For decades, people debate about the difference between sound and noise.
A sound is something which does not hurt the human being while a noise could make you feel uncomfortable.
In the 90’s, a big improvement in the design and quality of car interiors has led to new noises in the automotive. Those noises were not noticeable before, covered by louder sounds coming from wind, tire/road contact and of course engines.
Rattling, Creaking, and Squeaking
Currently, drivers and passengers want to travel with more comfort like they would be in their living room listening to their Hi-Fi or just talking together. But now, in the cockpit, Rattling, Creaking, and Squeaking are no longer faded out by those external and surrounding noises.
Knowing social networks impact, noises in a car could very quickly cause negative brand perception influencing buying decisions. Unhappy drivers, due to those little cracking and rattling noises, are then driving NVH (Noise Vibration & Harshness) teams crazy at all OEM’s !
Therefore, Noise dampening is becoming a key “spec” in the car development, and not only in the premium segment… Even more crucial in the EV’s which by definition don’t face the engine noises issues…
But…, where are noises coming from?
Noises arise when you have contact between parts assembled in relative motion, or moving onto each other (sliding, rotating). The nature of materials and the shape of the parts can make a lot of a difference in noise generation (ABS/PC often used now in car interiors).
Interesting enough, everyone should realize that 95% of that noise comes from either boundary friction or mixed friction according to the famous Stribeck curve.
Wet or dry ?
Lubrication can then help you out and easily kill almost every noise.
Dry lubrication (mainly based on Anti Friction Coatings, AFC) leads to decrease surface vibration in static contacts and is very efficient for preventing the famous ‘stick slip’ effect in a sliding movement… The solid additives (PTFE, MoS2, Graphite) present in the AFC’s, play a key role for friction reduction .The type of binder (epoxy, Poly-Amide-Imide, Acrylates resins) are critical for good adhesion, temperature and wear resistance.
Nice features for AFC’s: They are not temperature dependent as they can be fully operational from -70°C on, and they can be invisible to the passengers by being transparent ;-)
And wet?
Wet lubricants on the other hand, will bring a much better damping feeling to your movement on the entire surface. Greases, oils or dispersions will therefore be more efficient in case of shocks and push movements.
You can imagine that quality and quantity of solid lubricants would play a major role… They do, but the thickener type for greases will also be essential to noise absorption. Polyurea thickeners will give you a fantastic damping feeling in case of push movements while complex soaps, thanks to their high shearing resistance over time will be perfect for gears and actuators. Finally the right choice of base oil viscosity will also play a major role in absorbing your noises.
Solutions for almost every noise
At Bechem we take those issues very seriously with our dry lubricants, Berucoat AK range, and our wet ones Berulub FR, FH and Berusoft ranges.
Door panel is a typical good example in NVH application. Friction occurs between the door plastic panel and the painted door frame, amplified by the volume of the door. Using an anti-friction coating such as Berucoat AK 978, sprayed on the plastic panel before being assembled on the door solves all squeaking little noises generated by the torsion of the body while driving. Invisible to the eye, Berucoat AK 978 is also temperature resistant without any leakage from -40 to +85°C.
Electric motors and actuators used for comfort and safety can often generate heavy “Sssshhhh” noises while being actuated. For example, plastic gears rotating onto other plastic or metal ones should be using the most adapted grease. Here the Berulub FR and FH series in various formulations will dampen the noise very efficiently but also improve life time and durability by being fully compatible with most of materials. Noise reduction will last longer thanks to their thickeners, and the solid additives will improve greatly the coefficient of friction from static to dynamic movement.
And now EV’s…
Recent improvements in acoustic dampening in the cockpit reveal new noises which were not noticeable before and this trend will even increase with the Ev’s. Meaning that this area is becoming a key focus for OEMs, and we don’t even talk about haptic feeling which is a quality expectation from end users too… but this is another story!
For more info, please contact us : info@bechem.fr or 00 33 3 90 20 84 20.
www.bechem.com
