JP2003061295A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for inexpensively sealing a rolling bearing regardless of a thin spindle motor. SOLUTION: In the spindle motor 1, a rotor hub 6 is supported rotatably by a shaft 3 on a substrate 2 via a rolling bearing 4, and an annular cap 9 is filled into an annular space that is surrounded by the outer periphery surface of the shaft, the upper end face of the bearing, and the inner periphery surface of the rotor hub. In the spindle motor 1, an annular inner projection 9a and an outer projection 9b that project downward are formed at the inner and outer ends of the cap. A first annular recess 3b that is open upward is provided between the inner wheel of the baring and the outer periphery surface of the shaft. A second annular recess 6d that is open upward is provided between the outer wheel of the bearing and the inner periphery surface of the rotor hub. At the same time, the inner and outer projections are accommodated in the first and second annular recesses, respectively. Additionally, the inner projection is clamped and fitted to the inner wheel of the bearing. Then, the outer projection is not contact with any of the outer wheel of the bearing and the rotor hub.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor, and can be suitably used for a thin spindle motor such as a hard disk drive motor.

[0002]

2. Description of the Related Art Generally, a spindle motor for driving a hard disk has a shaft b provided vertically on a substrate a and a rolling bearing c having an inner ring fixed to the shaft b as shown in FIG.
The rotor hub d is rotatably supported by the shaft b via the shafts 1 and c2. For the rolling bearings c1 and c2,
Grease is filled so that a large number of balls or rollers interposed between the inner and outer rings can rotate smoothly. If the fine particles of the grease scatter when the rotor hub d rotates and adhere to the hard disk, a data crash occurs. Therefore, it is necessary to prevent the grease from leaking out of the motor.

As a means for preventing grease leakage, a base plate a having a shaft b is originally provided below the rolling bearings c1 and c2 as described above, and the gap between the base plate a and the rotor hub d becomes a labyrinth to form a labyrinth seal. Also serves as. On the other hand, since the substrate a does not exist above the rolling bearings c1 and c2, the outer peripheral surface of the shaft b, the upper end surface of the upper bearing c1 and the inner peripheral surface of the rotor hub d are exclusively used to prevent grease leakage. The annular seal members e1 and e2 in the annular space surrounded by
Alternatively, a structure in which a cap (not shown) is loaded is known. When loading the seal members e1 and e2, a labyrinth structure is formed on the seal members e1 and e2 themselves. When mounting the cap, the cap is tightly fitted to one of the shaft and the rotor hub, and the gap between the cap and the other is made minute enough to prevent grease from leaking.

[0004]

However, since the above-mentioned seal member forms a labyrinth by combining the fixed seal member e1 fixed to the shaft b and the rotary seal member e2 fixed to the rotor hub d, it is inevitable. However, the shape is complicated, the manufacturing cost is high, and the loading operation is complicated. Further, since the thin spindle motor cannot increase the axial length of the seal member, it is difficult to form a sufficient labyrinth.

On the other hand, when the cap is loaded, the precision of the above-mentioned minute gap is determined not only by the precision of the cap but also by the precision of the outer peripheral surface of the shaft and the inner peripheral surface of the rotor hub, resulting in high manufacturing cost. In addition, since a thin spindle motor cannot increase the axial length of the cap, it is difficult to secure a sufficient axial length of the minute gap to the extent that it can be contained in the gap even if the grease scatters. Therefore, an object of the present invention is to provide a structure capable of inexpensively sealing a rolling bearing even with a thin spindle motor.

[0006]

In order to solve the problem, in a spindle motor of the present invention, a shaft is vertically provided on a substrate, and a rotor hub is rotatably supported on the shaft via a rolling bearing. In a spindle motor in which an annular cap is mounted in an annular space surrounded by the outer peripheral surface of the shaft, the upper end surface of the bearing and the inner peripheral surface of the rotor hub,
An annular inner protrusion and an outer protrusion that protrude downward are formed on the inner edge and the outer edge of the cap, respectively, and a first annular recess that opens upward is provided between the inner ring of the bearing and the outer peripheral surface of the shaft. A second annular recess that opens upward is provided between the outer ring and the inner peripheral surface of the rotor hub, the inner protrusion and the outer protrusion are housed in the first and second annular recesses, respectively, and the inner protrusion is a shaft or It is characterized in that it is tightly fitted to the inner ring of the bearing, and the outer protrusion is not in contact with either the outer ring of the bearing or the rotor hub.

