JP2505304B2 - Idle control device for multi-cylinder engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an idle control device for a multi-cylinder engine that reduces engine rotation fluctuation during idling in a multi-cylinder engine.

[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 fuel state causes the intake pipe shape to become complicated, the intake distribution between the cylinders to become non-uniform, and the like. A slight difference in combustion temperature between cylinders caused by the cooling path, variations in the combustion chamber volume of each cylinder, manufacturing variations such as piston shape, and differences in fuel injection amount due to injector manufacturing errors, etc. It is thought to be caused by slight variations.

Therefore, the idle rotation speed can be made smooth by controlling the combustion state of each cylinder substantially uniformly.

Fuel injection control and ignition timing control can be considered as means for uniformly controlling the combustion state of each cylinder, but the fuel injection control must be controlled within the theoretical air-fuel ratio range, and the control range is greatly limited. To be done.

On the other hand, in the ignition timing control, there is a problem in controllability because the combustion state of the engine fluctuates remarkably with a slight advance or retard correction.

Therefore, for example, as disclosed in Japanese Patent Application Laid-Open No. 2-64252, there is one that controls both fuel injection control and ignition timing control at the same time.

In the publication, when the engine is in an idle state, the amount of change in angular velocity for a predetermined period is calculated for each cylinder, and the difference in the amount of change in angular velocity between the cylinders becomes a predetermined value based on the amount of change in angular velocity. As described above, the correction amount of each cylinder is calculated, the basic ignition timing and the basic injection amount of each cylinder are corrected by the correction amount, and the combustion state is controlled for each cylinder to reduce the exhaust cleanliness at the time of idling and the idling speed. Techniques for suppressing fluctuation are disclosed.

Specifically, for example, in the case of a 4-cylinder engine, the average value of the angular velocities of the # 1 and # 2 cylinders during a predetermined period at idle. When the absolute value of the difference | ΔNE1 | is larger than the specified value, it is determined that the combustion states of both cylinders are not in equilibrium, and each average value And the magnitude relationship with Is the average value of # 2 cylinder When the combustion state of the # 1 cylinder is worse than that of the # 2 cylinder, the ignition timing correction amount is increased by a predetermined amount to advance the # 1 cylinder by a predetermined amount to generate the # 1 cylinder. While increasing the torque, the # 2 cylinder is retarded by the same amount to reduce the torque generated in the # 2 cylinder. In the case of, the reverse is done to make the torques of the # 1 and # 2 cylinders uniform, and the ignition timings of the # 3 and # 4 cylinders are similarly corrected to make the torques of the # 3 and # 4 cylinders uniform. Further, the ignition timing is corrected so that the average value of the angular velocities of the # 1 and # 2 cylinder groups and the average value of the angular velocities of the cylinder groups # 3 and # 4 are balanced.

Furthermore, after that, similarly, the equilibrium state of the # 1 and # 2 cylinders is determined, and the average value of the # 1 cylinder is determined. Is the average value of # 2 cylinder If the combustion state of the # 1 cylinder is worse than that of the # 2 cylinder, the fuel consumption of the # 1 cylinder is increased by a predetermined amount by increasing the fuel injection amount correction amount by a predetermined amount. The same amount as the torque generated by #
Reduce the fuel consumption of the two cylinders to reduce the torque generated by the # 2 cylinder. In the case of, the reverse is done to make the torques of the # 1 and # 2 cylinders uniform, and the fuel injection amounts of the # 3 and # 4 cylinders are similarly corrected to make the torques of the # 3 and # 4 cylinders uniform. I am trying to let you. Further, by correcting the fuel injection amount so that the average value of the angular velocities of the cylinder groups # 1 and # 2 and the average value of the angular velocities of the cylinder groups # 3 and # 4 are balanced, Average value Are corrected to be equal to each other, the fuel state of each cylinder is made uniform, and the fluctuation of the idle speed is suppressed, and
By keeping the sum of the correction amount of each cylinder of the ignition timing and the sum of the correction amount of each cylinder of the fuel injection amount to be zero at all times, the total air-fuel ratio viewed from all the cylinders is made to match the target air-fuel ratio, and the ignition timing is set to the target ignition. It is possible to control the combustion states of all the cylinders so as not to deviate from the target operating point in time with the timing, and suppress deterioration of exhaust gas cleanliness.

[Problems to be Solved by the Invention] However, in the above-mentioned prior art example, in order to make the generated torques among the respective cylinders in the respective cylinder groups equal to each other,
Set the ignition timing correction amount to correct the unbalanced state between the cylinders, and then set the fuel injection amount correction amount to correct the unbalanced state between the cylinder groups to match the torque generated between the cylinder groups. Therefore, two correction terms are used when setting the ignition timing in each cylinder, and two correction terms are also used for each cylinder when setting the fuel injection amount in each cylinder. Therefore, the control system is complicated. In addition, there is a disadvantage that the calculation load on the control device increases.

Further, generally, the change in the combustion state (change in generated torque) due to the ignition timing correction is larger than that due to the fuel injection amount correction, and the volume efficiency fluctuates greatly with a slight ignition timing correction, while the fuel injection amount is slightly changed. Even if the correction is made to 1, the correction effect as great as the ignition timing correction cannot be obtained. In the above prior art, the ignition timing is preferentially corrected for each cylinder, and then the fuel injection amount is corrected. Therefore, in order to improve the control accuracy, the ignition timing correction amount is updated by a fine value. In addition, the ignition timing control accuracy must be improved, a control device with a very high resolution is required, and there is a disadvantage that the cost is increased.

In view of the above circumstances, the present invention suppresses complication of a control system and an increase in calculation load in a control device, and makes the combustion state of each cylinder uniform without using a control device with high resolution. An object of the present invention is to provide an idle control device for a multi-cylinder engine that can suppress fluctuations in engine speed and suppress deterioration of exhaust gas purification performance.

[Means for Solving the Problems] To achieve the above object, an idle control device for a multi-cylinder engine according to the present invention, as shown in FIG. 1, is an operating state detecting means M1 for detecting the operating state of the engine, and a combustion state. Crank angle detection means M2 that outputs a signal that can identify the cylinder in the stroke and a signal that corresponds to a predetermined crank angle, idle determination means M3 that determines the idle state of the engine from the engine operating state, and the engine idle state When, the difference in engine rotation fluctuation for each predetermined crank angle is detected,
Combustion state determination means M4 for determining the combustion state of the combustion stroke cylinder by comparing the engine rotation variation difference with the upper limit value and the lower limit value, and the engine in the idle state, the rotation variation difference of the cylinder has the upper limit value. When it exceeds, or when the injection correction amount of the cylinder exceeds the allowable upper limit value, the injection correction amount of the cylinder is reduced by a set amount, and the injection correction amounts of other cylinders are adjusted corresponding to the reduction amount. Equal distribution increase,
In the idle state, when the rotation fluctuation difference of the cylinder is lower than the lower limit value, or when the injection correction amount of the cylinder is lower than the allowable lower limit value, the injection correction amount of the cylinder is increased by the set amount and the increase amount is increased. Correspondingly, the injection correction amount setting means M5 for setting the injection correction amount for each of the other cylinders by reducing the distribution equally.
When the engine is in the idle state and the injection correction amount of the cylinder exceeds the allowable upper limit value, the ignition timing correction amount of the cylinder is advanced by the set amount, and when the injection correction amount of the cylinder is lower than the allowable lower limit value. , An ignition timing correction amount setting means M6 for setting the ignition timing correction amount of the cylinder with a set amount retarded, and a basic injection amount is calculated based on the engine operating state, and when the engine shifts to an idle state, the basic injection amount corresponds to the corresponding cylinder. Injection amount calculation means M7 for calculating the fuel injection amount for each cylinder by correcting with the injection correction amount, fuel supply means M8 for supplying fuel to the corresponding cylinder based on the output of the injection amount calculation means, and engine operation Ignition timing calculation means M9 for calculating the basic ignition timing based on the state, and when shifting to the idle state, the basic ignition timing is corrected by the ignition timing correction amount of the corresponding cylinder to calculate the ignition timing for each cylinder; And ignition means M10 based on the output of the calculation means for igniting the mixture of the corresponding cylinder, characterized in that it comprises a.

