Vacuum microwave thawing machine

Abstract

This invention provides a vacuum microwave thawing machine that can suppress the occurrence of sparks within the thawing chamber. [Solution] The device comprises a metal chamber 20 having a thawing chamber R1 for containing the object to be thawed, a vacuum pump 30 for reducing the pressure inside the thawing chamber R1, a magnetron 34 for generating microwaves to irradiate the thawing chamber R1, a metal stirrer 50 disposed inside the thawing chamber R1 for diffusing the microwaves inside the thawing chamber R1, a shaft member 80 inserted through a through hole 22 formed in the rear side wall portion 20D of the chamber 20, a motor 62 for rotating the shaft member 80 with an axis along the longitudinal direction of the shaft member 80 as the pivot axis, and a fastening member 90 for attaching the stirrer 50 to one end 81 of the shaft member 80, wherein the shaft member 80 and the fastening member 90 are each made of synthetic resin.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a vacuum microwave thawing machine.

Background Art

[0002] Conventionally, a vacuum microwave thawing machine that irradiates a thawing object with microwaves in a thawing chamber under a reduced pressure lower than atmospheric pressure to thaw the thawing object is known, and an example thereof is described in Patent Document 1 below. The vacuum microwave thawing machine can thaw the thawing object (such as food ingredients) without destroying the cells of the thawing object while suppressing the temperature unevenness between the surface and the core by repeatedly performing heating by microwaves and sublimation cooling under a reduced pressure state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vacuum microwave thawing machine, microwaves are irradiated onto a thawing object in a thawing chamber under a reduced pressure state. Therefore, there is a concern about a situation where sparks are generated in the thawing chamber. If sparks are generated in the thawing chamber, the components arranged in the thawing chamber may be damaged.

[0005] The technology disclosed in this specification has been completed based on the above circumstances, and an object thereof is to provide a vacuum microwave thawing machine capable of suppressing a situation where sparks are generated in the thawing chamber.

Means for Solving the Problems

[0006] As a means to solve the above problems, the vacuum microwave thawing machine disclosed herein comprises a metal chamber having a thawing chamber for containing an object to be thawed; a depressurization device for reducing the pressure inside the thawing chamber; a microwave generator for generating microwaves to be irradiated into the thawing chamber; a metal stirrer disposed inside the thawing chamber for diffusing the microwaves inside the thawing chamber; a shaft member inserted through a through-hole formed in the wall of the chamber, with one end in the longitudinal direction disposed inside the thawing chamber and the other end in the longitudinal direction disposed outside the thawing chamber; a rotating device disposed outside the thawing chamber and connected to the other end, for rotating the shaft member with an axis along the longitudinal direction of the shaft member as the pivot axis; and a fastening member for attaching the stirrer to the one end of the shaft member, wherein the shaft member and the fastening member are each made of synthetic resin.

[0007] Furthermore, the shaft member comprises a shaft member body portion inserted through the through hole and one end portion provided on the end face of the shaft member body portion on the stirrer side, wherein the one end portion of the shaft member is inserted from the wall portion side into a stirrer-side through hole formed through the stirrer, and then inserted into a mounting hole formed in the fastening member, and a female screw portion is formed on the inner surface of the mounting hole which is screwed into a male screw portion formed on the outer circumferential surface of the one end portion, and the fastening member can be configured to clamp the stirr between itself and the end face. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vacuum microwave thawing machine that can suppress the occurrence of sparks in the thawing chamber. [Brief explanation of the drawing]

[0009] [Figure 1] Perspective view of the vacuum microwave thawing machine of Embodiment 1 [Figure 2] Side cross-sectional view of a vacuum microwave thawing machine (corresponding to the view taken along line II-II in Figure 3) [Figure 3]Planar cross-sectional view of a vacuum microwave thawing machine (corresponding to the view taken along line III-III in Figure 4) [Figure 4] Front cross-sectional view of a vacuum microwave thawing machine [Figure 5] A diagram showing the irradiation port and two stirrers located on the rear wall (corresponding to the diagram cut along the VV line in Figure 3). [Figure 6] Cross-sectional view showing the shaft member (corresponding to the view cut along the line VI-VI in Figure 5) [Figure 7] Cross-sectional view showing the shaft member of the comparative example. [Figure 8] Perspective view showing connecting member and photosensor [Figure 9] Diagram showing the positional relationship between the detection unit and the detected unit (stirrer in the first state). [Figure 10] Diagram showing the positional relationship between the detection unit and the detected unit (stirrer in second state) [Figure 11] This diagram shows the state where the detected part has rotated forward beyond the detection part 97A. [Figure 12] This diagram shows the state where the detected unit is located between detection units 96A and 97A. [Figure 13] Cross-sectional view showing the shaft member of Embodiment 2 [Figure 14] Cross-sectional view showing the shaft member of Embodiment 3 [Figure 15] Diagram showing the positional relationship between the detection unit and the detected unit in Embodiment 4 (stirrer in second state) [Figure 16] This diagram shows the state in which the detected unit 392 is detected by the detection unit 397A. [Figure 17] This diagram shows the positional relationship between the detection unit and the detected unit in Embodiment 5 (stirrer in the first state). [Figure 18] Diagram showing the positional relationship between the detection unit and the detected unit (stirrer in second state) [Figure 19] This diagram shows the state in which the detected units 491 and 492 are detected by the detection units 496A and 497A, respectively. [Modes for carrying out the invention]

