JP2003169648A - Vacuum microwave thawing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum microwave thawing machine enabling its lightweightness to be attained while securing chamber rigidity and enabling its thawing efficiency to be improved. <P>SOLUTION: This vacuum microwave thawing machine works as follows: a containing chamber 9 compartmented with a chamber 10 and a door 11 is depressurized by a vacuum pump 46 and a to-be-thawed object is irradiated with microwaves emitted from a microwave generator 22 and thawed on a turntable 15; wherein the chamber 10 is monolithically molded with metallic aluminum, and at least the inner surface of the chamber 9 represents a concavely curved surface and is specularly finished to raise its microwave reflective efficiency and turn reflected microwaves toward the turntable 15. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum microwave defroster for irradiating a material to be defrosted by irradiating it with microwaves while repeatedly performing a depressurization step and a decompression step.

[0002]

2. Description of the Related Art A conventional vacuum microwave defroster is an apparatus for irradiating microwaves in a depressurizing process to heat and thaw an object to be defrosted while repeatedly performing a depressurizing process and a recompressing process. A vacuum pump for depressurizing the storage chamber partitioned by the door, a pressure restoring unit for restoring the pressure in the storage chamber depressurized by the vacuum pump, and a microwave generator for irradiating the storage chamber with microwaves are provided.

The chamber in this kind of vacuum microwave defroster is a box body using a stainless plate or an iron plate, and is devised such that the plate thickness is increased so as to withstand the atmospheric pressure that acts when the inside pressure is reduced. And increased the strength.

[0004]

The conventional vacuum microwave defroster, in particular, defrosts while repeatedly performing the depressurization step and the depressurization step, the depressurization and the depressurization are repeated many times in one thawing. As a result, a load is repeatedly applied to the chamber, and the chamber is required to have high strength as compared with a device that is simply thawed in a depressurized state. In order to satisfy such requirements and give the chamber high strength,
Since it was made of a thick stainless plate or iron plate, the weight of the device was naturally increased.

Further, since the stainless steel plate and the iron plate have a large electric resistance on the surface, microwave wall loss occurs, which is one of the causes for lowering the heating efficiency.

Therefore, the present invention has been made in view of the above circumstances.
An object of the present invention is to provide a vacuum microwave defroster capable of reducing the weight while ensuring the rigidity of the chamber and improving the defrosting efficiency.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been proposed in view of the above, and the one according to claim 1 is a vacuum pump for depressurizing a storage chamber defined by a chamber and a door, and a storage chamber. A microwave generator that irradiates microwaves and a turntable provided in the chamber are provided, and microwaves are radiated to heat the object to be thawed on the turntable while repeatedly performing the depressurization process and the pressure restoration process. In the vacuum microwave defroster for performing defrosting, the chamber is integrally formed of aluminum and at least the inner surface of the storage chamber has a concave curved surface.

A second aspect of the present invention is the vacuum microwave defroster according to the first aspect, wherein the concave curved surface is mirror-finished and an insulating film is formed.

According to a third aspect of the present invention, the concave curved surface is
The vacuum microwave defroster according to claim 1 or 2, wherein the microwave has a curvature that reflects the microwave toward the object to be defrosted on the turntable.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing the appearance of the vacuum microwave defroster of this embodiment. FIG. 2 is a schematic diagram showing main components in the vacuum microwave defroster of this embodiment.

As shown in FIG. 1, in the vacuum microwave defroster 1 of this embodiment, a food container 3 for accommodating an object to be thawed such as frozen food is arranged on an upper part of a casing 2, and A machine storage unit 4 for storing a drive motor, a vacuum pump, and the like, which will be described later, is arranged in the lower portion, and a control unit 5 for storing a control device is provided in the uppermost portion, and a front panel of the control unit 5 is provided. , A display unit 6 for displaying the weight of the defrosted object, the defrosting time, etc.
And an operation unit 7 for inputting power on / off and various setting values. A caster 8 for facilitating the movement of the main defroster 1 is provided on the lower surface of the casing 2 of the vacuum microwave defroster 1.

