JP3999070B2

JP3999070B2 - Microwave firing furnace

Info

Publication number: JP3999070B2
Application number: JP2002224351A
Authority: JP
Inventors: 裕之松尾; 浩通大滝
Original assignee: Nihon Ceratec Co Ltd; Taiheiyo Cement Corp
Current assignee: Taiheiyo Cement Corp; NTK Ceratec Co Ltd
Priority date: 2002-08-01
Filing date: 2002-08-01
Publication date: 2007-10-31
Anticipated expiration: 2022-08-01
Also published as: JP2004069074A

Description

【０００１】
【発明の属する技術分野】
本発明は、マイクロ波加熱によりセラミックス等の被焼成物を焼成するマイクロ波焼成炉に関する。
【０００２】
【従来の技術】
近時、マイクロ波加熱によってセラミックスを焼成する技術が開発され、種々の提案がなされている。例えば、特許第2654903号においては被焼成体をマイクロ波焼成炉内で予熱し、炉内温度と被焼成体の表面温度との差を制御しながらマイクロ波によりセラミックスを焼結する方法が開示されている。この際、被焼成体にマイクロ波を効率よく吸収させるために、マイクロ波焼成炉の断熱部材としてマイクロ波の吸収の少ないセラミックスファイバーボードが用いられている。
【０００３】
【発明が解決しようとする課題】
しかしながら、前記マイクロ波焼成炉は焼成段階で断熱部材であるセラミックスファイバーボードが被焼成物等の重量により変形し、被焼成物が沈み込んでしまうという課題があった。
本発明はかかる事情に鑑みてなされたものであって、焼成時に断熱部材が変形しない構造のマイクロ波焼成炉を提供することを目的とする。
【０００４】
【課題を解決するための手段】
本発明者等は、マイクロ波焼成炉での焼成工程において、被焼成物などの重量により断熱部材が変形する原因について鋭意検討を重ねた。その結果、断熱部材としてのセラミックスファイバーボードの高温強度が低いため、焼成時に被焼成物などの重量に耐えきれず変形するためであるとの結論を得た。
そこで、このような課題を解決するためにさらに検討を重ねた結果、内側断熱部材の底下面と外側断熱部材の底上面の間に多孔質セラミックスを設置することが有効ではないかとの知見に基づいて本発明を完成したものである。
【０００５】
すなわち、上述した本発明の目的は、被焼成物が収容される炉本体と、マイクロ波を発振して前記炉本体に導くマイクロ波発生手段とを具備するマイクロ波焼成炉において、前記炉本体は、少なくとも二重の断熱部材を有し、かつ、内側断熱部材の底下面と外側断熱部材の底上面の間に気孔率５０〜９５％の多孔質セラミックスを具備することを特徴とするマイクロ波焼成炉によって達成される。
【０００６】
【発明の実施の形態】
本発明では、被焼成物が収容される炉本体と、マイクロ波を発振して前記炉本体に導くマイクロ波発生手段とを具備するマイクロ波焼成炉において、前記炉本体は、少なくとも二重の断熱部材を有し、かつ、内側断熱部材の底下面と外側断熱部材の底上面の間に気孔率５０〜９５％の多孔質セラミックスを具備するマイクロ波焼成炉を提案している。
【０００７】
本発明において、前記多孔質セラミックスの気孔率を５０〜９５％とした理由は、多孔質セラミックスの気孔率が５０％未満の場合は、多孔質セラミックスの断熱効果が小さいために、外側断熱部材に被焼成物などの発熱物からの熱が伝導し、断熱部材が熱変形し易くなり好ましくないからである。
