Seat sliding device

A seat sliding device, comprising:

• an upper rail fixedly mounted on a seat and extending in a third direction, said seat sliding in said third direction, said upper rail having a substantially flat base portion, being mounted on said seat;
• two side wall portions;
• two flange portions;
• said upper rail having an upper rail cross section defined by said base portion extending in a first direction which is approximately perpendicular to said third direction, said base portion having two side ends, said side wall portions extending from said side ends of said base portion, respectively, in a second direction which is approximately perpendicular to said first and third directions, respectively, said side wall portions having respective ends distal from said base portion, said flange portions extending from said distal ends of said side wall portions, respectively, at least in the first direction;
• a lower rail being fixedly mounted on a vehicle body having a substantially flat base portion, two side wall portions and two flange portions, and having a lower rail cross section that is substantially identical to said upper rail cross section taken along said first and second directions;
• and
• a rolling member for assisting said upper rail when sliding along said lower rail in said third direction by rolling inside said upper and lower rails;
• and wherein, said upper and lower rails form a seat sliding body while engaging with each other in said third direction, said seat sliding body having a unitary cross section taken in said first and second directions, said unitary cross section being defined by a first length in said first direction and a second length in said second direction, said first and second lengths being approximately equal wherein said rolling member includes a pair of rolling members;
• a retainer for supporting said pair of rolling members in said seat sliding body, said retainer having a base portion and first and second supporting holes, said base portion of said retainer being arranged in said seat sliding body in said second direction, said first and second supporting holes being provided in said second direction in said base portion of said retainer;
• and wherein, said rolling members have first and second shafts protruding from side faces on said rolling members at positions of the rotational axis thereof, said first shaft abutting against said side wall portions of said upper and lower rails, said second shaft being fitted in said supporting holes of said retainer.