Spindle motor

Abstract

To provide a spindle motor that reduces the burden of disassembly work. [Solution] The spindle motor 3 comprises at least one set of components bonded together with a thermoplastic adhesive. For example, at least one set of the rotor hub 21 and magnet 22, and the base member 6 and stator core 11 are bonded together with a thermoplastic adhesive.

Description

TECHNICAL FIELD

[0001] The present invention relates to a spindle motor.

BACKGROUND ART

[0002] A hard disk drive device or an optical disk device is equipped with a spindle motor. A spindle motor is a rotational drive device that rotates a magnetic disk or an optical disk about its rotational central axis. The spindle motor includes a stator fixed to a housing, and a rotor hub that rotates together with the aforementioned disk (see Patent Document 1).

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In recent years, demands for recycling of waste have been increasing. Spindle motors, which are industrial products, are provided with rare components such as magnets, and similar demands may arise. However, to ensure that spindle motors can withstand unexpected vibrations and deformations, their constituent components are firmly fixed using strong adhesives or press-fitting. Therefore, when discarding a spindle motor, the work burden for disassembling each constituent component and sorting by material tends to increase easily.

[0005] An object of the present invention is to provide a spindle motor that can at least reduce the burden of disassembly work.

MEANS FOR SOLVING THE PROBLEMS

[0006] A spindle motor according to one aspect of the present invention includes at least one set of constituent members bonded to each other with a thermoplastic adhesive. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a spindle motor that can at least reduce the burden of disassembly work. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing an example of the configuration of a hard disk drive equipped with a spindle motor according to the first embodiment. [Figure 2] Figure 2 is a cross-sectional view of a spindle motor according to the first embodiment. [Figure 3A] Figure 3A is a cross-sectional view showing an example of mounting between the shaft and base member in the first embodiment. [Figure 3B] Figure 3B is a cross-sectional view showing an example of mounting between the shaft and base member in the first embodiment. [Figure 4] Figure 4 is a cross-sectional view of a spindle motor according to the second embodiment. [Figure 5A] Figure 5A is a cross-sectional view showing an example of shaft-to-rotor hub mounting in the second embodiment. [Figure 5B] Figure 5B is a cross-sectional view showing an example of shaft-to-rotor hub mounting in the second embodiment. [Modes for carrying out the invention]

[0009] Several embodiments will be described below with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. The spindle motor in the embodiments is, for example, a brushless DC motor. In the following description, a hard disk drive is given as an example of its application. However, the application of the spindle motor in the embodiments is not limited to hard disk drives, but can also be applied to devices that rotate disks, such as optical disc drives (not shown). The shape of the components of the spindle motor is not limited to the shapes shown in the drawings of each embodiment. That is, the shape of the components can be designed arbitrarily as long as they perform their function.

[0010] Furthermore, for the sake of explanation, we define the axial, circumferential, and radial directions. The axial direction AD is the extension direction of the central axis A shown in Figure 1. The central axis A is the reference axis for the shaft 30, rotor hub 21, and stator 10, and is also the rotation center of the rotor hub 21. The circumferential and radial directions are defined with respect to the central axis A. In addition, in the axial direction AD in Figure 1, the direction from bottom to top is defined as upward, and the opposite direction is defined as downward.

[0011] [First Embodiment] (Hard disk drive) First, the first embodiment will be described. As shown in Figure 1, the hard disk drive 1 comprises at least a plurality of disks (platters) 2, a spindle motor 3, and a head assembly 4. These, along with their related devices (components), are housed in a housing 5.

[0012] The housing 5 comprises a base member 6 and a cover 7. A recess 6c is formed in the base member 6. The recess 6c forms a housing space 8. Various components such as the disk 2, spindle motor 3, and head assembly 4 are housed in the housing space 8. The cover 7 covers the recess 6c (housing space 8) from above. This seals the housing space 8. The material of the base member 6 and cover 7 is, for example, an aluminum alloy, but other non-magnetic metals or alloys may also be used.

[0013] The base member 6 is a plate-shaped metal member having an inner surface 6a that forms a recess 6c and an outer surface 6b that faces the opposite side of the inner surface 6a. A cylindrical portion 9 is formed on the inner surface 6a. The cylindrical portion 9 protrudes into the housing space 8 with the central axis A as its center. The stator core 11 of the spindle motor 3 is attached to the outer circumferential surface 9a of the cylindrical portion 9. Furthermore, a support hole 9b is formed in the cylindrical portion 9, concentric with the cylindrical portion 9. The lower end portion 30b of the shaft 30, which will be described later, is inserted through the support hole 9b.