[Operation] According to the present invention, in the idle state, the combustion state of the combustion stroke cylinder is determined by comparing the engine rotation variation difference for each predetermined crank angle with the upper limit value and the lower limit value. When it exceeds the value, it is determined that the torque generated in the cylinder is too high for other cylinders, the injection correction amount of the cylinder is reduced by the set amount, and the injection of other cylinders is performed corresponding to the reduction amount. Reduce the correction amount by even distribution.

Further, when the rotation fluctuation difference of the cylinder is lower than the lower limit value, it is determined that the torque generated in the cylinder is too low compared to the other cylinders, and the injection correction amount of the cylinder is increased by a set amount and the increased amount is dealt with. Then, the injection correction amount of each of the other cylinders is reduced equally, and the basic fuel injection amount is corrected by the injection correction amount of the corresponding cylinder to calculate the fuel injection amount for each cylinder to calculate the fuel injection amount for the corresponding cylinder. Supply fuel.

Further, when the generated torque of the cylinder is low, the injection correction amount is increased to increase the generated torque of the cylinder, and when the injection correction amount exceeds the allowable upper limit value, the correction upper limit of fuel injection is reached. Judgment, the injection correction amount of the cylinder is corrected by the set amount reduction, the ignition timing correction amount of the cylinder is advanced by the set amount, and the injection of the other cylinders is injected corresponding to the injection correction amount reduction amount of the cylinder. Increase the correction amount evenly.

On the other hand, when the torque generated in the cylinder is high, the injection correction amount is repeatedly reduced to reduce the torque generated in the cylinder, and when the injection correction amount falls below the allowable lower limit value, the correction lower limit limit due to fuel injection is reached. Judgment, the injection correction amount of the cylinder is corrected by the set amount increase, the ignition timing correction amount of the cylinder is retarded by the set amount, and the injection of the other cylinders is injected corresponding to the injection correction amount increase of the cylinder. The correction amount is equally distributed and reduced, and the basic injection amount and the basic ignition timing are corrected by the injection correction amount and the ignition timing correction amount to set the fuel injection amount and the ignition timing for each cylinder.

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

2 to 10 show a first embodiment of the present invention, FIG. 2 is an overall schematic view of an engine control system, FIG. 3 is a front view of a crank rotor and a crank angle sensor, and FIG. 4 is a cam rotor. FIG. 5 is a front view of the cam angle sensor, FIG. 5 is a conceptual diagram of a basic ignition timing map, FIG. 6 is a time chart showing the relationship between cylinder pressure fluctuation, crank pulse, cam pulse, and engine speed, and FIG. FIG. 8 is a flowchart showing a cylinder-by-cylinder fuel injection control procedure, FIG. 9 is a flowchart showing a cylinder-by-cylinder ignition timing control procedure, and FIG. 10 is a cylinder-by-cylinder average difference rotation speed. 6 is a time chart showing a relationship between a cylinder-specific invalid injection correction pulse width and a cylinder-specific ignition timing learning correction value.

(Structure) Reference numeral 1 in FIG. 2 is a multi-cylinder engine, and in FIG.
A cylinder horizontally opposed engine is shown. An intake manifold 3 is communicated with an intake port 2a formed in a cylinder head 2 of the engine 1, a throttle chamber 5 is communicated upstream of the intake manifold 3 through an air chamber 4, and an intake air is upstream of the throttle chamber 5. An air cleaner 7 is attached via a 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.

Further, an injector (fuel supply means) is provided immediately upstream of each cylinder port 2a of each cylinder of the intake manifold 3.
10 are arranged. Further, an ignition plug 11 is attached to each cylinder of the cylinder head 2 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 body 1, and a crank angle formed by an electromagnetic pickup or the like for detecting a protrusion (or slit) corresponding to a predetermined crank angle on the outer periphery of the crank rotor 15. A sensor 16 is provided oppositely, and a cam rotor 17 is provided continuously to the camshaft 1c which makes a half rotation with respect to the crankshaft 1b. A cam angle sensor 18 is provided at the outer circumference of the cam rotor 17 oppositely.

As shown in FIG. 3, protrusions (or slits) 15a, 15b, 15c are formed on the outer periphery of the crank rotor 15. These protrusions 15a, 15b, 15c are formed at positions before compression top dead center (BTDC) θ1, θ2, θ3 of each cylinder.
Cycle 1.2 from the transit time between a and 15b (where: =
1 / ω ω: angular velocity) is calculated, and the period 2.3 is calculated from the transit time between the protrusions 15b and 15c. In addition, the above protrusion 1
5b shows the reference crank angle when setting the ignition timing ADV.

As shown in FIG. 6, 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. In general, 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 about 10 ° A.

Further, as shown in FIG. 6, in the embodiment, the valve 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 cylinder. Since the combustion pressure immediately after opening the exhaust valve is drastically reduced, 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 advanced side from ℃ A, the section between the crank angles BTDCθ2, θ3 of the projections 15b, 15c is hardly affected by the combustion between the 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. 4, 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. 6, 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.

Further, after detecting the cam pulse 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 corresponding 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 body 1 is fixedly installed in the engine body 1,
Further, the cooling water temperature sensor 20 is exposed to the cooling water passage (not shown) without the riser formed on the enter manifold 3.

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 of this control device 31
2, ROM33, RAM34, backup RAM35 (non-volatile RAM)
Further, the I / O interface 36 is connected to each other via the bus line 37, and a predetermined stabilizing 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, and when the key switch 40 is turned on and the relay contact of the control relay 39 is closed, power for control is supplied to each part and is directly connected to the battery 41, and the key switch is 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 the I I / O interface 36 output port, spark plug 1
1 is connected via an igniter 25, and the injector 10 is connected via a drive circuit 42.

The ROM 33 stores a control program, fixed data and the like. As fixed data, there is a basic ignition timing map MPθBASE described later.

Further, the RAM 34 stores output signals of the respective sensors after data processing, data processed by the CPU 32, and the like. In addition, the backup RAM 35 is always turned on regardless of the key switch 40.
Even if it is turned off and the operation of the engine is stopped, the stored contents do not disappear, and the invalid injection correction pulse width data for each cylinder, which will be described later,
Also, ignition timing correction learning value data and the like are stored.

Further, in the CPU 32, according to the control program stored in the ROM 33, the RAM 34 and the backup RAM are
Based on various data stored in 35, injector
Calculates the fuel injection pulse width for 10 or ignition timing.

The idle control function of the control device 31 includes an idle determination means for determining the idle state of the engine from the operating state of the engine, and an engine rotation fluctuation difference for each predetermined crank angle when the engine is in the idle state. Combustion state discrimination means for discriminating the combustion state of the combustion stroke cylinder by comparing the engine rotation fluctuation difference with the upper limit value and the lower limit value, and when the engine is in the idle state and the rotation fluctuation difference of the cylinder exceeds the upper limit value. Or the injection correction amount of the cylinder exceeds the allowable upper limit value, the injection correction amount of the cylinder is reduced by a set amount, and the injection correction amounts of other cylinders are set in correspondence with the reduction amount. When the distribution amount is increased, and in the idle state, the difference in rotation fluctuation of the cylinder is lower than the lower limit value, or when the injection correction amount of the cylinder is lower than the allowable lower limit value, An injection correction amount setting means for increasing the injection correction amount of the cylinder by a set amount and setting the injection correction amount of each of the other cylinders by equally dividing and reducing the injection correction amount, and setting the injection correction amount for the cylinder in the idle state. When the injection correction amount of the cylinder exceeds the allowable upper limit value, the ignition timing correction amount of the cylinder is advanced by a set amount, and when the injection correction amount of the cylinder is lower than the allowable lower limit value, the ignition timing correction amount of the cylinder is set. Ignition timing correction amount setting means for delaying and setting the amount, and calculating the basic injection amount based on the engine operating state, and when shifting to the idle state, the basic injection amount is corrected by the above-mentioned injection correction amount of the corresponding cylinder and Injection amount calculation means for calculating the fuel injection amount of
Ignition timing calculating means for calculating the basic ignition timing based on the engine operating state and correcting the basic ignition timing with the above-mentioned ignition timing correction amount of the corresponding cylinder to calculate the ignition timing for each cylinder when shifting to the idle state is included. ing.

