Bridgestone Corp developed a seat pad that reduces vibration transmitted from the driver's seat to the driver by 30% in a running vehicle.
A seat pad is a cushion to be embedded under a seat surface. It improves ride comfort by reducing vibration transmitted to the driver.
Mazda Motor Corp employed the new seat pad for its "CX-9" and "CX-5" SUVs (sport utility vehicles).
The hardness of the seat pad differs in each part of the pad. A soft material is used for the seat surface on which a passenger's buttocks are placed, and a harder material is used for the surrounding part. As a result, it not only reduces vibration but also improves the retention of the passenger.
To improve the performance of vibration absorption, Bridgestone changed the materials of urethane. Usually, urethane is synthesized by using polyol and isocyanate as main materials. The ratio between polyol and isocyanate is 6:4 in many cases.
In general, the higher the ratio of isocyanate, the harder the urethane becomes. Bridgestone realized the new seat pad not by changing the ratio but by procuring polyol and isocyanate with different physical properties.
Bridgestone developed the pad in consideration of the change in demand from autoakers. In the past, they were developing auto seats while focusing on the reduction of weight and price. In recent years, the focus is being shifted to the reduction of noise and vibration in the aim of improving ride comfort.
"When electric vehicles (EVs) become more widely used, passengers will be more sensitive to vibration," the company said.
Noise and vibration at the time of driving a vehicle can be reduced by replacing an engine with a motor. Then, the ratio of vibration transmitted from the road surface will increase. Bridgestone plans to eliminate the discomfort that passengers feel in a vehicle by focusing on a frequency band of 4-12Hz, which humans can easily feel.