JP2505311B2 - Engine idle control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an engine idle control method for smoothing engine rotation during idling.

[Prior Art] In recent years, the engine idle speed tends to be kept low due to demands such as improved fuel efficiency and quietness. However, when the idle speed is lowered, the rotation tends to become unstable, which results in comfort and start. Performance is significantly impaired.

Generally, this fluctuation in rotation is considered to be caused by the variation in the combustion state among cylinders.This variation in the combustion state causes the intake pipe shape to become complicated, the intake distribution ratio to become uneven due to intake interference between the cylinders, etc. A slight difference in combustion temperature between cylinders caused by the cooling path, variations in combustion chamber volume of each cylinder, manufacturing variations in piston shape, etc., and air-fuel ratio of each cylinder caused by differences in combustion injection amount due to injector manufacturing error, etc. It is thought to be caused by slight variations.

Therefore, it is extremely important to know the combustion state of each cylinder in order to obtain stable idle rotation, and various means for grasping the combustion state of each cylinder have been conventionally developed.

For example, in JP-A-59-82534, each cylinder #i
(For four cylinders, i = 1 to 4) Differential rotation ΔN # which is the difference between the instantaneous engine speed NL # i before the combustion stroke and the instantaneous engine speed NH # i after the combustion stroke. i (△ N #
i = NH # i-NL # i) is obtained for each cylinder, and then the average value ΔNA of all cylinders of the differential rotation ΔN # i of each cylinder #i and the differential rotation ΔN # i of each cylinder #i are obtained. And compare each cylinder #
By controlling the differential rotation ΔN # i of i to be equal to the average differential rotation ΔNA of all cylinders, smooth idle rotation is attempted.

In this prior art, paying attention to the fact that there is a correlation between the combustion state of each cylinder and the above-mentioned differential rotation ΔN # i, the average differential rotation ΔNA of all cylinders is used as a reference, and the deviation from this reference I am trying to estimate the combustion state of cylinder #i, but the combustion of each cylinder is in the ignition order (for example, # 1 → # 3 → # 2
→ Since it is continuously repeated according to # 4), even if control is performed to bring the differential rotation ΔN # i of each cylinder #i closer to the average differential rotation ΔNA of all cylinders, Between the differential rotation ΔN # i−1 and the differential rotation ΔN # i of the current combustion stroke cylinder #i, or between the differential rotation ΔN # i of the current combustion stroke cylinder #i.
If there is a difference between the differential rotation speed ΔN # i + 1 of the cylinder # i + 1 after one combustion stroke and the differential rotation speed ΔN # i + 1, the engine rotation tends to be uneven and the stability is significantly impaired.

Since the reference value is the average differential rotation ΔNA of all cylinders,
Depending on the fuel state, this all-cylinder average differential rotation ΔNA itself tends to always fluctuate. If this all-cylinder average differential rotation ΔNA fluctuates, the combustion state of each cylinder estimated based on this all-cylinder average differential rotation ΔNA In addition, the combustion state factor of the other cylinders when setting the all cylinder average differential rotation ΔNA is included, and it becomes difficult to accurately grasp the combustion state of each cylinder.

Further, since the combustion injection control must be performed within the stoichiometric air-fuel ratio range, the control range is significantly limited,
Obtaining satisfactory results is practically difficult.

Furthermore, as a means for controlling the combustion state of each cylinder,
Ignition timing control other than fuel injection control is conceivable. However, in ignition timing control, the combustion state of the engine changes remarkably with a slight advance or retard correction, and thus controllability is difficult.

Therefore, for example, as disclosed in Japanese Patent Application Laid-Open No. 2-64252, engine rotation fluctuation is detected for each predetermined crank angle, and based on this rotation fluctuation, fuel injection amount and ignition timing of a cylinder having a large fluctuation difference are detected. There is one that corrects both.

[Problems to be Solved by the Invention] By the way, when simultaneously controlling the fuel injection amount and the ignition timing in one engine, if either one is set and then the other is not set based on this set value, an effective air-fuel ratio is obtained. When controllability and ignition timing controllability cannot be obtained, for example, when the increase correction and the advance correction are simultaneously performed for a cylinder with a negative rotational fluctuation difference (cylinder with a poor combustion state), The difference in the air-fuel ratio and the torque fluctuation with respect to the cylinder will increase and the feeling will be deteriorated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine idle control method capable of accurately grasping the combustion state of the cylinder and obtaining smooth engine rotation during idle. .

[Means for Solving the Problems] (1) In order to achieve the above object, a first engine idle control method according to the present invention performs work by combustion of a cylinder before one combustion stroke when the engine is in an idle state. From the difference between the momentum in the non-combustion section and the average value of the momentum in the two combustion stroke cylinders and the current combustion stroke cylinder in the non-working section, the combustion state determination value for the one combustion stroke cylinder is obtained. When the combustion state determination value of the cylinder before the first combustion stroke exceeds the combustion state determination allowable upper limit value, the injection correction amount of the cylinder before the first combustion stroke in the next cycle is reduced by a set amount,
When the combustion state determination value is lower than the combustion state determination permission lower limit value, the injection correction amount of the cylinder before the first combustion stroke in the next cycle is increased by a set amount, and the injection correction amount further increases the injection correction allowable upper limit value. If it exceeds, the ignition timing correction amount of the cylinder is advanced by a set angle, the injection correction amount is decreased by the set amount, and if the injection correction amount of the cylinder before the first combustion stroke is lower than the injection correction allowable lower limit value, The ignition timing correction amount of the cylinder is retarded by a set angle, and the injection correction amount is increased by a set amount.

(2) In order to achieve the above object, the second engine idle control method according to the present invention is such that, when the engine is in the idle state, the momentum of a section in which the combustion of the current combustion stroke cylinder is not performed and one combustion stroke. From the difference between the momentum in the section where the front cylinder is not working due to combustion and the average value of the estimated momentum in the section where one cylinder is not working due to the combustion after the combustion stroke, the combustion state determination value of the current combustion stroke cylinder is calculated. If the combustion state determination value of the current combustion stroke cylinder exceeds the combustion state determination allowable upper limit value, the injection correction amount of the current combustion stroke cylinder in the next cycle is reduced by a set amount, and this combustion state determination value is When it is lower than the combustion condition determination allowable lower limit value, the injection correction amount of the current combustion stroke cylinder in the next cycle is increased by a set amount, and when this injection correction amount exceeds the injection correction allowable upper limit value. When the ignition timing correction amount of the cylinder is advanced by a set angle, the injection correction amount is decreased by a set amount, and when the injection correction amount of the current combustion stroke cylinder is lower than the injection correction allowable lower limit value, the ignition timing correction of the cylinder is performed. The amount is retarded by the set angle and the injection correction amount is increased by the set amount.

[Operation] (1) According to the first engine idle control method described above, the combustion state determination value of the cylinder before the first combustion stroke is the average of the momentum of the sections before and after which the combustion stroke cylinder is not working due to combustion. Since it is judged based on the value, when comparing the average value of all cylinders and the value of the cylinder concerned, the combustion state of the cylinder is included in the average value of all cylinders, and the average of all cylinders including the combustion state of the cylinder concerned. By comparing the value with the cylinder concerned, the combustion state of the cylinder concerned will be judged and the reliability deteriorates.
When the average value of all cylinders is used, each momentum of all cylinders + the relevant cylinder must be stored. However, in the present invention, the average value of all cylinders is not used, and combustion of the relevant cylinder (cylinder before one combustion stroke) is performed. Due to the difference between the momentum of the non-working section and the average value of the momentum of the non-working section of the cylinders adjacent to the cylinder in the ignition order not including the combustion state of the cylinder Since the state is determined, it is possible to directly determine whether the combustion state of the cylinder is adjacent to the adjacent cylinders in the ignition order, and the combustion state of the cylinder can be accurately determined. It is only necessary to store the respective momentums of the above, and it becomes possible to judge the combustion state of the cylinder in more real time.

