阅读说明：本技术 护套加热器 (Sheath heater ) 是由 花待年彦 关谷健二 桥本大辅 平野智资 泷本优 高原刚 荒木良仁 巽新 川崎孝 外 于 2018-04-03 设计创作，主要内容包括：提供一种提高了可靠性的细径护套加热器。本发明的一个实施方式的护套加热器具备金属护套、发热丝、绝缘材料以及连接端子,所述发热丝为带状,以具有间隙的方式配置于所述金属护套内,并相对于所述金属护套的轴向旋转而配置在所述金属护套内,所述绝缘材料配置于所述间隙中,所述连接端子配置于所述金属护套的一端,分别与所述发热丝的两端电连接。(Provided is a small-diameter sheath heater with improved reliability. A sheath heater according to an embodiment of the present invention includes a metal sheath, a heater wire, an insulating material, and connection terminals, wherein the heater wire is arranged in the metal sheath in a band shape with a gap and is arranged in the metal sheath so as to rotate in an axial direction of the metal sheath, the insulating material is arranged in the gap, and the connection terminals are arranged at one end of the metal sheath and are electrically connected to both ends of the heater wire, respectively.)

1. A sheathed heater comprising:

A metal sheath;

A heating wire that is in a band shape, is disposed in the metal sheath with a gap, and is disposed in the metal sheath so as to rotate in an axial direction of the metal sheath;

an insulating material disposed in the gap; and

And the connecting terminals are arranged at one end of the metal sheath and are respectively electrically connected with two ends of the heating wire.

2. The sheath heater of claim 1,

In the region where the heat generating wires are arranged in two rows within the metal sheath, the heat generating wires are configured in a double-helix structure.

3. The sheath heater of claim 1,

The insulating material is inorganic insulating powder.

4. The sheath heater of claim 1,

The metal sheath is aluminum, the heating wire is nickel-chromium alloy, and the insulating material is magnesium oxide.

Technical Field

The present invention relates to sheath heaters. And more particularly to a small diameter sheathed heater.

Background

The sheath heater is generally a structure in which a heating wire is held in a metal tubular sheath (sheath) and a gap between the metal sheath and the heating wire is filled with an insulating material having good thermal conductivity. Since the surface of the heating element is electrically insulated, the sheath heater can directly heat gas, liquid, metal, and the like. Further, the sheath heater can be laid out (designed, shaped) in an arbitrary shape, and is used for various purposes because of its convenience. Therefore, in order to be able to lay out more complicated shapes corresponding to various demands, there is an increasing demand for a sheath heater having a smaller diameter. On the other hand, since the sheath heater heats the heating wire by supplying electricity thereto, measures for improving the durability of the heating wire are also required.

For example, a sheath heater having a plurality of heating wires in a single metal sheath is disclosed in patent document 1. Generally, heating is performed using one of a plurality of heating wires, with the aim of recovering easily and quickly by switching the power supply circuit to the other heating wire when this heating wire is broken.

(Prior art document)

(patent document)

Patent document 1: japanese laid-open patent publication No. 2002-151239

Disclosure of Invention

(problems to be solved by the invention)

However, the sheath heater described in patent document 1 takes measures against a broken wire of the heating wire, and does not take measures against a broken wire of the heating wire. Further, the diameter reduction of the sheath heater is not involved.

One of the problems of the embodiments of the present invention is to provide a small-diameter sheath heater with improved reliability.

(measures taken to solve the problems)

One embodiment of the present invention provides a sheath heater including a metal sheath, a heater wire, an insulating material, and connection terminals, wherein the heater wire is arranged in the metal sheath in a band shape with a gap and is arranged in the metal sheath so as to rotate in an axial direction of the metal sheath, the insulating material is arranged in the gap, and the connection terminals are arranged at one end of the metal sheath and are electrically connected to both ends of the heater wire, respectively.

In another embodiment, the heating wire may be arranged in a double-helix structure in a region that is formed in two rows (two axes) in the metal sheath.

In addition, in another form, the insulating material may be an inorganic insulating powder.

In addition, in another aspect, the metal sheath may be aluminum, the heating wire may be nichrome, and the insulating material may be magnesium oxide.

Drawings

Fig. 1A is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 1B is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 2A is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 2B is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 2C is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 2D is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 3A is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 3B is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

fig. 4A is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 4B is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 4C is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 4D is a sectional structural view showing a sheath heater according to an embodiment of the present invention.

