JP5552920B2

JP5552920B2 - Ceramic heater

Info

Publication number: JP5552920B2
Application number: JP2010145335A
Authority: JP
Inventors: 博之村井
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2010-06-25
Filing date: 2010-06-25
Publication date: 2014-07-16
Anticipated expiration: 2030-06-25
Also published as: JP2012009338A

Description

本発明は、被加熱流体の流路壁に固定され、通電により発熱し被加熱流体を加熱するセラミックヒータに関し、例えば、燃焼式ヒータの着火源やディーゼルエンジンのグロープラグ、排ガス浄化装置の昇温用熱源等として好適なものである。 The present invention relates to a ceramic heater fixed to a flow path wall of a fluid to be heated and generating heat by energization to heat the fluid to be heated. For example, an ignition source of a combustion heater, a glow plug of a diesel engine, an exhaust gas purification device It is suitable as a heat source for temperature.

この種のセラミックヒータとして、特許文献１には、挿入方向に向かって内径寸法が連続的に小さくなっている被取付部材側テーパ部が形成された穴部を有する被取付部材に対し、前記穴部に挿入して取り付けるようにしたセラミックヒータであって、一端側に通電によって発熱する発熱部を有し、他端側に前記発熱部に通電するための通電リード部が電気的に接続されたセラミック発熱体と、前記セラミック発熱体の外周面に接合され、一端より前記セラミック発熱体の前記一端側が露出し、他端より前記セラミック発熱体の他端側が露出するように、前記セラミック発熱体を被覆するハウジングとを備え、前記ハウジングの外周面には、前記被取付部材における前記穴部の前記被取付部材側テーパ部に対応したテーパ形状を有する取付手段側シール部と、前記穴部に固定可能な取付部とが一体に形成されており、前記取付部によって前記ハウジングを前記穴部に固定したときに、前記取付手段側シール部は押圧され前記被取付部材側テーパ部に当接するようになっていることを特徴とするセラミックヒータが開示されている。 As this type of ceramic heater, Patent Document 1 discloses that the above-mentioned hole is provided for a mounted member having a hole portion in which a mounted member side tapered portion whose inner diameter dimension is continuously reduced toward the insertion direction is formed. A ceramic heater that is inserted into and attached to a part, has a heat generating part that generates heat when energized at one end side, and is electrically connected with an energization lead part for supplying current to the heat generating part at the other end side The ceramic heating element is bonded to an outer peripheral surface of the ceramic heating element, and the one end side of the ceramic heating element is exposed from one end and the other end side of the ceramic heating element is exposed from the other end. And a housing having a taper shape corresponding to the attached member side tapered portion of the hole portion of the attached member on the outer peripheral surface of the housing. A side seal portion and an attachment portion that can be fixed to the hole portion are integrally formed. When the housing is fixed to the hole portion by the attachment portion, the attachment means side seal portion is pressed and the cover portion is pressed. A ceramic heater is disclosed that is configured to abut on the attachment member side taper portion.

また、特許文献２には、棒状の形態を有すると共に自身の先端部に抵抗発熱体が埋設されたセラミックヒータと、該セラミックヒータの外周面に締まり嵌め状態にて取り付けられた金属嵌合部材とを備えたグロープラグにおいて、前記金属嵌合部材と前記セラミックヒータとの間に、前記金属嵌合部材よりも軟質の金属層が形成されていることを特徴とするグロープラグが開示されている。 Patent Document 2 discloses a ceramic heater having a rod-like shape and having a resistance heating element embedded in its tip, and a metal fitting member attached to the outer peripheral surface of the ceramic heater in an interference fit state. A glow plug is disclosed in which a softer metal layer than the metal fitting member is formed between the metal fitting member and the ceramic heater.

これらのセラミックヒータに用いられているセラミック発熱体は、例えば、炭化タングステン（ＷＣ）、二硅化モリブデン（ＭｏＳｉ_２）及び二硅化タングステン（ＷＳｉ_２）等の導電性セラミックを用いて射出成形等の公知の方法により略Ｕ字形に形成して抵抗発熱体とし、タングステン（Ｗ）等の導電性材料を用いて所定の形状に形成した一対のリード部を抵抗発熱体の両端部に接続し、さらに、これらを窒化硅素Ｓｉ_３Ｎ_４等の絶縁性セラミックによって覆い、ホットプレス等の公知の方法により一体的に焼結した後、切削加工によって絶縁性セラミックの内部に埋設されたリード部の先端を絶縁性セラミックの表面に露出させ、これにメッキ等を施し端子電極を形成し、絶縁性セラミックの内部に埋設された抵抗発熱体への通電を可能としている。
セラミック発熱体は、このような複雑な工程を経て形成され、しかも、焼結後の硬度が高く、切削加工が容易ではないことから、比較的単純な円柱状に形成されている。
このため、従来技術では、略円柱状に形成されたセラミック発熱体は、略筒状に形成された金属製のハウジングや嵌合部材内に挿通され、ロウ付けや締まり嵌め等によって固定され、さらに、発熱部が被加熱流体中に露出するように被取付部に固定される。この際、特許文献１にあるように、ハウジングに設けた取付手段側シール部によって気密性が確保され、被加熱流体の外部への漏れを防止している。
加えて、特許文献１のセラミックヒータでは、セラミック発熱体とハウジングとが焼き嵌め等の嵌合によって組み付けられた上に、セラミック発熱体とハウジングとの間隙に銀ロウや銅ロウ等のロウ材を流し込んでロウ付けすることによって接合強度を高くしている。 The ceramic heating elements used in these ceramic heaters are known, for example, injection molding using conductive ceramics such as tungsten carbide (WC), molybdenum disilicide (MoSi ₂ ) and tungsten disilicide (WSi ₂ ). By forming a substantially U shape by the above method to form a resistance heating element, a pair of lead portions formed in a predetermined shape using a conductive material such as tungsten (W) is connected to both ends of the resistance heating element, These are covered with an insulating ceramic such as silicon nitride Si ₃ N ₄ and sintered together by a known method such as hot pressing, and then the tip of the lead embedded in the insulating ceramic is insulated by cutting. Is exposed to the surface of the insulating ceramic, plated to form terminal electrodes, and energized to the resistance heating element embedded in the insulating ceramic Is possible.
The ceramic heating element is formed through such a complicated process, and since it has high hardness after sintering and is not easy to cut, it is formed in a relatively simple columnar shape.
For this reason, in the prior art, the ceramic heating element formed in a substantially cylindrical shape is inserted into a metal housing or fitting member formed in a substantially cylindrical shape, and fixed by brazing, interference fitting, or the like. The heat generating portion is fixed to the attached portion so as to be exposed in the heated fluid. At this time, as disclosed in Patent Document 1, airtightness is ensured by an attachment means side seal provided in the housing, and leakage of the heated fluid to the outside is prevented.
In addition, in the ceramic heater of Patent Document 1, the ceramic heating element and the housing are assembled by fitting such as shrink fitting, and a brazing material such as silver brazing or copper brazing is provided in the gap between the ceramic heating element and the housing. The bonding strength is increased by pouring and brazing.

近年、セラミックヒータの即暖化を図るべくセラミック発熱体の発熱温度は、１０００℃以上に高温化する傾向にあり、また、燃焼炉や排気管に搭載されるセラミックヒータにおいては、燃焼ガスや燃焼排気等の高温の気体に晒されるため、ハウジグの先端部が５００℃に達する場合もある。
このため、従来のセラミックヒータでは、セラミック発熱体を保持するハウジングには、加工の容易性、耐熱性等の観点から、ステンレス等の耐熱性金属材料が広く用いられている。 In recent years, the heat generation temperature of ceramic heating elements has tended to increase to 1000 ° C. or more in order to immediately warm the ceramic heater. In addition, in ceramic heaters mounted on combustion furnaces and exhaust pipes, combustion gases and combustion The tip of the housing may reach 500 ° C. because it is exposed to a high-temperature gas such as exhaust gas.
For this reason, in the conventional ceramic heater, a heat-resistant metal material such as stainless steel is widely used for the housing that holds the ceramic heating element from the viewpoint of ease of processing, heat resistance, and the like.

ところが、セラミック発熱体の熱膨張係数は、３．５×１０^−６／℃（〜１００℃）であるのに対し、耐熱性金属材料として、例えば、ＳＵＳ４３０の場合、１０．４×１０^−６／℃（〜１００℃）の熱膨張係数を有し、一般にハウジングとして用いられているステンレスの熱膨張係数は、１０〜１３×１０^−６／℃（〜１００℃）であり、セラミック発熱体の熱膨張係数の３倍以上である。
このため、高温環境下では、金属製のハウジングの熱膨張係数と、セラミック発熱体の熱膨張係数の違いから、高温時においてハウジングがセラミック発熱体よりも遥かに大きく軸方向及び径方向に膨張することになり、ハウジングとセラミック発熱体との軸方向の相対変位が生じる。
エンジン等の運転状況の変化に伴う冷熱環境下に晒されたときに、高温環境下では、熱に晒されたハウジングには、時間の経過と共に高温側の先端部から、低温側の基端部に掛けて温度が低くなる温度勾配が形成され、その温度勾配にならい、先端部ほど膨張量が多いため、先端軸方向及び外径方向に向かって末広がりに膨張し、一時的に先端側におけるセラミック発熱体の締まり嵌めが解放される。 However, while the thermal expansion coefficient of the ceramic heating element is 3.5 × 10 ⁻⁶ / ° C. (˜100 ° C.), as a heat resistant metal material, for example, in the case of SUS430, 10.4 × 10 ^−6. The thermal expansion coefficient of stainless steel generally used as a housing is 10-13 × 10 ⁻⁶ / ° C. (˜100 ° C.). It is at least 3 times the thermal expansion coefficient.
For this reason, under a high temperature environment, the housing expands in the axial direction and the radial direction at a high temperature much larger than the ceramic heating element due to the difference between the thermal expansion coefficient of the metal housing and the thermal expansion coefficient of the ceramic heating element. As a result, an axial relative displacement between the housing and the ceramic heating element occurs.
When exposed to a cold environment accompanying changes in the operating conditions of the engine, etc., the housing exposed to heat in a high temperature environment will change from the high temperature side tip to the low temperature side base end over time. A temperature gradient that lowers the temperature is formed, and the tip portion has a larger amount of expansion according to the temperature gradient, so that the tip portion expands gradually toward the tip axis direction and the outer diameter direction, and temporarily ceramics on the tip side. The interference fit of the heating element is released.

