JP2008309035A - 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 required injection time InjT which is a required value of time when a fuel injection valve jets fuel per one combustion cycle according to an accelerator operation amount of a driver (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 positively determined to be longer than the injectable time InjMax, the load increase operation of the fuel pump is executed so as to increase fuel supply pressure. <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 present invention, a required injection time calculating means for calculating a required injection time, which is a required value of a time required for the fuel injection valve to inject fuel per combustion cycle, according to the accelerator operation amount of the driver; Injectable time calculating means for calculating an available injection time per combustion cycle based on the rotation speed of the output shaft of the internal combustion engine, and determining means for determining whether or not the required injection time is greater than the available injection time And a fuel pump control means for controlling the operation of a fuel pump that supplies fuel to the fuel injection valve, wherein the fuel pump control means determines that the required injection time is greater than the possible injection time by the determination means. When an affirmative determination is made, the fuel pump is operated to increase the load so that the fuel supply pressure increases.

  According to this, when it is determined affirmative that the required injection time is longer than the injectable time, the fuel pump is operated to increase the load so that the fuel supply pressure increases. Therefore, since the injection amount injected per unit time from the fuel injection valve increases, even if the injection possible time is the same, the injection amount injected during the injection possible time increases. Therefore, it is possible to reduce the frequency of falling into a state in which an amount of fuel that becomes the optimum air-fuel ratio with respect to the required intake air amount according to the accelerator operation amount as the alternative fuel is mixed into the regular fuel, and the air-fuel ratio is reduced. It is possible to suppress the shift to the lean side from the optimum value.

  According to a second aspect of the present invention, after the affirmative determination is made, the fuel pump control means gradually increases the supply pressure until the determination by the determination means changes to the negative determination. .

  According to this, the supply pressure gradually increases until the negative determination is changed (until the required injection time is changed to the injection possible time or less), and thus the supply pressure is increased until the air-fuel ratio becomes the 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, a mixture ratio that is a ratio of a normal fuel that is not expected to be positively determined by the determination means and a mixed fuel other than the normal fuel is set to a load increase due to the load increase operation. Mixing ratio estimation means for estimating based on the quantity is provided.

  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.

Then, as described above, the following invention can be applied when the fuel pump is operated to increase the load.
The invention according to claim 5 is characterized in that the fuel pump control means performs on / off control of the fuel pump, and performs the load increasing operation by increasing a duty ratio of the on / off control.
In the seventh aspect of the invention, the fuel pump control means controls the operation of the fuel pump so that the supply pressure becomes a target pressure, and increases the target pressure to cause the load increase operation. It is characterized by that.
In a ninth aspect of the present invention, a relief valve that returns fuel to the upstream side of the fuel pump in the fuel supply path from the fuel pump to the fuel injection valve when the supply pressure is equal to or higher than a set value. And the fuel pump control means performs the load increasing operation by changing the set value to be high.

  Regarding the relief valve, for example, a relief valve that can change the set value may be adopted, and the set value may be switched according to the determination result of the determination unit, or a plurality of relief valves having different set values may be switched. It may be installed to switch which relief valve is used according to the determination result of the determination means.

  In the invention according to claims 6 and 8, the fuel pump control means continues the load increasing operation after the affirmative determination is made until the determination by the determination means changes to the negative determination, and the normal fuel And a mixing ratio estimating means for estimating a mixing ratio that is a ratio of the mixed fuel to the mixed fuel, and the mixing ratio estimating means according to claim 6 is configured to increase the duty ratio by the fuel pump control means. The mixture ratio estimation means according to claim 8 is estimated based on an increase amount of the target pressure by the fuel pump control means.

  According to these, it is possible to estimate the mixing ratio between 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 present invention, there is provided an internal combustion engine control system comprising: the internal combustion engine control device according to the above invention; and at least one of a fuel pump for supplying fuel to the fuel injection valve and the fuel injection valve. is there. According to this internal combustion engine control system, the various effects described above can be exhibited in the same manner.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the 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, and the duty ratio of the on / off control is fixed at a preset value in a normal time when the load increasing operation described later is not performed. 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 fuel pump 19a 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 to eliminate this concern, the process proceeds to step S17, and the fuel pump 19a is operated to increase the load so as to increase the fuel pressure in the delivery pipe 19b.

  In order to increase the fuel pressure in the delivery pipe 19b, the duty ratio of the on / off control of the fuel pump 19a may be increased. Therefore, in step S17, a correction command is issued so as to set the pump drive duty ratio to a high value for load increase operation. More specifically, a load increase correction command flag is set. When such a load increase correction command is issued, the duty ratio is increased in the pump control routine of FIG. 3 described later.

