Abstract: A turbocharger includes a compressor wheel and shaft assembly in which a threaded connection is provided between the shaft and the compressor wheel. A pair of pilot surfaces on the shaft and on the compressor wheel are located on either end of the threaded sections of the shaft and compressor wheel, and are displaced radially from the threads. Accordingly, the piloting functions which assure concentricity between the shaft and compressor wheel are kept entirely separate from the attachment function provided by the threads, thereby permitting the concentricity between the compressor wheel and shaft to be held to tighter tolerances than would be possible if the threads also performed a piloting function.

Abstract: An improved compressor wheel assembly for a turbocharger or the like includes a centrifugal compressor wheel having a boreless hub to substantially improve wheel fatigue life. The compressor wheel is formed as by casting to include an integral and internally threaded mounting sleeve extending coaxially from the boreless hub. In the assembly, the mounting sleeve extends through an opening in a compressor backplate for threaded connection to a turbocharger shaft, with a thrust collar spacer being interposed between axially facing shoulders defined respectively on the mounting sleeve and shaft to ensure accurate axial positioning of the components. An annular seal flange on the thrust collar spacer extends axially into the backplate opening in generally concentric spaced relation about the mounting sleeve. This seal flange is adapted to carry one or more seal rings for engaging the backplate, thereby sealing the passage of the mounting sleeve and shaft through the backplate opening.