Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 1 of 133 PageID #: 60
`
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`Exhibit
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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 2 of 133 PageID #: 61
`I 1111111111111111 11111 1111111111 11111 1111111111 lllll 111111111111111 11111111
`US008737017Bl
`
`c12) United States Patent
`Abe
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,737,017 Bl
`May 27, 2014
`
`(54) SPINDLE MOTOR AND DISK DRIVE
`APPARATUS
`
`(71) Applicant: Nidec Corporation, Kyoto (JP)
`
`(72)
`
`Inventor: Hiroyuki Abe, Kyoto (JP)
`
`8,164,850 B2 *
`8,215,842 B2 *
`8,508,882 Bl *
`8,514,515 B2 *
`2007/0127156 Al
`2008/0068744 Al
`2012/0050911 Al
`
`............. 360/98.07
`4/2012 Gomyo et al.
`7/2012 Maruyama et al ............ 384/100
`8/2013 Tamaoka et al ............ 360/99.08
`8/2013 Iwasaki et al .............. 360/99.08
`6/2007 Byun et al.
`3/2008 Nakazawa et al.
`3/2012 Tamaoka et al.
`
`(73) Assignee: Nidec Corporation, Kyoto (JP)
`
`FOREIGN PATENT DOCUMENTS
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`JP
`JP
`JP
`JP
`
`2004-135467 A
`2004-166497 A
`2008-097803 A
`2012-055075 A
`
`4/2004
`6/2004
`4/2008
`3/2012
`
`(21) Appl. No.: 13/804,726
`
`(22)
`
`Filed:
`
`Mar. 14, 2013
`
`Related U.S. Application Data
`
`(60)
`
`Provisional application No. 61/727,886, filed on Nov.
`19, 2012.
`
`(30)
`
`Foreign Application Priority Data
`
`Nov. 19, 2012
`
`(JP) ................................. 2012-252876
`
`(51)
`
`(2006.01)
`
`Int. Cl.
`GllB 19120
`(52) U.S. Cl.
`USPC ....................................................... 360/99.08
`( 58) Field of Classification Search
`CPC ......................................................... Gl lB 5/39
`USPC ....................................................... 360/99.08
`See application file for complete search history.
`
`OTHER PUBLICATIONS
`
`Tamaoka et al., "Spindle Motor Having Magnetic Circuit for Stator
`and Rotor Magnet, and Storage Disk Drive Having the Same,", U.S.
`Appl. No. 13/033,778, filed Feb. 24, 2011.
`Tamaoka et al., "Spindle Motor Having Magnetic Circuit for Stator
`and Rotor Magnet, and Storage Disk Drive Having the Same,", U.S.
`Appl. No. 13/568,207, filed Aug. 7, 2012.
`Abe, "Spindle Motor and Disk Drive Apparatus,", U.S. Appl. No.
`13/798,278, filed Mar. 13, 2013.
`
`* cited by examiner
`
`Primary Examiner - Mark Blouin
`(74) Attorney, Agent, or Firm - Keating & Bennett, LLP
`
`(57)
`
`ABSTRACT
`A spindle motor of a disk drive apparatus includes a base unit,
`a stator core, a covered cylindrical rotor hub, a rotor magnet,
`and a bearing mechanism. The height of the stator core in an
`axial direction is about 50% or more and about 70% or less of
`the height of the stator. A torque constant Kt of torque gen(cid:173)
`erated between a stator and a rotor magnet is about 4 mN·m/ A
`or more and about 6 mN·m/A or less. A motor constant Km is
`about 2 mN·m/(A-v'Q) or more and about 4 mN·m/(A-v'Q) or
`less.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`7,190,549 B2
`7,876,005 B2 *
`
`3/2007 Byun et al.
