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International Journal of Automotive Technology 2003;4(4): 165-172. |
| SPIN LOSS ANALYSIS OF FRICTION DRIVES: SPHERICAL AND SEMI-SPHERICAL CVT |
| J. KIM1, K. H. CHOI2 |
1Seoul National University
2Korea Railroad Research Institute |
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| ABSTRACT |
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This article deals with the spin loss analysis of friction drive CVTs, especially for the cases of S-CVT and SS-CVT. There are two main sources of power loss resulting from slippage in the friction drive CVTs, spin and slip loss. Spin loss, which is also a main design issue in traction drives, results from the elastic contact deformation of rotating bodies having different rotational velocities. The structure and operating principles of the S-CVT and SS-CVT are first reviewed briefly. And to analyze the losses resulting from slippage, we reviewed previous analyses of the friction mechanism. A modified classical friction model is proposed, which describes the friction behavior including Stribeck (i.e., pre-sliding) effect. It is also performed an in-depth study for the velocity fields generated at the contact regions along with a Hertzian analysis of deflection. Hertzian results were employed to construct the geometric parameters and normal pressure distributions of the contact surface with respect to elastic and plastic deformations. With analytic formulations of the relative velocity field, deflection, and friction mechanism of the S-CVT and SS-CVT, quantitative analyses of spin loss for each case are carried out. As a result, explicit models of spin loss were developed. |
| Key Words:
Spin loss, continuously variable transmission, S-CVT, SS-CVT, Friction |
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