Then, based on the combustion state determination value, the fuel injection amount of the cylinder before the first combustion stroke in the next cycle is increased,
Alternatively, when the amount is reduced and the amount of fuel injection is increased or reduced, when the amount reaches a control limit in a range of a set air-fuel ratio such as a theoretical air-fuel ratio, the ignition timing is advanced or retarded, and When advanced, the fuel injection amount is reduced by a predetermined amount, and when retarded, the fuel injection amount is increased by a predetermined amount to widen the idle control and improve controllability.

(2) According to the second engine idle control method described above, the combustion state determination value of the current combustion stroke cylinder indicates the average value of the momentum and the estimated momentum of the section in which the combustion stroke cylinder before and after the current combustion stroke cylinder is not working due to combustion. Because it is judged as a standard,
Similar to the first engine idle control method, the momentum of a section in which work is not performed due to combustion of the cylinder (current combustion stroke cylinder) and the combustion state of the cylinder are not included, and the ignition order is set for the cylinder. Since the combustion state of the cylinder concerned is judged from the difference between the momentum and the average value of the estimated momentum in the non-working sections of the cylinders adjacent to each other in the front and rear, the fuel state of the cylinder concerned with respect to the adjacent cylinders in the ignition order The combustion state of the cylinder can be determined directly and accurately, and the momentum of each cylinder and the front and rear cylinders in the ignition order need only be stored, and the combustion state of the cylinder can be determined in more real time. Is possible.

Then, based on the combustion state determination value, the fuel injection amount of the current combustion stroke cylinder in the next cycle is increased or decreased, and the increase or decrease of the fuel injection amount is the theoretical air-fuel ratio or the like. When the control limit is reached within the set air-fuel ratio range, the ignition timing is advanced or retarded, and when advanced, the fuel injection amount is reduced by a predetermined amount, and when retarded, fuel injection is performed. The amount is increased to a predetermined amount to widen the idle control and improve controllability.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings.

1 to 12 show a first embodiment of the present invention, and FIG. 1 is a flowchart showing a combustion state discriminating means for each cylinder,
FIG. 4 is a flow chart showing the procedure for setting the fuel injection pulse width for each cylinder, FIG. 3 is a flow chart showing the procedure for setting the ignition timing for each cylinder, FIG. 4 is a conceptual diagram showing a basic combustion state determination method for each cylinder, and FIG. 6 is a schematic diagram of an engine control system, FIG. 7 is a front view of a crank rotor and a crank angle sensor, FIG. 8 is a front view of a cam rotor and a cam angle sensor, and FIG. 9 is a basic diagram. Ignition timing map conceptual diagram, FIG. 10 is a cylinder pressure fluctuation, crank pulse, cam pulse, and a time chart showing engine rotation fluctuation, FIG. 11 is a cylinder-by-cylinder combustion state comparison value, a cylinder-by-cylinder average combustion state determination value, FIG. 12 is a time chart showing the invalid injection pulse width for each cylinder, and FIG. 12 is a time chart showing the ignition timing correction learning value for each cylinder.

(Structure) Reference numeral 1 in FIG. 6 is an engine, and in the drawing, a 4-cylinder horizontally opposed engine is shown. An intake manifold 3 is attached to an intake port 2a formed in a cylinder head 2 of the engine 1.
And the throttle chamber 5 is connected to the upstream side of the intake manifold 3 via the air chamber 4.
An air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6.

An intake air amount sensor (a hot wire type air flow meter in the figure) 8 is provided immediately downstream of the air cleaner 7 in the intake pipe 6, and a throttle valve 5a provided in the throttle chamber 5 is provided with a throttle valve 5a. An opening sensor 9a and an idle switch 9b that detects the fully closed throttle valve are connected in series.

An injector 10 is arranged immediately upstream of each intake port 2a of each cylinder of the intake manifold 3. Further, an ignition plug 11 is attached to each cylinder of the cylinder head 2 so as to expose the ignition part at the tip to the combustion chamber. An ignition coil 11a is integrally attached to the ignition plug 11.

The injector 10 is communicated with a fuel tank 13 via a fuel passage 12, and a fuel pump 14 is provided in the fuel passage 12.

A crank rotor 15 is attached to the crank shaft 1b of the engine 1, and a crank angle sensor including an electromagnetic pickup for detecting a protrusion (or slit) corresponding to a predetermined crank angle on the outer circumference of the crank rotor 15. 16 are provided opposite to each other, and a cam rotor 17 is provided continuously to the camshaft 1c that makes a half rotation with respect to the crankshaft 1b, and a cam angle sensor 18 is provided opposite to the outer circumference of the cam rotor 17.

As shown in FIG. 7, protrusions 15a, 15b, 15c are formed on the outer periphery of the crank rotor 15. These protrusions 15a, 15
b, 15c are formed at the positions before the compression top dead center (BTDC) θ1, θ2, θ3 of each cylinder, and the cycle f1.2 (here, f = 1 / ω) from the passage time between the protrusions 15a, 15b. ω: angular velocity) is calculated, and the period f2.3 is calculated from the passage time between the protrusions 15b and 15c. Further, the protrusion 15b indicates a reference crank angle when the ignition timing ADV is set.

As shown in FIG. 10, the crank angle B of the protrusions 15b and 15c is
TDC θ2 and θ3 are ignition timing (time) ADV during idle operation
It is set before and after. Generally, the ignition timing during idle operation is around 20 ° C BTDC, and even if ignition is performed at this crank angle, the combustion pressure does not rise sharply up to 10 ° A after that.

Further, as shown in FIG. 10, in the embodiment, the opening timing of the exhaust valve of each cylinder is set to be slightly retarded from the ignition reference crank angle BTDCθ2 of the next combustion stroke cylinder. Since the combustion pressure immediately after the exhaust valve is opened sharply decreases, the combustion pressure has almost no effect at the crank angle BTDCθ3.

Therefore, the crank angle θ3 of the protrusion 15c is set to BTDC10.
If it is set to the advance side from ℃ A, the section between the crank angles BTDCθ2, θ3 of the projections 15b, 15c is hardly affected by the combustion between the angular cylinders, that is, the combustion stroke cylinder and the next combustion stroke. It is a section where there is no work due to combustion with the cylinder.

Further, as shown in FIG. 8, the cylinder discriminating projections (or slits) 17a, 17b, 17c are provided on the outer periphery of the cam rotor 17.
Are formed. The protrusion 17a is formed at the position of θ4 after the compression top dead center of the # 3 and # 4 cylinders (ATDC), and the protrusion 17b is composed of three protrusions, and the first protrusion is the compression top dead of the # 1 cylinder. It is formed at the position of the point (ATDC) θ5, and the protrusion 17c is composed of two protrusions, and the first protrusion is # 2.
It is formed at a position of θ6 after compression top dead center (ATDC) of the cylinder.

In the illustrated embodiment, θ1 = 97 ° C. A, θ2 = 65 ° C. A,
θ3 = 10 ° C, θ4 = 20 ° C, θ5 = 5 ° C, θ6 = 20
℃ A, θ (2-3) = 55 ℃ A, this arrangement,
As shown in FIG. 10, for example, when the cam angle sensor 18 is θ
When the cam pulse of 5 (protrusion 17b) is detected, it can be determined that the crank pulse detected by the crank angle sensor 16 thereafter is a signal indicating the crank angle of the # 3 cylinder.

In addition, after the cam pulse of θ5, θ4 (protrusion 17a)
When the cam pulse of No. 2 is detected, it can be determined that the crank pulse detected by the crank angle sensor 16 thereafter indicates the crank angle of the # 2 cylinder. Similarly, θ6 (projection
The crank pulse after detecting the cam pulse of 17c) is #
It shows the crank angle of four cylinders, and the above θ6
When the cam pulse of θ4 (protrusion 17a) is detected after the cam pulse of, the crank pulse detected thereafter can be determined to indicate the crank angle of the # 1 cylinder.