`1/2011 Ichizaki
`
`310/67 R
`
`16 Claims, 28 Drawing Sheets
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 3 of 133 PageID #: 62
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`May 27, 2014
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`Sheet 1 of 28
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`US 8,737,017 Bl
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`Fig. 1
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`

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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 4 of 133 PageID #: 63
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`U.S. Patent
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`May 27, 2014
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`Sheet 2 of 28
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`US 8,737,017 Bl
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`Fig. 2
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`

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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 5 of 133 PageID #: 64
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`U.S. Patent
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`Sheet 3 of 28
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`US 8,737,017 Bl
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`223
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`62
`
`Fig. a
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`

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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 6 of 133 PageID #: 65
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`U.S. Patent
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`May 27, 2014
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`Sheet 4 of 28
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`US 8,737,017 Bl
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`1
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`H2
`
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`
`Fig. 4
`
`

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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 7 of 133 PageID #: 66
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`U.S. Patent
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`May 27, 2014
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`Sheet 5 of 28
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`US 8,737,017 Bl
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`G1
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`T1
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`Fig. 5
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`

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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 8 of 133 PageID #: 67
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`U.S. Patent
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`May 27, 2014
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`Sheet 6 of 28
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`US 8,737,017 Bl
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`
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 9 of 133 PageID #: 68
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`U.S. Patent
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`May 27, 2014
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`Sheet 7 of 28
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`
`

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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 10 of 133 PageID #: 69
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`U.S. Patent
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`May 27, 2014
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`Sheet 8 of 28
`
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`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 11 of 133 PageID #: 70
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`U.S. Patent
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`May 27, 2014
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`Sheet 9 of 28
`
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 12 of 133 PageID #: 71
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`U.S. Patent
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`May 27, 2014
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`Sheet 10 of 28
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`
`Fig. 10
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 13 of 133 PageID #: 72
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`U.S. Patent
`
`May 27, 2014
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`Sheet 11 of 28
`
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`
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 14 of 133 PageID #: 73
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`U.S. Patent
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`May 27, 2014
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`Sheet 12 of 28
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 15 of 133 PageID #: 74
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`U.S. Patent
`
`May 27, 2014
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`Sheet 13 of 28
`
`US 8,737,017 Bl
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`
`Fig. 18
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 16 of 133 PageID #: 75
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`U.S. Patent
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`May 27, 2014
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`Sheet 14 of 28
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`US 8,737,017 Bl
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 17 of 133 PageID #: 76
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`U.S. Patent
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`May 27, 2014
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`Sheet 15 of 28
`
`US 8,737,017 Bl
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 18 of 133 PageID #: 77
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`U.S. Patent
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`May 27, 2014
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`Sheet 16 of 28
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`Fig. 16
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 19 of 133 PageID #: 78
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`U.S. Patent
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`May 27, 2014
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`Sheet 17 of 28
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`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 20 of 133 PageID #: 79
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`U.S. Patent
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`May 27, 2014
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`Sheet 18 of 28
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 21 of 133 PageID #: 80
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`U.S. Patent
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`May 27, 2014
