JPH05234665A - Ceramic exothermic body - Google Patents
Ceramic exothermic bodyInfo
- Publication number
- JPH05234665A JPH05234665A JP3182492A JP3182492A JPH05234665A JP H05234665 A JPH05234665 A JP H05234665A JP 3182492 A JP3182492 A JP 3182492A JP 3182492 A JP3182492 A JP 3182492A JP H05234665 A JPH05234665 A JP H05234665A
- Authority
- JP
- Japan
- Prior art keywords
- resistor
- silicone
- sintered body
- content
- silicon nitride
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明はディーゼルエンジンの始
動促進用グロープラグや、各種燃焼機器の点火用ヒータ
ー及び加熱機器の加熱用ヒーターに用いられる高温用の
セラミック発熱体に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature ceramic heating element used for glow plugs for accelerating the starting of diesel engines, ignition heaters for various combustion equipment and heating heaters for heating equipment.
【０００２】[0002]
【従来の技術】従来よりディーゼルエンジンの始動促進
に用いられるグロープラグや各種点火用及び加熱用ヒー
ターとして、耐熱金属製のシース内に耐熱絶縁粉末を充
填し、該耐熱絶縁粉末中に、ニッケル（Ｎｉ）−クロム
（Ｃｒ）等を主体とする高融点金属線から成る発熱抵抗
体を埋設したシーズヒーターや、高電圧の火花放電を利
用する各種点火装置が使用されていた。2. Description of the Related Art Conventionally, as a glow plug used for accelerating the starting of a diesel engine and various ignition and heating heaters, a heat resistant insulating powder is filled in a sheath made of a heat resistant metal, and nickel ( A sheathed heater in which a heating resistor made of a refractory metal wire mainly composed of Ni) -chromium (Cr) or the like is embedded, and various igniters utilizing high-voltage spark discharge have been used.
【０００３】しかしながら、前記シーズヒーターは耐熱
金属製のシース内に充填された耐熱絶縁粉末を介して発
熱抵抗体の熱を伝えるため、短時間の急速昇温が困難で
ありその上、耐摩耗性や耐久性に劣るという問題がある
他、前記火花放電を利用した各種点火装置も、点火時に
雑音等の電波障害を生じたり、確実な点火という観点か
らの信頼性に欠け、未着火の場合の安全性に問題がある
等の欠点があった。However, since the sheathed heater transfers the heat of the heat-generating resistor through the heat-resistant insulating powder filled in the sheath made of heat-resistant metal, it is difficult to rapidly raise the temperature in a short time and, in addition, it has abrasion resistance. In addition to the problem of poor durability, various ignition devices using the spark discharge also cause radio interference such as noise at the time of ignition, lack of reliability from the viewpoint of reliable ignition, in the case of unignition There were drawbacks such as safety issues.
【０００４】そこで、短時間の急速昇温が可能で、電波
障害が発生せず、しかも確実に点火して安全性を確保
し、雰囲気を問わず長時間の使用が可能であり、耐摩耗
性と耐久性に優れた信頼性の高い発熱体として、無機導
電材から成る発熱抵抗体をセラミック焼結体中に埋設し
たセラミック発熱体が、広く利用されるようになってき
た。Therefore, the temperature can be rapidly raised in a short time, no radio wave interference occurs, and the ignition is surely performed to ensure safety, and it can be used for a long time regardless of the atmosphere, and is wear-resistant. As a highly reliable and highly reliable heating element, a ceramic heating element in which a heating resistor made of an inorganic conductive material is embedded in a ceramic sintered body has been widely used.
【０００５】なかでも、耐熱衝撃性及び高温強度が他の
セラミックスよりも著しく優れた窒化珪素質焼結体をヒ
ーターの基体として使用し、一般にタングステン（Ｗ）
やモリブデン（Ｍｏ）等の高融点金属もしくはこれらの
化合物より成る発熱抵抗体を基体中に埋設したり、前記
高融点金属もしくはこれらの化合物を主体とする発熱抵
抗体ペーストを前記基体上にパターン印刷して焼成一体
化してなるものが、広く利用されている。Above all, a silicon nitride sintered body having a heat shock resistance and a high temperature strength remarkably superior to those of other ceramics is used as a substrate of a heater, and in general, tungsten (W) is used.
