Multi-point thermocouple, temperature sensing mechanism, and mold for continuous casting

Abstract

This invention aims to improve the time response of temperature measurement and to realize a multi-point thermocouple that eliminates temperature variations due to the position of the contacts when measuring the temperature inside a device where heat flow is unidirectional. [Solution] A multipoint thermocouple 1 having multiple temperature-measuring contacts 4, wherein the contact point between the metal of the first electrode 11 and the metal of the second electrode 12 is the temperature-measuring contact 4 of the thermocouple, and the cylindrical outer cylinder 2 forms the first electrode 11, and the outer cylinder 2 has two or more wires (second electrode wires 3) forming the second electrode 12 inside the outer cylinder 2, all of the second electrode wires 3 are in contact with the inner surface of the outer cylinder 2 to form the temperature-measuring contacts 4, all of the temperature-measuring contacts 4 are arranged in the same direction in the circumferential direction 15 of the outer cylinder 2, the first electrode 11 and the second electrode 12 are insulated from each other except for the temperature-measuring contacts 4, and furthermore the second electrode wires 3 are insulated from each other.

Description

[Technical Field]

[0001] The present invention relates to a multi-point thermocouple, a temperature measuring mechanism, and a mold for continuous casting, and in particular to measuring the internal temperature of a device in which the heat flow direction is unidirectional at multiple points simultaneously with high accuracy and high temporal resolution. [Background technology]

[0002] A thermocouple utilizes the phenomenon where an electromotive force is generated between two different conductive materials at the point of contact, depending on the temperature of that point, and measures the temperature of that junction. In the industrial field, thermocouples that use two different metals as the first and second electrodes, with a junction at one end of each electrode, are widely used.

[0003] For example, when measuring the temperature distribution of a heat-receiving surface with a certain area, it is necessary to increase the number of temperature measurement points as much as possible to improve the spatial resolution of the temperature distribution. Alternatively, if the temperature changes moment by moment, it is necessary to improve the time response of the temperature measurement to sensitively capture temperature changes.

[0004] To increase the number of temperature measurement points using thermocouples, it is convenient to use a multi-point thermocouple that can measure temperature at multiple points with a single unit. Many inventions have been made to meet this need.

[0005] Since the presence of thermocouples disrupts the heat flow within the device, it is desirable to keep the outer diameter of multi-point thermocouples as small as possible. One method used in this regard is to share one of the first or second electrodes; for example, Patent Document 1 discloses a multi-point thermocouple technology in which one electrode is shared. However, the temperature sensing junction is housed within a protective tube, which is disadvantageous in terms of the time response of temperature measurement.

[0006] In thermocouples housed within protective tubes, the time response of temperature measurement can be improved by making the protective tube itself the first electrode, and such a technique is disclosed in Patent Document 2. However, in Figures 1 to 4, which show embodiments of Patent Document 2, a structure is disclosed in which the temperature sensing junctions are evenly arranged in the circumferential direction of the cross-section. This does not resolve the problem that when measuring the temperature inside a device where heat flow is unidirectional, the temperature measurement value varies depending on the position of the junctions within the cross-section of the protective tube.

[0007] Patent Document 3 discloses a multi-point temperature measuring device in which the reference junctions of multiple thermocouples are placed in a common temperature measuring unit, and the temperature measuring junctions of each thermocouple are placed at multiple points aligned on a line to measure the temperature at the multiple points, characterized in that one of the two metal wires constituting each thermocouple is a common metal wire used for each thermocouple. This invention is suitable when it is necessary to determine the temperature at multiple points aligned on a line. However, because the thermocouple consists of two metal wires, it lacks rigidity, making it difficult to install in narrow spaces, and in cases where installation is difficult, the use of a protective tube is necessary. Furthermore, Patent Documents 1 to 3 do not disclose the specific dimensions of the thermocouple, and therefore cannot solve the problems of the present invention. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Utility Model Publication No. 58-189940 [Patent Document 2] Japanese Utility Model Publication No. 3-71666 [Patent Document 3] Japanese Patent Publication No. 2003-57120 [Overview of the project] [Problems that the invention aims to solve]

[0009] Compared to the conventional technology, the present invention provides a multi-point thermocouple, a temperature sensing mechanism, and a mold for continuous casting that improve the time response of temperature measurement by arranging multiple temperature sensing junctions on a narrow outer diameter, and solves the problem of variations in the measured temperature and its time response depending on the position of the junctions when measuring the temperature inside a device where heat flow is unidirectional. [Means for solving the problem]

