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| Illustration 1 | g06210152 |
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(1) Housing
(2) Plate (3) Backing plate (4) Impeller (5) Turbine (6) Output shaft (7) Pump drive gear (8) Carrier (9) Torque converter inlet passage for oil (10) Oil passage for lockup clutch (11) Stator (12) Cam -Freewheel (13) Turbine hub (14) Lockup clutch piston (15) Torque converter outlet passage for oil (16) Clutch disc | |
The lockup clutch permits the machine to operate in direct drive to keep the power loss at a minimum. The one-way clutch holds the stator when the torque converter drive is used. The one-way clutch allows the stator to turn freely when direct drive is used.
The torque converter is operated with pressurized oil. The maximum inlet pressure is controlled by the torque converter inlet ratio valve. The outlet pressure is controlled by the outlet relief valve and by downstream restrictions.
The engine flywheel turns housing (1), backing plates (3) and impeller (4). Impeller (4) directs oil onto the blades of turbine (5). This action causes turbine (5) to turn. Turbine (5) directs the oil onto stator (11).
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| Illustration 2 | g06086655 |
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(12) Cam - Freewheel
(17) Race (18) Spring (19) Slot (20) Cam Surface (21) Roller | |
Stator (11) is connected to cam - freewheel (12) by the spline. When the hydraulic oil forces stator (11) in the opposite direction to turbine (5), rollers (21) are forced into the narrow end of slot (19). This action prevents the cam and stator assembly from rotating around the carrier. Since the cam is held stationary, the stator cannot turn and the one-way clutch is locked up.
Stator (11) now directs most of the oil back to impeller (4). The remainder of the oil goes out of the torque converter. The oil, that goes back to impeller (4) from stator (11), moves in the same direction as the rotation of impeller (4). Since this oil is moving in the same direction as impeller (4), the torque output from the torque converter is multiplied.
The output torque requirement can be less than or equal to the input torque. This situation can occur when ground speed is high and the resistance is low. Then, turbine (5) will be turning quickly. The oil that flows through turbine (5) strikes the back of the stator blades. This action causes stator (11) to start turning in the same direction as turbine (5). Cam - freewheel (12) then rotates so that rollers (21) occupy the wide end of slot (19). Stator (11) is then free to rotate around the stator race. The oil then flows through turbine (5) and out of the converter.
Turbine (5) turns turbine hub (13). The turbine hub (13) turns output shaft (6). Power is sent through the output shaft (6) to the lower splined transfer gear. The lower splined transfer turns the upper transfer gear splined to the output shaft and yoke. The yoke then transmits power to the transmission planetary group.
When the transmission is in the forward direction, the torque convertor will automatically lock up in second, third, and fourth gear speed. This feature will occur, when conditions are appropriate. When the transmission is in the reverse direction, the torque convertor will automatically lock up in second, third, and fourth gear speed. This feature will occur, when conditions are appropriate. This feature provides more efficient operation for high speeds and for carrying loads.
The lockup clutch function is not available in the first gear speed in the forward direction.
The following conditions must be present in order for the Power Train ECM to activate the lockup clutch:
- The torque converter output speed is greater than 1315 rpm
- The torque converter output speed is less than 2425 rpm
- The neutralizer pedal must not be depressed
- The torque converter lockup switch must be in the ON position
The lockup clutch is engaged when the four conditions are met again in the new selected gear. The lockup clutch is disengaged when the torque converter output speed drops below 1250 ± 50 rpm.
To prevent engine over speed, the lockup clutch will disengage when the torque converter output speed exceeds 2425 RPM.
Torque Converter Lockup Clutch Modulating Valve
The lockup clutch modulating valve is on the torque converter updrive housing. The lockup clutch modulating valve, modulates hydraulic pressure to the lockup clutch. The lockup clutch modulating valve has a solenoid, which is activated by the Power Train ECM. The lockup clutch modulating valve is a three-way, proportional pressure control valve. When the Power Train ECM sends maximum current to the solenoid, pressure in the lockup clutch is at the maximum. When the current from the Power Train ECM is at a minimum, the pressure in the lockup clutch is at the minimum.