JP2005048890A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable spindle motor in which a working fluid leakage from a tapered capillar seal hardly occurs to the outside.
A first circulating flow 30a of a working fluid flows from a first thrust bearing 18a into the working fluid channels 27a and 27b having a wider channel than the first thrust bearing 18a and operates with the first thrust bearing 18a. The vicinity of the seal portion 22 formed at the connection portion with the fluid flow paths 27a and 27b can be depressurized more than before, and the occurrence of outflow of the working fluid from the seal portion 22 can be prevented. The second circulating flow 30b flows from the second thrust bearing 18b into the working fluid passages 27a and 27b having a wider passage, and the second thrust bearing 18b and the working fluid passages 27a and 27b. The vicinity of the seal portion 23 formed at the connection portion can be depressurized more than before, and the occurrence of outflow of working fluid from the seal portion 23 can be prevented.
[Selection] Figure 1

Description

  The present invention relates to a spindle motor that uses a hydrodynamic bearing, and can be suitably used for a highly reliable spindle motor that is strictly required to suppress leakage of working fluid, such as a hard disk drive.

  The spindle motor built in the hard disk drive has been replaced with a fluid bearing having higher rotational accuracy than the conventional ball bearing as the storage capacity of the hard disk has increased.

6 to 12 show a conventional spindle motor using a hydrodynamic bearing.
As shown in FIG. 6, the base end of the shaft 3 is supported and fixed in the shaft hole 2 formed in the base 1. A stator core 5 provided with a winding 4 is attached to the base 1 with the shaft 3 at the center.

  The rotor-side hub 6 is inserted into the shaft 3 and pivotally supported so that the annular magnet 8 is opposed to the teeth of the stator core 5 via a yoke 7 on the outer periphery of the hub 6. It is attached.

  The hub 6 includes an inner sleeve 9, an outer sleeve 10, and a hub body 11 in consideration of workability. As shown in FIG. 7A, the inner sleeve 9 is formed with flat portions 12a and 12b in which the opposing positions on the outer periphery are cut into a plane over the longitudinal direction. 8A and 8B, the inner sleeve 9 is press-fitted inside the outer sleeve 10 as shown in FIG. 8C, and the outer sleeve 10 into which the inner sleeve 9 has been press-fitted is shown in FIG. As shown in FIG. 4D, the hub body 11 is press-fitted.

  When the hub 6 is inserted into the shaft 3 and the motor is stopped, one end surface of the inner sleeve 9 is in contact with the thrust surface 13 a of the flange-shaped flange portion 13 formed in the middle of the shaft 3.

  After inserting the hub 6, a seal plate 14 is press-fitted inside the outer sleeve 10 at the tip of the shaft 3, and the seal plate 14 is disposed close to the other end surface of the inner sleeve 9.

  In the gap formed between the outer circumference of the shaft 3 and the inner circumference of the inner sleeve 9, and the gap formed between the flat portions 12 a and 12 b of the inner sleeve 9 and the inner circumferential surface of the outer sleeve 10, the working fluid 15 is provided. Filled.

  Further, as shown in FIG. 9, dynamic pressure generating grooves 16 are formed in the upper and lower portions of the inner peripheral surface of the inner sleeve 9. Dynamic pressure generating grooves (not shown) are also formed on both end faces of the inner sleeve 9.

  When the winding 4 of the spindle motor is energized, the hub 6 rotates around the shaft 3 with respect to the base 1 by the magnetic action of the attraction and repulsion between the teeth of the stator core 5 and the annular magnet 8. By this rotation, the dynamic pressure generating grooves 16 of each part scrape the working fluid 15 and the dynamic pressure 15 is fed to form the first and second radial bearings 17 a and 17 b at the end of the inner sleeve 9. Is done.

  Further, the working fluid is positively applied to the gap between the thrust surface 13a of the flange portion 13 of the shaft 3 and the one end face of the inner sleeve 9, and the gap between the lower face of the seal plate 14 and the other end face of the inner sleeve 9. 15 is fed to form first and second thrust bearing portions 18a and 18b.

In this manner, the hub 6 rotates stably and continuously with the working fluid interposed between the hub 6 and the shaft 3. For example, see (Patent Document 1).
As another conventional example, as shown in FIG. 12, first and second radial bearing portions 20a and 20b separated by a gas interposition portion 19 are formed, and a hole 21 communicating the gas interposition portion 19 with the outside is formed. The structure which formed the sleeve 9 in the sleeve is proposed. For example, see (Patent Document 2) and (Patent Document 3).
JP 2001-112214 A JP 2000-98146 A JP-A-9-217735

  In the spindle motor shown in FIGS. 6 and 7, a prototype includes a tapered capillar seal 22 formed by the tapered outer peripheral surface of the flange portion 13 of the shaft 3 and the inner peripheral surface of the outer sleeve 10. Some of the working fluid 15 leaked.

Analysis of the prototype in which the working fluid leaked revealed the following mechanism of working fluid leakage.
The movement of the fluid level of the bearing where the working fluid leak occurred was observed.

