JP4110381B2 - Hydrodynamic bearing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrodynamic bearing device, and more particularly to a hydrodynamic bearing device capable of preventing damage to a hydrodynamic pressure generation surface due to leakage of a lubricating fluid to the outside and precession of a bearing.
[0002]
[Prior art]
As a bearing device for supporting a high-speed rotating device such as a spindle motor used for a magnetic disk or an optical disk, a dynamic pressure bearing device (dynamic pressure fluid bearing) is adopted. In general, a hydrodynamic bearing device is formed with a plurality of dynamic pressure grooves on either one of mutually opposing surfaces (dynamic pressure surfaces) of two members such as a shaft and a sleeve that are relatively rotatable. It is the structure which filled fluids, such as lubricating oil agent, liquids, such as a liquid metal, or various gases between opposing surfaces. With this configuration, the dynamic pressure bearing device generates pressure (dynamic pressure) in the fluid by the pumping action of the dynamic pressure groove when the two members rotate relative to each other, and supports the two members in a non-contact manner by the dynamic pressure. .
[0003]
FIG. 4 is a schematic cross-sectional view showing the structure of a conventional hydrodynamic bearing device. This example shows a radial dynamic pressure bearing in which a thrust (axial) load is supported by a pivot bearing formed at the tip of a shaft member. This radial dynamic pressure bearing is constituted by a substantially cylindrical sleeve 1 whose one opening is sealed, and a shaft 2 which is inserted from the other opening of the sleeve 1 and is fitted to the inner periphery thereof. . The upper part in the figure (the upper part in the axial direction) will be described as the sealed end side in the dynamic pressure bearing, and the lower part in the figure (the lower part in the axial direction) will be described as the open end side in the dynamic pressure bearing.
[0004]
In the sleeve 1, a lid member (thrust plate) 12 is fitted into the closed end side opening of the cylindrical body 11, and the cylindrical body 11 and the lid member 12 are integrally formed using an adhesive or the like. Further, the shaft 2 is inserted from the opening on the sealed end side of the sleeve 1 and is rotatably fitted with a slight gap on the inner periphery of the sleeve 1. The shaft end 2a of the shaft 2 is formed in a hemispherical shape and is disposed so that the tip thereof is in contact with the lid member 12, and functions as a pivot bearing that supports an axial load. The gap between the shaft 2 and the sleeve 1 is filled with a lubricating fluid (not shown), and a capillary seal portion is formed in the opening on the open end side of the sleeve 1 to the outside of the lubricating fluid. To prevent leakage.
[0005]
On the outer peripheral surface 2x of the shaft 2, a radial dynamic pressure groove 21 on the hermetic bone side or a V-shaped pattern on the hermetic end side in the circumferential direction and a radial on the open end side are adjacent to each other at a predetermined distance in the axial direction. A dynamic pressure groove 22 is formed. The band-like region 23 between the radial dynamic pressure grooves 21 and 22 is provided to prevent interference of dynamic pressure generated by these dynamic pressure grooves 21 and 22, and this configuration allows the shaft to 2 and the sleeve 1 rotate relative to each other, the non-dynamic pressure generating band 33 is sandwiched between the outer peripheral surface 2x of the shaft 2 and the inner peripheral surface 1x of the sleeve 1 and the adjacent axially sealed end side and The closed end side dynamic pressure generating band 31 and the open end side dynamic pressure generating band 32 are formed on the open end side, respectively.
[0006]
In the dynamic pressure bearing device configured as described above, one of the inner peripheral surface 1x of the sleeve 1 and the outer peripheral surface 2x of the shaft 2 in the two dynamic pressure generating bands 31 and 32 is tapered as shown in the sectional view of FIG. Relative rotation is achieved by making the gap d1 between the sleeve 1 and the shaft 2 on the adjacent side (non-dynamic pressure generation band 33 side) in the dynamic pressure generation bands 31, 32 larger than the gap d2 on both ends of the sleeve. Proposals have been made to collect the oil (lubricating fluid) at the time in the non-dynamic pressure generating zone 33 and prevent the dynamic pressure generating surface from running out of oil (for example, see Patent Document 1).
