JP2950082B2 - Liquid permittivity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid dielectric constant measuring apparatus for measuring the methanol content of a methanol mixed fuel supplied to a combustor of an automobile engine or the like from the dielectric constant of the fuel.

[0002]

2. Description of the Related Art In recent years, gasoline mixed with methanol has been introduced as a vehicle fuel in order to reduce oil consumption and reduce air pollution caused by vehicle exhaust gas. If such a methanol-mixed fuel is used in an engine adapted to the air-fuel ratio of gasoline fuel, the actual air-fuel ratio becomes lean (lean) because methanol has a smaller stoichiometric air-fuel ratio than gasoline, making it difficult to operate. Become. Therefore, conventionally, the methanol content in the methanol-mixed fuel was measured, and the air-fuel ratio, the ignition timing, and the like were adjusted according to the measured value.

In order to measure the methanol content, there have been proposed a technique for detecting the dielectric constant of a methanol-mixed fuel and a technique for measuring the refractive index. The inventors have disclosed a method of measuring a dielectric constant among these methods as disclosed in Japanese Patent Application No. 3-2248.
No. 8 is proposed. Hereinafter, a method of measuring the dielectric constant will be described with reference to FIGS.

FIG. 9 is a block diagram of a conventional permittivity measuring device, and FIG. 10 is a diagram showing an equivalent circuit of a sensor section of the conventional permittivity measuring device. FIG. 9A is an electric circuit diagram, and FIG. ) Is a configuration diagram. FIG. 11 is a graph showing the output characteristics of a conventional permittivity measuring device. In these figures, reference numeral 1 denotes a conventional permittivity measuring device, which comprises a sensor section 3 to which fuel 2 is supplied and a measuring circuit section 4. As the fuel 2, a methanol mixed fuel obtained by mixing methanol with gasoline is used.

[0005] The sensor portion 3 is a cylindrical insulating tube 5 having a bottom and a conductive material which is attached to the insulating tube 5 so as to close the opening of the insulating tube 5 and forms a fuel container together with the insulating tube 5. A flange 6, an electrode 7 made of a conductive material inserted into the inside of the insulating tube 5, a coil 8 attached to a position on the outer peripheral portion of the insulating tube 5 facing the electrode 7, Are formed from two nipples 9 and the like for passing the fuel 2 through the hollow portion.

[0006] The insulating tube 5 is integrally formed of an insulator such as ceramic or oil-resistant plastic. The flange 6 is formed in a substantially disk shape so as to close the opening of the insulating tube 5, and two nipples 9 are fixedly secured at positions on the outer peripheral side of the insulating tube 5. Further, a fuel seal 10 is interposed between the flange 6 and the insulating pipe 5, so that the fuel 2 does not leak out of the insulating pipe. The flange 6 is grounded via a lead wire 6a.

The electrode 7 is formed in a substantially cylindrical shape by a conductive material, and is formed integrally with the flange 6. The electrode 7 is arranged so that its axis coincides with the axis of the insulating tube 5, and the interval between the outer peripheral surface and the inner peripheral surface of the insulating tube 5 is the same at both ends in the axial direction. ing. That is, the fuel passage 11 is provided between the insulating pipe 5 and the electrode 7.
Is formed.

The coil 8 is a single-layer wound coil and is wound around the outer circumference of the insulating tube 5. The lead 8a on the excitation side is connected to the measurement circuit section 4 described later, and the lead 8b on the side opposite to the excitation side is grounded.

The measuring circuit section 4 is connected to a lead 8a of the coil 8 to form a series circuit with the coil 8, and a signal to which signals at both ends of the series resistor 12 are applied.
The phase comparator 13, a low-pass filter 14 connected to the output side of the 0 ° phase comparator 13, and a predetermined reference voltage V corresponding to the output of the low-pass filter 14 and the phase 0 °
a reference integrator 15 to which ref is applied, a voltage controlled oscillator 16 to which the output of the comparison integrator 15 is applied, an output amplifier 17 to amplify the output of the voltage controlled oscillator 16 and apply the amplified output to the series circuit; And a frequency divider 18 for the output frequency of the voltage controlled oscillator 16.

