JP4025641B2 - Ceramic heater - Google Patents

Description

【００５１】
表１から明らかなように、本発明の範囲外である試料番号１、２、８、９、１４、１５は耐久試験前後の抵抗変化率が１３．３％以上と大きく、しかもいずれも耐久試験後にはセラミック体４にクラックが認められた。なお、従来例は試料番号１、２に相当する。
【００５２】
これに対し、本発明のセラミックヒータ１はいずれも抵抗変化率が６．０％以下と小さく、セラミック体４にもクラックは発生しなかった。抵抗変化率が６．０％以下のものは耐久評価後のクラックは発生しておらず、セラミック体４の半径Ｒ１と、金属板８の内周面の曲率半径Ｒ２の差（Ｒ１−Ｒ２）が本発明の範囲内であれば応力の集中が回避され、その結果、電極取り出し用の金属板８の接続強度が大幅に改善されていることが確認できた。
【００５３】
尚、本発明のセラミックヒータ１は前記実施例に限定されるものではなく、前記金属層７及び金属板８の形状は、本発明の主旨を逸脱しないものであればいかなる形状でも良く、またセラミック体４の断面形状も用途に応じて種々の変更が可能であり、また発熱体２を平行に複数配設して多層構造とし、各発熱体２を直列にあるいは並列に接続した構造としたものに適用しても同様の効果を奏するものである。
【００５４】
【発明の効果】
上記のように、本発明のセラミックヒータは、電極取り出し部におけるセラミック体の曲率半径をＲ１（ｍｍ）、金属板の内周面の曲率半径をＲ２（ｍｍ）、金属層の平均厚みをｔ（ｍｍ）としたとき、−０．１≦（Ｒ１−Ｒ２）＜ｔ、かつ、金属層の平均厚みが３０〜１５０μｍとなるように形成されている。これにより、常温付近から高温まで急速に昇温することを長時間にわたり反復したり、高温下で発熱させて飽和状態で長時間、連続稼働したりしても、リード線を接続した電極取り出し金属板との接合部が長期的な加熱冷却の反復に耐える強度を有し、かつ耐熱衝撃性、高温安定性に優れ、昇温特性の良好な耐久性に優れたセラミックヒータが得られる。
【００５５】
また、前記金属層が、Ａｕ−Ｃｕ合金、もしくはＡｇ−Ｃｕ合金、Ａｕ−Ｎｉ合金を主成分とするロウ材とすれば、使用中の熱サイクルに対して耐久性良好なセラミックヒータとすることができる。
【００５６】
そして、前記金属層が、活性金属としてバナジウム（Ｖ）又はチタン（Ｔｉ）を含有することによりセラミック体に対する前記金属層の接合強度をさらに向上させることができる。
【００５７】
また、金属板の周辺部とセラミック基体との間に形成される金属層の厚みを３０〜１５０μｍとすることにより金属層とセラミック基体の間の熱膨張差による応力を低減させ、耐久性をさらに改善することができる。
【図面の簡単な説明】
【図１】（ａ）は、本発明のセラミックヒータの斜視図であり、（ｂ）はそのＸ−Ｘ線断面図である。
【図２】本発明のセラミックヒータにおけるセラミック体の製造工程を説明するための図である。
【図３】本発明のセラミックヒータの要部断面図である。
【符号の説明】
１：セラミックヒータ
２：発熱部
３：第２リード部
４：セラミック体
５：リード部
６：電極引出部
７：金属層
８：金属板
９：リード金具[0001]
BACKGROUND OF THE INVENTION
The present invention is excellent in thermal shock resistance and high temperature stability, and has excellent temperature rise characteristics and durability, such as heaters for ignition or vaporization of various combustion devices such as petroleum fan heaters, various sensors and measuring devices such as oxygen sensors, electronic Heaters for general household electrical appliances such as parts, industrial equipment, hot water heaters, soldering irons, etc., and glow plugs for internal combustion engines that rapidly preheat the auxiliary combustion chamber when starting diesel engines or idling The present invention relates to a ceramic heater for high temperature used in a direct current or alternating current power source applied to the above.
