Drum brakes are also called block brakes. They are braked by pressing the brake pads on the brake wheels.
The drum brake uses the brake transmission mechanism to make the brake shoe press the brake pads against the inside of the brake drum, thereby generating braking force, slowing down the wheels or stopping within the shortest distance as required to ensure driving safety, and Ensure that the car is parked reliably and cannot slide automatically.
Press brake shoe direction Drum brakes use the brake shoes to squeeze the brake drum to obtain braking force, which can be divided into two types: internal tension and external beam. The inner drum brake uses the inner cylindrical surface of the brake drum as the working surface and is widely used in modern automobiles; the outer beam drum brake uses the outer cylindrical surface of the brake drum as the working surface. Car parking brake.
Press the actuator Drum brakes can be divided into wheel-cylinder brakes and cam brakes according to the form of the brake shoe opening device (also referred to as the actuating device), as shown in Figure 1. Wheel-cylinder brakes use hydraulic brake wheel cylinders as brake shoe actuation devices, which are mostly used in hydraulic braking systems; cam-type brakes use cams as actuation devices, which are mostly used in pneumatic brake systems.
Force by pressing the brake shoe Wheel cylinder brakes can be divided into follower shoes, double collar shoes (one-way action, two-way action), double follower shoes, self-increasing force (one-way action, two-way action) according to the force of the brake shoes. Role) and other types
advantage Drum brakes are inexpensive to manufacture and conform to traditional designs. During the braking process of a four-wheeled car, the load of the front wheel usually accounts for 70% -80% of the total load of the car due to the effect of inertia. The braking force of the front wheel is greater than that of the rear wheel. In order to save costs, manufacturers use the brake method of the front disc and the rear drum. However, for heavy vehicles, because the speed is generally not very high, and the durability of the brake shoes is higher than the disc brakes, many heavy vehicles still use a four-wheel drum design.
Disadvantage Drum brakes have much worse braking performance and heat dissipation. Drum brakes have poor braking force stability. The braking force varies greatly on different roads and is not easy to control. Due to the poor heat dissipation performance, a large amount of heat can be accumulated during braking. Under the influence of high temperature, the brake pads and drums are prone to extremely complicated deformation, which is prone to brake decay and chattering, which causes the braking efficiency to decrease. In addition, after using the drum brake for a period of time, it is necessary to periodically adjust the gap of the brake shoes, and even to remove the entire brake drum to clean up the accumulated brake powder.