JP2007040482A - Method of manufacturing fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a fluid bearing device having high cleanliness and assembled at low cost. <P>SOLUTION: The fluid bearing device 1 comprises an inner member 8 having a shaft 2 and a sintered metallic sleeve 7 fixed to the inner periphery of the shaft 2; a housing 9 forming a radial bearing clearance between itself and the inner member 8; and radial bearing parts R1, R2 supporting the inner member rotatably in a radial direction with a lubricating film of a fluid formed in the radial bearing clearance. In manufacturing such a fluid bearing device 1, the shaft 2 serving as a sizing pin 12 in sizing a sintered body 11 used as the sleeve 7, is pressed into the inner peripheral surface 11a of the sintered body 11. The inner member 8 with the sleeve 7 fixed to the shaft 2 is thereby formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a hydrodynamic bearing device in which a shaft member is rotatably supported by a fluid lubricating film generated in a bearing gap. The hydrodynamic bearing device manufactured by this method includes information devices such as magnetic disk devices such as HDD, optical disk devices such as CD-ROM, CD-R / RW, and DVD-ROM / RAM, and magneto-optical disks such as MD and MO. It is suitably used for a spindle motor of a device, a polygon scanner motor of a laser beam printer (LBP), a color wheel of a projector, or a small motor such as an electric device such as an axial fan.

  In addition to high rotational accuracy, the various motors are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor. In recent years, the use of a fluid bearing having characteristics excellent in the required performance has been studied or actually used. .

  This type of hydrodynamic bearing includes a hydrodynamic bearing having a dynamic pressure generating portion for generating a dynamic pressure in the lubricating fluid in the bearing gap, and a so-called true circular bearing having no dynamic pressure generating portion (with a bearing cross section). It is roughly divided into a perfect circle bearing).

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, both a radial bearing portion that supports a shaft member in the radial direction and a thrust bearing portion that supports the shaft direction in a thrust direction may be configured by dynamic pressure bearings. is there. As a radial bearing portion in this type of hydrodynamic bearing device (dynamic pressure bearing device), for example, a region where a plurality of dynamic pressure grooves are arranged as a dynamic pressure generating portion is formed on the inner peripheral surface of a sintered sleeve made of sintered metal. In addition, it is known that a radial bearing gap is formed between the surface on which the dynamic pressure generating portion is formed and the outer peripheral surface of the shaft member facing the surface (for example, see Patent Document 1).

Usually, a sintered metal bearing sleeve is obtained by compression-molding a metal powder containing Cu powder, Fe powder, or both into a predetermined shape with a corresponding molding die, and sintering this compression-molded body ( For example, see Patent Document 2). Also, this type of bearing sleeve is often fixed to the inner periphery of a housing disposed on the outer diameter side thereof by a fixing means such as press-fitting in the assembly process of the hydrodynamic bearing device.
JP 2003-239951 A Japanese Patent Laid-Open No. 11-182551

  However, with this type of fixing method (fixing method with press-fitting), it is inevitable that contamination will occur at the time of fixing, so if it is used as it is, contamination will be mixed into the lubricating oil filled inside the bearing. The cleanliness of the bearing device may be adversely affected. Moreover, in order to remove this contamination, it is necessary to perform careful cleaning after fixing, and an increase in cost is inevitable.

  An object of the present invention is to provide a method of manufacturing a hydrodynamic bearing device that has high cleanliness and can be assembled at low cost.

  In order to solve the above-mentioned problems, the present invention provides an inner member having a shaft and a sleeve made of sintered metal with the shaft fixed to the inner periphery, an outer member forming a radial bearing gap between the inner member, and a radial bearing. A method of manufacturing a hydrodynamic bearing device including a radial bearing portion that rotatably supports an inner member in a radial direction with a lubricating film of a fluid generated in a gap. A method of manufacturing a hydrodynamic bearing device, characterized by being used as a mold.

  The present invention is characterized in that, in a configuration in which a sleeve made of sintered metal is fixed to a shaft of a rotating inner member instead of an outer member, the shaft is used as an inner mold when the sleeve is compacted. is there. According to such a method, after the compression molding, the green compact formed as the sleeve can be integrally fixed to the shaft used as the inner mold, and it is not necessary to press-fit the fixing of the sleeve as in the prior art. Accordingly, it is possible to avoid contamination due to the fixing of the sleeve and to obtain a high cleanliness inside the bearing.

