JP5411728B2 - Air-fuel ratio learning control device for internal combustion engine - Google Patents

Description

The present invention includes a fuel injection valve that injects fuel into an intake passage, an oxygen sensor that detects a residual oxygen concentration in exhaust gas that flows through the exhaust passage, a throttle valve that controls the amount of intake air that flows through the intake passage, A throttle sensor that detects a throttle opening that is an opening of the throttle valve; a rotational speed sensor that detects an engine rotational speed; and the fuel injection valve based on detection values of the oxygen sensor, the throttle sensor, and the rotational speed sensor A control unit for controlling the fuel injection amount from the engine, and the control unit determines a basic fuel injection amount based on the throttle opening and the engine speed for setting the air-fuel ratio to the target air-fuel ratio, and A feedback correction coefficient determined according to the detection value of the oxygen sensor and a value determined for each engine load while learning to change according to changes over time of the internal combustion engine While the aging-dependent correction coefficient to obtain a fuel injection amount not based on at least the intake pressure and atmospheric pressure by multiplying the basic fuel injection quantity, a plurality of loads each region comprising a plurality of O ₂ feedback region The present invention relates to an air-fuel ratio learning control device for an internal combustion engine that performs fuel injection control independently.

An air-fuel ratio learning control apparatus for an internal combustion engine in which a plurality of O ₂ feedback regions for feedback of the air-fuel ratio are set and O ₂ feedback control is independently performed for each of these regions is known from Patent Document 1.

Japanese Patent No. 2631580

Those disclosed in Patent Document 1, the O ₂ feedback control based on the detected value of the oxygen sensor, but in consideration of the temporal change or the like due to deterioration of the engine it is possible to obtain an appropriate fuel injection state, O ₂ feedback In the region, the fuel injection amount is controlled so that the air-fuel ratio becomes stoichiometric (theoretical air-fuel ratio). By the way, when the internal combustion engine is in an operating state in the high rotation / high throttle opening range, the fuel injection amount is set to an air fuel ratio (rich air fuel ratio) higher than stoichiometric to prevent the internal combustion engine from becoming hot ( (Injection cooling) is preferable, but if O ₂ feedback control is executed in such an operating state, injection cooling may not be achieved. Further, when the internal combustion engine is in an operating state in the low rotation / low throttle opening range, the amount of air sucked into the internal combustion engine is small, so the combustion amount is also small, and it is difficult to expect high-precision O ₂ feedback control. .

In operating region defined on the basis of the order engine speed and the throttle opening degree, a region where O ₂ feedback control is executed, is set and not executed region, in a region where the O ₂ feedback control is not executed, the area In general, the fuel injection correction is performed so as to obtain an appropriate operation state. In addition, this correction is generally made based on the detection result of the atmospheric pressure sensor, the intake pressure sensor, or the atmospheric temperature sensor.

However, in an internal combustion engine mounted on a small vehicle such as a motorcycle, there are strict restrictions on the mounting space of components, and there is a demand to reduce the fuel injection system cost. It has been considered to establish a fuel injection system without using an intake pressure sensor or the like. In such a case, a technique is required that enables appropriate fuel injection in a region where the O ₂ feedback control as described above is not executed.

The present invention has been made in view of such circumstances, and learning of the air-fuel ratio of an internal combustion engine that can perform appropriate fuel injection in a region other than the O ₂ feedback control region while eliminating the need for an intake pressure sensor or the like. An object is to provide a control device.

In order to achieve the above object, the present invention provides a fuel injection valve that injects fuel into an intake passage, an oxygen sensor that detects a residual oxygen concentration in exhaust gas flowing through the exhaust passage, and an intake air amount that flows through the intake passage. A throttle valve that controls the throttle valve, a throttle sensor that detects a throttle opening that is the opening of the throttle valve, a rotation speed sensor that detects the engine speed, and detection of the oxygen sensor, the throttle sensor, and the rotation speed sensor A control unit for controlling the fuel injection amount from the fuel injection valve based on the value, the control unit determines the basic fuel injection amount for setting the air-fuel ratio as the target air-fuel ratio to the throttle opening and the engine rotation The feedback correction coefficient determined according to the detection value of the oxygen sensor and the change over time of the internal combustion engine While the learning and while the engine load aging-dependent correction determined for each coefficient to obtain a fuel injection amount not based on at least the intake pressure and atmospheric pressure by multiplying the basic fuel injection quantity, a plurality of O ₂ feedback In the air-fuel ratio learning control apparatus for an internal combustion engine that performs fuel injection control independently for each of a plurality of load regions including a region, the control unit includes the feedback correction coefficient and the correction for change with time in a plurality of the O ₂ feedback regions. Fuel injection control using a coefficient is performed, and in the load region other than the O ₂ feedback region, the feedback correction coefficient is set to “1”, and the correction coefficient corresponding to aging change is adjacent to the O ₂ feedback region. defined as the value at in the first feature to run a control fuel injection Isei.

