JPH01257245A - Measuring apparatus for mixing ratio of fuel for internal combustion engine - Google Patents

Abstract

PURPOSE:To optimize the mixing ratio of a mixed fuel, by a method wherein the part of a light-transmitting body dipped in the mixed fuel is shaped in a curve. CONSTITUTION:The part of a light-transmitting body 1 used for measuring a refractive index, i.e. an optical waveguide, which is dipped in a mixed fuel 2 is made to be an optical waveguide shaped in a curve having a curvature. By the method wherein the part of the optical waveguide dipped in the fuel is shaped in the curve having the curvature, a light transmitted straight from a light-emitting element 12 to a light- sensing element 13 is eliminated. A light incident on the curved part of the optical waveguide at every incident angle is reflected repeatedly in a plurality of times at the same reflection angle on the interface between the waveguide and the fuel, and as the result, all the lights not meeting the condition of total reflection leak outside the optical waveguide and are not sensed. By these two effects, the quantity of transmitted light taken out as a light-sensing signal is made to be dependent on the refractive index of the fuel at 100% substantially, and therefore the sensitivity of a sensor, i.e. S/N, is increased. Based on the output signal of the element 13 being dependent on the refractive index of this fuel 2, the mixing ratio of the fuel 2 is measured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus for determining the type or fuel mixture ratio of gasoline, alcohol, etc., or a mixture thereof used as fuel for an internal combustion engine. It is related to the system.

[Background of the Invention] In response to stricter exhaust gas regulations and the depletion of oil resources, plans are underway to shift the fuel for internal combustion engines such as automobile engines from gasoline to alcohol in the future. For example, the use of methanol fuel in automobiles is being attempted not only in Japan but also in other countries around the world from the viewpoint of reducing exhaust emissions and saving oil.

However, in order for methanol vehicles to become widely popular,
At the same time as the production of methanol vehicles, a methanol supply facility (
(methanol stand) is required. Therefore, the practical application of methanol vehicles is first of all limited to local buses and mail cars, which have a limited driving range, but it is difficult to put them into practical use in private passenger cars, where an unspecified number of people drive around freely. It was a common belief.

As a way out of the chicken-and-egg relationship of ``There is no use building methanol cars because there are no methanol stations. There is no use building methanol stations because there are no methanol cars...'', it is possible to drive on either methanol or gasoline. There is a car. This is a car that automatically adjusts the engine's two-fuel supply amount and ignition timing according to the mixing ratio of methanol and gasoline.
This is what is called an "exible fuel vehicle".

Since the number of methanol stations is small at the early stage of commercialization of methanol vehicles, the use of such FFVs is effective. In this way, a mixed fuel of gasoline and alcohol will be used for the time being, so a system is needed to measure the mixture ratio and control the engine fuel.

[Prior Art] Conventionally, such a system and a sensor used therein have been disclosed in US Pat. No. 4,438,749, 1984.
March 2015 (Fuel supply system), JP-A-62-11204
Publication No. 0, Utility Model Application Publication No. 82-81046 and Utility Model Application No. 81046
There is one disclosed in Japanese Patent No. 2-81047 (both related to a mixture ratio sensor).

In all of the above-mentioned known examples, the sensor section made of a transparent body is mainly described, and the peripheral circuit configuration and the system configuration mainly including the temperature correction means are described. The summary is explained below.

These systems consist of an optical waveguide made of a linear light-transmitting material, a sensor section consisting of a light source LED and a detector photodiode (PD) mounted opposite to each other at both ends of the optical waveguide, and a sensor section consisting of a light source LED and a detector photodiode (PD) mounted on opposite ends of the optical waveguide, and the surroundings and interface of the linear optical waveguide. It consists of a fuel passage and an analog circuit.

The analog circuit outputs the mixture ratio of the mixed fuel and is supplied to the control circuit to perform combustion control. Note that since the amount of light emitted by the LED of the sensor light source fluctuates depending on the temperature, there are some examples of means for correcting the amount of light such as employing a temperature-compensating light emitting element (for example, Japanese Patent Laid-Open No. 82-1
12040).

