JP4405049B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply amount control apparatus for an internal combustion engine that performs learning control of an air-fuel ratio.
[0002]
[Prior art]
An average value of the air-fuel ratio correction coefficient is calculated and the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is controlled using the average value at the time of air-fuel ratio feedback control. Japanese Patent Publication No. 7-11701 discloses that the operation is performed when the vaporized fuel is equal to or lower than a predetermined value.
In addition, in order to prevent deterioration of exhaust characteristics due to the supply of high-concentration evaporated fuel to the engine at the beginning of the purge, the purge flow rate is reduced from the normal purge flow rate at the start of the purge, and after that, It is known to increase the purge flow rate so as to approach the normal purge flow rate as time passes.
[0003]
[Problems to be solved by the invention]
However, in the conventional apparatus, particularly in the apparatus that estimates the purge concentration according to the air-fuel ratio correction amount, the calculated purge concentration is the actual purge concentration in a state where the purge is more normally restricted at the beginning of the purge. If the learning permission is judged based on this purge concentration, the purge concentration is judged to be low even though high concentration fuel vapor is actually purged. May be permitted, and the learning value may be shifted due to the influence of the evaporated fuel.
In addition, when learning is performed to prevent the influence of purging, it may be possible to stop the purging so that it is not affected by the purging. In this case, the amount that can be purged is increased by increasing the frequency of learning. There is a problem that evaporative fuel accumulates in the canister.
[0004]
The present invention has been made to solve such a problem, and is a fuel supply amount control device for an internal combustion engine that can calculate the learned value with high accuracy by preventing the influence of evaporated fuel without stopping the purge. The purpose is to provide.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 is an operation state detection means for detecting the operation state of the internal combustion engine (for example, the intake pipe absolute pressure sensor 10 and the rotation information sensor 14 in FIG. 2 of the embodiment). A basic fuel amount calculating means for calculating a basic fuel amount supplied to the internal combustion engine in accordance with the operating state (for example, a basic fuel injection amount calculation unit 54 in FIG. 2 of the embodiment), and an exhaust gas from the internal combustion engine Air-fuel ratio detection means (for example, the upstream O2 sensor 17 in FIG. 2 of the embodiment) provided in the system for detecting the air-fuel ratio in the exhaust, and supplied to the internal combustion engine according to the output of the air-fuel ratio detection means Feedback control means for calculating an air-fuel ratio correction amount for controlling the air-fuel ratio of the air-fuel mixture (for example, the air-fuel ratio F / B coefficient calculation unit 51 in FIG. 2 of the embodiment), and a learning value of the air-fuel ratio correction amount Air-fuel ratio learning value calculation means (for example, the air-fuel ratio learning value storage unit 53 in FIG. 2) of the embodiment, and the internal combustion engine according to the basic fuel amount, the air-fuel ratio correction amount, and the air-fuel ratio learning value In a fuel supply amount control apparatus for an internal combustion engine having fuel supply amount calculation means (for example, a fuel injection amount calculation unit 55 in FIG. 2 of the embodiment) for calculating the amount of fuel supplied to the intake system of the internal combustion engine To supply purge A purge control means for controlling the amount (for example, the purge control valve 44 in FIG. 1 of the embodiment) and a purge concentration estimation means for estimating the concentration of evaporated fuel by the purge control means based on the air-fuel ratio correction amount (for example, The purge concentration estimation unit 62) in FIG. 2 of the embodiment and the concentration of the evaporated fuel estimated by the purge concentration estimation means Is less than the specified value Learning permission means (e.g., the air-fuel ratio learning execution determination unit 58 in FIG. 2 of the embodiment) that sometimes permits calculation of the air-fuel ratio learning value; Air flow rate detecting means, target purge flow rate basic value calculating means for calculating a target purge flow rate basic value by multiplying the air flow rate by a predetermined target purge rate, and determining that the target purge flow rate basic value is greater than a predetermined limit value When the target purge flow rate value is set, the predetermined limit value is set to the first target purge flow rate value, and when the target purge flow rate basic value is determined to be equal to or less than the predetermined limit value, the target purge flow rate basic value is set to the first target purge flow rate value. Limit value setting means for setting the purge throttle coefficient setting means for gradually increasing the purge target coefficient to the first target purge flow rate value as time elapses after the purge starts, and the first target purge. A purge flow rate calculation means for calculating a second target purge flow rate value by multiplying the flow rate value by the purge throttle coefficient; When purge is started by the purge control means The purge amount is determined based on the second target purge flow rate value obtained by limiting the first target purge flow rate value by the purge throttle coefficient. Purge limiting means for limiting (for example, purge flow rate calculation unit 61 in FIG. 2 of the embodiment), purge Quantity A predetermined time with the start of the limit set Timer means and the purge limiting means purge The amount limit ends, and , Learning permission determination prohibiting means (for example, the air-fuel ratio learning execution determination unit 58 in FIG. 2 of the embodiment) that does not perform the learning permission determination by the learning permission means until the predetermined time has elapsed; A purge flow rate ratio calculating unit for calculating a purge flow rate ratio by dividing the second target purge flow rate value by the target purge flow rate basic value, and limiting the purge amount by the purge limit unit; and After the predetermined time elapses, the learning permission means determines the learning permission determination means based on the predetermined values set to different values according to the purge flow rate ratio. It is characterized by performing.
[0006]
According to such a configuration, when the purge amount is limited at the beginning of the purge start and for a predetermined time thereafter, the learning permission is not determined by the learning permission means, and based on the previous learning permission determination result, the learning permission / Denial is determined. For this reason, the purge amount is lower than usual. Lose weight In the case of restriction, even if there is a deviation between the actual purge concentration and the estimated purge concentration, erroneous learning of the air-fuel ratio based on the estimated purge concentration can be effectively prevented. Thus, the learning value of the air-fuel ratio can be calculated with high accuracy.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes an internal combustion engine body for generating power of an in-line 4-cylinder in which an intake valve and an exhaust valve (not shown) are provided in each cylinder.
[0008]
An intake pipe 2 of the internal combustion engine is connected to a combustion chamber of each cylinder of the internal combustion engine body 1 via a branch portion (intake manifold) 11. A throttle valve 3 is arranged in the middle of the intake pipe 2. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3, and an electric signal corresponding to the throttle valve opening θTH is output and supplied to the ECU 5. An auxiliary air passage 6 that bypasses the throttle valve 3 is provided in the intake pipe 2, and an auxiliary air amount control valve 7 is arranged in the middle of the auxiliary air passage 6. The auxiliary air amount control valve 7 is connected to the ECU 5, and the valve opening amount is controlled by the ECU 5.
[0009]
An intake air temperature (TA) sensor 8 is mounted on the upstream side of the throttle valve 3 in the intake pipe 2, and a detection signal thereof is supplied to the ECU 5. A chamber 9 is provided between the throttle valve 3 of the intake pipe 2 and the intake manifold 11, and an intake pipe absolute pressure (PBA) sensor (operating state detection means) 10 is attached to the chamber 9. A detection signal of the intake pipe absolute pressure sensor 10 is supplied to the ECU 5.
[0010]
An internal combustion engine water temperature (TW) sensor 13 is attached to the internal combustion engine body 1, and a detection signal thereof is supplied to the ECU 5. The ECU 5 is connected to a rotation information sensor (operating state detection means) 14 for detecting information related to the rotation of the crankshaft (not shown) of the internal combustion engine body 1, and the rotation information sensor 14 rotates the crankshaft. A signal corresponding to the angle is supplied to the ECU 5. The rotation information sensor 14 is a cylinder discrimination sensor that outputs a signal pulse (hereinafter referred to as “CYL signal pulse”) at a predetermined crank angle position of a specific cylinder of the internal combustion engine body 1, and a top dead center at the start of the intake stroke of each cylinder ( TDC), a TDC sensor that outputs a TDC signal pulse at a crank angle position before a predetermined crank angle (every crank angle in a four-cylinder engine) and a constant crank angle cycle shorter than the TDC signal pulse (for example, a cycle of 30 °). The CRK sensor generates a pulse (hereinafter referred to as “CRK signal pulse”), and a CYL signal pulse, a TDC signal pulse, and a CRK signal pulse are supplied to the ECU 5. These signal pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of the engine speed Ne.