According to the spindle motor of the present invention, since the inner projection of the cap is tightly fitted to the inner ring of the shaft or the bearing, the radial position of the cap is determined by it. Since the outer protrusion of the cap is housed in the second annular recess without contacting either the outer ring of the bearing or the rotor hub, the upper end surface of the bearing is covered with the cap and the annular recess not in contact with the outer protrusion. And form a labyrinth seal. In this labyrinth seal, the cap serves as only one sealing member of the labyrinth, and the other sealing member also serves as the bearing or the rotor hub, so that the cap itself can be thin. Therefore, even a thin spindle motor can sufficiently form the labyrinth in the axial direction. Moreover, since the shape of the cap is simple, it is easy to process and load.

As a method of providing the first and second annular recesses, for example, (1) the thickness of the inner ring is made different in the axial direction so that the inner diameter of the inner ring of the bearing is larger than the outer diameter of the shaft only at the upper end. As a result, the space formed between the upper end of the inner ring and the outer peripheral surface of the shaft is defined as a first annular recess. (2) The outer ring of the outer ring of the bearing has a smaller outer diameter than the inner diameter of the rotor hub. It is possible to make the space formed between the upper end of the outer ring and the rotor hub the second annular recess by varying the thickness in the axial direction, but the thickness of the inner ring and the outer ring is originally the outer diameter of the shaft. Since it is smaller than the thickness of the rotor hub and the thickness of the rotor hub, it is preferable that the thickness is uniform from the viewpoint of strength.

Therefore, (3) the outer diameter of the upper end portion of the shaft is made smaller than the inner diameter of the bearing, and the space formed by the small outer diameter portion and the inner ring serves as the first annular recess, and (4) the rotor hub It is preferable that the inner diameter of the upper end portion is larger than the outer diameter of the bearing, and the space formed by the large inner diameter portion and the outer ring is the second annular recess. Further, since the thickness of the rotor hub is considerably larger than the radius of the shaft and the thickness of the inner and outer rings, by providing the annular recess with such a configuration, the labyrinth can have a large overall length and the sealing performance can be improved. You can The bearing preferably has an outer ring whose axial dimension is larger than that of the inner ring. This is because the labyrinth gap between the outer protrusion and the outer ring can be elongated in the axial direction.

In the spindle motor of the present invention, the substrate and the rotor hub have a labyrinth seal effect below the bearing as described above. To further enhance the effect, it is preferable that the substrate and the rotor hub have the following shapes. That is, the board has an inner plate having a flange protruding upward at the outer edge while standing the shaft, and a hole into which the inner plate is fitted, and a flange joined to the flange of the inner plate at the inner edge of the hole. It shall consist of an outer plate.

On the other hand, the rotor hub has a third annular recess which is open downward in the radial direction from the bearing. Then, both flanges are housed without contacting the third annular recess. With this structure, a labyrinth-like gap is formed between the third annular concave portion and both flanges, the labyrinth sealing effect is improved, and the inner plate and the outer plate are simply butted and compared to each other. A large joint surface between the inner plate and the outer plate can be secured, and the joint strength between the both plates increases. Furthermore, the rotor hub is usually supported on the shaft via two rolling bearings arranged in the axial direction. In such a case, in the present invention, it is the upper bearing that forms the labyrinth gap between the bearing or the rotor hub, but if the lower rolling bearing is provided below the upper bearing so as to contact the lower bearing, Since it is easy to apply to a motor having a small size, and the upper and lower bearings mutually determine axial positions, it is not necessary to provide positioning means on the outer circumference of the shaft or the inner circumference of the rotor hub, which is preferable.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 FIGS. 1 and 2 show an embodiment of a spindle motor of the present invention.
Will be described with reference to. FIG. 1 is an axial sectional view showing a spindle motor according to an embodiment, and FIG. 2 is an enlarged view of a II portion of FIG.

The spindle motor 1 comprises a substrate 2 and a shaft 3. Inner rings 4a, 5a of an upper ball bearing 4 and an lower ball bearing 5 are axially and tightly fitted to the shaft 3 on the axially upper side and axially lower side, respectively. Then, the rotor hub 6 is tightly fitted to the outer rings 4b, 5b of the upper ball bearing 4 and the lower ball bearing 5, so that the rotor hub 6 passes through the both ball bearings 4, 5 and the shaft 3
It is rotatably supported with respect to. Double ball bearings 4, 5
Indicates that the outer ring 4b, 5b has the axial dimension of the inner ring 4a, 5a.
Of the outer races 4b, 5b so that the facing end faces of the outer races 4b, 5b are in contact with each other.

The substrate 2 is an inner plate 2a on which the shaft 3 is erected vertically.
And an annular outer plate 2b arranged outside thereof and fitted to the inner plate 2a, the shaft 3 being fixed on the center of the inner plate 2a,
The stator 7 is fixed on the main surface of the outer plate 2b. A flange 2c protruding upward is formed on the outer edge of the inner plate 2a. Further, a flange 2d protruding upward is also formed on the inner edge of the outer plate 2b, and at the same time when the inner plate 2a and the outer plate 2b are fitted (after fitting?), These flanges 2c,
2d are pressed against each other.

