Spindle drive for longitudinally adjusting a motor vehicle seat

A spindle drive for longitudinally adjusting a motor vehicle seat comprising

• an adjustment rail being longitudinally adjustable relative to a body mounted rail and
• an adjusting mechanism including spindle comprising an external thread, a driving worm comprising a first external toothing and connected to a driving device and a spindle nut comprising a second external toothing and an internal toothing, the second external toothing of the spindle nut engaging with the first external toothing of the driving worm and the internal toothing of the spindle nut engaging with the external thread of the spindle,
• wherein the spindle nut is formed by a hybrid spindle nut comprising a functional part arranged in the force flux between the driving worm and the spindle and at least one strengthening part deflecting crash forces from the adjustment rail into the spindle,
• wherein the spindle nut is formed in at least one centre section cylindrically with an external cylindrical mantle surface and two front faces laterally delimiting the cylindrical mantle surface, wherein the external toothing of the spindle nut is formed by recesses pointing radially inwards in the outer cylindrical mantle surface of the spindle nut, wherein the external toothing extends from a first front face along the cylindrical mantle surface towards another, second front face with a tooth depth decreasing towards the second front face, and
• wherein the internal toothing of the spindle nut is shifted in longitudinal direction to the external toothing of the spindle nut such that a central plane of the external toothing continuing vertical to the longitudinal direction is spaced apart to a central plane of the internal toothing.