JPH03124940A - Ignition timing control device for engine - Google Patents

Abstract

PURPOSE:To make the generated torque constant by performing air-fuel ratio feedback correction even at the time of idling, estimating the air-fuel ratio in a cylinder based on the air-fuel ratio feedback correction quantity, and correcting the ignition timing based on this estimated value. CONSTITUTION:An injection quantity determining means 36 corrects the basic injection quantity Tp with the air-fuel ratio feedback correction quantity alphaeven at the time of idling to determine the fuel injection quantity Ti to be outputted. This injection quantity Ti is injected to an intake system via a fuel injection device 37. A cylinder air-fuel ratio estimating means 39 estimates the air-fuel ratio in a cylinder for each injection or for each preset rotating speed based on the correction quantity alpha and its change speed, and an ignition timing correction quantity calculating means 40 obtains the ignition timing correction quantity CTADV so that the generated torque obtained from this estimated value coincides with the preset required torque in response to the estimated value FBYA. The basic ignition timing PADV is corrected by the correction quantity CTADV, and the ignition timing ADV to be outputted by an ignition timing determining means 41 is determined.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an ignition timing control device for an engine.

(Prior Art) Feedback correction of the air-fuel ratio is a correction for constantly maintaining the air-fuel ratio at the stoichiometric air-fuel ratio in the feedback control region in order to make the three-way catalyst function efficiently. The air-fuel ratio is detected by an oxygen sensor, and the average air-fuel ratio is controlled to the stoichiometric air-fuel ratio by changing the air-fuel ratio feedback correction coefficient a. , p. 111).

However, if air-fuel ratio feedback control is performed even when idling, torque fluctuations will occur due to deviations from the stoichiometric air-fuel ratio, so stop air-fuel ratio feedback control during idling (
clamp).

(Problem to be solved by the invention) By the way, in such a device, if there is a change in the intake temperature or a slight change in the load by one revolution due to the stoppage of the air-fuel ratio feedback control during idling, the air-fuel ratio will change to the stoichiometric air-fuel ratio. As the fuel ratio shifts to the rich or lean side, the conversion rate of the three-way catalyst deteriorates, causing harmful gases (NOx, CO1HC,
) emissions will increase.

This invention has been made by focusing on such conventional problems, and while performing air-fuel ratio feedback correction even during idling, the air-fuel ratio feedback correction amount obtained by performing this correction is used to adjust the cylinder air-fuel ratio. It is an object of the present invention to provide a device that can maintain the generated torque constant by predicting the predicted value and applying an ignition timing correction amount having an opposite phase to the phase of the predicted value.

(Means for Solving the Problems) As shown in FIG.
and a load (for example, the intake air amount Qa), a means 33 for calculating the basic injection jtTp based on the detected values of the rotation speed N and the load, and a means 33 for detecting the air-fuel ratio in the exhaust gas. A sensor 34, a means 35 for calculating an air-fuel ratio feedback correction amount α based on the sensor detection value, and a means 35 for calculating the air-fuel ratio feedback correction amount α even during idling, correcting the basic injection amount T I) with this correction amount a even during idling, and injecting the fuel to be output. means 36 for determining the quantity Ti; a device 37 for injecting this injection fi 71 i into the intake system; and means 38 for calculating the basic ignition timing PADV based on the detected values of the rotational speed N and the load;
means 39 for predicting the cylinder air-fuel ratio for each injection or for each predetermined rotational speed based on the air-fuel ratio feedback correction amount a and its rate of change; Find the ignition timing correction HCTADV so that the generated torque obtained from
and means 41 for correcting the basic ignition timing PADV using the ignition timing correction amount CTADV to determine the ignition timing ADV to be output. It also includes a device 42 that performs ignition based on a signal of α fire timing ADV.

(Function) When the air-fuel ratio feedback control is clamped during idling, the air-fuel ratio may vary slightly, which worsens the softening rate of the three-way catalyst.

In contrast, in the present invention, feedback control of the air-fuel ratio is performed even during idle, and the average air-fuel ratio of all cylinders is maintained at the required air-fuel ratio (stoichiometric air-fuel ratio).

