To provide a back door structure for a vehicle capable of suppressing the generation of noise in the vehicle caused by the vibration of a back door, and easily adjusting a vibration mode of the back door.
In this back door structure, the back door 14 is divided into two of an upper side door 18 and a lower side door 20, and intermediate sections of the lower side door 20 in a vertical direction at both ends in a vehicle width direction are rotatably connected by a pair of lock mechanisms 28 around an axis of rotation along the vehicle width direction. This constitution makes upper sides and lower sides of the lock mechanisms 28 reverse in the phase of vibration of the back door 14, and suppresses a variation in pressure in a vehicle compartment caused by the vibration of the back door 14. Thus, the noise generated between the upper section and the lower section of the back door 14 is offset, and the volume of the noise can be reduced. Moreover, the mechanical structure of the lock mechanism 28 establishes the reversal (inversion) of the phase of the vibration, therefore, the variation in a vibration mode caused by deterioration with age or a temperature change can be reduced (or brought to zero).
Kato Kazunori
Katsuichi Nishimoto
Hiroshi Fukuda