Oil separator

An oil separator, comprising:

• a substantially cylindrical container main body;
• an introduction flow channel having an opening into an inner wall of said container main body, and that is substantially vertically connected to said container main body;
• a partition wall member facing said opening of said introduction flow channel and extending along said inner wall of said container main body;
• an upper end member sealing a space between an upper end of said partition wall member and said inner wall of said container main body;
• and
• a side end member sealing a space between a first side end of said partition wall member and said inner wall of said container main body, the first side end being closer to the opening of the introduction flow channel than a second side end of said partition wall member opposite the first side end,
• wherein said second side end of said partition wall member is open with respect to said container main body,
• wherein a lower end of said partition wall member, which is opposite the upper end, is open with respect to said container main body,
• wherein a gap between said partition wall member and said inner wall of said container main body has a width that is not more than an inner diameter of said introduction flow channel, the width of said gap being at a maximum at least at said second side end which is open with respect to said container main body,
• wherein a length of an outer circumference of said partition wall member in a horizontal direction from a position facing a center of said introduction flow channel to the open side end is longer than a half of the inner diameter of said introduction flow channel and shorter than a half of a circumferential length of said inner wall of said container main body,
• wherein said partition wall member is arranged such that the width of said gap between said partition wall member and said inner wall of said container main body is at a minimum at the side end sealed by said side end member and is gradually wider toward the open side end,
• wherein the length of the outer circumference of said partition wall member in the horizontal direction from the position facing the center of said introduction flow channel to the open side end is longer than one sixth of the circumferential length of said inner wall of said container main body and shorter than one third of the circumferential length of said inner wall of said container main body,
• wherein a vertical length of said partition wall member at the open side end is longer than a vertical length of said partition wall member at the side end sealed by said side end member, and
• wherein said upper end member is downwardly inclined from a part of said upper end member above said introduction flow channel toward the open side end of said partition wall member.