[0011]
A fuel injection valve 12 having a constant fuel injection amount per unit time is provided for each cylinder slightly upstream of the intake valve of the intake manifold 11, and each fuel injection valve 12 is connected to a fuel pump (not shown). The fuel injection timing and the fuel injection time (the valve opening time, that is, the injection amount) are controlled by a signal from the ECU 5. An ignition plug (not shown) of the internal combustion engine body 1 is also electrically connected to the ECU 5, and the ignition timing θIG is controlled by the ECU 5.
[0012]
The exhaust pipe 16 is connected to the combustion chamber of the internal combustion engine body 1 via a branch portion (exhaust manifold) 15. An upstream oxygen concentration sensor (hereinafter referred to as “upstream O 2 sensor”) 17 is attached to the exhaust pipe 16 of the exhaust system immediately downstream of the portion where the branch portions 15 gather. Further, a three-way catalyst 19 is disposed on the downstream side of the upstream O2 sensor (air-fuel ratio detecting means) 17, and a downstream oxygen concentration sensor (hereinafter referred to as “downstream O2 sensor”) is arranged downstream of the three-way catalyst 19. ) 18 is installed. The three-way catalyst 19 purifies HC, CO, NOx, etc. in the exhaust gas.
[0013]
The upstream O2 sensor 17 is connected to the ECU 5 and outputs an electrical signal (high level on the rich side and low level on the lean side) that changes suddenly before and after the theoretical air-fuel ratio, and supplies the electrical signal to the ECU 5. The downstream O2 sensor 18 has a characteristic that its output changes abruptly before and after the stoichiometric air-fuel ratio, and its output becomes a high level on the rich side and a low level on the lean side. The downstream O2 sensor 18 is connected to the ECU 5, and the detection signal is supplied to the ECU 5. Further, an atmospheric pressure sensor 21 for detecting the atmospheric pressure is connected to the ECU 5, and a detection signal is supplied to the ECU 5.
[0014]
The exhaust gas recirculation mechanism 30 includes an exhaust gas recirculation path 31 that connects the chamber 9 of the intake pipe 2 and the exhaust pipe 16, and an exhaust gas recirculation valve (EGR valve) 32 that is provided in the middle of the exhaust gas recirculation path 31 and controls the exhaust gas recirculation amount. And a lift sensor 33 that detects the valve opening degree of the EGR valve 32 and supplies the detection signal to the ECU 5. The EGR valve 32 is an electromagnetic valve having a solenoid, and the solenoid is connected to the ECU 5 so that the valve opening degree can be changed linearly by a control signal from the ECU 5.
[0015]
The evaporative fuel processing device 40 purges evaporative fuel generated in a fuel tank 41 that stores fuel into the intake system of the internal combustion engine body 1. The fuel tank 41 is connected to a canister 45 through a passage 42, and the canister 45 is connected to the chamber 9 of the intake pipe 2 via the purge passage 43. The canister 45 incorporates an adsorbent that adsorbs the evaporated fuel generated in the fuel tank 41 and has an outside air intake. A two-way valve 46 including a positive pressure valve and a negative pressure valve is disposed in the middle of the passage 42, and a purge control valve (purge control means) 44 that is a duty control type electromagnetic valve is disposed in the middle of the purge passage 43. Is provided. The purge control valve 44 is connected to the ECU 5 and is controlled according to a signal from the ECU 5.
[0016]
The ECU 5 shapes input signal waveforms from the various sensors described above, corrects the voltage level to a predetermined level, changes the analog signal value to a digital signal value, and a central processing circuit (CPU). And a storage circuit composed of ROM and RAM for storing various calculation programs executed by the CPU, various maps and calculation results described later, and various electromagnetic valves and spark plugs such as the fuel injection valve 12 and the purge control valve 44. And an output circuit for outputting a drive signal.
[0017]
The ECU 5 calculates the fuel injection time TOUT of the fuel injection valve 12 based on the various internal combustion engine operation parameter signals described above, and outputs a signal for driving the fuel injection valve 12 based on the calculation result. That is, the ECU 5 constitutes a control device 50 for an internal combustion engine that controls the internal combustion engine with various sensors.
[0018]
For example, as shown in FIG. 2, the ECU 5 calculates an air-fuel ratio correction amount for controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine in accordance with the output of the upstream O2 sensor 17. An air-fuel ratio F / B coefficient calculation unit (feedback control means) 51 that calculates an air-fuel ratio feedback coefficient (air-fuel ratio correction coefficient) KO2 according to the air-fuel ratio VO2 detected by the O2 sensor 17 and an upstream O2 sensor 17 And an O2 sensor inversion period calculation unit (inversion period calculating means) 52 for calculating the inversion period FPVO2 of the air-fuel ratio VO2.
[0019]
Further, the learning value of the air-fuel ratio correction amount is calculated. More specifically, the average value KO2MEN of the air-fuel ratio feedback coefficient calculated by the air-fuel ratio F / B coefficient calculation unit 51 is calculated and the average of the air-fuel ratio feedback coefficient is calculated. An air / fuel ratio learning value KTIM is calculated based on the value KO2MEN, and an air / fuel ratio learning value storage unit (air / fuel ratio learning value calculation) that updates and stores the air / fuel ratio learning value KTIM at a storage position corresponding to the operating state of the internal combustion engine at the time of calculation. Means) 53 and the basic fuel amount to be supplied to the internal combustion engine in accordance with the operating state, more specifically, the basic fuel for retrieving the basic fuel injection amount TIM from the storage position corresponding to the operating state of the internal combustion engine. And an injection amount calculation unit (basic fuel amount calculation means) 54.
[0020]
Further, the amount of fuel supplied to the internal combustion engine is calculated in accordance with the basic fuel amount, the air-fuel ratio correction amount, and the air-fuel ratio learning value. More specifically, the air-fuel ratio learning is performed from the storage position corresponding to the operating state of the internal combustion engine. A fuel injection amount calculation unit (fuel supply amount calculation means) 55 that searches for a value KTIM and sets a fuel injection time TOUT corresponding to the fuel injection amount injected into the internal combustion engine based on the air-fuel ratio learning value KTIM; A fuel injection output unit 56 that drives the fuel injection valve 12 for a set fuel injection time TOUT; an intake air amount correlation value calculation unit 57 that calculates an intake air amount correlation value NTI that correlates to the intake air amount to the internal combustion engine; have.
[0021]
Furthermore, when the purge is started by the purge control valve 44, the purge amount is gradually increased until the target evaporated fuel amount with the passage of time, and the purge flow rate calculation unit (purge control means) 61 is based on the air-fuel ratio correction amount. The purge concentration estimation unit (purge concentration estimation means) 62 for estimating the concentration of the evaporated fuel by the purge control valve 44 and the learning value of the air-fuel ratio when the concentration of the evaporated fuel estimated by the purge concentration estimation unit 62 is low are calculated. An air-fuel ratio learning execution determination unit (learning permission means, learning permission determination prohibition means) 58.
[0022]
The air-fuel ratio learning execution determination unit 58 does not perform the learning permission determination when the amount of evaporated fuel is limited, and the inversion that permits the air-fuel ratio learning value storage unit 53 to execute the update storage of the air-fuel ratio learning value KTIM. The permitted range of the cycle FPVO2 is determined according to the intake air amount correlation value NTI to the internal combustion engine, and when the inversion cycle FPVO2 is outside the determined permitted range, the air-fuel ratio learned value KTIM by the air-fuel ratio learned value storage unit 53 Stop execution of update storage.
[0023]
The control content of the fuel injection control by the ECU 5 will be described below.
