Compressor wheel shaft with recessed portion
A turbocharger assembly includes a compressor wheel with a base surface, a nose surface, a z-plane disposed between the base surface and the nose surface and a bore extending from the base surface to the nose surface and a shaft that includes a first pilot surface disposed in the bore of the compressor wheel at a position between the z-plane and the nose surface, a second pilot surface disposed in the bore of the compressor wheel at a position between the z-plane and the base surface, and a recessed surface disposed between the first pilot surface and the second pilot surface. A nut adjustably disposed on the shaft adjacent to the nose surface can tension the shaft to apply a compressive load between the base surface and the nose surface of the compressor wheel. Various other examples of devices, assemblies, systems, methods, etc., are also disclosed.
1. A turbocharger assembly comprising:
a housing that comprises a turbine side, a compressor side and a bore that extends from the compressor side to the turbine side;
a bearing disposed in the bore of the housing;
a compressor wheel that comprises a base surface, a nose surface, a z-plane disposed between the base surface and the nose surface and a bore extending from the base surface to the nose surface;
a shaft rotatably supported by the bearing in the bore of the housing wherein the shaft comprises
a free end, an opposing turbine wheel end, a shoulder disposed between the free end and the turbine wheel end, wherein the shoulder and the free end define a compressor wheel portion of the shaft that comprises
a first pilot surface disposed in the bore of the compressor wheel at a position between the z-plane and the nose surface and having a first pilot diameter,
a second pilot surface disposed in the bore of the compressor wheel, in part between the z-plane and the base surface and in part between the z-plane and the nose surface of the compressor wheel, and having a second pilot diameter that exceeds the first pilot diameter,
a first recessed surface disposed between the first pilot surface and the second pilot surface, and
a second recessed surface disposed between the second pilot surface and the shoulder and at least in part between the z-plane and the base surface of the compressor wheel;
a back plate disposed between the compressor wheel and the housing, wherein the back plate comprises a back plate bore;
a thrust collar disposed at least in part in the back plate bore and about the shaft between the bearing and the base surface of the compressor wheel, wherein the thrust collar comprises an interior surface that seats the shoulder of the shaft;
a locating pin that locates the bearing in the bore of the housing between the thrust collar and the turbine wheel; and
a nut adjustably disposed on the shaft adjacent to the nose surface of the compressor wheel wherein adjustment of the nut tensions the compressor wheel portion of the shaft to apply a compressive load between the base surface and the nose surface of the compressor wheel.
2. The turbocharger assembly of claim 1 wherein the first pilot comprises an axial length that is less than an axial length of the second pilot.
3. The turbocharger assembly of claim 1 comprising a third recessed surface disposed between the first pilot and the free end of the turbocharger shaft.
4. The turbocharger assembly of claim 3 comprising threads disposed between the third recessed surface and the free end of the turbocharger shaft.
5. The turbocharger assembly of claim 1 wherein the thrust collar and the nut apply the compressive load to the base surface and the nose surface of the compressor wheel.
6. The turbocharger assembly of claim 1 wherein the compressive load applies a tensile load to the shaft.
7. The turbocharger assembly of claim 1 wherein the compressive load applies a tensile load to the shaft between the shoulder of the shaft and a portion of the shaft contacted by the nut.
8. The turbocharger assembly of claim 1 wherein the nut comprises threads and wherein the shaft comprises threads for adjustment of the nut on the shaft.
9. The turbocharger assembly of claim 1 wherein a relationship exists between the applied compressive load and number of turns of the nut.
10. The turbocharger assembly of claim 1 wherein the compressor wheel comprises a linear thermal coefficient of expansion that exceeds a linear thermal coefficient of expansion of the shaft.
11. The turbocharger assembly of claim 1 wherein the compressor wheel comprises aluminum and wherein the shaft comprises steel.
12. The turbocharger assembly of claim 1 wherein the recessed surface disposed between the first pilot surface and the second pilot surface comprises a length to minimize axial tilt of the compressor wheel with respect to the shaft.
13. The turbocharger assembly of claim 12 wherein the length defines a distance between the first pilot surface and the second pilot surface.
14. The turbocharger assembly of claim 1 wherein the second pilot surface comprises a press-fit surface press-fit into the bore of the compressor wheel.
15. The turbocharger assembly of claim 14 wherein the first pilot surface comprises a play surface having a diameter less than a diameter of the bore of the compressor wheel.