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| Illustration 1 | g00395468 |
Lockup clutch and synchronizing valve (1) Lockup clutch solenoid (2) Passage from the transmission charging pump section (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 parking brake release pump section (34) Drain passage (35) Passage to the selector and pressure control valve | |
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| Illustration 2 | g00347197 |
Lockup clutch and synchronizing valve (3) Signal oil passage from the lockup clutch solenoid (5) Passage for transmission lubrication oil (6) Relay valve (31) Body of lockup clutch and synchronizing valve (33) Passage from parking brake release pump section | |
The Power Train Electronic Control Module (Power Train ECM) will energize the lockup clutch solenoid when direct drive is necessary. 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. The machine will then be in torque converter drive. The engine will be hydraulically connected to the transmission.
When the Power Train ECM sends the signal to deactivate, the solenoid will stop flow to passage (3). Spring (8) will push spool (7) back to the original position. As a result, pilot oil to passage (19) is blocked. When the solenoid is deactivated, oil is blocked in passage (3). This keeps passage (3) full of oil so that there is no delay when the solenoid is activated. Pressure in passage (3) is not enough to move spool (7) .
When the Power Train ECM sends a signal to lockup solenoid (1) to activate, the solenoid will allow transmission oil to flow from passage (2) to passage (3). Signal oil will flow through passage (3) to relay valve (6). The signal oil in passage (3) causes spool (7) to act against spring (8). Passage (4) is now open to passage (19) and pilot oil will flow to selector piston (11). The transmission oil in passage (3) flows into the passage for transmission lubrication (5) .
When pilot oil pushes selector piston (11), oil flows through line (32) to the lockup clutch in the torque converter.
Pressure oil from the parking brake release pump section enters the body of lockup clutch and synchronizing valve (31) at passage (33). Pressure reduction valve (29) allows some of the oil into pilot oil passage (4). Oil pressure in pilot passage (4) will be approximately 1725 kPa (250 psi).
A portion of the pump oil goes through an orifice in pressure reduction valve (29). Ball check valve (27) is then opened. This 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 the Power Train ECM activates lockup clutch solenoid (1), oil is allowed to flow into signal oil passage (3). 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 the passage for transmission lubrication oil (5). 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 increase gradually. This gradual increase due to the movement of the spool 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 hydraulic tank.
Releasing the Lockup Clutch
When the Power Train ECM deactivates lockup clutch solenoid (1), the lockup clutch solenoid blocks the flow of oil through passage (3) to relay valve (6). 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 passage (3). This keeps signal oil passage (3) full so that there are no delays when lockup clutch solenoid (1) is reactivated.
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.