Cred ca amandoua variantele sunt valabile. Si cred ca de asta li se spune cuplaj bimetalic si vascocuplaj. Eu am gasit un alt articol despre cuplaje: "Most cars that have an engine-driven cooling fan have a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator. This type of clutch is a special viscous clutch, much like the viscous coupling sometimes found in all-wheel drive cars. The fluid in the clutch gets thicker as it heats up, causing the fan to spin faster to catch up with the engine rotation. When the car is cold, the fluid in the clutch remains cold and the fan spins slowly, allowing the engine to quickly warm up to its proper operating temperature" http://www.howstuffworks.com/clutch.htm (mai in josul paginii) "Rear wheel drive cars with longitudinal engines usually have cooling fans driven by the engine. The fan is not always needed and it takes horsepower from the engine to turn. These fans have a thermostatically controlled viscous fan clutch. As the fluid in the fan clutch gets hot, it gets thicker making the fan turn faster. The fan clutch is located in the air stream and reacts to the temperature of the air. It also helps the engine reach operating temperature by not engaging until it's needed." http://autorepair.about.com/cs/coolingsyst...aa081801a_2.htm Cred ca pe langa acel bimetal influentat de fluxul de aer, si uleiul se dilata la temperatura ridicata care o primeste prin intermediul axului. Nu cred ca se poate dilata un ulei la temperatura care ii vine dinspre radiator. E la fel ca si materia organica din termostat care la o anumita temperatura, 83 de grade si mai mult, deschide termostatul. Cred ca acel bimetal deschide rezervorul, iar uleiul este dilatat de caldura venita de la ax. Cand temperatura scade, bimetalul inchide, uleiul revine in fatza unde e racit cu ajutorul profilului cu fante. Dar vascozitatea uleiului face ca ventilatorul sa mearga mai greu, nu doar ca bimetalul da drumul la ulei. Daca uleiul nu ar primi caldura de la ax, nu ar avea nici un rezultat.