  In addition, according to the above method, the assembly of the inner member (fixing of the sleeve and the shaft) can be included in the sleeve forming step, so that the corresponding steps can be simplified and the cost can be reduced.

  In order to solve the above problems, the present invention provides an inner member having a sintered metal sleeve having a shaft and a shaft fixed to the inner periphery, and an outer member that forms a radial bearing gap between the inner member, A method of manufacturing a hydrodynamic bearing device including a radial bearing portion that rotatably supports an inner member in a radial direction by a fluid lubrication film generated in a radial bearing gap. A method of manufacturing a hydrodynamic bearing device, characterized by being used as a mold.

  As described above, when the sleeve is sized, the sizing sleeve can be fixed to the shaft by using the shaft as the inner mold. Thus, the assembly can be simplified and the cost can be reduced. Depending on the sizing configuration, contamination may occur. However, as in the present invention, if contamination occurs in the assembly process of the component (inner member), this can be easily done before the final assembly of the hydrodynamic bearing device. Can be washed. Therefore, it is possible to avoid contamination from remaining in the hydrodynamic bearing device incorporating these inner members.

  In order to solve the above problems, the present invention provides an inner member having a sintered metal sleeve having a shaft and a shaft fixed to the inner periphery, and an outer member that forms a radial bearing gap between the inner member, In a hydrodynamic bearing device including a radial bearing portion that rotatably supports an inner member in a radial direction by a fluid lubrication film generated in a radial bearing gap, the inner peripheral surface of the sleeve is formed by the outer peripheral surface of the shaft. A hydrodynamic bearing device is provided.

  In this way, when the inner member that rotates relative to the outer member is composed of the shaft and the sleeve, the shaft may have a straight shape, and therefore, for example, a shaft having a complicated outer surface shape such as a flange-integrated shaft may be used. Cost reduction can be achieved compared to the case of forming. In addition, the shaft usually brings its outer peripheral surface into contact with the radial bearing gap and causes sliding contact with the facing sleeve (see Patent Document 1). Is merely a fixed surface with the sleeve, and therefore it is not necessary to consider the slidability with the sleeve or the workability of the outer peripheral surface. Therefore, with respect to this axis, it is possible to omit processing for obtaining high surface accuracy such as heat treatment and finish surface processing, and it is possible to reduce costs in this respect.

  As described above, according to the present invention, it is possible to provide a method for manufacturing a hydrodynamic bearing device that can prevent contamination as much as possible, has high cleanliness, and can be assembled at low cost.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a hydrodynamic bearing device 1 according to an embodiment of the present invention. This spindle motor is used in a disk drive device such as an HDD, and is opposed to the hydrodynamic bearing device 1 and the disc hub 3 mounted on the shaft 2 of the hydrodynamic bearing device 1 through, for example, a radial gap. A stator coil 4, a rotor magnet 5, and a bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The disk hub 3 holds one or a plurality (two in FIG. 1) of a disk-shaped information storage medium (hereinafter simply referred to as a disk) D such as a magnetic disk on its outer periphery. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by an exciting force generated between the stator coil 4 and the rotor magnet 5, and accordingly, the disk hub 3 and the disk are rotated. The disk D held by the hub 3 rotates integrally with the shaft 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes an inner member 8 having a shaft 2 and a sleeve 7, a housing 9 that houses the inner member 8 on the inner periphery, and a seal portion 10 that is fixed to the housing 9. Here, the housing 9 corresponds to the outer member. For convenience of explanation, the bottom 9b side of the housing 9 will be described below, and the side opposite to the bottom 9b (opening side of the housing 9) will be described below.

  As shown in FIG. 2, the housing 9 includes a cylindrical portion 9a and a bottom portion 9b integrally formed at the lower end of the cylindrical portion 9a. The housing 9 can also be formed of a metal material, and a resin based on a crystalline resin such as LCP, PPS, or PEEK, or a mixture of these crystalline resins with an amorphous resin such as PSU, PES, or PEI. It can also be formed from a composition. Examples of the resin composition constituting the housing 9 include fibrous fillers such as glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, carbon fibers, carbon black, and graphite. In addition, carbon nanomaterials, fibrous or powdery conductive fillers such as various metal powders, and the like can be used in an appropriate amount according to the purpose.