Here, when the movement of the liquid level of the tapered capillar seal 23 (upper seal) was observed, it was confirmed that the liquid level dropped simultaneously with the start of rotation.
A prototype bearing with a working fluid leak was disassembled and measured. As a result, as shown in FIG. 10, it was confirmed that the inner peripheral surface of the first radial bearing 17a was deformed in a tapered shape, and the gap between the shaft 3 was narrowed.

From the observation result of the fluid level movement of the working fluid of the upper seal 23 and the deformation of the first radial bearing 17a, the working fluid leakage process can be assumed as follows.
That is, the pressure of the working fluid of the first radial bearing 17a whose clearance with the shaft 3 is narrower than that of the second radial bearing 17b and the second radial bearing whose clearance with the shaft 3 is wider than that of the first radial bearing 17a. The pressure of the working fluid 17b is higher in the first radial bearing 17a, and as shown in FIG. 11, an oil flow 24 from the first radial bearing 17a to the second radial bearing 17b is generated. Passing through the second thrust bearing 18b, passing between the flat portions 12a, 12b of the inner sleeve 9 and the inner peripheral surface of the outer sleeve 10 toward the flange portion 13, the flange portion 13 and the inner sleeve 9 Circulates the working fluid 15 from the first radial bearing 17a to the second radial bearing 17b as a whole. It seems to have occurred.

The cross-sectional area of the flow passing toward the flange portion 13 between the tapered capillaries 12a, 12b where the working fluid leaks and the inner peripheral surface of the outer sleeve 10 is b1, and the first thrust bearing 18a If the cross-sectional area is b2, and the cross-sectional area of the tapered capillar seal 22 is b3,
b1 >> b2 >> b3
Then, it can be estimated that the working fluid leakage 25 from the tapered capillar seal 22 to the outside has occurred due to the pressure increase in the vicinity of the inlet of the tapered capillar seal 22 generated by the difference in the cross-sectional area of (b1-b2). “B2 >> b3” indicates that b3 is sufficiently smaller than b2.

  An object of the present invention is to provide a highly reliable spindle motor in which working fluid leakage from a tapered capillar seal to the outside hardly occurs based on the above assumption.

  The spindle motor of the present invention forms a working fluid flow between the radial bearing and the thrust bearing that can reduce the pressure in the seal portion of the filled working fluid as compared with the conventional one, thereby making it difficult for the working fluid to leak from the seal portion. It is characterized by that.

  The spindle motor according to claim 1 of the present invention is characterized in that dynamic pressure is applied to at least one of the opposing surfaces of the shaft and a sleeve inserted through the shaft, and at least one of the opposing surfaces on the side of the shaft facing the end surface of the sleeve. A generating groove is formed, and a working fluid is filled between the shaft and the sleeve and between the opposing surface on the side of the shaft facing the end surface of the sleeve, and the shaft and the shaft are caused by magnetic action between the rotor and the stator. One of the sleeves rotates with respect to the other to generate a dynamic pressure in the working fluid, forming first and second radial bearings at the end of the sleeve, and the side of the shaft facing the end surface of the sleeve Forming a first and second thrust bearing between the first and second thrust bearings, and a working fluid flow path connecting the first and second thrust bearings to the sleeve; A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path, and the first radial bearing and the first thrust bearing through the communication hole; A first circulating flow in which the working fluid returns to the communication hole through the working fluid channel, and the second radial bearing, the second thrust bearing, and the working fluid flow through the communication hole. The shape of the gap between the shaft and the sleeve is set so that a second circulating flow is formed in which the working fluid returns to the communication hole through the passage.

  According to this configuration, the first circulating working fluid flows from the first thrust bearing into the working fluid passage having a wider passage than the first thrust bearing, and the first thrust bearing and the working fluid passage. The vicinity of the seal portion formed at the connection portion can be depressurized more than before, and the occurrence of outflow of the working fluid from the seal portion can be prevented. Similarly, the second circulating flow of working fluid flows from the second thrust bearing into the working fluid channel having a wider flow path than the second thrust bearing, and the second thrust bearing and the working fluid channel The vicinity of the seal portion formed at the connection portion can be depressurized as compared with the conventional case, and the occurrence of outflow of the working fluid from the seal portion can be prevented.

  The spindle motor according to claim 2 of the present invention is characterized in that, in claim 1, the shape of the inner peripheral surface of the sleeve is set so that the first circulation flow and the second circulation flow are formed. To do.

  According to a third aspect of the present invention, the spindle motor according to the first aspect is characterized in that the shape of the peripheral surface of the shaft is set so that the first circulating flow and the second circulating flow are formed. .

