JPS60204937A - Air-fuel ratio learning control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a fuel control method in an internal combustion engine such as a gasoline engine. Ensures that standard characteristics are always obtained without the need for special adjustments.
c.Regarding an air-fuel ratio control method.

[Background of the invention]

As interest in environmental conservation by preventing air pollution and depletion of energy resources increases, efforts are being made to comprehensively control the operating conditions of automobile gasoline engines to improve exhaust gas conditions.
For this reason, there has been a demand for a control device that can improve fuel efficiency.

A microcomputer is used to increase the number of signals from sensors that provide various data representing the engine's operating status, such as the cooling water temperature sensor and the 02 sensor that detects the presence or absence of oxygen in exhaust gas, to determine fuel supply amount and ignition timing. Electronic engine control devices (hereinafter referred to as EECs) have come into use, which perform various controls such as idle speed and exhaust gas recirculation amount to ensure that the engine is always in the best possible operating condition. Nine.

An example of a system applied to this more EEC'e fuel injection type internal combustion engine is proposed in Japanese Patent Laid-Open No. 134721/1982, and this conventional example will be explained with reference to FIGS. 1 and 2.

Figure 1 is a partial cross-sectional view schematically showing the entire engine control system. In Figure 5, intake air is supplied to the air cleaner 2. The air is supplied to the throttle chamber 4 through an intake pipe 6 and into a cylinder 8 . The gas burned in the cylinder 8 is discharged from the cylinder 8 through an exhaust pipe 10 into the atmosphere.

The throttle chamber 4 is provided with an injector 12 for injecting fuel.
The fuel ejected from the throttle chamber 4 is atomized in the air passage of the throttle chamber 4 and mixed with the intake air to form a mixture, and this mixture passes through the intake pipe 6 and when the intake valve 20 is opened.
A throttle valve 14 is provided near the outlet of the injector 12 that is supplied to the combustion chamber of the cylinder 8. The throttle valve 14 is configured to be mechanically interlocked with the accelerator pedal and is driven by the driver.

An air passage 22 is provided upstream of the throttle valve 14 of the throttle chamber 4, and a hot wire air flow meter made of an electric heating element, that is, a flow rate sensor 24 is disposed in this air passage 22, and the flow rate is adjusted according to the air flow velocity. A changing electrical signal AP is taken out. Since the flow rate sensor 24 made of this heating element (hot wire) is provided in the bypass air passage 22,
It is protected from high-temperature gas generated during pack-fire from the cylinder 8, and is also protected from being contaminated by dust and the like in the intake air. The outlet of the bypass air passage 22 is opened near the narrowest part of the venturi, and the inlet thereof is opened on the upstream side of the venturi.

The injector 12 is constantly supplied with pressurized fuel from the fuel tank 30 via the fuel pump 32, and when an injection signal from the control circuit 60 is given to the injector 12, the fuel is fed from the injector 12 into the suction pipe 6. Fuel is injected.

The air-fuel mixture taken in from the intake valve 20 is compressed by the piston 50 and combusted by a spark from one spark plug (not shown), and this combustion is converted into kinetic energy.

The cylinder 8Vi is cooled by cooling water 54. The temperature of this cooling water is measured by a water temperature sensor 56, and this measured value TW is used as the engine temperature.

Exhaust pipe 10 to 0! A sensor 142 is provided.

The presence or absence of 02 in the exhaust gas is measured and a measured value λ is output.

Further, a crank angle sensor (not shown) is provided on the crankshaft, which outputs a reference angle signal and a position signal at each reference crank angle and at each fixed angle (for example, 0.5 degrees) according to the rotation of the engine.

The output of the crank angle sensor, the output signal λ of the water temperature sensor 56, the output signal λ of the TW-Os sensor 142, and the heating element 24
The injector 12 and the ignition coil are driven by the output of a control circuit 60 consisting of a microcomputer or the like.In addition, the throttle chamber 4 has a bypass 26 that straddles the throttle valve 14 and communicates with the intake pipe 6. This bypass 26 is provided with a bypass valve 61 whose opening and closing are controlled.

