The working principle of the first generation of automotive wheel hub bearings (usually referring to traditional rolling bearing designs widely used in the early to mid-20th century) is mainly based on rolling friction replacing sliding friction. Its core structure and working mechanism can be decomposed as follows:
1. Infrastructure
Inner and outer rings: The inner ring is fixed to the wheel axle, and the outer ring is connected to the wheel hub.
Rolling element: Steel ball bearings or rollers (initially mainly ball bearings) evenly distributed between the inner and outer rings.
Retainer: Separate rolling elements to ensure uniform distribution and reduce collision friction.
Sealing element: Simple grease seal (early no labyrinth seal) to prevent grease leakage and impurities from entering.
2. Working principle
Load transmission: The contact force between the wheel and the ground is transmitted to the rolling elements through the outer ring, and then dispersed to the inner ring and the axle.
Rolling motion: When the wheel rotates, the rolling elements roll between the inner/outer raceway, and the friction coefficient decreases from 0.1-0.5 of the sliding bearing to 0.002-0.005.
Lubrication method: relying on manually filled lubricating grease (calcium based or sodium based), requiring regular maintenance (refilling every 5000-10000 kilometers).
3. Key characteristics
Pre tightening force design: By applying initial pressure through axial displacement of the inner and outer rings, the clearance of the rolling elements is suppressed, and the rigidity is improved (but excessive tightening will exacerbate wear).
Integrated installation: The bearing unit is non removable and needs to be replaced as a whole if damaged (later developed into a repairable separate design).
Material limitations: ordinary carbon steel (such as GCr15) is used, without the application of modern surface hardening technology (such as carburizing), with a lifespan of approximately 100000 kilometers.
4. Limitations
Poor sealing: Simple sealing is prone to water ingress/impurities, leading to lubrication failure and early wear.
Frequent maintenance: It is necessary to regularly disassemble the wheel hub and replenish lubricating grease, which increases labor costs.
Insufficient thermal stability: Lubricating grease is prone to deterioration under high loads, exacerbating the risk of rolling element slippage.
Comparison of Technological Evolution
Characteristics: First generation wheel hub bearings, modern wheel hub bearings
Rolling element type: Steel ball, ceramic ball, asymmetric roller
Lubrication method: Manual lubricating grease, maintenance free grease/oil lubrication for life
Sealing structure single lip sealing ring labyrinth+rubber composite seal
Lifespan of 100000 kilometers and 300000 kilometers+
Integrated function without ABS sensor/speed encoder
The first generation of wheel hub bearings revolutionized vehicle energy efficiency through rolling friction, but their design required frequent maintenance, driving the evolution towards maintenance free and high sealing performance in the future.