Vacuum microwave thawing machine

Abstract

In a vacuum microwave thawing machine, the thawed state of the object being thawed is stabilized at the end of the process without increasing the thawing time. [Solution] The control device 60 is configured to use, in defrosting control, the vacuum level sensor 58 is located between the vacuum pump 30 and the defrosting chamber R1, and in defrosting control, the control device 60 is located in a piping 37 that connects the vacuum pump 30 and the defrosting chamber R1, and switches between a connected state and a disconnected state. The control device 60 is located between the vacuum pump 30 and the piping 37 and the piping 37 and detects the vacuum level, which is the internal pressure inside the defrosting chamber R1, when the piping 37 is connected. The control device 60 is configured to use, in defrosting control, the vacuum level detected by the piping 37 in the connected state, as well as the pressure value detected by the piping 60 in the disconnected state.

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 under reduced pressure (or vacuum) conditions 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 its cells while suppressing temperature unevenness between the surface and the core by repeatedly performing heating with microwaves and sublimation cooling under reduced pressure. The vacuum microwave thawing machine described in Patent Document 1 below detects the vacuum pressure (degree of vacuum) inside the chamber (thawing chamber), and is configured to determine that thawing is complete when the degree of vacuum, which is at equilibrium during the depressurization process, reaches a target value. [Prior art documents] [Patent Documents]

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

[0004] In the vacuum microwave thawing machine described in Patent Document 1, etc., the vacuum pump's capacity is unstable for a while immediately after starting operation, and the vacuum level at which equilibrium is reached may vary due to the pressure increase caused by the evaporation of moisture from the object being thawed. This variation can lead to variations in the thawed state of the object at the end of the process, even if the target value is the same. While it is possible to suppress this variation by pre-warming up the vacuum pump, the thawing time will also be increased by the amount of time spent warming up.

[0005] This invention has been made in view of such circumstances, and aims to stabilize the thawed state of the object being thawed at the end of the process in a vacuum microwave thawing machine without increasing the thawing 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, A valve is provided in the piping connecting the vacuum pump and the thawing chamber, and switches between a connected state where the vacuum pump and the thawing chamber are in communication and a disconnected state where they are disconnected. A vacuum sensor is provided between the vacuum pump and the on-off valve in the piping, and detects the vacuum level, which is the internal pressure inside the thawing chamber, when the on-off valve is in the communication state. Furthermore, The control device is The depressurization process involves alternately performing a depressurization step, in which the internal pressure of the thawing chamber is reduced by the vacuum pump, and a repressurization step, in which the internal pressure of the thawing chamber is restored by the pressure regulating valve while the vacuum pump is operating, while simultaneously irradiating the chamber with microwaves from the microwave generator at intervals. This repeatedly performs microwave heating and sublimation cooling in a reduced pressure state, and the thawing control is performed by repeatedly carrying out this thawing cycle consisting of microwave heating and sublimation cooling to thaw the object to be thawed. A vacuum microwave thawing machine characterized in that, in the thawing control, in addition to the vacuum level detected by the vacuum level sensor in the communication state, a pressure value detected by the vacuum level sensor in the disconnected state is used.

[0007] In vacuum microwave thawing machines, the vacuum level sensor (pressure sensor) is generally installed directly in the thawing chamber. In contrast, the vacuum microwave thawing machine disclosed in this application has an on-off valve and a vacuum level sensor installed in the middle of the piping connecting the vacuum pump and the thawing chamber, and the vacuum level sensor makes it possible to detect the pressure inside the piping when it is isolated from the thawing chamber. In the depressurization process, when the internal pressure of the thawing chamber reaches an equilibrium state, the internal pressure at that equilibrium state (equilibrium vacuum level) is determined by the balance between the capacity of the vacuum pump and the pressure increase due to the evaporation of moisture from the thawed material. Therefore, if there is variation in the capacity of the vacuum pump, for example, if the vacuum pump has not been warmed up, it will cause variation in the equilibrium vacuum level, which in turn will lead to variation in the thawed state of the material at the end of the thawing process. In the vacuum microwave thawing machine disclosed herein, for example, even after the system is shut off by an on / off valve after reaching an equilibrium state, the pressure inside the piping is reduced by the vacuum pump. However, the pressure difference from the time the system is shut off until the piping reaches an equilibrium state can detect the pressure increase due to the evaporation of water from the object being thawed, and the thawing state can be accurately determined by the magnitude of this pressure increase. Therefore, the vacuum microwave thawing machine disclosed herein can stabilize the thawing state of the object being thawed at the end of the process without being affected by variations in the performance of the vacuum pump.

