JP2000058244A - Heating method for material contained in metal can and induction coil assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating method for rapidly thawing a frozen material such as fruit juice contained in a metal can. SOLUTION: An induction cod 3 is arranged in the outer periphery of a metal can 1, current is supplied to the induction coil 3 from a power source device 4, and heat is generated in the metal can itself to thaw a frozen body 2a inside. By controlling power supplied to the induction coil 3, the surface temperature of the metal can 1 is kept at a specified temperature, and temperature rising of liquid is suppressed to prevent the quality deterioration of a contained material. By monitoring the amount of power supplied, a thawing state in the frozen material inside is estimated, thawing finishing time is judged, and unmanned operation is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating an object contained in a metal can such as a drum for storage, transportation, etc., for example, in order to improve the handleability, and a method therefor. For the induction coil assembly used for, in particular, solid containers such as fruit juice, soup, coffee extract, etc. stored in a frozen state are melted into a liquid state, lard, gelatin, jelly, etc. The present invention relates to a heating method suitable for use in heating a fluid (strictly speaking, a highly viscous liquid, which behaves like a solid) to increase fluidity.

[0002]

2. Description of the Related Art It has been widely practiced to store beverages such as fruit juices and soups in drums in a frozen state for storage and transportation. Such frozen matter cannot be handled as it is during subdivision for commercialization or component adjustment, so it is thawed or thawed for better handling, but avoids quality deterioration at the time of thawing. Therefore, it is necessary to heat so that the liquid temperature after thawing does not exceed a predetermined upper limit (for example, about 15 to 20 ° C. in the case of fruit juice). Therefore, conventionally, heating and thawing have been performed at room temperature or in a hot water bath (a method of immersing in hot water and heating).

[0003]

However, when thawing at room temperature is performed, it takes 10 minutes to thaw one drum.
It takes around 0 hours, so space occupation,
There was an unfavorable problem in production, such as waiting for the process. On the other hand, the hot water bath method requires a large hot water bath for immersing the drum can, and thus has a problem that the equipment cost is increased and the running cost is also increased. Also,
Even with the hot water method, it is necessary to set the water temperature close to the upper limit temperature so that the liquid temperature after thawing does not exceed a predetermined upper limit. In this case, the thawing speed cannot be too high. The thawing speed can be increased by increasing the temperature of the hot water. However, in that case, it is necessary to quickly lower the hot water temperature when the can wall temperature is too high, but since the hot water bath has a large amount of hot water, the temperature does not immediately decrease even if cold water is injected. However, it is difficult to control the temperature, so that a great deal of attention is required so that the temperature of the can wall does not rise excessively and the contents are degraded. There was also a problem that required. Furthermore, when thawing fruit juice etc., the frozen matter is 5%
Finish thawing with the remaining amount, but leave it at room temperature,
In both hot water decoction methods, there is a problem that it is difficult to automate the thawing process because the operator judges the end of the thawing by looking inside the drum. These problems are not limited to the case of thawing, but also occur when heating a solid fluid such as lard, gelatin, jelly or the like contained in a drum can in order to increase the fluidity and improve the handleability.

[0004] The present invention has been made in view of such problems, and heating for improving the handleability of the contents contained in a metal can such as a drum can, for example, heating for thawing or fluidizing, is performed at room temperature. It is an object of the present invention to provide a heating method which can be performed in a shorter time than heating by standing, and which can be performed promptly and without deterioration in quality with lower initial cost and running cost as compared with the hot water decoction method. . It is another object of the present invention to provide an induction coil assembly used for the heating.

[0005]

Means for Solving the Problems The present inventors have studied to solve the above problems, and as a result, induction heating of the metal can causes the metal can itself to generate heat, thereby efficiently removing the internal contents from a large area. The metal can can be heated well and the temperature of the metal can can be easily controlled by controlling the input power for induction heating. Can be held,
The present inventors have learned that good thawing or fluidization can be performed, and have completed the present invention.

That is, according to the method for heating an object contained in a metal can of the present invention, an induction coil is arranged so as to surround a metal can that stores an object for storage, transportation, etc. It is characterized in that the can is heated and the contents in the metal can are heated. According to this configuration of the present invention, since the metal can itself generates heat by induction heating and heats the internal container with the heat, heat is transmitted to the container from a large area, and the temperature of the metal can is reduced. Even if the temperature is kept low, the amount of heat transfer can be increased, so that quick heating is possible. In addition, since the temperature control is easy, the can wall temperature can be set to a desired temperature, and the quality of the stored items does not deteriorate. For this reason,
It can be suitably used for thawing frozen matter or improving the fluidity of a solid fluid. In addition, the induction coil used for induction heating and its power supply device have lower initial cost and lower running cost than the device for performing the hot water decocting method. Therefore, the method of the present invention is more economical than the hot water decoction method. is there.
Furthermore, by monitoring the input power to the induction coil, or by temporarily stopping energization and measuring the temperature drop,
The heating state in the metal can can be monitored, and the end of heating can be automatically determined.

