JP2009044903A - Fluid dynamic pressure bearing motor, and information recording and reproducing device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid dynamic pressure bearing motor which can suppress the vibration caused by its rotation and can be thinned, and to provide an information recording and reproducing device equipped with the same. <P>SOLUTION: The fluid dynamic pressure bearing motor 2 comprises a bearing member 1 having a radial bearing part 9a and a thrust bearing part 9b, each with dynamic pressure generation grooves formed and a rotor 6 having a bearing part 6A and a flange part 6B, and in which a lubricating fluid 10 is sealed so as to freely circulate. The bearing member 1 is equipped with a bypass-flow passageway for communicating mutual openings which are provided at a position, outwardly in the radial direction from the radial bearing part 9a in both end surfaces in the axial direction; in the rotor 6, the bearing part 6A and the flange part 6B are formed integrally; and the flange part 6B is equipped with a flat surface part 6c for receiving dynamic pressure and a groove part 6d, which is opposed to the opening part at one end surface in the axial direction of the bearing member 1 and serves as a recessed part to the flat surface part 6c, thereby forming the passage of the lubricating fluid 10 on the other end surface side, in the axial direction of the bearing member 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fluid dynamic bearing motor and an information recording / reproducing apparatus including the same.

Conventionally, for example, in an information recording / reproducing apparatus such as a hard disk drive or an optical disk drive, a fluid dynamic pressure bearing is sometimes used as a bearing in order to reduce the size, the thickness, and the rotational accuracy.
For example, in Patent Document 1, as such a fluid dynamic pressure bearing, a pressure release bypass passage that communicates two radial bearing portions is provided, and a dynamic pressure generating groove provided in each radial bearing portion is provided. Even if the shape (groove length), etc. is in an unbalanced state, an amount of lubricating fluid equivalent to the unbalanced pumping force resulting from the passage is passed through the bypass passage for pressure release, and the radial bearing portion on the high pressure side To the low pressure side radial bearing portion, and the pressure balance between the two radial bearing portions is achieved, so that the thrust bearing portion is not affected by the unbalanced state of the radial bearing portion. A hydrodynamic bearing device is described that prevents fluctuation of the flying height in the bearing portion.
In this dynamic pressure bearing device, an annular groove deeper than the dynamic pressure generating groove is formed in the opening on the thrust bearing portion side of the pressure release bypass passage, and the rotor surface opposed to the thrust bearing portion is configured by one plane. Has been. And the axial part of the rotor is protrudingly provided by this plane part.
JP 2004-11897 A

However, the fluid dynamic pressure bearing motor using the conventional fluid dynamic pressure bearing as described above has the following problems.
In the technique described in Patent Document 1, by providing the pressure release bypass passage, the influence on the thrust bearing portion due to the unbalanced state of the radial bearing portion can be eliminated. However, for example, if irregularities or burrs occur on the rotor surface facing the annular groove of the thrust bearing due to processing errors, etc., each time these irregularities or burrs cross the opening of the pressure release bypass passage, the opening A pressure fluctuation occurs, and dynamic pressure vibration corresponding to the number of openings in the pressure release bypass pipe is excited. As a result, for example, when this fluid dynamic bearing motor is used in an information recording / reproducing apparatus such as a hard disk drive, disturbance fluctuation such as RRO (Repeatable Run Out) synchronized with the rotation of the recording medium occurs, and information is read. , There is a problem of disturbing writing.
Although it is conceivable to increase the depth of the annular groove in the thrust bearing part to suppress pressure fluctuations due to irregularities and burrs that occur during processing, the radial bearing part is not long enough to reduce the moment rigidity of the bearing. There is a problem of end up. If the length of the radial bearing portion is to be secured, there is a problem that the thickness of the motor increases.
Further, it is conceivable to improve the processing accuracy of the rotor and reduce the occurrence of unevenness and burrs, but in this case, there is a problem that the manufacturing cost increases.

