JP2001324370A - Level meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a level meter capable of accurately detecting a liquid level over a wide measurement range. SOLUTION: This level meter is provided with a sensor part 10 having first and second electrodes 14 facing each other for measuring a liquid level inside a container on the basis of electric resistance between the first and second measurement electrodes 14 in liquid. In the level meter, at least, the first electrode is constructed of a plurality of measurement electrodes 14-1-14-3 spaced mutually in the liquid level varying direction, and the liquid level is measured on the basis of electric resistance between these measurement electrodes and the second electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level measuring device for electrically detecting a liquid level.

[0002]

2. Description of the Related Art A liquid level measuring device is known which detects a liquid level in a container based on the electric resistance of a liquid interposed between a pair of electrodes facing each other. According to such a liquid level measuring device, the electric resistance between the electrodes changes in response to a change in the liquid level in a manner illustrated in FIG.

[0003]

As is apparent from FIG. 15, in the above-mentioned conventional liquid level measuring apparatus, after the liquid level has increased to some extent, the amount of change in the interelectrode resistance with respect to the change in the liquid level decreases. Because of the tendency, the measurement accuracy of the liquid level in the region a where the amount of change in the inter-electrode resistance is small decreases. Therefore, in this conventional liquid level measuring device, the measuring range of the liquid level from which a highly reliable measurement result can be obtained is limited. An object of the present invention is to provide a liquid level measuring device capable of accurately detecting a liquid level over a wide measuring range in view of such a situation.

[0004]

According to a first aspect of the present invention, there is provided a sensor unit in which a plurality of pairs of measuring electrodes opposed to each other are vertically arranged, and an array area of each of the pairs of measuring electrodes is used as a liquid level detection area. And a liquid level calculating means for calculating a liquid level based on the electric resistance between the pair of the measuring electrodes. According to a second aspect of the present invention, a pair of opposing compensating electrodes is added below the lowermost pair of the pairs of measuring electrodes, and the pair of compensating electrodes is immersed in a liquid. Based on the electric resistance, a liquid level measurement error due to a difference in liquid type and / or liquid temperature is corrected. In a third aspect of the present invention, the pair of measurement electrodes and the pair of compensation electrodes are each formed of a pair of concentrically arranged cylindrical electrodes having different diameters. According to a fourth aspect of the present invention, there is provided a sensor unit in which a plurality of measurement electrodes are vertically arranged, one measurement electrode facing the measurement electrodes is provided, and an arrangement area of the plurality of measurement electrodes is a liquid level detection area. And a liquid level calculating means for calculating a liquid level based on an electric resistance between the plurality of measuring electrodes and the one measuring electrode facing the measuring electrodes. According to a fifth aspect of the present invention, a compensating electrode facing the one measuring electrode is added below the lowermost electrode among the measuring electrodes, and the compensating electrode immersed in a liquid and the 1 A liquid level measurement error due to a difference in liquid type and / or liquid temperature is corrected based on the electric resistance between the two measurement electrodes. According to a sixth aspect of the present invention, a valve body is formed at a lower end of the housing having a hollow structure, the valve body being vertically movably supported by the housing and opening and closing a liquid inlet formed at a lower part of the hollow part. To apply to a liquid filling valve having a stem and a vent tube extending from a lower end of the stem for insertion into the container and communicating with a gas passage formed in the stem. A pair of measurement electrodes is provided on the vent tube.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid level measuring apparatus according to the present invention includes a sensor unit 10 and a processing unit 20 connected to the sensor unit 10, as shown in FIG.

[0006] As shown in FIG.
A pair of elongated substrates 11 made of S or the like are opposedly connected via a spacer 12, and SU
Compensation electrode 13 made of metal such as S, platinum, chromium, etc.
It has a configuration in which a measurement electrode 14-1, a second measurement electrode 14-2, and a third measurement electrode 14-3 are provided.

