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2022 Novermber the First week UNIM Technical Knowledge: Installation of motor vehicle bearings

Whether the bearing is installed correctly affects the accuracy, service life and performance. Therefore, the installation of bearings should be fully studied and installed according to the operating standards. The structure, fit and condition of the bearing vary. Generally, the inner ring needs interference fit because the bearing rotates. Cylindrical hole bearing is usually pressed in with a press or hot assembly. In the case of taper hole, it is directly installed on the taper shaft or installed with a sleeve. Before assembly of sliding bearing, check that the contact surface of the parts must be smooth and free of burrs, and clean with kerosene or gasoline to keep the bearing parts clean; When installing the bearing seat, the bearing bush or shaft must be sleeved on the bearing seat and corrected according to the center of the bearing bush or sleeve. The centers of all bearings on the same transmission shaft shall be in the same straight line, and their coaxiality shall be within the specified range. Put the shaft on, and check the contact condition on the surface of each bearing pad with the display agent; The contact surface between the bottom surface of the bearing seat and the engine body shall be uniform and tight; The bearing pedestal must be firmly fixed on the machine body. When the equipment is running, the bearing pedestal shall not have relative displacement with the machine body; In all parts of the bearing, only relative sliding movement is allowed between the journal and the bushing, and no relative movement is allowed between other parts. If the bearing pad or sleeve also rotates with the journal, and sliding occurs in the bearing seat, this is not allowed; When lapping or adjusting the clearance, ensure that the bearing has a good contact surface and a reasonable clearance; It must be ensured that the lubricating oil can flow freely into the bearing and that there is sufficient lubricating oil in the bearing to form an oil film; To ensure the quality of the sealing device, oil shall not leak out of the bearing.


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Before assembling the integral sliding bearing, first check the surface condition of the shaft sleeve and bearing hole, and whether the fit interference amount meets the requirements. Polish and clean the burrs or rust on the fitting surface with a scraper or an oilstone. Then scrape the shaft sleeve according to the journal and leave a certain clearance. The clearance value is generally 01001~01002d, and d is the diameter of the journal. When assembling integral sliding bearings, they are generally pressed with a press or manually. If there is no press or the shaft sleeve is installed in a single piece, the hammer can be used to knock and press in. At this time, in order to prevent the shaft sleeve from being damaged, the hammer cannot be directly hit on the shaft sleeve. When striking, a hardwood pad or a soft metal pad should be padded, and a guide sleeve or a guide shaft should be used. The press in speed should not be too fast to facilitate alignment and avoid pressure deviation. When matching the shaft sleeve, in order to reduce the friction resistance between the mating surfaces, a thin layer of lubricating oil should be coated on the outside of the shaft sleeve. For some shaft sleeves with very thin and long thickness, in order to prevent deformation and crushing, the temperature difference method of heating the bearing body or cooling the shaft sleeve should be adopted. After the assembly of the shaft sleeve is completed, its inner diameter shall be measured and checked again and compared with the measurement results before assembly. If the inner neck of the shaft sleeve is reduced due to too tight assembly, it shall be scraped. The bearing whose inner journal is not reduced shall also be scraped to make the contact point between the shaft sleeve and the journal reach the specified standard.

 

The bearing bush (common name of split sliding bearing) shall be thoroughly cleaned and inspected before installation. During cleaning, kerosene or gasoline can be used for soaking or scrubbing; During inspection, a small copper hammer can be used to gently tap along the surface of the Babbitt alloy lining in sequence. If there is a crisp sound, it indicates that the casting quality of Babbitt alloy and the bonding quality with the tile bottom are excellent; If it emits low turbidity or hoarse sound, it indicates that there may be sand holes, holes, cracks or double skin in the babbitt alloy, or the bonding between the babbitt alloy and the tile bottom is not good. If defects are found, repair welding or replace new pads according to the severity of defects.

 

When installing the bearing, the installation method shall be determined according to the bearing structure and its size as well as the matching nature between components. The general principle is that the installation pressure shall be directly applied to the end face of the tight fitting seat ring, and the installation pressure shall not be transmitted indirectly through the rolling element.

 

Requirements for installation surface and installation site. If there are iron chips, burrs, ash layers and other foreign matters in the bearing, the bearing will generate noise and vibration during operation, and even damage the raceway and rolling body. Therefore, before installing the bearing, it is necessary to ensure that the installation surface and installation environment are clean. The bearing must be installed in a dry and clean environment. Before installation, carefully check the machining quality of the fitting surface of the shaft and housing, the end face of the shoulder, the groove and the connecting surface. All mating and connecting surfaces must be carefully cleaned and deburred, and the unmachined surface of the casting must be cleaned of molding sand.

The bearing must be cleaned before installation. The bearing surface is coated with antirust oil, which must be carefully cleaned with clean gasoline or kerosene, and then coated with clean high-quality or high-speed high-temperature lubricating grease before installation and use. Cleanliness has great influence on bearing life and vibration noise. However, totally enclosed bearings do not need to be cleaned and oiled. Generally, grease or lubricating oil can be used for bearings. When grease lubrication is used, the grease with excellent properties such as no impurities, oxidation resistance, rust prevention and pressure resistance shall be selected. The filling amount of lubricating grease is 30%~60% of the volume of bearing and bearing box, which should not be too much. Double row tapered roller bearing with sealing structure and water pump shaft bearing have been filled with lubricating grease, which can be directly used by users and can not be cleaned again.

 

Preparation of bearings. As the bearing has been treated with rust prevention and packaged, do not open the package until the temporary installation. In addition, the antirust oil coated on the bearing has good lubrication performance, and it can be used directly without cleaning for general purpose bearings or bearings filled with lubricating grease. However, for instrument bearings or bearings used for high-speed rotation, use clean cleaning oil to wash away the rust proof oil. At this time, the bearing is easy to rust and cannot be placed for a long time. Before installing the bearing, apply mechanical oil to the mating surfaces of the shaft and housing that have passed the inspection.

 

Inspection of shaft and housing. Clean the bearing and housing, make sure there is no scar or burr left by machining, and there must be no abrasive, molding sand, chips, etc. in the housing. Secondly, check whether the size, shape and processing quality of the shaft and housing conform to the drawings. Measure the journal and housing journal in several places. Also, carefully check the fillet size between the shaft and the housing and the perpendicularity of the shoulder.

 

More about UNIM Wheel Hub Bearing:

The main function of hub bearing of UNIM is to bear load and provide accurate guidance for the rotation of 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.

 

 Wheel Hub Bearing 

 


2022-11-04