Advanced Vehicle Technology 2 Episode 5 pdf

5.9.3 Hydraulic control system (Fig. 5.28) The speed ratio setting control is achieved by a spur type hydraulic pump and control unit which supplies oil pressure to both primary and secondary sliding pulley servo cylinders (Fig. 5.28). The ratio settings are controlled by the pressure exerted by the larger primary servo cylinder which accordingly moves the sliding half pulley axially inwards or outwards to reduce or increase the output speed setting respectively. This primary cylinder pressure causes the secondary sliding pulley and smaller secondary servo cylinder to move proportionally in the opposite direction against the resistance of both the return spring and the secondary cylinder pressure, this being necessary to provide the correct clamping loads between the belt and pulleys' walls. The cylinder pressure necessary to prevent slippage of the belt varies from around 22 bar for the pull away lowest ratio setting to approximately 8 bar for the highest overdrive setting. The speed ratio setting and belt clamping load control is achieved via a primary pulley position senser road assembly. Fig. 5.26 Illustration of pulley and belt under- and overdrive speed ratios Fig. 5.27 Steel belt construction 152 However, engine and road speed signals are pro- vided by a pair of pitot tubes which sense the rate of fluid movement, this being a measure of speed, be it either under the influence of fluid flow caused by the engine's input or by the output drive relating to vehicle speed. 5.9.4 Epicyclic gear train construction and description (Figs 5.25 and 5.28) Drive in both forward and reverse direction is obtained by a single epicyclic gear train controlled by a forward multiplate clutch and a reverse multiplate brake, both of which are of the wet type Fig. 5.28 Transaxle continuously variable belt and pulley transmission layout 153 (immersed in oil) (Fig. 5.25). The forward clutch is not only used for engagement of the drive but also to provide an initial power take-up when driving away from rest. The epicyclic gear train consists of an input planetary carrier, which supports three sets of double planetary gears, and the input forward clutch plates. Surrounding the planetary gears is an internally toothed annulus gear which also supports the rotating reverse brake plates. In the centre of the planetary gears is a sun gear which is attached to the primary pulley drive shaft. Neutral or park (N or P position) (Fig. 5.28) When neutral or park position is selected, both the multi- ple clutch and brake are disengaged. This means that the annulus gear and the planetary gears driven by the input planetary carrier are free to revolve around the sun gear without transmitting any power to the primary pulley shaft. The only additional feature when park position is selected is that a locking pawl is made to engage a ring gear on the secondary pulley shaft, thereby preventing it from rotating and causing the car to creep forward. Forward drive (D or L position) (Fig. 5.28) Select- ing D or L drive energizes the forward clutch so that torque is transmitted from the input engine drive to the right and left hand planetary carriers and planet pins, through the forward clutch clamped drive and driven multiplates. Finally it is transferred by the clutch outer casing to the primary pulley shaft. The forward gear drive is a direct drive causing the planetary gear set to revolve bodily at engine speed with no relative rotational movement of the gears themselves. Reverse drive (R position) (Fig. 5.28) Selecting reverse gear disengages the forward clutch and energizes the reverse multiplate brake. As a result, the annular gear is held stationary and the input from the engine rotates the planetary carrier (Fig. 5.28). The forward clockwise rotation of the carrier causes the outer planet gears to rotate on their own axes as they are compelled to roll round the inside of internally toothed annular gear in an anticlockwise direction. Motion is then transferred from the outer planet gears to the sun gear via the inner planet gears. Because they are forced to rotate clockwise, the meshing sun gear is directionally moved in the opposite sense anticlockwise, that is in the reverse direction to the input drive from the engine. 