JP3685623B2 - Ceramic heater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rod-shaped ceramic heater in which a base material on which a heating resistor is interposed is wound around a soot tube. The ceramic heater of the present invention is used as a heat source for automobile oxygen sensors, a glow plug for internal combustion engines, a heat source for petroleum vaporizers such as a petroleum fan heater, or a ceramic heater for semiconductor heating.
[0002]
[Prior art]
Ceramic heaters generally have a melting point such as platinum, molybdenum, tungsten, etc. on the surface of a green sheet of desired shape (fired to become a ceramic substrate) such as a flat plate or cylinder obtained by pressure molding, extrusion molding, etc. It is manufactured by thickly printing a paste containing a high metal to form a heating resistor pattern and firing these together. A typical example is a ceramic heater obtained by integrally firing using alumina as the main component constituting the ceramic substrate and tungsten as the refractory metal. Since this ceramic heater is stable at high temperatures, it has been often used for applications exposed to high temperatures, such as automotive oxygen sensors or glow plugs.
In addition, since the heating resistor is oxidized and deteriorated by oxygen in the air when it is used while exposed to the outside air, the structure does not come into contact with the outside air by a method such as sandwiching between two ceramic substrates. Is often taken. For this reason, it is necessary to provide a conduction path from the terminal portion provided on the surface of the base material to the heating resistor inside the ceramic heater by some means such as providing a through hole with conductivity inside the ceramic base material. is there.
And a heater terminal is connected to a terminal part, and it can be made to heat without making a heating resistor contact with outside air by supplying electric power.
[0003]
[Problems to be solved by the invention]
However, when a grease sheet or the like on which the heating resistor pattern is formed is wound around a cylindrical soot tube, breakage such as cracks or cracks is likely to occur from the through hole serving as the conduction path. Further, when a force in a different direction is applied between the heater terminal and the ceramic heater, the ceramic base material tends to cause stress such as cracks or breakage due to stress concentration on the conduction path. In particular, as shown in FIG. 5, when a plurality of small-diameter conduction paths 3 and 3 ′ are provided on a straight line in the longitudinal direction of the base material, cracks are easily formed between the conduction paths 3 and 3 ′. The outside air enters between the base materials from such cracks and through holes, and the heating resistor comes into contact with the outside air and is oxidized and deteriorated to cause breakage.
[0004]
The present invention solves the above-described problems, and an object of the present invention is to provide a ceramic heater that prevents the heating resistor from being damaged by preventing the ceramic base material from being damaged from the conduction path. .
[0005]
[Means for Solving the Problems]
The ceramic heater of the first invention includes a soot tube, a first base material wound and joined to the soot tube, a second base material joined to the first base material, the first base material and the second base material. A heat-generating resistor interposed between the materials, a terminal portion provided on the surface of the second base material, and the terminal portion and the terminal portion of the heat-generating resistor are electrically connected to penetrate the second base material. In the ceramic heater comprising a plurality of conduction paths, the conduction paths are not arranged linearly in the longitudinal direction of the second base material.
[0006]
The ceramic heater according to the second aspect of the invention is manufactured so that the conduction path does not exist immediately below the heater terminal joined to the terminal portion.
[0007]
The “first base material” and the “second base material” can use ceramics as a material, and high-temperature high-strength ceramics such as alumina (Al ₂ O ₃ ) and alumina-like ceramics such as mullite or spinel. Can be the main component. In these examples, alumina is preferred. By using such a material, the heating resistor can be protected in a high temperature environment.
[0008]
Moreover, arbitrary methods can be used as a preparation method of each said base material, For example, producing by sintering the green sheet of a predetermined shape can be mentioned.
The shape of the “tubular tube” is arbitrary, and various shapes such as a cylindrical shape and a rod shape can be given. In addition, the cross-sectional shape can be any shape such as a circle, an ellipse, a quadrangle, a hexagon, and the like. This soot tube can also be formed of ceramics mainly composed of high-temperature and high-strength ceramics such as alumina and ceramics similar to alumina such as mullite or spinel.
[0009]
Examples of the material of the “heating resistor” include mainly tungsten and molybdenum. Further, these components can be used by mixing refractory metal components such as platinum and rhodium, or these can be used alone for improving the resistance characteristics. In addition, as long as it does not have a bad influence, the same oxide etc. as each base material may be mixed a little.
[0010]
Examples of the “conduction path” include those in which a conductive film is provided on the inner surface of the through hole or a conductive material is filled.
The “longitudinal direction of the second base material” is a direction parallel to the axial length direction of the soot tube, and is a direction orthogonal to the winding direction of the second base material (circumferential direction of the soot tube). Means. Further, it is also parallel to the heater terminal arrangement direction shown in the second invention.
