JP2010112531A - Hydrodynamic pressure bearing device and motor with the bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrodynamic pressure bearing device surely reducing sliding abrasion during starting and stoppage. <P>SOLUTION: A shaft member 2 rotatably supported by a housing 7 and a bearing sleeve 8 includes a shaft part 21, and a flange part 22 integrally or separately provided on a lower end of the shaft part 21. One magnetic pole 23 constituting a part of the flange part 22 is formed by a permanent magnet, and the other magnetic pole 11 is attached in a position for generating magnetic force in the thrust direction between the one magnetic pole 23 and it, for example, a lower end surface side of a bottom 7b of the housing 7. The other magnetic pole 11 forms an electromagnet, and includes a magnetic core 12, and a coil 13 wound around the magnetic core 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluid dynamic bearing device and a motor equipped with the bearing device.

  The fluid dynamic bearing device supports a shaft member or a bearing member in a relatively rotatable manner via a fluid film generated in a bearing gap. This type of bearing device is particularly excellent in rotational accuracy, quietness, etc. during high-speed rotation, and is suitably used as a bearing device for motors mounted on various electrical devices including information devices. Specifically, as a bearing device for a spindle motor in magnetic disk devices such as HDD, optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, magneto-optical disk devices such as MD and MO, etc. Alternatively, it is preferably used as a bearing device for a motor such as a polygon scanner motor of a laser beam printer (LBP), a color wheel motor of a projector, or a fan motor.

  In this type of bearing device, the shaft member is inserted into the inner periphery of the bearing sleeve, and a radial bearing gap may be formed between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve. Further, in the case of a shaft member having a flange portion, between one end surface of the flange portion and a surface opposite to this end surface (for example, the end surface of the bearing sleeve) or the other end surface and opposite to this end surface A thrust bearing gap may be formed between the surface to be engaged (for example, the bottom surface of the housing) (see, for example, Patent Document 1 below).

  Recently, the number of disks tends to increase as the capacity of HDDs and the like increases. For this reason, the fluid dynamic pressure bearing device for controlling the rotation of these discs is also required to have a configuration corresponding to an increase in the weight of the rotating body. More specifically, there is a demand for measures to reduce sliding wear during start / stop in accordance with an increase in the weight of the rotating body including the shaft member.

As an example of the above measures, for example, in Patent Document 2 below, the magnetic center of the stator coil and the magnetic center of the rotor magnet of the spindle motor incorporating the dynamic pressure bearing unit are opposite to the load load (for example, the load due to its own weight). A configuration is disclosed that is shifted by a predetermined distance in the thrust direction so that a magnetic attractive force acts in the direction. In addition, by adopting this configuration, when the opposing surfaces of the two thrust plates fixed to the main shaft via the radial cylindrical portion rotatably support both end surfaces of the radial sleeve, a load in the thrust direction due to its own weight is applied. It is described that the wear between the thrust plate and the radial sleeve is reduced and reduced.
JP 2003-239951 A Japanese Patent No. 3099033

  However, since the configuration of Patent Document 2 uses a magnet and a coil that are used for rotational driving of the motor to apply the floating force of the rotating body, the rotational force and the floating force cannot be applied at different timings. Therefore, it is impossible to give an appropriate levitation force. In particular, since the power supply to the coil is stopped when the rotation is stopped, it is impossible to apply a force for stopping the ground contact of the flange portion at an early stage. In addition, when a levitation force is applied at a position away from the center of the rotating body to the outer diameter side as in Patent Document 2, the posture of the rotating body is likely to be unstable, and when the posture is greatly collapsed There is a risk that the rotating body partially contacts the bearing surface. In addition, the above problem is particularly noticeable at the start or stop of rotation where the rotational force is insufficient and the posture tends to become unstable.

  In view of the above circumstances, in the present specification, it is a technical problem to be solved by the present invention to provide a fluid dynamic bearing device that can reliably reduce sliding wear during start-up or stop.

  The solution to the above problem is achieved by the fluid dynamic bearing device according to the present invention. That is, this fluid dynamic pressure bearing device includes a shaft member having a flange portion, a bearing member that relatively supports the shaft member, and a thrust bearing formed between at least one end surface of the flange portion and an end surface of the bearing member. A fluid dynamic pressure bearing device having a gap, characterized in that the flange portion or a part of the fluid dynamic bearing device has one magnetic pole and the other magnetic pole capable of generating a magnetic force in the thrust direction between the magnetic pole and the magnetic pole. It is attached.

  In this way, the flange portion is set as one magnetic pole, and a magnetic force is generated between the flange portion and the other magnetic pole. For example, when a force repelling each other by the magnetic force is generated between the two magnetic forces, It is possible to impart appropriate levitation force by applying force and levitation force at different timings. Moreover, according to the said structure, the levitating force with respect to a shaft member is provided to the position close | similar to the rotation center directly with respect to a flange part. Therefore, the said flange part can be floated at an early stage, maintaining the horizontal attitude | position of a shaft member (flange part).

