The “Three-in-One” Integrated Electric Drive Axle Process: The Secrets of Packaging the Motor, Electronic Control, and Reducer

The “Three-in-One” Integrated Electric Drive Axle Process: The Secrets of Packaging the Motor, Electronic Control, and Reducer

Amid the rapid development of the new energy vehicle industry, the electric drive axle, as a core power component, directly determines the vehicle’s range, power output, and driving experience through its performance and efficiency. In traditional electric drive systems, the motor, electronic control, and reducer are often implemented as separate modules, which not only take up a lot of space and are relatively heavy, but also suffer from issues such as signal transmission delays and significant energy loss. The emergence of the “three-in-one” integrated electric drive axle process has completely overcome this limitation. Through a highly integrated design, these three core components are packaged into a cohesive whole, becoming a key breakthrough in achieving the goals of “lightweight, high efficiency, and miniaturization” for new energy vehicles. Today, we will delve into the technical details of the “three-in-one” integrated electric drive axle process and explore the “secrets of synergy” among the motor, electronic control, and reducer during the packaging process.

I. Why “three-in-one” integration? The Inevitability of Integration from the Perspective of Industry Pain Points

Before exploring the technical details of the “three-in-one” integration process, we must first understand that integration isn’t simply for its own sake; it’s an inevitable choice for the new energy vehicle industry to meet the demands of upgraded performance. Traditional distributed electric drive systems face three core pain points in practical applications:

1. “Dual Redundancy” of Space and Weight

In traditional electric drive systems, the motor, electronic control, and reducer each have their own independent housing, cooling system, and connecting piping. For example, in a distributed design, the three components weigh approximately 180 kg and occupy over 0.8 m³ of chassis space. This not only squeezes the space for the battery pack (directly impacting range), but also increases the vehicle’s unsprung mass, resulting in increased handling and fuel consumption. However, through shared housings and simplified piping, “three-in-one” integration can reduce weight by 20%-30% and space by over 30%, providing greater flexibility in vehicle layout. 2. “Double Losses” of Energy and Signals

In a distributed design, the motor and reducer are connected by a drive shaft, resulting in mechanical friction losses. The high-voltage and signal wiring harnesses between the electronic control and the motor are long, resulting not only in energy losses due to wiring resistance (approximately 5%-8%) but also in signal transmission delays that can affect motor control accuracy (e.g., response speeds as slow as 0.1-0.3 seconds). “Three-in-one” integration, however, reduces energy losses to less than 2% and signal delays to microseconds through “zero-distance” connection, directly improving electric drive system efficiency.

3. “Double Complexity” of Cost and Maintenance

Distributed components require separate design, production, and testing, resulting in complex supply chain management and high costs. Furthermore, troubleshooting individual components is difficult (e.g., separate testing of the motor, electronic control, and reducer is required), resulting in low maintenance efficiency. “Three-in-one” integration, through modular design, reduces the number of components (by approximately 40%), lowering R&D and production costs while facilitating integrated diagnostics and maintenance, improving the user experience.

Precisely because of these pain points, the “three-in-one” integrated electric drive axle has become a mainstream industry trend. According to industry data, by 2025, the penetration rate of “three-in-one” integrated electric drive axles in global new energy vehicles will exceed 70%, becoming standard equipment in mid-to-high-end models.

II. The Core of “Three-in-One” Integration: A Technical Breakdown of the “Cooperative Packaging” of the Three Major Components

“Three-in-one” integration is not simply about “packaging” the motor, electronic control, and reducer together. Rather, it addresses the “coordination” issues of these three components in terms of structure, thermal management, and electromagnetic compatibility. The packaging design of each component must balance its own performance with overall compatibility. The following analysis details the integration of these three core components:

1. Motor: From “Independent Cooling” to “Shared Thermal Management,” Balancing Power and Space

As the core of power output, the key to motor packaging lies in “how to minimize size while ensuring heat dissipation efficiency and power density.” Traditional motors use independent water-cooling jackets, but in a “three-in-one” integration, the motor’s cooling system must be shared with the electronic control and reducer, requiring “thermal flow coordination” in the structural design.

