Integrated vs. Distributed Electric Drive Axles for Commercial Vehicles: Which Will Become the Trend?
As automotive powertrain architectures evolve from decentralized layouts to highly integrated systems, configurations such as "motor + electric drive axle" and distributed electric drive systems have gradually emerged.
Thanks to its unique structural design, the electric drive axle eliminates the need for a traditional gearbox in pure electric vehicles, significantly reducing energy loss during power transmission. As a result, it is widely believed that integrated electric drive axle solutions and distributed electric drive systems will become the mainstream development trends for future pure electric trucks.
Previously, at industry forums and technical seminars, Sany Heavy Truck analyzed development trends in electric drive powertrains for heavy-duty trucks, while Yutong New Energy Commercial Vehicles showcased its strategic layout related to electric drive axle technologies.
At present, the mainstream electric drive solutions for new energy commercial vehicles mainly include central drive, integrated electric drive axle, and distributed drive systems.
Types of Electric Drive Systems for Commercial Vehicles
The central drive layout is similar to that of traditional fuel vehicles, replacing the internal combustion engine and transmission with an integrated drive motor + transmission unit.
The integrated electric drive axle, which can be classified into parallel-axis, coaxial, and vertical-axis structures, integrates the traditional drive axle with the motor and transmission. This solution occupies less space, reduces system weight, improves transmission efficiency, and enhances vehicle driving range.
The distributed drive system, including wheel-side motor drive and hub motor drive, places motors on both sides of the axle. This configuration offers higher mobility and efficiency but comes with high costs and strict environmental requirements. At present, it is mainly applied in buses and high-end vehicle models.
Definition and Advantages of Integrated Electric Drive Axles
An integrated electric drive axle primarily consists of three core components: a drive motor, inverter, and electric drive transmission. Fundamentally, it remains a drive axle, but the power source is shifted from an internal combustion engine to an electric motor. Most integrated electric drive axles embed the motor directly into the axle assembly, achieving lightweight design, high integration, and superior efficiency.
In simple terms, an integrated electric drive axle combines the motor with the rear axle, enabling the axle to perform the functions of the engine, gearbox, rear axle, and differential in a single unit. This design eliminates the need for a drive shaft and significantly reduces gearbox size.
Compared with conventional transmission systems, integrated electric drive axles reduce overall system space, allowing more batteries to be installed to extend driving range. Their specialized designs also enable adaptation to various operating conditions, meeting the requirements of buses, light trucks, and other commercial vehicles.
Currently, integrated electric drive axles have been widely adopted in new energy light trucks. Differences among manufacturers mainly lie in integration level, material selection, and weight, while the overall structural principles remain similar.
Key Features of Integrated Electric Drive Axles
Modern integrated electric drive axles typically include:
Drive motors
Gearboxes
Differentials
Braking systems
Air suspension systems
Axle housings and wheel hubs
Their key characteristics include:
High integration of motor, transmission, and differential with a compact structure
High transmission efficiency, with motor power directly driving the wheels
Automatic transmission capability, keeping the motor operating within an optimal efficiency range
Regenerative braking, enabling energy recovery and extended driving range
Four Key Advantages of Integrated Electric Drive Axles
1. Simpler Structure
Traditional motor-based solutions consist of separate components such as motors, universal drive shafts, and axles, resulting in long transmission chains and complex structures.
In contrast, integrated electric drive axles eliminate the drive shaft, reduce component count, and simplify system architecture.
2. Easier Vehicle Layout
Integrated electric drive axles are mounted directly onto the chassis, occupying less space and simplifying vehicle layout.
Traditional solutions require separate arrangement of motors, drive shafts, and axles, increasing layout complexity.
3. Higher Energy Efficiency and Environmental Benefits
The highly integrated structure minimizes power loss, reduces energy consumption, and increases vehicle driving range.
4. Technological Advantages
Compared with traditional rear axles, integrated electric drive axles offer a wider adjustable speed ratio and higher energy recovery capability, aligning with future new energy vehicle development trends.
Definition and Advantages of Distributed Wheel-Side Motor Drive Systems
At the Shanghai Auto Show, industry experts noted that new energy commercial vehicles are gradually transitioning from central drive systems to distributed electric drive solutions. These systems feature high efficiency, low energy consumption, and reduced operating costs, while also supporting lightweight vehicle design.
Distributed electric drive systems mainly include hub motor drives and wheel-side motor drives, both of which enable independent wheel control.
Differences Between Wheel-Side Motor Drive and Hub Motor Drive
1. Installation Position
Hub motors are installed concentrically within the wheel, while wheel-side motors are mounted eccentrically beside the wheel.
2. Transmission Method
Wheel-side motors transmit power to the wheels through a drive shaft, whereas hub motors are directly connected to the wheel via the rotor or stator.
3. Technical Routes
Wheel-side motors generally adopt internal rotor designs. Hub motors use either internal or external rotor configurations.
Internal rotors provide higher speed with lower torque, while external rotors deliver lower speed with higher torque.
4. Operation Mode
Wheel-side motors typically use high-speed motors combined with fixed-axis or planetary gear reduction. Hub motors mainly adopt direct drive or planetary gear reduction solutions.
Challenges of Distributed Electric Drive Axles
Distributed electric drive axles enable flexible configurations such as front-wheel drive, rear-wheel drive, or four-wheel drive. They also allow differential steering through independent wheel speed control, significantly reducing turning radius.
However, both hub motors and wheel-side motors face challenges including:
High torque density requirements
Strict demands on motor control accuracy
High standards for noise control, heat dissipation, braking, sealing, and durability
Very high system costs
At present, their overall application performance remains less mature than integrated electric drive axles, and the market still requires further validation.
Mainstream Heavy Trucks Are Actively Deploying Electric Drive Axles
Although commercial vehicle participation at the 2023 Shanghai Auto Show was relatively limited, both domestic and international component suppliers such as TEPKOS and Bosch showcased new energy commercial vehicle powertrain solutions, including electric drive axles.
TEPKOS Product Recommendation
As a trusted OEM supplier of global mobility solutions, Shanghai TRION (brand: TEPKOS) is at the forefront of integrated electric drive axle development, providing high-performance EV axle solutions for commercial vehicles worldwide.
Our integrated electric drive axles offer:
High Integration & Compact Structure
Integrating the motor, transmission, differential, and inverter into a single unit, significantly reducing space occupation and vehicle weight.
Superior Transmission Efficiency
Achieving transmission efficiency exceeding 94%, maximizing driving range and energy savings.
Strong Environmental Adaptability
Customized solutions for diverse operating conditions, including hot and humid climates, high-standard European roads, and harsh off-road environments.
Intelligent Performance
Supporting precise torque distribution and regenerative braking, seamlessly integrated with vehicle control systems to enhance safety and efficiency.
Contact us today to discover how our integrated electric drive axles can enhance your vehicle's performance and market competitiveness.
