JPH0479187A - High frequency heating device - Google Patents

Abstract

PURPOSE:To eliminate the dispersion of the output power and the like of a micro-wave oscillation source when a high frequency heating device is mass-produced by using dielectric material such as resin and the like as a reference load, storing the output voltage equivalent value of a micro-wave detecting sensor at the time of high frequency heating, to a memory section as a constant, and thereby using the constant. CONSTITUTION:The block of resin the shape of which is defined, and the block of dielectric material composed of fluid such as water and the like which comes in a container made of resin having low dielectric constant such as polypropylene are used as a reference load in place of a frozen food, and when the shape of the container housing the aforesaid block is heated by micro waves, the output voltage of a micro wave detecting sensor 11 similar to the case of the frozen food is to be acquired. And the voltage is stored as a constant in a mechanical memory section such as a variable resistor or in an electrical memory section such as a non-volatile semiconductor for storing the output voltage equivalent value after operation process by a micro computer 18 has been over. And the aforesaid constant is used to compute heating time required and also to determine the high frequency output of a magnetron for thawing the frozen food. By this constitution, the output voltage of the micro wave detecting sensor can thereby be prevented from being dispersed when a high frequency heating device is mass-produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-frequency heating device for automating the thawing of frozen foods.

BACKGROUND ART Conventionally, in order to automate the thawing of frozen foods, there is a conventional method of measuring the weight of the frozen foods and calculating the heating time based on the correlation with the measured weight. Frozen food 1 as shown in Figure 12
3 is measured by a weight sensor 39 and input to the microcomputer 18. The measured weight and heating time are determined from the relationship shown in FIG. Therefore, the accuracy of weight measurement directly affects thawing performance, and accuracy can be guaranteed by adjusting the zero gram point of the scale.

Problem to be Solved by the Invention However, the output voltage of the microwave detection sensor is affected by the conversion efficiency of the microwave detection sensor itself, the finished dimensions of the heating chamber, and variations in the microwave power oscillation source such as the magnetron. The output voltage also changes depending on the amount and temperature of frozen food, resulting in defects such as incomplete thawing or overcooked food.

A microwave detection sensor is a sensor that estimates weight from the change in output voltage when heated by microwaves, and like a weight sensor, it requires a certain degree of weight accuracy as a scale.

However, the information obtained from the microwave detection sensor is not the direct weight of the frozen food in the heating chamber, but the indirect weight estimated by capturing changes in the output voltage. The weight is determined by the output voltage applied. Furthermore, it is desirable to have a microwave detection sensor output voltage that is the same as when actual frozen food is heated using microwaves, but in order to perform adjustment work on actual frozen food at the production site of high-frequency heating equipment, it is necessary to handle the frozen food properly. There was a problem in maintaining the equipment to store it, and it was not possible to calibrate it with something whose weight was known, like a weight sensor.

When calibrating the microwave detection sensor of a high-frequency heating device at a production factory, solid objects with a fixed shape are easier to handle, but after the high-frequency heating device is sold, it is necessary to make adjustments during service by replacing parts. The case is familiar! ! It is necessary to be able to perform calibrations of the same quality as in the production factory.

In addition, the time required for calibration is that in the case of a weight sensor, it can be adjusted in 2 to 3 seconds because it simply measures the weight, but a microwave detection sensor detects the means of microwave heating itself, so it is generally used for uniform heating of turntables etc. Since the microwave electric field is disturbed by the means, it is necessary to average the equalization period of the uniform heating means, and additional time is added to stabilize the microwave oscillation, which takes about 10 seconds, making adjustment easier. A means was needed.

Means for Solving the Problems In order to solve the above problems, the high frequency heating device of the present invention includes:
Instead of a frozen food as the load to be heated, a lump of resin with a limited shape or a block of dielectric material made of a liquid such as water contained in a container made of a resin with a low dielectric constant such as polypropylene is used, and this is used as a reference load. When the shape of the container containing the frozen food is microwave-heated, the microwave detection sensor output voltage at the same time as the frozen food can be obtained, and a variable resistor is used to store the output voltage equivalent value after calculation processing by the microcomputer. 1) 94 is stored as a constant in an electrical storage unit such as a non-volatile semiconductor, and calculates the heating time for thawing the frozen food and determines the high frequency output of the magnetron. It is what it is.

