JPH07245899A - Brushless motor - Google Patents

Abstract

PURPOSE:To prevent the outflow of oil into a magnetic disk region by holding the base oil of grease, which is sealed into a rolling bearing and flows out by the action of the centrifugal force caused by rotation in an oil sump surrounded with the edge of a magnet, the edge of a yoke member and the edge of a rotor. CONSTITUTION:The centers of the axial directions of a stator core 2, a magnet 10 and a yoke member 7 are made to agree, respectively. Thus, the balance of magnetic attracting forces for the stator core 2 is obtained. Then, sealing material is applied on the opposite edge of an edge 23. The space between the rotor l and the yoke member 7 or between the rotor and the magnet 10 is perfectly sealed, respectively. An oil absorbing member comprising polyurethane foam, glass fiber or the like is arranged in an oil sump 8. Thus, the outflow of base oil from a lower rolling bearing 15b into a magnetic disk region 20 is perfectly prevented. In this way, the functional faults and the defective operation of a magnetic disk device 19 are decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a magnetic disk drive in the OA field, which is required to be small and thin, and a brushless motor of a high-speed rotation type used in a laser beam printer.

[0002]

2. Description of the Related Art Generally, in a magnetic disk apparatus in the field of OA, if dust adheres to or collides with a very narrow gap between a magnetic disk and a magnetic head, it will hinder the operation of writing and reading data. The air in the device needs to be kept clean. Therefore, by putting the whole motor with the magnetic disk and the magnetic head in a sealed case,
The dust intrusion from the outside is prevented and the air in the magnetic disk area is kept clean to enhance the reliability of the magnetic disk device.

In recent years, magnetic disk devices have become smaller and smaller due to the downsizing trend of computers used.
The brushless motor tends to be faster because of its thinner shape, lower noise, larger capacity, and shorter access time. The gap between the magnetic disk and the magnetic head during the rotation of the clean magnetic disc area was about 0.2 μm, but the gap is now 0.1 μm or less to achieve high density. It is getting smaller.

Among them, in a brushless motor for rotating a magnetic disk, it is impossible to supply oil to the transfer surface of the rolling bearing with the magnetic disk attached, so grease containing a thickener is added to the base oil. Rolling bearings are used.

A conventional brushless motor will be described below with reference to the drawings. FIG. 4 is a sectional view of a conventional brushless motor (hereinafter abbreviated as a motor). In FIG. 4, 11 is a circular bracket made of aluminum, and this bracket 11 has a hole 26 at the center into which the shaft 12 can be inserted. The printed circuit board 4 is fixed to the inner surface of the bracket 11 by adhesion or the like. Reference numeral 2 denotes a stator core in which an insulating member made of epoxy resin is coated on all surfaces such as both end surfaces, and an exciting winding 3 is wound around the stator core. The stator core 2 is fixed to the bracket 11 after the exciting winding 3 is wound, and the end of the exciting winding 3 is soldered to the soldering land (not shown) of the printed board 4.

Reference numeral 1 denotes a rotor made of an aluminum material, on which at least one magnetic disk 19 or a polygon mirror (not shown) can be mounted. And
An upper rolling bearing 15a and a lower rolling bearing 15b are mounted on the rotor 1 via a spacer portion 14 at positions axially separated from each other. Reference numeral 21 denotes a grease scattering prevention member, which is attached to the outer ring of the lower rolling bearing 15b and the base oil that constitutes the grease enclosed in the rolling bearing is separated from the grease by centrifugal force, and even if it flows out, the magnetic disk area 2
It has a puddle structure that does not scatter to zero.

After that, the yoke member 7 and the magnet 10 are fixed to the rotor open end 6 of the rotor 1, the shaft 12 is inserted into the inner ring of the upper rolling bearing 15a and the lower rolling bearing 15b, and the upper rolling bearing 15a and the upper rolling bearing 15a are bonded to each other. It is fixed while applying a preload to the lower rolling bearing 15b. In this way, the assembly of the rotating body 13 having the shaft 12 is completed.

The shaft 12 is inserted and fixed in a hole 26 in the center of the bracket 11, and the rotor 1 is rotatably supported by the shaft 12 fixed to the bracket 11 as a fulcrum. A magnetic fluid seal 17 is placed on the upper part of the upper rolling bearing 15a via a seal mounting member 16, and a magnetic fluid 18 is injected to seal between the upper rolling bearing 15a and the magnetic disk area 20. As the magnetic disk 19 rotates at high speed, the area A, which is 27, becomes negative pressure,
The grease filled in the upper rolling bearing 15a is easily scattered, but the magnetic fluid seal 17 and the magnetic fluid 18 cause the upper rolling bearing 15a and the magnetic disk area 20 to be dispersed.
Since there is a seal between the upper rolling bearing 15a
The grease generated from the magnetic disk area 20 is prevented from being scattered and transferred to the clean magnetic disk area 20 to prevent the magnetic disk area 20 from being contaminated.

