JP2001263929A - Thawing cabinet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize thawing by reducing a temperature unevenness when heated. SOLUTION: In the case of irradiating a material 2 to be thawed with a microwave from a microwave generating means 3, a chilled gas is circulated from a chilled gas generating means 9 to a thawing chamber 1 to cool the material and to sufficiently thaw the material into its interior, while preventing a deterioration of a quality of the material due to an overheat of its surface part. Then, a temperature difference between the material 2 and the circulating chilled gas is calculated by a chilled temperature calculating means 15. The circulating gas temperature is controlled based on the calculated result so that the difference becomes a constant value. Thus, even when thawing of the material is advanced so that its temperature rises, disturbance of the thawing of its interior due to excessive cooling of the surface part is prevented, and uniform thawing without temperature unevenness can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thawing cabinet mainly used for business purposes for thawing frozen foods, and more particularly to a means for improving thawing quality.

[0002]

2. Description of the Related Art FIG.
As shown in FIG. 1, there is known a method of irradiating microwaves from a microwave generating means (magnetron) 3 to an object 2 contained in a thawing chamber 1 to defrost the object 2 by dielectric heating. . At that time, a change in the surface temperature of the material 2 to be thawed is measured by the temperature sensor 4, and the output and irradiation time are controlled by the microwave control means 5 based on the signal, so that the deterioration of the food due to the excessive irradiation of the microwave is prevented. Preventing.

[0003]

However, since frozen foods generally contain a lot of water and microwaves are easily absorbed by water, meat and fish with a high water content are absorbed by the surface of the microwaves, and the thawing inside the foods is particularly difficult. There is a problem that it is difficult to be. Further, as a solution, when the output of the microwave is increased, there is a problem that the surface of the object to be thawed is excessively heated and its quality is impaired. Therefore, it is necessary to take a certain amount of time for thawing while suppressing output and wait for temperature equalization by heat conduction in order to thaw the object to be satisfactorily deep inside, and it is not possible to perform high-quality thawing in a short time. It was difficult.

[0004] The inventors of the present invention have conducted research on these problems and found a means for solving them, and have previously filed a patent application (see Japanese Patent Application Laid-Open No. 2000-80). The gist of the invention according to this application is to cool the surface of the object to be defrosted with cold air when irradiating the object with microwaves and defrosting the object, thereby increasing the output of the microwave and increasing the power of the object to be defrosted. While promoting internal thawing, the purpose is to prevent excessive temperature rise on the surface of the object to be thawed due to cold air, thereby preventing quality deterioration.

The object of the present invention is to further improve the thawing quality on the basis of the invention according to the above-mentioned application, and in particular, to promote uniform thawing by reducing temperature unevenness during heating. It is intended to appropriately cope with a difference in the packaging form of food.

[0006]

In order to solve the above-mentioned problems, the present invention provides a thawing chamber for accommodating an object to be defrosted, and a microwave generating means for irradiating the object to be defrosted with microwaves. A cooling chamber partitioned by the thawing chamber and a partition, a cool air generating means for generating cool air in the cooling chamber, a cool air circulating means for circulating cool air between the cooling chamber and the thawing chamber, First temperature measuring means for measuring the temperature of the object to be thawed, second temperature measuring means for measuring the temperature of the circulating cold air, and the microwave generating means based on a signal from the first temperature measuring means The following means are provided in a thawing cabinet comprising: a microwave control means for controlling the operation of the chiller; and a cool air temperature control means for controlling the temperature of the circulating cool air based on signals from the first and second temperature measuring means. Shall take

That is, first, the temperature of the object to be thawed increases with the progress of thawing, and the temperature difference from the cold air gradually increases.
Because the amount of heat exchange between the material to be thawed and the cool air is proportional to the temperature difference,
If this temperature difference is widened, the surface of the object to be defrosted is excessively cooled, and as a result, the thawing time inside the object to be defrosted is prolonged due to heat conduction from the surface. Therefore, the present invention provides a temperature difference calculating means for calculating a temperature difference between the object to be thawed and the circulating cool air, and controls the circulating cool air temperature based on the calculation result so that the temperature difference becomes a constant value. (Claim 1). By controlling the temperature difference to be a constant value, even when thawing of the object to be thawed and the temperature rises, it is possible to prevent the internal thawing from being hindered by excessive cooling of the surface. Can be.

