Analysis and Guidelines for Design of Efficient Power-Split Systems

Gabriela Achtenova; Tomas Budinsky

doi:10.4271/2012-01-0304

The article is divided into two parts. The first part is dedicated to the analysis of mechanical systems by means of the matrix method. The power of the matrix method lies in its easy implementation in computer calculations. In this article we will present the program “SunGear.” This program is devoted to calculation of such Power-split systems and complete analysis of mechanical stepped planetary gearboxes.

The second part of the article will describe the analysis of Power-split systems. In our study we focus on Power-split systems with mechanical CVT. The analysis will be presented by means of two examples:

a)
IVT (no shift elements) with the spread from reverse (ratio equals −2) up to the overdrive with a ratio of 0,6. The power is split between CVT (spread 0,25 up to 4) and mechanical gear set. The differential (planetary or bevel gear device with 2 degrees of freedom) is placed on the input or on the output of the mechanism. A set of 24 different compositions of mechanisms which fulfill the given kinematic constraints was obtained. The comparison of all found solutions is made mainly based on the overall efficiency and magnitude of circulating power. According to the analysis the guidelines for design of an efficient IVT system were developed.
b)
Power-split CVT, where the combination of differential, CVT and mechanical gearset is made mainly to increase the torque capacity in case of usage of mechanical CVT and for increase of efficiency in case of usage of hydrodynamic of hydrostatic CVT. As distinct from the IVT's the Power-split CVT systems can be designed without circulating power. The guidelines of design of Power-split CVT systems without circulating power will be presented.