Spindle motor and hard disk drive

Abstract

To provide a spindle motor in which a hole formed on a surface of a rotor hub is sealed.SOLUTION: A spindle motor comprises a stationary part 10, a rotary part 20 which is rotated with respect to the stationary part 10, and a shaft 70 which is connected to the rotary part 20. The rotary part 20 consists of a metal material containing an inclusion, and a hole 80H exposed on a surface of the rotary part 20 is filled with a resin material.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a spindle motor and a hard disk drive device.

Background Art

[0002] A special motor called a spindle motor is used in a hard disk drive device. The spindle motor plays a role in supporting and rotating a recording disk, which is a recording medium. In the spindle motor, the recording disk is supported by a rotating rotor hub. If the machining accuracy of the rotor hub is poor, it will cause the recording disk to vibrate. Therefore, the rotor hub is manufactured by high-precision cutting. Accordingly, a free-cutting steel suitable for high-precision cutting is used as the material of the rotor hub.

[0003] Free-cutting steel is a steel material added with free-cutting components. The free-cutting components do not combine with the metal structure of the steel material and exist as inclusions. Therefore, due to the rotational movement of the rotor hub and the vibration generated in the rotor hub, inclusions may fall off from the surface of the rotor hub. The fallen inclusions may become particulate contaminants and contaminate the inside of the hard disk device.

[0004] Patent Document 1 discloses a rotor hub of a spindle motor manufactured by using plastic working and cutting working in combination. By plastic working, the inclusions in the free-cutting steel are deformed and inclined, so that the fall-off of the inclusions from the rotor hub is suppressed.

Prior Art Documents

Patent Documents

[0005] [[ID=?]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, if machining is performed on an area where inclusions are present, the surface of the inclusions may be worn away, creating holes. When such holes are formed on the rotor hub surface, the inclusions become more prone to falling out.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a spindle motor in which holes formed on the rotor hub surface are sealed. [Means for solving the problem]

[0008] To solve the above problems, a spindle motor is provided comprising a stationary part, a rotating part that rotates relative to the stationary part, and a shaft member connected to either the stationary part or the rotating part, wherein the rotating part is made of a metal material containing inclusions, and a resin material is filled into holes exposed on the surface of the rotating part. [Effects of the Invention]

[0009] According to the present invention, since the holes exposed on the surface of the rotating part are filled with resin material, the holes can be sealed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of the hard disk drive unit 1. [Figure 2] This is a partial cross-sectional view of the spindle motor 3. [Figure 3] This is an enlarged image of hole 80H in section III of Figure 2. [Figure 4] This is a flowchart illustrating the impregnation process. [Figure 5] This is a partial cross-sectional view of the spindle motor 103. [Figure 6] This is a partial cross-sectional view of the spindle motor 303. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are subject to various technically preferred limitations for carrying out the present invention, but the scope of the present invention is not limited to the following embodiments and illustrated examples.

[0012] Figure 1 is a perspective view showing the configuration of the hard disk drive unit 1. Figure 2 is a partial cross-sectional view showing an example of a spindle motor 3 used in the hard disk drive unit 1.

[0013] Here, as shown in Figure 2, the direction parallel to the central axis of the shaft 70 (described later) is defined as the axial direction, the direction around the central axis of the shaft 70 is defined as the circumferential direction, and the direction perpendicular to the axial direction is defined as the radial direction. For the sake of explanation, the axial direction is defined as the up-down direction, with the rotating part 20 side being above the stationary part 10 and the stationary part 10 side being below.

[0014] <Hard disk drive> The hard disk drive unit 1 comprises a housing 2, a spindle motor 3, a recording disk 4, and a bearing device 5.

[0015] The housing 2 comprises a case 6 and a cover 7. The case 6 has a bottomed box shape with one side of a roughly rectangular parallelepiped open. The cover 7 is a plate-shaped member that closes the open side of the case 6. The cover 7 is fastened to the case 6 using fastening means such as screws. A sealing means (not shown) is provided between the case 6 and the cover 7, thereby forming a housing 2 with a sealed internal space S together with the case 6.

[0016] The internal space S of the housing 2 is filled with air or helium gas, which has a lower density than air. In addition to air or helium gas, the internal space S may also be filled with, for example, nitrogen gas or a mixture of helium and nitrogen gas. The internal space S houses the spindle motor 3, the recording disk 4, and the bearing device 5.

[0017] The spindle motor 3 rotatably supports a plurality of recording disks 4. Details of the structure of the spindle motor 3 will be described later.

[0018] A plurality of recording disks 4 are provided and are supported by the spindle motor 3 such that their respective disk surfaces face each other. A gap is formed between each of the recording disks 4.

[0019] The bearing device 5 swingably supports a plurality of swing arms 8 disposed in the gaps between the respective recording disks 4.

[0020] The swing arm 8 has a magnetic head 9 at its tip. The magnetic head 9 applies magnetism to the recording disk 4 and reads magnetism from the recording disk 4. When the swing arm 8 swings, the magnetic head 9 moves over the recording disk 4.

[0021] When the spindle motor 3 rotates, the recording disk 4 also rotates. In that state, when the swing arm 8 swings, the magnetic head 9 moves over the rotating recording disk 4. Then, the magnetic head 9 applies magnetism to the recording disk 4 to record data on the recording disk 4. Also, the magnetic head 9 reads magnetism from the recording disk 4 to read the data stored on the recording disk 4.

[0022] <Spindle Motor> Next, the detailed configuration of the spindle motor 3 will be described. As shown in FIG. 2, the spindle motor 3 includes a stationary part 10 and a rotating part 20 that rotates with respect to the stationary part 10 via a bearing mechanism.

