JP2848880B2 - High-temperature heating element, method for manufacturing the same, and method for manufacturing ceramic heating device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature heating element including an aluminum nitride mounting substrate and a heating conductor coated on the substrate.

[Conventional technology]

As is well known, high-temperature heating elements of the above type are widely used in the automotive industry, for example, as a starting aid for smooth start-up of diesel engines, especially for the production of preheating plugs, heating adapters or ceramic heating devices as hot bodies. Used.

A ceramic heating device known from DE 3512483 discloses, for example, MoSi ₂ powder and S
It consists of a sintered element heating element made of a mixture of i ₃ N ₄ powder, an electrically insulating ceramic sintered body, and a current supply device. The heating element in this known heating device consists of a sinter made of a mixture consisting of a mixture of MoSi ₂ powder and Si ₃ N ₄ powder, in this case Si ₃ N
The particle diameter of ₄ powder is larger than that of MoSi ₂ powder.

Furthermore, ceramic heating devices which can be used, for example, as preheating plugs for diesel engines, and in which a sinter made of a mixture of MoSi ₂ and Si ₃ N ₄ is used for the production of ceramic heating bodies, It is known from DE-A-334 27 53.

Further, from German Offenlegungsschrift 3011297, a ceramic body made of silicon nitride, Sialon, aluminum nitride and silicon carbide and a metal body made of tungsten or molybdenum embedded in the ceramic body are disclosed. It is known that the high-temperature heating element to be made has a plate shape or a string shape.

It is also known from DE 33 33 144 A1 that an inlet burner for an internal combustion engine is fitted with a heating device consisting of a tungsten heating resistor embedded in a ceramic material. . This ceramic material is made of, for example, silicon nitride (Si ₃ N ₄ ).

Also, a cylindrical ceramic heating element known from U.S. Pat. No. 4,035,135 includes a heating resistance ceramic material such as aluminum oxide and forsterite, and a molybdenum coating applied over the ceramic material. The heat generating resistor is made of a conductive metal paste such as a manganese paste or a tungsten paste.

From JP-A-54-109536, there is also a ceramic heating device for a glow plug composed of a disk-shaped ceramic plate and a resistor made of molybdenum, tungsten or manganese printed thereon. Are known.

From West German Patent Application Publication No. 3307109,
A device for injecting fuel into a combustion chamber of a diesel engine, which has an injection nozzle and a glowing body which is wetted by a jet of fuel, is known. In this case, the red-hot body is mounted on the end face of the injection nozzle on the combustion chamber side and has a groove surrounded by a heatable wall for passing the fuel jet and partially evaporating. The heating element may be made of ceramic, and the heating element may be formed by a metal coating applied on the surface of the ceramic.

More commonly known are AlN ceramic mounting substrates, which are characterized by high thermal conductivity, high electrical insulation with high temperature resistance, high rigidity, good mechanical properties, and good heat exchange capacity. it can be used connexion printed thick film technology, although the old thick film paste is inserted, which is carried out in the same manner as are known for printing a substrate mounting made Al ₂ O ₃ ceramic .

Disadvantages of these known ceramic heating elements are:
That they cannot withstand extremely high temperatures, that they cannot withstand sufficient thermal shock, that the heating conductor printed on the ceramic mounting board is not sufficiently tight,
And the manufacturing cost is high.

[Configuration of the invention]

On the other hand, the high-temperature heating element according to the present invention has the features of claim 1, and has the advantage that it can be manufactured at low cost because it is based on a relatively inexpensive heating conductor material. It can withstand very high temperatures (about 1400 ° C), molybdenum disilicide adheres much better on aluminum nitride than on silicon nitride, and a uniform temperature distribution ensures good heat transfer And the ability to withstand sufficient thermal shock, and the like.

The manufacture of the high-temperature heating resistor according to the invention is advantageously carried out as follows. That is, a heating conductor made of a molybdenum disilicide paste is printed on a mounting substrate made of aluminum nitride by a thick film technique, and the paste is adapted for adjusting electric resistance and / or improving a coefficient of thermal expansion as necessary. Up to 40% by volume,
The printed mounting substrate is sintered at a temperature of 1600-1800 ° C. under a protective gas and subsequently aged.

The production of the high-temperature heating element according to the invention is further advantageously carried out, for example, as follows. In other words, a heating conductor made of molybdenum disilicide paste is printed on a mounting substrate made of aluminum nitride by thick film technology,
The paste may optionally include a substance for adjusting the electrical resistance and / or for adapting the coefficient of thermal expansion.
It can contain up to 40% by volume, apply another aluminum nitride mounting substrate on top of the printed aluminum nitride mounting substrate, and sinter the mounting substrates stacked in a sanitary manner across the heating conductor.