FIG. 3 is a plan view showing an arrangement of the electrodes 13, 14-1 to 14-3, and FIG.
It is sectional drawing by a line. As shown in FIG. 4, an electrical insulating material 15 made of alumina or the like is provided on a substrate 11, and a compensation electrode 13 and measurement electrodes 14-1 to 14-3 are provided.
Are arranged on the insulating material 15 in such a manner that the compensating electrodes 13 are located at the lowermost part and a minute space (for example, 1 mm) is formed therebetween.

Accordingly, in the sensor section 10 shown in FIG. 2, the compensation electrode 13 and the measurement electrodes 14-1 to 14-3 provided on one substrate 11 are replaced with the compensation electrode 13 and the measurement electrode 14 provided on the other substrate 11, respectively. 14-1 to 14-3. In this example, the vertical length l ₀ of the compensating electrode 13 is set to 10 mm, and the measuring electrode 14-1
Vertical width length l ₁ to l ₁ of ～14-3 is set to 25mm, respectively.

The sensor section 10 is applied to, for example, a liquid filling valve 30 shown in FIG. This liquid filling valve 30
The container 60 is filled with the liquid 60 (beverage such as cola, beer, etc.) stored in the filler bowl 40 and constitutes a part of a well-known rotary liquid filling machine together with the filler bowl 40.

The filler bowl 40 is formed of a hollow annular body and is supported so as to be rotatable about its axis. The liquid filling valve 30 is connected to the bottom of the filler bowl 40 via a liquid supply pipe 41,
Many are arranged at predetermined intervals in the circumferential direction of zero.

The liquid filling valve 30 includes a housing 31 having a hollow structure, and a stem 32 supported by the housing 31 so as to be vertically movable through a hollow portion 31a of the housing 31. The stem 32 has a valve body 3 at the lower end.
2a and a gas passage 32b along the axis thereof is formed inside. The drive cylinder 33 is connected to the upper part, and the vent tube 34 is detachably screwed to the lower end.

As shown in FIG.
Are disposed in the vent tube 34. The vent tube 34 has a lower end cut obliquely, a spreader 34a protruding from the outer peripheral surface thereof, and a vent hole 34b formed at a position above the lower end by a predetermined length.

The operation of the filling valve 30 will be described below. When the drive cylinder 33 shown in FIG. 5 extends, the stem 32 moves downward. Accordingly, as shown by a chain line in FIG. 6, a packing 32c provided on the lower surface side of the valve body 32a.
Abuts on a valve seat 31b provided on the housing 31,
The filling valve 30 is closed.

The empty container (bottle in this example) 50 is raised from a standby position to a filling position shown by a lifting means (not shown). Accordingly, the sensor unit 10 is inserted into the container 50 from the mouth of the container 50. At this time, the container 5 is guided by the centering cup 35.
0 is located on the central axis. The upper surface of the mouth of the container 50 is sealed by the packing 36.

When the container 50 is set as described above, the drive cylinder 33 shown in FIG. 5 is retracted. As a result, the valve body 32a is connected to the valve seat 3 as shown by the solid line in FIG.
1b, the liquid inlet formed in the lower part of the hollow portion 31a of the housing 31 is opened, so that the beverage 60 in the filler bowl 40 is supplied to the supply pipe 41 and the housing 31.
Flows into the container 50 through the hollow portion 31a.

At this time, the gas in the container 50 flows into the vent tube 34 through the lower end of the vent tube 34 and the vent hole 34b, and then passes through the passage 32 of the stem 32.
(b) Returned to the head space of the filler bowl 40 via the horizontal passage 31c provided in the housing 31 and the counter line 42.

As shown in FIG. 1, one of the electrodes 13, 14-1, 14-2, and 14-3 of the sensor unit 10 sequentially outputs the output of the AC power supply 22 in a time division manner via a changeover switch element 21A. The frequency is connected to, for example, 4 KHz), and the other electrodes 13, 14-1, 14-2, and 14-3 are connected to the switch element 2A interlocked with the switch element 21A.
1B, it is sequentially connected to the R-V converter 23 in a time-sharing manner.

