JPH0529775B2 - - Google Patents

Description

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

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

Ti = T _P × COEF × α + T _S , where T _P is the basic injection amount, T _P = K × Q/N
It is. K is a constant, Q is the intake air flow rate, and N is the engine speed. COEF 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. T _S is a voltage correction amount, which is used to correct changes in the injection amount of the electromagnetic injection valve due to changes in battery voltage.

For air-fuel ratio feedback control, an O ₂ sensor is installed in the exhaust system to detect the actual air-fuel ratio.
The slice level determines whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio, and the fuel injection amount is controlled according to the stoichiometric air-fuel ratio. Therefore, the above-mentioned air-fuel ratio feedback correction coefficient α is determined. 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 (PI) control to ensure stable control.

In other words, the output of the _O2 sensor is compared with the slice level, and if it is higher or lower than the slice level, the air-fuel ratio is rich (lean) without suddenly increasing or decreasing the air-fuel ratio. At first, the air-fuel ratio is controlled to be lowered (raised) by P, and then gradually lowered (raised) by I minutes to make the air-fuel ratio leaner (richer).

However, in the region where λ control is not performed, α=
1 and obtain a predetermined air-fuel ratio 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 due to factors such as variations in the valve, pressure regulator, control unit), non-linearity of the pulse width-flow rate characteristic of the fuel injector, and changes in operating conditions. Since this occurs, feedback control is performed.

However, if the base air-fuel ratio deviates from λ=1, it takes time to settle the step in the base air-fuel ratio to λ=1 by feedback control when the operating range changes significantly. For this reason, the PI constant is increased, which causes overshoot and undershoot, resulting in poor controllability.
In other words, if the base air-fuel ratio deviates from λ=1, the air-fuel ratio will be controlled within a range that deviates considerably from the stoichiometric air-fuel ratio.

As a result, the three-way catalyst is operated at a point where its conversion efficiency is poor, and not only does the cost increase due to an increase in the amount of precious metal in the catalyst, but the conversion efficiency further deteriorates as the catalyst deteriorates, forcing the catalyst to be replaced. There was a problem.

Therefore, by setting the base air-fuel ratio to λ = 1 through learning, it is possible to eliminate deviations from λ = 1 caused by steps in the base air-fuel ratio during transients, and to reduce the PI constant, improving controllability. A learning control device for the base air-fuel ratio was devised to reduce the cost of the catalyst.

In other words, the learning correction coefficient α _L corresponding to engine operating conditions such as engine speed and load is stored in RAM.
When calculating the injection amount Ti, the basic injection amount T _P is corrected by α _L as shown in the following equation.

Ti=T _P ×COEF×α×α _L +T _S Then, the learning of α _L proceeds as follows.

(i) Detect the engine operating conditions and α in a steady state.

(ii) Search for α _L that has been learned and stored up to now in accordance with the engine operating conditions.

(iii) Create a new α _L from α and α _L at a predetermined update rate.
Set and memorize.

Furthermore, in Japanese Patent Application No. 58-132894, the present applicant utilized the above-mentioned learning control device, and even in areas where λ control is not performed, flow rate changes due to wear and clogging of fuel injection valves, changes in ambient temperature, atmospheric pressure, etc. proposed a system that can effectively correct the air-fuel ratio in response to changes in the type (component) of gasoline.

That is, in the above learning control device,
If all learning results deviate in the same direction (rich side or lean side) in the map of learning correction coefficients using the engine operating conditions as a parameter on RMM, the basic injection amount is set in the direction that corrects the minimum value of the deviation. The calculation constant (the so-called K constant) is modified so that it can cope with clogging of the fuel injection valve and changes in air density even in a region where λ control is not performed.

However, in reality, in the learning correction coefficient map, the operating range in which the learning correction coefficient is stored is divided into fine sections in order to improve learning accuracy. Since it is rare for a station to remain in a steady state even if it only passes through it temporarily during driving, it often remains unlearned for a long period of time.

Therefore, it takes a long time for all the learning correction coefficients to deviate from their initial values, and there is little chance that all of them deviate in the same direction, so it is not always possible to correct the constant K well.

