View
216
Download
0
Category
Preview:
Citation preview
7
Modules
Damper
The Flywheel
and Damper Assembly
In reciprocating engines, the unevennessof the combustion sequence inducestorsional vibration in the crankshaft.
This torsional vibration is transmittedto the transmission and results inresonant vibration, producing noise andoverloading components inthe transmission.
The flywheel and damper assemblyand the dual-mass flywheel dampentorsional vibration and ensure theengine runs quietly.
In the 3.0-liter V6 engine, engine torque istransmitted to the transmission through aflywheel and damper assembly.
Because four-cylinder engines do notrun as smoothly as six-cylinder engines,a dual-mass flywheel is used infour-cylinder engines.
SSP 228/004
Dual-MassFlywheel
SSP 228/032
Flywheel
8
Modules
Sectional View of Transmission
For better representation,the oil pump and the transfercase are shown folded on thecutting plane.
9
Modules
SSP 228/040
Housing, Screws, Bolts
Hydraulic Parts/Control
Electronic Transmission Control
Shafts, Gears
Plate Clutches
Pistons, Torque Sensors
Bearings, Washers, Circlips
Plastics, Seals, Rubber
Color Definitions
10
Modules
The Forward Clutch/Reverse
Clutch with Planet Gear Set
In contrast to multi-step automatictransmissions, such as the 01V, which usea torque converter, separate clutches areused for forward and reverse travel in theAudi CVT design. These “wet plateclutches” are also used to executegearshifts in multi-step automatictransmissions. They are used for drivingoff and transmitting the torque to theauxiliary reduction gear step. The drive-offprocess and torque transmission aremonitored electronically and regulatedelectro-hydraulically.
The electro-hydraulically controlled wetplate clutch has the following advantagesover a torque converter:
• Low weight
• Very little installation space is required
• Adaptation of clutch engagementcharacteristic to driving situation
• Adaptation of slip torque todriving situation
• Protective function in the event ofoverloading or misuse
SSP 228/005
Reverse Clutch
ForwardClutch
Planet Carrier
Input Pulley Set 1(Auxiliary Reduction Gear Step)
Forward Clutch/Reverse Clutchwith Planetary Gear Train
Planetary GearsTransmissionInput Shaft
Ring Gear
11
Modules
The Planetary Gear Train
The planetary gear train is constructed as aplanet reversing gear set and its onlyfunction is to change the rotational directionof the transmission for backing up.
The reduction ratio in the planetary geartrain is 1:1 when backing up.
Assignment of Components
The sun gear (input) is linked to thetransmission input shaft and the steelplates on the forward clutch.
The planet carrier (output) is linked to thedrive gear, the auxiliary reduction gear step,and the lined plates on the forward clutch.
The ring gear is connected to theplanetary gears and the lined plates on thereverse clutch.
SSP 228/008
Steel Plates and Lined Plateson Forward Clutch
Ring GearSteel Plates and Lined Plateson Reverse Clutch
Sun Gear Input Pulley Set 1(Auxiliary ReductionGear Step)
Planet Carrier withPlanetary Gears
TransmissionInput Shaft
12
Modules
Power Flow in the Planetay Gear Train
Torque is transferred to the planetary geartrain via the sun gear which is connected tothe input shaft and drives the planetarygears 1.
Planetary gears 1 drive planetary gears 2,which are in mesh with the ring gear.
Planet Carrier
The planet carrier (output planetary geartrain) is stationary because it acts as theinput for the auxiliary reduction gear stepand the vehicle is still not moving.
The ring gear idles and rotates athalf engine speed in the direction ofengine rotation.
SSP 228/033
Direction of Rotation of Components when
Engine is Running and Vehicle is Stationary
Transmission Input Shaftwith Sun Gear
Ring Gear
Planetary Gear 2Planetary Gear 1
13
Modules
Power Flow During Forward Travel
The steel plates on the forward clutch arelinked to the sun gear and the lined platesare linked to the planet carrier.
SSP 228/009
When the forward clutch is engaged, itconnects the transmission input shaft tothe planet carrier (output). The planetarygear train is locked and rotates in the samedirection as the engine; the torquetransmission ratio is 1:1.
