JPH0612697B2 - Electromagnetic induction type heating plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electromagnetic induction heating plate. The use of the product of the present invention is indoor heating, prevention of snow melting or freezing of the structure itself, and the like.

[Conventional technology]

An induction skin current heating tube (hereinafter referred to as “prototype”), which is one of the skin current heating tubes, is well known, and is widely used in the field of surface heating, for example, described in “Electrical Engineering Handbook” edited by the Institute of Electrical Engineers, 1978 edition. ing. The heating tube is also a "simple induction current heating tube" (hereinafter referred to as "simplified type") whose production is easy to carry out [Patent Application Publication No. 58-16,104 (March 29, 1983), Patent No. No. 1,185,318 (Showa 59 1
20th of the month)].

Although the above-mentioned heating tubes are all ferromagnetic steel tubes, the relationship between the thickness t _{1 of the} tube and the skin depth S ₁ of the alternating current was different between the “prototype” and the “simple type”. .

That is, the former has the relationship of the following expression (1), and the t ₁ > 2S ₁ (1) has the relationship of the following expression (2).

0.5S ₁ <t ₁ <2S ₁ (2) On the other hand, the configuration common to both is that the number of tubes in one set is two or multiples when the power source used is a single phase, or three when three phases or The point is a multiple of that.

Further, in the simple type, when there are a plurality of sets of two or three heating pipes, the thickness t ₁ of the heating pipes is smaller than t _{1 in the} equation (1) and leaks to the outside of the pipe. In order to prevent magnetic flux, it was necessary to bring adjacent sets of heat generating tubes in parallel close to each other and electrically connect both ends of the heat generating tubes in each set.

Now, as is well known, the skin depth S ₁ (cm) of the alternating current according to the above equations (1) and (2) is defined as follows: the resistivity of the heating steel pipe is ρ (Ωcm), and the relative permeability is When μγ (-) and the frequency of the alternating current are (Hz), And S ₁ is about 0.1 cm when is the commercial frequency.

(Problems to be Solved by the Invention) As described above, the known prototype has a wall thickness t ₁ larger than that of the simplified type, as is apparent from the comparison between the equations (1) and (2). Therefore, secondary processing is difficult depending on the purpose. On the other hand, in the case of the simplified type, the wall thickness t ₁ is thin, but the configuration of the simplified type may not be appropriate depending on the purpose of use because it is necessary to closely adjoin adjacent tubes in parallel.

Therefore, in the present invention, the wall thickness t ₁ of the heating tube is determined by the above equation (2).
However, the present invention intends to solve the generation of the leakage voltage due to the leakage magnetic flux from the heat generating tube by means other than the simple type.

Since the present invention is an electromagnetic induction type heating plate as is clear from the title of the invention, the ferromagnetic heating steel pipe having the relation of the above-mentioned formula (2) is used, but in order to prevent leakage flux, the formula (2) is used. In addition to the condition of (t ₁ + t ₂ )> (S ₁ + S ₂ ), (S ₂ ≧ S ₁ ).
A metal plate having a skin depth S ₂ and a wall thickness t ₂ determined in (4) is used as a constituent element. This metal plate is a ferromagnetic material under normal conditions, but it is not an essential condition. In equation (4), S ₂
Is determined by the equation (3) like S ₁ . If the steel pipe and the metal plate are made of the same material, the resistivity ρ,
Since the relative permeability μγ is the same value, S ₂ = S ₁ and
The formula (4) naturally satisfies (t ₁ + t ₂ )> 2S ₁ (5), and if a ferromagnetic tube or ferromagnetic plate on the market is used as the steel tube or metal plate, the passbook S ₂ becomes S ₁ The same is about 0.1 cm. The grounds for deriving the formula (4) are as follows. In other words, The Denketsu Kyokai: “Denketsu” No. 25, January 1986 issue, SECT method (1) Pages 6, 7 and 11, 12 and Gihodo; Published April 15, 1965, Electrodynamics Basic (Section 7-03) pp. 157-162 Analogy was made from plated conductors.

To further explain, referring to the above formula (2), when rewriting the formula (4) by the upper limit and the lower limit of t ₁ , S ₁ ≧ S ₁ is satisfied. Therefore, when t _{1 is} the upper limit t _{1 to} 2S ₁ , t ₂ >. When (S ₂ −S ₁ ) ≧ 0 t ₂ lower limit t _{1 to} 0.5S ₁ , t ₂ > (S ₂ +0.5
S ₁ ).

The upper limit of the time t ₂ is, t ₂ by analogy with the above equation (1)> because it is 2S _2, it is needless to say that will be t ₂ ～2S ₂ about unless special circumstances.

[Object of the Invention]

As is apparent from the above, an object of the present invention is to provide an electromagnetic induction heating plate in which a group of constituent tubes is joined to a metal plate according to the purpose of heating. It is another object of the present invention to provide a heat generating plate which can easily prevent leakage magnetic flux and can keep the outer peripheral metal plate resistant to touch.

[Means for solving problems]

The present invention has the following main constitution (1) and embodiment constitutions (2) to (5).

(1) a wall thickness t _1, the skin depth of the alternating current and inserted through the induction current heating pipe components made of insulated wire in the ferromagnetic steel pipe and tube is S _1, and the t ₁ S ₁ has a relationship of 0.5S ₁ <t ₁ <2S ₁ (2), and if the alternating current power supply for energizing the induction current heating tube with the ferromagnetic steel tube is a single phase, the even number is 3 In the case of a phase, three or a multiple thereof is preferably a tube group parallel to each other and having a gap, and the tube group has a wall thickness of t.
₂ is welded, adhered or fitted to a metal plate such that the depth of the alternating current flowing through the inner surface thereof is S _2, and at least both ends of the adjacent steel pipes are electrically connected to each other. And further connected so that one or more insulated electric wires inserted into the ferromagnetic steel pipe become one series electric wire for each phase for the entire pipe group, and to the AC power source, The insulated wire has a primary circuit, the ferromagnetic tube has a secondary circuit, and the thickness t _{2 of the} metal plate and the skin depth S ₂ of the alternating current are (t ₁ + t ₂ )> ( S ₁ + S ₂ ), (S ₂ ≧ S ₁ ).
An electromagnetic induction heating plate characterized by being determined from equations (2) and (4) so that (4).

(2) The electromagnetic induction heating plate according to the above item (1), wherein the cross-section of the ferromagnetic steel pipe is rectangular or circular.

(3) The electromagnetic induction heat generating plate according to item (1), wherein the gap between adjacent ferromagnetic steel pipes is 1 to 20 times the outer diameter of the steel pipes.

(4) The electromagnetic induction heat generating plate according to the item (1), which is formed by using a metal plate having a regular wave shape or a square groove shape as the metal plate.

(5) The above-mentioned first method in which the surface of the metal plate on which the ferromagnetic steel pipe is mounted is surrounded by a metallic back plate and side plates to electrically form a closed circuit.
The electromagnetic induction type heating plate according to the item (1).

Prior to describing the present invention with the following embodiments, a prototype induction skin current heating tube and a simplified induction skin current heating tube will be described with reference to the drawings.

FIG. 8 is a schematic cross-sectional view for explaining the simplest prototype and simple model in the case where the power source is single-phase alternating current and FIG. 9 is three-phase alternating current.

8 and 1 are a pair of ferromagnetic steel pipes, both ends of which are
7 and 8 are electrically connected, and a single-phase AC power source 4 and an insulated electric wire 3 penetrating the steel pipes 1 and 2 form a primary circuit,
A current 5 flows. On the other hand, since the steel pipes 1 and 2 are connected by 7 and 8, a secondary circuit is formed and a current 6 flows.

In such a circuit, if the steel pipe 1,
If the wall thickness of 2 is in the relation of the above-mentioned formula (1), the magnitudes of the primary current and the secondary current are almost equal, and since the flow directions of these currents are opposite, leakage flux is generated outside the tube. Without, and
The secondary current flows in the range of the depth S ₁ of the inner skin of the exothermic tube to generate heat, and does not flow to the outer surface of the tube, so that it can be used as a safe heating element.

On the other hand, in the simplified type, the wall thickness t ₁ and the depth S ₁ are determined by the above formula (2).
Therefore, the primary current 5 (hereinafter referred to as i ₁ ) and the secondary current 6 are
(Hereinafter, i ₂ ) are not equal to each other, so that a leakage magnetic flux is generated in the space outside the steel pipes 1 and 2, and a voltage having opposite directions appears on the outer surfaces of the steel pipes 1 and 2. This voltage is
Could be reduced by closely
Since it does not become completely zero over the entire outer circumference of the steel pipe, the total length of the steel pipes 1 and 2 is also limited.

The above is the description of the prototype and simple induction heating tubes.

Next, FIG. 9 shows the case where the power source has three phases and the primary circuit thereof is connected in a star shape. In the figure, 9, 10, 11
Is a heat generating tube made of a ferromagnetic steel tube, 12, 13, 14
Forms a primary circuit with insulated wires, one of which is the terminal of the three-phase power supply 15 and the other is a star-shaped connection by the connection 22,
Primary currents 23, 24, and 25 flow, respectively.

The heating tubes 9, 10, 11 are connected 16, 17, 18, 1.
Since it is connected as one body with 9, 20, 21 etc., a secondary circuit is formed and currents 26, 27, 28 are made to flow, but
Depending on whether the condition (1) or (2) is met, it becomes a prototype or a simplified model, and the same precautions as in the case of the single-phase circuit in FIG. 8 are required.

An embodiment of the present invention will be described based on the above description of the known art.

FIG. 1 is a schematic view of an embodiment of a panel heater (electromagnetic induction type heating tube) which is an example of the present invention, FIG. 2 is an XY cross sectional explanatory view of FIG. 1, and FIG. 2 is an enlarged view of a portion A in FIG. 2, and 29 in these figures means a ferromagnetic steel pipe such as 1 or 2 in FIG. 8 or 5, and in FIG.
There are twelve. Reference numeral 30 denotes an insulated wire that penetrates through the heating tube, which passes through the 12 heating tubes in series in the figure and is connected to a single-phase power source by an outlet 31 to form a primary circuit.
Although the insulated wire 30 is shown by one wire in FIG. 1, it may be penetrated by 7 wires and one or more wires as shown in FIG. 3, and the result is 3 wires shown in FIG. As shown in the case of (1), when viewed as a whole wire, one wire is connected in series.
As shown in both figures, the purpose of making a plurality of tubes is to increase the voltage and decrease the current per heating tube, and the patent application publication No. Sho 52-14854 "Heating tube to increase the applied voltage". The same considerations as those known in. The meaning of each number in FIG. 4 is the same as in FIG. 8 described above except for the electric wire 30.

The wall thickness t ₁ of the heating tube 29 used in the present invention is calculated by the above formula (2).
Since there is only a thickness given by the relation of, when there is a gap g between adjacent heating pipes as shown in FIG. 1 or 2, as a natural result, as shown in FIG. A leakage magnetic field is generated in the portion of the gap g. This causes a gap width g and a primary current i ₁ and a secondary current as shown by H = {g, (i ₁ −i ₂ )} (6). It becomes a function of the difference of i ₂ , and the larger g and (i ₁ −i ₂ ) are, the larger H is. Since this is an alternating magnetic field, an electric field e ₂ proportional to H is generated on the outer surface of the heating tube. To do. However, in the present invention, in order to reduce H, that is, e ₂ and to not affect humans and animals, the above formula (5)
The heat generating tube 29 is arranged and coupled as shown in FIGS. 1 and _{2 to} the metal plate 32 having a thickness t ₂ corresponding to the above relationship, preferably the metal plate covers 33 (bottom plate) and 34 (shown in FIGS. 2 and 3). Together with the side plate), the magnetic flux leaks to the outside of the heat generating plate of the present invention, that is, plays the role of voltage shielding.

By the way, among the two conditions given by the above equations (2) and (5), it is decided that t ₁ is independently determined from t ₂ in the equation (2) because when t ₁ becomes too thin, The next current becomes small, that is, the amount of heat generated in the heating tube becomes small,
This is because the usefulness as a heating tube is lost, and usually t ₁
It is most preferable that the thickness is approximately equal to S ₁ if processing and other circumstances permit.

The above-mentioned outer tube gap g can be freely determined according to the specific purpose of use of the heat-generating plate of the present invention, but in order to keep the temperature distribution on the surface of the heat-generating plate less biased, the outer diameter of the heat-generating tube is 1 to 20. Double, preferably 2 to 10 times.

Further, the method of connecting the heating tube to the metal plate 32 is not limited, but in order to facilitate the construction and assembly of the product of the present invention, a method such as welding, bonding (using an adhesive), or fitting is usually performed. Easy to do. In FIG. 3, the exothermic tube 29 of a square piece is welded 36 to the back surface of the metal plate 32.

