JP2025008159A - Spindle motor and hard disk drive - Google Patents

Abstract

To provide a spindle motor having a construction that a processing oil used at finishing processing of a sleeve and a case hardly leaks to an upper end surface of the sleeve.SOLUTION: A spindle motor 3 comprises: a bearing sleeve 40 which is extended in a shaft direction and is cylindrically formed; and a case 50 that is extended in the shaft direction and is cylindrically formed, and to which an inner peripheral surface 51a is bonded in a state where it faces an outer peripheral surface 41b of the bearing sleeve 40. In the bearing sleeve 40, a first flat surface 45 extended in a radial direction orthogonal to the shaft direction is formed on an end surface of a first end part 44 as one end part, and a second end part 73 as an end part of a first bonding part 71 formed by the outer peripheral surface 41b and the inner peripheral surface 51a that are bonded is separated from the first flat surface 45 in the shaft direction. The first end part 44 is projected in the shaft direction with respect to the second end part 73.SELECTED DRAWING: Figure 2

Description

The present invention relates to a spindle motor and a hard disk drive.

A type of spindle motor with a rotating shaft is known (see, for example, Patent Document 1). This type of spindle motor supports the shaft on the inner circumferential surface of a cylindrical sleeve part that is press-fitted into a cylindrical case. Lubricating oil is filled between the sleeve part and the shaft, and when the shaft rotates, it functions as a fluid dynamic bearing.

The ends of the sleeve components face the rotor hub and the flange of the shaft, which are rotating components, so they require high surface accuracy. Therefore, the sleeve components are press-fitted into the case and then finished.

JP 2006-200583 A

During finish processing, processing oil is used in the processing area. Processing oil can seep into the gap between the case and the sleeve component, and can seep out over time. If the seeped processing oil passes through the upper end surface of the sleeve and mixes with the lubricating oil filled between the sleeve component and the shaft, it can cause the lubricating oil to deteriorate.

The present invention aims to provide a structure in which the processing oil used during the finishing process of the sleeve and case in a spindle motor is less likely to seep out onto the upper end surface of the sleeve.

To solve the above problems, a spindle motor is provided that includes a sleeve formed into a cylindrical shape extending in the axial direction, and a case formed into a cylindrical shape extending in the axial direction and joined with its inner peripheral surface facing the outer peripheral surface of the sleeve, in which the sleeve has a first plane extending in a radial direction perpendicular to the axial direction at an end face of a first end, one end of the sleeve, a second end, which is an end of a first joint formed by the joined outer peripheral surface and inner peripheral surface, is separated from the first plane in the axial direction, and the first end protrudes in the axial direction relative to the second end.

According to the present invention, the processing oil used during the finishing process of the sleeve and case in the spindle motor is less likely to seep out onto the upper end surface of the sleeve.

FIG. 1 is a perspective view of a hard disk drive device 1. FIG. 2 is a partial cross-sectional view of the spindle motor 3. FIG. 11 is a partial cross-sectional view of a spindle motor 3 in a first modified example. FIG. 11 is a partial cross-sectional view of a spindle motor 3 in a second modified example.

Below, an embodiment of the present invention will be described with reference to the drawings. However, the embodiment described below has various limitations that are technically preferable for implementing the present invention, but the scope of the present invention is not limited to the following embodiment and illustrated examples.

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

As shown in FIG. 2 etc., the direction parallel to the central axis of the shaft 80 described later is the axial direction, the direction around the central axis of the shaft 80 is the circumferential direction, and the direction perpendicular to the axial direction is the radial direction. For the sake of explanation, the axial direction is the up-down direction, and the rotating part 20 side relative to the stationary part 10 is the top, and the stationary part 10 side is the bottom.

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

The housing 2 comprises a case 6 and a cover 7. The case 6 is a box-like shape that is roughly a rectangular parallelepiped with one side open and closed at the bottom. The cover 7 is a plate-like member that covers the open side of the case 6. The cover 7 is fastened to the case 6 using screws 7A. A sealing means (not shown) is provided between the case 6 and the cover 7, so that the cover 7 together with the case 6 forms the housing 2 having a sealed internal space S.

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

The spindle motor 3 rotatably supports multiple recording disks 4. The detailed structure of the spindle motor 3 will be described later.