[0011]
[Action]
In the base material wound around the soot tube, cracks are likely to occur in a direction perpendicular to the normal winding direction. In addition, cracks are likely to occur from grooves or through holes provided in the substrate. For this reason, as shown in 1st invention, generation | occurrence | production of a crack can be prevented by not arranging the said conduction path linearly in the said direction.
In addition, cracks are likely to occur when a force is locally applied to the groove or the through hole. For this reason, as shown in 2nd invention, by not providing the said conductive path directly under a heater terminal, it can prevent that the force by bending etc. of a heater terminal is added to the said conductive path, and generation | occurrence | production of a crack can be prevented. .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, as shown in FIGS. 1-4, the ceramic heater of this invention is demonstrated in detail by an Example.
(1) Structure of ceramic heater As shown in FIG. 1, FIG. 2 and FIG. 4, this ceramic heater comprises a first base material 11 and a second base material 12 made of ceramics mainly composed of alumina, and a heating resistor. 2 is provided.
The first base material 11 is a base material on the side wound around the soot tube 4. Moreover, the 2nd base material 12 is a member used as the outermost periphery (outermost surface) of this ceramic heater, and is provided with terminal part 13a, 13b in an outer peripheral surface. As shown in FIGS. 1 to 3, the terminal portions 13 a and 13 b are portions that are metalized in a square plate shape to have conductivity, and heater terminals 5 a and 5 b for supplying power to the heating resistor 2, Conductive paths 3, 3 'connected to the heating resistor 2 are connected to each other.
[0013]
The heating resistor 2 is formed as shown in FIG. 1, and is made by firing tungsten. And it is comprised by the heat generating part 21 of the front end side, the anode side terminal part 22a and cathode side terminal part 22b of the rear end side, and lead parts 23a and 23b which connect the heat generating part 21 and both terminal parts 22a and 22b. .
[0014]
As shown in FIGS. 1 to 4, the conductive paths 3, 3 ′ are through holes provided with conductivity at two locations on the terminal portions 13 a, 13 b, and the length of the second base material 12. The terminal portion 13a is not arranged linearly with respect to the direction, that is, the direction parallel to the axial length direction of the soot tube 4 and perpendicular to the winding direction of the second base material 12. , 13b are arranged at both ends on the diagonal line. Further, the conduction paths 3 and 3 'are formed by coating the inner surface of the through hole with tungsten to make it conductive. Furthermore, the opening surface of the conduction path 3 is blocked by silver brazing and nickel plating.
The both ends 22a and 22b are connected to the anode side and cathode side terminal portions 13a and 13b through the conduction path 3. Furthermore, heater terminals 5a and 5b connected to a power source (not shown) are joined to both terminal portions 13a and 13b.
[0015]
(2) Manufacturing method of ceramic heater The 1st base material 11 and the 2nd base material 12 which comprise this ceramic heater were produced using two green sheets.
a) Preparation of green sheet 8 parts by weight of polyvinyl butyral and 4 parts by weight of dibutyl phthalate with respect to 100 parts by weight of a blend of alumina powder and a small amount of powder such as Y ₂ O ₃ added as required 70 parts by weight of a total amount of methyl ethyl ketone and toluene were added and mixed with a ball mill to form a slurry. Thereafter, degassing was performed under reduced pressure, and two green sheets having a thickness of 0.3 mm were prepared by a doctor blade method.
[0016]
b) Printing of heating resistor pattern A pre-prepared tungsten paste is screen-printed to a thickness of 25 μm by a thick film printing method on one surface of one green sheet and baked to form the heating resistor 2. The pattern which becomes the heat generation part 21, the terminal part 22a, the terminal part 22b, and the lead parts 23a and 23b by baking was formed. In this pattern, the width of the portion that becomes the heat generating portion 21 is 400 μm, the length in the longitudinal direction of the same portion is 20 mm, and the width of the portion that becomes the lead portions 23a and 23b is 2.5 mm. The total length of the green sheet is 65 mm.
[0017]
c) Fabrication of ceramic heater molded body After that, a heating resistor pattern is printed so as to electrically connect the anode side terminal portion 22a and the anode side terminal portion 13a, and the cathode side terminal portion 22b and the cathode side terminal portion 13b, respectively. A through hole was formed in the green sheet, and a tungsten paste was supplied to the through hole to coat the inner surface. Next, terminal portions 13a and 13b are printed at a predetermined position on the other surface of the green sheet by a thick film printing method using a tungsten paste, and then one surface of another green sheet is formed on one surface of the green sheet. Was crimped. Next, the other surface of the other green sheet was wound around the soot tube 4, and the outer periphery was pressed to obtain a ceramic heater molded body.
