JP2009110881A - High temperature sheath heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high temperature sheath heater which can be used at a high temperature of 1,000°C or more. <P>SOLUTION: The sheath heater has an exothermic wire 3 wound in coil shape held in a metallic sheath, powder insulators filled in the gap between the metallic sheath 2 and the exothermic wire 3, and an electrode 6 for current flowing to the exothermic wire 3 installed at the end portion of the metallic sheath 2. The electrode 6 is constructed of a strand electrode part 7 which is connected to the exothermic wire 3 and in which a plurality of wire rods made of the same material as the exothermic wire 3 are stranded, a first rod-shape electrode part 8 which is connected to the strand electrode part 7 and has a lower electric resistance than the strand electrode part 7 and has a lower melting point, and a second rod-shape electrode part 9 which is connected to the first rod-shape electrode part 8 and has a further lower electric resistance than the first rod-shape electrode part 8 and a lower melting point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheath heater in which a heating wire is held in a metal sheath, and particularly to a sheath heater having a high temperature specification exceeding 1000 ° C.

  The sheath heater has a heating wire in which a nichrome wire is wound in a coil shape and is held in a metal sheath, and a gap between the metal sheath and the heating wire is filled with magnesia (MgO) powder as an insulating material at a high density. It is common.

  In this type of sheathed heater, the heating wire is completely shielded from the air and gas in the environment of use, so it is less likely to oxidize or corrode, has a longer life than the bare wire, is economical, and is easy to handle.

  Specifically, since (a) the heating wire is housed in an electrically insulated state in the metal sheath, it can be disposed without considering insulation. As a result, the mounting structure becomes simple and can be easily mounted and removed. Further, since the metal sheath can be bent into a desired shape, it can be attached to a complicated portion that must be bent.

  (b) Since the metal sheath and the heating wire are insulated, they can be heated by directly contacting an object to be heated such as water or oil.

  (c) Since magnesia is densely filled between the metal sheath and the heating wire, heat conduction between the metal sheath and the heating wire is good, and since the sheath is made of metal, the sheath and the sheath are covered. Heat conduction with the heated object is also good. Thereby, the thermal efficiency is high and the running cost is low.

  (d) Since the heating wire is insulated and kept airtight with chemically stable high-purity magnesia, there is little oxidation and deterioration of the heating wire even if it is used for a long time. Insulation resistance is less likely to occur. In addition, even when used in locations subject to vibrations or in corrosive environments, the heating wire is not directly affected by these effects and has a long life.

  However, the above-described conventional sheath heater has a disadvantage that the use upper limit temperature cannot be set high.

  The melting point of the nichrome wire, which is the heating wire of the sheath heater, is about 1400 ° C., and it is necessary to allow a temperature margin as a safety factor for this temperature in use. In addition, even if the filling rate of magnesia powder as an insulating material is increased and the heat conduction between the heating wire and the metal sheath is maximized, a temperature gradient is generated between the heating wire and the metal sheath, resulting in a temperature difference. It is inevitable that this occurs.

  Although this temperature difference varies depending on the amount of heat transferred to the object to be heated, the heat generation of the metal sheath surface temperature is obtained by adding the temperature difference generated between the heating wire and the metal sheath to the temperature margin for the melting point of the heating wire. As the final temperature margin for the linear melting point, 400 ° C. is normally used as a reasonable value from the actual results, and the upper limit for use of the metal sheath surface temperature is about 1000 ° C. (1400 ° C.-400 for the nichrome heating wire). ° C).

  In addition, when copper having a low electrical resistance, which is widely used in electric circuit materials, is used as an electrode for energizing the heating wire, the melting point of copper is about 1083 ° C., which is lower than that of the heating wire. In order to avoid the dissolution of copper at the joint between the electrode and the electrode, the surface temperature of the metal sheath must be limited to a temperature lower by about 300 ° C. than the 1000 ° C.

  In order to reduce such a restriction on the upper limit temperature for use, various electrode materials and sheath heaters with electrode structures have been prototyped, particularly for electrode parts with severe temperature restrictions. Typical examples are shown in FIGS.

  FIG. 5 shows a sectional structure of the sheath heater, and FIG. 6 shows a sectional structure of the sheath heater terminal portion.

