JPS6090944A - Air-fuel ratio learning control apparatus for electronically controlled fuel injection type internal-combustion engine - Google Patents

Abstract

PURPOSE:To obtain stable controllability of an engine, by executing learning control to converge the base air-fuel ratio to lambda=1 (lambda is the excess air ratio), and thereby minimizing deviation of the excess air ratio from lambda=1 caused by the change of the base air- fuel ratio at the time of transient operation of the engine. CONSTITUTION:The base injection quantity Tp is calculated by an arithmetic means 1 from the engine speed N and the quantity Q of intake air, and comparison is made between the actual air-fuel ratio detected by an O2-sensor and the theoretical air-fuel ratio. Further, an air-fuel ratio feedback correction factor alpha is determined by a correction factor determining means 2 by way of proportional plus integral control, and a learning correction factor alphaL stored in an RAM to correspond to the conditions of engine operation is searched at a searching means 3. The learning correction factor alphaL is renewed successively by adding a certain part of the deviation DELTAalpha between the correction factor alpha and a reference value to the learning correction factor alphaL by a renewing means 4, and then the injection quantity Ti is calculated by an arithmetic means 5 by correcting the base injection quantity Tp by use of the renewed data and the correction factor alpha.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a learning control device for a desired fuel-fuel ratio in an electronically controlled fuel injection type internal combustion engine.

<Background Art> In an electronically controlled fuel injection type internal combustion engine, the injection amount Ti is determined by the following equation.

T 1 = Tp
X Q/N. K is a constant, Q is the intake air flow rate,
N is the engine speed. C0EF is various correction coefficients. α is an air-fuel ratio feedback correction coefficient for air-fuel ratio feedback control (λ control) to be described later. Ts is a voltage correction amount, which is used to correct changes in the injection flow rate of the fuel injection valve due to fluctuations in battery voltage.

Regarding λ control, an 02 sensor is installed in the exhaust system to detect the actual air-fuel ratio, and the slice level determines whether the air-fuel ratio is higher than or thinner than the stoichiometric air-fuel ratio, and the fuel is adjusted to the stoichiometric air-fuel ratio. Therefore, the above-mentioned air-fuel ratio feedback correction coefficient α is determined, and by changing this α, the air-fuel ratio is maintained at the stoichiometric air-fuel ratio.

Here, the value of the air-fuel ratio feedback correction coefficient α is changed by proportional-integral (Pl) control to achieve stable control.

That is, the output voltage of the 027 sensor is compared with the slice level, and if it is higher or lower than the slice level,
If the air-fuel ratio is rich (lean) without suddenly enriching or reducing the air-fuel ratio, first lower (raise) by P, then gradually lower (raise) one minute at a time. control the air-fuel ratio to make it leaner (richer).

However, in a region where λ control is not performed, α is clamped to 1, and a desired air-fuel ratio is obtained by setting various correction coefficients COEF.

By the way, if the base air-fuel ratio when α = 1 in the λ control region could be set to the stoichiometric air-fuel ratio (λ = 1), feedback control would not be necessary. The deviation of the base air-fuel ratio from λ = 1 may occur due to factors such as variations in the fuel injection valve (injection valve, pressure regulator, control unit), changes over time, non-linearity of the pulse width-flow rate characteristic of the fuel injection valve, and changes in operating conditions and environment. , so feedback control is performed.

However, if the base air-fuel ratio deviates from λ=1, it takes time to stabilize the step in the base air-fuel ratio to λ=1 through feedback control when the operating range changes significantly. And for this we need the constant of proportionality and integration (P/
Since the I minute) is increased, overshoot and undershoot error occur, resulting in poor controllability. However, if the base air-fuel ratio deviates from λ21, the nitrogen-fuel ratio will be controlled within a range with a slight deviation from the stoichiometric air-fuel ratio.

As a result, the three-way catalyst has to be operated at a point where its conversion efficiency is low, which not only increases costs due to the increase in precious metals in the catalyst, but also necessitates replacement of the catalyst due to further deterioration of conversion efficiency due to deterioration of the catalyst. There was a problem.

Therefore, in Japanese Patent Application No. 58-76221, the present applicant has learned to set the base air-fuel ratio to λ = 1, thereby eliminating the deviation from λ = 1 caused by the step in the base air-fuel ratio during transient periods. We have proposed a base air-fuel ratio learning control device that makes it possible to improve controllability by making it possible to reduce the amount of air and fuel, and to reduce the cost of the catalyst.

That is, a map of the learning correction coefficient αL corresponding to engine operating conditions such as engine speed and load is provided in the RAM, and when calculating the injection amount Ti, the basic injection amount T is calculated as shown in the following formula.
Correct p by α.

