JP2008309034A - Internal combustion engine control device and internal combustion engine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine control device and internal combustion engine control system which suppress the problem that air-fuel ratio is deviated to the lean side from an optimum value, which is concerned when alternate fuel is mixed into normal fuel. <P>SOLUTION: The control device calculates a required opening of a throttle valve on the basis of a required intake amount in response to an accelerator tread down amount by an driver, required injection time InjT which is a required value of time when a fuel injection valve jets fuel per one combustion cycle on the basis of the required intake amount (S14) and injectable time InjMax in which injection can be executed per one combustion cycle on the basis of engine rotation speed (S15), and determines whether or not the required injection time InjT is longer than the injectable time InjMax (S16). When the required injection time InjT is determined to be longer than the injectable time InjMax, the reduction compensation of the required opening is executed so as to reduce the opening (S17). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device and an internal combustion engine control system that control an operating state of an internal combustion engine.

In general, a required injection time, which is a required value of the time during which the fuel injection valve injects fuel per combustion cycle of an internal combustion engine, is calculated according to a driver's accelerator operation amount (for example, Patent Document 1). reference). Then, by operating the valve body of the combustion injection valve so as to be the required injection time, an amount of fuel corresponding to the accelerator operation amount is injected. For example, in a spark ignition type internal combustion engine such as a gasoline engine, the required intake air amount is calculated according to the accelerator operation amount, and the required injection time is calculated so as to obtain an optimum air-fuel ratio with respect to the required intake air amount. Yes.
JP 2006-183500 A

  By the way, in recent years, alcohol fuel or the like has attracted attention as an alternative fuel for gasoline and light oil (hereinafter referred to as regular fuel). For example, when the alternative fuel is replenished with the regular fuel remaining in the fuel tank to make the mixed fuel, the mixed fuel is injected from the fuel injection valve. In this case, the following problems occur. The present inventor has obtained the knowledge of obtaining.

  That is, for example, when it is attempted to obtain an excess air ratio equivalent to that of gasoline by using alcohol fuel, it is known that a fuel injection amount larger than that of gasoline (for example, about 1.6 times) is required. That is, with respect to the output torque of the internal combustion engine obtained by injecting for a predetermined time, the output torque obtained when injecting mixed fuel in which alcohol is mixed in gasoline is smaller than that in the case of injecting 100% gasoline. Therefore, in the case of mixed fuel, it is necessary to make the injection time longer than in the case of 100% gasoline.

  Then, the above-described required injection time per combustion cycle may exceed the time (injectable time) that can be injected per one combustion cycle (720 ° C. A). In particular, in the operation region where the output shaft rotation speed (engine rotation speed) of the internal combustion engine is set to a high speed rotation, the time required for one combustion cycle is shortened, so the injection possible time is also shortened, and the required injection time is the injection possible time. It becomes easy to fall into the state that exceeds.

As described above, when the required injection time exceeds the injection possible time, there arises a problem that the air-fuel ratio shifts to the lean side from the optimum value. In particular, when the internal combustion engine is a gasoline engine, lean combustion due to air-fuel ratio leaning increases the amount of HC and O ₂ flowing into the catalyst device due to, for example, an unstable combustion state. HC and O ₂ may burn in the catalyst device, and as a result, the catalyst device may become hot and deteriorate.

  The present invention has been made in order to solve the above-described problems, and its purpose is a problem that the air-fuel ratio shifts to a leaner side than the optimum value, which is a concern when alternative fuel is mixed in regular fuel. An internal combustion engine control device and an internal combustion engine control system for suppressing the above are provided.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  In the first aspect of the invention, the required opening degree calculation means for calculating the required opening degree of the intake air amount control valve based on the required intake air amount corresponding to the driver's accelerator operation amount, and the fuel injection valve is the fuel per one combustion cycle. Required injection time calculating means for calculating a required injection time that is a required value of the time to inject fuel, and an injection possible time calculation for calculating an available injection time per combustion cycle based on the rotational speed of the output shaft of the internal combustion engine And a determination means for determining whether or not the required injection time is greater than the possible injection time, and when the determination means determines that the required injection time is greater than the allowable injection time, Opening degree correction means for reducing the degree of correction.

  According to this, when an affirmative determination is made that the required injection time is greater than the injectable time, the required opening degree of the intake air amount control valve is reduced and corrected. Therefore, the actual intake air amount is smaller than the required intake air amount calculated according to the accelerator operation amount. Therefore, even if a situation occurs in which the amount of fuel that is the optimum air-fuel ratio for the required intake air amount according to the accelerator operation amount cannot be injected as the alternative fuel is mixed into the regular fuel, the air-fuel ratio is optimal. Shifting to the lean side from the value can be suppressed.

  In recent years, instead of driving the intake valve with an intake cam, a mechanism for driving with an electromagnetic actuator has been developed. In this case, the intake amount can be adjusted by controlling the operation of the intake valve. It becomes possible. The “intake air amount control valve” according to the present invention is not limited to a throttle valve that is attached to an intake pipe and adjusts the intake air amount, and includes the above-described intake valve driven by an electromagnetic actuator.