Next, the operation of the dielectric constant measuring apparatus configured as described above will be described. The sensor unit 3 shown in FIG. 9 is schematically constituted by an LC parallel equivalent circuit as shown in FIG. In FIG. 10B, L is the coil 8
, Cf is the capacitance generated between the coil 8 and the electrode 7 that changes according to the dielectric constant ε of the fuel 2 in the fuel passage 11, and Cs is the insulation of the insulating tube 5 that protects the coil 8 from the fuel 2. Capacitor with substance as dielectric, Cp is lead 8a
Are the capacitances independent of the dielectric constant ε of the fuel 2, such as the stray capacitance parasitic to. Here, when the frequency of the high-frequency signal applied to the lead 8a of the sensor section 3 is changed, parallel LC resonance is exhibited. That is, the parallel resonance frequency f at this time is generally expressed by the following equation (1) using the symbols in FIG.

[0011]

(Equation 1) In the equation (1), a and b are constants determined by the shape of the sensor unit 3. For example, it depends on the diameter and thickness of the insulating tube 5, the geometric capacity determined by the distance between the electrode 7 and the coil 8, the dielectric constant of the material of the insulating tube 5, and the self-inductance of the coil 8. Since the resonance frequency f depends on the dielectric constant ε of the fuel 2 as shown in the above equation (1), the resonance frequency f decreases as the dielectric constant ε of the fuel 2 increases. In addition, in a mixed fuel in which methanol and gasoline are mixed at an arbitrary ratio, the resonance frequency f depends on the content of methanol.
Is known to change. This is shown in FIG.
As can be seen from the figure, the output frequency (resonance frequency) decreases as the methanol content increases.
That is, by detecting a signal corresponding to the resonance frequency f, the methanol content can be measured based on the dielectric constant ε of the fuel 2.

The measuring circuit section 4 is configured to detect the above-mentioned resonance frequency f. Hereinafter, the operation of the measurement circuit unit 4 will be described in more detail. First, a high-frequency signal is applied from the amplifier 17 to the series circuit of the resistor 12 and the coil 8 with the methanol mixed fuel 2 flowing in the fuel passage 11, and is applied to the signal at both ends of the resistor 12, in other words, to the series circuit. The high-frequency voltage signal and the high-frequency voltage signal applied to the coil 8 are input to the 0 ° phase comparator 13, where the phases of the two are compared.

Here, if a high-frequency voltage signal having a frequency equal to the resonance frequency f is applied to the series circuit, the current-voltage phase of the sensor section 3 becomes 0 °. The phase difference is 0 °. 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, the current-voltage phase of the sensor unit 3 is advanced by more than 0 °. Is greater than 0 ° with respect to the phase of the high-frequency signal applied to the series circuit.

For this reason, the output of the 0 ° phase comparator 13 is converted into a DC voltage corresponding to a phase difference via a low-pass filter 14, and this DC voltage and a DC voltage Vref corresponding to a phase difference of 0 ° are converted. It is input to a comparison integrator 15 to integrate the difference therebetween, and the output of the comparison integrator 15 is connected to the series circuit by a resistor 1.
Voltage-controlled oscillator 1 applying a high-frequency signal via
6, a phase locked loop is formed.

The voltage controlled oscillator 16 controls the phase difference between the high frequency voltage signals at both ends of the resistor 12 to be 0 ° by the phase locked loop, so that the oscillation frequency of the voltage controlled oscillator 16 is always the parallel frequency. It becomes the resonance frequency f. Therefore, the output frequency of the voltage controlled oscillator 16 is divided to an appropriate frequency via the frequency divider 18 to obtain the parallel resonance frequency f
Is obtained. Further, if attention is paid to the fact that the oscillation frequency of the voltage controlled oscillator 16 and the control input voltage correspond one to one, the output of the low-pass filter 14 can be taken out as the voltage output Vout.

[0016]

However, in the conventional dielectric constant measuring device constructed as described above, if the different sensor is used as shown in FIG. There was a problem that would change. This depends on the insulation tube 5 depending on the sensor.
This is because the geometric capacitance changes due to variations in the wall thickness and the distance between the insulating tube 5 and the electrode 7.

That is, the output of the sensor tends to fluctuate easily, and it has been difficult to accurately measure the methanol content.

The present invention has been made to solve such a problem, and an object of the present invention is to enable fine adjustment of sensor output for each sensor.