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`Sheet 19 of 28
`
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`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 22 of 133 PageID #: 81
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`U.S. Patent
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`May 27, 2014
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`Sheet 20 of 28
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`US 8,737,017 Bl
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`11
`
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 23 of 133 PageID #: 82
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`U.S. Patent
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`May 27, 2014
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`Sheet 21 of 28
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`US 8,737,017 Bl
`
`Fig. 21
`
`

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`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 24 of 133 PageID #: 83
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`U.S. Patent
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`May 27, 2014
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`Sheet 22 of 28
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`US 8,737,017 Bl
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`1
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`Fig. 22
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 25 of 133 PageID #: 84
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`U.S. Patent
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`May 27, 2014
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`Sheet 23 of 28
`
`US 8,737,017 Bl
`
`-E
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`
`ROTOR MAGNET THICKNESS T1 (mm)
`
`Fig. 2:3
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 26 of 133 PageID #: 85
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`U.S. Patent
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`May 27, 2014
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`Sheet 24 of 28
`
`US 8,737,017 Bl
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`
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 27 of 133 PageID #: 86
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`U.S. Patent
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`May 27, 2014
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`Sheet 25 of 28
`
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 28 of 133 PageID #: 87
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`U.S. Patent
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`May 27, 2014
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`Sheet 26 of 28
`
`US 8,737,017 Bl
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`
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 29 of 133 PageID #: 88
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`U.S. Patent
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`May 27, 2014
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`Sheet 27 of 28
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`US 8,737,017 Bl
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`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 30 of 133 PageID #: 89
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`U.S. Patent
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`May 27, 2014
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`Sheet 28 of 28
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`US 8,737,017 Bl
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`
`Fig. 28
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 31 of 133 PageID #: 90
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`US 8,737,017 Bl
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`1
`SPINDLE MOTOR AND DISK DRIVE
`APPARATUS
`
`BACKGROUND OF THE INVENTION
`
`5
`
`2
`is made of an Nd-Fe-B bond magnet. The height of the
`stator core in an axial direction is about 50% or more and
`about 70% or less than the height of the stator, for example. A
`torque constant Kt of torque generated between the stator and
`the rotor magnet is about 3 mN·m/A or more and about 4.5
`mN·m/A or less, for example. A motor constant Km is about
`1 mN·m/(A-v'Q) or more and about 2 mN·m/(A-v'Q) or less,
`for example.
`According to various preferred embodiments of the inven-
`10 tion, it is possible to generate sufficient torque and to shorten
`a startup time using a thin motor.
`The above and other elements, features, steps, characteris(cid:173)
`tics and advantages of the present invention will become more
`apparent from the following detailed description of the pre-
`15 ferred embodiments with reference to the attached drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`1. Field of the Invention
`The present invention relates to a spindle motor and more
`specifically to a spindle motor for a disk drive apparatus.
`2. Description of the Related Art
`In the related art, a spindle motor (hereinafter, simply
`referred to as a "motor") is mounted in a disk drive apparatus
`such as a hard disk drive. In an outer rotor-type motor dis(cid:173)
`closed in JP-A-2004-135467, a rotor set includes a rotating
`hub body of a cup shape and a drive magnet. A stator set
`includes a stator core and a drive coil wound on the stator
`core. The drive magnet of the motor disclosed in JPA-2004-
`135467 is fixed to an inner circumferential surface of an
`annular standing wall part of the rotating hub body, and faces
`an outer circumferential surface of the stator core. When the
`motor is driven, a magnetic action is generated between the
`drive magnet and the drive coil. Further, JP-A-2008-97803
`discloses a motor in which a permanent magnet is disposed to
`face an outer circumferential side of an electromagnet.
`However, in recent years, as thinner disk drive apparatuses
`are demanded, it is necessary to further reduce the thickness 25
`of the motor mounted in the disk drive apparatus.
`
`FIG. 1 is a diagram illustrating a disk drive apparatus
`20 according to a first preferred embodiment of the present
`invention.
`FIG. 2 is a cross-sectional view illustrating a spindle motor
`according to a preferred embodiment of the present invention.
`FIG. 3 is a plan view illustrating a stator according to a
`preferred embodiment of the present invention.
`FIG. 4 is an enlarged view of a portion of a spindle motor
`according to a preferred embodiment of the present invention.
`FIG. 5 is an enlarged view of a portion of a spindle motor
`according to a preferred embodiment of the present invention.
`FIG. 6 is a diagram illustrating the relationship between the
`thickness of a rotor magnet and an air gap and a torque
`constant according to a preferred embodiment of the present
`invention.
`FIG. 7 is a diagram illustrating the relationship between the
`thickness of a rotor magnet and an air gap and a motor con(cid:173)
`stant according to a preferred embodiment of the present
`invention.
`FIG. 8 is a diagram illustrating the relationship between the
`height of a stator core and the diameter of a conducting wire
`and a core height ratio according to a preferred embodiment
`of the present invention.
