JPH11332201A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor which can securely prevent oil from leaking to the outside of the motor. SOLUTION: A gap 20 is formed between an upper bearing 5 and a cap 10. A difference 21 in level is provided on the lower surface of the cap 10 at a position about one third of the width of the cap 10 from its outer circumference so as to have the larger width of the gap 20 in the axial direction on an outer ring 5b side than that on an inner ring 5a side. For that purpose, the depth of a recess 11 formed in a hub 7 in order to fit the cap 10 to the hub 7 is selected to have the bottom of the recess 11 positioned above the position of the top surface of the outer ring 5b by a predetermined distance. With this constitution, the gap 20 which has a larger width in the axial direction on the outer ring 5b side than on the inner ring 5b can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor used for driving a magnetic disk such as a hard disk.

[0002]

2. Description of the Related Art A spindle motor used for driving a hard disk which is a magnetic disk is conventionally configured as shown in FIG. In FIG. 7, 1 is a base, 2 is an insertion hole formed in the center of the base 1, 3 is a shaft fitted in the insertion hole 2, 4 is a core 4a attached to the base 1 and wound around the core 4a. Winding 4b
Are upper bearings and lower bearings, which are fitted to the upper and lower ends of the shaft 3 in a state where the inner rings 5a and 6a are preloaded.

[0003] Reference numeral 7 denotes a hub made of a non-magnetic material such as aluminum and the like, on which the hard disk D is mounted, which is fitted to the outer races 5b and 6b of the dual bearings 5 and 6, and 8 denotes iron or the like attached to the peripheral edge of the lower end of the hub A rotor yoke 9 made of the magnetic material described above is mounted on the inside of the rotor yoke 8, and is a driving magnet disposed to face the stator 4, and 10 is a cylindrical cap covering the upper bearing 5. The cap 10 is fitted into the recess 11 on the upper surface of the hub 7 such that the shaft 3 is loosely inserted into the central through hole. At this time, in order to facilitate positioning at the time of assembling, the lower peripheral edge of the outer ring 5 of the upper bearing 5
b (see FIG. 8).

As described above, since the inner race 5a of the upper bearing 5 is externally fitted to the upper end of the shaft 3 in a state where a preload is applied, a gap is formed between the upper part of the inner race 5a and the lower surface of the cap 10. Further, between the inner peripheral surface of the cap 10 fitted in the recess 11 of the hub 7 as a rotating member and the shaft 3, a space is formed between the upper part of the inner ring 5a of the upper bearing 5 and the lower surface of the cap 10. A gap having an interval smaller than the gap is formed, and the rust-preventive oil of the upper bearing 5 and the base oil of the lubricating oil scatter and adhere to the disk D due to the pressure difference caused by the size of the gap between the two gaps. A so-called labyrinth seal structure for prevention is formed.

[0005]

However, in the case of the spindle motor having such a structure, the base oil of the rust-preventive oil and the lubricating oil that oozes from the upper bearing 5 when the motor rotates is used.
Due to the capillary action, the oil accumulates in the gap between the shaft 3 and the cap 10 (the elliptical portion indicated by the broken line in FIG. 8). This causes problems such as the inability to read and write information, which is a problem.

An object of the present invention is to provide a spindle motor that can reliably prevent oil leakage to the outside of the motor.

[0007]

In order to solve the above-mentioned problems, a gap is provided between the cap and the bearing, and the gap between the gap and the inner ring side of the bearing is different from that of the bearing. It is characterized by being different on the outer ring side.

[0008] According to such a configuration, a difference is generated in the pressure generated when the motor rotates between the inner ring side and the outer ring side of the bearing in which the gaps in the axial direction are different. However, the pressure at this time is
It is the sum of the atmospheric pressure, the pressure due to the airflow generated by the rotation of the rotating member, and the pressure due to the thermal expansion of the air.

[0009] By utilizing the flow of air due to such a pressure difference, it becomes possible to trap oil leaking from the bearings so as not to leak outside the motor.

Further, the present invention is characterized in that an axial interval of the gap on the outer ring side of the bearing is larger than an inner ring side of the bearing.