Multiple recording disks 4 are provided and supported by the spindle motor 3 so that their disk surfaces face each other. A gap is formed between each recording disk 4.

The bearing device 5 swingably supports multiple swing arms 8 that are positioned in the gaps between each of the recording disks 4.

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

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

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

(Stationary part)
The stationary portion 10 includes a base plate 30 , a bearing sleeve 40 , a case 50 , and a stator core 60 .

The base plate 30 is a metal member. The base plate 30 is formed with a through hole 31, a circumferential groove portion 32, and a circumferential wall portion 33.

The through hole 31 is a hole for fixing the case 50. The through hole 31 is provided so as to penetrate the base plate 30 in the axial direction. The through hole 31 is cylindrical, and the inner diameter of the cylinder is approximately the same as or larger than the outer diameter of the case 50.

The circumferential groove portion 32 is formed radially outward of the through hole 31. The circumferential groove portion 32 is an annular groove that is arranged coaxially with the central axis of the through hole 31 when viewed in the axial direction.

The circumferential wall portion 33 is formed as an annular wall portion that protrudes axially upward from the bottom surface of the circumferential groove portion 32 when viewed in the axial direction. The diameter of the circumferential wall portion 33 is larger than the diameter of the through hole 31.

The bearing sleeve 40 rotatably supports the shaft 80. The bearing sleeve 40 is a cylindrical brass member that extends in the axial direction. The bearing sleeve 40 has a main body portion 41, a flange portion 42, and a through hole 43.

The main body 41 is a cylindrical member extending in the axial direction. The main body 41 has an inner circumferential surface 41a, an outer circumferential surface 41b, and a first end 44. The inner circumferential surface 41a faces the shaft 80, and the outer circumferential surface 41b faces the case 50. The first end 44 is the upper axial end of the main body 41.

The flange portion 42 is a member that extends radially from the main body portion 41. The flange portion 42 extends radially outward from the first end portion 44 and is provided around the entire circumferential circumference of the first end portion 44. A first plane 45 is formed on the axial upper surface of the flange portion 42. The outer diameter of the flange portion 42 is equal to the outer diameter of the case 50. The outer diameter of the flange portion 42 may be smaller than the outer diameter of the case 50.

The through hole 43 is a hole formed on the radially inner side of the main body 41. When viewed in the axial direction, the through hole 43 is formed so as to penetrate the main body 41 in the axial direction.

The case 50 holds the bearing sleeve 40 and is fixed to the base plate 30. The case 50 is a cylindrical iron member such as stainless steel that extends in the axial direction. The bearing sleeve 40 is press-fitted into the inside of the case 50. The case 50 has a case main body 51, a through hole 52, and a lower end recess 53.

The case body 51 is a cylindrical member extending in the axial direction. The case body 51 has an inner peripheral surface 51a and an outer peripheral surface 51b. The inner peripheral surface 51a faces the outer peripheral surface 41b of the body 41, and the outer peripheral surface 51b faces the inner peripheral surface of the through hole 31 of the base plate 30. A second plane 54 is formed at the upper axial end of the case body 51.

The through hole 52 is a hole formed on the radially inner side of the case body 51. When viewed in the axial direction, the through hole 52 is formed so as to penetrate the case body 51 in the axial direction. The bearing sleeve 40 is inserted into the through hole 52. The through hole 52 is continuous with the lower end recess 53.

The lower end recess 53 is a recess provided at the lower end of the case body 51. The lower end recess 53 is a cylindrical space that is provided so as to be coaxial with the central axis of the through hole 52 when viewed in the axial direction. The lower end recess 53 opens downward. The diameter of the lower end recess 53 is larger than the diameter of the through hole 52. A counter plate 55 is attached to the lower end recess 53.

The counter plate 55 is a disk-shaped lid that is inserted into the lower end recess 53 from below the case body 51. The counter plate 55 closes the lower end recess 53.

