JPS6055111B2 - High frequency thawing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency defrosting device, and is aimed at improving the detection sensitivity of high frequency overcurrent.

Conventional dielectric heating generally performs defrosting work using a high frequency of several MH2 or more.

For example, dielectric heating thawing is performed by applying a high voltage at a relatively low frequency such as 13MH2 to two upper and lower electrodes configured to sandwich the object to be thawed. When a defrosting operation is performed by supplying high frequency energy to an object to be thawed, some parts of the object are likely to be thawed first depending on the shape and components of the object. Trip (gravy) occurs when there is a partial rise in temperature on the surface like this.
flows out. A large number of trips will not occur if the defrosting process is carried out only once, but if the defrosting process is used several times, the mounting plate in the defrosting chamber (made of an insulating material) - Blood market + 1... or 1 ・ 1 - Since the relative dielectric constant of trip, which is water, is extremely large, the high-frequency electric field is concentrated.

Therefore, trips cause tracking. Furthermore, the mounting plate, which is an insulator, causes tracking, resulting in carbonization, smoke generation, and
There is a risk of fire, etc. For this reason, a high-frequency current detection switch is provided that detects the high-frequency current and stops the high-frequency oscillation operation when an overcurrent exceeding a predetermined value flows. however,
The above-mentioned high frequency current varies depending on the size, type, temperature, etc. of the object to be thawed. Therefore, the operating value of the high frequency current detection switch is
It is necessary to consider various cases and make decisions. On the other hand, when the object to be thawed is small and the electrode is brought close to the object at the start of thawing, the trip is already in contact with the wall surface of the thawing chamber and tracking is occurring, the high-frequency current is as follows. It is smaller than the operating value, and the high frequency oscillation operation cannot be stopped. In other words, the tracking of the trip progresses, and finally the tracking of the mounting plate occurs.
The high frequency current detection switch finally works. As described above, in the conventional defrosting device, the operation of the high-frequency current detection switch was insufficient, and a part of the defrosting device was damaged. The present invention provides a high-frequency decompressing device that eliminates the conventional drawbacks, and one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 are the configuration and block diagram of this embodiment, and show the upper electrode 2 configured on the top of the object to be thawed,
A lower electrode 3 is configured below the object 1 to be thawed, and both electrodes 2,
A high frequency voltage is applied between the 3 parts to heat and thaw the object 1 due to the dielectric loss of the object 1 to be thawed.

4 is an insulating cover that covers the upper electrode 2, and 5 is a mounting plate on which the object 1 to be thawed is placed.

Numerals 6 and 7 are a high-voltage power supply unit 6 that supplies high-frequency energy to the object 1 to be thawed, and a high-frequency oscillator unit 7, which are shielded to prevent radio waves from leaking to the outside, and are connected to the high-voltage power supply unit 6 by a power supply line 8.

Reference numerals 9 and 10 indicate power supply lines for feeding power to the upper electrode 2 and the lower electrode 3, respectively.

11 is a thawing chamber that stores the object to be thawed 1; 12 is an upper electrode 2;
This is a motor that moves the machine up and down.

The upper electrode 2 and the defrosting chamber 11 are connected to the ground side, and the lower electrode 3 is connected to the high voltage side. Reference numeral 13 denotes a high-frequency current detection switch, which detects high-frequency current and at the same time stops high-frequency oscillation in the case of overcurrent exceeding a predetermined value.

14 is a control circuit that performs defrosting sequence control based on the information from the high-frequency current detection switch 13. At the start of defrosting, the upper electrode 2 is moved away from the object to be thawed 1 for a predetermined time and a high-frequency voltage is applied, so that the high-frequency current is If it is above a predetermined value, the high frequency oscillation operation is stopped, and if it is below a predetermined value, the upper electrode 2 is moved closer to the object to be thawed 1 to perform thawing.

The upper electrode 2 is moved by sending a signal from a control circuit 14 to an electrode movable circuit 15 to drive a motor 12. FIG. 3 shows the relationship between the electrode distance and the high-frequency current when the trip is in contact with the wall surface of the thawing chamber and tracking is occurring at the start of thawing.

When the upper electrode 2 is farther away from the object 1 to be thawed and the electrode distance is larger (D1 in the figure), the high frequency current is large;
When approaching the object to be thawed (D2 in the figure), the high frequency current is small. This phenomenon is due to the following reasons. In the case of D1 where the electrode distance is large, there is a trip between the lower electrode 3 and the wall surface of the thawing chamber, so the upper and lower electrodes 2
, 3, the electric field is concentrated between the lower electrode 3 and the wall surface of the defrosting chamber, tracking is likely to occur, and a large amount of high-frequency current flows. On the other hand, D2 where the upper electrode 2 is approaching the object 1 to be thawed
In this case, since the electric field is applied to the entire object 1 to be thawed, the concentration of the electric field between the lower electrode 3 and the wall surface of the thawing chamber is reduced, and the occurrence of tracking is alleviated compared to the case D1. As mentioned above, it is better to place the upper electrode 2 further away from the object 1 to be thawed.
Detection sensitivity increases. FIG. 4 shows the size of the object to be thawed and the magnitude of the high frequency current.

In A, the trip has not flowed out, in B, the trip has flowed out and is in contact with the wall of the thawing chamber, and in C, the trip situation is the same as in B, when the upper electrode 2 is approaching the object 1 to be thawed. , when the upper electrode 2 is moved away. Now, if the operation setting value of the high-frequency current detection switch 13 is Ip, it will not operate in the state B in the figure for small objects 1 to be thawed. In the embodiment of the present invention, the upper electrode 2 is moved away from the object 1 to be thawed at the start of thawing (state C), and a current exceeding the operating setting value 1p flows in any case. As described above, in the present invention, when thawing is started, the upper electrode is moved away from the object to be thawed and a high frequency voltage is applied, so that it is possible to detect with high sensitivity that the trip is in contact with the wall surface of the thawing chamber.

Therefore, since the start of thawing is detected and shut off, the mounting plate will not be damaged.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a high-frequency decompression device showing an embodiment of the present invention, FIG. 2 is a block diagram of the same device, and FIGS. 3 and 4 are characteristic diagrams of high-frequency current. 1...Object to be thawed, 2, 3...Electrode, 6
...High voltage power supply section, 7...High frequency oscillator, 13...High frequency current detection switch, 14...
...Control circuit.

Claims (1)

[Claims] 1. A thawing chamber that stores items to be thawed, a high-voltage power supply section and a high-frequency oscillator section that supply high-frequency energy, a pair of electrodes, and a high-frequency current detection switch that detects high-frequency current and simultaneously stops high-frequency oscillation in the event of overcurrent. and a control circuit that moves the electrode away from the object to be thawed and applies a high-frequency voltage at the start of defrosting based on information from the high-frequency current detection switch.