JP3700326B2 - High frequency heating element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency heating device applied to a high-frequency utilizing device that realizes heating / cooking of food, drying of clothes, or the like, a device that absorbs unnecessary radiation in a space, and a sensor that detects the amount of unnecessary radiation. is there.
[0002]
[Prior art]
Conventionally, this type of member that absorbs high frequency to generate heat is applied to, for example, a heater in a high-frequency heating device such as an oven microwave oven, or is provided in the heating chamber of the high-frequency heating device to detect the electric field strength in the heating chamber. Application of devices is under consideration.
[0003]
Regarding application to an oven microwave oven, the performance required of a high-frequency heating element is a necessary condition for a high-frequency heating element with a high temperature rise and a high ultimate temperature, as opposed to an electric heater.
[0004]
One prior art for this is Japanese Patent Laid-Open No. 6-223960. This publication discloses a high-frequency heating element in which at least one of iridium oxide, ruthenium oxide and rhodium oxide is supported on a substrate made of a ceramic refractory having a honeycomb structure. It is disclosed that the base material is preferably cordierite having good workability with respect to silicon carbide, porcelain semiconductors and the like.
[0005]
On the other hand, there is JP-A-6-185740, for example, for measuring the electric field strength in the heating chamber. According to this publication, the high-frequency absorption heating element disposed at a predetermined position in the heating chamber generates heat according to the high-frequency electric field strength applied to the heating element and raises the temperature. It discloses that the temperature change of the heating element is detected, the heating state of the object to be heated is judged, and the operation of the high frequency generation source is controlled.
[0006]
[Problems to be solved by the invention]
However, conventional high-frequency heating elements for heater replacement mainly disclose the material composition that constitutes the heating elements with the main aim of having a high ultimate temperature as the heating element and good rising temperature rise characteristics. However, when applied to an oven microwave oven that is one of high-frequency heating devices, for example, in order to practically cook food to be cooked that exists at a certain distance from the heating element, a predetermined amount of food is used. The amount of heat needs to be continuously applied, and the surface temperature must be continuously maintained at 170 ° C. or higher for a predetermined time in order to scorch the food surface. When a high frequency is continuously supplied to the heating element in order to generate a predetermined amount of heat, there is a problem that the heating element melts due to a continuous temperature rise. Therefore, it is necessary to intermittently supply the high frequency at an appropriate cycle. However, the heating element having a good start-up performance has a problem that the temperature rapidly decreases when the high frequency supply is stopped because the heat capacity is small. .
[0007]
In addition, when the shape is comparable to the size of the food (for example, 200 mm square), a high-frequency heating distribution is generated on the surface of the heating element, and thus there is a problem that temperature rise characteristics are deteriorated.
[0008]
Furthermore, the conventional high-frequency heating element applied to a member that generates heat in accordance with the high-frequency electric field strength absorbs the high frequency reflected in the heating chamber without being absorbed by the food to be heated and generates heat. . The high frequency reflected from the food is repeatedly reflected on the wall surface forming the heating chamber and gradually absorbed by the food. In this case, in the heating chamber containing food, the high frequency that repeats absorption and reflection forms a specific high frequency distribution in the heating chamber. Since this high-frequency distribution changes depending on the type, amount and shape of the object to be heated, even if a plurality of limited heating elements are arranged, the heating element exhibits heat generation characteristics corresponding to the cooking condition of the object to be heated. Had the problem that it was quite difficult unless improvements were made to the structure of the heating element.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a substrate of a honeycomb structure composed of a refractory and heat-resistant member that generates heat by absorbing a high frequency, and a member having a high relative dielectric constant in the high-frequency body used in the substrate of the honeycomb structure. The high-frequency heating element has a filled configuration.
