Electrically heatable primary catalytic converter

Details Electrically heatable primary catalytic converter Electrically heatable primary catalytic converter

1997-04-04

1999-05-18

Tran, Hien

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Waste gas purifier

422119, 60300, 219541, 219552, 174102P, 174118, F01N3/10

Patent

active

059049030

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to an electrically heatable primary catalytic converter having a metal housing, a catalyst provided in the housing and exposed to an exhaust gas stream, an electrical resistive heater and a connecting lead fed to the heater from the outside through an opening.
Primary catalytic converters of this type are known in a plurality of embodiments and have proved their value. However, it is disadvantageous that the electrical connecting lead is a problem. Thus, plastic-coated connecting leads are unsuited for a moisture- and gas-type connection at high temperatures and in corrosive media, as for example in the exhaust from internal combustion engines. In addition, clamp or screw connections made of conventional conducting materials, such as copper, nickel, or other alloys, cannot be used since they cannot ensure permanently reliable electrical connections because of the oxidation and/or corrosion of the interfaces. In particular, high contact resistances develop. On the one hand, if precious metals or precious metal coatings are used on the conducting materials, high costs result. On the other hand, the temperature in the connecting area of the primary catalytic converter can only be reduced by costly design measures. In view of the limited space for accommodation of such primary catalytic converters, functional disadvantages must be taken into account as a result of such measures, for example limitation of the exhaust gas stream to areas remote from the contacts.


SUMMARY OF THE INVENTION

Hence, the goal of the invention is to provide a permanently reliable electrical connection. This goal is achieved in an electrical primary catalytic converter providing the electrical connecting lead as a metal jacket lead with at least one internal conductor insulated therefrom electrically by a mineral. The metal jacket lead is guided through the opening into the metal housing and connected therewith in a gas-tight manner by welding or soldering along the edge of the opening.
Thus, for example, a metal jacketed lead with at least one internal conductor insulated from it electrically by means of a mineral is used as the electrical connecting lead. The internal conductor is positively connected with the electrical resistance heater, for example, by welding or soldering (Wolfram (tungsten) inert gas (WIG) laser or spot welding). The metal jacketed lead is also fed through an opening in the metal housing and connected with the latter in a gas-tight manner by welding or soldering along the edge of the opening. Thus assurance is provided in simple fashion that firstly the gas tightness of the housing is guaranteed and secondly the connecting lead can be connected reliably in a permanent fashion despite being located in a hot and corrosive environment.
Further improvements on the invention are possible. In particular, a screw or clamp connection to the internal conductor can be welded, soldered, or crimped at the cold end of the metal jacketed lead, namely the lead located outside the housing. In addition, an electrically insulating sheath can be mounted over the connection at the cold end as moisture protection. Preferably, a mineral electrical insulating layer is located between the metal jacket and the internal conductor, said layer consisting for example of MgO and/or Al.sub.2 O.sub.3, quartz, or glass. The internal conductor can be made of an alloy containing copper and/or aluminum and/or iron and/or nickel. Preferably, the aluminum content of the internal conductor is 3-10 weight percent, the iron content is up to 4 weight percent, and the nickel content is up to 5 weight percent. Preferably, both ends of the metal jacketed lead are sealed tightly to protect against loss of insulation as well as the penetration of gases, moisture, and contamination that reduce the insulation resistance. Synthetic resins are particularly suitable for this purpose at the cold end, while ceramic adhesives are used at the hot or cold end, especially adhesives based on aluminum oxide or magnesiu

REFERENCES:
patent: 2334756 (1943-11-01), Eichinger
patent: 4300381 (1981-11-01), Sugiuchi et al.
patent: 4413169 (1983-11-01), Cameron
patent: 4475029 (1984-10-01), Yoshida et al.
patent: 4572940 (1986-02-01), Tijs
patent: 4998341 (1991-03-01), Jones
patent: 5238650 (1993-08-01), Sheller et al.

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