一方、低温環境下では、冷却により、膨張したハウジングの先端部ほど急激な冷却によって、基端軸方向及び内径方向に向かって早く収縮する。
このとき、伝熱によって熱が移動する基端側は、加熱時・冷却時とも、先端側に比べ、温度変化に時間的遅れが生じる。
このため、先端側が冷却され収縮が開始したときに、ハウジング内部に残留する熱の移動によって基端側は依然膨張する傾向にあり、実質的に、ハウジングの先端部が膨張前のセラミック発熱体を保持していた位置よりも先端側の位置でセラミック発熱体の締め付けを開始することとなる。 On the other hand, under a low-temperature environment, due to cooling, the tip of the expanded housing rapidly contracts in the proximal axial direction and the inner diameter direction due to rapid cooling.
At this time, the base end side where heat is transferred by heat transfer has a time delay in temperature change compared to the front end side during heating and cooling.
For this reason, when the distal end side is cooled and contraction starts, the proximal end side still tends to expand due to the movement of heat remaining inside the housing, and the distal end portion of the housing substantially does not expand the ceramic heating element before expansion. Tightening of the ceramic heating element is started at a position closer to the tip side than the held position.

さらに、冷却状態で時間が経過するとハウジングの基端部も次第に冷却され軸方向・径方向ともに収縮する。
このとき、既に冷却収縮を完了した先端部が拘束点となるため、基端部はこの拘束点に向けて収縮することとなり、相対的にセラミック発熱体が基端側に向かって引き込まれることになる。 Furthermore, when time elapses in the cooling state, the base end portion of the housing is gradually cooled and contracts in both the axial direction and the radial direction.
At this time, since the distal end portion that has already completed the cooling shrinkage becomes a restraint point, the proximal end portion shrinks toward the restraint point, and the ceramic heating element is relatively drawn toward the proximal end side. Become.

即ち、冷熱環境下ではハウジングの先端面とセラミック発熱体の先端面との距離が冷熱の繰り返しによって相対的に変化し続けることとなり、ハウジングの先端面からセラミック発熱体の突出する長さが徐々に短くなる「発熱体引込現象」を生じることが判明した。
また、セラミック発熱体とハウジングとの間に介装されたロウ材は、高温環境下では先端側が先に軟化し、セラミック発熱体の拘束力が弱まるが、冷却過程では、相対的に先端側が先に硬化するため先端側が拘束点となって、相対的にセラミック発熱体を基端側へ引き込む傾向が強くなる。
このような発熱体引込現象によってセラミック発熱体の突出長さが変化すると、セラミックヒータによって加熱される被加熱流体の温度にも影響を与え、正確な加熱温度の制御が困難となる虞もある。 That is, in a cold environment, the distance between the front end surface of the housing and the front end surface of the ceramic heating element continues to change relatively by repeated cooling, and the length of the protrusion of the ceramic heating element from the front end surface of the housing gradually increases. It has been found that a “heating element pull-in phenomenon” that becomes shorter occurs.
In addition, the brazing material interposed between the ceramic heating element and the housing softens the tip side first in a high temperature environment and weakens the restraining force of the ceramic heating element, but the tip side is relatively first in the cooling process. Therefore, the tip side becomes a restraint point, and the tendency to draw the ceramic heating element relatively to the base end side becomes stronger.
When the protrusion length of the ceramic heating element changes due to such a heating element pull-in phenomenon, the temperature of the fluid to be heated heated by the ceramic heater is also affected, and it may be difficult to accurately control the heating temperature.

そこで、本発明はかかる実情に鑑みて、冷熱環境下での発熱体引き込み現象の発生を抑制し、信頼性の高いセラミックヒータを提供することを目的とする。 Therefore, in view of such circumstances, an object of the present invention is to provide a highly reliable ceramic heater that suppresses the occurrence of a heating element pull-in phenomenon in a cold environment.

第１の発明では、一対の電極を具備し、該電極に接続され外部に設けた通電装置からの通電により発熱するセラミック発熱体と、該セラミック発熱体の外周に嵌着され、上記セラミック発熱体の先端側の発熱部を被取付部材の内側に取付固定するためのハウジングと、上記ハウジングと上記セラミック発熱体を接合する接合手段とを具備するセラミックヒータにおいて、上記接合手段が、上記ハウジングの先端側で、冷熱環境下に晒される部分に設けた第１の接合手段と、上記ハウジングの基端側で、冷熱環境下から離隔した部分に設けた第２の接合手段からなり、上記第１の接合手段は、上記ハウジングの冷熱環境下に晒される先端側と上記発熱体との間隙にロウ材を充填して形成した第１の発熱体ロウ接部によって構成すると共に、上記第２の接合手段は、上記ハウジングとは独立に設けて上記セラミック発熱体を覆う略環状に形成された環状固定部材と、該環状固定部材と上記セラミック発熱体との間隙にロウ材を充填して形成した第２の発熱体ロウ接部と、上記環状固定部材と上記ハウジング、又は、ハウジングに結合された部材との間隙にロウ材を充填して形成した環状固定部材ロウ接部とによって構成することを特徴とする（請求項１）。 In the first aspect of the present invention, a ceramic heating element comprising a pair of electrodes and generating heat by energization from an energization device connected to the electrodes and provided outside, and fitted on the outer periphery of the ceramic heating element, the ceramic heating element A ceramic heater comprising: a housing for mounting and fixing the heat generating portion on the tip end side of the attached member; and a joining means for joining the housing and the ceramic heating element, wherein the joining means is a tip of the housing. the side, a first bonding means provided on a portion exposed under cold environment, with the base end side of the housing, Ri Do the second joining means provided in the spaced portion from under cold environment, the first The joining means is constituted by a first heating element brazing portion formed by filling the gap between the heating element exposed to the cold environment of the housing and the heating element with a brazing material. The joining means 2 includes an annular fixing member that is provided independently of the housing and covers the ceramic heating element, and a brazing material is filled in a gap between the annular fixing member and the ceramic heating element. The second heating element brazing portion formed and an annular fixing member brazing portion formed by filling a brazing material in a gap between the annular fixing member and the housing or the member coupled to the housing. (Claim 1).

第１の発明によれば、上記ハウジングの先端側が冷熱サイクルに晒されたとき、上記セラミック発熱体の熱膨張係数と上記ハウジングの熱膨張係数との差により、上記セラミック発熱体に対して上記ハウジングの先端側の相対変位が生じ得る状況においても、冷熱環境下に晒され、接合強度の変化を伴う上記第１の接合手段に比べ、冷熱環境下から離隔し温度変化の少ない位置に設けられた上記第２の接合手段の接合力は、温度変化による接合力の変化がなく安定しており、冷熱サイクルに伴う上記ハウジングの膨張と収縮によって発生する上記セラミック発熱体を基端側に引込もうとする発熱体引込力に抗して上記セラミック発熱体の基端側を強固に拘束、保持するため、発熱体引込現象が生じ難くなる。
特に、本発明によれば、上記ハウジングの先端が冷熱サイクルに晒された時に上記第１のロウ接部の接合強度が弛む虞があるが、上記第２の接合手段として設けた上記第２の発熱体ロウ接部及び上記環状固定部材ロウ接部によって強固に保持されているため、相対的に接合強度の高い第２の接合手段によって発熱体引込現象が阻止される。
このとき、高温環境下において、上記第１のロウ接部は軟化するものの、上記ハウジングと上記セラミック発熱体との間隙から被取付部材内の被加熱流体の排出を阻止すると共に、被加熱流体若しくはセラミック発熱体からの熱を上記ハウジングの先端側を介して、被取付部材側へ伝熱させる。
一方、上記環状固定部材は、上記ハウジングと温度変化の少ない位置に設けられた上記環状固定部材ロウ接部を介して接合されているため、上記ハウジングに比べ相対的にヤング率の低い上記環状固定部材ロウ接部が緩衝部材なる上に、上記ハウジングの基端側は、先端側に比べて温度変化が少ないため、上記ハウジングの先端側が冷熱サイクルによる膨張と収縮を繰り返しても、その影響を受けることがない。 According to the first aspect of the present invention, when the front end side of the housing is exposed to a cooling cycle, the housing with respect to the ceramic heating element due to the difference between the thermal expansion coefficient of the ceramic heating element and the thermal expansion coefficient of the housing. Even in a situation where relative displacement on the front end side of the steel plate can occur, it is exposed to a cold environment and is provided at a position that is separated from the cold environment and has a small temperature change compared to the first bonding means that involves a change in bonding strength. The joining force of the second joining means is stable with no change in joining force due to temperature change, and attempts to draw the ceramic heating element generated by expansion and contraction of the housing accompanying a cooling cycle to the proximal end side. Since the base end side of the ceramic heating element is firmly restrained and held against the heating element pulling force, the heating element pulling phenomenon hardly occurs.
In particular, according to the present invention, when the front end of the housing is exposed to a thermal cycle, the bonding strength of the first brazing contact portion may be loosened. Since it is firmly held by the heating element brazing portion and the annular fixing member brazing portion, the heating element pull-in phenomenon is prevented by the second joining means having relatively high joining strength.
At this time, although the first brazed portion is softened under a high temperature environment, the heated fluid in the mounted member is prevented from being discharged from the gap between the housing and the ceramic heating element, and the heated fluid or Heat from the ceramic heating element is transferred to the attached member side through the front end side of the housing.
On the other hand, since the annular fixing member is joined to the housing via the annular fixing member brazing portion provided at a position where temperature change is small, the annular fixing has a relatively low Young's modulus compared to the housing. In addition to the member brazing portion being a buffer member, the base end side of the housing is less susceptible to temperature changes than the tip end side, so that the housing is affected even if the tip end side of the housing repeatedly expands and contracts due to a thermal cycle. There is nothing.