  The inner member 8 includes a shaft 2 and a sleeve 7 fixed to the outer periphery of the shaft 2 and is accommodated in the inner periphery of the housing 9.

  The shaft 2 is formed of a metal material such as stainless steel, for example, and has a circular shape with a constant diameter. A sleeve 7 is fixed to one end (lower end) of the shaft 2, and a disk hub 3 is fastened and fixed to the other end (upper end) by means such as press-fitting.

  The sleeve 7 is formed of a sintered metal porous body mainly composed of a material selected from Cu, Fe, or an alloy thereof, and is fixed to the outer peripheral surface 2a of the shaft 2 by a method described later. .

  A plurality of dynamic pressure grooves 7a1 and 7a2 are arranged in a herringbone shape as a radial dynamic pressure generating portion, for example, as indicated by a broken line portion in FIG. 2, on the entire outer peripheral surface 7a of the sleeve 7 or a partial cylindrical region. Two regions are formed apart in the axial direction. The regions for forming the dynamic pressure grooves 7a1 and 7a2 are opposed to the inner peripheral surface 9a1 of the cylindrical portion 9a of the housing 9, and when the inner member 8 rotates, the first radial bearing portion R1 and the second radial bearing portion R1 are formed between the inner peripheral surface 9a1 and the inner peripheral surface 9a1. A radial bearing gap is formed in each of the radial bearing portions R2 (see FIG. 2).

  Although not shown in the figure, for example, an area where a plurality of dynamic pressure grooves are arranged in a spiral shape is formed on the entire lower surface 7b of the sleeve 7 or on a part of the annular area as a thrust dynamic pressure generator. This dynamic pressure groove forming region faces the upper end surface 9b1 of the bottom portion 9b of the housing 9, and forms a thrust bearing gap of the first thrust bearing portion T1 with the upper end surface 9b1 when the inner member 8 rotates (see FIG. 2).

  Although not shown in the drawing, a region where a plurality of dynamic pressure grooves are arranged in a spiral shape is formed on the entire upper surface 7c of the sleeve 7 or a part of the annular region as a thrust dynamic pressure generator. This dynamic pressure groove forming region faces a lower end surface 10b of a seal portion 10 to be described later, and forms a thrust bearing gap of the second thrust bearing portion T2 with the lower end surface 10b when the inner member 8 rotates (see FIG. 2). In addition to the spiral shape described above, the herringbone shape shown in FIG. 2 can be adopted as an arrangement mode of the dynamic pressure grooves in the thrust dynamic pressure generating portion.

  The seal portion 10 is formed in an annular shape with, for example, a resin material or a metal material, and the sleeve 7 of the inner member 8 is accommodated between the lower end surface 10b and the upper end surface 9b1 of the bottom portion 9b. Arranged around the circumference. The inner peripheral surface 10a of the seal portion 10 has a taper shape, and forms a seal space S between the outer peripheral surface 2a of the opposing shaft 2 and increases in the radial direction. In this embodiment, the sum of the thrust bearing gaps of both thrust bearing portions T1 and T2 is defined by managing the axial position of the seal portion 10 with respect to the housing 9.

  The hydrodynamic bearing device 1 having the above configuration is filled with lubricating oil, and the hydrodynamic bearing device 1 is completed. At this time, the oil level of the lubricating oil filled in the internal space of the housing 9 is always located in the seal space S.

  When the inner member 8 is rotated, a region (a region where two dynamic pressure grooves 7a1 and 7a2 are formed) on the outer peripheral surface 7a of the sleeve 7 that rotates integrally with the shaft 2 is formed on the inner peripheral surface 9a1 of the housing 9. And through a radial bearing gap. As the inner member 8 rotates, the lubricating oil in the radial bearing gap is pushed toward the axial center of each of the dynamic pressure grooves 7a1 and 7a2, and the pressure rises. By such a dynamic pressure action of the dynamic pressure groove, the first radial bearing portion R1 and the second radial bearing portion R2 that support the inner member 8 in a non-contact manner so as to be rotatable in the radial direction are configured.