[0002]
[Prior art]
Conventionally, as various ignition and heating heaters such as glow plugs used for accelerating start-up of diesel engines, various sheathed heaters in which a heating resistor made of a refractory metal wire or the like is embedded in a sheath made of a heat-resistant metal, However, various ignition devices using spark discharge have been widely used, but all of them are difficult to rapidly increase in temperature, and are inferior in wear resistance and durability. In addition to being prone to radio interference such as noise, there are drawbacks such as lack of reliability in terms of reliable ignition.
[0003]
Therefore, ceramic firing is a reliable heating element with excellent heat transfer efficiency, rapid heating, no radio interference, reliable ignition, high safety, and excellent wear resistance and durability. A ceramic heating element carrying, bonding, or embedding a heating element composed of a bonded body, a refractory metal, a compound thereof, and various inorganic conductive materials mainly composed of them, and various heaters including a glow plug of an internal combustion engine Has come to be widely used as.
[0004]
In general, a ceramic heater having a high-melting-point metal heat generating portion provided on the surface or inside of an alumina ceramic is known as a ceramic heating element. However, alumina (Al ₂ O ₃ ) used as an electrical insulating material is resistant to thermal shock. Since the ceramic body of the ceramic heating element is inferior in heat resistance and high temperature strength, it is a non-oxide ceramic with excellent heat resistance, thermal shock resistance and oxidation resistance, especially heat resistance, high temperature strength, high heat capacity, Silicon nitride ceramics with good electrical insulation are widely used as ceramic bodies for high-temperature ceramic heating elements that can be rapidly heated.
[0005]
Next, a conventional ceramic heater 1 using silicon nitride ceramic will be described with reference to the drawings. In FIG. 1, a ceramic heater 1 includes a substantially U-shaped heat generating portion 2 mainly composed of WC embedded in one end of a ceramic body 4 made of a cylindrical or columnar silicon nitride sintered body. The second lead 3, the lead wire 5, the lead wire 5 and the electrode lead-out portion 6 connected to both ends of the heat generating portion 2 are built in, and the end of the electrode lead-out portion 6 is exposed on the surface of the ceramic body 4. It is formed to do. These are electrically connected structures.
[0006]
As shown in Patent Document 1, a metal layer 7 is formed on the electrode lead-out portion 6 exposed on the side surface of the end portion of the ceramic body 4 and is connected to an external power source 9. The Ni metal plate 8 bonded to each other was bonded by the metal layer 7.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-25675
[Problems to be solved by the invention]
Thus, even if the ceramic body 4 and the lead metal fitting 9 are joined via the metal plate 8 that constitutes the joining stress relaxation material, the durability test in which the temperature of the electrode take-out portion 6 is repeatedly heated and cooled to temperatures of 40 ° C. and 450 ° C. In the case of repeated heating and cooling over 500 cycles, there is a problem that residual stress is generated around the brazed portion of the metal plate 8, cracks grow, and bonding strength decreases.
[0009]
As a result, peeling of the lead metal fitting 9 or the crack extends to the internal lead wire 5, oxygen enters from the gap around the lead wire 5, the heating element 2 is oxidized, and the durability of the ceramic heater 1 deteriorates. There was a problem of lack of long-term reliability.
[0010]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and its purpose is to have a strength at which a joint portion of an electrode extraction metal plate to which a lead fitting is joined can withstand repeated heating and cooling over a long period of time, and cracks and the like do not occur. Heating of ignition or vaporization of various combustion equipment with excellent thermal shock resistance, high temperature stability and good temperature rise characteristics, heating of various sensors and measuring equipment, electronic parts, industrial equipment, general household electrical appliances, etc. Another object of the present invention is to provide a high-temperature ceramic heater suitable for a heater for an internal combustion engine and a glow plug for an internal combustion engine.
[0011]
[Means for Solving the Problems]
Ceramic heater of the present invention includes a cylindrical or cylindrical ceramic body, are embedded in the ceramic body, a heating unit made of an inorganic conductive material which generates heat by energization, electrically connected to the electrode extraction portion in the heat generating unit When a metal layer electrically connected to said electrode extraction portion, and the electrode extraction portion and electrically connected to the curved metal plate via the metal layer, lead metal fitting connected to the metal plate The radius of curvature of the ceramic body in the electrode lead-out portion is R1 (mm ), the radius of curvature of the inner peripheral surface of the metal plate is R2 (mm ), and the average thickness of the metal layer is t (mm). -0.1 ≦ (R1-R2) <t and the average thickness of the metal layer is 30 to 150 μm .
