Working Principle of Automotive Drum Brake System

Today, let's talk about the working principle of a car drum brake system. There are several types of drum brake systems in terms of structure, such as wheel cylinder open brake, cam open brake, and wedge wheel brake. The wheel cylinder open brake can be divided into leading and trailing shoe brakes, double leading shoe brakes, and self increasing force brakes. Some people are already confused when it comes to this. To put it simply, the difference between different drum brakes lies in the way they push the brake shoes, but the core working principle is that the brake shoes are pushed open, and the friction plates on the brake shoes rub against the rotating brake drum, resulting in braking. Today, we will choose the most common type of wheel cylinder open leading and trailing shoe drum brake to explain its working principle. This type of brake mainly consists of brake drum, brake base plate, brake shoe pads, brake shoe limit device, brake wheel cylinder, reset spring, clearance adjustment mechanism, and other parts. When the driver presses the brake pedal, the pedal will transfer the braking force to the vacuum booster pump, which can amplify the stepped braking force and convert it into the hydraulic pressure of the brake master cylinder in the car's hydraulic system. Due to the incompressibility of the hydraulic oil used in the automotive hydraulic system, the pressure of the brake master cylinder is transmitted through the hydraulic oil to the brake master cylinder (brake wheel cylinder) located inside the drum brake, and the piston inside the cylinder is pushed outward by the pressure to push the brake shoes. The friction plate connected to the outer side of the brake shoe rubs against the rotating brake drum, converting kinetic energy into thermal energy, causing the vehicle to slow down and ultimately come to a stop.

Author: Gao Cheng Rubbing Wu Yaozhong

Link: https://zhuanlan.zhihu.com/p/432411161

Source: Zhihu

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