Fig. 5 is a sectional structural view showing a sheath heater according to a first embodiment of the present invention.

Fig. 6A is a CT scan image of a sheath heater according to a first embodiment of the invention.

Fig. 6B is a 3D image of a sheath heater according to a first embodiment of the invention.

Detailed Description

Embodiments of the invention disclosed in the present application will be described below with reference to the drawings. However, the present invention can be carried out in various ways without departing from the gist thereof, and is not limited to the description of the embodiments described below.

In addition, for more clear explanation, the drawings schematically show the width, thickness, shape, and the like of each part as compared with the actual form, but the drawings are only an example and do not limit the explanation of the present invention. In the present specification and the drawings, the same reference numerals are given to members having the same functions as those of the members already described with reference to the already described drawings, and redundant descriptions are omitted.

(first embodiment)

(Structure of sheath Heater)

The structure of the sheath heater according to the first embodiment of the present invention will be described with reference to fig. 1A, 1B, and 2A to 2D. The sheath heater of the first embodiment of the present invention has a heating mechanism. Further, the sheath heater of the first embodiment may be used to directly heat gas, liquid, metal, or the like. However, the sheath heater according to the first embodiment is not limited to be used only for the object.

fig. 1A and 1B are sectional structural views showing a sheath heater according to an embodiment of the present invention. As shown in fig. 1A and 1B, the sheath heater of the first embodiment includes a band-shaped heating wire 20, an insulating material 30, a metal sheath 40, and a connection terminal 50.

Referring to fig. 1A, the heater 20 is disposed in a cylindrical metal sheath 40 with a gap, and the heater 20 and the metal sheath 40 are insulated by an insulating material 30 disposed in the gap. In fig. 1A, the metal sheath 40 is shown in a shape closed at one end, but is not limited thereto, and may be in a shape open at both ends. The heating wire 20 is disposed to reciprocate in the metal sheath 40 in the cylindrical axis direction, and both ends of the heating wire 20 are disposed at one end of the metal sheath 40. That is, in most of the metal sheath 40 in the cylindrical axial direction, one heating wire 20 is arranged in two rows (double axis). The heating wires 20 arranged in the metal sheath 40 are arranged with a gap, and are insulated by the insulating material 30 arranged in the gap.

FIG. 1B is a cross-sectional view of C-C' of FIG. 1A. Referring to fig. 1B, the width d1 of the band-shaped heater 20 is preferably in the range of 0.1mm to 2.0 mm. The thickness d2 of the band-shaped heater 20 is preferably in the range of 0.1mm to 0.5 mm. The inner diameter d3 of the metal sheath 40 is preferably in the range of 3.0mm to 4.0 mm. The thickness d4 of the metal sheath 40 is preferably in the range of 0.5mm to 1.0 mm. The outer diameter d5 of the metal sheath 40 is preferably in the range of 3.5mm to 5.0 mm. The sheath heater 120 of the present embodiment can have a small diameter while maintaining reliability by having the above-described configuration. By making the diameter of the sheath heater 120 smaller, the sheath heater 120 can be laid out in a fine pattern shape.

In a cross section orthogonal to the cylindrical axis, the shortest distance g1 between the metal sheath 40 and each heater 20 disposed in the metal sheath 40 is preferably in a range of 0.3mm to 1.0 mm. The shortest distance g1 between the metal sheath 40 and the heater 20 is more preferably in the range of 0.4mm to 1.0 mm. The insulation between the metal sheath 40 and the heating wire 20 can be ensured by setting the distance g1 between the metal sheath 40 and the heating wire 20 to 0.3mm or more. The diameter of the sheath heater 120 can be reduced by setting the distance g1 between the metal sheath 40 and the heating wire 20 to 1.0mm or less. The sheath heater 120 of the present embodiment can be reduced in diameter while maintaining reliability by using the band-shaped heating wire 20. By making the diameter of the sheath heater 120 smaller, the sheath heater 120 can be laid out in a fine pattern shape.

