Immersion heater

Abstract

To provide an immersion heater capable of more increasing the maximum heat.SOLUTION: An immersion heater 1 comprises: a coil-like heat generation body 4; a first lead wire part 6 that is connected to a base end part of the heat generation body 4; and a second lead wire part 8 that is connected to a tip end part of the heat generation body 4. The first lead wire part 6 is arranged to an external part of the heat generation body 4. The second lead wire part 8 includes: a base end side conductive wire part 8W; and a tip end side conductive wire part 8E. The tip end side conductive wire part 8E includes a plurality of single wires 10 that is electrically connected with the base end side conductive wire part 8W, and passes through an inner direction of the heat generation body 4. At least two or more single wires 10 are arranged to a width direction cross to its longer direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an immersion heater that heats (and keeps warm) molten metal, which is a liquid metal. [Background technology]

[0002] As a heater, a heater 300 shown in FIG. 5 of Japanese Patent No. 6760534 (Patent Document 1) is known. This heater 300 has a cylindrical member 330 with one end sealed and the other end open, and a heat generating member 320 disposed therein. The heat generating member 320 has a coil-shaped portion and a linear portion passing through the inside of the coil-shaped portion. An end of the coiled portion of heat generating member 320 on the open end side of cylindrical member 330 is connected to first lead wire 380A. An end of the linear portion of heat generating member 320 on the open end side of cylindrical member 330 is connected to second lead wire 380B. Like heat generating member 120, heat generating member 320 may be constructed of the same material and shape along its entire length, or may have multiple materials and shapes along its entire length in order to intentionally generate temperature changes along its entire length, and as further specific examples, only examples of multiple materials are disclosed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6760534 Summary of the Invention [Problem to be solved by the invention]

[0004] The heater described above has room for improvement in the maximum power that can be applied to the heat generating member 320, and also in the maximum amount of heat that can be generated. A primary object of the present invention is to provide an immersion heater capable of increasing the maximum heat output. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, the invention described in claim 1 comprises a coil-shaped heating element, a first lead wire portion connected to a first end of the heating element, and a second lead wire portion connected to a second end of the heating element, wherein the first lead wire portion is arranged outside the heating element, the second lead wire portion has a first portion and a second portion, the second portion is electrically connected to the first portion and passes inside the heating element, and further has a plurality of single wires, at least two of which are arranged in a width direction that intersects with the longitudinal direction. The invention described in claim 2 is characterized in that in the above invention, at least one of the heating element and each of the single wires is made of molybdenum or a molybdenum alloy. The invention as set forth in claim 3 is characterized in that, in the above invention, at least one of the first lead wire portion and the first portion includes a stranded wire made of nichrome. The invention described in claim 4 is characterized in that, in the above invention, it further comprises a first connecting portion interposed between the heating element and the first lead wire portion, the first lead wire portion having a first pipe portion, and the heating element and the first pipe portion being joined to the first connecting portion. The invention described in claim 5 is characterized in that, in the above invention, the first connection part has a first ring part and a pole part, the heating element is joined to the first ring part, and the first pipe part is joined to the pole part. The invention described in claim 6 is characterized in that, in the above invention, the second portion has a terminal, and the individual single wires are bundled by the terminal. The invention described in claim 7 is characterized in that, in the above invention, the terminals are crimped to bundle the individual single wires. The invention described in claim 8 is characterized in that, in the above invention, it further comprises a second connection portion interposed between the heating element and the second part, and the heating element and the terminal are joined to the second connection portion. The invention described in claim 9 is characterized in that, in the above invention, the second connection portion has a second ring portion and a plate portion, the heating element is joined to the second ring portion, and the terminal is joined to the plate portion. The invention described in claim 10 is characterized in that, in the above invention, the first portion has a second pipe portion, and the second pipe portion is joined to the second portion. The invention described in claim 11 is characterized in that, in the above invention, the second part has a terminal, each of the single wires is bundled by the terminal, and the second pipe part is joined to the terminal. The invention described in claim 12 is characterized in that, in the above invention, it further comprises a tubular portion arranged outside the heating element and a filler arranged between the tubular portion and the heating element, and the filler is a powdered, highly thermally conductive filler. [Effects of the Invention]