This bypass valve 61 faces the bypass 26 provided around the throttle valve 141, and is controlled to open and close by a pulse current, and the entire cross-sectional area of the bypass 26 is changed depending on the amount of lift.This lift IF is controlled by the control circuit. The drive unit is driven and controlled by the output of 60. That is, the second control circuit 60 generates an opening/closing cycle signal to control the drive unit, and the drive unit adjusts the lift amount of the bypass valve 61 based on this opening/closing cycle signal.

The EGFL control valve 90 controls the passage between the exhaust pipe 10 and the suction pipe 6, and the amount of EGR flowing from the exhaust pipe 10 to the suction pipe 6 is controlled.

Therefore, by controlling the injector 12 in FIG. 1, the air-fuel ratio (
The bypass valve 61 and the injector 12 control the engine speed during idling (ISO), and further control the amount of EGR.

Figure 2 shows a combination of control circuits 60 using a microcomputer.
(hereinafter referred to as CPU), read-only memory 104 (hereinafter referred to as ROM), and random access memory 106
(hereinafter referred to as RAM) and an input/output circuit 108. The CPU 102 calculates the input data from the input/output circuit 108 using various programs stored in the ROM 104, and sends the calculation results back to the input/output circuit 104.
Return to 08. The intermediate memory required for these operations is RA.
M106t - Use. CPUI 02゜ROM104
．． RAM106. Various types of data are exchanged between the input/output circuits 108 via a path line 110 consisting of a data bus, a control bus, and an address bus.

The input/output circuit 108 inputs and outputs 1-bit information to a first analog-digital converter 122 (hereinafter referred to as ADCI), a second analog-digital converter 124 (hereinafter referred to as ADC2), and an angle signal processing circuit 126. Discrete input/output circuit 128 (hereinafter referred to as DI) for
(denoted as O) has an input means.

The ADCI includes a battery voltage detection sensor 132 (hereinafter referred to as VB).
(hereinafter referred to as TWS) and cooling water temperature sensor 56 (hereinafter referred to as TWS)
, the atmospheric temperature sensor 136 (hereinafter referred to as TAS), the adjustment voltage generator 138 (hereinafter referred to as ■几S), the throttle sensor 140 (hereinafter referred to as 0TH8-), and the 02 sensor 142 (hereinafter referred to as 0TH8-).
The output from the multiplexer 162 (hereinafter referred to as 02S)
(hereinafter referred to as MPX) - MPX162 selects one of these and inputs it to analog-digital conversion circuit 164 (hereinafter referred to as ADC).ADC1
The digital value that is the output of 64 is held in a register 166 (hereinafter referred to as REG).

In addition, the flow rate sensor 24 (hereinafter referred to as AFS) is the ADC2.
124, analog/digital, conversion circuit 1
72 (hereinafter referred to as ADC), the signal is converted into digital data and set in a register 174 (hereinafter referred to as BEG).

The angle sensor 146 (hereinafter referred to as ANGLS) outputs a signal indicating a reference crank angle, for example, 180 crank angle (hereinafter referred to as REF), and a signal indicating a minute angle of 0, for example, 1 degree crank angle (hereinafter referred to as PO8). , are applied to the angle signal processing circuit 126, where the waveform is shaped.

DIO (1281 has an idle switch 148 (hereinafter referred to as ID) that operates when the throttle valve 14 has returned to the fully closed position).
LE-8W) and top gear switch 150 (denoted as LE-8W)
(hereinafter referred to as TOP-8W) and starter switch 152
(hereinafter referred to as 5TART-8W) is input.

Next, a pulse output circuit and a controlled object based on the calculation result of CPtJ will be explained. Injector control circuit 113
4 (hereinafter referred to as INJC) is a circuit that converts the digital value of the calculation result into a pulse output. Therefore, the pulse INJ having a pulse width corresponding to the fuel injection intake is INJC11.
Made in 34.

Applied to injector 12 via AND gate 1136'.