  The sheath heater shown in both figures has a configuration in which the heating wire reciprocates within the metal sheath, so two electrodes are provided at one end of the sheath heater, but one electrode is provided at each end of the sheath heater. Some are also available.

  As shown in both drawings, the sheath heater 30 houses a heating wire 32 in a metal sheath 31. The heating wire 32 has a double coil structure, and the tip (left side in the figure) is joined at the end on the metal cap 33 side. In addition, what provided the electrode at the both ends of the sheath heater has a single coil structure because the heating wire does not reciprocate.

  Two electrodes 34 are arranged on the right side of the heating wire 32, and a nickel or nickel alloy rod is used as a material of the electrode 34. In the figure, 35 is magnesia powder as an insulating material.

  The electrode 34 has a conductor cross-sectional area larger than that of the heat generating part H, and is not coiled like the heat generating part H but has a short circuit length. The calorific value of is small.

  If the length of the electrode 34 is increased to some extent, the influence of heat conduction from the heat generating portion H is reduced, and the temperature of the rear end portion 36 of the sheath heater 30 can be lowered, so that the rear end portion 36 is shown in FIG. A seal sleeve 37 as shown is attached by welding, caulking or the like.

  The electrode 34 and the lead wire 38 are connected in the seal sleeve 37. After the connection, the seal sleeve 37 is filled with magnesia powder 39 as an insulating material. In addition, in order to prevent a decrease in insulation due to moisture intrusion, the end of the seal sleeve 37 is sealed with an epoxy resin or the like to form a seal portion 40. In the figure, reference numeral 41 denotes a lead wire insulation coating.

  7 shows a manufacturing method of the sheath heater 30 shown in FIG. 5, in which FIG. 7 (a) is a perspective view, FIG. 7 (b) is a cross-sectional view taken along the line AA in FIG. FIG. 6C is a cross-sectional view taken along the line BB.

  In these drawings, a metal sheath 31 having a diameter larger than the finished outer diameter is prepared, and an insulator cylinder 39a obtained by sintering magnesia powder into a cylindrical shape is inserted into the metal sheath 31, and the insulator cylinder 39a is inserted into the insulator cylinder 39a. Further, the heating wire 32 is wound and the insulator shaft 39b incorporating the electrode 34 is inserted.

  When this is swaged so that the outer diameter of the metal sheath 31 becomes a predetermined finished size, both the insulator cylinder 39a and the insulator shaft 39b are broken and pulverized.

  Next, if the rear end side end portion of the metal sheath 31 is cut and the magnesia powder 39 is removed, the sheath heater 30 shown in FIG. 5 is obtained.

  As described above, the sheath heater of FIGS. 5 to 7 uses nickel or a nickel alloy having a high temperature resistance as an electrode material, and suppresses heat generation by expanding its cross-sectional area, etc., and lowers the connecting portion temperature with the lead wire, By these, the restriction | limiting of the use upper limit temperature restrict | limited by the electrode part is aimed at.

  However, since the sheath heater manufactured in this manner uses a high-temperature nickel-resistant alloy wire having an electrical resistivity equivalent to that of the heating wire 32 as the electrode 34, the electrode 34 also generates heat to some extent.

  As described above, in the electrode portion, it is necessary to lower the temperature of the electrode 34 to a temperature at which the lead wire (including the conductive wire and the insulation coating) 38 and the seal portion 40 are not damaged, but the sheath heater is set to a high temperature specification of 1000 ° C. or higher. In this case, due to heat generation of nickel or a nickel alloy, in order to lower the temperature, there arises a problem that the length of the electrode 34 must be extended to an unpractical length.

  Further, if there is a considerable amount of heat generated in a portion other than the heat generating portion H, there is a problem that a portion where the heating target is not desired to be heated is heated.

  If the electrode 34 is made of a material having a high melting point and a low electric resistivity, it is considered that the above problem can be solved, but such a material is not found at present.

  The present invention has been made in view of the above-described problems in conventional sheath heaters, and provides a high-temperature sheath heater that can be used at a high temperature of, for example, 1000 ° C. or higher.

