JPH05312755A - Detecting apparatus for concentration of alcohols of fuel - Google Patents

Abstract

PURPOSE:To obtain the concentration detection apparatus, of alcohols of a fuel, wherein the detection accuracy of the concentration of methanol can be enhanced. CONSTITUTION:A fuel with which methanol has been mixed is made to flow through an insulated pipe 1; a conductive electrode 3 is installed inside the insulated pipe 1; a single-layer winding coil 4 is wound on the outside of the insulated pipe 1 so as to be faced with the conductive electrode 3; a variable capacitor 9 is connected in parallel with the single-layer winding coil 4; a parallel-resonant circuit is formed. The capacity of the variable capacitor 9 is made variable in such a way that the resonance frequency of a prescribed fuel having a permittivity within a range of 10 to 25 becomes a definite value. The methanol can be detected with high accuracy irrespective of an irregularity in the accuracy of a sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in engines for automobiles and the like, for example, alcohols of fuels for detecting the concentration of alcohols from a fuel obtained by mixing alcohols such as methanol with gasoline or light oil. The present invention relates to a concentration detecting device.

[0002]

2. Description of the Related Art In recent years, fuels in which methanol is mixed with gasoline have been introduced for automobiles in various countries such as the United States and Europe in order to reduce the consumption of oil and the air pollution caused by automobile exhaust gas. is there. When such a methanol mixed fuel is used as it is in an engine matched to the air-fuel ratio of gasoline fuel, the theoretical air-fuel ratio of methanol is smaller than that of gasoline, so the air-fuel ratio becomes lean,
Since the operation becomes difficult, the methanol content in the methanol mixed fuel is detected, and the air-fuel ratio, the ignition timing, etc. are adjusted according to the detected values.

Conventionally, as a method of detecting the methanol content as described above, a method of detecting the dielectric constant of the methanol mixed fuel and a method of detecting the refractive index have been mainly proposed. Among these methods, the inventors have applied for a patent as Japanese Patent Application No. 03-022488 as a method for detecting the dielectric constant. Hereinafter, this method will be described with reference to the drawings.

FIG. 11 is a configuration diagram showing the configuration of an embodiment described in Japanese Patent Application No. 03-022488, that is, a configuration diagram of a fuel dielectric constant detecting device. This FIG.
In the figure, C is a sensor part, 1 is an inner cylindrical insulating tube formed of an insulator such as ceramic or oil-resistant plastic, and the fuel is guided into the inside, and 3 is provided inside the insulating tube 1, and its cylindrical surface Is a cylindrical conductive electrode that is substantially parallel to the columnar surface of the insulating tube 1 and is coaxial with the insulating tube 1, and 4 is a unitary electrode wound at a position facing the conductive electrode 3 outside the insulating tube 1. It is a layer winding coil. Also, 4a and 4b are single layer winding coils 4
2 is a fuel passage formed between the inner peripheral surface of the single-layer winding coil 4 and the outer peripheral surface of the conductive electrode 3 by separating the tube wall of the insulating tube 1.

Reference numeral 5 denotes a flange to which the conductive electrode 3 is attached and which is joined to the insulating tube 1 through the fuel seal 7 to form a fuel container as a whole. Here, the flange 5 is formed integrally with the conductive electrode 3. 6 is a nipple that guides fuel to the fuel passage 2. Through this nipple 6, fuel enters the fuel passage 2 in the direction of arrow A1 and is discharged in the direction of arrow A2.

On the other hand, B indicates a detection circuit section. Reference numeral 10 in the detection circuit section B is a series resistance ( _RS is a resistance value) which is connected to the lead 4a of the single-layer winding coil 4 to form a series circuit, and 11 is a signal at both ends of the series resistance 10. 0 degree phase comparator, 12 is a 0 degree phase comparator 11
Is inputted, and a low-pass filter for extracting a low-pass component of the output, 13 is a comparison integral for comparing and integrating the output of the low-pass filter 12 and a predetermined reference voltage V _ref corresponding to a phase of 0 degree. , 14 is a voltage-controlled oscillator to which the output of the comparator / integrator 13 is connected, 15 is an amplifier for amplifying the output of the voltage-controlled oscillator 14, and a series circuit of the series resistor 10 and the single-layer winding coil 4 and the 0-degree phase comparator. It is an amplifier that outputs 11
Reference numeral 6 is a frequency divider for the output frequency of the voltage controlled oscillator 14.

