JPS62186039A - Engine combustion control device - Google Patents

Abstract

PURPOSE:To obtain optimum ignition timing immediately after transition to the three-dimensional operating region by controlling the ignition timing in compliance with the difference between the three-dimensional air-to-fuel ratio and the target air-to-fuel ratio determined according to the load, and thereby providing good response to transition of engine into the specified three- dimensional operating region. CONSTITUTION:This device uses a control means e and controls the quantity of inhaled air or fuel so as to get the target air-to-fuel ratio on the basis of output from an air-to-fuel ratio sensing means a. If a three-dimensional region sensing means c senses that the engine is in the specified three-dimensional operating region, a target setting means d changes the target air-to-fuel ratio to three-dimensional air-to-fuel ratio. An ignition timing setting means g makes setting of the ignition timing on the basis of the engine load sensed by a load sensing means b, and when the engine has made transition to the three- dimensional operating range, the abovementioned ignition timing shall undergo a correction in compliance with the difference between the three-dimensional air-to-fuel ratio and the target air-to-fuel ratio to be determined according to the current operating condition of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for controlling the combustion state of an engine such as an automobile.

(Prior art) In recent years, demands on automobile engines have become more sophisticated.
There is a tendency for mutually contradictory issues such as reduced exhaust gas, high output, and low fuel consumption to be achieved at a high level.

In order to address these issues, combustion control under ultra-lean air-fuel ratios has been attempted, such as "Internal Combustion Engine, Vol. 23, No. 12 J, October 1984 issue, pp. 33-40, published by Sankaido. There is a lean burn device described in .This device performs feedback control of the air-fuel ratio up to the ultra-lean air-fuel ratio region based on the output of a lean sensor that can detect air-fuel ratios over a wide range from stoichiometric to lean to meet the above requirements. In this case, unlike the characteristic where the stoichiometric air-fuel ratio is constant during steady driving, a lean air-fuel ratio is set as the target value even in some acceleration regions.

For example, in the normal acceleration range, the air-fuel ratio is 22.5, in the steady driving range, the air-fuel ratio is 21.5, and when idling, the air-fuel ratio is 15°5.
It is said that In addition, under full load conditions, the output air-fuel ratio is 12 to 1
3 to ensure vehicle power performance.

As the air-fuel ratio shifts to such a lean air-fuel ratio, NOx tends to decrease significantly, which is in line with recent reductions in NOx emissions. However, on the other hand, the adaptable air-fuel ratio range that satisfies both the NOx emission level to satisfy exhaust gas regulations and the allowable torque fluctuation level is narrow, and precise air-fuel ratio control is required.

By the way, in order to maintain drivability and clear NOx emissions within the regulation value during transient periods, it is necessary to change the equal air-fuel ratio, but current technology (i.e., conventional equipment) does not maintain the equal air-fuel ratio during transient Precise control to maintain this is still difficult.

Therefore, at present, the air-fuel ratio is enriched during transient periods so as not to impede drivability. However, if the engine is enriched halfway just to ensure drivability, the amount of NOx emissions will increase and it will not be possible to meet recent demands.

Therefore, in order to eliminate such problems, the applicant focused on the original function of the three-way catalyst, and temporarily set the target air-fuel ratio to the three-way air-fuel ratio (for example, λ = 1) when transitioning to a transient state. At approximately the same time as this application, we proposed an engine combustion control device that meets recent demands by reducing NOx emissions while ensuring drivability.

(Problems to be Solved by the Invention) By the way, the device related to the above-mentioned prior application is excellent in that it attempts to achieve at a high level the conflicting demands of reducing NOx and ensuring drivability. However, from the viewpoint of further improving drivability, it has been found that the following method is preferable.

In other words, when transitioning to three-way operation, fuel is immediately supplied so that λ = 1, but in this case, the ignition timing is determined by 8 from the table map, which uses the engine load (for example, intake air amount and rotational speed) as a parameter. It is determined by looking up the value. However, as is well known, the optimal value of ignition timing is also restricted by the air-fuel ratio, for example, MBT and N
Considering the amount of Ox emissions, the optimal ignition timing is within a limited range.

Therefore, in response to a sudden change in the air-fuel ratio as described above, the calculation of the ignition timing is delayed (calculation time is required for lookup), making it difficult to provide the optimum required ignition timing.

