Mechanism of Disc Brake Squeal

Abstract

This paper deals with the generation mechanisms of the low frequency squeals generated in a rigid type of a car and a bicycle disc brake experimentally. In the case of out-of-plane squeal generated in a car disc brake, the natural frequencies of the out-of-plane vibration of the disc and caliper are close to the squeal frequency, and the out-of-plane squeal was concluded to be caused by the excitation of the coupled out-of-plane vibration of the disc and caliper by Coulomb friction. The vibration modes of the brake units during squealing are also investigated. Additionally, the relationship between the rate of squeal occurrence and both the direction of disc rotation and the effect of pad cut area are investigated. And the effect of the rubber installation to the pads on squeal is also investigated. In the case of in-plane squeal generated in a bicycle disc brake, it has been made clear that the squeal is mainly a torsional vibration of the disc and hub in the in-plane direction of the disc surface caused by dry friction which the frictional characteristics have a negative slope with respect to the relative velocity.