DE900913C - Spark plug isolator - Google Patents

Description

Spark plug insulator Addendum to additional patent 897 671 The invention relates Insulators such as those used for spark plugs in internal combustion engines and in particular the further design of the isolators according to patent 897 671.

The insulators manufactured according to the main patent consist of a mixture of alumina with z to 150 / ", preferably 2.5 to 50 /, zirconium silicate. According to the invention, silicic acid-containing substances were added to this mixture so that mullite is formed during firing.

The insulators obtained according to the invention therefore exist chemically considered, from A12 03, Si OZ and Zr 02. Those described in more detail below Insulators have a high thermal conductivity, so that the one made from them Spark plug insulator has a longer service life than the previously common porcelain insulators which tend to overheat under harsh operating conditions and then Cause preignition and poor engine operation. The isolators according to the invention also have very good electrical insulation properties; especially at high temperatures, and are very resistant to sudden temperature surges, which is a particularly desirable property for spark plug insulators with their rapid Temperature change and the wide operating temperature range.

The starting materials are preferred for best results Used in conjunction with each other by a substantial proportion of the clay and the greater proportion of silica, preferably in the form of aluminum silicates, such as cyanite, andalusite, sillimannite or mullite can be added. The cyanite is particularly preferred due to its cheap availability in stores. Where plastic Processing methods to be applied will also be clay in terms of its added plastic properties. The zirconia is preferably in the form of Zircon, d. H. introduced as zirconium silicate.

Good insulators are obtained within the following mixing ratios: Alumina 0 to 95 ° / a, zircon 2 to 10%, cyanite 2 to 98 ° / a.

Of course, instead of the above-mentioned compounds the equivalent compounds mentioned above can be used. The specified Mixing numbers were based on the known mineralogical compounds because these are the cheapest for non-plastic processing.

A particularly favorable one in the mixing range given above The composition consists of clay 63.50, ", zircon 2, 50! o, burnt cyanite 349ö! ".

An insulator made from this mixture has particularly high Mechanic solidity; its compressive strength is 2,000 kg / qcm (29 zoo pounds per square inch), and its insensitivity to temperature surges is high.

An addition of up to 10 per cent. Talc, its use per se in similar Mass is known, lowers the firing temperature, and a small addition of, for example up to 5% chromium oxide increases the thermal conductivity, measured by the performance of the spark plug insulator. Mixtures with less than about 25 ° / a clay require one Processing using non-plastic methods. Preferably a non-plastic one Processing method used, although others are known in the ceramic art Methods can be used. Here the raw materials are initially like this finely ground that 10 per cent. or less on a sieve with 12,000 meshes / sq. cm (325 mesh per linear inch), then preferably with resin and lubricant by grinding so long, until a large part of the inorganic material is mixed has a grain fineness between ö and 5 microns. The resulting product will by mixing with water and rubbing through a sieve of the desired mesh size grained. Then it is dried to the required moisture, preformed, pressed to final shape and dried. He is in this state Molded body so firm that it can be handled comfortably. Depending on its composition it is then placed in a suitable kiln at temperatures between 16 "o to 18" o ° fired, whereby the binder disappears and the ceramic material becomes a dense, impermeable structure sintered together.

The moldings can also be used for the production of porcelain insulators common plastic methods. The raw material must be at least Contains 25% or more of clay to give the dough the desired plasticity. Good insulators are obtained from a mixture of the following composition: 70% Tafel corundum (Tabular Corundum), 25e / 0 English Ball Clay, 5% zirconia or zircon.

The ingredients are mixed together in a vacuum kneader, Shaped in a leather-hard condition and at 1770 ° (Orton cone 32) into one fired solid sintered body. The resulting insulator has a high compressive strength and improved tensile strength and heat quality and good electrical resistance at high temperatures, in addition to better resistance to temperature surges.

When using mixtures with a clay content, the moldings can be used also by pressing in rubber molds or using the usual plastic methods Manufacture shapes by kneading or on the extrusion press, with the dry briquettes can optionally be reworked mechanically. It turned out that if Florida kaolin is used instead of plastic clay (English Ball clay) as a molding agent in plastic mixtures, the thermal conductivity of the Isolator can increase.

The clay can be added in various commercial forms, z. B. as after the Baeyer process burnt alumina than burnt at high temperature Clay, which is sold under the name Tabular Corundum, or as molten clay.

The zirconia is preferably added as zircon; one can but they also, if desired, in the form of chemically precipitated and lower Use temperature fired zirconium oxide. The zircon itself is fired in or in the molten state.

Where the alumina is applied in excess of the amount which results in mullite when fired with cyanite, the end product consists of mullite, corundum and zirconium silicate glass. With small amounts or in the absence of unbound Alumina in general, the bodies consist mainly of mullite and zirconium silicate Glass.

Instead of the cyanite expressly mentioned in the claims and the zirconia, the other substances mentioned above can be used which, when fired, produce practically the same end product.

Claims (2)

PATI: NTANSPPLCIIE: 1. Method of manufacturing spark plug insulators according to patent 897 671, which contain Ale 03, Si 02 and Zr 02, characterized in that that base materials with 2 to = o% zirconium, silica bound to alumina, e.g. B. Cyanite, andalusite, sillimanite or mullite, in amounts corresponding to 2 to 98% cyanite is added so that at the firing temperature used from 16 "o to 18" o ° a dense, non-porous, made of clay; Product made up of mullite and zirconium silicate glass arises. 2. The method according to claim 1, characterized in that the basic mass Composed of 63.5 per cent alumina, 2.5 per cent zircon and 24 per cent burnt cyanite will. Cited publications: German Patent No. 664 943; french U.S. Patent No. 527,237; British Patent Nos. 113 959, 422 47'4.