The present invention contains subject matter related Japanese Patent Application JP 2006-216337 filed in the Japan Patent Office on Aug. 9, 2006, the entire contents of which being incorporated herein by reference.
1. Field of the Invention
The present invention relates to a bearing unit in which a dynamic fluid bearing adapted to receive a rotary shaft inserted thereinto is covered by a unit main body and to a motor using the bearing unit.
2. Description of the Related Art
Then, a description is made of how the gap portion 37 tapered axially-inwardly from the slide bearing 31 provides a non-contact rotational seal for retaining lubricating oil inside the bearing unit.
Fluid tends to move in a narrower width due to the capillary phenomenon. If it is intended to retain lubricating oil inside the bearing unit, then the bearing unit is preferably provided with a gap that is tapered in cross-section toward the inside thereof. The lubricating oil in the gap thus tapered will move toward the inside of the bearing unit for retainment.
In this case, the drawing pressure P generated by the capillary phenomenon is represented by the equation, P=2γ cos θ/r, where γ is surface tension occurring between lubricating oil and a lubricating oil-contact object (if this object is the shaft 34, it is made of stainless steel or duralumin; if the object is the gap-forming member 38, it is made of metal or resin), θ is a contact angle between the lubricating oil and the lubricating oil-contact object and r is a width of the gap portion 37.
That is to say, P∝1/r; therefore, the lubricating oil is drawn toward the inside of the bearing unit having a smaller gap width r for retainment.
In this way, the non-contact rotational seal 30a in the related art can seal the lubricating oil of the rotational portion in a non-contact manner by devising the shape of the seal portion and using the surface tension of the lubricating oil. Because of the non-contact seal, the non-contact rotational seal 30a is of an excellent lubricating oil sealing system that has no torque loss and maintains excellent rotational-mechanical accuracy such as no axial vibration.
Like the bearing unit 30 shown in
The gap portion 47 of the bearing unit 40 shown in
Similarly, the bearing unit 50 shown in
In other words, the bearing unit 50 is not distinctive in playing the role of positively drawing the lubricating oil into the inside but prevents the mist of the lubricating oil splashing resulting from the rotation of the shaft 54 from diffusing outward for reuse.
As described above, the non-contact seals in the related art cannot overcome the defects in which since it is necessary to provide a tapered gap in the axial direction, thinning is difficult, and while it is intended to provide thinning, since the seal is not located on the outflow path of the lubricating oil, it is difficult to prevent the leakage of the lubricating oil.
According to an embodiment of the present invention, there is provided a bearing unit including: a dynamic pressure fluid bearing adapted to receive a rotary shaft inserted thereinto; a unit main body surrounding the outside of the fluid bearing; a lid member covering an upper opening of the unit main body with the rotary shaft inserted into the fluid bearing; lubricating oil poured into the unit main body; and an oil thrower ring rotating together with the rotary shaft in a space defined between an upper end of the fluid bearing and the lid member; wherein a gap defined between the lid member and the oil thrower ring is tapered in cross-section so as to be progressively reduced in the distance therebetween as the gap is spaced apart from the center of the rotary shaft.
According to another embodiment of the present invention, there is provided a motor using the bearing unit described above.
In the embodiment of the present invention described above, the oil thrower ring rotating together with the rotary shaft is provided between the upper portion of the dynamic pressure fluid bearing and the lid member and the gap defined between the oil thrower ring and the lid member is tapered in cross-section so as to be reduced in the distance therebetween as it is spaced apart from the center of the rotary shaft. Thus, the path of the lubricating oil is partitioned by the oil thrower ring to extend along a direction perpendicular to the rotary shaft in a reciprocative manner. In addition, the lubricating oil can be led toward the inside of the bearing unit by the gap tapered between the oil thrower ring and the lid member.
In particular, according to the invention, since the oil thrower ring is rotated together with the rotary shaft, the lubricating oil can forcibly be led toward the inside of the bearing unit by the centrifugal force resulting from the rotation of the oil thrower ring.
Accordingly, the present invention can produce the following effects. The gap which is tapered in cross-section so as to be progressively reduced in the distance thereof as it is spaced apart from the center of the shaft can extend the path of the lubricating oil in the direction perpendicular to the shaft. Thus, the entire bearing unit can be reduced in thickness. In addition, the direction of the surface tension of the tapered portion conforms to the direction of the centrifugal force resulting from the rotation of the oil thrower ring. The path of the lubricating oil is elongate and has a labyrinth structure. Thus, excellent lubricating oil retaining performance can be exhibited.
As described above, the bearing unit according to the embodiments of the invention is thin and can provide excellent lubricating oil retaining performance; therefore, the motor mounted with the bearing unit of the invention can suitably applied to electronic equipment such as personal computers and video equipment such as televisions which require thinness and a long life. In addition, the bearing unit of the invention is such that the oil thrower ring also serves as a locking member of the rotary shaft; therefore, the number of component parts can be reduced compared with that of the related art.
Preferred embodiments of the present invention will hereinafter be described with reference to the drawings.
The non-contact seal 10a of the bearing unit 10 according to the embodiment has a feature that the oil thrower ring 15 and the gap-forming member 18 form the gap portion tapered in cross-section in a direction of drawing lubricating oil into the inside of the bearing unit and the oil thrower ring 15 is rotated integrally with the shaft 14.
That is to say, the direction of drawing the lubricating oil into the tapered gap portion 17 conforms to the direction of a centrifugal force generated by the rotation of the oil thrower ring 15. Therefore, performance can be provided for more firmly retaining lubricating oil.
The slide bearing 11 is a dynamic pressure fluid bearing in which lubricating oil is interposed between the shaft 14 and the slide bearing 11 to radially support the bearing 11 for rotation with low friction. The lubricating oil is filled inside the stator member 11 and is prevented from leaking upward by the gap-forming member 18 covering the upper opening of the stator member 16.
