JP2016099266A - Liquid level detecting device and liquid level detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level detecting device that can detect a liquid level accurately.SOLUTION: This liquid level detector 13 (a liquid level detecting device) is the liquid level detector 13 that detects a liquid level of molten metal 1 received in a supply tank 41. The liquid level detector is arranged in the supply tank 41, and includes a temperature sensor 11 and a heater 12 arranged adjacent to a temperature sensing part 11a of the temperature sensor 11 inside. The liquid level detector 13 is configured to determine that a tip 14 of the liquid level detector 13 are in contact with the molten metal 1 when temperature detected by the temperature sensor 11 becomes equal to or less than a threshold.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid level detection device and a liquid level detection system.

  Conventionally, a liquid level detection device is known (see, for example, Patent Document 1). Patent Document 1 discloses a solder supply device including a liquid level sensor that detects the level of liquid solder contained in a container. The liquid level sensor includes two electrode bars installed at fixed positions in the container. And it is comprised so that it may supply with electricity when the two electrode sticks are contacting the liquid level of the liquid solder in a container, and the liquid level is located in the height position of an electrode stick. .

JP 2007-149784 A

  However, in the liquid level sensor described in Patent Document 1, two electrodes are formed on the liquid surface of the liquid solder due to a liquid solder splash adhering to the insulating portion that insulates the container and the electrode rod and causing a short circuit. There is a problem that it may not be possible to accurately detect whether or not the bar is in contact.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a liquid level detection device and a liquid level detection system capable of accurately detecting the liquid level. It is to be.

  In order to achieve the above object, a liquid level detection device according to a first aspect of the present invention is a liquid level detection device that detects a liquid level of a molten metal contained in a container, and is disposed in the container. A liquid level detection unit that includes a temperature sensor and a heater disposed in the vicinity of the temperature measurement unit of the temperature sensor. When the temperature detected by the temperature sensor falls below a threshold value, the liquid level detection unit It is comprised so that it may be judged that the front-end | tip part and molten metal contacted. The “molten metal” is a wide concept including not only the molten metal but also the solid state at the time of liquid level measurement when the molten metal is in a solid state. The “liquid level” is a broad concept including not only the liquid level of the molten metal but also the surface of the molten metal in a solid state.

  In the liquid level detection device according to the first aspect of the present invention, as described above, when the heater is disposed in the vicinity of the temperature measuring portion of the temperature sensor, and the temperature detected by the temperature sensor becomes equal to or lower than the threshold value In addition, it is configured to determine that the tip of the liquid level detection unit and the molten metal are in contact with each other. Here, when the tip of the liquid level detection unit and the molten metal are not in contact with each other, the temperature detected by the temperature sensor is relatively high due to the heat generated from the heater. On the other hand, when the tip of the liquid level detection unit and the molten metal come into contact with each other, the temperature detected by the temperature sensor becomes relatively low because heat generated from the heater is transferred to the molten metal. Therefore, in the present invention, it can be easily determined that the tip of the liquid level detection unit and the molten metal are in contact with each other based on the fact that the temperature measured by the temperature sensor has become equal to or lower than the threshold value. Further, as described above, the temperature sensor is included in the liquid level detection unit, so that the temperature sensor inside the liquid level detection unit can be used even when an oxide adheres to the outer surface of the liquid level detection unit. Since the surface of the liquid is not electrically affected by the deposits, the liquid level can be detected with high accuracy.

  In the liquid level detection apparatus according to the first aspect, preferably, the heater is configured to emit heat having a temperature higher than the melting temperature of the molten metal. If comprised in this way, when the front-end | tip part of a liquid level detection part and molten metal contact, since the heat | fever emitted from the heater will be transmitted to molten metal, the front-end | tip part of liquid level detection part and molten metal There is a temperature difference between the temperatures detected by the temperature sensor before and after contact with each other. Thereby, it is easily determined based on the detection result of the temperature sensor that the tip of the liquid level detection unit and the molten metal are in contact with each other.

  In the liquid level detection device according to the first aspect, preferably, a plurality of liquid level detection units are provided, and the plurality of liquid level detection units are arranged in the container so that the height positions of the respective front end portions are different. Has been. If comprised in this way, the liquid level of a molten metal will be detected which liquid level detection part by determining which tip part of the liquid level detection part of several liquid level detection parts contacted the molten metal. It is possible to determine whether it is located in the vicinity of the front end portion. Thereby, the height position of the liquid level can be detected in a plurality of stages.

  In this case, preferably, the liquid level detection unit includes a first liquid level detection unit in which each of the front end portions is disposed at the first height position, and a second height lower than the first height position. A second liquid level detection unit disposed at the first position, and a third liquid level detection unit disposed at a third height position between the first height position and the second height position, including. If comprised in this way, based on judging that the front-end | tip part of the 1st liquid level detection part arrange | positioned in the highest position (1st height position) and the molten metal contacted, By stopping the replenishment, the overflow of the molten metal from the container can be suppressed. Further, based on the determination that the tip of the second liquid level detection unit disposed at the lowest position (second height position) is not in contact with the molten metal, processing using the molten metal By stopping the process, it is possible to prevent the processing from being performed in a state where the molten metal is insufficient. Further, based on determining whether or not the tip of the third liquid level detection unit arranged at the intermediate position (third height position) and the molten metal are in contact with each other, By determining whether or not the molten metal replenishment operation can be started (replenishment is started in a non-contact state), replenishment can be started at an appropriate timing.

  In the liquid level detection apparatus provided with a plurality of the liquid level detection units, preferably, the plurality of liquid level detection units are arranged in the container in a bundled state. If comprised in this way, unlike the case where a some liquid level detection part is arrange | positioned in the state mutually spaced apart, the attachment area | region which attaches a some liquid level detection part to a container can be made small.

  In the liquid level detection device according to the first aspect, preferably, the tip of the liquid level detection unit has a substantially hemispherical shape. With this configuration, when the liquid level falls below the tip of the liquid level detector, the molten metal adhering to the tip of the liquid level detector drops quickly, so the liquid level detector The molten metal adhering to the tip is quickly removed from the tip of the liquid level detector. Thereby, it can suppress that the state to which the molten metal adhered to the front-end | tip part of a liquid level detection part is maintained.

