JP7779733B2 - Dynamic pressure bearing motor, disk drive device, and method for assembling base and bearing - Google Patents

Description

The present invention relates to a hydrodynamic bearing motor, a disk drive device, and a method for assembling a base and a bearing.

In products that use hydrodynamic bearing motors, the bearing that supports the rotating rotor and the base are fixed together with adhesive. When a hydrodynamic bearing motor is driven, the rotor becomes electrically charged. Therefore, to prevent the rotor from becoming charged, it is necessary to electrically ground the bearing that supports the rotor.

For example, Patent Document 1 discloses a technology that uses a conductive adhesive to secure the bearing to the base. Because the bearing and base are secured in a conductive state, the bearing is grounded to the base via the conductive adhesive.

JP 2013-133941 A

However, if the bearing and base are fixed together using only conductive adhesive, the adhesive's low strength makes the bonded area brittle. This makes it more susceptible to cracks caused by thermal expansion or external forces. On the other hand, if a high-strength regular adhesive is used, other means must be used to ground the bearing to the base.

The present invention was made in consideration of the above circumstances, and aims to provide a hydrodynamic bearing motor in which the bearing is fixed in a grounded state to the base portion.

To solve the above problems, the hydrodynamic bearing motor comprises a bearing, a rotating section rotatably supported by the bearing, a base section arranged coaxially with the central axis of the rotating section and having a cylindrical section into which the bearing is inserted, a layer of conductive adhesive between the outer peripheral surface of the bearing and the inner peripheral surface of the cylindrical section, and a layer of fixing adhesive that fixes the bearing to the cylindrical section.

In the hydrodynamic bearing motor of the present invention, the bearing is fixed in a grounded state to the base portion.

1 is a cross-sectional view of a hydrodynamic bearing motor 1. FIG. FIG. 2 is an enlarged view of part II in FIG. 1 . 3 is a cross-sectional view of the III-III portion of FIG. 1 as viewed from the axial direction. FIG. 3 is an enlarged view of part IV in FIG. 2 . 10 is a flowchart of a method for assembling the bearing sleeve 20 to the base plate 10. 2 is a cross-sectional view of the hydrodynamic bearing motor 1 before the bearing sleeve 20 is assembled to the base plate 10. FIG. 1 is a cross-sectional view of a hydrodynamic bearing motor 1 having a hole 111 instead of a through hole 11. FIG.

Embodiments of the present invention will be described below with reference to the drawings. However, while the embodiments described below are subject to various limitations that are technically preferable for implementing the present invention, the scope of the present invention is not limited to the following embodiments and illustrated examples.

<<1. Configuration of a hydrodynamic bearing motor>>
1 is a cross-sectional view showing the configuration of a dynamic pressure bearing motor 1. The dynamic pressure bearing motor 1 includes a stationary part 2 and a rotating part 3 that rotates relative to the stationary part 2 via a bearing mechanism.

Here, as shown in Figure 1 etc., the direction parallel to the central axis of the shaft 30 (described later) is referred to as the axial direction, the direction around the central axis of the shaft 30 is referred to as the circumferential direction, and the direction perpendicular to the axial direction is referred to as the radial direction. For the sake of explanation, the axial direction is referred to as the up-down direction, and the rotating part 3 side relative to the stationary part 2 is referred to as the top, and the stationary part 2 side is referred to as the bottom.

<Stationary part>
The stationary portion 2 includes a base plate 10 , a bearing sleeve 20 , and a stator core 40 .

The base plate 10 (an example of a base portion) is a metal member. As shown in FIGS. 1 and 6 , the base plate 10 is formed with a through hole 11, a circumferential groove 12, and a circumferential wall portion 13. The through hole 11 (an example of a cylindrical portion) is a hole for fixing the bearing sleeve 20 and is provided so as to penetrate the base plate 10 in the axial direction. The through hole 11 is cylindrical, with the inner diameter of the cylinder being approximately the same as or larger than the outer diameter of the bearing sleeve 20. The circumferential groove portion 12 is formed radially outward from the through hole 11. The circumferential groove portion 12 is an annular groove provided coaxially with the central axis of the through hole 11. The circumferential wall portion 13 is formed as an annular wall surface portion that protrudes axially upward along the through hole 11 from the bottom surface of the circumferential groove portion 12. The circumferential wall portion 13 separates the through hole 11 from the circumferential groove portion 12.