Oil Pressure for ClutchTorque Flow
Forward Clutch
Planetary Gear Train
14
Modules
Power Flow in Reverse
The lined plates of the reverse clutchare connected to the ring gear and thesteel plates are connected to thetransmission housing.
When the reverse clutch engages, it holdsthe ring gear and thereby prevents thetransmission housing from rotating.
SSP 228/010
Reverse Clutch
Torque is then transmitted to the planetcarrier, which begins to rotate in theopposite direction to the engine. Thevehicle moves in reverse.
Road speed is limitedelectronically when thevehicle is in reverse.
The Variator remains in thestarting torque ratio.
Oil Pressure for ClutchTorque Flow
Ring Gear
15
Modules
Accelerator Pedal AngleEngine SpeedNominal Engine SpeedTransmission Input Speed, Pulley Set 1Transmission Output Speed, Pulley Set 2
20
40
60
80
100
1000
01 2 3 4 5 6 7 8 9 10
2000
3000
4000
0
Accelerator Pedal100% Depressed
Eng
ine
Spe
ed
Time in Seconds SSP 228/052
20
40
60
80
100
1000
01 2 3 4 5 6 7 8 9 10
2000
3000
4000
0
Eng
ine
Spe
ed
Time in Seconds SSP 228/053
AcceleratorPedal 60%Depressed
20
40
60
80
100
1000
01 2 3 4 5 6 7 8 9 10
2000
3000
4000
5000
6000
0
Eng
ine
Spe
ed
Time in Seconds SSP 228/054
Accelerator Pedal100% Depressed+ Kickdown
The Clutch Control
Clutch Engagement
Engine speed controls CVT clutchengagement to initiate vehicle motion.
The accelerator pedal angle and applicationspeed set by the driver and the control maprequirements of the Transmission ControlModule J217 determine the clutchengagement characteristics for eachvehicle start from rest.
Depending upon the specific driver inputsfor each start, the Transmission ControlModule J217 sets a nominal engine speedat which clutch engagement will take place.
With the vehicle at rest, moderateapplication of the accelerator pedal(characterized by slow movement to asmall accelerator pedal angle) initiates thetransition from engine idling speed toclutch engagement speed at a relativelylow engine speed. Short clutch slip timesand low engine speed at clutchengagement will provide the best fueleconomy.
For a performance start from rest, heavyapplication of the accelerator pedal (quickmovement to a large accelerator pedalangle) initiates the transition from engineidling speed to clutch engagement enginespeed at a higher engine rpm. The greatertorque developed at higher engine rpmyields faster vehicle acceleration.
Differences in engine type andperformance characteristics also have aneffect on CVT clutch engagementcharacteristics.
16
Modules
Electronic Control
The following parameters are used forclutch control:• Engine speed• Transmission input speed• Accelerator pedal position• Engine torque• Brake applied• Transmission oil temperatureThe Transmission Control Module J217calculates the nominal clutch pressurefrom these parameters and determinesthe control current for Pressure ControlValve -1- for Automatic Transmission N215.The clutch pressure, and thereforethe engine torque to be transmitted by theclutch, changes almost in proportion tothe control current (refer to “HydraulicControl,” page 17).Automatic Transmission Sender -1- forHydraulic Pressure G193 registers theclutch pressure (actual clutch pressure) inthe hydraulic control. Actual clutch pressureis continuously compared to the nominalclutch pressure calculated by theTransmission Control Module J217.The actual pressure and specified pressureare checked continuously for plausibilityand corrective action is taken if these twovalues deviate from one another by morethan a certain amount (refer to “SafetyShut-Off,” page 18).To prevent overheating, the clutch iscooled and clutch temperature is monitoredby the Transmission Control Module J217(for more detailed information, refer to“The Clutch Cooling System,” page 23, and“Overload Protection,” page 18).