[0007] The present invention also provides an induction coil assembly that can be easily attached to a metal can for induction heating the metal can. That is, the induction coil assembly of the present invention allows a flexible induction coil formed in a spiral shape having a size surrounding a metal can containing a frozen body or the like, and allows the spiral induction coil to expand and contract. However, a configuration having a coil holding means for restricting the pitch of the helix when stretched most to a value suitable for heating the metal can, and a fixture for attaching the coil holding means to the metal can It was done. According to this configuration,
When storing the induction coil assembly, the storage space can be reduced by shortening the whole, and at the time of use, the induction coil assembly can be covered with a metal can placed at an appropriate position, and the spiral of the induction coil can be reduced. By stretching the whole so that the pitch becomes a length suitable for heating and holding the metal can with a fixture, the induction coil can be easily and appropriately arranged on the outer periphery of the metal can to perform induction heating.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION According to the method of heating contents contained in a metal can according to the present invention, an induction coil is arranged so as to surround the metal can, and electricity is supplied to the induction coil to cause the metal can to generate heat. It is characterized by heating the contents. The metal can to be subjected to this heating method is not used exclusively for heating, but is used for storing and transporting the contents, and is naturally made of a material which can be induction heated. As a typical example,
Commonly used drums can be mentioned.

The object to be heated in the metal can and the purpose of heating the metal can are not particularly limited, and operations such as dispensing the object in the metal can and adjusting the components can be easily performed. As much as possible, it is preferable to apply the present invention to heating for improving the handleability of the contents in the metal can. More specifically, it is preferable to apply the heating method of the present invention in order to make a container a solid material that can be melted or whose fluidization is improved by heating, and to melt or fluidize it. Such a solid material has poor heat conduction and is difficult to heat, so that the effect of the application of the present invention is great. In addition, since the heating method of the present invention can precisely control the temperature of the metal can wall, the upper limit of the heating temperature of the container can be easily controlled, and therefore, for the container in which the upper limit of the heating temperature is regulated. It is preferable to apply the present invention. More specifically, fruit juice, soup,
The heating method of the present invention is suitable for melting (thawing) solid contents such as coffee extract or heating for fluidizing solid fluids such as lard, gelatin and jelly.

Hereinafter, the present invention will be described in more detail with reference to the drawings by taking the thawing of frozen matter such as fruit juice as an example. FIG. 1 shows an embodiment of the present invention,
1 is a metal can such as a drum can or the like, 2 is a container such as fruit juice stored therein, 2a is a frozen portion of the container, that is, a frozen body, and 2b is a liquid generated by melting the frozen body. The present invention is characterized by utilizing induction heating for thawing the frozen body 2a. At the time of thawing, the induction coil 3 is arranged so as to surround the metal can 1 and is connected to the power supply device 4. Further, in order to control the power supplied to the induction coil 3, a temperature detecting end 5 is attached to the wall surface of the metal can 1, and the signal is input to the control device 6 of the power supply device 4. Here, the configuration of the induction coil 3 is arbitrary as long as it can induction heat the can wall of the metal can 1, for example, a spiral shape surrounding the metal can 1, a ring surrounding the metal can 1 (In this case, a plurality of ring-shaped coils are connected in series or in parallel and used), a plurality of coils configured to heat only a part of the circumferential direction of the metal can 1, 1 can be used as appropriate, and FIG. 1 shows a case where one spiral induction coil is used. Further, the induction coil 3 may be configured to be attached to the metal can 1 placed at an appropriate position by surrounding the metal can 1 as shown by holding the metal can 1 itself through an appropriate attaching means. Alternatively, a configuration in which the metal can 1 is held by a holding mechanism unrelated to the metal can 1 and arranged so as to surround the metal can 1 as shown in the drawing may be used.

Next, a decompression method using the above-described apparatus will be described. As shown in FIG. 1A, after the induction coil 3 is arranged around the metal can 1 and the temperature detecting end 5 is attached to the outer surface of the metal can 1, the power is supplied to the induction coil 3 by the power supply 4 and the metal is turned on. The outer peripheral wall of the can 1 is induction heated to cause the metal can 1 itself to generate heat. As a result, the temperature of the can wall rises, the heat of the can wall is transmitted to the frozen body 2a inside, and the frozen body 2a is gradually thawed. Then, most of the frozen matter 2a is thawed, and FIG.
As shown in (b), when a small amount of frozen matter 2a (for example, about 5% of the whole frozen matter) remains (the determination method at this time will be described later), the power supply to the induction coil 3 is stopped. ,
Finish the decompression work. The reason why the thawing is terminated when a small amount of the frozen matter 2a remains is to prevent the temperature of the liquid 2b from rising in the subsequent process with the frozen matter 2a.

In the above-described thawing operation, if the temperature of the liquid 2b is too high, a heating odor or discoloration may occur (for example, in the case of citrus juice, a problem occurs if the liquid 2b is exposed to more than 15 ° to 20 ° C. for a long time). ). Therefore, in order to suppress the rise of the liquid temperature, the temperature of the outer surface of the can wall is detected by the temperature detecting end 5, and the temperature is set to a preset temperature in consideration of the allowable maximum temperature of the liquid. To control the input power P to the power supply. Thereby, thawing can be performed while the liquid temperature is suppressed to a certain value or less, and the problem that a heated odor is generated in the container 2 can be avoided.