  The spindle motor according to claim 4 of the present invention is characterized in that dynamic pressure is applied to at least one of the opposing surfaces of the shaft and a sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve. A generating groove is formed, and a working fluid is filled between the shaft and the sleeve and between the opposing surface on the side of the shaft facing the end surface of the sleeve, and the shaft and the shaft are caused by magnetic action between the rotor and the stator. One of the sleeves rotates with respect to the other to generate a dynamic pressure in the working fluid, forming first and second radial bearings at the end of the sleeve, and the side of the shaft facing the end surface of the sleeve Forming a first and second thrust bearing between the first and second thrust bearings, and a working fluid flow path connecting the first and second thrust bearings to the sleeve; A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path, and the first radial bearing and the first thrust bearing through the communication hole; A first circulating flow in which the working fluid returns to the communication hole through the working fluid channel, and the second radial bearing, the second thrust bearing, and the working fluid flow through the communication hole. The shape of the dynamic pressure generating groove is set so as to form a second circulating flow in which the working fluid returns to the communication hole through the passage.

  The spindle motor according to claim 5 of the present invention is characterized in that dynamic pressure is applied to at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces on the side of the shaft facing the end surface of the sleeve. A generating groove is formed, and a working fluid is filled between the shaft and the sleeve and between the opposing surface on the side of the shaft facing the end surface of the sleeve, and the shaft and the shaft are caused by magnetic action between the rotor and the stator. One of the sleeves rotates with respect to the other to generate a dynamic pressure in the working fluid, forming first and second radial bearings at the end of the sleeve, and the side of the shaft facing the end surface of the sleeve Forming a first and second thrust bearing between the first and second thrust bearings, and a working fluid flow path connecting the first and second thrust bearings to the sleeve; A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path, and the first radial bearing and the first thrust bearing through the communication hole; A first circulating flow in which the working fluid returns to the communication hole through the working fluid channel, and the second radial bearing, the second thrust bearing, and the working fluid flow through the communication hole. Among the parameters for determining the shape of the gap between the shaft and the sleeve and the shape of the dynamic pressure generating groove so that a second circulating flow is formed in which the working fluid returns to the communication hole through the passage. A plurality of parameters are set.

  The spindle motor according to claim 6 of the present invention is characterized in that dynamic pressure is applied to at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve. A generating groove is formed, and a working fluid is filled between the shaft and the sleeve and between the opposing surface on the side of the shaft facing the end surface of the sleeve, and the shaft and the shaft are caused by magnetic action between the rotor and the stator. One of the sleeves rotates with respect to the other to generate a dynamic pressure in the working fluid, forming first and second radial bearings at the end of the sleeve, and the side of the shaft facing the end surface of the sleeve Forming a first and second thrust bearing between the first and second thrust bearings, and a working fluid flow path connecting the first and second thrust bearings to the sleeve; A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path, and the first radial bearing and the first thrust bearing through the communication hole; The first circulating flow in which the working fluid returns to the communication hole through the working fluid flow path, or the second radial bearing, the second thrust bearing, and the working fluid flow through the communication hole. The shape of the gap between the shaft and the sleeve is set so that a second circulating flow is formed in which the working fluid returns to the communication hole through the passage.

  The spindle motor according to claim 7 of the present invention is characterized in that, in claim 6, the shape of the inner peripheral surface of the sleeve is set so that the first circulating flow or the second circulating flow is formed. To do.

  The spindle motor according to claim 8 of the present invention is characterized in that, in claim 6, the shape of the peripheral surface of the shaft is set so that the first circulation flow and the second circulation flow are formed. .

The spindle motor according to claim 9 of the present invention is characterized in that dynamic pressure is applied to at least one of the opposing surfaces of the shaft and a sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve. Forming a generating groove,
The working fluid is filled between the shaft and the sleeve and between the opposing surface on the shaft side facing the end surface of the sleeve, and one of the shaft and the sleeve is the other by the magnetic action of the rotor and the stator. And the working fluid generates a dynamic pressure to form first and second radial bearings at the end of the sleeve, between the end surface of the sleeve and the facing surface on the shaft side facing the sleeve. The first and second thrust bearings are formed at the same time, and the operation between the working fluid flow path connecting the first and second thrust bearings to the sleeve and the first and second radial bearings is performed. A communication hole for flowing a fluid to the working fluid flow path, and via the communication hole to the communication hole through the first radial bearing, the first thrust bearing, and the working fluid flow path. The first circulation in which the working fluid returns Or a second circulating flow is formed in which the working fluid returns to the communication hole through the second radial bearing, the second thrust bearing, and the working fluid flow path via the communication hole. Thus, the shape of the dynamic pressure generating groove is set as described above.

  The spindle motor according to claim 10 of the present invention is characterized in that dynamic pressure is applied to at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve. A generating groove is formed, and a working fluid is filled between the shaft and the sleeve and between the opposing surface on the side of the shaft facing the end surface of the sleeve, and the shaft and the shaft are caused by magnetic action between the rotor and the stator. One of the sleeves rotates with respect to the other to generate a dynamic pressure in the working fluid, forming first and second radial bearings at the end of the sleeve, and the side of the shaft facing the end surface of the sleeve First and second thrust bearings are formed between the first and second thrust bearings, and a working fluid flow path connecting the first and second thrust bearings to the sleeve; A communication hole for flowing a working fluid between the first and second radial bearings to the working fluid flow path, and the first radial bearing and the first thrust bearing through the communication hole; The first circulating flow in which the working fluid returns to the communication hole through the working fluid flow path, or the second radial bearing, the second thrust bearing, and the working fluid flow through the communication hole. Among the parameters for determining the shape of the gap between the shaft and the sleeve and the shape of the dynamic pressure generating groove so that a second circulating flow is formed in which the working fluid returns to the communication hole through the passage. A plurality of parameters are set.

