JP2005220766A - Air-fuel ratio controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the driveability by suppressing the change width of air-fuel ratio of each cylinder to a rich side and a lean side, irrespective of the restriction in the arrangement composition of the internal combustion engine, etc. <P>SOLUTION: In the internal combustion engine consisting of V-type four-cycle two cylinders, air-fuel ratio feedback correction factors FAF, FAF1 (S108, S113) in an air-fuel feedback control can be transited as desired corresponding to the output voltage of an oxygen sensor independently, an engine rotational speed NE, a throttle opening TA, and a suction pressure PM for each cylinder in which the exhaust passage independently connected to each exhaust port differs in distance. Therefore, even when the time when exhaust gas from the exhaust port of the internal combustion engine reaches the oxygen sensor differs in the cylinder different in the distance of the exhaust passage, the change width to the rich side and the lean side of the air-fuel ratio can be suppressed. Consequently, the combustion in each cylinder of the internal combustion engine is stabilized to enable the improvement in the driveability. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine that appropriately controls the fuel injection amount supplied to the internal combustion engine in accordance with the difference in the arrangement configuration of the exhaust passage for each cylinder.

Conventionally, as a prior art document related to an air-fuel ratio control device for an internal combustion engine, one disclosed in Japanese Patent Laid-Open No. 1-177435 is known. In this system, air-fuel ratio feedback control is performed based on signals from a plurality of air-fuel ratio detection means. When feedback control of some cylinders is started, torque fluctuation due to the difference in air-fuel ratio for each cylinder group is suppressed. However, a technique for starting feedback control early is shown.
JP-A-1-177435 (first page to second page)

In the foregoing, air-fuel ratio feedback is provided based on an output signal of an oxygen (O ₂ ) sensor (air-fuel ratio sensor) that is disposed in the exhaust passage of each cylinder group of the internal combustion engine and detects the oxygen concentration in the exhaust gas. By independently changing the air-fuel ratio feedback correction coefficient in the control, the air-fuel ratio of the air-fuel mixture for each cylinder group is adjusted to the vicinity of the theoretical air-fuel ratio.

  By the way, for example, when it takes a long time for the exhaust gas from the exhaust port to reach the oxygen sensor due to restrictions on the arrangement configuration of the internal combustion engine, the air-fuel ratio feedback correction is performed by the output signal from the oxygen sensor. If the skip amount or the integral constant in the coefficient is changed, the fluctuation range of the air-fuel ratio feedback correction coefficient is increased, so that a considerable delay occurs in the air-fuel ratio of the air-fuel mixture. As a result, the fluctuation range of the air-fuel ratio of the air-fuel mixture to the rich side and the lean side becomes large.

  Further, in the case of an internal combustion engine consisting of V-type multiple cylinders in which the cylinders are arranged back and forth in a V-shape, the direction of the exhaust passage connected to the front cylinder of the internal combustion engine due to arrangement restrictions Must be longer than the exhaust passage connected to the rear cylinder. Then, the distance from the exhaust port to the oxygen sensor arranged for detecting the oxygen concentration of the exhaust gas in each exhaust passage of the internal combustion engine is also longer in the front cylinder than in the rear cylinder.

  For this reason, the fluctuation range of the air-fuel ratio feedback correction coefficient in the air-fuel ratio feedback control differs between the front cylinder and the rear cylinder. Specifically, as shown in FIG. 12B, the fluctuation range W1 of the air-fuel ratio feedback correction coefficient FAF1 due to the output voltage VOX1 from the oxygen sensor connected to the front cylinder and disposed in the exhaust passage having a long distance. However, as shown in FIG. 12 (a), the fluctuation width W of the air-fuel ratio feedback correction coefficient FAF due to the output voltage VOX from the oxygen sensor connected to the rear cylinder and disposed in the exhaust passage having a short distance becomes larger. It becomes. Note that TDR, TDL, TDR1, and TDL1 in the figure are empty on the opposite side to the inversion direction when the oxygen sensor output voltages VOX and VOX1 undergo an inversion transition through the determination voltage between the rich side and the lean side. This is a delay time for delaying the timing for skipping the fuel ratio feedback correction coefficients FAF and FAF1.

  As a result, the fluctuation range and the fluctuation cycle of the air-fuel ratio of the air-fuel mixture to the rich side and the lean side are different for each cylinder, and in particular, in a vehicle with a light vehicle weight such as a two-wheeled vehicle, drivability deteriorates. there were. Also, if the fluctuation range and fluctuation cycle of the air-fuel ratio of the air-fuel mixture to the rich side and the lean side are different between the front cylinder and the rear cylinder, the required catalyst capacity will differ, and if the capacity setting is not appropriate, emission There was a defect that caused deterioration.

  Accordingly, the present invention has been made to solve such a problem, and suppresses the fluctuation range of the air-fuel ratio of the air-fuel mixture of each cylinder to the rich side and the lean side regardless of restrictions on the arrangement configuration of the internal combustion engine. Thus, an object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine capable of improving drivability and further improving emission by optimizing the catalyst capacity of each cylinder.

  According to the air-fuel ratio control apparatus for an internal combustion engine of claim 1, the oxygen concentration is detected at a position where the distance from the exhaust port is different in an exhaust passage having a different length for each cylinder, the internal combustion engine having a plurality of V-type cylinders. The reversal direction discriminating means discriminates the reversal direction when the detection value corresponding to the oxygen concentration by the oxygen concentration detection means undergoes reverse transition through the judgment value between the rich side and the lean side. The delay time for delaying the timing for skipping the air-fuel ratio feedback correction coefficient in the air-fuel ratio feedback control by the delay time setting means and the air-fuel ratio feedback correction coefficient by the skip amount setting means are skipped on the opposite side to the reverse direction. Integral for gradually changing the air-fuel ratio feedback correction coefficient by means of setting the skip amount and integral constant for The integral delay time for delaying the timing for setting the integral constant by the integral delay time setting means is set based on the physical quantity that changes in accordance with the running state of the vehicle and the operating state of the internal combustion engine detected by the physical quantity detecting means. The fuel injection amount supplied to each cylinder is controlled by the fuel injection amount control means in accordance with the delay time, skip amount, integration constant, and air-fuel ratio feedback correction coefficient that is transited by the integration delay time. As a result, the air-fuel ratio feedback is achieved even if the exhaust gas from the exhaust port of the internal combustion engine differs in the time until the exhaust gas reaches the oxygen concentration detecting means in the cylinders having different exhaust passage distances in the internal combustion engine composed of V-type multiple cylinders. Since the air-fuel ratio feedback correction coefficient in the control can be changed as desired, the fluctuation range of the air-fuel ratio between the rich side and the lean side can be suppressed for each cylinder, and variations among the cylinders can be eliminated. As a result, combustion for each cylinder of the internal combustion engine is stabilized and drivability is improved.

