It is well accepted that metal chains in continuously variable transmissions have been proven to be efficient, durable and quiet. However, due to design restrictions application of chain driven CVT's in production today are limited to the 1 to 2 litre engine range.
This paper discusses the development of a CVT chain which offers greater flexibility in design parameters as well as more load capability due to unique design features. To date, known chain systems feature either: 1) load blocks in compression, riding on flexbands, 2) load blocks mounted on chain links in tension or 3) loadpins protruding from chain links in tension. All these systems feature distinct elements (to transmit torque from transmission sheaves (pulleys) to chain links in tension.
Referring to US Patent no. 4,591,353 [Reber] the chain system discussed in this paper no longer requires extra load elements as it features uniquely designed chain links capable of transmitting circumferential, was well as axial loads simultaneously, thereby greatly simplifying chain construction.
Advanced cold forming, blanking and heat treatment methods are needed to allow mass production of chain parts to the required high precision and quality levels. Development of these processes in connection with test procedures and specifications are discussed and highlighted.
Performance data, durability data, together with noise, evaluation and design recommendations will conclude the technical part of the presentation.