JP7464831B2 - rice cooker - Google Patents

Description

The present invention relates to a rice cooker equipped with an induction heating coil and a circuit board.

Some rice cookers are of the electromagnetic induction heating type, which uses an induction heating coil as a heating means. In these electromagnetic induction heating type rice cookers, the magnetic field generated by the induction heating coil does not only act on the heating element and cause eddy currents to flow, but can also act on other electronic components and cause eddy currents to flow. For example, a circuit board on which various electronic components are mounted can generate radiated noise when it is subjected to the magnetic field generated by the induction heating coil.

It has therefore been proposed to place a shielding member such as a metal plate between the induction heating coil and the circuit board to suppress the generation of noise. In the rice cooker disclosed in Patent Document 1, a shielding member made of a metal plate such as an aluminum plate 76 is placed between position 71 where the connection terminal of the IH coil is located and filter board 41 where noise capacitor 72 and power supply terminals are located, which are located inside rear projection 26. This makes it possible to reduce noise leakage to the outside.

JP 2014-200516 A

As mentioned above, in order to suppress noise generated between the induction heating coil and the circuit board, it is common to provide a separate shielding member such as a metal plate.

The present invention aims to provide a rice cooker that can reduce noise generated between the induction heating coil and the circuit board without the need for a separate component to suppress the noise.

A rice cooker according to one aspect of the present invention includes a housing, an inner pot disposed inside the housing, an induction heating coil disposed on the outer surface of the inner pot, and a circuit board disposed outside the inner pot inside the housing and having a circuit pattern on the side facing the induction heating coil. In this rice cooker, a conductive pattern is provided on the surface of the circuit board on which the circuit pattern is provided, at least partially covering a noise generating portion of the circuit pattern. In this rice cooker, the conductive pattern is formed in a portion located between the induction heating coil and the noise generating portion.

In the rice cooker according to one aspect of the present invention described above, at least one of the noise generating parts may be an AC circuit.

In the rice cooker according to one aspect of the present invention described above, at least one of the noise generating parts may be an inverter circuit.

In the rice cooker according to one aspect of the present invention described above, at least one of the noise generating parts may be a switching power supply circuit.

A rice cooker according to one aspect of the present invention includes a housing, an inner pot disposed inside the housing, an induction heating coil disposed on an outer surface of the inner pot, and a circuit board disposed outside the inner pot inside the housing and having a circuit pattern on the side facing the induction heating coil. In this rice cooker, a conductive pattern is provided on the surface of the circuit board on which the circuit pattern is provided, the conductive pattern covering at least a portion of the noise generating portion in the circuit pattern, and the conductive pattern overlaps at least a portion of the noise generating portion.

As described above, according to one aspect of the present invention, the rice cooker can reduce noise without providing a separate component for suppressing noise generated between the induction heating coil and the circuit board.

1 is a perspective view showing the external configuration of a rice cooker according to an embodiment of the present invention; FIG. 2 is a cross-sectional view showing an internal configuration of the rice cooker shown in FIG. 2 is a circuit diagram showing the configuration of various circuits formed on a circuit board provided in the rice cooker shown in FIG. 1 . 2 is a schematic diagram showing a circuit pattern formed on a surface of a circuit board provided in the rice cooker shown in FIG. 1 . FIG. 5 is a schematic diagram showing the circuit pattern shown in FIG. 4 in which AC circuit patterns are color-coded. FIG. 5 is a schematic diagram showing the circuit pattern shown in FIG. 4 in which the inverter circuit pattern is color-coded; FIG. 5 is a schematic diagram showing the circuit pattern shown in FIG. 4 in which the switching power supply circuit pattern is color-coded; FIG. 5 is a schematic diagram illustrating a first shield pattern and a second shield pattern in different colors in the circuit pattern illustrated in FIG. 4. 5 is a schematic diagram showing the circuit patterns shown in FIG. 4 that are covered by a shield pattern in different colors; FIG. 1 is a graph showing the results of a noise measurement test carried out in an example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

In this embodiment, an induction heating type rice cooker 1 (hereinafter referred to as rice cooker 1) will be used as an example of a rice cooker according to the present invention.

(Overall configuration of rice cooker)
First, the overall configuration of a rice cooker 1 according to the present embodiment will be described. Fig. 1 shows the external appearance of the rice cooker 1. Fig. 2 shows the internal configuration of the rice cooker 1. The rice cooker 1 is mainly composed of a main body 10 and a lid 50. The lid 50 covers the upper opening of the main body 10 in an openable and closable manner.

The main body 10 mainly includes a housing 11, an inner pot 12, an opening/closing lever 51, a hinge section 52, an induction heating coil 13, a circuit board 21, a heat sink 22, a power plug 41, and a cord reel 42. In the following description of the rice cooker 1, the side on which the opening/closing lever 51 is provided is referred to as the front side of the rice cooker 1, and the side on which the hinge section 52 is provided is referred to as the rear side of the rice cooker 1.