Accordingly, the RV converter 23 has a current corresponding to the electric resistance between the opposing electrodes 13,
A current corresponding to the electric resistance between the two electrodes, a current corresponding to the electric resistance between the opposing electrodes 14-2, and a current corresponding to the electric resistance between the opposing electrodes 14-3 are sequentially input in a time-sharing manner. The R-V converter 23 is configured by a resistor bridge circuit or the like, and converts the input current to a corresponding voltage. Then, the output of the R-V converter 23 is applied to the CPU 25 via the A / D converter 24.

Now, assuming that the electric resistance between each compensation electrode 13 or each measurement electrode 14 is R, this electric resistance is given by the following equation (1). R = ρ (L / S) (1) where ρ: resistivity of the beverage L: distance between electrodes S: surface area of electrode immersed in beverage

Therefore, when the liquid level of the beverage 60 flowing into the container 50 shown in FIG. 5 reaches the lower end of each compensating electrode 13, the electric resistance between the compensating electrodes 13 decreases as the liquid level rises thereafter. In the embodiment illustrated in FIG. Then, when the liquid level rises until each compensating electrode 13 is completely immersed in the beverage 60, that is, when the liquid level based on the lower end of each compensating electrode 13 becomes equal to or more than the vertical width l _{0 of the} electrode 13, The electric resistance between the compensation electrodes 13 becomes constant.

The liquid level-resistance characteristic shown by a solid line in FIG. 7 relates to a reference beverage of a predetermined liquid type having a certain temperature,
The liquid level-resistance characteristics shown by the solid line relate to any beverage having a different temperature and / or liquid type from the reference beverage. Here, the resistivity of the reference beverage is ρ ₀ , the resistivity of the arbitrary beverage is ρ ₀ + Δρ, and the total surface area of the compensation electrode 13 is S
_{Assuming that 0} (vertical width l ₀ × width width w ₀ ), the electrical resistance R ′ between the compensating electrodes 13 in a state where each compensating electrode 13 is completely immersed in the above-mentioned arbitrary beverage is represented by the following equation (2). It is represented as R ′ = (ρ ₀ + Δρ) L / S ₀ = ρ ₀ (L / S ₀ ) + Δρ (L / S ₀ ) = R ₀ + ΔR ₀ (2) where R _{0 is} the resistivity R of the reference beverage Electric resistance based on ₀ ΔR ₀ : Electric resistance based on Δρ of resistivity difference from the reference beverage

The electric resistance R ₀ based on the resistivity ρ ₀ of the reference beverage is known in advance by experiments. Further, the shift electric resistance ΔR ₀ based on the shift Δρ of the resistivity can be obtained by subtracting the electric resistance R ₀ from the measurement result R ′ of the electric resistance based on the arbitrary beverage. In addition,
The shift resistance ΔR ₀ based on the shift Δρ of the resistivity has a positive polarity when the resistivity is shifted to a higher side, and has a negative polarity when shifted to a lower side.

Therefore, if the liquid level-resistance characteristic of the reference beverage shown in FIG. 8 is obtained in advance, the resistance (R) obtained by subtracting the electric resistance ΔR ₀ from the electric resistance R of an arbitrary beverage measured by the measuring electrode 14 is obtained. Based on (−ΔR ₀ ) and the above characteristics, the liquid level 1 of the above-mentioned arbitrary beverage can be obtained based on the lower end of the electrode 14. The electric resistance R ₀ based on the resistivity ρ ₀ of the reference beverage and the liquid level-resistance characteristic of the reference beverage are stored in the memory 26 shown in FIG. 1 in advance.

FIG. 9 shows an example of a liquid level measurement procedure executed in the CPU 25. In this procedure, first, at step 100, it is determined whether or not the compensation electrode 13 is completely immersed in the beverage.

The electric resistance between the compensating electrodes 13 is determined when the liquid level of the beverage rises to a height corresponding to the vertical width of the electrodes 13 (10 mm in this example), as indicated by the symbol A in FIG. That is, when the compensation electrode 13 is completely immersed in the beverage, the compensation electrode 13 shows a constant size. So, CP
U25 determines that the compensation electrode 13 has immersed in the beverage 60 when the electrical resistance between the compensation electrodes 13 sampled via the switch element 21B has become constant.

