Jacketed axial magnetic bearing
The invention relates to a jacketed axial magnetic bearing for a rotary machine having a rotor in contact with a gaseous atmosphere that is corrosive, acid, or carrying particles, the bearing comprising a rotor armature in the form of a disk secured to the rotor and placed in the gaseous atmosphere, and a stator magnetic circuit secured to a stationary support device and placed facing the rotor armature, the magnetic circuit of the stator comprising at least one coil and a ferromagnetic body placed in a metallic protective enclosure. The protective enclosure comprises firstly an annular support of channel section with a web and inner and outer flanges presenting a thickness of several millimeters and a length that is less than the length of the stator magnetic circuit, and secondly an annular jacket in the form of a channel-section cover machined from a solid piece and thus without welds, the jacket having inner and outer flanges and a closure web presenting a thickness smaller than the thicknesses of the inner and outer flanges, the free ends of the inner and outer flanges of the jacket being welded to the free ends of the inner and outer flanges of the annular support.
1. A jacketed axial magnetic bearing for a rotary machine having a rotor in contact with a gaseous atmosphere that is corrosive, acid, or carrying particles, the bearing comprising a rotor armature in the form of a disk secured to the rotor and placed in said gaseous atmosphere, and a stator magnetic circuit secured to a stationary support device and placed facing said rotor armature, the magnetic circuit of the stator comprising at least one coil and a ferromagnetic body placed in a metallic protective enclosure, wherein said protective enclosure comprises firstly an annular support of channel section with a web and inner and outer flanges presenting a thickness of several millimeters and a length that is less than the length of the stator magnetic circuit, and secondly an annular jacket in the form of a channel-section cover machined from a solid piece and thus without welds, the jacket having inner and outer flanges and a closure web presenting a thickness smaller than the thicknesses of the inner and outer flanges, the free ends of the inner and outer flanges of the jacket being welded to the free ends of the inner and outer flanges of said annular support.
2. A bearing according to claim 1 , wherein the annular jacket is shrink-fitted on said ferromagnetic body.
3. A bearing according to claim 1 , wherein the annular jacket includes flexibility grooves formed in the inner and outer flanges.
4. A bearing according to claim 1 , including at least first and second O-rings disposed on either side of the weld between the inner flange of the jacket and the inner flange of the annular support, and third and fourth O-rings disposed on either side of the weld between the outer flange of the jacket and the outer flange of the annular support.
5. A bearing according to claim 4 , wherein each of said first, second, third, and fourth O-rings comprises a pair of O-rings providing double sealing.
6. A bearing according to claim 1 , wherein the annular jacket and the annular support are made of magnetic stainless steel of the 17-4 PH type, or of Inconel.
7. A bearing according to claim 1 , wherein the closure web of the annular jacket presents thickness lying in the range 0.3 mm to 2 mm.
8. A bearing according to claim 1 , wherein the welds between the jacket and the annular support are formed on walls presenting thickness greater than 3 mm.
9. A bearing according to claim 1 , wherein the welds between the jacket and the annular support are made by laser welding, by electron bombardment, or by TIG welding.
10. A bearing according to claim 1 , wherein the airgap between the rotor armature and the stator magnetic circuit lies in the range 0.4 mm to 1.2 mm.
11. A bearing according to claim 2 , wherein the annular jacket presents a coefficient of expansion that is smaller than that of the ferromagnetic body.