[0014] The containment space 8 may be filled with a gas of lower density than air. Such gases may be, for example, helium, nitrogen, or a mixture of helium and nitrogen. To prevent leakage of the gas filled in the containment space 8, the cover 7 may have a double-lid structure consisting of a first cover 7a and a second cover 7b. In this case, the first cover 7a is attached to the base member 6 so as to sandwich a sealing member S, such as an O-ring, which is installed between the cover and the base member 6. The second cover 7b is fixed to the base member 6 by adhesive or welding, etc., so as to cover the entire first cover 7a.

[0015] The head assembly 4 comprises a plurality of arms 4a, a plurality of heads (magnetic heads) 4b, and an actuator 4c. The plurality of arms 4a are spaced apart along the axial direction AD and are located on each side of each disk 2 in the axial direction AD. The bases of the plurality of arms 4a are integrated and are pivotably supported by a pivot bearing portion (not shown) attached to a part of them.

[0016] The head 4b is located at the tip of the arm 4a corresponding to the head and faces the surface of the disk 2 corresponding to the head. The head 4b is a magnetic device and writes or reads information from the disk 2.

[0017] The actuator 4c is a drive mechanism that swings the plurality of arms 4a and moves each head 4b to a predetermined position. The actuator 4c includes, for example, a voice coil motor configured by a coil (not shown) attached to the proximal end side of the arm 4a and a magnet (not shown) attached to the base member 6.

[0018] A connector C is attached to the base member 6. The connector C is fixed to a mounting hole 6d formed in the base member 6 using an adhesive, and is electrically connected to the actuator 4c in the accommodation space 8. Further, a cable (not shown) from the control circuit of the hard disk drive device 1 is connected to the connector C using a predetermined connector.

[0019] Control information for the actuator 4c is input from a control circuit (not shown) to the actuator 4c via the connector C. Thereby, the arm 4a swings in a predetermined direction based on the control information. Information to be written to the disk 2 and information read from the disk 2 are transmitted between the control circuit and the head 4b via the connector C.

[0020] (Spindle motor) As shown in Figure 2, the spindle motor 3 includes a stator 10 and a rotor 20. The spindle motor 3 according to the first embodiment has a shaft 30 as a constituent member of the stator 10. That is, the shaft 30 according to the first embodiment is stationary relative to the rotatable rotor 20.

[0021] The spindle motor 3 rotationally drives the plurality of disks 2. Each disk 2 is mounted coaxially with the central axis of the spindle motor 3 (that is, the central axis A). The plurality of disks 2 are pressed toward a flange 25c formed at the lower portion of the rotor hub 21 by a clamp 27 (see Figure 1) attached to the upper portion of the rotor hub 21.

[0022] When the clamp 27 is tightened, the central edges of the multiple disks 2 are held between the clamp 27 and the flange 25c and retained on the rotor hub 21. As a result, the multiple disks 2 rotate together with the spindle motor 3. Note that the number of disks 2 held by the spindle motor 3 is not limited to the 10 disks shown in Figure 1.

[0023] (Stator) The stator 10 comprises a base member 6, a shaft 30, a stator core 11, and a coil 12. As described above, the base member 6 is provided with a cylindrical portion 9, and the cylindrical portion 9 is provided with a support hole 9b. The support hole 9b penetrates the base member 6 with the central axis A as its center. Furthermore, an annular groove 6f is formed on the radially outer side of the cylindrical portion 9 on the inner surface 6a of the base member 6, extending circumferentially with the central axis A as its center.

[0024] The shaft 30 is a rod-shaped metal member having a circular cross-section and extending in the axial direction AD. The lower end 30b of the shaft 30 is attached to the support hole 9b by press-fitting or adhesive. A bottomed hole 30c is formed in the lower end 30b, extending to near the center of the shaft 30. The bottomed hole 30c connects a side hole 30e that communicates with the separator portion 32 and a side hole 30f that communicates with the space between the end cap 26 and the cylindrical portion 9. In addition, a screw hole 30d is formed in the upper end 30a of the shaft 30 for fixing the first cover 7a (see Figure 1) to the shaft 30.

