Base plate, spindle motor, disk drive device, and method of manufacturing the base plate

Abstract

To provide a base plate that can reduce occurrence of shrinkage cavities, a spindle motor, a disk drive apparatus, and a manufacturing method of the base plate.SOLUTION: In a disk drive apparatus, a base plate 41 is a part of a housing of a disk drive apparatus and includes a base body that is a casting product and an electrodeposition coating film covering at least a part of a surface of the base body. The base body has a bottom plate 411 rectangular as viewed from an axial direction, a pivot post 413, and a protrusion 414. The bottom plate extends perpendicular to a rotation axis C of a disk and a swing axis D of a head. The rotation axis extends vertically. The swing axis is arranged at a different position from the rotation axis and extends vertically. The head reads or writes information from or to the disk. The pivot post protrudes upward from an upper surface of the bottom plate along the swing axis. The protrusion is provided protruding radially outward from a peripheral surface of the pivot post and protruding to the upper surface of the bottom plate.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A case body (base plate) that is a part of the housing of a conventional disk drive device has a rectangular bottom surface and an actuator mounting portion (pivot post) that protrudes upward from the top surface of the bottom surface (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-127064 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the case body disclosed in the above-mentioned patent document has a problem that the flow of molten metal to the actuator mounting portion during casting is poor, and shrinkage cavities may occur in the actuator mounting portion, which may cause helium gas filled inside the housing to leak to the outside through the actuator mounting portion.

[0005] An object of the present invention is to provide a base plate capable of reducing the occurrence of shrinkage cavities and a method for manufacturing a base plate. [Means for solving the problem]

[0006] An exemplary base plate of the present invention is a base plate that becomes part of the housing of a disk drive device, and has a base body that is a casting, and an electrocoating film that covers at least a part of the surface of the base body. The base body has a bottom plate portion that is rectangular when viewed from the axial direction, a pivot post, and a protruding portion. The bottom plate portion extends perpendicular to the rotation axis of the disk and the oscillation axis of the head. The rotation axis extends vertically. The oscillation axis is disposed at a position different from the rotation axis and extends vertically. The head reads or writes information from or to the disk. The pivot post protrudes upward from an upper surface of the bottom plate portion along the oscillation axis. The protruding portion protrudes radially outward from the circumferential surface of the pivot post and is provided protruding from the upper surface of the bottom plate portion.

[0007] The exemplary method for manufacturing a base plate of the present invention is a method for manufacturing a base plate of a casting that becomes a part of the housing of a disk drive device, and includes a casting step, a cutting step, and an electro-deposition coating step, in that order. In the casting step, a base body having a rectangular bottom plate portion as viewed from the axial direction, a pivot post, and a bridge is integrally cast using a mold. The bottom plate portion extends perpendicularly to the rotation axis of the disk and the oscillation axis of the head, and is rectangular as viewed from the axial direction. The rotation axis extends vertically. The oscillation axis is disposed at a position different from the rotation axis and extends vertically. The head reads or writes information from the disk. The pivot post protrudes upward from an upper surface of the bottom plate portion along the oscillation axis. The bridge protrudes radially outward from a peripheral surface of the pivot post and spans an upper surface of the bottom plate portion. In the cutting step, the bridge is cut. In the electro-deposition coating step, an electro-deposition coating film is formed on the surface of the base body. Effect of the Invention