  The present invention has been made in view of the above-described problems, and is capable of suppressing the generation of vibration associated with rotation and reducing the thickness of the fluid dynamic pressure bearing motor and information recording including the fluid dynamic pressure bearing motor. An object is to provide a playback device.

In order to solve the above problems, the invention according to claim 1 includes a radial bearing portion and a thrust bearing portion in which dynamic pressure generating grooves are respectively formed on the inner peripheral surface and the axial end surface of the substantially cylindrical body. A space having a bearing member, a rotor having a shaft portion inserted into the radial bearing portion and a flange portion facing the thrust bearing portion, and the space between the radial bearing portion and the thrust bearing portion and the rotor; A fluid dynamic bearing motor in which a lubricating fluid is circulated so that the bearing member has openings provided at both ends in the axial direction at locations radially outward from the radial bearing. The rotor includes a shaft portion and a flange portion that are integrally formed, and the flange portion receives the dynamic pressure while facing the thrust bearing portion. A surface portion and an annular groove facing the opening at one end surface in the axial direction of the bearing member and serving as a recess with respect to the planar portion, and the opening at the other end surface side in the axial direction of the bearing member And the flow path of the said lubricating fluid is formed in the range which covers the said radial bearing part at least.
According to this invention, the shaft portion of the rotor and the plane portion of the flange portion are supported via the lubricating fluid between the radial bearing portion and the thrust bearing portion of the bearing member, respectively, and the radial bearing portion is started together with the start of rotation of the rotor. The bearing member is rotationally supported in a non-contact state by the dynamic pressure of the lubricating fluid generated in the dynamic pressure generating groove of the thrust bearing portion.
At that time, the annular groove provided in the rotor and the flow path of the lubricating fluid on the other end surface side in the axial direction of the bearing member are communicated with each other by the bypass flow passage provided in the bearing member. Lubricating fluid is filled in each of the passage, the flow path of the lubricating fluid on the other end surface side in the axial direction, and the inside of the radial bearing portion.
As a result, even if fluid pressure imbalance occurs in the axial direction of the radial bearing during rotation of the rotor, the lubricating fluid moves in the annular groove and the bypass flow passage, thereby reducing fluid pressure imbalance. .
In addition, since an annular groove serving as a recess with respect to the flat surface portion is provided opposite to the one opening portion of the bypass flow path, the space facing the opening portion is wider than the space facing the flat surface portion, and the vicinity of the opening portion is increased. Since the fluid pressure is less affected by the processing accuracy on the rotor side, vibration due to the processing accuracy of the rotor at the position facing the opening can be suppressed.
In addition, the annular groove is provided in the flange portion of the rotor in which the shaft portion and the flange portion are integrally formed together with the flat portion, so that compared with the case where the flat portion and the shaft portion are manufactured and then joined together. Thus, the groove depth of the annular groove can be increased. Therefore, the groove depth of the annular groove can be appropriately set without reducing the length of the radial bearing portion of the bearing member. As a result, it is possible to reduce the pressure fluctuation due to the machining error of the groove bottom surface of the annular groove, thereby reducing the vibration of the rotor.
In addition, since the annular groove serves as a clearance groove when processing the flat portion, the processing of the flat portion is facilitated.

According to a second aspect of the present invention, in the fluid dynamic bearing motor according to the first aspect, the annular groove is provided adjacent to a base end portion of the shaft portion.
According to the present invention, since the annular groove is provided at the base end portion of the shaft portion, it becomes a clearance groove when processing the shaft portion, so that the processing of the shaft portion is facilitated.

In the invention according to claim 3, in the information recording / reproducing apparatus, the fluid dynamic pressure bearing motor according to claim 1 or 2, the recording medium mounted on the fluid dynamic pressure bearing motor, and the recording medium, A recording / reproducing head that performs at least one of information reading and information writing.
According to the present invention, since the information recording / reproducing apparatus includes the fluid dynamic bearing motor according to the first or second aspect, the same effects as the first or second aspect of the invention can be achieved.