[0019]

SUMMARY OF THE INVENTION According to the present invention, there is provided a dielectric material for a liquid.
The rate measuring device is configured to coil an insulating member having a coil and an electrode.
To be relatively movable in the axial direction of the
In the direction of movement in the part facing the excitation side of the coil
The capacitance adjustment wall close to the insulating member
It is formed.

[0020]

According to the present invention, the electrode is moved with respect to the insulating member.
Change the distance between the capacitance adjustment wall and the excitation side of the coil.
The sensor part using the liquid to be measured as a dielectric
Changes in capacitance.

[0021]

[0022]

[0023]

EXAMPLE 1 An example of a dielectric constant measuring apparatus will be described in detail with reference to FIGS. FIG. 1 is a configuration diagram of a dielectric constant measuring apparatus , and FIG .
FIG. 4 is a perspective view of a sensor unit of the rate measuring device , in which main parts are cut away and drawn. 3A and 3B are diagrams for explaining the output deviation when the distance between the capacitance adjusting member and the coil is changed. FIG. 3A shows the position of the capacitance adjusting member, and FIG. It is a graph which shows the difference of the output deviation for every position. FIG. 4 is a graph showing output characteristics before and after adjustment of the permittivity measuring device . In these drawings, the same or equivalent members as those described in FIGS. 9 to 11 are denoted by the same reference numerals, and detailed description is omitted.

In FIG. 1, reference numeral 21 denotes a dielectric constant measuring device . This dielectric constant measuring device 21 is configured similarly to the conventional dielectric constant measuring device 1 shown in FIG. 9 except that the structure of the sensor section 3 is different. In the sensor section 3 of the dielectric constant measuring device 21, the electrode 7 is formed in a cylindrical shape with a bottom, and the coil 8 is disposed inside the electrode 7. The opening of the electrode 7 is closed by the flange 6.

As the material of the electrode 7, titanium, stainless steel, aluminum whose surface is anodized, and the like are preferable in terms of resistance to the fuel 2.

The coil 8 is embedded in a columnar insulator 22 supported and fixed to the flange 6 and inserted together with the columnar insulator 22 into the electrode 7. In addition,
The cylindrical insulator 22 is molded with the coil 8 inserted so that a thin wall 22a having a uniform thickness is formed between the outer peripheral surface and the coil 8. The columnar insulator 22 is disposed so that the axis is aligned with the bottomed cylindrical electrode 7, and the distance between the outer peripheral surface and the inner peripheral surface of the electrode 7 is equal at both axial ends. It is configured to be. That is, the electrode 7 faces the coil 8, and the fuel passage 11 is provided between the electrode 7 and the columnar insulator 22. The coil 8 is connected to a lead 8a.
Is configured such that the excitation side connected to the upper side in FIG.

Reference numeral 23 denotes a columnar conductor as a capacitance adjusting member . The columnar conductor 23 is formed in a substantially cylindrical shape by using a conductive material, and has a threaded portion 23 a screwed to the electrode 7.
And a columnar portion 23b formed integrally with the screw portion 23a.
It is composed of And, this columnar conductor 23
Is mounted on the peripheral wall on the opening side of the electrode 7 so as to penetrate the peripheral wall in the radial direction. This mounting position is a portion facing a portion on the excitation side of the coil 8. The columnar portion 23b is slidably fitted into the through hole 24 of the electrode 7. A fuel seal 10 is interposed in the fitting portion to prevent the fuel 2 from leaking.

That is, the columnar conductor 23 is electrically connected to the electrode 7 by contact, and the screw 23a is screwed into the screw hole of the electrode 7 so that the column 23b approaches the excitation side of the coil 8 from the outside in the radial direction. Conversely, by loosening the screw portion 23a, the columnar portion 23b is separated from the excitation side portion of the coil 8.

Since the measuring circuit section 4 has no difference from the conventional one, only the schematic configuration will be described here. That is, the methanol mixed fuel 2 is
, The high-frequency signal supplied from the amplifier 17 to the series circuit of the resistor 12 and the coil 8 and the high-frequency signal applied to the coil 8 are input to the 0 ° phase comparator 13 and compared in phase. The output of the 0 ° phase comparator 13 is converted into a DC voltage corresponding to a phase difference via a reduction pass filter 14, and a DC voltage V corresponding to a phase difference of 0 ° is obtained.
ref is input to the comparison integrator 15 to integrate the difference between the two, and the output of the comparison integrator 15 is input to the voltage controlled oscillator 16 to form a phase locked loop. The voltage controlled oscillator 16 controls the phase difference between the high-frequency voltage signals at both ends of the resistor 12 to be 0 ° by the synchronous loop, so that the oscillation frequency of the voltage controlled oscillator 16 always becomes the parallel resonance frequency f.

