JXR652050交叉圆锥滚子轴承 薄壁轴承 轴承型号 bearing type 尺 寸，mm boundary dimensions 额定动负荷，N basic dynamic load rating 系数 coefficient K d D T R 双列径向 double-row (radial) 推力 Thrust JXR652050 310 425 45 2.5 82200 102000 0.46