[0025] The stator core 11 is an annular metal member having multiple teeth 11a and a central hole 11b that penetrates in the axial direction AD, and is attached to the base member 6. For example, the stator core 11 is attached to the outer circumferential surface 9a of the cylindrical portion 9. The stator core 11 is composed of multiple electromagnetic steel sheets stacked in the axial direction AD, and together with the rotor hub 21 or yoke 23 (shown by the dotted line in Figure 2) of the rotor 20, it constitutes a magnetic circuit. The multiple teeth 11a are spaced apart in the circumferential direction and protrude radially outward. A coil 12 is wound around each tooth 11a so as to generate magnetic flux in the radial direction. That is, the multiple coils 12 are spaced apart in the circumferential direction. Also, a part of the inner cylindrical portion 24 of the rotor hub 21 is located in the central hole 11b.

[0026] A pair of bearing members 31, 31 are attached to both ends of the shaft 30 in the axial direction AD. The pair of bearing members 31, 31 are spaced apart from each other in the axial direction AD, with a separator portion 32 separating the lubricating oil vertically. Each bearing member 31 has a substantially conical shape and, in cooperation with the inner circumferential surface of the through hole 24a, constitutes a fluid dynamic pressure sliding bearing that rotatably supports the rotor 20, which will be described later. The minute gap between each bearing member 31 and the inner circumferential surface of the through hole 24a is filled with lubricating oil that forms a lubricating film when the rotor 20 rotates. The lubricating oil is, for example, an oil based on PAO (poly-alpha-olefin), ester-based oil, etc.

[0027] (Rotor) The rotor 20 has a rotor hub 21 and a plurality of magnets 22. The rotor hub 21 is rotatably mounted around the stator 10 by the pair of bearing members 31, 31 described above. The rotor hub 21 has an inner cylindrical portion 24 and an outer cylindrical portion 25, and is formed of a magnetic metal such as stainless steel or a non-magnetic metal such as aluminum.

[0028] The inner cylindrical portion 24 and the outer cylindrical portion 25 may be formed integrally (i.e., as a single component) or as separate components. In the latter case, the inner cylindrical portion 24 is formed as a so-called sleeve through which the shaft 30 and the bearing member 31 are inserted, and is located radially inward of the outer cylindrical portion 25, and is fixed to the outer cylindrical portion 25 by adhesive or welding.

[0029] The inner cylindrical portion 24 is a cylindrical member that extends in the axial direction AD with respect to the central axis A. The inner cylindrical portion 24 has a through hole 24a that extends in the axial direction AD with respect to the central axis A. The shaft 30 and the bearing member 31 are inserted through the through hole 24a, and the bearing member 31 is located on each side of the shaft 30 in the axial direction AD. The diameter (inner diameter) of the through hole 24a changes along the axial direction AD so as to form a minute gap between the rotor hub 21 and each of the shaft 30 and the bearing member 31.

[0030] The outer cylindrical portion 25 is a cylindrical member that extends in the axial direction AD with respect to the central axis A, and is located radially outside the inner cylindrical portion 24. The outer cylindrical portion 25 has an outer circumferential surface 25a and an inner circumferential surface 25b located radially inside the outer circumferential surface 25a. Both surfaces extend circumferentially with respect to the central axis A.

[0031] The inner circumferential surface 25b of the outer cylindrical portion 25 forms an annular opening 21a between it and the outer circumferential surface 24b of the inner cylindrical portion 24. The stator core 11 and the coil 12 are located in the opening 21a.

[0032] The outer cylindrical portion 25 has the flange 25c described above. The flange 25c is located at the lower part of the outer peripheral surface 25a. The flange 25c also protrudes radially outward from the outer peripheral surface 25a and is formed in an annular shape that extends circumferentially around the central axis A. Together with the clamp 27 attached to the upper part of the rotor hub 21, the flange 25c grips and holds the central edges of the multiple disks 2.

[0033] The multiple disks 2 are held together by a clamp 27 and a flange 25c, along with spacers 28 (see Figure 1) that are arranged alternately with each disk 2. The spacers 28 are located between two adjacent disks 2 in the axial direction AD, forming a space (gap) between them from which the arm 4a can swing.

[0034] Multiple magnets 22 are attached to the inner circumferential surface 25b of the rotor hub 21 (outer cylindrical portion 25). The multiple magnets 22 are arranged in the circumferential direction, alternating their polarity. Each magnet 22 of the rotor 20 faces the coil 12 of the stator 10 (in other words, the tip of the teeth 11a). The magnets 22 are rare-earth magnets such as neodymium magnets. However, the magnets 22 are not limited to neodymium magnets.

