The use of anti-friction ball bearings in a unique arrangement does not require the use of lubricating oil from the
internal combustion engine lubricating
system and permits
close coupling of the bearings and a compact
turbocharger. A
turbocharger bearing housing forms a
coolant jacket with an inner bearing engaging portion that has two bearing engagement surfaces engaged with the outer races of two anti-friction bearings whose inner races carry rotating shaft,
turbine and compressor of the
turbocharger. The anti-friction bearings are, preferably, angular contact ball bearings, and the two bearing engagement surfaces of the bearing housing are closely spaced, providing a turbocharger shaft of minimal length and substantially reducing the
thermal expansion of the shaft. The
coolant jacket protects the anti-friction bearings from
exposure to the
extreme heat of the
exhaust gas driven
turbine, notwithstanding their increased proximity due to the shortened turbocharger shaft. In addition, an external motor-generator may be carried by the compact turbocharger, and its motor may be connected to the turbocharger rotor
assembly by a permanent,
solid connector and stay connected throughout the entire operating range of the turbocharger. In such
assembly, the electronic motor-
generator control is mounted on the motor housing and energizes the motor from battery power during the engine acceleration period up to approximately the torque peak speed; thereafter, the control changes to a generator mode when
excess energy is available in the engine
exhaust gas.