  According to the fluid dynamic pressure bearing motor and the information recording / reproducing apparatus including the same according to the present invention, since the annular groove facing the opening of the thrust bearing portion is provided on the rotor side, the radial bearing portion can be rotated without shortening. It is possible to suppress the occurrence of vibration and achieve an effect that the thickness can be reduced.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
A fluid dynamic bearing motor according to an embodiment of the present invention will be described together with an information recording / reproducing apparatus including the fluid dynamic bearing motor.
FIG. 1 is a schematic perspective view showing a schematic configuration of an information recording / reproducing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic axial sectional view showing a schematic configuration of the fluid dynamic bearing motor according to the embodiment of the present invention. Fig.3 (a) is a top view which shows schematic structure of the bearing member used for the fluid dynamic pressure bearing motor which concerns on embodiment of this invention. FIG.3 (b) is AA sectional drawing of Fig.3 (a). Fig.4 (a) is a bottom view which shows schematic structure of the rotor used for the fluid dynamic bearing motor which concerns on embodiment of this invention. FIG. 4B is a cross-sectional view taken along the line BB in FIG.

The hard disk drive 100 (information recording / reproducing apparatus) of this embodiment can be suitably used for a storage device of a personal computer, for example.
As shown in FIG. 1, the schematic configuration of the hard disk drive 100 includes a recording medium driving device 3 that rotationally drives a magnetic disk 4 (recording medium) in a housing 30, and a magnetic material that is rotationally driven by the recording medium driving device 3. A head that floats close to the disk 4 and reproduces an information signal composed of magnetic information on the magnetic disk 4 or records an information signal composed of an electrical signal input from the outside as magnetic information on the magnetic disk 4 31 (recording / reproducing head), a suspension beam 32 holding the head 31, a carriage 33 for moving the head 31 held by the suspension beam 32 in the radial direction on the magnetic disk 4, and control of each part of the hard disk drive 100. The control part 34 to perform is provided.
Although not particularly illustrated, for example, a known hard disk drive device configuration such as a cover for covering the housing 30 and a connection cable is naturally provided.

As shown in FIG. 2, the recording medium driving device 3 is configured by attaching a magnetic disk 4 to a motor 2 (fluid dynamic pressure bearing motor) having a fluid dynamic pressure bearing using a lubricating fluid 10.
As the lubricating fluid 10, oil or the like used for a known fluid dynamic pressure bearing can be appropriately employed.
The schematic configuration of the motor 2 includes a motor housing 8, a stator 5, a bearing member 1, and a rotor 6.
As long as the rotor 6 is supported by the bearing body 9 that constitutes the fluid dynamic pressure bearing, the stator 5 and the rotor 6 may be configured appropriately according to the type of the motor 2. For example, an inner rotor type or outer rotor type spindle motor can be employed. In the following, the case of an inner rotor type spindle motor will be described as an example.

  The motor housing 8 is formed into a flat bottomed cylindrical shape whose general shape opens to the upper side in the figure, and a cylindrical hole extending upward in the figure to stand the bearing member 1 on the upper side in the figure at the center of the bottom. Shaped bearing body fixing | fixed part 8a is provided. For this reason, a stator accommodating portion 8b that is an annular space for accommodating the stator 5 is formed between the inner surface of the outer wall of the motor housing 8 and the outer peripheral surface of the bearing body fixing portion 8a.

The stator 5 includes a stator core 5a and a coil 5b, and is fixed to a step-shaped fixing portion protruding from an inner peripheral surface and a bottom portion of the outer wall of the motor housing 8 at an outer edge portion of the stator core 5a.
The stator core 5a is a plate-like member in which a magnetic material such as a silicon steel plate is punched out by, for example, pressing, and the appropriate number of layers are laminated, and the surface of the laminated body is coated with an insulating film. The shape of the stator core 5a in a plan view is such that, for example, a tooth-pole portion in which a T-shaped projecting piece in a plan view is extended radially inward is formed to form a plurality of magnetic poles on the inner peripheral side of the annular core back portion. A plurality are provided at equal pitches in the direction. For example, a three-phase motor can be configured by setting the tooth pole portion to a multiple of 3, for example, nine.
The coil 5b is wound around each tooth pole portion of the stator core 5a. For example, in the case of configuring a three-phase motor, a three-phase coil is configured by winding every two of the nine tooth pole portions of the stator core 5a.
Each coil 5b is wired to a not-shown printed circuit board or the like, and is electrically connected to a control unit 34 that controls the coil current.