[0035] A pair of end caps 26, 26 are attached to the rotor hub 21. Each end cap 26 is located on each side of the pair of bearing members 31, 31 in the axial direction AD, and is attached to the upper end of the inner cylindrical portion 24 or the outer cylindrical portion 25, and to the lower end of the inner cylindrical portion 24, respectively. The end caps 26 are annular members with holes through which the shaft 30 can be inserted, preventing lubricating oil from each bearing member 31 from leaking to the outside. The diameter (inner diameter) of the hole in the end cap 26 is such that a small gap is formed between the end cap 26 and the shaft 30 in the radial direction. This prevents contact between the end cap 26 and the shaft 30, maintaining the smooth rotation of the rotor hub 21. Also, as shown in Figure 2, the diameter (maximum diameter) D3 of the end cap 26 attached to the upper end of the inner cylindrical portion 24 may be less than or equal to the diameter D2 of the inner cylindrical portion 24. In other words, when viewed from the axial direction AD, the end cap 26 may have a diameter that does not protrude radially outward from the inner cylindrical portion 24.

[0036] The rotor 20 may have a yoke 23, as shown by the dotted line in Figure 2. In this case, the yoke 23 is formed in an annular or tubular shape centered on the central axis of the rotor hub 21 (for example, central axis A) and is attached to the inner circumferential surface 25b of the rotor hub 21 (outer cylindrical portion 25). Multiple magnets 22 are attached to the inner circumferential surface 23b of the yoke 23. If the rotor hub 21 is made of a non-magnetic metal such as aluminum, the yoke 23 is made of a magnetic material such as a magnetic metal. On the other hand, if the rotor hub 21 is made of a magnetic material such as stainless steel, the material of the yoke 23 is not limited to a magnetic material, and the yoke 23 is made of a non-magnetic metal or resin that does not contribute to the configuration of the magnetic circuit.

[0037] (adhesion) At least one set of components of the spindle motor 3 are bonded to each other with a thermoplastic adhesive. That is, at least one of several sets of components that would conventionally be bonded with an anaerobic thermosetting adhesive or joined by welding is bonded with a thermoplastic adhesive. In other words, the components of the spindle motor 3 to which the thermoplastic adhesive is bonded are, for example, the metal (alloy) structure or magnet that makes up the spindle motor 3.

[0038] For example, at least one pair of the rotor hub 21 and magnet 22, and the base member 6 and stator core 11 may be bonded to each other. In the former case, the magnet 22 is bonded to, for example, the inner circumferential surface 25b of the rotor hub 21, or, if the rotor 20 has a yoke 23, to the inner circumferential surface 23b of the yoke 23. In the latter case, for example, the stator core 11 is bonded to the outer circumferential surface 9a of the cylindrical portion 9.

[0039] The thermoplastic adhesive used in this embodiment has the property of not softening and maintaining its adhesiveness within the operating temperature range of the hard disk drive 1. For example, the adhesive has a glass transition temperature that is at least higher than the upper limit of the operating temperature of the hard disk drive 1 (e.g., 80°C) and below the Curie point of the magnet 22. Such a thermoplastic adhesive is, for example, a hot melt adhesive. The thermoplastic adhesive mainly contains, for example, an acrylic resin. However, the components of the thermoplastic adhesive are arbitrary as long as the above conditions are met. The thermoplastic adhesive does not contain conductive components and is not mixed with conductive particles in an amount that electrically connects the components in contact with the adhesive.

[0040] The set of components bonded to each other by the thermoplastic adhesive is not limited to the set described above. For example, the shaft 30 may be bonded to the base member 6 by the thermoplastic adhesive. Specifically, the lower end portion 30b of the shaft 30 may be bonded to a support hole 9b formed in the base member 6. In this case, as shown in Figure 3A, the diameter (inner diameter) Dh1 of the support hole 9b is slightly larger than the diameter (outer diameter) Ds of the shaft 30. This creates a small gap G between the inner circumferential surface 9d of the support hole 9b and the outer circumferential surface 30g of the shaft 30. The thermoplastic adhesive 40 remains in this gap G, and the shaft 30 is bonded to the base member 6.

[0041] Furthermore, if the lower end portion 30b of the shaft 30 is bonded to the support hole 9b, the lower end portion 30b may be press-fitted into a portion of the support hole 9b in the axial direction AD. This press-fitting can strengthen the fastening of the shaft 30 to the support hole 9b.