また、多孔質セラミックスの気孔率が９５％を越えて大きい場合は、マトリックス部分のセラミックスが少ないため多孔質セラミックス自体の強度が小さく、さらに耐荷重が小さくなるため好ましくない。
【０００８】
ここで、多孔質セラミックスの製造方法としては公知の有機物とセラミックス粉末からなる成形体を焼結しても得られるし、公知の有機物多孔体にセラミックス原料スラリーを含浸させたものを乾燥後に焼結しても得られる。また、ハニカム状の多孔質セラミックス板から所望の形状のものを切り出して用いても良い。
【０００９】
次に、前記炉本体としては、被焼成物の配置空間の外側に少なくとも二重の断熱部材を有し、最内側の断熱部材のマイクロ波吸収特性が被焼成物のマイクロ波吸収特性と同じまたは近似しているものを用いることが好ましい。その理由は、これにより、被焼成物の外部と内部との温度差を小さくして均一に焼成することができるからである。また、外側の断熱部材は比熱の小さいものを用いることがさらに好ましい。
【００１０】
以下、本発明のマイクロ波焼成炉の概略構成を示す断面図である図１を用いて、本発明の実施の形態について具体的に説明する。
マイクロ波焼成炉１は、ステンレス鋼からなる箱状の炉本体２と、炉本体２の外側に設けられたマイクロ波発信器３と、マイクロ波を炉本体２内に導く導波管４、炉本体２内でマイクロ波を攪乱するマイクロ波攪乱器５とを備えている。
【００１１】
炉本体２の内部には、外側断熱部材６および内側断熱部材７の２つの断熱部材が設けられており、内側断熱部材７に囲まれた空間が被焼成物Ｓが配置される被焼成物配置空間となっている。
内側断熱材７としては、マイクロ波吸収特性が被焼成物Ｓと同じかまたは近似している材料が用いられ、典型的には、被焼成物Ｓと同じ材料が用いられる。
また、外側断熱部材６としては、好ましくはマイクロ波の吸収が少なく、かつ比熱の小さい材料が用いられ、例えば、セラミックスファイバーボード等が用いられている。
多孔質セラミックス８は、内側断熱部材７の底下面と外側断熱部材６の底上面の間に設置される。
【００１２】
このように構成されるマイクロ波焼成炉１においては、まず、図示しない炉蓋を開けて炉本体２内に被焼成物Ｓを配置し、次いで炉蓋を閉じ、焼成処理を開始する。
焼成工程で、マイクロ波発振器３の出力を上昇させて所定の速度で炉本体２内の被焼成物Ｓの温度を上昇させ、被焼成物Ｓの材質に応じた温度で所定時間保持する。これにより、所望の焼結体が得られる。
ここで、炉本体２内には内側断熱部材７としてマイクロ波吸収特性が被焼成物Ｓのマイクロ波吸収特性と同じまたは近似している材料を用いれば、焼成の際の被焼成物Ｓの内部と外部との温度差が小さく、均一に焼成することができる。
【００１３】
以下、本発明の実施例と比較例により本発明を具体的に説明する。
炉本体の内部には、外側断熱部材および内側断熱部材の２つの断熱部材を設け、このうち内側断熱部材としては表１に示した被焼成物と同じ材質の焼結体からなる断熱部材を配置し、外側断熱部材としては、セラミックスファイバーボードを配置した。次に、内側断熱部材の底下面と外側断熱部材の底上面の間に多孔質セラミックスを設置した。
ここで、多孔質セラミックスの材質と多孔率しては表１の実施例１〜３および比較例１〜２に示したものを用いた。また、表１に示した材質と形状からなる成形体を被焼成物として、表１に示した加熱温度と保持時間で焼成処理を行った。
このようにして、外側断熱部材として配置したセラミックスファイバーボードの多孔質セラミックスと接している部分に変形が起こるかどうかの評価を行った。
【００１４】
【表１】

