Coil substrate, inductive heating cooker, or contactless power supply device

Abstract

To suppress loss of a coil when a high-frequency current is flown and at the same time prevent the coil from generating heat unevenly.SOLUTION: The present invention relates to a coil substrate formed by laminating a plurality of pattern layers in which a coil pattern is formed. The coil substrate has a plurality of current route patterns formed by serially connecting the coil patterns and connecting an input terminal and an output terminal to each other. A part or all of the current route patterns divide in parallel in the middle from the input terminal to the output terminal and join together from the division part to the output terminal.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a coil substrate used in an induction heating cooker or a non-contact power supply. [Background technology]

[0002] A conventional induction heating cooker, as shown in Patent Document 1, has a structure in which an eddy current is generated on the surface of an object to be heated by passing a current through a thin coil formed on a printed circuit board, thereby inductively heating the object to be heated. In this type of cooking device, there is a need to pass a high-frequency current through the thin coil in order to improve heating efficiency and reduce the size of the coil.

[0003] However, when a high-frequency current is passed through a coil, magnetic flux is concentrated at the inner and outer periphery of the coil, causing a proximity effect and increasing AC resistance. As a result, there is a problem that losses at the inner and outer periphery of the coil and the amount of heat generated from these losses increase. Furthermore, since heat does not escape as easily in a thin coil as in a wound coil, if heat is generated unevenly, for example, at the inner circumference due to high-frequency current, the inner diameter side may overheat, which may lead to failure.

[0004] Such problems also commonly occur when a high-frequency current is passed through an electromagnetic induction coil used in contactless power supply. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent application No. 2016-77445 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present invention has been made to solve all of the above-mentioned problems at once, and its objective is to suppress coil losses when high-frequency current is passed through it, while at the same time avoiding uneven heat generation in one part of the coil. [Means for solving the problem]

[0007] In other words, the coil board of the present invention is a coil board formed by stacking a plurality of pattern layers on which coil patterns are formed, and is formed by connecting the coil patterns in series. It has a plurality of current path patterns connecting input terminals and output terminals, and some or all of the current path patterns branch off in parallel midway from the input terminal to the output terminal, and merge between the branching points and the output terminal.

[0008] With a coil substrate configured in this manner, in areas where the AC resistance is high, the current path pattern can be branched in parallel to reduce the flow of current, thereby reducing coil loss and preventing uneven heat generation in those areas.

[0009] The pattern layer is either a first pattern layer that is connected to the other pattern layer on the output terminal side via a conductor formed on the inner periphery of the coil pattern, or a second pattern layer that is connected to the other pattern layer on the output terminal side via a conductor formed on the outer periphery of the coil pattern, and it is preferable that a part or all of the current path pattern branches off at the first pattern layer and merges at the other pattern layer. In this case, a branched current path pattern is provided in the inner circumference where the proximity effect is large and heat tends to accumulate, thereby reducing the current flowing in the inner circumference, more effectively reducing losses and suppressing overheating of the inner circumference.

[0010] The branched current path patterns may preferably join together in the second pattern layer. In this way, the current path pattern can be concentrated on the inner circumference, thereby achieving equal heating between the inner circumference, where heat tends to accumulate, and the outer circumference, where heat does not accumulate as easily as the inner circumference, and extending the life of the coil.

[0011] When a path from a branch point to a junction point is defined as a branch path among all paths of a current path pattern, the path lengths of the branch paths branched from the same current path pattern are preferably equal. In this way, the impedance of each branch path branched off from the same junction path can be made uniform.

[0012] It is preferable that a plurality of the pattern layers are interposed between the first pattern layer provided with a branching portion and the second pattern layer provided with a joining portion. This allows for a flexible arrangement of parallel connections while merging and branching.

[0013] The width of the current path pattern from branching to joining is narrower than the width of the current path pattern before branching or after joining. In this way, the width of the current path pattern is narrow in the area where the magnetic flux is concentrated, so that the coil loss due to the skin effect can be reduced and uneven heat generation in that area can be avoided.

