Spindle motor, hard disk drive device, and manufacturing method of spindle motor

Abstract

To provide a spindle motor in which a bottom surface of a base plate is less likely to generate dust.SOLUTION: A spindle motor 3 includes a base plate 30 having a through hole 31, a bearing sleeve 40 inserted into the through hole 31, and a rotating portion 20 rotatably supported with respect to the bearing sleeve 40. The base plate 30 has a front surface 133 facing the rotating portion 20, a back surface 134 facing back with respect to the front surface 133, and a rib 136 formed so as to protrude from the back surface 134. The back surface 134 is formed in at least a partial region including the through hole 31, and has a planar portion 135 having a machined first surface 137. The rib 136 has a second surface 138 machined to be parallel to the first surface 137, and the first surface 137 and the second surface 138 are covered by a coating film 140.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a spindle motor, a hard disk drive, and a method for manufacturing a spindle motor. [Background technology]

[0002] Hard disk drives are required to have a high data storage capacity. However, because the size of hard disk drives is determined by standards, it is required to increase the depth of the recess in the base plate that houses the recording disk on which data is recorded, without changing the thickness of the base plate of the spindle motor that constitutes the hard disk drive.

[0003] Incidentally, Patent Document 1 describes machining the surface of a rib provided on the bottom surface of the base plate. The rib is provided as a reference surface for assembling the spindle motor. For this reason, the surface of the rib is precisely finished by machining and is provided so as to be higher than the surrounding surfaces. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 7,914,858 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, the inventors considered machining the peripheral surface of the rib on the bottom surface of the base plate in the same way as the surface of the rib, which made it possible to reduce the dimensional tolerance of the height of the surface of the rib and the peripheral surface of the rib, and thought that by moving the bottom plate constituting the bottom surface toward the surface of the rib by the amount of the reduced dimensional tolerance, it would be possible to deepen the depth of the recess without changing the thickness of the base plate.

[0006] However, when the surface of the rib and the surface surrounding the rib are machined, there is a possibility that the contact area will generate dust when the surface of the rib and the surface surrounding the rib come into contact with jigs or other components during the spindle motor assembly process.

[0007] An object of the present invention is to provide a spindle motor in which the bottom surface of the base plate is less likely to generate dust. [Means for solving the problem]

[0008] In order to solve the above problems, there is provided a spindle motor comprising: a base plate having a through hole, a support member inserted into the through hole, and a rotating part rotatably supported on the support member, wherein the base plate has one surface facing the rotating part, another surface facing away from the one surface, and a rib formed to protrude from the other surface, the other surface having a planar portion formed in at least a portion of an area including the through hole and having a machined first surface, the rib having a second surface machined to be parallel to the first surface, and the first surface and the second surface are covered with a paint film. Effect of the Invention

[0009] According to the present invention, the bottom surface of the base plate is less likely to generate dust. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a hard disk drive 1. [Diagram 2] FIG. 2 is a partial cross-sectional view of the spindle motor 3. [Diagram 3] FIG. [Figure 4] 4 is a schematic cross-sectional view taken along line AA in FIG. 3. [Diagram 5] 4 is a flowchart of a method for manufacturing the spindle motor 3. [Figure 6] FIG. 2 is a bottom view of a conventional base plate 30. [Figure 7] FIG. 7 is a schematic cross-sectional view taken along line BB in FIG. 6. [Figure 8] FIG. 11 is a bottom view of the base plate 30 in a modified example. [Figure 9] 9 is a schematic cross-sectional view taken along line CC in FIG. 8. [Figure 10] FIG. 11 is a bottom view of the base plate 30 in a modified example. [Figure 11] FIG. 11 is a schematic cross-sectional view taken along the line DD in FIG. [Figure 12] FIG. 11 is a partial cross-sectional view of a spindle motor 203 according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0013] 2 and other figures, the direction parallel to the central axis of shaft 70 (described later) is defined as the axial direction, the direction around the central axis of 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, and the rotating part 20 side relative to stationary part 10 is defined as the top, and the stationary part 10 side is defined as the bottom.

