The application of lightweight materials for new crankcase
concepts implies comprehensive design considerations to achieve
weight reductions as close as possible to the potential of the
selected material. A specific approach for inline and V-engine
crankcase concepts is discussed in detail. Engine weight reduction
can also be achieved through "Downsizing." Modern
technologies applied to existing engine concepts increase the
power-weight ratio, the engine''s capability and therefore
its marketing value. The use of lightweight materials for diesel
and gasoline engines within one engine family allows a combined
production and a less costly machining.
Aluminum and magnesium alloys are, due to their high relative
strength (tensional strength and e-modulus divided by their
material densities), suitable for weight-reduced components which
need to be designed for a specific target strength. However, the
low absolute values of tensional strength and e-modulus must be
taken into account by geometric measures to ensure the high
structural stiffness required for modern crankcases. One example
for an adapted design concept is the AVL-patented trussing concept
which employs stiff hollow structures as oil-retaining channels in
the stressed outer walls of the crankcase.
Different design concepts were investigated to ensure a stiff
integration of the main bearings in the crankcase structure. An FE
analysis was conducted on a deep-skirt concept with standard
bearing caps and alternatively with a partly cast-in crack concept
and on a bed-plate concept with thick main bearing shells and
optionally with reinforcing cast-in structures. The analysis takes
static, dynamic and thermal loads into account and results in the
peak firing pressure limits of each concept. The limits in
combination with other relevant parameters are used to define the
best-suited lightweight design concept for the specific structural
requirements of each engine type.
AVL''s new lightweight design strategies allow a
significant reduction of engine mass compared to conventional
concepts and represent an important contribution to reduce the
overall vehicle weight.