  In the integral constant setting means in the air-fuel ratio control apparatus for an internal combustion engine according to claim 2, the integral constant of the cylinder having a long exhaust passage distance is set to be smaller than that of a cylinder having a short exhaust passage distance. The fluctuation range of the coefficient toward the rich side and the lean side can be set to be equal regardless of the distance of the exhaust passage. As a result, the fluctuation range of the air-fuel ratio toward the rich side and the lean side is suppressed.

  In the integral delay time setting means in the air-fuel ratio control device for an internal combustion engine according to claim 3, the integral delay time of the cylinder having the long exhaust passage distance is set longer than that of the cylinder having the short exhaust passage distance, so that the air-fuel ratio is set. The fluctuation range of the feedback correction coefficient to the rich side and the lean side can be set equally regardless of the distance of the exhaust passage, and as a result, the fluctuation range of the air-fuel ratio to the rich side and the lean side is suppressed.

  The air-fuel ratio control apparatus for an internal combustion engine according to claim 4 is provided in the exhaust gas among the catalysts that are disposed at different positions from the exhaust port in the exhaust passage and purify exhaust gas discharged from the internal combustion engine for each cylinder. The catalyst capacity of the catalyst corresponding to the amount of exhaust gas in the exhaust passage having a different length for each cylinder is set by setting the catalyst capacity of the longer passage distance to be larger than that of the shorter exhaust passage distance. Is optimized to reduce emissions.

  In the air-fuel ratio control apparatus for an internal combustion engine according to claim 5, among the catalysts for purifying exhaust gas discharged from the internal combustion engine for each cylinder, the number of cells with the longer exhaust passage distance is shorter and the exhaust passage distance is shorter. By setting a larger number, the respective catalyst capacities of the catalysts corresponding to the exhaust gas amounts in the exhaust passages having different lengths for each cylinder are optimized, and the emission is reduced.

  In the air-fuel ratio control apparatus for an internal combustion engine according to claim 6, among the catalysts for purifying exhaust gas discharged from the internal combustion engine for each cylinder, only the longer exhaust passage distance is divided into two parts, so that each cylinder is divided. The respective catalyst capacities of the catalysts corresponding to the exhaust gas amounts in the exhaust passages having different lengths are optimized to reduce the emission.

  In the air-fuel ratio control apparatus for an internal combustion engine according to claim 7, among the catalysts for purifying the exhaust gas discharged from the internal combustion engine for each cylinder, only the longer exhaust passage distance is divided into two, and the oxygen concentration detection means By disposing one on the upstream side, the respective catalyst capacities of the catalysts corresponding to the exhaust gas amounts in the exhaust passages having different lengths for each cylinder are optimized, and the emission is reduced. The catalyst in the long exhaust passage helps to be difficult to be activated due to the influence of the wind received during traveling.

  In the air-fuel ratio control apparatus for an internal combustion engine according to claim 8, the catalyst for purifying the exhaust gas discharged from the internal combustion engine for each cylinder is divided into two regardless of the distance of the exhaust passage, and upstream of the oxygen concentration detection means. By arranging each one on the side, the respective catalyst capacities of the catalysts corresponding to the exhaust gas amounts in the exhaust passages having different lengths for each cylinder are optimized, and the emission is reduced. In the long exhaust passage, it is difficult to be activated due to the influence of the wind during driving, and the catalyst in the exhaust passage with a short distance and the catalyst in the exhaust passage with a long distance are each divided into two parts, and the layout design The degree of freedom in is increased.

  In the air-fuel ratio control apparatus for an internal combustion engine according to claim 9, combustion is performed for each cylinder by mounting an internal combustion engine composed of a plurality of V-type cylinders connected to exhaust passages having different lengths independently for each cylinder. As a result, the vehicle shock is reduced, drivability is improved, and the catalyst capacity of the catalyst for each cylinder is optimized, so that emission can be reduced well.

  Hereinafter, the best mode for carrying out the present invention will be described based on examples.

  FIG. 1 is a schematic diagram showing a cylinder with a short exhaust passage distance and its peripheral devices in an internal combustion engine composed of a V-type four-cycle two-cylinder in a motorcycle to which an air-fuel ratio control apparatus for an internal combustion engine according to an embodiment of the present invention is applied. It is a block diagram.

  In FIG. 1, an internal combustion engine 1 is configured as a V-type 4-cycle 2-cylinder spark ignition type, and its intake air passes through an air cleaner 2, an intake passage 3, and a throttle valve 4 from the upstream side in the intake passage 3. It is mixed with fuel injected from a fuel injection valve 5 and distributed and supplied from the intake port 6 into each cylinder as an air-fuel mixture having a predetermined air-fuel ratio. The cylinder head of the internal combustion engine 1 is provided with an ignition plug 7 for each cylinder, and a high voltage is applied from the ignition coil / igniter 8 to the ignition plug 7 of each cylinder at each ignition timing. Is ignited. The exhaust gas burned in each cylinder of the internal combustion engine 1 passes through the three-way catalyst 13 disposed on the downstream side of the exhaust passage 12 from the exhaust port 11 and is discharged into the atmosphere.

  An intake air temperature sensor 21 is disposed in the air cleaner 2, and the intake air temperature THA [° C.] flowing into the air cleaner 2 is detected by the intake air temperature sensor 21. An intake pressure sensor 22 is disposed in the intake passage 3, and the intake pressure sensor 22 detects an intake pressure PM [kPa: kilopascals] on the downstream side of the throttle valve 4. The throttle valve 4 is provided with a throttle opening sensor 23, which detects the throttle opening TA [°] of the throttle valve 4. A water temperature sensor 24 is disposed in the cylinder block of the internal combustion engine 1, and the coolant temperature THW [° C.] in the internal combustion engine 1 is detected by the water temperature sensor 24. The crankshaft (not shown) of the internal combustion engine 1 is provided with a crank angle sensor 25, which is based on a crank angle signal composed of the number of pulses generated per unit time as the crankshaft rotates by the crank angle sensor 25. The engine speed NE [rpm] is detected. Further, a cam angle sensor 26 is disposed on the cam shaft (not shown) of the internal combustion engine 1, and the cam angle sensor 26 detects a cam shaft rotation angle θ 2 [° CA (Crank Angle)].

  Further, an oxygen sensor 27 is disposed on the upstream side of the three-way catalyst 13 in the exhaust passage 12, and the output voltage VOX [V corresponding to the oxygen concentration on the upstream side of the three-way catalyst 13 in the exhaust passage 12 by the oxygen sensor 27. : Bolt] is detected. An air-fuel ratio (A / F) sensor may be provided in place of the oxygen sensor 27 to detect the air-fuel ratio in the exhaust gas discharged from the internal combustion engine 1 linearly. In addition, a power supply voltage sensor 29 is provided in the in-vehicle battery (not shown), and the power supply voltage sensor 29 detects the power supply voltage VB [V].