  In the liquid level detection device according to the first aspect described above, preferably, the threshold value includes a first threshold value when the temperature of the container is adjusted to a temperature at which the molten metal melts, and is detected by a temperature sensor. When the temperature is equal to or lower than the first threshold value, it is determined that the tip of the liquid level detection unit and the molten metal are in contact with each other. If comprised in this way, based on the detection result of a temperature sensor by using a 1st threshold value, the front-end | tip part of a liquid level detection part and the molten metal in the molten state are contacting easily? It is determined whether or not.

  In the liquid level detection device according to the first aspect, preferably, the threshold value includes a second threshold value when the temperature of the container is not adjusted to a temperature at which the molten metal is melted, and is detected by a temperature sensor. When the temperature becomes equal to or lower than the second threshold value, it is determined that the solidified molten metal is in contact with the tip of the liquid level detection unit. If comprised in this way, based on the detection result of a temperature sensor by using a 2nd threshold value, whether the front-end | tip part of a liquid level detection part and the molten metal in the solidified state will contact easily. Is judged.

  In the liquid level detection device according to the first aspect, preferably, the threshold value is a temperature when the tip of the liquid level detection unit is in contact with the molten metal, and a part of the tip of the liquid level detection unit. Is set between the temperature when the liquid is connected to the molten metal. With this configuration, it is determined that the tip of the liquid level detector is in contact with the molten metal without being confused with the case where a part of the tip of the liquid level detector is connected to the molten metal. Can do.

  A liquid level detection system according to a second aspect of the present invention is a liquid level detection system for detecting a liquid level of a molten metal contained in a container, and is disposed in the container, and is a temperature sensor and a temperature sensor of the temperature sensor. When the temperature detected by the temperature sensor falls below a threshold value, the tip of the liquid level detection unit and the molten metal contacted each other And a controller for replenishing the molten metal in the container or stopping the processing using the molten metal, and the liquid level detecting unit is arranged such that each tip is disposed at the first height position. A first liquid level detecting unit and a second liquid level detecting unit disposed at a second height position lower than the first height position, and the control unit includes: When it is determined that the tip and the molten metal are in contact with each other, the replenishment of the molten metal into the container is stopped, and the second When the distal end portion of the face detecting section and the molten metal is determined to be a non-contact is configured to stop the treatment with the molten metal.

  In the liquid level detection system according to the second aspect of the present invention, as described above, when the control unit determines that the tip of the first liquid level detection unit and the molten metal are in contact with each other, the inside of the molten metal container When the replenishment is stopped and it is determined that the tip of the second liquid level detection unit is not in contact with the molten metal, the process using the molten metal is stopped. Accordingly, the replenishment of the molten metal is stopped based on the determination that the tip of the first liquid level detection unit arranged at a high position (first height position) and the molten metal are in contact with each other. Thereby, the overflow of the molten metal from a container can be suppressed. Further, based on determining that the tip of the second liquid level detection unit disposed at a low position (second height position) is not in contact with the molten metal, processing using the molten metal is performed. By stopping, it can suppress that a process is performed in the state where molten metal is insufficient. Further, as described above, the temperature sensor is included in the liquid level detection unit, so that the temperature sensor inside the liquid level detection unit can be used even when an oxide adheres to the outer surface of the liquid level detection unit. Therefore, it is possible to provide a liquid level detection system capable of accurately detecting the liquid level.

  According to the present invention, as described above, it is possible to provide a liquid level detection device and a liquid level detection system that can accurately detect a liquid level.

It is the figure which showed the structure of the liquid level detection system by 1st Embodiment of this invention. It is a front view of the liquid level detection part of the liquid level detection system by 1st Embodiment of this invention. It is an enlarged view of the front-end | tip part of the liquid level detection part of the liquid level detection system by 1st Embodiment of this invention. (A) The figure which shows the state which has separated the liquid level detection part from the molten metal, (b) The figure which shows the state which is contacting the molten metal, (c) A part of front-end | tip part is connected with the molten metal. It is a figure which shows a state. It is a figure for demonstrating operation | movement of the liquid level detection system by 1st Embodiment of this invention. It is a figure for demonstrating the experiment conducted about the detection of the temperature of a molten metal. It is a figure for demonstrating experiment when there is no temperature control of a supply tank. It is a front view of the liquid level detection part of the liquid level detection system by 2nd Embodiment of this invention. It is a figure for demonstrating operation | movement of the liquid level detection system by 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, the configuration of the liquid level detection system 10 according to the first embodiment will be described with reference to FIG. The liquid level detection system 10 is provided in the metal filling device 100.

  As shown in FIG. 1, the metal filling apparatus 100 includes a processing unit main body 20, a pressing unit 30, a molten metal supply mechanism unit 40, a molten metal recovery mechanism unit 50, a disposal mechanism unit 60, a decompression mechanism unit 70, and a gas supply mechanism unit. 80. The liquid level detection system 10 is provided in the molten metal supply mechanism 40.

  The processing unit main body 20 includes a first main body 21 provided with a recess 21 a and a holding hole 21 b, and a second main body 22 provided so as to face the first main body 21. The semiconductor wafer 200 is held in the holding hole 21 b of the first main body 21. And the process chamber 23 of an airtight state is formed by the 2nd main-body part 22 being assembled | attached to the 1st main-body part 21. FIG. Further, the first main body portion 21 and the second main body portion 22 are heated to a temperature equal to or higher than the melting point (200 ° C.) of the solder by a heating portion (not shown) so that the molten metal 1 to be described later supplied to the processing chamber 23 does not solidify. Has been.

  The pressing portion 30 is configured by an actuator such as a hydraulic cylinder, and is configured to press the second main body portion 22 in the Z1 direction.

  The molten metal supply mechanism unit 40 includes a supply tank 41 that stores the molten metal 1, a supply pump 42, and a valve gate 43. The molten metal 1 is made of solder, for example. The supply tank 41 is connected to the supply pump 42 via the open / close valve 44. Further, the supply tank 41 accommodates the molten metal 1 heated to a temperature higher than the melting point of the molten metal 1 in a molten state that is a liquid. Further, the inside of the supply tank 41 can be brought into an atmospheric pressure state (a state where air exists) or a vacuum state by the decompression mechanism unit 70. The supply tank 41 is an example of the “container” in the present invention.

