Glass melting heater

Abstract

This heater for melting glass includes a heat generating member that contains carbon (C) and that radiates a heat ray when supplied with power, and a metal cylindrical member which accommodates the heat generating member and one end of which is closed, wherein: the heat generating member includes, in the extension axis direction of the heater, a first heat generating portion and a second heat generating portion; the first heat generating portion is disposed in a position closer to said one end of the cylindrical member than the second heat generating portion; and if X (Ω / m) is the resistance per unit length in the extension axis direction of the first heat generating portion, and Y (Ω / m) is the resistance per unit length in the extension axis direction of the second heat generating portion, the following formula holds: (1) ... (1 / 30)X<Y<(1 / 2)X.

Description

[Technical field]

[0001] The present invention relates to a heater for melting glass. [Background technology]

[0002] In the glass making process, a pair of electrodes is often used in producing molten glass in a melting furnace.

[0003] Each electrode is attached to the bottom of the melting furnace in a "vertical" orientation so as to penetrate the bottom. Molten glass can be obtained by passing a current through the electrode set in such an arrangement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-193268 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a conventional glass melting method, when molten glass is directly heated, an alternating current is applied between electrodes inserted in the molten glass to heat the molten glass by Joule heating. For this reason, through holes for inserting the electrodes are formed in the bottom of the melting furnace.

[0006] The dimensions of the cross sections perpendicular to the extension direction of these through holes are usually selected to be sufficiently larger than the dimensions of the cross sections perpendicular to the axial direction of the electrodes, in order to prevent the electrodes or the melting furnace from being damaged when the electrodes come into contact with the side walls that form the through holes due to the difference in thermal expansion between the material of the melting furnace and the material of the electrodes during the production of molten glass.

[0007] However, due to such a dimensional design, there is a possibility that the molten glass may leak from a "gap" between the side wall and the electrode during production of the molten glass. To avoid this, a cooling member is usually provided around the electrode.

[0008] A portion of the cooling member is positioned so as to face the lower surface of the bottom of the melting furnace when the electrode is inserted into the melting furnace.

[0009] By supplying a coolant such as air or water to the cooling member installed in this manner, the molten glass that falls through the gap during the production of molten glass can be solidified midway through the process. Furthermore, the solidified glass layer can be used as a sealant for closing the gap.

[0010] However, such a cooling member is not very desirable from the viewpoint of the efficiency of heating the glass, that is, the presence of such a cooling member acts to lower the temperature of the molten glass at the bottom of the melting furnace, and therefore the efficiency of heating the glass decreases.

[0011] In addition, since the electrodes themselves are not heating elements, in order to provide the entire molten glass with a desired temperature history under such circumstances, additional equipment is required to allow the molten glass to circulate by convection. For example, it is necessary to enlarge the melting furnace or install a stirring device. However, such measures lead to an increase in the cost of the manufacturing equipment.

[0012] The present invention has been made in consideration of the above background, and an object of the present invention is to provide a heater for melting glass that can significantly improve the heating efficiency of molten glass compared to conventional heaters. [Means for solving the problem]

[0013] In the present invention, there is provided a heater for melting glass, comprising: A heat generating member containing carbon (C) that radiates heat rays when powered; a metallic cylindrical member having one closed end for accommodating the heat generating member; having The heating member has a first heating portion and a second heating portion along the extending axis direction of the heater. The first heating portion is disposed at a position closer to the one end of the cylindrical member than the second heating portion. When the resistance per unit length along the extending axis direction of the first heating portion is X (Ω / m) and the resistance per unit length along the extending axis direction of the second heating portion is Y (Ω / m), (1 / 30)X < Y < (1 / 2)X (Equation (1)) a heater is provided such that the inequality holds.

Advantages of the Invention

[0014] In the present invention, it is possible to provide a heater for melting glass that can significantly improve the heating efficiency of molten glass as compared with the prior art.

Brief Description of the Drawings

[0015] [Figure 1] It is a diagram schematically showing a state when a conventional electrode is installed in a melting furnace. [Diagram 2] It is a diagram schematically showing a configuration example of a heater according to an embodiment of the present invention. [Diagram 3] It is a diagram schematically showing a state when a heater according to an embodiment of the present invention is installed in a melting furnace. [Figure 4] It is a diagram schematically showing another form of the first heating portion in a heater according to an embodiment of the present invention. [Diagram 5] It is a diagram schematically showing a state when a heater according to another embodiment of the present invention is installed in a melting furnace.

Modes for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] First, a conventional glass melting method and its problems will be described with reference to FIG.