Furthermore, after the cam pulse is detected by the cam angle sensor 18, it can be determined that the crank pulse detected by the crank angle sensor 16 indicates the reference crank angle (θ1) of the cylinder.

The crank angle sensor 16 and the cam angle sensor 18 constitute a crank angle detecting means, and the cam angle sensor 18 alone may constitute the crank angle detecting means by changing the cam pulse pattern.

On the other hand, a knock sensor 19 for detecting knock from the vibration of the engine 1 is fixed to the engine 1, and a cooling water temperature sensor 20 is provided in a cooling water passage (not shown) forming a riser formed in the intake manifold 3. Is facing.

An O2 sensor 22 faces an exhaust pipe 21 communicating with the exhaust port 2b of the cylinder head 2. The code
23 is a catalytic converter, 24 is a vehicle speed sensor, and 25 is an igniter.

(Circuit configuration of control device) On the other hand, reference numeral 31 is a control device including a microcomputer, etc., and a CPU (central processing unit) 3
2, RAM33, ROM34, backup RAM (non-volatile RAM) 3
5, and the I / O interface 36 is connected to each other via the bus line 37, and a predetermined stable variable voltage is supplied from the constant voltage circuit 38.

The constant voltage circuit 38 is connected to the battery via the control relay 39.
41, when the key switch 40 is turned on and the relay contact of the control relay 39 is closed, the control battery is supplied to each part, and the battery 41 is directly connected to the backup RAM 35. Supply backup power even when 40 is turned off.

In addition, to the input port of the above I / O interface 36,
Each sensor 8,9a, 16,18,19,20,22,24, and the idle switch 9b are connected, the positive terminal of the battery 41 is connected, the terminal voltage is monitored, and
I / O interface 36 output port, spark plug 11
The ignition coil 11a is connected via the igniter 25, and the injector 10 is connected via the drive circuit 42.

The ROM 34 stores a control program, fixed data and the like. The fixed data includes a basic ignition timing map MPθBASE, an initial set value, and various reference value data to be compared when making a determination.

Further, the RAM 33 stores data after processing the output signals of the respective sensors, data processed by the CPU 32, and the like. Furthermore, the backup RAM 35 is always supplied with power regardless of the key switch 40, and even if the engine is stopped by turning off the key switch 40, the stored contents will not be lost. , And ignition timing correction learning value data are stored.

Further, the CPU 32 calculates the fuel injection pulse width Ti for the injector 10 or the ignition timing ADV for each cylinder based on various data stored in the RAM 33 and the backup RAM 35 according to the control program stored in the ROM 34.

In the control device 31, in addition to general fuel injection control and ignition timing control, each cylinder #i
The fuel state (i = 1 to 4) is individually judged, and based on the judgment result, the fuel injection control and the ignition timing control are comprehensively controlled so as to smooth the idle rotation.

The basic concept of this cylinder-by-cylinder combustion state determination method will be described with reference to FIGS.

FIG. 4 shows fluctuations in engine speed during idle rotation. For example, in the case of a 4-cylinder engine, combustion stroke cylinder #
i follows the ignition order (for example, # 1 → # 3 → # 2 → # 4)
Since the combustion stroke cylinders are not overlapped before and after the combustion stroke cylinder #i, the combustion stroke cylinders do not overlap each other before and after the combustion stroke cylinder #i finishes combustion and before the next combustion stroke cylinder # i + 1. There is a section that is not affected by combustion, that is, does not perform work due to so-called combustion.

For example, as shown in FIG. 4, when the engine rotational speeds, which are the momentum of moments in the section where the fuel of the cylinders # 1 to # 4 is not working, are N # 1 to N # 4, respectively, a smooth engine is obtained. In order to obtain rotation, it is desirable that the engine speeds N # 1 to N # 4 of the cylinders # 1 to # 4 are all uniform.

In this embodiment, focusing on the fact that there is a very strong correlation between the combustion state of each cylinder #i and the engine speed N # i, the combustion state is determined for each cylinder.

That is, in the combustion state determination method according to this embodiment,
The average value of the engine speed N # i of the current combustion stroke cylinder #i and the engine speed N # i-2 of the cylinder # i-2 before two combustion strokes ((N # i-2 + N # i) / 2 and 1 Cylinder #i before combustion stroke
-1 engine speed N # i-1 is compared, and this comparison value (this is the combustion state determination value here) Is in the minus section, it is determined that the combustion state of the cylinder # i-1 is bad, and when it is on the plus side, the combustion state is good.

Then, based on this determination result (combustion state determination value),
Each cylinder # i-1 is controlled by comprehensively controlling the fuel injection pulse width and the ignition timing in the next cycle of the cylinder # i-1.
The combustion state is corrected so that it changes smoothly and smoothly according to the ignition order, and finally the combustion state of each cylinder # i-1 is controlled to be substantially uniform, that is, to converge to ΔN # i-1 = 0.

In the following, the comparison value Δ of each cylinder # i-1 before one combustion stroke
A method of calculating N # i-1 will be specifically described.

Further, in order to prevent control hunting and the like, as shown in FIG. 5, a constant dead zone region (+) ΔNU, (−) ΔNL is provided, and the comparison value ΔN # i-1 is the dead zone region (+). △
The controllability is further improved by controlling so as to be within NU, (-) ΔNL.

In the following, a correlation equation between the engine speed N in the section where combustion is not performed and the combustion state of the cylinder, that is, the indicated mean effective pressure Pi is shown.

First, when expressing the state where the engine is rotating, I: Moment of inertia N: Engine speed Ti: Instruction torque Tf: Friction torque If we replace it with pressure, Pi: Mean effective pressure indicated Pf: Friction loss effective pressure.

According to the experiment, the engine speed N after combustion of each cylinder #i
Based on #i and the time change ΔT in the section for detecting the engine speed N # i (for example, corresponding to the section (θ2-θ3) in FIG. 10), dN / dt in the above equation (3) is obtained. As a result, a very strong correlation was obtained.

Therefore, by obtaining the engine speed after combustion of each cylinder, the indicated mean effective pressure Pi, that is, the combustion state can be estimated, and by comparing with the engine speed of the adjacent combustion stroke cylinder, It is possible to judge the quality of combustion in the stroke cylinder.

(Operation) Next, a specific idle control procedure executed by the control device 31 will be described with reference to the flowcharts shown in FIGS.

This idle control is performed by the cylinder-by-cylinder average combustion state determination value setting procedure (FIG. 1) and the fuel injection pulse width setting procedure (second procedure).
Fig.), Ignition timing setting procedure (Fig. 3).
It should be noted that this flowchart is executed for each cylinder every predetermined period.

: Cylinder combustion state determination value setting procedure: As shown in FIG. 1, first in step (abbreviated as "S" hereinafter) 101, the vehicle speed S set based on the output signal of the vehicle speed sensor 24 and the output of the idle switch 9b. And read, S102
To determine if it is idle.

Vehicle speed S = 0, idle switch ON (throttle fully closed)
If the vehicle speed is S = 0, or if the vehicle speed S ≠ 0, or if the idle switch is OFF (throttle open), it is determined that the vehicle is running and the routine exits.

When it is determined that the cam is idle and the process proceeds to S103, the cam angle sensor 18
From the cam pulse output from the current combustion stroke cylinder #i (i
= 1,3,2,4). Next, in S104, the crank pulse for detecting BTDCθ2, θ3 output from the crank angle sensor 16 is determined by the interruption of the cam pulse.

Then, in S105, the elapsed time t2,3 between the crank pulses for detecting the BTDC θ2, θ3 determined in S104 and the θ2,
The period f2,3 is calculated from the included angle (θ2-θ3) of θ3 (f2,3 ← dt2,3 / d (θ2-θ3)).

Next, in S106, the engine speed N # i of the section in which the combustion of the current combustion stroke cylinder #i is not working is calculated from the cycle f2,3 calculated in S105, and stored in a predetermined address of the RAM 33 (N # I ← 60 / f2,3).