When the immersion of the compensation electrode 13 is determined,
The shift resistance ΔR ₀ is calculated based on the above equation (2) (step 101). Then, the electric resistance R between the measurement electrodes 14-1 (for a change in the liquid level, for example, as indicated by reference numeral B 1 in FIG. 10) It is determined whether or not the resistance obtained by subtracting the deviation resistance ΔR ₀ is equal to or more than a predetermined minimum value and equal to or less than a predetermined maximum value (step 102).

The predetermined maximum value is a resistance value between the electrodes when the liquid level of the reference beverage reaches the lower end of each measurement electrode 14-1, and the predetermined minimum value is This is the resistance value between each electrode when the liquid level of the reference beverage reaches the upper end of each measurement electrode 14-1. The maximum value and the minimum value are actually measured values, and are stored in the memory 26 shown in FIG. 1 in advance.

On the other hand, the resistance obtained by subtracting the shift resistance ΔR ₀ from the electric resistance R between the measurement electrodes 14-1 is obtained by converting the electric resistance R as the electric resistance of the reference beverage. Therefore, in step 102, it is determined whether or not the liquid level of an arbitrary beverage exists within the range of the first measurement electrode 14-1 (step 102).

If it is determined that the liquid level of the beverage exists in the range of the first measurement electrode 14-1, the switch element 2
The electrode 14-1 is determined based on the electric resistance R between the measurement electrodes 14-1 sampled via 1B, the shift resistance ΔR _0, and the liquid level-resistance characteristic of the reference beverage shown in FIG.
The liquid level 1 of the beverage is calculated with reference to the lower end of the liquid, and the liquid level from the reference point of the sensor unit 10 (in this example, the lower end of the substrate 11 shown in FIG. 2) is calculated based on the liquid level l. (Step 103).

When the liquid level calculation processing in step 103 is completed, or when it is determined in step 102 that the liquid level of the beverage 60 does not exist in the range of the first measurement electrode 14-1, the processing in step 102 It is determined whether or not the liquid level of the beverage is within the range of the second measurement electrode 14-2 based on a method according to the determination method (Step 10).
4). Then, when the liquid level of the beverage is within the range of the second measurement electrode 14-2, the liquid level calculation processing according to the liquid level calculation processing in step 103 is executed (step 10).
5). The electric resistance R between the second measurement electrodes 14-2 is:
With respect to the change of the liquid level, the liquid level changes in a manner as shown by reference numeral B2 in FIG.

When the liquid level calculation processing in step 105 is completed, or when it is determined in step 104 that the liquid level of the beverage does not exist within the range of the second measurement electrode 14-2, the liquid level of the beverage is determined. The surface is the third measurement electrode 14-3.
Is determined based on a method similar to the determination method in step 102 (step 10).
6) If the liquid level of the beverage is present within the range of the third measurement electrode 14-3, the liquid level calculation processing according to the liquid level calculation processing in step 103 is executed (step 10).
7). The electric resistance R between the third measurement electrodes 14-3 sampled via the switch element 21B changes in a manner as indicated by reference numeral B3 in FIG. 10 with respect to a change in the liquid level.

When the liquid level calculation processing in step 107 is completed, or when it is determined in step 106 that the liquid level of the beverage does not intervene between the third measurement electrodes 14-3, the liquid is transferred to the container 50. It is determined whether or not the filling of the beverage has been completed (step 108). If the filling has not been completed, the procedure returns to step 102.

In step 108, step 10
By comparing the liquid level calculated in 3, 105 and 107 with the target liquid level, it is determined whether or not the filling of the beverage is completed. Note that the target liquid level differs depending on the shape of the container 50 and the like. Therefore, the CPU 25 takes in the target liquid level corresponding to the container 50 currently used from a host computer or the like (not shown) via the communication interface 27 shown in FIG.

