EP1811814A2

EP1811814A2 - High-frequency heating device

Info

Publication number: EP1811814A2
Application number: EP07100994A
Authority: EP
Inventors: Kayoko Zougou
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp
Priority date: 2006-01-23
Filing date: 2007-01-23
Publication date: 2007-07-25
Also published as: EP1811814A3; CN101008500B; CN101008500A; JP2007192518A

Abstract

To provide a high-frequency heating device characterized by detecting temperatures at a plurality of temperature detecting points by temperature detecting means so that the presence/absence of a cooking dish may be decided from the plural temperatures detected.

The high-frequency heating device comprises: a heating chamber 1 for housing an object 6 to be heated; a cooking dish 3 having an electric wave heating member applied thereto for placing the object 6, a dish receiving shelf 2 for placing the cooking dish 3; temperature detecting means 8 for detecting the temperature of an object; heating means 7 for heating the object 6 and the cooking dish 3; and heating control means 12 for controlling a heating pattern and a heating time period. Temperature detecting means 11 detects the temperatures at a plurality of temperature detecting points, and decides the presence/absence of the cooking dish 3 from the temperatures detected.

Description

[Technical Field]

The present invention relates to controls of a high-frequency heating device having a cooking dish.

[Background Art]

In the prior art, the heating device of this kind detects the cooking dish with a magnet outside of a heating chamber (as referred to Patent Document 1).
Fig. 4 shows a constitution of a heating device of the prior art, as described in Patent Document 1. As shown in Fig. 4, the heating device is constituted to include: a heating chamber 1; dish receiving shelves 2 disposed on the right and left side walls of the heating chamber; rectangular dishes (or cooking dishes) 3 mounted on the dish receiving shelves; magnets 4 disposed outside of the heating chamber for detecting the rectangular dishes; and detecting means 5 for responding to the motions of the magnets 4.
[Patent Document 1] JP-A-10-196961

[Disclosure of the Invention]

[Problems that the Invention is to Solve]

However, the aforementioned constitution of the prior art needs the magnets and switches as the detecting means. This need raises problems that the detecting means has to be disposed in the limited space, and that the detecting means raises the cost.
When a cooking dish having an electric wave heater applied thereto is used, the following problems occur in case the cooking dish is not detected. At first, a heating pattern using the cooking dish raises at first the temperature of the electric wave heater with the high-frequency electromagnetic waves, and then heats an object with the radiation heat of a heater. Thus, the object can be given baking colors on its two faces without being turned back. If, however, not the cooking dish having the electric wave heater applied thereto but an ordinary cooking dish (or the cooking dish having no electric wave absorber applied thereto) is used for the heating operation, there arises a problem that a backing state occurs to raise the temperature of the inner wall of a heating chamber abnormally (or to cause red spots).
The invention contemplates to solve the aforementioned problems of the prior art, and has an object to provide a high-frequency heating device characterized by detecting temperatures at a plurality of temperature detecting points by temperature detecting means so that the presence/absence of a cooking dish may be decided from the plural temperatures detected.

[Means for Solving the Problems]

In order to solve the aforementioned problems of the prior art, according to the invention, there is provided a high-frequency heating device comprising: a heating chamber for housing an object to be heated; a cooking dish having an electric wave heater applied thereto for placing the object; a dish receiving shelf for placing the cooking dish thereon; temperature detecting means for detecting the temperature of an object; heating means for heating the object and the cooking dish; and control means for deciding the presence/absence of the cooking dish from either the temperatures detected by the temperature detecting means at a plurality of temperature detecting points or the temperature change.
Thus, the presence/absence of the cooking dish having the electric wave heater applied thereto can be detected without placing the magnets or switches.

[Effects of the Invention]

The high-frequency heating device of the invention is enabled to prevent the abnormal temperature rise due to the baking or the like with the electric waves by detecting the presence/absence of the cooking dish having the electric wave heater applied thereto, while using the temperature detecting means for detecting the temperature of the object.