[0010]
According to the present invention, the high relative permittivity member can reduce the propagation speed when the high frequency wave propagating to the high frequency heating element propagates through the structure of the high frequency heating element. On the other hand, a member that absorbs high frequency in the structure and generates heat sufficiently absorbs high frequency at a slow propagation speed, so that heat generation is promoted.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a high-frequency heat generation comprising a honeycomb structure base made of a fire-resistant and heat-resistant member that generates heat by absorbing high frequency, and a member having a high relative dielectric constant in the high-frequency band to be used. The body. As a result, the high relative permittivity member slows the propagation speed when the high-frequency wave propagating to the high-frequency heating element propagates through the structure of the high-frequency heating element. On the other hand, a member that generates heat by absorbing a high frequency in the structure sufficiently absorbs high frequency energy from a high frequency with a slow propagation speed and promotes heat generation.
[0012]
In addition, by using a structure to which a member having a high relative dielectric constant is added, a high-frequency heating element corresponding to a desired high frequency to be used can be configured by changing the relative dielectric constant of the same substrate.
[0013]
In addition, it is possible to disperse and dispose members having a high relative dielectric constant throughout the high-frequency heating element to equalize the effective relative dielectric constant of the heating element when viewed from the high frequency. Thereby, the propagation speed can be reduced in the high-frequency heating body with respect to the high-frequency waves propagating from all directions.
[0014]
In addition, a member having a high relative dielectric constant is filled at one end side of the honeycomb structure. Thereby, in the member which absorbs a high frequency, the area | region which actually absorbs a high frequency is limited, A heat capacity can be made small and a temperature rising characteristic can be made favorable.
[0015]
Further, the high-frequency heating element is a structure having air permeability. As a result, the amount of heat generated by the high-frequency heating element can be transmitted to an object to be heated at a remote position. Moreover, when using a high frequency heat generating body as a sensor, a high frequency heat generating body can be cooled by ventilation | gas_flowing and can be reset to an initial state.
[0016]
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
As a member that generates heat by absorbing a high frequency used in the high frequency heating element of the present invention, various known materials are used. For example, it is a powder or sintered material such as a ceramic, ceramic, silicon carbide, carbon black, charcoal, etc. whose main component is a ferrite, perovskite structure, and the particle size of the powder or the porosity of the sintered material is not particularly limited, Preferably, the heat generating member acts as an insulator, and an auxiliary material is selected for firing.
[0018]
The relative dielectric constant of the high dielectric constant member is appropriately selected depending on the high frequency band to be used. For example, when the high frequency band used is a 2450 MHz band used in a microwave oven, the spatial propagation wavelength is about 12 cm, and the effective propagation wavelength when propagating through a high relative permittivity member is the reciprocal of the square root of the relative permittivity. In view of the fact that it is proportional to the above, it is preferable to use a material having a relative dielectric constant of 10 or more and 200 or less that provides a practical structural dimension.
[0019]
Examples of the high dielectric constant member used in this frequency band include titanium oxide, a dielectric mainly composed of a perovskite structure, and silicon carbide using beryllium oxide as a binder.
[0020]
In addition, for a higher frequency band, a member having a relative permittivity value equal to or lower than the above value, such as alumina, aluminum nitride, mullite, cordierite, or the like is selected. Furthermore, for lower frequency bands, members having a relative dielectric constant of 200 or more, for example, dielectrics (SrTiO3 ↓, PbTiO3 ↓, PbZrO3 ↓, Pb (Zr1 ↓-↓ x ↓) whose main component is the composition of the perovskite structure. The structure of the high-frequency heating element can be made compact by selecting Tix ↓) O3 ↓ etc.
[0021]
(Example 1)
FIG. 1 is a configuration diagram of a high-frequency heating element according to Embodiment 1 of the present invention.
[0022]
In the figure, the high-frequency heating element 10 includes a base 11 having a honeycomb structure using the above-described fire-resistant and heat-resistant member that absorbs high-frequency and generates heat, and the high ratio described above from one end to the other end of the group of through holes 12 in the honeycomb structure. The group of dielectric members 13 is alternately filled in the group of through holes 12 in the honeycomb structure.
[0023]
The substrate 11 having a honeycomb structure can use various structures corresponding to the high-frequency band to be used, but a quadrangular through hole structure is convenient for production processing. In addition, for maintaining the mechanical strength of the structure, for example, the density of the through-hole 12 group is preferably 50 to 200 cells / in 2 and the wall thickness of the honeycomb is preferably 0.1 to 1 mm. Furthermore, the porosity of the wall portion of the honeycomb can be selected up to about 60% as an upper limit.
