JPH0869873A - High-frequency heating apparatus - Google Patents

Abstract

PURPOSE: To provide a compact booster transformer by facilitating installation of a shielding body to prevent mixed contact of a primary winding and a secondary winding on a transformer bobbin. CONSTITUTION: A booster transformer 25 of a high-frequency heating apparatus is provided with plural winding, resinous bobbins 26 to wind the windings and a core 19 composed of a material having high magnetic permeability, and the booster transformer 25 having a shielding body 28 composed of a conductive material arranged between a primary winding 6 and a secondary winding 7, is provided. A wire rod is formed of a single wire rod, and electric obtained from this wire rod is supplied to a fan motor 24 to cool the booster transformer 25 with constitution which is wound round the bobbins 26 and whose one end is connected to a casing.

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 foods 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 The circuit operation of a conventional high-frequency heating device will be described with reference to FIG. The commercial power supply 1 is full-wave rectified by the diode bridge 2, converted into a high frequency voltage of several tens of kilohertz by the semiconductor switching element 4 driven by the control circuit 3, and applied to the primary winding 6 of the step-up transformer 5. Then, a high-frequency high voltage of several thousand kilovolts is generated in the secondary winding 7 of the step-up transformer 5, and the high-frequency high voltage is rectified by a voltage doubler rectifier circuit including capacitors 8a and 8b and diodes 9a and 9b. A high voltage is applied to the wave generator 10. The heater winding 11 of the step-up transformer 5 is connected to the filament 12 of the microwave generator 10 to heat the filament 12. The microwave generator 10 emits microwaves by heating the filament 12 and applying a high voltage.

At this time, the voltage doubler rectifying circuit between the anode of the microwave generator 10 and the step-up transformer 5 is the casing 1 of the microwave oven.
The housing 13 is electrically connected to the housing 3, and is grounded to the ground.

Further, the quaternary winding 14 of the step-up transformer 5 is connected to a motor 15 having a cooling fan, and the electric power from the quaternary winding 14 causes the step-up transformer 5, the semiconductor switching element 4, the magnetron 10, etc. To cool. As shown in FIG. 5, the quaternary winding 14 is wound in the groove of the bobbin.

However, in the above-mentioned conventional configuration, when the primary winding 6 and the secondary winding 7 of the step-up transformer 5 come into electrical contact with each other for some reason, the casing 13 of the microwave oven is not grounded to the ground. It was very dangerous because the housing 13 of the microwave oven had a high voltage of several thousand kilovolts.

Further, when the miniaturization of the microwave oven is advanced,
It is indispensable to downsize the power source part of the microwave oven, and the step-up transformer 5 also needs to be downsized. Then, the distance between the primary winding 6 and the secondary winding 7 of the step-up transformer 5 becomes small, and the risk of electrical contact between the primary winding 6 and the secondary winding 7 for some reason increases. There was a problem.

In order to solve the above problem, the following method of electrically shielding the primary winding 6 and the secondary winding 7 has been performed. That is, in FIG. 5, the bobbin 16 made of resin for winding the winding is separately prepared as the bobbin 16 for the primary winding and the bobbin 17 for the secondary winding. Joint 1 on bobbin 16
6a, the bobbin 17 is provided with a joint 17a. Then, after inserting the annular shield plate 18 made of a conductive material into the joint portion of the bobbin 16, the bobbins 16 and 1 are connected.
7 and the shield plate 18 between the primary winding 6 and the secondary winding 7.
Was getting an integrated bobbin with. The annular shield plate 18 is partially cut out so as not to electrically form a closed circuit.

[0008]

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

Another problem is that the bobbin requires a groove for arranging each of the primary winding, the secondary winding, the heater winding, the quaternary winding, and the shield, so that the transformer becomes large.

An object of the present invention is to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a high-frequency heating apparatus having a step-up transformer having a compact structure and a shield mounted thereon.

[0011]

In order to solve the above-mentioned problems, the step-up transformer of the high-frequency heating apparatus of the present invention comprises a plurality of windings, a resin bobbin around which the windings are wound, and a high magnetic permeability material. And a step-up transformer having a shield made of a conductive material and arranged between the primary winding and the secondary winding, wherein the wire is formed of a single wire and wound around the bobbin. In addition, one end of the wire is connected to the housing, and the power obtained from this wire is supplied to the fan motor that cools the step-up transformer.

[0012]

In the present invention, the shield between the primary winding and the secondary winding has a winding-like structure using a wire, so that the shield can be easily attached to the bobbin.