When a non-contact type temperature sensor is used as the first temperature measuring means, the temperature of only the object to be defrosted cannot be measured due to the expansion of the field of view of the sensor and the positional relationship of the object to be defrosted. It may happen that the ambient temperature other than the defrosted material and the average value of these and the temperature of the material to be defrosted are measured. Therefore, the present invention provides a temperature selection means for selecting a signal to be used for control from the plurality of signals of the first temperature measurement means, and the microwave control means and the cold air temperature control means provide a selection signal from the temperature selection means. Each of the above-mentioned controls is performed by using (Claim 2). This makes it possible to appropriately control the microwave output and the circulating cool air temperature by selecting only the temperature of the object to be thawed.

In the non-contact type temperature sensor, the emissivity may change due to the packaging form of the material to be thawed, and the measured temperature value may be shifted. Therefore, the present invention provides a signal from the first temperature measuring means. A packaging determining means for determining a packaging form of the object to be thawed on the basis of the above (claim 3). This makes it possible to appropriately control the microwave output and the circulating cool air temperature in accordance with the packaging form. In that case,
It is preferable to provide a cool air circulation control means for controlling the wind speed of the circulating cool air in accordance with a signal from the packaging determination means (claim 4). By doing so, the temperature inside the thawing chamber should be as uniform as possible, while taking care not to dry the material to be thawed.
The amount (wind speed) of the circulating cool air can be appropriately controlled.

[0010] In any of the above thawing boxes, the first
A plurality of signals from the temperature measuring means may be ranked from the highest temperature, and control may be performed using an arbitrary number of the signals from an arbitrary rank (claim 5).
Of the plurality of temperatures of the object to be thawed measured by the first temperature measuring means, the use of the highest temperature has the advantage of not thawing too much, but the unthawed portion remains in a state where many unthawed parts remain. Differences may occur. Therefore, by using, for example, an average value of an arbitrary number of temperatures from an arbitrary order, it is possible to reduce the variation in the thawing state. In this case, the plurality of ranked signals are further divided into arbitrary groups each having an arbitrary number, and the control is performed using the temperature difference between the two groups. It can be carefully managed (claim 6).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a longitudinal sectional view showing a basic structure of a thawing box according to the present invention. In FIG. 1, the thawing room is made of a heat insulating wall having a heat insulating layer such as urethane foam,
The inside is partitioned into a thawing chamber 1 and a cooling chamber 7 by a partition wall 6. The heat insulating wall is lined with a stainless steel plate, for example, which reflects microwaves easily. On the side surface of the thawing chamber 1, there is provided a microwave generating means 3 comprising a magnetron and a waveguide, and the microwave whose irradiation output and irradiation time are controlled by the microwave control means 5 is accommodated in the thawing chamber 1. Irradiate the thawing material 2.

Above the thawing chamber 1, a first temperature measuring means 8 for measuring the surface temperature of the material 2 to be thawed is provided.
The first temperature measuring means 8 may be a non-contact type temperature sensor such as an infrared temperature sensor or a contact type temperature sensor.
Non-contact type temperature sensor can measure multiple points at the same time,
For example, if a 4 × 4 array type is used, as shown in FIG. 6, it is possible to simultaneously measure the temperature distribution at 16 locations of the object 2 to be thawed. The non-contact type temperature sensor is preferably buried in a heat insulating wall as shown in the drawing so as not to be damaged by microwaves. It is preferable to set the size so that only the temperature signal from 2 passes. However, as long as the microwave can be cut off, it may be installed inside the thawing chamber 1. As the contact type temperature sensor, an optical fiber type sensor which can be used in a microwave is preferable.