The operating principle of the sensor described above is to detect changes in the fuel composition by changes in the refractive index. It is detected as a change in the amount of light reaching the area. In this case, since the refractive index of the liquid changes depending not only on the components but also on the temperature, it is necessary to detect the temperature of the fuel and correct the temperature of the sensor. Said U.S. Pat. No. 4.438
．． In No. 749, this temperature correction is performed in an analog circuit by adding a constant bias according to the temperature of the fuel to the signal level.

[Problems to be Solved by the Invention] The conventional system as described above, particularly the sensor section, has the following problems.

l) Of the light incident from the light emitting element LED, the incident angle is 0
The light close to `` and 0'' reaches the light receiving element PD without being reflected even once at the interface between the optical waveguide and the fuel. This amount of light is independent of the refractive index of the fuel, and therefore does not depend on the components of the fuel. Therefore, this amount of light becomes a large bias component or background for the amount of detected light,
If this is regarded as a noise component N, it results in a decrease in sensitivity, that is, S/N.

2) When this system is installed in a car, etc., it is required to be maintenance-free, but when fuel such as gasoline is used at high temperatures, a portion of it undergoes metamorphosis, which may adhere to the surface of the optical waveguide. It becomes dirty and causes a decrease in the sensitivity of the sensor itself. Therefore, it is necessary to carry out regular pregnancy inspection maintenance mainly to remove dirt. 3) When installed in a car, the operating environment temperature
Full functionality is required between 0°C and +110°C. Conventional temperature correction methods cannot adequately compensate for this requirement.

This invention was made to solve the above-mentioned problems, and focuses on determining the fuel mixture ratio apl, which is the most important factor in engine fuel control, and develops an optimal measuring device for the mixture ratio of mixed fuel. The purpose is to scale.

Means for Solving the Problem] In order to solve the above problems, a fuel mixture ratio measuring device for an internal combustion engine according to the present invention has a system configuration based on a combination of the requirements shown below. .

(1) The transparent body used for refractive index measurement, that is, the part of the optical waveguide to be immersed in the mixed fuel was made into a curved optical waveguide having a curvature.

(2) The transparent body has two light input ends, two light emitting elements made of LEDs with different wavelengths are attached to these light input ends, and these two LEDs are turned on in a time-sharing manner. A two-wavelength signal processing circuit is provided to input the light into the optical waveguide and separate the output signal of the photodetector (PD) into signals for each wavelength in synchronization with the lighting of the LED. Based on this, a correction circuit was introduced to correct the ap+ constant error due to dirt attached to the transparent body.

(3) Temperature correction means was provided by immersing a thermometer in the mixed fuel and calculating the correction amount as a function of both the temperature signal and the light intensity signal from the light receiving element.

[Operation] The operation of each of the above-mentioned requirements constituting this invention will be sequentially explained below.

(1゛) By making the portion of the leading waveguide immersed in the fuel into a curved shape with curvature, there is no direct light passing from the light emitting element to the light receiving element. The light incident on the bending part of the leading waveguide at any angle of incidence is reflected multiple times at the interface between the waveguide and the fuel at the same reflection angle, and as a result, all light that does not satisfy the conditions for total internal reflection exits the optical waveguide. Words that leak into the light and are received no longer exist. Due to these two effects, the amount of transmitted light extracted as a light reception signal is almost 100% dependent on the refractive index of the fuel, so the sensitivity of the sensor, that is, the S/N
increase.

(2゛) By performing two-wavelength measurement using two light sources, it is possible to perform correction to exclude the influence of dirt attached to the surface of the leading waveguide.

The reason is explained as follows. When the light-transmitting body becomes dirty due to deposits on its surface, the light reflected here is not only specularly reflected, but is also scattered, thereby attenuating the amount of detected light.

