Hiroshi Yamauchi

Theoretical analysis of tire acoustic cavity noise and proposal of improvement technique

Abstract This paper describes an investigation into interior road noise caused by the acoustic cavity resonance inside the tire–wheel assembly when a passenger car is running. First of all, we researched some characteristics of the acoustic cavity resonance inside the tire–wheel assembly. Next, we derived the equation of motion of the acoustic cavity system and explained the characters theoretically. Then, we proposed a technique to reduce the peak level of the acoustic cavity natural frequency. Finally, we made prototype wheels and confirmed their validity.

Theoretical Analysis and Proposition to Reduce Self-Excited Vibration of Automotive Shock Absorber

Knock noise induced by automotive shock absorbers has serious influence on driving comfort and vehicle quality. Some research focusing on knock noise had been introduced in the past. However there is the unidentified phenomenon that has been unnoticed. This paper describes the new theory to clarify one of the unidentified phenomenon and proposes the equation for stability assessment which is useful on designing stage of development. First of all, the characteristics of the unidentified rod vibration of shock absorbers are investigated experimentally. Second, the new theory is established on the basis of the non-linear physical model with friction forces between piston and cylinder. This theory shows that the unstable vibration, so called the Self Excited Vibration, can be induced by not only friction property but also structure of rod and piston. Third, the equation for stability assessment, which is useful on designing stage of development, is proposed on the basis of new theory. Finally, the appropriate structure of shock absorbers is prototypically made and verification test is demonstrated to confirm the equation for stability assessment.