  Also, by arranging a pair of magnetic poles separately from the motor drive unit (coil and magnet) that applies a rotational force to the shaft member, for example, a force that attracts each other by magnetic force is generated between the magnetic poles. In this case, the attractive force can be applied to the flange portion even after the power supply to the motor drive portion is stopped. As a result, the shaft member that rotates by inertia can be quickly brought into contact with the bearing surface and stopped, and by reducing the time to stop, the sliding wear that occurs during that time can be reduced. .

  From the viewpoint of efficiently shortening the time required for the flange portion to float, the pair of magnetic poles is controlled so that a repulsive force is generated between the magnetic poles at the start of relative rotation between the shaft member and the bearing member. May be. Also, from the viewpoint of efficiently shortening the time required for stopping the grounding of the flange portion, when the application of the rotational force to the shaft member or the bearing member is stopped, the magnetic force is controlled so as to be generated between both the magnetic poles. May be.

  Alternatively, if both the ascent time and the stop time are to be shortened, by reversing the direction of one of the magnetic poles, at the start of relative rotation between the shaft member and the bearing member, a repulsive force due to the magnetic force is generated between both magnetic poles. It may be controlled to generate an attractive force due to a magnetic force when the rotation force is applied to the shaft member or the bearing member.

  Here, the fluid dynamic pressure bearing device according to the present invention may be provided with a dynamic pressure generating part for generating a fluid dynamic pressure action in the thrust bearing gap. Further, the magnetic force generated between the two magnetic poles may be controlled to a magnitude that assists in rotating and floating the flange portion or stopping the grounding. This is because a sufficient force can be applied to the flange portion to float by the fluid film or the dynamic pressure action generated in the thrust bearing gap. Further, when the flange portion is rotationally levitated by combining these configurations, the levitation force required for each component (a pair of magnetic poles and thrust dynamic pressure generating portion) can be small. Therefore, the size of the bearing device can be maintained.

  As described above, when it is necessary to adjust the magnitude of the magnetic force, it is desirable that at least one of the magnetic poles is composed of an electromagnet. According to this, the magnitude of the magnetic force generated between the two magnetic poles, and hence the repulsive force or attractive force, can be controlled according to the magnitude of the supplied current. In consideration of the ease of power supply, the fixed-side magnetic pole (the other magnetic pole provided on the bearing member side in the case of shaft rotation, or one of the flange portions or a part thereof in the case of shaft fixing) The magnetic pole) may be composed of an electromagnet, and the rotation-side magnetic pole may be composed of a permanent magnet.

  Moreover, regarding the arrangement position of the other magnetic pole, for example, the other magnetic pole may be arranged at a position facing the flange portion in the thrust direction. When considering the shape of the flange portion, it is sufficient in terms of magnetic efficiency to arrange the other magnetic pole at this position. Alternatively, the other magnetic pole may be arranged on the outer diameter side of the flange portion. If it can be arranged on the outer diameter side, there is an advantage that it is not necessary to increase the axial dimension of the apparatus. Moreover, the part located between at least both magnetic poles among bearing members may be comprised with a nonmagnetic material. According to this configuration, even if another object exists between the magnetic poles, the magnetic force (magnetic flux) generated between the magnetic poles easily passes through the object. Therefore, the magnetic force can be reflected in the repulsive force or attractive force of the flange portion without releasing it.

  The fluid dynamic pressure bearing device according to the above description is, for example, a motor including the fluid dynamic pressure bearing device and a drive unit that applies a driving force for relative rotation operation and stop operation in the fluid dynamic pressure bearing device. Can be provided. Therefore, in this case, the motor includes a drive unit (for example, a coil and a magnet) for applying a rotational force and a pair of magnetic poles for applying a floating force or an attractive force to the flange unit.

  As described above, according to the present invention, it is possible to provide a fluid dynamic pressure bearing device that can reliably reduce sliding wear during start-up or stop.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In the following description, the “up and down” direction is merely defined for easy understanding of the positional relationship between components in each drawing, and the installation direction, usage mode, and manufacturing method of the fluid dynamic bearing device It does not specify etc. The same applies to other embodiments described later.

  FIG. 1 is a cross-sectional view of a main part of a spindle motor for information equipment incorporating a fluid dynamic bearing device according to the present invention. This spindle motor is used in a disk drive device such as an HDD, for example, and a plurality of pairs of fluid dynamic bearing devices 1 that rotatably support a shaft member 2 to which a hub 3 is attached are opposed to each other via a radial gap. Stator coil 4 and rotor magnet 5 (motor drive unit), and a bracket 6. The stator coil 4 is fixed to the bracket 6, and the rotor magnet 5 is fixed to the hub 3. The housing 7 of the fluid dynamic bearing device 1 is fixed to the inner periphery of the bracket 6. As shown in the figure, the hub 3 holds one or a plurality of disks D (two in FIG. 1). In the spindle motor configured as described above, when the stator coil 4 is energized, a rotational force is applied to the hub 3 to which the rotor magnet 5 is attached by a radial magnetic force generated between the stator coil 4 and the rotor magnet 5. Accordingly, the disk D held by the hub 3 rotates integrally with the shaft member 2.