A heating resistor made of a high melting point metal such as molybdenum or molybdenum (Mo) or a compound thereof is embedded in a substrate, or a heating resistor paste mainly containing the high melting point metal or a compound thereof is pattern-printed on the substrate. Those that are integrated by firing are widely used.
【０００６】しかしながら、前記窒化珪素質焼結体をヒ
ーターの基体とするセラミック発熱体は、前記焼結体の
粒界相が一般に低融点のガラス質を形成していることか
ら、通電加熱によりセラミック発熱体が１０００℃を越
えると、粒界相の軟化による窒化珪素質焼結体の強度劣
化や、印加電圧による粒界相のイオン移動から組織劣化
を引き起こし、発熱抵抗体と窒化珪素質焼結体の熱膨張
差により、発熱抵抗体近傍の窒化珪素質焼結体にクラッ
クを生じたり、耐酸化性に劣る等の欠点があった。However, since the grain boundary phase of the sintered body generally forms a glass material having a low melting point, the ceramic heating element using the silicon nitride sintered body as the base material of the heater is heated by electric heating. When the heating element exceeds 1000 ° C., the strength of the silicon nitride sintered body is deteriorated due to the softening of the grain boundary phase and the structure is deteriorated due to the ion migration of the grain boundary phase due to the applied voltage. Due to the difference in thermal expansion between the bodies, there are drawbacks such as cracks in the silicon nitride sintered body near the heating resistor and poor oxidation resistance.
【０００７】そこで前記窒化珪素質焼結体の粒界相を結
晶化することにより、高温での粒界相の軟化によるセラ
ミック焼結体の強度劣化を防止し、かつ印加電圧による
粒界相のイオン移動を阻止して、発熱抵抗体近傍の窒化
珪素質焼結体がクラックを発生したり、窒化珪素質焼結
体自体が組織劣化を引き起こしたりすることを防止せん
としたセラミック発熱体が提案されている（特開平１−
３１３３６２号公報参照）。Therefore, by crystallizing the grain boundary phase of the silicon nitride sintered body, the strength deterioration of the ceramic sintered body due to the softening of the grain boundary phase at high temperature is prevented, and the grain boundary phase of the sintered body is reduced by the applied voltage. Proposed ceramic heating element that prevents ion migration and prevents the silicon nitride sintered body near the heating resistor from cracking and the silicon nitride sintered body itself from causing structural deterioration. (JP-A-1-
See Japanese Patent No. 3133362).
【０００８】[0008]
【発明が解決しようとする課題】しかしながら、前記窒
化珪素質焼結体を基体とするセラミック発熱体は、耐酸
化性に劣るＳｉ3 Ｎ4 ・Ｙ2 Ｏ3 等に代表されるメリラ
イト相や４Ｙ2 Ｏ3 ・ＳｉＯ2 ・Ｓｉ3 Ｎ4 等に代表さ
れるＹＡＭ相の結晶相を生成したり、それ以外に、必ず
少量と言えども低融点のガラス質を結晶粒界に残留して
しまう。However, the ceramic heating element based on the above-mentioned silicon nitride sintered body is a melilite phase represented by Si 3 N 4 .Y 2 O 3 having poor oxidation resistance and 4Y. Besides, a crystal phase of a YAM phase typified by 2 O 3 , SiO 2 , Si 3 N 4 and the like is generated, and besides, a glass material having a low melting point remains at the crystal grain boundaries even if it is a small amount.
【０００９】しかも、前記グロープラグや各種点火用及
び加熱用ヒーターとしてのセラミック発熱体は、一般に
点火時には１０００〜１３００℃もの高温となり、中に
は点火した火炎に曝されて１３５０℃を越えるものもあ
る。Moreover, the glow plugs and ceramic heating elements as various ignition and heating heaters generally have a high temperature of 1000 to 1300 ° C. when ignited, and some of them are exposed to an ignited flame and exceed 1350 ° C. is there.
