JPS63205443A - Air-fuel ratio controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress variation of air-fuel ratio effectively by setting correction factors being required when basic fuel supply quantity is feedback corrected corresponding to a relation between a detected value and a target value of air-fuel ratio, in due consideration of variation rate of air-fuel ratio. CONSTITUTION:Means B sets a basic fuel supply quantity for a target air-fuel ratio based on an operating condition of engine detected through means A. Air-fuel ratio detected through means C is compared with a target air-fuel ratio through means D, so as to set factors necessary for feedback correction of the basic fuel supply quantity. Furthermore, means F sets modified value of the correction factors based on a variation rate of air-fuel ratio detected through means E. Furthermore, means G sets a fuel supply quantity based on the basic fuel injection, correction factors and modification values being set respectively through means B, D, F. Then, means H supplies such quantity of fuel as set by means G to the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an air-fuel ratio control device in an internal combustion engine.

<Prior Art> In an internal combustion engine equipped with an electronically controlled fuel injection device, a fuel injection valve is opened by a drive pulse signal given in synchronization with the rotation of the engine, and during the valve opening period, fuel is injected at a predetermined pressure. is to be injected. Therefore, the fuel injection amount is controlled by the pulse width of the drive pulse signal, and if this pulse width is set as Ti and the control signal corresponds to the fuel injection amount, then in order to obtain the stoichiometric air-fuel ratio, which is the target air-fuel ratio, Ti is determined by the following formula. determined by.

Ti-Tp・C0EF・α+Ts However, Tp is a basic pulse width corresponding to the basic injection amount and is called the basic injection amount for convenience. Tp=to-Q/N, K is a constant, Q
is the engine intake air flow rate, and N is the engine speed. C0EF
are various correction coefficients such as water temperature correction. α is a feedback correction coefficient for air-fuel ratio feedback control (λ control) to be described later. Ts is a voltage correction element, which is used to correct changes in the injection flow rate of the fuel injector due to fluctuations in battery voltage.

Regarding λ control, an O2 sensor is installed in the exhaust system to detect the actual air-fuel ratio, and the IJ?
Therefore, the feedback correction coefficient α mentioned above is determined, and by changing this α, the stoichiometric air-fuel ratio is maintained.

Here, the value of the feedback correction coefficient α is the proportional integral (P
I) It is changed by control and stable control is achieved.

In other words, by comparing the output voltage of the 0□ sensor, if the air-fuel ratio is higher or lower than the slice level, the air-fuel ratio is not suddenly enriched or lean, and if the air-fuel ratio is rich (lean). At first, it is lowered (raised) by P, and then it is gradually lowered (raised) one minute at a time to control the air-fuel ratio so that it becomes lean < (rich) (see Fig. 7).

However, under conditions where λ control is not performed, α is clamped and a desired air-fuel ratio is obtained by setting various correction coefficients COFF.

<Problems to be Solved by the Invention> However, in the method described above in which the feedback correction coefficient is determined by so-called PI control during air-fuel ratio feedback control, the control only takes into account the magnitude relationship between the air-fuel ratio and the stoichiometric air-fuel ratio. As a result, the amount of overshoot and undershoot becomes large, and as a result, the fluctuations in the air-fuel ratio are too large, generating a large surge torque that worsens the ride comfort and the purification efficiency of the exhaust purification catalyst is poor <Co, HC.

There were problems such as the inability to sufficiently suppress emissions of NOx and the like.

The present invention has been made by focusing on such conventional problems, and by setting the feedback correction coefficient in consideration of the speed of change in the air-fuel ratio, it is possible to more effectively control fluctuations in the air-fuel ratio. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can stabilize engine rotation by reducing surge torque and improve exhaust purification performance.

<Means for Solving the Problems> For this reason, the present invention, as shown in FIG. The basic fuel supply amount setting means to be set, the air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture taken into the engine, and the detected air-fuel ratio and the target air-fuel ratio are compared, and depending on the magnitude relationship between the two, feedback correction coefficient setting means for setting a feedback correction coefficient for feedback correction of the basic fuel supply amount; air-fuel ratio detected value change rate calculation means for calculating the change rate of the detected value by the air-fuel ratio detection means; and air-fuel ratio detection means. Feedback correction coefficient correction value setting means for setting a correction value of the feedback correction coefficient for correcting the feedback coefficient set by the feedback correction coefficient setting means based on the rate of change of the value; and the basic fuel supply amount setting means. Fuel supply amount setting means for setting the fuel supply amount based on the set basic fuel supply amount, the feedback correction coefficient set by the feedback correction coefficient setting means, and the correction value set by the feedback correction coefficient correction value setting means; ,.

and fuel supply means for supplying fuel to the engine in response to a fuel supply signal corresponding to the fuel supply amount set by the fuel supply amount setting means.