The housing 11 mainly constitutes the outer shape of the main body 10. Inside the housing 11, the inner pot 12, the induction heating coil 13, the circuit board 21, the heat sink 22, and the cord reel 42 are housed.

The inner pot 12 is a bowl-shaped pot that opens upward. The inner pot 12 is made of a multi-layer body (clad material) of various aluminum alloys and stainless steel alloys. The inner pot 12 can be induction heated by the induction heating coil 13.

The opening/closing lever 51 is located on the front side of the rice cooker 1. The opening/closing lever 51 is configured to be able to swing up and down. When the user swings the opening/closing lever 51 downward, the engagement between the lid body 50 and the main body 10 is released, and the lid body 50 opens.

The hinge portion 52 is located on the opposite side of the opening/closing lever 51 (i.e., the rear side of the rice cooker 1). The hinge portion 52 attaches the lid body 50 to the main body 10 so that the lid body 50 can rotate freely relative to the main body 10. The hinge portion 52 biases the lid body 50 in the opening direction. The hinge mechanism 150 is located above the rear side of the main body 10.

The induction heating coil 13 is an induction heating source that inductively heats the inner pot 12 and is disposed on the bottom wall and the lower end of the side wall of the outer surface of the inner pot 12.

The circuit board 21 is disposed at the lower rear side inside the housing 11. The circuit board 21 is formed of a printed wiring board or the like. That is, the circuit board 21 has a circuit pattern formed of a conductive material on at least one of the front and back surfaces of an insulating board. As described below, the circuit board 21 has circuit patterns formed thereon that have various functions such as an AC power supply, an inverter, and a switching power supply.

As shown in FIG. 2, the circuit board 21 is arranged so that the board surface is aligned in a substantially vertical direction. In other words, the circuit board 21 is placed vertically. Specifically, the circuit board 21 is arranged so as to face the outer peripheral surface (back surface) of the rear side of the inner pot 12. Note that, since the induction heating coil 13 is attached to the outer surface of the lower end of the side wall of the inner pot 12, the circuit board 21 is also arranged so as to face the induction heating coil 13.

The circuit board 21 has a circuit pattern on the surface facing the induction heating coil 13. Note that a circuit pattern may also be formed on the surface of the circuit board 21 opposite the side facing the induction heating coil 13. In the following, for convenience, the surface of the circuit board 21 facing the induction heating coil 13 is referred to as the front surface 21A, and the surface opposite the side facing the induction heating coil 13 is referred to as the back surface.

The heat sink 22 is a component that efficiently exchanges heat with the outside air. The heat sink 22 is mounted on the surface 21A of the circuit board 21. Note that various electronic components other than the heat sink 22 are mounted on the surface 21A of the circuit board 21.

The power plug 41 is provided at the end of the power cord. When the power cord is stored in the cord reel 42, the power plug 41 is located at the lower end on the rear side of the main body 10 (see Figure 1).

The cord reel 42 includes a power cord and an automatic winding mechanism. The cord reel 42 is located at the rearmost part of the housing 11. As shown in FIG. 2, the cord reel 42 is located so as to face the rear surface of the circuit board 21.

The lid 50 is rotatably attached to the main body 10 via the hinge 52.

(Circuit board configuration)
Next, a detailed description will be given of the configuration of the circuit board 21. An example of various circuits formed on the circuit board 21 is shown in FIG.

As shown in FIG. 3, the circuit board 21 is mainly provided with an AC power supply 31, an AC circuit 32 (noise generating section), a filter circuit 33, an inverter circuit 34 (noise generating section), a switching power supply circuit 35 (noise generating section), and a diode bridge 36.

Of these circuit elements, the AC circuit 32, the inverter circuit 34, and the switching power supply circuit 35 can be noise sources. When these noise sources are more strongly affected by the magnetic field generated by the induction heating coil, the noise generation becomes more noticeable.

Therefore, the circuit board 21 has a shield pattern (conductive pattern) on the surface 21A on which various circuit patterns are provided, which at least partially covers the noise generating parts of the circuit patterns. The shield pattern is made of a conductive material (conductor). In this embodiment, the shield pattern is made of a thin metal film (e.g., copper foil) that constitutes the various circuit patterns on the circuit board 21.

Figure 4 shows an example of a circuit pattern formed on the surface 21A (the surface facing the induction heating coil 13) of the circuit board 21. In this embodiment, the circuit pattern on the surface 21A of the circuit board 21 is mainly formed of a first conductor layer 71 and a second conductor layer 72. The second conductor layer 72 is formed on the upper layer of the first conductor layer 71. The first conductor layer 71 and the second conductor layer 72 are formed so as to partially overlap. The portion where the first conductor layer 71 and the second conductor layer 72 overlap is called an overlapping portion 73. An insulating layer (not shown) is provided between the first conductor layer 71 and the second conductor layer 72. The first conductor layer 71 and the second conductor layer 72 are partially conductive through a conductor via or the like provided in the overlapping portion 73.