  At the same time, the thrust bearing gap between the lower end surface 7b (dynamic pressure groove forming region) of the sleeve 7 and the upper end surface 9b1 of the bottom portion 9b of the housing 9 and the upper end surface 7c of the sleeve 7 (dynamic pressure groove). An oil film of lubricating oil is formed in the thrust bearing gap between the forming region) and the lower end surface 10b of the seal portion 10 opposite to this by the dynamic pressure action of the dynamic pressure groove. The pressure of these oil films forms a first thrust bearing portion T1 and a second thrust bearing portion T2 that support the inner member 8 in a non-contact manner so as to be rotatable in both thrust directions.

  Thus, in this embodiment, since the outer peripheral surface of the inner member 8 that forms the radial bearing gap with the inner peripheral surface 9a1 of the housing 9 is formed by the sleeve 7 made of sintered metal, the inner member 8 Along with the rotation, a centrifugal force acts on the lubricating oil held in the internal holes of the sleeve 7. Thus, the seepage of the lubricating oil from the outer peripheral surface of the inner member 8 (the outer peripheral surface 7a of the sleeve 7) to the radial bearing gap is promoted, and the lubricating oil from the radial bearing gap to the inside of the inner member 8 (sleeve 7) is promoted. Return is suppressed. Therefore, a sufficient amount of lubricating oil can always be maintained in the radial bearing gap, and the oil film rigidity (bearing rigidity) in the radial direction can be increased.

  In the present embodiment, the sleeve 7 made of sintered metal is arranged on the rotating body (inner member 8) side, and the outer peripheral surface 7a of the sleeve 7 and the inner peripheral surface 9a1 of the housing 9 serving as the outer member. A radial bearing gap is formed between them. In accordance with this configuration (the product of the present invention) and, for example, the hydrodynamic bearing device described in Patent Document 1, the sleeve portion is fixed to the outer member, and a radial bearing gap is formed between the sleeve portion and the shaft ( In comparison with the conventional product, the radial bearing gap can be arranged on the radially outer side of the product of the present invention than the conventional product. As a result, the radial bearing area (oil film forming area) can be increased, and the bearing rigidity can be increased as compared with the conventional product. In addition, as long as the required rigidity of the bearing is ensured, it is not necessary to define the width of the radial bearing gap with high accuracy. Therefore, it is possible to further reduce costs by eliminating the trouble of finishing the outer peripheral surface 7a of the sleeve 7 and the inner peripheral surface 9a1 of the housing 9 forming the radial bearing gap with high accuracy.

  Hereinafter, the manufacturing method of the hydrodynamic bearing device 1 according to the embodiment of the present invention will be described focusing on the forming process of the sleeve 7. In this embodiment, a case where the sleeve 7 is fixed to the shaft 2 during the sizing process of the sleeve 7 will be described.

  FIG. 3 schematically shows a processing apparatus used in a process of sizing the sleeve 7 (hereinafter referred to as a sintered body 11) in a stage after the compacting and after a sintering process. The processing apparatus in this embodiment includes a sizing pin 12 to be the shaft 2 for press-fitting the inner peripheral surface 11a of the cylindrical sintered body 11, a die 13 for sizing the outer peripheral surface 11b of the sintered body 11, and sintering. The first punch 14 (upper punch) and the second punch 15 (lower punch) that restrain both end surfaces in the axial direction of the body 11 from the vertical direction (axial direction) are configured as main elements.

  Since the sizing pin 12 is for press-fitting the inner peripheral surface 11a of the sintered body 11, the outer diameter dimension d1 thereof is larger than the inner diameter dimension d2 of the sintered body 11 before sizing. In this case, the pressure input to the sintered body 11 of the sizing pin 12 is managed by the difference between the diameters d1 to d2 (press fitting allowance).

  On the outer periphery of the sizing pin 12, an upper punch 14 is slidably inserted in the vertical direction. The sizing pin 12 and the upper punch 14 are moved up and down by independent drive sources. Among these, since the sizing pin 12 is used as the shaft 2 of the hydrodynamic bearing device 1 after sizing, the sizing pin 12 is detachably attached to the sizing processing device. The die 13 is driven up and down independently of the sizing pin 12 and the upper punch 14 by driving means (not shown). In this embodiment, the lower punch 15 is fixed to a stationary member (for example, a pedestal) of the apparatus.