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-120661
[Problems to be solved by the invention]
By the way, in the dynamic pressure bearing device as described above, the lubricating fluid leaks to the sleeve open end side due to the differential pressure of the dynamic pressure generated by the two radial dynamic pressure grooves formed adjacent to each other in the axial direction. May occur.
[0009]
In addition, when the shaft or sleeve on the rotating side causes precession (conical swing), the shaft and the sleeve come into contact in the vicinity of both axial end portions of the sleeve inner peripheral surface where the amount of swing increases. There has been a problem that damage such as scratches occurs on the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve.
[0010]
The present invention has been made in view of such circumstances, and has a long dynamic life by preventing the occurrence of damage and the like due to precession of the bearing while suppressing leakage of the lubricating fluid to the outside. It aims at providing a bearing device.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is characterized in that a shaft is rotatably fitted with a slight gap on the inner periphery of a sleeve whose one opening is sealed. between the outer peripheral surface and the inner circumferential surface of the sleeve, the axial circumferentially axially opposite sides of the strip-shaped Hido pressure generating zone, to either of the shaft outer circumferential surface or in the sleeve peripheral surface A closed end side dynamic pressure generating zone and an open end side dynamic pressure generating zone each having a herringbone or V-shaped radial dynamic pressure groove formed in a direction symmetrical to each other are provided , and in the gap between the shaft and the sleeve, with lubricating fluid is filled, the dynamic pressure generated by the dynamic pressure groove when the relative rotation of the shaft and the sleeve, in the dynamic pressure bearing apparatus for supporting a relative rotation of these shafts and the sleeve in a non-contact, said The clearance between the shaft and the sleeve on the sleeve sealing end side and the non-dynamic pressure generation band side of the closed end side dynamic pressure generation band is defined as a first gap and a second gap, respectively. the gap between the shaft and the sleeve in the hydrodynamic band side and the sleeve open end, a third gap respectively, when a fourth gap, the first gap is larger than the second gap, and the fourth The shaft outer peripheral surface has a shape in which the gap is formed larger than the third gap, and the difference between the first gap and the second gap is larger than the difference between the fourth gap and the third gap. Alternatively, the inner peripheral surface of the sleeve is formed .
[0012]
As a specific configuration example of a dynamic pressure bearing device of this, the with dynamic pressure grooves are formed on the outer circumferential surface of the shaft, said inner sleeve in each dynamic pressure generating zone facing the dynamic pressure grooves peripheral surface, a configuration that is formed in a tapered shape in the axial direction can be suitably employed (claim 2).
[0013]
According to the present invention, in the hydrodynamic bearing device that supports the relative rotation of the shaft and the sleeve in a non-contact manner due to the dynamic pressure generated in the two radial dynamic pressure generation bands adjacent in the axial direction, precession occurs in the rotation. In this case, the desired goal is achieved by forming a larger clearance (diameter in the radial direction) between the shaft and the sleeve near the sealed end and near the open end of the sleeve where the deflection of the rotating body increases. It is something to try.
[0014]
That is, according to the present invention, the radial gap (second gap and third gap) between the sleeve and the shaft on the adjacent side (non-dynamic pressure generation band side) in the dynamic pressure generation band portions on the closed end side and the open end side. Therefore, even if rotation of the hydrodynamic bearing device causes precession by forming a large gap (first gap and fourth gap) on both ends of the sleeve in each dynamic pressure generation zone, Contact between the shaft and the sleeve can be prevented.
[0015]
In addition to the above-described configuration, the hydrodynamic bearing device according to the present invention also provides dynamic pressure generation on the sealed end side as a means for preventing leakage of the lubricating fluid filled between the shaft and the sleeve to the sleeve open end side. The difference between the first gap on the closed end side in the belt and the second gap on the non-dynamic pressure generating band side is the fourth gap on the open end side and the non-dynamic pressure generating band in the dynamic pressure generating band on the open end side. Either the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve facing the shaft is formed in a shape larger than the difference with the third gap on the side.