  The invention according to claim 2 is characterized in that the opening degree correction means gradually corrects the required opening degree after the affirmative determination is made until the determination by the determination means changes to the negative determination. And

  According to this, until the negative determination is made (until the required injection time changes to the injection possible time or less), the required opening degree of the intake air amount control valve is reduced to be gradually reduced, so that the required opening amount of the intake air amount control valve is reduced. The degree is corrected so as to decrease until the air-fuel ratio reaches an optimum value. Therefore, the air-fuel ratio can be set to an optimum value.

  According to a third aspect of the present invention, the required injection time calculating means calculates the required injection time so that the actual air-fuel ratio approaches the target air-fuel ratio. When the air / fuel ratio becomes lean, the increase is corrected so that the actual air / fuel ratio approaches the target air / fuel ratio, and the required injection time becomes longer. As a result, an affirmative determination state is made such that the required injection time is longer than the injectable time. Therefore, it is desirable to apply the invention according to claim 1 or 2 when calculating the required injection time so that the actual air-fuel ratio approaches the target air-fuel ratio.

  According to a fourth aspect of the present invention, the determination unit repeatedly performs the determination at a predetermined cycle. After the affirmative determination is made, the determination unit determines whether the determination signal is obtained until a release signal is acquired. The opening is corrected so as not to exceed the opening corrected by the opening correction means.

  According to this, once an affirmative determination is made, an operation in which the actual intake air amount is smaller than the required intake air amount calculated according to the accelerator operation amount (hereinafter referred to as a degenerate operation) until a release signal is acquired. ) Will be continued. And since the degenerate operation state is an operation state in which the output torque corresponding to the accelerator operation amount is not obtained, the driver who has operated the accelerator can feel an abnormality. Therefore, the function as the abnormality notifying means can be exhibited while suppressing the problem that the air-fuel ratio shifts to the lean side as described above.

  The invention according to claim 5 is characterized in that the release signal is a signal output when fuel is supplied to the fuel tank. Specific examples of the release signal include an output signal from a detection unit that detects opening and closing of the fuel cap, an output signal from a detection unit that detects the remaining amount of fuel in the fuel tank, and the like.

  For example, if the fuel to be replenished to the fuel tank next time is regular fuel, the state of the mixed fuel may not be affirmative. According to the above invention, the regular fuel is replenished next time. It is preferable to maintain the degenerate operation when the determination is not positive.

  In the invention of claim 6, required injection time calculation means for calculating a required injection time, which is a required value of the time during which the fuel injection valve injects fuel per combustion cycle, according to the accelerator operation amount of the driver; Overrun control means for reducing the output of the internal combustion engine when the rotational speed of the output shaft of the internal combustion engine exceeds an upper limit value, and the injection possible time that can be injected per combustion cycle based on the rotational speed of the output shaft An affirmative determination is made that the required injection time is greater than the possible injection time by the determination means; and a determination means for determining whether or not the required injection time is greater than the possible injection time. An upper limit correction means for reducing the upper limit in a case where the upper limit is corrected.

  According to this, when an affirmative determination is made that the required injection time is longer than the injectable time, the upper limit value used by the overrun control means is reduced and corrected. As a result, the frequency at which the engine rotation speed becomes high speed exceeding the upper limit is reduced, so the frequency at which the possible injection time becomes shorter than the required injection time is reduced, and thus the frequency at which an affirmative determination is made can be suppressed. . Therefore, as an alternative fuel such as alcohol fuel is mixed into regular fuel such as gasoline, it has become impossible to inject an amount of fuel that provides an optimal air-fuel ratio with respect to the required intake amount according to the accelerator operation amount. However, it can be suppressed that the air-fuel ratio shifts to the lean side from the optimum value.

  According to a seventh aspect of the present invention, the determination means repeatedly performs the determination at a predetermined cycle, and after acquiring the affirmative determination, until the release signal is acquired, regardless of the determination result by the determination means. The upper limit value corrected by the upper limit value correcting means is maintained.

  According to this, once an affirmative determination is made, the above-described degenerate operation state is continued until a release signal is acquired. And since the degenerate operation state is an operation state in which the output torque corresponding to the accelerator operation amount is not obtained, the driver who has operated the accelerator can feel an abnormality. Therefore, the function as the abnormality notifying means can be exhibited while suppressing the problem that the air-fuel ratio shifts to the lean side as described above.

  The invention according to claim 8 is characterized in that the release signal is a signal output when fuel is supplied to the fuel tank. Specific examples of the release signal include an output signal from a detection unit that detects opening and closing of the fuel cap, an output signal from a detection unit that detects the remaining amount of fuel in the fuel tank, and the like.

  For example, if the fuel to be replenished to the fuel tank next time is regular fuel, the state of the mixed fuel may not be affirmative. According to the above invention, the regular fuel is replenished next time. It is preferable to maintain the degenerate operation when the determination is not positive.

  According to the ninth aspect of the present invention, the correction ratio by the correction unit is set to a mixture ratio that is a ratio between the normal fuel that is not expected to be positively determined by the determination unit and the mixed fuel other than the normal fuel. It is characterized by comprising a mixture ratio estimating means for estimating based on the above.

  According to this, it is possible to estimate the mixture ratio of the regular fuel and the mixed fuel while eliminating the need for a sensor such as an alcohol concentration sensor that detects the concentration of the mixed fuel. Incidentally, if the intake air amount, fuel injection amount, ignition timing, etc. are controlled in a state where the mixing ratio is unknown, the operating state of the internal combustion engine deteriorates, causing problems such as emission deterioration. If the above-mentioned various controls are performed based on the above, the problem can be suppressed.

