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What is Wheel Hub Bearings, How Much of its Information Do You Learn More?

Wheel hub bearings are used at the axle of automobiles to bear the weight and provide precise guidance for the rotation of the wheel hub, which bear both axial and radial loads, and are an important part of the automobile's load and rotation.

Name	Wheel Hub bearings
Type	bearings
Function	auto car

Introduction
Conventional bearings for automobile wheels are combined with two sets of tapered roller bearings or ball bearings, and the mounting, greasing, sealing, and clearance adjustment of the bearings are carried out on the automobile production line. This structure makes it difficult, costly, and unreliable to assemble at the automobile production plant, and the bearings need to be cleaned, oiled, and adjusted when the automobile is maintained at the service point.

Brief introduction
Wheel bearing unit is in the standard angular contact ball bearings and tapered roller bearings on the basis of the development of the two sets of bearings as a whole, with good assembly performance, can be omitted clearance adjustment, light weight, compact structure, large load capacity, for the sealed bearings can be loaded into the grease in advance, omit the external hub seals and maintenance-free, etc., has been widely used in sedans, also has a gradual expansion of the application of the trend of the laden vehicles.

Development history
In the past, wheel bearings for cars were most often used in pairs with single row tapered roller or ball bearings. With the development of technology, wheel hub units have been widely used in cars. The use of wheel bearing units is growing in scope and volume, and has now developed into the third generation.

The first generation consisted of double row angular contact bearings.

The second generation has a flange on the outer raceway for fixing the bearing, which can simply be slipped onto the axle and fixed with a nut. This makes maintenance of the vehicle easier.

The third generation wheel bearing unit is a bearing unit that is compatible with the anti-lock brake system ABS. The hub unit is designed with an inner flange and an outer flange, the inner flange is bolted to the drive shaft and the outer flange mounts the entire bearing together.


Fourth generation wheel bearing

The fourth generation of wheel hub bearing unit is to make the isokinetic universal joint and the bearing as a whole, which solves the disadvantage of the existing technology that the size of the hub increases due to the integrated structure of the hub and the isokinetic universal joint, resulting in the increase of the weight of the hub. The development of the fourth generation of wheel hub bearing units has been successful, and it is believed that they will soon be applied to various types of automobiles on a large scale. The characteristics of these units are: no need to adjust the bearing assembly clearance, bearing assembly process is more reasonable, weight reduction volume reduction, a one-time grease can be used almost permanently, reducing the overall production costs, more conducive to large-scale popularity.

Technology and Development Trends

High Performance Seals
Because the wheel bearing is very close to the ground and high temperature brake discs and other parts, need to adapt to a variety of complex road conditions and harsh driving environment. Therefore, bearing seals must have good anti-grease leakage performance, but also must have good heat resistance, anti-mud and sewage performance.

Shaking and rolling technology
The third generation of wheel bearings generally use shaking and rolling technology to self-locking half inner ring, using shaking and rolling technology when the axial load to produce plastic deformation of the hub spindle end, so that the hub spindle and half inner ring connected to one. Compared with the traditional nut fastening, the third-generation wheel bearing with rocker rolling technology helps to reduce the volume and weight, and at the same time reduces the cost and improves the reliability of the wheel bearing. At the same time, it eliminates the need to adjust the position of internal components when assembling them into a vehicle.

Lightweighting and miniaturisation
The second and third generation wheel bearing structures are designed with finite element analysis to ensure that the flange has sufficient rigidity while reducing its volume and weight as much as possible, where the rigidity of the third generation wheel bearing is the tilt angle of the hub flange relative to the outer ring flange. By integrating and miniaturising the design to reduce the weight of the axle, the second-generation wheel bearing is 180g lighter than the first-generation, while the third-generation wheel bearing further reduces the weight by 120g.

Low friction torque
An important measure to reduce automotive fuel consumption is to design wheel bearings with low frictional torque, while the main factors affecting the bearing frictional torque are the type of bearing and preload, and the bearing seals account for a large proportion of the frictional torque component. Therefore, improving the seal design to reduce the friction moment can significantly improve the performance of wheel bearings. From the first generation of wheel bearings to the latest fourth generation, the friction torque is obviously reduced gradually.

ABS Technology
ABS is a kind of automobile safety control device with the advantages of anti-skid, anti-locking and so on, in the automobile emergency braking through the detection of wheel speed, automatic adjustment of braking force to prevent the wheels from locking, shorten the braking distance. The rotation speed is detected by magnetic sensors mounted on the parts that rotate with the wheels and fixed on the vehicle body in the vicinity. There are two types of hub units with ABS sensors: one is placed inside the hub with the sensor mounted on other parts, and the other is placed inside the hub together with the sensor (known as a hub unit with sensor).

Precautions
Worn or damaged wheel bearings or hub units can lead to unsuitable and costly failures of your vehicle on the road, or even cause injury to your safety. Please note the following in the use and installation of wheel bearings.

1. To ensure maximum safety and reliability, it is recommended that you check the wheel bearings frequently, regardless of the age of the vehicle - look out for early warning signs of wear: including any friction noises when turning or unusual deceleration of the suspension combination wheel when cornering.

For rear-wheel drive vehicles it is recommended that the front wheel bearings should be lubricated when the vehicle reaches 38,000 kilometres. When replacing the brake system, inspect the bearings and replace the oil seals.

2. If you hear a noise coming from the wheel bearing area, first, it is important to locate where the noise is occurring. There are many moving parts that may be producing the murmur, and there may be some rotating parts that are in contact with non-rotating parts. If the noise is confirmed to be in the bearings, the bearings may be damaged and need to be replaced.

3, because the front hub leads to similar operating conditions on both sides of the bearing failure, it is recommended to replace them in pairs even if only one bearing is bad.

4. Wheel bearings are sensitive and require the use of proper methods and appropriate tools in all cases. In the process of storage, transport and installation, the parts of the bearings must not be damaged. Some bearings require greater pressure to be pressed in, so special tools are needed. Be sure to refer to the car manufacturing instructions.
5, the installation of bearings should be in a clean and tidy environment, 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 strike the bearing with a hammer, and take care that the bearing does not fall on the ground (or similarly mishandled). The condition of the shaft and housing should also be checked before mounting. Even minor wear can lead to a poor fit, which can cause early bearing failure.