[0012]
In the ceramic heater of the present invention, the metal layer is made of a brazing material mainly composed of an Au—Cu alloy, an Ag—Cu alloy, or an Au—Ni alloy.
[0013]
The ceramic heater according to the present invention is characterized in that the metal layer contains vanadium (V) or titanium (Ti) as an active metal, and the ceramic heater according to the present invention includes a peripheral portion of the metal plate, The thickness of the metal layer formed between the ceramic substrate and the ceramic substrate is 30 to 150 μm.
[0014]
[Action]
The ceramic heater according to the present invention includes a metal layer and an electrode containing an active metal due to a stress generated by a difference in thermal expansion between a ceramic body of a ceramic heating element by repeated heating and cooling during operation and a metal plate for extracting the electrode. Prevents damage to bonding strength between the take-out part and ceramic body, curved electrode take-out metal plate, etc., and prevents the occurrence of cracks around the brazed part of cylindrical or columnar ceramic heating elements that make up ceramic heaters. Can be improved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the ceramic heater of the present invention will be described in detail. Fig.1 (a) is a perspective view which shows one Embodiment of the ceramic heater 1 of this invention, FIG.1 (b) is the XX sectional drawing.
[0016]
The ceramic heater 1 includes a substantially U-shaped heat generating portion 2 mainly composed of WC embedded in one end portion of a ceramic body 4 made of a columnar silicon nitride sintered body, and a first connected to this. 2 lead portion 3, lead portion 5 electrically connected to both ends of the second lead portion, electrode extraction portion 6 connected to the lead portion 5 and exposed at the other side surface, and lead metal fitting to the metal layer 7 9 is formed of a substantially cylindrical shape composed of a metal plate 8 to which the lead 9 is connected, and the lead portion 5 is a conductor mainly composed of WC, or a W wire, or a combination thereof, The resistance value is lowered and the heat generated by energization is adjusted to be smaller than that of the heat generating portion 2.
[0017]
FIG. 2 is a development view showing a manufacturing method of the ceramic body 4. The heating element 2, the second lead part 3, the lead wire 5, and the electrode lead-out part 6 are sequentially installed on the surface of the ceramic production form 4a, and two layers are stacked, and another ceramic molded body 4a is further stacked thereon. Integral firing is performed by hot press firing. Thereafter, the sintered body is cylindrically processed to form a ceramic body 4.
[0018]
The ceramic body 4 constituting the ceramic heater of the present invention has an arbitrary shape such as a U shape or a W shape when the block-like or layer-like heat generating portion 2 is viewed in plan view. The ceramic body 4 is formed by a method such as printing or transfer, or the linear heat generating portion 2 is wound in a coil shape or bent, and the heat generating portion 2 is embedded in the ceramic body 4. A lead wire 5 made of a W material or the like may be electrically connected to both ends of the wire.
[0019]
FIG. 3 is a cross-sectional view of the main part of the cylindrical or columnar ceramic heater 1 of FIG. 1, wherein the radius of curvature of the ceramic body 4 is R1 (mm), the radius of curvature of the metal plate 8 is R2 (mm), and the metal layer 7 When the average thickness of t is (mm), if the relationship of −0.1 ≦ (R1−R2) <t is satisfied, when the metal plate 8 is bonded to the ceramic body 4 via the metal layer 7, The melted metal layer 7 has a force that pulls the metal plate 8 toward the ceramic body 2 due to the surface tension, so that the thickness of the metal layer 7 is reduced at the outer periphery of the metal plate 8, and the metal layer 7 and the metal plate The stress due to the difference in thermal expansion between the ceramic body 4 and the ceramic body 4 is relieved, and good durability is exhibited against the heat cycle during use.