  According to a tenth aspect of the invention, there is provided an internal combustion engine control device comprising: the internal combustion engine control device according to the invention described above; and at least one of an intake air amount control valve for adjusting an intake air amount and a fuel injection valve for injecting fuel. System. According to this internal combustion engine control system, the various effects described above can be exhibited in the same manner.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

(First embodiment)
In this embodiment, an internal combustion engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine. In the control system, an electronic control unit (hereinafter referred to as an ECU) that functions as an internal combustion engine control device. As a center, the control of the fuel injection amount, the control of the ignition timing, and the like are carried out. First, an overall schematic configuration diagram of the internal combustion engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting an intake air amount (intake amount) is provided downstream of the air cleaner 12. Yes. A throttle valve 14 (intake air amount control valve) whose opening degree is adjusted by a throttle actuator 15 such as a DC motor is provided on the downstream side of the air flow meter 13. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 15. In the present embodiment, a single throttle valve 14 is provided for a plurality of cylinders. However, a throttle valve 14 may be provided for each cylinder. The intake air amount may be controlled independently of the combustion chamber 23.

  A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10, and in the intake manifold 18, an electromagnetically driven fuel injection valve that injects fuel near the intake port of each cylinder. 19 is attached.

  The fuel path from the fuel tank 19T to the fuel injection valve 19 is provided with an electric fuel pump 19a. The fuel pump 19a according to this embodiment is an in-tank type installed in the fuel tank 19T, and the fuel in the fuel tank 19T is supplied to the delivery pipe 19b by the fuel pump 19a, and each fuel injection valve is supplied from the delivery pipe 19b. 19 is distributed.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. By the opening operation, the exhaust gas after combustion is discharged to the exhaust pipe 24 (exhaust passage).

  A spark plug 27 is attached to each cylinder head of the engine 10 for each cylinder, and a high voltage is applied to the spark plug 27 at a desired ignition timing through an ignition device (not shown) including an ignition coil. . By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 27, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a catalyst 31 such as a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas. The exhaust gas is detected as an object of detection on the upstream side of the catalyst 31. An A / F sensor 32 for detecting the fuel ratio (oxygen concentration) is provided.

  Further, the cylinder block of the engine 10 includes a coolant temperature sensor 33 that detects a coolant temperature, and a crank angle sensor 35 that outputs a rectangular crank angle signal at every predetermined crank angle of the engine (for example, at a cycle of 30 ° CA). It is attached. In addition, in this control system, an accelerator sensor 36 that detects an accelerator operation amount (accelerator pedal depression amount) by a driver and an atmospheric pressure sensor 37 that detects atmospheric pressure are provided.

  The ECU 40 is composed mainly of a microcomputer (hereinafter referred to as a microcomputer) 41 composed of a CPU, ROM, RAM, EEPROM, and the like as is well known, and by executing various control programs stored in the ROM, an engine for each time Various controls of the engine 10 are performed according to the operating state. That is, detection signals are input to the microcomputer 41 of the ECU 40 from the various sensors described above. The microcomputer 41 calculates the fuel injection amount, ignition timing, throttle opening, and the like based on various detection signals that are input as needed, and controls the drive of the fuel injection valve 19, the ignition device, and the throttle actuator 15. Specifically, the microcomputer 41 sets the target air-fuel ratio based on the engine operating state each time, and the actual air-fuel ratio calculated from the output value of the A / F sensor 32 matches the target air-fuel ratio. Air-fuel ratio feedback control is performed.

  Further, the ECU 40 performs on / off control of the operation of the fuel pump 19a. In a normal time, the duty ratio of the on / off control is fixed to a preset value. When the discharge pressure of the fuel discharged from the fuel pump 19a exceeds the threshold value, the pressure regulator 19c is operated to return the fuel to the fuel tank 19T. Therefore, the fuel pressure in the delivery pipe 19b is kept at a predetermined value within a range not exceeding the threshold value.

  Since the fuel pump 19a is an in-tank type and the pressure regulator 19c is provided in the fuel tank 19T, fuel with a discharge pressure exceeding the threshold value is not supplied to the delivery pipe 19b. That is, a returnless type in which return piping from the delivery pipe 19b to the fuel tank 19T is eliminated is employed.

  By the way, it is known that when the alcohol fuel is mixed into the gasoline in the fuel tank 19T and the mixed fuel is injected from the fuel injection valve 19, a larger fuel injection amount is required than gasoline. In the present embodiment, a countermeasure is preferably taken when the state is changed from a state of 100% gasoline to a state in which alcohol fuel is mixed.

  Hereinafter, the control content of the throttle actuator 15 by the ECU 40 for the purpose of dealing with the above will be described based on the flowcharts shown in FIGS. This process is repeatedly executed by the microcomputer 41 in the ECU 40 at a predetermined time period (for example, 10 msec period).

  First, in step S10 of FIG. 2, the actual intake air amount is calculated based on the value measured by the air flow meter 13. Next, in step S11, a basic fuel time Base per cylinder is calculated based on the calculated intake air amount. The basic fuel time Base is calculated so as to increase as the intake air amount increases.