Here, the relationship between the base plate 30, the bearing sleeve 40, and the case 50 will be described. The bearing sleeve 40 is pressed into the case body 51 from the axially upper side so that the outer peripheral surface 41b of the body 41 faces the inner peripheral surface 51a of the case body 51. At this time, the bearing sleeve 40 is pressed into the case body 51 until the lower surface of the flange 42 contacts the second flat surface 54 of the case body 51. In this way, the bearing sleeve 40 and the case 50 are joined. Then, the outer peripheral surface 41b and the inner peripheral surface 51a are joined to form the first joint 71. In addition, the lower surface of the flange 42 and the second flat surface 54 are joined to form the second joint 72. Since the lower surface of the flange 42 contacts the outer peripheral surface 41b, the end of the second joint 72 on the outer peripheral surface 41b side is continuous with the first joint 71.

The second end 73, which is the axially upper end of the first joint 71, is in contact with the lower surface of the flange portion 42. Therefore, the second end 73 is separated in the axial direction from the first plane 45, which is the upper surface of the flange portion 42, by the thickness of the flange portion 42.

Flange portion 42 is provided so as to extend radially outward from first end portion 44. Second end portion 73 is in contact with the lower surface of flange portion 42. Therefore, first end portion 44 protrudes axially from second end portion 73 by the thickness of flange portion 42.

In addition, one end of the second joint 72 (the end on the outer circumferential surface 41b side) is continuous with the first joint 71 at a second end 73, which is the axially upper end of the first joint 71. In addition, the other end of the second joint 72, a third end 74, is the radially outer end of the second joint 72 that expands in the radial direction. Therefore, the third end 74 is located radially outward from the second end 73.

When the bearing sleeve 40 is joined to the case 50, the lower end of the main body 41 is spaced axially above the upper surface of the counter plate 55. Between the lower end of the main body 41 and the upper surface of the counter plate 55, a shaft flange 82 of the shaft 80 (described later) is disposed.

In the case of a bearing sleeve and case of a conventional structure, after the bearing sleeve is pressed into the case, the upper and lower end faces of the bearing sleeve and case are finished (e.g., ground). Therefore, the processing oil used during the finishing process may enter the gap at the joint between the bearing sleeve and the case. However, in this embodiment, the bearing sleeve 40 is pressed into the case 50 after the first plane 45, which is the upper surface of the flange portion 42, is finished. Therefore, after the bearing sleeve 40 is pressed into the case 50, there is no need to finish the first plane 45 again. In other words, the finishing process is performed only on the lower end faces of the bearing sleeve 40 and the case 50.

The case 50 to which the bearing sleeve 40 is joined is inserted into the through hole 31 so that the outer peripheral surface 51b of the case body 51 faces the inner peripheral surface of the through hole 31 of the base plate 30. The case 50 is inserted into the through hole 31 with adhesive applied to one or both of the outer peripheral surface 51b and the inner peripheral surface of the through hole 31, and is fixed to the through hole 31 by the adhesive hardening.

The stator core 60 is a member in which multiple annular electromagnetic steel plates are stacked in the axial direction when viewed in the axial direction. The stator core 60 is placed inside the circumferential groove portion 32 and fixed by a method such as gluing. The stator core 60 extends radially outward and has multiple pole teeth (salient poles) arranged along the circumferential direction. Coils 61 are wound around the pole teeth. The stator core 60 generates magnetic flux when a current flows through the coils 61.

(Rotating part)
The rotating part 20 has a shaft 80 , a rotor hub 90 , and a rotor magnet 100 .

The shaft 80 is a member that serves as the rotating shaft of the spindle motor 3. The shaft 80 is rotatably supported inside the bearing sleeve 40. The shaft 80 has a columnar shaft portion 81 and a shaft flange portion 82. The shaft portion 81 and the shaft flange portion 82 of the shaft 80 are integrated.

The shaft portion 81 is a cylindrical shaft member. The shaft portion 81 has a shaft flange portion 82 integrally formed with a lower shaft end portion 83. The shaft portion 81 is disposed inside the bearing sleeve 40 so that the shaft end portion 83 on which the shaft flange portion 82 is provided is on the lower side. In other words, the outer peripheral surface of the shaft portion 81 is surrounded by the inner peripheral surface 41a of the main body portion 41. The outer peripheral surface of the shaft portion 81 and the inner peripheral surface 41a face each other with a small gap between them. A radial dynamic pressure generating groove 84 is formed on the outer peripheral surface of the shaft portion 81.

