JPS6171585A - High frequency heating device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high frequency heating device which has a double insulation structure and eliminates the need for grounding work.

Conventional structure and its problems Conventional high-frequency heating devices (hereinafter simply referred to as microwave ovens) with a ground terminal, for example, can be used in the event that electrical leakage occurs in the fusible metal parts of the microwave oven due to insulation deterioration. Electric shock can occur, so the idea was to install grounding work on the ground terminal to bypass the electric shock current and reduce the electric shock current that flows to the human body to a safe level, thereby ensuring safety.

However, even if a grounding terminal is provided, grounding work must be done after the microwave is purchased, and there is a possibility that the work will not be done for various reasons, making it difficult to ensure safety.

In the case of high-rise condominiums, it would be good if the electrical outlets were equipped with ground terminals, but since only about 30% of them are currently equipped with such terminals, most of them have ground wires that are several meters to more than 10 meters long. It is necessary to extend the ground pole and drive the earth pole into the ground, which is not implemented due to the high construction cost. In particular, it becomes increasingly difficult to carry out grounding work because it is necessary to redo the grounding work when relocating or relocating.

In addition, even if you are not in a high-rise apartment building, you may have to make a hole in the wall to pass the ground wire through to seal the windows of the Aluminum Sasonyu, or if you try to drive it into the ground, you will be told that the ground pole cannot be driven in because it is made of concrete. Currently, there are many cases in which grounding work is not carried out for various reasons. In one survey, the range of about 40-50% was
The current situation is that it is being used without any grounding work being done.

Furthermore, even if a grounding pole has been driven into the ground and grounding work has been carried out, the place where the grounding pole will be driven is dry or, due to construction work, a place where glass stones have been laid on the surface to improve drainage. If this happens, low ground resistance will increase, making it impossible to ensure sufficient safety. In addition, there is a possibility of corrosion of the ground electrode or breakage of the ground wire, and the conventional method of installing a ground terminal is such that safety can only be ensured on the premise of sufficiently reliable grounding work. Ta.

On the other hand, with the recent spread of microwave ovens, they have become lighter and more compact, and there is a tendency for microwave ovens to be used anywhere, not just on the table, and that can be used without being fixed. Conventional microwave ovens with ground terminals, which require grounding work, are inconvenient.

Purpose of the Invention The present invention solves the above-mentioned conventional drawbacks, and aims to provide a microwave oven with a double insulation structure.In particular, the secondary high voltage side of the isolation transformer is completely isolated from the power supply side. The aim is to create a double insulation structure for the range, with the secondary high voltage still using the conventional insulation specifications.

Structure of the Invention In order to achieve the above object, the insulating transformer of the present invention has one end of the high voltage secondary side directly connected to the metal part of the heating cabinet or outer box (hereinafter referred to as "Nyashi") to which the magnetron is connected as in the past. In this configuration, the high voltage at the other end of the high voltage secondary side does not leak to the primary power supply side, and the high voltage secondary side is completely separated from the primary power supply side by the chassis. No, it is essentially shielded by surrounding it from the primary power supply side with the chassis, and even if insulation deterioration occurs, the high voltage on the secondary side will be prevented from bridging to the primary power supply side. This has the effect of safely protecting the human body from electric shock caused by the high voltage of the microwave.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a magnetron 2 is connected to a chassis 1, and an isolation transformer 3. High voltage capacitor 4. There are high voltage diodes 5, which are mounted together at the rear of the range. The isolation transformer 3 has a primary coil 6 connected to the power supply side.
and a high-voltage secondary coil are wound in sections, and a metal plate 8 is provided between them as a cross-contact prevention plate, and this is directly connected to the core of the transformer 3. A metal plate 22 extending from the magnetron is installed interposed between the low voltage primary coil and the high voltage secondary wiring. One end of the high voltage secondary coiler is directly connected to the core of the transformer 3, and the core is electrically connected to the shear 71. Therefore, 1 of the high voltage secondary coil 7
The end, metal plate 8 as well as metal plate 22 are both connected to the chassis.

On the other hand, the power cord 9 is connected to the operation panel 10, and is connected to the control circuit drive power transformer 11, the cooling motor 12, the relay 1
Components directly connected to the primary power source, such as the magnetron 2 and the transformer 3, are separated from the secondary high-voltage section by a metal wall and are mounted close to the front where the operation panel (not shown) is located. Note that these parts directly connected to the primary power source are double insulated from the power source and accessible parts such as the chassis 1. A door 14 is provided at the front to take in and take out food, which is an object to be heated.