The bearing member 1 includes a bearing body 9 and a lid member 15 as shown in FIGS.
The bearing body 9 has a substantially cylindrical sleeve shape with an axial length H, and a flange portion 9f that slightly protrudes radially outward is provided at one axial end portion.
At the other end portion in the axial direction, a step hole portion 9g having a circular diameter larger than the inner diameter of the sleeve and having a diameter reduced in two steps from the other end surface toward the one end surface side is formed. For this reason, the sleeve inner peripheral surface of the bearing body 9 has an axial length h (however, between the one axial end surface of the bearing main body 9 and the bottom surface position of the stepped hole 9g inside the other axial end surface. , H <H).
The large-diameter hole portion of the step hole portion 9g constitutes a lid attachment portion 9d to which the lid member 15 is attached.

  Further, the outer shape of the intermediate portion in the axial direction of the bearing body 9 is reduced from a proximal end portion of the flange portion 9f toward the other end side in the axial direction, and then has a substantially constant diameter from the other end in the axial direction. The cylindrical surface is formed. The outer diameter of the cylindrical surface on the other end side is set to fit with the inner diameter of the bearing main body fixing portion 8a without any gap, and a fitting portion 9e for fixing the bearing main body 9 to the bearing main body fixing portion 8a is provided. It is composed.

When the rotor 6 rotates on the axial end surface of the flange portion 9f, a dynamic pressure is generated in the axial direction (thrust direction) by the lubricating fluid 10 interposed between the rotor 6 and FIG. As shown, a thrust bearing portion 9b having a plurality of dynamic pressure generating grooves 13 formed in a part of a smooth plane perpendicular to the axis is provided.
The shape of the dynamic pressure generating groove 13 can be provided in a known appropriate shape according to the rotation direction of the rotor 6 or the required dynamic pressure. For example, a configuration in which the groove width is reduced from the outer peripheral side to the inner peripheral side of the thrust bearing portion 9b and arranged in a spiral shape can be employed.

When the rotor 6 rotates on the sleeve inner peripheral surface of the bearing body 9, dynamic pressure is generated in the radial direction (radial direction) by the lubricating fluid 10 interposed between the rotor 6 and FIG. As shown in FIG. 2, a radial bearing portion 9a having a plurality of dynamic pressure generating grooves 14 formed in a part of a smooth cylindrical surface is provided.
The shape of the dynamic pressure generating groove 14 can be provided in a known appropriate shape according to the rotational direction of the rotor 6 or the required dynamic pressure. For example, as shown in FIG. 3B, well-known herringbone-type dynamic pressure generating grooves provided in two rows in the axial direction can be employed.

  In the vicinity of the outer peripheral side of the radial bearing portion 9a, a plurality of communication passages 9c (bypass flow passages) penetrating from the thrust bearing portion 9b to the bottom surface of the stepped hole portion 9g are provided concentrically with respect to the center of the radial bearing portion 9a. Yes. Although the number of the communication passages 9c may be one or more as appropriate, in the present embodiment, two are provided at positions facing each other across the central axis of the radial bearing portion 9a.

  As the material of the bearing body 9, for example, an appropriate material such as metal or ceramics can be adopted. In addition, the bearing body 9 may be formed integrally with the same material, for example, the radial bearing portion 9a and the thrust bearing portion 9b may be manufactured separately and assembled into a pair. .

As shown in FIG. 2, the lid member 15 is a plate-like member for sealing the other end side of the bearing body 9 in a liquid-tight manner, and is fixed to the lid mounting portion 9 d of the bearing body 9.
For this reason, the cover member 15 has a distance corresponding to the depth of the small-diameter hole portion of the step hole portion 9g to the two communication passages 9c that open to the bottom surface of the step hole portion 9g and the radial bearing portion 9a. They are arranged facing each other in a separated state.