In a cross section orthogonal to the cylindrical axis, the distance g2 between the heating wires 20 disposed in the metal sheath 40 is preferably in the range of 0.3mm to 2.0 mm. The shortest distance g2 between the heating wires 20 disposed in the metal sheath 40 is more preferably in the range of 0.4mm to 1.0 mm. The insulation of the heating wire 20 can be ensured by setting the distance g2 between the two rows of heating wires 20 to 0.3mm or more. The diameter of the sheath heater 120 can be reduced by setting the distance g2 between the two rows of heating wires 20 to 2.0mm or less. The sheath heater 120 of the present embodiment can maintain a small diameter with reliability by using the band-shaped heating wire 20. By making the diameter of the sheath heater 120 smaller, the sheath heater 120 can be laid out in a fine pattern shape.

The heater 20 includes a connection terminal 50a and a connection terminal 50b at both ends thereof, and the heater 20 is electrically connected to the connection terminal 50a and the connection terminal 50b at both ends thereof, respectively. Here, when the connection terminal 50a and the connection terminal 50b are not particularly distinguished, they are collectively referred to as the connection terminal 50. The sheath heater 120 of the present embodiment has a double-shaft single-terminal structure in which two connection terminals 50 are disposed at one end of the sheath heater 120. One end of the sheath heater 120 having the connection terminal 50 is connected to an external device (heater controller, power supply, etc.). The sheath heater 120 is heated by electric power supplied from an external device, thereby controlling the temperature of the sheath heater 120.

In the region where the heating wire 20 is arranged in two rows (two axes) in the metal sheath 40, the band-shaped heating wire 20 is disposed to rotate in the cylindrical axis direction of the metal sheath 40. The band-shaped heater 20 extends in the cylindrical axis direction in a state where the major axis of the heater 20 rotates in the direction perpendicular to the cylindrical axis of the metal sheath 40. That is, each heating wire 20 is wound in a spiral shape. The rotary axes of the two rows of the heating wires 20 are arranged substantially parallel to the cylindrical axis direction of the metal sheath 40. By disposing the heating wire 20 in a wound state, the length of the heating wire 20 disposed in the metal sheath 40 can be increased, and the resistance value of the sheath heater 120 can be increased. Further, the heater 20 is disposed in a wound state and is elastic, so that disconnection during thermal expansion can be suppressed. Therefore, for example, even if the difference in the thermal expansion coefficients of the metal sheath 40 and the heat generating wire 20 is large, the sheath heater 120 with improved reliability can be provided.

The length of the heating wire 20 disposed in the metal sheath 40 in the cylindrical longitudinal direction of the metal sheath 40 when the heating wire is spirally rotated once, that is, the rotational pitch L1 is preferably 3.0mm or less. The rotational pitch L1 of the heating wire 20 disposed in the metal sheath 40 is more preferably 2.5mm or less, and further preferably 2.0mm or less. By setting the rotational pitch L1 of the heating wire 20 disposed in the metal sheath 40 to 3.0mm or less, the sheath heater 120 can be provided which suppresses disconnection during thermal expansion and improves reliability.

fig. 2A to 2D are sectional structural views showing a sheath heater according to an embodiment of the present invention. Fig. 2A to 2D are sectional views of the sheath heater 120 shifted by one quarter pitch (L1/4) at a time in the cylindrical axial direction of the metal sheath 40. The arrangement of the heater 20 in the present embodiment will be described in detail with reference to fig. 2A to 2D. The broken line in fig. 2A indicates the trajectory of the heating wire 20 when the heating wire 20 is rotated in a single rotation into a spiral shape. Referring to fig. 2A to 2D, when the heating wires 20 are moved by a quarter pitch (L1/4) in the cylinder axis direction, the heating wires are rotated by 90 degrees around the rotation axis. The rotation axis of each heater 20 is parallel to the cylinder axis direction, and is separated by a distance g2 of two rows (two axes) of heaters 20.

The width d1 of the heater 20 forms a plane direction substantially perpendicular to the normal line of the rotation plane. That is, the surface of the band-shaped heating wire 20 is a tangent plane of the rotation surface. Further, the planar directions of the two rows (two axes) of the heating wires 20 are substantially parallel. The central axes of the respective heating wires 20 are substantially aligned in a direction in which the central axes are spirally rotated in the cylindrical axial direction of the metal sheath 40, and the rotational pitch L1 is also substantially the same. By matching the rotational direction of each heater wire 20 with the rotational pitch L1, the distance g2 between the two rows of heater wires 20 can be kept constant, and the reliability of the sheath heater 120 can be maintained. However, the present invention is not limited to this, and the rotational direction and/or the rotational pitch L1 of each heater 20 may be different. The sheath heater 120 of the present embodiment is designed to maintain reliability even in consideration of the rotation of the heating wire 20 by satisfying the above conditions.

