JP7227494B2 - Ground structure of heating cooker - Google Patents

Description

TECHNICAL FIELD The present invention relates to a grounding structure for a heating cooker (household appliance).

Household electric appliances have power consumption parts such as drive circuits and control circuits, and in addition, exteriors and frames are often made of non-conductive plastic. In addition, since the design influences the commercial value, priority is given to the design of the external shape, and the power consumption part is arranged in a space with no margin.

In recent years, microcomputers are used in control circuits. Further, in many cases, the drive circuit adopts an inverter system. Such electronic circuits generate noise because they handle high frequencies. In addition, the power supply circuits in home appliances are often located away from power consuming parts such as drive circuits and control circuits. It will be wired.

In such a situation, the voltage line and the ground line themselves can also serve as antennas, so electromagnetic waves from the outside of the home appliance may also flow into the power consumption part as noise.

These noises are usually reduced by shielding the power dissipating parts. However, there are some noises that cannot be eliminated just by shielding the power consumption part. In such a case, it may be possible to eliminate the noise by routing the ground wire.

In Patent Document 1, a digital circuit element is mounted on a printed circuit board, and a single protection relay that protects a device by generating a power supply cutoff signal (trip signal) upon detection of a short circuit in a power device, or is installed in a home appliance such as a washing machine. Disclosed are grounding structures for microcomputer-equipped electronic devices and stand-alone controllers for various machines such as lathe factories.

Here, when the housing case for the printed board in which the electronic circuit element is mounted is made of metal, as shown in FIG. There is a disclosure of a technique for taking out the ground through the housing by doing so.

Japanese Patent Application Laid-Open No. 2002-084079

As disclosed in Japanese Unexamined Patent Application Publication No. 2002-100001, when the housing on which the printed circuit board is mounted is conductive, noise can be reduced by grounding the housing itself. However, when a ground wire is routed between a plurality of power consumption parts, it becomes easy to pick up noise, and there is a problem that sufficient noise countermeasures cannot be taken.

SUMMARY OF THE INVENTION In view of the above problems, the present invention relates to a grounding structure that has room for noise countermeasures in home electric appliances having a plurality of power consumption parts.

More specifically, the ground structure according to the present invention is
A grounding structure for a home appliance having a power supply circuit board that supplies power to a plurality of power consuming parts,
a board-side ground wire provided for each of the power consumption parts;
a power supply side ground wire connected to the power supply side ground electrode of the home appliance;
a conductive plate having a through-hole that can be fastened to each of the power-supply-side ground wire and the substrate-side ground wire;
Having a base on which the conductive plate is placed,
the base is formed of a portion of a non-conductive board cover that holds the power circuit board;
The conductive plate is arranged on the opposite side of the power circuit board with the base therebetween .
In the above structure, the present invention further includes a detachable bottom plate, and the conductive plate is configured to be fastened to the base from the bottom plate side through the through hole.

According to the grounding structure of the present invention, when attaching the substrate-side ground wire from the power consuming part to the conductive plate to which the power supply-side ground wire is connected, the attachment position can be selected, and the substrate-side ground wires or the power supply-side ground wire can be selected. By intersecting with , noise countermeasures can be taken even after the form of the product is completed.

Further, in the structure described above, the present invention is characterized in that the power supply-side ground wire and the substrate-side ground wire are connected to the through hole by fastening with screws. With such a structure, the power-supply-side ground wire and the substrate-side ground wire fixed to the conductive plate can be fixed without changing their positions and postures, so the noise countermeasure effect is reduced due to the movement or use of the product. never

Further, according to the present invention, in the structure described above, the conductive plate has a notch formed in at least one portion of the edge thereof. As a result, since the conductive plate is always fixed at the same position with respect to the base to which it is attached, it is possible to suppress the difference in the noise countermeasure effect for each product even when mass-producing the same product.

Further, in the structure described above, the present invention is characterized in that identification symbols are displayed in the through-holes to which the power-supply-side ground wire and the board-side ground wire of the conductive plate can be fastened. With such a structure, it is possible to indicate in the design procedure which ground wire should be connected to which through-hole and in what order, so differences in noise suppression effects for each product can be suppressed. can be done.