[0010] <Embodiment 1> Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 12. The vacuum microwave thawing machine 10 of the present embodiment performs heating by microwave at intervals of time in a state where the inside of the thawing chamber R1 is depressurized, so that the heating by microwave and the sublimation cooling by the depressurized state are repeated, suppressing the temperature unevenness between the surface and the core, and capable of thawing without destroying the cells of the object to be thawed (food). In a part of the drawings, directions are indicated using the symbols F, B, L, R, U, D, which respectively represent the front side (front side), the back side (rear side), the left side, the right side, the upper side, and the lower side when the vacuum microwave thawing machine 10 is viewed from the front.

[0011] As shown in FIGS. 1 to 3, the vacuum microwave thawing machine 10 of the present embodiment has a horizontally long rectangular parallelepiped-shaped box-like thawing machine body 11 that opens forward, a door 12 that opens and closes the thawing chamber R1 arranged on the right side of the thawing machine body 11, a front panel 13 that covers the front of the machine chamber R2 arranged on the left side of the thawing machine body 11, and four casters 14 provided at the four corners on the lower surface of the thawing machine body 11. The vacuum microwave thawing machine 10 of the present embodiment has a top plate 15 arranged on the upper surface of the thawing machine body 11 and is of a table type that can be moved by the four casters 14.

[0012] The vacuum microwave thawing machine 10 includes a chamber 20 having a thawing chamber R1 for accommodating the object to be thawed. The chamber 20 is made of metal (for example, stainless steel, etc.) and is a substantially rectangular parallelepiped-shaped box body having a front opening 21. As shown in FIG. 2, the door 12 is configured to close the front opening 21 of the chamber 20.

[0013] As shown in Figures 2 and 3, the chamber 20 is provided with shelf supports 25 for accommodating trays 24 (shelves) that serve as a support area for placing items to be thawed. The shelf supports 25 are provided in pairs, on the left wall 20A and the right wall 20B of the chamber 20, respectively. Multiple shelf supports 25 (four pairs in this embodiment) are provided at intervals 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. The shelf supports 25 are formed from pipe members made of stainless steel or the like, and are attached to the left and right walls 20A and 20B in a U-shape when viewed from above, protruding into the chamber 20.

[0014] As shown in Figures 3 and 4, the vacuum microwave thawing machine 10 of this embodiment includes a vacuum pump 30 (pressure reducing device) for reducing the pressure inside the chamber 20 (thawing chamber R1), a first control valve 32 and a second control valve 33 for restoring (increasing) the pressure inside the chamber 20, a magnetron 34 (microwave generator) for generating microwaves to irradiate the thawing chamber R1, 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 inside the machine room R2.

[0015] As shown in Figure 4, the vacuum pump 30 is connected to the ceiling wall 20C 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 extending from the left wall 20A of the chamber 20. Piping 38 is branched, and the first control valve 32 and the second control valve 33 are connected to each of the branched pipes, respectively. 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. In other words, the first control valve 32 is for fine-tuning the pressure in the thawing chamber R1 during the thawing operation, and the second control valve 33 is for rapidly introducing outside air into the thawing chamber R1 after thawing is complete, etc., to return the pressure in the thawing chamber R1 to atmospheric pressure.

[0016] As shown in Figure 3, the magnetron 34 is positioned at the left rear 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 side wall 20D of the chamber 20. As shown in Figure 5, an irradiation port 42 is formed approximately in the center of the rear side wall 20D 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.

