JPH05163976A - Injection quantity controller for alcohol mixed fuel - Google Patents

Abstract

PURPOSE:To provide a proper air fuel ratio by preventing the actual amount of injection from being changed according to alcohol concentration due to effects of viscosity and so on of alcohol. CONSTITUTION:The reference quantity of injection Tp is calculated at a step 2 based on the quantity of an inlet air Q and a rotational speed N of an engine, and so on, and the quantity of dynamic injection (q) based on a gasoline is calculated at a step 3. The quantity of static injection Qm of a methanol mixed gasoline is corrected and calculated at a step 4, and the quantity of injection Tt of the methanol mixed gasoline is calculated based on am injection time (t) calculated at a step 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection amount control device for alcohol-mixed fuel, which is preferably used for controlling the injection amount of fuel mixed with alcohol such as methanol.

[0002]

2. Description of the Related Art Recently, as fuel for automobile engines,
Alcohol mixed gasoline containing alcohol such as methanol has been used instead of pure gasoline. Further, since the stoichiometric air-fuel ratio A / F naturally changes between the genuine gasoline and the alcohol-blended gasoline, the injection amount of the fuel injected and supplied to the engine, the ignition timing, etc. also differ.

Here, when genuine gasoline with an alcohol concentration of 0% is used, the fuel injection amount Ti is

[0004]

[Equation 1] Ti = TP × α × α ′ × Coef + TS where TP: basic injection amount α: air-fuel ratio A / F feedback correction coefficient α ′: basic air-fuel ratio A / F learning correction coefficient Coef: various correction coefficients TS : Calculated as the battery voltage correction coefficient.

At this time, the air-fuel ratio A / F feedback correction coefficient α is corrected based on the oxygen concentration signal from the oxygen sensor, and the basic air-fuel ratio A / F learning correction coefficient is calculated from the basic injection amount TP and the engine speed N. By learning-correcting α ′ and outputting an injection pulse having a pulse width corresponding to the injection amount Ti to the injection valve of the engine, the injection amount T from this injection valve
The amount of fuel corresponding to i is injected to control the theoretical air-fuel ratio A / F to 14.7.

As described above, the stoichiometric air-fuel ratio when using genuine gasoline as the fuel is A / F of 14.7, while the stoichiometric air-fuel ratio when using methanol having an alcohol concentration of 100%. It is necessary to control the A / F to be 6.5, and the theoretical air-fuel ratio A / F is about twice different when the alcohol concentration is in the range of 0 to 100%.

Therefore, when alcohol-blended gasoline is used, the fuel injection amount Ti0 is calculated from the above equation 1

[0008]

## EQU2 ## Ti0 = Mk × TP × α × α '× Coef + TS where Mk is a constant determined by the alcohol concentration.

Therefore, an engine using alcohol-blended gasoline is equipped with an alcohol concentration measuring device as an alcohol concentration detecting means called an alcohol sensor, and the output voltage corresponding to the alcohol concentration is taken out to output the output voltage. Based on the value, the operation of Equation 2 is performed.

As the alcohol concentration measuring device of this type, a resistance type alcohol concentration measuring device for detecting the alcohol concentration based on the difference in conductivity between gasoline and alcohol, and an electrostatic device utilizing a change in dielectric constant of alcohol-blended gasoline. Known are a capacitance type alcohol concentration measuring device and an optical alcohol concentration measuring device utilizing a change in refractive index.

[0011]

By the way, in the above-mentioned prior art, the injection amount TiO of the alcohol-mixed fuel is calculated by the equation 2, and an injection pulse having a pulse width corresponding to this injection amount TiO is output to the injection valve. As a result, fuel is only injected from this injection valve.

However, considering the injection flow rate from the actual injection valve, for example, the dynamic injection amount q when the valve body of the injection valve is opened and closed for 1000 strokes, this dynamic injection amount q is the injection time. In contrast, as shown in FIG. 4, the characteristic curve Mo is shown by a solid line in the case of gasoline fuel having a methanol concentration of zero, and the characteristic curve M100 is shown as a dotted line in the case of alcohol fuel having a methanol concentration of 100%. In the case of alcohol fuel, there is a problem that the dynamic injection amount q decreases by the difference Δq even in the same injection time as compared with gasoline fuel, the air-fuel ratio becomes lean, and the output of the engine decreases.

This is the flow rate Q of the fuel injected from the injection valve.
n is

[0014]

[Equation 3] However, Co: flow coefficient A: flow area of injection valve γ: specific weight of fuel g: gravitational acceleration Δp: pressure difference between inside and outside of injection valve, so flow coefficient Co is viscous depending on alcohol concentration in fuel It is understood that the fuel flow rate Qn changes according to the difference in the physical property values, such that the fuel flow rate Qn decreases as the alcohol concentration increases.

