JPS6233713B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a high-frequency thawing machine that prevents abnormal local heating and thaws objects uniformly and efficiently regardless of their shape, size, or type. .

Conventionally, uniform thawing methods for thawing frozen products using high-frequency dielectric heating include thawing by applying high-frequency energy intermittently or by gradually attenuating the intensity.
It was equipped with a cooling device and thawed the food while cooling it. However, these methods cannot sufficiently suppress local temperature rises, and no measures are taken for the type, size, or shape of the object to be thawed. This may result in items with a target temperature rise, supplying more high-frequency energy than necessary, or cooling them more than necessary (if a cooling device is available), or thawing them efficiently. It was difficult to exist.

In order to thaw uniformly, the size of the item to be thawed,
It is necessary to supply high-frequency energy with an appropriate strength to the shape, etc.; if the strength is stronger than necessary, excess high-frequency energy will be concentrated in areas that thaw quickly (melted water is more likely to melt than ice). (The dielectric loss is larger and energy is absorbed more easily), and the heating phenomenon in that part progresses further, creating a vicious cycle, resulting in local discoloration or boiling. Also, if the strength is weaker than necessary, it will take a long time to defrost. Therefore, in order to efficiently and uniformly decompress, high frequency energy of appropriate strength is required.

The present invention eliminates the conventional drawbacks and automatically sets the optimal high-frequency energy intensity regardless of the type, size, or shape of the object to be thawed, resulting in efficient and uniform thawing without local heating. The present invention provides a high-frequency decompressor that does

FIG. 1 shows a schematic configuration of a high-frequency thawing machine, in which an upper electrode 2 is configured with a predetermined gap above the object 1 to be thawed, and a lower electrode 3 is formed 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. Reference numerals 6 and 7 denote a high-voltage power supply unit and a high-frequency oscillator that supply high-frequency energy to the object 1 to be thawed, which are shielded to prevent radio waves from leaking to the outside and connected to the high-voltage power supply unit via a power supply line 8. Reference numerals 9 and 10 indicate power supply lines that respectively supply power to the upper and lower electrodes 2 and 3, and the power supply line 9 is covered with a shield wall 11 to prevent radio waves from leaking to the outside. 12 is a thawing chamber in which the object 1 to be thawed is stored.

FIG. 2 is a block diagram of a high-frequency decompressor according to an embodiment of the present invention, in which a step-up transformer 61 and a rectifier circuit 6 of a high-voltage power supply section 6 are connected to a low-frequency AC power supply.
DC power is applied to the high frequency oscillator 7 via the high frequency oscillator 2, and the high frequency oscillator 7 converts the DC power into high frequency power of 10 to 100 MHz, and applies a high voltage between the upper and lower electrodes 2 and 3 to thaw the object 1. Heat. For example, 130 is a controllable switching circuit that closes any contact according to a command from the control circuit 13, changes the DC voltage applied to the high frequency oscillator 7, and changes the high frequency output applied between the electrodes 2 and 3. The control circuit 13 is a detection circuit 1 that detects an input current to indirectly detect the high frequency output of the high frequency oscillator 7.
31, the input current is detected, and in addition to this output information processing circuit 132, the information processing circuit 132 performs a comparison operation with the storage circuit 133, and the output control circuit 134 operates the switching circuit 130 to set a predetermined high frequency output. It's getting old. Further, the switching circuit 130 that sets the high frequency output may be set discontinuously or continuously by switching taps.

To summarize the operation, when the object to be thawed 1 is placed between the electrodes 2 and 3 and connected to a low frequency AC power source,
Initially, an arbitrary DC voltage is applied to the high frequency oscillator 7, a high frequency output is applied between the electrodes 2 and 3, and thawing of the object 1 to be thawed begins. At this time, the magnitude of the high frequency output varies depending on the size, shape, etc. of the object 1 to be thawed.
Naturally, a corresponding input current is also flowing. Therefore, the detection circuit 131 detects this current, the information processing circuit 132 and the memory circuit 133 determine the optimum strength of the high frequency output to be applied to the object 1 to be thawed, and the output control circuit 134 sends the command to the switching circuit 130. The DC power supply voltage is set so that the optimum high-frequency output is produced. Here, the initial input current is detected by detecting the magnitude of the input current or the initial increase rate of the input current.

