JPH05217667A - High frequency heating device - Google Patents

Abstract

PURPOSE:To prevent the body exteriors from getting high potential simply even when the primary and secondary windings of a booster transformer in the power supply of a high frequency heating device contact electrically. CONSTITUTION:An electroconductive shield plate 19 to shield electrically the primary winding 6 of a booster transformer 3 in the power supply part from its secondary winding 7 is formed from two two U-form electroconductive plates in such a structure that the two plates are inserted from the sides to the coil bobbin between the primary and secondary windings 6, 7. Accordingly the two windings 6, 7 contact each other electrically to prevent the body exteriors from getting a high potential. Because the shield plate can be accomplished by such a simple process as inserting two plates from the sides, manufacture of the booster transformer can be automated and the costs be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device for heating food by microwaves, and more particularly to a structure for electrically shielding the primary winding and the secondary winding of its power source section.

[0002]

2. Description of the Related Art A conventional high-frequency heating device is shown in FIG. 1
Is a diode bridge, 2 is a semiconductor switching element,
Reference numeral 3 is a step-up transformer, and 4 is a microwave generator. 5
Is the exterior of the microwave oven body. The commercial power supply is full-wave rectified by the diode bridge 1, converted into a high frequency voltage of several tens of kilohertz by the semiconductor switching element 2, and applied to the primary winding 6 of the transformer 3. Then step-up transformer 3
A high frequency high voltage of several thousand kilovolts is generated in the secondary winding 7 of the. The high frequency high voltage is rectified by a voltage doubler rectifying circuit including a capacitor and a diode, and the high voltage is applied to the microwave generator 4 to cause the microwave generator 4 to emit microwaves.

At this time, the anode of the microwave generator 4 and one terminal C of the secondary circuit of the step-up transformer 3 are electrically connected to the exterior 5 of the microwave oven main body, and the exterior 5 is grounded to the ground. Is configured.

However, in the above-mentioned conventional configuration, if the point A of the primary winding 6 and the point B of the secondary winding 7 of the transformer are electrically contacted with each other for some reason, the exterior of the microwave oven main body becomes grounded. If it was not grounded, the exterior 5 of the microwave oven body would be at a high voltage of several thousand kilovolts, which was extremely dangerous.

Further, when promoting miniaturization of microwave ovens,
Miniaturization of the power supply part of the microwave oven is indispensable, and miniaturization of the step-up transformer is also required. Then, the distance between the primary winding 6 and the secondary winding 7 of the step-up transformer becomes small,
There is a problem that the risk that the primary winding 6 and the secondary winding 7 are in electrical contact with each other for some reason is increased.

In order to solve the above problems, the primary winding and
The following method of electrically shielding the next winding has been performed. That is, in FIG.
Coil bobbin 28 for secondary winding and coil bobbin 3 for secondary winding
8 and 8 are produced separately. The coil bobbin 28 is provided with a joint portion 28a, and the coil bobbin 38 is provided with a joint portion 38a. Then, at the joint of the coil bobbin 28, as shown in FIG.
After inserting an annular shield plate 29 made of a conductive material as shown in (b), the coil bobbins 28, 29 are screwed in 1
The integrated coil bobbin having the shield plate 29 between the secondary winding 6 and the secondary winding 7 is obtained. The annular shield plate 29 is partially cut out so as not to electrically form a closed circuit.

[0007]

However, the above-mentioned structure has a problem that the manufacturing process of the coil bobbin of the step-up transformer is complicated and it is difficult to automate it as described above.

SUMMARY OF THE INVENTION The present invention solves the conventional problems, and an object of the present invention is to provide a coil bobbin equipped with a shield plate with a simple structure.

[0009]

In order to solve the above problems, the coil bobbin of the high frequency heating apparatus of the present invention has the following structure.

That is, it comprises a microwave generator, a power converter comprising a semiconductor switching element, a step-up transformer and the like for supplying electric power to the microwave generator, and a cooling means for cooling the microwave generator. The step-up transformer has a shield plate between the primary winding and the secondary winding, which is made of a plurality of conductive materials and is provided so as to be an electrically open circuit. It is configured to be electrically connected. The shield plate is composed of two parts having the same U-shape.

[0011]

Since the present invention comprises a plurality of shielding plates,
The shield plate can be easily sandwiched between the secondary winding and the secondary winding.

[0012]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a circuit diagram of the high frequency heating apparatus of the present invention. In FIG. 1, 1 is a diode bridge, 2 is a semiconductor switching element, 3 is a step-up transformer, and 4 is a microwave generator. Reference numeral 5 represents the exterior of the microwave oven main body.

As shown in FIG. 2, the step-up transformer 3 includes a primary winding 6, a secondary winding 7, and a resinous cylindrical bobbin 18 around which they are wound, a primary winding and a secondary winding. And a core 20 made of a material having a high magnetic permeability. Then, as shown in FIG. 3, the cylindrical bobbin 18 is configured such that a part of the core 20 is inserted into the central portion of the cylinder.

