JP2001173485A - Fuel injection control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve dispersion in an air-fuel ratio between cylinder under an influence of canister purge, and to make the air-fuel ratio of all cylinders uniform. SOLUTION: Which of right and left cylinders is examined to be the object for the present fuel injection calculation (S202), a fuel distribution correcting coefficient KFBD established from a basic distribution correcting coefficient KFBDB for compensating a basic different in an intake air distribution rate between cylinders, and a canister purge distribution correcting coefficient KCPDB for compensating a different in a distribution rate between cylinders of evaporated gas supplied by evaporated purging, is made to be smaller than the cylinder in a left bank side, with reference to the cylinder in a right bank side which relatively tends to enrich (S203, S204). A basic injection pulse width Tp is corrected with the fuel distribution correcting coefficient KFBD and another correcting coefficient to establish a fuel injection pulse width Ti (S205 to S207). Therefore, the amount of fuel to the cylinder in the right bank side is relatively decreased to be smaller than the cylinder in the left bank side, thereby resolving variations of an air-fuel ratio between cylinders owing to the differences in the intake air distribution rate and the evaporated gas distribution rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an engine for eliminating variations in air-fuel ratio between cylinders.

[0002]

2. Description of the Related Art Conventionally, in the air-fuel ratio control of an engine, one air-fuel ratio sensor is provided in a collective portion of an exhaust passage, and the detection result of this one air-fuel ratio sensor, that is, the average air-fuel ratio of all cylinders, A system that performs feedback control as a target is generally employed. In such a system, there is a problem that the air-fuel ratio varies among the cylinders due to a difference in intake characteristics between the cylinders.

To cope with this, Japanese Patent Laid-Open Publication No. Hei 6-2008
No. 09 discloses an oxygen sensor (air-fuel ratio sensor) for detecting an average air-fuel ratio in an exhaust duct where exhaust manifolds are gathered, and an air-fuel ratio of each cylinder is detected in an exhaust manifold of each cylinder. The air-fuel ratio of each cylinder is compared by comparing each time when the average air-fuel ratio is controlled to be rich and lean with respect to the target air-fuel ratio and the rich and lean time of each cylinder. A technology has been disclosed which detects a shift in the air-fuel ratio and corrects the air-fuel ratio for each cylinder based on the detected shift.

Japanese Patent Application Laid-Open No. 9-49451 discloses that when controlling the fuel supply amount by using a smaller number of air-fuel ratio sensors than the number of cylinders, one of a plurality of cylinders is used as a reference cylinder. The difference between the fuel supply characteristic for the reference cylinder and the fuel supply characteristic for each cylinder other than the reference cylinder is detected as a correction value for each cylinder, and the fuel supply characteristic for the cylinder is determined by the detected correction value for each cylinder. By correcting,
A technique is disclosed in which the air-fuel ratio of each cylinder is controlled to be equal to the average air-fuel ratio.

[0005]

However, the prior art does not consider the difference in the distribution ratio of the evaporative gas supplied by the canister purge between the cylinders, and when the canister purge is not performed, the air-fuel ratio variation of each cylinder is not considered. However, once the canister purge is executed, the difference in the distribution characteristics of the evaporative gas becomes a disturbance, and the air-fuel ratio between the cylinders fluctuates. There is a possibility that the running performance may be degraded due to a surge or the like due to a variation in fuel ratio, or idle vibration may be induced.

The present invention has been made in view of the above circumstances, and has been made in view of the above circumstances. A fuel injection control device for an engine capable of eliminating variations in the air-fuel ratio between cylinders due to the influence of a canister purge and making the air-fuel ratio uniform in all cylinders. It is intended to provide.

[0007]

In order to achieve the above object, the present invention is directed to a basic distribution correction for compensating for a difference in basic intake distribution ratio between cylinders due to an intake characteristic of an engine. A basic distribution correction coefficient setting means for setting a coefficient, a canister purge distribution correction coefficient setting means for setting a canister purge distribution correction coefficient for compensating for a difference in distribution rate between cylinders of the evaporative gas supplied by the canister purge, Fuel distribution correction coefficient setting means for correcting the fuel injection amount for each bank or cylinder by using the basic distribution correction coefficient and the canister purge distribution correction coefficient to set a fuel distribution correction coefficient for compensating for variations in the air-fuel ratio; The fuel injection amount set based on the engine operation state is corrected by the fuel distribution correction coefficient, and the final fuel injection amount for the engine is adjusted. Characterized in that a fuel injection quantity setting means for setting the amount.

According to a second aspect of the present invention, in the first aspect of the present invention, the basic distribution correction coefficient setting means corresponds to the basic state of the engine corresponding to an engine warm-up completion state and an engine operating state excluding a high load region. It is characterized in that a distribution correction coefficient is set.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the canister purge distribution correction coefficient setting means is configured to perform non-idle operation under an operating state in which compensation by the basic distribution correction coefficient is performed. The canister purge distribution correction coefficient is determined according to the operating state in which it is determined that the evaporative gas purge is being performed based on the open / close state of the actuator that adjusts the purge amount of the canister purge and the air-fuel ratio state. It is characterized by setting.

[0010] The invention according to claim 4 is the invention according to claims 1, 2, 3
In the invention according to any one of the above, the canister purge distribution correction coefficient setting means may include a distribution coefficient preset as a basic value for compensating for a difference in a distribution ratio between the cylinders of the evaporative gas when the canister purge is performed, The canister purge distribution correction coefficient is corrected by a canister purge distribution correction feedback value set by weighted averaging of the air-fuel ratio feedback correction coefficient.

That is, according to the present invention, a basic distribution correction coefficient for compensating for a difference in the basic intake distribution ratio between the cylinders due to the intake characteristics of the engine, and the amount of the evaporative gas supplied by the canister purge. A canister purge distribution correction coefficient for compensating for the difference in the distribution ratio between cylinders is set, and the air-fuel ratio is corrected by correcting the fuel injection amount for each bank or cylinder using the basic distribution correction coefficient and the canister purge distribution correction coefficient. A fuel distribution correction coefficient for compensating for the variation in Then, the fuel injection amount set based on the engine operating state is corrected by the fuel distribution correction coefficient to set the final fuel injection amount for the engine, thereby eliminating the air-fuel ratio variation between cylinders.

In this case, the invention according to claim 2 sets the basic distribution correction coefficient in accordance with the engine warm-up completion state and the engine operating state excluding the high load region. Evaporation gas is reliably purged based on the open / closed state of the actuator that adjusts the purge amount of the canister purge and the air-fuel ratio state in an operating state in which the canister purge distribution correction coefficient is compensated by the basic distribution correction coefficient. Is set in accordance with the operation state in which it is determined that is performed.

Further, according to the present invention, the distribution coefficient preset as a basic value for compensating for the difference in the distribution ratio between the cylinders of the evaporative gas during the canister purge is weighted by the air-fuel ratio feedback correction coefficient. The canister purge distribution correction coefficient is set by performing correction using the canister purge distribution correction feedback value set on average.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 12 relate to a first embodiment of the present invention. FIG. 1 is a flowchart of a cylinder discrimination / engine speed calculation routine, FIG. 2 is a flowchart of a fuel injection control routine, and FIG. 3 is a basic distribution correction coefficient setting routine. FIG. 4 is a flowchart of a canister purge distribution correction coefficient setting routine; FIG. 5 is a flowchart of an air-fuel ratio feedback correction coefficient setting routine;
6 is an explanatory diagram of basic distribution correction conditions, FIG. 7 is a time chart showing the relationship between canister purge, air-fuel ratio for each cylinder, and air-fuel ratio feedback correction coefficient, and FIG. 8 is a crank pulse, cylinder discrimination pulse, combustion stroke cylinder. FIG. 9 is a schematic diagram of an engine control system, FIG. 10 is a front view of a crank rotor and a crank angle sensor, and FIG. 11 is a front view of a cam rotor and a cylinder discrimination sensor. FIG. 12 is a circuit diagram of the electronic control system.

