JPH02223365A - Spindle motor - Google Patents

Abstract

PURPOSE:To prevent the head crash of a hard disc drive by arranging a back yoke on the surface facing a magnet via stator in a hub rotatably fitted to a motor housing via shaft. CONSTITUTION:A back yoke 7 is arranged on the surface facing a magnet 5 via stator 6, i.e., on the surface side opposite to the surface facing the magnet 5 of the stator 6 in a hub 4 rotatably fitted to a motor housing 2 by a shaft 3. Therefore, a labyrinth seal 17 is constituted by a little space 14 between the magnet 5 and stator 6 and by little spaces 15, 16 between the stator 6 and back yoke 7 communicating with the space 14, and the labyrinth seal 17 can seal scattered particles of grease, etc., generated from bearings 9, 10 in the hub 4 and can prevent the scattered particles of grease, etc., from sticking to a hard disc. Thus, it is possible to prevent the head crash of the hard disc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spindle motor suitable for use in a hard disk drive.

[Summary of the Invention] The present invention provides a method in which a stator is attached to a motor housing (stator frame), and a magnet is attached to a hub that is rotatably attached to the motor housing via a shaft so as to face the stator. In the spindle motor, the hub is provided with a back yoke on a surface facing the magnet via the stator, thereby forming a so-called labyrinth seal between the back yoke and the stator and between the stator and the magnet. hand,
It is possible to seal off particles of pairing fleece generated from a bearing that attaches a motor housing or hub to the shaft, and the back yoke reduces eddy current loss, thereby reducing power consumption and improving motor efficiency. It is designed to make it possible to achieve the following.

[Prior Art] As a spindle motor used in a hard disk drive, a spindle motor is formed in a dish shape as shown in FIG.
A motor housing (stator frame) 1o2 having a bearing cylinder part 101 in the center thereof, a shaft 105 rotatably mounted within the bearing cylinder part 101 via a pair of upper and lower bearings 103, 104, and By press-fitting the upper end of the shaft 105 into the bearing hole 106 in the center of the cover plate, a covered cylindrical hub 107 attached to the shaft 105 and a magnet (rotor) attached to the inner peripheral surface of the hub 107 are connected. ) 108, a stator 21 consisting of a laminated iron core 109 and a coil 110 attached to the outer circumferential surface of the bearing cylinder portion 101 while facing the magnet 108, and an upper end portion of the shaft 105 ( Above the upper bearing 103) is a sleeve 1 made of magnetic material.
12 is attached, while a magnetic fluid seal 113 for dustproofing is attached to the inner circumferential surface of the upper end of the bearing cylinder portion 101 facing the sleeve l12.

The magnetic fluid seal 113 is connected to the bearing 103.1.
04, especially the scattered grease particles generated from the upper bearing 103 and the magnet I08 and the stator 111.
and the flange portion 102a of the motor housing 102.
This is to prevent the liquid from leaking out of the hub 107 through the space between the hard disk drive and the flange 107a of the hub 7, adhering to the disk, etc., and causing a head crash of the hard disk drive.

[Problems to be Solved by the Invention] Incidentally, in a spindle motor using the above-mentioned conventional magnetic fluid seal 113, scattered particles of grease generated from the bearing 103 are attached to the flange portion 102a of the motor housing 102 and the flange portion 107a of the hub 107. Although it is possible to prevent the particles from sticking to the hard disk through the cracks, there are problems as described below.

(1) Although magnetic fluid seals have excellent airtightness and dustproof properties, they have low pressure resistance, and when subjected to impact during transportation, magnetic fluid may blow out and adhere to hard disks, causing head crashes.

(2) Magnetic fluid seals are expensive and no longer meet market needs in the field of read disk drives, where lower prices are desired.

The present invention has been made for the purpose of solving the above-mentioned conventional problems and providing a dustproof seal that is resistant to impact and is inexpensive.

[Means for Solving the Problems] A motor housing, a shaft attached to the motor housing, a hub rotatably attached to the motor housing by the shaft, and a magnet attached to the hub. In a spindle motor including a stator attached to the motor housing while facing the magnet, the hub has a surface that faces the magnet via the stator, that is, a surface of the stator that faces the magnet. A back yoke was placed on the opposite side.

[A labyrinth seal is formed by a small gap between the acting co-magnet and the stator, and a small gap between the stator and the back yoke that are connected to this, and the labyrinth seal prevents the scattered grease particles generated from the bearing from entering the hub.] to prevent these scattered grease particles from adhering to the hard disk.

Furthermore, the back yoke reduces eddy current loss, thereby reducing power consumption and improving motor efficiency.

[Example] Next, embodiments of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows a sectional view of the first embodiment. In the figure, 1 is a spindle motor, and the motor I has a motor housing 2, a shaft 3 attached to the motor housing 2,
A hub 4 is rotatably attached to the motor housing 2 by the shaft 3, a magnet 5 is attached to the hub 4, and the hub 4 is attached to the motor housing 2 in a state facing the magnet 5. It includes a stator 6 and a back yoke 7 provided on the hub 4 such that the stator 6 is sandwiched between the magnet 5 and the magnet 5.

The motor housing 2 is made in the shape of a disc, and a bearing cylinder part 8 is provided in the center, and the lower end of the shaft 3 is press-fitted into the bearing cylinder part 8, and the shaft 3 is attached to the motor housing. It is placed upright in the center of 2.