[0014] Further, an induction heating cooker or a non-contact power supply device using the above-described coil substrate is also one embodiment of the present invention. Effect of the Invention

[0015] According to the present invention configured in this manner, it is possible to suppress loss in the coil when high-frequency current is passed through it, while at the same time preventing uneven heat generation in one part of the coil. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing an overall configuration of an induction heating cooker according to an embodiment of the present invention; [Diagram 2]FIG. 4 is a schematic diagram showing a laminated structure of the coil substrate in the embodiment. [Diagram 3] FIG. 2 is a plan view illustrating a schematic configuration of a coil substrate in the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing wiring of a coil substrate in the embodiment. [Diagram 5] 5A and 5B are schematic diagrams showing modified examples of wiring of the coil substrate in the embodiment. [Figure 6] 5A and 5B are schematic diagrams showing modified examples of wiring of the coil substrate in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of an electromagnetic induction coil according to the present invention will be described with reference to the drawings.

[0018] <Configuration of induction heating cooker> The induction heating cooker 100 of this embodiment inductively heats an object to be heated, which is a cooking utensil such as a cooking pot placed on a top plate 1 (tabletop), and is configured so that the object to be heated can be placed anywhere on the top plate and heated.

[0019] Specifically, as shown in FIG. 1, the induction heating cooker 100 includes a top plate 1 on which an object to be heated is placed, a plurality of heating coils 2 for heating the object to be heated, an inverter circuit 3 for supplying alternating current to the heating coils 2, and a control device 4 for controlling the inverter circuit 3.

[0020] The top plate 1 has a flat mounting surface on the front side on which an object to be heated is placed, and is a flat plate made of an electrically insulating material such as glass or ceramic.

[0021] The heating coil 2 is disposed on the rear (lower) side of the top plate 1, and here, multiple heating coils 2 are disposed in a two-dimensional array (vertical and horizontal matrix) in a plan view, as shown in Fig. 1. When a current is passed through the heating coil 2, a magnetic flux is generated toward the top plate 1, which generates an eddy current on the surface of an object to be heated placed on the top plate, thereby inductively heating the object to be heated. Here, as viewed from the heating coil 2, the direction toward the top plate 1 is defined as the upward direction, and the opposite direction is defined as the downward direction.

[0022] The heating coil 2 is a thin coil in the form of a sheet provided on a substrate, specifically formed as a printed circuit board (coil substrate 20) made of photoresist or the like. Here, each of the multiple heating coils 2 has the same shape and size, but the shape and size may be changed as appropriate. The specific configuration of the coil substrate 20 will be described later.

[0023] The inverter circuit 3 converts the AC voltage supplied from the power source into an arbitrary driving frequency and outputs it to the heating coil 2. The inverter circuit 3 here is of a full-bridge type using switching elements, but a half-bridge type may also be used.

[0024] The control device 4 physically comprises a CPU, a memory, an input means, etc., and functionally controls the inverter circuit 3 by the CPU and its peripheral devices working together in accordance with the program stored in the memory.

[0025] <Specific Configuration of Coil Substrate 20> As shown in FIG. 2, the coil substrate 20 has an input terminal 21 to which AC power is input from the inverter circuit 3, an output terminal 22 to be connected to a resonant capacitor or the like, and a plurality of current path patterns L connecting the input terminal 21 and the output terminal 22.

[0026] 2 and 3, the coil substrate 20 is a printed circuit board formed by laminating a plurality of pattern layers (four layers in this example) on which the coil patterns CP are formed. In this manner, a plurality of coil patterns CP are formed by being stacked coaxially in the heating coil 2. Note that it is not necessary for all of these coil patterns CP to be stacked coaxially, and they may be stacked with a shift. Further, the pattern layers are insulated by insulating materials provided between the layers, but are partially electrically connected by conductors 23 (through holes) provided on the inner and / or outer periphery of the coil pattern CP.

[0027] In this specification, the multiple laminated pattern layers will be referred to as the first layer, second layer, third layer, . . . in order from the layer closest to the top plate 1. In the present embodiment, the four pattern layers are connected in order from the first layer to the fourth layer, as shown in Fig. 2. An input terminal 21 is provided on the outer periphery of the coil pattern CP of the first layer, and an output terminal 22 is provided on the outer periphery of the coil pattern CP of the fourth layer.

[0028] The pattern layers are divided into two types: a first pattern layer PL1 and a second pattern layer PL2. The first pattern layer PL1 is connected to other pattern layers on the output terminal 22 side at the inner periphery of the coil pattern CP. The second pattern layer PL2 is connected to other pattern layers on the output terminal 22 side at the outer periphery of the coil pattern CP.

