Case study to stationary noise in drum brake systems 2008-36-0545
Drum Brake system used in light vehicles could shown a noise when the driver applies the brake pedal or during the parking brake lever actuation when the vehicle is stationary. This behavior is more common in low cost vehicles due the poor acoustic isolation, vehicles equipped with ABS brake and in vehicles with automatic transmission, that the driver applies the brake pedal constantly.
There are several factors that can contribute to noise generation as vehicle acoustic isolation, physical properties of friction material, shoes geometry, back plate deflection, springs and brake shoes backing points. Even these factors, there are also the pressure and the position of shoes.
This study shows a methodology to find out the root cause of the noise and technical changes necessaries to reduce or avoid the noise occurrence.
At first, a vehicle was identified and the vibration was measured where was possible to find out the component which had the highest amplitude and the frequency of vibration.
The next step was removing the complete drum brake and reproduces the noise in a test bench. For that it was necessary to pulse the brake system with a high pressure for a long time. This difference is related to the position of the shoes on the back plate. Noise pressure and amplitude found in lab were similar to the vehicle.
Starting from this point, several proposals were tested in order to identify the root cause of noise.