The initial temperature and frozen state of the active food are detected by a microwave detection sensor. That is, the distribution state of microwaves within the heating chamber is affected by the state of the food. Therefore, if the distribution of microwaves is detected by some means, the condition of the food can be known. Microwave detection sensors apply this principle. The microwave detection sensor detects the microwave energy in the heating chamber with a detection diode, smoothes it, and converts it into an output voltage as a DC signal. When the food in the heating chamber is frozen, the amount of energy reflected from the food is relatively large due to the characteristics of microwave heating, and this amount of reflected energy is inversely proportional to the weight. As heating progresses and the amount of energy absorbed by the food increases, the amount of energy reflected gradually decreases. Therefore, by observing changes in the output voltage of the microwave detection sensor, it is possible to determine the heating state of the food. The weight of the food can be estimated from the correlation with the output of the microwave detection sensor at the beginning of heating, and since there is a correlation between the initial temperature of the food and changes in the heating state, the change in the output voltage of the microwave detection sensor over a certain period of time can be estimated by If you are looking at
You can know the initial temperature of food. Once the estimated weight and initial temperature are known, the required thawing energy can be easily calculated.
You can know the heating time and heating output.

On the other hand, when mass-producing high-frequency heating equipment, there are variations in the microwave detection sensor, the finished dimensions of the heating chamber, the output power of the microwave oscillation source such as a magnetron, etc. However, the output voltage of the microwave detection sensor is different, and as a result, it has been difficult to obtain satisfactory thawing results. Since the output voltage of the microwave detection sensor can be calibrated by placing it in a container, there is no need for special equipment such as a freezer, and the provision of a simple container allows for accurate calibration during service such as parts replacement. Can be calibrated.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings.

In FIG. 1, the high frequency waves excited by the mag 7tron 1 are guided into the heating chamber 3 by the waveguide 2, and the food 13 is guided into the heating chamber 3.
be absorbed into. A microwave detection sensor (hereinafter referred to as a detection sensor) 1) is mounted on the ceiling of the heating chamber 3 at right angles to the hole 12. The food 13 is placed on a turntable 14 for uniform heating, and the turntable 14 is rotated by a turntable motor 15. On the other hand, the intensity of the microwave measured by the detection sensor 1) is amplified as an output voltage by an amplifier circuit 16 and then input to a microcomputer (hereinafter referred to as microcomputer) 18. Inside the microcomputer, a voltage value determined by the resistance value of the variable resistor 38 is input, and is calculated between it and the previously input output voltage of the detection sensor, and a high-voltage power supply 36 drives the magnetron 1 that generates microwaves. driving time,
Control output power. Adjustment of the variable resistor 38 is performed by setting the operation of the microcomputer 18 to a detection sensor calibration mode and then adjusting the numerical value displayed on the display section 36 to a specified value.

FIG. 2 is an exploded perspective view of the detection sensor 1), which is composed of a copper foil pattern 19 etched on a printed circuit board 20 and a chip component 21, and an antenna 22 formed by etching is drilled into a heating chamber 3. Mounting is provided via a plate 23 facing the sagging hole 12. Microwaves leaking from the heating chamber 3 through the hole 12 are captured by the antenna 22.

Further, FIG. 3 shows an electrical circuit diagram of the detection sensor 1). The microwave voltage detected by the detection diode 24 passes only the low frequency component by the filter part 25, and is passed through the smoothing part 2.
6, it is converted into a direct current and becomes the output voltage of the detection sensor 1N.

Figure 4 shows the relationship between the output of the detection sensor 1) and the weight of the food. The weight W can be estimated from the characteristic that the detection sensor output at the beginning of heating is smaller as the weight of the food increases. The weight can be correctly estimated from the output voltage if the conversion corresponding to the thick line in the figure can be performed, for example, 1.0■
For an output voltage of , this translates to 310 g. but,
If the output voltage from the detection sensor is high or low, the result will be erroneous, such as 225g or 450g, and this will affect the defrosting performance.