As shown in FIGS. 1 and 2, the main body of the food container 3 in the vacuum microwave defroster 1 of this embodiment is constituted by a hollow container-shaped chamber 10 having an opening at the front surface. Is formed as a pressure-proof airtight container made of aluminum having an inner wall structure capable of blocking electromagnetic waves. A door 11 that can close the inside of the chamber 10 in a hermetically closed state is provided at the front opening of the chamber 10.
Is attached so as to be openable and closable via a hinge portion at the right end of the front surface, and a handle 12 to be gripped at the time of opening and closing the door 11 is attached to the left side of the front surface, which is the opening side of the door 11. The storage chamber 9 is defined by the door 11 and the door 11. Although not shown in the drawing, the flange portion 10 ′ of the chamber 10 facing the back surface of the door 11 is airtight with an electromagnetic wave sealing material made of metal mesh for preventing electromagnetic waves from leaking to the outside. Airtight sealing material to maintain is installed. In addition, in FIG. 2, the description of the reinforcing rib 19 described later is omitted, and the chamber 1
Details of 0 and the door 11 will be described later.

At the bottom of the chamber 10, there is a rotary shaft 13
Is supported by a bearing 14 and is rotatably provided in an upright state. A turntable for placing an object to be defrosted on the upper end of the rotating shaft 13 facing the chamber and rotating with the rotating shaft 13. 15 is removably attached, and a table drive motor 16 is connected to the base end of the rotary shaft 13 via a reduction mechanism.

At the center of the rear surface of the chamber 10, microwaves are radiated into the chamber 10 through a straight waveguide 20 and a reducer waveguide 21 that communicate with the inside of the chamber 10, and the turntable 15 is provided. A microwave generator 22 for heating the object to be thawed placed thereon is connected. In the present embodiment, a magnetron is adopted as the microwave generator 22, and a pressure partition wall made of a glass plate that easily transmits microwaves is provided in the flange connection portion 23 between the straight waveguide 20 and the reducer waveguide 21. Is installed.

A discharge detection sensor 30 is provided on the back surface of the chamber 10 to detect a discharge generated in the chamber 10 due to microwave irradiation.
As the discharge detection sensor 30, a UV sensor that determines the presence or absence of a discharge phenomenon by detecting ultraviolet rays (UV) is used. Further, a vacuum pressure sensor 31 that detects the pressure inside the chamber 10 is provided above the chamber 10.

At the top of the chamber 10, there is provided an atmosphere release valve 40 for releasing the internal pressure to the atmosphere, and a pressure regulating valve 41 for adjusting the pressure inside the chamber 10, and on the back surface of the chamber 10, the inside thereof is provided. Decompression system 43 for decompressing
A vacuum pump 46 driven by a pump drive motor 45 is connected to the pressure reducing system 43 via a check valve 44. The pump drive motor 45 and the vacuum pump 46 are connected to the inside of the machine housing section 4. It is stored in.

The atmosphere opening valve 40 and the pressure regulating valve 41 are constituted by, for example, electromagnetic valves in order to enable opening / closing control by the control device housed in the control section 5. The pressure regulating valve 41 may be provided in the middle of the pressure reducing system 43, for example, connected between the chamber 10 and the check valve 44 so that oxygen is unlikely to enter the chamber 10 in the pressure recovery step.

The chamber 10 is a horizontal container integrally formed of aluminum and having an opening on the front surface.
As shown in, the inner surface of the storage chamber side is formed as a gentle concave curved surface 18. In the present embodiment, the outer surface of the chamber 10 is also formed with a curvature along the concave curved surface 18 of the storage chamber-side inner surface, but in the present invention, at least the storage chamber-side inner surface is formed as the concave curved surface 18. Good. Therefore, the required strength can be easily obtained even if the weight is reduced by using aluminum, and the microwaves that have collided with the inner surface of the chamber on the storage chamber side can be collected in the central portion of the storage chamber.

The curvature of the concave curved surface 18 depends on the chamber 10.
The microwave that has collided with the inner surface of the storage chamber is set to have a curvature that reflects toward the object to be defrosted on the turntable 15. For this curvature, it is preferable to adopt a curvature conforming to a curve having a focus such as a parabola or a hyperbola, and to set the focus on the turntable 15. Therefore, it is possible to irradiate the object to be thawed with the microwave reflected by the inner surface of the chamber 10 on the storage chamber side, and to improve the thawing efficiency.

