JP3165778B2 - Induction heating coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating coil used in a cooker such as a rice cooker and an electromagnetic cooker.

[0002]

2. Description of the Related Art Conventionally, as an induction heating coil used in a cooker, a litz wire formed by twisting several tens of enamel wires has been used. Since the litz wire is expensive to manufacture and the work of arranging it spirally is complicated, in recent years, instead of such a litz wire, as shown in FIG. Conductor 3 made of foil
An induction heating coil 31 in which the coils 3 are arranged in a spiral state has been proposed and put into practical use (Japanese Utility Model Laid-Open Publication No. 55-57997,
See JP-A-6-302377. When a high-frequency current is applied to the induction heating coil 31, as shown in FIG. 20, an alternating magnetic field is formed in a direction orthogonal to the spiral direction of the coil. It generates heat due to Joule heat.

[0003]

However, FIG.
As shown in (2), since the magnetic flux density is large near the center of the induction heating coil 31, eddy currents around the lines of magnetic force passing through the band-shaped conductor 33 near the center of the coil are concentrated. As a result, the temperature near the center of the coil becomes high (about 200 ° C.), and there is a problem that the substrate 32 and its surrounding members are deteriorated. Therefore, as shown in FIG. 22, it is conceivable to reduce heat generation by narrowing the width of the coil into a plurality of lanes 35, 36, and 37 in the spiral direction and minimizing the eddy current caused by lines of magnetic force penetrating the coil. However, in this case, since the length of the inner lane 37 is shorter and the resistance is smaller than that of the outer lane 35, the current concentrates on the inner lane 37 and the temperature rises. The present invention has been made in view of such a problem, and has as its object to provide an induction heating coil that can suppress heat generation near the center of the coil and prevent a rise in temperature.

[0004]

According to a first aspect of the present invention, there is provided an induction heating coil in which a strip-shaped conductor is spirally arranged on a substrate surface. The strip-shaped conductor near the center is thinned into a plurality of lanes in the spiral direction, and the lengths of all the lanes are made the same by rearranging the thinned lanes on the way. Here, as the rearrangement of the lanes, the following 2
One embodiment is preferred. First, one of the innermost lane and the outermost lane is cut off in the middle and disposed on the other side to conduct with each other. Second, the lane on the inner circumference side and the lane on the outer circumference side are cut off in the middle, respectively, so as to conduct each other. Also,
The range in which the strip-shaped conductor is thinned is several turns at least near the center of the spiral. Of course, it may be thinned over all turns.

According to a second aspect of the present invention, a band-shaped conductor at least near the center on the substrate surface is thinned into a plurality of lanes in a spiral direction, and the width of the inner lane of the thinned lane is changed to the outer lane. The electrical resistance of all lanes is made equal by making the width relatively smaller than the width of the lane.
According to a third aspect of the present invention, the strip-shaped conductor at least near the center on the substrate surface is thinned into a plurality of lanes in a spiral direction, and each lane including the thinned at least the inner peripheral lane is cut off on the way to connect a resistor. The electrical resistance of all lanes is made the same by making them conductive with each other. According to a fourth aspect of the present invention, the strip-shaped conductor at least near the center on the substrate surface is thinned in a spiral direction into a plurality of lanes, and a predetermined length of each lane including at least the thinned lane on the outer peripheral side is provided. The electrical resistance of all lanes is made the same by connecting the parallel resistance.

[0006]

According to the first, second, third and fourth aspects of the present invention, the strip conductor on the substrate surface is thinned into a plurality of lanes in the spiral direction. Eddy current is reduced, and heat generation near the center of the coil is suppressed. In the first invention, the length of all the lanes is the same when the inner lane passes through the outer circumference on the way or the lane on the outer circumference passes through the inner circumference on the way. Current flows through Second
In the invention, the width of the lane on the inner peripheral side is smaller than that of the outer peripheral side,
Since all lanes have the same electric resistance, current flows uniformly in each lane. In the third and fourth inventions, since the electrical resistance of all lanes is the same due to the resistance provided for each lane, a uniform current flows in each lane. As described above, in any of the inventions, a uniform current flows through each of the thinned lanes, so that the inner lane does not generate heat intensively.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an induction heating coil 1 according to an embodiment of the first invention. On the surface of the substrate 2, a band-shaped conductor 3 made of copper, silver, gold, aluminum or another conductive material having a small specific resistance is spirally disposed. The strip-shaped conductor 3 is thinned in the spiral direction into three lanes 5, 6, and 7 having the same width except for both ends 4 (only one end is shown).
As shown in FIG. 2, the first lane 5 on the outer peripheral side is cut at a point A on the way from the center end 4 to the outside in the spiral direction. The second lane 6 in the middle and the third lane 7 on the inner peripheral side are A in which the first lane 5 is cut.
It bends outward at the point and moves on the extension of the outer lane and the intermediate lane, respectively. Further, a new first lane 5a is disposed inside the moved third lane 7 and on an extension of the inner peripheral lane.