[0016]
That is, when the gap between the two dynamic pressure generating bands is formed so as to widen toward both ends of the sleeve, these dynamic pressure generating bands include both ends in the axial direction (sleeve sealed end side and sleeve open end side). A flow of lubricating fluid toward the Therefore, at the open end of the sleeve, the pressure increases due to the movement of the lubricating fluid, and there is a possibility that leakage to the outside may occur. However, in the hydrodynamic bearing device of the present invention, the gap between the sleeve and the shaft is configured so that the flow of the lubricating fluid toward the sleeve closed end side becomes stronger. Will be pushed to the side. Therefore, the hydrodynamic bearing device of the present invention can suppress the leakage of the lubricating fluid to the sleeve open end.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing the structure of a hydrodynamic bearing device according to a first embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the structural member which has the same function as a prior art example. Further, the gap between the shaft 2 and the sleeve 1 on the sleeve 1 sealed end side and the non-dynamic pressure generating band 33 side of the sealed end side dynamic pressure generating band 31 is defined as D1 (first gap) and D2 (second gap), respectively. ), And the gap between the shaft 2 and the sleeve 1 on the non-dynamic pressure generating band 33 side of the open end side dynamic pressure generating band 32 and the open end side of the sleeve 1 are D3 (third gap) and D4 (fourth), respectively. This will be described as a gap.
[0018]
The basic structure of the hydrodynamic bearing device according to the first embodiment is the same as that of the conventional example, and is inserted from the substantially cylindrical sleeve 1 whose one opening is sealed, and the other opening of the sleeve 1, It is comprised from the shaft 2 fitted by the inner periphery. In the sleeve 1, a lid member (thrust plate) 12 is fitted into an opening on the closed end (upper side in the drawing) side of the cylindrical body 11, and the cylindrical body 11 and the lid member 12 are integrally formed using an adhesive or the like. Has been. The shaft 2 is inserted through an opening on the open end (lower side in the drawing) side of the sleeve 1 and is rotatably fitted in the inner periphery of the sleeve 1 with a slight gap. The gap between the shaft 2 and the sleeve 1 is filled with a lubricating fluid, and a capillary seal portion is formed at the opening on the open end side of the sleeve 1 to prevent leakage of the lubricating fluid to the outside. It is illustrated.
[0019]
Similarly to the conventional example, the radial dynamic pressure groove 21 on the hermetic bone or V-shaped sealed end side of the herringbone or V-shaped pattern is also provided on the outer peripheral surface 2x of the shaft 2 at positions adjacent to each other at a predetermined distance in the axial direction. A radial dynamic pressure groove 22 on the open end side is formed. Further, between the outer peripheral surface 2x of the shaft 2 and the inner peripheral surface 1x of the sleeve 1, the sealed end side dynamic pressure generating band 31 and the open end are respectively provided on both sides in the adjacent axial direction with the non-dynamic pressure generating band 33 interposed therebetween. A side dynamic pressure generating zone 32 is formed.
[0020]
The hydrodynamic bearing device according to the present embodiment is characterized in that the gap between the shaft 2 and the sleeve 1 in each of the dynamic pressure generating bands 31 and 32 is larger at both axial ends than the non-dynamic pressure generating band 33 (D1> D2 , D4> D3), and the difference between the gap D1 on the closed end side dynamic pressure generating band 31 and the gap D2 on the non-dynamic pressure generating band 33 side is the open end in the open end side dynamic pressure generating band 32. The inner peripheral surface 1x of the sleeve 1 in each of the dynamic pressure generating bands 31 and 32 is larger than the difference between the gap D4 on the side and the gap D3 on the non-dynamic pressure generating band 33 side (D1-D2> D4-D3). , Are each formed in a tapered shape.
[0021]
With the above configuration, the hydrodynamic bearing device according to the present embodiment is capable of precessing (conical swinging) when the shaft 2 or the sleeve 1 on the rotating side is caused to rotate relative to the shaft 2 and the sleeve 1. Since the gaps (D1, D4) on both ends of the sleeve where the deflection due to the precession is large are formed widely, the shaft 1 and the sleeve 2 are unlikely to come into contact with each other, and damage such as scratches may occur. Can be prevented.