  Next, in step S12, the fuel increase value is calculated based on the engine speed calculated based on the signal output from the crank angle sensor 35 and the intake pressure calculated based on the value measured by the intake pipe pressure sensor 17. Calculate CmpHv. The fuel increase value CmpHv is calculated so as to increase as the engine speed and the intake pressure increase.

  Next, in step S13, the fuel correction value CmpAf is calculated based on the deviation (actual air fuel ratio-target air fuel ratio) between the actual air fuel ratio calculated based on the value measured by the A / F sensor 32 and the target air fuel ratio. To do. The fuel correction value CmpAf is calculated so as to increase as the deviation increases, and is a correction value for bringing the actual air-fuel ratio closer to the target air-fuel ratio.

Next, in step S14 (required injection time calculation means), a required injection time InjT of fuel to be injected per cylinder is calculated based on the following calculation formula.
InjT = Basic fuel time Base x Fuel increase value CmpHv x Fuel correction value CmpAf
If the fuel injection valve 19 is opened for the required injection time InjT, the pressure in the delivery pipe 19b is maintained at a predetermined value, so that an amount of fuel corresponding to the required injection time InjT is supplied to the fuel injection valve. 19 will be injected. In step S11, the basic fuel time Base is calculated on the assumption that an amount of fuel corresponding to the required injection time InjT is injected during one combustion cycle.

  Next, in step S15 (injectable time calculating means), a maximum injectable time InjMax is calculated based on the engine speed. In the present embodiment, 700 ° C. A is the maximum injectable crank angle in one combustion cycle 720 ° C., and the time required for the crankshaft to rotate by 700 ° C. is the maximum injectable time InjMax.

  Next, in step S16 (determination means), it is determined whether or not the required injection time InjT is greater than the injectable time InjMax. If a positive determination is made that InjT> InjMax, there is a concern that the injection amount becomes insufficient and the actual air-fuel ratio shifts from the target air-fuel ratio to the lean side. If the affirmative determination (S16: YES) is made in order to eliminate this concern, the process proceeds to step S17 (opening correction means) to forcibly reduce the throttle opening to reduce the actual intake air amount. To alleviate the above concerns. That is, in step S17, a correction command is issued so as to gradually close the throttle valve and limit the opening. Specifically, a flag for the opening restriction correction command is set. When such an opening restriction correction command is issued, the throttle opening is reduced in a throttle control routine of FIG.

  On the other hand, when a negative determination is made in step S16 that InjT> InjMax is not satisfied (S16: NO), the process proceeds to step S18, and whether or not the throttle opening is an opening corresponding to the accelerator depression amount (required intake air amount). Determine whether. If it is determined that the opening does not correspond to the required intake air amount (S18: NO), in the subsequent step S19, the throttle valve 14 is gradually adjusted so as to return the restricted opening to the opening corresponding to the required intake air amount. A correction command is opened. Specifically, a flag for a required opening degree return correction command is set.

  FIG. 3 is a flowchart showing the contents of the throttle opening control process for calculating the control value output from the ECU 40 to the throttle actuator 15. First, in step S20 (required opening calculation means), the throttle valve 14 The basic required opening THBase is calculated. Specifically, the basic required opening degree THBase of the throttle valve 14 is calculated based on the required intake air amount corresponding to the accelerator depression amount of the driver. Next, in step S21, it is determined based on the flag whether or not the opening restriction correction command in step S17 has been issued.

If it is determined that there is an opening restriction correction command (S21: YES), the presence / absence of opening restriction correction history is determined in subsequent step S22. If it is determined that there is no opening restriction correction history (S22: NO), a correction amount ΔTH as a reduction amount of the throttle opening due to opening restriction is calculated based on the following calculation formula in step S23.
ΔTH = ΔTH previous value + α
Note that the value of α in the calculation formula is fixed to a preset value.

In the subsequent step S24, the final control value THfin output from the ECU 40 to the throttle actuator 15 is calculated based on the following calculation formula.
THfin = basic required opening THBase + correction amount ΔTH
On the other hand, when it is determined that there is no opening restriction correction command (S21: NO), the process proceeds to step S25, and it is determined whether or not the determination in step S21 is currently switched from a positive determination to a negative determination. If it is determined that it has been switched this time (S25: YES), in step S26 (mixing ratio estimating means), a mixing ratio that is a ratio of gasoline to alcohol fuel is calculated. Specifically, first, the deviation between the control value THfin, which is the corrected opening, and the basic required opening THBase corresponding to the accelerator depression amount is calculated as the opening correction amount ΔTH. A map showing the relationship between the correction amount ΔTH and the mixture ratio is stored in advance, and the mixture ratio is calculated based on the correction amount ΔTH using the map.

  Next, in step S27, the correction amount ΔTH is compared with the previous correction amount ΔTH, and the larger value is stored in the backup RAM as the history correction amount ΔTHM. The value of the history correction amount ΔTHM stored in this way is deleted when the ignition switch is turned off. Or you may set so that it may be deleted, if the fuel supply to the fuel tank 19T is made. Alternatively, the history correction amount ΔTHM may be stored and held without deleting these.

