Search Results

A new CVT system driven by a dry hybrid V-belt having a higher transmitting capacity has been investigated for small cars. This paper reports dynamic FEM analysis of the CVT, simulating transmitting efficiency and dynamic strain acting on the belt running at high speeds. We constructed 3-dimensional models for both belt and pulley assembly. It is demonstrated that pulley rigidity and clearance between pulley shaft and movable pulley significantly affect the power transmitting efficiency of the system. Dimensional change of the belt due to permanent deformation of the rubber material also affects the efficiency at high-speed range at the end of belt life. The dynamic strain obtained by the FEM simulated life of the belt in a bench test successfully.

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.

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 Euler's 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.

An implicit finite element (FE) model was developed to accurately analyze the power transmitting mechanisms of CVT using a dry hybrid V-belt. The numerically analyzed results well agreed with the experimental results. The effects of angle mismatching of pulley groove and flange deflection on the power transmission were examined by using the present approach. The calculated results showed that the blocks were subjected to an over-load due to the pulley flange tilting. The angle mismatching between the pulley groove angle and the block wedge angle strongly affected the power transmission at both steady and transitional states. It was also found that the block tilting in the pulley groove affected the power transmission.

A new discrete model was developed in order to analyze the power transmitting mechanisms of a dry hybrid V-belt CVT not only at steady states but also at transitional states where the speed ratio was changing. Block tilting in the pulley was considered in the advanced numerical model as well as pulley deformation due to pulley thrust. The validity of the present model was well confirmed by comparing the calculated results on transmitting and normal forces with the former experimental results. The calculated results showed that both block tilting and pulley deformation meaningfully affected the pulley thrust ratio between the driving and the driven pulleys.

The purpose of this paper is to analyze the force distribution between pulleys and blocks of a newly developed CVT belt. Three components of the force (transmitting force, normal force and frictional force) were measured directly using a newly devised pulley. The experimental results reveal that the transmitting force distribution on the driving pulley is similar to that on the driven pulley as long as blocks do not slip while the distribution of the normal force component for both pulleys does not resemble each other as well as the distribution of friction force in the radial direction of the pulley. It is also found that no idle arc exists in the contact arc of both driven and driving pulleys even in the case that the transmitting torque is low. The experimental force distribution is compared with a theory based on the discrete spring model taking no consideration of slippage between the pulley and the blocks.