  In the initial state shown in FIG. 3, the sintered body 11 that is the workpiece is disposed on the upper end surface of the lower punch 15. The die 13 is disposed on the outer diameter side of the sintered body 11 while accommodating the entire outer peripheral surface 11b of the sintered body 11 and leaving a slight gap between the die 13 and the outer peripheral surface 11b. The sizing pin 12 and the upper punch 14 are arranged axially upward with respect to the sintered body 11.

  As shown in FIG. 4, the sizing pin 12 is lowered from the initial state described above, and the sizing pin 12 is press-fitted into the inner periphery of the sintered body 11. At this time, since the outer peripheral surface 11 b of the sintered body 11 is restrained from displacement in the outer diameter direction by the die 13, the inner peripheral surface 11 a of the sintered body 11 is pressed by the press-fitting of the sizing pins 12. As a result, the sintered body 11 is sized in the radial direction, and the sintered body 11 is fixed to the sizing pin 12 in a state where the clamping force for the sizing pin 12 is maintained. In the illustrated example, the upper punch 14 is lowered together with the sizing pin 12, and the upper punch 14 is pressed against the upper end surface of the sintered body 11. Thereby, the sintered compact 11 is restrained from the axial direction both sides by the upper and lower punches 14 and 15, and is sized in the axial direction.

  After the above process is completed, as shown in FIG. 5, the upper punch 14 is raised in a state where the radial restraint state by the sizing pin 12 and the die 13 is maintained, and the axial compression force is released. Next, the die 13 is lowered to release the pressing force in the inner diameter direction of the sintered body 11. Finally, the sizing pin 12 is separated from the sizing processing device, and the sintered body 11 fixed to the sizing pin 12 is taken out from the processing device. Thereafter, if necessary, by forming dynamic pressure generating portions such as dynamic pressure grooves 7a1 and 7a2 on the outer peripheral surface 11b of the sintered body 11, a sleeve 7 as a finished product is formed. Is formed on the shaft 2 as the sizing pin 12, that is, the inner member 8 is formed.

  As described above, the sizing of the inner peripheral surface 11a of the sintered body 11 is performed by press-fitting the sizing pin 12 serving as the shaft 2 into the inner peripheral surface 11a. Compared with the case of press-fitting and fixing, the amount of press-fitting (press-fitting area) can be reduced by the inner and outer peripheral surfaces of the sleeve 7. Therefore, the occurrence of contamination during such press-fitting and fixing can be suppressed as much as possible. Even if contamination occurs, this contamination is generated when the sleeve 7 is fixed to the outer periphery of the shaft 2. Therefore, after fixing, the inner member 8 can be easily washed. Contamination does not remain in the hydrodynamic bearing device 1 incorporated in the inner periphery of 9 (outer member). Accordingly, it is possible to maintain high cleanliness inside or around the bearing and to exhibit high bearing performance, motor performance, or disk reading / writing performance.

  Further, according to this method, the sleeve 7 can be fixed to the shaft 2 simultaneously with the sizing of the sintered body 11, so that the assembly process of the hydrodynamic bearing device 1 can be simplified and the cost can be reduced. It becomes.

  Moreover, in this embodiment, after sizing the sintered body 11 (after fixing to the sizing pin 12), prior to releasing the radial compression force, the axial compression force is released, so that the sintered body 11 Springback occurs preferentially in the axial direction. Therefore, the amount of springback in the outer diameter direction that occurs when the sintered body 11 is pulled out from the die 13 can be made relatively small, whereby the space between the sintered body 11 and the sizing pin 12 (sleeve 7 and shaft 2). Thus, it is possible to secure a high fixing force. Of course, if the fixing force between the two is ensured, the radial compression force can be released prior to the release of the axial compression force. Alternatively, in order to reinforce the fixing force between the two, it is also possible to apply a method in which an adhesive is applied in advance to the inner peripheral surface 11a of the sintered body 11 and then the sizing pin 12 serving as the shaft 2 is press-fitted. is there.