第２の発明では、上記環状固定部材が、上記一対の電極の一方に接合されている（請求項２）。 In the second aspect of the invention, the annular fixing member is joined to one of the pair of electrodes (claim 2).

第２の発明によれば、上記環状固定部材を介して上記一対の電極の一方が、ハウジングに接地状態となるため、上記セラミック発熱体への通電を図るべく接続される一方の通電線を排することができるのに加え、このようないわゆるボディアース型のセラミックヒータにおいて、冷熱環境下におけるセラミック発熱体の引込現象が抑制されているため、接地電極の剥離が生じ難くなり、セラミックヒータの信頼性が向上する。
According to the second invention, since one of the pair of electrodes is grounded to the housing via the annular fixing member, one of the conducting wires connected to energize the ceramic heating element is removed. In addition, the so-called body earth type ceramic heater can suppress the pulling-in phenomenon of the ceramic heating element in the cold environment, so that it is difficult for the ground electrode to peel off, and the reliability of the ceramic heater is reduced. Improves.

本発明の第１の実施形態におけるセラミックヒータの概要を示す断面図。Sectional drawing which shows the outline | summary of the ceramic heater in the 1st Embodiment of this invention. 従来のセラミックヒータの問題点である発熱体引込現象を（ａ）〜（ｄ）の順を追って説明するための説明図。Explanatory drawing for demonstrating the heating element drawing phenomenon which is a problem of the conventional ceramic heater in order of (a)-(d). 本発明の効果を確認するために行った試験方法並びにその結果を示し（ａ）は、本発明の実施例の計測位置を示す断面図、（ｂ）は比較例の計測位置を示す断面図、（ｃ）は、試験条件を示す特性図、（ｄ）は、本発明の効果を比較例と共に示す特性図。(A) is a cross-sectional view showing a measurement position of an embodiment of the present invention, (b) is a cross-sectional view showing a measurement position of a comparative example, (C) is a characteristic diagram which shows test conditions, (d) is a characteristic diagram which shows the effect of this invention with a comparative example. （ａ）は、本発明の第１の実施形態におけるセラミックヒータの変形例を示す要部断面図、（ｂ）は、他の変形例を示す要部断面図。(A) is principal part sectional drawing which shows the modification of the ceramic heater in the 1st Embodiment of this invention, (b) is principal part sectional drawing which shows another modification. （ａ）は、本発明の第２の実施形態におけるセラミックヒータの概要を示す要部断面図、（ｂ）はその変形例を示す要部断面図。(A) is principal part sectional drawing which shows the outline | summary of the ceramic heater in the 2nd Embodiment of this invention, (b) is principal part sectional drawing which shows the modification. 本発明の第３の実施形態におけるセラミックヒータの概要を示す断面図。Sectional drawing which shows the outline | summary of the ceramic heater in the 3rd Embodiment of this invention. 本発明の第３の実施形態におけるセラミックヒータの変形例を示す要部断面図。The principal part sectional drawing which shows the modification of the ceramic heater in the 3rd Embodiment of this invention. 本発明の第４の実施形態におけるセラミックヒータの概要を示す断面図。Sectional drawing which shows the outline | summary of the ceramic heater in the 4th Embodiment of this invention. 比較例として示す従来のセラミックヒータの概要を示す断面図。Sectional drawing which shows the outline | summary of the conventional ceramic heater shown as a comparative example.

図１を参照して、本発明の第１の実施形態におけるセラミックヒータ１について説明する。
なお、本発明において、セラミックヒータ１に接続される図略の通電装置側を基端側、セラミックヒータ１が挿入、固定される被取付部材側を先端側と称する。
本実施形態におけるセラミックヒータ１は、セラミックヒータ１が取り付けられる被取付部材６０に装着され、セラミック発熱体１０の基端側表面に形成された一対の電極として設けられた発熱体電極部１１１、１２１に接続された一つの通電線１１４、１２４を介して外部に設けた図略の通電装置に接続され、通電により発熱し、被取付部材６０の内側の被加熱流体６００の加熱に用いられ、例えば、内燃機関から排出される燃焼排気を加熱して排気浄化装置再生のための熱源としたり、寒冷地仕様のディーゼル車等において冷却水を加熱する燃焼式ヒータの着火源としたり、ディーゼル機関の着火の補助を行ったりするのに好適なものである。 With reference to FIG. 1, the ceramic heater 1 in the 1st Embodiment of this invention is demonstrated.
In the present invention, the energization device side (not shown) connected to the ceramic heater 1 is referred to as a base end side, and the attached member side to which the ceramic heater 1 is inserted and fixed is referred to as a front end side.
The ceramic heater 1 according to the present embodiment is mounted on a mounted member 60 to which the ceramic heater 1 is mounted, and the heating element electrode portions 111 and 121 provided as a pair of electrodes formed on the proximal end surface of the ceramic heating element 10. Is connected to an unillustrated energization device provided outside via one energization line 114, 124 connected to, and generates heat when energized, and is used to heat the heated fluid 600 inside the mounted member 60. The combustion exhaust discharged from the internal combustion engine is heated to be used as a heat source for regeneration of the exhaust purification device, or used as an ignition source for a combustion heater that heats cooling water in a diesel vehicle having a cold district specification. It is suitable for assisting ignition.

セラミックヒータ１は、通電により発熱するセラミック発熱体１０と、セラミック発熱体１０の先端側に位置する発熱部を被取付部材６０の内側の被加熱流体６００中に取付固定するためのハウジング３０とによって構成されている。
さらに、セラミック発熱体１０の中腹が、第１の接合手段によって、ハウジング３０の先端側の冷熱環境下に晒される部分に接合され、ハウジング３０の先端からセラミック発熱体１０の発熱部が被加熱流体６００中に露出している。 The ceramic heater 1 includes a ceramic heating element 10 that generates heat when energized, and a housing 30 for mounting and fixing a heating part located on the tip side of the ceramic heating element 10 in a heated fluid 600 inside the mounted member 60. It is configured.
Further, the middle part of the ceramic heating element 10 is joined to the portion exposed to the cold environment on the distal end side of the housing 30 by the first joining means, and the heating part of the ceramic heating element 10 is heated from the distal end of the housing 30 to the fluid to be heated. 600 is exposed.

ハウジング３０は、セラミック発熱体１０を挿入保持する発熱体挿入孔３０１が設けられ、基端側外周には、ハウジングネジ部３０２を締め付けるための六角部３０３が設けられ、先端側外周側には、被取付部材６０に螺結するためのハウジングネジ部３０２（雄ねじ）が設けられ、六角部３０３とハウジングネジ部３０２との間には、被取付部材６０に設けた被取付部材側テーパ部６１２と当接し気密性を保持するハウジングシール部３０４が設けられている。 The housing 30 is provided with a heating element insertion hole 301 for inserting and holding the ceramic heating element 10, a hexagonal portion 303 for tightening the housing screw portion 302 is provided on the base end side outer periphery, and a distal end side outer periphery side is provided. A housing screw portion 302 (male screw) for screwing to the attached member 60 is provided, and between the hexagonal portion 303 and the housing screw portion 302, the attached member side taper portion 612 provided on the attached member 60 and A housing seal portion 304 is provided that contacts and maintains airtightness.