[0006] A major advantage of the present invention is that it provides an immersion heater capable of increasing the maximum heat output. [Brief explanation of the drawings]

[0007] [Figure 1] Figure 1A is a schematic diagram of the tip of an immersion heater according to the present invention, and Figure 1B is a schematic partial end view of the heating element in Figure 1A. [Figure 2] Figure 2A is a view of Figure 1B as seen from the proximal end side, and Figure 2B is a view of Figure 1B as seen from the distal end side. [Figure 3] Fig. 3A is a schematic diagram of the distal end side conductor portion of the second lead wire portion of Fig. 1B, and Fig. 3B is a view of Fig. 3A as seen from the distal end side. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention and modifications thereof will be described with reference to the accompanying drawings. The present invention is not limited to the following embodiments and modifications.

[0009] Fig. 1A is a schematic diagram of the tip end of an immersion heater 1 according to this embodiment. Fig. 1B is a schematic partial end view of the heating element 4 in Fig. 1A. Fig. 2A is a diagram of Fig. 1B as viewed from the base end side. Fig. 2B is a diagram of Fig. 1B as viewed from the tip end side. The immersion heater 1 comprises a tubular portion 2, a heating element 4, a first lead wire portion 6, a first connection portion 7, a second lead wire portion 8, a second connection portion 9, a sealing portion (not shown), and a filler (not shown). The immersion heater 1 is intended to heat (and keep warm) molten aluminum (molten aluminum). Note that the immersion heater 1 may also be used to heat molten metals of other metals such as zinc and iron, or may be used to heat other materials. The molten aluminum is intended for use in aluminum die-cast products, but may also be used for other purposes. When heating an object, typically, the tip of the immersion heater 1 is inserted into the object from above, and the immersion heater 1 is positioned so that the longitudinal direction of the immersion heater 1 is in the up-down direction. However, the immersion heater 1 may also be used in a position other than such a position in which it faces up-down.

[0010] The tubular portion 2 is a cylindrical tube made of ceramics. The tip of the tubular portion 2 is closed, forming a closed end (sealed end) in a semispherical shape. The proximal end of the tubular portion 2 is open and serves as an open end. The material of the tubular portion 2 is not limited to ceramics. The shape of the tubular portion 2 is not limited to having a closed end and an open end, and may be, for example, a shape in which both ends are open. The shape of the tip of the tubular portion 2 is not limited to a hemispherical shape.

[0011] The heating element 4 has a single coil shape as a whole, and generates heat when electricity is applied. The heating element 4 extends from a base end (first end) to a tip end (second end). The heating element 4 is placed inside the tubular portion 2. The heating element 4 is arranged on the tip side inside the tubular portion 2. The tubular portion 2 is arranged outside the heating element 4 and covers the heating element 4. The tubular portion 2 protects the heating element 4. The heating element 4 is made of molybdenum (including molybdenum alloys, the same applies hereinafter). The melting point of molybdenum is approximately 2500°C, which is higher than the melting point of nichrome wire (approximately 1400°C, heat-resistant temperature 1150°C). Therefore, compared to heating elements made of nichrome wire, a higher heating temperature can be obtained, resulting in greater output. The thermal expansion coefficient of molybdenum is 4.8 x 10 -6 [K -1 ] and the thermal expansion coefficient of nichrome wire (14 × 10 -6 [K -1 Therefore, compared to a heating element made of nichrome wire, the heating element 4 made of molybdenum is less susceptible to metal fatigue due to expansion and contraction, and the occurrence of wire breakage in the heating element 4 is suppressed. The heating element 4 may be in the form of a multiple coil, etc. The material of the heating element 4 may be other than molybdenum.

