Vacuum microwave thawing machine

Abstract

In a vacuum microwave thawing machine with a configuration that adjusts the microwave irradiation time, the generation of vacuum discharge is suppressed. [Solution] The heating time during repressurization T2 and the heating time during depressurization T3 are set according to the weight of the object to be thawed. The heating time during depressurization T3 is set to the upper limit of the range in which vacuum discharge does not occur or to a time slightly shorter than the upper limit. The heating time during repressurization T2 is set considering the amount of irradiation power during the depressurization heating process so that the amount of irradiation power to the object to be thawed in one thawing cycle is obtained.

Description

[Technical Field]

[0001] This invention relates to a vacuum microwave thawing machine. [Background technology]

[0002] Vacuum microwave thawing machines have been known for thawing objects by irradiating them with microwaves in a reduced pressure state (or vacuum state) lower than atmospheric pressure. One example of such a machine is described in Patent Document 1 below. Vacuum microwave thawing machines can thaw food without damaging the cells of the food while suppressing temperature unevenness between the surface and the core by repeatedly performing heating with microwaves and sublimation cooling in a reduced pressure state. In a vacuum microwave thawing machine, the lower the pressure (vacuum level) in the thawing chamber, the more likely vacuum discharge will occur due to microwave irradiation. If a vacuum discharge occurs, for example, a protective device will activate and stop the thawing operation. Therefore, the vacuum microwave thawing machine described in Patent Document 1 below is configured to start microwave irradiation after the vacuum level reaches a lower limit that does not cause vacuum discharge in the repressurization process, and to continue microwave irradiation until just before the vacuum level reaches a lower limit that does not cause vacuum discharge after moving to the depressurization process. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 3662530 [Overview of the project] [Problems that the invention aims to solve]

[0004] The vacuum microwave thawing machine described in Patent Document 1 above was designed to adjust the timing of the start and stop of microwave irradiation based on the degree of vacuum. In contrast, there are also vacuum microwave thawing machines that adjust the microwave irradiation time, for example, considering the simplification of control. Even in vacuum microwave thawing machines with such a configuration, it is desirable to prevent vacuum discharge.

[0005] This invention has been made in view of such circumstances, and aims to suppress the generation of vacuum discharge in a vacuum microwave thawing machine configured to adjust the microwave irradiation time. [Means for solving the problem]

[0006] To solve the above problems, the vacuum microwave thawing machine disclosed in this application has the following structure. (1) A vacuum microwave thawing machine comprising: a thawing chamber for containing an object to be thawed; a vacuum pump for reducing the pressure inside the thawing chamber; a pressure regulating valve for restoring the pressure inside the thawing chamber; a microwave generator for generating microwaves to irradiate the thawing chamber; and a control device for controlling the vacuum microwave thawing machine, The control device performs a depressurization process to defrost the object to be thawed by repeatedly performing a depressurization process, in which the vacuum pressure inside the thawing chamber is reduced to an equilibrium state using the vacuum pump, and a repressurization process, in which the vacuum pressure at the equilibrium state is restored to an upper limit using the pressure regulating valve, while irradiating with microwaves from the microwave generator at intervals, thereby repeatedly performing a thawing cycle consisting of heating by microwaves and sublimation cooling in a reduced pressure state. The microwave heating step in the thawing cycle includes a heating step during pressurization in which microwaves are irradiated after transitioning to the pressurization step, and a heating step during depressurization in which microwaves are irradiated continuously from the heating step during pressurization after transitioning from the pressurization step to the depressurization step. The thawing control is configured to set a heating time during recompression, which is the time for performing the heating process during recompression, and a heating time during decompression, which is the time for performing the heating process during decompression, according to the weight of the object to be thawed. The heating time during decompression is set to the upper limit value within the range where vacuum discharge does not occur or a time slightly shorter than the upper limit value, and the heating time during recompression is set so that the amount of irradiation power to the object to be thawed in one thawing cycle can be obtained in consideration of the amount of irradiation power in the heating process during decompression. A vacuum microwave thawing machine characterized by this.