  As shown in FIGS. 2 and 4, the schematic shape of the rotor 6 is inserted into the radial bearing portion 9a of the bearing body 9 in a state filled with the lubricating fluid 10, and the tip surface is a small-diameter hole having a stepped hole portion 9g. A shaft body portion 6A (shaft portion) substantially aligned with the bottom surface is provided, a flange portion 6B is extended radially outward from the proximal end side of the shaft body portion 6A, and the shaft body portion 6A extends from the outer edge portion of the flange portion 6B. A cylindrical sleeve portion 6C is extended in the axial direction on the distal end side, and an outer flange portion 6D is formed to extend radially outward from an intermediate portion of the outer surface of the sleeve portion 6C.

The inner diameter of the sleeve portion 6C is larger than the outer diameter of the bearing body fixing portion 8a of the motor housing 8, and the height of the sleeve portion 6C is such that the front end surface of the sleeve portion 6C has a sufficient clearance from the stator housing portion 8b. It is said that the height is high enough to be opposed.
Further, in the sleeve portion 6C, the outer diameter of the portion closer to the base end side than the position of the outer flange portion 6D is set to a size that allows the magnetic disk 4 to be positioned by fitting into the mounting hole of the magnetic disk 4. And constitutes a disk fitting portion 6 f which is a positioning boss for the magnetic disk 4.
In the sleeve portion 6C, the outer diameter of the portion on the distal end side with respect to the position of the outer flange portion 6D is set to a dimension that can be fitted into the drive magnet 7 facing the stator core 5a.

  The outer diameter of the outer flange portion 6D is such that the magnetic disk 4 is mounted on the upper surface side (upper side in FIG. 2), so that the disk mounting portion 6b composed of a plane orthogonal to the central axis of the shaft body portion 6A is formed It is a dimension which can fix the axial direction edge part of the drive magnet 7 to (lower side of FIG. 2).

  The drive magnet 7 is composed of an annular permanent magnet magnetized with a pattern in which the magnetic poles alternate in the circumferential direction, and is composed of the lower surface of the outer flange portion 6D and the outer peripheral surface of the sleeve portion 6C on the lower surface side of the outer flange portion 6D. It is fixed to the attaching portion 6g by, for example, adhesion. Thus, the radially inner tip portion of the stator core 5a of the stator 5 accommodated in the stator accommodating portion 8b is opposed to the magnetized portion of the drive magnet 7.

  On the central axis of the shaft body portion 6A, a screw hole 6a is provided from the flange portion 6B side. The screw hole 6a is obtained by positioning the magnetic disk 4 with the disk fitting part 6f and screwing the disk pressing member 12 made of, for example, a plate spring or the like with the fixing screw 17 in a state where the magnetic disk 4 is mounted on the disk mounting part 6b. It is for fixing.

The surface on the shaft body portion 6A side (the lower surface side in FIG. 2) of the flange portion 6B is orthogonal to the central axis of the shaft body portion 6A and is in a region radially outward from the opening of the communication passage 9c of the radial bearing portion 9a. Opposing annular flat surface portions 6c are provided. A groove 6d (annular groove) forming an annular recess with respect to the flat surface portion 6c is provided adjacent to the base portion of the flat surface portion 6c and the shaft body portion 6A.
The depth d of the groove 6d is set deeper than the dynamic pressure generating groove 13 provided in the radial bearing 9a. For example, the depth of about 0.05 mm to 0.1 mm is suitable for the dynamic pressure generating groove 13 of about 10 μm.
The outer diameter of the plane portion 6 c is slightly larger than the outer diameter of the flange portion 9 f of the bearing body 9. A cylindrical portion 6e that covers the radial side surface of the flange portion 9f in the axial direction is formed from the outer peripheral portion of the flat portion 6c toward the axial direction on the distal end side of the shaft body portion 6A.
On the radially outer side of the cylindrical portion 6e, there is a seating surface for fixing a retaining member 11 for retaining the rotor 6 and sealing the lubricating fluid 10 in the circumferential direction between the sleeve portion 6C and the base end portion. A retaining attachment portion 6h is formed.

