JPS5939872B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device having a metal body that connects a heating chamber and the outside of the heating chamber, and its purpose is to prevent leakage of high-frequency waves from a penetration part of the heating chamber wall of the metal body. .

Generally, it is well known that this type of device, such as a microwave oven, uses high frequency waves of about 2450 MH2 to cook food, but in recent years, heating using high frequency waves alone causes brown spots on the heated items. Since this is not possible, a heater is installed inside the heating chamber, power is supplied from outside the open space, and the heat generated by the heater is used to achieve the burnt edges.

In addition, elements to detect the temperature and humidity of the object to be heated during heating by high frequency are built into the open circuit, and the output of these elements is used to control the high frequency heating and automatically heat the object to the desired heating state. A device was also devised to do this. However, a common problem occurred in both cases. Whether the heater is operated in the heating chamber or various detection devices are placed in the heating chamber, lead wires insulated from the heating chamber wall are used to transmit the power or signals necessary to drive those devices. is necessary. This lead wire connects the power source outside the heating chamber or the input/output of the control device and each terminal of the components inside the heating chamber, so while high frequency is generated inside the heating chamber, the electric field of this high frequency You will be exposed. At this time, a portion of the high frequency waves travels through the lead wire and escapes to the outside of the heating chamber, resulting in so-called high frequency leakage. Therefore, in the past, a choke structure was used in the part of the lead wire that penetrates the heating chamber, or a capacitor was used to equivalently bring the lead wire's impedance to the open wall close to zero and short the high frequency waves on the heating chamber wall. A method has been adopted to prevent it from getting out of the heating chamber.

However, in both cases it was far from perfect. Figure 1 shows a conventional example and an example of its leakage amount.

As shown in FIG. 1, the choke method varies greatly depending on the lead length outside the heating chamber, that is, the external impedance. In addition, in the capacitor type, the force u changes significantly depending on the load condition inside the heat chamber. In the chi-yoke method, the leads connected to the outside of the chi-yoke cause mismatching with the leads inside the chi-yoke, and in the capacitor method, the electric field strength inside the heating chamber changes depending on the condition of the object to be heated inside the heating chamber. capacitor with constant impedance (because the heating frequency is almost constant)
This is because if the electric field strength in the heating chamber increases, the amount that cannot be dropped onto the heating chamber wall will have to be conducted outside the heating chamber. In other words, leakage of radio waves from the lead wires insulated from the heating chamber wall, which are drawn out from the heating chamber to the outside, could not be suppressed under all conditions. The present invention was developed in view of the above circumstances, and makes it possible to reliably suppress radio wave leakage to near zero under any conditions. Embodiments of the present invention will be described below with reference to FIGS. 2 to 5.

2 to 4 are schematic diagrams of the main body of a high-frequency heating device embodying the present invention. A heating chamber 2 is provided in the main body 1, and a door having a door screen 3a is provided at the front opening of the heating chamber 2. 3 is provided so that it can be opened and closed freely.

Further, in the lower part of this heating chamber 2, there is provided a rotary mounting table 4 driven by a magnet 1, and in the upper part, as shown in FIG. A high frequency electromagnetic wave is supplied into the heating chamber 2 from a high frequency oscillator 7 via a waveguide 8. The electric heating and high-frequency heating can be selectively performed using knobs on the front operation panel 9.
That is, 10 in FIG. 1 is a short-time timer [15 minutes] for operating the high-frequency oscillator 7, and 11 is a long-time timer [15 minutes].
2 hours], 12 is the output selector switch [600W or 1
80W], 13 is an operation switch that prompts the start of heating, and 14 is a pilot lamp that indicates when the heating operation is in progress, all of which are for high frequency heating. Further, 15 is a timer (1 hour) for setting the heating time of electric heating, and 16 is a pilot lamp that indicates when electric heating is in progress. On the other hand, the heater 6 is electrically connected to the outside of the heating chamber via a radio wave leakage prevention mechanism 18 provided on the rear wall 17 of the heating chamber, and receives electric power necessary for electrothermal heating.

The details of the radio wave leakage prevention mechanism 18, which is the gist of the present invention, are explained in the fourth section.
As shown in the figure. The heater 6 used in this embodiment is a sheathed heater because of its robustness and ease of use.

However, due to the characteristics of the sheathed heater, the outer pipe 20 cannot be directly connected to the rear wall 17 of the heating chamber due to the stability of the insulation properties between the heating wire 19 and the outer pipe 20. Therefore, the outside of the pipe 20 that penetrates the heating chamber rear wall 17 is wrapped with an insulator A2l to prevent the pipe 20 from directly touching the heating chamber rear wall 17. Therefore, if there is no radio wave leakage prevention mechanism 18, a very large amount of high frequency waves will leak from this part, causing radio wave interference due to an increase in spurious waves outside the main body, and heating and deteriorating various parts inside the main body, which is dangerous. For this reason, also in this example, a metal cylindrical cavity A22 and a cylindrical cavity B2 are connected to the rear wall 17 of the heating chamber and provided approximately concentrically with the pipe 20.
A chiyoke structure consisting of 3 is provided to prevent radio wave leakage.