Next, the operation of the dielectric constant measuring device 21 configured as described above will be described. In adjusting the capacitance of the sensor section 3, the distance between the columnar portion 23b and the coil 8 is changed by changing the screwing amount of the columnar conductor 23 into the electrode 7. That is, as shown in FIG. 3, by increasing the dimension x of the columnar conductor 23 projecting inward from the inner peripheral surface of the electrode 7, the output deviation gradually decreases, and the resonance frequency f decreases. For this reason,
As the distance is reduced, the capacitance (Cf) of the sensor unit 3 using the fuel 2 as a dielectric is increased, and the resonance frequency f is reduced according to the equation (1).

In FIG. 3, the columnar conductor 23 is attached near the ground side (P1) of the coil 8, the coil conductor 8 is attached near the excitation side (P3) of the coil 8, and the middle (P2). It also shows how the output deviation changes for each of the cases where the device is mounted. That is, at P1, the output deviation hardly changes and maintains a constant value even when the protrusion dimension x of the columnar conductor 8 is changed. The output deviation increases as the position approaches the excitation side (P3). This is because the electric field on the excitation side is stronger than that on the ground side. Based on this, the mounting position of the columnar conductor 23 was set to a position close to the excitation side of the coil 8. In order to widen the output adjustment range in the sensor section, the area of the tip surface of the columnar section 23b may be increased.

FIG. 4 shows the adjustment result. FIG. 2 is a graph showing the output of the sensor unit adjusted by the adjustment liquid having the dielectric constant at the α point. In FIG. 2, two sensor units, a sensor 1 indicated by a dashed line and a sensor 2 indicated by a broken line, were adjusted. The results are shown. As can be seen from the figure, the detection accuracy is improved and the variation between the sensor units is reduced as compared with before the adjustment.

In the adjustment of the sensor unit, the environment to be adjusted is always the same for each sensor unit, and the components are not changed.
The fuel 2 or the reagent (for example, a primary reagent ethanol) having a dielectric constant in the range of 5 is introduced into the fuel passage 11 as an adjusting liquid. And if, for example, the circuit described above is used,
Adjusted to sensor output fout at that time becomes an output f ₀ as a reference in the adjustment liquid, after adjustment, is fixed so as not to move the columnar conductor 23 to the electrode 7 by an adhesive or the like.

The adjusting liquid has a dielectric constant of 0
It is appropriate to select one in the range of ε = 10 to 25 from the range of ε = 2 to 33 corresponding to a dielectric constant of 〜100%. FIG. 4 shows the relationship between the methanol output rate and the sensor output frequency fout in the case of using ethanol with ε = 25 as the adjusting liquid α. If the adjustment liquid is IPA, ethanol or the like within the range of ε = 10 to 25, the output error with respect to the full scale of the output is minimized in the entire concentration range.

Therefore, when the columnar conductor 23 is brought into contact with or separated from the coil 8, the capacitance of the sensor unit 3 using the fuel 2 as a dielectric material changes. Can be easily corrected even if the variation occurs.

Example 2 In the above example , the columnar conductor as the capacitance adjusting member is provided so as to be able to advance and retreat in the radial direction of the coil. However, as shown in FIG. 5, it can be provided so as to be movable in the axial direction of the coil. .

FIG. 5 is a sectional view showing another example of the sensor section in which the moving direction of the capacitance adjusting member is changed. In the figure, the same or equivalent members as those described in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. In this example , a ring-shaped conductor 31 is provided instead of the columnar conductor. This ring-shaped conductor 31
The conductive material is formed in an annular shape, and is disposed coaxially with the electrode 7, the coil 8, and the like on the inner periphery of the electrode 7. The ring-shaped conductor 31 has an outer diameter of a bottomed cylindrical electrode 7.
Is set to a dimension that slides on the inner peripheral surface of the electrode 7, and is movable in the axial direction while sliding on the inner peripheral surface of the electrode 7. That is, the ring-shaped conductor 31 is electrically connected to the electrode 7 by contact.