[0018]
d) Firing of ceramic heater molded body The ceramic heater molded body obtained as described above was discharged at 250 ° C., and then fired in a hydrogen atmosphere at 1550 ° C. for 1 hour and 30 minutes. A ceramic heater having a diameter of 2.5 mm and a length of 65 mm in which the base material 11, the second base material 12, the heating resistor 2, the anode side and cathode side terminal portions 13 a and 13 b, and the alumina soot tube 4 were integrated was obtained. Conductive paths 3, 3 'were formed by through holes covered with tungsten paste. The resistance of this ceramic heater at room temperature was set to 5.0Ω. In use, both the anode and cathode terminal portions 13a and 13b are plated with nickel, and the heater terminals 5a and 5b are joined to both terminal portions 13a and 13b with a silver brazing material. Further, both the silver solder surface and the heater terminals 5a and 5b are protected by nickel plating.
[0019]
(3) Effect of Ceramic Heater The ceramic heater manufactured in this manner is provided with the conduction paths 3 and 3 ′ on diagonal lines of the terminal portions 13 a and 13 b, and is linear with respect to the longitudinal direction of the second substrate 12. The conduction paths 3 and 3 'are not arranged immediately below the heater terminals 5a and 5b. For this reason, even if a force is applied to the heater terminals 5 a and 5 b and a load is applied to the terminal portions 13 a and 13 b, no stress is transmitted to the conductive paths 3 and 3 ′, and the straight line extends in the longitudinal direction of the second conductive path 12. Since the conductive paths 3 and 3 ′ are spaced apart from each other, the conductive paths 3 and 3 ′ are not easily cracked. Similarly, when the green sheet is wound around the soot tube 4, it is also difficult for cracks to enter from the through hole.
Furthermore, since the conductive paths 3 and 3 'and the periphery thereof are covered with silver brazing and nickel plating, even if cracks occur in the periphery of the conductive paths 3 and 3', the outside air remains in the heater unless the terminal portions 13a and 13b are destroyed. There is no intrusion.
[0020]
In the present invention, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention depending on the purpose and application. That is, the arrangement of the conduction paths 3 and 3 ′ can be arranged not only in the diagonal arrangement shown in the embodiment but also in the circumferential direction of the soot tube. In addition, the shape of the soot tube can be not only the cylindrical shape shown in the embodiment but also a solid body of a columnar shape. Furthermore, the number of conduction paths is not limited to 2, but can be 3 or more.
[0021]
【The invention's effect】
In the ceramic heater of the present invention, the arrangement of a plurality of conduction paths for supplying power to the heating resistor in the heater is arranged so as not to be linear in the longitudinal direction of the base material, and so as not to be directly under the heater terminal. Since it arrange | positioned, damage to the base material from a conduction path can be prevented.
In addition, by covering the conduction path and its surroundings, outside air does not easily enter the heater even if the periphery of the conduction path is damaged.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view for explaining a ceramic heater for a cylindrical soot tube according to the present embodiment.
FIG. 2 is a schematic view showing a state in which the ceramic heater is wound around a cylindrical soot tube and used.
FIG. 3 is a partially enlarged view for explaining the periphery of the terminal portion of the ceramic heater of the present embodiment.
FIG. 4 is a cross-sectional view for explaining the periphery of the terminal portion of the ceramic heater of the present embodiment.
FIG. 5 is a partial enlargement around a terminal portion for explaining a conventional ceramic heater in which a plurality of conduction paths are arranged linearly with respect to the longitudinal direction of the base material and immediately below the heater terminal. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11; 1st base material, 12; 2nd base material, 13a, 13b; Terminal part, 2; Heating resistor, 21; Tip side heat generating part of heating resistor, 22a, 22b; Terminal part, 23a, 23b; Part, 3, 3 '; conduction path, 4; soot pipe, 5a, 5b; heater terminal.

Claims (2)

A soot pipe, a first base material wound around and joined to the soot pipe, a second base material joined to the first base material, and heat generated between the first base material and the second base material A resistor, a terminal portion provided on the surface of the second base material, and a plurality of conduction paths provided through the second base material for electrically connecting the terminal portion and the terminal portion of the heating resistor; A ceramic heater comprising: the conductive path is not arranged linearly in the longitudinal direction of the second base material. The ceramic heater according to claim 1, wherein the conduction path does not exist immediately below the heater terminal joined to the terminal portion.

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