The sensors 8, 9a, 16, 18, 18, 19, 20, 22, 24, the idle switch 9b and the like constitute an operating state detecting means, and the ignition plug 11, the ignition coil 11a, the igniter 25.
Etc. constitute the ignition means.

(Operation) Next, the idle control procedure by the control device 31 will be described in the seventh step.
This will be described with reference to the flowcharts shown in FIGS.

This idle control is performed by the average difference rotational speed calculation procedure (7th
Fig.), A fuel injection control procedure (Fig. 8), and an ignition timing control procedure (Fig. 9). It should be noted that these flowcharts are executed for each cylinder for each predetermined cycle.

: Average difference rotational speed calculation procedure: First, in step (hereinafter referred to as "S") S101, vehicle speed S
Read the idle switch output.
It is determined from the vehicle speed S and the idle switch output read in step 3 whether the current operating state is idle.

Vehicle speed S = 0, idle switch ON (throttle fully closed)
In the case of, the vehicle is determined to be idle, the process proceeds to S103, and the vehicle speed S ≠
If 0, or if the idle switch is OFF (throttle fully closed), it is judged that the vehicle is running and the routine is exited.

In S103, the combustion stroke cylinder #i (i = 1,3,2,4) is determined from the cam pulse output from the cam angle sensor 18. 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 2.3 is calculated from the angle (θ2−θ3) between θ3 (2.3 = dt2.3 / d (θ2−θ3)).

Next, in S106, the engine speed NNEW is calculated from the cycle 2.3 calculated in S105 (NNEW ← 60 / 2.3).

Then, in S107, a section in which no combustion work is performed by the combustion stroke cylinder #i based on the difference between the engine speed NNEW calculated in S106 and the engine speed NOLD of the cylinder # i-1 calculated in the previous routine. (See FIG. 6) The differential rotation speed ΔN # i is calculated (ΔN # i ← NNEW-NOLD), and S108
Then, the previous engine speed NOLD stored in the predetermined address of the RAM 34 is updated with the current engine speed NNEW calculated in S106 (NOLD ← NNEW).

Then, in S109, the differential rotation speed ΔN calculated in S107 above.
#I and the previous average differential rotational speed ΔNA # i (-1) of the cylinder #i stored at a predetermined address of the RAM 34, the average differential rotational speed ΔNA #, which is an example of the engine rotational fluctuation difference of this time. i is calculated from the weighted average of the weighting coefficient (weight of the weighted average) r (ΔNA # i ← ((2 ^r −1) × ΔNA # i (−
1) + ΔN # i) / 2 ^r ), store at the corresponding address in RAM 34.

After that, in S110, the previous average differential rotation speed ΔNA # i (-of the cylinder #i stored in the predetermined address of the RAM 34 is stored.
1) is the average differential rotational speed ΔNA # i obtained in S109 above
Update (ΔNA # i (-1) ← ΔNA # i), and the routine exits.

Since NOLD has not been set in the first routine, the routine jumps to S107, and in the first routine for each cylinder, ΔNA # i (-1) ← 0 is exited.

As shown in FIG. 6, in the case of a 4-cycle 4-cylinder engine, the engine speed NNEW calculated based on the cycle 2.3.
Is executed every 180 ° C., the cycle 2.3 for measuring between cylinders is common.

Therefore, for example, when paying attention to the cylinder # 1, if the previously calculated engine speed NOLD is subtracted from the engine speed NNEW calculated this time, the differential rotation speed Δ of the cylinder # 1.
N # 1 is obtained, and on the other hand, when looking at cylinder # 3, by setting the engine speed NNEW of cylinder # 1 to NOLD, the differential rotation speed Δ from the engine speed NNEW of cylinder # 3 thereafter.
N # 3 can be obtained.

The engine speed of the cylinders that are common to each other is N
When 4.1, N1.3, N3.2 and N2.4 are used, the differential rotation speed of each cylinder is as follows.

ΔN # 1 = N1.3−N4.1 ΔN # 3 = N3.2−N1.3 ΔN # 2 = N2.4−N3.2 ΔN # 4 = N4.1−N2.4 By the way, the above differential rotation speed Experiments have shown that ΔN # i has a strong correlation with the indicated mean effective pressure Pi, that is, the combustion state of the cylinder. Therefore, as described above, by determining the differential rotation speed ΔN # i, the quality of the combustion state (indicated average effective pressure) of each cylinder #i can be estimated.

The relationship between the differential rotation speed ΔN # i and the indicated mean effective pressure is shown below.

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 crank angle for detecting the rotation speed and the crank angle width for calculating the speed are set to θ2.3 as described above,
That is, if set before and after the combustion stroke, 4 cycles 4
In the case of a cylinder engine, as a result of obtaining dN / dt in the above formula (3) based on the above-mentioned differential rotation speed ΔN # i and the temporal change ΔT (180 ° C A) between them, a very strong correlation is found. can get.

In this case, if the fluctuation of ΔT (180 ° C A) is negligible and the effective friction loss pressure Pf is also considered to be constant, then from the above formula (3), ΔN = K × Pi−PF (4) K , PF: The constant holds.

Therefore, the indicated mean effective pressure Pi, that is, the combustion state can be estimated for each cylinder by obtaining the differential rotation speed ΔN of each cylinder.

If the differential rotation speed ΔN # i of each cylinder #i is individually brought close to “0”, the combustion state of each cylinder can be made uniform.

On the other hand, in the above formula (3), assuming that the friction average effective pressure Pf is constant and the constant C is set and the proportional constant is K, Therefore, by obtaining K and C in advance, the indicated mean effective pressure Pi can be obtained.

According to this equation (5), the indicated mean effective pressure Pi can be more accurately estimated from the differential rotation speed ΔN by differentiating the differential rotation speed ΔN with respect to time.

Further, by obtaining the average differential rotation speed ΔNA # i by the weighted average, it is possible to correct variations in the measurement error of the cylinder and temporary rotation speed fluctuations.

: Fuel Injection Control Procedure: Next, the fuel injection control procedure will be described with reference to FIG.

In addition, the battery 41 is removed due to vehicle repair etc.,
Invalid injection correction 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 normal backup RAM 35 is stored, and whether the value of this constant is broken is stored in a specific address of the ROM 33. If the constant value is broken, it is determined by comparing it with the reference value (if the constant value stored in the backup RAM is not broken, the constant value and the reference value are the same). Shows that the invalid injection correction pulse width Ts # i for each cylinder is Ts / n (Ts: for example, the combined value ΣTs, n of the invalid injection pulse widths of the cylinders when the battery voltage is 14V) assuming that the battery 41 is removed. : Number of cylinders, n = 4 for 4-cylinder engine,
The value of Ts / n is stored in the ROM 33 in advance. ), The ignition timing correction learning value LADV # i for each cylinder is initialized to 0, and the value of the constant stored in the specific address of the backup RAM 35 is reset to the reference value. When the constant value of the backup RAM 35 is not broken at the next start, the invalid injection correction pulse width Ts # i and the ignition timing learning value LADV # i are not initialized.

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

First, in S201, the engine operating condition parameters are read from the output signals of the sensors 8, 9a, 16, 18, 19, 20, 22, 24, and the idle switch 9b, and in S202, fuel injection is performed based on the crank pulse and cam pulse. The corresponding cylinder #i is determined.

Next, in S203, idle switch 9b, 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)
If the vehicle speed is S ≠ 0 or if the idle switch is OFF, it is determined that the vehicle is in the idle release state and the routine proceeds to S205.

