Torque Converter - Operation

OPERATION









The torque converter housing has a unique shape to incorporate the torque converter clutch and flex plate connection. The torque converter uses the typical turbine, impeller and stator assemblies found in a standard torque converter assembly. The torque converter drives the pump through the splines on the inside of the hub. The torque converter uses a multi-disc torque converter clutch system that improves the durability and the holding pressure in the lock-up circuit. The torque converter incorporates a turbine dampening system. This system suppresses torsional vibrations from the engine to ensure optimal shift quality and reduce noise and vibration concerns.

TURBINE

When the fluid that was put into motion by the impeller blades strikes the blades of the turbine, some of the energy and rotational force is transferred into the turbine and the input shaft. This causes both of them (turbine and input shaft) to rotate in a clockwise direction following the impeller. As the fluid is leaving the trailing edges of the turbine's blades it continues in a "hindering" direction back toward the impeller. If the fluid is not redirected before it strikes the impeller, it will strike the impeller in such a direction that it would tend to slow it down.

STATOR

Torque multiplication is achieved by locking the stator's over-running clutch to its shaft. Under stall conditions (the turbine is stationary), the oil leaving the turbine blades strikes the face of the stator blades and tries to rotate them in a counterclockwise direction. When this happens the over-running clutch of the stator locks and holds the stator from rotating. With the stator locked, the oil strikes the stator blades and is redirected into a "helping" direction before it enters the impeller. This circulation of oil from impeller to turbine, turbine to stator, and stator to impeller, can produce a maximum torque multiplication of about 2.0:1. As the turbine begins to match the speed of the impeller, the fluid that was hitting the stator in such as way as to cause it to lock-up is no longer doing so. In this condition of operation, the stator begins to free wheel and the converter acts as a fluid coupling

TORQUE CONVERTER CLUTCH (TCC)

In a standard torque converter, the impeller (2) and turbine are rotating at about the same speed and the stator (3) is freewheeling, providing no torque multiplication. By applying the turbines piston and friction material (9) a total converter engagement can be obtained. The result of this engagement is a direct 1:1 mechanical link between the engine and the transmission.

HYDRO-MECHANICAL AND ELECTRICAL

The torque converter clutch (TCC) is engaged and released by the transmission control module assembly (TCMA). The TCC can be engaged and controlled in any forward gear from 1 through 8. In addition, the 8HP45 transmission incorporates a neutral idle control (NIC) function. Instead of the engine continuing to drive the converter when the vehicle comes to rest, the converter is partially disconnected from the driveline so only a slight residual load remains. Decoupling of the torque converter during NIC is accomplished by allowing clutch B to slip.

TCC RELEASE
When the TCC is open, the TCC piston is pushed to its default position by torque converter chamber pressure. The torque converter switch valve (SV-TC) provides pressure for torque converter operation which has been regulated by the converter pressure regulating valve (TC-V). After exiting the torque converter, fluid moves into the cooling and lubrication circuits. The converter pressure retention valve (TCH1-V) ensures the torque converter pressure is a minimum of 0.35 bar (5 psi) when the TCC is open.

TCC APPLY
When the TCC solenoid is energized, fluid is directed to the torque converter switch valve (SV-TC) and TCC lockup valve (TCC-V). The TCC lockup valve directs fluid to the TCC and torque converter chamber. The torque converter switch valve directs fluid exiting the converter chamber to a secondary pressure retention valve (TCH2-V) which is calibrated to retain 1.0 bar (14.5 psi) of pressure in the converter. The torque converter switch valve also directs line pressure to the cooler and lubrication circuit.