Next, the operation of the fuel dielectric constant detection device shown in FIG. 11 will be described. The sensor section C can be roughly replaced by an equivalent circuit of the sensor section C shown by a broken line in FIG. 3 (an equivalent circuit diagram of the sensor section in the present invention described later). This Figure 3
, L is the inductance of the single-layer winding coil 4, C _f
Is a capacitance generated between the single-layer winding coil 4 and the conductive electrode 3 which changes according to the dielectric constant ε of the fuel in the fuel passage 2,
C _S is the capacitance of the insulating tube 1 that protects the single-layer winding coil 4 from the fuel, and C _P is the capacitance of the fuel such as the stray capacitance parasitic on the lead 4a and the input capacitance of the 0 ° phase comparator 11. It is a capacitance independent of the dielectric constant ε.

When the frequency applied to the lead 4a of the sensor section C in FIG. 11 is changed, parallel LC resonance is exhibited. That is, the parallel resonance frequency f at this time is roughly represented by the following "Equation 1" using the symbols in the figure.

[0009]

[Equation 1]

Here, K, a and b are constants determined by the shape of the sensor portion C. For example, it depends on the diameter and thickness of the insulating tube 1, the dielectric constant of the material of the insulating tube 1, the distance between the conductive electrode 3 and the single-layer winding coil 4, the self-inductance of the single-layer winding coil 4, and the like. As shown in "Equation 1", the resonance frequency f becomes lower as the permittivity ε of the fuel becomes larger. In addition, in an arbitrary mixed fuel of methanol and gasoline, the output frequency f changes roughly as shown in FIG. 12 depending on the content ratio of methanol. That is, by detecting the signal corresponding to the output frequency f, the permittivity ε of the fuel, and thus the methanol content in the methanol mixed fuel, can be detected.

The detection circuit section B in FIG. 11 is configured to detect the parallel resonance frequency f, and the description of the detection circuit section B will be continued below. In this FIG.
A high frequency signal is given from the amplifier 15 to the series circuit of the series resistor 10 and the single-layer winding coil 4 while the methanol mixed fuel is flowing in the fuel passage 2, and both ends of the series resistor 10, that is,
The high-frequency signal voltage applied to the series circuit and the high-frequency voltage signal applied to the single-layer winding coil 4 are 0-degree phase comparators 1.
It is input to 1, and the phases of both are compared.

Now, if a high frequency voltage signal having the same frequency as the resonance frequency f is applied to the series circuit of the series resistor 10 and the single-layer winding coil 4, the voltage-current phase difference of the sensor section C becomes 0 degree. Therefore, the phase difference of the high frequency voltage across the series resistor 10 is 0 degree.

On the other hand, if a high frequency voltage signal having a frequency lower than the resonance frequency f is applied to the series circuit,
Since the current-voltage phase of the sensor unit C leads 0 degrees,
The phase difference of the high frequency voltage across the series resistor 10 is greater than 0 degrees with reference to the phase of the high frequency signal applied to the series circuit. Therefore, the output of the 0-degree phase comparator 11 is converted into a DC voltage corresponding to the phase difference via the reduction filter 12, and the DC voltage and the reference voltage V _ref corresponding to the phase difference of 0 degrees are compared and integrator 13 To the voltage-controlled oscillator 14 applying a high frequency signal to the series circuit through the series resistor 10 to integrate the difference between the two and the phase locked loop. Is formed.

The voltage-controlled oscillator 14 controls the phase-locked loop so that the phase difference between the high-frequency voltage signals across the series resistor 10 becomes 0 degrees.
The oscillation frequency of 4 is always the parallel resonance frequency f. Therefore, the output frequency of the voltage controlled oscillator 14 is divided by the frequency divider 1
The frequency is divided into an appropriate frequency via 6 and the parallel resonance frequency f
A frequency output f _out corresponding to is obtained. Further, noting that the oscillation frequency of the voltage controlled oscillator 14 and the control input voltage have a one-to-one correspondence, the output of the low pass filter 12 is taken _out as the voltage output V _out .

