Disc brake, also known as disc brake, is named after its shape as the name suggests. It is hydraulically controlled and its main parts include brake disc, wheel cylinder, brake caliper, oil pipe, etc. The brake disc is made of alloy steel and fixed on the wheel and rotates with the wheel.
Disc brakes are of hydraulic type and controlled by hydraulic pressure. The main parts include brake disc, wheel cylinder, brake caliper, oil pipe, etc. The disc brake has the advantages of fast heat dissipation, light weight, simple structure and convenient adjustment. Especially under high load, it has good high temperature resistance, stable braking effect, and is not afraid of mud and water invasion. When driving in winter and bad road conditions, many cars use disc brakes such as flat brake disc, perforated brake disc and scribed brake disc. Among them, scribed brake disc has better braking effect and ventilation and heat dissipation capacity.
Disc brakes have been widely used in cars, but except for all wheels on some high-performance cars, they are mostly used only as front wheel brakes, which cooperate with the drum brakes of the rear wheels in order to have higher directional stability when braking. In trucks, disc brakes are also used, but there is still a considerable distance from popularization.
Brake disc
1. Brake disc diameter
The diameter D of the brake disc should be as large as possible. At this time, the effective radius of the brake disc is increased, which can reduce the clamping force of the brake caliper and reduce the unit pressure and working temperature of the pad. Limited by the rim diameter, the diameter of the brake disc is usually 70% - 79% of the rim diameter. The upper limit shall be taken for vehicles with a total mass greater than 2T.
2. Brake disc thickness
The thickness of the brake disc has an effect on the quality of the brake disc and the temperature rise during operation. In order to reduce the mass, the thickness of the brake disc should not be too large; In order to reduce the temperature, the thickness of the brake disc should not be too small. The brake disc can be made solid, or a ventilation hole can be cast in the middle of the brake disc for heat dissipation and ventilation. Generally, the thickness of solid brake disc can be 10-20mm, the thickness of ventilated brake disc can be 20-50mm, and 20-30mm is more used. In case of emergency braking under high-speed movement, the brake disc will form thermal deformation and tremble. In order to improve the heat dissipation performance of the friction surface of the brake disc, the brake disc is mostly made into a ventilated brake disc with a hole in the middle, which can reduce the temperature of the brake disc by 20% ~ 30%.
Friction pad
Friction pad refers to the friction material pressed on the brake disc by the clamp piston. The friction lining block is divided into friction material and base plate, which are directly pressed and embedded together. The ratio of the outer radius to the inner radius of the friction pad and the recommended outer radius to the inner radius of the friction pad shall not be greater than 1.5. If this ratio is too large, there is a large difference between the peripheral speed of the outer edge and the inner side of the pad during operation, the wear is uneven, the contact area is reduced, and finally the braking torque changes greatly.
For the working area a of disc brake pad, it is recommended to select it in the range of 1.6 ~ 3.5 (kg / cm2) according to the vehicle mass occupied by the brake pad per unit area.
The brake disc is made of steel and fixed on the wheel. The slave cylinder is fixed on the bottom plate of the brake, and the two friction plates on the brake caliper are installed on both sides of the brake disc respectively. The piston of the slave cylinder is driven by the hydraulic pressure transmitted by the oil pipe to push the friction plate against the brake disc for friction braking. It acts like clamping the rotating plate with pliers and forcing it to stop.
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