Why the Reverse Rotation of an Electric Motor is Not Used in Vehicles Instead of Combustion Engines

Consider the Toyota Prius I own. Its hybrid system utilizes electric motors for reverse driving, reducing the load on the combustion engine. The fact that the engine is only engaged for forward driving is a testament to the efficiency and design of modern hybrid vehicles. Initially, I erroneously believed the car had a mechanical Continuously Variable Transmission (CVT) with separate electric motors for power assistance.

Complexity vs. Reliability

Upon closer inspection, I was pleasantly surprised to discover that the Prius has a less complex drivetrain than traditional multi-speed automatics with hydraulic gear drives. The use of fixed ratio electric motors enhances reliability by leveraging their ability to perform tasks that multi-clutch gear trains could not achieve, such as smooth acceleration and deceleration.

The Hybrid Synergy Drive, as advertised by Toyota, serves as the variable speed automatic transmission. This system reduces the stress and wear on the engine, allowing it to operate at lower RPMs and for shorter periods. This is a significant advantage over the combustion engine, which is subject to more frequent and intense wear.

Comparison with Fully Electric Vehicles

While the Prius offers a robust hybrid system, fully electric vehicles (EVs) can achieve even greater simplicity. A single electric motor with fixed gearing can power the vehicle, reducing the number of components and improving reliability. This setup is akin to using a set of suspenders and a belt to hold up your pants – one of them is enough for the job.

Reverse Gear Mechanism

Interestingly, in some hybrid cars, the electric motor can run in reverse without the need for a separate reverse gear. This is made possible through the electric motor's capability to generate torque in the opposite direction. This feature not only simplifies the drivetrain but also reduces the weight and complexity of the vehicle.

Advantages and Drawbacks

The use of electric motors for reverse driving in hybrid vehicles has several advantages, including:

Reduced Engines Stress: The engine is less likely to reach high RPMs or undergo frequent reversals, reducing its overall stress and wear.

Smooth Operation: Electric motors can provide smooth and silent operation, enhancing the driving experience.

Improved Efficiency: The electric motor can be more efficient in reverse operation, particularly in hybrid systems where the engine is not always engaged.

However, there are also some drawbacks to consider:

Complexity: While the drivetrain is simplified compared to traditional multi-speed automatics, it is still more complex than a fully electric vehicle with a single motor.

Energy Consumption: Running the electric motor in reverse may consume more energy, particularly if the battery is depleted.

Conclusion

While the reverse rotation of an electric motor in hybrid vehicles offers certain advantages in terms of drivetrain simplicity and reliability, it is not a universal solution. The integration of electric motors for reverse driving in hybrid systems is a blend of technical ingenuity and practicality. Fully electric vehicles, on the other hand, present a simpler, more reliable alternative with fewer components to break down.

As technology evolves, the debate between hybrid and fully electric drivetrains will continue, with each offering unique benefits and challenges. The choice ultimately depends on the specific requirements and preferences of the user, as well as the evolving standards of automotive design and manufacturing.