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The blade impact force at the top and bottom reversal points contributes significantly to wiper system noise. This paper describes a newly developed process to simulate blade reversal behavior. The results of this simulation can provide necessary insight into reducing blade reversal noise. As a result of simulation under various conditions, it is shown that the reversal impact force can be reduced by modifying the maximum rubber neck rotational angle and the rubber neck rotational spring constant. It is also shown that the reaction force at the top and bottom reversal points can be adjusted by modifying the arm head twist angle.

This paper describes the self-excited brush vibrations which induce chirp noises in the permanent-magnet direct-current blower motors (150 W) used in automobile air-conditioners. Based on regeneration of the brush noises and analysis of the brush vibration measurements, we can distinguish two types of brush vibration: one is a high frequency mode, 10 - 20 kHz, which results from coupling the pitching mode and the radial-direction mode of brush; the other is a low frequency mode of the brush which vibrates together with the insulator disk holding the two brushes, 1 - 5 kHz, which results from coupling the yawing mode and the rolling mode. Dynamic models of these two types of vibration and the motion equations are constructed by analyzing the brush vibration measurements, and the mechanisms of generation are confirmed by the eigenvalues and eigenvectors obtained from the motion equations.