JPH0742945A - Method and apparatus for controlling the weight determination and cooking of food in a microwave oven - Google Patents

Abstract

(57) [Summary] Cooking room (4) and microwave generator or magnetron
In order to determine the weight of the food (9) placed in the microwave oven (1) equipped with (2), the cooking is performed during the process of operating the magnetron (2) at the scheduled power for the scheduled time. In a method of determining the weight of the food by measuring the heat of a detector (12) composed of a microwave detecting substance disposed in the chamber (4), and controlling the cooking method of these foods,
The heat of the detection body (12) arranged on the wall (6) of the cooking chamber (4) that is not shielded by the food (9) is located outside the cooking chamber at a position corresponding to the detection body (12). And the change in the electrical characteristics of the parts (16, 17) respectively arranged at positions corresponding to a part of the wall portion not related to the detection body is measured.

Description

Detailed Description of the Invention

[0001]

This invention relates to determining the weight of food contained in a microwave oven equipped with a cooking chamber and microwave generator, or magnetron, to provide the magnetron with a scheduled power over a scheduled time. And method for determining the weight of the food and controlling the cooking method of the food by measuring the heat of a detection body made of a microwave detection material disposed in the cooking chamber during the process of operating at Is.

[0002]

2. Description of the Related Art Generally, in a microwave oven equipped with a microprocessor for controlling the operation of a magnetron, the cooking method (defrosting, thawing plus heating or thawing plus cooking) of food is determined by the weight of the food, the type of food and the requirement of the user. It is possible to plan ahead by setting the type of cooking method to be used. These data allow the microprocessor to control the operation of the magnetron with respect to the power and time needed to obtain the desired recipe. In order to determine the weight of the food placed in the microwave oven and to set the operation of the magnetron based on this and to control the cooking process of said food, the food is frozen or in any case at a low temperature. In some cases it is known to measure the amount of water contained in the food. This measurement of the amount of water in the food is the subject of the earlier application of the applicant's application, which is in a suitable recess in the case of the oven, below the food. It uses a detection body composed of a microwave detection substance arranged at. These microwave detectors absorb the microwave generated by the magnetron to various extents depending on the water content contained in food and the temperature of the food. The greater the amount of water present in the food, the less microwave will reach the detector below the food and the detector will be barely heated.

Since the percentage of water in food is proportional to the weight of the food itself for each food type, the weight of the food can be determined by indirectly measuring such water content. To measure such water content, a probe is associated with the microwave detector, the temperature of the detector is measured with this probe, and the measured data is supplied to a normal microprocessor to determine the water content present in food. By knowing, the microprocessor can use such information to determine the weight of the food, set the operation of the magnetron, and control the cooking of the food.

In this regard, the temperature / time heating characteristics of such a detector consisting of a microwave sensing substance become linear within a short period of microwave application, the slope of this straight line depending on the weight of the food. It was confirmed that the change was surprising.

At the end of such a short microwave application period T, the slope of said straight line, or a straight line parallel to the time axis and passing through a point where the temperature / time line has reached after a time period t, and the temperature axis. If any of the intersections are measured, the microprocessor will receive information corresponding to the weight of the food, and based on this information, also consider the information the user has provided to the microprocessor regarding the type of food and the required cooking method. It is clear that the operating power of the magnetron and the cooking time and cooking mode can be fixed.

Although satisfactory results can be obtained with the solution as described above, the construction is particularly complex in the planes forming the seat for the microwave detector or element and the seat for the probe. Furthermore, since the heating degree (heat) of the sensing element depends on the microwave penetration rate of the food located above the sensing element, the data received by the microprocessor may be incorrect due to a mistake in putting the food into the cooking chamber. This results in erroneous control of the magnetron's operation and the way it cooks food. Furthermore, once the microwave sensing element became hot, it could not be reused to determine the weight of other foods to be cooked until the sensing element was cooled, and the sensing element was touched. Otherwise, the weight determination will be inaccurate. Finally, the use of probes to measure the temperature of microwave detectors adds to the cost of oven construction.

[0007]

The object of the present invention is to determine the weight of the food to be cooked, and thus far more control over the cooking process of the food than can be obtained in a conventional oven. Another object of the present invention is to provide a method for determining the weight of food that can be improved and a microwave oven. Another object of the present invention is to provide an oven of the kind set forth which allows control of the magnetron and food recipes to be much simpler and at a lower capital cost than the methods used in conventional ovens. To provide. Another object of the present invention is to enable the cooking control of the magnetron and food to be carried out effectively, safely and in a reliable manner, and such control is performed in the oven without waiting time for cooling the microwave sensing element. It is an object of the present invention to provide a microwave oven which can be operated during the continuous operation period.

