JP2007315487A - Dynamic pressure bearing device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve production efficiency by reducing the number of manufacturing processes of a dynamic pressure bearing device. <P>SOLUTION: An injection gate 11 is provided at a position opposing a metal part 2 arranged in a molding die in an axial direction in injection-molding a resin part of a bearing member. Molten resin injected from the injection gate 11 presses the metal part 2 and the inner bottom surface 2b of the metal part 2 is pressed against a second molding die 12b formed at a molding pin 12 to form a thrust dynamic pressure generating part B on the metal part 2. Consequently, since the thrust dynamic pressure generating part B can be formed simultaneously by injection-moulding the resin part 3, the number of manufacturing processes of the bearing member can be reduced and production efficiency can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft member by a hydrodynamic action generated in a lubricating film in a bearing gap, and a manufacturing method thereof.

  Due to its high rotational accuracy and quietness, the hydrodynamic bearing device is an information device, for example, a magnetic disk drive device such as HDD, an optical disk drive device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, MD, Suitable for spindle motors such as magneto-optical disk drive devices such as MOs, small motors such as fan motors used for laser beam printer (LBP) polygon scanner motors, projector color wheels, cooling fans for electrical equipment, etc. Can be used.

  For example, a hydrodynamic bearing device disclosed in Patent Document 1 includes a shaft member, a bottomed cylindrical resin housing having a shaft member inserted into an inner periphery thereof, and a bottom surface of the housing. And a metal part (thrust member) facing each other through a thrust bearing gap, and a thrust dynamic pressure generating part that is formed on an end surface of the metal part and generates a dynamic pressure action on the lubricating fluid in the thrust bearing gap. Thus, by reducing the material cost by making the housing resin, the wear resistance of the thrust dynamic pressure generating part is improved by forming the thrust dynamic pressure generating part on the end surface of the metal part. Can do.

JP 2005-114164 A

  However, in the hydrodynamic bearing device as described above, it is necessary to arrange the metal part in which the thrust dynamic pressure generating part is formed in advance on the bottom part of the separately formed housing, which increases the number of processes and reduces the production efficiency. I was invited.

  An object of the present invention is to reduce the number of manufacturing steps of a hydrodynamic bearing device and improve production efficiency.

  In order to solve the above-mentioned problems, the present invention provides a shaft member, a metal part facing the shaft member through a thrust bearing gap, a resin part formed by injection molding using the metal part as an insert part, and a metal part. This is a method for manufacturing a hydrodynamic bearing device having a thrust dynamic pressure generating section that generates a dynamic pressure action on the lubricating fluid in the bearing gap, and corresponds to the thrust dynamic pressure generating section when the resin part is injection molded. Forming a thrust dynamic pressure generating part on the metal part by placing the metal part between the molding die having the shape and the injection gate and pressing the metal part against the molding die with the pressure of the resin injected from the injection gate It is characterized by.

  In order to solve the above problems, the present invention provides a shaft member, a metal portion opposed to the end surface of the shaft member via a thrust bearing gap, a resin portion injection-molded using the metal portion as an insert component, and a metal portion. In the hydrodynamic bearing device having a thrust dynamic pressure generating portion that is formed and generates a dynamic pressure action on the lubricating fluid in the thrust bearing gap, the injection gate trace of the resin portion is formed at a position facing the metal portion in the axial direction. It is characterized by that. Here, the gate mark refers to a location where the gate position when filling the molten resin into the molding die during injection molding can be determined from the molded product, for example, among the resin solidified inside the gate during injection molding, Including the part remaining on the surface of the molded product even after gate cutting. Alternatively, a gate removal trace formed when the remaining portion is removed by machining or the like is included.

  As described above, in the present invention, a molding die having a shape corresponding to the thrust dynamic pressure generating portion is formed in a mold for injection molding the resin portion, and the metal portion is disposed between the molding die and the injection gate. Then, the thrust dynamic pressure generating portion is formed on the metal portion by pressing the metal portion against the forming die with the pressure of the resin injected from the injection gate. Thereby, since the thrust dynamic pressure generating portion can be formed simultaneously with the injection molding of the resin portion, the number of manufacturing steps of the dynamic pressure bearing device can be reduced, and the production efficiency can be improved. The injection gate trace of the resin part thus molded is formed at a position facing the metal part in the axial direction. The pressure of the resin injected from the injection gate (hereinafter referred to as “injection resin pressure”) refers to the pressure (hereinafter referred to as “injection pressure”) caused by the injected resin colliding with the metal part, and the cavity. This is the pressure applied to the resin (hereinafter referred to as “holding pressure”) in order to maintain the pressure in the cavity after the inside is filled with the resin, and the metal part is pressed by at least one of these pressures.

