High pressure rheology and traction characteristics of traction oil

Practical toroidal-type continuously variable transmissions (CVT) is subjec t to extremely severe operating conditions, namely, maximum contact pressur e is very high at 3 GPa or higher, rolling speed exceeds over 30 mis and lu bricant temperature goes up over 120 degrees C. The objective of this resea rch is to grasp the traction characteristics of extremely severe EHL contac t conditions. The phase diagram of a synthetic traction oil to 2 GPa was fi rst made up by high pressure density measurements and others. The bulk modu lus and the shear modulus of a traction oil at quasi-static condition were evaluated using a phase diagram. The results indicated that the bulk modulu s, shear modulus and limiting shear stress of oil are closely related to th e oil molecular packing parameter T-VE-T (T-VE : viscoelastic solid transit ion temperature, T : oil temperature). Next, the EHL traction of a traction oil was measured by the two disc machine and the four disc machine. The re sults indicated that the maximum traction coefficient is closely related to T-VE-T, also. It was verified that the traction characteristics of extreme ly severe conditions were also based on the phase diagram of traction oil.