  As described above, the spindle motor of the present invention fills the working fluid between the shaft and the sleeve inserted through the shaft and between the opposing surface on the side of the shaft facing the end surface of the sleeve. The first and second radial bearings are formed at the end of the shaft, the first and second thrust bearings are formed between the end surface of the sleeve and the facing surface on the side of the shaft facing the sleeve, A working fluid channel connecting the first and second thrust bearings, and a communication hole through which the working fluid between the first and second radial bearings flows into the working fluid channel; Via the first radial bearing, the first thrust bearing and the working fluid flow path through the hole, the first circulating flow returning the working fluid to the communication hole, and the communication hole. The second radial bearing; The shape of the gap between the shaft and the sleeve is set so that a second circulating flow is formed in which the working fluid returns to the communication hole through the second thrust bearing and the working fluid flow path. Or setting the shape of the dynamic pressure generating groove, or setting a plurality of parameters among the parameters for determining the shape of the gap between the shaft and the sleeve and the shape of the dynamic pressure generating groove, The shape of the gap between the shaft and the sleeve is set so that the first circulating flow or the second circulating flow is formed, the shape of the dynamic pressure generating groove is set, the shaft Since a plurality of parameters among the parameters for determining the shape of the gap between the sleeve and the sleeve and the shape of the dynamic pressure generating groove are set, the connecting portion between the first thrust bearing and the working fluid flow channel is set. Seal part formed The vicinity of the seal portion formed in the connection portion between the near or second thrust bearing and the working fluid flow path can be depressurized as compared with the conventional case, and the outflow of the working fluid can be prevented. A spindle motor can be realized.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
In addition, the same code | symbol is attached | subjected and demonstrated to the thing which performs the effect | action similar to a prior art example.
(Embodiment 1)
1 to 4 show (Embodiment 1) of the present invention.

2A shows the AA ′ cross section of the spindle motor shown in FIG. 2B, and FIG. 3 shows the BB ′ cross section of FIG.
The shaft 3 is supported and fixed in the shaft hole 2 formed at the base end in the base 1. A stator core 5 provided with a winding 4 is attached to the base 1 with the shaft 3 at the center.

  The rotor-side hub 6 is inserted into the shaft 3 and pivotally supported so that the annular magnet 8 is opposed to the teeth of the stator core 5 via a yoke 7 on the outer periphery of the hub 6. It is attached.

  The hub 6 includes an inner sleeve 9, an outer sleeve 10 and a hub body 11. In the case of a hard disk drive, a hard disk 26 is attached to the hub body 11 as indicated by a virtual line in FIG.

  As shown in FIG. 2A, the inner sleeve 9 is formed with flat portions 12a and 12b in which the opposing positions on the outer periphery are cut into a plane over the longitudinal direction. The inner sleeve 9 is press-fitted inside the outer sleeve 10, and working fluid channels 27 a and 27 b are formed between the inner sleeve 9 and the outer sleeve 10. The outer sleeve 10 into which the inner sleeve 9 is press-fitted is press-fitted into the hub body 11. As can be seen by comparing FIG. 2 with FIG. 6 of the conventional example, the hub fit position 28 to the outer sleeve 10 of the hub body 11 shown in FIG. 2 is press-fitted shallower than in the case of FIG. The occurrence of deformation as shown in FIG. 11 on the inner peripheral surface of the inner sleeve 9 generated by press-fitting the hub body 11 into the outer sleeve 10 is reduced.

  When the hub 6 is inserted into the shaft 3 and stopped, one end surface of the inner sleeve 9 is in contact with the thrust surface 13 a of the flange-shaped flange portion 13 formed in the middle of the shaft 3.

As shown in FIG. 4, dynamic pressure generating grooves 16 a and 16 a are formed in the upper and lower portions of the inner peripheral surface of the inner sleeve 9.
After inserting the hub 6, a seal plate 14 is press-fitted inside the outer sleeve 10 at the tip of the shaft 3, and the seal plate 14 is disposed close to the other end surface of the inner sleeve 9.

  Dynamic pressure generating grooves (not shown) are also formed on both end faces of the inner sleeve 9. As shown in FIGS. 2A and 2B, the inner sleeve 9 is formed with communication holes 29, 29 for connecting the inner peripheral surface and the outer peripheral surface.