  When this injection gate is formed in a dot shape, the pressure of the injected resin can be increased, and thus the thrust dynamic pressure generating portion can be more reliably formed.

  As described above, according to the present invention, the number of manufacturing steps of the hydrodynamic bearing device can be reduced and the production efficiency can be improved.

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

  FIG. 1 shows a hydrodynamic bearing device 1 according to a first embodiment of the present invention. The hydrodynamic bearing device 1 includes a shaft member 5 and a bottomed cylindrical bearing member 4 in which the shaft member 5 is inserted into the inner periphery. The bearing member 4 includes a metal part 2 and a resin part 3 that holds the metal part 2. For convenience of explanation, the following explanation will be made with the closed side of the metal part 2 as the lower side and the opening side as the upper side.

  The shaft member 5 is formed in a cylindrical shape with a metal material such as SUS. The outer peripheral surface 5a of the shaft member 5 is opposed to the inner peripheral surface 2a of the metal portion 2 via a radial bearing gap, and the lower end surface 5b of the shaft member 5 is opposed to the inner bottom surface 2b of the metal portion 2 via a thrust bearing gap. opposite.

  The metal part 2 is formed in a bottomed cylindrical shape by, for example, electroforming. Specifically, first, a master is immersed in a solution containing a metal used for the metal part 2 and the solution is energized (so-called electrolytic plating), or by a chemical reaction without energization (so-called electroless). Plating) and depositing the metal part 2 on the surface of the master. Then, the metal part 2 is formed by separating the metal part 2 and the master. The metal part 2 is not limited to electroforming, and can be formed by other processing methods such as turning, pressing, and forging.

  On the entire inner surface or a part of the cylindrical region of the metal part 2, a plurality of unillustrated dynamic pressure grooves are formed in two herringbone-shaped regions separated in the axial direction. Radial dynamic pressure generating portions A1 and A2 (shown by cross hatching in FIG. 1).

  A region where a plurality of dynamic pressure grooves (not shown) are arranged in a spiral shape is formed in a ring shape on the entire inner surface or a part of the annular region of the inner bottom surface 2b of the metal portion 2, and this region becomes a thrust dynamic pressure generating portion B (see FIG. 1 is indicated by cross-hatching).

  The resin portion 3 covers the outer peripheral surface and the lower end surface of the metal portion 2 and is formed by injection molding using the metal portion 2 as an insert part. Below, the injection molding process of the resin part 4 is demonstrated using FIG.2 and FIG.3.

  As shown in FIG. 2, the mold used in this injection molding process includes a fixed mold 6 and a movable mold 7. The fixed mold 6 includes a first fixed mold 61 and a second fixed mold 62 disposed on the inner periphery of the first fixed mold 61. The first fixed mold 61 includes an inner peripheral surface 61a and an inner bottom surface 61b extending from the lower end of the inner peripheral surface 61a toward the inner diameter, and a sprue 10 for injecting molten resin at the center of the inner bottom surface 61b. And the injection gate 11 (in this embodiment, a dotted gate) is formed.

  The second fixed mold 62 is integrally provided with a holding part 62a fitted to the inner peripheral surface 61a of the first fixed mold 61, and a cylindrical molding part 62b disposed on the inner diameter side of the holding part 62a. The molding portion 62b is supported by the holding portion 62a in a cantilever shape so as to be elastically deformable via a fixing portion 62c extending from the lower end of the inner peripheral surface of the holding portion 62a toward the inner diameter. In the present embodiment, the first fixed mold 61 and the second fixed mold 62 are formed separately, but they may be integrally formed.