[0029] In this embodiment, the first and third layers are configured as the first pattern layer PL1, and the second and fourth layers are configured as the second pattern layer PL2. The coil pattern CP of the first layer (third layer) which is the first pattern layer PL1 and the coil pattern CP of the second layer (fourth layer) which is the second pattern layer PL2 connected to the output terminal side of the first layer (third layer) are connected in series via conductors 23a formed on the inner periphery of each coil pattern CP. In addition, the second layer coil pattern CP, which is the second pattern layer PL2, and the third layer coil pattern CP, which is the first pattern layer PL1 connected to the output terminal side of the second layer, are connected in series via conductors 23b formed on the outer periphery of each coil pattern CP.

[0030] As shown in Fig. 2, the current path pattern L is formed by connecting the coil patterns CP of each pattern layer in series via a conductor 23. In Fig. 2, a plurality of current path patterns L are collectively represented by a single line.

[0031] As shown in Fig. 3, a plurality of coil patterns CP are formed in parallel on each pattern layer. The coil pattern CP of this embodiment has a spiral shape, and the plurality of spiral shapes are wound around a common center so as not to overlap with each other. Note that the coil pattern CP may be made up of a plurality of coil elements having a roughly rectangular shape in plan view as shown in Fig. 2, or may be made up of a plurality of coil elements having a circular shape in plan view, and the shape of the coil elements is not limited to these. Furthermore, although the number of turns of the coil pattern CP in this embodiment is seven, this number of turns may be changed as appropriate.

[0032] 3 and 4, a part or all of the current path pattern L in this embodiment branches midway from the input terminal 21 to the output terminal 22, and merges between the branch point 24 and the output terminal 22. Of the entire paths of the current path pattern L, the path from the branch point 24 to the junction point 25 is referred to as a branch path, and the other paths are referred to as a junction path.

[0033] In this embodiment, the branch point 24 is provided in the first layer (first pattern layer PL1) of the four pattern layers of the coil substrate 20, and the junction point 25 is provided in the fourth layer (second pattern layer PL2). The branch point 24, the junction point 25, the branch path, and the junction path will be described in detail below.

[0034] In this embodiment, the branching point 24 and the merging point 25 are provided in the intermediate portion between the inner periphery and the outer periphery of the coil pattern CP of the first layer (first pattern layer PL1) or the fourth layer (second pattern layer PL2), respectively. Here, the intermediate portion refers to the intermediate portion of the spiral shape of the coil pattern CP of the pattern layer, and may be, for example, a turn other than the innermost or outermost turn among the total number of turns of the coil pattern CP. For example, in the case of a 10-turn coil pattern CP, it is preferable that the intermediate portion is located 4 to 6 turns from the outer side. The position of the intermediate portion may be different between the first pattern layer PL1 and the second pattern layer PL2.

[0035] Specifically, in the current path pattern L of this embodiment, as shown in Fig. 3 and Fig. 4, five junction paths are provided in parallel (1a, 1b, ..., 1e), and each junction path branches into two, so that ten branch paths are provided in parallel (1a1, 1a2, 1b1, 1b2, ..., 1e2). Note that the third, fourth, and fifth current path patterns L (1c, 1d, 1e) are omitted in Fig. 4. In this embodiment, the first layer, which is the top layer, and the fourth layer, which is the bottom layer, are provided with junction paths and branch paths, but the second and third layers, which are intermediate layers, are provided with only branch paths.

[0036] As mentioned above, the total number of turns of the coil pattern CP in each pattern layer is 7, and in each current path pattern L (1a, 1b, etc.) in Figure 4, the number after the - (hyphen) indicates the cumulative number of turns of the coil pattern CP counted from the input terminal 21 side.

[0037] In addition, the branch point 24 is provided between the third and fourth turns from the outer periphery of the coil pattern CP of the first layer (first pattern layer PL1), and the merging point 25 is provided between the third and fourth turns from the outer periphery of the coil pattern CP of the fourth layer (second pattern layer).

[0038] It is preferable that the path lengths of the branch paths branched from one junction path are uniform. Specifically, uniform path lengths mean that the variation in each path length is 5% or less. In addition, when a high-frequency current of 50 kHz or more is supplied to the heating coil 2, it is preferable that the variation in each path length is 1% or less.

[0039] In this embodiment, in order to equalize the path length of each branch path, the arrangement of each branch path is different in each of the multiple laminated pattern layers. Specifically, the arrangement order of each branch path is reversed between the first pattern layer PL1 and the second pattern layer PL2. For example, when the branch paths are arranged in the order of 1a1, 1a2, 1b1, 1b2, ..., 1e2 from the outside of the coil pattern CP in the first pattern layer PL1, the branch paths are arranged in the order of 1e2, 1e1, 1d2, 1d1, ..., 1a1 from the outside of the coil pattern CP in the second pattern layer PL2.