[0023] (Stationary Part) The stationary part 10 has a base plate 30, a bearing sleeve 40, a stator core 50, and a magnetic attraction plate 60.

[0024] The base plate 30 is a metal member. A through hole 31, a circumferential groove part 32, a circumferential wall part 33, and a plate recess 34 are formed in the base plate 30.

[0025] The through-hole 31 is a hole for fixing the bearing sleeve 40. The through-hole 31 is provided so as to penetrate the base plate 30 in the axial direction. The through-hole 31 is cylindrical, and the inner diameter of the cylinder is approximately the same as or larger than the outer diameter of the bearing sleeve 40.

[0026] The circumferential groove 32 is formed on the radially outer side of the through hole 31. The circumferential groove 32 is an annular groove provided so as to be coaxial with the central axis of the through hole 31 when viewed in the axial direction.

[0027] The circumferential wall portion 33 is formed radially outside the through hole 31 and inside the circumferential groove portion 32. The circumferential wall portion 33 is an annular wall provided so as to be coaxial with the central axis of the through hole 31 in an axial view, and it protrudes upward in the axial direction.

[0028] The plate recess 34 is formed radially inward of the circumferential wall portion 33. The plate recess 34 is a cylindrical space provided so as to be coaxial with the central axis of the through hole 31 in an axial view, and it opens upward. The diameter of the plate recess 34 is larger than the outer diameter of the through hole 31. The plate recess 34 is connected axially to the upper side of the through hole 31.

[0029] The bearing sleeve 40 rotatably supports the shaft 70. The bearing sleeve 40 is a cylindrical iron component such as stainless steel. The bearing sleeve 40 is inserted into the through hole 31 (see Figure 2). The bearing sleeve 40 is fixed to the through hole 31 by adhesive applied to one or both sides of the outer circumferential surface of the bearing sleeve 40 and the inner circumferential surface of the through hole 31. The bearing sleeve 40 is provided with a radial dynamic pressure generating groove 41 and a thrust dynamic pressure generating groove 42.

[0030] The radial dynamic pressure generating grooves 41 are provided on the inner circumferential surface 40a of the bearing sleeve 40. In this embodiment, the radial dynamic pressure generating grooves 41 are formed on the inner circumferential surface 40a in a continuous row in the circumferential direction, and two rows are formed with an interval between them in the axial direction.

[0031] The thrust dynamic pressure generating groove 42 is provided on the end face 44 of the axially upper sleeve end 43a of the bearing sleeve 40. The thrust dynamic pressure generating groove 42 is provided in an annular shape so as to be coaxial with the central axis of the bearing sleeve 40 when viewed in the axial direction.

[0032] A large-diameter recess 45 and a small-diameter recess 46 are formed continuously in the axial direction at the axial lower sleeve end 43b of the bearing sleeve 40. A counter plate 47 is attached to the large-diameter recess 45.

[0033] The large-diameter recess 45 is formed at the sleeve end 43b. The large-diameter recess 45 is a cylindrical space provided so as to be coaxial with the central axis of the through hole 31 in an axial view. The large-diameter recess 45 opens downward.

[0034] The small-diameter recess 46 is formed on the upper side of the large-diameter recess 45 at the sleeve end 43b. The small-diameter recess 46 is a cylindrical space provided so as to be coaxial with the central axis of the through hole 31 in an axial view. The small-diameter recess 46 is connected to the large-diameter recess 45 in the axial direction. The diameter of the small-diameter recess 46 is smaller than the diameter of the large-diameter recess 45. As a result of the formation of the small-diameter recess 46 at the sleeve end 43b, the bearing sleeve 40 has an annular surface 48 in an axial view and an inner circumferential surface 49 in the circumferential direction.

[0035] The counter plate 47 is a disc-shaped cover inserted into the large-diameter recess 45 from below the sleeve end 43b. The counter plate 47 closes the large-diameter recess 45 and the small-diameter recess 46. The counter plate 47 is made of iron, such as stainless steel. The outer diameter of the counter plate 47 is approximately equal to the inner diameter of the large-diameter recess 45. The axial thickness of the counter plate 47 is approximately equal to the depth of the large-diameter recess 45.

[0036] When the counter plate 47 is inserted into the large-diameter recess 45, the outer edge of the counter plate 47 and the inner edge of the large-diameter recess 45 are joined by laser welding. In this way, the counter plate 47 is fixed to the bearing sleeve 40 without any gaps and closes the large-diameter recess 45 and the small-diameter recess 46.

[0037] The stator core 50 is a component formed by stacking multiple annular electromagnetic steel sheets in the axial direction when viewed axially. The stator core 50 is placed inside the circumferential groove 32 and fixed by adhesive or other methods. The stator core 50 has pole teeth (salient poles) that extend radially outward and are arranged in multiple locations along the circumferential direction. Coils 51 are wound around the pole teeth. The stator core 50 generates magnetic flux when current flows through the coils 51.

[0038] The magnetic attraction plate 60 is a component that stabilizes the rotation of the rotor hub 80, which will be described later. The magnetic attraction plate 60 is made of, for example, a magnetic material. The magnetic attraction plate 60 generates a magnetic flux in accordance with the current supplied to the coil 51. The magnetic attraction plate 60 is installed radially outward from the stator core 50 in the circumferential groove 32.

[0039] (Rotating part) The rotating part 20 includes a shaft 70, a rotor hub 80, and a rotor magnet 90.

[0040] The shaft 70 (an example of a shaft member) is the rotating shaft of the spindle motor 3. The shaft 70 is rotatably supported inside the bearing sleeve 40. The shaft 70 has a columnar shaft portion 71 and a flange portion 72. The shaft portion 71 and the flange portion 72 of the shaft 70 are integrated.