On the other hand, when the predicted value of the cylinder air-fuel ratio is calculated in synchronization with the injection timing, this air-fuel ratio predicted value FBYA is
This well represents the air-fuel ratio of the air-fuel mixture formed from the amount of fuel that flows into the cylinder after a stepwise increase in fuel amount.

When the ignition timing is corrected in accordance with this air-fuel ratio prediction value so that the generated torque obtained from this prediction value matches the predetermined required torque, a 7-rat torque characteristic is obtained.

(Example) FIG. 2 is a system diagram of one embodiment.

In the figure, intake air passes from an air cleaner 2 through an intake pipe 3, and fuel is injected from an injector 4 toward each intake boat of the engine 1 based on an injection signal Si. Also,
An ignition device comprising a power transistor 14 receiving an ignition signal, a spark plug 15, etc. ignites the gas within the cylinder. The gas burned in the cylinder is exhausted from the exhaust pipe 5.
The combustion gas is introduced into the catalytic converter 6 through the combustion gas, where harmful components (Co, HC, NOx) in the combustion gas are purified by a three-way catalyst and discharged.

The amount of intake air Qa upstream of the throttle valve is true wire type air 7
Detected by the 0-meter (engine load sensor) 7,
The flow rate is controlled by an intake throttle valve 8 that is linked to the accelerator pedal. Note that the type of air meter 70-meter 7 may be a hot film type, as long as it measures the amount of intake air.

The opening TVO of the throttle valve 8 is detected by a throttle valve opening sensor 9, and the rotation speed N of the engine 1 is detected by a crank angle sensor (engine rotation speed sensor) 10. Further, the cooling water temperature TW of the water jacket is detected by a water temperature sensor 11, and the oxygen concentration in the exhaust gas is detected by an oxygen sensor (air-fuel ratio sensor) 12. The oxygen sensor 12 used is one whose output changes suddenly at the stoichiometric point, or one which has characteristics capable of detecting a wide range of air-fuel ratios from rich to rich.

Furthermore, the operation of the starter motor is controlled by the start switch 13.
Detected by

Above air 70-meter 7. Crank valve opening sensor 9I crank angle sensor 10. Outputs from the water temperature sensor 12 and start switch 13 are input to a control unit 20.

The control unit 20 is 113°35.3 in FIG.
6. It has all the functions as 38-41, and CPU21. R
OM22. It is composed of a RAM 23 and an I10 port 24. The CPU 21 takes in necessary external data from the I10 boat 24 according to the program written in the ROM 22, and processes the processing values necessary for fuel injection control while exchanging data with the RAM 23. , I process the data as necessary.
10 output to boat 24.

Signals from various sensors and switches are input to the I10 boat 24, and an injection signal Si and an ignition signal are output from the I10 boat 24.

The ROM 22 stores calculation programs for the CPU 21, and the RAM 23 stores data used in calculations in the form of tables, maps, etc.

@Figure 3 to Figure 145 are routines showing the contents performed by the CPU 21. Here, the fuel injection pulse width Ti is determined as a common value for all cylinders, but since the ignition timing is determined for each cylinder, the symbol (F
BYA, CTADV, and ADV) are distinguished by adding a cylinder number n at the end.

First, FIG. 3 shows a routine executed in synchronization with the injection timing. This routine does not run out even if it is executed at every predetermined number of revolutions.

In Sl, cylinder discrimination is performed. If the cylinder is number n, select n.

S2 is a part that performs the function of the cylinder air-fuel ratio predicting means 39 in FIG. Calculate using formula 〇.

FBYAn=ffXX+FBYAn-+X(1-X)・
...■ However, in formula 0, FBYAn-1 is the previous FBY
Let it mean the value of An. Moreover, ×E%1 is a weighted average coefficient.

This equation 0 calculates the first-order delay of α as the predicted value F B Y A n
That is. This means that when the injection amount from the injector is increased in steps, the amount of fuel flowing into the cylinder actually increases with a - next lag, as shown by the broken lines in Figures 10 and 11. Therefore, in order to obtain the air-fuel ratio feedback correction coefficient for the middle of this response, it is necessary to calculate it with a -order lag.