Here, the set temperature of the outer surface of the can wall is determined so that the liquid temperature does not exceed the allowable maximum temperature, and may be set to a constant value throughout the thawing period, or may be stepwise or continuous over time. It may be set so as to change in a dynamic manner.
In general, the liquid temperature is lower than the outer surface temperature of the can wall, and the difference tends to become smaller as the thawing progresses.
Even when 5% is melted (usually when thawing is completed), a temperature difference of about 3 to 5 ° C. is generated. Therefore,
As an example of the set temperature of the outer surface of the can wall, a constant value that is higher than the allowable maximum temperature of the liquid by about 3 to 5 ° C. throughout the thawing period, for example, a constant value of about 18 to 25 ° C. for citrus juice. By controlling the outer surface of the can wall at the constant set temperature during the thawing period, the liquid inside can be prevented from exceeding the maximum allowable temperature. In such a temperature setting of the can wall, the amount of heat transfer per unit area cannot be increased so much because the temperature gradient is small. However, since most of the outer peripheral surface of the metal can 1 contributes to heat transfer and the heat transfer area is large, The amount of heat transfer as a whole can be considerably large, and for example, a 200-liter drum can be thawed in about 15 hours. However, the power supplied to the induction coil 3 is considerably smaller than that of general induction heating, for example, since it is only necessary to reach the room temperature at a slow speed.
Since the current may be about W, the value of the current flowing through the induction coil 3 is also small, and therefore, the water cooling of the induction coil 3 is unnecessary. That is,
Heating with very small power loss and very high efficiency can be performed. However, when the wall surface of the metal can 1 is heated using an electric heater, the heater has the highest temperature and its temperature is much higher than that of the induction coil.
An extremely large heat dissipation loss and, consequently, a power loss occur, so that highly efficient heating as in the method of the present invention cannot be expected at all. As another example of the set temperature of the outer surface of the can wall,
At the start of thawing, keep the solution temperature within the range not exceeding the maximum allowable temperature, and gradually or continuously lower the solution temperature over time so that the temperature does not exceed the maximum allowable temperature. 3-5 ° C above maximum allowable liquid temperature before
An example in which the set temperature is changed so that the temperature is not higher than the high temperature can be given. When such a set temperature is employed, the amount of heat to be heated can be increased as compared with the case where the above-mentioned constant value is employed, and prompt thawing becomes possible.

Next, a method of judging the end of decompression will be described.
There are two methods for judging the end of the thawing: a method using the input power value and a method using the temperature drop on the outer surface of the can wall at the time of temporarily stopping the current supply to the induction coil. First, a method using the input power value will be described.

In FIG. 1, an electric power is supplied to an induction coil 3 by a power supply device 4 to cause the can wall of the metal can 1 to generate heat.
The frozen body 2a in the inside is thawed. At this time, the electric power P supplied to the induction coil 3 is controlled so that the outer surface temperature of the can wall becomes a preset constant temperature. During the thawing, the temperature distribution of the can wall of the metal can 1 and the portion adjacent thereto is schematically shown in FIG. That is, immediately after the outer surface of the can wall 1a is heated to the predetermined set temperature T,
Due to the presence of a considerable amount of low-temperature frozen matter 2a inside, the amount of liquid 2b is small and its temperature is also low. Therefore, it has the temperature distribution shown by curve 11 in FIG. At the same time, the thawing proceeds and the frozen body 2a becomes extremely small and the amount of the liquid 2b increases, and the temperature distribution becomes as shown by a curve 12. Therefore, the temperature gradient in the can wall 1a is
It is large immediately after the outer surface of the can wall reaches the set temperature, but becomes smaller with the progress of thawing thereafter. The temperature gradient in the can wall 1a is proportional to the amount of heat transferred to the inside through the can wall 1a, and the amount of heat transfer is substantially equal to the amount of heat input to the can wall by the induction coil 3 (the wall of the metal can 1). Since the temperature is close to the normal temperature, the amount of heat released to the outside is small and can be ignored.) Since this heat input is proportional to the input power P to the induction coil 3, the heat input P to the induction coil 3 is eventually Decreases as thawing progresses.

Accordingly, the outer surface temperature of the can wall 1a and the electric power P applied to the induction coil 3 with respect to the lapse of time from the start of thawing to the end of thawing are as shown by curves 15 and 16 in the graph of FIG. That is, the outer surface temperature indicated by the curve 15 rises from the start of thawing, and is maintained at the predetermined temperature T when it reaches the predetermined temperature T. On the other hand, the input power P is kept constant at the start of thawing, but gradually decreases as thawing progresses to some extent. The magnitude of the input power P at that time is proportional to the temperature gradient of the can wall, that is, the amount of heat input, as described with reference to FIG. 2, and the amount of heat input is the remaining amount of the frozen body 2a in the metal can 1. It is according to the ratio. Therefore, if the relationship between the applied power P and the remaining amount ratio of the frozen body 2a is measured by an experiment in advance, the thawing state (remaining ratio) of the frozen body 2a can be estimated from the value of the applied power P, the frost remaining percentage of time to be completed (e.g., 5%) can be obtained input power value P ₁ against.

In FIG. 1, the controller 6 stores a frozen ice remaining amount ratio at the end of thawing (for example, based on the relationship between the input power P and the remaining amount ratio of the iced water 2a) obtained by an experiment in advance. input power value P ₁ corresponding to 5%) is input. During the thawing operation, the control device 6 controls the input power P to the induction coil 3 so that the can wall temperature becomes the predetermined set temperature T, and monitors the input power value. value, at the time when decreased to input power value P ₁ set, stopping the energization of the induction coil 3 is judged to have reached the desired thawing state, ends the thawing operation. As described above, the thawing state inside can be monitored from the input power value without monitoring the inside of the metal can 1 visually or the like, and the thawing operation can be automatically terminated when the predetermined thawing state is reached.

