JPH05107099A - Liquid level meter - Google Patents

Abstract

PURPOSE:To improve the thermal efficiency of element heating and make response speed rapid and exact on a liquid level meter for detecting the liquid level of liquid gas and the like. CONSTITUTION:A heating element 11 is provided on a ceramic board of finely divided chips and the upper face of the heating element is covered with an insulator. A heat-sensitive body 12 is laminated on the upper face of the insulator and the upper face of the heat-sensitive body is covered with a protection film to form unit chip elements, and then specified number of the unit chip elements are connected each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level meter used for detecting the liquid level of liquefied gas such as liquid nitrogen.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed and put into practical use as means for detecting the liquid level of liquefied gas such as liquid nitrogen. First, the first method is, for example, Japanese Patent Laid-Open No. 59-
As disclosed in Japanese Patent No. 132315, a thermosensitive element is wound with a heater, and the second method is, for example, JP-A-60-
As disclosed in Japanese Unexamined Patent Publication No. 64220 and Japanese Unexamined Patent Publication No. 62-255822, there are resistors using a platinum resistor or a carbon resistor as a resistor.

[0003]

In the first method described above, since the heat sensitive element is heated by the heater wound outside, heat also flows into the liquid at the same time, and the thermal efficiency of element heating is poor. , Causing unnecessary evaporation of the liquid to be detected. The second method utilizes self-heating of the resistor to detect the presence or absence of liquid by detecting an increase or decrease in the resistance value of the resistor due to the difference in heat dissipation coefficient between liquid and gas. It is detecting. For this reason, the heating power supply that requires a large capacity and the measurement constant-current power supply that requires stability and accuracy are the same, and as a constant-current power supply, the range of voltage variation is large and the fluctuation of the current value is almost zero. Not a stable power supply is needed. In particular, in order to detect the position of the liquid surface at many measurement points, a large number of power sources are required, or when resistors are connected in series and arranged, this is an important problem. Further, when the resistors are connected in series, a change in the amount of heat that causes a change in resistance between the inside and outside the liquid, a change in the amount of loss of the liquid, and a change in element sensitivity are caused. The present invention has been made in view of the above circumstances, and simplifies the heating power supply and the measurement power supply by separating the heating unit and the liquid level detection unit of the liquid level meter element, and the thermal efficiency of element heating. It is an object of the present invention to provide an accurate liquid level meter which is good, has little liquid loss, and has a fast response speed.

[0004]

In order to achieve the above-mentioned object, the present invention provides a heating element on a subdivided chip-shaped ceramic substrate, forms an insulating film covering the upper surface of the heating element, A thermosensitive thick film was laminated on the upper surface of the film, and the upper surface of the thermosensitive thick film was covered with a protective film to form a unit chip element, and a predetermined number of the unit chip elements were connected to form a liquid level detection unit. In addition, a heat-generating resistor and a heat-sensitive thick film are formed in parallel on the same surface of a chip-shaped ceramic substrate while maintaining electrical insulation from each other, and protection that also functions to reduce the temperature distribution in the chip element is provided. Cover with a film to make a unit chip element, or provide a heating resistor on one side of a chip-shaped ceramic substrate, and further cover the upper surface with a protective film with an adiabatic function, and heat-sensitive material thickness on the other side. A unit chip element was formed by forming a film and covering it with a protective film, and a predetermined number of these unit chip elements were connected to form a liquid level detection unit.
In the above-mentioned unit chip element, a material such as ruthenium oxide-based ceramics, a nichrome alloy, a manganin alloy, or the like, whose resistance value hardly changes in the temperature range in which the liquid surface is detected is used as the heating element. In addition, the heat sensitive material is made of an oxide containing copper, manganese, nickel, iron, cobalt, etc., which has a negative temperature coefficient whose resistance value decreases with increasing temperature at a temperature near the boiling point of the liquid to be detected. Ceramics, materials such as platinum, nickel, tungsten, molybdenum, etc. having a positive temperature coefficient whose resistance value increases with increasing temperature, or various types of materials adjusted as heat sensitive bodies at temperatures near the boiling point of the liquid to be detected. The material is used. The unit chip elements are connected to each other and connected to a power source by connecting the heating elements of the elements in series, in parallel, or by a combination thereof in accordance with the resistance value, and connecting to a relatively stable constant voltage or constant current power source. The heat sensitive body is connected to a very stable measuring constant current power source with small capacity connected in series. The detection output terminals are connected from both ends.

