What causes the noise of the H series right angle gearbox to exceed the standard?

The main reasons for the excessive noise of the H-series right angle gearbox connected to the diesel engine are abnormal gear meshing, machining and assembly errors, and poor lubrication. Among them, the three main causes are small overlap, excessive tooth surface roughness, and deteriorated or insufficient lubricating oil, accounting for more than 60% of on-site fault cases. In addition, bearing damage, box resonance, and seal failure can significantly exacerbate the noise of the right angle gearbox. The following is a systematic analysis:
1、 Improper design and parameter selection
The overlap is too small
·The coincidence degree reflects the number of teeth involved in meshing at the same time. If the design is too small, it will result in prolonged single tooth bearing time, increased impact force, and periodic "clicking" sound.
·Insufficient longitudinal overlap of helical gears can also cause axial vibration and increased noise.
Unreasonable parameter matching
 
·Improper pressure angle can increase the normal force on the tooth surface and exacerbate vibration noise;
·The mismatch between helix angle and tooth width affects the smoothness of meshing, leading to an increase in noise.
Improper or unreformed tooth profile
·Gears lacking modification are prone to edge contact under load, resulting in local stress concentration and impact noise.
2、 Processing and manufacturing precision defects
Excessive base joint error and tooth profile error
·For every 0.01mm increase in error, the noise level can be significantly improved under high-speed overload;
·Accumulated pitch error can also cause low-frequency noise, especially during high torque transmission.
The surface roughness is too large
·The tooth surface is like "sandpaper friction", producing high-frequency vibrations and sharp whistling sounds;
·Rough surfaces also accelerate wear, further exacerbating noise issues.
Material and heat treatment issues
·Insufficient wear resistance of materials (such as POM, PA66) or high-temperature softening (TPEE failure at 64 ℃) can lead to tooth deformation and increased noise.
 
3、 Assembly and installation errors
Center distance deviation and axis parallelism difference
 
·Causing gear misalignment, tooth making noise, and periodic abnormal noise, deformation of the box cover can increase the noise by 12dB;
·Installing bearings too tightly or too loosely can also disrupt the balance of operation and cause a "rustling" sound.
Poor alignment of the coupling
·When the axis deviation of the diesel engine gearbox pump is greater than 0.1mm, alternating loads are generated, inducing vibration and noise coupling.
Loose fasteners
·Loose anchor bolts and flange connections cause gaps between components, resulting in knocking noise.
4、 Lubrication system failure
Insufficient or deteriorated lubricating oil
·Low oil level or aging of the oil can cause the lubricating film to rupture, resulting in high temperature and harsh noise caused by direct metal friction;
·Poor quality oil is prone to oxidation and the formation of sludge, which can block the oil circuit and exacerbate friction and abnormal noise.
Improper selection of lubricant
·Lack of long-lasting low-noise lubricating grease, noise can increase by more than 20% and accelerate wear;
·The hardening of lubricating grease at low temperatures and softening at high temperatures can both affect the lubrication effect.
Sealing failure leads to contamination
·Dust and water vapor intrusion cause emulsification failure of lubricating grease, rusting of metal parts, and increased friction leading to noise.
5、 Operation and operating conditions factors
Load and speed fluctuations
·Fluctuations in input torque, frequent start stop or overload operation can exacerbate gear impact and vibration noise.
Bearing malfunction
·Cracks in the raceway and wear of the rollers can produce periodic "clicking" sounds mixed with buzzing, which are signals for bearing distress.
Structural resonance amplification noise
·When the meshing frequency approaches the natural frequency of the box, the amplitude is amplified, and the noise increases dramatically at a specific speed;
·Due to gradual meshing, helical gears produce 3-10dB less noise than spur gears, and reasonable selection can reduce noise.