【００１０】このような状況で長時間の連続通電を行っ
た場合、前記低融点のガラス質のイオン移動を阻止する
ことができず、更に、前記粒界相の結晶も酸化されてイ
オン移動を起こし、パイプ状金具近傍の露出した窒化珪
素質焼結体の側面にクラックを生じたり、組織劣化を起
こし、セラミック発熱体の寿命が急激に短くなってその
機能を失い、耐久性と信頼性に欠けるという課題があっ
た。When continuous energization is carried out for a long time in such a situation, it is impossible to prevent the migration of the low melting glassy ions, and the crystals of the grain boundary phase are also oxidized to cause the ion migration. It causes a crack on the side surface of the exposed silicon nitride sintered body near the pipe-shaped metal fittings or causes deterioration of the structure, which shortens the life of the ceramic heating element rapidly and loses its function. There was a problem of lacking.
【００１１】[0011]
【発明の目的】本発明は前記欠点に鑑み開発されたもの
で、その目的は高温で長時間の連続使用が可能である耐
酸化性及び耐久性に優れたセラミック発熱体を提供する
ことにある。SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned drawbacks, and an object thereof is to provide a ceramic heating element excellent in oxidation resistance and durability which can be continuously used at a high temperature for a long time. ..
【００１２】[0012]
【課題を解決するための手段】本発明のセラミック発熱
体は、無機導電材から成る発熱抵抗体を希土類元素及び
酸化珪素を含有して成る窒化珪素質焼結体中に埋設した
セラミック発熱体において、前記窒化珪素質焼結体は希
土類元素を酸化物換算した含有量に対する酸化珪素（Ｓ
ｉＯ2 ）の含有量のモル比が１．０〜２．５であること
を特徴とするものである。The ceramic heating element of the present invention is a ceramic heating element in which a heating resistor made of an inorganic conductive material is embedded in a silicon nitride sintered body containing a rare earth element and silicon oxide. The silicon nitride-based sintered body contains silicon oxide (S
The molar ratio of the content of iO 2 ) is 1.0 to 2.5.
【００１３】本発明のセラミック発熱体において、窒化
珪素質焼結体中の希土類元素を酸化物換算した含有量に
対する酸化珪素（ＳｉＯ2 ）の含有量のモル比、即ち、
ＳｉＯ2 の含有量（モル％）／希土類元素を酸化物換算
した含有量（モル％）の値が１．０未満では、前記メリ
ライト相やＹＡＭ相が生成され、該結晶相は耐酸化性が
悪く酸化されやすいことから、高温度で長時間、例えば
数千サイクル以下の通電でイオン移動を起こして粒界相
が酸化されて体積膨張し、パイプ状金具近傍の露出した
窒化珪素質焼結体の側面で、かつ埋設した発熱抵抗体の
陽極側の側面にクラックが発生し、とりわけ埋設した発
熱抵抗体が酸化されやすくなって断線してしまう。In the ceramic heating element of the present invention, the molar ratio of the content of silicon oxide (SiO 2 ) to the content of the rare earth element in the silicon nitride sintered body converted to oxide, that is,
When the value of the content of SiO 2 (mol%) / the content of the rare earth element converted to oxide (mol%) is less than 1.0, the melilite phase or the YAM phase is generated, and the crystal phase has an oxidation resistance. Since it is easily oxidized badly, the grain boundary phase is oxidized and volume-expanded due to ion migration caused by energization at high temperature for a long time, for example, several thousand cycles or less, and the exposed silicon nitride sintered body near the pipe-shaped metal fittings. On the anode side of the embedded heating resistor, the embedded heating resistor is apt to be oxidized, resulting in disconnection.
【００１４】一方、前記モル比が２．５を越えると、結
晶中の粒界相にＳｉＯ2 ガラスに代表される低融点ガラ
スを発生し、前記のような使用条件下では、１０００サ
イクル程度で低融点ガラスのイオン移動により、強度劣
化を起こして発熱抵抗体と窒化珪素質焼結体との熱膨張
差から、パイプ状金具近傍の露出した窒化珪素質焼結体
の側面で、かつ埋設した発熱抵抗体の陰極側の側面にク
ラックを発生する。On the other hand, when the molar ratio exceeds 2.5, a low melting point glass represented by SiO 2 glass is generated in the grain boundary phase in the crystal, and under the above-mentioned conditions of use, it takes about 1000 cycles. Due to the ion migration of the low melting point glass, the strength was deteriorated, and due to the difference in thermal expansion between the heating resistor and the silicon nitride sintered body, it was embedded on the exposed side surface of the silicon nitride sintered body near the pipe-shaped metal fitting. A crack is generated on the cathode side surface of the heating resistor.