[0022]
In addition, since the inclination of the sleeve inner peripheral surface 1x in the sealed end side dynamic pressure generating band 31 is larger than the inclination of the inner peripheral surface 1x in the open end side dynamic pressure generating band 32, it is sealed from the open end side (upper side in the drawing). The flow of the lubricating fluid toward the end side (downward in the figure) becomes stronger, and the lubricating fluid is pushed into the sleeve sealing end side (pump-in effect). Therefore, the hydrodynamic bearing device in the present embodiment can also exhibit the effect of preventing leakage of the lubricating fluid to the open end side.
[0023]
In the above-described embodiment, the shape of the sleeve inner peripheral surface 1x in each of the dynamic pressure generating bands 31, 32 is tapered, but the shape of the sleeve inner peripheral surface 1x that directs the lubricating fluid toward both ends of the sleeve. Is not limited to this example. For example, as shown in FIG. 2, at the approximate center in the axial direction of each of the dynamic pressure generating bands 31, 32, the sleeves on both ends of the dynamic pressure generating bands 31, 32 are disposed. A stepped portion that widens the gap may be formed.
[0024]
Next, a second embodiment of the present invention will be described.
FIG. 3 is a schematic cross-sectional view showing the structure of the hydrodynamic bearing device according to the second embodiment of the present invention. In this dynamic pressure bearing device, a thrust dynamic pressure bearing for supporting an axial load is formed at one end of the shaft 2 in addition to the radial dynamic pressure bearing similar to that of the first embodiment.
[0025]
The shaft 2 used in the second embodiment has the same radial dynamic pressure grooves 21 and 22 as those in the first embodiment formed on the outer peripheral surface 2x thereof, and has a disk-like shape at one end thereof. A flange portion 2b is provided. Further, herringbone or V-shaped thrust dynamic pressure grooves 24 and 25 are formed in the circumferential direction on both end faces 2y and 2z of the flange portion 2b, respectively. In the sleeve 1, a circumferential step portion 11 a into which the flange portion 2 b of the shaft 2 can be fitted is formed in the opening on the sealed end (upper side in the drawing) side of the cylindrical body 11, and the shaft 2 is fitted. Then, a lid member (thrust plate) 12 is fitted into the opening and sealed, and integrated with an adhesive or the like. The relative rotation between the flange portion 2 b of the shaft 2 and the sleeve 1 is caused by the dynamic pressure in the thrust direction generated between the flange portion end surface 2 y of the shaft 2 and the circumferential step end surface 1 y of the sleeve 1, and the shaft 2. This is supported in a non-contact manner by the dynamic pressure in the thrust direction generated between the flange portion end surface 2x and the inner surface 12z of the lid member 12.
[0026]
Further, the structure of the radial dynamic pressure bearing portion in this dynamic pressure bearing device is the same as that of the first embodiment, and the shaft 2 and the sleeve in the closed end side dynamic pressure generating band 31 and the open end side dynamic pressure generating band 32. 1 is larger at both axial ends than the non-dynamic pressure generating band 33 side (D1> D2, D4> D3), and is not stationary with the gap D1 on the sealed end side in the sealed end side dynamic pressure generating band 31. The difference between the gap D2 on the pressure generation band 33 side is larger than the difference between the gap D4 on the open end side in the open end side dynamic pressure generation band 32 and the gap D3 on the non-dynamic pressure generation band 33 side (D1-D2> D4). -D3) As shown, the inner peripheral surface 1x of the sleeve 1 in the dynamic pressure generating bands 31, 32 is formed in a tapered shape.
[0027]
For this reason, the hydrodynamic bearing device according to the present embodiment makes it difficult for the shaft 2 and the sleeve 1 to come into contact with each other even when the rotation of the shaft 2 or the sleeve 1 causes a precession motion (conical swinging). The occurrence of damage can be prevented. In addition, the flow of the lubricating fluid toward the closed end side becomes stronger than the open end side, and the lubricating fluid is pushed into the closed end (thrust dynamic pressure bearing) side, so that leakage of the lubricating fluid to the open end side is prevented. Can be prevented.