In the above-described embodiment, the temperature of the outer surface of the can wall during thawing is controlled so as to be a predetermined set temperature T. However, the present invention is not limited to this case. The set temperature of the outer wall surface may be changed over time. For example, in the early stage of thawing, the liquid temperature does not rise so much, so set the can wall temperature high, increase the amount of heat input, and after thawing has progressed to a certain extent, set the can wall temperature low to suppress the rise in liquid temperature. Alternatively, a change may be made such that the can wall temperature is set so as to gradually decrease as the thawing progresses. The predetermined temperature set forth in the claims does not only mean a constant value, but also includes a case where the numerical value (temperature setting value) is variable. Even when the set temperature is changed over time, at the end of thawing, the set temperature of the outer surface of the can wall is the fixed set temperature T shown in FIG. The amount ratio can be monitored and the end of thawing can be determined.

Next, a description will be given of a method of temporarily stopping the current supply to the induction coil, grasping the falling speed of the can wall temperature at that time, and judging the end of the thawing based on this. Even in the implementation of this method, in FIG. 1, the electric power supplied to the induction coil 3 is controlled by the power supply device 4 and the power P applied to the induction coil 3 is controlled so that the outer surface temperature of the can wall becomes a predetermined constant temperature. While the can wall of the metal can 1 is being heated, the frozen body 2a in the metal can 1 is thawed. Again, in this case,
Can wall 1a for elapse of time from the start of thawing to the end of thawing
The outer surface temperature rises from the start of thawing as shown by a curve 15A in FIG. 4, and is maintained at that temperature when a predetermined set temperature T is reached.

When the current to the induction coil 3 is temporarily stopped during the thawing and at an appropriate time t ₁ after the temperature reaches the set temperature T, the can wall 1 a is cooled by the contents 2 in the can. As a result, the outer surface temperature decreases as shown by the curve 15a. At this time, there is a correlation between the temperature drop rate and the remaining amount of the frozen body 2a in the metal can 1, and it has been found that the lower the remaining amount of the frozen body 2a, the slower the temperature drop. That is,
The time at which the current to the induction coil is temporarily stopped is denoted by t ₁ ,
When the measurement is performed a plurality of times with different values such as t ₂ , t ₃ , t ₄ , t _5, etc., the curves 15a, 15b, 15c, 1
The temperature drops indicated by 5d, 15e, etc. occur, and the temperature drop becomes slower as the time becomes later, that is, as the remaining amount of the frozen matter 2a decreases. Here, factors used to quantitatively compare the temperature drop at the time of stopping the energization include a temperature drop rate immediately after the stop of the energization,
The temperature drop rate at the time when an appropriate time has elapsed since the stop of the power supply, the average temperature drop rate during a certain time after the stop of the power supply, the amount of temperature drop during the fixed time after the stop of the power supply, and the like. Although it may be adopted, it is particularly preferable to employ the temperature drop amount (ΔT in FIG. 4) during a certain period of time (Δt in FIG. 4) from the stop of energization because the detection is easy and the accuracy is high. . In this case, if the predetermined time Δt from the stop of energization to the measurement of the temperature drop amount is set to about 2 to 5 minutes, in most cases, necessary temperature detection accuracy, reproducibility, stability, and the like are obtained. be able to.

At times t ₁ , t ₂ , t ₃ , t ₄ , t _5, etc. measured from the start of energization as described above, energization of the induction coil is temporarily stopped, and the temperature drop ΔT at that time is measured. By graphing, a curve 17 shown in FIG. 5 is obtained. When the same measurement is performed on the same type of decompression target, a curve similar to the curve 17 is obtained as shown by the curves 17 'and 17 ". The curves 17' and 17" are different from the curve 17 in the time axis direction. Is shifted in the direction of the time axis. For example, the temperature drop amount at the measurement time t ₁ of the curve 17 is reduced by the temperature drop amount ΔT _{1 at the} curves 17 ′ and 17 ″.
Is adjusted to the measurement time t ₁ of the curve 17,
The curves 17 ′ and 17 ″ had characteristics that substantially overlapped the curve 17. This indicates that a certain amount of temperature drop (for example, ΔT
_This means that a constant relationship is always established between the thawing time counted from the time point ₁ ) and the temperature drop amount ΔT. Note that in FIG.
The reason why 7 'and 17 "are shifted in the time axis direction is that the initial state of the container 2 to be measured (the frozen content ratio, the temperature, and the like) is different, and thus the time required for reaching the fixed frozen content remaining amount. Is different.

Next, each measurement time (t ₁₎ for the curve 17
To t ₅ ), the values obtained by measuring the ratio of the amount of frozen solids are C ₁ , C ₂ , C ₃ , C ₄ , and C ₅ , and the relationship between the ratio of the amount of frozen solids and the temperature drop ΔT is graphed Then, a curve 18 shown in FIG. 6 is obtained. This curve 18 shows that even if the same experiment is repeated with the same lot of frozen matter, the remaining amount of frozen matter is 10%.
In the above region, it can be regarded as a characteristic curve obtained in substantially the same shape and having sufficient reproducibility. In addition, when the remaining amount of frozen matter is reduced to about 5%, the dispersion of the measured values becomes large and the reproducibility of the characteristic curve 18 is lowered. This is because the frozen matter is broken and dispersed and becomes close to the temperature detection position. This is for drifting or moving away. The reproducibility can be improved by increasing the temperature measurement points and employing the average value of the measured temperatures.

