JPH02103889A - High-frequency heating device - Google Patents

Abstract

PURPOSE:To require no earthing work of a box body and to prevent an overheating of a shield member by providing plural rod-form materials of non-magnetic bodies while insulating them each other between the primary winding and the secondary winding of a boosting transformer, and connecting the rod-form materials to the core or to the box body of the boosting transformer while connecting their one ends electrically. CONSTITUTION:Between the primary winding 31 of a boosting transformer 30, and the secondary winding 33 and a heater winding 36, a shield member 37 is provided near the primary winding side, and the member 37 is connected to a core 32, practically being connected to a box body 6. As a result, the high voltage circuit of the output side from the winding 33 is composed to be sealed in a shield space with the potential same as the box body 6. Consequently, the generation of a mixing contact between the primary and the secondary windings is prevented, and it is not necessary to a carry out the earthing work. The shield member is plural rod-form materials 50 composed of a non-magnetic material, and they are buried to an insulating holder plate 51, being insulated each other and arranged in the longitudinal direction. An induction heating phenomenon of the member 37 by a high-frequency magnetic flux can be suppressed to a low value and an over-heating is prevented, accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device such as a microwave oven for heating foods, fluids, etc., and more specifically, to an improvement of its power supply device.

2. Description of the Related Art Conventionally, as is well known, a power supply device for a microwave oven is composed of a power supply circuit mainly composed of a ferro-resonant transformer 2 as shown in FIG. Magnetron 5 is usually 3-4k
Since the operating voltage was V, the circuit voltage of the secondary circuit of the step-up transformer 2 was extremely high and dangerous. Therefore, the casing 6 of the microwave oven was always grounded to the earth 7 during use.

Problems to be Solved by the Invention In the configuration of the conventional microwave oven power supply device as described above, as shown in FIG. (e.g.
If point P and point Q come into contact), if the ground wire 10 is provided, the casing 6 will be kept at the ground potential and the fuse 11 will blow, so there is no danger even if a person touches it. Does not occur.

However, if this ground wire 10 is not provided,
Alternatively, if the ground wire is poorly installed and a contact accident occurs at points P and Q, the housing 6 will be at a very high potential (e.g. 2kV), and if a person touches it, they will receive an electric shock. You'll end up dead. Therefore, the ground wire 10
is indispensable, and the installation work is also troublesome because it is necessary to ensure a sufficiently low impedance grounding.

That is, in the conventional technology, strict earthing is essential for microwave ovens, which causes problems such as troublesome installation work and troublesome movement after installation, making it difficult to use.

Means for Solving the Problems The present invention has been made in order to solve the above-mentioned disadvantages, and has the configuration described below.

That is, a power supply section that receives power from a commercial power supply or a battery, etc., a frequency converter that converts the power of the power supply section into high-frequency power, a step-up transformer that steps up the output of the frequency converter, and an output of the step-up transformer. A plurality of non-magnetic rod-shaped materials are arranged insulated from each other between the primary winding and the secondary winding of the step-up transformer, and one end of the rod-shaped material is provided with a magnetron that is energized by a magnetron. All of them are electrically connected to form a shielding member, and this shielding member is connected to the core or casing of the step-up transformer.

Effect With the above configuration, a shielding member having substantially the same potential as the casing can be provided between the primary winding and the secondary winding of the step-up transformer, and the high voltage circuit on the secondary side of the step-up transformer can be connected to the casing. It becomes possible to confine it within a shielded space with the same potential. Furthermore, since the step-up transformer is used to step up the power converted into a high frequency by a frequency converter, it has an extremely compact structure, and the high-voltage circuit can be easily confined within a shielded space. Furthermore, since the shielding member is constructed by arranging a plurality of non-magnetic rod-shaped materials insulated from each other and electrically connecting only one end of the shielding member, the primary winding and the secondary winding Due to the high frequency magnetic flux induced by
The eddy current generated in this shielding member can be suppressed to an extremely low level.

