JPH09310647A - Fuel additive supply device - Google Patents

Abstract

(57) Abstract: A fuel additive supply device capable of adding an optimum amount of a fuel additive to a fuel based on an air-fuel ratio learning coefficient. SOLUTION: An internal combustion engine 10 is supplied with fuel by an amount corresponding to a valve opening time by a fuel injection valve 12, and a residual oxygen concentration in exhaust gas is detected by an oxygen sensor 18. In the control unit 19, not only the air-fuel ratio correction coefficient based on the output of the oxygen sensor, but also the air-fuel ratio learning coefficient for correcting the steady deviation of the air-fuel ratio of the exhaust gas due to the variation of the fuel injection valve or the secular change. Is calculated. Then, the valve opening time of the fuel injection valve is calculated based on the air-fuel ratio correction coefficient and the air-fuel ratio learning coefficient, and it is assumed that the air-fuel ratio learning coefficient indicates the degree of corrosion and wear of the fuel injection valve. The amount of the fuel additive is controlled according to the above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel additive supply device, and more particularly to a fuel additive supply device capable of adding an optimum amount of fuel additive according to the operating condition of an engine.

[0002]

2. Description of the Related Art Recently, it has been attempted to use a high-concentration alcohol-mixed fuel containing alcohol as a main component instead of pure gasoline in a spark engine. However, when a high-concentration alcohol-blended fuel is used, corrosion and wear occur on the metal sliding portion due to the mixed encore.

Particularly in an engine that supplies fuel by means of a fuel injection valve, it is inevitable that exhaust emission or drivability will be deteriorated because the flow characteristics of the fuel injection valve will change due to this corrosion and wear. In order to solve this problem, a fuel additive capable of injecting into the fuel tank an additive for suppressing corrosion / wear of metal sliding parts according to the alcohol concentration of the fuel stored in the fuel tank A supply device has already been proposed (see Japanese Patent Laid-Open No. 7-279780).

[0004]

However, in the fuel additive supply system according to the above-mentioned proposal, the fuel injection valve is injected depending on the alcohol concentration because the flow characteristic of the fuel injection valve varies within a predetermined allowable range. It is not guaranteed that the additive amount is the optimum amount. Furthermore, since the operating condition of the engine after the additive injection is not fed back, the additive concentration cannot be optimally adjusted.

The present invention has been made in view of the above problems, and is intended to eliminate the deviation of the air-fuel ratio due to variations in manufacturing of the fuel control valve or aging in air-fuel ratio feedback control using an air-fuel ratio sensor. It is an object of the present invention to provide a fuel additive supply device capable of adding an optimum amount of additive based on the air-fuel ratio learning coefficient.

[0006]

A fuel additive supply system according to the present invention is a fuel tank for storing a mixed fuel, a fuel supply means for supplying the mixed fuel stored in the fuel tank to an internal combustion engine, and an internal combustion engine. Air-fuel ratio correction coefficient which is installed in the exhaust port to detect the concentration of a specific component in the exhaust gas discharged from the exhaust gas, and the air-fuel ratio correction coefficient which is calculated according to the output of the air-fuel ratio detection means Means, an air-fuel ratio learning coefficient calculation means for calculating an air-fuel ratio learning coefficient according to a deviation of the moving average value of the air-fuel ratio correction coefficient calculated by the air-fuel ratio correction coefficient from the reference value, and an air-fuel ratio correction coefficient calculation A fuel supply time adjusting means for adjusting the fuel supply time of the fuel supplying means according to the air-fuel ratio correction coefficient calculated by the means and the air-fuel ratio learning coefficient calculated by the means, and the air-fuel ratio learning coefficient calculation Comprising a fuel additive injection amount control means for controlling the injection amount of the fuel tank of the fuel additive in accordance with the air-fuel ratio learning coefficient calculated in stages, a.

In this device, the injection amount of the fuel additive into the fuel tank is controlled according to the air-fuel ratio learning coefficient which is a parameter reflecting the corrosion / wear state of the metal sliding portion of the fuel injection valve. .

[0008]

1 is a block diagram of a fuel additive supply system according to the present invention, showing an intake port 1 of an internal combustion engine 10.
The fuel stored in the fuel tank 13 is supplied to the fuel injection valve 12 installed at No. 1, and the fuel is injected from the fuel injection valve 12 into the fuel port 11. The fuel additive stored in the fuel additive tank 14 is injected into the fuel tank 13 via the filling pump 15 and the solenoid valve 16.