In this way, the pressure in the gap is
The outer ring side having a larger axial interval is lower than the inner ring side, and the air in this gap flows from the inner ring side having a higher pressure to the outer ring side having a lower pressure. On the other hand, the oil to be sealed moves radially outward due to the centrifugal force accompanying the rotation of the motor, and the movement of the oil due to the above-described air flow is opposite to the movement of the oil due to such a centrifugal force. In addition, oil is trapped between the outer ring side of the bearing and the cap.

[0012] Here, as the axial distance of the gap, for example, the axial distance between the inner ring and the cap of the bearing is at least about 1.5 times the step between the inner ring and the outer ring after preloading, and the outer ring of the bearing and the cap are Is preferably at least about 1.5 times the axial distance between the inner ring and the cap.

[0013] Further, according to the present invention, a gap is provided between the cap and at least an inner ring of the bearing, and a flange is provided on the shaft, and the flange is disposed in the gap. It is characterized by.

In this case, it is possible to prevent oil leaking from the bearing from leaking out of the motor through the wall surface of the shaft by the flange member.

Further, the present invention is characterized in that a gap larger than an axial distance between the flange member and the inner ring of the bearing is provided between the cap and the outer ring of the bearing.

With this configuration, the oil transmitted through the wall surface of the shaft can be shut off by the flange-shaped member, and the gap between the cap and the outer ring of the bearing having a large gap is utilized by utilizing the pressure difference based on the difference in the gap in the axial direction. Oil can be trapped in the motor, so that oil seeping out of the motor can be more effectively prevented.

Further, the present invention is characterized in that a gap is provided between the cap and at least the inner ring of the bearing, and a circumferential groove communicating with the gap is formed on a peripheral surface of the shaft. I have.

According to such a configuration, oil leaked from the bearing can be stored in the groove on the shaft peripheral surface due to the pressure difference between the gap between the shaft and the cap and the groove on the shaft peripheral surface. It is possible to prevent the seepage of oil into the oil.

At this time, if a gap larger than the gap in the axial direction of the gap is provided between the outer ring of the cap and the bearing, a gap between the cap and the outer ring of the bearing having a large gap is formed due to a pressure difference during rotation of the motor. Oil can be prevented from leaking to the outside of the motor.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described with reference to FIG. Note that the basic structure of the spindle motor in this embodiment is substantially the same as that shown in FIGS. 7 and 8, and therefore, the differences from FIG. 7 and FIG. Will be described.

As shown in FIG. 1, the upper bearing 5 and the cap 1
0, a gap 20 is formed on the lower surface of the cap 10 so that the gap in the axial direction of the gap 20 is larger on the outer ring 5b side than on the inner ring 5a side from the outer peripheral edge thereof. A step 21 is formed at the position. At this time, the depth of the recess 11 for fitting the cap 10 formed in the hub 7 is made shallower than in FIG. 8 so that the bottom 23 of the recess 11 is a predetermined amount larger than the upper end surface of the outer ring 5 b of the upper bearing 5. Is set to be located only above. By doing so, the axial interval on the outer ring 5b side of the gap 20 is set to a desired value. The axial distance of the gap 20 on the inner ring 5 a side is set to a desired value by adjusting the step 21 of the cap 10.

As described above, by increasing the axial interval of the gap 20 on the outer ring 5b side, the pressure of the outer ring 5b having a larger interval becomes lower than that of the inner ring 5a side. The air in the gap 20 flows from the inner ring 5a having a higher pressure to the outer ring 5b having a lower pressure. Here, the pressure is the sum of the atmospheric pressure, the pressure due to the air flow generated by the rotation of the hub 7 with respect to the shaft 3, and the pressure due to the thermal expansion of the air.

As shown in FIG. 1, the axial distance ta between the inner ring 5a of the upper bearing 5 and the cap 10 is about 1.5 times the step between the inner ring 5a and the outer ring 5b after the preload, and 5 between the outer race 5b and the cap 10 in the axial direction tb
Is about 1.0 of the axial distance ta between the inner ring 5a and the cap 10.
Each is set to five times.

The oil leaked from the upper bearing 5 moves radially outward due to centrifugal force accompanying the rotation of the motor. Therefore, the oil is trapped between the outer ring 5b of the gap 20 and the cap 10 by the movement of the oil due to the centrifugal force and the movement of the oil due to the flow of the air caused by the above-described pressure difference.