[0018] FIG. 1 shows a schematic diagram of a conventional pair of electrodes 20 installed in a glass melting furnace 1 .

[0019] As shown in Fig. 1, a glass melting furnace 1 has a structure capable of accommodating molten glass MG in an accommodating space 2. Specifically, the melting furnace 1 has a side portion 3 and a bottom portion 5 surrounded by the side portion 3. The bottom portion 5 has an upper surface 7 and a lower surface 9. The upper surface 7 is the surface of the bottom portion 5 that contacts the molten glass MG, and the lower surface 9 is the surface of the bottom portion 5 opposite to the upper surface 7.

[0020] The melting furnace 1 has a through hole 10 in the bottom 5 that penetrates from the upper surface 7 to the lower surface 9 .

[0021] The electrode 20 is composed of a body 22 and a lead member 24. The body 22 is composed of, for example, a rod-shaped platinum or molybdenum.

[0022] The lead member 24 is disposed near one end of the body 22. The other end (referred to as the "tip") 26 of the body 22 is inserted into the accommodation space 2 through the through hole 10 in the bottom 5 of the melting furnace 1.

[0023] Generally, the dimension of the cross section perpendicular to the extension direction of the through hole 10 is selected to be sufficiently larger than the dimension of the cross section perpendicular to the axial direction of the main body 22 of the electrode 20 .

[0024] 1 shows only one pair of electrodes 20. However, in practice, many more pairs of electrodes 20 are installed in the accommodation space 2 of the melting furnace 1.

[0025] As shown in FIG. 1, an electrode 20 is typically provided with a cooling member 12 .

[0026] The cooling member 12 has a first portion 13 and a second portion 15. The first portion 13 of the cooling member 12 is provided at a position facing the lower surface 9 of the bottom portion 5 of the melting furnace 1 when the electrode 20 is inserted into the melting furnace 1. The second portion 15 of the cooling member 12 is provided at a position facing the side wall 11 that forms the through hole 10 of the bottom portion 5 of the melting furnace 1. A coolant such as air or water is circulated through the cooling member 12.

[0027] In this configuration, the lead members 24 of the electrodes 20 are connected to a power supply device 28 such as an external voltage source. This allows current to flow between the two electrodes 20 via the molten glass, and the molten glass can be electrically heated. As a result, the molten glass can be heated to a desired temperature. The storage space 2 of the melting furnace 1 is filled with molten glass MG, and the molten glass MG is Joule heated by passing an AC current between the electrodes inserted in the molten glass.

[0028] A "gap" 17 exists between the through hole 10 formed in the bottom 5 of the melting furnace 1 and the electrode 20. Therefore, there is a possibility that the molten glass MG may leak to the outside from this gap 17 during heating of the molten glass MG.

[0029] In order to deal with such leakage, the cooling member 12 is used. That is, by supplying a refrigerant to the first portion 13 and the second portion 15 of the cooling member 12, the molten glass MG moving along the gap 17 can be cooled and solidified midway along the side wall 11. In addition, the solidified glass layer can be used as a sealant for the gap 17.

[0030] However, second portion 15 of cooling member 12 is installed on upper surface 7 of bottom portion 5 of melting furnace 1, i.e., at a position relatively close to molten glass MG. Therefore, second portion 15 of cooling member 12 acts in a direction to lower the temperature of molten glass MG. In particular, it becomes difficult to quickly increase the temperature of molten glass MG above second portion 15 of cooling member 12. As a result, a problem may occur in which the heating efficiency of molten glass decreases.

[0031] In addition, since the first portion 13 of the cooling member 12 is installed at a position relatively far from the molten glass MG, the influence of reducing the temperature of the molten glass MG is less than that of the second portion 15.

[0032] On the other hand, in one embodiment of the present invention, there is provided a heater for melting glass, a heating member containing carbon (C) that radiates heat rays by power supply, a metal cylindrical member with one end closed that houses the heating member, and having the heating member has a first heating portion and a second heating portion along the extending axis direction of the heater, and the first heating portion is disposed at a position closer to the one end of the cylindrical member than the second heating portion, when the resistance per unit length along the extending axis direction of the first heating portion is X (Ω / m) and the resistance per unit length along the extending axis direction of the second heating portion is Y (Ω / m), (1 / 30)X < Y < (1 / 2)X (Equation (1)) a heater is provided in which the equation holds.

[0033] In one embodiment of the present invention, instead of the electrode 20, the molten glass MG is heated using a heater. Further, the heater according to one embodiment of the present invention has a configuration in which a heating member is housed in a metal cylindrical member.