Therefore, the present inventors set the methanol concentration C in the gasoline blended with methanol to 0%, 30%, 5%, for example.
Experiments were conducted on the behavior of the static injection amount Qm per minute when changing to 0%, 85% and 100%, and the static injection amount characteristics represented by the characteristic lines I1 and I2 shown in FIG. 5 were confirmed.

That is, in the injection valve having the characteristic line I1, the static injection amount Qm is based on the methanol concentration C,

[0017]

## EQU4 ## It can be obtained as Qm = -0.0513C + 201.09, and the static injection amount Qm for other injection valves having the characteristic line I2 is

[0018]

It has been found that the value can be calculated as Qm = -0.0548C + 206.2.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention corrects the static injection amount per unit time based on the alcohol concentration in the fuel so that the fuel injection amount is alcohol. It is an object of the present invention to provide an injection amount control device for an alcohol-mixed fuel, which can prevent the concentration from increasing with an increase in the concentration and can optimize the fuel injection amount.

[0020]

The structure adopted by the present invention to solve the above-mentioned problems is the intake air amount detecting means for detecting the intake air amount of the engine and the rotation speed detecting means for detecting the engine speed. An alcohol concentration detecting means for detecting the alcohol concentration in the fuel injected and supplied to the engine; and a correction for correcting the static injection amount of the fuel per unit time based on the alcohol concentration detected by the alcohol concentration detecting means. The calculation means and the injection quantity calculation means for calculating the injection quantity of the fuel based on the static injection quantity by the correction calculation means, the intake air quantity, and the engine speed.

[0021]

With the above structure, the static injection amount per unit time is corrected and calculated according to the alcohol concentration, and the fuel injection amount is calculated based on the corrected static injection amount. It can be optimized according to the amount, and it is possible to prevent the air-fuel ratio of the engine from becoming lean as the alcohol concentration increases.

[0022]

Embodiments of the present invention will be described below with reference to FIGS.

In the figure, 1 is the intake air amount Q of the engine.
An air flow meter as an intake air amount detecting means for detecting the engine speed 2 and a crank angle sensor 2 as a rotational speed detecting means for detecting the engine speed N.
Is mounted near the crankshaft or camshaft (not shown) of the engine.

Reference numeral 3 denotes an alcohol sensor as an alcohol concentration detecting means. The alcohol sensor 3 is constituted by a capacitance type or optical type alcohol sensor or the like, for example, a fuel flow path including a fuel tank, a fuel pipe, etc. (Not shown), either. Then, the alcohol sensor 3 detects the concentration C of methanol in the methanol-blended gasoline as the alcohol-blended fuel flowing in the fuel flow path, and outputs the detection signal to the control unit 5 described later.

Reference numeral 4 denotes an injection valve for injecting methanol-mixed gasoline toward the combustion chamber of the engine, and the injection valve 4 outputs an injection pulse having a pulse width corresponding to an injection amount Tt described later from the control unit 5. Thus, the valve is repeatedly opened and closed to inject a proper amount of methanol-mixed gasoline corresponding to the injection amount Tt. Then, the methanol-mixed gasoline injected from the injection valve 4 is mixed with intake air in the combustion chamber of the engine or the like, and becomes a mixture to be burned to derive a rotational output from the crankshaft of the engine, thereby producing an air-fuel ratio Rationalize.

Further, 5 is a control unit composed of a microcomputer or the like, and the control unit 5 has an air flow meter 1, a crank angle sensor 2, an alcohol sensor 3 and a water temperature sensor on the input side.
An oxygen sensor (neither is shown) or the like is connected, and the injection valve 4 or the like is connected to the output side. The control unit 5 stores the program shown in FIG. 3 and the like in its memory circuit, and performs an injection amount calculation process of methanol mixed gasoline.

In the storage circuit of the control unit 5, when a constant K described later, a static injection amount Qo of gasoline with 0% methanol, a correction coefficient β and an injection time of 2.5 mS are stored in the storage area 5A. The dynamic injection amount q2.5 based on the gasoline is stored. Here, the dynamic injection amount q of fuel such as gasoline is set with respect to the injection time t as the characteristic line shown in FIG. 2, and the inclination θ of this characteristic line is tan θ = Qm with respect to the static injection amount Qm. Since it will be / 60,

[0028]

[Equation 6] Is required.

The injection amount control device for methanol-blended gasoline according to this embodiment has the above-mentioned configuration. Next, the injection amount calculation process by the control unit 5 will be described with reference to FIG.

First, when the processing operation is started, in step 1, the intake air amount Q, the engine speed N, the methanol concentration C, etc. are read from the air flow meter 1, the crank angle sensor 2, the alcohol sensor 3, etc., and the process proceeds to step 2. The basic injection amount Tp is

[0031]

[Equation 7] However, K: is calculated as a constant. Then, in step 3, the basic injection amount T
The dynamic injection quantity q based on gasoline is calculated from p.