The oil thrower ring 15 is perpendicularly attached to the shaft 14 to partition the gap between the upper surface of the slide bearing 11 and the gap-forming member 18. This forms the gap portion 17 on the upper side of the oil thrower ring 15 and a gap portion 13 on the lower side thereof.
There is provided a small gap between the end of the oil thrower ring 15 and the gap-forming member 18. Specifically, a lubricating oil flow passage A is formed which extends between the upper portion of the slide bearing 11 and the gap between the gap-forming member 18 and the shaft 14 as indicated with a dashed line in
Further, the configuration of the present embodiment has the tapered gap portion 17 provided on the mid-course of the lubricating oil flow passage A and a long course from the sliding portion relative to the shaft 14 to the external portion of the bearing and provide a labyrinth structure, which can exhibit an effect of sufficiently retaining lubricating oil.
Needless to say, this configuration intends to prevent the lubricating oil from flowing out from the gap portion 13 between the slide bearing 11 and the oil thrower ring 15 via the tapered gap portion 17. Therefore, the other portions such as the fastening portion of the stator member 16 to the gap-forming member 18 and the fastening portion of the shaft 14 to the oil thrower ring 15 may be sealed by an adhesive, laser welding or a sealing member such as rubber.
The bearing unit 10 configured as described above can reliably prevent leakage of the lubricating oil by the tapered gap portion 17 drawing the lubricating oil from the center of the shaft 14 to the outside thereof and by the action of the centrifugal force resulting from the shaft 14 and the oil thrower ring 15.
The non-contact seal 10a is distinctive in providing a continuously tapered gap formed as below. A gap portion 13 between the upper portion of a slide bearing 11 and an oil thrower ring 15 is tapered in cross-section toward a sliding surface, i.e., the center of the shaft 14. In addition, a gap portion 17 between the oil thrower ring 15 and a gap-forming member 18 is progressively reduced in the distance therebetween with increasing distance from the sliding surface, i.e., the center of the shaft 14.
In the embodiment shown in
Similarly to the above embodiments, the bearing unit 10 of the third embodiment forms the continuously tapered gaps. Thus, the tapered shape is increased in length to enhance performance for drawing the lubricating oil.
The configuration of the present embodiment provides the same performance of drawing the lubricating oil as that of the embodiment shown in
Since the oil thrower ring 15 formed integrally with the shaft 14 is provided, a process of separately attaching an oil thrower ring 15 to the shaft 14 can be omitted. In addition, the number of component parts can be reduced and reliability resulting from the integral formation can be increased.
In general, if at least a radial bearing device is a dynamic pressure bearing formed with herring bone-shaped or axially shaped dynamic pressure generating grooves, it is significantly important to retain lubricating oil indispensable to form an oil film. The non-contact seals 10a of the embodiments can provide an effect sufficient to cope with this. Needless to say, also the thrust bearing device may be a dynamic pressure bearing.
The housing 62 is provided outside the bearing unit 10. The bearing unit 10 is secured to the base plate 61 via the housing 62. Coils composed of the cores 64 and windings 65 are attached to the housing 62. The coils are opposed to the magnets 68 of the rotor 60 rotatable with a shaft of the bearing unit 10. The rotor 60 is provided with a plurality of the impellers 66. The impellers 66 rotate together with the rotor 60 to generate air flow.
Any one of the bearing units according to the embodiments described above is used as the bearing unit 10 of such a fan motor to reduce the thickness of the entire fan motor. In addition, it is possible to effectively prevent lubricating oil from leaking from the bearing unit 10, thereby enhancing reliability of the fan motor.
A description is next made of a method of manufacturing the bearing unit according to the present embodiment. For the bearing units 10 according to the first, second, third and fourth embodiments shown in
Thereafter, the gap-forming member 18 is pressably put on the upper portion of the slide bearing 11 assembled into the stator member 16. The lubricating oil is injected into the inside defined by the stator member 16 and the gap-forming member 18. Incidentally, the lubricating oil may be injected before the shaft is inserted after the slide bearing 11 has been assembled into stator portion 16.
Unit molding may be conceivable in which the slide bearing 11, the shaft 14 and the oil thrower ring 15 are assembled along with molding of the stator member 16 in addition to the manufacturing method described above.
Then, the inner structure configured as described above is disposed in a cavity 101 of left and right molds 100 and gripped by the molds 100. Specifically, the gap-forming member 18 and the lower support member 18a are disposed in the cavity 101 of the molds 100 while the shaft 14 extending from the gap-forming member 18 is gripped and held by the molds 100. In this state, melting resin is poured into the cavity 101 of the molds 100 and cured. Then, the left and right molds 100 are opened and the bearing unit 10 is taken out therefrom. In this way, the bearing unit 10 in which the internal structure is assembled into the stator member 16 can be unit-molded as shown in
Incidentally, while the bearing units 10 according to the embodiments are each applied to the fan motor as described above, the present invention is not limited to this. The present invention can be applied to motor equipment (e.g., various types of memory media drives) other than the fan motor.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
Number | Date | Country | Kind |
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2006-216337 | Aug 2006 | JP | national |
Number | Name | Date | Kind |
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6948852 | Oelsch | Sep 2005 | B2 |
Number | Date | Country |
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2002-098146 | Apr 2002 | JP |
2003-130066 | May 2003 | JP |
2004-036892 | Feb 2004 | JP |
2005-127514 | May 2005 | JP |
2005-315408 | Nov 2005 | JP |
2006-64171 | Mar 2006 | JP |
Number | Date | Country | |
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20080036319 A1 | Feb 2008 | US |