The bearing sleeve 20 (an example of a bearing) is a cylindrical member that rotatably supports the shaft 30. The bearing sleeve 20 is inserted into the through hole 11 (see Figure 1). In the state shown in Figure 1, the outer peripheral surface 20B of the bearing sleeve 20 faces the inner peripheral surface 11A of the through hole 11. As shown in Figure 2, a layer of fixing adhesive 70 and a layer of conductive adhesive 71 are formed between the outer peripheral surface 20B and the inner peripheral surface 11A. The bearing sleeve 20 is fixed to the stationary part 2 by being adhered to the inner peripheral surface 11A of the through hole 11 by the layer of fixing adhesive 70.

A shaft 30 is placed inside the bearing sleeve 20. The inner circumferential surface 20A of the bearing sleeve 20 surrounds the outer circumferential surface 30B of the shaft 30, with the inner circumferential surface 20A and the outer circumferential surface 30B facing each other across a minute gap. This minute gap is filled with a conductive lubricating fluid (not shown).

The fixing adhesive 70 is used to adhere the bearing sleeve 20 to the inner surface 11A of the through hole 11 and secure it to the stationary part 2. The fixing adhesive 70 spreads over the entire area between the outer surface 20B and the inner surface 11A, and forms an adhesive layer by hardening while in contact with both the outer surface 20B and the inner surface 11A. The formation of the layer of fixing adhesive 70 secures the bearing sleeve 20 to the stationary part 2.

The conductive adhesive 71 is an adhesive that is electrically conductive. The conductive adhesive 71 hardens while in contact with both the outer peripheral surface 20B and the inner peripheral surface 11A at a specific location near the lower end between the outer peripheral surface 20B and the inner peripheral surface 11A, forming an adhesive layer. The formation of the conductive adhesive 71 layer provides electrical conductivity between the bearing sleeve 20 and the base plate 10.

Furthermore, as shown in Figure 3, the layer of conductive adhesive 71 is adjacent to the layer of fixing adhesive 70 in the circumferential direction. Because the layer of conductive adhesive 71 is protected by the layer of fixing adhesive 70, cracks are less likely to occur.

Furthermore, as shown in Figure 4, the conductive adhesive 71 that flows out from between the outer peripheral surface 20B and the inner peripheral surface 11A forms a ball-shaped adhesive mass 72 that contacts both the lower end surface 20C and the inner peripheral surface 11A of the bearing sleeve 20. The formation of the adhesive mass 72 establishes electrical conductivity between the bearing sleeve 20 and the base plate 10.

In addition, the lower end of the bearing sleeve 20 is formed with a large-diameter recess 23 that opens downward, and a small-diameter recess 24 that opens upward from the top surface of the large-diameter recess 23.

A counter plate 22 is attached to the large diameter recess 23. The counter plate 22 is a disk-shaped lid that covers the small diameter recess 24 and the large diameter recess 23 from the lower end side of the bearing sleeve 20. The counter plate 22 prevents the thrust plate 21 (described below) placed in the small diameter recess 24 from moving downward and coming out of the bearing sleeve 20. The counter plate 22 is circular, and its outer diameter is approximately equal to the inner diameter of the large diameter recess 23. The axial thickness of the counter plate 22 is also approximately equal to the depth of the large diameter recess 23. The counter plate 22 is fixed tightly to the bearing sleeve 20 by press-fitting, bonding, welding, or other methods.

A thrust plate 21 is placed in the small diameter recess 24. The thrust plate 21 is an annular flange member that extends radially and is formed at the lower end of the shaft 30. The thrust plate 21 prevents axial movement of the shaft 30. The thrust plate 21 is annular, and its outer diameter is smaller than the inner diameter of the small diameter recess 24. The axial thickness of the thrust plate 21 is also smaller than the depth of the small diameter recess 24.