[0008] Furthermore, the vacuum microwave thawing machine with the above configuration can be configured in various ways as shown below.

[0009] (2) The depressurization step involves reducing the vacuum level, which is the internal pressure of the thawing chamber, until it reaches an equilibrium state. The vacuum microwave thawing machine according to item (1), wherein the control device, after reaching the equilibrium state in the depressurization process, is shut off by the on / off valve, and the change in pressure from the equilibrium vacuum, which is the vacuum level in the equilibrium state detected by the vacuum level sensor, is used for the thawing control.

[0010] (3) The control device performs a thawing state estimation step of estimating the thawing state of the object to be thawed based on the amount of pressure drop detected by the vacuum sensor during a set time after setting the shut-off state, for the vacuum microwave thawing machine according to item (2).

[0011] (4) In the thawing state estimation step, when the amount of drop becomes equal to or greater than a set value, it is determined that the thawing of the object to be thawed has ended or will end soon, for the vacuum microwave thawing machine according to item (3).

[0012] (5) After the end of the thawing state estimation step, the control device causes a transition to the repressurization step, for the vacuum microwave thawing machine according to item (3) or (4).

Advantages of the Invention

[0013] According to the present invention, in a vacuum microwave thawing machine, it is possible to stabilize the thawing state at the end of the object to be thawed without increasing the thawing time.

Brief Description of the Drawings

[0014] [Figure 1] Perspective view of the vacuum microwave thawing machine of the embodiment [Figure 2] Side cross-sectional view of the vacuum microwave thawing machine [Figure 3] Planar cross-sectional view of the vacuum microwave thawing machine [Figure 4] Front cross-sectional view of the vacuum microwave thawing machine [Figure 5] Schematic circuit diagram of the vacuum microwave thawing machine [Figure 6] Block diagram showing the functional configuration of the control device [Figure 7] Timing chart at the start of thawing control [Figure 8] Timing chart at the end of thawing control

Embodiments for Carrying Out the Invention

[0015] <Configuration of the 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 5. 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] In this embodiment, the vacuum microwave thawing machine 10, as shown in the schematic circuit diagram in Figure 5, has a line valve 56, which is an electromagnetic on / off valve, installed in the piping 37 connecting the vacuum pump 30 and the thawing chamber R1. This line valve 56 allows switching between a connected state and a disconnected state between the vacuum pump 30 and the thawing chamber R1. A vacuum level sensor 58 is also installed in the piping 37 between the line valve 56 and the vacuum pump 30 to detect the vacuum level, which is the internal pressure of the thawing chamber R1. When the line valve 56 is in a connected state, the vacuum level sensor 58 can detect the vacuum level of the thawing chamber R1. On the other hand, when the line valve 56 is in a disconnected state, the vacuum level sensor 58 is not connected to the thawing chamber R1 and detects the pressure inside the piping 37 which is reduced in pressure by the vacuum pump 30.

[0024] The control box 36 houses a control device 60 (see Figure 6), 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, line valve 56, vacuum level sensor 58, etc. By executing various programs stored in the ROM, the connected equipment is controlled.

[0025] 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. An operating unit 70 is provided on the front panel 13, and this operating unit 70 is also connected to the control device 60. The operating unit 70 mainly consists of an operation board located 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.

[0026] <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 7 and 8. 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, and the line valve 56 is normally open and is in the open state.

[0027] 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 58 is the 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.

[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 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, so that the amount of irradiation power increases continuously as the weight of the object being thawed increases. Specifically, 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 set to a value where 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 7 and 8). BThe 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] Once the depressurization process begins and the depressurization heating time T3 has elapsed, the magnetron 34 is shut down, and the three stirrers 50, 52, and 54 are also shut down. This depressurization process is carried out until the vacuum 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 during the thawing cycle is confirmed based on the detection results of the vacuum sensor 58. Specifically, the current measurement value is compared with the previous measurement value for a set time within the depressurization process, and the depressurization process is terminated if the difference remains smaller than the set value. In other words, one thawing cycle consisting of microwave heating and sublimation cooling is completed.

