected air-fuel ratio KACT is calculated as an equivalence ratio. Further, an O ₂ sensor 86 is disposed between the catalyst beds of the catalyst device 56, and outputs a signal that reverses whenever the oxygen concentration in the exhaust gas changes from the stoichiometric air-fuel ratio to rich or lean.

  A fuel level sensor 88 is disposed in the main fuel tank 26 and outputs a signal corresponding to the fuel level.

  An accelerator opening sensor 90 is provided in the vicinity of the accelerator pedal, and outputs a signal corresponding to the accelerator position (indicating the engine load) AP indicating the amount by which the driver depresses the accelerator pedal. A vehicle speed sensor 92 is provided in the vicinity of the drive shaft (not shown), and a pulse signal is output per rotation of the drive shaft, and an atmospheric pressure sensor 94 is provided at an appropriate position of the FFV, depending on the atmospheric pressure PA. Output the signal.

  The output of the sensor group described above is input to the ECU 40. The ECU 40 includes a microcomputer, and includes a CPU, ROM, RAM, A / D conversion circuit, input / output circuit, and counter (all not shown). The ECU 40 counts the crank angle signal among the input signals to calculate (detect) the engine speed NE, and counts the output of the vehicle speed sensor 92 to calculate (detect) the vehicle speed VP.

  Based on the input value and the calculated value, the ECU 40 calculates the fuel injection amount and the like according to the command stored in the ROM, as described below, and calculates the intake valve 20 from the engine speed NE and the intake pipe absolute pressure PBA. The valve timing and the lift amount are changed between two characteristics, high and low.

  FIG. 2 is a block diagram functionally explaining the operation of the ECU 40.

  Reference numeral 40a denotes a fuel injection amount calculation block, in which a fuel injection amount TOUT to be supplied to the engine 10 is calculated according to the detected operating state.

  That is, the basic fuel injection amount TIM is calculated according to the engine load, and in the air-fuel ratio feedback control for controlling the detected air-fuel ratio KACT to the target air-fuel ratio KCMD (more precisely, the target air-fuel ratio correction coefficient KCMD). The air-fuel ratio correction coefficient (air-fuel ratio feedback correction coefficient) KAF is calculated in accordance with the deviation of the difference, and other correction coefficients such as the alcohol concentration correction coefficient (alcohol concentration learning value) KREFBS are calculated to correct the basic fuel injection amount. Thus, the fuel injection amount TOUT is calculated.

  In the fuel injection amount calculation block 40a, the limit value of the air-fuel ratio correction coefficient KAF is set, and when the limit value is changed when the alcohol concentration is learned, when the air-fuel ratio correction coefficient KAF reaches the limit value, It is configured to change the limit value.

  Based on the calculated fuel injection amount TOUT, the main injector 24 is driven. Since the alcohol fuel has poor startability when the engine coolant temperature TW is low, the sub fuel is injected by driving the sub injector 32 in addition to the main injector 24 when the engine 10 is started.

  Reference numeral 40b denotes an alcohol concentration learning block in which the alcohol concentration contained in the fuel is learned based on the air-fuel ratio correction coefficient KAF. In other words, the alcohol concentration correction coefficient KREFBS is updated by calculating the alcohol concentration learning value KREFX by smoothing the air-fuel ratio correction coefficient KAF and multiplying it by the previous alcohol concentration correction coefficient KREFBS. The alcohol concentration correction coefficient KREFBS is sent to the block 40a.

  Reference numeral 40c denotes an ignition timing calculation block in which an ignition timing to be supplied to the engine 10 is calculated according to the detected operating state, and ignition of the spark plug 44 is controlled based on the calculated ignition timing. .

  Reference numeral 40d denotes a throttle opening control value calculation block, in which a throttle opening control value is calculated, and the DC motor 22 is driven based thereon.

  FIG. 3 is a flowchart showing the fuel injection amount calculation processing in block 40a. The illustrated program is executed at a predetermined crank angle near the TDC of each cylinder.

