Multistep transmission of a layshaft type

A multi-speed transmission (1), of countershaft design for a double clutch transmission, having a main countershaft (9) and a hollow countershaft (12) arranged concentrically thereto, and having two load-shift elements (2, 3), in which a first half of the load-shift elements (2, 3) is in active connection with a drive unit and a second half of the load-shift elements (2,3) is connected to a gearbox input shaft (5, 6), respectively, and in which the gearbox input shafts (5, 6);

• the countershafts (9, 12) are mounted in a housing (16) and are actively connected to gear wheels (7, 8, 9B to 9E, 10, 11, 12A, 13A to 13E), which respectively intermesh in pairs as gear wheel pairs (ZP1 to ZP7) and can be either connected or disconnected in order to reduce an overall gear ratio of a power flow, the main countershaft (9) is mounted directly on the housing (16) via a first bearing mechanism (15) in an area of a first end and in a hollow countershaft (12) via a second bearing mechanism (17) and a third bearing mechanism (18) in an area of a second end, while the hollow countershaft (12) is mounted directly in the housing (16) via a fourth bearing mechanism (19) in an area end that faces toward an end of the main countershaft (12) that is mounted in the hollow countershaft (9).

The multi-speed transmission according to 13, wherein the first bearing mechanism (15) and the fourth bearing mechanism (19) are fixed bearings and the second bearing mechanism (17) and the third bearing mechanism (18) are floating bearings.

The multi-speed transmission according to 13, wherein the first bearing mechanism (15) is a fixed bearing and the second bearing mechanism (17), the third bearing mechanism (18), and the fourth bearing mechanism (19) are all floating bearings.

The multi-speed transmission according to 15, wherein the hollow countershaft (12) is additionally supported in an axial direction on the main countershaft (9) via two thrust bearing mechanisms (20, 21).

The multi-speed transmission according to 15, wherein the hollow countershaft is additionally supported in an axial direction on the housing via two thrust bearing mechanisms.

The multi-speed transmission according to 13, wherein the first bearing mechanism (15), the second bearing mechanism (17), and the fourth bearing mechanism (19) are respectively configured as a bearing that support loads that act in a radial direction and in a defined axial direction.

The multi-speed transmission according to 18, wherein the first bearing mechanism (15) is configured so that axial forces that act in a direction of an end of the main countershaft (9) that is directly mounted on the housing (16) can be supported in the housing (16) via the first bearing mechanism (15).

The multi-speed transmission according to 18, wherein the fourth bearing mechanism (19) is configured so that axial forces acting in a direction of an end of the main countershaft (9) mounted in the hollow countershaft (12) can be supported in the housing (16) via the fourth bearing mechanism (19).