  The supply pump 42 is connected to the valve gate 43. The supply pump 42 is configured to pressurize the molten metal 1 stored in the supply tank 41 and discharge it to the valve gate 43. The supply pump 42 is composed of, for example, a plunger pump. The supply tank 41 is connected to a supplementary pipe 45 for supplementing the molten metal 1 to the supply tank 41. From the replenishment pipe 45, the molten metal 1 is replenished to the supply tank 41 by batch-type replenishment in which the replenishment amount per time is a constant amount. In addition, the outside of the supply tank 41 is heated to 300 ° C. by a temperature adjusting unit 46 including a heater. In addition, the temperature adjustment unit 46 is provided with a thermometer 47.

  Here, in the first embodiment, the supply tank 41 is provided with a liquid level detection system 10 that detects the liquid level of the molten metal 1 accommodated in the supply tank 41. As shown in FIG. 2, the liquid level detection system 10 is provided with a liquid level detection unit 13 disposed in the supply tank 41. The liquid level detection unit 13 is an example of the “liquid level detection device” in the present invention.

  Further, in the first embodiment, as shown in FIG. 2, the upper end liquid level detection unit 13 a in which the respective leading end portions 14 a, 14 b and 14 c are arranged at the height position h <b> 1 from the bottom portion 41 a of the supply tank 41. And a lower limit liquid level detector 13b disposed at a height position h2 lower than the height position h1, and an intermediate liquid disposed at a height position h3 between the height position h1 and the height position h2. Three liquid level detectors 13 with the surface detector 13c are provided. Specifically, the tip end portion 14 a of the upper limit liquid level detection unit 13 a is located above the supply tank 41. Further, the front end portion 14 b of the lower limit liquid level detection unit 13 b is located in the vicinity of the bottom 41 a of the supply tank 41. One liquid level detection unit 13 can detect the liquid level at one place (one height position), and three upper limit liquid level detection units 13a, a lower limit liquid level detection unit 13b, and an intermediate liquid level. The detection unit 13c can detect three liquid level heights. The upper limit liquid level detection unit 13a, the lower limit liquid level detection unit 13b, and the intermediate liquid level detection unit 13c are examples of the “liquid level detection unit” in the present invention. The upper limit liquid level detection unit 13a, the lower limit liquid level detection unit 13b, and the intermediate liquid level detection unit 13c are respectively the “first liquid level detection unit”, “second liquid level detection unit”, and “third” of the present invention. It is an example of a "liquid level detection part." In addition, the height position h1, the height position h2, and the height position h3 are respectively the “first height position”, “second height position”, and “third height position” of the present invention. It is an example.

  In the first embodiment, the upper limit liquid level detection unit 13a, the lower limit liquid level detection unit 13b, and the intermediate liquid level detection unit 13c are arranged in the supply tank 41 in a bundled state. Specifically, the upper limit liquid level detection unit 13a, the lower limit liquid level detection unit 13b, and the intermediate liquid level detection unit 13c (specifically, the support unit 131 that supports the liquid level detection unit 13, see FIG. 3) are flange portions. 16 are bundled into one in a state of being inserted into 16. Then, by attaching the flange portion 16 to the lid portion 41b of the supply tank 41, the respective leading end portions 14a, 14b and 14c of the upper limit liquid level detection unit 13a, the lower limit liquid level detection unit 13b and the intermediate liquid level detection unit 13c. Is arranged in the supply tank 41. Further, a temperature sensor terminal 17 and a heater terminal 18 are provided on the opposite side of the liquid level detection unit 13 from the tip end part 14. The temperature sensor terminal 17 is connected to a control unit 19 to be described later, and is configured to transmit a temperature signal detected by the temperature sensor 11 to the control unit 19. Further, the heater terminal 18 is connected to a power source (not shown) and is configured to supply a constant current to the heater 12. The constant current is, for example, 0.5A.

  Further, as shown in FIG. 3, the liquid level detection unit 13 is supported by a support unit 131 that supports the liquid level detection unit 13 (a portion above the portion partitioned by the dotted line in FIG. 3). Inside the liquid level detection unit 13, a temperature sensor 11 and a heater 12 disposed in the vicinity of the temperature measurement unit 11 a of the temperature sensor 11 are provided. In addition, the temperature sensor 11 and the heater 12 are arranged as one set inside the liquid level detection unit 13, and a relatively simple circuit is obtained. The liquid level detection unit 13 includes a protective tube (sheath) 15 including the temperature sensor 11 and the heater 12 inside. The protective tube 15 is made of a metal such as stainless steel or nickel alloy. In addition, the material of the protective tube 15 is preferably selected so that the wire diameter of the protective tube 15 can be reduced in consideration of certain corrosion resistance. When the corrosion resistance against solder is further required, a protective film may be attached to the surface of the protective tube 15. Moreover, the temperature sensor 11 is comprised by the thermocouple, for example. A heater 12 is provided adjacent to the temperature sensor 11 in the vicinity of the temperature measuring unit 11 a on the distal end side of the temperature sensor 11. The heater 12 is configured to be supplied with a constant current. In the first embodiment, the heater 12 is configured to emit heat having a temperature higher than the melting temperature of the molten metal 1. For example, the outside of the supply tank 41 is heated to 300 ° C. by the temperature adjustment unit 46, and the heater 12 is 300 at the temperature of the supply tank 41 and the molten metal 1 when the supply tank 41 is empty. It is comprised so that the heat | fever of the temperature of 360 degreeC higher than degreeC may be emitted.

  Moreover, in 1st Embodiment, the front-end | tip part 14 of the liquid level detection part 13 has a substantially hemispherical shape. Specifically, the distal end portion 14 of the protective tube 15 is formed in a substantially hemispherical shape.

  In the first embodiment, as shown in FIG. 1, the liquid level detection system 10 is provided with a control unit 19. The control unit 19 is connected to the liquid level detection unit 13 and is configured to receive a temperature-related signal from the temperature sensor 11 of the liquid level detection unit 13. The control unit 19 is configured to determine that the tip portion 14 of the liquid level detection unit 13 and the molten metal 1 are in contact when the temperature detected by the temperature sensor 11 is equal to or lower than the threshold value. .

