CA1301258C - Automatic heating apparatus - Google Patents
Automatic heating apparatusInfo
- Publication number
- CA1301258C CA1301258C CA000565405A CA565405A CA1301258C CA 1301258 C CA1301258 C CA 1301258C CA 000565405 A CA000565405 A CA 000565405A CA 565405 A CA565405 A CA 565405A CA 1301258 C CA1301258 C CA 1301258C
- Authority
- CA
- Canada
- Prior art keywords
- heating
- food
- heated
- weight
- sensor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/66—Circuits
- H05B6/68—Circuits for monitoring or control
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Electric Ovens (AREA)
- Control Of High-Frequency Heating Circuits (AREA)
Abstract
Abstract:
Automatic heating apparatus, e.g. a microwave oven, is provided with a gas sensor for detecting gas or steam generated from an object being heated and a weight sensor for detecting the weight of the object. The signal level of the gas sensor indicates whether the change in the amount of gas or steam in the exhaust has reached a pre-determined value, whereby to detect the kind and condition of the object to be heated. The change of the signal level of the gas sensor is also watched in comparison with the predetermined value in the detection time period based on the weight of the food detected by the weight sensor, whereby to decide whether to continue or stop heating.
Automatic heating apparatus, e.g. a microwave oven, is provided with a gas sensor for detecting gas or steam generated from an object being heated and a weight sensor for detecting the weight of the object. The signal level of the gas sensor indicates whether the change in the amount of gas or steam in the exhaust has reached a pre-determined value, whereby to detect the kind and condition of the object to be heated. The change of the signal level of the gas sensor is also watched in comparison with the predetermined value in the detection time period based on the weight of the food detected by the weight sensor, whereby to decide whether to continue or stop heating.
Description
Automatic heating apparatus The present invention relates to an automatic heating apparatus that is designed Eor automation of cooking by employing a gas sensor and a weight sensor to detect the condition of an object being cooked.
Such apparatus for automatically controlling the heating time of a food ha.s been widely used. An automatic electronic oven is one example of such apparatus that has been highly appreciated in terms of convenience of use, and accordingly has occupied a large share of the oven market. Such apparatus has been developed in various types, such as one equipped with a gas sensor that reacts to steam or various kinds of gases generated during heating of the food, or an infrared ray sensor for detecting the surface temperature of the food, or a thermistor Eor detecting the temperature of air El.owing in and out of the heating chamber. The manner of heating depends on the kind and condition of the food in any one of the above-described types. A representative example is USP Re.
31,094 issued January 25, 1980.
To enable the prior art to be described with the aid of diagrams, the figures of tke drawings will first be listed.
Fig. 1 is a perspective view of a main body of an ~k 1~30~258 automatic heatlng apparatus:
Fig. 2 ls an enlarged front view of an operating panel of a conventional automatic heating apparatus:
Fig. 3 iS a graph showing the relationship of the detection and the control of a reheat key of the apparatus of Fig. 2;
Fig. 4 is a front elevational view of an operating panel, on an enlarged scale, of a conventional heating apparatus;
Fig. 5 is a graph showing the relationship of the detection and the control of a reheat key of conventional automatic heating apparatus;
Fig. 6 is a graph showing the control of a weight sensor of the conventional apparatus of Fig. 5 Figs. 7(a) and 7(b) are graphs showing the detection and the control of a reheat key in conventional automatic heating apparatus:
Fig. 8 is a front elevational view, on an enlarged scale, of an operating panel of an automatic heating apparatus according to one preferred embodiment of the present invention Figs. 9(a) and 9(b) are graphs showing the relationship of the detection and control of a reheat key of the apparatus of Fig. 8;
Figs. lO(a) and lO(b) are graphs for judging the food group to be reheated in the apparatus of Fig. 8;
Fig. 11 is a diagram showing the structure of the apparatus of Fig. 8;
Fig. 12 is a circuit diagram of the apparatus of Fig.
8 and Figs. 13 and 14 are flow-charts of the control program of the apparatus of Fig. 8.
Fig. 1 is a perspective view of the prior art referred to above, Fig. 2 being a front view of the operating panel of the apparatus of Fig. 1. In Fig. 1, a door 2 can be ~30~58 freely opened or closed in the front face of a main body 1. The apparatus has many select keys 4 arranged on an operating panel 3 located in the front face of the main body 1 to select the manner of heating depending on the temperature, condition and kind of food. In the category of food for reheating, five select keys, namely, for "cold boiled rice", "soup", "curry/stew", "frozen boiled rice"
and "frozen curry" are arranged for suitahle selection.
The reason Eor these five select keys resides in the fact that, if the heating operation is stopped when steam or gas is generated from the food or when the surface tempera-ture of the food reaches a predetermined temperature, some kinds of foods may not yet be sufficiently heated at the center, thus requiring further heating, the time for which, however, varies for each Eood. E'ig. 3 shows the relation-ship of heating time to the amount of steam generated from the food and detected by the gas sensor. In the graph of Fig. 3, Tl is the time spent before the first detection point when a predetermined amount of steam is detected by the gas sensor. When cold boiled rice is reheated, it is good to stop heating when the generation of steam is detected. In the case of reheating soup, it is still lukewarm, and requires to be heated for an additional time KlxTl, K1 heing constant and selected from experience to be 0.1-0.5. In the case of a ~elly-like curry or stew, it is necessary to apply further heat for a t;me K2xT], in addition to the time T1, K2 being 0.3-0.8. For frozen rice with ]ittle moisture that has been obtained by freezing cold boiled rice, it is necessary to reduce the caloric value of the heating from the time Tl when steam is detected, and to heat for a further time K3xT2 beyond the time T2 which is a second detection point when a predetermined amount of steam is detected from the food after the entirety of the frozen food has been defrosted, 13(~1258 ~ 4 --K3 being 0.01-0.5. Also, for frozen curry with m~ch moisture, which has been obtained by freezing cold curry, it can be heated to a suitable temperature if the curry is fully defrosted, with the heating caloric value reduced 5 from time Tl, and further heated for a time K4xT2 after time T2 when the predetermined amount of steam is detected to be generated, K4 being 0.3-2Ø The reason why the value of K is different for each food is that the steam is generated in a different way by each food, and the reason 10 why the caloric va]ue is reduced or not during heating is that the initial temperature condition is different for each food, depending upon whether it is frozen or not.
Since the heat conductivity and the convection properties are different for each food, and steam generation starts locally in some foods, the value of K is different for almost every food.
In consequence, a user of the prior art heating apparatus has been obliged to select from several select keys one key that is most suitable for the food to be heated. However, since only 5-6 menus can be indicated at most on the keyboard of the apparatus, the user is required to consult a cookbook or the like to ascertain whether a food that is not indicated on the keyboard is able to be cooked automatically. For example, if there is a wish to reheat macaroni, an inexperienced user does not know which key to select. Market surveys reveal that the automatic heating function is not highly utilized, although much reheating is done. This is because it is a burden for the user to find out which key to select.
Accordinq to the above-described apparatus of one type, reheating is performed by selection of a key from among many select keys that are arranged in accordance with the kind and the initial temperature of the food to be heated. On the other hand, according to apparatus of another type, foods are classified into two groups, i.e.
~30~258 frozen foods and cold foods, and two select keys are arranged Eor respectively reheating frozen foods and cold foods. The operation of reheating in this latter apparatus will be described with reference to the operating panel shown in Fig. 4.
Heating apparatus of the latter type is provided with a gas sensor and a weight sensor which detects the weight of the food to be heated, such as disclosed in USP
4,590,350. For heating the group of cold foods, the thres-hold value for detection of the gas sensor is set high,and the heating time is calculated by the weight sensor in accordance with the total weight of the food (including the packing). The apparatus is so arranged that both the gas sensor and the weight sensor are controlled in a parallel relation. Accordingly, food having a small K
value is heated on the basis of the weight detected by the weight sensor, whi]e food having a large K value is heated on the basis of time and the amount of moisture detected by the gas sensor. For heating the group of frozen foods, the caloric value is changed from the first detection point when steam is detected as being generated by the food, and then heating is continued. Thereafter, the ratio of the time before the second detection point when it is detected that the generated amount of steam reaches a predetermined amount with respect to the time lag between the Eirst detection point and the second detection point is obtained. Thus an additional heating factor K
corresponding to the calculated time ratio is obtained.
When the value of K is small, the food is determined to have less moisture and to be easy to warm, and therefore the additional heating time KxT is made short. On the contrary, when the value of K is large, the food to be heated is regarded to be full of moisture and hard to warm, with a long additional heating time KxT.