[0034] In such a configuration, the cylindrical member can be heated by a radiation method using heat rays from the heating element, and the molten glass MG can be heated using the heated cylindrical member.

[0035] Further, in the heater according to one embodiment of the present invention, a heating member containing carbon (C) is used.

[0036] Here, when a metal that is often used for the heat generating member of a heater (e.g., a material containing one or more selected from molybdenum, tungsten, tantalum, niobium, iridium, platinum, and rhodium) is used as the heat generating member of the heater according to one embodiment of the present invention, the heat generating member may deform under its own weight while the heater is in use. This is because the temperature of the molten glass MG often reaches 1600°C or higher, and therefore the heat generating member may reach 1800°C or higher.

[0037] However, in one embodiment of the present invention, a heat generating member containing carbon (C) is used, which is less deformed even at high temperatures of 1800° C. or more. Therefore, in one embodiment of the present invention, deformation of the heat generating member during use can be significantly suppressed.

[0038] Furthermore, in the heater according to one embodiment of the present invention, the heat generating member has a first heat generating portion and a second heat generating portion.

[0039] In this case, the first heating part of the heater, which reaches a higher temperature, is installed in the space in the melting furnace 1 where the molten glass MG is contained, and the second heating part, which does not reach as high a temperature as the first heating part, can be arranged so as to face the through hole 10 (or its side wall 11) provided in the bottom 5 of the melting furnace 1.

[0040] In addition, the boundary between the first heat generating portion and the second heat generating portion may be slightly shifted toward the storage space 2 or the through hole 10 from the upper surface 7 of the bottom 5 of the melting furnace 1, as long as it does not affect the melting of the glass.

[0041] When the heater according to one embodiment of the present invention is disposed in this manner with respect to the melting furnace 1, the temperature of the through hole 10 (or its side wall 11) in the bottom 5 of the melting furnace 1 can be kept at an appropriate temperature without rising too much. Therefore, even if the second portion 15 of the cooling member 12 is not used at all, or the cooling ability of the second portion 15 of the cooling member 12 is reduced, or the length of the second portion 15 of the cooling member 12 is shortened to increase the distance from the accommodation portion 2 of the melting furnace 1, the molten glass MG can be moved along the gap 17 over a significant length in the gap 17, and the molten glass MG can be solidified while protecting the heater surface.

[0042] As a result, in one embodiment of the present invention, it is possible to alleviate the problem that the molten glass MG is easily cooled and difficult to heat in the upper part of the second portion 15 of the cooling member 12. That is, it is possible to significantly increase the heating efficiency in the process of producing the molten glass MG.

[0043] Furthermore, in the conventional electrode 20, when the body 22 is made of molybdenum, a problem of high-temperature oxidation may occur. That is, when the body 22 is exposed at the portion facing the through hole 11, the body 22 may be oxidized by high-temperature air, causing a problem of deterioration of the electrode.

[0044] In contrast to this, in one embodiment of the present invention, due to the above-mentioned effect, the molten glass MG can be moved along the gap 17, and the surface of the heater can be covered with solidified glass. Therefore, in one embodiment of the present invention, a material that is easily oxidized in high-temperature air, such as molybdenum, can be used as the cylindrical member.

[0045] (Heater for melting glass according to one embodiment of the present invention) Next, with reference to FIG. 2, a configuration example of a heater according to an embodiment of the present invention will be described.

[0046] An example of the structure of a heater according to an embodiment of the present invention is shown in schematic form in Fig. 2. Fig. 2 generally shows a cross section along an extension axis of a heater according to an embodiment of the present invention. However, a portion of a heat generating member 120, which will be described later, is drawn in a non-cross-sectional form for clarity.

[0047] As shown in FIG. 2, a heater 100 according to one embodiment of the present invention (hereinafter referred to as a "first heater") has a generally rod-like configuration extending from a first heater end 102A to a second heater end 102B.

[0048] The first heater end 102A is closed by a cover member 170. The second heater end 102B is closed by a closed end of a cylindrical member 130 described later. Therefore, an internal space 110 that is isolated from the outside world is formed inside the first heater 100.

[0049] The internal space 110 can be controlled to a desired atmosphere by a gas supply means and / or a gas exhaust means (not shown) installed in the first heater 100. In particular, the internal space 110 is preferably kept in a non-oxidizing gas atmosphere in order to suppress oxidation of various members housed in the internal space 110 during use of the first heater 100. For example, the internal space 110 may be filled with an inert gas such as argon during use.

[0050] Referring again to FIG. 2, the first heater 100 has a heat generating member 120 and a cylindrical member 130 .

