According to the state of the art, automatic transmissions, in particular for motor vehicles, comprise planetary gear sets that are shifted by means of friction elements or shifting elements and are typically connected to a start-up element that is subject to a slip effect and is alternatively provided with a lock-up clutch, such as a hydrodynamic torque converter or a fluid coupling.
In general, automatically shiftable vehicle transmissions of planetary design are subject to continuous development and improvement. Thus, such transmissions should require low construction costs, in particular a small number of shifting elements, and, upon a sequential shifting operation, should avoid double gearshifts, i.e. the switching on and off of two shifting elements, such that, during gearshifts in defined gear groups, only one shifting element is changed. In addition, fuel consumption should be reduced with such transmissions; this may occur, on the one hand, by reducing internal transmission losses and, on the other hand, by operating the internal combustion engine at the ideal operating point. In order to run the internal combustion engine at its ideal operating point, it is particularly important to, with a large gear spread, realize small gear steps, which results in the increase in the number of gears.
DE10 2008 064 113 A1 shows a transmission arrangement of an automatic transmission for a motor vehicle comprising ten forward gears, which features a first planetary transmission, which is designed as a simple planetary transmission, and features a first rotating element, which acts as a fixed element, a second rotating element, which provides a reduced rotation speed, and a third rotating element, which is directly connected to an input shaft and acts as an input element. The known transmission also comprises a second simple planetary gear, which features a fourth rotating element, which is directly connected to the second rotating element, a fifth rotating element, which is optionally connected to a transmission housing by inserting a first brake, and a sixth rotating element, which is optionally connected to a transmission housing by inserting a second brake, whereas a first coupling optionally connects at least two rotating elements of the fourth, fifth and sixth rotating elements. Furthermore, a third planetary transmission composed of one planetary transmission with a single pinion and one planetary transmission with a double pinion is provided; this features a seventh rotating element, which is directly connected to the sixth rotating element, an eighth rotating element, which is optionally connected to the input shaft by inserting a second coupling and is optionally connected to the transmission housing by inserting a third brake, a ninth rotating element, which is connected to an output shaft, and a tenth rotating element, which is connected to the fourth rotating element by inserting a third coupling, whereas a fourth coupling is arranged between the seventh rotating element and the eighth rotating element.
For transmissions with a high number of gears, the problem arises that the number of transmission components and thus the construction costs greatly increase, depending on the number of gears. In addition, due to the higher number of transmission components, the internal efficiency of the transmission decreases, such that the optimization of consumption is partially compensated through the high number of gears.