  In the present embodiment, among the internal combustion engine 1 composed of V-type four-cycle two-cylinder engine that corresponds to a cylinder having a long exhaust passage distance, an exhaust passage 12 ', a three-way catalyst 13', oxygen, and the like are used as necessary. The sensor 27 'and its output voltage VOX1 [V] are distinguished.

  On the other hand, the fuel pumped up from the fuel tank 31 by the fuel pump 32 is pumped in the order of the fuel pipe 33, the fuel filter 34, the fuel pipe 35, and the delivery pipe 36, and is distributed and supplied to the injectors 5 of each cylinder. Excess fuel in the delivery pipe 36 is returned into the fuel tank 31 through a path of a pressure regulator 37 and a return pipe 38. The pressure regulator 37 adjusts the fuel pressure in the delivery pipe 36 so that the differential pressure between the fuel pressure (fuel pressure) in the delivery pipe 36 and the intake pressure becomes constant.

  Further, the air cleaner 2 and the exhaust passage 12 immediately after the exhaust port 11 of the internal combustion engine 1 are connected by a secondary air passage 41, and the air from the air cleaner 2 is taken as secondary air in the middle of the secondary air passage 41. A secondary air control valve 42 is provided for introduction into the passage 12 as appropriate.

  An ECU (Electronic Control Unit) 50 that controls the operating state of the internal combustion engine 1 includes a CPU 51 as a central processing unit that executes various known arithmetic processes, a ROM 52 that stores a control program and a control map, and various data. The RAM 53, the B / U (backup) RAM 54, etc. are stored as the logic operation circuit, and the final fuel injection described later is input to the input port 55 for inputting the detection signals from the various sensors and the injector 5 as the various actuators. Time (corresponding to final fuel injection amount) TAU, control signal Ig to ignition coil / igniter 8, control signal Ip to fuel pump 32, and control signal Ia to secondary air control valve 42. Connected through.

  Next, a description will be given based on the flowchart of FIG. 2 showing the processing procedure of the fuel injection time (fuel injection amount) calculation in the CPU 51 in the ECU 50 used in the air-fuel ratio control apparatus of the internal combustion engine according to one embodiment of the present invention. To do. The fuel injection time calculation routine is repeatedly executed by the CPU 51 immediately before the fuel injection timing to each cylinder. Each map used in this embodiment is stored in the ROM 52 in advance.

  In FIG. 2, first, the engine speed NE based on the crank angle signal detected by the crank angle sensor 25 in step S101 is read. Next, the routine proceeds to step S102, where the throttle opening degree TA detected by the throttle opening degree sensor 23 is read. Next, the process proceeds to step S103, and the intake pressure PM detected by the intake pressure sensor 22 is read. Next, the routine proceeds to step S104, where it is determined whether the cylinder has a short distance in the exhaust passage 12.

  If the determination condition in step S104 is satisfied, that is, the rear cylinder has a short distance of the exhaust passage 12 of the internal combustion engine 1 and the distance from the exhaust port 11 to the oxygen sensor 27 is short, the process proceeds to step S105 and is read in step S101. A map for a cylinder with a short distance of the exhaust passage 12 using the engine speed NE [rpm], the throttle opening TA [°] read in step S102, and the intake pressure PM [kPa] read in step S103 as parameters. A basic fuel injection time TP is calculated based on (not shown). Next, the process proceeds to step S106, where the invalid fuel injection time TV is calculated corresponding to the power supply voltage VB to the injector 5 detected by the power supply voltage sensor 29. In step S107, the distance of the exhaust passage 12 using the intake air temperature THA [° C.] detected by the intake air temperature sensor 21 and the cooling water temperature THW [° C.] detected by the water temperature sensor 24 as parameters is determined. Various correction coefficients K are calculated based on a map (not shown) for a short cylinder.

  Next, the process proceeds to step S108, and an air-fuel ratio feedback correction coefficient FAF calculation process for a cylinder having a short distance of the exhaust passage 12 described later is executed. Next, the process proceeds to step S109, the basic fuel injection time TP calculated in step S105, the invalid fuel injection time TV calculated in step S106, various correction coefficients K calculated in step S107, and calculated in step S108. Based on the air-fuel ratio feedback correction coefficient FAF, the final fuel injection time TAU for the cylinder having a short distance in the exhaust passage 12 is calculated by the following equation (1), and this routine is finished.

(Equation 1)
TAU ← TP * K * FAF + TV (1)

  On the other hand, if the determination condition of step S104 is not satisfied, that is, the front cylinder has a long distance of the exhaust passage 12 'of the internal combustion engine 1, and the distance from the exhaust port 11' to the oxygen sensor 27 'is long, the process proceeds to step S110. Then, the exhaust passage 12 'using the engine speed NE [rpm] read in step S101, the throttle opening TA [°] read in step S102, and the intake pressure PM [kPa] read in step S103 as parameters. The basic fuel injection time TP1 is calculated based on a map (not shown) for cylinders with a long distance. Next, the process proceeds to step S111, where the invalid fuel injection time TV is calculated corresponding to the power supply voltage VB to the injector 5 detected by the power supply voltage sensor 29. Next, the process proceeds to step S112, and the distance of the exhaust passage 12 'using the intake air temperature THA [° C] detected by the intake air temperature sensor 21 and the cooling water temperature THW [° C] detected by the water temperature sensor 24 as parameters. Various correction coefficients K1 are calculated based on a map (not shown) for a long cylinder.

  Next, the process proceeds to step S113, and an air-fuel ratio feedback correction coefficient FAF1 calculation process is executed in a cylinder having a long distance of the exhaust passage 12 'described later. Next, the process proceeds to step S114, the basic fuel injection time TP1 calculated in step S110, the invalid fuel injection time TV calculated in step S111, various correction factors K1 calculated in step S112, and calculated in step S113. Based on the air-fuel ratio feedback correction coefficient FAF1, the final fuel injection time TAU1 in the cylinder having the long exhaust passage 12 'is calculated by the following equation (2), and this routine is finished.

(Equation 2)
TAU1 ← TP1 * K1 * FAF1 + TV (2)

  Next, based on the flowchart of FIG. 3 showing the processing procedure of the air-fuel ratio feedback correction coefficient FAF for the cylinder having the short distance of the exhaust passage 12 in step S108 of FIG. The description will be given with reference.

  Here, FIG. 4 shows delay times TDR, TDL corresponding to the throttle opening TA [°] from fully closed to fully open as a load with the engine rotational speed NE [rpm] in the cylinder having a short distance of the exhaust passage 12 as a parameter. It is a map for calculating integration delay times KDR and KDL, integration constants KII and KID, and skip amounts KSI and KSD. Of these, the delay times TDR and TDL may be calculated only by the engine speed NE [rpm], regardless of the engine speed NE [rpm] and the throttle opening degree TA [°]. FIG. 5 is a time showing the relationship between the output voltage VOX of the oxygen sensor 27 disposed in the cylinder having a short distance of the exhaust passage 12 and the air-fuel ratio feedback correction coefficient FAF corresponding to the processing of FIG. 2 and FIG. It is a chart. This air-fuel ratio feedback correction coefficient FAF calculation routine is repeatedly executed by the CPU 51 at predetermined time intervals.