[0007] The vacuum microwave thawing machine disclosed in the present application assumes a configuration in which, in the microwave heating process, the time for performing the heating process during recompression and the time for performing the heating process during decompression can be adjusted according to the weight of the object to be thawed. In the heating process during decompression, as the pressure (vacuum degree) in the thawing chamber decreases, vacuum discharge due to microwave irradiation becomes more likely to occur. However, the vacuum microwave thawing machine disclosed in the present application sets the heating time during decompression as short as possible and the heating time during recompression as long as possible, so that the occurrence of vacuum discharge can be suppressed. However, if the heating time during decompression is made too short, the recompression process will become long, the thawing cycle will become long, and ultimately, the time until the object to be thawed is thawed will become long. On the other hand, the vacuum microwave thawing machine disclosed in the present application can shorten the thawing time of the object to be thawed while suppressing the occurrence of vacuum discharge in order to ensure the maximum heating time during decompression.

[0008] Also, in the vacuum microwave thawing machine having the above configuration, it is possible to adopt various modes shown below.

[0009] (2) The control device is configured to perform PWM control on the output of the microwave generator. The thawing control is configured to be able to change the duty ratio in the PWM control with respect to the weight of the object to be thawed. The vacuum microwave thawing machine according to item (1), wherein the duty cycle, the heating time during repressurization, and the heating time during depressurization are set according to the weight of the object to be thawed, such that the amount of irradiation power to the object to be thawed in one thawing cycle gradually increases as the weight of the object to be thawed increases, and the amount of irradiation power per unit weight of the object to be thawed in one thawing cycle gradually decreases as the weight of the object to be thawed increases.

[0010] (3) The vacuum microwave thawing machine according to item (2), wherein the heating time during depressurization is a constant time regardless of the weight of the object to be thawed, and the duty cycle and the heating time during repressurization are changed according to the weight of the object to be thawed.

[0011] (4) The vacuum microwave thawing machine according to item (2) or (3), wherein the thawing control is set such that the duty cycle increases in steps as the weight of the object to be thawed increases.

[0012] (5) The vacuum microwave thawing machine according to any one of items (1) to (4), wherein the heating time during depressurization is 1 / 3 or less of the heating time during restoration. [Effects of the Invention]

[0013] According to the present invention, in a vacuum microwave thawing machine configured to adjust the microwave irradiation time, the generation of vacuum discharge can be suppressed. [Brief explanation of the drawing]

[0014] [Figure 1] Perspective view of the vacuum microwave thawing machine according to the embodiment. [Figure 2] Side cross-sectional view of a vacuum microwave thawing machine [Figure 3] Planar cross-sectional view of a vacuum microwave thawing machine [Figure 4] Front cross-sectional view of a vacuum microwave thawing machine [Figure 5] Block diagram showing the functional configuration of the control unit. [Figure 6]Timing chart for when defrosting control starts [Figure 7] Timing chart at the end of defrosting control [Figure 8] This table shows an example of irradiation power and irradiation time set relative to the weight of the object to be thawed, as well as the amount of irradiation power and the amount of irradiation power per unit weight in one thawing cycle. [Figure 9] Graph showing the relationship between the amount of irradiation power per unit weight and the weight of the object being thawed. [Figure 10] Flowchart of the remaining time display switching program executed in the control device shown in Figure 5. [Modes for carrying out the invention]

[0015] <Configuration of a vacuum microwave thawing machine> The configuration of the vacuum microwave thawing machine 10, which is an embodiment of the present invention, will be described with reference to Figures 1 to 4. In this embodiment, the vacuum microwave thawing machine 10 heats the thawing chamber R1 with microwaves at time intervals while under reduced pressure. This repeatedly performs microwave heating and sublimation cooling under reduced pressure, suppressing temperature unevenness between the surface and the core, and enabling thawing without damaging the cells of the food. Note that in some parts of the drawings, the symbols F, B, L, R, U, and D are used to indicate direction, representing the front, back, left, right, top, and bottom sides, respectively, when the vacuum microwave thawing machine 10 is viewed from the front.

[0016] The vacuum microwave thawing machine 10 of this embodiment comprises a box-shaped thawing machine body 11 that is horizontally elongated and rectangular in shape and opens to the front, a door 12 that opens and closes a thawing chamber R1 located to the right of the thawing machine body, a front panel 13 that covers the front of the machine room R2 located to the left of the thawing machine body 11, and four casters 14 provided at the four corners on the bottom surface of the thawing machine body. The vacuum microwave thawing machine 10 of this embodiment has a top plate 15 located on the top surface of the thawing machine body 11 and is a table type that can be moved by the four casters 14.

