JPS61188884A - High frequency heater - 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] Industrial Application Field The present invention prevents electric shock accidents caused by high voltage on the secondary side by surrounding the high voltage secondary side circuit with a metal body to prevent contact with the power supply side. The present invention also relates to a high-frequency heating device in which the charging part on the power supply side has a double insulation structure, thereby eliminating the need for grounding work.

Conventional technology In the unlikely event that insulation deteriorates between the high-voltage secondary circuit and the power supply side, and high voltage leaks to the fusible metal part of the range, the conventional high-frequency heating device (hereinafter simply referred to as the range) Install a ground terminal on the fusible metal part and conduct grounding work to the ground.
The invention attempts to ensure safety by bypassing the electric shock current that flows through the human body to a safe level.0 Problems that the invention aims to solveHowever, the above-mentioned high voltage In this case, there were two problems and it was difficult to ensure safety.

The first issue is the extent to which grounding work will be carried out. Even if a microwave oven is equipped with a grounding terminal, grounding work must be done after purchasing the microwave oven, and there is a possibility that it will not be carried out for various reasons, making it difficult to ensure safety. In other words, in the case of high-rise condominiums, it is sufficient if the electrical outlet is equipped with a ground terminal, but this is currently around 30
Most of them are not implemented due to the high construction cost, as it is necessary to extend the ground wire several meters or more than ten meters and drive the ground pole into the ground. In particular, it becomes increasingly difficult to carry out grounding work because it is necessary to redo the grounding work when transferring jobs or moving homes.

Also, even if you are not in a high-rise building, you will want to seal the windows of the aluminium, so you will have to make a hole in the wall for the ground wire to pass through, and even if you try to drive it into the ground, you will not be able to connect the ground wire because it is made of concrete. The current situation is that there are many cases where grounding work is not carried out because it is not possible to do so.

According to one survey, approximately 40% to 50% of microwave ovens are currently being used without any grounding.Furthermore, even if the earthing pole had been driven into the ground and the grounding had been done, If the location where the ground electrode is to be driven is dry or where gravel has been laid on the ground surface to improve drainage due to construction work, grounding resistance will increase and sufficient safety will not be ensured. On the other hand, the ground resistance value can be set to about 100Ω if a 5QI+m carbon rod earth pole is driven into the ground, but it is 200Ω.
If a high voltage close to 0V leaks, a leakage current of 20 amperes will flow9. Considering the worst case scenario, if the resistance of the human body is about SaO2, the electric shock current flowing through the human body will be several amperes. It becomes a value. Therefore, it is impossible to suppress the electric shock current to a value of 1 mA or less, which is said to be a safe level for the human body. There is also the possibility of corrosion of the ground electrode or breakage of the ground wire, so the conventional method of installing a ground electrode is a performance that ensures safety only on the premise of reliable grounding work. , it is extremely difficult to ensure safety against high voltage leakage of nearly 200 ov.

Second, with the recent spread of microwave ovens, they have become lighter and more compact, and there is a trend for microwave ovens that can be used not only on the table but also be moved freely. Conventional ranges with ground terminals, which are fixed to the ground, are becoming inconvenient.

Means for Solving the Problems The present invention surrounds the high-voltage secondary side circuit with a metal body, and in order to prevent contact with the power supply side, in addition to the metal chassis housing the heating chamber and the high-frequency generator, The core of the high voltage transformer, the metal case of the high voltage capacitor,
The high-voltage secondary circuit is connected to the metal case of the magnetron oscillator and the metal wall constructed by adding a cross-contact prevention plate that is directly connected and fixed to the core between the high-voltage secondary coil of the high-voltage transformer and the power source primary coil. has a closed configuration, and
The primary coil on the power supply side of the high voltage transformer and the components on the power supply side have a double insulation or reinforced insulation structure.

If the high-voltage insulator deteriorates due to the high-voltage secondary circuit being enclosed by a metal wall and a current leakage occurs, one end of the high-voltage secondary side is connected to the chassis, so if the high-voltage secondary circuit is enclosed with a metal wall, A closed circuit is created. This phenomenon is similar to when a high-voltage rectifier suffers dielectric breakdown, and the fuse in the power supply circuit blows to notify a failure condition, just as in conventional ranges. Therefore, insulation from the power source side is maintained, so cross contact does not occur.

In addition, since double insulation structure only requires measures for the secondary coil and power supply circuit components, it is much easier to achieve than double insulation on the high voltage secondary side, and the spatial distance between the chassis and the Since the distance between the power supply charging parts is 8 meters or less, and if an insulator is used, the distance is 2.5 meters, this can be achieved without significantly increasing the conventional dimensions. As a result, there is no need for grounding work, the device can be easily moved from one place to another, and it is easier to ensure safety compared to conventional systems that rely on unreliable grounding work.

