Fluid Dynamic Bearing Motor For Use With A Range Of Rotational Speed Rated Disc Drive Memory Device Products

Abstract

A fluid dynamic bearing motor and method are provided for use with various disc drive memory device products differently rated by operational rotational speed. The operational speeds are those speeds measured during reading and writing memory operations to the memory device. In an aspect, the present invention meets full operating requirements, including stiffness and power requirements, at multiple rated speeds for use with either standard or high-end performance disc drive products. Costs associated with a dedicated manufacturing line for high-end products are substantially reduced. A single manufacturing line can serve both standard and high-end disc drive memory device products. The present invention is especially useful in reducing costs of 2.5 inch notebook products that are typically marketed in two levels of performance, namely, 5400 RPM standard performance products and 7200 RPM high performance products.

1 . A fluid dynamic bearing motor, for incorporation into a range of rotational speed rated hard disc drive memory device products, comprising:
 a.) a stationary component and a rotatable component, wherein the stationary component and the rotatable component have facing surfaces positioned for relative rotation; and   b.) a bearing system:
 i. defined between the stationary component and the rotatable component; 
 ii. configured to reduce bearing stiffness sensitivity and power sensitivity to temperature change; 
 iii. configured to keep run current below a first predetermined limit when the rotatable component rotates at a first rotational speed; and 
 iv. configured to keep run current below a second predetermined limit without exceeding a voltage supply to the motor when the rotatable component rotates at a second rotational speed, when:
 1. the first rotational speed is less than the second rotational speed; and 
 2. the first rotational speed and the second rotational speed are rotational speeds during at least one of a reading operation and a writing operation to the hard disc drive memory device. 
 
   
     
     
         2 . The fluid dynamic bearing motor as in  claim 1 , further comprising a fluid contained within the bearing system having a viscosity ratio of less than 3.0, the viscosity ratio calculated by the fluid viscosity at 0 degrees Celsius (° C.) divided by the fluid viscosity at 25° C. 
     
     
         3 . The fluid dynamic bearing motor as in  claim 1 , further comprising a fluid contained within the bearing system having a viscosity ranging from 70 centipoise (cP) to 4 cP when the bearing system fluid temperature ranges from −10 degrees Celsius (° C.) to 70° C. 
     
     
         4 . The fluid dynamic bearing motor as in  claim 1 , further comprising a fluid contained within the bearing system having a viscosity index of less than 160. 
     
     
         5 . The fluid dynamic bearing motor as in  claim 1 , wherein the run current first predetermined specification limit and the run current second predetermined specification limit are determined when the bearing system fluid temperature is about −10 degrees Celsius (° C.) to about 70° C. 
     
     
         6 . The fluid dynamic bearing motor as in  claim 1 , wherein the run current first predetermined specification limit and the run current second predetermined specification limit are determined when the bearing system fluid temperature is one of: about −20° C. to about 10° C., and about 20° C. to about 40° C. 
     
     
         7 . The fluid dynamic bearing motor as in  claim 1 , wherein the stationary component material has a different coefficient of thermal expansion as compared to the rotational component material, configured to increase the bearing gap situated therebetween as the bearing system temperature decreases. 
     
     
         8 . The fluid dynamic bearing motor as in  claim 7 , wherein one of the facing surfaces comprises one of aluminum, brass, bronze, plastic, copper-based sintered metals, and polyimide with graphite filler, and the second facing surface comprises one of stainless steel, 400 series stainless steel, iron-based sintered metals, ceramic, carbide, and nitride. 
     
     
         9 . The fluid dynamic bearing motor as in  claim 1 , wherein the stationary component is structured the same for the first rotational speed and the second rotational speed, the rotatable component is structured the same for the first rotational speed and the second rotational speed, and the bearing system is structured the same for the first rotational speed and the second rotational speed. 
     
     
         10 . The fluid dynamic bearing motor as in  claim 9 , wherein the fluid dynamic bearing motor has a maximized torque constant that is equal to or less than a maximum torque constant for a motor that operates at the second rotational speed. 
     
     
         11 . The fluid dynamic bearing motor as in  claim 1 , further comprising a first base assembly and a first stator assembly connected to the stationary component when the motor operates at the first rotational speed, and a second base assembly and a second stator assembly connected to the stationary component when the motor operates at the second rotational speed, wherein the rotatable component is structured the same for the first rotational speed and the second rotational speed, wherein the bearing system is structured the same for the first rotational speed and the second rotational speed, wherein the first base assembly and the first stator assembly are structured differently than the second base assembly and the second stator assembly, and wherein the first stator assembly winding voltage is greater than the second stator assembly winding voltage. 
     
     
         12 . The fluid dynamic bearing motor as in  claim 11 , wherein the fluid dynamic bearing motor has a maximized torque constant that is equal to or less than a maximum torque constant for a motor that operates at the first rotational speed. 
     
     
         13 . The fluid dynamic bearing motor as in  claim 1 , wherein the fluid dynamic bearing is defined between facing surfaces comprising one of a shaft and a sleeve, a thrustplate and a sleeve, and a sleeve and a second surface defining a thrust bearing therebetween. 
     
     
         14 . The fluid dynamic bearing motor as in  claim 1 , wherein the bearing system contains fluid, the bearing fluid selected from the group consisting of diesters, polyol esters, polyalphaolefins, perfluoropolyethers and mineral hydrocarbons. 
     
     
         15 . The fluid dynamic bearing motor as in  claim 14 , wherein the bearing fluid containing at least one of an anti-oxidant additive effective to reduce oxidation of the bearing fluid, an anti-wear additive effective to reduce wear of the facing surfaces, an anti-corrosion additive effective to reduce corrosion of the facing surfaces, and a conductivity enhancing additive. 
     
     
         16 . The fluid dynamic bearing motor as in  claim 1 , wherein the bearing system contains a bearing fluid that is 3-methyl-1,5-pentanediol-di-n-nonanoate. 
     
     
         17 . The fluid dynamic bearing motor as in  claim 1 , wherein the bearing system contains fluid containing an additive to reduce the rate of viscosity decrease of the bearing fluid as a function of increasing temperature. 
     
     
         18 . The fluid dynamic bearing motor as in  claim 1 , wherein the first rotational speed is 5400 rotations per minute (RPM), and the second rotational speed is 7200 RPM. 
     
     
         19 . The fluid dynamic bearing motor as in  claim 1 , wherein the first rotational speed is a speed in the range of 3600 rotations per minute (RPM) to 15,000 RPM, and the second rotational speed is a speed in the range of 3600 RPM to 15,000 RPM. 
     
     
         20 . A method to enable a fluid dynamic bearing motor to meet operational requirements for a range of rotational speed rated hard disc drive memory device products, comprising:
 i.) minimizing bearing stiffness sensitivity and bearing power sensitivity to temperature;   ii.) setting bearing dimensions to meet bearing stiffness required for reading and writing operations to the range of rotational speed rated hard disc drive memory device products;   iii.) maintaining run current below a first predetermined limit during motor operation when a rotatable component rotates at a first rotational speed; and   iv.) maintaining run current below a second predetermined limit without exceeding a voltage supply to the motor during motor operation when the rotatable component rotates at a second rotational speed;   wherein the bearing is defined between a stationary component and the rotatable component, wherein the stationary component and the rotatable component have facing surfaces positioned for relative rotation, wherein the first rotational speed is less than the second rotational speed, and wherein the first rotational speed and the second rotational speed are rotational speeds during at least one of a reading operation and a writing operation to the hard disc drive memory device.   
     
     
         21 . The method as in  claim 20 , further comprising maximizing rotational torque of the motor without exceeding the voltage supply to the motor. 
     
     
         22 . The method as in  claim 20 , wherein the temperature ranges from about −10 degrees Celsius (° C.) to about 70° C. 
     
     
         23 . The method as in  claim 20 , wherein minimizing bearing stiffness sensitivity and bearing power sensitivity to temperature comprises utilizing a fluid contained within the bearing having a viscosity ratio of less than 3.0, calculated by the fluid viscosity at 0 degrees Celsius (° C.) divided by the fluid viscosity at 25° C. 
     
     
         24 . The method as in  claim 20 , wherein minimizing bearing stiffness sensitivity and bearing power sensitivity to temperature comprises utilizing a material for the stationary component that has a different coefficient of thermal expansion as compared to the rotational component material, configured to increase the bearing gap situated therebetween as the bearing temperature decreases. 
     