<Object of the invention> The present invention was made in view of the above circumstances, and
The learning results of the learning control device can be used more effectively, and changes in the air-fuel ratio based on various factors in the region where λ control is not performed can be better compensated for, further improving air-fuel ratio control performance. The purpose is to

<Structure of the Invention> Therefore, as shown in FIG. 1, the present invention includes a basic injection amount calculation means for calculating the basic injection amount from a constant, an intake air flow rate, and an engine speed, and an O ₂ sensor provided in the exhaust system. an air-fuel ratio feedback correction coefficient setting means for setting an air-fuel ratio feedback correction coefficient by proportional-integral control by comparing the actual air-fuel ratio detected based on a signal from the engine; Correspondingly, there is a learning correction coefficient search means for searching a learning correction coefficient stored in a map on the RAM, an air-fuel ratio feedback learning correction coefficient means for setting an air-fuel ratio feedback correction coefficient, and an air-fuel ratio feedback learning correction coefficient means for setting an air-fuel ratio feedback correction coefficient. Correspond to this based on engine operating conditions.
A learning correction coefficient search means for searching a learning correction coefficient stored in a map on the RAM, and setting a new learning correction coefficient from the air-fuel ratio feedback correction coefficient and the learning correction coefficient, and using the learning correction coefficient in the RAM.
learning correction coefficient updating means for updating data for the same engine operating conditions; 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; drive pulse signal output means for outputting a drive pulse signal corresponding to the injection amount to the fuel injection valve;
A predetermined percentage or more of all the learning correction coefficients in the map above are learned a predetermined number of times (including once)
learning history determining means for determining whether or not the learning history has been updated; and if the learning history has been updated by a predetermined percentage or more, determining whether or not a predetermined percentage or more of these learning correction coefficients deviate from the initial value in the same direction. and a constant correction means that corrects the constant according to the amount of deviation when the predetermined percentage or more deviates in the same direction.

<Example> Examples will be described below.

Figure 2 shows the hardware configuration.

1 is CPU, 2 is P-ROM, 3 is for learning control
CMOS-RAM, 4 is an address decoder.
Note that a backup power supply circuit is used for the RAM 3 in order to retain the memory contents even after the key switch is turned off.

The hot wire air flow meter 5 is used as an analog input signal to the CPU 1 for controlling the fuel injection amount.
intake air flow rate signal from the throttle sensor 6, throttle opening signal from the throttle sensor 6, water temperature signal from the water temperature sensor 7, exhaust oxygen concentration signal from the _O2 sensor 8,
There is a battery voltage from the battery 9, which is adapted to be input via an analog input interface 10 and an A/D converter 11. 1
2 is an A/D conversion timing controller.

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, for example, from the crank angle sensor 17
A reference signal every 180 degrees and a position signal every 1 degree are inputted via a one-shot multi-circuit 18. In addition, the vehicle speed sensor 19
The vehicle speed signal is inputted via the 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 waveform control circuit 21.

Here, the CPU 1 performs input/output operations, arithmetic processing, etc. according to a program (stored in the ROM 2) based on the flowchart (fuel injection amount control routine) shown in FIG. 3, and controls the fuel injection amount.

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

The intake air flow rate Q obtained from the signal from the air flow meter 5 at S1 and the crank angle sensor 17
The basic injection amount T _P (=K×Q/N) is calculated from the engine rotation speed N obtained from the signal from the engine.

Set various correction coefficients COEF in S2.

In S3, the output voltage of the O ₂ sensor 8 and the slice level voltage are compared and the air-fuel ratio feedback correction coefficient α is set by proportional-integral control. However, in a region where λ control is not performed, α is clamped to 1.

In S4, a voltage correction amount T _S is set based on the battery voltage from the battery 9.

In S5, the operating region is divided into multiple areas using, for example, engine speed N and basic injection amount (load) T _P as parameters indicating the engine operating state, and a learning correction coefficient α _L , which will be described later, is stored for each area. The area where the current (N, T _P ) exists is searched from the map (stored in the RAM 3), and the data indicating the area is transferred to the specified location A of the address decoder 4.
Set to .

In S6, the current (N,
The data in the area where T _P ) exists is compared with the data in the area where (N, T _P ), which was previously searched and was also set at address LA of the address decoder 4, exists, and it is determined whether they are the same. . and,
If YES, that is, if it is determined that the operating states are substantially the same, the process advances to S7.

In S7, the output voltage of O ₂ sensor 8 (see Figure 4)
It is determined whether or not it has been reversed n times after the determination in S6 becomes YES, and if YES, the process advances to S8.