T 1=TpXcOEFXα×αL+Ts and αL
Proceed with the following steps to learn.

1) Engine operating conditions and α in steady state
and detect.

11) Search for αL that has been learned and stored up to now in accordance with the engine operating conditions.

111) A new αL is set and stored using a weighted average or the like from the α and αL.

By the way, in the above-mentioned method of setting and updating a new αL using a weighted average from α and αL, although it is possible to suppress the deviation of the base air-fuel ratio from λ = 1 to a certain value or less, it is not always possible to Since convergence control is not performed to approach λ=1, there is still room for improvement.

<Purpose of the Invention> In view of the above-mentioned circumstances, the present invention provides learning to converge the base air-fuel ratio to λ=1 to further improve controllability during transient periods and further promote cost reduction of catalysts. The purpose is to make it possible.

<Configuration of the Invention> For this reason, the present invention, as shown in FIG. desired fuel ratio feedback correction coefficient setting means for comparing the actual air-fuel ratio detected based on the signal with the stoichiometric air-fuel ratio and setting the air-fuel ratio feedback correction coefficient by proportional-integral control; A learning correction coefficient search means for searching a learning correction coefficient stored in the RAM corresponding to the operating conditions; and a learning correction coefficient that calculates a deviation amount between the air-fuel ratio feedback correction coefficient and a reference value by a predetermined ratio under predetermined operating conditions. learning correction coefficient updating means for setting a learning correction coefficient by adding it to the coefficient and updating the data of the learning correction coefficient for the same engine operating condition in the RAM; The fuel injection valve is configured to include an injection amount calculation means for calculating the injection amount by multiplying the injection amount by the fuel injection amount, and a drive pulse signal output means for outputting a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve.

<Example> Examples will be described below.

Figure 2 shows the hardware configuration.

1 is CPU, 2 is P-ROM, 3 is 0MO for learning control
8-4°C AM, 4 is an address decoder. Furthermore, )t
For AM3, a bank-up power supply circuit is used to retain the memory contents even after the key switch is turned off.

Analog input signals to CPtJI for controlling the fuel injection amount include the intake air flow rate signal from the hot wire airflow meter 5, and the throttle sensor? The throttle opening signal from 6, the water temperature signal from water temperature sensor γ, the exhaust oxygen concentration signal from 027 sensor 8, and the battery voltage from battery 9 are input to analog input interface 10 and A.
The signal is input via a /D converter 11.

12 is the A/D conversion timing CoroDraw 2.

Digital input signals include ON/OFF signals from an idle switch 13, a start switch 14, and a neutral switch 15, and these are inputted via a digital input interface 16.

In addition, a reference signal every 180'' and a position signal every 1° from the crank angle sensor 1T are inputted via the one-shot multi-circuit 18. A vehicle speed signal is input via a waveform shaping circuit 20.

An output signal from the CPU 1 (a drive pulse signal to the fuel injection valve) is sent to the fuel injection valve 22 via a current control circuit 21.

Here, the CPU 1 executes a program (RO
(stored in M2), performs input/output operations, calculation processing, etc., and controls the fuel injection amount.

Next, the flowchart shown in FIG. 3 will be explained.

The basic injection amount Tp (
=KXQ/N).

In S2, various correction coefficients C0EF are set.

In S3, the output voltage of the 02 sensor 8 and the slice level voltage are compared, and the air-fuel ratio feedback correction coefficient α is set by proportional-integral control.

In S4, a voltage correction numerator s is set based on the battery voltage from the battery 9.

In S5, a map is created in which the operating region is divided into a plurality of areas based on parameters indicating the engine operating state, such as engine speed N and basic injection amount (load) Tp, and a learning correction coefficient αL, which will be described later, is stored for each area. (stored in RAM3) to the current (N.

Tp) is searched for, and data indicating the area is set in a predetermined location A of the address decoder 4.

In S6, the current (N.

The data in the area where Tp) exists is searched previously (N,
Tp) is compared with the data of the area where it exists, and it is determined whether they are the same. If YES, that is, if it is determined that the operating conditions are substantially the same, the process advances to S7.

In S7, the output voltage of 02 sensor 8 (see Figure 4) is 8.
After the determination in step 6 becomes YES, it is determined whether or not it has been reversed n times, and in the case of YES, the process advances to S8.

That is, S6 and S7 are provided to determine whether the operating state is a steady state or not! ri, S6. If both determinations in S7 are YES, it is determined that the state is in a steady state. Such a steady state determination method can be performed easily and with high accuracy, but it can also be determined based on, for example, whether or not a predetermined time f has elapsed with the vehicle speed constant, the =\A position in neutral, and the throttle pJ degree constant. -C may also be used. If the determination in either S6 or S7 is NO, it is determined that the state is unsteady, and in this case, 88 to SI described later
Proceed to 811 without performing learning up to O.