[0017] The thawing machine body 11 is equipped with a chamber 20 on its right side. The chamber 20 is made of a metal such as stainless steel and is a roughly rectangular box-shaped body with a front opening 21. The door 12 closes the front opening 21 of the chamber 20, and the chamber 20 and the door 12 form a thawing chamber R1 inside. The door 12 is rotatable by a hinge 22 provided on the right end of the front side of the thawing machine body and can be opened to the right. By opening the door 12, the object to be thawed can be placed in or removed from the chamber 20, and the door 12 can be closed in a tight contact with the chamber 20 by a lever 12A provided on the door 12, thereby creating a sealed space in the thawing chamber R1.

[0018] The chamber 20 is provided with shelf supports 25 for accommodating trays 24 on which the items to be thawed are placed. The shelf supports 25 are arranged in pairs, left and right, and are provided on the side walls on both sides of the chamber 20. Multiple shelf supports 25 (four pairs in this embodiment) are provided, spaced apart in the vertical direction. As a result, multiple levels (four levels) of trays 24 can be accommodated in the chamber 20 along the vertical direction.

[0019] As shown in Figures 3 and 4, the vacuum microwave thawing machine 10 of this embodiment includes a vacuum pump (pressure reducer) 30 for reducing the pressure inside the chamber 20 (thawing chamber R1), a first control valve 32 and a second control valve 33 for increasing the pressure inside the chamber 20, a magnetron 34 (microwave generator) for generating microwaves, an inverter 35 for controlling the output of the magnetron 34, and a control box 36 for housing control boards and the like. These vacuum pump 30, first control valve 32, second control valve 33, magnetron 34, inverter 35, and control box 36 are located in the machine room R2.

[0020] As shown in Figure 4, the vacuum pump 30 is connected to the ceiling of the chamber 20 by piping 37, and sucks air from inside the chamber 20 through piping 37 to reduce the pressure in the thawing chamber R1. On the other hand, the first control valve 32 and the second control valve 33 increase the pressure in the thawing chamber R1 by allowing outside air to flow into the chamber 20. As shown in Figures 3 and 4, the first control valve 32 and the second control valve 33 are connected to piping 38 that extends from the left wall of the chamber 20. Piping 38 is branched, and the first control valve 32 and the second control valve 33 are connected to the ends of each branch. Both the first control valve 32 and the second control valve 33 are solenoid valves, but the first control valve 32 can adjust the flow rate, while the second control valve 33 switches between open and closed. The first control valve 32 is a pressure regulating valve used to restore the pressure in the thawing chamber R1 to a predetermined level during thawing, and the second control valve 33 is an atmospheric release valve used to rapidly introduce outside air into the thawing chamber R1 after thawing is complete, thereby returning the pressure in the thawing chamber R1 to atmospheric pressure. Hereinafter, the first control valve 32 will be referred to as the pressure regulating valve 32, and the second control valve 33 will be referred to as the atmospheric release valve 33.

[0021] The magnetron 34 is located at the rear left of the chamber 20. The magnetron 34 emits microwaves into a metal waveguide 40. The waveguide 40 extends horizontally at the rear of the chamber 20, and its tip is connected to the rear wall of the chamber 20. An irradiation port 42 is formed approximately in the center of the rear wall of the chamber 20, and microwaves propagating through the waveguide 40 are emitted into the chamber 20 from the irradiation port 42. The irradiation port 42 is covered by a lid 44 made of a material that transmits microwaves but blocks the passage of gas, such as glass. This lid 44 allows microwaves to be emitted from the irradiation port 42 into the thawing chamber R1 while the thawing chamber R1 is kept under vacuum.

[0022] The vacuum microwave thawing machine 10 of this embodiment is equipped with three stirrers 50, 52, and 54 for diffusing the microwaves emitted into the thawing chamber R1. The first stirrer 50 and the second stirrer 52 are positioned on the rear wall of the chamber 20, facing each other with the irradiation port 42 in between. The third stirrer 54 is provided on the ceiling wall.