セラミック発熱体１０は、略円柱状に形成された耐熱性絶縁部１０１の先端側に内蔵された略Ｕ字型の抵抗発熱体１００と、抵抗発熱体１００と外部に設けられた通電装置との導通を図る一対の発熱体リード部１１０、１２０と、各リード部１１０、１２０に導通して耐熱性絶縁部１００の表面に引き出された一対の電極として設けられた発熱体電極部１１１、１２１とによって構成されている。
抵抗発熱体１００には、二硅化モリブデンＭｏＳｉ_２、炭化硅素ＳｉＣ、炭化タングステンＷＣ等の公知の導電性セラミック材料が用いられ、耐熱性絶縁部１００には、窒化硅素Ｓｉ_３Ｎ_４等の公知の絶縁性セラミック材料が用いられ、リード部１１０、１２０には、タングステンＷ等の公知の導電性金属材料が用いられている。
セラミック発熱体１０は、抵抗発熱体１００と一対のリード部１１０、１２０とを射出成形等の公知の方法により所望の形状に形成した後、抵抗発熱体１００とリード部１１０、１２０とを所望の位置に配設し、これらを耐熱性絶縁部１００が一体的に覆うようにして、ホットプレス等の公知の成形方法により１７００℃〜１８００℃で一体的に焼成した後、外形を所望の形状に切削し、リード部１１０、１２０の先端を耐熱性絶縁部１００の表面に露出させ、さらに、リード部１１０、１２０の先端には、メッキ等の公知の方法により一対の発熱体電極部１１１、１２１が形成されている。 The ceramic heating element 10 includes a substantially U-shaped resistance heating element 100 built in the front end side of the heat-resistant insulating portion 101 formed in a substantially cylindrical shape, and the resistance heating element 100 and an energization device provided outside. A pair of heating element lead portions 110 and 120 for conducting electricity, and a heating element electrode portion 111 and 121 provided as a pair of electrodes that are electrically connected to the lead portions 110 and 120 and are drawn to the surface of the heat-resistant insulating portion 100, It is constituted by.
A known conductive ceramic material such as molybdenum disilicide MoSi ₂ , silicon carbide SiC, tungsten carbide WC, or the like is used for the resistance heating element 100, and a known heat resistant insulating portion 100 such as silicon nitride Si ₃ N ₄ or the like is used. An insulating ceramic material is used, and a known conductive metal material such as tungsten W is used for the lead portions 110 and 120.
In the ceramic heating element 10, the resistance heating element 100 and the pair of lead portions 110 and 120 are formed into a desired shape by a known method such as injection molding, and then the resistance heating element 100 and the lead portions 110 and 120 are formed in a desired shape. After being baked integrally at 1700 ° C. to 1800 ° C. by a known molding method such as hot pressing so that the heat-resistant insulating part 100 is integrally covered, the outer shape is made into a desired shape. Cutting is performed to expose the tips of the lead portions 110 and 120 on the surface of the heat-resistant insulating portion 100. Further, the tips of the lead portions 110 and 120 are paired with a pair of heating element electrodes 111 and 121 by a known method such as plating. Is formed.

本実施形態においては、第１の接合手段として、ハウジング３０の先端側の冷熱環境下に晒される部分が発熱体１０の中腹を締まり嵌めすると共に、ハウジング３０の先端の内周壁とセラミック発熱体１０の外周との間隙にロウ材を充填した第１の発熱体ロウ接部２３が形成されている。
さらに、セラミック発熱体１０の一対の発熱体電極部１１１、１２１は、冷熱環境から離隔したハウジング３０の基端側に露出している。
セラミック発熱体１０の一の発熱体電極部１１１が形成された位置で、第２の接合手段によって、セラミック発熱体１０とハウジング３０の基端側の冷熱環境から離隔した部分とが接合されている。 In the present embodiment, as the first joining means, the portion exposed to the cold environment on the front end side of the housing 30 tightly fits the middle of the heating element 10, and the inner peripheral wall of the front end of the housing 30 and the ceramic heating element 10. A first heating element brazing portion 23 filled with a brazing material is formed in a gap with the outer periphery of the first heating element.
Further, the pair of heating element electrodes 111 and 121 of the ceramic heating element 10 are exposed on the proximal end side of the housing 30 separated from the cold environment.
At a position where one heating element electrode portion 111 of the ceramic heating element 10 is formed, the ceramic heating element 10 and a portion separated from the cold environment on the proximal end side of the housing 30 are joined by the second joining means. .

さらに、本実施形態においては、第２の接合手段として、ハウジング３０の基端側の冷熱環境から離隔された部分で、セラミック発熱体１０の表面に引き出された一の発熱体電極部１１１を覆うように略環状に形成された環状固定部材として設けられた電極接続金具２０を締まり嵌めすると共に、電極接続金具２０の内周面２０１とセラミック発熱体１０の発熱体電極部１１１の引き出された表面との間隙にロウ材を充填した第２の発熱体ロウ接部２１と、電極接続金具２０の底面２０２とハウジング３０の基端側表面３０５との間隙にロウ材を充填した環状部材ロウ接部２２とが形成されている。
また、本実施形態においては、電極接続金具２０は、先端側が外径方向に向かって鍔状に拡径されたフランジ部が形成されており、底面２０２の面積を大きくすることによってハウジング３０の基端側表面３０５との接合強度を高くしてある。
発熱体電極部１１１、１２１にはそれぞれ、環状の電極接続金具２０、１２２が嵌着され、発熱体電極部１１１、１２１と電極接続金具２０、１２２との僅かな間隙に加熱溶融したロウ材を浸透させロウ付けされて導通が確保されている。
電極接続金具２０、１２２には、それぞれ、通電線端子部１１３、１２３が接続され、これらに接続して通電線１１４、１２４が外部に引き出されている。 Further, in the present embodiment, as the second joining means, the one heating element electrode portion 111 drawn out to the surface of the ceramic heating element 10 is covered with a portion separated from the cooling environment on the proximal end side of the housing 30. Thus, the electrode connection fitting 20 provided as an annular fixing member formed in a substantially annular shape is tightly fitted, and the inner peripheral surface 201 of the electrode connection fitting 20 and the heating element electrode portion 111 of the ceramic heating element 10 are drawn out. A second heat generating member brazing portion 21 in which a brazing material is filled in a gap between the annular member and an annular member brazing portion in which a brazing material is filled in the gap between the bottom surface 202 of the electrode connection fitting 20 and the proximal end surface 305 of the housing 30. 22 is formed.
Further, in the present embodiment, the electrode connection fitting 20 has a flange portion whose tip end is enlarged in a bowl shape toward the outer diameter direction, and the base of the housing 30 is increased by increasing the area of the bottom surface 202. The bonding strength with the end surface 305 is increased.
Ring-shaped electrode connection fittings 20 and 122 are fitted to the heating element electrode portions 111 and 121, respectively, and brazing material heated and melted in a slight gap between the heating element electrode portions 111 and 121 and the electrode connection fittings 20 and 122. It is infiltrated and brazed to ensure conduction.
Conductive wire terminal portions 113 and 123 are connected to the electrode connection fittings 20 and 122, respectively, and the conductive wires 114 and 124 are drawn to the outside by being connected thereto.

本実施形態において、電極接続金具２０は、セラミック発熱体１０への通電を行う通電線１１４との電気的導通を図ると共に、セラミック発熱体１０をハウジング３０の冷熱環境から離隔した部分と接合するための第２の接合手段としても用いられている。
なお、ロウ材としては、の銀ロウ（融点７５０〜９００℃）や、銅ロウ（融点１０５０〜１１５０℃）等を用いることができる。
また、第１の発熱体ロウ接部２３、第２の発熱体ロウ接部２１を設けるに際して、セラミック発熱体１０の表面にＮｉメッキ、Ｃｒメッキ等のメタライズ層を形成する下地処理を所定の範囲に施すことによって、メタライズ層の形成されたセラミック発熱体１０の表面とロウ材との濡れ性が向上し、所望の範囲にのみロウ接部２１、２３を形成することができる。 In the present embodiment, the electrode connection fitting 20 is intended to be electrically connected to the energization line 114 for energizing the ceramic heating element 10 and to join the ceramic heating element 10 to a portion of the housing 30 that is separated from the cold environment. It is also used as the second joining means.
As the brazing material, silver brazing (melting point: 750 to 900 ° C.), copper brazing (melting point: 1050 to 1150 ° C.), or the like can be used.
Further, when the first heating element brazing part 23 and the second heating element brazing part 21 are provided, a ground treatment for forming a metallized layer such as Ni plating or Cr plating on the surface of the ceramic heating element 10 is performed within a predetermined range. As a result, the wettability between the surface of the ceramic heating element 10 on which the metallized layer is formed and the brazing material is improved, and the brazing contact portions 21 and 23 can be formed only in a desired range.

被取付部材６０には、ヒータ取付穴部６１０が設けられ、セラミックヒータ１が挿入され、ヒータ取付穴部６１０の内周には、被取付部材側ネジ部６１１（雌ネジ部）が形成され、ヒータ取付穴部６１０の先端側には、挿入方向に向かって内径が連続的に縮径する、略すり鉢状の被取付部材側テーパ部６１２が形成され、セラミックヒータ１のハウジングネジ部３０２を被取付部材側ネジ部６１１に螺結すると、ヒータ側に設けたハウジングシール部３０４と被取付部材側に設けた被取付部材側テーパ部６１２とが当接し、気密性が確保され、被加熱流体６００の流出が阻止されている。 The mounted member 60 is provided with a heater mounting hole 610, the ceramic heater 1 is inserted therein, and a mounted member side screw 611 (female screw) is formed on the inner periphery of the heater mounting hole 610. On the tip end side of the heater mounting hole 610, a substantially mortar-shaped mounting member side tapered portion 612 whose inner diameter continuously decreases in the insertion direction is formed, and the housing screw portion 302 of the ceramic heater 1 is covered. When screwed into the attachment member side threaded portion 611, the housing seal portion 304 provided on the heater side and the attached member side tapered portion 612 provided on the attached member side come into contact with each other, airtightness is ensured, and the heated fluid 600 The outflow is blocked.