The present invention, in addition to the first feature, a plurality of the O ₂ feedback region, a second feature that it is set the so throttle opening becomes narrower decreases.

The present invention, in addition to the configuration of the first or second aspect, in the control unit, to the boundary between the plurality of the load range is determined with a hysteresis and third features.

In addition to any one of the configurations of the first to third features, the present invention provides the control unit that sets the correction coefficient for aging when the engine operating state shifts between the plurality of load regions. A fourth feature is that the fuel injection control is performed so as to gradually approach the value of the new load destination load region.

According to the first aspect of the present invention, since the control unit is not based on at least the intake pressure and the atmospheric pressure in the fuel injection control, it is unnecessary to use the intake pressure sensor and the atmospheric pressure sensor in the fuel injection control system. While achieving a reduction in system cost and a reduction in the number of parts, in a load region other than the O ₂ feedback region, the feedback correction coefficient is set to “1” and the correction coefficient corresponding to aging is set as a value in the adjacent O ₂ feedback region. since the control fuel injection Isei determined, O ₂ can perform air-fuel ratio control by the fuel injection reflecting the aging of the internal combustion engine even in a region other than the feedback control region. Particularly in the low throttle opening range, it becomes possible to perform air-fuel ratio control that captures engine degradation such as friction change of the internal combustion engine, intake amount change due to soot adhering to the throttle valve, and in the high throttle opening range, Although the characteristic of the output deviation of the throttle sensor tends to depend on the throttle opening, an appropriate air-fuel ratio can be set by referring to the O ₂ feedback region close to the throttle opening.

Also, in the load region other than the O ₂ feedback control region, than the feedback correction coefficient shall be determined as "1", it is possible to prevent a lean air-fuel ratio other than O ₂ feedback control region.

According to the third feature of the present invention, since a plurality of O ₂ feedback regions are set so as to become narrower as the throttle opening becomes smaller, it is finer in a low throttle opening region that is easily affected by deterioration of the bypass valve or the like. More appropriate air-fuel ratio control can be performed by performing proper learning control.

  According to the fourth feature of the present invention, since the boundary between the load regions is determined with hysteresis, it is possible to prevent chattering from occurring near the boundary.

  Furthermore, according to the fifth feature of the present invention, it is possible to suppress a rapid change in the fuel injection amount when the operating state of the engine shifts between load regions.

It is a figure which shows the whole structure of an internal combustion engine. It is a block diagram which shows the structure of a control unit. It is a flowchart which shows the procedure which defines the feedback correction coefficient for every load area | region of an engine, and a time-dependent change correction coefficient. It is a figure which shows the map for searching the load area | region of an engine. O ₂ is a diagram showing a feedback region. It is a figure which overlaps and shows FIG. 4 and FIG. It is a flowchart which shows the subroutine which determines a feedback correction coefficient and a time-dependent change correction coefficient in the some engine load area | region set below the setting minimum throttle opening. It is a flowchart which shows the subroutine which determines a feedback correction coefficient and a time-dependent change correction coefficient in the some engine load area | region set more than the setting upper limit throttle opening. It is a flowchart which shows the subroutine which defines the process sequence at the time of an engine load area | region shifting. It is a flowchart which shows the subroutine which defines the process sequence at the time of basic mode transfer. It is a flowchart which shows the subroutine which defines the procedure of changing a time-dependent change correction coefficient gradually with transfer of an engine load area | region.

