Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-02-03
2001-03-27
Marmor, Charles A. (Department: 3681)
Bearings
Rotary bearing
Plain bearing
C384S114000, C384S905000
Reexamination Certificate
active
06206572
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a bearing device which can be suitably used in an environment in which the temperature largely changes.
Conventionally, a bearing device is used in which a shaft having dynamic pressure grooves is fitted into a sleeve made of a copper alloy.
In such a bearing device of the prior art, the sleeve and the shaft are made of materials of different kinds and have different coefficients of thermal expansion. Therefore, such a bearing device has a problem in that, when the temperature is changed, the gap between the sleeve and the shaft is largely changed and the supporting performance due to a dynamic pressure is lowered.
SUMMARY OF THE INVENTION
Consequently, it is an object of the invention to provide a bearing device in which the bearing performance is not lowered even when the temperature is changed.
In order attain the object, the bearing device is a bearing device in which a supporting portion and a supported portion are rotatably fitted to each other, and characterized in that one of the supporting portion and the supported portion has a surface layer on a surface of a body of the one portion, the surface layer having a coefficient of thermal expansion which is smaller than a coefficient of thermal expansion of the body, and the coefficient of thermal expansion of the body is larger than a coefficient of thermal expansion of the other one of the supporting portion and the supported portion.
In the bearing device, the coefficient of thermal expansion of the body of one of the supporting portion and the supported portion is larger than that of the other portion, and the surface layer having a coefficient of thermal expansion which is smaller than that of the body of the one portion is disposed on the surface of the body of the one portion. Even when the temperature of the bearing device is changed, therefore, influence of thermal expansion of the body having a larger coefficient of thermal expansion is suppressed or relaxed by the surface layer having a smaller coefficient of thermal expansion. Consequently, variation due to heat in the gap between the supporting portion and the supported portion can be reduced. As a result, even when the temperature is changed, the bearing performance is not lowered.
The bearing device of the invention is characterized in that a bearing surface of at least one of the supporting portion and the supported portion has dynamic pressure generating grooves.
The bearing device of the invention is a dynamic pressure bearing device. In such a dynamic pressure bearing device, the distance between the supporting portion and the supported portion largely affects the generated dynamic pressure. However, variation due to thermal expansion in the distance between the supporting portion and the supported portion is suppressed by the surface layer. Therefore, the supporting performance due to the dynamic pressure of the dynamic pressure bearing device is less changed by a temperature change.
The bearing device of the invention is characterized in that the supported portion is made of stainless alloyed steel, the body of the supporting portion is made of a copper alloy, and the surface layer is a nickel plated layer.
In the bearing device of the invention, even when the temperature of the bearing device is changed, influence of thermal expansion of the body of the supporting portion which is made of a copper alloy having a larger coefficient of thermal expansion is suppressed or relaxed by the nickel plated layer having a smaller coefficient of thermal expansion. Therefore, variation due to a temperature change in the gap between the supporting portion and the supported portion can be reduced. As a result, even when the temperature is changed, the performance of the bearing device is stable.
The bearing device of the invention is characterized in that the surface layer covers the whole of the surface of the body.
In the bearing device of the invention, since the whole of the surface of the body having a larger coefficient of thermal expansion is covered by the surface having a smaller coefficient of thermal expansion, thermal expansion of the body is suppressed or reduced by the surface layer. In the bearing device, even when the temperature is changed, therefore, the gap between the supporting portion and the supported portion is hardly varied. Consequently, it is possible to obtain a bearing device which is highly resistant to a temperature change.
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Kobayashi Yasuhiro
Matsue Shinji
Takahashi Takeshi
Takamura Yasuo
Jacobson Price Holman & Stern PLLC
Koyo Seiko Co. Ltd.
Marmor Charles A.
Parekh Ankur
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