Writer: Eric Bearing Limited
NSK recently announced that it has developed a new method of using high-strength materials to manufacture passenger car-specific hub assembly bearings by cold rolling. Cold forging can increase the strength compared with hot forging, but it requires several times the forming pressure during processing. The company uses the "side extrusion method" to form large-area flanges with lower pressure to achieve lower pressure forming.
In terms of ensuring the reliability of strength, etc., while achieving lightweight, customer requirements are getting higher and higher.
Compared with the previous hot forging, cold-rolled forming has improved work hardening and surface finish, so the strength can be improved. After the strength is increased, the disc flange can correspondingly reduce the weight by 30% by changing the shape, etc., thereby reducing the overall wheel hub assembly by more than 15%. However, cold forming is more difficult to process than hot forging.
Aiming at the problem of increasing forming pressure, the flange part is squeezed after pressing the shaft part, thereby reducing the area of the forming part. Squeeze the shaft with a smaller area to form the flange with a larger area. The area where pressure is applied from beginning to end remains unchanged during processing. NSK 7906CTYNDULP4 bearings online . pls click here :
Wheel bearing repair and maintenance methods
Wheel bearings are important moving parts of automobiles. The hub axle is responsible for reducing the frictional resistance when the chassis is running and maintaining the normal driving of the car. If the hub bearing fails, it may cause noise, bearing heating, etc., especially the front wheel is more obvious, and it is easy to cause dangerous phenomena such as out of control. Therefore, the hub bearings must be maintained on schedule.
1. Inspection of hub bearing
(1) When inspecting the tightness of the wheel hub bearing, first erect the axle of the wheel at one end of the inspected wheel hub, and use the support bench, shelter wood and other tools to safely set up the car.
(2) Turn the inspected wheel several times by hand to see if the rotation is stable and if there is abnormal noise. If the rotation is not stable and there is a friction sound, it means that the braking part is abnormal; if there is no noise, the rotation is not stable and sometimes tight and sometimes loose, indicating that the bearing part is abnormal. When the above abnormal phenomenon occurs, the hub should be disassembled. For small cars, when inspecting the wheel bearings, hold the upper and lower sides of the tire with both hands, pull the tire back and forth with both hands, and repeat it many times. If it is normal, there should be no feeling of looseness and blockage; if there is obvious looseness in the swing, the wheel hub should be disassembled and inspected.
(3) Inspection on braking. Usually when checking the wheel hub bearing, check the wheel brake device. If there are oil traces on the inside of the tire, it is probably caused by the brake cylinder or brake oil pipe leakage. The cause should be found out in time and eliminated.
2. Maintenance of hub bearing
Before disassembling the hub, you should make preparations for hub maintenance, stop the car and erect the axle to ensure the safety of maintenance operations.
(1) Remove the decorative cover and dust cover of the hub axle head;
(2) Remove the tire nuts and tires, taking care not to damage the threads of the tire bolts. If it is a disc brake, remove the brake and use it to remove the lock ring or lock pin.
(3) Remove the hub with special tools;
(4) Scrape off the old grease in the bearing, journal and hub cavity, clean the hub bearing and journal with detergent and dry it with a cloth, and then wipe the inner cavity of the hub with a cloth.
(5) Check the hub bearing and the bearing race. If there are cracks, fatigue peeling and loose rollers, the bearing should be replaced. If pitting is found on the bearing race, the bearing should also be replaced.
(6) Check the fit between the inner diameter of the bearing and the journal. The fit gap should not be greater than 0.10mm. When measuring the journal, it should be measured at the upper and lower parts of the vertical ground (the place is the large wear part). If the fit gap exceeds the specified limit of use, the bearing should be replaced to restore the normal fit gap. Burrs and pits on the journal are not allowed to narrow the gap.
(7) After all parts meet the requirements, apply grease to the inner bearing and put it in the wheel hub.
(8) Pay attention when applying grease to the bearing cavity. The grease should be squeezed into the bearing until the grease emerges from the other side of the bearing. Apply a thin layer of grease to the hub cavity and the axle head cover to prevent rust. Be careful not to apply too much grease in the hub cavity, otherwise it will affect heat dissipation and braking.
(9) Install the hub and outer bearing back on the journal, screw on the adjusting nut of the shaft head by hand, and then tighten the adjusting nut according to the specified torque with the shaft head wrench. After tightening the nut, you should turn the hub a few turns left and right to see the installation of the bearing; on the other hand, make the bearing and the seat ring fit correctly by turning. At this time, the bearing tightness is appropriate and the wheel rotates freely without feeling the axial clearance.
(10) Then install the lock plate, fixing nut, tire, dust cover and decorative cover in sequence.
(11) After adjusting the wheel hub bearing, drive for a certain mileage (about 10km) and stop for inspection. It is used to wipe the temperature of the wheel hub. If the heat is generated, the bearing should be adjusted too tightly. It should be re-adjusted and the bearing tightness should be properly relaxed.