Abstract:
An axial-gap type storage disk drive motor and storage disk drive configuration is disclosed. The motor includes a stator around retaining cylinder retaining a support sleeve, a storage-disk-carrying rotor, and radial and thrust bearings having striation patterns on the bearing surfaces to develop controlled radial and thrust load-bearing dynamic pressure in an intervening lubricating fluid. The thrust bearing is formed between the upper end of the support sleeve and the rotor. A set of salient poles projecting axially inward is furnished on a bottom face of the rotor hub, axially opposing the stator. The configuration establishes a reluctance type motor: energizing the stator magnetically attracts axially the salient poles on the rotor hub in imparting rotational power thereto. Meanwhile, the magnetic attractive force imparted in the rotor is designed to balance the thrust load-bearing pressure generated in the thrust bearing. The configuration enables the motor to be made thinner and eliminates the need for rotor magnets, curtailing the number of parts, reducing costs, and preventing magnetic contamination caused by magnetic powder/particles from the motor.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to motors for driving storage disks in order to drive, for example, hard disks and like storage disks, as well as to storage disk drive devices provided with the motors. In particular the present invention relates to a motor, and to a storage-disk drive device for rotary-driving storage disks with the motor, wherein fluid dynamic pressure bearings function to support the rotor rotatively against the stator element. 
     2. Description of Related Art 
     Motors, and storage-disk drive devices for rotary-driving storage disks with the motors, have been known conventionally wherein fluid dynamic pressure bearings are employed for relative, rotational support of a shaft and a sleeve member encompassing the shaft. 
     Japanese Laid-Open Patent Application No. 10-267036 discloses a storage disk drive motor used in a disk drive device. The disk drive motor includes a bracket, a cylindrical sleeve fixedly attached to the approximate center of the bracket, a shaft inserted within the sleeve, and a rotor hub fixed to one end of the shaft for integrally rotating with the shaft. A rotor magnet is attached to the inner peripheral surface of the rotor hub. A stator is disposed on the bracket so as to oppose the rotor magnet in the radial direction, and such that the magnetic centers of the rotor magnet and the stator are set apart axially, i.e., not coincident. As a means for supporting the radial load, the motor also has a pair of radial bearings formed by the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, at an axial separation. At the same time, as a means for supporting the thrust (axial) load, the motor also has a thrust bearing formed by an end face of the shaft, and a thrust plate that occludes the bottom portion of the sleeve and axially opposes the shaft end face. 
     When electric current is supplied to the stator in conventional disk-drive motors, a rotating magnetic field is generated between the rotor magnet and the stator, which rotates the rotor hub in a predetermined direction. When the rotor hub rotates, a lubricating fluid flows in a predetermined direction through dynamic-pressure generating grooves in the radial and thrust bearings, which develops dynamic pressure that supports the rotor hub axially against the shaft. 
     Further, by forming the thrust bearing portion on the end face of the shaft and the thrust plate only, pressure for supporting the thrust load acts unidirectionally only, in the axial direction. Meanwhile the magnetic centers of the rotor magnet and the stator are at an axial displacement, which compels a magnetic attractive force between the rotor magnet and the bracket, by which the magnetic attractive force and the thrust load-bearing pressure of the thrust bearing are balanced. 
     In conventional disk-drive devices, as in the foregoing, the magnetic attractive force between the rotor magnet and the stator is in balance with the thrust load bearing pressure acting in the axial direction unidirectionally only. Nevertheless, when the motor rotates at low speed, or is accelerating/decelerating, the thrust load bearing pressure does not balance the magnetic attractive force. Out of balance the magnetic attractive force is exaggerated and brings bearing component parts into contact, leading to their progressive detrition. As a result, the reliability of the motor deteriorates. 
     Personal computers employing storage disk drive devices driven by conventional motors continue to be made smaller and thinner. Thus the motors that rotate the storage disk in such disk drives presumably are to be made smaller and thinner as well. The magnetic attractive force acting between the stator and rotor magnet establishes a balancing mechanism between the two in their axial opposition. The axial positions and tilt of the stator and rotor magnet affect the magnetic attractive force, however, making this balancing mechanism unsuitable for thinner-type disk drive devices, which require high precision in assembly to maintain stability in device performance. 
     Other conventional fluid dynamic pressure bearings are known, such as is disclosed in Japanese Laid-Open Patent Application No. 10-69713. Therein a rotor magnet axially opposes the stator, and dynamic pressure-generating grooves are formed superficially on one end of the shaft, without a thrust plate being employed. 
     The motor employs fluid dynamic pressure bearings for rotary support of the rotor hub without contact. In this case, since the rotor magnet and stator are arranged in axial opposition, during rotation of the motor magnetic attractive and repulsive forces repeatedly occur, which destabilizes the rotor hub rotation. 