`FIG. 9 is a diagram illustrating the relationship between the
`height of a stator core and the diameter of a conducting wire
`and a motor constant according to a preferred embodiment of
`45 the present invention.
`FIG. 10 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a torque constant according to a preferred embodi(cid:173)
`ment of the present invention.
`FIG. 11 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and the number oflayers of the conducting wire accord(cid:173)
`ing to a preferred embodiment of the present invention.
`FIG. 12 is a diagram illustrating the relationship between
`55 the height of a stator core and the diameter of a conducting
`wire and a core height ratio according to a preferred embodi(cid:173)
`ment of the present invention.
`FIG. 13 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`60 wire and a motor constant according to a preferred embodi(cid:173)
`ment of the present invention.
`FIG. 14 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a torque constant according to a preferred embodi-
`65 ment of the present invention.
`FIG. 15 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`
`SUMMARY OF THE INVENTION
`
`According to an exemplary preferred embodiment of the 30
`present invention, a spindle motor of a disk drive apparatus
`includes a base unit, a stator, a rotor hub, a rotor magnet, and
`a bearing mechanism. The stator includes a stator core and a
`plurality of coils. The plurality of coils is mounted to the
`stator core. The stator is disposed above the base unit. The 35
`rotor hub includes a cover portion and a side wall portion, and
`has a covered cylindrical shape. The cover portion is posi(cid:173)
`tioned above the stator. The side wall portion extends down(cid:173)
`ward from an outer edge of the cover portion. The rotor
`magnet is positioned outside the stator in a radial direction 40
`thereof and is fixed to an inner circumferential surface of the
`side wall portion of the rotor hub. The bearing mechanism
`supports the rotor hub and the rotor magnet to be rotatable
`with respect to the base unit and the stator. The rotor magnet
`is made of an Nd-Fe-B bond magnet. The height of the
`stator core in an axial direction is about 50% or more and
`about 70% or less than the height of the stator, for example. A
`torque constant Kt of torque generated between the stator and
`the rotor magnet is about 4 mN·m/A or more and about 6
`mN·m/A or less, for example. A motor constant Km is about 50
`2 mN·m/(A-v'Q) or more and about 4 mN·m/(A-v'Q) or less,
`for example.
`According to another exemplary preferred embodiment of
`the present invention, a spindle motor of a disk drive appara(cid:173)
`tus includes a base unit, a stator, a rotor hub, a rotor magnet,
`and a bearing mechanism. The stator includes a stator core
`and a plurality of coils. The plurality of coils is mounted to the
`stator core. The stator is disposed above the base unit. The
`rotor hub includes a cover portion and a side wall portion, and
`has a covered cylindrical shape. The cover portion is posi(cid:173)
`tioned above the stator. The side wall portion extends down(cid:173)
`ward from an outer edge of the cover portion. The rotor
`magnet is positioned outside the stator in a radial direction
`thereof and is fixed to an inner circumferential surface of the
`side wall portion of the rotor hub. The bearing mechanism
`supports the rotor hub and the rotor magnet to be rotatable
`with respect to the base unit and the stator. The rotor magnet
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 32 of 133 PageID #: 91
`
`US 8,737,017 Bl
`
`5
`
`3
`wire and the number oflayers of the conducting wire accord(cid:173)
`ing to a preferred embodiment of the present invention.
`FIG. 16 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a core height ratio according to a preferred embodi-
`ment of the present invention.
`FIG. 17 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a motor constant according to a preferred embodi-
`ment of the present invention.
`FIG. 18 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a torque constant according to a preferred embodi(cid:173)
`ment of the present invention.
`FIG. 19 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and the number oflayers of the conducting wire accord(cid:173)
`ing to a preferred embodiment of the present invention.
`FIG. 20 is a diagram illustrating a disk drive apparatus 20
`according to a second preferred embodiment of the present
`invention.
`FIG. 21 is a cross-sectional view illustrating a spindle
`motor according to a preferred embodiment of the present
`invention.