  Hereinafter, an embodiment of the present invention will be described with reference to the attached FIGS. 1 to 11. First, in FIG. 1, for example, a piston 12 is provided in a cylinder bore 11 of a water-cooled internal combustion engine E mounted on a motorcycle. An intake device 14 for supplying an air-fuel mixture to a combustion chamber 13 that is slidably fitted and faces the top of the piston 12, and an exhaust device 15 for exhausting exhaust gas from the combustion chamber 13 Connected to a cylinder head 16 of the internal combustion engine E, an intake passage 17 is formed in the intake device 14, and an exhaust passage 18 is formed in the exhaust device 15. A spark plug 20 is attached to the cylinder head 16 so that the tip of the combustion head 13 faces the combustion chamber 13.

  The intake device 14 is provided with a throttle valve 21 for controlling the amount of intake air flowing through the intake passage 17 so that it can be opened and closed, and for injecting fuel into the intake passage 17 on the downstream side of the throttle valve 21. The fuel injection valve 22 is attached. In addition, a bypass passage 27 that bypasses the throttle valve 21 is connected to the intake passage 17, and the amount of air flowing through the bypass passage 27 is adjusted by the armature 28. The exhaust device 15 is provided with a catalytic converter 25.

  The ignition timing by the spark plug 20, the fuel injection amount from the fuel injection valve 22, and the operation of the actuator 28 are controlled by a control unit C. The control unit C includes an opening of the throttle valve 21. The detected value of the throttle sensor 26 for detecting the throttle opening degree, the detected value of the rotational speed sensor 30 for detecting the rotational speed of the crankshaft 29 connected to the piston 12, and the water temperature sensor for detecting the water temperature of the engine cooling water The detected value of 31 and the detected value of the oxygen sensor 32 attached to the exhaust device 15 on the downstream side of the catalytic converter 25 are input so as to detect the residual oxygen concentration in the exhaust gas flowing through the exhaust passage 18.

In FIG. 2, the part of the control unit C that controls the injection amount of the fuel injection valve 22 is referred to a map 33 based on the rotational speed obtained by the rotational speed sensor 30 and the throttle opening obtained by the throttle sensor 26. On the other hand, the basic fuel injection amount calculating means 34 for determining the basic fuel injection amount for obtaining the target air-fuel ratio and the feedback correction coefficient are calculated so as to approach the target air-fuel ratio based on the oxygen concentration obtained by the oxygen sensor 32, and O ₍₂₎ Feedback correction coefficient calculation means 35 for performing feedback control, correction means 36 for correcting the basic fuel injection amount based on the correction amount obtained by the feedback correction coefficient calculation means 35, and the final result obtained by the correction means 36 And a final fuel injection time calculating means 37 for obtaining a fuel injection time corresponding to the fuel injection amount, and at least the intake pressure. And configured to obtain the fuel injection amount without following the atmospheric pressure.

  The feedback correction coefficient calculating means 35 includes a rich / lean determination unit 38 that determines the rich / lean degree of exhaust gas based on the oxygen concentration detected by the oxygen sensor 32, and the determination result of the rich / lean determination unit 38. And a parameter calculation unit 39 for correcting the feedback correction coefficient and the basic fuel injection amount. The parameter calculation unit 39 stores the parameters in the nonvolatile storage unit 40 such as an EPROM or a flash memory at a predetermined cycle, and when the ignition key is turned on (system startup), the parameter calculation unit 39 stores the parameters from the nonvolatile storage unit 40. Read.

  Thus, in the parameter calculation unit 39, the integrated correction for air-fuel ratio control based on the detection value of the oxygen sensor 32 is performed by the feedback correction coefficient KO2 and the temporal change corresponding correction coefficient KBU periodically stored in the nonvolatile storage unit 40. The coefficient KT is calculated as KT ← (KO2 × KBU). Here, the time-dependent correction coefficient KBU is determined for each engine load while learning to change according to changes over time such as deterioration of the internal combustion engine E, and is recorded in the nonvolatile recording unit 40 at a predetermined cycle. Even after the ignition key is turned off (system stop), the value is held and read when the system is started, and learning control is performed.

The feedback correction coefficient KO2 is a variable that is primarily used at predetermined intervals when O ₂ feedback control is performed. Basically, feedback control is performed based on the feedback correction coefficient KO2, and the air-fuel ratio is determined. Is brought close to the target air-fuel ratio. Thus, the feedback correction coefficient KO2 is determined based on the rich / lean determination result in the rich / lean determination unit 38.