  FIG. 2 shows the fluid dynamic pressure bearing device 1. The fluid dynamic pressure bearing device 1 shown in FIG. 1 is used, for example, in a vertical position, and includes a housing 7, a bearing sleeve 8 fixed to the inner periphery of the housing 7, and a shaft inserted into the inner periphery of the bearing sleeve 8. The member 2, a seal member 10 that seals the other end opening side of the housing 7, one magnetic pole 23 that forms part of the flange portion 22 of the shaft member 2, and the other magnetic pole 11 are provided. In this case, the rotation axis direction of the shaft member 2 coincides with the vertical direction. The housing 7 and the bearing sleeve 8 correspond to the above-described bearing member.

  The housing 7 is formed in a bottomed cylindrical shape with a metal material such as brass or a resin material, for example. Specifically, the housing 7 includes a cylindrical portion 7a, a bottom portion 7b formed integrally with the lower end of the cylindrical portion 7a, and a magnetic pole attaching portion 7c for attaching the other magnetic pole 11. In this case, the outer peripheral surface 8d of the bearing sleeve 8 is appropriately bonded to the inner peripheral surface 7a1 of the cylindrical portion 7a, such as bonding (including loose bonding or press-fitting bonding), press-fitting, welding (including ultrasonic welding or laser welding). It is fixed by means of Further, the bottom portion 7b has a substantially disk shape, and a dynamic pressure groove arrangement region having an arrangement mode similar to that in FIG. 4 (the direction of the spiral is reversed) is formed on the entire upper surface 7b1 or a partial region thereof. The This dynamic pressure groove arrangement region faces the lower end surface 22b of the flange portion 22 in the state of the finished product shown in FIG. 2, and the second thrust bearing portion T2 described later is formed between the lower end surface 22b and the shaft member 2 when rotating. The thrust bearing gap is formed. Although illustration is omitted, the bottom 7b is formed separately from the cylindrical portion 7a, and the bottom of this separate body is fixed to the lower end of the cylindrical portion 7a by appropriate means such as press-fitting, bonding, and welding. Also good.

  The bearing sleeve 8 is formed in a cylindrical shape with, for example, a porous body of sintered metal mainly containing iron or copper (including those alloyed with each other) or both. Besides the sintered metal, the bearing sleeve 8 can be formed of a soft metal material such as brass or another porous body (for example, a porous resin) that is not a sintered metal. If the bottom portion 7b is formed separately from the cylindrical portion 7a as described above, the bearing sleeve 8 is formed integrally with the housing 7 as an insert part, or both the portions 7 and 8 are formed integrally with the same material. It is also possible to do.

A region in which a plurality of dynamic pressure grooves are arranged as a radial dynamic pressure generating portion is formed on the entire or a part of the inner peripheral surface 8a of the bearing sleeve 8. In this embodiment, for example, as shown in FIG. 3, regions where a plurality of dynamic pressure grooves 8a1 and 8a2 having different inclination angles are arranged in a herringbone shape are formed at two locations separated in the axial direction. In this embodiment, the dynamic pressure grooves 8a1 and 8a2 are arranged asymmetrically in the axial direction in order to intentionally create a circulation of lubricating oil inside the bearing. Explaining in the form illustrated in FIG. 3, the dynamic pressure groove 8a1 arrangement region above the axial center m (the seal member 10 side) of the region (so-called band portion) between the dynamic pressure grooves 8a1 and 8a2 adjacent in the axial direction. the axial dimension X ₁ of is formed to be larger than the axial dimension X ₂ of the lower dynamic pressure grooves 8a2 sequence region. The dynamic pressure groove 8a1 and 8a2 arrangement region located on the lower side of the inner peripheral surface 8a (the side close to a thrust bearing gap described later) is formed symmetrically in the axial direction with the axial center as a boundary.

  As shown in FIG. 4, a region where a plurality of dynamic pressure grooves 8 b 1 are arranged in a spiral shape is formed as a thrust dynamic pressure generating portion on the entire surface or a partial region of the lower end surface 8 b of the bearing sleeve 8. This dynamic pressure groove 8b1 arrangement region is opposed to the upper end surface 22a of the flange portion 22 in the finished product state, and is a thrust bearing of the first thrust bearing portion T1, which will be described later, between the upper end surface 22a when the shaft member 2 rotates. A gap is formed (see FIG. 2).