     Where these conventional motors thus requiring rotor magnets are employed in a hard-disk drive, magnetic powder or particles produced when the magnet is formed or during motor assembly is liable to stick to the recording surface of the storage disk that the motor drives, or to the disk magnetic data read/write head. This causes magnetic contamination that hinders correct reading and writing of data, or worse, destroys data recorded on the disk. Further, the expense of the magnet itself increases the cost of motors in which such magnets are used, and of storage disk drive devices employing the motors. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a thin storage disk drive motor. 
     Another object is to provide a storage disk drive motor that is simple in construction and operates with sufficient stability. 
     A further object of the present invention is to provide a storage disk drive motor which is manufactured and assembled easily. 
     A yet other object of the invention is to provide a storage disk drive motor the manufacturing costs of which are reduced. 
     A yet further object is to configure a storage disk drive motor for low electric-power consumption. 
     Further, an object of the present invention to configure a storage disk drive device furnished with a storage disk drive motor that is made thin, is readily manufactured and assembled, and moreover inexpensive, and at the same time is low power-consuming. 
     A still further object of the present invention is to provide a thin motor that is simple in construction and operates with high stability. 
     A still another object of the present invention is to provide a disk drive device which is thin and reliable due to thinness and stability of a disk drive motor provided therein. 
     A still other object of the present invention is to provide a thin reluctance motor that is simple in construction and operates with high stability. 
     A storage disk drive motor of the present invention is provided with: a stationary member; a rotary member on which at least one storage disk is loaded for rotating freely relative to the stationary member; and a thrust bearing generating thrust load-supporting pressure in response to rotation of the rotary member. A plurality of projections jutting axially inward is provided on the rotary member and a stator is provided on the stationary member so as to oppose axially the aforesaid plurality of projections. Electro-magnetic force arising due to energization and/or excitation in the stator magnetically attracts the rotary member axially inward. The thrust bearing generates thrust load-bearing pressure that acts axially outward only, which balances the magnetic attractive force by the stator for the rotary member and the thrust load-bearing pressure that develops in the thrust bearing. 
     The storage disk drive motor of the present invention is furnished with a plurality of salient poles jutting axially inward on the bottom face of the rotary member, and is organized in a so-called axial-gap type motor construction wherein the stator and the salient poles oppose axially. At the same time a so-called reluctance type motor construction is established, wherein the motor gains rotational power through excitation of the stator to magnetically attract the salient poles provided on the bottom face of the rotary member. Therefore, the electromotive force of the stator magnetically attracts the rotary member axially, balancing it with the thrust load-bearing pressure generated in the thrust bearing, acting axially outward only. In addition, rotor magnets being unnecessary for reluctance-type motors curtails the number of parts, reduces costs, and at the same time prevents magnetic contamination caused by magnetic powder and/or particles from the motor from occurring. 
     Preferably, the salient poles are formed integrally with the rotary member, which is made from a magnetic material. Wherein the rotary member is to be made from an non-magnetic material, the salient poles can be formed by laminating a plurality of thin, wafer-shaped magnetic elements, fitted with a means for fastening them to the bottom face of the rotary member. 
     Forming the thrust bearing between the upper end-face of a sleeve of the stationary member and the bottom face of the rotary member also enables slimming down of the storage disk drive motor, while maintenance of posture—e.g., of the core deflection—when the rotary member rotates is controlled with a radial bearing generating radial load-supporting pressure in response to rotation of the rotary member. 
     Furthermore, the rotary member positioned in the upper portion of the motor comprises a part of the thrust bearing. Therefore, posture-control during rotation is facilitated compared with the situation in which rotation is supported by a shaft descending from the rotary member—for example, such as wherein a thrust plate is utilized. At the same time, susceptibility to margin of error in the elements comprising the thrust bearing, as well as in the precision and strength of the shaft and the rotary member connections, is slight, which facilitates assembly and enables improved productivity of the motors. Further, within the tolerance ranges of the superficial precision of the rotary member bottom face, and of the sleeve upper end face that compose the thrust bearing, the micro-gap between the thrust bearing can be set smaller (narrower). This boosts bearing rigidity of the thrust bearing, and improves the thrust load-bearing pressure. 
