JPH062980U - Brushless motor - Google Patents

Abstract

(57) [Abstract] [Purpose] In a brushless motor used in a magnetic disk device in the field of OA, with a high quality that can prevent grease of a bearing mounted on a fixed shaft from scattering from the bearing space to a clean magnetic disk area. Provide an inexpensive brushless motor. [Structure] A hub 8 having an outer diameter portion on which a plurality of magnetic disks can be mounted in a clean magnetic disk area 29, and an upper bearing 15a of the two bearings inserted in the second inner peripheral portion 13 of the hub. The magnetic fluid seal 17 disposed on the first shaft, the first protruding portion 22 attached to the fixed shaft 12, the outer diameter of the lower bearing 15b, and the third inner peripheral portion 2 of the hub.
A holder 26 having a second protrusion portion 23 extending in the axial direction with a small gap between 0 and 0, and a flat portion 24 for positioning a disc spring for applying a preload to a bearing.
A brushless motor having:
Due to the labyrinth effect of the minute spaces 25 provided on both sides of the protruding portion, the grease of the bearing can be prevented from being scattered and transferred to a clean magnetic disk area.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure of a brushless motor used in a magnetic disk device in the OA field, which requires a small size and a thin shape.

[0002]

[Prior art]

 Generally, in a magnetic disk device in the OA field, if dust adheres to or collides with a very narrow gap between the magnetic disk and the magnetic head, the operation will be hindered during data writing and reading, so a magnetic disk is mounted. The brushless motor keeps the magnetic disk area clean by enclosing the entire motor to which the magnetic disk is attached in a sealed case to prevent dust from entering.

In recent years, with the trend of downsizing of computers used in magnetic disk devices, there has been an increasing demand for miniaturization, thinness, low noise, low power consumption, and large capacity. The gap between the magnetic disk and the magnetic head during rotation is currently about 0.2 μm, but this gap will become smaller in the future to achieve higher density.

Among them, in a brushless motor that rotationally drives a magnetic disk, it is impossible to supply oil to the bearing with the magnetic disk attached, and thus a grease-filled type bearing is used.

Hereinafter, a conventional brushless motor will be described with reference to the drawings. FIG. 3 shows a cross-sectional view of a conventional brushless motor (hereinafter abbreviated as a motor). In FIG. 3, reference numeral 11 denotes a circular bracket made of aluminum. A fixed shaft 12 made of stainless steel is press-fitted and fixed in a hole at the center of the bracket 11, and the printed board 4 is adhered to the inner surface of the bracket 11. It is fixed. Reference numeral 2 denotes a stator core whose both end surfaces are coated with an insulating member 21 made of epoxy resin, and an exciting winding 3 is wound around the stator core 2. The stator core 2 is fixed to the bracket 11 side of the fixed shaft 12 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. . A fixing member 7 for positioning the disc spring 6 is attached to the side opposite to the bracket of the stator core 2 attached to the fixed shaft 12.

Reference numeral 1 denotes a rotor, and a magnet 10 is inserted and bonded to a first inner peripheral portion 9 of a hub 8 made of a cylindrical iron-based material having an outer diameter portion 5 of the magnetic disk 28 that can be installed. Then, the upper bearing 15a and the lower bearing 15b are attached to the second inner peripheral portion 13 of the hub 8 via the spacer 14 at positions axially separated from each other, and the partial assembly of the rotor 1 is completed.

Then, in the rotor 1, after two disc springs 6 are inserted into the fixed member 7 fixed to the fixed shaft 12, the inner rings of the upper bearing 15 a and the lower bearing 15 b are located at the center of the bracket 11. After being inserted into the fixed shaft 12, a preload is applied to bond them. The rotor 1 having the magnet 10 is rotatably supported by a fixed shaft 12 fixed to a bracket 11 as a fulcrum.

A magnetic fluid seal 17 is placed on the upper portion of the upper bearing 15 a via a member 16, and a magnetic fluid 18 is injected to seal between the upper bearing 15 a and a magnetic disk area 29. The grease of the bearing generated from the upper bearing 15a is prevented from being scattered and transferred to the clean magnetic disk area 29 to prevent the magnetic disk area 29 from being contaminated.

The fluid scattering prevention cover 19 attached to the upper part of the magnetic fluid seal 17 prevents the magnetic fluid 18 from scattering to the vicinity of the magnetic disk even if the magnetic fluid 18 scatters due to the centrifugal force during rotation of the motor. It is provided to do so.

In addition, the flange 33 of the hub 8 has a labyrinth structure in which an annular third protruding portion 27 and a fourth protruding portion 34 formed in a part of the bracket 11 are formed with a small gap therebetween. Has become.

The labyrinth blocks the air flow between the bearing space 31 having the bearing and the magnetic disk area 29, and the grease of the bearing generated from the lower bearing 15b is scattered and transferred to the clean magnetic disk area 29. This prevents the magnetic disk area 29 from being contaminated.

[0012]

[Problems to be solved by the device]

 However, in the above-mentioned conventional configuration, dust can be prevented from entering the magnetic disk area from the outside, but the speed of the motor is increased to shorten the access time (generally 3600 rpm, but recently 4400 rpm, or 5400 rpm, etc. are required.) Then, the grease of the bearing is scattered during rotation, and the oil adheres to the magnetic disk, which tends to impair the function of the magnetic disk device and cause malfunction. .

