JP3634710B2 - Steam generating apparatus and microwave oven provided with the apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steam generator that generates water vapor by heating water, and a microwave oven equipped with the steam generator.
[0002]
[Prior art]
In a so-called microwave oven that circulates hot air in the heating chamber and supplies microwaves to cook food contained in the chamber, so that the heating chamber is further filled with water vapor. The food is prevented from drying, or the temperature inside the cabinet is made uniform and the cooking time is shortened by the latent heat of the water vapor itself. Conventionally, as a steam generation method of a cooking device equipped with a steam generator for such a purpose, water is brought into contact with water by contacting an insulated heating wire to obtain water vapor, or water droplets are applied to a hot plate heated to a high temperature. A method of generating water vapor by blowing water is used.
[0003]
[Problems to be solved by the invention]
However, in these methods, a predetermined time is required for raising water to the boiling temperature or heating the hot plate to a high temperature. Therefore, there is a problem that water vapor cannot be obtained quickly when necessary. In addition, if water vapor is to be obtained quickly, it is necessary to maintain water in a boiling state or a state close to it even when water vapor is not needed, or to maintain a hot plate at a high temperature. Energy, which is not suitable for the recent demand for power saving.
[0004]
Furthermore, in the method in which water is boiled by heat conduction from a heating element such as a heating wire, water is boiled remarkably at the point of contact with the heating element, and when water is bumped, surrounding water droplets are rolled up together to form water vapor. No minute water droplets are generated at the same time. As a result, water vapor and minute water droplets are mixed, which is not preferable for the purpose of cooking as described above. Specifically, when steaming cooking or the like is performed, there is a problem that water droplets adhere to the surface of the food and the food surface becomes rough.
[0005]
The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to obtain water vapor quickly without requiring preheating, and the water vapor is of a quality that does not mix with water droplets. An object of the present invention is to provide a steam generator that can be expensive. Another object of the present invention is to provide a microwave oven that can quickly supply steam when necessary and perform appropriate cooking.
[0006]
[Means for Solving the Problems]
The first steam generator according to the present invention, which has been made to solve the above problems,Microwave generation means, a waveguide for guiding the generated microwave, a structure that is disposed in the waveguide and holds water infiltrated therein, the structure is accommodated therein, and a tubular structure is formed on the upper surface. A container having a water injection port and a steam discharge port, and a tubular drainage port at the lower part, each of which is exposed to the outside through an opening provided at a corresponding position of the waveguide. At least a part of the exposed portion of the ends of the water outlet, the steam outlet and the drain outlet is surrounded by a metal tubular body that is integral with the waveguide or connected to the waveguide without any gap.It is characterized by that.
[0007]
The second steam generator according to the present invention is:Microwave generation means, a waveguide for guiding the generated microwave, a structure that is disposed in the waveguide and holds water infiltrated therein, the structure is accommodated therein, and the waveguide The water injection port and the steam discharge port connected to the external pipe through the openings provided at the corresponding positions of the top surface, the same as the container provided with the drain port at the bottom, and the water injection port, the steam discharge port and the drain port were connected. Water detection means for detecting that any of the pipes is filled with water, and control means for controlling the microwave generation means to adjust the energy intensity of the microwave supplied to the waveguide. And the control means stops the generation of the microwave in the microwave generation means when the water detection means detects that the pipe is full of water.It is characterized by that.
[0008]
According to the present inventionThe microwave oven includes a heating chamber that accommodates an object to be heated, a microwave generation unit, a waveguide that guides the microwave generated by the microwave generation unit to the heating chamber, and the microwave oven. A structure for infiltrating and holding water, a water supply means for supplying water to the structure, and a container containing the structure inside and provided with a water injection port, a steam discharge port, and a drain port. Prepared,
The water injection port, the steam discharge port and the drain port of the container are each connected to an external pipe through an opening provided at a corresponding position of the waveguide, and the other end of the external pipe connected to the steam discharge port is the heating unit. Connected to the roomIt is characterized by that.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 1 according to the present inventionSecondIn this steam generator, steam is generated by the following operation. That is, water is supplied to the structure by the water supply means while supplying microwaves into the waveguide by the microwave generation means. Then, the supplied water immediately infiltrates into the structure and is held inside. When the microwave passes through the structure, the water held in the structure is heated by the microwave, the temperature rises in a short time, and vaporizes and expands. The vapor generated inside the structure in this way exits from the entire surface of the structure through the communicating holes. Further, in the process, when it comes into contact with water whose temperature has not risen sufficiently, once vaporized water vapor is deprived of latent heat and condensed. Therefore, the entire structure is soaked, and as a result, steam is generated uniformly from the entire structure.
