Electric heating – Microwave heating – With control system
Reexamination Certificate
2000-08-11
2001-05-08
Leung, Philip H. (Department: 3742)
Electric heating
Microwave heating
With control system
C219S494000, C099S325000, C374S149000
Reexamination Certificate
active
06229130
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-184162, filed Jun. 29, 1999; the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heating apparatus for cooking such as microwave ovens in which a frozen food (as a target food item to be cooked) placed on a turntable in a cavity as a heating chamber is thawed and heated by irradiating a microwave of a high frequency to the food item.
2. Description of the Related Art
In many conventional heating apparatus for cooking such as microwave ovens to control a heating process by detecting a temperature of a target food to be heated by using an infrared ray (IR) sensor of a non-contact type, it is impossible to accurately detect a temperature of an area which is smaller in size than the detection field of the IR sensor (or the field of view of the IR sensor), because the detection field of the IR sensor is so elliptical in shape that the IR sensor outputs the average value of a temperature distribution in the detection field of the IR sensor.
For example, when the detection field of the IR sensor overlaps only with a boundary area (or the end part) of a target food to be detected, in other words, when a part in the detection field of the IR sensor overlaps with the boundary area of the food, the temperatures of both the target food and a background area in which there is no target food are averaged. In this case, it is impossible to obtain an accurate temperature of the food. In order to avoid this conventional drawback, when the detection field of the IR sensor is set to narrow, the resolution of the IR sensor becomes high and the occurrence that the detection field of the IR sensor overlaps with the boundary area of the food can be small, but it is impossible to avoid any occurrence that the detection field of the IR sensor overlaps with the boundary area of the food completely. Thus, even if the detection field of the IR sensor is set to narrow, the detected temperature in the above case also has an inaccurate value. In addition, to narrow the detection field of the IR sensor greatly causes to decrease the sensitivity of the IR sensor and to decrease the function of noise immunity, so that the accuracy of the detection by the IR sensor becomes low.
If the number of IR elements forming the IR sensor is only one, it is impossible to set the detection field of the IR sensor into a narrow area because it is necessary to keep a widely detectable area in a heating chamber of the heating apparatus for cooking.
Furthermore, even if the IR sensor comprises a plurality of the IR elements in order to detect a plurality of detection areas in the heating chamber in the heating apparatus for cooking, it is possible to set the detection field of each IR element to narrow, but, there still remains the drawback that it is impossible to detect: the temperature of the boundary area (or the end part) of the target food accurately.
During a thawing process in practical cooking, for example, the temperature of a localized area becomes increased by uneven cooking of the target food, uneven heating of the target food, and the like, the part of the target food becomes a half cooked state (namely, a half-boiled state) or a boiled state. This case often occurs at a boundary area of the target food. The conventional heating apparatus for cooking such as microwave ovens cannot solve this drawback because the conventional heating apparatus for cooking cannot detect accurately the increasing of the temperature of the boundary area of the target food, so that it cannot prevent: to cause the half-cooking state or the uneven state of the target food.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is, with due consideration to the drawbacks of the conventional technique, to provide a heating apparatus for cooking such as microwave ovens that is capable of accurately detecting a temperature of a boundary area of (such as the end part of) a target food to be cooked placed on a turntable in a heating chamber (or a cavity). That is to say, an object of the present invention is to provide the heating apparatus for cooking that is capable of accurately detecting the temperature of the boundary area (such as the end part of the target food) of the target food even if one detection field of an IR sensor simultaneously covers both the boundary area of the target food and the background area where no target food is placed. More concretely, although the temperature of the detection field where both the part of the target food and the background are detected simultaneously is changed in general according to the ratio of both the areas of the part of the target food and the background, an object of the present invention is to provide the heating apparatus for cooking that is capable of accurately calculating the temperature of the target food to be cooked by detecting the temperature of the background and the ratio between the target food and the background in a boundary detection field of the IR sensor.
In accordance with a preferred embodiment of the present invention, a heating apparatus for cooking comprises a heating chamber, heating means, infrared ray (IR) detection means, temperature calculation means, heating process control means, and detection target judgment means. In the heating chamber, a target food to be cooked is placed and then heated. The heating means irradiates a microwave on the target food. The infrared ray (IR) detection means having a plurality of detection elements for detecting a plurality of detection areas in the heating chamber by a non-contact manner. The temperature calculation means calculates temperatures of the plurality of detection areas based on the detection results obtained by the IR detection means. The heating process control means controls a heating process for the target food based on calculation results obtained by the temperature calculation means. The detection target judgment means judges a type of each detection area in the heating chamber corresponding to each of the plurality of detection elements based on a detected initial temperature distribution of the heating chamber. There are following three types as the type of the detection area: a direct detection area where there is only a part or entire of the target food and the target food is directly detected; a boundary detection area where there are both a part or entire of the target food and a background simultaneously; and a background area where there is no target food. In the heating apparatus for cooking according to the present invention, then heating process control means controls the heating process based on the detection results obtained by the detection target judgment means.
The heating apparatus for cooking as another preferred embodiment of the present invention further comprises background temperature detection means for detecting a temperature of the background in the heating chamber during the cooking of the target food, and temperature calculation means for the target food for calculating a calculation temperature of the target food based on temperatures detected in the direct detection area where only the target food is directly detected and for calculating a calculation temperature of each part in the target food in the boundary detection field where both the part of the target food and the background are detected simultaneously.
In the heating apparatus for cooking as another preferred embodiment of the present invention, the detection target judgment means detects the initial temperature distribution of the heating chamber, and judges the type of the detection field detected by each detection element in the IR detection means. The type is selected in the three cases: The direct detection field where only the target food is detected; The boundary detection field where both the part of the target food and the background are dete
Furuta Kazuhiro
Kakizawa Toshio
Kako Hidenori
Kabushiki Kaisha Toshiba
Leung Philip H.
Pillsbury & Winthrop LLP
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