On the other hand, in order to compensate for such calculation delays, it is possible to increase the map area and make it more precise.
According to this, it is not a good idea as it will lead to high costs.

(Purpose of the Invention) Therefore, the present invention provides that the required ignition timing characteristic changes approximately linearly when the air-fuel ratio is used as a parameter (see the seventh section described below).
(see figure), and when the engine shifts to a predetermined three-way operating range, the ignition timing is corrected according to the difference between the target air-fuel ratio and the three-way air-fuel ratio, which is determined according to the engine load at that time. Accordingly, the present invention aims to provide an engine combustion control device that optimizes the ignition timing immediately upon transition to the three-way operation region and meets recent demands at low cost.

(Structure of the Invention) The engine combustion control device according to the present invention, as shown in the basic conceptual diagram in FIG. The detection means includes a three-way region detection means C that detects that the engine is in a predetermined three-way operation region, and a three-way region detection means C that sets a target air-fuel ratio according to the engine load, and sets the target air-fuel ratio in at least a part of steady running. a target setting means d that sets the target air-fuel ratio to be leaner than the stoichiometric air-fuel ratio, and changes the target air-fuel ratio to the three-way air-fuel ratio when the engine shifts to a predetermined three-way operating region;
A control means e for controlling the supply amount of intake air or fuel so that the target air-fuel ratio is achieved based on the output of the air-fuel ratio detection means a, and operating the supply amount of intake air or fuel based on the signal from the control means e. an operating means f for setting the ignition timing based on the engine load, and a target air-fuel ratio and a three-way air-fuel ratio that are determined in accordance with the engine load at that time when the engine shifts to a predetermined three-way operating region. The ignition timing setting means g corrects the ignition timing according to the difference between Regardless, the ignition timing is optimized.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 7 are diagrams showing an embodiment of the present invention.

First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes an engine, in which intake air is supplied from an air cleaner 2 to each cylinder through an intake pipe 3, and fuel is injected by an injector (operating means) 4 based on an injection signal Si. An ignition plug 5 is attached to each cylinder, and the ignition plug 5 is supplied with a high-pressure pulse Pi from a high-pressure generation unit 6 consisting of an ignition coil, a distributor, and the like. The spark plug 5 and the cylinder pressure generation unit 6 constitute an ignition means 7 that ignites the air-fuel mixture, and the ignition means 7 generates and discharges a high-pressure pulse Pi based on the ignition signal Sp.

Then, the air-fuel mixture in the cylinder is ignited and exploded by the discharge of the high-pressure pulse Pi, and becomes exhaust gas, which passes through the exhaust pipe 8 and enters the catalytic converter 9. ) is purified by a three-way catalyst and discharged.

The intake air flow rate Qa is the flap type air flow make 1.
0 and controlled by a throttle valve 11 in the intake pipe 3. The opening TVO of the throttle valve 11 is detected by the throttle valve opening sensor 12, and the intake air pressure PB in the intake pipe 3 is detected by the throttle valve opening sensor 12.
is detected by the pressure sensor 13. Further, a swirl valve 14 is provided in the intake pipe 3 near the intake port, and the swirl valve 14 opens and closes based on a control signal Sv input to a solenoid valve 16 that controls the negative pressure applied to the drive valve 15. This creates a so-called swirl from the intake port into the cylinder to improve combustion.

The rotational speed N of the engine 1 is detected by the crank angle sensor 17, and the temperature Tw of the cooling water flowing through the water jacket is detected by the crank angle sensor 17.
is detected by the water temperature sensor 18.

Further, the oxygen concentration in the exhaust gas is detected by an oxygen sensor (air-fuel ratio detection means) 19, and the oxygen sensor 19 outputs V
A type in which i changes uniquely over a wide range of air-fuel ratios from rich to lean regions is used.

The air flow meter 10 and crank angle sensor 17
constitutes the load detection means 20, and the load detection means 20
The signals from each sensor 12, 13, 18, 19 are input to the control unit 30. The control unit 30 performs air-fuel ratio control, ignition timing control, and swirl control based on these sensor information G.

