JPH0742944A - Method and apparatus for determining weight of food introduced into microwave oven - Google Patents

Abstract

PURPOSE: To improve cooking control by measuring the temperature of a microwave detector for a specified time during a specified period of a magnetron in order to determine the weight of a food and cooling the detector down to a specified temperature and keeping that temperature thereby determining the weight of a food to be cooked. CONSTITUTION: A microwave oven 1 comprises a magnetron 2 disposed on top 3 of a cooking chamber 4 having opposite side walls 5, 6 and a bottom wall 7. A plate 8 for supporting a food 9 is mounted on the upper surface of the bottom wall 7. The magnetron 2 is driven by a microprocessor circuit 11 through a wire 10. A microwave detector 12 is arranged on one side wall 6 while a temperature sensor 14 and a chill generator 15 are arranged on the structure 13 at a position corresponding to the detector 12. Temperature of the detector 12 is measured for a specified time during a specified period of the magnetron 2 in order to determine the weight of the food 9. The detector 12 is then cooled down to a specified temperature and kept at that temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION To control the operating power of a microwave generator or magnetron and the cooking time of food, a method for determining the weight of food placed in a cooking chamber and in a microwave oven equipped with said magnetron. And the device.

[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 can be planned in advance 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 fix the operating power of the magnetron without the user having to manually key in the weight of the food and to enable the magnetron to automatically control the cooking method of the food, for example, weighing The food is placed on a support to which the device or simpler scale is attached and its weight is determined. Therefore, the scale can simply send food weight data to the microprocessor simply by placing the food in the oven.

Although the above-mentioned systems are often used, they are expensive, and the mechanism of the weight measuring device is extremely sensitive and delicate, so that when the food is inserted into the oven and There are a number of drawbacks such as / and fragility during operation of the oven.

Alternatively, in order to automatically control the cooking method (for example, thawing food) in the microwave oven, a weight sensor is provided inside the oven to change the weight of the food as the cooking progresses. There is also a method of measuring. The weight sensor in this case is connected to a microprocessor which, on the basis of a preset program and the data obtained by the sensor, activates the microwave generator and thus defrosts when the weight of food reaches a predetermined value. Stop.

As a modified example of the above, there is also an oven provided with an infrared sensor for measuring the surface temperature of food.
These sensors activate a microwave generator by means of a control member connected to the microprocessor and also deactivate the microwave generator when the surface temperature of the food reaches a predetermined value.

The microwave ovens of any of the above cases are expensive and cumbersome to construct. Furthermore, the data obtained by the sensors do not always reflect on the food, especially the true thaw level achieved inside the food.

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 method of the food, the food is frozen, or in any case It is known to measure the amount of water contained in the food when it is also cold. The measurement of the amount of water in the food in this way is the gist of the earlier application of the applicant's application,
This uses a sensing body composed of a microwave sensing material placed below the food in a suitable recess provided in the case of the oven. 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 type of food, 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 characteristic of such a detector consisting of a microwave sensing substance is 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 the 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 arrangement 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.

[0013]

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 type described above which allows for controlling the cooking of the magnetron and food in a much simpler manner than conventional ovens.

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 there is no waiting time for cooling the microwave sensing element. Another object of the present invention is to provide a microwave oven which can be operated during continuous operation of the oven.

[0016]

SUMMARY OF THE INVENTION The present invention is directed to controlling the operating power of a microwave generator or magnetron and the cooking time of the foodstuffs in a cooking chamber and in a microwave oven equipped with said magnetrons. In a method for determining weight, the temperature of a detector made of a microwave sensing material provided in the cooking chamber at a location not shielded by food is measured for a predetermined time during a certain working stroke of the magnetron at a predetermined power. By determining the weight of the food, cooling the detector, returning the temperature of the detector to a constant value, and maintaining the temperature at this constant value. To do.

The present invention further determines the weight of food placed in the cooking chamber and in a microwave oven equipped with said magnetron to control the operating power of the microwave generator or magnetron and the cooking time of the food. In the device, the device comprises a detection body made of a microwave detection substance provided at an arbitrary position on the wall of the cooking chamber where it is not shielded by food, and the detection body is associated with temperature detection means and cooling means. Both means are electrically connected to a microprocessor circuit so that the microprocessor circuit causes the cooling means to cool the detection body based on the measurement value of the heating temperature of the detection body by the microwave, and the detection is performed. It is characterized in that the body is cooled and the temperature of the detection body is kept constant.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A microwave oven, generally designated 1 in FIG. 1, comprises a microwave generator or magnetron 2 mounted on top 3 of a cooking chamber 4 having side walls 5 and 6 and a bottom wall or base 7. It has.

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, a known microwave detector 12 is positioned on an arbitrary wall portion (side wall 6 in this example) of the cooking chamber 4. This detector (which is not shielded by food 9) is advantageously formed by depositing a microwave sensing coating layer of suitable thickness on the wall 6.

A temperature sensor 14 and a cool air generating means 15 are arranged at a position corresponding to the detection body 12 in the structure 13 of the oven 1. This cold air generating means is connected to a power supply circuit comprising electric wires 16 and 17 and is connected to a microprocessor circuit.
Advantageously, it is a known Peltier effect cell controlled by 11.