[0041] The shaft portion 71 is a cylindrical shaft member. The shaft portion 71 has a flange portion 72 integrally attached to its lower shaft end portion 73. The shaft portion 71 is positioned inside the bearing sleeve 40 with the shaft end portion 73, to which the flange portion 72 is attached, facing downwards. In other words, the outer circumferential surface of the shaft portion 71 is surrounded by the inner circumferential surface 40a of the bearing sleeve 40. The outer circumferential surface of the shaft portion 71 and the inner circumferential surface 40a of the bearing sleeve 40 face each other with a small gap between them. Alternatively, instead of the inner circumferential surface 40a of the bearing sleeve 40, a radial dynamic pressure generating groove 41 may be formed on the outer circumferential surface of the shaft portion 71.

[0042] The flange portion 72 is an annular flange member that expands radially in an axial view. The flange portion 72 is positioned in the small-diameter recess 46 when the shaft 70 is supported by the bearing sleeve 40. The outer diameter of the flange portion 72 is smaller than the inner diameter of the small-diameter recess 46. The upper surface of the flange portion 72 faces the annular surface 48 formed by the small-diameter recess 46 in the bearing sleeve 40, separated by a small gap. The lower surface of the flange portion 72 faces the upper surface of the counter plate 47, separated by a small gap. The side surface of the flange portion 72 faces the inner circumferential surface 49, separated by a small gap. By positioning the flange portion 72 between the annular surface 48 and the counter plate 47, axial movement of the flange portion 72 and the shaft 70 is prevented.

[0043] Lubricating oil is filled between the shaft 70 and the bearing sleeve 40. Specifically, the lubricating oil is filled between the outer circumferential surface of the shaft portion 71 and the inner circumferential surface 40a of the bearing sleeve 40, between the upper surface of the flange portion 72 and the annular surface 48, between the lower surface of the flange portion 72 and the upper surface of the counter plate 47, and between the side surface of the flange portion 72 and the inner circumferential surface 49.

[0044] The rotor hub 80 is a component that rotates together with the shaft 70. The rotor hub 80 is attached to the upper end of the shaft 70 and connected to the shaft 70. The rotor hub 80 has a disc portion 81, a first cylindrical portion 82, a second cylindrical portion 83, and an outer edge portion 84. The manufacturing method of the rotor hub 80 will be described later.

[0045] The disc portion 81 is a disc-shaped member that is coaxial with the central axis of the shaft 70 when viewed in the axial direction. The disc portion 81 has a rotor hub through hole 85. The rotor hub through hole 85 is located at the center of the disc portion 81 when viewed in the axial direction. The disc portion 81 is fixed to the shaft 70. Specifically, the disc portion 81 is fixed to the shaft 70 by inserting the upper end of the shaft 70 into the rotor hub through hole 85 and fixing it by methods such as press-fitting or adhesive. When the shaft 70 is supported by the bearing sleeve 40, the disc portion 81 faces the end face 44 of the bearing sleeve 40 with a small gap between them.

[0046] The first cylindrical portion 82 is a cylindrical member having thickness in the radial direction. The first cylindrical portion 82 is provided so as to be coaxial with the central axis of the rotor hub through hole 85 in an axial view, and protrudes downward in the axial direction. The inner diameter of the first cylindrical portion 82 is larger than the outer diameter of the bearing sleeve 40. The inner circumferential surface of the first cylindrical portion 82 faces the outer circumferential surface of the bearing sleeve 40 with a gap between them. The outer diameter of the first cylindrical portion 82 is smaller than the inner diameter of the circumferential wall portion 33. The outer circumferential surface of the first cylindrical portion 82 faces the inner circumferential surface of the circumferential wall portion 33 with a gap between them.

[0047] The second cylindrical portion 83 is a cylindrical member having thickness in the radial direction. The second cylindrical portion 83 is provided so as to be coaxial with the central axis of the rotor hub through hole 85 in an axial view, and protrudes downward in the axial direction. The second cylindrical portion 83 is provided on the outer edge of the disc portion 81.

[0048] The outer edge portion 84 is an annular member. The outer edge portion 84 is provided at the lower end of the second cylindrical portion 83. The outer edge portion 84 protrudes radially outward from the second cylindrical portion 83 and is formed in a flange shape. Multiple recording disks 4 are installed above the outer edge portion 84 and radially outward from the second cylindrical portion 83 (see Figure 1).

[0049] Lubricating oil is filled between the rotor hub 80 and the bearing sleeve 40. Specifically, the lubricating oil is filled between the lower surface of the disc portion 81 located axially inward from the first cylindrical portion 82 and the end face 44 of the axially upper sleeve end portion 43a of the bearing sleeve 40.

[0050] The rotor magnet 90 is an annular member having a magnetic pole structure in which the polarity reverses along the circumferential direction in an axial view, in the order N, S, N, S… In this embodiment, the rotor magnet 90 is attached to the inner circumferential surface of the second cylindrical portion 83. The rotor magnet 90 is located in approximately the same position as the stator core 50 in the axial direction and in approximately the same position as the magnetic attraction plate 60 in the radial direction.

[0051] <Spindle motor operation> When current is applied to the coil 51, the magnetic attraction and repulsion forces between the magnetic poles of the rotor magnet 90 and the pole teeth of the stator core 50 switch. As a result, the rotating part 20 rotates relative to the stationary part 10 with the shaft 70 as its axis of rotation.