  Note that whether or not fuel has been replenished is determined by an output signal from the detection means 38 (see FIG. 1) that detects opening and closing of the fuel cap or from a detection means that detects the remaining amount of fuel in the fuel tank. This may be performed based on an output signal or the like. In other words, the storage of the history is maintained until an output signal (release signal) from the detection means is acquired.

  In the subsequent step S28, the final control value THfin output from the ECU 40 to the throttle actuator 15 is set as the basic required opening degree THBase. If it is determined in step S25 that the switch has not been made at this time (S25: NO), the process proceeds to step S28 without calculating the mixture ratio in step S26, and the control value THfin is set as the basic required opening THBase. I do.

  On the other hand, if the history is stored in step S27, it is determined in step S22 that there is a history of opening restriction correction. In this case, the stored history correction amount ΔTHM is corrected to the correction amount ΔTH in step S29. Set as. That is, once switching from the presence of the opening restriction correction command to the absence thereof (S25: YES), the history correction amount ΔTHM at that time is calculated (S26) and stored (S27), and thereafter, the opening restriction correction command is present. If this is the case (S22: YES), the basic required opening degree THBase is reduced by the stored history correction amount ΔTHM without executing the calculation of the correction amount ΔTH in step S23 (S24).

  FIG. 4 illustrates an example in the case where the drive of the fuel pump 19a is controlled based on the determination of InjT> InjMax in step S16. FIG. 4A shows a change in the engine rotational speed NE calculated based on a signal output from the crank angle sensor 35. The solid line in FIG. 4B shows the change in the maximum injection possible time InjMax, and the dotted line shows the change in the required injection time InjT per cylinder when alcohol fuel is not mixed. FIG. 4C shows a change in the throttle opening according to the control value THfin.

  As shown in FIG. 4, the maximum injectable time InjMax decreases as the engine speed increases due to an increase in the accelerator depression amount, and the maximum injectable time InjMax increases as the engine speed decreases. When the maximum injectable time InjMax decreases as the engine speed increases and reaches the time point t1, the required injection time InjT is greater than the maximum injectable time InjMax because alcohol fuel is mixed in the gasoline. growing.

  At this time t1, the determination of InjT> InjMax in step S16 shifts from a negative determination to a positive determination. Then, as long as the positive determination state of InjT> InjMax continues, the control value THfin gradually decreases by α by the processing in step S23 and the like, and the throttle opening gradually decreases. Then, as the actual intake air amount decreases, the actual air-fuel ratio approaches the target air-fuel ratio. Therefore, the fuel correction value CmpAf in step S13 becomes small, and the value of the required injection time InjT becomes small. Then, the determination of InjT> InjMax in step S16 changes from a positive determination to a negative determination, and the control value THfin changes at a balanced value so that InjT = InjMax. Such an equilibrium state continues from time t2 to time t3.

  Thereafter, when the maximum injection possible time InjMax rises as the engine speed decreases due to a decrease in the accelerator depression amount and reaches the time point t3, the required injection time InjT becomes smaller than the maximum injection possible time InjMax, and InjT> InjMax in step S16 The determination process will continue the negative determination.

  After that, when the required injection time InjT becomes longer than the maximum injectable time InjMax again due to an increase in the accelerator depression amount or the like, the history correction amount ΔTHM is stored as shown by the one-dot chain line in FIG. However, the throttle opening is reduced and limited.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  (1) When the required injection time InjT becomes longer than the maximum injectable time InjMax due to alcohol fuel being mixed in the gasoline, the throttle opening is reduced to limit the opening. Therefore, the actual intake air amount becomes smaller than the required intake air amount calculated according to the accelerator depression amount. Therefore, even if alcohol fuel is mixed into gasoline, the actual air-fuel ratio becomes the target even if the fuel becomes in an amount that provides an optimal air-fuel ratio with respect to the required intake air amount according to the accelerator depression amount. It is possible to suppress a problem that the air-fuel ratio (for example, the stoichiometric air-fuel ratio) is shifted to the lean side.

(2) Here, when lean combustion is caused by the air-fuel ratio lean, for example, the combustion state becomes unstable, HC and O ₂ flowing into the catalyst 31 increase, and these HC and O ₂ are converted into the catalyst. There is a concern that the catalyst 31 burns near 31 and as a result, the catalyst 31 becomes high temperature and deteriorates. On the other hand, according to the present embodiment, since the air-fuel ratio can be prevented from shifting to the lean side as described above, the above-mentioned concern can be solved.

  (3) Once switching from the presence of the opening restriction correction command to the absence (S25: YES), the history correction amount ΔTHM at that time is stored (S27), and after that, when there is an opening restriction correction command ( In S22: YES, the basic required opening degree THBase is decreased by the stored history correction amount ΔTHM without executing the calculation of the correction amount ΔTH in step S23 (S24). Therefore, the degenerate operation state in which the actual intake air amount is smaller than the required intake air amount according to the accelerator depression amount is continued. Since the degenerate operation state is an operation state in which the output torque corresponding to the accelerator depression amount is not obtained, the driver who has depressed the accelerator pedal can feel an abnormality. Therefore, the function as the abnormality notifying means can be exhibited while suppressing the problem that the air-fuel ratio shifts to the lean side as described above.

  (4) During the period (t1 to t2, t3) in which the required injection time InjT is longer than the maximum injectable time InjMax, correction for reducing and limiting the throttle opening is continued. For example, it can approach the stoichiometric air-fuel ratio).