[0017] The vacuum microwave thawing machine 10 is equipped with three stirrers 50, 52, and 54 that diffuse the microwaves emitted into the thawing chamber R1. Each stirrer 50, 52, and 54 is made of metal (e.g., stainless steel) and is located inside the thawing chamber R1. As shown in Figure 5, stirrers 50 and 52 are located on the rear wall 20D of the chamber 20. More specifically, stirrer 50 is located on the upper right of the rear wall 20D, and stirrer 52 is located on the lower left of the rear wall 20D. Stirrer 54 is located on the ceiling wall 20C, as shown in Figure 2.

[0018] As shown in Figure 5, the stirrer 52 is a disc-shaped plate. The stirrer 52 is rotated by a motor 52B (see Figure 3) with its center as the axis of rotation. The stirrer 52 has openings 53 of various shapes, such as fan-shaped and triangular. Although not shown, the stirrer 54 is also a disc-shaped plate similar to the stirrer 52, and has openings of various shapes, such as fan-shaped and triangular. The stirrer 54 is rotated by a motor 54B with its center as the axis of rotation.

[0019] As shown in Figure 5, the stirrer 50 comprises a disc portion 64 and an extension portion 65 extending radially from the disc portion 64. The disc portion 64 is a disc-shaped plate material, similar to stirrs 52 and 54, and has openings 64A of various shapes, such as fan-shaped and triangular. The extension portion 65 extends with a certain width and is generally rectangular in shape. In other words, when the stirrer 50 is rotated by the motor 62, the extension portion 65 passes in front of the irradiation port 42. However, the stirrer 50 is designed to oscillate within a defined angular range so that the extension portion 65 does not come into contact with the ceiling wall portion 20C and the right side wall portion 20B (details will be described later). In other words, the stirrer 50 reciprocates so that the extension portion 65 moves along the surface of the rear side wall portion 20D and crosses the irradiation port 42.

[0020] Multiple elongated holes 66 are formed through the extension portion 65. The length of these elongated holes 66 is less than half the wavelength of microwaves (approximately 12 cm in this embodiment). Since microwaves cannot pass through holes with a diameter of less than half a wavelength, they cannot pass through the elongated holes 66 of the extension portion 65. However, due to the presence of the elongated holes 66, the extension portion 65 acts like an uneven surface for microwaves. In other words, when microwaves strike the extension portion 65, they are diffusely reflected, allowing for more effective diffusion.

[0021] Furthermore, if the extension 65 of the stirrer 50 does not overlap the irradiation port 42, the microwaves emitted from the irradiation port 42 will be directed towards the object to be thawed placed on the tray 24 without being blocked by the extension 65. If a large amount of microwaves are directed directly from the irradiation port 42 towards the object to be thawed, there is a risk of uneven heating. Therefore, the vacuum microwave thawing machine 10 is equipped with a shielding plate 70 to block some of the microwaves that are directed directly from the irradiation port 42 towards the object to be thawed.

[0022] As shown in Figure 4, the shielding plate 70 has a plurality of slits 72. The width (vertical dimension) of each of the plurality of slits 72 is set to be less than half the wavelength of the microwave. Since the slits 72 extend horizontally, they allow the transverse wave component, which is the horizontal component of the microwave, to pass through, while the vertical width being less than half the wavelength of the microwave allows them to block (reflect) the longitudinal wave component, which is the vertical component of the microwave. Therefore, the shielding plate 70 can block most of the microwaves directed from the irradiation port 42 towards the object to be thawed, and in particular, it can almost completely block microwaves directed directly from the irradiation port 42 towards the object to be thawed, thereby suppressing concentrated heating of the object to be thawed. In addition, the slits 72 of the shielding plate 70 act as an uneven shape with respect to microwaves, similar to the elongated holes 66 of the stirrer 50 described above, so that microwaves are diffusely reflected and effectively diffused into the thawing chamber R1.

[0023] Furthermore, the three stirrers 50, 52, and 54 are covered by a cover member 76, as shown in Figures 2 and 3. This prevents the user's hand from coming into contact with the three stirrers 50, 52, and 54 when inserting or removing an object to be thawed into the thawing chamber R1. The cover member 76 is made of a material that can transmit microwaves (for example, polypropylene or polyethylene).

[0024] Next, the configuration related to the installation and driving of the stirrer 50 will be described. As shown in Figure 6, the vacuum microwave thawing machine 10 is located outside the thawing chamber R1 (behind the rear wall portion 20D) and includes a motor 62 (rotating device) for rotating the stirrer 50, a shaft member 80 for connecting the stirrer 50 and the motor 62, and a fastening member 90 for attaching the stirrer 50 to one end 81 of the shaft member 80.