The sheath heater 120 of the present embodiment has a circular cross-sectional shape. Since the sectional shape of the sheath heater 120 is circular, the sheath heater 120 can be easily bent into a desired shape. However, the sectional shape of the sheath heater 120 is not limited thereto, and may have any shape as long as the above conditions are satisfied, and may be deformed into any shape.

The ribbon-shaped heating wire 20 may use an electric conductor that generates joule heat by being energized. Specifically, a metal selected from tungsten, tantalum, molybdenum, platinum, nickel, chromium, and cobalt may be included. The metal may also be an alloy comprising these metals, such as an alloy of nickel and chromium, and may also be an alloy comprising nickel, chromium and cobalt. In the present embodiment, a nickel-chromium alloy is used as a material of the heating wire 20.

The insulating material 30 is disposed to suppress electrical connection between the heater 20 and other components. That is, a material that sufficiently insulates the heater 20 from other components may be used. Further, the thermal conductivity of the material used for the insulating material 30 may preferably be 10W/mK or more. The thermal conductivity of the material used for the insulating material 30 is 10W/mK or more, so that the heat generated by the heater 20 can be efficiently transmitted to the metal sheath 40. As the insulating material 30, magnesium oxide, aluminum oxide, boron nitride, aluminum nitride, or the like can be used. In the present embodiment, a powder of magnesium oxide (MgO) is used as the insulating material 30. The thermal conductivity of the magnesium oxide (MgO) compact is about 10W/mK.

The thermal conductivity of the material used for the metal sheath 40 may preferably be 200W/mK or more. By setting the thermal conductivity of the material used for the metal sheath 40 to 200W/mK or more, the heat energy generated by the heating wire 20 can be efficiently transmitted to the object to be heated.

Further, the coefficient of thermal expansion of the material used for the metal sheath 40 may preferably be 25X 10-6/K or less. In the present embodiment, aluminum is used as the material of the metal sheath 40. However, the material of the metal sheath 40 is not limited to this, and materials such as aluminum (Al), titanium (Ti), and stainless steel (SUS) may be used. By setting the coefficient of thermal expansion of the material used for the metal sheath 40 to 25X 10-6/K or less, disconnection of the heating wire 20 due to thermal expansion of the metal sheath 40 can be suppressed, and the sheath heater 120 with high reliability can be provided.

As described above, the sheath heater 120 of the present embodiment can be reduced in diameter by having the band-shaped heating wire 20. By making the diameter of the sheath heater 120 smaller, the sheath heater 120 can be laid out in a fine pattern shape. By disposing the ribbon-shaped heating wire 20 in the sheath heater 120 in a spirally rotating state, disconnection of the heating wire 20 during thermal expansion can be suppressed, and for example, even if the difference in thermal expansion coefficient between the metal sheath 40 and the heating wire 20 is large, the sheath heater 120 with improved reliability can be provided.

(second embodiment)

(Structure of sheath Heater)

The structure of the sheath heater according to the second embodiment of the present invention will be described with reference to fig. 3A, 3B, and 4A to 4D. Fig. 3A and 3B are sectional structural views illustrating a sheath heater according to an embodiment of the present invention. As shown in fig. 3A and 3B, the sheath heater of the second embodiment has a band-shaped heating wire 20, an insulating material 30, a metal sheath 40, and a connection terminal 50, as in the first embodiment. Since the sheath heater 130 of the second embodiment is the same as that of the first embodiment except for the arrangement of the heating wire 20 in the metal sheath 40, the description of the overlapping configuration and components is omitted, and the difference will be mainly described.

Referring to fig. 3A, the heater 20 is disposed in the cylindrical metal sheath 40 with a gap, and the heater 20 and the metal sheath 40 are insulated by the insulating material 30 disposed in the gap. In fig. 3A, the metal sheath 40 is shown in a shape closed at one end, but is not limited thereto, and may be in a shape open at both ends. The heating wire 20 is disposed to reciprocate in the metal sheath 40 in the cylindrical axis direction, and both ends of the heating wire 20 are disposed at one end of the metal sheath 40. That is, in most of the metal sheath 40 in the cylindrical direction, one heating wire 20 is arranged in two rows (double axis). Each of the heating wires 20 arranged in the metal sheath 40 is arranged to have a gap, and is insulated by the insulating material 30 arranged in the gap.