  In FIG. 3, first, in step S201, it is determined whether an execution condition for air-fuel ratio feedback control is satisfied. Here, the execution conditions of the air-fuel ratio feedback control include, for example, that the cooling water temperature THW of the internal combustion engine 1 is equal to or higher than a predetermined temperature, a predetermined time has elapsed after the start, the fuel is not being cut, and the like. In addition, air-fuel ratio feedback control by the oxygen sensor 27 is performed.

  When the determination condition of step S201 is satisfied, that is, when all the above-described execution conditions are satisfied, the process proceeds to step S202, and the engine speed NE based on the crank angle signal detected by the crank angle sensor 25 is read. Next, the process proceeds to step S203, and the throttle opening degree TA detected by the throttle opening degree sensor 23 is read. Next, the process proceeds to step S204, and in order to calculate the air-fuel ratio feedback correction coefficient FAF, the map shown in FIGS. 4A and 4B is used as a parameter with the engine speed read in step S202 as a parameter. The delay time TDR at the time of rich inversion and the delay time TDL at the time of lean inversion corresponding to the throttle opening degree TA [°] read in (1) are calculated.

  Next, in step S205, in order to calculate the air-fuel ratio feedback correction coefficient FAF, FIGS. 4 (c), 4 (d), 4 (e), 4 (f), 4 (g), Based on the map shown in FIG. 4 (h), the integral delay time KDR at the time of rich inversion corresponding to the throttle opening degree TA [°] read in step S203 using the engine speed NE [rpm] read in step S202 as a parameter. , Integration constant KII, skip amount KSI, integral delay time KDL during lean inversion, integration constant KID, and skip amount KSD are calculated.

  Next, the process proceeds to step S206, where it is determined whether the output voltage VOX of the oxygen sensor 27 is equal to or higher than the determination voltage α. The determination voltage α is set to be in the vicinity of 0.45 [V] corresponding to the theoretical air-fuel ratio. When the determination condition of step S206 is satisfied, that is, when the output voltage VOX of the oxygen sensor 27 is higher than the determination voltage α and on the rich side from the theoretical air-fuel ratio (time t0 to time t3 shown in FIG. 5), the process proceeds to step S207. After the inversion from the lean side to the rich side, it is determined whether the delay time (time from time t0 to time t1 shown in FIG. 5) TDR calculated in step S204 has elapsed. When the determination condition in step S207 is not satisfied, that is, after the reverse from the lean side to the rich side, the delay time TDR has not elapsed, the process proceeds to step S208, and the air-fuel ratio feedback correction coefficient FAF is calculated by the integration calculated in step S205. The amount is increased by the constant KII, and this routine is terminated.

  On the other hand, when the determination condition in step S207 is satisfied, that is, when the delay time TDR has elapsed after reversal from the lean side to the rich side (time t1 shown in FIG. 5), the process proceeds to step S209, and is the first time? Is determined. When the determination condition of step S209 is satisfied, that is, the first time (time t1 shown in FIG. 5), the process proceeds to step S210, and the air-fuel ratio feedback correction coefficient FAF is decreased by the skip amount KSD calculated in step S205, This routine ends.

  When the determination condition in step S209 is not satisfied, that is, when it is not the first time (time t1 to time t4 shown in FIG. 5), the process proceeds to step S211 and the integral delay time calculated in step S205 (shown in FIG. 5). It is determined whether the time KDR has elapsed (time from time t1 to time t2). When the determination condition of step S211 is satisfied, that is, when the integration delay time KDR has elapsed (time t2 shown in FIG. 5), the process proceeds to step S212, and the air-fuel ratio feedback correction coefficient FAF is calculated by the integration calculated in step S205. The amount is reduced by a constant KID, and this routine is terminated. Note that if the determination condition of step S211 is not satisfied, that is, if the integration delay time KDR has not elapsed, step S212 is skipped, and this routine ends.

  On the other hand, when the determination condition of step S206 is not satisfied, that is, when the output voltage VOX of the oxygen sensor 27 is less than the determination voltage α and is leaner than the stoichiometric air-fuel ratio (time t3 to time t6 shown in FIG. 5), step The process proceeds to S213, and after the inversion from the rich side to the lean side, it is determined whether the delay time (time from time t3 to time t4 shown in FIG. 5) TDL calculated in step S204 has elapsed. . When the determination condition of step S213 is not satisfied, that is, when the delay time TDL has not elapsed after the inversion from the rich side to the lean side, the process proceeds to step S212, and the air-fuel ratio feedback correction coefficient FAF is calculated by the integration calculated in step S205. The amount is reduced by a constant KID, and this routine is terminated.

  On the other hand, when the determination condition in step S213 is satisfied, that is, when the delay time TDL has elapsed after reversing from the rich side to the lean side (time t4 shown in FIG. 5), the process proceeds to step S214, and is it the first time? Is determined. When the determination condition in step S214 is satisfied, that is, the first time (time t4 shown in FIG. 5), the process proceeds to step S215, and the air-fuel ratio feedback correction coefficient FAF is increased by the skip amount KSI calculated in step S205, This routine ends.

  On the other hand, when the determination condition of step S214 is not satisfied, that is, when it is not the first time (time t4 to time t7 shown in FIG. 5), the process proceeds to step S216, and the integral delay time calculated in step S205 (shown in FIG. 5). It is determined whether the time KDL has elapsed (from time t4 to time t5). When the determination condition in step S216 is satisfied, that is, when the integration delay time KDL has elapsed (time t5 shown in FIG. 5), the process proceeds to step S208, and the air-fuel ratio feedback correction coefficient FAF is calculated by the integration calculated in step S205. The amount is increased by the constant KII, and this routine is terminated. If the determination condition in step S216 is not satisfied, that is, if the integration delay time KDL has not elapsed, step S208 is skipped, and this routine is terminated.

  On the other hand, when the determination condition of step S201 is not satisfied, that is, when one of the above-described conditions for air-fuel ratio feedback control is not satisfied, the process proceeds to step S217, and the air-fuel ratio feedback correction coefficient FAF is set to “1.0”. This is the end of this routine.

  Next, based on the flowchart of FIG. 6 showing the processing procedure of the air-fuel ratio feedback correction coefficient FAF1 for the cylinder with the long distance of the exhaust passage 12 'in step S113 of FIG. Will be described with reference to FIG.

  Here, FIG. 7 shows delay times TDR1, TDL1 corresponding to the throttle opening degree TA [°] from fully closed to fully open as a load with the engine speed NE [rpm] in the cylinder having a long exhaust passage 12 'as a parameter. , Integration delay times KDR1, KDL1, integration constants KII1, KID1, and skip amounts KSI1, KSD1 are calculated.

