HOW THE SILICONE OIL ACTS IN THE VISCOUS CLUTCH OF YOUR VEHICLE COOLING SYSTEM

September 8, 2021

Viscous clutches developed in Cojali use a viscous fluid, known as silicone oil, which is in charge of transferring the movement of the input shaft to the clutch frame, where the fan is attached.

The silicone oil corresponds to a polydimethylsiloxane fluid (PDMS). It is an organic polymer which contains silicon and presents flow properties that adapt perfectly to the operation of a viscous clutch. The PDMS is colourless and is generally considered inert, non-toxic and not very flammable.

This fluid is synthesised at a lot of viscosity levels, from barely viscous to semi-solid. The PDMS molecules contain very flexible chains, which results in very high levels of viscoelasticity. This means that at high temperatures this fluid acts as a viscous fluid, similar to honey. However, at low temperatures it acts as an elastic solid, similar to rubber.

The power transmitted between the input shaft and the clutch frame depends on the viscosity of the silicone oil and this, at the same time, on the temperature, as we have mentioned before.

Currently, at the clutch assembly line of Cojali there is an automatic dispensing system of silicone oil, which distributes 4 types of silicone oil, depending on their viscosity. This machine is programmed to supply a determined quantity of fluid of each viscosity, depending on the power needs that we want to transmit according to the clutch reference at issue.

During the development of any clutch reference, in Cojali we consider vitally important two fundamental variables: quantity and viscosity of the silicone oil, since both of them determine the clutch power transmission capacity. A proper control of these variables is indispensable for the correct performance of the clutch.

Now that you know the function of the silicone oil in our viscous clutches, do not miss out on them!