Further, since the shield between the primary winding and the secondary winding also serves as the power source of the motor for driving the cooling fan of the step-up transformer, the step-up transformer can be miniaturized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

The circuit operation of the high-frequency heating apparatus of the present invention is similar to that of the conventional example, but the step-up transformer 25 of the high-frequency heating apparatus of the present invention prevents the primary winding 6 and the secondary winding 7 from touching each other. A shield 28 is provided, and the shield 28 is connected to the housing 13 via a printed circuit board, and the housing 13 is grounded. A motor 24 with a cooling fan is connected to the shield 28, and the electric power generated in the shield 28 is rectified and smoothed to drive the motor 24 to drive the booster transformer 2.
Cool 5 Further, the semiconductor switching element 4, the magnetron 10, etc. can also be cooled.

Next, the step-up transformer 25 of the present invention will be described with reference to FIG. The step-up transformer 25 includes a primary winding 6, a secondary winding 7, a heater winding, a resin bobbin 26 around which these windings are wound, a ferrite core 19, and the primary winding 6 and the secondary winding 7. A shield 28 made of a urethane-coated copper wire is provided between them. The shield 28 is wound around the bobbin 26 in a spiral shape and is wound a plurality of times so as to electrically form an open circuit. The bobbin 26 has a flange that mechanically and electrically separates the windings, and the flange secures an electrically insulating distance between the windings. This shield 28 has a distance between the secondary winding and the shield equal to that of the secondary winding.
The flanges are arranged so that the distance is 1/2 or less of the distance of the next winding. Furthermore, since the shields 28 are wound in close contact with each other, as shown in FIG. 3, the plane distance B between the adjacent windings forming the shield 28 and the secondary winding 6 penetrating the bobbin 26 and the shield. It is easy to satisfy the relationship such as A> B during the linear distance A between 28, and a substantial shielding effect can be obtained even when the insulation of the bobbin 26 is broken. That is, the distance A between the primary winding 6 and the shield 28 is usually several mm, while the distance B between adjacent lines of the shield 28 is twice the thickness of the urethane coating 28-a of the winding. ,
The distance B when using 0 type electric wire having a conductor diameter of 0.5 is 0.
It is 05 mm. Here, it is clear that A> B.

Both ends of the winding constituting the shield 26 are fixedly connected to two metal square pins attached to the bobbin 26 to serve as terminals.

With the above construction, even if the insulation of the secondary winding 6 or the insulation of the bobbin 26 is broken for some reason, it is possible to prevent the primary and secondary contact from occurring.

Further, by connecting both ends of the shield 26 to a motor for driving a cooling fan, the shield 26 can also be used as a quaternary winding.

[0020]

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

(1) Even if the insulation of the secondary winding of the step-up transformer is destroyed due to some cause, it is possible to prevent the primary and secondary contact from occurring, and it is possible to provide an extremely safe high frequency heating device. I can.

(2) Since the shield is formed of a wire into a winding shape, it is easy to attach the shield to the bobbin of the step-up transformer at the manufacturing stage, and automation is possible.

(3) Since the shield and the quaternary winding of the cooling fan power supply are also used, a compact step-up transformer can be provided.

[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 perspective sectional view of a main part of a high-voltage transformer of the high-frequency heating device.

FIG. 3 is a sectional view of a main part of a high-voltage transformer of the high-frequency heating device.

FIG. 4 is a circuit diagram of a conventional high frequency heating device.

FIG. 5 is a side sectional view of a step-up transformer of a conventional high-frequency heating device.

[Explanation of symbols]

 6 primary winding 7 secondary winding 13 housing 19 core 24 fan motor 25 step-up transformer 26 bobbin 28 shield

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruo Suenaga 1006, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Shiro Takeshita 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Villa Daisuke 1006, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 1006 Kadoma, Kadoma-shi, Fuchu Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A winding having a plurality of windings, a resin bobbin around which the windings are wound, and a core made of a high magnetic permeability material, wherein the primary winding and the secondary winding are provided between the primary winding and the secondary winding. A step-up transformer having a shield made of a conductive material that electrically shields the next winding is formed, the shield is formed of a single wire rod, and one end of the shield is wound around the bobbin and connected to a housing, A high frequency heating device configured to supply electric power obtained from the shield to a load. 2. The high frequency heating device according to claim 1, wherein the electric power obtained from the shield is supplied to a motor for driving a fan for cooling the step-up transformer. 3. The high-frequency heating device according to claim 1, wherein the coated electric wire is closely attached and wound in a spiral shape.