[0012] The first lead wire portion 6 supplies power to the heating element 4 . The first connecting portion 7 is made of metal (for example, stainless steel), and connects the heating element 4 and the first lead wire portion 6. The first connecting portion 7 is interposed between the heating element 4 and the first lead wire portion 6. The first connecting portion 7 is connected to the end portion of the heat generating element 4 on the open end (base end) side. The first lead wire portion 6 is disposed outside the heating element 4. The first lead wire portion 6 and the heating element 4 are aligned in the longitudinal direction.

[0013] The second lead wire portion 8 supplies power to the heating element 4 . The second connection portion 9 is made of metal (for example, stainless steel) and connects the heating element 4 and the second lead wire portion 8. The first connection portion 7 is interposed between the heating element 4 and the second lead wire portion 8. The second connecting portion 9 is connected to the end portion of the heat generating element 4 on the closed end (tip) side. The tip of the second lead wire portion 8 passes radially inward of the heating element 4. The second lead wire portion 8 passes inside the heating element 4.

[0014] The base end of the first lead wire portion 6 and the base end of the second lead wire portion 8 are connected to a power source (not shown) via a control device (not shown). The power supply here is single-phase AC. The control device controls the power supplied from the power source to the heating element 4 to control the heat generation in the heating element 4. The power supply may be DC, three-phase AC, or other. The voltage of the power supply may be selected appropriately.

[0015] The sealing portion is disposed at the open end of the tubular portion 2 and closes the open end. The first lead wire portion 6 and the second lead wire portion 8 pass through the sealed portion.

[0016] The filler is filled into the tubular portion 2 . The main component of the filler (the component that is the majority by weight or volume) is magnesium oxide (magnesia, MgO). Here, the filler contains 90% or more MgO by volume. MgO is a highly thermally conductive filler with excellent thermal conductivity. The thermal conductivity of MgO is approximately 60 W / m·K (watts per meter per kelvin). The thermal conductivity of the filler is close to that of MgO. The filler covers the heating element 4. The filler is in contact with the inner surface of the tip of the tubular portion 2. The filler is arranged around the heating element 4 and holds it in place. The filler is arranged between the tubular portion 2 and the heating element 4. The filler is filled in the area including the first connection portion 7 and further towards the tip. The filler also enters between adjacent loop portions of the coil-shaped heating element 4. Because the filler holds the heating element 4 and enters the gaps in the heating element 4, adjacent portions of the heating element 4 are prevented from coming into contact with each other due to expansion when heated, etc., and the heating element 4 is protected from electrical leakage. The filler mainly prevents oxygen from coming into contact with the molybdenum heating element 4, suppressing oxidation of the heating element 4 in a high-temperature environment and preventing embrittlement due to oxidation. As a result, the life of the heating element 4 is at least as long as that of heating elements made of other materials, making it sufficient. The main component of the filler may be something other than magnesium oxide. The filler material may be MgO only. The filler may also be in a form other than powder, such as a spherical shape. Furthermore, the filler may be filled further forward than the tip of the first lead wire portion 6 and the tip of the second lead wire portion 8, or further forward than the sealing portion.

[0017] An example of a method for manufacturing the immersion heater 1 will now be described. First, the first connection portion 7 is connected to the tip end of the first lead wire portion 6 , and the first connection portion 7 is connected to the base end of the heating element 4 . Further, a second connection part 9 is connected to the tip of the second lead wire part 8 , and the second connection part 9 is connected to the tip of the heating element 4 . Next, the integrated heating element 4 , first lead wire portion 6 , first connection portion 7 , second lead wire portion 8 and second connection portion 9 are placed inside the tubular portion 2 . Next, a filler is placed in the tubular portion 2 . Subsequently, a sealing portion is formed at the proximal end of the tubular portion 2 .