Then, in S107, the engine speeds N # i-1 and 2 in the section not in work due to the combustion of the cylinder # i-1 before one combustion stroke, which is set in the routine of the previous time and the routine before the time and stored in the predetermined address of the RAM 33. Engine speed N # i-2 in a section not performing work due to combustion of cylinder # i-2 before the combustion stroke
Read and. As shown in FIG. 10, the ignition order is # 1 → # 3 →
In the case of # 2 → # 4, if the current combustion stroke cylinder #i is # 3, the cylinder # i-1 before one combustion stroke is # 1, and the cylinder # i-2 before two combustion strokes is # 4.

Further, the engine speed N # in the initial routine
i-1 and N # i-2 are set to N # i-1 = N # i-2 = N # i.

Next, at S108, the engine speed N #-in the section where no work is performed due to the combustion of the cylinder # i-1 before the first combustion stroke.
1, the engine speed N # 1 and the cylinder #i before the second combustion stroke #i in a section where the work is not performed due to the combustion of the current combustion stroke cylinder #i
State of the cylinder # i-1 before one combustion stroke from the difference of the average value (N # i + N # i-2) / 2 from the engine speed N # i-2 in the section where no work is performed due to the combustion of -2 Comparison value △ N #
Find i-1.

ΔN # i-1 ← N # i-1-((N # i + N # i-2)
/ 2} After that, in S109, the combustion state comparison value obtained in S108 above △
N # i-1 and the previous average combustion state determination value ΔNA # i of the cylinder # i-1 stored at a predetermined address of RAM 33.
-1 (-1), the average combustion state determination value ΔNA # i-1 of the cylinder # i-1 at this time is represented by the weight r
It is obtained from the weighted average of and stored in a predetermined address of the RAM 33. The above-mentioned average combustion state determination value ΔNA # i-
1 (-1) is set to 0.

△ NA # i-1 ← {(2 ^r -1) × △ NA # i-1) (-
1) + ΔN # i−1)} / 2 ^r Then, in S110, the previous average combustion state determination value ΔN of the cylinder # i−1 stored in the predetermined address of the RAM 33.
A # i-1 (-1) is the current average combustion state determination value ΔNA #
Update with i-1 (ΔNA # i-1 (-1) ← ΔNA # i-
1) Then, the routine goes out.

As described above, in this embodiment, the combustion state comparison value ΔNA # i-1 obtained in S108 is not directly used as the combustion state determination value, but the combustion state of the cylinder # i-1 is calculated by the weighted average processing in S109. Therefore, it is possible to obtain stable controllability in the fuel injection pulse width setting described below without making a sudden response to a temporary output fluctuation and measurement error.

: Fuel Injection Pulse Width Setting Procedure: Next, the fuel injection pulse width setting procedure will be described with reference to the flowchart of FIG.

In addition, the battery 41 is removed by repairing the vehicle,
Invalid injection pulse width TS # i and ignition timing correction learning value LADV # for each cylinder stored in the backup RAM 35
The data of i may be broken and become a meaningless value. Therefore, at the time of initialization, in order to detect whether the battery 41 has been removed, a constant determined in a specific address of the backup RAM 35 is normally stored, and whether the value of this constant is broken is stored in a specific address of the ROM 34. When the value of the constant is broken, it is determined by comparing with the reference value (when the value of the constant stored in the backup RAM 35 is not broken, the value of the constant and the reference value are the same). Shows that the invalid injection pulse width Ts # i for each cylinder is TS / n (TS;
Total value of ineffective injection pulse width of each cylinder at battery voltage 14V ΣTs, n; number of cylinders, in case of 4-cylinder engine n = 4, TS / n
The value of is stored in advance in the ROM 34. ), The ignition timing correction learning value LADV # i for each cylinder is initialized to 0, and the constant value stored in the specific address of the backup RAM 35 is reset to the reference value. If the constant value of the backup RAM 35 is not broken at the next startup, the invalid injection pulse width Ts # i, the ignition timing correction learning value
LADV # i is not initialized.

Normally, the following processing is repeatedly executed according to the control program.

First, S201, each sensor 8,9a, 16,18,19,20,22,24, and read the engine operating state from the output signal of the idle switch 9b, in S202, based on the crank pulse and cam pulse fuel injection compatible cylinder #I is determined.

Next, in S203, the idle switch 9b and the vehicle speed sensor 24
From the output signal of, it is determined whether the current operating state is idle.

Idle switch ON at vehicle speed S = 0 (throttle fully closed)
In the case of, it is determined that the vehicle is idle, the process proceeds to S204, and the vehicle speed S ≠ 0,
Alternatively, when the idle switch is OFF, it is determined that the idle state is released and the process proceeds to S205.

When the routine proceeds to S205, the fuel injection pulse width Ti of the fuel injection corresponding cylinder #i is obtained by the following equation as usual, and the routine jumps to S221.

Ti ← Tp × α × COEF + Ts Tp = K ・ Q / N Tp: Basic fuel injection pulse width (basic injection amount) α: Air-fuel ratio feedback correction coefficient COEF: Various increase correction coefficient ts: Set based on battery terminal voltage VB Voltage correction pulse width for correcting the invalid injection pulse width Q: intake air amount N: engine speed K: correction constant based on theoretical air-fuel ratio, injector injection characteristics, number of cylinders, etc. Meanwhile, in S203 above, it is determined to be idle. Then, in S204, the invalid injection pulse width as the injection correction amount of the corresponding cylinder #i stored in the predetermined address of the backup RAM 35.
Ts # i is read out, and in S206, this invalid injection pulse width Ts # i
And a preset invalid injection pulse width allowable upper limit value TsLIMH are compared, and when TsLIMH> Ts # i, the invalid injection pulse width Ts #
When it is determined that there is a margin for correction on the upper limit side of i, the process proceeds to S207,
When TsLIMH ≦ Ts # i, the invalid injection pulse width Ts # i
Is determined to have reached the upper limit value, and the process proceeds to S208.

In S206, when it is determined that TsLIMH> Ts # i and the process proceeds to S207,
The invalid injection pulse width Ts # i is compared with a preset invalid injection pulse width allowable lower limit value TsLIML, and TsLIML <Ts # i,
That is, when TsLIML <Ts # i <TsLIMH, the cylinder #
It is determined that the invalid injection pulse width Ts # i of i is within the allowable limit, and the process proceeds to S209. When TsLIML ≧ Ts # i, the invalid injection pulse width Ts # i reaches the lower limit value. And proceeds to S210.

Note that the above-mentioned allowable injection pulse width allowable limit values TsLIMH, TsLIM
L is the air-fuel ratio of the cylinder #i becomes overrich even if the invalid injection pulse width Ts # i is added when the basic fuel injection amount Tp is corrected by various increase corrections such as warm-up increase and air conditioner increase. Alternatively, it is set in advance as a limit value that does not make it over-lean by experimentally.

Further, in S207, it is determined that TsLIME <Ts # i and S209
If you proceed to, you can use the cylinder combustion state determination program
The average combustion state determination value ΔNA # i stored in the address corresponding to the cylinder #i in RAM 33 is read. In addition,
In the above-mentioned cylinder-by-cylinder combustion state determination program, the above-mentioned average combustion state determination value ΔNA # i is indicated by ΔNA # i−1, and the average combustion state determination value Δ read out by the fuel injection pulse width setting program this time is Δ. NA # i is a value obtained based on the data in the previous cycle of the cylinder #i.

Next, in S211, this average combustion state determination value ΔNA # i is compared with a preset allowable upper limit value ΔNU, and ΔNA # i ≦
If ΔNU, proceed to S212. If ΔNA # i> ΔNU, then the cylinder #i is a cylinder #i that is adjacent to the front and rear in the ignition order.
It is determined that the combustion state is too good for −1, # i + 1, and the process proceeds to S215 to correct the amount of invalid injection pulse width Ts # i.

