Introduction
Bearings are one of the important components in automobiles, as well as vulnerable and safety parts. It plays a role in supporting loads, and the traction, braking force, lateral force, and vertical force Z of the car are ultimately transmitted to the bearings.
With the continuous increase in the number of cars in China, bearing damage caused by improper selection, assembly, or use has occasionally led to tire detachment during driving, posing a serious threat to the safety of passengers. Drawing on the improvement methods after some bearing detachment accidents in China and some classic layout structures in the axle industry, several typical anti loosening structures for wheel hub bearings are summarized to provide reference and reference value for design and use.
1. Anti loosening principle related to bearing matching
To prevent looseness of wheel hub bearings, ensure effective preloading of wheel hub bearings, and prevent wheel edge detachment accidents caused by bearing burning. When designing wheel hub bearings, an anti loosening structure needs to be installed. The first choice to prevent bearing looseness is to ensure that the bearing is assembled in place, and to standardize the fitting relationship and tolerance between the bearing and the shaft, hole, and edge; The second step is to design structures or components that prevent bearing loosening.
When fitting with a shaft or hole: for a half floating bridge, an interference fit must be used between the inner ring and the shaft, and a transition or interference fit should be used between the outer ring and the hole; For fully floating bridges, clearance or slight transition fit should be used between the inner ring and the shaft, and interference fit should be used between the outer ring and the hole.
2. Introduction to the structure of axial anti loosening
We divide wheel edge structures into two categories to distinguish them:
I. Adopting a wheel edge structure with two single row tapered bearings or a wheel edge structure with one hub unit (as shown in Figure 1), this type of structure can gradually adjust the preload of the bearings and lock them;
II. The wheel edge structure using a single cone bearing, ball bearing, or wheel hub unit (as shown in Figure 2) cannot adjust the preload of the bearing during the tightening process of this type of structure.
The above only applies to the traditional drum type rear axle, and the caliper equipped with the disc type rear axle itself has anti loosening function, so it will not be discussed here.
For Class I wheel edge structure: adopt a "bearing nut+locking washer+locking screw or locking pin" structure, with the "bearing nut" achieving step-by-step preloading of the bearing and the "locking plate+locking pin" achieving preloading and tightening of the bearing; The bearing nut of type d wheel edge in Figure 1 has been treated with rubber at the end to prevent loosening, replacing the function of the locking plate and locking nail.
Figure 1 Wheel edge structure of two single row tapered bearings or one wheel unit
For Class II wheel edge structures: use "bearing nuts+anti loosening washers" or "snap springs" to achieve fastening of the bearing inner race. In Figure 2, the thickness of the thin gasket added between the outer shell and the axle body is used to adjust the preload of the hub bearing on the e-type wheel edge; Figure 2. The f type wheel edge adopts deep groove ball bearings, and axial preloading is not carried out during the assembly process; Figure 2. The g-type wheel edge adopts a wheel hub unit, and a large axial clearance has been preset for the wheel hub unit before assembly. During the assembly process, only press the bearing in place and limit it with a circlip.
Figure 2 Wheel edge structure of a single cone bearing, ball bearing, or wheel unit
3. Introduction to axial anti detachment structure
The occurrence of extreme accidents such as wheel edge detachment requires two conditions to be met simultaneously: firstly, severe damage to the wheel hub bearing caused by some reason; Secondly, there are no limit devices installed on the bridge to prevent the tires from driving out rotating parts such as the half axle or wheel core. The limiting element to prevent wheel edge detachment should only be used as an auxiliary preventive measure, and the primary measure should be to prevent bearing damage.
Usually, reasonable selection of bearings with appropriate load-bearing capacity during design to ensure sufficient service life of the bearings, ensuring normal installation and appropriate preload during assembly, and paying attention to maintenance during use can effectively prevent bearing damage.
In limited structural space, the set limit components should be able to prevent or delay the wheel edge detachment. Several typical limiting methods are introduced as follows:
I. Full floating bridge (as shown in Figure 1. a, Figure 3. h, i): Using bearing nuts as limiting elements. Due to its outer diameter being larger than the small diameter of the outer ring of the outer bearing, even if the bearing is burnt or the wheel edge is not detached, it will not cause accidents. The improved structure of Figure 3. i not only achieves progressive preloading of bearings, but also has thicker limiting elements, which should be prioritized.
II. Use a semi floating bridge with a bearing (as shown in Figure 4. j, k): Use a brake base plate with an inner diameter smaller than the inner ring of the bearing, or an anti detachment washer with an outer diameter larger than the outer ring of the bearing as a limiting element.
Figure 3 Before and after the improvement of the wheel edge locking structure of a certain type of passenger car
Figure 4 Semi floating bridge of wheel unit
III. Semi floating bridge with hub unit (as shown in Figure 4. l): In the initial design, the tire centerline was placed near the outer bearing side to ensure that the service life of the inner bearing is higher than that of the outer bearing; Even if the outer bearing is damaged, the inner bearing can still prevent the wheel edge from coming out. During this period, maintenance personnel are able to detect abnormalities and handle them properly.
4. Conclusion
On the premise of ensuring sufficient design life of the bearings, two types of anti loosening structures for wheel hub bearings are recommended to ensure the safety of passengers in extreme cases due to bearing damage:
1) For a fully floating bridge, priority should be given to selecting the "bearing nut+locking washer+locking screw" method, while reasonably designing its theoretical adjustment angle value;
2) For semi floating bridges, thicker brake soleplates should be preferred as limiting components.
More about VAFEM Wheel Hub Bearings:
VAFEM Hub units are designed to allow rear wheels, especially in passenger cars, to turn on an axle even under heavy loads.
Features:
magnetic, electric, and mechanic ABS
with and without ABS
flange only
Steel Material: GCr15/52100/100Cr6
Steel Type: Forged
Ball Grade: G10
Grease: Shell
As a precious high quality wheel hub bearings manufacturer and supplier in China, VAFEM can guarantee the quality and precision of the products through complete testing technology and advanced equipment. Please come to buy wheel hub bearings at the best price and quality from VAFEM. Please contact us for any questions!
2023-09-23