First, the overall structure of the engine will be described with reference to FIG. In this figure, reference numeral 1 denotes an engine, and in this embodiment, a cylinder block 1a is divided into two banks (a left bank on the right side and a right bank on the left side) on both sides of the crankshaft 1b, and the cylinder block 1a is divided into right banks. 1 shows a horizontally opposed four-cylinder engine in which # 1 and # 3 cylinders are arranged and # 2 and # 4 cylinders are arranged in a left bank.

A cylinder head 2 is provided in each of the left and right banks of the cylinder block 1a of the engine 1.
Each cylinder head 2 has an intake port 2a and an exhaust port 2
b is formed. An intake manifold 3 is communicated with the intake port 2a.
A throttle chamber 5 is communicated via an air chamber 4 in which intake passages of the respective cylinders are gathered. An air cleaner 7 is mounted on an upstream side of the throttle chamber 5 via an intake pipe 6 and communicates with an air intake chamber 8. .
In addition, an exhaust manifold 9 is provided in the exhaust port 2b.
An exhaust pipe 10 communicates with the exhaust pipe 10, and a catalytic converter 11 is interposed in the exhaust pipe 10 and communicates with a muffler 12.

The throttle chamber 5 is provided with a throttle valve 5a linked to an accelerator pedal, and a bypass passage 13 for bypassing the throttle valve 5a is branched from the intake pipe 6. The bypass passage 13 is provided with an idle speed control valve (ISC valve) 14 for controlling the idle speed by adjusting the amount of bypass air flowing through the bypass passage 13 at the time of idling. The ISC valve 14
In the present embodiment, an electronic control unit 50 described later (see FIG. 12)
The valve opening is adjusted according to the duty ratio of the control signal output from the controller.

Further, an injector 15 is disposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3, and communicates with a fuel tank 17 via a fuel supply path 16. An in-tank type fuel pump 18 is provided in the fuel tank 17, and fuel from the fuel pump 18
The fuel is fed to the injector 15 and the pressure regulator 20 through the fuel filter 19 interposed in the fuel supply passage 16 and returned to the fuel tank 17 from the pressure regulator 20 to regulate the fuel pressure to the injector 15 to a predetermined pressure. Is done.

Further, from the upper portion of the fuel tank 17, a discharge passage 21 for discharging the fuel vapor generated in the fuel tank 17 extends, and an adsorbing portion made of activated carbon or the like is provided via a two-way valve 22. The canister 23 communicates with an upper portion of the canister 23. The canister 23 is provided with a fresh air introduction port communicating with the atmosphere at a lower portion, and a purge passage 24 for introducing a mixture (evaporation gas) of fresh air from the fresh air introduction port and the evaporated fuel gas stored in the adsorption section. It extends from the top.

The purge passage 24 is provided with a canister purge control (CPC) duty solenoid valve 25 as an actuator for adjusting the purge amount of the evaporative gas in the middle of the purge passage 24, and the right side of the air chamber 4 downstream of the throttle valve 5 a. It is connected to the bank side and opened. The CPC duty solenoid valve 25 is
Similar to the ISC valve 14, an electronic control unit 50 (see FIG.
) Is adjusted in accordance with the duty ratio of the control signal output from the control signal output from the second control signal.

On the other hand, an ignition plug 26 for exposing a discharge electrode at the tip to the combustion chamber 1c is attached to each cylinder of the cylinder head 2, and an igniter 28 is attached to the ignition plug 26.
Is connected to an ignition coil 27.

Next, sensors for detecting the operating state of the engine will be described. Air cleaner 7 for intake pipe 6
A thermal intake air amount sensor 30 using a hot wire or a hot film or the like is interposed directly downstream of the throttle valve 5.
A throttle sensor 31 having a built-in throttle opening sensor 31a and an idle switch 31b that is turned on when the throttle is fully closed is provided in series.

The cylinder block 1a of the engine 1
A knock sensor 32 is mounted on the cooling water passage 33. A cooling water temperature sensor 34 faces a cooling water passage 33 communicating the left and right banks of the cylinder block 1a. An O2 sensor 35 is provided upstream of the catalytic converter 11.

The crankshaft 1b of the engine 1
A crank angle sensor 37 is provided on the outer periphery of a crank rotor 36 which is axially mounted on the cam shaft 1d. A cylinder discriminating sensor 39 for discriminating a fuel injection target cylinder and an ignition target cylinder is provided in opposition.

As shown in FIG. 10, the crank rotor 36 has projections 36a, 36b, 36c formed on its outer periphery, and these projections 36a, 36b, 36c are connected to the cylinders (# 1, # 2 and # 2, respectively). 3, # 4 cylinder) before compression top dead center (BTDC) θ1, θ2, θ3. In the present embodiment, θ1 = 97 ° CA, θ2
= 65 ° CA, θ3 = 10 ° CA.

Further, as shown in FIG.
8 are provided on the outer periphery of the projections 38a, 38b, 38 for cylinder discrimination.
c, the projection 38a is formed at a position θ4 after the compression top dead center (ATDC) of the # 3 and # 4 cylinders, the projection 38b is composed of three projections, and the first projection is the ATD of the # 1 cylinder.
It is formed at the position of Cθ5. Further, when the projection 38c is 2
ATDC of # 2 cylinder
It is formed at the position of θ6. In the present embodiment, θ4 = 20 ° CA, θ5 = 5 ° CA, θ6 = 20 °
CA.

As shown in the time chart of FIG. 8, the crank rotor 36 and the cam rotor 38 are rotated by the rotation of the crankshaft 1b and the camshaft 1d along with the operation of the engine. 37, θ1, θ2, θ3 (BTDC 97 °, 65
, 10 °) is output every 1/2 engine revolution (180 ° CA). On the other hand, each projection of the cam rotor 38 is detected by the cylinder discrimination sensor 39 between the θ3 crank pulse and the θ1 crank pulse, and a predetermined number of cylinder discrimination pulses are output from the cylinder discrimination sensor 39.

An electronic control unit 50 (FIG. 1)
2), the engine rotation speed (engine speed) NE is calculated based on the input interval time Tθ of the crank pulse output from the crank angle sensor 37, and the combustion stroke of each cylinder (for example, # 1 cylinder) → # 3 cylinder → # 2
The current combustion stroke cylinder, fuel injection target cylinder, and ignition target cylinder are determined based on a pattern of (cylinder → # 4 cylinder) and a value obtained by counting a cylinder determination pulse from the cylinder determination sensor 39 by a counter.

Next, an electronic control unit (ECU) 50 for electronically controlling the engine 1 will be described with reference to FIG. The ECU 50 includes a CPU 51, a ROM 52, a RAM 5
3. Backup RAM 54, counter / timer group 5
And a constant voltage circuit 5 for supplying a stabilized power supply to each unit, mainly comprising a microcomputer having an I / O interface 56 connected to each other via a bus line.
7. A peripheral circuit such as a drive circuit 58 and an A / D converter 59 connected to the I / O interface 56 is built in.

The counter / timer group 55 generates various counters such as a free-run counter, a counter for counting the input of a cylinder discrimination sensor signal (cylinder discrimination pulse), a fuel injection timer, an ignition timer, and a periodic interrupt. Timers such as a timer for periodic interruption, a timer for measuring an input interval of a crank angle sensor signal (crank pulse), and a watchdog timer for monitoring a system abnormality are collectively referred to for convenience. A timer is used.

The constant voltage circuit 57 is connected to the battery 61 via the first relay contact of the power supply relay 60 having two relay contacts, and is also directly connected to the battery 61. When the switch is turned on and the contact of the power supply relay 60 is closed, power is supplied to each unit in the ECU 50, while the ignition switch 62 is turned on.
Irrespective of ON / OFF of the backup RAM5
4 is supplied with power for backup. Further, the fuel pump 18 is connected to the battery 61 via a relay contact of the fuel pump relay 63. The power supply relay 60
A power supply line for supplying power from the battery 61 to each actuator is connected to the second relay contact.

The input port of the I / O interface 56 is connected to an ignition switch 62, an idle switch 31b, a knock sensor 32, a crank angle sensor 37, a cylinder discriminating sensor 39, a vehicle speed sensor 40 for detecting a vehicle speed, and the like. The A / D converter 59
, The intake air amount sensor 30, the throttle opening sensor 31a, the cooling water temperature sensor 34, the O2 sensor 35, and the like are connected, and the battery voltage VB is input and monitored.

