Patent ID: 6717308
Filing Date: 2004-04-06
Classification: F16C,H02K

Abstract:
An electric spindle motor having a thrust bearing separate from a radial bearing, comprising:a base plate; a rotatable assembly including a rotatable sleeve extending substantially perpendicular from said base plate along a rotational axis, wherein said rotatable assembly is supported by said base plate; a radial bearing including a stationary shaft securely coupled to said base plate, and extending within said sleeve along said rotational axis and spaced therefrom to define a first clearance gap and a liquid situated within said first clearance gap for providing at least radial stiffness for said rotatable sleeve; a thrust plate and a thrust plate supporter securely coupling said thrust plate to said base plate; a thrust bearing securely coupled to said rotating assembly, wherein said thrust bearing is shaped complementary with said thrust plate and spaced apart therefrom to form a second clearance gap, said thrust bearing being separate from radial bearing, and a gas fluid situated within said second clearance gap for providing at least axial stiffness for said rotatable assembly; a stator for causing the rotation of said rotatable assembly; a magnetic device operated by an electrical current for moving said rotatable assembly away from said base plate substantially along said rotational axis so that said rotatable assembly is less supported by said base plate during rotation of said rotating assembly, said magnetic device including a stator lamination with coil securely coupled to said thrust plate supporter and a magnetic plate securely coupled to said rotatable assembly, and a magnetic preloading means including a permanent magnet mounted to said magnetic plate to urge said separate thrust bearing into a rotatable assembly stop position for preventing free movement of said rotatable assembly when said current is not supplied to said magnetic device.