  In the following description, it is obtained by multiplying the start-time increase correction term KAST, the acceleration correction term KACC calculated according to the acceleration, and the deceleration correction term KDEC calculated according to the deceleration calculated in a separate routine in S10. Let the product be ktotaltmp.

  Next, the routine proceeds to S12, where the intake air temperature correction term KTA calculated in accordance with the intake air temperature TA, the atmospheric pressure correction term KPA calculated in accordance with the atmospheric pressure PA, and the engine cooling water temperature TW, which are similarly calculated in another routine. Is multiplied by the water temperature correction term KTW calculated in this way, and the product thus obtained is defined as ktatwpa.

  Next, in S14, the two correction terms obtained by the processing of S10 and S12 are multiplied, and the obtained value is set as the multiplication correction term integrated value KTTL.

  Next, in S16, the fuel injection amount TOUT to be supplied to the engine 10 is calculated according to the equation shown.

  In the equation shown in S16, KREFBS: alcohol concentration correction coefficient, KAF: air-fuel ratio correction coefficient, KCMD: target air-fuel ratio or target air-fuel ratio correction coefficient (the air-fuel ratio is indicated by the equivalent ratio in the same manner as the detected air-fuel ratio KACT. KTTL: Multiplication correction term integrated value, TIM (basic fuel injection amount after warm-up, preset characteristics (map)) Engine load Gair (calculated by searching for the amount of air used for one combustion obtained by dividing the output Q of the air flow meter 74 by the engine speed NE), KEVACT: canister purge (intake system) Correction coefficient (fuel vapor recirculated to the fuel), KCTMFFV: alcohol transpiration correction coefficient (correction coefficient of alcohol vapor mixed in oil (lubricating oil)) A. All fuel injection amounts including the final fuel injection amount TOUT are defined by the valve opening time of the main injector 24.

Figure 4 is a flow chart showing the calculation processing of the air-fuel ratio correction coefficient KAF in the fuel injection amount calculation processing at block 4 0a. The illustrated program is also executed at a predetermined crank angle near the TDC of each cylinder.

  Explaining below, in S100, a deviation DKCMD between the target air-fuel ratio KCMD and the detected air-fuel ratio KACT is calculated, and the process proceeds to S102, where the deviation DKCMD is multiplied by a proportional gain KPAF to calculate a P term (proportional term) KPF in the PID control law. Proceeding to S104, the deviation DKCMD is multiplied by the integral gain KIAF, and the previous value kift is added to calculate the I term (integral term) kift.

  Next, in S106, the difference obtained by subtracting the previous deviation DKCMDP from the deviation DKCMD is multiplied by the differential gain KDAF to calculate the D term (differential term) KDF in the PID control law.

  Next, in S110, the proportional term KPF, the integral term kift, and the derivative term KDF are added, and the resulting sum is used as the air-fuel ratio correction coefficient KAF.

  Next, the process proceeds to S112, where it is determined whether the air-fuel ratio correction coefficient KAF calculated in S110 is lower than the lower limit value (limit value) KAFALL, in other words, whether the lower limit value has been reached. The value KAFALL is used as the air-fuel ratio correction coefficient KAF.

Next, in S116, the (second predetermined value described above) value was reduced corrected by subtracting the Karine KAFAL predetermined value DKAFCHGAL from the lower limit value KAFALL, the process proceeds to S118, an upper limit value (limit value) predetermined value from KAFALH DKAFCHGAL A value obtained by subtracting (the above-described second predetermined value) and correcting the decrease is set as a temporary value KAFAH.

  FIG. 5 is a time chart for explaining the above-described processing.

  That is, in this embodiment, the alcohol concentration contained in the fuel is learned by the air-fuel ratio correction coefficient KAF, more specifically, the value KREFX obtained by smoothing it. A limit value (defined by the upper limit value KAFALH and the lower limit value KAFALL) that limits the change of the correction coefficient KAF is set. In this case, when the alcohol concentration is learned, the limit value is changed when the air-fuel ratio correction coefficient reaches the limit value.

