Mitsuhiko Takahashi

Study on Noise Generation Mechanism for Dry Hybrid Type CVT - Influence of Block Motions and Surface Roughness of Pulley on Sound Pressure

In order to reveal the mechanism of noise generation from CVT (Continuously Variable Transmissions) using a dry hybrid V-belt, the power spectrum of sound from a two-pulley CVT system and its variation with respect to rotational speed were measured. The experimental results showed that the frequency of the first peak in the power spectrum of the observed sound linearly increased with increasing the rotational speed of the pulley. The sound frequency of the first peak coincides with the frequency derived from the belt block pitch and the belt speed. Then, sound intensity analyses were conducted to identify noise sources of CVT. The experimental results reveal that unpleasant sound whose frequency is high occurs due to the collision or slip between CVT blocks and the pulley groove at the entrance and the exit of V-groove pulleys. Pulley surface roughness strongly affects the noise level. Additionally, the location of noise source varies due to surface roughness of the pulley groove. Movement of blocks in the radial direction at the entrance of the pulley groove is strongly related to the noise.

Improvement of Transmittable Torque of CVT Using Hybrid V-Belt Under Lubricated Condition

The purpose of this study is to show the effective method to increase the transmittable torque for continuously variable transmissions (CVT) using hybrid block V-belts under lubrication. The influence of belt geometry on the maximum transmittable torque of CVT was discussed while four types of belt were used, having different dimensions of either upper or lower arms of H-shaped blocks. The effect of lubrication between the belt and the pulley on the transmittable torque was investigated based on the Stribeck curve in order to examine the change of frictional state of contact surface and the power transmitting efficiency. The micro-grooving technique was also applied to the CVT blocks to obtain the high transmittable torque and stable lubrication. The test results suggested that the maximum transmittable torque was expected at a high belt velocity condition if the positive projection of the tension members exists for CVT even under the lubricating condition. The lubricant state between the belt and the pulley should be divided into three modes based on the Stribeck curve; boundary lubrication mode, mixed lubrication mode and hydrodynamic lubrication mode. Both higher transmittable torque and power transmitting efficiency are achieved if the boundary lubrication mode is kept. The micro-grooving technique applied to the contact surface of the blocks also contributed to increase the maximum transmittable torque for CVT using hybrid V-belts when CVT was operated at high belt velocity.Copyright

Study on New Developed CVT Having Third Pulley, Tensioner Using Dry Hybrid V-Belts - How Does It Transmit Power at Both Steady and Transitional States?

A new three-pulley CVT (Continuously Variable Transmission) with a tensioner has been developed using dry hybrid V-belts. It can transmit higher torque than conventional two-pulley CVT without a tensioner, because the tensioner increases not only a lap angle where power is transmitting but also it can always keep the belt tension optimum. This study shows whether the Eulers power transmitting theory is applicable to the tensioner type CVT to characterize the CVT operation for preliminary design. The tensioner type CVT has also high shifting speed and it does not need large thrusts on both driving and driven pulleys during shifting since the minimum tension for torque transfer is assured in the slack-side string. The FEM analysis revealed the shifting mechanism and showed that the transmitting force distribution in the pulley groove for the newly developed CVT is almost the same as that for the conventional CVT.