The circuit pattern shown in FIG. 4 includes circuit elements such as an AC power supply 31, an AC circuit 32, a filter circuit 33, an inverter circuit 34, a switching power supply circuit 35, and a diode bridge 36.

In FIG. 5, the pattern of the AC circuit 32 among the circuit patterns on the circuit board 21 is shown in different colors. In the example shown in FIG. 5, the AC circuit 32 is provided on the left side of the front surface 21A of the circuit board 21. With reference to FIGS. 4 and 5, it can be seen that the AC circuit 32 is mainly formed of the first conductor layer 71 and the second conductor layer 72.

In FIG. 6, the pattern of the inverter circuit 34 among the circuit patterns on the circuit board 21 is shown in different colors. In the example shown in FIG. 6, the inverter circuit 34 is provided from the center to the right side on the front surface 21A of the circuit board 21. With reference to FIGS. 4 and 6, it can be seen that the inverter circuit 34 is mainly formed by the first conductor layer 71, the second conductor layer 72, and the overlapping portion 73. As shown in FIG. 3, the inverter circuit 34 is connected to the induction heating coil 13.

In FIG. 7, the pattern of the switching power supply circuit 35 among the circuit patterns on the circuit board 21 is shown in different colors. In the example shown in FIG. 7, the switching power supply circuit 35 is provided mainly on the lower left side from the center on the surface 21A of the circuit board 21. With reference to FIG. 4 and FIG. 7, it can be seen that the switching power supply circuit 35 is mainly formed of the first conductor layer 71.

In FIG. 8, the shield patterns among the circuit patterns on the circuit board 21 are shown in different colors. In the example shown in FIG. 8, the shield pattern is composed of a first shield pattern 61 and a second shield pattern 62. The first shield pattern 61 is connected to the reference potential (GND) in the circuit board 21. On the other hand, the second shield pattern 62 is not connected to the reference potential (GND) in the circuit board 21. With reference to FIG. 4 and FIG. 8, it can be seen that the first shield pattern 61 and the second shield pattern 62 are formed in the second conductor layer 72.

In the area where the first shield pattern 61 and the second shield pattern 62 are formed, a part of the AC circuit 32, a part of the inverter circuit 34, and a part of the switching power supply circuit 35, which may be noise sources, are formed in the area corresponding to the overlapping portion 73. These are formed of the first conductor layer 71.

In FIG. 9, the shielded portions of the circuit pattern by the first shield pattern 61 or the second shield pattern 62 are shown in different colors. In the example shown in FIG. 9, the first shield pattern 61 that covers part of the AC circuit 32 is indicated by 61a. In the example shown in FIG. 9, the first shield pattern 61 that covers part of the switching power supply circuit 35 is indicated by 61b. In the example shown in FIG. 9, the second shield pattern 62 that covers part of the inverter circuit 34 is indicated by 62a.

In this embodiment, among the circuit patterns that can be noise sources, at least a portion of the AC circuit 32 and the switching power supply circuit 35 are covered with a first shield pattern 61 connected to a reference potential. This makes it possible to suppress mutual interference between the radiation noise of the AC circuit 32 and the switching power supply circuit 35 and the radiation noise of the induction heating coil 13, and to reduce the level of noise leaking to the outside. Since the first shield pattern 61 is the reference potential (GND) of the circuit board 21, the shield pattern can absorb or reflect the radiation noise from the induction heating coil 13. This further improves the effect of suppressing leakage of radiation noise to the outside of the housing 11.

In addition, in this embodiment, at least a portion of the inverter circuit 34, which is one of the circuit patterns that can be a noise source, is covered by a second shield pattern 62 that is not connected to the reference potential. This makes it possible to prevent mutual interference between the radiation noise of the inverter circuit 34 and the radiation noise of the induction heating coil 13, thereby reducing the level of noise leaking to the outside.

(Example)
A test was conducted to measure noise leaking to the outside in the rice cooker 1 according to the present embodiment. The conditions for the noise measurement test were as follows.

(Test condition)
The noise measurement test was conducted in accordance with the measurement methods stipulated in Chapter 2 of the Electrical Appliance and Material Safety Law and the Radio Law. The equipment used to measure noise is as follows:
Anechoic chamber, field intensity meter, preamplifier, log periodic antenna, biconical antenna

As a comparative example, a similar noise measurement test was conducted using rice cooker B, which has the same configuration as rice cooker 1 except that it does not have a shielding pattern.