Figure @2 is a perspective view of the insulating transformer 3. The primary coil 6 has a terminal 16 for wiring to a power supply circuit, and is double insulated from the core 16 by an insulating paper 17. The high-voltage secondary coil 7 is separated from the primary coil 6 by a necessary spatial distance, for example, 10 or more distances. Although it is insulated from the core 16 by an insulating paper 18, it is not double insulated. In other words, an alternating current of approximately 20 ooV is generated in the high voltage secondary circuit, but in order to provide double insulation, it is necessary to provide a spatial distance of 20 mm or more between the core 16 and the primary coil 6. Satisfied insulation paper 1
8 is unrealistic as it is larger than the coil. Furthermore, currently, there are no clear standards or design standards for the double insulation of 2oooV42 against high voltage, and no international consensus has been established regarding the double insulation structure of the insulating paper 18. Currently, there are no microwave ovens with double insulation structure.

In the present invention, the metal plate 8, the metal beak plate 22, etc. are provided, and the distance of the metal plate 8 from the secondary coil 7 and the distance between the components on the secondary high voltage side and the metal plate 22, etc. By making the distance of the secondary coil 6 and the distance between the parts on the secondary high voltage side and the parts on the primary power supply side sufficiently smaller, it is possible to reduce the distance between the insulation transformer 3 of the conventional dimensions and the parts of the secondary high voltage measurement. By completely separating the secondary high voltage side from the primary power supply side with normal insulation, a range with double insulation structure was realized.

The operation of the above configuration will be explained below.

FIG. 3 shows one implementation circuit of the present invention.

Suppose that the human body 19 is operating the microwave and is touching the heating chamber, for example. The heating chamber and the metal part of the box constitute the chassis 1 as described above.

Since the ledge is now connected to the power source drawn from the pole transformer, one end 21 of the 100V tortoise #20 is grounded to the ground.

Cooling motor 12° relay 13. Directly connected to 10oV power supply circuit. Control circuit drive power transformer 11. power cord 9
In addition, all parts on the power supply side, such as the primary coil 6 of the isolation transformer 3, are protected from the chassis 1 by double insulation, so there is no fear of electrical leakage.

On the other hand, the secondary coil 7 of the isolation transformer 3 has approximately 2000
7 high voltage is generated. One end 22 of the secondary coil 7 is connected to the chassis 1 via the core 16 of the transformer 3. Since the metal plate 8 directly connected to the core 16 and the metal plate 22 directly connected to the chassis substantially separate the high voltage side from the high voltage side, in the unlikely event that the secondary coil 7 on the secondary high voltage side Even if the insulation at point A deteriorates, it will not be directly connected to the primary coil 6.

For example, consider a case where a high voltage becomes conductive to the shear 71 as a result of insulation deterioration. When the conductive point A is connected to /safe 1 via a low resistance r, the current only flows through /safe 1 and does not flow to the human body 19.

That is, as shown in FIG. 4, when a bridge occurs between the primary coil 6 and the secondary coil 7 in a conventional microwave oven with a ground terminal, a high voltage of 2000 μm passes through the human body 19.
An electric shock current will flow, creating an extremely dangerous situation. Primary coil 6
When and the secondary coil 7 are bridged with a resistance value R (R=○),
The circuit shown by the arrow is formed, including power supply 1o○■, high voltage 2
Since the next voltage of 2000V is applied to this circuit,
For example, if the resistance of the human body is reduced to 5Q○Ω, an electric shock current of nearly 20A will pass through the human body, resulting in instant death.

At this time, even if a conventional microwave oven is equipped with a ground terminal and is grounded to the earth with a resistance of 100 ohms as specified, approximately 3.4 A of current will flow through the human body. If this current flows through the human body, the current international standard is 30m.
A...The flow time product of the hood coupling is considered to be the safe limit that does not cause cardiac/yonok death, so in this case,
It can be seen that if the electric shock continues for 0.01 seconds or more, it becomes dangerous.

Therefore, even if the earth is grounded, it is extremely dangerous and safety cannot be guaranteed if there is a bridge between the primary and secondary coils of the Zessho Transformer due to poor insulation. It can be said that.

Furthermore, in the present invention, there is no fear of being impressed by the secondary voltage and hill pressure of 2000V, so it can be said that the structure is extremely safe compared to the conventional one.

In addition, in FIG. 1, the high voltage capacitor 4 and high voltage diode 5, which are components of the secondary high voltage circuit, are connected to the core 6 of the transformer 3.
It is separated from the components of the power supply circuit by the metal case of the magnetron 2 and the metal plate 22.

That is, since the distance between the components on the high voltage secondary side and the shear 7 is configured to be shorter than the distance between the components on the low voltage power supply side and the components on the high voltage secondary side, There is no possibility that the side will be connected to the low voltage power supply side.

Figure @5 shows another embodiment in which the high-voltage side electrical components and the low-voltage power supply side components are separated by effectively utilizing a cooling air guide as a metal wall.