SSP 228/075
Transmission ControlModule J217
Automatic Transmission Sender-1- for Hydraulic Pressure G193
Pressure Control Valve -1- forAutomatic Transmission N215
17
Modules
Hydraulic Control
Clutch pressure is proportional to enginetorque and is not dependent on thesystem pressure.A constant pressure of approximately73 psi (500 kPa) is applied by the pilotpressure valve to the Pressure ControlValve -1- for Automatic Transmission N215.Pressure Control Valve -1- for AutomaticTransmission N215 produces a controlpressure which controls the position of theclutch control valve depending on thecontrol current calculated by theTransmission Control Module J217.A high control current results in a high
control pressure.
The clutch control valve controls the clutchpressure and therefore also regulates theengine torque to be transmitted.
The clutch control valve is suppliedwith system pressure and produces clutchpressure in accordance with the activationsignal from Pressure Control Valve -1- forAutomatic Transmission N215.A high control pressure results in a high
clutch pressure.
The clutch pressure flows via the safetyvalve to the manual selector valve.The manual selector valve transfers clutchpressure either to the forward clutch(position D) or to the reverse clutch(position R), depending on the selectorlever position. The non-pressurizedclutch is vented into the oil sump.In selector lever positions N and P, thesupply is shut off via the manual selectorvalve and both clutches are vented intothe oil sump.
ReverseClutch
ManualSelectorValve
ForwardClutch
SafetyValve
Pressure ControlValve -1- for AutomaticTransmission N215
PilotPressureValve
ClutchControlValve
P R N D
SSP 228/011
ATF Depressurized
Clutch PressureSupply Pressure
Pilot Control PressureControl Pressure
In the Oil Sump
18
Modules
Safety Shut-Off
A safety-critical malfunction has occurredif actual clutch pressure is clearly higherthan specified clutch pressure. In this case,the clutch is depressurized regardless ofthe manual selector valve position andother system states.
A safety shut-off is implemented viathe safety valve and enables the clutchto open quickly.
The safety valve is activated by SolenoidValve 1 N88. At control pressures aboveapproximately 58 psi (400 kPa), the supplyto the clutch control valve is shut off andthe connection to the manual selectorvalve in the oil sump is vented.
Overload Protection
Using a model calculation, the TransmissionControl Module J217 calculates the clutchtemperature from clutch slip, engine torqueto be transmitted, and transmission oiltemperature. Engine torque is reduced ifthe measured clutch temperature exceedsa defined threshold because of excessload on the clutch.
Engine torque can be reduced to the upperend of the idling speed range. It is possiblethat the engine will not respond to theaccelerator pedal for a short period of time.The clutch cooling system ensures a shortcooling-down time. Maximum enginetorque is quickly available again. Overloadof the clutch is almost impossible.
SSP 228/082
Switched Position After Safety Shut-Off
Vented into Oil Sump/Depressurized
Clutch Pressure
Supply Pressure
Pilot Control Pressure
Control pressure
In the Oil Sump
ForwardClutch
ManualSelectorValve
SafetyValve
ClutchControlValve
SolenoidValve 1N88
P RN D
ReverseClutch
19
Modules
Clutch Control when Vehicle
Is Stationary (Slip Control)
The slip control function sets the clutch to adefined slip torque (clutch torque) when theengine is running at idling speed and a driveposition is selected. The vehicle behaves inthe same way as an automatic transmissionwith a torque converter.
Selective clutch pressure adaptation resultsin an input torque which causes the vehicleto ”creep.”
Input torque is varied within defined limitsdepending on vehicle operating state andvehicle road speed. The contact pressureapplied by the taper pulleys is sensed byAutomatic Transmission Sender -2- forHydraulic Pressure G194. This informationis used for precision clutch torque control.
BrakePedal NotPressed
Because contact pressure is proportional tothe actual engine input torque presentat pulley set 1, clutch torque can beprecisely calculated and controlled usingAutomatic Transmission Sender -1- forHydraulic Pressure G193 (for more detailedinformation, refer to “The Torque Sensor,”page 33).
Slip control allows the vehicle tobe maneuvered when parkingwithout pressing the acceleratorpedal and therefore enhancesdriving comfort.