[0028]
In the embodiment described above, the sleeve inner peripheral surface 1x in each of the dynamic pressure generating bands 31 and 32 has a tapered shape. However, as in the first embodiment, instead of the tapered shape, A stepped portion may be provided at substantially the center in the axial direction in the pressure generating bands 31 and 32 so that the lubricating fluid is directed toward both ends of the sleeve.
[0029]
In the above two embodiments, the example in which the lubricating fluid is directed to both ends of the sleeve is provided on the inner peripheral surface 1x of the sleeve 1, but this tapered shape is the outer periphery of the shaft 1. It may be provided on the surface 2x.
[0030]
Still further, the radial dynamic pressure groove and the thrust dynamic pressure groove may be provided on either side of the shaft or the sleeve, and the present invention is equally applicable to either type of dynamic pressure bearing device of shaft rotation or sleeve rotation. be able to.
[0031]
【The invention's effect】
As described above in detail, according to the hydrodynamic bearing device of the present invention, the lubricating fluid filled between the shaft and the sleeve is prevented from leaking to the sleeve open end side, and the rotation of the bearing precesses. Even if it occurs, it is difficult for the shaft and the sleeve to come into contact with each other, troubles such as damage to these members are prevented, and a fluid dynamic bearing device having a long life can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the structure of a fluid dynamic bearing device according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing a step shape of a sleeve inner peripheral surface 1x in the hydrodynamic bearing device according to the first embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing the structure of a fluid dynamic bearing device according to a second embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing the structure of a conventional hydrodynamic bearing device.
FIG. 5 is a schematic cross-sectional view showing the shape of a sleeve inner peripheral surface 1x in another conventional hydrodynamic bearing device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sleeve 1x Inner peripheral surface 2 Shaft 2x Outer peripheral surface 2a Shaft end 11 Cylindrical body 12 Cover member 21,22 Radial dynamic pressure groove 23 Band-shaped area | region 24,25 Thrust dynamic pressure groove 31 Sealed end side dynamic pressure generating band 32 Opening End-side dynamic pressure generation zone 33 Non-dynamic pressure generation zone

Claims (2)

A shaft is rotatably fitted to the inner periphery of the sleeve, with one opening sealed, with a slight gap between them, and the circumferential direction between the outer peripheral surface of the opposing shaft and the inner peripheral surface of the sleeve A herringbone or V-shaped radial dynamic pressure groove symmetrical in the axial direction is formed on either the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve on both sides in the axial direction across the belt-like non-dynamic pressure generating band. A closed end side dynamic pressure generating zone and an open end side dynamic pressure generating zone are provided, and a gap between the shaft and the sleeve is filled with a lubricating fluid, and the relative rotation of the shaft and the sleeve In the hydrodynamic bearing device that supports the relative rotation of the shaft and the sleeve in a non-contact manner by the dynamic pressure generated in the hydrodynamic groove,
The clearance between the shaft and the sleeve on the sleeve sealing end side and the non-dynamic pressure generating band side of the sealed end side dynamic pressure generating zone is defined as a first gap and a second gap, respectively. When the gap between the shaft and the sleeve on the non-dynamic pressure generating band side and the sleeve open end side is the third gap and the fourth gap, respectively, the first gap is larger than the second gap, and the fourth gap Is formed larger than the third gap, and the difference between the first gap and the second gap is larger than the difference between the fourth gap and the third gap. A hydrodynamic bearing device in which a surface or an inner peripheral surface of the sleeve is formed. The dynamic pressure groove is formed on the outer peripheral surface of the shaft, and the inner peripheral surface of the sleeve in each of the dynamic pressure generating zones facing the dynamic pressure groove is formed in a tapered shape in the axial direction. The hydrodynamic bearing device according to claim 1.

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