When proceeding to S205, the fuel injection pulse width (fuel injection amount) Ti of the fuel injection corresponding cylinder #i is obtained by the following formula 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 The voltage correction pulse width for correcting the invalid injection pulse width Q: intake air amount N: engine speed K: correction constant due to stoichiometric air-fuel ratio, injector injection characteristics, number of cylinders, etc. Meanwhile, in S203 above, it is determined to be idle. When proceeding to S204, the invalid injection correction pulse width Ts # i as the injection correction amount of the corresponding cylinder #i stored in the predetermined address of the backup RAM 35 is read out, and at S206, this invalid injection correction pulse width Ts # i and The set invalid injection correction pulse width allowable upper limit value TsLIMH is compared, and if TsLIMH> Ts # i, it is determined that there is a margin for correction on the upper limit side of the invalid injection correction pulse width Ts # i, and the process proceeds to S207. , TsLIMH <Ts #i, invalid And elevation correction pulse width Ts # i is determined to have reached the upper limit value
Proceed to S208.

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

The above-mentioned invalid injection correction pulse width allowable limit value TsLIMH, T
If the basic fuel injection amount Tp is corrected by various increase corrections such as warm-up increase and air conditioner increase correction, sLIML makes the air-fuel ratio of the cylinder #i over-rich or over-lean even if the above values are added. The limit value to be set is a value that is set in advance through experiments or the like.

In addition, in S207, it is determined that TsLIML <Ts # i and S209
In step S2, the average differential rotation speed ΔNA # i of the cylinder #i calculated by the average differential rotation speed calculation program is read, and S2
In step 11, this average differential rotation speed ΔNA # i is compared with the preset average differential rotation speed allowable upper limit value ΔNu, and ΔNA # i ≦ ΔNu
In this case, it is determined that the average differential rotation speed ΔNA # i is lower than the average differential rotation speed allowable upper limit value, and the process proceeds to S212, where the average differential rotation speed ΔNA # i and the preset average differential rotational speed allowable lower limit value ΔNL are set. When ΔNA # i ≧ ΔNL, the average rotational speed difference ΔNA # i of the cylinder #i is within the allowable value, that is, the ideal combustion state (ΔNu ≧ ΔNA # i
≧ ΔNL) and proceeds to S220.

On the other hand, if ΔNA # i ≧ ΔNu in S211, the combustion state of the cylinder #i is too good, and the cylinder #i is compared with the other cylinders.
It judges that the generated torque is too high, and proceeds to S215.
If ΔNA # i <ΔNL in S212, it is determined that the combustion state of the cylinder #i is too bad and the generated torque of the cylinder #i is too low for each of the other cylinders, and the process proceeds to S218.

Further, in S206, it is determined that the invalid injection correction pulse width Ts # i of the cylinder #i has reached the upper limit value TsLIMH (TsLIMH ≦ Ts # i), and when the process proceeds to S208, the backup RAM3
A value obtained by advancing the ignition timing correction learning value LADV # i as the ignition timing correction amount of the cylinder #i stored at the predetermined address of 5 at the set crank angle C (for example, C = 1 ° C. A). Update (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 # i, the ignition timing correction learning value LADV It is determined that #i has not reached the advance limit correction value LmtADV yet, and the process proceeds to S215.

On the other hand, when LADV # i ≦ LmtADV # i, it is determined that this ignition timing correction learning value LADV # i has reached the advance limit, and S2
At 14, the ignition timing correction learning value LADV # i stored at the predetermined address of the backup RAM 35 is updated with the advance limit correction value LmtADV (LADV # i ← LmtADV), and the routine proceeds to S215.

Further, in S207, the invalid injection correction pulse width of the cylinder #i concerned
It is determined that Ts # i 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 retard limit correction value LmtRTD. If LADV # i <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.

Then, when proceeding from S211, S213, or S214 to S215, the invalid injection correction pulse width Ts # i of the cylinder #i stored in the backup RAM 35 is updated with a value obtained by subtracting the preset pulse width ΔTs. (Ts # i
← Ts # i-ΔTs), other cylinders # (i + 1, ..., i + n-
1) (n: number of cylinders) invalid injection correction pulse width TS # (i + 1,
, I + n-1) is the equal distribution value ΔTs / of the above pulse width ΔTs
Update with the value added by (n-1) (TS # (i + 1,
…, I + n-1) ← TS # (i + 1, ..., i + n-1) + ΔTs /
(N-1)), the process proceeds to S219.

On the other hand, when the process proceeds from S212, S216, or S217 to S218, the invalid injection correction pulse width Ts # i of the cylinder #i stored in the backup RAM 35 is updated with a value obtained by adding the preset pulse width ΔTs. Do with (Ts # i ←
Ts # i + ΔTs), other cylinders # (i + 1, ..., i + n-1)
Of the invalid injection correction pulse width TS # (i + 1, ..., i + n-1) is updated by a value obtained by subtracting the pulse width ΔTs by the equal distribution value ΔTs / (n-1) (TS # (i + 1, ..., i + n -1) ← TS #
(I + 1, ..., i + n-1)-[Delta] Ts / (n-1)), and proceeds to S219.

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

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, the same correction effect as the ignition timing correction cannot be obtained. Therefore, by correcting the fuel amount when the ignition timing is advanced, and by correcting the fuel amount when retarding the ignition timing, the combustion variation between the cylinders #i can be controlled more finely. In addition to being able to do so, 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. Set crank angle C
With advanced angle correction or retard angle correction, volume efficiency increases,
Alternatively, the above-mentioned invalid injection correction pulse width Ts # i
By decreasing or increasing the value of the invalid injection correction pulse width Ts # i within the allowable limit value (TsLIMH> Ts # i> TsLI
ML), fuel correction can be restarted, and idle speed control becomes a wider range.

Further, in S215 or S218, the invalid injection correction pulse width Ts # i of the cylinder #i is reduced or increased by the set value ΔTs, and the other cylinders # (i + 1, ..., i + n-
1) Invalid injection correction pulse width TS # (i + 1, ..., i + n-
Since 1) is equally distributed and corrected by ΔTs / (n-1), the total air-fuel ratio does not fluctuate and the air-fuel ratio controllability is good.

When the process proceeds from S215 or S218 to S219, each cylinder # stored in the predetermined address of RAM 34
Average difference rotational speed ΔNA # (i, i + 1, ... i + n-1)
Clear all +1, ... i + n-1) and (ΔNA # (i, i +
1, ... i + n-1) ← 0), proceed to S220. Since this average rotational speed difference ΔNA # i is obtained by a weighted average, the fuel injection or ignition timing of the cylinder #i is determined by the invalid injection correction pulse width Ts # i or the ignition timing correction learning value LADV # i. Even if properly corrected, the average differential rotation speed ΔNA # i does not always immediately fall within the allowable range (ΔNu ≦ ΔNA # i ≦ NL), but the average differential rotation speed of all cylinders # (i, i + 1 ... i + n−1). If ΔNA # (i, i + 1 ... i + n-1) is not cleared, an erroneous determination may occur in the next and subsequent operation cycles.

Then, the above S212, or, if proceeding from S219 to S220, the basic fuel injection pulse width Tp set based on the engine operating state parameters read in S201, the air-fuel ratio feedback correction coefficient α, various increment correction coefficients COEF, and ,
The fuel injection pulse width Ti is set from the following equation based on the invalid injection correction pulse width Ts # i read in S204 or set in S215 or S218.

Ti = Tp × α × COEF + Ts # i After that, in S221, the drive signal corresponding to the fuel injection pulse width Ti set in S220 is applied to the injector of the corresponding cylinder #i.
Outputs to 10 at a predetermined timing, and exits the routine.

Ignition Timing Control Procedure: The ignition timing control procedure will be described with reference to FIG.

First, in S301, a crank pulse and a cam pulse are read, and in S302, cylinder discrimination is performed based on the crank pulse and the cam pulse read in 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 and θ2 determined in S303 and the θ1 and
The period 1.2 is calculated from the angle of inclination (θ1−θ2) of θ2 (1.2 = dt1.2 / d (θ1−θ2)).