However, it has been found that when the wavelengths of light used for the 391 constant differ, this attenuation rate differs. Considering this knowledge, if the sensor light amount signal for the wavelength λ λ is 1゛2 E,,E2, the degree of dirt is expressed by the variable ξ, and the attenuation rate is γ, the attenuation due to dirt is E-exp(- 7ξ
) E o ·(1) [When λ-λ1] E-exp(-7ξ) E o ·(2) [When λ-λ2] It is expressed as follows. (See Figure 7) Here E. is the signal when it is not dirty.

By eliminating ξ from the above two equations, the following equation is obtained.

That is, depending on the degree of contamination ξ at the time of measurement, E is determined from the value of γ1°γ and the light amount signals E and E2. Since this is required, correction for the decrease in sensitivity due to dirt is performed. In other words, regardless of the degree of contamination ξ, the attenuation rates γ and γ due to the two wavelengths and the actual All values E and E of each light amount signal at that time
From this, the light amount signal E when there is no dirt. This means that the correction value of can be found.

(3") The temperature correction means configured in this invention was obtained from the following reasons and knowledge, and the temperature correction in the measurement of the mixture ratio of the mixed fuel is performed by storing the concentration and temperature correction coefficients in a table by a computer. This is carried out by table lookup calculation or function calculation using an analog circuit shown in the embodiment shown in FIG. 2, which will be described later.

In other words, if the temperature coefficient of the solution refractive index does not depend on the solution concentration, the refractive index can be temperature-corrected by bias correction proportional to temperature, as in the method of the above-mentioned U.S. Pat. No. 4,438.749. .

However, in reality, as shown in FIG. 5 below, the temperature coefficient of refractive index increases as the concentration increases. Therefore, in order to realize temperature correction over a wide temperature range, the correction amount must be determined based on two factors: temperature and concentration. In this invention, since the concentration is an unknown quantity, it is corrected by a function calculation that makes each signal a function from the temperature signal of a thermometer immersed in the mixed fuel and the light amount signal obtained depending on the refractive index. quantity is required. This calculation means will be explained with reference to an analog circuit diagram (FIG. 6) of the embodiment described later.

Note that the concentration of the solution 7 is determined by the refractive index using an optical densitometer that constitutes the main part of the mixing ratio measuring device of the present invention.
The basic calculation method for the 1111 constant will be explained. This calculation method is currently being applied for in Japanese Patent Laid-Open No. 122242/1989 by the present inventors.

The refractive index and concentration of a solution (medium) with multiple components are determined by the well-known Lorentz-Lorenz relation %
Formula % Here, n: refractive index pi: i-component polarizability N1: number of i-component atoms in unit volume Therefore, the concentration Ni can be determined by measuring the refractive index n. Note that the wavelength λ is assumed to be constant here.

In addition, in equation (1), [XI]: Concentration of component i contributing to refractive index fluctuation g: Number of components contributing to refractive index fluctuation: Contribution of other components (constant) Contribution of change in [x1] is considered to be weak, so
Equation (5) can be linearly approximated as follows.

The above is the calculation standard equation for this measurement method. When the above equation (5) is applied to the case of a mixed fuel of alcohol and gasoline, n-α[A] ten β...(6).

[^] is the alcohol concentration, and the alcohol concentration [A] can be determined by measuring the refractive index.

In addition, this concentration meter is equipped with a thermometer using a temperature sensor in the measuring section as well as a refractometer using a refractive index probe, so if the temperature of the solution to be 811 constant changes, the temperature will change depending on the refractive index as described above. Since the influencing temperature dependence is corrected, the accuracy of al determination of the concentration is improved.

Furthermore, the measured values of the temperature and refractive index, that is, the amount of transmitted light, are sent to a signal processing circuit (data processing device) using a microcomputer, etc., and are compared with a function or table stored in a memory section in advance to calculate the concentration. Therefore, it is possible to constantly monitor the concentration, that is, the mixing ratio, by performing the calculation online and changing accurate 1lllJ constant data.