<Operation> Based on the engine operating state detected by the engine operating state detecting means, the basic fuel supply amount setting means sets the basic fuel supply amount corresponding to the target air-fuel ratio.

On the other hand, the air-fuel ratio detected by the air-fuel ratio detection means is compared with the target air-fuel ratio by the feedback correction coefficient setting means, and a feedback correction coefficient for feedback-correcting the basic fuel supply amount is set according to the magnitude relationship between the two. .

The feedback correction coefficient correction value setting means sets a correction value of the feedback correction coefficient based on the rate of change of the air-fuel ratio detection value detected by the air-fuel ratio change rate detection means.

The fuel supply amount setting means sets the fuel supply amount based on the basic fuel supply amount, feedback correction coefficient, and feedback correction coefficient correction value set by each of the setting means.

The fuel supply means supplies fuel to the engine in response to a fuel supply signal corresponding to the fuel supply amount set in this way.

<Example> Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows the configuration of an air-fuel ratio control device (electronically controlled fuel injection device) for an internal combustion engine according to the present invention.

In the figure, an internal combustion engine 1 includes an air cleaner 2°, an intake duct 3. Throttle chamber 4 and intake manifold 5
Air is inhaled through.

The intake duct 3 is provided with a hot wire flow meter 6 that detects the intake air flow rate Q, and outputs a voltage signal Us corresponding to the intake air flow rate Q. The throttle chamber 4 is provided with a throttle valve 7 that operates in conjunction with an accelerator pedal (not shown) to control the intake air flow rate Q. Intake manifold 5
An electromagnetic fuel injection valve 8 as a fuel supply means is provided for each cylinder, and a control unit 10 (D injection M
The valve is driven to open by the t pulse signal, and fuel is injected and supplied into the intake manifold 5 by being pressure-fed from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator. Further, a water temperature sensor 1 is provided to detect the cooling water temperature Tw in the cooling jacket 14 of the engine, and an air-fuel ratio sensor 1 is provided to detect the air-fuel ratio in the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas in the exhaust passage 12. An oxygen sensor 13 is provided as a detection means.

The control unit 10 detects the engine rotation speed N by counting the crank unit angle signal output from the crank angle sensor 9 in synchronization with the engine rotation for a certain period of time or by measuring the cycle of the crank reference angle signal.

Hot wire flow meter6. Crank angle sensor 9 and water l sensor 11
constitutes an engine operating state detection means.

The control unit 10 calculates the fuel injection amount Ti based on the various detection signals detected as described above, and drives and controls the fuel injection valve 8 based on the set fuel injection amount Ti.

The air-fuel ratio control by the control unit 10 is performed in a third manner.
This will be explained according to the flowchart shown in the figure and FIG.

FIG. 3 shows a routine for setting a feedback correction coefficient LAMBDA and a correction value for LAMBDΔ used in calculating the fuel injection amount, and this routine is executed every revolution of the engine.

In step (denoted as S in the figure; the same applies hereinafter) 1, the output voltage S from the oxygen sensor 14 is read.

In step 2, the output voltage S is compared with a reference voltage corresponding to the stoichiometric air-fuel ratio, and a deviation voltage Δ is obtained by subtracting the latter from the former.
An integral error E is set according to S.

Specifically, as shown in FIG. 5, where the deviation voltage ΔS1 reaches its maximum positive value, E becomes the maximum positive value PB (for example, 1), ΔS
, corresponds to a positive median value, E is a positive median value PM,
Where ΔS corresponds to a small positive value, E is the minimum positive value P
Where S, ΔS1 corresponds to a value near 0, E is O2ΔS,
where E corresponds to a small negative value, E is the minimum negative value NS,
Where ΔS corresponds to a negative medium value, E is a negative medium value NM.

When ΔS1 reaches its maximum negative value, it is set to the maximum negative value NB (for example, −1).

In step 3, the integral error E is compared with 0, and when E>0, that is, the air-fuel ratio is rich, step 4
, and determines whether this is the first time the lean to rich state has been reversed.

When it is determined that it is the first time, the process proceeds to step 5, where the feed puncture correction coefficient LAMBDA is subtracted by a predetermined proportional bone Pt from the previous value, and from the second time onward, the process proceeds to step 6, where a predetermined integral IL (PI, >>It).

