JP2001185329A - Mounting method of metal-clad sheet heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mounting method in which a sheet heating element with a wide heat transfer area is fixed to a water-flow pipe overhang mounted to elastically and closely contact with the heated object. SOLUTION: A sheet heating element with power-feeding conductor is contained in a metal tubular molding molded in a given shape without any joints or through fusion joint. The metal-clad sheet heating element, both end openings of which are sealed by an insulation material, is mounted on a plane heated part of the heated goods being elastically press fit with a fitting member. The above metal-clad sheet heating element is so molded to have a plane area not less than 25% of total surface area, and also, the above fitting member comprises an insertion part for fitting with a three-dimensional structure situated near the heated place and a metal-clad sheet heating element holding part integrally formed with the above insertion member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat portion to be heated (a copper plate forming an outer wall of a heat exchanger), such as a heat exchanger of a water heater, and to a portion near the heated portion. The present invention relates to a method for mounting a metal-coated planar heating element in close contact with a heated object having a three-dimensional structure (a copper pipe as a water pipe) using an elastic force of a mounting member.

[0002]

2. Description of the Related Art The prior art will be described with reference to an example of a heating element for preventing freezing used in a water heater. Conventionally, various types of heating elements have been proposed as heating elements for heating a heat exchanger of a water heater to prevent freezing of water in a water passage pipe. Examples of commonly used heating elements include, for example, A tubular heating element having a structure in which a winding type heating element is housed in a ceramic tubular molded body, and a void portion thereof is filled with an inorganic insulator,
There is one that is installed along a position in contact with the outer wall of the heat exchanger and the water pipe, and is fixed with a stopper having a substantially U-shaped cross section.
Further, as another example, for example, a tubular heating element (a so-called thin-tube heater) having a structure in which a winding type heating element is accommodated in a thin metal tube made of stainless steel or the like and a gap portion thereof is filled with an inorganic insulating material is used. Some are wrapped around the outer wall of the exchanger.

[0003]

However, according to the above-mentioned conventional configuration, there are the following problems. First, although the former heating element is in contact with both the outer wall of the heat exchanger and the water pipe, there is a problem that the contact area is small and the heating efficiency is poor because of linear contact. Also, the work of attaching the heating element to the heat exchanger is a two-step operation of installing the heating element at a predetermined position and attaching the stopper at a predetermined position. Was. On the other hand, also in the latter heating element, there is a problem that the contact area with the outer wall of the heat exchanger is a line contact, so that the contact area is small and the heating efficiency is poor.

[0004] Regarding the problem of poor heating efficiency, it is only necessary to increase the contact area between the heating element and the object to be heated. For example, instead of a tubular heating element, a planar heating element having a large heat transfer area is used. It is conceivable to use a heating element. As a method of attaching the planar heating element to the heat exchanger, for example, a heating spring is pressed against the outer wall of the heat exchanger by a retaining spring fitted to two water pipes arranged substantially parallel to the outer wall of the heat exchanger. A method of attaching and fixing is conceivable. However, in the case of this method, the installation is difficult depending on the arrangement of the water pipes, and the installation is limited, for example, it is necessary to prepare another mounting member.

[0005] To prevent the mounting of the heating element from being restricted, a method in which the heating element is fixed to one water pipe by a cantilever is considered. No stable surface contact state has been obtained.

The present invention has been made based on such a point, and an object of the present invention is to fix a planar heating element having a large heat transfer area to a single water passage pipe in a cantilever manner, and to be heated. An object of the present invention is to provide a mounting method capable of elastically contacting an object.

[0007]

In order to achieve the above object, a method of mounting a metal-coated planar heating element according to the present invention is to provide a metal tubular molding having no joints or a fusion-bonded metal molded into a predetermined shape. A metal-coated planar heating element in which a planar heating element provided with a power supply conductor is housed in the body and the openings at both ends of the planar heating element are sealed with an insulating material, and a mounting member is used for a planar heating portion of an object to be heated. A method for mounting a metal-coated sheet heating element to be elastically pressed and mounted, wherein the metal-coated sheet heating element is formed so that the area of a plane portion is 25% or more of the total surface area. In addition, the mounting member includes a fitting portion that fits with the three-dimensional structure located near the heating portion, and a metal-coated planar heating element holding portion that is formed integrally with the fitting portion. It is characterized by the following. At this time, the mounting member has a connecting portion provided with spring elasticity by bending between the fitting portion and the metal-coated planar heating element holding portion, and the three-dimensional portion located near the heating portion is provided. With the structure as a fulcrum, it is conceivable to mount the metal-coated planar heating element by pressing it elastically against a planar heating portion of the object to be heated.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A metal-coated sheet heating element used in the present invention is made of metal which has no joint or is melt-joined and formed so that the area of a plane portion is 25% or more of the total surface area. A tubular heating element, a planar heating element housed in the tubular molding body, a power supply conductor electrically connected to the planar heating element and led out from one or both ends of the tubular molding, And an insulating material for sealing the openings at both ends of the tubular molded body.

[0009] The tubular molded body is made of stainless steel, carbon steel, iron,
It is formed by using a metal such as brass, copper, or aluminum as a constituent material in accordance with the size and shape of a planar heating element described later. In the present invention, it is an essential requirement that the flat portion be formed so as to have an area of 25% or more of the total surface area. This is because if the area of the plane portion is less than 25% of the total surface area, a sufficient contact area with the object to be heated cannot be obtained, and the heating efficiency is reduced. As a forming method, for example, a cylindrical pipe made of the above metal material,
A method of obtaining a tubular molded body of a predetermined shape by performing plastic working such as press working, rolling drawing, or the like, and forming a tubular body of a predetermined shape by performing welding, welding, brazing, etc. on a plate made of the above metal material. And a method of pultruding the above-mentioned metal material to obtain a tubular molded body having a predetermined shape.

The planar heating element accommodated in the above-mentioned tubular molded body is formed by arranging a conventionally known resistor made of a metal wire or a metal foil in a predetermined pattern or a winding shape, such as mica or ceramic. Insulation is provided by sandwiching or wrapping it with an insulating material made of an inorganic material, an organic polymer material such as silicone rubber, fluoro rubber, fluoro resin, etc., and a structure in which a power supply conductor is electrically connected to both ends. is there.

The power supply conductor has a structure in which a conventionally known conductor material is appropriately subjected to insulation treatment, and is electrically connected to the resistor of the sheet heating element via a connection terminal or the like without or through the connection terminal. An example of a method of connecting to a resistor without using a connection terminal or the like will be described with reference to a case where a mica plate laminated heater is used as a planar heating element. First, a laminated mica plate heater has a structure in which a nickel-chromium alloy wire as a resistor is wound at a predetermined pitch on a mica plate as a core material and sandwiched from above and below by a mica plate as an insulating material. ,
Both ends of the nickel-chromium alloy wire are extended by a predetermined length in the same direction. Then, a pure nickel wire as a power supply conductor is twisted at a predetermined pitch with the extended nickel chromium alloy wire to electrically connect the two. This method is preferable because the number of components can be reduced because connection terminals and the like can be eliminated.

As the lead-out structure of the power supply conductor to the outside of the tubular molded body, there are a structure of leading out from both ends of the tubular molded body to the outside;
A structure in which one end of the tubular molded body is led to the outside is conceivable. Either structure may be adopted, but it is preferable to adopt a structure that is led out from one end of the tubular molded body, since the wiring work of the power supply conductor is easy.

The insulating material for sealing the openings at both ends of the tubular molded body is made of a conventionally known insulating material in consideration of heat resistance and waterproofness required in actual use, workability during manufacturing work, productivity, and the like. It is appropriately selected from among them. For example, inorganic materials such as ceramics, and organic polymer materials such as silicone rubber, synthetic rubber, urethane rubber, fluorine rubber, epoxy resin, and fluorine resin are exemplified.

The metal-coated sheet-like heating element having the above-mentioned structure is mounted in close contact with the flat heating portion of the object to be heated by the elastic force of the mounting member. This attachment member is formed by, for example, bending a plate-like body made of a metal material such as stainless steel, carbon steel, or a copper alloy, so that a fitting portion that fits at least with a three-dimensional structure located in the vicinity of a heated portion is formed. And a metal-coated planar heating element holding portion formed integrally with the fitting portion. On this occasion,
Between the fitting portion and the metal-coated planar heating element holding portion, for example,
In the case of a configuration with a connection part formed into a substantially rectangular shape in cross section by bending, the metal-coated sheet heating element can be connected to the spring elastic force of the connection part regardless of the surface shape or inclination of the heated part. It is possible to mount the device in a close contact state by using the device.

As means for holding the metal-coated sheet heating element, there are a method of holding the metal-coated sheet heating element by grasping it with a plurality of claws provided on the holding portion, and a method of holding the metal-coated sheet heating element with the claws. A method of holding the body by welding and further holding it by welding with a metal coating of the metal-coated sheet heating element, a method of holding the holding part by welding the metal coating of the metal-coated sheet heating element, and the like can be considered.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Note that this embodiment is an example in which the present invention is applied to heating of a water flow pipe in a heat exchanger main body of a water heater.

EXAMPLE 1 As shown in FIG. 1, a metal-coated planar heating element 1 according to this example has both ends opened with an insulating material 2 made of silicone rubber and has a length of 156 mm and a thickness of 0.5 mm. A nickel-chromium alloy wire as a resistor is wound around a stainless steel tubular molded body 3 (having a flat area of 60% of the total surface area) having an outer height of 4.5 mm and an outer width of 21.6 mm and a substantially elliptical cross section. A planar heating element 4 (thickness: 3.2 mm, width: 18.5 m) composed of a mica plate laminated heater in which a mica plate serving as a core material is sandwiched from above and below by a mica plate serving as an insulating material.
m, 151 mm in length). Here, the tubular molded body 3 is obtained by pressing a cylindrical stainless steel pipe having an outer diameter of 15 mm formed by pultrusion molding into a substantially elliptical cross section. The power supply conductor indicated by reference numeral 5 is made of a pure nickel wire electrically connected by twisting to a nickel-chromium alloy wire extended from the sheet heating element 4, and two wires from one end of the tubular molded body 3 are combined. It is led out in the same direction and is insulated and coated with a glass braided silicone rubber tube 6.

On the other hand, the mounting member 7 is formed by bending a stainless steel plate having a thickness of 0.4 mm to provide a spring elasticity, and has a substantially U-shaped cross section of a water pipe fitting portion 7a; And a metal-coated planar heating element holding portion 7b integrally formed with the metal-coated planar heating element 7a. keeping.

Example 2 A metal-coated planar heating element 1 having the same structure as that of Example 1 was held by using a mounting member 8 having a structure as shown in FIG. The mounting member 8 is formed by bending a stainless steel plate having a thickness of 0.4 mm to provide a spring elasticity, and has a substantially U-shaped cross section for a water pipe fitting portion 8a, and is integrally formed with the fitting portion 8a. Between the formed metal-coated planar heating element holding part 8b, a connecting part 8d having a substantially L-shaped cross section, which is provided with spring elasticity by bending, is provided. The metal-coated planar heating element 1 is held by a plurality (three in this case) of claw portions 8c.

Comparative Example 1 Conventionally, a ceramic tubular heating element generally used for heating a heat exchanger of a water heater and a stopper having a substantially U-shaped cross section were prepared. Since the lead wires of this heating element are led out from both ends of the tubular heating element, one lead wire is folded in the lead-out direction of the other lead wire, and then the lead wire is brought into contact with the heating portion. It was inserted into a metal spring to prevent damage to the coating.

Here, the following tests were conducted to evaluate the workability and the heating efficiency of the above three types of heating elements to be heated. First, as shown in FIG.
In the center of a copper plate 9 having a thickness of 0 mm, a width of 360 mm and a thickness of 0.3 mm, an outer diameter of 12.7 mm, a length of 400 mm, and a thickness of 1.0
An object to be heated having a structure in which a copper pipe 10 mm was joined was prepared, and the above three types of heating elements were attached to the lower part of the center of the copper pipe 10. In both Example 1 and Example 2, the heating element could be attached in close contact with the planar heating portion (copper plate 9) of the object to be heated. Further, in both the first embodiment and the second embodiment, only one process of fitting the fitting portion of the mounting member to the copper pipe is required. However, in the comparative example 1, the operation of installing the heating element at a predetermined position, And two steps of the work of attaching the to a predetermined position, which required two steps. Next, in a measurement box installed in a constant temperature bath set at an ambient temperature of 3 ° C., a predetermined power is applied to the heating elements of Example 1, Example 2, and Comparative Example 1 to generate heat, and the surface of the object to be heated is heated. The temperature was measured. The measurement points were the eight points shown in FIG. Table 1 shows the results.

[0022]

[Table 1]

According to the results shown in Table 1, the copper plate (measuring point to
) And copper pipes (measurement points to), the temperatures of Examples 1 and 2 were higher than those of Comparative Example 1 and the heating efficiency was excellent. This can be considered to be because the contact area between the heating element and the object to be heated is larger in Examples 1 and 2 than in Comparative Example 1.