Therefore, according to the first embodiment, oil leaking from the upper bearing 5 can be trapped between the outer ring 5b of the gap 20 and the cap 10, and it is ensured that the oil leaks to the outside of the motor. Can be prevented.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. The basic structure of the spindle motor according to the present embodiment is the same as that of the first embodiment.
It is almost the same as the embodiment, except for the following points.

That is, as shown in FIG. 2, a step 25 is provided on the lower surface of the cap 10 at a position approximately one-half from the outer peripheral edge thereof, and the gap 20 between the upper bearing 5 and the cap 10 in the axial direction is reduced. The outer ring 5b is larger than the inner ring 5a. At this time, similarly to the above-described first embodiment, as shown in FIG. 2, the axial distance ta between the inner ring 5a of the upper bearing 5 and the cap 10 is determined by the difference in level between the inner ring 5a and the outer ring 5b after preloading. The axial distance tb between the outer ring 5b of the upper bearing 5 and the cap 10 is set to about 1.5 times the axial distance ta between the inner ring 5a and the cap 10, respectively.

Therefore, according to the second embodiment, the same effect as that of the first embodiment can be obtained.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIG. The basic structure of the spindle motor according to the present embodiment is the same as that of the first embodiment.
This embodiment is almost the same as that of the first embodiment except for the following points.

As shown in FIG. 3, a concave portion 30 is formed substantially two-thirds from the inner peripheral edge of the lower surface of the cap 10, and the outer peripheral edge of the lower surface of the cap 10 is formed on the outer race 5 of the upper bearing 5.
The cap 10 is fitted into the recess 11 of the hub 7 so as to abut on the upper surface of the hub b. Thus, the gap 32 is formed between the upper bearing 5 and the recess 30 of the cap 10.

A washer 34, which is a flange member, is fitted to the upper end of the shaft 3, and the cap 10 and the upper bearing 5 are fitted.
A washer 34 is disposed in the gap 32 between the first and second members. At this time, the axial distance tc between the washer 34 and the inner ring 5a of the upper bearing 5 is set to be about 1.5 times the step between the inner ring 5a and the outer ring 5b after the preload. The flange-shaped member is not particularly limited to the washer 34, and may be a member that can be fitted to the shaft 3 or a member that is formed integrally with the shaft 3 if possible.

Therefore, according to the third embodiment, by fitting the washer 34 to the shaft 3 and disposing it in the gap 32, the oil leaking from the upper bearing 5 by the washer 34 travels along the wall surface of the shaft 3. Can be prevented from seeping out of the motor.

(Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIG. The basic structure of the spindle motor according to the present embodiment is the same as that of the third embodiment.
This embodiment is almost the same as that of the first embodiment except for the following points.

As shown in FIG. 4, the cap 10 is fitted into the recess 11 of the hub 7 so that the gap between the outer peripheral edge of the lower surface of the cap 10 and the outer ring 5b of the upper bearing 5 is separated by te in the axial direction. I have. Thus, the gap 36 is also formed between the outer ring 5b of the upper bearing 5 and the cap 10.

However, the washer 34 provided in the gap 32
The axial distance td between the inner races 5a of the upper bearing 5 is equal to the axial distance td of the inner race 5a after the preload, as in the case of the third embodiment.
The axial distance te of the gap 36 between the outer ring 5b and the cap 10 is set to about 1.5 times the step of the outer ring 5b.
It is set to be about 1.5 times the axial distance td between a and the washer 34.

Therefore, according to the fourth embodiment, by fitting the washer 34 to the shaft 3 and disposing it in the gap 32, the oil leaking from the upper bearing 5 by the washer 34 travels along the wall surface of the shaft 3. To prevent the liquid from oozing out of the motor.
Oil that moves radially outward due to the pressure difference between 2 and 36 can be prevented from accumulating in the gap 36 between the outer ring 5b of the upper bearing 5 and the cap 10 and seeping out to the outside of the motor.