The radial dynamic pressure generating grooves 84 are provided on the outer peripheral surface of the shaft portion 81. In this embodiment, the radial dynamic pressure generating grooves 84 are formed in a continuous row in the circumferential direction on the outer peripheral surface of the shaft portion 81, and are formed in two rows spaced apart in the axial direction.

The shaft flange portion 82 is an annular flange member that expands radially when viewed in the axial direction. The shaft flange portion 82 is joined to the shaft end portion 83 and is integral with the shaft portion 81. The outer diameter of the shaft flange portion 82 is smaller than the inner diameter of the case main body portion 51. A thrust dynamic pressure generating groove 85 is formed on each of the upper and lower surfaces of the shaft flange portion 82.

The thrust dynamic pressure generating groove 85 is provided on the upper and lower surfaces of the shaft flange portion 82. The thrust dynamic pressure generating groove 85 is provided in an annular shape so as to be coaxial with the central axis of the shaft flange portion 82 when viewed in the axial direction.

When the shaft 80 is supported by the bearing sleeve 40, the shaft flange portion 82 is disposed between the lower end of the main body portion 41 and the upper surface of the counter plate 55. The upper surface of the shaft flange portion 82 faces the annular surface 46, which is the axially lower end surface of the main body portion 41, across a small gap. The lower surface of the shaft flange portion 82 faces the upper surface of the counter plate 55 across a small gap. The side surface of the shaft flange portion 82 faces the inner peripheral surface 51a of the case main body portion 51 across a small gap. By disposing the shaft flange portion 82 between the annular surface 46 and the counter plate 55, axial movement of the shaft 80 is prevented.

Lubricating oil is filled between the shaft 80 and the bearing sleeve 40 and between the case 50. Specifically, the lubricating oil is filled between the outer peripheral surface of the shaft portion 81 and the inner peripheral surface 41a of the main body portion 41, between the upper surface of the shaft flange portion 82 and the annular surface 46, between the lower surface of the shaft flange portion 82 and the upper surface of the counter plate 55, and between the side surface of the shaft flange portion 82 and the inner peripheral surface 51a of the case main body portion 51.

The rotor hub 90 is a member that rotates together with the shaft 80. The rotor hub 90 is attached to the upper end of the shaft 80 and is connected to the shaft 80. The rotor hub 90 has a disk portion 91, a cylindrical portion 92, and an outer edge portion 93.

The disk portion 91 is a disk-shaped member that is coaxial with the central axis of the shaft 80 when viewed in the axial direction. The disk portion 91 has a rotor hub through hole 94. The rotor hub through hole 94 is provided at the center of the disk portion 91 when viewed in the axial direction. The disk portion 91 is fixed to the shaft 80. Specifically, the upper end of the shaft 80 is inserted into the rotor hub through hole 94, and the disk portion 91 is fixed to the shaft 80 by a method such as press-fitting or adhesive.

The cylindrical portion 92 is a cylindrical member having a thickness in the radial direction. The cylindrical portion 92 is arranged so as to be coaxial with the central axis of the rotor hub through hole 94 when viewed in the axial direction, and protrudes axially downward. The cylindrical portion 92 is arranged on the outer edge of the disc portion 91. The inner diameter of the cylindrical portion 92 is larger than the outer diameter of the bearing sleeve 40. The inner peripheral surface of the cylindrical portion 92 faces the outer peripheral surface of the bearing sleeve 40 with a gap therebetween.

The outer edge portion 93 is an annular member. The outer edge portion 93 is provided at the lower end of the cylindrical portion 92. The outer edge portion 93 protrudes radially outward from the cylindrical portion 92 and is formed in a flange shape. A plurality of recording disks 4 are installed above the outer edge portion 93 and radially outward from the cylindrical portion 92 (see FIG. 1).

The rotor magnet 100 is an annular member having a magnetic pole structure magnetized with polarity inverted N, S, N, S... along the circumferential direction when viewed in the axial direction. In this embodiment, the rotor magnet 100 is attached to the inner peripheral surface of an annular yoke 101 attached to the lower end of the outer edge portion 93. The rotor magnet 100 is located in approximately the same position as the stator core 60 in the axial direction, and is located between the stator core 60 and the inner peripheral surface of the circumferential groove portion 32 in the radial direction.

