JP3762103B2 - Ceramic heater - Google Patents

Description

【００５３】
尚、本発明のセラミックヒ−タは前記実施例に限定されるものでなく、前記接合パッド及び接合応力緩和材の形状は、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、またセラミック発熱体の断面形状も用途に応じて種々の変更が可能で有り、また発熱抵抗体を平行に複数配設して多層構造とし、各発熱抵抗体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】
叙上の如く、本発明によれば、セラミックスを絶縁部材とし、通電により発熱する無機導電材から成る発熱部を具備したセラミックヒータにおいて、電極取り出し部を接合応力緩和材の端部より０．２ｍｍ以上内部に設けることにより、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−ド線を接続した接合応力緩和材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−タを得ることができる。
【図面の簡単な説明】
【図１】セラミックヒータの参考例を示しており、（Ａ）は全体の側面図、（Ｂ）は電極金具接合部分の断面図、（Ｃ）は電極金具接合部分の平面図である。
【図２】図１（Ｂ）の拡大図である。
【図３】本発明の実施形態を示しており、（Ａ）は電極金具接合部分の平面図、（Ｂ）は電極金具接合部分の断面図である。
【符号の説明】
１：セラミックヒータ
２：メタライズ部
３：金属金具
４：リードピン
５：電極取り出し部
６：引き出し部
７：絶縁部材
８：接合近傍部
９：曲面[0001]
BACKGROUND OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is excellent in thermal shock resistance and high temperature stability, and has excellent temperature rise characteristics and durability. Various sensors such as an ignition or vaporization heater for various combustion equipment such as a petroleum fan heater and an oxygen sensor. Heating heaters for general household electrical appliances such as hot water heaters, soldering irons, etc., as well as measuring equipment, electronic parts, industrial equipment, as well as auxiliary combustion chambers when starting or idling diesel engines, etc. The present invention relates to a high-temperature ceramic heater used in a direct current or alternating current power source applied to a glow plug for an internal combustion engine that rapidly preheats the heat.
[0002]
[Prior art]
Conventionally, various types of sheathed heaters in which a heating resistor made of a refractory metal wire is embedded together with a heat-resistant insulating powder in a cylindrical body made of a heat-resistant metal have been widely used as various heating and ignition heaters.
[0003]
However, when the sheathed heater is used as a glow plug for an internal combustion engine that is used to quickly preheat the auxiliary combustion chamber when starting or idling a diesel engine, rapid temperature rise is difficult, and in addition, wear resistance In addition, there is a disadvantage that it is inferior in durability such as heat resistance and corrosion resistance.
[0004]
Therefore, it has excellent heat transfer efficiency, rapid temperature rise, and excellent durability such as wear resistance, heat resistance, corrosion resistance, etc. A ceramic heating element in which a heating resistor composed of a refractory metal, a compound thereof, and various inorganic conductive materials containing them as a main component is supported, bonded, or embedded in a ceramic sintered body. Has been widely used, and accordingly, has been applied as various other heating and ignition heaters.
[0005]
In general, ceramic heaters are known in which a ceramic refractory metal heating part is provided on the surface or inside of an alumina ceramic, but alumina (Al ₂ O ₃ ) used as an electrical insulating material is a thermal shock. Insulating members of ceramic heating elements are non-oxide ceramics with excellent heat resistance, thermal shock resistance and oxidation resistance, especially excellent heat resistance, high temperature strength and low heat capacity. Silicon nitride ceramics with good electrical insulation are widely used as insulating members for high-temperature ceramic heating elements that can be rapidly heated.
[0006]
A lead member connected to the heat generating portion made of an inorganic conductive material is led out on the side surface of the end portion of the ceramic heating element to form an electrode extraction portion, and nickel (Ni) or the like is formed in the electrode extraction portion as necessary. A metallized metal layer is deposited on the metallized metal, and a lead wire connected to an external power source is brazed and bonded via a bonding pad portion made of the metallized metal layer to form a ceramic heater. Has been.
[0007]
However, since the brazing material used for the brazing requires heat resistance, a brazing material for high temperature such as silver brazing is used, and therefore, the brazing joint is heated at a high temperature. In the cooling process, a residual stress is generated due to a difference in thermal expansion between the ceramic of the insulating member and the metal of the lead wire, and the bonding strength between the ceramic and the lead wire is lowered.