     Employing the foregoing storage disk drive motor, moreover, enables a storage disk drive device of the present invention to be slimmed, readily manufactured and assembled, lowered cost, and low power-consuming. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical section view schematically illustrating principal component configuration in a storage disk drive device of the present invention; 
     FIG.  2 (A) is a plan view schematically illustrating the stator of a storage disk drive motor employed in a storage disk drive device of the present invention; 
     FIG.  2 (B) is a plan view schematically illustrating salient poles of a storage disk drive motor employed in a storage disk drive device of the present invention; 
     FIG. 3 is a schematic circuit diagram of a drive circuit for a storage disk drive motor employed in a storage disk drive device of the present invention; 
     FIG. 4 is a vertical section view outlining a principal component configuration of a storage disk drive motor employed in a storage disk drive device of the present invention in a first embodiment; 
     FIG. 5 is a fragmentary section view illustrating a specific example of a radial bearing for the motor shown in FIG. 4; 
     FIG. 6 is a fragmentary section view illustrating a specific example of a thrust bearing for the motor shown in FIG. 4; 
     FIG. 7 is a fragmentary section view illustrating another specific example of a radial bearing for the motor shown in FIG. 4; 
     FIG. 8 is a fragmentary vertical section view outlining a principal component configuration of bearing sections in a storage disk drive motor employed in a storage disk drive device of the present invention in a second embodiment; 
     FIG. 9 is a fragmentary section view illustrating a specific example of a radial bearing for the motor shown in FIG. 8; 
     FIG. 10 is a fragmentary section view illustrating a specific example of a thrust bearing for the motor shown in FIG. 8; 
     FIG. 11 is a fragmentary section view illustrating another specific example of a radial bearing for the motor shown in FIG. 8; 
     FIG. 12 is a fragmentary section view illustrating another specific example of a thrust bearing for the motor shown in FIG. 8; and 
     FIG. 13 is a fragmentary section view illustrating still another specific example of a radial bearing for the motor shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings the following explains embodiments of a storage disk drive device in connection with the present invention; the present invention is not, however, limited to the respective embodiments illustrated below. 
     FIG. 1 is a vertical section view schematically illustrating a configurational outline of chief parts in a storage disk drive device of the present invention. 
     Referring to FIG. 1, the storage disk drive device is provided with: a base element  202  on which the storage disk drive motor is supported; a housing  200  formed by the base element  202  and an upper cover  206 , and in turn forming a clean chamber  204  for accommodating the storage disk drive motor; and a clamp element  212  fixed by a screw  210  to the rotor hub of the storage disk drive motor for retaining a storage disk such as a hard disk carried by the rotor hub of the storage disk drive motor. 
     FIG.  2 (A) and  2 (B) depict the stator and salient poles of a storage disk drive motor employed in the storage disk drive device of the present invention shown in FIG.  1 . 
     As shown in FIG.  2 (A), six magnetic poles wound with stator windings  216 ,  218 ,  220 ,  222 ,  224  and  226  are disposed evenly spaced circumferentially to compose the stator  214  for the storage disk drive motor of the present invention. A later-described rotor hub provided with salient poles  228 ,  230 ,  232  and  234  shown in FIG.  2 (B) axially opposes the stator  214 , wherein an axial-gap type reluctance motor is configured. Also, each pair of the stator windings  216  and  222 ,  218  and  224 , and  220  and  226  are respectively connected in series with each other in the same direction, constituting triple-phase stator windings. 
     Electric current staggered by 120° phases sequentially energizes the stator winding pairs  216  and  222 ,  218  and  224 , and  220  and  226  on the stator  214  configured in the foregoing manner, which forms a rotating magnetic field around the magnetic poles of the stator  214 . In the magnetic attraction of the salient poles  220  through  234  to the rotating magnetic field, the rotor hub follows the switching of the stator windings being energized, rotating about its axis of rotation. 
     FIG. 3 depicts a drive circuit for controlling energization of the stator windings  216  through  226  of the stator  214 . 
     The drive circuit  236 , as shown in FIG. 3, is provided with: transistor Tr 1  connected in series to stator windings  216  and  222 ; transistor Tr 2  connected in series to stator windings  218  and  224 ; transistor Tr 3  connected in series to stator windings  220  and  226 ; and a control circuit  238  that controls switching the transistors Tr 1  through Tr 3  ON/OFF. Further, a direct-current power source E is connected respectively to each of the series circuits for the stator windings  216 ,  222  and transistor Tr 1 , the stator windings  218 ,  224  and transistor Tr 2 , and the stator windings  210 ,  222  and transistor Tr 3 . 
     Further, control terminals  238   a,    238   b  and  238   c  are associated with control circuit  238 . When a control signal is input to control terminal  238   a,  transistor Tr 1  is conductive (ON) while the signal is being input; transistors Tr 2  and Tr 3  are ON while a control signal is input to control terminal  238   b  and to control terminal  238   c,  respectively. Accordingly, the stator winding connected to the ON transistor is energized. Also, to prevent transistor breakdown by the reverse electromotive force induced in the stator windings when the transistors go OFF from ON, it is preferable to have a protection diode connected in parallel to each transistor. 