  As shown in FIG. 3, an annular groove 8 c 1 having a wedge-shaped cross section is formed at an intermediate position in the radial direction of the upper end surface 8 c of the bearing sleeve 8. Further, on the inner diameter side of the upper end surface 8c from the annular groove 8c1, radial grooves 8c2 connecting the annular groove 8c1 and the inner peripheral surface 8a are formed at a plurality of locations in the circumferential direction. The annular groove 8c1 and the radial groove 8c2 form a lubricating oil circulation path in the bearing inner space together with an axial groove 8d1 described later, thereby ensuring a smooth lubricating oil supply state.

  A plurality of (for example, three) axial grooves 8 d 1 extending in the axial direction are formed on the outer peripheral surface 8 d of the bearing sleeve 8. These axial grooves 8d1 are formed at positions spaced apart from each other at equal intervals in the circumferential direction.

  In this embodiment, the sealing member 10 as a sealing means is formed separately from the housing 7 and is fixed to the inner periphery of the upper end of the housing 7 by appropriate means such as press fitting, adhesion, welding, welding or the like. Here, the seal member 10 is fixed to the housing 7 in a state where the lower end surface 10 b of the seal member 10 is in contact with the upper end surface 8 c of the bearing sleeve 8. The material of the seal member 10 is not particularly limited, and various metal materials or resin materials can be used as long as the material is not likely to cause oil leakage such as a porous material. Of course, the sealing member 10 can be integrally formed of the same material as the housing 7.

  A tapered seal surface 10 a is formed on the inner periphery of the seal member 10, and a seal space S is formed between the seal surface 10 a and the upper outer peripheral surface of the shaft portion 21. In a state where the lubricating oil is filled in the fluid dynamic pressure bearing device 1, the oil level of the lubricating oil is always maintained in the seal space S.

  The shaft member 2 includes a shaft portion 21 and a flange portion 22 provided integrally or separately at the lower end of the shaft portion 21. In this embodiment, the shaft member 2 is fixed by fixing an annular flange portion 22 formed separately from the shaft portion 21 to the lower end of the shaft portion 21 using appropriate fixing means such as press-fitting, bonding, and caulking. Is configured.

  The shaft portion 21 is formed of, for example, stainless steel, and as shown in FIG. 2, on the outer periphery thereof, the dynamic pressure grooves 8 a 1 and 8 a 2 provided on the inner peripheral surface 8 a of the bearing sleeve 8 are radially opposed to each other in the radial direction. It has a bearing surface 21a. In this embodiment, cylindrical radial bearing surfaces 21a having a perfect circular cross-sectional profile over the entire length in the axial direction are provided at two locations spaced apart in the axial direction. Between these radial bearing surfaces 21a, 21a, a suspicious portion having a smaller diameter than the radial bearing surface 21a is provided. The radial bearing surface 21a preferably has excellent surface accuracy (shape accuracy), and even if appropriate finishing such as appropriate heat treatment or grinding is applied to the radial bearing surface 21a as necessary. Good.

  In this embodiment, the one magnetic pole 23 is composed of a permanent magnet, and forms a part of the flange portion 22 by being fixed to the lower end of the shaft portion 21 in a substantially annular state. . In this embodiment, one magnetic pole 23 is disposed so that the upper end surface 22a side is an N pole and the lower end surface 22b side is an S pole. That is, the magnetic field around one of the magnetic poles 23 is set so as to show the lines of magnetic force extending from the lower end surface 22b side to the upper end surface 22a side.

The material is not particularly limited, and any material can be used as long as it can be magnetized, that is, as long as it is a magnetic material. For example, if the flange portion 22 is composed of the magnetic material itself, considering that the thrust bearing surface is composed of the both end faces 22a and 22b, for example, ferrite-based SUS or the like can be relatively hard and wear resistant. An excellent magnetic material can be used. Of course, as in this embodiment, in the case where the sliding layer 24 having excellent slidability is formed on the surface thereof (which is better if it has excellent wear resistance), the hardness and wear resistance are improved. General magnetic materials can be used without consideration, for example, alnico magnets, ferrite magnets, samarium cobalt (SmCo ₅ , Sm ₂ Co ₁₇ ) magnets, neodymium (Nd ₂ Fe ₁₄ B) magnets, samarium iron nitrogen (Sm A known permanent magnet such as a ₂ Fe ₁₇ N ₃ ) magnet formed in an annular shape can be used as one magnetic pole 23.

  Also, the production method is not particularly limited, and for example, it can be formed by cutting, casting, or sintering. In addition, when one magnetic pole 23 is comprised with the permanent magnet which consists of a sintered metal, the adhesive force of the sliding layer 24 increases by forming the sliding layer 24 mentioned later by insert molding of the one magnetic pole 23. FIG. This is because if it is made of a sintered metal, a large number of pores are opened on its surface, and a molten resin (or metal) enters the inside of one magnetic pole 23 from the opening.