[0040] In this embodiment, an adjustment path is provided on the inner periphery of the coil pattern CP for adjusting the path length of the current path pattern L. This adjustment path may be provided on the outer periphery of the coil pattern CP.

[0041] The width of the branch path is preferably narrower than the width of the merging path. Specifically, in this embodiment, the total width of the branch paths branched from one merging path is designed to be equal to the width of one merging path before branching (or after merging). Specifically, the equivalent width is preferably about ±1% of the ratio of the total width of the branch paths to the width of such a merging path. Note that the width of the merging path and the width of the branch paths may be equal.

[0042] <Effects of this embodiment> According to the induction heating cooker 100 configured as described above, in the portion where the AC resistance of the current path pattern L is large, the current flowing through the current path pattern L can be reduced by branching it in parallel, so that the loss in the coil can be reduced and uneven heat generation in that portion can be prevented.

[0043] In addition, since the branched current path pattern L is provided at the inner circumference of the coil pattern CP where the proximity effect is large and the AC resistance is large and heat is likely to accumulate, it is possible to suppress overheating of the inner circumference while further enhancing the effect of reducing loss by branching the current path pattern L.

[0044] Furthermore, in the heating coil 2 of this embodiment, multiple coil patterns CP are stacked coaxially, and the magnetic flux density is increased at the inner and outer circumferential parts of the coil pattern CP by the amount of stacking. Therefore, providing the current path pattern L in this manner is highly effective in reducing losses and suppressing overheating. Furthermore, among the multiple stacked pattern layers, the middle layers (third and fourth layers) are more likely to accumulate heat than the top layer (first layer) and bottom layer (fourth layer), and a branch path is provided in these layers, which makes it possible to prevent overheating of the middle layers.

[0045] In this embodiment, a branch point 24 is provided in the first pattern layer PL1 (first layer), and a junction point 25 is provided in the second pattern layer PL2 (fourth layer) arranged closer to the output terminal 22 than the first layer, so that a branch path can be provided biased toward the inner periphery of the coil pattern CP, and the influence of the proximity effect is large, and the current flowing in the inner periphery where heat is likely to accumulate can be reduced, so that overheating of the inner periphery can be suppressed while reducing losses more effectively. Also, the inner periphery where heat is likely to accumulate and the outer periphery where heat is not as likely to accumulate as the inner periphery can be made uniform in temperature, thereby extending the life of the electromagnetic induction coil.

[0046] In addition, since the path lengths of the branch paths branched off from one merging path are equal, the impedances of the branch paths can be made uniform.

[0047] Since the width of the branch path is narrower than the width of the junction path, it is possible to reduce the loss of the coil due to the skin effect and to prevent uneven heating in that portion.

[0048] <Modified embodiment> In the above embodiment, the current path pattern L branches in the first pattern layer and joins in the second pattern layer, but the present invention is not limited to this. The current path pattern L may branch in the second pattern layer or join in the first pattern layer. It is sufficient that the current path pattern L branches in a portion with high AC resistance, thereby reducing the current flowing in the branched path.

[0049] The coil substrate 20 in the above embodiment is formed by laminating four pattern layers, but the number of laminated pattern layers may be two as shown in FIG. 5, or any number more than one.

[0050] In the above embodiment, intermediate layers (second and third layers) not having a branch point 24 or a junction point 25 are interposed between the first layer (first pattern layer PL1) having a branch point 24 and the fourth layer (second pattern layer PL2) having a junction point 25, but two or more such intermediate layers may be provided.

[0051] Furthermore, when three or more pattern layers are stacked, one or more pattern layers may be provided closer to the input terminal than the first pattern layer PL1 in which the branch point 24 is provided, or closer to the output terminal than the second pattern layer PL2 in which the junction point 25 is provided. In other words, pattern layers without a branch path may be stacked. If a branch path is provided in any of the multiple stacked pattern layers, the coil loss can be reduced.

[0052] Although the branch path in the above embodiment is provided to be located on the inner periphery of the coil pattern CP, it may be provided to be located on the outer periphery. Since the magnetic flux is concentrated also on the outer periphery of the coil and the AC resistance is large due to the proximity effect, by branching the current path pattern L in parallel on the outer periphery of the coil pattern CP to reduce the current flow, it is possible to reduce the loss of the coil and prevent uneven heat generation in that part.