[Example] Examples of the present invention and a few characteristic data and others will be described below with reference to the drawings.

Embodiment 1; Figure 1 is a cross-section of a fuel sensor part that is connected in series to the fuel system piping (see Figure 4 for the mounting position) supplied to the internal combustion engine, and one part of which is immersed in the mixed fuel to be measured. It is a configuration explanatory diagram. This sensor section is composed of a refractive index sensor mainly consisting of a refractive index probe (hereinafter referred to as probe) and a temperature sensor consisting of a thermometer.

In the figure, reference numeral 1 denotes a U-shaped probe having an optical waveguide made of quartz glass or pyrex glass as a transparent body.

3 is a thermistor thermometer for a temperature sensor that is immersed in the mixed fuel 2 in the same way as the probe 1, and is airtightly fitted into a flange 6 forming a lid of a sensor container 5 that is connected to the pipe 4 together with the probe 1. is being held. The flange 6 is attachably attached to the sensor container 5 via an O-ring 7.

The attachment part to the flange 6, which is the gripping member of the probe 1, is
In particular, a metal reflective film 8 such as silver is formed on the contact interface between the optical waveguide 1 and the flange 6 by vapor deposition or sputtering on the straight part on the light input side, and then attached using a small backing 9. In this case, instead of the metal reflective film 8, a cladding layer coated with a translucent substance having a lower refractive index than the optical waveguide 1, such as 81 potting agent, may be formed.

As described above, the light input end 10 and the light output end 1 of the probe 1 are
1 is attached so as to be located substantially on the upper surface of the flange 6. At the top of the light input end 10 is an LED light emitting element 12 for a light source, and beside it is a PD light receiving element 14 for monitoring the amount of light.
, PD light receiving elements 13 for measurement are installed above the light emitting ends 11, respectively. Note that a flange lid 15 is attached to the flange 6 to block light from the outside.

A connector 1G is provided on the flange lid 15, and includes a light emitting element 12.12a, a light receiving element 13.13a, 14,
Input and output lines for the thermometer 3 are wired, and transmission and reception to and from an analog circuit (not shown) are performed via cables.

The above constitutes the first component of the present invention, and by making the portion of the transparent body immersed in the mixed fuel 2 a curved leading wave path, the refractive index of the mixed fuel 2 can be adjusted to AIIJ.
The probe 1 is a refractive index sensor for determining the refractive index.

In the above-mentioned Example 1, the case where the probe 1 is used has a guide waveguide having a U-shaped curvature, but other curved shapes as shown in FIG. 2 may be used.

In other words, (a) in Figure 2 has a circular 0-shape, (b) has a 8-shape consisting of two circles, and (e) has a gourd-shaped curvature.1 All of them are the same as the U-shape described above. It has the function and effect of =.

FIG. 3 is a diagram showing the output characteristics of the sensor with respect to gasoline concentration using the U-shaped probe 1, compared with a conventional straight probe for gasoline-methanol mixed fuel when the temperature and light source wavelength are constant. It is. In other words, this is a calibration characteristic diagram when focusing only on gasoline. In the figure, the horizontal axis is the gasoline concentration, and the vertical axis is the percentage amount of transmitted light.

As is clear from Figure 3, gasoline concentration is 0 to 100%.
The curve (I) of the output change of a conventional straight probe over the range of
is a change of about 30%, whereas the characteristic curve (II) of the curved probe of the present invention shows a change of about 90%,
This shows that the sensitivity as a detection characteristic has been significantly improved. This shows that the measurement resolution of the mixing ratio has been significantly improved, and it can be said that the performance is highly satisfactory.

Embodiment 2; FIG. 4 shows another embodiment of the present invention, in which the probe 1 of Embodiment 1 is used to measure two wavelengths and is used as a means for correcting the mixing ratio Δ-1 constant error due to dirt on the probe. FIG. This optical densitometer is constructed in accordance with the pending application in Japanese Patent Application No. 81-122242.