[0010]
In the steam generator according to the present invention, it is desirable to reduce the leakage of microwaves from the waveguide as much as possible in order to reduce unnecessary radiation and increase the efficiency of steam generation. According to the present inventionFirstIn this steam generator, the structure for holding water is accommodated in a container, and the tubular water inlet, steam outlet and drain outlet provided in the container are externally provided through openings provided at corresponding positions of the waveguide. It is exposed to. For this reason, when the pipe is filled with water, the microwave may leak to the outside using the water as a propagation medium. However, since a part of the exposed portion of the conduit is surrounded by a metal tubular body that is integral with or connected to the waveguide without gaps, the cross-sectional shape and length of the tubular body are reduced by the microwave. By appropriately determining according to the frequency, leakage of microwaves through water in the pipe line can be prevented.
[0011]
Further, in order to prevent leakage of microwaves more reliably and to prevent the cross-sectional area of the pipeline from becoming extremely small, it is according to the present invention.SecondIn this steam generator, the water detection means detects that water is filled in the water injection port, the steam discharge port, or the drain port, or is almost in the same state. The control unit receives the detection result and controls the microwave generation unit to stop the generation of the microwave. According to this configuration, when the microwave is likely to leak to the outside through the water filled in the pipeline, the generation of the microwave is actively stopped, so that the leakage of the microwave can be surely prevented. . Various types of water detection means can be used, but it is preferable that the presence or absence of water can be detected indirectly from the outside of the pipe without providing a member such as an electrode in the pipe. For example, an optical detection means that utilizes the difference in light transmittance or reflectance depending on the presence or absence of water may be used.
[0012]
By the way, in such a steam generator, when performing microwave heating only of water held in the structure in the waveguide, it is preferable that both ends of the waveguide are short-circuited ends, When this steam generator is applied to a microwave oven, at least one end surface of the waveguide, preferably the end surface facing the microwave generating means is an open end, and this is connected to the heating chamber, and the microwave Can be supplied to the heating chamber.
[0013]
That is, the present invention relates toRudenAccording to the structure of the child range, the microwave power supply for vaporization of the water held in the structure and the cooking of the heated object such as food stored in the heating chamber by one microwave generating means Also serves as a microwave power feed. Therefore, when it is necessary to supply steam during cooking, as long as water is supplied to the structure, steam can be quickly generated and fed into the heating chamber.
[0014]
AlsoSince the structure is covered with a container, even if water exceeding the vaporization capacity is supplied and not retained by the structure, water is discharged from the drain through the external pipe, so water leaks into the waveguide. Absent. Further, since the steam generated from the structure is sent from the steam outlet through the external pipe to the heating chamber, the steam does not enter the waveguide or even if it enters, very little is required. Therefore, it is possible to prevent an undesirable spark discharge in a magnetron oscillator antenna or the like which is normally charged at a high voltage, and to reduce damage such as corrosion.
[0015]
【Example】
Hereinafter, an embodiment of a steam generator according to the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram showing a steam generator 10 according to the present embodiment, and FIG. 2 is a schematic cross-sectional view taken along the line A-A ′ in FIG. 1.
[0016]
In FIG. 1, a waveguide 11 is a rectangular metal waveguide having a rectangular cross-sectional structure having a width of about 90 mm and a height of about 40 mm, and having both ends 11a and 11b having a length of about 250 mm closed. is there. In the vicinity of one end face 11a of the waveguide 11, a magnetron 12 for generating a microwave is attached so as to protrude the antenna 12a inside. A container 13 having a porous body 14 therein is disposed at a position spaced apart from the other end face 11b of the waveguide 11 by a predetermined distance.
[0017]
The container 13 is made of, for example, quartz glass, and has a tubular water injection port portion 13a and a vapor discharge port portion 13b on the upper surface, and also has a tubular drainage port portion 13c on the lower surface. The water injection port portion 13a, the steam discharge port portion 13b, and the drain port portion 13c are all disposed so as to protrude outward from the opening drilled in the waveguide 11. In addition, the material of the container 13 is not limited to this, Preferably it should just be a material which is hard to be heated with a microwave, ie, a low dielectric constant and a low dielectric loss tangent.
