JPH03283142A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To prevent the release of the dust generated from ball bearings and to facilitate and flatten assembly by providing sealing means to provide a labyrinth effect between the annular wall part provided on a rotor and the annular wall part of a motor housing rotated by maintaining the state facing the above- mentioned wall part in proximity thereto. CONSTITUTION:The annular wall parts which face in proximity to each other and extend in the axial direction of the rotor 36 are positioned around the ball bearing 43 and are respectively provided on the rotor 36 and the motor housing 31. The air tending to pass the spacing between the wall parts 34 facing each other and the sealing part 39a of the peripheral wall part 39 is rapidly expanded in a hollow groove 47 and the pressure thereof is dropped, by which the kinetic energy is reduced. The dust released from the ball bearing 43 is prevented from passing the spacing between the wall parts 34 provided around the ball bearing 43 and the sealing part 39a of the peripheral wall part 39 by such labyrinth effect. The motor is flattened in this way and the number of the parts of the motor is reduced, by which the construction is simplified and the assembly is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC brushless motor used for spindle motors of hard disk drives, scanner motors for laser beam printers, and the like.

[Prior Art] FIG. 4 shows an example of a conventional DC brushless motor for an integrated disk drive device. This motor is of a type in which the hub 2 of the rotor 1 does not have a rotor shaft in its center.

That is, a fixed shaft 5 is fitted and attached to a shaft portion 4 integral with the motor housing 3, and a stator 6 is attached to the outer periphery of the intermediate portion of this shaft 5. The hub 2 is rotatably supported on the fixed shaft 5 via a pair of ball bearings 7.8 disposed at its upper and lower ends. The hub 2 is formed from a hub body 2a and a hub end plate 2b. In FIG. 4, 9 is a rotor magnet, 10 is a shield case to which the motor is attached, and A is a sealed internal space of the shield case 10. At least one magnetic disk is attached to this DC brushless motor by fitting into the peripheral wall 2c of the hub 2.
It is designed to rotate at a rotational speed of pm.

FIG. 5 shows another example of a conventional DC brushless motor for a hard disk drive. This motor is of a type in which a hub 12 of a rotor 11 has a rotor shaft 13 in its center, and this rotor shaft 13 is rotatably supported by a motor housing 16 via a pair of ball bearings 14,15.

That is, the rotor shaft 13 is rotatably supported inside a cylindrical portion 17 that is integrated with the motor housing 16 via a pair of ball bearings 14 and 15, and the stator 18 is attached to the outside of the cylindrical portion 17. ing. In FIG. 5, 19 is a rotor magnet, 20 is a shield case to which the motor is attached, and A is an internal space of the shield case 20.

This DC brushless motor includes a peripheral wall portion 12 of a hub 12.
At least one magnetic disk is fitted to the hub 12 and rotated together with the hub 12 at a rotational speed of 360 rpm.

This DC brushless motor is provided with a magnetic fluid seal 21 supported at the upper end of the cylindrical portion 17.

This seal 21 is arranged above the upper ball bearing 14 and seals between the cylindrical portion 17 and the root portion of the rotor shaft 13.

[Problems to be Solved by the Invention] Incidentally, in hard disk drives, it is required to further improve the recording density on the disk-shaped media (magnetic disks). It is theoretically known that one method for achieving this is to move a head that writes data information to or reads data from the medium as close as possible to the medium. For this purpose, it is necessary that the amount of dust contained in the internal space of the shield case that houses the media is below a certain level.

On the other hand, it is also known that grease is contained inside a ball bearing, and when the temperature of the ball bearing increases due to its operation, dust is emitted from the ball bearing using the grease as a source.

In the conventional motor shown in FIG. 4 above, the upper ball bearing 7
Since it directly faces the internal space A of the shield case 10, there is a problem in that dust emitted from the ball bearing 7 during operation enters the internal space A.

In this case, when the head is brought closer to the media, dust emitted from the ball bearing will be caught between them, causing a data crash. Therefore, the motor structure shown in FIG. 4 is inappropriate for further improving the recording density on media.