On the other hand, the output port of the I / O interface 56 has a relay coil of the fuel pump relay 63,
The SC valve 14, the injector 15, the CPC duty solenoid valve 25, and the like are connected via a drive circuit 58, and the igniter 28 is connected.

In the CPU 51, the I / O interface 5 is controlled in accordance with the control program stored in the ROM 52.
The detection signal from the sensors and switches, the battery voltage, etc., which are input via the CPU 6, are processed, and various data stored in the RAM 53 and various learning value data stored in the backup RAM 54 are stored in the ROM 52. The fuel injection amount for each cylinder, the ignition timing for each cylinder, the control duty for the ISC valve 14,
The control duty for the PC duty solenoid valve 25 is calculated, and engine control such as fuel injection control for each cylinder, ignition timing control for each cylinder, idle speed control, and canister purge control is performed.

Here, in the horizontally opposed four-cylinder engine 1 of the present embodiment, each cylinder (# 1, # 3 cylinder) on the right bank side becomes each cylinder on the left bank side due to structural intake characteristics and the like. (# 2, # 4 cylinders), the intake air distribution ratio is lower than that of the left bank side cylinders (# 1, # 3 cylinders) as shown by the broken line in FIG. (# 2, # 4 cylinders)
Tend to be relatively richer than the air-fuel ratio. Further, the purge passage 24 is connected to the right bank side of the air chamber 4 due to restrictions on mounting conditions and the like. Therefore, when executing the canister purge, each cylinder on the left bank side is connected to each cylinder on the right bank side. The distribution rate of evaporative gas increases,
The air-fuel ratio of each cylinder on the right bank side becomes relatively richer than the air-fuel ratio of each cylinder on the left bank side, and when purging is performed, the variation in the air-fuel ratio among the cylinders further increases as indicated by the broken line in FIG. there's a possibility that.

For this reason, in the fuel injection control by the ECU 50, a fuel correction coefficient for compensating for a difference in the basic intake distribution ratio between the cylinders due to the structural intake characteristic of the engine 1 and the fuel correction coefficient are supplied by an evaporative purge. A basic distribution correction coefficient KFBDB and a canister purge distribution correction coefficient KCPDB are defined as fuel correction coefficients for compensating for the difference in the distribution ratio of the evaporative gas between cylinders, and the fuel injection amount is corrected by these correction coefficients KFBDB and KCPDB. Then, a fuel distribution correction coefficient KFBD for compensating the variation in the air-fuel ratio between the cylinders is set.

Then, the fuel injection amount set based on the engine operating state is corrected by a fuel distribution correction coefficient KFBD, which is caused by a difference in intake distribution between cylinders and a difference in distribution of evaporative gas between cylinders during canister purging. Then, the air-fuel ratios of the cylinders of the right bank, which are made richer relative to the cylinders of the left bank, are compensated, and the air-fuel ratios of all the cylinders are made uniform.

That is, the ECU 50 includes functions as basic distribution correction coefficient means, canister purge distribution correction coefficient setting means, fuel distribution correction coefficient setting means, and fuel injection amount setting means according to the present invention. The function of each means is realized by the routines shown in FIGS.

Hereinafter, processing relating to fuel injection control by the ECU 40 will be described with reference to the flowcharts shown in FIGS.

First, the ignition switch 62 is turned on.
Then, when the power is supplied to the ECU 50, the system is initialized, and each flag and each counter are initialized except for data such as various learning values stored in the backup RAM 54. Then, when the engine is started, a cylinder discrimination / engine speed calculation routine shown in FIG. 1 is executed every time a crank pulse is input from the crank angle sensor 37.

In this cylinder discriminating / engine rotational speed calculating routine, when the crank rotor 36 rotates with the engine operation and a crank pulse is input from the crank angle sensor 37, first, in step S101, the presently input crank is input. Which of the crank angles θ1, θ2, and θ3 the pulse corresponds to is determined based on the input pattern of the cylinder discrimination pulse from the cylinder discrimination sensor 39, and step S
At 102, the cylinders such as the current combustion stroke cylinder, the ignition target cylinder, and the fuel injection target cylinder are determined from the input pattern of the crank pulse and the cylinder determination pulse.

That is, as shown in the time chart of FIG. 8, for example, if there is a cylinder discrimination pulse input between the input of the previous crank pulse and the input of the current crank pulse, the current crank pulse is The crank pulse can be identified as a θ1 crank pulse, and the crank pulse input next time can be identified as a θ2 crank pulse.

If there is no cylinder discrimination pulse input between the previous and current crank pulse inputs, and there is a cylinder discrimination pulse input between the last and previous crank pulse inputs, the current crank pulse is equal to the θ2 crank pulse. The crank pulse input next time can be identified as the θ3 crank pulse. Further, when there is no cylinder discrimination pulse input between the previous and current times, and between the last and last crank pulse inputs, the currently input crank pulse can be identified as the θ3 crank pulse, and the next input crank pulse can be identified. The pulse can be identified as a θ1 crank pulse.

Here, in the four-cycle four-cylinder engine 1 according to the present embodiment, the combustion stroke is # 1 → # 3 → # 2
As shown in the time chart of FIG. 8, the cylinder to be ignited reaches the compression top dead center with respect to the current (current) combustion stroke cylinder #i at the time of output of the cylinder discrimination pulse.
The (i + 1) cylinder, the fuel injection target cylinder at this time, is the # (i + 3) cylinder that is two cylinders later.

Accordingly, when three cylinder discrimination pulses are input (the θ5 cylinder discrimination pulse corresponding to the projection 38b) between the previous and current crank pulse inputs, the next top dead center of the compression is # 3 cylinder, and It can be determined that the combustion stroke cylinder is # 1 cylinder, the ignition target cylinder is # 3 cylinder, and the fuel injection target cylinder is # 4 cylinder, two cylinders after it. When two cylinder discrimination pulses are input between the previous and current crank pulse inputs (the θ6 cylinder discrimination pulse corresponding to the projection 38c), the next compression top dead center is # 4 cylinder, and the current combustion stroke cylinder is Can be determined as cylinder # 2, the cylinder to be ignited is cylinder # 4, and the cylinder to be injected with fuel is cylinder # 3.

If one cylinder discrimination pulse is input between the previous and current crank pulse inputs (the .theta.4 cylinder discrimination pulse corresponding to the projection 38a) and the previous compression top dead center discrimination is for the # 4 cylinder. The next compression top dead center is # 1 cylinder, the current combustion stroke cylinder is # 4 cylinder, and the ignition target cylinder is #
One cylinder and the fuel injection cylinder can be determined to be # 2 cylinders. Similarly, when one cylinder discrimination pulse is input between the previous and current crank pulse inputs and the previous compression top dead center determination was # 3 cylinder, the next compression top dead center is # 2 cylinder, The current combustion stroke cylinder can be determined as # 3 cylinder, the ignition target cylinder is # 2 cylinder, and the fuel injection target cylinder is # 1 cylinder.

Thereafter, from step S102 to step S
Proceeding to 103, the time from the previous crank pulse input to the present crank pulse input measured by the crank pulse input interval timer is read, and the crank pulse input interval time Tθ (the input interval time between the θ1 crank pulse and the θ2 crank pulse) is read. Tθ12, the input interval time Tθ23 between the θ2 crank pulse and the θ3 crank pulse, or the input interval time Tθ31 between the θ3 crank pulse and the θ1 crank pulse) is detected.

Then, the process proceeds to a step S104, in which the angle between the crank pulses corresponding to the crank pulse identified this time is read, and the current engine speed NE is calculated based on the angle between the crank pulses and the crank pulse input interval time Tθ. Is stored at a predetermined address in the RAM 53 and the processing exits from the routine.

Incidentally, the angle between the crank pulses is known,
In the present embodiment, the angle between the θ1 crank pulse and the θ2 crank pulse is 32 ° CA, and the angle between the θ2 crank pulse and the θ3 crank pulse is 55 ° C.
A, The angle between the θ3 crank pulse and the θ1 crank pulse is 93 ° CA.