[0010] In other words, the gist of this invention is as follows: [1] A multi-point thermocouple having a plurality of such temperature-measuring junctions, wherein the contact point between the metal of the first electrode and the metal of the second electrode is used as the temperature-measuring junction of the thermocouple. A cylindrical outer tube with a diameter of 1.00 to 2.40 mm and a thickness of 0.02 to 0.34 mm forms the first pole, and the outer tube has two or more wires forming the second pole (second pole wires) inside, all of which are in contact with the inner surface of the outer tube to form the temperature sensing junction. A connecting line extending in the longitudinal direction of the outer cylinder is assumed on the inner surface of the outer cylinder, and the connecting line is positioned in the same orientation in the circumferential direction of the outer cylinder at any position in the longitudinal direction of the outer cylinder, and all of the temperature sensing junctions are positioned along the connecting line in the longitudinal direction of the outer cylinder. A multi-point thermocouple characterized in that, apart from the temperature sensing junction, the first and second electrodes are insulated, and the second electrode wires are further insulated from each other.

[0011] [2] The multipoint thermocouple according to [1], characterized in that when the thermal conductivity of the outer cylinder is λ (W / (mK)) and the thickness of the outer cylinder is d (m), it satisfies equation (1). λ / d ≥ 60000W / (m 2 K)...Equation (1) [3] The multipoint thermocouple according to [1] or [2], characterized in that the outer surface of the outer cylinder is insulated. [4] A multipoint thermocouple according to any one of [1] to [3], characterized in that constantan is used as the metal of the first electrode and copper is used as the metal of the second electrode. [5] In the cross-section of the internal space of the outer cylinder, the cross-sectional area is 1.00 mm 2The multi-point thermocouple according to any one of [1] to [4], characterized by having 4.0 or more second polar lines per unit area.

[0012] A temperature measuring mechanism provided by contacting the multi-point thermocouple according to any one of [1] to [5] with a temperature measuring target, wherein the thermal conductivity of the outer cylinder is lower than the thermal conductivity of the material of the temperature measuring target.

[0013] A mold for continuous casting made of copper or a copper alloy, characterized in that the multi-point thermocouple according to any one of [1] to [5] is disposed inside the mold.

Advantages of the Invention

[0014] Thus, according to the present invention, a multi-point thermocouple can be obtained that has a large number of temperature measuring contacts within limited external dimensions, is excellent in the time response of temperature measurement with respect to a specific heat flow direction, and can solve the problem that the measured temperature and its time response vary depending on the position of the contacts.

Brief Description of the Drawings

[0015] [Figure 1] A view showing a multi-point thermocouple, where (A) is a sectional view taken along the A-A arrow, (B), (C), and (D) are sectional views taken along the B-B, C-C, and D-D arrows respectively, and (E) is a view taken along the E-E arrow. [Figure 2] A view showing a multi-point thermocouple, where (A) is a sectional view taken along the A-A arrow, (B) is a sectional view taken along the B-B arrow, and (C) is a view taken along the C-C arrow. [Figure 3] A sectional view showing a multi-point thermocouple. [Figure 4] A view showing a multi-point thermocouple, where (A) is a sectional view taken along the A-A arrow and (B) is a sectional view taken along the B-B arrow. [Figure 5] A view showing a multi-point thermocouple, where (A) is a sectional view taken along the A-A arrow and (B) is a sectional view taken along the B-B arrow. [Figure 6] A view showing a multi-point thermocouple, where (A) is a sectional view taken along the A-A arrow, (B) is a sectional view taken along the B-B arrow, and (C) is a view taken along the C-C arrow. [Figure 7]This figure shows the time course of temperature measured by a thermocouple. [Modes for carrying out the invention]

[0016] This invention relates to a multi-point thermocouple 1 (see Figure 1) having multiple temperature-measuring junctions 4, where the contact point between the metal of the first electrode 11 and the metal of the second electrode 12 is the temperature-measuring junction 4 of the thermocouple, as well as a temperature-measuring mechanism using the multi-point thermocouple and a mold for continuous casting. A thermocouple is a thermometer that measures the temperature difference through the thermoelectric voltage generated at a contact point by creating a circuit by bringing together two dissimilar metals, the metal of the first electrode and the metal of the second electrode, at a contact point. The contact point of the circuit consists of a hot junction and a cold junction, and the temperature of the object to be measured is measured at the hot junction. Here, the hot junction is called the temperature-measuring junction. Electrical resistance welding can be used to form the temperature-measuring junction. In this disclosure, a numerical range represented by "~" means a range that includes the numbers before and after "~" as the lower and upper limits, unless otherwise specified.