Next, in S305, the engine speed N1.2 is calculated based on the cycle 1.2 calculated in S304 (N1.2 ← (60/1,
2).

Then, in S306, the intake air amount Q is calculated based on the output signal of the intake air amount sensor 8, and in S307, the intake air amount Q calculated in S306 and the engine speed calculated in S305.
Engine load (basic fuel injection pulse width) based on N1.2
Calculate Tp (Tp ← K × Q / N1.2 K: constant).

Then, in S308, the engine load Tp calculated in S307 is calculated.
Then, the basic ignition timing θBASE is set based on the basic ignition timing map MPθBASE (see FIG. 5) using the engine speed N1.2 calculated in S305 as a parameter.

Further, in S309, the knock control value θNK is set according to the output signal of the knock sensor 19.

Then, in S310, the output value of the vehicle speed sensor 24 and the output of the idle switch 9b are read, and in S311, if the vehicle speed S ≠ 0, or if the idle switch is OFF (throttle fully closed), the idle release state is determined, Go to S312, again
When the vehicle speed S = 0 and the idle switch is ON (throttle is fully closed), it is determined that the vehicle is in the idle state, and the process proceeds to S313.

In S312, the basic ignition timing θBASE set in S308 is corrected by the knock control value θNK set in S309 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 S313, the ignition timing correction learning value LADV # i of the corresponding cylinder #i set by the above-described program of fuel injection control is read out, and in S314, the above-mentioned S308
The basic ignition timing θBASE set in step S309 is corrected by the knock control value θNK set in step S309 and the ignition timing correction learning value LADV # i read in step S313 to set the ignition timing θIG.
Is calculated (θIG ← θBASE + θNK + LADV # i).

Then, in S315, the ignition time ADV is set from the ignition timing θIG calculated in S312 or S314 and the cycle 1.2 calculated in S304 (ADV ← θIG × 1.2).

Next, in S316, the ignition time ADV set in S315 is set by a timer, and in S317, the θ2 pulse is used as a trigger to start time measurement, and in S318, 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 correction pulse width Ts according to the above program
The setting state of #i and the ignition timing correction learning value LADV # i will be described with reference to the time chart of FIG. 10 by taking the average differential rotation speed ΔNA # i of the cylinder #i as an example.

For example, when the combustion state of the # 1 cylinder is poor and the average differential rotation speed ΔNA # 1 becomes lower than the average differential rotational speed allowable lower limit value ΔNL, the set pulse width ΔTs is set to the invalid injection correction pulse width Ts # 1 of the cylinder # 1. By adding (Ts # 1 ← Ts # 1 + ΔTs), the fuel injection pulse width Ti for the cylinder # 1 is increased. On the other hand, the invalid injection correction pulse Ts # for each of the other cylinders # (2 ... i)
(2 ... i) is subtracted by ΔTs (n-1) (n: number of cylinders) (Ts
# (2 ... i) ← Ts # (2 ... i) -ΔTs / (n-1)),
Prevent the total air-fuel ratio from fluctuating. Then, the average rotational speed difference ΔNA # i of each cylinder #i is reset (elapsed time t1).

Next, the invalid injection correction pulse width Ts # 1 of the cylinder # 1
When the effective injection correction pulse width allowable upper limit value TsLIMH is reached, the invalid injection correction pulse width Ts # 1 is subtracted by the set pulse width ΔTs (Ts # 1 ← Ts # 1-ΔTs), and the cylinder #
The fuel injection pulse width Ti for 1 is decreased, and the invalid injection correction pulse width Ts # (2
Add ΔTs / (n-1) to (i) (Ts # (2 ... i) ← T
s # (2 ... i) + ΔTs / (n-1)), and the ignition timing correction learning value LADV # 1 of the cylinder # 1 is set to the crank angle C.
Use to correct the lead angle (LADV # 1 ← LADV # 1-C). And
The average rotational speed difference ΔNA # i of each cylinder #i is reset (elapsed time t2).

As a result, the amount of decrease in the fuel injection pulse width Ti and the ignition timing
The average differential rotation speed ΔNA # 1 of the cylinder # 1 is increased due to the synergistic effect with the increase in volumetric efficiency caused by advancing the ADV.
Can be set within the allowable range.

Also, for example, the combustion state of the cylinder # 1 is too good,
Average differential rotation speed ΔNA # 1 is the average differential rotation speed allowable upper limit value ΔN
When u is exceeded, the invalid injection correction pulse width Ts of the cylinder # 1 concerned
Subtract the set pulse width ΔTs from # 1 (Ts # 1 ← Ts # 1-
ΔTs), and the fuel injection pulse width Ti for the cylinder # 1 is reduced. Then, ΔTs / (n-1) is added to the invalid injection correction pulse width Ts # (2 ... i) of each of the other cylinders # (2 ... i) (Ts # (2 ... i) ← Ts # (2 ... i). i) + ΔTs / (n-
1)), keep the total air-fuel ratio constant. Also, for each cylinder #
Reset the average differential rotation speed ΔNA # i of i (elapsed time
t3).

Then, the invalid injection correction pulse width Ts # 1 of the cylinder # 1
Has reached the ineffective injection correction pulse width allowable lower limit value TsLIML, the set pulse width Δ is set in this ineffective injection correction pulse width Ts # 1.
Ts is added (Ts # 1 ← Ts # 1 + ΔTs) to increase the fuel injection pulse width Ti for the cylinder # 1 and the invalid injection correction pulse width Ts # (2 ... i) of the other cylinder # (2 ... i). )
ΔTs / (n-1) is subtracted from (Ts # (2 ... i) ← Ts #
(2 ... i) -ΔTs / (n-1)), and the cylinder #
The ignition timing correction learning value LADV # 1 of 1 is retarded at the set crank angle C (LADV # 1 ← LADV # 1 + C). Next, the average rotational speed difference ΔNA # i of each cylinder #i is reset (elapsed time t4).

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

(Second Embodiment) FIG. 11 is a flowchart showing a cylinder-by-cylinder fuel injection control procedure according to the second embodiment of the present invention. The same steps as those in FIG. 8 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 calculating the average rotational speed difference ΔNA # i is the same as that in the first embodiment (FIG. 7), and the description thereof is omitted.

First, when proceeding from S201 and S202 to S401, the fuel injection pulse width Ti is obtained based on the engine operating state parameter detected 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 S402, and the corresponding cylinder # stored in the predetermined address of the backup RAM 35 #
The correction pulse width Tc # i of i is read out, and the correction pulse width Tc # i and the preset correction pulse width allowable upper limit value TcLI in S403 are read.
MH is compared, and if TcLIMH> Tc # i, the correction pulse width Tc
When it is determined that the correction of the upper limit value of #i has a margin, the process proceeds to S404. When TcLIMH ≦ Tc # i, the correction pulse width Tc # i is determined to reach the upper limit value, and the process proceeds to S208.

In S403, when it is determined that TcLIMH> Tc # i and the process proceeds to S404,
The correction pulse width Tc # i is compared with a preset correction pulse width allowable lower limit value TcLIMH, and when TcLIML <Tc # i, that is, TcLIML <Tc # i <TcLIMH, the correction pulse width Tc of the cylinder #i is compared. It is determined that #i is within the allowable limit, and the process proceeds to S209. If TcLIML ≧ Tc # i, the correction pulse width Tc # i is determined to have reached the lower limit value, and the process proceeds to S210.

The correction pulse width allowable limit values TcLIMH and TcLIML have the same values for the cylinder #i even if these values are added to the fuel injection pulse width Ti.
The air-fuel ratio is set to a limit value which is not over-riched or over leaned, which is obtained in advance by experiments or the like.

When it is determined that TcLIML <Tc # i in S404 and the process proceeds to S209, the average differential rotation speed ΔNA # i of the cylinder #i is read out, and in S211, the average differential rotation speed ΔNA # i and the preset average differential rotation speed are set. Compared with the allowable speed upper limit value ΔNu, ΔNA # i ≦
If ΔNu, the process proceeds to S212, and the average difference rotational speed allowable lower limit value Δ
Compared with NL, ΔNA # i ≧ ΔNL, that is, ΔNu ≧ Δ
If NA # i ≧ ΔNL, the process proceeds to S407.