[Brief Description of the Drawings]

Fig. 1 is an exterior view showing a constitution of a high-frequency heating device of Mode of Embodiment 1 of the invention.
Fig. 2 is an enlarged view of an operation unit of the same high-frequency heating device.
Fig. 3 is a flow chart showing the control contents of the same high-frequency heating device.
Fig. 4 is a constitution view of a heating device of the prior art.

[Best Mode for Carrying Out the Invention]

A first invention is constituted to comprise a heating chamber for housing an object to be heated; a cooking dish having an electric wave heater applied thereto for placing the object; a dish receiving shelf for placing the cooking dish thereon; temperature detecting means for detecting the temperature of an object; heating means for heating the object and the cooking dish; and control means for deciding the presence/absence of the cooking dish from either the temperatures detected by the temperature detecting means at a plurality of temperature detecting points or the temperature change. Thus, it is possible to detect the presence/absence of the cooking dish having the electric wave heater applied thereto.
A second invention is constituted such that the temperature detecting means is constituted to detect the temperature of the object placed on the cooking dish, and such that the control means is constituted to control the heating pattern and/or the heating time period of the object on the basis of the output of the temperature detecting means. As a result, the presence/absence of the cooking dish having the electric wave heater applied thereto can be detected without mounting the magnets or switches.
Especially in the first or second invention, according to a third invention, the presence/absence of the cooking dish is decided with the plural temperatures which are selected under a predetermined condition from the plural temperatures detected by the temperature detecting means. As a result, the portion, where the difference in the temperature is prominent due to the presence/absence of the cooking dish having the electric wave heater applied thereto, can be extracted to detect the presence/absence of the cooking dish precisely.
Especially in the first to third inventions, according to a fourth invention, the predetermined condition for selecting the plural temperatures from the detected temperatures is a plurality. As a result, the presence/absence of the cooking dish can be detected no matter what position the cooking dish is placed at, in the case of plural dish receiving shelf positions.
In the first to fourth inventions, according to a fifth invention, the control means selects the plural temperatures detected by the temperature detecting means, under the predetermined condition, and decides it to stop the heating operation that no cooking dish exists in case the detected temperatures are at or lower than a predetermined temperature. As a result, it is possible to prevent the abnormal temperature rise such as the baking or the like due to the electric waves.
A sixth invention is characterized by comprising display means for urging, in case the absence of the cooking dish is decided, the cooking dish to be inserted.
A seventh invention is characterized by comprising voice generating means for urging, in case the absence of the cooking dish is decided, the cooking dish to be inserted.
Modes of embodiment of the invention are described in the following with reference to the accompanying drawings. Here, these modes of embodiment should not limit the invention.

(Mode of Embodiment 1)