Further, according to the present invention, in the structure described above, the through holes are arranged in a line in the conductive plate. With such a structure, it is easy to confirm the position of the through hole provided in the conductive plate, and erroneous installation of the ground wire is less likely to occur. Therefore, it is possible to suppress the difference in the noise countermeasure effect for each product.

Further, according to the present invention, in the structure described above, the through holes for fixing the conductive plate and the base are formed between the through holes arranged in a row. With such a structure, even if the number of through-holes increases, it is easy to identify the positions of the through-holes, and erroneous installation of the ground wire is less likely to occur. Therefore, it is possible to suppress the difference in the noise countermeasure effect for each product.

Moreover, this invention is a heating cooker which has said grounding structure. The cooker has at least three power consuming parts: a control circuit for IH, a circuit for controlling the operation of the cooker, and a power supply circuit. These power consuming parts tend to generate noise because high-frequency currents flow therethrough. Moreover, in many cases, the entire product is made of plastic, and the housing cannot ensure grounding. Therefore, by mounting the grounding structure according to the present invention, it is possible to take measures against noise by changing the connection order of the grounding wire to the conductive plate even after the outer shape of the product is completed.

The internal structure of a rice cooker is shown, (a) is a longitudinal cross-sectional view of the whole, (b) is an enlarged view of a power circuit board. FIG. 2 is a perspective view of the power circuit board of FIG. 1 that is turned upside down and viewed from the front side; FIG. 2 is a perspective view of the power circuit board in FIG. 1 that is turned upside down and viewed from the rear side; FIG. 4 is a perspective view of a conductive plate of a ground structure; It is a perspective view around the base of a ground structure. It is a figure which shows the conventional ground structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment, which is an example of the present invention, will be described below with reference to the drawings. Note that a heating cooker (rice cooker) is used to describe the grounding structure according to the present invention. However, the ground structure according to the present invention is not limited to rice cookers. In the rice cooker, the display panel side is defined as "front" and the opposite side is defined as "rear". Further, when describing the board of the power consumption part, the side on which the electronic components are arranged on the board is called the "front side", and the opposite side is called the "back side".

INDUSTRIAL APPLICABILITY The grounding structure 1 according to the present invention can be suitably used for home electric appliances. Here, the term "home appliance" refers to a device that is mainly used at home. Examples include washing machines, refrigerators, air conditioners, microwave ovens, rice cookers, electric pots, hot plates, and the like. Among these, it can be suitably used for those having an operation control board for controlling the operation of each device with a microcomputer and a drive control board for controlling the drive, and the whole (housing) being made of plastic. Therefore, it can be suitably used for rice cookers, electric pots, hot plates and the like.

Here, the housing made of plastic means that the housing is non-conductive (or low-conductive) and grounding to the housing is meaningless for noise countermeasures.

In addition, home appliances, together with an operation control board and a drive control board, rectify or convert a power supply (commercial power from an outlet) voltage to obtain a desired direct current (or voltage) or a desired alternating current (or alternating voltage). ) usually has a power supply circuit board that converts These boards are also called "power dissipating parts". In the present invention, there are at least two power consuming parts.

Also, each power consuming part has its own ground wire. A ground line is a line that connects the grounds of the substrates that constitute each power consuming part. Each ground line does not need to be one for the power consuming part, and a plurality of ground lines may be provided. The ground wire from the power consumption part is called the "board side ground wire".

A separate power line (so-called hotline) is supplied to each power consumption part. These power lines are usually placed between the power supply circuit board and each power consuming part. In the present invention, the board-side ground wire may be a twisted wire or a concentric wire with the power line.

Next, a more specific description will be given with reference to the drawings. FIG. 1 shows the internal structure of a rice cooker 30 equipped with an induction heating device. FIG. 1(a) is a longitudinal sectional view of the whole. The rice cooker 30 is equipped with an inner pot 40. - 特許庁A heating coil 42 is arranged at the bottom of the inner pot 40 to heat the inner pot 40 by induction heating. It is the drive control board 70 that controls the induction heating.

An operation panel 38 is provided in front of the rice cooker 30 so that the user can instruct the operation of the rice cooker 30 . Operations from the operation panel 38 and overall control of the rice cooker 30 are performed by the operation control board 60 .