[0017] 《First Embodiment》 The multi-point thermocouple of the first embodiment, as shown in Figure 1, has a cylindrical outer cylinder 2 and two or more wires inside it. The cross-sectional shape of the cylindrical outer cylinder 2 does not need to be a perfect circle; it may be elliptical. If the cross-sectional shape of the outer cylinder 2 is elliptical, the aspect ratio (major axis / minor axis) is preferably 2.0 or less. The cylindrical outer cylinder 2 forms the first pole 11 of the thermocouple, and the two or more wires inside the outer cylinder 2 form the second pole wires 3 as the second pole 12. All one end of the second pole wires 3 is in contact with the inner surface of the outer cylinder 2 to form a temperature sensing junction 4.

[0018] As shown in Figure 1(E), a connecting line 13 is assumed to extend along the longitudinal direction 14 of the outer cylinder 2 on the inner surface of the outer cylinder 2. The connecting line 13 is positioned in the same orientation in the circumferential direction 15 of the outer cylinder 2 at any position along the longitudinal direction 14 of the outer cylinder 2. All of the temperature sensing junctions 4 are positioned along the connecting line 13 along the longitudinal direction 14 of the outer cylinder 2. As a result, all of the temperature sensing junctions 4 are positioned in the same orientation in the circumferential direction 15 of the outer cylinder 2. Here, it is not necessary for the temperature sensing junctions 4 to be in a position that perfectly coincides with the assumed connecting line 13 in the circumferential direction; if the angle between the temperature sensing junction 4 and the connecting line 13 in the circumferential direction is 5° or less, the temperature sensing junctions 4 can be said to be positioned along the connecting line 13.

[0019] To achieve the first objective of the present invention, "to arrange many temperature sensing junctions on a narrow outer diameter," it is necessary to make one of the poles a common pole. In this embodiment, this condition is met by making the outer cylinder 2 itself the common pole, the first pole 11. For the second objective of the present invention, "to improve the time response of temperature measurement," it is also reasonable to make the outer cylinder 2 itself the first pole 11 rather than housing the temperature sensing junctions inside a protective tube. For the third objective of the present invention, "to reduce the variation in measured temperature due to the position of the junctions in a device where heat flow is unidirectional and measure the temperature with high accuracy," in this embodiment, the assumed connection line 13 is positioned in the same orientation in the circumferential direction 15 of the outer cylinder 2 at any position in the longitudinal direction 14 of the outer cylinder 2, and all of the temperature sensing junctions 4 are arranged along the connection line 13 in the longitudinal direction 14 of the outer cylinder 2. As a result, all of the temperature sensing junctions 4 are positioned in the same orientation in the circumferential direction 15 of the outer cylinder 2. By positioning this temperature sensing junction line towards the upstream side of the heat flow direction 16, as shown in Figure 1(A), the time response of the temperature measurement can be maximized.

[0020] The conductive materials constituting the first electrode 11 and the second electrode 12 of the thermocouple are required to be insulated from each other, except for the temperature sensing junction 4. This is because insufficient insulation can generate electromotive force elsewhere besides the temperature sensing junction 4, resulting in noise in the temperature measurement. Therefore, in this embodiment, the first electrode 11 and the second electrode 12 are insulated from each other, except for the temperature sensing junction 4, and furthermore, the second electrode wires 3 are insulated from each other. As a result, each thermocouple in the multi-point thermocouple forms an independent circuit with the outer cylinder 2 of the first electrode 11, the temperature sensing junction 4, and the second electrode wires 3. On the other hand, the outside of the outer cylinder does not necessarily need to be insulated.

[0021] In manufacturing a multi-point thermocouple 1, a thin sheet of material, such as a thin sheet of constantan, can be used to form the outer cylinder 2. Numerous temperature-measuring junctions 4 with the second electrode wire 3 are formed on one side of the sheet. This sheet is then rolled up to form the outer cylinder 2, thus creating the multi-point thermocouple 1. In this case, the ends of the rolled sheet do not necessarily need to be joined; as shown in Figure 3(A), they may have an open gap 17. Alternatively, as shown in Figure 3(B), the ends of the rolled sheet may overlap to form an overlap 18. This configuration allows the multi-point thermocouple 1 to be placed in a long hole in a copper plate, which is the object to be measured. When heated, the outer cylinder 2 deforms in a direction that increases its diameter, improving contact between the inner wall of the long hole and the outer cylinder 2, thereby reducing the temperature measurement error.

[0022] The diameter of the outer cylinder 2 shall be in the range of 1.00 to 2.40 mm. If the diameter of the outer cylinder 2 is 1.00 mm or more, it is relatively easy to drill an elongated hole corresponding to the diameter of the outer cylinder 2. If the diameter of the outer cylinder 2 is 2.40 mm or less, the effect of the thermocouple on the heat flow will be relatively small. If the cross-sectional shape of the outer cylinder 2 is elliptical, the diameter of the outer cylinder 2 shall be calculated as "(major axis + minor axis) / 2".

