JPH0696845A - Sheathed heater and heating device provided with sheathed heater - Google Patents

Abstract

PURPOSE:To prevent multiplicative heating of a power insulating material, and to prevent fusion of a sheath, since electricity flows in a conductor when a heating wire is disconnected by local excess heating by having the conductor in the sheath opposed to the heating wire at a small interval in the vicinity of the heating wire. CONSTITUTION:Extended parts b1, b2 of terminal pins 16, 17 are formed in an integrated manner with inner end parts 16b, 17b, and are protruded in the diameter of a heating wire 13. An conductor is thus provided, which is opposed to the heating wire 13 at a small interval in closer proximity to the heating wire 13 than a sheath 12. When the heating wire 13 is disconnected due to local excess heat, electricity flows in the extended parts b1, b2. Even when the electric resistance of a power insulating material 11 is degraded due to the local excess heat, an electric leak to the side of the sheath 12 is prevented. Since the route electricity flowing in the material 11 is shorter than that to the sheath 12, heat generation due to the electric resistance can be reduced. Multiplicative heating of the power insulting material is thus prevented, and fusion of the sheath is also prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheathed heater, and more particularly to a sheathed heater used for home electric appliances and industrial products.

[0002]

2. Description of the Related Art Generally, a sheathed heater of this type includes a metallic sheath having a powder insulating material filled therein, and a heating wire disposed in the sheath and extending in a substantially coil shape along the center line direction of the sheath. And electrically connected to the winding end of the heating wire,
Further, it is provided with a pair of terminal pins held by an insulator that seals both ends of the sheath.

According to the above construction, electricity can be applied to the heating wire by the terminal pin to cause the heating wire to generate heat. Here, the electricity flowing through the heating wire does not flow into the sheath because it is insulated by the powder insulating material.

[0004]

However, when the sheathed heater is continuously used for a long time, the heating wire is gradually thinned to cause local overheating and disconnection. At the same time, the heating wire causes leakage of electricity to the sheath. It has been known so far that the phenomenon of fusion of the sheath occurs. When the sheath is melted, there are problems such that the powder insulating material is scattered to the outside and a spark is generated on the surface of the sheath.

In the past, however, the reason why the sheath melts at the time of wire breakage, in particular, the relationship between the meltdown of the sheath and the electric leakage from the heating wire to the sheath, has not been sufficiently clarified, and therefore sufficient measures for sheath meltdown can be taken. There wasn't. The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheathed heater that can reliably prevent fusion of the sheath.

Another object of the present invention is to provide a heating device having the sheathed heater.

[0007]

As a result of earnest research, the inventor of the present application has found that when local overheating occurs in a heating wire, the insulation of the powder insulating material deteriorates, and after the heating wire is broken, electricity is generated from the sheath. It was discovered that it tried to flow to the side with great resistance. Then, the heat generated by the electric resistance of the powder insulating material whose insulating property is deteriorated synergistically causes the portion where the local overheating is generated to become overheated and elucidates the mechanism that the sheath is fused. The first aspect has been completed.

That is, the sheathed heater according to the first aspect of the present invention is provided with a metal sheath having a powder insulating material filled therein, and a sheath disposed inside the sheath. The sheathed heater has a substantially coil shape along the center line direction of the sheath. A sheathed heater including an extending heating wire and a pair of terminal pins electrically connected to a winding end of the heating wire and held by an insulator that seals both ends of the sheath. It is characterized in that a conductor is provided at a position closer to the heat generating line than the sheath and opposed to the heat generating line at a slight interval.

The conductor may be an extension portion having one end electrically extended integrally with one of the terminal pins. Further, the conductor may be arranged within the diameter of the heating wire. Further, the present inventor found that the above problem can be solved by regarding the coil itself as one heating element and setting the wattage per unit area to a predetermined value, and completed the second aspect of the present invention. Came to let.

That is, the sheathed heater according to the second aspect of the present invention is composed of a metallic sheath having a powder insulating material filled therein and a heating wire, and the sheath in a state of extending along the center line direction of the sheath. In a sheathed heater including a heating wire coil disposed inside, the heating wire coil is
It is characterized in that the coil surface watt density KWD represented by the following general formula (F1) is set within the range of the following inequality formula (F2).

