Abstract: A coupling mechanism for a vehicle body having mutually pivotable first and second frames comprises an axle fixed to the first frame, a rotating member fixed to the second frame and rotatably mounted around the axle, and a torsional resistance module that is actuated when the axle and the rotating member rotate relative to each other. The torsional resistance module includes two force magnifying mechanisms connected between the first frame and the rotating member. A buffering member is disposed between the force magnifying mechanisms. When the buffering member is pressed, a relative torsional resistance is provided between the first and second frames through transmission of the force magnifying mechanisms. The torsional resistance has a non-linear relationship with a relative rotational angle between the first and second frames.