However, as mentioned above, with this structure alone, if the wiring to the lead wire 24 for power supply changes or the installation position of the heater pipe 20 shifts even slightly, the matching will shift and the amount of radio wave leakage will increase. . Therefore, in the present invention, the heater 6 in the cylindrical cavity B23 is
A metal cylindrical cavity C25 was spot-welded to the cylindrical cavity B23 in a substantially cylindrical shape with the insulator A2l in the penetrating portion of the insulator A21. In this way, a capacitance is created between the cylindrical cavity C25 and the terminal fittings A26 and B27 of the heating wire 19 in the heater 6. This means that a circuit that shoots high frequency waves using the capacitor described at the beginning is created in this part, and as a result, this radio wave leakage prevention mechanism is different from the above-mentioned chioke method and capacitor method as shown in Figure 1. This combination of features means that if you look at it differently, the radio wave attenuation means are stacked in two stages, making it possible to significantly reduce the amount of leakage. moreover,
According to this embodiment, the length of the cylindrical cavity C25 is made approximately half of the length of the cylindrical cavity A22, and the length of the cylindrical cavity B23 is made to take into account the fact that there is no chiyoke effect for even high frequencies, which is a drawback of the chiyoke structure. By adjusting the length, the chi-yoke effect on even high frequencies can be greatly increased, and as a result, the spurious level from the main body 1 can be significantly reduced, eliminating radio interference and making the device safer. We were able to. In this embodiment, a terminal fitting C28 is provided outside the cylindrical cavity B23 and is detachably connected to the terminal fitting B27 to supply power to the heater 6. 6 is made detachable from the heating chamber 2 side, making it easy to clean the inside of the heating chamber. In this embodiment, an insulator B29 and an insulating plate 30 made of a phenol laminate are provided on the outside of the cylindrical cavity B23 as a holder for the terminal fitting C28, and the insulating plate 30 is made of a phenol laminate and is electrically insulated from the mounting base 31. Fixed. Further, 32 is ferrite rubber, which has the effect of absorbing high frequencies and further reducing the amount of radio wave leakage.

33 is a silicon laminate, and the ferrite rubber 32 is
This ensures insulation between the terminal fitting C28 and the mounting base 31 even if the insulation resistance is lost due to exposure to high temperatures.

With the above configuration, in this embodiment, as shown in the data shown in the figure below, the amount of radio wave leakage from the part connected to the power supply of the heater 6 is significantly reduced, including even harmonics, compared to the conventional one, as shown in the data shown in the figure below. We were able to eliminate radio interference and make it safe and easy to use.

In this embodiment, the cylindrical cavity C25 is different from the cylindrical cavity B23, but it goes without saying that the cylindrical cavity B23 may be drawn instead.

As is clear from the above description, the high-frequency heating device of the present invention has a chi-yoke structure provided to prevent leakage of radio waves at the part where the metal body penetrates the outer wall of the heating chamber where high-frequency waves are radiated.
Furthermore, by adding a cylindrical cavity with a surface facing the surface of the metal body, the radio wave leakage prevention effect of the capacitor method is combined with the radio wave leakage prevention effect of the chiyoke method, resulting in a significant radio wave leakage prevention effect. It is.

[Brief explanation of the drawing]

Figure 1 is a comparison diagram showing the radio wave leakage effect of the conventional high-frequency heating device, the chiyoke method and the capacitor method.
The figure is a schematic perspective view showing one embodiment of the high-frequency heating device of the present invention, FIG. 3 is a schematic diagram of the main part of the device, and FIG. 4 is an enlarged sectional view of section A in FIG. 3. 2... Heating chamber, 6... Heater, 7...
...High frequency oscillator, 17...Rear wall of heating chamber,
18...Radio wave leakage prevention mechanism, 22...
Cylindrical cavity Al23...Cylindrical cavity B
l24...Lead line for power supply, 25.
...Cylindrical cavity Cl26, 27...
Terminal fittings.

Claims (1)

[Scope of Claims] 1. A high-frequency generator that radiates high-frequency waves into a heating chamber, a metal body that penetrates the heating chamber wall, and a cylindrical cavity A with three different diameters on the outer wall of the heating chamber that the metal body penetrates, B, C
and the cylindrical cavity C is a cylindrical cavity B.
The cylindrical cavity A is arranged coaxially with the inner part of the cylindrical cavity B, and the cylindrical cavity A is arranged coaxially with the outside of the cylindrical cavity B, so that the diametrical dimension of the cylindrical cavity A and the cylindrical cavity B is equal to the fundamental wave and odd harmonics. as a choke against, and
The high frequency heating device is configured such that the length of the cylindrical cavity C and the depth of the cylindrical cavity B operate as a choke for even harmonics such as the second harmonic. 2. The high-frequency heating device according to claim 1, wherein the metal body is a power supply line to a heater built into the heating chamber. 3. The high-frequency heating device according to claim 1, wherein the metal body is a lead wire of an element for detecting the temperature and humidity of the object to be heated.