~O~Z58 ~ ow heating of the cold food group is carried out in the prior art apparatus wil~ be explained with reference to the graph of Fig. 5 which shows the change of the steam detection points by the gas sensor in accordance with the lapse of the heating time. Three points marked * are the conventional detection points of Fig. 3, while the "reheat"
point is a new detection point disclosed in USP 4,590,350.
The new detection point has a considerably higher threshold value, as compared with the conventional ones, and is positioned approximately at the center of the conventional finishing points for "soup" and "curry/stew". "Soup" is finished a little hotter at the new detection point, and "curry/stew" which is in a jellied state is still a little lukewarm at the new detection point, which is no in-convenience in practice use. On the contrary, however,"cold boiled rice" is considerably overheated at the new detection point and would be turned solid into a rubber-like material. Therefore, the weight sensor is employed to prevent col~ boiled rice or some kinds of soups from being overheated. Detection points of the gas sensor by the new threshold value are plotted in Fig. 6 for each menu. In this arrangement of the apparatus, cold boiled rice and consomme soup are overheated, while curry and noodles are finished in an almost favorahle condition.
Therefore, overheating oE the cold boiled rice and consomme soup is arranged to be solved in the following manner. The total weight (including the weight of a container) of the food is measured by the weight sensor, and the necessary cooking time for the food is calculated on the basis of the detected total weight of the food. The measurement by the weight sensor is controlled in parallel (by OR logic) with the detection by the gas sensor. At this time, if the calculation formula is suitably selected, only such menus as cold boiled rice, consomme or milk that would be overheated if based on the detection by the gas 1~0~;~58 sensor can he heated on the basis of measurement of the weight sensor. This is because, slnce cold boiled rice, consomme soup or milk is generally put in, for example, a rice bowl or a teacup having a large capacity (150-~00 cc) in comparison with its own weight (7n-200 g), the weight of the Eood with respect to the total weight is large.
Accordingly, the detection hy the gas sensor in the case of the cold boiled rice, consomme soup or milk is delayed as compared with the case of noodles or curry/stew, if they have the same total weight, and therefore cold boiled rice, consomme soup or milk is located at the upper limit as shown in Fig. 6. Thus, cold boiled rice, consomme soup or milk can be automatically cooked on the basis of detection by the weight sensor.
From experiments, it is found that the above-mentioned calculation formula can be expressed by a linear expression To=AWo, wherein the constant A is most preferably 0.3 or so (To (second) and Wo(g)). Cold boiled rice, consomme soup or milk is heated well after the weight time as expressed above. Moreover, when curry, noodles or a small amount of cooked vegetables (1/2 cup) is heated for the weight time, the result is better than when it is heated on the basis of detection bv the gas sensor. That is, the weight sen.sor is effective to improve a poor correspondence to the volume of the food of the gas sen.sor (to avold too late a stopping of heating).
Hereinafter, how the group of frozen foods is heated in the prior art devices will be described.
The food is started to be heated by a high output, as shown in Fig. 7. As heating of the food proceeds, the power is s~7itched to a low output, as shown in Fig. 7(a).
When the gas sensor detects the generation of a small amount of steam or gas from the food, that is, at the first detection point, the power is switched to low. The reason why the heating power is switched from high to low ~A0~ 258 is that, since the food is vigorously heated in the beginning hy the high output, most of the heating takes place in only a limited part of the food which suddenly discharges a great amount of steam. Therefore, a large part of the food is sufficiently heated when the second detection point comes, i.e. heating is interrupted earlier.
Accordingly, by changing the heating power from high to low, the heat in the limited part of the food where the heating is advanced can be transmitted to other parts of the food. Thus, while heating continues, the temperature of the entire body of food is raised to suddenly increase the amount of steam or gas per unit time at the time detection time point. When the signal level of the gas sensor reaches the second detection point in accordance with an increase in the amount of steam generated from the food, an additional heating time KxT2 after the second detection point is obtained based on the ratio of the time from the start of heating to the second detection point with respect to the time lag between the first detection point and the second detection point. Heating is further continued for the additional heating time and then stopped.
During the time lag between the first detection point and the second detection point, the food which has been partly heated is entirely warmed, and accordingly, the time lag between the first detection point and the second detection point expresses the conduction speed of the heat in the material of the food. On the other hand, the time from the start of heating to the second detection point indi-cates the volume of the food. Therefore, the food can be expressed with a genera1 characteristic value identifying the material and the volume of the food by the above-mentioned time ratio. If heating is continued after the second detection point for an additional heating time corresponding to the product KxT2 of the additional heating time factor K which is obtained on the basis of the ~30~2S8 characteristic value and the time period T2 from the start of heating to the second detection point, the food can be heated in a manner suitable for its kind and volume.
The foregoing description is related to the reheating of the cold food group and the frozen food group in heating apparatus of the first and second types. As shown in Fig.
4, two select keys are allotted in the prior art heating apparatus for reheating the cold foods and the froæen foods respectively. However, since there are among the frozen foods some that can be eaten raw if they are only defrosted, the select keys may be divided into a "defrost"
key and the "defrost-reheat" key. However, this brings about dangerous possibilities for an erroneous operation by the user. From the above viewpoint, it is desired to provide one select key for reheating of all groups of foods in the best condition.
Accordingly, an essential object of the present invention is to provide automatic heating apparatus having a single select key assigned for the reheating operation, which has been classified into reheating of the cold food group and reheating of the frozen food group in the con-ventional heating apparatus, thereby to enhance convenience for use.
To this end, the invention consists of an automatic heating apparatus comprising a heating means for heating an object to be heated; a control means for controlling said heating means; a first sensor means for detecting the weight of said object to be heated; a second sensor means for detecting gas or steams generated from said object to be heated; and an input means for selecting a heating sequence, wherein said control means lncludes a detection means for detecting the weight of said object to be heated by said first sensor means, a calculation means for calculating an identification time period to judge the kind of object to be heated on the basis of the detected ~:~0~2S8 weight, a timer means for indicating that heating is performed for said identification time period, a comparison means for comparing the change value of the signal level detec~ed by said second sensor means with a predetermined identification value when said identification time has passed, an identification means for identifying the kind of said object to be heated on the basis oE the comparison result, and a changing means for changing the heating sequence depending on the identified kind of object to be heated.
The invention also consists of an automatic heating method comprising the steps of: (1) operating a heating sequence select key and an input key for starting heating, with an object to be heated placed in a heating chamber;
Such apparatus for automatically controlling the heating time of a food ha.s been widely used. An automatic electronic oven is one example of such apparatus that has been highly appreciated in terms of convenience of use, and accordingly has occupied a large share of the oven market. Such apparatus has been developed in various types, such as one equipped with a gas sensor that reacts to steam or various kinds of gases generated during heating of the food, or an infrared ray sensor for detecting the surface temperature of the food, or a thermistor Eor detecting the temperature of air El.owing in and out of the heating chamber. The manner of heating depends on the kind and condition of the food in any one of the above-described types. A representative example is USP Re.
31,094 issued January 25, 1980.
To enable the prior art to be described with the aid of diagrams, the figures of tke drawings will first be listed.
Fig. 1 is a perspective view of a main body of an ~k 1~30~258 automatic heatlng apparatus:
Fig. 2 ls an enlarged front view of an operating panel of a conventional automatic heating apparatus:
Fig. 3 iS a graph showing the relationship of the detection and the control of a reheat key of the apparatus of Fig. 2;
Fig. 4 is a front elevational view of an operating panel, on an enlarged scale, of a conventional heating apparatus;
Fig. 5 is a graph showing the relationship of the detection and the control of a reheat key of conventional automatic heating apparatus;
Fig. 6 is a graph showing the control of a weight sensor of the conventional apparatus of Fig. 5 Figs. 7(a) and 7(b) are graphs showing the detection and the control of a reheat key in conventional automatic heating apparatus:
Fig. 8 is a front elevational view, on an enlarged scale, of an operating panel of an automatic heating apparatus according to one preferred embodiment of the present invention Figs. 9(a) and 9(b) are graphs showing the relationship of the detection and control of a reheat key of the apparatus of Fig. 8;
Figs. lO(a) and lO(b) are graphs for judging the food group to be reheated in the apparatus of Fig. 8;
Fig. 11 is a diagram showing the structure of the apparatus of Fig. 8;
Fig. 12 is a circuit diagram of the apparatus of Fig.
8 and Figs. 13 and 14 are flow-charts of the control program of the apparatus of Fig. 8.
