Planetary Continuously Adjustable Gear Train with Force Closure of Planet Gear and Central Gear: from Idea to Design
One of the reasons constraining use of a continuously adjustable gear train with compound polysector gear wheels in general and its most perspective version that is a planetary continuously adjustable gear train in particular is its design complexity. For example, a complex design of the mechanism for regulation of transmission gear ratio is specified by the use of involute gearing that requires a presence of backlash and bottom clearances for normal functioning and, therefore, autonomous but synchronous movement of a planet gear, as well as sectors of a central gear. In order to simplify the design of especially this mechanism for continuously adjustable gear train the paper justifies a transition to a backlash-free gearing and during this process either a planet gear or sectors of central gear are forcibly moving for regulation of the transmission ratio without losing contact with the mating element. Contact constancy of interacting elements under load is ensured by their force closure which is meant to overcome an action of gearing forces. The paper describes options for implementation of backlash-free gearing as a result of planet gear and central gear force closure, each variant is characterized by selection of active (con-trolled) and passive (execution of force closure) gear element. In the case of gear transmission with planet pinion coaxial tooth rims it is appropriate to implement a version with involute gearing, passive planet gear and active gear sectors of central gears. In the case of gear transmission with planet pinion opposite tooth rims the most acceptable option is with the cycloidal pin wheel gear, active planet gear and passive gear sectors of central gears. The paper proposes to carry out the force closure for teeth of gear components by means of an elastic element (a spring). A method for determination of parameters for an elastic element has been described depending on a planet gear design and the paper also shows simplification level in the gear design. Keywords: planetary continuously adjustable gear train, backlash-free gearing, shaped spring, simplification of design