SSP 228/013
Automatic TransmissionSender -1- forHydraulic Pressure G193
29.5 psi(40 Nm)
Automatic TransmissionSender -2- forHydraulic Pressure G194
20
Modules
Special Feature of the Slip Control
A special feature of the slip control isthe reduction of slip torque when thevehicle is stationary and the brakes areactuated. As a result, the engine is notrequired to develop so much torque (theclutch is also open wider).
This has a positive effect on fuel economy.Noise from the engine running at idlespeed when the vehicle is stationary isreduced and much less pressure has tobe applied to the brake pedal to stopthe vehicle.
SSP 228/012
11.1 psi(15 Nm)
If the vehicle rolls back when standingon a slope with only light pressureapplied to the brake, the clutch pressureis increased to immobilize the vehicle (“hill-holder” function).
By using two transmission output speedsenders (Sender for Transmission OutputRPM G195 and Sender -2- for TransmissionOutput RPM G196) it is possible todistinguish between forward travel andreverse travel, which makes the hill-holderfunction possible (for further information,please refer to “Sensors,” page 63).
BrakePedalPressed
Automatic TransmissionSender -1- forHydraulic Pressure G193
Automatic TransmissionSender -2- forHydraulic Pressure G194
0 (0)
37 (50)
74 (100)
111 (150)
148 (200)
184 (250)
221 (300)
10000 2000 3000 4000 5000 6000 7000
Eng
ine
Torq
ue in
lbs-
ft (N
m)
21
Modules
The Micro-Slip Control
The micro-slip control serves to adapt theclutch control (see description of adaptationprocess, page 22) and dampen the torsionalvibration induced by the engine.
In the part-throttle range, the clutchcharacteristics are adapted up to an enginetorque of 118 lbs-ft (160 Nm).
In the engine speed range up toapproximately 1800 rpm and at enginetorques up to approximately 162 lbs-ft(220 Nm), the clutch operates in what isknown as “micro-slip” mode. In thisoperating mode, a slip speed (speeddifferential) of approximately 5 rpm to 20rpm is maintained between thetransmission input shaft and pulley set 1.
SSP 228/092
For this purpose, the Transmission ControlModule J217 compares the signalgenerated by Sensor for Transmission RPMG182 with the engine speed, makingallowance for the auxiliary reduction gearstep. Sensor for Transmission RPM G182registers the rotation of pulley set 1.
As the term “micro-slip”suggests, clutch slip is kept ata minimum so no noticeablepenalties in lining wear and fueleconomy occur.
Engine Speed in RPM
Approximately1800 RPM
Clutch Closed
Micro-Slip Control Range
Adaptation Range During Micro-Slip Control:Up to Approximately 118 lbs-ft (160 Nm)
22
Modules
Clutch Control Adaptation
To be able to control the clutch comfortablyin any operating state and throughout itsservice life, the relationship betweencontrol current and clutch torque has to beupdated continuously.
This is necessary because thecoefficients of friction of the clutchesare constantly changing.
The coefficient of friction is dependent onthe following factors:
• Transmission oil (quality, aging, wear)
• Transmission oil temperature
• Clutch temperature
• Clutch slip
To compensate for these influences andoptimize clutch control, the relationshipsbetween control current and clutch torqueare adapted in slip control mode and in thepart-throttle range.
Adaptation in Slip Control Mode
(Brake Pressed):
As mentioned already, a defined clutchtorque is set in slip control mode.The Transmission Control Module J217observes the relationship between thecontrol current from Pressure Control Valve-1- for Automatic Transmission N215 andthe data from Automatic TransmissionSender -2- for Hydraulic Pressure G194(contact pressure) and stores these data.The actual data are used for calculatingnew characteristics.
Here, “adaptation” meanslearning new pilot control values.
Adaptation in Part-Throttle Range
In the part-throttle range, adaptation isperformed in micro-slip control mode.In this operating mode the TransmissionControl Module J217 compares the enginetorque from the Motronic Engine ControlModule J220 to the control current fromPressure Control Valve -1- for AutomaticTransmission N215 and stores these data.The actual data are used for calculatingnew characteristics (see “Micro-SlipControl,” page 21).
Summary:
The adaptation function serves to maintaina constant clutch control quality.
The adaptation data also have an effecton the calculation of clutch pressure athigher transmission torques (clutch fullypositively engaged).
