JPH01221886A - High-frequency heating device - Google Patents

Abstract

PURPOSE:To suppress an abnormal heating at the periphery of a loading table by making the distance between a bottom wall opposite to the loading table shorter than the rotation area of a churning plate in which the electric field is varied, concentrating the high-frequency energy to the loading area of a substance to heat, and ventilating between the loading table and the bottom wall. CONSTITUTION:The heating device is composed to rotate a churning device 9 of electric field along almost all the area of the loading area of a substance to heat 10, and the substance 10 is heated by a strong and even electric field. Although the loading table 11 is heated at the same time, the heat is absorbed to the substance 10. In this case, the distance between the bottom wall 3 and the loading table 11 is made shorter than the set area of the substance to heat 10, to weaken the electric field applied to the loading table 11. Furthermore, through ventilating holes 25-29 furnished where the distance between the loading table 11 and the bottom wall 3 is shorter, the ventilation at the part is carried out to apply a cooling air. An abnormal heating at the periphery of the loading table can be prevented consequently.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-frequency power supply method for a high-frequency heating device, and relates to a high-frequency power supply method for a high-frequency heating device, and the present invention relates to a high-frequency power supply method for a high-frequency heating device, in which yellow heating phenomenon caused by high-frequency waves in the heating chamber is prevented in a device having high-frequency power supply means on the upper and lower walls of the heating chamber. 0 Conventional Technology In general, in this type of heating device, when it is desired to obtain a high output device, a plurality of high frequency generating means are provided and are operated in parallel within the same heating chamber. A method is adopted in which a structure is provided to guide the high frequency waves generated by each high frequency generating means. In particular, for the purpose of high output and uniform heating, high frequency waves are introduced into the heating chamber. A method of heating from the top and bottom is also used.

FIG. 3 schematically shows a side cross section of a high frequency generator having such a configuration.

Circular power feed ports 4 and 6 for supplying high-frequency waves to the heating chamber are provided in a portion of the top wall 2 and bottom wall 3, respectively, which constitute the heating chamber 1. At the center of the power feed ports 4, 5, a power feed antenna 6.7 supported by a dielectric material is rotatably supported around the center of the power feed port 4.6. Each of the antennas 6, 7 has one end protruding into the heating chamber 1, and has stirring plates 8, 9 near the end surface for stirring the electric field. The stirring plate 8.9 may be directly fixed to the antenna 6.7, or may be coupled via a dielectric.

Above the stirring plate at the bottom, a mounting table 11 for a heated object 10 made of a dielectric material such as glass is supported by a support piece 13 provided on a side wall 12 forming the heating chamber. An end outside the heating chamber of the O antenna 6.7. The section includes two magnetrons 14.15 and a waveguide 16.15 as high frequency generators provided at the rear of the heating chamber.
17 for high frequency coupling. Further, at the end of the antenna 6.7 on the waveguide 16.17 side, a waveguide 16.
The output shafts of drive motors 18 and 19 provided outside the antenna 17 are coupled, and the antenna 6.7 is rotated around the center of the feed ports 4 and 6 while the magnetron 14.15 is generating high frequency waves. With the above configuration, the object to be heated 1 is placed on the mounting table 11 in the heating chamber 1.
By placing the 0 and supplying power to the magnetrons 14 and 16 as required, it is possible to heat the object from above and below, and at a maximum of twice the output.

Problems to be Solved by the Invention One of the problems with the high-frequency heating device having such a configuration is the phenomenon of abnormal overheating of the portion of the mounting table on which the object to be heated is not placed. Due to the presence of dielectric loss due to high frequency energy, the mounting table 11 is heated at the same time as the object to be heated, and the heat is absorbed by the object in the area where the object is present, but in the area where there is no object to be heated. In some cases, even a highly heat-resistant dielectric material such as crystallized glass, which has a melting point of 1000° C. or higher, is locally melted. As a result, the entire mounting table will be destroyed due to the generation of thermal stress, and if the heating operation is repeated, the possibility of this happening becomes extremely high due to heat accumulation. This could cause burns to the user, and could even cause a fire to break out from inside the refrigerator or even cause the entire device to catch fire, creating an extremely dangerous situation. Conventionally, as a countermeasure for this, for example, a thermostat (20) etc. was installed on the wall of the heating chamber as a means to prevent excessive temperature rise.If the temperature inside the refrigerator rose abnormally, this switch would be activated.
Magnetro: /14. '16's input power was cut off to stop the heating operation, but as the high frequency output increases, the local heating phenomenon becomes more intense.
At temperatures below 0°C, the operating temperature of the thermostat, which is set to prevent malfunctions during normal operation, cannot be reached and the thermostat does not function satisfactorily.