S3 is a part that performs the function of the ignition timing correction amount calculation means 40 in FIG.
['] Request for mail.

The contents of this table are shown in Figure 6. The predicted value FBYA
An advance amount is given when n is smaller than 1.0 (value for the required air-fuel ratio). This is because if FBYA n is smaller than 1.0, it means that the air-fuel ratio of the nth cylinder is on the dust side than the required value and the required torque (predetermined) is not obtained. In some cases, this is to generate the required torque by advancing the ignition timing and increasing the combustion pressure.

On the other hand, when FBYAn is larger than 1.0 (the air-fuel ratio is on the rich side), torque greater than the required torque is generated for the n-th cylinder, so by retarding the ignition timing, the generated torque is reduced to the required torque.

Here, in order to obtain the ignition timing correction amount according to the air-fuel ratio deviation from the required air-fuel ratio, the cylinder air-fuel ratio is predicted in S2 with respect to the air-fuel ratio feedback correction coefficient related to this air-fuel ratio deviation. However, it may be configured such that the cylinder air-fuel ratio during the response is learned and predicted using the oxygen sensor output. In this case, the deviation (
After correcting the weighted average coefficient X accordingly, the ignition timing correction amount is set for each cylinder. Furthermore, the exhaust air-fuel ratio differs slightly from the cylinder internal air-fuel ratio due to the presence of residual gas in the cylinder, and is accompanied by cycle delays and exhaust pipe delays, so it is better to correct these factors before use.

FIG. 4 shows a routine for setting the ignition timing.

In Sll, it is determined whether it is idle or under low load, and if so, the process advances to S12.

S12 is a part that performs the function of the ignition timing determining means 41 in FIG. 1, and here, the cylinder-specific ignition timing correction amount CT A D
Basic ignition timing PADV [' common to gold cylinders at V n
By correcting BTDCI, the ignition timing A can be adjusted for each cylinder.
DVn[″ Find BTDCI.

ADVn=PADV+CTADVn-■ In S13, the determined cylinder-specific ignition timing ADVn is transferred to the timer of the 2I10 boat 24. This is the ignition timing set, 1
For the No. 1 cylinder, ignition is performed at this ADVn timing.

On the other hand, if the Sll determines that the time is not idle or low load, the process advances to S14 and ADVn=PADV
shall be. This is because the rotation is stable in operating ranges other than when idling or when the load is low, so torque fluctuations are not very noticeable, so there is no need to correct the ignition timing.

Figure 5 shows the background noise, for example 10n+s
is executed once.

S21 is a part that performs the function of the basic injection amount calculation means 33 in FIG. The common basic injection pulse width Tp[+asl is determined using the following formula (2).

Tp=(Qa/N)XK...■ However, K is a constant for determining the basic air-fuel ratio.

S22 is a part that performs the function of the injection amount determining means 36 of IIN, and here, the synchronous injection nozzle (input width Ti [Tsuru S1) is determined by the following equation.

Ti = Tp

In addition, air-fuel ratio feed noise correction coefficient a1
In the subroutine, every 1/2 rotation of the engine (
In the case of a four-cylinder engine, the air-fuel ratio is calculated based on the actual air-fuel ratio obtained from the oxygen sensor output.

The content of this α is known. However, it differs from the conventional example in that air-fuel ratio feed pump control is performed even during idle.

In S23, the basic ignition timing PADV ['BTD
Find C].

In S24, a weighted average coefficient X[%1 is determined from the cooling water temperature Tw with reference to a predetermined table. The contents of this table are shown in FIG. Here, X determines the rate of change of the predicted value FBYAn.

This rate of change largely depends on the behavior of the wall flow portion of the fuel injected from the innoctor to the intake boat, and the wall flow portion depends more or less on the cooling temperature Tw, so the cooling water temperature TW is used as a parameter.

Here, the operation of this example will be explained with reference to FIG. 9.