In FIG. 4, A is a light source circuit, B is a signal processing device, and parts other than A and B correspond to the parts shown in the embodiment of FIG. , 1 to 14 are the same reference numerals as those used in FIG. 1, so explanations of each part will be omitted. In addition,
17.17a are optical fibers that guide the amount of light emitted from the light emitting elements 12.12a to the light receiving cable 14 for monitoring the amount of light;
18 is a microcomputer built into the signal processing device B.

There are two light input ends of the probe 1, 10.10a, and LED light emitting elements 12, 12 with wavelengths λ and λ2, respectively.
a is arranged. Light emitting element 12. The light incident on the probe 1 from L2a is emitted from the light output end 11 of the probe 1, and is detected as the amount of transmitted light by the PD light receiving element 13 for measurement. On the other hand, 17.17a is an optical fiber, and the light from each light emitting element 12.12a passes through these optical fibers 17.17a and is detected by the PD light receiving element 14 for monitoring to obtain a light amount monitor signal.

A is a light source circuit, which includes an oscillator O8C and a gate signal generator GS.
G, which causes the light emitting elements 12 and 12a to emit light, and transmits gate signals to the sample and hold circuits SHI, SH2, SH3, and SH4 of the signal processing device B. The output of the light-receiving probe 13 for measurement is amplified by an amplifier A1, and each wavelength λ1 . The light is transmitted to sample and hold circuits SHI and SH2 as light for each λ2. Further, the signal detected by the monitor light receiving element 14 is amplified by an amplifier A2 and sent to sample and hold circuits SH3 and SH4 to adjust and control the amplification factor of each measurement signal.

In the optical densitometer as described above, light with wavelengths λ1 and λ2 is simultaneously incident on the probe 1 from two light-emitting elements 12 and 12a with different wavelengths in a time-sharing manner, and the light is transmitted to the light-receiving element 13 for measurement. The transmitted light signal detected by
The light amount monitor signal detected in step 4 is synchronously detected and manually input to the sample-and-hold circuits SH3 and SH4 corresponding to the above-mentioned SHI and SH2, respectively, and the respective outputs are input to the microcomputer 18 of the signal processing circuit B for signal processing. , and output it separately as refractive index or concentration for each wavelength. By doing so, it becomes possible to measure two wavelengths with one probe, and measurement can be performed without being affected by individual differences due to probe characteristics.

In addition, in order to correct temperature fluctuations in the light amount of the light emitting element 12.12a, the light guided by the optical fiber 17.17a is monitored by the monitoring light receiving element 14, and this light amount monitor signal is sent to the SH3, Since the amplification factor of the measurement signal for each wavelength is processed and adjusted by the microcomputer 18 after being transmitted to SH4, it is possible to eliminate the influence of the light output signal due to light intensity fluctuations, improving measurement accuracy. do.

In addition to the above-mentioned computer processing correction of the monitor light amount signal, a light source light amount control circuit shown in FIG. 5 is added, and the light emitting element! 2.12a It is also possible to make the amount of light from the light source constant. That is, as shown in FIG.
The light from the monitor passes through the optical fiber 17 to the monitoring light receiving element■
4, the amplifier 19 detects the fluctuation in the light amount, and the fluctuation is fed back to the control power source of the light emitting element 12, thereby controlling the light amount of the light emitting element 12 and making the light source light amount constant.

The thermistor thermometer 3 is immersed in the mixed fuel as shown in the figure, and its output is read and input into the microcomputer 11 as fuel temperature measurement data at appropriate times. SW is an interrupt switch for setting the sensitivity correction coefficient based on this input.

Using the two-wavelength optical densitometer as described above, it is possible to correct errors caused by probe contamination in measuring the gasoline-alcohol fuel mixture ratio. That is, as explained in equation (2) above, the respective light quantity signals E 2 at wavelengths λ 2 and λ2.