Embodiment Hereinafter, the configuration of a microwave oven according to an embodiment of the present invention will be explained with reference to the drawings.

As shown in FIGS. 1a and 1b, a high frequency wave is radiated from a magnetron oscillator 2 into a heating chamber 1 in which food is stored and cooked. The high-voltage transformer 3 that drives the magnetron 2 is an insulating transformer that is divided into a power supply coil 4 and a secondary high-voltage coil 6, which are connected by a fixing screw 22, and are separated into upper and lower parts when removed. Therefore, the plan view of FIG. 1 shows the heating chamber separated by removing the fixing screw 22 and the fixing screw 21 of the magnetron 2.

The core 7 is electrically connected and fixed to the metal chassis 6.

A metal plate 8 is directly connected to the core 7 and fixed between the power supply side coil 4 and the secondary high voltage side coil 6.

As shown in the figure, the metal plate 8 constitutes a metal wall extending substantially perpendicularly from the core 7 and standing at right angles to the core 7, which has a sufficiently large height that the power supply side coil 4 and the secondary high voltage side coil 6 cannot be seen through. are doing. High voltage capacitor 9 is arranged on chassis 6 such that the metal case constitutes one metal wall.

That is, in the embodiment, the high voltage circuit 1o includes the high voltage diode 1
transformer core 7 located on chassis e, including 1
, the metal plate 8, the metal case of the high-voltage capacitor 9, and the metal case of the magnetron 2.
Since the high-voltage circuit is enclosed in a metal case whose top and bottom are constituted by the bottom surface 12 and the chassis 6, there is no possibility that the live parts of the high-voltage circuit will directly come into contact with the power supply side.

In this way, the high voltage circuit 10 arranged on the chassis 6 is
After wiring work from above, all you have to do is cover the heating chamber 1 from above and tighten it with the fixing screws 22 and the fixing screws 21 of the magnetron 2, so the work procedure is easy and there is no need to run long high-voltage wires. Various effects can be expected, such as eliminating the need to erect special metal walls.

Continuity of these metal walls is ensured during each tightening operation by the mounting screws 21 of the magnetron 2, the fixing screws 22 of the heating chamber 1 and the chassis 6, and the fixing screws (not shown) of the high voltage transformer 3 and high voltage capacitor 9. be done.

Next, the power supply side charging section connects the primary coil 4 of the high voltage transformer 3.
, the terminal portion 16, the fan motor coil 16, the latch switch 17, the time switch 18, the power cord 19, and the power supply side low voltage wiring 20 correspond to this. A simple method for double-insulating these live parts on the power supply side will be described.

In Fig. 2, the secondary coil 4 has double insulation consisting of basic insulation and additional insulation from the core 7,
It has a more extended shape, and on the primary coil 4 side of the metal plate 8,
Similarly, double insulation consisting of basic insulation and additional insulation is applied. Returning to Figure 1, the power supply circuit side refers to the high voltage secondary side terminal 13.
A primary coil terminal 16 is provided on the opposite side.

In FIG. 3, a method of double-insulating the power supply side low-voltage wiring 20 from the chassis and the heating chamber will be described.

The fan motor bracket 25 to which the resin fan motor mounting plate and air guide are attached has a groove 26 in a direction that intersects the direction in which the low voltage wiring 2o is routed.
A flange 27 is provided, and the thickness of these seven flanges is set to a predetermined spatial distance, for example, 2.4 mm or more. When wiring, the lead wire is passed along this groove 26 and then inserted into the terminal 16 of the transformer secondary coil 4 or the terminal of the fan motor coil 16. By managing and bundling the wires with a small length margin to prevent loose wires, you can reduce the
Since the pressure wire 20 has the flange 27, a spatial distance of 2.4 groups or more is always maintained between it and the metal wall of the upper heating chamber bottom surface 12. Therefore, double insulation can be achieved from the metal wall 12 and the chassis 6 with a simple structure by using the insulation coating of the low voltage wiring 20 as basic insulation and using the spatial distance of 2.4 mm as additional insulation.

