Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1994-08-24
1997-10-07
LaBalle, Clayton E.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 90, 384107, H02K 708, H02K 709, F16C 3204
Patent
active
056752016
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention generally relates to a bearing structure, and more specifically, it relates to a composite bearing structure, having a prescribed load, for supporting a rotator rotating at a high speed.
BACKGROUND INFORMATION
In recent years there has been achieved an increase in storage capacity and reduction in access time of a hard disk driver (hereinafter referred to as "HDD"). Therefore, a high rotational speed and high rotational accuracy are required for a spindle motor for driving the HDD. In a sliding part of this rotating apparatus, a ball bearing has generally been employed for a bearing part, for example. So far as a conventional ball bearing has been employed, however, the upper withstandable rotational speed has been about 10000 r.p.m., due to a problem of seizure or wear.
In order to drive a precision motor requiring such a high rotational speed and high rotational accuracy at a higher speed, it has been proposed to employ an air bearing (dynamic pressure gas bearing) of ceramics such as SiC or Si.sub.3 N.sub.4 for a rotary sliding part. When a rotator is driven in a rotating apparatus employing such an air bearing, air is forcibly introduced at least into a clearance between a radial bearing body or a thrust bearing body and the rotator through a groove. Thus, the air pressure in the clearance is increased and the rotator is driven at a high speed and supported by an air bearing which is provided between the respective members. In order to implement high-speed rotation in such a manner, rotational accuracy during high-speed rotation is maintained by the air bearing, and a thrust-directional load which is applied to the rotator is supported by the air bearing. Further, the aforementioned radial bearing body and the rotator can withstand sliding between the respective members in a low-speed range during starting/stopping of the rotator since the same are formed by ceramics materials respectively.
When a conventional radial bearing body which is formed by ceramics such as Si.sub.3 N.sub.4 is employed in high-speed rotation exceeding 5000 r.p.m., however, an impactive knock wear phenomenon is caused by contact between bearing members. Namely, sliding between the respective members is caused in a high-speed operating range when abrupt radial impact force is applied to the rotator during high-speed rotation. It has been difficult for a conventional ceramics sintered body to withstand the high-speed sliding. Even if a radial bearing body or a thrust bearing body has been formed by an air bearing body consisting of a ceramics sintered body as described above, therefore, it has been difficult to support a radial impact force abruptly applied to a rotator during high-speed rotation, although rotational accuracy in high-speed rotation has been maintained and a thrust-directional load applied to the rotator has been supported.
When the aforementioned air bearing member is made of a ceramics material, further, high machining or production and assembling accuracy is required for the ceramics member, which leads to an increase in manufacturing cost. Further, it is necessary to use the air bearing in a clean environment since it must be protected from penetration of dust. Thus, the structure related to the air bearing is complicated such that a closed or sealed container may be required to enclose the same, and hence the space is disadvantageously increased. In order to solve such a problem, a bushing type slide bearing body which is made of ceramics may be used as a bearing body for high-speed rotation.
FIG. 11 is a longitudinal sectional view schematically showing the structure of a conventional bushing type slide bearing body made of ceramics. This bushing type slide bearing body comprises two thrust slide bearing bodies 81 and 82, and pairs of radial slide bearing bodies and rotators 83 and 84. The bushing type slide bearing body having such a structure can withstand sliding between the respective members in a low-speed range or region during starting/stopping. However,
REFERENCES:
patent: 3377113 (1968-04-01), Wilson
patent: 3950039 (1976-04-01), Huber et al.
patent: 5043615 (1991-08-01), Oshima
patent: 5142173 (1992-08-01), Konno et al.
patent: 5280208 (1994-01-01), Komura et al.
Wear of Si.sub.3 N.sub.4 Ceramics Measured with Various Testers M. Iwasa et al. Yogyo-Kyokai-Shi, 1985 pp. 73-80.
Higuchi Matsuo
Katayama Tetsuya
Komura Osamu
Matsunuma Kenji
Miyake Masaya
Fasse W. F.
Fasse W. G.
LaBalle Clayton E.
Sumitomo Electric Industries Ltd.
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