[0018]
The water inlet 13a is connected to a water supply pipe 15 provided with a flow rate adjusting valve 18, and when the flow rate adjusting valve 18 is opened, the water supplied through the water supply pipe 15 enters the container 13 from the water inlet 13a. It comes to be supplied. The porous body 14 is a solid that has a large number of fine pores that communicate with each other inside, and the water is infiltrated from the surface to the inside by sequentially guiding the water into the communicated pores. Can do.
[0019]
An opening 11c is provided in the wall surface of the waveguide 11 below the container 13, and an infrared light receiving sensor 20 is disposed outside the opening 11c. The detection output of the infrared light receiving sensor 20 is input to the temperature detection unit 21, and the temperature detection result is given to the control unit 22. The control unit 22 can be configured mainly with a microcomputer or the like, for example, and controls the high-frequency power source 23 that supplies power to the magnetron 12 and the flow control valve 18 according to a control program given in advance.
[0020]
The general operation when the steam generator 10 generates steam is as follows. The control part 22 adjusts the opening degree of the flow control valve 18 appropriately, and allows water to flow to the water inlet 13a with a predetermined flow rate. The flow rate at this time may be such that water drops from the water injection port 13a onto the upper surface of the porous body 14. Since the dropped water quickly infiltrates into the porous body 14 by the capillary action of the pores, the water does not flow down into the container 13 if the flow rate is set appropriately as described later. The control unit 22 also controls the high frequency power supply 23 so as to start supplying current to the magnetron 12. Thereby, the magnetron 12 oscillates at a predetermined frequency (for example, 2.45 GHz), and the microwave is supplied into the waveguide 11. The microwave propagated inside the waveguide 11 passes through the wall surface of the container 13 and further attempts to pass through the porous body 14. At this time, water held in the porous body 14 becomes a load. That is, microwave energy is given to water, and the water is instantly vaporized. At the same time as water is vaporized, the water rapidly expands and goes out of the porous body 14 through the communicating holes. And it is taken out through the steam delivery pipe 16 from the steam outlet 13b.
[0021]
In the steam generating apparatus 10 of the present embodiment, a microwave that allows a flow rate of water corresponding to a desired steam flow rate to be obtained by the flow rate control valve 18 and that exceeds the energy required to vaporize the water at that flow rate. By controlling the drive current so as to be supplied to the waveguide 11, all the water supplied to the container 13 can be vaporized. Of course, even when water that cannot be infiltrated into the porous body 14 is supplied into the container 13, the excess water is discharged outside through the drain port 13 c and is not stored in the container 13.
[0022]
For example, when the flow control valve 18 is out of order or when water is not supplied to the water supply pipe 15, the microwave is continuously supplied without water infiltrating into the porous body 14. Even if the porous body 14 itself is formed of a material that is relatively difficult to be heated by microwaves as will be described later, the porous body 14 itself is heated as a load if there is no load of water. An excessive temperature rise may damage the porous body 14. When there is no load of water, the remaining microwave that has not been absorbed by the porous body 14 is reflected by the end face 11b of the waveguide 11, returns to the magnetron 12, and heats the magnetron 12 itself. Even if there is no such undesired heating, continuing to generate microwaves in a state where there is no object to be heated or is extremely short means that wasteful power is consumed.
[0023]
The infrared light receiving sensor 20 and the temperature detection unit 21 are used to eliminate such a problem. That is, in the state in which water is infiltrated into the porous body 14 almost constantly, the temperature of the porous body 14 itself does not increase so much, but when the water disappears or is extremely short, the temperature of the porous body 14 itself increases. go. As the temperature rises, the intensity of infrared rays emitted from the porous body 14 increases, and the temperature detection unit 21 detects the temperature of the porous body 14 based on the light reception signal from the infrared light receiving sensor 20. The control unit 22 compares the detected temperature with a predetermined value, and when the detected temperature exceeds the predetermined value, determines that water is not supplied, and reduces or reduces the drive current to the magnetron 12. The high frequency power supply 23 is controlled to stop. Thereby, the energy of the microwave is reduced or the oscillation is stopped, and an excessive temperature rise of the porous body 14 and heating of the magnetron 12 itself can be avoided.