As is apparent from the characteristic curves 17 and 18 shown in FIGS. 5 and 6, the metal can 1 is induction-heated while controlling so that the outer surface temperature of the metal can 1 is maintained at a constant set temperature T. When thawing the frozen solid 2a inside, the temperature drop ΔT when the energization is temporarily stopped for a certain time Δt temporarily and the ratio of the remaining frozen solid have a fixed relationship (curve 1).
8) Also, there is a certain relationship between the temperature drop ΔT and the thawing time (curve 17). Therefore,
If the characteristics shown by curves 17 and 18 are obtained by performing a thawing experiment on the thawing object, the energization to the induction coil is temporarily stopped at an appropriate time during thawing, and the outer surface of the can wall after a lapse of a certain time Δt By measuring the temperature drop ΔT of the temperature and comparing the measured value with the curve 18 obtained in advance, the thawing state (remaining ratio) of the frozen body 2a can be estimated. You can ask.

Next, the above-mentioned temperature drop ΔT is measured,
A specific method for detecting the end of thawing from the measured value will be described. The thawing is completed when the remaining amount of frozen solids reaches 5%. A thawing experiment was performed in advance, and FIGS.
The curves 17 and 18 shown in FIG.
% Suitable tolerance in the amount of temperature drop [Delta] T ₁₀ corresponding to (±
The value obtained by adding α) is input to the control device 6 shown in FIG. 1 as a determination reference value. The time t (for example, about one hour in the case of grapefruit juice) required for the remaining amount of frozen matter to decrease from 10% to 5% is also represented by curve 17 in FIG.
And input it as the continuation set time. And
The controller 6 controls the input power P to the induction coil 3 so that the outer surface of the can wall becomes the set temperature T during the thawing operation, and energizes the induction coil 3 every time a predetermined time elapses during the thawing. The temperature is temporarily stopped for a predetermined time Δt, and the temperature drop ΔT during the elapse of the predetermined time Δt is detected, and is compared with a previously input determination reference value. When the detected value reaches the determination reference value (at this time, the remaining amount is about 10%), after the energization is resumed, the energization is continued for a preset continuation set time, and thereafter, , End the energization. Thereby, the energization is stopped when the remaining amount is almost 5%, the thawing can be completed, and the thawing operation is automatically terminated when the predetermined thawing state is reached without monitoring the inside of the metal can 1 visually or the like. it can. Here, the smaller the allowable range used for setting the determination reference value and the time interval for measuring the amount of temperature drop, the closer the remaining amount of frozen matter at the end of thawing can be to 5% of the target. May be set as appropriate according to the accuracy of. Also, the time interval for measuring the temperature drop amount does not need to be always constant during the thawing period, for example,
The interval may be set large at the beginning of thawing, and may be changed to a small interval when the temperature drop approaches the determination reference value.

In the above operation, the reason why the temperature drop of 10% is adopted as the judgment reference value is that the remaining temperature after defrosting is close to 5% and the reproducibility of the temperature drop is still high. (Because the variation in the detected temperature drop is small), and the target remaining amount of the determination reference value can be appropriately changed as necessary. In addition, when the variation of the temperature drop amount at the remaining amount of 5% is reduced by increasing the temperature detection position, the temperature drop amount for the remaining amount of 5% is adopted as the determination reference value, and the detected temperature drop amount is used. Thawing may be terminated as soon as the amount reaches the criterion value.

In the above embodiment, the end of thawing is determined based on the time when the measured temperature drop reaches the determination reference value (ΔT ₁₀ ± α). The present invention is not limited thereto, and can be changed as appropriate. For example, an experiment was conducted in which thawing was performed while controlling the outer surface of the can wall to a predetermined set temperature T in advance, and as shown in FIGS. 5 and 6,
Relationship between the temperature drop ΔT and the thawing time (curve 17), and the relationship between the temperature drop ΔT and the remaining ratio of the frozen matter 2a (curve 1)
8), and the relationship between the remaining amount ratio of the frozen matter and the required energization time required until the remaining amount ratio at that time decreases to 5% (curve 19 in FIG. 7) is also obtained, and the obtained characteristic curve is obtained. 18,
19 (FIG. 7) is input to the control device 6 shown in FIG.
During the thawing operation, the control device 6 controls the input power P to the induction coil 3 so that the outer surface of the can wall is at the set temperature T.
Is temporarily stopped for a predetermined time Δt, and the temperature drop amount ΔT at the time when the predetermined time Δt has elapsed is detected and compared with the previously input characteristic curve 18. Then, as shown in FIG. 7, the measured temperature drop ΔT _N
When the temperature drops to a value approaching the temperature drop amount ΔT ₁₀ with respect to 0% (see point P) and is estimated to be lower than the temperature drop amount ΔT ₁₀ at the next measurement, the frozen object remaining amount ratio C _N at that time is obtained and The required energization time for the frozen solid remaining amount ratio C _{N is} obtained from the characteristic curve 19 (see point Q), and thereafter the energization is continued for the determined required energization time t _N and the energization is terminated. Thereby, the energization is stopped when the remaining amount is almost 5%, the thawing can be completed, and the thawing operation is automatically terminated when the predetermined thawing state is reached without monitoring the inside of the metal can 1 visually or the like. it can.

The method of determining the end of thawing using the temperature drop ΔT has been described above. The measurement of the temperature drop ΔT is used not only for determining the end of thawing, but also in the metal can 1. It can also be used to determine the abnormality of the contents 2. That is, when induction heating and thawing are performed while controlling the outer wall temperature of the metal can 1 at a predetermined set temperature T, the temperature drop ΔT reaches a certain temperature drop as described with reference to FIG. There is a certain relationship with the thawing time counted from the point of time. Therefore, a thawing experiment was performed in advance, and FIG.
If a characteristic curve 17A indicating the relationship between the temperature drop amount ΔT and the elapsed time is obtained, if the characteristic at the time of thawing deviates from the characteristic curve 17A, there is an abnormality in the contents in the can ( For example, the density is different). The present invention also provides a method for determining an abnormality using this principle. That is,
In the method of determining an abnormality according to the present invention, the temperature drop amount ΔT is detected at an appropriate time interval, and the detected value is compared with a characteristic curve 17A obtained in advance by an experiment or the like. If it is larger, it is determined that the content is abnormal.