  A sliding layer 24 that is more slidable than one magnetic pole 23 is formed around one magnetic pole 23. Therefore, in this case, both the upper end surface 22 a and the lower end surface 22 b of the flange portion 22 are constituted by the sliding layer 24. The material of the sliding layer 24 is not particularly limited, and various materials can be used. Specifically, the sliding layer 24 can be formed of a material having excellent slidability such as fluorine resin, and is formed so as to cover the surface of one magnetic pole 23 as a coating. In this case, for example, the sliding layer 24 is formed integrally with the one magnetic pole 23 by performing injection molding of resin using the one magnetic pole 23 as an insert part. Of course, the sliding layer 24 can also be formed with a film other than the resin film. For example, a hydrocarbon film such as a ceramic film or a DLC film can be formed on one magnetic pole 23 by vapor deposition or plating. .

  The other magnetic pole 11 is attached to the other magnetic pole 11 at a position where a magnetic force in the thrust direction can be generated with the one magnetic pole 23, for example, at the lower end surface side of the bottom 7b of the housing 7, as shown in FIG. Yes. Specifically, the other magnetic pole 11 forms a so-called electromagnet, and includes a magnetic core 12 and a coil portion 13 wound around the magnetic core 12. Then, by fitting the magnetic core 12 to the magnetic pole mounting portion 7c provided on the lower end surface side of the bottom portion 7b, the other magnetic pole 11 formed by winding the coil portion 13 around the magnetic core 12 is positioned and fixed. In this case, the upper end surface of the substantially disc-shaped magnetic core 12 and the lower end surface of one magnetic pole 23 constituting the flange portion 22 face each other in the thrust direction via the bottom portion 7 b of the housing 7. Moreover, the center axis line (normal line) is in agreement.

  In addition, a power source or control means (both not shown) is connected to the coil portion 13 constituting the other magnetic pole 11 via a conducting wire, and current in either positive or negative direction is supplied to the coil portion 13. Thus, a magnetic force is generated in the winding core direction of the coil portion 13, here in the thrust direction. Further, the power supply mode to the coil unit 13 is controlled by the control means. Specifically, at the start of relative rotation of the shaft member 2, current in either positive or negative direction is supplied to the coil portion 13 so that the upper end side of the coil portion 13 is the S pole and the lower end side is the N pole. The magnetic poles 11 and 23 can be controlled so that a repulsive force is generated between them. Further, when the application of the rotational force to the shaft member 2 by the motor drive unit (the stator coil 4 and the rotor magnet 5) is stopped, the coil unit 13 has an N pole on the upper end side and an S pole on the lower end side. 13 is supplied with a current in the direction opposite to that at the start of rotation, so that the magnetic poles 11 and 23 can be controlled so as to generate an attractive force.

  After assembling the above-described components into a form conforming to a predetermined procedure and FIG. 2, the bearing internal space (the region indicated by the dotted pattern in FIG. 2) is filled with lubricating oil, so that the fluid dynamics as a finished product is obtained. The pressure bearing device 1 is obtained. As the lubricating oil filled in the fluid dynamic bearing device 1, various oils can be used. However, when provided for a disk drive device such as an HDD, the temperature change during use or transportation is changed. Considering this, an ester-based lubricating oil excellent in low evaporation rate and low viscosity, such as dioctyl sebacate (DOS), dioctyl azelate (DOZ) and the like can be suitably used.

  In the fluid dynamic pressure bearing device 1 configured as described above, when the shaft member 2 rotates, the dynamic pressure grooves 8a1 and 8a2 of the bearing sleeve 8 are arranged on the radial bearing surfaces 21a and 21a of the shaft portion 21 via the radial bearing gap. Facing each other. As the shaft member 2 rotates, the lubricating oil is pushed toward the axial center of the dynamic pressure grooves 8a1 and 8a2 in any of the upper and lower dynamic pressure grooves 8a1 and 8a2 arrangement regions, and the pressure rises. Due to the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2, the first radial bearing portion R1 and the second radial bearing portion R2 that rotatably support the shaft member 2 in the radial direction are separated from each other in the axial direction. Are configured in two places (see FIG. 2 for both).

  Further, the thrust bearing gap between the arrangement region of the dynamic pressure grooves 8b1 provided on the lower end surface 8b of the bearing sleeve 8 and the upper end surface 22a of the flange portion 22 opposed thereto, and the upper end surface 7b1 of the bottom portion 7b of the housing 7 are provided. An oil film of lubricating oil is formed in the thrust bearing gap between the provided dynamic pressure groove array region and the lower end surface 22b of the flange portion 22 facing this region by the dynamic pressure action of the dynamic pressure groove. The first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft member 2 in the thrust direction in a non-contact manner are configured by the pressure of these oil films (see FIG. 2 for both).