As shown in FIGS. 2 and 3, the exothermic steel pipe 29 has a rectangular cross section because the contact area between the pipe and the metal plate 32 (the wall thickness t ₂ thereof is determined by the equation (5)) is large. In order to improve the heat transfer and to facilitate and ensure the welding of the pipe and the metal plate. This is because the wall thickness t ₁ of the heating tube 29 is as thin as about 0.1 cm even when the working current is a normal commercial frequency, and welding may be difficult depending on the circumstances. However, various other auxiliary methods (for example, for heat transfer cement) can be used to improve the heat transfer described above, so that the cross-sectional shape of the heat-generating steel pipe can adopt a circular shape or another economically efficient shape.

Also, an adhesive may be used to bond the metal plate 32 and the heating tube 29. In this case, the adhesive must of course have the required heat resistance,
In addition, the electrical connection (most simply, welding) between adjacent heating pipes shown by 7 and 8 in FIG. 8 must be ensured.

In addition, as a method of connecting the metal plate 32 and the heat generating tube 29, a fitting method as shown in FIG. 7 (described later) can be adopted.

Now, FIG. 1 as an embodiment will be described more specifically. In the figure, the cross section of the heating tube 29 is a square cross section of 10 × 22 mm, the thickness t ₁ thereof is about 1.2 mm, and the metal plate 32 has t ₂ = 2.3 m.
m, area: 800 x 1800 mm, insulated wire that is passed through the pipe 1
When the current flowing through the book was about 9 A, the heat generation was about 500 W.

The metal plates 33 (bottom plates) and 34 (side plates) in FIGS. 2 and 3 do not have to have the same plate thickness as the steel plate 32 to which the heat generating tube 29 is attached. Although not provided, there was almost no leakage magnetic flux outside the space created by both end plates (the front side in FIGS. 2 and 3 and the opposite side), and it could be used practically.

Therefore, the metal plate 32 plays a main role of electromagnetic shielding, and this thickness t ₂ is one of the main conditions in the construction of the present invention.
Next, in FIGS. 2 and 3, when heat radiation needs to be performed only from the surface of the metal plate 32, it is effective to provide the heat insulating layer 35, but this is only one of the embodiments of the present invention. No, it is not an essential constituent feature of the present invention.

The above is a heating plate using the present invention as room heating or a snow melting plate, but the present invention can also be used as a construction material for roof snow melting or roof freeze prevention.

FIGS. 6 and 7 are schematic diagrams showing an example of its implementation.
The figure is a schematic cross-sectional view taken along the line XY in FIG. In FIG. 38, a metal plate 32 is a roof plate for a house that is covered with a metal plate 32. The metal plate 32 has a recess 37 provided at a gap g, and a ferromagnetic heating steel pipe 29 is fitted into this recess 37, and 29 is a primary current. shows a case with three insulated wire through the i _1. In such a structure, the heat generating tube 29 can serve not only as a heat generating tube but also as a roof structural material.

Furthermore, in the case of snow melting on the roof, if you allow the surrounding circumstances,
It is not necessary to melt the entire snow, and if only the contact between the roof 32 and the snow (not shown) is melted, the melted water becomes a lubricating liquid between the snow and the roof plate 32, and most of the snow is covered. Easily falls from the roof to the ground.

(Function) The present invention differs from the original induction skin current heating tube in that the heating tube alone prevents leakage voltage outside the heating tube, or the simple induction current heating tube has a single-phase structure. Is 2 and 3
In the case of the phase, it is not the case that the three heating tubes are closely attached to each other to prevent the generation of the leakage voltage to the outside of the heating tube. It plays a role of preventing voltage leakage to the outside.

Of course, in this case, the metal plate (especially 32) generates heat due to the presence of the vortex flow due to the leakage magnetic flux in the metal plate, but this is extremely small at a few percent or less of the heat generation amount of the heat generating tube, and the main heat generation is the heat generation. This is done in an insulated wire that carries the secondary and primary currents flowing in the tube.

(Effects of the Invention) According to the present invention, a thin-walled heating tube can be used in place of a large-walled heating tube, so that not only processing is easy, but also the overall weight is light and the vicinity of the heating tube is The leakage magnetic flux is prevented by utilizing the metal plate in Fig. 2. At that time, the slight secondary current flowing in the metal plate does not cause a loss but has a heat generating effect, so that the efficiency as a whole does not decrease. , The same effect as the original skin current heating tube can be expected.