[0018] The first lead wire portion 6 has a conductor portion 6W and a first pipe portion 6P. The conductor portion 6W is a stranded wire made by twisting together a plurality of (for example, 120) nichrome single wires (for example, 0.8 mm (millimeter) in diameter). Note that the conductor portion 6W may be made of a material other than nichrome. Because the conductor portion 6W is a stranded wire, its own heat generation is suppressed compared to when it is a single wire. Therefore, melting of the conductor portion 6W due to its own heat generation and the heat generated by the heating element 4 is suppressed. Furthermore, because the conductor portion 6W is a stranded wire, its flexibility is greater than when it is a single wire. Therefore, stress generated by expansion and contraction is more easily absorbed, and breakage of the conductor portion 6W is suppressed. Furthermore, because the conductor portion 6W is a stranded wire, collective breakage due to metal fatigue that can occur with a single wire is suppressed. Furthermore, the first lead wire portion 6 can supply sufficient current to a heating element 4 that is compatible with larger output, such as a heating element 4 made of molybdenum. From the viewpoint of suppressing melting, the current density in the conductor portion 6W is preferably 3 A / mm 2 (amperes per square millimeter) or less. In order to prevent the diameter from becoming too large, obtain sufficient flexibility, and reduce costs, the current density in the conductor portion 6W is preferably 1 A / mm 2 That is all. The first pipe portion 6P is made of stainless steel and is cylindrical. The first pipe portion 6P is disposed radially outward from the tip of the conductor portion 6W. The first pipe portion 6P contacts the tip of the conductor portion 6W and is electrically connected to the tip. The first pipe portion 6P may be made of a material other than stainless steel.

[0019] The first connection portion 7 has a first ring portion 7R and a pole portion 7P. The first ring portion 7R is ring-shaped. The pole portion 7P is columnar and is welded to one side of the first ring portion 7R. The pole portion 7P and the first ring portion 7R may be joined by a method other than welding. Similarly, at least one of the connections and joining of other portions is not limited to welding or the like. The pole portion 7P and the first ring portion 7R may be integral from the beginning of their formation. Furthermore, the arrangement of the pole portion 7P relative to the first ring portion 7R is not limited to that described above. The pole portion 7P and the first ring portion 7R may be made of different materials.

[0020] The ring-shaped base end portion of the heating element 4 is welded to the surface of the tip side of the first ring portion 7R. The first pipe portion 6P of the first lead wire portion 6 is welded to the base end surface of the pole portion 7P. The presence of the first pipe portion 6P makes it easier to weld the first lead wire portion 6 to the first connection portion 7 compared to directly welding the end of the conductor portion 6W, which is a stranded wire. The first pipe portion 6P also prevents the conductor portion 6W, which is a stranded wire, from fraying.

[0021] The second lead wire portion 8 has a base end side conductor portion 8W (first portion), a second pipe portion 8P, and a tip end side conductor portion 8E (second portion).

[0022] The base end conductor portion 8W is configured similarly to the conductor portion 6W of the first lead wire portion 6. The base-end conductor portion 8W may be different from the conductor portion 6W.

[0023] The second pipe section 8P is configured similarly to the first pipe section 6P, although the second pipe section 8P may be different from the first pipe section 6P. The second pipe portion 8P is disposed radially outward from the tip of the base-side conductor portion 8W. The second pipe portion 8P contacts the tip of the base-side conductor portion 8W and is electrically connected to the tip.

[0024] Fig. 3A is a schematic diagram of the tip-side conductor portion 8E of the second lead wire portion 8. Fig. 3B is a diagram of Fig. 3A as viewed from the tip side. The distal conductor portion 8E has a plurality of (for example, thirteen) solid wires 10, a proximal terminal portion 11, and a distal terminal portion 12.

