To obtain a traction drive fluid improved in power transmission capacity and capacity as a hydraulic control fluid or a wet friction control fluid by using a naphthene-ring-containing ester.
The fluid comprises a naphthene-ring-containing ester represented by the formula (wherein R1, R2, R3, R4, R5, and R6 are each independently hydrogen or a 1-8C alkyl (optionally containing a naphthene ring). It is desirable that the fluid comprises this ester and at least one member selected among mineral oils and synthetic oils having a molecular weight of 150-800. Further, it is desirable that the fluid contains a viscosity improver. A particularly desirable example of the viscosity improver is an ethylene/α-olefin copolymer having a number-average molecular weight of above 800 to 150,000 or a product of hydrogenation thereof. Further, it is desirable that the fluid contains an ashless dispersant and a phosphorus additive.
KONO JUNYA
SHIRAHAMA SHINICHI
OKAWA TETSUO
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