When the high dielectric constant filling member 13 group is a sintered product, the filling member 13 group is fixed to the base 11 using an inorganic binder. In addition, when powder is used as the high dielectric constant filling member 13 group, after filling, both ends of the filling portion are sealed with an inorganic binder (not shown), and the filling member 13 group is stored and held in the base 11. To do.
[0024]
The main body of the high-frequency heating element 10 can be heat-treated at a high temperature of several hundred degrees or more after the filled powder is stored and held in the base 11. According to this method, for example, when titanium oxide powder is used as the group of filling members 13, the phase transition to rutile titanium oxide can be ensured by high-temperature treatment, and a filling member having a high dielectric constant can be obtained.
[0025]
Next, the operation and action will be described.
[0026]
A description will be given below as a high frequency band using the 2450 MHz band used in the microwave oven.
[0027]
When the honeycomb structure has a through-hole density of 200 cells / square inch, a wall thickness of 0.4 mm, the refractory and heat-resistant member 11 is made of silicon carbide, and the filling member 13 group is made of titanium oxide, a free space propagation wavelength of about 12 cm in the 2450 MHz band is obtained. The high-frequency heating element 10 recognizes the high-frequency heating element 10 macroscopically because it cannot distinguish the arrangement of the individual through holes 12 of the high-frequency heating element 10. When the effective dielectric constant of the high-frequency heating element at this frequency was measured, the value was about 12. Accordingly, the high-frequency propagation wavelength in the high-frequency heating body in the 2450 MHz band is about 35.3 mm.
[0028]
When 30 mm is used as the thickness of the high-frequency heating element 10 in the direction of the through-hole, the high-frequency wave propagated from the direction of the through-hole can be present in the high-frequency heating element 10 for about 0.85 wavelengths. The upper propagation speed becomes slower. The base 11 absorbs high-frequency energy from a high frequency with a low propagation speed, and heat generation is promoted.
[0029]
Further, the filling member 12 group is a refractory and heat-resistant member and acts as a heat load on the base 11, so that the heat capacity can be increased by the presence of the filling member 12 group.
[0030]
When the high frequency heating element was 30 mm square and 400 W was supplied as high frequency energy, the time required to reach 700 ° C. was 100 seconds. Further, the temperature decrease rate until the temperature reached 300 ° C. after the high-frequency supply was stopped was 67 ° C./min after a sudden decrease of about 20 ° C. immediately after the stop. When the filling member was not used in the same structure, the temperature reached 700 ° C. in 85 seconds. Further, after the high-frequency supply was stopped, the temperature dropped at 80 ° C./min after a sudden drop of about 40 ° C. immediately after the stop. In the above test, the cooling air (1 m3 ↑ / min) ventilated to cool the magnetron, which is the high frequency generator, is 4 mm in diameter and 7.5 mm in pitch provided on the side of the heating chamber containing the high frequency heating element. It flows into the heating chamber through the arranged holes.
[0031]
According to the above test, the start-up performance is somewhat lowered due to the increase in the heat capacity of the high-frequency heating element by the filling member, but the performance is practically sufficient considering the comparison with the heater. Further, the temperature drop immediately after the high frequency supply is stopped is reduced to about ½. Therefore, in order to prevent melting of the high-frequency heating element, the temperature drop of the heating element when the high-frequency supply is interrupted, for example, in a cycle of 10 seconds can be suppressed to about 30 ° C., and a desired amount of heat can be supplied. It can be heated and cooked.
[0032]
Furthermore, the structure of Example 1 has air permeability and ventilates air so that when it acts as a heating element, the generated heat is transmitted to an object to be heated at a distant position, and cooking of food or clothing It can be used as a heat flow for drying. On the other hand, when acting as a sensor, the high frequency heating element can be cooled and the sensor signal can be reset to the initial state when repeatedly cooking.
