Seat track mechanism for vehicle
A seat track mechanism for a vehicle, includes a lower rail mounted to a vehicle floor; an upper rail supported by the lower rail and slidable relative to the lower rail; and spherical rotators held between the lower and upper rails, the spherical rotators rolling via a sliding movement of the upper rail. One of the upper rail and the lower rail includes at least one horizontal flat portion parallel to a widthwise direction of the seat track mechanism and parallel to a direction of the sliding movement of the upper rail, and the other of the upper rail and the lower rail includes at least one rotator supporting recess having a circularly arcuate shape in cross section which is uniform in a lengthwise direction of the seat track mechanism, the spherical rotators being held between the rotator supporting recess and the horizontal flat portion.
1. A seat track mechanism capable of mounting to a vehicle, comprising:
a lower rail mountable to a vehicle floor;
an upper rail supported by said lower rail to be slidable relative to said lower rail;
wherein said upper rail includes at least two horizontal flat portions substantially parallel to a widthwise direction of said seat track mechanism and substantially parallel to a direction of said sliding movement of said upper rail; and
wherein said upper rail comprises:
a central portion having an inverted U-shaped cross section; and
two anti-detaching portions which are formed on opposite sides of said central portion in a widthwise direction thereof to prevent said upper rail from being detached from said lower rail,
wherein said two anti-detaching portions apply a component force on said central portion so as to urge said central portion to increase a width thereof by abutting against two flanges formed on said lower rail, respectively, when a pulling load in a direction obliquely upward and lateral is imposed on said upper rail.
2. The seat track mechanism according to claim 1 , wherein each said two anti-detaching portions produces a component force urging a free end thereof that abuts against associated one of said two flanges to tilt toward a widthwise center of said upper rail about an axis substantially parallel to a lengthwise direction of said upper rail when said pulling load is imposed on said upper rail.
3. The seat track mechanism according to claim 2 , wherein said free end of each anti-detaching portion of said upper rail is positioned closer to said central portion of said upper rail than said axis, and
wherein an angle of a line connecting said free end of each anti-detaching portion with said axis relative to a vertical direction is greater than an angle of said direction of said pulling load.
4. The seat track mechanism according to claim 1 , wherein said lower rail comprises two deformation preventive portions which are positioned adjacent to said opposite sides of said central portion of said upper rail to prevent said width of said central portion of said upper rail from increasing.
5. The seat track mechanism according to claim 1 , wherein said two anti-detaching portions of said upper rail are provided as a pair which are respectively positioned on opposite sides of said central portion of said upper rail in said widthwise direction thereof to be substantially bisymmetrical to each other.
6. The seat track mechanism according to claim 1 , wherein said central portion and said two anti-detaching portions of said upper rail are formed to have a general Ω-shape in cross section taken along a plane orthogonal to a direction of sliding movement of said upper rail relative to said lower rail wherein the general Ω-shape has a flat top with straight sides extending downward then outward then upward then at an angle upward and inward.
7. The seat track mechanism according to claim 1 , wherein the seat track mechanism additionally comprises upper and lower spherical rotators held between said lower rail and said upper rail, wherein said spherical rotators roll according to a sliding movement of said upper rail, and wherein the upper spherical rotators have a smaller diameter than the lower spherical rotators.