  Returning to the description of the flowchart of FIG. 4, when the result in S112 is negative, the program proceeds to S120, in which it is determined whether the feedback correction coefficient KAF calculated in S110 is equal to or higher than the upper limit value KAFALH, in other words, whether the upper limit value has been reached. When the result is affirmative, the routine proceeds to S122, where the upper limit value KAFALH is set as the air-fuel ratio correction coefficient KAF.

Next, in S124, the (first predetermined value mentioned above) increases the correction value by adding a predetermined value DKAFCHGAL the lower limit value KAFALL as Karine KAFAL, the process proceeds to S126, the above-mentioned predetermined value DKAFCHGAL (the upper limit value KAFALH The first corrected predetermined value) is added and corrected for increase, to be a provisional value KAFAH.

  The values subtracted in S116 and S118 and the values added in S124 and S126 are the same value DKAFCHGAL, but they may be different. In that sense, in the claims, the value added in S124 and S126 is described as a first predetermined value, and the value subtracted in S116 and S118 is described as a second predetermined value.

If negative in S120 proceeds to S130, the lower limit KAFALL determines whether less than basic value KAFLML (second base value mentioned above). When the result in S130 is affirmative, the program proceeds to S132, in which it is determined whether the air-fuel ratio correction coefficient KAF is greater than or equal to the center value KAFALCNT.

When the result in S132 is affirmative, the routine proceeds to S134, where the value corrected by adding the predetermined value DKAFCHGAL (the above-mentioned fourth predetermined value) to the lower limit value KAFALL is set to kafal, the process proceeds to S136, and the predetermined value DKAFCHGAL is set to the upper limit value KAFALH. A value obtained by adding and correcting (the above-described fourth predetermined value) is set to kafah.

The program then proceeds to S138, Kafal performs a limiting process to limit thereto when exceeding the basic value KAFLML (second base value mentioned above), the value of the processed and Karine KAFAL, the process proceeds to S140, Kafah groups present When the value KAFLMTH (the above-described first basic value) is exceeded, limit processing limited to that is performed, and the value after processing is set as a provisional value KAFAH.

On the other hand, the process proceeds to S142 if negative in S130, the upper limit KAFALH determines whether exceeds the basic value KAFLMTH (first basic value above). When the result in S142 is affirmative, the program proceeds to S144, in which it is determined whether the air-fuel ratio correction coefficient KAF is equal to or less than the center value KAFALCNT.

When the result is affirmative in S144, the process proceeds to S146, and a value obtained by subtracting the predetermined value DKAFCHGAL (the above-mentioned third predetermined value) from the lower limit value KAFALL and corrected to decrease is set to kafal. The process proceeds to S148, and the predetermined value DKAFCHGAL A value obtained by subtracting (the above-described third predetermined value) and correcting the decrease is defined as kafah.

The program then proceeds to S150, Kafal performs a limiting process to limit thereto when below a basic value KAFLML (second base value mentioned above), the value of the processed and Karine KAFAL, the process proceeds to S152, Kafah groups present When the value is lower than the value KAFLMTH (the above-described first basic value) , limit processing limited to that is performed, and the value after processing is set as a temporary value KAFAH.

  On the other hand, when the result in S142, S132, or S144 is negative, the process proceeds to S154, where the lower limit value KAFALL is used as the temporary value KAFAL, and the process proceeds to S156, where the upper limit value KAFALH is used as the temporary value KAFAH.

  FIG. 6 is a flowchart showing the calculation process of the air-fuel ratio correction coefficient KAF of the fuel injection amount calculation block 40a. The illustrated program is also executed at a predetermined crank angle near the TDC of each cylinder.

  To explain below, in S200, it is determined whether or not the bit of the flag F_FCFFVDN is 1. Since this bit is set to 1 when learning of alcohol concentration is completed in another routine, the determination in S200 means whether or not learning of alcohol concentration is completed. The alcohol concentration learning will be described later.

When the result in S200 is negative, the program proceeds to S202, in which the characteristics shown in FIG. 7 are searched using the alcohol concentration correction coefficient KREFBS, the maximum limit value KAFALLMTH is searched, and the program proceeds to S204. Similarly, the alcohol concentration correction coefficient KREFBS is shown in FIG. The characteristic is searched and the minimum limit value KAFALLMTL is searched.

