Integrated drive sprocket and gear for balance shaft
View Patent ↗An idler shaft assembly for an internal combustion engine provides significant cost savings eliminates processing and assembly steps, and provides accurate orientation of components. The idler shaft assembly includes a shaft adapted for rotation about a first axis. A one-piece sprocket and gear assembly is received on the shaft. A sprocket portion of the one-piece assembly has a first diameter that cooperates with an associated drive chain that is driven by the crankshaft, and a gear portion of the one-piece assembly has a second diameter that cooperates with an associated gear of an associated balance shaft.
1. In an internal combustion engine having a crankshaft and an idler shaft assembly operatively associated therewith, the idler shaft assembly including:
a shaft adapted for rotation about a first axis;
a one-piece integrated sprocket and gear received on the shaft, said one-piece integrated sprocket and gear comprising;
a sprocket portion having a first diameter that cooperates with an associated drive chain that is driven by the crankshaft;
a gear portion having a second diameter that cooperates with an associated gear of an associated balance shaft;
wherein said one-piece integrated sprocket and near overall is heat treated by a first heat treatment process, and wherein only one of said sprocket portion and said gear portion is further heat treated by a second heat treatment process that is different than the first heat treatment process so that said sprocket portion has a different hardness relative to said gear portion.
2. The invention of claim 1 wherein the sprocket portion is located axially outward on the shaft relative to the gear portion.
3. The invention of claim 2 wherein the first diameter of the sprocket portion is larger than the second diameter of the gear portion.
4. The invention of claim 1 wherein the first diameter of the sprocket portion is larger than the second diameter of the gear portion.
5. A method of forming a one-piece integrated sprocket and gear, said method comprising:
providing a shaft having a first axis;
removing material from said shaft to define an integrated one-piece sprocket and gear comprising first and second reduced diameter lands, a sprocket located between said first and second lands, and a gear located adjacent said second land at a location spaced from said sprocket, wherein said sprocket and gear have dissimilar diameters;
heat treating both said sprocket and said gear of said one-piece integrated sprocket and gear using a first heat treatment process;
heat treating only one of said sprocket and gear of said one-piece integrated sprocket and gear by a second heat treatment process that is different than the first heat treatment process so that said sprocket has a different hardness as compared to said gear.
6. The method of claim 5 wherein the second heat treatment process comprises induction heat treating the sprocket.
7. The method of claim 6 wherein the first heat treatment process comprises carburizing.
8. The method of claim 7 wherein the first heat treatment process is performed before the second heat treatment process.