As shown in FIG. 2, the retaining member 11 is fixed to the retaining mounting portion 6h, the inner diameter portion is located close to the lower side of the lower end surface of the flange portion 9f, and the inner peripheral surface is a bearing. It is an annular member having a substantially trapezoidal cross section, which is close to the taper portion in the vicinity of the flange portion 9 f of the main body 9. Thereby, the outer edge part of the flange part 9f of the bearing main body 9 can be covered close to the U-shaped cross section together with the flat part 6c and the cylindrical part 6e of the rotor 6.
For this reason, when the lubricating fluid 10 is sealed between the rotor 6 and the bearing body 9, the lubricating fluid 10 can be sealed by capillary action.

In this embodiment, such a rotor 6 is manufactured as an integral part by cutting a block of a metal material such as stainless steel.
For this reason, for example, it becomes easy to obtain the accuracy of the perpendicularity between the flat surface portion 6c and the shaft body portion 6A as compared with a construction method in which the shaft body portion 6A processed separately is fixed to the flange portion 6B.
Further, since the flange portion 6B and the shaft body portion 6A are integrated, even if the thickness of the flange portion 6B in the vicinity of the base end portion of the shaft body portion 6A is reduced compared to the above-described separate construction method, There is less influence on strength and accuracy. Therefore, when the groove 6d is set to a certain depth h, the thickness of the flange 6B can be made thinner than that in the separate construction method. As a result, the motor 2 can be thinned.

Further, according to the rotor 6 of the present embodiment, when the rotor 6 is cut, the groove portion 6d is formed adjacent to the base end portion of the shaft body portion 6A. Therefore, when the shaft body portion 6A is cut, The groove 6d can serve as a machining clearance groove. Since the shaft body portion 6A in the range of the depth d of the groove portion 6d does not face the radial bearing portion 9a, even if the processing accuracy of the shaft diameter and surface roughness is inferior, dynamic pressure formation is not affected. Therefore, the shaft body portion 6A can be easily processed.
Further, the groove 6d can also serve as a machining clearance groove when the flat portion 6c is cut. Therefore, it is not necessary to finish the corner portion where the flat surface portion and the shaft body portion intersect with each other like the case where the flat surface portion is provided up to the base end portion of the shaft body portion without providing the groove portion 6d. Since the body part 6A can be finished separately, processing becomes easy.

In the method of assembling the motor 2 having such a configuration, first, the lid member 15 is attached to the lid attaching portion 9d of the bearing body 9 to seal the other end surface side of the bearing body 9, and the sleeve of the bearing body 9 is A lubricating fluid 10 made of appropriate oil is introduced. On the other hand, after the drive magnet 7 is attached to the magnet attachment portion 6g, the shaft body portion 6A of the rotor 6 is inserted into the radial bearing portion 9a so that the flat portion 6c and the radial bearing portion 9a face each other. assemble.
At this time, as shown in FIG. 2, the lubricating fluid 10 in the sleeve of the bearing main body 9 is filled in the gap between the rotor 6 and the opposed surfaces of the bearing main body 9 and the lid member 15 and the communication path 9 c. For this reason, the lubricating fluid 10 is filled between the hole bottom surface of the stepped hole portion 9g, the tip end surface of the shaft body portion 6A, and the lid member 15, and between the groove portion 6d and the thrust bearing portion 9b, respectively. The lubricating fluid 10 on the thrust bearing portion 9b and the lubricating fluid 10 on the lid member 15 side communicate with each other through the passage 9c.
Next, the retaining member 11 is inserted from the fitting portion 9e side of the bearing body 9 and fixed to the retaining attachment portion 6h. Thereby, the lubricating fluid 10 is sealed between the fine gaps in the vicinity of the flange portion 9f.
In this way, a fluid dynamic bearing unit having the rotor 6 as a rotor is formed.

