Experimental Study of cooling of Continuously Variable Transmission (CVT) in Scooter 2014-01-2003

The continuously variable transmission (CVT), which was conceptualized more than 500 years ago, is just now beginning to replace traditional transmissions in some automobiles. It is mostly used in scooter transmission. Engine power is transmitted to wheel through belt drive between two pulleys. The diameter of belt contact with pulley can change continuously and hence provide infinite gear ratios between driver and driven shafts. This technology leads to a smoother ride of vehicle. Heat is generated inside CVT due to friction between drive belt and clutch pulley. Amount of heat generated is even more due to clutch slippage during acceleration and deceleration. This will affect the service life of CVT components such as front movable drive (FMD), clutch pulley, clutch outer, and belt. In scooters generally, air cooling is preferred over liquid cooling. Cooling is achieved by incorporating centrifugal fan inside CVT housing. For better durability/service life, the degree of heat generated at CVT components should be minimal.

The objective of this work is to identify the parameters causing change in temperature of CVT components and to evaluate its surface temperature in accordance with changed parameters. With reference to this, experiments were conducted with requisite design modification inside CVT housing, which enhances cooling effect. Amongst, variables determining air flow rate, are studied and their effect on temperature inside CVT housing is observed experimentally. Keeping the previous variables unaltered, further design modifications related to air flow pattern are done and cumulative effect of all variables is observed.

Experiments were performed on an 110cc scooter engine by following customer driving pattern on chassis dynamometer. Results showed that design modifications intended for better cooling effect, has brought down temperature at CVT components. So, desired cooling effect is observed inside CVT housing imparting better service life of CVT components.