[0025] The shaft member 80 comprises a cylindrical shaft member body portion 82 inserted through a through hole 22 formed in the rear wall portion 20D (the wall portion constituting the chamber) of the chamber 20, and one end portion 81 provided on the end face 82A of the shaft member body portion 82 on the stirrer 50 side. The shaft member 80 has one end portion 81 in the longitudinal direction positioned inside the thawing chamber R1, and the other end portion 83 in the longitudinal direction positioned outside the thawing chamber R1. The shaft member body portion 82 is slidably mounted against the inner surface of the through hole 22. A sealing member (such as an O-ring or oil seal) is provided between the shaft member body portion 82 and the through hole 22 to ensure airtightness inside the chamber 20.

[0026] One end 81 of the shaft member 80 is cylindrical in shape with a smaller diameter than the shaft member body 82. The one end 81 is inserted from the rear wall 20D side (left side in Figure 6) into a stirrer-side through hole 67 formed through the center of the disc portion 64 of the stirrer 50, and then inserted into a mounting hole 91 formed in the fastening member 90. A female threaded portion 91A is formed on the inner surface of the mounting hole 91, which is screwed into a male threaded portion 81A formed on the outer circumference of the one end 81. The fastening member 90 is a hexagonal nut in front view, and is configured to clamp the stirrer 50 (more specifically, the edge of the stirrer-side through hole 67 in the disc portion 64) between itself and the end face 82A of the shaft member body 82. The shaft member 80 and the fastening member 90 are each made of synthetic resin and have insulating properties. The synthetic resins constituting the shaft member 80 and the fastening member 90 can be, for example, polyphenylene sulfide (PPS), but are not limited to these.

[0027] The motor 62 rotates the shaft member 80 using an axis along the longitudinal direction of the shaft member 80 as the pivot axis. The motor 62 is connected to the other end 83 of the shaft member 80 via a substantially cylindrical pin 85 and a substantially cylindrical connecting member 93. The drive shaft 62A of the motor 62 is inserted from the rear side (left side in Figure 6) into a through hole 93A formed through the connecting member 93. One end of the pin 85 is inserted from the front side into the through hole 93A, and the other end of the pin 85 is fitted into a recess 83A formed in the other end 83 of the shaft member 80. In this way, the drive shaft 62A and the shaft member 80 are connected via the connecting member 93 and the pin 85, and the rotation of the drive shaft 62A causes the shaft member 80 (and thus the stirrer 50) to rotate. The pin 85 may be integrated with the connecting member 93.

[0028] Furthermore, as shown in Figures 6 and 8, a plate-shaped disc portion 94 is integrally formed on the outer circumferential surface of the connecting member 93. As shown in Figure 8, a rectangular detected portion 95 is formed at the outer circumferential end of the disc portion 94, extending radially from the disc portion 94. As shown in Figure 5, the stirrer 50 is configured so that the extension portion 65 swings within a defined angular range. The detected portion 95 is configured to rotate in conjunction with the rotation of the shaft member 80. In other words, the detected portion 95 is configured to swing in conjunction with the swinging of the stirrer 50.

[0029] As shown in Figure 8, the photosensors 96 and 97 are positioned to correspond to the oscillation range of the detected part 95. The photosensors 96 and 97 each have detection units 96A and 97A, respectively, capable of detecting the presence or absence of the detected part 95. The detection units 96A and 97A are each composed of a light-emitting unit and a light-receiving unit arranged opposite each other. By positioning the detected part 95 between the light-emitting unit and the light-receiving unit, the light from the light-emitting unit to the light-receiving unit is blocked, making it possible to detect the detected part 95. Note that the position sensor for detecting the position of the detected part 95 is not limited to the photosensors and can be changed as appropriate.

[0030] The photosensors 96 and 97 and the motor 62 are electrically connected to the control unit 98. This allows the control unit 98 to control the operation of the motor 62 based on signals from the photosensors 96 and 97. The control unit 98 is located, for example, in the control box 36 described above, and is capable of controlling the operation of each component of the vacuum microwave thawing machine 10 (vacuum pump 30, first control valve 32, second control valve 33, magnetron 34, inverter 35, motors 52B and 54B).