An oxygen sensor 18 for detecting the residual oxygen concentration in the exhaust gas is installed in the exhaust port 17 of the internal combustion engine. The fuel additive supply device is controlled by the control unit 19, which is, for example, a microcomputer system, and is centered on the bus 191.
PU 192, memory 193, output interface 19
4 and an input interface 195.

The fuel injection valve 12, the filling pump 15, and the solenoid valve 16 are driven by the operation signal output from the output interface 194, and the detection signal detected by the oxygen sensor 18 is sent to the control unit 19 via the input interface 195. Is read. FIG. 2 is a flowchart of a fuel additive injection routine executed by the control unit 19, which is executed at predetermined time intervals.

In step 20, the integrated value Σ of the valve opening time of the fuel injection valve 12 calculated by the fuel injection routine described later.
It is determined whether τ is greater than or equal to a predetermined value T.
Here, the predetermined value T is a fuel additive injection interval, and is set as, for example, the time required to consume half of the fuel stored in the fuel tank 13. When a negative determination is made in step 20, that is, when the predetermined value T has not elapsed since the previous injection into the fuel additive, this routine is directly ended.

When the affirmative determination is made in step 20, that is, when the predetermined value T has elapsed since the previous injection into the fuel additive, the routine proceeds to step 21, where the air-fuel ratio correction coefficient calculation routine described later is calculated. It is determined whether or not the absolute value of the learning coefficient KG is equal to or larger than a predetermined allowable range (for example, 1 ± 0.02). When a negative determination is made in step 21, that is, when the absolute value of the air-fuel ratio learning coefficient KG is within the allowable range, the fuel injection valve 12 is accurately controlled according to a fuel injection routine described later, and corrosion of the metal sliding portion The wear may be considered less advanced and fuel additive injection is not required and the routine ends directly.

Conversely, when an affirmative decision is made in step 21,
That is, when the absolute value of the air-fuel ratio learning coefficient KG deviates from the permissible value B, the fuel injection valve 12 is not accurately controlled according to the fuel injection routine described later, and corrosion and wear of the metal sliding portion progress. It is determined that the fuel is added and the injection of the fuel additive is necessary, and the process proceeds to step 22. That is, when the air-fuel ratio learning coefficient KG is equal to or larger than the maximum allowable value (for example, 1.02), the actual fuel injection amount is decreased and the air-fuel ratio is largely biased to the lean side. On the other hand, assuming that the valve opening timing is delayed although the valve closing timing is not delayed, the fuel additive is injected to improve the sliding of the metal sliding portion.

On the contrary, when the air-fuel ratio learning coefficient KG is equal to or smaller than the allowable minimum value (for example, 0.98), the actual fuel injection amount increases and the air-fuel ratio largely deviates to the rich side. Assuming that the valve closing timing has been delayed in spite of not delaying the valve opening timing with respect to the command from 19, fuel additive is injected to improve sliding of the metal sliding portion. In step 22, a fuel additive injection time T _i is determined. The injection time T _i of the fuel additive can be set as a function of the fuel level L in the fuel tank 13, for example.

T _i = T _i (L) Next, in step 23, a start command to the filling pump 15 and a valve opening command to the solenoid valve 16 are output, and in step 24 the fuel additive injection time T Wait until _i has passed. When the injection time T _i has elapsed, an affirmative decision is made in step 24, and the operation proceeds to step 25, in which it is assumed that the injection of the predetermined amount of fuel additive has ended, a stop command to the filling pump 15 and a valve close command to the solenoid valve 16. Is output.

Finally, in step 26, the fuel injection valve 1
The integrated value Στ of the valve opening time of 2 is reset to "0" and this routine is finished. FIG. 3 is a flowchart of an air-fuel ratio correction coefficient calculation routine executed by the control unit 19,
It is executed at predetermined time intervals. First, at step 30, it is determined whether the air-fuel ratio feedback control condition is satisfied. Specifically, the air-fuel ratio feedback control by the oxygen sensor 18 is allowed when all of the following conditions are satisfied. (1) The cooling water temperature is equal to or higher than a predetermined temperature. (2) The engine is not starting. (3) The amount of fuel should not be increased by increasing the amount at startup. (4) The output of the oxygen sensor 18 is inverted once or more. (5) The fuel is not being cut.

When all of the above conditions are satisfied and the air-fuel ratio feedback control by the oxygen sensor 18 is allowed, an affirmative decision is made in step 30 and the routine proceeds to step 31, where the output V _S of the oxygen sensor 18 is read. Next, a delay process is executed in step 32, an air-fuel ratio correction coefficient calculation process is executed in step 33, and this routine is ended.