If the air-fuel ratio feedback control is clamped during idle, the air-fuel ratio will vary between cylinders even if there is a change in intake temperature, a slight load change, or a rotation change, and the conversion rate of the three-way catalyst will deteriorate. Then, a is calculated assuming that idling is also in the air-fuel ratio feedback control range, and this α
Since the average air-fuel ratio of all cylinders is maintained at the required air-fuel ratio, the conversion rate of the three-way catalyst is not deteriorated.

Note that α in FIG. 9 is a waveform resulting from proportional-integral operation.

However, torque fluctuations occur due to fluctuations in α due to feedback control. This is because, as shown in Fig. 8, when the ignition timing is constant, if the air-fuel ratio ~/F deviates to the rich side or lean side, the generated torque will be different, so the feedback control The torque inside is
As shown by the broken line in FIG. 9, it fluctuates slowly at low frequencies.

On the other hand, in this example, the predicted value F of the air-fuel ratio feedback correction coefficient for each cylinder is synchronized with the injection timing.
When B Y A II is calculated, this predicted value F B
The phase of the change in Y A n coincides with the torque fluctuation indicated by the broken line. This is because, according to the predicted value F[3YAn, the response delay due to the fuel wall flow portion of the fuel injected from the injector to the intake boat is accurately grasped for each injection and for each cylinder. This is because Y An accurately corresponds to the air-fuel ratio deviation from the required air-fuel ratio of the first cylinder, that is, the torque fluctuation.

Therefore, when the ignition timing correction amount CT ADV n is determined for each cylinder according to the predicted value F B Y A n,
This change in the correction amount CT A D V n has exactly the opposite phase to the torque fluctuation indicated by the broken line, and in the half cycle in which the torque decreases, the advance angle correction value is increased according to the degree of this decrease, and conversely, the torque In the half cycle in which the value increases, a retard angle correction value is given in accordance with the degree of this increase.

As a result, the torque characteristic is 7rat as shown by the solid line.

Furthermore, the cylinder-by-cylinder 7-direct-fire timing control, which is performed to eliminate such torque fluctuations, is performed not only during idling but also during low load, thereby preventing surges, which can be a problem in this soft operating range.

10 to 12 show a second embodiment, and this example takes into consideration the injection timing and the distance from the injector to the intake valve.

This means that when the injection timing is relatively close to the intake stroke and the injection is performed late (late injection) or when the distance from the injector to the intake valve is large, the injection timing may be changed as shown in Figures 10 and 11. This is because the response characteristics are different from those when the injection is made earlier (early injection). In other words, in response to a stepwise increase in the injection amount (shown by the solid line), the response of fuel supply in the case of early injection is approximately first-order delayed as shown by the broken line, so the predicted value FBYAn is calculated by adding the weighted average to α once. This can be represented by On the other hand, in the case of late injection or early injection, if the distance from the injector to the intake valve is long,
Since the response of the first intake is delayed, the sono response becomes like the dashed line, so it cannot be approximated by the -order delay. Note that both Figures 10 and 11 show the response characteristics of the amount of fuel flowing into the cylinder when the fuel injection amount increases stepwise, and Figure 10 shows the horizontal axis as the number of intakes. In contrast, FIG. 11 shows it as a waveform model. Further, FIG. 12 shows examples of injection pulses for early injection and post-M injection.

Therefore, in the case of late injection or when the distance from the ink to the intake valve is long, calculating the predicted value FBYAn for each cylinder using the following two equations can approximate the response characteristic in the case of late injection.

FOFBYAn=ffXX 10 FOFBYA Low+X(1-X+)・・・■FB
YAn=FOFBYAnXY 10FOFBYAn-IX (1-Yl)...■Tsuyori,
These equations give two first-order delays to α, and this makes it possible to create a rise delay with good viscosity.

In the formulas (1) and (2), X+yY+[%J is a weighted average coefficient, FOBBYAn [anonymous number] is a first-order lag constant of α for each cylinder, and FOBBYAn-1 is FOBBYAn of the moe cycle.