[0020]
For this purpose, adjustment of the amount of the metal layer 7 is also necessary. It is preferable to adjust the coating amount of the metal layer 7 so as to be within a variation range of ± 15% with respect to the volume represented by (average thickness of the metal layer 7) × (area of the metal layer 7).
[0021]
Here, the average thickness t of the metal layer 7 is obtained by averaging the thickness of the outer peripheral portion of the metal plate 8 and the thickness of the center of the metal plate 8.
[0022]
On the other hand, when (R1-R2) is smaller than -0.1 (mm), the metal layer 7 is difficult to be formed on the entire surface of the metal plate 8, and a nest is generated in the metal layer 7, and cracks occur due to stress concentration. There is a problem that occurs. When (R1-R2) is equal to or greater than t (mm), the gap between the end of the metal plate 8 and the ceramic body 4 becomes large, the thickness of the metal layer 7 at the end of the metal plate 8 increases, and the ceramic body 4 There arises a problem that cracks are generated due to residual stress due to a difference in thermal expansion between the metal layers 7.
[0023]
The metal plate 8 for taking out an electrode to which the lead metal fitting 9 of the present invention is joined is composed of the ceramic body 4 generated by the cooling process after heating and joining with the metal layer 7 containing the active metal and the heat generated by the heating and cooling during operation. Any material can be used as long as it can relieve the expansion difference, but the ceramic body 4 has a thermal expansion coefficient of 3.0 to 5.4 × 10 ⁻⁶ / ° C. which is close to 3.0 to 7. A metal plate 8 of 5 × 10 ⁻⁶ / ° C. is desirable.
[0024]
The metal plate 8 is iron (Fe) -based such as Fe—Ni—Co alloy or Fe—Ni alloy having a Young's modulus of 14 to 15 × 10 ³ kg / mm ² in that it is easily plastically deformed. From the point that an alloy is optimal and the stress generated by the thermal expansion difference can be sufficiently absorbed by the plastic deformation of the metal plate 8 itself, the corners of the metal plate 8 are chamfered or rounded to avoid stress concentration. It is more preferable to carry out processing.
[0025]
Further, the metal plate 8 of the electrode take-out part that adheres to the metal layer 7 has a surface area of the metal layer 7 to which the metal plate 8 is bonded in order to avoid stresses due to thermal expansion differences being concentrated in a narrow range. However, conversely, if it exceeds 80%, the outer periphery of the metal plate 8 where the stress concentrates and the outer periphery of the metal layer 7 approach each other and the stress concentrates to generate a crack. Therefore, the bonding area is preferably 20 to 80% of the surface area of the metal layer 7, and the outer peripheral portion of the metal plate 8 may not overlap any edge of the outer peripheral portion of the metal layer 7. desirable.
[0026]
On the other hand, the electrode lead-out portion 6 may be the exposed exposed surface, but the connection reliability can be further improved by applying a metal coating such as Ni and forming the metal layer 7 thereon. Further, as the lead metal fitting 9 connected to the metal plate 8, Ni wire having a low coefficient of thermal expansion can be applied.
[0027]
The thickness of the metal layer 7 around the metal plate 8 is preferably 30 to 150 μm. If the thickness of the metal layer 7 exceeds 150 μm, the thickness of the metal layer 7 is increased, and cracks are likely to occur due to thermal stress caused by a difference in thermal expansion, which is not preferable. Further, if the thickness of the metal layer 7 is less than 30 μm, the amount of metal forming the metal layer 7 is reduced, so that a nest is generated in the metal layer 7 and the joint portion of the lead metal fitting 9 is floating from the metal plate 8. In such a case, there is a problem in that the lead fitting 9 may be broken due to stress on the lead fitting 9.
[0028]
And as the metal layer 7 in this invention, it is based on Au-Cu alloy, or Au-Cu alloy, Au-Ni alloy, the total amount is 90 to 99 weight%, and the remainder 1 to 10 weight% is V, Examples include those containing one or more active metals of Mo, Ti, Zr, Hf, and Mn. The active metals may be contained in the form of nitrides, carbides, hydrides, and the like. Thereby, durability of the ceramic heater 1 with respect to the heat cycle in use can be improved. The metal layer 7 preferably contains vanadium (V) or titanium (Ti) as an active metal.
