# US 5,707,154 A · Hydrodynamic fluid pressure bearings > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,707,154 A - Document ID: US5707154A - Status: Granted - Kind: A - Application number: 08/771,298 - Filed: 1996-12-20 - Granted: 1998-01-13 - Earliest claimed: 1995-12-26 - Assignees: Nidec Corporation - Inventors: Yoshikazu Ichiyama - Web page: https://patentgrep.com/patent/US5707154A ## CPC - F16C 33/107: {Grooves for generating pressure} - F16C 17/107: {with at least one surface for radial load and at least one surface for axial load} - F16C 33/10: Construction relative to lubrication {(lubrication in general F16N)} - G11B 19/2009: {Turntables, hubs and motors for disk drives; Mounting of motors in the drive (means for clamping of disk to turntable G11B17/022 and subgroups)} - F16C 2240/40: Linear dimensions, e.g. length, radius, thickness, gap - F16C 2370/12: Hard disk drives or the like - F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A hydrodynamic bearing device includes a gap between a shaft and shaft holder. One of the shaft and shaft holder has a recess for separating by capillary action lubricant at an upper portion of the gap above the recess from lubricant at a lower portion of the gap below the recess. The separated lubricant at the recess forms a gas interposition in order to reduce lubricant resistance. A hole formed in the shaft or shaft holder communicates the air interposition to the external atmosphere to prevent air expansion and the build-up of bubbles in the lubricant which could otherwise cause contamination and leakage. An axially extending storage groove supplies by capillary action lubricant from either the upper or lower portion to the other portion if lubricant in the other portion decreases due to vaporization or leakage, whereby the loss of lubricant is minimized and the operating life of the surrounding components are increased. ## Claims ### Claim 1 A hydrodynamic bearing device comprising: a shaft member having an outer bearing surface defining at least one annular recess; a sleeve member having an inner bearing surface for receiving and supporting said shaft member for relative rotation of the shaft member and the sleeve member, the inner bearing surface opposing the outer bearing surface leaving a bearing gap therebetween, the sleeve member being provided with a communicating hole to the external atmosphere, and the inner bearing surface of the sleeve member forming an axially extending storage groove thereon; a bearing liquid filled in said bearing gap, at least one of the inner and outer bearing surfaces being provided with at least one bearing groove for generating a hydrodynamic pressure in said bearing fluid during the relative rotation of said shaft member and said sleeve member; and a supporting member for supporting the shaft member against a thrust load acting thereon, said bearing liquid being provided at an upper portion of the bearing gap above the recess and at a lower portion of the bearing gap below the recess, the bearing liquid at the upper and lower portions of the bearing gap being separated from one another at the recess to form a gas space for reducing viscosity resistance of the bearing liquid between the shaft member and the sleeve member, the storage groove communicating the bearing liquid by capillary action from one of the lower and upper portions of the bearing gap to the other portion of the bearing gap, and the communicating hole connecting the gas space to the outer atmosphere. ### Claim 2 (depends on 1) A hydrodynamic bearing device according to claim 1, wherein said annular recess of said shaft member is disposed at an axial center portion of said shaft member and the axial length of said annular recess is substantially equal to the axial length of said storage groove. ### Claim 3 (depends on 1) A hydrodynamic bearing device according to claim 1, wherein said supporting member includes a thrust plate fixed on the shaft member, said sleeve member surrounding the thrust plate to form a part of the gap which is continuous and filled with the bearing liquid. ### Claim 4 (depends on 1) A hydrodynamic bearing device according to claim 1, wherein the upper end portion of the inner bearing surface of said sleeve member is tapered to form a capillary or surface tension seal for preventing said bearing liquid from leaking to the outside of said bearing gap. ### Claim 5 (depends on 1) A hydrodynamic bearing device according to claim 1, wherein the shaft member is tapered at both ends of the annular recess to form a surface tension seal. ### Claim 6 (depends on 5) A hydrodynamic bearing device according to claim 5, wherein said shaft member is milled at one of the ends of the annular recess to an elongated and moderately tapered form. ### Claim 7 (depends on 1) A hydrodynamic bearing device according to claim 1, wherein the sleeve member has at least one axially extending communicating groove at the outer circumferential surface, the communicating groove being connected with the communicating hole for the communication of the gas space with the outer atmosphere. ### Claim 8 (depends on 1) A hydrodynamic bearing device according to claim 1, wherein the storage groove is located at a portion diametrically opposite from the annular recess. ### Claim 9 A motor comprising: a shaft; a cylindrical sleeve for receiving and supporting said shaft for