[0008]
Therefore, in order to eliminate such drawbacks, it has been proposed to braze and bond between ceramics and metal using a Ni plate as a bonding stress relaxation material (Japanese Patent Laid-Open No. 7-25675).
[0009]
[Problems to be solved by the invention]
However, applying the technique of pre-Symbol bonding ceramics and a metal by means of a bonding stress relaxation material for bonding leads of the ceramic heater, even as the bonding strength was the same bonded using a brazing material containing a high active metal As with the conventional example, there was a problem in terms of durability.
[0010]
That is, in the durability test in which heating and cooling are repeatedly performed at a temperature of 40 ° C. and 450 ° C. assuming the temperature of the electrode extraction part, although it can withstand short-term tests, it is not suitable for repeated heating and cooling over 500 cycles. The residual stress is generated in the vicinity of the brazed portion of the ceramic heater due to the difference in coefficient of thermal expansion up to 9.4 to 11.8 × 10 ⁻⁶ / ° C. between the ceramic and Ni of the bonding stress relaxation material, Cracks grow due to repeated heating and cooling, resulting in a decrease in bonding strength.As a result, peeling of the bonding stress relieving material, oxidation of the heat generating part from the cracks, and the resistance change of the ceramic heater itself cause durability. There was a problem of deterioration and lack of long-term reliability.
[0011]
OBJECT OF THE INVENTION
The present invention has been made in view of the above-mentioned problems, and the purpose thereof is to have the strength that the joining of the electrode fittings of the ceramic heater can withstand repeated heating and cooling over a long period of time, cracks do not occur, and impact resistance. Heating heaters for ignition and vaporization of various combustion devices with excellent high temperature stability and good temperature rise characteristics, heaters for various sensors and measuring devices, electronic parts, industrial equipment, general household electrical appliances, and more An object of the present invention is to provide a high-temperature ceramic heater suitable for a glow plug for an internal combustion engine.
[0012]
[Means for Solving the Problems]
As a result of investigating the above problems, the present inventors have found that, in the bonding pad portion made of a metal layer containing an active metal that electrically connects the electrode extraction portion and the bonding stress relaxation material, the electrode extraction portion and the bonding stress relaxation material. It has been found that the positional relationship between and has an effect on resistance change and durability. Thus, it has been found that the above problem can be solved by controlling the positions of the electrode lead-out portion and the bonding stress relaxation material. This makes it possible to obtain a ceramic heater having excellent durability with little resistance change.
[0013]
The ceramic heater according to the present invention includes a heating element embedded in ceramics, a part of an electrode take-out portion connected to the heating element is exposed, and a lead wire is bonded to the exposed portion using a brazing material. The material is fixed. This ceramic heater has a plurality of electrode take-out portions, at least one electrode take-out portion is located 0.2 mm or more inside the end portion of the bonding stress relaxation material, and at least one other electrode take-out portion has a bonding stress. Located outside the end of the cushioning material.
[0014]
Good Mashiku is an end portion of the bonding stress relaxation material, chamfer or curved portion is provided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the ceramic heater of the present invention will be described in detail.
[0016]
Figure 1 is a reference diagram shows the ceramic heater formed by joining the electrode fitting by brazing, (A) is an overall view, (B) is a cross-sectional shape of the bonding stress relief member junction, (C) is bonded stress It is the top view which showed the external appearance of the buffer material junction part.
[0017]
In FIG. 1, reference numeral 1 denotes a ceramic heater provided with an exothermic part mainly made of an inorganic conductive material which generates heat when energized in an insulating member 7 made of a ceramic sintered body, 2 is a metallized part, and 3 is a joint stress relaxation material. 4 is a lead pin made of Ni or the like spot welded to the electrode fitting, 5 is an electrode take-out portion made mainly of an inorganic conductive material, 6 is a W lead pin that electrically connects the heat-generating portion and the electrode take-out portion, etc. It is the drawer part which consists of.
[0018]
And as shown in FIG.1 (C), the electrode extraction part 5 is provided inside the electrode metal fitting 3, and the distance G from the edge part of the electrode metal fitting 3 is 0.2 mm or more. Therefore, durability can be improved even if electricity is supplied from the lead pin 4 and heating and cooling are repeated as will be described in detail later.
[0019]
FIG. 2 is a further enlarged view of FIG.