In a plurality of O ₂ feedback regions, the parameter calculation unit 39 calculates a temporal change correspondence correction coefficient KBU for each O ₂ feedback region based on the engine speed NE and the throttle opening TH, and responds to the change over time. integrated correction coefficient KT (= KO2 × KBU) calculates using the correction factor KBU, the load range of the engine other than the O ₂ feedback control region, aging corresponding correction coefficient of the O ₂ feedback area adjacent to the load area KBU Is used to control the fuel injection amount.

  The processing procedure in the parameter calculation unit 39 will be described. In FIG. 3, in step S1, the engine load NE and the throttle opening TH are searched for in which region the engine load is. That is, as shown in FIG. 4, a set lower limit throttle opening TH02L and a set upper limit throttle opening THO2H, and a plurality of set throttle openings THFB0, THFB1, THFB2, THFB3 between the set lower limit and upper limit throttle openings THO2L, THO2H. Is set in advance so that TH02L <THFB1 <THF2 <THB3 <THO2L is satisfied as the engine speed NE increases. Moreover, for each set throttle opening TH02L, THFB1, THFB2, THFB3, and THO2L, the value on the increase side of the throttle opening TH is indicated by a solid line, and the value on the decrease side of the throttle opening TH is indicated by a broken line. And is set with hysteresis.

On the other hand, the O ₂ feedback region includes a set lower limit rotational speed NLOP, a set upper limit rotational speed NHOP, and an idle region upper limit rotational speed NTHO2L, a set lower limit throttle opening degree THO2L, and a set upper limit throttle opening degree THO2H, as indicated by the oblique lines in FIG. It is set as an area determined by. In addition, the idle region upper limit rotational speed NTHO2L is indicated by a solid line on the increase side of the engine rotational speed NE, and a value on the decrease side of the engine rotational speed NE by a broken line. The upper limit throttle opening THO2H is set with hysteresis, with the value on the increase side of the throttle opening TH shown by a solid line and the value on the decrease side of the throttle opening TH shown by a broken line. ing.

Thus, when the regions determined in FIG. 4 and FIG. 5 are overlapped, it becomes as shown in FIG. 6, and a plurality of load regions including a plurality of O ₂ feedback regions are set based on the engine speed NE and the throttle opening TH. In this embodiment, six O ₂ feedback regions are indicated by numbers “1” to “6”, and regions other than the O ₂ feedback region are “0” and “7”. It is shown with a number of “11”.

Moreover, the boundaries between the plurality of load areas shown in FIG. 6 are determined with hysteresis, and the O ₂ feedback area indicated by “1” to “6” becomes narrower as the throttle opening TH becomes smaller. It is set to be.

  In FIG. 3 again, after the search in step S1 is completed, steps S2 to S7 are assigned to a subroutine for executing processing for each area. That is, when it is confirmed in step S2 that TH <THO2L, the process proceeds from step S2 to step S8 to determine the feedback correction coefficient KO2 and the time-varying correction coefficient KBU in the region of TH <THO2L, and THO2L ≦ TH ≦ THBO0. When it is confirmed in step S3, the process proceeds from step S3 to step S9 to determine the feedback correction coefficient KO2 and the time-dependent change correction coefficient KBU in the region of THO2L ≦ TH ≦ THFB0, and confirm that THFB0 <TH ≦ THFB1. When confirmed in step S4, the process proceeds from step S4 to step S10 to determine a feedback correction coefficient KO2 and a temporal change correction coefficient KBU in the region of THFB0 <TH ≦ THFB1, and that THFB1 <TH ≦ THFB2. When it is confirmed in step S5, the process proceeds from step S5 to step S11, the feedback correction coefficient KO2 and the temporal change corresponding correction coefficient KBU in the region of THFB1 <TH ≦ THFB2 are determined, and it is determined in step S6 that THFB2 <TH ≦ THFB3. When confirmed, the process proceeds from step S6 to step S12, and the feedback correction coefficient KO2 and the time-varying correction coefficient KBU are determined in the region of THFB2 <TH ≦ THF3, and when it is confirmed in step S7 that THFB3 <TH <THO2H. When the process proceeds from step S7 to step S13, the feedback correction coefficient KO2 and the temporal change corresponding correction coefficient KBU are determined in the region of THFB3 <TH <THO2H, and it is confirmed that TH ≧ THO2H, Determining the time course corresponding correction factor KBU in the area of TH ≧ THO2H proceeds to step S14 from. When the subroutine processing in steps S8 to S14 is completed, a determination is made to gradually shift the aging change correction coefficient KBU in step S15.