Then, when proceeding to S212, the average combustion state determination value ΔN
A # i is compared with a preset allowable lower limit value ΔNL, and ΔN
When A # i ≧ ΔNL, the average combustion state determination value ΔNA # i of the cylinder #i is within the allowable range, that is,
When it is determined that the combustion state is ideal (ΔNU ≧ ΔNA # i ≧ ΔNL), the process proceeds to S202, and when ΔNA # i <ΔNL, the cylinder #i is a cylinder adjacent to the front and rear in the ignition order. # I-1, # i +
It is judged that the combustion state is bad for 1 and invalid injection pulse width Ts
The process proceeds to S218 to increase and correct #i.

The permissible limit values ΔNU and ΔNL are, as shown in FIG. 5, dead zones with respect to the average combustion state determination value ΔNA # i.

On the other hand, in S206, the invalid injection pulse width of the cylinder #i concerned
It is determined that Ts #i has reached the upper limit value TsLIMH (TsLI
MH ≦ Ts # i), the process proceeds to S208, and the ignition timing correction learning value LADV # is stored as the ignition timing correction amount of the cylinder #i stored in a predetermined address of the backup RAM 35 in order to improve the combustion state by the ignition advance. i is updated with a value advanced by the set crank angle C (for example, C = 1 ° C. A) (LADV # i
← LADV # i-C).

Next, in S213, the ignition timing correction learning value LADV # i set in S208 is compared with a preset advance limit correction value LmtADV. If LADV # i> LmtADV, the ignition timing correction learning value LADV # i is compared. Is judged to have not reached the advance limit correction value LmtADV yet, and the routine proceeds to S215.

On the other hand, when LADV # i ≦ LmtADV, it is determined that the ignition timing correction learning value LADV # i has reached the advance limit, and S214
Then, the ignition timing correction learning value LADV # i stored in the predetermined address of the backup RAM 35 is set to the advance limit correction value.
Update with LmtADV (LADV # i ← LmtADV) and proceed to S215. In the actual idle control, in the normal state, even though both the invalid injection pulse width Ts # i and the ignition timing correction learning value LADV # i reach the correction limit, the combustion of the cylinder #i concerned is performed. The condition that the condition is not improved is unlikely to occur.

Further, in S207, the invalid injection correction pulse width of the cylinder #i concerned
It is determined that Ts # ii is less than or equal to the lower limit value TsLIML (TsLIML ≥ Ts #
i), when proceeding to S210, the ignition timing correction learning value of the cylinder #i stored in the predetermined address of the backup RAM 35.
Set LADV # i to the set crank angle C (for example, C = 1 ° C A)
Update with the value delayed by (LADV # i ← LADV # i +
C).

Next, in S216, the ignition timing correction learning value LADV # i set in S210 is compared with the preset retardation limit correction value LmtRTD. If LADV # 1 <LmtRTD, the ignition timing correction learning value is compared.
It is determined that LADV # i has not reached the retard limit correction value LmtRTD yet, and the process proceeds to S218.

On the other hand, when LADV # i ≧ LmtRTD, it is determined that the ignition timing correction learning value LADV # i has reached the retard limit, and S217
Then, the ignition timing correction learning value LADV # i stored in the predetermined address of the backup RAM 35 is updated with the retard limit correction value LmtRTD (LADV # i ← LmtRTD), and the process proceeds to S218.

The advance limit correction value LmtADV and the retard limit correction value LmtRTD are previously obtained from experiments and the like within a range that does not cause misfire when the ignition timing θIG is set.

When the process proceeds from S211, S213 or S214 to S215, the cylinder #i invalid injection pulse width Ts # i stored in the backup RAM 35 is updated with a value obtained by subtracting the preset pulse width ΔTs. (Ts # i ← Ts # i- △ T
s) and proceed to S219.

On the other hand, when proceeding from S212, S216, or S217 to S218, the invalid injection pulse width Ts # i of the cylinder #i stored in the backup RAM 35 is updated by a value obtained by adding the preset pulse width ΔTs. (Ts # i ← Ts # i + △ Ts),
Proceed to S219.

The pulse width ΔTs is set in consideration of the output fluctuation amount when the ignition timing is corrected with the set crank angle C, the response characteristic due to the fuel injection correction, and the like.

Further, the ignition timing control has a larger correction effect than the fuel injection control, and a slight correction of the ignition timing causes a large variation in volume efficiency. On the other hand, even if the fuel injection pulse width is slightly corrected, a large correction effect such as the above ignition timing correction cannot be obtained. Therefore, by correcting the fuel amount when the ignition timing is advanced and correcting the fuel amount when retarding the ignition timing, it is possible to more finely control the fuel variation between the cylinders. In addition to the above, for example, even if the invalid injection correction pulse width Ts # i reaches the allowable limit values TsLIMH, TsLIML as a result of the fuel increase or decrease correction, the ignition timing correction learning value LADV # i is set to the set crank. The above-mentioned invalid injection pulse width Ts # i
By increasing or decreasing the amount, the invalid injection correction pulse width Ts # i is within the allowable limit value (TsLIMH> Ts # i> TsLI
ML), fuel correction can be restarted, and the idle speed control becomes wider range.

Then, when the process proceeds from S215 or S218 to S219, RA
Each cylinder # (i, i−1,
i−2, i−3 ...) Average fuel state determination value ΔNA # (i, i−1,
i-2, i-3 ...) are all cleared (△ NA # (i, i-1, i-2, i
-3 ...) ← 0) and proceed to S220.

Since the average combustion state determination value ΔNA # i of each cylinder is obtained by the weighted average, the above-mentioned invalid injection pulse width Ts
Average combustion state determination value ΔNA # i even if #i is properly corrected
Does not always fall within the permissible range (ΔNU ≧ ΔNA # i ≧ NL), but the average fuel state determination value ΔNA # of all cylinders # (i, i-1, i-2, i-3 ...) If i (i, i−1, i−2, i−3 ...) Is not cleared, there is a possibility that an erroneous determination may occur in the next and subsequent operation cycles.

Then, when proceeding from S212 or S219 to S220, the basic fuel injection pulse width (basic injection amount) Tp set based on the engine operating condition read in S201, the air-fuel ratio feedback correction coefficient α, and various increment corrections The fuel injection pulse width is based on the coefficient COEF and the invalid injection pulse width Ts # i read out in S204 or set in S215 and S218.
Set Ti from the following formula.

Ti ← Tp × α × COEF + Ts # i Then, in S221, a drive signal corresponding to the fuel injection pulse width Ti set in S205 or S220 is output to the injector 10 of the corresponding cylinder #i at a predetermined timing, and the routine exits.

Thus, when the invalid injection pulse width Ts # i of each cylinder #i is within the predetermined permissible range (TsLIMH> Ts # i> TsLIML), the average combustion state determination value ΔNA # i exceeds the permissible limit value. If (NA # i> ΔNU or ΔNA # i <
ΔNL), learning can be achieved by reducing or increasing the invalid injection pulse width Ts # i of the corresponding cylinder #i by a predetermined pulse width ΔTs to obtain a combustion state that is almost uniform in all cylinders, and the output is low. Even if you can get a smooth idle rotation.

: Cylinder Ignition Timing Setting Procedure: The cylinder ignition timing setting procedure will be described with reference to the flowchart of FIG.

First, in step S301, the crank pulse and the cam pulse are read, and in step S302, the ignition corresponding cylinder #i is determined based on the crank pulse and the cam pulse read in step S301.

Then, in S303, the output from the crank angle sensor 16
The crank pulse for detecting BTDC θ1 and θ2 is determined from the interruption of the cam pulse.

Then, in S304, the elapsed time t1,2 between crank pulses for detecting the BTDC θ1, θ2 determined in S303 and the θ1,
The period f1,2 is calculated from the included angle (θ1-θ2) of θ2 (f1,2 ← dt1,2 / d (θ1-θ2)).

Next, in S305, the engine speed N1,2 is calculated based on the cycle f1,2 calculated in S304 (N1,2 ← 60 / f1,2).

