| 摘要 |
<p>A vehicular internal-gear-type oil pump provided with (a) a circular pump chamber defined by a pump body and a pump cover, (b) an annular driven gear which has internal teeth, and an outer circumferential surface opposed to an inner circumferential surface defining said pump chamber, and which is rotatably supported by the inner circumferential surface defining said pump chamber, and (c) a drive gear which has external teeth engaging with the internal teeth of said driven gear and which is disposed rotatably about an axis of rotation thereof eccentric with respect to an axis of rotation of said driven gear, to rotate said driven gear, characterized in that wherein: said driven gear has a plurality of first dynamic pressure generating grooves formed in local areas of its outer circumferential surface; and each of said first dynamic pressure generating grooves has a depth in a radial direction of the driven gear, which depth is determined such that a gap ratio which is a ratio of a distance of a gap from a bottom of said first dynamic pressure generating groove to said inner circumferential surface to a distance of a gap from the outer circumferential surface of said driven gear to said inner circumferential surface is held within a predetermined range in which a dynamic pressure generated by said first dynamic pressure generating grooves and changing as a function of said gap ratio has a maximal value and in which a fluid friction coefficient generated on the basis of said first dynamic pressure generating grooves and changing as a function of said gap ratio has a minimal value.</p> |