  The working fluid 15 includes a clearance between the outer periphery of the shaft 3 and the inner periphery of the inner sleeve 9, a clearance between the end surface of the inner sleeve 9 and the flange portion 13, and an end surface of the inner sleeve 9 and the seal plate 14. Not only the gap but also the communication holes 29, 29 and the working fluid channels 27a, 27b are filled, and no air passage is formed in the working fluid channels 27a, 27b.

Further, as shown in FIG. 4, the dynamic pressure generating grooves 16a and 16b formed on the inner peripheral surface of the inner sleeve 9 have an inner length L1 and an outer length L2 from the dynamic pressure generating groove folding point. Then
L1> L2
Is formed.

  When the winding 4 of the spindle motor is energized, the hub 6 rotates around the shaft 3 with respect to the base 1 by the magnetic action of the attraction and repulsion between the teeth of the stator core 5 and the annular magnet 8. Due to this rotation, the dynamic pressure generating grooves 16a, 16b,... Of each part scrape the working fluid 15 to generate dynamic pressure, and the working fluid 15 is positively fed into the gap between the inner sleeve 9 and the shaft 3. Thus, first and second radial bearings 17 a and 17 b are formed at the end of the inner sleeve 9.

  Further, the working fluid is fed into the gap between the thrust surface 13 a of the flange portion 13 of the shaft 3 and the one end face of the inner sleeve 9 and the gap between the seal plate 14 and the other end face of the inner sleeve 9. First and second thrust bearings 18a and 18b are formed.

  When the dynamic pressure generating grooves 16a and 16b of “L1> L2” are formed in the inner sleeve 9 as described above, when the hub 6 rotates, as shown in FIG. 1, the first and second radial bearings 17a, In 17b, a flow of the working fluid is generated from the inside toward the outside.

  The working fluid (first circulating flow) 30a of the first radial bearing 17a from the inside toward the outside passes through the first thrust bearing 18a and is formed between the inner sleeve 9 and the outer sleeve 10. It flows into the working fluid flow paths 27a and 27b.

  Similarly, the working fluid (second circulating flow) 30b of the second radial bearing 17b from the inside toward the outside passes through the second thrust bearing 18b and is formed between the inner sleeve 9 and the outer sleeve 10. Into the working fluid flow paths 27a and 27b.

  The working fluid in the working fluid flow paths 27a and 27b flows from the outer side to the inner side of the inner sleeve 9 and passes through the communication holes 29 and 29. The first radial bearing 17a and the first radial bearing 17a Supplied and circulated between the two radial bearings 17b.

In this case, the dimension of each gap is F1 as the cross-sectional area of the flow of the working fluid in the communication holes 29 and 29, F2 as the cross-sectional area of the flow of the working fluid in the first and second radial bearings 17a and 17b. When the cross-sectional area of the working fluid flow in the fluid flow paths 27a and 27b is F3 and the cross-sectional area of the working fluid flow in the first and second thrust bearings 18a and 18 is F4, for example,
F1>F2>F3> F4
Met. Further, when the cross-sectional area of the taper capillary seal 23 between the flange portion 13, the outer sleeve 14, and the outer sleeve 10 is F5,
F4 >> F5
It is. “F4 >> F5” indicates that F5 is sufficiently smaller than F4.

  In this way, the communication holes 29 and 29 are formed in the inner sleeve 9, and the dynamic pressure generation in the dynamic pressure generating grooves 16a and 16b of the inner sleeve 9 is performed so that the working fluid circulates from the inner side to the outer side of the inner sleeve 9. When the groove turn-back point is set, the communication hole 29 passes through the communication holes 29 and 29 to the communication hole 29 through the first radial bearing 17a, the first thrust bearing 18a, and the working fluid channels 27a and 27b. The first circulating flow 30a to which the working fluid 15 returns, and the second radial bearing 17b, the second thrust bearing 18b, and the working fluid flow paths 29a and 29b via the communication hole 29 are used for the above-described operation. A second circulating flow 30 b is formed in which the working fluid returns to the communication hole 29.

  When attention is paid to the pressure state in the vicinity of the inlet of the tapered capillar seal 22 in this case, the inlet of the tapered capillar seal 22 has a sectional area F3 in which the working fluid of the first thrust bearing 18a having the sectional area F4 is larger than the sectional area F4. Since the sectional area F5 of the tapered capillar seal 22 is sufficiently smaller than the sectional area F4, the working fluid of the first thrust bearing 18a is used for the working fluid. Since the pressure drops when flowing into the flow paths 27a and 27b and the working fluid pressure acting on the inlet of the tapered capillar seal 22 is lower than before, even if the cross-sectional area F5 of the taper capillar seal 22 is the same as before, Leakage of working fluid to the outside can be prevented.

The tapered capillary seal 23 between the seal plate 14 and the outer sleeve 10 can also prevent leakage of the working fluid to the outside for the same reason.
Note that (Patent Document 2) describes a structure in which a hole 21 is formed in a sleeve as shown in FIGS. 12 (a) and 12 (b). This spindle motor has a first radial bearing 20a. The second radial bearing 20 b is separated from the inner sleeve 9 inside (upper and lower separation type structure), and bubbles generated in the working fluid are discharged to the outside of the bearing through the holes 21 and the air passages 31. Since the working fluid does not flow through the hole 21 because it is intended to be discharged, the purpose and action are different from those of (Embodiment 1), suggesting a specific configuration of (Embodiment 1). Not a thing.