[0023] The wall thickness of the outer cylinder 2 shall be in the range of 0.02 to 0.34 mm. For the second objective of the present invention, "to improve the time response of temperature measurement," a thickness of 0.34 mm or less is sufficient. 0.20 mm or less is preferable. In order to ensure the durability and rigidity (ease of handling) of the outer cylinder, the wall thickness of the outer cylinder must be 0.02 mm or more. 0.05 mm or more is preferable, and 0.10 mm or more is even more preferable.

[0024] The diameter of the second electrode wire 3 of the present invention is preferably 0.05 mm or more, considering durability. A diameter of 0.10 mm or more is more preferable. Furthermore, the diameter of the second electrode wire 3 is preferably 0.30 mm or less, considering the number of temperature sensing junctions. A diameter of 0.20 mm or less is more preferable.

[0025] 《Second Embodiment》 The multi-point thermocouple of the second embodiment is characterized in that, when the thermal conductivity of the outer cylinder is λ (W / (mK)) and the thickness of the outer cylinder is d (m), it satisfies equation (1). λ / d≧60000 W / (m 2 K)...Equation (1) The multi-point thermocouple of the present invention is preferably used by being embedded in a mold for continuous casting. The mold for continuous casting is made of copper or a copper alloy. When measuring the temperature distribution of the mold in the longitudinal direction of the multi-point thermocouple of the present invention, if the thermal conductivity of the outer cylinder is higher than the thermal conductivity of the material being measured, the heat flow in the longitudinal direction of the outer cylinder caused by the temperature gradient in the longitudinal direction of the outer cylinder of the material being measured will amplify the error in the measured temperature. On the other hand, if the thermal conductivity of the outer cylinder is low and the wall thickness of the outer cylinder is large, the time response of the temperature measurement will decrease. As a result of the inventor's experimental research, if equation (1) is satisfied, a practically sufficient time response for temperature measurement inside the copper plate of a mold for continuous casting can be obtained. Therefore, the multi-point thermocouple of the second embodiment is designed to satisfy the above equation (1).

[0026] 《Third Embodiment》 The multi-point thermocouple of the third embodiment has an insulating coating (not shown) on the outside of the outer cylinder. The multi-point thermocouple of the present invention is often used by inserting it into a pore in a conductive material, such as a mold for continuous casting. If the pore is made of a conductive material and the outer cylinder, which is the outer circumference of the multi-point thermocouple, comes into contact with the pore, and an electromotive force is generated in the longitudinal or circumferential direction of the pore, it is desirable to have an insulating coating on the outside of the outer cylinder. However, since the insulating coating worsens the time response of temperature measurement, it is desirable to electrically remove the effect of the electromotive force generated in the pore by passing it through a bandpass filter or the like, if possible, without using an insulating coating. Suitable insulating coatings include enamel resin, epoxy resin, tyranno resin, polyimide, rubber, etc.

[0027] 《Fourth Embodiment》 In the fourth embodiment, the multi-point thermocouple uses constantan as the metal for the first electrode 11 and copper as the metal for the second electrode 12. Constantan is an alloy consisting of copper, nickel, and impurities. To achieve the first objective of this invention, "arranging many temperature sensing junctions on a narrow outer diameter," it is desirable to create a thin wire from a material that is soft, has excellent workability, and has high electrical conductivity, and use it as the second electrode wire 3. Copper is an easily available material that meets these conditions. Furthermore, constantan, an alloy of nickel and copper, has excellent corrosion resistance, making it suitable as the material for the outer cylinder 2. Therefore, it is desirable to select copper-constantan as the material for the thermocouple.

[0028] 《Fifth Embodiment》 The multi-point thermocouple of the fifth embodiment has a cross-sectional area of ​​1.00 mm² in the cross-section of the internal space of the outer cylinder 2. 2 It has 4.0 or more secondary polar lines per unit. As a preferred condition for achieving the first objective of the present invention, "arranging many temperature sensing junctions in a narrow outer diameter," specifically, the cross-sectional area of ​​the internal space of the outer cylinder is 1.00 mm². 2 It is defined as having 4.0 or more temperature sensing junctions per unit area. The density of temperature sensing junctions is the cross-sectional area of ​​the inner space of the outer cylinder, 1.00 mm². 2 A score of 5.0 or higher per person is even preferable.

[0029] 《Sixth Embodiment》 The temperature measuring mechanism of the sixth embodiment is a temperature measuring mechanism in which the multi-point thermocouple of the first to fifth embodiments is provided in contact with the object to be measured, characterized in that the thermal conductivity of the outer cylinder 2 is lower than the thermal conductivity of the material of the object to be measured. This makes it possible to fully enjoy the benefits of satisfying equation (1) of the second embodiment.