5.9.5 Performance characteristics (Fig. 5.29) With D drive selected and the car at a standstill with the engine idling, the forward clutch is just sufficiently engaged to produce a small amount of transmission drag (point 1). This tends to make the car creep forwards which can be beneficial when on a slight incline (Fig. 5.29). Opening the throttle slightly fully engages the clutch, causing the car to move positively forwards (point 2). Depressing the accelerator pedal further sets the speed ratio accord- ing to the engine speed, road speed and the driver's requirements. The wider the throttle is opened the lower the speed ratio setting will be and the higher the engine speed and vice versa. With a light constant throttle opening at a minimum of about 1700 rev/min (point 3) the speed ratio moves up to the greatest possible ratio for a road speed of roughly 65 km/h which can be achieved on a level road. If the throttle is opened still wider (point 4) the speed ratio setting will again change up, but at a higher engine speed. Fully depressing the accelerator pedal will cause the engine speed to rise fairly rapidly (point 5) to about 4500 rev/min and will remain at this engine speed until a much higher road speed is attained. If the engine speed still con- tinues to rise the pulley system will continue to change up until maximum road speed (point 6) has been reached somewhere near 5000 rev/min. Partially reducing the throttle open then causes the pulley combination to move up well into the overdrive speed ratio setting, so that the engine speed decreases with only a small reduction in the car's cruising speed (point 7). Even more throttle reduction at this road speed causes the pulley combination speed ratio setting to go into what is known as a backout upshift (point 8), where the overdrive speed ratio reaches its maximum limit. Opening the throttle wide again brings about a kickdown downshift (point 9) so that there is a surplus of power for acceleration. A further feature which provides engine braking when driving fast on winding and hilly slopes is through the selection of L range; this changes the form of driving by preventing an upshift when the throttle is eased and in fact causes the pulley combination to move the speed ratio towards an underdrive situation (point 10), where the engine operates between 3000 and 4000 rev/min over an extensive road speed range. The output torque developed by this continuously variable transmission approaches the ideal 154 constant power curve (Fig. 5.29) in which the torque produced is inversely proportional to the car's road speed. 5.10 Five speed automatic transmission with electronic-hydraulic control 5.10.1 Automatic transmission gear train system (Fig. 5.30) This five speed automatic transmission system is broadly based on a ZF design. Power is supplied though a hydrodynamic three element torque converter incorporating an integral disc type lock-up clutch. The power drive is then directed though a Ravigneaux type dual planetary gear train which provides five forward gears and one reverse gear; it then passes to the output side via a second stage single planetary gear train. The Ravigneaux planetary gear train has both large and small input sun gears, the large sun gears mesh with three long planet gears whereas the small sun gears mesh with three short planet gears; both the long and the short planet gears are supported on a single gear carrier. A single ring-gear meshing with the short planet gear forms the output side of the planetary gear train. Individual gear ratios are selected by applying the input torque to either the pinion carrier or one of the sun gears and holding various other members stationary. 