Method of restricting rotational speed of an engine of a handheld power tool, control arrangement, and handheld power tool

A control arrangement configured to restrict a rotational speed of a crankshaft of an internal combustion engine of a handheld power tool, wherein the internal combustion engine comprises:

• the crankshaft,
• a cylinder,
• a piston arranged in the cylinder and being connected to the crankshaft,
• an ignition device configured to ignite an air/fuel mixture in the cylinder,
• an air inlet system for conducting air to the cylinder,
• a throttle valve arranged in the air inlet system, and
• an electric actuator arrangement configured to move the throttle valve between an open position and a closed position,
• wherein the throttle valve is configured to restrict flow of air through the air inlet system when positioned in the closed position,
• and wherein the control arrangement is configured to, when the rotational speed of the crankshaft reaches above an upper threshold speed:
• retard an ignition timing of the ignition device from an initial ignition timing to a retarded ignition timing, and
• control the electric actuator arrangement to move the throttle valve towards the closed position.

A handheld power tool comprising an internal combustion engine for powering a tool of the handheld power tool,

• wherein the internal combustion engine comprises:
• the crankshaft,
• a cylinder,
• a piston arranged in the cylinder and being connected to the crankshaft,
• an ignition device configured to ignite an air/fuel mixture in the cylinder,
• an air inlet system for conducting air to the cylinder,
• a throttle valve arranged in the air inlet system, and
• an electric actuator arrangement configured to move the throttle valve between an open position and a closed position,
• wherein the throttle valve is configured to restrict flow of air through the air inlet system when positioned in the closed position,
• and wherein the handheld power tool comprises a control arrangement configured to, when the rotational speed of the crankshaft reaches above an upper threshold speed:
• retard an ignition timing of the ignition device from an initial ignition timing to a retarded ignition timing, and
• control the electric actuator arrangement to move the throttle valve towards the closed position.