On the other hand, if it is determined in step S211 that ΔNA # i> ΔNu,
If it is determined at S212 that ΔNA # i <ΔNL at S212, the process proceeds to S406.

Further, when the process proceeds from S403 to S208, S213, S214, or proceeds from S211 or S213 to S405, the correction pulse width Tc # i of the cylinder #i stored at the predetermined address of the backup RAM 35 is set in advance. Set pulse width ΔTc
Update with the value subtracted in (Tc # i ← Tc # i-Δ
Tc), and the correction pulse width TC # (i + 1, ..., i + n-1) of each of the other cylinders # (i + 1, ..., i + n-1) by the equal distribution value ΔTc / (n-1) of the pulse width ΔTc. Update with the added value (TC # (i + 1, ..., i + n-1) ← TC # (i + 1, ..., i + n)
-1) + ΔTc / (n-1)), and proceeds to S219.

On the other hand, if the process proceeds from S404 to S210, S216, S217, or proceeds from S212 or S216 to S406, the correction pulse width Tc # i of the cylinder #i stored at the predetermined address of the backup RAM 35 is set in advance. Set pulse width ΔTc
It is updated with the value added in (Tc # i ← Tc # i + Δ
Tc), and the correction pulse width TC # (i + 1, ..., i + n-1) of each of the other cylinders # (i + 1, ..., i + n-1) by the equal distribution value ΔTc / (n-1) of the pulse width ΔTc. Update with the subtracted value (TC # (i + 1, ..., i + n-1) ← TC # (i + 1, ..., i + n
-1) -ΔTc / (n-1)), the process proceeds to S219.

The pulse width ΔTc 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.

Next, the process proceeds from S405 and S406 to S219, where each cylinder # (i, i + 1, ... i +) stored in the RAM 34 at a predetermined address is stored.
n−1) average differential rotation speed ΔNA # (i, i + 1, ... i + n−
1) is cleared and (ΔNA # (i, i + 1, ... i + n-
1) ← 0), and proceed to S407.

Then, when the process proceeds from S219 or S212 to S407, the fuel injection pulse width Ti set in S401 is changed to S4.
It is read at 02 or is corrected by the correction pulse width Tc # i set at S405 or S406 (Ti ← Ti + Tc # i). When the process proceeds from S203 or S407 to S221, a drive signal corresponding to the fuel injection pulse width Ti set in S401 or S407 is output to the injector 10 of the cylinder #i at a predetermined timing, and the routine is exited. .

Since the ignition timing control procedure in this embodiment is the same as that in the first embodiment (FIG. 9) described above, description thereof will be omitted.

(Third Embodiment) FIGS. 12 to 14 show a third embodiment of the present invention, FIG. 12 is a flowchart showing a procedure for calculating an average difference angular acceleration for each cylinder, and FIG. 13 is a fuel injection control procedure for each cylinder. FIG. 14 is a time chart showing the relationship among crank pulse, cam pulse, engine speed and angular acceleration.

In this embodiment, the rotational fluctuation difference of each cylinder #i is replaced with the average differential angular acceleration Δ (dN / dt) A # i instead of the average differential rotational speed ΔNA # i shown in the first and second embodiments. It's something I asked for.

: Average difference angular acceleration calculation procedure: Since S101 to S105 are common to the first embodiment (FIG. 7),
Only the flowchart from S106 onward (the portion surrounded by the broken line in FIG. 7 is different) will be described.

When the engine speed NNEW is calculated in S106 based on the cycles 2 and 3 set in S105, the process proceeds to S501, and the engine speed NNEW is time-differentiated to calculate the angular acceleration (dN / dt) NEW.

Then, in S502, the engine angular acceleration (dN / dt) NEW calculated in S501 and the engine angular acceleration (dN / dN / in the case of four cylinders i = 1,3,2,4) calculated last time are calculated. dt) OLD
And the difference angular acceleration Δ (dN / dt) #i of the section (section θ2-θ3 in FIG. 14) where the work is not performed due to combustion of the combustion stroke cylinder #i (((N (dN / dt ) # I ← (dN / d
t) NEW- (dN / dt) OLD), in S503, the previous engine angular acceleration (dN / dt) O stored at the specified address in RAM 34.
The engine angular acceleration (dN / d
t) Update with NEW ((dN / dt) OLD ← (dN / dt) NEW).

Then, in S504, the difference angular acceleration Δ calculated in S502 above.
Based on (dN / dt) #i and the previously calculated average differential angular acceleration Δ (dN / dt) A # i (−1) of the cylinder #i, the current average differential angular acceleration Δ (dN / dN of the cylinder. dt) A # i is calculated from the weighted average of the weighting factors r shown in the following equation.

Δ (dN / dt) A # i ← ((2 ^r −1) × Δ (dN / dt) A # i (−1) + Δ (dN / dt) #i) / 2 ^r However, the average difference angle at the first time The acceleration Δ (dN / dt) A # i is set to “0”.

Then, in step S505, the average differential angular acceleration Δ of the cylinder #i calculated in step S504 is calculated using the average differential angular acceleration Δ (dN / dt) A # i of the cylinder #i stored in the RAM 34 at the predetermined address.
(DN / dt) A # Update i (-1) (Δ (dN / dt) A #
i (−1) ← Δ (dN / dt) A # i).

: Fuel injection control procedure: As described above, in this embodiment, the average difference angular acceleration Δ (dN / d
t) Since the rotation fluctuation of each cylinder #i is determined based on A # i, the first embodiment (FIG. 8) and the second embodiment (11th embodiment)
Only the flow chart of the part surrounded by the broken line in FIG.

That is, when the process proceeds from S207 (or S404) to S601, the average differential angular acceleration Δ (dN / dt) A # i of the cylinder #i concerned.
Is read out and this average difference angular acceleration Δ (dN / dt) A is read in S602.
#I and the preset average difference angular acceleration allowable upper limit value Δ (dN / d
t) u, and Δ (dN / dt) A # i <Δ (dN / dt) u
In the case of, the process proceeds to S603 and the average difference angular acceleration Δ (dN / dt) A
#I is compared with the average lower limit angular acceleration Δ (dN / dt) L, and Δ (dN / dt) A # i ≧ Δ (dN / dt) L, that is,
If Δ (dN / dt) u ≧ Δ (dN / dt) A # i ≧ Δ (dN / dt) L, the process proceeds to S220 (or S407).

On the other hand, when it is determined in S602 that Δ (dN / dt) A # i> Δ (dN / dt) u, the process proceeds to S215 (or S405), and
When it is determined in S603 that Δ (dN / dt) A # i <Δ (dN / dt) L, the process proceeds to S218 (or S406).

Then, the above S215 (or S405), S218 (or
From S406) to S604, the average differential angular acceleration Δ (dN / dt) A # (i, i + 1, ... i + n) of each cylinder # (i, i + 1, ... i + n-1) stored in the predetermined address of the RAM 34. -1) are all cleared and (Δ (dN / dt) A # (i, i + 1, ... i + n-
1) ← 0), and proceed to S220 (or S407).

Note that FIG. 14 shows the correlation between the engine speed and the engine angular acceleration. As described above, by using the angular acceleration obtained by differentiating the engine speed with respect to time, the time factor is taken into consideration. Then, the accuracy can be further improved.

Further, the ignition timing control is the same as that of the first embodiment, and the 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 an average difference cycle calculation procedure for each cylinder.
FIG. 16 is a flowchart showing a fuel injection control procedure for each cylinder.

In this embodiment, the difference in rotational fluctuation between the cylinders #i is calculated as the average rotational speed difference ΔNA # i shown in the first and second embodiments, or the average difference angular acceleration Δ (shown in the third embodiment. dN / d
t) Instead of A # i, the average difference period ΔA # i is used.