Fig. 1 is a perspective view of the prior art referred to above, Fig. 2 being a front view of the operating panel of the apparatus of Fig. 1. In Fig. 1, a door 2 can be ~30~58 freely opened or closed in the front face of a main body 1. The apparatus has many select keys 4 arranged on an operating panel 3 located in the front face of the main body 1 to select the manner of heating depending on the temperature, condition and kind of food. In the category of food for reheating, five select keys, namely, for "cold boiled rice", "soup", "curry/stew", "frozen boiled rice"
and "frozen curry" are arranged for suitahle selection.
The reason Eor these five select keys resides in the fact that, if the heating operation is stopped when steam or gas is generated from the food or when the surface tempera-ture of the food reaches a predetermined temperature, some kinds of foods may not yet be sufficiently heated at the center, thus requiring further heating, the time for which, however, varies for each Eood. E'ig. 3 shows the relation-ship of heating time to the amount of steam generated from the food and detected by the gas sensor. In the graph of Fig. 3, Tl is the time spent before the first detection point when a predetermined amount of steam is detected by the gas sensor. When cold boiled rice is reheated, it is good to stop heating when the generation of steam is detected. In the case of reheating soup, it is still lukewarm, and requires to be heated for an additional time KlxTl, K1 heing constant and selected from experience to be 0.1-0.5. In the case of a ~elly-like curry or stew, it is necessary to apply further heat for a t;me K2xT], in addition to the time T1, K2 being 0.3-0.8. For frozen rice with ]ittle moisture that has been obtained by freezing cold boiled rice, it is necessary to reduce the caloric value of the heating from the time Tl when steam is detected, and to heat for a further time K3xT2 beyond the time T2 which is a second detection point when a predetermined amount of steam is detected from the food after the entirety of the frozen food has been defrosted, 13(~1258 ~ 4 --K3 being 0.01-0.5. Also, for frozen curry with m~ch moisture, which has been obtained by freezing cold curry, it can be heated to a suitable temperature if the curry is fully defrosted, with the heating caloric value reduced 5 from time Tl, and further heated for a time K4xT2 after time T2 when the predetermined amount of steam is detected to be generated, K4 being 0.3-2Ø The reason why the value of K is different for each food is that the steam is generated in a different way by each food, and the reason 10 why the caloric va]ue is reduced or not during heating is that the initial temperature condition is different for each food, depending upon whether it is frozen or not.
Since the heat conductivity and the convection properties are different for each food, and steam generation starts locally in some foods, the value of K is different for almost every food.
In consequence, a user of the prior art heating apparatus has been obliged to select from several select keys one key that is most suitable for the food to be heated. However, since only 5-6 menus can be indicated at most on the keyboard of the apparatus, the user is required to consult a cookbook or the like to ascertain whether a food that is not indicated on the keyboard is able to be cooked automatically. For example, if there is a wish to reheat macaroni, an inexperienced user does not know which key to select. Market surveys reveal that the automatic heating function is not highly utilized, although much reheating is done. This is because it is a burden for the user to find out which key to select.
Accordinq to the above-described apparatus of one type, reheating is performed by selection of a key from among many select keys that are arranged in accordance with the kind and the initial temperature of the food to be heated. On the other hand, according to apparatus of another type, foods are classified into two groups, i.e.
~30~258 frozen foods and cold foods, and two select keys are arranged Eor respectively reheating frozen foods and cold foods. The operation of reheating in this latter apparatus will be described with reference to the operating panel shown in Fig. 4.
Heating apparatus of the latter type is provided with a gas sensor and a weight sensor which detects the weight of the food to be heated, such as disclosed in USP
4,590,350. For heating the group of cold foods, the thres-hold value for detection of the gas sensor is set high,and the heating time is calculated by the weight sensor in accordance with the total weight of the food (including the packing). The apparatus is so arranged that both the gas sensor and the weight sensor are controlled in a parallel relation. Accordingly, food having a small K
value is heated on the basis of the weight detected by the weight sensor, whi]e food having a large K value is heated on the basis of time and the amount of moisture detected by the gas sensor. For heating the group of frozen foods, the caloric value is changed from the first detection point when steam is detected as being generated by the food, and then heating is continued. Thereafter, the ratio of the time before the second detection point when it is detected that the generated amount of steam reaches a predetermined amount with respect to the time lag between the Eirst detection point and the second detection point is obtained. Thus an additional heating factor K
corresponding to the calculated time ratio is obtained.
When the value of K is small, the food is determined to have less moisture and to be easy to warm, and therefore the additional heating time KxT is made short. On the contrary, when the value of K is large, the food to be heated is regarded to be full of moisture and hard to warm, with a long additional heating time KxT.
~O~Z58 ~ ow heating of the cold food group is carried out in the prior art apparatus wil~ be explained with reference to the graph of Fig. 5 which shows the change of the steam detection points by the gas sensor in accordance with the lapse of the heating time. Three points marked * are the conventional detection points of Fig. 3, while the "reheat"
point is a new detection point disclosed in USP 4,590,350.
The new detection point has a considerably higher threshold value, as compared with the conventional ones, and is positioned approximately at the center of the conventional finishing points for "soup" and "curry/stew". "Soup" is finished a little hotter at the new detection point, and "curry/stew" which is in a jellied state is still a little lukewarm at the new detection point, which is no in-convenience in practice use. On the contrary, however,"cold boiled rice" is considerably overheated at the new detection point and would be turned solid into a rubber-like material. Therefore, the weight sensor is employed to prevent col~ boiled rice or some kinds of soups from being overheated. Detection points of the gas sensor by the new threshold value are plotted in Fig. 6 for each menu. In this arrangement of the apparatus, cold boiled rice and consomme soup are overheated, while curry and noodles are finished in an almost favorahle condition.
Therefore, overheating oE the cold boiled rice and consomme soup is arranged to be solved in the following manner. The total weight (including the weight of a container) of the food is measured by the weight sensor, and the necessary cooking time for the food is calculated on the basis of the detected total weight of the food. The measurement by the weight sensor is controlled in parallel (by OR logic) with the detection by the gas sensor. At this time, if the calculation formula is suitably selected, only such menus as cold boiled rice, consomme or milk that would be overheated if based on the detection by the gas 1~0~;~58 sensor can he heated on the basis of measurement of the weight sensor. This is because, slnce cold boiled rice, consomme soup or milk is generally put in, for example, a rice bowl or a teacup having a large capacity (150-~00 cc) in comparison with its own weight (7n-200 g), the weight of the Eood with respect to the total weight is large.
Accordingly, the detection hy the gas sensor in the case of the cold boiled rice, consomme soup or milk is delayed as compared with the case of noodles or curry/stew, if they have the same total weight, and therefore cold boiled rice, consomme soup or milk is located at the upper limit as shown in Fig. 6. Thus, cold boiled rice, consomme soup or milk can be automatically cooked on the basis of detection by the weight sensor.
From experiments, it is found that the above-mentioned calculation formula can be expressed by a linear expression To=AWo, wherein the constant A is most preferably 0.3 or so (To (second) and Wo(g)). Cold boiled rice, consomme soup or milk is heated well after the weight time as expressed above. Moreover, when curry, noodles or a small amount of cooked vegetables (1/2 cup) is heated for the weight time, the result is better than when it is heated on the basis of detection bv the gas sensor. That is, the weight sen.sor is effective to improve a poor correspondence to the volume of the food of the gas sen.sor (to avold too late a stopping of heating).
Hereinafter, how the group of frozen foods is heated in the prior art devices will be described.
The food is started to be heated by a high output, as shown in Fig. 7. As heating of the food proceeds, the power is s~7itched to a low output, as shown in Fig. 7(a).
When the gas sensor detects the generation of a small amount of steam or gas from the food, that is, at the first detection point, the power is switched to low. The reason why the heating power is switched from high to low ~A0~ 258 is that, since the food is vigorously heated in the beginning hy the high output, most of the heating takes place in only a limited part of the food which suddenly discharges a great amount of steam. Therefore, a large part of the food is sufficiently heated when the second detection point comes, i.e. heating is interrupted earlier.
Accordingly, by changing the heating power from high to low, the heat in the limited part of the food where the heating is advanced can be transmitted to other parts of the food. Thus, while heating continues, the temperature of the entire body of food is raised to suddenly increase the amount of steam or gas per unit time at the time detection time point. When the signal level of the gas sensor reaches the second detection point in accordance with an increase in the amount of steam generated from the food, an additional heating time KxT2 after the second detection point is obtained based on the ratio of the time from the start of heating to the second detection point with respect to the time lag between the first detection point and the second detection point. Heating is further continued for the additional heating time and then stopped.