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

[0015] The housing 2 includes a base plate 30 and a cover 7. The base plate 30 has a box-like shape with one side of a substantially rectangular parallelepiped open and closed at the bottom. The cover 7 is a plate-like member that closes the open side of the base plate 30. The cover 7 is fastened to the base plate 30 using screws 7A. A sealing means (not shown) is provided between the base plate 30 and the cover 7, so that the cover 7, together with the base plate 30, forms the housing 2 having a sealed internal space S.

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

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

[0018] A plurality of recording disks 4 are provided and supported by the spindle motor 3 so that their disk surfaces face each other. In this embodiment, eleven or more recording disks 4 are supported by the spindle motor 3. Gaps are formed between each of the recording disks 4.

[0019] The bearing device 5 swingably supports a plurality of swing arms 8 that are disposed in the gaps between the respective recording disks 4 and on the uppermost surfaces of the 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 also reads magnetism from the recording disk 4. When the swing arm 8 swings, the magnetic head 9 moves above the recording disk 4.

[0021] When the spindle motor 3 rotates, the recording disk 4 also rotates. In this state, when the swing arm 8 swings, the magnetic head 9 moves over the rotating recording disk 4. The magnetic head 9 then imparts magnetism to the recording disk 4, and records data on the recording disk 4. The magnetic head 9 also reads magnetism from the recording disk 4, and reads out the data recorded on the recording disk 4.

[0022] As a recording method for the hard disk drive 1, a thermally assisted magnetic recording (HAMR) method may be adopted.

[0023] <Spindle motor> Next, a detailed configuration of the spindle motor 3 will be described. Fig. 2 is a partial cross-sectional view showing the configuration of the spindle motor 3. The spindle motor 3 includes a stationary part 10 and a rotating part 20 that rotates relative to the stationary part 10 via a bearing mechanism.

[0024] (Stationary part) The stationary portion 10 includes a base plate 30, a bearing sleeve 40 (an example of a support member), a stator core 50, and a magnetic attraction plate 60.

[0025] The base plate 30 is a metal member. As shown in Fig. 3 and Fig. 4, the base plate 30 has an upper side of an accommodating recess 131 for accommodating the recording disk 4 or the like, and a bottom plate 132 that serves as a bottom surface separating the inside and outside of the accommodating recess 131. A manufacturing method for the base plate 30 will be described later.

[0026] The accommodating recess 131 is formed by recessing the upper surface of the base plate 30. The accommodating recess 131 accommodates the recording disk 4 and the bearing device 5 in addition to the components of the spindle motor 3. A bottom plate 132 is formed at the bottom of the accommodating recess 131.

[0027] The bottom plate 132 has a front surface 133 (an example of one surface), a back surface 134 (an example of the other surface), and ribs 136. The front surface 133 is an upper surface of the bottom plate 132 that faces the rotating unit 20 and the recording disk 4. The back surface 134 is a surface of the bottom plate 132 facing away from the front surface 133. Facing away here means back to back, and the back surface 134 is a surface of the bottom plate 132 opposite the front surface 133 (i.e., the lower surface or back surface of the bottom plate 132). The ribs 136 are formed so as to protrude downward from the back surface 134. The ribs 136 are provided on the edges of the two long sides of the rectangular bottom plate 132 when viewed from below.

[0028] As shown in FIG. 2, a through hole 31, a circumferential groove portion 32, a circumferential wall portion 33, and a plate recess portion 34 are formed on a surface 133 side of the base plate 30.

[0029] The through hole 31 is a hole for fixing the bearing sleeve 40. The through hole 31 is provided so as to axially penetrate the bottom plate 132. 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.

[0030] The circumferential groove portion 32 is formed radially outward of the through hole 31. The circumferential groove portion 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.

[0031] The circumferential wall portion 33 is formed radially outward of the through hole 31 and inward of 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 when viewed in the axial direction, and protrudes upward in the axial direction.

[0032] The plate recess 34 is formed on the radially inner side 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 when viewed in the axial direction, and 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 to the upper side of the through hole 31 in the axial direction.

[0033] As shown in FIG. 4, a flat portion 135 is formed on the rear surface 134 side of the base plate 30.

[0034] The flat portion 135 is a flat portion formed in a region including the through-hole 31 on the rear surface 134. The flat portion 135 has a first surface 137 that has been machined. The size of the first surface 137 is the same as that of the flat portion 135. The first surface 137 is covered with a coating film 140 in a machined state.