[0053] In the current path pattern L of the above embodiment, the number of merging paths and the number of branching paths are designed to be five and ten, respectively, but the number of paths connected to the input terminal 21 and the output terminal 22 and the number of paths branched at the branch point 24 may be changed as appropriate. Specifically, the current path pattern L may be branched at the branch point 24 into three or more paths.

[0054] In the above embodiment, the multiple current path patterns L branch off at the middle of the same pattern layer and merge at the same pattern layer, but each current path may be separated or merged independently, for example, may branch off or merge at different pattern layers. If the current path pattern L branches off at a portion of the coil substrate 20 where the AC resistance is high, it is possible to prevent uneven heat generation in a part of the coil while suppressing the loss of the coil.

[0055] Although each current path pattern L in the above embodiment branches and merges once between the input terminal 21 and the output terminal 22, it may branch and merge multiple times between the input terminal 21 and the output terminal 22. For example, as shown in Fig. 6, the current path pattern L may separate and merge twice, such as branching at a middle part of the first layer (first pattern layer PL1), merging at a middle part of the second layer (second pattern layer PL2), branching again at a middle part of the third layer (first pattern layer PL1), and merging again at a fourth layer (second pattern layer PL2). For example, when four or more pattern layers are stacked, a branch path can be provided in the inner periphery of the coil pattern CP of each pattern layer by configuring the current path pattern L branched in each first pattern layer PL1 to join in the second pattern layer PL2 on the output terminal 22 side (below) as viewed from the first pattern layer PL1. This reliably reduces the current flowing in the inner periphery and reduces losses, while achieving uniform heating between the inner periphery, where heat is likely to accumulate, and the outer periphery, where heat is not as likely to accumulate as in the inner periphery, and thus extending the life of the coil.

[0056] Moreover, the current path pattern L that has once branched may branch further.

[0057] In the above embodiment, the input terminal 21 is provided on the first layer on the top plate 1 side, and the output terminal 22 is provided on the bottom fourth layer, but the arrangement of the input terminal 21 and the output terminal 22 may be reversed.

[0058] In the above embodiment, the first to fourth pattern layers are connected in order from the layer closest to the top plate 1, but the connection order of each pattern layer may be changed as appropriate. Specifically, the pattern layers may be connected in the order of the first layer → the third layer → the second layer → the fourth layer, while leaving the positions of the input / output terminals 21 and 22 as in the above embodiment. In this case, the first and second layers become the first pattern layer PL1, and the third and fourth layers become the second pattern layer PL2.

[0059] The coil substrate described in the above embodiment may be used in a contactless power supply device.

[0060] Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0061] 100...Induction heating cooker 1 Top plate 2. Heating coil 20 Coil substrate 21 Input terminal 22 Output terminal 23 Conductor 23a...Conductor 23b...Conductor 24 Branch point 25 Junction 3. Inverter circuit 4. Control equipment PL1: First pattern layer PL2: Second pattern layer L Current path pattern CP coil pattern

Claims

1. A coil substrate formed by laminating a plurality of pattern layers on which coil patterns are formed, The coil patterns are connected in series, and the coil patterns have a plurality of current path patterns connecting input terminals and output terminals, a coil substrate, wherein a part or all of the current path patterns branch in parallel midway from the input terminal to the output terminal, and merge between the branching points and the output terminal.

2. the pattern layer is either a first pattern layer that is connected to another pattern layer on the output terminal side at an inner periphery of the coil pattern, or a second pattern layer that is connected to another pattern layer on the output terminal side at an outer periphery of the coil pattern, The coil substrate according to claim 1 , wherein a part or all of the current path pattern branches off in the first pattern layer and joins with another of the pattern layers.

3. The coil substrate according to claim 2 , wherein the branched current path patterns meet in the second pattern layer.

4. If a path from a branch point to a junction point among the entire paths of the current path pattern is defined as a branch path, 2. The coil substrate according to claim 1, wherein the branched paths of the same current path pattern are configured to have equal path lengths.

5. 4. The coil substrate according to claim 3, wherein a plurality of said pattern layers are interposed between said first pattern layer having a branching portion and said second pattern layer having a joining portion.

6. 2. The coil substrate according to claim 1, wherein a width of the current path pattern from branching to joining is narrower than a width of the current path pattern before branching or after joining.

7. An induction heating cooker or a non-contact power supply device using the coil substrate according to any one of claims 1 to 6.

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