Patent ID: 7665586

Claim:
A crash box having a tubular body having a flat cross sectional shape with a flatness of at least 1.3 and at most 2.0, characterized in that over the entire length of the tubular body in the axial direction, the transverse cross-sectional shape in the axial direction of the tubular body is a polygon, for at least a first side forming the polygon, when the angle formed by second and third sides which adjoin the first side is α, the relationship between the length (L 1 ) of the first side and the distance (L 2 ) between two ends of the second and third sides which do not intersect the first side satisfies the following equation (1), 0< L 1/ L 2<1/{2×sin(α/2)+1} (1) wherein the equation means that the length L 1 is less than a length of either of the second and third sides, the angle α is at least 100° and at most 140°, and the flatness is defined by the ratio (L 2 /L 4 ) of the distance (L 2 ) to the distance (L 4 ) wherein the distance (L 2 ) is as defined above and the distance (L 4 ) is a distance between the first side and a fourth side which form the polygon and which are approximately parallel and separated by a distance (L 4 ), wherein, when an impact is applied in the axial direction from one end of the tubular body in the axial direction, the tubular body, by virtue of the transverse cross-sectional shape and satisfying the equation relating to the first, second and third sides, absorbs the impact energy by the sides of the tubular body buckling in a uniform fashion along the length of the tubular body.