ハウジング３０の先端側は、セラミック発熱体１０への通電と停止のみならず、燃焼式ヒータの燃焼と停止や、ディーゼル機関の燃焼と停止等の被加熱流体６００の温度変化等の冷熱サイクルに晒される。
このとき、セラミック発熱体１０の熱膨張係数（約３．５×１０^−６／℃）とハウジング３０の熱膨張係数（例えば、ＳＵＳ４３０の場合は、１０．４×１０^−６／℃）との差により、セラミック発熱体１０に対してハウジング３０の先端側の相対変位が生じ得る状況においても、冷熱環境下に晒され、接合強度の変化を伴う第１の接合手段（２３）に比べ、冷熱環境下から離隔し温度変化の少ない位置に設けられた第２の接合手段（２０、２１、２２）の接合力は、温度変化による接合力の変化がなく安定しており、冷熱サイクルに伴うハウジング３０の膨張と収縮によって発生するセラミック発熱体１０を基端側に引込もうとする発熱体引込力に抗してセラミック発熱体１０の基端側を強固に拘束、保持するため、発熱体引込現象が生じ難くなる。 The front end side of the housing 30 is exposed not only to energization and stop of the ceramic heating element 10 but also to a cooling cycle such as combustion and stop of a combustion heater, temperature change of the heated fluid 600 such as combustion and stop of a diesel engine. It is.
At this time, the thermal expansion coefficient of the ceramic heating element 10 (about 3.5 × 10 ⁻⁶ / ° C.) and the thermal expansion coefficient of the housing 30 (for example, 10.4 × 10 ⁻⁶ / ° C. in the case of SUS430) Even in a situation where relative displacement of the front end side of the housing 30 may occur with respect to the ceramic heating element 10 due to the difference, it is exposed to a cold environment and compared with the first bonding means (23) accompanied by a change in bonding strength. The bonding force of the second bonding means (20, 21, 22) provided at a position separated from the environment and having a small temperature change is stable without a change in the bonding force due to the temperature change, and the housing accompanying the cooling cycle. In order to firmly restrain and hold the base end side of the ceramic heating element 10 against the heating element pulling force to pull the ceramic heating element 10 generated by the expansion and contraction of the base 30 toward the base end side, the heating element pulling phenomenon Raw It becomes hard.

また、高温環境下において、第１のロウ接部（２３）は軟化するものの、ハウジング３０とセラミック発熱体１０との間隙から被取付部材６０内の被加熱流体６００の排出を阻止すると共に、被加熱流体６００若しくはセラミック発熱体１０からの熱をハウジング３０の先端側を介して、被取付部材６００側へ伝熱させる。
一方、環状固定部材として設けられた電極接続金具２０は、ハウジング３０と温度変化の少ない位置に設けられた環状固定部材ロウ接部２２を介して接合されているため、ハウジング３０に比べ相対的にヤング率の低い環状固定部材ロウ接部２２が緩衝部材となる上に、ハウジング３０の基端側は温度変化が先端側に比べて少ないため、ハウジング３０の先端側が冷熱サイクルによる膨張と収縮を繰り返しても、その影響を受けることがない。 Further, although the first brazing portion (23) is softened under a high temperature environment, the heated fluid 600 in the mounted member 60 is prevented from being discharged from the gap between the housing 30 and the ceramic heating element 10, and the covered portion is covered. Heat from the heating fluid 600 or the ceramic heating element 10 is transferred to the attached member 600 side through the distal end side of the housing 30.
On the other hand, the electrode fitting 20 provided as an annular fixing member is joined to the housing 30 via an annular fixing member brazing portion 22 provided at a position where the temperature change is small. The annular fixing member brazing portion 22 having a low Young's modulus serves as a buffer member, and the proximal end side of the housing 30 undergoes less temperature change than the distal end side. However, it will not be affected.

なお、本実施形態においては、発熱体電極部１１１は、電極接続金具２０を介してハウジング３０とボディアース状態となっているが、被取付部材６０が燃焼排気管等の著しく酸化され易い環境に置かれている場合等には、ハウジング３０と被取付部材６０との接地状態が必ずしも良好となるとは限らず、この場合、電極接続金具２０に通電線１１４を接続することにより、確実な接地を図ることができる。 In the present embodiment, the heating element electrode portion 111 is in a body grounded state with the housing 30 via the electrode connection fitting 20, but the mounted member 60 is in an environment that is remarkably easily oxidized, such as a combustion exhaust pipe. In such a case, the grounding state between the housing 30 and the mounted member 60 is not necessarily good, and in this case, the conductive wire 114 is connected to the electrode connection fitting 20 to ensure reliable grounding. Can be planned.

ここで、比較例として図９に示す従来のセラミックヒータ１ｚの概要について説明すると共に、図２を参照して、従来のセラミックヒータ１ｚの問題点について説明する。
図９に示すように、従来のセラミックヒータ１ｚは、挿入方向に向かって内径寸法が連続的に小さくなっている被取付部材側テーパ部６１２ｚが形成されたヒータ取付穴部６１０ｚを有する被取付部材６０ｚに対し、ヒータ取付穴部６１０ｚに挿入して取り付けるようにしたセラミックヒータであって、被加熱流体に晒される先端側に通電によって発熱する抵抗発熱体１００ｚを有し、基端側に抵抗発熱体１００ｚに通電するための一対のリード部１１０ｚ、１２０ｚが電気的に接続されたセラミック発熱体１０ｚと、セラミック発熱体１０ｚの外周面に接合されている。
さらに、セラミックヒータ１ｚは、被加熱流体側の一端よりセラミック発熱体１０ｚの先端側が露出し、他端よりセラミック発熱体１０ｚの基端側が露出するように、セラミック発熱体１０ｚを被覆するハウジング３０ｚとを備え、ハウジング３０ｚの外周面には、被取付部材６０ｚにおけるヒータ取付穴部６１０ｚの被取付部材側テーパ部６１２ｚに対応したテーパ形状を有するハウジングシール部３０４ｚと、ヒータ取付穴部６１０ｚに設けた被取付部材側ネジ部６１１ｚ（雌ねじ）に固定可能なハウジングネジ部３０２ｚ（雄ねじ）とが一体に形成されており、ハウジングネジ部３０２ｚによってハウジング３０ｚをヒータ取付穴部６１０ｚに固定したときに、ハウジングシール部３０４ｚが押圧され被取付部材側テーパ部６１２ｚに当接するようになっている。
また、セラミック発熱体１０ｚとハウジング３０ｚとは、略筒状に形成されたハウジング３０ｚの発熱体挿通孔３０１ｚの空間部にロウ材を配置し、セラミック発熱体１０ｚの基端側から、スペーサ２１１ｚを嵌め込み、空間部ＣＶ_３０ｚ内にスペーサ２１１ｚを配置し、さらに、セラミック発熱体１０ｚの基端側から、スペーサ２１１ｚと当接するまでセラミック発熱体１０ｚの発熱体電極部１１０ｚに環状の電極接続金具１１２ｚを嵌め込み、その上端面にロウ材を配置し、さらに、セラミック発熱体１０ｚの基端部に露出する発熱体電極部１２１ｚに環状の電極接続金具１２２ｚを嵌め込み、その端面にロウ材を配置し、これらを熱処理することにより、各部に配置されたロウ材が溶融し部材間の隙間に流れ、これが固まることで、セラミック発熱体１０ｚとは、ハウジング３０ｚ、電極接続金具１１２ｚ、１２２ｚと接合されている。
従来のハウジング３０ｚを構成する発熱体保持部材３００ｚは、ステンレス等の耐熱性金属材料によって形成されており、その熱膨張係数は、例えば、ＳＵＳ４３０の場合、１０．４×１０^−６／℃（〜１００℃）である。
また、従来のセラミックヒータ１ｚでは、一般的に、ロウ接部２０ｚを形成するに当たりロウ材として銀ロウ（融点７５０〜９００℃）が用いられている。 Here, an outline of the conventional ceramic heater 1z shown in FIG. 9 will be described as a comparative example, and problems of the conventional ceramic heater 1z will be described with reference to FIG.
As shown in FIG. 9, the conventional ceramic heater 1 z has a mounted member having a heater mounting hole 610 z formed with a mounted member-side tapered portion 612 z whose inner diameter is continuously reduced in the insertion direction. 60 z is a ceramic heater that is inserted into the heater mounting hole 610 z and attached thereto, and has a resistance heating element 100 z that generates heat when energized on the distal end side exposed to the fluid to be heated, and resistance heating on the proximal end side. A pair of lead portions 110z and 120z for energizing the body 100z are joined to an electrically connected ceramic heating element 10z and an outer peripheral surface of the ceramic heating element 10z.
Further, the ceramic heater 1z includes a housing 30z that covers the ceramic heating element 10z so that the distal end side of the ceramic heating element 10z is exposed from one end of the heated fluid side and the proximal end side of the ceramic heating element 10z is exposed from the other end. And a housing seal portion 304z having a taper shape corresponding to the attached member side tapered portion 612z of the heater attachment hole portion 610z in the attachment member 60z, and the heater attachment hole portion 610z are provided on the outer peripheral surface of the housing 30z. A housing screw portion 302z (male screw) that can be fixed to the attached member side screw portion 611z (female screw) is integrally formed. When the housing 30z is fixed to the heater attachment hole portion 610z by the housing screw portion 302z, the housing The seal portion 304z is pressed to the attached member side taper portion 612z. So that the contact.
Further, the ceramic heating element 10z and the housing 30z have a brazing material disposed in a space portion of the heating element insertion hole 301z of the housing 30z formed in a substantially cylindrical shape, and a spacer 211z is provided from the base end side of the ceramic heating element 10z. The spacer 211z is disposed in the space portion CV _30z , and the annular electrode connection fitting 112z is further attached to the heating element electrode portion 110z of the ceramic heating element 10z from the proximal end side of the ceramic heating element 10z until it contacts the spacer 211z. The brazing material is arranged on the upper end surface of the fitting, and the annular electrode connecting fitting 122z is fitted on the heating element electrode portion 121z exposed at the base end portion of the ceramic heating element 10z, and the brazing material is arranged on the end face. By heat-treating, the brazing material arranged in each part melts and flows into the gaps between the members, and solidifies. The ceramic heating element 10z is joined to the housing 30z and the electrode connection fittings 112z and 122z.
The heating element holding member 300z constituting the conventional housing 30z is made of a heat-resistant metal material such as stainless steel, and the thermal expansion coefficient thereof is 10.4 × 10 ⁻⁶ / ° C. (for example, in the case of SUS430). 100 ° C.).
Further, in the conventional ceramic heater 1z, silver brazing (melting point: 750 to 900 ° C.) is generally used as a brazing material for forming the brazing contact portion 20z.