During the time lag between the first detection point and the second detection point, the food which has been partly heated is entirely warmed, and accordingly, the time lag between the first detection point and the second detection point expresses the conduction speed of the heat in the material of the food. On the other hand, the time from the start of heating to the second detection point indi-cates the volume of the food. Therefore, the food can be expressed with a genera1 characteristic value identifying the material and the volume of the food by the above-mentioned time ratio. If heating is continued after the second detection point for an additional heating time corresponding to the product KxT2 of the additional heating time factor K which is obtained on the basis of the ~30~2S8 characteristic value and the time period T2 from the start of heating to the second detection point, the food can be heated in a manner suitable for its kind and volume.
The foregoing description is related to the reheating of the cold food group and the frozen food group in heating apparatus of the first and second types. As shown in Fig.
4, two select keys are allotted in the prior art heating apparatus for reheating the cold foods and the froæen foods respectively. However, since there are among the frozen foods some that can be eaten raw if they are only defrosted, the select keys may be divided into a "defrost"
key and the "defrost-reheat" key. However, this brings about dangerous possibilities for an erroneous operation by the user. From the above viewpoint, it is desired to provide one select key for reheating of all groups of foods in the best condition.
Accordingly, an essential object of the present invention is to provide automatic heating apparatus having a single select key assigned for the reheating operation, which has been classified into reheating of the cold food group and reheating of the frozen food group in the con-ventional heating apparatus, thereby to enhance convenience for use.
To this end, the invention consists of an automatic heating apparatus comprising a heating means for heating an object to be heated; a control means for controlling said heating means; a first sensor means for detecting the weight of said object to be heated; a second sensor means for detecting gas or steams generated from said object to be heated; and an input means for selecting a heating sequence, wherein said control means lncludes a detection means for detecting the weight of said object to be heated by said first sensor means, a calculation means for calculating an identification time period to judge the kind of object to be heated on the basis of the detected ~:~0~2S8 weight, a timer means for indicating that heating is performed for said identification time period, a comparison means for comparing the change value of the signal level detec~ed by said second sensor means with a predetermined identification value when said identification time has passed, an identification means for identifying the kind of said object to be heated on the basis oE the comparison result, and a changing means for changing the heating sequence depending on the identified kind of object to be heated.
The invention also consists of an automatic heating method comprising the steps of: (1) operating a heating sequence select key and an input key for starting heating, with an object to be heated placed in a heating chamber;
(2) starting heating of the object to be heated, while the weight of the object to be heated (including the packing) is measured, and the initial state of the food to be heated in the gas sensor section is watched; (3) calculating the indentification time for judging the kind of the food to ~e heated on the basis of said watched welght value; (4) comparing the difference amount (change amount) between the state in the gas sensor section when the time passed from the start of heating reaches said identification time period and in the initial state, with a predetermined value; and (5) selecting a heating sequence from among many heating sequences based on the comparison result of the difference arnount with the predetermined value.
With reference to Fig. 8, showing an operating panel of automatic heating apparatus of the present invention, various select keys 4 are arranged on the operating panel 3. It is arranged that every reheating operation is per-formed ~y depression of a single "mighty reheat" key 5.
Although two reheat keys are provided in the prior art devices, respectively for the cold food group and the frozen food group (referring to Fig. 4), a single "already-cooked reheat~ key 5 is enough for both the cold food group and the frozen food group according to the present invention. The reason for this will be made clear hereinbelow.
The apparatus is provided with two sensors. A first sensor is a weight sensor which detects the total weight of the food (including the packing). One example of such a weight sensor as above is a weight sensor manufactured by the assignee of the present application, Matsushita Electric Industrial Co., Ltd., which is in the form of an air condenser having two ceramic base plates with metallic films attached so that the metallic films are opposite each other through an air layer. In the Matsushita weight sensor, the capacity of the condenser is changed in accordance with the scale of the weight load. Thus, the total weight of the food to be heated is detected by the first sensor means when the food is started to be heated, and the time value Tw is calculated on the basis of the detected weight. On the other hand, a second sensor means is a gas sensor which detects gas or steam generated from the food. The gas sensor is, for example, a specific humidity sensor ~Neo-humi-SERAM~, manufactured by Matsushita Electric Industrial Co., Ltd., or a gas sensor manufactured by Le Figaro.
Fig. 9 shows detection points by the gas sensor and the detection time of the food by the weight sensor, etc.
Specifically, Fig. 9(a) shows the case where the cold food group is heated, and Fig. 9(b) shows the case where the frozen food group is heated. The operation common to both cases is that the total weight of the food is detected when the food is started to be heated, and it is watched se~uentially whether the amount of steam generated from the Eood before the time point Tw calculated on the basis of the detected total weight of the food is changed, such watching taking the form of the signal level of the gas * Trade Mark ,~ .
,i~
13~258 sensor changing from the initial value V by the level ~g or hy the level ah. Wlth a change by the level ah observed at the time point Tw, the food to be heated is judged to be the cold food group, and the food is continuously heated as it is. On the other hand, without the change by the level h observed at the time point Tw, the food to be heated is determined to be the frozen food group, and the heating caloric value is switched while the food is con-tinuously heated. By noting the time period Tw determined by the total weight of the food, the food can be classified into the group of cold foods or the group of frozen foods, because it has been made clear from experiments that, as shown in Fig. 10(a), the cold food group displays the change ~h earlier than the calculated time point Tw=AxW+~, while the frozen food group shows the change ~h later than the time point Tw=AxW+~. Logically explaining the above-described phenomenon, even when a cold food and a frozen food having the same weight are heated by the same heating caloric value, the initial temperature of the food is different, that is, the initial temperature of the frozen food is below the freezing point, whereas that of the cold food is above 0C. Even if the cold food had been placed in a refrigerator, the initial temperature thereof is about 5C. Consequently, the accumulative heating caloric value necessary for raising the initial temperature of the food to the boiling temperature at which steam is generated from the food is different, and the time period representing the difference of the accumulative heating caloric value is longer in the frozen food than in the cold food. In the manner as above, according to the present invention, the food to be heated can be classified into the cold food group or the frozen food group in the same single heating sequence, and therefore a single select key can perform automatic reheating of various ~3~2513 kinds of foods such as "cold boiled rice", "soup", "curry/stew", "frozen rice" or "frozen curry".
It has been found by experiment that the formula for identifying the food to be heated on the basis of its 5 weight can be expressed by a linear expression: Tw=AxW+B
wherein constant A is optimum at about 0.25, and constant B is optimum at about 30, with Tw being seconds, W being grams, and B being seconds. Even when the total weight of the cold food is different +200g from that of the frozen lO food, because of the weight difference of the packing, the identification of the food is done correctly. Therefore, by this linear expression, the food can be heated in a manner suitab]e to its nature.
The construction of the apparatus will now be 15 described.
Referring to Fig. 11, various commands inputted through depression of the selected key 4 on the operating panel 3 are read in a control section 6 and displayed in a predetermined manner, thus control]ing the progress of the 20 heating. Reference numeral 5 indicates a "reheat" key.
Food 8 to be heated is placed in a chamber 7 and heated by a magnetron 9 which is a high-frequency generating means. The supply of power to the magnetron 9 is contro]led by the control section 6 through a driver 10.
25 A fan 11 is provided to coo] the magnetron 9 and at the same time to venti]ate the chamber 7. In a guide 12 for discharging the exhaust out of the apparatus there is provided a second sensor means, namely, a gas sensor ]3 which detects gas or steam generated from the food, thereby 30 giving information on the heating condition to the control section 6 through a detector circuit 14.
The apparatus is also provided with a first sensor means, i.e., a weight sensor 15 which detects the total weight of the food 8 on a platform 16. The control section 35 6 is formed of microcomputers. The gas sensor 13, which - ~4 -makes use of the fact that an electric characteristic such as the resistance value of a sensor element or capacity of a condenser is changed as the density or the amount of the liquid component of the steam and an aromatic organic gas 5 or an aromatic inorganic gas, etc. in the air is changed, is served by a specific humidity sensor manufactured by Matsushita Electric Industrial Co., Ltd. or Tokyo Shibaura Co., Ltd., or a gas sensor produced by Le Figaro. A
pressure gauge of an air condenser system manufactured by 10 Matsushita Electric Industrial Co., Ltd. may be employed for the weight sensor 15.
Although the formula for ohtaining the detection time of the food by the weight sensor is a linear expression T2=AxW+B (A and B are constants) in the present embodiment, 15 an expression of a higher degree can be selected. Needless to say the value of the level ~h is peculiar to the apparatus, and the most suitable value can be selected for each apparatus.