  On the other hand, if a negative determination is made in step S16 that InjT> InjMax is not satisfied (S16: NO), the process proceeds to step S18 to determine whether or not the pump drive duty ratio is a normal value. If it is determined that the value is not the normal value (S18: NO), a correction command is issued to return the pump drive duty ratio from the high value to the normal value in the subsequent step S19. Specifically, a normal value correction command flag is set.

  FIG. 3 is a flowchart showing the contents of the pump control process for calculating the control value output from the ECU 40 to the fuel pump 19a. First, in step S20, the basic duty ratio DutyBase of the fuel pump 19a is calculated. Next, in step S21, it is determined based on the flag whether or not a load increase correction command in step S17 has been issued.

If it is determined that there is a load increase correction command (S21: YES), the presence or absence of load increase correction history is determined in the subsequent step S22. If it is determined that there is no load increase correction history (S22: NO), in step S23, the duty ratio increase amount ΔDuty is calculated based on the following calculation formula.
ΔDuty = previous value of ΔDuty + 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 Dutyfin output from the ECU 40 to the fuel pump 19a is calculated based on the following calculation formula.
Dutyfin = Basic duty ratio DutyBase + Increase amount ΔDuty
On the other hand, if it is determined that there is no load increase correction command (S21: NO), the process proceeds to step S25, and it is determined whether 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), the mixing ratio, which is the ratio of gasoline to alcohol fuel, is shown in FIGS. 4 (a) and 4 (b). Calculate using a map.

  The solid line in FIG. 4A is a map showing the relationship between the injection amount TAU actually injected from the fuel injection valve 19 and the basic duty ratio DutyBase, and the injection amount TAU and the basic duty ratio according to the engine speed. The relationship with DutyBase is mapped. In step S26, first, a deviation ΔDuty between the control value Dutyfin, which is the corrected duty ratio, and the basic duty ratio DutyBase is calculated using the map of FIG. Then, the mixture ratio is calculated based on the deviation ΔDuty using the map of FIG. 4B showing the relationship between the deviation ΔDuty and the mixture ratio.

  Incidentally, the mixture ratio may be calculated using a map shown in FIG. 4C instead of FIG. FIG. 4C is a map showing the relationship between the value obtained by multiplying the required injection time InjT by the engine rotational speed NE and the basic duty ratio DutyBase. According to this map, the map is used in FIG. Deviation ΔDuty can be obtained in the same manner as in FIG.

  Next, in step S27, the deviation ΔDuty is compared with the previous deviation ΔDuty, and the larger value is stored in the backup RAM as the history deviation ΔDutyM. Note that the value of the history deviation ΔDutyM 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 Dutyfin output from the ECU 40 to the fuel pump 19a is set as the basic duty ratio DutyBase. 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 process of setting the control value Dutyfin as the basic duty ratio DutyBase is performed. 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 load increase correction. In this case, the stored history deviation ΔDutyM is set as the increase amount ΔDuty in step S29. To do. In other words, once switching from the presence of the load increase correction command to the absence (S25: YES), the history deviation ΔDutyM at that time is calculated (S26) and stored (S27), and thereafter there is a load increase correction command. In (S22: YES), the basic duty ratio DutyBase is increased by the stored history deviation ΔDutyM without executing the calculation of the increase amount ΔDuty in step S23 (S24).

  FIG. 5 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. 5A 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. 5B 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 no alcohol fuel is mixed. FIG. 5C shows a change in the pump drive duty ratio according to the control value Dutyfin.

  As shown in FIG. 5, 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 Dutyfin gradually increases by α by the processing in step S23 and the like, and the pump drive duty ratio gradually increases from the normal value. Thereafter, the value is maintained after time t2 when the pump drive duty ratio becomes 100%.

  Thereafter, when the maximum injection possible time InjMax rises as the engine speed decreases due to the accelerator depression amount decreasing and reaches the time point t3, the required injection time InjT becomes shorter than the maximum injection possible time InjMax. That is, the fuel can be injected in an amount corresponding to the required injection time InjT. At this time t3, the determination process of InjT> InjMax in step S16 shifts from a positive determination to a negative determination. Then, the pump drive duty ratio returns from 100% to the normal value by the process of step S19.

  After that, when the required injection time InjT becomes larger than the maximum injection possible time InjMax again, the pump drive duty ratio increases so as to become the value of the stored history deviation ΔDutyM, as shown by the one-dot chain line in FIG. Will be.

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

  (1) A load increasing operation in which the drive duty ratio of the fuel pump 19a is increased when the required injection time InjT is greater than the maximum injection possible time InjMax due to alcohol fuel being mixed in the gasoline. Become. Accordingly, the fuel pressure in the delivery pipe 19b increases and the amount of fuel injected from the fuel injection valve 19 per unit time increases, so even if the maximum injectable time InjMax is the same, the fuel is injected during the injectable time. The injected amount increases. Therefore, it is not possible to inject an amount of fuel (an amount corresponding to the required injection time InjT) that is the optimum air-fuel ratio with respect to the required intake amount according to the accelerator operation amount as alcohol fuel is mixed into the gasoline. It is possible to reduce the frequency of falling into a state, and to suppress problems such as the air-fuel ratio deviating from the optimum value 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) Since the load increasing operation of the fuel pump 19a is continued during the period (t1 to t3) 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 theoretical air-fuel ratio). You can get closer to.

