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Road noise was reduced by the use of a new material, polyethylene naphthalate (PEN), in the noise reduction band. Radial tires for passenger cars have a cord layer (called a breaker) under the rubber layer (tread), which comes into contact with the ground. The breaker absorbs and disperses localized deformation and shock on the tread. Vibration was significantly reduced by replacing the conventional nylon noise reduction band between the two layers with a PEN version, because PEN is six times more effective than nylon in holding the breaker in place, thereby minimizing interior noise. The rigidity of the breaker was improved by using a larger number of thinner filaments.
The reduction of pattern noise was achieved by adopting an original “chaos” layout and optimizing the angle and distribution of grooves.
Matsumoto recalls, “We improved the handling stability of tires over 17 inches in diameter in particular by attaching fiber reinforced rubber (FRR) to the sides. FRR contains short fiber that has good longitudinal but limited lateral elasticity. It is rubber mixed with short fiber 500µm long and 10µm thick. We also used a natural material called biochemical filler (BCF), which has the effect of reducing rolling resistance and improves performance on wet surfaces. The tire needed repeated performance testing during the design process, because many new materials are used, including PEN. That was the hardest part of the project.”
Simulation technology came into its own at the performance testing and checking stage. Sumitomo Rubber has its own supercomputer simulation technology called Digi-tyre, and went on to develop a more advanced version known as Digital Rolling Simulation II (DRSII), which was used extensively in the development of the Veuro.
DRSII’s strength lies in the ability to simulate driving a vehicle with tires attached right from the design stage, reproducing both tire behavior and road conditions. It enabled Sumitomo Rubber to carry out repeated tests for the Veuro for all types of cars and road conditions, including how the tires reacted to the road surface when driving in wet conditions.
Matsumoto explains, “DRSII technology not only cut the design and development lead time, but also made it possible to develop an excellent, all-round performer without a trade-off between handling and comfort, and fuel consumption and wet performance.”
Needless to say, the tire was ultimately road tested on real vehicles. Matsumoto says the data from road tests were very close to the DRSII simulation results—a testament to the sophistication of the simulation technology. |
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| A road noise simulation on the Digital Rolling Simulation II (DRS II). Newly designed tires get “road tested” in digital space during their evolution to becoming even better tires. |
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| Real road tests are also essential for achieving better performance. This Inside Drum Test Machine is some of the latest specialized testing equipment for measuring tire force moment on wet, dry, and ice surfaces. |
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