Production AVT Development: Lotus and Eaton’s Electrohydraulic Closed-Loop Fully Variable Valve Train System

Authors

J. Turner, S. A. Kenchington, Lotus Engineering, Norwich, UK; D. A. Stretch, Eaton Automotive, Southfield, MI, USA

Year

2004

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 566

Summary

Lotus and Eaton are collaborating to bring a production closed loop control Fully Variable Valve Timing system, known as Active Valve Train (AVT), to market in the 2008-9 timeframe. The system uses electrohydraulic operation, movement of the engine poppet valves being initiated by oil flow into and out of a hydraulic chamber which is controlled by fast acting electrohydraulic servo valves developed by the two companies. This in turn allows infinitely variable timing, duration and lift. The system, which is currently being engineered in prototype form for an OEM, will allow ready application of many advanced engine control strategies, such as throttleless operation, Controlled Auto Ignition (or Homogeneous Charge Compression Ignition), fast start, variable firing order, differential cylinder loading and ultimately air hybridisation. However, to gain acceptance in the marketplace, the two partners understand that productionisation must not come at the expense of high Bill Of Materials cost, and in controlling that requirement, the performance of the system must not be allowed to suffer. This paper relates the present developmental status of the system from a valve control standpoint and describes some of the design features which have been adopted to fulfil the above requirements. An estimate of BOM costs for a typical light duty automotive application is also given.

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