More specifically, at an appropriate point during thawing,
The energization is temporarily stopped, the temperature drop ΔT is measured, and the measured value is plotted on the characteristic curve 17A of FIG. 8 (for example,
(Point A in FIG. 8) Then, after a lapse of a certain time t _M , the energization is temporarily stopped again to measure the temperature drop ΔT, and the measured value (for example, point B in FIG. 8) and the characteristic curve 17A are compared. Detect deviation. If the displacement is abnormally large, it is determined that the content is abnormal. By performing such an abnormality detection operation once or a plurality of times during thawing, it is possible to detect a contained abnormality without opening the metal can 1.

In the above-described embodiment, the thawing completion timing is determined using the characteristic curves shown in FIGS. 4 to 8 obtained when thawing is performed while maintaining the outer wall surface temperature of the metal can 1 at a fixed set temperature T, and Error detection is being performed. By the way, these characteristics vary depending on the contents, but the present inventors have confirmed that the properties greatly depend on the Brix value (sugar content = soluble solids) of the contents regardless of the type of the contents. There was found. Therefore, these characteristics can be
If the rix value is determined in advance, it is possible to deal with various items. Generally, not only the name of the contents but also the Brix value are displayed for the contents of the metal can 1, so that upon thawing, the above-described method can be performed immediately by utilizing the characteristics corresponding to the Brix value. Can be implemented.

In the embodiments described above, the metal can 1
One helical induction coil 3 is arranged and thawing is performed on almost the entire outer periphery of, but a plurality of induction coils can be used if necessary. FIG. 9 shows an embodiment in that case. Is shown. In this embodiment, two helical induction coils 3A and 3B are arranged vertically on the outer periphery of the metal can 1, and are respectively provided with power supply devices 4A and 4B.
Is connected. In this embodiment, in the initial stage of thawing, both the induction coils 3A and 3B are energized to perform thawing, and when the frozen body 2a becomes small and floats above the metal can 1, the lower induction coil The energization of 3B is stopped, and thawing is performed only with the upper induction coil 3A. Thereby, unnecessary heating of the liquid 2b can be avoided, the rise in liquid temperature can be suppressed, and energy loss can be reduced. Further, the induction coil used for thawing is not limited to a spiral or ring-shaped one surrounding the periphery of the metal can 1 as shown in FIG. 1 or FIG. 9, but as shown in FIG. A plurality of coils 3C extending in the axial direction of the metal can 1 may be arranged so as to surround the metal can 1, or an arc-shaped coil 3D may be formed so as to surround the metal can 1 as shown in FIG. In addition, various arrangements are possible, such as a configuration in which the members are arranged in multiple stages in the axial direction.

Next, an induction coil assembly suitable for use in carrying out the method of the present invention will be described. FIG. 11 shows one embodiment of the induction coil assembly. The induction coil assembly 20 includes a flexible induction coil 21 formed in a helical shape having a size surrounding the metal can 1, and the helical induction coil 21 is allowed to expand and contract. A coil holding means 22 for restraining the spiral pitch to a value suitable for heating the metal can 1, and a hook or the like provided at one end of the coil holding means 22 for attaching to the metal can 1 Tool 23 and a magnet 24 and the like provided at the opposite end.

As the flexible induction coil 21, any conductor having flexibility, for example, a copper wire can be used. In particular, a large number of insulating-coated copper wires (for example, enameled copper wires) are twisted, It is preferable to use a litz wire whose entire structure is covered with an insulating tube. This litz wire is constructed by twisting a large number of copper wires, so it has high flexibility.In addition, since each copper wire is insulated from each other, the current flows evenly to each copper wire and concentrates on the skin side. Nor. For this reason, a large current can flow even when high-frequency power is supplied, and furthermore, since the whole is covered with the insulating tube, even if it comes into contact with the metal can 1, there is an advantage that there is no short circuit and it is safe. I have. In addition, as the flexible induction coil 21, a conductive thin strip (strip) made of copper or the like is also used.
This is preferable because it has advantages such as good heat dissipation, so that it does not overheat itself, and has such a large area that uniform heating is possible. Preferably, the strip is also provided with an insulating coating. Examples of the coil holding means 22 include a cloth, a net, and the like formed in a cylindrical shape. The induction coil 21 is attached to the cloth, the net, or the like by a method such as sewing or binding. It is good. Alternatively, the induction coil 21 may be connected at a plurality of positions in the circumferential direction, for example, in a direction parallel to the central axis of the helix with a string, a thread, a tape, or the like so as to have a constant pitch. When the coil holding means 22 having such a configuration is used, it is lightweight and soft.
The advantage of easy handling is obtained. If the upper end of the tubular cloth is sealed, the heat radiation loss can be kept small even in winter or the like.