FIG. 5(a) is an external view of the reference load 17 used for calibrating the detection sensor. Based on the output voltage when a block of resin material such as hakelite or epoxy is placed in the center of a turntable in a heating chamber and heated with microwaves.1! Calibrate the detection sensor by adjusting the value. Because it has a fixed shape, it is easy to handle and convenient for mass production of high-frequency heating devices.

FIG. 9 is a diagram showing the data flow inside the microcomputer 18. The output vO of the detection sensor 1) is amplified by the amplifier circuit 16 and becomes LO. A value corresponding to the output voltage when the reference load is heated is stored as a voltage value in a variable resistor connected to the outside of the microcomputer 18 as an input value L1 of the microcomputer 18. The variable resistor 38 divides the reference voltage of the microcomputer and inputs a voltage value to the microcomputer. In the memory, the partial pressure value determined by the resistance value of the variable resistor on the 3rd day is compared with the value taken into the microcomputer and the value prepared in advance in the microcomputer, and the result is displayed on the display section 35. This can be achieved by operating the variable resistor while viewing the contents. The value handled inside the microcomputer is called the level, and the relationship between the detection sensor output voltage and the level is determined as shown in Figure 10.

The normal detection sensor output voltage LO is amplified by calculation inside the microcomputer 18 using a soft amplifier 27 inside the microcomputer, and becomes L level. The amplification factor Af of the soft amplifier 27 is determined by setting the output level when the reference load is heated to the reference load output value 28Lref level, which is stored in a variable resistor 38 outside the microcomputer, and is changed to the reference value 30Lref each time thawing and heating is performed. Compared to Leher, the soft gain is calculated as Af = Lref / Ll. The weight W is calculated by the W calculating section 29, and the heating time T is calculated by the T calculating section 32. The heating output processing section 34 determines the heating sequence for the magnetron, and the heating time T is set in the timer section 33, which drives the high voltage power supply 36 to control the oscillation power and time of the magnetron. The content being subtracted is also displayed on the external display unit 35.

A lump of resin is very easy to handle as an object as a reference load, but if high-frequency heating is continued repeatedly, the temperature of the resin will rise and the shape or dielectric constant will change, making accurate calibration difficult. In addition to requiring cooling, it was not a familiar load when it became necessary to recalibrate when replacing parts of the high-frequency heating device. FIG. 5(b) is an external view of a reference load container 19 for calibrating the detection sensor with a familiar load. The container is made of a material with a relatively low dielectric constant, such as polypropylene, and there is a means to adjust the output voltage to a reference value when water is placed in the container and heated with high frequency. When District 6 uses this standard load container,
This is a diagram showing the relationship between the amount of water put into the tank and the output voltage.The output voltage is not necessarily proportional to the amount of water, and especially in areas where the amount of water is very small and the load is light and is called dry firing, the output voltage will change as shown in ab and c in Figure 16. is not stable, but there are parts such as 250cc where the output voltage is constant even if the amount of water changes slightly. It is desirable to use a container with such a stable part for calibration. On the other hand, when using a container with a small bottom area as shown in Figure 7, the relationship between water volume and output voltage is slightly different, although the overall trend is similar to that shown in Figure 6. The output voltage fluctuates greatly due to changes in water volume, and there is no stable part. Under such conditions, precise water flow control is required to maintain a certain output voltage, making the shape difficult to use. FIG. 8 summarizes the trends in the shape of the container and the degree of stability of the output voltage, and shows the relationship between the bottom area of the container and the stability of the output voltage.

For calibration, use a container with a shape that provides good stability of the output voltage with respect to the amount of load.

As an adjustment method when storing the reference load output value in the variable resistor, take into consideration the display contents of the display section 35 level in Fig. 9, and set Lref and right in the left two digits of the display section as shown in Fig. 1) (a). Conventionally, a means was used to display Ll in two digits and adjust the variable resistor so that the contents of the left and right two digits matched, but the method shown in the figure (
In b), by displaying the value after calculating Ll-Lref and adjusting it to zero, the adjustment work can be completed in a short time. Furthermore, when the adjustment value is intentionally raised or lowered, compared to method (a), method (b) is used.
It is easier to deal with and covers a wider range, such as 2nd level higher.