[0025] Each of the single wires 10 is made of molybdenum. The diameter of each of the single wires 10 is, for example, 1.5 mm. The material of each of the single wires 10 may be other than molybdenum. Furthermore, at least one of the material and diameter of some of the single wires 10 may be different from the material of the other single wires 10. At least one of the material and diameter of the single wires 10 may be three or more different. Some or all of the single wires 10 are aligned in a direction (width direction) that intersects with the longitudinal direction. That is, at least two or more single wires 10 are aligned in the width direction. For example, in FIG. 3, six single wires 10 are aligned in the width direction, and the remaining seven single wires 10 are aligned in the width direction adjacent to these. The width direction may also be considered as the direction perpendicular to the longitudinal direction.

[0026] The base-end terminal portion 11 is made of metal (e.g., stainless steel) and is cylindrical. The cross section of the base-end terminal portion 11 in the width direction is oval. The base ends of all the single wires 10 are bundled and joined by being inserted into the base-end terminal portion 11 and crimped. The tip terminal portion 12 is made of metal (e.g., stainless steel) and is cylindrical. The widthwise cross section of the tip terminal portion 12 is oval. The tips of all the solid wires 10 are bundled and joined by being crimped while inserted into the tip terminal portion 12. The length of the base end terminal portion 11 in the longitudinal direction is longer than the length of the tip end terminal portion 12 in the longitudinal direction. The shape etc. of the base end terminal portion 11 and the shape etc. of the tip end terminal portion 12 may be the same as or different from each other.

[0027] The second connection portion 9 has a second ring portion 9R and a plate portion 9B. The second ring portion 9R is ring-shaped. The plate portion 9B is in the shape of a plate, and is welded to the center of the second ring portion 9R. The plate portion 9B and the second ring portion 9R may be integrally formed by pressing or the like. The arrangement of the plate portion 9B relative to the second ring portion 9R is not limited to the above. The plate portion 9B and the second ring portion 9R may be made of different materials.

[0028] The ring-shaped tip portion of the heating element 4 is welded to the surface of the base end side of the second ring portion 9R. The tip terminal 12 of the tip conductor portion 8E of the second lead wire portion 8 is welded to the center of the base end surface of the plate portion 9B. The presence of the tip terminal 12 makes it easier to weld the first lead wire portion 6 to the first connection portion 7 compared to when the ends of the individual wires 10 are directly welded. In addition, the tip terminal 12 prevents the individual wires 10 from separating.

[0029] The length of the tip-side conductor portion 8E is longer than the length of the heating element 4. The base end of the tip-side conductor portion 8E protrudes beyond the base end of the heating element 4 on the base-end side. Because the single wires 10 passing through the heating element 4 are aligned in the width direction, it is easier to ensure the rigidity of each single wire 10 (tip-side conductor portion 8E) compared to when a single conductor is used instead of each single wire 10. This prevents breakage and other problems that can occur when the tip-side conductor portion 8E is subjected to an external force such as a torsional force from the second connection portion 9 or the like. Furthermore, since multiple single wires 10 are used, the maximum current that can be applied becomes larger. In particular, a sufficient current can be applied to a heating element 4 that is compatible with a larger output, such as a heating element 4 made of molybdenum. From the viewpoint of preventing each single wire 10 from fusing, the current density in each single wire 10 is preferably 2 A / mm 2 The following is said to be true. Furthermore, since a plurality of single wires 10 are used, the number of single wires 10 can be adjusted according to the magnitude of the required maximum output, thereby reducing costs while meeting the required current.

[0030] In the second lead wire portion 8, the distal conductor portion 8E is joined to the proximal conductor portion 8W. More specifically, the base terminal 11 of the tip conductor 8E is welded to the second pipe 8P joined to the tip of the base conductor 8W. The base end of the base terminal 11 is welded to the tip of the second pipe 8P. The base terminal 11 and the second pipe 8P overlap in the longitudinal direction. However, the base terminal 11 and the second pipe 8P may also overlap in the width direction, etc. The distal conductor portion 8E and the proximal conductor portion 8W are easily joined together by the proximal terminal portion 11 and the second pipe portion 8P. The proximal terminal portion 11 prevents the individual wires 10 from separating, and the second pipe portion 8P prevents the proximal conductor portion 8W from fraying.

