SPROCKET-INTEGRATED HOUSING AND MANUFACTURING METHOD THEREOF

摘要

PURPOSE: A sprocket-integrated housing and a manufacturing method thereof are provided to remove a part-assembling process and cut down the manufacturing cost by integrating a sprocket portion and a housing portion and to secure favorable sliding property and strength by a nitrided layer of the proper thickness. CONSTITUTION: A sprocket-integrated housing(10) used for a variable valve timing mechanism and composed of a sintered body made of a ferrous powder material comprises a sprocket portion(11) being a substantially annular shape and having teeth(11a) on an outer circumference(11b) and a housing portion(12) having a plurality of recesses(13) extending from an inner circumference(12a) arranged in the sprocket portion. 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 is formed by a gas soft nitriding treatment subsequent to the steam treatment.