  In the above example, a part of the outer peripheral surface of the inner sleeve 9 is made flat in the length direction and the working fluid channels 27 and 27b are formed between the inner sleeve 9 and the inner peripheral surface. The working fluid flow paths 27a and 27b for connecting the first and second thrust bearings 17a and 17b can be formed by processing the inner peripheral surface of the outer sleeve 10 without processing the outer peripheral surface of the sleeve 9.

(Embodiment 2)
FIG. 5 shows a configuration of a main part of (Embodiment 2) of the present invention.
In (Embodiment 1) shown in FIG. 4, the shape of the dynamic pressure generating groove is changed from the dynamic pressure generating groove return point to the inner length so that the first and second circulation flows 30a and 30b are formed. The length L1 is made longer than the outer length L2 to form the first and second circulation flows from the inner side to the outer side of the inner sleeve 9, but in this (Embodiment 2), the inner peripheral surface of the sleeve Is different from (Embodiment 1) in that the shape is set so that the first circulating flow 30a and the second circulating flow 30b are formed.

  Specifically, in FIG. 5, the dynamic pressure generating groove turn-back point is “L1 = L2”, and the shape of the gap between the shaft 3 and the sleeve 9 is the first and second circulation flows 30a, 30b. In order to set the inner sleeve 9 to be formed, the inner peripheral surface of the inner sleeve 9 is formed with tapered surfaces 32a and 32b that are wider from the inside toward the outside. Others are the same as in (Embodiment 1), and the same parts are denoted by the same reference numerals.

(Embodiment 3)
In (Embodiment 1) shown in FIG. 4, the shape of the dynamic pressure generating groove of the inner sleeve 9 is set. Specifically, the inner length L1 from the dynamic pressure generating groove return point is set to the outer length. The first and second circulation flows from the inner side of the inner sleeve 9 to the outer side are formed longer than L2, but the depth of the dynamic pressure generating groove is different between the inner side and the outer side of the inner peripheral surface of the inner sleeve 9. Even if the first and second circulation flows 30a and 30b are formed, leakage of the working fluid can be prevented.

(Embodiment 4)
In each of the above embodiments, the shape of the dynamic pressure generating groove is set so that the first and second circulation flows 30a and 30b are formed, or the shape of the gap between the shaft 3 and the sleeve is formed. However, a plurality of parameters among parameters determining the shape of the gap between the shaft and the sleeve and the shape of the dynamic pressure generating groove are set as the first and second circulation flows 30a and 30b. Even if formed, leakage of the working fluid can be prevented.

  Specifically, for example, as in (Embodiment 2), the shape of the inner peripheral surface of the inner sleeve 9 is formed by a tapered surface in which the cylindricity of the inner peripheral surface of the inner sleeve 9 becomes wider outward from the inside. In addition to the setting of these parameters, the shape of the dynamic pressure generating groove of the inner sleeve 9 is made to be different from the inner and outer lengths from the dynamic pressure generating groove turning point as in (Embodiment 3). By setting the parameter to, leakage of the working fluid can be prevented even when the first and second circulation flows 30a and 30b are formed.

(Embodiment 5)
In each of the above-described embodiments, specific examples have been described in which each parameter is set so that not only the first circulating flow 30a but also the second circulating flow 30b is formed, but in the vicinity of the first thrust bearing 17a. When only the leakage of the working fluid from the tapered capillary seal 22 is improved, the shaft 3 and the sleeve 9 are formed so that only the first circulation flow 30a is formed through the communication hole 29. Parameters for determining the shape of the gap between the shaft 3, setting the shape of the dynamic pressure generating groove 16 a, and determining the shape of the gap between the shaft 3 and the sleeve and the shape of the dynamic pressure generating groove By setting a plurality of parameters, the outflow of the working fluid can be prevented, and a highly reliable spindle motor can be realized.

  Similarly, when only the leakage of the working fluid from the tapered capillary seal 23 in the vicinity of the second thrust bearing 18b is to be improved, the shaft and the shaft are formed so that only the second circulating flow 30b is formed. Parameters for determining the shape of the gap between the sleeve, setting the shape of the dynamic pressure generating groove, and determining the shape of the gap between the shaft and the sleeve and the shape of the dynamic pressure generating groove By setting a plurality of parameters, it is possible to prevent the working fluid from flowing out and to realize a highly reliable spindle motor.