That is, the control unit 30 has functions as a three-dimensional area detection means, a target setting means, a control means, and an ignition timing setting means, and includes a CPU 31, ROM, 31, RA
It is composed of M33 and I10 ports 34. C.P.
The U31 takes in necessary external data from the I10 port 34 according to the program written in the ROM 32, and while exchanging data with the RAM 33, performs arithmetic processing on necessary processing values, etc. The data processed accordingly is output to the I10 boat 34. I10 boat 34 has sensor group 12.13.18.1
The signals from 9.20 are input, and the injection signal Si, control signal Sv, and ignition signal Sp are output from the I10 port 34. The ROM 32 stores calculation programs for the CPU 31, and the RAM 33 stores data used in calculations in the form of a map or the like.

Next, the effect will be explained.

FIG. 3.5 is a flowchart showing the combustion control program written in the ROM 32.

FIG. 3 shows a program for ternary region discrimination, and this program is executed once every predetermined time (every 5 m5 ec).

First, the signal TVO from the throttle valve opening sensor 12 is read at Pl and A/D converted. Next, in P2, a difference value ΔTVO of the throttle valve opening degree TVO within a predetermined unit time is calculated, and in P3, this is compared with a predetermined acceleration determination value A (A>O). Note that ΔT■0 may be calculated, for example, by calculating the difference (difference between the previous value and the current value) each time this program is executed.

When ΔTVO>A, it is determined that acceleration is occurring, and the acceleration flag KF is set at P4, and the process proceeds to P. When ΔTVO<A,
Judging that it is not accelerating, lower the acceleration flag KF at P6 and P
, proceed to . Thereby, acceleration can be accurately and reliably determined. Note that the determination of acceleration is not limited to the above example; for example, the differential value dTVo/dt of the throttle valve opening degree TVO may be obtained and this may be compared with a predetermined value to determine acceleration.

P, the elapsed time T after the throttle valve 11 leaves the fully closed position
c to a predetermined value t. Compare with. This is because immediately after the throttle valve 11 opens from fully closed, the degree of acceleration required is greater than when the engine 1 accelerates from steady running.In response, the air-fuel ratio is enriched (λ=1). This is for the purpose of achieving this goal. . Tc<t
o, the acceleration flag KF is determined at P7, and when T≧t0, the process proceeds to P. When KF=1 at P7, it is determined that the enrichment condition is present due to an acceleration request, and the ternary flag SF is set at P9, and the current routine is ended. On the other hand, P,
When the No command is followed at ,P, it is determined that the enrichment condition is not present, and the ternary flag SF is lowered at P, and the routine is ended.

In this way, when the engine 1 shifts to a predetermined acceleration state, the air-fuel ratio is changed to λ when it is under enrichment conditions associated with an acceleration request.
It is determined whether the three-way condition that it is desirable to force the transition to =1 is satisfied.

FIG. 4 shows the above-mentioned ternary conditions in a time chart. In FIG. 4, when the throttle valve 11 opens from the fully closed position, when the subsequent elapsed time Tc is within the range of the predetermined value t0, the acceleration flag KF becomes KF=1 as shown in FIG. Former flag SF is set. And TC=tO
When KF=0 at the timing, the ternary flag SF is lowered at the same timing.

FIG. 5 shows a combustion control program, which is executed in synchronization with engine rotation.

First, the flow rate of air actually taken into each cylinder per cylinder (hereinafter referred to as cylinder flow rate) QACYL is calculated based on pH. The reason for performing such calculations is to obtain accurate air flow rate information even during transient times.If the accuracy of this information is poor, the injection amount cannot be effectively manipulated in air-fuel ratio control. This is to accommodate control.

Therefore, calculation of the cylinder airflow amount QACYL will be explained.

The calculation of QACYL is illustrated in the case of acceleration as shown in FIG. 6 as an example.

In FIG. 6, when the accelerator is started to be depressed at the timing t=Q and the throttle valve opening TVO starts to change, the waveform PBX obtained by signal processing the main waveform PB of the pressure sensor 13 has a period t2 due to the pulsation suppressing effect. It starts to change with a delay. In addition, the pressure correction flow rate value QACY predicted based on the PBX
Although L' has also been corrected considerably, it is still the same as period 1.
It starts to change with a delay of (1, < tz), and there is a difference between the hunting part (ΔQACYL) in the figure and the true air flow rate QACYL that is expected to be taken into the cylinder.

Therefore, the detection accuracy of the air flow rate decreases during such a transient period. This example corrects this problem.

First, QACYL' is calculated according to the following equation (2).