[0051] The heat generating member 120 is housed in the internal space 110. Meanwhile, the cylindrical member 130, together with the above-mentioned cover member 170, is a member that divides the internal space 110 of the first heater 100, and the cylindrical member 130 protects each of the members housed in the internal space 110. One end of the cylindrical member 130 is closed, and this closed end corresponds to the second heater end portion 102B of the first heater 100.

[0052] The cylindrical member 130 is made of a heat-resistant metal.

[0053] The heating member 120 functions as a heating element that generates heat upon energization. The heating member 120 is made of a conductive material and contains carbon (C).

[0054] The heating member 120 has a first heating part 122 and a second heating part 124 that are electrically connected to each other. The first heating part 122 is disposed closer to the second heater end 102B than the second heating part 124.

[0055] Although difficult to visually recognize from FIG. 2, one end of the first heating part 122 of the heating member 120, i.e., the end opposite to the end connected to the second heating part, is electrically connected to the first lead wire 180A. Also, one end of the second heating part 124, i.e., the end opposite to the end connected to the first heating part, is electrically connected to the second lead wire 180B.

[0056] The first lead wire 180A is led out to the outside of the internal space 110 through a first opening 172A provided in the lid member 170. Similarly, the second lead wire 180B is led out to the outside of the internal space 110 through a second opening 172B provided in the lid member 170. To prevent the first lead wire 180A from contacting the lid member 170, a first insulating member 175A is attached to the first opening 172A of the lid member 170. Similarly, to prevent the second lead wire 180B from contacting the lid member 170, a second insulating member 175B is attached to the second opening 172B of the lid member 170.

[0057] Here, in the first heater 100, in the first heating part 122, when the resistance per unit length along the extension axis direction of the first heater 100 is X (Ω / m), and in the second heating part 124, when the resistance per unit length along the extension axis direction of the first heater 100 is Y (Ω / m), (1 / 30)X < Y < (1 / 2)X (Equation (1)) is satisfied.

[0058] Hereinafter, resistances X and Y per unit length will be simply referred to as "resistance X" and "resistance Y," respectively.

[0059] Therefore, during use of the first heater 100, the first heating element 122 can reach a higher temperature than the second heating element .

[0060] In the present application, the resistance X of the first heat generating portion 122 does not need to be constant over the entire length, and may increase or decrease within a range of less than ±25%. The same is true for the resistance Y of the second heat generating portion 124.

[0061] Furthermore, there may be a portion (hereinafter referred to as a "transition region") between the first heat generating portion 122 and the second heat generating portion 124 that exhibits a resistance between the two, i.e., a resistance smaller than resistance X and larger than resistance Y. Such a change in resistance may occur, for example, in a form in which the cross-sectional area of ​​the transition region gradually increases from the portion in contact with the first heat generating portion 122 to the portion in contact with the second heat generating portion 124. In the case of such a configuration, the "boundary" between the first heat generating portion 122 and the second heat generating portion 124 is defined as the portion in the transition region that exhibits a resistance value intermediate between X and Y.

[0062] Furthermore, the resistance per unit length of the transition region between the first heat generating portion 122 and the second heat generating portion 124 may be smaller than Y. Such a change in resistance may occur, for example, when the first heat generating portion 122 and the second heat generating portion, which are manufactured separately, are joined via a thick joining member with high rigidity.

[0063] In such a configuration, the "boundary" between the first heat generating portion 122 and the second heat generating portion 124 is defined as the axial midpoint of the joining member.

[0064] <How to calculate resistance X and Y> Here, the method for calculating the resistances X and Y will be described.

[0065] The resistance X per unit length of the first heat generating part 122 and the resistance Y per unit length of the second heat generating part 124 are calculated by the general-purpose thermal fluid analysis software STAR-CCM+ (manufactured by SIEMENS). A specific explanation will be given by taking the resistance X per unit length of the first heat generating part 122 as an example. 1. Import the shape data of the heat generating member 120 in STL format into STAR-CCM+. 2. Enter the physical property values, such as the electrical conductivity, of the material used in the heat generating member 120. At this time, the electrical conductivity is set to the value at room temperature, and is not temperature dependent. 3. Calculation is performed under the condition that an arbitrary current I flows through both terminals of the heat generating member connected to the lead wire, and the output distribution N (W / m 2 ) is required. 4. Two planes are set that are perpendicular to the axial direction of the heat generating member 120 and have a distance L between them. The output distribution N of the area sandwiched between these two planes is integrated to obtain the output P(W) of said area. In this case, one plane is set as a plane that crosses the upper end of the heat generating member 120, and the other plane is set as a plane that crosses the boundary between the first heat generating part 122 and the second heat generating part 124, thereby obtaining the output P of the first heat generating part 122. 5. Output P is converted to current I 2 Dividing by gives the resistance R of the area. 6. Resistance R divided by distance L gives resistance X per unit length.