[0024]
Here, a preferable material of the porous body 14 will be described. As described above, the porous body 14 generates heat when receiving microwaves in a situation where the water to be heated is not supplied, and the waveguide 11 is unlikely to radiate heat from the inside. May become hot. In order to avoid it as much as possible, the material of the porous body 14 is hard to be heated by microwaves, that is, the dielectric loss is small, and more preferably, the dielectric constant is about one-tenth that of water to be heated. Materials should be used. As a suitable material, quartz glass having a dielectric constant of 3 to 4 and a dielectric loss tangent (so-called tan δ) of about 1 × 10 −4 can be mentioned. Suitable for practical use. That is, in ceramic, a microscopic material such as fine plastic beads is mixed into a raw material to form a desired shape, which is sintered at a high temperature. Then, the minute body sublimates, and the portion remains as a pore to become a porous body. Specifically, a zirconia ceramic mainly composed of ZiSiO4 is suitable as the ceramic, and those having a dielectric loss tangent of about 5.4 × 10 −4 are available.
[0025]
Further, in this embodiment, since the temperature of the porous body 14 can be suppressed to 100 or several tens of degrees or less, a synthetic resin material such as polytetrafluoroethylene (trade name: Teflon) having relatively low heat resistance is used. It is also possible. Such resins are available with low loss and low dielectric constant comparable to quartz glass.
[0026]
As in this embodiment, performing microwave heating by infiltrating water, which is an object to be heated, into the porous body 14 has the following two important advantages.
[0027]
The first is that the microwaves emitted by the magnetron 12 can be easily passed and absorbed, and the reflected power can be suppressed. In the inside of the waveguide 11, an electromagnetic field intensity distribution based on an in-tube wavelength (determined by a free space wavelength and a tube width) is generally generated by the microwave. When water, which is a heated load, is arranged inside such a waveguide 11, the aspect of the electromagnetic field intensity distribution greatly changes because the dielectric constant is as large as 70 to 80. In practice, it is difficult to perfectly match the impedance in the waveguide 11, and a reflected wave is usually generated. Such reflection from the load side is likely to occur at the interface where the change in dielectric constant is large, as in the case of changing from air to water. Therefore, in order to suppress the reflected power on the surface of the object to be heated and introduce the microwaves into the water to the maximum, the dielectric constant of water must be as small as possible. Of course, although the dielectric constant of water itself cannot be lowered, when water is infiltrated into the porous body 14 having a low dielectric constant made of quartz glass or the like, the apparent dielectric constant is reduced according to the porosity. can do.
[0028]
According to our experiments, water with a dielectric constant of 78 has a porosity of 16.1% (absorbs 6.6 mL of water in a 41.1 mL volume) and a dielectric constant of 4 When the porous body 14 is infiltrated and filled, the apparent dielectric constant is 34.1 with respect to 2.3 GHz microwave and can be reduced to about a half. I understand. Thus, in order to suppress the reflected power, it is desirable that the porosity is as low as possible. However, on the other hand, if the porosity is lowered, the amount of water that can be infiltrated also decreases, and if the desired steam flow rate is large, the volume of the porous body 14 must be increased. Therefore, an appropriate porosity may be selected according to the shape of the waveguide 11. Practically, the porosity may be appropriately determined within a range of about 5 to 30%.
[0029]
Further, if the distribution of the pores is extremely non-uniform, the water distribution itself in the porous body 14 becomes non-uniform. Therefore, uneven heating due to microwaves is likely to occur, and there is a risk of reducing the efficiency of steam generation. Therefore, in order to generate steam almost uniformly from the entire porous body 14, it is usually desirable that the pores are distributed as uniformly as possible. The term “uniform distribution” here means that there is no unintentional unevenness in the distribution of the porosity, and as described later, the porosity within the porous body 14 for a specific purpose. It is not included to have a predetermined distribution.
[0030]
The second advantage is that homogeneous steam can be obtained as compared with the case where water is boiled and evaporated by heat conduction from a sheathed heater or the like. The water infiltrated into the porous body 14 does not necessarily receive a microwave having a uniform intensity, but an electromagnetic field is internally generated depending on the apparent dielectric constant, the size of the porous body 14 and the frequency of the microwave. A strong and weak distribution is formed. For this reason, the part where the electric field is strong has strong energy, becomes hotter than the other parts, and steam is generated earlier. However, when the steam is discharged to the outside through the communicating holes in the porous body 14, if the heat is still not sufficient and it contacts the low temperature part, the steam releases the heat of condensation while liquefying again. Will do. For this reason, even if the porous body 14 has uneven heating energy, local heating is small, and as a result, steam is generated from almost the entire porous body 14. Thereby, when heating with the sheathed heater immersed in water, the vapor | steam which does not contain a water droplet is obtained compared with the vapor | steam which entrained the water droplet accompanying bumping easily.