  The movable die 7 includes a first end surface 7a that abuts on the end surface of the first fixed die 61, and a second end surface 7b that abuts on the end surface of the second fixed die 62. A fixed hole is formed at the center of the second end surface 7b. 7c is formed, and the molding pin 12 is inserted and fixed in the fixing hole 7c. The forming pin 12 includes first forming molds 12a1 and 12a2 for forming dynamic pressure generating portions A1 and A2 on the inner peripheral surface 2a of the metal portion 2 on the outer peripheral surface 12a, and the lower end surface of the metal portion 2 A second molding die 12b for forming the dynamic pressure generating part B is provided on the inner bottom surface 2b (see FIG. 3). The metal part 2, which is an electroformed product separated from the master, is extrapolated to the molding pin 12, and in this state, the movable part 7 is brought into contact with the fixed mold 6 and clamped to thereby form the metal part 2 and the molding. The pin 12 is positioned in the mold. In the present embodiment, the first end surface 7a and the second end surface 7b are provided via a step in the axial direction, but they may be provided on the same plane.

  At the time of clamping, the cavity 13 is formed by the second end surface 7b of the movable mold 7, the inner bottom surface 61b of the first fixed mold 61, and the inner peripheral surface 62b1 of the molding portion 62b of the second fixed mold 62, and the first 2 A hydraulic space 63 is formed by the radial gap between the holding portion 62a and the molding portion 62b of the fixed die 62 and the second end surface 7b of the movable die 7 (see FIGS. 2 and 3A). . The interiors of the hydraulic space 63 and the hydraulic path 9 are filled with oil.

  Thereafter, as shown in FIG. 3B, the molten resin is injected into the cavity 13 through the sprue 10 and the gate 11 provided in the fixed mold 6. As shown by the arrow in FIG. 3B, the molten resin injected from the gate 11 flows in the outer diameter direction after colliding with the lower end surface 2c of the metal part 2 disposed at a position facing the gate 11. . The metal part 2 is pressed by the collision of the injected resin (injection pressure). Thereafter, when the cavity 13 is filled with resin, pressure is applied to the resin in the cavity 13 via the gate 11 in order to keep the pressure in the cavity 13 constant (pressure holding). The inner bottom surface 2b of the metal part 2 is pressed against the second mold 12b formed on the lower end surface of the inner mold 12 by at least one of the injection pressure and the holding pressure (pressure of the injection resin). As a result, the shape of the second molding die 12b is transferred to the inner bottom surface 2b1 of the metal part 2, and the thrust dynamic pressure generating part B is formed.

  Thus, in the present invention, by providing the gate 11 at a position facing the lower end surface 2c of the metal part 2 in the axial direction, the metal part 2 can be reliably pressed by the pressure of the injection resin. Thereby, since the thrust dynamic pressure generating part B can be performed simultaneously with the injection molding of the resin part 3, the number of manufacturing steps of the bearing member 4 can be reduced, and the production efficiency can be improved. In addition, when the injection gate 11 is formed like a dot as in the present embodiment, the pressure of the injection resin, particularly the injection pressure, can be increased, so that the thrust dynamic pressure generating portion B can be formed more reliably.

  When the oil filled in the hydraulic space 63 is pressurized through the hydraulic path 9 after the resin is solidified, the inner peripheral surface 62b1 of the molding part 62b of the second fixed mold 62 is elastically reduced in diameter, and the resin part 3 The metal part 2 is pressed from the outer periphery through the inner periphery, and the inner peripheral surface 2a of the metal part 2 is elastically reduced in diameter (see FIG. 3C). Thereby, the inner peripheral surface 2a of the metal part 2 is pressed against the first molding dies 12a1 and 12a2 formed on the outer peripheral surface 12a of the molding pin 12, and the shape of the first molding dies 12a1 and 12a2 is changed to the inner periphery of the metal part 2. Transferred to the surface 2a, radial dynamic pressure generating portions A1 and A2 are formed.

  Thereafter, when the pressure applied to the oil in the hydraulic space 63 is released, the inner peripheral surface 62b1 of the molding portion 62b of the second fixed mold 62 and the inner peripheral surface 2a of the metal portion 2 are elastically expanded in diameter. The radial dynamic pressure generating parts A1 and A2 on the inner peripheral surface 2a of the metal part 2 that have bitten into the first molds 12a1 and 12a2 are peeled off from the first molds 12a1 and 12a2. As a result, a minute gap is formed between the radial dynamic pressure generating portions A1 and A2 and the first molding dies 12a1 and 12a2. Therefore, when the molding pin 12 and the bearing member 4 are separated, the radial dynamic pressure generating portion A1. Since the axial interference between A2 and the first molds 12a1 and 12a2 can be avoided or reduced, damage to the radial dynamic pressure generating portions A1 and A2 can be avoided. On the other hand, since the thrust dynamic pressure generating part B does not interfere with the second molding die 12b at the time of mold release, there is no fear of damage.