[0033] 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. Conventional vacuum microwave thawing machines use this equilibrium vacuum level P. k However, once the target vacuum level was reached, the system determined that the temperature of the object being thawed had reached the target temperature and terminated the thawing control. However, this equilibrium vacuum level P k The equilibrium vacuum P is determined by the balance between the capacity of the vacuum pump 30 and the pressure increase due to the evaporation of moisture from the thawed material. Therefore, if there is variation in the capacity of the vacuum pump 30, for example, if the vacuum pump 30 has not been warmed up, the equilibrium vacuum P will be affected. k This results in variations, which in turn leads to variations in the thawed state of the thawed material at the end of the process.

[0034] Therefore, in this embodiment, the vacuum microwave thawing machine 10 is configured to perform a thawing state estimation process to estimate the thawing state of the object to be thawed after the completion of the thawing cycle, or more specifically, after the internal pressure in the thawing chamber R1 has reached equilibrium during the depressurization process. In the thawing state estimation process, first, as shown in Figures 7 and 8, the line valve 56 is closed, thereby shutting off the thawing chamber R1 and the vacuum pump 30. This shut-off state is maintained for a set time T4 (60 seconds in this embodiment).

[0035] During this time, the vacuum pump 30 continues to operate, and the portion of the piping 37 on the side of the line valve 56 to the vacuum pump 30 is depressurized. Then, during the set time T4, it approaches a vacuum state and reaches equilibrium. In other words, the amount of pressure drop ΔP detected by the vacuum sensor 58 during this set time T4 corresponds to the pressure increase (saturated vapor pressure) due to the evaporation of water from the thawed material. Therefore, the larger this saturated vapor pressure ΔP is, the more thawing is progressing, and the detected saturated vapor pressure ΔP should be equal to the target value ΔP. 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, since the vacuum sensor 58 is affected by ambient temperature, temperature correction is necessary. Also, in the manufacturing process of the vacuum microwave thawing machine 10 of this embodiment, it is necessary to calibrate the vacuum sensor 58 by comparing it with a reference pressure gauge after it has been installed. Unlike conventional vacuum microwave thawing machines, the thawing completion pressure is not measured as an absolute value (equilibrium vacuum P k) If we try to make a judgment based on this, it is necessary to measure minute pressures with very high precision, and high precision is also required for correction and calibration. Since the vacuum microwave thawing machine 10 of the present embodiment makes a judgment based on the pressure decrease amount ΔP, it is hardly affected even if there are deviations in temperature correction or deviations in the reference pressure gauge, and the thawing state can be accurately estimated. Incidentally, at the time of factory shipment, calibration of the vacuum sensor can be surely performed using a reference pressure gauge. However, for example, when the vacuum sensor is replaced after being shipped to the market, it may be difficult to perform strict calibration using a reference pressure gauge. Even when such strict calibration cannot be performed, since the vacuum microwave thawing machine 10 of the present embodiment makes a judgment based on the pressure decrease amount ΔP, the thawing state can be accurately estimated.

[0037] In the thawing state estimation step, it is not determined whether the saturated vapor pressure ΔP has reached the target value ΔP O Rather, it is determined whether the saturated vapor pressure ΔP has reached a first threshold value ΔP1 set to a value smaller than the target value. This first threshold value ΔP1 is set to a value corresponding to whether sublimation cooling is not necessary and thawing can be completed only by microwave heating to some extent at the end of the thawing cycle. When the saturated vapor pressure ΔP is smaller than the first threshold value ΔP1, the thawing cycle continues. Specifically, the line valve 56 is closed, the pressure regulating valve 32 is opened at a predetermined opening degree, and the pressure recovery step is started. On the other hand, when the saturated vapor pressure ΔP becomes equal to or higher than the first threshold value ΔP1, it is determined that sublimation cooling is not necessary, and the final thawing process described below is performed.

[0038] Incidentally, as shown in Figure 7, the thawing state estimation process is performed even after the aforementioned thawing preparation process is completed. This is because, for example, thawing control may be started for an object that has been partially thawed, and even in such cases, it is determined whether to proceed with the normal thawing cycle, the final thawing process described above, or whether thawing control is necessary. In other words, if the thawing state estimation process is not performed, the thawing cycle will always be executed, which may lead to overheating of the object that has been partially thawed. However, with the vacuum microwave thawing machine 10 of this embodiment, it is possible to avoid situations where overheating occurs.