[0066] The resistance Y per unit length of the second heat generating portion 124 can also be obtained in a similar manner by dividing the area into one surface that crosses the lower end of the heat generating member 120 and another surface that crosses the boundary between the first heat generating portion 122 and the second heat generating portion 124.

[0067] Next, the operation of the first heater 100 having such a configuration will be described with reference to FIG.

[0068] Fig. 3 shows a schematic diagram of a state in which a first heater 100 is installed in a glass melting furnace 1. The configuration of the melting furnace 1 has already been described with reference to Fig. 1. Therefore, a detailed description of the configuration of the melting furnace 1 will be omitted here, except for matters related to one embodiment of the present invention.

[0069] It should be noted that in the example shown in Figure 3, the first portion 13 of the cooling member 12 in Figure 1 is attached to the bottom portion 5 of the melting furnace 1, not to the first heater 100. Also, in the example shown in Figure 3, the second portion 15 of the cooling member 12 in Figure 1 has been removed.

[0070] 3, when the first heater 100 is used, the first heater 100 is first installed in the melting furnace 1. The first heater 100 is installed in a "vertical" orientation such that the second heater end portion 102B side is inserted into the accommodation space 2 through the through hole 10 in the bottom portion 5 of the melting furnace 1.

[0071] Next, glass raw material is supplied into the accommodation space 2 of the melting furnace 1 .

[0072] Thereafter, a current is supplied to the first lead wire 180A and the second lead wire 180B of the first heater 100 using a power supply device (not shown in FIG. 3). This causes the heat generating member 120 to be resistance heated, and the cylindrical member 130 is heated by this radiation. Furthermore, the molten glass MG is heated by the heat from the cylindrical member 130.

[0073] Here, a gap 17 exists between the through hole 10 formed in the bottom 5 of the melting furnace 1 and the first heater 100. For this reason, in the conventional glass melting method, a cooling member 12 has been used to suppress leakage of the molten glass MG (see FIG. 1).

[0074] However, when the first heater 100 is used, it is possible to suppress the temperature drop of the molten glass at the bottom of the furnace caused by the cooling member 12 that has been conventionally used.

[0075] This effect will be explained below.

[0076] As described above, in the first heater 100, the heat generating member 120 has the first heat generating portion 122 and the second heat generating portion 124 along the extension axis direction of the first heater 100. The first heat generating portion 122 is disposed in the internal space 110 of the first heater 100 at a position closer to the second heater end portion 102B than the second heat generating portion 124.

[0077] Therefore, when the first heater 100 is installed in the melting furnace 1, the first heater 100 can be disposed relative to the melting furnace 1 such that the height position of the first heat generating part 122 corresponds to the accommodation space 2 of the melting furnace 1, and the height position of the second heat generating part 124 corresponds to the through hole 10 of the melting furnace 1. In other words, the first heater 100 can be installed relative to the melting furnace 1 such that the first heat generating part 122 enters the accommodation space 2 and the second heat generating part 124 faces the through hole 10.

[0078] Furthermore, the relationship of the above-mentioned formula (1) holds between the first heat generating portion 122 and the second heat generating portion 124. Therefore, the first heat generating portion 122 can provide more heat toward the cylindrical member 130 than the second heat generating portion 124.

[0079] Therefore, the cylindrical member 130 can provide more heat energy to the outside at the position corresponding to the first heat generating portion 122, while reducing the amount of heat provided to the outside at the position corresponding to the second heat generating portion 124. As a result, the temperature in the gap 17 can be significantly reduced compared to the accommodation space 2.

[0080] In this case, the molten glass MG moving from the accommodation space 2 through the gap 17 is solidified on the way therethrough, so that the gap 17 can be sealed with a glass layer.

[0081] In this manner, when first heater 100 is used, it is possible to suppress the decrease in temperature of molten glass caused by cooling member 12 that has been conventionally used.

[0082] Therefore, when the first heater 100 is used, it is possible to significantly improve the heating efficiency when producing molten glass.

[0083] Furthermore, if a heater were simply used instead of a conventional electrode, the temperature of the bottom 5 of the melting furnace 1 would become too high, which could promote erosion of the components of the bottom 5. However, in the first heater 100, the second heat generating part 124 does not reach a temperature as high as that of the first heat generating part 122. Therefore, in the first heater 100, the erosion of the bottom 5 of the melting furnace 1 can be significantly suppressed.

