Current Status and Development Trends of Electric Vehicle Transmissions
Author:
Release Time:
2025-07-12
As a transmission device that coordinates the engine’s rotational speed with the vehicle’s actual driving speed, the conventional gearbox is designed to fully harness the engine’s performance. Specifically, since the engine operates most efficiently within a relatively narrow RPM range—typically around 1,000 to 4,000 rpm—if the engine’s RPM falls below this range, it won’t be able to deliver sufficient torque; on the other hand, if the engine’s RPM rises too high, it will enter an inefficient operating state. Therefore, during driving, gasoline-powered vehicles must shift gears to adjust the gear ratio, thereby keeping the engine’s RPM within its optimal operating range. For gasoline-powered vehicles, without a gearbox, the vehicle simply wouldn’t be able to run normally.
Electric vehicles aren't entirely devoid of gearboxes—rather, the reduction gear can be seen as a single-speed transmission, which in fact is also a type of gearbox. Because electric motors have a relatively wide operating range (typically from 0 to 15,000 rpm), they can deliver high torque even at low speeds or even at zero speed, and maintain constant power output at high speeds. As a result, the motor’s characteristics closely match the vehicle’s requirements, eliminating the need for multi-speed transmissions; instead, it suffices to add either a single-stage reduction gear or a two-speed transmission.
Currently, most pure electric vehicles sold in China do not have a physically present transmission. Many people may notice gearshift levers or gear-position indicators on the instrument panel of some models, but these are actually simulated gear positions designed to appeal to consumers—electric motors themselves don't require a gear-based transmission mechanism to operate stably across various rotational speeds. Moreover, pure electric vehicles cannot be equipped with conventional transmissions for two main reasons: First, conventional transmissions are far too bulky and heavy relative to the size and weight of an electric vehicle. Given that the battery pack already occupies most of the underbody space, there simply isn't enough room left for such a transmission. Second, conventional transmissions have insufficient transmission efficiency. Additionally, considering the weight of the transmission itself, it could even reduce the vehicle's actual driving range.
Given the above circumstances, virtually all pure electric vehicles on the market are equipped with single-speed transmissions. The advantages include low cost, simple and easy installation, low failure rate, minimal power loss, and compact size. However, the disadvantages are that once the electric vehicle reaches its maximum speed, there is no room for further acceleration; thus, the vehicle’s speed is inherently limited. Moreover, a single gear ratio typically cannot simultaneously optimize both the power performance and fuel efficiency of a pure electric vehicle.
Multi-speed transmission: The existing motor characteristics are often insufficient to meet the vehicle’s power and efficiency requirements under all operating conditions. Equipping the vehicle with a multi-speed transmission allows for adjustment of the motor’s output performance.
Speed Enhancement: By increasing the operating speed of the motor and adopting appropriate transmission systems and control strategies, the allowable range of regenerative braking can be broadened, enabling the vehicle to adapt to a wider variety of operating conditions and thereby extending its driving range. Currently, many major automakers have already achieved motor speeds exceeding 14,000 rpm. As drive motors continue to become faster, the trend toward higher-speed transmissions in electric vehicles will also gain momentum.
Modularity: Integrating the motor and transmission into a single unit makes the vehicle’s overall structure more compact and enhances its performance, while also simplifying control and reducing costs. The integrated design and management control of modular electromechanical coupling drive systems represent the future direction for electric vehicle powertrain development.
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