Then, in S306, the basic fuel injection pulse width Tp set by another program (for example, the fuel injection pulse width setting program) is read, and in S307, the basic fuel injection pulse width (engine load) Tp read in S306, The basic ignition timing θBASE is set based on the basic ignition timing map MPθBASE (see FIG. 9) using the engine speed N1,2 calculated in S305 as a parameter.

Further, in S308, the knock control value θNK is set according to the output signal of the knock sensor 19.

Then, in S309, it is determined whether or not the vehicle is in the idle state based on the output value of the vehicle speed sensor 24 and the output of the idle switch 9b. When the vehicle speed S ≠ 0 or the idle switch is OFF (throttle fully closed), it is determined that the idle is released, and the process proceeds to S310. When the vehicle speed S = 0 and the idle switch is ON (throttle fully closed). , It is determined that it is in the idle state, and the process proceeds to S311.

In S310, the basic ignition timing θBASE set in S307 is corrected by the knock control value θNK set in S308 to calculate the ignition timing θIG (θIG ← θBASE + θNK).

On the other hand, if it is determined to be idle and the process proceeds to S311, the ignition timing correction learning value LADV # i of the corresponding cylinder #i set by the above-mentioned program of fuel injection control is read out, and in S312, the above-mentioned S307
The basic ignition timing θBASE set in step S308 is corrected by the knock control value θNK set in step S308 and the ignition timing correction learning value LADV # i read in step S311 to correct the ignition timing θIG.
Is calculated (θIG ← θBASE + θNK + LADV # i).

Then, in S313, the ignition time ADV is set from the ignition timing θIG calculated in S310 or S312 and the cycle f1,2 calculated in S304 (ADV ← θIG × f1,2).

Next, in S314, the ignition time ADV set in S313 is set by a timer, and in S315, the timing is started by using the θ2 pulse as a trigger, and in S316, when the ignition time is reached, the corresponding cylinder #i
An ignition signal is output to the igniter 25 of and the routine is exited.

Next, the invalid injection pulse width Ts # i according to the above program
An example of the setting state of the ignition timing correction learning value LADV # i will be described with reference to the time charts of FIGS. 11 and 12.

For example, the fuel state comparison value ΔN # 1 of the cylinder # 1 obtained at the elapsed times t1 and t2 is on the minus side as shown in (a), and the weighted average combustion state determination as shown in (b) is performed. The value ΔNA # 1 is lower than the allowable lower limit value ΔNL (ΔN
When A # 1 <△ NL), the combustion condition is bad, so (c)
As shown in, the invalid injection pulse width Ts # 1 of the cylinder # 1
Add the set pulse width ΔTs to (Ts # 1 ← Ts # 1 + ΔT
s), the fuel injection pulse width Ti of the cylinder # 1 is increased.

At this time, since the fuel injection pulse width Ti of the cylinder # 1 is increased, the total air-fuel ratio of all the cylinders shifts to the rich side. Therefore, as shown in (c) to (f), the O ₂ sensor output is changed. The air-fuel ratio feedback correction coefficient α based on this works to perform the correction control to the lean side, and the amount of the cylinder # 1 increased,
The fuel injection pulse width Ti of all cylinders is distributed and reduced almost evenly. When the O ₂ sensor is inactive after the start, the amount of increase in the start and the water temperature are increased, and since the increase in the pulse width ΔTs is relatively small with respect to the increase rate, the invalid injection pulse width There is no big problem even if Ts # 1 is increased.

Then, after the calculation of the cylinder # 1 increase correction is completed, the average combustion state determination value ΔNA # (1,3,2,4) of each cylinder # (1,3,2,4)
4) Reset.

Further, as a result of increasing the invalid injection pulse width Ts # 1 of the cylinder # 1, as shown by the elapsed time t3, when the allowable upper limit value TsLIMH is reached, this invalid injection pulse width Ts # 1 is set to the set pulse width ΔTs. Is subtracted (Ts # 1 ← Ts # 1-ΔTs), the fuel injection pulse width Ti is reduced, and as shown in FIG.
The ignition timing correction learning value LADV # 1 of the cylinder # 1 is advanced and corrected with the set crank angle C (LADV # 1 ← LADV # 1-C).

As a result, the amount of decrease in the fuel injection pulse width Ti and the ignition timing
The average combustion state determination value ΔN of the cylinder # 1 is synergized with the increase in volume efficiency caused by advancing ADV.
A # 1 can be set within the set allowable range without causing overrich.

Also, for example, the cylinder # obtained at the elapsed times t4 and t5
The combustion state comparison value ΔN # 3 of No. 3 is on the plus side as shown in (a), and as shown in (b), the weighted average combustion state determination value ΔNA # 3 of the cylinder # 3 is allowable. Upper limit △
When the value becomes higher than NU (ΔNA # 3> ΔNU), it is determined that the combustion state of the cylinder # 3 is too good, and as shown in (d), the invalid injection pulse width Ts # 3 to the set pulse width Δ Ts is subtracted (Ts # 3 ← Ts # 3-ΔTs), and the fuel injection pulse width Ti of the cylinder # 3 is reduced.

Further, at this time, the total air-fuel ratio of all cylinders deviates to the lean side by the amount by which the fuel injection pulse width Ti of the cylinder # 3 is reduced, so that as shown in (c) to (f), it is based on the O ₂ sensor output. The air-fuel ratio feedback correction coefficient α works to correct to the rich side, and the fuel injection pulse width Ti of all the cylinders is evenly distributed and increased by the reduction amount of the cylinder # 3.

Then, after the calculation of the increase correction of the cylinder # 3 is completed, the average combustion state determination value ΔNA # (1,3, of the square cylinder # (1,3,2,4)
2,4) is reset.

Further, as a result of the reduction correction of the invalid injection pulse width Ts # 3 of the cylinder # 3, as shown by the elapsed time t6, the allowable lower limit value sLIML
When it reaches, the width ΔTs set to this invalid injection pulse width Ts # 3 is added (Ts # 3 ← Ts # 3 + ΔTs), and the cylinder #
The fuel injection pulse width Ti of No. 3 is increased and, as shown in FIG. 12, the ignition timing correction learning value LADV # of the cylinder # 3 is increased.
3 is corrected with the set crank angle C (LADV # 3 ← LADV
# 3 + C). Next, the average combustion state determination value ΔNA # (1,3,2,4) of each cylinder # (1,3,2,4) is reset.

 As a result, the same effect as described above can be obtained.

In this way, the fuel state comparison value ΔN # (1,
3,2,4) converge to 0.

(Second Embodiment) FIG. 13 is a flow chart showing a cylinder-by-cylinder combustion state determination procedure according to the second embodiment of the present invention.

The same steps as those in FIG. 1 of the first embodiment are designated by the same reference numerals.

In this embodiment, the engine speed N # i-1 in the section where the combustion is not performed after the combustion of the cylinder # i-1 before the first combustion stroke and the work is performed by the combustion of the cylinder # i + 1 after the first combustion stroke. The engine speed N # i + 1 (-in the section not working by the fuel one cycle before of the cylinder # i + 1 to be adopted as the estimated value of the engine speed in the section not performing
(1) is compared with the engine speed N # i in the section where the combustion of the current combustion stroke cylinder #i is not working to determine the combustion state of the current combustion stroke cylinder #i. is there.

The combustion state determination procedure will be described below with reference to the flowchart.

First, proceed from S101 to S106 in the same procedure as in FIG.
At 01, cylinder # i- before the first combustion stroke stored in RAM33
The engine speed N # i-1 of the section not performing work by combustion of 1 and the cylinder speed of the cylinder # i + 1 used as the estimated engine speed of the section not performing work by combustion of the cylinder # i + 1 after one combustion stroke Engine speed N # i + 1 (-1) in a section not working due to combustion one cycle before
And in S402, the average value of the engine speed N # i of the combustion stroke cylinder #i obtained in S106 and the engine speed N # i−1, N # i + 1 (−1) read in S401. And the combustion state comparison value ΔN of the combustion stroke cylinder #i.
#I is calculated.

