JP4778401B2 - 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 Patent Document 1, an oxygen concentration sensor for detecting the oxygen concentration in exhaust gas is provided in an exhaust system of a multi-fuel internal combustion engine containing alcohol, and a correction coefficient is used according to a deviation between the output of the oxygen concentration sensor and a target air-fuel ratio. In an internal combustion engine that controls an air-fuel ratio, a technique is disclosed in which an alcohol mixing ratio is detected from the magnitude of a correction coefficient, and a target air-fuel ratio is corrected according to the detected value.

  Patent Document 2 discloses a technique for increasing the amount of fuel to prevent overheating of the exhaust purification device when any one of the throttle opening, the engine speed, and the intake air amount exceeds a predetermined value.

Further, Patent Document 3 discloses that when the catalyst temperature is equal to or higher than a predetermined value, or when the engine speed and the intake pipe pressure are equal to or higher than a predetermined value, the catalyst temperature becomes equal to or higher than a predetermined value. It is disclosed that the catalyst temperature is lowered by gradually decreasing the throttle opening so as to be the catalyst protection throttle opening.
JP 63-5131 A Japanese Unexamined Patent Publication No. 53-40128 Japanese Patent Application Laid-Open No. 08-165942

  In the oxygen concentration sensor, the detection deviation due to individual variation increases as the air-fuel ratio departs from the stoichiometric air-fuel ratio. Therefore, as in the technique described in Patent Document 2, control is performed to increase the amount of fuel to prevent overheating of the exhaust purification device. At this time, it has been conventionally performed to secure a necessary fuel increase amount by stopping the feedback control and performing the open loop control.

  In an internal combustion engine for a flexible fuel vehicle (hereinafter referred to as “FFV”) as described in Patent Document 1, when the alcohol concentration is changed from low to high by refueling, before the learning of the alcohol concentration is completed. When the fuel increase described in Patent Document 2 is performed, the feedback control is stopped, and as a result, the fuel injection amount is insufficient to prevent overheating of the exhaust purification device.

  Note that, as in the technique described in Patent Document 3, when the catalyst temperature is equal to or higher than a predetermined value, if the control is performed to always decrease the throttle opening, the engine output decreases and the output required by the driver cannot be obtained. There is an inconvenience.

  Accordingly, the object of the present invention is to solve the above-mentioned problems and to suppress the shortage of the fuel injection amount due to the difference between the learned value of the alcohol concentration and the actual alcohol concentration when the feedback control is stopped, and the internal combustion engine for FFV It is to provide a control device.

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 of the fuel, an alcohol concentration learning means for learning the alcohol concentration contained in the fuel based on the calculated air-fuel ratio correction coefficient, and based on the learned alcohol concentration An internal combustion engine comprising: an alcohol concentration correction coefficient calculating means for calculating an alcohol concentration correction coefficient for the fuel injection amount; and a feedback control means for executing air-fuel ratio feedback control for matching the detected air-fuel ratio with a target air-fuel ratio. in the control device, e Bei control switching means for switching the stop and execution of the air-fuel ratio feedback control in accordance with the operating state, the control switches Means, until said learning of the alcohol concentration is complete, while the continued air-fuel ratio feedback control, after learning of the alcohol concentration is completed sets the first rich limit air-fuel ratio rich limit air-fuel ratio, the Until the learning of the alcohol concentration is completed, a second rich limit air-fuel ratio richer than the first rich limit air-fuel ratio is set as the rich limit air-fuel ratio, and the target air-fuel ratio is set to the rich limit air-fuel ratio. When the value exceeds the rich side, the air-fuel ratio feedback control is stopped .

  In the control apparatus for an internal combustion engine according to claim 2, the control switching means stops the air-fuel ratio feedback control and completes the learning of the alcohol concentration when the load of the internal combustion engine is equal to or greater than a predetermined value. Until then, the upper limit value of the throttle opening is set so that the load of the internal combustion engine does not exceed the predetermined value.