KWD = W / {π (D + 2d) L} (F1) In the formula, W is electric power, π is circular constant, D is the coil center diameter of the heating wire coil, d is the heating wire diameter, and L is It is the heat generation length of the heating wire coil housed in the sheath. KWD ≦ 5.1 × DT (F2) In the formula, DT is the sheath (1) from the outer diameter surface of the heating wire coil (CL).
It is the insulation distance to the inner diameter surface of 2).

In the sheathed heater according to the third aspect of the present invention, a spiral heating wire is inserted inside the inner layer sheath along the longitudinal direction thereof, and a heater portion filled with a powder insulating material and an inner layer sheath are provided. The heater part was inserted into the outer layer sheath having a diameter larger than that of the sheath, and the outer layer part was filled with the powder insulating material and both ends of the outer layer sheath were incompletely sealed with a heat resistant resin. It is characterized by that.

The heating device of the present invention further comprises a metallic sheath having a powder insulating material filled therein, a heating wire disposed in the sheath and extending in a substantially coil shape along the center line direction of the sheath, and heat generation. Electrically connected to the winding end of the wire, and
It includes a pair of terminal pins held by an insulator that seals both ends of the sheath, and opposes the position inside the sheath closer to the heat generating line than the sheath at a slight distance from the heat generating line. It has a sheathed heater provided with a conductor, a circuit for supplying a heating current from a power source to the sheathed heater, and a current fuse for blocking power supply when the current flowing through the circuit reaches a threshold value. I am trying.

[0014]

According to the sheathed heater of the first aspect of the present invention, the conductor is provided in the sheath at a position closer to the heat generating line than the sheath and facing the heat generating line with a slight gap therebetween. Therefore, when the heating wire is locally overheated and the heating wire is broken, the electricity that should flow through the broken portion flows to the conductor. As a result, even if the electric resistance of the powder insulating material in the portion where the local overheating occurs is deteriorated, it is possible to prevent the electric leakage to the sheath side. Moreover, because of this, the path of electricity flowing through the powder insulating material is shorter than the path of electricity flowing toward the sheath side, so that heat generation due to electric resistance can be reduced as much as possible.

In particular, when the conductor is arranged within the diameter of the heating wire, electricity can be collected in the center of the sheath and leakage to the sheath can be prevented more reliably. . According to the sheathed heater of the second aspect of the present invention, since the heating wire coil is set to the predetermined coil surface watt density KWD, even if the sheath is locally overheated and the heating wire is melted, Will never blow out.

Further, according to the sheathed heater in the third aspect of the present invention, a heater portion in which a heating wire is inserted,
The heater section is divided into the outer layer section that is inserted, and both ends of the outer layer sheath are incompletely sealed with a heat-resistant resin, and air is supplied to the powder insulating material inside the outer layer section. Since there is no heating wire in the part, deterioration of the powder insulation material in the outer layer part can be suppressed compared to deterioration of the powder insulation material in the inner layer part, and further, the fusing of the sheath due to the disconnection of the heating wire, etc. You can stop with.

On the other hand, according to the heating device having the above structure, when the current flowing through the circuit reaches the threshold value, the current fuse blocks the power supply, and the leakage current can be prevented from flowing from the sheathed heater.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a partially cutaway schematic sectional view showing a first embodiment of the present invention. Referring to the figure,
The sheathed heater 10 in the embodiment of FIG.
Powder insulation material 1
1 is a metal sheath 12 filled inside, and a sheath 1
2, a heating wire 13 extending in a substantially coil shape along the center line direction of the sheath 12, and a winding end of the heating wire 13 are electrically connected, and both ends of the sheath 12 are sealed. It is provided with a pair of terminal pins 16 and 17 held by insulators 14 and 15.

The powder insulating material 11 is magnesia or magnesia to which nickel oxide or iron oxide is added. The sheath 12 is made of a stainless steel pipe or more preferably a corrosion and heat resistant superalloy (for example, NCF8).
00: Commodity name Incoloy 800), and is set to various sizes and shapes (for example, U-shape and W-shape) according to the application.

As the heating wire 13, an alloy heating element containing chromium or the like formed in a substantially coil shape is preferably used. The insulators 14 and 15 are annular seal portions 14a and 15a which are press-fitted and fixed to the inner diameter of the end portion of the sheath 12,
Together with the seal portions 14a and 15a, insulator covers 14b and 15b that close the end surface of the sheath 12 are formed. A heat resistant resin such as a silicone resin or a fluororesin can be used for the seal portions 14a and 15a. When heat-resistant resin is used for the seal portions 14a and 15a, a so-called incomplete sealing type sheathed heater in which the inside of the sheath 12 is not completely sealed is configured.
On the other hand, it is also possible to adopt low melting point glass as the seal portions 14a and 15a. In this case, a so-called full-sealing type sheath heater in which the inside of the sheath 12 is completely sealed is configured.

Each of the terminal pins 16 and 17 is a rod made of stainless steel and formed in a cylindrical shape. Each terminal pin 16, 17 has a corresponding insulator 1
Outer end 16 protruding from the sheath 4 and 15 to the outside of the sheath 12
a, 17a and the inner end portion 1 protruding inside the sheath 12
6b, 17b, and each outer end 16a, 17
“A” is configured to be connectable to a power supply circuit (not shown), and the winding ends of the heating wire 13 are fixed to the inner ends 16b and 17b while being electrically connected.

With the above construction, in the embodiment of FIG. 1, the inner end portion 1 of each terminal pin 16, 17 is
Small-diameter extending portions b1 and b2 are integrally extended to 6b and 17b. Each of the extended portions b1 and b2 is formed by cutting or rolling the inner end portions 16b and 17 respectively.
b is formed concentrically and integrally with b, and by projecting into the diameter of the heating wire 13, the sheath 1 in the sheath 12
The conductor is arranged closer to the heat generating line 13 than 2 and faces the heat generating line 13 with a slight gap therebetween.

When manufacturing the substantially rod-shaped sheathed heater 10 as in the first embodiment, the outer dimensions of the sheathed heater 10 are predetermined by assembling the respective parts into a unit and rolling them by rolling. Set to the dimension.
In this process, a tensile force acts on the heating wire 13, so that the heating wire 13 is stretched between the terminal pins 16 and 17.

According to the sheathed heater 10 in the configuration of the first embodiment, the sheath heater 10 extends in the sheath 12 at a position closer to the heat generating wire 13 than the sheath 12 with the heat generating wire 13 being slightly spaced apart therefrom. Since the installation parts b1 and b2 are provided, when the heating wire 13 is locally overheated and the heating wire 13 is disconnected, the electricity that should flow through the disconnected part flows to the extension parts b1 and b2. As a result, even if the electric resistance of the powder insulating material 11 in the portion where the local overheating has occurred is deteriorated, it is possible to prevent the electric leakage to the sheath 12 side, and furthermore, the path of the electricity flowing to the powder insulating material 11 is thereby prevented Since it is shorter than the path when flowing to the sheath 12 side,
Generation of heat due to electric resistance can be reduced as much as possible.

Therefore, according to the first embodiment, it is possible to prevent the powder insulating material 11 from being synergistically heated, so that there is a remarkable effect that the fusing of the sheath 12 can be prevented. Further, as described above, since the heating wire 13 is stretched between the terminal pins 16 and 17 by performing the rolling process at the time of manufacturing the sheathed heater 10, the number of windings of the winding end portion of the heating wire 13 is kept constant. However, local overheating tends to occur, but in the first embodiment, the extended portions b1 and b2 are formed on both terminal pins 16 and 17.
Since the extended portions b1 and b2 face the heating wire 13 in the vicinity of the corresponding winding ends, the extended portions b1 and b2 are located in the vicinity of the winding end of the heating wire 13 where local overheating is likely to occur. There is also an advantage that the electric leakage can be effectively prevented.

The sheathed heater 20 of FIG. 2 showing the second embodiment.
In, in the pair of terminal pins 16 and 17,
The extended portion b1 is integrally extended only on one of the terminal pins 16 and is projected over substantially the entire length of the heating wire 13,
The tip portion is opposed to the end surface of the inner end portion 17b of the other terminal pin 17 with a slight gap. As a result, the base end portion of the extended portion b1 is connected to one terminal pin 1
The heating wire 13 is made to face in the vicinity of the winding end on the 6 side, and the tip of the extended portion b1 is made to face the heating wire 13 in the vicinity of the winding end on the other terminal pin 17 side.

Also in the above-mentioned structure, electricity which is about to leak due to local overheating can be made to flow to the extended portion b1, so that the same effect as the first embodiment can be obtained.
In the sheathed heater 30 of FIG. 3 showing the third embodiment,
A conductive rod 18 as a conductive body, which is a member separate from the terminal pins 16 and 17, is arranged in the sheath 12. The conductive rod 18 is made of, for example, a stainless steel rod, and is inserted into the diameter of the heating wire 13 (that is, a position closer to the heating wire 13 than the sheath 12) to generate the heating wire 1.
3 and each of the terminal pins 16 and 17 are opposed to each other with a slight interval. As a result, also in the third embodiment, both ends of the conductive rod 18 are connected to the heating wire 13 near the corresponding winding ends of the terminal pins 16 and 17, respectively.
Is facing.

The sheathed heater 3 in the configuration of the third embodiment.
Even at 0, electricity that is about to leak due to local overheating can be made to flow to the conductive rod 18, so that the same effect as that of the first embodiment can be obtained. Next, the above-mentioned first
The coil surface watt density KWD in the third embodiment will be described in detail.

Referring to FIGS. 1 and 4, this coil surface watt density KWD is defined by the following general formula (F1). KWD = W / {π (D + 2d) L} (F1) In the formula, W is electric power, π is the circular constant, D is the coil center diameter of the heating wire coil CL, d is the heating wire 13 diameter, and L is the sheath. 12
It is the heat generation length of the heating wire coil CL housed inside.

The above general formula (F1) is used for the heating wire coil CL.
The present inventor studies the relationship between the insulation distance DT between the inner surface of the sheath 12 and the surface of the heating wire coil CL and the fusing of the sheath 12 by expressing itself as a substantially cylindrical heating element. It was used in the process. The coil surface watt density KWD is determined by the following procedure. That is, the rating and the wattage are determined according to the application of the sheathed heater 10 (20, 30). Next, the making resistance and the wire diameter d of the heating wire 13 are determined according to the determined rating and wattage. Further, according to the determined making resistance and the wire diameter d, the making resistance of the heating wire ÷ the resistance per unit of the heating wire = [(voltage) ² ÷ wattage] ÷ the resistance value per unit of the heating wire is calculated. Thus, the total input wire length (the total length of the portion of the heating wire 13 that constitutes the heating wire coil CL) is determined.

If the total input wire length and heat generation length are constant, the coil pitch is determined to be a constant value by determining the coil center diameter. Therefore, by determining either one, the constant coil length is determined. A heating wire coil CL having a surface watt density KWD can be constructed. The inventor of the present application has found that the coil surface watt density KWD has a certain relationship with the insulation distance DT in the fusing phenomenon of the sheath 12, and when the coil surface watt density KWD is set within the range of the following inequality (F2), It was found in detail from the measurement result of FIG. 5 described later that the sheath 12 does not melt even when local overheating occurs.

KWD ≦ 5.1 × DT (F2) In the formula, DT is the sheath 1 from the outer diameter surface of the heating wire coil CL.
2 is the insulation distance to the inner diameter surface of 2 (see FIG. 4). As described above, according to the sheathed heater in the embodiment shown in FIGS. 1 to 3, since the heating wire coil CL is set to the predetermined coil surface watt density KWD, local overheating occurs in the heating wire 13 and the heating wire 13 is generated. Even if 13 melts, the sheath 12 does not melt.

[Specific Example] In order to obtain a sheathed heater having a rating of 200 V and 1 kW, the following powder insulating material 11, sheath 12 and heating wire 13 are adopted, and the insulation distance DT is 1.
Heating wire coil CL1 having various coil surface watt density KWD within a range of 75 mm to 3.60 mm
-CL12 (total input wire length = 565 mm) was manufactured. The heating wire coils CL1 to CL12 are the coil surface watt density K
WD relates to a specific example of the present invention that satisfies the above inequality (F2) (that falls within the region DN1 in the graph of FIG. 5), and the heating wire coils CL13 to CL22 have the coil surface watt density KWD that is equal to the above inequality ( F2) according to a comparative example that does not satisfy F2) (those that fall within the region DN2 in the graph of FIG. 5). In this specific example, in order to clarify the relationship between the coil surface watt density KWD and the insulation distance DT, the extended portions b1 and b2 and the conductive rod 18 are omitted. - powdered insulating material fee magnesium oxide (2.9 g / cm ^3), the sheath corrosion Superalloys (NCF800: diameter = 10 mm, wall thickness = 0.75), heating wire nickel - chrome wire (wire diameter d = 0.4 mm , Total input wire length = 4.657m, resistance per unit = 8.59Ω /
m) First, since the making resistance of the heating wire 13 is [(200) ² ÷ 1000] = 40Ω, the total making wire length of the heating wire 13 is 40Ω ÷ 8.59Ω / m = 4.657m.

From this heating line 13, the heating length L = 5
When obtaining the heating wire coil CL of 65 mm, if the coil center diameter D is set to 3.4 mm, for example, the coil surface watt density KWD is 1000 / [π (0.34 + 0.08) × 56 from the above general formula (F1). .5] = 13.4 W / cm ² , which corresponds to a sheathed heater employing the heating wire coil CL9.

The diameter of the heating wire coil CL9 is the coil center diameter D + 2d = 3.4 + 0.8 = 4.2 mm, and the sheath 12 having an outer diameter of 11.4 mm and a wall thickness of 0.75 mm is adopted. As a result, the insulation distance DT is 2.
It is set to 85 mm. Thus, the coil surface watt density KWD of the heating wire coil CL9 satisfies the above inequality (2) and is set within the region DN1.

On the other hand, the diameter of the heating wire coil CL13 is also 4.
2mm, outer diameter 10.6mm, wall thickness 0.75
The insulation distance DT is set to 2.45 by adopting the mm seeds. Therefore, the heating wire coil CL
The coil surface watt density KWD of 13 is the heating wire coil C
Although it is the same value as L9, it does not satisfy the above inequality (2) and is set in the region DN2.

Next, a voltage of 110% of the rated voltage was applied to the sheathed heater having the heating wire coils CL1 to CL22 to inspect the fusing phenomenon of the sheath, and the sheathed heater (heating wire coils CL1 to CL12) according to a specific example was examined. In any of the sheathed heaters (1), the sheath 12 did not melt even if a voltage was applied after the heating wire 13 melted. On the other hand, the sheathed heater (heating wire coil CL according to the comparative example)
13 to CL22) is a heating wire 13
When a voltage was applied after fusing, the sheath 12 flew.

In particular, the heating wire coils CL13, CL14,
Although the insulation distance DT of CL19 and CL22 is larger than that of the heating wire coils CL2 and CL3, the sheath 12 is melted and cut. From this, the insulation distance DT
It has been clarified that the fusing of the sheath 12 cannot be prevented even if a large value is taken. FIG. 6 showing a fourth embodiment.
In the sheath heater 40, the inner layer sheath 19 that covers the heating wire 13 is provided in the sheath 12, and the inner layer sheath 19
Form a conductor. More specifically, the inner layer sheath 19 is a tubular body made of stainless steel or a corrosion-resistant heat-resistant superalloy, and is filled with the powder insulating material 11 inside, and the low melting point glass 14c fixed at both ends. , 15c for complete sealing. The inner-layer sheath 19 is arranged at a position closer to the heating wire 13 than the sheath 12, and covers the entire heating wire 13 with a slight distance from the heating wire 13.

The sheathed heater 4 in the configuration of the fourth embodiment.
Even at 0, electricity that is about to leak due to local overheating can be passed to the inner layer sheath 19, so that the same effect as that of the first embodiment can be obtained. Further, in the sheathed heater 40 of the embodiment shown in FIG. 6, the inner layer sheath 19, the heating wire coil CL, and the powder insulating material 11 constitute the heater portion 1 having the heating wire 13, and the heat resistant resin 14a.
The sheath 12 that has been incompletely sealed with, the powder insulating material 111 filled in the sheath 12, and the like constitute the outer layer portion 2. Therefore, since the powder insulating material 111 inside the outer layer 2 is supplied with air and there is no heating wire in the outer layer 2, deterioration of the powder insulating material 111 in the outer layer 2 is prevented from occurring in the heater 1. It is possible to suppress the deterioration of the powder insulating material 11 compared to the deterioration of the powder insulating material 11, and further, there is an advantage that the fusion of the sheath due to the disconnection of the heating wire 13 can be stopped only by the inner layer sheath 19.

Since the heater portion 1 has substantially the same structure as the sheathed heater 40 whose both ends are completely sealed with the low melting point glass 4, the heater portion 1 is like an incompletely sealed type sheathed heater 40 immediately after energization. Thus, it is possible to obtain the one whose temperature can be immediately raised without lowering the initial insulation resistance. Next, an example of using the sheathed heaters 10, 20, 30, 40 will be described in detail with reference to FIG. 7.

FIG. 7 is a schematic wiring diagram of an electric stove as a heating device. A power supply circuit 70 including a power supply 72 and a heater side circuit 75 including the sheathed heaters 10 to 40 are electrically connected to the duty ratio controller 71 shown in the figure, and a switch mechanism (not shown) is operated. The energization of the sheath heaters 10 to 40 from the power supply 72 is controlled by controlling the ratio of the energization time to the interval (energization rate) of the energization rate controller 71. 7
3 is a pilot lamp.

Here, if local overheating occurs in the sheathed heaters 10-40 for some reason, magnesia in that portion is deteriorated and a minute current is generated, so that the extended portions b1 and b2 as the above-described conductors (see FIG. 1). , See FIG. 2) and the conductive rod 1
8 (see FIG. 3) or the inner layer sheath 19 (see FIG. 6). If this state continues for a long time and the leakage current becomes large, a leakage current may also occur in the sheath 12, and eventually a large leakage current may flow from the sheath heaters 10 to 40 to the metal member forming the electric stove body or the like.

In order to solve such a problem, in the conventional heating device employing the sheathed heater 74, as shown in FIG. 8, the leakage current detecting means sw for detecting the leakage current of the sheath portion of the sheathed heater 74 is provided. Heater side circuit 7
5, the power supply to the sheathed heater 74 is stopped when the leakage current from the sheathed heater 74 exceeds the threshold value.

However, when this structure is adopted in the sheathed heaters 10 to 40 of this embodiment, the conductors (extended parts b1 and b2, the conductive rods 18, the inner layer sheath 19) are provided while the leakage current to the heater part 1 is very small. As a result of flowing to the side, since electricity does not flow to the sheath 12, there is a problem that the leakage current cannot be detected by the leakage current detection means sw unless the leakage current becomes considerably large. Therefore, the conventional leak current detecting means sw is used as the sheathed heaters 10 to 4 of this embodiment.
Even if it is diverted to 0, while the leakage current is very small, the abnormal state of the sheathed heaters 10 to 40 cannot be detected, and there is a problem that the abnormality cannot be detected until a large leakage current occurs and the safety is poor. It was

Therefore, even if the leakage current of the sheath 12 is small, the currents of the power supply circuit 70 and the heater side circuit 75 increase,
Taking advantage of the occurrence of overcurrent in each of the circuits 70 and 75, in the embodiment shown in FIG. The current fuse H is provided in the power supply circuit 70 to prevent power supply when the voltage reaches 0.5 times.

If the configuration of FIG. 7 is adopted, when the current of the power supply circuit 70 reaches the above threshold value, the current fuse H blocks the power supply, so that a large leakage current is prevented from flowing from the sheathed heaters 10-40. However, the user of the product can be prevented from receiving an electric shock. Further, since the current fuse H is adopted, it is possible to provide the inexpensive power supply circuit 70. Moreover, by disconnecting the current fuse H, it is possible to detect an abnormality in the sheathed heaters 10-40.

Although the current fuse H is provided in the power supply circuit 70 in the embodiment of FIG.
May be provided in the heater side circuit 75. Further, as the heating device, in addition to the electric stove, various electric devices such as electric home appliances such as an oven toaster and industrial products such as an electric furnace may be used, and various other devices within a range not changing the gist of the present invention. It is possible to make design changes.

[0048]

As described above, according to the sheathed heater in the first aspect of the present invention, it is possible to prevent the powder insulating material from being synergistically heated, and as a result, to prevent the fusion of the sheath. You can According to the sheathed heater of the second aspect of the present invention, since the heating wire coil is set to the predetermined coil surface watt density KWD, even if the sheath is locally overheated and the heating wire is melted, Will never blow out.

Further, according to the sheathed heater of the third aspect of the present invention, the fusion of the sheath due to the breakage of the heating wire can be stopped only by the inner layer sheath. Therefore, according to the sheathed heater of the present invention, the powder insulating material is not scattered outside the sheath due to the fusing of the sheath and the spark is not generated on the sheath surface, and it is possible to obtain the one excellent in safety. Produce an effect.

Further, according to the heating device of the present invention, when the current in the circuit reaches the threshold value, the current fuse blocks the power supply, so that a large leakage current is prevented from flowing from the sheathed heater and the product user It is possible to obtain a remarkable effect that it is possible to prevent electric shock from being generated and ensure safety. Further, since the current fuse is used, there is an advantage that it is possible to provide an inexpensive circuit. Moreover, it is possible to detect an abnormality in the sheathed heater by breaking the current fuse.

[Brief description of drawings]

FIG. 1 is a partially cutaway schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a partially cut-away schematic cross-sectional view showing another embodiment of the present invention.

FIG. 3 is a partially omitted schematic sectional view showing still another embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a coil surface watt density in the embodiment of FIGS. 1 to 3.

FIG. 5 is a graph showing the relationship between coil surface watt density and insulation distance.

FIG. 6 is a partially cutaway schematic sectional view showing still another embodiment of the present invention.

FIG. 7 is a schematic wiring diagram of an electric stove as a heating device.

FIG. 8 is a schematic wiring diagram of an electric stove having a conventional sheathed heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 heater part 2 outer layer part 10 sheath heater 20 sheath heater 30 sheath heater 40 sheath heater 11 powder insulating material 12 sheath 13 heating wire 14 insulator 15 insulator 16 terminal pin 17 terminal pin 18 conductive rod (conductor) 19 inner layer sheath ( Conductor) b1 extended portion (conductor) b2 extended portion (conductor)

Front page continuation (72) Yoshiki Hayashi, No. 1 Nishiichitsuya, Settsu, Osaka Prefecture Daikin Industries, Ltd. Yodogawa Manufacturing Co., Ltd. (72) Noriaki Hoshino, No. 1 Nishiichitsuya, Settsu City, Osaka Daikin Industries, Ltd. Yodogawa Factory

Claims (6)

[Claims] 1. A metallic sheath (12) in which a powder insulating material (11) is filled, and a metallic sheath (12) disposed inside the sheath (12) and having a substantially coil shape along the center line direction of the sheath (12). A heating wire (13) extending in the direction of the wire and a pair of insulating members (14, 15) electrically connected to the winding ends of the heating wire (13) and sealing both ends of the sheath (12). In a sheathed heater equipped with terminal pins (16, 17), in the sheath (12), a heating wire (13) is provided rather than the sheath (12).
A sheathed heater characterized in that conductors (18, 19, b1, b2) facing the heating wire (13) at a slight distance are provided at a position close to the. 2. One end of the conductor is the terminal pin.
The sheathed heater according to claim 1, wherein the sheathed heater is an extended portion (b1, b2) electrically extended integrally with any one of (16, 17). 3. The sheathed heater according to claim 1, wherein the conductors (18, b1, b2) are arranged within a diameter of the heating wire (13). 4. A metal sheath (12) having a powder insulating material (11) filled therein, and a heating wire (13). The sheath (12) extends in the direction of the center line of the sheath (12). In a sheathed heater provided with a heating wire coil (CL) arranged in the sheath (12), the heating wire coil (CL) has a coil surface watt density KWD represented by the following general formula (F1). The inequality (F
A sheathed heater which is set within the range of 2). KWD = W / {π (D + 2d) L} (F1) In the formula, W is electric power, π is circular constant, D is the coil center diameter of the heating wire coil (CL), and d is the diameter of the heating wire (13). , L is a sheath (12)
It is the heat generation length of the heating wire coil (CL) housed inside. KWD ≦ 5.1 × DT (F2) In the formula, DT is the sheath (1) from the outer diameter surface of the heating wire coil (CL).
It is the insulation distance to the inner diameter surface of 2). 5. A heater part (1) in which a spiral heating wire (13) is inserted in the inner layer sheath (19) along its longitudinal direction and which is filled with a powder insulating material (11). The heater section (1) is inserted inside the outer sheath (12) having a larger diameter than the inner sheath (19), and the powder insulation material is used.
A sheathed heater characterized in that the outer layer sheath (12) is filled with (111) and both ends of the outer layer sheath (12) are incompletely sealed with a heat resistant resin (14a, 15a). 6. A metal sheath (12) having a powder insulating material (11) filled therein, and a sheath (12) provided inside the sheath (12).
A heating wire (13) extending in a substantially coil shape along the center line direction of
And a pair of terminal pins (16, 17) electrically connected to the winding ends of the heating wire (13) and held by insulators (14, 15) sealing both ends of the sheath (12). Including the above, in the sheath (12), at a position closer to the heating line (13) than the sheath (12), facing the heating line (13) with a slight gap, the conductor (18, 19, b1, b2) sheathed heater
(10,20,30,40) and the circuit (70,75) that supplies the heating current from the power supply (72) to the sheath heater (10,20,30,40) and the circuit (70,75). A heating device comprising: a current fuse (H) that blocks power supply when the current reaches a threshold value.