(Embodiment 6)
In each of the above embodiments, the shaft 3 is fixed to the base 1 and the shaft inserted type spindle motor in which the sleeve inserted through the shaft is on the rotation side has been described as an example. The shaft 3 can be configured in the same way with a shaft rotation type spindle motor in which the end is fixed to the base 1 and the shaft 3 supported by the sleeve is on the rotation side. And a dynamic pressure generating groove is formed on at least one of the facing surfaces of the sleeve inserted through the shaft and at least one of the facing surfaces of the shaft facing the end surface of the sleeve, and the shaft and the sleeve And a working fluid is filled between the end surface of the sleeve and the facing surface on the side of the shaft facing the end surface of the sleeve. One side of the shaft rotates with respect to the other to generate dynamic pressure in the working fluid, forming first and second radial bearings at the end of the sleeve, and the side of the shaft facing the end surface of the sleeve The same can be applied to the sleeve motor in which the first and second thrust bearings are formed between the opposite surfaces.

  Specifically, when the dynamic pressure generating shafts of the first and second radial bearings are formed on the shaft 3 side, the inner length from the dynamic pressure generating groove return point is made longer than the outer length. The depth of the dynamic pressure generating groove is made different between the inner side and the outer side of the inner peripheral surface of the bearing, thereby forming the first and second circulation flows 30a and 30b from the inner side to the outer side of the inner sleeve 9.

(Embodiment 7)
In each of the above embodiments, the cylinder of the inner sleeve 9 is used as a specific example in which the shape of the gap between the shaft and the sleeve is set so that the first and second circulation flows 30a and 30b are formed. Although the case where the degree is set so as to form the first and second circulation flows 30a and 30b has been described as an example, the first and second circulation flows 30a and 30b are formed. The same applies to the case where the shape of the gap between the shaft and the sleeve is determined by setting the shape of the peripheral surface of the shaft 3.

  The spindle motor of the present invention can be used for a drive motor such as a hard disk drive that is strictly required to prevent leakage of working fluid.

The expanded sectional view which shows the flow direction of the working fluid of the spindle motor in (Embodiment 1) of this invention The horizontal sectional view (a) of the principal part of the embodiment and the AA 'sectional view of this (a) BB 'sectional view of FIG. Sectional drawing which shows the dynamic pressure generating groove formed in the inner sleeve of the embodiment Sectional drawing which shows the shape of the internal peripheral surface of the inner sleeve of the spindle motor in (Embodiment 2) of this invention Front sectional view of a conventional spindle motor 6 is a horizontal cross-sectional view (a) of the main part of FIG. Press-in process diagram of inner sleeve, outer sleeve and hub body in the conventional example Sectional drawing which shows the dynamic pressure generating groove formed in the inner sleeve in the conventional example FIG. 7A is a front cross-sectional view of a prototype in which a working fluid leak has occurred in the conventional example, showing a BB ′ cross section of FIG. The enlarged view which shows the flow direction of the working fluid of FIG. Horizontal sectional view of main part of another conventional example (a) and AA 'sectional view of (a)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 2 Shaft hole 3 Shaft 5 Stator core 6 Hub 8 Ring magnet 9 Inner sleeve 10 Outer sleeve 11 Hub main body 12a, 12b Plane part 13 Flange part 13a Thrust surface 15 Working fluid 16a, 16a Dynamic pressure generating groove L1 Dynamic pressure generating groove return Length L2 from point to outside Length 17a, 17b Length from outer side where dynamic pressure generating groove is turned back First and second radial bearings 18a, 18b First and second thrust bearings 22, 23 Taper capillary seals 27a, 27b Fluid passage 28 Hub-fit position 29, 29 Communication hole 30a First circulation flow 30b Second circulation flow 32a, 32b Tapered surface of inner sleeve

Claims (11)