[0031]
Next, a steam generator according to another embodiment of the present invention will be described with reference to FIG. This steam generator has the same basic configuration as that of FIG. 1 for generating steam, but based on the magnitude of the reflected power in the waveguide 11 instead of the temperature of the porous body 14. The oscillation intensity of the magnetron 12 is adjusted.
[0032]
That is, the directional coupler 30 is attached outside the opening 11d provided in the waveguide 11 between the antenna 12a of the magnetron 12 and the porous body 14 as a load. In the directional coupler 30, an anti-reflection terminator 31 is connected to an output connector that receives incident power (energy transmitted from the antenna 12a toward the porous body 14), while reflected power (on the porous body 14 side). The microwave detection unit 32 is connected to an output connector that receives energy reflected from the antenna 12a toward the antenna 12a. In the microwave detection unit 32, a signal proportional to the magnitude of the reflected power is obtained. Most of the reflected power at the mounting position of the directional coupler 30 returns to the magnetron 12 and is consumed as heat inside. Therefore, as the reflected power is larger, the temperature rise of the magnetron 12 is larger, and the upper limit of the allowable operating temperature is easily reached. In addition, in an almost no-load state where there is no water or insufficient water, the electric field in the waveguide 11 may become abnormally high and spark discharge may be locally generated.
[0033]
Therefore, in this steam generator, the control unit 22 receives the measured value of the reflected power in the waveguide 11 from the microwave detection unit 32, and when it rises above a predetermined value, the reflected power further increases. The high frequency power supply 23 is controlled so as to reduce the drive current to the magnetron 12 so as not to cause a failure. As is well known, a DC high-voltage power supply of about 3.5 to 4 kV is necessary as a power supply for the magnetron 12, and in a commercially available microwave oven, a half-wave voltage doubler rectification power supply using an iron resonant transformer and a current control function in recent years. A high-frequency inverter power supply with is adopted. Therefore, specifically, the oscillation power of the magnetron 12 can be adjusted by performing duty cycle control of the commercial frequency in the former and by controlling the output current of the inverter in the latter. Thereby, undesired phenomena such as abnormal temperature rise and spark discharge as described above can be avoided.
[0034]
In the above example, an attempt was made to suppress the oscillation intensity of the magnetron 12, that is, the magnitude of the incident power, by focusing only on the magnitude of the reflected power. The ratio of the reflected power to the power may be calculated, and the drive current to the magnetron 12 may be reduced when there is no load or a value close to that value. According to this, since the magnitude of the reflected power is further suppressed, it is effective in extending the life of the magnetron 12. Moreover, since the electric power of the magnetron 12 can be appropriately controlled according to the load amount, that is, the amount of water that is the heating object, it is also effective for power saving.
[0035]
By the way, in the structure shown in FIG.1 and FIG.3, the water injection inlet part 13a, the vapor | steam discharge outlet part 13b, and the drain outlet part 13c which were integrally formed in the container 13 were pulled out from the inside of the waveguide 11 to the exterior. Yes. The water injection port 13a may be filled with water supplied from a water storage tank, a water tap or the like through the flow rate control valve. In addition, when water supply exceeding the steam generation capacity is performed, excess water may be accumulated in the container 13, thereby filling the drain port 13 c with water. Furthermore, the steam discharge port 13b may be in a state equivalent to a state where steam condenses inside the pipe and is substantially filled with water. Thus, in the state where each tubular entrance / exit is filled with water, the microwave in the waveguide 11 may leak to the outside using the water as a propagation medium.
[0036]
FIG. 4 is a configuration diagram of a main part of a steam generator provided with means for preventing such microwave leakage. In this figure, only the periphery of the container 13 is shown.
[0037]
In this steam generator, in order to prevent leakage of microwaves, portions exposed to the outside of the waveguide 11 in the water injection port portion 13a, the steam discharge port portion 13b, and the drain port portion 13c are arranged on the outer wall of the waveguide 11. And a metal tube 11e connected without a gap. That is, in order to prevent the leakage of microwaves as described above, the shape may be such that the microwaves cannot pass even when each pipe line is filled with water. That is, the cut-off frequency of the pipe line may be set to be higher than the oscillation frequency of the magnetron. By setting the cross-sectional shape and length of the metal tube 11e to appropriate dimensions, even when the water injection port portion 13a, the steam discharge port portion 13b, and the drain port portion 13c are filled with water, microwaves do not pass. can do.