Then, the result of the cylinder discrimination of the current combustion stroke cylinder is referred to in the fuel injection control routine of FIG. 2 executed at predetermined intervals, and the respective data of the combustion stroke cylinder and the engine speed NE are read out. The fuel injection pulse width Ti that determines the fuel injection amount corresponding to the relevant combustion stroke cylinder is set, and is set to the injection timer of the relevant fuel injection cylinder.

In the fuel injection control routine of FIG. 2, first,
In step S201, basic fuel injection that determines a basic fuel injection amount using the intake air amount Q based on a signal from the intake air amount sensor 30 and the engine speed NE calculated in the above-described cylinder discrimination / engine speed calculation routine. Pulse width Tp
Is calculated (= K × Q / Ne; K is an injector characteristic correction constant), and in step S202, the current fuel injection amount calculation is performed for the right bank cylinders (# 1, # 3 cylinders). Check whether or not.

As a result, if the fuel injection amount is being calculated for the right bank cylinders (# 1 and # 3 cylinders), the process proceeds from step S202 to step S203, where the engine 1
Basic distribution correction coefficient KFBD for compensating for a difference in intake distribution ratio between basic cylinders due to the structural intake characteristics of the engine.
B and a canister purge distribution correction coefficient KCPDB for compensating for the difference in the distribution ratio of the evaporative gas supplied by the evaporative purge between the cylinders, and a fuel distribution correction for correcting the fuel injection amount to compensate for the variation in the air-fuel ratio. Coefficient K
Set the FBD.

In this embodiment, the basic distribution correction coefficient KFBDB and the canister purge distribution correction coefficient KCPDB are different between the left and right banks, and between cylinders in the same bank,
It is assumed that the basic distribution correction coefficient KFBDB and the canister purge distribution correction coefficient KCPDB are the same.

The basic distribution correction coefficient KFBDB is set by a basic distribution correction coefficient setting routine shown in FIG. Further, the canister purge distribution correction coefficient KCPDB
Is set by a canister purge distribution correction coefficient setting routine of FIG. 4 described later. In the canister purge distribution correction coefficient setting routine, the air-fuel ratio feedback correction coefficient LAMBDA set by the air-fuel ratio feedback correction coefficient setting routine of FIG. 5 is processed. The canister purge distribution correction coefficient KCPDB is set using the obtained value.

On the other hand, in step S202, when calculating the fuel injection amount for the left bank cylinders (# 2 and # 4 cylinders), the process proceeds from step S202 to step S204, where the basic distribution correction coefficient KFBDB and the canister purge distribution correction coefficient are calculated. The fuel distribution correction coefficient KF is calculated by using KCPDB.
BD is set to compensate for the air-fuel ratio of each cylinder in the left bank, which leans relatively to each cylinder in the right bank.

More specifically, if it is time to calculate the fuel injection amount for the right bank cylinders (# 1 and # 3 cylinders), step S
At 203, a correction term (1-KCPDB) based on the canister purge distribution correction coefficient KCPDB from a correction term (1-KFBDB) where the basic distribution correction coefficient KFBDB is a negative term.
Is subtracted to set a fuel distribution correction coefficient KFBD (KFB
D ← (1−KFBDB) − (1−KCPDB)) When calculating the fuel injection amount for the left bank cylinders (# 2 and # 4 cylinders), the basic distribution correction coefficient KF is determined in step S204.
A correction term (1-KCPDB) based on the canister purge distribution correction coefficient KCPDB is added to a correction term (1 + KFBDB) having BDB as a positive term, and a fuel distribution correction coefficient KFB is added.
Set D (KFBD ← (1 + KFBDB) + (1-
KCPDB)).

That is, the fuel distribution correction coefficient KFBD for the # 1 and # 3 cylinders on the right bank side is changed to the basic distribution correction coefficient KFBDB and the canister purge distribution correction coefficient KCPD.
B, while giving and setting the correction term (1-KCPDB) as a negative term, the fuel distribution correction coefficient KFBD for the # 2 and # 4 cylinders on the left bank side is changed to the basic distribution correction coefficient K
FBDB and canister purge distribution correction coefficient KCPDB
, The fuel distribution correction coefficient for the right bank side # 1, # 3 cylinders is made smaller than the fuel distribution correction coefficient for the left bank side # 2, # 4 cylinders. By making it smaller, # on the right bank side
The fuel amount for the # 1, # 3 cylinders is changed to # 2, # 4 on the left bank side.
The amount is relatively reduced compared to the cylinders, and the variation in the air-fuel ratio between the cylinders due to the difference between the intake distribution ratio and the evaporative gas distribution ratio is eliminated.

After setting the fuel distribution correction coefficient KFBD in step S203 or step S204, the process proceeds from step S205 to step S205, in which the amount of fuel is increased only at the time of start during operation of the starter motor to improve startability. An increase coefficient KST, a full increase coefficient KFULL for increasing the fuel and improving the output performance in an operation state where output is required when the throttle is fully opened or at a high load, and an air-fuel ratio corresponding to lean burn operation. Various correction coefficients KHOS are set by multiplying a lean amount reduction coefficient KLEAN for lean correction and a value obtained by adding other correction coefficients (KHOS ← KST × (KFULL
+ KLEAN + ...)).

Next, the process proceeds to step S206, where even if the basic fuel injection pulse width Tp deviates from the inherent characteristics of the injector 15 and the intake air amount sensor 30, precise control for each operation region is performed. The air-fuel ratio allocating coefficient KMR for enabling the air-fuel ratio feedback correction coefficient LAMBDA for converging the air-fuel ratio to the target air-fuel ratio based on the output voltage of the O2 sensor 35, and the production of the intake air amount measurement system and the fuel supply system -Fuel ratio learning correction coefficient K for quickly correcting the deviation of the air-fuel ratio due to the variation of
Air-fuel ratio correction term based on BLRC (LAMBDA + KBL)
RC-1), a correction term (KHOS + KACC-KD) based on the above-described fuel distribution correction coefficient KFBD, various correction coefficients KHOS, an acceleration increase coefficient KACC, and a deceleration decrease coefficient KDC.
C) multiplying by an adhesion correction coefficient KX for correcting the effect of fuel adhering to the port wall surface, etc., and obtain an effective injection pulse width Te.
(Te ← Tp × KMR × (LAMBDA + K
BLRC-1) × KFBD × (KHOS + KACC-K
DC) × KX).

Thereafter, the process proceeds to step S207, in which the effective fuel injection pulse width Te is added to the invalid pulse width Ts for compensating for the invalid injection time of the injector 15 which changes according to the battery voltage VB, and the final fuel injection is performed. The fuel injection pulse width Ti that determines the amount is set (Ti ← Te + T
s) In step S208, the fuel injection pulse width Ti is set in the injection timer of the corresponding cylinder #i, and the routine exits.

Next, a description will be given of a basic distribution correction coefficient setting routine of FIG. 3 for setting a basic distribution correction coefficient KFBDB for compensating for a difference in intake distribution ratio for each cylinder.

The basic distribution correction coefficient setting routine is executed at predetermined intervals. First, in step S301, the engine cooling water temperature TW is set to a set value TWF for judging completion of warm-up.
A check is made to see if it exceeds the BD (for example, 50 ° C.). If TW ≦ TWFBD and the warm-up of the engine is not completed, the process proceeds from step S301 to step S30.
In step S303, the basic distribution correction condition establishment flag FBC is cleared (FBC ← 0). In step S303, the basic distribution correction coefficient KFBDB is cleared to 0 corresponding to substantially no correction (KFBDB ← 0). Exit.

The basic distribution correction condition satisfaction flag FBC is a flag for indicating that a condition (basic distribution correction condition) that is an operating state subject to fuel correction by the basic distribution correction coefficient KFBDB is satisfied. It is set to FBC = 1, cleared to FBC = 0 when the condition is not satisfied, and referred to in a canister purge distribution correction coefficient setting routine of FIG. 4 described later.