[0084] (Components of the first heater 100) Next, each component included in the heater according to an embodiment of the present invention will be described in more detail. For clarity, each component will be described using the first heater 100 as an example. Therefore, when referring to each component, the reference numerals shown in FIG. 2 will be used.

[0085] (First heater 100) The outer shape of the first heater 100 is not particularly limited. The first heater 100 may have, for example, a substantially cylindrical or substantially prismatic shape. The cross section perpendicular to the extension axis direction of the first heater 100 may be substantially circular, substantially elliptical, substantially triangular, substantially rectangular (including trapezoidal), or any other polygonal shape.

[0086] In the following description, it is assumed, as an example, that the cross section of the first heater 100 is substantially circular.

[0087] (Internal space 110 and cover member 170) The interior space 110 in which the heat generating member 120 is housed preferably has a low oxygen partial pressure during use of the first heater 100 .

[0088] For this reason, the internal space 110 may be filled with a non-oxidizing gas such as a reducing gas and / or an inert gas. The reducing gas may be hydrogen, and the inert gas may be one or more selected from the group consisting of argon, helium, neon, krypton, xenon, radon, and nitrogen.

[0089] Additionally or alternatively, the interior space 110 may be adjusted to be at approximately atmospheric pressure when the first heater 100 is in use.

[0090] To achieve such an environment, the lid member 170 may be provided with one or more ports in communication with the interior space 110. Gas may be filled into the interior space 110 or gas may be evacuated from the interior space 110 via these ports.

[0091] The configuration of the lid member 170 is not particularly limited as long as it can properly maintain the environment of the internal space 110. Therefore, a description of the lid member 170 will be omitted here.

[0092] (heat generating member 120) The heat generating member 120 has a first heat generating portion 122 and a second heat generating portion 124. Both the first heat generating portion 122 and the second heat generating portion 124 can be made of a material containing carbon (C).

[0093] Materials containing carbon (C) include, for example, graphite and carbon fiber reinforced carbon composite materials (CC composites).

[0094] Such carbon materials have the characteristic of being less deformed even at high temperatures of 2000° C. or more. Therefore, by forming the heat generating member 120 from a material containing carbon, the problem of the heat generating member 120 deforming under its own weight while the first heater 100 is in use can be significantly suppressed.

[0095] This also allows the first heater 100 to be used in a "portrait" orientation as shown in FIG.

[0096] Here, the first heat generating portion 122 and the second heat generating portion 124 are configured to satisfy the above-mentioned formula (1).

[0097] In other words, in order to satisfy the above-mentioned formula (1), the second heat generating portion 124 may have a different material and / or a different shape from the first heat generating portion 122.

[0098] The shape of the first heat generating part 122 is not particularly limited. The first heat generating part 122 may have, for example, a cylindrical shape having periodic slits as shown in Fig. 2. Alternatively, the first heat generating part 122 may be in the shape of a coil, a rod (solid), a plate, or a tube (hollow), etc.

[0099] FIG. 4 shows an example of a three-dimensional view of the heat generating member 120. In FIG.

[0100] 4, the first heat generating portion 122 has a configuration in which a plurality of slits are provided in a hollow, substantially cylindrical conductor along the extension axis direction of the first heater 100. The slits are provided alternately from a first direction (e.g., the upper side in FIG. 4) and a second direction opposite to the first direction (e.g., the lower side in FIG. 4).

[0101] Similarly, the shape of the second heat generating part 124 is not particularly limited. The second heat generating part 124 may have, for example, a tubular (hollow) shape as shown in Fig. 4 with a small number of slits (two in Fig. 4) provided along the extension axis direction of the first heater 100.

[0102] Alternatively, the second heating part 124 may be in a coil shape, a rod shape (non-hollow), a plate shape, or the like. Further, when the first heating part 122 and the second heating part 124 are in a cylindrical shape having periodic slits in a spiral shape, the first heating part 122 and the second heating part 124 may have slits provided at different periods. Alternatively, when the first heating part 122 and the second heating part 124 are in a cylindrical shape having a plurality of slits along the extending axis direction of the first heater 100, as shown in FIG. 4, the first heating part 122 and the second heating part 124 may have slits with different periods. Alternatively, the shapes of the first heating part 122 and the second heating part 124 may be different shapes.

