2
مکانیک::
میللنگ
This includes the friction between the piston rings, piston skirt, and cylinder wall; friction in the wrist pin, big end, crankshaft, and camshaft bearings; friction in the valve mechanism; friction in the gears, or pulleys and belts, which drive the camshaft and engine accessories.
Boundary lubrication occurs between engine parts during starting and stopping (bearings, pistons, and rings), and during normal running at the piston ring/ cylinder interface at top and bottom center crank positions, between heavily loaded parts, and between slow moving parts such as valve stems and rocker arms, and crankshaft timing gears and chains.4
This phenomenon occurs in connecting rod and crankshaft bearings where periodic metal-to-metal contact results from sudden breaks in the oil film.
Some of the components of hydrodynamic lubrication friction and turbulent dissipation will be dependent on mean piston speed rather than crankshaft rotational speed N.
For conventional engine geometries, crankshaft rotational speed is usually used to scale the total friction data rather than mean piston speed,5,6 though more detailed models must include both these variables.
واژگان شبکه مترجمین ایران