[0031] The control unit 98 rotates the stirrer 50 by rotating the drive shaft 62A of the motor 62. As shown in Figure 5, the stirrer 50 is configured to rotate (oscillate) between a first state in which the extension 65 is in a predetermined position close to the right side wall 20B, and a second state in which the extension 65 is in a predetermined position close to the ceiling wall 20C. In Figure 5, the stirrer 50 in the first state is shown by a dashed line, and the extension 65 in the first state is denoted by reference numeral 65A. In Figure 5, the stirrer 50 in the second state is shown by a solid line. In the following description, the clockwise rotation of the stirrer 50 (and thus the drive shaft 62A) in Figure 5 will be referred to as forward rotation (indicated by arrow A1), and the counterclockwise rotation of the stirrer 50 in Figure 5 will be referred to as reverse rotation (indicated by arrow A2). In other words, when the stirrer 50 rotates forward, it moves from the first state to the second state, and when it rotates backward, it moves from the second state to the first state.

[0032] When the stirrer 50 is in the first state, the detected part 95 is detected by the detection unit 96A, as shown in Figure 9. When the stirrer 50 is in the second state, the detected part 95 is detected by the detection unit 97A, as shown in Figure 10. The control unit 98 rotates the stirrer 50 forward when it is in the first state, and then reverses the rotation when it enters the second state (the detected part 95 is detected by the detection unit 97A). The control unit 98 also reverses the rotation when it enters the second state, and then rotates the stirrer 50 forward when it enters the first state (the detected part 95 is detected by the detection unit 96A). This makes it possible to oscillate the stirrer 50 between the first and second states.

[0033] Furthermore, if the detected part 95 is not detected by the detection unit 97A within a predetermined time T1 (for example, 10 seconds) after the stirrer 50 in the first state has started to rotate forward, the control unit 98 stops the motor 62 and stops the forward rotation of the stirrer 50. This allows the forward rotation of the stirrer 50 to be stopped before the extension 65 contacts the ceiling wall 20C if the photosensor 97 does not operate correctly due to electrical noise or the like. If the photosensor 97 does not operate correctly, it is possible that the detected part 95 may be rotating forward beyond the detection unit 97A, as shown in Figure 11. For this reason, if the detected part 95 is not detected by the detection unit 97A within a predetermined time T1 after the stirrer 50 in the first state has started to rotate forward, the control unit 98 stops the forward rotation of the stirrer 50 and then reverses the rotation of the stirrer 50. This allows the detected part 95 to pass the detection unit 97A and then proceed toward the detection unit 96A, as shown in Figure 12. The predetermined time T1 is set to be longer than the time required for the detected unit 95 to rotate from the detection unit 96A to the detection unit 97A, and shorter than the time required for the extension 65 of the stirrer 50 in the first state to rotate and come into contact with the ceiling wall 20C.

[0034] Furthermore, the control unit 98 performs similar control when the stirrer 50 is in reverse rotation. Specifically, if the detected unit 95 is not detected by the detection unit 96A within a predetermined time T2 (for example, 10 seconds) after the stirrer 50 in the second state has reversed rotation, the control unit 98 stops the reverse rotation of the stirrer 50 and then starts the stirrer 50 in forward rotation. This allows the reverse rotation of the stirrer 50 to be stopped before the extension 65 comes into contact with the right side wall 20B.

[0035] Next, the effects of this embodiment will be described. The vacuum microwave thawing machine 10 of this embodiment includes a metal chamber 20 having a thawing chamber R1 for containing the object to be thawed, a vacuum pump 30 (depressurization device) for reducing the pressure inside the thawing chamber R1, a magnetron 34 (microwave generator) for generating microwaves to be irradiated into the thawing chamber R1, a metal stirrer 50 disposed inside the thawing chamber R1 for diffusing microwaves into the thawing chamber R1, and a through hole 22 formed through the rear side wall portion 20D (wall portion constituting the chamber) of the chamber 20, The device comprises a shaft member 80, one end 81 in the longitudinal direction of which is located inside the thawing chamber R1, and the other end 83 in the longitudinal direction of which is located outside the thawing chamber R1; a motor 62 (rotating device) located outside the thawing chamber R1 and connected to the other end 83, which rotates the shaft member 80 using an axis along the longitudinal direction of the shaft member 80 as the pivot axis; and a fastening member 90 for attaching the stirrer 50 to one end 81 of the shaft member 80. The shaft member 80 and the fastening member 90 are each made of synthetic resin.

