JPS6256633B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a door seal structure for a high frequency heating device. Conventional configurations and their problems In recent years, high-frequency heating devices have become a daily necessity in every household, and their technological capabilities have progressed, particularly in the field of door seal structures to prevent radio wave leakage. Hereinafter, a conventional high frequency heating device as described above will be explained with reference to the drawings. FIG. 1 is an external perspective view of a conventional high-frequency heating device, and FIG. 2 is a sectional view of a main part of FIG. 1. In FIG. 1, 1 is a main body, 2 is a heating chamber that accommodates an object to be heated, and 3 is an object to be heated. Heat generated by a magnetron (not shown) is in heating chamber 2.
A high frequency of 2450 MHz is applied to dielectrically heat the object 3 housed in the heating chamber 2. 4 is heating chamber 2
A door whose front opening can be opened and closed freely, 5 is the main body 1
A hinge 6 located at the lower end of the door 4 and connecting the door 4 and the front opening of the heating chamber 2 is a handle provided at the upper end of the door 4 to facilitate opening and closing. Reference numeral 7 denotes a peephole provided so that the state of the heated object 3 during heating can be checked from the outside. In FIG. 2, 8 is the front wall of the heating chamber facing the door 4, 9 is the outer shell of the stainless steel door, and 10
11 is the outer frame of the door, and 11 is the inner frame of the door, each forming a cavity with a length of 1/4λg to form a chiyoke structure, and furthermore, the inner ends of the outer frame 10 and the inner frame 11 are aligned. . Reference numeral 12 denotes a punching plate that allows confirmation of the inside of the heating chamber 2. The punching plate 12 is made of metal and has many small diameter holes (small holes). Reference numeral 13 indicates an inner glass plate provided so that the inside of the heating chamber 2 can be checked, 14 indicates a packing for fixing the inner glass plate 13, and 15 indicates an outer end of the outer frame 10, facing the front wall of the heating chamber. Reference numeral 16 denotes a substantially U-shaped mounting plate provided in order to prevent the screws for connecting the outer frame 10 and inner frame 11 from protruding from the surface. and is connected to the inner frame 11 in a bag-like manner. 17 is a mounting screw that connects the outer frame 10, the punching plate 12,
The inner frame 11 is fixed with invisible screws. 18 is a chiyoke groove to prevent radio wave leakage, 19
20 is a resin frame for preventing unnecessary objects from entering the check groove 18, and 20 is a slit plate that improves the function of preventing radio waves from leaking to the outside of the outer frame 1.
It is provided parallel to the outer end 15 of 0. Reference numeral 21 denotes an outer glass plate, a cover that prevents the user from directly touching the punching plate 12 and smoke from entering, and 22 a resin window frame that fixes the outer glass plate 21. However, the above configuration has the following drawbacks. The facing surfaces of the outer frame 10 and the mounting plate 16 are electrically insulated because the inner frame 11 and the mounting plate 16 are enamel-treated. However, since this opposing surface is the end of the chiyoke groove, this is where the chiyoke current value is maximum.
Furthermore, this is also the place where the wall current of the heating chamber 2 flows.
Both of these currents, ie, the wall current and the wall current, flow mostly through the mounting screw 17. However, since the mounting screws 17 are tightened by cutting the taps on the enamel-treated mounting plate 16 by themselves, the electrical connection between the mounting plate 16 and the mounting screws 17 is insufficient, and the mounting plate 16 and the mounting screws are damaged during tightening. 1
Due to the decrease in the microwave penetration depth due to the increase in the magnetic permeability μ of No. 7, the resistance to microwave current in this part was much higher than in other parts. For that reason,
Heat is generated at the mounting screws 17, transmitted through the mounting plate 16, and heats the inner frame 11. As a result, when the user takes out the object to be heated 3 from inside the heating chamber 2, burns and the like occur, resulting in a lack of safety. Purpose of the Invention In view of the above drawbacks, the present invention provides a safe high-frequency heating device that prevents heat generation at the attachment portion of the outer frame and inner frame of the door and does not cause burns when the object to be heated is taken out of the heating chamber. This is what we provide. Structure of the Invention In order to achieve the above object, the high frequency heating device of the present invention is provided with a heating chamber for accommodating an object to be heated, a high frequency oscillator, and a door that can open and close a front opening of the heating chamber, The door has an inner frame on the outer periphery to prevent leakage of high frequency waves, a yoke groove having a depth of 1/4 wavelength from the outer peripheral end face of the inner frame and forming a yoke with the outer frame, and a yoke groove formed in the heating chamber. has a shield plate having a plurality of small holes for observing from the outside, and the shield plate is sandwiched between the inner frame, the outer frame, and a mounting plate, and further fixed with a plurality of mounting screws. A slit hole having a length of approximately 1/2 wavelength is provided in the circumferential direction of the chain yoke groove near the mounting screw. DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 3a is a sectional view of a main part of a high-frequency heating device according to an embodiment of the present invention, FIG. 3b is a perspective view of the main part, and FIG. 3c is a distribution diagram of electric field and current of the same device. Components that are the same as those in FIGS. 1 and 2 are designated by the same numbers and their explanations will be omitted. In FIG. 3a, 23 is a slit hole provided in the center of the mounting plate 16 that is long in the circumferential direction, approximately 1/2 wavelength long and 2 to 3 mm wide, and is symmetrical about the mounting screw 17. Moreover, they are provided at the top and bottom. In this embodiment, this set of slit holes 23 are provided at four locations in the upper, lower, left, and right center mounting portions. Also,
24 is a space surrounded by the inner frame 11 and the mounting plate 16. The misalignment of the high frequency oscillation frequency of the cheese yoke structure due to the provision of the slit hole 23 can be avoided by the slit plate 2 provided in the cheese yoke groove 18.
This is corrected by changing the position and shape of 0. By adopting the above configuration, the temperature of the inner frame 11 can be significantly reduced. That is, by providing the slit hole 23, the current in this portion can be made zero, that is, the current can be made to be a discharge end. Further, the position of the maximum current is located at a position approximately 1/4 wavelength from the slit hole 23, as shown in FIG. 3c. Therefore, almost no microwave current flows through the mounting screw 17, and even if the contact resistance or penetration depth becomes shallow, the amount of heat generated will be extremely small. On the other hand, although the current is at its maximum near the end of the slit hole 23, there is no part such as the mounting screw 17 where the current flows in a concentrated manner, and local heat generation does not occur.
Furthermore, as in this embodiment, the slit hole 23 is made approximately 1/2
By setting the wavelength, the standing wave of the electric field can be established most efficiently, and at the same time, this slit hole 23 has the function of an antenna, so that even greater effects can be obtained as follows. did it. The upper slit hole 23 efficiently excites a part of the radio waves that have entered the chiyoke groove 18 into the space 24 surrounded by the inner frame 11 and the mounting plate 16.
The radio waves that have entered the interior are excited by the slit hole 23 at the bottom, and some of the excited radio waves are caused by the inner glass plate 13.
is heated, and the rest returns to heating chamber 2. On the other hand, on the other hand, the radio waves traveling from the heating chamber 2 side to the end of the inner glass plate 13 are transmitted to the chiyoke groove 1 by a completely opposite process.
8, but when it passes through the two slit holes 23, the electric field phase is adjusted and the inner frame 11
It passes between the front wall 8 of the heating chamber and returns to the inside of the heating chamber 2. Due to this, the outer frame 10 and the punching plate 12
The amount of radio waves leaking can be reduced. Table 1 shows the conventional example without the slit hole 23 and the slit hole 2 when generating a high frequency output of 2KW.
3 shows the difference in temperature rise after 1 minute of no-load operation in this example. As is clear from the table, by providing the slit holes 23, it was possible to significantly reduce the temperature rise between the mounting screws 17 and the inner frame 11.