[0008]

SUMMARY OF THE INVENTION The present invention schedules a magnetron for a scheduled time to determine the weight of food contained in a microwave oven containing a cooking chamber and microwave generator, or magnetron. In the method of determining the weight of the food by measuring the heat of a detection body made of a microwave detection material disposed in the cooking chamber during the process of operating with the electric power, and controlling the cooking method of these foods, The heat of the detector disposed on the wall of the cooking chamber that is not shielded by the food corresponds to the position outside the cooking chamber that corresponds to the detector and a part of the wall that is not related to the detector. It is characterized in that it is measured by comparing changes in the electrical characteristics of the components respectively arranged at the positions. The present invention further provides for determining the weight of food contained in a microwave oven comprising a cooking chamber and microwave generator, or magnetron, during the process of operating the magnetron at a scheduled power for a scheduled time. Determining the weight of the food by measuring the heat of the detection body made of a microwave detection substance disposed in the cooking chamber,
And, in the device for controlling the cooking method of these foods, the device is provided with a detection body made of a microwave detection substance provided at an arbitrary position on the wall of the cooking chamber that is not shielded by food, and the detection body is provided outside the cooking chamber. Electrical parts having temperature variable characteristics, which are respectively arranged at a position corresponding to the body and a position corresponding to a part of the wall portion not related to the detection body.

[Embodiment] Referring to FIGS. 1 to 3, FIG.
The microwave oven, collectively referred to as 1 in FIG.
It comprises a microwave generator or magnetron 2 mounted on the top 3 of a cooking chamber 4 having a bottom wall or base 7. A support plate 8 made of, for example, ceramic or terracotta for food is seated on the base 7. The magnetron 2 is operated via a wire 10 by a conventional microprocessor circuit 11 which changes its power as required. According to the present invention, any wall of the cooking chamber 4 (side wall 6 in this example)
A known microwave detector 12 is positioned at. Advantageously, the detector is formed by depositing a microwave sensing coating layer of suitable thickness on the wall 6. A recess 14 is provided in the structure 13 of the oven 1 at a position corresponding to the coating layer 12 (hereinafter referred to as a detector), and a wall 15 of the recess opposite to the side wall 6 is electrically connected. Position resistors 16 and 17. In particular,
The resistor 16 is disposed on the wall portion 15 corresponding to the detector 12 on the side wall 6, while the resistor 17 is disposed at a position corresponding to a portion of the side wall 6 not related to the detector 12. .

Oven structure 13 between the walls 6 and 15
The metal thick portion 18 of the also acts as a microwave shield for the resistors 16 and 17, so that these resistors are well protected against microwaves and thus impair the operating characteristics of the resistors. Absent. Resistors 16 and 17 are placed in electrical circuit 20 which is connected to microprocessor 11 by line 21. This circuit 20 has a known configuration for measuring the resistance value of the resistors 16 and 17 which change due to the heating of the detector 12 and the wall 6 of the cooking chamber 4 in which the detector is mounted. It is not shown in detail for the sake of simplicity. The circuit 20 is, for example, a known Wheatstone bridge, in which two resistors of known constant value are connected to the resistors 16 and 17 so that the values of the electrical parameters (current and voltage) are known. For the magnetron 2
Of the resistor 16 during the operation of the oven 1 and
Deviations of 17 characteristics (constant or deviations from the reference value of these resistors) can be determined by the microprocessor. It is well known that the resistance value of a resistor changes with temperature. From this, by measuring the deviation of the above values from the reference value during the cooking of the food, the microprocessor can determine the weight of the food and the degree of heating of the food, i.e. control the cooking process of the food. can do.

In this regard, the method according to the invention shall be described in the context of the operation of the oven shown in FIG. The food placed on the plate 8, for example meat, is thawed and prepared for cooking. To do so, the user first switches on the magnetron 2 in a known manner, for example by means of a pushbutton on the front side of the oven 1. The user then sets the type of food (in this case meat) and the type of recipe (defrosting and cooking). When the push button is actuated, the microprocessor 11 operates the magnetron 2 with a predetermined constant power (hereinafter referred to as "test power") for a short time t hereinafter referred to as a test period, for example, 10 to 15 seconds. Let The operation of the magnetron 2 causes a small amount of the microwave 100 to be absorbed by the frozen food, but most of the microwave is absorbed by the detector 12, so that the detector is heated. At the same time circuit 2
0, in particular resistors 16 and 17, shall be energized. Following this, the microprocessor 11 measures the resistance value for the resistor defined during this test phase. Since heat is conducted to the resistor 16 by heating the detection body,
The electrical characteristics of this resistor change. However, the wall 6 of the cooking chamber 4 is not heated, and even if heated, is negligible, since the food in this test stroke releases a minimum amount of energy as it is still almost frozen. Very few. Therefore, the resistance value of the resistor 17 does not change.

In this way, and by the time the food 9 has finished thawing (after this thawing, the food 9 gives off steam which heats these walls of the cooking chamber 4). The variable resistance value of the resistor 16 is measured by means of a particularly known configuration of ## EQU1 ## and the rate at which the detector 12 is heated, and thus the weight of the food 9, is calculated on the basis of this measured value and a preset program. In this regard,
It was surprisingly confirmed by experiments that the rate of change of the temperature of the detector 12 is related to the weight of the food put in the cooking chamber 4 of the oven 1. Weight of food 9 and detector
The relationship between the heating rate of 12 and the heating rate of 12 is shown in FIG. The above relationship can also be defined by various intersections with a straight temperature axis parallel to the time axis passing through the point on the straight line of the characteristic at the end of the test period t. A group of straight lines similar to the straight line in FIG. 4 can be obtained for the same food but with varying weights.

As mentioned above, these characteristics (ie, the data regarding the heating rate of the sensing body 12) are the characteristics of the sensing element in the microwave generated by the magnetron operating at the test power for a time equal to the test period. It was obtained experimentally by exposing These data show that the detectors 12 were placed in a microwave oven containing frozen foods of different weights and types (such as meat, fish, vegetables, legumes and grains).
Is obtained by positioning. Therefore, depending on the weight of the food 9, the detection body 12 is heated according to any of the characteristic curves A, B, C, D or E. Following this, the resistor
The temperature of 16 also becomes different during the test period t, and the electrical characteristics of this resistor 16 (in particular, its resistance value) increase or decrease. On the basis of this, the microprocessor 11 can calculate the heat transferred to the resistor 16 and thus the energy absorbed by the detector 12 according to known formulas. Thus the microprocessor has food 9
Determine the weight of. The microprocessor sets and controls the operation of the magnetron 2 based on the evaluation of the weight of the food 9 and the data on the kind of food the user gives to the microprocessor and the kind of cooking selected by the user to control the food to the user. Can be cooked as desired.

In particular, the parameters operated by the microprocessor are the operating power of the magnetron, the cooking period and the power applied during this cooking period, which are constant or variable according to suitable reference values for obtaining optimum cooking results. Can be done. During the above test run, the microwaves continue to hit the food 9, which is gradually thawed. If this thawing continues, the food will gradually absorb more microwaves, and the microwaves will no longer be absorbed to the same extent by the detector 12. When the thawing is completed, most of microwave 100 is absorbed by food 9,
The temperature of 12 rises at a slower rate than the temperature in the period of the initial thawing process, for example, the portion C1 of the straight line C in FIG.
As shown in. Since the resistor 16 is exposed to any temperature change of the detection body 12, its resistance value increases or decreases, and the change in the resistance value is measured by the microprocessor 11. In particular, if the temperature gradient of the detector 12 changes after the food is thawed (point C2 in FIG. 4), the microprocessor 11 should detect the different increments of the resistance value and stop the operation of the magnetron 2 according to the preset program. Work on the magnetron.

In practice, the microprocessor 11 is
At the exact moment when the temperature gradient of 12 changes, that is, at the point C2 in FIG. 4 (that is, the point where the increment of the resistance changes), rather than acting on the magnetron, at a slightly delayed temperature (for example, Work on the magnetron at point 4 (C3). In this way, the microprocessor 11 can also determine the weight of food and measure the degree of cooking. If necessary, the oven 1 allows the sensor 12 to be used to determine the weight of the food, without the need to wait until the sensor 12 has cooled down before the food 9
Can be used to cook other foods after cooking. After the above cooking, the walls 5, 6 and 7 of the cooking chamber 4 are
Is getting hot. Resistor changing due to this heat
The resistance value of 17 is detected by the microprocessor 11. Based on the resistance value of the resistance value 17 measured by the microprocessor 1 (this measurement is performed in the same manner as described for the resistor 16), the microprocessor 11 can calculate the temperature in the oven 1. This temperature is used by the microprocessor as a reference value to calculate the degree of heating of the sensing element 12 and thus the weight of the food in the oven.

Therefore, when the oven 1 is reused, the detector is heated as described above. For the reasons described above and in the manner as pointed out, the microprocessor 11 is
The heating degree of is calculated from the increment of the resistance value of the resistor 16. By comparing the temperature calculated based on the increment of the resistance value of the resistor 16 with the temperature calculated based on the increment of the resistance value of the resistor 17, the microprocessor causes the heating rate of the sensing element, and The weight of food in the cooking chamber 4 can be calculated as described above. As an example of the present invention, an example of using an electric resistor as an electric component used to measure the heating degree of a detection body made of a microwave detection substance has been described, but for this purpose, a capacitor, an inductor, a semiconductor or the like is used. Other components whose electrical properties change with temperature can also be used, such as means. Although the example using such a part is different from the examples described so far, it is clear that it belongs to the scope of the present invention.