【００１５】よって窒化珪素質焼結体中の希土類元素を
酸化物換算した含有量に対する酸化珪素（ＳｉＯ2 ）の
含有量のモル比は、１．０〜２．５、望ましくは１．３
〜１．９の範囲に特定される。Therefore, the molar ratio of the content of silicon oxide (SiO 2 ) to the content of the rare earth element in the silicon nitride sintered body converted to oxide is 1.0 to 2.5, preferably 1.3.
Is specified in the range of ˜1.9.
【００１６】[0016]
【実施例】以下、本発明のセラミック発熱体を図面に基
づき詳細に説明する。図１は、本発明の一実施例に係る
ディーゼルエンジンの始動促進用に使用されるグロープ
ラグに適用したセラミック発熱体を示す。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The ceramic heating element of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a ceramic heating element applied to a glow plug used to accelerate starting of a diesel engine according to an embodiment of the present invention.
【００１７】図１において、１は窒化珪素質焼結体３中
に発熱抵抗体２を埋設したセラミック発熱体であり、セ
ラミック発熱体１には段差部８を有するパイプ状金具４
を外嵌めして発熱抵抗体２のリード部５に接続するよう
にろう付けして一方の電極端子として導出し、更に、パ
イプ状金具４と取付金具６とが重なる部分で少なくとも
取付金具６の先端内側に設けた段座７より取付金具６の
先端側に間隙を有するようにして、前記パイプ状金具４
の段差部８を取付金具６の先端内側に設けた段座７に導
電性ガスケット９を介して当接することにより電気的に
接続固着させている。In FIG. 1, reference numeral 1 is a ceramic heating element in which a heating resistor 2 is embedded in a silicon nitride sintered body 3, and the ceramic heating element 1 has a pipe-shaped metal fitting 4 having a step portion 8.
Is externally fitted and brazed so as to be connected to the lead portion 5 of the heat generating resistor 2 and led out as one electrode terminal. Further, at least a portion of the mounting metal fitting 6 at which the pipe-shaped metal fitting 4 and the mounting metal fitting 6 overlap each other. The pipe-shaped metal fitting 4 is provided so that there is a gap on the front end side of the mounting bracket 6 from the step seat 7 provided inside the front end.
The stepped portion 8 is electrically contacted and fixed to the stepped seat 7 provided inside the front end of the mounting member 6 through the conductive gasket 9.
【００１８】一方、セラミック発熱体１の後端部には、
パイプ状金具４と同時にろう接した他方の発熱抵抗体２
のリード部１０と接続する電極取出部１１の端面に、絶
縁体１２に挿通したフランジを有する端子棒１３が当接
され、取付金具６の後端周縁を絶縁体１２の端面で加締
めて固着し、パイプ状金具４と取付金具６をろう接せず
に加圧接合して負電極とするとともに、セラミック発熱
体１の後端部にろう接した電極取出部１１と端子棒１３
も同様に加圧接合して正電極とし、端子棒１３にベーク
ライト等の絶縁性ワッシャー１４をナット１５で固定す
ることにより取付金具６の負電極と、端子棒１３の正電
極とが絶縁されてグロープラグが構成されている。On the other hand, at the rear end of the ceramic heating element 1,
The other heating resistor 2 brazed at the same time as the pipe-shaped metal fitting 4
The terminal rod 13 having a flange inserted in the insulator 12 is brought into contact with the end surface of the electrode lead-out portion 11 connected to the lead portion 10, and the rear end peripheral edge of the mounting bracket 6 is caulked and fixed by the end surface of the insulator 12. Then, the pipe-shaped metal fitting 4 and the mounting metal fitting 6 are pressure-bonded without brazing to form a negative electrode, and the electrode lead-out portion 11 and the terminal rod 13 which are brazed to the rear end portion of the ceramic heating element 1 are formed.