  Among these, the integral constants KII1 and KID1 are set smaller than the integral constants KII and KID in FIG. 4, and the integral delay times KDR1 and KDL1 are set longer than the integral delay times KDR and KDL in FIG. The skip amounts KSI1, KSD1 may be set equal to the skip amounts KSI, KSD in FIG. The delay times TDR1 and TDL1 may be calculated only by the engine speed NE [rpm], regardless of the engine speed NE [rpm] and the throttle opening degree TA [°].

  FIG. 8 shows an output voltage VOX1 [V] of an oxygen sensor 27 'disposed in a cylinder having a long distance of the exhaust passage 12' corresponding to the processing of FIGS. 2 and 6, and an air-fuel ratio feedback correction coefficient FAF1. It is a time chart which shows the relationship. The air / fuel ratio feedback correction coefficient FAF1 calculation routine is repeatedly executed by the CPU 51 at predetermined time intervals.

  In FIG. 6, first, in step S301, it is determined whether an execution condition for air-fuel ratio feedback control is satisfied. Here, the execution conditions of the air-fuel ratio feedback control include, for example, that the cooling water temperature THW of the internal combustion engine 1 is equal to or higher than a predetermined temperature, a predetermined time has elapsed after the start, the fuel is not being cut, and the like. In addition, air-fuel ratio feedback control is performed by the oxygen sensor 27 '.

  When the determination condition of step S301 is satisfied, that is, when all the above-described execution conditions are satisfied, the process proceeds to step S302, and the engine speed NE based on the crank angle signal detected by the crank angle sensor 25 is read. Next, the process proceeds to step S303, where the throttle opening degree TA detected by the throttle opening degree sensor 23 is read. Next, in step S304, in order to calculate the air-fuel ratio feedback correction coefficient FAF1, the map shown in FIG. 7A and FIG. 7B is used as a parameter with the engine speed read in step S302 as a parameter. The delay time TDR1 at the time of rich inversion and the delay time TDL1 at the time of lean inversion corresponding to the throttle opening degree TA [°] read in step S1 are calculated.

  Next, in step S305, in order to calculate the air-fuel ratio feedback correction coefficient FAF1, FIG. 7 (c), FIG. 7 (d), FIG. 7 (e), FIG. 7 (f), FIG. Based on the map shown in FIG. 7 (h), the integral delay time KDR1 at the time of rich inversion corresponding to the throttle opening degree TA [°] read in step S303 using the engine speed NE [rpm] read in step S302 as a parameter. , Integral constant KII1, skip amount KSI1, integral delay time KDL1 during lean inversion, integral constant KID1, and skip amount KSD1 are calculated.

  Next, the process proceeds to step S306, where it is determined whether the output voltage VOX1 of the oxygen sensor 27 ′ is equal to or higher than the determination voltage α. The determination voltage α is set to be in the vicinity of 0.45 [V] corresponding to the theoretical air-fuel ratio. When the determination condition of step S306 is satisfied, that is, when the output voltage VOX1 of the oxygen sensor 27 'is higher than the determination voltage α and on the rich side from the theoretical air-fuel ratio (time t00 to time t03 shown in FIG. 8), the process proceeds to step S307. Then, after inversion from the lean side to the rich side, it is determined whether the delay time (time from time t00 to time t01 shown in FIG. 8) TDR1 calculated in step S304 has elapsed. When the determination condition in step S307 is not satisfied, that is, after the reverse from the lean side to the rich side, the delay time TDR1 has not elapsed, the process proceeds to step S308, and the air-fuel ratio feedback correction coefficient FAF1 is calculated by the integration calculated in step S305. The amount is increased by the constant KII1, and this routine is terminated.

  On the other hand, when the determination condition in step S307 is satisfied, that is, when the delay time TDR1 has elapsed after the reversal from the lean side to the rich side (time t01 shown in FIG. 8), the process proceeds to step S309. Is determined. When the determination condition of step S309 is satisfied, that is, when it is the first time (time t01 shown in FIG. 8), the process proceeds to step S310, and the air-fuel ratio feedback correction coefficient FAF1 is decreased by the skip amount KSD1 calculated in step S305, This routine ends.

  Then, when the determination condition of step S309 is not satisfied, that is, when it is not the first time (time t01 to time t04 shown in FIG. 8), the process proceeds to step S311 and the integral delay time calculated in step S305 (shown in FIG. 8). It is determined whether (time from time t01 to time t02) KDR1 has elapsed. When the determination condition in step S311 is satisfied, that is, when the integration delay time KDR1 has elapsed (time t02 shown in FIG. 8), the process proceeds to step S312 and the air-fuel ratio feedback correction coefficient FAF1 is calculated by the integration calculated in step S305. The amount is reduced by the constant KID1, and this routine is terminated. If the determination condition in step S311 is not satisfied, that is, if the integration delay time KDR1 has not elapsed, step S312 is skipped, and this routine is terminated.

  On the other hand, when the determination condition in step S306 is not satisfied, that is, when the output voltage VOX1 of the oxygen sensor 27 'is less than the determination voltage α and on the lean side from the theoretical air-fuel ratio (time t03 to time t06 shown in FIG. 8). The process proceeds to step S313, and after inversion from the rich side to the lean side, it is determined whether the delay time (time from time t03 to time t04 shown in FIG. 8) TDL1 calculated in step S304 has elapsed. The If the determination condition in step S313 is not satisfied, that is, after the reverse from the rich side to the lean side, the delay time TDL1 has not elapsed, the process proceeds to step S312 and the air-fuel ratio feedback correction coefficient FAF1 is calculated by the integration calculated in step S305. The amount is reduced by the constant KID1, and this routine is terminated.

  On the other hand, when the determination condition in step S313 is satisfied, that is, when the delay time TDL1 has elapsed after reversal from the rich side to the lean side (time t04 shown in FIG. 8), the process proceeds to step S314, and is the first time? Is determined. When the determination condition in step S314 is satisfied, that is, the first time (time t04 shown in FIG. 8), the process proceeds to step S315, and the air-fuel ratio feedback correction coefficient FAF1 is increased by the skip amount KSI1 calculated in step S305. This routine ends.

  On the other hand, when the determination condition of step S314 is not satisfied, that is, when it is not the first time (time t04 to time t07 shown in FIG. 8), the process proceeds to step S316 and the integral delay time calculated in step S305 (shown in FIG. 8). (Time from time t04 to time t05) It is determined whether or not KDL1 has elapsed. When the determination condition in step S316 is satisfied, that is, when the integration delay time KDL1 has elapsed (time t05 shown in FIG. 8), the process proceeds to step S308, and the air-fuel ratio feedback correction coefficient FAF1 is calculated by the integration calculated in step S305. The amount is increased by the constant KII1, and this routine is terminated. If the determination condition in step S316 is not satisfied, that is, if the integration delay time KDL1 has not elapsed, step S308 is skipped, and this routine ends.