High clutch pressures are not required,which ultimately has a positive effecton efficiency.
23
Modules
The Clutch Cooling System
The clutches are cooled by a separateoil flow in order to protect them fromexposure to excessively high temperatures(particularly when driving away underhard acceleration).
To minimize power losses due to clutchcooling, the cooling oil flow is directedwhere it is needed by a cooling oil controlmodule integrated into the valve body.
Additional cooling oil is supplied by asuction jet pump (entrainment pump)without placing a demand on oil
Forward Clutch
SSP 228/064
pump capacity.
To optimize clutch cooling, the cooling oilflows only to the power-transmitting clutchpulley set.
The cooling oil and the pressurized oil ofthe forward clutch flow through the hollowtransmission input shaft. The two oilcircuits are separated from one another bya steel tube, the “inner part.”
An “oil divider” located at the oil outletbores on the transmission input shaftguides the cooling oil flow to the forwardclutch and the reverse clutch.
Oil Divider withDiaphragm Spring andStop Ring with Openings
Diaphragm SpringDistributor Disc
Inner Part
Stop Ring
Oil Divider
Reverse Clutch
24
Modules
Cooling the Forward Clutch
If the forward clutch is engaged, thecylinder (thrust plate) of the forward clutchpresses the oil divider back.
In this position, the cooling oil flows pastthe front face of the oil divider and throughthe forward clutch.
Cooling the Reverse Clutch
If the forward clutch is not operated(when the engine is running at idling speedor when the reverse clutch is operated),the oil divider is in its basic position.
In this position, the cooling oil flows to theoil divider and is rerouted to the reverseclutch by a distributor plate. Branches in thedistributor pulley duct cooling oil to theplanetary gear train and provide thenecessary lubrication there.
SSP 228/014
Forward Clutch Reverse Clutch
Cylinder
Oil Pressure for Clutch
Clutch Cooling Oil Flow
25
Modules
Hydraulic Clutch Cooling Control
The clutch cooling system cuts inat the same time as the clutch controlis activated.
The Transmission Control Module J217applies a defined control current toSolenoid Valve 1 N88. This produces acontrol pressure which switches the clutchcooling valve.
SSP 228/045
The clutch cooling valve transfers pressurefrom the cooler return pipe to the suctionjet pump (entrainment pump).
The pressurized oil is used to operate thesuction jet pump (entrainment pump) (forfurther details, refer to “The Suction JetPump (Entrainment Pump),” page 46).
Pilot Control Pressure
Control Pressure
In the Oil Sump
To Manual Selector Valve
To Cooler Return Pipe
SafetyValve
SolenoidValve 1N88
Pressure ControlValve -1- for AutomaticTransmsiion N215
ClutchCoolingValve
PilotPressureValve
Suction Jet Pump(Entrainment Pump)with Check Valve
To theClutches
ATF Depressurized
Cooling Oil Flow
Oil from Cooler Return Pipe
26
Modules
The Auxiliary Reduction Gear Step
Due to constraints on space, torque istransmitted to the Variator through anauxiliary reduction gear step.
SSP 228/017
The auxiliary reduction gear step hasdifferent reduction ratios to accommodatedifferent engines to the transmission. As aresult, the Variator is operated within itsoptimum torque range.
PlanetaryGear Train
Pulley Set 1
Auxiliary ReductionGear Step
27
Modules
The Variator
The basic operating principle of theVariator has been explained on page 3. Thespecial features and functions of themultitronic® Variator are described on thefollowing pages.
The Concept of the Variator Used in the
multitronic®
The operation of the Variator is based onwhat is known as the dual-piston principle.A special feature of the multitronic®Variator is the torque sensor integrated inpulley set 1 (for more detailed informationrefer to “The Torque Sensor,” page 33).
Pulley sets 1 and 2 each have a separatepressure cylinder for pressing the taperpulleys as well as a separate variabledisplacement cylinder for transmissionratio adjustment.
The dual-piston principle makes it possibleto change the transmission ratio veryquickly by applying a small amount ofpressure. This ensures that the taperpulleys maintain sufficient contact pressureat a relatively low oil pressure level.