  In the sizing step, a thrust dynamic pressure generating portion including a plurality of dynamic pressure grooves can be formed in the sintered body 11 serving as the sleeve 7. In that case, for example, a die having a shape corresponding to the thrust dynamic pressure generating portion is provided in advance on the lower end surface of the upper punch 14 or the upper end surface of the lower punch 15, thereby restraining the sintered body 11 from both sides in the axial direction. By doing so, the thrust dynamic pressure generating portion can be formed simultaneously with the axial sizing.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

  In the above embodiment, the case where the shaft 2 as the sizing pin 12 is press-fitted into the inner periphery while the outer peripheral surface 11b of the sintered body 11 is constrained by the die 13 has been described. As long as it is used as the sizing pin 12), for example, the sleeve 7 and the shaft 2 can be fixed also by a method in which the die 13 is press-fitted into the outer periphery while the inner peripheral surface 11a of the sintered body 11 is constrained by the sizing pin 12. it can. For example, FIG. 6 shows an embodiment thereof. In a sizing processing apparatus provided with a sizing pin 12, a die 13, and upper and lower punches 14 and 15 serving as the shaft 2, the sintered body 11 ′ is an upper end surface of the lower punch 15. It is placed on top. In the figure, the inner peripheral surface 11a 'of the sintered body 11' has an inner diameter that allows the sizing pin 12 to be inserted. In contrast, a predetermined press-fitting allowance (see FIG. 6) is ensured between the outer peripheral surface 11b 'and the inner peripheral surface of the die 13 to be press-fitted.

  In the state shown in FIG. 6, that is, in the state where the sizing pin 12 is inserted into the inner periphery of the sintered body 11 ′ and both axial end surfaces of the sintered body 11 ′ are constrained by the upper and lower punches 14 and 15. The die 13 is moved (raised) in the direction of the middle arrow, and the outer peripheral surface 11b ′ of the sintered body 11 ′ is press-fitted. Thereby, the inner peripheral surface 11 a ′ of the sintered body 11 ′ is pressed by the sizing pin 12, and the sintered body 11 ′ is fixed to the sizing pin 12. At the same time, the sintered body 11 'is sized in the axial direction and the radial direction.

  According to this method, even if contamination occurs when the sleeve 7 is fixed to the sizing pin 12 (shaft 2), the contamination is applied to the outer peripheral surface 11b ′ of the sintered body 11 ′ press-fitted into the die 13. Arise. Therefore, cleaning can be easily performed, and a situation in which contamination remains in the hydrodynamic bearing device 1 as a finished product can be avoided.

  In the embodiment shown in FIG. 3 to FIG. 6, the case where the sleeve 7 is fixed to the shaft 2 during the sizing process of the sleeve 7 has been described. 7 and the shaft 2 can be fixed. Hereinafter, an embodiment in that case will be described.

  FIG. 7 conceptually shows a process of compression-molding the metal powder M, which is a raw material of the sleeve 7, into a predetermined shape (in this embodiment, the cylindrical shape shown in FIG. 3). The compacting device in this embodiment corresponds to the forming pin 16 for forming a portion corresponding to the inner peripheral surface of the sleeve 7 after completion, the die 17 for forming a portion corresponding to the outer peripheral surface 7a, and the upper end surface 7c. An upper punch 18 for forming a portion to be formed and a lower punch 19 for forming a portion corresponding to the lower end surface 7b are configured as main elements. In addition, since the shaping | molding pin 16 is used as the axis | shaft 2 of the hydrodynamic bearing apparatus 1 after compacting, it is mounted | worn with the said compacting apparatus so that attachment or detachment is possible.

  The forming pin 16 is inserted into the inner periphery of the die 17, and its upper end surface 16 b is located on the same plane as or above the upper end surface 17 b of the die 17. The upper end portion of the lower punch 19 is inserted into the inner periphery of the die 17, and the axial filling amount of the metal powder M becomes a predetermined value due to the axial interval from the upper end surface 19 a of the lower punch 19 to the upper end surface 17 b of the die 17. Is set.

  As the metal powder M to be filled, the above-mentioned metal powder is used as a base material. Of course, if necessary, these metal powders may be blended with a lubricant such as graphite or the same material as the shaft 2 or a material powder having a linear expansion coefficient in consideration of the difference in thermal expansion from the shaft 2. You can also.

  The mold region (cavity) related to the compacting process is defined by the outer peripheral surface 16a of the molding pin 16, the inner peripheral surface 17a of the die 17, and the upper end surface 19a of the lower punch 19, and is defined. A predetermined amount of metal powder M is filled in the region.

  From the state shown in FIG. 7, the upper punch 18 is first lowered, and the lower end surface 18a is pressed against the metal powder M being filled. Then, as shown in FIG. 8, the upper punch 18 is further lowered from the position where the lower end surface 18a is pressed (broken line position in the figure), and the metal powder M is compressed from the upper side in the axial direction. As described above, the metal powder M filled in the cavity is compressed in the axial direction in a state in which the radial direction is constrained, and is formed into, for example, a green compact having a shape shown in FIG.

  Thereafter, although not shown, the forming pin 16 and the upper and lower punches 18 and 19 are raised together (relatively moved upward with respect to the die 17), and the upper end surface 19a of the lower punch 19 is located above the die 17. The height is raised to the same height as the end face 17b or a position slightly higher than the upper end face 17b. From this position, only the upper punch 18 is further raised, the molding pin 16 is separated from the molding compression device, and the molding pin 16 is pulled out from the lower punch 19 together with the powder compact. As a result, an integral product of the shaft 2 as the molding pin 16 and the compacting body formed around the shaft 2 is obtained. Thereafter, the inner member 8 having the shaft 2 and the sleeve 7 with the shaft 2 fixed to the inner periphery is formed by sintering and sizing the integrated product of the shaft 2 and the green compact.

  Thus, when the metal powder M is compression-molded, the compression molded body (sleeve 7 before sintering) is obtained by using the shaft 2 as the molding pin 16 for molding a portion corresponding to the inner peripheral surface of the sleeve 7. And the shaft 2 can be integrated. As a result, no press-fitting into the sleeve 7 is required to fix the sleeve 7 to the shaft 2, so that the occurrence of contamination can be avoided and the cleaning operation can be further simplified. Of course, as long as the shaft 2 is used as an inner mold (in this case, the molding pin 16) at the time of compacting the metal powder M, a method other than the above can be adopted. In the compacting process, after the metal powder M is compressed, the die 17 is first lowered, and then the upper punch 18 is raised with respect to the molding pin 16 and the lower punch 19 to remove the molded product from the mold. Although the case of taking out was described, it is also possible to take a procedure in which the die 17 is lowered after the upper punch 18 is first raised.

  In the above embodiment, the case where the sleeve 7 is formed in a cylindrical shape having both ends opened and fixed to the shaft 2 has been described. However, the present invention is not necessarily limited to this form. For example, in the above compacting process, the metal pin M is filled with the upper end surface 16b of the molding pin 16 below the upper end surface 17b of the die 17, and the metal is formed using the solid upper punch 18. The powder M can also be compression molded. In this case, the bottomed cylindrical sleeve 7 whose one end in the axial direction is closed and the inner member 8 having the shaft 2 fixed to the inner periphery thereof can be obtained.

  Further, in order to increase the fixing force between the shaft 2 and the sleeve 7, although not shown in the figure, a forming pin 16 or a sizing pin 12 provided with an arbitrarily shaped different diameter portion (for example, a convex portion or a concave portion) on the outer peripheral surface is used. You can also In this case, the different diameter portion acts as a retaining or detent for the sleeve 7 with respect to the shaft 2.

  Further, when the hydrodynamic bearing device 1 is used, for example, illustration is omitted for the purpose of preventing the pressure balance between the space facing the lower end surface 7b of the sleeve 7 and the space facing the upper end surface 7c from being lost. Between the inner peripheral surface of the sleeve 7 and the outer peripheral surface of the shaft 2, it is also possible to form a through hole for allowing lubricating oil to flow between the two spaces. As such through-holes, for example, during compression molding of the metal powder M, compression molding is performed by using a molding pin 16 provided with one or a plurality of protrusions extending in the axial direction on the outer periphery thereof (sleeve 7). An axial groove can be formed on the inner periphery of the. Alternatively, at the time of sizing the sintered body 11 having a perfect circular inner peripheral surface, by using a sizing pin 12 having one or more axial grooves formed on the outer periphery, the axial grooves can be directly used as through holes. Can be used. In any case, the groove size should be designed so that the groove is not filled by sizing.