Fig 12 is a circuit diagram showing the construction of the circuit controlled by a micro-computer 17. A
command inputted from the select key 4 to input terminals I0-I3 of the microcomputer 17 is decoded in the micro-computer 17, to generate a predetermined output. For example, when the "reheat" key is depressed, the micro-computer 17 makes the display "Al" in a display section18. The display section 18 is driven to be dynamically turned on in order to decrease the s:ignal lines. Lighting data is outputted to data outputs D0-D7 and a digital control signal is outputted to digital outputs S0-S4. The digital control signal is also used for sweeping of the key matrix 4. An output of the gas sensor 13 is inputted to an A/D conversion input terminal A/D of the micro-computer 17 in which the change of the resistance value as a result of the change of the steam amount is measured.
~0~258 - l5 -An output of the weight sensor 15 is inputted to the input terminal T~ of the microcomputer 17 through a detection circuit 19. The detector circuit 19 is formed by an oscillation circuit and a bridge circuit, etc.
Upon starting of heating, relay control outputs R0 and Rl are outputted from the microcomputer 17 through a driver 20. A relay switch 21 controls outputting of the microwave through intermittent operatlon thereof, and a relay switch 22 controls the supply of electricity to the heating apparatus. The magnetron 9 serves to supply the microwave energy to the heating chamber. The apparatus also has a motor 23 for the cooling fan, etc., a light 24 inside the apparatus, a door switch 25 operated con-currently with opening or closlng of the door, and a bu%zer 26 for notifying the user of the end of the heating process.
Figs. 13 and 14 are flow-charts of the control program.
First, the microcomputer 17 and the control circuit are initialiæed by initial setting. Then, the display decoder is controlled in the manner as explained with reference to Fig. 12. Thereafter, it is judged whether cooking is being carried out. If cooking is not being performed, an inputted key is read. When the "reheat" key is selected, with the food to be heated inside the heating chamber, and the "heating start" key is depressed, then heating is started. Simultaneously with this, the weight (Wg) and the initial humidity condition (V0 level) of the food to be heated are detected by the weight sensor and the gas sensor, respectively. Then, three heating stop time periods, TLl, TL2 and TL3, together with an identification time period Tw for stopping heating in accordance with the condition of the food, are calculated (a). Meanwhile, upon start of heating, the humidity condition (V) is kept watched, and also the passed time (T) is continuously 1:~0~258 observed (b). In order to stop heating of food among the cold food group, such as cold boiled rice that is easy to warm and fast to generate steam in the heating stop time period TLl calculated on the basis of the Eood weight, it is arranged to watch whether the amount of steam generated from the food is changed by the g level corresponding to the change of the signal level of the gas sensor. When the humidity change by the g level is noticed, with the time period TLl passed, heating is immediately stopped (c). At this time, if either one of the above conditions is not satisfied, that is, the humidity change of the g level is not observed or the time TLl is not passed, heating is not stopped, but it is determined whether the passed time T is the time period Tw which is obtained on the basis of the food weight (d) (1-3 levels are designated for g). When the passed time T is over the time T2, it is compared and detected whether the food is heated so much that the steam generated from the food changes the signal level of the gas sensor by the h level, or whether the amount of the generated steam is too small to cause a change by the h level. As a result, one of the first heating processes for the cold food group and the second heating process Eor the frozen Eood group is selected for the heating sequence (e) (5-12 levels are assigned for h). In this manner, the food is classified by the presence or absence of a change over the h level of the signal level of the gas sensor in comparison with the lnitial value in the time period Tw determined on the basis of the food weight.
According to the second heating process for the frozen food group, heating by the microwave energy is inter-mittently done as shown in Fig. 14(f). The humidity condition (V), the passed time (T), etc. are watched (g).
It is determined whether or not the passed time (T) is beyond the heating stop time TL2 which is calculated on ~l301258 the basis of the Eood weight W (h). The value of f is so determined that there is no ~ood that has been heated over the time TL2 and is reheated, and which generates too small an amount of steam to bring about the change of the f level. In other words, the value of f is so set as to prevent the dangerous state that food that is too dry or unfit for reheating is continuously heated and scorched or set on fire. In the case where the signal level of the gas sensor is changed hy the f level, heating is continued.
However, if the signal level of the gas sensor is not changed by the f level, the food is regarded as being in a dangerous condition and heating is stopped (i) (2-5 levels are selected for f). Even for heating of the frozen food group, the time when the h level change in the signal level of the gas sensor is observed as the food is heated to become warm is memorized as the first detection time point Tl (j), with the aim that when the passed time is beyond the TL3 calculated on the basis of the food weight, it can be detected either that the food is fully heated for automatic heating and cooking, or that the food is in such a condition that not enough steam is generated from the food to make the heating condition ready for automatic heating and cooking in spite of the h level change observed in the signal level of the gas sensor. If insufficient steam is generated from the food, heating is stopped to prevent the food being heated too much and scorched or set on fire (k). Thereafter, the food is heated enough before the second detection point when the signal level of the gas sensor is a times the initial value V0, with the generated steam filling the heating chamber (Q). The time period passed before the second detection point is memorized as T2. The time factor K for setting an additional heating time is calculated on the basis of the ratio of the time lag (T2-Tl) between the first detection ~:301258 point T1 and the second detection point T2 with respect to the passed time period T2, so that the additional heating time is obtained by the product of the passed time period T2 and the factor K (m). Thus, heating is continued for the additional time KxT2, to complete heating of the frozen food in the second heating process.
Although heating is carried out slowly by the inter-mittent supply of electromagnetic energy in such second heating process, it goes without saying that the food to be heated can be supplied with small heat, such as the heat of an electric heater or of gas combustion, thereby to realize heating of the whole frozen food in a moderate manner.
Moreover, also in the case of reheating of cold food in the first heating process, for identifying the kind of food to be heated, an additional heating time factor K is calculated based on the ratio of the time lag (T2-Tl) between the first detection point Tl when the h level change in the signal level of the gas sensor due to the steam generated from the food is observed and the second detection point T2 when the change of the signal level of the gas sensor due to the generation of steam from the food becomes ~ times the initial value V, with respect to the time period T2 passed before the second detection point. The additional heating time KxT2 is then obtained by the product of the calculated additional heating time factor K and the passed time T2. After heating Eor the additional heating time, heating is EinalLy stopped.
Since the additional heating time KxT2 is calculated based on the time lag between the first detection point and the second detection point, which time lag changes depending on the material and the amount of food and the condition of the container of the food, the additional heating time KxT2 can be determined to correspond to the condition of the food, whether it is cold food or frozen i3~)~258 food.
The additional heating time factor K ca]culated on the basis of the ratio (T2-Tl )/T2 reflects the condition of the food as follows. The time lag between the first detection point and the second detection point reflects the difference of the food, namely, that the food to be heated has low heat conductivity and needs a long time to be totally heated or that the food can be heated fast in a short time. Further, when the food is covered with a wrapping made of a transparent resinous film, time is necessary beEore the steam is generated from the food and gathered in the food so much as to break the wrapping after the food gets warm, and a large amount of steam is generated all at once after the wrapping is broken.
Accor~ingly, the time lag between the first detection point and the second detection point becomes small. On the contrary, without wrapping, steam is generated gradually in accordance with the temperature rise of the food, and therefore the first detection point comes soon in a short heating time, resulting in a larger time lag between the first detection point and the second detection point. As described above, the time lag differs depending on whether the food is wrapped or not, or by the characteristic of the heat conductivity of the food, etc.
Moreover, when the total weight of the Eood is large, the time before generation of steam from the whole of the food becomes long. Therefore, if only the time lag between the first detection point and the second detection point is taken into consideration, it is difficult to determine what the time lag results from, namely, the difference of the kind of the food, whether the food is easy to generate steam per unit weight, or whether the food is easy to warm. Beca~se of this fact, the time period T2 passed before the second detection point is employed for representing the total weight of the food, and the ratio of the time lag hetween the fiest detection point and the second detection point with respect to the passed time before the second detection point are calculated.
Accordingly, the ratio can be regarded as a characteristic value of the food, in consideration of the material, condition, and total weight of the food.
As is made clear from the foregoing description, the automatic heating apparatus described herein has the following effects and merits.
(l) The apparatus employs both a gas sensor and a weight sensor, so that it watches how much the signal level of the gas sensor is changed as compared with the initial value thereof at the start of heating in the time calculated on the basis of the weight of the food (including the packing), thereby to detect the presence of a large change of the signal level over the predetermined value. Reheating can thus be performed by depression of a signal "mighty reheat" key. Accordingly, the user of the apparatus need not be concerned with which key to select, and therefore the operating efficiency is remarkably improved. Nevertheless, the finished menus are as good as in the conventional heating apparatus having 4-5 select keys.