  (5) The mixing ratio, which is the ratio of gasoline to alcohol fuel, is calculated by a correction amount ΔTH (correction amount) that is a deviation between the control value THfin that is the corrected opening degree and the basic required opening degree THBase corresponding to the accelerator depression amount. It is calculated based on the history correction amount ΔTHM which is the maximum value of (size). Therefore, it is possible to calculate (estimate) the mixture ratio of gasoline and alcohol fuel while eliminating the need for a sensor such as an alcohol concentration sensor that detects the concentration of alcohol fuel.

(Second Embodiment)
In the present embodiment, when the engine speed exceeds the upper limit value NEL, the overrun fuel that lowers the engine output by fully closing the throttle opening and cutting the fuel injection from the fuel injection valve 19. Cut control (see step S41 in FIG. 6) is executed. In the first embodiment, by performing the opening limit correction that reduces the throttle opening, the intake amount is reduced and the required injection time InjT is reduced, so that InjT> InjMax in step S16. Is suppressed from being affirmative. On the other hand, in this embodiment, the value of the required injection time InjT is reduced by reducing the upper limit value NEL used in the over-run fuel cut control, so that the determination of InjT> InjMax in step S16 is affirmative. It is restrained to become.

  More specifically, FIG. 5 and FIG. 6 are flowcharts showing the control contents of the fuel injection valve 19 by the ECU 40 according to this embodiment, and the steps for performing the same processing as the processing in FIG. 2 and FIG. The same code | symbol is attached | subjected and the description is used. The hardware configuration is the same between the present embodiment and the first embodiment.

  As shown in FIG. 5, if it is determined in step S16 that the required injection time InjT is greater than the injectable time InjMax, the process proceeds to step S171 (upper limit correction means), and over-run fuel cut control is performed. A correction command is issued so as to lower the upper limit value NEL used in the above. On the other hand, if it is determined in step S16 that InjT> InjMax is not satisfied, the process proceeds to step S181 to determine whether or not the upper limit value NEL is a normal value. If it is determined that the value is not the normal value (S181: NO), a correction command is issued to return the upper limit value NEL to the normal value in the subsequent step S191.

  In the process shown in FIG. 6, first, in step S30, the normal upper limit value NELBase (normal value) is read. Next, in step S31, it is determined based on the flag whether or not a correction command for lowering the upper limit value in step S171 has been issued.

If it is determined that there is an upper limit lowering correction command (S31: YES), in the subsequent step S32, it is determined whether there is a history of upper limit lowering correction. If it is determined that there is no upper limit decrease correction history (S32: NO), in step S33, the decrease amount ΔNEL of the upper limit NEL is calculated based on the following calculation formula.
ΔNEL = ΔNEL previous value−β
Note that the value of β in the calculation formula is fixed to a preset value.

In the subsequent step S34, the final upper limit value NELfin is calculated based on the following calculation formula.
Pfin = normal upper limit value NELBase−decrease amount ΔNEL
The drive of the fuel injection valve 19 is controlled so as to be the final upper limit value NELfin.

  On the other hand, if it is determined that there is no upper limit lowering correction command (S31: NO), the process proceeds to step S35, and it is determined whether or not the determination in step S31 has been switched from an affirmative determination to a negative determination this time. If it is determined that it has been switched this time (S35: YES), in step S36 (mixing ratio estimation means), a mixing ratio, which is a ratio of gasoline to alcohol fuel, is calculated using a map. The map used here stores the relationship between the decrease amount ΔNEL of the upper limit value NEL and the mixture ratio in advance, and the mixture ratio is calculated so that the larger the value of the decrease amount ΔNEL, the greater the mixing ratio of alcohol fuel. The

  Next, in step S37, the decrease amount ΔNEL is compared with the previous decrease amount ΔNEL, and the larger value is stored as the history decrease amount ΔNELM. Note that the value of the history decrease amount ΔNELM stored in this way is deleted when the ignition switch is turned off. Or you may set so that it may be deleted, if the fuel supply to the fuel tank 19T is made. Alternatively, the history decrease amount ΔNELM may be stored and held without performing these deletions.

  Note that whether or not fuel has been replenished is determined by an output signal from the detection means 38 (see FIG. 1) that detects opening and closing of the fuel cap or from a detection means that detects the remaining amount of fuel in the fuel tank. This may be performed based on an output signal or the like.

  In the subsequent step S38, the final upper limit value NELfin is set as the normal upper limit value NELBase. If it is determined in step S35 that the current switching has not been performed (S35: NO), the process proceeds to step S38 without calculating the mixing ratio in step S36, and the final upper limit value NELfin is set to the normal upper limit value NELBase. Perform the process.

  On the other hand, if the history is stored in step S37, it is determined in step S32 that there is a history of upper limit value reduction correction. In this case, the stored history decrease amount ΔNELM is reduced to the decrease amount ΔNEL in step S39. Set as. That is, once switching from the presence of the upper limit lowering correction command to the absence (S35: YES), the history lowering amount ΔNELM at that time is calculated (S36) and stored (S37), and thereafter, the upper limit lowering correction command is present. If this is the case (S32: YES), the normal upper limit value NELBase is decreased by the stored history decrease amount ΔNELM without executing the calculation of the decrease amount ΔNEL in step S33 (S34).