As shown in FIG. 4, the shield plate 19 is composed of two conductor plates 119a and 119b having the same shape. The plurality of conductor plates 119a and 119b are electrically connected to the microwave oven main body exterior 5, respectively. As shown in FIGS. 1 and 2, the shield plate 19 includes the primary windings 6 and 2
The secondary winding 7 is arranged between the secondary windings 7, and when the direction of the secondary winding 7 is seen from the direction of the primary winding 6, the secondary winding 7 is completely hidden by the shield plate 19. Further, an insulator 21 is arranged between the conductor plates 119a and 119b of the shield plate 19 composed of a plurality of pieces. This is because when the two conductor plates 119a and 119b forming the shield plate 19 are electrically contacted with each other, a closed circuit is formed, a short-circuit current flows, heat is generated, and the shield plate and the booster coil are damaged. Is.
In the embodiment shown in FIG. 4, the shield plate 19 has two U-shaped conductor plates 119a and 119b partially overlapped with each other so that the secondary winding 7 side is seen from the primary winding 6 side. At this time, the secondary winding 7 is completely hidden by the shield plate 19. An insulator 21 is arranged between the conductor plates 119a and 119b so that the conductor plates 119a and 119b do not come into electrical contact with each other.

Two U-shaped conductor plates 119a and 119b
Are electrically connected to one terminal C of the step-up transformer 3, and the terminal C is electrically connected to the exterior 5 of the microwave oven.

As the insulator 21, a heat resistant and moisture resistant film or plate is suitable. Alternatively, the conductor plate 119a
The insulating material 21 may be omitted if an insulating layer is provided on at least one of the surfaces 119b and 119b by painting or the like and the overlapping portion is electrically sufficiently insulated.

When the insulation of the secondary winding of the step-up transformer is broken at the point B, for example, in the above structure, the shielding plate 19 is provided between the primary winding 6 and the secondary winding 7, so that the secondary winding is wound. Is there a short circuit between the point B and the shield plate of the line to create a short circuit of point B-shield plate-point C-high voltage coil-point B, causing a short-circuit current, which causes the safety device to disconnect the circuit from the power supply? However, the booster transformer 3 will not be thermally damaged, and the exterior 5 will not be exposed to high pressure.

In this embodiment, the shield plate 19 is U-shaped, and the conductor plates 119a and 119b may be inserted from both sides of the coil bobbin 18. Therefore, the coil bobbin may be a single bobbin for both the primary and secondary windings. As in the conventional case, the primary winding and the secondary winding are separately manufactured, and the bobbin is attached after the shield plate is attached. No need to be integrated. In addition, the shield mounting work can be automated because it is only inserted.

In this embodiment, an example of using two U-shaped conductor plates having the same shape as the shield plate has been described above.
The shape is not limited to the U shape and is not limited to the same shape, and may be any shape as long as the insertion shield plate can be easily formed from the side surface.

In the present embodiment, an example in which two conductor plates are used as the shielding plate has been described, but two or more conductor plates may be used as long as the object of the present invention is achieved.

[0022]

As described above, according to the high frequency heating apparatus of the present invention, the following effects can be obtained.

(1) When the primary circuit and the secondary circuit of the step-up transformer are electrically contacted with each other for some reason,
Even if the earth is not grounded, the exterior of the microwave oven body will have a high voltage, and it will not endanger the person using the microwave oven.

(2) Since the shield plate is composed of a plurality of shield plates, it is easy to attach the shield plate to the bobbin of the step-up transformer at the manufacturing stage, and automation is possible.

(3) Since the shielding plate is composed of parts having the same shape, it is easy to procure parts.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high frequency heating device according to an embodiment of the present invention.

FIG. 2 is a partial sectional view of a step-up transformer of the same high-frequency heating device.

FIG. 3 is a plan view of a step-up transformer of the same high-frequency heating device.

FIG. 4 is a plan view of a shielding portion of the high frequency heating device.

FIG. 5 is a circuit diagram of a conventional high frequency heating device.

FIG. 6A is a sectional view of the coil bobbins for the primary winding and the secondary winding, and FIG. 6B is a perspective view of the shielding plate.

[Explanation of symbols]

 2 semiconductor switching element 3 booster transformer 4 microwave generator 5 exterior 6 primary winding 7 secondary winding 19 shield plate 30 power converter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Nakabayashi 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Shiro Takeshita, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial

Claims (2)

[Claims] 1. A microwave generator, a power converter for supplying electric power to the microwave generator, which comprises a semiconductor switching element, a step-up transformer and the like, and the step-up transformer comprises a primary winding and a secondary winding. And a shield plate made of a plurality of conductive materials and provided so as to electrically form an open circuit, and the shield plate is electrically connected to the exterior of the main body. 2. The high-frequency heating device according to claim 1, wherein the shielding plate is composed of two U-shaped parts having the same shape.