Next, in S206, when the temporary value KAFAH exceeds the maximum limit value KAFALLMTH, limit processing is performed to limit it, and the temporary value KAFAH is set as the upper limit value KAFALH. Next, in S208, when the temporary value KAFAL falls below the minimum limit value KAFALLMTL, limit processing is performed to limit it, and the temporary value KAFAL is set to the lower limit value KAFALL.

On the other hand, the process proceeds to S210 when the result is affirmative in S200, based on the present value KAFLMTH (first base value described above) as the upper limit value KAFALH, the process proceeds to S212, based on the present value KAFLML the (second base value mentioned above) The lower limit value is KAFALL.

  Next, in S214, the sum obtained by adding the obtained upper limit value KAFALH and lower limit value KAFALL is divided by 2, and the resulting quotient is set as the center value KAFALCNT.

  FIG. 8 is a flowchart showing processing in the alcohol concentration learning block 40b. The illustrated program is also executed at a predetermined crank angle near the TDC of each cylinder.

  In the following, it is determined whether or not the flag F_PGDLY bit is set to 1 in S300. Since this flag is set to 1 when canister purge is stopped in another routine, the determination in S300 means whether or not canister purge is stopped.

  When the result in S300 is negative, the subsequent processing is skipped. When the result is affirmative, the process proceeds to S302, and it is determined whether or not the engine speed NE exceeds a predetermined high speed NKREFXH. When the result in S302 is affirmative, the subsequent processing is skipped. When the result is negative, the process proceeds to S304, in which it is determined whether or not the intake air temperature TA exceeds a predetermined high intake air temperature TAREF.

  When the result in S304 is affirmative, the subsequent processing is skipped. When the result is negative, the process proceeds to S306, and it is determined whether or not the bit of F_OCTMMCND is “1”. Since this bit is set to 1 when this flag is in a region where the influence of transpiration of alcohol fuel mixed in oil is large in another routine, the determination in S306 is to determine whether or not it is in such a region. Equivalent to.

  When the result in S306 is negative, the program proceeds to S308, in which it is determined whether or not the intake pipe absolute pressure PBA exceeds a predetermined low load value PBAREFXL. When the result is affirmative, the program proceeds to S310 and the intake pipe absolute pressure PBA is determined to be a predetermined high load value PBAREFFXH. Judge whether it is less than.

  If the determination in S306 is affirmative, the process proceeds to S312 to determine whether or not the intake pipe absolute pressure PBA exceeds a predetermined low load value PBAREFXLFFV. If the determination is negative, the subsequent processing is skipped and if the determination is positive. The process proceeds to S310.

  When the result in S310 is negative, the subsequent processing is skipped. When the result is affirmative, the process proceeds to S314. As shown in the figure, the weighted average is performed using the weighting coefficient C, so that the air-fuel ratio correction coefficient KAF is smoothed. A density learning value KREFX is calculated.

  Thus, when the canister purge is stopped and the engine operating state is in the predetermined operating range, the air-fuel ratio correction coefficient KAF is smoothed to calculate the alcohol concentration learning value KREFX.

  FIG. 9 is a flowchart showing similarly the processing of the alcohol concentration learning block 40b. The illustrated program is also executed at a predetermined crank angle near the TDC of each cylinder.

  In the following, it is determined whether or not the bit of the flag F_FSPAFFB is set to 1 in S400. Since this bit is set to 1 when the wide area air-fuel ratio sensor 84 has failed in another routine, the processing of S400 is equivalent to determining it.

  When the result in S400 is negative, the program proceeds to S402, in which it is determined whether the bit of the flag F_FCFFVDN is set to 1.

  FIG. 10 is a time chart for explaining the alcohol concentration learning.

S402 flags when bit F_FC shown in FIG. 10 (fuel cut execution flag) and F_KALCOK (alcohol concentration correction coefficient learning completion flag) is set to 1, the bit in another routine is set to 1.

