JPH065361A - High frequency heating device - Google Patents

Abstract

PURPOSE:To indirectly detect a heating temperature of an object to be heated with high accuracy by detecting electric field strength in a heating chamber. CONSTITUTION:A heating temperature computing means 6e for an object to be heated for control output computes a heating temperature of the object to be heated based on a data from a heating output computing means 6b obtained by computation of electric field strength obtained by a microwave absorbing member 4, a data from a weight detection circuit 6c by means of a weight detection sensor 5, and a data from an individual material specific heat constant storing means 6d, so as to control a high frequency heat source 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating apparatus provided with means for detecting the electric field strength of a microwave supplied to a heating chamber in the heating chamber in order to detect the heating temperature of an object to be heated. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as means for detecting the heating temperature of an object to be heated in a high-frequency heating device, indirectly, one which detects the ambient temperature in the heating chamber by a temperature sensor, one which detects it by an infrared sensor, or There is one in which a temperature sensor is directly inserted into a heated object to directly detect the temperature.

[0003]

When the heating temperature of the object to be heated is detected using these detecting means, in the ambient temperature detecting method, the temperature of the object to be heated is indirectly detected via the air in the heating chamber. Therefore, the cooling heat of the magnetron, the heat of the turntable motor, etc. are also detected at the same time, and the error becomes large. In addition, the method using the infrared sensor can detect only the heating temperature of the surface of the object to be heated. Furthermore, in the method of directly inserting the temperature sensor into the object to be heated, the temperature detection accuracy is improved, but it is not preferable in terms of hygiene or aesthetics. It is practically impossible because the connection line of the temperature sensor is tangled.

The present invention has been made to solve the above-mentioned problems, and detects the strength of the electric field in the heating chamber to eliminate the need to insert a temperature sensor directly into the object to be heated.
The object is to accurately detect the heating temperature of the object to be heated.

[0005]

In the high frequency heating apparatus of the present invention, means for detecting the strength of the electric field in the heating chamber is provided, and the heating output generated on the object to be heated is detected based on the detected strength of the electric field. I tried to ask.

[0006]

The strength of the electric field in the heating chamber can be obtained by calculating the quantity of heat generated in the means for detecting the strength of the electric field in the heating chamber or the quantity of heat required to cool the electric field. The heating output of the object to be heated can be obtained by detecting the strength of the electric field in the heating chamber. The heating temperature of the object to be heated is determined by the correlation between the heating output of the object to be heated and the weight.

[0007]

[Example] The heating temperature of the object to be heated, the heating output consumed by the object to be heated and the weight of the object to be heated are:

[0008]

[Equation 1]

In order to obtain the heating temperature of the object to be heated by the relational expression of, the heating output consumed by the object to be heated, the weight of the object to be heated, and the specific heat due to the material of the object to be heated may be known.

However, even if the microwave output of the high-frequency heat source of the high-frequency heating device is constant, the heating output consumed by the object to be heated is significantly high depending on the type, volume and shape of the object to be heated. Therefore, a means for detecting the heating output is required.

The microwave output from the high-frequency heat source of the high-frequency heating device is absorbed by the object to be heated and heated, but the remaining microwave remains in the heating chamber. This residual microwave is a value obtained by subtracting the heating output consumed by the object to be heated from the microwave output from the high-frequency heat source, that is,

[0012]

[Equation 2]

Therefore, if the residual microwave energy is detected by the electric field strength detecting means installed in the heating chamber, the above heating output can be obtained by the calculation of the equation (2).

[0014] For the residual microwave, a currently available sensor is, for example, a microwave absorbing material. The residual microwave is absorbed by the microwave absorber installed in the heating chamber and heats it, so the strength of the electric field of this residual microwave is detected by measuring the temperature rise value of the microwave absorber. it can. Note that a simple electric field strength meter can measure only the slope of the potential of the residual microwave.

FIG. 3 is a graph showing the relationship between the heating output and the temperature rise value of the microwave absorbent when the capacity of the object to be heated is changed, as an example.

An embodiment according to the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a sectional view of the essential portions of an embodiment of the present invention.

