What is a flexible coupling and why use one?

A flexible coupling connects two shafts while accommodating misalignment (angular, parallel, axial) and damping vibrations. They protect connected equipment from shock loads and torsional vibration, extending bearing and seal life.

How do I select the right service factor?

Service factors account for load characteristics. Uniform loads (fans, pumps) use 1.0-1.5. Moderate shock (compressors, mixers) use 1.5-2.0. Heavy shock (crushers, presses) use 2.0-3.0 or higher. Always check manufacturer catalogs for specific applications.

What is torsional stiffness in a coupling?

Torsional stiffness (Ct) is the torque required per unit angle of twist, measured in Nm/rad. Higher stiffness means more accurate motion transmission but less vibration damping. DIN 740 defines dynamic and static stiffness values.

Why is natural frequency important for coupling selection?

The torsional natural frequency of the coupling-shaft system must be separated from excitation frequencies (typically shaft speed and its multiples) by at least 20%. Resonance causes excessive vibration and coupling failure.

What is DIN 740 and how does it apply to couplings?

DIN 740 is a German standard for flexible shaft couplings. Part 2 covers torsional vibration characteristics, defining how to measure and specify dynamic torsional stiffness, damping, and the coupling's influence on system natural frequencies.

免費工程工具 #081

彈性聯軸器計算器

依據 DIN 740 計算彈性聯軸器所需的扭矩額定值、扭轉剛性與自然頻率。選擇聯軸器類型並輸入運轉條件。

DIN 740 聯軸器選型扭轉分析

功率 (kW)

轉速 (RPM)

服務係數 (K_A)

聯軸器類型

慣量 — 驅動側 (kg·m²)

慣量 — 被驅動側 (kg·m²)

快速預設

結果

所需聯軸器扭矩額定值

—

額定扭矩 (T_n)

—

扭轉剛性 (C_t)

—

自然頻率 (f_n)

—

運轉頻率

—

頻率比 (f_n/f_op)

—

額定扭矩

聯軸器傳遞的額定扭矩由功率與轉速導出：

P — 傳遞功率 (kW)
n — 轉速 (RPM)
T_n — 額定扭矩 (N·m)

所需扭矩額定值

依據 DIN 740，聯軸器必須針對包含使用係數的設計扭矩進行額定：

其中 K_A 為考量動態負載的應用/使用係數。

扭轉自然頻率

對於由聯軸器連接的兩慣量系統：

C_t — 聯軸器的動態扭轉剛性 (N·m/rad)
J₁, J₂ — 質量慣性矩 (kg·m²)

使用係數指南

K_A	負載特性	典型應用
1.0	均勻負載	風機、離心泵浦、輕型輸送機
1.25	輕微衝擊	皮帶輸送機、發電機、離心鼓風機
1.5	中等衝擊	往復式壓縮機、容積式泵浦
1.75	重衝擊	攪拌機、球磨機、橡膠擠出機
2.0–3.0	極端/反轉	破碎機、壓機、剪斷機、軋鋼機

⚠️ 注意： 自然頻率應至少與運轉頻率及其諧波保持 20% 的距離，以避免扭轉共振。DIN 740-2 建議 f_n/f_op > 1.2 或 f_n/f_op < 0.8。

範例 — 15 kW 壓縮機驅動

已知： P = 15 kW, n = 1500 RPM, K_A = 1.5

T_n = 9549 × 15 / 1500 = 95.5 N·m

T_req = 1.5 × 95.5 = 143.2 N·m

選擇 T_max ≥ 143.2 N·m 的聯軸器