[0023] The control box 36 houses a control device 60 (see Figure 5), which controls the vacuum microwave thawing machine 10 configured as described above. The control device 60 is primarily a computer with a CPU, ROM, and RAM, and is connected to the vacuum pump 30, pressure regulating valve 32, atmospheric release valve 33, magnetron 34 (more specifically, inverter 35), three stirrers 50, 52, and 54, etc. By executing various programs stored in the ROM, the connected equipment is controlled.

[0024] As shown in Figures 3 and 4, the machine room R2 is equipped with a magnetron fan 62 for cooling the magnetron 34 and an inverter fan 64 for cooling the inverter 35. Both the magnetron fan 62 (more specifically, the magnetron fan motor) and the inverter fan 64 (more specifically, the inverter fan motor) are connected to the control device 60. A vacuum sensor 66 for detecting the vacuum pressure inside the thawing chamber R1 is provided on the side wall of the chamber 20, as shown in Figure 3, and this vacuum sensor 66 is also connected to the control device 60. Furthermore, an operation unit 70 is provided on the front panel 13, and this operation unit 70 is also connected to the control device 60. The operation unit 70 mainly consists of an operation board provided on the rear side of the front panel 13, and includes a touch panel display device 72 and a start switch 74 connected to the operation board.

[0025] <Control of a vacuum microwave thawing machine (thawing control)> (1) Thawing preparation process The defrosting control performed by the control device 60 will be explained with reference to the timing charts in Figures 6 and 7. When the user places the tray 24 on which the object to be defrosted is placed inside the chamber 20, closes the door 12, and presses the defrosting start button displayed on the display device 72, the defrosting control begins. When the defrosting control begins, a defrosting preparation process is performed first. In the defrosting preparation process, the magnetron fan 62 and the inverter fan 64 are started, and the atmospheric release valve 33, which is normally open, is closed. Then, the vacuum pump 30 is activated to start depressurizing the defrosting chamber R1. The pressure regulating valve 32 is normally closed and is in the closed state.

[0026] The depressurization in this thawing preparation process is carried out until the vacuum level in the thawing chamber R1 converges to an equilibrium state. Specifically, in this embodiment, the vacuum level P detected by the vacuum level sensor 66 is set to a threshold P. A The vacuum level P is determined to reach equilibrium when the pressure is reduced from the point where it reaches 5.0 Torr (in this embodiment) until a set time T0 (160 sec in this embodiment) has elapsed, and the system then proceeds to the normal thawing cycle.

[0027] Furthermore, during the thawing preparation process, the thawing time is estimated from the weight of the object to be thawed. The weight of the object to be thawed can be input via the display device 72, and the thawing time is estimated based on the input weight. Generally, vacuum microwave thawers cannot estimate the remaining thawing time in minute increments. The remaining thawing time can only be estimated when the vacuum level P reaches equilibrium during the thawing cycle, which will be explained later, that is, when one thawing cycle is completed. Therefore, the estimated thawing time is approximate. Accordingly, in this embodiment, it is determined whether the thawing time is 60 minutes or less, 45 minutes or less, or 30 minutes or less. The vacuum microwave thawer 10 of this embodiment has a section on the display device 72 that displays the remaining thawing time, and during this thawing preparation, it displays "Predicting". When the thawing cycle starts, one of the following will be displayed, corresponding to the thawing time determined above: "60 minutes remaining", "45 minutes remaining", or "30 minutes remaining".

[0028] (2) Thawing cycle When the vacuum level P reaches equilibrium, the pressure regulating valve 32 is opened to a predetermined degree, and the repressurization process to restore the internal pressure of the thawing chamber R1 is started. At the same time, the three stirrers 50, 52, and 54 are also activated. When the vacuum level P is low (hereinafter referred to as low vacuum level P), there is a possibility of vacuum discharge occurring when microwaves are irradiated, so the magnetron 34 is set to start operating later than the start of the repressurization process. Specifically, after waiting for a waiting time T1 from the start of the repressurization process, the magnetron 34 is activated and microwaves are irradiated into the thawing chamber R1, and microwave heating of the object to be thawed begins.