Note that to measure the output voltage, a microwave detection sensor requires sufficient time to average the output voltage using a turntable or the like that is normally used to uniformly heat the sensor.

Effects of the Invention As described above, according to the present invention, when the weight and initial temperature of the object to be heated are detected by a non-contact detection sensor, when mass producing a high frequency heating device, the output signal of the detection sensor itself and the finish of the heating chamber are Affected by variations in size and oscillation sources such as microwave power magnetrons, the output signal values differ even for frozen foods of the same shape and weight, and as a result, it has been difficult to obtain satisfactory thawing results. Easy-to-handle lumps of resin or easily available water can be used for calibration to suppress variations in the output voltage of the detection sensor, so no special equipment is required, and it can also be used for calibration during service such as parts replacement. Preparing a simple container has the effect of allowing for more accurate handling.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of a high-frequency heating device that is an embodiment of the present invention, FIG. 2 is an exploded perspective view of a detection sensor of the same device, FIG. 3 is an electric circuit diagram of a detection sensor of the same device, and FIG.
The figure is a characteristic diagram of the weight of the frozen food heated by the device and the output voltage of the detection sensor, Figure 5 (a) is a perspective view of a lump of resin used to calibrate the detection sensor of the device, and Figure 5 (b) is A perspective view of the standard load container containing water used to calibrate the detection sensor of the same device, Figure 6 is a characteristic diagram of water volume and output voltage when using the standard load container of the same device, and Figure 7 is a diagram of the characteristics of the same device. A characteristic diagram of the output voltage when using load containers of different shapes. Figure 8 is a characteristic diagram of the inner bottom area of the standard load container of the same device and output voltage stability. Figure 9 is a diagram of the microcomputer of the same device. Fig. 10 is a diagram showing the principle of the processing contents, and Fig. 10 is a characteristic diagram of the output voltage of the device and the level handled by the microcomputer.
) Figures (a), (bl is a front view of the display section when adjusting the level of the device, Figure 12 is a system configuration diagram of a conventional high-frequency heating device using a weight sensor, Section 13 is a frozen food It is a characteristic diagram of the weight and heating time of 1... magnetron, 3... heating chamber,
1)...Microwave detection sensor, 16...
...Amplification circuit, 18...Microcomputer. Name of agent: Patent attorney Shigetaka Awano Haka 1 person! -m- Marinetron TI [I Heat Chamber Microwave Detection Sensor 1) 10w1 Microcomputer Fig. 2 Fig. Fig. Fig. Fig. Fig. 10 Fig. 1 Fig. 1 (α) Cb) Ll -lz” Figure 12, 13N

Claims (3)

[Claims] (1) a heating chamber in which food is placed, a magnetron that supplies microwave energy to the food in the heating chamber, and a microwave detection sensor that detects the amount of microwave energy reflected from the frozen food in the heating chamber; A microcomputer that processes the output voltage from the microwave detection sensor, and an output voltage equivalent to the output voltage after the microcomputer processes the output voltage of the microwave detection sensor when the reference load in the heating chamber is heated by microwaves. The microwave detection sensor has a mechanical storage unit such as a variable resistor or an electrical storage unit such as a non-volatile semiconductor storage element for storing values, and the reference load is made of a dielectric material such as resin and is heated by high frequency. A high-frequency heating device comprising a control means that stores an output voltage equivalent value as a coefficient in the storage unit, and uses the coefficient when calculating a heating time for thawing the frozen food and determining a high-frequency output of a magnetron. (2) Claim 1, wherein the reference load is comprised of a liquid such as water contained in a container made of a resin with a low dielectric constant such as polypropylene.
The high frequency heating device described. (3) The high-frequency heating device according to claim 2, wherein when the output voltage equivalent value is stored in the storage unit, the difference from a reference value previously stored in the microcomputer is displayed on the display unit.