  Specifically, whether the tip 14a of the upper limit liquid level detector 13a, the tip 14b of the lower limit liquid level detector 13b, and the tip 14c of the intermediate liquid level detector 13c are in contact with the molten metal 1, respectively. To be judged. That is, when it is determined that the tip portion 14a of the upper limit liquid level detection unit 13a is in contact with the molten metal 1, the liquid level is positioned higher than the tip portion 14a of the upper limit liquid level detection unit 13a. It is detected. Similarly, when it is determined that the tip 14b of the lower limit liquid level detection unit 13b is in contact with the molten metal 1, the liquid level is positioned higher than the tip 14b of the lower limit liquid level detection unit 13b. Is detected. Further, when it is determined that the tip 14c of the intermediate liquid level detection unit 13c is in contact with the molten metal 1, the liquid level is positioned higher than the tip 14c of the intermediate liquid level detection unit 13c. It is detected. Thus, since it is determined whether each of the three upper limit liquid level detection units 13a, the lower limit liquid level detection unit 13b, and the intermediate liquid level detection unit 13c is in contact with the molten metal 1, the liquid level detection system 10 Various liquid level controls can be performed using

  Here, the threshold value includes a first threshold value when the temperature of the supply tank 41 is adjusted to a temperature at which the molten metal 1 melts. The first threshold value is set to 330 ° C., for example. Then, when the temperature detected by the temperature sensor 11 is equal to or lower than the first threshold value, the control unit 19 makes contact between the tip 14 of the liquid level detection unit 13 and the molten molten metal 1. It is configured to be judged. Note that “in contact” means that the liquid level of the molten metal 1 is equal to or higher than the height position of the tip 14 of the liquid level detection unit 13, as shown in FIG. In addition, the state where the liquid level of the molten metal 1 is less than the height position of the tip part 14 of the liquid level detection unit 13 and a part of the tip part 14 is connected to the molten metal 1 is excluded. The threshold value includes a second threshold value when the temperature of the supply tank 41 is not adjusted to the temperature at which the molten metal 1 melts. The second threshold value is set to 70 ° C., for example. Then, when the temperature detected by the temperature sensor 11 is equal to or lower than the second threshold value, the control unit 19 makes contact between the tip 14 of the liquid level detection unit 13 and the solidified molten metal 1. It is configured to be judged.

  Moreover, the control part 19 is comprised so that the whole metal filling apparatus 100 may be controlled. Specifically, the control unit 19 controls the opening and closing of the valve gate 43 and the opening / closing valve 44 and also controls the driving of the supply pump 42 so that the molten metal 1 accommodated in the supply tank 41 is supplied to the valve. It is configured to be supplied to the processing chamber 23 through the gate 43. And the control part 19 is comprised so that the molten metal 1 may be replenished to the tank 41 for supply by controlling the pump etc. which are provided in the piping 45 for replenishment.

  Next, with reference to FIG. 4A to FIG. 4C, a change in temperature detected by the temperature sensor 11 when the molten metal 1 comes into contact with the tip portion 14 of the liquid level detection unit 13 will be described.

First, heat loss from the liquid level detection unit 13 will be described. The heat loss Pl from the liquid level detection unit 13 is expressed by the following formula (1) using the convection heat loss Pc, the radiant heat loss Pr, and the loss Ps due to heat conduction to the support unit 131 that supports the liquid level detection unit 13. It is represented by
Pl = Pc + Pr + Ps (1)

The convective heat loss Pc is determined by using the convective heat transfer coefficient h of the surrounding material of the liquid level detection unit 13, the temperature Ts of the liquid level detection unit 13, the temperature Ta of the supply tank 41, and the surface area A of the liquid level detection unit 13. It is represented by the following formula (2).
Pc = h × (Ts−Ta) × A (2)

The radiant heat loss Pr is expressed by the following equation using the emissivity ε, the Stefan-Boltzmann constant σ, the temperature Ts of the liquid level detector 13, the temperature Ta of the supply tank 41, and the surface area A of the liquid level detector 13. It is represented by (3).
Pr = ε × A × σ × (Ts ⁴ −Ta ⁴ ) (3)

In addition, the loss Ps due to heat conduction to the support 131 supporting the liquid level detection unit 13 is the thermal conductivity λ, the cross-sectional area B, the length L of the support 131, the temperature Ts of the liquid level detection unit 13, and the supply Using the temperature Ta of the tank 41, it is expressed by the following equation (4).
Ps = λ / L × (Ts−Ta) × B (4)

  Next, as shown in FIG. 4A, the liquid level of the molten metal 1 is lower than the height position of the front end part 14 of the liquid level detection unit 13, and the front end part 14 of the liquid level detection unit 13 and the molten metal The state where 1 is not in contact will be described. Hereinafter, the state shown in FIG. 4A is referred to as a “non-contact state”. Here, the amount of heat Pin is supplied from the heater 12 of the liquid level detection unit 13, and the temperature Ts of the liquid level detection unit 13 is set higher than the temperature Ta of the supply tank 41. Thereby, the temperature Ts of the liquid level detection unit 13 is stabilized at the temperature Tsh in a state where the heat loss Pl and the amount of heat Pin expressed by the above formula (1) are in equilibrium. Here, when the inside of the supply tank 41 is not vacuum (for example, in the case of air), the convective heat loss Pc has a predetermined value, and when the inside of the supply tank 41 is vacuum, the convective heat loss Pc is 0. become.

  Next, as shown in FIG. 4 (b), the liquid level of the molten metal 1 is higher than the height position of the tip part 14 of the liquid level detection unit 13, and the tip part 14 of the liquid level detection unit 13 is The state in contact with 1 will be described. Hereinafter, the state as shown in FIG. 4B is referred to as a “contact state”. Here, when the liquid level detection unit 13 contacts the molten metal 1, convective heat loss due to the molten metal 1 is newly generated in addition to convective heat loss Pc due to air (0 in the case of vacuum). As a result, when the amount of heat Pin is constant, the temperature Tsh in an equilibrium state cannot be maintained, and the temperature Ts of the liquid level detection unit 13 reaches a temperature at which the increased heat loss Pl and the amount of heat Pin are balanced. Decreases. The contact state is detected by detecting this decrease in temperature. Note that the convective heat loss Pc due to the molten metal 1 is very large compared to the convective heat loss Pc due to air, so that the liquid level detector 13 may or may not have the convective heat loss Pc due to air. The temperature Ts is greatly reduced. Specifically, the heat transfer coefficient is a complicated value that is affected by the flow state such as convection. On the other hand, if conditions other than the material are the same, the heat transfer coefficient greatly depends on the heat conductivity. Air conductivity is 0.024 W / (mK) with respect to 55 W / (mK), and there is a difference of 1000 times or more. That is, the temperature drop when the supply tank 41 changes from the non-contact state to the contact state is remarkable both in the atmospheric pressure state (air is present) and in the vacuum state. Therefore, the same explanation is valid whether air is present or not (vacuum).