The number of unit chip elements to be connected can be selected according to the number of liquid surface positions to be detected, or to match the liquid gas container such as liquid nitrogen. in this case,
A power source for a heating element that requires a large capacity is not required to have such stability, and since the resistance value of the heating element hardly changes between liquid and outside the liquid, either a constant current power source or a constant voltage power source may be used. It is easy to design and connect. Further, a power source for a heat sensitive body is required to have high accuracy, stability, reliability, etc., but a constant current power source having a small capacity is sufficient, which is advantageous in circuit design and the like. Furthermore, since there is almost no change in the resistance value of the heating element due to temperature, unnecessary fluctuations in the amount of heat generated due to the temperature difference between inside and outside the liquid do not occur. Further, since the element has the film structure of the heat generating element and the heat sensitive element on the ceramic substrate, the element heating efficiency is high, and therefore, the wasteful loss of the liquid is prevented.

[0006]

Embodiments will be described below with reference to the drawings. Figure 1
FIG. 3 is an enlarged principle view showing a liquid level meter according to the present invention. In the figure, the unit chip elements 1 have the same structure, and a required number of them are connected. The unit chip element 1
Although the structure will be described later, a unit chip element 1 portion connected by a predetermined number serves as a liquid level detection unit. The heating element power source 2 is connected to the heating element 11 inside the unit chip element.
The heating element is for clarifying the temperature gradient between the inside of the liquid and the outside of the liquid in the state where the liquid level detecting portion is inserted into the liquid container. In addition, the heat sensitive thick film is
12 is provided and the constant current power supply 3 for liquid level measurement is connected. Here, as a liquid level detection principle, a constant power is supplied from the heating element power source 2 to the heating element 11, and the constant temperature power source 3 for measuring the liquid level is also applied to the heat sensitive body thick film 12. A constant current is supplied while being measured by the ammeter 5, and at this time, the liquid level is measured from the voltage value detected by each voltmeter 4.

2 to 5 are examples of exploded views for explaining the structure of a unit chip constituting a liquid level meter. First, FIG.
Then, the heating element 11 is bent and formed on the ceramic substrate 13, and the insulating film 14 is formed on the upper surface thereof as shown in FIG. Next, as shown in FIG. 4, a heat-sensitive material thick film 12 is bent and formed on the upper portion thereof.
The protective film 15 was formed as shown in FIG. In short, the heating resistor, the insulator, and the heat-sensitive body are sequentially formed on the ceramic substrate, and finally the upper surface is covered with the protective film to form a laminated structure. In the actual unit chip element, an alumina substrate and a yttria-stabilized zirconia substrate having a 10 mm square and a thickness of 0.5 to 0.7 mm were used as the ceramic substrate. Further, each film of the heat generating resistor, the insulator, the heat sensitive member and the protective film was formed as in the following example of manufacturing the element.