[0033]
(Example 2)
FIG. 2 is a configuration diagram of a high-frequency heating element according to the second embodiment of the present invention.
[0034]
In the figure, the configuration of the high-frequency heating element 14 different from that shown in FIG. 1 is that the group of members 15 having a high relative dielectric constant is offset toward one end of the through-holes of the substrate 11 of the honeycomb structure and all the through-holes 12 are filled. It is.
[0035]
Next, the operation and action will be described. The substrate and the member having a high relative dielectric constant will be described using the same members as described above.
[0036]
The effective relative dielectric constant of the high-frequency heating element viewed from the filling side was about 52. Therefore, when the propagation wavelength in the high-frequency heating element including the filling member is about 17.0 mm, the thickness of the high-frequency heating element in the through-hole direction is 30 mm, and the filling length in the through-hole direction of the filling member 15 group is 15 mm. The high frequency that can be present on the filling member side is equivalent to 0.88 wavelengths. On the other hand, since the weight of the refractory and heat-resistant member that absorbs high frequency and generates heat in the region where the filling member exists is smaller than that of the first embodiment, the heat capacity can be reduced. Due to this effect, the high-frequency energy absorbed is almost the same, but heat generation can be further promoted.
[0037]
Further, such a honeycomb structure and a structure of a high-frequency heating element in which a member having a high relative dielectric constant is filled in the through hole can be used as a sensor for detecting electric field strength. When used as this type of sensor, in order to make the high-frequency wave propagating in the structure to be ¼ or more of the effective propagation wavelength, the thickness in the penetration direction when the structure of the first embodiment and the jiu-jitsu member are used. Is 9 mm or more, and in the configuration in which all the through holes of Example 2 are filled, it may be 4.5 mm or more. In addition, when it is necessary to make it thinner in practice, a member having a higher relative dielectric constant may be used as the filling member. By having a high frequency of 1/4 or more of the effective propagation wavelength in the structure, it is possible to absorb the high frequency energy from the weak high frequency that has propagated and raise the temperature due to heat generation.
[0038]
In addition, as described above, a high-frequency heating element corresponding to a desired high-frequency can be configured by changing the relative dielectric constant of the same substrate by adding a member having a high relative dielectric constant. can do.
[0039]
(Example 3)
FIG. 3 is a configuration diagram of a high-frequency heating element according to the third embodiment of the present invention.
[0040]
The base 17 of the high-frequency heating element 16 in the figure is composed of a honeycomb structure made of a material having a high relative dielectric constant. The through hole 18 group of the base body 17 is adhesively bonded to the base body 17 at one end in the through hole direction with a sealing member 19 group made of an inorganic material, and closes one end of the through hole. The 20th group is a member that generates heat by absorbing the high frequency inserted and added from the side of the through hole 18 group that is not closed, and the member to be used can be selected from the members described above.
[0041]
The group of members 20 that generate heat by absorbing high frequency is a member that is integrated with the base material 17 and can be used repeatedly over a long period of time, or a member that absorbs high-frequency energy, generates heat, burns, and disappears as a gas. It can also be used.
[0042]
In the structure used for a long period of time, by using a configuration in which the other end face of the group of through holes 18 is also closed by a sealing member, it is possible to facilitate the use of a powder material as a member that absorbs high frequency and generates heat. it can.
[0043]
In this case, since the flow of the powder is regulated by the honeycomb structure of the substrate 17, the powder can be dispersed and arranged in a desired state throughout the high-frequency heating element.
[0044]
Next, functions and effects will be described.
[0045]
Since the substrate 17 is formed of a member having a high relative dielectric constant, the propagation speed of the high frequency propagating through the honeycomb structure is reduced. Thereby, the honeycomb structure can make high frequency energy stay longer in time compared with free space. This residence time is proportional to the square root of the effective relative dielectric constant of the honeycomb structure. By adding a group of members 20 that generate heat by absorbing high-frequency energy in such a structure, the member that generates heat by absorbing high-frequency energy can sufficiently absorb high-frequency energy and promote heat generation.
