| 摘要 |
PURPOSE:To make a casing high longevity through making it hard to be cracked by forming a groove-shaped recess portion relieving the concentration of stress in the vicinity of the corner portion, which is within the range of being pressured highly at a time of operation, of a corner portion made up of a perimeter- wall portion and the inside-surface of a bottom portion. CONSTITUTION:A groove-shaped recess portion 40 is formed at a position which is 't' distant from a corner portion 35 make up of a perimeter-wall portion covering the outer perimeter of both gears and the inside surface of a bottom portion within the range of being pressured highly at a time of the casing main- body 3 of a gear pump being used. Hereupon, t<=about 0.5 mm is desirable. As above, the groove-shaped recess portion 40 which relieves the concentration of stress at the corner portion 35 is provided at a high pressure portion where a crack is apt to occur during the use of the casing main body 3 housing a pair of gears. Therefore, even if stress is repeatedly generated at the corner portion 35, a crack is made to be hard to occur. Accordingly, the casing main body 3 can be made to be of high longevity through being made to be hard to be cracked in spite of a use for many hours.
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