[0035] The rib 136 has a machined second surface 138. The second surface 138 is formed by machining a lower end face of the rib 136 so as to be parallel to the first surface 137. The second surface 138 is covered with a paint film 140 in the machined state.

[0036] The bearing sleeve 40 rotatably supports the shaft 70. The bearing sleeve 40 is a cylindrical iron member made of stainless steel or the like that extends in the axial direction. The bearing sleeve 40 is inserted into the through hole 31 (see FIG. 2). The bearing sleeve 40 is fixed to the through hole 31 with an adhesive that is applied to one or both 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 radial dynamic pressure generating grooves 41 and thrust dynamic pressure generating grooves 42.

[0037] 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 in a continuous row in the circumferential direction on the inner circumferential surface 40a, and are formed in two rows spaced apart in the axial direction.

[0038] The thrust dynamic pressure generating groove 42 is provided in an 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.

[0039] A large diameter recess 45 and a small diameter recess 46 are formed continuously in the axial direction at the axially lower sleeve end 43b of the bearing sleeve 40. A counter plate 47 is attached to the large diameter recess 45.

[0040] The large diameter recess 45 is formed in the sleeve end portion 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 when viewed in the axial direction. The large diameter recess 45 opens downward.

[0041] The small diameter recess 46 is formed above 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 when viewed in the axial direction. 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. By forming the small diameter recess 46 at the sleeve end 43b, the bearing sleeve 40 is formed with an annular surface 48 that is annular when viewed in the axial direction, and an inner peripheral side surface 49 in the circumferential direction.

[0042] The counter plate 47 is a disk-shaped cover that is inserted into the large diameter recess 45 from below the sleeve end 43b. The counter plate 47 covers the large diameter recess 45 and the small diameter recess 46. The counter plate 47 is a member 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.

[0043] 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.

[0044] The stator core 50 is a member in which a plurality of annular electromagnetic steel plates are laminated in the axial direction when viewed in the axial direction. The stator core 50 is disposed inside the circumferential groove portion 32 and fixed by a method such as adhesive. The stator core 50 extends radially outward and has a plurality of pole teeth (salient poles) disposed along the circumferential direction. Coils 51 are wound around the pole teeth. The stator core 50 generates magnetic flux when a current flows through the coils 51.

[0045] The magnetic attraction plate 60 is a member that stabilizes the rotation of the rotor hub 80 described later. The magnetic attraction plate 60 is made of, for example, a magnetic material. The magnetic attraction plate 60 is disposed radially outward of the stator core 50 in the circumferential groove portion 32.

[0046] (Rotating part) The rotating part 20 has a shaft 70 , a rotor hub 80 , and a rotor magnet 90 .

[0047] The shaft 70 is a member that serves as a 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. In the shaft 70, the shaft portion 71 and the flange portion 72 are integral with each other.

[0048] The shaft portion 71 is a cylindrical shaft member. The shaft portion 71 has a flange portion 72 integrally formed with a lower shaft end portion 73. The shaft portion 71 is disposed inside the bearing sleeve 40 so that the shaft end portion 73 with the flange portion 72 is on the lower side. That is, the outer peripheral surface of the shaft portion 71 is surrounded by the inner peripheral surface 40a of the bearing sleeve 40. The outer peripheral surface of the shaft portion 71 and the inner peripheral surface 40a of the bearing sleeve 40 face each other with a small gap therebetween. Note that the radial dynamic pressure generating grooves 41 may be formed on the outer peripheral surface of the shaft portion 71 instead of the inner peripheral surface 40a of the bearing sleeve 40.

[0049] The flange portion 72 is an annular flange member that expands in the radial direction when viewed in the axial direction. The flange portion 72 is joined to a shaft end portion 73 and is integral with the shaft portion 71. The outer diameter of the flange portion 72 is smaller than the inner diameter of the small diameter recess 46. Thrust dynamic pressure generating grooves 74 are formed on the upper and lower surfaces of the flange portion 72.

[0050] The thrust dynamic pressure generating groove 74 is provided on the upper and lower surfaces of the flange portion 72. The thrust dynamic pressure generating groove 74 is provided in an annular shape so as to be coaxial with the central axis of the flange portion 72 when viewed in the axial direction.