The processing in step S8 is executed according to the procedure shown in FIG. 7. In step S21 in FIG. 7, it is determined whether or not the flag FNLOP is “1”. Thus, the flag FNLOP becomes “1” when the engine speed NE is larger than the set lower limit speed NLOP (NLOP <NE), and when FNLOP is “0”, that is, when NE ≦ NLOP, Proceeding from step S21 to step S22, in this step S22 the KBU region KBUZN is set to “0” assuming that the engine operation region is in the region “0” other than the O ₂ feedback region shown in FIG. 6, and the next step S23 Thus, the temporal change correction coefficient KBUN is set to the value KBU1 of the region “1” which is the O ₂ feedback region adjacent to the region “0”.

If it is confirmed in step S21 that FNLOP is “1”, the process proceeds from step S21 to step S24, where it is determined whether NE <NTHO2L. If it is determined that NE <NTHO2L, step S21 is performed. In S25, assuming that the engine operating region is in the O ₂ feedback region in the idling state and is in the region “1” shown in FIG. 6, the KBU region KBUZN is set to “1”. The corresponding correction coefficient KBUN is set to the value KBU1 of the O ₂ feedback area “1”, and the feedback correction coefficient KO2N is set to the value KO21 of the area “1”.

Further, when it is determined in the above step S24 that NTHO2L ≦ NE, the engine operating region is a region other than the O ₂ feedback region in step S27 and is in the region “7” shown in FIG. KBUZN is set to “7”, and in the next step S 28, the temporal change corresponding correction coefficient KBU is set to the value KBU _{2 of} the O ₂ feedback region “2” adjacent to the region “7”.

In the subroutine of steps S9 to S13 in FIG. 3, processing similar to that shown in FIG. 7 is performed. In step S9, the time-dependent change of the feedback region “2” in the range of THO2L ≦ TH ≦ THFB0. Corresponding correction coefficient KBUN is set to the value of area “2” KBU2 and feedback correction coefficient KO2N is set to the value of area “2”, and the temporal change corresponding correction coefficient KBUN of area “7” adjacent to feedback area “2” is set. Is defined as KBU2 which is the value of the O ₂ feedback region “2”. In step S10, the correction coefficient KBUN of the feedback region “3” over time in the range of THFB0 <TH ≦ THFB1 is set to KBU3 which is the value of region “3”, and the feedback correction coefficient KO2N is the value of region “3”. And the temporal change correction coefficient KBUN in the region “8” adjacent to the feedback region “3” is determined as KBU3 which is the value of the O ₂ feedback region “3”. In step S11, the time-varying correction coefficient KBUN of the feedback region “4” in the range of THFB1 <TH ≦ THFB2 is set to the value “KBU4” of the region “4”, and the feedback correction coefficient KO2N is set to the value of the region “4”. Then, the correction coefficient KBUN corresponding to change with time in the area “9” adjacent to the feedback area “4” is set to KBU4 which is the value of the O ₂ feedback area “4”. In step S12, the time-varying correction coefficient KBUN of the feedback region “5” in the range of THFB2 <TH ≦ THFB3 is set to the value “KBU5” of the region “5”, and the feedback correction coefficient KO2N is set to the value of the region “5”. The time-dependent change correction coefficient KBUN in the area “10” adjacent to the feedback area “5” is set to KBU5 which is the value of the O ₂ feedback area “5”. In step S13, the correction coefficient KBUN of the feedback region “6” over time in the range of THFB3 <TH ≦ TH02H is set to the value “KBU6” of the region “6”, and the feedback correction coefficient KO2N is set to the value of the region “6”. The time-dependent change correction coefficient KBUN in the region “11” adjacent to the feedback region “6” is set to KBU6 which is the value of the O ₂ feedback region “6”.

The processing in step S14 is executed according to the procedure shown in FIG. 8. In step S31 of FIG. 8, the KBU region KBUZN is set to “11”, and in the next step S32, the temporal change corresponding correction coefficient KBUN is The value KBU6 of the region “6” that is the O ₂ feedback region adjacent to the region “11” is determined.