  Moreover, although the above embodiment demonstrated the case where the area | region which arranged the several dynamic pressure grooves 7a1 and 7a2 in the herringbone shape was formed in the outer peripheral surface 7a of the sleeve 7, this invention is not restricted to the said structure. The present invention can be similarly applied to a dynamic pressure generating unit having another configuration.

  For example, as a dynamic pressure generating portion molded on the outer peripheral surface 7a, although not shown in the drawings, axial grooves are formed at a plurality of locations in the circumferential direction and between the inner peripheral surfaces 9a1 of the housings 9 facing each other. The present invention can be applied to a so-called step bearing in which a radial gap (bearing gap) that changes in a step shape is formed. Alternatively, the present invention is applied to a so-called multi-arc bearing in which a plurality of circular arc surfaces are arranged in the circumferential direction and a wedge-shaped radial clearance (bearing clearance) is formed between the opposing circular inner peripheral surfaces 9a1. The invention can be applied. The formation method of these dynamic pressure generating parts depends on the shape of the dynamic pressure generating part, but in addition to the above sizing process, a collection of a small amount of ink including rolling process, press process, laser processing, ink jet method, etc. Forming processing by the body can be used.

  Further, in the above embodiment, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 and causes a dynamic pressure action in the radial bearing gap or the thrust bearing gap. A fluid capable of causing a dynamic pressure action, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

1 is a cross-sectional view of a spindle motor for information equipment incorporating a hydrodynamic bearing device according to an embodiment of the present invention. It is sectional drawing of a hydrodynamic bearing apparatus. It is a figure which shows notionally an example of the sizing process of a sleeve part. It is a figure which shows notionally an example of the sizing process of a sleeve part. It is a figure which shows notionally an example of the sizing process of a sleeve part. It is a figure which shows notionally the other example of the sizing process of a sleeve part. It is a figure which shows notionally an example of the compression molding process of metal powder. It is a figure which shows notionally an example of the compression molding process of metal powder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrodynamic bearing device 2 Shaft 3 Disc hub 4 Stator coil 5 Rotor magnet 6 Bracket 7 Sleeve portion 7a Outer peripheral surface 7a1, 7a2 Dynamic pressure groove 7b Lower end surface 7c Upper end surface 8 Inner member 9 Housing 9a1 Inner peripheral surface 9b1 Upper end surface 10 Seal portion 10b Lower end surface 11 Sintered body 11a Inner peripheral surface 12 Sizing pin 13 Die 14 Upper punch 15 Lower punch 16 Molding pin 17 Die 18 Upper punch 19 Lower punch D Disc d1 Outer diameter d2 Inner diameter M Metal powder S Seal space R1, R2 Radial bearing part T1, T2 Thrust bearing part

Claims (3)

An inner member having a shaft and a sleeve made of sintered metal with the shaft fixed to the inner periphery, an outer member forming a radial bearing gap between the inner member, and an inner member with a lubricating film of fluid generated in the radial bearing gap A method of manufacturing a hydrodynamic bearing device including a radial bearing portion rotatably supported in a radial direction,
A method of manufacturing a hydrodynamic bearing device, wherein a shaft is used as an inner mold when a sleeve of an inner member is compacted. An inner member having a shaft and a sleeve made of sintered metal with the shaft fixed to the inner periphery, an outer member forming a radial bearing gap between the inner member, and an inner member with a lubricating film of fluid generated in the radial bearing gap A method of manufacturing a hydrodynamic bearing device including a radial bearing portion rotatably supported in a radial direction,
A method of manufacturing a hydrodynamic bearing device, wherein a shaft is used as an inner mold when sizing a sleeve of an inner member. An inner member having a shaft and a sleeve made of sintered metal with the shaft fixed to the inner periphery, an outer member forming a radial bearing gap between the inner member, and an inner member with a lubricating film of fluid generated in the radial bearing gap A hydrodynamic bearing device including a radial bearing portion rotatably supported in a radial direction,
A hydrodynamic bearing device in which an inner peripheral surface of a sleeve is formed by an outer peripheral surface of a shaft.

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