| 摘要 |
A dynamic pressure bearing is provided which has a lubricant fluid reservoir space that can easily cope with increasing and decreasing of a lubricant fluid, and that can surely prevent leakage of the lubricant fluid to the outside caused by thermal expansion due to temperature rise, from occurring, and which can be processed relatively easily. In order to attain the object, a radial dynamic bearing is formed between a sleeve 2 and a shaft 1 which is vertically fitted into the sleeve 2, and, in an inner peripheral face of the sleeve, a first tapered portion 2c in which the diameter is gradually increased toward the outer side in a radial direction as downward moving from an opening 4 between the shaft 1 and the sleeve 2 formed in an upper end part, to the middle, and a second tapered portion 2e in which the diameter is gradually decreased toward the outer side in a radial direction as moving from the middle toward the lower side are disposed. An inclination angle beta of the second tapered portion 2e with respect to the shaft is 4° to 10°, and an inclination angle alpha of the first tapered portion 2c with respect to the shaft is smaller than the inclination angle beta of the second tapered portion with respect to the shaft. The axial length of the first tapered portion is shorter than that of the second tapered portion.
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