  On the other hand, if the determination condition in step S301 is not satisfied, that is, if any one of the above-described conditions for air-fuel ratio feedback control is not satisfied, the process proceeds to step S317, and the air-fuel ratio feedback correction coefficient FAF1 is set to “1.0”. This is the end of this routine.

  As described above, the air-fuel ratio control apparatus for an internal combustion engine according to this embodiment includes exhaust passages 12, 12 'having different lengths that are independently connected to each cylinder of the internal combustion engine 1 composed of a V-type four-cycle two-cylinder. As oxygen concentration detecting means for detecting the oxygen concentration of the exhaust gas exhausted from the internal combustion engine 1 for each cylinder, which is disposed in the exhaust passages 12, 12 'at different positions from the exhaust ports 11, 11'. Oxygen sensors 27 and 27 'and physical quantity detection means for detecting engine rotational speed NE, throttle opening degree TA, and intake pressure PM as physical quantities that change with the traveling state of the motorcycle and the operating state of the internal combustion engine 1 for each cylinder. Output voltage VOX, VOX1 as the detected values according to the oxygen concentration by the crank angle sensor 25, the throttle opening sensor 23, the intake pressure sensor 22, and the oxygen sensors 27, 27 'on the rich side An inversion direction discriminating means that is achieved by the ECU 50 that discriminates the inversion direction for each cylinder when the inversion is made through a judgment voltage α as a judgment value between the lean side and the inversion discriminated by the inversion direction discrimination means. On the opposite side to the direction, delay times TDR, TDL, TDR1, TDL1 for delaying the timing for skipping the air-fuel ratio feedback correction coefficients FAF, FAF1 in the air-fuel ratio feedback control are set to the engine speed NE and the throttle opening TA. Based on the delay time setting means achieved by the ECU 50 that is set for each cylinder, and the skip amounts KSI, KSD, KSI1, KSD1 for skipping the air-fuel ratio feedback correction coefficients FAF, FAF1, engine speed NE and throttle opening Achieved by ECU 50 that is set for each cylinder based on TA ECU 50 that sets the skip amount setting means and the integration constants KII, KID, KII1, KID1 for gradually changing the air-fuel ratio feedback correction coefficients FAF, FAF1 for each cylinder based on the engine speed NE and the throttle opening TA. And integral delay times KDR, KDL, KDR1, and KDL1 for delaying the timing for setting the integral constants KII, KID, KII1, and KID1 based on the engine speed NE and the throttle opening TA. Integration delay time setting means achieved by ECU 50 set for each cylinder, delay times TDR, TDL, TDR1, TDL1, skip amounts KSI, KSD, KSI1, KSD1, integration constants KII, KID, KII1, KID1, integration delay Time KDR, KDL, KDR1, Fuel injection amount control means achieved by ECU 50 for controlling final fuel injection time (fuel injection amount) TAU, TAU1 supplied to each cylinder in accordance with air-fuel ratio feedback correction coefficients FAF, FAF1 that are transitioned by DL1 To do. The air-fuel ratio control apparatus for an internal combustion engine according to the present embodiment is such that the internal combustion engine 1 is mounted on a two-wheeled vehicle.

  That is, the air-fuel ratio feedback control is performed for each cylinder in the internal combustion engine 1 composed of a V-type four-cycle two-cylinder engine and having different distances between the exhaust passages 12 and 12 'independently connected to the exhaust ports 11 and 11'. The air-fuel ratio feedback correction coefficients FAF and FAF1 at can be changed as desired according to the output voltages VOX and VOX1, the engine speed NE, the throttle opening degree TA, and the intake pressure PM of the oxygen sensors 27 and 27 '. For this reason, even if the exhaust gas from the exhaust ports 11 and 11 ′ of the internal combustion engine 1 reaches the oxygen sensors 27 and 27 ′ in different cylinders with different distances between the exhaust passages 12 and 12 ′, the empty passages are different. The fluctuation range of the fuel ratio to the rich side and the lean side can be suppressed. As a result, combustion for each cylinder of the internal combustion engine 1 is stabilized, and in particular, when mounted on a two-wheeled vehicle having a light vehicle weight, vehicle shock can be reduced and drivability can be improved.

  Further, the integral constant setting means achieved in the ECU 50 of the air-fuel ratio control apparatus for the internal combustion engine of the present embodiment is the integral constants KII1 and KID1 of the cylinder having a long distance of the exhaust passage 12 'and the distance of the exhaust passage 12 is short. It is set smaller than the cylinder. As a result, the fluctuation range of the air-fuel ratio feedback correction coefficients FAF, FAF1 to the rich side and the lean side can be set equally regardless of the distance of the exhaust passage. As a result, the air-fuel ratio to the rich side and the lean side of the air-fuel ratio can be set. The fluctuation range can be suppressed.

  The integral delay time setting means achieved by the ECU 50 of the air-fuel ratio control apparatus for the internal combustion engine of the present embodiment uses the integral delay times KDR1 and KDL1 of the cylinder having a long distance of the exhaust passage 12 'as the distance of the exhaust passage 12. Is set longer than a short cylinder. As a result, the fluctuation range of the air-fuel ratio feedback correction coefficients FAF, FAF1 to the rich side and the lean side can be set equally regardless of the distance of the exhaust passage. As a result, the air-fuel ratio to the rich side and the lean side of the air-fuel ratio can be set. The fluctuation range can be suppressed.

  Next, the catalyst capacity of the three-way catalyst 13, 13 'disposed in the exhaust passages 12, 12' of different lengths connected independently for each cylinder of the internal combustion engine 1 comprising a V-type four-cycle two-cylinder. The optimization will be described with reference to FIG. Here, FIG. 9 is a schematic diagram showing the configuration of the main part of a two-wheeled vehicle equipped with an internal combustion engine 1 composed of a V-type four-cycle two-cylinder. 14, 14 'in the figure are mufflers and two-dot chain lines indicate front and rear wheels. Indicates the tire outer diameter. Note that the intake system and the fuel supply system mounted on the upper portion of the internal combustion engine 1 in FIG. 9 have been described in FIG.

  As described above, the final fuel is determined according to the air-fuel ratio feedback correction coefficients FAF and FAF1 of the exhaust passages 12 and 12 'having different lengths connected independently for each cylinder of the internal combustion engine 1 composed of the V-type four-cycle two-cylinder. The injection times TAU and TAU1 are calculated, and the drivability in the motorcycle is improved by optimizing the air-fuel ratio of the air-fuel mixture for each cylinder based on these final fuel injection times TAU and TAU1.