[0036] In this embodiment, the motor 62 rotates the shaft member 80, thereby rotating the stirrer 50 and diffusing microwaves within the thawing chamber R1. This allows for more uniform heating and thawing of the object to be thawed. Since the motor 62 is located outside the thawing chamber R1, the size of the thawing chamber R1 can be ensured compared to a configuration where the motor 62 is located inside the thawing chamber R1. Furthermore, by making the stirrer 50 and chamber 20 from metal with excellent microwave reflectivity, microwaves can be diffused more effectively. However, if the stirrer 50 and chamber 20 are made of metal, there is a concern that sparks (discharges) may occur between the stirrer 50 and chamber 20 when microwaves are irradiated, due to the influence of the microwaves. Sparks are more likely to occur when the distance between the two metal members (conductive members) is small, and are even more likely to occur when the space (thawing chamber R1) is under reduced pressure.

[0037] Incidentally, as a fastening structure for attaching the stirrer to the shaft member, a structure can be considered in which a metal female screw 8 embedded in one end of the shaft member 7 is attached to the stirrer 50 using a metal male screw 9, as shown in the comparative example in Figure 7. In such a structure, the female screw 8 is located closer to the rear side wall 20D (chamber wall) than the stirrer 50. Also, since the female screw 8 is in contact with the stirrer 50 via the male screw 9, the male screw 9 and the female screw 8 are electrically connected to the stirrer 50. For this reason, sparks are particularly likely to occur between the female screw 8 and the rear side wall 20D during microwave irradiation.

[0038] Furthermore, if sparks occur, there is a risk that the shaft member 7 will carbonize, requiring the shaft member 7 to be replaced. In addition, the vacuum microwave thawing machine 10 is equipped with a detection means (for example, a means for detecting ultraviolet light generated when sparks occur, not shown) for detecting sparks in the thawing chamber R1, and the control unit 98 stops the magnetron 34 when it detects sparks in the thawing chamber R1. Therefore, if sparks occur, the thawing time of the object to be thawed will be prolonged.

[0039] In contrast, according to this embodiment, since the shaft member 80 and the fastening member 90 are each made of synthetic resin, it is possible to suppress the situation in which the shaft member 80 and the fastening member 90 make electrical contact with the stirrer 50. Therefore, it is possible to suppress the occurrence of sparks between the shaft member 80 and the rear wall portion 20D, and between the fastening member 90 and the rear wall portion 20D. As a result, it is possible to suppress the occurrence of sparks compared to the configuration in which the stirrer 50 is attached to the shaft member 7 using metal female screws 8 and male screws 9 (configuration in Figure 7).

[0040] Furthermore, in order to suppress sparks, it is necessary to ensure a certain distance between the two metal members. In this embodiment, in order to suppress sparks, it is sufficient to ensure a predetermined distance L0 between the stirrer 50 and the rear wall portion 20D (see Figure 6). In contrast, in the comparative example shown in Figure 7, in order to suppress sparks, it is necessary to ensure a predetermined distance L0 between the female screw 8 and the rear wall portion 20D, and consequently, the distance L2 between the stirrer 50 and the rear wall portion 20D becomes larger than the distance L1. In other words, with the configuration of this embodiment, the distance between the stirrer 50 and the rear wall portion 20D can be reduced compared to the comparative example, thereby saving space.

[0041] Furthermore, according to this embodiment, the shaft member 80 comprises a shaft member body portion 82 inserted through the through hole 22 and an end portion 81 provided on the end face 82A of the shaft member body portion 82 on the stirrer 50 side. The end portion 81 of the shaft member 80 is inserted from the rear wall portion 20D side into the stirrer-side through hole 67 formed through the stirrer 50, and then inserted into a mounting hole 91 formed in the fastening member 90. A female screw portion 91A is formed on the inner surface of the mounting hole 91, which is screwed into a male screw portion 81A formed on the outer circumferential surface of the end portion 81, and the fastening member 90 is configured to sandwich the stirrer 50 between itself and the end face 82A.

[0042] When assembling the stirrer 50 to the shaft member 80, the stirrer 50 can be temporarily fixed to the shaft member 80 by inserting one end 81 of the shaft member 80 into the through hole 67 on the stirrer side. Subsequently, the stirrer 50 can be clamped between the end face 82A and the end face 82A by fastening the female threaded portion 91A of the fastening member 90 to the male threaded portion 81A of the shaft member 80 (final fixing). In this way, with the above configuration, the stirrer 50 can be temporarily fixed to the shaft member 80 and then permanently fixed with the fastening member 90, thus improving the workability of the assembly process.