On the other hand, the conventional motor shown in FIG.
can be prevented from entering. However, since the magnetic fluid seal 20 is used, the number of parts is large, the assembly and structure are complicated, and the magnetic fluid seal 20
Since this requires a space for the motor, there is a problem in that the height dimension of the entire motor is large.

An object of the present invention is to provide a DC brushless motor that can prevent dust generated from ball bearings from being released to the outside with a simple structure, is easy to assemble, and can be made flat.

[Means for Solving the Problems] In order to achieve the above object, the DC brushless motor of the present invention includes a rotor having a storage section with an open bottom surface and a rotor magnet attached to the storage section; A motor housing having a support member in the center, a pair of ball bearings rotatably supporting the rotor with respect to the support member, and a stator housed in the housing and attached to the motor housing. The rotor and the motor housing are provided with annular wall portions that are closely opposed to each other and extend in the axial direction of the rotor, respectively, located around the ball bearing, and between these wall portions are provided annular wall portions that extend in the axial direction of the rotor. A sealing means is provided that performs air sealing by a labyrinth effect during rotation.

Further, in order to achieve the same object, the DC brushless motor of the present invention has a cylindrical part in the center and has an annular wall part around the cylindrical part extending in the axial direction of the cylindrical part. a housing, having an annular circumferential wall portion on the periphery that faces closely to the inner circumferential surface of the wall portion of the housing, and having an end wall that closes the upper end of the circumferential wall portion; a hub having a rotor shaft inserted into the cylindrical part in the center thereof and rotatably supported by the cylindrical part via a pair of ball bearings, and a rotor attached to the inner peripheral surface of the peripheral wall part of the hub. a rotor having a magnet; and a stator that is housed in a storage portion with an opening on the lower surface formed between a peripheral wall of the hub, a rotor shaft, and an end wall, and is attached to the motor housing, and The surface of either one of the annular wall of the motor housing and the annular circumferential wall of the rotor facing the other wall is a smooth surface, and the surface of the other wall is smooth. A concave groove extending throughout the circumferential direction on the opposite surface,
At least one is provided.

Furthermore, in order to achieve the same object, the DC brushless motor of the present invention has a fixed shaft connected to the center thereof, and an annular wall extending in the axial direction of the fixed shaft around the fixed shaft. a motor housing having an outer circumferential wall portion on its periphery, a center hole into which the fixed shaft is inserted, and an outer circumferential surface closely facing the inner circumferential surface of the annular wall so that the fixed shaft and inserted between the annular wall and -
an end wall having an annular inner circumferential wall rotatably supported by the fixed shaft via a pair of ball bearings inside the outer circumferential wall, and connecting the upper ends of both the inner and outer circumferential walls; A rotor comprising knobs each having a cover plate attached to the end wall so as to close the upper end opening of the center hole, and a rotor magnet attached to the inner circumferential surface of the outer circumferential wall of the hub. , a stator mounted to the motor housing and housed in a storage portion with a lower opening formed between the inner and outer wall portions and the end wall, the annular wall of the opposing motor housing; and the inner circumferential wall of the rotor, the surface of one of the walls facing the other wall is a smooth surface, and the surface of the other wall facing the smooth surface has a surface in the circumferential direction. At least one groove is provided throughout the entire surface.

[Function] In the DC brushless motor of the present invention, dust emitted from the ball bearing during its operation passes between the annular walls located around the ball bearing and facing each other in close proximity to the motor frame. and the hub.

However, when the rotor rotates, its annular wall (the circumferential wall of the hub or the inner circumferential wall of the hub) remains in close opposition to the annular wall of the motor housing. Dynamic pressure with different pressure values between parts is
They are formed axially adjacent to each other by sealing means.

In other words, a portion where the dynamic pressure is high and a portion where the dynamic pressure is low are consecutively provided. Therefore, in a portion where the dynamic pressure between the two walls is low, the air that is about to pass between the two walls can be rapidly expanded to lower the pressure and attenuate the kinetic energy of the air. . In other words, this labyrinth effect prevents the dust emitted from the ball bearing from leaking into the outside, such as the internal space of the shield case, through the space between the two walls provided around the ball bearing. .

