Evaluation of DC motors for clamping force mechanism in an electro-mechanical continuously variable transmission

Abstract

Continuously variable transmission (CVT) uses a metal pushing V-belt and pulley system to vary its ratio between the transmission’s input and output. Conventionally, the ratio and the belt’s clamping force are adjusted using a hydraulic system. However, during operation, continuous hydraulic pressure is required to ensure that the belt’s clamping force is always sufficient, resulting in a rather significant losses in the CVT. Thus, an electro-mechanical CVT (EM CVT) is proposed, where the hydraulic system is replaced with a power screw system actuated by a DC motor. As a result, the aforementioned losses can be eliminated since the clamping force can be maintained using the self-lock capability of the power screw system. In this paper, the performance of various DC motors are evaluated, in terms of rated torque, size and weight, so that the most suitable one can be determined for application in the EM CVT. Based on the evaluation process, DC motor type D5BLD450-24A-30S from DMKE Motor Co. is selected since it has a rated torque of 1.4Nm (ranked 2nd highest, the highest at 1.8Nm), relatively small size with a length of 107mm (ranked the smallest) and a weight of 3.2kg (ranked 2nd lowest, the lowest at 3.0kg).