Reference numeral 32 denotes a round bar for adjusting the position of the ring-shaped conductor 31, which is fixed to the electrode 7 by a fixing screw 33. The fixing screw 33 extends along the axial direction of the electrode 7 and is screwed to the outer periphery of the electrode 7. That is, by tightening or loosening the fixing screw 33 to the electrode 7, the ring-shaped conductor 31 is connected to the fuel passage 11.
The inside moves up and down in the figure. In other words, the ring-shaped conductor 31 moves back and forth with respect to the excitation side portion of the coil 8.

The sensor unit 3 utilizes the fact that the change rate of the capacitance is different between the ground side and the excitation side even if the opposing distance with the coil peripheral surface is not changed. This can be understood from the graph of FIG. 3 showing the output deviation with respect to the change of the facing distance x. For example, assuming that the thickness of the ring-shaped conductor 31 is x, the positions thereof are P1 and P1.
The output deviation can be increased by changing to 2, P3. Further, in order to change the adjustment range of the sensor output, a structure may be adopted in which the inner peripheral surface of the ring-shaped conductor 31 approaches the coil 8.

Example 3 In Examples 1 and 2 described above, an example is shown in which the electrodes and coils are formed in a substantially cylindrical shape and are arranged coaxially. However, as shown in FIG. 6, they are formed in a substantially disk shape and face each other. You can also. FIG. 6 is a cross-sectional view showing another example of the sensor unit in which a substantially disc-shaped electrode is opposed to a disc-shaped coil. In the figure, the same or equivalent members as those described in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The coil 8 shown in FIG. 6 is formed in a disk shape on the coil substrate 34, and is integrally formed with the coil substrate 34 on a disk-shaped insulator 35 made of an insulator such as plastic. This molding is performed so that a thin wall 35a having a uniform thickness is formed between the coil 8 and the surface of the disc-shaped insulator 35. Further, the coil 8 has an excitation side located at the center of the disk,
The outer peripheral side is formed to be the ground side. That is, the lead 8a connected to the measurement circuit unit (not shown) is derived from the center of the coil 8, and the grounded lead 8b is derived from the outer periphery of the coil.
8b penetrates through the coil substrate 34 and the disc-shaped insulator 35 and is led out.

The disc-shaped insulator 35 containing the coil 8 is attached so as to close the lower opening of the cylindrical plastic case 36. The cylindrical container-shaped plastic case 36 has a bottom surface (the upper side in the figure).
The electrode 7 is insert molded, and a nipple 36a for guiding the fuel 2 to the fuel passage 11 is integrally molded. And this cylindrical container-shaped plastic case 36
The disc-shaped insulator 35 is fixed to the lower opening portion of. This fixation is performed by the cylindrical plastic case 36.
After fitting the disc shape into the lip and positioning it, the opening edge of the lower opening portion is melted and caulked. Further, it can be fixed by welding by ultrasonic welding or the like. In this case, the material of the cylindrical plastic case 36 is a disc-shaped insulator 3
The same thing as 5 may be used. In addition, the disc-shaped insulator 3
A fuel seal 10 is interposed between the plastic case 5 and the cylindrical plastic case 36 in order to prevent the fuel 2 from leaking.

The disk-shaped electrode 7 used in this example has a structure in which a disk portion faces the disk-shaped coil 8, and a boss portion 38 for mounting a columnar conductor 37 as a capacitance adjusting member at the center. Are formed. The columnar conductor 37 is also formed of a conductive material, and has a threaded portion 37 a that is screwed into the inner peripheral thread of the boss portion 38, a columnar portion 37 b that is in sliding contact with the inner peripheral surface of the boss portion 38, and a fuel that penetrates through the electrode 7. The conductive rod 37c faces the passage 11. The columnar conductor 37 is also electrically connected to the electrode 7 by contact.

Therefore, by screwing or loosening the columnar conductor 37 into or out of the electrode 7, the conductive rod 37c comes into contact with or separates from the excitation side portion of the coil 8, and the electrostatic force of the sensor unit 3 using the fuel 2 as a dielectric material. Since the capacitance changes, it is possible to easily correct even if the capacitance of the manufactured sensor unit 3 varies.

In order to change the adjustment range of the sensor output, the area of the tip end surface of the conductive rod 37c of the columnar conductor 37 may be changed as in the example shown in FIG.