In S8, the average value α of the current and past values of the air-fuel ratio feedback correction coefficient α during steady operation is calculated. This can be done by calculating the average value every time the rotation is performed, but for example, you can calculate the average value from the time when the increase/decrease in the value of α is reversed until it is reversed, or the average value of only the value of α at the time of reversal. The value may be increased, and in this way, the control center of α in the steady state can be set more accurately.

In S9, the engine rotation speed N and the basic injection amount Tp to R
The learning correction coefficient αL corresponding to N and Tp stored in the area where the above-mentioned (N, Tp) exists in AM3 is searched. Note that all the values of αL stored in the map are αLL12 at the time when learning has not started.

The SIO calculates the learning correction coefficient αL retrieved in S9 and the average value α of the air-fuel ratio feedback correction coefficients calculated in 88 according to the following formula, sets the value as a new learning correction coefficient αL, and sets αL as the new learning correction coefficient αL. Update the value in the corresponding area of the map.

αL−αL+Δα/M In addition, Δα represents the deviation amount between α and the reference value Δα=α−αλ
=1, the base preparation αλ21 is generally 1.0.

Also, M is a constant.

At 811, the data of the previous area (N, Tp) set in the address LA of the address decoder 4 is transferred to the data of the current area (N, Tp) set in the address A.

Tp) is updated by transferring the data in the area.

Finally, in 812, the injection amount Ti is calculated according to the following equation.

Ti=TpxcOEFXαXαL+Injection amount T above TS
i is calculated, and a drive pulse signal corresponding to this injection amount Ti is given to the fuel injection valve 22 at a predetermined timing via the current control circuit 21.

As a result, the learning value αL is updated based on the deviation amount Δα between the average value α of the air-fuel ratio feedback correction coefficient α in the steady state and the reference value in order to reduce this deviation amount.
The base air-fuel ratio is adjusted to λ= without any
It is possible to converge to λ = 1, reduce the deviation from λ = 1 as much as possible during transients, and accordingly reduce the PI constant, thereby sufficiently improving controllability. This can greatly contribute to reducing catalyst costs.

In addition, when learning G L, M determines the rate at which 1 difference amount Δα is added.
The value of α may be constant, but if it is proportional to the engine speed, the PI control coefficient of α can be decreased as the injection cycle increases, allowing for highly accurate injection amount control.

Alternatively, the learning correction coefficient may be updated by directly calculating the deviation amount between α and the reference value without averaging α, and adding the deviation amount by a predetermined percentage.

<Effects of the Invention> As explained above, according to the present invention, the base air-fuel ratio is
Since the configuration is configured to perform learning so as to converge to 1, it is possible to reduce as much as possible the deviation from λ = 1 caused by the step in the base air-fuel ratio during transient times, and to reduce the PI constant accordingly. As a result, extremely stable controllability can be obtained, and in turn, the three-way catalyst can be used in areas with high conversion efficiency, reducing costs by reducing the amount of precious metals and eliminating the need to replace the catalyst.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a hardware configuration diagram showing an embodiment of the invention, Fig. 3 is a flowchart showing the control process of the above embodiment, and Fig. 4 is an implementation of the same. FIG. 2 is a characteristic diagram of the output voltage of the 02 sensor used in the example. 1...CPU 3...CMO8-RAM for learning control
5...Air flow meter 8...02 sensor 1T
...Crank angle sensor 22...Fuel injection valve time Applicant: Japan Electronics Co., Ltd. Representative Patent Attorney Fujio Sasashima

Claims (1)

[Claims] The basic injection amount calculating means calculates the basic injection amount from the intake air flow rate and engine speed, and the actual air-fuel ratio detected based on the signal from the 02 sensor installed in the exhaust system is compared with the theoretical air-fuel ratio. an air-fuel ratio feedback correction coefficient setting means for setting an air-fuel ratio feedback correction coefficient by proportional-integral control, and a learning means for retrieving a learning correction coefficient stored in a RAM corresponding to engine operating conditions such as engine speed and load. A correction coefficient retrieval means sets a new learning correction coefficient by adding the deviation amount between the air-fuel ratio feedback correction coefficient and the reference value under a predetermined operating condition to a predetermined ratio learning correction coefficient. learning correction coefficient updating means for updating learning correction coefficient data; injection quantity calculation means for calculating the injection quantity by multiplying the basic injection quantity by the air-fuel ratio feedback correction coefficient and the learning correction coefficient; 1. An air-fuel ratio learning control device for an electronically controlled fuel injection type internal combustion engine, comprising drive pulse signal output means for outputting a drive pulse signal corresponding to the fuel injection amount to a fuel injection valve.