QACYL'=PBX+αΔPB ・・・・・・0
In Equation 0, PBX is a waveform obtained by signal processing the output of the pressure sensor 13 to suppress pulsation, and ΔPB is a difference value of the intake pressure PB within a predetermined unit time. Also,
α is a function of the rotation speed N.

The reason for performing such a calculation is to predict the amount of air entering the cylinder when determining the injection amount, since air is drawn into the cylinder later than fuel. The prediction is made by adding ΔPB multiplied by α to the processed result.

On the other hand, in order to correct the deviation of the hunting part mentioned above,
Focusing on the throttle valve opening TVO that starts to move the earliest, a flow rate correction value ΔQACYL, which is a deviation correction amount, is calculated according to the following equation.

ΔQACYL= (ΔTVO/N)XINTQA...
...■ In formula 0, INTQA is the air flow rate QAC at the initial stage of the transition.
YL, in which case a change in the throttle valve opening TVO is used. This second represents the air flow rate under operating conditions with ΔTVO/N, that is, the difference value ΔTVO per revolution (difference in throttle valve opening TVO per predetermined unit time), and this
This means that by multiplying by TQA, it is possible to sufficiently correct the deviation in the correlation between the actual air flow rate and the calculated flow rate amount based on sensor information. This ΔQACYL is added to QACYL'(QACYL=ΔQACYL+QACYL")
As shown in the figure, is correlated with the change in the throttle valve opening TVO, and corresponds accurately to the true flow rate of air that is expected to be taken into the cylinder.

That is, by accurately calculating the amount of intake air during acceleration, the accuracy of detecting the flow rate of air taken into the cylinder can be dramatically improved. Note that, of course, the improvement in detection accuracy is achieved not only in the above-mentioned example of acceleration but also in the case of deceleration.

Then, when the correction by ΔQACYL is completed, QACY
The air flow rate is calculated by L', and QACYL
When ' becomes equal to PBK, the air flow rate is thereafter calculated based on the output of the flap type air flow meter 10. However, after QACYL''=PBK, the air flow rate may be calculated directly from the output of the pressure sensor 13.

In this way, because it is based on accurate air flow information,
Injection amount control, which will be described later, will also be more precise.

Now, with the above in mind, let's return to the program again.

After passing through pH, a fuel delay correction coefficient C0EF is calculated using PUS. This is to correct the fuel amount during transient times. The value is determined by the vaporization of the fuel and the wall flow rate, but specifically, it is calculated based on the magnitude of acceleration/deceleration, engine warm-up and operating conditions, and whether or not the engine has been started.

Next, PI3 determines the three-way flag SF, and when 5F=1, it is determined that the three-way condition is satisfied, and PI4 sets the target air-fuel ratio KMR to the three-way air-fuel ratio (hereinafter referred to as three-way KMR). ) and proceed to pus. The three-way air-fuel ratio is the air-fuel ratio that allows the original function of the three-way catalyst to be effectively demonstrated.
In this embodiment, this is set to the stoichiometric air-fuel ratio of λ=1. P
At I5, the ignition correction amount ΔADV is calculated according to the following equation.

ΔADV=R・ (ternary KMR-MAPKMR)...
...■ However, in the equation, R: constant 0, MAPKMR is a normal target air-fuel ratio, and is determined by looking up from a predetermined table map according to the engine load at that time. As in the conventional example, the normal target air-fuel ratio KMR is set widely mainly in the lean air-fuel ratio region, taking into consideration the so-called lean burn system.

Here, the relationship with the optimum required ignition timing using the target air-fuel ratio KMR as a parameter is shown as shown in FIG. Note that KMR is a factor that indicates the air-fuel ratio,
Strictly speaking, the relationship is the reciprocal of A/F, as shown by the following equation (2).

KMR-A/F=K (constant), -, KMR=-F/A ・・・・・・■ However, F
:Fuel amount A:Air amount As is clear from FIG. 7, the required ignition timing changes approximately linearly with respect to KMR. If KMR changes from now on, the optimum value of the required ignition timing at that time will also change according to KMR, and once KMR is determined, the required ignition timing is also uniquely determined.

This means that the required ignition timing can be immediately determined in response to a change in KMR. Based on this principle, the ignition correction amount ΔAD■ calculated by the formula
It is positioned as a variable for correcting ADV.

Next, the final ignition timing ADV is calculated at P according to the following equation.