5.10.2 Gear train power flow for individual gear ratios D drive range Ð first gear (Fig. 5.31) With the position selector lever in D drive range, the one way clutch (OWC) holds the front planet carrier while multiplate clutch (B) and the multiplate brake (G) are applied. Power flows from the engine to the torque converter pump wheel, via the fluid media to the output turbine wheel. It is then directed by way of the input shaft and the applied multiplate clutch (B) to the front planetary large sun gear (S L ). With the front planet carrier (C F ) held stationary by the locked one way clutch (OWC), power passes from the large sun gear (S L ) to the long planet gears (P L ) in an anticlockwise direction. The long planet gear (P L ) therefore drives the short planet gears (P S ) in a clockwise direction thus compelling the front annular ring gear (A F ) to move in a clockwise direction. Power thus flows from the front annular ring gear (A F ) though the rear intermediate shaft to the rear planetary gear annular ring gear (A R )in a clockwise direction. With the rear sun gear (S R ) held stationary by the applied multiplate brake (G), the rear planet gears (P R ) are forced to roll around the fixed sun gear in a clockwise direction, this in turn compels the rear planet carrier (C R )and the output shaft also to rotate in a clockwise direction at a much reduced speed. Thus a two stage speed reduction produces an overall underdrive Fig. 5.29 CVT speed and torque performance characteristics 155 Crown wheel Bevel pinion Final drive Front planetary gear train Parking cog Pawl Transfer shaft Rear planetary gear train CLC T P (2+3+5)B E S RC A DC B A C F (4+5)C C OWC Input from engine Input shaft Front intermediate shaft Rear intermediate shaft Output shaft A F P L S S S L F OWC F RB (1+2+R)B G D A R P R C R S R Transfer gears P S Clutch Brakes A B C D E F G HC Fig. 5.30 Five speed and reverse automatic transmission (transaxle/longitudinal) layout 156 Brake G applied Rear planetary gears (RPG) Front planetary gear train Input Output Input Output Rear planetary gear train Output gear Output shaft Rear intermediate shaft OWC locked Front intermediate shaft Input shaft Input from engine OWC S P T E A B C C F A F S S S L P L OWC G D A R P R C R S R F CLC Clutch A applied Front planetary gears (FPG) C R A R S R P R S L A R P S P L C F S S Fig. 5.31 Five speed and reverse automatic transmission power flow first gear 157 first gear. If the `2' first gear is selected multiplate brake (F) is applied in addition to the multiplate clutch (B) and multiplate brake (G). As a result instead of the one way clutch (OWC) allowing the vehicle to freewheel on overrun, the multiplate brake (F) locks the front planetary carrier (C F ) to the casing. Consequently a positive drive exists between the engine and transmission on both drive and overrun: it thus enables engine braking to be applied to the transmission when the transmission is overrunning the engine. D drive range Ð second gear (Fig. 5.32) With the position selector lever in D drive range, multiplate clutch (C) and multiplate brakes (B) and (G) are applied. Power flows from the engine via the torque converter to the input shaft, it then passes via the multiplate clutch (B) to the first planetary large sun gear (S L ). With the multiplate brake (E) applied, the front planetary small sun gear (S S )is held stationary. Consequently the large sun gear (S L ) drives the long plant gears (P L ) anticlockwise and the short planet gears (P S ) clockwise, and at the same time, the short planet gears (P S ) are compelled to roll in a clockwise direction around the stationary small sun gear (S S ). The drive then passes from the front planetary annular ring gear (A F ) to the rear planetary annular ring gear (A R ) via the rear intermediate shaft. With the rear sun gear (S R ) held stationary by the applied multiplate brake (G) the clockwise rotation of the rear annular ring gear (A R ) compels the rear planet gears (P R ) to roll around the held rear sun gear (S R ) in a clockwise direction taking with it the rear carrier (C R ) and the output shaft at a reduced speed. Thus the overall gear reduction takes place in both front and rear planetary gear trains. D drive range Ð third gear (Fig. 5.33) With the position selector lever in D drive range, multiplate clutches (B) and (D), and multiplate brake (E) are applied. Power flows from the engine via the torque converter to the input shaft, it then passes via the multiplate clutch (B) to the front planetary large sun gear (S L ). With the multiplate brake (E) applied, the front planetary small sun gear (S S )is held stationary. This results in the large sun gear (S L ) driving the long planet gears (P L ) anticlockwise and the short planet gears (P S ) clockwise, and simultaneously, the short