ΔN # i ← N # i-{(N # i-1 + N # i + 1 (-
1)) / 2} After that, in S403, the combustion state comparison value ΔN obtained in S402 above
#I and the previous average combustion state determination value ΔNA # i of the combustion stroke cylinder #i stored in a predetermined address of RAM 33
Based on (-1), the average combustion state determination value ΔNA # i of the current combustion stroke cylinder #i is obtained from the weighted average of the weight r shown in the following equation and stored in a predetermined address of the RAM 33.

ΔNA # i ← {(2 ^r −1) × NA # i (−1) + ΔN # i} / 2 ^r Then, in S404, the combustion stroke cylinder #i stored in the predetermined address of the RAM 33. Of the previous average combustion state determination value ΔNA # i (-1) to the current average combustion state determination value Δ
Update with NA # i (△ NA # i (-1) ← △ NA # i),
Out of routine.

According to this embodiment, after determining the combustion stroke cylinder #i, the average combustion state determination value ΔNA # i of the cylinder #i can be set.

Then, based on the average combustion state determination value ΔNA # i set by the combustion state determination program, in the next cycle, the fuel injection pulse width Ti of the cylinder #i shown in FIG. 2 of the first embodiment is set. Increase or decrease the specified amount.

In this embodiment, cylinder #i after one combustion stroke
The engine speed N in the previous cycle as an estimated value of the engine speed in the section where no work is performed due to +1 combustion
# I + 1 (-1) is adopted, but not limited to this, for example, a simple average value or a weighted average value of the engine speed # i + 1 up to several cycles before the cylinder # i + 1 is adopted as the estimated value. Good.

(Third Embodiment) FIG. 14 is a flow chart showing a procedure for setting the fuel injection pulse width for each cylinder according to the third embodiment of the present invention.

The same steps as those in FIG. 2 of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, first, the fuel injection pulse width Ti is obtained,
At the time of idling, the fuel injection pulse width Ti is corrected by the correction pulse width Tc # i as the injection correction amount to perform the idle control.

The correction pulse width Tc # i is stored in a predetermined address of the backup RAM 35 corresponding to each cylinder, and the initial set value is 0 when data is corrupted.
The procedure for setting the average combustion state determination value ΔNA # i is the same as that in the first embodiment (FIG. 1) and the second embodiment (FIG. 13), and the description thereof will be omitted.

First, when proceeding from S201 and S202 to S501, the fuel injection pulse width Ti is obtained based on the engine operating state read in S201 (Ti ← Tp × α × COEF + Ts).

Next, in S203, it is determined whether or not the current operation state is idle, and if it is in the idle release state, the process jumps to S221. On the other hand, if it is determined that the cylinder is in the idle state, the process proceeds to S502 and the corresponding cylinder # stored in the predetermined address of the backup RAM 35 #
The correction pulse width Tc # i of i is read, and the correction pulse width Tc # i and the preset correction pulse width allowable upper limit value TcLI in S503 are read.
MH is compared, and if TcLIMH> Tc # i, the correction pulse width Tc
It is determined that the correction on the upper limit side of #i has a margin, and the process proceeds to S504. If TcLIMH ≦ Tc # i, the correction pulse width Tc # i
Is determined to have reached the upper limit value, and the process proceeds to S208.

In S503, it is determined that TcLIMH> Tc # i and the process proceeds to S504,
The correction pulse width Tc # i is compared with a preset correction pulse width allowable lower limit value TcLIML. If TcLIML <Tc # i, that is, TcLIML <Tc # i <TcLIMH, the correction pulse width Tc It is determined that #i is within the allowable range, and the process proceeds to S209.

Note that the above correction pulse width allowable limit values TcLIMH, TcLIML
Is a limit value that is set in advance by experiments or the like as a limit value that does not make the air-fuel ratio of the cylinder #i overrich even if this value is added to the fuel injection pulse width Ti, or does not become lean.

Further, when it is determined that TcLIML <Tc # i in S504 and the process proceeds to S209, the average combustion state determination value ΔNA # i of the cylinder #i is read, and the average fuel state determination value ΔNA # i is preset in S211. The allowable upper limit value ΔNU is compared, and ΔNA # i ≦ Δ
If NU, the process proceeds to S212. If ΔNA # i> ΔNU, it is determined that the combustion state is too good, and the correction pulse width Tc # i
Proceed to S505 to correct the weight loss.

Then, when proceeding to S212, the average combustion state determination value ΔNA # i
Is compared with a preset allowable lower limit value ΔNL, and ΔNA # i
≧ ΔNL, that is, ΔNU ≧ ΔNA # i ≧ ΔNL,
Since the combustion state is ideal, the process directly proceeds to S507. When ΔNA # i <ΔNL, the combustion state is bad, and therefore the process proceeds to S506 to increase the correction pulse width Tc # i. Further, when the process proceeds from S503 to S208, S213, S214, or from S211 to S505, the correction pulse width Tc # i of the cylinder #i stored in a predetermined address of the backup RAM 35 is set to a preset pulse width Δ. Update with the value subtracted by Tc (Tc # i
← Tc # i-ΔTc), and proceeds to S219.

On the other hand, when the process proceeds from S504 to S210, S216, S217, or from S212 to S506, the correction pulse width of the cylinder #i stored at the predetermined address of the backup RAM 35.
Tc # i is updated with a value obtained by adding the preset pulse width ΔTc (Tc # i ← Tc # i + ΔTc), and the process proceeds to S219.

The pulse width ΔTc is set in consideration of the output fluctuation amount when the ignition timing is corrected at the set crank angle C, the response characteristic due to the fuel injection correction, and the like.

After that, when the process proceeds from S505 or S506 to S219, each cylinder # stored in the predetermined address of RAM 33
(I, i−1, i−2, i−3 ...) Average combustion state determination value ΔNA #
Clear all (i, i−1, i−2, i−3 ...) and (ΔNA #
(I, i−1, i−2, i−3 ...) ← 0), the process proceeds to S507.

Then, when proceeding from S219 or S212 to S507, the fuel injection pulse width Ti set in S501 is set to S502.
Or read with the correction pulse width Tc # i set in S505 or S506 (Ti ← Ti + Tc # i), and in S221, a drive signal corresponding to the combustion injection pulse width Ti is output to the cylinder #i. Output to the injector 10 at a predetermined timing,
Out of routine.

Since the ignition timing setting procedure in this embodiment is the same as that in the first embodiment (FIG. 3) described above, description thereof will be omitted.

(Fourth Embodiment) FIGS. 15 and 16 show a fourth embodiment of the present invention, and FIG. 15 is a flow chart showing a cylinder-by-cylinder combustion state determination procedure.
The figure is a flowchart showing the procedure for setting the fuel injection pulse width for each cylinder.

In this embodiment, the engine speed N # i of the section in which the combustion stroke cylinder #i is not working due to combustion is weighted and averaged for each cylinder to obtain the average engine speed NA # i. -1 average engine speed NAi-1
And 2 cylinders before combustion stroke # i-2 and current combustion stroke cylinder #
The average combustion state determination value ΔNA # i-1 of the cylinder # i-1 before one combustion stroke is obtained from the difference between the average engine speeds NA # i-2 and NA # i of i. It is a thing.

According to this embodiment, since the engine speed is obtained as a value smoothed by the weighted average, it is possible to effectively prevent erroneous determination especially in a period with a small sampling number, such as immediately after shifting to idle. .

 Hereinafter, description will be given according to the flowchart.

From S101 to S106, the same routine as that of the first embodiment (FIG. 1) is executed, and in S601, the engine speed N # in the section where no work is performed by the combustion of the current combustion stroke cylinder #i obtained in S106. i and the cylinder #i of one cycle before
The average engine speed NA # i of the current combustion stroke cylinder #i is calculated from the weighted average of the weight r based on the average engine speed NA # i (-1) calculated in the combustion state determination flowchart of (-1).