[0042] The position where the lower end portion 30b is press-fitted into the support hole 9b may be further inside the support hole 9b (on the inner side of the support hole 9b in the axial direction AD) than the opening 9c of the support hole 9b facing the rotor hub 21. In this case, as shown in Figure 3B, the diameter Dh1 of the support hole 9b is slightly larger than the diameter Ds of the shaft 30 in the region 51 extending inward from the upper end of the axial direction AD of the opening 9c, and approximately equal to the diameter Ds of the shaft 30 in the region 52 extending inward from region 51. The adhesive 40 may be limited to only the upper or lower region 51 of the axial direction AD. Note that the location of region 51 also includes the case where the opening 9c is only the portion that has been tapered and chamfered.

[0043] Alternatively, the diameter Dh1 of the support hole 9b may be constant in both region 51 and region 52, while the diameter Ds of the shaft 30 may be slightly smaller than the diameter Dh1 of the support hole 9b in region 51 and approximately equal to the diameter Dh1 of the support hole 9b in region 52. In this case as well, the adhesive 40 may remain only in the region 51 on the upper or lower side of the axial direction AD. When the support hole 9b is a through hole, region 51 is formed on one or both sides of region 52 in the axial direction AD. In the former case, it is preferable that region 51 is located on the front side of region 52, i.e., on the upper side of the axial direction AD in the support hole 9b, in the direction of press-fitting the shaft 30 into the support hole 9b. Furthermore, when region 51 is provided on both sides of region 52, the lengths of each region 51 along the axial direction AD may be the same or different.

[0044] At least a portion of the support hole 9b in region 51 may be tapered toward the opening of the support hole 9b. In this case, the tapered portion guides the insertion of the shaft 30 into the support hole 9b.

[0045] The length L2 of the region 52 along the axial direction AD is set to a value that does not make the process of softening the adhesive 40 and removing the shaft 30 from the support hole 9b excessively burdensome. For example, this length L2 is set to be less than or equal to half the length L1 of the region 51 along the axial direction AD. If region 51 is provided on both sides of region 52, the length L2 is set to be less than or equal to half the sum of the lengths L1 of each region 51.

[0046] The inner cylindrical portion 24 and the outer cylindrical portion 25 of the rotor hub 21 may be bonded to each other with a thermoplastic adhesive. In this case, the maximum diameter D1 of the inner cylindrical portion 24 may be smaller than the diameter (inner diameter) D2 of the central hole 11b of the stator core 11. Furthermore, one of the pair of end caps 26, 26 may be attached to the upper end of the inner cylindrical portion 24, and its diameter D3 may be smaller than the maximum diameter D1 of the inner cylindrical portion 24.

[0047] (effect) As described above, in this embodiment, at least one set of components of the spindle motor 3 are bonded to each other with a thermoplastic adhesive. Therefore, when disassembling the spindle motor 3, it can be disassembled simply by heating and softening the bonded areas. In other words, the burden of disassembling the spindle motor 3 can be reduced. For heating the bonded areas, known methods such as blowing hot air using a heat gun or dielectric heating can be employed.

[0048] At least one pair of the rotor hub 21 and magnet 22, and the base member 6 and stator core 11, may be bonded to each other with a thermoplastic adhesive. In the former case, the magnet 22 can be removed without applying excessive stress to it. That is, damage to the magnet 22 can be suppressed when separating the magnet 22 from the rotor hub 21. In the latter case, similar to the former, damage to the coil 12 wound around the stator core 11 can be suppressed when separating the stator 10 from the base member 6.

[0049] Furthermore, at least a portion of the shaft 30 located within the support hole 9b (i.e., the lower end portion 30b) may be bonded to the support hole 9b with a thermoplastic adhesive. In this case, removal of the shaft 30 becomes easier compared to the state in which the shaft 30 is press-fitted into the entire support hole 9b. Damage to the shaft 30 is also reduced, and the number of reusable shafts 30 increases. Note that when the shaft 30 is press-fitted into a portion of the support hole 9b, it is also possible to suppress axial misalignment of the shaft 30 relative to the support hole 9b while maintaining easy removal of the shaft 30.

[0050] Furthermore, each end cap 26 may be bonded to the rotor hub 21 (inner cylindrical portion 24) with a thermoplastic adhesive. This makes it easier to remove the end caps 26, and also makes it easier to remove the shaft 30 and bearing member 31 from the rotor hub 21. In addition, since the end caps 26 are not welded to the rotor hub 21, the rotor hub 21 is not damaged during disassembly, and the rotor hub 21 can be reused.