In the cooling chamber 7, a cold air generating means 9 comprising, for example, an evaporator of a refrigerator is installed, and a partition wall 6 having a large number of holes through which microwaves can pass but cold air can pass.
, Cool air is supplied from the cooling chamber 7 to the thawing chamber 1.
In the cooling chamber 7, a second temperature measuring means 10 composed of, for example, a thermocouple is provided, and the temperature of the cold air generated by the cold air generating means 9 is determined based on a signal from the second temperature measuring means 10. It is controlled by the temperature control means 11. When an evaporator of a refrigerator is used as the cool air generating means 9, the cool air temperature is controlled to a desired value by ON / OFF of the refrigerator and adjustment of the refrigerant evaporation temperature by an electronic expansion valve. The thawing chamber 1 and the cooling chamber 7 are connected by a cool air passage 12, and a cool air circulating means 13 composed of, for example, a fan with a variable air volume is provided in the middle of the cool air passage 12. By the operation of the cool air circulation means 13, cool air circulates between the cooling chamber 7 and the thawing chamber 1 as shown by arrows, and cools the surface of the object 2 to be thawed. A partition 14 similar to the partition 6 is provided on a surface of the cold air passage 12 which is in contact with the thawing chamber 1.

The basic operation control of the defroster shown in FIG. 1 is as follows. Here, FIGS. 7 to 13 are explanatory diagrams of the operation control, and refer to those diagrams in the description of each embodiment. In FIG. 1, in the initial stage of thawing, as shown in the diagram of FIG. 7, the cold air temperature is set to a low temperature of, for example, −20 ° C., and the object to be thawed 2 is irradiated with microwaves. The temperature of the material 2 to be thawed rises due to the irradiation of microwaves, but since the surface is cooled by cold air, the temperature inside (in the center) is higher. Therefore, the surface temperature of the material 2 to be thawed is monitored by the first temperature measuring means 8, and when this temperature reaches, for example, -10 ° C, the cool air temperature is switched to, for example, -5 ° C. This allows
Originally, the surface portion which is easily heated by the microwave rapidly rises in temperature, and the whole object 2 is thawed to -5 ° C.

On the other hand, as for the microwave irradiation, as shown in the diagram of FIG. 8, the output is set to a large value, for example, 355 W, so that the temperature rises to the center of the object 2 at the initial stage of thawing. Then, while irradiating the microwave, the surface temperature of the material 2 to be thawed is measured by the first temperature measuring means in FIG.
As shown in FIG. 8, multiple points (in FIG. 8, 16 ×
), And when the temperature difference between two points, for example, the point reaches, for example, 3 ° C., the microwave output is reduced to, for example, 145 W. As a result, while the temperature rise in the high-temperature portion is suppressed, the temperature in the low-temperature portion rises with the help of heat conduction from the high-temperature portion, and the temperature in the low-temperature portion approaches the high-temperature portion to make the temperature uniform, This repetition suppresses temperature unevenness. FIG. 8 shows an example in which the output is switched in two stages. However, the output can be switched in three or more stages.
In addition, when the temperature difference between the surface portion and the inside becomes too large, the temperature rise on the surface is slow only by switching the cool air temperature described in FIG. 7 and the thawing time is long, the output is increased once, and the temperature difference is reduced. An operation of reducing the size can be performed.

When a non-contact type temperature sensor is used as the first temperature measuring means 8 and multiple points of temperature are measured, a plurality of (for example, 16) temperatures measured in the above control are ranked from the highest temperature. Any number of temperatures from a predetermined order can be used for control. For example, if the first temperature, that is, the control of the cool air temperature and the microwave output using only the maximum temperature, for example, when thawing fresh tuna, if thawing is stopped at the maximum temperature of 20 ° C., It is possible to suppress a decrease in quality such as burning of tuna. Further, for example, if an average value of, for example, two temperatures is used from the seventh temperature, it means that control is performed using the two temperature distributions. As the number of temperatures used increases, the Control can be performed in consideration of temperature unevenness.

