Hi,

I am a mechanical design engineer and mostly involve in gear design (spur and helical). So far I have designed gears for better strength and life characteristics. I never tried to work on their noise and vibration part. Can somebody explain me the parameters that I should keep in mind for low noise and vibration? Thanks for your help.

 

Hi there,

I do motors and generators, but - balance and smooth meshing; helcial gears make less noise than spur gears.

tony

 

Hi Tony,

Thanks. But can you be more specific about any parameter like profile deviation, pitch error etc.?

 

For smooth running of a gear pair, the contact ratios play a great part. In the case of Spur gears the Radial Contact ratio and in the case of a Helical Gear both the radial and Axial contact ratio are important. Generally the contact ratio should be more than 1 preferably more than 1.2. At times gear pairs are corrected for S0 correction (CD remains at the theoretical value) to have a higher addendum value on the smaller pinion and a shorter addendum on the gear.
Contact ratio explained means that as a tooth engages and then leaves the mating teeth another tooth should have already engaged the drive.
Apart from the above Lubrication and Profile correctness also plays a part.

 

Thanks Sciyer...

 

There are many factors that can induce and affect gear noise. Geometrical inaccuracy of the gears being the main cause of noise.
ie:
pitch error,
eccentricity of gears and or shafts.
Shaft misalignment, in manufacture as well as due to loading of the mesh, gears can be crowned to minimize this affect.
Tooth finish, a poor tooth finish can induce noise but too smooth a finish can also cause noise, ringing due to insufficient lubrication between teeth under load. Teeth that have a good machined finish tends to retain oil.
Poor lubrication, insufficient as well as too much lubrication at speed.
Poor bearing mounting, weak casings or mounting can attenuate drive noise frequencies. Pulsed load input as opposed to a smooth input.
To minimize gear noise the gears and mountings should be sturdy enough to transmit the loading have good geometrical accuracy, the gears should be have addendum correction for ratios other than 1 to 1. They should be crowned and have tip relief with good lubrication. The list does go on and on.

 

Thanks, blackball. I feel that gave me a good information.

 

I think you got the name incorrectly.

 

I'm sorry vic... It was not intentional...
@Sciyer - Must have been thankful, if you had left me a private message...

 

It is also good idea to try to compensate for errors using a pair of helical gears in which one can move axially to compensate for errors or wear slacks. You can use flat springs or elastic elements. A greeting.