The seal means provided in place of the magnetic fluid seal is formed by at least one groove on one of the opposing walls and a smooth surface on the other wall, and therefore does not require special parts. In addition, since this sealing means is located around the ball bearings rather than overlapping the pair of ball bearings, it does not cause an increase in the height of the motor.

Furthermore, in claim 2, since the sealing means is provided using the peripheral wall of the hub having a high peripheral speed, the dynamic pressure generated between both wall parts can be increased, and therefore the machining accuracy of the groove can be improved. Can be made lower.

Similarly, in claim 3, since the sealing means is provided using the inner circumferential wall provided on the hub without using the outer circumferential wall of the hub, the height for mounting the rotated member attached to the outer circumferential wall is increased. The height dimension is not limited, and a large height dimension for forming the sealing means can be ensured without being restricted by the above-mentioned rotated member.

[Example] Hereinafter, a DC brushless motor for a hard disk drive shown in FIGS. 1 and 2 will be described.

Reference numeral 31 in FIG. 1 is a motor housing attached to the shield case 32. A cylindrical portion 33 serving as a support member is integrally protruded from the housing 31 and is located at the center thereof. This cylindrical portion 33 has a cylindrical shape and is provided facing upward.

An annular wall portion 34 is integrally formed in the motor housing 31 so as to be located around the cylindrical portion 33 .

This wall portion 34 is formed to extend in the axial direction of the cylindrical portion 33, and its inner circumferential surface 34a is formed of a smooth surface. A stator 35 is attached to the outer surface of the cylindrical portion 33.

A rotor 36 including a hub 37 and a rotor magnet 38 is rotatably supported by the motor housing 31 . In other words, the hub 37 of the rotor 36 is an integral piece having a cylindrical peripheral wall portion 39, an end wall 4o, and a rotor shaft 41. The peripheral wall portion 39 extends in the axial direction of the cylindrical portion 33, and its upper end is closed by an end wall 40, and a rotor shaft 41 projects downward from the center of the end wall 40. . Therefore, the bubble 37 has a storage section 42 whose bottom surface is open. Such a rotor 36 is manufactured by inserting the rotor shaft 41 into the cylindrical portion 33, and
A pair of upper and lower ball bearings 43, 44 arranged between these two
It is rotatably supported via. In this attached state, the stator 35 is housed in the housing section 42.

The rotor magnet 38 is provided on the inner peripheral surface of the peripheral wall portion 39.
is attached to the outer surface of the peripheral wall portion 39,
A collar 45 protruding from and close to the upper end of the wall portion 34 is provided. A magnetic disk (not shown) as a rotated member is fitted and attached to a portion of the peripheral wall portion 39 above the collar 45 . Note that 46 in FIG. 1 is a threaded hole formed in the end wall 40, into which a screw (not shown) for fixing the magnetic disk is screwed.

The seal portion 39a below the collar 45 of the peripheral wall portion 39
It becomes. That is, the seal portion 39a is close to and opposed to the inner circumferential surface 34a of the wall portion 34. The gap G (see FIG. 2) between the opposing surfaces of both wall portions 34 and 39 is approximately 0.1 to 0.2 mm. A plurality of grooves 47 are provided on the outer circumferential surface of the seal portion 39a and serve as sealing means between the seal portion 39a and the wall portion 34. These grooves 47
is formed over the entire circumferential direction of the seal portion 39a. Then, as shown in FIG. 2, the depth B of each groove 47 is
is about 0.1 to 0.2 m, and the width C is about 0.1 to 0.2 m.
It is about 8m long. The width of the protrusion 48 formed between adjacent grooves 47 is approximately 0.4 m.

In the DC brushless motor for driving a disk having the above configuration, the ball bearing 43.44
Dust is emitted from the Among them, the lower ball bearing 44
Since the dust emitted from the shield case 31 is emitted outside the shield case 31, it does not pose a problem.