Further, the plurality of ranked temperatures can be divided into arbitrary groups by an arbitrary number, and the cool air temperature and the microwave output can be controlled by using the temperature difference between the two groups. . For example, a plurality of measured temperatures are divided into two groups, high and low, and an average value of, for example, two temperatures from the highest temperature of the high temperature group and an average value of, for example, two temperatures from the lowest temperature of the low temperature group are used. If control is performed so that the temperature difference is within 2 ° C., for example, the temperature distribution (temperature unevenness) in the object 2 can be suppressed to within 2 ° C. and uniform thawing can be performed.

FIG. 2 shows an embodiment according to the first aspect. In FIG. 2, the difference from FIG. 1 is that a temperature difference calculating unit that calculates a temperature difference between the object 2 and the cool air based on signals from the first temperature measuring unit 8 and the second temperature measuring unit 10. 15 is provided. The cool air temperature control means 11 controls the cool air temperature based on the calculation result of the temperature difference calculation means 15 so that the temperature difference between the object 2 and the cool air becomes a constant value. For example, when the temperature difference is set to 5 ° C., the temperature difference between the surface temperature of the object 2 to be defrosted measured by the first temperature measuring means 8 and the cool air temperature measured by the second temperature measuring means 10 becomes 5 ° C. Thus, the cool air temperature control means controls the cool air temperature. FIG. 9 shows the temperature changes of the object 2 and the cool air in that case. The amount of heat exchange between the object 2 and the cool air is proportional to the temperature difference. By controlling the temperature difference to be kept at a constant value, the thawing of the object 2 proceeds and the temperature rises. Also in this case, the surface of the object 1 is not overcooled, and it is prevented from being cooled by the heat conduction from the surface and hindering the thawing inside.

FIG. 3 shows an embodiment according to the second aspect. 3 differs from FIG. 1 in that a temperature selecting means 16 for selecting a signal used for control from a plurality of signals of the first temperature measuring means 8 is provided. If the temperature of the cryopreservation temperature of the material 2 to be thawed, for example, -40 ° C., is set in the temperature selection means 16, the temperature selection means 16 determines the temperature of the cryopreservation temperature of the material 2 to be thawed by the first temperature measurement means 8. Are compared with each other (see FIG. 6), a signal having a temperature difference of a constant value, for example, 3 ° C. or less is regarded as the temperature of the object 2 and a temperature exceeding 3 ° C. is regarded as a temperature other than the temperature of the object. Judgment is made and only the temperature of the object 2 to be used for control is selected. Thereby, in the case of controlling using, for example, the highest temperature among the temperatures measured by the first temperature measuring means 8, for example, the cryopreservation temperature of the thawing object 2 is -40 ° C, and the cold air temperature is -20 ° C.
In this case, the temperature of the inner wall of the thawing chamber 1 cooled by the cool air and the temperature of the wrapped portion of the thawing object 2 are erroneously recognized as the maximum temperature of the thawing object 2, and the danger of controlling the cool air temperature and the microwave output can be avoided. .

FIG. 4 shows an embodiment according to claim 3. In FIG. 4, the difference from FIG. 1 is that a packaging judgment unit 17 for judging the packaging form of the material 2 to be thawed based on the signal of the first temperature measurement unit 8 is provided. In the commercial thawing box, the type of the object 2 to be thawed is limited and the type of the packaging form is also limited as compared with the household microwave oven. Therefore, the packaging form is specified by the packaging determination unit 17 as follows. That is, when a non-contact temperature sensor of a 4 × 4 array type capable of multipoint measurement is used as the first temperature measuring means 8 as shown in FIG. Considering the case where the pack is wrapped in close contact with the film, the pack transmits microwaves but does not transmit infrared rays, whereas the wrap substantially transmits infrared rays.