  In subsequent step S40, the actual engine speed NE and the final upper limit value NELfin are compared in magnitude, and if it is determined that NE> NELfin (S40: YES), in step S41 (overrun control means). If the fuel injection cut control is executed and it is determined that NE> NELfin is not satisfied (S40: NO), the fuel injection cut control is canceled and the drive of the fuel injection valve 19 is controlled based on the required injection time InjT.

  Next, an aspect of the processing of FIGS. 5 and 6 will be described with reference to FIG. A dotted line in FIG. 7A indicates a change in the upper limit value NEL of the over-run fuel cut control, and a solid line indicates a change in the engine speed NE. The solid line in FIG. 7B shows the change in the maximum injection possible time InjMax, and the dotted line shows the change in the required injection time InjT per cylinder when alcohol fuel is not mixed.

  As shown in FIG. 7, the maximum injectable time InjMax decreases as the engine speed increases due to the increase in the accelerator depression amount, and the maximum injectable time InjMax increases as the engine speed decreases. When the maximum injectable time InjMax decreases as the engine speed increases and reaches a time point t4, the required injection time InjT is greater than the maximum injectable time InjMax because alcohol fuel is mixed in the gasoline. growing.

  At time t4, the determination of InjT> InjMax in step S16 shifts from a negative determination to a positive determination. Then, as long as the positive determination state of InjT> InjMax continues, the upper limit value NELfin gradually decreases by β and the upper limit value NEL gradually decreases by the processing in step S33 and the like. Then, the maximum injectable time InjMax increases as the engine speed NE decreases due to the fuel injection cut control. Then, the determination of InjT> InjMax in step S16 changes from a positive determination to a negative determination, and the final upper limit value NELfin changes at a balanced value so that InjT = InjMax. Such an equilibrium state continues from time t5 to time t6.

  Thereafter, when the maximum injection possible time InjMax increases with the decrease in the engine speed NE due to the accelerator depression amount and reaches the time point t6, the required injection time InjT becomes smaller than the maximum injection possible time InjMax, and InjT> InjMax in step S16 This determination process will continue the negative determination.

  After that, when the required injection time InjT again becomes larger than the maximum injectable time InjMax due to an increase in the accelerator depression amount or the like, the upper limit value NEL becomes smaller and restricted so as to become the stored history decrease amount ΔNELM.

  According to the present embodiment described in detail above, the following effects can be obtained in the same manner as in the first embodiment.

  (1) When the required injection time InjT becomes longer than the maximum injectable time InjMax, the final upper limit value NELfin of the fuel injection cut control is decreased. As a result, the frequency at which the engine rotational speed NE is rotated at a high speed exceeding the upper limit value NEL is reduced, so the frequency at which the maximum injectable time InjMax is shortened to the extent that the affirmative determination is made is reduced. Therefore, as an alternative fuel such as alcohol fuel is mixed into regular fuel such as gasoline, it has become impossible to inject an amount of fuel that provides an optimal air-fuel ratio with respect to the required intake amount according to the accelerator depression amount. However, it is possible to suppress the problem that the air-fuel ratio shifts to the lean side from the optimum value.

(2) Here, when lean combustion is caused by the air-fuel ratio lean, for example, the combustion state becomes unstable, HC and O ₂ flowing into the catalyst 31 increase, and these HC and O ₂ are converted into the catalyst. There is a concern that the catalyst 31 burns near 31 and as a result, the catalyst 31 becomes high temperature and deteriorates. On the other hand, according to the present embodiment, since the air-fuel ratio can be prevented from shifting to the lean side as described above, the above-mentioned concern can be solved.

  (3) Once switching from the presence of the upper limit lowering correction command to the absence (S35: YES), the history lowering amount ΔNELM at that time is stored (S37), and when there is an upper limit lowering correction command thereafter ( In S32: YES, the normal upper limit value NELBase is decreased by the stored history decrease amount ΔNELM without executing the calculation of the decrease amount ΔNEL in step S33 (S34). Therefore, the degenerate operation state in which the actual intake air amount is smaller than the required intake air amount according to the accelerator depression amount is continued. Since the degenerate operation state is an operation state in which the output torque corresponding to the accelerator depression amount is not obtained, the driver who has depressed the accelerator pedal can feel an abnormality. Therefore, the function as the abnormality notifying means can be exhibited while suppressing the problem that the air-fuel ratio shifts to the lean side as described above.

  (4) Since the over-run fuel cut control is continued during the period (t4 to t5, t6) in which the required injection time InjT is longer than the maximum injectable time InjMax, the air-fuel ratio is set to the target air-fuel ratio (for example, the stoichiometric air-fuel ratio). ).

  (5) The mixing ratio, which is the ratio between gasoline and alcohol fuel, is calculated based on the history reduction amount ΔNELM, which is the maximum value of the decrease amount ΔNEL (correction magnitude) of the upper limit value NEL. Therefore, it is possible to calculate (estimate) the mixture ratio of gasoline and alcohol fuel while eliminating the need for a sensor such as an alcohol concentration sensor that detects the concentration of alcohol fuel.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Further, the characteristic structures of the respective embodiments may be arbitrarily combined.

