The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 19, 1998
Filed:
Aug. 29, 1994
Tadayoshi Hayashi, Saitama, JP;
Shinichi Kikuchi, Saitama, JP;
Honda Giken Kogyo Kabushiki Kaisha, Tokyo, JP;
Abstract
A bottom washcoat layer 2 and a top washcoat layer 3 including alumina (Al.sub.2 O.sub.3) are sequentially laminated onto the surface of a monolith carrier 1. Cerium, zirconium and palladium are carried in the bottom washcoat layer 2, and platinum, rhodium, barium and cerium are carried in the top washcoat layer 3. The cerium content in the top washcoat layer 3 is set smaller than that in the bottom washcoat layer 2. This causes the hydrocarbon conversion performance of rhodium and the nitrogen conversion performance of platinum in the top washcoat layer 3 to be balanced properly, while maintaining the hydrocarbon conversion performance of palladium in the bottom washcoat layer, thereby providing an improved exhaust gas purification performance as a whole. In addition, platinum and palladium carried in separate washcoat layers make it possible to inhibit the formation of a platinum-palladium alloy under high temperature conditions to prevent a reduction in exhaust gas purification effect. Further, the heat deterioration of cerium can be inhibited by zirconium, and the alumina surface area can be stabilized by barium, thereby providing an improved durability of the catalyst under high temperature conditions.