Engineers from Tula State University have patented a planetary gearbox design that provides ten forward gears and four reverse gears. Compared to the predecessor described in the patent, the number of gears increased from eight to fourteen — by 75%. The development is proposed for use in transmissions of passenger cars and trucks, buses, tractors, and other self-propelled equipment.
The design is based on a single planetary mechanism with short and long planet gears — toothed wheels that rotate on a carrier and interact with central gears.
Three friction clutches and five brakes are responsible for selecting the gear ratio. By changing the combinations of engaged elements, the gearbox transmits rotation from the input shaft to the output shaft with different gear ratios.
As a prototype, the developers used an earlier planetary gearbox designed for six forward gears and two reverse gears. The new version adds additional gears and two brakes. This allowed increasing the number of available modes without resorting to several separate planetary mechanisms.
The developers associate the increase in the number of gears with the ability to more accurately select the gear ratio for the load. This is relevant for machines that have to operate both on and off roads. The patent specifically mentions tractors, quarry dump trucks, and off-road vehicles: for them, gears with a high gear ratio, allowing for traction modes, may be useful.
However, fourteen gears is a calculated result of the kinematic scheme, not a confirmed characteristic of a production gearbox. The patent contains no data on the creation of a physical prototype, tests, efficiency, permissible torque, unit mass, or its service life. The practical advantages of the design are yet to be evaluated in relation to a specific machine.