In the sensor section 10 of the liquid level measuring apparatus according to the above-described embodiment, a plurality of measuring electrodes 14-1 to 14-1 are arranged within the measuring range without using an electrode having a length over the measuring range.
4-3 are arranged. Therefore, according to the liquid level measuring apparatus according to this embodiment, as is clear from the comparison between FIGS. 10 and 15, the change in the liquid level in the area a shown in FIG. 15 is converted into a sufficiently large change in the electric resistance. As a result, the liquid level can be accurately detected over a wide measurement range.

It should be noted that the CPU 25 executes the above-mentioned step 108
When it is determined that the filling is completed, a filling completion signal is output to the output circuit 28 shown in FIG. As a result, a valve closing signal is output from the output circuit 28 and the cylinder 33 shown in FIG. 5 is extended, and as a result, the filling valve 30 is closed.

In the above embodiment, as shown in FIG. 1, the AC power supply 22 is used as a power supply for resistance measurement.
It is also possible to use a direct current as this power supply.
However, if an alternating current is passed through the beverage, the beverage may be electrolyzed and its dielectric constant may change. Therefore, it is desirable to employ the AC power supply 22.

By the way, instead of the sensor unit 10 shown in FIG. 2, the sensor units 10-1 to 10-4 shown in FIGS.
It is also possible to use Sensor unit 1 shown in FIG.
Reference numeral 0-1 denotes a configuration in which the compensation electrode 13 and the measurement electrodes 14-1 to 14-3 are provided on one base 11, and one long electrode 16 is provided on the other base 11. Have. The lower end of the electrode 16 has the other base 11.
The shape is set so that it is located below the lower end of the electrode 13 on the side and the upper end is located above the upper end of the electrode 14-3. The electrode 16 is directly connected to the power supply 22 shown in FIG.

In the sensor section 10-2 shown in FIG. 12, a pair of compensation electrodes 13 'and a pair of measurement electrodes 14-1' to 14-3 'are mounted on the inner peripheral surface of a cylindrical base 17 so as to face each other. Having a configuration. In this sensor unit 10-2, each electrode 1
3 'and 14-1' to 14-3 'have curved shapes, and these electrodes are arranged along the inner peripheral surface of the base 17.

The sensor unit 10-3 shown in FIG.
Electrodes 13 'and 14-1' to 14-
Instead of 3 ', one long electrode 1 having a curved shape
6 'is attached. Note that the electrode 16 'corresponds to the electrode 16 shown in FIG.

The sensor section 10-4 shown in FIG. 14 has a cylindrical compensating electrode 13 "and measuring electrodes 14-1" to 14-3 "attached to the inner peripheral surface of a cylindrical base 17, and the base 17 has An electrode mounting rod 18 is provided along the center axis, and the electrodes 13 ″ and 14
Small diameter cylindrical compensation electrode 1 facing -1 "to 14-3"
9 and cylindrical measurement electrodes 19-1 to 19-3. Of course, instead of mounting the electrodes 19 and 19-1 to 19-3 separated from each other, it is also possible to provide one electrode covering the entire circumference of the electrode mounting rod 18, and furthermore, it is also possible to provide one electrode mounting rod 1
It is also possible to use 8 itself as an electrode.

The vent tube 34 shown in FIG. 6 may be used as the base 17 shown in FIGS. In addition, the arrangement number of the measurement electrodes 14 in each sensor unit described above can be appropriately increased or decreased according to the size of the measurement range. The liquid level measuring device according to the above embodiment is applied to the filling valve 30 of the rotary beverage filling machine, but can of course be effectively applied to the detection of the liquid level in an ordinary tank or the like.

[0042]

According to the liquid level measuring apparatus of the present invention, there is provided a sensor section in which a plurality of pairs of measuring electrodes opposed to each other are arranged up and down. Since the liquid level is calculated based on the liquid level, the liquid level can be accurately detected over a wide measurement range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a liquid level measuring device according to the present invention.

FIG. 2 is a perspective view showing the appearance of a sensor unit.

FIG. 3 is a plan view showing an arrangement of electrodes in a sensor unit.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a sectional view of a main part of the rotary liquid filling machine.

FIG. 6 is an enlarged sectional view showing an embodiment in which a sensor unit is mounted on a filling valve.