[Table] As explained above, the effect of this example is the outer frame 1
Between the outer frame 10 and the punching plate 12, the leakage of radio waves can be reduced.
There is no need to worry so much about the state of contact between the screws 17, and the product no longer generates heat near the mounting screws 17, making it a safe product. Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4a is a sectional view of a main part of a high-frequency heating device according to a second embodiment of the present invention. Components that are the same as those in FIG. 3 are given the same numbers and their explanations will be omitted. In the figure, 11c is an inner frame, and 30 and 31 are slit holes. This embodiment differs from the first embodiment in that since the mounting screws 17 protrude into the heating chamber 2, there is no mounting plate 16, so the inner frame 11c
The point is that a slit hole is provided in the hole. In this case as well, the fourth
As is clear from Figure b, the slit holes 30, 31 are provided at the same positions as in the first embodiment. With this configuration, the same effects as the first embodiment can be expected. Furthermore, in this embodiment, the slit hole 30 is connected to the cheese yoke groove 18 and the heating chamber 2.
This slit hole 30 is located between the door 4
It is also possible to suppress wave leakage from the outer peripheral edge of the tube. Effects of the Invention As described above, the present invention can obtain the following effects. (1) There is no heat generation at the mounting screw part, making it highly safe to handle without worrying about burns. (2) It is possible to have a safe configuration in which radio waves from the heating chamber do not leak.

[Brief explanation of the drawing]

Figure 1 is an external perspective view of a conventional high-frequency heating device.
FIG. 2 is a sectional view of the main part of the same, FIG.
Figure b is a perspective view of the main parts of the same device, Figure 3c is a distribution diagram of the electric field and current of the same equipment, Figure 4a is a sectional view of the main parts of a high frequency heating device in another embodiment of the present invention, and Figure 4
Figure b is a perspective view of the main parts of the device. 2... Heating chamber, 3... Heated object, 4... Door,
7...Peephole, 10...Outer frame, 11...Inner frame,
12...Punching plate, 16...Mounting plate, 17...
...Mounting screw, 18...Chiyoke groove, 23, 30,
31...Slit hole.

Claims (1)

[Scope of Claims] 1. A heating chamber for accommodating an object to be heated, a high-frequency oscillator, and a door that can open and close a front opening of the heating chamber, and the door prevents leakage of high-frequency waves to the outer periphery. an inner frame for heating, a chiyoke groove that constitutes a chiyoke by the outer peripheral end face of the inner frame and the outer frame, and a peephole consisting of a shield plate having a plurality of small holes for observing the inside of the heating chamber from the outside. , the shield plate is sandwiched between the inner frame, the outer frame, and the mounting plate, and is fixed by a plurality of mounting screws, and the shield plate has a groove extending approximately 1/2 in the circumferential direction of the chiyoke groove near the mounting screws. High frequency heating device with a slit hole the length of the wavelength. 2. The high-frequency heating device according to claim 1, wherein the slit hole provided near the mounting screw is provided near the packing provided at the terminal end of the cheese yoke groove and the periphery of the observation window, and the two are spatially communicated with each other. .