Thus, the parameter calculation unit 39 sets the feedback correction coefficient KO2 to “1” in the load region other than the O ₂ feedback region, and sets the aging correction coefficient KBU to a value in the adjacent O ₂ feedback region. And an integrated correction coefficient KT (= KO2 × KBU) is calculated. In FIG. 6, in the load region other than the O ₂ feedback region and numbered “0”, the O ₂ feedback region “ In the load region other than the O ₂ feedback region and numbered “7”, the time variation corresponding correction coefficient KBU2 in the O ₂ feedback region “2” is selected. select, O ₂ in the load area which is other than the feedback region number "8" are assigned, in an O ₂ feedback control region "3" Select the time course corresponding correction coefficient KBU3, O ₂ be other than the feedback region in the load area indicated by the number "9", and select the time course corresponding correction coefficient KBU4 in O ₂ feedback control region "4", In the load region other than the O ₂ feedback region and numbered “10”, the correction coefficient KBU5 corresponding to the aging change in the O ₂ feedback region “5” is selected, and the number “10” is located outside the O ₂ feedback region. In the load region to which “11” is attached, the temporal change corresponding correction coefficient KBU6 in the O ₂ feedback region “6” is selected.

  The process of step S15 in FIG. 3 is executed according to the procedure shown in FIG. 9. In step S41 of FIG. 9, whether or not the previous KBU area KBUZN1 is equal to the current KBU area KBUZN, that is, the engine load area. If there is no transition, the flag FZCHANGE is set to “0” in step S42 and the process proceeds to step S44. If there is a transition, the flag FZCHANGE is set to “1” in step S43. Proceed to S44.

  In step S44, it is confirmed whether or not the flag FKBUSFT is “1”. This flag FKBUSFT is “1” when the engine load region is gradually shifting, “0” when it is not gradually shifting, and when it is determined that FKBUSFT is “0”, step S45. Then, it is confirmed whether or not the flag FZCHANGE is “1”. When it is determined that the flag FZCHANGE is “1”, the process proceeds to step S46. In step S46, it is confirmed whether or not the flag F1STZX is “1”. This flag F1STZX indicates whether or not the determination of the KBU region has been performed after the engine is started. When the determination has been made, the flag F1STZX is “1”. Thus, when the flag F1STZX is “0” and it is determined in step S46 that the determination of the KBU area has not been performed, in step S47, the KBU process at the time of shifting to the basic mode is executed. If it is determined in step S46 that the determination of the KBU region has been performed, the process proceeds from step S46 to step S48, and a process of gradually shifting the time-varying correction coefficient KBU when executing the load region is executed.

  If it is determined in step S44 that the flag FKBUSFT is “1” and the load range of the engine is gradually shifting, the process proceeds from step S44 to step S49. In step S49, the flag FZCHANGE is “1”. If it is determined that the flag FZCHANGE is “0”, the process proceeds from step S49 to step S50 to execute a process of gradually shifting the correction coefficient KBU over time in the same region, and in step S49. When it is determined that the flag FZCHANGE is “1”, the process proceeds from step S49 to step S51, and processing is performed when the load region is switched during the gradual transition of the correction coefficient KBU corresponding to aging.

  The processing in step S47 in FIG. 9 is executed according to the procedure shown in FIG. 10. In step S61 in FIG. 10, the temporal change correspondence correction coefficient KBU is set as the temporal change correspondence correction coefficient KBUN of the current load region. In step S62, the flag FZCHANGE is set to “0” and the flag F1STZX is set to “1”.

  Further, the process of step S48 in FIG. 9 is executed according to the procedure shown in FIG. 11. In step S71 of FIG. 11, the previous time-dependent change correction coefficient KBU1 is changed to the time-dependent change corresponding correction coefficient KBUN of the load area at the transfer destination. That is, it is confirmed whether or not it is equal to or less than the target value (KBU1 ≦ KBUN). If KBUN <KBU1, the flag FKBUINC is set to “0” in step S72 in order to perform a process of reducing the temporal change corresponding correction coefficient KBU.

  In the next step S73, a predetermined value DKBUSFT is subtracted from the previous time-dependent correction coefficient KBU1 to determine a buffer KBUBUF for the time-dependent correction coefficient KBUN, and in step S74, the buffer KBUBUF responds to the time-dependent change in the load area at the destination. It is determined whether or not the correction coefficient KBUN is equal to or less. When it is confirmed that KBUBUF ≦ KBUN, in step S75, the time-dependent correction coefficient KBUN of the destination load region is determined as the time-dependent correction coefficient KBU, and in step S76, the flag KBUSFT is set to “0”. The flag HZCHANGE is set to “0”.

