Learn how torque converters work in automatic transmissions. Discover the parts and principles behind their operation, along with common problems.
Introduction
A torque converter is a fluid coupling that transmits power from the engine to the transmission in an automatic transmission vehicle. It’s a crucial component that allows the engine to continue running even when the vehicle is stopped, and enables smooth shifting between gears while driving. In this article, we will explore the basic principles of how torque converters work.
Parts of a Torque Converter
A torque converter consists of three primary parts: the impeller, turbine, and stator. The impeller is connected to the engine and is responsible for generating fluid flow in the converter. The turbine is connected to the transmission and is responsible for transferring power from the converter to the transmission. The stator sits between the impeller and turbine and is responsible for redirecting fluid flow during operation.
Impeller
The impeller is a fan-like component that is attached to the engine’s crankshaft. As the engine runs, the impeller spins, causing fluid to move through the torque converter. The impeller blades are curved in a way that creates a low-pressure area behind them, causing fluid to be drawn into the center of the impeller. This fluid is then accelerated outwards towards the turbine.
Turbine
The turbine is a fan-like component that is attached to the transmission’s input shaft. As the fluid from the impeller hits the turbine blades, it causes the turbine to rotate, transferring power from the engine to the transmission. The turbine blades are shaped in such a way that they can efficiently capture and utilize the kinetic energy of the fluid flow.
Stator
The stator is a stationary component that sits between the impeller and turbine. Its primary function is to redirect the flow of fluid as it moves through the torque converter. The stator blades are curved in a way that allows them to redirect fluid flow back towards the impeller during certain operating conditions, increasing the torque converter’s efficiency.
How a Torque Converter Works
When the engine is running, the impeller is spinning, creating fluid flow in the torque converter. This fluid flow causes the turbine to rotate, transferring power to the transmission. As the vehicle comes to a stop, the impeller continues to spin, keeping the engine running even when the vehicle is stationary. When the driver accelerates, the fluid flow in the torque converter increases, causing the turbine to rotate faster and transferring more power to the transmission.
Torque Converter Stall
One essential aspect of a torque converter is its ability to “stall” at a certain engine speed. Stall speed refers to the engine speed at which the torque converter can no longer transmit power to the transmission efficiently. When the engine speed exceeds the stall speed, the torque converter begins to slip, reducing power transfer efficiency. Stall speed can vary depending on the size and design of the torque converter and is an important consideration when selecting a torque converter for a specific application.
Torque Converter Lockup
To increase efficiency, many modern torque converters also feature a lockup clutch that connects the impeller and turbine directly, bypassing the fluid coupling. Lockup occurs at highway speeds when the vehicle is cruising, reducing the power loss that occurs due to fluid coupling. The lockup clutch is typically controlled by the vehicle’s transmission control module, which engages the clutch at the appropriate speeds to maximize fuel efficiency.
Conclusion
Torque converters are a critical component in modern automatic transmissions, allowing for smooth shifting and efficient power transfer. Understanding how they work is essential for anyone working on or driving a vehicle equipped with an automatic transmission.
Torque Converter Problems
While torque converters are designed to last the life of the vehicle, they can develop problems over time. Some of the most common issues include:
Fluid Leaks
Torque converters contain hydraulic fluid, and leaks can occur due to worn seals or gaskets. A fluid leak can cause the torque converter to fail and result in serious damage to the transmission.
Torque Converter Shudder
A shudder can occur when the torque converter fails to transmit power efficiently, causing the engine to vibrate or shake. This problem can be caused by worn bearings or a damaged impeller or turbine.
Overheating
Excessive heat can damage the torque converter, causing it to fail. Overheating can be caused by low fluid levels or dirty fluid, and it’s essential to address the issue promptly to prevent further damage.
Conclusion
In conclusion, torque converters are an essential component in automatic transmissions. They allow for smooth shifting between gears and efficient power transfer from the engine to the transmission. Understanding how they work is crucial for anyone who works on or drives a vehicle with an automatic transmission. Regular maintenance, such as changing the transmission fluid, can help prevent common torque converter problems and extend the life of the component.
