Compressor

Abstract

A compressor 201 comprising a compressor wheel 2, a driveshaft 4, and an electric motor (6, Fig. 1), a rotating group 16 coupled to the driveshaft and a static group 18; The rotating group 16 comprises a rotor 208 of the electric motor and the static group comprising a stator 210 of the electric motor; The driveshaft 4 extends along a shaft axis and couples the compressor wheel to the rotor such that rotation of the rotor causes rotation of the compressor wheel 2 about the shaft axis; The motor is arranged with the rotor 208 extending along the shaft axis and the stator 210 extending around the rotor 208 and substantially coaxial therewith such that a stator magnetic field generated in the stator 210 can interact with a rotor magnetic field of the rotor 208 to cause it to rotate; The rotating group 16 is arranged on the shaft axis relative to the static group 18 such that a resultant magnetic force on the driveshaft can be generated along the shaft axis away from the compressor wheel 2. The invention aims to improve useful life expectancy of bearings.

Claims

1. A compressor comprising a compressor wheel, a driveshaft, and an electric motor, a rotating group coupled to the driveshaft and a static group, the rotating group comprising a rotor of the electric motor and the static group comprising a stator of the electric motor, the driveshaft extending along a shaft axis and coupling the compressor wheel to the rotor such that rotation of the rotor causes rotation of the compressor wheel about the shaft axis, the motor being arranged with the rotor extending along the shaft axis and the stator extending around the rotor and substantially coaxial therewith such that a stator magnetic field generated in the stator can interact with a rotor magnetic field of the rotor to cause the rotor to rotate, the rotating group is arranged on the shaft axis relative to the static group such that a resultant magnetic force on the driveshaft can be generated along the shaft axis away from the compressor wheel.

2. A compressor as claimed in claim 1, in which rotating group consists of the rotor of electric motor.

3. A compressor as claimed in claim 1 or claim 2, in which the static group consists of the stator of the electric rotor.

4. A compressor as claimed in any preceding claim, in which the compressor includes a housing having a first bearing surface and the driveshaft includes a second bearing surface and in which the first bearing surface and second bearing surface cooperate to limit movement of the driveshaft relative to the housing along the shaft axis in a first direction towards the compressor wheel.

5. A compressor as claimed in claim 4, in which a thrust bearing is arranged between the first and second bearing surfaces.

6. A compressor as claimed in claim 5, in which the thrust bearing is an air bearing.

7. A compressor as claimed in any preceding claim, in which a midpoint of a rotating group magnetic field is offset along the shaft axis towards the compressor wheel from a midpoint of a static group magnetic field.

8. A compressor as claimed in any preceding claim, in which the rotor has a rotor length between a first rotor end and a second rotor end along the shaft axis and the stator has astator length between a first stator end and a second stator end along the shaft axis and wherein a rotor midpoint of the rotor length is offset along the shaft axis towards the compressor wheel from a stator midpoint of the stator length.

9. A compressor as claimed in claim 8, in which the rotor magnetic field is substantially symmetrical about a rotor midpoint of the rotor length and the stator magnetic field is substantially symmetrical about the stator midpoint of the stator length.

10. A compressor as claimed in claim 8 or claim 9, in which the rotor midpoint of the rotor length is offset from a stator midpoint of the stator length by more than 1mm.

11. A compressor as claimed in claim 8, in which the rotor midpoint of the rotor length is offset from a stator midpoint of the stator length by more than 3mm.

12. A compressor as claimed in any of claims 8 to 10, in which the rotor midpoint of the rotor length is offset from a stator midpoint of the stator length by no more than 10mm.

13. A compressor as claimed in any preceding claim in which the compressor is a single stage compressor.

14. A compressor as claimed in any preceding claim in which the resultant magnetic force on the driveshaft that can be generated along the shaft axis away from the compressor wheel is at least 10N.

15. A method of compensating for compressor wheel thrust in a compressor, the compressor a compressor wheel, a driveshaft, and an electric motor, a rotating group coupled to the driveshaft and a static group, the rotating group comprising a rotor of the electric motor and the static group comprising a stator of the electric motor, the driveshaft extending along a shaft axis and coupling the compressor wheel to the rotor such that rotation of the rotor causes rotation of the compressor wheel about the shaft axis, the motor being arranged with the rotor extending along the shaft axis and the stator extending around the rotor and substantially coaxial therewith and the method comprising:controlling an input to the static group to generate a static group magnetic field including a stator magnetic field in the stator;arranging the rotating group on the shaft axis relative to the static group such that a resultant magnetic force on the driveshaft is generated along the shaft axis; andallowing the stator magnetic field to interact with the rotor magnetic field of the rotor such that the rotor is caused to rotate about the shaft axis and drive the compressor wheel and allowing a static group magnetic field to interact with a rotating group magnetic field such that a compensatory force is generated on the driveshaft along the shaft axis in a5 direction away from the compressor wheel.

16. A method as claimed in claim 15, in which the compressor is as claimed in any of claims 1 to 14.1016

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