Motor having a hydrodynamic pressure bearing

A motor comprising:

• a shaft;
• a disk-shaped thrust plate fixed to said shaft;
• a housing surrounding said shaft and supporting said shaft and said thrust plate, with a gap being formed between inner surrounding surfaces of said housing and outer surfaces of said shaft and said thrust plate for rotation of said shaft and said thrust plate relative to said housing, said gap having a first portion formed between one planar surface of said thrust plate and a first confronting inner surface of said housing, said gap also having a second portion formed between a circumferentially extending portion of said outer surface of said thrust plate and a second confronting inner surface of said housing, bearing grooves being formed on a surface defining said first and second portions of said gap;
• lubricant disposed in said first and second portions of said gap forming a single hydrodynamic thrust bearing and a single hydrodynamic radial bearing so as to generate hydrodynamic pressure acting on axially and radially direction;
• and
• means for generating counterbalancing forces against said hydrodynamic pressure of said hydrodynamic thrust bearing such that said single hydrodynamic thrust bearing and said counterbalancing force generating means cooperatively support axial loads acting on said shaft and said thrust plate against said housing in axial directions.

A spindle motor comprising:

• a shaft;
• a single, disk-shaped thrust plate fixed endwise to said shaft, said thrust plate therein forming a substantially planar disk surface at the end of said shaft and having a substantially planar annular surface opposite the disk surface and an outer circumferential surface between the disk and annular surfaces;
• a housing closely surrounding said thrust plate fixed to said shaft, said housing including
• a cover section having a cover surface axially opposing the disk surface of said thrust plate by a cover section small gap at least along the circumferentially peripheral margin of said thrust plate,
• a ring section encircling said shaft and having a ring surface axially opposing the annular surface of said thrust plate by a ring section small gap at least along the circumferentially peripheral margin of said thrust plate, and
• a cylindrical section having an inner cylindrical surface radially opposing the circumferential surface of said thrust plate by a cylindrical section small gap along said thrust plate in axial thickness, the cylindrical section small gap therein continuous with the cover section small gap and the ring section small gap;
• a lubricant filling the continuous small gaps;
• one and only one hydrodynamic-pressure thrust bearing including
• hydrodynamic pressure-generating grooves formed in one surface selected from the ring surface of the ring section of said housing, the annular surface of said thrust plate, the disk surface of said thrust plate, and the cover surface of the cover section of said housing, and
• the small gap between the selected surface and its axially opposing surface, wherein said small gap between the selected surface and its axially opposing surface extends radially inward from the circumferentially peripheral margin of said thrust plate;
• a single hydrodynamic-pressure radial bearing continuous with said single hydrodynamic-pressure thrust bearing, said hydrodynamic-pressure radial bearing including
• hydrodynamic pressure-generating grooves formed in one surface selected from the circumferential surface of said thrust plate and the inner cylindrical surface of the cylindrical section of said housing, and
• the small gap between the selected surface and its radially opposing surface;
• and
• means for magnetically counterbalancing hydrodynamic pressure generated in said single hydrodynamic pressure thrust bearing when the spindle motor spins.