[0029]
If the amount of the active metal is less than 1% by weight, the effect of improving the bonding strength is not seen, and if it exceeds 10% by weight, the baking temperature of the metal layer 7 is increased and a large residual stress is generated during cooling, causing cracks. Therefore, it is limited to the above range, and 1 to 5% by weight is most desirable. From the viewpoint of preventing short circuit due to migration or the like, the metal layer 7 is most preferably one containing Au as a main component of a noble metal.
[0030]
If the metal layer 7 is electrically connected to the electrode lead-out part, the metal layer 7 can be provided by being pulled out from the electrode lead-out part. The curved surface is within a range of 20 to 80% of the surface area of the metal layer 7. It suffices if the metal plate 8 for taking out the electrode has a substantially bonded area.
[0031]
As a material of the ceramic body 4 in the ceramic heater 1 of the present invention, a ceramic body 4 made of a ceramic sintered body of non-oxide ceramics such as silicon nitride ceramics and aluminum nitride ceramics, and oxide ceramics such as alumina and mullite. Consists of. In particular, in non-oxide ceramics, cracks are prevented from occurring in the ceramic body 4 due to fatigue due to thermal cycles during use due to the stress due to the thermal expansion difference between the metal layer 7, the metal plate 8, and the ceramic body 4. It is effective for.
[0032]
For example, in silicon nitride ceramics, the grain boundary phase is composed of a crystal phase or glass phase containing a group 3a element of the periodic table of the sintering aid component, silicon, or the like, but preferably monosilicate ( It is preferable to deposit a crystal phase composed of RE ₂ SiO ₅ ) or disilicate (RE ₂ Si ₂ O ₇ ) as a main phase. This is because the precipitation of the monosilicate or disilicate enhances the oxidation resistance of the ceramic body 4 at a high temperature. Further, in connection with the precipitating disilicate in the grain boundary phase of the ceramic body 4, the oxide equivalent weight of the total rare earth elements of the ceramic body 4, the molar ratio of SiO ₂ in terms of the impurity oxygen is It is preferably 2 or more from the viewpoint of oxidation resistance, and is preferably controlled to 5 or less from the viewpoint of densification of the sintered body.
[0033]
Moreover, as alumina as an example of oxide ceramics, silica (SiO ₂ ) 2 to 6% by weight, Macnesia (MgO) 1 to 3% by weight, calcia (CaO) 1 to 3 with respect to 88 to 95% by weight of alumina. Those containing% by weight can be used.
[0034]
The inorganic conductive material constituting the heating element 2 is added in a small amount to the non-oxide ceramic sintered body, which is the ceramic body 4, so that the thermal expansion difference or reactivity between the heating element 2 and the ceramic body 4 is increased. May be adjusted.
[0035]
In order to prevent the cracks due to the difference in thermal expansion from the ceramic body 4 and to prevent the resistance from increasing with respect to the main component of the inorganic conductive material so as to control the grain growth thereof, silicon nitride, boron nitride One or more of aluminum nitride or silicon carbide may be contained in the heating element 2, and the amount thereof is, for example, 5 to 30 parts by weight of silicon nitride and boron nitride (BN) with respect to 100 parts by weight of the main component. The ratio is preferably 1 to 20 parts by weight, aluminum nitride is 1 to 15 parts by weight, and silicon carbide is 3 to 15 parts by weight.
[0036]
Further, the inorganic conductive material of the heating element 2 is a resistor mainly composed of a refractory metal such as W, Mo, Ti, or a carbide, silicide, nitride, or the like of a refractory metal such as WC, MoSi ₂ , or TiN. In view of the difference in thermal expansion from the ceramic forming the ceramic body 4 and the difficulty of reacting with them even at high temperatures, those containing WC or W as the main component are preferred.
[0037]
【Example】
Next, the ceramic heater 1 of the present invention was evaluated as described in detail below.
[0038]
First, Si ₃ N ₄ powder having a specific surface area of 7 to 15 m ² / g, 10 to 15% by weight of Yb ₂ O ₃ as an oxide of rare earth element, and less than 5% by weight of MoSi ₂ , Al ₂ O ₃ A suitable amount of each is added as a sintering aid, and if necessary, MoSi ₂ , Mo ₂ C, WSi ₂ , WO ₃ , WC, etc. are appropriately added as a colorant and a coefficient of thermal expansion, and wetted in a ball mill for 24 hours. Mixed.