: Average difference cycle calculation procedure: Since S101 to S105 are common to the first embodiment (FIG. 7), description thereof will be omitted, and only a flowchart of a portion corresponding to a portion surrounded by a broken line in FIG. 7 will be described.

When the cycles 2 and 3 are calculated in S105 (see FIG. 7), S
Proceed to step 701, and the current cycle 2, 3 calculated in S105 and RAM34
The cycle 2,3OLD calculated in the previous routine stored in the specified address of
From the combustion stroke cylinder #i (if four cylinders, i =
1,3,2,4) to calculate the difference period Δf # i in the section where there is no work due to combustion (Δf # i ← 2,3−2,3OLD).

Next, in step S702, the previous cycle 2,3OLD stored in the predetermined address of the RAM 34 is updated with the current cycle 2,3 calculated in step S105 (2,3OLD ← 2,3).

Then, in S703, the difference cycle Δf # i calculated in S701 is calculated.
And the average difference cycle ΔfA # i of the cylinder #i calculated last time
Based on (-1), the current average difference period ΔA # i is calculated from the weighted average of the weighting factors r shown in the following equation.

ΔA # i ← ((2 ^r −1) × ΔA # i (−1) + Δ # i / 2 ^r Note that the initial average difference period ΔA # i is “0”.

Thereafter, in S704, the average difference cycle ΔA # i of the cylinder #i stored in the predetermined address of the RAM 34 is calculated using the average difference cycle ΔA # i of the cylinder #i calculated in S703.
1) is updated (ΔA # i (-1) ← Δ (A #
i).

: Fuel injection control procedure: In this embodiment, the rotational fluctuation of each cylinder #i is determined based on the average difference cycle ΔA # i. Therefore, the first embodiment (FIG. 8) and the second embodiment (FIG. Only the flowchart enclosed by the broken line in Fig. 11) is different.

In other words, if you proceed from S207 (or S404) to S801,
The average difference cycle ΔA # i of the cylinder #i is read out and S802
Then, the average difference period ΔA # i is compared with a preset average difference period allowable shortest value Δs, and if ΔA # i ≧ Δs, the process proceeds to S803, and the average difference period ΔA # i and the average difference period allowable maximum are The value ΔL is compared, and ΔA # i ≦ Δ
When L, that is, Δs ≦ ΔA # i ≦ ΔL, the value is within the allowable value, and thus the process proceeds to S220 (or S407).

On the other hand, when it is determined in step S802 that ΔA # i <Δs, the average difference cycle ΔA # i of the cylinder #i is too short, and thus the process proceeds to step S215 (or S405), and in step S803, ΔA # i.
If it is determined that i> ΔL, the average difference cycle ΔA # i of the cylinder #i is too long, and the process proceeds to S218 (or S406).

Then, the above S215 (or S405), S218 (or
When proceeding from S406) to S804, the average difference cycle ΔA # i (i, i + i, ... i + n-1) of each cylinder # (i, i + i, ... i + n-1) stored in the predetermined address of RAM 34 is cleared. (ΔfA # (i, i + 1, ... i + n-1) ← 0), S220
(Or go to S407).

In this embodiment, when detecting the engine speed fluctuation, the engine speed NNEW is obtained by dividing the cycles 2 and 3 once.
Since the cycles 2 and 3 are used as they are without using, the calculation load due to the division processing is reduced and the calculation time is shortened.

(Fifth Embodiment) FIG. 17 and subsequent drawings show a fifth embodiment of the present invention, and FIG. 17 is a flowchart showing a procedure for calculating the average differential angular velocity for each cylinder,
FIG. 1 is a flowchart showing a fuel injection control procedure for each cylinder,
FIG. 19 is a flowchart showing a procedure for calculating ignition timing for each cylinder.

In this embodiment, the rotational fluctuation difference of each cylinder #i is obtained from the average difference angular velocity ΔωA # i.

: Average difference angular velocity calculation procedure: Since S101 to S104 are common to the first embodiment (FIG. 7), description thereof will be omitted.

After the crank pulse is discriminated in S104, the elapsed time t2,3 between the crank pulses for detecting BTDC θ2, θ3 discriminated in S104 and the angle of inclination between θ2 and θ3 (θ2-θ3) in S901.
And the angular velocity ω2,3 is calculated from (ω2,3 ← d (θ2-θ
3) / dt2,3).

After that, in S902, the engine angular velocity ω2,3NEW of the current routine calculated in S901 above and the engine angular velocity ω2,3OLD calculated in the previous routine are not used to perform combustion by the combustion stroke cylinder #i. Differential angular velocity Δω
#I is calculated (Δω # i ← ω2,3NEW−ω2,3OLD) and S903
Then, the previous engine angular speed ω2,3OLD stored in the predetermined address of the RAM 34 is updated with the current engine angular speed ω2,3NEW calculated in S901. (Ω2,3OLD ← ω2,3NE
W).

Then, in S904, the difference angular velocity Δω # calculated in S902 above.
i and the average differential angular velocity ΔωA of the cylinder #i calculated last time
Based on #i (-1), the current average difference angular velocity ΔωA # i
Is calculated from the weighted average of the weighting factors r shown in the following equation.

ΔωA # i ← ((2 ^r −1) × ΔωA # i (−1) + Δω # i) / 2 ^r Note that the initial average differential angular velocity ΔωA # i is “0”.

Thereafter, in S905, the data stored in the predetermined address of the RAM 34 is updated with the average differential angular velocity ΔωA # i of the cylinder #i calculated in S904 (ΔωA # i (-1) ← Δ
ωA # i).

: Fuel injection control procedure: In this embodiment, since the rotational fluctuation of each cylinder #i is determined based on the average difference angular velocity ΔωA # i, the first embodiment (FIG. 8) and the second embodiment ( Only the flowchart enclosed by the broken line in FIG. 11) is different.

That is, when the process proceeds from S207 (or S404) to S1001, the average angular velocity ΔωA # i of the cylinder #i is read and S1
In 002, this average angular velocity ΔωA # i is compared with a preset average angular velocity upper limit value Δωu. If ΔωA # i ≦ Δωu, the process proceeds to S1003, and the average difference angular velocity ΔωA # i is compared with the average angular velocity lower limit value ΔωL. , ΔωA # i ≧ ΔωL,
That is, when Δωu ≧ ΔωA # i ≧ ΔωL, the value is within the allowable value, and thus the process proceeds to S220 (or S407).

On the other hand, if it is determined in S1002 that ΔωA # i> Δωu, the process proceeds to S215 (or S405), and in S1003, ΔωA # i> Δωu
When it is determined that A # i <ΔωL S218 (or S406)
Proceed to.

Then, S215 (or S405), S218 (or S40
When the process proceeds from 6) to S1004, all the average differential angular velocities ΔωA # (i, i + i, ... i + n-1) of each cylinder # (i, i + i, ... i + n-1) stored in the predetermined address of RAM34 are cleared. (ΔωA # (i, i + i, ... i + n-1) ← 0), S220
(Or go to S407).

: Ignition Timing Control Procedure: In the first embodiment (FIG. 9), the ignition timing is set based on the cycles 1 and 2, but in this embodiment, the ignition timing is set based on the angular velocities ω 1 and 2. It is different in that it is.

After the crank pulse is discriminated in S303, the elapsed time t1,2 between crank pulses for detecting BTDC θ1, θ2 discriminated in S303 and the angle of inclination (θ1-θ) between θ1 and θ2 are discriminated in S1101.
2) and the angular velocity ω1,2 is calculated from (ω1,2 ← d (θ1-
θ2) / dt1,2).

Next, in S1102, the angular velocities ω1,2 calculated in S1101 above
Calculate the engine speed N1,2 based on (N1,2 ← 60 × ω
1,2).

In S1103, the ignition timing ADV is set from the ignition timing θIG calculated in S312 or S314 and the angular velocities ω1,2 calculated in S1101 (ADV ← θIG / ω1,2).