[0038]
However, in particular, the drain outlet 13c and the steam outlet 13b, if only the leakage of the microwave is focused on and the cross section of the pipe is made too small, the flow path resistance is increased and smooth drainage and steam are prevented from being discharged. Therefore, in the example of FIG. 4, as the second microwave leakage prevention means, the photoelectric switch 40 is provided in which the infrared light emitting unit 40a and the infrared light receiving unit 40b are arranged facing each other with the transparent drain port 13c interposed therebetween. The infrared light is emitted from the infrared light emitting unit 40a to the pipe, and the change in the amount of passing light according to the difference in the refractive index due to the presence or absence of water is detected. When a control unit (not shown) determines that the drain port 13c is filled with water based on a detection signal from the photoelectric switch 40, the control unit cuts off the drive current to the magnetron 12. Thereby, the microwave is prevented from leaking outside the waveguide 11. Of course, such a water filling detection means can be provided not only in the drain port 13c but also in other pipes.
[0039]
Next, a modification of the shape of the porous body 14 in the steam generator according to the present invention will be described. FIG. 5 is a configuration diagram of a main part of a steam generator using a porous body 14 having a shape different from that of the above embodiment, FIG. 6 is a side longitudinal sectional view of the porous body 14 in FIG. 5, and FIG. 3 is an external perspective view of a body 14. FIG. As described above, if the porous body 14 has a small reflected power at the interface with the air, the microwave is efficiently absorbed accordingly. In order to reduce the reflected power, it is preferable that the incident light is incident at an appropriate oblique angle rather than the boundary surface being perpendicular to the microwave traveling direction. Therefore, in this example, the ratio of the porous body 14 to the cross-sectional area of the waveguide 11 is minimized so that the side facing the magnetron antenna (not shown) is on the left side, and gradually increases as the distance from the antenna increases. The porous body 14 has a pointed shape with a substantially isosceles side surface whose ratio increases. According to this, since the microwave hits the surface of the porous body 14 at a small incident angle, it is difficult to be reflected, and efficiently enters the inside of the porous body 14 to microwave-heat water.
[0040]
In addition, as described above, when the porosity of the porous body 14 is reduced, the shape may be relatively large in order to increase the water absorption amount. However, as the volume increases, it occurs at the center. The flow resistance when the high-pressure steam is jetted to the outside through the fine communication holes is increased, and a high expansion pressure is easily generated inside. Although it is desirable that the porous body 14 has such a strength that it does not rupture even under such an expansion pressure, in order to more reliably avoid the risk of rupture, the porous body 14 is shown in FIG. As shown, vent holes 14a are provided at appropriate intervals. As a result, the steam generated in the inner deep portion quickly escapes to the outside through the vent hole 14a, so that the internal expansion pressure does not become extremely high and the explosion is avoided.
[0041]
FIG. 8 is a configuration diagram of a main part of a steam generator using a porous body 14 having another shape. In this example, a cusp-shaped porous body 14 having a substantially triangular right side is used. Thereby, the same effect as the example shown in FIG. 5 is acquired.
[0042]
Furthermore, not only the side facing the antenna 12a has a pointed shape, but also the side facing the end surface 11b of the waveguide 11 has a pointed shape, so that the microwave reflected by the end surface 11b is porous. Since the material 14 is efficiently absorbed, the rate at which the microwave energy is used for vaporization of water is further improved.
[0043]
Further, as described above, the same effect can be obtained as follows without actually forming the porous body 14 into a pointed shape. As already explained, the reflection of microwaves at the interface becomes more severe as the change in dielectric constant increases. Considering the interface between the porous body infiltrated with water and air, the greater the water content, the higher the dielectric constant, and the greater the reflection at the interface with air. Since the water content depends on the porosity, the lower the porosity, the smaller the dielectric constant. However, when the porosity is low, there is a problem that the obtained steam flow rate is small. Therefore, in order to solve this, the porosity is lowered near the surface of the porous body 14 so that the dielectric constant when water infiltrates is relatively lowered, while the porosity is increased in the inner deep portion. It is conceivable to keep a large amount of water infiltrated. That is, it is preferable to have a structure in which the porosity is inclined so that the porosity increases toward the inner depth.
[0044]
Thus, in order to give an inclination to the porosity, for example, two kinds of porcelain powders having different particle sizes are used in the manufacturing process. After the fine porcelain powder is overlaid on the coarse porcelain powder, when vibration is applied, the fine porcelain powder penetrates into the gaps between the coarse porcelain powder and fills the space, and they are mixed appropriately and empty. A powder with an inclined porosity can be produced. When this is heat-treated in a firing furnace to weld and recombine the powder, a structure as shown in FIG. 9 is formed. That is, in the structure having the cross-sectional shape shown in FIG. 9, the porosity increases from the top to the bottom. By forming the porous body 14 by such a method, the reflection of the microwave on the surface can be suppressed and the microwave can be efficiently introduced into the inner deep portion.