The ECU 5 executes one control cycle from START to EXIT in the flowchart of fuel injection control shown in FIG. 3, for example, every time a TDC signal pulse is output from the TDC sensor.
[0024]
A basic fuel injection amount map in which a basic fuel injection amount (basic fuel injection time) TIM is set corresponding to each operation state defined by the engine speed Ne and the intake pipe absolute pressure Pb is stored in the memory circuit of the ECU 5. First, in step SA1, the engine rotational speed Ne at that time is detected from the output of the rotation information sensor 14, and the intake pipe absolute pressure Pb at that time is detected from the output of the intake pipe absolute pressure sensor 10. Then, the basic fuel injection amount TIM for the operating state defined by the engine speed Ne and the intake pipe absolute pressure Pb is searched for and read out from the basic fuel injection amount map. The calculation of the basic fuel injection amount TIM is executed by the basic fuel injection amount calculation unit 54 corresponding to the basic fuel amount calculation means of the present invention.
[0025]
The battery backup RAM constituting the storage circuit of the ECU 5 has a RAM area (storage position) set for each operating state defined by the engine speed Ne and the intake pipe absolute pressure Pb, and each of these RAM areas is empty. An air-fuel ratio learning value map in which the fuel ratio learning value KTIM is set correspondingly is stored. In step SA2, the air-fuel ratio learning value map is detected from the engine speed Ne and the intake pipe absolute pressure Pb at that time from the air-fuel ratio learning value map. The air-fuel ratio learning value KTIM in the RAM area for the operating state of the internal combustion engine is retrieved and read.
[0026]
Here, for example, as shown in FIG. 4, the air-fuel ratio learning value map described above has eight regions (horizontal in FIG. 4) in which the engine speed Ne is partitioned by nine lattice points of # NKTIM + 0 to # NKTIM + 8. 8 × 8 = 64 RAMs by dividing the intake pipe absolute pressure Pb into eight areas (vertical direction in FIG. 4) partitioned by nine grid points of # PKTIM + 0 to # PKTIM + 8. The air-fuel ratio learning values of KTIM0 to KTIM63 are set and stored for each RAM area. Further, apart from this air-fuel ratio learning value map, an air-fuel ratio learning value KTIM64 used when the internal combustion engine is idling is set and stored.
[0027]
The initial value of the air-fuel ratio learning value KTIM is 1.0, and the air-fuel ratio learning value is an air-fuel ratio described later that is executed every predetermined time (10 ms) separately from the flowchart of the fuel injection control shown in FIG. It is corrected and updated as necessary in the calculation process of the air-fuel ratio learning value KTIM executed in the calculation process of the feedback coefficient KO2.
[0028]
When the air-fuel ratio learned value KTIM is read from the air-fuel ratio learned value map, interpolation calculation is performed. That is, first, as shown in FIG. 5, an intermediate value between adjacent grid points that divide the RAM area is set as a grid point for interpolation calculation. Specifically, for example, with respect to grid points # NKTIM2, # NKTIM3, # PBKTIM3, # PBKTIM4 that divide the RAM area, (NKTIM2 + NKTIM3) / 2, (PBKTIM3 + PBKTIM4) / 2 is set as a grid point A1 for interpolation calculation, and the grid For point # NKTIM3, # NKTIM4, # PBKTIM3, # PBKTIM4, (NKTIM3 + NKTIM4) / 2, (PBKTIM3 + PBKTIM4) / 2 are set as the grid point A2 for interpolation calculation, and grid points # NKTIM4, # NKTIMIM5, # PBKTIM3, # PBKTIM3, # PBKTIM3 On the other hand, (NKTIM4 + NKTIM5) / 2, (PBKTIM3 + PBKTIM4) / 2 are set as the interpolation calculation grid point A3, and the grid points # NKTIM2, # NKTIM3, # PBKTIM4, #PBKT For M5, (NKTIM2 + NKTIM3) / 2, (PBKTIM4 + PBKTIM5) / 2 is set as a grid point A4 for interpolation calculation, and for grid points # NKTIM3, # NKTIM4, # PBKTIM4, # PBKTIM5, (NKTIM3 + NKTIM4) / 2, (+ PBKTIM) ) / 2 is the interpolation calculation grid point A5, and for the grid points # NKTIM4, # NKTIM5, # PBKTIM4, # PBKTIM5, (NKTIM4 + NKTIM5) / 2, (PBKTIM4 + PBKTIM5) / 2 is the interpolation calculation grid point A6, and , Lattice points # NKTIM2, # NKTIM3, # PBKTIM5, # PBKTIM6, (NKTIM2 + NKTIM3) / 2, (PBKTIM5 + PBKTIM6) / 2 A7, and for grid points # NKTIM3, # NKTIM4, # PBKTIM5, # PBKTIM6, (NKTIM3 + NKTIM4) / 2, (PBKTIM5 + PBKTIM6) / 2 are set as a grid point A8 for interpolation calculation, and grid points # NKTIM4, # NKTIM5, # PBKTIM5 , # PBKTIM6, (NKTIM4 + NKTIM5) / 2 and (PBKTIM5 + PBKTIM6) / 2 are set as the interpolation calculation grid point A9. Then, the four interpolation calculation grid points (interpolation calculation grid points A1, A1 shown in FIG. 5) that are closest to the position corresponding to the engine speed Ne and the intake pipe absolute pressure Pb (for example, the position A0 shown in FIG. 5). A2, A4, and A5) are calculated, and interpolation calculation is performed so as to weight each distance from these four interpolation calculation grid points.
[0029]
Further, the correction according to the following equation is performed on the KTIM thus calculated by interpolation using the atmospheric pressure correction coefficient KTKPA calculated from the detection value of the atmospheric pressure sensor 21 by the search based on the atmospheric pressure correction table shown in FIG. .
KTIM = (KTIM−1.0) × KTKPA + 1.0
[0030]
Further, in the memory circuit of the ECU 5, separately from the flowchart of the fuel injection control shown in FIG. 3, the calculation is performed by the calculation process of an air-fuel ratio feedback coefficient (air-fuel ratio correction coefficient) KO2T, which will be described later, executed every predetermined time (10 ms). The air / fuel ratio feedback coefficient KO2T thus stored is stored, and in step SA3, the air / fuel ratio feedback coefficient KO2T is read as the air / fuel ratio feedback coefficient KO2.
[0031]
In step SA4, the ECU 5 reads the basic fuel injection amount TIM read in step SA1, the air-fuel ratio learning value KTIM read in step SA2, the air-fuel ratio feedback coefficient KO2 read in step SA3, and the state of the battery at that time. Based on the correction value TIVB according to the above, the fuel injection time (opening time of the fuel injection valve 12) TOUT corresponding to the fuel injection amount injected into the internal combustion engine TOUT is set based on the following equation: become.
TOUT = TIM * KTIM * KO2 + TIVB
This calculation is executed by the fuel injection amount calculation unit 55 corresponding to the fuel supply amount calculation means of the present invention.
[0032]
Then, the ECU 5 opens the fuel injection valve 12 only during the fuel injection time TOUT calculated in this way. The fuel injection output unit 56 executes the valve opening drive of the fuel injection valve 12.
[0033]
When the fuel injection time TOUT is thus calculated in step SA4 and the fuel injection valve 12 is opened, the fuel injection control process of FIG. 2 is terminated.
[0034]
Next, calculation processing for calculating the air-fuel ratio feedback coefficient KO2T used in step SA3 of the fuel injection control flowchart described above, and calculation of this air-fuel ratio feedback coefficient KO2T used in step SA2 of the fuel injection control flowchart. The calculation process for calculating the air-fuel ratio learning value KTIM executed in step SB15 during the process will be described.