  Incidentally, as shown in FIG. 3C, the molding portion 62b at the time of pressurization of the oil in the hydraulic space 63 hardly displaces on the fixed portion 62c side of the molding portion 62b, and the displacement amount increases toward the upper side in the figure. Since it becomes large, it is inclined and deformed with respect to the position of the molding part 62b before pressing (indicated by a dotted line in FIG. 3C). For this reason, when the inner peripheral surface 2a of the metal part 2 is pressed against the forming die, the groove depth of the lower radial dynamic pressure generating part A2 is shallower than the groove depth of the upper radial dynamic pressure generating part A1. There is. In this case, by adjusting the thickness applied to the molding portion 62b and the pressure applied to the oil in the hydraulic space 63, and adjusting the deformation amount of the molding portion 62b, the radial dynamic pressure generating portion A2 exhibits sufficient dynamic pressure action. A groove depth that can be obtained can be obtained.

  When the fixed mold 6 and the bearing member 4 are separated, the resin solidified in the gate 11 is automatically cut or cut by the gate cut mechanism, and a part of the resin cut to the gate corresponding position of the resin portion 3 is obtained. It remains as gate trace 11a. The gate trace 11a may be removed by machining or the like. In this case, the removal trace of the gate trace 11a remains on the lower end surface 3b of the resin portion 3 (see FIG. 1).

  The shaft member 5 is inserted into the integral part of the metal part 2 and the resin part 3 thus formed, that is, the inner periphery of the bearing member 4, and the space formed between the shaft member 5 and the bearing member 4 is lubricated. The fluid dynamic bearing device 1 is completed by filling the oil.

  Various lubricants can be used as the lubricating oil filled in the hydrodynamic bearing device 1. For example, ester lubricants excellent in low evaporation rate and low viscosity, such as dioctyl sebacate (DOS), dioctyl, etc. Azelate (DOZ) or the like can be used.

  In the dynamic pressure bearing device 1 having the above-described configuration, when the shaft member 5 rotates, the radial dynamic pressure generating portion in which the lubricating oil in the radial bearing gap is formed on the inner peripheral surface 2a of the metal portion 2 as the shaft member 5 rotates. The herringbone-shaped dynamic pressure grooves as A1 and A2 are pushed into the axial center side, and the pressure rises. In this manner, the radial bearing portions R1 and R2 that support the shaft member 5 in the radial direction in a non-contact manner are configured by the dynamic pressure action of the lubricating oil generated by the radial dynamic pressure generating portions A1 and A2, respectively.

  At the same time, the thrust dynamic pressure generating section B generates a dynamic pressure action on the lubricating oil in the thrust bearing gap, thereby forming a thrust bearing section T that supports the shaft member 5 in a non-contact manner in the thrust direction.

  The embodiment of the present invention is not limited to the above. In the above embodiment, the case where the metal part 2 is formed of a metal material by forging or electroforming is shown. However, for example, when the metal part 2 is formed of sintered metal, the inside of the sintered metal is impregnated. Since the lubricating oil is sequentially supplied to the thrust bearing gap, the lubricity can be further improved.

  Further, in the above embodiment, the case where the herringbone-shaped dynamic pressure groove is formed as the radial dynamic pressure generating portion is shown, but not limited to this, for example, the spiral-shaped dynamic pressure groove as the radial dynamic pressure generating portion Alternatively, a multi-arc bearing, a step bearing, or the like can be employed. In addition, a spiral-shaped dynamic pressure groove is used as the thrust dynamic pressure generating portion. For example, a herringbone-shaped dynamic pressure groove, a step bearing, or a corrugated bearing (the step bearing has a corrugated shape) ) Etc. can also be adopted.

  Further, in the above embodiment, the radial dynamic pressure generating portion is formed on the metal portion, but may be formed on the inner peripheral surface of the molding resin. Moreover, you may form a radial dynamic-pressure generation | occurrence | production part not on the internal peripheral surface of a bearing member but on the outer peripheral surface of the shaft member facing this surface.