Fig. 1 is an exterior view showing a constitution of a high-frequency heating device of the first embodiment of the invention.
In Fig. 1, reference numeral 6 designates an object to be heated such as a food, which is carried on a cooking dish 3 having an electric wave heater applied, for example, thereto and placed in a dish receiving shelf 2 in a heating chamber 1. A high-frequency wave generating device 7 for generating high-frequency electromagnetic waves is fed with the electric power through a waveguide tube 8. In the power feed port from the waveguide tube 8 to the heating chamber 1, there is disposed a stirrer 9 for diffusing the high-frequency electromagnetic waves from the high-frequency heating device 7 thereby to feed them homogeneously to the entire heating chamber.
A hole 10 is formed in the upper wall face of the heating chamber 1, and an infrared sensor 11a acting as temperature detecting means is disposed near the hole 10. The infrared sensor 11a is provided with a sensor driving device 11b and can change an input direction. As a result, the temperature detecting position can be shifted from end to end of the heating chamber 1, and this end-to-end movement is called the "one scan". Moreover, the infrared sensor 11a is provided with eight detecting elements, each of which: detects either the infrared dose in the heating chamber 1 through the hole 10 or, when the cooking dish 3 is placed, the infrared dose of the surface of the cooking dish 3 or the heated object 6 placed on the cooking dish 3; and inputs the detected signal to control means 12. In response to this signal output, the control means 12 is constituted to decide the presence/absence of the cooking dish, and, in the case of absence, to stop the heating operation and to inform the user, by using the later-described display unit or a voice generating unit 19, why the heating operation has been ended before the cooking is not completed, and how to deal with the problem. On the basis of the aforementioned signal output, moreover, the control means 12 is constituted to control the heating pattern and/or the heating time period of the object on the basis of the aforementioned signal output.
Here, the detecting positions of the eight detecting elements of the infrared sensor 11a are made not to become different for the individual scans but to detect the temperature of the position.
Fig. 2 shows an operation unit. Numeral 15 designates the display unit made of a liquid crystal or the like; numeral 16 a start key for starting the heating operation; numeral 12 a cancel key for stopping the heating operation; and numeral 18 a double-sided grill key.
The actions and operations of the high-frequency heating device thus constituted are described in the following with reference to Fig. 3.
At first, the user places the object 6 on the cooking dish 3 having the electric wave heater applied thereto, and houses and places the dish receiving shelf 2 in the heating chamber 1. After this, the user selects the double-sided grill key 18 on the operation unit. Next, the user sets the heating time period (at S101), and pushes the start key 16 (at S102) to start the heating operation.
At S103, it is confirmed that the start key 16 has been depressed, and the routine returns to S101 if the cancel key 17 is depressed prior to the start key 16.
After the cooking started, the control means 12 sends at first a signal to a driving power source 13 or the drive power source of the high-frequency heating device 7 to start not only the dielectric heating operation (at S104) but also the fetch of the detection signal of the infrared sensor 11a (at S105). Simultaneously with this, the sensor driving device 11b is driven to fetch the detection signal (at S106) while changing the input angle of the infrared sensor 11a. The fetch of the eight elements of the infrared sensor 11a is performed at an interval of 0.35 seconds, so that the data (or 152 points) of one screen of the heating chamber 1 can be fetched by nineteen times. The detection signal of the infrared sensor 11a is fetched while moving the sensor driving device 11b always to a predetermined time.
If, at a predetermined time (at S107), the detected temperatures of the detection points selected under a predetermined condition are higher than a decision threshold value (at S108), it is decided that the cooking dish having the electric heater applied thereto is placed, and the heating operation is continued (at S109).
In case the user either erroneously unused the cooking dish having the electric wave heater applied thereto or used the ordinary cooking dish having no electric wave heater, the detected temperatures of the detection points selected under the predetermined condition are at or lower than the decision threshold value, and the high-frequency heating device 7 is turned OFF (at S110) to end the heating operation (at S111). This end is informed by utilizing the display unit 15 or the voice generating unit 19. In case the heating operation is ended by deciding that the cooking dish having the electric wave heater applied thereto is absent, the user is urged to insert the cooking dish by the display means or the voice means, so that the user can be informed why the heating operation was ended before the cooking is not completed and what should be done.
In this embodiment thus far described, for the predetermined time period, the detected temperatures of the detection points selected under the predetermined condition are compared with the decision threshold value. As a result, the presence/absence of the cooking dish having the electric wave heater applied thereto can be decided to prevent the abnormal temperature rise due to the baking or the like thereby to retain the safety.
In this high-frequency heating device, the detection points selected under the predetermined condition can be determined from experiments. One example of the experiments is described. At first in the high-frequency heating device, as well known in the art, the electric wave distribution in the heating chamber 1 is previously known according to the position, in which the cooking dish is placed, that is, a first step 2a, a second step 2b or a third step 2c of the dish receiving shelf 2. At the so-called "preliminarily heating time", when the object is not placed on the cooking dish 3, it is possible to specify the point which takes the highest temperature after a predetermined time, e.g., one minute. Therefore, a condition A provides a plurality of points, at which the temperature rises the highest in case the cooking dish 3 having the electric wave heater applied thereto is placed on the dish receiving shelf 2a at the first step, and a condition B provides a plurality of points, at which the temperature rises the highest in case the cooking dish 3 having the electric wave heater applied thereto is placed on the dish receiving shelf 2b at the second step.
The decision threshold values are also so determined from experiments as to correspond to the conditions A, B, - - -, and so on, respectively. When the detected temperatures of the detection points selected by any decision are at or lower than the decision threshold values, the heating operation is ended by deciding that there is no cooking dish having the electric wave heater applied thereto.
This selection of the detection point has been described on the case of a preliminary heating operation, which is performed without the object placed on the cooking dish. However, the invention should not be limited thereto but could also be set even in case the object is suddenly started without any preliminary heating operation by placing it on the cooking dish.
Here, the infrared sensor 11 of this embodiment utilizes the sensor for detecting the temperature of the object placed on the cooking dish 3, and the control means 12 is constituted to control the heating pattern and/or the heating time of the object 6 with the output from that sensor. Therefore, the infrared sensor 11 is advantageous in that it is unnecessary to provide a cooking dish detecting infrared sensor separately, and in that not only the detection of the presence/absence of the cooking dish but also the homogenous or efficient heating operation of the object being cooked can be performed. It is needless to say that a separate infrared sensor for detecting the presence/absence of the cooking dish can be separately provided.
Moreover, this embodiment has been described on the case, in which the decision of the presence/absence of the cooking dish is performed with the temperature itself, but the decision may also be made in terms of the temperature change such as the temperature changing rate or the temperature gradient for a predetermined time period.
Moreover, the temperature detecting means for detecting the temperature has been described on the case, in which the infrared sensor has the eight elements for detecting the infrared ray. The number of the elements should not be limited to eight but may be an optimum one according to the size or the like of the heating chamber 1. Sensors other than the infrared sensor may also be used, if they can detect the temperature in the heating chamber at a plurality of points.

