Torque Converter: Description and Operation

DESCRIPTION
The transmission uses a pressure plate-style torque converter. The torque converter for the transmission is a four-element converter. It contains the standard three elements which transmit and multiply torque:
- impeller
- turbine
- stator

Plus a torque converter clutch for increased fuel economy in third and fourth gears.





OPERATION
The operation of the torque converter components is as follows:
- Rotation of the converter housing and impeller set the fluid in motion.
- The turbine reacts to the fluid motion from the impeller, transferring rotation to the geartrain.
- The stator redirects fluid going back into the impeller, allowing for torque multiplication.
The addition of a torque converter clutch to the torque converter provides a mechanical link between the converter housing and the engine, allowing for direct transfer of power from the engine to the geartrain.

The converter clutch pressure plate is applied and released by fluid pressure, which is controlled by the Powertrain Control Module (PCM) through an Electronic Pressure Control (EPC) solenoid in the main control valve body.

IMPELLER AND COVER
The primary functions of the impeller and cover assembly are to drive the impeller blades, contain hydraulic fluid and provide a mating surface for the converter clutch pressure plate. In addition, the impeller hub drives the fluid pump gear.

TURBINE
The turbine is a sectioned, donut-shaped steel stamping that is splined to the input shaft. It is driven by fluid from the impeller and transmits this power to the geartrain. Because of its basic shape, the turbine automatically directs fluid back to the impeller.

REACTOR
The stator, also called the reactor redirects the fluid flow returned to the impeller from the turbine so that the fluid moves in the same direction as engine/impeller rotation. This action aids in torque multiplication because it adds torque to that already supplied by the engine. The stator contains a one-way clutch which holds it stationary when torque multiplication is necessary, but allows freewheeling at higher speeds when torque multiplication is not necessary.

TORQUE CONVERTER CLUTCH
The pressure plate attaches to the back of the turbine and can be applied against the cover to allow for a mechanical transfer of engine torque to the geartrain. This occurs mainly in third and fourth gears when torque multiplication is no longer necessary. (Converter clutch application may also occur in second gear under certain conditions.)

The pressure plate works much like a regular mechanical clutch. Apply, release and controlled slip of the clutch are controlled by opposing fluid forces on each side of the pressure plate.