[0008] According to an exemplary embodiment of the present invention, it is possible to provide a base plate and a method for manufacturing the base plate that can reduce the occurrence of shrinkage cavities. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a vertical cross-sectional view of a disk drive device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing a schematic view of a base plate according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a top view showing a schematic diagram of a base plate according to an embodiment of the present invention. [Figure 4] FIG. 4 is a vertical cross-sectional view that illustrates a base plate according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a flowchart showing a manufacturing process of a base plate according to an embodiment of the present invention. [Figure 6] FIG. 6 is an explanatory diagram illustrating a manufacturing process of the base plate according to the embodiment of the present invention. [Figure 7] FIG. 7 is an explanatory diagram illustrating a manufacturing process of the base plate according to the embodiment of the present invention. [Figure 8] FIG. 8 is an explanatory diagram illustrating a manufacturing process of the base plate according to the embodiment of the present invention. [Figure 9] FIG. 9 is an explanatory diagram illustrating a manufacturing process of the base plate according to the embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram illustrating a manufacturing process of the base plate according to the embodiment of the present invention. [Figure 11] FIG. 11 is an explanatory diagram illustrating a manufacturing process of the base plate according to the embodiment of the present invention. [Figure 12] FIG. 12 is an explanatory diagram illustrating the first processed surface of the base plate according to the embodiment of the present invention. [Figure 13] FIG. 13 is an explanatory diagram illustrating the first processed surface of the base plate according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the drawings. In this specification, the rotation axis C of the disk 50 and the oscillation axis D of the head extend parallel to each other at different positions. In addition, in this application, the direction parallel to the rotation axis C or the oscillation axis D is called the "axial direction", the direction perpendicular to the oscillation axis is called the "radial direction", and the direction along the arc centered on the rotation axis C or the oscillation axis D is called the "circumferential direction". In addition, in this application, the axial direction is the up-down direction, and the cover 42 side is the upper side with respect to the base plate 41, and the shape and positional relationship of each part will be described. However, this definition of the up-down direction is not intended to limit the orientation of the base plate 41 and the disk drive device 1 according to the present invention when used.

[0011] (1. Configuration of Disk Drive Unit) A disk drive device 1 according to an exemplary embodiment of the present invention will be described below. Fig. 1 is a vertical cross-sectional view of a disk drive device 1 according to an embodiment of the present invention.

[0012] The disk drive device 1 is a hard disk drive and includes a spindle motor 2, a disk 50, a head 31, an arm 32, a swing mechanism 33, and a housing 40.

[0013] The housing 40 accommodates therein the spindle motor 2, the disk 50, the head 31, and the arm 32.

[0014] The inside of the housing 40 is filled with a gas having a lower density than air. Specifically, the inside of the housing 40 is filled with helium gas. Note that instead of helium gas, hydrogen gas or the like may be filled.

[0015] The housing 40 is formed by casting a metal die-cast member made of an aluminum alloy. However, the die-cast member may be made of a metal other than an aluminum alloy.

[0016] The housing 40 has a base plate 41 and a cover 42. Inside the housing 40, the disk 50, the spindle motor 2, and the access unit 30 are arranged on the base plate 41. An upper opening of the base plate 41 is closed by the cover 42. The base plate 41 will be described in detail later.

[0017] The spindle motor 2 supports the disk 50 and rotates the disk 50 about a rotation axis C. That is, the disk 50 is rotated about the rotation axis C by the spindle motor 2. The spindle motor 2 has a stationary part 10 and a rotating part 20. The stationary part 10 is stationary relative to the housing 40. The rotating part 20 is supported rotatably with respect to the stationary part 10.

[0018] The stationary part 10 has a stator 12 and a bearing unit 13. In addition, a part of a base plate 41 constitutes the stationary part 10. That is, the spindle motor 2 has a base plate 41. The base plate 41 extends perpendicularly to the rotation axis C below the rotating part 20. The base plate 41 is a part of the spindle motor 2 and also a part of the housing 40. The stator 12 and the bearing unit 13 are fixed to the base plate 41.

[0019] The stator 12 includes a stator core 12a, which is a magnetic body, and a plurality of coils 12b. The stator core 12a includes a plurality of teeth 12c that protrude radially outward. The plurality of coils 12b are formed of conductive wires wound around the teeth 12c.

[0020] The bearing unit 13 rotatably supports the shaft 21 on the rotating part 20 side. The bearing unit 13 uses, for example, a fluid dynamic bearing mechanism.

[0021] The rotating part 20 has a shaft 21, a hub 22, and a magnet 23. The shaft 21 is a columnar member extending in the axial direction. The lower end of the shaft 21 is accommodated inside the bearing unit 13.

[0022] Hub 22 is fixed to the upper end of shaft 21 and expands radially outward. The upper surface of outer circumferential portion 22a of hub 22 supports disk 50. Magnet 23 is fixed to the inner circumferential surface of hub 22 and disposed facing stator 12 at a predetermined distance radially outward. Magnet 23 is annular, and the inner circumferential surface of magnet 23 is magnetized with N poles and S poles alternately in the circumferential direction.