[0035]
First, calculation processing for calculating the air-fuel ratio feedback coefficient KO2T according to the output of the upstream O2 sensor 17, that is, the air-fuel ratio will be described with reference to the flowchart of FIG. Note that one control cycle from START to EXIT in the flowchart of the calculation process of the air-fuel ratio feedback coefficient KO2T shown in FIG. 7 is executed, for example, every predetermined time (10 ms).
[0036]
First, in step SB1, whether or not the output of the upstream O2 sensor 17 has been reversed is determined based on the inversion of the flag F_PVREF. That is, the output of the upstream O2 sensor 17, that is, the air-fuel ratio VO2 fluctuates with a cycle as shown in FIG. 8A. In the ECU 5, as shown in FIG. When the output VO2 fluctuates from the lean (0V) side to the rich (1V) side and exceeds a predetermined threshold value B1 close to 1V, the flag F_PVREF is set to “1”, while the upstream O2 sensor 17 When the output fluctuates from the rich (1V) side to the lean (0V) side, a process of resetting the flag F_PVREF to “0” is performed when it falls below a predetermined threshold value B2 close to 0V. In step SB1, it is determined whether or not the flag F_PVREF is inverted (0 → 1 or 1 → 0) from the previous one cycle.
[0037]
If the flag F_PVREF is inverted in step SB1, it is determined whether or not the flag F_PVREF is 1 in step SB2. If the flag F_PVREF is 1 in step SB2, that is, if the current air-fuel ratio is on the rich side, the rich timer value RDLY is set in the delay timer TRLDLY in step SB3, while the flag in step SB2 If F_PVREF is 0, that is, if the current air-fuel ratio is on the lean side, the lean timer value LDLY is set in the delay timer TRLDLY in step SB4. The delay timer TRLDLY is automatically counted down every predetermined time after being set.
[0038]
After step SB3 and after step SB4, the flag F_KO2WIN is set to “0” in step SB5.
[0039]
If the flag F_PVREF is not inverted in step SB1, it is determined in step SB6 whether the delay timer TRLDLY = 0. If delay timer TRLDLY = 0 in step SB6, it is determined in step SB7 whether flag F_PVREF is 1.
[0040]
If the flag F_PVREF is 1 in step SB7, that is, if the current air-fuel ratio is on the rich side, it is determined in step SB8 whether or not the flag F_KO2WIN = 1. If the flag F_KO2WIN is not 1 in step SB8, a value obtained by subtracting the predetermined value KO2WR for dramatically correcting from the current air-fuel ratio feedback coefficient KO2T in step SB9 is set as a new air-fuel ratio feedback coefficient KO2T. In step SB10, the flag F_KO2WIN is set to “1”. On the other hand, if the flag F_KO2WIN = 1 in step SB8, the value obtained by subtracting the predetermined value IL for gradually correcting from the current air-fuel ratio feedback coefficient KO2T in step SB11 is the new current air-fuel ratio feedback coefficient. Let it be KO2T.
[0041]
If the flag F_PVREF is not 1 in step SB7, that is, if the current air-fuel ratio is on the lean side, it is determined in step SB12 whether the flag F_KO2WIN = 1. If the flag F_KO2WIN is not 1 in step SB12, a value obtained by adding a predetermined value KO2WL for dramatically correcting the current air-fuel ratio feedback coefficient KO2T in step SB13 is set as a new air-fuel ratio feedback coefficient KO2T. In step SB10, the flag F_KO2WIN is set to “1”. On the other hand, if the flag F_KO2WIN = 1 in step SB12, a value obtained by adding a predetermined value IR for gradually correcting the current air-fuel ratio feedback coefficient KO2T in step SB14 is a new air-fuel ratio feedback coefficient KO2T. And
[0042]
After step SB5, when the determination at step SB6 is NO, after step SB10, after step SB11, and after step SB14, in step SB15, calculation processing of the air-fuel ratio learning value KTIM (described later) I do. When the process of step SB15 is finished, the calculation process for calculating the air-fuel ratio feedback coefficient KO2T shown in FIG. 7 is finished.
[0043]
Here, the above will be described in light of the timing chart shown in FIG. 9. When the flag F_PVREF changes from “0” to “1” at time t1, the determination in step SB1 becomes YES, and the determination in step SB2 Is YES, the timer value RDLY is set to the delay timer TRLDLY in step SB3, and the flag F_KO2WIN is set to “0” in step SB5.
[0044]
Then, in the next control cycle, the determination in step SB1 is NO, and the air-fuel ratio feedback coefficient KO2T is maintained as it is until the delay timer TRLDLY = 0 in step SB6 (time points t1 to t2). At time t2 when the delay timer TRLDLY = 0 in step SB6, the current air-fuel ratio is on the rich side and the flag F_PVREF = 1, so that the determination in step SB7 is YES, and further in step SB8 the flag F_KO2WIN = 1 becomes NO, and a value obtained by subtracting the predetermined value KO2WR for dramatically correcting from the current air-fuel ratio feedback coefficient KO2T in step SB9 is set as a new air-fuel ratio feedback coefficient KO2T. In step SB10, the flag F_KO2WIN is set to “1”.
[0045]
Then, in the next control cycle, the determination in step SB8 is YES, and in step SB11, a value obtained by subtracting a predetermined value IL for gradually correcting from the current air-fuel ratio feedback coefficient KO2T is set as a new current empty cycle. The fuel ratio feedback coefficient is KO2T. Then, step SB11 is repeated until the determination of inversion of the next flag F_PVREF is YES in step SB1, and the air-fuel ratio feedback coefficient KO2T is gradually decreased (time t2 to t3).
[0046]
Next, when the flag F_PVREF changes from “0” to “1” at time t3, the determination in step SB1 is YES, the determination in step SB2 is NO, and the timer value LDLY is set to the delay timer in step SB4. TRLDLY is set, and the flag F_KO2WIN is set to “0” in step SB5.
[0047]
Then, in the next control cycle, the determination in step SB1 is NO, and the air-fuel ratio feedback coefficient KO2T is maintained as it is until the delay timer TRLDLY = 0 in step SB6 (time points t3 to t4). When the delay timer TRLDLY = 0 in step SB6, since the current air-fuel ratio state is on the lean side at time t4 and the flag F_PVREF = 1 is not satisfied, the determination in step SB7 is NO, and the flag is further determined in step SB12. F_KO2WIN = 1 becomes NO, and a value obtained by adding a predetermined value KO2WL for dramatically correcting to the current air-fuel ratio feedback coefficient KO2T in step SB13 is set as a new air-fuel ratio feedback coefficient KO2T. In step SB10, the flag F_KO2WIN is set to “1”.
[0048]
Then, in the next control cycle, the determination in step SB12 is YES, and in step SB14, a value obtained by adding a predetermined value IR for gradually correcting to the current air-fuel ratio feedback coefficient KO2T is set as a new current empty cycle. The fuel ratio feedback coefficient is KO2T. Then, step SB14 is repeated until the determination of inversion of the next flag F_PVREF is YES in step SB1, and the air-fuel ratio feedback coefficient KO2T is gradually increased (time t4 to t5).
[0049]
The air-fuel ratio feedback coefficient KO2T is calculated as described above.
The calculation process of the air-fuel ratio feedback coefficient KO2T is executed by the air-fuel ratio F / B coefficient calculation unit 51 corresponding to the feedback control means of the present invention.
[0050]
Next, the calculation process for calculating the air-fuel ratio learning value KTIM executed in step SB15 of the above-described calculation process of the air-fuel ratio feedback coefficient KO2T will be described based on the flowcharts of FIGS.
[0051]
First, in step SC1 of FIG. 10, whether or not the flag F_PVREF in the previous control cycle is “0” and the flag F_PVREF in the current control cycle is “1”, that is, the output VO2 of the upstream O2 sensor 17 is It is determined whether or not the lean side is reversed to the rich side.
[0052]
If the determination in step SC1 is NO, the counter CPPVO2 is incremented by “1” in step SC2.
[0053]
Next, in step SC3, whether or not the flag F_PVREF in the previous control cycle is “1” and the flag F_PVREF in the current control cycle is “0”, that is, the output VO2 of the upstream O2 sensor 17 is rich. It is determined whether or not it has reversed from the lean side to the lean side.
[0054]
If the determination in step SC3 is yes, in step SC4, the current air-fuel ratio feedback coefficient KO2T is stored as the minimum value KO2MIN of the air-fuel ratio feedback coefficient.
[0055]
When the determination at step SC3 is NO and after step SC4, the flag F_KTIMG is set to “0” at step SC5.
[0056]
If the determination in step SC1 is YES, that is, if the output VO2 of the upstream O2 sensor 17 is inverted from the lean side to the rich side, the counter CFPVO2 is stored as the inversion cycle FPVO2 in step SC6. In step SC7, the counter CPPVO2 is set to “0”, and in step SC8, the current air-fuel ratio feedback coefficient KO2T is stored as the maximum value KO2MAX of the air-fuel ratio feedback coefficient.
[0057]
Next, in step SC9, the minimum value KO2MIN and the maximum value KO2MAX of the air-fuel ratio feedback coefficient are added and divided by 2, thereby calculating the average value KO2MEN of the air-fuel ratio feedback coefficient. In step SC10, the flag F_KTIMG is set to “1”.
[0058]
Here, the above will be described in light of the timing chart shown in FIG. 9. When the flag F_PVREF changes from “0” to “1” at time t1, the determination in step SC1 becomes YES, and in step SC7, the counter CFPVO2 Is “0”.
[0059]
In the next control cycle, the determination in step SC1 is NO, and in step SC2, the counter CPPVO2 is incremented by “1”. Then, from the time point t1 when the flag F_PVREF changes from “0” to “1”, the determination at step SC1 becomes YES, that is, from 0 until the time point t5 when the flag F_PVREF changes from “0” to “1”. In step SC6, the counter CFPVO2 incremented by 1 for each control cycle is stored as the inversion cycle FPVO2. Note that such calculation of the inversion period FPVO2 is performed in the O2 sensor inversion period calculation unit 52.
[0060]
If the flag F_PVREF changes from “1” to “0” at time t3, the determination at step SC3 is YES, and at step SC4, the air-fuel ratio feedback coefficient KO2T at that time is stored as the minimum value KO2MIN. Thereafter, when the flag F_PVREF changes from “0” to “1” at time t5, the determination in step SC1 becomes YES, and in step SC8, the air-fuel ratio feedback coefficient KO2T at that time is set to its maximum value. While storing as KO2MAX, the average value KO2MEN is calculated and stored in step SC9. Then, when the inversion period FPVO2 is calculated in step SC6 and the average value KO2MEN of the air-fuel ratio feedback coefficient is calculated in step SC9, the flag F_KTIMG indicating that these calculations are completed is set to “1” in step SC10.
[0061]
Here, the average value KO2MEN of the air-fuel ratio feedback coefficient is obtained from the average of the maximum value KO2MAX and the minimum value KO2MIN, but after the flag F_PVREF changes from “1” to “0”, the flag F_PVREF becomes “1”. Alternatively, the average value may be obtained by adding the air-fuel ratio feedback coefficient KO2T obtained in all the control cycles from when the value is changed to “0” and dividing by the number of additions.
[0062]
After step SC5 and after step SC10, in step SW1 of FIG. 11, it is determined whether or not “1” indicating that purge is being performed is set in the flag value of the flag F_PGACT. If the determination result is “YES”, that is, if the purge is being performed, the process proceeds to step SW2, and if “NO”, that is, if the purge is stopped, the processing after step SW2 is skipped, and FIG. The process proceeds to step SC11.
[0063]
In step SW2, it is determined whether or not “1” indicating permission of learning permission determination executed in step SW6 described later is set in the flag value of the flag F_PGKTIM. If the determination result is “YES”, the process proceeds to step SW3, and if “NO”, the process proceeds to step SW21. Here, the flag F_PGKTIM is set to “0” at the time of starting.
The processing of step SW2 is executed by the air-fuel ratio learning execution determination unit 58 corresponding to the learning permission determination prohibiting means of the present invention.
[0064]
In step SW3, a predetermined timer value #TMKIST is set in the down timer TKIST.
In step SW4, it is determined whether the timer value of the down timer TKTIGO set in step SW21 described later is “0”. If the determination result is “YES”, the process proceeds to step SW11, and if “NO”, the process proceeds to step SW5.
In step SW11, “0” indicating prohibition of learning permission judgment executed in step SW6 described later is set in the flag value of the flag F_PGTIM.
[0065]
In step SW12, “0” indicating prohibition of learning of the air-fuel ratio is set in the flag value of the flag F_PKTIMOMOK, all the processes after step SC11 in FIG. .
In step SW5, which is executed when the determination result in step SW4 is “NO”, a determination process is performed to determine whether the barge density is high. This determination process will be described later with reference to FIG.
[0066]
In step SW6, it is determined whether or not the flag value of the flag F_PKTIMOMOK is “1” indicating the learning permission of the air-fuel ratio. If the determination result is “YES”, that is, if the air-fuel ratio learning is performed, FIG. The process proceeds to step SC11. If “NO”, that is, if the air-fuel ratio learning is not performed, all the processes after step SC11 in FIG. 12 are skipped, and the calculation process of the air-fuel ratio learned value KTIM ends.
The processing of step SW6 is executed by the air-fuel ratio learning execution determination unit 58 corresponding to the learning permission means of the present invention.
[0067]
In step SW21 that is executed when the determination result in step SW2 is “NO”, a predetermined timer value #TMKTIGO is set in the timer TKTIGO.
In Step SW22, it is determined whether the timer value of the timer TKTIST is “0”. When the determination result is “YES”, the process proceeds to step SW23, and when it is “NO”, all the processes after step SC11 in FIG. 12 are skipped, and the calculation process of the air-fuel ratio learning value KTIM is ended.
[0068]
In step SW23, if the flag value of the flag F_PGKTIM is set to “1” indicating prohibition of the learning permission determination executed in step SW6, all the processes after step SC11 in FIG. The calculation process of the learning value KTIM ends.
If the learning process shown in FIG. 11 is continuously performed, the learning value is shifted by learning the influence of the purge. Therefore, the learning process shown in FIG. 11 is performed in predetermined cycles #TMKTIGO, #TMKTIIST (for example, 20 Every minute).
[0069]
In step SC11 of FIG. 12, the air-fuel ratio learning value KTIM in the RAM area detected from the engine speed Ne and the intake pipe absolute pressure Pb at that time is retrieved and read from the air-fuel ratio learning value map (see FIG. 4). . In step SC12, it is determined whether or not there is a change (shift to another RAM area) in the RAM area in which the air-fuel ratio learning value KTIM is stored during one inversion period measurement, and there is a change in the RAM area. In this case, since the operating state has changed, the flag F_KTIMA indicating that is set to “1” in step SC13.
[0070]
If there is no change in the RAM area in step SC12 and if the flag F_KTIMA is set to “1” in step SC13, it is determined in step SC14 whether or not the flag F_KTIMG = 1. If the flag F_KTIMG = 1 is not satisfied. Since the inversion period FPVO2 and the average value KO2MEN of the air-fuel ratio feedback coefficient are not calculated, the processing of the flowcharts shown in FIGS. 10 to 12, that is, step SB15 of the flowchart shown in FIG.
[0071]
If the flag F_KTIMG = 1 in step SC14, that is, if the inversion period FPVO2 and the average value KO2MEN of the air-fuel ratio feedback coefficient are calculated, it is determined in step SC15 whether the flag F_IDLE = 1. The flag F_IDLE is set to “1” under a predetermined condition in which it is determined that the internal combustion engine is in an idling state, and is set to “0” under a predetermined condition in which it is determined that the internal combustion engine is not in an idling state.