Ignition pulse generation circuit 1138 (hereinafter referred to as IGNC)
is a register that sets the ignition timing (hereinafter referred to as ADV)
And the primary current of the ignition coil 1! It has a register (hereinafter referred to as DWL) for setting the start time, and these data are set by the CPU. The pulse IGN is generated based on the set data and is applied via the AND gate 1140 to the amplifier 62 for supplying the primary current to the ignition coil. l5CC
) 1142 through an AND gate 1144'. l5OC
1142 has a register l5CD for setting the pulse width and a register l8CP for setting the pulse period.

The EGR amount control pulse generation circuit 1178 (hereinafter referred to as EG C) that controls the EG control valve 9 has a register EGRD for setting a value representing the duty of the pulse, and a register EGRP for setting the value representing the period of the pulse. The output pulse EGR of this EGRC is AND
It is applied to transistor 90 via gate 1156.

Further, the 1-bit input/output signal is controlled by the circuit DIO (128). Input signals include IDI, E-8W signal, and 5TART-8W signal.

There is a TOP-8W signal. Further, the output signal includes a pulse output signal for driving the fuel pump. This D
IO is a register DDRI 92 for determining whether a terminal is used as an input terminal.

Register DOUT194 for latching output data
and is provided.

Mode register 11604-! Registers (hereinafter referred to as M) that hold instructions for commanding various states inside the input/output circuit 108
For example, this mode register 116
AND gate 11 by setting the instruction to 0
36. 1140. 1144° and 1156 are all activated or deactivated. By setting a command in the MOD register 1160 in this way, it is possible to control the stop and start of output of INJC, IGNC, and I19CC.

A signal DIOI for controlling the fuel bomb 32 is output to DIO (128). Therefore, if such EEC is applied, almost all controls related to the internal combustion engine, such as A/F control, can be appropriately performed.・It can fully meet the strict exhaust gas regulations for automobiles.・
Moreover, an engine with excellent fuel efficiency can be obtained.In the A/F control in such an EEC, for example, control data for the injector 12 is obtained from data AF' representing the intake air amount t and engine rotation speed data N. Gain,
It is well known that the result is corrected by feedback control using data from the 02 sensor 142 to obtain a predetermined A/F.

According to this type of control technology, even if the injection pulse deviates from the value that obtains the optimum air-fuel ratio I due to variations in mechanical parts, sensors, actuators, changes over time, environmental changes, etc., specific components in the exhaust gas will be detected. The injection pulse is controlled to the optimum value by detecting it with the concentration total 02 sensor 142 and performing feedback correction according to the detected value. The above control works effectively when the engine operating condition is steady or changing slowly, but in transient operating conditions where the engine operating condition changes suddenly, feedback of the air-fuel ratio is required. Because the correction cannot follow the operating conditions, the air-fuel ratio of one engine deviates significantly from the optimum value.As a result, the purification efficiency of the catalytic converter, which is used to reduce harmful components in exhaust gas, deteriorates significantly.

Learning control has been proposed as a method for adjusting the injection pulse to an optimal value when the air-fuel ratio deviates significantly.

An example of learning control is JP-A-57-26229. According to this bulletin.

The average value of the air-fuel ratio correction coefficient determined by the concentration of specific components in the exhaust gas when the engine is in idle operation is determined.The error correction amount is determined by learning control so that the average value falls within a predetermined range. Find the average image of the air-fuel ratio correction coefficient determined by the concentration of a specific component in the exhaust gas when operating at a predetermined rotation speed different from Determination: The overall error correction t'i is determined by determining the component that fluctuates depending on the rotational speed from the error correction amounts for idling and non-idling as a function of the rotational speed. This type of method has problems with an increase in program blue due to differences in processing during idle and non-idling, convergence due to error correction amount by learning control, and unambiguousness of correction amount depending on rotation speed.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an air-fuel ratio control method that eliminates the drawbacks of the prior art described above and allows easy learning of air-fuel ratio correction coefficients.