[0039]
Thereafter, each of the obtained sludge was spray-dried and granulated, and the granulated body was used to produce a flat shaped shaped body 4a by a press molding method.
[0040]
Next, using a paste prepared by adding a solvent to a mixed powder of 80% by weight of WC fine powder and 20% by weight of Si ₃ N ₄ fine powder, a U-shaped pattern is obtained by screen printing or the like. In particular, the heating element 2 was formed on the surface of the generated shaped body 4a so as to be located within about 5 mm from the tip of the sintered body.
[0041]
Further, the second lead 3 is formed at a predetermined position by using a paste composed of fine powders of 92 wt% WC and 8 wt% BN so that both ends of the heat generating element 2 partially overlap each other. .
[0042]
At that time, the electrode lead-out portion 6 is made of the same composition as the second lead 3 at the other end of the generated shape 4a, and two rectangular patterns are formed in parallel to the side of the generated shape 4a in the same manner as described above. Each was formed by arrangement.
[0043]
Next, a W wire having a diameter of 0.3 mm is electrically connected to the pattern of the lead part and the electrode take-out part, respectively, on each generated shape 4a on which the heating element 2 part, the second lead 3, and the electrode trading part 6 are printed. The ceramic body 4 having a substantially rectangular parallelepiped shape is mounted by hot press firing at a temperature of 1780 ° C. for 1 hour or more in a reducing atmosphere after placing another generation shape 4a thereon. Got.
[0044]
The substantially rectangular parallelepiped ceramic body 4 was processed into a cylindrical shape by centerless.
[0045]
Thereafter, the metal layer 7 is deposited in a 3 mm square shape by screen printing so as to be connected to the exposed portion of the electrode lead portion 6 of the ceramic body 4, and the metal layer 7 is heated at 1000 ° C. in a vacuum furnace. Baked.
[0046]
Next, as shown in Table 1 on the metal layer 7, when the radius of curvature of the ceramic body 4 is R1, the radius of curvature of the inner peripheral surface of the metal plate 8 is R2, and the thickness of the metal plate 8 is 0.20 mm , (R1-R2) are set, and the metal plate 8 made of an Fe-Ni-Co alloy, on which a lead fitting 9 made of Ni having a diameter of 0.6 mm is welded, is placed in a vacuum furnace, 900 The connection was made at a temperature of ˜1200 ° C.
[0047]
In addition, as a ceramic heater made of alumina, a heating element made of W is incorporated, an electrode pad made of W in the electrode lead-out portion, a metal layer made of Au—Cu solder with an average thickness of 50 μm, and Fe—Ni—Co with a thickness of 200 μm. A ceramic heater having a metal plate made of an alloy and having (R1-R2) of 0 mm was produced.
[0048]
Using the ceramic heater for evaluation 1 obtained in this way, after a continuous standing durability test that is exposed to a temperature of 600 ° C. for 1000 hours, and a cooling cycle in which the steps of exposure to both temperatures of 40 ° C. and 450 ° C. are one cycle. Was evaluated by the following method for the connection state of each metal plate 8 for taking out the electrodes after the endurance test.
[0049]
First, the resistance value of the ceramic heater 1 before and after the durability test is measured to obtain the maximum value of the resistance change rate, and the periphery of the connection portion of the metal plate 8 for taking out the electrode after the thermal cycle durability test is a penetration test method. Inspection with a microscope was performed to check for cracks.
[0050]
[Table 1]

[0051]
As is apparent from Table 1, Sample Nos. 1, 2, 8, 9, 14, and 15 which are outside the scope of the present invention have a large resistance change rate of 13.3% or more before and after the endurance test, and all are endurance tests. Later, cracks were observed in the ceramic body 4. The conventional example corresponds to sample numbers 1 and 2.