In the state shown in Figure 1, the upper surface of the thrust plate 21 and the lower surface 24C of the bearing sleeve 20 formed in the small diameter recess 24 face each other across a small gap. Furthermore, the lower surface of the thrust plate 21 and the upper surface of the counter plate 22 face each other across a small gap. These small gaps are filled with a conductive lubricating fluid (not shown).

Thrust dynamic pressure generating grooves are provided on at least one of the upper surface of the thrust plate 21 or the lower surface 24C of the bearing sleeve 20. Furthermore, thrust dynamic pressure generating grooves are also provided on at least one of the lower surface of the thrust plate 21 or the upper surface of the counter plate 22.

The stator core 40 is a component made up of multiple annular electromagnetic steel plates stacked in the axial direction. The stator core 40 is placed inside the circumferential groove portion 12 and fixed to the outer surface of the circumferential wall portion 13 by adhesive or other methods. The stator core 40 also has multiple pole teeth (salient poles) that extend radially outward and are arranged along the circumferential direction. Coils 41 are wound around the pole teeth. When current flows through the coils 41, the stator core 40 generates magnetic flux.

<Rotating part>
The rotating part 3 has a shaft 30 , a rotor hub 50 , and a rotor magnet 60 .

The shaft 30 is a generally rod-shaped member that serves as the rotating shaft of the hydrodynamic bearing motor 1 and is disposed inside the bearing sleeve 20. Radial hydrodynamic grooves 31 are provided on at least one of the inner peripheral surface 20A of the bearing sleeve 20 or the outer peripheral surface 30B of the shaft 30 that faces the inner peripheral surface 20A. In the example of Figure 1, the radial hydrodynamic grooves 31 are formed in a continuous row in the circumferential direction on the outer peripheral surface 30B, and in two rows spaced apart in the axial direction.

The rotor hub 50 is attached to the upper end of the shaft 30 and rotates together with the shaft 30. The rotor hub 50 has a disk portion 51, a cylindrical portion 52, and an outer edge portion 53. The disk portion 51 is a disk-shaped member positioned above the bearing sleeve 20 and coaxial with the central axis of the shaft 30. A through hole 54 is provided in the center of the disk portion 51. The disk portion 51 is fixed to the shaft 30 by fixing the upper end of the shaft 30 into the through hole 54 by means of press-fitting, adhesive, or other methods. The lower surface of the disk portion 51 faces the upper surface of the bearing sleeve 20 with a gap between them. The cylindrical portion 52 is a cylindrical member with a constant radial thickness and extends downward from the outer edge of the lower surface of the disk portion 51. The inner diameter of the cylindrical portion 52 is larger than the outer diameter of the bearing sleeve 20, and the inner circumferential surface of the cylindrical portion 52 faces the outer circumferential surface 20B with a gap between them. The outer diameter of the cylindrical portion 52 is the same as the outer diameter of the disc portion 51. The outer edge portion 53 is a member that protrudes radially outward from the lower end of the cylindrical portion 52 and extends circumferentially in a flange-like shape around the entire circumference.

The rotor magnet 60 is an annular member with a magnetic pole structure in which the polarity reverses in the circumferential direction: N, S, N, S... The rotor magnet 60 is attached to the inner surface of an annular yoke 61 attached to the lower end of the outer edge portion 53. The rotor magnet 60 is located approximately in the same position as the stator core 40 in the axial direction, and is located between the stator core 40 and the inner surface of the circumferential groove portion 12 in the radial direction. The yoke 61 suppresses leakage of magnetic flux from the rotor magnet 60.

<Operation of a hydrodynamic bearing motor>
When the coil 41 is energized, a magnetic attractive force and a magnetic repulsive force are generated between the magnetic poles of the rotor magnet 60 and the pole teeth of the stator core 40. As a result, the rotating part 3 rotates relative to the stationary part 2 with the shaft 30 as the rotation axis.

The shaft 30 rotates relative to the bearing sleeve 20. At this time, the lubricating fluid is pressurized by the radial dynamic pressure generating grooves 31, generating dynamic pressure. The generated dynamic pressure supports the shaft 30 radially out of contact with the bearing sleeve 20.