In FIG. 1, 1 is a heating chamber for containing an object 7 to be heated, 2 is a high-frequency heat source such as a magnetron, 3 is a waveguide for sending microwaves from the high-frequency heat source 2 to the heating chamber 1, and 4 is a waveguide. A microwave absorber as an electric field strength detection sensor is provided at an appropriate position on the wall surface in the heating chamber 1, 5 is a weight detection sensor and is placed below the object to be heated 7, and 6 is a control means. Yes, data from the microwave absorber 4 and the weight detection sensor 5 are input to control the high frequency heat source 2. Reference numeral 8 is a turntable, and its driving means is omitted.

FIG. 2 is a block diagram of the control means 6 of FIG.

In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals. The control means 6 includes a temperature detection storage circuit 6a from the microwave absorber 4, a heating output calculation means 6b connected to the microwave absorption material 4, a weight detection circuit 6c connected to the weight detection sensor 5, and a specific heat constant for each material to be heated. Storage means 6
d, a heating temperature calculation means 6e for processing the data to be heated, and the like, which controls the high-frequency heat source 2.

First, when the user places the object 7 to be heated on the turntable 8 of the heating chamber 1 and presses the heating switch and the material selection switch (neither is shown), the high-frequency heating apparatus is operated by the weight of FIG. The weight is detected by the detection sensor 5 and its detection circuit 6c. Further, the microwave absorber 4 and its temperature detection storage circuit 6a measure the temperature of the microwave absorber 4 and store it.

After that, the high-frequency heating device generates microwaves from the high-frequency heat source 2, the microwaves are sent to the heating chamber 1 through the waveguide 3, are absorbed by the object 7 to be heated, and start heating, The absorber 4 is also heated by the residual microwave.

After a lapse of a certain time from the start of heating, the high-frequency heating device again detects the temperature of the microwave absorber 4 by the microwave absorber 4 and its temperature detection storage circuit 6a, and stores the temperature stored in advance at the start of heating. The difference from the temperature of the microwave absorbing material 4 is calculated by the heating output calculating means 6b.
Here, the calculated temperature rise value of the microwave absorbent 4 has a relationship with the heating output as shown in FIG. 3 as described above. It is possible to calculate the heating output consumed by.

Next, in the high-frequency heating apparatus, the heating temperature calculation means 6e for the object to be heated is the above-mentioned heating output calculation means 6
When the heating output value of b, the weight value stored at the start of heating, and further accuracy are required, data such as the specific heat of the object to be heated is input from the material-specific specific heat constant storage means 6d, thereby The heating temperature of the object to be heated is calculated using the equation (1).

Next, an embodiment in which the strength of the electric field is obtained from the amount of heat for cooling the heat generated by the microwave absorbent will be described in comparison with the above-mentioned embodiment.

In the above-mentioned embodiment, when the strength of the electric field in the heating chamber is detected using the microwave absorbing material, the temperature rise value of the microwave absorbing material per unit time is detected and the strength of the electric field is calculated. However, in this method, the temperature of the microwave absorber constantly rises during heating, and the microwave absorber is overheated under a long-time heating condition, resulting in destruction.

Further, the temperature rise value of the microwave absorbers currently available at the time of microwave absorption generally has a temperature characteristic, which must be taken into consideration when converting to the strength of the electric field. A detection error will occur during conversion.

As means for detecting the strength of the electric field in the heating chamber, instead of detecting the temperature rise value of the microwave absorbing material, the cooling means for preventing the temperature rise is controlled and the control amount, that is, the cooling heat amount is detected. As a result, the temperature rise value of the microwave absorber can be equivalently detected.

The temperature rise value of the microwave absorber is

[0030]

[Equation 3]

The temperature rise value of the microwave absorbing material of the formula (3) is

[0032]

[Equation 4]

The relational expression of is satisfied.

In the conventional method of detecting the temperature rise value of the microwave absorbing material, the cooling heat quantity is made constant by natural heat dissipation in the equation (4), and the temperature of the microwave absorbing material and its ambient temperature are set under the condition. For example, it is detected by a temperature sensor such as a thermistor.