The yoke 101 suppresses leakage of magnetic flux from the rotor magnet 100. The cylindrical portion 92 or the outer edge portion 93 may be disposed between the stator core 60 and the inner peripheral surface of the circumferential groove portion 32, and the annular yoke 101 may be attached to the inner peripheral surface of the cylindrical portion 92 or the inner peripheral surface of the outer edge portion 93. In this case, the rotor magnet 100 is attached to the inner peripheral surface of the yoke 101 so as to face the stator core 60.

<Spindle motor operation>
When the coil 61 is energized, a magnetic attraction force and a magnetic repulsion force are generated between the magnetic poles of the rotor magnet 100 and the pole teeth of the stator core 60. As a result, the rotating part 20 rotates relative to the stationary part 10 with the shaft 80 as the rotation axis.

The shaft 80 rotates relative to the bearing sleeve 40. At this time, the lubricating oil is pressurized by the radial dynamic pressure generating grooves 84, generating dynamic pressure in the lubricating oil. The generated dynamic pressure supports the shaft 80 in a radially non-contact state relative to the bearing sleeve 40.

When the shaft 80 rotates, the shaft flange portion 82 also rotates. At this time, the lubricating oil is pressurized by the thrust dynamic pressure generating groove 85, generating dynamic pressure in the lubricating oil. The generated dynamic pressure supports the shaft 80 in a non-contact state in the axial direction relative to the bearing sleeve 40 and the thrust plate 55.

＜Effects＞
The spindle motor 3 of this embodiment comprises a bearing sleeve 40 formed in a cylindrical shape extending in the axial direction, and a case 50 formed in a cylindrical shape extending in the axial direction and joined with an inner circumferential surface 51a facing an outer circumferential surface 41b of the bearing sleeve 40, and the bearing sleeve 40 has a first plane 45 extending radially perpendicular to the axial direction on the end face of a first end 44, which is one end of the bearing sleeve 40, and a second end 73, which is an end of a first joint 71 formed by the joined outer circumferential surface 41b and inner circumferential surface 51a, is separated from the first plane 45 in the axial direction, and the first end 44 protrudes in the axial direction relative to the second end 73.

According to the above spindle motor 3, the first plane 45, which is the upper end surface of the bearing sleeve 40, and the second end 73, which is the upper end of the first joint 71, are separated in the axial direction, so even if the processing oil used in the finishing process that has soaked into the gap of the first joint 71 comes out of the gap and reaches the second end 73, it is unlikely to reach the first plane 45. Therefore, the processing oil is unlikely to mix with the lubricating oil of the fluid dynamic bearing filled between the bearing sleeve 40 and the shaft 80 via the first plane 45. As a result, deterioration of the lubricating oil is unlikely to occur, and the life of the spindle motor 3 can be extended.

In addition, in the spindle motor 3 according to this embodiment, the bearing sleeve 40 has a cylindrical main body 41 and a flange 42 that extends radially from the axial end of the main body 41 and has a first plane 45, and the case 50 has a second plane 54 joined to the flange 42 on the side of the first axial end 44, and the second joint 72 formed by the joined flange 42 and second plane 54 is continuous with the first joint 71.

According to the above spindle motor 3, since the bearing sleeve 40 has a flange portion 42, the first plane 45, which is the upper surface of the flange portion 42, is finished before the bearing sleeve 40 is pressed into the case 50. Furthermore, when the bearing sleeve 40 is pressed into the case 50, the upper end surface is composed only of the first plane 45. Therefore, after the bearing sleeve 40 is pressed into the case 50, there is no need to machine the first plane 45 again. In other words, since processing oil does not seep into the gap of the first joint portion 71, processing oil does not seep out from the gap of the first joint portion 71.

The hard disk drive device 1 according to this embodiment also includes a spindle motor 3.

With the above hard disk drive device 1, the lubricating oil in the fluid dynamic bearing used in the spindle motor 3 is less likely to deteriorate, and the life of the spindle motor 3 is long. Therefore, the life of the hard disk drive device 1 is extended.

<Modification>
The spindle motor 3 may be a combination of the modifications described below.