ADV=MAPADV-ΔADV ・・・・・・00
In the formula, the basic ignition timing M A P A D V is determined by calculating the optimum value from a predetermined table map (three-dimensional map) according to the cylinder flow air 1i QACYL and rotation speed N as parameters and the engine load (the same goes for MAPKMR described above). Look amp and decide.

Therefore, MAPADV uniquely corresponds to MAPKMR at that time.

On the other hand, if 5F=0 in steps P and 3 above, it is determined that the three-way condition is not satisfied, and PI? Ignition correction amount ΔADV
Set it to zero and proceed to Pl&.

The final ignition timing ADV set in this way is based on the crank angle reference signal Re from the crank angle sensor 17.
In response to ADV, it is set in the I10 port 34 in a predetermined interrupt routine, and the air-fuel mixture is ignited at a timing corresponding to ADV.

Next, PI3 calculates the fuel injection amount Ti according to the following equation, and PI9 sets this to the I10 boat 34, and the routine ends.

Ti=QACYLxKMRxCOEF This corresponds to the air flow rate per cylinder, and corrections based on intake air temperature are also taken into consideration.

In this case, in this embodiment, QACYL is calculated based on the output of air flow meter 0 in the steady state, and when the transition to the transient state occurs, correction is added based on the throttle valve opening TVO and the signal PB of the pressure sensor 3 as described above. Calculated by

ALPHA is a correction coefficient when the injection amount is feedback-controlled based on the air-fuel ratio detected by the oxygen sensor 7 so as to reach the target value KMR.

In this way, when the lean operation shifts to the three-way operation region, the air-fuel ratio immediately changes to λ=
1 (hereinafter referred to as three-way control).

At this time, the ignition timing is immediately corrected by a correction amount of ΔADV according to the difference between the ternary KMR and the target air-fuel ratio MAPKMR determined according to the engine load at that time, and the optimal final ignition timing ADV is set. Ru. Unlike the device of the prior application, the above-mentioned ignition correction accompanying the transition to three-way control does not go through a process of table lookup at the time of transition, and is instantaneously executed by simple arithmetic processing. Therefore, the optimum required ignition timing can be provided by sufficiently following the above-mentioned sudden change in the air-fuel ratio, and the operability of the engine 1 can be further improved.

Furthermore, since ignition correction requires simple calculation processing, there is no need to increase the basic ignition timing MAPADV area, and an engine combustion control device that meets recent demands can be provided at low cost.

(Effects) According to the present invention, it is possible to immediately optimize the ignition timing at low cost when transitioning to the three-way operation region, further improving engine drivability and meeting recent demands. A high-level engine combustion control device can be provided.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 7 are diagrams showing an embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a diagram showing an embodiment of the present invention.
The figure is a flowchart showing the program for determining the ternary region, FIG. 4 is a time chart for explaining the effect of establishing the three-way condition, FIG. 5 is a flowchart showing the combustion control program, and FIG. A waveform diagram for explaining the effect of air flow rate calculation, Fig. 7 shows the target air-fuel ratio KM.
FIG. 3 is a diagram showing the relationship between R and required ignition timing. 1...Engine, 4...Injector (operating means), 7...
...Ignition means, 19...Oxygen sensor (air-fuel ratio detection means), 20
...Load detection means (three-way area detection means, type setting means, control means, ignition timing setting means).

Claims (1)

[Scope of Claims] a) air-fuel ratio detection means for detecting the air-fuel ratio of the intake air-fuel mixture; b) load detection means for detecting the load of the engine; and c) a means for detecting that the engine is in a predetermined three-way operation region. d) setting a target air-fuel ratio according to the engine load, setting the target air-fuel ratio to be leaner than the stoichiometric air-fuel ratio during at least a part of steady driving, and controlling the engine to a predetermined level; e) a target setting means that changes the target air-fuel ratio to a three-way air-fuel ratio when shifting to a three-way operation region, and e) controlling the supply amount of intake air or fuel to reach the target air-fuel ratio based on the output of the air-fuel ratio detection means. f) an operating means for manipulating the amount of intake air or fuel supplied based on a signal from the control means; and g) a control means for setting the ignition timing based on the engine load and causing the engine to perform a predetermined three-way operation. h) ignition timing setting means for correcting the ignition timing according to the difference between the target air-fuel ratio and the ternary air-fuel ratio determined in accordance with the engine load at that time; An engine combustion control device comprising: ignition means for igniting an air-fuel mixture based on a signal;