The rice cooker 30 has a power line for connecting to a commercial power supply (not shown) on the rear side, and converts the commercial power from the power line into direct current (or predetermined alternating current), or A power supply circuit board 50 for removing noise is provided.

The operation control board 60, the drive control board 70, and the power supply circuit board 50 are power consumption parts. Power lines are provided between the operation control board 60 and the drive control board 70 and the power supply circuit board 50 (not shown). At least one board-side ground wire is provided for each of the operation control board 60, the drive control board 70, and the power supply circuit board 50. FIG.

Next, FIG. 1B is an enlarged view of the power circuit board 50 portion, and FIG. 2 is a perspective view of the peripheral structure of the power circuit board 50 viewed from the front side. 3 shows a perspective view of the peripheral structure of the power supply circuit board 50 as seen from the rear side. 2 and 3 are shown upside down with respect to the installation state of FIG. 1(b) so that the ground structure 1 faces upward. Also, the power circuit board 50 and the board cover 4 are schematically shown, and a part of the side plate 32 of the housing to which the electronic components 54 on the power circuit board 50 and the power connector 34 are attached is shown by dotted lines.

The power circuit board 50 is held by the board cover 4 . The board cover 4 may be made of a non-conductive material such as plastic. Conductive plate 2 is provided at the lower end of substrate cover 4 . Since the conductive plate 2 is arranged on the bottom side of the rice cooker 30 in this way, it is easy to perform assembly or maintenance without the bottom plate 44 (see FIG. 1(a)). .

A ground wire 100 connected to the ground electrode 34a of the power connector 34 is a power supply side ground wire. Hereinafter, it will be referred to as "power supply side ground wire 100". The power-side ground wire 100 is not directly connected to the power circuit board 50, the operation control board 60, or the drive control board 70, but is connected to the conductive plate 2 once.

Also, the ground of the power supply circuit board 50 is connected to the conductive plate 2 by the ground wire 101 . The ground wire 101 is the board-side ground wire 101 . Similarly, the ground of the operation control board 60 is connected to the conductive plate 2 by a board-side ground wire 102 , and the ground of the drive control board 70 is connected to the conductive plate 2 by a board-side ground wire 103 .

The power supply circuit board 50 is connected to the power supply terminal 34b of the power supply connector 34 by wiring 106 and wiring 107, and receives commercial power. Further, power is sent to the operation control board 60 through the wiring 104 and to the drive control board 70 through the wiring 105 . Therefore, the wirings 104 to 107 are so-called hot lines.

The conductive plate 2 is attached to a base 6 provided at the edge of the board cover 4 holding the power circuit board 50 . The base 6 is a flat surface along the side surface of the board cover 4 and protrudes from the edge of the board cover 4 like an eave. The board cover 4 and the base 6 may be integrally formed. The conductive plate 2 is fastened to the base 6 with fixing screws 8 . An identification symbol 6i is displayed on the base 6 at a position corresponding to the through hole.

The identification symbol 6i is not particularly limited as long as it is a symbol that can identify individual through holes of the conductive plate 2 . In FIG. 2, the numbers are indicated as "1, 2, . . . , 5". However, it may be letters such as alphabets, or figures such as circles and triangles.

The board-side ground wires 101 to 103 and the power-supply-side ground wire 100 each have a connecting round connector joined to each end, and are fastened to the conductive plate 2 with screws 10 . Therefore, the fastened state does not move or displace even when the rice cooker 30 is moved.

FIG. 4 shows a perspective view of the conductive plate 2, and FIG. 5 shows an enlarged perspective view around the base 6. As shown in FIG. The conductive plate 2 is made of a good conductive plate material having a constant thickness. For example, metals such as copper, iron and aluminum can be suitably used. The plate thickness is preferably set to a thickness exceeding half the diameter of the shaft of the fixing screw 8 (see FIG. 2). For example, if the shaft of the fixing screw 8 has a diameter of 5 mm, the conductive plate 2 has a thickness of 2.5 mm or more. Setting the thickness thicker in this manner is effective for noise countermeasures.

The example of the conductive plate 2 shown in FIG. 4 shows a case in which through holes are formed in a line. By arranging the through-holes in a row, it is less likely that the through-holes will be mistaken. However, the through-holes may be arranged in a circular or arcuate arrangement.

