COOLING APPARATUS

A cooling apparatus that cools a cooling target object while causing the cooling target object generate internal heat by an electromagnetic wave and that is capable of efficiently producing a subcooling state of the cooling target object is provided. The cooling apparatus includes a refrigeration machine which cools the cooling target object, an electromagnetic wave irradiation device which irradiates the cooling target object with an electromagnetic wave so as to cause the internal heat generation in the cooling target object and has a variable frequency of the irradiating electromagnetic wave, and a controller which controls operations of the refrigeration machine and the electromagnetic wave irradiation device and which performs a subcooling operation of cooling the cooling target object using the refrigeration machine while irradiating the cooling target object with an electromagnetic wave. The controller performs a preliminary operation of controlling the electromagnetic wave irradiation device such that the electromagnetic wave irradiation device irradiates the cooling target object with the electromagnetic waves of various frequencies by changing the frequency of the electromagnetic wave to be irradiated to determine a subcooling operation frequency which is a frequency of the electromagnetic wave to be irradiated to the cooling target object by the electromagnetic wave irradiation device in the subcooling operation. The controller controls the electromagnetic wave irradiation device so that the electromagnetic wave irradiation device irradiates the electromagnetic wave of the subcooling operation frequency determined in the preliminary operation in the subcooling operation.

TECHNICAL FIELD

The present invention relates to a cooling apparatus which cools a cooling target object in a subcooling zone by cooling the cooling target object in a state in which the cooling target object is irradiated with an electromagnetic wave.

BACKGROUND ART

In general, when an object, such as food, is frozen, moisture is frozen and ice crystals are generated, and therefore, cellular tissue constituting the object is damaged. Such a damage of the cellular tissue causes concentration at a time of freezing or drip at a time of thawing resulting in deterioration of quality of the object. The damage of cellular tissue of an object becomes more significant as the object slowly passes through a temperature zone referred to as a maximum ice crystal production zone where ice crystals most easily grow larger at a time of freezing of the object.

Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2001-245645) describes a cooling apparatus which cools an object (object to be cooled) while making the object generate internal heat by irradiating the object with an electromagnetic wave so that the object passes through the maximum ice crystal production zone in a short time and damage of cell tissue of the object is reduced. Such a cooling apparatus may produce a subcooling state of an object. When such a cooling apparatus reduces a temperature of an object to a temperature lower than the maximum ice crystal production zone in the subcooling state, and thereafter, the internal heat generation of the object caused by the electromagnetic wave is stopped, a period of time for the object freezing in the maximum ice crystal production zone may be reduced.

According to Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2001-245645), the internal heat generation of the object is caused by using an electromagnetic wave of a frequency which realizes a relative dielectric loss constant of ice which is larger than a relative dielectric loss constant of water or an electromagnetic wave of a frequency which realizes a small difference between the relative dielectric loss constant of ice and the relative dielectric loss constant of water so that generation of ice crystals is reduced and miniaturization and homogeneous distribution of ice crystals are attained. For example, use of an electromagnetic wave having such a frequency for internal heat generation contributes to reduce deterioration of quality of the object.

SUMMARY OF THE INVENTION

Technical Problem

However, the frequency of an electromagnetic wave for the internal heat generation may not be selected only based on the viewpoint described above. For example, a frequency of an electromagnetic wave which is appropriate for production of a subcooling state of an object varies depending on composition of the cooling target object. In particular, to produce the subcooling state of an object with less power consumption, it is important to select a frequency of an electromagnetic wave in consideration of composition of the cooling target object.

To address this issue, an appropriate frequency of an electromagnetic wave may be selected in advance using samples of cooling target objects. However, in a case where objects processed by the cooling apparatus are not specified, it is actually difficult to perform an operation of selecting a frequency of an electromagnetic wave which is appropriate for all potential objects. Furthermore, for example, even the same type of objects may have actually different components, and thus it is not necessarily the case that the frequency of the electromagnetic wave which is appropriate for the sample is also appropriate for an actual cooling target object.

The present invention is to provide a cooling apparatus that cools a cooling target object while causing the object generate internal heat by an electromagnetic wave and that is capable of efficiently producing a subcooling state of the cooling target object with less power consumption.

Solution to Problem

A cooling apparatus according to a first aspect of the present invention includes a refrigeration machine, an electromagnetic wave irradiation device, and a controller. The refrigeration machine cools a cooling target object. The electromagnetic wave irradiation device irradiates the cooling target object with an electromagnetic wave so as to cause internal heat generation in the cooling target object. A frequency of an electromagnetic wave to be irradiated from the electromagnetic wave irradiation device is variable. The controller controls operations of the refrigeration machine and the electromagnetic wave irradiation device and performs a cooling operation of cooling the cooling target object by using the refrigeration machine while irradiating the electromagnetic wave to the cooling target object. The controller performs a preliminary operation of controlling the electromagnetic wave irradiation device such that the electromagnetic wave irradiation device irradiates the cooling target object with the electromagnetic waves of various frequencies by changing the frequency of the electromagnetic wave to be irradiated to determine a cooling operation frequency. The cooling operation frequency is a frequency of an electromagnetic wave which is irradiated to the cooling target object by the electromagnetic wave irradiation device in the cooling operation. The controller controls the electromagnetic wave irradiation device so that the electromagnetic wave irradiation device irradiates the electromagnetic wave of the cooling operation frequency determined in the preliminary operation in the cooling operation.

The cooling apparatus according to the first aspect does not determine a frequency of the electromagnetic wave to be irradiated to the cooling target object in advance for each cooling target object. The cooling apparatus according to the first aspect performs the preliminary operation of determining the frequency of the electromagnetic wave to be irradiated by actually using the cooling target object. Therefore, the cooling operation may be performed using the electromagnetic wave of an appropriate frequency for any type of cooling target object.

A cooling apparatus according to a second aspect of the present invention is the cooling apparatus of the first aspect and further includes a temperature sensor which measures a temperature of the cooling target object. The controller determines, in the preliminary operation, the cooing operation frequency in accordance with the temperature measured by the temperature sensor at a time of irradiation with electromagnetic waves of each of various frequencies.

The cooling apparatus according to the second aspect irradiates the cooling target object with the electromagnetic wave while changing the frequency and determines a frequency (that is, the cooling operation frequency) of the electromagnetic wave to be used in the cooling operation in accordance with temperatures of the cooling target object obtained when each of the various frequencies is used. Therefore, the cooling apparatus may determine the frequency of the electromagnetic wave which causes efficient internal heat generation in the cooling target object, as the cooling operation frequency. As a result, the cooling apparatus may produce the subcooling state of the object with high efficiency and less power consumption.

A cooling apparatus according to a third aspect of the present invention is the cooling apparatus of the second aspect and the controller determines, in the preliminary operation, the cooling operation frequency in accordance with a change rate of the temperatures measured by the temperature sensor at the time of irradiation with the electromagnetic waves of each of the various frequencies.

The cooling apparatus according to the third aspect irradiates the cooling target object with the electromagnetic wave while changing the frequency and determines the cooling operation frequency in accordance with the change rate of the temperatures of the cooling target object obtained when each of the various frequencies is used. Therefore, the cooling apparatus may easily determine the frequency of the electromagnetic wave which causes efficient internal heat generation in the cooling target object, as the cooling operation frequency. Consequently, the cooling apparatus may produce the subcooling state of the object with high efficiency and less power consumption.

A cooling apparatus according to a fourth aspect of the present invention is the cooling apparatus of the second aspect or the third aspect, and the controller performs the preliminary operation when the temperature detected by the temperature sensor is higher than an upper limit value of a maximum ice crystal production zone and a freezing point of the cooling target object.

Note that the maximum ice crystal production zone is a range from −1 to −5° C. Note that the freezing point of the cooling target object may be included in the range of the maximum ice crystal production zone or may be higher than the maximum ice crystal production zone.

The cooling apparatus according to the fourth aspect may determine the cooling operation frequency without damaging the cooling target object by ice crystals since the cooling operation frequency is determined before the cooling target object is cooled and the temperature of the cooling target object reaches the maximum ice crystal production zone where cell tissue of the cooling target object is significantly damaged and before the cooling target object starts freezing.

A cooling apparatus according to a fifth aspect of the present invention is the cooling apparatus of the fourth aspect, and the controller performs the cooling operation after the preliminary operation so as to cool the cooling target object to a temperature lower than the upper limit value of the maximum ice crystal production zone.

The cooling apparatus according to the fifth aspect cools the cooling target object to a temperature lower than the upper limit value of the maximum ice crystal production zone in a state in which the cooling target object is irradiated with an electromagnetic wave after an appropriate frequency of the electromagnetic wave (the cooling operation frequency) is determined. Therefore, the cooling apparatus may cause the cooling target object to enter the subcooling state, without freezing the cooling target object, by using the electromagnetic wave of the frequency which causes efficient internal heat generation in the cooling target object.

A cooling apparatus according to a sixth aspect of the present invention is any one of the cooling apparatuses of the second to fifth aspects, and an output of the electromagnetic wave irradiated by the electromagnetic wave irradiation device is variable. The controller controls, in the cooling operation, an output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device in accordance with the temperature detected by the temperature sensor.