     The following describes, with reference to FIG. 4 through 13, a storage disk drive motor employed in the storage disk drive device illustrated in FIG.  1 . 
     FIG. 4 is a vertical section view schematically illustrating a configurational outline of chief parts in a storage disk drive motor  1  employed in the storage disk drive device according to a first embodiment of the present invention. 
     The storage disk drive motor  1  in FIG. 4 includes a rotor hub  2  and a shaft  4 . The rotor hub  2  is composed of: an approximately disk-shaped upper wall portion  2   a;  a cylindrical circumferential wall portion  2   b  depending from the periphery of the upper wall portion  2   a;  and a flange portion  2   c  projecting radially outward from the lower end of the circumferential wall portion  2   b  to support the storage disk  208 , which is indicated in FIG. 4 by phantom lines. The shaft  4  constitutes part of a rotary component. One end of the shaft  4  is fixedly fitted in the central portion of the upper wall portion  2   a  of the rotor hub  2 . A support sleeve  6 , a hollow cylindrical element, rotatively supports the shaft  4 . The support sleeve  6  may be relatively thinner axially than would appear from the figures. A retaining cylinder  10  retains the support sleeve  6 ; the retaining cylinder  10  is anchored into a bracket  12  centrally. The bracket  12  is attached to the base element  202 , shown in FIG.  1 . Disk-shaped cover  8  is engage-fitted into the retaining cylinder  10  at the lower end of the inner periphery of the support sleeve  6 , closing off the opening on one side of the hollow cylindrical support sleeve  6 . 
     A lubricating fluid such as lubrication oil is retained in the micro-gaps formed between the upper wall portion  2   a  of the rotor hub  2 , the shaft  4 , the support sleeve  6 , and the cover  8  by capillarity. Radial bearing portions  19  and  20  are configured for generating radial load-bearing pressure in the lubricating fluid  14  by the action of radial dynamic pressure-generating grooves  16  and  18 . Indicated in FIG. 4 by hidden lines, the grooves  16  and  18  are formed on the inner circumferential surface of the support sleeve  6  radially opposing the outer circumferential surface of the shaft  4 . Furthermore, a thrust bearing portion  24  is configured for generating thrust load-bearing pressure in the lubricating fluid  14  by the action of thrust dynamic pressure-generating grooves  22 . Indicated in FIG. 4 by hidden lines, the grooves  22  are formed on the bottom face of the upper wall portion  2   a  axially opposing the upper end face of the support sleeve  6 . 
     The radial dynamic pressure-generating grooves  16  and  18  as well as the thrust dynamic pressure-generating grooves  22  are for convenience indicated by hidden lines in FIG. 4, but their specific shapes/configurations will later be described in detail with reference to the drawings. 
     The salient poles  228  through  234 , depicted in FIG.  2 (B), are formed spaced at regular circumferential intervals on the underside of the upper wall portion  2   a  of the rotor hub  2 , from which they project axially downward to oppose axially, at a gap, the stator windings  216  through  226  of the stator  214 , depicted in FIG.  2 (A). With the shaft  4  supported within the element  6  and the cover  8 , the salient poles  228  through  234  cooperate with the stator windings  216  through  226  to drive the rotor hub  2  and the shaft  4 . 
     In the storage disk drive motor, the stator windings  216  through  226  of the stator  214 , as being energized in the manner described above magnetically attract the salient poles  220  through  234 . Tailing the switching as the FIG. 3 drive circuit  236  energizes the windings, the rotor hub  2  rotates on its axis of rotation. Sliding wear can arise from the components that form the radial bearing portions  19  and  20  and the thrust bearing portion  24  contacting at motor actuation/halting and during low-speed rotation when sufficient load-bearing pressure cannot be generated. To reduce sliding wear, the electromagnetic force by the stator  214  attracting the three salient poles is preferably controlled by intermittent energization of or low-current supply to the stator windings  216  through  226 , during the period until the rotor hub  2  reaches a predetermined number of revolutions. 
     The salient poles  228  through  234  are formed integrally with the rotor hub  2  out of a magnetic material, or can be prepared by such means as fastening on the rotor hub  2  salient poles formed by laminating a plurality of thin, wafer-shaped magnetic elements. 