If any of the above conditions (1) to (5) is not satisfied, a negative determination is made in step 30 and the routine proceeds to step 34, where the air-fuel ratio correction coefficient is set to "1.0".
To end this routine. FIG. 4 shows step 3
It is a flowchart of the delay process executed in 2, and is executed in order to stabilize the output when the oxygen sensor 18 is reversed in a short time.

In step 32a, it is determined whether the output V _S of the oxygen sensor 18 is less than or equal to the reference value V _R (for example, 0.45 V). When a positive determination is made in step 32a,
That is, when the exhaust gas is lean, the routine proceeds to step 32b, where it is judged if the delay counter CDLY is positive. If the affirmative decision is made in step 32b, step 3
In 2c, the delay counter CDLY is reset to "0" and the process proceeds to step 32d. When a negative determination is made in step 32b, the process directly proceeds to step 32d.

In step 32d, the delay counter CDLY is decremented, and in step 32e it is determined whether the delay counter CDLY is less than or equal to the lean delay time TDL. When the affirmative determination is made in step 32e, that is, when the lean delay time TDL or more has elapsed since the output of the oxygen sensor 18 was inverted from rich to lean, the delay counter CDLY is set to the lean delay time TDL in step 32f, and step 32g With the air-fuel ratio flag F
F is set to "0", and this processing ends. If a negative determination is made in step 32e, that is, if the lean delay time TDL has not elapsed since the output of the oxygen sensor 18 was inverted from rich to lean, this process is directly ended.

Here, the lean delay time TDL is a delay time for delaying the inversion of the air-fuel ratio flag FF when the output of the oxygen sensor 18 is inverted from rich to lean, and is defined as a negative value. When a negative determination is made in step 32a, that is, when the exhaust gas is rich, the process proceeds to step 32h, and it is determined whether the delay counter CDLY is negative.

When the affirmative judgment is made at step 32h, the delay counter CDLY is reset to "0" at step 32i and the routine proceeds to step 32j. When the negative judgment is made at step 32h, the routine directly proceeds to step 32j. The delay counter CDLY is incremented in step 32j, and the delay counter C is incremented in step 32k.
It is determined whether DLY is longer than the rich delay time TDR.

When a positive determination is made in step 32k, that is, when the rich delay time TDR has elapsed since the output of the oxygen sensor 18 was inverted from lean to rich, the delay counter CDLY is set to the rich delay time T in step 32l.
Set to DR and set the air-fuel ratio flag FF in step 32m.
Set to "1" to end this process. Step 3
When a negative determination is made at 2k, that is, after the output of the oxygen sensor 18 is inverted from lean to rich, the rich delay time TD
When R has not elapsed, this process is ended directly.

Here, the rich delay time TDR is a delay time for delaying the inversion of the air-fuel ratio flag FF when the output of the oxygen sensor 18 is inverted from lean to rich, and is defined as a positive value. FIG. 5 is a flowchart of the air-fuel ratio correction coefficient calculation process executed in step 33, in which the air-fuel ratio correction coefficient and the air-fuel ratio learning coefficient for controlling the exhaust gas air-fuel ratio to the stoichiometric air-fuel ratio are calculated.

At step 33a, it is determined whether the air-fuel ratio flag FF has been inverted. When the determination is affirmative, that is, when the air-fuel ratio flag FF is reversed, the process proceeds to step 33b, and it is determined whether the air-fuel ratio flag FF is "0". Step 33
If the affirmative decision is made in b, it is assumed that the state is reversed from rich to lean, and in step 33c the air-fuel ratio correction coefficient FAF
Is increased stepwise by the following equation and the process proceeds to step 33e.

FAF ← FAF + RSR When a negative determination is made in step 33b, it is assumed that lean is reversed to rich, and in step 33d the air-fuel ratio correction coefficient FAF is stepwise reduced by the following equation and the process proceeds to step 33e. FAF ← FAF-RSL In step 33e, the moving average value FAFAV of the air-fuel ratio correction coefficient FAF is calculated by the following equation.

FAFAV ← FAFAV + η ・ (FA
F-FAFAV) Here, η is a weighting coefficient. In step 33f, the existence area of the moving average value FAFAV is checked, and if it is equal to or larger than a predetermined upper limit value (for example, 1.005), step 33g.
Then, the air-fuel ratio learning coefficient KG is increased by a predetermined amount (for example, 0.002), and the routine proceeds to step 33m.