Similarly, pressure bonding is performed to form a positive electrode, and by fixing an insulating washer 14 such as Bakelite to the terminal rod 13 with a nut 15, the negative electrode of the mounting bracket 6 and the positive electrode of the terminal rod 13 are insulated. A glow plug is constructed.
【００１９】また、セラミック発熱体１は、図２に示す
ような断面が半円形の棒状に成形した窒化珪素質成形体
１６上に発熱抵抗体２を載置した後、その上面に別の窒
化珪素質成形体１７を重ねて加圧焼成して一体化したも
のである。Further, in the ceramic heating element 1, after the heating resistor 2 is placed on the silicon nitride molding 16 formed into a rod shape having a semicircular cross section as shown in FIG. 2, another nitriding is performed on the upper surface thereof. The silicon-based compact 17 is overlaid, pressure-fired and integrated.
【００２０】尚、本発明のセラミック発熱体において、
無機導電材から成る発熱抵抗体としてはタングステン
（Ｗ）、モリブデン（Ｍｏ）、レニウム（Ｒｅ）等の高
融点金属の他、例えばタングステンカーバイド（Ｗ
Ｃ）、窒化チタン（ＴｉＮ）、モリブデンシリサイド
（ＭｏＳｉ2 ）や硼化ジルコニウム（ＺｒＢ2 ）等の第
４ａ族、第５ａ族、第６ａ族の炭化物または窒化物等か
ら成る線材、あるいは薄層状に形成したものが好適に用
いられる。In the ceramic heating element of the present invention,
Examples of the heating resistor made of an inorganic conductive material include high melting point metals such as tungsten (W), molybdenum (Mo), and rhenium (Re), as well as tungsten carbide (W).
C), titanium nitride (TiN), molybdenum silicide (MoSi 2 ), zirconium boride (ZrB 2 ), etc. 4a, 5a, 6a carbide or nitride wire or thin layer What was formed is used suitably.
【００２１】本発明のセラミック発熱体を評価するにあ
たり、先ず、比表面積が１２ｍ2 ／ｇ、含有する不可避
不純物としての酸素量、即ち酸化珪素（ＳｉＯ2 ）が３
重量％以下で、結晶のα化率が９７％である窒化珪素
（Ｓｉ3 Ｎ4 ）粉末に、焼結助材としての希土類元素の
酸化物およびアルミナ（Ａｌ2 Ｏ3 ）と、窒化珪素質焼
結体中の酸素量調整用としての酸化珪素（ＳｉＯ2 ）の
配合量を種々設定した原料粉末を２４時間、ボールミル
にて湿式混合する。In evaluating the ceramic heating element of the present invention, first, the specific surface area is 12 m 2 / g and the amount of oxygen contained as inevitable impurities, that is, silicon oxide (SiO 2 ) is 3.
A silicon nitride (Si 3 N 4 ) powder having a crystallinity ratio of 97% by weight or less, a rare earth element oxide and alumina (Al 2 O 3 ) as a sintering aid, and a silicon nitride material. Raw material powders having various amounts of silicon oxide (SiO 2 ) for adjusting the amount of oxygen in the sintered body are wet mixed in a ball mill for 24 hours.
【００２２】かくして得られた混合物の泥漿を噴霧乾燥
して造粒し、プレス成形法により断面が半円形の棒状の
窒化珪素質成形体１６、１７を作製する。The slurry thus obtained is spray-dried and granulated, and rod-shaped silicon nitride compacts 16 and 17 each having a semicircular cross section are produced by a press molding method.
【００２３】次に、該成形体１６の平面上に、略Ｕ字形
状のコイル状タングステン線と該コイル状タングステン
線に接続したリード部５、１０を構成するタングステン
線とから成る発熱抵抗体２を載置し、該発熱抵抗体２を
挟むように前記同形状の別の窒化珪素質成形体１７を重
ねて加圧焼成した。Next, on the plane of the molded body 16, a heating resistor 2 comprising a substantially U-shaped coiled tungsten wire and a tungsten wire forming the lead portions 5 and 10 connected to the coiled tungsten wire. Was placed, and another silicon nitride compact 17 having the same shape was stacked so as to sandwich the heat generating resistor 2 and was fired under pressure.