  As shown in FIG. 8, the air-fuel ratio feedback correction coefficient FAF ′ in the exhaust passage 12 ′ having a long distance has a period longer than the air-fuel ratio feedback correction coefficient FAF in the exhaust passage 12 having a short distance, as shown in FIG. become longer. In order to cope with this, it is understood that the allowable amount for exhaust gas purification should be changed between the three-way catalyst 13 'of the exhaust passage 12' having a long distance and the three-way catalyst 13 of the exhaust passage 12 having a short distance. .

  Therefore, as shown in FIG. 9, the catalyst capacity of the three-way catalyst 13 'disposed in the exhaust passage 12' having a long distance is larger than the catalyst capacity of the three-way catalyst 13 disposed in the exhaust passage 12 having a short distance. Also set larger. Thereby, the catalyst capacity for each cylinder is optimized, and the emission can be improved. It is also effective to change the catalyst density and catalyst components supported on the three-way catalysts 13, 13 '.

  As described above, the air-fuel ratio control apparatus for the internal combustion engine of this embodiment is disposed in the exhaust passages 12 and 12 ′ at positions where the distances from the exhaust ports 11 and 11 ′ are different, and is discharged from the internal combustion engine 1. Three-way catalysts 13, 13 'for purifying the exhaust gas for each cylinder are provided, and the three-way catalysts 13, 13' have a capacity of the catalyst having a longer distance of the exhaust passage 12 'than that of a shorter distance of the exhaust passage 12. Is also set larger. As a result, the respective catalyst capacities of the three-way catalysts 13 and 13 'corresponding to the exhaust gas amounts in the exhaust passages 12 and 12' having different lengths for each cylinder can be optimized, and emission can be reduced.

  FIG. 10 shows the three-way catalyst 13 disposed in the exhaust passages 12 and 12 'having different lengths connected independently for each cylinder of the internal combustion engine 1 composed of the V-type four-cycle two cylinders in FIG. , 13 ′ are explanatory diagrams showing a modification of the number of cells and the arrangement. In FIG. 10, the same components as those in FIG. 9 or equivalent parts are denoted by the same reference numerals and symbols, and detailed description thereof is omitted.

  As described above, the final fuel is determined according to the air-fuel ratio feedback correction coefficients FAF and FAF1 of the exhaust passages 12 and 12 'having different lengths connected independently for each cylinder of the internal combustion engine 1 composed of the V-type four-cycle two-cylinder. The injection times TAU and TAU1 are calculated, and the drivability in the motorcycle is improved by optimizing the air-fuel ratio of the air-fuel mixture for each cylinder based on these final fuel injection times TAU and TAU1.

  As shown in FIG. 8, the air-fuel ratio feedback correction coefficient FAF ′ in the exhaust passage 12 ′ having a long distance has a period longer than the air-fuel ratio feedback correction coefficient FAF in the exhaust passage 12 having a short distance, as shown in FIG. become longer. In order to cope with this, it is understood that the allowable amount for exhaust gas purification should be changed between the three-way catalyst 13 'of the exhaust passage 12' having a long distance and the three-way catalyst 13 of the exhaust passage 12 having a short distance. .

  Therefore, as shown in FIG. 10, the number of cells arranged in the long exhaust passage 12 'is two three-way catalysts 13a' and 13b ', and the three-way catalyst arranged in the short exhaust passage 12 is used. More than 13. Further, the three-way catalyst 13a ', 13b' disposed in the exhaust passage 12 'having a long distance is divided into two, and the total catalyst capacity of the three-way catalyst 13a', 13b 'is arranged in the exhaust passage 12 having a short distance. It is set larger than the catalyst capacity of the three-way catalyst 13 provided. Further, the three-way catalyst 13a 'is disposed upstream of the oxygen sensor 27' disposed in the exhaust passage 12 'having a long distance. Thereby, the catalyst capacity for each cylinder is optimized, and the emission can be improved. It is also effective to change the catalyst density and catalyst components supported on the three-way catalysts 13, 13 ', 13b'.

  Thus, in the air-fuel ratio control apparatus for the internal combustion engine of the present embodiment, the three-way catalysts 13, 13a ', 13b' have two cells with the longer distance of the exhaust passage 12 ', and the exhaust passage 12 More than the shorter distance. Further, the three-way catalyst 13, 13a ', 13b' divides only the one having a longer distance of the exhaust passage 12 'into two parts, and one three-way catalyst 13a' is disposed upstream of the oxygen sensor 27 '. is there. As a result, the respective catalyst capacities of the three-way catalysts 13, 13a ', 13b' corresponding to the exhaust gas amounts in the exhaust passages 12, 12 'having different lengths for each cylinder are optimized, thereby reducing emissions. In addition, the exhaust passage 12 'having a long distance can help to be hardly activated due to the influence of the wind received during traveling.

  FIG. 11 shows three elements arranged in the exhaust passages 12, 12 ′ having different lengths connected independently for each cylinder of the internal combustion engine 1 composed of the V-type four-cycle two cylinders in FIG. It is explanatory drawing which shows the other modification of the cell number and arrangement | positioning of the catalyst 13,13 '. In FIG. 11, the same components as those in FIGS. 9 and 10 or equivalent parts are denoted by the same reference numerals and symbols, and detailed description thereof is omitted.

  As described above, the final fuel is determined according to the air-fuel ratio feedback correction coefficients FAF and FAF1 of the exhaust passages 12 and 12 'having different lengths connected independently for each cylinder of the internal combustion engine 1 composed of the V-type four-cycle two-cylinder. The injection times TAU and TAU1 are calculated, and the drivability in the motorcycle is improved by optimizing the air-fuel ratio of the air-fuel mixture for each cylinder based on these final fuel injection times TAU and TAU1.

  As shown in FIG. 8, the air-fuel ratio feedback correction coefficient FAF ′ in the exhaust passage 12 ′ having a long distance has a period longer than the air-fuel ratio feedback correction coefficient FAF in the exhaust passage 12 having a short distance, as shown in FIG. become longer. In order to cope with this, it is understood that the allowable amount for exhaust gas purification should be changed between the three-way catalyst 13 'of the exhaust passage 12' having a long distance and the three-way catalyst 13 of the exhaust passage 12 having a short distance. .

  Therefore, as shown in FIG. 11, the number of cells disposed in the exhaust passage 12 'having a long distance is set to two three-way catalysts 13a' and 13b ', and the number of cells disposed in the exhaust passage 12 having a short distance is set to 2. Three three-way catalysts 13a and 13b are provided. Further, the three-way catalyst 13a ', 13b' disposed in the exhaust passage 12 'having a long distance and the three-way catalyst 13a, 13b disposed in the exhaust passage 12 having a short distance are respectively divided into two. Then, the total catalyst capacity of the three-way catalysts 13a ′ and 13b ′ is set larger than the total catalyst capacity of the three-way catalysts 13a and 13b. Further, the three-way catalyst 13a 'is disposed upstream of the oxygen sensor 27' disposed in the exhaust passage 12 'having a long distance, and the three-way catalyst 13a is disposed in the exhaust passage 12 having a short distance. 27 on the upstream side. Thereby, the catalyst capacity for each cylinder is optimized, and the emission can be improved. It is also effective to change the density of the catalyst and the catalyst components carried on the three-way catalysts 13a, 13b, 13a ', 13b'.