The cooling apparatus according to the sixth aspect may change the output of the electromagnetic wave when a sign indicating that the cooling target object is to be frozen in the maximum ice crystal production zone is detected or when the internal heat generation of the cooling target object becomes excessive in terms of the cooling capacity of the refrigeration machine. Therefore, the cooling apparatus may efficiently perform subcooling without freezing the cooling target object.

A cooling apparatus according to a seventh aspect of the present invention is any one of the cooling apparatuses according to the second to sixth aspects, and in the cooling operation, the controller stops irradiation with the electromagnetic wave to the cooling target object performed by the electromagnetic wave irradiation device while continuing cooling with the refrigeration machine after the cooling target object is cooled such that the temperature detected by the temperature sensor is lowered to a predetermined temperature which is lower than a lower limit value of the maximum ice crystal production zone.

The cooling apparatus according to the seventh aspect stops the irradiation with the electromagnetic wave after the cooling target object is cooled to the predetermined temperature which is lower than the lower limit value of the maximum ice crystal production zone and the cooling is continued. Therefore, the cooling apparatus may reduce a period of time for the cooling target object freezing in the maximum ice crystal production zone and freeze the cooling target object while deterioration of quality of the cooling target object is reduced.

A cooling apparatus according to an eighth aspect of the present invention is any one of the cooling apparatuses according to the first to seventh aspects, and a frequency of an electromagnetic wave to be irradiated to the cooling target object in the cooling operation is determined in one of frequency bands of a medium wave, a short wave, a ultrashort wave, a microwave, and a centimetric wave.

The cooling apparatus according to the eighth aspect cools the cooling target object while performing high frequency dielectric heating or microwave heating on the cooling target object so as to cause the cooling target object to enter the subcooling state without freezing the cooling target object.

Advantageous Effects of Invention

The cooling apparatus according to the first aspect of the present invention does not determine the frequency (the cooling operation frequency) of the electromagnetic wave to be irradiated to the cooling target object for each cooling target object in advance. The cooling apparatus according to the first aspect of the present invention performs the preliminary operation of determining the frequency of the electromagnetic wave to be irradiated by actually using the cooling target object. Therefore, the cooling apparatus may perform the cooling operation using an electromagnetic wave of an appropriate frequency for any type of cooling target object.

The cooling apparatuses according to the second and third aspects of the present invention may determine the frequency of the electromagnetic wave which causes efficient internal heat generation in the cooling target object as the cooling operation frequency and may produce a subcooling state of the object with high efficiency and less power consumption.

The cooling apparatus according to the fourth aspect of the present invention may determine the cooling operation frequency without damaging the cooling target object by ice crystals.

The cooling apparatus according to the fifth aspect of the present invention may cause the cooling target object to enter the subcooling state, without freezing the cooling target object, by using the electromagnetic wave of the frequency which is efficient for the internal heat generation of the cooling target object.

The cooling apparatus according to the sixth aspect of the present invention may cause the cooling target object to efficiently enter the subcooling state without freezing the cooling target object.

The cooling apparatus according to the seventh aspect of the present invention may reduce a period of time for the cooling target object freezing in the maximum ice crystal production zone and freeze the cooling target object while deterioration of quality of the cooling target object is reduced.

The cooling apparatus according to the eighth aspect of the present invention may cools the cooling target object while performing high frequency dielectric heating or microwave heating on the cooling target object so as to cause the cooling target object to enter the subcooling state without freezing the cooling target object.

DESCRIPTION OF EMBODIMENTS

Embodiments of a cooling apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

Note that the embodiments below are merely concrete examples of the present invention and do not limit the technical scope of the present invention. The embodiments below may be appropriately changed without departing from the scope of the present invention.(1) Overall Configuration

A cooling apparatus100of an embodiment of the present invention cools a cooling target object M, such as food. The cooling apparatus100cools the cooling target object M while irradiating the cooling target object M with an electromagnetic wave so as to cool the cooling target object M in a subcooling zone.

For example, the cooling apparatus100is used for a large freezer for business use. However, the present invention is not limited to this and the cooling apparatus100may be used for a freezer container for transportation or a refrigerator for home use.

First, a difference between a time change in a temperature of an cooling target object M when the cooling target object M is cooled without irradiating the cooling target object M with the electromagnetic wave in conventional methods and a time change in a temperature of the cooling target object M when the cooling target object M is cooled in the subcooling zone by irradiating the cooling target object M with the electromagnetic wave using the cooling apparatus100will be described with reference toFIG. 6.FIG. 6(a)is a diagram schematically illustrating the time change in a temperature of the cooling target object M when the cooling target object M is cooled without irradiating the cooling target object M with the electromagnetic wave.FIG. 6(b)is a diagram schematically illustrating the time change in a temperature of the cooling target object M when the cooling target object M is cooled using the cooling apparatus100.

In the case where the cooling target object M is cooled without irradiating the object M with the electromagnetic wave, when a temperature of the cooling target object M reaches its freezing point (in many cases, a certain temperature in a maximum ice crystal production zone (−5 to −1° C.)), the cooling target object M starts freezing. When the cooling target object M starts freezing, most cooling capacity of a refrigeration machine is used for phase transition of the cooling target object M. Therefore, after the start of freezing, the temperature of the cooling target object M is barely changed until completion of the freezing. When the freezing is completed, the temperature of the cooling target object M falls again (refer toFIG. 6(a)).

On the other hand, in the case where the cooling target object M is cooled using the cooling apparatus100, the cooling target object M is cooled in the subcooling zone while irradiating the cooling target object M with the electromagnetic wave. Therefore, the cooling target object M does not freeze and the temperature thereof falls even when reaching the freezing point or the maximum ice crystal production zone. When the temperature of the cooling target object M reaches a certain temperature, and then, the cooling apparatus100stops irradiation with the electromagnetic wave, the cooling target object M starts freezing and the temperature of the cooling target object M is once increased to the freezing point. The temperature of the cooling target object M is barely changed until the freezing is completed, and when the freezing is completed, the temperature of the cooling target object M falls again (refer toFIG. 6(b)).

When the cooling target object M is cooled using the cooling apparatus100, the following effect is obtained. That is, a period of time required for freezing (a period of time from the start of the freezing to the end of the freezing) may be reduced when compared with the case where the cooling target object M is cooled without irradiating the cooling target object M with the electromagnetic wave. Furthermore, in the case where the cooling target object M is cooled using the cooling apparatus100, the following effect is obtained. That is, a time in the maximum ice crystal production zone (a period of time from when the freezing is started to when the freezing is terminated and reaching a lower limit value of the maximum ice crystal production zone) may be reduced when compared with the case where the cooling target object M is cooled without irradiating the cooling target object M with the electromagnetic wave. Consequently, generation of ice crystal in the cooling target object M is reduced during the freezing, and accordingly, deterioration of quality of the object may be suppressed. Operation of the cooling apparatus100which realizes such a change in temperature of the cooling target object M will be described hereinafter.

A configuration of the cooling apparatus100will be described.

The cooling apparatus100mainly includes a casing110, a refrigeration machine200, an electromagnetic wave irradiation device300, a controller400, a cooling target object temperature sensor500, and a casing temperature sensor600(refer toFIGS. 1 and 2).

The casing110is a case defining a cooling space110atherein. The cooling space110aaccommodates and cools the cooling target object M. The cooling space110ais surrounded by walls of the casing110(including a ceiling surface, side surfaces, and a bottom surface, not illustrated). The walls of the casing110are insulated by insulating material. The casing110has a door (not illustrated) used to introduce the cooling target object M into the cooling space110aand introduce the cooling target object M from the cooling space110a.

The refrigeration machine200cools the cooling space110ainside the casing110using a vapor compression refrigeration cycle. The refrigeration machine200includes a casing outside unit200aserving as a heat source side unit and a casing inside unit200bserving as a use side unit (refer toFIG. 1). The casing outside unit200aand the casing inside unit200bare connected to each other through a liquid-refrigerant connection pipe202and a gas-refrigerant connection pipe204(refer toFIG. 1). The casing inside unit200bblows the cooling space110awith cold air so as to reduce a temperature in the cooling space110aand cool the cooling target object M in the cooling space110a.

The electromagnetic wave irradiation device300irradiates the cooling target object M with the electromagnetic wave so as to cause internal heat generation in the cooling target object M. The electromagnetic wave irradiation device300performs dielectric heating on the cooling target object M by irradiating the cooling target object M with an electromagnetic wave of a high frequency. A pair of electrodes310used to irradiate the cooling target object M with an electromagnetic wave is disposed inside the cooling space110a(refer toFIG. 1). The cooling target object M by the cooling apparatus100is disposed between the pair of electrodes310so as to be irradiated with the electromagnetic wave. Note that the cooling target object M may not be in contact with the electrodes310. Furthermore, a stand on which the cooling target object M is to be mounted and which is formed of material allowing the electromagnetic wave to pass may be disposed between the cooling target object M and one of the electrodes310, for example.