[0023] When a driving current is supplied to the coil 12b, a magnetic flux is generated in the teeth 12c. Then, an interaction of the magnetic flux between the teeth 12c and the magnet 23 generates a circumferential torque. As a result, the rotating part 20 rotates about the rotation axis C relative to the stationary part 10. The disk 50 supported by the hub 22 rotates together with the rotating part 20 about the rotation axis C.

[0024] The disks 50 are circular information recording media having a hole in the center. The disks 50 are mounted on the spindle motor 2 and are arranged in parallel to each other in the axial direction at equal intervals via spacers (not shown).

[0025] The head 31 magnetically reads or writes information from or to the disk 50. The arm 32 is attached to the tip of a pivot post 413 (described later) of the base plate 41 via a bearing 32a. The head 31 is provided at the tip of the arm 32.

[0026] The swing mechanism 33 is a mechanism for swinging the arm 32 and the head 31. When the swing mechanism 33 is driven, the arm 32 swings about the swing axis D. That is, the head 31 swings about the swing axis D by the swing mechanism 32 via the arm 32. At this time, the head 31 moves relative to the disk 50 and approaches and accesses the rotating disk 50.

[0027] (2. Detailed configuration of the base plate) Fig. 2 is a perspective view showing the base plate 41, and Fig. 3 is a top view showing the base plate 41. Fig. 4 is a vertical cross-sectional view showing the base plate 41. Note that the gate trace portion 412a shown in Fig. 4 has been removed in a manufacturing process of the base plate 41, which will be described later, but is shown for the sake of explanation.

[0028] The base plate 41 has a base body 41a which is a casting, and an electrodeposition coating film 41b which covers the surface of the base body 41a.

[0029] The base body 41a is formed in a box shape that is open at the top, and has a bottom plate portion 411, a peripheral wall portion 412, a pivot post 413, and a protrusion portion 414. The bottom plate portion 411 is rectangular when viewed from the axial direction, and extends perpendicular to the rotation axis C and the oscillation axis D.

[0030] The peripheral wall portion 412 is formed of a plurality of walls that extend upward from the outer periphery of the bottom plate portion 411 and surround the periphery of the bottom plate portion 411. The cover 42 is disposed on the upper end surface of the peripheral wall portion 412 and is fixed thereto by, for example, screws. The peripheral wall portion 412 also has a gate mark 412a to which the gate 214 was connected during casting, and the gate mark 412a is disposed on the outer surface of the peripheral wall portion 412 that intersects with the protruding direction T of the protruding portion 414.

[0031] The pivot post 413 is formed in a cylindrical shape and protrudes upward from the upper surface of the bottom plate portion 411 along the oscillation axis D. The pivot post 413 has an annular pedestal portion 413a that protrudes radially outward from the peripheral surface of the base portion. By providing the pedestal portion 413a, the rigidity of the base portion of the pivot post 413 can be improved.

[0032] Protrusion 414 protrudes radially outward from the circumferential surface of pivot post 413 toward gate mark 412a, and is provided so as to protrude onto the upper surface of bottom plate portion 411. Providing protrusion 414 improves the rigidity of pivot post 413. Furthermore, protrusion 414 protruding toward gate mark 412a can prevent pivot post 413 from deforming toward disc 50.

[0033] The bottom plate portion 411 has a first recess 411a and a second recess 411b. The first recess 411a is adjacent to the protruding portion 414 in the protruding direction T on a first processed surface 71 described later, and is formed such that the upper surface of the bottom plate portion 411 is recessed axially downward. By providing the first recess 411a, the weight of the base plate 41 can be reduced. Furthermore, by providing the first recess 411a, interference between the upper surface of the bottom plate portion 411 and components around the pivot post 413 can be reduced, and components can be arranged near the base of the pivot post 413. The first recess 411a is formed so that the length in the width direction perpendicular to the protruding direction T increases toward the protruding direction T.

[0034] The protrusion 414 and the first recess 411a are formed when cutting a bridge 415 (described below) that is formed during casting.