Therefore, if the initial temperature (freezing storage temperature) of the material 2 to be thawed is -40.degree. C. and the temperature of the cold air is -20.degree. As shown in FIG. 10, all of the 16 temperature signals substantially detect the temperature -40 ° C. of the object 2 to be thawed. On the other hand, in the case of pack packaging, -20 ° C., which is approximately the same as the cold air temperature, is detected. Therefore, if a window hole 18 for temperature measurement is made on the upper surface of the pack as shown in FIG. 11 and a wrap is provided on that portion to prevent drying, as shown in FIG. At the location of the window hole 18, the temperature signal is detected at -40 ° C, which is close to the temperature of the material 2 to be defrosted, and at other locations, -20 ° C, which is substantially the same as the cold air temperature, is detected. Packaging determination means 17
When the two temperatures of -40 ° C and -20 ° C are detected at the same time, it is determined that the package is a pack package. When the initial temperature and the cold air temperature of the material 2 to be thawed are the same, for example, -20 ° C., the detected temperatures at all points are -20 ° C., and the packaging form cannot be determined. In this case, as shown in the diagram of FIG. 13, the packaging form is determined by using the difference in the rate of temperature rise immediately after microwave irradiation due to the difference in microwave absorption between the object 2 and the pack. I do. The temperature rise rate is, for example,
(-20 ° C → -15 ° C) / 10 seconds, while the pack (-20 ° C →
-19 ° C) / 10 seconds. The following cool air temperature control is performed according to the determination result. That is, in the case of pack packaging, the cold air temperature is set to a lower temperature than in the other cases (wrap packaging, unpackaged), and the temperature difference from the cold air is increased.
Thereby, it is possible to supplement that the heat exchange between the object to be thawed and the cool air is prevented by the pack packaging.

FIG. 5 shows an embodiment according to the fourth aspect. In FIG. 5, a cool air circulation control means 19 for changing the wind speed (air volume) of the circulating cool air by the cool air circulation means 13 according to the judgment by the packaging judgment means 17 in FIG. 4 is provided. For example, when the packaging determination unit 17 determines that the package is packed, the cool air circulation control unit 19 sets the wind speed to, for example, 2.0 m / sec, which is a large value, and controls the wind speed of the cool air circulation unit 13. Thereby, even if a plurality of packed objects 2 are simultaneously placed in the thawing chamber 1,
There is no stagnation point in the air, and cold air is blown evenly to all the thawing objects 2, while the thawing objects 2 are packed in a pack, so that drying does not occur even if the wind speed is high. . On the other hand, when it is determined that the material to be thawed 2 is not packaged, the cool air circulation control unit 19 sets the wind speed to, for example, a small
Set to 0.7m / sec. As a result, some stagnation of the wind occurs in the thawing chamber 1, but thawing is performed with priority on quality such that drying of the object 2 is prevented.

[0023]

As described above, according to the present invention, while increasing the output of microwaves to promote thawing inside the object to be thawed, the excessive temperature rise on the surface of the object to be thawed is suppressed by the cool air. In addition to being able to perform high-quality thawing, detailed control is performed while considering the characteristics of the temperature sensor, the arrangement and number of objects to be thawed in the thawing room, the packaging state of the object to be thawed, Thaw quality can be further improved by suppressing the variation and drying of the thawing state of the material to be thawed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a basic configuration of a defroster according to the present invention.

FIG. 2 is a longitudinal sectional view showing an embodiment of a thawing box according to claim 1 of the present invention.

FIG. 3 is a longitudinal sectional view showing an embodiment of a thawing box according to claim 2 of the present invention.

FIG. 4 is a longitudinal sectional view showing an embodiment of a defroster according to claim 3 of the present invention.

FIG. 5 is a longitudinal sectional view showing an embodiment of a defroster according to claim 4 of the present invention.

6A and 6B are explanatory diagrams of multipoint temperature measurement of an object to be thawed by a non-contact type temperature sensor, where FIG. 6A is a side view and FIG. 6B is a plan view.

FIG. 7 is a diagram illustrating cold air temperature control in FIG. 1;

FIG. 8 is a diagram illustrating microwave control in FIG. 1;

FIG. 9 is a diagram illustrating cold air temperature control in FIG. 2;

FIG. 10 is a diagram illustrating a temperature measured by the temperature sensor of FIG. 6 when an object to be thawed is not packaged.

11A and 11B are explanatory diagrams of multi-point temperature measurement of the material to be thawed in the pack package by the temperature sensor of FIG. 6, wherein FIG. 11A is a side view and FIG.
Is a plan view.