  Below, the case where the hydrodynamic bearing apparatus 1 formed with the manufacturing method which concerns on this invention is integrated in the fan motor used for the cooling fan etc. of an electric equipment is shown.

  FIG. 4 is a cross-sectional view conceptually showing a fan motor incorporating the fluid dynamic bearing device 1. This fan motor includes a hydrodynamic bearing device 1 that supports a shaft member 5 in a non-contact manner in a freely rotatable manner, a rotor 33 attached to the shaft member 5, a fan 34 attached to an outer diameter end of the rotor 33, and a radius, for example. A stator coil 36 and a rotor magnet 37 that are opposed to each other via a gap in a direction (radial direction), and a casing 35 that accommodates these and has an upper end surface and a part of a side surface that are open. It is called a radial gap type fan motor. The stator coil 36 is attached to the outer periphery of the hydrodynamic bearing device 1, and the rotor magnet 37 is attached to the rotor 33. As a form of the fan motor, a so-called axial gap type fan motor in which the stator coil 36 and the rotor magnet 37 are opposed to each other via a gap in the axial direction (axial direction) can be used (not shown).

  When the stator coil 36 is energized, the rotor magnet 37 is rotated by the electromagnetic force between the stator coil 36 and the rotor magnet 37, whereby the rotor 33 and the fan 34 rotate integrally with the shaft member 5. When the fan 34 rotates, outside air is drawn in the direction of arrow Y in FIG. 1 from the upper end opening 35a of the casing 35, and the air in the casing is discharged from the side opening 35b in the direction of arrow X. Such a fan motor is installed such that other devices are cooled by the airflow discharged from the side opening 35b, or the lower end surface faces another device (shown by a one-dot chain line in FIG. 8). Then, the heat of the other device is transmitted to the fan motor, and the heat transmitted to the fan motor by the airflow is radiated to the outside, so that the device can be cooled.

  The hydrodynamic bearing device 1 as described above can be applied not only to a fan motor but also to a spindle motor used for a disk starting device of an HDD or the like.

1 is a cross-sectional view showing a fluid dynamic bearing device 1. 4 is a cross-sectional view showing an injection molding process of a resin part 3. FIG. FIG. 4 is a cross-sectional view showing (a) a state before injection molding, (b) a step of forming a thrust dynamic pressure generating portion simultaneously with injection molding, and (c) a step of forming a radial dynamic pressure generating portion in a molding die. It is sectional drawing which shows the fan motor incorporating the fluid dynamic bearing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Metal part 3 Resin part 4 Bearing member 5 Shaft member 6 Fixed type | mold 7 Movable type | mold 9 Hydraulic path 10 Sprue 11 Gate 11a Gate trace 12 Molding pin 12a1, 12a2 1st shaping | molding die 12b 2nd shaping | molding die 13 Cavity A1, A2 Radial dynamic pressure generating part B Thrust dynamic pressure generating part R1, R2 Radial bearing part T Thrust bearing part

Claims (4)

A shaft member, a metal part facing the shaft member through a thrust bearing gap, a resin part injection-molded with the metal part as an insert part, and a metal part, generates a hydrodynamic action on the lubricating fluid in the thrust bearing gap A method for manufacturing a hydrodynamic bearing device including a thrust dynamic pressure generating unit,
When the resin part is injection-molded, the metal part is arranged between a mold having a shape corresponding to the thrust dynamic pressure generating part and the injection gate, and the metal part is pressed against the mold by the pressure of the resin injected from the injection gate. Thus, a method of manufacturing a hydrodynamic bearing device, wherein a thrust dynamic pressure generating portion is formed on a metal portion.   The method of manufacturing a hydrodynamic bearing device according to claim 1, wherein the injection gate is formed in a dot shape. A shaft member, a metal part facing the shaft member through a thrust bearing gap, a resin part injection-molded with the metal part as an insert part, and a metal part, generates a hydrodynamic action on the lubricating fluid in the thrust bearing gap A hydrodynamic bearing device including a thrust dynamic pressure generating unit
A hydrodynamic bearing device, wherein an injection gate trace of a resin portion is formed at a position facing an axial direction of a metal portion.   The hydrodynamic bearing device according to claim 3, wherein the injection gate trace is formed in a dot shape.

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