FIG. 3B is a cross-sectional view of C-C' of FIG. 3A. Referring to fig. 3B, the width d1 of the band-shaped heater 20 is preferably in the range of 0.1mm to 2.0 mm. The thickness d2 of the band-shaped heater 20 is preferably in the range of 0.1mm to 0.5 mm. The inner diameter d3 of the metal sheath 40 is preferably in the range of 3.0mm to 4.0 mm. The thickness d4 of the metal sheath 40 is preferably in the range of 0.5mm to 1.0 mm. The outer diameter d5 of the metal sheath 40 is preferably in the range of 3.5mm to 5.0 mm. The sheath heater 130 of the present embodiment can have a small diameter while maintaining reliability by having the above-described configuration. By making the diameter of the sheath heater 130 smaller, the sheath heater 130 can be laid out in a fine pattern shape.

In a cross section orthogonal to the cylindrical axis, the shortest distance g1 between the metal sheath 40 and each heater 20 disposed in the metal sheath 40 is preferably in a range of 0.3mm to 1.0 mm. The shortest distance g1 between the metal sheath 40 and the heater 20 is more preferably in the range of 0.4mm to 1.0 mm. The insulation between the metal sheath 40 and the heating wire 20 can be ensured by setting the distance g1 between the metal sheath 40 and the heating wire 20 to 0.3mm or more. The diameter of the sheath heater 130 can be reduced by setting the distance g1 between the metal sheath 40 and the heating wire 20 to 1.0mm or less. The sheath heater 130 of the present embodiment can be reduced in diameter while maintaining reliability by using the band-shaped heating wire 20. By making the diameter of the sheath heater 130 smaller, the sheath heater 130 can be laid out in a fine pattern shape.

In a cross section orthogonal to the cylindrical axis, the distance g2 between the heating wires 20 disposed in the metal sheath 40 is preferably in the range of 0.3mm to 2.0 mm. The shortest distance g2 between the heating wires 20 disposed in the metal sheath 40 is more preferably in the range of 0.4mm to 1.0 mm. The insulation of the heating wire 20 can be ensured by setting the distance g2 between the two rows (two axes) of heating wires 20 to 0.3mm or more. The diameter of the sheath heater 130 can be reduced by setting the distance g2 between the two rows (twin axes) of heating wires 20 to 2.0mm or less. The sheath heater 130 of the present embodiment can be reduced in diameter while maintaining reliability by using the band-shaped heating wire 20. By making the diameter of the sheath heater 130 smaller, the sheath heater 130 can be laid out in a fine pattern shape.

The heater 20 includes a connection terminal 50a and a connection terminal 50b at both ends thereof, and the heater 20 is electrically connected to the connection terminal 50a and the connection terminal 50b at both ends thereof, respectively. Here, when the connection terminal 50a and the connection terminal 50b are not particularly distinguished, they are collectively referred to as the connection terminal 50. The sheath heater 130 of the present embodiment has a biaxial single-terminal structure in which two connection terminals 50 are disposed at one end of the sheath heater 130. One end of the sheath heater 130 having the connection terminal 50 is connected to an external device (heater controller, power supply, etc.). The sheath heater 130 is heated by power supplied from an external device, thereby controlling the temperature of the sheath heater 130.

In the region where the heating wires 20 are arranged in two rows (two axes) in the metal sheath 40, the band-shaped heating wires 20 are arranged to rotate in the cylindrical axis direction of the metal sheath 40. The band-shaped heater 20 extends in the cylindrical axis direction in a state where the major axis of the heater 20 rotates in the direction perpendicular to the cylindrical axis of the metal sheath 40. Further, the rotation axes of the respective heating wires 20 are arranged in a substantially uniform state. That is, the two rows (two shafts) of the heating wires 20 are wound in a double spiral shape. The rotation axes of the two rows (two axes) of the heating wires 20 are arranged substantially parallel to the cylindrical axis direction of the metal sheath 40. By disposing the heating wire 20 in a wound state, the length of the heating wire 20 disposed in the metal sheath 40 can be increased, and the resistance value of the sheath heater 130 can be increased. Further, the heater 20 is disposed in a wound state, and thus has elasticity, and is prevented from being broken during thermal expansion. Therefore, for example, even if the difference in the thermal expansion coefficients of the metal sheath 40 and the heat generating wire 20 is large, the sheath heater 130 having improved reliability can be provided.