[0052] The shaft 70 rotates relative to the bearing sleeve 40. During this rotation, the lubricating oil is pressurized by the radial dynamic pressure generating groove 41, generating dynamic pressure in the lubricating oil. This generated dynamic pressure supports the shaft 70 radially relative to the bearing sleeve 40 in a non-contact manner.

[0053] As the shaft 70 rotates, the rotor hub 80 rotates relative to the bearing sleeve 40. At this time, the lubricating oil is pressurized by the thrust dynamic pressure generating groove 42, generating dynamic pressure in the lubricating oil. Due to the generated dynamic pressure, the rotor hub 80 is supported axially in a non-contact manner relative to the bearing sleeve 40.

[0054] <Manufacturing method for rotor hubs> Next, the manufacturing method of the rotor hub 80 will be described. The rotor hub 80 is manufactured by high-precision machining. Therefore, the material used for the rotor hub 80 is free-cutting steel suitable for high-precision machining.

[0055] The rotor hub 80 is formed by machining a base material made of free-cutting steel. As shown in the image in Figure 3, holes 80H are formed on the surface of the formed rotor hub 80. The holes 80H are minute indentations exposed on the surface of the rotor hub 80 or elongated holes along the longitudinal direction. The maximum diameter of the opening of the holes 80H is, for example, 50 micrometers or less. The holes 80H are formed, for example, when inclusions of the free-cutting component mixed with the metal component of the free-cutting steel are partially removed by machining, or when the inclusions are detached from the metal component due to external force from the machining. In addition, when machining is performed on the free-cutting steel, minute gaps between the metal component of the free-cutting steel and the inclusions are exposed on the surface.

[0056] In this embodiment, the rotor hub 80 seals the aforementioned holes 80H by filling them with a resin material. Impregnation treatment is used as the method for filling the holes 80H with the resin material.

[0057] <Impregnation process for rotor hub> Next, the impregnation treatment performed on the rotor hub 80 will be described. In this embodiment, vacuum pressure impregnation treatment is employed. Figure 4 is a flowchart of each step of the vacuum pressure impregnation treatment. The vacuum pressure impregnation treatment consists of six steps from S11 to S16. Note that the impregnation treatment is not limited to vacuum pressure impregnation treatment; any impregnation treatment method can be employed, such as vacuum impregnation treatment without the pressurization step, or immersion impregnation treatment in which the rotor hub 80 is immersed in the impregnation material.

[0058] (S11) S11 is the vacuuming process. The operator places the rotor hub 80 inside a chamber that can be depressurized and pressurized, and closes the chamber lid. Next, the operator depressurizes the inside of the chamber to create a vacuum (1 kPa or less).

[0059] (S12) S12 is the liquid filling process. The operator draws the impregnating material into the chamber, which is under vacuum. Here, acrylic resin is used as the impregnating material. Alternatively, other resin materials commonly used in impregnation treatments, such as epoxy resin, may be used as the impregnating material.

[0060] (S13) S13 is the pressurization process. The operator pressurizes the inside of the chamber into which the impregnating material has been drawn. This fills the holes 80H of the rotor hub 80 with the impregnating material. After allowing time to pass until a sufficient amount of impregnating material has filled the holes 80H, the operator depressurizes the inside of the chamber and removes the impregnating material from inside the chamber. Next, the operator confirms that the pressure inside the chamber is equal to the outside air pressure, opens the lid of the chamber, and removes the rotor hub 80 from inside the chamber.

[0061] (S14) S14 is the deliquidation process. The operator places the rotor hub 80, which has been removed from inside the chamber, into a centrifuge. The operator then operates the centrifuge to remove any excess impregnating material adhering to the surface of the rotor hub 80. Next, the operator stops the centrifuge and removes the rotor hub 80 from it.

[0062] (S15) S15 is the cleaning process. The worker places the rotor hub 80, which has been removed from the centrifugal separator, into the washing machine. Next, the worker operates the washing machine and repeatedly washes the rotor hub 80 with water and hot water to further remove any excess impregnating material adhering to the surface of the rotor hub 80. Then, the worker stops the washing machine and removes the rotor hub 80 from it. After that, the worker places the rotor hub 80 into the centrifugal separator. Then, the worker operates the centrifugal separator to remove any moisture adhering to the surface of the rotor hub 80. Next, the worker stops the centrifugal separator and removes the rotor hub 80 from it.

[0063] (S16) S16 is the curing process. The worker immerses the rotor hub 80 in hot water to cure the impregnating material filling the holes 80H. After the impregnating material has cured, the worker removes the rotor hub 80 from the hot water and dries it. In addition to immersing the rotor hub in hot water, another method for curing the impregnating material is to heat-cur the rotor hub in an oven or similar device.

[0064] <Confirmation of the effect of sealing the holes> For rotor hubs 80 of the same shape formed by machining, samples were prepared with the aforementioned impregnation treatment and samples without impregnation treatment. The number of particles was measured using the liquid particle counting method, a commonly used dust generation measurement method, in the following procedure. First, the samples were immersed in a container of ultrapure water, and the entire container was exposed to ultrasound for a predetermined time. Next, the number of particles contained in the ultrapure water in the container was measured using a liquid particle measuring device. As a result, the number of particles in the sample without impregnation treatment was 100, while the number of particles in the sample with impregnation treatment was 39. In other words, it was confirmed that the rotor hub 80 with impregnation treatment could reduce the number of particles that fell off compared to the rotor hub without impregnation treatment.

[0065] <Effects> The spindle motor 3 according to this embodiment comprises a stationary part 10, a rotating part 20 that rotates relative to the stationary part 10, and a shaft 70 connected to the rotating part 20. The rotating part 20 is made of a metal material containing inclusions, and a resin material is filled into holes 80H exposed on the surface of the rotating part 20.

