JPH0226052B2 - - 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 increase correction coefficient, COEF=1+Ktw+Kas+Kai+Kmr.
Ktw is the water temperature increase correction coefficient, Kas is the start and post-start increase correction coefficient, Kai is the after-idle increase correction coefficient,
Kmr is the mixture correction coefficient. 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.

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 to maintain the stoichiometric air-fuel ratio. 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) at a rate of 1 minute to make the air-fuel ratio leaner (richer).

However, in the region where λ control is not performed, α
=1.

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 base air-fuel ratio λ may vary due to factors such as variations in the valves, pressure regulators, control units), changes over time, non-linearity of the pulse width-flow rate characteristics of the fuel injector, and changes in operating conditions and environment.
Since a deviation from =1 occurs, feedback control is performed.

However, if the base air-fuel ratio deviates from λ = 1, when the operating range changes significantly, the step in the base air-fuel ratio can be adjusted to λ = 1 using feedback control.
It takes time to control PI. 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.

<Object of the invention> In view of the above-mentioned actual situation, the present invention sets the base air-fuel ratio to λ = 1 by learning, thereby eliminating the deviation from λ = 1 caused by the step in the base air-fuel ratio during transient times, and The purpose is to improve controllability by making it possible to reduce the PI constant, and thereby reduce the cost of the catalyst.

<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 detects a steady state when the change in opening is less than a predetermined value, and when the steady state is detected, the weighted average of the air-fuel ratio feedback correction coefficient and the learning correction coefficient is calculated and the value is used for new learning correction. coefficient and its learning correction coefficient.
learning correction coefficient correction means for updating data for the same engine operating condition in RAM; 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; The fuel injection valve is configured to include a drive pulse signal output means for outputting a drive pulse signal corresponding to the injection amount to the fuel injection valve.

<Example> Examples will be described below.

FIG. 2 shows the hardware configuration.

1 is CPU, 2 is P-ROM, 3 is for learning control
CMOS-RAM, 4 is an address decoder.

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 at S1 and the crank angle sensor 17
The basic injection amount Tp (=K×Q/N) is calculated from the engine speed N obtained from the signal from the engine.

Set various increase correction coefficients COEF in S2.

In S3, 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.

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

Engine speed N and basic injection amount (load) at S5
Search for learning correction coefficient α ₀ from Tp. The map of the learning correction coefficient α ₀ with respect to the rotational speed N and the load Tp is stored in the rewritable RAM 3, and all α ₀ =1 at the time when learning has not started.

S6 to S9 are provided to detect a steady state, and S6 determines a change in vehicle speed based on the signal from the vehicle speed sensor 19, and S7 determines the gear position based on the signal from the neutral switch 15. Then, in S8, a change in the throttle opening degree is determined based on the signal from the throttle sensor 6, and in S9, it is determined whether a predetermined time has elapsed, and if it is within the predetermined time, the process returns to S6. In this way, the change in vehicle speed is less than a predetermined value within a predetermined time, and the gear is engaged.
Further, if the change in the throttle opening is less than or equal to a predetermined value, it is determined that the state is steady, and the learning correction coefficient α ₀ is corrected in S10 and S11. 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, The learning correction coefficient α ₀ is not corrected in S10 and S11.

In addition, methods such as rich/lean reversal of the O ₂ sensor output, α status, and combination of operating parameters can be considered to detect the steady state, but when considering response and matching, it is possible to (Other than neutral), it is easy to judge on the condition that a predetermined period of time elapses after the combination of throttle opening changes reaches a predetermined state.

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

Current air-fuel ratio feedback correction coefficient α in S10
and the learning correction coefficient α ₀ retrieved from the engine speed N and the load Tp (see next page), and the weighted average value is set as the new learning correction coefficient α ₀ .

α ₀ ← (α+(M−1)×α ₀ )/M M is a constant At S11, a new learning correction coefficient α ₀ is written to the corresponding engine speed N and load Tp in the RAM 3. That is, the data in RAM3 is updated.

