Strain Analysis of Belt Element-Pulley Interaction of an Automobile CVT under Actual Vehicle Speed Condition

In order to improve shift response, durability and transmission efficiency of the CVT system, it is essential to precisely understand the behavior of individual belt elements. Although there have been some previous works measuring the strain or load on belt elements, they have been performed for speed ranges that are far below actual vehicle operation speeds due to limits in measurement techniques. We therefore developed measurement equipment that can be fitted on a CVT belt to enable measurement during actual CVT operation, and obtained the strain on belt elements under transient conditions including acceleration and transmission ratio shifts. The results showed that the strain peaks due to normal force on V faces of elements around the entrance and/or exit of the pulleys. The bending component of the strain fluctuated on the straight section from the secondary pulley to the primary pulley. The results of a finite element method analysis indicated that the compression forces between elements acted on rocking edges unequally, which was determined by the entering the behavior of belt elements on the pulley. These results demonstrate that our unique method makes it possible to obtain an understanding of a phenomenon that was not previously verifiable under the conditions of actual CVT operation.