planet gears (P S ) are compelled to roll in a clockwise direction around the stationary small sun gear (S S ). Consequently, the annular ring gear (A F ) is also forced to rotate in a clockwise direction but at a reduced speed to that of the input large sun gear (S L ). The drive is then transferred from the front planetary annular ring gear (A F ) to the rear planetary annular ring gear (A R ) via the rear intermediate shaft. With the multiplate clutch (D) applied the rear planetary sun gear (S R ) and rear annular ring gear (A R ) are locked together, thus preventing the rear planet gears from rotating independently on their axes. The drive therefore passes directly from the rear annular ring gear (A R ) to the rear carrier (C R ) and output shaft via the jammed rear planet gears. Thus it can be seen that the overall gear reduction is obtained in the front planetary gear train, whereas the rear planetary gear train only provides a one-to-one through drive. D drive range Ð fourth gear (Fig. 5.34) With the positive selector lever in D drive range, multiplate clutches (B), (C) and (D) are applied. Power flows from the engine via the torque converter to the input shaft, it then passes via the multiplate clutch (B) to the front planetary large sun gear (S L ) and via the multiplate clutch (C) to the front planetary planet-gear carrier (C F ). Consequently both the large sun gear and the planet carrier rotate at the same speed thereby preventing any relative planetary gear motion, that is, the gears are jammed. Hence the output drive speed via the annular ring gear (A F ) and the rear intermediate shaft is the same as that of the input shaft speed. Power is then transferred to the rear planetary gear train by way of the front annular ring gear (A F ) and rear intermediate shaft to the rear planetary annular ring gear (A R ) and rear intermediate shaft to the rear planetary annular ring gear (A R ). However, with the multiplate clutch (D) applied, the rear annular ring gear (A R ) becomes locked to the rear sun gear (S R ); the drive therefore flows directly from the rear annular ring gear to the rear planet carrier (C R )and output shaft via the jammed planet gears. Thus there is no gear reduction in both front and rear planetary gear trains, hence the input and output rotary speeds are similar. D drive range Ð fifth gear (Fig. 5.35) With the position selector lever in D drive range, multiplate clutches (C) and (D) and multiplate brake (E) are applied. Power flows from the engine via the torque converter to the input shaft, it then passes via the multiplate clutch (C) to the front planetary planet 158 Brake G applied Rear planetary gears (RPG) Front planetary gear train Input Output Input Output Rear planetary gear train Output gear Output shaft Rear intermediate shaft Front intermediate shaft Input shaft Input from engine OWC S P T E A B C C F A F S S S L P L OWC G D A R P R C R S R F CLC Clutch A applied Front planetary gears (FPG) C R A R S R P R S L A F P S P L C F S S Brake C applied Fig. 5.32 Second gear 159 Clutch F applied Rear planetary gears (RPG) Front planetary gear train Input Output Input Output Rear planetary gear train Output gear Output shaft Rear intermediate shaft Front intermediate shaft Input shaft OWC S P T E A B C C F A F S S S L P L OWC G D A R P R C R S R F CLC Clutch A applied Front planetary gears (FPG) C R A R S R P R S L A F P S P L C F S S Brake C applied Fig. 5.33 Third gear 160 Front planetary gear train Input Output Input Output Rear planetary gear train Output gear Output shaft Rear intermediate shaft Front intermediate shaft Input shaft Input from engine OWC S P T E A B C C F A F S S S L P L OWC G D A R P R C R S R F CLC C R A R S R P R S L P S P L C F S S Fig. 5.34 Fourth gear 161 [...]... MPC MPB MPB MPC E S A B C F G D OWC RV-E RV-G BV-E BV-G 176 CPV BV-D RGV NRV CLCV CV-B CPCV Y to LUB (T/C)V CV-C LPV TV (5- 4) PRV BV-F TV (4 -5) SV-3 MPV MOD-PV SV -2 2 PRV -2 SPV SV-1 177 EPRV-1 PRV-1 P MV1 MV2 EPRV -2 Y MV3 ETCU GCPS EPRV-3 1 2 3 D N R P EPRV-4 FIQ (torque) Fig 5. 42 TVP (acceleration) Hydraulic/electronic transmission control system ± second gear SS engine/trans Transmission program... MPC MPC MPB MPB MPC E S A B C F G D OWC RV-E RV-G BV-E BV-G 1 82 CPV BV-D RGV NRV CLCV CV-B (T/C)V CPCV Y CV-C to LUB TV (5- 4) LPV PRV PRV BV-F TV (4 -5) SV-3 MPV MOD-PV SV -2 5 PRV -2 SPV SV-1 183 EPRV-1 PRV-1 P MV1 MV2 EPRV -2 NRV Y MV3 ETCU GCPS 1 2 3 D N EPRV-3 R P FIQ (torque) Fig 5. 