In the present invention, a heating wire wound in a coil shape is held in a sheath, a gap between the metal sheath and the heating wire is filled with a powder insulating material, and the end of the metal sheath is energized to the heating wire. In a sheath heater provided with an electrode for
The electrode is connected to the heating wire, and a twisted wire electrode portion obtained by twisting a plurality of wires made of the same material as the heating wire,
A first rod-shaped electrode portion connected to the stranded wire electrode portion, having a lower electrical resistance and a lower melting point than the stranded wire electrode portion;
A high-temperature sheath heater connected to the first rod-shaped electrode portion and composed of a second rod-shaped electrode portion having a lower electrical resistance and a lower melting point than the first rod-shaped electrode portion.

  In the present invention, it is preferable that the first rod-shaped electrode portion has a larger cross-sectional area than the stranded electrode portion, and the second rod-shaped electrode portion has substantially the same cross-sectional area as the first rod-shaped electrode portion.

In the present invention, when the heating wire is reciprocated in the metal sheath and connected to the two electrodes provided at the end of the sheath heater, the first rod-shaped electrode portion is used as the two electrodes. And the second rod-like electrode part is constituted by a pair of electrode pieces formed by dividing a cylindrical body in its axial direction,
One end of the heating wire is connected to one electrode piece of the first rod-shaped electrode portion through the stranded wire electrode portion,
The other end of the heating wire is connected to the other electrode piece of the first rod-like electrode portion through the stranded wire electrode portion,
It can comprise from what filled the powder insulating material between said pair of electrode pieces.

  In the present invention, the first rod-shaped electrode portion can be made of nickel or a nickel alloy.

  In the present invention, the second rod-shaped electrode portion can be made of copper or a copper alloy.

  In the present invention, the heating wire can be composed of platinum rhodium.

  In the present invention, the powder insulating material can be composed of boron nitride.

  According to the present invention, as a terminal structure of the high-temperature sheath heater, a seal sleeve is connected to an end portion of the metal sheath, the second rod-shaped electrode portion is connected to a lead wire in the seal sleeve, and nitriding is performed in the seal sleeve. This is a high-temperature sheath heater filled with boron and sealed with a sealing material.

  According to the present invention, it is possible to provide a high-temperature sheath heater that can be used, for example, for high temperatures of 1000 ° C. or higher.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

  Fig.1 (a) is a longitudinal cross-sectional view which shows the structure of the high temperature sheath heater based on this invention, The same figure (b) is CC sectional drawing of Fig.1 (a).

1 Structure of sheath heater In both figures, the sheath heater 1 is provided with a heating coil 3 having a double coil structure in a metal sheath 2, and the tip side (left side in the figure) of the heating wire 3 is an end portion on the metal cap 4 side. It is joined with.

  Insulating material powder 5 is filled to insulate electricity flowing through the heating wire 3 and to conduct only heat. The double coil structure is the same as the double coil structure described in FIG.

  The metal sheath 2 is made of nickel-based heat resistant steel that can withstand high temperatures of 1000 ° C. or higher.

  The heating wire 3 is made of platinum rhodium, and the melting point of this platinum rhodium (platinum ratio 60 to 95%) is about 1900 ° C.

  The insulating powder 5 is made of boron nitride having a higher thermal conductivity than magnesia.

  The electrode 6 includes a stranded wire electrode portion 7, a nickel rod electrode portion (first rod electrode portion) 8 made of nickel or nickel alloy, and a copper rod electrode portion (second rod shape) made of copper or copper alloy. Electrode portion) 9, and each electrode portion is connected by welding to constitute one electrode 6. The stranded wire electrode portion 7 is composed of a bundle of about six platinum rhodium wires, which are the same material as the heating wire 3, to form a stranded wire.

  The nickel rod electrode portion 8 halves the electrode cylindrical material in the axial direction to form a pair of electrode pieces 8a and 8b, and by scraping the opposing surfaces 8c and 8d of the electrode pieces 8a and 8b, the gap D is formed. It is to be secured. The gap D functions as an insertion passage E for inserting a lever plate 5c, which will be described later.

  In the same manner as the nickel rod electrode portion 8, the copper rod electrode portion 9 halves the electrode column material in the axial direction to form a pair of electrode pieces 9a and 9b, and scrapes the facing surfaces of the electrode pieces 9a and 9b. Thus, an insertion passage F communicating with the insertion passage E is secured.

2 Configuration of Sheath Heater Terminal Unit FIG. 2 is an enlarged longitudinal sectional view showing the configuration of the sheath heater terminal unit.