[0030] 《Seventh Embodiment》 The seventh embodiment is a mold for continuous casting made of copper or a copper alloy, characterized in that the multi-point thermocouple of the present invention is arranged inside the mold.

[0031] Figure 1 schematically shows a multi-point thermocouple 1 according to the first embodiment. The outer cylinder 2 also serves as the first electrode 11, and four temperature sensing junctions 4 are arranged along the inner surface and connection line 13. The four second electrode wires 3 are covered with insulating tubing as insulating coating 5 up to the vicinity of the temperature sensing junctions 4, and are insulated from the outer cylinder 2 of the other second electrode wires 3 or the first electrode 11.

[0032] In the temperature measuring mechanism using the multi-point thermocouple 1 of the present invention, it is preferable to use the temperature measuring junction 4 facing the upstream side of the heat flow direction 16 of the object to be measured, as shown in Figure 1(A). The third embodiment is one in which insulating paint is applied to the surface of the outer cylinder 2. The fourth embodiment is one in which, in Figure 1, the outer cylinder 2 which is the first electrode 11 is made of constantan and the second electrode wire 3 is made of copper. [Examples]

[0033] (Example 1) A multi-point thermocouple 1 was constructed with the specifications shown in Table 1. Where "Outer cylinder" is written under "First pole" in Table 1, as shown in Figures 1 and 6, the outer cylinder 2 is the first pole 11, and the temperature sensing junction 4 is located on the inner surface of the outer cylinder 2. Where "Common wire" is written under "First pole," as shown in Figure 4, the first pole 11 is a single copper wire (first pole wire 6), and the temperature sensing junction 4 is provided as the contact point between the first pole wire 6 and the second pole wire 3. Where "Individual wire" is written under "First pole," as shown in Figure 5, the number of first pole wires 6 is the same as the number of second pole wires 3, and individual first pole wires 6 and second pole wires 3 are joined to form the temperature sensing junction 4. The cross-sectional area of ​​the internal space of the outer cylinder 2 is 2.27 mm² in all cases. 2It is as follows.

[0034]

Table 1

[0035] In Invention Example 1 of Table 1, as shown in FIG. 2, one form of a multi-point thermocouple is shown. A constantan tube with an outer diameter of 1.90 mm and an inner diameter of 1.70 mm (wall thickness 0.10 mm) is used as the outer cylinder 2. Inside the outer cylinder 2, as the second pole wire 3, 13 copper wires with an outer diameter of 0.20 mm are arranged after being covered with an insulating tube (insulating coating 5) made of polyimide with an outer diameter of 0.40 mm. Polyimide is an insulating resin with excellent heat resistance and can be used in the present invention. In FIG. 1, for convenience of explanation, only 4 second pole wires 3 are arranged, but actually, as shown in FIG. 2, many second pole wires 3 can be arranged.

[0036] In Invention Example 1 (FIG. 2), it is an embodiment in which 13 temperature measurement contacts 4 are arranged in the cross-sectional area of 2.27 mm of the internal space of the outer cylinder 2, and the number of temperature measurement contacts per 1.00 mm of the cross-sectional area of the internal space of the outer cylinder 2 is 5.73, which is an embodiment that meets the requirements of the fifth embodiment. 2 In Invention Example 1 (FIG. 2), it is an embodiment in which 13 temperature measurement contacts 4 are arranged in the cross-sectional area of 2.27 mm of the internal space of the outer cylinder 2, and the number of temperature measurement contacts per 1.00 mm of the cross-sectional area of the internal space of the outer cylinder 2 is 5.73, which is an embodiment that meets the requirements of the fifth embodiment. 2 It is an embodiment that meets the requirements of the fifth embodiment.

[0037] Also, Invention Example 1 (FIG. 2) can be suitably used for measuring the temperature inside the copper plate when it is inserted into a through hole with a diameter of 2.00 mm drilled in the copper plate constituting the mold for continuous casting as the multi-point thermocouple 1 used in the temperature measurement mechanism of the sixth embodiment and the mold for continuous casting of the seventh embodiment. At this time, the thermal conductivity of the copper plate constituting the mold is 395 W / (mK), while the thermal conductivity of the constantan constituting the outer cylinder 2 is 24 W / (mK), which is smaller than the thermal conductivity of the copper plate that is the temperature measurement object. Furthermore, the value obtained by dividing the thermal conductivity λ (W / (mK)) of the outer cylinder 2 by the wall thickness d (m) of the outer cylinder is 240000 W / (m 2 K), which satisfies the formula (1), so it is an embodiment that meets the conditions of the second embodiment.