[0009]

However, in the above-mentioned conventional configuration, the magnetic disk drive increases the rotation speed of the motor to shorten the access time (generally 3600 rpm).
However, recently, it has been rotating at 7200 rpm or more. Then, the centrifugal force acts on the magnetic fluid during the rotation, and the magnetic fluid is scattered to the outside along with the rotation, and adheres to the magnetic disk to cause a phenomenon of adsorption between the magnetic disk and the magnetic head, causing a malfunction.

When the scattering of the magnetic fluid progresses, the seal between the upper rolling bearing 15a and the magnetic disk area 20 is impaired, and the grease generated from the upper rolling bearing 15a is scattered and transferred to the clean magnetic disk area. As a result, grease adheres to a very narrow gap between the magnetic disk and the magnetic head, which hinders data writing and reading operations.

When rotating at a high speed, the base oil which constitutes the grease sealed in the rolling bearing is separated from the grease by the centrifugal force, and the separated base oil is transmitted on the surface of the rotating body and the magnetic disk It flows into the area 20,
The magnetic disk 19 adheres to the magnetic disk 19 to cause an adsorption phenomenon between the magnetic disk 19 and the magnetic head to cause a malfunction.
The grease scattering prevention member 21 attached to the outer ring of the lower rolling bearing 15b needs to have a sufficiently large space to store the base oil in order to achieve a sufficient effect on the outflow of the base oil of the grease. Since it is necessary to make the grease scattering prevention material 21 large in the axial direction, it is not suitable for a small and thin motor. Further, since it is necessary to newly provide the grease scattering prevention material 21, the structure becomes complicated and the number of parts cannot be reduced. Moreover,
When the grease scattering prevention member 21 is attached to the outer ring of the lower rolling bearing 15b, about 50% of the axial dimension of the outer ring of the lower rolling bearing 15b is used for coupling with the grease scattering prevention member 21, so the lower rolling bearing 15b and the rotor The rigidity of the magnetic disk 19 and the polygon mirror is insufficient because the connection with 1 is insufficient, and as a result, when the magnetic disk 19 or the polygon mirror is rotated at a high speed, the vibration during rotation becomes large and there is no margin for reliability. Had.

The present invention solves the above-mentioned problems of the prior art in that the grease of the rolling bearing scatters and moves to a clean magnetic disk area at high speed rotation, and the base oil of the grease of the rolling bearing moves to the magnetic disk area. It is an object of the present invention to provide a small and thin brushless motor which can prevent outflow and has high quality, has a small number of parts, and has good whirling.

[0013]

To achieve this object, a brushless motor according to the present invention has an end surface A of a magnet, an end surface B of a yoke member, an inner diameter surface of a rotor, and an end surface C of a rotor.
An oil reservoir surrounded by and has an axial distance between the end face A and the end face C smaller than an axial distance between the end face B and the end face C, and holds the sealant on the end face opposite to the end face B. It is equipped with an oil absorbing member.

[0014]

Operation The oil is surrounded by the end surface 1 of the magnet, the end surface 2 of the yoke member, the inner diameter surface of the rotor, and the end surface 3 of the rotor, and is enclosed in a rolling bearing that flows out by the action of centrifugal force due to rotation. By holding the base oil of the grease, the grease is prevented from flowing out to the magnetic disk area.

Further, a sealant is held on the end face opposite to the end face B to completely prevent the base oil flowing out from the gap between the rotor and the yoke member and between the yoke member and the magnet.
Further, by disposing the oil absorbing member in the oil sump, the base oil can be more surely held in the oil sump.

[0016]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

1, FIG. 2 and FIG. 3 are sectional views of a motor according to an embodiment of the present invention. The same parts as those of the conventional structure are designated by the reference numerals in the conventional example and the description thereof is omitted. .

In FIGS. 1, 2 and 3, 1 is a rotor made of an aluminum material, to which at least one magnetic disk 19 or a polygon mirror (not shown) can be mounted. An upper rolling bearing 15a and a lower rolling bearing 15b are mounted on the rotor 1 at positions axially separated from each other via a spacer portion 14, and a yoke member 7 and multiple poles are magnetized to the rotor open end 6 of the rotor 1. The magnet 10 is fixed.

Upper rolling bearing 15a and lower rolling bearing 1
The shaft 12 is inserted into the inner ring of 5b and is fixed to the upper rolling bearing 15a and the lower rolling bearing 15b by applying an appropriate preload by adhesion. In this way, the assembly of the rotating body 13 having the shaft 12 is completed. Reference numeral 2 denotes a stator core in which an insulating member made of epoxy resin is coated on all surfaces such as both end surfaces, and an exciting winding 3 is wound around the stator core.
After the excitation winding 3 is wound on the stator core 2, the printed board 4 is formed.
Are fixed to the stator core 2, and the ends of the excitation winding 3 are soldered to soldering lands (not shown) of the printed board 4. Then, the shaft 12 is inserted into a central hole of the base 30 of the magnetic disk device and attached by a fixing screw 31, and the rotating body 13 is rotatably supported with the shaft 12 as a fulcrum.