The results are shown in Figure 10. In Figure 10, A indicates the results for rice cooker 1, which is provided with a shielding pattern, and B indicates the results for rice cooker B, which is not provided with a shielding pattern.

As shown in Figure 10, it was confirmed that in the 100 MHz frequency band, the noise level (A) of the rice cooker with a shield pattern was approximately 10 dB lower than the noise level (B) of the rice cooker without a shield pattern.

From the above, it was confirmed that the level of noise leaking to the outside can be reduced by providing a conductive shield pattern to cover at least a portion of the circuit pattern on the circuit board 21 that may be a source of noise.

(summary)
As described above, the rice cooker 1 according to this embodiment includes the main body 10 and the lid 50. The main body 10 includes the housing 11 and the inner pot 12 disposed inside the housing 11. An induction heating coil 13 is provided on the outer surface of the inner pot 12. Furthermore, within the housing 11, a circuit board 21 is provided on the outside of the inner pot 12. The circuit board 21 has a circuit pattern on at least the side facing the induction heating coil 13.

On the surface 21A on which the circuit pattern of the circuit board 21 is provided, a first shield pattern 61 or a second shield pattern 62 is provided to at least partially cover locations in the circuit pattern that may be noise sources (e.g., the AC circuit 32, the inverter circuit 34, and the switching power supply circuit 35).

According to the above configuration, the effects of radiated noise can be suppressed by utilizing a pattern of conductive material (conductive pattern) formed on the circuit board, without the need for a separate shielding member to block radiated noise. This allows the space inside the housing 11 to be used effectively. In addition, after each component, including the shielding member, is temporarily installed in a predetermined position inside the housing to deal with noise, there is no need to change the design of the structure inside the housing based on the results of noise testing.

In this embodiment, the AC circuit 32, the inverter circuit 34, and the switching power supply circuit 35 are given as examples of circuit elements on the circuit board 21 that can be noise sources, but the circuit elements that can be noise sources are not limited to these. In another embodiment of the present invention, a conductive pattern can be formed so as to at least partially cover the circuit elements that can be noise sources provided on the circuit board.

In addition, in this embodiment, the first shield pattern 61 or the second shield pattern 62 is formed so as to cover a part of the AC circuit 32, a part of the inverter circuit 34, and a part of the switching power supply circuit 35 (see FIG. 9). It is preferable to make the formation area of these shield patterns as large as possible without interfering with the formation of patterns of other circuit elements. This can further reduce the level of noise leaking to the outside.

In addition, in this embodiment, a shield pattern is formed to cover each of the AC circuit 32, the inverter circuit 34, and the switching power supply circuit 35, but in another embodiment, a shield pattern may be formed to cover at least one of the AC circuit 32, the inverter circuit 34, and the switching power supply circuit 35. Since the AC circuit 32 is more likely to be a source of noise among the circuit elements, the circuit board 21 may have only a shield pattern that covers a portion of the AC circuit 32.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, configurations obtained by combining the configurations of the embodiments described in this specification are also included in the scope of the present invention.

1: Pressure rice cooker (rice cooker)
10: Main body 11: Housing 12: Inner pot 13: Induction heating coil 21: Circuit board 32: AC circuit (noise generating part)
34: Inverter circuit (noise generating part)
35: Switching power supply circuit (noise generating part)
61: First shield pattern (conductor pattern)
61a: AC circuit shield pattern (conductor pattern)
61b: Shield pattern for switching power supply circuit (conductor pattern)
62: Second shield pattern (conductor pattern)
62a: Shield pattern (conductor pattern) for inverter circuit

Claims (5)

A housing and
An inner pot disposed inside the housing;
an induction heating coil disposed on an outer surface of the inner pot;
a circuit board disposed outside the inner pot in the housing and having a circuit pattern on a side facing the induction heating coil;
a conductive pattern is provided on a surface of the circuit board on which the circuit pattern is provided, the conductive pattern at least partially covering a noise generating portion of the circuit pattern ;
The conductive pattern is formed in a portion located between the induction heating coil and the noise generating portion. At least one of the noise generating units is an AC circuit.
The rice cooker according to claim 1. At least one of the noise generating units is an inverter circuit.
3. The rice cooker according to claim 1 or 2. At least one of the noise generating units is a switching power supply circuit.
The rice cooker according to any one of claims 1 to 3. A housing and
An inner pot disposed inside the housing;
an induction heating coil disposed on an outer surface of the inner pot;
a circuit board that is disposed on the outside of the inner pot in the housing and has a circuit pattern on a side facing the induction heating coil;
Equipped with
a conductive pattern covering at least a part of a noise generating portion of the circuit pattern is provided on a surface of the circuit board on which the circuit pattern is provided,
The conductive pattern overlaps at least a portion of the noise generating portion.

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