In the control device for an internal combustion engine according to claim 3 , a target air-fuel ratio correction coefficient of a fuel injection amount is calculated according to the target air-fuel ratio, and the first rich limit air-fuel ratio is calculated from the air-fuel ratio. The air-fuel ratio correction coefficient according to the deviation between the detected value based on the individual difference of the detecting means and the air-fuel ratio when the fuel injection amount corresponding to the target air-fuel ratio correction coefficient is injected is the restart of the learning of the alcohol concentration. Is set to be less than the range of change that causes

In the control apparatus for an internal combustion engine according to claim 4 , a target air-fuel ratio correction coefficient for the fuel injection amount is calculated according to the target air-fuel ratio, and a fuel increase coefficient for cooling the exhaust system catalyst device The catalyst protection air-fuel ratio obtained by adding a margin is set to the target air-fuel ratio, and the second rich limit air-fuel ratio is set to a detection value based on an individual difference of the air-fuel ratio detection means and the target air-fuel ratio correction coefficient. The air-fuel ratio correction coefficient corresponding to the deviation from the air-fuel ratio when the corresponding fuel injection amount is injected is set so as not to exceed the margin.

In the control device for an internal combustion engine according to claim 5 , the air-fuel ratio for catalyst protection is set according to the temperature of the catalyst device estimated from the load of the internal combustion engine, and the learning of the alcohol concentration is completed. Until that time, the upper limit value of the throttle opening is set to the throttle opening corresponding to the load of the internal combustion engine in which the catalyst protection air-fuel ratio does not become richer than the second rich limit air-fuel ratio.

According to claim 1, since air-fuel ratio feedback control is continued until learning of the alcohol concentration is completed, the fuel injection amount due to the difference between the learned value of the alcohol concentration for calculating the alcohol concentration correction coefficient and the actual alcohol concentration Deficiency can be suppressed. In addition to the above-described effects, the rich limit air-fuel ratio at which the air-fuel ratio feedback control is stopped is set to a richer value before the alcohol concentration learning is completed, thereby expanding the air-fuel ratio feedback control region. be able to.

  In the control apparatus for an internal combustion engine according to claim 2, in addition to the above-described effect, the upper limit value of the throttle opening is set to be equal to or less than the load of the internal combustion engine where the air-fuel ratio feedback control is switched to the open loop control. The air-fuel ratio feedback control can be reliably continued until the concentration learning is completed.

In the control apparatus for an internal combustion engine according to claim 3 , in addition to the above-described effect, it is possible to prevent the air-fuel ratio correction coefficient from changing more than a predetermined value due to variations in the detected value based on individual differences in the air-fuel ratio detection means. Re-learning of unnecessary alcohol concentration can be avoided.

In the control apparatus for an internal combustion engine according to claim 4 , in addition to the above-described effect, the air-fuel ratio for catalyst protection in which the air-fuel ratio correction coefficient does not exceed a margin due to variations in detection values based on individual differences in the air-fuel ratio detection means. By setting to, it is possible to secure an increase in fuel necessary for cooling the catalyst device.

In the control device for an internal combustion engine according to claim 5 , in addition to the above-described effect, the load of the internal combustion engine is controlled so that the catalyst device can be reliably protected even during air-fuel ratio feedback control. The catalyst device can also be reliably protected while continuing the air-fuel ratio feedback control before the learning is completed. In addition, it is possible to minimize the limit of the throttle opening that reduces the output.

  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 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 in accordance with 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, an air-fuel ratio correction coefficient (air-fuel ratio is determined in accordance with the deviation thereof. The feedback injection coefficient (KAF) is calculated, 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, thereby calculating the fuel injection amount TOUT. .

  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.

  The alcohol concentration learning will be described with reference to FIG. 3. 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. 3, 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 Is corrected 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

  Returning to the description of FIG. 2, reference numeral 40 c represents 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 is performed via the ignition device based on the calculated ignition timing. The ignition of the plug 44 is controlled.

  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. 4 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.