  In the figure, a metal seal sleeve 10 is welded to the sheath heater terminal portion.

  In this seal sleeve 10, the copper rod electrode portion 9 of the electrode 6 and the lead wire conductor 11 are connected. After the connection, powder boron nitride 12 is filled in the seal sleeve 10 as an insulating material. In addition, in order to prevent a decrease in insulation due to moisture intrusion, the end portion of the seal sleeve 10 is sealed with an epoxy resin or the like to form a seal portion 13. In the figure, reference numeral 14 denotes a lead wire insulation coating.

3 Manufacturing Method of Sheath Heater FIG. 3 is a perspective view showing a manufacturing method of the sheath heater 1.

  In the figure, an insulator cylinder 5a obtained by sintering boron nitride powder is inserted into a metal sheath 2 having a diameter larger than the finished outer diameter, and an insulator shaft 5b and an insulator plate 5c are further inserted into the insulator cylinder 5a. Insert in one piece.

  A double spiral groove 5d (see FIG. 3B) is formed on the outer surface of the body portion of the insulator shaft 5b so as to be wound with the heating wire 3 embedded therein. The heating wire 3 is wound along the winding.

  A linear groove 5e (see FIG. 3C) for positioning the stranded electrode portion 7 is formed at the rear end (right side in FIG. 3A) of the lever shaft 5b. The stranded electrode portion 7 is fitted into the groove 5e.

  The linear grooves 5e are formed so as to face each other in the radial direction and to be parallel to the axial direction of the lever shaft 5b. The purpose of forming the groove in the insulator shaft 5b in this way is to increase the filling rate of the insulating material powder by eliminating the gap between the metal sheath 2 as much as possible.

  Further, an insulator plate 5c obtained by sintering boron nitride powder is inserted into the insertion paths E and F (see FIG. 1) formed in the nickel bar electrode part 8 and the copper bar electrode part 9.

  The heating wire 3, the stranded wire electrode portion 7, the nickel rod electrode portion 8, and the copper rod electrode portion 9 are welded in advance before inserting the insulator shaft 5b and the insulator plate 5c, and the front side of the nickel rod electrode portion 8 Two notches 15 (see FIG. 3A) for welding the stranded electrode portion 7 are formed at the end.

  The outer diameter of the insulator shaft 5b is configured to be equal to the outer diameter of the nickel rod electrode portion 8 and the copper rod electrode portion 9 into which the insulator plate 5c is inserted (see 3 (d) in the figure). Is inserted into the insulator cylinder 5a and further swallowed into the metal sheath 2.

  When the outer diameter of the metal sheath 2 is reduced to a predetermined finished size by the swaging, the insulator cylinder 5a, the insulator shaft 5b, and the insulator plate 5c are each broken and pulverized to form the insulating material powder 5.

  Next, as shown in FIG. 4A, the metal sheath 2 at the end of the sheath heater 1 is cut off and the insulating powder 5 is removed as shown in FIG. The sheath heater 1 shown in FIG. 1 is obtained.

  A seal sleeve 10 is attached to the copper rod electrode portion 9 of the sheath heater 1, that is, a temperature-decreased portion by welding, caulking or the like, and the copper rod electrode portion 9 and the lead wire conductor 11 are connected.

  After the connection, the sheath sleeve terminal structure shown in FIG. 2 is obtained by filling the seal sleeve 10 with powdered boron nitride as an insulating material and sealing the end of the seal sleeve 10 with an epoxy resin or the like.

  The effects obtained by the sheath heater terminal structure having the above-described configuration are as follows.

  In FIG. 2, the stranded wire electrode portion 7 is formed in a stranded wire formed by twisting a plurality of heating wires 3, so that the cross-sectional area is formed larger than that of the heating wire 3. Since the length is short, the amount of heat generated per unit length in the longitudinal direction is smaller than that of the heating wire 3.

  Thereby, the temperature at the right end in the figure of the stranded wire electrode portion 7 is low, and there is no possibility that the nickel rod electrode portion 8 welded to the stranded wire electrode portion 7 is damaged by the temperature. The melting point of nickel is about 1455 ° C.

  Moreover, since the cross-sectional area of the nickel bar electrode part 8 is formed larger than the cross-sectional area of the stranded electrode part 7, the electrical resistance can be reduced and the amount of heat generated by the nickel bar electrode part 8 can be suppressed. Can be done.

