Mahle Has New Shifting Roller System for Commercial Vehicles
Mahle GmbH has released a shifting roller system designed to achieve variable valve timing that is adapted to the different engine operating conditions.
The company says this capability enables functionalities to manage exhaust gas temperature and save fuel or even an engine braking function.
Thanks to an adjustable cam follower, the system can be brought into contact with one of the two cam lobes, which have different profiles. The electrically actuated function has a simple and robust design. Depending on the lift curve of the second cam lobe, the engine can be operated as a permanent brake, for exhaust gas temperature management, or for use with Miller cycles.
Compared with adjustable cam segments on the camshaft, the moving masses in the Shifting Roller System are significantly smaller, according to Mahle. This results in lower actuating forces and reduced installation space. Many of the advantages of the Mahle shifting roller system are due to its electric actuation. Electrically actuated systems work reliably because they are temperature independent, allow selective cylinder activation, and switch between the operating states quickly and cleanly.
Details on the functionalities follow.
Engine brake: When used as an engine brake, the Mahle Shifting Roller System achieves a braking effect close to the retarder, even at low speeds, thanks to its two-stroke mode. It also offers a performance advantage in comparison with hydraulically actuated systems. The braking effect of the Mahle system is at approximately the same level as the engine output. Furthermore, no additional components or systems are required for the engine brake. As the cylinders can be activated individually, the engine brake can be actuated gradually and adapted to the current brake power requirements.
Exhaust gas temperature management: Opening the exhaust valves sooner allows the exhaust gas temperature to be increased while keeping fuel consumption low. Exhaust gas with a higher enthalpy allows earlier SCR catalyst light-off or regeneration of the particulate filter under partial-load operation.
Miller/Atkinson cycle: Closing the intake valves earlier or later allows the effective compression ratio to be reduced, thereby lowering the combustion temperature and pressure. Part of the compression work is thus transferred to the turbocharger.
For more information, visit www.mahle.com.