[0031] In the second lead wire portion 8, a tip-side conductor portion 8E that enters the inside of the heating element 4 is provided separately from a base-side conductor portion 8W that exits from the inside of the heating element 4. Therefore, in the second lead wire portion 8, the distal end side conductor portion 8E and the proximal end side conductor portion 8W can be separately produced depending on the important characteristics inside and outside the heating element 4. That is, it is more important to ensure the ability to withstand external forces and higher heat resistance while appropriately ensuring the maximum allowable current and heat resistance corresponding to high output within the heating element 4. Therefore, in the tip-side conductor portion 8E, the individual molybdenum single wires 10 are aligned in the width direction. Additionally, outside the heating element 4, it is more important to improve efficiency and extend life by suppressing heat generation in the second lead wire portion 8 while appropriately ensuring the maximum possible current flow and heat resistance corresponding to high output. Therefore, the base end conductor portion 8W is a twisted wire made of multiple single wires twisted together.

[0032] An example of the operation of such an immersion heater 1 will be described below. The user turns on the power to generate heat from the heating element 4 of the immersion heater 1. The heat from the heating element 4 is efficiently transferred to the tubular portion 2 by the filler. The user can heat the molten aluminum by immersing the tip of the tubular portion 2 from above into the molten aluminum in the molten aluminum tank, and the molten aluminum is heated by heat transfer from the heating element 4 through the filler and the tubular portion 2. The control device controls the amount of heat generated by the heating element 4. Here, a temperature sensor (not shown) electrically connected to the control device detects the temperature of the molten aluminum and transmits a temperature signal indicating that temperature to the control device, and the control device controls the amount of heat generated by the heating element 4 according to the temperature associated with the received temperature signal. The maximum heat generation (maximum output) of the heating element 4 can be made greater by using a heating element 4 made of molybdenum than by using a heating element 4 made of nichrome. The oxidation of molybdenum, which leads to embrittlement of the heating element 4, is suppressed by disposing a filler around the heating element 4.

[0033] The above-described immersion heater 1 provides the following functions and effects. That is, the immersion heater 1 comprises a coil-shaped heating element 4, a first lead wire portion 6 connected to the base end of the heating element 4, and a second lead wire portion 8 connected to the tip end of the heating element 4, the first lead wire portion 6 being arranged outside the heating element 4, the second lead wire portion 8 having a base end conductor portion 8W and a tip end conductor portion 8E, the tip end conductor portion 8E being electrically connected to the base end conductor portion 8W and passing inside the heating element 4, and further having a plurality of single wires 10, at least two or more of which are aligned in a width direction intersecting the longitudinal direction. Therefore, an immersion heater 1 is provided that can increase the maximum heat generation amount.

[0034] The heating element 4 and each of the single wires 10 are made of molybdenum or a molybdenum alloy, so that the immersion heater 1 can achieve a greater maximum heat output than a heating element made of nichrome. Furthermore, at least one of the first lead wire portion 6 and the base-end conductor portion 8W includes a nichrome stranded wire. Therefore, at least one of the first lead wire portion 6 and the base-end conductor portion 8W passing outside the heating element 4 is prevented from melting due to self-heating, and improved flexibility prevents wire breakage due to stress, and further prevents all wire breakage due to metal fatigue.

[0035] Furthermore, the immersion heater 1 is equipped with a first connection portion 7 interposed between the heating element 4 and the first lead wire portion 6, and the first lead wire portion 6 has a first pipe portion 6P, and the heating element 4 and the first pipe portion 6P are joined to the first connection portion 7. The first connection portion 7 also has a first ring portion 7R and a pole portion 7P, and the heating element 4 is joined to the first ring portion 7R, and the first pipe portion 6P is joined to the pole portion 7P. This makes it easier to connect the heating element 4 and the first lead wire portion 6 in a state that can handle sufficient current.