[0051] The flange portion 72 is disposed in the small diameter recess 46 when the shaft 70 is supported by the bearing sleeve 40. The upper surface of the flange portion 72 faces the annular surface 48 formed in the bearing sleeve 40 by the small diameter recess 46 across a small gap. The lower surface of the flange portion 72 faces the upper surface of the counter plate 47 across a small gap. The side surface of the flange portion 72 faces the inner circumferential side surface 49 across a small gap. By disposing 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.

[0052] Lubricating oil is filled between the shaft 70 and the bearing sleeve 40. Specifically, the lubricating oil is filled between the outer peripheral surface of the shaft portion 71 and the inner peripheral 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 peripheral side surface 49.

[0053] The rotor hub 80 is a member that rotates together with the shaft 70. The rotor hub 80 is attached to the upper end of the shaft 70 and is connected to the shaft 70. The rotor hub 80 has a disk portion 81, a first cylindrical portion 82, a second cylindrical portion 83, and an outer edge portion 84.

[0054] The disk portion 81 is a disk-shaped member that is coaxial with the central axis of the shaft 70 when viewed in the axial direction. The disk portion 81 has a rotor hub through hole 85. The rotor hub through hole 85 is provided at the center of the disk portion 81 when viewed in the axial direction. The disk portion 81 is fixed to the shaft 70. Specifically, the upper end of the shaft 70 is inserted into the rotor hub through hole 85 and fixed by a method such as press fitting or adhesive, thereby fixing the disk portion 81 to the shaft 70. When the shaft 70 is supported by the bearing sleeve 40, the disk portion 81 faces the end face 44 of the bearing sleeve 40 with a small gap therebetween.

[0055] The first cylindrical portion 82 is a cylindrical member having a 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 when viewed in the axial direction, and protrudes axially downward. 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 therebetween. 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 therebetween.

[0056] The second cylindrical portion 83 is a cylindrical member having a thickness in the radial direction. The second cylindrical portion 83 is provided so as to be coaxial with the center axis of the rotor hub through hole 85 when viewed in the axial direction, and protrudes axially downward. The second cylindrical portion 83 is provided on the outer edge of the disk portion 81.

[0057] 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. A plurality of recording disks 4 are installed above the outer edge portion 84 and radially outward from the second cylindrical portion 83 (see FIG. 1).

[0058] 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 disk portion 81 axially inward of the first cylindrical portion 82 and the end surface 44 of the sleeve end 43a on the axially upper side of the bearing sleeve 40.

[0059] The rotor magnet 90 is an annular member having a magnetic pole structure magnetized with polarities inverted as N, S, N, S... along the circumferential direction when viewed in the axial direction. 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 at approximately the same position as the stator core 50 in the axial direction, and at approximately the same position as the magnetic attraction plate 60 in the radial direction.

[0060] <Spindle motor operation> When the coil 51 is energized, a magnetic attraction force and a magnetic repulsion force are generated between the magnetic poles of the rotor magnet 90 and the pole teeth of the stator core 50. As a result, the rotating part 20 rotates relative to the stationary part 10 with the shaft 70 as the rotation axis.

[0061] The shaft 70 rotates relative to the bearing sleeve 40. At this time, dynamic pressure is generated in the lubricating oil as the lubricating oil is pressurized by the radial dynamic pressure generating grooves 41 and the thrust dynamic pressure generating grooves 74. The generated dynamic pressure supports the shaft 70 in a non-contact state relative to the bearing sleeve 40 in the radial and axial directions.

[0062] 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 grooves 42, generating dynamic pressure in the lubricating oil. The generated dynamic pressure supports the rotor hub 80 relative to the bearing sleeve 40 in a non-contact state in the axial direction.

[0063] <Base plate manufacturing method> Next, a method for manufacturing the base plate 30 will be described. Fig. 5 is a flowchart showing the method for manufacturing the base plate 30. The method for manufacturing the base plate 30 is composed of three steps: a molding step S11, a machining step S12, and a painting step S13. The work in these steps is performed by, for example, a working robot.

