Exhaust gas turbocharger for an internal combustion engine and method of operating an exhaust gas turbocharger

[0013] In an exhaust gas turbocharger for an internal combustion engine comprising a compressor and a turbine interconnected by a shaft in a rotationally fixed manner, and an electric machine which can be connected to the exhaust gas turbocharger via a clutch, the exhaust gas turbocharger can be driven at least temporarily by a disk-shaped flywheel rotatably supported on the shaft and being operable selectively by the turbine and by an electro-dynamic structure for improving the response behavior of the exhaust gas turbocharger.

[0014] In this way, the power requirement for accelerating the exhaust gas turbocharger does not have to be met by an electric machine since the energy necessary to accelerate the exhaust gas turbocharger is transmitted to the exhaust gas turbocharger with a high power density by the rotational energy of the flywheel. Where necessary, the connection between the flywheel and the exhaust gas turbocharger is established or eliminated by means of the clutch. Furthermore, the flywheel can be driven by an electric machine. The electric machine compensates for the frictional losses occurring at the flywheel. Where necessary, it can accelerate the flywheel or generate energy. The power demand which is incurred for compensating the frictional losses or for accelerating the flywheel is low so that the load on the onboard power system is negligible. The clutch is composed of a disk which is connected in a rotationally fixed manner to a shaft of the exhaust gas turbocharger, a pole structure, a yoke and a coil, an air gap preventing friction between the disk connected to the exhaust gas turbocharger and the pole structure.

[0015] In a particular embodiment, the flywheel comprises the pole structure for increasing the effective flywheel. In addition, the pole structure is part of the clutch via which the exhaust gas turbocharger can be coupled to the flywheel or the electric machine.

When there is a sudden increase in the load and / or rotational speed of the internal combustion engine, the exhaust gas turbocharger reacts in a delayed manner because of its mass inertia.

If the exhaust gas turbocharger is configured for the rated power point of the internal combustion engine, it is generally too large for rapid response in the lower and intermediate load and rotational speed ranges and, because of its mass inertia, provides results in an unsatisfactory operating behavior of the internal combustion engine in terms of engine torque, agility and consumption.

With such a high power consumption, current motor vehicle onboard power systems are at their power limit.

The electric machine's rotor which is connected to the exhaust gas turbocharger substantially reduces the dynamics of the exhaust gas turbocharger in the unsupported operating range owing to the mass inertia of its rotor.