✅ 同步带轮实例5:20M 同步带轮,齿数 Z = 12 节距 P = 20.00 mm 节顶距 C = 4.32 mm(20M标准) 计算: 节径 d = (12 × 20.00) / π = 240 / 3.1416 ≈ 76.40 mm 外径 do = 76.40 - 2 × 4.32 = 76.40 - 8.64 = 67.76 mm ✅ 结果:外径 ≈ 67.76 mm