The concave curved surface 18 of the chamber 10 is mirror-finished, and an insulating film is formed on the surface by alumite treatment or the like. Therefore, the microwave reflection efficiency is good, and it is possible to prevent the wall surface from being heated by the microwave. When an insulating film such as alumite is formed, mechanical scratches and the like can be prevented, and at the same time, microwave discharge can be prevented. Further, the concave curved surface 18 and the mirror-finished surface work together to efficiently reflect the microwaves to turntable 1
It is possible to irradiate the object to be thawed on No. 5 and perform more efficient thaw.

FIG. 3 is a perspective view showing the outer wall of the chamber in the microwave defroster of this embodiment. As shown in the drawing, a thick reinforcing rib 19 is integrally formed on the outer wall 10a of the chamber 10. The reinforcing rib 19 is orthogonal to at least one position on each of the upper, lower, left, right and rear outer surfaces of the outer wall 10a. As described above, four reinforcing ribs 19 are connected to the straight waveguide 20 on the rear surface with the phase thereof changed by 90 degrees. Therefore, by integrally forming the reinforcing rib 19 on the outer wall 10a of the chamber 10, it is possible to reduce the wall thickness, that is, to reduce the weight while ensuring the rigidity of the chamber 10, and it is particularly high with respect to the atmospheric pressure acting in a reduced pressure state. The rigidity can be secured.

The door 11 that closes the front opening of the chamber 10 is a rectangular door integrally formed of aluminum, and as shown in FIG. 2, the surface on the storage chamber 9 side is formed as a concave curved surface 17. . Therefore, it is possible to easily obtain the required strength even if the weight is reduced, and it is possible to secure high rigidity especially against the atmospheric pressure acting in the reduced pressure state.

The concave curved surface 17 of the door 11 is mirror-finished and has an insulating film formed on the surface by alumite treatment or the like. Therefore, the microwave reflection efficiency is good, and it is possible to prevent the wall surface from being heated by the microwave. By forming an insulating film such as alumite, it is possible to prevent mechanical scratches and the like, and also to prevent electric discharge due to microwaves generated in a portion in contact with the chamber 10. If the metal that covers the outer circumference of the electromagnetic wave sealing material is made of the same material as the chamber, electrolytic corrosion can be prevented.

Further, the curvature of the concave curved surface 17 is set to such a curvature that the microwave is reflected toward the turntable. For this curvature, for example, a curvature according to a curve having a focus such as a parabola or a hyperbola is adopted. Therefore, in combination with the shape of the inner surface of the chamber 10 on the storage chamber side, the microwaves can be efficiently reflected and applied to the object to be thawed on the turntable, and the thaw can be performed more efficiently.

Next, the vacuum microwave defrosting method of the present embodiment, which is carried out under the control of the controller 50 using the vacuum microwave defroster 1 as described above, will be described. Figure 4
FIG. 4 is an explanatory diagram showing a defrosting cycle in the vacuum microwave defroster 1 of the present embodiment.

As shown in FIG. 4, the vacuum microwave defroster 1 of this embodiment irradiates microwaves while repeatedly performing the depressurizing steps G, G ', G "... And the depressurizing steps F, F' ... This is a device for heating and thawing the object to be thawed by M, M '... The vacuum pump 46 continues to operate not only in the depressurizing step but also in the recompressing step.

As a preparatory step for thawing, first, the door 11 on the front side is opened and an object to be thawed such as frozen food is placed on the turntable 15, and then the door 11 is closed again to make a hermetically sealed state. The object to be thawed is placed inside. The atmosphere opening valve 40 and the pressure regulating valve 41 are closed.

Next, the pump drive motor 45 is driven to operate the vacuum pump 46, and the pressure reduction in the chamber 10 is started via the pressure reduction system 43. Then, the atmospheric pressure of 101.
The degree of pressure reduction gradually decreases from 3 kPa (760 Torr) through point A, and pressure reduction step G is performed up to pressure reduction equilibrium region B. In this pressure reduction step G, the material to be thawed is preliminarily dried.