Figures 13 to 17 show the third embodiment, Figures 13 to 15 correspond to Figures 3 to 5, Figure 16 corresponds to Figure 7, and Figure 17 corresponds to Figure 9. ing. In this example, the predicted value of the internal air-fuel ratio and the ignition timing correction amount calculated from this predicted value are determined not for each cylinder but as a common value for all cylinders. For example, in a 4-cylinder engine, as shown in the MS13 diagram, the predicted value F of the cylinder air-fuel ratio common to all cylinders is calculated every 1/2 transmission.
BYA is determined, and from this predicted value FBYA, an ignition M correction amount CTADV common to all cylinders is determined.

However, regarding the rate of change Y [%] in S31, the first
As shown in FIG. 6, a value smaller than the rate of change X in FIG. 7 is used.

According to this example, as shown in FIG. 17, although some torque fluctuation remains compared to the case of FIG. 9, the torque fluctuation is significantly suppressed compared to the conventional example.

(Effects of the Invention) This invention performs air-fuel ratio feedback correction even during idling, predicts the cylinder air-fuel ratio from the air-fuel ratio feedback correction amount, and based on this predicted value, the torque generated by this predicted value is determined in advance. Since we decided to increase or decrease the ignition timing to match the specified required torque,
It is possible to prevent deterioration of exhaust emissions during idling while preventing torque fluctuations due to air-fuel ratio feedback control during idling.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of this invention, Fig. 2 is a control system diagram of one embodiment, Figs. Figure 7 shows the ignition timing correction amount CTADV for each cylinder in this example.
A diagram showing the characteristics of n and the weighted average coefficient
The figure is a waveform chart for explaining the operation of the embodiment. Figures 10 and 11 are diagrams showing the response characteristics of the pond embodiment;
Figure m12 is a waveform diagram showing drive pulses for early injection and late injection in this other embodiment. 13 to ttS15 are flowcharts for explaining the control operation of another embodiment, FIG. 16 is a diagram showing the characteristics of the weighted average coefficient Y of this other embodiment, and FIG. 17 is a flowchart for explaining the control operation of another embodiment. It is a waveform diagram for explaining the effect|action of the Example of another pond. DESCRIPTION OF SYMBOLS 1... Engine, 3... Intake pipe, 4... Innoecta (fuel injection device), 7... Air 70-meter (engine load sensor), 9... Throttle valve opening sensor, 10
...Crank angle sensor (engine speed sensor), 1
1...Cooling water temperature sensor, 15...Spark plug, 20
...Control unit, 31...Engine speed sensor, 32...Engine load sensor, 33...
Basic injection amount calculation means, 34... air-fuel ratio sensor, 35.
...Air-fuel ratio feeback correction amount calculation means, 36...
Injection amount determining means, 37...Fuel injection device, 38...
Basic ignition timing calculation means, 39... Cylinder air-fuel ratio prediction means, 40... Ignition timing correction amount calculation means, 41...
- Ignition timing determining means, 42...Ignition device. 281 Fig. 3 Fig. 4 $9 Fig. 10 Fig. 11 Fig. 12 Intake stroke □'Mum Ji=knee Fig. DV Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. Tw ("C) I Conventional

Claims (1)

[Claims] A sensor that detects the engine speed and load,
A means for calculating the basic injection amount based on the detected values of the rotation speed and load, a sensor for detecting the air-fuel ratio in the exhaust gas, a means for calculating the air-fuel ratio feedback correction amount based on the sensor detected value, and an idle At times, the basic injection amount is corrected by the correction amount to determine the fuel injection amount to be output, a device for injecting this injection amount into the intake system, and a device based on the detected values of the rotation speed and load. means for calculating the basic ignition timing based on the air-fuel ratio feedback correction amount and its rate of change; means for predicting the cylinder air-fuel ratio for each injection or for each predetermined rotation speed; and a predicted value of the cylinder air-fuel ratio. means for determining an ignition timing correction amount so that the generated torque obtained from this predicted value matches a predetermined required torque; and a means for correcting the basic ignition timing with this ignition timing correction amount and outputting 1. An ignition timing control device for an engine, comprising means for determining the desired ignition timing, and a device for igniting based on a signal of the determined ignition timing.