[0020]
In FIG. 2, the joining vicinity portion 8 of the metallized portion 2 with the electrode fitting 3 is in a state of being raised on the end face of the electrode fitting 3. The end portion of the joint surface of the electrode fitting 3 is eluted into the metallized portion 2, and the edge is a curved surface 9.
[0021]
When the electrode fitting 3 is joined by brazing , the metallization rises to the end face of the fitting and the metallization tends to gather, and it is considered that the stress is concentrated. Further, it has been confirmed that the three components of the electrode fitting diffuse during metallization, the metallization composition is changed, and the hardness of the metallization is increased. Therefore, it is considered that the stress of the metallization itself increases and the overall stress is increased.
[0022]
Therefore, if the electrode take-out part 5 and the end of the electrode fitting 3 that is a joining stress relaxation material overlap, a crack is formed in the electrode take-out part 5 having low strength, resulting in a resistance change of the ceramic heater 1 itself and the like. Deteriorated and lacked long-term reliability .
[0023]
Next, the implementation form of the present invention.
[0024]
FIG. 3A is a surface view of a stress relaxation material bonding portion provided with two electrode extraction portions, and FIG. 3B is a sectional view of the same.
[0025]
In FIG. 3, a plurality of electrode extraction portions 5 are provided, one electrode extraction portion 5 b is provided 0.2 mm or more inside the end of the electrode fitting 3 that is a stress relaxation member, and the other electrode extraction portion 5 a It is formed on the outside. In this embodiment, since the electrode extraction part 5a is connected to the metallization part 2, even in long-term heating and cooling (40 → 500 ° C.), the resistance change is small and the reliability of the ceramic heater can be greatly improved. .
[0026]
In the present invention, the inorganic conductive material of the heat generating portion is 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 , TiN or the like. Resistors are preferable, and those having WC or W as the main component are preferable from the viewpoint that the thermal expansion difference from the nitride-based ceramic sintered body of the insulating member and that it is difficult to react with them even at high temperatures. It is.
[0027]
Needless to say, the constituent components of the inorganic conductive material forming the heat generating portion may be added to the nitride ceramic sintered body as the insulating portion to adjust the difference in thermal expansion and reactivity.
[0028]
Further, with respect to the main component of the inorganic conductive material, in order to prevent the crack due to the difference in thermal expansion from the insulating member by controlling its growth and not to increase the resistance, silicon nitride, nitridation as a dispersant One or more of boron, aluminum nitride, or silicon carbide may be contained, and the weight thereof is, for example, 5 to 30 parts by weight of silicon nitride and 1 to 20 parts by weight of boron nitride with respect to 100 parts by weight of the main component. It is desirable that aluminum is 1 to 15 parts by weight and silicon carbide is 3 to 15 parts by weight.
[0029]
On the other hand, the heat generating part constituting the ceramic heater in the present invention may be in the form of a block, a line, or a layer, and the insulating member is bent in a U-shape therebetween, wound in a coil, It can be bent in a zigzag shape to form an arbitrary shape such as a U-shape or a W-shape when the heat generating part is viewed in plan, and can be supported on, bonded to, or buried in an insulating member It can be applied in various shapes such as a laminated structure of two or more layers with an insulator in the various shapes, and a lead portion made of a W material or the like may be electrically connected to both ends thereof.
[0030]
In addition, silicon nitride, silicon carbide, sialon, aluminum nitride, or the like can be applied to the insulating member made of a nitride ceramic sintered body, and ceramics such as alumina can also be used.
[0031]
On the other hand, the electrode fitting 3 joined to the metallized part 2 has a thermal expansion coefficient of 3.0 to 5.4 × 10 ⁻⁶ / ° C., which is approximately 3.0 to 7.5 × 10 ⁻⁶ / ° C. Metal is preferred.
[0032]
In addition, by using a soft metal wire such as a Ni wire connected to the electrode fitting 3 by spot welding or the like, it is possible to reduce a physical load such as vibration during use being directly transmitted to the joint.
[0033]
The electrode fitting 3 is most preferably an Fe-based alloy such as an Fe—Ni—Co alloy or Fe—Ni alloy having a Young's modulus of 14 to 15 × 1000 kg / mm ² from the viewpoint of being easily plastically deformed. From the viewpoint that the stress generated by the thermal expansion difference can be absorbed by plastic deformation of the electrode fitting 3 itself, it is desirable to reduce the thickness to about 0.1 to 0.5 mm. It is more preferable that the corner portion of the metal fitting 3 is chamfered or rounded to avoid stress concentration.
