German supplier Schaeffler has revealed that it is about to begin volume production of its electromechanical camshaft phasing units to be installed in a Japanese engine.
The company says using this type of unit instead of the current standard hydraulic systems allow the camshaft to adjust more quickly and accurately to the prevailing engine operating conditions, reducing consumption and harmful emissions while simultaneously increasing comfort during stop/start operation.
Schaeffler says the electromechanics make it possible to phase the camshaft at speeds up to 600 crank angle degrees per second, and that the hydraulic systems operate from two to 10 times more slowly, irrespective of the engine speed and temperature.
The increased dynamics of electromechanical phasing units allow very fast reactions to changes in load, even at low engine speeds, such as when the driver suddenly kicks down on the gas pedal while the engine is overrunning.
Unlike hydraulic systems, the reaction speed to a change in load is not dependent on the oil supply. In some cases, it is no longer necessary to have a larger engine oil pump which has a subsequent benefit in terms of improvements to fuel consumption.
The company also says that stopping and starting the engine is much smoother with electromechanical camshaft phasing units, because it is possible to start the ICE without any noticeable judder. This is because, up to 200rpm, the engine runs with reduced compression as the camshaft can be positioned as required before the engine starts.
During acceleration, valve control times are synchronized with the injection so that there is a soft onset of compression; when compression and ignition are correctly adjusted, the result is smooth engine startup.
The electric motor used also contributes to the phasing accuracy as it serves not only as an actuator but also as a sensor. In addition to the position recognition already in use with hydraulic systems, usually four times per camshaft rotation, in the electrical system, the rotor position is checked continuously by integral sensors and assessed by an electronic control system.
The precise position of the camshaft is therefore always known. Schaeffler has developed the DC motor in-house.
“Overall, we can see a clear trend to highly versatile valve trains,” said Martin Scheidt, senior vice president of R&D engine systems at Schaeffler. “The strict CO? regulations mean that more and more automotive manufacturers are using cylinder deactivation systems.”
October 14, 2015