[Summary of the invention]

In order to achieve this object, two aspects of the present invention are provided in which, when the air-fuel ratio correction coefficient goes outside the preset upper and lower limits, a predetermined change in the air-fuel ratio correction coefficient within one cycle of change is provided. [Embodiments of the Invention] Below, the air-fuel ratio learning control method according to the present invention will be described. , will be explained in detail with reference to the illustrated embodiment.

One embodiment of the present invention has the same hardware configuration as the conventional EEC explained in FIGS. 1 and 2, but the control operation by the control circuit 60 including a microcomputer is different. Some of the programs provided are different.

First, in 'fcEEC' shown in Figures 1 and 2, the fuel injection by the 2 injector 12 is performed intermittently in synchronization with the rotation of the engine.The fuel injection amount is controlled by one injection. This is done by controlling the valve opening time of the injector 12 during operation, that is, the injection time Ti.

Therefore, in one embodiment of the present invention, this injection time Ti is determined as follows.

Ti-α・Tp-Kl・(1+ΣKit ・・・・・・
(1) Number Tp; Basic fuel injection time α; Air-fuel ratio correction coefficient Kt; Learning coefficient KI; Various correction coefficients Qm; Intake air flow rate N: Engine rotation speed, that is, from engine intake air flow '1ltQA and rotation speed N The basic fuel injection time Tp is determined by equation (2).

The stoichiometric air-fuel ratio (A/P = 14.71) is roughly obtained, and the air-fuel ratio is corrected by feedback by changing the air-fuel ratio correction coefficient α based on the signal from the Ox sensor 142 to obtain a more accurate stoichiometric air-fuel ratio. In addition, the learning coefficient Kt is used to correct variations in characteristics and aging of various actuators and sensors involved in air-fuel ratio control.

First, the learning coefficient Kt will be explained. 0! Nansa 14
2 is a 21 direct signal (high,
low level voltage). Based on this binary signal,
It is well known that air-fuel ratio control is performed by increasing or decreasing the air-fuel ratio correction coefficient α stepwise and then gradually increasing or decreasing it. 02
The state f of the air-fuel ratio correction coefficient α that detects whether the air-fuel ratio is rich or lean based on the sensor output signal λ! : Shown in Figure 3.

Here, when the signal of the 02 sensor is reversed, the air-fuel ratio correction coefficient α is the extreme value when the air-fuel ratio changes from lean to rich, αrnax, and the extreme value when the air-fuel ratio changes partially from rich to αmin. shall be. In this embodiment, the maximum value αmax of the air-fuel ratio correction coefficient exceeds the upper limit (U, Ll, or the minimum value αmln exceeds the lower limit +L, L)
When the air-fuel ratio correction coefficient value is lower than 1.0, the deviation Ktf learning amount from the air-fuel ratio correction coefficient value 1.0 is set. This calculation of the learning amount Kt is performed in all areas where feedback correction is being performed by the 02 sensor.

Figure 4 shows the table in which learning @Tr(t is written.
In this table, Ktt- is written at division points determined by the basic fuel injection time Tp and the engine speed N. This learning timing is performed when the 1 division point does not change, and when the number of times when the maximum value αmax, I & small value αmln of the air-fuel ratio coefficient is outside the range of the upper limit value or the lower limit value becomes 0. The table shown in FIG. 4 is defined as a learning map.

Next, an example of a learning routine for learning coefficient (learning #) Kt will be described with reference to FIG. Processing according to this flowchart is done after the engine starts.

Steps 300 to 332'1 are repeated as often as necessary. 1. At step 302, it is determined whether or not the 02 feedback control is in progress, and the result is Yes.
In this case, the process advances to step 304.

If the result is NO, proceed to step 332. Step 3
At 04, the signal from the 02 sensor is z=l (theoretical air-fuel ratio A
/F-14, 71f: Determine whether it crossed or not. If the result is NO, the process goes to step 332 and performs a well-known integration process (not shown). If the result is Yes,
Step 306Vc advances.

02 Check the inverted state of the sensor. When the air-fuel ratio changes from lean to rich, the process proceeds to step 308, where it is checked whether the maximum value αIIIax of the air-fuel ratio coefficient is greater than or equal to the upper limit value, and if it is greater than the upper limit value, the process proceeds to step 310.