In this fluid dynamic pressure bearing unit, the lubricating fluid 10 is sealed between the bearing body 9 and the inner surface of the rotor 6, that is, between the thrust bearing portion 9 b and the radial bearing portion 9 a and the inner surface of the rotor 6. ing.
Since the bearing member 1 is provided with the two communication passages 9c, the flow path of the lubricating fluid 10 formed between the lid member 15 and the bottom of the stepped hole 9g of the bearing body 9 is The flow path formed between the thrust bearing portion 9b and the groove portion 6d communicates with each other. As a result, a flow path capable of communicating the lubricating fluid 10 between the one end side and the other end side of the radial bearing portion 9a is formed in a radially outer portion of the radial bearing portion 9a.

On the other hand, in the motor housing 8, the stator 5 is assembled in the stator housing portion 8b, and a printed board (not shown) or the like is attached. And the fitting part 9e of a fluid dynamic pressure bearing unit is fitted to the bearing main body fixing | fixed part 8a, and each is fixed.
In this way, the motor 2 is assembled.
Next, the magnetic disk 4 is attached to the disk mounting portion 6 b and fixed by the disk pressing member 12, thereby completing the recording medium driving device 3.

Next, the operation of the hard disk drive 100 of this embodiment will be described focusing on the operation of the motor 2.
The motor 2 rotates the rotor 6 when the coil current is supplied by the control unit 34. In the lubricating fluid 10 in the vicinity of the radial bearing portion 9a and the thrust bearing portion 9b, dynamic pressure is generated by the action of the dynamic pressure generating grooves 13 and 14, respectively. Therefore, the rotor 6 is floated and supported on the bearing body 9 in the axial direction and the radial direction via the lubricating fluid 10, and rotates while maintaining a non-contact state.
In general, if there is a machining error in the dynamic pressure generating groove 13 or the flat surface portion 6c, the dynamic pressure in the poorly machined portion of the thrust bearing portion 9b fluctuates at a rotational frequency or an integer multiple of the rotational frequency. In this embodiment, since the lubricating fluid 10 is communicated through the groove 6d and the bypass flow passage, the balance of dynamic pressure in the radial bearing portion 9a is caused. By this, it is possible to freely flow between one end side and the other end side of the radial bearing portion 9a. Therefore, the imbalance of the axial dynamic pressure of the radial bearing portion 9a can be reduced. For this reason, it is possible to reduce the vibration and the deterioration of the rotation accuracy due to the fluctuation of the dynamic pressure.

In the motor 2, the lubricating fluid 10 is communicated with the bypass flow passage by providing the groove 6 d on the rotor 6 side. For this reason, the axial length of the radial bearing portion 9a can be increased compared to the case where the annular groove portion is provided in the inner peripheral portion of the thrust bearing portion, and the moment rigidity of the bearing can be improved.
Further, as described above, the motor 6 can be made thin in combination with the rotor 6 having the shaft body portion 6A and the flange portion 6B formed integrally.

  In the above description, the thrust bearing portion of the bearing member has been described as an example in which the flat portion of the rotor and the annular groove are opposed to each other. However, the dynamic pressure generating groove of the thrust bearing portion opposed to the annular groove is Since it does not contribute much to the generation, the dynamic pressure generation groove may be provided only in the portion facing the plane.

Further, in the above description, the example in which the annular groove is provided only on the rotor side has been described, but when the axial length of the radial bearing portion can be sufficiently secured, the position facing the annular groove of the rotor, You may make it provide an annular groove also in a thrust bearing part.
FIG. 5 shows a motor 20 of such a modification. In the motor 20, instead of the thrust bearing portion 9b of the bearing body 9 of the motor 2, a thrust portion in which a groove portion 90d that is an annular groove and a spiral dynamic pressure generating groove similar to the thrust bearing portion 9b are formed from the inner peripheral side. The bearing part 90b is provided. Moreover, it replaces with the radial bearing part 9a, and the radial bearing part 90a from which only the length differs from the radial bearing part 9a is provided. According to such a structure, the inner surface (groove part 6d) of the flange part 6B facing the opening part of the communicating path 9c When the distance and space between the groove 6d and the groove 90d are set to a required size, the distance and space can be divided into the groove 6d and the groove 90d, so that the depth of the groove 6d is made shallower. can do. Therefore, the height of the flange portion 6B of the rotor 6 can be reduced.