【００２４】かくして得られた焼結体の側面を研磨して
前記リード部５の一部を露出させ、少なくとも該露出部
にメタライズ法やメッキ法等によりニッケル（Ｎｉ）等
の金属被膜を形成した後、パイプ状金具４に内挿し還元
ガス雰囲気中で銀ろうにて接合する。The side surface of the thus obtained sintered body is polished to expose a part of the lead portion 5, and a metal coating film of nickel (Ni) or the like is formed on at least the exposed portion by a metallizing method or a plating method. After that, it is inserted into the pipe-shaped metal fitting 4 and joined with silver brazing in a reducing gas atmosphere.
【００２５】一方、前記焼結体の端部に露出したリード
部１０に、線材より成る電極取出部１１を同様に銀ろう
にて接合した後、取付金具６の先端部に内挿し、該取付
金具６と前記パイプ状金具４、及びセラミック発熱体１
の後端部にろう接した電極取出部１１と端子棒１３を加
圧接合してそれぞれ正負の電極とし、評価用のグロープ
ラグを作製した。On the other hand, the lead-out portion 10 exposed at the end of the sintered body is similarly joined with an electrode lead-out portion 11 made of a wire by silver brazing, and then inserted inside the tip of the mounting metal fitting 6 to attach the same. Metal fitting 6, the pipe-shaped metal fitting 4, and ceramic heating element 1
A glow plug for evaluation was produced by pressure-bonding the electrode lead-out portion 11 and the terminal rod 13 brazed to the rear end portion thereof to form positive and negative electrodes.
【００２６】また、同時に前記窒化珪素質成形体のみを
同一条件で加圧焼成した窒化珪素質焼結体を酸素量分析
用及び抗折強度評価用試料とし、酸素・窒素分析装置に
より窒化珪素質焼結体の全酸素量を測定し、窒化珪素
（Ｓｉ3 Ｎ4 ）粉末中に含有する不可避不純物としての
酸素量と、焼結助剤として添加した希土類元素の酸化物
およびアルミナ（Ａｌ2 Ｏ3 ）量から算出した酸素量を
差引きし、残余の酸素量がシリコン（Ｓｉ）と反応して
シリカ（ＳｉＯ2 ）を形成するとしてその量を算出し
た。At the same time, a silicon nitride sintered body obtained by pressure-calcining only the silicon nitride molded body under the same conditions was used as a sample for oxygen content analysis and bending strength evaluation, and a silicon nitride material was analyzed by an oxygen / nitrogen analyzer. The total amount of oxygen in the sintered body was measured, and the amount of oxygen as an unavoidable impurity contained in the silicon nitride (Si 3 N 4 ) powder and the oxide of a rare earth element added as a sintering aid and alumina (Al 2 O 4 3 ) The amount of oxygen calculated from the amount was subtracted, and the amount of residual oxygen was calculated as reacting with silicon (Si) to form silica (SiO 2 ).
【００２７】一方、波長分散型Ｘ線マイクロアナライザ
ーにより希土類元素を定量し、希土類元素の酸化物換算
の含有量を算出した。On the other hand, the rare earth element was quantified by a wavelength dispersive X-ray microanalyzer, and the content of the rare earth element in terms of oxide was calculated.
【００２８】更に、前記評価用試料を使用して、常温と
１４００℃での抗折強度をＪＩＳ３点曲げ強度試験法に
基づき測定した。また、前記評価用試料を使用して、Ｘ
線回折装置によりＹＡＭ相の結晶相を有無とともにピー
ク強度の大小を同定した。Further, the bending strength at room temperature and 1400 ° C. was measured using the above-mentioned evaluation sample based on the JIS three-point bending strength test method. In addition, using the evaluation sample, X
The magnitude of the peak intensity was identified by the presence or absence of the crystal phase of the YAM phase by a line diffractometer.