Structural Integration: Integrated Design of the Rotor and Reducer Input Shaft

The output shaft of a traditional motor is connected to the reducer input shaft via a coupling, which results in play and friction losses. In a “three-in-one” integration, the motor rotor and reducer input shaft are forged using an integrated forging process, eliminating the coupling. This not only shortens the axial length (by approximately 15%-20%) but also eliminates mechanical connection losses, improving transmission efficiency. Furthermore, the motor stator housing and reducer housing utilize a shared aluminum alloy design, reducing material usage and weight.

Thermal Management: Series water cooling with the electronic control ensures even heat distribution.

During motor operation, the primary heat sources are the stator windings (copper losses) and the iron core (iron losses), while the heat source for the electronic control is the IGBT module (switching losses). The “three-in-one” integration utilizes a series-connected water cooling channel: coolant first flows through the electronically controlled IGBT module (requiring low-temperature heat dissipation, optimally 50-60°C), then through the motor stator water cooling jacket (requiring medium-temperature heat dissipation, optimally 70-80°C), and finally returns to the radiator. This design not only fully utilizes the coolant’s temperature gradient but also reduces the number of water cooling lines (from three to one), minimizing the risk of leakage.

For example, a car company’s “three-in-one” electric drive axle achieves a motor power density of 4.5kW/kg (compared to approximately 3.2kW/kg for conventional motors), achieving a peak efficiency of 97.5%, and reducing the size by 25% compared to conventional motors.

2. Electronic Control: From “Independent Layout” to “Close to the Motor,” Achieving “Zero-Distance Control”
The electronic control system (primarily consisting of the IGBT module, MCU controller, capacitors, etc.) is the “brain” of the motor. The core of its packaging is to “shorten the distance from the motor, reduce signal and power losses, and address electromagnetic compatibility (EMC) issues.”

Layout Integration: The electronic control module is “embedded” in the motor end cap, shortening wiring harness length.

Traditionally, the electronic control and motor require a high-voltage wiring harness (voltage 300-800V) and a signal wiring harness, which can be 1-1.5 meters long. In the “three-in-one” integration, the electronic control module is directly embedded in the rear end cover of the motor. This shortens the high-voltage wiring harness to 10-20 cm, reduces line resistance by over 80%, and reduces power loss by 60%. Simultaneously, the signal harness is shortened to 5-10 cm, reducing signal transmission latency from 0.1 seconds to less than 50 microseconds, significantly improving motor control accuracy (for example, torque response speed is increased by 30%).

Electromagnetic Compatibility: A “Shielding + Grounding” Dual Design Addresses Interference Issues

Motors generate strong electromagnetic radiation during operation, and the electronic control MCU is extremely sensitive to electromagnetic interference. To address this, the “three-in-one” integration utilizes a “double shielding” design: a metal shielding layer (such as copper foil) is added between the electronic control module housing and the motor end cover, and a shielding mesh (such as tinned copper wire) is wrapped around the high-voltage wiring harness. Furthermore, the electronic control and motor share a common ground electrode, reducing ground resistance and further minimizing electromagnetic interference. Through these designs, the EMC test pass rate of the electronic control system can be increased to over 99%, preventing control failures caused by interference.

3. Reducer: From “Independent Lubrication” to “Shared Oil with the Motor,” Simplifying System Design

The reducer’s function is to convert the high speed of the motor to the lower speed of the wheels. The key to its packaging lies in “how to share the lubrication and cooling system with the motor while ensuring gear transmission efficiency.”

Lubrication Integration: Sharing “Oil Cooling + Splash Lubrication” with the motor to Reduce Component Count

Traditional reducers use independent splash lubrication (lubricant oil generated by rotating gears lubricates the bearings and gears), while the motor is water-cooled. In the “three-in-one” integration, a shared “oil cooling + splash lubrication” system is designed: The reducer’s lubricating oil is pumped into the oil channel between the motor’s stator and rotor via an oil pump, cooling the motor. The oil then flows back to the reducer housing, where it splashes through the gears to lubricate the reducer’s bearings and gears. This design not only eliminates the need for a water cooling jacket for the motor but also reduces the number of lubricating oil pumps (from two to one), resulting in a simpler system architecture. Oil cooling also offers higher heat dissipation efficiency than water cooling (oil has a greater specific heat capacity than water and is in direct contact with the heat source), reducing motor temperature by 10-15°C and extending service life.

Structural Integration: The reducer housing and motor casing are die-cast as a single unit, improving rigidity.