`FIG. 22 is an enlarged view of a portion of a spindle motor
`according to a preferred embodiment of the present invention.
`FIG. 23 is a diagram illustrating the relationship between
`the thickness of a rotor magnet and an air gap and a torque
`constant according to a preferred embodiment of the present
`invention.
`FIG. 24 is a diagram illustrating the relationship between
`the thickness of a rotor magnet and an air gap and a motor
`constant according to a preferred embodiment of the present
`invention.
`FIG. 25 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a core height ratio according to a preferred embodi(cid:173)
`ment of the present invention.
`FIG. 26 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a motor constant according to a preferred embodi(cid:173)
`ment of the present invention.
`FIG. 27 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and a torque constant according to a preferred embodi(cid:173)
`ment of the present invention.
`FIG. 28 is a diagram illustrating the relationship between
`the height of a stator core and the diameter of a conducting
`wire and the number oflayers of the conducting wire accord(cid:173)
`ing to a preferred embodiment of the present invention.
`
`10
`
`4
`Further, in the following description, the "parallel" direc(cid:173)
`tion includes both a parallel and an approximately parallel
`direction. Further, in the following description, the "orthogo(cid:173)
`nal" direction includes both an orthogonal and an approxi(cid:173)
`mately orthogonal direction.
`FIG. 1 is a longitudinal sectional view illustrating a disk
`drive apparatus 1 that includes a spindle motor (hereinafter,
`simply referred to a "motor") according to a first exemplary
`preferred embodiment of the invention. The disk drive appa(cid:173)
`ratus 1 is preferably a hard disk drive having a width of about
`2.5" and a thickness of about 7 mm. The disk drive apparatus
`1 preferably includes two disks 11, a motor 12, an access unit
`13, a housing 14, and a clamper 151. The motor 12 rotates the
`disk 11 that stores information. The access unit 13 performs at
`15 least one of reading and writing ofinformation with respect to
`two disks 11. The motor 12 is preferably a three-phase brush(cid:173)
`less motor.
`The housing 14 preferably includes a first housing member
`141 and a second housing member 142 of a plate shape. The
`disk 11, the motor 12, the access unit 13, and the clamper 151
`are accommodated inside the first housing member 141. The
`second housing member 142 is inserted into the first housing
`member 141 to define the housing 14. It is preferable that an
`inner space of the disk drive apparatus 1 be a clean space
`25 where dust or dirt is not present or is very minute.
`Two disks 11 are vertically disposed above and below a
`spacer 153, and are clamped to the motor 12 by the clamper
`151. The access unit 13 includes a head 131, an arm 132, and
`a head movement mechanism 133. The head 131 moves close
`30 to the disk 11 to magnetically perform at least one of reading
`and writing of information. The arm 132 supports the head
`131. As the head movement mechanism 133 moves the arm
`132, the head 131 relatively moves with respect to the disk 11.
`With such a configuration, the head 131 accesses a desired
`35 position of the disk 11 in a state where the head 131 moves
`close to the rotating disk 11.
`FIG. 2 is a longitudinal sectional view illustrating the
`motor 12 according to a preferred embodiment of the present
`invention. The motor 12 is preferably an outer rotor type, and
`40 includes a stationary portion 2 that is a fixed assembly, a
`rotating portion 3 that is a rotating assembly, and a bearing
`mechanism 4. The stationary portion 2 preferably includes a
`base plate 21 that is a base unit having an approximate plate
`shape, the stator 22, an insulating bushing 23, a magnetic
`45 member 24, and a wiring substrate 25. The base plate 21 is a
`portion of the first housing member 141 in FIG. 1. The stator
`22 is disposed above the base plate 21, and preferably
`includes a stator core 221 and a coil 222. A portion of the
`stator core 221 in the radial direction is fixed around a cylin-
`50 drical holder 211 of the base plate 21. The magnetic member
`24 has an arnmlar shape with reference to a central axis Jl, and
`preferably is fixed to an upper surface 212 of the base plate 21
`by, for example, an adhesive. In the stationary portion 2, a
`conducting wire 223 of the coil 222 is inserted together with
`55 the insulating bushing 23 into a through hole of the base plate
`21 in the state of passing through the insulating bushing 23.
