The main function of hub bearing is to bear load and provide accurate guidance for the rotation of hub. It bears both axial load and radial load, so it is a very important part. The traditional bearings for automobile wheels are composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of bearings are carried out on the automobile production line. This kind of structure makes it difficult to assemble, high cost and poor reliability in the automobile factory, and when the automobile is in the maintenance point, it also needs to clean, oil and adjust the bearing. Hub bearing unit is developed on the basis of standard angular contact ball bearing and tapered roller bearing. It integrates two sets of bearings. It has the advantages of good assembly performance, omitting clearance adjustment, light weight, compact structure, large load capacity, pre loading grease for sealed bearings, omitting external hub sealing and avoiding maintenance. It has been widely used in cars, There is also a trend to gradually expand the application in trucks.
In the past, single row tapered roller or ball bearings were mostly used in pairs. With the development of technology, car hub unit has been widely used in cars. The application scope and quantity of hub bearing unit are increasing day by day, and now it has developed to the third generation: the first generation is composed of double row angular contact bearings. The second generation has a flange used to fix the bearing on the outer raceway, which can simply cover the bearing on the axle and fix it with nuts. Make the maintenance of the car easier. The third generation of hub bearing unit is the combination of bearing unit and anti lock brake system ABS. The hub unit is designed with inner flange and outer flange. The inner flange is fixed on the drive shaft with bolts, and the outer flange installs the whole bearing together. Worn or damaged hub bearing or hub unit will make your vehicle have inappropriate and high cost failure on the road, and even cause harm to your safety.
In the use and installation of hub bearing, please pay attention to the following matters:
1. In order to ensure the maximum safety and reliability, it is recommended that you should always check the hub bearing no matter how old the vehicle is - pay attention to the early warning signal of bearing wear, including any friction noise during rotation or abnormal deceleration of suspension combination wheel during turning. For rear wheel drive vehicles, it is recommended that the front hub bearing should be lubricated when the vehicle runs to 38000 km. When replacing the brake system, check the bearing and replace the oil seal.
2. If you hear the noise from the hub bearing, first of all, it is important to find the location of the noise. There are many moving parts that may produce noise, or some rotating parts may contact with non rotating parts. If the noise in the bearing is confirmed, the bearing may be damaged and need to be replaced.
3. Because the working conditions of bearing failure on both sides of the front hub are similar, even if only one bearing is damaged, it is recommended to replace it in pairs.
4. The hub bearing is sensitive, so it is necessary to use the correct method and appropriate tools in any case. During the process of storage, transportation and installation, the components of the bearing shall not be damaged. Some bearings need to be pressed in with high pressure, so special tools are needed. Be sure to refer to the car manufacturing instructions.
5. The bearing should be installed in a clean and tidy environment, fine particles into the bearing will shorten the service life of the bearing. It is very important to keep a clean environment when replacing bearings. It is not allowed to knock the bearing with a hammer. Pay attention not to drop the bearing on the ground (or similar improper handling). Before installation, the condition of shaft and bearing seat should also be checked. Even slight wear will lead to poor fit, resulting in early failure of bearing.
6. For the hub bearing unit, do not attempt to disassemble the hub bearing or adjust the sealing ring of the hub unit, otherwise the sealing ring will be damaged and water or dust will enter. Even the raceway of the seal ring and inner ring are damaged, resulting in permanent failure of the bearing.
7. There is a magnetic thrust ring in the seal ring of ABS bearing, which can not be impacted, impacted or collided with other magnetic fields. Take them out of the box before installation and keep them away from the magnetic field, such as the motor or power tool used. When installing these bearings, observe the ABS alarm needle on the instrument panel through the road condition test to change the operation of the bearings.
8. For hub bearings equipped with ABS magnetic thrust ring, in order to determine which side the thrust ring is installed on, a light object * can be used near the edge of the bearing, and the magnetic force generated by the bearing will attract it. When installing, point the side with magnetic thrust ring inward, facing the sensitive element of ABS. Note: incorrect installation may result in failure of the brake system.
9. Many bearings are sealed and do not need to be greased throughout their life. Other unsealed bearings, such as double row tapered roller bearings, must be lubricated with grease during installation. Due to the different sizes of the inner cavity of the bearing, it is difficult to determine how much grease to add. The most important thing is to ensure that there is grease in the bearing. If there is too much grease, the excess grease will leak out when the bearing rotates. General experience: during installation, the total amount of grease should account for 50% of the bearing clearance.
10. When installing the lock nut, the torque varies greatly due to different bearing types and bearing seats
In the process of maintenance, it is often found that some cars have large driving noise. Check the tires for abnormal wear and there is no obvious abnormal noise when turning the wheels on the lift. This phenomenon is often caused by the abnormal damage of the hub bearing. The so-called abnormal refers to the damage of the bearing caused by the installation. The front wheel bearing of automobile is generally double row ball bearing. If the bearing is installed by hammering, or by pressing the inner ring of the bearing when the bearing is installed into the bearing seat, the raceway of the bearing on one side will be damaged. When the vehicle is running, it makes noise. When the wheels are off the ground, there is no obvious noise due to the better side of the raceway. Correct installation operation is the key to long service life of bearing
When one of the four wheel hub bearings of the vehicle is damaged, you will hear a continuous buzzing sound in the vehicle when the vehicle is in motion. It's hard to tell where the sound comes from. I feel that the whole car is full of this buzzing sound, and the faster the speed is, the louder the sound is. The following is the judgment method:
Method 1: open the window and listen to whether the sound comes from outside the car;
Method 2: after increasing the speed (when the buzz is loud), put the gear in neutral and let the vehicle slide. Observe whether the noise comes from the engine. If the buzz does not change when sliding in neutral, it is mostly the problem of the wheel bearing;
Method 3: stop the car temporarily, get off the car and check whether the temperature of the wheel axle is normal. The method is: touch the four wheel hubs with your hands respectively, and roughly feel whether their temperature is consistent (when the gap between the brake shoes and pads is normal, the temperature of the front and rear wheels is different, and the front wheels should be higher). If you feel that the difference is not big, you can continue to drive slowly to the maintenance station;
Method 4: lift the car with a lift (release the handbrake and shift into neutral gear before). When there is no lift, you can lift the wheels one by one with a jack. Turn the four wheels quickly by hand. When you encounter a problem axle, it will make a sound, which is completely different from other axles. With this method, you can easily distinguish which axle has a problem.
If there are cracks, pitting or ablation on the hub bearing, it must be replaced. Before installing a new bearing, grease it first, and then reassemble it in reverse order. After replacement, the bearing must rotate flexibly without impurity and vibration.