Electric heating – Metal heating – Of cylinders
Patent
1991-08-28
1993-10-19
Leung, Philip H.
Electric heating
Metal heating
Of cylinders
219 1055E, H05B 668
Patent
active
052548198
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a high-frequency heating apparatus in which the condition of a food is estimated by detecting the state of electromagnetic waves in a heating chamber such that operation of devices is controlled.
BACKGROUND OF THE INVENTION
In recent years, a trend that thawing of foods by the use of high-frequency heating apparatuses is automated has become predominant. Conventionally, a procedure has been followed in which the weight of a food is inputted by keys to control automatic timing or the weight is measured by using a weight sensor for automatically detecting the weight of the food such that the food is heated for a corresponding one of optimum heating periods preset for different weights of foods, respectively.
Furthermore, Japanese Patent Publication No. 52-2133 proposes that a microwave detecting element, namely, an antenna be disposed in a heating chamber so as to utilize a characteristic that the electric power of microwaves detected by the microwave detecting element which have not been absorbed by a food is inversely proportional to the weight of the food. Hereinbelow, this arrangement is described with reference to FIG. 1. A frozen food 2 is placed in a heating chamber 1 and waves 4 are irradiated over the food 2 from a wave irradiator 3. At this time, a portion 5 of the waves, which has not been absorbed by the food 2, is sensed by an antenna 6 mounted in the heating chamber 1 and then is subjected to detection by a detection circuit 7 so as to be delivered to a controller 8. Since the quantity of the waves sensed by the antenna 6 is inversely proportional to the amount absorbed by the food 2, the weight of the food 2 can be judged and thus, its optimum heating period can be set.
However, in the known high-frequency heating apparatus referred to above, in the case where state of waves in the heating chamber is sensed by using the antenna and the detection circuit in order to detect state of the food in the heating chamber, the detection level changes greatly depending on the construction of the antenna, construction of the detection circuit, mounting accuracy of the antenna and the detection circuit, influence of any external magnetic field, etc. Thus, a problem arises that this constitutes an extremely unstable factor for determination of subsequent sequences requiring estimation of the weight of the food, etc.
DISCLOSURE OF THE INVENTION
The present invention eliminates such conventional drawbacks and has for its object to provide an optimum finished state of cooking in which control of operating devices based on detection of the state of electromagnetic waves by the use of an antenna and a detection circuit is performed remarkably stably.
In order to accomplish this object, a high-frequency heating apparatus according to the present invention comprises: a heating chamber for accommodating a food; a wave irradiator for irradiating microwaves so as to heat the food; an antenna for sensing state of the microwaves in the heating chamber; a detection circuit for performing detection of the microwaves detected by the antenna; and a controller for controlling operation of various operating devices in accordance with an output of the detection circuit; wherein the detection circuit is formed on a double-sided board having copper foil applied to opposite faces of the board material.
The antenna can likewise be formed by copper foil on a printed board.
Furthermore, the antenna and the detection circuit can be formed on the same board.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view showing an arrangement of a prior art high-frequency heating apparatus provided with an antenna;
FIG. 2 is a schematic view showing an arrangement of a high-frequency heating apparatus according to one embodiment of the present invention;
FIG. 3 is an exploded perspective view showing an arrangement of a main portion of the high-frequency heating apparatus of the present invention;
FIG. 4 is a plan view showing an arrangement of one embodiment of an antenna;
FIG
REFERENCES:
patent: 3778717 (1973-12-01), Okoshi et al.
patent: 4211911 (1980-07-01), Dehn
patent: 4341937 (1982-07-01), Staats
patent: 4520250 (1985-05-01), Ishihara et al.
patent: 4853703 (1989-08-01), Murakami et al.
Kashimoto Takashi
Moriyama Satomi
Sakai Shin-ichi
Yamaguchi Kimiaki
Yoshino Koji
Leung Philip H.
Matsushita Electric - Industrial Co., Ltd.
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