One of these through holes is a fixing through hole 2a through which a screw 8 for fixing the conductive plate 2 itself to the base 6 is passed. The other five are fastening screw holes 2b to which board-side ground wires 101, 102, 103, etc. (see FIG. 2) are fastened. The fixing through hole 2a is formed between the fastening screw holes 2b. By doing so, it becomes easier to distinguish between the fastening screw holes 2b. The fastening screw hole 2b is internally threaded. This is to facilitate fastening while fixing the positions of the substrate-side ground wires 101, 102, and 103. FIG. However, it is also possible to use a simple through-hole with an unbroken female screw, and fix the board-side ground wires 101, 102, and 103 by a combination of a screw and a nut.

A notch 2c is formed at one edge 2d in the longitudinal direction of the conductive plate 2, which looks like a corner cut off. This notch 2c makes it possible to easily confirm the position where the ground wire is to be fastened, thereby preventing miswiring.

FIG. 5 is an enlarged perspective view showing the base 6 extending from the board cover 4 and its surroundings. As described above, the base 6 is formed so as to extend from the edge 2d of the substrate cover 4 like an eave. A fixing screw hole 6a is formed at a position corresponding to the fixing through hole 2a formed in the mounted conductive plate 2 (see FIG. 4).

On the other hand, a fastening through-hole 6b is formed at a position corresponding to the fastening screw hole 2b (see FIG. 4) of the conductive plate 2. As shown in FIG. When fastening screws 10 having a length exceeding the thickness of the conductive plate 2 are used, the fastening through-holes 6b are formed to have a size such that the tips of these screws 10 can be inserted.

A wall 6c is formed on the base 6 in the longitudinal direction along the edge of the conductive plate 2 in the width direction. By forming the wall 6c in this way, the positioning of the conductive plate 2 is facilitated. Further, even if the fastening through-holes 6b are not formed, it is possible to prevent the conductive plate 2 from co-rotating at the time of attachment.

Moreover, in this embodiment, the wall 6c is formed along the shape of the notch 2c. As described above, erroneous wiring of the ground wire can be prevented by forming the notch 2c in the conductive plate 2 itself. Therefore, the structure is such that the conductive plate 2 cannot be arranged in the opposite direction. Therefore, erroneous wiring can be reliably prevented.

A method of using the grounding structure 1 according to the present invention will be described below. In assembly, the notch 2c of the conductive plate 2 is aligned with the wall 6c that can be fitted to the notch 2c of the base 6, and the fixing through hole 2a and the fixing screw hole 6a are aligned and fastened with bolts or the like.

Next, the power supply side ground wire 100 and the board side ground wires 101, 102 and 103 are fastened to the fastening screw holes 2b of the conductive plate 2, and the noise state of the rice cooker 30 is checked in this state. Noise conditions can be conveniently measured using a spectrum analyzer.

If the noise level is high as a result of the measurement, the mounting positions of the power supply side ground wire 100 and the substrate side ground wires 101, 102, and 103 are changed, they are fastened again, and the noise state is measured. Here, by changing the attachment positions of the power supply-side ground wire 100 and the substrate-side ground wires 101, 102, and 103, the state of noise changes. In particular, crossing each other's ground lines changes the noise state. Then, a suitable connection state with low noise is determined.

The noise of the rice cooker 30 is mostly determined by the design of the power supply circuit board 50 , the operation control board 60 and the drive control board 70 and the state of arrangement within the rice cooker 30 . Therefore, if the connection state of each ground wire to the conductive plate 2 that can sufficiently reduce the noise level is known, the other rice cookers 30 can also be set to the same connection state of the ground wire, so that the noise state can be reduced to any product. can manufacture the rice cooker 30 of the same degree.

For example, the power supply-side ground wire 100 may be fastened to the second fastening through-hole 6b, and the substrate-side ground wires 101, 102, and 103 may be fastened to the first, fifth, and fourth fastening through-holes 6b, respectively. Assuming that a good noise state can be obtained, other rice cookers 30 of the same design can also reproduce a similar noise state by connecting each ground wire to the conductive plate 2 in the same manner. .