(2) The poor correspondence of the gas sensor to the weight of food is improved by the weight sensor. There-fore, the heating can be so controlled as to be stopped even when a small increase of the amount of steam generated from the food is detected in the time calculated on the basis of the total weight of the food detected by the weight sensor, thus preventing overheating of foods that generates little steam.
(3) Even when the amount of steam generated from the food is not so much as to change the signal level of the gas sensor to a predetermined level, although the weight of the food is enough, or the signal level of the gas ~301~58 sensor is not chanqed due to hreakage of the gas sensor, i.e., even under particular conditions for automatic heating, it can be prevented that the precious food is heated too much and scorched. Moreover, even if the 5 apparatus is operated without any food in the heating chamber, since it will happen that no change is brought about in the slgnal level of the gas sensor correspondinq to a predetermined amount before the heating time detected on the basis of the detection of the weight sensor, heating 10 is safely stopped in quite a short time.
With reference to Fig. 8, showing an operating panel of automatic heating apparatus of the present invention, various select keys 4 are arranged on the operating panel 3. It is arranged that every reheating operation is per-formed ~y depression of a single "mighty reheat" key 5.
Although two reheat keys are provided in the prior art devices, respectively for the cold food group and the frozen food group (referring to Fig. 4), a single "already-cooked reheat~ key 5 is enough for both the cold food group and the frozen food group according to the present invention. The reason for this will be made clear hereinbelow.
The apparatus is provided with two sensors. A first sensor is a weight sensor which detects the total weight of the food (including the packing). One example of such a weight sensor as above is a weight sensor manufactured by the assignee of the present application, Matsushita Electric Industrial Co., Ltd., which is in the form of an air condenser having two ceramic base plates with metallic films attached so that the metallic films are opposite each other through an air layer. In the Matsushita weight sensor, the capacity of the condenser is changed in accordance with the scale of the weight load. Thus, the total weight of the food to be heated is detected by the first sensor means when the food is started to be heated, and the time value Tw is calculated on the basis of the detected weight. On the other hand, a second sensor means is a gas sensor which detects gas or steam generated from the food. The gas sensor is, for example, a specific humidity sensor ~Neo-humi-SERAM~, manufactured by Matsushita Electric Industrial Co., Ltd., or a gas sensor manufactured by Le Figaro.
Fig. 9 shows detection points by the gas sensor and the detection time of the food by the weight sensor, etc.
Specifically, Fig. 9(a) shows the case where the cold food group is heated, and Fig. 9(b) shows the case where the frozen food group is heated. The operation common to both cases is that the total weight of the food is detected when the food is started to be heated, and it is watched se~uentially whether the amount of steam generated from the Eood before the time point Tw calculated on the basis of the detected total weight of the food is changed, such watching taking the form of the signal level of the gas * Trade Mark ,~ .
,i~
13~258 sensor changing from the initial value V by the level ~g or hy the level ah. Wlth a change by the level ah observed at the time point Tw, the food to be heated is judged to be the cold food group, and the food is continuously heated as it is. On the other hand, without the change by the level h observed at the time point Tw, the food to be heated is determined to be the frozen food group, and the heating caloric value is switched while the food is con-tinuously heated. By noting the time period Tw determined by the total weight of the food, the food can be classified into the group of cold foods or the group of frozen foods, because it has been made clear from experiments that, as shown in Fig. 10(a), the cold food group displays the change ~h earlier than the calculated time point Tw=AxW+~, while the frozen food group shows the change ~h later than the time point Tw=AxW+~. Logically explaining the above-described phenomenon, even when a cold food and a frozen food having the same weight are heated by the same heating caloric value, the initial temperature of the food is different, that is, the initial temperature of the frozen food is below the freezing point, whereas that of the cold food is above 0C. Even if the cold food had been placed in a refrigerator, the initial temperature thereof is about 5C. Consequently, the accumulative heating caloric value necessary for raising the initial temperature of the food to the boiling temperature at which steam is generated from the food is different, and the time period representing the difference of the accumulative heating caloric value is longer in the frozen food than in the cold food. In the manner as above, according to the present invention, the food to be heated can be classified into the cold food group or the frozen food group in the same single heating sequence, and therefore a single select key can perform automatic reheating of various ~3~2513 kinds of foods such as "cold boiled rice", "soup", "curry/stew", "frozen rice" or "frozen curry".
It has been found by experiment that the formula for identifying the food to be heated on the basis of its 5 weight can be expressed by a linear expression: Tw=AxW+B
wherein constant A is optimum at about 0.25, and constant B is optimum at about 30, with Tw being seconds, W being grams, and B being seconds. Even when the total weight of the cold food is different +200g from that of the frozen lO food, because of the weight difference of the packing, the identification of the food is done correctly. Therefore, by this linear expression, the food can be heated in a manner suitab]e to its nature.
The construction of the apparatus will now be 15 described.
Referring to Fig. 11, various commands inputted through depression of the selected key 4 on the operating panel 3 are read in a control section 6 and displayed in a predetermined manner, thus control]ing the progress of the 20 heating. Reference numeral 5 indicates a "reheat" key.
Food 8 to be heated is placed in a chamber 7 and heated by a magnetron 9 which is a high-frequency generating means. The supply of power to the magnetron 9 is contro]led by the control section 6 through a driver 10.
25 A fan 11 is provided to coo] the magnetron 9 and at the same time to venti]ate the chamber 7. In a guide 12 for discharging the exhaust out of the apparatus there is provided a second sensor means, namely, a gas sensor ]3 which detects gas or steam generated from the food, thereby 30 giving information on the heating condition to the control section 6 through a detector circuit 14.
The apparatus is also provided with a first sensor means, i.e., a weight sensor 15 which detects the total weight of the food 8 on a platform 16. The control section 35 6 is formed of microcomputers. The gas sensor 13, which - ~4 -makes use of the fact that an electric characteristic such as the resistance value of a sensor element or capacity of a condenser is changed as the density or the amount of the liquid component of the steam and an aromatic organic gas 5 or an aromatic inorganic gas, etc. in the air is changed, is served by a specific humidity sensor manufactured by Matsushita Electric Industrial Co., Ltd. or Tokyo Shibaura Co., Ltd., or a gas sensor produced by Le Figaro. A
pressure gauge of an air condenser system manufactured by 10 Matsushita Electric Industrial Co., Ltd. may be employed for the weight sensor 15.
Although the formula for ohtaining the detection time of the food by the weight sensor is a linear expression T2=AxW+B (A and B are constants) in the present embodiment, 15 an expression of a higher degree can be selected. Needless to say the value of the level ~h is peculiar to the apparatus, and the most suitable value can be selected for each apparatus.
Fig 12 is a circuit diagram showing the construction of the circuit controlled by a micro-computer 17. A
command inputted from the select key 4 to input terminals I0-I3 of the microcomputer 17 is decoded in the micro-computer 17, to generate a predetermined output. For example, when the "reheat" key is depressed, the micro-computer 17 makes the display "Al" in a display section18. The display section 18 is driven to be dynamically turned on in order to decrease the s:ignal lines. Lighting data is outputted to data outputs D0-D7 and a digital control signal is outputted to digital outputs S0-S4. The digital control signal is also used for sweeping of the key matrix 4. An output of the gas sensor 13 is inputted to an A/D conversion input terminal A/D of the micro-computer 17 in which the change of the resistance value as a result of the change of the steam amount is measured.
~0~258 - l5 -An output of the weight sensor 15 is inputted to the input terminal T~ of the microcomputer 17 through a detection circuit 19. The detector circuit 19 is formed by an oscillation circuit and a bridge circuit, etc.
Upon starting of heating, relay control outputs R0 and Rl are outputted from the microcomputer 17 through a driver 20. A relay switch 21 controls outputting of the microwave through intermittent operatlon thereof, and a relay switch 22 controls the supply of electricity to the heating apparatus. The magnetron 9 serves to supply the microwave energy to the heating chamber. The apparatus also has a motor 23 for the cooling fan, etc., a light 24 inside the apparatus, a door switch 25 operated con-currently with opening or closlng of the door, and a bu%zer 26 for notifying the user of the end of the heating process.
Figs. 13 and 14 are flow-charts of the control program.