  Further, as shown in FIG. 4C, the liquid level of the molten metal 1 is located in the vicinity of the tip 14 of the liquid level detector 13, and a part of the tip 14 of the liquid level detector 13 is melted. The state connected to the metal 1 will be described. Hereinafter, the state as shown in FIG. 4C is referred to as a “partially contacted state”. In the partial contact state, the liquid level detection unit 13 partially contacts the molten metal 1, thereby causing convective heat loss due to the molten metal 1. On the other hand, compared to the contact state of FIG. 4B, the degree of decrease in the temperature Ts of the liquid level detection unit 13 is in the contact state because the contact area between the liquid level detection unit 13 and the molten metal 1 is small. It is considered to be smaller than that. In the partial contact state, the same explanation is valid whether there is convection heat loss Pc due to air or not (vacuum) as in the above contact state.

  Next, using the above equations (1) to (4), numerical values are applied specifically, and each state of FIGS. 4 (a) to 4 (c) will be described. Below, the case where the inside of the tank 41 for supply is a vacuum is demonstrated.

  First, the temperature Ta of the supply tank 41 was heated to 300 ° C. Here, in the non-contact state shown in FIG. 4A, a heat amount Pin of 0.75 W was supplied to the liquid level detection unit 13 (heater 12). As a result, the temperature Ts of the liquid level detector 13 was stabilized at 362 ° C. At this time, the convective heat loss Pc was 0, the radiant heat loss Pr was 0.08 W, and the heat conduction loss Ps was 0.67 W.

  Next, in the contact state shown in FIG. 4B, the temperature Ts of the liquid level detection unit 13 was stabilized at 319 ° C. As the temperature Ts of the liquid level detection unit 13 decreases, the radiant heat loss Pr becomes 0.02 W, and the heat conduction loss Ps decreases to 0.2 W. On the other hand, a convective heat loss Pc occurs and the heat loss Pl Is balanced with a heat loss Pl of 0.75 W.

  Next, in the partial contact state shown in FIG. 4C, the heat of the heater 12 is transferred through the molten metal 1 attached to a part of the tip 14 of the liquid level detection unit 13. The temperature Ts of the detector 13 increased from 319 ° C. to 338 ° C. That is, the heat loss Pl in the partial contact state is smaller than the heat loss Pl in the contact state. Further, the temperature of 338 ° C. corresponds to a temperature at which ¼ of the surface area A of the liquid level detection unit 13 is stable while being in contact with the molten metal 1.

  Thus, the temperature detected by the temperature sensor 11 changes according to the height position of the liquid level of the molten metal 1. And based on this temperature change, the molten metal 1 is set by setting a threshold value between the temperature Ts of the liquid level detection unit 13 in the contact state and the temperature Ts of the liquid level detection unit 13 in the partial contact state. It is possible to determine whether or not the liquid level is in contact with the tip 14 of the liquid level detector 13. It should be noted that the threshold value is preferably high for improving the certainty of detection of the liquid level and low for heat resistance and prevention of molten metal deterioration. Moreover, the calculation in the description of FIG. 4A to FIG. 4C is a model showing a concept for obtaining a threshold value, and when a more appropriate threshold value is obtained, a heat conduction simulation is performed. Find it.

  Next, the operation of the control unit 19 of the liquid level detection system 10 will be described with reference to FIG.

  When the control unit 19 determines that the upper limit liquid level detection unit 13a is in a contact state, the control unit 19 stops the refilling of the molten metal 1 into the supply tank 41 and stops the metal filling device 100 because it detects an abnormality. Let Moreover, when the control part 19 judges that the upper limit liquid level detection part 13a is a non-contact state, the metal filling apparatus 100 is a normal state.

  Further, when the control unit 19 determines that the lower limit liquid level detection unit 13b is in a contact state, the metal filling device 100 is in a normal state and can perform the next process using the molten metal 1. State. Moreover, when the control part 19 judges that the minimum liquid level detection part 13b is a non-contact state, the next process using the molten metal 1 is stopped. If the next process is being processed, the process is continued.

  When the control unit 19 determines that the intermediate liquid level detection unit 13c is in contact, the supply tank 41 is not replenished with the molten metal 1. Further, when it is determined that the intermediate liquid level detection unit 13c is in contact with the supply tank 41 while the molten metal 1 is being replenished, the replenishment is continued until one replenishment of the molten metal 1 is completed. In addition, when the control unit 19 determines that the intermediate liquid level detection unit 13c is in a non-contact state, the molten metal 1 can be replenished to the supply tank 41.

  Specifically, the control unit 19 increases the molten metal 1 in the supply tank 41, and when the contact state of the upper limit liquid level detection unit 13a is continuously detected, the supply tank 41 for the molten metal 1 is detected. Stop refilling inside. Moreover, the control part 19 stops the process of the metal filling apparatus 100, when the molten metal 1 in the tank 41 for supply reduces and the non-contact state of the minimum liquid level detection part 13b is detected continuously. Further, when it is determined that the intermediate liquid level detection unit 13c has changed from the contact state to the non-contact state, the control unit 19 determines that the molten metal replenishment operation to the supply tank can be started. Further, when the control unit 19 determines that the upper limit liquid level detection unit 13a is in a contact state and the intermediate liquid level detection unit 13c is in a non-contact state, the upper limit liquid level detection unit 13a is in a contact state and the lower limit liquid level When it is determined that the surface detection unit 13b is in the non-contact state, the liquid level detection unit 13c is determined when the intermediate liquid level detection unit 13c is in the contact state and the lower limit liquid level detection unit 13b is in the non-contact state. It is determined that there are 13 abnormalities (failures).