Here, the decompression equilibrium region is a region where the decompression degree extremely decreases for a certain period of time. For example, the decompression degree (ΔP) in 30 seconds (Δt) is ΔP / Δt <13.
It is understood that when the pressure reaches 3 Pa (0.1 Torr), the pressure reduction equilibrium region is reached, but the equilibrium pressure in the pressure reduction equilibrium region fluctuates due to the saturated vapor pressure in the chamber 10. In addition,
Whether or not the pressure reduction equilibrium region has been reached is determined by the control device based on the pressure signal from the vacuum pressure sensor 31.

After performing the depressurizing step G to the depressurizing equilibrium region B, the pressure regulating valve 41 is opened at a predetermined opening degree described later to shift to the repressurizing step F, and the depressurizing degree of the repressurizing step F is vacuum. At the point C after the lower limit P1 at which discharge does not occur (set to 1.33 kPa (10 Torr) with some margin in this embodiment), the microwave irradiation M by the magnetron 22 is started. When the pressure is restored to the preset pressure upper limit value D, the control device closes the pressure regulating valve 41 based on the pressure signal from the vacuum pressure sensor, and then shifts to the pressure reducing step G ′ again. Then, the microwave irradiation M by the magnetron 22 is continued until the decompression degree reaches the lower limit value P1 at which the vacuum discharge does not occur and the object to be thawed is heated at the point A ', and at the point A' Stop irradiation.

Further, in this embodiment, the lower limit value P1 of the degree of pressure reduction at which the vacuum discharge does not occur is 1.3 as described above.
It is set to 3 kPa (10 Torr). That is, the degree of pressure reduction in the pressure recovery step F is 1.33 kPa (10 Tor
At the point C after exceeding r), the magnetron 22
The microwave irradiation M is started by, the pressure is restored to a preset rebound pressure upper limit value D, and then the pressure reducing step G ′ is performed again, and the pressure reduction degree reaches 1.33 kPa (10 Torr) before the point A ′. The microwave irradiation M by the magnetron is continued until the object to be thawed is heated. In this way, since the microwave irradiation M is performed from the middle of the recompression step F to the decompression step G ′, as compared with the conventional method of irradiating only in the decompression step, one defrosting cycle consisting of the recompression step and the decompression step. It is possible to secure a sufficient irradiation time in.

The return pressure upper limit value D is a variable pressure value set by the output of the magnetron 22 for irradiating microwaves, the decompression ability of the vacuum pump 46, and the volume of the chamber 10. In this embodiment, the pressure regulating valve is used. 41 throttle valve 41 '
By adjusting the aperture of 6.66kPa (50T
orr). Therefore, 6.66 kP
When the pressure is restored to a (50 Torr), the leak from the pressure regulating valve 41 and the suction capacity of the vacuum pump 46 are balanced, and 6.66 kPa (50 Torr) unless the pressure regulating valve 41 is closed.
r) is maintained and the pressure does not rise.

In this embodiment, the return pressure upper limit value D is
The pressure value of is set appropriately according to the output of the magnetron 22 for irradiating microwaves, the decompression ability of the vacuum pump 46, and the volume of the chamber 10, so that there is no excess or deficiency of microwaves before entering the vacuum discharge generation region. Irradiation time can be taken and the pressure can be reduced efficiently.

In this embodiment, the vacuum pressure sensor 31 is used as a means for detecting that the rebound pressure upper limit value D has been reached.
However, the present invention is not limited to this, and may be stopped by timer control.

After the microwave irradiation is stopped, the object to be thawed is sublimated and cooled in the pressure reduction process from the point A'to the pressure reduction equilibrium region B '. After heating the object to be thawed by irradiating microwaves to the point A'in the depressurization step G ', the object to be thawed is sublimated and cooled in the depressurization process from the point A'to the depressurization equilibrium region B'. When the object to be thawed is heated by irradiation with microwaves, the temperature of the surface of the object to be thawed becomes higher than the temperature of the central part, and if heating is continued as it is, inconveniences such as drip on the surface will occur. This is because sublimation cools the surface portion to reduce the temperature difference between the inside and outside.

