เครื่องคำนวณความถี่ข้อบกพร่องของโซ่ลูกกลิ้ง

Tooth meshing frequency (TMF) is the rate at which chain links engage with sprocket teeth. It equals the number of teeth on the driving sprocket multiplied by the shaft rotational frequency: TMF = Z₁ × RPM / 60.

This frequency is a dominant vibration source in chain drives and its amplitude increases with worn or damaged teeth.

Chain link frequency is the rate at which one complete revolution of the chain loop occurs. It equals the tooth meshing frequency divided by the total number of links:

f_chain = Z₁ × RPM / (60 × N_links)

A defect on a single chain link (tight link, damaged roller) will produce vibration at this frequency.

Chain wear typically increases the amplitude of tooth meshing frequency and its harmonics (2×, 3×, 4× TMF). Key indicators:

• Rising TMF harmonics — chain elongation, worn sprocket teeth
• Sidebands around TMF at chain link frequency — modulation from chain defects
• Broadband noise increase — severe wear, loose chain
• 1× chain frequency peak — single defective or tight link

Common causes include:

• Chain wear and elongation (pitch growth)
• Misaligned sprockets
• Improper chain tension (too tight or too loose)
• Worn sprocket teeth (hooked teeth profile)
• Damaged or stiff chain links
• Polygonal (chordal) effect — inherent to chain drives

The polygonal (chordal) effect occurs because a chain wraps around a sprocket as a polygon rather than a smooth circle. This causes periodic speed variation at the tooth meshing frequency.

The effect is more pronounced with fewer teeth on the sprocket. Using sprockets with 21 or more teeth significantly reduces the chordal action. The speed variation is approximately ±(1 − cos(180°/Z)) × 100%.