JP2566940B2 - 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, for example, an induction coil 1 having a structure shown in FIG. 7 is used. This induction coil 1 is formed by bundling 40 thin copper wires (diameter 0.1 mm) and twisting them together to form a coil conductor 3 by further combining 8 together.
Is wound for 65 turns, for example. 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 make the frequency (40 to 50 KHz) higher than about 30 KHz and to increase the number of turns, for example, three times or more. If the frequency is increased and the number of turns is increased, the coil resistance greatly increases due to the skin effect of the coil conductor 3, and it is conceivable to make the copper wire thinner as a countermeasure against this. However, if the copper wire is made thinner, the increase in resistance due to the skin effect can be suppressed,
There is a drawback that the increase in resistance 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 they are, that is, the closer the twisted lines are, 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 the proximity effect between the twisted wires and suppressing an increase in resistance of the induction coil 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 made into a structure by a multi-stage superposition in which twisted lines are further twisted, and the number of lines forming the stranded lines at all stages for making a structure from the multi-stage superposition is set to 2. It is a thing.

(Operation) According to the means described above, since the number of strands forming all the strands for forming the structure by multi-stage superposition is 2, the multiple strands are simply bundled and twisted together. Compared to the ones, the twisted lines have different directions. Therefore, the increase in resistance due to the proximity effect that occurs when a high-frequency current flows through the stranded wire, and thus the coil conductor wire, is lower than that of the conventional one in which the stranded wire is aligned.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

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 appropriately 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 stranded wire, which is formed by, for example, bundling 40 copper wires (diameter 0.1 mm) and twisting them together. Then, only two of these primary strands 17 are fitted together again as shown in FIG.
To form a third twisted wire 19 by twisting only two strands 18 of the secondary wire, and finally, twisting only two wires 19 of the third twisted wire into a fourth twisted wire or coil conductor 20. Is formed. That is, in the present embodiment, the coil conductor 20 has a structure of four-stage multi-stage stacking, and the coil conductor 20 has three layers from the second stage to the final fourth stage.
At each stage, the number of lines forming each twisted line is set to 2. That is, it is set so that the number of twisted wires forming the twisted wires in all the steps for forming the structure by the multi-step overlapping is two. And the coil wire thus formed
The induction coil 14 is formed by winding the 20 around, for example, 65 turns.

Here, FIG. 6 shows the experimental results obtained by measuring the coil resistance of the induction coil 14 of the present embodiment in comparison with that of the conventional structure. In FIG. 6, the solid line shows the coil resistance of the induction coil 14 in the present 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. 7 was used. As described above, the induction coil 1 is formed by bundling 40 copper strands and twisting them to form a twisted wire, and further bundling 8 twisted wires and twisting them together. Therefore, in each of the induction coils 14 and 1, the cross-sectional area of the entire copper wire is the same, and therefore 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, the difference in the coil resistance increases as the frequency of the current increases. It is considered that this is caused by the difference in the structure of the coil conductor wire that constitutes the.

For example, paying attention to the two primary twisted lines 17 forming the secondary twisted line 18 in this embodiment, the directions of the primary twisted lines 17 are aligned with each other so that they are like the arrows shown in FIG. There are always different directions. On the other hand, the direction of the twisted wire 2 of the coil conductor 1 having the conventional structure is bundled and twisted so that the twisted wire 2 is aligned in a certain direction. Furthermore,
In the case of the one shown in FIG. 4, the twisted wires are not in close contact with each other, and the distance between the twisted wires is larger than in the conventional case. 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.

Furthermore, as a result of examining the influence of the number of lines forming the twisted line on the proximity effect, it was found that the proximity effect can be most effectively suppressed when the number of lines is 2. That is, considering the case where the secondary twisted line 21 is formed by the three primary twisted lines 17 as shown in FIG. 5, in this case, the direction of the two twisted lines of the three primary twisted lines 17 is Since the wires are aligned and the wires are closely attached to each other, the proximity effect is more likely to occur than in the case of two wires, and the coil resistance is increased. In this respect, in the present embodiment, since the number of twisted wires after the secondary twisted wire 18 is 2, the increase in resistance due to the proximity effect can be minimized.

Besides, the present invention is not limited to what has been described above 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-tiered structure in which twisted wires are further twisted together, and all of the features for constructing the multi-tiered structure. Since the number of twisted wires forming the twisted wire in the step of is set to 2, the twisted wires become uneven in direction, and
Since they do not adhere to each other, the proximity effect between the twisted wires can be suppressed, and the excellent effect that the coil resistance of the induction coil with respect to the high frequency current can be reduced is exhibited.

[Brief description of drawings]

1 to 6 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, FIG. 3 is a schematic block diagram, and FIG. Is a schematic diagram of a twisted wire showing a state where the number of twisted wires is 2, FIG. 5 is a schematic diagram of a twisted wire showing a state where the twisted wire is 3, FIG. 6 is a coil resistance-frequency characteristic diagram in an induction coil, FIG. The drawing is a view corresponding to FIG. 1 of a coil conductor wire having a conventional structure. In the figure, 14 is an induction coil, 15 is a pan (heated body), 17 is a twisted wire, 18 is a primary twisted wire (twisted wire), 19 is a secondary twisted wire (twisted wire), and 20 is a coil conductor.

Claims (1)

(57) [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 structure in which twisted wires are further twisted. The number of twisted wires forming all the twisted wires for forming a structure from the multi-step overlapping is 2
An induction heating cooker characterized in that