[0036] Additionally, the distal conductor portion 8E has a proximal terminal portion 11 and a distal terminal portion 12, and each of the single wires 10 is bundled by the distal terminal portion 12 and the proximal terminal portion 11. The distal terminal portion 12 and the proximal terminal portion 11 are crimped together to bundle the single wires 10. This makes it easier to arrange multiple single wires 10. Furthermore, the immersion heater 1 is provided with a second connection portion 9 interposed between the heating element 4 and the tip side conductor portion 8E, and the heating element 4 and the tip side terminal portion 12 are joined to the second connection portion 9. This makes it easier to connect the heating element 4 and the tip side conductor portion 8E in a state that is capable of handling a sufficient current. The second connection portion 9 has a second ring portion 9R and a plate portion 9B, the heating element 4 is joined to the second ring portion 9R, and the tip terminal portion 12 is joined to the plate portion 9B. This makes it easier to connect the heating element 4 and the tip conductor portion 8E in a state that can handle sufficient current. Furthermore, the common tip terminal portion 12 allows the bundling of each single wire 10 and joining to the plate portion 9B to be performed more efficiently.

[0037] Furthermore, the proximal conductor 8W has a second pipe 8P, which is joined to the distal conductor 8E, making it easier to couple the proximal conductor 8W and the distal conductor 8E in a state that allows sufficient current to flow. The distal conductor portion 8E has a proximal terminal portion 11, and the individual wires 10 are bundled by the proximal terminal portion 11, and the second pipe portion 8P is joined to the proximal terminal portion 11. This makes it easier to couple the proximal conductor portion 8W and the distal conductor portion 8E in a state that can handle sufficient current. Furthermore, the common proximal terminal portion 11 allows for more efficient bundling of the individual wires 10 and joining to the second pipe portion 8P.

[0038] Furthermore, the immersion heater 1 includes a tubular portion 2 disposed outside the heating element 4, and a filler disposed between the tubular portion 2 and the heating element 4. The filler is a powdered, highly thermally conductive filler. This allows heat from the heating element 4 to be transferred more efficiently to the tubular portion 2. The heating element 4 is also more effectively protected from oxidation. In particular, in the case of a heating element 4 made of molybdenum, embrittlement due to oxidation is suppressed. [Example]

[0039] Hereinafter, more specific examples will be described in accordance with the above-described embodiments of the present invention. The present invention is not limited to the following examples.

[0040] First, the heating temperature of the heating element 4 was tested. An immersion heater 1, which had a tubular portion 2 containing a molybdenum heating element 4 and a filler covering it, was immersed in molten aluminum, and the temperature of the heating element 4 was raised to 1280°C (theoretical value) by applying electric power (single-phase AC). At this time, the temperature of the molten aluminum was 780°C. The effective output of the immersion heater 1 was 20.1 kW (kilowatts). The internal temperature of the immersion heater 1 was approximately 980°C. This internal temperature exceeded the internal temperature of the nichrome heating element 4, which is normally 850°C and has an upper limit of 950°C. The conductor portion 6W and the base-side conductor portion 8W were nichrome stranded wires made of 120 0.8 mm diameter single wires. The tip-side conductor portion 8E was made of molybdenum and had 13 1.5 mm diameter single wires 10 arranged in two rows widthwise. The first pipe portion 6P, the second pipe portion 8P, the tip-side terminal portion 12, the base-side terminal portion 11, the first connection portion 7, and the second connection portion 9 were made of stainless steel. The tip-side terminal portion 12 and the base-side terminal portion 11 were crimped, while the others were welded. Such temperature rise of the heating element 4 continued for two months, during which no break in the heating element 4 was observed.

