Gearbox mechanism and seat sliding device provided with the gearbox mechanism

A gearbox mechanism comprising:

• a first gear;
• a second gear disposed to intersect with the first gear and meshing with the first gear;
• and
• a gearbox in which the first gear and the second gear are rotatably housed, wherein
• the first gear includes a first gear portion disposed at a center portion of the first gear in an axial direction and meshing with the second gear, and a pair of first shaft portions smaller in outer diameter than the first gear portion and disposed on both sides of the first gear portion in an axial direction,
• the gearbox includes a first housing section in which the first gear portion is housed, a pair of shaft hole portions smaller in diameter than the first housing section and in which the first shaft portion is housed, and a second housing section configured to communicate with the first housing section on one side in an intersecting direction intersecting with the axial direction of the first gear and the axial direction of the second gear and in which the second gear is housed,
• a bearing bush is disposed between the first shaft portion and the shaft hole portion,
• the gearbox includes a first divided body and a second divided body which are divided in the axial direction of the second gear,
• a shaft projection projecting toward an opposite divided body and a through-hole into which the shaft projection is inserted are formed in divided surfaces of the first divided body and the second divided body,
• the divided surfaces of the first divided body and the second divided body are formed at offset positions that are offset to the first divided body side in an intersecting direction with respect to an axis center of the first gear,
• a second recess on the second divided body side including the shaft hole portions includes a second semicircular arc portion formed concentrically with the axis center of the first gear, and a second linear portion which is formed continuous to both ends of the second arc portion and extends linearly toward the first divided body side in the intersecting direction, and
• a first recess on the first divided body side including the shaft hole portions includes a first linear portion which is formed at a position superposed on the axis center of the first gear in the intersecting direction and extends linearly in a direction orthogonal to the intersecting direction, and a quarter-arc-shaped first portion which is formed continuous to both ends of the first linear portion and has the same radius of curvature as the second arc portion.