Patent ID: 8292116

Claim:
An oil tank structure, comprising: a cylindrical tank; an oil introducer that is provided in a sidewall of said cylindrical tank and introduces oil in a direction tangential to said sidewall; at least one groove-like passage that is provided along a circumference of said sidewall of said cylindrical tank to allow said introduced oil to flow in and out of said groove-like passage; an oil cooler that is provided on said sidewall of said cylindrical tank and cools said groove-like passage; and an outlet in a bottom of said cylindrical tank, wherein said groove-like passage has an opening on a side of a central axis of said sidewall of said cylindrical tank, and said groove-like passage is provided such that at least one of: a groove depth thereof gradually decreases from an upper position to a lower position on said sidewall, and a groove width gradually increases from said upper position to said lower position on said sidewall.