[0038] On the other hand, when the multi-point thermocouple of Invention Example 1 (Figure 2) is used to measure the temperature distribution inside JIS standard SUS304 (hereinafter referred to as SUS304), which is a stainless steel with a low thermal conductivity of 16.5 W / mK, the preferred requirements of the temperature measuring mechanism of the sixth embodiment are not met. In this case, the temperature gradient in the longitudinal direction of the outer cylinder of the SUS304, which has a low thermal conductivity, tends to be large, and the heat flow in the longitudinal direction of the outer cylinder caused by this large temperature gradient affects the measured temperature value, resulting in an apparent gradual measurement of the temperature gradient, which is undesirable.

[0039] Furthermore, since general-purpose copper wires and polyimide insulating tubes can be used for the multi-point thermocouple in Invention Example 1 (Figure 2), a multi-point thermocouple can be manufactured at low cost.

[0040] Furthermore, in a multi-point thermocouple, the materials of each part are not limited to those used in Invention Example 1 (Figure 2). For example, the thermocouple may be a platinum-platinum rhodium alloy, and the insulating material of the insulating coating 5 may be ceramic powder filled into the space inside the outer cylinder 2 instead of being in the form of a ceramic tube or tube. Since the thermal conductivity of platinum is 72 W / (mK) and the thermal conductivity of platinum rhodium is 51 W / (mK), which is lower than that of copper, the requirements of the temperature measuring mechanism of the sixth embodiment can be met even when measuring the temperature inside a copper plate using these materials.

[0041] Invention Example 2 (Figure 6) is an example in which the second electrode wire 3 has a diameter of 0.35 mm and is inserted into a protective tube (insulating coating 5) with an outer diameter of 0.55 mm, compared to Invention Example 1 (Figure 2). When the diameter of the second electrode wire 3 is large, the number of second electrode wires 3, i.e., the number of temperature sensing contacts, decreases significantly from 13 in Invention Example 1 (Figure 2) to 7.

[0042] Table 1 shows Invention Example 3, which has the shape shown in Figure 2 and is a form of multi-point thermocouple with a larger wall thickness and outer diameter of the outer cylinder compared to Invention Example 1. The outer cylinder 2 is made of a constantan tube with an outer diameter of 2.30 mm and an inner diameter of 1.70 mm (wall thickness of 0.30 mm), and 13 copper wires with an outer diameter of 0.20 mm are arranged inside the outer cylinder 2 as second electrodes 3, each covered with a polyimide insulating tube (insulating coating 5) with an outer diameter of 0.40 mm. Polyimide is an insulating resin with excellent heat resistance and can be used in the present invention.

[0043] In Invention Example 3, the cross-sectional area of ​​the internal space of the outer cylinder 2 is 2.27 mm². 2 In this embodiment, 13 temperature sensing contacts 4 are arranged, and the cross-sectional area of ​​the internal space of the outer cylinder 2 is 1.00 mm². 2 The number of temperature-measuring junctions per unit is 5.73, and this embodiment satisfies the requirements of the fifth embodiment.

[0044] Furthermore, Invention Example 3 can be suitably used as a multi-point thermocouple 1 for the temperature measuring mechanism of the 6th embodiment and for the mold for continuous casting of the 7th embodiment. It is inserted into a 2.40 mm diameter elongated hole drilled in a copper plate constituting a mold for continuous casting of steel, and can be used for temperature measurement inside the copper plate. In this case, the thermal conductivity of the copper plate constituting the mold is 395 W / (mK), while the thermal conductivity of the constantan constituting the outer cylinder 2 is 24 W / (mK), which is smaller than the thermal conductivity of the copper plate being measured. Moreover, the value obtained by dividing the thermal conductivity λ (W / (mK)) of the outer cylinder 2 by the wall thickness d (m) of the outer cylinder is 80000 W / (m 2 Since K) satisfies the above formula (1), this is an embodiment that satisfies the conditions of the second embodiment.

[0045] Table 1 shows Invention Example 4, which has the shape shown in Figure 2 and represents one form of a multi-point thermocouple in which the wall thickness and outer diameter of the outer cylinder are further increased compared to Invention Example 1. In this example, a Chromel (90%Ni-10%Cr) tube with an outer diameter of 2.38 mm and an inner diameter of 1.70 mm (wall thickness of 0.34 mm) is used as the outer cylinder 2, and thirteen wires of Alumel (95%Ni-2%Al-2%Mn-1%Si) with an outer diameter of 0.20 mm are arranged inside the outer cylinder 2 as second electrodes 3, each covered with a polyimide insulating tube (insulating coating 5) with an outer diameter of 0.40 mm. Polyimide is an insulating resin with excellent heat resistance and can be used in the present invention.

