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located in the cylinder. The reciprocating movement of the piston
then is used to drive the vehicle powered by the engine.
It is desirable to vary the point during the reciprocation cycle
of the piston at which the fuel-air mixture is ignited, i.e. a point
between “bottom dead center” and ''top dead center”, to provide
optimum operation of the engine. Thus, as one example the
optimum point of ignition during acceleration can differ from that
for a normal running operation. Because the piston usually is
driven by a rotating crank shaft, the ignition point often is
expressed in terms of degrees of advancement with respect to top
dead center, in other words the position with respect to degrees of
rotation of the rotating crank shaft ahead of the top dead center
position.
Typically, different engine operating speeds, which usually are
expressed in revolutions per minute, will be associated with
different engine conditions. For example, higher engine speeds
often are associated with acceleration. Thus, it has been considered
that the point of ignition during the reciprocation cycle of the
piston should be varied, depending on the engine operating speed
at the particular time, and engine ignition control systems can be
programmed to vary the ignition point depending on the engine
speed.
Other factors can affect the optimum ignition timing. For
example, an engine operating shortly after start-up may require a
different relationship between ignition timing and engine speed
(hereinafter “ignition pattern”) than an engine that has been
operating from some time. Consideration has been given in the
past to a system that allows the user to switch between two
different ignition patterns. This has not been completely
satisfactory in optimizing engine performance.
[21] Under the title “Summary of the Invention” in the disclosure part of the specification, one
finds the replication of the claims. The only paragraph worth reproducing is the following, at
page 2 of the 738 Patent:
Summary of the Invention
The present invention seeks to provide a two-cycle engine that
enjoys improved performance by selecting from a plurality of
relationships between ignition timing and engine speed (ignition