In step S301, TW>
If it is TWFBD and the engine has been warmed up, the process proceeds from step S301 to step S304 to check whether the basic fuel injection pulse width Tp representing the engine load is smaller than a set value TPFBD (see FIG. 6). Tp
If ≧ TPFBD, it is determined that the basic distribution correction condition is not satisfied, and the process exits the routine through the above-described steps S302 and S303. If Tp <TPFBD, the process further proceeds to step S3
At 05, it is checked whether or not the full increase coefficient KFULL is 0.

As a result, in step S305, K
If FULL ≠ 0, it is similarly determined that the basic distribution correction condition is not satisfied, and the routine exits through the above-described steps S302 and S303. If KFULL = 0, it is determined that the basic distribution correction condition is satisfied, and the process proceeds to step S306. The distribution correction condition satisfaction flag FBC is set to 1 (FBC ← 1),
In step S307, the set value FBDB is set to the basic distribution correction coefficient KFBDB (KFBDB ← FBDB), and the routine exits.

That is, the cooling water temperature TW becomes equal to the set value TWFB.
D, the engine has been fully warmed up, and as shown in FIG. 6, the basic fuel injection pulse width Tp representing the engine load is smaller than a set value TPFBD that does not fall within the full increase range, and the full increase coefficient KFULL. Is 0 and is in the region excluding the high load, since the difference in intake air distribution ratio among the cylinders is large and the effect of the air-fuel ratio variation between the cylinders is large, the basic distribution correction condition is satisfied. The set value FBDB is set in the basic distribution correction coefficient KFBDB to be an effective value (KFBDB ≠ 0) for substantially performing fuel correction.

The set value FBDB is obtained under the above-mentioned conditions.
A fuel injection correction rate (correction rate for the fuel injection pulse width) suitable for equalizing the air-fuel ratio between the cylinders in accordance with the difference in the intake air distribution ratio between the cylinders is obtained in advance by simulation or experiment and fixed data. The set value F is stored in the ROM 52. For example, when the difference in the intake air distribution ratio between the cylinders of the engine 1 of the present embodiment is ± 3%.
The basic distribution correction coefficient KFBDB is set with BDB = 3%.

On the other hand, when TW ≦ TWFBD and the engine has not been warmed up and the engine is cold, the effectiveness of the distribution correction is low.
In the high load operation of UL ≠ 0, since the difference in the intake distribution ratio between the cylinders is relatively small, KFBDB = 0 is set, and there is substantially no fuel correction by the basic distribution correction coefficient KFBDB.

Next, the canister purge distribution correction coefficient setting routine of FIG. 4 for setting the canister purge distribution correction coefficient KCPDB for compensating for the difference in the evaporative gas distribution rate for each cylinder when executing the canister purge will be described.

The canister purge distribution correction coefficient setting routine shown in FIG. 4 is executed at predetermined intervals.
In 401, the value of the basic distribution correction condition satisfaction flag FBC is referred to, the operating state where the basic distribution correction condition is satisfied, that is, the difference in the intake air distribution ratio between the cylinders is large, and the influence of the variation in the air-fuel ratio between the cylinders is large. Investigate whether the operating state is in the area.

Then, in step S401, the FBC
= 0, and if the basic distribution correction condition is not satisfied, the condition inversion determination flag FCC is cleared to 0 in step S402 (FCC ← 0), and step S403 is performed.
Then, the canister purge distribution correction coefficient KCPDB is set to 1.0 corresponding to substantially no correction (KCPDB ←
1.0), exit the routine.

The condition inversion discrimination flag FCC is a flag for indicating that the condition (canister purge distribution correction condition), which is an operation state subject to fuel correction by the canister purge distribution correction coefficient KCPDB, has been changed from unsatisfied to satisfied. When the condition is reversed from not satisfied to satisfied condition, F
CC = 1 is set.

In step S401, FBC =
In step 1, if the basic distribution correction condition is satisfied, the process proceeds from step S401 to step S404 to check whether the idle switch 31b is OFF, that is, whether the idle switch 31b is in the non-idle state. When the idle switch 31b is in the idle state of ON, it is determined that the canister purge distribution correction condition is not satisfied, and the aforementioned steps S402 and S403 are performed.
, And the idle switch 31b is turned off.
If F is in the non-idle state, in step S405,
It is determined whether the control duty CPCD for the CPC duty solenoid valve 25 is CPCD # 0 and the CPC duty solenoid valve 25 is open.

The control duty CPCD for the CPC duty solenoid valve 25 depends on the engine load such as the basic fuel injection pulse width and the engine speed as disclosed in Japanese Patent Application Laid-Open No. 9-88737 by the present applicant. A basic duty value (map value) CPCMAP suitable for the engine operation state is given by a map as a parameter, and the average value of the air-fuel ratio feedback correction coefficient LAMBDA is compared with a determination threshold to determine the level of the evaporation concentration. The basic duty value CPCMAP is corrected by a correction coefficient set accordingly and set.

Then, in step S405, the CP
When CD = 0 and the CPC duty solenoid valve 25 is closed and the canister purge is not executed, similarly, it is determined that the canister purge distribution correction condition is not satisfied, and the routine exits through the above-described steps S402 and S403, and exits from the CPCD. $ 0 CPC duty solenoid valve 25
Is opened, the process proceeds to step S406, and it is determined whether or not a value obtained by weighted averaging the air-fuel ratio feedback correction coefficient LAMBDA (hereinafter referred to as a canister distribution correction feedback value) CPDLMD is 1.0 or less.

Here, the air-fuel ratio feedback correction coefficient L
The air-fuel ratio feedback correction coefficient setting routine of FIG. 5 for setting AMBDA will be described.

The air-fuel ratio feedback correction coefficient setting routine shown in FIG. 5 is executed at predetermined intervals.
At 501, it is determined whether an F / B condition (air-fuel ratio feedback condition) is satisfied. The F / B condition is NE =
0, when the engine is not rotating, when the engine is cranked, and when the time after engine start is an initial state in which any of the conditions within the set time is satisfied, the output voltage VO2 of the O2 sensor 35 does not reach the set value and falls within a predetermined range When the state is an inactive state in which the state does not continue for a set time or longer, or during an engine transient operation state such as during acceleration / deceleration, during fuel cut, etc., it is determined that the F / B condition is not satisfied. F / B
It is determined that the condition is satisfied.

If the F / B condition is not satisfied, the flow advances from step S501 to step S502 to clear and initialize a first-time inversion discrimination flag FR described later (F).
(R ← 0), in step S503, the air-fuel ratio feedback correction coefficient LAMBDA is set to LAMBDA = 1.0, and the routine exits. That is, when the air-fuel ratio feedback condition is not satisfied, the air-fuel ratio feedback correction coefficient LAMBDA becomes 1. Fixed or clamped to O
The air-fuel ratio feedback correction based on the output from the second sensor 35 is stopped.

On the other hand, if the F / B condition is satisfied in step S501, the process proceeds from step S501 to step S50.
4 and thereafter, the output voltage VO2 of the O2 sensor 35 and the slice level SL which is a determination value for determining the air-fuel ratio state.
The air-fuel ratio feedback correction coefficient LAMBDA is set by proportional-integral control (PI control) in accordance with the result of the comparison.

That is, in step 504, the output voltage VO2 of the O2 sensor 35 is read, and the output voltage VO2 of the O2 sensor
By comparing O2 with the slice level SL, it is determined whether the current air-fuel ratio is shifted to the rich side or the lean side with respect to the stoichiometric ratio. If VO2 ≧ SL and the air-fuel ratio is shifted to the rich side, the process proceeds to step 505, and the value of the first reversal determination flag FR is referred to.

The first inversion discriminating flag FR is a flag for judging the first time when the air-fuel ratio is inverted from the lean side to the rich side or the first time when the air-fuel ratio is inverted from the rich side to the lean side. From the rich side to the rich side, then 1 → 0, and from the rich side to the lean side, 0 → 1.

Therefore, when the air-fuel ratio is rich and FR = 1
Is the first time when the air-fuel ratio is reversed from the lean side to the rich side, and therefore, the process proceeds from step S505 to step S50.
Then, as shown in FIG. 7, the air-fuel ratio feedback correction coefficient LAMBDA is skipped in the negative direction by the proportional constant PD of the PI control (LAMBDA ← LAMBD).
A-PD), and at step S508, the inversion first-time determination flag F
Clear R (FR ← 0) and exit the routine.