In the electromagnetic wave irradiation device300, the frequency of the electromagnetic wave to be irradiated is variable. The electromagnetic wave irradiation device300may change the frequency of the electromagnetic wave to be irradiated within a predetermined settable frequency range (in a range between a minimum frequency fmin and a maximum frequency fmax). The settable frequency range includes regions of a medium wave (300 kHz to 3 MHz), a short wave (3 to 30 MHz), and an ultrashort wave (30 to 300 MHz), for example. The settable frequency range is, for example, a range from 1 MHz to 50 MHz but is not limited to. It is preferable that the settable frequency range is designed such that the frequencies appropriate for high frequency dielectric heating to be performed on cooling target objects by the cooling apparatus100is included in this range. Note that the electromagnetic wave irradiation device300may set an arbitrary value (or consecutively change a value) within the settable frequency range as a frequency value, or may set only a plurality of discrete values within the settable frequency range as the frequency values.

Furthermore, an output (wattage) of the electromagnetic wave to be irradiated is variable in the electromagnetic wave irradiation device300. The electromagnetic wave irradiation device300may change the output of the electromagnetic wave to be irradiated, within a predetermined settable output range (in a range between a minimum output Smin and a maximum output Smax). The settable output range is designed as a range appropriate for subcooling of a cooling target object by the cooling apparatus100. For example, an upper limit value (the maximum output Smax) in the settable output range is preferably set such that the cooling target object M is not frozen even if a temperature of the cooling target object M falls to the maximum ice crystal production zone when the refrigeration machine200operates with a predetermined cooling capacity and the electromagnetic wave irradiation device300irradiates the cooling target object M with the electromagnetic wave at the maximum output Smax. Furthermore, for example, a lower limit value (the minimum output Smin) in the settable output range is preferably set such that a temperature of the cooling target object M falls when a temperature of the cooling target object M is higher than an upper limit value of the maximum ice crystal production zone, the refrigeration machine200operates with a predetermined cooling capacity, and the electromagnetic wave irradiation device300irradiates the cooling target object M with the electromagnetic wave at the minimum output Smin. In other words, it is preferable that the minimum output Smin is set such that an amount of generated heat inside the cooling target object M obtained at the time of irradiation with the electromagnetic wave of the maximum output Smin does not exceed the predetermined cooling capacity of the refrigeration machine200. Note that the electromagnetic wave irradiation device300may set an arbitrary value (or consecutively change a value) within the settable output range as an output value, or may set only a plurality of discrete values within the settable output range as the output values.

The controller400controls operations of the refrigeration machine200and the electromagnetic wave irradiation device300. The controller400performs three types of operation (including a preliminary operation, a normal cooling operation, and a subcooling operation) by controlling the operations of the refrigeration machine200and the electromagnetic wave irradiation device300. In other words, the controller400causes the cooling apparatus100to execute the three types of operation (including the preliminary operation, the normal cooling operation, and the subcooling operation) by controlling the operations of the refrigeration machine200and the electromagnetic wave irradiation device300. Note that the cooling apparatus100may execute other types of operation.

The preliminary operation is performed to determine a subcooling operation frequency f1. The subcooling operation frequency f1is a frequency of an electromagnetic wave which is irradiated from the electromagnetic wave irradiation device300to the cooling target object M at a time of the subcooling operation described below. The preliminary operation does not aim for cooling of the cooling target object M.

Specifically, the controller400operates the electromagnetic wave irradiation device300without operating the refrigeration machine200in the preliminary operation. The controller400changes the frequency of the electromagnetic wave which is irradiated from the electromagnetic wave irradiation device300and controls the electromagnetic wave irradiation device300such that the cooling target object M is irradiated with electromagnetic waves of various frequencies in the preliminary operation. The controller400then determines, in the preliminary operation, the subcooling operation frequency f1which is a frequency of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300to the cooling target object M in the subcooling operation. The determination of the subcooling operation frequency f1performed by the controller400will be described later.

In the normal cooling operation, the refrigeration machine200is operated to cool the cooling target object M in a state in which the electromagnetic wave irradiation device300is stopped.

The subcooling operation is an example of a cooling operation. The controller400performs the subcooling operation after the preliminary operation (that is, after the subcooling operation frequency f1is determined). In the subcooling operation, the controller400controls the operations of the refrigeration machine200and the electromagnetic wave irradiation device300such that the refrigeration machine200cools the cooling target object M in a state in which the electromagnetic wave irradiation device300irradiates the cooling target object M with the electromagnetic wave. Note that the controller400controls the electromagnetic wave irradiation device300, in the subcooling operation, so that the electromagnetic wave irradiation device300irradiates the electromagnetic wave of the subcooling operation frequency f1determined in the preliminary operation. The cooling apparatus100performs the subcooling operation mainly for the purpose of cooling the cooling target object M in the subcooling zone.

In the subcooling operation, the controller400controls the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300to the cooling target object M in accordance with a temperature of the cooling target object M which is measured by the cooling target object temperature sensor500described below. The control of the output of the electromagnetic wave from the electromagnetic wave irradiation device300which is performed by the controller400in the subcooling operation will be described later.

The cooling target object temperature sensor500measures a temperature of the cooling target object M. In particular, the cooling target object temperature sensor500measures a surface temperature of the cooling target object M in this embodiment.

For example, the cooling target object temperature sensor500is a noncontact type infrared sensor which measures a surface temperature of the cooling target object M by detecting an infrared ray generated by the cooling target object M. The cooling target object temperature sensor500is electrically connected to the controller400. A signal based on the temperature of the cooling target object M detected by the cooling target object temperature sensor500(a signal for notifying the controller400of the measured temperature of the cooling target object M) is transmitted to the controller400.

The casing temperature sensor600measures a temperature of the cooling space110aof the casing110. For example, the casing temperature sensor600is a thermistor. The casing temperature sensor600is electrically connected to the controller400. A signal in accordance with a temperature of the cooling space110adetected by the casing temperature sensor600(a signal for notifying the controller400of a measured temperature of the cooling space110a) is transmitted to the controller400.

Note that a type of the cooling target object temperature sensor500and a type of the casing temperature sensor600of this embodiment are merely examples, and various sensors may be used as long as the sensors are capable of measuring a temperature of the cooling target object M and a temperature of the cooling space110a.(2) Detailed Configuration

The devices included in the cooling apparatus100, specifically the refrigeration machine200, the electromagnetic wave irradiation device300, and the controller400will be described in detail.(2-1) Refrigeration Machine

The refrigeration machine200mainly includes the casing outside unit200a,the casing inside unit200b,and a refrigeration machine controller290(refer toFIG. 1).

In the refrigeration machine200, a compressor210, a four-way switching valve220, a second heat exchanger250, an expansion valve260, and an accumulator280of the casing outside unit200a,and a first heat exchanger230of the casing inside unit200bare connected to one another through a refrigerant pipe so as to configure a refrigerant circuit.(2-1-1) Casing Inside Unit

The casing inside unit200bmainly includes the first heat exchanger230and a casing inside fan240(refer toFIG. 1).

For example, the first heat exchanger230is a cross-fin type fin-and-tube heat exchanger including a heat transfer tube and a plurality of fins. The first heat exchanger230is connected to the liquid-refrigerant connection pipe202and the gas-refrigerant connection pipe204by the refrigerant pipes (refer toFIG. 1). The first heat exchanger230functions as an evaporator for refrigerant (a cooler) in the normal operation when the cooling target object M is cooled and functions as a condenser for refrigerant (a radiator) in a defrost operation. Note that the defrost operation is performed to remove frost formed on the second heat exchanger250. A detailed description of the defrost operation is omitted.

The casing inside fan240is driven by a motor for a fan (not illustrated). The fan motor is preferably an inverter type motor. The casing inside fan240supplies air to the first heat exchanger230so as to facilitate heat exchange between the air and the refrigerant in the first heat exchanger230. Furthermore, the casing inside fan240supplies the air which has flown through the first heat exchanger230and which has been cooled by heat exchange with the refrigerant to the cooling space110aso as to reduce a temperature in the cooling space110aand cool the cooling target object M placed in the cooling space110a.(2-1-2) Casing Outside Unit

The casing outside unit200amainly includes the compressor210, the four-way switching valve220, the second heat exchanger250, the expansion valve260, a casing outside fan270, and the accumulator280(refer toFIG. 1).

The casing outside unit200afurther includes a refrigerant pipe group206which connects the compressor210, the four-way switching valve220, the second heat exchanger250, the expansion valve260, and the accumulator280to one another (refer toFIG. 1). The refrigerant pipe group206includes a suction pipe206a,a discharge pipe206b,a first gas refrigerant pipe206c,a liquid refrigerant pipe206d,and a second gas refrigerant pipe206e(refer toFIG. 1).

The connection between the components included in the casing outside unit200athrough the refrigerant pipe group206will be described. The suction pipe206ais used to connect a suction port of the compressor210and the four-way switching valve220to each other. The accumulator280is disposed in the suction pipe206a.The discharge pipe206bis used to connect a discharge port of the compressor210and the four-way switching valve220to each other. The first gas refrigerant pipe206cis used to connect the four-way switching valve220and the second heat exchanger250on a gas side to each other. The liquid refrigerant pipe206dis used to connect the second heat exchanger250on a liquid side and the liquid-refrigerant connection pipe202to each other. The expansion valve260is disposed in the liquid refrigerant pipe206d.The second gas refrigerant pipe206eis used to connect the four-way switching valve220and the gas-refrigerant connection pipe204to each other.

