Method for controlling the limiting of the rotational speed of a combustion engine

摘要

A method controls the rotational speed limiting of an engine in a handheld work apparatus. The crankshaft of the engine drives a worktool via a clutch which engages in dependence on the motor rotational speed. Above an engaging speed of the clutch, a drive connection with the crankshaft is made and below the engaging speed, the drive connection is interrupted. A speed control unit monitors the rotational speed of the engine and includes a rotational speed lock circuit which limits the speed to a limit below the engaging speed. During the start of the engine, the lock circuit is switched on; it is switched off after the engine has been taken into operation when a deactivation signal is present, wherein the deactivation signal is generated when an operation change signal of the work apparatus is detected.

主权项

1. A method for controlling the rotational speed limiting of a combustion engine in a handheld work apparatus, the combustion engine including: a cylinder having a combustion chamber delimited by a piston; the piston being configured to drive a crankshaft via a connecting rod; the crankshaft being configured to drive a worktool via a clutch which engages in dependence on a rotational speed (n) of the combustion engine whereby a drive connection with the crankshaft is made above an engaging rotational speed of the clutch and is interrupted below the engaging speed; a spark plug arranged in the combustion chamber; and, an ignition arrangement configured to drive said spark plug, the ignition arrangement including a rotational speed control unit for the rotational speed (n) of the combustion engine and a rotational speed lock circuit which limits the rotational speed (n) of the combustion engine to a limit rotational speed (nG) below the rotational speed at which the clutch engages which clutch closes in dependence upon the rotational speed (n) of the combustion engine; said method comprising the steps of:
switching on the rotational speed lock circuit when starting the combustion engine; detecting when an operating change signal of said combustion engine is present; generating a deactivation signal when the operating change signal of said combustion engine has been detected; switching off the rotational speed lock circuit only during operation of the combustion engine after the deactivation signal is generated; deriving the operating change signal from the slope of the course of the current rotational speed (n) of said combustion engine as a function of time; and, generating the operating change signal then when there is an increase in rotational speed per unit of time (Δn/Δt) which exceeds a pregiven threshold value.