JPH07279960A - Dynamic bearing device - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the number of parts while reducing the size. [Structure] A shaft 1 is composed of a magnet 2 magnetized in the axial direction and pole pieces 3a and 3b provided on both sides of the magnet 2. A sleeve 6 made of a non-magnetic material is fixed to the inner peripheral surface of the hole 5 of the motor hub 4. The shaft 1 is rotatably arranged inside the sleeve 6. Thus, unlike the conventional example, the magnet 2 is integrated not as the outer side but as the shaft 1 so as to function as the central axis, so that the size of the apparatus in the radial direction can be reduced and the overall size can be reduced. Further, unlike the conventional example, the cylindrical member for supporting the magnet is not required, so that the number of parts can be reduced and the cost can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing device used for a hard disk drive (HHD), a polygon mirror or the like.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view of a conventional dynamic bearing device of this type, in which a cylindrical magnet (permanent magnet) 42 and this magnet 42 are provided on the inner peripheral surface of a motor hub 41 which constitutes a housing. A pair of cylindrical members 43a, 43b made of a magnetic material are provided which are joined to the upper and lower ends. The magnet 42 is magnetized in the axial direction. A cylindrical sleeve 44 made of a non-magnetic material is arranged on the inner peripheral surface of the magnet 42 and the cylindrical members 43a and 43b. An insertion hole 45 is formed in the axis of the sleeve 44, and a shaft 46 is arranged in the insertion hole 45 so as to be rotatable relative to each other. The shaft 46 is made of a magnetic material, and a pair of magnetic pole pieces 47 a, 4 made of a magnetic material are provided on the shaft 46 located above and below the sleeve 44.
7b is provided. This pair of pole pieces 47a, 4
7b is formed in the shape of a ring disk, and the sleeve 4
4 are arranged so that gaps 48a and 48b are formed on the upper surface side and the lower surface side, respectively, and are fixed to the shaft 46. Also, gaps 49a, 4a are formed between the inner peripheral surfaces of the tubular members 43a, 43b and the outer peripheral surfaces of the pole pieces 47a, 47b.
9b is formed, and a gap 50 is also formed between the outer peripheral surface of the shaft 46 and the inner peripheral surface of the sleeve 44.

Here, the magnetic fluid 51 is enclosed in the gaps 50, 48a, 48b, and the surfaces forming the gaps 50, 48a, 48b, that is, the inner peripheral surface of the insertion hole 45, the outer periphery of the shaft 46. Surface, upper pole piece 47
The lower surface of a, the upper surface of the lower pole piece 47b, and the upper and lower surfaces of the sleeve 44 are surface-treated to generate dynamic pressure in the magnetic fluid 51 by the rotation of the motor hub 41. That is, a journal bearing is formed between the inner peripheral surface of the sleeve 44 and the outer peripheral surface of the shaft 46, and both end surfaces of the sleeve 44 and the pole pieces 47 a, 47.
The inner surface of b constitutes a thrust bearing.
The pole pieces 47a and 47b also form a seal portion. That is, the upper cylindrical member 43a, the upper pole piece 47a, and the shaft 4 are sequentially arranged by the magnet 42.
6, the magnetic circuit that returns to the magnet 42 via the lower pole piece 47b and the lower tubular member 43b is configured, so that the magnetic fluid 51 is sealed in the gaps 49a and 49b.

[0004]

However, in the conventional dynamic pressure bearing device shown in FIG. 3, since the magnet 42 is arranged outside the bearing portion, the size in the radial direction (radial direction) becomes large and the size is small. However, there is a problem in that the number of parts is increased.

The present invention has been made in order to solve the above-mentioned conventional drawbacks, and an object thereof is to provide a dynamic pressure bearing device capable of reducing the size and the number of parts. It is in.

[0006]

Therefore, a dynamic pressure bearing device according to a first aspect of the present invention includes a shaft 1 composed of an axially magnetized magnet 2 and a pole piece 3a provided on at least one end surface side of the magnet 2. A motor hub 4 having a hole 5 provided in the shaft core, a cylindrical sleeve 6 arranged on the inner peripheral surface of the hole 5 of the motor hub 4, and an outer peripheral surface of the shaft 1 loosely fitted inside the sleeve 6. And the sleeve 6
Oil 1 enclosed in a gap 9 formed between the inner peripheral surfaces of the
1 and the magnetic fluid 11 is held in the magnetic path from the pole piece 3a to the motor hub 4, and the working oil 11 is sealed thereby.

