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| Illustration 1 | g00285614 |
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) Lubrication passage for transmission (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 | |
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| Illustration 2 | g00285612 |
Lockup clutch and synchronizing valve (3) Signal oil passage from the lockup clutch solenoid (5) Lubrication passage for transmission (33) Passage from parking brake release pump section | |
The Electronic Programmable Transmission Control (EPTC II) 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.
The oil comes from the transmission charging section of the transmission gear pump. When EPTC II sends a signal to lockup clutch solenoid (1) to activate, the solenoid will allow transmission oil to flow from passage (2) to passage (3). Some of the oil in passage (3) flows to the selector and pressure control valve. The rest of the oil flows to relay valve (6) that is mounted on the torque converter. Signal oil will flow from passage (2) 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). Some of the transmission oil in passage (3) flows into passage (5) for transmission lubrication.
When EPTC II sends the signal to deactivate, the solenoid will stop flow to passage (35). Spring (36) pushes spool (37) back to the original position. Oil flow from passage (2) to passage (3) is blocked. Spring (8) will push spool (7) back to the original position. As a result, torque converter oil to passage (19) is blocked. When the solenoid is deactivated, signal oil will flow from passage (5) into passage (3). The flow of signal oil keeps passage (3) full of oil. Thus, there is no delay when the solenoid is activated. Pressure from passage (5) is not enough to move spool (7) .
The lockup clutch solenoid valve controls the operation of the lockup clutch and synchronizing valve of the torque converter. Pressure oil in outlet line (32) engages the lockup clutch. This oil comes from the parking brake release pump section. The oil splits at the parking and secondary brake valve. Some of the oil goes through inlet line (33) into valve body (31). The remaining oil goes into the parking and secondary brake valve.
Pressure oil from the parking brake release pump enters the body of lockup clutch and synchronizing valve (31) at passage (33). Pressure reduction valve (29) reduces the oil pressure at passage (33). At this pressure, the oil can be used as pilot oil.
Some of the oil pressure from passage (33) is open to pilot oil passage (4). A portion of this 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 EPTC II activates lockup clutch solenoid (1), oil is allowed to flow through signal oil passage (3) 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 hydraulic tank.
Releasing the Lockup Clutch
When the EPTC II deactivates lockup clutch solenoid (1), the lockup clutch solenoid stops the flow of signal 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 from lubrication passage (5) for the transmission remains in signal oil passage (3). The lubrication oil keeps signal oil passage (3) full. Thus, 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.