In the third and fourth embodiments, the case was described in which the washer 34 was fitted to the shaft 3 so as to block oil transmitted along the wall surface of the shaft 3. A washer is inserted into the recess 11 of the hub 7 or the recess 3 of the hub 7.
The oil transmitted through the 0 wall or the inner wall of the hub 7 may be blocked.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIG. Note that the basic structure of the spindle motor in this embodiment is substantially the same as that shown in FIGS. 7 and 8, and therefore, the differences from FIG. 7 and FIG. Will be described.

As shown in FIG. 5, the outer diameter of the portion of the shaft 3 facing the cap 10 is formed smaller than the outer diameter of the portion where the upper bearing 5 is fitted, that is, the inner diameter of the upper bearing 5. A circumferential groove 41 is formed in the circumferential surface of the shaft 3 so as to communicate with the gap 40 between the inner ring 5 a of the upper bearing 5 fitted and fitted outside and the cap 10.

As described above, the clearance 40 is formed on the peripheral surface of the shaft 3.
Is formed, a pressure difference is generated between the groove 41 and the gap between the shaft 3 and the cap 10 which are extremely narrow at the time of rotation of the motor, and the air flow caused by the pressure difference causes the upper bearing 5 to flow from the upper bearing 5. The leaked oil moves to the low pressure groove 41 and is trapped in the groove 41.

Therefore, according to the fifth embodiment, since oil can be trapped in the groove 41 formed on the peripheral surface of the shaft 3, it is possible to prevent the oil from seeping out of the motor.

(Sixth Embodiment) A sixth embodiment of the present invention will be described with reference to FIG. The basic structure of the spindle motor according to the present embodiment is the same as that of the fifth embodiment.
This embodiment is almost the same as that of the first embodiment except for the following points.

That is, as shown in FIG. 6, a step 44 is provided on the lower surface of the cap 10 at a position approximately one-half from the outer peripheral edge thereof, and the gap 45 between the upper bearing 5 and the cap 10 in the axial direction is The outer ring 5b is larger than the inner ring 5a. At this time, the axial distance tf between the inner ring 5a of the upper bearing 5 and the cap 10 is about 1.5 times the step between the inner ring 5a and the outer ring 5b after the preload, and the outer ring 5 of the upper bearing 5
The axial distance tg between b and the cap 10 is the inner ring 5a,
Each is set to about 1.5 times the axial interval tf between the caps 10.

In this case, due to a pressure difference between the gap between the shaft 3 and the cap 10 and the groove 41, oil leaked from the upper bearing 5 accumulates in the groove 41 on the peripheral surface of the shaft 3 and the rotation of the motor occurs. The oil is trapped between the outer ring 5b of the gap 45 and the cap 10 by the movement of the oil due to the centrifugal force and the movement of the oil due to the flow of air caused by the pressure difference based on the difference in the axial distance between the gaps 45.

Therefore, according to the sixth embodiment, it is possible to reliably prevent the oil leaking from the upper bearing 5 from seeping out of the motor.

In the fifth and sixth embodiments described above, the outer diameter of the portion of the shaft 3 facing the cap 10 is
Although the case where the outer diameter of the upper bearing 5 is smaller than the inner diameter of the portion where the upper bearing 5 is fitted is described above, the outer diameter of the shaft 3 need not be particularly changed in this way.

In the first, second, and sixth embodiments, the gap 2 provided between the upper bearing 5 and the cap 10 is provided.
0, 45 in the axial direction, the outer ring 5b
Although the case where the side is enlarged has been described, the outer ring 5b
By making the side larger, oil that moves outward in the gaps 20 and 45 due to centrifugal force at the time of motor rotation has the advantage that it tends to accumulate in the gap on the outer ring 5b side with a large gap, but the gaps 20 and 45 have an advantage. Is not necessarily the outer ring 5b
It is not necessary to make the side larger, and the inner ring 5a side may be made larger.

Further, the present invention is not limited to the above embodiments, and various changes other than those described above can be made without departing from the gist of the present invention.

[0049]

As described above, according to the first aspect of the present invention, when the motor rotates, a pressure difference is generated between the inner ring side and the outer ring side of the bearing having different gaps in the axial direction. Thereby, the oil leaked from the bearing can be trapped on the side where the gap is large, and it is possible to provide a spindle motor that can reliably prevent oil leakage to the outside of the motor.