Further, above the bearing cylinder portion 8 of the shaft 3 is an upper portion.

Lower pair of bearings9. The inner ring side of the IO is press-fitted, and a pair of upper and lower bearings 9. A hub 4 is attached to the outer ring side of IO.

The hub 4 has a bearing hole 1' in the center made of a magnetic material.
By press-fitting the outer ring sides of the upper and lower bearings 9.1 into the bearing holes 11, these bearings 9. It is rotatably attached to the shaft 3 via the IO. Further, a ring-shaped groove 12 having a predetermined depth and a predetermined width is cut from the lower surface side to the upper surface side of the hub 4.
The inner circumferential surface side of 2 is a magnet mounting surface 13, and the outer circumferential surface side thereof is a back yoke 7.

Further, the magnet 5 is formed in a cylindrical shape and is attached to the magnet attachment surface 13.

The stator 6 is formed into a cylindrical shape with a slightly larger diameter than the magnet 5, and its lower end is attached to the motor housing 2 with its upper end inserted between the magnet 5 and the back yoke 7.

The magnets 5 and the stator 6 and the stator 6 and the back yoke 7 are connected to each other through a gap 14 between the upper end surface of the stator 6 and the bottom surface of the concave groove of the hub 5. gaps 15 and 16 are formed, and these gaps 14
．． 15 and 16 constitute a labyrinth seal 17.

Note that 18 is a stator connector provided in the motor housing 2, and power is supplied to the stator 6 from an external motor drive circuit through the connector 18. 19 is a preload spring interposed between the outer rings of the upper and lower bearings 9 and 10. 20 is an upper cover plate that closes the upper end opening of the bearing hole 1 of the hub 4.

The spindle motor l of the first embodiment has the above-mentioned configuration, and includes bearings 9. Scattered particles of grease generated from the IO are sealed inside the hub 4 by the labyrinth seal 17 formed by the gaps 14 to 16.

In the embodiment, the hub 4 is made of a magnetic material and a part of the hub 4 is used as the back yoke 7, but the hub 4
may be made of a non-magnetic material, and the back yoke 7 made of a magnetic material may be attached thereto.

FIG. 2 shows a second embodiment of the present invention, in which the spindle motor 1 is formed into a so-called flat type.

In this embodiment, the lower part of the motor housing 2 includes:
A back yoke 7 consisting of a cylindrical portion 21 and a ring-shaped bottom portion 22 is attached.

Further, the magnet 5 is formed in a flat ring shape and is attached to the lower surface of the hub 4. Similarly to the magnet 5, the stator 6 is also formed in a flat ring shape, and the back yoke 7 is shaped like a ring. It is attached to the upper surface side of the motor housing 2 while being sandwiched between the bottom portion 22 and the magnet 5.

There is a slight gap 23 between the magnet 5 and the stator 6, the circumferential surface of the stator 6, and the cylindrical portion 2 of the back yoke 7.
A labyrinth seal 26 is formed by a small gap 24 between the stator 6 and the ring-shaped bottom 22 of the back yoke 7 and a small gap 25 between the stator 6 and the ring-shaped bottom 22 of the back yoke 7.

Note that other constituent parts are the same as those in the first embodiment, so the same parts are given the same reference numerals and redundant explanation will be omitted.

The spindle motor l of the second embodiment has the above-mentioned configuration, with the magnet 5 and stator 6 being flat,
Since it is provided on the lower surface side of the motor housing 2, there is an effect that the motor can be made smaller.

[Effects of the Invention] As explained above, in the spindle motor of the present invention, since the back yoke is arranged so that the stator is sandwiched between the magnets, the following effects can be obtained.

(1) A labyrinth seal is formed by a small gap between the magnet and the stator and a small gap between the stator and back yoke connected to this, and the labyrinth seal prevents scattered grease particles generated from the bearing from reaching the hub. By preventing the grease from flowing out, it is possible to reliably prevent head crashes caused by scattered grease particles adhering to the disk.

(2) Since the labyrinth seal is constructed using a magnet, stator, and back yoke, the structure is simple and the cost can be lowered compared to conventional magnetic fluid seals.
It is also strong against impact, and there is no need to worry about head crushers caused by blowing out magnetic material.

(3) Since the back yoke is arranged so as to sandwich the stator between the magnet and the stator, the back yoke can suppress the occurrence of eddy current loss and reduce power consumption.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of a spindle motor of the present invention, FIG. 2 is a sectional view of a second embodiment, and FIG. 3 is a sectional view of a conventional example. l...Spindle motor, 2...Motor housing, 3...Axis, 4...Hub, 5...Magnet, 6
... Stator, 7... Back yoke. September 8, 1998 Patent Application No. 42685 6 Contents of the amendment (1) "Read disk" described on page 4, line 18 is replaced with "hard disk". ” is corrected. (2) "Head Crusher" written on page 11, line 18 is corrected to "head crush". Name of the invention Spindle motor Above 3. Relationship with the person making the amendment case

Claims (1)

[Claims] (1) A motor housing, a shaft attached to the motor housing, a hub rotatably attached to the motor housing by the shaft, a magnet attached to the hub, and a shaft facing the magnet. a stator that is attached to the motor housing in a state in which the spindle motor is mounted, and a back yoke is disposed on the hub so as to sandwich the stator between the hub and the magnet.