  Hereinafter, the effect | action which both the magnetic poles 11 and 23 exert on the shaft member 2 is demonstrated. First, as shown in FIG. 5, when a rotational force is applied to the hub 3 and the shaft member 2 by the motor driving portion (the stator coil 4 and the rotor magnet 5), the lower end surface 22b of the flange portion 22 is the bottom of the housing due to its own weight. The rotation starts from a state where the upper end surface 7b1 of 7b is in contact. Then, by increasing the rotational speed, an oil film of lubricating oil is generated in the gap between the lower end surface 22b of the flange portion 22 and the upper end surface 7b1 of the bottom portion 7b, and as a result, the flange portion 22 completely floats from the bottom portion 7b. . During this time, that is, from when the flange portion 22 starts to rotate until it floats by a predetermined gap, the coil portion 13 has a positive and negative predetermined orientation so that the upper end side is the S pole and the lower end side is the N pole. The repulsive force due to the magnetic force is generated between the magnetic poles 11 and 23 by supplying the current. As a result, the time required from when the flange portion 22 starts to rotate until it completely floats can be shortened, and sliding wear that occurs in the flange portion 22 during that time can be reduced. Further, in this embodiment, since the dynamic pressure groove array region having a predetermined shape is formed on the upper end surface 7b1 of the bottom portion 7b facing the ground-side end surface 22b of the flange portion 22, the thrust bearing gap between the both surfaces 22b and 7b1 is formed. This causes the dynamic pressure action of the lubricating oil. Therefore, the time required for the flange portion 22 to float can be further shortened by the combination of the dynamic pressure action and the repulsive force due to the magnetic force.

  Next, as shown in FIG. 6, from the state where the shaft member 2 is rotated by receiving the rotational force from the motor drive unit, for example, the energization of the stator coil 4 is stopped and the rotational force is applied to the shaft member 2. When stopped, the flange portion 22 continues to rotate due to inertia, and gradually descends toward the upper end surface 7b1 of the bottom portion 7b by its own weight, and eventually comes into contact with the upper end surface 7b1 and stops. During this time, that is, between when the rotational force is no longer applied to the flange portion 22 and until it stops after contacting the upper end surface 7b1, the upper end side of the coil is N pole and the lower end side is S pole. By supplying positive and negative currents, an attractive force is generated between the magnetic poles 11 and 23 by a magnetic force. As a result, the time required for the flange portion 22 to be grounded and completely stopped can be shortened, and sliding wear occurring in the flange portion 22 during that time can be reduced. In particular, the rotational force is eliminated by disposing the other magnetic pole 11 (here, the magnetic core 12) at a position facing the one magnetic pole 23 forming the main part of the flange portion 22 in the thrust direction as in this embodiment. Thus, only the repulsive force or attractive force in the thrust direction can be applied. Accordingly, it is possible to further reduce the time required for the rotation to stop without giving unnecessary rotational force to the flange portion 22 or the time from the grounding to the complete stop.

  In addition, when supplying current to the coil unit 13 continuously from the start of rotation to the stop of rotation, the magnitude of the repulsive force is set so that the repulsive force applied to the flange unit 22 does not become excessive after the flange unit 22 floats. It is preferable to control by the magnitude of the current supplied to the unit 13. Further, when the thrust bearing portions T1 and T2 are formed on the both end faces 22a and 22b side of the flange portion 22 as in this embodiment, the repulsive force or attractive force caused by the magnetic force generated between the magnetic poles 11 and 23 is generated. It is also possible to control so as to be applied only during the floating period of the flange portion 22 or during the descent stop period. That is, when the thrust bearing portions T1 and T2 are formed on both end sides of the flange portion 22, if a repulsive force is further applied after the flange portion 22 has floated, the position closer to the lower end surface 8b of the bearing sleeve 8 than the design position. There is a possibility that the flange portion 22 is supported in a non-contact manner. In this case, since the required thrust bearing gap cannot be obtained, the balance between the upper and lower fluid pressures is lost, and the flange portion 22 may not be stably supported in a non-contact manner. For this reason, in this support mode, when the flange portion 22 reaches a predetermined position (for example, an intermediate position between the lower end surface 8b and the upper end surface 7b1), the energization to the coil portion 13 is stopped, and the flange portion 22 is appropriately set. You may make it support non-contact at a high height. Similarly, when the application of the rotational force to the shaft member 2 is stopped and the flange portion 22 is grounded to the upper end surface 7b1, the application of the attractive force after the contact is merely pressing the flange portion 22 against the upper end surface 7b1. In order to avoid sliding wear due to excessive pressing, energization of the coil portion 13 may be stopped at the time of grounding or immediately before grounding.

  Although one embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to the above embodiment. Hereinafter, another embodiment of a fluid dynamic pressure bearing device to which the present invention can be applied or a motor equipped with the bearing device will be described with reference to FIGS.

  For example, regarding the positional relationship between the magnetic poles 11 and 23, in the above embodiment, the case where the other magnetic pole 11 is disposed at a position facing the flange portion 22 (one magnetic pole 23) via the housing 7 in the thrust direction is described. However, of course, it is not limited to this. For example, the other magnetic pole 11 can be disposed on the outer diameter side of the flange portion 22 via a stationary member such as the housing 7.