[0072]
In step SC15, if the flag F_IDLE = 1, that is, if the internal combustion engine is in an idling state, in step SC16, the inversion cycle FPVO2 stored in step SC6 is higher than the lower threshold value # FPVO2IL. It is determined whether or not it is within one learning permission range defined by the threshold value # FPVO2IH, that is, whether # FPVO2IL ≦ FPVO2 ≦ # FPVO2IH, and if # FPVO2IL ≦ FPVO2 ≦ # FPVO2IH is not described later The update storage of the air-fuel ratio learning value KTIM executed in steps SC22 to SC24 is stopped. Here, since the engine load hardly changes when the engine is in the idling state, only the determination as to whether or not the inversion cycle FPVO2 is within the predetermined range is performed. The air / fuel ratio learning execution determination unit 58 determines whether to stop execution of update storage of the air / fuel ratio learning value KTIM.
[0073]
If the flag F_IDLE is not 1 in step SC15, that is, if the internal combustion engine is not idling, an intake air amount correlation value NTI that is correlated with the intake air amount to the internal combustion engine is calculated in step SC17. The intake air amount correlation value NTI is calculated by the intake air amount correlation value calculation unit 57.
[0074]
In step SC17, first, the engine speed Ne and the intake pipe absolute pressure Pb are detected, and the basic fuel injection quantity TIM for the operating state defined by the engine speed Ne and the intake pipe absolute pressure Pb is determined as the basic fuel injection quantity. Search and read on the map. Then, the calculation is performed from the basic fuel injection amount TIM and the engine speed Ne by the following formula.
Intake air amount correlation value NTI = engine speed Ne × basic fuel injection amount TIM
[0075]
Since the basic fuel injection amount TIM is a fuel injection amount per unit rotation, the fuel injection amount per unit time can be obtained by multiplying the basic fuel injection amount TIM by the engine speed Ne, and the fuel injection amount per unit time. Is a value corresponding to the amount of intake air per unit time.
[0076]
Here, in the storage circuit of the ECU 5, there is a threshold table shown in FIG. 17 in which the lower threshold data # FPVO2NNL and the upper threshold data # FPVO2NNH are set in correspondence with each intake air amount correlation value NTI. It is remembered. That is, in FIG. 17, the upper line C1 set for each value of the intake air amount correlation value NTI indicates the upper threshold data, and the lower line C2 indicates the lower threshold data.
[0077]
In step SC18, the lower threshold data # FPVO2NNL and the upper threshold data # FPVO2NNH for the intake air amount correlation value NTI calculated in step SC17 are retrieved from the threshold table and read out, and the lower side read out The threshold data # FPVO2NNL is set as the lower threshold value FPVO2NL, and the upper threshold data # FPVO2NNH is set as the upper threshold value FPVO2NH.
[0078]
In step SC19, whether or not the inversion cycle FPVO2 stored in step SC6 is within the learning permission range defined by the lower threshold value FPVO2NL and the upper threshold value FPVO2NH, that is, FPVO2NL ≦ FPVO2 ≦ FPVO2NH. If it is determined that there is no FPVO2NL ≦ FPVO2 ≦ FPVO2NH, the execution of the update storage of the air-fuel ratio learning value KTIM executed in steps SC22 to SC24 described later is stopped. That is, when the engine is not in the idling state, the engine load fluctuates, so it is determined whether or not the inversion cycle FPVO2 is in the learning permission range set for each engine load. The air / fuel ratio learning execution determination unit 58 determines whether to stop execution of update storage of the air / fuel ratio learning value KTIM.
[0079]
If # FPVO2IL ≦ FPVO2 ≦ # FPVO2IH in Step SC16 described above and if FPVO2NL ≦ FPVO2 ≦ FPVO2NH in Step SC19, it indicates that the operation state has changed due to a change in the RAM area in Step SC20. It is determined whether or not the flag F_KTIMA is “1”.
[0080]
If F_KTIMA = 1 in step SC20, F_KTIMA is set to “0” in step SC21, and the processing of the flowcharts shown in FIGS. 10 to 12, that is, step SB15 of the flowchart shown in FIG. That is, since the operation state is not a steady state but a transitional state, execution of update storage of the air-fuel ratio learning value KTIM is stopped. The air / fuel ratio learning execution determination unit 58 determines whether to stop execution of update storage of the air / fuel ratio learning value KTIM.
[0081]
If F_KTIMA = 1 is not satisfied in step SC20, in step SC22, the deviation DKO2MEN is calculated by subtracting the reference value 1.00 from the average value KO2MEN of the air-fuel ratio feedback coefficient calculated in step SC9.
[0082]
In step SC23, a value obtained by adding the deviation DKO2MEN to the air-fuel ratio learned value KTIM (KTIMnOLD) read from the RAM area of the air-fuel ratio learned value map corresponding to the operating state in step SC11 is a new air-fuel ratio learned value KTIM. (KTIMnNEW) is updated and stored in the same RAM area. The update storage of the air-fuel ratio learning value KTIM is executed by the air-fuel ratio learning value storage unit 53.
[0083]
Further, in step SC24, limit processing is performed to keep the air-fuel ratio learned value KTIM between a predetermined lower limit value #KTIMLL and a predetermined upper limit value #KTIMLH. That is, if the air-fuel ratio learning value KTIM is not less than the lower limit value #KTIMLL and not more than the upper limit value #KTIMLH, the air-fuel ratio learning value KTIM is left as it is. When the air-fuel ratio learning value KTIM exceeds the predetermined lower limit value #KTIMMLH, this is set as the upper limit value #KTIMMLH.
[0084]
After performing the process of step SC24, the process of the flowchart shown in FIGS. 10 to 12, that is, step SB15 of the flowchart shown in FIG.
[0085]
Next, a determination process for determining whether the barge density executed in step SW5 in FIG. 11 is high will be described with reference to the flowchart in FIG.
[0086]
First, in step SX1, it is determined whether the canister purge control throttle coefficient KPGT is “1.0”. The calculation process for calculating the canister purge control throttle coefficient KPGT will be described later with reference to FIG.
If the determination result of step SX1 is “YES”, the process of step SX2 is skipped and the process proceeds to step SX3.
[0087]
On the other hand, if the decision result in the step SX1 is “NO”, the process advances to a step SX2, and a predetermined timer value #TMKTID is set in the timer TKTID.
This timer TKTID is a timer for waiting until the estimated purge concentration reaches the actual purge concentration.
[0088]
Next, in step SX3, it is determined whether or not the value set in the timer TKTID is “0”. If the determination result is “NO”, the determination process for determining whether the barge density is high is terminated, and if “YES”, the process proceeds to step SX4.
[0089]
In step SX4, it is determined whether the purge flow rate ratio QRATE is “1.0”. If the determination result is “NO”, that is, if “purge flow rate constant purge”, the process proceeds to step SX11. If “YES”, that is, if “intake air amount proportional purge”, the process proceeds to step SX5. .
The purge flow rate ratio QRATE is set in step SV6 in FIG. 14 described later.
[0090]
In step SX5 and step SX11, it is determined whether the air flow rate QAIR is within a predetermined range. The air flow rate QAIR is calculated according to the following equation using the basic fuel injection amount TIM, the engine speed NE, and a predetermined coefficient #KQAIR.
Air flow rate QAIR =
Basic fuel injection amount TIM x engine speed NE x 2 x coefficient #KQAIR
[0091]
In step SX5, it is determined whether the purge concentration is within an accurate range, that is, whether the air flow rate QAIR is not less than the lower limit value #QAIRPLL and not more than the upper limit value #QAIRPLH. If the determination result is “NO”, the determination process for determining whether the purge concentration is high is terminated, and if “YES”, the process proceeds to step SX6.
[0092]
On the other hand, in step SX11, whether the air flow rate QAIR is within the region where the purge concentration estimated value can be accurately determined, that is, whether the air flow rate QAIR is not less than the lower limit value #QAIRPHL and not more than the upper limit value #QAIRPHH. judge. If the determination result is “NO”, the determination process for determining whether the purge concentration is high is terminated, and if “YES”, the process proceeds to step SX12.