[0066] With the spindle motor 3 described above, the holes 80H exposed on the surface of the rotating part 20 are filled with resin material, thus sealing the holes 80H. Furthermore, because the holes 80H are sealed, it becomes difficult for inclusions to fall out of the holes 80H.

[0067] Furthermore, in this embodiment, the spindle motor 3 has a rotating part 20 in contact with lubricating oil filled between it and the stationary part 10.

[0068] With the spindle motor 3 described above, the hole 80H in the rotating part 20 is sealed. Therefore, inclusions fall out of the rotating part 20 and are less likely to come into contact with the lubricating oil filled between the rotating part 20 and the stationary part 10, thus preventing the lubricating oil from deteriorating.

[0069] Furthermore, in this embodiment, the spindle motor 3 has a resin material filling the holes 80H by impregnation.

[0070] According to the spindle motor 3 described above, the resin material is filled into the holes 80H by impregnation treatment. Impregnation treatment is a treatment method used to seal holes formed in a component. In particular, vacuum pressure impregnation treatment fills the target component with resin material by applying pressure after vacuuming, making it easy to fill even minute holes with resin material. Therefore, even minute holes 80H are easily filled with resin material without gaps, and leakage of sealing of holes 80H is unlikely to occur.

[0071] Furthermore, the impregnation process involves filling the target component with resin material, and then washing the component to remove any excess resin material adhering to the surface. Therefore, the 80H holes can be filled with resin material without causing any dimensional changes in the target component.

[0072] Furthermore, in this embodiment, the spindle motor 3 has acrylic resin filled in the hole 80H.

[0073] According to the spindle motor 3 described above, since the hole 80H is filled with acrylic resin, which is a common resin, no special resin material is required to seal the hole 80H.

[0074] Furthermore, in this embodiment, the spindle motor 3 has a rotor hub 80 as its rotating part 20.

[0075] With the spindle motor 3 described above, resin material is filled into the holes 80H exposed on the surface of the rotor hub 80, making it less likely for inclusions to fall out of the rotor hub 80.

[0076] Furthermore, the hard disk drive unit 1 according to this embodiment includes a spindle motor 3.

[0077] With the hard disk drive described above, since the hole 80H of the rotating part 20 is sealed, it is difficult for intervening material to fall out of the rotating part 20. Therefore, the inside of the hard disk drive 1 is easily kept clean.

[0078] <Variation> In the above embodiment, the spindle motor 3 had a rotating part 20 that included a shaft 70, and a rotor hub 80 that rotated integrally with the shaft 70. However, a spindle motor may also have a stationary part that includes a shaft, and a rotor hub that rotates around the shaft. Such a spindle motor will be described below.

[0079] (1) Variation 1 The hard disk drive 1 may be equipped with a spindle motor 103 as shown in Figure 5, instead of the spindle motor 3 described in the above embodiment.

[0080] <Spindle Motor> The spindle motor 103 comprises a stationary part 110 and a rotating part 120 that rotates relative to the stationary part 110 via a bearing mechanism.

[0081] (Stationary part) The stationary unit 110 includes a base plate 130, a sleeve 140, a stator core 150, a magnetic attraction plate 160, and a shaft 170.

[0082] The base plate 130 is a metal component. The base plate 130 has a through hole 131, a circumferential groove 132, and a circumferential wall 133.

[0083] The through-hole 131 is a hole for fixing the sleeve 140. The through-hole 131 is provided so as to penetrate the base plate 130 in the axial direction. The through-hole 131 is cylindrical, and the inner diameter of the cylinder is approximately the same as or larger than the outer diameter of the sleeve 140.

[0084] The circumferential groove 132 is formed on the radially outer side of the through hole 131. The circumferential groove 132 is an annular groove provided so as to be coaxial with the central axis of the through hole 131 when viewed in the axial direction.

[0085] The circumferential wall portion 133 is formed as an annular wall surface that protrudes axially upward from the bottom surface of the circumferential groove portion 132 along the through hole 131 when viewed in the axial direction. The circumferential wall portion 133 separates the through hole 131 and the circumferential groove portion 132.

[0086] The sleeve 140 fixes the shaft 170 to the base plate 130 and forms a dynamic pressure bearing between itself and the rotating part 120. The sleeve 140 is a cylindrical iron component such as stainless steel. The sleeve 140 is inserted into the through hole 131. The sleeve 140 is fixed to the through hole 131 by adhesive applied to one or both sides of the outer surface of the sleeve 140 and the inner surface of the through hole 131. The sleeve 140 has a sleeve through hole 141 and a sleeve recess 142.

[0087] The sleeve through-hole 141 is located at the center of the sleeve 140 in an axial view and is provided to penetrate the sleeve 140 in the axial direction. The diameter of the sleeve through-hole 141 is approximately the same as, or larger than, the outer diameter of the shaft 170.

[0088] The sleeve recess 142 is a circular recess formed in the sleeve 140 in an axial view. The sleeve recess 142 is provided coaxially with the central axis of the sleeve through-hole 141 in an axial view. The sleeve recess 142 connects to the sleeve through-hole 141 and is formed on the upper side of the sleeve through-hole 141. A thrust dynamic pressure generating groove 143 is formed on the bottom surface of the sleeve recess 142. The thrust dynamic pressure generating groove 143 is provided in an annular shape in an axial view.

[0089] The stator core 150 is a component formed by stacking multiple annular electromagnetic steel sheets in the axial direction when viewed axially. The stator core 150 is placed inside the circumferential groove 132 and fixed by methods such as adhesive bonding. The stator core 150 has pole teeth (salient poles) that extend radially outward and are arranged in multiple locations along the circumferential direction. Coils 151 are wound around the pole teeth. The stator core 150 generates magnetic flux when an electric current flows through the coils 151.

