5108 Operating description of the electro hydraulic control unit

To simplify the various solenoid valve, clutch and brake engagement sequences for each gear ratio Table 5.6 has been included.

Neutral and park position (Fig. 5.39) With the selector lever in neutral or park position, fluid is delivered from the oil-pump to the selector position valve 'SPV', modulation pressure valve 'MOD-V', pressure reduction valves 'PRV-1' and 'PRV-2', shift valve 'SV-1', traction/coasting valve '(T/C)V' and clutch valve 'CV-G'. Regulating fluid pressure is supplied to the torque converter 'TC' via the converter pressure valve 'CPV' and to the lubrication system by way of the lubrication pressure valve 'LPV'. At the same time regulated constant fluid pressure (5 bar) is supplied to the solenoid valves 'MV1, MV2 and MV3' via the pressure reduction valve 'PRV-1', and the electronic pressure regulating valves 'EPRV-(1-4)' via the pressure reduction valve 'PRV-2'. In addition controlling modulation pressure is relayed to the spring chamber of clutch valves 'CV-B, CV-C and CV-D' and brake valve 'CV-F' via the modulation pressure valve 'MOD-PV'. Neutral and parking position has the following multiplate clutch solenoid valves and electronic pressure regulator valves activated:

1 multiplate brake 'MPB-G'.

2 solenoid valves 'MV1 and MV3'.

3 electronic pressure regulating valves 'EPRV-1 and EPRV-2'.

First gear (Fig. 5.41) Engagement of first gear is obtained by applying the one way clutch 'OWC' and multiplate clutch and multiplate brake 'MPC-B and MPB-G' respectively. This is achieved in the following manner:

1 Moving selector position valve 'SPV' into D drive range. Fluid pressure from the selector position valve 'SPV' then passes via the traction valves 'TV (4-5) and TV (5-4)' respectively to clutch valve 'CV-B', it therefore permits fluid pressure to apply the multiplate clutch 'MPC-B'.

2 Energizing solenoid valves 'MV1 and MV2' opens both valves. Solenoid valve 'MV1' applies a reduced constant fluid pressure to the left-hand side of shift valves 'SV-1 and SV-3'. Shift valve 'SV-1' shifts over to the right-hand side against the tension of the return spring blocking the fluid pressure passage leading to clutch valve 'CV-D', however shift valve 'SV-3' cannot move over since a similar reduced constant pressure is introduced to the spring end of the valve via solenoid valve 'MV2'. Solenoid valve 'MV2' applies reduced constant pressure to the left-hand side of shift valve 'SV-2' and the right-hand side of shift valve 'SV-3'; this pushes the shift valve 'SV-2' to the right and so prevents shift valve 'SV-3' also being pushed to the right by fluid pressure from solenoid valve 'MV1' as previously mentioned.

3 Electronic pressure regulator valve 'EPRV-1' supplies a variable regulated fluid pressure to the modulation pressure valve 'MOD-PV', this pressure being continuously adjusted by the electronic transmission control unit 'ETCU' to suit the operating conditions. Electronic pressure regulating valve 'EPRV-3 supplies a variable controlling fluid pressure to brake and retaining valves 'BV-G and RV-G' respectively, enabling fluid pressure to apply the multiplate brake 'MPB-G'.

Second gear (Fig. 5.42) Engagement of second gear is obtained by applying multiplate clutch 'MPC-B' and the multiplate brakes 'MPB-E and MPB-G'. This is achieved in the following manner with the selector position valve in the D drive range:

1 Multiplate clutch and brake 'MPC-B and MPB-G' respectively applied as for first gear.

2 Solenoid valves 'MV1 and MV2' are energized, thus opening both valves. Fluid pressure from 'MV1' is applied to the left-hand side of both 'SV-1 and SV-3'; however, only valve SV-1 shifts over to the right-hand side. At the same time fluid pressure from solenoid valve 'MV2' shifts valve 'SV-2' over against the return-spring tension and also pressurizes the spring end of shift valve 'SV-3'. This prevents shift valve 'SV-3' moving over to the right-hand side when fluid pressure from solenoid valve 'MV-1' is simultaneously applied at the opposite end.