  FIG. 5 is a flowchart showing switching determination processing between execution and cancellation of air-fuel ratio feedback control according to the operating state in the processing in the fuel injection amount calculation block 40a. 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_KREFBSON is set to 1 in S100. Since this flag is set to 1 when the update of the alcohol concentration correction coefficient in another routine, in other words, the execution of the alcohol concentration learning is completed, the determination in S100 determines whether or not the alcohol concentration learning is completed. This is equivalent to judging whether or not.

  When the result in S100 is affirmative, the process proceeds to S102, where KCMDFBH (first rich limit air-fuel ratio) is set as the rich limit air-fuel ratio KCMDFBHFFV. (Second rich limit air-fuel ratio) is set. KCMDFBHPRE (second rich limit air-fuel ratio) is set to a richer value than the first rich limit air-fuel ratio KCMDFBH.

  Next, in S106, it is determined whether or not the target air-fuel ratio KCMD is equal to or less than the rich limit air-fuel ratio KCMDFBHFFV. Since the target air-fuel ratio KCMD is set at an equivalence ratio, the value increases as the air-fuel ratio becomes richer. Therefore, the determination in S106 is equivalent to determining whether or not the target air-fuel ratio KCMD is on the theoretical air-fuel ratio side with respect to the rich limit air-fuel ratio.

  Since the target air-fuel ratio KCMD is indicated by the equivalence ratio as described above, the target air-fuel ratio KCMD functions as a target value in the air-fuel ratio feedback control and corrects the basic fuel injection amount TIM according to the target air-fuel ratio. It also functions as a fuel ratio correction coefficient.

  Further, in another routine, the target air-fuel ratio KCMD is set to a catalyst protection air-fuel ratio obtained by adding a fuel increase coefficient for cooling the catalyst device 56 and a margin (variation width) when the load of the engine 10 is large.

  When the result is affirmative in S106, the process proceeds to S108, and the bit of the flag F_AFFB is set to 1, while when the result is negative, the process proceeds to S110, and the bit of the flag F_AFFB is reset to 0. Setting the bit of the flag F_AFFB to 1 means executing the air-fuel ratio feedback control, and resetting it to 0 means stopping the air-fuel ratio feedback control and shifting to open loop control.

  Since the KCMD (catalyst protection air-fuel ratio) exceeds a predetermined value when the load of the engine 10 (absolute pressure in the intake pipe PBA) is equal to or greater than a predetermined value, the processing of S106 and S110 is performed with the load of the engine 10 equal to or greater than the predetermined value. Is equivalent to stopping the air-fuel ratio feedback control.

  Thus, in this embodiment, the air-fuel ratio feedback control is continued until learning of the alcohol concentration is completed.

  More specifically, after the alcohol concentration learning is completed, the first rich limit air-fuel ratio KCMDFBHFFV is set as the rich limit air-fuel ratio KCMDFBHFFV, while the rich limit air-fuel ratio KCMDFBHFFV is set until the alcohol concentration learning is completed. When the second rich limit air-fuel ratio KCMDFBHPRE richer than the first rich limit air-fuel ratio KCMDFBH is set and the target air-fuel ratio KCMD exceeds the rich limit air-fuel ratio to the rich side, the air-fuel ratio feedback control is stopped. Thus, the air-fuel ratio feedback control is easily continued until learning of the alcohol concentration is completed.

  Note that, when the air-fuel ratio correction coefficient KAF changes by a predetermined value or more, the alcohol concentration learning is resumed. Therefore, the first rich limit air-fuel ratio KCMDFBH is different from the individual difference of the wide-range air-fuel ratio sensor 84. The air-fuel ratio correction coefficient KAF according to the deviation between the detected value based on the detected air-fuel ratio and the air-fuel ratio when the fuel injection amount corresponding to the target air-fuel ratio correction coefficient KCMD is injected is less than the change width that causes the alcohol concentration learning to resume. Is set as follows.

