793D Off-Highway Truck Power Train: Torque Converter & Transfer Gears

The torque converter is driven by the engine flywheel. The torque converter consists of an impeller, a turbine, a lockup clutch, and a stator with a one-way clutch. The lockup clutch permits the machine to operate in direct drive in order 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 the torque converter drive is not used.

The torque converter housing is fastened to the flywheel housing. The torque converter housing provides the oil reservoir for the transmission hydraulics and the torque converter hydraulics. Also, a pump and three valves are attached to the torque converter housing. The flange of the output shaft of the torque converter is connected to the drive shaft.

The transmission is driven by the torque converter in NEUTRAL and in REVERSE. In FIRST speed, torque converter drive is used at lower ground speeds. In FIRST speed, direct drive is used at higher ground speeds. The lockup clutch is activated in FIRST speed when the machine reaches a certain ground speed. During shifts from FIRST speed through SIXTH speed, torque converter drive is momentarily activated in order to provide smoother shifts. When the transmission clutches are engaged, the lockup clutch engages and the transmission is in direct drive.

Table 1

Operation of the Torque Converter For Transmission Speed
Transmission Speed	Torque Converter Drive	Direct Drive with an Engaged Lockup Clutch
Reverse	X
Neutral	X
First	X	X
Second		X
Third		X
Fourth		X
Fifth		X
Sixth		X

Torque Converter Drive

Torque converter that is in torque converter drive (1) Rotating housing (2) Turbine (3) Impeller (4) Drive gear for the torque converter and transmission gear pump (5) Outlet passage for torque converter oil (6) Output shaft (7) Carrier (8) Inlet passage for torque converter oil (9) One-way clutch (10) Lockup clutch (11) Hub(12) Stator

The engine flywheel turns rotating housing (1) which turns impeller (3). The impeller directs the oil to the blades of turbine (2). This will cause the turbine to turn. The turbine directs the oil to stator (12). This causes the stator to try to turn in the opposite direction of the turbine. The movement of the stator causes the rollers of one-way clutch (9) to move between stator (12) and the carrier for the stator. The action of the one-way clutch keeps the stator from rotation. The stator now directs most of the oil back to impeller (3). The remainder of the oil goes out of the torque converter through outlet passage (5). The oil, that goes back to impeller (3) from stator (12), moves in the same direction as the rotation of the impeller.

Turbine (2) turns hub (11). Hub (11) turns output shaft (6). Power is sent through the output yoke to the drive shaft and the transfer gears of the transmission.

One-Way Clutch

(12) Stator (13) Race (14) Cam for the one-way clutch (15) Rollers (16) Cage (17) Springs (18) Slot(19) Cam surface

The one-way clutch functions in order to keep the stator stationary up to higher torque converter output speeds. Stator (12) is connected to the cam (14) through splines. As a result, stator (12) rotates with cam (14), and race (13) is stationary. Roller cage (16) is located between cam (14) and race (13). Spring (17) is partially inserted in a tab at the top and at the bottom of cage (16). At lower turbine speeds, spring (17) forces the tab of cage (16) to the right in slot (18). This forces roller cage (16) to rotate clockwise. Then, rollers (15) move against the surfaces (19) of cam (14). The rollers wedge between cam (14) and race (13). This action locks stator (12) to race (13) which is stationary. The stator then returns oil to the impeller which multiplies the torque output of the torque converter.

As the speed of turbine (2) approaches the speed of impeller (3), the force of hydraulic oil overcomes the force of the rollers (15) that are wedged. The hydraulic oil acts in a clockwise direction on stator (12). The stator (12) then free wheels in the same direction as the impeller (3) and turbine (2). The stator (12) also free wheels when the speed of turbine (2) exceeds the speed of impeller (3). This occurs during downhill coasting when the transmission is engaged.

Direct Drive

Torque converter that is in direct drive (1) Rotating housing (2) Turbine (3) Impeller (4) Drive gear for the torque converter and transmission gear pump (5) Inlet passage for lockup clutch oil (6) Output shaft (7) Distributor (8) One-way clutch (9) Discs (10) Plates (11) Lockup clutch (12) Piston (13) Hub(14) Stator

Lockup Clutch

Lockup clutch (11) is part of the torque converter. The lockup clutch (11) is located between the engine flywheel and the turbine (2). The lockup clutch is engaged when the transmission is in SECOND through SIXTH speeds. The lockup clutch will engage in FIRST speed as the output speed of the transmission increases. When the lockup clutch is engaged, impeller (3) and turbine (2) turn at the same speed as the engine and there is no loss of power in the torque converter. The connection between the engine and the transmission is now direct.

The main components of lockup clutch (11) are piston (12), plates (10), and discs (9) .

Operation

Rotating housing (1) is connected to the engine flywheel by splines. Rotating housing (1) is fastened to impeller (3) by bolts. Piston (12) and plates (10) are also connected to rotating housing (1) by splines. Discs (9) and output shaft (6) are connected to hub (13) by splines. Turbine (2) is fastened to hub (13) .

When the lockup clutch solenoid is activated, the lockup clutch and synchronizing valve sends pressure oil through inlet passage (5) in distributor (7). The oil goes through a passage in the center of output shaft (6). The oil then goes through a passage in rotating housing (1) to piston (12). The pressure of the oil causes piston (12) to move toward disc (9). This causes plates (10) and discs (9) to be held together. Plates (10) and discs (9) will now turn at the same speed. The clutch becomes a direct connection between rotating housing (1) through hub (13) to output shaft (6) .

This causes turbine (2) and impeller (3) to turn at the same speed. Stator (14) turns freely. At this time, the torque converter is not in operation and the machine is in direct drive.

The flow of power is from rotating housing (1), through lockup clutch (11), hub (13), output shaft (6), and the yoke. The power goes directly through the torque converter to the drive shaft. The drive shaft sends the power to the transfer gears of the transmission.

When the lockup clutch is not engaged, the operation of the torque converter is normal.

Transfer Gears

Components of the transfer gears (1) Shims (2) Drive gear (3) Yoke (4) Driven gear (5) Case(6) Shims

The transfer gears are in the transfer gear case that is fastened to the front of the transmission case. The drive shaft connects the torque converter to yoke (3) .

Yoke (3) is connected to drive gear (2) by splines. The teeth on drive gear (2) are engaged with the teeth on driven gear (4). Driven gear (4) is connected by splines to the input shaft of the transmission.

Yoke (3) turns drive gear (2). Drive gear (2) turns driven gear (4). Driven gear (4) turns the input shaft of the transmission.

Shims (1) are used to make adjustments to the end play of drive gear (2). Shims (6) are used to make adjustments to the end play of driven gear (4) .

Oil for the lubrication of the transfer gears comes from the transmission lubrication circuit. The oil comes through a passage in the transmission case to a passage in transfer gear case (5). Some of this oil goes into a tube assembly. The tube assembly sprays oil on drive gear (2) and on driven gear (4). The gears throw the oil around inside transfer gear case (5). This provides lubrication for the bearings in the transfer gear case. The extra oil in the bottom of transfer gear case (5) goes through a drain passage into the transmission case.

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793D Off-Highway Truck Power Train: Torque Converter & Transfer Gears 2013-01-02T21:05:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown