JPH07118377B2 - Induction heating cooker - Google Patents

Description

Description: [Object of the Invention] (Industrial field of application) The present invention relates to an induction heating cooker in which a high-frequency current is passed through an induction coil to induction-heat an object to be heated.

(Prior Art) Conventionally, in this type of induction heating cooker, an induction coil 1 having a structure shown in FIG. 6, for example, has been used. In this induction coil 1, 36 thin copper wires (0.1 mm in diameter) are bundled and twisted together to form a twisted wire 2 to form a coil conductor 3, and a coil conductor 3 is formed. It is formed by winding 65 turns. The twisted structure is used to suppress an increase in resistance due to the skin effect that occurs when a high frequency current is passed through the induction coil 1.

(Problems to be solved by the invention) By the way, recently, there is a demand for induction heating of an aluminum or copper pan having a smaller skin resistance than that of an iron pan. It is necessary to increase the frequency (40 to 50 KHz) higher than about 30 KHz) and to increase the number of windings, for example, three times or more. When the frequency is increased and the number of turns is increased, the skin resistance of the coil conductor 3 greatly increases the coil resistance. Therefore, it is conceivable to make the copper wire finer as a countermeasure. However, if the copper wire is made thinner, the resistance increase due to the skin effect can be suppressed, but the resistance increase due to the proximity effect cannot be sufficiently suppressed. Here, the proximity effect means that when currents flow in adjacent conductors, they affect each other, causing a bias in the current distribution, increasing the resistance of the conductors, and thus the direction of the current, that is, the direction of each conductor. The closer the conductors are, the closer the conductors are to each other, and the larger the number of turns, the greater the influence of the proximity effect.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an induction heating cooker capable of suppressing an increase in resistance of an induction coil with respect to a high frequency current.

[Structure of the Invention] (Means for Solving Problems) The present invention relates to an induction heating cooker in which a high-frequency current is passed through an induction coil formed by winding a coil wire to induction-heat an object to be heated. Is a multi-stage aggregate structure in which aggregate lines are further aggregated, and at least one stage of aggregate lines is formed by knitting.

(Operation) According to the means described above, since any one of the assembly lines is formed by braiding, the assembly line is more easily compared to the assembly line in which many strands are simply bundled together. The orientations of the strands forming the are not uniform. Therefore, the increase in resistance due to the proximity effect that occurs when a high-frequency current flows through the assembly wire, and thus the coil conductor wire, is lower than that of the conventional one in which the directions of the strands are aligned.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

First, in FIG. 3, 11 is a DC power supply circuit, which rectifies the commercial power supply 12 and supplies DC power to the inverter main circuit 13. Reference numeral 14 is an induction coil described later, and a resonance circuit is formed by the induction coil 14 and a resonance capacitor (not shown). Then, a high frequency current is made to flow from the inverter main circuit 13 to this resonance circuit.
Reference numeral 15 is a pan to be heated, which is placed above the induction coil 14 via the top plate 16 as shown in FIG. 2 and is heated when induction coil 14 is supplied with a high frequency current. It is like this.

Now, the structure of the induction coil 14 will be described in detail with reference to FIG. Reference numeral 17 is a primary assembly line, which is formed by, for example, bundling 36 copper wires (diameter 0.1 mm) and twisting them together. Then, only three of these primary assembly lines 17 are knitted as shown in FIG. 4 to form a secondary assembly line 18, and finally three of these secondary assembly lines 18 are bundled and twisted to form a tertiary assembly line 18. The assembly line or coil conductor 19 is formed. That is, in this embodiment, the coil conducting wire 19 has a three-stage assembly structure, and the second-stage secondary assembly line 18 is formed by braiding three primary assembly lines 17.
The induction coil 14 is formed by winding the coil conductor wire 19 thus formed, for example, for 65 turns.