When the moving average value FAFAV is less than or equal to a predetermined lower limit value (for example, 0.995), the air-fuel ratio learning coefficient KG is decreased by a predetermined amount in step 33h and the process proceeds to step 33m. When the moving average value FAFAV is between the lower limit value and the upper limit value, the air-fuel ratio learning coefficient KG is not updated and the process directly proceeds to step 33l. When a negative determination is made in step 33a,
That is, when the air-fuel ratio flag FF is not inverted, the routine proceeds to step 33i, where it is determined whether the air-fuel ratio flag FF is "0".

When the affirmative determination is made in step 33i, it is assumed that the lean state continues, and in step 33j, the air-fuel ratio correction coefficient FAF is slightly increased by the following equation, and the routine proceeds to step 33m. FAF ← FAF + KIR When a negative determination is made in step 33i, it is assumed that the rich state continues, and in step 33k, the air-fuel ratio correction coefficient FAF is slightly reduced by the following equation and the process proceeds to step 33m.

FAF ← FAF-KIL In step 33m, the air-fuel ratio correction coefficient FAF is limited to the maximum value (for example 1.2) and the minimum value (for example 0.8), and this processing is ended. This is to prevent overrich or overlean even when the air-fuel ratio correction coefficient FAF becomes too large or too small.

FIG. 6 is a flow chart of the fuel injection routine executed by the control unit 19, which is executed every predetermined crank angle. Intake air amount Q in step 61
And the basic fuel injection amount TAUP is calculated from the internal combustion engine speed Ne based on the following equation. TAUP ← α · Q / Ne where α is a constant.

In step 62, the basic fuel injection amount TA
UP, air-fuel ratio correction coefficient FAF and air-fuel ratio learning coefficient KG
From this, the fuel injection valve opening time TAU is calculated based on the following equation. TAU ← β · TAUP · FAF · KG + γ where β and γ are constants. In step 63, the fuel injection valve opening time TAU is output via the output interface 194 to control the opening and closing of the fuel injection valve 12.

In step 64, the integrated value Στ of the fuel valve opening time
Is updated and this routine ends. In the above embodiment, the fuel is supplied by the fuel injection valve, but the present invention can be applied to the case where a carburetor is used.

[0034]

According to the fuel additive supply device of the present invention, in the air-fuel ratio feedback control for maintaining the air-fuel ratio of the exhaust gas at the stoichiometric air-fuel ratio, the variation of the flow characteristic of the fuel injection valve or the secular change is compensated. To determine whether the fuel injection valve is sliding or not based on the air-fuel ratio learning correction coefficient that is introduced to control the injection amount of the fuel additive based on the air-fuel ratio learning correction coefficient. It becomes possible to add agents.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel additive supply device.

FIG. 2 is a flowchart of a fuel additive injection routine.

FIG. 3 is a flowchart of an air-fuel ratio correction coefficient calculation routine.

FIG. 4 is a flowchart of delay processing.

FIG. 5 is a flowchart of an air-fuel ratio correction coefficient calculation process.

FIG. 6 is a flowchart of a fuel injection routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 11 ... Intake pipe 12 ... Fuel injection valve 13 ... Fuel tank 14 ... Fuel additive tank 15 ... Filling pump 16 ... Electromagnetic valve 17 ... Exhaust pipe 18 ... Oxygen sensor 19 ... Control part

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Claims (1)

[Claims] 1. A fuel tank for storing a mixed fuel, a fuel supply means for supplying the mixed fuel stored in the fuel tank to an internal combustion engine, and a concentration of a specific component in exhaust gas discharged from the internal combustion engine. Air-fuel ratio detection means for, an air-fuel ratio correction coefficient calculation means for calculating an air-fuel ratio correction coefficient according to the output of the air-fuel ratio detection means, of the air-fuel ratio correction coefficient calculated by the air-fuel ratio correction coefficient calculation means Air-fuel ratio learning coefficient calculation means for calculating an air-fuel ratio learning coefficient according to the deviation of the moving average value from the reference value, and the air-fuel ratio correction coefficient and the air-fuel ratio learning coefficient calculation means calculated by the air-fuel ratio correction coefficient calculation means. According to the air-fuel ratio learning coefficient calculated by the air-fuel ratio learning coefficient calculation means, a fuel supply time adjusting means for adjusting the fuel supply time of the fuel supply means according to the air-fuel ratio learning coefficient calculated in And a fuel additive injection amount control means for controlling an injection amount of the fuel additive into the fuel tank.