[0035] The second recess 411b is formed by recessing the lower surface of the bottom plate portion 411, which faces the pivot post 413 in the axial direction, toward the axially upper side. The second recess 411b is a truncated cone-shaped recess, and is circular when viewed from below. That is, the inner diameter of the second recess 411b is gradually smaller toward the axially upper side. By providing the second recess 411b, the weight of the base plate 41 can be further reduced. In addition, as will be described later, by providing the second recess 411b, the flow of molten metal can be redirected upward during casting, and the flow of molten metal toward the tip end side of the pivot post 413 can be promoted.

[0036] (3. Manufacturing method of base plate) Fig. 5 is a flow chart showing the manufacturing process of the base plate 41. Figs. 6 to 10 are explanatory views for explaining the manufacturing process of the base plate.

[0037] 6, the peripheral portion of the mold 201 and the peripheral portion of the mold 202 are brought into contact with each other in the up-down direction to form a cavity 210 between the mold 201 and the mold 202. The cavity 210 has a shape corresponding to the shape of the base body 41a. The cavity 210 also communicates with a gate 214 extending along the opposing surfaces of the mold 201 and the mold 202. An outer end of the gate 214 opens to the outside of the mold 201 and the mold 202.

[0038] In addition, an air vent passage (not shown) for venting air from within the cavity 210 is provided on the opposing surfaces of the mold 201 and the mold 202 in addition to the gate 214. The outer end of the air vent passage is open to the outside of the mold 201 and the mold 202.

[0039] The cavity 210 has a plate-shaped portion 211, a protrusion 212, and a depression 213. Molten metal flows into the plate-shaped portion 211, and a bottom plate portion 411 is formed.

[0040] The protrusion 212 has a columnar portion 212a and a guide portion 212b. The columnar portion 212a is formed in a columnar shape and extends axially upward from the plate-like portion 211. Molten metal flows into the columnar portion 212a to form a pivot post 413.

[0041] Guide portion 212b protrudes from a part of the circumferential surface of cylindrical portion 212a toward gate 214, and has an inclined surface 212c that slopes downward toward gate 214. Guide portion 212b is formed in a triangular shape, into which molten metal flows to form bridge 415 (see FIG. 8). Guide portion 212b is formed so that its length in the width direction perpendicular to protruding direction T increases toward protruding direction T.

[0042] The recessed portion 213 faces the columnar portion 212a in the up-down direction, and when the molten metal flows into the plate-shaped portion 211, a second recessed portion 411b is formed.

[0043] In step S2, molten metal is injected into cavity 210 through gate 214. The molten metal is, for example, a molten aluminum alloy. When the molten metal is injected into cavity 210, the air in cavity 210 or the gas generated from the molten metal is pushed out of mold 201 and mold 202 through the air vent passage. This allows the molten metal to spread throughout cavity 210.

[0044] At this time, the molten metal that has flowed into the plate-like portion 211 from the gate 214 is more likely to flow into the columnar portion 212a via the guide portion 212b.

[0045] Guide portion 212b is formed such that the length in the width direction perpendicular to protruding direction T increases toward the front in protruding direction T, and molten metal is smoothly guided from guide portion 212b to cylindrical portion 212a. In addition, inclined surface 212c guides molten metal to the tip of cylindrical portion 212a, making it easier to flow into it. Furthermore, recessed portion 213 changes the direction of the flow of molten metal upward, making it easier to flow into cylindrical portion 212a. Thus, by providing bridge 415 when casting pivot post 413, it is possible to reduce the occurrence of shrinkage cavities in pivot post 413.

[0046] In step S3, after the molten metal has permeated the cavity 210, the molten metal is cooled and hardened. As a result, a base body 41a (see FIG. 7) is formed inside the cavity 210. A chill layer (not shown) is formed on the surface of the base body 41a. The chill layer is formed in the area where the molten metal comes into contact with the molds 201 and 202 and hardens quickly when the molten metal hardens. The chill layer, where the molten metal has an effect on it more quickly than other areas, has fewer impurities and a higher metal density.

[0047] 7, the base body 41a is released from the pair of molds 201, 202. At this time, the peripheral wall portion 412 has a gate mark 41d protruding from the outer surface. The gate mark 41d is formed by hardening of the molten metal accumulated in the gate 214 and the air vent passage (not shown).