  Thus, in the air-fuel ratio control apparatus for the internal combustion engine of the present embodiment, the three-way catalyst 13a, 13b, 13a ', 13b' is divided into two regardless of the distance of the exhaust passages 12, 12 ', and the oxygen sensor One-way three-way catalyst 13a, 13a 'is arranged upstream from 27, 27'. As a result, the respective catalyst capacities of the three-way catalysts 13a, 13b, 13a ', 13b' corresponding to the exhaust gas amounts in the exhaust passages 12, 12 'having different lengths for each cylinder are optimized to reduce emissions. In addition, the exhaust passage 12 'having a long distance can help to be hardly activated due to the influence of the wind received during traveling. Further, the three-way catalysts 13a and 13b in the exhaust passage 12 having a short distance and the three-way catalysts 13a 'and 13b' in the exhaust passage 12 'having a long distance are each divided into two parts, so that the degree of freedom in arrangement design is increased. Can be increased.

FIG. 1 is a schematic configuration diagram showing one cylinder of an internal combustion engine composed of a V-type four-cycle two-cylinder in a two-wheeled vehicle to which an air-fuel ratio control apparatus for an internal combustion engine according to an embodiment of the present invention is applied and its peripheral devices. . FIG. 2 is a flowchart showing a procedure for calculating the fuel injection time in the CPU in the ECU used in the air-fuel ratio control apparatus for an internal combustion engine according to one embodiment of the present invention. FIG. 3 is a flowchart showing a processing procedure of air-fuel ratio feedback correction coefficient calculation for a cylinder having a short exhaust passage distance in FIG. FIG. 4 is a map for calculating the delay time, the integral delay time, the integral constant, and the skip amount corresponding to the throttle opening with the engine speed as a parameter in FIG. FIG. 5 is a time chart showing the relationship between the output voltage of the oxygen sensor disposed in the exhaust passage having a short distance corresponding to the processing of FIGS. 2 and 3 and the air-fuel ratio feedback correction coefficient. FIG. 6 is a flowchart showing a processing procedure for calculating an air-fuel ratio feedback correction coefficient for a cylinder having a long exhaust passage distance in FIG. FIG. 7 is a map for calculating the delay time, the integral delay time, the integral constant, and the skip amount corresponding to the throttle opening with the engine speed as a parameter in FIG. FIG. 8 is a time chart showing the relationship between the output voltage of the oxygen sensor disposed in the exhaust passage having a long distance corresponding to the processing of FIGS. 2 and 6 and the air-fuel ratio feedback correction coefficient. FIG. 9 is a schematic diagram showing a configuration of a main part of a two-wheeled vehicle equipped with an internal combustion engine composed of a V-type four-cycle two-cylinder to which an air-fuel ratio control apparatus for an internal combustion engine according to an embodiment of the present invention is applied. FIG. 10 is an explanatory view showing a modification of the number of cells and the arrangement relationship of the three-way catalyst in FIG. FIG. 11 is an explanatory view showing another modification of the number of cells and the arrangement relationship of the three-way catalyst in FIG. FIG. 12 is a time chart showing the relationship between the output voltage of the oxygen sensor disposed in the exhaust passage having a different distance and the air-fuel ratio feedback correction coefficient in the conventional air-fuel ratio control apparatus for an internal combustion engine.

Explanation of symbols

1 an internal combustion engine 12 exhaust passage 13 a three-way catalyst 27 oxygen (O ₂₎ sensor 50 ECU (electronic control unit)

Claims (9)

Exhaust passages of different lengths connected independently for each cylinder of an internal combustion engine consisting of V-type multiple cylinders;
Oxygen concentration detection means that is disposed at different positions from the exhaust port in the exhaust passage and detects the oxygen concentration of the exhaust gas discharged from the internal combustion engine for each cylinder;
Physical quantity detection means for detecting, for each cylinder, a physical quantity that changes in accordance with a running state of a vehicle or an operating state of the internal combustion engine;
A reversal direction discriminating means for discriminating a reversal direction for each cylinder when a detection value according to the oxygen concentration by the oxygen concentration detection means undergoes a reversal transition through a determination value between the rich side and the lean side;
A delay time for delaying the timing for skipping the air-fuel ratio feedback correction coefficient in the air-fuel ratio feedback control is set for each cylinder based on the physical quantity, on the opposite side to the reverse direction determined by the reverse direction determining means. Delay time setting means;
Skip amount setting means for setting a skip amount for skipping the air-fuel ratio feedback correction coefficient for each cylinder based on the physical amount;
An integration constant setting means for setting an integration constant for gradually changing the air-fuel ratio feedback correction coefficient for each cylinder based on the physical quantity;
An integral delay time setting means for setting an integral delay time for delaying the timing for setting the integral constant for each cylinder based on the physical quantity; and
Fuel injection amount control means for controlling the fuel injection amount to be supplied to each cylinder in accordance with the delay time, the skip amount, the integration constant, and the air-fuel ratio feedback correction coefficient that is transited by the integration delay time. An air-fuel ratio control apparatus for an internal combustion engine characterized by the above.   2. The air-fuel ratio of the internal combustion engine according to claim 1, wherein the integral constant setting unit sets the integral constant of a cylinder having a long exhaust passage distance smaller than that of a cylinder having a short exhaust passage distance. Control device.   2. The internal combustion engine according to claim 1, wherein the integral delay time setting means sets the integral delay time of a cylinder having a long exhaust passage distance longer than that of a cylinder having a short exhaust passage distance. Air-fuel ratio control device. A catalyst that is disposed in each of the exhaust passages at different positions from the exhaust port and purifies exhaust gas discharged from the internal combustion engine for each cylinder;
2. The air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein the catalyst has a larger catalyst capacity when the distance of the exhaust passage is longer than when the distance of the exhaust passage is shorter.   5. The air-fuel ratio control apparatus for an internal combustion engine according to claim 4, wherein the catalyst sets a larger number of cells with a longer distance of the exhaust passage than that with a shorter distance of the exhaust passage.   The air-fuel ratio control apparatus for an internal combustion engine according to claim 4 or 5, wherein the catalyst divides only the longer exhaust passage distance into two.   6. The internal combustion engine according to claim 4, wherein only one of the exhaust passages having a longer distance is divided into two, and one catalyst is disposed upstream of the oxygen concentration detection means. Air-fuel ratio control device.   6. The internal combustion engine according to claim 4, wherein each of the catalysts is divided into two regardless of the distance of the exhaust passage, and one catalyst is disposed upstream of the oxygen concentration detection means. Engine air-fuel ratio control device.   The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 8, wherein the internal combustion engine is mounted on a motorcycle.

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