[0090] The magnetic attraction plate 160 is a component that stabilizes the rotation of the rotor hub 180, which will be described later. The magnetic attraction plate 160 is made of, for example, a magnetic material. The magnetic attraction plate 160 generates a magnetic flux in accordance with the current supplied to the coil 151. The magnetic attraction plate 160 is installed radially outward from the stator core 150 in the circumferential groove 132.

[0091] The shaft 170 is a cylindrical metal member. The outer diameter of the shaft 170 is approximately the same as, or smaller than, the inner diameter of the sleeve through-hole 141. The lower end of the shaft 170 is inserted into the sleeve through-hole 141. The shaft 170 is fixed to the sleeve through-hole 141 by adhesive applied to one or both sides of the outer circumferential surface of the shaft 170 and the inner circumferential surface of the sleeve through-hole 141, and is connected to the sleeve 140. The shaft 170 has a radial dynamic pressure generating groove 171 and a flange portion 172.

[0092] The radial dynamic pressure generating grooves 171 are provided on the outer circumferential surface of the shaft 170 in the portion inserted into the rotor hub 180, which will be described later. In this modified example, the radial dynamic pressure generating grooves 171 are formed on the outer circumferential surface of the shaft 170 in a continuous row in the circumferential direction, and two rows are formed with an interval between them in the axial direction.

[0093] The flange portion 172 is formed integrally with the shaft 170 at the upper end of the shaft 170. The flange portion 172 has a cylindrical portion 173, a protruding portion 174, and a thrust dynamic pressure generating groove 175.

[0094] The cylindrical portion 173 is a member having a cylindrical shape coaxial with the central axis of the shaft 170. The cylindrical portion 173 is formed at the axial upper end of the flange portion 172.

[0095] The projection 174 is an annular-shaped member coaxial with the central axis of the shaft 170. The projection 174 is formed to protrude radially outward from the lower end of the cylindrical portion 173. The outer peripheral surface 176 of the projection 174 is inclined in the axial direction. Therefore, comparing the upper surface 174a and the lower surface 174b of the projection 174, the outer diameter of the lower surface 174b is larger than the outer diameter of the upper surface 174a.

[0096] The thrust dynamic pressure generating groove 175 is formed on the lower surface 174b of the protrusion 174. The thrust dynamic pressure generating groove 175 is provided in an annular shape when viewed in the axial direction.

[0097] (Rotating part) The rotating part 120 includes a rotor hub 180, a rotor magnet 190, and an end cap 200.

[0098] The rotor hub 180 is a component that rotates relative to the sleeve 140 and the shaft 170. The rotor hub 180 is positioned on the outside of the shaft 170, with a portion of its lower part positioned in the sleeve recess 142. The rotor hub 180 has an inner cylindrical wall portion 181, a disc portion 182, an outer cylindrical wall portion 183, an outer edge portion 184, a vertical wall portion 185, and an annular groove 186. The manufacturing method of the rotor hub 180 will be described later.

[0099] The inner cylindrical wall portion 181 is a substantially cylindrical member. A gap 210a is formed between the lower end surface of the inner cylindrical wall portion 181 and the bottom surface of the sleeve recess 142 of the sleeve 140. A rotor hub through hole 187 is formed at the center of the inner cylindrical wall portion 181 (the part corresponding to the rotation center of the rotor hub 180), and penetrates the rotor hub 180 in the axial direction. The diameter of the rotor hub through hole 187 is larger than the outer diameter of the shaft 170. The shaft 170 is inserted into the rotor hub through hole 187. A gap 210b is formed between the inner circumferential surface of the rotor hub through hole 187 and the outer circumferential surface of the shaft 170.

[0100] The disc portion 182 is a disc-shaped member that is coaxial with the center of the inner cylindrical wall portion 181 when viewed in the axial direction. The disc portion 182 is formed radially outward from the upper end side of the inner cylindrical wall portion 181.

[0101] The outer cylindrical wall portion 183 is a cylindrical member having thickness in the radial direction. The outer cylindrical wall portion 183 is provided so as to be coaxial with the center of the inner cylindrical wall portion 181 in an axial view, and protrudes downward in the axial direction. The outer cylindrical wall portion 183 is provided on the outer edge of the disc portion 182.

[0102] The outer edge portion 184 is an annular member. The outer edge portion 184 is provided at the lower end of the outer cylindrical wall portion 183. The outer edge portion 184 protrudes radially outward from the outer cylindrical wall portion 183 and is formed in a flange shape. Multiple recording disks 4 are installed above the outer edge portion 184 and radially outward from the outer cylindrical wall portion 183 (see Figure 1).

[0103] The vertical wall portion 185 is an annular member. The vertical wall portion 185 is provided on the upper surface of the disc portion 182 radially outward from the rotor hub through hole 187 and protrudes axially upward. The flange portion 172 is housed in the space radially inward of the vertical wall portion 185. A gap 210c is formed between the upper surface of the disc portion 182 radially inward from the vertical wall portion 185 and the lower surface 174b of the protruding portion 174.

[0104] The annular groove 186 is used for positioning and fixing the end cap 200. The annular groove 186 is provided on the upper surface of the disc portion 182, radially outward from the vertical wall portion 185.