Means for Solving the Problems The present invention aims to prevent such abnormal heating of the mounting table, by comparing the distance between the mounting table and the opposing bottom wall with the rotating region of the stirring plate where the electric field changes, By shortening the other parts, the high-frequency electric field in the parts outside the rotation area is weakened, and the high-frequency energy is concentrated in the area where the object to be heated is placed.
In addition, ventilation is provided between the mounting table and the bottom wall to suppress abnormal heating of parts of the mounting table other than the area where the object to be heated is placed.

The strength of the high-frequency electric field applied to the working table portion depends on the high-frequency standing waves generated within the heating chamber.

That is, the electric field on the surface of the bottom wall is 0, and when looking at the antinode of the standing wave, the electric field strength becomes stronger as the distance from the wall increases. The heating area is set so that the strongest electric field is applied to the heated object.
The distance from the wall is set. Furthermore, a structure is provided in which an electric field stirring means rotates over almost the entire region, so that the object to be heated is heated by a strong and uniform electric field. At the same time, the mounting table is also heated, but since the heat generated on the mounting table is absorbed by the object to be heated, no abnormal heating phenomenon of the mounting table occurs in this part.

On the other hand, in the area other than the area where the object to be heated is placed, where the mounting table faces the bottom wall, there is little effect on fluctuations in the electric field due to the rotation of the stirring means, and local heating by standing waves tends to occur. Compared to the area where the object is placed, the electric field applied to the mounting table is weakened by shortening the distance between the bottom wall and the mounting table, thereby suppressing abnormal heating of the mounting table.

However, with this method alone, the outer periphery of the object to be heated, especially the upper surface thereof, cannot be heated because the high frequency waves emitted from the bottom wall side are blocked by the bottom surface of the object to be heated. In the present invention, the second
A high-frequency electromagnetic wave is radiated around the heating chamber along the earthen wall by the power feeding means, and is reflected by each wall surface.Another stirring plate installed near the earthen wall stirs the electric field and waves the top and side surfaces of the object to be heated. It can be heated. Furthermore, heating by high frequency waves in areas other than the area where the object to be heated is placed can be further suppressed by ventilating this area through a vent provided in the area where the distance between the mounting table and the bottom wall is short and applying cooling air. Ru.

Embodiment An embodiment of the present invention will be explained with reference to FIGS. 1 and 2. Note that the same numbers are given to the same components as those described in the conventional example.

As shown in the figure, a circular high-frequency power feeding port 6f is provided as a power feeding means in the center of the bottom wall 3 of the heating chamber, and an antenna 7 and a flat stirring plate 9 fixed to the tip thereof are placed at the center of the feeding port 6, as in the conventional case. The F magnetrons 14 and 16 are rotatably supported on a drive motor 19 and rotated during oscillation.

The bottom wall 3 constituting the heating chamber 1 is provided with a circular constricted portion 21 having a size equal to or smaller than the mounting area of the object to be heated and having a radius substantially the same as the radius of rotation of the stirring plate 9. In this example, the bottom surface of the heating chamber is 330 m wide x 310 m deep, and
The diameter of the constricted portion is 250 mm. The depth of the aperture is such that sufficient electric field strength can be obtained in the mounting area, that is, when the high frequency of the embodiment is 2450 MH1, the depth of the aperture is determined from the lower end (feed port part) of the aperture part 21 to the mounting table. The height is approximately 26m. The periphery of the constriction part 21 is a bowl-shaped 60° inclined surface 2"2t, and the outer side thereof is the upper wall of the processing chamber 1, which has a distance of about 10 m from the side wall of the heating chamber 1 to the mounting table 11. 2 is provided with a circular constriction part 23 having a radius similar to the rotation radius of the stirring plate 90.This constriction part 2
Similarly, a power feed port 4 is provided in the center of the power feed port 4, and an antenna 6 and a stirring plate 8 fixed to the tip thereof are rotatably supported around the center of the power feed port 4 as described above. At 18, L remagnetrons 14 and 15 rotate during oscillation to radiate high frequency waves into the heating chamber 1 and stir it. An inclined surface 24 is provided around the periphery 1500 of the constriction portion 23, and the outer side thereof forms a surface 20 m lower than the surface on which the power supply port 4 is provided, and is connected to the side wall portion.