図２（ａ）は、常温時におけるセラミック発熱体１０ｚとハウジング３０ｚとの位置関係を簡単に示したものである。
本図（ｂ）に示すように、高温環境下では、熱膨張係数の大きなハウジング３０ｚの高温側が軸方向及び外径方向に大きく伸び、熱膨張係数の小さなセラミック発熱体１０ｚの伸びは、ハウジング３０ｚの伸びに比べ小さく、それぞれの先端面の相対的な距離は小さくなる。
高温環境下で熱に晒されたハウジング３０ｚには、時間の経過と共に高温側の先端部から、低温側の基端部に掛けて温度が低くなる温度勾配が形成され、その温度勾配にならい、先端部ほど、先端軸方向及び外径方向に向かって末広がりに膨張し、一時的に先端側におけるセラミック発熱体の締り嵌めが解放される。
また、ハウジング３０ｚとセラミック発熱体１０ｚとの間隙を埋めるロウ材は高温環境下に晒されることにより軟化し、保持力が弱まる。
さらに、本図（ｃ）に示すように。低温環境下では、冷却により、膨張したハウジング１０ｚの先端部ほど急激な冷却によって、基端軸方向及び内径方向に向かって早く収縮する。
このとき、伝熱によって熱が移動する基端側は、加熱時・冷却時とも、先端側に比べ、温度変化に時間的遅れが生じ、基端側の保持力が相対的に弱くなる。
このため、先端側が冷却され収縮が開始したときに、ハウジング３０ｚ内部に残留する余熱の移動によって基端側は依然膨張する傾向にあり、実質的に、ハウジング３０ｚの先端部が膨張前のセラミック発熱体１０ｚを保持していた位置よりも先端側の位置でセラミック発熱体の締め付けを開始することとなる。
本図（ｄ）に示すように、さらに、冷却状態で時間が経過するとハウジング１０ｚの基端部も次第に冷却され軸方向・径方向ともに収縮する。
この時、既に冷却収縮を完了した先端部が拘束点となるため、基端部はこの拘束点に向けて収縮することとなり、相対的にセラミック発熱体１０ｚが基端側に向かって引き込まれることになる。
即ち、冷熱環境下ではハウジングの先端面とセラミック発熱体の先端面との距離が冷熱の繰り返しによって相対的に変化し続けることとなり、ハウジングの先端面からセラミック発熱体の突出する長さが徐々に短くなる。
本図（ａ）に示すように、常温時にハウジング３０ｚからの付きだし長さＬ_０であったセラミック発熱体１０ｚは、本図（ｄ）に示すように、冷熱サイクル後のハウジング３０ｚからの付き出し長さＬ_１がΔＬだけ短くなる「発熱体引込現象」を生じる。
また、セラミック発熱体１０ｚとハウジング３０ｚとの間隙に充填されたロウ材２０ｚは、高温環境下では先端側が先に軟化し、セラミック発熱体１０ｚの拘束力が弱まるが、冷却過程では、相対的に先端側が先に硬化するため先端側が拘束点となって、相対的にセラミック発熱体１０ｚを基端側へ引き込む傾向がさらに強くなる。 FIG. 2A simply shows the positional relationship between the ceramic heating element 10z and the housing 30z at room temperature.
As shown in FIG. 5B, in a high temperature environment, the high temperature side of the housing 30z having a large thermal expansion coefficient extends greatly in the axial direction and the outer diameter direction, and the ceramic heating element 10z having a small thermal expansion coefficient extends in the housing 30z. The relative distance between the respective tip surfaces is small compared to the elongation of.
In the housing 30z exposed to heat in a high temperature environment, a temperature gradient is formed in which the temperature decreases from the distal end portion on the high temperature side to the proximal end portion on the low temperature side as time elapses. The distal end portion expands toward the distal end in the axial direction and the outer diameter direction, and the interference fit of the ceramic heating element on the distal end side is temporarily released.
Further, the brazing material filling the gap between the housing 30z and the ceramic heating element 10z is softened by exposure to a high temperature environment, and the holding power is weakened.
Furthermore, as shown in FIG. Under a low temperature environment, due to cooling, the tip of the expanded housing 10z contracts rapidly toward the proximal axial direction and the inner diameter direction due to rapid cooling.
At this time, the base end side where heat is transferred by heat transfer has a time delay in temperature change compared to the front end side during heating and cooling, and the holding force on the base end side becomes relatively weak.
For this reason, when the distal end side is cooled and contraction starts, the proximal end side still tends to expand due to the movement of residual heat remaining inside the housing 30z, and the distal end portion of the housing 30z is substantially heated before the expansion. Tightening of the ceramic heating element is started at a position closer to the tip side than the position where the body 10z is held.
As shown in FIG. 4D, when the time elapses in the cooling state, the proximal end portion of the housing 10z is gradually cooled and contracts in both the axial direction and the radial direction.
At this time, since the distal end portion that has already completed the cooling shrinkage becomes a restraint point, the proximal end portion shrinks toward the restraint point, and the ceramic heating element 10z is relatively drawn toward the proximal end side. become.
That is, in a cold environment, the distance between the front end surface of the housing and the front end surface of the ceramic heating element continues to change relatively by repeated cooling, and the length of the protrusion of the ceramic heating element from the front end surface of the housing gradually increases. Shorter.
As shown in the figure (a), the ceramic heating element 10z out a length of L ₀ per from the housing 30z in normal temperature, as shown in the figure (d), attached to the housing 30z after thermal cycle A “heating element pull-in phenomenon” occurs in which the length L ₁ is shortened by ΔL.
In addition, the brazing material 20z filled in the gap between the ceramic heating element 10z and the housing 30z is softened at the tip side first in a high temperature environment, and the binding force of the ceramic heating element 10z is weakened. Since the distal end side hardens first, the distal end side becomes a restraint point, and the tendency to relatively draw the ceramic heating element 10z toward the proximal end side is further increased.

図３を参照して、本発明の効果を確認するために行った試験について説明する。
図３（ａ）に示すような、本発明の第１の実施形態におけるセラミックヒータ１と、比較例として本図（ｂ）に示すような従来のセラミックヒータ１ｚに対して、ヒータ温度を１３５０℃まで昇温し、３分間加熱した後、１分間強制冷却して、ロウ接部における先端側（Ａ部）と基端側（Ｂ部）を、本図（ｃ）に示すような冷熱サイクルに晒した後、セラミック発熱体のハウジングからの突き出し長さＬ、Ｌｚを計測し、その変化から発熱体引込量ΔＬの変化を調査し、その結果を本図（ｄ）に示す。
本図(ｄ)に示すように、比較例として示した従来のセラミックヒータ１ｚでは、冷熱サイクルが１５０００回を超えた辺りから、発熱体の引込現象が観察され、２５０００回の冷熱サイクルに晒した後には、発熱体引込量ΔＬは０．７ｍｍとなった。一方、本発明の実施例として示したセラミックヒータ１では、２５０００回の冷熱サイクルに晒した後も、発熱体引込現象は発生せず、冷熱環境に晒され温度変化の大きい先端側（Ａ部）のみならず、温度変化の少ないハウジング３０の基端側（Ｂ部）でセラミック発熱体１０を保持固定することにより、発熱体引込現象の抑制を図る本発明の効果が確認された。 With reference to FIG. 3, the test performed in order to confirm the effect of this invention is demonstrated.
As compared with the ceramic heater 1 according to the first embodiment of the present invention as shown in FIG. 3A and the conventional ceramic heater 1z as shown in FIG. And then forcibly cooled for 1 minute, and the tip side (A part) and the base end side (B part) in the brazing contact part are subjected to a cooling cycle as shown in FIG. After the exposure, the projecting lengths L and Lz of the ceramic heating element from the housing were measured, and the change in the heating element drawing amount ΔL was investigated from the change, and the result is shown in FIG.
As shown in this figure (d), in the conventional ceramic heater 1z shown as a comparative example, the retraction phenomenon of the heating element was observed when the cooling cycle exceeded 15000 times, and it was exposed to 25,000 cooling cycles. Later, the heating element drawing amount ΔL became 0.7 mm. On the other hand, in the ceramic heater 1 shown as an example of the present invention, the heating element pull-in phenomenon does not occur even after exposure to 25,000 cooling cycles, and the tip side (part A) is exposed to the cooling environment and has a large temperature change. In addition, the effect of the present invention for suppressing the heating element pull-in phenomenon was confirmed by holding and fixing the ceramic heating element 10 on the base end side (B portion) of the housing 30 with little temperature change.

