A Self-Energizing Dual-Phase-Shift Camshaft Timing Pulley 930819
A novel concept from FORD is described which exploits the internal torque fluctuations inherent in the cam-shaft drive train and directs them by way of a mechanical one-way clutch to cause phase change of the camshaft automatically between two locked positions. No external power is necessary for actuation and a light weight trigger is used to initiate the phase change.
The Dual-Phase-Shift (DPS) pulley was designed by INA and developed at FEV. First prototypes are currently being tested on live engines. The key features of the pulley are explained in this paper and test data on the performance of the phase shift is presented. The design is unique in its simplicity and is sufficiently compact to fit inside the dimensions of a conventional timing belt pulley.
The DPS pulley can therefore be installed on current production engines requiring only minor modifications and replacing the normal timing belt pulley. For engines with dual camshafts, by installing one DPS pulley on each camshaft, dual independent phase control can be achieved.
The described concept was designed and tested as part of joint investigations by FORD Powertrain Research and INA into alternative systems for camshaft phasing. Whilst the main activities were concentrated on systems with hydraulic actuation, this smart mechanical system was investigated since it offers 2-step operation with only small engine changes for adaptation.