When the air-fuel ratio is rich and FR = 0, the air-fuel ratio feedback correction coefficient LAMB has already been set.
Since DA is skipped in the negative direction by the proportional constant PD, the process proceeds from step S505 to step S507, and as shown in FIG. 7, the air-fuel ratio feedback correction coefficient LAMBDA is set to the integral constant ID of PI control.
Gradually decreases with each execution of the routine (LAMBDA ←
(LAMBDA-ID), and the process exits the routine via the above-described step S508.

On the other hand, in step S504, VO2
If <SL is on the air-fuel ratio lean side, step S504
Then, the process proceeds to step S509, and similarly, the value of the reversal first-time determination flag FR is referred to. When the air-fuel ratio is lean and FR = 0, it is the first time that the air-fuel ratio has been inverted from the rich side to the lean side, so the process proceeds to step S510.
As shown in FIG. 7, the air-fuel ratio feedback correction coefficient LA
MBDA is skipped in the plus direction by the proportional constant PU (LAMBDA ← LAMBDA + PU), and in step S512, the inversion initial discrimination flag FR is set to 1 (FR ← 1), and the routine exits.

When the air-fuel ratio is on the lean side and FR = 1, the air-fuel ratio feedback correction coefficient LAMB has already been set.
Since the DA is skipped in the positive direction by the proportional constant PU, the process proceeds from step S509 to step S511, and the air-fuel ratio feedback correction coefficient LAMBDA is routinely executed by the PI control integration constant IU as shown in FIG. (LAMBDA ← L
AMBDA + IU), and exits the routine via the above-described step S512.

The above-mentioned air-fuel ratio feedback correction coefficient LAMBDA is weighted and averaged as shown by a broken line in FIG. 7 when the canister purge is executed, and is used as a feedback value CPDLMD for canister purge distribution correction. Step S
At 406, the value of the canister purge distribution correction feedback value CPDLMD is 1.0 or less, indicating a rich air-fuel ratio or a stoichiometric air-fuel ratio, and the purge by opening the CPC duty solenoid valve 25 is not an air purge but a purge of evaporative gas. Check to see if it has been performed reliably.

As a result, in step S406, C
If PDLMD> 1.0 and the state is a lean air-fuel ratio, it is determined that the canister purge distribution correction condition is not satisfied, and the routine exits through steps S402 and S403 described above. If CPDLMD ≦ 1.0, the rich air-fuel ratio or the theoretical In the case of the air-fuel ratio state, it is determined that the canister purge distribution correction condition is satisfied, and the process proceeds to step S407 to refer to the value of the condition reversal determination flag FCC.

If FCC = 0 and the first time the canister purge distribution correction condition has shifted from not satisfied to satisfied, the process proceeds from step S407 to step S408, where the canister purge distribution correction feedback value CPD is obtained.
LMD is converted to the current air-fuel ratio feedback correction coefficient LAMB.
Initial setting is performed by DA (CPDLMD ← LAMBDA), the condition inversion determination flag FCC is set in step S409 (FCC ← 1), and the process proceeds to step S411.

If FCC = 1 and the condition that the canister purge distribution correction condition is satisfied continues, the process proceeds from step S407 to step S410, where the weighted average processing of the air-fuel ratio feedback correction coefficient LAMBDA by the following equation is performed. Calculates the canister purge distribution correction feedback value CPDLMD, and proceeds to step S411. CPDLMD ← [(α-1) × CPDLMD + LA
MBDA] / α, where α: weighting factor

The weighting coefficient α is a smoothing coefficient KCPDLM
(Where KCPDL ≧ 1) is a power exponent and is given by a power of 2, for example, KCPDL = 8 and α = 256
Feedback correction coefficient LAM by weighted average of
The BDA is processed to calculate a canister purge distribution correction feedback value CPDLMD. Note that the annealing coefficient KC
The PDLM obtains an optimum value in advance by simulation or experiment, and is stored in the ROM 52 as fixed data.

In step S411, the distribution coefficient KFCP, which is set in advance as a basic value for compensating for the difference in the distribution ratio of the evaporative gas between the cylinders during execution of the canister purge, is replaced with the canister purge distribution correction feedback value CPDLMD. The canister purge distribution correction coefficient KCPDB is corrected by multiplication according to the air-fuel ratio state, and an effective value (KCPDB ≠ 1.
0) (KCPDB ← CPDLMD × KFC)
P), exit the routine.

The distribution coefficient KFCP is obtained in advance by simulation or experiment or the like to determine the maximum difference between the distribution ratios of the evaporative gas supplied during the purge between the cylinders, and is stored in the ROM 52 as fixed data. When the maximum difference rate of the distribution ratio of the evaporative gas of the engine 1 between the cylinders is ± 9%, the distribution coefficient KFCP is set to 9%.

That is, the air-fuel ratio feedback correction coefficient LAMBD is added to the distribution coefficient KFCP representing the maximum difference between the distribution rates of the evaporative gas supplied by the purge among the cylinders.
A is multiplied by a canister purge distribution correction feedback value CPDLMD obtained by performing a weighted averaging process on A to set a canister purge distribution correction coefficient KCPDB (KCPDB ≠
1.0), in the above-described fuel injection control routine, the canister purge correction term (1-KCPDB) is used in the equation for calculating the fuel distribution correction coefficient KFBD (steps S203 and S204 in FIG. 2), and the fuel is supplied by purging. Compensate for the variation in the air-fuel ratio between the cylinders according to the difference in the actual distribution ratio between the cylinders of the evaporative gas, and make the air-fuel ratio between the cylinders uniform according to the difference in the distribution ratio between the cylinders for the evaporative gas. Therefore, it is possible to obtain an appropriate fuel injection amount.

On the other hand, an operation state in which the canister purge distribution correction condition is not satisfied, that is, an operation state in which the basic distribution correction condition is not satisfied and the correction of the difference in the intake air distribution ratio between the cylinders is low (the engine is not completely warmed up). (When the engine is cold or running under a high load), or when the engine is idle, or when the CPC duty solenoid valve 25 is closed and purge is not being performed, or even when the purge is being performed, the air-fuel ratio feedback correction coefficient LAMBDA Feedback value CPDL for canister purge distribution correction by weighted average value
MD exceeds 1.0 and indicates an air-fuel ratio lean, and the purge amount of the evaporated fuel adsorbed on the canister 23 is substantially small, or the purge of the evaporated fuel has already been completed, and only the air purge, that is, the empty purge is performed. Is being performed,
The canister purge distribution correction coefficient KCPDB is set to 1.0, and the fuel distribution correction coefficient K in the fuel injection control routine is set.
The canister purge correction term (1-KC
PDB) is set to 0 and no correction is made.

This eliminates variations in the air-fuel ratio between the cylinders due to structural intake characteristics and the like, and variations in the air-fuel ratio between the cylinders due to the difference in the evaporative gas distribution rate during canister purge. However, as shown by the solid line in FIG. 7, the air-fuel ratio between the cylinders can be made uniform, the exhaust emission can be improved, the running performance can be prevented from deteriorating due to surges caused by the variation in the air-fuel ratio between the cylinders, Vibration prevention and the like can be achieved.

FIGS. 13 to 15 relate to the second embodiment of the present invention. FIG. 13 is a flowchart of a fuel injection control routine, FIG. 14 is a flowchart of a basic distribution correction coefficient setting routine, and FIG. 15 is a canister purge distribution correction coefficient. It is a flowchart of a setting routine.

The second embodiment deals with a case where the basic intake distribution ratio between cylinders due to the structural intake characteristics and the distribution ratio between cylinders of the evaporative gas supplied by purging are different for all cylinders. And the basic distribution correction coefficient K
FBDB, canister purge distribution correction coefficient KCPDB
Are set individually for the # 1 to # 4 cylinders, respectively.