[0105] The rotor magnet 190 is an annular member having a magnetic pole structure in which the polarity reverses along the circumferential direction in an axial view, in the order N, S, N, S…. The rotor magnet 190 is attached to the inner circumferential surface of the outer cylindrical wall portion 183. The rotor magnet 190 is located in approximately the same position as the stator core 150 in the axial direction and in approximately the same position as the magnetic attraction plate 160 in the radial direction.

[0106] The end cap 200 prevents leakage of lubricating oil used in the hydrodynamic bearing section. The end cap 200 is a substantially cylindrical member. The end cap 200 has a top plate portion 201 and a side wall portion 202.

[0107] The top plate portion 201 is a circular member. An end cap through hole 203 is formed in the center of the top plate portion 201. The cylindrical portion 173 of the flange portion 172 is inserted through the end cap through hole 203. The inner circumferential surface of the end cap through hole 203 is positioned to be in close proximity to and facing the outer circumferential surface of the cylindrical portion 173.

[0108] The side wall portion 202 is an annular member. The side wall portion 202 is provided so as to be coaxial with the center of the top plate portion 201 in an axial view, and protrudes downward in the axial direction. The side wall portion 202 is provided on the outer edge of the top plate portion 201. The side wall portion 202 is housed in the annular groove 186 with its inner circumferential surface fitted into the vertical wall portion 185. The end cap 200 is fixed to the rotor hub 180 by means of fixing the side wall portion 202 to the vertical wall portion 185 and the annular groove 186 by means of adhesive or welding.

[0109] Lubricating oil is filled between the rotor hub 180 and the sleeve 140, and between the rotor hub 180 and the shaft 170. Specifically, lubricating oil is filled into gaps 210a, 210b, and 210c.

[0110] <Spindle motor operation> When current is applied to the coil 151, the magnetic attraction and repulsion forces between the magnetic poles of the rotor magnet 190 and the pole teeth of the stator core 150 switch. As a result, the rotating part 120 rotates around the shaft 170 relative to the stationary part 110.

[0111] The rotor hub 180 rotates relative to the shaft 170. During this rotation, the lubricating oil is pressurized by the radial dynamic pressure generating groove 171 and the thrust dynamic pressure generating groove 175, generating dynamic pressure in the lubricating oil. The dynamic pressure generated by the radial dynamic pressure generating groove 171 supports the rotor hub 180 radially in a non-contact state relative to the shaft 170. In addition, the dynamic pressure generated by the thrust dynamic pressure generating groove 175 supports the rotor hub 180 axially in a non-contact state relative to the shaft 170.

[0112] The rotor hub 180 rotates relative to the sleeve 140. During this rotation, the lubricating oil is pressurized by the thrust dynamic pressure generating groove 143, generating dynamic pressure in the lubricating oil. The dynamic pressure generated by the thrust dynamic pressure generating groove 143 supports the rotor hub 180 in a non-contact manner in the axial direction relative to the sleeve 140.

[0113] <Manufacturing method for rotor hubs> Next, the manufacturing method of the rotor hub 180 will be described. The rotor hub 180 is formed by high-precision machining, similar to the embodiment described above. At this time, holes 80H are formed on the surface of the formed rotor hub 180, similar to the rotor hub 80. The rotor hub 180 seals the holes 80H by filling them with a resin material. It is preferable to use an impregnation treatment as the method for filling the holes 80H with the resin material. Since the impregnation treatment is the same as described above, a detailed explanation will be omitted.

[0114] (2) Modification example 2 The hard disk drive 1 may be equipped with a spindle motor 303 as shown in Figure 6, instead of the spindle motor 3 described in the above embodiment.

[0115] <Spindle Motor> The spindle motor 303 comprises a stationary part 310 and a rotating part 320 that rotates relative to the stationary part 310 via a bearing mechanism.

[0116] (Stationary part) The stationary section 310 includes a base plate 330, a shaft 340, and a stator core 350.

[0117] The base plate 330 is a metal component. The base plate 330 has a through hole 331, a circumferential groove 332, and a circumferential wall 333 formed therein.

[0118] The through-hole 331 is a hole for fixing the shaft 340. The through-hole 331 is provided so as to penetrate the base plate 330 in the axial direction. The through-hole 331 is cylindrical, and the inner diameter of the cylinder is approximately the same as or larger than the outer diameter of the shaft 340.

[0119] The circumferential groove 332 is formed on the radially outer side of the through hole 331. The circumferential groove 332 is an annular groove provided so as to be coaxial with the central axis of the through hole 331 when viewed in the axial direction.

[0120] The circumferential wall portion 333 is formed as an annular wall portion that protrudes axially upward from the bottom surface of the circumferential groove portion 332 when viewed in the axial direction. The diameter of the circumferential wall portion 333 is larger than the diameter of the through hole 331.

[0121] The shaft 340 is a cylindrical metal member. The shaft 340 has, in order from the lower end, a through-hole insertion portion 341, a first mounting portion 342, and a second mounting portion 343. These portions are spaced apart in the axial direction.

[0122] The through-hole insertion portion 341 is inserted into and joined to the through-hole 331. If the outer diameter of the through-hole insertion portion 341 is larger than the diameter of the through-hole 331, the through-hole insertion portion 341 is inserted into and joined to the through-hole 331, for example by press-fitting. In this way, the shaft 340 is fixed and connected to the base plate 330. If the outer diameter of the through-hole insertion portion 341 is smaller than the diameter of the through-hole 331, the through-hole insertion portion 341 is inserted into the through-hole 331 and then joined to the through-hole 331 by a method such as adhesive bonding.

[0123] The lower conical bearing member 361 is fixed to the first mounting portion 342, and the upper conical bearing member 362 is fixed to the second mounting portion 343 (see Figure 6). The lower conical bearing member 361 and the upper conical bearing member 362 have conical outer surfaces, with the conical outer surfaces facing radially outward.