図４を参照して、本発明の第１の実施形態におけるセラミックヒータの変形例１ａ、１ｂについて説明する。
なお、上記第１の実施形態と同様の構成については同じ符号を付したので説明を省略し、相違点を中心に説明する。以下の実施形態においても同様である。
第１の実施形態において、は、本発明の要部である環状固定部材として設けた電極接続金具２０に導通線端子部１１３を接続し、外部に導通線１１４を引き出した例を示したが、本図（ａ）に示すように、電極接続金具２０は、ハウジング３０の基端側にロウ接されているため、セラミック発熱体１０を保持するだけでなく、ハウジング３０を介して発熱体電極部１１１が、接地状態となるため、セラミック発熱体１０への通電を図るべく接続される通電線１１４を排することができる。
加えて、このようないわゆるボディアース型のセラミックヒータ１ａにおいて、冷熱環境下におけるセラミック発熱体の引込現象が抑制されているため、接地電極となる発熱体電極部１１１と電極接続金具２０との間に設けたロウ接部２１の剥離が生じ難くなり、セラミックヒータの信頼性が向上する。
また、上記実施形態においては、環状固定部材として、電極接続金具２０を、下端に外径方向に向かって広がる鍔部を設けた断面略Ｌ字型に形成したが、本図（ｂ）に示すように、電極接続金具２０ｂを略筒状に形成し、内周壁２０１とセラミック発熱体１０の表面１０２とをロウ付けし、底面２０２ｂとハウジング３０ｂの上面３０５ｂとをロウ付けしてある。
さらに、電極接続金具２０ｂをハウジング３０ｂに挿嵌させ、ハウジング３０ｂによって電極接続金具２０ｂの外周を締め嵌めしても良い。 With reference to FIG. 4, modifications 1 a and 1 b of the ceramic heater according to the first embodiment of the present invention will be described.
In addition, since the same code | symbol is attached | subjected about the structure similar to the said 1st Embodiment, description is abbreviate | omitted and it demonstrates centering around difference. The same applies to the following embodiments.
In the first embodiment, the example in which the conductive wire terminal portion 113 is connected to the electrode connection fitting 20 provided as the annular fixing member, which is the main part of the present invention, and the conductive wire 114 is drawn to the outside is shown. As shown in FIG. 5A, the electrode fitting 20 is brazed to the proximal end side of the housing 30, so that it not only holds the ceramic heating element 10 but also the heating element electrode section via the housing 30. Since 111 is in a grounded state, the conducting wire 114 connected to energize the ceramic heating element 10 can be removed.
In addition, in such a so-called body ground type ceramic heater 1a, the pulling-in phenomenon of the ceramic heating element in a cold environment is suppressed, so that the heating element electrode portion 111 serving as the ground electrode and the electrode connecting bracket 20 are not connected. Peeling of the brazing contact portion 21 provided on the ceramic heater hardly occurs, and the reliability of the ceramic heater is improved.
Moreover, in the said embodiment, although the electrode connection metal fitting 20 was formed in the substantially L-shaped cross section which provided the collar part which spreads toward an outer-diameter direction as an annular fixing member, it shows to this figure (b). Thus, the electrode connection fitting 20b is formed in a substantially cylindrical shape, the inner peripheral wall 201 and the surface 102 of the ceramic heating element 10 are brazed, and the bottom surface 202b and the upper surface 305b of the housing 30b are brazed.
Furthermore, the electrode connection fitting 20b may be inserted into the housing 30b, and the outer periphery of the electrode connection fitting 20b may be tightened by the housing 30b.

図５を参照して、本発明の第２の実施形態におけるセラミックヒータ１ｃとその変形例１ｄについて説明する。
上記実施形態においては、ハウジング３０、３０ｂは、ステンレス等の金属材料によって、一体的に形成した例を示したが、本実施形態においては、ハウジング３０ｃを、略筒状に形成された発熱体保持部材３００ｃと、別体に設けたニップルナット状の発熱体取付部材３１０との複数の部材によって構成し、発熱体保持部材３００ｃと、電極接続金具２０ｃとを接合している点が相違する。
本実施形態においては、発熱体保持部材３００ｃは、両端が開口し、一方の端に外径方向に張り出す鍔部３１１が設けられており、鍔部３１１の基端側表面には、セラミックヒータ１ｃの中心軸に対して直交する水平面をなし、後述する押圧部３０７によって被取付部材方向に押圧される受圧部３１２が設けられ、鍔部３１１の先端側表面には、挿入方向に向かって連続的に縮径する略円錐テーパ状の稜面を有する取付手段側シール部３０４ｃが設けられている。
発熱体取付部材３１０は、ステンレス等の耐熱性金属材料を用いて略筒状に形成されており、基端側外周に六角部３０３が設けられ、先端側外周にハウジングネジ部３０２が設けられ、先端には、ハウジングネジ部３０２を被取付部材側ネジ部６１１ｃに螺結したときに、受圧部３１２を被取付部材方向に押圧する押圧部３０７が形成されている。
また、発熱体取付部材３１０を被取付部材６０ｃに螺結する際に、発熱体保持部材３００ｃの回転を伴わないように、発熱体取付部材３１０の内径３０６と、発熱体保持部材３００ｃの外径との間には間隙が形成されている。
このようにハウジング３０ｃを、発熱体保持部材３００ｃと、発熱体取付部材３１０の複数の部材によって構成することによって、上記実施形態と同様の効果に加え、セラミックヒータ１ｃを被取付部６０ｃに組み付ける際に、発熱体取付部材３１０を回転させても、通電線１１４、１２４が捻れることがなく、組み付けの作業性が向上すると共に、導通線１１４、１２４とセラミック発熱体１０との接続部に捻りを生じないので、第２の発熱体ロウ接部２１ｃが剥離する虞がない。さらに、本図（ｂ）に示すように、導通線１１４を廃した構成としても良い。本図に示したいずれの実施形態においても上記実施形態と同様に、発熱体引込現象の発生を抑制し、信頼性の高いセラミックヒータが実現できる。 With reference to FIG. 5, the ceramic heater 1c and its modification 1d in the 2nd Embodiment of this invention are demonstrated.
In the above embodiment, the housings 30 and 30b are integrally formed of a metal material such as stainless steel. However, in the present embodiment, the housing 30c is held in a substantially cylindrical shape with a heating element. The member 300c and the nipple nut-like heating element mounting member 310 provided separately are configured by a plurality of members, and the heating element holding member 300c and the electrode connection fitting 20c are joined.
In the present embodiment, the heating element holding member 300c is provided with a flange 311 that is open at both ends and that projects in the outer diameter direction at one end, and a ceramic heater is provided on the proximal end surface of the flange 311. A pressure receiving portion 312 is provided that forms a horizontal plane perpendicular to the central axis of 1c and is pressed in the direction of the attached member by a pressing portion 307, which will be described later. The tip surface of the flange portion 311 is continuous in the insertion direction. An attachment means side seal portion 304c having a substantially conical taper-shaped ridge surface that is reduced in diameter is provided.
The heating element mounting member 310 is formed in a substantially cylindrical shape using a heat-resistant metal material such as stainless steel, a hexagonal portion 303 is provided on the outer periphery on the base end side, and a housing screw portion 302 is provided on the outer periphery on the distal end side. A pressing portion 307 that presses the pressure receiving portion 312 in the direction of the attached member when the housing screw portion 302 is screwed to the attached member side screw portion 611c is formed at the tip.
Further, when the heating element mounting member 310 is screwed to the mounted member 60c, the inner diameter 306 of the heating element mounting member 310 and the outer diameter of the heating element holding member 300c are not accompanied by the rotation of the heating element holding member 300c. A gap is formed between the two.
In this way, when the housing 30c is constituted by a plurality of members of the heating element holding member 300c and the heating element mounting member 310, in addition to the same effects as in the above embodiment, the ceramic heater 1c is assembled to the mounted portion 60c. In addition, even if the heating element mounting member 310 is rotated, the conductive wires 114 and 124 are not twisted, so that the workability of the assembly is improved and the connecting portion between the conductive wires 114 and 124 and the ceramic heating element 10 is twisted. Therefore, there is no possibility that the second heating element brazing portion 21c is peeled off. Furthermore, as shown in this figure (b), it is good also as a structure which eliminated the conducting wire 114. FIG. In any of the embodiments shown in the figure, similar to the above-described embodiment, the occurrence of the heating element pull-in phenomenon is suppressed, and a highly reliable ceramic heater can be realized.