[0029] The control device 60 performs PWM control on the magnetron 34 to adjust the irradiation power of the magnetron 34. Specifically, the irradiation power is adjusted by changing the output and duty cycle of the magnetron 34 according to the weight of the object being thawed. In the vacuum microwave thawing machine 10 of this embodiment, the settings are as shown in the table in Figure 8, and the output and duty cycle of the magnetron 34 are set to increase in steps as the weight increases, and the irradiation power is also set to increase in steps. Furthermore, the control device 60 also adjusts the amount of irradiation power in one thawing cycle by adjusting the microwave irradiation time according to the weight of the object being thawed, and is set so that the amount of irradiation power increases continuously as the weight of the object being thawed increases. Specifically, as shown in Figure 8, within the range where the output and duty cycle of the magnetron 34 are set to the same value, the irradiation time is set to increase as the weight of the object being thawed increases.

[0030] In the repressurization process, the vacuum level is such that the pressure-boosting capacity of the pressure-regulating valve 32 and the pressure-reducing capacity of the vacuum pump 30 are balanced (P in Figures 6 and 7). B The pressure will rise to (as specified). Then, after microwave irradiation for a predetermined time in this state, the pressure regulating valve 32 is closed, and the process moves to the depressurization step. Note that microwave irradiation continues even after moving to the depressurization step. However, since there is a risk of vacuum discharge occurring if the vacuum level decreases, the microwave irradiation time in the depressurization step is set so that microwave irradiation can be performed for the longest possible time without causing a vacuum discharge.

[0031] As described above, the microwave heating process, which involves heating with microwaves, includes a heating process during pressurization, in which microwaves are irradiated after transitioning to the pressurization process, and a heating process during depressurization, in which microwaves are irradiated continuously from the heating process during pressurization after transitioning from the pressurization process to the depressurization process. As previously mentioned, the total irradiation time, which is the sum of the heating time during pressurization (T2) and the heating time during depressurization (T3), is adjusted according to the weight of the object to be thawed. In this embodiment, the heating time during depressurization (T3) is set to a constant time (10 seconds in this embodiment) regardless of the weight of the object to be thawed. Taking this into consideration, the irradiation power (output and duty cycle of the magnetron 34) and the heating time during pressurization (T2) are set so that the amount of irradiation power increases with increasing weight of the object to be thawed. Therefore, in this embodiment, the vacuum microwave thawing machine 10 transitions to the depressurization process after the heating time during pressurization (T2) has elapsed since the start of microwave irradiation. Specifically, as the weight of the object being thawed increases, the repressurization heating time T2 is increased. However, to prevent this repressurization heating time T2 from becoming too long, the irradiation power (both the output and duty cycle of the magnetron 34) is set to increase in stages, as mentioned earlier.

[0032] On the other hand, as shown in the comparative examples in Figures 8 and 9, even if the irradiation power per thawing cycle is set to increase as the weight of the object to be thawed increases, the irradiation power per unit weight (1 kg) of the object to be thawed does not increase continuously between 1.7 kg and 1.8 kg, but tends to increase when the weight is between 1.8 kg and 2.1 kg. In this comparative example, there is a risk that the thawing time will be longer for smaller weights, or that vacuum discharge may occur due to the high irradiation power when the weight of the object to be thawed is between 1.8 kg and 2.1 kg.

[0033] In contrast, as shown in Figures 8 and 9, the vacuum microwave thawing machine 10 of this embodiment is set so that the amount of irradiation power per 1 kg of material to be thawed gradually decreases as the weight of the material to be thawed increases. This makes it possible to balance the thawing time with respect to the weight of the material to be thawed while suppressing vacuum discharge, thereby ensuring stable thawing quality.

[0034] Once the depressurization process begins and the depressurization heating time T3 has elapsed, the operation of the magnetron 34 is stopped, and the three stirrers 50, 52, and 54 are also stopped. This depressurization process is carried out until the vacuum level reaches equilibrium. After microwave irradiation ends during the depressurization process, the material to be thawed is cooled by sublimation. The equilibrium state of the vacuum level during the thawing cycle is confirmed based on the detection results of the vacuum sensor 66. Specifically, the current measurement value is compared with the previous measurement value for a set time within the depressurization process, and if the difference remains smaller than the set value, the depressurization process is terminated. In other words, one thawing cycle consisting of microwave heating and sublimation cooling is completed.