Traditional reducers and motors are connected via flanges, which creates gaps and compromises overall rigidity. The “three-in-one” integration utilizes an aluminum alloy die-casting process, integrating the reducer housing and motor casing into a single unit. This eliminates gaps and improves overall rigidity (by approximately 30%), reducing vibration and noise during operation (by 5-8dB). Furthermore, die-casting reduces the number of components (e.g., eliminating flange bolts), lowering production costs.

III. The Value of “Three-in-One” Integration: Beyond “Small and Light,” but More Efficient and Economical

Through the coordinated packaging of the motor, electronic control, and reducer, the “three-in-one” integrated electric drive axle not only achieves “lightweight and miniaturization,” but also delivers multiple benefits in terms of efficiency, cost, and reliability. These advantages can be summarized into three core aspects:

1. Improved Efficiency: From “Component Efficiency” to “System Efficiency”
“Three-in-one” integration reduces mechanical connection losses (such as couplings and drive shafts), electrical energy losses (such as high-voltage wiring harnesses), and heat dissipation losses (such as shared thermal management), thereby increasing the overall efficiency of the electric drive system to 94%-96% (compared to the approximately 88%-90% efficiency of traditional distributed systems). For example, for a pure electric vehicle with a range of 500km, equipping it with a “three-in-one” integrated electric drive axle can increase its range by approximately 50km (a 10% increase) and reduce power consumption by 1-2kWh per 100km, directly alleviating users’ range anxiety.

2. Cost Reduction: From “Multiple Component Costs” to “Modular Costs”

“Three-in-one” integration reduces the number of components by approximately 40% (e.g., eliminating separate housings, water cooling jackets, and oil pumps), lowering R&D, production, and supply chain costs (reducing total costs by approximately 15%-20%). Furthermore, modular design improves production efficiency (reducing production line cycle times by approximately 25%) and facilitates mass production. For automakers, this means they can provide customers with higher-performance products while controlling costs. For customers, vehicle purchase and maintenance costs are also reduced (e.g., extended maintenance intervals and easier troubleshooting).

3. Reliability Improvement: From “Multiple Failure Points” to “Fewer Failure Points”

In traditional distributed systems, the connections between the motor, electronic control, and reducer (such as couplings, wiring harnesses, and flanges) are a high-prone point of failure (accounting for approximately 60% of electric drive system failures). By reducing the number of connecting components, “three-in-one” integration reduces the number of failure points (reducing the number of failure points by approximately 50%). At the same time, a shared thermal management and lubrication system ensures more stable operating temperatures across all components, reducing failures caused by overheating (such as motor burnout and IGBT damage). According to data from one automaker, vehicles equipped with a “three-in-one” integrated electric drive axle can reduce the failure rate of the electric drive system to below 0.5% (compared to approximately 1.5% for traditional systems), improving user reliability.

Fourth, Future Trends: From “Three-in-One” to “Multi-in-One,” Integration Never Ends

With the continuous advancement of new energy vehicle technology, “three-in-one” integration is not the end point. In the future, it will evolve towards “multi-in-one” integration (such as adding a DC/DC converter and an onboard charger (OBC)), further enhancing system integration. For example, one automaker has launched a “five-in-one” integrated electric drive axle, integrating the motor, electronic control, reducer, DC/DC converter, and OBC, further reducing the size by 15% and improving efficiency by another 2%.

At the same time, with the application of silicon carbide (SiC) devices (SiC’s switching losses are over 50% lower than those of IGBTs), the efficiency of “three-in-one” integrated electric drive axles will be further improved. Furthermore, the maturity of processes such as 3D printing and integrated die-casting will make the design of integrated structures more flexible and cost-effective. It is foreseeable that future electric drive axles will develop towards greater integration, higher efficiency, and greater intelligence, becoming a key manifestation of the core competitiveness of new energy vehicles.

Conclusion
The “three-in-one” integration process for electric drive axles epitomizes the new energy vehicle industry’s shift from “component innovation” to “system innovation.” It’s not a simple “1+1+1=3″ solution. Instead, through the coordinated packaging of the motor, electronic control, and reducer, it achieves a value enhancement of “1+1+1>3″—smaller size, lighter weight, higher efficiency, lower cost, and more reliable performance. For car companies, mastering the “three-in-one” integrated technology means mastering the core power code of new energy vehicles; for users, models equipped with the “three-in-one” integrated electric drive axle will bring a better driving experience.