The heat generating plate of the present invention is not only capable of freely adjusting the density of the arrangement of the heat generating tubes and the magnitude of the current to be applied, but also the size and shape of the heat generating plate itself can be freely designed, and it is a part of the structure. As a result, the heating device can be economically maintained and managed as compared with the case where the heating device is separately attached. Further, the heating tube and the metal plate can be made of different materials.

This means that, for example, the heating pipe is a normal steel pipe and the metal plate 3
By using a steel material to which a slight amount of chrome is added for 2, it becomes possible to have corrosion resistance without impairing its magnetism, and as a result, it becomes possible to improve the economical efficiency of the product of the present invention.

[Brief description of drawings]

1 is an explanatory view of an electromagnetic induction type heating plate of the present invention, FIG. 2 is an XY cross-sectional explanatory view of FIG. 1, and FIG. 3 is A of FIG.
FIG. 4 is an enlarged view of the part, FIG. 4 is an explanatory view when three insulated wires are passed through the heating pipe, and FIG. 5 is an electric field distribution in the heating steel pipes 1 and 2, leakage at the outer gap g portion. It is a schematic diagram for explaining the relationship between the magnetic field, the primary current i ₁ flowing in the insulated wire 3, and the secondary current i ₂ flowing in the heating steel pipe. FIG. 6 shows a house 36 covered with a metal plate 32 showing a specific application of the present invention, and a heating steel pipe 29 is fitted into 37 of FIG. 7 showing the enlarged convex portion thereof. 8 and 9 are schematic sectional views showing the principle of a single-phase or three-phase induction skin current heating tube which is the basis of the present invention. In these figures, the numbers represent: 1, 2, 9, 10, 11, 29: Ferromagnetic steel tube 3, 12, 13, 14: Insulated wire for making a primary circuit 4, 15: AC power supply 7, 8, 16, 17, 18, 19, 20 , 21: Electrical connection of heat-generating steel pipe 22: Star-shaped connection point 5 (or i ₁ ), 23, 24, 25: primary current 6 (or i ₂ ), 26, 27, 28: secondary current 30: Insulation Electric wire 31: Power outlet, 32: Metal plate 33, 34: Metal plate cover, 35: Heat insulating layer g: Outer space of pipe, 36: Welded portion 37: Convex portion of metal plate 32, 38: House

Claims (5)

[Claims] 1. An induction current heating tube comprising a ferromagnetic steel tube having a wall thickness of t ₁ and a skin depth of an alternating current of S ₁ and an insulated wire inserted in the tube, and the t ₁ and S ₁ have a relationship of 0.5S ₁ <t ₁ <2S ₁ (2), and if the alternating-current power supply for energizing the induction current heating tube with the ferromagnetic steel tube is a single-phase, In the case of three phases, three tubes or multiples thereof are preferably tube groups parallel to each other and having a gap, and the tube groups have a wall thickness of t.
₂ is welded, adhered or fitted to a metal plate such that the depth of the alternating current flowing through the inner surface thereof is S _2, and at least both ends of the adjacent steel pipes are electrically connected to each other. And further connected so that one or more insulated electric wires inserted into the ferromagnetic steel pipe become one series electric wire for each phase for the entire pipe group, and to the AC power source, The insulated wire is a primary circuit, the ferromagnetic tube is a secondary circuit, and the thickness t _{2 of the} metal plate and the skin depth S ₂ of the alternating current are (t ₁ + t ₂ )> (S ₁ + S ₂ ), (S ₂ ≧ S ₁ ), an electromagnetic induction heating plate characterized by being determined from equations (2) and (4) so that (4). 2. The electromagnetic induction heating plate according to claim 1, wherein the ferromagnetic steel tube has a rectangular cross section or a circular cross section. 3. The electromagnetic induction heat generating plate according to claim 1, wherein the gap between adjacent ferromagnetic steel pipes is 1 to 20 times the outer diameter of the steel pipes. 4. The electromagnetic induction heat generating plate according to claim 1, wherein the metal plate is a metal plate having a regular corrugated shape or a square groove shape. 5. The electromagnetic induction heat generation according to claim 1, wherein the surface of the metal plate having the ferromagnetic steel tube attached thereto is surrounded by a metallic back plate and side plates to electrically form a closed circuit. Board.