When the shaft 30 rotates, the thrust plate 21 rotates relative to the bearing sleeve 20 and counter plate 22. At this time, dynamic pressure is generated as the lubricating fluid is pressurized by thrust dynamic pressure generating grooves provided on at least one of the upper surface or lower surface 24C of the thrust plate 21 and thrust dynamic pressure generating grooves provided on at least one of the lower surface of the thrust plate 21 or the upper surface of the counter plate 22. The generated dynamic pressure supports the thrust plate 21 in a non-contact state in the axial direction relative to the bearing sleeve 20 and counter plate 22.

<Disk drive device>
The hydrodynamic bearing motor 1 of this embodiment is attached to a disk drive device. The disk drive device includes a substantially rectangular parallelepiped case, the hydrodynamic bearing motor 1 arranged in the case, a plurality of recording disks attached to the outer periphery of the cylindrical portion 52, and a magnetic head that applies magnetism to the recording disks or reads magnetism from the recording disks.

When the hydrodynamic bearing motor 1 rotates, multiple recording disks rotate. A magnetic head moves over the rotating recording disks, applying magnetism to the recording disks or reading magnetism from the recording disks. In this way, the disk drive records information on the recording disks and reads information recorded on the recording disks.

<<2. How to assemble the base plate and bearing sleeve>>
Next, a method for assembling the base plate 10 and the bearing sleeve 20 of the hydrodynamic bearing motor 1 according to this embodiment will be described with reference to FIGS.

Figure 5 is a flowchart showing an example of a method for assembling the bearing sleeve 20 to the base plate 10. The assembling method consists of four steps, S10 to S13. The assembling method is performed, for example, by a work robot.

(S10)
In step S10, a fixing adhesive 70 is applied to the inner peripheral surface 11A of the base plate 10 near the upper end thereof.

The work robot applies the fixing adhesive 70 to a predetermined position on the inner circumferential surface 11A. The predetermined position is near the upper end of the inner circumferential surface 11A. The fixing adhesive 70 is applied in a ring-shaped pattern circumferentially to the inner circumferential surface 11A. Note that while Figure 6 shows an example in which the adhesive is applied in a single circumferential line, it may also be applied in two or more circumferential lines. Furthermore, as long as it is possible to secure the base plate 10 and the bearing sleeve 20 together, it is not limited to applying the adhesive in a ring-shaped pattern. However, from the perspective of ensuring the strength to secure the base plate 10 and the bearing sleeve 20 together, it is preferable that the fixing adhesive 70 be applied in an amount that spreads over the entire inner circumferential surface 11A. The fixing adhesive 70 has a lower viscosity before hardening than the conductive adhesive 71.

(S11)
Step S11 is a step of applying a conductive adhesive 71 to the vicinity of the lower end of the inner circumferential surface 11A.

The work robot applies conductive adhesive 71 to a predetermined position on the inner circumferential surface 11A. The predetermined position is near the lower end of the inner circumferential surface 11A. That is, the conductive adhesive 71 is applied to a position on the inner circumferential surface 11A that is axially spaced from the position where the fixing adhesive 70 is applied. In FIG. 6 , the conductive adhesive 71 is applied to one location near the lower end of the inner circumferential surface 11A. Note that the conductive adhesive 71 may also be applied to multiple locations near the lower end of the inner circumferential surface 11A. Furthermore, because electrical conductivity is established between the base plate 10 and the bearing sleeve 20 via an adhesive mass 72 that contacts the lower end surface 20C and the inner circumferential surface 11A, it is preferable that a sufficient amount of conductive adhesive 71 be applied to the inner circumferential surface 11A to form an adhesive mass 72.

(S12)
S12 is a process of inserting the bearing sleeve 20 into the through hole 11 from the side where the fixing adhesive 70 is applied. In this embodiment, as shown in Fig. 6, the bearing sleeve 20 is inserted into the through hole 11 in a state where the components other than the base plate 10 and the bearing sleeve 20 are assembled.