[0046]
For example, carbon black or charcoal powder has a large high-frequency loss. Therefore, when high-frequency energy of several hundred W or more is supplied, the powder becomes red hot in a short time.
[0047]
If such a phenomenon is used, for example, charcoal-grilled cooking is possible.
[0048]
Further, even when the supplied high frequency energy is extremely low compared with the above, such as unnecessary radiation propagating in space, the high frequency energy is effectively absorbed. If such a phenomenon is used, it can be used as a means for absorbing unnecessary radiation, for example, a wall material of a building (including heat insulation) or an unnecessary radiation preventing part of a high-frequency utilizing device.
[0049]
According to such a configuration of the high-frequency heating element, a desired heat generation amount or absorption amount can be easily obtained by selecting a high-frequency absorption member having a desired high-frequency absorption performance in the frequency band to be used.
[0050]
In the description of the above embodiment, the 2450 MHz band used in the microwave oven is described as an example of the frequency band to be used. However, the present invention is applicable to other frequency bands such as a mobile radio band and a television band. Structures can be applied.
[0051]
In addition, the heating member has been described as an example of application to an oven microwave oven that generates heat to a high temperature of several hundred degrees Celsius or charcoal grilling, but it is not limited to such a high temperature and has propagated Any member that efficiently absorbs high frequency may be used.
[0052]
【The invention's effect】
As described above, the present invention has the following effects.
[0053]
(1) A member with a high relative dielectric constant slows down the high-frequency propagation loss rate that propagates through the high-frequency heating element. A member that generates heat by absorbing a high frequency existing around a member having a high relative dielectric constant can sufficiently absorb high frequency energy from the high frequency of the slow propagation speed and promote heat generation.
[0054]
(2) A heating element corresponding to a desired high frequency can be configured by changing the relative permittivity of the same base by adding a member having a high relative permittivity to the base of the refractory and heat-resistant member. Can do.
[0055]
(3) The honeycomb structure substrate is filled with high relative dielectric constant members, so that the high relative dielectric constant members are dispersed throughout the high frequency heating element, and the effective relative dielectric constant of the heating element when viewed from the high frequency is Equalization can be achieved. As a result, a course propagating from all directions can be slowed down in the high-frequency heat generating body, and absorption of high-frequency energy and heat generation can be promoted.
[0056]
(4) The structure in which a member having a high relative dielectric constant is offset toward one end of the honeycomb structure and the region that actually absorbs the high frequency is limited in the member that absorbs the high frequency, and the heat capacity is reduced to raise the temperature. The characteristics can be improved.
[0057]
(5) Since the high-frequency heating element has a breathable structure, the amount of heat generated by the high-frequency heating element can be transmitted to the object to be heated at a remote position. Moreover, when using a high frequency heat generating body as a sensor, a high frequency heat generating body can be cooled by ventilation | gas_flowing and can be reset to an initial state.
[Brief description of the drawings]
1 is a configuration diagram of a high-frequency heating element of Example 1 of the present invention. FIG. 2 is a configuration diagram of a high-frequency heating element of Example 2 of the present invention. FIG. 3 is a configuration of a high-frequency heating element of Example 3 of the present invention. Figure [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10, 14, 16 High frequency heating element 11 Honeycomb structure base | substrate 13 which consists of a fire-resistant heat-resistant member 13, 15 High dielectric constant member 17 Honeycomb structure base | substrate 20 which consists of a high relative dielectric constant member 20 The member which absorbs a high frequency and heat | fever-generates

Claims (4)

1. A high-frequency heating element comprising a honeycomb structure base comprising a fire-resistant and heat-resistant member that generates heat by absorbing high frequencies, and a member having a high relative dielectric constant in the high-frequency band to be used. The high-frequency heating element according to claim 1 , comprising a structure in which members having the high relative dielectric constant are alternately filled in the through holes of the honeycomb structure. The high-frequency heating element according to claim 1, wherein a member having a high relative dielectric constant is filled at one end side of the honeycomb structure. The high frequency heating element according to any one of claims 1 to 3, wherein the structure has air permeability.

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