  When the result in S402 is affirmative, the process proceeds to S404, and it is determined whether or not the bit of the flag F_KREFBSON is set to 1. This flag is set to 1 when the alcohol concentration correction coefficient is updated, in other words, when the execution of the alcohol concentration learning is completed, so the determination in S404 is generally denied and the process proceeds to S406, as shown in the figure. The product obtained by multiplying the alcohol concentration correction coefficient KREFBS by the alcohol concentration learning value KREFX is defined as KREFBST.

  Next, the process proceeds to S408, and when KREFBST exceeds the max value or falls below the min value, limit processing is performed to limit it, and the processed value is set to KREFBS. The process proceeds to S410, and the bit of the flag F_KREFBSON described above is set to 1 .

  As described above, the processing from S404 to S410 means processing for updating the alcohol concentration correction coefficient KREFBS when learning of the alcohol concentration is completed and updating of the alcohol concentration correction coefficient is permitted. The previous alcohol concentration value before starting learning means an alcohol concentration correction coefficient KREFBS before update.

  On the other hand, when the result in S402 is negative, the program proceeds to S412 and it is determined whether or not the bit of the flag F_WOT is set to 1. This flag is set to 1 when the target air-fuel ratio KCMD and the target air-fuel ratio correction coefficient KCMD are enriched in order to protect the catalyst device 56 in another routine. .

  When the result in S412 is affirmative, the process proceeds to S414, and it is determined whether or not the bit of F_AFFB is set to 1. Since this bit is set to 1 when the above-described air-fuel ratio feedback control is executed in another routine, it is determined in S414.

  When the result in S414 is negative, the program proceeds to S416, in which it is determined whether or not the bit of the alcohol concentration correction coefficient learning completion flag F_KALCOK is set to 1. When the result in S416 is affirmative, the process proceeds to S404. When the result is negative, the process proceeds to S418, and the bit of the flag F_KREFBSON is reset to 0. The same applies when the result in S414 is affirmative. If the determination in S400 is affirmative, the process proceeds to S420 and S422, and values such as the alcohol concentration correction coefficient are set to 1.0 (no correction).

  The alcohol concentration learning will be described with reference to FIG. 10. In this embodiment, the alcohol concentration is learned (detected) based on the alcohol concentration learning value KREFX obtained by smoothing the air-fuel ratio correction coefficient KAF. E100 to E22 are planned as fuels, but the alcohol concentration correction coefficient KREFBS is set to an initial value so as to be a value corresponding to E64 in the middle (1.0, no correction).

  As shown at the left end of FIG. 10, when the fuel is switched to E100 by refueling when using E64, the air-fuel ratio correction coefficient KAF and the alcohol concentration learning value KREFX that changes the same change accordingly, and the alcohol concentration correction coefficient KREFBS is modified to 1.2.

  After that, when the fuel is switched to E22 by refueling from the flag F_REFUELFFFV (refueling determination) at the end, the air-fuel ratio correction coefficient KAF and the learning value KREFX are inverted, and the alcohol concentration correction coefficient is corrected to 0.8. The