[0051] The inner cylindrical portion 24 and the outer cylindrical portion 25 of the rotor hub 21 may be bonded to each other with a thermoplastic adhesive. In this case, the outer cylindrical portion 25 can be removed from the inner cylindrical portion 24 while the inner cylindrical portion 24 is supported on the shaft 30 via the bearing member 31.

[0052] Furthermore, if the stator core 11 is bonded to the base member 6 with a thermoplastic adhesive, the maximum diameter D1 of the inner cylindrical portion 24 may be smaller than the diameter (inner diameter) D2 of the central hole 11b of the stator core 11. In this case, with the inner cylindrical portion 24 supported on the shaft 30 via the bearing member 31, the outer cylindrical portion 25 can be removed from the inner cylindrical portion 24, and the stator core 11 can be removed upward from the base member 6 (cylindrical portion 9).

[0053] [Second Embodiment] Next, a second embodiment will be described. As shown in Figure 4, the shaft 30 of the spindle motor 3 according to the second embodiment is provided as a component of the rotor 20. That is, the shaft 30 according to the first embodiment is fixed to the base member 6 and is stationary relative to the rotatable rotor 20. In contrast, the shaft 30 according to the second embodiment is attached to the rotor hub 21 and is rotatably provided relative to the stator 10.

[0054] Furthermore, the shaft 30 according to the second embodiment, together with the sleeve 35 described later, constitutes a hydrodynamic fluid bearing. Therefore, the spindle motor 3 according to the second embodiment does not have the pair of bearing members 31, 31 applied in the first embodiment. The following describes the configurations resulting from these differences, and components common to the first embodiment are denoted by the same reference numerals, and redundant explanations are omitted.

[0055] (Stator) The stator 10 according to the second embodiment includes a sleeve 35 in addition to the base member 6, stator core 11, and coil 12 described above. The sleeve 35 is a tubular metal member that rotatably supports the shaft 30. The sleeve 35 is attached to a support hole (first support hole) 9b formed in the cylindrical portion 9 of the base member 6 by press-fitting or adhesive.

[0056] The sleeve 35 has a through hole 35a that extends in the axial direction AD with respect to the central axis A. Furthermore, a first recess 35c is formed at the lower end 35b of the sleeve 35 as part of the through hole 35a. The first recess 35c forms a disc-shaped space centered on the central axis A. Below the first recess 35c, a second recess 35d is further formed as part of the through hole 35a. The second recess 35d opens at the lower end of the sleeve 35. The second recess 35d also forms a disc-shaped space centered on the central axis A. However, the diameter (inner diameter) of the second recess 35d is larger than the diameter (inner diameter) of the first recess 35c.

[0057] A counter plate 36 is attached to the second recess 35d by welding or adhesive. The counter plate 36 is a metal cover member that faces the lower end (end) 30b of the shaft 30 in the through hole 35a and closes the through hole 35a from below the sleeve 35. The counter plate 36 is formed in a disc shape with a central axis A, and its diameter (outer diameter) is approximately equal to the diameter of the second recess 35d. Also, the axial thickness AD of the counter plate 36 is approximately equal to the depth of the second recess 35d.

[0058] (Rotor) The rotor 20 according to the second embodiment has the rotor hub 21 and a plurality of magnets 22 as described above. The rotor hub 21 has an inner cylindrical portion 24 and an outer cylindrical portion 25, similar to the first embodiment. The inner cylindrical portion 24 has a through hole (second support hole) 24a, similar to the first embodiment. However, unlike the through hole 24a according to the first embodiment, the shaft 30 is attached (fixed) to the through hole 24a according to the second embodiment by press-fitting or adhesive.

[0059] The rotor 20 according to the second embodiment further includes a shaft 30. The shaft 30 according to the second embodiment is rotatably supported within a through hole 24a of the sleeve 35. As described above, the upper end 30a of the shaft 30 is attached to the through hole 24a by press-fitting or adhesive. As a result, the shaft 30 and the rotor hub 21 rotate as a single unit.

[0060] At least a portion of the upper end 30a of the shaft 30 may be bonded to the through hole 24a. For example, as shown in Figure 5A, the diameter (inner diameter) Dh2 of the through hole 24a is slightly larger than the diameter Ds of the shaft 30. This creates a small gap G between the inner circumferential surface 24d of the through hole 24a and the outer circumferential surface 30g of the shaft 30. The adhesive 40 remains in this gap G, and the shaft 30 is bonded to the base member 6.

[0061] Furthermore, if the upper end portion 30a of the shaft 30 is bonded to the through hole 24a, the upper end portion 30a may be press-fitted into a portion of the through hole 24a in the axial direction AD. This press-fitting can strengthen the fastening of the shaft 30 to the through hole 24a.

[0062] The position where the upper end portion 30a is press-fitted into the through hole 24a may be further inside the through hole 24a (inside the through hole 24a in the axial direction AD) than the opening 24c of the through hole 24a facing the sleeve 35. In this case, as shown in Figure 5B, the diameter Dh2 of the through hole 24a is slightly larger than the diameter Ds of the shaft 30 in the region 53 extending inward from the lower end of the axial direction AD of the opening 24c, and approximately equal to the diameter Ds of the shaft 30 in the region 54 extending inward from region 53. The adhesive 40 may be limited to only the upper or lower region 51 of the axial direction AD. Note that the location of region 53 also includes the case where it is only the tapered chamfered portion of the opening 24c.

[0063] Alternatively, the diameter Dh2 of the through-hole 24a may be constant in both region 53 and region 54, while the diameter Ds of the shaft 30 may be slightly smaller than the diameter Dh2 of the through-hole 24a in region 53 and approximately equal to the diameter Dh2 of the through-hole 24a in region 54. In this case as well, the adhesive 40 may remain only in the region 51 on the upper or lower side of the axial AD. Region 53 is formed on one or both sides of region 54 in the axial AD. In the former case, region 53 is located on the front side of region 54 in the direction of press-fitting the shaft 30 into the through-hole 24a, that is, in the range through which the upper end 30a passes before being press-fitted into the through-hole 24a. Furthermore, when region 53 is provided on both sides of region 54, the lengths of each region 53 along the axial AD may be the same or different.

[0064] At least a portion of the through-hole 24a in region 53 may be tapered toward the opening of the through-hole 24a. In this case, the tapered portion guides the insertion of the shaft 30 into the through-hole 24a.

[0065] The length L4 of the region 54 along the axial direction AD is set to a value that does not make the process of softening the adhesive 40 and removing the shaft 30 from the through hole 24a excessively burdensome. For example, this length L4 is set to be less than or equal to half the length L3 of the region 53 along the axial direction AD. If regions 53 are provided on both sides of region 54, the length L4 is set to be less than or equal to half the sum of the lengths L3 of each region 53.

[0066] A flange 30h is provided at the lower end 30b of the shaft 30. The flange 30h is formed in an annular shape around the central axis A and is located within the first recess 35c. The length (thickness) of the flange 30h in the axial direction AD is slightly less than the length (depth) of the first recess 35c in the same direction.

[0067] A radial dynamic pressure generating groove (not shown) having a well-known shape is provided on at least one of the outer circumferential surface 30g of the shaft 30 and the inner circumferential surface 35e of the through hole 35a formed in the sleeve 35. In addition, in the axial direction AD, a thrust dynamic pressure generating groove (not shown) having a well-known shape is provided on at least one of the opposing surfaces of the flange 25c and the first recess 35c. This thrust dynamic pressure generating groove is also provided on at least one of the opposing surfaces of the flange 25c and the counter plate 36 in the axial direction AD.

[0068] (effect) As described above, in the second embodiment as well, at least one set of components of the spindle motor 3 are bonded together with a thermoplastic adhesive. For example, similar to the first embodiment, at least one set of the rotor hub 21 and magnet 22, and the base member 6 and stator core 11 are bonded together with a thermoplastic adhesive. This reduces the burden of disassembling the spindle motor 3. Also, similar to the first embodiment, valuable components such as the magnet 22 and coil 12 can be separated without damaging them.

[0069] The sleeve 35 may be bonded to the support hole (first support hole) 9b formed in the base member 6 (cylindrical portion 9) using a thermoplastic adhesive. Similarly, the shaft 30 may also be bonded to the through hole (second support hole) 24a formed in the rotor hub 21 using a thermoplastic adhesive. This makes removal easier compared to when the sleeve 35 and shaft 30 are installed by press-fitting. In addition, damage to the rotor hub 21, shaft 30, and sleeve 35 is reduced, and the number of reusable parts increases.

[0070] The shaft 30 may be press-fitted into a portion of the through hole 24a. In this case, axial misalignment of the shaft 30 relative to the through hole 24a can be suppressed while maintaining easy removal of the shaft 30.