[0045]
The steam generator described above is an example in which the porous body 14 is disposed inside the waveguide 11 having a short-circuited end closed at both ends, but the waveguide 11 is necessarily necessarily short-circuited at the end face in the longitudinal direction. There is no. For example, when the steam generator according to the present invention is applied to a microwave oven, the heating chamber itself for heating food has a structure that does not leak microwaves. It is reasonable to open the end face and connect to the heating chamber.
[0046]
Hereinafter, a configuration example of such a microwave oven will be described with reference to FIGS. In the example shown in FIG. 10, one end face (end face corresponding to 11 b in FIG. 1) of the waveguide 11 of the steam generator 10 having the configuration shown in FIG. 1 is opened and connected to the lower portion of the heating chamber 50. One end of a steam supply pipe 53 connected to a steam outlet 13 b extending from the container 13 is connected to the upper portion of the heating chamber 50.
[0047]
In this configuration, a part of the microwave radiated from the antenna 12 a of the magnetron 12 is used to vaporize water infiltrated into the porous body 14, and other microwaves are supplied to the heating chamber 50 and heated. It is used to cook food (not shown) accommodated in the chamber 50. In addition, the stirring blade 51 is provided in the bottom part of the heating chamber 50, and the microwave supplied in the heating chamber 50 is stirred, and it is made to hit foodstuffs uniformly. In addition, a partition wall 52 made of a material that allows microwaves to pass through, such as ceramic, is provided above the stirring blade 51. The partition wall 52 prevents the vapor supplied to the upper portion of the heating chamber 50 from diffusing to the bottom portion, thereby preventing the vapor from returning into the waveguide 11.
[0048]
Thus, in the structure in which the waveguide 11 and the heating chamber 50 are connected, the container 13 in which the porous body 14 is housed can be eliminated. That is, the waveguide 11 itself can be used as a steam supply pipe to the heating chamber 50. FIG. 11 shows an example of such a configuration. In this microwave oven, a water supply pipe 15 is connected to the waveguide 11, and water is dropped onto the porous body 14 through the water supply pipe 15. Thereby, water infiltrates into the porous body 14, and the steam generated by being heated by the microwave radiated from the magnetron 12 is supplied to the heating chamber 50 together with the microwave. Further, in order to prevent the vapor generated from the porous body 14 or the water overflowing without being infiltrated into the porous body 14 from reaching the antenna 12a of the magnetron 12, there is a gap between the porous body 14 and the antenna 12a. A partition wall 56 made of quartz glass or a corresponding material is provided.
[0049]
According to this configuration, the steam supply pipe for guiding the steam generated in the porous body 14 to the heating chamber 50 is not necessary, so that the structure is simplified and the cost is low. In addition, since water that has not completely infiltrated into the porous body 14 flows into the heating chamber 50, it is desirable to provide an appropriate drainage port at the bottom of the heating chamber 50.
[0050]
As shown in FIGS. 10 and 11, the greatest advantage of adopting the structure in which the waveguide 11 is connected to the heating chamber 50 is for cooking the food in the heating chamber 50, which is the original purpose of the microwave oven. The microwave power supply and the microwave power supply for generating steam can be shared by one magnetron 12. That is, when water is infiltrated into most of the pores of the porous body 14, most of the microwave energy is consumed for generating steam, and conversely, when the supply of water is stopped, the dielectric constant, Most of the microwave energy is guided into the heating chamber 50 without being absorbed by the porous body 14 having a small dielectric loss tangent. When the intermediate amount of water is supplied, the food in the heating chamber 50 is heated by microwaves, and at the same time, steam is provided.
[0051]
However, since most of the microwaves emitted from the magnetron 12 pass through the porous body 14, if the proportion of microwaves absorbed by the porous body 14 increases, the microwave energy supplied to the heating chamber 50 correspondingly increases. May weaken and heat cooking may take time. A configuration for improving this point is shown in FIG.
[0052]
That is, the waveguide to which the magnetron 12 is attached includes the porous body 14 inside, and the upper waveguide 111 connected to the upper part of the heating chamber 50 and the lower waveguide connected to the lower part of the heating chamber 50. 112 is branched into two. As a result, most of the microwaves radiated from the antenna 12a and traveling in the upper waveguide 111 are used to vaporize the water infiltrated into the porous body 14, while the microwaves radiated from the antenna 12a to be guided downward. The microwave traveling in the wave tube 112 is supplied to the heating chamber 50 as it is and used for cooking food.