`An end portion of the conducting wire 223 is preferably
`bonded to the wiring substrate 25 by soldering or the like.
`The rotating portion 3 preferably includes a rotor hub 31
`60 and a rotor magnet 32. The rotor hub 31 has an approximately
`covered cylindrical shape. The rotor hub 31 preferably
`includes a cover portion 311, a side wall portion 312, a hub
`tube portion 313, and a disk mounting portion 314. The cover
`portion 311 is positioned above the stator 22. The hub tube
`65 portion 313 has a cylindrical shape with reference to the
`central axis Jl, and extends downward from a lower surface
`3 lla of the cover portion 311 on the outside of the bearing
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`In the following description, an upper side of a motor in a
`central axis direction thereofin FIG. 1 is simply referred to as
`an "upper side", and a lower side thereofis simply referred to
`as a "lower side". A vertical direction does not represent a
`positional relationship or a direction when being assembled
`in an actual device. Further, a direction parallel or substan(cid:173)
`tially parallel to a central axis is referred to as an "axial
`direction", a direction that is orthogonal or substantially
`orthogonal to the central axis with reference to the central axis
`is simply referred to as a "radial direction", and a circumfer(cid:173)
`ential direction with reference to the central axis is simply
`referred to as a "circumferential direction".
`
`

`

`Case 1:21-cv-00052-UNA Document 1-1 Filed 01/18/21 Page 33 of 133 PageID #: 92
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`US 8,737,017 Bl
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`5
`mechanism 4. The side wall portion 312 extends downward
`from an outer edge of the cover portion 311. The disk drive
`apparatus 314 extends outward from the side wall portion 312
`in the radial direction. The disk 11 in FIG.1 is mounted on the
`disk mounting portion 314.
`The rotor magnet 32 is fixed to an inner circumferential
`surface 312a of the side wall portion 312, and is positioned
`outside the stator 22 in the radial direction. The rotor magnet
`32 is a tube portion made of, for example, a neodymium bond
`magnet (Nd-Fe-B BOND MAGNET). The magnet mem- 10
`ber 24 is positioned below the rotor magnet 32. A magnetic
`attraction force is generated between the rotor magnet 32 and
`the magnetic member 24.
`Torque is generated between the stator 22 and the rotor
`magnet 32 when the motor 12 is driven. A torque constant Kt 15
`of the torque generated between the stator 22 and the rotor
`magnet 32 is preferably about 4 mN·m/A or more and about
`6 mN·m/A or less for example. Further, a motor constant Km
`is preferably about 2 mN·m/(A-v'Q) or more and about 4
`mN·m/(A-v'Q) or less, for example. The motor constant Km is 20
`defined as Km=Kt/v'(R) using the torque constant Kt and a
`conducting wire resistance value R of the coil 222.
`The bearing mechanism 4 preferably includes a shaft por(cid:173)
`tion 41, a sleeve 42, a sleeve housing 43, a thrust plate 44, a
`cap portion 45, and a lubricant 46. The shaft portion 41 25
`extends downward from the inner portion of the cover portion
`311 in the radial direction. The shaft portion 41 and the rotor
`hub 31 are preferably defined by a single connected mono(cid:173)
`lithic member. A female screw portion 411 is preferably
`arranged inside the shaft portion 41 over its entire length. A 30
`male screw 152, for example, shown in FIG. 1 is preferably
`screw-coupled with the female screw portion 411 at the center
`of the cover portion 311. However, any other type of fastener
`other than the male screw 152 could be used if so desired.
`Thus, the clamper 151 is fixed to the motor 12, and the disk 11 35
`is clamped to the rotor hub 31.