First, the microcomputer 17 and the control circuit are initialiæed by initial setting. Then, the display decoder is controlled in the manner as explained with reference to Fig. 12. Thereafter, it is judged whether cooking is being carried out. If cooking is not being performed, an inputted key is read. When the "reheat" key is selected, with the food to be heated inside the heating chamber, and the "heating start" key is depressed, then heating is started. Simultaneously with this, the weight (Wg) and the initial humidity condition (V0 level) of the food to be heated are detected by the weight sensor and the gas sensor, respectively. Then, three heating stop time periods, TLl, TL2 and TL3, together with an identification time period Tw for stopping heating in accordance with the condition of the food, are calculated (a). Meanwhile, upon start of heating, the humidity condition (V) is kept watched, and also the passed time (T) is continuously 1:~0~258 observed (b). In order to stop heating of food among the cold food group, such as cold boiled rice that is easy to warm and fast to generate steam in the heating stop time period TLl calculated on the basis of the Eood weight, it is arranged to watch whether the amount of steam generated from the food is changed by the g level corresponding to the change of the signal level of the gas sensor. When the humidity change by the g level is noticed, with the time period TLl passed, heating is immediately stopped (c). At this time, if either one of the above conditions is not satisfied, that is, the humidity change of the g level is not observed or the time TLl is not passed, heating is not stopped, but it is determined whether the passed time T is the time period Tw which is obtained on the basis of the food weight (d) (1-3 levels are designated for g). When the passed time T is over the time T2, it is compared and detected whether the food is heated so much that the steam generated from the food changes the signal level of the gas sensor by the h level, or whether the amount of the generated steam is too small to cause a change by the h level. As a result, one of the first heating processes for the cold food group and the second heating process Eor the frozen Eood group is selected for the heating sequence (e) (5-12 levels are assigned for h). In this manner, the food is classified by the presence or absence of a change over the h level of the signal level of the gas sensor in comparison with the lnitial value in the time period Tw determined on the basis of the food weight.
According to the second heating process for the frozen food group, heating by the microwave energy is inter-mittently done as shown in Fig. 14(f). The humidity condition (V), the passed time (T), etc. are watched (g).
It is determined whether or not the passed time (T) is beyond the heating stop time TL2 which is calculated on ~l301258 the basis of the Eood weight W (h). The value of f is so determined that there is no ~ood that has been heated over the time TL2 and is reheated, and which generates too small an amount of steam to bring about the change of the f level. In other words, the value of f is so set as to prevent the dangerous state that food that is too dry or unfit for reheating is continuously heated and scorched or set on fire. In the case where the signal level of the gas sensor is changed hy the f level, heating is continued.
However, if the signal level of the gas sensor is not changed by the f level, the food is regarded as being in a dangerous condition and heating is stopped (i) (2-5 levels are selected for f). Even for heating of the frozen food group, the time when the h level change in the signal level of the gas sensor is observed as the food is heated to become warm is memorized as the first detection time point Tl (j), with the aim that when the passed time is beyond the TL3 calculated on the basis of the food weight, it can be detected either that the food is fully heated for automatic heating and cooking, or that the food is in such a condition that not enough steam is generated from the food to make the heating condition ready for automatic heating and cooking in spite of the h level change observed in the signal level of the gas sensor. If insufficient steam is generated from the food, heating is stopped to prevent the food being heated too much and scorched or set on fire (k). Thereafter, the food is heated enough before the second detection point when the signal level of the gas sensor is a times the initial value V0, with the generated steam filling the heating chamber (Q). The time period passed before the second detection point is memorized as T2. The time factor K for setting an additional heating time is calculated on the basis of the ratio of the time lag (T2-Tl) between the first detection ~:301258 point T1 and the second detection point T2 with respect to the passed time period T2, so that the additional heating time is obtained by the product of the passed time period T2 and the factor K (m). Thus, heating is continued for the additional time KxT2, to complete heating of the frozen food in the second heating process.
Although heating is carried out slowly by the inter-mittent supply of electromagnetic energy in such second heating process, it goes without saying that the food to be heated can be supplied with small heat, such as the heat of an electric heater or of gas combustion, thereby to realize heating of the whole frozen food in a moderate manner.
Moreover, also in the case of reheating of cold food in the first heating process, for identifying the kind of food to be heated, an additional heating time factor K is calculated based on the ratio of the time lag (T2-Tl) between the first detection point Tl when the h level change in the signal level of the gas sensor due to the steam generated from the food is observed and the second detection point T2 when the change of the signal level of the gas sensor due to the generation of steam from the food becomes ~ times the initial value V, with respect to the time period T2 passed before the second detection point. The additional heating time KxT2 is then obtained by the product of the calculated additional heating time factor K and the passed time T2. After heating Eor the additional heating time, heating is EinalLy stopped.
Since the additional heating time KxT2 is calculated based on the time lag between the first detection point and the second detection point, which time lag changes depending on the material and the amount of food and the condition of the container of the food, the additional heating time KxT2 can be determined to correspond to the condition of the food, whether it is cold food or frozen i3~)~258 food.
The additional heating time factor K ca]culated on the basis of the ratio (T2-Tl )/T2 reflects the condition of the food as follows. The time lag between the first detection point and the second detection point reflects the difference of the food, namely, that the food to be heated has low heat conductivity and needs a long time to be totally heated or that the food can be heated fast in a short time. Further, when the food is covered with a wrapping made of a transparent resinous film, time is necessary beEore the steam is generated from the food and gathered in the food so much as to break the wrapping after the food gets warm, and a large amount of steam is generated all at once after the wrapping is broken.
Accor~ingly, the time lag between the first detection point and the second detection point becomes small. On the contrary, without wrapping, steam is generated gradually in accordance with the temperature rise of the food, and therefore the first detection point comes soon in a short heating time, resulting in a larger time lag between the first detection point and the second detection point. As described above, the time lag differs depending on whether the food is wrapped or not, or by the characteristic of the heat conductivity of the food, etc.
Moreover, when the total weight of the Eood is large, the time before generation of steam from the whole of the food becomes long. Therefore, if only the time lag between the first detection point and the second detection point is taken into consideration, it is difficult to determine what the time lag results from, namely, the difference of the kind of the food, whether the food is easy to generate steam per unit weight, or whether the food is easy to warm. Beca~se of this fact, the time period T2 passed before the second detection point is employed for representing the total weight of the food, and the ratio of the time lag hetween the fiest detection point and the second detection point with respect to the passed time before the second detection point are calculated.
Accordingly, the ratio can be regarded as a characteristic value of the food, in consideration of the material, condition, and total weight of the food.
As is made clear from the foregoing description, the automatic heating apparatus described herein has the following effects and merits.
(l) The apparatus employs both a gas sensor and a weight sensor, so that it watches how much the signal level of the gas sensor is changed as compared with the initial value thereof at the start of heating in the time calculated on the basis of the weight of the food (including the packing), thereby to detect the presence of a large change of the signal level over the predetermined value. Reheating can thus be performed by depression of a signal "mighty reheat" key. Accordingly, the user of the apparatus need not be concerned with which key to select, and therefore the operating efficiency is remarkably improved. Nevertheless, the finished menus are as good as in the conventional heating apparatus having 4-5 select keys.
(2) The poor correspondence of the gas sensor to the weight of food is improved by the weight sensor. There-fore, the heating can be so controlled as to be stopped even when a small increase of the amount of steam generated from the food is detected in the time calculated on the basis of the total weight of the food detected by the weight sensor, thus preventing overheating of foods that generates little steam.
(3) Even when the amount of steam generated from the food is not so much as to change the signal level of the gas sensor to a predetermined level, although the weight of the food is enough, or the signal level of the gas ~301~58 sensor is not chanqed due to hreakage of the gas sensor, i.e., even under particular conditions for automatic heating, it can be prevented that the precious food is heated too much and scorched. Moreover, even if the 5 apparatus is operated without any food in the heating chamber, since it will happen that no change is brought about in the slgnal level of the gas sensor correspondinq to a predetermined amount before the heating time detected on the basis of the detection of the weight sensor, heating 10 is safely stopped in quite a short time.
(4) Even when the food weight is enough, and the signal level of the gas sensor is changed by the generated steam to a predetermined first level change, but not to a second level change, namely, even when dry food is heated 15 or a frozen meat bun contained in a large heavy container is heated, under particular conditions for automatic heating, such an accident that the food is overheated and scorched can be prevented, since it is arranged to stop heating by the time calculated on the basis of the food 20 weight. Further, even if noises from outside, such as the microwaves of the heating apparatus, discharging noises of a relay contact or induction surge noises of the trans-former or motor arrive at the control section during heating, and consequently the normal change of the signal level of the gas sensor is not transmitted to the control section, heating is stopped by the time calculated on the basis of the food weight, without keeping heating until the signal level of the gas sensor reaches the level at the second detection point (impossible level). The apparatus of the present invention is thus safe.
