NTN Corporation developed seal rings for automotive transmissions that deliver low torque, low wear and fewer oil leaks by optimising the plastic composite material composition, as well as incorporating a specially shaped lubrication groove on the surface of the seal rings.
Automatic transmissions (ATs) and continuously variable transmissions (CVTs) use four to ten plastic seal rings with an outer diameter of 15mm to 60mm. Seal rings are installed between the shaft and housing that move in relative motion within the oil hydraulic circuits of transmissions, and slide together so that oil remains sealed in.
The newly developed low-torque seal ring uses polyether ether ketone (PEEK) plastic featuring special filler, and incorporates a V-shaped lubrication groove formed on the surface of the seal ring during injection moulding. This V-shaped groove has been given an optimal design that reduces the contact area between the shaft groove surfaces incorporated with the seal rings, while maintaining its oil leak characteristics. Improvements have also been made to the oil feed performance on the sliding surface to increase lubrication conditions. These developments have led to a 60% reduction in shaft rotation torque compared to conventional products, as well as improve the amount of wear by up to 1/10.