JPS6356414B2 - - 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=Tp×COEF×α+Ts Here, Tp is the basic injection amount, Tp=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. Ts is a voltage correction amount, which is used to correct fluctuations in battery voltage.

Regarding λ control, an O ₂ 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 richer or leaner than the stoichiometric air-fuel ratio, and fuel is injected to achieve the stoichiometric air-fuel ratio. For this purpose, the above-mentioned air-fuel ratio feedback correction coefficient α is determined, and by varying this α, the stoichiometric air-fuel ratio is maintained.

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 set various correction coefficients COEF to obtain the desired air-fuel ratio.

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. valves, pressure regulators,
control unit) variations and changes over time,
Feedback control is performed because the base air-fuel ratio deviates from λ=1 due to factors such as non-linearity of the pulse width-flow rate characteristic of the fuel injection valve and changes in operating conditions and environment.

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 purpose, the proportionality and integral constants (P/I) are 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 the 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, the deviation from λ = 1 caused by the step in the base air-fuel ratio during transient times can be eliminated, and the P/I
A learning control device for the base air-fuel ratio has been devised, which aims to improve controllability by making it possible to reduce the amount of air-fuel ratio, thereby reducing the cost of the catalyst.

That is, a map of learning correction coefficients αo 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 Tp is corrected by αo as shown in the following equation.

Ti=Tp×COEF×α×αo+Ts Then, the learning of αo proceeds in the following steps.

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

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

(iii) αo is newly set by weighted average from α and αo and stored.

By the way, when adopting such a learning control device, if the P/I component is made small from the beginning, the transient response will be This will lead to deterioration. Conversely, when learning progresses and the base air-fuel ratio reaches λ = 1, a large P/I
If λ control is performed in minutes, the air-fuel ratio will fluctuate around λ=1, causing fluctuations in the rotational speed, etc.

<Object of the Invention> In view of the above-mentioned circumstances, the present invention monitors the progress of learning in the learning control device described above, and corrects the P/I portion of the λ control accordingly. The purpose is to further demonstrate the effectiveness of learning control.

<Structure of the Invention> For this reason, the present invention, as shown in FIG.
an air-fuel ratio feedback correction coefficient setting means that compares the actual air-fuel ratio detected based on the signal from the _O2 sensor with the stoichiometric air-fuel ratio and sets an air-fuel ratio feedback correction coefficient by proportional-integral control; A learning correction coefficient search means for searching a learning correction coefficient stored in RAM corresponding to engine operating conditions such as load, steady state detection means for detecting a steady state, and air-fuel ratio feedback correction when a steady state is detected. A learning correction coefficient correction means takes a weighted average of the coefficient and the learning correction coefficient, sets the value as a new learning correction coefficient, and updates data for the same engine operating condition in the RAM with the learning correction coefficient; an injection amount calculation means for calculating an injection amount by multiplying a fuel ratio feedback correction coefficient and a learning correction coefficient; a drive pulse signal output means for outputting a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve; Update count means for counting the number of updates of the learning correction coefficient, and proportionality for changing the proportional and integral constant (P/I minute) in the proportional-integral control of the air-fuel ratio feedback correction coefficient setting means as the count value increases. and integral constant correction means.

<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.

As digital input signals, there are ON/OFF signals from an alarm 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 calculation 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 and the crank angle sensor 17 at S1
The basic injection amount Tp (K=K×Q/N) is calculated from the engine rotational speed N obtained from the signal from the engine.

In S2, various correction coefficients COEF are set.

In S3, the count value C of an update counter (counted up in S15 and cleared in S4, which will be described later) that counts the number of updates of the learning correction coefficient αo is compared with a predetermined value, and if it is greater than the predetermined value, S
After clearing the count value C in step 4 and decreasing the P/I portion of the λ control by a predetermined amount in step S5, the process proceeds to step S6. If it is less than the predetermined value, the process directly proceeds to S6 without changing the P/I portion.

In S6, the output from the O ₂ sensor 8 is compared with the slice level, and an air-fuel ratio feedback correction coefficient α is set by proportional-integral control based on the P/I component.

In S7, a voltage correction amount Ts is set based on the battery voltage from the battery 9.