The hydrodynamic bearing device according to a second aspect of the present invention includes a magnet 2 magnetized in the axial direction, a pole piece 3a provided on at least one end surface side of the magnet 2, and the magnet 2 and the pole piece 3a. Shaft 1 which is arranged in a corner portion and has a substantially ring-shaped bearing member 13 whose outer peripheral surface side is the first inclined surface 14, and a hole 5 in the shaft core.
And a hole 5 of the motor hub 4
The first inclined surface 1 of the bearing member 13 disposed on the inner peripheral surface of the
Between the outer peripheral surface of the shaft 1 and the inner peripheral surface of the sleeve 6 which are loosely fitted inside the sleeve 6 and the second inclined surface 15 facing the outer peripheral surface 4 of the sleeve 6. Has a working oil 11 enclosed in a gap 9 formed in the above, and holds the magnetic fluid 11 in a magnetic path from the pole piece 3a to the motor hub 4, whereby the working oil 11 is held.
Is characterized in that it is sealed.

[0008]

In the dynamic pressure bearing device according to claim 1, the hydraulic oil 11
A magnet 2 for forming a magnetic circuit for sealing is used as the shaft 1. Therefore, the size in the radial direction can be reduced as compared with the conventional example in which the magnet 2 is arranged outside the shaft 1. Further, the tubular member used to support the magnet 2 in the conventional example is not required.

Further, in the hydrodynamic bearing device of the second aspect, the magnet 2 for forming the magnetic circuit for sealing the hydraulic oil 11 is used as the shaft 1. Therefore, the size in the radial direction can be reduced as compared with the conventional example in which the magnet 2 is arranged outside the shaft 1. Further, the tubular member used to support the magnet 2 in the conventional example is not required. Further, the first inclined surface 14 of the bearing member 13 on the shaft 1 side and the second inclined surface 15 of the sleeve 6 are opposed to each other so that the radial load and the thrust load during rotation are received by one bearing member 13. ing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the dynamic pressure bearing device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a vertical sectional view showing an embodiment of a dynamic pressure bearing device of the present invention. In the figure, 1 is a shaft, and a magnet 2
And a pair of pole pieces 3a and 3b.
The magnet 2 is formed in a cylindrical shape and is magnetized in the axial direction thereof, and in the illustrated example, the upper side is an N pole and the lower side is an S pole. The pole pieces 3a and 3b fixed to the end faces on both sides of the magnet 2 are made of a magnetic material and are formed into a substantially disc shape. The outer diameters of the pole pieces 3a and 3b are formed to be larger than the outer diameter of the magnet 2, and the ends of the pole pieces 3a and 3b are formed so as to protrude from the magnet 2 in the radial direction.

The motor hub 4 is made of a magnetic material and has a hole 5 formed in its shaft core. Hole 5 in this motor hub 4
A cylindrical non-magnetic sleeve 6 is fixed to the inner peripheral surface of the. The inner hole of the sleeve 6 is used as an insertion hole 7, and the shaft 1 is loosely fitted in the insertion hole 7 so as to be relatively rotatable. And a magnet 2 that constitutes the shaft 1.
The length of the sleeve 6 is slightly shorter than the axial length of the sleeve 6, and a gap 8a is formed between the upper surface of the sleeve 6 and the lower surface of the peripheral portion of the upper pole piece 3a. A gap 8b is also formed between the pole piece 3b on the side and the upper surface of the peripheral portion. Further, a gap 9 is formed between the outer peripheral surface of the magnet 2 and the inner peripheral surface of the sleeve 6. A gap 10 is also formed between the peripheral end surfaces of the pole pieces 3a, 3b and the inner peripheral surface of the motor hub 4 above and below the sleeve 6.
a and 10b are formed. The gaps 8a, 8b, 9,
A magnetic fluid 11 as hydraulic oil is enclosed in 10a and 10b.

Here, the surfaces forming the gaps 9 and 8a, 8b, that is, the inner and upper and lower surfaces of the sleeve 6, the outer peripheral surface of the magnet 2, the lower surface of the upper pole piece 3a, and the lower pole piece 3b. The upper surface is surface-treated so as to generate a dynamic pressure in the magnetic fluid 11 by the relative rotation of the motor hub 4. The shaft 1 constitutes the radial load, and the pole pieces 3a and 3b bear the thrust load.

The pole pieces 3a, 3b constitute a seal portion, and the magnet 2 constituting the shaft 1
The upper pole piece 3a, the motor hub 4,
Since the magnetic circuit 12 returning to the magnet 2 via the lower pole piece 3b is formed, a magnetic field is formed in the gaps 10a, 10b, and the magnetic fluid 11 is sealed in the gaps 10a, 10b. This sealing action prevents leakage of fluid in the gaps 9 and 8a, 8b.

In the above structure, when the motor hub 4 rotates, dynamic pressure is generated in the magnetic fluid 11 enclosed in the gaps 9 and 8a, 8b, and the dynamic pressure is generated on the outer peripheral surface of the shaft 1 and the pole piece 3a. 3b, respectively. At this time, the radial load in the radial direction is supported by the shaft 1, and the axial thrust load is in each pole piece 3a, 3b.
The shaft 1 will be supported via.

