JPH0215280Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a high-frequency heating device, and particularly to a device for preventing excessive temperature rise of a dielectric saucer on which an object to be heated is placed in a microwave oven.

BACKGROUND TECHNOLOGY In general, in order to prevent burnout of the device due to abnormal heating of the saucer of this type of high-frequency heating device, as shown in FIG. is provided to indirectly detect the temperature of the saucer 1, and when a temperature detection element such as a temperature fuse or thermostat 3 reaches a certain temperature or higher, the generation of high frequency waves is automatically stopped.

(Publication of Utility Model Publication No. 52-9064, Publication of Utility Model Number 53-35794).

Problems to be Solved by the Invention However, in such a temperature overrise prevention device, since the heat conductivity of the saucer 1, that is, glass or resin is low, there are cases where there are very few objects to be heated 4,
If the saucer is locally and rapidly heated by a pattern based on the electric heating mode due to an erroneous operation without an object to be heated, the effect will be small, and furthermore, slight dimensional variations in the shape of the heating chamber or Due to the non-uniformity of the material of the saucer 1 itself, the position of local heating is not constant, which makes detection even more difficult. During continuous operation, the temperature of the thermostat gradually rises,
It was said that a malfunction would occur during normal operation, and it was not practical from the point of view of preventing abnormal heating of the saucer 1.

The present invention solves the conventional problem of preventing abnormal heating of the saucer, and aims to provide a device that has a simple configuration, reliably detects abnormality, and prevents the risk of burning out the main body. It is.

Means for Solving the Problems The high-frequency heating device of the present invention guides the infrared rays emitted by the saucer to the outside of the heating chamber via a photoconductor and detects this amount with an infrared detector. The structure is such that the temperature is detected and the generation of high frequency waves is stopped before the temperature of the saucer reaches a high enough temperature to cause burnout of the set.

Effect Generally, the relationship between thermal radiation energy and temperature in the case of a black body is expressed by Plank's law. In other words, the energy per unit wavelength radiated from a blackbody at temperature TK into the hemisphere at wavelength σ is w/σ (w cm
^-2 Γμm ^-1 ) is expressed as wσ=C ₁ σ ^-5 [exp(C ₂ /σT)−1] ^-1 , and (C ₁ =3.74×10 ^-4 (w cm ^-2 μm ^Four )
C ₂ = 1.439×10 ^-4 (μm・K)) This radiation energy changes depending on the wavelength, and the Peak value σm of that wavelength is
As shown by Wien's displacement law, σm=C ₃ /T (C ₃ = 2897 (μmΓK)), the peak wavelength of the radiant energy distribution tends to shift toward shorter wavelengths as the temperature increases. It has been known.

Since the saucer used in this invention is not a blackbody,
Although it does not show a single spectrum, we focused on the fact that the peak naturally shifts to shorter wavelengths as the temperature rises, and we observed an increase in the amount of near-infrared rays emitted when the saucer becomes abnormally high temperature. detect,
When a level higher than a set value is detected, the input power for oscillation of the high frequency generator is cut off.

Embodiment An overtemperature rise prevention device according to an embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1a, a small hole 4 in a part of the end of the saucer 1 is used for detecting infrared visible light traveling inside the saucer.
will be established. The saucer 1 is made of transparent glass that can transmit infrared and visible light. A small hole 5 that does not cause high-frequency wave leakage is also provided in a portion of the heating chamber wall 2 facing the detection small hole 4, and furthermore, the saucer 1 is fixed at a predetermined position in the heating chamber, and A small hole 7 is also provided in the packing rubber 6 provided between the saucer 1 and the heating chamber wall 2 to prevent foreign matter from entering the lower part of the saucer. An optical fiber 8 is provided, one end of which is inserted laterally into the detection small hole 4, and is fixed with an inorganic adhesive 9 with little high frequency loss. The tip of the optical fiber 8 is conical, and the small detection hole on the receiving tray 1 side is also a conical hole in accordance with this taper, so that the tapered surfaces are in close contact with each other.

The other end of the optical fiber is connected to an infrared detector 11 provided outside the heating chamber 10 shown in FIG. 1b.