  In the above description, the example in which the annular groove is provided adjacent to the proximal end portion of the shaft portion of the rotor has been described. However, when sufficient processing accuracy is obtained, the annular groove is formed at the proximal end portion of the shaft portion. An annular groove may be provided at a position spaced radially from the base end portion of the shaft portion of the rotor, leaving a flat portion adjacent thereto.

In the above description, the information recording / reproducing apparatus is described as an example of an apparatus capable of recording information signals and reproducing information signals. However, if the fluid dynamic pressure bearing motor of the present invention is provided, the information recording / reproducing apparatus may Signal recording or information signal reproduction may be performed.
The information recording / reproducing apparatus is not limited to a hard disk drive, and may be an apparatus using a recording medium other than a magnetic disk, such as an optical disk drive or a magneto-optical disk drive. Further, the recording medium may be provided detachably with respect to the fluid dynamic pressure bearing motor.

1 is a schematic perspective view showing a schematic configuration of an information recording / reproducing apparatus according to an embodiment of the present invention. 1 is a schematic axial sectional view showing a schematic configuration of a fluid dynamic bearing motor according to an embodiment of the present invention. It is a top view which shows schematic structure of the bearing member used for the fluid dynamic pressure bearing motor which concerns on embodiment of this invention, and its AA sectional drawing. It is the bottom view which shows schematic structure of the rotor used for the fluid dynamic pressure bearing motor which concerns on embodiment of this invention, and its BB sectional drawing. It is typical axial sectional drawing which shows schematic structure of the fluid dynamic bearing motor which concerns on the modification of embodiment of this invention.

Explanation of symbols

1 Bearing member 2, 20 Motor (fluid dynamic pressure bearing motor)
3 Recording medium drive 4 Magnetic disk (recording medium)
5 Stator 6 Rotor 6A Shaft (shaft)
6B Flange part 6c Plane part 6d Groove part (annular groove)
9, 90 Bearing body 9a, 90a Radial bearing portion 9b, 90b Thrust bearing portion 9c Communication path (bypass flow path)
10 Lubricating fluid 13, 14 Dynamic pressure generating groove 15 Lid member 31 Head (recording / reproducing head)
100 Hard disk drive (information recording / reproducing device)

Claims (3)

A bearing member having a radial bearing portion and a thrust bearing portion in which a dynamic pressure generating groove is formed on each of an inner peripheral surface and an axial end surface of the substantially cylindrical body, and a shaft portion inserted into the radial bearing portion and the thrust bearing A fluid dynamic pressure bearing motor in which a lubricating fluid is sealed in a space between the radial bearing portion and the thrust bearing portion and the rotor. There,
The bearing member is
Provided with bypass flow passages for communicating between openings provided in a radially outer portion from the radial bearing portion at both axial end faces;
The rotor is
The shaft portion and the flange portion are integrally formed,
The flange portion is opposed to the thrust bearing portion and receives a dynamic pressure, and
An annular groove facing the opening at the one end surface in the axial direction of the bearing member and serving as a recess with respect to the planar portion;
The fluid dynamic bearing motor according to claim 1, wherein a flow path of the lubricating fluid is formed in a range covering at least the opening and the radial bearing portion on the other end surface side in the axial direction of the bearing member.   The fluid dynamic bearing motor according to claim 1, wherein the annular groove is provided adjacent to a proximal end portion of the shaft portion. The fluid dynamic bearing motor according to claim 1 or 2,
A recording medium mounted on the fluid dynamic bearing motor;
An information recording / reproducing apparatus comprising: a recording / reproducing head that performs at least one of information signal recording and information signal reproduction on the recording medium.

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