[0064] (S11) The molding process S11 is a process for molding the base plate 30 by casting. The working robot pours molten metal such as aluminum into a die-casting die having a cavity with the same shape and size as the base plate 30. Then, when the molten metal in the cavity cools and solidifies, the working robot opens the die-casting die and removes the base plate 30 from the die-casting die.

[0065] (S12) The machining process S12 is a process for machining the base plate 30. The work robot performs machining on the locations requiring high precision, i.e., the inward surface of the accommodation recess 131, the surface of the flat portion 135, and the lower end surface of the rib 136. Note that machining in this embodiment refers to cutting using an end mill or the like, or grinding using a grinder or the like. A first surface 137 is formed on the flat portion 135 by machining, and a second surface 138 is formed on the lower end surface of the rib 136 by machining.

[0066] (S13) The painting step S13 is a step of painting the surface of the base plate 30. In this embodiment, electrodeposition painting is performed on the base plate 30. Here, the electrodeposition painting is a process in which a member to be painted is immersed in a tank filled with paint, and the paint is adhered to the surface of the member to be painted by passing an electric current through the paint, and then the paint is dried and thermally cured.

[0067] The working robot immerses the base plate 30 in a tank filled with paint and turns on electricity. Then, when the working robot lifts the base plate 30 from the tank, the paint adheres to the surface of the base plate 30. Next, the working robot carries the base plate 30 with the paint adhered thereto into a baking furnace. The baking furnace heats the base plate 30 at a temperature of about 200°C to 220°C for about 10 to 60 minutes. Then, a coating film 140 is formed on the surface of the base plate 30, including the first surface 137 and the second surface 138.

[0068] <Effects> In this embodiment, the spindle motor 3 comprises a base plate 30 having a through hole 31, a bearing sleeve 40 inserted into the through hole 31, and a rotating part 20 rotatably supported relative to the bearing sleeve 40. The base plate 30 has a surface 133 facing the rotating part 20, a back surface 134 facing away from the surface 133, and a rib 136 formed to protrude from the back surface 134. The back surface 134 has a flat portion 135 formed in at least a portion of the area including the through hole 31 and having a machined first surface 137. The rib 136 has a second surface 138 machined to be parallel to the first surface 137. The first surface 137 and the second surface 138 are covered with a paint film 140.

[0069] According to the above-described spindle motor 3, the first surface 137 and the second surface 138 on the rear surface 134 side, which are likely to come into contact with jigs or other components during the assembly work of the spindle motor 3, are covered with the coating film 140. Therefore, even if the first surface 137 and the second surface 138 come into contact with jigs or other components, the bottom surface of the base plate 30 is less likely to generate dust.

[0070] 6 and 7, the flat portion 135 and the rib 136 on the back surface 134 side are painted without being machined, or only the lower end face of the rib 136 is machined after being painted. For this reason, the dimensional tolerance of the height h from the flat portion 135 to the lower end face of the rib 136 is large.

[0071] On the other hand, according to the above spindle motor 3, the flat portion 135 has a machined first surface 137, and the rib 136 has a machined second surface 138 so as to be parallel to the first surface 137, so that the dimensional tolerance of the height H from the first surface 137 to the second surface 138 is small. Therefore, the position of the bottom plate 132 can be moved downward by the amount of the reduced dimensional tolerance without changing the thickness of the base plate 30, thereby increasing the depth of the accommodating recess 131. As a result, the number of recording disks 4 that can be accommodated in the accommodating recess 131 can be increased.

[0072] The hard disk drive 1 also includes a spindle motor 3 .

[0073] According to the above-described hard disk drive device 1, the spindle motor 3 does not easily generate dust even if a jig or other parts come into contact with the first surface 137 and the second surface 138, and therefore dust is also not easily generated during the assembly process of the hard disk drive device 1.

[0074] Furthermore, since the spindle motor 3 can accommodate a larger number of recording disks 4 in the accommodation recess 131 than in the past, it is possible to provide a hard disk drive device 1 capable of storing a large amount of data.

[0075] In this embodiment, the manufacturing method of the spindle motor 3 includes a molding process S11 of forming the base plate 30 by casting, a machining process S12 of machining the flat portion 135 and the ribs 136 formed on the base plate 30 to form a first surface 137 on the flat portion 135 and a second surface 138 parallel to the first surface 137 on the ribs 136, and a painting process S13 of forming a paint film 140 on a surface of the base plate 30 including the first surface 137 and the second surface 138.