     The support sleeve  6  is formed from metallic material such as copper/copper alloy, or stainless steel. In order to communicate the radial bearing portions  19  and  20  with the external atmosphere, first and second ventilation bores  30  and  32  are formed in the support sleeve  6 . The first ventilation bore  30  is formed in the radial direction so as to open on the outer circumferential surface, exposing the radial bearing portions  19  and  20  and the support sleeve  6  to the open air. The second ventilation bore  32  opens on the lower end axially of the radial bearing portion  19 . An annular depression  34  is formed at the position where the first ventilation bore  30  opens on the inner circumferential surface of the support sleeve  6 , meanwhile forming an air intervention  36  for mediating air in between the annular depression  34  and the outer circumferential surface of the shaft  4 . The radial bearing portions  19  and  20  are axially separated by the air intervention  36 . Further, the second ventilation bore  32  is connected to a communicating channel  38  formed in the axial direction so as to open at the upper end face of the support plate  6 . 
     The radial bearing portions  19  and  20  are liberated to the external atmosphere by the first ventilation bore  30  and the second ventilation bore  32 , as well as the communicating channel  38 . Bubbles are liable to appear in the lubricating fluid  14  intervening in the radial bearing portions  19  and  20  when the lubricant fluid  14  is filled in the micro-gaps, or when the fluid  14  is agitated by the grooves  16 , which are herringbone shaped, and the grooves  18 , which are spiral shaped, during rotation of the motor. The bubbles discharge to the exterior of the bearing through the first and second ventilation bores  30  and  32  as well as the communicating channel  38 , thus preventing the lubricating fluid  14  from leaking out to the exterior of the bearing by thermal expansion of the bubbles due to temperature elevation in the motor. 
     A circular projection  2   d,  furthermore, is formed on the bottom face of the upper wall portion  2   a  of the rotor hub  2 , opposing the circumferential surface of the support plate  6  at a spacing. At the radially outward end of the thrust bearing portion  22 , a tapered seal  40  is provided that is a sealing structure formed cooperatively by the circular projection  2   d  and the support sleeve  6 . 
     Moreover, an annular notch  4   a  is formed on the lower end of the shaft  4 . A ring element  42  is fastened into the annular notch  4   a,  protruding radially outward from the circumferential surface of the shaft  4 . An annular recess  6   a  is formed in the inner circumferential surface of the support sleeve  6  at a position opposing the ring element  42 . The annular recess  6   a  accommodates the ring element  42  to form a structure that prevents the shaft  4  from slipping out. Further, the ring element  42  is attached to the shaft  4  projecting axially somewhat lower than the lower end of the shaft  4 . And the micro-gap between the end face of the shaft  4  and the cover  8  is set comparatively larger than the micro-gaps between the other components, and functions as a reservoir for the lubricating fluid  14 . Accordingly, it should be understood that neither the ring element  42  nor the surfaces defining the micro-gap between the end face of the shaft  4  and the cover  8  function to provide thrust load-bearing pressure during rotational operation of the motor. 
     Through the foregoing configuration accordingly: with energization in the stator windings  216  through  226  the set of salient poles  228  through  234  provided on the bottom face of the rotor hub  2  is magnetically attracted; the rotor hub  2  and the shaft  4 , in response to the switching as the control circuit  236  shown in FIG. 3 energizes the windings, are rotationally driven within the support sleeve  6  and the cover  8 ; in the thrust bearing portion  24 , by rotation of the rotor hub  2 , the lubricating fluid  14  in the gap between the rotor hub  2  upper wall portion  2   a  and the support sleeve  6  generates, by the action of the herringbone grooves  22  a thrust load-bearing pressure acting axially outward only; in the radial bearing portions  19  and  20 , furthermore, with the rotation of the shaft  4 , the lubricating fluid  14  in the gap between the shaft  4  and the support sleeve  6  generates a radial load-bearing pressure by the action of the herringbone grooves  16  and the spiral groves  18 . 
     Therein, the magnetic attractive force toward the bracket  12  (axially inward) that is imparted to the rotor hub  2  and the shaft  4  by the stator  214 , and the thrust load-bearing pressure generated in the thrust bearing portion  24  balance into equilibrium. 
     As described in the foregoing, the thrust bearing portion  24  is provided between the upper wall portion  2   a  of the rotor hub  2  and the support sleeve  6 . The configuration is such that the magnetic attractive force in the rotor hub  2  due to the stator  214  balances buoyancy in the rotary component (the rotor hub  2 , the shaft  4 , etc.) that the thrust bearing portion  24  generates. It is therefore unnecessary to configure the thrust bearing to generate thrust load-bearing pressure upward and downward in the vertical direction along the axis as in conventional structures, thereby reducing the bearing-constituting components that demand precision manufacturing, which facilitates managing the production process and serves to lower the cost of the storage disk drive motor. 