FIG. 7 shows a dielectric constant measuring apparatus according to the present invention.
This will be described in detail. First Embodiment A dielectric constant measuring apparatus shown in FIG.
It has a structure that changes the distance between the two so that it can move freely
You.

FIG. 7 is a sectional view showing a sensor section of the dielectric constant measuring apparatus according to the present invention . In the figure, the same or equivalent members as those described in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. The electrode 7 shown in FIG. 7 is formed in a cylindrical shape with a bottom, and a columnar insulator 22 is mounted in a hollow portion thereof. This columnar insulator 22
A coil 8 is buried by integral molding, and one end is screwed into a screw hole 41 formed in the bottom of the electrode 7, and the other end is slidably fitted into an opening of the electrode 7. The fuel seal 10 is interposed in this fitting portion. The coil 8 is buried so that a thin wall 22 a having a uniform thickness is formed between the coil 8 and the outer peripheral surface of the insulator 22. When the columnar insulator 22 is mounted on the electrode 7, the coil 8 is connected to the electrode 7. The structure is such that the axes coincide.

That is, the columnar insulator 22 is
1, a large-diameter portion 43 that closes the opening of the electrode 7, a small-diameter portion 44 between the screw portion 42 and the large-diameter portion 43 and in which the coil 8 is embedded. Is formed from. The small diameter portion 44 is formed thinner than other portions so that the fuel passage 11 is formed between the small diameter portion 44 and the inner peripheral surface of the electrode 7. Further, both ends in the axial direction of the small diameter portion 44 are
It is tapered so that the diameter gradually increases as the distance from the coil-embedded portion increases. The inclination angle of the tapered portion is gentler on the screw portion 42 side than on the large diameter portion 43 side.

That is, the columnar insulator 22 is
By screwing 2 into the screw hole 41, the electrode 7 moves to the right in the figure along the axial direction with respect to the electrode 7, and moves to the left by loosening the electrode 7. A lead 8a for connecting the coil 8 to a measurement circuit (not shown) passes through the screw portion 42 and is led out. A lead 8b for grounding the coil 8 is led out through the large-diameter portion 43 and led out. ing. For this reason, the excitation side of the coil 8 is located near the screw portion 42.

The portion of the electrode 7 facing the excitation side of the coil 8 is provided on the excitation side portion of the coil 8 when the cylindrical insulator 22 is moved to the screwing side (right side in the figure) with respect to the electrode 7. The slope 45 gradually narrows the distance between
Are formed. This inclined surface 45 constitutes the capacitance adjusting wall according to the present invention .

In the sensor section 3 thus configured, the columnar insulator 22 is screwed into the electrode 7 and moved with respect to the electrode 7, whereby the excitation side portion of the coil 8 and the electrode 7 are formed on the inclined surface 45. The capacitance can be increased from the relationship that the facing distance becomes narrower.

Therefore, by screwing or loosening the columnar insulator 22 with respect to the electrode 7, the capacitance of the sensor section 3 changes, and the sensor output can be adjusted. For this reason, even if a large number of manufactured sensor units 3 have a variation in capacitance, it can be easily corrected.

The adjustment range of the sensor output can be changed by changing the inclination angle and the diameter of the inclined surface 45 of the electrode 7.

Second Embodiment In the first embodiment, an example is shown in which the electrode is formed in a cylindrical shape and a coil is inserted therein. However, as shown in FIG. 8, the electrode is inserted inside the coil. It can also be a structure that does. FIG. 8 is a sectional view showing another embodiment of the sensor unit in which the electrodes are positioned inside the coil. In the figure, the same or equivalent members as those described in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 8, reference numeral 46 denotes a cylindrical insulating tube around which the coil 8 is wound. The cylindrical insulating tube 46 is provided on the cylindrical thin wall 46a around which the coil 8 is wound around the outer periphery, a nipple portion 46b, and both axial sides of the coil 8 to support the electrodes 7 described later. The bosses 46c and 46d are integrally formed. The left end of the coil 8 in the figure is an excitation side, and the other end is a ground side.