  Next, with reference to FIG. 6 and FIG. 7, the experiment performed about the detection of the temperature of the molten metal 1 accommodated in the tank 41 for supply is demonstrated.

  In this experiment, as shown in FIGS. 1 and 2, an upper limit liquid level detection unit 13a, a lower limit liquid level detection unit 13b, and an intermediate liquid level detection unit 13c are arranged in the supply tank 41. Further, the supply tank 41 was heated to 300 ° C. higher than the melting point of the molten metal 1 so that the molten metal 1 was accommodated in a molten state that is a liquid.

  First, as shown in FIG. 6, the molten metal 1 is not stored in the supply tank 41 at time t <b> 0 which is the initial state. At this time, the temperature detected by the temperature sensor 11 of the upper limit liquid level detection unit 13a was about 363 ° C. Further, the temperature detected by the temperature sensors 11 of the lower limit liquid level detection unit 13b and the intermediate liquid level detection unit 13c was about 362 ° C.

  Next, at time t1, the supply of the molten metal 1 to the supply tank 41 was started. As a result, immediately after time t1, the temperature detected by the temperature sensor 11 of the lower limit liquid level detection unit 13b began to rapidly decrease. Further, at the time t2, the temperature detected by the temperature sensor 11 of the intermediate liquid level detector 13c starts to rapidly decrease.

  Next, at time t3, the temperatures detected by the respective temperature sensors 11 of the intermediate liquid level detection unit 13c and the lower limit liquid level detection unit 13b were approximately 310 ° C. Thereby, at the time t3, it can be considered that the intermediate liquid level detection unit 13c and the lower limit liquid level detection unit 13b are in a contact state (see FIG. 4B).

  Next, at time t4, discharging of the molten metal 1 from the supply tank 41 was started. Then, immediately after time t4, the temperature detected by the temperature sensor 11 of the intermediate liquid level detector 13c began to rise. Thereby, in the time after time t4, the intermediate liquid level detection part 13c is in the state which has changed from the contact state (refer FIG.4 (b)) to the partial contact state (refer FIG.4 (c)). It is believed that there is.

  Further, as shown in FIG. 6, at the time t5, the temperatures detected by the temperature sensors 11 of the upper limit liquid level detection unit 13a, the intermediate liquid level detection unit 13c, and the lower limit liquid level detection unit 13b are 362.1 ° C. It was confirmed that the temperature was 337.9 ° C and 318.6 ° C. That is, at time t5, the upper limit liquid level detection unit 13a is in a non-contact state, the intermediate liquid level detection unit 13c is in a partial contact state, and the lower limit liquid level detection unit 13b is in a contact state. . From the above results, the first threshold value when the temperature of the supply tank 41 is adjusted to the temperature at which the molten metal 1 melts is set to 330 ° C., which is the temperature between the contact state and the partial contact state. By doing so, it has been found that it is possible to determine whether or not the tip 14 of the liquid level detector 13 is in contact with the molten metal 1.

  Further, as shown in FIG. 7, when the temperature of the supply tank 41 is not adjusted to the temperature at which the molten metal 1 melts (35 ° C.), the molten metal 1 is supplied and then discharged, and after a certain time has elapsed. At the time corresponding to the time t5, which is the time of, the temperatures detected by the temperature sensors 11 of the upper limit liquid level detection unit 13a, the intermediate liquid level detection unit 13c, and the lower limit liquid level detection unit 13b are 232.0 ° C, It was confirmed to be 72.6 ° C and 36.8 ° C. That is, it is considered that the upper limit liquid level detection unit 13a is in a non-contact state, the intermediate liquid level detection unit 13c is in a partial contact state, and the lower limit liquid level detection unit 13b is in a contact state. From the above results, the second threshold value when the temperature of the supply tank 41 is not adjusted to the temperature at which the molten metal 1 melts is set to 70 ° C., which is the temperature between the contact state and the partial contact state. By doing so, it has been found that it is possible to determine whether or not the tip 14 of the liquid level detector 13 is in contact with the molten metal 1.

  The application conditions of the first threshold value are a state where the temperature of the supply tank 41 is stable at 300 ° C. ± 10 ° C., and the heater 12 is in an ON state. The application condition of the second threshold is that the temperature of the supply tank 41 is about 35 ° C. and the heater 12 is ON. Whether the molten metal 1 is in contact or not in contact is not determined while the temperature of the supply tank 41 is rising or falling.

  In the first embodiment, the following effects can be obtained.

  In the first embodiment, as described above, the heater 12 is disposed in the vicinity of the temperature measuring unit 11a of the temperature sensor 11, and the temperature detected by the temperature sensor 11 is a threshold value (first threshold value, second threshold value). It is configured to determine that the tip portion 14 of the liquid level detection unit 13 and the molten metal 1 are in contact with each other when the threshold value is equal to or less than the threshold value. Here, when the tip 14 of the liquid level detection unit 13 and the molten metal 1 are not in contact with each other, the temperature detected by the temperature sensor 11 due to the heat generated from the heater 12 is relatively high. On the other hand, when the tip portion 14 of the liquid level detection unit 13 and the molten metal 1 are in contact with each other, the heat detected by the heater 12 is transferred to the molten metal 1, so that the temperature detected by the temperature sensor 11 is Relatively low. Therefore, in the first embodiment, based on the fact that the temperature measured by the temperature sensor 11 is equal to or lower than the threshold value, it is easily determined that the tip 14 of the liquid level detector 13 and the molten metal 1 are in contact. can do. Further, as described above, by configuring the temperature sensor 11 to be included in the liquid level detection unit 13, even when an oxide adheres to the outer surface of the liquid level detection unit 13, Since the surface of the internal temperature sensor 11 is not electrically affected by the deposits, the liquid level can be detected with high accuracy.