In this embodiment, as described above, the air-fuel ratio detecting means (wide-area air-fuel ratio sensor 84) for detecting the air-fuel ratio KACT in the exhaust, and the fuel according to the deviation DKCMD between the detected air-fuel ratio KACT and the target air-fuel ratio KCMD. Air-fuel ratio correction coefficient calculating means (fuel injection amount calculation blocks 40a, S100 to S110) for calculating the air-fuel ratio correction coefficient KAF of the injection amount TOUT, and the alcohol concentration contained in the fuel based on the calculated air-fuel ratio correction coefficient KAF Alcohol concentration learning means (alcohol concentration learning blocks 40b, S300 to S314, S400 to S422), and upper and lower limit value setting means (fuel injection amount) for setting the upper limit value KAFALH and the lower limit value KAFALL of the air-fuel ratio correction coefficient KAF from calculation block 40a, S200 S214), said alcohol concentration learning means Center value between the lower limit value changing means over to change the upper limit value KAFALH and the lower limit value KAFALL when learning (S126 from block 40a, S112, S116 from S118, S124), and the upper limit KAFALH and the lower limit KAFALL KAFALCNT In the control device for the internal combustion engine (engine) 10 including the center value calculating means (blocks 40a, S214) for calculating the upper limit value, the upper / lower limit value changing means , While the upper limit value and the lower limit value are respectively corrected to be increased by DKAFCHGAL (first predetermined value), when the air-fuel ratio correction coefficient reaches the lower limit value, the lower limit value and the upper limit value are set to DKAFCHGAL ( the second predetermined value) by decreasing correction, the air-fuel ratio correction coefficient KAF is the upper limit KAFA When the value is equal to or less than H and equal to or greater than the lower limit value KAFALL (S112, S120), the upper limit value KAFALH is greater than KAFLMTH (first basic value) and the air-fuel ratio correction coefficient KAF is equal to or less than the center value KAFALCNT ( In S142 and S144), the upper limit value KAFALH and the lower limit value KAFALL are each corrected to decrease by DKAFCHGAL (third predetermined value) (S146 to S148), and the lower limit value KAFALL is changed to the basic value KAFLMTH (first basic value). When the air-fuel ratio correction coefficient KAF is greater than or equal to the center value KAFALCNT (S130, S132), the upper limit value KAFALH and the lower limit value KAFALL are DKAFCHGAL (No. (Predetermined value of 4) is increased (S134 to S136).

  As described above, the limit values (upper limit value KAFALH, lower limit value KAFALL) of the air-fuel ratio correction coefficient KAF of the fuel injection amount TOUT calculated according to the deviation DKCMD between the detected air-fuel ratio KACT and the target air-fuel ratio KCMD are corrected by the air-fuel ratio correction. It is configured to change when the coefficient reaches the limit value, in other words, it is configured not to change unless the air-fuel ratio correction coefficient reaches the limit value. Even when the air-fuel ratio correction coefficient changes greatly due to the influence of the above, since the change is suppressed by the limit value, the stability of the air-fuel ratio control can be ensured even when the alcohol concentration is learned.

In addition to the above noted effects, since the variation width itself of the air-fuel ratio correction coefficient KAF is not changed, the maximum value of the deviation of the air-fuel ratio correction coefficient KAF also becomes possible to not change, thus further improving the stability of the air-fuel ratio control Can be secured. As described above, the second predetermined value of the first predetermined value is also the same value DKAFCHGAL, but may be another value.

Also, together with the upper and lower limit value setting means sets the upper limit value and the lower limit value between the maximum limit KAFALLMTH and minimum limit KAFALLMTL, alcohol concentration calculated by the learning of the alcohol concentration learning means, more specifically depending on the alcohol concentration correction coefficient KREFBS, said to change the maximum limit KAFALLMTH and the minimum limit value KAFALLMTL (S202, S204) Owing to this configuration, in addition to the effects mentioned above, better ensuring the stability of the air-fuel ratio control can do. That is, the upper and lower limit values KAFALLMTH and KAFALLMTL of the air-fuel ratio correction coefficient KAF are determined by the alcohol concentration. However, by changing the limit value according to the alcohol concentration correction coefficient KREFBS, unnecessary change of the limit value can be suppressed. In addition, the stability of the air-fuel ratio control can be further ensured. Therefore, it is possible to optimally achieve both alcohol concentration learning and air-fuel ratio control.

Further, the upper and lower limit value changing means, the alcohol concentration previous value before the alcohol concentration learning means starts learning, according to a more previous value of the specific alcohol concentration correction coefficient KREFBS is (S406 from S410), the maximum since it is configured as to change the a limit value the minimum limit value, in addition to the effects mentioned above, the stability of the air-fuel ratio control can be ensured better.

That is, the air-fuel ratio correction coefficient KAF maximum minimum limit KAFALLMTH, but KAFALLMTL depends alcohol concentration, alcohol concentration correction coefficient before the limit value starts to alcohol concentration learning KREFBS, i.e., to change in accordance with the previous value Thus, an unnecessary change in the limit value can be suppressed, and the stability of the air-fuel ratio control can be further ensured. Therefore, it is possible to optimally achieve both alcohol concentration learning and air-fuel ratio control.

