Electromagnetic valve actuator and valve guide having reduced temperature sensitivity

摘要

An internal combustion engine includes an electromagnetic valve actuator having an armature between upper and lower electromagnets with a stem extending through one electromagnet and guided by a bushing with increased clearance about at least a portion of the inner circumference in at least a middle portion of the bushing to reduce oil shear length and associated viscous friction in the actuator. A two-piece intake/exhaust valve guide includes a lower half with a stepped outer diameter cooperating with a counter-bored hole in the cylinder head to provide a positive stop. The upper and lower halves of the valve guide have increased clearance relative to the valve stem around at least a portion of the inner circumference to reduce oil shear length and associated viscous friction. Reducing viscous friction of the actuator and associated valve guide improves system robustness by decreasing the system sensitivity to temperature.