[0015]

However, in this conventional fuel dielectric constant detecting device, the wall thickness of the insulating tube 1 and the insulating tube 1 and the conductive electrode 3 are controlled by the sensor although the methanol content does not change. Since the distance between them varies, the geometrical capacity changes, which makes it difficult to accurately detect the methanol content.

The present invention has been made in order to solve the above-mentioned problems, and provides a device for detecting the concentration of alcohols in fuel, which can always detect the content of alcohols such as methanol with high accuracy. The purpose is
Another object of the present invention is to obtain a fuel alcohol concentration detection device capable of finely adjusting the capacity of the variable capacitor and detecting the alcohol content rate with higher accuracy.

[0017]

A fuel alcohol concentration detecting device according to the present invention is provided in the middle of a fuel passage through which an alcohol mixed fuel in which a predetermined amount of alcohol is added to gasoline or light oil flows. A fuel is introduced between the conductive electrode and the conductive electrode, and a single-layer winding coil in which the pillar surfaces of the coil are arranged so as to be separated from the conductive electrode with a predetermined gap and face each other. A variable capacitor connected in parallel with the layer-wound coil and having a dielectric constant within the range of 10 to 25, the capacitance of which can be adjusted so that the resonance frequency with the single-layer coil has a constant value, and the variable capacitor and the variable capacitor. And a means for detecting the resonance frequency with the layer winding coil.

Further, a variable capacitor capable of finely adjusting the capacitance by changing the facing area of the electrodes formed on both the front and back surfaces of the substrate is provided.

[0019]

According to the present invention, the variable capacitor connected in parallel with the single-layer winding coil makes it possible to maintain a constant resonance frequency between the variable capacitor and the single-layer winding coil in a predetermined fuel having a dielectric constant in the range of 10 to 25. If the resonance frequency is detected by adjusting the capacitance of the variable capacitor so that the resonance frequency of the single-layer winding coil that depends on the permittivity of the fuel is adjusted, it corresponds to the content ratio of alcohols in the fuel. The permittivity can be detected.

Also, the capacitance is finely adjusted by changing the facing areas of the electrodes on both the front and back surfaces of the substrate of the variable capacitor, and the alcohol content can be detected with high accuracy.

[0021]

【Example】

Example 1. An embodiment of a fuel alcohol concentration detecting device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment thereof. This FIG. 1 corresponds to the conventional fuel dielectric constant detection device shown in FIG. 11, and in the description of the configuration, the same parts as those in FIG. 11 are designated by the same reference numerals. A is a sensor unit, 1 is a cylindrical insulating tube made of an insulating material such as ceramics or oil resistant plastic, and the fuel is introduced into the inside. Reference numeral 3 denotes a columnar conductive electrode which is provided inside the insulating tube 1 and has a columnar surface of the insulating tube 1 substantially parallel to the columnar surface of the insulating tube 1 and coaxial with the insulating tube 1. The conductive electrode 3 is preferably titanium, stainless steel, aluminum whose surface is alumite-treated, or the like in terms of resistance to fuel.

Reference numeral 4 denotes a single-layer winding coil wound at a position facing the conductive electrode 3 outside the insulating tube 1, 4a and 4b denote leads of the single-layer winding coil 4, and 2 denotes a single-layer winding coil 4. A fuel passage 5 formed between the inner peripheral surface and the wall of the insulating tube 1 and between the outer peripheral surface of the column of the conductive electrode 3 is attached to the conductive electrode 3 to connect the insulating tube 1 and the fuel seal 7. It is a flange that is joined via the above to form a fuel container as a whole, and here is shown an example in which the conductive electrode 3 is integrally formed.
Reference numeral 6 is a nipple that guides fuel into the fuel passage 2, and 9 is a variable capacitor connected in parallel with the single-layer winding coil 4.

The variable capacitor 9 constitutes a parallel resonance circuit with the single-layer winding coil 4, and its resonance frequency corresponds to the permittivity of fuel, that is, the methanol content. The fuel is gasoline or a methanol mixed fuel to which a predetermined amount of methanol in diesel oil is added, and the dielectric constant corresponding to the methanol content is a fuel having a dielectric constant in the range of 10 to 25. The capacitance of the variable capacitor 9 can be adjusted so that a certain value is shown.