The aluminum nitride mounting substrate, which can be printed with molybdenum disilicide paste using thick film technology, uses a suitable commercially available aluminum nitride foil, which in addition to aluminum nitride, decomposes at the sintering temperature. It contains a binder that can be evaporated or evaporated. This is the so-called pressed green AlN mounting substrate or sintered mounting substrate.

The thickness of the aluminum nitride mounting substrate may vary, but it is mainly 0.3 to 3 mm, especially 0.5 to 2.0 mm
Is advantageous.

If necessary, relatively small amount of sintering grant agent may for inclusion as additives such as Y ₂ O ₃ in use is aluminum nitride are mounted substrate.

Typical materials that can be added to the molybdenum disilicide for electrical resistance adjustment and / or for tailoring for improved coefficient of thermal expansion include aluminum oxide and aluminum nitride.

〔The invention's effect〕

The high-temperature heating element according to the invention can be used for the production of various types of ceramic heating devices and for various applications. Of particular importance is the automotive industry. Here, for example, in order to smoothly start the diesel engine, this heating element may be installed with a heating element and an inlet burner for manufacturing a preheating plug, a glow plug, a red hot body and the like. This means that the high-temperature heating element according to the invention can be installed in a manner known per se for use in fastening elements and can be connected to a conventional current supply unit.

Particularly advantageous is that the production of the high-temperature heating element according to the invention can be used mechanically many times. Advantageously, the heating element has a width of 3 to 10 mm and a length of 10 to 50 mm.

When mounted in a preheating plug, the heating element according to the invention is implemented in particular as a rotationally symmetric body. The molybdenum disilicide conductor tracks are then printed, for example, on a hot pressed aluminum nitride solid bar or on a foil wound around a solid bar.

In the case of a preheating plug, the diameter of this heating element is 3-6 m
m, the protruding length is 10-30mm, and the rod length is 20-60mm.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a high-temperature heating element according to the invention, which is drawn in a simplified and enlarged manner with emphasis. This high-temperature heating element includes a mounting substrate 1, a heating conductor 2, and connection terminals.
3a and 3b. The mounting substrate 1 is, for example, a commercially available AlN foil having a thickness of 1 mm, on which a heating conductor is printed by a silk screen printing (Natsusen) method, in particular, by using a squeezing device or a tatami brush. 2 is printed together with the connection terminals 3a and 3b. In the case shown, the heating conductor is in the form of a zigzag wave, but may of course have any other shape.

What is used for printing is a molybdenum disilicide paste having the following composition.

Commercially available MoSi ₂ powder 69.8% by weight Rotating oil composed of the following components 30.2% by weight Ethyl cellulose 6.0% by weight α-terpine oil 79.0% by weight Benzyl alcohol 15.0% by weight On the top, the second mounting substrate 4 (which is not printed) is covered with almost the same thickness except for the connection terminals 3a and 3b. The combined substrates are then sintered at a high temperature of 1600 ° C. and a pressure of 5 mbar in a nitrogen atmosphere containing 10% of hydrogen for as long as 2 hours. The mounting substrate 4 functions to prevent oxidation.

However, if the mounting substrate 1 has been sintered together with the printed heating conductor 2 under a protective gas, especially a forming gas, at a temperature of 1600-1800 ° C. and then subjected to an aging process, the mounting substrate 1 It is not necessary to cover 1 with the other mounting substrate 4. This aging process is carried out, for example, by heating the printed and sintered mounting substrate in an oxidizing atmosphere for as long as 2 to 6 hours. By such treatment, the SiO ₂ protective layer is formed, and this layer sufficiently protects the heating conductor even in an oxidizing / reducing atmosphere.

The printed mounting board is the second mounting board 4
In any case, the heating conductor is firmly fixed on the AlN mounting substrate, whether or not it is covered by the AlN.

The connection terminals may be metallized in a conventional manner. For example, the heating conductor can be contacted via a protective gas flammable thick layer paste on a base of copper, nickel, gold, or the like, or by currentless separation from nickel-copper.

2 differs from that of FIG. 1 in that the AlN mounting substrate is made of a flexible AlN green foil 5.
After covering the connection terminals 7a and 7b with the heating conductor 6, a 25 micron thick AlN paste and an organic binder (for example, ethyl cellulose, alpha terpin) are placed on a part of the foil 5 supporting the heating conductor 6. Print a paste layer consisting of oil, benzyl alcohol).