The compressor210drives a compression mechanism by a motor (not illustrated) so as to suck gas refrigerant of a low pressure from the suction pipe206aand discharge gas refrigerant of a high pressure which has been compressed by the compression mechanism to the discharge pipe206b.The compressor210is preferably an inverter compressor.

The four-way switching valve220is a mechanism which changes a direction in which the refrigerant flows. In the cooling operation on the cooling target object M, as illustrated by a solid line inFIG. 1, the four-way switching valve220connects the suction pipe206aand the second gas refrigerant pipe206e,and in addition, connects the discharge pipe206band the first gas refrigerant pipe206c.On the other hand, in the defrost operation, as illustrated by a dotted line inFIG. 1, the four-way switching valve220connects the suction pipe206aand the first gas refrigerant pipe206c,and in addition, connects the discharge pipe206band the second gas refrigerant pipe206e.

For example, the second heat exchanger250is a cross-fin type fin-and-tube heat exchanger including a heat transfer tube and a plurality of fins. The second heat exchanger250functions as a condenser for refrigerant when the cooling target object M is cooled and functions as an evaporator for refrigerant in the defrost operation.

The expansion valve260is an example of an expansion mechanism which reduces pressure of the refrigerant supplied to the liquid refrigerant pipe206d.The expansion valve260is an electric expansion valve having a variable opening degree.

The casing outside fan270is driven by a motor for a fan (not illustrated). The casing outside fan270supplies air to the second heat exchanger250so as to facilitate heat exchange between the air and the refrigerant in the second heat exchanger250.

The accumulator280is a gas-liquid separator which separates the refrigerant supplied to the suction pipe206ainto a gas phase and a liquid phase so as to avoid liquid compression in the compressor210(to avoid supply of the refrigerant of the liquid phase to the compressor210).(2-1-3) Refrigeration Machine Controller

The refrigeration machine controller290is a computer which controls the operation of the refrigeration machine200. For example, the refrigeration machine controller290is a micro controller unit (MCU) including a central processing unit (CPU) and a memory. Although the refrigeration machine controller290is drawn in the casing outside unit200ainFIG. 1, the refrigeration machine controller290may include an MCU included in the casing outside unit200aand an MCU included in the casing inside unit200bthat work together to control the operation of the refrigeration machine200.

Although not illustrated, the refrigeration machine controller290is electrically connected to the components included in the refrigeration machine200, such as the compressor210, the four-way switching valve220, the fan motor of the casing inside fan240, the expansion valve260, and the fan motor of the casing outside fan270. The refrigeration machine controller290controls the refrigeration machine200when the CPU executes programs stored in the memory.

Note that, in the refrigeration machine200controlled by the refrigeration machine controller290, in the normal operation (the operation for cooling the cooling target object M), the refrigerant discharged from the compressor210is supplied through the four-way switching valve220to the second heat exchanger250, heat of the refrigerant is discharged to the air outside the casing110, and the refrigerant is condensed. The refrigerant condensed in the second heat exchanger250is expanded when passing the expansion valve260. Thereafter, the refrigerant is supplied to the first heat exchanger230and absorbs heat from the air of the cooling space110aso as to be evaporated.

The refrigeration machine controller290is also electrically connected to the controller400(refer toFIGS. 1 and 2). The refrigeration machine controller290controls operations of the components included in the refrigeration machine200in response to an instruction for operating or stopping the refrigeration machine200and an instruction for adjusting cooling capacity issued by the controller400. For example, the cooling capacity of the refrigeration machine200is controlled by increasing or reducing an amount of wind of the casing outside fan270by changing a rotation speed of the fan motor included in the casing outside fan270(the cooling capacity becomes larger when an amount of wind is increased, and the cooling capacity becomes smaller when an amount of wind is reduced). Furthermore, the cooling capacity of the refrigeration machine200is controlled, for example, by controlling a temperature of the air after heat exchange with the refrigerant at the first heat exchanger230to be increased or reduced by changing a speed of the compressor210. The cooling capacity is increased when the temperature of the air obtained after heat exchange with the refrigerant at the first heat exchanger230is reduced and the cooling capacity is reduced when the temperature of the air obtained after heat exchange with the refrigerant at the first heat exchanger230is increased.(2-2) Electromagnetic Wave Irradiation Device

The electromagnetic wave irradiation device300mainly includes the pair of electrodes310and a high frequency power source320.

The pair of electrodes310is formed of metal, for example. Each of the pair of electrodes310has a plate like shape. However, the shape of the pair of electrodes310is not limited to the plate like shape and other shapes may be employed. The pair of electrodes310is disposed so as to face each other as a pair in the cooling space110aof the casing110. In other words, the electrodes310are disposed in parallel to each other as a pair.

The electrodes310are connected to the high frequency power source320(refer toFIG. 1). Note that the electrodes310may be connected to the high frequency power source320through a load matching circuit (not illustrated).

A frequency and an output of the high frequency power source320are variable. The high frequency power source320uses a self-oscillation circuit, for example. Note that the high frequency power source320is not limited to this and may use a forced-oscillation circuit.

The high frequency power source320is electrically connected to the controller400and controlled by the controller400. The electromagnetic wave irradiation device300switches between performing and stopping of irradiation with the electromagnetic wave in response to an instruction issued by the controller400to the high frequency power source320. Furthermore, the electromagnetic wave irradiation device300changes the frequency of the electromagnetic wave to be irradiated, within the settable frequency range (in the range between the minimum frequency fmin and the maximum frequency fmax) described above in response to an instruction issued by the controller400to the high frequency power source320.

Moreover, the electromagnetic wave irradiation device300changes the output of the electromagnetic wave to be irradiated, within the settable output range (in the range between the minimum output Smin and the maximum output Smax) described above in response to an instruction issued by the controller400to the high frequency power source320.(2-3) Controller

The controller400is a computer which controls the operations of the refrigeration machine200and the electromagnetic wave irradiation device300. The controller400includes a CPU and a memory similarly to general computers. The controller400controls the operations of the refrigeration machine200and the electromagnetic wave irradiation device300when the CPU executes programs for operation control of the cooling apparatus100stored in the memory.

The controller400is electrically connected to the refrigeration machine controller290so as to control the operation of the refrigeration machine200(refer toFIG. 2). Furthermore, the controller400is electrically connected to the high frequency power source320to control the operation of the electromagnetic wave irradiation device300(refer toFIG. 2). Moreover, the controller400is electrically connected to the cooling target object temperature sensor500and the casing temperature sensor600(refer toFIG. 2) and receives a signal indicating a temperature of the cooling target object M transmitted from the cooling target object temperature sensor500and a signal indicating a temperature of the cooling space110atransmitted from the casing temperature sensor600.

Although it is assumed that a computer executes a program as the controller400so as to control the cooling apparatus100in this embodiment, the controller400may realize the similar control by hardware.(3) Operation of Cooling Apparatus

Operation of the cooling apparatus100will be described hereinafter.

The cooling apparatus100performs at least three types of operation (including the preliminary operation, the normal cooling operation, and the subcooling operation) as described above when the controller400controls the operations of the refrigeration machine200and the electromagnetic wave irradiation device300.

Specifically, when an operation start switch (not illustrated) of the cooling apparatus100is pressed, for example, the controller400causes the cooling apparatus100to execute the various operations in accordance with a flowchart ofFIG. 3.

First, the controller400performs a preliminary operation so as to determine the frequency (the subcooling operation frequency f1) of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300to the cooling target object M in the subcooling operation to be performed later (step51). Note that a temperature of the cooling target object M at a start of operation of the cooling apparatus100is higher than an upper limit value (−1° C.) of the maximum ice crystal production zone. In other words, the preliminary operation is performed when a temperature of the cooling target object M detected by the cooling target object temperature sensor500is higher than the upper limit value of the maximum ice crystal production zone. Furthermore, the preliminary operation is preferably performed when a temperature of the cooling target object M detected by the cooling target object temperature sensor500is higher than the freezing point of the cooling target object M (that is, when being in a state in which freezing of the cooling target object M has not been started).

In the preliminary operation, the operations of the refrigeration machine200and the electromagnetic wave irradiation device300are mainly controlled by a subcooling operation frequency determination unit410which is one of functional units of the controller400. The subcooling operation frequency determination unit410determines the subcooling operation frequency f1by a method described below. The preliminary operation (including the operations of the refrigeration machine200and the electromagnetic wave irradiation device300in the preliminary operation and the method for determining the subcooling operation frequency f1employed in the subcooling operation frequency determination unit410) will be described later in detail.

After the preliminary operation is performed, the controller400starts the normal cooling operation (step S2). Specifically, in step S2, the controller400starts the operation of the refrigeration machine200while the operation of the electromagnetic wave irradiation device300is stopped.

In step S3, the controller400determines whether a temperature detected by the cooling target object temperature sensor500is lower than a first temperature T1. The determination in step S3is repeatedly performed until it is determined that the temperature detected by the cooling target object temperature sensor500is lower than the first temperature T1.

The first temperature T1is a predetermined value higher than the upper limit value (−1° C.) of the maximum ice crystal production zone. Furthermore, the first temperature T1is preferably higher than the freezing point of the cooling target object M. The freezing point of the cooling target object M may be included in a range of the maximum ice crystal production zone in many cases, but may be higher than the upper limit value of the maximum ice crystal production zone. An appropriate value which is not higher than freezing points of various objects M to be cooled is preferably selected as the first temperature T1. The first temperature T1is for example 0° C., but is not limited to.

