Front upper structure of automotive vehicle

Abstract

A hood structure for absorbing an impact applied to a hood (31) of an automotive vehicle at collision has: a hood outer panel (33) for closing an engine room (35); at least one impact absorb body (43) disposed under the hood outer panel, for absorbing the impact applied to the hood when deformed; and an engine (37) disposed under the impact absorb body, for stopping the deformed impact absorb body. Here, to reduce head injury criterion (HIC) effectively at a shortest possible stoke of the hood outer panel, an impact energy absorption rate of the impact absorb body and a total hollow gap formed between the hood outer panel (33) and the engine (37) are both determined in such a way that an impact energy generated at collision can be absorbed in accordance with an ideal impact energy absorption waveform Cm representative of an ideal relationship between reaction force (F) and stroke (S) of the deformed hood outer panel. The ideal impact waveform Cm can be obtained by calculation on the basis of an amount of impact energy required to be absorbed at collision and in accordance with the HIC derivation formulae (1) and (2). Since the impact absorb body is deformed at collision at a relatively moderate energy absorption rate to generate a secondary reaction force required for the ideal impact waveform Cm, the head impact characteristics can be securely improved.