In this embodiment, the cooling heat quantity of the equation (4) is
The cooling means is controlled so as to be the same as the amount of heat for heating, that is, the heating temperature of the microwave absorbing material is set to 0.
Then, the temperature rise value of the microwave absorbing material is equivalently obtained by detecting the cooling heat amount.

FIG. 4 is a sectional view of the main part of the high frequency heating apparatus according to this embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals. 4 is different from FIG. 1 in that microwave absorber temperature measuring means 11, microwave absorber ambient temperature measuring means 12, and microwave absorber cooling means 13 are provided. It is different from the control means 6 of FIG.

FIG. 5 is a block diagram of the control means 10 in FIG. 4 and its peripherals.

In FIG. 5, a high frequency heat source 2, a microwave absorber temperature measuring means 11, a microwave absorber ambient temperature measuring means 12, a microwave absorber cooling means 13 and the like are connected to the control means 10. Further, inside the control means 10, the microwave absorbing material temperature detecting means 10a, the microwave absorbing material surrounding temperature detecting means 10b, their temperature comparing circuit 10c, the cooling amount controlling means 10d, the cooling amount detecting means 10 are provided.
e, an electric field strength calculation means 10f based on information from the cooling amount detection means 10e, and the like are provided.

First, when the user mounts the object 7 to be heated on the turntable 8 of the heating chamber 1 and presses the heating switch and the material selection switch (neither is shown), the high frequency heating apparatus is operated by the microwave of FIG. The temperature of the absorbing material 4 is measured by the microwave absorbing material temperature measuring means 11 and its temperature detecting means 1.
0a, and the ambient temperature of the microwave absorber 4 at that time is detected by the microwave absorber ambient temperature measuring means 12 and its temperature detection circuit 12b. After that, the high frequency heating device generates microwaves from the high frequency heat source 2,
The microwave is sent to the heating chamber 1 through the waveguide 3,
While being absorbed by the object 7 to be heated and starting heating, the microwave absorbing material 4 is also heated by the residual microwave.

During heating, the high-frequency heating device always compares the temperature of the microwave absorber 4 and its surrounding temperature with the temperature comparison circuit 10c.
When the temperature of the microwave absorber becomes higher than the ambient temperature, the temperature comparison circuit 10c transmits a voltage value (see FIG. 6) proportional to the temperature difference to the next cooling amount control means 10d. FIG. 6 is a graph showing the relationship between the temperature difference between the microwave absorber and its ambient temperature and the output voltage of the temperature comparison circuit 10c.

The cooling amount control means 10d drives the microwave absorbing material cooling means 13 (for example, a cooling fan, a Peltier effect element, etc.) by the input voltage value to cool the microwave absorbing material 4. At this time, the high-frequency heating device includes the microwave absorbent temperature measuring means 11, the temperature detecting means 10a, and the microwave absorbent surrounding temperature measuring means 1.
2. The temperature detecting means 12b and the temperature comparing circuit 10c for comparing the temperatures are constantly compared between the microwave absorber 4 and its surrounding temperature, and the temperature difference is input to the cooling amount control means 10d as a proportional voltage value. To do.

The cooling amount control means 10d keeps the microwave absorbing material cooling means 13 until the proportional voltage value becomes 0 voltage value.
Thus, the cooling of the microwave absorbing material 4 is continued. That is,
This high-frequency heating device controls so that the difference between the temperature of the microwave absorbing material 4 and its surrounding temperature is always 0. This is because the heating heat amount and the cooling heat amount of the microwave absorbing material 4 are always controlled to be the same. Means to be done.

On the other hand, the cooling amount control means 10d supplies a voltage value proportional to the controlled cooling amount (for example, the product of the rotation speed of the fan and its driving time or the power of the Peltier effect element) to the next electric field. To the strength calculation means 10f. Since this voltage value is proportional to the amount of heating heat of the microwave absorbing material 4, the calculating means 10f has preset cooling heat amount (= heating heat amount) and electric field strength data as shown in FIG. 7, for example. The strength of the electric field in the heating chamber is calculated by

Needless to say, data such as weight and specific heat can be input to this high-frequency heating device.

