The automotive wheel hub unit has a certain degree of high temperature resistance, but it needs to be strictly controlled within a reasonable range to ensure safety and reliability. Its high temperature resistance is mainly reflected in the following aspects:
1. Normal operating temperature range
Wheel hub overall temperature:
Under normal driving conditions, the wheel hub temperature is usually between 45 ℃ and 80 ℃. Among them:
The inner ring near the axle: due to its proximity to a heat source (such as the brake system), the temperature is relatively high, generally ranging from 60 ℃ to 80 ℃.
The outer ring away from the axle: dissipates heat through air and heat dissipation holes, with a lower temperature of about 30 ℃ to 50 ℃.
.Temperature under extreme working conditions:
Continuous braking or high-speed driving: Wheel hub temperature may rise to 80 ℃ to 100 ℃, but it is still within a safe range.
. Heavy vehicles or special operating conditions: For example, wet axle hubs may have a thermal equilibrium temperature exceeding 200 ℃ when braking frequency is high, but stability needs to be maintained through heat dissipation design (such as coolant circulation).II. Effects of High Temperature on Wheel Hub Units
Material Performance Changes:
The viscosity of the lubricating grease for wheel hub bearings decreases at high temperatures, which may lead to a decrease in oil film thickness and exacerbate wear between the rolling elements and raceways.
. Metal materials (such as bearing steel) may undergo thermal expansion at high temperatures, affecting fitting accuracy and even causing biting or bonding.System stability risk:
When the hub temperature exceeds 120 ℃, it is necessary to stop the vehicle immediately for inspection, otherwise it may cause hub deformation, bearing failure or brake system performance degradation, endangering driving safety.
. Continuous high temperature will accelerate the aging of rubber components (such as sealing rings) and shorten the service life of wheel hub units.III. High temperature resistant design guarantee
Material selection:
The wheel hub bearings are made of high-temperature resistant alloy steel (such as GCr15), and their high-temperature hardness and wear resistance are improved through heat treatment processes.
.The lubricating grease should be of high temperature type (such as lithium based composite grease), which can work stably in the range of -40 ℃ to 150 ℃.
.Heat dissipation optimization:
Aluminum alloy wheels have a thermal conductivity three times that of steel wheels, resulting in higher heat dissipation efficiency and reduced risk of high temperatures.
. Some models are equipped with perforated/lined brake discs or ventilated disc brakes to improve heat dissipation performance.Thermal balance test:
The wheel hub unit needs to pass a high-temperature durability test (such as 135 ℃ ambient temperature, 1050rpm speed, 200 hours of continuous operation) to ensure that it does not fail under extreme working conditions.
.IV. User Precautions
Temperature Monitoring:
Use an infrared thermometer to regularly check the wheel hub temperature and avoid exceeding 85 ℃ (abnormal threshold).
. During summer or after prolonged driving, stop and rest to allow the wheels to cool naturally.Maintenance suggestion:
Clean the brake caliper guide pin and apply lubricating grease every 20000 kilometers to reduce friction and heat generation.
. Check the condition of the wheel hub bearings every 40000 kilometers and replace the lubricating grease or bearing components if necessary. Troubleshooting: If the hub temperature rises abnormally, check the brake system (such as poor caliper return or brake disc deformation) or bearing lubrication.Avoid frequent sudden braking or prolonged continuous braking to reduce thermal load.