Additive Formulation for Reducing Noise in Chain CVTs

Abstract

Chain continuously variable transmissions (chain CVTs) are known as promising technology due to their high torque capacity. However, they generate noise and vibration problems due to their flexible structure. The present study aimed to address these issues by developing a chain CVT fluid with two strategies inspired by the Stribeck curve. The first strategy aimed to reduce the friction coefficient in the boundary lubrication regime, while the second sought to increase the lower limit speed of the fluid film lubrication regime. Ball-on-disc tests were conducted for rolling/sliding contacts lubricated by test lubricants with and without three common additives. Results showed that the combination of oleylamine (as a friction modifier), tricresyl phosphate (as an extreme pressure agent), and calcium sulfonate (as a detergent) effectively met the objectives of both strategies. Evaluations by chain box tests using a practical chain CVT unit revealed that this combination of additives reduced noise generation by 6 dB, demonstrating the successful development of a low-noise chain CVT fluid.