In addition, when it is determined in step 3 that E<O, that is, when the air-fuel ratio is lean, the process proceeds to step 7, where it is determined whether or not this is the first time that the change from rich to lean has occurred. Proceed to step 8 and add the predetermined proportional bone P and l to the previous value of LAMBDA, and from the second time onward, proceed to step 9.
Then, a predetermined integral IR (PR>>IR) is added.

When it is determined that E=O in step 3, LAMBDA
is not increased or decreased and is held at the previous value.

The above feedback correction coefficient L A M B D A
The functions of steps 1 to 9 for setting 1 constitute a feedback correction coefficient setting means.

Next, in steps 10 to 12, a correction value PID for correcting the feedback correction coefficient LAMBDA is set.

First, in step 10, a proportional error E is set in accordance with the deviation voltage ΔS2 obtained by subtracting the previous output voltage from the current output voltage of the oxygen sensor 14.

In this case as well, the sixth
As shown in the figure, in the range of the positive maximum value to the negative maximum value of the deviation voltage ΔS2, the proportional error E is set to the positive maximum value PB, the positive intermediate value P
M, minimum positive value ps, o.

7 of negative minimum value NS, negative intermediate value NM, and negative maximum value NB
Set in stages.

The proportional error ΔE in this case is set as a value corresponding to the rate of change of the output voltage (air-fuel ratio detection value) of the oxygen sensor 14.

Therefore, the function of step 10 constitutes air-fuel ratio detection value change rate detection means.

Next, in step 11, the feedback correction coefficient LAMBDΔ
When setting the corrected value of , so-called fuzzy inference is applied to calculate the fuzzy quantity U in that case.

To put it simply, fuzzy inference (control '4B) considers certain fuzzy quantities, such as the proposition that the manipulated variable (controlled variable) should be made positive or negative relative to the input quantity (detected value), This fuzzy amount is weighted to set the manipulated variable.

There are some complicated methods for setting fuzzy quantities, such as setting fuzzy quantities for each first-order difference and second-order difference of the control deviation, and calculating them collectively from each fuzzy quantity. As a relatively simple method, the proportional error Δ
By weighting E in consideration of the integral error E, the fuzzy amount U is set as shown in FIG.

That is, when 8E, which corresponds to the rate of change of the air-fuel ratio detection value, is a large positive value, that is, when the air-fuel ratio changes in the rich direction, the air-fuel ratio is suppressed from becoming excessively rich due to overshoot. In order to achieve this, the correction control amount for correcting the air-fuel ratio in the lean direction should be increased. However, similarly ΔE
Even if is a large positive value, if the integral error E corresponding to the detected value of the air-fuel ratio is a large negative value, that is, when the air-fuel ratio is lean, the feedback correction coefficient is set to a large value in the rich direction. Therefore, it is better to increase the correction control amount in the lean direction to quickly control the enrichment due to overshoot, but when E is a large positive value, that is, when the air-fuel ratio is rich. Since the feedback correction coefficient is set to a large value in the lean direction, if the correction control amount in the lean direction based on 8E is made too large, lean will proceed too much due to undershoot, so it should not be made too large. .

Therefore, a positive value of the fuzzy quantity U is controlled to correct the rich direction (increasing the feedback correction coefficient L A M B D A), and a negative value is controlled to the lean direction '4B (L
If AMBDA corresponds to (decrease correction) and the magnitude of the absolute value corresponds to the certainty of performing each correction control, Δ
The larger E is a positive value, and the larger the value of E is a negative value, the larger the fuzzy quantity U is a negative value, and the larger ΔE is a negative value, and the larger the value of E is a positive value. The fuzzy quantity U is increased to a positive value. In addition, in the case of the fuzzy quantity U, the maximum value PB of pressure (for example, 1) to the negative maximum value N is the same as in the case of E and 8E.
Set in 7 steps up to B (eg -1).

In step 12, a correction value PID of the feedback correction coefficient LAMBDA is calculated according to the fuzzy amount U set as described above.

As shown in FIG. 8, this is done by increasing the correction value PID by which LAMBDA is multiplied, so that the larger the positive value of the fuzzy quantity U is, the larger the increase correction amount of LAMBDA is.
For example, the maximum value -1, 05), when U=O, PID is set to 1 so that no correction is performed, and the larger the negative value of the fuzzy amount, the smaller the correction value PID is (for example, the minimum value -0
, 95).

The functions of steps 10 to 12 above constitute a feedback correction coefficient correction value setting means.