     Moreover, using a reluctance motor as a storage disk drive motor wherein the motor drive power is gained by magnetically attracting a ferromagnetic material makes rotation of the rotor hub  2  stable, and improves the rotation characteristics—compared with permanent magnet motors wherein during rotation magnetic attraction and repulsion repeat continually. 
     In addition, absence of a permanent magnet avoids magnetic contamination due to magnetic powder or particles produced when the permanent magnet is formed, or wherein the motor is assembled. This particularly suits storage disk drive devices such as hard disk drives, which require clean space, and at the same time reduces the number of parts and lowers cost. 
     With reference to FIG.  5  through FIG. 7, the following describes in detail the specific shape and form of the radial dynamic-pressure generating grooves  16  and  18  as well as the thrust dynamic pressure generating grooves  22 , indicated by hidden lines in FIG. 4, and formed in the radial bearing portions  19  and  20  as well as the thrust bearing portion  24 . 
     As radial dynamic-pressure generating grooves  18 , in FIG. 5 spiral striations are formed in the upper radial bearing portion  20 , for urging lubricating fluid  14  toward the thrust bearing portion  24  when the rotor hub  2  and the shaft  4  rotate. Further, herringbone striations are formed in the lower radial bearing portion  19  as radial dynamic-pressure generating grooves  16 . Spiral upper-side grooves  16   a  and spiral lower-side grooves  16   b  having roughly the same length in the axial direction, connected by bends  16   c,  are for urging lubricating fluid  14  from either direction toward the bends  16   c  when the rotor hub  2  and the shaft  4  rotate. 
     Now, as shown in FIG. 6 so-called pump-in type spiral striations are formed in the thrust bearing portion  24  as thrust dynamic-pressure generating grooves  22 , for urging lubricating fluid  14  toward the shaft  4 —in other words, in the direction of the upper radial bearing portion  20 —when the rotor hub  2  and shaft  4  rotate. 
     Herein, by the action of the upper radial bearing portion  20  and thrust bearing portion  24 , the pressure of the lubricating fluid  14  sustained in the gap continuing from the thrust bearing portion  24  to the upper radial bearing portion  20  is highest adjacent the boundary between the two. Conversely, the pressure is lowest in the lubricating fluid  14  maintained adjacent the axial lower end of the upper radial bearing portion  20 , as well as adjacent the outer end radially of the thrust bearing portion  24 . Therefore, bubbles remaining in the lubricating fluid  14  sustained in the upper radial bearing portion  20 , the thrust bearing portion  24 , and at the boundary between them, gradually travel through the first ventilation bore  30  and tapered seal  40  to the low-pressure region just described. The bubbles are discharged to the exterior and prevented from remaining in the lubricating fluid  14 . 
     The radial dynamic-pressure generating grooves  18  shown in FIG. 5 in the upper radial bearing portion  20  are constituted from spiral striations. Instead, as shown in FIG. 7 the radial dynamic-pressure generating grooves  18  can be herringbone striations wherein spiral upper-side grooves  18   a   1  and spiral lower-side grooves  18   b   1  are connected by bends  18   c   1 , with the lower-side grooves  18   b   1  being axially longer than the spiral upper-side grooves  18   a   1 . The bends  18   c   1  are axially biased (asymmetrical in the axial direction) so as to urge lubricating fluid  14  toward the thrust bearing portion  24  when rotor hub  2  and shaft  4  rotate. And the radial dynamic-pressure generating grooves  16  on the lower radial bearing portion  19  can be herringbone striations. Spiral upper-side grooves  16   a   1  and spiral lower-side grooves  16   b   1  that are of roughly the same axial length are connected by bends  16   c   1 , and urge lubricating fluid  14  from either direction toward the bends  16   c  when the rotor hub  2  and the shaft  4  rotate. 
     With reference to FIG. 8 the following explains a second embodiment of the present invention. 
     FIG. 8 is fragmentary vertical section view schematically showing an outline of the chief-part configuration of bearing components in a storage disk drive motor of the present invention in a second embodiment. Elements that effect the same operations/results as corresponding elements in FIG. 4 are marked identically, and their explanation is omitted. 
     The configuration of the storage disk drive motor shown in FIG. 8 is approximately the same as that of the foregoing first embodiment of the present invention. In a storage disk drive motor of the present invention in the second embodiment, however, the hollow cylindrical support element  46  that rotatively supports the shaft  44  is formed from a porous, oil-containing metallic material. The lubricant-impregnated material is obtained by pressure forming and sintering machining-powdered graphite/cast iron flakes. In this case, formed in the support element  46  is an annular recess  46   a  that which receives a ring element  42  fit in an annular notch  44   a  on the shaft  44 , forming a structure that stops the shaft  44  from slipping out. Also, in FIG. 8, likewise with FIG. 4 in illustrating a motor in the first embodiment of the present invention, radial dynamic pressure-generating grooves  48  and thrust dynamic pressure-generating grooves  52  are for convenience indicated by hidden lines. Their specific shapes/configurations will later be described in detail with reference to the drawings. 