  Thus, since the temperature at the right end of the nickel bar electrode part 8 is further lowered, the copper bar electrode part 9 welded to the nickel bar electrode part 8 is not damaged by the temperature. The melting point of copper is about 1083 ° C.

  Moreover, since the cross-sectional area of the electrode pieces 9a and 9b in the copper bar electrode part 9 is formed to be substantially the same size as the electrode pieces 8a and 8b of the nickel bar electrode part 8, it is larger than the cross-sectional area of the stranded electrode part 7. Since the electrical resistivity of copper is large and extremely small, the amount of heat generated in the copper bar electrode portion 9 is extremely small, and a sufficient temperature drop can be obtained without taking a long electrode length as in the prior art. .

  In this way, a rod-shaped electrode that can divide the cylinder into half and secure a large cross-sectional area is joined to the stranded wire electrode portion 7, and the rod-shaped electrode is connected to the nickel rod electrode portion 8 having high temperature resistance and the electrical resistivity. By configuring in combination with the small copper rod electrode part 9, it becomes possible to reduce the temperature of the electrode part to the allowable temperature of the sealing material and the lead wire constituting the seal sleeve with a short electrode length. Moreover, the calorific value of the electrode part can be suppressed to a small value.

  Accordingly, even if the sheath heater for high temperature is configured, the adverse effect that the part of the object to be heated that is not intended to be heated is heated by the electrode portion is also improved.

  Further, according to the sheath heater terminal structure, a sufficient temperature drop can be obtained. Therefore, when platinum rhodium having a high melting point is used as the heating wire 3, the heating wire and the surface of the metal sheath due to the high temperature are added to the temperature margin of 400 ° C. Even if the temperature margin with respect to the melting point of the heating wire is set to 500 ° C, the metal sheath surface temperature can be used up to 1400 ° C.

  Furthermore, since boron nitride having a higher thermal conductivity than magnesia is used as the insulating material powder 5, the temperature margin itself is reduced.

  In addition, the cross-sectional area of the said nickel bar electrode part 8 and the said copper bar electrode part 9 is about 8 times the cross-sectional area of the strand wire electrode part 7, Comparing the electrical resistivity of each part in a use temperature range, The platinum rhodium of the electrode part 7 and the nickel of the nickel bar electrode part 8 are equivalent, and the copper of the copper bar electrode part 9 is about 1/5 of them.

  Therefore, the calorific value per unit length in the nickel bar electrode part 8 is about 1/8 of the stranded electrode part 7 made of platinum rhodium, and the calorific value per unit length of the copper bar electrode part 9 is platinum rhodium. It becomes about 1/40 of the stranded electrode portion 7 made of

  The configuration of the sheath heater shown in FIG. 1 and the embodiment of the sheath heater terminal structure shown in FIG. 2 will be described.

Length of heat generating part H: 20 mm
Heating wire 3 material: platinum rhodium (80% platinum, 20% rhodium)
Heating wire 3 outer diameter: φ0.5mm
Metal sheath 2 material: NCF600
Metal sheath 2 length: 270 mm
Outer diameter of metal sheath 2: φ9.2 mm
Seal sleeve 10 material: SUS304
Outer diameter of seal sleeve 10: φ34mm
Twisted wire electrode part 7: Twisted wire in which six heating wires are bundled. Length of stranded wire electrode part 7: 20 mm
Half-cracked bar electrode material: Nickel (or nickel alloy) and copper (or copper alloy)
The outer diameter of the half cracked rod-shaped electrode (see the outer diameter D ′ in FIG. 1B): 5.7 mm
Half cracked bar electrode length: 175mm
The above configuration shows an example of the high-temperature sheath heater of the present invention. The outer diameter of the heating wire 3, the length of the heating portion H, the ratio of platinum and rhodium in the heating wire material, the metal sheath, and the seal sleeve The material of can be suitably changed according to the usage object of the high-temperature sheath heater.

  In the above embodiment, since the operating temperature is assumed to be 1200 ° C., NCF600 is adopted as the metal sheath 2, but the material of the metal sheath 2 is the same as that of another high temperature resistant material, for example, the heating wire 3. If it is made of a material, the operating temperature can be further increased to 1400 ° C.