On the other hand, the internal structure of the detection circuit section B is the same as that of the conventional example shown in FIG. 11, and the same parts as those in FIG. 11 are designated by the same reference numerals to avoid redundant description of the structure.

FIG. 2 is an external perspective view of the sensor section A, in which a part of the insulating tube 1 is cut away. 3 is an equivalent circuit of the sensor unit A, and FIG. 4 is a schematic diagram of the sensor unit A corresponding to the equivalent circuit diagram of FIG. This Figure 3,
In both figures of FIG. 4, C _P is the line capacitance and input capacitance generated in the single-layer winding coil 4, C _S is the capacitance in which the insulating material of the insulating tube 1 that protects the single-layer winding coil 4 from the fuel is a dielectric, C
_f is the capacity using the fuel as a dielectric, C _x is the variable capacitor 9
Where L is the inductance of the single-layer winding coil 4, the parallel resonance frequency f is approximately represented by the following "Equation 2",
The parallel resonance frequency f depends on the permittivity ε of the fuel, and the permittivity ε
Becomes larger, it decreases.

[0026]

[Equation 2]

The adjustment of the capacitance C _X as the variable capacitor 9 as shown in FIG. 5 makes the environment for adjustment always the same, and the composition of the predetermined fuel or the dielectric constant within the range of 10 to 25 without changing the composition. If a test liquid (eg, first-grade reagent ethanol) is introduced into the fuel passage 2 and, for example, the circuit shown in the above embodiment is used, the detection output f _out by the detection circuit B of the sensor unit A at that time is the test result. The knob 9a (see FIG. 2) of the variable capacitor 9 is adjusted so as to show the minimum value among the variations in the output of the sensor unit in the liquid, and after the adjustment, the knob 9a is fixed so as not to move with an adhesive or the like.

The test liquid has a dielectric constant of methanol 0 to 1
It is appropriate to select one within the range of ε = 10 to 25 from the range of ε = 2 to 33 corresponding to the dielectric constant of 00%. The sensor output frequency f _out is shown. That is, FIG. 6 shows the sensor output frequency with respect to the methanol content in methanol gasoline when cyclohexane having a dielectric constant ε = 2 is used as a reagent liquid, and FIG. 7 shows IPA having a dielectric constant ε = 9 as a reagent liquid. The sensor output frequency with respect to the methanol content rate in the methanol gasoline at the time of being shown is shown. FIG. 8 shows the sensor output frequency with respect to the methanol content in methanol gasoline when methanol having a dielectric constant ε = 33 is used as a reagent solution.

As is clear from FIG. 6, when cyclohexane is used as the test solution, the error of methanol 100% is maximum, and the error is 0 at 0%. Further, as shown in FIG. 8, when methanol is used as the test liquid, the error is 0 when the methanol is 100%, and the error is maximum when the methanol is 0%. Further, as shown in FIG. 7, when IPA is used as the test liquid, the error is 0 at 60% methanol, and the error becomes maximum at 0%.

As can be seen from these examples, when cyclohexane or methanol having a dielectric constant ε = 10 to 25 out of the range is used as the test liquid, the detection accuracy is small or large in the range of methanol content. Remarkably, if selected as a test liquid such as IPA or ethanol having a dielectric constant ε = 10 to 25, the methanol content can be detected accurately in the entire concentration range.

Example 2. Although the single-layer winding coil 4 of the sensor unit A and the conductive electrode 3 are coaxial with each other in the above embodiment,
It does not necessarily have to be coaxial, and it suffices that an electrostatic capacitance due to the fuel exists between the columnar surface of the single-layer winding coil 4 and the conductive electrode 3.

Example 3. Further, in the above-mentioned embodiment, the case of using for detecting the methanol content is exemplified, but it can be widely applied for detecting the alcohol content in other liquids by selecting the test liquid.

Example 4. FIG. 9 is a perspective view showing another embodiment of the variable capacitor 9. The electrodes 9c and 9d are provided on the upper and lower surfaces of the substrate 9b to form the variable capacitor. With this configuration, the electrodes 9c,
By removing the area of 9d, the electrodes 9c, 9
By changing the facing area of d, the capacitance can be changed,
The capacity can be finely adjusted, and there is an effect that the methanol content can be detected more accurately.

