Reducing vehicle weight is a key task for automotive engineers to meet future
emission, fuel consumption, and performance requirements. Weight reduction of
cylinder head and crankcase can make a decisive contribution to achieving these
objectives, as they are among the heaviest components of a passenger car
powertrain.
Modern passenger car cylinder heads and crankcases have greatly been optimized in
terms of cost and weight in all-aluminum design using the latest conventional
production techniques. However, it is becoming apparent that further significant
weight reduction cannot be expected, as processes such as casting have reached
their limits for further lightweighting due to manufacturing restrictions. Here,
recent developments in the additive manufacturing (AM) of metallic structures is
offering a new degree of freedom.
As part of the government-funded research project LeiMot [Lightweight Engine
(Eng.)] borderline lightweight design potential of a passenger car cylinder head
with the use of automated structural optimization is investigated. A
four-cylinder 2.0 L series production Diesel engine cylinder head is taken as
basis in terms of bolting and gas flow channels.
With the newly gained design freedom by AM, it is demonstrated that a cylinder
head with up to 30% weight reduction in comparison to the reference cylinder
head can be realized through a novel stiffness concept, while fulfilling the
mechanical requirements. The optimized design is initially validated by CAE
methods for the hot operational conditions and worst-case circumstances.
Required material properties are determined through manufactured specimens. A
prototype cylinder head is manufactured using the LPBF (laser powder bed fusion)
process, and hardware durability is validated on a hydro-pulse test bench under
the maximum cylinder pressure of the reference Diesel engine. Subsequently, a
material analysis is performed, and optimization potentials at the component
geometry and printing parameters are investigated to further improve material
properties and hence fatigue performance.