     A blanking (blinding) process may be applied to at least the portion of the upper end face of the support element  46  that faces the thrust dynamic pressure-generating grooves  52  and constitutes the dynamic pressure-acting face of the support element  46 , i.e., part of a thrust bearing portion  54 . Blanking may also be applied to at least the portion of the inner circumferential surface of the support element  46  that faces the radial dynamic pressure-generating grooves  48  and constitutes a radial bearing  50  portion. The dynamic pressure generated as such acts as a load-bearing pressure. The process of blanking the dynamic pressure-acting face may be carried out by such means as compressing an oil-impregnated metallic material, impregnation-hardening a synthetic polymer, or plating. 
     Forming the support element  46  from the porous, oil-impregnated metallic material as described above enables communication of the radial bearing  50  portion with the outer atmosphere via holes within the oil-impregnated metallic material. This therefore renders unnecessary a separate communicating channel or like configuration for communicating the radial bearing portion  50  with the outer air. Like the first embodiment of the present invention illustrated in FIG. 4, when filling with the lubricating fluid  14  or when the motor is rotating, bubbles generated within the lubricating fluid  14  sustained in the radial bearing portion  50  are discharged to the bearing exterior through the holes. This prevents the lubricating fluid  14  from leaking out to the exterior of the bearing by, due to temperature elevation in the motor, thermal expansion of the bubbles. Thus the motor configuration is further simplified, which serves in cost reduction. 
     Further, blanking the dynamic pressure-acting face of the support element  46  prevents load-bearing pressure generated in the radial bearing portion  50  and the thrust bearing portion  54  from escaping to the exterior of the bearing, without compromising the firmness of the bearing. 
     In addition, forming the support element  46  from the oil-impregnated metallic material further reduces sliding wear arising from the components configuring the radial bearing portion  50  and the thrust bearing portion  54  contacting when the motor rotates at low speed, or is accelerating/decelerating and when sufficient load-bearing pressure cannot be generated. 
     With reference to FIG.  9  through FIG. 13, the following describes in detail the specific shape and form of the radial bearing portion  50  and the thrust bearing portion  54 , as well as the radial dynamic-pressure generating grooves  48  and the thrust dynamic pressure generating grooves  52 , indicated by hidden lines in FIG. 8, formed in the respective radial bearing portions  50  and  54 . 
     For the radial bearing portion  50  in FIG. 9, herringbone striations  481  and  482  are furnished as a pair separated in the axial direction. Spiral upper-side grooves  48   a   1  and spiral lower-side grooves  48   b   1  set to be longer axially than the spiral upper-side grooves  48   a   1 , connected by bends  48   c   1  are formed in the upper radial bearing portion  501  as radial dynamic pressure-generating grooves  48 . These herringbone striations  481  are axially biased (asymmetrical in the axial direction) toward the bends  48   a   1  so as to urge lubricating fluid  14  toward the thrust bearing portion  54  when the rotor hub  2  and the shaft  44  rotate. Spiral upper-side grooves  48   a   2  and spiral lower-side grooves  48   b   2  having roughly the same length axially, connected by bends  48   c   2 , are formed in the lower radial bearing portion  502  as radial dynamic pressure-generating grooves  48  also. These herringbone striations  482  are for urging lubricating fluid  14  from either direction toward the bends  48   c   2  when the rotor hub  2  and the shaft  44  rotate. Further, as shown in FIG. 10, so-called pump-in type spiral striations are formed in the thrust bearing portion  54  as thrust dynamic-pressure generating grooves  52 , for urging lubricating fluid  14  toward the shaft  44 —in other words, in the upper radial bearing portion  501  direction—when the rotor hub  2  and shaft  44  rotate. 
     Herein, as indicated by diagonal lines in FIG. 9, the blanking process on the support element  46  formed from the oil-impregnated metallic material is effected on the surface continuing from the thrust bearing portion  54 —wherein the pressure within the lubricating fluid  14  is high due to the action of the upper radial bearing portion  501  and the thrust bearing portion  54 —to the upper radial bearing portion  501 . The surface corresponding to the herringbone striations  482  for the lower radial bearing portion  502  is also blanked. 