Note that the determination in step S3is performed to avoid that the temperature of the cooling target object M falls to a temperature lower than the upper limit value of the maximum ice crystal production zone in the normal cooling operation and freezing of the cooling target object M starts without being subcooled. Therefore, the determination process in step S3is preferably executed with a comparatively short time interval (a time interval being set such that a temperature of the cooling target object M which was higher than the first temperature T1in a preceding determination will not become lower than the upper limit value of the maximum ice crystal production zone in a next determination).

When it is determined that a temperature detected by the cooling target object temperature sensor500is lower than the first temperature T1in step S3, the controller400starts the subcooling operation (step S4). In other words, the controller400starts the operation of the electromagnetic wave irradiation device300.

In the subcooling operation, the operations of the refrigeration machine200and the electromagnetic wave irradiation device300are mainly controlled by an electromagnetic wave output/freezing capacity controller420which is one of the functional units of the controller400. The electromagnetic wave output/freezing capacity controller420controls the output of the electromagnetic wave to be irradiated from the electromagnetic wave irradiation device300and the cooling capacity of the refrigeration machine200in a method described below. The subcooling operation will be described hereinafter in detail.

In step S4, when a predetermined condition is satisfied, the controller400stops the operation of the electromagnetic wave irradiation device300being operated. In other words, when a predetermined condition is satisfied in step S4, the controller400starts the normal cooling operation (step S5). It will be described later in what case the process proceeds from step S4to step S5. The entire cooling target object M enters a frozen state by performing the normal cooling operation for a predetermined period of time in step S5. The controller400then controls the refrigeration machine200such that a predetermined temperature of the frozen cooling target object M is maintained.

The preliminary operation and the subcooling operation will be described further in detail hereinafter.(3-1) Preliminary Operation

The operation of the cooling apparatus100in the preliminary operation is mainly controlled by the subcooling operation frequency determination unit410of the controller400as illustrated in a flowchart ofFIG. 4, for example. Note that, although not described hereinafter, the subcooling operation frequency determination unit410appropriately obtains a temperature of the cooling target object M detected by the cooling target object temperature sensor500in the preliminary operation.

When the preliminary operation is started, the subcooling operation frequency determination unit410sets the frequency f of the electromagnetic wave to be irradiated from the electromagnetic wave irradiation device300to the minimum frequency fmin (step S11) of the predetermined settable frequency range. Then, the subcooling operation frequency determination unit410controls the electromagnetic wave irradiation device300such that the electromagnetic wave irradiation device300starts irradiation with the electromagnetic wave (step S12). Note that the subcooling operation frequency determination unit410preferably sets an output S of an electromagnetic wave irradiated from the electromagnetic wave irradiation device300to a constant value (the minimum output Smin, for example) in the preliminary operation.

In step S13, it is determined whether a predetermined period of time (5seconds, for example) has elapsed after the electromagnetic wave irradiation device300started the irradiation with the electromagnetic wave of a current frequency f. The process in step S13is repeatedly performed until it is determined that the predetermined period of time has elapsed after the electromagnetic wave irradiation device300started the irradiation with the electromagnetic wave of the current frequency f.

In step S14, the subcooling operation frequency determination unit410calculates a change rate of the temperature of the cooling target object M obtained when the electromagnetic wave of the frequency f is irradiated in accordance with a temperature of the cooling target object M obtained when the electromagnetic wave irradiation device300starts irradiation with the electromagnetic wave of the current frequency f, a temperature of the cooling target object M obtained when a predetermined period of time has elapsed after the electromagnetic wave irradiation device300started the irradiation with the electromagnetic wave of the current frequency f (a current temperature of the cooling target object M), and the predetermined period of time. Then, the subcooling operation frequency determination unit410stores a value of the frequency f and the calculated change rate of the temperature of the cooling target object M obtained when the electromagnetic wave of the frequency f is irradiated by relating them with each other in a memory that is not illustrated.

In step S15, it is determined whether the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is smaller than the maximum frequency fmax of the settable frequency range. When the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is smaller than the maximum frequency fmax in the settable frequency range, the process proceeds to step S16, and when the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is the maximum frequency fmax, the process proceeds to step S17.

When the process proceeds to step S16, the subcooling operation frequency determination unit410increases the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300from the currently used frequency by Δf. For example, Δf is a value obtained by dividing a value, obtained by subtracting the minimum frequency fmin from the maximum frequency fmax, by a certain integer. Although the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is increased by a certain amount (Δf) every time the process in step S16is performed in this embodiment, the present invention is not limited to this. For example, in a case where the number of possible frequencies, including F1, F2, F3, . . . FN (F1(=fmin)<F2<F3. . .<FN (=fmax)), of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is N, the frequency f of the electromagnetic wave may be changed in a step-by-step manner from F1to F2, from F2to F3, and so on every time the process in step S16is executed.

When the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is changed in step S16, the process returns to step S13and it is determined whether a predetermined period of time has elapsed after the irradiation with the electromagnetic wave of the frequency f started. When it is determined that the predetermined period of time has elapsed in step S13, the subcooling operation frequency determination unit410calculates the change rate of the temperature of the cooling target object M obtained when the electromagnetic wave of that frequency f is irradiated (step S14). Furthermore, in step S14, the subcooling operation frequency determination unit410stores the value of the frequency f and the change rate of the temperature of the cooling target object M, which is obtained when the electromagnetic wave of the frequency f is irradiated, by relating them with each other in the memory that is not illustrated. These processes are repeatedly performed until it is determined that the frequency f irradiated from the electromagnetic wave irradiation device300is fmax in step S15.

In step S17, the subcooling operation frequency determination unit410specifies a maximum value in the change rates (which are stored in the memory that is not illustrated) of the temperature of the cooling target object M which are calculated in the process of steps S14which is performed a plurality of times, and determines a value of the frequency associated with the maximum change rate as the subcooling operation frequency f1. In other words, the subcooling operation frequency determination unit410determines the subcooling operation frequency f1in accordance with temperatures measured by the cooling target object temperature sensor500when the electromagnetic wave of each of various frequencies is irradiated in the preliminary operation. More specifically, the subcooling operation frequency determination unit410determines the subcooling operation frequency f1in accordance with the change rate of the temperature measured by the cooling target object temperature sensor500when electromagnetic wave of each of various frequencies is irradiated in the preliminary operation.

Thereafter, in step S18, the subcooling operation frequency determination unit410stops the operation of the electromagnetic wave irradiation device300so as to stop the irradiation with the electromagnetic wave to the cooling target object M. After step S18, the process proceeds to step S2.

Note that the operation of the cooling apparatus100in the preliminary operation described hereinabove is merely an example and the present invention is not limited to this.

For example, a period of time in which electromagnetic wave of each of various frequencies is irradiated to the cooling target object M may not be constant. For example, it may be determined whether a period of time which has elapsed after the irradiation with the electromagnetic wave of each of the various frequencies to the cooling target object M started exceeds the predetermined period of time in step S13, and change rates of temperatures of the cooling target object M which are measured by the cooling target object temperature sensor500when the irradiation with the electromagnetic wave of each of the various frequencies is performed may be calculated using the different elapsed times in step S14.

Furthermore, when periods of time in which the irradiation with the electromagnetic waves of the various frequencies to the cooling target object M are constant, for example, change amounts of temperatures measured by the cooling target object temperature sensor500may be calculated in step S14. Then, in step S17, the subcooling operation frequency determination unit410may specify a maximum value in change amounts of the temperatures of the cooling target object M which are calculated in the process in steps S14which are performed a plurality of times, and determine a value of the frequency associated with the maximum value as the subcooling operation frequency f1.

Although the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is changed to be larger in a step-by-step manner in the preliminary operation in the flowchart ofFIG. 4, the present invention is not limited to this. For example, the frequency f of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300may be changed to be smaller from the maximum frequency fmax in a step-by-step manner in the preliminary operation.

Furthermore, order of the steps in the flowchart ofFIG. 4may be changed as far as consistency of a purpose of calculation of the subcooling operation frequency f1is maintained, for example. Step S17and step S18may be switched, for example.

Furthermore, although the irradiation with an electromagnetic wave is continuously performed in a period of time from when the irradiation with the electromagnetic wave is started in step S12to when the irradiation with an electromagnetic wave is stopped in step S18in the flowchart ofFIG. 4, the present invention is not limited to this. For example, the irradiation with an electromagnetic wave performed by the electromagnetic wave irradiation device300may be stopped and restarted every time the frequency of the electromagnetic wave to be irradiated is changed.

Furthermore, for example, although the frequency of the electromagnetic wave is changed in a range between the minimum frequency fmin and the maximum frequency fmax within the settable frequency range in the flowchart ofFIG. 4, the present invention is not limited to this. For example, the subcooling operation frequency determination unit410may change the frequency of the electromagnetic wave to be irradiated, in a partial range within the settable frequency range.(3-2) Subcooling Operation

The subcooling operation of the cooling apparatus100is mainly controlled by the electromagnetic wave output/freezing capacity controller420of the controller400in accordance with a flowchart ofFIG. 5, for example.

