JP4936184B2 - Induction heating type liquid level sensor - Google Patents

Description

  The present invention relates to an induction heating type liquid level sensor using electromagnetic induction heating, and more particularly to an induction heating type liquid level sensor that detects a liquid level by measuring a heat dissipation state after heating the sensor itself. .

  As a method for detecting the liquid level, a float switch using a reed switch or an electrode type which is determined by a conductive switch is generally used. If the liquid to be measured is general salt water or tap water, it can be detected by a float switch or an electrode sensor.

On the other hand, Patent Document 1 describes a liquid level detection method. According to this liquid level detection method, when a predetermined heating area on one side of a metal level tube is heated, the temperature difference between the upper and lower liquid levels that fluctuates inside is detected, and the difference in thermal conductivity between gas and liquid is detected. This is a method for confirming whether or not the liquid level exists in the heating zone. In the liquid level detection apparatus for executing the liquid level detection method, a heating device such as a heater is installed on one side of the metal level tube, and a sensor such as a thermocouple is arranged on the opposite side of the metal level tube. When the metal level tube is heated with a heater or the like, a temperature difference occurs depending on whether or not there is liquid inside the metal tube, and the difference in temperature is intended to measure the liquid level inside the metal tube. is there.
JP 59-52718

  However, there are some liquids that cannot be adapted by conventional float switches. For example, in a liquid in which foreign matter is mixed, a float switch is inappropriate because it is interposed between the stem and the float and the float tends to cause a sliding failure. Moreover, even a viscous liquid such as honey may adhere to the floats, floats, stoppers, etc. and cause sliding failure.

  Furthermore, the heat resistance temperature of the reed switch is normally 150 ° C., but there are cases where oil and the like rise to 150 ° C. or higher. As described above, there are cases where the reed switch or the like cannot be used due to its limited heat-resistant temperature. Further, when the float is detached, the float floats in the tank, and there is a risk that it will be mixed into the tank or the interlocking device as a foreign substance and cause a malfunction.

  Further, in the conventional optical sensor, when dirty liquid is detected, a malfunction occurs if dirt is attached to the detection surface of the sensor or condensation occurs. Furthermore, with an electrode sensor, detection with an insulating liquid such as oil is difficult because electricity is difficult to pass.

  On the other hand, in the case where a heating zone, a sensor, or the like is arranged through a metal level tube as in Patent Document 1, even if a temperature difference occurs depending on whether or not there is a liquid inside the metal tube, the sensor is heated after being heated. It takes a long time to detect the temperature, and the temperature during heating may affect the liquid.

  Therefore, the present invention was created to solve the above-mentioned problems, and by using electromagnetic induction heating, problems caused by insufficient sliding, such as floats of float switches, are eliminated, and foreign matter adheres. It can be easily removed, and it has a very high heat resistance temperature, and accurately detects the three levels of the liquid level, standard condition and drought condition without affecting the liquid to be measured. An object of the present invention is to provide an induction heating type liquid level sensor capable of performing

In order to achieve the above-mentioned object, the first means in the present invention is to mount an electromagnetic induction heating body 10 in a bottomed cylindrical container 1 formed of a metal material having thermal conductivity, and the electromagnetic induction heating body. The temperature sensor 2 is arranged above and below the temperature sensor 2, and the temperature sensor 2 senses the temperature change at the top and bottom of the electromagnetic induction heating body 10 from when the electromagnetic induction heating body 10 is heated until the heat is radiated through the container 1. In the induction heating type liquid level sensor provided to detect the height of the surrounding liquid level, the electromagnetic induction heating body 10 has a coil 12 wound around an intermediate portion of a bobbin 11 made of a magnetic material, The outer peripheral surfaces of the upper and lower ends of the bobbin 11 are bonded to the inside of the container 1 having high thermal conductivity with a heat conductive adhesive, and the temperature sensor 2 is attached to the upper and lower ends of the bobbin 11 as a heat conductive adhesive. Are glued together .

