793D Off-Highway Truck Power Train: Oil Cooler (Torque Converter and Transmission), Torque Converter Inlet and Outlet Relief Valves & Lockup Clutch and Synchronizing Valve (Torque Converter)

1.-Oil Cooler (Torque Converter and Transmission)

Location of the torque converter and transmission oil cooler (1) Passage for inlet oil(2) Torque converter and transmission oil cooler

The oil cooler for the torque converter and for the transmission is located on the right side of the engine. Engine coolant from the water pump goes through oil cooler (2). The engine coolant then goes into the cylinder block.

Oil from the torque converter screen comes through passage (1) in order to be cooled. The oil is then returned to the torque converter sump.

2.-Torque Converter Inlet and Outlet Relief Valves

Location of torque converter relief valves (1) Torque converter inlet relief valve(2) Torque converter outlet relief valve

Torque converter inlet relief valve (1) Torque converter inlet relief valve (2) Spool (3) Shims (4) Passage to torque converter sump(5) Inlet passage

Torque converter outlet relief valve (6) Torque converter outlet relief valve (7) Shims (8) Inlet passage (9) Outlet passage to torque converter screen(10) Spool

Torque converter inlet relief valve (1) and torque converter outlet relief valve (6) are installed on the outside of the torque converter housing. The operation of both relief valves is identical.

Torque converter inlet relief valve (1) controls the maximum pressure of the oil that is flowing into the torque converter. Supply oil comes from the torque converter charge pump section. The oil flows through the torque converter hydraulic filter. Before this oil flows into the torque converter, the oil is open to torque converter inlet relief valve (1) at inlet passage (5). Spool (2) will open when the pressure is above the relief pressure. When spool (2) is shifted, oil will flow through passage (4) to the torque converter sump. The relief pressure can be adjusted with shims (7) .

Torque converter outlet relief valve (6) controls the minimum pressure of the oil that is inside the torque converter. Oil exits the torque converter through passage (8). If the oil is above the pressure setting of the torque converter outlet relief valve, spool (10) will be shifted. This allows the oil to exit through passage (9). Then, the outlet oil goes through the torque converter screen to the remainder of the circuit. The relief pressure can be adjusted with shims (7).

3.-Lockup Clutch and Synchronizing Valve (Torque Converter)

Note: The ICM transmission hydraulic control on the 793D functions differently than most other current ICM transmission hydraulic controls with a dual stage relief valve. A special procedure in the Power Train Testing and Adjusting, "Transmission Hydraulic Control (Pressure Pack) - Test and Adjust" describes the proper order for adjusting the pressures of the pump for transmission charging and the clutch supply rail in torque converter drive and direct drive. The oil that is flowing from the pump for transmission charging also supplies the torque converter lockup clutch. If the pump pressure is set too low in direct drive, the supply oil for the torque converter lockup clutch will be low. If the supply pressure to the torque converter lockup clutch is low, the lockup clutch will slip and a premature failure may occur. Refer to the Power Train System Operation, "Transmission Hydraulic Control" in order to understand the operation of the transmission hydraulic control.

Lockup clutch and synchronizing valve (1) Lockup clutch solenoid (2) Passage from the pump for transmission charging (3) Signal oil passage (4) Pilot oil passage (5) Passage for transmission lubrication oil (6) Relay valve (7) Spool (8) Spring (9) Cover (10) Load piston body (11) Selector piston (12) Load piston (13) Pilot oil passage (14) Springs (15) Drain passage (16) Modulation reduction valve (17) Ball check valve (18) Shuttle valve (19) Pilot oil passage (20) Drain passage (21) Spring (22) Passage (23) Drain passage (24) Load piston plug (25) Load piston orifice (26) Pump oil passage (27) Ball check valve (28) Drain passage (29) Pressure reduction valve (30) Spring (31) Body of the lockup clutch and synchronizing valve (32) Passage to lockup clutch (33) Passage from pump for transmission charging (34) Drain passage(35) Passage to Station "D" in the selector and pressure control valve

Lockup clutch and synchronizing valve (3) Signal oil passage from the lockup clutch solenoid (5) Passage for transmission lubrication oil(33) Passage from pump for transmission charging

When direct drive is necessary, the lockup clutch solenoid will be energized. During direct drive, the engine is mechanically connected to the transmission by the activation of the lockup clutch. When direct drive is not necessary, the lockup clutch solenoid will be deactivated. Oil pressure will be used to drive the torque converter. In torque converter drive, some of the power from the engine will be transmitted to the transmission through this hydraulic power.