relative rotation of the shaft and the cylindrical sleeve, the shaft and sleeve respectively having an outer cylindrical surface having at least one annular recess and an inner cylindrical surface which oppose each other to form a clearance gap around said shaft, the sleeve member being provided with a communication hole to the external atmosphere, and the inner cylindrical surface of the sleeve forming an axially extending storage groove thereon; a cup-shaped member having a cylindrical portion, said cup-shaped member being secured to an upper end portion of said shaft; a magnet secured to an inner cylindrical surface of said cup-shaped member; a stator core fixed to an outside of said sleeve; at least one of inner and outer surfaces of respective said sleeve and said shaft having at least one pressure generating groove in said clearance gap; an inner end portion of said shaft having a support member for supporting the shaft against a thrust load; and a bearing liquid filling in said clearance gap, the bearing liquid being provided at an upper portion of the clearance gap above the recess and at a lower portion of the clearance gap below the recess, the bearing liquid at the upper and lower portions of the clearance gap being separated from one another at the recess to form a gas space for reducing viscosity of the bearing liquid between the shaft and the cylindrical sleeve, the storage groove communicating the bearing liquid by capillary action from one of the lower and upper portions of the clearance gap to the other portion of said gap, and the communication hole connecting the gas space to the outer atmosphere. ### Claim 10 (depends on 9) A motor according to claim 9, wherein said annular recess of said shaft is disposed at an axial center portion of said shaft and the axial length of said annular recess is substantially equal to the axial length of said storage groove. ### Claim 11 (depends on 9) A motor according to claim 9, wherein said support member includes a thrust plate fixed on the shaft, said sleeve surrounding the thrust plate to form a part of the clearance gap which is continuous and filled with the bearing liquid. ### Claim 12 (depends on 11) A motor according to claim 11, wherein the sleeve has at least one axially extending communication groove at the outer circumferential surface, the communication groove being connected with the communication hole for connecting the gas space with the outer atmosphere. ### Claim 13 (depends on 11) A motor according to claim 11, wherein the storage groove is located at a portion diametrically opposite from the annular recess. ### Claim 14 (depends on 9) A motor according to claim 9, wherein the upper end portion of the inner cylindrical surface of said sleeve is tapered to form a capillary or surface tension seal for preventing said bearing liquid from leaking out to the outside of said clearance gap. ### Claim 15 (depends on 9) A motor according to claim 9, wherein the shaft is tapered at both ends of the annular recess to form surface tension seals. ### Claim 16 (depends on 15) A motor according to claim 15, wherein said shaft is milled at one of the ends of the annular recess to an elongated and moderately tapered form. ### Claim 17 A hydrodynamic bearing structure for supporting a rotator carrying a load for rotating, said hydrodynamic bearing structure comprising: a shaft member having an outer bearing surface defining at least one annular recess; a cylindrical sleeve member for receiving and supporting said shaft member for relative rotation of the shaft member and the cylindrical sleeve member, the sleeve member having an inner bearing surface provided with an axially extending storage groove thereon, and having a communication hole to the external atmosphere; a bearing gap formed in a clearance between said inner bearing surface and said outer bearing surface and a bearing liquid in said bearing gap; at least one bearing groove for generating a hydrodynamic pressure in said bearing liquid formed on at least one surface of said inner and outer bearing surfaces; and a supporting member for supporting the shaft member against a thrust load, the bearing liquid being provided at an upper portion of the bearing gap above the recess and at a lower portion of the bearing gap below the recess, the bearing liquid at the upper and lower portions of the bearing gap being separated from one another at the recess to form a gas space for reducing viscosity resistance of the bearing liquid between the shaft member and the sleeve member, the storage groove communicating the bearing liquid by capillary action from one of the lower and upper portions of the bearing gap to the other portion of said gap, and the communication hole connecting the gas space to the outer atmosphere. ### Claim 18 (depends on 17) A hydrodynamic bearing structure according to claim 17, wherein said annular recess of said shaft member is disposed at an axial center portion of said shaft member and the axial length of said annular recess is substantially equal to the axial length of said storage groove. ### Claim 19 (depends on 17) A hydrodynamic bearing structure according to claim 17, wherein said supporting member includes a thrust plate fixed on the shaft member, said sleeve member surrounding the thrust plate to form a part of the bearing gap which is continuous and filled with the bearing liquid. ### Claim 20 (depends on 17) A hydrodynamic bearing structure according to claim 17, wherein the upper end portion of the inner bearing surface of said sleeve member is tapered to form a capillary or surface tension seal for preventing said bearing liquid from leaking out to the outside of said bearing gap. ### Claim 21 (depends on 17) A hydrodynamic bearing structure according to claim 17, wherein the shaft member is tapered at both ends of the annular recess to form surface tension seals. ### Claim 22 (depends on 21) A hydrodynamic bearing structure according to claim 21, wherein the shaft member is milled at one of the ends of the annular recess to an elongated and moderately tapered form. ### Claim 23 (depends on 17) A hydrodynamic bearing structure according to claim 17, wherein the sleeve member has at least one axially extending communication groove at the outer circumferential surface, the communication groove being connected with the communication hole for connecting the gas space with the outer atmosphere. ### Claim 24 (depends on 17) A hydrodynamic bearing structure according to claim 17, wherein the storage groove is located at a portion diametrically opposite from the annular recess. ### Claim 25 A motor comprising: a shaft; a sleeve for receiving said shaft to allow relative rotation of the shaft and the sleeve, the shaft and the sleeve defining a gap therebetween, an axially extending storage groove formed on one of the shaft and the sleeve; a hydrodynamic fluid filling the gap; a hydrodynamic pressure groove and an atmosphere vent hole formed on one of the shaft and the sleeve for causing a hydrodynamic pressure in the fluid during relative rotation of the shaft and the sleeve; and a hydrodynamic bearing structure including an annular recess formed on at least one of the shaft and the sleeve on a surface that confronts the gap, the recess extending around the shaft to form an enlarged space in the gap to separate the hydrodynamic fluid, said hydrodynamic fluid being provided at an upper portion of the gap above the recess and at a lower portion of the gap below the recess, the hydrodynamic fluid at the upper and lower portions of the gap being separated from one another at the enlarged space for reducing viscosity of the hydrodynamic fluid between the shaft and the sleeve, the storage groove communicating the hydrodynamic fluid by capillary action from one of the lower and upper portions of the gap to other portion of the gap, and the vent-hole connecting the enlarged space to the outer atmosphere. ### Claim 26 (depends on 25) The motor according to claim 25, wherein the gap between said sleeve and said shaft is tapered at an end of the gap and at both ends of the enlarged space to form surface tension seals. ### Claim 27 (depends on 26) The motor according to claim 26, wherein said shaft is milled at one of the ends of the enlarged space to an elongated and moderately tapered form. ### Claim 28 (depends on 27) The motor according to claim 27, further including a thrust plate that is integral with the shaft, and wherein the sleeve has an enlarged diameter portion for surrounding the thrust plate leaving a gap therebetween, the gap around the thrust plate communicating with the gap between the sleeve and the shaft. ### Claim 29 (depends on 25) The motor according to claim 25, wherein the annular recess is formed on the shaft and the storage groove is formed on the sleeve. ### Claim 30 (depends on 29) The motor according to claim 29, wherein the annular recess and the storage groove is disposed to face each other. ### Claim 31 A hydrodynamic bearing construction for an electric motor comprising: a shaft; a sleeve member for relatively rotatably receiving the shaft, the shaft and the sleeve member cooperating to form a clearance gap between the shaft and the sleeve member; a bearing liquid filling the gap; means for causing dynamic pressure in the liquid during the relative rotation of the shaft and the sleeve member in order to support the shaft and the sleeve member; means for forming an annular space in the gap to separate the bearing liquid thereat; and means for partially communicating the separated liquid. ### Claim 32 (depends on 31) A hydrodynamic bearing construction according to claim 31, wherein the dynamic pressure causing means includes at least one bearing groove formed on one of the surfaces of the shaft and the sleeve that confront at the gap. ### Claim 33 (depends on 31) A hydrodynamic bearing construction according to claim 31, wherein the annular space forming means includes at least one annular recess formed at least on one of the shaft and the sleeve, the bearing liquid being provided at an upper portion of the gap above the recess and at a lower portion of the gap below the recess to form a gas space for reducing viscosity resistance of the bearing liquid between the shaft and the sleeve. ### Claim 34 (depends on 33) A hydrodynamic bearing construction according to claim 33, further comprising means for communicating the gas space with the outer atmosphere. ### Claim 35 (depends on 31) A hydrodynamic bearing construction according to claim 31, wherein the communicating means includes at least one axially extending storage groove for communicating the bearing liquid by capillary action from one of the lower and upper portion of the gap to the other portion of the gap.