[0008] The end of the first lane 5 and the new first lane 5
The start end of the lane 5a is electrically connected to the back side of the substrate 2 by a jumper wire 8 as shown in FIG. Note that instead of using this jumper wire 8, FIG.
As shown in (2), conduction may be provided by a printed wiring pattern 9 formed on the back surface of the substrate 2 in advance. Alternatively, as shown in FIG. 5, the surface of the substrate 2 may be electrically connected by the heat-resistant coated wire 8a. Similarly, the lane is moved at two points B and C during one turn of the vortex of the induction heating coil 1. This kind of lane movement
It is performed over the entire length in the spiral direction. As a result,
The first lanes 5, 5a,... And the second lanes 6, 6a,.
And the third lanes 7, 7a,... Are all the same length,
It has the same electrical resistance.

Both ends 4 of the induction heating coil 1 having the above configuration.
When a high-frequency voltage is applied to the other lanes (not shown), the lanes 5, 5a,..., 6, 6a,..., 7, 7a,. , 6,6
, 7, 7a, ..., a high-frequency current flows uniformly, and an alternating magnetic field is formed in a direction orthogonal to the spiral direction of the induction heating coil 1. Then, a pan (not shown) placed in the magnetic field generates heat by Joule heat due to the eddy current, and cooking is performed.

An eddy current is generated in the band-shaped conductor 3 by the magnetic lines passing through the band-shaped conductor 3 among the magnetic lines forming the alternating magnetic field around the induction heating coil 1, and the band-shaped conductor 3 has a plurality of lanes 5, 5a,. 6, 6a,..., 7, 7a,..., The eddy current around the line of magnetic force is smaller than that of the conventional non-thinned induction heating coil (see FIG. 17). It is getting smaller. Therefore, heat generated by the eddy current is small. Also, the thinned lanes 5, 5a, ..., 6, 6a, ..., 7, 7a, ... have the same length and the same electric resistance, so that current concentrates on any of the lanes. And no local heat is generated. As a result, the present inventors have confirmed that the temperature near the center of the induction heating coil 1 can be reduced from the conventional 200 ° C. to about 110 ° C.

FIG. 6 shows an induction heating coil 1 according to another embodiment of the first invention. The strip-shaped conductor 3 arranged in a spiral state on the substrate 2 is thinned into five lanes 5, 5 ', 6, 7', 7 having the same width in the spiral direction. The outer lanes 5, 5 'and the inner lanes 7', 7 excluding the intermediate lane 6 are separated at one point A in the spiral direction. Then, as shown in FIG.
Are electrically connected to the innermost lane 7. The outer lane 5 ′ adjacent to the innermost lane 5 is also electrically connected to the inner lane 7 ′ adjacent to the outermost lane 7.
The method of conduction is performed by any of the methods shown in FIGS. As a result, all the lanes 5, 5 ', 6, 7' and 7 have the same electric resistance, and the operation and effect are the same as those in the embodiment of FIG. In this embodiment, since the lane is not bent and the lane is divided at one position, there is an advantage that the shape of the spiral is simplified.

FIG. 8 shows an induction heating coil 1 according to an embodiment of the second invention. The strip-shaped conductor 3 arranged in a spiral state on the substrate 2 has three lanes 5, 6, 7 in the spiral direction.
It is thinned. In this embodiment, lanes 5, 6, 7
However, as shown in FIG. 9, the lane width is the smallest in the inner lane 7 and becomes larger in the order of the intermediate lane 6 and the outer lane 5 as shown in FIG. As a result, all the lanes 5, 6, and 7 have the same electric resistance. Therefore, also in this embodiment, the eddy current due to the magnetic lines of force passing through the lanes 5, 6, and 7 is reduced, and the lanes 5, 6, and 7 are also reduced.
, The heat generated by the induction heating coil 1 is suppressed.

FIG. 10 shows an induction heating coil 1 according to an embodiment of the third invention. The strip-shaped conductor 3 arranged in a spiral state on the substrate 2 has three lanes 5, 6 in the spiral direction.
7 is thinned. Figure 1 shows the width of each lane 5,6,7
As shown in FIG. 1, the length in the spiral direction is the shortest in the inner lane 7 and the longest in the outer lane 5. However, each lane 5, 6, 7 is divided at one place,
On the back side, it is electrically connected by resistors R5, R6, and R7. Resistance R5, R of each lane 5, 6, 7
6 and R7, the resistance value of the inner lane 7 is the largest and the resistance value of the outer lane 5 is the smallest. As a result, the electrical resistance of each of the lanes 5, 6, and 7 is the same. Therefore, also in this embodiment, the eddy current due to the magnetic lines of force passing through the lanes 5, 6, and 7 is reduced, and the current in each of the lanes 5, 6, and 7 is uniform.
Heat generation is suppressed. The outer lane 5 does not need to be cut off in the middle, but in this case, the resistances R6 and R7 of the other lanes are determined based on the resistance of the outer lane 5.