SSP 228/018
Starting Torque Ratio
Pulley Set 2
Pulley Set 1
ChainTorque Sensor
28
Modules
Adjustment
A suitable supply of pressurized oil isrequired due to the heavy demands on theadjustment dynamics. To minimize therequired quantity of oil, the variabledisplacement cylinders have a smallersurface area than the pressure cylinders.Therefore, the quantity of oil needed foradjustment is relatively small.
This makes high adjustment dynamics andhigher efficiency possible despite the lowdelivery rate of the oil pump.
The diaphragm springs in pulley set 1and the coil springs in pulley set 2 createa defined basic chain tension (contactpressure) when the hydraulic systemis depressurized.
In the depressurized state, the Variatorfor the starting torque ratio is adjusted bythe spring force of the coil springs inpulley set 2.
SSP 228/019
End Torque Multiplication Ratio (Overdrive)
Pressure Cylinder Diaphragm Spring
Torque Sensor Variable Taper Pulley
Pulley Set 1
VariableDisplacementCylinder
Pulley Set 2
Variable Taper PulleyPressure Cylinder
Pressure Spring
VariableDisplacementCylinder
29
Modules
Contact Pressure
High contact pressures are requiredbetween the taper pulley and the chain totransmit the torque the engine develops.The contact pressure is produced byadjusting the oil pressure in the pressurecylinder as appropriate.
According to the principles of hydraulics, aresultant force (contact pressure) can bevaried as a function of pressure andeffective area.
The pressure cylinders have a largersurface area and can therefore apply therequired contact pressure with less oilpressure. The relatively low oil pressure isalso more efficient.
Towing
When the vehicle is being towed, pulley set2 drives pulley set 1 and there is a dynamicpressure buildup in the variabledisplacement cylinder and pressure cylinderof the pulley sets.
The system is designed in such a waythat the reduction ratio is adjusted toapproximately 1:1 by the dynamic pressurebuild-up in the Variator. Pulley set 1 andthe planetary gear train are thus protectedfrom excessively high engine speeds.
The diaphragm springs in pulley set 1 assistwith this process.
For more detailed informationregarding dynamic pressurebuild-up, refer to “The SplashOil Cover,” page 38.
Also observe the towinginformation given in “Towing,”page 91.
SSP 228/081
DiaphragmSpring inPulley Set 1
SSP 228/080
Resultant Force1124 lbs (5 000 N)
Effective Area15.50 in2
(100 cm2)
Pressure72.5 psi(500 kPa)
Resultant Force1124 lbs (5 000 N)
Effective Area7.75 in2 (50 cm2)
Pressure 145 psi(1 000 kPa)
30
Modules
The Transmission Control
Electronic Control
The Transmission Control Module J217has a dynamic control program forcalculating the nominal transmission inputspeed. It is an improved version of thedynamic shift program (DSP) already beingused in multi-step automatic transmissions.The driver input and vehicle operating stateare evaluated to provide the best gear ratioin every driving situation (see “DynamicControl Program,” page 82).
The dynamic control program calculates anominal transmission input speeddepending on conditions.
The Sensor for Transmission RPM G182registers the actual transmission inputspeed at pulley set 1.
The Transmission Control Module J217calculates a control current for PressureControl Valve -2- for AutomaticTransmission N216 based on an actual-value/setpoint comparison. PressureControl Valve -2- for AutomaticTransmission N216 produces a controlpressure for the hydraulic reduction valvewhich is almost proportional to thecontrol current.
Transmission control is monitored bychecking the plausibility of the signals fromSensor for Transmission RPM G182 andSender for Transmission Output RPM G195as well as the engine speed.
SSP 228/076
TransmissionControl Module J217
Pressure Control Valve -2- forAutomatic Transmission N216
Sensor forTransmissionRPM G182
Sender forTransmissionOutput RPM G195
31
Modules
SSP 228/076
Hydraulic Transmission Control
Pressure Control Valve -2- for AutomaticTransmission N216 is supplied witha constant pressure of approximately73 psi (500 kPa) by the pilot pressurevalve. Pressure Control Valve -2- forAutomatic Transmission N216 producesa control pressure corresponding tothe control current calculated by theTransmission Control Module J217, whichinfluences the position of the hydraulicreduction valve.