The work robot inserts the bearing sleeve 20 into the base plate 10, which is fixed using a fixture or the like, from the side of the through hole 11 where the fixing adhesive 70 is applied (the upper end side of the through hole 11 in Figure 6). At this time, the outer peripheral surface 20B of the bearing sleeve 20 is inserted facing the inner peripheral surface 11A. When the bearing sleeve 20 is further inserted into the through hole 11, the lower end surface 20C of the bearing sleeve 20 comes into contact with the fixing adhesive 70. When the bearing sleeve 20 is further inserted from this state, the fixing adhesive 70 seeps between the outer peripheral surface 20B and the inner peripheral surface 11A, and the lower end surface 20C pushes out the remaining fixing adhesive 70 in the insertion direction (downward in Figure 6).

(S13)
S13 is a step of inserting the bearing sleeve 20 into the through hole 11 until the bearing sleeve 20 reaches a predetermined position.

The work robot further inserts the bearing sleeve 20 into the through-hole 11 until the lower end surface 20C reaches the position where the conductive adhesive 71 is applied. When the bearing sleeve 20 is further inserted in this state, the fixing adhesive 70 extruded onto the lower end surface 20C comes into contact with the conductive adhesive 71. Because the viscosity of the fixing adhesive 70 is lower than that of the conductive adhesive 71, the fixing adhesive 70 does not easily mix with the conductive adhesive 71 and tends to wrap around the conductive adhesive 71. Therefore, the fixing adhesive 70 is extruded onto the lower end surface 20C while avoiding the conductive adhesive 71 in the circumferential direction. When the bearing sleeve 20 is further inserted, a portion of the lower end surface 20C comes into contact with the conductive adhesive 71. When the bearing sleeve 20 is further inserted in this state, the portion of the lower end surface 20C that is in contact with the conductive adhesive 71 extrudes the conductive adhesive 71 in the insertion direction, while the remaining portion extrudes the fixing adhesive 70 in the insertion direction. At this time, the conductive adhesive 71 penetrates between the outer peripheral surface 20B and the inner peripheral surface 11A, while the lower end surface 20C pushes out the remaining conductive adhesive 71 in the insertion direction (downward in Figure 6). The work robot stops inserting the bearing sleeve 20 when the lower end surface 20C reaches a predetermined position. This predetermined position is the bottom end of the inner peripheral surface 11A.

Here, the fixing adhesive 70 is pushed out toward the lower end surface 20C while avoiding the conductive adhesive 71 in the circumferential direction, so the layer of conductive adhesive 71 and the layer of fixing adhesive 70 are adjacent to each other in the circumferential direction between the outer peripheral surface 20B and the inner peripheral surface 11A, as shown in FIG. 3. Note that in this embodiment, the layer of conductive adhesive 71 and the layer of fixing adhesive 70 are adjacent to each other and in contact with each other, but they do not necessarily have to be in contact with each other.

In addition, in this embodiment, the conductive adhesive 71 further extruded from the lower end surface 20C forms an adhesive mass 72 in contact with the lower end surface 20C and the inner circumferential surface 11A, as shown in Figure 4.

After step S13 is completed, the fixing adhesive 70 and conductive adhesive 71 are cured by leaving them at room temperature, heating, irradiating them with light, or other methods. As the fixing adhesive 70 hardens, the base plate 10 and bearing sleeve 20 are fixed together via the layer of fixing adhesive 70. As the conductive adhesive 71 hardens, the base plate 10 and bearing sleeve 20 are electrically connected via the layer of conductive adhesive 71 and adhesive mass 72. In other words, the bearing sleeve 20 is grounded to the base plate 10.

<Effects>
In the above embodiment, the hydrodynamic bearing motor 1 comprises a bearing sleeve 20, a rotating part 3 rotatably supported by the bearing sleeve 20, a base plate 10 arranged coaxially with the central axis of the rotating part 3 and having a through hole 11 into which the bearing sleeve 20 is inserted, and a layer of conductive adhesive 71 having electrical conductivity between the outer peripheral surface 20B of the bearing sleeve 20 and the inner peripheral surface 11A of the through hole 11, and a layer of fixing adhesive 70 that fixes the bearing sleeve 20 to the through hole 11.

