1-9 Gear Noise
This figure indicates the results of a survey conducted by a manufacturer that produces gears for automobile, machine tools and speed reducers.
Cause of noise and vibration :
- Accuracy of gears
- Accuracy of assembly
- Tooth surface finish
- Configuration of gearbox
- Lubrication of gears
- Bearing
- Material of gears
- Design of gears
- Motor and variation of load
- Driving condition
- Shaft and shaft alignment
- Configuration of gears
- Wear of gears
- Surface damage on gears
- Others
Broken down by the factors contributing to gear noise, it becomes :
- Design.......35%
- Fabrication.......30%
- Usage.......20%
- Assembly.......15%
Causes (Items assumed to have effects on noise) :
- Bad tooth contact
- Large pitch error
- Large tooth profile error
- Oscillating torque load on the gear shaft
- Poor tooth surface finish
- Center distance is too small
- Rotation is too fast
- Ball and roller bearings are causing noise
- Gearbox is amplifying noise
- Deformation of gear due to heat treating
In order to manufacture gears that minimize noise during operation :
- Reduce the pitch error
- Reduce the tooth profile error
- Reduce the runout error
- Reduce the lead error
- Modify tooth surface by crowning
- Tip relieving may correct pitch error from tooth deformation
- Remove sharp corners of tooth by chamfering
- Eliminate the roughness on the tooth surface
- Increase the contact ratio – bigger contact ratio lowers the noise
- Try to design gearboxes as close to round shape as possible
- Use a flexible coupling between the prime mover and the gearbox
- Machine the mounting holes of gearbox precisely so that gears can be mounted accurately
- When assembling gears into gearbox, care must be taken that gears come in contact properly – to avoid edge contact
To improve surface finish, gears are generally shaved or ground. Spiral bevel gears are lapped or ground.
Left : Crowning of tooth
Right : Chamfering of tooth
Example of edge contact
This figure shows an example of data regarding noise level as a result of test on KHK stock gears.
▲ - ▲ : S45C without heat treatment
(SS2.5-24, SS2.5-48)
△ - △ : Plastic
(PS2.5-24, PS2.5-48)
● - ● : S45C Tooth surface high-frequency induction hardened and ground
(SSG2.5-24, SSG2.5-48)
○ - ○ : SCM415 Overall carburizing and quenching, tooth surface ground
(MSGB2.5-24, MSGB2.5-48)
Noise level of KHK stock gears 1984 - 1985
Vertical line – Decibel (db)
Horizontal line – n 1(rpm)
Related links :
齿轮的噪音
Spur Gears – Main page of spur gears
How to reduce Gear Noise – A page of Gear Technical Reference