Magnet retention on rotors
View Patent ↗Permanent magnets are mounted on a rotor of an electrical motor by an apparatus that keeps an adhesive bonding layer between the magnet and rotor in compression over wide variations in temperature and speed of rotation. The mechanical stresses on the magnets are controlled using compliant layers and spacers. The apparatus allows the removal and replacement of individual magnets.
1. A magnet retainer for securing permanent magnets to a rotor body, comprising:
a retainer body having an opening and a pair of angled surfaces each adapted to engage an angled surface of a neighboring permanent magnet;
a fastening device disposed in the opening and adapted to engage the rotor body and thereby radially secure the retainer body to the rotor body; and
a spring mechanism disposed between the fastening device and the retainer body to exert a force on the neighboring permanent magnets, the force being responsive to a centrifugal force during rotation of the rotor body.
2. The retainer of claim 1 , wherein the fastening device is a threaded bolt.
3. The retainer of claim 1 , wherein the spring mechanism comprises at least one disc spring.
4. The retainer of claim 1 , further comprising at least one axial retainer secured to an end of the retainer body, the axial retainer adapted to prevent axial movement of a permanent magnet.
5. A permanent magnet rotor, comprising:
a rotor body having a cylindrical surface and a circumference;
a plurality of permanent magnets disposed on the cylindrical surface at equal intervals of the circumference, each permanent magnet having a pair of angled surfaces;
an adhesive layer disposed between each permanent magnet and the cylindrical surface; and
a plurality of magnet retainers, each magnet retainer disposed between a neighboring pair of the permanent magnets, each magnet retainer comprising:
a retainer body having an opening and a pair of angled surfaces each configured to engage one of the angled surfaces of a respective one of the permanent magnets;
a fastening device disposed in the opening and adapted to engage the rotor body to thereby secure the retainer body to the rotor body; and
a spring mechanism disposed between the fastening device and the retainer body, the spring mechanism exerting a force to secure a respective one of the neighboring pairs of permanent magnets to the cylindrical surface of the rotor body, the force being responsive to a centrifugal force during rotation of the permanent magnet rotor.
6. The permanent magnet rotor of claim 5 , further comprising a plurality of axial retainers, each axial retainer disposed at an end of a magnet retainer, the axial retainers adapted to prevent axial movement of a permanent magnet.
7. The permanent magnet rotor of claim 5 , further comprising a spacer disposed between each permanent magnet and the rotor body.
8. The permanent magnet rotor of claim 7 , wherein the spacer is an open-mesh screen.
9. The permanent magnet rotor of claim 5 , further comprising a compliant layer between one of the angled surfaces of each retainer body and one of the angled surfaces of a respective one of the permanent magnets.
10. The permanent magnet rotor of claim 5 , wherein the fastening device is a threaded bolt.
11. The permanent magnet rotor of claim 5 , wherein the spring mechanism comprises at least one disc spring.
12. A permanent magnet rotor, comprising:
a rotor body having a cylindrical surface and a circumference;
a plurality of permanent magnets disposed on the cylindrical surface at equal intervals of the circumference, each permanent magnet having a pair of angled surfaces;
an adhesive layer disposed between each permanent magnet and the rotor body;
an open-mesh screen disposed between each permanent magnet and the cylindrical surface;
a plurality of magnet retainers, each magnet retainer disposed between a neighboring pair of the permanent magnets, each magnet retainer comprising:
a retainer body having an opening and a pair of angled surfaces each configured to engage one of the angled surfaces of a respective one of the permanent magnets;
a fastening device at least partially disposed in the opening and adapted to engage the rotor body to thereby secure the retainer body to the rotor body; and
a spring mechanism disposed between the fastening device and the retainer body, the spring mechanism exerting a force to secure a respective one of the neighboring pairs of permanent magnets to the cylindrical surface of the rotor body, the force being responsive to a centrifugal force during rotation of the permanent magnet rotor; and
a plurality of axial retainers, each axial retainer disposed at an end of a magnet retainer and being adapted to prevent axial movement of a permanent magnet.
13. The permanent magnet rotor of claim 12 , further comprising a compliant layer between the angled surfaces of the retainer bodies and the angled surfaces of the permanent magnets.