(1) Modification 1
3, the bearing sleeve 40 may be a bearing sleeve 140 that does not have the flange portion 42. The bearing sleeve 140 has a main body portion 141 and a through hole 143.

The main body 141 is a cylindrical member extending in the axial direction. The main body 141 has an inner circumferential surface 141a, an outer circumferential surface 141b, and a first end 144. The inner circumferential surface 141a faces the shaft 80, and the outer circumferential surface 141b faces the case 50. The first end 144 is the axially upper end of the main body 141.

A first plane 145 is formed on the end face of the first end 144. A first recess 147 is provided radially outward from the first plane 145.

The first recess 147 extends radially outward from the first plane 145 along the circumferential direction. The first recess 147 is provided around the entire circumference radially outward from the first plane 145. The first recess 147 has a depth in the axial direction. The first recess 147 has a constant radial width in the axial direction.

The through hole 143 is a hole formed on the radially inner side of the main body portion 141. When viewed in the axial direction, the through hole 143 is formed so as to penetrate the main body portion 141 in the axial direction.

The relationship between the base plate 30, the bearing sleeve 140, and the case 50 will now be described. The bearing sleeve 140 is pressed into the case body 51 from the axially upper side so that the outer peripheral surface 141b of the body 141 faces the inner peripheral surface 51a of the case body 51. At this time, the bearing sleeve 140 is pressed into the case body 51 until the first plane 145 and the second plane 54 of the case body 51 are flush with each other in the axial direction. The outer peripheral surface 141b and the inner peripheral surface 51a are then joined to form the first joint 171.

The second end 173, which is the axially upper end of the first joint 171, is at the same position in the axial direction as the lower end of the first recess 147. Therefore, the second end 173 is separated from the first plane 145 in the axial direction by the depth of the first recess 147.

The first end 144 also protrudes from the lower end of the first recess 147. Therefore, the first end 144 protrudes in the axial direction relative to the second end 173 by the depth of the first recess 147.

(2) Modification 2
4, the case 50 may be a case 150 having a second recess 156. In this case, the bearing sleeve may be the bearing sleeve 140 described in the first modification example, or may be a bearing sleeve 240 that does not have a first recess 147. Here, a combination of the case 150 and the bearing sleeve 240 will be described.

The bearing sleeve 240 has a main body 241 and a through hole 243.

The main body 241 is a cylindrical member extending in the axial direction. The main body 241 has an inner circumferential surface 241a, an outer circumferential surface 241b, and a first end 244. The inner circumferential surface 241a faces the shaft 80, and the outer circumferential surface 241b faces the case 50. The first end 244 is the axially upper end of the main body 241. A first plane 245 is formed on the end face of the first end 244.

The through hole 243 is a hole formed on the radially inner side of the main body portion 241. When viewed in the axial direction, the through hole 243 is formed so as to penetrate the main body portion 241 in the axial direction.

The case 150 has a case body 151, a through hole 152, a lower end recess 153, and a second recess 156.

The case body 151 is a cylindrical member extending in the axial direction. The case body 151 has an inner peripheral surface 151a and an outer peripheral surface 151b. The inner peripheral surface 151a faces the outer peripheral surface 241b of the body 241, and the outer peripheral surface 151b faces the inner peripheral surface of the through hole 31 of the base plate 30. A second plane 154 is formed at the axial upper end of the case body 151. A second recess 156 is provided radially inward of the second plane 154.

The second recess 156 extends circumferentially radially inward of the second plane 154. The second recess 156 is provided around the entire circumference radially inward of the second plane 154. The second recess 156 has a depth in the axial direction. The second recess 156 has a constant radial width in the axial direction.

The through hole 152 is a hole formed on the radially inner side of the case body 151. When viewed in the axial direction, the through hole 152 is formed so as to penetrate the case body 151 in the axial direction. The bearing sleeve 240 is inserted into the through hole 152. The through hole 152 is continuous with the lower end recess 153.

The lower end recess 153 is a recess provided at the lower end of the case body 151. The lower end recess 153 is a cylindrical space that is provided so as to be coaxial with the central axis of the through hole 152 when viewed in the axial direction. The lower end recess 153 opens downward. The diameter of the lower end recess 153 is larger than the diameter of the through hole 152. A counter plate 55 is attached to the lower end recess 153.