According to the present invention, there is no waiting period for cooking various foods by controlling the electric power of the magnetron and the cooking method itself by the microprocessor circuit based on the weight of each food put in the cooking chamber 4. You can repeatedly try the oven without. The control in this case is always accurate for each cook and is not affected by the previous cook conditions. The method according to the invention is very practical, and the construction of the device according to the invention is simpler, cheaper and more reliable and superior than those of conventional analog devices.

[Brief description of drawings]

1 is a partial schematic cross-sectional view of a microwave oven constructed in accordance with the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

3 is a cross-sectional view taken along the line III-III in FIG.

FIG. 4 shows the temperature change of the microwave sensor used in the oven according to the present invention, when the food having different weights or different kinds of foods having the same weight are put in the oven. It is a time-temperature characteristic view.

[Explanation of symbols]

 1 Microwave Oven 2 Magnetron 4 Cooking Room 5, 6, 7 Cooking Room Wall 8 Support Plate 9 Food 11 Microprocessor 12 Microwave Detector 13 Oven Structure 14 Recess 16, 17 Resistor 20 Electric Circuit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ivano Flatini Italy Varese Reguno Via Rome 464 (72) Inventor Carlo Montanari Italy Milan Via Monte Ortigara 22

Claims (11)

[Claims] 1. A microwave oven (1) comprising a cooking chamber (4) and a microwave generator or magnetron (2).
A microwave sensing material placed in the cooking chamber (4) during the process of operating the magnetron (2) at a scheduled power for a scheduled time to determine the weight of the food (9) contained therein. A method of determining the weight of said foodstuffs by measuring the heat of a sensing body (12) consisting of, and controlling the cooking of these foodstuffs, the wall of said cooking chamber (4) not being shielded by said foodstuffs (9). The heat of the detection body (12) arranged in the section (6)
The change in the electrical characteristics of the parts (16, 17) arranged outside the cooking chamber at the position corresponding to the detection body (12) and the position corresponding to a part of the wall portion not related to the detection body, respectively. A method of determining the weight of food in a microwave oven and controlling the cooking method, characterized by measuring by comparison. 2. A change in the electrical characteristic of one of the parts (17) is used to define a reference value, the reference value and a change in the electrical characteristic of the other one (16) of the part being used. A method according to claim 2, characterized in that the weights of the foodstuffs successively placed in the oven (1) can be determined and the cooking method of these foodstuffs can be controlled by comparison. 3. A microwave oven (1) comprising a cooking chamber (4) and a microwave generator or magnetron (2).
A microwave sensing material placed in the cooking chamber (4) during the process of operating the magnetron (2) at a scheduled power for a scheduled time to determine the weight of the food (9) contained therein. In a device for determining the weight of the food by measuring the heat of a sensing body (12) consisting of, and controlling the cooking method of these foods, the device is a wall (5, 6) of the cooking chamber (4). ,
The detection body (12) made of a microwave detection substance provided at an arbitrary position which is not shielded by the food (9) in (7), and the position corresponding to the detection body (12) and the detection body outside the cooking chamber. Electrical parts (16, 1) having temperature variable characteristics, which are respectively arranged at positions corresponding to a part of the unrelated wall portion.
7) A device for determining the weight of food contained in a microwave oven and controlling the cooking method, comprising: 4. The oven comprising the electrical components (16, 17)
One side wall (1) of the recess (14) provided in the structure (13) of (1)
5) and the recess (14) is provided at a position corresponding to the wall (6) in the cooking chamber (4) in which the microwave detector (12) is disposed. The device of claim 3, wherein 5. The microwave detection body (12) is formed by depositing a microwave detection coating layer having an appropriate thickness on a wall portion (6) of the cooking chamber (4). Item 5. The device according to item 3 or 4. 6. The electric component (16, 17) is incorporated into an electric circuit (20) connected to a microprocessor circuit (11) for controlling the operation of the microwave generator or magnetron (2), 4. Device according to claim 3, characterized in that the circuit is of a known construction, in which the microprocessor (11) is able to measure changes in the electrical properties of the electrical components (16, 17). 7. Device according to claim 3, characterized in that the electrical components (16, 17) are resistors. 8. The device according to claim 7, wherein the resistor is a semiconductor element. 9. Device according to claim 6, characterized in that the resistors (16, 17) are arranged in an electric circuit (20) of known Wheatstone bridge structure. 10. Device according to claim 3, characterized in that the electrical components (16, 17) are inductors. 11. The device of claim 3, wherein the electrical component is a capacitor.