Noise, Vibration, and Harshness (NVH) in gearboxes are influenced by several factors, which can broadly be categorized into design, material, manufacturing, and operational factors. Here are some key factors affecting NVH in gearboxes: ### Design Factors: 1. **Gear Geometry**: - **Tooth Profile**: Involute profiles can help reduce noise. - **Helix Angle**: Helical gears are generally quieter than spur gears. - **Module and Pressure Angle**: Affect the load distribution and contact pattern. 2. **Gear Alignment**: - **Shaft Alignment**: Misalignment can cause uneven load distribution and increased noise. - **Bearing Support**: Proper bearing support reduces vibrations. 3. **Casing Design**: - **Stiffness**: A more rigid casing can reduce vibration transmission. - **Damping Materials**: Use of damping materials can absorb vibrations. ### Material Factors: 1. **Material Quality**: - **Homogeneity**: Uniform material properties ensure consistent performance. - **Damping Properties**: Materials with higher damping capacity can reduce NVH. 2. **Heat Treatment**: - **Hardening**: Proper hardening reduces wear and noise. - **Stress Relief**: Reduces internal stresses that can cause vibrations. ### Manufacturing Factors: 1. **Precision of Machining**: - **Surface Finish**: Smoother surfaces result in quieter operation. - **Dimensional Accuracy**: High accuracy reduces deviations that cause noise and vibration. 2. **Assembly Quality**: - **Tolerances**: Tight tolerances ensure proper gear meshing. - **Balancing**: Properly balanced components reduce vibrations. ### Operational Factors: 1. **Load Conditions**: - **Load Variation**: Fluctuating loads can increase noise and vibration. - **Shock Loads**: Sudden loads can cause high stress and noise. 2. **Lubrication**: - **Type and Quality of Lubricant**: Proper lubrication reduces friction and noise. - **Lubricant Condition**: Contaminated or degraded lubricants can increase NVH. 3. **Speed of Operation**: - **Operating Speed**: Higher speeds can increase noise due to higher frequency vibrations. - **Resonance**: Operating at a resonant frequency can amplify vibrations. ### Environmental Factors: 1. **Temperature**: - **Thermal Expansion**: Changes in temperature can affect clearances and alignments. - **Lubricant Viscosity**: Temperature affects the viscosity of lubricants, influencing NVH. 2. **External Vibrations**: - **Mounting Conditions**: How the gearbox is mounted can affect the transmission of external vibrations. - **Adjacent Equipment**: Vibrations from nearby machinery can influence gearbox NVH. Addressing NVH in gearboxes typically involves optimizing these factors through careful design, material selection, precise manufacturing, and proper maintenance practices.