  FIG. 7 shows an example thereof. In the fluid dynamic bearing device 1 according to FIG. 7, the other magnetic pole 11 is provided on the outer diameter side of the flange portion 22 and on the outer periphery of the housing 7. Specifically, a small diameter portion 7d for attaching the other magnetic pole 11 is formed on the outer periphery of the lower end of the cylindrical portion 7a of the housing 7, and the other magnetic pole 11 (here, an air-core coil portion) is formed on the small diameter portion 7d. Is attached to generate a magnetic force in the thrust direction inside the coil. Therefore, as shown in FIG. 7, by disposing the flange portion 22 inside the other magnetic pole 11, a repulsive force or attractive force due to a magnetic force is generated between the one magnetic pole 23 constituting the flange portion 22 and the other magnetic pole 11. Can be generated.

  FIG. 8 shows another example. In the motor provided with the fluid dynamic bearing device 1 according to the same figure, the other magnetic pole 11 of the motor bracket 6 that holds the fluid dynamic bearing device 1 on the inner periphery is shown. It is provided at a predetermined position on the inner periphery. Specifically, a large-diameter portion 6a for attaching the other magnetic pole 11 is formed on the inner peripheral surface of the bracket 6, and the other magnetic pole 11 (again, the air-core coil portion) is attached to the large-diameter portion 6a. By attaching, a magnetic force in the thrust direction is generated inside the coil. Therefore, as shown in FIG. 8, by arranging the flange portion 22 on the inner diameter side of the other magnetic pole 11, a magnetic force is generated between one magnetic pole (not shown) constituting the flange portion 22 and the other magnetic pole 11. It is possible to generate a repulsive force or attractive force due to.

  7 and 8, the housing 7 interposed between the magnetic poles 11 and 23 is preferably made of a nonmagnetic material such as aluminum, copper (including an alloy), or resin. This is because the escape of the magnetic force generated in the other magnetic pole 11 is reduced as much as possible to contribute to an increase in repulsive force or attractive force with the one magnetic pole 23. From the same viewpoint, in the embodiment shown in FIG. 2, it is desirable that at least the bottom 7b of the housing 7 is formed of a nonmagnetic material.

  In the above description, the case where the flange portion 22 or one of the magnetic poles 23 forming a part thereof is constituted by a permanent magnet and the other magnetic pole 11 is constituted by an electromagnet has been exemplified. It is not limited. For example, one of the magnetic poles 23 can be an electromagnet and the other magnetic pole 11 can be a permanent magnet, or both the magnetic poles 11 and 23 can be composed of electromagnets. For example, when one of the magnetic poles 23 is an electromagnet, an appropriate coil portion is disposed on the outer diameter side of one of the magnetic poles 23 as illustrated in FIGS. By forming the magnetic pole from a soft magnetic material capable of repeatedly generating / disappearing the magnetic pole, the one magnetic pole can be used as an electromagnet in combination with the coil portion. Of course, both the magnetic poles 11 and 23 can be composed of permanent magnets as long as it only needs to assist the floating or grounding stop at the start of rotation of the flange portion.

  In the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are exemplified by the configuration in which the dynamic pressure action of the lubricating oil is generated by the dynamic pressure grooves having a herringbone shape or a spiral shape. The configuration to which the present invention can be applied is not limited to this.

  For example, as the radial bearing portions R1 and R2, although not shown, a so-called step-like dynamic pressure generating portion in which axial grooves are formed at a plurality of locations in the circumferential direction, or a plurality of circular arc surfaces in the circumferential direction. A so-called multi-arc bearing in which a wedge-shaped radial gap (bearing gap) is formed between the outer peripheral surfaces (radial bearing surfaces 21a, 21a) of the opposing shaft member 2 may be employed.

  Alternatively, the inner peripheral surface 8a of the bearing sleeve 8 serving as a radial bearing surface is a perfect circular inner peripheral surface not provided with a dynamic pressure groove or arc surface as a dynamic pressure generating portion, and is a perfect circle facing the inner peripheral surface. A so-called perfect circle bearing can be constituted by the outer peripheral surface of the shape.

  One or both of the thrust bearing portions T1 and T2 are also not shown in the figure, but a plurality of radial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction in a region serving as a thrust bearing surface. It can also be configured by a step bearing or a corrugated bearing (having a corrugated waveform such as an end face).

  In the above embodiment, the case where the dynamic pressure generating portions are all provided on the fixed side (the housing 7 and the bearing sleeve 8) has been described, but part or all of the dynamic pressure generating portions are provided on the rotating side (the shaft portion 21 and the flange portion). 22). Specifically, it is possible to provide the above-described dynamic pressure generating portion at one or more of the outer peripheral surfaces (radial bearing surfaces 21a, 21a) of the shaft member 2 and both end surfaces 22a, 22b of the flange portion 22. .