[0045]

According to the present invention, the weight of the object to be heated at the start of heating and the data depending on the kind of the material are input, so that the object to be heated can be heated without directly inserting the temperature sensor into the object to be heated. Since it can detect the temperature,
It is particularly suitable for detecting the heating temperature of objects to be heated, such as tofu and eggs, where a temperature sensor cannot be inserted. Further, the heating temperature detection method of the present invention is different from the method of detecting one point of the object to be heated by the temperature sensor and the method of detecting the surface temperature of the object to be heated, and the heating output and weight consumed by the object to be heated. Since it is a method that calculates from data related to the object to be heated such as specific heat, it is an average heating temperature of the object to be heated, and is also suitable for detecting the temperature of the object to be heated with poor heat transfer coefficient such as gratin and stew. There is.

The high dielectric constant material, which is the material of the microwave absorbing material used in the present invention, generally has poor temperature characteristics in terms of detection accuracy, and the strength of the electric field is detected by the temperature rise value. At times, this effect is greatly affected, but by cooling this so that the temperature of the microwave absorbing material is always constant, there is no detection error due to the temperature characteristics of the microwave material.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an embodiment of the present invention.

FIG. 2 is a block diagram of a control unit shown in FIG.

FIG. 3 is a graph showing a relationship between a heating output and a temperature rise value of a microwave absorbent.

FIG. 4 is a cross-sectional view of an essential part of another embodiment of the present invention.

5 is a block diagram of the control circuit of FIG.

FIG. 6 is a graph showing the relationship between the difference between the temperature of the microwave absorbing material and its surrounding temperature and the output voltage of the temperature comparison circuit.

FIG. 7 is a graph showing the relationship between the amount of cooling heat of the microwave absorber and the strength of the electric field in the heating chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating chamber 2 High frequency heat source 3 Waveguide 4 Microwave absorber 5 Weight detection sensor 6 Control means 6a Temperature detection storage circuit 6b Heating output calculation means 6c Weight detection circuit 6d Material specific heat constant storage means 6e Heating temperature of heated object Calculation means 7 Object to be heated 8 Turntable 10 Control means 10a Microwave absorber temperature detection means 10b Microwave absorber ambient temperature detection means 10c Temperature comparison circuit 10d Cooling amount control means 10e Cooling amount detecting means 10f Electric field strength calculating means 11 Microwave Absorber Temperature Measuring Means 12 Microwave Absorber Surrounding Temperature Measuring Means 13 Microwave Absorber Cooling Means

Claims (5)

[Claims] 1. A heating chamber for containing an object to be heated, a high-frequency heat source for generating microwave energy supplied to the heating chamber, a means for detecting the electric field strength of the heating chamber, and a detected electric field strength. A high-frequency heating device having means for calculating a heating output consumed by the object to be heated based on the above, and means for calculating a heating temperature of the object to be heated from the result. 2. A heating chamber for containing an object to be heated, a high-frequency heat source for generating microwave energy to be fed to the heating chamber, a means for detecting the strength of an electric field in the heating chamber, and a weight for the object to be heated. A high-frequency heating apparatus having: means for calculating, a means for calculating a heating output consumed by the object to be heated based on the detected strength of the electric field, and an output for calculating a heating temperature of the object to be heated from these results. 3. The high-frequency heating device according to claim 1, wherein the output for detecting the strength of the electric field detects the strength of the electric field by detecting the temperature rise value of the microwave absorbent during heating. . 4. A heating chamber for accommodating an object to be heated, a high frequency heat source for generating microwave energy supplied to the heating chamber, a means for detecting the strength of an electric field in the heating chamber, and a strength of the electric field is detected. A high-frequency heating device having a cooling means for controlling the cooling means, a means for controlling the cooling means, and a means for calculating the strength of the electric field in the heating chamber by the cooling heat amount. 5. The high frequency heating apparatus according to claim 4, wherein a microwave absorbing material is used as a means for detecting the strength of the electric field, and a means for detecting its temperature during heating and a means for detecting its ambient temperature are provided.