[0046] In Invention Example 4, the cross-sectional area of ​​the internal space of the outer cylinder 2 is 2.27 mm². 2 In this embodiment, 13 temperature sensing contacts 4 are arranged, and the cross-sectional area of ​​the internal space of the outer cylinder 2 is 1.00 mm². 2 The number of temperature-measuring junctions per unit is 5.73, and this embodiment satisfies the requirements of the fifth embodiment.

[0047] Furthermore, Invention Example 4 can be suitably used as a multi-point thermocouple 1 for the temperature measuring mechanism of the 6th embodiment and for the mold for continuous casting of the 7th embodiment. It is inserted into an elongated hole with a diameter of 2.48 mm drilled in a copper plate constituting a mold for continuous casting of steel, and can be used for temperature measurement inside the copper plate. In this case, the thermal conductivity of the copper plate constituting the mold is 395 W / (mK), while the thermal conductivity of the chromel constituting the outer cylinder 2 is 19.3 W / (mK), which is smaller than the thermal conductivity of the copper plate to be measured. On the other hand, the value obtained by dividing the thermal conductivity λ (W / (mK)) of the outer cylinder 2 by the wall thickness d (m) of the outer cylinder is 56765 W / (m 2 Since K) does not satisfy the above formula (1), this embodiment does not satisfy the conditions of the second embodiment.

[0048] The multi-point thermocouple in Comparative Example 1 (Figure 4) in Table 1 replaces the outer cylinder 2 with a SUS304 protective tube with an outer diameter of 2.10 mm and an inner diameter of 1.70 mm (wall thickness of 0.20 mm). Furthermore, instead of using the outer cylinder 2 as the first electrode 11, a single first electrode wire 6 is placed inside the outer cylinder 2, and the first electrode wire 6 is a constantan wire. The reason why the wall thickness of the outer cylinder 2 (protective tube) in Comparative Example 1 (Figure 4) is greater than that of Invention Example 1 (Figure 2) is because SUS304 is hard and difficult to mold to a wall thickness of 0.10 mm. In Comparative Example 1 (Figure 4) as well, since the first electrode 11 is shared by a single first electrode wire 6, the cross-sectional area of ​​the internal space of the outer cylinder 2 is 2.27 mm². 2 This allows for the placement of a large number of temperature sensing junctions 4, up to 12 points. However, in Comparative Example 1 (Figure 4), since the temperature sensing junctions 4 are located inside the protective tube (outer cylinder 2), the time response of temperature measurement is reduced compared to Invention Example 1 (Figure 2).

[0049] The multi-point thermocouple in Comparative Example 2 (Figure 5) is similar to that in Comparative Example 1 (Figure 4), but the outer cylinder 2 is replaced with a SUS304 protective tube with an outer diameter of 2.10 mm and an inner diameter of 1.70 mm (wall thickness of 0.20 mm), and six pairs of normal thermocouples, each consisting of a first electrode wire 6 and a second electrode wire 3, are arranged inside. In the multi-point thermocouple of Comparative Example 2 (Figure 5), a common electrode is not used as the first electrode 11, so the cross-sectional area of ​​the internal space of the outer cylinder 2 is 2.27 mm². 2 In this case, the temperature sensing junctions 4 are arranged at only six points. Furthermore, in Comparative Example 2 (Figure 5), the temperature sensing junctions 4 are located inside a protective tube, and in Figure 5, the first temperature sensing junction 4A is near the outer cylinder 2, the third temperature sensing junction 4B is near the center of the outer cylinder 2, and the sixth temperature sensing junction 4C is positioned 180° differently in the circumferential direction 15 of the outer cylinder 2. When the upstream direction of the heat flow direction 16 is the direction of the first temperature sensing junction 4A, the sixth temperature sensing junction 4C faces the downstream side of the heat flow, so the time response of the temperature sensing junction 4C is reduced compared to Invention Example 1 (Figure 2).

[0050] (Example 2) A molten iron container with a 200 mm square cross-section and a depth of 400 mm was prepared. The molten iron container was formed on all four sides and the bottom surface of a copper plate, and was capable of containing molten iron inside. Cooling water with an inlet water temperature of 35°C was flowed over the entire outside of the molten iron container at a flow rate of 8 m / s. One side of the molten iron container was made of a 15 mm thick copper plate, and a 300 mm deep elongated hole was drilled in the vertical direction of this copper plate. The diameter of the elongated hole was 0.20 mm larger than the outer diameter of the thermocouple, and the shortest distance between the elongated hole and the working surface of the copper plate was standardized to 6 mm. The multi-point thermocouple of Invention Example 1 (Figure 2), the multi-point thermocouple of Comparative Example 1 (Figure 4), and the multi-point thermocouple of Comparative Example 2 (Figure 5) were inserted into this elongated hole. The temperature measurement results of the copper plate 150 mm above the bottom of the container were compared when molten iron at 1550°C was poured into the molten iron container.