[0093]
In step SX6 and step SX12, it is determined whether the purge correction coefficient KAFEVACT is equal to or less than a predetermined upper limit value. Note that the magnitude relationship between these upper limit values is #PGCJUDL (for example, 0.10)># PGCJUDH (for example, 0.05).
Further, the purge correction coefficient KAFEVACT is set in step SR6 of FIG. 16 described later.
[0094]
In any of step SX6 and step SX12, if the determination result is “YES”, the process proceeds to step SX7, and if “NO”, the process proceeds to step SX13.
In step SX7, “1” indicating permission of learning of the air-fuel ratio is set as the flag value of flag F_PKTIMOM. In step SX13, “0” indicating that learning of the air-fuel ratio is prohibited is set as the flag value of flag F_PKTIMOMOK. Thus, the determination process for determining whether the barge density is high is completed.
[0095]
Next, a main flow for controlling the purge control valve 44 so that the purge flow rate becomes the optimum flow rate will be described based on the flowchart of FIG. This main flow is executed every 80 ms.
First, in step SV1, an air flow rate QAIR calculation process is performed. This air flow rate QAIR is calculated according to the following equation.
[0096]
Air flow rate QAIR =
Basic fuel injection amount TIM x engine speed NE x 2 x coefficient #KQAIR
In step SV2, it is determined whether “1” indicating that purge is being performed is set in the flag value of the flag F_PGACT. When the determination result is “NO”, that is, when the purge is stopped, the process proceeds to step SV21, and “0%” indicating full closure is set to the purge control valve drive duty value DOUTPGC.
[0097]
Next, in step SV22, the initial value #KPGTINI is set in the canister purge control throttle coefficient KPGT, and the control process of the purge control valve 44 is ended.
If the determination result in step SV2 is “YES”, that is, if purge is being performed, the process proceeds to step SV3, and it is determined whether the flag value of the flag F_FC is “1” indicating that the fuel cut is being performed.
[0098]
If the determination result in step SV3 is “YES”, that is, if the fuel cut is being performed, the process proceeds to step SV11, and the initial value #KPGTINI is set in the canister purge control throttle coefficient KPGT.
Next, in step SV12, the purge control valve drive duty value DOUTPGC is set to “0%” indicating full closure, and the control process of the purge control valve 44 is terminated.
[0099]
If the determination result in step SV3 is “NO”, that is, if the fuel cut is not being performed, the process proceeds to step SV4 to calculate the target purge control valve drive duty value PGCMD of the purge control valve 44 so as to achieve the target purge flow rate. .
The calculation process of the target purge control valve drive duty value PGCMD will be described later with reference to FIG.
[0100]
In step SV5, the target purge control valve drive duty value PGCMD calculated in step SV4 is set to the purge control valve drive duty value DOUTPGC.
In step SV6, a value obtained by dividing the target purge flow rate QPGC by the target purge flow rate basic value QPGCBASE is set to the purge flow rate ratio QRATE, and the control process of the purge control valve 44 is ended.
[0101]
Next, the calculation process of the target purge control valve drive duty value PGCMD executed in step SV4 of FIG. 14 will be described based on the flowchart of FIG.
First, in step ST1, a value obtained by multiplying the air flow rate QAIR by a predetermined target purge rate #KQPGB is set as a target purge flow rate basic value QPGCBASE.
[0102]
Next, the target purge flow rate basic value QPGCBASE is limited. Specifically, first, in step ST2, it is determined whether the target purge flow rate basic value QPGCBASE is larger than a predetermined purge flow rate upper limit value #QPGMAX. If the determination result is “YES”, the process proceeds to step ST11, and the purge flow rate upper limit value #QPGMAX is set to the target purge flow rate value QPGCMD.
[0103]
On the other hand, if the determination result in step ST2 is “NO”, the process proceeds to step ST3, where the target purge flow rate basic value QPGCBASE is set to the target purge flow rate value QPGCMD.
The case where the target purge flow rate value QPGCMD is set in step ST3 is “intake air amount proportional purge”, and the purge flow rate ratio QRATE is “1”. Further, when the target purge flow rate value QPGCMD is set in step ST11, the “purge flow rate constant purge” is set, and the purge flow rate ratio QRATE is a value smaller than “1”.
[0104]
In step ST4, the value set in the canister purge control throttle coefficient KPGT is incremented by a predetermined addition value #DKPGT. Thereby, the purge amount is gradually increased as time passes.
The process of step ST4 is executed by the purge flow rate calculation unit 61 corresponding to the purge limiting means of the present invention.
[0105]
Next, limit processing of the canister purge control throttle coefficient KPGT is performed. Specifically, first, in step ST5, it is determined whether or not the canister purge control throttle coefficient KPGT is larger than “1.0”. If the determination result is YES, the process proceeds to step ST6 and the canister purge control throttle coefficient is determined. Set “1.0” to KPGT. On the other hand, when the determination result of step ST5 is “NO”, step ST6 is skipped.
[0106]
In step ST7, a value obtained by multiplying the target purge flow rate value QPGCMD set in step ST3 or step ST11 by the canister purge control throttle coefficient KPGT calculated in step ST4 is set in the target purge flow rate value QPGC. .
[0107]
Next, in step ST8, a process for converting the purge flow rate into a duty value is executed, and the target purge control valve drive duty value PGCMD calculation process is terminated. In this conversion processing, a value obtained by multiplying the target purge flow rate QPGC by a predetermined coefficient #KDUTY and further dividing this by the differential pressure KDPBG is set as the target purge control valve drive duty value PGCMD. The differential pressure KDPBG is obtained by searching a correlation table with the intake pipe absolute pressure.
[0108]
Next, a calculation process for calculating the purge correction coefficient KAFEVACT used in the determination process of step SX6 and step SX12 of FIG. 13 will be described based on the flowchart of FIG.
[0109]
First, in step SR1, it is determined whether or not “1” indicating that feedback control is being performed is set in the flag value of the flag F_AFFB. If the determination result is “YES”, that is, if feedback control is being performed, the process proceeds to step SR21.
[0110]
In step SR21, it is determined whether the value obtained by subtracting DKAFEXL from the air-fuel ratio learned value KREFX during the purge stop is greater than the air-fuel ratio feedback coefficient KO2. If the determination result is “YES”, the process proceeds to step SR22, and the purge concentration is higher than the estimated value, so the predetermined addition value #DKEVAPOP is incremented to the purge concentration coefficient KAFEV.
[0111]
On the other hand, if the determination result in step SR21 is “NO”, the process proceeds to step SR23, and the value obtained by adding DKAFEVXH to the air-fuel ratio learning value KREFX being purged is obtained from the air-fuel ratio feedback coefficient KO2. Is also determined to be small. If the determination result is “YES”, the process proceeds to step SR24, and since the purge concentration is thinner than the estimated value, the predetermined subtraction value #DKEVAPOM is decremented from the purge concentration coefficient KAFEV.
[0112]
When the determination result in step SR1 is “NO”, that is, when the feedback control is not being performed, the purge concentration coefficient KAFEV is limited.
Specifically, first, in step SR3, it is determined whether the purge concentration coefficient KAFEV is greater than “0”. If the determination result is “NO”, the process proceeds to step SR4, and “0” is set to the purge concentration coefficient KAFEV.
[0113]
On the other hand, if the decision result in the step SR3 is “YES”, the process advances to a step SR31 to determine whether the purge concentration coefficient KAFEV is larger than a predetermined limit value #KAFEVLMT. If the determination result is “YES”, the process proceeds to step SR32, and the limit value #KAFEVLMT is set to the purge concentration coefficient KAFEV. On the other hand, if the determination result in step SR31 is “NO”, step SR32 is skipped.
[0114]
Next, in step SR5, a target purge correction coefficient KAFEVACZ is calculated. This target purge correction coefficient KAFEVACZ is calculated according to the following equation.