Therefore, it is possible to prevent the shielding member itself from being inductively heated to a high temperature and wasteful power consumption, and also to prevent an adverse effect on the frequency converter.

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

In the figure, a power supply unit 23 is formed by a commercial power supply 1, a fuse 11, a diode bridge 20, an inductor 21, and a capacitor 22, creating a unidirectional power supply. The power is supplied to the control circuit 25 by the resistor 24,
The control circuit 25 controls the transistor 26 to be 20k, for example.
Switching operation is performed at a high frequency of Hz to IMHz. 2
7 is a diode, and 28 is a resonant capacitor, which constitute a resonant inverter (frequency converter) 29. Therefore, high frequency power having a frequency equal to the switching frequency of the transistor 26 is supplied to the primary winding 31 of the step-up transformer 30, and a high voltage output is generated to the secondary winding 33 which is magnetically coupled via the core 32. do. This output is rectified by a capacitor 34 and a diode 35, and then supplied to the magnetron 5. Since the cathode of the magnetron 5 is heated by the heater winding 36, the magnetron 5 oscillates and generates radio wave output, making dielectric heating possible. The detailed operation of the resonant inverter 29 is already well known and will therefore be omitted.

A shielding member 37 is provided between the primary winding 31, the secondary winding 33, and the heater winding 36 of the step-up transformer 30 at a position close to the primary winding.
and is substantially connected to the housing 6 of the high frequency heating device.

Therefore, due to the presence of the shielding member 37, the high voltage circuit on the output side of the high voltage secondary winding 33 is substantially confined within a shielded space having the same potential as the housing 6. Therefore, even if some kind of failure occurs in the high-voltage secondary winding and the insulation is broken, contact with the primary winding 31 and so-called contact between the primary and secondary windings can be prevented. In particular, the step-up transformer 30 has a configuration that boosts the output of the resonant inverter 29 and is very compact. Therefore, the configuration of the shielding member 37 can be simple and small, and the high-voltage circuit can be confined within the shielding space. It's extremely simple.

FIG. 2 is a cross-sectional view showing the structure of the step-up transformer 30. In the figure, the same reference numerals as in FIG. 1 are corresponding components, and detailed explanations will be omitted.

The shielding member 37 is attached to the bobbin 40 of the primary winding 31 as shown in the figure, and shields the secondary winding 33 via a space layer 42 with the bobbin 41 of the secondary winding 33.

This shielding member 37 is connected to the core 32 at its inner diameter portion 43 and to the casing 6 by a lead wire 44 .

With this structure, the secondary winding 33 and the heater winding 36 are shielded from the primary winding 31, and even if the secondary winding 33 fails for some reason and the insulation is broken, the primary winding 31 and the secondary winding It is possible to prevent the windings 33 from coming into contact with each other and causing the potential of the casing 6 to become abnormally high. Therefore, there is no need to further ground the casing 6 to the earth with a ground wire, and it is possible to provide a safe and easy-to-use high-frequency heating device.

Since it is essential to place the shielding member 37 between the primary winding 31 and the secondary winding 33 as shown in the figure, the adverse effects of the high frequency magnetic flux generated by them cannot help but become extremely large.

FIG. 3 is a diagram showing the structure of a shielding member 37 for preventing the adverse effects of this high-frequency magnetic flux.

50 is a rod-shaped material made of a non-magnetic material such as stainless steel, aluminum, or aluminum, and has a diameter of 0.3 to 0.
The conductor may be in the shape of a round bar of about 5wn, or a rectangular bar or band-shaped conductor with a cross-sectional area equivalent to that.

As shown in the figure, the plurality of rod-shaped materials 50 are embedded in an insulating support plate 51, and are insulated from each other and arranged vertically. And one end of them is
It is configured to be connected to the housing 6 by connecting rods 52 and 53. Of course, instead of being connected to the casing 6, the rod-shaped material 50 may be protruded into the central hole 54 through which the core of the step-up transformer passes, and may be brought into contact with the core itself as shown in FIG.

