Schaeffler North America

Variable valve train systems

Switching finger follower

Switching finger followers allow switching between two valve lift lengths (valve lift switching) or between full lift and zero lift (valve or cylinder deactivation) in engines with an overhead camshaft. As a result, the thermodynamic efficiency of the engine can be optimised as a function of the engine load.

The switching lever consists of two nested levers, the inner and outer lever. The inner lever (primary lever) is supported on the hydraulic pivot element and the engine valve. The roller in cam contact transmits the small valve lift to the valve. The outer lever (secondary lever) is supported on the inner lever on the valve side by a rotation axis. The outer housing is positioned against the inner housing on the end stop by a lost motion spring. Both housing parts can be linked by means of a coupling mechanism. In the locked condition, the high lift is transmitted via the sliding surfaces on the outer lever to the valve.

Modifications compared to standard valve train:

  • Camshaft with triple cam used
  • Switching valve integrated in oil circuit
  • ECU with data map for controlling switching valve

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