JPS648250B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high-frequency thawing device, and its purpose is to detect the end of thawing according to the type, size, and shape of the object to be thawed, and to perform time-appropriate thawing. .

Conventional high-frequency thawing machines use a method in which defrosting is performed by setting a timer for a defrosting time calculated from experience, depending on the type, size, and shape of the object to be thawed. Even though a rough defrosting time has been determined, it has been difficult to set a defrosting time for each individual. Therefore, there have been cases where the set time is incorrectly set and the time is taken longer than necessary, or the product is over-thawed and abnormally heated. In addition, in view of the speed, it was difficult to use because the timer had to be set each time depending on the item to be thawed.

The present invention eliminates the conventional drawbacks and provides a high-frequency thawing machine that automatically detects the end of thawing and thaws the object in a timely manner, regardless of the type, size, or shape of the object to be thawed. An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a high-frequency thawing machine, in which an upper electrode 2 is constructed with a predetermined gap provided above the object 1 to be thawed, and a lower electrode 3 is provided below the object 1 to be thawed.
A high frequency voltage is applied between both electrodes 2 and 3 to heat and thaw the object 1 due to dielectric loss. 4 and 5 are insulating covers that insulate the upper and lower electrodes 2 and 3. 6 and 7 are the items to be thawed 1
A high-voltage power supply section and a high-frequency oscillator supplying high-frequency energy to the high-voltage power supply section are shielded to prevent radio waves from leaking to the outside, and are connected to the high-voltage power supply section by a power supply line 8. Reference numerals 9 and 10 are power supply lines that feed power to the upper and lower electrodes 2 and 3, respectively. Reference numeral 11 is a thawing chamber in which the object 1 to be thawed is stored.

FIG. 2 is a block diagram of a high-frequency thawing machine according to an embodiment of the present invention. DC power is applied from a low-frequency AC power source to a high-frequency oscillator 7 via a high-voltage power supply section 6.
Convert to 100MHz high frequency power and connect the upper and lower electrodes 2,
A high voltage is applied between 3 and 3 to heat the object 1 to be thawed. 1
20 is a controllable switching circuit that opens and closes contacts according to commands from the control circuit 12, and turns on and off the power.
It is for cutting. The control circuit 12 indirectly picks up the high frequency output of the high frequency oscillator 7 with a current transformer 121, and picks up the high frequency output of the high frequency oscillator 7 with a frequency detection circuit 122.
converts the frequency into an electrical signal and sends it to the information processing circuit 12.
In addition to 3, if the rate of change in frequency within a certain period of time falls below a certain value, the power supply control circuit 124 operates the switching circuit 120 to turn off the power. For example, a high frequency electrical signal picked up by a current transformer 121 is converted into a pulse by a frequency detection circuit 122 and output to an information processing circuit 123. The information processing circuit 123 stores the number of pulses for a certain period of time, compares the previously stored number of pulses with the current number of pulses, and if the difference is less than one value, determines that the rate of change in frequency is constant, and turns off the power supply. The configuration is such that a signal is sent to the control circuit 124 to operate the switching circuit 120 and turn off the power. Note that in this example, the oscillation frequency is detected indirectly using the current transformer 121, but of course the output may be directly taken out from a part of the oscillation circuit and input into the frequency detection circuit 122. Generally, when a certain amount of energy is applied to a frozen product, the change in temperature during thawing is as shown by the dotted line in Figure 3. In other words, in the early stages of thawing, the energy given to the thawed object turns into sensible heat, causing its temperature to rise rapidly, but as thawing progresses and the temperature approaches the melting point, the given energy is taken away as latent heat. The product temperature will almost no longer rise. Conversely, when the product temperature hardly increases, it can be said that the product temperature has reached the melting point, and it can be said that thawing is completed. The third part compares the change in high frequency oscillation frequency when defrosting with a high frequency thawing machine at the same time as the change in product temperature.
It is a diagram. From this figure, it can be seen that the oscillation frequency changes in accordance with the product temperature, that the oscillation frequency decreases rapidly at the beginning of thawing, and hardly changes near the end of thawing. This is because, as can be seen from the high-frequency oscillator 7 in FIG. 2, the portion consisting of the object 1 to be thawed and the upper and lower electrodes 2 and 3 forms part of the resonant circuit of the high-frequency oscillator 7 as a capacitor. This is because the oscillation frequency is determined by the temperature of the object to be thawed.

As mentioned above, the oscillation frequency rapidly decreases at the beginning of defrosting, and remains almost unchanged at the end of defrosting.It has been found that this tendency occurs regardless of the type, size, and shape of the object to be defrosted, so changes in the oscillation frequency By constantly detecting the rate of change and knowing when the rate of change falls below a certain value, you will know when the defrosting is finished.

Based on this principle, the operation of this embodiment can be summarized as follows: When the object 1 to be thawed is installed between the electrodes 2 and 3 and connected to a low frequency AC power source, a DC voltage is applied to the high frequency oscillator 7, and the electrode 2 , 3, and the thawing of the object 1 to be thawed begins. The oscillation frequency at this time varies depending on the type, size, etc. of the object 1 to be thawed. The current transformer 121 picks it up, the frequency detection circuit 122 captures it as an electrical signal, the information processing circuit 123 detects the rate of change in the oscillation frequency, and when the thawing progresses and the rate of change in the oscillation frequency falls below a certain value, the power is turned on. Control circuit 1
24 operates the switching circuit 120 to turn off the power.

As described above, according to the present invention, the power is automatically turned off when the temperature of the object to be thawed approaches the melting point and thawing is completed, regardless of the type, size, or shape of the object. It is possible to provide a high-frequency thawing machine that can obtain an optimal thawing state without excessive thawing or abnormal heating without performing such troublesome operations.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing a high-frequency thawing machine according to an embodiment of the present invention, Fig. 2 is a block diagram of the same high-frequency thawing machine, and Fig. 3 is the relationship between oscillation frequency and product temperature with respect to elapsed time during thawing. FIG. 1...Object to be thawed, 2, 3...Electrode, 6...High voltage power supply unit, 7...High frequency oscillator, 11...Defrosting chamber,
12...control circuit, 122...frequency detection circuit,
123... Information processing circuit.

Claims (1)

[Claims] 1 Equipped with a thawing chamber that stores the object to be thawed, a high-frequency oscillator that supplies high-frequency energy to the object to be thawed, and upper and lower electrodes that apply high voltage to perform thawing by dielectric heating. It has a frequency detection circuit that extracts the oscillation frequency as an electrical signal, and an information processing circuit that detects the rate of change in frequency and issues a command when it falls below a certain value, and automatically detects the end of defrosting based on the command of this information processing circuit. Thawing machine.