Usually, the cooling fan motor 12 is placed at the rear to cool the magnetron 2 and high voltage transformer 3. Magnetron for cooling 2. In order to effectively guide the air to the high voltage transformer 3, an air guide 23 with an orifice and a magnetron 2 are installed.
After cooling, the hot air is guided into the heating chamber, and the energy of the hot air is used to help raise the temperature of the heated object, and the steam is discharged outside the chamber, allowing the microwave to be effectively absorbed into the heated object. However, this hollow air guide 24 is made of metal, and a part of the air guide E25 extends to guide cold air to the back side of the transformer 3.

The transformer 3 is directly connected to the core 16 and has a magnetro/
A metal plate 22 is attached to separate the high voltage wiring 26 to 2 from the coil 6 of the low voltage power source.

With the above configuration, the air guides 23 and 24 provided for the cooling structure, the air guide B25, and
Metal plates 8, 22 and magnet) on 2. transformer core 1
6, it is possible to completely separate components on the power supply side and components on the high voltage secondary side.

Therefore, in FIG. 5, power cord 9. 1 operation panel.

A power transformer 11 for driving the control circuit, a cooling motor 12,
By making only the parts directly connected to the primary power supply side circuit, such as the relay 13, double insulation structure, double insulation of the range can be realized.

As described above, according to the present embodiment, in the isolation transformer in which one end of the high voltage secondary side is directly connected to the chassis, the high voltage secondary coil and the low voltage power supply side primary coil are wound separately, and the secondary coil and the primary coil are wound separately. A metal plate directly connected to the core is provided between the secondary coils, and the distance between the metal plate and the secondary coil is shorter than the distance between the secondary coil and the primary coil, and the metal plate 2
The distance between the high voltage secondary side parts and the chassis is made shorter than the distance between the high voltage secondary side parts and the power supply side parts using a metal wall directly connected to the primary coil and the power supply side. By doubly insulating the parts connected to the shunt from the shunt, not only does grounding work become unnecessary, but it also prevents electric shocks caused by the high voltage on the secondary side, making it extremely safe compared to conventional methods. This has the effect of enabling a high range of

Effects of the Invention As described above, according to the present invention, it is possible to realize a microwave oven with a double insulation structure although it has an extremely simple structure, and it has many effects such as high safety and ease of use as described below. Obtainable.

(1) Since there is no need for grounding work, there are not only no construction costs but also the following advantages.

B. It has become possible to freely choose the location where the microwave oven is installed, and especially lightweight and compact microwave ovens can now be moved to the required location for use.

B. Regarding grounding work, the work itself depends on the situation after purchasing the range, and there were concerns about corrosion of the ground electrode and breakage of the ground wire over time, but these concerns have completely disappeared.

(2) It is possible to make the microwave oven have a double insulation structure with the same shape as the conventional one, so the dimensions of the microwave oven remain the same and the cost is low. When considering construction costs, it has actually become cheaper.

(3) With conventional microwave ovens equipped with a ground terminal, it is almost impossible to prevent electric shock if, for example, the secondary high voltage bridges the primary coil, but with the present invention, This worry is completely eliminated, making it possible to create an extremely safe range.

[Brief explanation of the drawing]

Fig. 1 is a side view of a microwave oven which is an embodiment of the present invention;
The figure is a perspective view of the same isolation transformer, Figure 3 is a circuit diagram of the same implementation row, Figure 4 is a diagram explaining the path of electric current in a conventional range with a ground terminal, and Figure 5 is an air guide for cooling. FIG. 2 is a diagram showing an example in which a metal wall is effectively constructed by the following methods. 1...7 Yasi, 2-...Macnetron, 3
...Imaging transformer, 6...Primary coil, 7...Secondary coil, 8...Metal plate, 16
...Core, 19...Human body, 2o...
・Power supply, 21...One end of the power source that is grounded, 22...Metal plate, 23.24...Air guide, 25...Air guide Name of B0 agent Patent attorney Toshio Nakao and 1 other person Figure 1 Figure 2

Claims (3)

[Claims] (1) One end of the secondary side of the isolation transformer is directly connected to the chassis and core, and the high-voltage secondary coil of the high-voltage transformer and the low-voltage power supply side primary coil are separated, and a metal plate directly connected to the chassis is installed between them. The high-voltage secondary coil is separated from the low-voltage primary coil on the power supply side by a metal wall, and the secondary high-voltage side parts connected to the secondary coil and the low-voltage power supply side are also connected directly to the chassis. At least the distance between the parts on the secondary high voltage side and the metal wall is smaller than the distance between the parts on the secondary high voltage side and the parts on the low voltage power supply side, and the parts on the low voltage power supply side are double insulated. A high-frequency heating device with a built-in structure. (2) The high-frequency heating device according to claim 1, wherein the metal plate is directly connected to the core of the transformer and also serves as a heat sink for the core. (3) The high-frequency heating device according to claim 1, wherein the metal wall is configured by extending a part of the wall surface of the air guide.