[0043] <Embodiment 2> Embodiment 2 will be described with reference to Figure 13. Parts identical to those in the above embodiment are denoted by the same reference numerals, and redundant explanations are omitted. In this embodiment, the mounting structure of the stirrer to the shaft member differs from that of the above embodiment. As shown in Figure 13, a metal female screw portion 192 is embedded in the end face of the shaft member 180. A synthetic resin screw member 190 (fastening member) is inserted from the front through the stirrer-side through hole 67 of the stirrer 50, and a male screw portion 191 formed on the shaft of the screw member 190 is screwed into the female screw portion 192. In this way, the stirrer 50 is attached to the shaft member 180 by the screw member 190.

[0044] <Embodiment 3> Embodiment 3 will be described with reference to Figure 14. Parts identical to those in the above embodiments are denoted by the same reference numerals, and redundant explanations are omitted. In this embodiment, the mounting structure of the stirrer to the shaft member differs from that of the above embodiments. As shown in Figure 14, a recess 280A is formed on the end face of the shaft member 280 on the side of the stirrer 50, and a female threaded portion 292 is formed on the inner surface of the recess 280A. A bolt member 290 (fastening member) made of synthetic resin is inserted from the front through the stirrer-side through hole 67 of the stirrer 50, and a male threaded portion 291 formed on the shaft of the bolt member 290 is screwed into the female threaded portion 292. In this way, the stirrer 50 is attached to the shaft member 280 by the bolt member 290.

[0045] <Embodiment 4> Embodiment 4 will be described with reference to Figures 15 and 16. Parts identical to those in the above embodiments are denoted by the same reference numerals, and redundant explanations are omitted. In this embodiment, the configuration related to detecting the rotation of the stirrer 50 differs from that of the above embodiments. As shown in Figure 15, rectangular detectable parts 391, 392, 393, and 394 are formed on the outer peripheral end of the disc portion 94, protruding radially from the disc portion 94. The multiple detectable parts 391, 392, 393, and 394 are arranged in a line along the circumferential direction of the disc portion 94 (the rotation direction of the motor 62). In addition, in this embodiment, the arrangement of the detection units 396A and 397A (detection units of the photosensor) for detecting the detectable parts 391, 392, 393, and 394 differs from that of the above embodiments.

[0046] When the stirrer 50 is in the second state (see solid line in Figure 5), as shown in Figure 15, the detected part 391 located at the far end of the forward rotation side is detected by the detection part 397A of the photosensor. Although not shown, when the stirrer 50 is in the first state, the detected part 394 is detected by the detection part 396A. After the control unit 98 rotates the stirrer 50 in the forward direction when it is in the first state, the control unit 98 reverses the rotation of the stirrer 50 when it enters the second state (the detected part 391 is detected by the detection part 397A). After the control unit 98 reverses the rotation of the stirrer 50 when it is in the second state, the control unit 98 reverses the rotation of the stirrer 50 when it enters the first state (the detected part 394 is detected by the detection part 396A). This makes it possible to oscillate the stirrer 50 between the first state and the second state.

[0047] Furthermore, when the stirrer 50 is in the second state, if the motor 62 (and therefore the stirrer 50) rotates forward due to a malfunction in the motor 62 (for example, if the wiring is connected incorrectly when assembling the motor 62) (see arrow A1 in Figure 15), then, as shown in Figure 16, the detected part 392 (the detected part that is closer to the reverse rotation side relative to the detected part 391) is detected by the detection part 397A. In this case, the control unit 98 stops the motor 62. This allows the motor 62 to be stopped quickly if it rotates forward, and prevents the stirrer 50 (extension part 65) from coming into contact with the ceiling wall part 20C (see Figure 5). Also, although not shown, when the stirrer 50 is in the first state, if the motor 62 rotates in reverse, the detected part 393 (the detected part that is closer to the forward rotation side relative to the detected part 394) is detected by the detection part 396A. In this case, the control unit 98 stops the motor 62. This prevents the stirrer 50 from reversing from the first state and the extension 65 from coming into contact with the right side wall 20B (see Figure 5).

[0048] <Embodiment 5> Embodiment 5 will be described with reference to Figures 17 to 19. The same reference numerals are used for parts identical to those in the above embodiments, and redundant explanations are omitted. In this embodiment, the configuration related to the detection of rotation of the stirrer 50 differs from that of the above embodiments.

[0049] As shown in Figure 17, detection portions 491 and 492 are formed on the outer peripheral end of the disc portion 94. The detection portions 491 and 492 have a shape that extends along the circumferential direction of the disc portion 94 (the rotation direction of the stirrer 50). The detection portions 491 and 492 are arranged in a line along the circumferential direction of the disc portion 94 with a predetermined interval between them.

