An alternative approach to a camless SI engine with a fully variable valve train is a topology where the intake side of the valve train is equipped with electromagnetic actuators and the exhaust side is driven by a camshaft. This approach is reasonable since the most advantages of a variable valve train, like fuel efficiency, lower emissions and higher torque at low rpm, result from the variable valve timing on the intake side only. Furthermore, the most serious obstacles for electromagnetic actuators arise on the exhaust side. For instance, exhaust valve opening requires a higher actuator force to overcome combustion pressure. This becomes even worse for turbocharged engines. An electromagnetic intake valve train (EIVT) approach with a camshaft on the exhaust side is detached from the severe constraints resulting from the high gas forces on the exhaust side.
In this paper the design of a dedicated intake actuator for electromagnetic valve trains will be presented. After a short introduction, an overview of electromagnetic valve trains (EMVT) will be given. Detached from the obstacles of the exhaust side, a dedicated EIVT actuator will be designed. The magnetic circuit will be optimized by finite element calculations and finally, measurements will be compared with the simulations.
One of the new features of this linear actuator is that its armature can rotate like a normal engine valve, in contrast to common rectangular armature plates. This reduces friction losses and the axisymmetric design reduces manufacturing complexity. This actuator is optimized for high efficiency, design space and to work with the standard 14 V supply.