[0076] According to the above-described method for manufacturing the spindle motor 3, the base plate 30 formed by casting is machined to form the first surface 137 on the flat surface 135 and the second surface 138 on the rib 136. Then, the coating film 140 is formed on the surface of the base plate 30 including the first surface 137 and the second surface 138. This makes it possible to reduce the dimensional tolerance of the height H from the first surface 137 to the second surface 138. Furthermore, by protecting the first surface 137 and the second surface 138 with the coating film 140, it is possible to reduce the dimensional tolerance of the height H and to reduce the generation of dust during the assembly of the spindle motor 3.

[0077] <Modification> The hard disk drive 1 and spindle motor 3 may be modified in any combination of the modifications described below.

[0078] (1) Variation 1 8 and 9, the flat portion 135 may be spaced apart from the rib 136 on the back surface 134. Note that D1 in Fig. 8 indicates the diameter of the rotating portion 20 (outer edge portion 84) as viewed in the axial direction. Also, D2 in Fig. 8 indicates the diameter of the recording disk 4 as viewed in the axial direction.

[0079] The flat portion 135 is a flat portion formed in a circular shape in a region of the back surface 134 centered on the through hole 31. The diameter of the flat portion 135 is larger than D1 and D2. The flat portion 135 is separated from the rib 136 when viewed in the axial direction. The flat portion 135 has a first surface 137 that has been machined. The size of the first surface 137 is the same as the size of the flat portion 135. The first surface 137 is covered with a coating film 140 in a machined state. The shape of the flat portion 135 when viewed in the axial direction may be rectangular rather than circular.

[0080] As shown in FIG. 9, the bottom plate 132 is thick in the area where the flat portion 135 is formed, and the other portion of the bottom plate 132 (between the flat portion 135 and the rib 136 in FIG. 9) is thin.

[0081] When manufacturing such a base plate 30, the shape of the die-casting mold is changed in the molding step S11. That is, the shape of the cavity of the die-casting mold is such that the flat portion 135 and the rib 136 are separated on the back surface 134 of the base plate 30, as shown in Figures 8 and 9. By using such a die-casting mold, the base plate 30 in which the flat portion 135 is separated from the rib 136 on the back surface 134 is molded.

[0082] In the spindle motor 3 according to the above-described modified example, the flat portion 135 is spaced apart from the rib 136 on the back surface 134.

[0083] According to the above-described spindle motor 3, flat portion 135 is formed small because flat portion 135 is separated from rib 136. Therefore, the processing time required to machine flat portion 135 to form first surface 137 is short, and spindle motor 3 can be manufactured at low cost.

[0084] In the manufacturing method of the spindle motor 3 according to the above-described modified example, the molding step S11 molds the flat portion 135 and the rib 136 so that they are separated from each other on the rear surface 134 on which the flat portion 135 and the rib 136 are molded.

[0085] According to the above-described method for manufacturing spindle motor 3, flat portion 135 and rib 136 are molded separately on back surface 134, so that flat portion 135 can be molded small. As a result, the time required to machine first surface 137 on flat portion 135 in machining step S12 is shortened, and spindle motor 3 can be manufactured at low cost.

[0086] (2) Variation 2 As shown in FIGS. 10 and 11, the flat portion 135 may be larger than the rotating portion 20 (the outer edge portion 84) when viewed in the axial direction, and may be smaller than the size of the first modified example.

[0087] The flat portion 135 is formed in a circular shape in an area on the back surface 134 centered on the through hole 31. The diameter of the flat portion 135 is larger than D1. The flat portion 135 is separated from the rib 136 when viewed in the axial direction. The flat portion 135 has a first surface 137 that has been machined. The size of the first surface 137 is the same as the size of the flat portion 135. The first surface 137 is covered with a coating film 140 in a machined state. The shape of the flat portion 135 when viewed in the axial direction may be rectangular rather than circular.

[0088] As shown in FIG. 11, the bottom plate 132 is thick in the area where the flat portion 135 is formed, and the other portion of the bottom plate 132 (between the flat portion 135 and the rib 136 in FIG. 11) is thin.