FIG. 12 shows a strip-shaped conductor 3 of an induction heating coil according to a fourth embodiment of the present invention. The widths of the three lanes 5, 6 and 7 thinned in the spiral direction are the same, and the length in the spiral direction is the shortest in the inner lane 7 and the outer lane 5
Is the longest. However, the resistances R5, R6, and R7 are connected in parallel on the back surface of each of the lanes 5, 6, and 7 for a predetermined length. The combined resistance value of the conductors of predetermined lengths and the resistances R5, R6, R7 of the lanes 5, 6, 7 is the largest in the inner lane 7 and the smallest in the outer lane 5. As a result, the electrical resistance of each of the lanes 5, 6, and 7 is the same. Therefore, also in this embodiment, the eddy current due to the magnetic lines of force passing through the lanes 5, 6, and 7 is reduced, and the current in each of the lanes 5, 6, and 7 is uniform, so that the heat generation of the induction heating coil 1 is suppressed. . The resistance of each lane may be the same by adjusting the resistances R5 and R6 of the outer lane 5 and the intermediate lane 6 without providing the electric resistance R7 of the inner lane 7. 1 and 6,
In the induction heating coil 1 shown in FIGS. 8, 10 and 12, the lanes are thinned into a plurality of lanes over all the turns of the spiral. Good.

FIG. 13 shows the induction heating coil 1 described above.
Fig. 2 shows a rice cooker using the present invention. In this rice cooker, a bottomed container-shaped protection frame 13 is housed and fixed to a main body 12 to which a lid 11 is attached so as to be openable and closable, and a pot 14 is housed in the protection frame 13. In the protective frame 13, the first induction heating coil 1 is disposed at the center of the bottom outer surface, and the second induction heating coil 1a is disposed at the outer corner. A plurality of ferrites 15 are radially arranged below these coils 1 and 1a. As the first induction heating coil 1, any one of the induction heating coils shown in FIGS. 1, 6, 8, 10, or 12 is used. In addition, the second
As shown in FIG. 15, the induction heating coil 1a of FIG.
An annular flexible substrate 16 in which a strip-shaped conductor 17 is arranged in a spiral state is used.

The annular flexible substrate 16 is shown in FIG.
As shown in FIG. 4, the yield can be improved by removing the rectangular flexible substrate 16 'in a fan shape without waste. The fan-shaped flexible substrate 16 includes
The strip conductor 17 is formed in advance. This strip-shaped conductor 17
As shown in FIG. 16, the positions of both ends of the strip-shaped conductor 17 are previously shifted so that the strip-shaped conductor 17 is continuous in a spiral state when both ends of the flexible board 16 are aligned.
Instead, as shown in FIG. 17, both ends of the strip-shaped conductor 17 may be set at the same position, and the strip-shaped conductor 17 may be continuous in a spiral state when the both ends of the flexible substrate 16 are shifted. In any case, the abutting portions of the strip-shaped conductors 17 are electrically connected by other means such as soldering or eyelets as shown by dotted lines in the figure. The number of the abutting portions may be about three in relation to economic material removal.

The second induction heating coil 1a composed of the flexible substrate 16 connected in a ring as described above is
As shown in FIG. 15, the protective frame 13 is provided at a rounded corner on the outer periphery of the bottom and is appropriately held by an adhesive or the like. On the other hand, the rectangular first induction heating coil 1 is disposed and held at the bottom center of the protection frame 13. One end on the center side of the first induction heating coil 1 is connected to an inverter circuit 22 of an electric circuit described later, and the other end is connected to one end of the second induction heating coil 1a. The other end of the second induction heating coil 1a is connected to the DC power supply circuit 21.

FIG. 18 shows a circuit diagram of the electromagnetic induction heating device of the rice cooker. This device includes a DC power supply circuit 21, an inverter circuit 22, and a resonance circuit 23.
The DC power supply circuit 21 rectifies an AC voltage from an AC power supply 24 by a rectifier circuit 25 and smoothes the AC voltage by a coil 26 and a capacitor 27 to obtain a DC voltage. The inverter circuit 22 converts a DC voltage obtained by the DC power supply circuit 21 into a high-frequency voltage by a switching semiconductor 28 such as a transistor. The switching of the switching semiconductor 28 is controlled by an oscillation control circuit 29. The resonance circuit 23 includes a first induction heating coil 1 and a second induction heating coil 1a connected in series to the switching semiconductor 28 of the inverter circuit 22 and connected in series with each other. Resonant capacitor 3 connected in parallel to heating coils 1 and 1a
It consists of 0.