3 The electronic pressure regulating valves 'EPRV-1 and EPRV-3' have their controlling current reduced, thereby causing an increase in line pressure to the modulation valve MOD-PV and to both brake and retaining valves 'BV-G and RV-B' respectively. Consequently line pressure continues to apply the multiplate brake 'MPB-G'.

4 The electronic pressure regulating valve 'EPRV-2' has its controlling current reduced, thus progressively closing the valve, consequently there will be an increase in fluid pressure acting on the right-hand side of both brake and retaining valves 'BV-E and RV-E' respectively. As a result the brake valve 'BV-E' opens to permit line pressure to actuate and apply the multiplate brake 'MPB-E'.

Third gear (Fig. 5.43) Engagement of third gear is obtained by applying the multiplate clutches 'MPC-B and MPC-D' and the multiplate brake MPB-E.

The shift from second to third gear is achieved in the following manner with the selector position valve in the D drive range:

1 Multiplate clutch 'MPC-B' and multiplate brake 'MPB-E' are applied as for second gear.

2 Solenoid valve 'MV2' remains energized thus keeping the valve open as for first and second gear.

oo 2

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ff=m

ff=m

3 Solenoid valve 'MV3' is in the de-energized state, it therefore blocks line pressure reaching traction/ coasting valve '(T/C)V' via passage 'Y-Y'.

4 Electronic pressure regulating valves 'EPRV-1 and EPRV-2' de-energized, this closes the valves and increases their respective regulating fluid pressure as for second gear.

5 Electronic pressure regulating valve 'EPRV-3' control current is increased, this causes the valve to open and the regulating fluid pressure to collapse. The returning spring now moves the clutch and retaining valves 'CV-G and RV-G' respectively over to the right-hand side. Brake valve 'BV-G' now blocks the line pressure reaching the multiplate clutch MPB-G and releases (exhausts) the line pressure imposed on the annular shaped brake piston; the multiplate brake 'MPB-G' is therefore disengaged.

6 Solenoid valve 'MV1' is de-energized, this permits the shift valve 'SV-1' to return to the left-hand side. Subsequently line pressure now passes via the shift valve 'SV-1' to the clutch valve 'CV-D' and hence applies the multiplate clutch 'MPC-D'.

Fourth gear (Fig. 5.44) Engagement of fourth gear is obtained by applying the multiplate clutches 'MPC-B, MPC-C and MPC-D'.

The shift from third to fourth gear is achieved in the following manner with the selector position valve in the D drive range:

1 Multiplate clutches 'MPC-B and MPC-D' applied as for third gear.

2 Solenoid valves 'MV1 and MV3' de-energized and closed as for third gear.

3 Electronic pressure regulating valve 'EPRV-1' de-energized and partially closed, whereas 'EPRV-3' remains energized and open, both valves operating as for third gear.

4 Electronic pressure regulating valve 'EPRV-2' now progressively energizes and opens, this removes the control pressure from brake and retaining valves 'BV-E and RV-E' respectively. Line pressure to brake valve 'BV-E' is now blocked causing the release (exhausting) of fluid pressure via the brake valve 'BV-E' and the disengagement of the multiplate brake 'MPB-E'.

5 Fluid pressure now passes though to the multiplate clutch 'MPC-C' via shift valves 'SV-1 and SV-2', and clutch-valve 'CV-C'. Subsequently, the multiplate clutch 'MPC-C' is applied to complete the gear shift from third to fourth gear.

