Patent ID: 7179341
Filing Date: 2007-02-20
Classification: B22F,C23C,F01L

Abstract:
1. An integrated sprocket and housing which is used in a variable valve timing mechanism, the integrated sprocket and housing comprising: a sprocket portion which is formed in a substantially annular shape, and which has teeth on the outer circumference thereof; and a housing portion which is formed integrally with the sprocket portion as a sintered body made of a ferrous powder material so as to be disposed inside the sprocket portion, and which has recesses extending from an inner circumference of the housing portion, wherein the entire surfaces of the sprocket portion and the housing portion are covered with: a steam oxidized layer, which is formed by a steam treatment; and a nitrided layer which has a thickness in a range from 2 to 5 μm, is thinner than the steam oxidized layer, and is formed by a gas soft nitriding treatment subsequent to the steam treatment.