An automotive alternator is the primary power source in a vehicle’s electrical system. Its function is to supply power to all electrical consumers (except the starter motor) when the engine is running, including systems such as the radio, windshield wipers, power windows, and more. It also charges the vehicle’s battery to ensure stable energy storage and supply.
Automotive alternator bearings are critical components that directly affect efficiency, durability, and noise performance under high-speed and high-temperature operating conditions.
Bearing rings and rolling elements shall be manufactured from high-quality GCr15 bearing steel in accordance with GB/T 18254-2016.
The hardness and other heat treatment quality requirements shall comply with GB/T 34891-2017 or relevant product drawings.
This ensures:
High wear resistance
Excellent fatigue strength
Stable performance under high-speed rotation
For passenger vehicles, bearing cages are typically made of:
Glass fiber reinforced Polyamide 66 (PA66-GF)
Glass fiber reinforced Polyamide 46 (PA46-GF)
Material and product technical requirements shall comply with JB/T 7048-2011.
For commercial vehicles, cages are generally made of:
08, 10 steel sheet, or DC01 steel sheet
These materials shall comply with GB/T 28268-2012, or alternative materials with equivalent or superior performance may also be used.
Key requirements:
High mechanical strength
Good dimensional stability
Resistance to vibration and fatigue
For passenger vehicle bearings, sealing components must operate reliably within a temperature range of -40°C to 180°C.
For commercial vehicle bearings, sealing components must operate within -40°C to 150°C.
Other technical requirements (excluding rubber compounds for seals) shall comply with JB/T 6639-2015.
Key performance expectations:
Stable sealing under extreme temperature variation
Resistance to aging and deformation
Effective protection against contaminants
For passenger vehicle bearings:
Grease operating temperature range: -40°C to 180°C
Grease fill ratio: approximately 25%–30% of internal free volume
For commercial vehicle bearings:
Grease operating temperature range: -40°C to 150°C
Grease fill ratio: approximately 30%–35% of internal free volume
Performance requirements:
Long-life lubrication stability
Low friction torque
High thermal resistance
Excellent anti-wear performance
After testing for grease leakage, temperature rise, and dust resistance:
Sealing components must remain intact and undamaged
Grease leakage rate shall not exceed 2%
Other technical requirements shall comply with JB/T 7752-2017
Procedure:
Place the bearing in a high-temperature chamber at 105°C ± 2°C for 2 hours
Immerse vertically in water (depth: 200 mm, temperature: 20°C ± 2°C) for 10 minutes
Remove and dry the surface
Measure mass change
Test conditions:
Two nozzles positioned at the mid-point between inner and outer diameters
Opposed at 180°
Distance to seal face: 10 mm
Nozzle diameter: 3 mm
Water flow: 1 L/min
Temperature: 25°C ± 5°C
Rotation speed: 6000 r/min
Radial load: 5% Cr
Duration: 2 hours
Requirement:
No corrosion allowed on bearing surface
Mass increase after each test ≤ 0.1%
Procedure:
Heat at 130°C ± 2°C for 2 hours
Transfer to -40°C ± 2°C for 2 hours
Transition time between chambers ≤ 30 seconds
One cycle = heating + cooling
Total cycles: 10
Requirement:
Bearing must rotate smoothly after testing
Test conditions:
Temperature: 25°C ± 5°C
Radial load: 15% Cr
Speed: 1.2 × nmax (maximum alternator speed)
Operation: 30 seconds running + 30 seconds stop
Total cycles: 10
Requirement:
No abnormal noise or damage
Stable rotation after test
Conditions:
Temperature: 135°C
Radial load: 15% Cr
Passenger vehicle speed: 15,000 r/min
Commercial vehicle speed: 12,000 r/min
Test duration: ≥ 500 hours
Key requirements:
No seizure
No excessive wear
Stable lubrication performance
Conditions:
Temperature: 125°C
Radial load: 15% Cr
Acceleration: 0 → 18,000 r/min within 2 seconds
Hold: 15 seconds
Deceleration: 3 seconds to stop
One cycle: 20 seconds
Total cycles: 54,000
Requirement:
Stable rotation performance after test completion
Conditions:
Temperature: 25°C ± 5°C
Speed: 6000 r/min
Radial load: ≥ 15% Cr
Continuous test duration: ≥ 4 hours
Total test time: not less than 2L10 life rating
Requirement:
No fatigue failure
Stable rotational performance
JB/T 8167-2017 — Rolling Bearings: Automotive Alternator Bearing Technical Specifications