According to the present embodiment, the combustion state estimation is performed using the angular velocities ω2,3 as a substitute for the engine speed NNEW, so the calculation time for the combustion state estimation is shortened compared to the first embodiment.

[Effects of the Invention] As described above, according to the present invention, in the idling state, the combustion state of the combustion stroke cylinder is determined by comparing the engine rotation fluctuation difference for each predetermined crank angle with the upper limit value and the lower limit value. When the rotational fluctuation difference of the cylinder exceeds the upper limit value, it is determined that the torque generated in the cylinder is too high compared to the other cylinders, and the injection correction amount of the cylinder is reduced by the set amount and the reduction amount is reduced. Correspondingly, the injection correction amount of each of the other cylinders is equally distributed and reduced, and when the rotational fluctuation difference of the cylinder is lower than the lower limit value, it is determined that the torque generated in the cylinder is too low for the other cylinders. In addition to increasing the injection correction amount of the cylinder by the set amount, the injection correction amount of each of the other cylinders is equally distributed and decreased corresponding to the increase amount, and the basic fuel injection amount is corrected by the injection correction amount of the corresponding cylinder to correct the cylinder. Calculate the amount of fuel injection for each cylinder Since the fuel of the fuel injection amount is supplied, the total air-fuel ratio viewed from all cylinders is prevented from deviating from the target air-fuel ratio, and the combustion state of each cylinder is made uniform while suppressing the deterioration of exhaust gas purification performance. Rotational speed fluctuation can be suppressed.

Further, when the generated torque of the cylinder is low, the injection correction amount is increased to increase the generated torque of the cylinder, and when the injection correction amount exceeds the allowable upper limit value, the correction upper limit of fuel injection is reached. Judgment, the injection correction amount of the cylinder is corrected by the set amount reduction, the ignition timing correction amount of the cylinder is advanced by the set amount, and the injection of the other cylinders is injected corresponding to the injection correction amount reduction amount of the cylinder. Even if the correction amount is increased evenly, the torque generated in the cylinder is high, and the injection correction amount is repeatedly reduced to reduce the torque generated in the cylinder. It is determined that the correction lower limit limit has been reached, and the injection correction amount of the cylinder is corrected by increasing the set amount, the ignition timing correction amount of the cylinder is retarded by the setting amount, and the injection correction amount of the cylinder is increased. And then each other The fuel injection amount and the ignition timing are set for each cylinder by correcting the basic injection amount and the basic ignition timing based on the injection correction amount and the ignition timing correction amount. For each cylinder, the air-fuel ratio overrich and over lean can be prevented, and the correction term for suppressing the idle speed fluctuation can be controlled only by one term for setting the ignition timing and the fuel injection amount. It is possible to prevent the system from becoming complicated and the calculation load from increasing.

Further, the correction of the fuel injection amount with a small correction effect is prioritized, and it is determined that the injection correction amount reaches the allowable upper and lower limit values, the correction is insufficient with the fuel injection correction, and the air-fuel ratio in the cylinder is largely deviated from the target air-fuel ratio. The ignition timing is corrected to suppress the fluctuation of the idle speed because the ignition timing is corrected only when the combustion state is corrected and the fuel injection correction amount is returned to the original value to restart the fuel injection amount correction. Since the update of the correction amount is performed with the aim of achieving a large correction effect with a small amount compared to the update of the injection correction amount, it is not necessary to set the set amount for the update to an extremely fine value, and ignition timing control accuracy is required more than necessary. Can be realized without using a control device having high resolution.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing the basic concept of the present invention, and FIG.
1 to 10 show a first embodiment of the present invention, FIG. 2 is an overall schematic view of an engine control system, FIG. 3 is a front view of a crank rotor and a crank angle sensor, and FIG. 4 is a cam rotor and a cam angle. A front view of the sensor, FIG. 5 is a conceptual diagram of a basic ignition timing map, FIG. 6 is a time chart showing the relationship between cylinder pressure fluctuation, crank pulse, cam pulse, and engine speed, and FIG. 7 is an average by cylinder. FIG. 8 is a flow chart showing a differential rotation speed calculation procedure, FIG. 8 is a flow chart showing a cylinder-by-cylinder fuel injection control procedure, FIG. 9 is a flow chart showing a cylinder-by-cylinder ignition timing control procedure, and FIG. 10 is a cylinder-by-cylinder average differential rotation speed, by cylinder. A time chart showing the relationship between the invalid injection correction pulse width and the individual cylinder ignition timing correction learning value, FIG. 11 is a flowchart showing the individual cylinder fuel injection control procedure according to the second embodiment of the present invention, and FIGS. 12 to 14 Shows a third embodiment of the present invention,
FIG. 12 is a flowchart showing the procedure for calculating the average differential angular acceleration for each cylinder, FIG. 13 is a flowchart showing the procedure for controlling the fuel injection for each cylinder, and FIG. 14 is a time showing the relationship between crank pulse, cam pulse, engine speed and angular acceleration. Charts, FIG. 15 and FIG. 16 show a fourth embodiment of the present invention.
The figure is a flowchart showing the procedure for calculating the average difference period for each cylinder.
FIG. 16 is a flow chart showing the fuel injection control procedure for each cylinder, FIG. 17 and the following show the fifth embodiment of the present invention, and FIG. 17 is a flow chart showing the average difference angular velocity calculation procedure for each cylinder.
FIG. 18 is a flowchart showing the fuel injection control procedure for each cylinder.
FIG. 19 is a flowchart showing the ignition timing control procedure for each cylinder. M1 ... Engine operating state detecting means, M2 ... crank angle detecting means, M3 ... idle determining means, M4 ... fuel state determining means, M5 ... injection correction amount setting means, M6 ... ignition timing correction amount setting means , M7 ... injection amount calculation means, M8 ... fuel supply means, M9 ... ignition timing calculation means, M10 ... ignition means.

Claims (1)

(57) [Claims] 1. An operating state detecting means for detecting an operating state of an engine, a crank angle detecting means for outputting a signal capable of discriminating a cylinder in a combustion stroke and a signal corresponding to a predetermined crank angle, and an engine idle. Idle determination means for determining the state from the engine operating state, and when the engine is in the idle state, detects an engine rotation fluctuation difference for each predetermined crank angle, compares the engine rotation fluctuation difference with the upper limit value and the lower limit value, and Combustion state determination means for determining the combustion state of the combustion stroke cylinder, and when the engine is idle and the rotational fluctuation difference of the cylinder exceeds the upper limit value, or the injection correction amount of the cylinder exceeds the allowable upper limit value. When it exceeds, the injection correction amount of the cylinder is reduced by a set amount, the injection correction amounts of the other cylinders are equally distributed and increased according to the reduction amount, and In the dollar state, when the rotational fluctuation difference of the cylinder is lower than the lower limit value, or when the injection correction amount of the cylinder is lower than the allowable lower limit value, the injection correction amount of the cylinder is increased by the set amount and is increased by the amount. Correspondingly, the injection correction amount setting means for setting the injection correction amount for each of the other cylinders by equally reducing the amount, and when the injection correction amount for the cylinder exceeds the allowable upper limit value while the engine is in the idle state, An ignition timing correction amount setting means for advancing the ignition timing correction amount by a set amount and retarding the ignition timing correction amount for the cylinder by a set amount when the injection correction amount for the cylinder is lower than an allowable lower limit value; An injection amount calculation means for calculating the basic injection amount based on the operating state and correcting the basic injection amount by the injection correction amount of the corresponding cylinder to calculate the fuel injection amount for each cylinder when shifting to the idle state, and the above injection amount. Operator The fuel supply means for supplying fuel to the corresponding cylinder based on the output of the engine and the basic ignition timing is calculated based on the engine operating state, and when the engine shifts to the idle state, the basic ignition timing is corrected by the ignition timing correction amount of the corresponding cylinder. Idle control of a multi-cylinder engine, comprising: an ignition timing calculation means for calculating an ignition timing for each cylinder; and an ignition means for igniting an air-fuel mixture of corresponding cylinders based on an output of the ignition timing calculation means. apparatus.