As shown in FIG. 11 (c), the induction coil assembly 20 having the above-described structure can be reduced in storage space by shortening the entire length as shown in FIG. 11 (c), and can be easily carried. Then, in use, the induction coil assembly 20 is carried over the metal can 1 placed at an appropriate position, and is placed over the metal can 1, and as shown in FIGS. The attachment 23 is attached to the outer periphery of the upper end of the metal can 1 and the lower end is pulled so that the spiral pitch of the induction coil 21 becomes a length suitable for heating, and the lower end magnet 24 is attracted to the outer peripheral surface of the metal can 1. . Thus, the spiral induction coil 2 can be easily formed on the outer periphery of the metal can 1.
1 can be arranged at a predetermined pitch, and can be used for the above-described thawing operation. The induction coil 21 may be stretched to a predetermined pitch by attaching an appropriate weight instead of the magnet 24. When the induction coil 21 can be stretched to a predetermined pitch only by its own weight, the magnet 24 and the weight may be omitted.

[0034]

EXAMPLE Next, citrus juice contained in a 200-liter drum can was actually thawed, and the temperature of each part of the drum at that time was measured. The results are shown below. FIG. 12 shows a drum 31 used, an induction coil 33 attached to the drum 31 and a temperature detecting end (thermocouple) 35a.
It is a schematic sectional drawing which shows the arrangement | positioning state etc. of 35f. The induction coil 33 has a single spiral shape. Temperature detection end 3
5a to 35d were attached to the outer surface of the drum 31 and the second temperature detection terminal 35c from the top was used for controlling the power supplied to the induction coil. The temperature detecting ends 35e and 35f were attached to the inner surface of a plastic bag containing the juice in the drum 31 to measure the temperature of the juice.

Under these conditions, thawing was performed by controlling the temperature at the detection position at the temperature detecting end 35c to 25 ° C., and after 15 hours from the start of thawing, the amount of frozen solids was reduced to 5%. Decompression was completed because it reached. FIG. 13 is a graph showing the temperature change of each part during the thawing operation. In addition, the code | symbol attached to the curve of FIG. 13 has shown the corresponding temperature detection end. As can be seen from FIG. 13, about one hour after the start of thawing, the temperature of the can wall at the mounting position of the temperature detecting end 35c rises to about 25 ° C., and thereafter, the temperature is maintained and the heating of the juice inside is started. Thawing, which resulted in thawing progressing in a relatively short period of time. The temperature of the can wall at the time of heating varies depending on the position. However, since the temperature is highest at the position where the temperature detecting end 35c is attached, the upper limit of the internal liquid temperature is controlled by controlling the temperature at this position. It was confirmed that it could be suppressed. Further, the temperature detecting end 3
The juice temperature measured by 5e and 35f was 15
° C, which did not cause a decrease in fruit juice quality.

[Comparative Example] The same drum can thawed in the example was left in a room maintained at about 25 ° C, and spontaneously thawed. At this time, the temperature at the same place as that shown in FIG. 12 was measured. The results are shown in the graph of FIG. In addition, since the can wall temperature did not significantly differ depending on the measurement location, only the measured values at the temperature detection ends 35b and 35c are shown in the graph. As shown in FIG. 14, when left at room temperature, the can wall temperature rises very slowly, and the difference from the juice temperature is hardly observed. For this reason, the heating rate is extremely slow. As a result, it took about 100 hours to finish thawing when the amount of frozen solids reached 5%.

[0037]

As described above, the heating method of the present invention has a configuration in which the metal can is heated by the induction coil and the contents are heated. Heating can be performed in a shorter time than in the above case, and a wide dedicated space for heating is not required, and process control is facilitated. Also, by controlling the temperature of the metal can and keeping it below a predetermined temperature,
The heating temperature of the stored item can be kept below a predetermined value, and the quality of the stored item does not deteriorate. Furthermore, the induction coil used for induction heating and its power supply device have lower initial costs and lower running costs than the device for performing the hot water decoction method, and therefore the method of the present invention is more economical than the hot water decoction method. is there. Thus, the heating method of the present invention is heating to improve the handleability of the contents in the metal can, for example, thawing of solid contents such as fruit juice, soup, and coffee extract stored in a frozen state, It is very suitable for use in heating and fluidizing solid fluids such as lard, gelatin and jelly.

Further, the power supplied to the induction coil is controlled so as to maintain the outer surface temperature of the metal can at a predetermined set temperature, and the heating state of the internal container, for example, the thawing state, is estimated based on the power value. By judging the end time of heating, the state in the metal can, for example, the state in which a predetermined percentage of frozen matter remains at the time of thawing, and the thawing is ended without visual monitoring by the operator. And unmanned driving becomes possible.

Further, the power supplied to the induction coil is controlled so as to maintain the outer surface temperature of the metal can at a predetermined set temperature, and energization is performed. Measure the factors related to the temperature drop of the temperature, estimate the internal heating state by the measured value,
Even when the heating end point is determined, the state inside the metal can, without visual monitoring by the operator,
For example, it is possible to identify a state in which a predetermined percentage of frozen matter remains at the time of thawing and to end thawing, thereby enabling unmanned operation.

Further, the power supplied to the induction coil is controlled so as to maintain the outer surface temperature of the metal can at a predetermined set temperature, and energization is performed. The operation of measuring the factor related to the temperature drop of the metal can is repeated several times at intervals, and the abnormality of the container is detected from the obtained multiple measured values, so that the container in the metal can can be directly Abnormalities such as concentration abnormalities can be detected without inspection.

The induction coil assembly of the present invention has a structure in which a flexible induction coil is held by a coil holding means so as to be extendable and contractable, and the coil holding means is provided with a fixture for attaching to a metal can. Therefore, the storage space can be reduced by shortening and shortening the whole at the time of storage, and at the time of use, cover the induction coil assembly on a metal can placed at an appropriate position and use the mounting fixture to The induction coil can be easily attached to the outer circumference of the metal can by holding it in the can, and the heating of the contents contained in the metal can, such as thawing of frozen solids, can be performed easily and at any location. Can be.