By providing the hydrodynamic bearing motor 1 with a layer of conductive adhesive 71 and a layer of fixing adhesive 70 between the outer peripheral surface 20B and the inner peripheral surface 11A, the base plate 10 and bearing sleeve 20 are fixed together by the layer of fixing adhesive 70 and are electrically connected by the layer of conductive adhesive 71. In other words, the bearing sleeve 20 and base plate 10 can be fixed in a grounded state.

In addition, by providing a layer of fixing adhesive 70 specifically designed for adhesion between the outer peripheral surface 20B and the inner peripheral surface 11A, the base plate 10 and bearing sleeve 20 are securely fixed together. As a result, unnecessary force is less likely to be applied to the conductive adhesive 71 layer, making it less likely for cracks to occur in the conductive adhesive 71 layer. This makes it possible to maintain a grounded state between the bearing sleeve 20 and base plate 10.

In addition, in the hydrodynamic bearing motor 1 according to this embodiment, the layer of fixing adhesive 70 and the layer of conductive adhesive 71 are adjacent to each other in the circumferential direction of the rotating part 3.

With this configuration, the layer of fixing adhesive 70 is located on the outer edge of the layer of conductive adhesive 71, making the layer of conductive adhesive 71 less susceptible to the effects of heat, external forces, etc. This makes the layer of conductive adhesive 71 less susceptible to deterioration, and allows the bearing sleeve 20 and base plate 10 to maintain their grounded state.

Furthermore, the through hole 11 of the hydrodynamic bearing motor 1 according to this embodiment is a through hole that is open on both ends.

When the bearing sleeve 20 is inserted into such a through hole 11 to a predetermined position, an adhesive mass 72 contacting the lower end surface 20C and the inner peripheral surface 11A is formed at the edge of the opening of the through hole 11, and the bearing sleeve 20 and base plate 10 are grounded via the adhesive mass 72. Therefore, the bearing sleeve 20 and base plate 10 are electrically connected via the layer of conductive adhesive 71 and the adhesive mass 72, allowing the bearing sleeve 20 and base plate 10 to be more reliably grounded.

Furthermore, with the above-described configuration, the conductive adhesive 71 layer and adhesive mass 72 cover a wide area, so even if a crack occurs in the relevant area, it is unlikely to become insulated, and the grounding state between the bearing sleeve 20 and the base plate 10 can be maintained.

The disk drive device in this embodiment also includes a dynamic pressure bearing motor 1.

With this configuration, the recording disk of the disk drive device is mounted on the rotating part 3 of the hydrodynamic bearing motor 1. The recording disk becomes electrically charged when it rotates, but because the bearing sleeve 20 of the hydrodynamic bearing motor 1 and the base plate 10 are grounded, the charge on the recording disk flows to the base plate 10. As a result, the recording disk is prevented from becoming electrically charged, making the disk drive device less susceptible to breakdowns.

In the above embodiment, the method of assembling the base plate 10 and bearing sleeve 20 by inserting the bearing sleeve 20 into the through hole 11 provided in the base plate 10 includes the steps of applying a fixing adhesive 70 and a conductive adhesive 71 to the inner surface 11A of the through hole 11 at a fixed distance in the axial direction of the through hole 11, and, after applying the fixing adhesive 70 and the conductive adhesive 71, inserting the bearing sleeve 20 into the through hole 11 from the side where the fixing adhesive 70 has been applied so that the inner surface 11A faces the outer surface 20B of the bearing sleeve 20.

With this method, when the bearing sleeve 20 is inserted into the through hole 11, the fixing adhesive 70 and the conductive adhesive 71 spread between the outer peripheral surface 20B and the inner peripheral surface 11A, forming a layer of fixing adhesive 70 and a layer of conductive adhesive 71. Therefore, the layer of fixing adhesive 70, which is specialized for adhesion, securely fixes the bearing sleeve 20 to the base plate 10. The layer of conductive adhesive 71 also maintains the grounded state between the bearing sleeve 20 and the base plate 10. Furthermore, because the bearing sleeve 20 is inserted into the through hole 11 from the side where the fixing adhesive 70 is applied, the layer of fixing adhesive 70 is formed over the entire area between the outer peripheral surface 20B and the inner peripheral surface 11A in the insertion direction. As a result, the layer of fixing adhesive 70 more firmly fixes the bearing sleeve 20 to the base plate 10. In other words, the bearing sleeve 20 and the base plate 10 can be fixed in a grounded state.

Furthermore, when assembling the base plate 10 and bearing sleeve 20 using the above method, no new components, new adhesives, or additional components are required compared to the components of a conventional hydrodynamic bearing motor 1. Therefore, a hydrodynamic bearing motor 1 with the above-mentioned effects can be manufactured using the components of a conventional hydrodynamic bearing motor 1 as is.

In addition, the method for assembling the base plate 10 and bearing sleeve 20 in the above embodiment involves applying the fixing adhesive 70 near one axial end of the inner circumferential surface 11A, and applying the conductive adhesive 71 near the other axial end of the inner circumferential surface 11A.

With the above method, the fixing adhesive 70 is applied near one end of the inner circumferential surface 11A. Therefore, when the bearing sleeve 20 is inserted into the through hole 11, the fixing adhesive 70 penetrates between the outer circumferential surface 20B and the inner circumferential surface 11A, and the lower end surface 20C pushes the remaining fixing adhesive 70 from near one end of the inner circumferential surface 11A to near the other end. As a result, the fixing adhesive 70 spreads over the entire area between the outer circumferential surface 20B and the inner circumferential surface 11A. In other words, the bearing sleeve 20 and base plate 10 are fixed together by the fixing adhesive 70 that has spread over the entire inner circumferential surface 11A, thereby firmly fixing the bearing sleeve 20 and base plate 10 together.

In addition, because the bearing sleeve 20 and base plate 10 are firmly fixed together, external forces are less likely to act on the layer of conductive adhesive 71. As a result, cracks are less likely to occur in the layer of conductive adhesive 71, making it possible to maintain a grounded state between the bearing sleeve 20 and base plate 10.

Furthermore, in the method of assembling the base plate 10 and bearing sleeve 20 in the above embodiment, the viscosity of the fixing adhesive 70 is lower than the viscosity of the conductive adhesive 71.

With the above method, the viscosity of the fixing adhesive 70 is lower than that of the conductive adhesive 71, so the fixing adhesive 70 is less likely to mix with the conductive adhesive 71 when they come into contact. This means that the strength of the fixing adhesive 70 is less likely to decrease and the conductivity of the conductive adhesive 71 is less likely to be impaired by the two adhesives mixing.

Furthermore, because the viscosity of the fixing adhesive 70 is lower than that of the conductive adhesive 71, the fixing adhesive 70 penetrates between the outer peripheral surface 20B and the inner peripheral surface 11A, and when the lower end surface 20C pushes out the remaining fixing adhesive 70 in the insertion direction, it easily spreads over the entire area between the outer peripheral surface 20B and the inner peripheral surface 11A. As a result, the area of the fixing adhesive 70 layer is expanded, allowing the bearing sleeve 20 and base plate 10 to be firmly fixed together. Furthermore, because the fixing adhesive 70 easily wraps around the conductive adhesive 71, the fixing adhesive 70 layer easily protects the conductive adhesive 71 layer.

<Modification>
The modifications described below may be applied in combination.

(1) Modification 1
The through-hole 11 does not have to be a through-hole that is open at both ends. For example, the base plate 10 may have a cylindrical hole 111 as shown in FIG.

Hole 111 is a hole for fixing the bearing sleeve 20. Hole 111 is cylindrical, and the inner diameter of the cylinder is approximately the same as or larger than the outer diameter of the bearing sleeve 20. In addition, in Figure 7, hole 111 is open only on the top side and closed on the bottom side.