The electromagnetic induction heating body 10 of the second means is provided so as to be heated at 10 ° C. to 15 ° C., and the temperature sensor 2 detects a state in which the upper and lower sides of the electromagnetic induction heating body 10 radiate heat through the container 1. It is provided as follows.

The third means is provided with a control box 20 containing a circuit unit of the temperature sensor 2 and a power supply device for energizing the electromagnetic induction heating body 10 at a position away from the electromagnetic induction heating body 10. When the upper and lower temperature sensors 2 sense the state of radiating heat through the container 1 after being heated, the liquid level is located around the container 1 or the liquid level is not around the container 1; Or it is set as the means for solving a problem that it provided so that the three states of the state where a liquid level may be located between the up-and-down temperature sensors 2 around the said container 1 may be detected.

  According to the first aspect of the present invention, the electromagnetic induction heating body 10 is mounted in the bottomed cylindrical container 1 formed of a metal material having thermal conductivity, and the temperature sensors 2 are arranged above and below the electromagnetic induction heating body 10. The temperature sensor 2 senses the upper and lower temperature changes of the electromagnetic induction heating body 10 from the time when the electromagnetic induction heating body 10 is heated until the heat is radiated through the container 1, and the height of the liquid surface around the container 1 is detected. Therefore, there is no float like a float switch, and the problem of poor sliding does not occur.

  In addition, the heating action of the electromagnetic induction heating element 10 is characterized in that the heating efficiency is good compared to resistance heating such as nichrome wire, the loss of heat capacity is small, and the heating rate is fast. As a result, the sensing speed and sensing accuracy of the level sensor of the present invention can be increased, and there is also an energy saving effect.

  Furthermore, since the electromagnetic induction heating body 10 and the temperature sensor 2 are housed inside the container 1 and detect the liquid level around the container 1, the liquid level can be maintained even with viscous liquids such as honey and oil. It can be detected accurately. Moreover, it can be said that the structure is extremely hygienic because it can be easily wiped and cleaned even if foreign matter adheres around the container 1.

In the electromagnetic induction heating body 10, a coil 12 is wound around an intermediate portion of a bobbin 11 made of a magnetic material, and the outer peripheral surfaces of the upper and lower ends of the bobbin 11 are formed into a heat conductive adhesive inside the container 1 having high heat conductivity. Since the temperature sensor 2 is bonded to the upper and lower end portions of the bobbin 11, heat is radiated around the container 1 through the container 1 having high thermal conductivity after the electromagnetic induction heater 10 is heated. Therefore, the heat radiation state of the electromagnetic induction heating body 10 changes sensitively depending on the liquid surface state around the container 1. As a result, accurate liquid level detection becomes possible.

  In addition, the electromagnetic induction heating body 10 has the advantage that the bobbin 11 made of iron is bonded to the inside of the stainless steel container 1, so that the drop impact is less damaged and it is extremely easy to handle. Further, since the liquid level is detected at the upper and lower temperatures of the bobbin 11, the detection point can be easily changed by changing the length of the bobbin 11.

According to claim 2 , the electromagnetic induction heating body 10 is provided so as to be heated by 10 ° C. to 15 ° C., and the temperature sensor 2 detects a state in which the upper and lower sides of the electromagnetic induction heating body 10 radiate heat through the container 1. Therefore, the liquid level can be detected by slightly heating the electromagnetic induction heating body 10. Further, since the state of radiating heat is detected from the state where the electromagnetic induction heating body 10 is heated at 10 ° C. to 15 ° C., the detection time can be short.

In Claim 3 , since the control box 20 which accommodated the power supply device which supplies with electricity the circuit part of the said temperature sensor 2 and the electromagnetic induction heating body 10 in the position away from the said electromagnetic induction heating body 10 is provided, under high temperature Detection is also possible. As a result, although the limit heat-resistant temperature of the reed switch was 150 ° C., according to the present invention, it became possible to detect the liquid level such as oil rising to 150 ° C. or higher.

  In the present invention, the liquid level is located around the container 1, the liquid level is not around the container 1, or the liquid is interposed between the upper temperature sensor 2 and the lower temperature sensor 2 around the container 1. Since it is provided so as to detect the three states where the surface is located, the three states can be accurately detected with a very simple sensor structure.