[0071] The counter plate 36 may be bonded to the sleeve 35 with a thermoplastic adhesive. This makes it easy to remove the counter plate 36 and also makes it easy to remove the shaft 30 from the sleeve 35. Furthermore, since the counter plate 36 is not welded to the sleeve 35, the sleeve 35 is not damaged during disassembly and can be reused.

[0072] Like hot-melt adhesives, thermoplastic adhesives have a relatively shorter curing time than anaerobic thermosetting adhesives. Therefore, according to the embodiments described above, the production efficiency of spindle motors, and consequently the production efficiency of hard disk drives, can be improved, and the increase in manufacturing costs can be suppressed. In addition, there may be environments where vibration and temperature changes are minimal, and the adhesive strength of anaerobic thermosetting adhesives may be excessive. By using the hard disk drive according to this embodiment in such environments, the introduction cost of the hard disk drive can also be reduced.

[0073] Although several embodiments have been described above, the present invention is not limited thereto, and various modifications are possible without departing from the spirit of the invention. For example, the combination of components of a spindle motor that are bonded together with a thermoplastic adhesive is not limited to those described above. [Explanation of Symbols]

[0074] 3 Spindle motor 6 Base member 10 staters 11 Stator Core 12 coils 20 rotors 21 Rotor Hub 22 Magnets 23 York 26 End caps 30 shafts 31 Bearing member 35 sleeves 36 Counter Plates

Claims

1. It comprises at least one set of components bonded together by a thermoplastic adhesive, Spindle motor.

2. Base member and A stator core is attached to the base member, Multiple coils arranged in the circumferential direction and provided on the stator core, A rotor hub is rotatably mounted relative to the stator core, A magnet attached to the rotor hub and facing the coil, Equipped with, At least one set of the rotor hub and the magnet, and the base member and the stator core, are bonded to each other with a thermoplastic adhesive. The spindle motor according to claim 1.

3. Base member and A stator core is attached to the base member, Multiple coils arranged in the circumferential direction and provided on the stator core, A rotor hub is rotatably mounted relative to the stator core, A yoke attached to the rotor hub, A magnet attached to the yoke and facing the coil, Equipped with, At least one pair of the yoke and the magnet, and the base member and the stator core, are bonded to each other with a thermoplastic adhesive. The spindle motor according to claim 1.

4. A shaft is attached to a support hole formed in the base member, A pair of bearing members provided at both ends of the shaft and rotatably supporting the rotor hub, Equipped with, The shaft is bonded to the support hole with a thermoplastic adhesive. The spindle motor according to claim 2 or 3.

5. The shaft is press-fitted into a portion of the support hole. The spindle motor according to claim 4.

6. The position in which the shaft is press-fitted into the support hole is located further back than the opening of the support hole. The spindle motor according to claim 5.

7. The rotor hub is fitted with a pair of end caps located on both sides of the pair of bearing members, which prevent the lubricating oil from leaking out of each bearing member. Each of the end caps is bonded to the rotor hub with a thermoplastic adhesive. The spindle motor according to claim 4.

8. The rotor hub includes an inner cylindrical portion through which the shaft is inserted, and an outer cylindrical portion located radially outside the inner cylindrical portion. The inner cylindrical portion and the outer cylindrical portion are bonded to each other with a thermoplastic adhesive. The spindle motor according to claim 4.

9. The stator core is bonded to the base member with a thermoplastic adhesive. The maximum diameter of the inner cylindrical portion is smaller than the diameter of the central hole of the stator core through which a portion of the inner cylindrical portion is inserted. The spindle motor according to claim 8.

10. A sleeve is attached to the first support hole formed in the base member, A shaft is rotatably provided within the through hole of the sleeve and attached to a second support hole formed in the rotor hub, Equipped with, The sleeve is bonded to the first support hole with a thermoplastic adhesive. The shaft is bonded to the second support hole with a thermoplastic adhesive. The spindle motor according to claim 2 or 3.

11. The shaft is press-fitted into a portion of the second support hole. The spindle motor according to claim 10.

12. The position in which the shaft is press-fitted into the second support hole is located further back than the opening of the second support hole. The spindle motor according to claim 11.

13. The shaft is provided with a counter plate that faces the end of the shaft and closes the through hole of the sleeve, The counter plate is bonded to the sleeve with a thermoplastic adhesive. The spindle motor according to claim 10.

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