図６を参照して本発明の第３の実施形態におけるセラミックヒータ１ｅについて説明する。
本実施形態においては、発熱体保持部材３００ｅと発熱体取付部材３１０ｄとの間に、略筒状の導通線保護部材３３を介装し、セラミック発熱体１０の基端側に設けた発熱体電極部１１１、１２１、電極接続金具２０ｅ、１２２、導通線端子部１１３、１２３及び導通線１１４、１２４を覆い、基端部を封止部材３４を用いて封止固定してある。
導通線保護部材３３は、両端が開口する略筒状に形成された導通線保護基体３３０の保護部材先端部３３１を発熱体保持部材３００ｅの基端部を覆うように挿嵌し、保護部材先端部３３１において、発熱体保持部材３００ｅと溶接固定され、保護部材基端部３３２には、外部の通電制御装置に接続される一対の導通線１１４、１２４が挿通された封止部材３４が挿入され、加締め部３３３において、全周に渡り加締められ、導通線保護部材３３の基端側の開口が封止されている。
封止部材３４は、シリコンゴム等の弾性部材が用いられ、導通線１１４、１２４を保持、固定すると共に、導通線保護部材３３０の基端側を封止している。
本実施形態では、上記実施形態と複数箇所に接合手段を設けて発熱体１０と発熱体保持部材３００ｅとを接合することによって、発熱体引込現象が生じ難くなっているのに加え、導通線保護部材３３によって、セラミック発熱体１０の基端部に引き出された導通線とセラミック発熱体１０との接続部分が、外部からの浸水や、衝撃等から保護される。
本実施形態におけるセラミックヒータ１ｅを被取付部材として、燃焼機関の排ガス流路等の外部からの被水、石跳ね、振動等の過酷な使用環境に設けた場合でも高い信頼性を維持できる。 A ceramic heater 1e according to a third embodiment of the present invention will be described with reference to FIG.
In the present embodiment, a heating element electrode provided on the proximal end side of the ceramic heating element 10 with a substantially cylindrical conductive wire protection member 33 interposed between the heating element holding member 300e and the heating element mounting member 310d. The portions 111 and 121, the electrode connection fittings 20 e and 122, the conductive wire terminal portions 113 and 123, and the conductive wires 114 and 124 are covered, and the base end portion is sealed and fixed using the sealing member 34.
The conducting wire protection member 33 is inserted and fitted to cover the proximal end portion of the heating element holding member 300e so as to cover the base end portion of the heating element holding member 300e. In the portion 331, the heating element holding member 300e is welded and fixed, and in the protective member base end portion 332, the sealing member 34 into which a pair of conductive wires 114 and 124 connected to an external energization control device is inserted is inserted. The crimping portion 333 is crimped over the entire circumference, and the opening on the proximal end side of the conductive wire protection member 33 is sealed.
The sealing member 34 is made of an elastic member such as silicon rubber, holds and fixes the conductive wires 114 and 124, and seals the proximal end side of the conductive wire protection member 330.
In the present embodiment, by connecting the heating element 10 and the heating element holding member 300e by providing bonding means at a plurality of locations as in the above embodiment, the heating element pull-in phenomenon is less likely to occur, and in addition, the conductive line protection By the member 33, the connection portion between the conductive wire drawn out to the base end portion of the ceramic heating element 10 and the ceramic heating element 10 is protected from external water immersion, impact, and the like.
High reliability can be maintained even when the ceramic heater 1e according to the present embodiment is used as a member to be attached and is provided in a harsh usage environment such as flooding from outside such as an exhaust gas flow path of a combustion engine, rock jumping, and vibration.

図７を参照して、本発明の第３の実施形態におけるセラミックヒータの変形例１ｆについて説明する。
上記実施形態においては、本実施形態においては、セラミック発熱体１０への通電を一対の通電線１１４、１２４を介して行う例を示したが、本実施形態では、セラミック発熱体１０の一の発熱体電極部１１１ｂ（接地電極側）が電極接続金具２０ｆを介して発熱体保持部材３３０に直接的に接続されている。
このような、構成とすることにより、上記実施形態と同様の効果に加え、一の電極接続金具２０ｆ、通電線端子部１１３、通電線１１４をそれぞれ廃することが可能となり、製造が簡易となる。また、セラミック発熱体１０の体格を小さくできので、搭載性が向上する上に、製造コストの削減も可能となる。 With reference to FIG. 7, the modification 1f of the ceramic heater in the 3rd Embodiment of this invention is demonstrated.
In the above embodiment, in the present embodiment, the example in which the energization to the ceramic heating element 10 is performed via the pair of energization wires 114 and 124 is shown, but in this embodiment, one heating of the ceramic heating element 10 is performed. The body electrode portion 111b (ground electrode side) is directly connected to the heating element holding member 330 via the electrode connection fitting 20f.
By adopting such a configuration, in addition to the same effects as those of the above-described embodiment, the one electrode connecting fitting 20f, the energizing wire terminal portion 113, and the energizing wire 114 can each be eliminated, and the manufacturing is simplified. . Moreover, since the physique of the ceramic heating element 10 can be made small, the mountability is improved and the manufacturing cost can be reduced.

図８を参照して、本発明の第４の実施形態におけるセラミックヒータ１ｇについて説明する。上記実施形態においては、燃焼式ヒータの着火源や、燃焼排気の加熱源として用いた比較的小型のセラミックヒータを例に説明したが、本実施形態においては、ディーゼルエンジンの燃焼室又は副燃焼室を被取付部材６０ｇとし、着火を補助する長尺のグロープラグとして用いる場合について説明する。
上記実施形態においては、発熱体電極部１２１から外部への接続に通電線１２４を用いているが、本実施形態においては、発熱体電極部１２１に略筒状の電極接続金具１２２ｇを嵌着し、電極接続金具１２２ｇに連結して金属材料を略棒状に形成した通電中軸１２３ｇを接続している。
さらに、発熱体電極部１１１は、第２の接合手段である電極接続金具２０ｇを介して、発熱体保持部材３００ｇに接合されている。
発熱体保持部材３００ｇ及び発熱体固定部材３１０ｇは、長尺に形成されているが基本的な構造は、上記実施形態に示した発熱体保持部材３００ｃ及び発熱体固定部材３１０と同様である。
また、本実施形態においては、燃焼時の圧力上昇に対抗できるように、封止部材３４ｇとして、耐熱性セラミック粉末等が用いられている。 With reference to FIG. 8, the ceramic heater 1g in the 4th Embodiment of this invention is demonstrated. In the above embodiment, a comparatively small ceramic heater used as an ignition source of a combustion heater or a heating source of combustion exhaust has been described as an example. However, in this embodiment, a combustion chamber or auxiliary combustion of a diesel engine is used. A case will be described in which the chamber is a member to be attached 60 g and is used as a long glow plug for assisting ignition.
In the embodiment described above, the conductive wire 124 is used for connection from the heating element electrode portion 121 to the outside. However, in the present embodiment, a substantially cylindrical electrode connection fitting 122g is fitted to the heating element electrode portion 121. The middle shaft 123g is connected to the electrode connection fitting 122g to form a metal material in a substantially rod shape.
Further, the heating element electrode portion 111 is bonded to the heating element holding member 300g via the electrode connection fitting 20g which is the second bonding means.
Although the heating element holding member 300g and the heating element fixing member 310g are formed in a long shape, the basic structure is the same as that of the heating element holding member 300c and the heating element fixing member 310 shown in the above embodiment.
In the present embodiment, a heat-resistant ceramic powder or the like is used as the sealing member 34g so as to counter the pressure increase during combustion.

本発明は上記実施形態に限定するものではなく、一対の電極を具備し、該電極に接続され外部に設けた通電装置からの通電により発熱するセラミック発熱体と、該セラミック発熱体の外周に嵌着され、上記セラミック発熱体の先端側の発熱部を被取付部材の内側に取付固定するためのハウジングと、上記ハウジングと上記セラミック発熱体を接合する接合手段とを具備するセラミックヒータにおいて、上記ハウジングの先端側で、冷熱環境下に晒される部分に設けた第１の接合手段と、上記ハウジングの基端側で、冷熱環境下から離隔した部分に設けた第２の接合手段を設けることより、セラミックヒータのハウジングが冷熱サイクルに晒されたときに、ハウジングとセラミック発熱体との相対変位による発熱体引込現象を起こり難くする本発明の趣旨を逸脱しない限りにおいて適宜変更可能である。 The present invention is not limited to the above-described embodiment, and includes a ceramic heating element that includes a pair of electrodes and that generates heat when energized from an energization device that is connected to the electrodes and provided outside, and is fitted to the outer periphery of the ceramic heating element. A ceramic heater comprising: a housing for attaching and fixing a heat generating portion on the front end side of the ceramic heating element to an inside of a member to be attached; and a joining means for joining the housing and the ceramic heating element. By providing a first joining means provided in a portion exposed to a cold environment on the distal end side of the first and a second joining means provided in a portion separated from the cold environment on the base end side of the housing, A book that makes it difficult for the heating element to be pulled in due to the relative displacement between the housing and the ceramic heating element when the ceramic heater housing is exposed to a cold cycle. It can be appropriately changed without departing from the spirit of the light.

１セラミックヒータ
１０セラミック発熱体
２０電極接続金具（第２の接合手段）
２１第２の発熱体ロウ接部（第２の接合手段）
２２固定部材ロウ接部（第２の接合手段）
２３第１のロウ接部（第１の接合手段）
１１１、１２１発熱体電極部
３０ハウジング
６０被取付部材
６００被加熱流体 DESCRIPTION OF SYMBOLS 1 Ceramic heater 10 Ceramic heating element 20 Electrode connection metal fitting (2nd joining means)
21 2nd heat generating body brazing part (2nd joining means)
22 fixing member brazing portion (second joining means)
23 1st brazing part (1st joining means)
111, 121 Heating element electrode portion 30 Housing 60 Mounted member 600 Heated fluid

特開２００１−２８２９２号公報JP 2001-28292 A 特開２００３−５６８４８号公報JP 2003-56848 A

Claims

A ceramic heating element comprising a pair of electrodes and generating heat by energization from an energizing device connected to the electrodes and provided externally, and a heat generating part fitted on the outer periphery of the ceramic heating element, on the tip side of the ceramic heating element In a ceramic heater comprising a housing for mounting and fixing the inner side of a member to be mounted, and a joining means for joining the housing and the ceramic heating element,
The joining means includes a first joining means provided at a portion exposed to the cold environment on the distal end side of the housing, and a second joint provided at a portion separated from the cold environment on the proximal end side of the housing. Ri Do from the junction means,
The first joining means is constituted by a first heating element brazing portion formed by filling a brazing material in a gap between the front end side exposed to the cold environment of the housing and the heating element,
An annular fixing member that is formed in a substantially annular shape that covers the ceramic heating element by providing the second joining means independently of the housing;
A second heating element brazing portion formed by filling a brazing material in a gap between the annular fixing member and the ceramic heating element;
A ceramic heater comprising: an annular fixing member brazing portion formed by filling a gap between the annular fixing member and the housing or a member coupled to the housing with a brazing material .

The ceramic heater according to claim 1 , wherein the annular fixing member is joined to one of the pair of electrodes .