  If it is confirmed in step S74 that KBUBUF> KBUN, the process proceeds from step S74 to step S77. In step S77, the buffer KBUBUF is set as the correction coefficient KBU corresponding to secular change. In step S78, the flag KBUSFT is set to “1”, the flag HZCHANGE is set to “0”.

  When it is confirmed in step S71 that KBU1 ≦ KBUN, the flag FKBUINC is set to “1” in step S79 in order to perform a process for increasing the temporal change corresponding correction coefficient KBU.

  In the next step S80, a predetermined value DKBUSFT is added to the previous time-dependent correction coefficient KBU1 to define a buffer KBUBUF for the time-dependent correction coefficient KBUN. In step S81, the buffer KBUBUF changes with time in the load area at the transfer destination. It is determined whether or not the corresponding correction coefficient KBUN has been reached. Thus, when it is confirmed that KBUBUF ≧ KBUN, the time-varying correction coefficient KBUN of the destination load region is determined as the time-varying correction coefficient KBU in step S82, and the flag KBUSFT is set to “0” in step S83. The flag HZCHANGE is set to “0”.

  If it is confirmed in step S81 that KBUBUF <KBUN, the process proceeds from step S81 to step S82. In step S84, the buffer KBUBUF is set as the time-varying correction coefficient KBU. In step S85, the flag KBUSFT is set to “1”. HZCHANGE is set to “0”.

  According to such processing in steps S71 to S85, when a shift between engine load areas occurs, a predetermined value DKBUSFT is set to, for example, a crank, using the time-varying correction coefficient KBUN of the load area at the transfer destination as a target value. A process of gradually approaching the target value by performing subtraction or addition every 720 degrees of the corner is executed.

  Further, in steps S50 and S51 of FIG. 9, the same processing as the subroutine shown in FIG. 11 is executed. In step S50, the time-varying correction coefficient KBU is added to the predetermined value DKBUSFT even after the area is switched. Alternatively, a process of gradually changing by subtraction is executed, and in step S51, when the load area is switched during the gradual shift of the correction coefficient KBU with time, the target value in the new load destination load area is set. Then, a process of gradually changing the correction coefficient KBU with time change by adding or subtracting the predetermined value DKBUSFT is executed, and in step S51, when the load region is switched in the middle of gradually changing the correction coefficient KBU with time change, Time-varying correction coefficient KBU toward the target value in the new load destination load region The executes processing to gradually change by the addition or subtraction of a predetermined value DKBUSFT.

  In the basic injection amount calculating means 34, when the basic fuel injection amount is set to TO based on the map 33, the correcting means 36 obtains the corrected fuel injection amount T1 as (TO × KT), and the final fuel injection time calculating means 37. Obtains the fuel injection time corresponding to the final fuel injection amount (TO × KT). That is, the control unit C controls the fuel injection amount from the fuel injection valve 22 by performing learning control for bringing the air-fuel ratio based on the detection value of the oxygen sensor 32 close to the target air-fuel ratio.

Next, the operation of this embodiment will be described. The control unit C determines the basic fuel injection amount for setting the air-fuel ratio to the target air-fuel ratio based on the throttle opening and the engine speed, and is detected by the oxygen sensor 32. By multiplying the basic fuel injection amount by at least the feedback correction coefficient KO2 determined according to the value and the time-varying correction coefficient KBU determined for each engine load while learning to change according to the time-dependent change of the internal combustion engine E, at least the fuel injection control so as to obtain a fuel injection amount not based on the intake pressure and atmospheric pressure, although a plurality of O ₂ feedback region is performed independently for each pre no more load region, the O ₂ feedback control region In the load region other than the above, the feedback correction coefficient KO2 is set to “1” and the time-dependent change correction coefficient KBU is adjacent to the load correction coefficient KO2. The determined as the value of an O ₂ feedback control region to perform the control fuel injection Isei that.