Forming a dynamic pressure generating groove on at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve;
The working fluid is filled between the shaft and the sleeve and between the opposing surface on the shaft side facing the end surface of the sleeve, and one of the shaft and the sleeve is the other by the magnetic action of the rotor and the stator. And the working fluid generates a dynamic pressure to form first and second radial bearings at the end of the sleeve, between the end surface of the sleeve and the facing surface on the shaft side facing the sleeve. Forming first and second thrust bearings,
In the sleeve,
A working fluid flow path connecting the first and second thrust bearings;
A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path;
A first circulating flow through which the working fluid returns to the communication hole through the first radial bearing, the first thrust bearing, and the working fluid flow path through the communication hole, and the communication hole. Then, the shaft and the sleeve are formed so that a second circulating flow is formed in which the working fluid returns to the communication hole through the second radial bearing, the second thrust bearing, and the working fluid flow path. Spindle motor that sets the shape of the gap between. The spindle motor according to claim 1, wherein a shape of an inner peripheral surface of the sleeve is set so that the first circulation flow and the second circulation flow are formed. The spindle motor according to claim 1, wherein the shape of the peripheral surface of the shaft is set so that the first circulation flow and the second circulation flow are formed. Forming a dynamic pressure generating groove on at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve;
The working fluid is filled between the shaft and the sleeve and between the opposing surface on the shaft side facing the end surface of the sleeve, and one of the shaft and the sleeve is the other by the magnetic action of the rotor and the stator. And the working fluid generates a dynamic pressure to form first and second radial bearings at the end of the sleeve, between the end surface of the sleeve and the facing surface on the shaft side facing the sleeve. Forming first and second thrust bearings,
In the sleeve,
A working fluid flow path connecting the first and second thrust bearings;
A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path;
A first circulating flow through which the working fluid returns to the communication hole through the first radial bearing, the first thrust bearing, and the working fluid flow path through the communication hole, and the communication hole. The dynamic pressure generating groove is formed so as to form a second circulation flow in which the working fluid returns to the communication hole through the second radial bearing, the second thrust bearing, and the working fluid flow path. A spindle motor with a set shape. Forming a dynamic pressure generating groove on at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve;
The working fluid is filled between the shaft and the sleeve and between the opposing surface on the shaft side facing the end surface of the sleeve, and one of the shaft and the sleeve is the other by the magnetic action of the rotor and the stator. And the working fluid generates a dynamic pressure to form first and second radial bearings at the end of the sleeve, between the end surface of the sleeve and the facing surface on the shaft side facing the sleeve. Forming first and second thrust bearings,
In the sleeve,
A working fluid flow path connecting the first and second thrust bearings;
A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path;
A first circulating flow through which the working fluid returns to the communication hole through the first radial bearing, the first thrust bearing, and the working fluid flow path through the communication hole, and the communication hole. Then, the shaft and the sleeve are formed so that a second circulating flow is formed in which the working fluid returns to the communication hole through the second radial bearing, the second thrust bearing, and the working fluid flow path. A spindle motor in which a plurality of parameters are set among parameters for determining the shape of the gap between the groove and the shape of the dynamic pressure generating groove. Forming a dynamic pressure generating groove on at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve;
The working fluid is filled between the shaft and the sleeve and between the opposing surface on the shaft side facing the end surface of the sleeve, and one of the shaft and the sleeve is the other by the magnetic action of the rotor and the stator. And the working fluid generates a dynamic pressure to form first and second radial bearings at the end of the sleeve, between the end surface of the sleeve and the facing surface on the shaft side facing the sleeve. Forming first and second thrust bearings,
In the sleeve,
A working fluid flow path connecting the first and second thrust bearings;
A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path;
The first circulating flow that returns to the communication hole through the first radial bearing, the first thrust bearing, and the working fluid flow path via the communication hole, or the communication hole passes through the communication hole. Then, the shaft and the sleeve are formed so that a second circulating flow is formed in which the working fluid returns to the communication hole through the second radial bearing, the second thrust bearing, and the working fluid flow path. Spindle motor that sets the shape of the gap between. The spindle motor according to claim 6, wherein a shape of an inner peripheral surface of the sleeve is set so that the first circulating flow or the second circulating flow is formed. The spindle motor according to claim 6, wherein the shape of the peripheral surface of the shaft is set so that the first circulation flow and the second circulation flow are formed. Forming a dynamic pressure generating groove on at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve;
The working fluid is filled between the shaft and the sleeve and between the opposing surface on the shaft side facing the end surface of the sleeve, and one of the shaft and the sleeve is the other by the magnetic action of the rotor and the stator. And the working fluid generates a dynamic pressure to form first and second radial bearings at the end of the sleeve, between the end surface of the sleeve and the facing surface on the shaft side facing the sleeve. Forming first and second thrust bearings,
In the sleeve,
A working fluid flow path connecting the first and second thrust bearings;
A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path;
The first circulating flow that returns to the communication hole through the first radial bearing, the first thrust bearing, and the working fluid flow path via the communication hole, or the communication hole passes through the communication hole. The dynamic pressure generating groove is formed so as to form a second circulation flow in which the working fluid returns to the communication hole through the second radial bearing, the second thrust bearing, and the working fluid flow path. A spindle motor with a set shape. Forming a dynamic pressure generating groove on at least one of the opposing surfaces of the shaft and the sleeve inserted through the shaft, and at least one of the opposing surfaces of the shaft facing the end surface of the sleeve;
The working fluid is filled between the shaft and the sleeve and between the opposing surface on the shaft side facing the end surface of the sleeve, and one of the shaft and the sleeve is the other by the magnetic action of the rotor and the stator. And the working fluid generates a dynamic pressure to form first and second radial bearings at the end of the sleeve, between the end surface of the sleeve and the facing surface on the shaft side facing the sleeve. Forming first and second thrust bearings,
In the sleeve,
A working fluid flow path connecting the first and second thrust bearings;
A communication hole for flowing the working fluid between the first and second radial bearings to the working fluid flow path;
The first circulating flow that returns to the communication hole through the first radial bearing, the first thrust bearing, and the working fluid flow path via the communication hole, or the communication hole passes through the communication hole. Then, the shaft and the sleeve are formed so that a second circulating flow is formed in which the working fluid returns to the communication hole through the second radial bearing, the second thrust bearing, and the working fluid flow path. A spindle motor in which a plurality of parameters are set among parameters for determining the shape of the gap between the groove and the shape of the dynamic pressure generating groove. A hard disk drive device using the spindle motor according to claim 1.

Images