1) From E, the correlation between E and E2 can be determined using equation (2), and can be determined by correcting the light amount signal Eo when there is no dirt.

FIG. 6 is a graph showing experimentally determined correlations between El and E2 for several degrees of contamination of the probe under the same mixed fuel and at the same temperature. = f when λ-λ is on the horizontal axis
Iog (E1/Eo) is taken, and pog (E2/Eo) when λ-λ2 is taken on the vertical axis. From this figure, it can be seen that E
A certain linear relationship holds between t and E2, but this straight line does not have a slope of 45°, and it is found that there is a certain difference in the attenuation rate depending on the wavelength, and using this slope as a correction factor, 2 By adjusting the wavelength 1T11, it is possible to correct the measured value for probe dirt.

Embodiment 3: As shown in the embodiment of FIG. 4, in this invention, a thermometer is immersed in the mixed fuel and the temperature correction of the concentration, that is, the mixture ratio is performed based on this temperature signal. , ■ Correction calculation by microcomputer 18 and ■
This is done using either function calculation correction using an analog circuit. That is, (1) Temperature correction by microcomputer Focuses on any one of the mixed fuels, and stores the temperature coefficient of each concentration in the memory (ROM) of the computer 8 as a temperature correction coefficient.

At the time of measurement, the temperature coefficient according to the light amount signal is determined by table lookup, and from this and the temperature signal, the correction WE at the reference temperature is calculated.
seek.

In the second method, the correction amount may be stored in a memory as a two-dimensional table of density (light amount signal) and temperature, and the light amount signal may be looked up from the temperature signal at all+times.

Further, in order to improve the accuracy of the correction, the above correction may be repeated recursively using the corrected density (light amount signal).

FIG. 7 is a diagram showing the light quantity signal-temperature characteristic determined using the methanol concentration of the gasoline-methanol mixed fuel as a parameter. The horizontal axis shows a temperature signal, and the vertical axis shows a light amount signal, and is an explanatory diagram when temperature correction is performed from a graph for five samples with methanol concentrations of 0 to 100%. Therefore, this figure explains the concept of the computer-based temperature correction method using actual measurement graphs.

Looking at the diagram, 5% methanol from 0% to 100%
Each characteristic curve obtained for the sample is approximately a straight line, and its slope becomes the temperature correction coefficient. Now, in this characteristic diagram, if the light intensity signal E-E at the temperature T-T is taken, then the point A becomes the measured value. The temperature correction coefficient at this point A is determined by internal interpolation from the methanol 75% and 50% curves, and if the slope is shifted to the reference temperature T, it will intersect the mouth point, so the light amount after correction is determined at this point. It can be obtained as a signal E, and the methanol concentration at temperature T can be calculated from this correction value. The temperature correction means described above performs this calculation using a computer.

■ Temperature correction by functional calculation The correction amount is expressed as a function of density, that is, the light amount signal and temperature, and the correction amount is determined by calculation on a microcomputer.

For example, assuming that the temperature coefficient depends linearly on concentration, it is expressed by the following equation.

E-E + (aE +b) (T-T)CC
C...(7) Here, E: Light amount signal Eo: Light amount signal after correction (a degree) T: Temperature, To-reference temperature From equation (11), the following equation is obtained.

...(8) The correction function is expressed by equation (12).

Furthermore, if 1>a (T-T) holds, E-E-
(aE+b a b (T-T) l (T T c)・
...(9) Furthermore, E −E −(a E+b) (T−T ) −
(10) It can also be approximated as C.

Since the above calculation can also be performed by an analog circuit, the block circuit diagram in FIG. 7 shows the function correction when the functional form of equation (9) is used.

In the figure, after the light amount signal E and the temperature signal T are input to the linearization circuits 20 and 21, respectively, E is input to the amplifier A3.
T is the Tc signal from the resistor R4, which is T-T in the adder 22.
is sent to amplifier A4 as a signal.