[0124] The stator core 350 is a component formed by stacking multiple annular electromagnetic steel sheets in the axial direction when viewed axially. The stator core 350 is placed inside the circumferential groove 332 and fixed by methods such as adhesive bonding. The stator core 350 has pole teeth (salient poles) that extend radially outward and are arranged in multiple locations along the circumferential direction. Coils 351 are wound around the pole teeth. The stator core 350 generates magnetic flux when current flows through the coils 351.

[0125] (Rotating part) The rotating part 320 includes a rotor hub 370 and a rotor magnet 380.

[0126] The rotor hub 370 is a component that rotates relative to the shaft 340. The rotor hub 370 has an inner cylindrical wall portion 371, a disc portion 372, an outer cylindrical wall portion 373, and an outer edge portion 374. The manufacturing method of the rotor hub 370 will be described later.

[0127] The inner cylindrical wall portion 371 is a substantially cylindrical member. At the center of the inner cylindrical wall portion 371 (the part corresponding to the rotation center of the rotor hub 370), a rotor hub through hole 375 is formed, which penetrates the rotor hub 370 in the axial direction. The shaft 340 is inserted through the rotor hub through hole 375. The rotor hub through hole 375 has a lower conical inner surface 376 at its lower end and an upper conical inner surface 377 at its upper end.

[0128] The inner surface 376 of the lower cone faces the lower conical bearing member 361 via a small gap 390a. The inner surface 377 of the upper cone faces the upper conical bearing member 362 via a small gap 390b.

[0129] The disc portion 372 is a disc-shaped member that is coaxial with the center of the inner cylindrical wall portion 371 when viewed in the axial direction. The disc portion 372 is formed radially outward from the inner cylindrical wall portion 371.

[0130] The outer cylindrical wall portion 373 is a cylindrical member having thickness in the radial direction. The outer cylindrical wall portion 373 is provided so as to be coaxial with the center of the inner cylindrical wall portion 371 in an axial view, and protrudes upward and downward in the axial direction, respectively. The outer cylindrical wall portion 373 is provided on the outer edge of the disc portion 372.

[0131] The outer edge portion 374 is an annular member. The outer edge portion 374 is provided at the lower end of the outer cylindrical wall portion 373. The outer edge portion 374 protrudes radially outward from the outer cylindrical wall portion 373 and is formed in a flange shape. Multiple recording disks 4 are installed above the outer edge portion 374 and radially outward from the outer cylindrical wall portion 373 (see Figure 1).

[0132] The rotor magnet 380 is an annular member having a magnetic pole structure in which the polarity reverses along the circumferential direction in an axial view, in the order N, S, N, S…. The rotor magnet 380 is attached to the inner circumferential surface of the outer cylindrical wall portion 373. The rotor magnet 380 is located in approximately the same position as the stator core 350 in the axial direction.

[0133] Lubricating oil is filled into the minute gaps 390a and 390b. Furthermore, a dynamic pressure generating groove (not shown) is formed on at least one of the lower conical inner surface 376 and the lower conical bearing member 361, and on at least one of the upper conical inner surface 377 and the upper conical bearing member 362. This forms a fluid dynamic pressure bearing 391.

[0134] <Spindle motor operation> When current is applied to the coil 351, the magnetic attraction and repulsion forces between the magnetic poles of the rotor magnet 380 and the pole teeth of the stator core 350 switch. As a result, the rotating part 320 rotates around the shaft 340.

[0135] As the rotor hub 370 of the rotating part 320 rotates at high speed, the lubricating oil filled in the minute gap 390a between the lower conical inner surface 376 and the lower conical bearing member 361, and the minute gap 390b between the upper conical inner surface 377 and the upper conical bearing member 362, is pressurized by the dynamic pressure generating groove. As a result, dynamic pressure is generated in the fluid dynamic bearing 391. Due to the generated dynamic pressure, the rotor hub 370 rotates while being supported in a non-contact state with respect to the shaft 340, the lower conical bearing member 361, and the upper conical bearing member 362.

[0136] <Manufacturing method for rotor hubs> Next, the manufacturing method of the rotor hub 370 will be described. The rotor hub 370 is formed by high-precision machining, similar to the embodiment described above. At this time, holes 80H are formed on the surface of the formed rotor hub 370, similar to the rotor hub 80. The rotor hub 370 seals the holes 80H by filling them with a resin material. It is preferable to use an impregnation treatment as the method for filling the holes 80H with the resin material. Since the impregnation treatment is the same as described above, a detailed explanation will be omitted. [Explanation of Symbols]

[0137] 1…Hard disk drive unit, 3, 103, 303…Spindle motor, 10, 110, 310…Stationary part, 20, 120, 320…Rotating part, 70, 170, 340…Shaft (axis member), 80, 180, 370…Rotor hub, 80H…Hole

Claims

1. The stationary part, A rotating part that rotates relative to the stationary part, A shaft member connected to either the stationary part or the rotating part, A spindle motor comprising, The rotating part is made of a metal material containing inclusions made of free-cutting components that facilitate cutting, and the holes exposed on the surface by cutting the metal material are filled with resin material. The aforementioned resin material fills the holes by impregnation. The aforementioned surface is not covered with a coating. Spindle motor.

2. The rotating part comes into contact with the lubricating oil filled between it and the stationary part. The spindle motor according to claim 1.

3. The aforementioned resin material is acrylic resin. The spindle motor according to claim 1.

4. The rotating part is a rotor hub. The spindle motor according to claim 1.

5. A hard disk drive device comprising a spindle motor according to any one of claims 1 to 4.

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