The method according to the invention will be described in the context of describing 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 (for example, 1/2 power), hereinafter referred to as test power, for a short time t hereinafter referred to as test period, for example, 10 to 15 seconds. Let When the magnetron 2 is actuated, a very small amount of the microwave 100 is absorbed by the frozen food, but most of the microwave is absorbed by the microwave detector 12, so that the detector is heated. This heating is detected by the temperature sensor 14. Advantageously, the temperature sensor 14 is a known resistor having a negative temperature coefficient (ie an NTC sensor). At the time of heating the detection body 12, the microprocessor 11 energizes the Peltier cell 15 via the electric wires 16 and 17 based on the measured temperature information, and this cell absorbs energy from the detection body 12 in a known manner, Cool the detector (ie, transfer cold air to the detector). The hotter the detector 12, the greater the electrical energy that must be supplied to the cell 15 so that cold air can be transferred to the detector.

Surprisingly, it has been 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. Food 9
Fig. 2 shows the relationship between the weight of the sensor and the heating rate of the sensor 12.
Of the various curves with different slopes representing the heating rate, i.e., a straight line, and the above relationship is a straight temperature parallel to the time axis passing through a point on the characteristic straight line at the end of the test period t. It can also be defined by various points of intersection with the axis. A group of straight lines similar to the straight line in FIG. 2 is obtained for the same food but for varying weights.

As mentioned above, these characteristics (ie the data relating to the heating rate of the detector 12) are due to the microwaves generated by the magnetron operating at the test power for a time equal to the test period. It was obtained experimentally by exposing the detector. These data are stored in microwave ovens containing frozen foods of different weights and types (such as meat, fish, vegetables, beans and grains).
12 was obtained by locating it so that it would not be shielded by food as described above. Therefore, food 9
The detector 12 is heated according to any of the characteristic curves A, B, C, D or E depending on the weight of the sensor. Based on this, the microprocessor (the memory of which the processor already contains the above-mentioned characteristic curve) determines the weight of the food and at the same time applies the correct amount of energy to the Peltier cell 15 for cooling the sensing body 12. Can be supplied.

The microprocessor sets and controls the operation of the magnetron 2 based on an 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, The food can be cooked as desired by the user.

In particular, the parameters operated by the microprocessor are the operating power of the magnetron, the cooking period and the power applied during such cooking periods, which are constant according to suitable reference values for obtaining optimum cooking results. Or it can be variable.

In the method described above, the detector 12 is constantly maintained at a substantially constant temperature. Therefore, when 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, the oven is repeatedly used without waiting. be able to. This control is always accurate for each recipe and is not affected by the previous cooking conditions. The method according to the invention is very practical, and the construction of the device according to the invention is simpler and more reliable and superior than that of a conventional analog device.

[Brief description of drawings]

FIG. 1 is a partial schematic cross-sectional view of a microwave oven constructed according to the present invention.

FIG. 2 is a time chart showing a temperature change of a microwave detector used in an oven according to the present invention, which shows a temperature change of a detector when foods having different weights or foods having different weights and different kinds are put in the oven. -It is a temperature characteristic diagram.

[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 14 Temperature Sensor 15 Cooling Means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Claudio Sivanelli Italy Varese Travedona Via Enmedavi 18 (72) Inventor Mario Fiorori Italy Varese Brezo de Vedero Via Pianeza 4

Claims (6)

[Claims] 1. A method for determining the weight of food placed in a cooking chamber and a microwave oven comprising said magnetron to control the operating power of the microwave generator or magnetron and the cooking time of the food, comprising: Within the cooking chamber (4), the temperature of a detector (12) made of a microwave-sensing substance, which is provided in a position not shielded by the food (9), is used for a certain operating stroke of the magnetron (2) at a predetermined electric power. The weight of the food is determined by measuring the scheduled time during the period, and the detection body (12) is cooled so that the temperature of the detection body is returned to a constant value and maintained at this constant value. A method for determining the weight of food in a microwave oven, the method comprising: 2. An apparatus for determining the weight of food placed in a cooking chamber and in a microwave oven comprising said magnetron to control the operating power of the microwave generator or magnetron and the cooking time of the food, The device comprises a detection body (12) made of a microwave detection substance provided at an arbitrary position in the wall portion (5, 6, 7) of the cooking chamber (4) that is not shielded by food (9). The temperature detection means (14) and the cooling means (15) are associated with (12), and these both means are electrically connected to the microprocessor circuit (11),
As the cooling means (15) cools the detection body (12) by the microprocessor circuit based on the measured value of the heating temperature of the detection body (12) by microwaves, the detection body is cooled, An apparatus for determining the weight of food contained in a microwave oven, characterized in that the temperature of the detector is kept constant. 3. The detection body (12) made of a microwave detection material.
3. A device according to claim 2, characterized in that a microwave detection coating layer of suitable thickness is deposited on one of the side walls (5, 6, 7) of the cooking chamber (4). 4. Apparatus according to claim 2, characterized in that the temperature sensing means (14) is a resistor having a negative temperature coefficient. 5. Device according to claim 2, characterized in that the cooling means (15) are cells based on the Peltier effect. 6. The temperature detecting means (14) and the cooling means
Device according to any one of claims 2, 4 and 5, characterized in that the (15) is arranged in the body (13) of the oven (1) and is connected to the microprocessor circuit (11).