【００２９】一方、直流電源より評価用のグロープラグ
に通電して、１４００℃の温度に急速加熱した後、通電
停止して圧搾空気を吹きつけて強制冷却するのを１サイ
クルとする耐久試験を１００００サイクル実施し、該耐
久試験前後の抵抗値を測定して発熱抵抗体の抵抗変化率
を算出した。On the other hand, an endurance test in which one cycle consists of energizing a glow plug for evaluation from a DC power source to rapidly heat it to a temperature of 1400 ° C., then stopping energization and blowing compressed air to forcibly cool it is one cycle. After carrying out 10,000 cycles, the resistance value before and after the durability test was measured to calculate the resistance change rate of the heating resistor.
【００３０】更に、セラミック発熱体部のクラックの有
無を蛍光探傷法により検査するとともに、セラミック発
熱体の表面状態を顕微鏡にて観察した。以上の結果を表
１及び表２に示す。Further, the presence or absence of cracks in the ceramic heating element was inspected by a fluorescent flaw detection method, and the surface condition of the ceramic heating element was observed with a microscope. The above results are shown in Tables 1 and 2.
【００３１】[0031]
【表１】 [Table 1]
【００３２】[0032]
【表２】 [Table 2]
【００３３】表１及び表２から明らかなように、ＳｉＯ
2 （モル％）／希土類元素酸化物（モル％）のモル比が
１．０未満の試料番号１、１０、１７、２４は、パイプ
状金具近傍の露出した窒化珪素質焼結体の側面で、かつ
埋設した発熱抵抗体の陽極側の側面にクラックが発生
し、発熱抵抗体自体が断線している。As is clear from Tables 1 and 2, SiO
Sample Nos. 1, 10, 17, and 24 having a molar ratio of 2 (mol%) / rare earth element oxide (mol%) of less than 1.0 are the exposed side surfaces of the silicon nitride sintered body near the pipe-shaped metal fittings. A crack is generated on the side surface of the embedded heating resistor on the side of the anode, and the heating resistor itself is disconnected.
【００３４】また、ＳｉＯ2 （モル％）／希土類元素酸
化物（モル％）のモル比がともに２．５を越える試料番
号９、１６、２３、３０は、窒化珪素質焼結体の高温で
の抗折強度が低く、かつパイプ状金具近傍の露出した窒
化珪素質焼結体の側面で、かつ埋設した発熱抵抗体の陰
極側の側面にクラックを生じている。Further, sample numbers 9, 16, 23 and 30 in which both the SiO 2 (mol%) / rare earth element oxide (mol%) molar ratio exceeded 2.5 were measured at a high temperature of the silicon nitride sintered body. Has a low bending strength, and cracks are formed on the exposed side surface of the silicon nitride sintered body near the pipe-shaped metal fitting and on the side surface on the cathode side of the embedded heating resistor.
【００３５】それらに対して、本発明のセラミック発熱
体の窒化珪素質焼結体はいずれも高い抗折強度を保持
し、通電耐久試験においても何ら変化が認められなかっ
た。On the other hand, all of the silicon nitride sintered bodies of the ceramic heating element of the present invention maintained a high bending strength, and no change was observed in the electrical durability test.
【００３６】[0036]
【発明の効果】叙上の如く、本発明のセラミック発熱体
は、希土類元素を酸化物換算した含有量に対する酸化珪
素（ＳｉＯ2 ）の含有量のモル比が１．０〜２．５であ
る窒化珪素質焼結体中に無機導電材から成る発熱抵抗体
を埋設したことから、高温でも高い抗折強度を保持しな
がら、発熱抵抗体の正負いずれの電極側の窒化珪素質焼
結体にもクラックの発生は勿論、組織の劣化もなく、か
つ耐酸化性に優れ、とりわけ高温での長時間の繰り返し
使用が可能である耐久性と信頼性に優れたセラミック発
熱体を提供することができる。As described above, in the ceramic heating element of the present invention, the molar ratio of the content of silicon oxide (SiO 2 ) to the content of the rare earth element converted to oxide is 1.0 to 2.5. Since the heating resistor made of an inorganic conductive material is embedded in the silicon nitride sintered body, the silicon nitride sintered body on either the positive or negative electrode side of the heating resistor can be maintained while maintaining high bending strength even at high temperatures. Also, it is possible to provide a ceramic heating element which is free from cracks and deterioration of the structure, has excellent oxidation resistance, and can be repeatedly used especially at high temperature for a long time and which has excellent durability and reliability. ..
