US 8,555,831 B2Granted

Method for operating a two-stroke engine

AssigneeAndreas Stihl AG & Co. KG

InventorsAndreas Paa, Michael Harrer

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Abstract

A two-stroke engine (1) has a cylinder (2) defining a combustion chamber (3) delimited by a piston (5). The piston (5) drives a crankshaft (7) which is rotatably journalled in a crankcase (4). The crankcase (4) is connected to the combustion chamber (3) via a transfer channel (17) at at least one position of the piston. The two-stroke engine has an inlet (11) into the crankcase (4) and an outlet (19) from the combustion chamber. There is an arrangement to supply fuel, a control, and a device to determine the crankcase pressure (pKGH). A method to operate the two-stroke engine (1) includes determining the crankcase pressure (pKGH) during every engine cycle. The fluctuation in the crankcase pressure (pKGH) is determined and the fluctuation is compared to a limit value (Δplimit) to determine whether a combustion occurs during every engine cycle. In this way, a determination can be reliably made as to whether the two-stroke engine is running in a four-stroke mode.

Claims10

Dependent claims

A method for operating a two-stroke engine, said two-stroke engine configured as a single cylinder engine having a cylinder defining a combustion chamber;

said combustion chamber being delimited by a piston;
said piston being configured to drive a crankshaft rotatably mounted in a crankcase;
said crankcase being connected to said combustion chamber at least at one position of said piston via a transfer channel;
said two stroke engine having an inlet into said crankcase and an outlet out of said combustion chamber;
said two-stroke engine further having an arrangement configured to supply fuel, a control and a device determining crankcase pressure (pKGH) during engine cycles of said engine;
said method comprising the steps of:
determining said crankcase pressure (pKGH) for each engine cycle;
determining a mean value (pM) of said crankcase pressure (pKGH) from a plurality of values for said crankcase pressure (pKGH) measured during previous engine cycles;
in each one of said engine cycles, determining a fluctuation in said crankcase pressure (pKGH) determined in said one engine cycle as a difference between said determined crankcase pressure (pKGH) and said mean value (pM) of said crankcase pressure (pKGH);
and,
determining whether a combustion occurred during each engine cycle by comparing said difference to a limit value (Δplimit).

8 more elements

Dependencies are inferred from the claim text.