[0034]
Next, as the metallized portion 2 made of a noble metal containing an active metal in the present invention, the total amount of Au and / or Ag and one or more of Ni or Pd or any one of Cu, Co, and Si is included. 90 to 99% by weight, and the remaining 1 to 10% by weight contains one or more active metals of V, Mo, Ti, Zr, Hf, and Mn. You may make it contain with forms, such as a carbide | carbonized_material and a hydride.
[0035]
Further, 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 metallized layer becomes high, and a large residual stress is generated at the time of cooling. Therefore, the content is limited to the above range, and 1 to 5% by weight is most desirable.
[0036]
Further, from the viewpoint of preventing a short circuit due to migration that occurs when used in a DC power source such as an automobile application, the metallized portion 2 is most preferably one containing a precious metal as a main component and an active metal such as V or Ti in Au. desirable.
[0037]
Needless to say, the joining of the electrode fitting 3 and the metallized portion 2 may not be the entire joining as long as the necessary strength is ensured, but in order to avoid the concentration of stress due to the difference in thermal expansion, It is desirable that it does not overlap with any edge of the outer peripheral portion and the outer peripheral portion of the metallization.
[0049]
【Example】
As shown in FIG. 3, two electrode extraction portions 5 are provided, one is provided on the inner side of the stress relaxation material, and one is provided on the outer side, and 3000 cycles are repeated in the atmosphere of 40 ° C. to 500 ° C. The results of the resistance change rate when exposed are shown in Table 1 .
[0050]
From this result, sample No. 1 1-2 5, it resistance change is extremely small was confirmed. On the other hand, the distance between the electrode lead-out portion 5 and the end portion of the stress relaxation material is 0 mm and 0.1 mm . 1 to 10 were found to have a very high resistance change rate.
[0051]
From the above results, in the repetitive cycle of 40 ° C. to 500 ° C., two electrode take-out portions 5 are provided, one is provided 0.2 mm or more inside from the end of the joint stress relaxation material, and one is provided outside. It was confirmed that the reliability of the ceramic heater was greatly improved.
[0052]
[Table 1]

[0053]
The ceramic heater of the present invention is not limited to the above embodiment, and the shape of the bonding pad and the bonding stress relaxation material may be any shape as long as it does not depart from the gist of the present invention. The cross-sectional shape of the heating element can be variously changed according to the application, and a plurality of heating resistors are arranged in parallel to form a multilayer structure, and each heating resistor is 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, according to the present invention, in a ceramic heater having a heat generating portion made of an inorganic conductive material that uses ceramic as an insulating member and generates heat when energized, the electrode lead-out portion is 0.2 mm from the end of the joint stress relaxation material. Even if the temperature is rapidly raised from near room temperature to high temperature for a long time by providing it inside, or even if it is continuously operated for a long time in a saturated state by generating heat at high temperature, the lead wire The joint with the joint stress relaxation material connected to the ceramic heater has the strength to withstand repeated heating and cooling over a long period of time, and has excellent thermal shock resistance, high-temperature stability, and excellent durability. Can be obtained.
[Brief description of the drawings]
[1] shows a reference example of cell Ramikkuhita is a plan view of (A) is a side view of the whole, (B) is a sectional view of the electrode metal joint portion, (C) the electrode metal junction.
FIG. 2 is an enlarged view of FIG.
[Figure 3] shows the implementation form of the present invention, is a cross-sectional view of (A) a plan view of an electrode metal joint portion, (B) electrode metal junction.
[Explanation of symbols]
1: Ceramic heater 2: Metallized part 3: Metal fitting 4: Lead pin 5: Electrode extracting part 6: Leading part 7: Insulating member 8: Bonding vicinity part 9: Curved surface

Claims (2)

In a ceramic heater in which a heating element is embedded in ceramics, a part of an electrode take-out part connected to the heating element is exposed, and a bonding stress relaxation material is bonded to the exposed part using a brazing material.
A plurality of the electrode take-out portions;
At least one electrode extraction portion is positioned 0.2 mm or more inside from the end portion of the bonding stress relaxation material, and at least one other electrode extraction portion is positioned outside the end portion of the bonding stress relaxation material. Ceramic heater characterized by 2. The ceramic heater according to claim 1 , wherein a chamfered portion or a curved surface portion is provided at an end portion of the bonding stress relaxation material.

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