[Brief description of the drawings]

1A and 1B show an embodiment of the present invention, in which FIG. 1A is a schematic sectional view showing a state before starting thawing with an induction coil attached to a metal can, and FIG. Schematic sectional view shown

FIG. 2 is a graph for explaining a temperature distribution inside a can wall and its vicinity during thawing.

FIG. 3 is a graph showing temporal changes in can wall temperature and input power during thawing.

FIG. 4 is a graph showing a change with time of the outer surface temperature of a can wall when thawing is performed while repeatedly stopping power supply temporarily at appropriate intervals.

FIG. 5 is a graph showing the relationship between the amount of temperature drop and the thawing time when thawing is performed while temporarily stopping power supply at appropriate intervals.

FIG. 6 is a graph showing the relationship between the amount of temperature drop and the ratio of the amount of frozen solid when thawing is performed while temporarily stopping power supply at appropriate intervals.

FIG. 7 shows the relationship between the amount of temperature drop and the remaining amount of frozen matter and the relationship between the remaining amount of frozen matter and the required energization time when thawing is performed while temporarily stopping power supply at appropriate intervals. Graph

FIG. 8 is a graph showing the relationship between the amount of temperature drop and the thawing time when thawing is performed while temporarily stopping power supply at appropriate intervals.

FIG. 9 is a schematic sectional view showing another embodiment of the present invention.

FIGS. 10A and 10B are schematic perspective views showing still another embodiment of the present invention.

11A is a schematic sectional view showing a state where an induction coil assembly is attached to a metal can. FIG. 11B is a schematic side view thereof. FIG. 11C is a state before attaching the induction coil assembly to the metal can. Schematic sectional view

FIG. 12 is a schematic cross-sectional view showing an arrangement state of an induction coil and a temperature detecting end in an embodiment in which frozen fruit juice in a drum can is actually thawed.

FIG. 13 is a graph showing a temperature change of each part when thawing in the state shown in FIG. 12;

FIG. 14 is a graph showing a temperature change of each part when the drum shown in FIG. 12 is left at room temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal can 1a Can wall 2a Iced body 2b Liquid 3 Induction coil 4 Power supply device 5 Temperature detecting end 6 Control device 20 Induction coil assembly 21 Induction coil 22 Coil holding means 23 Mounting tool 24 Magnet 31 Drum can 33 Induction coil 35a to 35f Temperature Detection end

Continuation of the front page (72) Inventor Yoshimasa Hiramatsu 2-17-8 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Within the Technical Department of Dai-ichi High Frequency Industry Co., Ltd. No. 8 Daiichi High Frequency Industrial Co., Ltd. Engineering Department (72) Inventor Shinya Matsumoto 5-2-5 Yamazaki, Shimamoto-cho, Mishima-gun, Osaka Prefecture Inside of Suntory Limited Technology Development Center (72) Inventor, Yuji Saeki Shimamoto-cho, Mishima-gun, Osaka 5-2-5 Yamazaki, Suntory Limited Technology Development Center (72) Inventor Masio Kimura 1-1-1, Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka Pref.

Claims (9)

[Claims] 1. An induction coil is arranged so as to surround a metal can that stores an object for storage, transportation, and the like, and the induction coil is energized to generate heat so that the object in the metal can is heated. A method for heating an object contained in a metal can, characterized by heating. 2. The heating according to claim 1, wherein the heating is for improving the handleability of the contents in the metal can.
The method for heating the content in the metal can as described in the above. 3. An induction coil is arranged so as to surround a metal can containing a solid material that can be melted or whose fluidity is improved by heating for storage, transportation, etc., and energizes the induction coil. A method for heating an object contained in a metal can, comprising: causing a metal can to generate heat; and heating or melting or fluidizing the object contained in the metal can. 4. An electric power to be supplied to the induction coil is controlled so as to maintain an outer surface temperature of the metal can at a predetermined set temperature, an internal heating state is estimated based on the electric power value, and a heating end point is determined. The method for heating an object contained in a metal can according to any one of claims 1 to 3, wherein: 5. An energization is performed by controlling electric power supplied to the induction coil so as to maintain the outer surface temperature of the metal can at a predetermined set temperature, and the energization is temporarily stopped during the energization to control the outer surface of the can wall. 4. A container according to any one of claims 1 to 3, wherein a factor related to a temperature drop of the metal can is measured, an internal heating state is estimated based on the measured value, and a time point of completion of the heating is determined. How to heat things. 6. The power supply to the induction coil is controlled so as to maintain the outer surface temperature of the metal can at a predetermined set temperature, and energization is performed. The operation of measuring a factor related to the temperature drop of the object is repeated a plurality of times at intervals, and an abnormality of the stored object is detected from a plurality of measured values, The method according to any one of claims 1 to 3, wherein How to heat the contents in the metal can. 7. A helically formed flexible induction coil having a size surrounding a metal can containing a material to be heated, and the helical induction coil is allowed to expand and contract, but is extended most. An induction coil assembly comprising: coil holding means for restricting the spiral pitch to a value suitable for heating the metal can at times, and a fixture for attaching the coil holding means to the metal can. 8. The method according to claim 1, wherein the induction coil comprises a litz wire or a conductive strip in which a large number of insulating-coated copper wires are twisted and the whole is covered with an insulating tube. Item 8. The induction coil assembly according to Item 7. 9. The induction coil assembly according to claim 7, wherein the coil holding means is a cloth or a net formed in a cylindrical shape.