A New High-Performance Four-Stroke Engine for All-Position Use in Hand-Held Power Tools 2004-32-0075
This paper reviews the current and new mini-four-stroke engine technologies that are suitable to be implemented in light-weight outdoor power equipment. A new mixture lubrication setup has been developed for a very compact mini-four-stroke engine.
Special emphasis is laid on the design of the combustion chamber and the valve train. The paper derives how to systematically translate the user demands of a light weight engine to the new mini-four-stroke engine. The new STIHL 4-MIX-engine features an integral one-component cylinder including the cylinder head, two valves and a very simple drive train consisting of a plastic cam including a decompression mechanism. The valve train stands speeds in excess of 12000 rpm and it is also lubricated by the new mixture lubrication setup. The piston is used as an oil-mist pump. The engine has an output of 1.0 kW out of 31.4 cm3. Pressure indication work is used in order to optimize the combustion process.
The development effort and process of this new mini-four-stroke technology are very important and to a certain extent pioneering for the use of mini-four-stroke engines in all-position hand-held outdoor power equipment.