On the other hand, the dust emitted from the upper ball bearing 43 passes through the storage section 42 and then touches the wall 34 of the motor housing 31 and the peripheral wall 39 of the hub 37 of the rotor 36.
The shield case 3
There is a possibility of leakage inside the 2.

However, leakage of dust into the shield case 32 is prevented as follows.

That is, when the rotor 36 is rotated, the seal portion 39a of the peripheral wall 39 of the knob 137 is rotated while remaining close to and facing the wall 34 of the motor housing 31. Seal portion 3 of peripheral wall portion 39
Dynamic pressure is generated between the terminals 9a and 9a. In this case, the wall portion 34
Since the gap between the convex portion 48 and the convex portion 48 is narrow, a large dynamic pressure is generated therebetween, and between the concave groove 47 adjacent to the upper side of the convex portion 48 and the wall portion 34. Since the gear knobs of are wide, a small value of dynamic pressure is generated between them.

Therefore, air attempting to pass between the opposing wall portion 34 and the seal portion 39a of the peripheral wall portion 39 is rapidly expanded in the groove 47, its pressure is reduced, and its kinetic energy is attenuated. Due to this labyrinth effect,
The dust emitted from the ball bearing 43 is transferred to the seal portion 39a between the wall portion 34 and the peripheral wall portion 39 provided around the ball bearing 43.
It is prevented from passing between the In other words, the dust can be prevented from leaking into the internal space of the shield case 32. Therefore, the motor structure of this embodiment is suitable for promoting high-density recording on magnetic disks.

A wall portion 34 and a peripheral wall portion 39 are provided with sealing means.
The seal portion 39a is located around the ball bearings 43 and 44 rather than overlapping the pair of ball bearings 43 and 44, so it does not increase the height of the motor, and Since dust leakage can be prevented without using a magnetic fluid seal as described above, the height of the entire motor can be reduced and a flat motor can be obtained.

Moreover, the sealing means includes sealing portion 3 of peripheral wall portion 39.
The groove 47 provided in the groove 9a and the smooth inner circumferential surface 34 of the wall portion 34
Since it is formed from a and a, no special parts are required. Therefore, the number of parts can be reduced, the configuration can be simplified, and the number of assembly steps can be reduced, making it easy to assemble.

Moreover, since the circumferential wall portion 39 of the hub 37 is used as the wall portion of the hub 37 that faces the wall portion 34 of the motor housing 31, a large dynamic pressure can be generated by the circumferential wall portion 39 having a high circumferential speed. Therefore, even if the machining accuracy of the groove 47 is reduced, a large dynamic pressure is maintained between the wall portion 34 and the convex portion 48, and dust leakage can be reliably prevented.

Next, a second embodiment shown in FIG. 3 will be described.

Reference numeral 51 in FIG. 3 is a motor housing, and a fixed shaft 52 serving as a support member is provided in the center of the motor housing so as to pass through the motor housing in the vertical direction. The lower part of the fixed shaft 52, whose middle portion is connected to the housing 51, is fixed to a shield case 53 of the hard disk drive.

The motor housing 51 is provided with a cylindrical upward wall portion 54 extending in the axial direction of the fixed shaft 52 . This wall part 5
The inner circumferential surface 54a of No. 4 is formed of a smooth surface, and
A stator 55 is attached to the outer peripheral surface.

The fixed shaft 52 includes a hub 56 and a rotor magnet 5.
7 is rotatably supported.

That is, the hub 56 of the rotor 58 has a center hole 56a that penetrates in the vertical direction at its center, and has an outer circumferential wall 59, an inner circumferential wall 60, an end wall 61, and a cover plate 6.
2.

The parts other than the cover plate 62 are integrated, and the cover plate 62 is attached to the end wall 61 so as to close the upper end opening of the center hole 56a. The outer circumferential wall portion 59 has a cylindrical shape and has a cylindrical shape.
6, and the upper ends of this peripheral wall portion 59 and the inner peripheral wall portion 60 are integrally connected by an end wall 61. The inner peripheral wall portion 60 has a cylindrical shape extending in the axial direction of the fixed shaft 52 and is inserted between the wall portion 54 of the motor housing 51 and the fixed shaft 52. The inner and outer wall portions 59, 60 and the end wall 61 form a storage portion 63 whose lower surface is open.