1 is a schematic diagram showing an overall control apparatus for an internal combustion engine according to an embodiment of the present invention. It is a block diagram explaining operation | movement of the apparatus shown in FIG. 1, more specifically operation | movement of ECU (electronic control unit) in the apparatus shown in FIG. 3 is a flowchart showing a process for calculating a fuel injection amount TOUT in a fuel injection amount calculation block shown in FIG. 2. 3 is a flow chart showing a calculation process of an air-fuel ratio correction coefficient KAF in the fuel injection amount calculation block shown in FIG. It is a time chart explaining the process of FIG. Similarly, it is a flowchart showing a calculation process of an air-fuel ratio correction coefficient KAF in a fuel injection amount calculation block. 7 is an explanatory graph showing values used in the processing of FIG. 6. It is a flowchart which shows the process of the alcohol concentration learning block of FIG. FIG. 3 is a flow chart similarly showing processing of the alcohol concentration learning block of FIG. 2. FIG. It is a time chart explaining the alcohol concentration learning of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Internal combustion engine (engine), 16 Throttle valve, 22 DC motor, 24 Main injector, 26 Main fuel tank, 40 ECU (electronic control unit), 44 Spark plug, 56 Catalytic device, 62 Canister, 70 Valve mechanism, 72 Crank angle sensor, 74 Air flow meter, 76 MAP sensor, 80 Water temperature sensor, 84 Wide area air-fuel ratio sensor, 90 Accelerator opening sensor, 92 Vehicle speed sensor, 94 Atmospheric pressure sensor

Claims (3)

Air-fuel ratio detection means for detecting an air-fuel ratio in the exhaust, air-fuel ratio correction coefficient calculation means for calculating an air-fuel ratio correction coefficient of the fuel injection amount according to a deviation between the detected air-fuel ratio and the target air-fuel ratio, Alcohol concentration learning means for learning the alcohol concentration contained in the fuel based on the calculated air-fuel ratio correction coefficient, upper and lower limit value setting means for setting the upper limit value and the lower limit value of the air-fuel ratio correction coefficient, and the alcohol concentration learning A control apparatus for an internal combustion engine, comprising: upper and lower limit value changing means for changing the upper limit value and the lower limit value when the means learns; and a center value calculating means for calculating a center value of the upper limit value and the lower limit value When the air / fuel ratio correction coefficient reaches the upper limit value, the upper / lower limit value changing means increases and corrects the upper limit value and the lower limit value by a first predetermined value respectively, while the air / fuel ratio correction coefficient Said When it reaches the limit value, the upper limit value and the lower limit value only decreases the corrected second predetermined value, respectively, if the is the air-fuel ratio correction coefficient is the lower limit value or more below the upper limit, the upper limit When the air fuel ratio correction coefficient is greater than the first basic value and the air / fuel ratio correction coefficient is less than or equal to the center value, the upper limit value and the lower limit value are corrected to decrease by a third predetermined value, respectively, and the lower limit value is The upper limit value and the lower limit value are each increased by a fourth predetermined value when the air fuel ratio correction coefficient is smaller than the second basic value set smaller than the first basic value and the air / fuel ratio correction coefficient is equal to or greater than the center value. A control device for an internal combustion engine.   The upper and lower limit value setting means sets a maximum limit value indicating a maximum value that can change the upper limit value in an increasing direction, and a minimum limit value that can change the lower limit value in a decreasing direction, and the alcohol concentration 2. The control apparatus for an internal combustion engine according to claim 1, wherein the maximum limit value and the minimum limit value are changed in accordance with an alcohol concentration calculated by learning of learning means. 3. The internal combustion engine according to claim 2, wherein the upper and lower limit value changing means changes the maximum limit value and the minimum limit value according to a previous alcohol concentration value before the alcohol concentration learning means starts learning. Control device.

Images