A connector for connecting an impeller to a shaft is provided. The connector is formed as a unitary body. The connector has a sleeve portion which is frictionally connected on a radially outer surface of a shaft-side hub extension of the impeller. The connector further has a threaded portion carrying a thread which screws onto a corresponding threaded portion of the shaft, such that the connector provides a rotationally fixed connection between the impeller and the shaft. The hub extension has a central recess, and a part of the connector is inserted into the recess. The frictional connection between the sleeve portion and the radially outer surface of the hub extension transmits, in use, substantially all of the torque between the shaft and the impeller.
1. A connector for connecting an impeller to a shaft, wherein the connector is formed as a unitary body, the connector comprising:
a sleeve portion which is adapted to be frictionally connected on a radially outer surface of a shaft-side hub extension of the impeller, and
a threaded portion carrying a thread which is adapted to screw onto a corresponding threaded portion of the shaft such that the connector provides a rotationally fixed connection between the impeller and the shaft; and
wherein:
the hub extension has a central recess, and a part of the connector is inserted into the recess, a clearance being provided between the part of the connector inserted into the recess and a side surface of the recess such that there is no contact between the connector and any side surface of the recess; and
the frictional connection between the sleeve portion and the radially outer surface of the hub extension transmits, in use, all of the torque between the shaft and the impeller.
2. The connector of claim 1 , wherein the connector is configured to contact the impeller only on the radially outer surface of the hub extension.
3. The connector of claim 1 , wherein the hub extension has an end face, and the connector has an abutment portion which bears against the end face.
4. The connector of claim 3 , wherein the connector is configured to contact the impeller only on the radially outer surface of the hub extension and the end face of the hub extension.
5. The connector of claim 1 , wherein the part of the connector inserted into the recess includes the threaded portion of the connector.
6. The connector of claim 1 , wherein the connector is formed of a material having a greater strength than the material of the impeller and having a lower coefficient of thermal expansion than the material of the impeller.
7. The connector of claim 1 , wherein the sleeve portion extends over at least 50% of an axial length of the hub extension.
8. The connector of claim 1 , wherein the connector or the impeller has one or more centering portions having respective engagement surfaces which are adapted to engage with one or more corresponding centering portions of the shaft, the threaded portion of the connector and the centering portions of the connector or the impeller being distributed along the impeller axis.
9. The connector of claim 1 , wherein the impeller has a casing and the sleeve portion forms a seal with a section of the casing.
10. The connector of claim 1 , wherein the sleeve portion is formed with or carries a circumferential oil thrower formation at its radially outer surface.
11. An impeller having a shaft-side hub extension and fitted with a connector of claim 1 , the sleeve portion of the connector being frictionally connected on a radially outer surface of the hub extension.
12. The impeller fitted with a connector of claim 11 , wherein the impeller is a metal impeller.
13. The impeller fitted with a connector of claim 11 , which impeller is connected to a shaft having a corresponding threaded portion, the thread of the threaded portion of the connector screwing onto the corresponding threaded portion of the shaft.
14. A turbocharger having the connected impeller and shaft of claim 13 .