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Brake squeal noise is generally classified into two vibration modes of disc. One is called “out-of plane mode” which vibrates in disc’s out-of-plane direction. The other is “In-plane mode” which vibrates in disc’s in-plane direction, it means the disc is contracted partially or is extended. There are few “In-plane noise” analysis reports from Disc pad standpoint, so it has been unclear how disc pad contributes to “In-plane mode” until now. This paper confirms that we successfully analyzed direct pad vibration mode by laser scanning under in-plane mode condition. Based on these results, we assume that pad stiffness affected in-plane mode and carried out validation tests.

Previous studies have shown that the disc vibration mode during braking noise is not always the same and there are some types of mode. Until now, disc brake noise studies are reported regarding out of plane noise primarily, and there are many noise countermeasure methods. On the other hand, there is short research history of “Inplane mode noise” which disc vibrates to circumstance direction with extension and contraction movement. Therefore, there are few studies which are explained the noise mechanism in detail in the view point of pad. In this report, we discuss energy which flows into pad surface at inplane noise braking and focused friction force variation by the surface pressure change especially. The inflow energy was calculated by the pad’s displacement of disc rotating direction(ΔX) and pad thickness variation(Δh) which is acquired by 3D scanning laser Doppler measurement system. This technique was made in reference to the past research.