Case Study: Variable Valve Timing (VVT) Sprocket

Process: Conventional powder metallurgy

Density: 7.0 g/cc

Material: FL-4405 prealloyed steel

Secondary Operations: Grinding and sizing

Variable Valve Timing Sprocket
A 2018 Award of Distinction Winner in the Automotive—Engine category

End Use and Function

This award-winning, multifunction component is used in an overhead camshaft inline 3- and 4- cylinder engine. Variants of the engine include naturally aspirating multi-port injection with direct injected and turbocharged versions. These components are currently in use by a U.S. automotive manufacturer.

Fabrication

The fine pitch inverted tooth sprocket teeth are compacted to near net shape. The binder treated premix is crucial to meet the stringent requirements for roundness and perpendicularity of the major inside diameter. The complex shape requires a specially designed upper tooling arrangement to provide for stripping the part off of the upper core.
End-user qualification testing included durability; noise, vibration & harshness (NVH); calibration; and operating parameters were confirmed using firing engine dynamometer experiments. The finished VVT sprocket utilizes more than 98% of the compacted raw material weight.

Results

Significant cost savings was achieved by using conventional powder metallurgy. The application required a combination of properties, durability, complexity of shape and precision made possible by powder metallurgy technology. Competing technologies would have required a two-piece design generating costs of approximately 150% of the current production component.
The sprockets answer the system designer and engine manufacturer’s demands for durability, NVH, and price using PM’s efficient lean alloys, material utilization, and productivity in combination with precision from sizing and highly accurate grinding processes to produce a precision part at a cost that cannot be approached by other manufacturing technologies.