[0103] Alternatively, both the first heating part 122 and the second heating part 124 may be configured in a coil shape. Between the coil-shaped first heating part 122 and the coil-shaped second heating part 124, the number of turns and / or the thickness of the coil may be changed so as to satisfy the above-mentioned formula (1).

[0104] On the other hand, regarding the material, for example, the first heating part 122 may be composed of a CC composite having a first carbon content (C1), and the second heating part 124 may be composed of a CC composite having a second carbon content (C2). By selecting appropriate C1 and C2 and setting C1 < C2, the first heating part 122 and the second heating part 124 that satisfy the above-mentioned formula (1) can be configured.

[0105] In addition to this, or alternatively, for example, the first heating part 122 may be composed of a CC composite having a first porosity (P1), and the second heating part 124 may be composed of a CC composite having a second porosity (P2). By selecting appropriate P1 and P2 and setting P1 > P2, the first heating part 122 and the second heating part 124 that satisfy the above-mentioned formula (1) can be configured.

[0106] In addition to this, it is obvious to those skilled in the art who have examined the description of the present specification that various combinations are possible as the first heating part 122 and the second heating part 124.

[0107] As described in the foregoing formula (1), in order to compensate for the temperature drop at the bottom of the furnace by the cooling member, the resistance X (Ω / m) in the first heating part 122 and the resistance Y (Ω / m) in the second heating part 124 satisfy (1 / 30)X < Y. The relationship between the two is preferably (1 / 20)X < Y, and more preferably (1 / 10)X < Y.

[0108] On the other hand, the resistance X (Ω / m) and the resistance Y (Ω / m) satisfy Y < (1 / 2)X in order to suppress the erosion of the bottom of the furnace. The relationship between the two is preferably Y < (1 / 3)X, and more preferably Y < (1 / 4)X.

[0109] The temperature of the first heating part 122 during the use of the first heater 100 varies depending on the type of glass to be melted, but is, for example, in the range of 800°C to 2000°C. The temperature of the first heating part 122 may also be in the range of 900°C to 1800°C.

[0110] On the other hand, the temperature of the second heating part 124 during the use of the first heater 100 is 100°C or more lower than the temperature of the first heating part 122. The temperature of the second heating part 124 is preferably 200°C or more lower than the temperature of the first heating part 122, and preferably 300°C or more lower.

[0111] (Cylindrical member 130) The cylindrical member 130 is composed of a cylindrical metal with one end sealed as described above. The cylindrical member 130 may be composed of a material containing one or more selected from, for example, platinum, tungsten, iridium, rhodium, and molybdenum.

[0112] It is known that the oxidation resistance of some heat-resistant metals, such as molybdenum and tungsten, drops significantly in a certain temperature range. For example, the oxidation resistance of molybdenum drops significantly in a temperature range of about 400° C. or higher, and the oxidation resistance of tungsten drops significantly in a temperature range of about 500° C. or higher. This "dangerous" temperature range corresponds roughly to the temperature range to which the portion of the cylindrical member of the glass melting heater facing the side wall 11 of the bottom 5 of the melting furnace 1 is exposed.

[0113] Therefore, when metals such as molybdenum and tungsten are used as the cylindrical member of a heater for melting glass, there is a possibility that atmospheric oxidation will progress to a certain extent in the portion facing the side wall 11.

[0114] However, in the first heater 100, due to the above-mentioned effect, the gap 17 between the side wall 11 of the bottom 5 of the melting furnace 1 and the first heater 100 is sealed with the molten glass MG and a glass layer formed by solidifying the molten glass MG. In other words, the part of the cylindrical member 130 facing the side wall 11 is covered with a glass layer, and contact with the atmosphere is suppressed. In addition, in the first heater 100, the molten glass MG does not solidify immediately when it enters the gap 17 due to heating by the second heating part 124, but enters deep into the gap 17, and the cylindrical member 130 can be sealed with a glass layer up to the vicinity of the lower surface 9 of the bottom 5 of the melting furnace 1. Therefore, as shown in FIG. 5, when the second part 15 of the cooling member 12 is provided around the cylindrical member 130, the second part 15 can be installed at a position far from the storage space 2. This makes it possible to sufficiently prevent oxidation of the cylindrical member 130 and prevent a drop in the temperature of the molten glass MG in the storage space 2.

[0115] Therefore, in the first heater 100, even if the cylindrical member 130 is made of a metal containing molybdenum and tungsten, oxidation of the portion facing the side wall 11 can be significantly suppressed.

[0116] The open end of the cylindrical member 130 preferably has a shape that allows it to be flange-connected to the lid member 170, for example, a flange portion 139 as shown in Fig. 2. By flange-connecting the flange portion 139 to the lid member 170, the internal space 110 can be properly sealed.