[0053]
Note that the distribution ratio of the energy intensity of the microwaves radiated to the upper and lower waveguides 111 and 112 is appropriately changed by changing the mounting position of the magnetron 12 or giving the waveguide 11 an appropriate impedance. It can also be changed to
Further, in particular, when it is desired to increase the flow rate of the vapor delivered to the heating chamber 50, the porous body 14 is disposed inside the lower waveguide 112 in the same manner as the upper waveguide 111 and is infiltrated. Water may be vaporized to obtain steam.
[0054]
While embodiments of the invention have been illustrated and described above, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, such variations and modifications are encompassed within the scope of the claims herein.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a steam generator according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view taken along line A-A ′ in FIG. 1;
FIG. 3 is a configuration diagram of a steam generator according to another embodiment of the present invention.
FIG. 4 is a configuration diagram of a steam generator according to another embodiment of the present invention.
FIG. 5 is a configuration diagram of a main part of a steam generator according to another embodiment of the present invention.
FIG. 6 is a side longitudinal sectional view of the porous body in FIG.
7 is an external perspective view of the porous body in FIG. 5. FIG.
FIG. 8 is a configuration diagram of a main part of a steam generator according to another embodiment of the present invention.
FIG. 9 is a cross-sectional view showing an example of a distribution state of pores of another porous body.
FIG. 10 is a configuration diagram of an embodiment of a microwave oven equipped with a steam generator according to the present invention.
FIG. 11 is a configuration diagram of another embodiment of a microwave oven equipped with a steam generator according to the present invention.
FIG. 12 is a configuration diagram of another embodiment of a microwave oven equipped with a steam generator according to the present invention.
[Explanation of symbols]
10. Steam generator
11 ... Waveguide
111 ... Upper waveguide
112 ... Lower waveguide
11a, 11b ... end face
11c, 11d ... opening
11e ... Metal pipe
12 ... Magnetron
12a ... Antenna
13 ... container
13a ... Water inlet
13b ... Steam outlet
13c ... Drain port
14 ... Porous material
14a ... vent
15 ... Water supply pipe
16. Steam delivery pipe
18 ... Flow control valve
22 ... Control unit
23 ... High frequency power supply
30 ... Directional coupler
31 ... Non-reflective termination
32 ... Microwave detector
40 ... Photoelectric switch
50 ... Heating chamber
52, 56 ... partition wall
53 ... Steam supply pipe

Claims (3)

Microwave generation means, a waveguide for guiding the generated microwave, a structure that is disposed in the waveguide and holds water infiltrated therein, the structure is accommodated therein, and a tubular structure is formed on the upper surface. A water injection port and a steam discharge port, a tubular drainage port at the bottom, and a container provided so that each end thereof is exposed to the outside through an opening provided at a corresponding position of the waveguide,
At least a part of the exposed portions of the end portions of the water injection port, the steam discharge port, and the drain port are surrounded by a metal tubular body that is integral with the waveguide or connected to the waveguide without any gap. A steam generator characterized by that. Microwave generation means, a waveguide for guiding the generated microwave, a structure that is disposed in the waveguide and holds water infiltrated therein, the structure is accommodated therein, and the waveguide The water injection port and the steam discharge port connected to the external pipe through the openings provided at the corresponding positions of the top surface, the same as the container provided with the drain port at the bottom, and the water injection port, the steam discharge port and the drain port were connected. Water detection means for detecting that any of the pipes is filled with water, and control means for controlling the microwave generation means to adjust the energy intensity of the microwave supplied to the waveguide. Prepared,
The said control means stops the generation | occurrence | production of the microwave in the said microwave generation means, when it detects that the water is filled in piping by the said water detection means, The steam generator characterized by the above-mentioned . A heating chamber that houses an object to be heated, microwave generation means, a waveguide that guides the microwave generated by the microwave generation means to the heating chamber, and disposed in the waveguide, A structure body that is infiltrated and held, water supply means for supplying water to the structure body, a container that accommodates the structure body therein, and is provided with a water injection port, a steam discharge port, and a drain port,
The water injection port, the steam discharge port and the drain port of the container are each connected to an external pipe through an opening provided at a corresponding position of the waveguide, and the other end of the external pipe connected to the steam discharge port is the heating unit. A microwave oven characterized by being connected to a room .

Images