  (4) The mixing ratio, which is the ratio between gasoline and alcohol fuel, is calculated based on the history deviation ΔDutyM, which is the maximum value of the duty ratio increase amount ΔDuty (load increase amount) of the fuel pump 19a. 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. When the duty ratio is less than 100%, the mixture ratio can be estimated to a specific value using a map. However, when the duty ratio is 100% or more, the concentration is higher than the alcohol concentration when the duty ratio is 100%. What is necessary is just to presume that there exists.

(Second Embodiment)
In the first embodiment, the load increasing operation is performed by increasing the drive duty ratio of the fuel pump 19a. In the present embodiment, the fuel pressure (supply pressure) in the delivery pipe 19b is the target pressure. A configuration in which feedback control is performed to achieve (target fuel pressure) is performed, and the load is increased by increasing the target fuel pressure.

  6 and 7 are flowcharts showing the control content of the fuel pump 19a by the ECU 40 according to the present embodiment. Steps for performing the same processing as the processing in FIG. 2 and FIG. The explanation is used. Further, in the present embodiment, a fuel pressure sensor 19d (see the one-dot chain line in FIG. 1) that detects the fuel pressure in the delivery pipe 19b is provided. Other hardware configurations are the same as those in the first embodiment. A signal detected by the fuel pressure sensor 19d is input to the ECU 40.

  Then, as shown in FIG. 6, when 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, and the target fuel pressure is set to a high value for load increase operation. A correction command is issued. 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 target fuel pressure 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 target fuel pressure from the high value to the normal value in the subsequent step S191.

  In the process shown in FIG. 7, first, in step S30, the basic target fuel pressure PBase of the fuel pump 19a is calculated. Next, in step S31, it is determined based on the flag whether or not a load increase correction command in step S171 has been issued.

If it is determined that there is a load increase correction command (S31: YES), the presence / absence of load increase correction history is determined in the subsequent step S32. If it is determined that there is no load increase correction history (S32: NO), the target fuel pressure increase amount ΔP is calculated based on the following calculation formula in step S33.
ΔP = ΔP 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 target fuel pressure Pfin is calculated based on the following calculation formula.
Pfin = basic target fuel pressure PBase + increase amount ΔP
The drive of the fuel pump 19a is controlled so as to be the final target fuel pressure Pfin.

  On the other hand, if it is determined that there is no load increase correction command (S31: NO), the process proceeds to step S35, and it is determined whether the determination in step S31 has been switched from a positive 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 target fuel pressure increase amount ΔP and the mixing ratio in advance, and the mixing ratio is calculated such that the larger the increase amount ΔP, the greater the alcohol fuel mixing ratio. .

  Next, in step S37, the increase amount ΔP is compared with the previous increase amount ΔP, and the larger value is stored in the backup RAM as the history increase amount ΔPM. The history increase amount ΔPM 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 the subsequent step S38, the final target fuel pressure Pfin is set as the basic target fuel pressure PBase. If it is determined in step S35 that the switch has not been made this time (S35: NO), the process proceeds to step S38 without calculating the mixing ratio in step S36, and the final target fuel pressure Pfin is set to the basic target fuel pressure PBase. 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 load increase correction. In this case, the stored history increase amount ΔPM is set as the increase amount ΔP in step S39. Set. That is, once switching from the presence of the load increase correction command to the absence thereof (S35: YES), the history increase amount ΔPM at that time is calculated (S36) and stored (S37), and thereafter there was a load increase correction command. In the case (S32: YES), the basic target fuel pressure PBase is increased by the stored history deviation ΔPM without executing the calculation of the increase amount ΔP in step S33 (S34).

  Next, an aspect of the processing of FIGS. 6 and 7 will be described. This mode is the same mode as in FIGS. 5A and 5B when the duty ratio in FIG. 5C is read as the target fuel pressure P when compared with the mode by the processing of FIGS. . Also in this embodiment, at the time t2 when the final target fuel pressure Pfin increases and the duty ratio reaches 100%, the fuel pressure in the delivery pipe 19b does not increase even if the target fuel pressure Pfin further increases.