Note that it is assumed that the refrigeration machine200operates with predetermined cooling capacity when the subcooling operation is started. The predetermined cooling capacity is intermediate cooling capacity between minimum cooling capacity and maximum cooling capacity of the refrigeration machine200, for example. Note that the present invention is not limited to this and the predetermined cooling capacity may be the minimum cooling capacity of the refrigeration machine200or the maximum cooling capacity of the refrigeration machine200, for example. Furthermore, although not described hereinafter, the electromagnetic wave output/freezing capacity controller420appropriately obtains a temperature of the cooling target object M detected by the cooling target object temperature sensor500and a temperature of the cooling space110adetected by the casing temperature sensor600in the subcooling operation.

Here, the electromagnetic wave output/freezing capacity controller420sets the subcooling operation frequency f1as a frequency of an electromagnetic wave irradiated from the electromagnetic wave irradiation device300(step S21). The frequency of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is not changed in the subcooling operation.

Subsequently, the electromagnetic wave output/freezing capacity controller420sets a lower limit value (the minimum output Smin) of the settable output range as an output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300(step S22).

Then, the electromagnetic wave output/freezing capacity controller420causes the electromagnetic wave irradiation device300to start irradiation with the electromagnetic wave of the subcooling operation frequency f1set in step S21and the output S set in step S22(step S23). Specifically, the electromagnetic wave output/freezing capacity controller420starts the subcooling operation (an operation of cooling the cooling target object M by the refrigeration machine200in a state in which an electromagnetic wave is irradiated to the cooling target object M) in a state in which the minimum output Smin is set as the output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300.

Thereafter, the electromagnetic wave output/freezing capacity controller420detects a sign indicating that the cooling target object M is to enter a frozen state in accordance with a change rate of the temperature detected by the cooling target object temperature sensor500in the subcooling operation (step S24).

The detection of the sign indicating that the cooling target object M is to enter the frozen state is performed as follows.

When the cooling target object M is frozen, a temperature of the cooling target object M normally exhibits one of the following changes.

1) A temperature of the cooling target object M is substantially constant since heat is used for a phase change (refer to a state I inFIG. 6(a)).

2) A temperature of the cooling target object rises when a state of the cooling target object M is changed from the subcooling state to the frozen state (refer to a state II inFIG. 6(b)).

Here, the electromagnetic wave output/freezing capacity controller420detects a sign indicating that the cooling target object M is to enter the frozen state in accordance with the change rate of the temperature of the cooling target object M detected by the cooling target object temperature sensor500. Specifically, the electromagnetic wave output/freezing capacity controller420detects that there is the sign indicating that the cooling target object M is to enter the frozen state in a case where the change rate of the temperature of the cooling target object M detected by the cooling target object temperature sensor500is zero (including a case where an amount of reduction of the temperature of the cooling target object M is smaller than a predetermined value) or a positive value (in a case where the temperature is gradually increased).

When the sign indicating that the cooling target object M is to enter the frozen state is not detected in step S24, the process proceeds to step S25. When the sign indicating that the cooling target object M is to enter the frozen state is detected in step S24, the process proceeds to step S30.

In step S25, the electromagnetic wave output/freezing capacity controller420determines whether the temperature of the cooling target object M detected by the cooling target object temperature sensor500is equal to or lower than a predetermined second temperature T2. The second temperature T2is lower than the lower limit value (−5° C.) of the maximum ice crystal production zone. When it is determined that the temperature of the cooling target object M detected by the cooling target object temperature sensor500is equal to or lower than the second temperature T2in step S25, the process proceeds to step S26. When it is determined that the temperature of the cooling target object M detected by the cooling target object temperature sensor500is higher than the second temperature T2in step S25, the process returns to step S24.

In step S26, the irradiation with the electromagnetic wave to the cooling target object M performed by the electromagnetic wave irradiation device300is stopped while the cooling performed by the refrigeration machine200is maintained (the operation of the refrigeration machine200is continued), and the process proceeds to step S5inFIG. 3. In other words, the electromagnetic wave output/freezing capacity controller420stops the irradiation with the electromagnetic wave to the cooling target object M performed by the electromagnetic wave irradiation device300while the cooling performed by the refrigeration machine200is maintained after the cooling target object M is cooled such that the temperature of the cooling target object M detected by the cooling target object temperature sensor500is lowered to the second temperature T2. Note that the controller400preferably controls the refrigeration machine200so that the cooling capacity is increased (to the maximum cooling capacity, for example) when the process proceeds from step S26to step S5.

The case where the process proceeds from step S24to step S30(that is, the case where, in the subcooling operation, the electromagnetic wave output/freezing capacity controller420detects the sign indicating that the cooling target object M is to enter the frozen state in accordance with the change rate of the temperature of the cooling target object M detected by the cooling target object temperature sensor500) will now be described.

In step S30, the electromagnetic wave output/freezing capacity controller420determines whether the output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300to the cooling target object M is the upper limit value (the maximum output Smax) of the settable output range.

The electromagnetic wave output/freezing capacity controller420tends to maintain the subcooling state of the cooling target object M by increasing the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300as shown in step S31described below when detecting the sign indicating that the cooling target object M is to enter the frozen state. In contrast, when the maximum output Smax has been set as the output S of the electromagnetic wave, the process proceeds to step S26such that the electromagnetic wave output/freezing capacity controller420changes the subcooling operation to the normal cooling operation since it is difficult to maintain the subcooling state of the cooling target object M (it is difficult to increase the output S of the electromagnetic wave). When the electromagnetic wave output/freezing capacity controller420determines that the output S of the electromagnetic wave is not the maximum output Smax in step S30, the process proceeds to step S31.

In step S31, the electromagnetic wave output/freezing capacity controller420increases the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300to the cooling target object M by ΔS (a predetermined value). For example, ΔS is a value obtained by dividing a value, which is obtained by subtracting the minimum output Smin from the maximum output Smax, by a certain integer. In other words, the electromagnetic wave output/freezing capacity controller420controls the output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300to the cooling target object M in accordance with the temperature of the cooling target object M detected by the cooling target object temperature sensor500, or more specifically, in accordance with the change rate of the temperature of the cooling target object M detected by the cooling target object temperature sensor500(in a case where the change rate is zero or a positive value).

After the output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300to the cooling target object M is increased by ΔS in step S31, the process proceeds to step S32. In step S32, the electromagnetic wave output/freezing capacity controller420determines whether an amount of heat of internal heat generation of the cooling target object M generated by the electromagnetic wave is larger than the cooling capacity of the refrigeration machine200.

Specifically, the electromagnetic wave output/freezing capacity controller420determines whether a temperature of the cooling space110adetected by the casing temperature sensor600tends to be increased. When the electromagnetic wave output/freezing capacity controller420determines that the temperature of the cooling space110adetected by the casing temperature sensor600tends to be increased in step S32(determines that the amount of heat of the internal heat generation of the cooling target object M generated by the electromagnetic wave is larger than the cooling capacity of the refrigeration machine200), the process proceeds to step S40.

Furthermore, in step S32, the electromagnetic wave output/freezing capacity controller420determines whether the temperature of the cooling target object M continuously detected by the cooling target object temperature sensor500is continuously increased for a predetermined period of time or more.

The temperature of the cooling target object M rises when a state of the cooling target object M is changed from the subcooling state to the frozen state as described above. The sign indicating that the cooling target object M is to enter the frozen state is detected using this characteristic in step S24. However, if the temperature of the cooling target object M rises when the subcooling state of the cooling target object M is changed to the frozen state, the increase of the temperature terminates within a comparatively short period of time and the temperature of the cooling target object M becomes substantially constant. On the other hand, if the temperature of the cooling target object M continuously rises even after a predetermined period of time has elapsed, it may be conceivable that the amount of heat of the internal heat generation of the cooling target object M generated by the electromagnetic wave is larger than the cooling capacity of the refrigeration machine200. Therefore, when the electromagnetic wave output/freezing capacity controller420determines that the temperature of the cooling target object M detected by the cooling target object temperature sensor500continuously rises for the predetermined period of time or more in step S32, the process also proceeds to step S40.

Note that, when the electromagnetic wave output/freezing capacity controller420determines in step S32that the amount of heat of the internal heat generation of the cooling target object M generated by the electromagnetic wave is not larger than the cooling capacity of the refrigeration machine200, the process returns to step S24.

In step S40, the electromagnetic wave output/freezing capacity controller420controls the operations of the refrigeration machine200or the electromagnetic wave irradiation device300such that the cooling capacity of the refrigeration machine200becomes larger than the amount of heat of the internal heat generation of the cooling target object M generated by the electromagnetic wave.

Specifically, if the refrigeration machine200has a margin for increase of the cooling capacity in step S40, the electromagnetic wave output/freezing capacity controller420increases the freezing capacity of the refrigeration machine200. An amount of the increase in the freezing capacity in step S40may be appropriately determined. Furthermore, when the cooling capacity of the refrigeration machine200has been already at its maximum, the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is reduced by ΔS in step S40.