The fan motor coil 16 is connected to the fan motor bracket 2
6, latch switch 17 and time switch 1
8 is similarly attached to the resin operation plate 28, so that the predetermined insulation corresponding to the additional insulation is protected from the metal wall 4, the chassis 6, and the surface of the fusible part from the outside.
(approximately 0.8 rm or more) or spatial distance (approximately 2.4 mm
If the above) is ensured, basic insulation can be achieved with the conventional insulation specifications of the fan motor coil 16, latch switch 17, and time switch 18, so a double insulation structure can be realized relatively easily. . Further, regarding the power cord 19, the insulation coating is made into a double sheath, so that basic insulation and additional insulation can be easily realized. The portion penetrating the metal chassis 6 is achieved by integrally molding a bushing made of vinyl chloride or the like having a thickness of about 111II+ or more on the double sheath.

In addition, an insulating holder 30 is provided as appropriate to hold the low voltage wiring on the power supply side in the air and connect it to the metal wall as well as from the chassis 6 to 2.
Ensure a spatial distance of 4m or more or use PVC tubes (0,
It is possible to double insulate internal wiring that is already insulated (4m or more).

In either case, as long as the space is completely separated from the secondary high-voltage wiring, the specified spatial distance can be relatively easily secured using conventional parts using mounting brackets or holders made of resin insulators. , double insulation is easily achieved.

FIG. 4 shows a circuit diagram of the structure of the present invention.

In the figure, if the high voltage secondary side suffers dielectric breakdown and a large amount of leakage current flows between the high voltage secondary circuit and the terminal connected to the chassis 6, a fuse 31 on the power supply side will be activated.

Effects of the Invention As described above, in the microwave oven of the present invention, the secondary high voltage side is substantially enclosed by a metal wall, so even if the insulation on the secondary side deteriorates, the metal wall will be removed first. A leakage current occurs between the wall and the chassis ground point at one end of the secondary side, and the fuse in the power supply circuit blows in a short time.

Therefore, there is no possibility that the primary power supply side and the secondary high voltage side will come into direct contact with each other and cause an electric shock due to the secondary high voltage.

In addition, the secondary high voltage side is not enclosed by adding a special metal wall, but instead the conventional transformer core, high voltage capacitor, and magnetron metal case, and the metal plate installed on the high voltage transformer to prevent cross contact. Since the structure can be configured simply by devising the arrangement, the number of parts is reduced, and the secondary high voltage side can be prevented from coming into contact with the power supply side, and the length of the high voltage wiring can be shortened.

Furthermore, since double insulation is achieved with a relatively simple structure on the primary side, there is no increase in man-hours and the double insulation structure can be easily assembled, eliminating the need for grounding work for the range. It is extremely effective in practical terms, as it allows for easy movement and use.

[Brief explanation of drawings]

Figures 1a and b are a plan view of a chassis housing a high-frequency generator for a range according to an embodiment of the present invention, and a front cross-sectional view seen from the direction of the arrow in the rod view, and Figure 2 is a high-pressure FIG. 3 is a perspective view showing a transformer, FIG. 3 is a perspective view showing a fan motor bracket for double insulating the low-voltage internal wiring on the power supply side of the present invention, and FIG. 4 is a circuit diagram in an embodiment of the present invention. 1... Heating chamber, 2... Magnetron oscillator, 3... High voltage transformer, 6... Metal chassis, 7... Core, 8 ...Metal plate, 9...High voltage capacitor, 10...
・High voltage secondary circuit, 11... High voltage diode. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
-Ichibetsu omitted 1 7---Goataukai Tamekari 9--&Koshiden T

Claims (1)

[Claims] a heating chamber that stores and heats food; a high-frequency generator that radiates high-frequency waves into the heating chamber; a metal chassis that houses the high-frequency generator and shares a part of a metal wall adjacent to the heating chamber; A high voltage transformer with one end of the secondary side of the isolation transformer directly connected to the chassis and the transformer core, a high voltage capacitor having a metal case connected to the high voltage transformer secondary circuit, and a magnetron oscillator also having a metal case are mounted on the metal chassis. The high-voltage secondary coil and the power supply-side primary coil of the high-voltage transformer are divided into separate windings, and a metal plate is directly connected and fixed to the transformer core between them. ,
By surrounding the metal plate, the metal case of the high-voltage capacitor, the metal case of the magnetron, and the metal wall shared with the heating chamber with the metal chassis, and by connecting these metal parts conductively, the high-voltage secondary side can be virtually disconnected from the live part on the power supply side. The primary coil of the high-voltage transformer is double-insulated or reinforced insulated, and the power-supply side parts are attached to a resin frame. Insulate the metal wall of the heating chamber, the metal chassis, and the metal case of the high-voltage secondary circuit components by maintaining a specified distance, and at the same time maintain a specified distance from the parts that can be touched by fingers from the outside for double insulation. A high-frequency heating device configured with reinforced insulation.