  Further, the target air-fuel ratio correction coefficient KCMD of the fuel injection amount is calculated in accordance with the target air-fuel ratio, and the catalyst protection air-fuel ratio obtained by adding the fuel increase coefficient for cooling the exhaust system catalytic device 56 and the margin is set as the target. The second rich limit air-fuel ratio KCMDFBHPRE is set to the air-fuel ratio KCMD, and the second rich limit air-fuel ratio KCMDFBHPRE is the air-fuel ratio when the fuel injection amount corresponding to the detected value based on the individual difference of the wide-range air-fuel ratio sensor 84 and the target air-fuel ratio correction coefficient KCMD is injected. It is set so as not to exceed the margin according to the deviation from the fuel ratio.

  FIG. 6 is a flowchart showing the processing of the throttle opening control value calculation block 40d. 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 S200. Since this bit is set to 1 when a failure occurs in the wide-range air-fuel ratio sensor 84 in another routine, the processing of S200 corresponds to determining it.

  When the result in S200 is negative, the program proceeds to S202, in which it is determined whether or not the bit of the flag F_THOMXBREFV is set to 1. As will be described later, this flag has its bit set to 1 when control for limiting the throttle opening upper limit value is executed.

  When the result in S202 is affirmative, the program proceeds to S204, in which it is determined whether or not the bit of the flag F_THIDLE is set to 1. This flag is set to 1 when the throttle opening is larger than a predetermined idle opening (set near the throttle fully closed) in another routine.

  When the result in S204 is negative, the program proceeds to S206, where it is determined whether or not the alcohol concentration learning has been completed from the bit of the flag F_KREFBSON. When the result is negative, the program proceeds to S208, and the bit of the flag F_THOMXBREFV is set to 1. The same applies when affirmative is obtained in S200 and S204.

  Next, in S210, it is determined whether or not the bit of the flag F_VTEC is set to 1. Since this bit is set to 1 when the characteristic of the valve operating mechanism 70 is set to a higher characteristic in another routine, when the result is negative, the process proceeds to S212, and from the engine speed NE to FIG. In the meantime, THBREFVLG is calculated as the throttle opening upper limit value THOMXBREFV. When the result is affirmative, the routine proceeds to S214, and a characteristic (not shown) similar to the characteristic shown in FIG. 7 is determined from the engine speed NE. By searching, THBREFVHG is calculated as the upper limit value THOMXBREFV of the throttle opening.

  On the other hand, when the result in S206 is affirmative, the program proceeds to S216, in which the bit of the flag F_THOMXBREFV is reset to 0, and the program proceeds to S218, where the upper limit value THOMXBREFV of the throttle opening is set to the maximum value THOMAXM.

  When the result in S202 is negative, the program proceeds to S220, in which it is determined whether or not the bit of the flag F_CATWOT is set to 1. This flag is set to 1 when the temperature of the catalytic device 56 estimated from the value of the engine speed NE and the intake pipe absolute pressure PBA is equal to or higher than a predetermined value and the catalytic device 56 needs to be protected in another routine. Set. Accordingly, when the result in S220 is affirmative, the process proceeds to S206, and when the result is negative, the process proceeds to S216.

  In this manner, until the learning of the alcohol concentration is completed, the upper limit value of the throttle opening is set to the throttle opening corresponding to the load of the engine 10 in which the catalyst protection air-fuel ratio does not become richer than the second rich limit air-fuel ratio. Set to.

