Why is there a hole in the motorcycle disc brake and the car disc brake is a CD?

What does the hole in the motorcycle disc brake do?

Heat dissipation: Punching holes can accelerate the air flow on both sides of the brake disc and take away more heat generated by friction, thus maintaining better braking performance constancy. The whole braking process is actually a process in which kinetic energy is absorbed by the brake and converted into heat energy. When the vehicle brakes under heavy load (such as continuous downhill) or at high speed, the temperature of the brake will continue to rise sharply due to frequent work, and the side effect is that the friction of the brake disc material will decrease obviously. This phenomenon is called. Therefore, at the beginning of brake design, it is necessary to consider how to minimize or delay the thermal recession effect in this case, which is called thermal recession resistance. The whole process is to keep the braking efficiency unchanged.

Reduce braking noise: During the working process of the brake disc, the high-speed contact between the brake caliper and the brake disc will cause them to vibrate and make sharp or unpleasant noise, which will greatly affect the mood of the drivers and passengers. Therefore, each brake disc should be tested for its natural frequency, vibration mode and damping. After understanding these inherent characteristics, we should change its natural frequency by drilling holes to avoid * * * vibration, so as to achieve the purpose of reducing vibration and noise and prolonging service life.

Reduce the mass: The large hole can reduce the mass of the brake disc. It can be seen from the formula for calculating the braking performance of the vehicle that within a certain range, the lighter the vehicle, the better its braking efficiency. The directional stability of the vehicle during braking: that is, the vehicle does not run off, sideslip or lose its steering ability during braking.

Brake discs of automobiles are not all light. Brake discs are divided into solid brake discs and ventilated brake discs according to their structures. According to different materials, it can be divided into carbon fiber ceramic brake discs and metal brake discs. The solid brake disc has no special structure and is an integral disc. Ventilation discs usually have many holes leading to the center of the circle at the periphery, which are called air ducts. The ventilation disc of this kind of air duct is easier to make air convection through the air duct during the driving of the car, which is more breathable and more conducive to the heat dissipation of the brake disc. Generally, the outer surface of the ventilation disc is not perforated, but there is a perforated ventilation disc. Perforated ventilation disk is based on the ventilation disk, punching holes on the disk surface to ensure air circulation to the maximum extent and reduce thermal attenuation. Perforated ventilation disc has better thermal attenuation performance than ventilation disc. Too many holes will affect the strength of the brake disc, resulting in too low service life.