当柴油机曲轴曲拐的两个主轴承低于相邻轴承时,曲拐的两段主轴颈弯曲成塌腰形。若此时曲柄销转至上止点(见图1a),曲拐的两臂向外张开,会使两臂的距离(L_上)增大;若曲柄销转至下止点(见图1b),两臂则向内收拢,两臂之间的距离(L_下)减小。当曲拐 When the two crankshaft crankshaft crankshaft bearings are lower than the adjacent bearings, the crank of the two crank bend into a collapse-shaped. If the crank pin is turned to the top dead center (see Figure 1a), the arms of the bell crank open outward and the distance between arms (L_) will increase. If the crank pin goes to bottom dead center 1b), the arms are folded inward, the distance between the arms (L_ down) decreases. When the crank