[0050] When the stirrer 50 is in the first state (see the dashed line in Figure 5), the detected part 492 is detected by the detection unit 496A of the photosensor, as shown in Figure 17 (one end of the detected part 492 (the reverse-rotation end) overlaps with the detection unit 496A). Also, as shown in Figure 18, when the stirrer 50 is in the second state, the detected part 492 is detected by the detection unit 497A (the other end of the detected part 492 (the forward-rotation end) overlaps with the detection unit 497A). After rotating the stirrer 50 in the first state forward, the control unit 98 reverses the rotation of the stirrer 50 when the stirrer 50 enters the second state (the detected part 492 is detected by the detection unit 497A). Furthermore, after the control unit 98 reverses the rotation of the stirrer 50 in the second state, when the stirrer 50 returns to the first state (the detected unit 492 is detected by the detection unit 496A), it rotates the stirrer 50 forward. This makes it possible to oscillate the stirrer 50 between the first state and the second state.

[0051] Furthermore, when the stirrer 50 is in the second state, if the motor 62 malfunctions and rotates forward (see arrow A1 in Figure 18), as shown in Figure 19, the detected part 492 is detected by the detection part 497A, while the detected part 491 is detected by the detection part 496A. In this case, the control unit 98 stops the motor 62. This prevents the stirrer 50 from rotating forward from the second state and the extension part 65 from coming into contact with the ceiling wall part 20C (see Figure 5). Also, although not shown, when the stirrer 50 is in the first state, if the stirrer 50 rotates in reverse, the detected part 492 is detected by the detection part 496A, while the detected part 491 is detected by the detection part 497A. In this case, the control unit 98 stops the motor 62. This prevents the stirrer 50 from reversing from the first state and the extension 65 from coming into contact with the right side wall 20B (see Figure 5).

[0052] <Other Embodiments> The technologies disclosed herein are not limited to the embodiments described above in the description and drawings, but also include, for example, the following embodiments. (1) In the above embodiment, the stirrer 50 is shown as having a disc portion 64 and an extension portion 65, but the shape of the stirrer is not limited to that shown in the above embodiment and can be changed as appropriate. (2) In the above embodiment, the stirrer 50 is shown as having a configuration in which it oscillates within a predetermined range (a configuration in which it repeatedly rotates in the forward direction and in the reverse direction), but the invention is not limited thereto. For example, the stirrer 50 may rotate in one direction. [Explanation of Symbols]

[0053] 10... Vacuum microwave thawing machine, 20... Chamber, 20D... Rear wall of the chamber (wall portion constituting the chamber), 22... Through hole, 30... Vacuum pump (pressure reducing device), 34... Magnetron (microwave generator), 50... Stirrer, 62... Motor (rotating device), 67... Stirrer side through hole, 80, 180, 280... Shaft member, 81... One end of the shaft member, 81A... Male threaded portion, 82... Main body of the shaft member, 82A... End face on the stirrer side of the main body of the shaft member, 83... Other end of the shaft member, 90... Fastening member, 91... Mounting hole formed in the fastening member, 91A... Female threaded portion, R1... Thawing chamber, 190... Screw member (fastening member), 290... Bolt member (fastening member)

Claims

1. A metal chamber having a thawing chamber for containing the object to be thawed, A vacuum device for reducing the pressure inside the thawing chamber, A microwave generator that generates microwaves to be irradiated into the thawing chamber, A metal stirrer is placed inside the thawing chamber and diffuses the microwaves into the thawing chamber, A shaft member is inserted through a through-hole formed in the wall of the chamber, with one end in the longitudinal direction positioned inside the thawing chamber and the other end in the longitudinal direction positioned outside the thawing chamber, A rotating device is provided, which is located outside the thawing chamber and connected to the other end, and rotates the shaft member using an axis along the longitudinal direction of the shaft member as the pivot axis. The shaft member comprises a fastening member for attaching the stirrer to one end of the shaft member, A vacuum microwave thawing machine in which the shaft member and the fastening member are each made of synthetic resin.

2. The shaft member comprises a shaft member body portion inserted through the through hole, and the one end portion provided on the end face of the shaft member body portion on the stirrer side, The one end of the shaft member is inserted from the wall side into a through hole formed in the stirrer on the stirrer side, and then inserted into a mounting hole formed in the fastening member. A female threaded portion is formed on the inner surface of the mounting hole, which is screwed into the male threaded portion formed on the outer circumferential surface of the one end. The vacuum microwave thawing machine according to claim 1, wherein the fastening member is configured to sandwich the stirrer between itself and the end face.

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