45 TVP (acceleration) Hydraulic/electronic transmission control system ± fifth gear SS engine/trans Transmission program... CV-C to LUB TV (5- 4) LPV PRV BV-F BV-F TV (4 -5) SV-3 MPV MOD-PV SV -2 41 PRV -2 SPV SV-1 181 EPRV-1 PRV-1 P MV1 MV2 EPRV -2 Y MV3 ETCU GCPS EPRV-3 1 2 3 D N R P FIQ (torque) Fig 5. 44 TVP (acceleration) Hydraulic/electronic transmission control system ± fourth gear SS engine/trans Transmission program EPRV-4 CLC T TC P MPB MPC MPC MPC MPB MPB MPC E S A B C F G D OWC RV-E RV-G BV-E BV-G 1 82 CPV BV-D RGV... MPC MPC MPC MPB MPB MPC E S A B C F G D OWC RV-E RV-G BV-E BV-G 174 CPV BV-D RGV NRV CLCV CV-B CPCV Y (T/C)V CV-C to LUB LPV TV (5- 4) BV-F TV (4 -5) SV-3 MPV MOD-PV SV -2 1 PRV -2 SPV SV-1 1 75 EPRV-1 PRV-1 P MV1 MV2 EPRV -2 NRV Y MV3 ETCU GCPS EPRV-3 1 2 3 D N R P FIQ (torque) Fig 5. 41 TVP (acceleration) Hydraulic/electronic transmission control system ± first gear SS engine/trans Transmission program EPRV-4... MPC MPC MPB MPB MPC E S A B C F G D OWC RV-E BV-E RV-G BV-G 184 CPV BV-D RGV NRV CLCV CV-B (T/C)V CPCV Y CV-C to Lub LPV TV (5- 4) PRV PRV BV-F TV (4 -5) SV-3 MPV MOD-PV SV -2 R PRV -2 SPV SV-1 1 85 EPRV-1 PRV-1 P MV1 MV2 EPRV -2 NRV Y MV3 ETCU GCPS EPRV-3 1 2 3 D N R P FIQ (torque) Fig 5. 46 TVP (acceleration) Hydraulic/electronic transmission control system ± reverse gear SS engine/trans Transmission program... MPC MPC MPB MPB MPC E S A B C F G D OWC RV-G RV-E BV-G BV-E 178 CPV BV-D RGV NRV CLCV CV-B (T/C)V CPCV Y CV-C to LUB TV (5- 4) LPV PRV PRV BV-F TV (4 -5) SV-3 MPV MOD-PV SV -2 31 PRV -2 SPV SV-1 179 EPRV-1 PRV-1 P MV1 MV2 NRV EPRV -2 Y MV3 ETCU GCPS EPRV-3 1 2 3 D N R P FIQ (torque) Fig 5. 43 TVP (acceleration) Hydraulic/electronic transmission control system ± third gear SS engine/trans Transmission program... RV-G BV-E BV-G 168 CPV NRV BV-b RGV CLCV CV-B CPCV (T/C)V Y CV-C to LUB LPV TV (5- 4) PRV PRV BV-F TV (4 -5) SV-3 MPV MOD-PV SV -2 N SV-1 PRV -2 SPV 169 EPRV-1 PRV-1 MV1 PUMP (P) MV2 EPRV -2 Y MV3 Gear change position switch Electronic transmission control unit (ETCU) EPRV-3 1 2 3 D N R P Fuel injection quantity (torque) Fig 5. 39 Throttle valve position (acceleration) Hydraulic/electronic transmission control... (T/C)V 12 traction valves TV (4 5) and TV (5 4) 13 converter pressure valve CPV 14 converter pressure control valve CPCV 15 converter lock-up clutch valve CLCV 16 lubrication pressure valve LPV 17 solenoid (electro-magnetic) valves MV1, MV2 and MV3 18 electronic pressure regulating valves EPRV-1, EPRV -2, EPRV-3 and EPRV-4 19 multiplate clutch/brake MPC-A, MPC-B, MPC-C and MPC-D/MPB-E, MPB-F and MPB-G 20 ... valve PRV 21 non-return valve NRV Table 5. 6 Hydraulic/electronic automatic transmission control system solenoid valve, clutch and brake engagement sequence for different gear ratios for Figs 5. 39 5. 46 Solenoid valve ± clutch ± brake engagement sequence Gear range Solenoid valve logic Clutch and brake logic Solenoid valves 1 N/P neutral/park D 1st gear D 2nd gear D 3rd gear D 4th gear D 5th gear 2 1st gear... solenoid valves MV1, MV2 and MV3 1 0 0 0 .2 0.4 0.6 Control current (A) 0.8 Pressure reduction valve (PRV -2) (Fig 5. 39) The pressure reduction valve `PRV' reduces the main fluid pressure supply to an approximate constant 5 bar output pressure which is the necessary fluid pressure supply to operate the electronic pressure regulation valves EPRV-1, EPRV -2, EPRV-3 and EPRV-4 Fig 5. 40 Electronic pressure . engine's input or by the output drive relating to vehicle speed. 5. 9.4 Epicyclic gear train construction and description (Figs 5 . 25 and 5 .28 ) Drive in both forward and reverse direction is obtained. pulley position senser road assembly. Fig. 5 .26 Illustration of pulley and belt under- and overdrive speed ratios Fig. 5 .27 Steel belt construction 1 52 However, engine and road speed signals are. brake, both of which are of the wet type Fig. 5 .28 Transaxle continuously variable belt and pulley transmission layout 153 (immersed in oil) (Fig. 5 . 25 ). The forward clutch is not only used for

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