Air cycle machine with magnetic bearings

Abstract

An air cycle machine for producing a supply of cooled air and including a compressor rotor fixed to a shaft which is driven by a turbine rotor, the turbine serving to expand air which is pressurized by the compressor. Magnetic bearings support the shaft radially in a housing for rotation about a precisely established axis while a magnetic thrust bearing keeps the shaft in a precisely fixed axial position. The housing and the bearings are constructed as two split sections to permit the housing and the bearings to be separated radially and facilitate repair and/or replacement of the shaft and other internal components.

We claim: 
     
       1. An air cycle machine for an aircraft and comprising a housing, a shaft disposed in said housing and having a central axis, a compressor mounted on said shaft and having inlet means for receiving a pressurized gas to be compressed, a turbine mounted on said shaft in axially spaced relation with said compressor and having inlet means for receiving gas pressurized by said compressor, said turbine being driven by the gas pressurized by said compressor and acting through said shaft to drive said compressor, the pressurized gas received by said turbine expanding therein, being cooled as a result of expanding and being exhausted as chilled gas by said turbine, axially spaced bearings for radially supporting said shaft for rotation in said housing, each of said bearings comprising a plurality of electromagnets mounted within said housing and spaced angularly around said shaft, said electromagnets comprising selectively energizable electrical coil means for producing magnetic forces suspending said shaft radially within said housing, means for sensing the radial position of the axis of said shaft, means responsive to said sensing means for varying the energization of said coils to keep the axis of said shaft in coincidence with a predetermined axis, an additional bearing for maintaining said shaft in a predetermined axial position in said housing, said additional bearing comprising axially spaced and axially opposing electromagnets mounted within said housing and positioned substantially coaxial with said shaft, a disc rigid with and projecting radially from said shaft and located between said axially opposing electromagnets, said axially opposing electromagnets comprising selectively energizable electrical coil means for producing magnetic forces acting in axially opposing relation on said disc, means for detecting the axial position of said shaft, means responsive to said detecting means for varying the energization of the coils of said axially opposing electromagnets to keep said shaft in a predetermined axial position, a second disc rigid with . .an.!. .Iadd.and .Iaddend.projecting radially from said shaft, and annular permanent magnet means disposed in said housing in axially opposing relation with said second disc for producing a magnetic force biasing said second disc and said shaft axially in opposition to the pressurized gas entering said inlet means of said compressor. 
     
     
       2. An air cycle machine comprising a housing, a shaft disposed in said housing and having a central axis, said housing comprising first and second sections having mounting flanges mating with one another in a plane substantially coinciding with a plane containing said axis, axially spaced bearings for radially supporting said shaft for rotation in said housing, each of said bearings comprising first and second groups of electromagnets mounted in said first and second housing sections, respectively, and spaced angularly around said shaft, said electromagnets comprising selectively energizable electrical coil means for producing magnetic forces suspending said shaft radially within said housing, and connecting means for releasably securing said flanges to one another whereby said housing may be removed from said shaft by releasing said connecting means, by pulling said first housing section and said first group of electromagnets as a unit radially in one direction away from said shaft, and by pulling said second housing section and said second group of electromagnets as a unit radially in the opposite direction away from said shaft. 
     
     
       3. An air cycle machine as defined in claim 2 in which one-half of the electromagnets of each bearing are mounted in one housing section, the other one-half of the electromagnets of each bearing being mounted in the other housing section. 
     
     
       4. An air cycle machine as defined in claim 2 further including an additional bearing for maintaining said shaft in a predetermined axial position in said housing, said additional bearing comprising axially spaced and axially opposing electromagnets, a disc rigid with and projecting radially from said shaft and located between said axially opposing electromagnets, said axially opposing electromagnets comprising selectively energizable electrical coil means for producing magnetic forces acting in opposing relation on said disc, each of said axially opposing electromagnets including first and second electromagnets mounted in said first and second housing sections, respectively, and connected to the respective housing section to be pulled radially away from said shaft as a unit with the respective housing section. 
     
     
       5. An air cycle machine for an aircraft and comprising a housing, a shaft disposed in said housing and having a central axis, a compressor mounted on said shaft and having inlet means for receiving a pressurized gas to be compressed, a turbine mounted on said shaft in axially spaced relation with said compressor and having inlet means for receiving gas pressurized by said compressor, said turbine being driven by the gas pressurized by said compressor and acting through said shaft to drive said compressor, the pressurized gas received by said turbine expanding therein, being cooled as a result of expanding and being exhausted as chilled gas by said turbine, axially spaced bearings for radially supporting said shaft for rotation in said housing, each of said bearings comprising a plurality of electromagnets mounted within said housing and spaced angularly around said shaft, said electromagnets comprising selectively energizable electrical coil means for producing magnetic forces suspending said shaft radially within said housing, means for sensing the radially position of the axis of said shaft, means responsive to said sensing means for varying the energization of said coils to keep the axis of said shaft in coincidence with a predetermined axis, said housing comprising two sections having mounting flanges mating with one another in a plane substantially coinciding with a plane containing said predetermined axis, and connecting means for releasably securing said flanges to one another whereby said housing may be removed from said shaft by releasing said connecting means and pulling said housing sections radially in opposite directions away from said shaft, some of the electromagnets of each bearing being mounted within one of said housing sections, the remaining electromagnets of each bearing being mounted in the other of the housing sections whereby the electromagnets in each housing section are pulled radially away from said shaft when the housing section is pulled radially away from the shaft. 
     
     
       6. An air cycle machine as defined in claim 5 in which one-half of the electromagnets of each bearing are mounted in one housing section, the other one-half of the electromagnets of each bearing being mounted in the other housing section. .Iadd. 
     
     
       7.  A machine comprising a housing, a shaft disposed in said housing and having a central axis, said housing comprising first and second sections mating with one another in a plane substantially coinciding with a plane containing said axis, axially spaced bearings for radially supporting said shaft for rotation in said housing, each of said bearings comprising first and second groups of electromagnets mounted in said first and second housing sections, respectively, and spaced angularly around said shaft, said electromagnets comprising selectively energizable electrical coil means for producing magnetic forces suspending said shaft radially within said housing, and connecting means for releasably securing said sections to one another whereby said housing may be removed from said shaft by releasing said connecting means, by pulling said first housing section and said first group of electromagnets as a unit radially in one direction away from said shaft, and by pulling said second housing section and said second group of electromagnets as a unit radially in the opposite direction away from said shaft..Iaddend..Iadd.8. A machine as defined in claim 7 further including means for sensing the radial position of the shaft, and means responsive to the sensing means for varying the energization of said coils to keep the axis of said shaft in coincidence 
     
     
        with a predetermined axis..Iaddend..Iadd.9.  A machine as defined in claim 8 in which one-half of the electromagnets of each bearing are mounted in one housing section, the other one-half of the electromagnets of each bearing being mounted in the other housing section..Iaddend..Iadd.10. A machine as defined in claim 8 further including an additional bearing for maintaining said shaft in a predetermined axial position in said housing, said additional bearing comprising axially spaced and axially opposing electromagnets, a disc rigid with and projecting radially from said shaft and located between said axially opposing electromagnets, said axially opposing electromagnets comprising selectively energizable electrical coil means for producing magnetic forces acting in opposing relation on said disc, each of said axially opposing electromagnets including first and second electromagnets mounted in said first and second housing sections, respectively, and connected to the respective housing section to be pulled radially away from said shaft as a unit with the respective housing section..Iaddend.