The disclosure relates to a generator system for rail vehicles, for example, a system including a generator with a rotor and a stator, and a journal box unit. The journal box unit may include a bearing for mounting an axle, and a bearing housing. An end cap is arranged on the front face of the axle. The end cap is connected to the axle for co-joint rotation therewith, and the stator is connected to the bearing housing. A friction wheel is arranged on the outer circumferential surface of the end cap, the friction wheel being designed as the rotor of the generator.