Example 5. FIG. 10 is a perspective view showing the configuration of still another variable capacitor 9. This FIG. 10 is similar to the case of FIG. 9, and the electrodes 9c ₁ to 9c are formed on both front and back surfaces of the substrate 9b.
_The variable capacitor 9 provided with ₄ and 9d is shown. Of the electrode, either the front and back surfaces, for example, as shown in the drawing, as shown by electrodes 9c ₁ ~9c ₄ surface, and is formed into a strip. By configuring in this way,
By cutting pattern extending from any one of a strip-shaped electrodes 9c ₁ ~9c ₄ of the facing area is changed to the electrode 9d, can be used to adjust the capacitance as in the case of FIG. 9, readily capacity The effect is that fine adjustment of can be performed. Of course, if the strip-shaped electrodes are formed on both the front and back surfaces of the substrate 9b and the strip-shaped electrodes on the opposite front and back surfaces are cut as necessary, the capacitance can be varied in the same manner as described above.

[0035]

As described above, according to the present invention, the single-layer winding coil is provided in the middle of the fuel passage with the fuel interposed between the conductive electrode and the insulating tube which is the insulating layer. A variable capacitor is connected in parallel with the variable capacitor, and the capacitance of this variable capacitor is varied to adjust the resonance frequency so that the resonance frequency shows a certain value with a predetermined fuel having a dielectric constant in the range of 10 to 25. Since it has been set, there is an effect that the content rate of alcohols can always be detected accurately.

Further, since the variable capacitor can change the capacitance by scraping off a part of the electrodes formed on both the front and back surfaces of the substrate, the capacitance can be easily fine-tuned and the alcohol content can be detected with high accuracy. effective.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel alcohol concentration detecting device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a sensor unit according to the embodiment.

FIG. 3 is an equivalent circuit diagram of a sensor unit according to the above embodiment.

FIG. 4 is a schematic diagram of a sensor unit corresponding to the equivalent circuit diagram of FIG.

FIG. 5 is a perspective view showing a configuration of a variable capacitor according to the same embodiment.

FIG. 6 is an output frequency characteristic diagram according to the same example when cyclohexane is used as a test liquid.

FIG. 7 is an output frequency characteristic diagram according to the same example when IPA is used as a test solution.

FIG. 8 is an output frequency characteristic diagram according to the above-mentioned embodiment when methanol is used as a test liquid.

FIG. 9 is a perspective view showing another embodiment of the variable capacitor used in the fuel alcohol concentration detecting device of the present invention.

FIG. 10 is a perspective view showing still another embodiment of the variable capacitor used in the fuel alcohol concentration detecting device of the present invention.

FIG. 11 is a configuration diagram of a conventional fuel dielectric constant detection device.

FIG. 12 is a characteristic diagram of methanol content versus output frequency of a conventional fuel dielectric constant detection device.

[Explanation of symbols]

1 Insulation Tube 2 Fuel Passage 3 Conductive Electrode 4 Single Layer Winding Coil 4a Lead 4b Lead 9 Variable Capacitor 9a Knob 9b Substrate 9c Electrode 9c ₁ Electrode 9c ₂ Electrode 9c ₃ Electrode 9c ₄ Electrode 9d Electrode 10 Series Resistance 11 0 Degree Phase Comparison Unit 12 Low pass filter 13 Comparative integrator 14 Voltage controlled oscillator A Sensor unit B Detection circuit unit

Claims (2)

[Claims] 1. A conductive electrode provided in the middle of a fuel passage through which a fuel obtained by adding a predetermined amount of methanol to gasoline or light oil flows, and the fuel flows between the conductive electrode, A single-layer winding coil which is arranged so as to face a column surface of the coil while being separated from the conductive electrode by a predetermined distance, and 10 to 25 connected in parallel with the single-layer winding coil.
A variable capacitor whose capacitance can be adjusted so that the resonance frequency when resonating with the single-layer winding coil with a fuel having a dielectric constant within the range is a predetermined value, and the variable capacitor and the single-layer winding coil A device for detecting the alcohol concentration of fuel, comprising: means for detecting a resonance frequency. 2. The fuel alcohol concentration detection according to claim 1, wherein the variable capacitor has electrodes formed on both front and back surfaces of a substrate, and the capacitance is varied by reducing the facing area of the electrodes. apparatus.