Note that the electromagnetic wave output/freezing capacity controller420preferentially performs control of the freezing capacity of the refrigeration machine200in this embodiment, and controls the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300if it is not possible to control the freezing capacity of the refrigeration machine200. However, the present invention is not limited to this. For example, the freezing capacity of the refrigeration machine200and the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300may be simultaneously controlled. Furthermore, in this embodiment, the electromagnetic wave output/freezing capacity controller420controls both of the freezing capacity of the refrigeration machine200and the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300and this is preferable. However, the present invention is not limited to this and the electromagnetic wave output/freezing capacity controller420may control either one of the freezing capacity and the output of the electromagnetic wave.

After step S40, the process proceeds to step S41.

In step S41, the electromagnetic wave output/freezing capacity controller420determines whether an amount of heat of internal heat generation of the cooling target object M generated by the electromagnetic wave is larger than the cooling capacity of the refrigeration machine200. The determination process performed in step S41is the same as the determination process performed in step S32. When it is determined that the amount of heat of the internal heat generation of the cooling target object M generated by the electromagnetic wave is larger than the cooling capacity of the refrigeration machine200in step S41, the process proceeds to step S42. On the other hand, when it is determined that the amount of heat of the internal heat generation of the cooling target object M generated by the electromagnetic wave is not larger than the cooling capacity of the refrigeration machine200in step S41, the process returns to step S24.

In step S42, the electromagnetic wave output/freezing capacity controller420determines whether the cooling capacity of the refrigeration machine200is at its maximum and the output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is the minimum output Smin. When the cooling capacity of the refrigeration machine200is determined to be at its maximum and the output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is determined to be the minimum output Smin in step S42, the temperature of the cooling target object M is gradually increased if the electromagnetic wave irradiation device300continuously irradiates the cooling target object M with the electromagnetic wave. Therefore, the process proceeds to step S26and the subcooling operation is stopped and the operation of the cooling apparatus100is changed to the normal cooling operation. When it is determined that the cooling capacity of the refrigeration machine200is not at its maximum or the output S of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is not the minimum output Smin in step S42, the process returns to step S40.

Note that the operation of the cooling apparatus100in the subcooling operation described hereinabove is merely an example and the present invention is not limited to this.

For example, order of the steps in the flowchart ofFIG. 5may be appropriately changed. For example, the order of step S21and step S22may be switched.

For example, in step S32and step S41, it may be determined that the amount of heat of the internal heat generation of the cooling target object M generated by the irradiation with the electromagnetic wave is larger than the cooling capacity of the refrigeration machine200only when it is determined that the temperature of the cooling space110atends to be increased.(4) Characteristics(4-1)

The cooling apparatus100of the embodiment described above includes the refrigeration machine200, the electromagnetic wave irradiation device300, and the controller400which is an example of a control unit. The refrigeration machine200cools the cooling target object M. The electromagnetic wave irradiation device300irradiates the cooling target object M with the electromagnetic wave so as to cause internal heat generation in the cooling target object M. A frequency of an electromagnetic wave to be irradiated from the electromagnetic wave irradiation device300is variable. The controller400controls the operations of the refrigeration machine200and the electromagnetic wave irradiation device300and performs the subcooling operation for cooling the cooling target object M by using the refrigeration machine200while irradiating the electromagnetic wave to the cooling target object M. The subcooling operation is an example of the cooling operation. The controller400performs the preliminary operation of controlling the electromagnetic wave irradiation device300such that the electromagnetic wave irradiation device300irradiates the cooling target object M with the electromagnetic waves of various frequencies by changing the frequency of the electromagnetic wave to be irradiated to determine the subcooling operation frequency f1. The subcooling operation frequency f1is an example of the cooling operation frequency and a frequency of an electromagnetic wave which is irradiated from the electromagnetic wave irradiation device300to the cooling target object M in the cooling operation. The controller400controls the electromagnetic wave irradiation device300so that the electromagnetic wave irradiation device300irradiates the electromagnetic wave of the subcooling operation frequency f1determined in the preliminary operation in the cooling operation.

The cooling apparatus100does not determine a frequency of the electromagnetic wave to be irradiated to the cooling target object M in advance for each cooling target object. The cooling apparatus100performs the preliminary operation of determining the frequency of the electromagnetic wave to be irradiated by actually using the cooling target object M. Therefore, in the cooling apparatus100, the subcooling operation may be performed using the electromagnetic wave of an appropriate frequency for any type of cooling target object M.

On the other hand, for example, if an appropriate frequency of an electromagnetic wave is selected in advance using samples of the cooling target objects, in a case when objects processed by the cooling apparatus is not specified, it is actually difficult to perform the operation of selecting an appropriate frequency of the electromagnetic wave for all potential objects. Furthermore, for example, even the same type of objects may have actually different components, and thus it is not necessarily the case that the frequency of the electromagnetic wave which is appropriate for the sample is also appropriate for the actual cooling target object. For example, it is assumed that the cooling target object is meat and an appropriate frequency of the electromagnetic wave is selected for a sample of meat in advance. Even if that is the case, the frequency of the electromagnetic wave may not be appropriate for the subcooling operation for the cooling target object M since there are individual differences between meats in e.g. a ratio of lean to fat.(4-2)

The cooling apparatus100of the foregoing embodiment includes the cooling target object temperature sensor500as an example of the temperature sensor which measures a temperature of the cooling target object M. The controller400determines, in the preliminary operation, the subcooling operation frequency f1in accordance with a temperature measured by the cooling target object temperature sensor500at a time of irradiation with electromagnetic waves of each of various frequencies.

The cooling apparatus100irradiates the cooling target object M with the electromagnetic wave while changing the frequency and determines a frequency (that is, the subcooling operation frequency f1) of the electromagnetic wave to be used in the cooling operation in accordance with temperatures of the cooling target object M obtained in various frequencies. Therefore, the cooling apparatus100may determine the frequency of the electromagnetic wave which causes efficient internal heat generation in the cooling target object M, as the subcooling operation frequency f1. Consequently, the cooling apparatus100easily produces the subcooling state of the cooling target object M with high efficiency and less power consumption.(4-3)

The controller400of the cooling apparatus100in the foregoing embodiment determines, in the preliminary operation, the subcooling operation frequency f1in accordance with the change rate of the temperature measured by the cooling target object temperature sensor500at the time of irradiation with the electromagnetic waves of each of the various frequencies.

The cooling apparatus100irradiates the cooling target object M with the electromagnetic wave while changing the frequency and determines the subcooling operation frequency f1in accordance with the change rate of temperatures of the cooling target object M obtained when each of the various frequencies is used. Therefore, the cooling apparatus100may easily determines the frequency of the electromagnetic wave which causes efficient internal heat generation in the cooling target object M, as the subcooling operation frequency f1. Therefore, the cooling apparatus100may produce the subcooling state of the cooling target object M with high efficiency and less power consumption.(4-4)

The controller400of the cooling apparatus100in the foregoing embodiment performs the preliminary operation when the temperature detected by the cooling target object temperature sensor500is higher than the upper limit value (−1° C.) of the maximum ice crystal production zone (−1 to −5° C.).

The cooling apparatus100may determine the subcooling operation frequency f1without damaging the cooling target object M by ice crystals since the subcooling operation frequency f1is determined before the cooling target object M is cooled and the temperature of the cooling target object M reaches the maximum ice crystal production zone where cell tissue of the cooling target object M is significantly damaged.(4-5)

In the cooling apparatus100of the foregoing embodiment, the controller400performs the cooling operation after the preliminary operation so as to cool the cooling target object M to a temperature lower than the upper limit value of the maximum ice crystal production zone.

The cooling apparatus100cools the cooling target object M to a temperature lower than the upper limit value of the maximum ice crystal production zone in a state in which the cooling target object M is irradiated with the electromagnetic wave after an appropriate frequency of the electromagnetic wave (the subcooling operation frequency f1) is determined. Therefore, the cooling apparatus100may cause the cooling target object M to enter the subcooling state, without freezing the cooling target object M, by using the electromagnetic wave of the frequency which causes efficient internal heat generation in the cooling target object M.(4-6)

In the electromagnetic wave irradiation device300of the cooling apparatus100of this embodiment, the output of the electromagnetic wave to be irradiated is variable. The controller400controls, in the cooling operation, the output of an electromagnetic wave irradiated from the electromagnetic wave irradiation device300in accordance with the temperature detected by the cooling target object temperature sensor500.

The cooling apparatus100may change the output of the electromagnetic wave when a sign indicating that the cooling target object M is to be frozen in the maximum ice crystal production zone is detected or when the internal heat generation of the cooling target object M becomes excessive in terms of the cooling capacity of the refrigeration machine200. Therefore, the cooling apparatus100may efficiently perform subcooling without freezing the cooling target object M.(4-7)

In the cooling apparatus100in the foregoing embodiment, in the cooling operation, the controller400stops irradiation with the electromagnetic wave to the cooling target object M performed by the electromagnetic wave irradiation device300while continuing cooling with the refrigeration machine200after the cooling target object M is cooled such that the temperature detected by the cooling target object temperature sensor500is lowered to a predetermined temperature (the second temperature T2) which is lower than the lower limit value of the maximum ice crystal production zone.

