Patent ID: 7550887
Filing Date: 2009-06-23
Classification: F16C,H02K

Abstract:
1. A spindle motor comprising: a base plate; a shaft fixed to said base plate at lower end thereof, said shaft comprising an upper bushing and a lower bushing, wherein said lower bushing is located between said upper bushing and said base plate; a rotor assembly which is rotatable about said shaft, said rotor assembling including a first bore surface which confronts said upper bushing to define a first gap therebetween, and a second bore surface which confronts said lower bushing to define a second gap therebetween; a lubricant which is located in said first and second gaps, wherein an upper gas-liquid interface of said lubricant is located around said shaft at said upper bushing, and a lower gas-liquid interface of said lubricant is located around said shaft at said lower bushing; an upper cover which surrounds said shaft, and which is fixed to said rotor assembly and is spaced from said shaft to define a first clearance, wherein said first clearance extends around the shaft and is located between said upper cover and said shaft; and a lower cover which surrounds said shaft, and which is fixed to said rotor assembly and is spaced from said shaft to define a second clearance, wherein said second clearance extends around the shaft and is located between said lower cover and said shaft; wherein said first clearance is smaller than said second clearance such that a visual sight line to said upper gas-liquid interface does not exist through said first clearance from external said upper cover, and such that a visual sight line to said lower gas-liquid interface does exist through said second clearance from external said lower cover.