  In step S41 (overrun control means) according to the second embodiment, the throttle opening is fully closed and the fuel injection is cut off. For example, the throttle opening may be limited to a predetermined opening or less and the fuel injection amount may be limited to a predetermined amount or less.

  In the above embodiment, the internal combustion engine (engine 10) is a spark ignition internal combustion engine such as a gasoline engine, but may be a compression ignition internal combustion engine such as a diesel engine.

  The above embodiment is directed to the port injection type engine 10 in which the fuel injection valve 19 is attached to the intake manifold 18 or the intake pipe, but the fuel injection valve 19 is attached to the cylinder head and the fuel is directly injected into the combustion chamber 23. The direct injection type engine 10 for injection may be the target. However, in the case of the port injection type, the maximum injectable crank angle can be secured at about 700 ° C. during one combustion cycle 720 ° C., whereas in the direct injection type, the maximum injectable crank angle is the port injection. Therefore, the required injection time InjT becomes longer than the injectable time InjMax even if alcohol fuel is slightly mixed. Therefore, it is considered effective even when the direct-injection engine 10 is targeted.

  -It may replace with the mixture ratio calculation means by step S26 in FIG. 3, and step S36 in FIG. 7, and you may make it determine only the presence or absence of mixing of alcohol fuel. Specifically, if it is determined in step S21 that an opening restriction correction command has been made (S21: NO), it may be determined that alcohol fuel may be mixed, or step S31. If it is determined that the upper limit lowering correction command is issued (S31: NO), it may be determined that alcohol fuel may be mixed.

1 is an overall schematic configuration diagram of an internal combustion engine control system according to a first embodiment. The flowchart which shows the control content by ECU of FIG. The flowchart which shows the throttle control routine according to the processing content of FIG. FIG. 4 is a timing chart showing an aspect of the processing of FIG. 2 and FIG. 3. The flowchart which shows the control content by ECU which concerns on 2nd Embodiment. The flowchart which shows the pump control routine according to the processing content of FIG. The timing chart which shows the one aspect | mode by the process of FIG.5 and FIG.6.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 14 ... Throttle valve (intake amount control valve), 19 ... Fuel injection valve, 40 ... ECU (internal combustion engine control device, required opening degree calculation means), S14 ... Required injection time calculation means, S15 ... Injectable time calculation means, S16 ... determination means, S17 ... opening correction means, S20 ... required opening calculation means, S26, S36 ... mixing ratio estimation means, S36 ... overrun control means, InjMax ... injectable time, InjT ... required injection time.

Claims (10)

A required opening calculation means for calculating a required opening of the intake air amount control valve based on a required intake air amount corresponding to the accelerator operation amount of the driver;
A required injection time calculating means for calculating a required injection time which is a required value of the time during which the fuel injection valve injects fuel per combustion cycle;
Injectable time calculating means for calculating an injectable time that can be injected per combustion cycle based on the rotational speed of the output shaft of the internal combustion engine;
Determining means for determining whether or not the required injection time is greater than the injectable time;
An opening correction means for reducing the required opening when the determination means determines that the required injection time is greater than the injectable time;
An internal combustion engine control device comprising:   The said opening degree correction | amendment means carries out the reduction | decrease correction | amendment of the said required opening degree gradually until the determination by the said determination means changes to the said negative determination after the said affirmation determination is made. Internal combustion engine control device.   The internal combustion engine control apparatus according to claim 1 or 2, wherein the required injection time calculating means calculates the required injection time so that an actual air-fuel ratio approaches a target air-fuel ratio. The determination means repeatedly performs the determination at a predetermined cycle,
After the affirmative determination is made, until the release signal is acquired, the opening corrected by the opening correction means is limited so as not to exceed the determination result by the determination means. Item 4. The internal combustion engine control device according to any one of Items 1 to 3.   The internal combustion engine control device according to claim 4, wherein the release signal is a signal output when fuel is supplied to the fuel tank. A required injection time calculating means for calculating a required injection time, which is a required value of the time required for the fuel injection valve to inject fuel per combustion cycle, according to the accelerator operation amount of the driver;
Overrun control means for reducing the output of the internal combustion engine when the rotational speed of the output shaft of the internal combustion engine exceeds an upper limit;
Injectable time calculating means for calculating an available injection time per combustion cycle based on the rotation speed of the output shaft;
Determining means for determining whether or not the required injection time is greater than the injectable time;
An upper limit correction unit that reduces the upper limit when the determination unit determines that the required injection time is greater than the available injection time;
An internal combustion engine control device comprising: The determination means repeatedly performs the determination at a predetermined cycle,
The upper limit value corrected by the upper limit correction unit is maintained regardless of the determination result by the determination unit after acquiring the affirmative determination until the release signal is acquired. Internal combustion engine control device.   The internal combustion engine control device according to claim 7, wherein the release signal is a signal output when fuel is supplied to the fuel tank.   Mixing ratio estimation for estimating a mixing ratio, which is a ratio of a normal fuel that is not expected to be positively determined by the determination unit, and a mixed fuel other than the normal fuel, based on the magnitude of correction by the correction unit The internal combustion engine control device according to any one of claims 1 to 8, further comprising means. An internal combustion engine control device according to any one of claims 1 to 9,
At least one of an intake air amount control valve for adjusting the intake air amount and a fuel injection valve for injecting fuel;
An internal combustion engine control system comprising:

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