  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 target fuel pressure Pfin of the fuel pump 19a is increased to start the load increasing operation, and the fuel pressure in the delivery pipe 19b is increased. Therefore, since the injection amount injected per unit time from the fuel injection valve 19 increases, even if the maximum injection possible time InjMax is the same, the injection amount injected during the injection possible time increases. Therefore, it is possible to reduce the frequency of falling into a state in which an amount of fuel that becomes the optimum air-fuel ratio cannot be injected with respect to the required intake amount according to the accelerator operation amount as alcohol fuel is mixed in gasoline, and the air-fuel ratio is optimal It is possible to suppress problems such as shifting to a leaner side than the 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) Since the load increasing operation of the fuel pump 19a is continued during the period (t1 to t3) 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 theoretical air-fuel ratio). You can get closer to.

  (4) The mixing ratio, which is the ratio between gasoline and alcohol fuel, is calculated based on the history increase amount ΔPM, which is the maximum value of the target fuel pressure increase amount ΔP (load increase amount). 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.

(Third embodiment)
In the present embodiment, a pressure regulator 19c (relief valve) shown in FIG. 1 that can change the threshold value for the relief pressure is adopted, and the threshold value can be set by the ECU 40. In performing the above-described load increasing operation, means for increasing the threshold value is employed instead of means for increasing the target fuel pressure P. Also by this, the same effects as those of the above embodiments can be obtained. Further, the load increase amount can be estimated based on the amount and time when the threshold is increased, and the mixture ratio can be calculated based on the estimated load increase amount.

  Further, as a modification of the above configuration, a pressure regulator 19c having a fixed threshold value for the relief pressure may be applied, and two pressure regulators 19c having different threshold values may be switched and used. In this case, when performing the above-described load increase operation, the pressure regulator 19c may be switched to a relief pressure higher than that of one pressure regulator 19c. Also by this, the same effects as those of the above embodiments can be obtained. Further, the load increase amount can be estimated based on the amount and time when the threshold is increased, and the mixture ratio can be calculated based on the estimated load increase amount.

(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 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 S31 that a load increase correction command has been 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 pump control routine according to the processing content of FIG. 4 is a map used in the mixing ratio calculation process 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.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 19 ... Fuel injection valve, 19a ... Fuel pump, 40 ... ECU (internal combustion engine control apparatus, fuel pump control means), S14 ... Request injection time calculation means, S15 ... Injection possible time calculation means, S16 ... Determination means, S26, S36 ... mixing ratio estimation means, InjMax ... injection possible time, InjT ... required injection time.

Claims (10)

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;
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;
Fuel pump control means for controlling operation of a fuel pump for supplying fuel to the fuel injection valve;
With
The fuel pump control means causes the fuel pump to perform a load increase operation so that the fuel supply pressure becomes high when the determination means determines that the required injection time is greater than the injection possible time. An internal combustion engine control device.   2. The internal combustion engine according to claim 1, wherein after the affirmative determination is made, the fuel pump control unit gradually increases the supply pressure until the determination by the determination unit changes to the negative determination. 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.   Mixing ratio estimation for estimating a mixing ratio, which is a ratio of normal fuel that is not expected to be positively determined by the determining means, and mixed fuel other than the normal fuel, based on a load increase amount due to the load increasing operation The internal combustion engine control device according to claim 3, further comprising means.   3. The internal combustion engine control device according to claim 1, wherein the fuel pump control unit performs on / off control of the fuel pump and performs the load increasing operation by increasing a duty ratio of the on / off control. 4. . The fuel pump control means continues the load increasing operation until the determination by the determination means changes to the negative determination after the affirmative determination is made,
A mixture ratio, which is a ratio of normal fuel that is not expected to be positively determined by the determination unit, and mixed fuel other than the normal fuel, is estimated based on an increase in the duty ratio by the fuel pump control unit. The internal combustion engine control apparatus according to claim 5, further comprising a mixing ratio estimation unit configured to perform the mixing ratio estimation.   The fuel pump control means controls the operation of the fuel pump so that the supply pressure becomes a target pressure, and makes the load increase operation by increasing the target pressure. 3. The internal combustion engine control device according to 2. The fuel pump control means continues the load increasing operation until the determination by the determination means changes to the negative determination after the affirmative determination is made,
A mixture ratio, which is a ratio of a normal fuel that is assumed not to be positively determined by the determination unit, and a mixed fuel other than the normal fuel is estimated based on an increase amount of the target pressure by the fuel pump control unit. The internal combustion engine control device according to claim 7, further comprising a mixing ratio estimation unit configured to perform the mixing ratio estimation. A fuel supply path from the fuel pump to the fuel injection valve is provided with a relief valve that returns fuel to the upstream side of the fuel pump when the supply pressure is equal to or higher than a set value.
The internal combustion engine control device according to claim 1, wherein the fuel pump control means performs the load increase operation by changing the set value to be high. An internal combustion engine control device according to any one of claims 1 to 9,
At least one of a fuel pump for supplying fuel to the fuel injection valve and the fuel injection valve;
An internal combustion engine control system comprising:

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