Furthermore, on the outside of the inclined surface 22 of the bottom wall 3, there are two locations on the front left and right and two locations on the rear left and right, each with a diameter of 3.
Ventilation port consisting of a plurality of 1aI holes 25.26.27.
28 is provided. Further, in the heating chamber side wall 12, a vent hole 29 consisting of a plurality of similar small-diameter holes is provided in a portion below the mounting table 11 and above the joint portion with the bottom wall. The magnetron/16 related to high frequency radiation on the bottom wall of the heating chamber F has a configuration in which it is cooled by a blower motor 300 revolutions provided between the magnetron 16 and the side wall. An intake guide 31t is provided at the lower part of the intake part of the blower motor 3o to connect with the ventilation port 27, 28, 29, and while the high frequency is being generated, the blower motor 3o rotates to cool the magnetron 16 and , air from the lower part of the mounting table 11 is drawn out from the ventilation hole 28°29.30.

A portion of the cooling air of the main body is taken into the main body through the intake port 32 provided on the front of the main body,
26! It has a structure in which it is replenished by flowing into the lower part of the mounting table.

In addition, the front wall 33 forming the heating chamber 1t is provided with a door 34 which allows the object to be heated to enter so as to be openable and closable, so that leakage of high frequency waves is prevented by contact between the two. Further, the wind that has cooled the magnetron 15 is discharged to the outside of the main body from the exhaust port 36.

According to the above configuration, the high frequency waves radiated to the aperture part 21 at the bottom of the heating chamber 1 via the antenna 7 pass through the mounting table 11 and are directly absorbed by the bottom of the object to be heated 1o, or are directly absorbed by the inclined surface 22. It is reflected from this part. Sloped bottom wall 3
The direction of reflection depends on the angle of the inclined surface 22 relative to the surface where the power supply port is provided, but if the angle is t-46° or more with respect to the surface where the power supply port is provided, the high frequency waves will be reflected toward the center of the heating chamber and the heated It will face the bottom of object 1o.

In other words, the high frequency waves emitted by the magnetron 15 are transmitted to the antenna 7.
is emitted toward the bottom of the object to be heated 10 through
It becomes difficult to advance outward from the inclined surface 22. The flat stirring plate 9 changes the direction of high-frequency irradiation centered on the rotation axis of the high-frequency antenna 70 according to rotation, and also changes the standing of standing waves starting from the wall surface. The electric field is changed to prevent local heating of the bottom surface of the object to be heated 1o.

In this part of the mounting table 11, the object to be heated 1° absorbs heat and does not cause any abnormal heating phenomenon. Furthermore, the inclined surface 22
The high frequency waves emitted to the outside pass through the mounting table 11 and are radiated into the heating chamber 1, but as mentioned above, by reducing the distance from the bottom wall 3 to the mounting table 11 by 10 mm, this The electric field strength due to standing waves in the area has become low, and the area that previously had a temperature of 300°C or more after 10 minutes of main unit operation has been changed to 140°C.
``It is now possible to set it to C or lower - fI:,.

Furthermore, the flow of air that flows into between the bottom wall 3 and the mounting table 11 through the vents 2g and 26 and is discharged from the vents 27, 28, and 29 is near the surface of the mounting table 11 because it flows through a narrow space of 101111. The flow velocity is also much faster than that in the area where the object to be heated 1o is placed, that is, the constricted portion 21, and the cooling effect on the surface thereof is also extremely high. As a result, the temperature of the 140°C part of the punch for 10 minutes was further reduced to around 110°C. Furthermore, the constant flow of air prevents heat accumulation in this space, and there is no abnormal heating phenomenon exceeding 200°C outside the area where the heated object 1o is placed during long-term use. It is now possible to prevent the mounting table 11 from being destroyed.

On the other hand, with this method alone, it is the inner cone that sufficiently heats the top and side surfaces of the object to be heated 1o, but in the present invention, the power supply port 4 is also provided in the center of the earthen wall of the heating chamber. The antenna 6L9 can be sufficiently heated by the emitted high frequency waves.

The inclined surface 2 is created by the stirring plate 8 provided at the tip of the antenna 6.
The high frequency waves directed toward 4 are reflected by this inclined surface 24.

