Analysis of the Advantages of Coaxial Electric Axle Technology

As the new energy vehicle (NEV) market grows, the innovation and optimization of electric drive axle systems have become essential for enhancing vehicle performance. Among the emerging technologies, coaxial electric axles are gaining attention for their unique design and advantages. With their compactness and high efficiency, coaxial eAxles are becoming a preferred choice for some automotive manufacturers.

This article explores the structural features, key advantages, and application potential of coaxial electric axles, providing insights for industry professionals and manufacturers.

Key Structure of the Coaxial Electric Axle

The coaxial electric axle is characterized by having the motor shaft and output shaft aligned on the same axis. Its primary structure comprises two main components:

• Intermediate Powertrain: Includes the motor assembly and reducer; features an integrated design where the semi-reduction gearbox housing is combined with the motor housing.
• Wheel-Side Assembly: Consists of the left and right half-shafts, left and right axle housings, and braking components.

Technical Advantages of the Coaxial Electric Axle

Efficiency Advantages:

• Achieve a total transmission efficiency of 93.17%.
• Compared to multi-in-one rear-drive independent suspension electric axles, it reduces the need for two sets of high-speed bearings, improving mechanical efficiency by approximately 1%.

Application Advantages:

• The optimized chassis layout creates more space for battery placement.
• High load-bearing capacity, enhanced axle housing stiffness, and excellent durability.
• High transmission efficiency, more direct power output, and improved NVH performance.

Evolution of Electric Axles for Light Commercial Vehicles

1st Generation: Central Direct Drive

The first-generation e-powertrain system involved minimal modifications to existing ICE platforms. The motor replaced the traditional engine, transmitting power to the rear axle via a driveshaft.

Batteries were typically positioned on either side of the vehicle to improve handling and stability.

Advantages:

• Low cost and high compatibility with existing platforms.

Drawbacks:

• Retained the driveshaft and rear axle, occupying valuable chassis space;
• Limited battery capacity due to the need for a split battery layout, reducing driving range.

2nd Generation: Parallel-Axis Electric Axle

The second-generation e-powertrain system introduced the parallel-axis design, integrating the motor directly into the axle, forming a compact and efficient drive unit. The driveshaft was eliminated, freeing up more space for batteries and improving transmission efficiency.

Advantages:

• Simplified structure with improved maintainability and reduced costs;
• Increased space for batteries and better range.

Drawbacks:

• Offset motor center of gravity;
• Low-frequency vibration issues;
• NVH performance issues;
• Single-axis impact concerns.

3rd Generation: Coaxial Electric Axle

The third-generation coaxial electric axle integrates the motor and output shafts on the same axis. This improves the system's rotational stability and reduces vibrations and noise.

Advantages:

• Improved rotational stability, reducing vibrations and noise.
• Space savings and weight reduction with the motor housing bearing the axle load.
• Higher system efficiency by eliminating two sets of high-speed bearings.
• Better NVH performance with reduced center-of-gravity offset and minimized low-frequency vibrations.

Drawbacks:

• Higher costs and increased maintenance complexity.

Applications of Coaxial Electric Axle

The coaxial electric axle can be used in light commercial vehicles, such as (hybrid) electric vans, pickups, trucks, or buses. At Brogen, we have coaxial electric axle solutions for buses, suitable for buses from 5 meters to 8.5 meters, or 4.5-ton light trucks.

Key features:

• Highly-integrated transmission system with weight reduced by over 100 kg and passenger capacity increased by over 30%;
• Quiet driving experience with cabin noise under 70 dB, enhancing driving comfort;
• 100,000 km maintenance intervals for reduced lifecycle costs;
• Symmetrical layout balances unsprung mass and reduces suspension load impact.

Learn more here: https://brogenevsolution.com/coaxial-electric-axle-for-bus/

Discover our public transport solutions here: https://brogenevsolution.com/public-transport-electrification-solutions/

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