Next, the feedback correction coefficient L obtained as above
Fuel injection amount T using AMBDA and its modified value PID
The routine for calculating i will be explained according to the flowchart shown in FIG.

This routine is executed at regular intervals (for example, every 10 m5).

In step 21, the intake air flow rate Q detected by the hot wire flow meter 6 and the engine rotation speed N detected based on the signal from the crank angle sensor 9 are input.

In step 22, based on these intake air flow rate Q and engine rotational speed N, a basic fuel injection amount 'rp proportional to the intake air amount per unit rotation of the engine is calculated using the following equation.

'rp=K-Q/N (K is a constant) The functions of these steps 21 and 22 constitute the basic fuel supply amount setting means.

In step 23, various correction coefficients C0EF are set in accordance with the cooling water temperature Tw detected by the water temperature sensor 1, etc.

! In step 24, the voltage is set based on the battery voltage value.
□Set the pressure correction numerator s.

In step 25, it is determined whether the λ control condition is met.

Here, if the λ control condition is not present, for example, in a high rotation/high load region, the process proceeds to step 26, where the feedback correction coefficient LAMBDA and correction value PID are clamped to the previous value (or reference value), and step 28, which will be described later, is performed.
Proceed to.

In the case of the λ control condition, the process proceeds to step 27, where the feedback correction coefficient LAMBDA and correction value PID set in the routine shown in FIG. 3 are input.

In step 28, the fuel injection amount Ti is calculated according to the following equation.

T i =Tp −C0EF −LAMBDA
-PID+TsThe function of step 28 constitutes the fuel supply amount setting means.

When the fuel injection amount Ti is calculated in this way, that T
A drive pulse signal having a pulse width of i is applied to the fuel injection valve 8 at a predetermined timing in synchronization with engine rotation, and fuel injection is performed.

In the fuel injection control according to the present invention described above, the feedback correction coefficient LAMBDA is corrected by predicting the state of change in the air-fuel ratio using the correction value PID that is set based on the rate of change of the detected air-fuel ratio value. , it is possible to effectively suppress fluctuations in air-fuel ratio due to feedback control. Particularly in the case of this embodiment, as shown in FIG.
Since the ID can be set to a more appropriate value using fuzzy reasoning, the air-fuel ratio can be stabilized as much as possible, reducing surge torque, improving ride comfort, and increasing exhaust purification performance. .

<Effects of the Invention> As explained above, according to the present invention, the feedback control amount is corrected while predicting the change state of the air-fuel ratio based on the rate of change of the detected air-fuel ratio value, so that fluctuations in the air-fuel ratio can be corrected. This can be suppressed as much as possible, thereby promoting improvements in riding comfort and exhaust purification performance by reducing surge torque as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is a block diagram showing the configuration of an embodiment of the invention.
Flowchart showing the AMBDA and PID calculation routine, FIG. 4 is a flowchart showing the fuel injection amount calculation routine of the above embodiment, FIG. 5 is a map for setting the integral error E used in the above embodiment, and FIG. 6 is the same embodiment. Fig. 7 is a map for setting the fuzzy quantity U used in the above embodiment. Fig. 8 is a map for setting the correction value PID used in the above embodiment. Fig. 9 is a map for setting the correction value PID used in the above embodiment. It is a time chart which shows various state quantities at the time of control of an example. ■...Engine 6...Hot wire flow meter 8...Fuel injection valve 9...Crank angle sensor 10...Control unit 11...Water temperature sensor 13
...Oxygen sensor patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima

Claims (1)

[Scope of Claims] Engine operating state detection means for detecting the engine operating state; basic fuel supply amount setting means for setting the basic fuel supply amount based on the detected engine operating state; an air-fuel ratio detection means for detecting an air-fuel ratio of air; and a feedback correction coefficient for comparing the detected air-fuel ratio and a target air-fuel ratio and feedback-correcting the basic fuel supply amount according to the magnitude relationship between the two. feedback correction coefficient setting means for calculating the rate of change of the detected value by the air-fuel ratio detection means; feedback correction coefficient correction value setting means for setting a correction value of the feedback correction coefficient that corrects the feedback correction coefficient; and the basic fuel supply amount set by the basic fuel supply amount setting means, the feedback set by the feedback correction coefficient setting means. a fuel supply amount setting means for setting a fuel supply amount based on a correction coefficient and a correction value set by the feedback correction coefficient correction value setting means; and fuel corresponding to the fuel supply amount set by the fuel supply amount setting means. 1. An air-fuel ratio control device for an internal combustion engine, comprising: fuel supply means for supplying fuel to the engine in accordance with a supply signal.