The relationship between the base plate 30, the bearing sleeve 240, and the case 150 will now be described. The bearing sleeve 240 is pressed into the case body 151 from the axially upper side so that the outer peripheral surface 241b of the body 241 faces the inner peripheral surface 151a of the case body 151. At this time, the bearing sleeve 240 is pressed into the case body 151 until the first plane 245 and the second plane 154 of the case body 151 are flush with each other in the axial direction. The outer peripheral surface 241b and the inner peripheral surface 151a are then joined to form the first joint 271.

The second end 273, which is the axially upper end of the first joint 271, is located at the same position as the lower end of the second recess 156 in the axial direction. Therefore, the second end 273 is separated from the first plane 245 in the axial direction by the depth of the second recess 156.

The first end 244 also protrudes from the lower end of the second recess 156. Therefore, the first end 244 protrudes in the axial direction relative to the second end 273 by the depth of the second recess 156.

＜Effects＞
In the spindle motor 3 according to the first modification, the case 50 has a second plane 54 that is flush with the first plane 145 in the axial direction.

The bearing sleeve 140 of the spindle motor 3 according to the first modification has a first recess 147 that extends radially outward from the first plane 145 along a circumferential direction perpendicular to the radial direction and has a depth of the same width in the axial direction.

According to the above spindle motor 3, since the bearing sleeve 140 has the first recess 147, even if the processing oil that has soaked into the gap of the first joint portion 171 seeps out from the second end portion 173, it is structured to accumulate in the first recess 147. Therefore, the processing oil is unlikely to reach the first plane 145, and the processing oil is unlikely to mix with the lubricating oil of the fluid dynamic bearing.

The case 150 of the spindle motor 3 according to the second modification has a second recess 156 that extends radially inward of the second plane 154 along a circumferential direction perpendicular to the radial direction and has a depth of the same width in the axial direction.

According to the above spindle motor 3, the case 150 has the second recess 156, so even if the processing oil that has soaked into the gap of the first joint portion 271 seeps out from the second end portion 273, it is structured to accumulate in the second recess 156. Therefore, the processing oil is less likely to reach the first plane 245, and is less likely to mix with the lubricating oil of the fluid dynamic bearing.

1...Hard disk drive, 3...Spindle motor, 40, 140, 240...Bearing sleeve, 41, 141, 241...Main body, 41b, 141b, 241b...Outer periphery, 42...Flange, 44, 144, 244...First end, 45, 145, 245...First flat surface, 50, 150...Case, 51a, 151a...Inner periphery, 54, 154...Second flat surface, 71, 171, 271...First joint, 72...Second joint, 73, 173, 273...Second end, 147...First recess, 156...Second recess

Claims (6)

A sleeve formed in a cylindrical shape extending in an axial direction;
a case formed in a cylindrical shape extending in the axial direction and joined with an inner circumferential surface facing an outer circumferential surface of the sleeve;
Equipped with
The sleeve has a first flat surface formed on an end surface of a first end portion, the first flat surface extending in a radial direction perpendicular to the axial direction,
A spindle motor in which a second end, which is an end of a first joint formed by the joined outer peripheral surface and inner peripheral surface, is axially separated from the first plane, and the first end protrudes in the axial direction relative to the second end. The sleeve has a cylindrical main body portion and a flange portion extending in the radial direction from an axial end portion of the main body portion and having the first flat surface,
the case has a second flat surface joined to the flange portion on the side of the first end in the axial direction,
2. The spindle motor according to claim 1, wherein a second joint portion formed by the joined flange portion and the second flat surface is continuous with the first joint portion. The spindle motor of claim 1, wherein the case has a second plane that is flush with the first plane in the axial direction. The spindle motor according to claim 3, wherein the sleeve has a first recess that extends radially outward from the first plane along a circumferential direction perpendicular to the radial direction and has a depth of the same width in the axial direction. The spindle motor according to claim 3, wherein the case has a second recess extending radially inward from the second plane along a circumferential direction perpendicular to the radial direction and having a depth of the same width in the axial direction. A hard disk drive device equipped with a spindle motor according to any one of claims 1 to 5.

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