[0035] The thawing cycle is repeated, suppressing temperature variations between the surface and core of the object being thawed, and thawing without damaging the cells of the food. As the thawing cycle is repeated, the saturated vapor pressure in the thawing chamber R1 also increases with the rise in temperature of the object being thawed. Therefore, at the end of the depressurization process, or in other words, at the end of the thawing cycle, the equilibrium vacuum P k This will gradually increase. And, as shown in Figure 9, this equilibrium vacuum P k However, the target vacuum level P is the target vacuum level. O When this point is reached, the system determines that the temperature of the object being thawed has reached the target temperature and terminates the thawing control.

[0036] Furthermore, if it is determined that the vacuum level has reached equilibrium during the depressurization process and the thawing cycle has ended, a remaining time determination process (first remaining time estimation process) is performed. This remaining time determination process determines whether or not thawing can be completed in about two thawing cycles. In this embodiment, the target vacuum level PO and the target vacuum difference ΔP which is the difference from the equilibrium vacuum degree P of the current thawing cycle k is determined based on both the target vacuum difference ΔP O (=P O -P k ) and the difference in the equilibrium vacuum degree P of the current thawing cycle k and the equilibrium vacuum degree P of the previous current thawing cycle k-1 which is the difference in the previous vacuum degree ΔP k (=P k -P k-1 ). Specifically, when the target vacuum difference ΔP O is less than or equal to the first target difference threshold value ΔP O1 (1.0 Torr in this embodiment) and the difference in the previous vacuum degree ΔP k is greater than or equal to the previous difference threshold value ΔP k0 (0.10 Torr in this embodiment), it is determined that thawing can be completed in about 2 thawing cycles, and in the corresponding time, in this embodiment, it is estimated that the remaining thawing time is about 15 minutes. In this case, as shown in FIG. 7, "15 minutes remaining" is displayed on the display device 72.

[0037] Also, until it is determined that the remaining thawing time is 15 minutes by the above determination, the remaining thawing time is estimated according to the elapsed time since the start of the thawing control. That is, when the elapsed time is subtracted from the thawing time determined in the thawing preparation process and the result is 45 minutes or less, or 30 minutes or less, the display of the remaining time on the display device 72 is updated to "45 minutes remaining" or "30 minutes remaining".

[0038] (3) Final thawing process At the end of the thawing cycle, together with the remaining time determination, at the end of the thawing cycle, an end determination process (second remaining time estimation process) which is a determination process as to whether thawing can be completed only by a certain amount of microwave heating without sublimation cooling, that is, whether to execute the final thawing process, is also performed. This end determination process is based on whether the target vacuum difference ΔP O is less than or equal to the second target difference threshold value ΔP O2 ​​​​​​​​​​​(In this embodiment, it is determined by whether or not it is 0.40 Torr) or less, relative to the target vacuum level difference ΔP O The second target difference threshold ΔP O2 If the following conditions are met, it is determined that sublimation cooling is not necessary, and the final thawing process is performed.

[0039] The final thawing process is performed relative to the target vacuum level difference ΔP. O The microwave heating time is adjusted according to the magnitude of the vacuum. In this embodiment, the difference ΔP relative to the target vacuum is O The third target difference threshold ΔP O3 If the value is greater than (in this embodiment, 0.20 Torr), microwave irradiation is performed for the irradiation time (=T2+T3) shown in Figure 8, relative to the target vacuum level difference ΔP O The third target difference threshold ΔP O3 If the following conditions are met, microwave irradiation will be performed for half the irradiation time (=(T2+T3) / 2).

[0040] (4) Termination process Once the above irradiation time has elapsed, the termination process is performed. The termination process involves stopping the magnetron 34 and stirrs 50, 52, and 54, and opening the atmospheric release valve 33. Next, the vacuum pump 30 is also stopped, and the thawing control ends. In other words, the door 12 can be opened, and the object to be thawed can be removed. Incidentally, in the termination determination described above, the difference in vacuum degree relative to the target vacuum level ΔP O If the value becomes 0 or less, the termination process is performed without microwave irradiation.

[0041] Furthermore, when the final defrosting process is performed, the remaining time displayed on the display device 72 will change to "Finishing Soon," and the set time T will be displayed from the start of the termination process. E After 20 seconds (in this embodiment), the status will change to "Completed".