  In the first embodiment, as described above, the heater 12 is configured to emit heat at a temperature higher than the melting temperature of the molten metal 1. Thereby, when the tip 14 of the liquid level detector 13 and the molten metal 1 come into contact with each other, the heat generated from the heater 12 is transferred to the molten metal 1, so the tip 14 of the liquid level detector 13. There is a temperature difference between the temperatures detected by the temperature sensor 11 before and after the molten metal 1 comes into contact with the molten metal 1. As a result, it is easily determined based on the detection result of the temperature sensor 11 that the tip 14 of the liquid level detection unit 13 and the molten metal 1 are in contact.

  Further, in the first embodiment, as described above, the three liquid level detection units 13 are provided, and the plurality of liquid level detection units 13 are arranged in the supply tank 41 at the height positions of the respective front end portions 14. Arrange them differently. As a result, the liquid level of the molten metal 1 is detected by determining which of the liquid level detection units 13 the tip portion 14 of the liquid level detection unit 13 is in contact with the molten metal 1. It can be determined whether it is located in the vicinity of the tip portion 14 of the portion 13. As a result, the height position of the liquid level can be detected in a plurality of stages.

  In the first embodiment, as described above, the upper limit liquid level detection unit 13a in which the tip part 14a is disposed at the height position h1 and the tip part 14b at the height position h2 lower than the height position h1. A lower limit liquid level detection unit 13b that is disposed and an intermediate liquid level detection unit 13c in which the tip end portion 14c is disposed at a height position h3 between the height position h1 and the height position h2 are provided. Thereby, based on judging that the front-end | tip part 14a of the upper limit liquid level detection part 13a arrange | positioned in the highest height position h1 and the molten metal 1 contacted, by stopping the replenishment of the molten metal 1 The overflow of the molten metal 1 from the supply tank 41 can be suppressed. Moreover, the process using the molten metal 1 is stopped based on determining that the tip portion 14b of the lower limit liquid level detection unit 13b disposed at the lowest height position h2 is not in contact with the molten metal 1. By carrying out, it can suppress that a process is performed in the state where the molten metal 1 is insufficient. Further, based on determining whether or not the tip 14c of the intermediate liquid level detection unit 13c disposed at the intermediate height position h3 is in contact with the molten metal 1, the molten metal to the supply tank 41 is determined. By determining whether or not one replenishment operation can be started (replenishment is started in a non-contact state), replenishment can be started at an appropriate timing.

  In the first embodiment, as described above, the three liquid level detectors 13 are arranged in the supply tank 41 in a bundled state. Thereby, unlike the case where the three liquid level detection units 13 are arranged in a state of being separated from each other, it is possible to reduce the mounting area for attaching the three liquid level detection units 13 to the supply tank 41.

  Moreover, in 1st Embodiment, as mentioned above, it comprises so that the front-end | tip part 14 of the liquid level detection part 13 may have a substantially hemispherical shape. Accordingly, when the liquid level is lower than the tip part 14 of the liquid level detection unit 13, the molten metal 1 attached to the tip part 14 of the liquid level detection unit 13 is quickly dropped, so that the liquid level detection unit The molten metal 1 adhering to the tip portion 14 of 13 is quickly removed from the tip portion 14 of the liquid level detecting portion 13. As a result, it is possible to suppress the state where the molten metal 1 is attached to the tip portion 14 of the liquid level detection unit 13.

  In the first embodiment, as described above, the temperature detected by the temperature sensor 11 is provided by providing the first threshold value when the temperature of the supply tank 41 is adjusted to the temperature at which the molten metal 1 melts. However, when it becomes below a 1st threshold value, it comprises so that it may judge that the front-end | tip part 14 of the liquid level detection part 13 and the molten metal 1 are contacting. Thereby, based on the detection result of the temperature sensor 11 by using the first threshold value, is the tip 14 of the liquid level detector 13 and the molten metal 1 in a molten state in contact with each other easily? It is determined whether or not.

  In the first embodiment, as described above, the temperature detected by the temperature sensor 11 is provided by providing the second threshold value when the temperature of the supply tank 41 is not adjusted to the temperature at which the molten metal 1 melts. However, when it becomes below a 2nd threshold value, it is comprised so that it may judge with the solidified molten metal 1 contacting the front-end | tip part 14 of the liquid level detection part 13. FIG. Thereby, based on the detection result of the temperature sensor 11 by using the second threshold value, it is easily determined whether or not the distal end portion 14 of the liquid level detection unit 13 is in contact with the solidified molten metal 1. To be judged.

  In the first embodiment, as described above, the first threshold value and the second threshold value are set based on the temperature when the tip portion 14 of the liquid level detection unit 13 is in contact with the molten metal 1 and the liquid level. It is set between the temperature when a part of the tip 14 of the surface detection unit 13 is connected to the molten metal 1. Thereby, it is determined that the tip 14 of the liquid level detector 13 is in contact with the molten metal 1 without being confused with the case where a part of the tip 14 of the liquid level detector 13 is connected to the molten metal 1. can do.

(Second Embodiment)
Next, the configuration of the liquid level detection system 90 according to the second embodiment will be described with reference to FIG. In the second embodiment, unlike the first embodiment in which the three liquid level detectors 13 are provided, four liquid level detectors 91 are provided. The liquid level detection unit 91 is an example of the “liquid level detection device” in the present invention.

  The liquid level detection unit 91 includes an upper limit liquid level detection unit 91a, a lower limit liquid level detection unit 91b, a first intermediate liquid level detection unit 91c, and a second intermediate liquid level detection unit 91d. The tip 92a of the upper limit liquid level detector 91a, the tip 92b of the lower limit liquid level detector 91b, the tip 92c of the first intermediate liquid level detector 91c, and the tip 92d of the second intermediate liquid level detector 91d The respective height positions h11, h12, h13 and h14 have a relationship of h11> h14> h13> h12. The liquid level detection unit 91 is connected to the control unit 93. The upper limit liquid level detection unit 91a and the lower limit liquid level detection unit 91b are examples of the “first liquid level detection unit” and the “second liquid level detection unit” in the present invention, respectively. The first intermediate liquid level detection unit 91c and the second intermediate liquid level detection unit 91d are examples of the “third liquid level detection unit” in the present invention. The height position h11 and the height position h12 are examples of the “first height position” and the “second height position” in the present invention, respectively. The height position h13 and the height position h14 are examples of the “third height position” in the present invention. In addition, the other structure of 2nd Embodiment is the same as that of the said 1st Embodiment.