(2) Modification 2
In this embodiment, the fixing adhesive 70 is applied to the inner circumferential surface 11A in step S10, and then the conductive adhesive 71 is applied to the inner circumferential surface 11A in step S11. However, step S10 may be performed after step S11.

That is, the work robot applies conductive adhesive 71 near the lower end of the inner circumferential surface 11A (S11), and then applies fixing adhesive 70 near the upper end of the inner circumferential surface 11A (S10). Note that the fixing adhesive 70 is applied at a position axially separated from the position where the conductive adhesive 71 is applied. Then, in step S12, the work robot inserts the bearing sleeve 20 into the through hole 11 from the side where the fixing adhesive 70 is applied.

(3) Modification 3
The fixing adhesive 70 does not have to be applied near one end of the inner circumferential surface 11A. Furthermore, the conductive adhesive 71 does not have to be applied near the other end of the inner circumferential surface 11A. In this case, the fixing adhesive 70 is applied in a ring shape in the circumferential direction at a specific location on the inner circumferential surface 11A, and the conductive adhesive 71 is applied at a location on the inner circumferential surface 11A that is a certain distance away in the axial direction from the location where the fixing adhesive 70 is applied. Here, the location where the fixing adhesive 70 is applied is closer in the axial direction to the side where the bearing sleeve 20 is inserted than the location where the conductive adhesive 71 is applied. When the bearing sleeve 20 is inserted into the through hole 11, it first comes into contact with the fixing adhesive 70, and then comes into contact with the conductive adhesive 71.

(4) Modification 4
The order in which the components of the hydrodynamic bearing motor 1 are assembled may be different. For example, the rotor hub 50 may not be assembled to the shaft 30 when the bearing sleeve 20 is inserted into the through hole 11. In this case, the rotor hub 50 is assembled to the shaft 30 after the bearing sleeve 20 is inserted into the through hole 11.

1...hydrodynamic bearing motor, 3...rotating portion, 10...base plate (base portion), 11...through hole (cylindrical portion), 11A...inner peripheral surface, 20...bearing sleeve (bearing), 20B...outer peripheral surface, 30...shaft, 70...fixing adhesive, 71...conductive adhesive, 111...hole (cylindrical portion)

Claims (6)

A bearing,
a rotating portion rotatably supported by the bearing;
a base portion arranged coaxially with a central axis of the rotating portion and having a cylindrical portion into which the bearing is inserted;
a layer of conductive adhesive having electrical conductivity between an outer peripheral surface of the bearing and an inner peripheral surface of the cylindrical portion; and a layer of fixing adhesive for fixing the bearing to the cylindrical portion.
Equipped with
The layer of the fixing adhesive and the layer of the conductive adhesive are adjacent to each other in the circumferential direction of the rotating part.
Hydrodynamic bearing motor. 2. The hydrodynamic bearing motor according to claim 1 , wherein the cylindrical portion is a through hole having openings at both ends. 3. A disk drive device comprising the hydrodynamic bearing motor according to claim 1. A method for assembling a base part and a bearing by inserting a bearing into a cylindrical part provided in the base part,
applying a fixing adhesive and a conductive adhesive to an inner peripheral surface of the cylindrical portion at a predetermined distance in a direction of a cylindrical axis of the cylindrical portion;
a step of applying the fixing adhesive and the conductive adhesive, and then inserting the bearing into the cylindrical portion from the side where the fixing adhesive is applied so that the inner peripheral surface and the outer peripheral surface of the bearing face each other;
Including,
By inserting the bearing into the cylindrical portion, the layer of the fixing adhesive and the layer of the conductive adhesive are formed adjacent to each other in the circumferential direction of a rotating portion rotatably supported by the bearing.
How to assemble the base and bearing. 5. The method for assembling a base portion and a bearing according to claim 4, wherein the fixing adhesive is applied to the inner circumferential surface near one end in the direction of the cylindrical axis, and the conductive adhesive is applied to the inner circumferential surface near the other end in the direction of the cylindrical axis. 6. The method for assembling a base portion and a bearing according to claim 4 , wherein the viscosity of the fixing adhesive is lower than the viscosity of the conductive adhesive.