The rotor hub 6 extends radially outward along the surface of the substrate 2, and has flanges 2c, 2 on its lower surface.
An annular recess 6a for housing d and an annular recess 6b for housing the stator 7 are provided. A magnet 8 is attached to the inner surface of the recess 6b so as to face the outer peripheral surface of the stator 7. The upper end surface of the upper ball bearing 4 is made lower than the upper end surfaces of the shaft 3 and the rotor hub 6, and in a space surrounded by the outer peripheral surface of the shaft 3, the upper end surface of the upper ball bearing 4 and the inner peripheral surface of the rotor hub 6, A cap 9 which is concentric with the shaft 3 has an upper ball bearing 4
Is loaded so as to cover the upper ball bearing 4 without contacting the upper end surface of the.

The ball bearings 4 and 5 are filled with grease (not shown), but as described above, the lower ball bearing 5 exists below the upper ball bearing 4, and below the lower ball bearing 5 and the substrate. Since it is finally communicated to the outside through a labyrinth-shaped gap between the upper surface of 2 and the upper surface of 2, the labyrinth seal effect is produced, and the grease hardly leaks out of the motor from below the ball bearings 4 and 5.

On the other hand, in order to prevent grease from leaking to the outside from above the ball bearings 4 and 5, the following measures are taken in this embodiment. First, as shown in FIG. 2, the shaft 3 has an outer diameter smaller than the inner diameter of the bearing 4 from the upper end to at least a position lower than the upper end of the inner ring 4a. An annular concave portion 3b that opens upward is formed between the concave portion 3b and 4a. Further, the rotor hub 6 also has at least the outer ring 4 from the upper end.
The inner diameter is made larger than the outer diameter of the bearing 4 up to a position below the upper end of b, and another annular recess 6d that opens upward is formed between the large inner diameter portion 6c and the outer ring 4b due to the difference in diameter machining. Has been formed.

An annular inner protrusion 9a and an outer protrusion 9b are formed on the inner and outer edges of the cap 9 and project downward.
Are formed respectively. The inner diameter of the cap 9 is substantially equal to the outer diameter of the small outer diameter portion 3a, the inner peripheral surface of the cap 9 and the small outer diameter portion 3a are tightly fitted, and the end surface of the inner protrusion 9a is stepped by the small outer diameter portion 3a. By hitting 3c,
A cap 9 is fixed to the shaft 3. Therefore, the wall thickness of the inner protrusion 9a need only be such that the inner protrusion 9a is housed in the recess 3b and can withstand tight fitting with the small outer diameter portion 3a, and strict accuracy is not required. Further, the outer protrusion 9b is housed in the recess 6d in a non-contacting state with neither the upper ball bearing 4 nor the rotor hub 6, but with the outer peripheral surface of the upper ball bearing 4 and the inner peripheral surface of the rotor hub 6. Is designed to have a predetermined minute gap.

In this way, the upper ball bearing 4 is present above the lower ball bearing 5, and above the upper ball bearing 4 is the minute gap between the inner peripheral surface of the outer projection 9b and the outer peripheral surface of the upper ball bearing 4, and the end surface of the outer projection 9b. The labyrinth seal effect is produced because the passage to the outside finally passes through a labyrinth-like passage formed of a gap between the bottom of the recess 6d and a small gap between the outer peripheral surface of the outer protrusion 9b and the large inner diameter portion 6c of the rotor hub 6. Grease rarely leaks out of the motor from above 4 and 5. Moreover, in this case, the cap 9 serves only as one sealing member of the labyrinth, and the other sealing member is the upper ball bearing 4 (specifically, the outer ring 4b) and the rotor hub 6 (specifically, the large inner diameter portion 6c). , The cap 9 itself is thin enough. Therefore, even the thin spindle motor 1 as shown in the drawing can sufficiently form the labyrinth in the axial direction. Moreover, since the shape of the cap is simple, it is easy to process and load.

Embodiment 2 Another embodiment of the spindle motor of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a portion corresponding to FIG. 2 in the first embodiment, and the other portions are basically the same in shape and quality as those in the first embodiment, and therefore description and illustration thereof are omitted. Further, regarding the reference numerals of the drawings, the same reference numerals are used for the constituent elements corresponding to the constituent elements of the spindle motor of the first embodiment.