  Further, in the present embodiment, since the configuration in which two electrodes are provided at the rear end portion of the sheath heater is described, the heating wire has a double coil structure, but one electrode is provided at each end of the sheath heater. The present invention can also be applied to a sheath heater. However, in this case, since the heating wire does not reciprocate within the metal sheath, a single coil structure is obtained.

(a) is the longitudinal cross-sectional view which shows the structure of the sheath heater which concerns on this invention, (b) is the CC arrow directional cross-sectional view. It is an expanded longitudinal cross-sectional view which shows the structure of the sheath heater terminal part which concerns on this invention. (a) is a perspective view showing a manufacturing method of a sheath heater according to the present invention, (b) is a cross-sectional view taken along the line II, (c) is a cross-sectional view taken along the line JJ, and (d) is a cross-sectional view taken along the line K- It is K arrow sectional drawing. (a)-(c) is explanatory drawing which shows the edge part processing method of the sheath heater which concerns on this invention. It is a longitudinal cross-sectional view which shows the structure of the conventional sheath heater. It is an expanded longitudinal cross-sectional view which shows the structure of the conventional sheathed heater terminal part. (a) is a perspective view which shows the manufacturing method of the conventional sheath heater, (b) is the AA arrow sectional drawing, (c) is a BB arrow sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sheath heater 2 Metal sheath 3 Heating wire 4 Metal cap 5 Insulator powder 5a Insulator cylinder 5b Insulator shaft 5c Insulator plate 6 Electrode 7 Strand wire electrode part 8 Nickel bar electrode part 8a, 8b Electrode piece 9 Copper bar electrode part 9a, 9b Electrode Piece 10 Seal sleeve 11 Lead wire conductor 12 Powdered boron nitride 13 Seal portion 14 Lead wire insulation coating

Claims (8)

An electrode for holding a heating wire wound in a coil shape in a metal sheath, filling a gap between the metal sheath and the heating wire with a powder insulating material, and energizing the heating wire at an end of the metal sheath In the sheath heater provided with
The electrode is connected to the heating wire, and a twisted wire electrode portion obtained by twisting a plurality of wires made of the same material as the heating wire,
A first rod-shaped electrode portion connected to the stranded wire electrode portion, having a lower electrical resistance and a lower melting point than the stranded wire electrode portion;
A high-temperature sheath heater, comprising: a second rod-shaped electrode portion connected to the first rod-shaped electrode portion and having a lower electric resistance and a lower melting point than the first rod-shaped electrode portion.   The high-temperature sheath heater according to claim 1, wherein the first rod-shaped electrode portion has a larger cross-sectional area than the stranded electrode portion, and the second rod-shaped electrode portion has substantially the same cross-sectional area as the first rod-shaped electrode portion. The high-temperature sheath heater has a configuration in which the heating wire is wired in a state of reciprocating in the metal sheath and connected to the two electrodes provided at the end of the sheath heater,
As said two electrodes, said 1st rod-shaped electrode part and said 2nd rod-shaped electrode part consist of a pair of electrode piece formed by dividing the cylindrical body in the axial direction,
One end of the heating wire is connected to one electrode piece of the first rod-shaped electrode portion via the stranded wire electrode portion,
The other end of the heating wire is connected to the other electrode piece of the first rod-shaped electrode portion via the stranded wire electrode portion,
The sheath heater for high temperature according to claim 1 or 2, wherein a powder insulating material is filled between the pair of electrode pieces.   The high temperature sheath heater according to any one of claims 1 to 3, wherein the first rod-shaped electrode portion is made of nickel or a nickel alloy.   The high temperature sheath heater according to any one of claims 1 to 4, wherein the second rod-shaped electrode portion is made of copper or a copper alloy.   The sheath heater for high temperature according to any one of claims 1 to 5, wherein the heating wire is made of platinum rhodium.   The sheath heater for high temperature according to any one of claims 1 to 6, wherein the powder insulating material is made of boron nitride.   As a terminal structure of the high-temperature sheath heater, a seal sleeve is connected to an end of the metal sheath, the second rod-shaped electrode portion is connected to a lead wire in the seal sleeve, and the seal sleeve is filled with boron nitride. The high-temperature sheath heater according to any one of claims 1 to 7, which is sealed with a sealing material.

Images