The mounting substrate, shown schematically in FIG. 2a, is then wound into the form shown in FIG. 2b. The wound heating element is then sintered at a temperature in the range of 1600-1800 ° C. for about 2 hours. Then, the connection terminals 7a and 7b are covered with metal.

The rod-shaped preheating plug shown in FIG. 3 consists essentially of a plug casing 8, an aluminum nitride rod 10 and a printed molybdenum disilicide heating conductor 11 consisting of a heating element 9.
And a sheath 12 (terminal) soldered onto the aluminum nitride rod 10 (the aluminum rod 10 is pressed into the plug casing 8 via the sheath 12) and the aluminum It comprises a sheath 13 (terminal) soldered on a bar 10, an insulator 14 for protecting the heating conductor 11 from the terminal, an insulating disk 15, a round nut 16 and a terminal bolt 17.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a heating element according to the present invention mounted on a relatively hard AlN mounting foil, and FIGS. 2a and 2b are second embodiments of a heating element according to the present invention. FIG. 3 is a schematic view showing a state of being mounted on a relatively flexible AlN mounting foil, and FIG. 3 is a sectional view of a rod-shaped preheating plug using a heating element according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Mounting board, 2 ... Heating conductor, 3a, 3b ... Connection terminal, 4 ... Mounting board, 5 ... AlN green foil, 6
... heating conductor, 7a, 7b ... connection terminal, 8 ... plug casing, 9 ... heating element, 10 ... aluminum nitride rod, 11 ... heating conductor, 12 ... sheath, 13 ... sheath, 14
…… Insulator, 15… Insulated disk, 16… Round nut, 17 ……
Terminal bolt

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kurt Schmiet, Germany Dateschingen 4, Schyros Schuttrath 55 (72) Inventor Guyenter Knorr Schuttgart 1, Germany Brahmsweig 33 (56) References JP-A-53-40897 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 3/14 H05B 3/18 F23Q 7/00

Claims (9)

(57) [Claims] 1. A mounting substrate made of aluminum nitride and containing molybdenum disilicide applied on said substrate by thick film technology, and for adjusting electric resistance and / or improving coefficient of thermal expansion as required. In a high-temperature heating element provided with a heating conductor containing such a substance for adaptation, a ratio of the substance is not more than 40% by volume with respect to a thick film paste used for application on a substrate. High-temperature heating element characterized. 2. The high-temperature heating element according to claim 1, wherein the high-temperature heating element has a heating conductor made of a mixture of molybdenum disilicide and aluminum oxide and / or aluminum nitride. 3. A method for manufacturing a high-temperature heating element according to claim 1, wherein a heating conductor made of a molybdenum disilicide paste is printed by a thick film technique on a mounting substrate made of aluminum nitride, and said paste is required. Depending on the electrical resistance adjustment and / or the adaptation for the improvement of the coefficient of thermal expansion, the substance can contain up to 40% by volume, and the printed mounting substrate can be protected at a temperature of 1600-1800 ° C. by a protective gas. A method for producing a high-temperature heating body, characterized by sintering and then aging. 4. The method of claim 3 wherein the sintered material is aged by roasting in an oxidizing atmosphere. 5. The sintered material is treated with H ₂ 5 for about 2 hours.
The method of claim 4 wherein the roasted at a temperature of 1600 to 1800 ° C. in an atmosphere consisting of N ₂ containing 40%. 6. A method for manufacturing a high-temperature heating element according to claim 1, wherein a heating conductor made of molybdenum disilicide paste is printed on a mounting substrate made of aluminum nitride by a thick film technique, and the paste is used as required. Depending on the electrical resistance adjustment and / or the adaptation for the improvement of the coefficient of thermal expansion, it can contain up to 40% by volume of another aluminum nitride mounting on the printed aluminum nitride mounting substrate. A method for manufacturing a heating conductor, characterized by sintering a mounting substrate stacked in a sandwich shape with a substrate coated and a heating conductor interposed therebetween. 7. The method of claim 6, wherein the sintering is performed at a temperature in the range of 1600-1800 ° C. for about 2 hours. 8. The method according to claim 3, wherein a foil or a thin plate is used as the mounting substrate made of aluminum nitride.
The method described in the section. 9. A method for manufacturing a ceramic heating apparatus, comprising using the high-temperature heating element according to claim 1 or 2.