That is, when sublimation starts, the latent heat of vaporization is removed and the temperature of the surface portion decreases, and the heat of the surface portion moves (heat conduction) to the central portion to raise the temperature of the central portion. As a result, the temperature of the object to be thawed is made uniform, and the temperature of the object to be thawed rises as a whole, and the thawing is promoted. Further, since the temperature of the object to be thawed is made uniform while the thawing of the object to be thawed is promoted as a whole, there is a problem that the thawing progresses partially and a drip is generated, or the microwave is concentrated on this drip. Can be prevented.

In the present embodiment, when the pressure is returned to the pressure recovery step F and the pressure reduction degree in the pressure recovery step F exceeds the lower limit value P1 of 1.33 kPa (10 Torr) at which vacuum discharge does not occur, the point C is reached. The microwave irradiation M is started, and the pressure is restored to 6.66 kPa (50 Torr), which is the preset upper limit value D of pressure, and then the pressure reducing step G ′ is performed again, and the pressure reduction degree is a lower limit at which vacuum discharge does not occur. The microwave irradiation M is continuously heated until the value P1 reaches 1.33 kPa (10 Torr) of A ′, and the microwave irradiation M
After the stop, the defrosting cycle of sublimation cooling in the depressurization process up to the depressurized equilibrium zone B'is set as one cycle, and this defrosting cycle is repeated.

That is, in FIG. 4, after the depressurization step G'has been performed up to the depressurization equilibrium region B ', the process returns to the decompression step F', and the decompression degree of the decompression step F'is the lower limit value P1 at which vacuum discharge does not occur. At a point C'after exceeding a certain 1.33 kPa (10 Torr), microwave irradiation M'is restarted, and a preset recompression pressure upper limit D'is 6.66 kPa (50 Torr).
After returning to r), the process moves to the depressurization step G ″ again, and the microwave irradiation M ′ is performed before the depressurization degree reaches 1.33 kPa (10 Torr) of A ″ which is the lower limit P1 at which vacuum discharge does not occur. Is continuously heated, microwave irradiation is stopped again, and then a defrosting cycle of sublimation cooling in the decompression process up to the decompression equilibrium region B ″ is performed as the second cycle. Recompression in each recompression process F, F ′ ... The characteristics are
Since it depends on the setting of the throttle valve 41 'of the pressure-return valve 41,
It is constant in each thawing cycle, that is, the curve of the recompression curve is constant in each thawing cycle, which enables stable thawing.

As shown in FIG. 4, when such a thawing cycle is repeated, the saturated vapor pressure in the chamber 10 rises as the temperature of the object to be defrosted rises. The decompression degree of B ″ ... gradually increases as the defrosting cycle is repeated. Therefore, when the decompression degree in this decompression equilibrium region B, B ′, B ″ ... reaches a predetermined value, the defrosting cycle ends. To do. That is, the desired thawing temperature can be set by setting the saturated vapor pressure region, and if the reduced pressure equilibrium is reached in this set region, the thawing operation is terminated assuming that the desired thawing temperature has been reached. Then, the number of repetitive cycles of the defrosting cycle until reaching this set region varies depending on the mass of the object to be defrosted, the output of the magnetron 22, the depressurizing ability of the vacuum pump 46, etc., and in the present embodiment, P2A of FIG. Pressure value is 480Pa
(3.6 Torr), the pressure value of P2B is 453 Pa
(3.4 Torr), the reduced pressure equilibrium regions B, B ′,
When the degree of reduced pressure at B ″ ... reaches a value between P2A and P2B, it is assumed that the temperature of the object to be thawed has reached about −3 ° C., and the thaw cycle is terminated.

When the controller 50 determines the end of the thawing cycle, the atmosphere opening valve 40 is opened and
The power of the pump drive motor 45 is shut off and the vacuum pump 46
When the storage chamber 9 is stopped and the inside of the storage chamber 9 is returned to the atmospheric pressure, the door 11 can be opened and the object to be thawed at about −3 ° C. can be taken out from the chamber 10.