Other embodiments obtained by modifying the present embodiment will be described below. Each embodiment can be appropriately combined as long as there is no contradiction. In addition, the scope of the present invention is not limited to the content shown in each embodiment.

(1) In the above-described embodiment, the substrate cover 4 and the base 6 are integrally formed, but the base 6 may be attached to the substrate cover 4 as a separate member.

(2) In the above embodiment, the configuration in which the base 6 is provided on the board cover 4 is shown as an example. It does not matter if the configuration is such that

(3) In the above embodiment, the ground structure 1 is arranged on the bottom side of the rice cooker 30 in the installed state. , and may be placed at other locations as long as they are not easily affected by noise.

(4) In the above-described embodiment, the notch 2c is shaped like a chamfered corner of the conductive plate 2. However, the notch 2c can serve as a mark for the placement of the conductive plate 2 and can be engaged with the base 6. Any other shape may be used as long as it has such a shape. For example, a notch formed in an arc shape from the edge may be used.

(5) In the above-described embodiment, the configuration in which the surface of the conductive plate 2 and the surface of the power supply circuit board 50 are arranged at right angles is shown as an example. However, they may be parallel to each other or may be inclined.

(6) In the above embodiment, the fixing through-holes 2a for passing the screws 8 for fixing the conductive plate 2 to the base 6 and the fastening screw holes 2b for fastening the ground wire are formed in a straight line. An example configuration is shown. However, it does not matter if they are not arranged on a straight line. Alternatively, the fixing through hole 2a may be formed at a position apart from the fixing through hole 2a.

(7) In the above embodiment, the configuration in which the conductive plate 2 is fixed with one screw 8 is shown as an example. However, it may be configured to be fixed with a plurality of wires.

(8) In the above embodiment, the configuration using one conductive plate 2 was shown as an example. However, if it is configured as in the present invention, it is possible to stack a plurality of sheets as necessary, such as when a design change occurs, and versatility is high. In this case, conductive plates 2 having different shapes may be combined.

(9) In the above embodiment, the configuration in which the wall 6c is formed on the base 6 along the longitudinal direction of the conductive plate 2 is shown as an example. However, this wall 6c is not an essential component. Moreover, for the purpose of stabilization, it may be formed along the edge 2 d on the opposite side in the width direction of the conductive plate 2 .

The earthing structure 1 of the heating cooker of the present invention is useful not only for the heating cooker, but also for home electric appliances that use a commercial power supply and are susceptible to power supply noise.

2: Conductive plate 2a: Fixing through hole 2b: Fastening screw hole 2c: Notch 2d: Edge 6: Base 6a: Fixing screw hole 8: Screw (for fixing)
30: Rice cooker (heat cooker)
34a: ground electrode 50: power supply circuit board 60: operation control board 70: drive control board 100: power supply side ground wires 101 to 103: board side ground wires

Claims (8)

A grounding structure for a home appliance having a power supply circuit board that supplies power to a plurality of power consuming parts,
a board-side ground wire provided for each of the power consumption parts;
a power supply side ground wire connected to the power supply side ground electrode of the home appliance;
a conductive plate having a through-hole that can be fastened to each of the power-supply-side ground wire and the substrate-side ground wire;
Having a base on which the conductive plate is placed,
the base is formed of a portion of a non-conductive board cover that holds the power circuit board;
The ground structure , wherein the conductive plate is arranged on the opposite side of the power circuit board across the base . Furthermore, it has a removable bottom plate,
2. The grounding structure according to claim 1, wherein the conductive plate is configured to be fastened to the base from the bottom plate side through the through hole. 3. The grounding structure according to claim 1 , wherein said power supply side grounding wire and said board side grounding wire and said through hole are coupled by fastening with screws. 4. The grounding structure according to any one of claims 1 to 3, wherein a notch is formed in at least one portion of the edge of the conductive plate. 5. An identification symbol is displayed in the through hole to which each of the power-supply-side ground wire and the substrate-side ground wire of the conductive plate can be fastened. grounding structure as described in 6. The grounding structure according to claim 1, wherein said through-holes are arranged in a line in said conductive plate. 7. The ground structure according to claim 6, wherein the through holes for fixing the conductive plate and the base are formed between the through holes arranged in a row. A heating cooker having the ground structure according to any one of claims 1 to 7 .

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