The output of A3 is aE due to the output a from the resistor R1, and the output of A4 is ab(T-T) due to the ab stage setting of the resistor R3.
) and transmits it to the multiplier 24 via the adder 23 along with the output of the resistor R2. - On the other hand, the output of the adder 22 is input to the multiplier 24, multiplied, and sent to the adder 25, so the function calculation of equation (9) is performed as the total output E of the adder 25, and the temperature is corrected. You can get E.

Embodiment 4; FIG. 9 shows the fuel sensor section shown in the embodiment shown in FIG. FIG. 2 is a diagram of an operation control system for an automobile engine in which a control unit includes a mixing ratio aPI determining device, that is, an optical densitometer, including peripheral circuits such as B. FIG.

In FIG. 9, 50 is an engine cylinder of an internal combustion engine, and an injector 31 connected to a constant pressure fuel passage is opened at a branch part of an intake manifold 30 of the internal combustion engine. Fuel is injected toward the intake valve 32 of the cylinder 50.

The mixed fuel stored in the fuel tank 33 is transferred to the fuel pump 34.
The fuel filter 35 removes dust and the like, and the fuel is supplied to the injector 31. 3G is a pressure regulator for keeping the fuel pressure constant, and 37 is mainly composed of the probe 1 and thermometer 3 for detecting the mixing ratio of alcohol-gasoline mixed fuel shown in the embodiment of FIG. It is a fuel sensor.

On the other hand, intake air flows through an air cleaner 38, an air flow meter 39, a throttle valve 40, an intake passage 41, and a combustion chamber 42. The intake air flow m is measured by an air flow meter 39.

The control unit 43 receives a signal from an air flow meter 39, a signal from a crank angle sensor 44 built into the distributor, a signal from a cooling water temperature sensor 45,
Signal of λ sensor 46 that detects 2a degrees, fuel sensor 37
input the signal, calculate the injection amount of the injector 31,
This is a control device that drives an injector 31 using a built-in drive circuit to supply fuel to a combustion chamber 42 of an internal combustion engine.

FIG. 1O is a flowchart showing a procedure for calculating the fuel injection amount when combustion control is performed by the control unit 43 shown in the embodiment of FIG. 9. The flow will be explained below according to the flow of the flow items.

In response to the "start" command, the CPU reads the engine speed from the signal from the crank angle sensor 44 and the intake air amount from the signal from the air flow meter 38, and calculates the basic value (Tp) of the valve opening time of the injector 31. Next, water temperature sensor 4
The above Tp (injection amount) is corrected according to the engine temperature using the signal No. 5.

Next, the temperature signal from the thermometer 3 in the fuel sensor 37 is
If the fuel temperature is below the predetermined value of 16° C., a correction value for the alcohol-gasoline mixture ratio is calculated based on the fuel temperature and the light amount signal by the method shown in Examples 2 and 3 above. Using this value, an injection correction value based on the difference in fuel properties is calculated and newly stored in the memory within the control unit 43. Then, the injection amount is corrected using this value.

When the fuel temperature is above the predetermined value Tα°C, the fuel sensor 37 does not calculate the mixture ratio anew, but uses the previously calculated and stored value to correct the injection amount due to the difference in fuel properties. . The reason for this is that when the fuel temperature becomes high, the resolution of the fuel sensor 37 decreases and bubbles are generated in the fuel, making it impossible to obtain an accurate alcohol-gasoline mixture ratio.

Therefore, during a high-temperature restart, the period until the relatively cold fuel in the fuel tank 33 is sent to the fuel sensor 37,
The system waits for correction calculation of the injection amount.

Finally, the λ sensor 4 detects the 02 concentration in the exhaust gas.
The injection amount is corrected based on the signal B, and the response delay time of the injector 31 is corrected to determine the drive time of the injector 31, fuel is injected, and the series of fuel control operations is completed.