In S8, a corresponding learning correction coefficient α ₀ is searched from the engine speed N and the basic injection amount (load) Tp.
Note that the map of the learning correction coefficient αo for the rotational speed N and the basic injection amount Tp is stored in the rewritable RAM 3, and all αo=1 at the time when learning has not started. Furthermore, this map has approximately N=8 grids and Tp=4 grids.

S9 to S12 are provided to detect a steady state, and in S9, a change in vehicle speed is determined based on the signal from the vehicle speed sensor 19, and in S10, the gear position is determined based on the signal from the neutral switch 15. Then, in S11, a change in the throttle opening is determined based on the signal from the throttle sensor 6, and S1
In step 2, it is determined whether the predetermined time has elapsed or not, and if it is within the predetermined time, the process returns to S9. In this way, if the change in vehicle speed is less than or equal to a predetermined value within a predetermined time, the gear is engaged, and the change in throttle opening is less than or equal to a predetermined value, it is determined that the vehicle is in a steady state.
The learning correction coefficient α ₀ is corrected in S15. In addition, if the change in vehicle speed exceeds a predetermined value at any point within a predetermined time, if the vehicle speed becomes neutral, or if the change in throttle opening exceeds a predetermined value, it is determined that the state is in a transient state, S13~S1
The learning correction coefficient α ₀ in step 5 is not corrected.

The learning correction coefficient α ₀ is corrected as follows when it is determined that the steady state is present.

In S13, a weighted average (see the following formula) of the current air-fuel ratio feedback correction coefficient α, the learning correction coefficient α ₀ retrieved from the engine speed N and the basic injection amount Tp is taken, and the weighted average value is calculated as a new value. The learning correction coefficient α is set to ₀ .

α ₀ ← (α+(M-1)×α ₀ )/M M is a constant In S14, a new learning correction coefficient α ₀ is written to the corresponding engine speed N and basic injection amount Tp in the RAM 3. That is, the data in RAM3 is updated.

In S15, a count value C of an update number counter that counts the number of updates of the learning correction coefficient αo is incremented.

After determining the steady state and correcting the learning correction coefficient α ₀ , or after determining the transient state, S1
Proceed to step 6.

In S16, the injection amount Ti is calculated according to the following equation.

Ti=Tp×COEF×α×α ₀ +Ts Here, in the case of a steady state, the updated value as α ₀ is used, and in the case of a transient state, the retrieved value is used as is.

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.

Note that instead of counting the total number of updates of the learning correction coefficient αo, the number of updates for each grid point of the map is counted, and when all of the count values are equal to or greater than a predetermined value, the P/I is decreased. This is preferable because the progress of learning can be monitored more accurately.

In addition, if the P/I component is made excessively small, controllability deteriorates, so if necessary, the maximum value of the deviation of the air-fuel ratio feedback correction coefficient α is detected, and if a deviation occurs, the P/I portion is increased. You may also do so. Alternatively, a minimum value for P/I may be set in advance to prevent the amount from decreasing below that value.

<Effects of the Invention> As explained above, according to the present invention, the air-fuel ratio feedback correction coefficient during λ control is learned, the learning correction coefficient is set, and the base air-fuel ratio in the λ control region is learned using this learning correction coefficient. Therefore, λ=
1, it is possible to eliminate the deviation from λ=1 caused by a step in the base air-fuel ratio during a transient period, and to reduce the P/I component during λ control, thereby improving controllability. In particular, by counting the number of updates to the learning correction coefficient, the progress of learning is monitored, and as the learning progresses, the P/I component is reduced, resulting in extremely improved controllability and the state of the mixture ratio. Stabilize.

[Brief explanation of drawings]

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, and FIG. 3 is a flowchart of the same. 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 the 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 that compares and sets an air-fuel ratio feedback correction coefficient by proportional-integral control, and searches for a learning correction coefficient stored in RAM corresponding to engine operating conditions such as engine speed and load. a learning correction coefficient search means for detecting a steady state; a steady state detecting means for detecting a steady state; learning correction coefficient correction means for updating data for the same engine operating condition in RAM with the learning correction coefficient; and 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. a drive pulse signal output means for outputting a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve; an update count means for counting the number of updates of the learning correction coefficient; An air-fuel ratio learning control device for an electronically controlled fuel injection internal combustion engine, characterized in that the air-fuel ratio feedback correction coefficient setting means includes proportional and integral constant correction means for changing proportional and integral constants in the proportional-integral control of the air-fuel ratio feedback correction coefficient setting means.