[0039] (3) Final thawing process The final thawing process involves adjusting the microwave heating time according to the magnitude of the saturated vapor pressure ΔP. In this embodiment, the saturated vapor pressure ΔP is set to a second threshold ΔP2 (target value ΔP O If the saturated vapor pressure ΔP is less than the midpoint between the first threshold ΔP1, microwave irradiation will be performed for the irradiation time (=T2+T3) explained earlier. If the saturated vapor pressure ΔP is greater than or equal to the second threshold ΔP2, microwave irradiation will be performed for half the irradiation time (=(T2+T3) / 2). Note that if the saturated vapor pressure ΔP is less than the target value ΔP O If the process reaches this point, the termination process described below will be performed.

[0040] (4) Termination process Once the irradiation time for the final thawing process described above 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. This means that the door 12 can be opened, and the thawed material can be removed.

[0041] <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 6 and has various functional parts. More specifically, the control device 60 includes a defrosting control execution unit 80 that performs the above-mentioned defrosting control. The defrosting control execution unit 80 is composed of a defrosting preparation processing unit 82 that performs the aforementioned defrosting preparation processing, 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 defrosting state estimation processing unit 90 that estimates the defrosting state of the object to be defrosted. The defrosting state estimation processing unit 90 uses the pressure value detected by the vacuum sensor 58 when the line valve 56 is shut off, and estimates the defrosting state of the object to be defrosted based on the amount of pressure drop after the shut-off state.

[0042] <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.

[0043] In the above embodiment, the thawing state estimation step was to detect the amount of pressure decrease during the set time T4. However, for example, it may be determined that an equilibrium state has been reached when the detected rate of change in pressure becomes smaller than a threshold, and the thawing state of the object to be thawed may be estimated based on the amount of pressure decrease from the time the cutoff state was established until that point.

[0044] In the above embodiment, the system was configured to determine whether the thawing of the object being thawed was complete or about to be completed based on the amount of pressure drop in the shut-off state. However, it is also possible to configure the system to estimate the remaining thawing time based on the magnitude of the pressure drop. [Explanation of symbols]

[0045] 10... Vacuum microwave thawing machine, R1... Thawing chamber, 30... Vacuum pump (pressure reducer), 32... First regulating valve (pressure regulating valve), 33... Second regulating valve (atmospheric pressure release valve), 34... Magnetron (microwave generator), 56... Line valve, 58... Vacuum level sensor, 60... Control device, P... Vacuum level, P k …Equilibrium vacuum degree, ΔP…Saturated vapor pressure

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, A valve is provided in the piping connecting the vacuum pump and the thawing chamber, and switches between a connected state where the vacuum pump and the thawing chamber are in communication and a disconnected state where they are disconnected. A vacuum sensor is provided between the vacuum pump and the on-off valve in the piping, and detects the vacuum level, which is the internal pressure inside the thawing chamber, when the on-off valve is in the communication state. Furthermore, The control device is The depressurization process involves alternately performing a depressurization step, in which the internal pressure of the thawing chamber is reduced by the vacuum pump, and a repressurization step, in which the internal pressure of the thawing chamber is restored by the pressure regulating valve while the vacuum pump is operating, while simultaneously irradiating the chamber with microwaves from the microwave generator at intervals. This repeatedly performs microwave heating and sublimation cooling in a reduced pressure state, and the thawing control is performed by repeatedly carrying out this thawing cycle consisting of microwave heating and sublimation cooling to thaw the object to be thawed. A vacuum microwave thawing machine characterized in that, in the thawing control, in addition to the vacuum level detected by the vacuum level sensor in the communication state, a pressure value detected by the vacuum level sensor in the disconnected state is used.

2. The aforementioned depressurization step involves reducing the vacuum level, which is the internal pressure of the thawing chamber, until it reaches an equilibrium state. The vacuum microwave thawing machine according to claim 1, wherein the control device, after reaching the equilibrium state in the depressurization process, is shut off by the on / off valve, and the change in pressure from the equilibrium vacuum, which is the vacuum level in the equilibrium state detected by the vacuum level sensor, is used for the thawing control.

3. The vacuum microwave thawing machine according to claim 2, wherein the control device performs a thawing state estimation step of estimating the thawing state of the object to be thawed based on the amount of pressure decrease detected by the vacuum sensor during a set time after the shutdown state is established.

4. The vacuum microwave thawing machine according to claim 3, wherein the thawing state estimation step determines that the thawing of the object to be thawed has been completed or will be completed soon when the amount of decrease exceeds a set value.

5. The vacuum microwave thawing machine according to claim 3 or 4, wherein the control device moves to the repressurization step after the completion of the thawing state estimation step.

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