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Difficulty: MediumClutches and Transmissions

In an automotive automatic transmission, hydrodynamic fluid coupling within the torque converter transfers rotational power from the internal combustion engine to the transmission gearbox. In what sequential order does fluid and mechanical force transfer power through the torque converter components during acceleration?

  1. 1The engine crankshaft rotates the flexplate and bolted torque converter housing, spinning the internal impeller pump.
  2. 2Centrifugal force accelerates automatic transmission fluid outward along the curved vanes of the rotating impeller.
  3. 3High-velocity transmission fluid strikes the curved blades of the turbine, forcing the turbine assembly to spin.
  4. 4Fluid exiting the inner diameter of the turbine enters the stator, which redirects fluid flow smoothly back into the impeller.
  5. 5The rotating turbine transfers mechanical torque through its central splined hub directly to the transmission input shaft.

Answer

The correct sequence begins with the engine spinning the flexplate and converter housing, followed by centrifugal fluid acceleration from the impeller, fluid impact rotating the turbine, fluid redirection through the central stator to multiply torque, and final delivery of rotational force to the transmission input shaft via the splined turbine hub.
Power transfer through a torque converter starts mechanically at the flexplate, which spins the outer housing and impeller pump. The impeller slings automatic transmission fluid outward via centrifugal force into the turbine vanes, driving the turbine. Returning fluid from the turbine is redirected by the stator back toward the impeller to multiply torque, and the spinning turbine transfers output torque directly into the splined transmission input shaft.

Step-by-Step Solution

1
Identify the primary mechanical input from the engine to the converter.
The crankshaft rotates the flexplate, which directly drives the torque converter outer housing and integral impeller pump.
The torque converter housing is bolted directly to the flexplate, ensuring the impeller turns at engine speed.
2
Determine how the spinning impeller acts upon the transmission fluid.
Centrifugal force pushes hydraulic fluid outward across the impeller vanes at high velocity.
The impeller functions as a pump that converts rotational mechanical energy into fluid kinetic energy.
3
Trace the path of the discharged fluid to the driven member.
Pressurized fluid strikes the outer perimeter of the turbine vanes, causing the turbine to rotate.
Hydrodynamic force from the moving fluid transfers torque across the fluid coupling to the turbine.
4
Follow the fluid path through the central reaction component.
Fluid flowing out of the turbine passes through the stator blades, which redirect the flow into the impeller's rotation direction.
Redirecting fluid to assist the impeller rather than opposing it creates torque multiplication during vehicle acceleration.
5
Identify the final mechanical output entering the transmission gearbox.
The turbine's splined hub drives the transmission input shaft.
The turbine is mechanically coupled via splines to the transmission input shaft to power downstream planetary gearsets.

Key Concept

Hydrodynamic torque converter power flow and torque multiplication
Estimated Time:1m 15s
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Topics

Clutches and Transmissions

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