When a discharge phenomenon occurs in the chamber 10 for some reason, the discharge detection sensor 30 detects it by the generation of UV, and the control device 50 causes the magnetron 22 via the power supply control system 56. Is forcibly stopped to prevent damage to the inner wall of the chamber 10 and the like.

In each of the above embodiments, the product to be thawed has been described as a frozen food, but the product to be thawed to be thawed in the present invention is not limited to foods, and may be blood, serum, semen, medicines or the like.

[0043]

As is apparent from the above description, the vacuum microwave defroster of the present invention has the following effects. According to the invention of claim 1, since the chamber is integrally molded with aluminum and at least the inner surface of the storage chamber is a concave curved surface, it is easy to obtain the necessary strength even if the weight is reduced by aluminum, and the inner surface of the chamber on the storage chamber side is easily obtained. Microwaves that collide with can be collected in the central part of the storage chamber.

According to the second aspect of the present invention, since the concave curved surface is mirror-finished and the insulating film is formed, the microwave reflection efficiency can be improved and the heating of the wall surface by the microwave can be prevented. be able to. When an insulating film is formed, it is possible to prevent mechanical scratches and the like, and also to prevent electric discharge and electrolytic corrosion due to the microwave generated in the portion that comes into contact with the chamber. The durability can be secured.

According to the third aspect of the present invention, since the concave curved surface formed on the inner surface of the chamber on the storage chamber side is formed with a curvature that reflects the microwave toward the object to be thawed on the turntable, It is possible to irradiate the object to be defrosted with the microwave reflected by the inner surface of the chamber on the storage chamber side, and to improve the defrosting efficiency.

[Brief description of drawings]

FIG. 1 is a front view showing an appearance of a vacuum microwave defroster of the present embodiment.

FIG. 2 is a schematic diagram showing main components in the vacuum microwave defroster of the present embodiment.

FIG. 3 is a perspective view showing an outer wall of a chamber in the microwave defroster of the present embodiment.

FIG. 4 is an explanatory diagram showing a thawing cycle in the vacuum microwave thawing machine of the present embodiment.

[Explanation of symbols]

1 vacuum microwave defroster 2 housing 3 food storage 4 Machine storage 5 control unit 6 Display 7 Operation part 8 casters 9 storage rooms 10 chambers 10 'chamber flange 10a outer wall of chamber 11 doors 12 handles 13 rotation axis 14 bearings 15 turntable 16 table drive motor 17 Door concave curved surface 18 Concave curved surface of chamber 19 Reinforcing rib 20 Straight waveguide 21 Reducer Waveguide 22 Microwave generator (magnetron) 23 Flange connection 24 Airtight sealing material 25 Electromagnetic wave sealing material 26 First groove 27 Second groove 30 discharge detection sensor 31 Vacuum pressure sensor 40 atmosphere release valve 41 Pressure regulator 43 Decompression system 44 Check valve 45 Pump drive motor 46 vacuum pump 50 controller

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiki Sugiyama             244 Hinomae, Kamijima, Ohito-cho, Takata-gun, Shizuoka Prefecture               To electrostatic company (72) Inventor Takashi Asahara             244 Hinomae, Kamijima, Ohito-cho, Takata-gun, Shizuoka Prefecture               To electrostatic company F term (reference) 3K086 AA08 BA08 BB01 CA12 CB20                       CC01 CD28                 3K090 AA02 AA04 AB03 BA01 BB01                       BB12 BB13                 4B022 LQ06 LQ07 LT07

Claims (3)

[Claims] 1. A depressurizing step comprising a vacuum pump for depressurizing a storage chamber defined by a chamber and a door, a microwave generator for irradiating the storage chamber with microwaves, and a turntable provided in the chamber. In a vacuum microwave defroster that irradiates microwaves to heat and thaw the object to be thawed on the turntable while repeating the pressure-recovering step, the chamber is integrally molded with aluminum, and at least the inner surface of the storage chamber is A vacuum microwave defroster characterized by a concave curved surface. 2. The vacuum microwave defroster according to claim 1, wherein the concave curved surface is mirror-finished and an insulating film is formed. 3. The vacuum microwave defroster according to claim 1, wherein the concave curved surface has a curvature that reflects microwaves toward an object to be defrosted on a turntable.