[0117] Between flange portion 139 and cover member 170, an O-ring made of heat-resistant rubber or a metal gasket may be provided.

[0118] (First lead wire 180A and second lead wire 180B) The first lead wire 180A and the second lead wire 180B are made of a conductive material.

[0119] Here, when the resistance per unit length of the first lead wire 180A along the extension axis direction of the first heater 100 is Z1 (Ω / m), Z1 is only 1 / 30 or less of the resistance X per unit length of the first heat generating portion 122.

[0120] Similarly, when the resistance per unit length of the second lead wire 180B along the extension axis direction of the first heater 100 is Z2 (Ω / m), Z2 is only 1 / 30 or less of the resistance per unit length X of the first heat generating portion 122.

[0121] Therefore, it is clear from the above formula (1) that the first lead wire 180A and the second lead wire 180B do not correspond to the "second heat generating portion 124."

[0122] The maximum temperature that the first lead wire 180A and the second lead wire 180B reach is 400° C. or less even when the first heater 100 is in use.

[0123] (First insulating member 175A, second insulating member 175B) The first insulating member 175A is made of an insulating material and is also required to have a sealing function for properly sealing the gap between the first opening 172A of the cover member 170 and the first lead wire 180A.

[0124] Such insulating members having a sealing function are well known to those skilled in the art.

[0125] The same is true for the second insulating member 175B.

[0126] 1 is merely an example. It will be apparent to those skilled in the art that the configurations of the first insulating member 175A and the second insulating member 175B are not particularly limited as long as the first lead wire 180A and the second lead wire 180B can be appropriately taken out to the outside.

[0127] The configuration of the heater according to one embodiment of the present invention has been described above with reference to the first heater 100.

[0128] However, it is clear to those skilled in the art that the heater according to the embodiment of the present invention may have other configurations. For example, in the heater according to the embodiment of the present invention, the heat generating member is not limited to two, and may have three or more heat generating parts. In addition, various modifications are possible.

[0129] This application claims priority based on Japanese Patent Application No. 2019-230938, filed on December 20, 2019, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0130] 1 Melting furnace 2. Containment Space 3 Side 5 Bottom 7 Top side 9 Bottom side 10 Through hole 11 Side wall 12 Cooling material 13 First Part 15 Second Part 17 Gap 20 electrodes 22 Main unit 24 Lead material 26 Tip 28 Power Supply Equipment 100 First heater 102A First Heater End 102B Second heater end 110 Interior Space 120 Heat generating components 122 First heating element 124 Second heating element 130 Cylindrical member 139 Brim 170 Lid member 172A First Aperture 172B Second opening 175A First insulating member 175B Second insulating member 180A 1st lead 180B Second Lead MG Molten Glass

Claims

1. A heater for melting glass, A heat generating member containing carbon (C) that radiates heat rays when powered; a metallic cylindrical member having one closed end for accommodating the heat generating member; having the heat generating member has a first heat generating portion and a second heat generating portion along an extension axis direction of the heater, the first heat generating portion is disposed at a position closer to the one end of the cylindrical member than the second heat generating portion, the second heat generating portion is made of the same material as the first heat generating portion and has a different shape from the first heat generating portion, When the resistance per unit length of the first heat generating portion along the stretch axis direction is X (Ω / m) and the resistance per unit length of the second heat generating portion along the stretch axis direction is Y (Ω / m), (1 / 30)X<Y<(1 / 2)X (1) Formula holds true, heater.

2. The heater according to claim 1 , wherein the first and second heat generating portions are made of a carbon fiber reinforced carbon composite material.

3. 3. The heater according to claim 1, wherein the first heat generating portion has one shape selected from the group consisting of a rod shape, a coil shape, and a hollow cylinder shape with or without a slit.

4. The heater according to claim 1 , wherein the first heat generating portion and the second heat generating portion are disposed so as to be in physical contact with each other.

5. 5. The heater according to claim 1, wherein the cylindrical member is made of a material containing at least one selected from the group consisting of platinum, tungsten, iridium, rhodium, and molybdenum.

6. 5. The heater according to claim 1, wherein the cylindrical member is made of a material containing at least one of platinum and rhodium.

7. The heater according to claim 1 , further comprising a cooling member on a part of an outer periphery of the cylindrical member.

8. The heater according to claim 1 , wherein the heater is configured so as to be capable of controlling an atmosphere inside the cylindrical member.

9. The heater according to claim 1 , wherein a gas exists between the heat generating member and the cylindrical member.

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