     In the manner depicted in FIG. 11, spiral upper-side grooves  48   a   3  and spiral lower-side grooves  48   b   3  having roughly the same length axially, connected by bends  48   c   3  can be formed on the upper radial bearing portion  503  as radial dynamic pressure-generating grooves  48 . These herringbone striations  483  are for urging lubricating fluid  14  from either direction toward the bends  48   c   3  when the rotor hub  2  and the shaft  44  rotate. Spiral upper-side grooves  48   a   4  and spiral lower-side grooves  48   b   4  having roughly the same length axially, connected by bends  48   c   4  can be formed on the lower radial bearing portion  504 , also as radial dynamic pressure-generating grooves  48 . These herringbone striations  484  are for urging lubricating fluid  14  from either direction toward the bends  48   c   4  when the rotor hub  2  and the shaft  44  rotate. At the same time, as shown in FIG. 12, herringbone striations can make up the thrust dynamic pressure-generating grooves  52 . Spiral outer-side grooves  52   a  and spiral inner-side grooves  52   b  having roughly the same radial length are connected by bends  52   c,  and urge lubricating fluid  14  from either direction toward the bends  52   c  when the rotor hub  2  and the shaft  44  rotate. 
     Herein, as indicated by diagonal lines in FIG. 11, the blanking process on the support element  46  formed from the oil-impregnated metallic material is effected on the surfaces corresponding to the upper/lower radial bearing portions  503  and  504 , as well as to the respective dynamic pressure-generating grooves  483 ,  484  and  52  of the thrust bearing portion  54 . 
     In the foregoing specific examples illustrated in FIG. 9 and 11, the configuration described is one in which the radial bearing portions are furnished as an axially separated pair; it may, however, be one in which, as is shown in FIG. 13, only one radial bearing  50  is furnished. Herein, the radial dynamic pressure-generating grooves  48  in the radial bearing  50  may be formed as upper spiral grooves  48   a   5  and lower spiral grooves  48   b   5  having roughly the same length in the axial direction, connected by bends  48   c   5 . These herringbone striations develop dynamic pressure within the lubricating fluid  14  by urging the lubricating fluid  14  from either direction toward the bends  48   c   5  when the rotor hub  2  and the shaft  44  rotate. And thrust dynamic pressure-generating grooves  52  in the thrust bearing  54  may be utilized, the thrust dynamic pressure-generating grooves  52  constituted from herringbone striations for urging lubricating fluid  14  toward the bends  52   c  depicted in FIG.  12 . 
     Herein, as indicated by diagonal lines in FIG. 13, the blanking process on the support element  46  formed from the oil-impregnated metallic material is effected on the surfaces corresponding to the radial bearing portions  50  and the thrust bearing portion  54 , as well as to the respective dynamic pressure-generating grooves  48  and  52 . 
     The above embodiments of the present invention were described taking as an example the type of storage disk drive device in which the storage disk drive motor bracket  12  is mounted on a base element  202  in the storage disk drive device. Needless to say, the present invention may otherwise be applied in a so-called integral-base type storage disk drive device, in which a dual-functioning storage disk drive device base element  202  also serves as the bracket  12 . 
     Further, the fluid intervening among the radial bearing portions  19 ,  20  and  50 , and the thrust bearing portions  24  and  54  may be selected to suit from among air, lubricating oils and magnetic fluids, in accordance with the weighted support pressure and viscosity requirements. 
     The storage disk drive motor of the present invention establishes a so-called axial-gap type motor configuration wherein a plurality of salient poles projecting axially inward is provided on a rotary component containing a rotor hub. The stator provided on a stationary member and the salient poles are opposed in the axial direction. At the same time a so-called reluctance-type motor configuration is established, in which motor-rotating power is gained by exciting the stator to magnetically attract the salient poles provided on the rotary component. Therefore, the electromagnetic force of the stator magnetically attracting the rotor hub in the axial direction balances the thrust load-bearing force generated in the thrust bearing portions and acting axially outward only. The thrust load-bearing force is thus compensated. In addition, the fact that a rotor magnet is unnecessary in a reluctance-type motor reduces the number of parts and lowers the cost, and at the same time prevents magnetic contamination caused by motor magnet powder from occurring. 
     Moreover, as a storage disk drive motor, an axial-gap type reluctance motor constituted from salient poles provided on a rotary component, with which the stator is opposed axially, is employed. Thereby, the electromagnetic force of the stator magnetically attracting the rotor hub in the axial direction balances the thrust load-bearing force generated in the thrust bearing portions that acts axially outward only, thus compensating thrust load-bearing force. At the same time, the fact that a rotor magnet is unnecessary in a reluctance-type motor reduces the number of parts and lowers the cost, and meanwhile prevents magnetic contamination caused by motor magnet powder from occurring. 
     Various details of the present invention may be changed without departing from its spirit or its scope. Furthermore, the foregoing description of the embodiments according to the present invention is provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.