The electrode 7 used in this embodiment is formed in the shape of a round bar, and is supported by the bosses 46c and 46d so that its axis coincides with the axis of the cylindrical thin wall 46a and the coil 8. More specifically, the electrode 7 has a large-diameter portion 47 fitted into the inner peripheral portion of the boss portion 46c via the fuel seal 10, and a small-diameter portion 4 screwed into the other boss portion 46d through the shaft core of the coil 8.
The portion between the large-diameter portion 47 and the small-diameter portion 48 and facing the excitation-side portion of the coil 8 gradually becomes thinner from the large-diameter portion 47 to the small-diameter portion 48. The inclined surface 49 is formed. This inclined surface 49 constitutes the capacitance adjusting wall according to the present invention .

In the sensor section 3 thus configured, the electrode 7 is screwed into the cylindrical insulator 46 and moved with respect to the cylindrical insulator 46, so that the inclined surface 49 and the excitation-side portion of the coil 8 are connected to each other. Since the distance between the electrodes 7 and the electrodes 7 decreases, the capacitance can be increased.

Therefore, by screwing or loosening the electrode 7 with respect to the cylindrical insulator 46, the capacitance of the sensor section 3 changes and the sensor output can be adjusted. For this reason, even if a large number of manufactured sensor units 3 have a variation in capacitance, it can be easily corrected. To change the adjustment range of the sensor output,
The difference between the inclination angle and the diameter of the inclined surface 49 of the electrode 7 may be changed.

In addition, in each of the above-described embodiments, the example of measuring the methanol content of the methanol mixed fuel has been described.
The dielectric constant measuring device according to the present invention can be applied to a device for measuring the dielectric constant of a liquid other than the fuel.

[0060]

As described above, in the liquid dielectric constant measuring apparatus according to the present invention, the insulating member having the coil and the electrode are relatively movable in the axial direction of the coil, and the excitation side of the coil in the electrode member. Since a capacitance adjustment wall that is closer to the insulating member as it moves in one direction in the moving direction is formed in a portion facing the moving member, the electrode is moved with respect to the insulating member,
By changing the distance between the capacitance adjusting wall and the excitation side of the coil, the capacitance of the sensor unit using the liquid to be measured as a dielectric changes.

Therefore, even if a large number of sensor units are manufactured and the capacitance varies for each sensor unit, the capacitance can be corrected for each sensor. For this reason,
It is possible to provide a device that always accurately measures the methanol content regardless of variations between sensors.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a dielectric constant measuring device .

FIG. 2 is a perspective view of a sensor unit of the dielectric constant measuring device .

3A and 3B are diagrams for explaining an output deviation when the distance between the capacitance adjusting member and the coil is changed. FIG. 3A shows the position of the capacitance adjusting member, and FIG. Is a graph showing the difference in output deviation for each position.

FIG. 4 is a graph showing output characteristics before and after adjustment of the dielectric constant measurement device .

FIG. 5 is a cross-sectional view illustrating another example of the sensor unit in which the moving direction of the capacitance adjusting member is changed.

FIG. 6 is a cross-sectional view illustrating another example of a sensor unit in which a substantially disc-shaped electrode is opposed to a disc-shaped coil.

FIG. 7 is a sectional view showing a sensor unit of the dielectric constant measuring device according to the present invention .

FIG. 8 is a cross-sectional view showing another embodiment of the sensor unit in which an electrode is positioned inside a coil.

FIG. 9 is a configuration diagram of a conventional permittivity measuring device.

FIG. 10 is a diagram showing an equivalent circuit of a sensor unit of a conventional permittivity measuring device, wherein FIG. 10A is an electric circuit diagram, and FIG. 10B is a configuration diagram.

FIG. 11 is a graph showing output characteristics of a conventional permittivity measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 Fuel 3 Sensor part 7 Electrode 8 Coil 22 Columnar insulator 23 Columnar conductor 31 Ring-shaped conductor 35 Disk-shaped insulator 37 Columnar conductor 45 Inclined surface 46 Cylindrical insulator 49 Inclined surface

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 27/22 G01R 27/26

Claims (1)

(57) [Claims] An internal coil to which a high-frequency signal is applied;
An insulating member facing the coil and the insulating member
Between the electrode member filled with the liquid to be measured.
A sensor section, and the capacitance of the sensor section
Liquid dielectric constant measuring device for measuring the dielectric constant of
The insulating member and the electrode member along the axial direction of the coil.
To be relatively movable, and
In the direction of movement in the part facing the excitation side of the
Therefore, the capacitance adjustment that gradually narrows the gap with the insulating member
Liquid dielectric constant measuring device characterized by forming a wall
Place.