Actuator for an automotive steering system

A final control element for superimposed steering engagement in a vehicle steering system, having a superposition gear (12) which has two input shafts (13, 14) and one output shaft (15) and in which the transmission ratio between a change in the rotational angle at the first input shaft (13) and the change in the rotational angle at the output shaft, coaxial with the first input shaft (13), is variable by means of an electric motor (20), coupled to the second input shaft (14), as a function of predetermined parameters, such as the rotary speed of the first input shaft (13), characterized in that the superposition gear (12) has a two-stage, modified planetary gear (25), with a planet carrier (30), at least one and preferably at least three stepped planets (31), wherein the stepped planet comprises two axially aligned planet wheels (311, 312) connected to one another in a manner fixed against relative rotation and is held rotatably on the planet carrier (30), and with two sun wheels (32, 33);

• that the one planet wheel (311) of the at least one stepped planet (31) meshes with the one sun wheel (32), and the other planet wheel (312) of the stepped planet (31) meshes with the other sun wheel (33);
• that the first input shaft (13) is connected to one sun wheel (32), and the output shaft (15) is connected to the other sun wheel (33), in each case in a manner fixed against relative rotation;
• and that the planet carrier (30) is drivable via the first input shaft (14).