[0051] As schematically shown in Figure 7, the temperature of the copper plate measured using a thermocouple rose rapidly at a certain point, reaching a maximum temperature of 150°C to 200°C, and then gradually decreased as the solidification of the molten iron progressed.

[0052] As shown in Figure 7, the response time was defined as the time from the start of the temperature rise until the temperature reached 80% of the peak temperature. In the case of the multi-point thermocouple in Comparative Example 1 (Figure 4), the response time when the temperature sensing junction 4 was installed facing the direction of the working surface of the copper plate (upstream direction of the heat flow direction 16) was set to 100 (relative response time).

[0053] In the multi-point thermocouple of Invention Example 1 (Figure 2), when the temperature sensing junction 4 was installed facing the direction of the working surface of the copper plate (upstream direction of the heat flow direction 16), the relative response time became 41, which was reduced to less than half of the relative response time (100) of Comparative Example 1 (Figure 4).

[0054] Furthermore, when measuring temperature using the multi-point thermocouple in Comparative Example 2 (Figure 5), the relative response time was 100 at the first temperature measuring junction 4A, which is close to the working surface direction of the copper plate (upstream direction of the heat flow direction 16), similar to Comparative Example 1 (Figure 4). However, at the sixth temperature measuring junction 4C, located on the cooling surface side of the copper plate, or the third temperature measuring junction 4B, located near the center of the protective tube, the value was a large 130, indicating variation depending on the temperature measuring junction position. In this invention, a variation of ±5% or less in the relative response time was considered small.

[0055] Next, using Comparative Example 3, in which the wall thickness of the outer cylinder 2 was set to 0.50 mm, outside the range of the first embodiment, the same relative response time was measured for the multi-point thermocouple of Invention Example 1 (Figure 2). As a result, the relative response time was a large value of 210. Thus, when the wall thickness of the outer cylinder 2 was outside the range of the present invention, the time response of temperature measurement was found to be inferior. [Explanation of Symbols]

[0056] 1. Multipoint thermocouple 2 Outer cylinder 3. Second pole 4. Temperature sensing junction 4A First temperature measuring junction 4B Third temperature measuring junction 4C 6th temperature measuring junction 5. Insulating coating 6. First Polar Line 11 1st pole 12 2nd pole 13 Connecting Straight Lines 14 Longitudinal direction 15 Circumferential direction 16 Heat flow direction 17 Gap 18 Overlap

Claims

1. A multi-point thermocouple having a plurality of such temperature-measuring junctions, wherein the contact point between the metal of the first electrode and the metal of the second electrode is used as the temperature-measuring junction of the thermocouple. A cylindrical outer tube with a diameter of 1.00 to 2.40 mm and a thickness of 0.02 to 0.34 mm forms the first pole, and the outer tube has two or more wires forming the second pole (second pole wires) inside, all of which are in contact with the inner surface of the outer tube to form the temperature sensing junction. A connecting line extending in the longitudinal direction of the outer cylinder is assumed on the inner surface of the outer cylinder, and the connecting line is positioned in the same orientation in the circumferential direction of the outer cylinder at any position in the longitudinal direction of the outer cylinder, and all of the temperature sensing junctions are positioned along the connecting line in the longitudinal direction of the outer cylinder. A multi-point thermocouple characterized in that, apart from the temperature sensing junction, the first and second electrodes are insulated, and the second electrode wires are further insulated from each other.

2. The multi-point thermocouple according to claim 1, characterized in that when the thermal conductivity of the outer cylinder is λ (W / (mK)) and the thickness of the outer cylinder is d (m), it satisfies formula (1). λ / d ≥ 60000 W / (m ２ K) ······ Equation (1)

3. The multi-point thermocouple according to claim 1 or 2, characterized in that the outer surface of the outer cylinder has an insulating coating.

4. A multi-point thermocouple according to claim 1 or claim 2, characterized in that constantan is used as the metal of the first electrode and copper is used as the metal of the second electrode.

5. In the cross-section of the internal space of the outer cylinder, the cross-sectional area is 1.00 mm². ２ A multipoint thermocouple according to claim 1 or claim 2, characterized in that it has 4.0 or more second electrode wires per point.

6. A temperature measuring mechanism comprising a multi-point thermocouple as described in claim 2, provided in contact with a temperature to be measured, characterized in that the thermal conductivity of the outer cylinder is lower than the thermal conductivity of the material of the temperature to be measured.

7. A mold for continuous casting made of copper or a copper alloy, characterized in that a multi-point thermocouple according to claim 1 or claim 2 is arranged inside the mold.

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