As mentioned above, in order to perform uniform and efficient defrosting without local heating, it is important to apply a high frequency output of optimal intensity depending on the size, shape, type, etc. of the object to be defrosted. It goes without saying that this high frequency output changes depending on the voltage applied from the high voltage power supply, and any high frequency output can be set by changing this voltage. Furthermore, if this voltage is arbitrary and constant, the high frequency output will vary depending on the object to be thawed (particularly the difference in capacity). FIG. 3 shows the relationship between this high frequency output and the elapsed time. In this case, the thawed objects A and B have almost the same capacity, and the thawed object C has a small capacity. As shown in the figure, the initial high-frequency output varies depending on the capacity of the object to be thawed, q ₁ and q ₂ .Conversely, by detecting the magnitude of this high-frequency output, the size of the object to be thawed 1 can be determined. The difference can be estimated. Therefore, by determining the optimal high frequency output for each size of object to be thawed in advance through preliminary experiments and incorporating it into the memory circuit, the initial high frequency output at a certain voltage can be detected by the magnitude of the input current. It is possible to set the DC voltage that provides the optimum high-frequency output for the object to be thawed, and to proceed with subsequent thawing, resulting in the most efficient thawing. In addition, thawing objects A and B have almost the same capacity but different shapes, and in the case of thawing object A, high-frequency energy is concentrated in a part, causing local heating, and as shown in the figure. As shown in the figure, power suddenly enters a part of the object to be thawed, and a sudden rise in high-frequency output is observed. This phenomenon occurs when only some parts are thawed or over-thawed, while other parts are not yet thawed and do not heat up easily.
As a result, the defrosting time is delayed, and defrosting cannot be called efficient. Therefore, such a rapid increase in high-frequency output can be detected at an early stage (this phenomenon mostly occurs at the beginning of defrosting), and depending on the rate of increase, if the increase rate is large, the high-frequency output will become small. It is necessary to allow the thawing to progress gradually. Therefore, the increase rate is detected by the detection circuit 131 as before, and controlled by the information processing circuit 132 and the memory circuit 133, and the voltage is automatically set to prevent local heating. , which performs uniform and efficient defrosting.

Furthermore, although the present invention describes an embodiment in which the high frequency output is controlled by changing the DC voltage, it is also possible to make the upper and lower electrodes 2 and 3 movable as shown in FIG. Another possible method is to transmit a command from 13 to the electrode movable circuit 14 to change the inter-electrode distance D or the distance d between the object to be thawed and the electrode 2, thereby changing the intensity of the high-frequency output.

As is clear from the description of the above embodiments, according to the present invention, the capacity of the object to be thawed is determined based on the magnitude of the high-frequency output, and the strength of the high-frequency energy is set based on the capacity, and the high-frequency output is Since the shape of the object to be thawed is determined based on the rate of change and the intensity of high-frequency energy is set to prevent local heating, local abnormal heating can be prevented regardless of the volume and shape of the object to be thawed. Thawing can be performed uniformly and efficiently.

[Brief explanation of the drawing]

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 shows the relationship between high-frequency output and elapsed time for each object to be thawed. The characteristic diagram shown in FIG. 4 is a block diagram in another embodiment. DESCRIPTION OF SYMBOLS 1...Object to be thawed, 2, 3...Electrode, 6...High voltage power supply unit, 7...High frequency oscillator, 12...Defrosting chamber, 13...Control circuit.

Claims (1)

[Scope of Claims] 1. A thawing chamber that stores an object to be thawed, a high-frequency oscillator that supplies high-frequency energy to the object to be thawed, and a pair of electrodes are provided, and a high voltage is applied between the electrodes to perform thawing by dielectric heating. A high-frequency thawing machine is characterized in that it detects the initial high-frequency output and rate of change in various objects to be thawed, and automatically sets the strength of high-frequency energy depending on the magnitude thereof. 2. The high-frequency thawing machine according to claim 1, wherein the electrode is movable depending on the initial high-frequency output state.