  Moreover, although the above embodiment demonstrated the case where the flange part 22 was provided in the edge part of the axial part 21, the fixing position of the flange part 22 is not restricted especially in this. For example, although not shown in the drawings, the present invention can be applied to a fluid dynamic bearing device in which the flange portion 22 is fixed at an intermediate position in the axial direction of the shaft portion 21. Further, it is not always necessary to form the thrust bearing portions T1 and T2 (thrust bearing gaps) at the both end faces 22a and 22b of the flange portion 22, and any one end face side that may be grounded due to falling by its own weight. Only the thrust bearing portion (thrust bearing gap) may be formed. Similarly, although not shown in the drawings, the present invention is applied to a fluid dynamic bearing device in which the outer peripheral surface of the flange portion is a seal surface and a seal space is formed between the seal surface and a surface opposed in the radial direction. The invention can also be applied.

  In the above embodiment, the configuration in which the shaft member 2 rotates and is supported by the bearing sleeve 8 has been described. On the contrary, the bearing sleeve 8 side rotates and the shaft member 2 is rotated. The present invention can also be applied to a structure that is supported on the side. In this case, although not shown in the drawings, the bearing sleeve 8 is bonded and fixed to a member disposed on the outside thereof, rotates integrally with the outer member, and is supported by a shaft portion on the fixed side.

  Further, in the above embodiment, the lubricating oil is exemplified as the fluid for filling the fluid dynamic pressure bearing device 1 and forming a fluid film in the radial bearing gap or the thrust bearing gap. For example, a fluid such as air, a fluid lubricant such as a magnetic fluid, or a lubricating grease can be used.

It is principal part sectional drawing of the spindle motor provided with the fluid dynamic pressure bearing apparatus which concerns on one Embodiment of this invention. It is sectional drawing of a fluid dynamic pressure bearing apparatus. It is sectional drawing of a bearing sleeve. It is a bottom view of a bearing sleeve. It is a partial expanded sectional view for demonstrating the effect | action by the both magnetic poles provided in the flange part etc. FIG. It is a partial expanded sectional view for demonstrating the effect | action by the both magnetic poles provided in the flange part etc. FIG. It is sectional drawing of the fluid dynamic pressure bearing apparatus which concerns on other embodiment of this invention. It is principal part sectional drawing of the motor which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 3 Hub 4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 7a Cylindrical part 7a1 Inner peripheral surface 7b Bottom part 7b1 Upper end surface 7c Magnetic pole attaching part 7d Small diameter part 8 Bearing sleeve 8a1, 8a2 Dynamic pressure groove 8b1 Dynamic pressure groove 10 Seal member 11, 23 Magnetic pole 12 Magnetic core 13 Coil portion 21 Shaft portion 21a, 21a Radial bearing surface 22 Flange portion 22a Upper end surface 22b Lower end surface 24 Sliding layer R1, R2 Radial bearing portion T1, T2 Thrust bearing portion

Claims (11)

A fluid dynamic pressure bearing device comprising: a shaft member having a flange portion; a bearing member that relatively supports the shaft member; and a thrust bearing gap formed between at least one end surface of the flange portion and the end surface of the bearing member. In
A fluid dynamic bearing device comprising a flange portion or a part thereof as one magnetic pole, and further comprising the other magnetic pole capable of generating a magnetic force in a thrust direction with the magnetic pole.   The fluid dynamic bearing device according to claim 1, wherein at the start of relative rotation between the shaft member and the bearing member, control is performed so that a repulsive force is generated between the magnetic poles.   The fluid dynamic bearing device according to claim 1, wherein when the application of the rotational force to the shaft member or the bearing member is stopped, an attractive force due to a magnetic force is generated between both magnetic poles.   By reversing the direction of one of the magnetic poles, a repulsive force due to a magnetic force was generated between the magnetic poles at the start of relative rotation between the shaft member and the bearing member, and the application of the rotational force to the shaft member or the bearing member was stopped. 2. The fluid dynamic bearing device according to claim 1, wherein the fluid dynamic bearing device is controlled to generate an attractive force due to a magnetic force.   The fluid dynamic pressure bearing device according to claim 1, further comprising a dynamic pressure generating portion for generating a fluid dynamic pressure action in the thrust bearing gap.   The fluid dynamic bearing device according to any one of claims 1 to 5, wherein a magnetic force generated between both magnetic poles is controlled to a magnitude that assists rotation floating or grounding stop of the flange portion.   The fluid dynamic bearing device according to claim 1, wherein at least one of both magnetic poles is formed of an electromagnet.   The fluid dynamic bearing device according to claim 1, wherein the other magnetic pole is disposed at a position facing the flange portion in the thrust direction.   The fluid dynamic bearing device according to claim 1, wherein the other magnetic pole is disposed on the outer diameter side of the flange portion.   The fluid dynamic pressure bearing device according to any one of claims 1 to 9, wherein at least a portion of the bearing member located between both magnetic poles is formed of a nonmagnetic material.   A motor comprising the fluid dynamic pressure bearing device according to any one of claims 1 to 10 and a drive unit that applies power for a relative rotation operation and a stop operation of the fluid dynamic pressure bearing device.

Images