On the slope! ! By setting the angle to 3 to 500, the reflected high frequency waves are directed slightly inward from directly below,
It advances into the object to be heated 10. The distance between the mounting table 11 and the power supply port 4 is smaller than the distance from the power supply port 6, and is large enough to require a space for placing the object to be heated 10, which reduces the focusing ability of high frequencies. , the object to be heated installed directly below the inclined portion 24 is also sufficiently heated, and as a result, the object to be heated is sufficiently heated in the vertical direction. The amount of high frequency waves that enter into the heating chamber is reduced, and abnormal heating of the mounting table 11 is not caused even by the high frequency waves that are irradiated into the heating chamber from the power supply port 4.

In this embodiment, the angle of inclination of the inclined portions 22 and 24 is 60°.
However, depending on the dimensions of the heating chamber 10, the dimensions of the constriction section, or the type and shape of the object to be heated, this angle may vary depending on the degree of heating of the object 10 and the peripheral area of the mounting table 11. All optimum values are set according to the degree of temperature rise.In addition, the throttle V part 234+1 installed in the earthen wall
Even if it is not provided, it is possible to suppress the temperature rise of the mounting table 12 to some extent. That is, as described above, since the distance between the wall surface F and the outer circumferential portion of the mounting table is shorter than that in the stirring plate 90 rotation range, a sufficient high-frequency electric field for heating is not generated.

Furthermore, in this embodiment, in order to ventilate between the mounting table 11 and the bottom wall 3, a method was shown in which the air in this space is drawn out by negative pressure generated by a blower motor 300 revolutions.
In another embodiment, this space is ventilated by forcing air into this space from, for example, a vent 29 using a blower motor 3o, creating a positive pressure, and then discharging it to the outside of the heating chamber wall from other vents 25, 26, etc. It is also possible to do so. in this case,
Compared to the example, the air flow rate is higher, the mounting table is further cooled, and it is effective in suppressing abnormal heating.

Effects of the Invention With the above-described configuration, the present invention achieves the original purpose of preventing abnormal heating in the outer peripheral portion of the mounting table for the object to be heated, and at the same time can also obtain the following effects. 0 (1) The entry of high frequency waves into the contact area of the front wall of the heating chamber facing the door through which the object to be heated enters and exits the heating chamber is reduced, and the electric field is weakened. We were able to reduce the leakage of high frequency waves in this area.In addition, we were able to significantly reduce the heating phenomenon caused by high frequency waves in this area, and prevent burns caused by touching this contact area when entering and exiting the heated object. We were able to improve V safety so that it could be prevented.

(23) By providing a constriction part and an inclined part in the shade, and rotating the stirring plate within this part, fluctuations in the load impedance seen from the antenna are extremely reduced compared to conventional methods, and high-frequency waves that were conventionally absorbed by the mounting table are Combined with the fact that the heat is absorbed into the heated object from the bottom, heating efficiency can be greatly improved.

This tendency was particularly noticeable under light loads. In the example, when a constant input power ゛ is applied to the magnetron, the ratio of high frequency output at a water load of 260ao to a water load of 2J is 11゜, which is more than 80%, whereas the ratio of high frequency output when a water load of 260ao is conventionally about 60 to 66. It has now been possible to obtain
It is now possible to heat the object in 46 to 60 seconds, which used to take several minutes to heat.

[Brief explanation of the drawing]

The first figure is a plan sectional view showing the main part of the embodiment of the present invention,
The figure shows a side sectional view showing an embodiment of the present invention, and FIG. 3 shows a side sectional view showing a conventional example.
...Bottom wall, 6...Power supply port, 7...
・Antenna, 9... Stirring plate, 1o...
Heated object, 11... Placement table, 21...
Aperture part, 22... Slanted surface, 2B, 26.27
．． 28.29・・・Vent 0 Name of agent Patent attorney Toshio Nakao and 1 other person Figure 1 Figure 2 Figure 3 rM

Claims (1)

[Claims] A heating chamber is provided in the main body, and a high-frequency power supply means and a stirring plate that rotates around the power supply means are provided at the center of the upper wall and bottom wall constituting the heating chamber, respectively, and at least the bottom wall is a mortar-shaped mortar with an outer shape that is approximately the same as the rotating area of the stirring plate, which is equal to or smaller than the mounting area of the object to be heated, and is open toward the object to be heated around the rotation axis of the stirring plate. It is characterized by having a configuration in which a circular constriction part having a sloping surface around the circumference is provided, and a vent is provided outside the constriction part, and the part outside the constriction part is ventilated during heating operation. High frequency heating device.