  As a result, according to the present invention, for example, detection of the remaining amount of automobile engine oil, detection of the remaining amount of high-viscosity liquid such as honey, detection of liquid that reaches a high temperature (150 ° C. to 250 ° C.), wear powder due to sliding It can also be used in special environments such as detection of drinking water, etc.

  In the best mode of the level sensor of the present invention, the electromagnetic induction heating body 10 is mounted in a bottomed cylindrical container 1 formed of a metal material having thermal conductivity. The electromagnetic induction heating body 10 has a coil 12 wound around an intermediate portion of a bobbin 11 made of an iron magnetic body, and the upper and lower end outer peripheral surfaces of the bobbin 11 are placed inside a stainless steel container 1 with a heat conductive adhesive. Glued. The temperature sensor 2 is bonded to the upper and lower ends of the bobbin 11. A control box 20 containing a circuit unit of the temperature sensor 2 and a power supply device for energizing the electromagnetic induction heating body 10 is provided at a position away from the electromagnetic induction heating body 10. The upper and lower temperature sensors 2 detect that the electromagnetic induction heating body 10 is heated by 10 ° C. to 15 ° C. and then the upper and lower sides of the electromagnetic induction heating body 10 dissipate heat through the container 1. It is provided so as to detect three states: a state in which the liquid level is located around the container 1 or a state in which the liquid level is located between the upper temperature sensor 2 and the lower temperature sensor 2 around the container 1. In this way, the original purpose is achieved.

  An embodiment of the present invention will be described below. The main configuration of the level sensor of the present invention includes a container 1, an electromagnetic induction heating body 10, a temperature sensor 2, and a control box 20.

  The container 1 has a bottomed cylindrical shape made of a metal material having thermal conductivity, such as stainless steel, and houses the electromagnetic induction heating body 10 and the temperature sensor 2 therein. The container 1 in the illustrated example is provided with a lid 3 at the top of the opening, and leads 4 are connected through the lid 3 to a temperature sensor 2 and an electromagnetic induction heater 10 described later. Further, the gap between the lid 3 and the lead wire 4 is sealed with a filler 5 such as an epoxy resin to improve the sealing performance of the container 1. Reference numeral 6 in the figure denotes an attachment hole provided in the lid 3 and is used when the present invention is attached to an appropriate place.

  The electromagnetic induction heating body 10 is housed in the container 1, and the temperature sensor 2 senses the upper and lower temperatures of the electromagnetic induction heating body 10. In the illustrated electromagnetic induction heating body 10, a coil 12 is wound around an intermediate portion of a bobbin 11 having a substantially drum shape made of an iron magnetic body. Further, the upper and lower end portions of the bobbin 11 are bonded to the inner peripheral surface of the container 1 at the outer peripheral surface.

  In the present invention, the height of the liquid surface around the container 1 is detected by a temperature change from when the upper and lower ends of the bobbin 11 are heated until the heat is radiated through the container 1. Therefore, the electromagnetic induction heating body 10 is provided so that the temperature of the bobbin 11 is increased by 10 ° C. to 15 ° C. Then, depending on the state in which the upper and lower parts of the bobbin 11 radiate heat through the container 1, the liquid level is positioned around the container 1, the liquid level is not around the container 1, or the upper part around the container 1 It is provided so that it can detect three states in which the liquid level is located between the temperature sensor 2 and the lower temperature sensor 2.

  The illustrated electromagnetic induction heating body 10 has a litz wire wound around an iron bobbin 11 as a coil 12 having excellent heat resistance 65 times. This litz wire is composed of 30 wires each having a 30-core structure and an insulating coating, and has a structure in which 30 turns are wound 65 times. Temperature sensors are placed on the top and bottom of the iron bobbin and bonded with a heat conductive adhesive.

  Moreover, since it is desirable that the upper part and the lower part of the bobbin 11 of the electromagnetic induction heating body 10 are in close contact with the inner wall of the stainless steel metal fitting main body 1, they are intimately fixed with a heat conductive adhesive. This is to faithfully detect the heat dissipation state through the stainless steel container 1.