Next, in step 4, the static injection quantity Qm of the methanol-mixed gasoline is calculated from the equations (4) and (5) obtained based on the experimental data shown in FIG.

[0033]

## EQU8 ## Qm = Qo-.beta..times.C where Qo is the static injection amount of gasoline with a methanol concentration of 0%.

Here, the static injection amount Qo of gasoline is set to Qo = 204 cc / min and the correction coefficient β is set to β = 0.053 from the above equations 4 and 5.

Then, in step 5, the injection time t is calculated by the above equation 6 from the static injection amount Qm of the methanol mixed gasoline corrected and calculated based on the methanol concentration C by the above equation 8, and this injection time t is calculated as the injection time t. As the basic injection amount corresponding to the methanol concentration C of, the basic injection amount Tp in the above equation 1 is replaced with the injection time t, so that the injection amount Tt of the methanol-mixed gasoline is calculated in step 6.

[0036]

## EQU9 ## The calculation is made as Tt = t.times..alpha..times..alpha. '. Times.Coef + TS, and in step 7, the process returns to the main routine (not shown).

Thus, according to the present embodiment, the static injection rate of the methanol blended gasoline based on the gasoline dynamic injection quantity q calculated in step 3 shown in FIG. 3 and the methanol concentration C corrected in step 4 is calculated. Since the injection time t is calculated by substituting the injection amount Qm into the equation 6, the injection amount Tt is calculated by using the injection time t as the basic injection amount of the methanol mixed gasoline. When an injection pulse having a corresponding pulse width is output to the injection valve 4 to inject methanol-mixed gasoline, when the actual injection amount of methanol-mixed gasoline is gasoline whose methanol concentration is 0% as described in the prior art. By comparison, it can be prevented from decreasing with the increase of methanol concentration,
It is possible to optimize the injection amount of methanol mixed gasoline.

Therefore, in the present embodiment, when methanol-mixed gasoline is used as the fuel, it is possible to reliably prevent the air-fuel ratio of the engine from becoming lean as the methanol concentration C increases, and to improve the combustion efficiency and rotation of the engine. There are various effects such as stabilizing the output and optimizing the control of the injection amount.

In the above embodiment, step 4 of the program shown in FIG. 3 shows a concrete example of the correction calculation means which is a constituent feature of the present invention, and step 5 and step 6
Shows a specific example of the injection amount calculation means.

In the above embodiment, the intake air amount Q of the engine is detected by the air flow meter 1. However, instead of this, for example, a throttle sensor for detecting the opening degree of the throttle valve and an intake manifold The intake air amount detection means may be configured by a pressure sensor or the like that detects the boost pressure.

[0041]

As described above in detail, according to the present invention, the static injection amount of alcohol-mixed fuel per unit time is corrected and calculated according to the alcohol concentration, and the intake air amount is calculated based on the corrected static injection amount. Since the injection amount of the alcohol mixed fuel is calculated from the engine speed and the engine speed, it is possible to reliably prevent the actual injection amount from decreasing with the increase of the alcohol concentration due to the influence of the viscosity of the alcohol, etc. The air-fuel ratio can be optimized. Therefore, the combustion efficiency and the rotational output of the engine can be stabilized, and the control of the injection amount can be optimized.

[Brief description of drawings]

FIG. 1 is a control block diagram showing an injection amount control device for methanol-blended gasoline according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between injection time and dynamic injection amount.

FIG. 3 is a flowchart showing an injection amount calculation process.

FIG. 4 is a characteristic diagram showing a relationship between an injection time and a dynamic injection amount according to a conventional technique.

FIG. 5 is a characteristic diagram showing the relationship between methanol concentration and static injection amount.

[Explanation of symbols]

 1 Air flow meter (intake air amount detection means) 2 Crank angle sensor (rotation speed detection means) 3 Alcohol sensor (alcohol concentration detection means) 4 Injection valve 5 Control unit C Methanol concentration N Engine rotation speed Q Intake air amount Qm Static injection Quantity q Dynamic injection quantity

Claims (1)

[Claims] 1. An intake air amount detecting means for detecting an intake air amount of an engine, a rotation speed detecting means for detecting an engine speed, and an alcohol concentration detecting means for detecting an alcohol concentration in fuel injected and supplied to the engine. Correction calculation means for correcting the static injection amount of the fuel per unit time based on the alcohol concentration detected by the alcohol concentration detection means, the static injection amount by the correction calculation means, the intake air amount, the engine An injection amount control device for alcohol-mixed fuel, comprising an injection amount calculation means for calculating the injection amount of the fuel based on the number of revolutions.