As shown in FIG. 3, the upper end surface of the upper ball bearing 4 is made lower than the upper end surfaces of the shaft 3 and the rotor hub 6 as in the first embodiment, and the outer peripheral surface of the shaft 3 and the upper ball bearing 4 are The shaft 3 is provided in the space surrounded by the upper end surface and the inner peripheral surface of the rotor hub 6.
A concentric annular cap 9 is loaded so as to cover the upper ball bearing 4 without contacting the upper end surface of the upper ball bearing 4. Further, the outer protrusion 9b is housed in the recess 6d in a non-contacting state with neither the upper ball bearing 4 nor the rotor hub 6, but with the outer peripheral surface of the upper ball bearing 4 and the inner peripheral surface of the rotor hub 6. Is designed to have a predetermined minute gap. This point is also the same as the first embodiment.

However, the cap 19 is fixed to the inner ring 4a by tightly fitting the inner protrusion 9a and the inner ring 4a, and the inner protrusion 9a and the small outer diameter portion 3a of the shaft 3 are not in contact with each other. . Therefore, the small outer diameter portion 3a and the inner protrusion 9
It is not necessary to make dimensional accuracy with a strict.

Also in this embodiment, similarly to the first embodiment, the upper ball bearing 4 is present above the lower ball bearing 5, and the upper part thereof is located between the inner peripheral surface of the outer protrusion 9b and the outer peripheral surface of the upper ball bearing 4. Since a minute gap, a gap between the end surface of the outer protrusion 9b and the bottom of the recess 6d, and a minute gap between the outer peripheral surface of the outer protrusion 9b and the large inner diameter portion 6c of the rotor hub 6, finally reach the outside. , The labyrinth seal effect occurs,
Grease rarely leaks out of the motor from above the ball bearings 4 and 5. Moreover, since the cap 9 serves only as one sealing member of the labyrinth, the cap 9 itself is thin and sufficient, and is easy to process.

[0024]

As described above, according to the structure of the present invention, the cap loaded above the rolling bearing for the purpose of sealing serves as only one sealing member of the labyrinth, and the other sealing member is the bearing. Alternatively, since the rotor hub also serves, the labyrinth seal effect can be exhibited even if the cap has a thin and simple shape. Therefore, even with a thin spindle motor, the rolling bearing can be sealed at low cost.

[Brief description of drawings]

FIG. 1 is an axial sectional view showing a spindle motor according to a first embodiment.

FIG. 2 is an enlarged view of a portion II in FIG.

FIG. 3 is an axial sectional view showing a main part of a spindle motor according to a second embodiment.

FIG. 4 is an axial sectional view showing a conventional spindle motor.

[Explanation of symbols]

1 Spindle motor 2 substrates 3 axes 4 Upper ball bearing 5 Lower ball bearing 6 rotor hub 7 Stator 8 magnets 9 cap 9a inner protrusion 9b Outer protrusion

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H605 AA02 BB05 BB10 BB17 BB19                       CC04 DD03 DD05 DD17 EA05                       EA06 EB10 EB28 EB33                 5H621 HH01 JK08 JK10 JK19

Claims (5)

[Claims] 1. A shaft is vertically provided on a substrate, and a rotor hub is rotatably supported on the shaft via a rolling bearing.
In a spindle motor in which an annular cap is loaded in an annular space surrounded by the outer peripheral surface of the shaft, the upper end surface of the bearing, and the inner peripheral surface of the rotor hub, an annular inner protrusion protruding downward at the inner edge and the outer edge of the cap. And an outer protrusion, each of which has a first annular recess that opens upward between the inner ring of the bearing and the outer peripheral surface of the shaft, and opens upward between the outer ring of the bearing and the inner peripheral surface of the rotor hub. A second annular recess is provided, an inner protrusion and an outer protrusion are respectively housed in the first and second annular recesses, the inner protrusion is tightly fitted to the inner ring of the shaft or the bearing, and the outer protrusion is the outer ring of the bearing. A spindle motor characterized in that it is not in contact with either the rotor hub or the rotor hub. 2. The outer diameter of the upper end portion of the shaft is smaller than the inner diameter of the bearing, the small outer diameter portion and the inner ring form the first annular recess, and the inner diameter of the upper end portion of the rotor hub is smaller than that of the bearing. The spindle motor according to claim 1, wherein the spindle motor is larger than the outer diameter, and the second annular recess is formed by the large inner diameter portion and the outer ring. 3. The spindle motor according to claim 1, wherein, in the bearing, the outer ring has a larger axial dimension than the inner ring. 4. The substrate is formed with an inner plate having an outer edge and a flange protruding upward at the outer edge and a hole for fitting the inner plate. The inner edge of the hole is joined to the flange of the inner plate. The rotor hub has a third annular recess that is open downward in the radial direction outside the bearing, and both flanges are accommodated without contacting the third annular recess. Claims 1-3
The spindle motor according to any one of 1. 5. A spindle motor according to claim 1, wherein a second rolling bearing is provided below the bearing so as to be in contact therewith.