[0042] <Example of a control program> In the decompression control described above, the control to switch the display of the remaining decompression time on the display device 72 is performed, for example, by executing the remaining time display switching program shown in the flowchart in Figure 10. The decompression control program is executed repeatedly at predetermined time intervals. The remaining time display switching program will be described in detail below.

[0043] In the remaining time display switching program, first, in step 1 (which may be abbreviated as "S1" below; the same applies to other steps), it is determined whether or not the thawing cycle has not yet started. If it is before the start of the thawing cycle, that is, during the thawing preparation process, then in S2, it is determined whether or not P1 has been obtained whether or not it is the start of the thawing control or the time when the first depressurization has been completed. If P1 has not been obtained and it is the start of the thawing control, then in S3, "Predicting" is displayed on the display device 72. On the other hand, if P1 has been obtained, in S4, one of the following thawing times corresponding to the weight of the object to be thawed is displayed: "60 minutes remaining", "45 minutes remaining", or "30 minutes remaining".

[0044] In S1, if the defrosting cycle has started, in S5, it is determined whether or not the defrosting cycle has ended. If the defrosting cycle is still running, in S6, the elapsed time since the start of defrosting control is obtained, and in S7, one of the following is displayed depending on the time obtained by subtracting the elapsed time from the initially estimated defrosting time: '60 minutes remaining', '45 minutes remaining', or '30 minutes remaining'.

[0045] If S5 marks the end of the thawing cycle, then in S8, the aforementioned termination determination process, i.e., the difference ΔP relative to the target vacuum level, is performed. O The second target threshold ΔP O2 A determination is made as to whether or not the following is true: ΔP, the difference in vacuum relative to the target. O The second target threshold ΔP O2 If it is greater than the aforementioned remaining time determination process is performed. In other words, in S9, the difference ΔP relative to the target vacuum level is O The first target threshold ΔP O1 A determination is made as to whether or not the following is true, and in S10, the difference in vacuum level relative to the previous time ΔPk The threshold for the difference from the previous time is ΔP k0 A determination is made as to whether the above conditions are met. If neither of these conditions are met, then steps S6 and below are performed.

[0046] Furthermore, if both S9 and S10 are met, it is determined that the defrosting control will end after approximately two more defrosting cycles. In other words, in S11, "15 minutes remaining" is displayed on the display device 72.

[0047] On the other hand, in S8, the difference in vacuum degree relative to the target ΔP O The second target threshold ΔP O2 If the following is determined, it is determined that sublimation cooling is not necessary and that thawing control can be completed with only a certain amount of microwave heating, and the final thawing process and termination process are performed. If the final thawing process or termination process is being performed, in S12, the set time T is set from the start of the termination process. E A determination is made as to whether the set time T has elapsed. E If the specified time has not elapsed, in S13, the display device 72 will display "Completing Soon".

[0048] Furthermore, in S12, the set time T starts from the start of the termination process. E If the time elapses, in S14, the display device 72 will display "Complete". This completes the execution of the remaining time display switching program.

[0049] <Functional Configuration of Control Device> The control device 60 that performs the above-mentioned control has a functional configuration as shown in the block diagram in Figure 5 and has various functional parts. More specifically, the control device 60 includes a defrosting control execution unit 80 that performs the defrosting control described above. The defrosting control execution unit 80 is composed of a defrosting preparation processing unit 82 that performs the defrosting preparation processing described above, a defrosting cycle execution unit 84 that executes the defrosting cycle, a final defrosting processing unit 86 that performs the final defrosting processing, and a remaining time estimation unit 90 that estimates the remaining defrosting time and displays the remaining time on the display device 72.

[0050] The remaining time estimation unit 90 described above calculates the difference in vacuum degree ΔP relative to the target vacuum level. O and the difference in vacuum level compared to the previous time ΔP k As a first remaining time estimation process that estimates the remaining time based on both of the above, a remaining time determination processing unit (first remaining time estimation processing unit) 92 performs the aforementioned remaining time determination process, and the difference in vacuum degree relative to the target ΔP O Based on this, the system includes a termination determination processing unit (second remaining time estimation processing unit) 94 which performs the termination determination processing described above, as a second remaining time estimation process to estimate whether the remaining thawing time is less than or equal to the normal single microwave irradiation time. The remaining time determination processing unit 92 is configured to include a part that executes S9 to S11 of the remaining time display switching program, and the termination determination processing unit 94 is configured to include a part that executes S8 and S13 of the remaining time display switching program.