[0041] In addition, a high-load test was conducted under the following two conditions, in which immersion and empty heating were repeated, using an immersion heater 1 similar to the immersion heater 1 used in the above heat generation temperature test. That is, as the first condition, the internal temperature of the immersion heater 1 was cycled 68 times between the upper and lower limits of the temperature range of 350°C to 800°C (output of the immersion heater 1 was 3 kW to 7 kW), then the upper limit of the temperature range was proportionally raised to 900°C over 10 cycles, and then the internal temperature of the immersion heater 1 was cycled 29 times between the upper and lower limits of the temperature range of 350°C to 900°C (output of the immersion heater 1 was 3 kW to 8 kW). During these 107 cycles of immersion and dry heating, the internal temperature of the immersion heater 1 was returned to room temperature approximately every five cycles. As a second condition, the internal temperature of the immersion heater 1 was cycled 45 times between the upper and lower limits of the temperature range of 350°C to 1000°C (output of the immersion heater 1: 5.5kW to 15kW). During these 45 cycles of immersion and dry heating, the internal temperature of the immersion heater 1 was returned to room temperature approximately every 5 cycles. After the tests under each of the above conditions, the immersion heater 1 was inspected, and no breaks in the heating element 4 were found under any of the conditions. [Explanation of symbols]

[0042] 1··Immersion heater, 2··Tubular portion, 4··Heat generating element, 6··First lead wire portion, 6P··First pipe portion, 7··First connection portion, 7P··Pole portion, 7R··First ring portion, 8··Second lead wire portion, 8E··Tip side conductor portion (second portion), 8P··Second pipe portion, 8W··Base side conductor portion (first portion), 9··Second connection portion, 9B··Plate portion, 9R··Second ring portion, 10··Solid wire, 11··Base side terminal portion (terminal), 12··Tip side terminal portion (terminal).

Claims

1. A coil-shaped heating element; a first lead wire portion connected to a first end of the heating element; a second lead wire portion connected to a second end of the heating element; It is equipped with the first lead wire portion is disposed outside the heating element, the second lead wire portion has a first portion and a second portion, the second portion is electrically connected to the first portion, passes through the inside of the heating element, and further includes a plurality of solid wires; At least two of the single wires are arranged in a width direction that intersects with the longitudinal direction. An immersion heater characterized by:

2. At least one of the heating element and each of the solid wires is made of molybdenum or a molybdenum alloy.

2. The immersion heater according to claim 1.

3. At least one of the first lead wire portion and the first portion includes a nichrome stranded wire.

3. The immersion heater according to claim 1 or 2.

4. The heat generating element further includes a first connection portion interposed between the heat generating element and the first lead wire portion, the first lead wire portion has a first pipe portion, The heating element and the first pipe portion are joined to the first connection portion.

4. The immersion heater according to claim 1, wherein the heater is a heater having a diameter of 100 mm or less.

5. the first connection portion has a first ring portion and a pole portion, the heating element is joined to the first ring portion, The first pipe portion is joined to the pole portion.

5. The immersion heater according to claim 4.

6. the second portion has a terminal; Each of the single wires is bundled by the terminal.

6. The immersion heater according to claim 1, wherein the heater is a heater having a diameter of 100 mm or less.

7. The terminals are crimped to bundle the individual wires.

7. The immersion heater of claim 6.

8. Further, a second connection portion is provided between the heating element and the second portion, The heating element and the terminal are joined to the second connection portion.

8. The immersion heater according to claim 6 or claim 7.

9. the second connection portion has a second ring portion and a plate portion, the heating element is joined to the second ring portion, The terminal is joined to the plate portion.

9. The immersion heater of claim 8.

10. the first portion includes a second pipe portion; The second pipe section is joined to the second portion.

10. The immersion heater according to claim 1, wherein the heater is a heater having a diameter of 100 mm or less.

11. the second portion has a terminal; Each of the single wires is bundled by the terminal, The second pipe portion is joined to the terminal.

11. The immersion heater of claim 10.

12. Further, a tubular portion disposed outside the heating element; a filler disposed between the tubular portion and the heating element; It is equipped with The filler is a powdered, highly thermally conductive filler.

12. The immersion heater according to claim 1, wherein the heater is a heater having a diameter of 100 mm or less.

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