According to the second aspect of the present invention, when the motor rotates, the pressure on the outer ring side where the gap is large in the axial direction becomes lower than that on the inner ring side, and the air in this gap flows to the outer ring side and flows from the bearing to the outer ring side. Oil leaks to the outer ring side,
A spindle motor that can trap oil leaked from the bearing between the outer ring side of the bearing and the cap in combination with the action of centrifugal force accompanying the rotation of the motor, and can reliably prevent oil leakage to the outside of the motor. Can be provided.

According to the third aspect of the present invention, the flange-shaped member can prevent oil leaking from the bearing from transmitting along the wall surface of the shaft, so that the spindle can reliably prevent oil leakage to the outside of the motor. It becomes possible to provide a motor.

According to the fourth aspect of the present invention, the oil is trapped in the gap between the cap and the outer ring of the bearing having a large gap by utilizing the pressure difference based on the difference between the gaps in the axial direction. This makes it possible to more effectively prevent oil from seeping out of the motor.

According to the fifth aspect of the present invention, oil leaked from the bearing can be accumulated in the groove on the shaft peripheral surface due to the pressure difference between the gap between the shaft and the cap and the groove on the peripheral surface of the shaft. Therefore, it is possible to provide a spindle motor that can reliably prevent oil leakage to the outside of the motor.

According to the sixth aspect of the present invention, by providing a gap with a large axial interval between the cap and the outer ring of the bearing, a gap between the cap and the bearing with a large interval is generated due to a pressure difference during rotation of the motor. It is also possible to store oil in the gap between the outer rings, and it is possible to more effectively prevent seepage of oil to the outside of the motor.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a first embodiment of the present invention.

FIG. 2 is a partially cut front view of a second embodiment of the present invention.

FIG. 3 is a partially cutaway front view of a third embodiment of the present invention.

FIG. 4 is a partially cut front view of a fourth embodiment of the present invention.

FIG. 5 is a partially cut front view of a fifth embodiment of the present invention.

FIG. 6 is a partially cut front view of a sixth embodiment of the present invention.

FIG. 7 is a cutaway front view of a spindle motor as a background of the present invention.

FIG. 8 is an enlarged view of a part of the motor of FIG. 7;

[Explanation of symbols]

 Reference Signs List 3 shaft 4 stator 5 upper bearing 5a inner ring 5b outer ring 7 hub 9 driving magnet 10 cap 20, 32, 36, 40, 45 gap 34 washer (flange member) 41 groove

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 19/20 G11B 19/20 E H02K 5/173 H02K 5/173 A

Claims (6)

[Claims] A shaft, a bearing externally fitted to the shaft, a hub attached to the shaft via the bearing, a driving magnet fixed to the hub,
A spindle motor comprising: a stator disposed to face the driving magnet; and a cap mounted on the hub so that the shaft is loosely inserted and covering the bearing. A spindle motor, wherein a gap is provided between the inner ring side and the outer ring side of the bearing. 2. The spindle motor according to claim 1, wherein an axial interval of the gap on an outer ring side of the bearing is larger than an inner ring side of the bearing. 3. A shaft, a bearing externally fitted to the shaft, a hub attached to the shaft via the bearing, and a driving magnet fixed to the hub.
A spindle motor comprising: a stator disposed to face the driving magnet; and a cap mounted on the hub so that the shaft is loosely inserted and covering the bearing, wherein at least the cap and the bearing are provided. A spindle motor, wherein a gap is provided between the inner ring and the inner ring, and a flange is provided on the shaft, and the flange is disposed in the gap. 4. A gap, which is larger than an axial distance between the collar member and the inner ring of the bearing, is provided between the cap and the outer ring of the bearing.
A spindle motor according to item 1. 5. A shaft, a bearing externally fitted to the shaft, a hub attached to the shaft via the bearing, and a drive magnet fixed to the hub.
A spindle motor comprising: a stator disposed to face the driving magnet; and a cap mounted on the hub so that the shaft is loosely inserted and covering the bearing, wherein at least the cap and the bearing are provided. A spindle motor, wherein a gap is provided between the inner ring and the shaft, and a circumferential groove communicating with the gap is formed on a peripheral surface of the shaft. 6. The spindle motor according to claim 5, wherein a gap larger than an axial gap of the gap is provided between the cap and an outer ring of the bearing.