Sealing means 5 is attached to the upper portion of the upper rolling bearing 15a and is sealed with an adhesive 32 to seal between the rolling bearing 15a and the magnetic disk area 20. As a result, the grease generated from the upper rolling bearing 15a is prevented from being scattered and transferred to the clean magnetic disk area 20, so that the magnetic disk area 20 is prevented from being contaminated and the cleanliness is maintained.

From the lower rolling bearing 15b to the rotor open end 6
The stator core 2 is disposed in the space up to, the end surface A22 of the magnet 10 facing the stator core 2, the end surface B23 of the yoke member, and the inner diameter surface 2 of the rotor 1 are arranged.
5 and the oil sump 8 surrounded by the end surface C24 of the rotor 1
Are configured.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, in the oil sump 8, the axial distance between the end faces A22 and C24 is smaller than the axial distance between the end faces B23 and C24 so that the scattered oil and the outflow of the oil are stronger. I am doing something.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 3, by making the axial center of the stator core 2, the magnet 10 and the yoke member 7 coincide with each other, the magnetic attraction force to the stator core 2 is balanced. And the end surface B2
By applying the sealing material 33 to the end surface on the opposite side of 3, the gaps between the rotor 1 and the yoke member 7, or between the yoke member 7 and the magnet 10 can be completely sealed.

Further, the oil sump 8 has an oil absorbing member 34 made of polyurethane foam, glass fiber or the like.
By arranging, the base oil flowing out from the lower rolling bearing 15b can be completely prevented from flowing out to the magnetic disk area 20.

[0027]

As described above, according to the present invention, the oil flows out into the oil pool surrounded by the end surface 1 of the magnet, the end surface 2 of the yoke member, the inner diameter surface of the rotor, and the end surface 3 of the rotor by the action of centrifugal force due to the rotation. By holding the base oil of the grease filled in the rolling bearing, it is possible to prevent the grease from flowing out to the magnetic disk area. For this reason, it is possible to reduce the malfunctions and malfunctions of the magnetic disk device that have occurred due to the base oil of the grease flowing out adhering to the gap between the magnetic disk and the magnetic head.

Further, since the grease scattering prevention material is eliminated, the number of parts can be reduced, and a motor suitable for thin requirements can be provided.

Further, since the grease scattering prevention material is eliminated, all of the axial dimension of the outer ring of the lower rolling bearing can be used for coupling with the rotor, so that when the magnetic disk or polygon mirror, which is a load, is mounted, The rigidity with respect to the balance load is increased, and as a result, whirling when rotating the magnetic disk or the polygon mirror at high speed can be reduced, and a device with high reliability can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a motor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a motor according to another embodiment of the present invention.

FIG. 3 is a sectional view of a motor according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional motor

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotor 2 stator core 3 excitation winding 4 printing substrate 5 sealing means 6 rotor open end 7 yoke member 8 oil sump 9 space 10 magnet 11 bracket 12 shaft 13 rotor 14 spacer part 15a upper rolling bearing 15b lower rolling bearing 16 seal mounting member 17 Magnetic Fluid Seal 18 Magnetic Fluid 19 Magnetic Disk 20 Magnetic Disk Area 21 Grease Scatter Prevention Material 22 End Face A 23 End Face B 24 End Face C 25 Outer Diameter Face 26 Hole 27 Inner Diameter Part 29 Region A 30 Base 31 Fixing Screw 32 Adhesive 33 Sealing Agent 34 Oil absorbing member

Claims (4)

[Claims] 1. A shaft, a rotor rotatably supported by a pair of rolling bearings attached to the shaft, and one of the pair of rolling bearings, one end surface side of an upper rolling bearing being an inner diameter portion of the rotor. One end surface of the other lower rolling bearing of the pair of rolling bearings that is hermetically sealed with is located on the rotor open end side, and is arranged in the space from the lower rolling bearing to the rotor open end. A yoke member attached to the rotor, a magnet attached to the yoke member, a stator core fixed so as to face the magnet, an end surface A of the magnet, an end surface B of the yoke member, and an inner diameter surface of the rotor. A brushless motor provided with an oil reservoir surrounded by an end surface C of the rotor. 2. An end face A and an end face C which form an oil sump.
The brushless motor according to claim 1, wherein an axial distance between the end surface B and the end surface C is smaller than an axial distance between the end surface B and the end surface C. 3. The brushless motor according to claim 1, wherein the center of the axial dimension of the stator core and the magnet are aligned with that of the yoke member, and a sealant is arranged on the end face opposite to the end face B. 4. The brushless motor according to claim 1, wherein an oil absorbing member is attached to the oil sump.