[0048] In step S5, the gate mark 41d is cut. Fig. 8 is a perspective view of the base body 41a, and the base body 41a has a bridge 415 formed by the guide portion 212b. The bridge 415 protrudes radially outward from the peripheral surface of the pivot post 413 and spans the upper surface of the bottom plate portion 411. The gate mark 412a obtained by cutting the gate mark 41d protrudes slightly from the outer surface of the peripheral wall portion 412, leaving a mark.

[0049] In step S6, the bridge 415 is cut as shown in Fig. 9. The bridge 415 is cut, and the protrusion 414 and the first recess 411a are formed (see Fig. 2). The protrusion 414 is a trace of the bridge 415.

[0050] The protrusion 14 can improve the rigidity of the base of the pivot post 413. Moreover, by cutting the bridge 415 while leaving the protrusion 14, it is possible to prevent the pivot post 413 from being cut excessively. Moreover, by forming the first recess 411a and cutting the bridge 415, it is possible to arrange a component near the base of the pivot post 413. At this time, by forming the area of ​​the first recess 411a wider than the protrusion 14, it is possible to arrange the component closer to the base of the pivot post 413.

[0051] When cutting the bridge 415, the surface of the base body 41a is cut to form a first machined surface 71. The first machined surface 71 is formed on a part of the circumferential surface where the bridge 415 of the pivot post 413 was formed, the upper surface of the protruding portion 414, and the bottom surface of the first recessed portion 411a. That is, the first machined surface 71 is disposed across at least a part of the circumferential surface of the pivot post 413 and the upper surface of the protruding portion 414. The first machined surface 71 also extends further in the protruding direction from the upper surface of the protruding portion 414, and its tip is formed on the upper surface of the bottom plate portion 411. At this time, the first recessed portion 411a is adjacent to the protruding portion 414 on the first machined surface 71.

[0052] Also, the length of the width direction orthogonal to the protruding direction T of the first processed surface 71 is formed to be large as it moves away from the pivot spot 413 (see FIG. 3). At this time, the first processed surface 71 is formed to be small as it approaches the pivot spot 413, which can further prevent the pivot post 413 from being cut in excess when cutting the bridge 415. This can shorten the cutting processing time and suppress a decrease in the circularity accuracy of the pivot post 413.

[0053] In step S7, as shown in Fig. 10, an electrodeposition coating film 41b is formed on the surface of the base body 41a. The electrodeposition coating film 41b is formed, for example, by immersing the base body 41a in a coating material such as an epoxy resin and passing an electric current between the coating material and the base body 41a. As a result, the coating material adheres to the surface of the base body 41a, and the electrodeposition coating film 41b is formed on the surface of the base body 41a. At this time, the outer surface of the gate mark portion 412a is also covered with the electrodeposition coating film 41b.

[0054] In step S8, as shown in FIG. 11, the pivot post 413, which requires precision, is precisely shaped by cutting on the surface of the base body 41a.

[0055] At this time, by cutting the surface of the base body 41a, the electrodeposition coating film 41b is also cut, so that an area where the electrodeposition coating film 41b is not provided is formed on the entire circumferential surface of the pivot post 413 and on the upper surface of the protruding portion 414.

[0056] In step S8, the entire outer surface of the peripheral wall 412, including the gate mark 412a formed when the gate mark 41d was removed in step S5, is cut and shaped. At this time, the electrodeposition coating film 41b on the outer circumferential surface of the peripheral wall 412 is cut to form a second machined surface 72. That is, the second machined surface 72, which is formed by cutting the surface of the base body 41a, is formed on at least a part of the peripheral wall 412 so as to include at least a part of the gate mark 412. This makes it possible to shape the gate mark 412a formed by accumulation in the gate 214 and the air vent flow path (not shown) through a series of operations. This improves the workability in the cutting process.

[0057] In this embodiment, the second machined surface 72 is formed on the entire outer surface of the peripheral wall portion 412, but the second machined surface 72 may be formed only on one surface including the gate mark 412a of the peripheral wall portion 412. The second machined surface 72 may be formed across the one surface including the gate mark 412a of the peripheral wall portion 412 and at least one surface adjacent to that one surface.