After it is determined to be a steady state and the learning correction coefficient α ₀ is corrected, or after it is determined to be a transient state, S12
The injection amount Ti is calculated according to the following formula.

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.

In addition, considering matching, the map for the learning correction coefficient α ₀ may be approximately N = 8 grids, Tp = 4 grids,
It seems better to update α ₀ without interpolation, and to calculate Ti with interpolation.

Note that the parameters to be corrected by learning control may not be set separately, and for example, the K constant, Q-Us (air flow meter output) map, Kmr map, etc. may be corrected. However, if a bypass type hot wire air flow meter is used to measure the intake air amount using the single point injection (SRI) method, the influence of measurement errors may change depending on the rotation and boost, so correction using the Kmr map is necessary. It is considered a good idea to do so. In this case, the method determined by modifying the Kmr map itself and the method determined by matching
One possible method is to fix the Kmr map in the ROM and have a separate calibration Kmr map, but the latter is considered more advantageous when considering matching problems such as setting the λ control area. Therefore, calibration for learning control
It seems desirable to have the Kmr map on CMOS-RAM.

In addition, when performing such learning control, the key switch must be turned off in order to memorize and retain the learned and controlled contents.
Of course, RAM 3 can be backed up even after it is turned off, and a backup power supply circuit is used.
CMOS-RAM3 was used because it requires less holding current.

Furthermore, learning control is a method that modifies the control parameters by itself, so unless you constantly monitor whether the system is in a state where it can learn, learning will progress in a direction different from the original purpose. there is a possibility.

Therefore, in order to learn the air-fuel ratio, it is necessary that the output of the O ₂ sensor is normal.
It is always necessary to check whether the O ₂ sensor is in a state where it can learn.

For this purpose, for example, a monitor that determines whether the electromotive force of the O ₂ sensor is within the normal range, or a monitor that determines whether the rich/lean reversal period in the closed state is within the normal range. A monitor or the like may be used.

<Effects of the Invention> As explained above, according to the present invention, the air-fuel ratio feedback correction coefficient during air-fuel ratio feedback control is learned and the learning correction coefficient is set, and this is used to set the base air-fuel ratio of the λ control zone. By learning to set λ = 1, it is possible to eliminate deviations from λ = 1 caused by differences in the base air-fuel ratio during transients, and to reduce the PI constant during λ control, greatly improving controllability. improve. Therefore, the catalyst can be used at a location with high conversion efficiency, and in addition to cost reduction due to the reduction in the amount of precious metals, there is no need to replace the catalyst. In addition, if the change in vehicle speed is less than a predetermined value within a predetermined time, the gear is engaged, and the change in throttle opening is less than a predetermined value, a steady state is detected and learning is performed in the steady state. The reliability is improved, and since the steady state is detected using the above combination, the steady state can be detected with good matching with the response, and the reliability of learning is extremely high.

[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. 1...CPU, 3...CMOS for learning control
RAM, 5... Air flow meter, 6... Throttle sensor, 8... O ₂ sensor, 15... Neutral switch, 17... Crank angle sensor, 1
9...Vehicle speed 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. steady state detection means that detects a steady state when a change in vehicle speed is less than a predetermined value within a predetermined time, a gear is engaged, and a change in throttle opening is less than a predetermined value; Learning correction that takes a weighted average of the air-fuel ratio feedback correction coefficient and learning correction coefficient when a steady state is detected, uses that value as a new learning correction coefficient, and updates data for the same engine operating condition in RAM with the learning correction coefficient. coefficient correction means; injection amount calculation means for calculating 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 signal corresponding to the calculated injection amount for controlling the fuel injection valve. 1. A learning control device for an air-fuel ratio in an electronically controlled fuel injection type internal combustion engine, characterized in that it is provided with a drive pulse signal output means for outputting a drive pulse signal.