     
         25 . A fluid dynamic bearing motor, for incorporation into a range of rotational speed rated hard disc drive memory device products, comprising:
 a.) a stationary component and a rotatable component positioned for relative rotation; and   b.) a bearing system:
 i. defined between the stationary component and the rotatable component; 
 ii. configured for generating predetermined drag between the stationary component and the rotatable component; and 
 iii. having a drag profile ratio of less than 3.0 at least at both of a first rotational speed and a second rotational speed of the rotatable component, when:
 1. the bearing system temperature is between 0 degrees Celsius (° C.) and 25° C.; 
 2. the first rotational speed is less than the second rotational speed; and 
 3. the first rotational speed and the second rotational speed are rotational speeds during at least one of a reading operation and a writing operation to the hard disc drive memory device; 
 
   wherein the drag profile ratio is the bearing system drag at 0° C. divided by the bearing system drag at 25° C.   
     
     
         26 . The fluid dynamic bearing motor as in  claim 25 , further comprising a fluid contained within the bearing having a viscosity ratio of less than 3.0, calculated by the fluid viscosity at 0° C. divided by the fluid viscosity at 25° C. 
     
     
         27 . The fluid dynamic bearing motor as in  claim 25 , further comprising a fluid contained within the bearing that is 3-methyl-1,5-pentanediol-di-n-nonanoate. 
     
     
         28 . The fluid dynamic bearing motor as in  claim 25 , wherein the stationary component has a different coefficient of thermal expansion as compared to the rotational component, configured to increase the bearing gap situated therebetween as the bearing temperature decreases. 
     
     
         29 . The fluid dynamic bearing motor as in  claim 25 , further comprising a maximized motor rotational torque that does not exceed a voltage supply to the motor. 
     
     
         30 . The fluid dynamic bearing motor as in  claim 25 , wherein the first rotational speed is a speed in the range of 3600 rotations per minute (RPM) to 15,000 RPM, and the second rotational speed is a speed in the range of 3600 RPM to 15,000 RPM. 
     
     
         31 . The fluid dynamic bearing motor as in  claim 25 , further comprising a fluid contained within the bearing having a viscosity index of less than 160. 
     
     
         32 . The fluid dynamic bearing motor as in  claim 25 , wherein the stationary component and the rotational component define facing surfaces, one of the facing surfaces comprising one of aluminum, brass, bronze, plastic, copper-based sintered metals, and polyimide with graphite filler, and the second facing surface comprising one of stainless steel, 400 series stainless steel, iron-based sintered metals, ceramic, carbide, and nitride. 
     
     
         33 . The fluid dynamic bearing motor as in  claim 25 , wherein the stationary component is structured the same for the first rotational speed and the second rotational speed, the rotatable component is structured the same for the first rotational speed and the second rotational speed, and the bearing is structured the same for the first rotational speed and the second rotational speed. 
     
     
         34 . The fluid dynamic bearing motor as in  claim 33 , wherein the fluid dynamic bearing motor has a maximized torque constant that is equal to or less than a maximum torque constant for a motor that operates at the second rotational speed. 
     
     
         35 . The fluid dynamic bearing motor as in  claim 25 , further comprising a first base assembly and a first stator assembly connected to the stationary component when the motor operates at the first rotational speed, and a second base assembly and a second stator assembly connected to the stationary component when the motor operates at the second rotational speed, wherein the rotatable component is structured the same for the first rotational speed and the second rotational speed, wherein the bearing is structured the same for the first rotational speed and the second rotational speed, wherein the first base assembly and the first stator assembly are structured differently than the second base assembly and the second stator assembly, and wherein the first stator assembly winding voltage is greater than the second stator assembly winding voltage. 
     
     
         36 . The fluid dynamic bearing motor as in  claim 35 , wherein the fluid dynamic bearing motor has a maximized torque constant that is equal to or less than a maximum torque constant for a motor that operates at the first rotational speed. 
     
     
         37 . The fluid dynamic bearing motor as in  claim 25 , wherein the bearing contains fluid containing an additive to reduce the rate of viscosity decrease of the bearing fluid as a function of increasing temperature. 
     
     
         38 . The fluid dynamic bearing motor as in  claim 25 , wherein the stationary component and the rotational component are facing surfaces, the facing surfaces comprising one of a shaft and a sleeve, a thrustplate and a sleeve, and a sleeve and a second surface defining a thrust bearing therebetween.