【００１５】
（実施例の評価結果）
実施例１〜３に示した多孔質セラミックスを用いた場合は、外側断熱部材として配置したセラミックスファイバーボードには変形は生じなかった。
【００１６】
（比較例の評価結果）
これに対して、多孔率が本発明の範囲外で９７％と大きい多孔質セラミックスを用いた比較例１では、多孔質セラミックス自体が破損した。
次に、多孔率が本発明の範囲外で４０％と小さい多孔質セラミックスを用いた比較例２では、被焼成物などの発熱物からの熱伝導が大きいため、外側断熱部材として配置したセラミックスファイバーボードが変形した。
【００１７】
【発明の効果】
以上説明したように、本発明にて開示したように内側断熱部材の底下面と外側断熱部材の底上面の間に多孔質セラミックスを具備するマイクロ波焼成炉とすることにより、外側断熱部材の変形が発生せずに被焼成物を焼成できるマイクロ波焼成炉を得ることができる。
【図面の簡単な説明】
【図１】本発明のマイクロ波焼成炉の概略構成を示す断面図である。
【符号の説明】
１；マイクロ波焼成炉
２；炉本体
３；マイクロ波発振器
４；導波管
５；マイクロ波攪乱器
６；外側断熱部材
７；内側断熱部材
８；多孔質セラミックス
Ｓ；被焼成物[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microwave baking furnace for baking an object to be fired such as ceramics by microwave heating.
[0002]
[Prior art]
Recently, techniques for firing ceramics by microwave heating have been developed and various proposals have been made. For example, Japanese Patent No. 2654903 discloses a method in which a body to be fired is preheated in a microwave firing furnace, and ceramics are sintered by microwaves while controlling the difference between the furnace temperature and the surface temperature of the body to be fired. ing. At this time, in order to efficiently absorb the microwaves in the body to be fired, a ceramic fiber board with less microwave absorption is used as a heat insulating member of the microwave firing furnace.
[0003]
[Problems to be solved by the invention]
However, the microwave baking furnace has a problem that the ceramic fiber board, which is a heat insulating member, is deformed by the weight of the object to be fired and the object to be fired sinks in the firing stage.
This invention is made | formed in view of this situation, Comprising: It aims at providing the microwave baking furnace of a structure where a heat insulation member does not deform | transform at the time of baking.
[0004]
[Means for Solving the Problems]
The inventors of the present invention have made extensive studies on the cause of deformation of the heat insulating member due to the weight of the object to be fired in the firing step in the microwave firing furnace. As a result, it was concluded that the high temperature strength of the ceramic fiber board as the heat insulating member was low, and therefore it could not withstand the weight of the object to be fired during firing and deformed.
Therefore, as a result of further studies to solve such problems, based on the knowledge that it is effective to install porous ceramics between the bottom lower surface of the inner heat insulating member and the bottom upper surface of the outer heat insulating member. This completes the present invention.
[0005]
That is, the above-described object of the present invention is to provide a microwave firing furnace including a furnace main body in which an object to be fired is stored, and a microwave generating means that oscillates microwaves and guides it to the furnace main body. A microwave firing comprising at least a double heat insulating member and porous ceramics having a porosity of 50 to 95% between a bottom lower surface of the inner heat insulating member and a bottom upper surface of the outer heat insulating member Achieved with a furnace.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, in a microwave baking furnace comprising a furnace main body in which an object to be fired is stored, and a microwave generating means for oscillating microwaves and guiding them to the furnace main body, the furnace main body has at least double heat insulation. A microwave firing furnace having a member and having porous ceramics with a porosity of 50 to 95% between the bottom lower surface of the inner heat insulating member and the bottom upper surface of the outer heat insulating member is proposed.
[0007]
In the present invention, the porous ceramic has a porosity of 50 to 95% because, when the porosity of the porous ceramic is less than 50%, the heat insulating effect of the porous ceramic is small. This is because heat from a heat generating material such as an object to be fired is conducted and the heat insulating member is easily deformed by heat, which is not preferable.
Further, when the porosity of the porous ceramic exceeds 95%, it is not preferable because the ceramic of the matrix portion is small and the strength of the porous ceramic itself is small and the load resistance is small.
[0008]
Here, as a manufacturing method of porous ceramics, it can be obtained by sintering a molded body made of a known organic substance and ceramic powder, or a known organic porous body impregnated with a ceramic raw material slurry is sintered after drying. You can get it. Moreover, you may cut out and use the thing of a desired shape from a honeycomb-shaped porous ceramic board.
[0009]
Next, the furnace body has at least a double heat insulating member outside the arrangement space of the object to be fired, and the microwave absorption characteristic of the innermost heat insulating member is the same as the microwave absorption characteristic of the object to be fired or It is preferable to use an approximation. The reason for this is that, by this, the temperature difference between the outside and the inside of the object to be fired can be reduced and uniform firing can be achieved. Moreover, it is more preferable to use an outer heat insulating member having a small specific heat.
[0010]
Hereinafter, an embodiment of the present invention will be specifically described with reference to FIG. 1 which is a cross-sectional view showing a schematic configuration of a microwave baking furnace of the present invention.
Microwave heating furnace 1, a box-shaped furnace body 2 made of stainless steel, a