Let the deviation between αmlK and 1 be learning IKt. On the other hand, if the air-fuel ratio changes from rich to lean in step 306, proceed to step 312, and check whether the minimum value αmIn of the air-fuel ratio coefficient is less than or equal to the lower limit value.If it is less than the lower limit value, step 3
In step 14, the deviation between αm1tI and 1 is determined as learning 11) Kz. The process proceeds from steps 310 and 314 to step 316.

In step 316, dividing points of the learning map are calculated from the rotation axis of the engine speed and the load axis of the fuel injection time shown in FIG.

In step 318, it is checked whether the division point calculated - period ago and the current division point have changed.

If the division point has not changed, a counter is incremented at step 320. In step 322, when the counter reaches n[, the counter is cleared in step 326. In step 328, the learning amount Kt'lk calculated in steps 310 and 314 is added to the dividing point (address) calculated in step 316. Next, in step 330, the air-fuel ratio correction coefficient α is set to 1.0. In step 308, when αmaz is less than the upper limit value.

If αmln is less than the lower limit in step 312, and if it is determined in step 318 that the dividing point has changed, the process proceeds to step 324, where the counter is cleared, and then the process proceeds to 332.

Therefore, according to this embodiment, the learned value of the air-fuel ratio correction coefficient can be easily taken in, and can be taken in with less response delay.

In addition, in the above explanation, the maximum value αml of the air-fuel ratio correction coefficient
K and the deviation of the minimum value αmIn from 1.0, the total learning amount Kt
However, the present invention is not limited to the deviation from the standard value of the air-fuel ratio correction coefficient of 1.0, but the deviation from the standard value of 1.0, For example, the amount of deviation between the maximum value αm&X and 1.02 and the amount of deviation between the minimum value αml and 0.98 may be increased as the learning amount Kt.

In addition, in the above embodiment, the maximum value αn of the air-fuel ratio correction coefficient
'+ax and minimum value α1111! Although the deviation amount between l and a predetermined value is set as the learning iKz, the present invention is not limited to this, and the deviation amount between an arbitrary part of one cycle change of the air-fuel ratio correction coefficient α and the predetermined value is set as the learning amount Kt. It goes without saying that it may be taken in as .

〔Effect of the invention〕

As explained above, according to the present invention, the learning amount is increased based on the latest instantaneous value at the time of change of the air-fuel ratio correction coefficient, so the shortcomings of the prior art are eliminated and the response is quick with a simple configuration. Moreover, it is possible to perform appropriate learning control.・Air-fuel ratio learning that can always obtain standard characteristics without requiring special adjustments to account for variations in the characteristics of fuel control system sensors, actuators, etc. or changes over time. 0 that can easily provide a control method

[Brief explanation of drawings]

Fig. 1 is a schematic block diagram showing an example of an electronic engine control device, Fig. 2 is a block diagram showing an example of a control circuit, and Fig. 3 shows a learning operation in an embodiment of the air-fuel ratio learning control method according to the present invention. FIG. 4 is an explanatory diagram showing an example of a school fund map according to an embodiment of the present invention. FIG. 5 is a flowchart for explaining the operation of an embodiment of the present invention. 12... Injector, 24... Intake air flow rate sensor. 11 yen 1 porridge 7

Claims (1)

[Scope of Claims] 1. An air-fuel ratio learning control method comprising a sensor for detecting an air-fuel ratio based on exhaust gas components of an engine, and learning an air-fuel ratio correction coefficient based on a detection signal of the sensor. When the correction coefficient goes outside the preset upper and lower limits, the value of a predetermined portion of the change in one cycle of the air-fuel ratio correction coefficient and the standard value of the air-fuel ratio correction coefficient or its An air-fuel ratio learning control method characterized in that a deviation value from a nearby predetermined value is taken in as a learning value. '2. In claim 1, the learning value is increased when the same learning value is obtained a predetermined number of times or more while the engine operating conditions remain the same. An air-fuel ratio learning control method characterized by: