JP2000306658A - Immersion heater and heater unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency of heat transfer from a heater to an outer cylinder, by tightly adhering the heater to the inner surface of the outer tube in a further wide range. SOLUTION: An electric resistance heater 10 is mounted to a support body 5, inserted into an outer tube 2, and a thin plate is bent along the curved surface of the inner surface of the outer tube 2 to form the heater 10. The support body 5 includes a tubular body 5a made of ceramic paper or the like and a filler 5b that is filled into this tubular body 5a and has coefficient of thermal expansion larger than that of the outer tube 2. Current passage of the heater 10 has a meandering shape by forming a slit 11 zigzag in the thin plate. Heat generation of the heater 10 causes the filler 5b to thermally expand, the heater 10 is pressurized and adhered to substantially whole surface of the inner surface of the outer tube 2, and efficiency of contact heat transfer from the heater 10 to the outer tube 2 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion heater for use in, for example, a melting and heating furnace for aluminum or zinc, and more particularly, to an immersion heater in which an electric resistance heating element is attached to a support and inserted into an outer cylinder. It relates to a type heater.

[0002]

2. Description of the Related Art Conventionally, as an example of the above-mentioned immersion type heater, there is known an immersion type heater which is provided in an outer cylinder so as to be bent along a plate-like heating element as described in JP-A-8-293380. Have been. In the prior art, the heating element is brought into contact with the inner surface of the outer cylinder by thermal expansion of the heating element due to energization.

However, in the prior art, the heat generating element is brought into contact with the inner surface of the outer cylinder by causing the heat generating element to thermally expand by bringing both ends of the heat generating element into contact with insulators arranged between the heat generating elements. However, there is a possibility that the heating element may be partially inadequately adhered to the inner surface of the outer cylinder at the portion in contact with the insulator.

[0004]

SUMMARY OF THE INVENTION In view of the above prior art, the present invention relates to an immersion heater capable of improving the heat transfer efficiency from the heating element to the outer cylinder by bringing the heating element into close contact with the inner surface of the outer cylinder in a wider range. And a heater unit.

[0005]

In order to achieve the above object, a first characteristic configuration of the immersion heater according to the present invention is as follows. An electric resistance heating element is attached to a support, inserted into an outer cylinder, and a thin plate is formed. The heat generating element is formed by bending the heat generating element along the curved surface of the inner surface of the outer cylinder, and a member made of a material having a higher coefficient of thermal expansion than the outer cylinder is provided on the support.

According to this feature, by forming the heating element by bending the thin plate along the curved surface of the inner surface of the outer cylinder, the heating element can be completely adhered to the inner surface of the outer cylinder. Then, by providing a member of a material having a larger coefficient of thermal expansion than the outer cylinder on the support, the support is thermally expanded more than the outer cylinder by heating at the time of energizing the heating element. To the outer cylinder. In particular, by using a thin, easily deformable heating element, the heating element adapts to the inner surface of the outer cylinder and easily adheres to it, and in combination with the thermal expansion of the support, almost the entire surface of the heating element with the pressing force applied. Can be brought into close contact with the inner surface of the outer cylinder.

When the support is formed, it is preferable that the support is formed of a cylindrical body and a filler filled in the cylindrical body and having a larger coefficient of thermal expansion than the outer cylinder. This is because it is possible to prevent the filler from wrapping around between the heating element and the outer cylinder to reduce the heat transfer efficiency. Further, by forming the cylindrical body from a material capable of plastic deformation or elastic deformation, for example, ceramic paper or ceramic cloth, it is possible to provide a function as an interference material for holding the heating element and preventing excessive expansion of the filler. it can. Also, by providing the inclusions in the support, the amount of the filler can be reduced to prevent the filler from being excessively expanded.

The heating element is preferably formed with slits in a thin plate by press molding or the like. By forming the slits in the thin plate in a staggered manner, the current path of the heating element is formed in a meandering manner.
It is possible to adjust the resistance value within a fixed area of the outer cylinder.

By projecting a projection on one side of the heating element and orienting the projection toward the support, the heating element can be locked to the support to hold the heating element.

A feature of the heater unit used in the immersion type heater as described above is that a heating element is attached to the outer surface of a cylindrical body constituting a support, and the outer diameter is reduced before insertion into the outer cylinder. By making the inner diameter slightly smaller than the inner diameter, insertion into the outer cylinder becomes easy.

[0011]

As described above, according to the characteristic structure of the immersion heater and the heater unit according to the present invention, since the thin plate-shaped heating element is pressed from the entire inner surface toward the outer cylinder by heating at the time of energization. In addition, the heating element can be brought into close contact with the inner surface of the outer cylinder in a wider range than before. As a result, the efficiency of contact heat conduction from the heating element to the outer cylinder can be improved, and both effective use of electric energy and long-term use of the immersion heater can be achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The immersion heater 1 according to the present embodiment is used by inserting its longitudinal direction into the aluminum melting and keeping furnace in a horizontal or vertical direction. An input terminal for a heating element (not shown) is arranged above or outside the melting and heating furnace. The outer cylinder 2 is a ceramic cylindrical body mainly composed of silicon nitride, and has a front end sealed inside the furnace, and has a mounting flange and an input terminal on the other end side.

A heater unit 3 having a heating element 10 attached to the outer surface of a support 5 is inserted into the outer cylinder 2. The heater unit 3 is disposed mainly on the tip side of the outer cylinder 2 for disposing the heating element 10 in a part to be immersed in aluminum hot water in a melting and heat retaining furnace, from the input terminal outside the furnace to the heater unit 3. Are connected by an extension terminal. 1 and 2 are cross-sectional views and the like of the tip side portion.

The heating element 10 is formed by punching a slit 11 in a thin plate of, for example, Fe-Al-Cr by press molding or the like. The slits 11 are alternately formed in a zigzag manner so as to be opened on one of the left and right sides of a long thin plate, and form a meandering current path. Of course, the slit 11 may be formed in a pattern other than the staggered shape, or the heating element 10 without the slit 11 may be used. The heating element 10 is desirably formed thin so as to bend in accordance with the inner curved surface of the outer cylinder 2, and the width of the slit 11 is desirably narrow enough to have no problem in insulation. In addition, since each heating element 10 has its longitudinal direction oriented in the longitudinal direction of the outer cylinder 2,
Even if the heating element 10 itself expands due to thermal expansion, the heating element 1
There is no restriction on the both ends in the longitudinal direction of 0, and no undesired deformation due to thermal expansion of the heating element itself basically occurs.

The support 5 is formed by filling a cylindrical body 5a with powder 5b as a thermal expansion material. The powder 5b expands more thermally than the outer cylinder 2 by heating when the power is supplied to the heating element 10, so that the outer surface of the heating element 10 is pressed against the inner surface of the outer cylinder 2 and the heating element 1
The heat transfer efficiency from 0 to the outside of the outer cylinder 2 is improved. Cylindrical body 5
It is desirable that the thermal expansion material into a is granular or powder 5b in order to obtain a uniform pressing force on the heating element 10. The powder 5b as the thermal expansion material has insulation, fire resistance and a certain degree of heat insulation, and a material having a larger thermal expansion coefficient than the material of the outer cylinder 2 is suitable. For example, MgO (magnesium oxide), Al ₂ O ₃ (alumina), mica, zirconia and the like can be used. This powder 5b is a cylindrical body 5a
It may be one that solidifies after filling into the container. On the other hand, as a material of the outer cylinder 2, silicon nitride, sialon, aluminum nitride, or the like can be used.

The cylindrical body 5a is formed by rolling ceramic paper 6 in which ceramic fibers are thinly formed into a paper shape, and a joint 6 is formed to prevent the powder 5b from flowing out of the cylindrical body 5a.
b, a part of the ceramic paper 6 is overlapped. In the present embodiment, four heating elements 10 are used, and a protruding portion 6a formed by deforming the ceramic paper 6 due to thermal expansion of the powder 5b is located between the adjacent heating elements 10, 10. Further, the adjacent heating elements 10 are insulated from each other, thereby contributing to the prevention of the short circuit. The cylindrical body 5a can be appropriately elastically or plastically deformed in order to uniformly press the heating element 10 against the inner surface of the outer cylinder 2 and prevent the outer cylinder 2 from being damaged due to excessive thermal expansion of the powder 5b. The material is desirably used, and a ceramic fiber, such as a ceramic cloth, a silica cloth, or a ceramic wool cylindrical molded body, other than the ceramic paper 6, can be used.

It is necessary to prevent the pressing force accompanying the thermal expansion of the powder 5b from being released in the longitudinal direction of the outer cylinder 2 to reduce the pressing force on the inner surface of the outer cylinder 2. Therefore, although illustration is omitted,
One end of the support 5 is filled up to the distal end of the outer cylinder 2, and the other end of the support 5 is extended to the other end of the outer cylinder 2 than the heating element 10. In order to prevent the powder 5b from flowing out, it is desirable to close the end of the cylindrical body 5a or close the end of the cylindrical body 5a with a lid of a ceramic molded body or ceramic wool.

The heating element 10 may be fixed to the outer surface of the cylindrical body 5a with a joint 6b or an adhesive. FIG. 3 shows a structure for fixing the heating element 10 more firmly. When the slit 11 is punched and formed in the heating element 10, a small burr 1 is used.
Oa may occur as a projection. In the present embodiment, the burr 10a is intentionally oriented toward the cylindrical body 5a, and the burr 10a is cut into the cylindrical body 5a, so that the heating element 10 is combined with the inner surface of the outer cylinder 2 so that the heating element 10 is connected to the cylindrical body 5a. Fixed to
Moreover, the heating element 10 is brought into close contact with the inner surface of the outer cylinder 2. Although burrs 10a are continuously generated in the drawing,
The burr 10a may be generated intermittently in a saw shape or the like, or may be formed as a larger projection and cut into the cylindrical body 5a.

As shown in FIG. 2B, when the slit 11 is punched, a part of the thin plate is left and bent to form a locking piece 10b as a projection, which is cut into the cylindrical body 5a. You may let it. The locking piece 10b can be formed on the side edge of the thin plate forming the heating element 10, but from the viewpoint of material efficiency, the locking piece 10b is
It is more desirable to form it within 1. These projections 10a, 10
By providing b, it is possible to sufficiently hold the heating element 10 on the support 5 even if the support 5 undergoes thermal contraction during cooling after the immersion heater 1 is de-energized.

When manufacturing the immersion heater 1 or replacing the heater unit 3 at the time of disconnection, the heater unit 3 before filling the powder 5b into the outer cylinder 2 is inserted. The heater unit 3 includes a ceramic paper 6
The heating unit 10 is attached to the outer surface of a cylindrical body 5a formed by rolling the heater unit. The heater unit 3 can be easily attached to the outer cylinder 2 by forming the entire outer diameter slightly smaller than the inner diameter of the outer cylinder 2. So that it can be inserted into Although not shown, the distal end of the cylindrical body 5a is long enough to reach the distal end of the outer cylinder 2 and is closed, and the other end of the cylindrical body 5a is
It protrudes even longer than it does.

When the powder 5b is filled while being vibrated or pressurized into the cylindrical body 5a after the heater unit 3 is inserted into the outer cylinder 2, the heating element 10 and the protruding portion 6a come into contact with the inner surface of the outer cylinder 2. The cylindrical body 5a expands. If at least the joint 6b is impregnated with a binder or the like, it is possible to prevent the powder 5b from leaking from the joint 6b during filling. Needless to say, the entire cylindrical body 5a may be impregnated with a binder or the like at the time of production.

The powder 5b thermally expands more than the outer cylinder 2 due to the heating accompanying the energization of the heating element 10, and presses the heating element 10 against the inner surface of the outer cylinder 2 via the cylindrical body 5a. The cylindrical body 5a is held on the inner surface side of the outer cylinder 2 so as to be further expanded between the protruding portions 6a between the heating elements 10 and the slits 11 and to prevent the heating element 10 from being displaced.

Next, another embodiment of the present invention will be described below. It is to be noted that the same members as those in the first embodiment are denoted by the same reference numerals, and configurations that are not particularly mentioned are the same as those in the first embodiment.

In the second embodiment shown in FIG. 4, a cylindrical body 5a is formed by joining small pieces of four ceramic papers 6 together. In each joint 6b, a folded back 6c is provided at an end of one of the ceramic papers 6, and this folded back 6c is used as a protruding portion 6a by filling with powder 5b. The outer diameter of the heater unit 3 before filling the powder 5b shown in FIG. 4A is smaller than the inner diameter of the outer cylinder 2 as in the first embodiment. Then, after filling the powder 5b shown in FIG. 4B, the outer diameter of the heater unit 3 is expanded so that the heating element 10 is brought into close contact with the outer cylinder 2.