That is, S6 and S7 are provided to determine whether the operating state is in a steady state, and if the determinations in S6 and S7 are both YES, it is determined that the operating state is in a steady state. Such a steady state determination method is simple and can be performed with high accuracy, but other methods include, for example, a method of determining whether a predetermined time has elapsed with the vehicle speed constant, the gear position non-neutral, and the throttle opening constant. may be adopted. And S6 or
If any of the determinations in S7 is NO, it is determined that the state is unsteady, and in this case, the process proceeds to S11 without performing the learning in S8 to S10, which will be described later.

In S8, the average value of the current and past values of the air-fuel ratio feedback correction coefficient α during steady operation is calculated. The average value may be calculated each time the flow is performed, but for example, the average value from the time when the increase/decrease in the value of the air-fuel ratio feedback coefficient α is reversed until it is reversed, or the air-fuel ratio feedback coefficient at the time of reversal The average value of only the correction coefficient α may be determined, and in this way, the control center of α in a steady state can be determined more accurately.

In S9, engine speed N and basic injection amount T _P
From there, the learning correction coefficient α _L corresponding to (N, T _P ) stored in the area of the RAM 3 where (N, T _P ) exists is searched. Note that all values of α _L stored in the map are α _L =1 at the time when learning has not started.

In S10, the learning correction coefficient α _L found in S9
Calculation is performed according _{to the} following formula from Update.

α _L ← α _L + △α/M In addition, △α indicates the amount of deviation from the reference value, and △α
=-αλ=1, and the reference value αλ=1 is generally
It becomes 1.0. Further, M is a constant.

The value of M, which determines the rate at which the learning correction coefficient _αL is added to the deviation amount △α, may be constant, but if it is set to a value proportional to the engine speed, the PI control coefficient of α can be adjusted as the injection cycle increases. Since the fuel injection amount can be reduced by using the fuel injection amount, more accurate injection amount control can be performed.

Alternatively, the learning correction coefficient may be updated by directly determining the deviation amount between α and the reference value without averaging the air-fuel ratio feedback coefficient α, and adding the deviation amount by a predetermined percentage. .

In S11, the address LA indicated by the address decoder 4 is
The data of the previous area (N, T _P ) set at address A is updated by transferring the data of the current area (N, T _P ) set at address A.

S12 searches for the α _L map from RAM3, and S13 searches for the α _{L map} .
It is determined whether or not a predetermined percentage or more of all the learning correction coefficients α _L stored in the map have a history of being updated by learning. S13 judgment is YES
In this case, proceed to S14, and if the judgment in S13 is NO, proceed to S14.
Proceed to S20.

In S14, it is determined whether or not a predetermined percentage or more of the learning correction coefficients α _L of the learning correction coefficients α _L that have been updated by learning are shifted from the initial value to the + (increase) side. If the determination in S14 is YES, the process proceeds to S16, where the K constant is corrected to increase by a predetermined percentage, and then the K
All the learning correction coefficients α _L are reversely corrected to the decreasing side by the proportion that the fixed number of sheets has been increased. That is, the correction is made so that K×α _L =constant.

On the other hand, if the determination in S14 is NO, the process advances to S17, and among the learning correction coefficients α _L updated by learning,
The learning correction coefficient α _L of a predetermined percentage or more is −
It is determined whether it has shifted to the (decreasing) side. S17
If the determination is YES, the process proceeds to S18, where the K constant is corrected to decrease by a predetermined percentage, and then all learning correction coefficients α _L are reversely corrected to increase by the percentage by which the K constant is decreased (K× α _L = constant).

Further, if the determination in S13 or S17 is NO, that is, if the proportion of the updated learning correction coefficient α _L that deviates in either the + or − direction is less than a predetermined proportion, the process proceeds to S20.

In S20, the injection amount Ti is calculated according to the following formula.

Ti=T _P × COEF × α × α _L + T _S Here, in the case of a steady state, the learning correction coefficient α _L updated in S10 is used, and in the case of a transient state, the one updated in S10 is used. things are used.

The injection amount Ti is calculated in the above manner, and the drive pulse signal corresponding to this injection amount Ti is sent to the current waveform control circuit 21.
is applied to the fuel injection valve 22 at a predetermined timing.

On the other hand, in the region where λ control is not performed, the air-fuel ratio feedback correction coefficient α is 1.
At the same time, steps S5 to S19 are omitted, and α _L =1 in effect.

Therefore, the injection amount is given by the following equation.