6 Electronic pressure regulating valve 'EPRV-4' de-energizes and progressively closes. Control pressure now shifts converter pressure control valve 'CPCV' to the left-hand side and converter lock-up clutch 'CLCV' to the right-hand side. Fluid pressure is thus supplied via the converter lock-up clutch valve 'CLCV' to the torque converter 'TC', whereas fluid pressure reaching the left-hand side of the torque converter lock-up clutch chamber is now blocked by the converter lock-up clutch valve 'CLCV' and exhausted by the converter pressure valve 'CPV'. As a result fluid pressure within the torque converter pushes the lock-up clutch hard against the impeller rotor casing. Subsequently the transmission drive, instead of passing via fluid media from the impeller-rotor casing to the turbine-rotor output shaft, is now diverted directly via the lock-up clutch from the impeller-rotor casing to the turbine-rotor output shaft.

Fifth gear (Fig. 5.45) Engagement of fifth gear is obtained by applying the multiplate clutches 'MPC-C and MPC-D' and the multiplate brake 'MPB-E'.

The shift from fourth to fifth gear is achieved in the following manner with the selector position valve 'SPV' in the D drive range:

1 Multiplate clutches 'MPC-C and MPC-D' applied as for fourth gear.

2 Solenoid valve 'MV2' de-energized as for fourth gear.

3 Solenoid valve 'MV3' is energized, this allows fluid pressure via passage 'Y-Y' to shift traction/coasting valve '(T/C)V' over to the right-hand side. As a result fluid pressure is released (exhausts) from the spring side of the traction valve 'TV (5-4)', hence fluid pressure acting on the left-hand end of the valve now enables it to shift to the right-hand side.

4 Solenoid valve 'MV1' is energized, this pressurizes the left-hand side of the shift valves 'SV-1 and SV-3'. However, 'SV-1' cannot move over due to the existing fluid pressure acting on the spring end of the valve, whereas 'SV-3' is free to shift to the right-hand end. Fluid pressure from the clutch valve 'CV-E' now passes via shift valve 'SV-3' and traction/coasting valve '(T/C)V' to the traction valve 'TV (4-5)' causing the latter to shift to the right-hand side. Consequently traction valve 'TV (4-5)' now blocks the main fluid pressure passing through the clutch valve 'CV-B' and simultaneously releases the multiplate clutch 'MPC-B' by exhausting the fluid pressure being applied to it.

5 Electronic pressure regulating valve 'EPRV-2' de-energized and partially closed. Controlled fluid pressure now passes to the right-hand end of the clutch valve 'CV-E' and retaining valve 'RV-E', thus causing both valves to shift to the left-hand end. Fluid pressure is now permitted to apply the multiplate brake 'MPB-E' to complete the engagement of fifth gear.

6 Electronic pressure regulating valve 'EPRV-4' de-energized as for fourth gear. This causes the converter lock-up clutch 'CLC' to engage thereby by-passing the torque converter 'TC' fluid drive.

Reverse gear (Fig. 5.46) Engagement of reverse gear is obtained by applying the multiplate clutch 'MPC-A' and the multiplate brakes 'MPB-F and MPB-G'.

The shift from neutral to reverse gear is achieved in the following manner with the selector position valve 'SPV' moved to reverse drive position 'R'.

1 Multiplate brake 'MPB-G' applied as for neutral and park position.

2 Solenoid valve 'MV1' energized thus opening the valve. Constant fluid pressure now moves shift valves 'SV-1 and SV-3' over to the right-hand side.

3 Electronic pressure regulating valve 'EPRV-1' de-energized as for neutral position.

4 Electronic pressure regulating valves 'EPRV-3' de-energized and closed. Controlling fluid pressure is relayed to the brake valve 'BV-G' and retaining valve 'RV-G'. Both valves shift to the left-hand side thus permitting fluid pressure to reach and apply the multiplate brake 'MPB-G'.

5 Selector position valve 'SPV' in reverse position diverts fluid pressure from the fluid pump, directly to multiplate clutch 'MPC-A' and indirectly to multiplate brake 'MPB-F' via the selector position valve 'SPV', reverse gear valve 'RGV', shift valve 'SV-2' and the clutch valve 'CV-F'. Both multiplate clutch 'MPC-A' and multiplate brake 'MPB-F' are therefore applied.

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