In this embodiment, as described above, the air-fuel ratio detecting means (the wide-area air-fuel ratio sensor 84) for detecting the air-fuel ratio KACT in the exhaust, and the fuel injection according to the deviation between the detected air-fuel ratio KACT and the target air-fuel ratio KCMD. An air-fuel ratio correction coefficient calculating means (fuel injection amount calculation block 40a) for calculating the air-fuel ratio correction coefficient KAF of the amount, and an alcohol concentration for learning the alcohol concentration KREFX contained in the fuel based on the calculated air-fuel ratio correction coefficient KAF Learning means (alcohol concentration learning block 40b), alcohol concentration correction coefficient calculating means (alcohol concentration learning block 40b) for calculating an alcohol concentration correction coefficient KREFBS of the fuel injection amount based on the learned alcohol concentration KREFX, An air-fuel ratio fee for matching the detected air-fuel ratio KACT with the target air-fuel ratio KCMD. In the control device of the internal combustion engine (engine) 10 including feedback control means (fuel injection amount calculation block 40a) for executing back control, control switching means for switching between execution and cancellation of the air-fuel ratio feedback control according to the operating state. e Bei a (from S100 S110), the control switching means, until said learning of the alcohol concentration is complete, continue the air-fuel ratio feedback control, as rich limit air-fuel ratio KCMDFBHFFV after learning of the alcohol concentration is completed While setting the first rich limit air-fuel ratio KCMDFBH (S100 to S102), the rich limit air-fuel ratio KCMDFBHFFV is set to the second richer than the first rich limit air-fuel ratio until the learning of the alcohol concentration is completed. Rich limit air-fuel ratio KCMDFB It sets the PRE (S100, S104), when the target air-fuel ratio exceeds the rich limit air-fuel ratio to the rich side and the air-fuel ratio to stop the feedback control (S106 from S110) and as configuration.

As described above, since the air-fuel ratio feedback control is continued until the learning of the alcohol concentration is completed, the difference between the learning value of the alcohol concentration for calculating the alcohol concentration correction coefficient when the feedback control is stopped and the actual alcohol concentration The shortage of the fuel injection amount can be suppressed. In addition, the air / fuel ratio feedback control region can be expanded by setting the rich limit air / fuel ratio at which the air / fuel ratio feedback control is stopped to a richer value before learning of the alcohol concentration is completed.

  Further, the control switching means stops the air-fuel ratio feedback control when the load of the internal combustion engine is equal to or greater than a predetermined value (S106, S110), and loads the internal combustion engine until the learning of the alcohol concentration is completed. The upper limit value THOMXBREFV of the throttle opening is set so that does not exceed the predetermined value (S206 to S214).

  Thus, by setting the upper limit value of the throttle opening below the load of the engine 10 where the air-fuel ratio feedback control is switched to the open loop control, the air-fuel ratio feedback control can be reliably continued until the alcohol concentration learning is completed. it can.

  Further, a target air-fuel ratio correction coefficient KCMD of the fuel injection amount is calculated according to the target air-fuel ratio, and the first rich limit air-fuel ratio KCMDFBH is an individual of the air-fuel ratio detection means (wide area air-fuel ratio sensor 84). The change in the air-fuel ratio correction coefficient KCMD according to the deviation between the detected value based on the difference and the air-fuel ratio when the fuel injection amount corresponding to the target air-fuel ratio correction coefficient is injected causes the learning of the alcohol concentration to resume. It was configured so as to be set to be less than the width (S102).

  As a result, it is possible to prevent the air-fuel ratio correction coefficient KCMD from changing by a predetermined value or more due to variations in detection values based on individual differences in the wide-range air-fuel ratio sensor 84, thereby avoiding unnecessary relearning of the alcohol concentration.

  Further, a target air-fuel ratio correction coefficient KCMD of the fuel injection amount is calculated according to the target air-fuel ratio, and a catalyst protection air-fuel ratio obtained by adding a fuel increase coefficient for cooling of the exhaust system catalytic device 56 and a margin is obtained. The target air-fuel ratio is set, and the second rich limit air-fuel ratio is determined based on the detected value based on the individual difference of the air-fuel ratio detecting means (wide area air-fuel ratio sensor 84) and the fuel injection according to the target air-fuel ratio correction coefficient. The air-fuel ratio correction coefficient corresponding to the deviation from the air-fuel ratio when the amount is injected is set so as not to exceed the margin (S104).

  As a result, it is necessary to cool the catalyst device 56 by setting the air-fuel ratio correction coefficient KCMD to a catalyst-protecting air-fuel ratio that does not exceed the margin due to variations in detection values based on individual differences in the wide-range air-fuel ratio sensor 84. Fuel increase can be ensured.