Therefore, since the control unit C is not based on at least the intake pressure and the atmospheric pressure in the fuel injection control, it is not necessary to use the intake pressure sensor and the atmospheric pressure sensor in the fuel injection control system, thereby reducing the system cost and the number of parts. while achieving, at the load region other than O feedback area, and controls the fuel injection amount by using the aging-dependent correction coefficient KBU the O ₂ feedback control region adjacent to the load region, even in a region other than the O ₂ feedback control region It is possible to perform air-fuel ratio control by fuel injection reflecting changes with time of the internal combustion engine. Particularly in the low throttle opening range, it becomes possible to perform air-fuel ratio control that captures engine deterioration such as a change in friction of the internal combustion engine E, a change in intake amount due to the soot adhering to the throttle valve 21, and a high throttle opening range. In this case, the output deviation characteristic of the throttle sensor 26 tends to depend on the throttle opening, but an appropriate air-fuel ratio can be set by referring to the O ₂ feedback region close to the throttle opening.

The control unit C, because the O ₂ feedback territory Iki以 outside load region for executing the feedback correction coefficient KO2 as "1" constant Umate fuel injection control, lean air-fuel ratio other than O ₂ feedback control region Can be prevented.

In addition, since the O ₂ feedback region is set to become narrower as the throttle opening becomes smaller, fine learning control is performed in a low throttle opening region that is easily affected by the deterioration of the bypass valve, etc. Air-fuel ratio control can be performed.

  Further, in the control unit C, since the boundaries between the plurality of load areas are determined with hysteresis, it is possible to prevent chattering from occurring near the boundaries.

Furthermore, the control unit C performs the fuel injection control so that the temporal change correction coefficient KBU gradually approaches the value of the new transition destination load region when the engine operating state transitions between the plurality of load regions. It is possible to suppress a rapid change in the fuel injection amount when the engine operating state shifts between load regions.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

17 ... Intake passage 18 ... Exhaust passage 21 ... Throttle valve 22 ... Fuel injection valve 26 ... Throttle sensor 30 ... Revolution sensor 32 ... Oxygen sensor C ... Control unit E ... Internal combustion engine

Claims (4)

A fuel injection valve (22) for injecting fuel into the intake passage (17), an oxygen sensor (32) for detecting the residual oxygen concentration in the exhaust gas flowing through the exhaust passage (18), and a flow through the intake passage (17) A throttle valve (21) for controlling the amount of intake air, a throttle sensor (26) for detecting the throttle opening that is the opening of the throttle valve (21), and a rotation speed sensor (30) for detecting the engine speed A control unit (C) for controlling a fuel injection amount from the fuel injection valve (22) based on detection values of the oxygen sensor (32), the throttle sensor (28) and the rotation speed sensor (30). The control unit (C) determines a basic fuel injection amount based on the throttle opening and the engine speed for setting the air-fuel ratio to the target air-fuel ratio, and the oxygen sensor (32). The feedback correction coefficient (KO2) determined according to the detected value and the time-varying correction coefficient (KBU) determined for each engine load while learning to change according to the time-dependent change of the internal combustion engine (E) Fuel injection control is performed independently for each of a plurality of load areas including a plurality of O ₂ feedback areas while multiplying the basic fuel injection quantity so as to obtain a fuel injection quantity at least without being based on the intake pressure and the atmospheric pressure. In an air-fuel ratio learning control device for an internal combustion engine,
Wherein the control unit (C) is a plurality of the O ₂ feedback region performs fuel injection control using the feedback correction coefficient (KO2) and the change with time corresponding correction coefficient (KBU), also other than the O ₂ feedback control region the load region of the with determined feedback correction coefficient (KO2) as "1", the fuel injection Isei control determined as values at the O ₂ feedback region adjacent the change over time corresponding correction coefficient (KBU) An air-fuel ratio learning control device for an internal combustion engine characterized by being executed . A plurality of the O ₂ feedback region, the air-fuel ratio learning control apparatus according to claim 1 Symbol placement of the internal combustion engine, wherein said set to the throttle opening becomes narrower decreases. The air-fuel ratio learning control apparatus for an internal combustion engine according to claim 1 or 2 , characterized in that in the control unit (C), boundaries between a plurality of load regions are determined with hysteresis. The control unit (C) gradually adjusts the temporal change correction coefficient (KBU) to the value of the new load region when the engine operating state shifts between the load regions. The air-fuel ratio learning control apparatus for an internal combustion engine according to any one of claims 1 to 3 , wherein fuel injection control is performed.

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