The cooling apparatus100stops irradiation with an electromagnetic wave after the cooling target object M is cooled to the second temperature T2which is lower than the lower limit value of the maximum ice crystal production zone and the cooling is continued. Therefore, in the cooling apparatus100, the period of time for the cooling target object M freezing in the maximum ice crystal production zone may be reduced and the cooling target object M may be frozen while deterioration of quality of the cooling target object M is reduced.(4-8)

In the cooling apparatus100of the foregoing embodiment, the frequency of an electromagnetic wave irradiated to the cooling target object M in the cooling operation is determined in one of frequency bands of a medium wave, a short wave, and an ultrashort wave.

The cooling apparatus100may cools cooling target object M while performing high frequency dielectric heating on the cooling target object M so as to cause the cooling target object M to enter the subcooling state without freezing the cooling target object M.(5) Modifications

Modifications of the foregoing embodiment will be described hereinafter. Note that a part of or whole configurations of each of the various modifications may be combined with a part of or whole configurations of the other modifications as long as contradiction does not occur.(5-1) Modification A

In the foregoing embodiment, the settable frequency range of the electromagnetic wave irradiation device300is included in the regions of a medium wave, a short wave, and an ultrashort wave. However, it is usable, for example, if the settable frequency range of the electromagnetic wave irradiation device300includes a frequency which causes the internal heat generation in the cooling target object M and the settable frequency range of the electromagnetic wave may include regions other than the medium wave, the short wave, and the ultrashort wave.

For example, a frequency (the settable frequency range) of the electromagnetic wave which can be irradiated from the electromagnetic wave irradiation device300may include a frequency of at least one of frequency bands including an micro wave (300 MHz to 3 GHz), a centimetric wave (3 to 30 GHz), a millimetric wave (30 to 300 GHz), and a submillimetric wave (300 GHz to 3 THz). More preferably, a frequency of the electromagnetic wave which can be irradiated from the electromagnetic wave irradiation device300may include a frequency of at least one of the frequency bands including the micro wave (300 MHz to 3 GHz) and the centimetric wave (3 to 30 GHz). Note that, in a case where the electromagnetic wave irradiation device irradiates the electromagnetic wave of at least one of the frequencies in the micro wave (300 MHz to 3 GHz), the centimetric wave (3 to 30 GHz), the millimetric wave (30 to 300 GHz), and the submillimetric wave (300 GHz to 3THz), the electromagnetic wave irradiation device may irradiate the cooling target object M with an electromagnetic wave generated in a microwave generation device (magnetron), such as a microwave oven.

Furthermore, a frequency of the electromagnetic wave which can be irradiated from the electromagnetic wave irradiation device300may include frequencies which are out of the frequency bands described above and which realize cooling of the cooling target object M in the subcooling state.(5-2) Modification B

Although the cooling target object temperature sensor500measures a surface temperature of the cooling target object M in the foregoing embodiment, the cooling target object temperature sensor500is not limited to this and may measure a temperature of an inner portion of the cooling target object M. For example, the cooling target object temperature sensor500may be an optical fiber temperature sensor which measures a temperature of an inner portion of the cooling target object M by inserting an optical fiber probe.(5-3) Modification C

In the foregoing embodiment, when the temperature of the cooling target object M falls to the second temperature T2, the irradiation with the electromagnetic wave performed by the electromagnetic wave irradiation device300is stopped, and thereafter, the normal cooling operation is performed to freeze the cooling target object M, but the present invention is not limited to this. For example, the cooling apparatus100may continue the irradiation with the electromagnetic wave performed by the electromagnetic wave irradiation device300irrespective of a temperature of the cooling target object M so that the cooling target object M is maintained in the subcooling state.(5-4) Modification D

In the foregoing embodiment, the output of the electromagnetic wave is controlled by increasing or reducing the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300by the fixed amount (ΔS) in the subcooling operation, but the present invention is not limited to this.

For example, an amount of the control of the output of the electromagnetic wave in the subcooling operation may not be constant every time. Furthermore, an adjusting amount of the output when the output of the electromagnetic wave is increased in the subcooling operation and the adjusting amount of the output when the output of the electromagnetic wave is reduced in the subcooling operation may be different from each other.(5-5) Modification E

In the foregoing embodiment, the cooling apparatus100is operated such that the normal cooling operation is performed after the preliminary operation, and thereafter, the subcooling operation is performed, but the present invention is not limited to this. For example, the cooling apparatus100may execute the subcooling operation immediately after the preliminary operation. However, in terms of energy saving, it is preferable that the electromagnetic wave irradiation device300does not irradiate the electromagnetic wave when the temperature of the cooling target object M does not cause the freezing of the cooling target object M.(5-6) Modification F

In the foregoing embodiment, the refrigeration machine200is not operated in the preliminary operation, but the present invention is not limited to this. For example, the preliminary operation may be performed while the refrigeration machine200is operated so that quality of the cooling target object M is prevented from being deteriorated due to increase in temperature of the cooling target object M and reduction in temperature of the cooling target object M is realized in a short time.

Note that, in this case, the refrigeration machine200is preferably operated in constant cooling capacity in the preliminary operation. The subcooling operation frequency determination unit410preferably determines a frequency in which an increase rate in temperature of the cooling target object M is largest at a time of irradiation with the electromagnetic wave in each of various frequencies as the subcooling operation frequency f1. If temperature of the cooling target object M falls at the time of the irradiation with the electromagnetic wave in all of the various frequencies, the subcooling operation frequency determination unit410preferably determines a frequency in which a reduction rate in temperature is smallest at the time of the irradiation with the electromagnetic wave in each of the various frequencies as the subcooling operation frequency f1.(5-7) Modification G

Although the subcooling operation frequency f1is determined in accordance with the temperature of the cooling target object M in the preliminary operation in the foregoing embodiment, the present invention is not limited to this. For example, the subcooling operation frequency determination unit410may monitor a change in temperature of the cooling space110awhen the cooling target object M is irradiated with an electromagnetic wave and determine a frequency of the electromagnetic wave corresponding to the maximum increase in temperature as the subcooling operation frequency f1.(5-8) Modification H

Although both the preliminary operation and the subcooling operation are performed in the same casing110in the foregoing embodiment, the present invention is not limited to this. For example, the preliminary operation may be executed in another casing, and thereafter, the cooling target object M may be transported by a conveyer or the like into the casing110from that casing so that the normal cooling operation and the subcooling operation are performed in the casing110. In this case, the cooling apparatus100may include a plurality of electromagnetic wave irradiation devices and a plurality of cooling target object temperature sensors and different electromagnetic wave irradiation devices and different cooling target object temperature sensors may be used in the preliminary operation and the subcooling operation.

Note that the cooling apparatus100, for example, may include a plurality of electromagnetic wave irradiation devices and use different electromagnetic irradiation devices in the preliminary operation and the subcooling operation, even when the preliminary operation and the subcooling operation are performed in the same casing110.(5-9) Modification I

Although the electromagnetic wave irradiation device300of the foregoing embodiment performs the irradiation with the electromagnetic wave of frequencies within the settable frequency range using a single high frequency power source320, the present invention is not limited to this. For example, the electromagnetic wave irradiation device300may include a plurality of high frequency power sources320and use the different high frequency power source according to the frequency of the irradiated electromagnetic wave.(5-10) Modification J

The controller400of the foregoing embodiment may not be an independent device. For example, the refrigeration machine controller290of the refrigeration machine200may perform control similarly to the controller400.(5-11) Modification K

Although the electromagnetic wave output/freezing capacity controller420increases the freezing capacity of the refrigeration machine200or reduces the output S of the electromagnetic wave when it is determined that the heat amount of internal heat generation of the cooling target object M caused by irradiation with the electromagnetic wave is larger than the cooling capacity of the refrigeration machine200in the foregoing embodiment, the present invention is not limited to this.

For example, the electromagnetic wave output/freezing capacity controller420may increase the freezing capacity of the refrigeration machine200or reduce the output S of the electromagnetic wave when it is determined that the heat amount of internal heat generation of the cooling target object M caused by irradiation with the electromagnetic wave is relatively large compared to the cooling capacity of the refrigeration machine200. Specifically, the electromagnetic wave output/freezing capacity controller420may also increase the freezing capacity of the refrigeration machine200or reduce the output S of the electromagnetic wave when the temperature reduction rate of the cooling target object M is lower than a predetermined value.(5-12) Modification L

In the foregoing embodiment, the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is variable. Although the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300is preferably variable, the output of the electromagnetic wave irradiated from the electromagnetic wave irradiation device300may not be variable.

In this case, the cooling apparatus100may monitor whether or not the amount of internal heat generation of the cooling target object M generated by irradiation with the electromagnetic wave excesses the cooling capacity of the refrigeration machine200(the cooling apparatus100may control the refrigeration machine200such that the cooling capacity of the refrigeration machine200is increased when the amount of internal heat generation exceeds the cooling capacity) and the electromagnetic wave irradiation device300may stop irradiation with the electromagnetic wave when the temperature of the cooling target object M becomes lower than the second temperature T2.

INDUSTRIAL APPLICABILITY

The present invention is widely adaptable to cooling apparatuses which cool a cooling target object in a subcooling zone by irradiating the cooling target object with an electromagnetic wave.

REFERENCE SIGNS LIST

300Electromagnetic Wave Irradiation Device

M Cooling target object

CITATION LIST

Patent Literature