Preparation Example 1 A heating resistor was bent on a ceramic substrate 13 with a thickness of about 20 μm and a width of 1 mm by a screen printing method using a commercially available paste for ruthenium oxide type resistors as shown in FIG. And the resistance value was set to about 100 Ω. The insulator film 14 is made of a glass paste containing alumina and is formed on the entire surface of the insulator film 14 except for the lead terminals for connecting the heating resistors as shown in FIG.
It was formed to a thickness of -40 μm. As the heat sensitive film, a platinum thick film paste was used, and the width was 200 μm as shown in FIG.
It was bent to a thickness of 10 μm and formed so that the resistance value was about 20Ω at room temperature. Further, the protective film was formed with a thickness of about 20 μm on the entire surface using a paste similar to that of the insulating film, except for the lead-out terminals for connecting the heating resistor and the heat-sensitive body as shown in FIG. The film is baked at a baking temperature of 850 to 930 ° C.
I did it in. FIG. 6 shows the resistance value and the temperature change of the ruthenium oxide-based resistor film for a heating resistor used for manufacturing this element. In FIG. 6, the horizontal axis represents the temperature K and the vertical axis represents the resistance value R. FIG. 7 shows the temperature change of the resistance value of the platinum film for a heat sensitive body, and similarly to the above, the horizontal axis shows the temperature K and the vertical axis shows the resistance value R. FIG. 8 shows the relationship between the time and the output voltage when the device is taken out of the liquid nitrogen liquid out of the liquid in order to measure the liquid level detection sensitivity with one device according to the present production example. is there. Here, about 250 mW of electric power was supplied to the heating resistor, a constant current of 5 mA was passed through the platinum film for the heat sensitive element, and the time change of the output voltage across the platinum film was measured. As shown in the figure, the value of the output voltage doubled in about 60 seconds, and the liquid surface position could be detected with the upper sensitivity. The horizontal axis represents time (seconds) and the vertical axis represents output voltage (V).

Manufacturing Example 2 A heating resistor film and a heat-sensitive element are respectively formed by the same forming method as in Manufacturing Example 1 by providing a heating resistor film 11 on one surface (front surface) of a ceramic substrate 13 as shown in FIG. 9 (a). The heat-sensitive film 12 is provided on the other surface (back surface) shown in FIG. 9 (b). Further, a glass paste containing alumina was used as a protective film on each of the both surfaces in the same manner as in Preparation Example 1, and 50 to 100 μm was formed on the heating resistor film except for the lead terminals for connection.
A ceramic film having a thickness of about 20 μm was formed on the heat sensitive film. The firing was performed at the temperature of 850 to 930 ° C, similar to the production example 1.
I did it in. The liquid level detection sensitivity of one element according to this Preparation Example was measured under the same conditions as in Preparation Example 1 (FIG. 8). The result was about 80 seconds, which was almost the same as in Preparation Example 1, and the value of the output voltage doubled.

Manufacturing Example 3 In this manufacturing example, as shown in FIG.
It was formed on the same surface of the ceramic substrate 13 by bending while maintaining electrical insulation from each other. The heating resistor 11 was formed by bending the same paste as in Preparation Example 1 with a thickness of about 20 μm and a width of 500 μm, and its resistance value was about 100 Ω. Heat sensitive body 12
Using the same paste as in Preparation Example 1 and having a thickness of about 10 μm,
It is formed by bending with a width of 200 μm, and its resistance value at room temperature is about
It was set to 10Ω. Further, the protective film was formed in a thickness of about 20 μm on the entire surface by the same method as in the case of Preparation Example 1 except for the lead terminals for connection. Element 1 according to this fabrication example
The liquid level detection sensitivity for each piece was measured under the same conditions as in Preparation Example 1 (FIG. 8) and 2. The result is about the same as in Preparation Examples 1 and 2.
The output voltage doubled in 60 to 80 seconds.

In this preparation example, a screen printing paste used for forming a heating resistor was prepared by adding an organic vehicle to a nichrome alloy powder in which about 20% of glass powder was mixed. FIG. 11 shows the temperature change of the resistance value of the heating resistor film formed using this nichrome alloy paste. The formation of each film in the production of the element was carried out by the same method and conditions as in Production Examples 1, 2 and 3 for the insulating film, the heat sensitive film and the protective film except for the heating resistor film. In the case of manufacturing the element by the methods of Preparation Examples 1 and 2, the heating resistor film was formed by bending the ceramic substrate with a thickness of about 15 μm and a width of 500 μm, and the resistance value was about 10Ω. Also, Production Example 3
When the device is manufactured by the method of, the thickness is about 15 μm and the width is 300
The resistance value was set to about 10 Ω by bending with a thickness of μm. The firing was performed under the same conditions as in the above-mentioned preparation example. The liquid level detection sensitivity of one element according to this preparation example was measured under the same conditions as in preparation examples 1 (FIG. 8), 2 and 3. The result was about 60 to 80 seconds, which was almost the same as in Production Examples 1, 2 and 3, and the value of the output voltage doubled. Next, from the elements manufactured by the above method, those having the same manufacturing method and respective resistance values (the element of Manufacturing Example 1 was used for the following measurement) were selected, and as shown in FIG.
A liquid level meter composed of individual elements was produced. The elements were fixed on a glass / epoxy reinforced plastic plate 17 at intervals of 5 cm, and were labeled as 16a, 16b, 16c, 16d, 16e from the bottom. Further, the respective heating resistors and heat-sensitive bodies were connected in series, and voltage output terminals for liquid level measurement were attached from both ends of the heat-sensitive body.