NA # i ← {(2 ^r -1) × NA # i (-1) + N # i} / 2 ^r Then, in S602, the cylinder #i corresponding to one cycle before stored in the predetermined address of the RAM 33 is stored. The average engine speed NA # i (-1) is updated with the average engine speed NA # i obtained in S601 (NA # i (-1) ← NA #.
i).

Next, in step S603, set in the routine of the last time before and the time before, and RA
Cylinder # i- before one combustion stroke stored in the prescribed address of M33
Average engine speeds NA # i-1 and NA # in the sections where there is no work due to combustion of cylinders # i-2 before combustion strokes 1 and 2
i-2 is read, and in S604, an average value of the average engine speed NA # i of the current combustion stroke cylinder #i obtained in S601 and the average engine speed NA # i-2 read in S603,
The average combustion state determination value ΔNA # i-1 of one cylinder before the combustion stroke # NA # i-1 is set based on the difference from the average engine speed NA # i-1 read out in S603, and stored in a predetermined address of the RAM33. , Out of routine.

ΔNA # i-1 ← NA # i-1 − {(NA # i + NA # i-2) / 2} Then, in the cylinder-by-cylinder combustion injection pulse width setting program of FIG. S21 based on the set average combustion state determination value ΔNA # i
In 1 and S212, the combustion state of the cylinder #i is determined in the same manner as in the first embodiment (FIG. 2) described above, and in S601, each cylinder # (i, i- 1, i−2, i−
3) average engine speed NA # (i, i-1, i-2, i-3
...) are all cleared (NA # (i, i-1, i-2, i-3 ...) ←
0)

Note that the other routines are the same as those in the first embodiment, so the description thereof will be omitted.

Further, the present invention is not limited to the above-mentioned embodiments, and if it falls, the operating amount of the section in which there is no work due to combustion of each cylinder is not limited to the engine speed, but may be angular acceleration, cycle, angular velocity, or the like. Well, in particular, by using the angular acceleration obtained by differentiating the engine speed with respect to time, since the time factor is taken into consideration, the momentum can be accurately measured.

As described above, according to the present invention, when the average value of all cylinders is compared with the value of the cylinder, the average value of all cylinders includes the combustion state of the cylinder, and the combustion of the cylinder is performed. By comparing the average value of all cylinders including the state and the cylinder concerned, the combustion state of the cylinder concerned will be judged and the reliability deteriorates.
When using the average value of all cylinders, each momentum of all cylinders + the relevant cylinder must be stored. However, in the present invention, the average value of all cylinders is not used, and the section in which no work is performed by combustion of the relevant cylinder. Therefore, the combustion state of the cylinder is determined from the difference between the momentum and the average value of the momentum of the cylinders that do not include the combustion state of the cylinder and that are adjacent to each other in the ignition order. , It is possible to directly determine whether or not the combustion state of the cylinder is adjacent to both cylinders in the ignition order, and to accurately determine the combustion state of the cylinder, and to store the momentum of each of the cylinders before and after the cylinder in the ignition order + ignition order. It is possible to determine the combustion state of the cylinder in more real time, and according to the combustion state determination result of the corresponding cylinder, the combustion injection control and the ignition timing control at the idle time of the corresponding cylinder are performed. Since comprehensive control of people, the combustion state of each cylinder is uniform idle speed is stabilized, it is possible to obtain a smooth engine.

[Brief description of drawings]

1 to 12 show a first embodiment of the present invention, FIG. 1 is a flow chart showing a cylinder combustion state determination procedure, FIG. 2 is a flow chart showing a cylinder fuel injection pulse width setting procedure, and FIG. FIG. 4 is a flow chart showing the ignition timing setting procedure for each cylinder, FIG. 4 is a conceptual diagram showing a basic combustion state determination method for each cylinder, FIG. 5 is a conceptual diagram showing a dead zone region, and FIG. 6 is an outline of an engine control system. 7 and 8 are front views of the crank rotor and the crank angle sensor, FIG. 8 is a front view of the cam rotor and the cam angle sensor, and FIG. 9 is a conceptual diagram of the basic ignition timing map.
FIG. 10 is a time chart showing cylinder pressure fluctuation, crank pulse, cam pulse, and engine rotation fluctuation,
FIG. 11 is a time chart showing the combustion state comparison value for each cylinder, the average combustion state determination value for each cylinder, and the invalid injection pulse width for each cylinder.
FIG. 12 is a time chart showing the ignition timing correction learning value for each cylinder, FIG. 13 is a flow chart showing the procedure for determining the combustion state for each cylinder according to the second embodiment of the present invention, and FIG. 14 is according to the third embodiment of the present invention. Flowchart showing the fuel injection pulse width setting procedure for each cylinder, FIG. 15, FIG. 16 shows the fourth embodiment of the present invention, FIG. 15 is a flowchart showing the procedure for determining the combustion state for each cylinder, and FIG. 16 is for each cylinder It is a flow chart which shows a fuel injection pulse width setting procedure. #I ... Current combustion stroke cylinder, # i-1 ... 1 combustion stroke before cylinder, # i + 1 ... 1 combustion stroke after cylinder, # i-2 ... 2 combustion stroke before cylinder, N # i, N # i -1, N # i-2 ... Momentum in the non-working section due to combustion, Nli + 1 (-1) ...
… Estimated momentum, △ NA # i, △ NA # i-1 …… Combustion state determination value, △ NU …… Combustion state determination allowable upper limit value, △ NL …… Combustion state determination allowable lower limit value, Ts # i, Tc # i ... Injection correction amount,
TsLIMH, TcLIMH ... Injection correction allowable upper limit value, TsLIML, TcLIML
...... Injection correction allowable lower limit value, LADV # i …… Ignition timing correction amount.

Claims (2)

(57) [Claims] 1. When the engine is in an idle state, the momentum of a section in which one cylinder before combustion stroke is not working due to combustion, and the momentum in a section before two combustion stroke cylinders and present combustion stroke cylinders are not performing work. The combustion state determination value of the cylinder before the first combustion stroke is obtained from the difference from the average value of the momentum, and when the combustion state determination value of the cylinder before the first combustion stroke exceeds the combustion state determination allowable upper limit value, in the next cycle 1 above
When the injection correction amount of the cylinder before the combustion stroke is decreased by a set amount, and when the combustion state determination value is lower than the combustion state determination permission lower limit value, the injection correction amount of the cylinder before the first combustion stroke in the next cycle is increased by the set amount. If the injection correction amount exceeds the injection correction allowable upper limit value, the ignition timing correction amount of the cylinder is advanced by the set angle, the injection correction amount is decreased by the set amount, and An engine idle control method characterized in that, when the injection correction amount is lower than an injection correction allowable lower limit value, the ignition timing correction amount of the cylinder is retarded by a set angle and the injection correction amount is increased by a set amount. 2. When the engine is in an idle state, the momentum of a section not working by combustion of the current combustion stroke cylinder, the momentum of a section not working by combustion of one cylinder before the combustion stroke and after one combustion stroke The combustion state determination value of the current combustion stroke cylinder is determined from the difference from the average value of the estimated momentum in the section where the cylinder is not working due to combustion, and the combustion state determination value of the current combustion stroke cylinder is the combustion state determination allowable upper limit. If the value exceeds this value, the injection correction amount of the current combustion stroke cylinder in the next cycle is reduced by a set amount, and if the combustion state determination value is lower than the combustion state determination allowable lower limit value, the current combustion stroke in the next cycle is performed. When the injection correction amount of the cylinder is increased by a set amount and the injection correction amount exceeds the injection correction allowable upper limit value, the ignition timing correction amount of the cylinder is advanced by a set angle and the injection correction is performed. If the injection correction amount of the current combustion stroke cylinder is lower than the injection correction allowable lower limit value, the ignition timing correction amount of the cylinder is retarded by the set angle and the injection correction amount is increased by the set amount. Characteristic engine idle control method.