The length of the heating wire 20 disposed in the metal sheath 40 in the cylindrical longitudinal direction, i.e., the rotational pitch L2, when the heating wire is rotated once in a spiral shape is preferably 6.0mm or less. The rotational pitch L2 of the heating wire 20 disposed in the metal sheath 40 is more preferably 2.5mm or less, and further preferably 2.0mm or less. By setting the rotational pitch L2 of the heating wire 20 disposed in the metal sheath 40 to 6.0mm or less, disconnection during thermal expansion can be suppressed, and the sheath heater 130 with improved reliability can be provided. Further, in the region of two rows (two axes) of the heating wires 20 in the metal sheath 40, the shortest distance L3 in the rotation axis direction of each heating wire 20 is preferably 2.3mm or more. The insulation of the heating wire 20 can be ensured by setting the distance L3 between the two rows (two axes) of heating wires 20 to 2.3mm or more.

Fig. 4A to 4D are sectional structural views showing a sheath heater according to an embodiment of the present invention. Fig. 4A to 4D are sectional views of the sheath heater 130 shifted by one quarter pitch (L2/4) at a time in the cylindrical axial direction of the metal sheath 40. The arrangement of the heater 20 in the present embodiment will be described in detail with reference to fig. 4A to 4D. The broken line of fig. 4A indicates the trajectory of the heating wire 20 when the heating wire 20 is rotated once in a spiral shape. Referring to fig. 4 to 4D, when the quarter pitch (L2/4) is moved in the cylinder axis direction, the heaters 20 are rotated by 90 degrees about the same rotation axis. The rotation axis of the heater 20 is parallel to the cylinder axis direction.

the width d1 of the heater 20 forms a plane direction substantially perpendicular to the normal line of the rotation plane. That is, the surface of the band-shaped heating wire 20 is a tangent plane of the rotation surface. Further, the planar directions of the two rows (two axes) of the heating wires 20 are substantially parallel. The central axes of the respective heating wires 20 are shifted by 180 ° in the direction of the double helix in the cylindrical axis direction of the metal sheath 40, and the rotational pitch L2 is substantially the same. That is, the rotation of each heater 20 is staggered by 1/2 pitches. By making the rotational pitch L2 of the respective heating wires 20 uniform, the distance g2 between the two rows (two axes) of heating wires 20 can be kept constant, and the reliability of the sheath heater 130 can be maintained. However, the rotation direction of the heating wires 20 may be shifted from 180 °. The sheath heater 130 of the present embodiment can be designed to maintain reliability even in consideration of the rotation of the heating wire 20 as long as L3 is g2 or more, L3 being the shortest distance in the cylindrical axis direction of the metal sheath 40 of the two rows of heating wires 20.

The sectional shape of jacket heater 130 of the present embodiment is circular. By making the sectional shape of sheath heater 130 circular, sheath heater 130 can be easily bent into a desired shape. However, the sectional shape of the sheath heater 130 is not limited thereto, and may have any shape as long as the above conditions are satisfied, and may be deformed into any shape.

As described above, the sheath heater 130 of the present embodiment can be reduced in diameter by having the band-shaped heating wire 20. By making the diameter of the sheath heater 130 smaller, the sheath heater 130 can be laid out in a fine pattern shape. By arranging the band-shaped heating wire 20 in the sheath heater 130 in a state of rotating in a double spiral, disconnection of the heating wire 20 at the time of thermal expansion can be suppressed, and for example, even if the difference in thermal expansion coefficient between the metal sheath 40 and the heating wire 20 is large, the sheath heater 130 having improved reliability can be provided.

As embodiments of the present invention, the above embodiments can be combined and implemented as appropriate as long as they do not contradict each other. In addition, in the embodiments, if the gist of the present invention is achieved, a method in which a person skilled in the art performs addition, deletion, or design change of an appropriate member similarly falls within the scope of the present invention.

It is to be understood that the effects obtained by the present invention, which are obvious from the description of the present specification or can be easily predicted by those skilled in the art, are the effects of the present invention even if the effects are different from the effects of the above-described embodiments.