FIG. 5 shows an experimental result obtained by measuring the coil resistance of the induction coil 14 of this embodiment in comparison with that of the conventional structure.
In FIG. 5, the solid line shows the coil resistance of the induction coil 14 of this embodiment with respect to the high frequency current, and the broken line shows the coil resistance of the induction coil of the conventional structure with respect to the high frequency current.
As the induction coil having the conventional structure, the induction coil 1 shown in FIG. 6 was used. As mentioned above, this induction coil 1
Is formed by bundling 36 copper wires and twisting them together to form a gathering wire, and further bundling 9 of these gathering wires and twisting them together. Therefore which induction coil 14,1
Also in (1), since the cross-sectional area of the entire copper wire is the same, the coil resistance to the direct current is the same. As is clear from this experimental result, the higher the frequency of the high frequency current applied to each induction coil 14 and 1, the more the coil resistance of both increases, but the induction coil 1 of the conventional structure has an increased coil resistance when the frequency is increased. In contrast, the induction coil 14 of the present embodiment has a moderate increasing tendency, and at 50 KHz suitable for induction heating of a pan having a low skin resistance, the induction coil 14 of the present embodiment has a coil resistance of about 1 of the conventional value. / 2. Here, since the total cross-sectional area of the copper wire of each of the induction coil 14 and the induction coil 1 is the same, there is a large difference in the coil resistance as the frequency of the current increases. It is considered that this was caused by the difference in the aggregate structure of the coil conductors that compose 1.

For example, paying attention to the three primary assembly lines 17 forming the secondary assembly line 18 of the present embodiment, the directions of the respective primary assembly lines 17 are woven together so that they are uneven as shown in FIG. It has become. On the other hand, the direction of the assembly line 2 of the coil conductor 1 having the conventional structure is bundled and twisted to be aligned in a certain direction. This means that the induction coil 14 of the present embodiment has a smaller increase in coil resistance due to the proximity effect than the induction coil 1 having the conventional structure, which is in agreement with the experimental result.

Further, the secondary assembly line 18 in the induction coil 14 is the primary assembly line.
Since the primary assembly lines 17 are separated from each other in the secondary assembly line 18 and are in a rough state because they are formed by braiding 17, the coil assembly wire 3 of the conventional structure has The assembly lines 2 are in contact with each other and are in a dense state. Therefore, the induction coil 1 of this embodiment can further suppress the increase in coil resistance due to the proximity effect.

In this embodiment, the coil conductor 19 has a three-stage assembly structure, and the second-stage secondary assembly line 18 is formed by braiding three primary assembly lines 17. The number of gathering lines to be knitted is not limited to this. For example, a secondary assembly line formed by braiding
You may knit three more 18 to form a coil conductor,
Further, the number of assembly lines used for knitting may be four or more, and in any case, the increase in coil resistance due to the proximity effect can be suppressed as compared with the induction coil 1 having the conventional structure. Furthermore, the number of stages of the assembly is not limited to three, and any number of stages may be used. In short, at least one of the stages may be formed by knitting.

Besides, the present invention is not limited to the above description and shown in the drawings, and various modifications can be made without departing from the scope of the invention.

[Effects of the Invention] As is apparent from the above description, the present invention provides a coil conductor wire of an induction coil with a multi-stage assembly structure in which assembly wires are further assembled, and at least one assembly wire is formed by braiding. As a result, the assembly lines are not oriented in the same direction and are not in close contact with each other, whereby the proximity effect can be suppressed and the coil resistance of the induction coil with respect to the high frequency current can be reduced.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention. FIG. 1 is a sectional view of a coil wire, FIG. 2 is a partial vertical sectional view of an induction heating cooker, and FIG. 3 is a schematic block. FIG. 4 is a schematic diagram of an assembly line showing a braided state, FIG. 5 is a coil resistance-frequency characteristic diagram in an induction coil, and FIG. 6 is a diagram corresponding to FIG. In the figure, 14 is an induction coil, 15 is a pot (body to be heated), 17 is a primary assembly line (assembly line), 18 is a secondary assembly line (assembly line), and 19 is a coil conductor.

Claims (1)

[Claims] 1. A method for inductively heating a body to be heated by passing a high-frequency current through an induction coil formed by winding a coil wire, wherein the coil wire has a multi-stage assembly structure in which assembly wires are further assembled, and at least An induction heating cooker characterized in that the assembly line of the first stage is formed by braiding.