Conventionally, infrared rays have been detected using thermo-electrical resistance conversion using the pyroelectric effect or thermoelectromotive force, but in order to have the lowest possible cost in this application, A phototransistor is used as a conversion element. The spectral sensitivity characteristics of phototransistors have a peak sensitivity at 1 μm in the near-infrared region, and the sensitivity gradually decreases as the wavelength becomes longer.

The output of the phototransistor is amplified and sent to the high frequency output controller 12 as the output of the infrared detector 11.
It is connected to the. The high-frequency output controller 12 has a relay that cuts off the input power of the power supply 14 for driving the magnetron 13 that irradiates the heating chamber 10 with high-frequency waves. When light is detected, the relay is turned off and high frequency generation is stopped. In this embodiment, only one optical fiber is used, but a plurality of optical fibers may be provided at various positions to improve sensitivity.

With the above configuration, the following operations are performed.
For example, suppose that when no-load operation is performed due to misuse, a local heating phenomenon occurs in a part according to the electric field mode. The heated portion 15 increases dielectric loss and causes concentration of microwaves, becomes high temperature, and generates a large amount of infrared rays close to visible light. This infrared rays are also conducted to the ends through the interior of the saucer 1 itself. A part of the infrared rays enters the optical fiber 8, which has a conical tip and can enter from any direction. The infrared signal that is excited and converted into an electric signal that turns ON causes the high frequency output controller to stop the high frequency waves emitted from the magnetron 13, and the local heating of the saucer 1 is stopped at this point, thereby avoiding a dangerous situation.

Effects of the invention In the high-frequency heating device having the temperature overrise prevention device of the present invention configured as described above, as compared to the example using a conventional thermostat, as was the initial purpose, local heating can be generated at exactly which position. Even in such cases, we were able to quickly detect the occurrence of high frequency waves and ensure safety. If local heating occurs at the location shown in Figure 1b, it would have been impossible to detect using conventional methods due to the low thermal conductivity of glass, but according to the present invention, infrared rays It can instantly travel through the glass and stop the high-frequency irradiation. Furthermore, although the configuration of the present invention is simple, it was also possible to obtain the following effects.

First, compared to, for example, non-contact infrared detection devices, it is resistant to malfunctions caused by external noise. By arranging the optical fibers 8 laterally so as to detect only infrared rays, external light and infrared rays are hardly detected. In other words, most of the light that attempts to enter the receiver from outside the receiver is either reflected or refracted depending on the angle of incidence and passes through, so there is almost no external light or infrared rays that enters the optical fiber. It is.

Secondly, by achieving the above effect, the detection sensitivity of the infrared detector can be increased.
This further produced the following effects.

During normal operation, due to overheating of the liquid to be heated, etc.
When a so-called "boiling over" occurs on the heated object,
In the process of dripping and staying on the tray surface, water droplets form various shapes on the tray, and depending on the shape, the light from lamps used for lighting inside the refrigerator is refracted and sometimes enters the tray. This causes a considerable change in the visible light that passes through the glass fiber. As mentioned above, the phototransistor has a sensitivity peak at around 1 mm, and can sufficiently detect changes in this visible light.As a result, as soon as the level of visible light increases, high-frequency heating is stopped to prevent boiling. It has become possible to detect and stop heating, which improves ease of use and safety in cleaning work after use due to boiling of the heated object, and preventing carbonization due to overheating and ignition due to leaving the area unattended. It is possible to eliminate the problems caused by

[Brief explanation of the drawing]

FIG. 1a is a side sectional view of a main part of a high-frequency heating device according to an embodiment of the present invention, FIG. 1b is a configuration diagram of the same device, and FIG. 2 is a side sectional view showing a conventional example. 1... Glass saucer, 6... Packing rubber, 8
...Optical fiber, 10...Heating chamber, 11...Infrared detector, 13...Magnetron.

Claims (1)

[Scope of utility model registration request] Inside the main body, there is a heating chamber, a high-frequency generator that irradiates the heating chamber with high-frequency waves, and a transparent glass on which the object to be heated is placed, which is fixed via a gasket between the heating chamber wall and the heating chamber. A receiver having a detection port for detecting light or infrared rays conducted inside, an optical fiber having one end connected to the detection port, an infrared detector connected to the other end of the optical fiber, and the infrared detector. A high-frequency heating device comprising: a high-frequency output controller that controls the generation of high-frequency waves by the high-frequency generator according to the output, and controls the output of high-frequency waves by changes in infrared visible light generated inside the saucer.