【図１】本発明に係るセラミック発熱体をディーゼルエ
ンジンの始動促進用に使用されるグロープラグに適用し
た一実施例を示す一部破断面図である。FIG. 1 is a partially broken cross-sectional view showing an embodiment in which a ceramic heating element according to the present invention is applied to a glow plug used to accelerate starting of a diesel engine.
【図２】本発明に係るセラミック発熱体の製造工程を説
明するための斜視図である。FIG. 2 is a perspective view for explaining a manufacturing process of the ceramic heating element according to the present invention.
１ セラミック発熱体 ２ 発熱抵抗体 ３ 窒化珪素質焼結体 1 Ceramic heating element 2 Heating resistor 3 Silicon nitride sintered body
Claims (1)
素及び酸化珪素を含有して成る窒化珪素質焼結体中に埋
設したセラミック発熱体において、前記窒化珪素質焼結
体は希土類元素を酸化物換算した含有量に対する酸化珪
素（ＳｉＯ2 ）の含有量のモル比が１．０〜２．５であ
ることを特徴とするセラミック発熱体。1. A ceramic heating element in which a heating resistor made of an inorganic conductive material is embedded in a silicon nitride sintered body containing a rare earth element and silicon oxide, wherein the silicon nitride sintered body contains a rare earth element. A ceramic heating element, characterized in that the molar ratio of the content of silicon oxide (SiO 2 ) to the content converted into oxide is 1.0 to 2.5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3182492A JP2735725B2 (en) | 1992-02-19 | 1992-02-19 | Ceramic heating element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3182492A JP2735725B2 (en) | 1992-02-19 | 1992-02-19 | Ceramic heating element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05234665A true JPH05234665A (en) | 1993-09-10 |
| JP2735725B2 JP2735725B2 (en) | 1998-04-02 |
Family
ID=12341834
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3182492A Expired - Fee Related JP2735725B2 (en) | 1992-02-19 | 1992-02-19 | Ceramic heating element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2735725B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0874197A2 (en) | 1997-04-22 | 1998-10-28 | NGK Spark Plug Co. Ltd. | Ceramic heater, ceramic glow plug, and method of manufacturing the ceramic heater |
| US6274853B1 (en) | 1999-05-21 | 2001-08-14 | Ngk Spark Plug Co., Ltd. | Heating resistor, heating resistor for use in ceramic heater, and ceramic heater using the same |
| JP2022523471A (en) * | 2019-01-25 | 2022-04-25 | ウェーバー‐スティーブン プロダクツ エルエルシー | Pellet grill |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5997998A (en) * | 1998-03-31 | 1999-12-07 | Tdk Corporation | Resistance element |
| WO2007135773A1 (en) | 2006-05-18 | 2007-11-29 | Ngk Spark Plug Co., Ltd. | Ceramic heater and glow plug |
-
1992
- 1992-02-19 JP JP3182492A patent/JP2735725B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0874197A2 (en) | 1997-04-22 | 1998-10-28 | NGK Spark Plug Co. Ltd. | Ceramic heater, ceramic glow plug, and method of manufacturing the ceramic heater |
| US5883360A (en) * | 1997-04-22 | 1999-03-16 | Ngk Spark Plug Co., Ltd. | Ceramic heater ceramic glow plug and method of manufacturing the ceramic heater |
| US6274853B1 (en) | 1999-05-21 | 2001-08-14 | Ngk Spark Plug Co., Ltd. | Heating resistor, heating resistor for use in ceramic heater, and ceramic heater using the same |
| JP2022523471A (en) * | 2019-01-25 | 2022-04-25 | ウェーバー‐スティーブン プロダクツ エルエルシー | Pellet grill |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2735725B2 (en) | 1998-04-02 |
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