In this example, the following test was conducted to evaluate the heating efficiency in actual use. First, a heat exchanger 11 of a commercially available water heater as shown in FIG.
The above three types of heating elements were attached. Here, the wall surface of the heat exchanger 11 of the water heater is somewhat uneven, and the water pipe 12
A slight inclination was observed. Next, the ambient temperature is 0 ° C.
In a measurement box installed in a thermostat set at a predetermined temperature, a predetermined power is applied to the heating elements of Example 1, Example 2 and Comparative Example 1 to generate heat, and the heating target (heat exchanger of a water heater) is heated. The surface temperature was measured. The measurement points were the three points shown in FIG. Table 2 shows the results.

[0025]

[Table 2]

According to the results shown in Table 2, first, at each measurement point, the temperatures of Examples 1 and 2 are higher than those of Comparative Example 1 and the heating efficiency is superior. this is,
It can be considered that Example 1 and Example 2 have a larger contact area between the heating element and the object to be heated than Comparative Example 1. Next, comparing Example 1 and Example 2, the temperature of Example 2 is slightly higher than that of Example 1.
This means that the metal-coated planar heating element can be attached to the heat exchanger wall more closely in the second embodiment than in the first embodiment,
It can be considered that this is because the heat exchanger and the water pipe can be heated with excellent heating efficiency.

[0027]

As described above in detail, in the mounting method of the metal-coated planar heating element according to the present invention, the mounting member for bringing the heating target into close contact with the planar heating part is located at least in the vicinity of the heating part. It has a fitting part to be fitted with the three-dimensional structure, and a metal-coated sheet heating element holding part having a sufficient holding force to prevent the metal-coated sheet heating element from falling off from the mounting member. In addition, a metal-coated planar heating element having a large heat transfer area can be easily attached to an object to be heated only by a fitting portion provided integrally with a holding portion of the metal-coated planar heating element. Further, in the mounting member, by providing a connecting portion provided with spring elasticity between the fitting portion and the holding portion, regardless of the surface state of the object to be heated, the surface contact state between the heating element and the object to be heated can be achieved. Can be stably realized, and high heating efficiency can be obtained. Furthermore, when the feeding conductor electrically connected to the planar heating element is configured to be led out from one end of the tubular molded body, wiring work of the feeding conductor is easy, and
Since a metal spring or the like which has been conventionally required can be eliminated, the manufacturing cost is reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing an embodiment of the present invention, wherein FIG. 1A is a perspective view showing the configuration of a metal-coated planar heating element and a mounting member, and FIG. 1B is a side view.

FIGS. 2A and 2B are views showing an embodiment of the present invention, wherein FIG. 2A is a perspective view showing the configuration of a metal-coated planar heating element and a mounting member, and FIG. 2B is a side view.

FIG. 3 is a diagram showing a configuration of an object to be heated used when evaluating mounting workability and heating efficiency, and a surface temperature measurement location.

4A and 4B are diagrams showing a configuration of a heat exchanger of a water heater used for evaluating heating efficiency in actual use and a surface temperature measuring point, wherein FIG. 4A is a perspective view of the heat exchanger, and FIG. Is a development view.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 metal-coated planar heating element 2 insulating material 3 tubular molded body 4 planar heating element 5 power supply conductor 6 glass braided silicone rubber tube 7 mounting member 7a fitting portion 7b metal-coated planar heating element holding portion 7c claw portion 8 mounting member 8a fitting portion 8b metal-coated planar heating element holding portion 8c claw portion 8d connecting portion 9 copper plate 10 copper pipe 11 heat exchanger 12 water pipe

Claims (2)

[Claims] A planar heating element having a power supply conductor is accommodated in a metal tubular body having no joint or formed by melting and being formed into a predetermined shape, and both ends of the heating element are sealed with an insulating material. A method of mounting a metal-coated sheet heating element, wherein the stopped metal-coated sheet heating element is elastically pressed and attached to a planar heating portion of an object to be heated by using an attachment member. The coated planar heating element is formed so that the area of the plane portion is equal to or more than 25% of the total surface area, and the mounting member is configured to fit into a three-dimensional structure located near the heating part. And a metal-coated sheet heating element holding part integrally formed with the fitting part. 2. The mounting member has a connecting portion provided with spring elasticity by bending between a fitting portion and a metal-coated planar heating element holding portion, and is located near a heating portion. 2. The metal-coated planar heating element according to claim 1, wherein the three-dimensional structure is used as a fulcrum, and the metal-coated planar heating element is elastically pressed and mounted on a planar heating portion of the object to be heated. Implementation method.