Target purge correction coefficient KAFEVACZ
= Purge concentration coefficient KAFEV × Purge flow rate ratio QRATE
The processing of step SR5 is executed by the purge concentration estimation unit 62 corresponding to the purge concentration estimation means of the present invention.
[0115]
The purge concentration coefficient KAFEV is set in step SR4 or step SR32 of this flow, and the purge flow rate ratio QRATE is set in step SV6 of FIG. 14 described above.
In step SR6, the target purge correction coefficient KAFEVACZ calculated in step SR5 is set to the purge correction coefficient KAFEVACT, and the calculation process for calculating the barge correction coefficient KAFEVACT ends.
The fuel injection amount is corrected to decrease using the barge correction coefficient KAFEVACT calculated here.
[0116]
In the above embodiment, when the purge amount is limited at the beginning of the purge and after a predetermined time, the learning permission is not determined by the learning permission means, and the learning permission / I try to determine the disapproval.
As a result, when the purge amount is limited more than usual, a deviation occurs between the actual purge concentration and the estimated purge concentration. Based on this estimated purge concentration, a learning permission determination is made and the air-fuel ratio is determined. It is possible to effectively prevent erroneous learning of the air-fuel ratio, and the learning value of the air-fuel ratio can be calculated with high accuracy.
[0117]
In the above embodiment, the case where the intake air amount correlation value NTI obtained from the basic fuel injection amount TIM and the engine speed Ne is used has been described as an example, but instead of this intake air amount correlation value NTI, Of course, another intake air amount correlation value may be used, or a sensor for directly detecting the intake air amount of the internal combustion engine may be provided, and the intake air amount detected by this sensor may be used in place of the intake air amount correlation value NTI. Is possible.
[0118]
In the above embodiment, the case where the upstream O2 sensor 17 detects the air-fuel ratio has been described as an example, but it is also possible to detect the air-fuel ratio using a linear A / F sensor instead.
[0119]
【The invention's effect】
As described above in detail, according to the present invention, when the estimated purge concentration value shows the actual purge concentration, it is determined from the estimated purge concentration value that the influence of the purge is small, and the influence of the purge is small. Therefore, learning is permitted when it is determined that it is possible to calculate the learning value with high accuracy while preventing the influence of purge.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a control system according to an embodiment of the present invention.
FIG. 3 is a flowchart showing the contents of control of fuel injection control according to one embodiment of the present invention.
FIG. 4 is a diagram schematically showing an air-fuel ratio learning value map according to one embodiment of the present invention.
FIG. 5 is a diagram for explaining interpolation calculation of an air-fuel ratio learning value according to an embodiment of the present invention.
FIG. 6 is a diagram schematically showing an atmospheric pressure correction table used for correcting an air-fuel ratio learning value according to an embodiment of the present invention.
FIG. 7 is a flowchart showing the contents of control of calculation processing of an air-fuel ratio feedback coefficient according to one embodiment of the present invention.
FIG. 8 is a timing chart showing an output (a) of an O2 sensor and a state (b) of a flag F_PVREF according to an embodiment of the present invention.
FIG. 9 is a timing chart showing a value (a) of an air-fuel ratio feedback coefficient KO2 and a state (b) of a flag F_PVREF according to one embodiment of the present invention.
FIG. 10 is a flowchart showing a part of the control content of the calculation process of the air-fuel ratio learning value according to the embodiment of the present invention.
FIG. 11 is a flowchart showing the remaining part of the control content of the air-fuel ratio learning value calculation process according to one embodiment of the present invention (continuation of FIG. 10).
FIG. 12 is a flowchart showing the remaining part of the control content of the air-fuel ratio learning value calculation process according to one embodiment of the present invention (continuation of FIG. 11).
FIG. 13 is a flowchart showing the control contents of a determination process for determining whether the barge density is high or not, which is executed in step SW5 of FIG. 11;
FIG. 14 is a flowchart showing the contents of control of the purge control valve so that the purge flow rate becomes an optimum flow rate.
FIG. 15 is a flowchart showing the control content of a target purge control valve drive duty value calculation process executed in step SV4 of FIG. 14;
FIG. 16 is a flowchart showing control details of a purge correction coefficient calculation process used in the determination process of step SX6 and step SX12 of FIG. 13;
FIG. 17 is a threshold value table for determining permission to execute update storage of learning values used in the calculation processing of air-fuel ratio learning values according to one embodiment of the present invention.
[Explanation of symbols]
10 Intake pipe absolute pressure sensor (operating state detection means)
14 Rotation information sensor (operating state detection means)
17 Upstream O2 sensor (air-fuel ratio detection means)
44 Purge control valve (Purge control means)
51 Air-fuel ratio F / B coefficient calculation unit (feedback control means)
53 Air-fuel ratio learning value storage (air-fuel ratio learning value calculation means)
54 Basic fuel injection amount calculation unit (basic fuel amount calculation means)
55 Fuel injection amount calculation unit (fuel supply amount calculation means)
58 Air-fuel ratio learning execution determination unit (learning permission means)
61 Purge flow rate calculation unit (Purge limiting means)
62 Purge concentration estimation unit (purge concentration estimation means, learning permission judgment prohibition means)

Claims (1)

An operating state detecting means for detecting an operating state of the internal combustion engine;
Basic fuel amount calculating means for calculating a basic fuel amount supplied to the internal combustion engine according to the operating state;
An air-fuel ratio detecting means provided in an exhaust system of the internal combustion engine for detecting an air-fuel ratio in the exhaust;
Feedback control means for calculating an air-fuel ratio correction amount for controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine in accordance with the output of the air-fuel ratio detection means;
Air-fuel ratio learning value calculating means for calculating a learning value of the air-fuel ratio correction amount;
A fuel supply amount control device for an internal combustion engine, comprising: a fuel supply amount calculation means for calculating a fuel amount supplied to the internal combustion engine in accordance with the basic fuel amount, the air-fuel ratio correction amount, and the air-fuel ratio learning value;
Purge control means for controlling the amount of purge supplied to the intake system of the internal combustion engine;
Purge concentration estimation means for estimating the concentration of the evaporated fuel by the purge control means based on the air-fuel ratio correction amount;
Learning permission means for permitting calculation of the air-fuel ratio learning value when a value related to the concentration of the evaporated fuel estimated by the purge concentration estimating means is less than or equal to a predetermined value ;
Air flow detection means;
Target purge flow rate basic value calculating means for calculating a target purge flow rate basic value by multiplying the air flow rate by a predetermined target purge rate;
When it is determined that the target purge flow basic value is greater than the predetermined limit value, the predetermined limit value is set as the first target purge flow value, and the target purge flow basic value is determined to be equal to or less than the predetermined limit value. Limit value setting means for setting the target purge flow rate basic value to the first target purge flow rate value;
Purge purge coefficient setting means for setting the purge throttle coefficient so as to gradually increase until the first target purge flow rate value with the passage of time after the start of purge;
Purge flow rate calculation means for calculating a second target purge flow rate value by multiplying the first target purge flow rate value by the purge throttle coefficient;
A purge limiting means for limiting a purge amount based on the second target purge flow value obtained by limiting the first target purge flow value by the purge throttle coefficient when the purge is started by the purge control means;
Timer means for setting a predetermined time together with the start of limiting the purge amount ;
A learning permission determination prohibiting unit that does not perform a learning permission determination by the learning permission unit until the purge limit is finished by the purge limiting unit and the predetermined time has elapsed;
A purge flow ratio calculation means for calculating a purge flow ratio by dividing the second target purge flow value by the target purge flow basic value;
After the purge amount restriction by the purge restriction unit is completed and the predetermined time has elapsed, the learning permission unit is configured to perform the learning based on the predetermined value set to a different value according to the purge flow rate ratio. A fuel supply amount control apparatus for an internal combustion engine, wherein the determination is made by a learning permission means .

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