Aktiebolaget Electrolux

Husqvarna Ab

Bo I Jonsson

Lars Andersson

Göran Dahlberg

Hans Ström

Mats R Svensson

A crankcase scavenged two-stroke internal combustion engine () in which a piston ported air passage is arranged between an air inlet () and the upper part of a number of transfer ducts ('). The air inlet is equipped with a restriction valve (), controlled by at least one engine parameter, for instance the carburetor throttle control. The air inlet extends via at least one connecting duct (&#x2032;) to at least one connecting port (&#x2032;) in the engine's cylinder wall (). The connecting port (&#x2032;) is arranged so that when the piston is in a top dead center configuration, it is connected with flow paths (&#x2032;) embodied in the piston (). The flow paths (&#x2032;) extend to the upper part of a number of transfer ducts (&#x2032;), and the flow paths in the piston are arranged so that the recess (&#x2032;) in the piston that meets the respective transfer duct's port (&#x2032;) in a manner that the air supply is given an essentially equally long period, counted as crank angle or time, in relation to the fuel and air mixture inlet period.

Two-stroke internal combustion engine

Crankcase scavenged two-stroke internal combustion engine (), in which a piston ported air passage is arranged between an air inlet () and the upper part of a number of transfer ducts ('). The air inlet is equipped with a restriction valve (), controlled by at least one engine parameter, for instance the carburettor throttle control. The air inlet extends via at least one connecting duct (&#x2032;) to at least one connecting port (&#x2032;) in the engine's cylinder wall (). The connecting port (&#x2032;) is arranged so that it in connection with piston positions at the top dead center is connected with flow paths (&#x2032;) embodied in the piston (), which extend to the upper part of a number of transfer ducts (&#x2032;), and the flow paths in the piston are so arranged that the recess (&#x2032;) in the piston that meets the respective transfer duct's port (&#x2032;) is so arranged that the air supply is given an essentially equally long or longer period, counted as crank angle or time, in relation to the fuel and air mixture inlet period.

The present invention relates to a chain saw having a two-cycle or two-stroke engine. The present invention also relates to a hand-held power tool such as a chain saw, trimmer, or power cutter having a two-cycle or two-stroke engine. The present invention further relates to a method for the construction of a hand-held power tool such as a chain saw, trimmer, or power cutter having a two-cycle or two-stroke engine. The chain saw, trimmer, or power cutter has a housing for containing a two-cycle engine with a crankcase having scavenging ducts.

CHAIN SAW HAVING A TWO-CYCLE OR TWO-STROKE ENGINE, AND A HAND-HELD POWER TOOL SUCH AS A CHAIN SAW, TRIMMER, OR POWER CUTTER HAVING A TWO-CYCLE OR TWO-STROKE ENGINE, AND A METHOD FOR THE CONSTRUCTION THEREOF

Cylinder

The mold comprises an outer mold part (10) which defines a mold cavity (11). Walls of the outer mold part form the outer surface of the combined engine block and cylinder head. There also are first and second inner mold parts (12, 13) which extend into the mold cavity and are maintained a distance from each other. Each of the first and second inner mold parts have a cylindrical portion (12a, 13a) which, during the casting procedure, forms the cylinder bores in the engine block. The first and second inner mold parts (12, 13) also each have an upper portion (12b, 13b) situated above the cylindrical portion. During the casting procedure the upper portions form portions of a combustion chamber common to the cylinder bores. The mold further includes an third inner mold part (15) which extends through the outer mold part (10) and cooperates with the first and second inner mold parts (12, 13) to form the combustion chamber during the casting procedure.

Method of and mold for casting a combined engine block and cylinder head

The invention relates to a more complex but considerably more emission-poor two-stroke engine than the conventional one. The HC-emissions become zero when completely burned. CO is controlled by the mixture ratio and NO.sub.x becomes very low owing to the built-in EGR. A super charger (20) presses air through the cylinder after the power stroke and dilutes the exhaust gases. A carburettor unit (21) is fed by the super charger and presses an overrich gas mixture into the cylinder at the beginning of the compression stroke. A slide gate (22) controls the connection between the carburettor unit and the cylinder.

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Huskvarna, Sweden

Bo I Jonsson