The main function of hub bearing is to bear the load and provide accurate guidance for the rotation of the hub. It bears both axial load and radial load. It is a very important part. The traditional automobile wheel bearing is composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of the bearing are carried out on the automobile production line. This structure makes it difficult to assemble in the automobile factory, high cost and poor reliability. Moreover, when the automobile is maintained at the maintenance point, the bearing needs to be cleaned, oiled and adjusted. Hub bearing unit is developed on the basis of standard angular contact ball bearing and tapered roller bearing. It integrates the 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 free from maintenance. It has been widely used in cars and gradually expanded in trucks.
Installation and use
In the past, the wheel hub bearings of cars used to use single row tapered roller or ball bearings in pairs. With the development of technology, car hub units have been widely used in cars. The application scope and amount 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 on the outer raceway for fixing the bearing, which can simply sleeve the bearing onto the axle and fix it with nuts. Make the maintenance of the car easier. The third generation wheel hub bearing unit adopts the combination of bearing unit and anti lock brake system ABS. The hub unit is designed with an inner flange and an 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 wheel hub bearings or wheel hub units will cause inappropriate and costly failure of your vehicle on the road, and even harm your safety.
Please pay attention to the following items in the use and installation of hub bearing:
1. In order to ensure safety and reliability to the greatest extent, it is recommended that you 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 the suspension combination wheel during turning. For rear wheel drive vehicles, it is recommended to lubricate the front wheel hub bearing when the vehicle travels to 38000km. 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 where the noise occurs. There are many moving parts that may produce noise, or some rotating parts may come into 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 leading to the failure of bearings on both sides of the front hub are similar, it is recommended to replace them in pairs even if only one bearing is broken.
4. The hub bearing is sensitive, so it is necessary to adopt the correct method and appropriate tools in any case. During storage, transportation and installation, the components of the bearing shall not be damaged. Some bearings require high pressure, so special tools are required. Be sure to refer to the automobile manufacturing instructions.
5. The bearing should be installed in a clean and tidy environment. The entry of small particles into the bearing will also shorten the service life of the bearing. It is very important to maintain a clean environment when replacing bearings. It is not allowed to knock the bearing with a hammer, and pay attention not to drop the bearing on the ground (or similar improper treatment). Check the condition of the shaft and bearing seat before installation. Even slight wear will lead to poor fit, resulting in early failure of the 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 sealing ring and inner ring are damaged, resulting in permanent failure of the bearing.
7. There is a magnetic thrust ring in the sealing ring equipped with ABS device bearing, which can not be impacted, impacted or collided with other magnetic fields. Take them out of the packing box before installation and keep them away from the magnetic field, such as the motor or electric tool used. When installing these bearings, observe the ABS alarm pin on the instrument panel through the road condition test to change the operation of the bearings.
8. For the hub bearing equipped with ABS magnetic thrust ring, in order to determine which side the thrust ring is installed on, you can use a light and small thing * close to the edge of the bearing, and the magnetic force generated by the bearing will attract it. During installation, point one side with magnetic thrust ring inward and face the sensitive element of ABS. Note: incorrect installation may cause the function of the brake system to fail.
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 seep out when the bearing rotates. General experience: during installation, the total amount of grease should account for 50% of the bearing clearance.
Atlas of automobile hub bearing
Atlas of automobile hub bearing (5 sheets)
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 whether the tires are abnormally worn and whether the wheels turn on the lift without obvious abnormal noise. This phenomenon is often caused by abnormal damage of hub bearing. The so-called abnormal refers to the bearing damage caused by installation. The front wheel bearing of an automobile is generally a double row ball bearing. If a hammer is used to knock and install the bearing when installing the bearing, or if the bearing is installed by pressing the inner ring of the bearing when installing the bearing into the bearing seat, it will cause damage to the bearing raceway on one side. Noise is generated when the vehicle is running, and when the wheel is off the ground, there is no obvious noise due to the better side of the raceway. Correct installation and operation is the key to long bearing life.
What will happen if the wheel hub bearing is damaged
When one of the four wheel hub bearings of the vehicle is damaged, you will hear a continuous buzzing sound in the vehicle during driving. It is unclear where this sound comes from. It feels that the whole compartment 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 buzzing sound is large), put the gear in neutral and let the vehicle slide, and observe whether the noise comes from the engine. If the buzzing sound does not change when sliding in neutral, it is mostly due to the problem of wheel bearing;
Method 3: stop temporarily and get off to check whether the temperature of the wheel axle is normal. The method is: touch the four wheel hubs with your hand to roughly feel whether their temperatures are consistent (when the clearance of brake shoes and pads is normal, there is a difference in the temperature of the front and rear wheels, and the front wheel should be high). If you feel that the difference is small, you can continue to drive slowly to the maintenance station;
Method 4: lift the car with an elevator (release the handbrake and put it into neutral gear before). When there is no elevator, the wheels can be lifted one by one with a jack, and the four wheels can be rotated quickly by manpower. When a problematic axle is encountered, it will make a sound, which is completely different from other axles. It is easy to distinguish which axle has a problem with this method.
If there are cracks, pits or ablation on the hub bearing when it is seriously damaged, it must be replaced. Before installing a new bearing, apply lubricating grease first, and then reinstall it in the reverse order. The replaced bearing must rotate flexibly without clutter and vibration.