The third embodiment shown in FIG. 5 has basically the same configuration as the first embodiment, except that an inner cylinder 7 as an inclusion is provided in the powder 5b to reduce the filling amount of the powder 5b. Thus, excessive thermal expansion due to the powder 5b is adjusted. Further, by forming the inclusion with a member having an appropriate coefficient of thermal expansion, it is possible to adjust the pressure of pressing the heating element against the outer cylinder. Like the outer cylinder 2, the inner cylinder 7 is formed of ceramics, which is an example of a rigid body, and has both ends closed so that the powder 5b does not enter the inside. As inclusions, not only the inner cylinder 7 but also a large number of small lumps may be dispersed in the powder 5b. Further, the cylindrical body 5a is made of ceramics by interposing a plastic or elastically deformable material such as ceramic wool around the inner cylinder 7 or by forming the inclusion itself from a plastic or elastically deformable material. Excessive thermal expansion due to the powder 5b can be absorbed as in the case of the paper 6.

A material having a negative coefficient of thermal expansion can be used for the inclusions such as the inner cylinder 7 described above. Also, as the powder 5b, a mixed material having a positive coefficient of thermal expansion as a whole obtained by mixing a material having a large coefficient of thermal expansion and a material having a small or negative coefficient of thermal expansion may be used. Materials having a negative coefficient of thermal expansion include eucryptite, spodumene,
It is possible to use petalite, aluminum titanate, or the like, or a combination thereof.

In each of the above embodiments, the powder 5b is used as a filler for filling the cylindrical body 5a. However, a slurry or a gel filler may be used as the filler.
The filler may be a powder after filling, or may be solidified after filling or after heating.

In each of the above embodiments, four elongated thin plate-shaped heating elements 10 are arranged in the circumferential direction with the longitudinal direction thereof facing the longitudinal direction of the outer cylinder 2. The number can be appropriately changed according to the inner diameter of the outer cylinder 2. In addition, for example, one heating element may be rolled up and this one heating element may be arranged almost all around the support 5. That is, as long as the heating element has at least one divided portion within one circumference in the circumferential direction, unnecessary deformation due to thermal expansion of the heating element can be prevented.

The present invention can be embodied in various other forms without departing from the technical concept and main features. The embodiments described above are merely examples in all respects, and the present invention should not be interpreted in a limited manner.

It should be noted that the reference numerals written in the claims are merely for convenience of comparison with the drawings, and the present invention is not limited to the configuration of the attached drawings. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an immersion heater according to the present invention, wherein (a) shows a state when a heater unit is inserted, and (b) shows a state after the heater unit is inserted.

FIG. 2 is a side view of an immersion heater in which an outer cylinder is crushed.

3A is a sectional view taken along line AA in FIG. 2, and FIG.
FIG. 3 is a sectional view taken along line BB in FIG. 2.

FIGS. 4A and 4B are cross-sectional views of an immersion heater according to a second embodiment of the present invention, wherein FIG. 4A shows a state when a heater unit is inserted, and FIG. 4B shows a state after the heater unit is inserted.

FIG. 5 is a cross-sectional view of an immersion heater according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Immersion type heater 2 Outer cylinder 3 Heater unit 5 Support body 5a Cylindrical body 5b Powder (filler) 6 Ceramic paper 6a Projection 6b Seam 6c Folding 7 Inner cylinder (inclusion) 10 Heating element 10a Burr (protrusion) 10b Locking piece (projection) 11 Slit.

Claims (7)

[Claims] An electric resistance heating element (10) is supported on a support (5).
, And inserted into the outer cylinder (2), the thin plate is bent along the curved surface of the inner surface of the outer cylinder (2) to form the heating element (10), and the thin plate is attached to the support (5). Tube (2)
An immersion heater provided with a member made of a material having a larger coefficient of thermal expansion than that of the heater. 2. The support (5) includes a cylindrical body (5a) and a filler (5b) having a larger coefficient of thermal expansion than the outer cylinder (2) filled in the cylindrical body (5a). Claim 1 which has
2. The immersion heater according to 1. 3. The immersion heater according to claim 2, wherein the tubular body (5a) is made of ceramic paper (6) or ceramic cloth. 4. The immersion type according to claim 1, wherein the slits (11) are formed in a zigzag pattern in the thin plate so that the current path of the heating element (10) is formed in a meandering shape. heater. 5. The immersion heater according to claim 2, wherein an inclusion (7) is provided in the support (5). 6. A projection (10) on one side of the heating element (10).
a, 10b), and project the protrusions (10a, 10b).
The immersion heater according to any one of claims 1 to 5, wherein is oriented toward the support (5). 7. A heater unit for use in an immersion heater according to claim 1, wherein the heating element (10) is provided on an outer surface of a cylindrical body (5a) constituting the support (5). ) Is attached on the heater unit.