[Effects of the Invention] As described above, the present invention provides a 4-1 alcohol-gasoline internal combustion engine fuel mixture ratio fixing device. By making the portion curved with curvature, there is an effect that the detection sensitivity of the amount of transmitted light, which depends on the refractive index of the fuel, is greatly improved.

In addition, when measuring the refractive index mentioned above, we decided to perform two-wavelength measurements using light sources with different wavelengths, making it possible to measure concentration unaffected by dirt on the probe or optical waveguide.
This invention has the effect of providing a maintenance-free mixture ratio measuring device for, for example, an automobile engine operation control system in which the fuel mixture ratio n1 constant device is incorporated.

Furthermore, since a thermometer is installed in the sensor section of the above measuring device in addition to the probe to measure the fuel temperature, from this temperature signal and the amount of light transmitted through the light receiving element (H), a temperature correction value for the mixture ratio of the mixed fuel is calculated. By providing a temperature correction means for calculating , it is possible to maintain a constant mixing ratio of 4p1 that is not affected by large temperature fluctuations.

The sensor section can be mounted on one side with a probe and a thermometer attached to the flange surface, which simplifies the mechanism for mounting to the engine operation control system and greatly facilitates maintenance.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the cross-sectional configuration of a fuel sensor section showing an embodiment of the present invention, and FIGS. Figure 3 is a diagram showing the sensor output characteristics of the above U-shaped probe and the conventional straight probe. An explanatory diagram of the configuration of an optical densitometer with two wavelengths aPj constant showing another embodiment of the invention, FIG.
Figure 6 is a diagram showing the wavelength characteristics of transmitted light amount attenuation due to probe dirt, Figure 7 is a diagram showing the (light amount signal - temperature) characteristics with methanol concentration as a parameter, and Figure 8 is a diagram showing the temperature using an analog circuit. FIG. 9 is a block circuit diagram explaining the correction; FIG.
This figure is a flow explanatory diagram showing the fuel injection amount calculation means of the engine operation control system of FIG. 9. In the figure, 1 is a refractive index probe which is a transparent body, 2 is a mixed fuel, 3 is a thermometer, 5 is a sensor container, 6 is a flange,
8 is a metal reflective film, 10 is a light input end, 11 is a light output end, 12 is an LED light emitting element, 13 is a PD light receiving element for measurement, 14
17. 17a is an optical fiber, and 18 is a microcomputer. In addition, in the figures, the same reference numerals or corresponding parts are indicated.

Claims (3)

[Claims] (1) A light-emitting element, a light-receiving element, and a light-transmitting body that optically couples these light-emitting elements and light-receiving elements, and a portion of this light-transmitting body is immersed in a mixed fuel consisting of two types of fuel. is,
In the fuel mixture ratio measuring device for an internal combustion engine that measures the mixture ratio of the mixed fuel based on the output signal of the light receiving element that depends on the refractive index of the mixed fuel, the transparent body is immersed in the mixed fuel. A fuel mixture ratio measuring device for an internal combustion engine, characterized in that the portion is curved. (2) The light transmitting body has two light input ends, two light emitting elements with different wavelengths are attached to the two light input ends, and these two light emitting elements emit light in a time-sharing manner. a processing circuit that processes the received light output signal of the light receiving element in synchronization with the light emission of the two light emitting elements and separates the received light signal into a received light signal corresponding to the light emitted signal of each of the light emitting elements; and the separated light received signal. 2. The fuel mixture ratio measuring device for an internal combustion engine according to claim 1, further comprising a correction means for correcting a measurement error due to dirt attached to said transparent body based on the intensity of said light transmitting body. (3) A thermometer immersed in the mixed fuel to measure the temperature of the mixed fuel, and correction of the mixing ratio of the mixed fuel based on signals from the thermometer and a light receiving element provided on the transparent body. 2. The fuel mixture ratio measuring device for an internal combustion engine according to claim 1, further comprising temperature correction means for calculating the value.