FIG. 7 is a graph showing an example of liquid level-resistance characteristics of a reference beverage and an optional beverage.

FIG. 8 is a graph showing a method for obtaining a liquid level of an arbitrary beverage based on a liquid level-resistance characteristic of a reference beverage.

FIG. 9 is a flowchart showing an example of a liquid level detection procedure executed by the CPU shown in FIG. 1;

FIG. 10 is a graph illustrating a liquid level-resistance characteristic of each electrode of the sensor unit.

FIG. 11 is a longitudinal sectional view showing a first modification of the sensor unit.

FIG. 12 is a longitudinal sectional view showing a second modification of the sensor unit.

FIG. 13 is a longitudinal sectional view showing a third modification of the sensor unit.

FIG. 14 is a longitudinal sectional view showing a fourth modification of the sensor unit.

FIG. 15 is a graph illustrating a liquid level-resistance characteristic in a conventional liquid level measuring device.

[Explanation of symbols]

10, 10-1 to 10-4 Sensor unit 11, 17 Base 13, 13 ', 13 ", 19 Compensation electrodes 14-1 to 14-3, 14-1' to 14-3 ', 14-
1 "to 14-3", 19-1 to 19-3 Measurement electrode 16, 16 'Elongated electrode 18 Electrode support rod 20 Processing unit 21A, 21B Switch element 22 AC power supply 25 CPU 26 Memory 30 Filling valve 34 Vent tube 40 Filler bowl 50 Container 60 Beverage

Continuation of the front page (72) Inventor Sadahiro Abe 1 Nagoya Laboratory, Iwazuka-cho, Nakamura-ku, Nagoya City, Aichi Prefecture Inside the Nagoya Research Laboratory, Mitsubishi Heavy Industries, Ltd. No. 1 F term in Nagoya Machinery Works, Mitsubishi Heavy Industries, Ltd. (reference) 2F014 AA04 AA07 AB01 AB02 AB03 DA02 3E079 AA02 AB01 CC01 CD15 DD07 DD33 DD37 DD50 FF03 FF11

Claims (6)

[Claims] 1. A sensor unit in which a plurality of pairs of measurement electrodes opposed to each other are vertically arranged, and an arrangement area of each of the pairs of measurement electrodes is used as a liquid level detection area; A liquid level measuring device comprising: liquid level calculating means for calculating a liquid level based on resistance. 2. A pair of opposing compensating electrodes is added below an electrode pair located at a lowermost stage of the pair of measuring electrodes,
2. A liquid level measurement error due to a difference in liquid type and / or liquid temperature is corrected based on an electric resistance between the pair of compensating electrodes in a state of being immersed in the liquid. A liquid level measuring device according to item 1. 3. The liquid level measuring device according to claim 2, wherein the pair of measuring electrodes and the pair of compensating electrodes are each formed of a pair of cylindrical electrodes having different diameters concentrically arranged. 4. A sensor unit in which a plurality of measurement electrodes are vertically arranged, one measurement electrode facing the measurement electrodes is provided, and an arrangement area of the plurality of measurement electrodes is used as a liquid level detection area. A liquid level measuring device comprising: liquid level calculating means for calculating a liquid level based on electric resistance between the plurality of measuring electrodes and the one measuring electrode facing the measuring electrodes. 5. A compensating electrode facing the one measuring electrode is added below an electrode located at the lowest stage among the measuring electrodes, and the compensating electrode immersed in a liquid and the one Based on the electrical resistance between the measuring electrode and the liquid type and / or
5. The liquid level measuring device according to claim 4, wherein a liquid level measurement error due to a difference in liquid temperature is corrected. 6. A valve body which is supported by the housing so as to be able to move up and down and penetrates through a hollow portion of a housing having a hollow structure and which opens and closes a liquid inlet formed at a lower portion of the hollow portion is formed at a lower end portion. In order to be applied to a liquid filling valve having a stem and a vent tube extending from a lower end of the stem to be inserted into the container and communicating with a gas passage formed in the stem, The liquid level measuring device according to claim 1, wherein a pair of electrodes is provided on the vent tube.