Further, in order to block the air flow, it is desirable to reduce the gap area 35 (gap L1) of FIG. 4 showing the XX portion of FIG. 3, but in order to reduce the gap L1, There is a problem in that it is necessary to improve the machining accuracy of the third protrusion portion 27 and the fourth protrusion portion 34, and the cost becomes high. Further, if the gap L1 is made small, the heat generated in the stator core 2 during rotation is transferred to the third protruding portion 27 and the fourth protruding portion 34, and these heat expand and mechanical contact occurs. Had.

The present invention solves the above-mentioned conventional problems, and provides a high-quality and inexpensive brushless motor capable of preventing the grease of the bearing from scattering and moving to a clean magnetic disk area even at high speed rotation. With the goal.

[0015]

[Means for Solving the Problems]

 In order to achieve this purpose, the brushless motor of the present invention has an axial direction with a minute gap between the outer diameter of the lower bearing and the third inner peripheral portion of the hub, and the first protrusion attached to the fixed shaft. A holder having an extended second annular annular projection and a flat portion for positioning a disc spring for preloading the bearing is formed between the disc spring and the stator.

[0016]

[Action]

 With the above-described structure, the present invention forms a labyrinth with a minute gap between the second protrusion of the holder, the outer diameter of the lower bearing, and the third inner circumference of the hub, thereby blocking the air flow. It is possible to prevent the grease of the bearing from scattering to the clean magnetic disk area.

[0017]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 are sectional views of a motor according to an embodiment of the present invention. The same parts as those of the conventional structure are denoted by the reference numerals in the conventional example, and the description thereof will be omitted. In FIGS. 1 and 2, reference numeral 26 denotes a holder, which is attached to the fixed shaft 12 fixed in the central hole of the bracket 11, the outer diameter of the lower bearing 15b, and the third inner peripheral portion of the hub 8. The second projection portion 23 extends in the axial direction of the ring while having a minute gap 25 in it, and the flat portion 24 for positioning the disc spring 6 for preloading the lower bearing 15b. .

The first protruding portion 22 of the holder 26 is attached to the lower side of the fixed shaft, that is, the upper position of the stator core 2 attached to the bracket 11 side. The second protrusion portion 23 of the holder 26 forms a minute gap 25 in the axial direction between the outer diameter of the lower bearing 15b and the third inner peripheral portion 20 of the hub 8. And this minute gap constitutes a labyrinth.

[0020]

EFFECTS OF THE INVENTION The present invention has the above-described structure to form a labyrinth with a minute gap between the second protruding portion of the holder, the outer diameter of the lower bearing and the third inner peripheral portion of the hub, thereby allowing air to flow. The bearing grease can be prevented from scattering to the clean magnetic disk area. Therefore, it is possible to reduce the malfunctions and malfunctions of the magnetic disk device, which have been caused by the generated grease that is attached to the gap between the magnetic disk and the magnetic head.

Regarding the clearance area, since the outer diameter of the second protruding portion forming the labyrinth can be made smaller than the outer diameter of the fourth protruding portion of the motor in the conventional example, it is possible to reduce the clearance area for the same clearance L1. it can. Further, if the gap area is the same, it is possible to widen the gap, and it is not necessary to improve the machining accuracy of the second protrusion portion, so that a cheap motor can be provided. Further, since the gap can be made larger than that of the conventional motor, it is possible to prevent mechanical contact of the labyrinth portion and provide a motor of stable quality.

[Brief description of drawings]

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

2 is a partial cross-sectional view for explaining a holder portion in the motor of FIG.

FIG. 3 is a sectional view of a conventional motor

FIG. 4 is a bottom view of the XX partial cross section of FIG. 3;

[Explanation of symbols]

 2 stator core 3 excitation winding 5 outer diameter portion 6 disc spring 8 hub 9 first inner peripheral portion 10 magnet 11 bracket 12 fixed shaft 13 second inner peripheral portion 15a upper bearing 15b lower bearing 17 magnetic fluid seal 20 third inner peripheral portion 22 1st protrusion part 23 2nd protrusion part 24 Flat part 25 Micro gap 26 Holder 29 Magnetic disk area

Claims (1)

[Scope of utility model registration request] 1. A first hub having an outer diameter portion for mounting at least one magnetic disk in a magnetic disk area.
A magnet fitted into the inner peripheral portion, a stator core fixed to a fixed shaft that is opposed to the magnet with a gap and is press-fitted into a hole at the center of the bracket, and an excitation winding wound around the stator core. And two magnetic bearings inserted into the second inner peripheral portion of the hub, a magnetic fluid seal disposed on the upper bearing of the bearing, and a first protrusion portion attached to the fixed shaft. ,
It has a concentric ring-shaped second protrusion that extends in the axial direction with a minute gap between the outer diameter of the lower bearing and the third inner peripheral portion of the hub, and a disc spring for applying a preload to the bearing. A brushless motor having a holder that also has a flat portion for positioning.