In the induction heating apparatus having the above-described configuration, the AC voltage of the AC power supply 24 is rectified by the rectifier circuit 25, and is smoothed by the coil 26 and the capacitor 27 to become a DC voltage. This DC voltage is converted into a high-frequency voltage by switching of the switching semiconductor 28. The high frequency voltage is applied to an LC resonance circuit including the first and second induction heating coils 1 and 1a and the capacitor 27. Thereby, the first induction heating coil 1
Further, an eddy current is generated in the pot 14 (see FIG. 13) by the alternating magnetic field generated in the second induction heating coil 1b, and as a result, the pot 14 generates heat by Joule heat, and rice is cooked. As described above, since the first induction heating coil 1 is thinned into three lanes to suppress heat generation, the substrate 2 and other peripheral components do not deteriorate. In addition, since the temperature of the center of the coil 1 is not as high as that of the conventional case, there is no need to arrange a heat shield or a heat radiator near the coil, and the structure of the rice cooker is simplified and downsized.

[0020]

As is clear from the above description, the first,
According to the second, third and fourth inventions, the strip-shaped conductor on the substrate surface is thinned into a plurality of lanes in the spiral direction,
Since the electric resistance of each lane is the same, the eddy current due to the lines of magnetic force penetrating each lane near the center of the coil is reduced, and a uniform current flows through each lane. As a result, the eddy current due to the lines of magnetic force penetrating through each lane is reduced, and the current is not concentrated on the lane on the inner peripheral side, heat generation near the coil center is suppressed, and deterioration of members around the coil can be prevented. In addition, it is not necessary to take heat shielding or heat radiation measures, and the structure of the device can be simplified and downsized.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an induction heating coil according to the first invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a sectional view taken along line II of FIG. 2;

FIG. 4 is a sectional view showing a modification of FIG. 3;

FIG. 5 is a sectional view showing another modification of FIG. 3;

FIG. 6 is a plan view showing another embodiment of the induction heating coil of the first invention.

FIG. 7 is a partially enlarged view of FIG. 6;

FIG. 8 is a plan view showing an embodiment of the induction heating coil of the second invention.

FIG. 9 is a partially enlarged view of FIG. 8;

FIG. 10 is a plan view showing an embodiment of the induction heating coil of the third invention.

11 is a partially enlarged view of FIG.

FIG. 12 is a partially enlarged plan view showing an embodiment of the induction heating coil of the fourth invention.

FIG. 13 is a schematic sectional view of a rice cooker provided with the induction heating coil of the present invention.

FIG. 14 is a plan view of a flexible substrate.

15 is an exploded perspective view of the induction heating coil of the rice cooker shown in FIG.

FIG. 16 is a front view showing a connection portion of a flexible substrate.

FIG. 17 is a front view showing a modification of FIG. 16;

FIG. 18 is an electric circuit diagram of a rice cooker provided with the induction heating coil of the present invention.

FIG. 19 is a plan view of a conventional induction heating coil.

FIG. 20 is a cross-sectional view showing lines of magnetic force around a conventional induction heating coil.

FIG. 21 is a plan view showing a conventional induction heating coil.

FIG. 22 is a plan view of a thinned conventional induction heating coil.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Induction heating coil, 2 ... Board, 3 ... Strip conductor, 5 ... Outer side lane, 6 ... Middle lane, 7 ... Inner side lane.

Claims (4)

(57) [Claims] 1. An induction heating coil in which a strip-shaped conductor is spirally arranged on a substrate surface, wherein the strip-shaped conductor at least near the center on the substrate surface is thinned into a plurality of lanes in a spiral direction. An induction heating coil characterized in that all lanes have the same length by rearranging thinned lanes on the way. 2. An induction heating coil in which a strip-shaped conductor is spirally arranged on a substrate surface, wherein the strip-shaped conductor at least near the center on the substrate surface is thinned into a plurality of lanes in a spiral direction. An induction heating coil characterized in that the width of the inner lane among the thinned lanes is made relatively smaller than the width of the outer lane so that all lanes have the same electric resistance. 3. An induction heating coil in which a strip-shaped conductor is spirally arranged on a substrate surface, wherein the strip-shaped conductor at least near the center on the substrate surface is thinned into a plurality of lanes in a spiral direction. An induction heating coil, characterized in that lanes including at least the inner lane on the thinner side are cut off in the middle and are electrically connected to each other via resistors, so that all lanes have the same electric resistance. 4. An induction heating coil in which a strip-shaped conductor is spirally arranged on a substrate surface, wherein the strip-shaped conductor at least near the center on the substrate surface is thinned into a plurality of lanes in a spiral direction. An induction heating coil wherein the electrical resistance of all lanes is made the same by connecting a parallel resistance between predetermined lengths in the middle of each lane including at least the outermost lane which has been thinned.