FIG. 12 is a diagram illustrating a measured temperature of the object to be thawed in FIG. 11;

FIG. 13 is a diagram illustrating a difference in temperature change of the object to be defrosted depending on the packaging form when the initial temperature and the cold air temperature of the object to be defrosted are the same.

FIG. 14 is a longitudinal sectional view showing a conventional thawing box.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thawing chamber 2 Thawed object 3 Magnetron 4 Microwave control means 5 Heat insulation material 6 Partition wall 7 Cooling chamber 8 Cold air generation means 9 1st temperature measurement means 10 2nd temperature measurement means 11 Cold air temperature control means 12 Cold air passage 13 Cold air Circulation means 14 Partition wall 15 Temperature difference calculation means 16 Temperature selection means 17 Packaging judgment means 18 Window hole 19 Cold air circulation control means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kaoru Yamaguchi 1-1-1, Tanabeshinden, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term in Fuji Electric Co., Ltd. (reference) 4B022 LF02 LQ02 LQ07 LT07

Claims (6)

[Claims] 1. A thawing chamber for accommodating an object to be thawed, microwave generating means for irradiating the object to be defrosted with microwaves, a cooling chamber partitioned from the thawing chamber by a partition, A cool air generating means for generating cool air in the cooling chamber;
Cool air circulating means for circulating cool air between the cooling chamber and the thawing chamber, first temperature measuring means for measuring the temperature of the object to be thawed, and second temperature measurement for measuring the temperature of the circulating cool air Means, microwave control means for controlling the operation of the microwave generation means based on a signal from the first temperature measurement means, and the circulation based on signals from the first and second temperature measurement means. In a defroster provided with cool air temperature control means for controlling the temperature of cool air, a temperature difference calculating means for calculating a temperature difference between the object to be thawed and the circulating cool air is provided, and the temperature difference is calculated based on the calculation result. A thaw storage, wherein the temperature of the circulating cool air is controlled by the cool air temperature control means so as to be a constant value. 2. A thawing chamber for accommodating an object to be thawed, microwave generating means for irradiating the object to be defrosted with microwaves, a cooling chamber partitioned from the thawing chamber by a partition wall, A cool air generating means for generating cool air in the cooling chamber;
Cool air circulating means for circulating cool air between the cooling chamber and the thawing chamber, first temperature measuring means for measuring the temperature of the object to be thawed, and second temperature measurement for measuring the temperature of the circulating cool air Means, microwave control means for controlling the operation of the microwave generation means based on a signal from the first temperature measurement means, and the circulation based on signals from the first and second temperature measurement means. A defroster provided with cold air temperature control means for controlling the temperature of the cold air, wherein a temperature selection means for selecting a signal used for control from a plurality of signals of the first temperature measurement means is provided, and the microwave control means and A defroster characterized in that the cool air temperature control means performs each of the controls using a selection signal from the temperature selection means. 3. A thawing chamber for accommodating an object to be thawed, microwave generating means for irradiating the object to be thawed with microwaves, a cooling chamber partitioned from the thawing chamber by a partition, A cool air generating means for generating cool air in the cooling chamber;
Cool air circulating means for circulating cool air between the cooling chamber and the thawing chamber, first temperature measuring means for measuring the temperature of the object to be thawed, and second temperature measurement for measuring the temperature of the circulating cool air Means, microwave control means for controlling the operation of the microwave generation means based on a signal from the first temperature measurement means, and the circulation based on signals from the first and second temperature measurement means. A thawing cabinet having cold air temperature control means for controlling the temperature of cold air, wherein a packaging judgment means for judging a packaging form of the object to be thawed based on a signal from the first temperature measurement means is provided. Thaw storage. 4. A defroster according to claim 3, further comprising a cool air circulation control means for controlling a wind speed of said circulating cool air in response to a signal from said packaging judgment means. 5. A plurality of signals from said first temperature measuring means are ranked from the highest temperature, and control is performed using an arbitrary number of said signals from a predetermined rank. A defroster according to any one of claims 1 to 4. 6. The control method according to claim 5, wherein the plurality of ranked signals are divided into arbitrary groups each having an arbitrary number, and control is performed using a temperature difference between two groups. Thawing room.