FIG. 13 shows the measurement result of the liquid level meter of FIG. The measurement method uses a liquid nitrogen container in which the difference in temperature distribution in the container is not so large. First, with the entire liquid level gauge installed in the liquid container, the elements 16a, 16b,
16c is immersed in the liquid, and the liquid level is set to the intermediate position between the elements 16c and 16d. Next, pull out the liquid level meter about 5 cm upward (take out the element 16c to the outside of the liquid) and set the liquid level to the element 16b.
16c and the intermediate position. 120 seconds later, the liquid level gauge was pulled out again about 5 cm upward (element 16b was taken out of the liquid), and the liquid level was set to an intermediate position between elements 16a and 16b. After a further 120 seconds, the liquid level meter was returned downward by about 10 cm, and the liquid level was set to the intermediate position between the original elements 16c and 16d. At this time, the change in the output voltage across each element is recorded with the time since the liquid level meter was pulled out.
13 The output voltage across the devices 16b and 16c is about 60 seconds after the device is taken out of the liquid when the device is pulled out of the liquid level meter, as in the measurement results of each of the above production examples.
It doubled and returned to the original value within about 1 to 2 seconds after returning to the lower position after 240 seconds. Although the output voltage of the elements 16d and 16e changed slightly with the operation of the elements 16b and 16c in this operation (mainly the temperature distribution in the container affected), the element 16a
No change was seen in it. During this measurement, the heating resistor of each element was supplied with about 250 mW (about 1250 mW in total), but the measurement operation was performed with either a constant voltage power supply or a constant current power supply. The fluctuations within 2% stopped within about 2%, and there was almost no effect on the liquid level detection time. A constant current of 5 mA was applied to the heat sensitive body.

As described above, the present invention has made it possible to obtain a liquid level meter having sufficient liquid level detection sensitivity and having a simple power supply for the measurement system. In this embodiment, the ruthenium oxide ceramics and the nichrome alloy were used as the heating resistor, but the resistor whose resistance value hardly changes in the temperature range for detecting the liquid surface, for example, an alloy resistor such as a manganin alloy,
Alternatively, a ceramic resistor or the like may be used. In addition to platinum as the heat sensitive material, materials such as nickel, tungsten, molybdenum, etc. having a positive temperature coefficient whose resistance value increases with increasing temperature, and its resistance value decreases with increasing temperature. Ceramics made of oxides having a negative temperature coefficient such as copper, manganese, nickel, iron, cobalt, etc., and various materials adjusted as a heat sensitive body at a temperature near the boiling point of the liquid to be detected may be used. it is obvious.

[0014]

As described above, according to the present invention, a heating resistor and a heat sensitive body, or an insulator in some cases, is provided as a film structure on a chip-shaped ceramic substrate which is subdivided, and is covered with a protective film. To form a unit chip element,
Since a predetermined number of these unit chip elements are connected to each other to form the liquid level detection unit, the following effects are achieved. The element heating efficiency is high, the liquid level is detected quickly, and unnecessary loss of liquid is prevented. A partial failure of the liquid level detection unit can be easily repaired by replacing the unit chip element. It is possible to deal with various shapes and sizes of the container and the liquid surface position to be detected only by connecting the elements. Since the liquid level detection unit is formed by connecting the unit chip elements, only one type of device needs to be produced, which is economical and suitable for mass production. Also, the unit chip element itself is economical because it is integrally formed with a thick film, and is suitable for mass production. By electrically separating the heating resistor and the liquid level detecting heat sensitive body, it is possible to separate the heating power source that requires a large capacity from the constant current source for measurement that requires stability and accuracy. This made it possible to easily make an electrical structure. In particular,
The constant current power supply unit for measurement, which requires stability and accuracy, can be manufactured with a small capacity and is inexpensive. Further, by using a material whose resistance value hardly changes in the temperature range for detecting the liquid surface as the heating resistor, the heating power supply requiring a large capacity may be a constant current power supply or a constant voltage power supply, and the circuit design And the connection is easier. Further, a change in the amount of heat generated due to a resistance change between inside and outside the liquid, a change in the detection speed, a change in the evaporation amount of the liquid, etc. do not occur.