[0058] In step S8, the gate trace 412a is removed by cutting so that no trace remains, but in order to illustrate the trace where the gate was connected during casting, the gate trace 412a is shown by a dashed line in the drawing.

[0059] In step S9, the base body 41a is immersed in the impregnating agent. At this time, the impregnating agent is permeated into at least a part of the first machined surface 71 where the electrodeposition coating film 41b has been cut and into the second machined surface 72. The impregnating agent is, for example, an epoxy resin or an acrylic resin. As a result, minute cavities formed in the surface of the base body 41a in at least a part of the first machined surface 71 where the electrodeposition coating film 41b has been cut and into the second machined surface 72 are sealed with the impregnating agent. This makes it possible to prevent the helium gas filled inside the housing 40 from leaking to the outside through the first machined surface 71 and the second machined surface 72.

[0060] The impregnating agent has a lower viscosity than the coating material forming the electrodeposition coating film 41. Therefore, the impregnating agent can more easily penetrate into minute cavities formed on the surface of the base body 41a than the coating material forming the electrodeposition coating film 41.

[0061] As described above, the manufacturing method of the base plate 41, which is a casting that becomes a part of the housing 40 of the disk drive device 1, includes a casting step, a cutting step, an electrodeposition coating step, a shaping step, and an impregnation step, in that order. In the casting step, the base body 41a having the bottom plate portion 411, the pivot post 413, and the bridge 415 is integrally cast by the molds 201 and 202 (steps S1 to S4). In the cutting step, the bridge 415 is cut (step S6). In the electrodeposition coating step, the electrodeposition coating film 41b is formed on the surface of the base body 41a (step S7). In the shaping step, the surface of the base body 41a is cut and shaped (step S8). In the impregnation step, the processed surface of the base body 41a that is exposed from the electrodeposition coating film 41b is impregnated with an impregnating agent (step S9). By forming the pivot post 413 with the bridge 415, the occurrence of shrinkage cavities in the pivot post 413 can be reduced.

[0062] (4. Other) The above-mentioned embodiment is merely an example of the present invention. The configuration of the embodiment may be appropriately changed without exceeding the technical idea of ​​the present invention. Moreover, the embodiment may be combined to the extent possible. For example, the shape of the first processed surface 71 changes depending on the cutting area of ​​the bridge 415. FIG. 11 and FIG. 12 are explanatory diagrams for explaining the first processed surface 71, and as shown in FIG. 11, the entire area spanning the bottom plate portion 411 of the bridge 415 may be left as the protruding portion 414. At this time, the protruding portion 414 is arranged up to the tip of the first processed surface 71 in the protruding direction T. This can reduce the decrease in strength of the bottom plate portion 411 due to cutting.

[0063] 12, the bridge 415 may be cut flat without forming the first recess 411a. In this case, the first machined surface 71 extends further forward in the protruding direction T from the protruding portion 414, and the tip is disposed on the upper surface of the bottom plate portion 411. [Industrial Applicability]

[0064] The present invention can be used in a housing for a disk drive device such as a hard disk drive. [Explanation of symbols]

[0065] 1 Disk Drive Unit 2 Spindle motor 10 Stationary part 12 Stator 12a Stator core 12b Coil 12c Teeth 13 Bearing unit 20 Rotating section 21 Shaft 22 Hub 22a Outer periphery 23 Magnet 30 Access Section 31 Head 32 Arm 32a Bearing 33 Swing Mechanism 40 Case 41 Base Plate 41a Base body 41b Electrochemical coating 42 Cover 50 discs 71 1st machining surface 72 2nd machining surface 201, 202 Mold 210 Cavity 211 Plate-shaped part 212 Convex 212a Cylinder section 212b Guide part 212c slope 213 Depression Gate 214 411 Bottom plate part 411a First recess 411b Second recess 412 Peripheral wall section 412a Gate Remains 413 Pivot Post 413a Pedestal 414 Protrusion 415 Bridge C Rotational Axis D Swing Axis

Claims

1. A base plate that is a part of a housing of a disk drive device, A base body which is a casting; and an electrodeposition coating film covering at least a portion of the surface of the base body. The base body is A bottom plate portion having a rectangular shape when viewed from the axial direction; A pivot post and a protrusion; The bottom plate portion is The head extends perpendicular to the rotation axis of the disk, which extends vertically, and the oscillation axis of the head, which is disposed at a position different from the rotation axis and extends vertically, and reads or writes information from or to the disk; The pivot post protrudes upward from an upper surface of the bottom plate portion along the pivot axis, The protrusion protrudes from the peripheral surface of the pivot post in only one radially outward direction and is provided so as to protrude from the upper surface of the bottom plate portion.