  Further, the catalyst protection air-fuel ratio is set according to the temperature of the catalyst device estimated from the load of the internal combustion engine, and the upper limit value of the throttle opening is set to the catalyst until learning of the alcohol concentration is completed. The protective air-fuel ratio is set to a throttle opening degree corresponding to the load of the internal combustion engine that does not become richer than the second rich limit air-fuel ratio (S206 to S214).

  Thus, the load of the engine 10 is controlled so that the catalyst device 56 can be reliably protected even during the air-fuel ratio feedback control. Therefore, the catalyst is maintained while continuing the air-fuel ratio feedback control before the learning of the alcohol concentration is completed. The device 56 can also be reliably protected. In addition, it is possible to minimize the restriction on the throttle opening that reduces the output.

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. It is a time chart explaining the alcohol concentration learning 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. Similarly, it is a flowchart showing switching determination processing between execution and cancellation of air-fuel ratio feedback control according to the operating state in the fuel injection amount calculation block. 3 is a flowchart showing processing of a throttle opening control value calculation block shown in FIG. 7 is an explanatory graph showing characteristics of an upper limit value of a throttle opening used in the process of FIG. 6.

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 (5)

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, 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 alcohol concentration correction coefficient for calculating the alcohol concentration correction coefficient of the fuel injection amount based on the learned alcohol concentration In the control device for an internal combustion engine, comprising: calculating means; and feedback control means for executing air-fuel ratio feedback control for causing the detected air-fuel ratio to coincide with the target air-fuel ratio. Execution of the air-fuel ratio feedback control according to an operating state Bei give a control switching means for switching the stop and the control switching means, until the learning of the alcohol concentration is completed Continuing the air-fuel ratio feedback control, the one in which learning of the alcohol concentration is set to the first rich limit air-fuel ratio rich limit air-fuel ratio after completion until said learning of the alcohol concentration is complete the rich limit air A second rich limit air-fuel ratio that is richer than the first rich limit air-fuel ratio is set as the fuel ratio, and the air-fuel ratio feedback control is performed when the target air-fuel ratio exceeds the rich limit air-fuel ratio to the rich side. An internal combustion engine control device characterized by stopping the engine.   The control switching means stops the air-fuel ratio feedback control when the load on the internal combustion engine is equal to or higher than a predetermined value, and the load on the internal combustion engine does not become higher than the predetermined value until learning of the alcohol concentration is completed. 2. The control device for an internal combustion engine according to claim 1, wherein an upper limit value of the throttle opening is set as described above. A target air-fuel ratio correction coefficient for the fuel injection amount is calculated according to the target air-fuel ratio, and the first rich limit air-fuel ratio is calculated based on an individual difference of the air-fuel ratio detection means and the target air-fuel ratio correction. The air-fuel ratio correction coefficient according to the deviation from the air-fuel ratio when the fuel injection amount corresponding to the coefficient is injected is set to be less than the change width that causes the alcohol concentration learning to resume. The control apparatus for an internal combustion engine according to claim 1 . A target air-fuel ratio correction coefficient for the fuel injection amount is calculated in accordance with the target air-fuel ratio, and a catalyst protection air-fuel ratio obtained by adding a fuel increase coefficient for cooling the exhaust system catalytic device and a margin is set as the target air-fuel ratio. Further, the second rich limit air-fuel ratio is calculated as follows: a detection value based on an individual difference of the air-fuel ratio detection means and an air-fuel ratio when a fuel injection amount corresponding to the target air-fuel ratio correction coefficient is injected. control apparatus for an internal combustion engine according to claim 1, wherein said air-fuel ratio correction coefficient corresponding to the deviation and sets so as not to exceed the margin. The catalyst protection air-fuel ratio is set according to the temperature of the catalyst device estimated from the load of the internal combustion engine, and the upper limit value of the throttle opening is set until the learning of the alcohol concentration is completed. 5. The control device for an internal combustion engine according to claim 4, wherein an air-fuel ratio is set to a throttle opening corresponding to a load of the internal combustion engine that does not become richer than the second rich limit air-fuel ratio.

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