[Brief description of drawings]

FIG. 1 is an enlarged principle view showing a liquid level meter according to the present invention.

FIG. 2 is a diagram showing a heating resistor provided on a ceramic substrate according to an embodiment.

FIG. 3 is a diagram in which an insulator is provided on an upper surface of a heating resistor according to an embodiment.

FIG. 4 is a diagram in which a heat sensitive body is provided on an upper surface of an insulator in one embodiment.

FIG. 5 is a diagram in which the upper surface of the heat sensitive body in one example is covered with a protective film.

FIG. 6 is a diagram showing a change in resistance value of ruthenium oxide-based ceramics used as a heating resistor in this example with temperature.

FIG. 7 is a diagram showing changes in resistance value of platinum used as a heat-sensitive body in this example with temperature.

FIG. 8 is a diagram showing liquid level detection sensitivity of a unit chip element manufactured in one example.

FIG. 9 is a diagram showing a configuration of a unit chip element in another embodiment.

FIG. 10 is a diagram showing a configuration of a unit chip element in still another embodiment.

FIG. 11 is a diagram showing changes in the resistance value of the nichrome alloy used as the heating resistor in this example with temperature.

FIG. 12 is a diagram showing a liquid level meter including five unit chip elements manufactured in this example.

FIG. 13 is a diagram showing the liquid level detection sensitivity of the liquid level meter manufactured in this example.

[Explanation of symbols]

 1 unit Chip element 2 Heating power supply 3 Liquid level measuring power supply 4 Voltmeter 5 Ammeter 11 Heating resistor 12 Heat sensitive body 13 Ceramics substrate 14 Insulator 15 Protective film 16 Detecting part 17 Element fixing plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Shimizu Kenji Shimizu 5310, Sangejiri, Kumagaya, Saitama Prefecture Chichibu Cement Corporation Huain Ceramics Division (72) Ryozo Akihama 5310 Mikkaji, Kumagaya, Saitama Prefecture Chichibu Huain Ceramics Division, Cement Co., Ltd.

Claims (5)

[Claims] 1. A heating element is provided on a chip-shaped ceramic substrate that has been subdivided, an insulator is formed to cover the upper surface of the heating element, and a heat-sensitive element is laminated on the upper surface of the insulator.
A liquid level meter, wherein the upper surface of the heat sensitive body is covered with a protective film to form a unit chip element, and a predetermined number of the unit chip elements are connected to form a liquid level detection unit. 2. A unit chip element is formed by disposing a heating element and a heat sensitive element on the same upper surface of a subdivided chip-shaped ceramic substrate so as not to contact each other, and further covering the upper surface with a protective film. The liquid level gauge according to claim 1, which is characterized in that. 3. A unit chip element is provided with a heating element on one surface of a subdivided chip-shaped ceramic substrate, the upper surface of which is covered with a protective film having an adiabatic function, and the other surface is heat-sensitive. The liquid level meter according to claim 1, wherein the body is arranged and the upper surface thereof is covered with a protective film. 4. The heating element is made of a material whose resistance value hardly changes in the temperature range in which the liquid level is detected, and the heating element is made of a material whose resistance value changes largely at a temperature near the boiling point of the liquid. The liquid level meter according to claim 1 or 2 or 3. 5. The heating element is made of a material such as ruthenium oxide ceramics, a nichrome alloy, a manganin alloy, etc., whose resistance value hardly changes in the temperature range for detecting the liquid surface. The liquid level meter according to claim 2 or claim 3 or claim 4.