  Further, a control box 20 in which a circuit unit of the temperature sensor 2 and a power supply device for energizing the electromagnetic induction heating body 10 is provided at a position away from the electromagnetic induction heating body 10 is provided. In this control box 20, for example, a fixed state in which the liquid level is positioned between the upper and lower temperature sensors 2 around the container 1, a state in which the liquid level exceeds the container 1 and the liquid level is full, and the container 1 By setting a blue LED 21 indicating a fixed state, a yellow LED 22 indicating a full water state, and a red LED 23 indicating a drought state, etc., it is possible to grasp the situation at a glance. it can.

  In the level sensor of the present invention, current pulses are periodically applied to the coil 12 of the electromagnetic induction heating body 10. For example, the pulse is intermittently applied with a period of 450 kHz, energization time of 20 seconds, and heat dissipation time of 280 seconds. The heat at the top and bottom of the bobbin 11 of the electromagnetic induction heating body 10 heated by induction heating is radiated to the outside through the closely contacted stainless steel container 1. At this time, the state around the container 1 detects drought, middle and full water based on the state of the liquid surface around the container 1, for example, the speed of temperature change and the temperature difference between the upper and lower temperature sensors 2. By heating for 20 seconds, the temperature of the bobbin 11 rises by about 10 ° C. to 15 ° C. from before the heating.

  Next, the detection state of the temperature sensor 2 due to the difference in liquid level will be described. The basic principle is that the temperature of the bobbin 11 suddenly rises by induction heating for 20 seconds, and is transferred to the stainless steel container 1 that is in close contact with the bobbin 11 to be dissipated. Therefore, the upper and lower temperature sensors 2 measured the speed of heat dissipation and the temperature difference between the upper and lower portions of the bobbin 11.

表１は、容器１の周囲に液面がなく、渇水状態を検知したデータである。この表１において、次のことが分かる。
（ア）温度上昇スピードは速く温度上昇は２０秒間で約７℃である。
（イ）ボビン１１の上下での温度差はなく放熱時間は長い。
（ウ）放熱スピードは遅く、加熱前の温度に戻るには約１１８０秒必要であった。
（エ）この結果、温度上昇スピードが速くて上下の温度センサ２の差異がなければ、容器１の周囲は渇水状態と判断できる。

Table 1 shows data in which a drought condition is detected without a liquid level around the container 1. In Table 1, the following can be understood.
(A) The temperature rise speed is fast and the temperature rise is about 7 ° C. in 20 seconds.
(A) There is no temperature difference between the top and bottom of the bobbin 11, and the heat radiation time is long.
(C) The heat release speed was slow, and it took about 1180 seconds to return to the temperature before heating.
(D) As a result, if the temperature rise speed is fast and there is no difference between the upper and lower temperature sensors 2, it can be determined that the surroundings of the container 1 are in a drought state.

表２は、容器１の周囲に液面（水）があり、しかも、この液面が上下の温度センサ２の間に位置する状態を検知したデータである。この表２において、次のことが分かる。
（ア）ボビン１１の上部の温度上昇スピードは速く、２０秒間の加熱で約７℃である。
（イ）ボビン１１の下部の温度センサ２は温度上昇が遅く２０秒間の加熱で４℃である。
（ウ）ボビン１１上下の温度差は約３℃あった。
（エ）放熱スピードは速く、加熱前温度に戻るのに２８０秒であった。
（オ）このように、ボビン１１の上下に温度差があるときは、液面が上下の温度センサ２の間に位置する状態であることがわかる。

Table 2 shows data obtained by detecting a state in which there is a liquid level (water) around the container 1 and this liquid level is positioned between the upper and lower temperature sensors 2. In Table 2, the following can be understood.
(A) The temperature rise speed at the top of the bobbin 11 is fast, and is about 7 ° C. when heated for 20 seconds.
(A) The temperature sensor 2 below the bobbin 11 has a slow temperature rise and is 4 ° C. when heated for 20 seconds.
(C) The temperature difference between the top and bottom of the bobbin 11 was about 3 ° C.
(D) The heat release speed was fast, and it took 280 seconds to return to the temperature before heating.
(E) Thus, when there is a temperature difference between the upper and lower sides of the bobbin 11, it can be seen that the liquid level is located between the upper and lower temperature sensors 2.