microwave

transmitter 3 provided outside of the furnace body 2, the waveguide 4 for guiding the microwave into the furnace body 2, furnace The main body 2 includes a microwave disturbance device 5 for disturbing microwaves.
[0011]
Inside the furnace body 2, two heat insulating members, an outer heat insulating member 6 and an inner heat insulating member 7, are provided, and the object to be fired is disposed in a space surrounded by the inner heat insulating member 7. It is a space.
As the inner heat insulating material 7, a material having the same or similar microwave absorption characteristic as that of the object to be fired S is used. Typically, the same material as that of the object to be fired S is used.
The outer heat insulating member 6 is preferably made of a material with low microwave absorption and low specific heat, such as a ceramic fiber board.
The porous ceramic 8 is installed between the bottom lower surface of the inner heat insulating member 7 and the bottom upper surface of the outer heat insulating member 6.
[0012]
In the microwave firing furnace 1 configured as described above, first, a furnace lid (not shown) is opened, the object to be fired S is placed in the furnace body 2, and then the furnace lid is closed, and a firing process is started.
In the firing step, the output of the microwave oscillator 3 is increased to increase the temperature of the object to be fired S in the furnace body 2 at a predetermined speed, and the temperature is maintained at a temperature corresponding to the material of the material to be fired S for a predetermined time. Thereby, a desired sintered body is obtained.
Here, if a material whose microwave absorption characteristic is the same as or similar to the microwave absorption characteristic of the object to be fired S is used as the inner heat insulating member 7 in the furnace body 2, the inside of the object to be fired S during firing is used. And the temperature difference between the outside and the outside is small, and it can be fired uniformly.
[0013]
Hereinafter, the present invention will be described in detail by way of examples and comparative examples of the present invention.
Inside the furnace body, two heat insulating members, an outer heat insulating member and an inner heat insulating member, are provided, and among them, a heat insulating member made of a sintered body made of the same material as the material to be fired shown in Table 1 is arranged. A ceramic fiber board is disposed as the outer heat insulating member. Next, porous ceramics were installed between the bottom lower surface of the inner heat insulating member and the bottom upper surface of the outer heat insulating member.
Here, as the material and porosity of the porous ceramic, those shown in Examples 1 to 3 and Comparative Examples 1 and 2 in Table 1 were used. Moreover, the molded object which consists of a material and a shape shown in Table 1 was made into a to-be-baked object, and the baking process was performed with the heating temperature and holding time shown in Table 1.
In this way, it was evaluated whether or not deformation occurred in the portion of the ceramic fiber board disposed as the outer heat insulating member that was in contact with the porous ceramic.
[0014]
[Table 1]

[0015]
(Evaluation results of examples)
When the porous ceramics shown in Examples 1 to 3 were used, no deformation occurred in the ceramic fiber board disposed as the outer heat insulating member.
[0016]
(Evaluation result of comparative example)
On the other hand, in Comparative Example 1 using porous ceramics having a porosity as large as 97% outside the range of the present invention, the porous ceramics themselves were damaged.
Next, in Comparative Example 2 using a porous ceramic having a porosity of as small as 40% outside the range of the present invention, the ceramic fiber disposed as an outer heat insulating member because heat conduction from a heat generating material such as an object to be fired is large. The board was deformed.
[0017]
【The invention's effect】
As described above, the outer heat insulating member is deformed by using the microwave firing furnace having porous ceramics between the bottom lower surface of the inner heat insulating member and the bottom upper surface of the outer heat insulating member as disclosed in the present invention. It is possible to obtain a microwave baking furnace capable of baking an object to be fired without generation of.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of a microwave baking furnace of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Microwave baking furnace 2; Furnace main body 3; Microwave oscillator 4; Waveguide 5; Microwave disturbance device 6; Outer heat insulation member 7; Inner heat insulation member 8;

Claims

In a microwave baking furnace including a furnace body in which an object to be fired is stored, microwave generation means for oscillating microwaves , and a waveguide for guiding the microwave into the furnace body,
The furnace body has an outer heat insulating member and an inner heat insulating member, and both the outer heat insulating member and the inner heat insulating member surround a space, and the inner heat insulating member is included in the outer heat insulating member. and micro characterized by having a porosity of 50% to 95% of the porous ceramic to prevent deformation of the outer heat insulating member between the bottom upper surface of the bottom lower surface and the outer heat insulating member of the inner heat insulating member Wave firing furnace.