As has been described hereinabove, the present invention enables the operating keys to be simplified, with the heating apparatus provided with a gas sensor and a weight sensor, such as an electronic oven, an electric oven, a combination oven, or a gas oven. Moreover the 13~ 5l!3 heating apparatus according to the present invention is provided with sensors, not a single sensor, so as to detect the condition of the food to be heated time after time~ so that the heating time can be controlled properly to prevent overheating of the food. As a result, the heating apparatus of the present invention enjoys a great improvement in safety.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.
As has been described hereinabove, the present invention enables the operating keys to be simplified, with the heating apparatus provided with a gas sensor and a weight sensor, such as an electronic oven, an electric oven, a combination oven, or a gas oven. Moreover the 13~ 5l!3 heating apparatus according to the present invention is provided with sensors, not a single sensor, so as to detect the condition of the food to be heated time after time~ so that the heating time can be controlled properly to prevent overheating of the food. As a result, the heating apparatus of the present invention enjoys a great improvement in safety.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.
Claims (9)
1. An automatic heating apparatus comprising:
a heating means for heating an object, said heating means operable in a plurality of different heating modes;
a first sensor means for detecting the weight of an object;
a second sensor means for detecting the amount of gas or steam generated by an object as the object is heated by said heating means;
a control means operatively connected to said heating means, said first sensor means and said second sensor means for performing a heating controlling operation during which said control means controls said heating means to operate in one of said heating modes by selecting said one of said heating modes based on the weight detected by said first sensor means and the amount of gas or steam detected by said second sensor means;
an input means operatively connected to said control means for inputting a command to said control means to initiate said heating controlling operation; and said control means including a calculation means for calculating a detection time period based on the weight of an object detected by said first sensor means at the initiation of said heat controlling operation, a timer means for measuring the time that has lapsed from the initiation of said heating controlling operation, a comparison means for comparing the change in the amount of steam or gas detected by said second sensor means from the initiation of said heating controlling operation until said detection time period lapses with a predetermined value, identification means for categorizing the object based on the comparison made by said comparison means, and selecting means for selecting one of said heating sequences based on the categorization of the object by said identification means.
a heating means for heating an object, said heating means operable in a plurality of different heating modes;
a first sensor means for detecting the weight of an object;
a second sensor means for detecting the amount of gas or steam generated by an object as the object is heated by said heating means;
a control means operatively connected to said heating means, said first sensor means and said second sensor means for performing a heating controlling operation during which said control means controls said heating means to operate in one of said heating modes by selecting said one of said heating modes based on the weight detected by said first sensor means and the amount of gas or steam detected by said second sensor means;
an input means operatively connected to said control means for inputting a command to said control means to initiate said heating controlling operation; and said control means including a calculation means for calculating a detection time period based on the weight of an object detected by said first sensor means at the initiation of said heat controlling operation, a timer means for measuring the time that has lapsed from the initiation of said heating controlling operation, a comparison means for comparing the change in the amount of steam or gas detected by said second sensor means from the initiation of said heating controlling operation until said detection time period lapses with a predetermined value, identification means for categorizing the object based on the comparison made by said comparison means, and selecting means for selecting one of said heating sequences based on the categorization of the object by said identification means.
2. An automatic heating apparatus as claimed in claim 1, wherein said second sensor means is a humidity sensor for detecting absolute humidity.
3. An automatic heating apparatus as claimed in claim 1, wherein said control means performs said heating controlling operation based on the entire weight of the object disposed in the apparatus.
4. An automatic heating apparatus as claimed in claim 1, wherein said calculation means calculates said detection time period based on the following equation Tw=AxW+B
wherein Tw is said detection time period, A and B are constants and W is the weight of the object detected by said first sensor means.
wherein Tw is said detection time period, A and B are constants and W is the weight of the object detected by said first sensor means.
5. An automatic heating apparatus as claimed in claim 1, wherein said identification means categorizes the object on the basis of the material thereof, characteristics exhibited by the object associated with the heating thereof, and the weight of the object.
6. An automatic heating apparatus as claimed in claim 5, wherein said identification means categorizes the object by calculating three time periods at which a heated state of the object is evaluated, said time periods defined by the equations TL1=A1xW+B1 TL2=A2xW+B2 TL3=A2xW+B3 wherein TL1, TL2 and TL3 are said time periods, respectively, A1, A2, A3, B1, B2 and B3 are constants and W is the weight of the object detected by said first sensor means.
7. An automatic heating apparatus as claimed in claim 1, wherein said identification means stores a first detecting time T1 when the object obtains a first predetermined state while being heated, stores a second detecting time T2 when the object obtains a second predetermined state while being heated, and assigns a characteristic factor to the object based on the ratio of the time lag between when the second and the first detecting times are stored to the second detecting time, and said control means causes the object to be heated an additional time equal to the product of said factor and T2.
8. An automatic heating apparatus as claimed in claim 1, wherein said heating modes include a heating mode in which said heating means is operated continuously, and a heating mode in which said heating means is operated intermittently.
9. A method of controlling the operation of a heating means of an automatic heating apparatus having a heating chamber in which an object is placeable to be heated by the heating means and a select key for initiating the operation, said method comprising the steps of:
obtaining an initial weight of the object placed in the heating chamber of the automatic heating apparatus;
heating the object with said heating means;
monitoring the amount of steam or gas generated by the object as the object is heated;
calculating a detection time period based on the initial weight of the object obtained;
comparing the change in the amount of steam or gas generated by the object from the initiation of the heating of the object until the detection time period lapses with a predetermined value; and selecting a heating mode with which to control the operation of said heating means from among a plurality of heating modes based on the comparison made with said predetermined value.
obtaining an initial weight of the object placed in the heating chamber of the automatic heating apparatus;
heating the object with said heating means;
monitoring the amount of steam or gas generated by the object as the object is heated;
calculating a detection time period based on the initial weight of the object obtained;
comparing the change in the amount of steam or gas generated by the object from the initiation of the heating of the object until the detection time period lapses with a predetermined value; and selecting a heating mode with which to control the operation of said heating means from among a plurality of heating modes based on the comparison made with said predetermined value.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP106631/1987 | 1987-04-30 | ||
| JP62106631A JPH0762528B2 (en) | 1987-04-30 | 1987-04-30 | Heating device |
| JP180463/1987 | 1987-07-20 | ||
| JP62180463A JP2516991B2 (en) | 1987-07-20 | 1987-07-20 | Heating device |
| JP62180466A JP2516992B2 (en) | 1987-07-20 | 1987-07-20 | Heating device |
| JP180466/1987 | 1987-07-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1301258C true CA1301258C (en) | 1992-05-19 |
Family
ID=27310787
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000565405A Expired - Lifetime CA1301258C (en) | 1987-04-30 | 1988-04-28 | Automatic heating apparatus |
Country Status (3)
| Country | Link |
|---|---|
| KR (1) | KR910001968B1 (en) |
| AU (1) | AU588730B2 (en) |
| CA (1) | CA1301258C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114179103A (en) * | 2021-12-13 | 2022-03-15 | 深圳市普渡科技有限公司 | Robot, robot control method and device |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100507039B1 (en) * | 2002-11-14 | 2005-08-09 | 엘지전자 주식회사 | Simmering Control method in microwave oven |
| DE102019211291A1 (en) * | 2019-07-30 | 2021-02-04 | BSH Hausgeräte GmbH | Food processor and method for steaming food |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60131793A (en) * | 1983-12-20 | 1985-07-13 | 松下電器産業株式会社 | Automatic high frequency heater |
| JPS60258895A (en) * | 1984-06-04 | 1985-12-20 | 松下電器産業株式会社 | High frequency heater |
-
1988
- 1988-04-28 CA CA000565405A patent/CA1301258C/en not_active Expired - Lifetime
- 1988-04-28 AU AU15280/88A patent/AU588730B2/en not_active Ceased
- 1988-04-30 KR KR1019880005002A patent/KR910001968B1/en not_active IP Right Cessation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114179103A (en) * | 2021-12-13 | 2022-03-15 | 深圳市普渡科技有限公司 | Robot, robot control method and device |
Also Published As
| Publication number | Publication date |
|---|---|
| AU1528088A (en) | 1988-12-01 |
| KR880013416A (en) | 1988-11-30 |
| KR910001968B1 (en) | 1991-03-30 |
| AU588730B2 (en) | 1989-09-21 |
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