`A hub clamping method other than the existing clamping
`method (hereinafter, referred to as a "center clamping
`method") may alternatively be used. In the hub clamping
`method, a plurality of female screw portions is defined in the 40
`upper surface of the cover portion of the rotor hub, male
`screws are screw-coupled with the female screw portions, and
`thus, the clamper is fixed to the motor. In the hub clamping
`method, since the male screws are fixed to the cover portion,
`it is preferable to lower the height of the cover portion as 45
`much as the height of the male screw. Further, since the male
`screws are provided in the hub, the hub becomes thick. In a
`thin motor used by the disk drive apparatus having a thickness
`of about 7 mm or a thickness of about 5 mm, to be described
`later, in order to secure a space between the lower surface of 50
`the cover portion and the upper surface of the base plate, the
`center clamping method is effectively used.
`The shaft portion 41 is inserted inside the sleeve 42. The
`sleeve housing 43 is positioned inside the hub tube portion
`313. The sleeve 42 is fixed to an inner circumferential surface 55
`of the sleeve housing 43. The thrust plate 44 is fixed to a lower
`portion of the shaft portion 41 as the central male screw
`portion is screw-coupled with the female screw portion 411.
`The cap portion 45 is fixed to a lower end of the sleeve
`housing 43, and blocks a lower opening of the sleeve housing 60
`43.
`In the motor 12, the lubricant 46 preferably continuously
`fills a radial gap 471, a first thrust gap 472, and a second thrust
`gap 473. The radial gap 471 is a gap between an inner cir(cid:173)
`cumferential surface of the sleeve 42 and an outer circumfer- 65
`ential surface of the shaft portion 41. The first thrust gap 4 72
`is a gap between a lower surface of the sleeve 42 and an upper
`
`6
`surface of the thrust plate 44. The second thrust gap 473 is a
`gap between an upper surface of the sleeve 42 and an upper
`surface of the sleeve housing 43, and the lower surface 311a
`of the cover portion 311. Further, in the motor 12, the lubri-
`5 cant 46 also preferably continuously fills a second thrust gap
`474 and a sealing gap 475. The third thrust gap 474 is a gap
`between a lower surface of the thrust plate 44 and an upper
`surface of the cap portion 45. The sealing gap 475 is a gap
`between an inner circumferential surface of the hub tube
`portion 313 and an upper portion of an outer circumferential
`surface of the sleeve housing 43.
`A radial dynamic pressure groove sequence is provided on
`the inner circumferential surface of the sleeve 42. Further, a
`thrust dynamic pressure groove sequence is provided on the
`upper surface and the lower surface of the sleeve 42. In the
`radial gap 471, a radial dynamic pressure bearing unit 481 is
`preferably configured by the radial dynamic pressure groove
`sequence. In the first thrust gap 472 and the second thrust gap
`473, a first thrust dynamic pressure bearing unit 482 and a
`second thrust dynamic pressure bearing unit 483 are prefer(cid:173)
`ably configured by the thrust dynamic pressure groove
`sequence, respectively. When the motor 12 is driven, the shaft
`portion 41 and the thrust plate 44 are supported in a non(cid:173)
`contact manner with respect to the sleeve 42, the sleeve hous(cid:173)
`ing 43, and the cap portion 45 by the radial dynamic pressure
`bearing unit 481, the first thrust dynamic pressure bearing
`unit 482, and the second thrust dynamic pressure bearing unit
`483, that is, by the bearing mechanism 4. Thus, the rotor hub
`31 and the rotor magnet 32 are supported to be rotatable with
`respect to the base plate 21 and the stator 22.
`FIG. 3 is a plan view illustrating the stator 22. The stator 22
`includes the stator core 221 and the plurality of coils 222. The
`plurality of coils 222 is preferably mounted on the stator core
`221 by, for example, concentrated winding. The stator core
`221 includes a central portion 51 that has a circular or
`approximately circular shape with reference to the central
`axis Jl, and a plurality of teeth 52. The number of the teeth 52
`