[0052]
On the other hand, all the ceramic heaters 1 of the present invention had a resistance change rate as small as 6.0% or less, and no cracks were generated in the ceramic body 4. When the resistance change rate is 6.0% or less, cracks after durability evaluation did not occur, and the difference between the radius R1 of the ceramic body 4 and the radius of curvature R2 of the inner peripheral surface of the metal plate 8 (R1-R2) However, if it is within the range of the present invention, concentration of stress was avoided, and as a result, it was confirmed that the connection strength of the metal plate 8 for taking out the electrode was greatly improved.
[0053]
The ceramic heater 1 of the present invention is not limited to the above embodiment, and the metal layer 7 and the metal plate 8 may have any shape as long as they do not depart from the gist of the present invention. The cross-sectional shape of the body 4 can be variously changed according to the application, and a plurality of heating elements 2 are arranged in parallel to form a multilayer structure, and the heating elements 2 are connected in series or in parallel. Even if applied to the above, the same effect can be obtained.
[0054]
【The invention's effect】
As described above, in the ceramic heater of the present invention, the radius of curvature of the ceramic body at the electrode extraction portion is R1 (mm ), the radius of curvature of the inner peripheral surface of the metal plate is R2 (mm ), and the average thickness of the metal layer is t ( mm), −0.1 ≦ (R1−R2) <t 3 , and the average thickness of the metal layer is 30 to 150 μm . As a result, even if the temperature is rapidly increased from near room temperature to high temperature over a long period of time, or even if the heat is generated under high temperature and operated continuously for a long time in a saturated state, the electrode extraction metal connected with the lead wire A ceramic heater excellent in durability with excellent temperature rise characteristics and excellent thermal shock resistance and high-temperature stability can be obtained in which the joint with the plate has the strength to withstand repeated heating and cooling over a long period of time.
[0055]
In addition, if the metal layer is made of a brazing material mainly composed of an Au-Cu alloy, an Ag-Cu alloy, or an Au-Ni alloy, a ceramic heater having excellent durability against the heat cycle during use is obtained. Can do.
[0056]
And the joint strength of the said metal layer with respect to a ceramic body can further be improved because the said metal layer contains vanadium (V) or titanium (Ti) as an active metal.
[0057]
Further, by setting the thickness of the metal layer formed between the peripheral portion of the metal plate and the ceramic base to 30 to 150 μm, stress due to the difference in thermal expansion between the metal layer and the ceramic base is reduced, and durability is further increased. Can be improved.
[Brief description of the drawings]
FIG. 1A is a perspective view of a ceramic heater according to the present invention, and FIG. 1B is a sectional view taken along line XX.
FIG. 2 is a diagram for explaining a manufacturing process of a ceramic body in the ceramic heater of the present invention.
FIG. 3 is a cross-sectional view of a main part of the ceramic heater of the present invention.
[Explanation of symbols]
1: Ceramic heater 2: Heat generating part 3: Second lead part 4: Ceramic body 5: Lead part 6: Electrode lead part 7: Metal layer 8: Metal plate 9: Lead metal fitting

Claims (4)

A cylindrical or cylindrical ceramic body, are embedded in the ceramic body, a heating unit made of an inorganic conductive material which generates heat by energization, and the electrode extraction portion which is electrically connected to the heat generating unit, to the electrode extraction portion A ceramic heater comprising: a metal layer electrically connected; a curved metal plate electrically connected to the electrode lead-out portion through the metal layer ; and a lead fitting connected to the metal plate in,
When the radius of curvature of the ceramic body at the electrode extraction portion is R1 (mm ), the radius of curvature of the inner peripheral surface of the metal plate is R2 (mm ), and the average thickness of the metal layer is t (mm), −0. 1 ≦ (R1-R2) <t 3 , and an average thickness of the metal layer is 30 to 150 μm . The ceramic heater according to claim 1, wherein the metal layer is made of a brazing material mainly composed of an Au—Cu alloy, an Ag—Cu alloy, or an Au—Ni alloy. The ceramic heater according to claim 1, wherein the metal layer contains vanadium (V) or titanium (Ti) as an active metal. The ceramic heater according to claim 1, wherein the thickness of the metal layer formed between the peripheral portion and the ceramic body of the metal plate is 30 to 150 [mu] m.

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