Pressure oil from the pump for transmission charging enters the body of the lockup clutch and synchronizing valve at passage (33). Pressure reduction valve (29) allows some of the oil into pilot oil passage (4) .

A portion of the pump oil goes through an orifice in pressure reduction valve (29). Ball check valve (27) is then opened. Oil goes into a slug chamber at the end of the valve. The oil pressure in the slug chamber presses against the force of spring (30). When the pressure at passage (33) is higher than the force of spring (30), pressure reduction valve (29) will be pushed by the oil in the slug chamber. Pressure reduction valve (29) will compress spring (30). This opens drain passage (28) to pump oil. Pressure reduction valve (29) moves back and forth. This causes drain passage (28) to be blocked and opened. This maintains constant pressure in pilot oil passage (4) .

The oil that is flowing to pump oil passage (26) goes around the valve spool. This oil remains at full pump pressure.

Filling the Lockup Clutch

When lockup clutch solenoid (1) is activated, oil is allowed to flow into signal oil passage (3). Some of this oil goes to the transmission hydraulic control. The remainder of the oil goes into relay valve (6). The pressure of the oil in signal oil passage (3) causes spool (7) to act on spring (8). Pilot oil passage (19) is now open to the oil from pilot oil passage (4). The oil from passage (3) flows through lubrication passage (5) for the transmission. Pilot oil from pilot oil passage (19) pushes shuttle valve (18) in order to close drain passage (20). The pilot oil moves the ball that is inside the shuttle valve. Pilot oil from passage (19) flows through pilot passage (13) to the top of selector piston (11) .

This causes selector piston (11) and load piston (12) to move against the force of springs (14). This causes modulation reduction valve (16) to move against the force of spring (21). When modulation reduction valve (16) moves, the position of the valve spool connects passage (32) with pump oil passage (26). Drain passage (15) is blocked. Pump oil now fills the lockup clutch. Pump oil also goes through load piston orifice (25) and through passage (22). This oil then goes between selector piston (11) and load piston (12) .

Engaging the Lockup Clutch

The pressure of the clutch oil in passage (32) increases after the clutch is full of oil. Some of the oil from passage (32) goes through an orifice in modulation reduction valve (16). This oil opens ball check valve (17). The oil then goes into the slug chamber at the end of the valve. This pressure helps the springs push both modulation reduction valve (16) and load piston (12) upward. The oil that is flowing through load piston orifice (25) is delivered at a fixed rate. While load piston (12) is controlled by the oil from load piston orifice (25), modulation reduction valve (16) moves up and down. This causes the pressure in the lockup clutch to gradually increase. This gradual increase in pressure is called modulation. The modulation of modulation reduction valve (16) maintains a constant pressure in passage (32). When load piston (12) goes fully against the stop, modulation stops. The pressure in the lockup clutch is now at the maximum. The lockup clutch is engaged.

Two factors control the amount of time that is necessary for the maximum pressure in the lockup clutch to be reached. The two factors are the size of load piston orifice (25) and the force of springs (14). The force of springs (14) can be changed by removing shims from load piston (12) or by adding shims to load piston (12) .

Drain passages (15), (20), (23), (28), and (34) are connected. The return oil goes into the torque converter sump.

Releasing the Lockup Clutch

When lockup clutch solenoid (1) is deactivated, the lockup clutch solenoid blocks the flow of oil to signal oil passage (3). Spring (8) in relay valve (6) pushes spool (7). The position of spool (7) blocks pilot oil passage (4) from pilot oil passage (19). Oil will remain in signal oil passage (3). When signal oil passage (3) is full of oil, there is no delay when lockup clutch solenoid (1) is activated.

When pilot oil passage (19) does not receive pilot oil, the force of springs (14) moves selector piston (11) upward. This causes the pressure oil in pilot oil passage (13) to apply force against shuttle valve (18). This causes the ball inside the shuttle valve to move to the left. The oil pressure also causes shuttle valve (18) to open pilot oil passage (13) to drain passage (20). Selector piston (11) moves upward against load piston body (10) .

Passage (22) is now aligned with drain passage (23). The force of springs (14) moves load piston (12) fully against selector piston (11). Modulation reduction valve (16) moves up to the fullest extent as a result of the force of spring (21). In this position, pump oil in pump oil passage (26) cannot go into passage (32). Passage (32) is now open to drain passage (15). The pressure in the lockup clutch is released.

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793D Off-Highway Truck Power Train: Oil Cooler (Torque Converter and Transmission), Torque Converter Inlet and Outlet Relief Valves & Lockup Clutch and Synchronizing Valve (Torque Converter) 2013-01-02T21:01:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown