Directly behind the belt-pulley the oil-filled space for the drive-gears can be seen. It's lubrication requirements, and those of the bearings, are relatively small, thus, no connection with the engine-lubrication is necessary. The drive-gears provide for a contact-free running of the two long rotors. Above that, is the pressure chamber, and behind it, the vacuum chamber. A magnetic clutch can be integrated into the front drive-wheel. Then the charger only runs, when it is needed, not, e.g., during idling and in the partial load range.