| Bearing unit and motor and electric apparatus having bearing unit -> Monitor Keywords |
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Bearing unit and motor and electric apparatus having bearing unitRelated Patent Categories: Pumps, Motor Driven, Motor Within Rotary Pumping Member, Armature Within Pumping Member, Stator Within ArmatureBearing unit and motor and electric apparatus having bearing unit description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060292015, Bearing unit and motor and electric apparatus having bearing unit. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCES TO RELATED APPLICATIONS [0001] The present invention contains subject matter related to Japanese Patent Application JP 2005-185601 with the Japanese Patent Office on Jun. 24, 2005, the entire contents of which being incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to a bearing unit for supporting a rotary shaft for rotation or for supporting a rotatable member for rotation on a shaft, and a motor and an electronic apparatus which have a bearing unit. [0004] 2. Description of the Related Art [0005] Such a bearing unit for supporting a rotary shaft for rotation as shown in FIG. 15 is known in the past. [0006] Referring to FIG. 15, the bearing unit 100 shown is used to support a rotary shaft 101 for rotation thereon. The bearing unit 100 includes a radial bearing 104 for supporting the rotary shaft 101 in a circumferential direction, a thrust bearing 110 for supporting one end of the rotary shaft 101 in a thrust direction, and a housing 105 in which the radial bearing 104 and the thrust bearing 110 are accommodated. [0007] In the bearing unit 100, the radial bearing 104 cooperates with lubricating oil as viscous fluid filled in the housing 105 to form a dynamic pressure fluid bearing. A dynamic pressure generating groove 111 for generating dynamic pressure is formed on an inner circumferential face of the radial bearing 104 in which the rotary shaft 101 is fitted. [0008] The housing 105 in which the radial bearing 104 and the thrust bearing 110 are accommodated includes a tubular housing body 106, a bottom closing portion 107 and an upper closing member 108. The bottom closing portion 107 is formed integrally with the housing body 106 so as to close up one end side of the housing body 106, and forms one end side portion. The upper closing member 108 is provided on the other end side of the housing body 106 on which the housing body 106 is open. [0009] A shaft fitting hole 109 is provided at a central portion of the upper closing member 108, and the rotary shaft 101 supported for rotation on the radial bearing 104 accommodated in the housing 105 is fitted in the shaft fitting hole 109. The thrust bearing 110 is provided on the inner face side of the bottom closing portion 107 of the housing body 106. A bearing supporting portion 102 provided at the one end portion in the thrust direction of the rotary shaft 101 supported on the radial bearing 104 is supported for rotation on the thrust bearing 110. [0010] The thrust bearing 110 is formed as a pivot bearing which supports the bearing supporting portion 102 of the rotary shaft 101, which has an end formed in an arcuate or tapering shape, at a point. [0011] The housing 105 having the configuration described above is formed by attaching the radial bearing 104, thrust bearing 110 and rotary shaft 101 to the housing body 106 and then bonding the upper closing member 108 to the housing body 106 by a sealing portion 121. [0012] The rotary shaft 101 is supported at the bearing supporting portion 102 on one end side thereof by the thrust bearing 110 and at an outer circumferential face of a shaft portion body 103 thereof by the radial bearing 104. Further, the rotary shaft 101 is supported on the attaching portion 120 side provided on the other side thereof by the housing 105 such that the attaching portion 120 side thereof projects from the shaft fitting hole 109 provided in the upper closing member 108 of the housing 105. [0013] Further, a groove 116 is provided on the rotary shaft 101 between the bearing supporting portion 102 and the shaft portion body 103. An annular washer 115 serving as a coming off preventing member is provided in an opposing relationship to the groove 116 on the bottom closing portion 107. The washer 115 prevents the rotary shaft 101 from coming off from the housing 105. When the washer 115 is pushed by the bearing supporting portion 102 of the rotary shaft 101, it is deformed in a thrust direction to allow the bearing supporting portion 102 to be inserted into and thus attached to the groove 116. [0014] Incidentally, the shaft fitting hole 109 is formed with an inner diameter a little greater than the outer diameter of the shaft portion body 103 so that the rotary shaft 101 fitted in the shaft fitting hole 109 may rotate without slidably contacting with the inner circumferential face of the shaft fitting hole 109. At this time, the shaft fitting hole 109 is formed such that a gap 112 of a distance x sufficient to prevent lubricating oil 113 filled in the housing 105 from leaking from within the housing 105 is formed between the circumferential face of the shaft fitting hole 109 and the outer circumferential face of the shaft portion body 103. [0015] A tapering portion 114 is provided on the outer circumferential face of the rotary shaft 101 in an opposing relationship to the inner circumferential face of the shaft fitting hole 109. The tapering portion 114 is inclined so that the gap 112 formed between the outer circumferential face of the rotary shaft 101 and the inner circumferential face of the shaft fitting hole 109 increases toward the outer side of the housing 105. The tapering portion 114 forms a pressure gradient in the gap 112 formed between the outer circumferential face of the rotary shaft 101 and the inner circumferential face of the shaft fitting hole 109 to generate force which acts to draw the lubricating oil 113 filled in the housing 105 into the inside of the housing 105. Since, upon rotation of the rotary shaft 101, the lubricating oil 113 is biased so as to be drawn into the inside of the housing 105, the lubricating oil 113 enters the dynamic pressure generating groove 111 of the radial bearing 104 formed from a dynamic pressure fluid bearing with certainty to generate a dynamic pressure. Consequently, stabilized support of the rotary shaft 101 is implemented and besides leakage of the lubricating oil 113 filled in the housing 105 can be prevented. [0016] In the bearing unit 100 having the configuration described hereinabove with reference to FIG. 15, the rotary shaft 101 is exposed at just one end thereof on the shaft fitting hole 109 side but is covered with the housing member except a small gap of the shaft fitting hole 109. Therefore, the bearing unit 100 can prevent leakage of the lubricating oil 113 to the outside of the housing 105. Further, since just the gap of the shaft fitting hole 109 forms a communicating portion to the outside, scattering of the lubricating oil which may be caused by an impact can be prevented thereby to retain the lubricating oil with certainty. Further, in the bearing unit 100, the rotary shaft 101 can be prevented from coming off from the housing 105 by the washer 115. [0017] In short, since the bearing unit 100 can retain the lubricating oil 113 with certainty and prevent coming off of the rotary shaft 101, it can maintain the lubricating performance and the rotational performance to support the rotary shaft for rotation or support a rotary member for rotation on a shaft. [0018] For such a bearing unit as described above, it is demanded to further reduce deflection and so forth of a rotary shaft to enhance the rotational performance. In order to reduce deflection and so forth of a rotary shaft to enhance the rotational performance, it is necessary to raise the rigidity. To raise the rigidity of a bearing unit can be implemented, for example, by increasing the length in an axial direction of a radial bearing which forms the bearing unit. [0019] However, in the bearing unit 100 described above, the radial bearing which forms the bearing unit 100 is formed from a sintered member or the like, and there is a limitation to casting of the bearing unit 100 from a relationship between the diameter and the length in the axial direction. In this manner, the bearing unit has a limitation to increase of the rigidity and it is difficult to reduce deflection and so forth of a rotary member exceeding a predetermined condition. [0020] A bearing unit similar to the bearing unit 100 described hereinabove with reference to FIG. 15 is disclosed in Japanese Patent Laid-open No. 2003-130043 SUMMARY OF THE INVENTION [0021] There is a need for the present invention to provide a bearing unit and a motor and an electronic apparatus including a bearing unit by which the rigidity of a shaft can be raised to suppress deflection of the shaft and lubricating oil can be retained with certainty. 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