[0089] When manufacturing such a base plate 30, the shape of the die-casting mold is changed in the molding step S11. That is, the shape of the cavity of the die-casting mold is such that the flat portion 135 and the rib 136 are separated from each other on the back surface 134 of the base plate 30, and the size of the flat portion 135 is larger than D1, as shown in Figs. 10 and 11. By using such a die-casting mold, the base plate 30 is molded such that the flat portion 135 is separated from the rib 136 on the back surface 134, and the flat portion 135 is larger than the size of the rotating part 20 when viewed in the axial direction.

[0090] In the spindle motor 3 according to the above-described modified example, the flat portion 135 is larger than the rotating portion 20 when viewed in the axial direction of the rotation shaft of the rotating portion 20 .

[0091] A region of bottom plate 132 having the same size as rotating part 20 centered around through hole 31 as viewed in the axial direction is required to have strength to support the components of spindle motor 3. According to the above spindle motor 3, since the size of flat part 135 is larger than the size of rotating part 20 as viewed in the axial direction, the size of flat part 135 can be reduced without compromising strength. As a result, the processing time for forming first surface 137 can be shortened, and a cheaper spindle motor 3 can be manufactured while still satisfying the strength of bottom plate 132.

[0092] (3) Variation 3 The hard disk drive 1 may include a spindle motor 203 as shown in Fig. 12, instead of the spindle motor 3 described in the above embodiment. The spindle motor 203 includes a stationary part 210 and a rotating part 220 that rotates relative to the stationary part 210 via a bearing mechanism.

[0093] The stationary portion 210 includes a sleeve 230 and a shaft 240 (an example of a support member).

[0094] The sleeve 230 fixes the shaft 240 to the base plate 30. The sleeve 230 is a cylindrical member. The sleeve 230 is inserted into the through hole 31 and fixed to the through hole 31 by an adhesive. The sleeve 230 has a sleeve through hole 231.

[0095] The sleeve through hole 231 is provided at the center of the sleeve 230 when viewed in the axial direction, and is provided so as to axially penetrate the sleeve 230. The inner diameter of the sleeve through hole 231 is approximately the same as or larger than the outer diameter of the shaft 240.

[0096] The shaft 240 is a cylindrical member. The outer diameter of the shaft 240 is approximately the same as or smaller than the inner diameter of the sleeve through hole 231. The shaft 240 is fixed to the sleeve through hole 231 by an adhesive and connected to the sleeve 230. The rotating portion 220 is rotatably supported by the shaft 240. [Explanation of symbols]

[0097] 1...Hard disk drive, 3, 203...Spindle motor, 4...Recording disk, 20, 220...Rotating part, 30...Base plate, 31...Through hole, 40...Bearing sleeve (support member), 133...Front surface (one side), 134...Back surface (other side), 135...Planar part, 136...Rib, 137...First surface, 138...Second surface, 140...Paint film, 240...Shaft (support member)

Claims

1. A base plate having a through hole; A support member that is inserted into the through hole; A rotating portion rotatably supported by the support member; Equipped with The base plate is One surface facing the rotating portion; Another surface facing away from the one surface; A rib formed so as to protrude from the other surface; having the other surface has a flat portion having a machined first surface formed in at least a portion of the area including the through hole; the rib has a second surface machined parallel to the first surface; The first surface and the second surface are covered with a paint film. Spindle motor.

2. The flat portion is spaced apart from the rib on the other surface.

2. The spindle motor according to claim 1.

3. The planar portion is larger than the rotating portion when viewed in the axial direction of the rotation shaft of the rotating portion.

3. The spindle motor according to claim 2.

4. A hard disk drive comprising the spindle motor according to any one of claims 1 to 3.

5. a molding step of forming a base plate by casting; a machining step of machining the flat surface and the rib formed on the base plate to machine a first surface on the flat surface and a second surface parallel to the first surface on the rib; a coating process for forming a coating film on a surface of the base plate including the first surface and the second surface; A method for manufacturing a spindle motor comprising the steps of:

6. 6. The method for manufacturing a spindle motor according to claim 5, wherein the molding step comprises molding the flat portion and the rib apart from each other on the other surface on which the flat portion and the rib are molded.

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