2. The base plate according to claim 1 , further comprising a first machined surface that is machined from a surface of the base body and is disposed across at least a portion of the circumferential surface of the pivot post and an upper surface of the protruding portion.

3. The base plate according to claim 2 , wherein the first processed surface extends from an upper surface of the protruding portion in a protruding direction of the protruding portion and has a tip disposed on an upper surface of the bottom plate portion.

4. The base plate according to claim 3 , wherein a length of the first processed surface in a width direction perpendicular to the protruding direction increases with increasing distance from the pivot post.

5. The base plate according to claim 4 , wherein a length of a tip end portion of the first processed surface in a width direction perpendicular to the protruding direction is greater than a length of the protruding portion in the width direction perpendicular to the protruding direction.

6. A base plate according to any one of claims 3 to 5, wherein the bottom plate portion has a first recess on the first processed surface adjacent to the protrusion portion and formed with an upper surface recessed axially downward.

7. The base plate according to any one of claims 2 to 6, wherein at least a portion of the first processed surface is impregnated with an impregnating agent.

8. The base plate according to any one of claims 1 to 7, wherein the pivot post has an annular seat portion that protrudes radially outward from a peripheral surface of a base portion.

9. The base plate according to any one of claims 1 to 8, wherein the bottom plate portion has a second recess formed by recessing a lower surface axially opposite the pivot post in an axially upward direction.

10. The base body has a peripheral wall portion that extends upward from an outer periphery of the bottom plate portion and surrounds the bottom plate portion, The peripheral wall portion has a gate mark portion where a gate was connected during casting, the gate mark is disposed on an outer surface of the peripheral wall portion intersecting with a protruding direction of the protrusion, A base plate as described in any one of claims 1 to 9, wherein a second machined surface formed by cutting the surface of the base body is formed on at least a portion of the peripheral wall portion so as to include at least a portion of the gate mark portion.

11. The peripheral wall portion is The base plate according to claim 10 , wherein the second machined surface is formed across one surface of the peripheral wall portion including the gate mark and at least one surface adjacent to the one surface.

12. The base plate according to claim 10 , wherein the second machined surface is formed on the entire outer periphery of the peripheral wall portion.

13. The base plate according to any one of claims 10 to 12, wherein at least a portion of the second working surface is infiltrated with an impregnating agent.

14. The base plate according to claim 7 or 13, wherein the impregnating agent is an epoxy-based resin.

15. The base plate according to claim 7 or 13, wherein the impregnating agent is an acrylic resin.

16. A spindle motor comprising the base plate according to any one of claims 1 to 15.

17. A spindle motor according to claim 16; a disk rotated around the rotation axis by the spindle motor; a head that oscillates around the oscillating axis and reads or writes information from or to the disk.

18. 18. The disk drive device according to claim 17, wherein the inside of the housing is filled with a gas having a density lower than that of air.

19. A method for manufacturing a base plate of a casting that becomes a part of a housing of a disk drive device, comprising the steps of: a disk rotation axis extending vertically, a head swing axis disposed at a position different from the rotation axis, the head swing axis extending vertically, and the head reading or writing information from or to the disk; and a bottom plate portion extending perpendicularly to the disk rotation axis and rectangular in shape as viewed from the axial direction; a pivot post protruding upward from an upper surface of the bottom plate portion along the pivot axis; a bridge protruding radially outward from a peripheral surface of the pivot post and spanning an upper surface of the bottom plate portion; a cutting step of cutting the bridge; and an electrodeposition coating step of forming an electrodeposition coating film on the surface of the base body.

20. After the electrocoating step, a shaping step of cutting and shaping the surface of the base body; and an impregnation step of impregnating an impregnating agent into a processed surface of the surface of the base body that is exposed from the electrodeposition coating film.

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