Ti = T _P × COEF + T _S However, T _P = K × Q / N And, the K constant for basic injection amount T _P calculation is: When the learning correction coefficient α _L of a predetermined ratio or more has a history of updating due to learning, That is, when the value of the learning correction coefficient α _L is highly reliable due to learning, and the learning updated α _L
If a predetermined percentage or more of the deviation is in either + or - direction, it will be corrected, so the corrected K constant will be used from the next routine after the correction, and the flow rate change of the fuel injector 22 will be corrected. It is possible to effectively correct deviations in the base air-fuel ratio due to changes in ambient temperature, atmospheric pressure, etc. even in areas where λ control is not performed. Especially in the case of the single point injection (SPI) method, the fuel injection valve 22 is
Since it has a large influence on things like blockages, it can also be expected to have a fuil-safe effect.

Here, in the case of the present invention, the correction is performed when it is determined that the K constant should be substantially sufficiently corrected by determining the update history and learning tendency due to learning as described above. Therefore, compared to the case where the K constant is corrected only when all the learning correction coefficients α _L are shifted in the same direction, as shown in the above-mentioned Japanese Patent Application No. 132894/1982, there is an opportunity to perform correction effectively. increases and is highly practical.

In this embodiment, the learning history is determined by determining whether the learning correction coefficient α _L that has been updated by learning at least once is equal to or higher than a predetermined ratio. It may be determined whether the learned correction coefficient α _L is equal to or greater than a predetermined ratio, and the K constant is corrected under conditions where the learning correction coefficient α _L is more reliable.

Furthermore, in this embodiment, since the data of the learning correction coefficient α _L is increased or decreased at the stage of correcting the K constant, there is no need to affect the λ control at _all . Even when forced correction is not performed, the value of the learning correction coefficient α _L is automatically corrected through learning.

<Effects of the Invention> As explained above, according to the present invention, the learning correction coefficient α _L is used in the λ control to control the base air-fuel ratio so that it approaches λ=1 through learning, thereby temporarily reducing the base air-fuel ratio. λ caused by the difference in fuel ratio
Since the deviation from = 1 can be eliminated and the PI constant can be made small, controllability can be greatly improved, and the catalyst can be used in a place with high conversion efficiency, which reduces the cost of the catalyst by reducing the amount of precious metals. This eliminates the need for conversion.

In addition, since the K constant of the basic injection amount is corrected by determining the learning history and learning tendency of the learning correction coefficient α _L , the K constant can be corrected with sufficient reliability and extremely effectively. The base air-fuel ratio in the region where λ control is not performed is also λ
= 1, and it is possible to effectively deal with wear and clogging of the fuel injector, as well as changes in air density, etc. Specifically, this eliminates the need for an altitude sensor, etc., and provides excellent effects such as making it possible to reduce the cost of the control system.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of the present invention, Figure 2 is a block diagram showing the configuration of the present invention.
The figure is a hardware configuration diagram showing one embodiment of the present invention, FIG. 3 is a flowchart of the same embodiment, and FIG.
The figure is a diagram showing the output characteristics of the O ₂ sensor used in the above embodiment. 1...CPU, 3...CMOS for learning control
RAM, 5...Air flow meter, 8... _O2 sensor, 17...Crank angle sensor, 22...Fuel injection valve.

Claims (1)

[Claims] 1 Basic injection amount calculation means that calculates the basic injection amount from a constant, intake air flow rate, and engine speed, and the actual air-fuel ratio and stoichiometric air-fuel ratio detected based on the signal from the O ₂ sensor installed in the exhaust system. An air-fuel ratio feedback correction coefficient setting means for setting an air-fuel ratio feedback correction coefficient by integral control by comparing the values with A learning correction coefficient search means for searching for a correction coefficient, and learning for setting a new learning correction coefficient from the air-fuel ratio feedback correction coefficient and the learning correction coefficient, and updating data for the same engine operating condition in the RAM with the learning correction coefficient. correction coefficient updating means;
An injection amount calculation means that calculates the injection amount by multiplying the basic injection amount by an air-fuel ratio feedback correction coefficient and a learning correction coefficient, and a drive pulse that outputs a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve. a signal output means; a learning history determination means for determining whether or not a predetermined percentage or more of all the learning correction coefficients in the map on the RAM have been updated a predetermined number of times or more through learning; learning tendency determining means for determining whether or not a predetermined percentage or more of the learning correction coefficients deviate in the same direction with respect to the initial value; A learning control device for an air-fuel ratio in an electronically controlled fuel injection type internal combustion engine, comprising constant correction means for correcting the constant.