[Industrial Applicability]

As has been described hereinbefore, the high-frequency heating device according to the invention can detect the presence/absence of the cooking dish thereby to prevent the abnormal temperature rise due to the baking or the like by the electric waves, so that it can be applied not only to the home applications but also to the business applications.

Claims

A high-frequency heating device comprising:
a heating chamber for housing an object to be heated;

a cooking dish having an electric wave heater applied thereto for placing said object;

a dish receiving shelf for placing said cooking dish thereon;

temperature detecting means for detecting the temperature of an object;

heating means for heating said object and said cooking dish; and

control means for deciding the presence or absence of said cooking dish from either the temperatures or the temperature change detected by said temperature detecting means at a plurality of temperature detecting points.
A high-frequency heating device as set forth in claim 1, wherein the temperature detecting means is constituted to detect the temperature of the object placed on the cooking dish, and
wherein the control means is constituted to control the heating pattern and/or the heating time period of the object on the basis of the output of said temperature detecting means.
A high-frequency heating device as set forth in claim 1 or 2, wherein the control means decides the presence/absence of the cooking dish with the plural temperatures which are selected under a predetermined condition from the plural temperatures detected by the temperature detecting means.
A high-frequency heating device as set forth in any of claims 1 to 3, wherein the predetermined condition for selecting the plural temperatures from the detected temperatures is a plurality.
A high-frequency heating device as set forth in any of claims 1 to 4, wherein the control means selects the plural temperatures detected by the temperature detecting means, under the predetermined condition, and decides it to stop the heating operation that no cooking dish exists in case the detected temperatures are at or lower than a predetermined temperature.
A high-frequency heating device as set forth in any of claims 1 to 5, further comprising display means for urging, in case the absence of the cooking dish is decided, the cooking dish to be inserted.
A high-frequency heating device as set forth in any of claims 1 to 5, further comprising voice generating means for urging, in case the absence of the cooking dish is decided, the cooking dish to be inserted.