表３は、容器１の周囲に液面（水）があり、しかも、上下の温度センサ２より上に液面が位置し、満水状態になった状態を検知したデータである。この表３において、次のことが分かる。
（ア）ボビン１１の温度上昇スピードは遅く、２０秒間の加熱で約４℃である。
（イ）ボビン１１の上下の温度差はゼロに等しい。
（エ）放熱スピードは速く、加熱前温度に戻るのに１８０秒であった。
（オ）このように、温度上昇が遅く放熱スピードが速いと容器１の周囲は液体で満ちており、満水状態であると判断できる。

Table 3 shows data in which a liquid level (water) is present around the container 1 and the liquid level is located above the upper and lower temperature sensors 2 and a full state is detected. In Table 3, the following can be seen.
(A) The temperature rise speed of the bobbin 11 is slow and is about 4 ° C. when heated for 20 seconds.
(A) The temperature difference between the top and bottom of the bobbin 11 is equal to zero.
(D) The heat release speed was fast, and it took 180 seconds to return to the temperature before heating.
(E) As described above, when the temperature rise is slow and the heat dissipation speed is fast, it can be determined that the periphery of the container 1 is filled with liquid and is in a full state.

  In the present invention, the data of the temperature sensor 2 is analyzed based on the data in Tables 1 to 3, and the liquid level is located around the container 1 or the liquid level is not around the container 1 or It is provided so as to detect three states in which the liquid level is located between the upper and lower temperature sensors 2 around the container 1.

  The present invention is not limited to the illustrated example, and the design of the shape of the container 1, the size and shape of each component such as the electromagnetic induction heating body 10, the temperature sensor 2, and the change of the material are arbitrary. The present invention can be freely changed without departing from the scope of the present invention.

It is a partially cutaway perspective view showing an embodiment of the temperature sensor of the present invention. It is a perspective view which shows one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Temperature sensor 3 Cover body 4 Lead wire 5 Filler 6 Mounting hole 10 Electromagnetic induction heating body 11 Bobbin 12 Coil 20 Control box 21 Blue LED
22 Yellow LED
23 Red LED

Claims (3)

An electromagnetic induction heating body is mounted in a bottomed cylindrical container formed of a metal material having thermal conductivity, a temperature sensor is disposed above and below the electromagnetic induction heating body, and the electromagnetic induction heating body is heated. in the upper and lower induction heating type liquid level sensor provided to detect the height of the liquid surface of the container surrounding sensed by the temperature sensor the temperature change of the electromagnetic induction heating body to be radiated through the vessel, the In the electromagnetic induction heating body, a coil is wound around an intermediate portion of a bobbin made of a magnetic material, and the outer peripheral surfaces of the upper and lower ends of the bobbin are bonded to the inside of the container having high thermal conductivity with a heat conductive adhesive. An induction heating type liquid level sensor , wherein the temperature sensors are bonded to the upper and lower ends of the bobbin with a heat conductive adhesive .   The said electromagnetic induction heating body is provided so that it may heat 10 degreeC thru | or 15 degreeC, and the said temperature sensor is provided so that the upper and lower sides of an electromagnetic induction heating body may detect the state which thermally radiates through a container. Induction heating type liquid level sensor. A control box containing a circuit unit of the temperature sensor and a power supply device for energizing the electromagnetic induction heating body is provided at a position away from the electromagnetic induction heating body, and heat is radiated through the container after the electromagnetic induction heating body is heated. When the upper and lower temperature sensors sense the state, the liquid level is positioned around the container, the liquid level is not around the container, or the liquid level is positioned between the upper and lower temperature sensors around the container. The induction heating type liquid level sensor according to claim 1 or 2, which is provided so as to detect three states.

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