By arranging the rod-shaped materials so as to be insulated from each other, the induction heating phenomenon of the shielding member 37 caused by high-frequency magnetic flux can be suppressed to an extremely low level, which can prevent overheating, excessive total loss in the step-up transformer, or It is possible to prevent inconveniences such as abnormalities in the operation of the converter from occurring.

Furthermore, by maintaining the spacing between the rod-shaped materials 50 as shown in FIG. 4, it is possible to ensure substantial distance between the primary and secondary windings.

That is, the distance between the rod-shaped materials 50 is 211, and the shortest distance between the rod-shaped materials and the primary winding is 12 (i.e., the distance between the bobbin 40
By configuring the structure so that 11<1□ (the thickness of the brim), even if the shielding member 37 is configured with a row of rod-shaped materials 50, substantially sufficient shielding between the primary and secondary windings can be achieved. can be realized.

FIG. 5 is an external view showing another embodiment of the shielding member 37, in which two sets of 50.50' rod-shaped materials are arranged at right angles to each other and insulated from each other.

That is, as shown in FIG. 6, two rod-shaped materials 50 and 50' are embedded in an insulating support plate 51 at right angles to each other and in different vertical positions.

By electrically connecting only one end of each to the core or housing, it is possible to achieve shielding between the primary and secondary windings, and to significantly suppress induction heating of the winding itself. can.

Effects of the Invention As described above, according to the present invention, the output of the frequency converter is boosted by a step-up transformer and supplied to the magnetron,
A plurality of non-magnetic rod-shaped materials are arranged between the primary and secondary windings of a step-up transformer insulated from each other, and one end of each of the rod-shaped materials is electrically connected to form a shielding member. Since the step-up transformer is small, it is configured to be connected to the core or casing of the step-up transformer, so it is possible to achieve shielding between the primary and secondary windings with an extremely simple structure, and confine the high-voltage circuit within the shielded space. can. Therefore, high safety can be ensured without having to ground the casing to the earth, so it is possible to realize an easy-to-use high-frequency heating device that does not require grounding work. In particular, since the shielding member is constructed by electrically connecting only one end of mutually insulated rod-shaped materials, the shielding member is inductively heated by high-frequency magnetic flux, resulting in overheating and large power loss. It is possible to provide an easy-to-use high-frequency heating device that prevents problems such as destabilizing the operation of a frequency converter, does not require grounding work, maintains high safety and high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a high-frequency heating device showing an embodiment of the present invention, FIG. 2 is a sectional view showing the structure of a step-up transformer of the same device, FIG. 3 is a configuration diagram of a shielding member of the same device, and FIG. The figure is an enlarged sectional view showing the positional relationship between the same-speed helical member and the primary winding of the step-up transformer, and FIGS. 5 and 7 are circuit diagrams of a conventional high-frequency heating device. 5... Magnetron, 6... Housing, 2
3...Power supply unit, 29...Frequency converter, 30...Step-up transformer, 3I...1
Next winding, 32...core, 33...secondary winding, 37 shielding member, 50...rod-shaped material. Name of agent: Patent attorney Shigetaka Awano

Claims (1)

[Claims] a power supply section that receives power from a commercial power supply or a battery, etc.; a frequency converter that converts the power of the power supply section into high-frequency power;
It includes a step-up transformer that steps up the output of the frequency converter, and a magnetron that is energized by the output of the step-up transformer, and a non-magnetic material between the primary winding and the secondary winding of the step-up transformer. A high-frequency device configured such that a plurality of rod-shaped materials are arranged insulated from each other, one end of each of the rod-shaped materials is electrically connected to form a shielding member, and this shielding member is connected to the core or casing of the step-up transformer. heating device.