  Next, the operation of the control unit 93 of the liquid level detection system 90 will be described with reference to FIG.

  Here, the operations of the upper limit liquid level detection unit 91a and the lower limit liquid level detection unit 91b in the contact state and the non-contact state are the same as those in the first embodiment.

  When the controller 93 determines that the first intermediate liquid level detector 91c is in a non-contact state, the replenishment operation of the molten metal 1 from the supply tank 41 is started. When the controller 93 determines that the second intermediate liquid level detector 91d is in contact, the replenishment operation of the molten metal 1 from the supply tank 41 is stopped. Specifically, when the non-contact state of the first intermediate liquid level detection unit 91c continues for a certain period of time, the replenishment of the molten metal 1 is started and the replenishment is performed until the second intermediate liquid level detection unit 91d is in the contact state. Is called.

  The effect of the second embodiment is the same as that of the first embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first and second embodiments, an example using a thermocouple as the temperature sensor has been shown, but the present invention is not limited to this. For example, a resistance temperature detector other than a thermocouple may be used as the temperature sensor.

  In the first and second embodiments, the first threshold value is 330 ° C. and the second threshold value is 70 ° C., but the present invention is not limited to this. Here, the threshold value needs to be set to a temperature exceeding the temperature of the object. Specifically, the first threshold value needs to be set to a temperature exceeding 300 ° C., which is the temperature of the molten metal, and the second threshold value needs to be set to a temperature exceeding room temperature. That is, the threshold value is such that when the tip of the liquid level detection unit and the molten metal come into contact with each other, the temperature detected by the temperature sensor is lowered by transferring the heat generated from the heater to the molten metal. This is a condition for detecting a case.

  In the first embodiment, three liquid level detection units are provided in the liquid level detection system, and in the second embodiment, four liquid level detection units are provided in the liquid level detection system. The invention is not limited to this. For example, the liquid level detection system may be provided with a number of liquid level detection units other than three or four.

  Moreover, in the said 1st Embodiment, while being arrange | positioned in the tank for supply in the state which bundled three liquid level detection parts, in the 2nd Embodiment, in the state where four liquid level detection parts were bundled Although the example arrange | positioned in the tank for supply was shown, this invention is not limited to this. For example, three or four liquid level detection units may be arranged in the supply tank in a state of being separated from each other.

DESCRIPTION OF SYMBOLS 1 Molten metal 10, 90 Liquid level detection system 11 Temperature sensor 11a Temperature measuring part 12 Heater 13, 91 Liquid level detection part (liquid level detection apparatus)
13a, 91a Upper limit liquid level detection unit (liquid level detection unit, first liquid level detection unit)
13b, 91b Lower limit liquid level detection unit (liquid level detection unit, second liquid level detection unit)
13c Intermediate liquid level detector (liquid level detector, third liquid level detector)
14, 14a, 14b, 14c Tip section 17, 93 Control section 41 Supply tank (container)
91c 1st intermediate | middle liquid level detection part (a liquid level detection part, a 3rd liquid level detection part)
91d Second intermediate liquid level detection unit (liquid level detection unit, third liquid level detection unit)
92a, 92b, 92c, 92d Tip portion 100 Liquid level detection system h1, h11 Height position (first height position)
h2, h12 height position (second height position)
h3, h13, h14 Height position (third height position)

Claims (10)

A liquid level detection device for detecting the level of molten metal contained in a container,
A liquid level detection unit that is disposed inside the container and includes a temperature sensor and a heater disposed in the vicinity of the temperature measurement unit of the temperature sensor,
A liquid level detection device configured to determine that the tip of the liquid level detection unit and the molten metal are in contact with each other when a temperature detected by the temperature sensor is equal to or lower than a threshold value.   The liquid level detection device according to claim 1, wherein the heater is configured to emit heat having a temperature higher than a melting temperature of the molten metal. A plurality of the liquid level detection units are provided,
3. The liquid level detection device according to claim 1, wherein the plurality of liquid level detection units are arranged in the container so that the height positions of the respective leading end portions thereof are different.   The liquid level detection unit includes a first liquid level detection unit in which each front end is arranged at a first height position and a second height position lower than the first height position. A second liquid level detection unit, and a third liquid level detection unit disposed at a third height position between the first height position and the second height position. The liquid level detection device according to claim 3.   The liquid level detection device according to claim 3, wherein the plurality of liquid level detection units are arranged in the container in a bundled state.   The liquid level detection device according to claim 1, wherein a front end portion of the liquid level detection unit has a substantially hemispherical shape. The threshold value includes a first threshold value when the temperature of the container is adjusted to a temperature at which the molten metal melts,
When the temperature detected by the temperature sensor becomes equal to or lower than the first threshold value, the tip of the liquid level detection unit and the molten metal are determined to be in contact with each other. The liquid level detection apparatus of any one of Claims 1-6. The threshold value includes a second threshold value when the temperature of the container is not adjusted to a temperature at which the molten metal melts,
When the temperature detected by the temperature sensor becomes equal to or lower than the second threshold value, it is configured to determine that the solidified molten metal is in contact with the tip of the liquid level detection unit. The liquid level detection device according to any one of claims 1 to 7.   The threshold value is a temperature when the tip of the liquid level detection unit is in contact with the molten metal, and a temperature when a part of the tip of the liquid level detection unit is connected to the molten metal. The liquid level detection apparatus of any one of Claims 1-8 set between these. A liquid level detection system for detecting a liquid level of a molten metal contained in a container,
A liquid level detection unit disposed in the container and including a temperature sensor and a heater disposed in the vicinity of the temperature measurement unit of the temperature sensor;
When the temperature detected by the temperature sensor falls below a threshold value, it is determined that the tip of the liquid level detection unit and the molten metal are in contact with each other, and the molten metal is replenished in the container. Or a control unit that stops processing using the molten metal,
The liquid level detection unit includes a first liquid level detection unit in which each front end is arranged at a first height position and a second height position lower than the first height position. A second liquid level detection unit,
The control unit stops replenishment of the molten metal into the container when it is determined that the tip of the first liquid level detection unit is in contact with the molten metal, and the second liquid level detection unit A liquid level detection system configured to stop the processing using the molten metal when it is determined that the tip of the molten metal is not in contact with the molten metal.

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