[0051] <Other Embodiments> The present invention is not limited to the embodiments described above, and can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. For example, the following embodiments are also included within the technical scope of the present invention.

[0052] In the above embodiment, the heating time T3 during reduced pressure was fixed at 10 seconds, but it is not limited to that time. Depending on the performance of the vacuum pump 30, magnetron 34, etc., it is desirable that the time be the upper limit of the range in which vacuum discharge does not occur, or slightly shorter than that upper limit.

[0053] In the above embodiment, the heating time T3 under reduced pressure was a fixed value, but it does not have to be a fixed value.

[0054] The table in Figure 8 is an example, and if the amount of irradiation power in one thawing cycle increases in proportion to the weight of the object to be thawed, and the amount of irradiation power per unit weight of the object to be thawed gradually decreases in proportion to the weight of the object to be thawed, then the same effects as in the above embodiment can be obtained. [Explanation of symbols]

[0055] 10... Vacuum microwave thawing machine, 30... Vacuum pump (pressure reducer), 32... First control valve (pressure regulating valve), 33... Second control valve (atmospheric release valve), 34... Magnetron (microwave generator), 35... Inverter, 60... Control device, 66... ​​Vacuum level sensor, 72... Display device, T2... Heating time during pressure restoration, T3... Heating time during depressurization, P... Vacuum level, P k ... Equilibrium vacuum degree, P O …Target vacuum level

Claims

1. A vacuum microwave thawing machine comprising: a thawing chamber for containing the object to be thawed; a vacuum pump for reducing the pressure inside the thawing chamber; a pressure regulating valve for restoring the pressure inside the thawing chamber; a microwave generator for generating microwaves to irradiate the thawing chamber; and a control device for controlling the vacuum microwave thawing machine, The control device performs a depressurization process to defrost the object to be thawed by repeatedly performing a depressurization process, in which the vacuum pressure inside the thawing chamber is reduced to an equilibrium state using the vacuum pump, and a repressurization process, in which the vacuum pressure at the equilibrium state is restored to an upper limit using the pressure regulating valve, while irradiating with microwaves from the microwave generator at intervals, thereby repeatedly performing a thawing cycle consisting of heating by microwaves and sublimation cooling in a reduced pressure state. The microwave heating step in the thawing cycle includes a heating step during pressurization in which microwaves are irradiated after transitioning to the pressurization step, and a heating step during depressurization in which microwaves are irradiated continuously from the heating step during pressurization after transitioning from the pressurization step to the depressurization step. The thawing control is configured to set a heating time during the repressurization process and a heating time during the depressurization process according to the weight of the object to be thawed, the heating time during depressurization being set to an upper limit or slightly shorter than the upper limit within the range where vacuum discharge does not occur, and the heating time during repressurization being set to obtain the amount of irradiation power to the object to be thawed in one thawing cycle, taking into consideration the amount of irradiation power during the depressurization heating process. This is a vacuum microwave thawing machine.

2. The control device is configured to perform PWM control on the output of the microwave generator. The aforementioned defrosting control is The duty cycle in the PWM control can be changed with respect to the weight of the object being thawed. The vacuum microwave thawing machine according to claim 1, wherein the duty cycle, the heating time during repressurization, and the heating time during depressurization are set according to the weight of the object to be thawed, such that the amount of irradiation power to the object to be thawed in one thawing cycle gradually increases as the weight of the object to be thawed increases, and the amount of irradiation power per unit weight of the object to be thawed in one thawing cycle gradually decreases as the weight of the object to be thawed increases.

3. The vacuum microwave thawing machine according to claim 2, wherein the heating time during depressurization is a constant time regardless of the weight of the object to be thawed, and the duty cycle and the heating time during repressurization are changed according to the weight of the object to be thawed.

4. The vacuum microwave thawing machine according to claim 2 or 3, wherein the thawing control is set so that the duty cycle increases in stages as the weight of the object to be thawed increases.

5. The vacuum microwave thawing machine according to any one of claims 1 to 3, wherein the heating time during depressurization is 1 / 3 or less of the heating time during restoration.

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