As described above, in the hydrodynamic bearing device according to the above-described embodiment, the magnet 2 is integrated not as the outside but as the shaft 1 so as to function as the central axis unlike the conventional example. The size in the radial direction can be reduced, and the overall size can be reduced. Further, since the tubular member for supporting the magnet of the conventional example is not required, the number of parts can be reduced, and thus the cost can be reduced.

(Embodiment 2) Embodiment 2 is shown in FIG. In this embodiment, one member, the bearing member 13, is added to receive the radial load and the thrust load at the same location. That is, a non-magnetic, substantially ring-shaped bearing member 13 is provided at the upper and lower corners formed by the magnet 2 and the pole pieces 3a, 3b, and the bearing member 13 has a triangular cross section and is provided on the sleeve 6 side. The first inclined surface 14 is formed on the. The upper and lower inner sides of the sleeve 6 are also provided with a second inclined surface 15 that faces the first inclined surface 14. The first inclined surface 14 of the bearing member 13 and the second inclined surface 15 of the sleeve 6 are also surface-treated to generate dynamic pressure in the magnetic fluid 11.

In this embodiment, as shown in FIG. 2, the first inclined surface 14 of the bearing member 13 constituting the shaft 1 and the second inclined surface 15 on the sleeve 6 side face each other. The bearing portion can simultaneously receive a radial load in the radial direction and a thrust load in the axial direction during rotation. In this embodiment, since the bearing member 13 is subjected to the surface processing for generating the dynamic pressure, the magnetic property is higher than that in the case where the surface of the magnet 2 which is difficult to process is processed as in the first embodiment. Surface processing for generating a dynamic pressure in the fluid 11 can be easily performed.

Although the magnetic fluid 11 is used as the working oil sealed between the inner peripheral surface side of the sleeve 6 and the outer peripheral surface side of the magnet 2 in each of the above embodiments, the fluid is sealed. The magnetic fluid may be used only in the portion (between the pole piece and the motor hub), and only the oil may be used in the other portion, that is, the portion where the dynamic pressure of the bearing is generated.

In each of the above embodiments, the case where both ends of the shaft are sealed has been described, but the present invention can also be applied to the case of a dynamic pressure bearing device configured to seal only one end side. Furthermore, not only when rotating the motor hub side,
The present invention can be applied to a dynamic pressure bearing device having a structure for fixing the motor hub side.

[0020]

As described above, in the hydrodynamic bearing device according to the first aspect, the size can be reduced and the number of parts can be reduced.

Further, in the dynamic pressure bearing device according to the present invention, the surface processing for generating the dynamic pressure is applied to the bearing member, not to the hard-to-process magnet, so that the surface for generating the dynamic pressure to the magnetic fluid is formed. Can be easily processed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a dynamic pressure bearing device of the present invention.

FIG. 2 is a sectional view of Embodiment 2 of the dynamic pressure bearing device of the invention.

FIG. 3 is a cross-sectional view of a conventional dynamic pressure bearing device.

[Explanation of symbols]

 1 shaft 2 magnet 3a pole piece 3b pole piece 4 motor hub 5 hole 6 sleeve 8a gap 8b gap 9 gap 10a gap 10b gap 11 magnetic fluid 13 bearing member 14 first inclined surface 15 second inclined surface

Claims (2)

[Claims] 1. A shaft (1) comprising an axially magnetized magnet (2) and a pole piece (3a) provided on at least one end face side of this magnet (2), and a hole () 5) a motor hub (4), a cylindrical sleeve (6) arranged on the inner peripheral surface of the hole (5) of the motor hub (4), and the above-mentioned sleeve loosely fitted inside the sleeve (6). And a hydraulic fluid (11) enclosed in a gap (9) formed between the outer peripheral surface of the shaft (1) and the inner peripheral surface of the sleeve (6), and the pole piece (3a).
From the motor hub (4) to hold a magnetic fluid (11), thereby sealing the hydraulic oil (11). 2. A magnet (2) axially magnetized, a pole piece (3a) provided on at least one end face side of the magnet (2), and the magnet (2) and the pole piece (3a). A motor hub having a shaft (1) formed of a substantially ring-shaped bearing member (13) having a first inclined surface (14) on the outer peripheral surface side and arranged in the corner portion, and a hole (5) in the shaft core ( 4) and a second inclined surface (15) arranged on the inner peripheral surface of the hole (5) of the motor hub (4) and facing the first inclined surface (14) of the bearing member (13). A substantially cylindrical sleeve (6) formed on the end side, and formed between the outer peripheral surface of the shaft (1) loosely fitted inside the sleeve (6) and the inner peripheral surface of the sleeve (6). And a hydraulic oil (11) enclosed in a gap (9) A hydrodynamic bearing device, characterized in that a magnetic fluid (11) is retained in a magnetic path from the motor (3a) to the motor hub (4), thereby sealing the hydraulic oil (11).