In this case, the distribution ratio of intake air and the distribution ratio of evaporative gas of all cylinders are different from each other, and each cylinder (# 1, # 3 cylinder) on the right bank side is different from each cylinder (# 3 cylinder) on the left bank side.
The intake distribution ratio is lower than that of the cylinders # 2 and # 4, and the cylinders of the right bank (# 1 and # 3 cylinders) are higher than the cylinders of the left bank (# 2 and # 4 cylinders). An example in which a case where the distribution ratio of evaporative gas is high will be described.

For this reason, in the fuel injection control routine of the second embodiment shown in FIG. 13, steps S202 (determination of the injection amount calculation cylinder) and step S203 (right bank) in the fuel injection control routine of the first embodiment shown in FIG. Of the fuel distribution correction coefficient KFBD for each cylinder), step S
204 (fuel distribution correction coefficient KF for the cylinder in the left bank)
BD setting) is divided and changed into a plurality of steps corresponding to individual cylinders.

Similarly, since the basic distribution correction coefficient KFBDB and the canister purge distribution correction coefficient KCPDB are set for each cylinder, the basic distribution correction coefficient setting routine of the second embodiment shown in FIG. Steps S303 (the basic distribution correction coefficient KFBDB is set without correction) and step S307 (the basic distribution correction coefficient KFBDB is set to a value for which substantial correction is effective) of the basic distribution correction coefficient setting routine of one embodiment correspond to individual cylinders. In the canister purge distribution correction coefficient setting routine of the second embodiment shown in FIG. 15, in step S403 (canister purge distribution) of the canister purge distribution correction coefficient setting routine of the first embodiment shown in FIG. The correction coefficient KCPDB is set to no correction), step S411 (canister purge amount) Setting the real correction is active value) the correction coefficient KCPDB, split and change into a plurality of steps corresponding to the individual cylinders.

First, the fuel injection control routine of FIG. 13 will be described. After setting the basic fuel injection pulse width Tp in step S201, the flow advances to step S202-1 to check whether or not the injection amount of the # 1 cylinder is being calculated. , # 1 cylinder, the basic distribution correction coefficient KFBDB # 1 for the # 1 cylinder and the canister purge distribution correction coefficient KCPDB # 1 for the # 1 cylinder in step S203-1.
To set the fuel distribution correction coefficient KFBD (KFB
D ← (1-KFBDB # 1)-(1-KCPDB #
1)).

Also, in step S202-1, #
If it is not time to calculate the injection amount for one cylinder, step S20
The process proceeds from 2-1 to step S202-2 to check whether or not the calculation of the injection amount of the # 3 cylinder is being performed. If it is time to calculate the injection amount of the # 3 cylinder, the process proceeds from step S202-2 to step S203-2, where the basic distribution correction coefficient KFBDB # 3 for the # 3 cylinder and the canister purge distribution correction coefficient KCPDB # for the # 3 cylinder. 3 to set the fuel distribution correction coefficient KFBD (KFBD ← (1-KFBDB #
3)-(1-KCPDB # 3)).

Further, in step S202-2, #
If it is not time to calculate the injection amount of the three cylinders, step S202-
From step 2, the process proceeds to step S202-3, and it is checked whether or not the calculation of the injection amount of the # 2 cylinder is being performed. If it is time to calculate the injection amount of the # 2 cylinder, the process proceeds from step S202-3 to step S2
Proceeding to 04-1, the fuel distribution correction coefficient K is calculated based on the basic distribution correction coefficient KFBDB # 2 for the # 2 cylinder and the canister purge distribution correction coefficient KCPDB # 2 for the # 2 cylinder.
Set the FBD (KFBD ← (1 + KFBDB # 2)
+ (1-KCPDB # 2)).

In step S202-3, #
If the injection amount is not being calculated for the two cylinders, that is, if the injection amount is being calculated for the # 4 cylinder, step S202-3.
From step S204-2, the fuel distribution correction coefficient KFBD is set by the basic distribution correction coefficient KFBDB # 4 for the # 4 cylinder and the canister purge distribution correction coefficient KCPDB # 4 for the # 4 cylinder (KFBD ← (1 + K)
FBDB # 4) + (1-KCPDB # 4)).

Then, a fuel distribution correction coefficient KF is set for each cylinder.
After setting the BD, from the corresponding step to step S205
In step S206, the effective injection pulse width Te is set using the fuel distribution correction coefficient KFBD corresponding to the individual cylinder, the final fuel injection pulse width Ti is set in step S207, and the corresponding cylinder # is set in step S208. Set the i injection timer and exit the routine.

Next, in the basic distribution correction coefficient setting routine of FIG. 14, if the basic distribution correction condition is not satisfied by the condition determination in steps S301, S304, and S305, the basic distribution correction condition establishment flag FBC is cleared in step S302. , Steps S303-1, S303-2, S30
3-3, S303-4, # 1, # 2, #
Basic distribution correction coefficient KFBDB # 1, KF for cylinders # 3 and # 4
BDB # 2, KFBDB # 3, KFBDB # 4 are cleared to the corresponding 0 without correction (KFBDB # 1 ← 0, KF
BDB # 2 ← 0, KFBDB # 3 ← 0, KFBDB # 4
← 0), exit the routine.

Steps S301, S304, S3
If the basic distribution correction condition is satisfied in the condition determination at step S05, the process proceeds from step S305 to step S306 to set the basic distribution correction condition satisfaction flag FBC, and then proceeds to step S306.
307-1, S307-2, S307-3, S307-
4, the basic distribution correction coefficients KFBDB # 1, KFBDB # 2, and KFBD of the # 1, # 2, # 3, and # 4 cylinders, respectively.
B # 3 and KFBDB # 4 have set values FBDB1, FBDB2, and FBD for each cylinder corresponding to each of the cylinders # 1 to # 4.
B3 and FBDB4 are set (KFBDB # 1 ← FBD
B1, KFBDB # 2 ← FBDB2, KFBDB # 3 ←
FBDB3, KFBDB # 4 ← FBDB4), and exit the routine.

Here, the set values FBDB1, FDB for each cylinder
BDB2, FBDB3, and FBDB4 are appropriately fuel-injected to make the air-fuel ratio between the cylinders uniform according to the difference in the intake air distribution ratio between the cylinders under the condition of the basic distribution correction condition by simulation or experiment in advance. The correction ratio is obtained and stored as fixed data in the ROM 52. When the basic distribution correction condition is satisfied, the basic distribution correction coefficients for the # 1 to # 4 cylinders are determined by these set values FBDB1, FBDB2, FBDB3, and FBDB4. KFBDB #
1, KFBDB # 2, KFBDB # 3, KFBDB # 4
Is set for each cylinder.

Next, in the canister purge distribution correction coefficient setting routine of FIG. 15, steps S401, S404,
If the canister purge distribution correction condition is not satisfied in the condition determination in S405 and S406, the condition inversion determination flag FCC is cleared in step S402, and then the process proceeds to step S403.
-1, S403-2, S403-3, S403-4,
The canister purge distribution correction coefficients KCPDB # 1, KCPDB # 2, K for the # 1, # 2, # 3, and # 4 cylinders, respectively.
CPDB # 3 and KCPDB # 4 are set to 1.0 corresponding to no correction (KCPDB # 1 ← 1.0, KCPDB # 1
# 2 ← 1.0, KCPDB # 3 ← 1.0, KCPDB #
4 ← 1.0), and exits the routine.

Steps S401, S404, S4
If the canister purge distribution correction condition is satisfied in the condition determinations of steps S05 and S406, the feedback value CPDLMD for canister purge distribution correction is calculated using the air-fuel ratio feedback correction coefficient LAMBDA in steps S407 to S410.
Are obtained, steps S411-1, S411-2, S41
At 411-3 and S411-4, distribution coefficients KFCP1 and KFC for each cylinder corresponding to each of the cylinders # 1 to # 4, respectively.
P2, KFCP3, and KFCP4 are multiplied by a feedback value CPDLMD for canister purge distribution correction, and #
1, 2, 3, and 4 cylinder canister purge distribution correction coefficients KCPDB # 1, KCPDB # 2, KCPDB #
3, KCPDB # 4 is set (KCPDB # 1 ← CP
DLMD × KFCP1, KCPDB # 2 ← CPDLMD
× KFCP2, KCPDB # 3 ← CPDLMD × KFC
P3, KCPDB # 4 ← CPDLMD × KFCP4),
Exit the routine.