The rotor 58 having such a configuration has the center hole 56a of the hub 56 fitted into the fixed shaft 52, and a pair of upper and lower ball bearings 64.6 disposed between the hub 56 and the fixed shaft 52.
5, is rotatably supported by a fixed shaft 52,
In this mounted state, the stator 55 is housed in the housing portion 63.

The rotor magnet 57 is attached to the inner circumferential surface of the outer circumferential wall 59, and a magnetic disk (not shown) as a rotated member is fitted and attached to the outer circumferential surface of the outer circumferential wall 59. It looks like this.

The outer circumferential surface of the inner circumferential wall portion 60 is the inner circumferential surface 5 of the wall portion 54.
4a and is opposed to it. Both wall portions 54, 6
The gap between the two opposing surfaces is about 0.1 to 0.2 degrees.

A plurality of grooves 66 are provided on the outer circumferential surface of the inner circumferential wall portion 60 to serve as a sealing means between the inner circumferential wall portion 60 and the wall portion 54 . These grooves 66 are formed over the entire circumferential direction of the inner peripheral wall portion 60. Note that the depth of each groove 66 is 0.1 to 0.
The length is about 2m, and the width is about 0.8m.
Further, the width of the convex portion 67 formed between adjacent grooves 66 is approximately 0.4 mm.

In the DC brushless motor for driving a hard disk having the above configuration, dust is emitted from the ball bearings 64 and 65 as the motor operates.
The cover plate 62 prevents dust emitted from the shield case 53 from entering the shield case 53.

On the other hand, the dust emitted from the lower bearing 65 passes between the wall 54 of the motor housing 51 and the inner circumferential wall 60 of the hub 56 of the rotor 58, and then passes through the storage section 63. There is a possibility of leakage into the inside of the shield case 53.

However, since leakage of dust into the shield case 53 is prevented by the labyrinth effect created by the sealing means between the walls 54 and 60, the intended purpose of the present invention can be achieved. Note that the details of preventing dust leakage by this labyrinth effect are the same as in the first embodiment, so
The explanation thereof will be omitted here.

Furthermore, in this second embodiment, since the sealing means is provided using the inner circumferential wall 60 provided on the hub 56, the height dimension for attaching the magnetic disk attached to the outer circumferential wall 59 is not limited. In addition, the height dimension for forming the sealing means, that is, the length of the inner circumferential wall portion 60 can be ensured to be large without being restricted by the magnetic disk.

The present invention is not limited to the above embodiments. For example, in each of the above embodiments, the grooves 47 or 66 are provided on the outer peripheral surface of the peripheral wall 39 or the inner peripheral wall 60 so that they can be easily machined. It may be formed on the peripheral surface.

In the present invention, it is sufficient to have at least one groove 47, 66, and the groove 47, 66 may be provided on both of the opposing walls 34, 39 or 54, 60. . In addition, when the present invention is applied to a scanner motor for a laser beam printer, the dust leakage prevention effect of the sealing means causes the polygon mirror, which is a rotated member attached to the hub, to become cloudy due to the dust emitted from the ball bearing. This can be prevented.

[Effects of the Invention] Since the present invention is configured as described above, it has the following effects.

In the DC brushless motor according to claim 1, there is provided a sealing means for creating a labyrinth effect between the annular wall provided on the rotor and the annular wall of the motor housing that is rotated while maintaining close opposition thereto. With this sealing means, the air is rapidly expanded in the area where the dynamic pressure between the two walls is low, reducing the pressure and attenuating the kinetic energy, so that the dust released from the ball bearing can be removed. ,
Since the structure prevents leakage between the two walls provided around the ball bearing, the magnetic fluid seal that was conventionally required can be omitted. Therefore, the motor can be flattened, and the sealing means is formed of at least one groove on one of the opposing walls and a smooth surface on the other wall, and does not require special parts. Since there are no parts, the number of parts in the motor can be reduced, the structure can be simplified, and assembly can be simplified.

