Introduction to the performance of the hottest dis

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Introduction to disc brake performance

for vehicles traveling in mountainous areas in China, in order to avoid accidents caused by brake failure due to long-term braking, they have to stop frequently when going down long slopes to cool the brakes or use water to forcibly cool the brakes. The root cause of this problem is that the thermal stability of the braking efficiency of the ordinary drum brake is very poor. Generally speaking, the drum brake causes the brake temperature to rise due to long-time braking, and the braking effect will become worse after the temperature rises. This problem will be significantly improved after installing the disc brake, because even if the temperature rises significantly, the disc brake can almost maintain the same braking force as in the cold state. Compared with drum brake, disc brake has many obvious advantages

disc brake has obvious advantages

comparison between disc brake and drum brake. For users, compared with drum brake:

1 High thermal stability

when braking continuously for a long time, on the one hand, the working radius of the brake drum increases after thermal expansion, so the brake drum cannot maintain full contact with the brake shoe; On the other hand, when the temperature rises, the friction coefficient between the brake shoe lining and the brake drum decreases, thereby reducing the braking efficiency. For disc brakes, the axial thermal expansion of the brake disc is very small, while the radial thermal expansion has nothing to do with the braking performance. At the same time, the change of friction coefficient of brake friction pad and brake disc has little impact on braking performance, so the braking efficiency is reduced very little

2. High water stability

the brake friction pad has a high unit pressure on the brake disc, which is easy to squeeze out the water, so the braking efficiency will not be reduced much after being immersed in water. Due to the centrifugal force and the wiping effect of the brake friction pad on the brake disc, the sealing cover is well sealed, and it only needs one or two times of braking to restore normal after water is discharged. Because of the structure of drum brake, it needs more than ten times of braking to recover

3. Convenient maintenance

the automatic clearance adjustment mechanism is adopted to effectively reduce the maintenance workload. The mechanism can make the system automatically adjust the clearance with the wear of the brake friction pad and brake disc, so as to ensure the response time of braking. In addition, the caliper of the disc brake has a radial opening, as long as the wheel is removed It is very convenient to replace the brake friction pad; The ordinary drum brake not only needs to dismantle the wheel, but also needs a lot of work to replace the brake shoe itself

the disc brake not only improves the braking performance, but also greatly reduces its own quality. Therefore, more and more commercial vehicles in the United States and Europe began to use disc brakes instead of drum brakes. More and more passenger cars and trucks in China have begun to use disc brakes

structural features of WABCO pan disc brake

wabco pan series brake uses air as power, adopts floating caliper disc and single push rod actuation, and uses patented technology to control the oblique wear of brake friction pad. Under the condition of effectively reducing its own mass, the performance of the disc brake is guaranteed at the same time

disc brake is mainly composed of two parts: brake caliper and brake caliper bracket. The brake caliper bracket is directly connected to the axle through bolts, and the brake caliper is connected to the brake caliper bracket through guide pins. During braking, the brake caliper (including brake air chamber, brake friction pad, push plate, etc.) can move axially along the guide pin

the specific braking process is that the brake air chamber pushes the single push rod actuating mechanism and disc, and then pushes the right brake friction pad (for a clearer demonstration of the structure, the right brake friction pad is removed) close to the brake disc. The resulting reaction force pushes the brake air chamber and the brake caliper to move to the right along the guide pin to improve their resistance to deformation, and the brake caliper then pushes the left brake friction pad to compress the brake disc, As the brake disc rotates with the wheel, while the brake friction pad is relatively static, there will be relative movement between the two, resulting in friction, which is the braking force

1. Single push rod actuating mechanism

in the past Because the brake friction pad of the freight car is relatively large, in order to avoid pad wear, two push rods must be used. When adjusting the clearance, it is necessary to use a complex mechanism to synchronously adjust the two push rods, which increases the quality of the system and the probability of damage due to the large number of parts. WABCO has improved this A single push rod mechanism is introduced. Combined with the patented push plate, the number of parts is reduced under the condition of avoiding pad wear, so that the clearance adjustment mechanism and the actuating mechanism are combined into a compact and reliable whole

2. The specific clearance adjustment process of the automatic clearance adjustment mechanism

is as follows: only after the system completely overcomes the clearance between the friction plate and the brake disc, the swing of the brake swing rod (2) will drive the cylindrical pin (9) to move the transmission bushing (10)

the compression spring (11) is a one-way clutch and the friction ring (12) are combined with the adjusting nut through the conical surface pressed by the spring. If the clearance increases, the brake swing rod (12) will rotate the drive bushing (10) by an additional angle. This rotation will be transmitted to the adjusting nut (5), thereby turning the adjusting screw (8) out of an angle

if the friction plate contacts the brake disc, the friction torque in the adjusting nut (5) will be greater than the N torque that can be transmitted by the conical surface pressed by the spring. The adjustment nut cannot be turned by the rotation of the cone. That is to say, the adjustment function is related to the force

after the brake is released, the compression spring (11) is in a free state so that all parts will be separated. When the friction pad needs to be replaced, the adjusting nut (5) can be rotated by adjusting the nut (13) to release the friction pad

3. Brake friction and inch block wear sensor

when the brake friction pad has been excessively worn, if the brake cannot be replaced in time, the brake disc may be damaged, and more seriously, the vehicle will lose braking, which is very likely to cause an accident. In order to better improve the safety of the vehicle, WABCO's brake disc can be equipped with a wear sensor to cooperate with EBS, which can alarm the driver when the brake friction pad is 3mm and 2mm left respectively

specifications of WABCO disc brakes

according to the market demand, WABCO has launched three kinds of disc brakes to adapt to light, medium and heavy commercial vehicles respectively. Due to the advanced single push rod technology, WABCO's disc brake is the lightest known product of the same type. The specific parameters are as follows:

on the basis of the success of Pan brake, WABCO has developed a new generation disc brake which can be used in 22.5 "On the wheels of commercial vehicles.

precautions for installation and maintenance of WABCO disc brakes

installation and maintenance of disc brakes are very different from drum brakes. Installation or maintenance of disc brakes according to the operating habits of drum brakes may cause disc brakes to fail to work normally. The following points should be paid attention to when operating disc brakes:

1 be sure to leave Make enough movement allowance to avoid affecting the normal operation of the brake! This is because; With the wear of the brake disc and brake friction pad, the brake caliper and brake air chamber will move to the wheel side, up to 30~40mm in extreme cases, and the brake caliper and brake air chamber will move the central axis of the vehicle by about 1 mm each time

2 during each maintenance, the sealing of the guide pin, adjusting screw and the mounting surface of the brake chamber must be checked. This is because the working environment of the brake is very bad. Once water enters the system to produce corrosion or other corrosion, the whole brake will not work normally

3 the disc brake can automatically adjust the clearance, and it is not necessary to adjust the clearance in normal use. (end)

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