Also in this case, the distribution coefficient K for each cylinder
The FCP1, KFCP2, KFCP3, and KFCP4 determine the maximum difference between the distribution rates of the evaporative gas supplied by the purge among the cylinders in advance for each cylinder by simulation or experiment, and store them in the ROM 52 as fixed data. When the canister purge correction condition is satisfied,
Distribution coefficient KFCP1, KFCP2, KFCP for each cylinder
3, KFCP4 is multiplied by a canister purge distribution distribution correction feedback value CPDLMD, and canister purge distribution correction coefficients KCPDB # 1 and KCPDB for each cylinder.
# 2, KCPDB # 3, and KCPDB # 4 are set.

In the second embodiment, since the basic distribution correction coefficient KFBDB # i and the canister purge distribution correction coefficient KCPDB # i are individually set for each cylinder, the difference between the intake distribution ratio for each cylinder and The difference in the distribution ratio of the evaporative gas can be reliably eliminated, and the air-fuel ratio can be more effectively made uniform.

The present invention is not limited to each embodiment, but can be variously applied without departing from the present invention. For example, the calculation formula of the fuel distribution correction coefficient KFBD is based on the variation in the air-fuel ratio between the cylinders due to the difference in the intake distribution ratio between the cylinders, and the difference in the distribution ratio between the cylinders of the evaporative gas supplied by the purge. It can be changed appropriately according to the variation of the air-fuel ratio between the cylinders.

[0114]

As described above, according to the first aspect of the present invention, the basic distribution correction coefficient for compensating for the difference in the basic intake distribution ratio between the cylinders due to the intake characteristic of the engine, Using the canister purge distribution correction coefficient for compensating for the difference in the distribution ratio of the evaporative gas supplied by the canister purge between the cylinders, the fuel injection amount is corrected for each bank or each cylinder to compensate for variations in the air-fuel ratio. The fuel injection amount set based on the engine operating condition is corrected by the fuel distribution correction coefficient to set the final fuel injection amount for the engine. In addition, it is possible to eliminate the influence of the difference in the distribution characteristics of the evaporative gas between the cylinders during the execution of the canister purge, thereby eliminating the air-fuel ratio variation among the cylinders. And equalize the ratio, improvement of exhaust emission, the running of preventing deterioration due to a surge or the like due to variations in air-fuel ratio between the cylinders, it is possible to achieve idle vibration prevention.

In this case, according to the second aspect of the invention, the basic distribution correction coefficient is set in accordance with the engine warm-up completion state and the engine operating state excluding the high load region. In addition to the effects, it is possible to particularly effectively eliminate the air-fuel ratio variation between the cylinders in a region where the difference in the intake air distribution ratio between the cylinders is large.

Further, according to the third aspect of the present invention, the operation of opening and closing the actuator for adjusting the purge amount of the canister purge in a non-idle state under an operating state in which the canister purge distribution correction coefficient is compensated by the basic distribution correction coefficient. Since the setting is made in accordance with the operating state in which it is determined that the evaporative gas purge is being performed reliably based on the state and the air-fuel ratio state, in addition to the effects of the invention according to claim 1 or 2,
It is possible to prevent overcorrection in a state where the purge amount of the evaporative gas is substantially small or the purge of the evaporative gas has already been completed and the purging of only the air has been performed, so that the control reliability can be improved.

Further, according to the present invention, the distribution coefficient preset as a basic value for compensating for the difference in the distribution ratio of the evaporative gas between the cylinders during the execution of the canister purge, and the air-fuel ratio feedback correction coefficient are weighted. Since the canister purge distribution correction coefficient is set by correcting with the canister purge distribution correction feedback value set on average, in addition to the effects of the invention according to any one of claims 1, 2, and 3, Optimal correction according to the air-fuel ratio state can be performed, and controllability can be improved.

[Brief description of the drawings]

FIG. 1 relates to a first embodiment of the present invention,
Flowchart of engine speed calculation routine

FIG. 2 is a flowchart of a fuel injection control routine according to the first embodiment;

FIG. 3 is a flowchart of a basic distribution correction coefficient setting routine according to the first embodiment;

FIG. 4 is a flowchart of a canister purge distribution correction coefficient setting routine according to the first embodiment;

FIG. 5 is a flowchart of an air-fuel ratio feedback correction coefficient setting routine according to the first embodiment;

FIG. 6 is an explanatory diagram of a basic distribution correction condition.

FIG. 7: Canister purge, air-fuel ratio for each cylinder,
Chart showing the relationship between the air temperature and the air-fuel ratio feedback correction coefficient

FIG. 8 is a time chart showing a relationship among a crank pulse, a cylinder discrimination pulse, a combustion stroke cylinder, an ignition timing, and a fuel injection timing.

FIG. 9 is a schematic diagram of an engine control system according to the first embodiment;

FIG. 10 is a front view of the crank rotor and the crank angle sensor according to the first embodiment;

FIG. 11 is a front view of the cam rotor and the cylinder discrimination sensor.

FIG. 12 is a circuit diagram of the electronic control system according to the first embodiment;

FIG. 13 is a flowchart of a fuel injection control routine according to the second embodiment of the present invention.

FIG. 14 is a flowchart of a basic distribution correction coefficient setting routine.

FIG. 15 is a flowchart of a canister purge distribution correction coefficient setting routine;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine 23 ... Canister 25 ... CPC duty solenoid valve (actuator) 50 ... Electronic control device (Basic distribution correction coefficient means, canister purge distribution correction coefficient setting means, fuel distribution correction coefficient setting means, fuel injection amount setting means) KFBDB ... Basic distribution correction coefficient KCPDB canister purge distribution correction coefficient KFBD: fuel distribution correction coefficient KFCP: distribution coefficient CPDLMD: feedback value for canister purge distribution correction Ti: fuel injection pulse width (final fuel injection amount)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G301 HA06 HA08 HA14 JA05 KA05 KA07 KA09 LA04 MA01 MA11 NA02 NA08 ND01 ND21 ND36 ND41 NE06 NE15 NE16 NE23 PA04Z PA11Z PA14Z PA15A PB09Z PC08Z PD03A PE03Z PE04Z PE05Z PE08Z

Claims (4)

[Claims] 1. A basic distribution correction coefficient setting means for setting a basic distribution correction coefficient for compensating for a difference in basic intake distribution ratio between cylinders due to an intake characteristic of an engine, and evaporative gas supplied by a canister purge. A canister purge distribution correction coefficient setting means for setting a canister purge distribution correction coefficient for compensating for a difference in the distribution ratio between the cylinders, and for each bank or cylinder by the basic distribution correction coefficient and the canister purge distribution correction coefficient. Fuel distribution correction coefficient setting means for setting a fuel distribution correction coefficient for correcting the fuel injection amount to compensate for the variation in the air-fuel ratio; and correcting the fuel injection amount set based on the engine operating state using the fuel distribution correction coefficient. And a fuel injection amount setting means for setting a final fuel injection amount for the engine. Engine fuel control system. 2. The basic distribution correction coefficient setting means according to claim 1, wherein said basic distribution correction coefficient setting means sets the basic distribution correction coefficient in accordance with an engine warm-up completion state and an engine operating state excluding a high load region. A fuel injection control device for an engine according to any one of the preceding claims. 3. The canister purge distribution correction coefficient setting means includes a non-idle state, an open / close state of an actuator that adjusts a purge amount of a canister purge, and an air-fuel ratio under an operating state in which compensation by the basic distribution correction coefficient is performed. 2. The canister purge distribution correction coefficient is set in accordance with an operating state in which it is determined that the evaporative gas is being purged based on the state.
3. The fuel injection control device for an engine according to claim 2. 4. A canister purge distribution correction coefficient setting means, comprising: a distribution coefficient preset as a basic value for compensating for a difference in a distribution ratio of evaporative gas between cylinders during execution of a canister purge; 2. The canister purge distribution correction coefficient is corrected by a canister purge distribution correction feedback value that is set by weighted averaging.
The fuel injection control device for an engine according to any one of claims 2 and 3.