Furthermore, in the brushless motor according to the second aspect, since the sealing means is provided by using the peripheral wall of the hub having a high peripheral speed, the dynamic pressure generated between both walls can be increased, and therefore the concave groove can be increased. This also has the effect of lowering machining accuracy.

Similarly, in claim 3, since the sealing means is provided using the inner circumferential wall provided on the hub without using the outer circumferential wall of the hub, the height for mounting the rotated member attached to the outer circumferential wall is increased. There is also an effect that the height dimension is not limited, and a large height dimension can be secured for forming the sealing means without being restricted by the above-mentioned rotated member.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, and FIG.
FIG. 1 is a longitudinal sectional view of the entire motor, and FIG. 2 is an enlarged sectional view showing the area around the seal portion. FIG. 3 is a longitudinal sectional view of the entire motor showing a second embodiment of the present invention. FIGS. 4 and 5 are longitudinal sectional views showing different conventional motors. 31.51...Motor housing, 33...Cylinder part (
support member), 34.54...wall part, 35.55...
・Stator, 36.58...Rotor, 37.56...
・Hub, 38.57...Rotor magnet, 39...
・Peripheral wall part, 40.61... End wall, 41... Rotor shaft, 42° 63... Storage part, 4B, 44.64.65.
・・Ball bearing 47.66 ・・Concave groove (sealing means), 52
. . . Fixed shaft (supporting member), 62 . . . Lid plate.

Claims (1)

[Scope of Claims] 1. A rotor having a storage part with an open bottom surface and a rotor magnet attached to the storage part, a motor housing having a support member in the center, and a motor housing having a support member in the center thereof; a pair of ball bearings rotatably supported by the rotor; and a stator housed in the housing and attached to the motor housing; A wall portion is provided on each of the rotor and motor housing to be located around the ball bearing, and a sealing means is provided between the two wall portions for air sealing by a labyrinth effect when the rotor rotates. DC brushless motor. 2. A motor housing having a cylindrical portion in the center and an annular wall extending in the axial direction of the cylindrical portion around the cylindrical portion; It has opposing annular peripheral walls on the periphery and an end wall that closes the upper end of the peripheral wall, and is inserted into the cylindrical part at the center of the end wall and is connected to the cylinder through a pair of ball bearings. A rotor including a hub having a rotor shaft rotatably supported by a cylindrical portion, a rotor magnet attached to the inner peripheral surface of the peripheral wall portion of the hub, the peripheral wall portion of the hub, the rotor shaft, and an end. a stator mounted to the motor housing and housed in a storage section with a lower opening formed between the stator and the motor housing; The surface of one of the walls facing the other wall is a smooth surface, and the surface of the other wall facing the smooth surface has at least one groove extending throughout the circumferential direction. A DC brushless motor characterized by: 3. A motor housing having a fixed shaft connected to the center thereof and having an annular wall extending in the axial direction of the fixed shaft around the fixed shaft; It has a center hole into which the fixed shaft is inserted, and is inserted between the fixed shaft and the annular wall with the outer circumferential surface facing closely to the inner circumferential surface of the annular wall, and is inserted through a pair of ball bearings. an end wall having an annular inner circumferential wall rotatably supported by the fixed shaft inside the outer circumferential wall, and connecting the upper ends of the inner and outer circumferential walls;
and a rotor comprising a hub each having a cover plate attached to the end wall thereof so as to close the upper end opening of the center hole, and a rotor magnet attached to the inner circumferential surface of the outer circumferential wall portion of the hub. a stator mounted to the motor housing and housed in a storage section with a lower opening formed between the inner and outer circumferential walls and the end wall; The surface of one of the inner circumferential walls of the rotor, which faces the other wall, is a smooth surface, and the surface of the other wall, which faces the smooth surface, extends over the entire circumferential direction. A DC brushless motor characterized by having at least one groove.