A high control current leads to a highcontrol pressure.
The hydraulic reduction valve transfersthe adjusting pressure to the variabledisplacement cylinder of pulley set 1 or 2,depending on the control pressure.
Pulley Set 1
Starting Torque Ratio
Pulley Set 2
HydraulicReductionValve
PressureControl Valve-2- forAutomaticTransmissionN216
PilotPressureValve
From theOil Pump
Vented into Oil Sump
Oil Supply
Pilot Control Pressure
Control Pressure
In the Oil Sump
32
Modules
The hydraulic reduction valve is closed at acontrol pressure of between approximately26 and 32 psi (180 and 220 kPa). At a controlpressure of less than 26 psi (180 kPa), theadjusting pressure is transferred to variabledisplacement cylinder at pulley set 1, andthe variable displacement cylinder of pulleyset 2 is simultaneously vented to theoil sump. The Variator shifts the reductionratio towards the end torque multiplictionratio (overdrive).
If the control pressure is greater than32 psi (220 kPa), the adjusting pressure istransferred to the variable displacementcylinder at pulley set 2 and the variabledisplacement cylinder at pulley set 1 issimultaneously vented to the oil sump.The Variator shifts the reduction ratiotowards the starting torque ratio.
SSP 228/084
End Torque Multiplication Ratio (Overdrive)
Pulley Set 1
Pulley Set 2
HydraulicReductionValve
PressureControlValve -2- forAutomaticTransmissionN216
PilotPressureValve
From the Oil Pump
Vented into Oil Sump
Oil Supply
Pilot Control Pressure
Control Pressure
In the Oil Sump
33
Modules
The Torque Sensor
Contact Pressure Control
As mentioned before, a suitable oilpressure in the pressure cylinder gives aresultant contact pressure of the taperpulleys. If the contact pressure is too low,slippage of the chain will occur and thechain and pulley sets will be damaged. Anexcessively high contact pressure, on theother hand, will result in loss of efficiency.
The object, therefore, is to set the contactpressure of the taper pulleys as accuratelyand safely as possible according torequirements.
RampShell 1
SSP 228/021
A hydro-mechanical torque sensorintegrated in pulley set 1 statically anddynamically registers the actual torquetransmitted to a high degree of accuracyand sets the correct oil pressure in thepressure cylinders.
The engine torque is transferredto the Variator by the torquesensor only. The contact pressureis controlled hydro-mechanicallyby the torque sensor.
Ramp Shell 2
Pulley Set 1
RampShell 2
34
Modules
Design and Function
The torque sensor essentially comprisestwo shells with seven ramps betweenwhich steel balls are mounted in bearings.Ramp shell 1 is form-fitted to the outputgear of pulley set 1 (output gear wheel ofauxiliary reduction gear step). Ramp shell 2is connected to pulley set 1 by a groovedgearing that allows axial movement and issupported by the torque sensor piston. Thetorque sensor piston serves to regulate thecontact pressure and houses torque sensorspaces 1 and 2.
The shells can be rotated radiallytowards one another, converting thetorque to an axial force (due to the balland ramp geometry).
This axial force acts upon ramp shell 2 andmoves the torque sensor piston which is incontact with the shell.
The control edge of the torque sensorpiston now closes or opens the outlets intorque sensor space 1.
The axial force generated by thetorque sensor serves as a controlforce which is proportional to theengine torque.
The pressure which builds upin the pressure cylinder isproportional to the control force.
SSP 228/022
Torque Sensor Piston
Torque Sensor Space 1
Torque Sensor Space 2
Ramp Shell 1
Grooved Gearing
Ramp Shell 2
35
Modules
Torque sensor space 1 is directly connectedto the pressure cylinder.
The system is designed so the axial forcegenerated as a product of engine torqueand the pressure in the pressure cylinderform a force equilibrium.
In constant conditions of vehicle operation,the outlet bores are only partially closed.The pressure drop produced by opening theoutlet bores (torque sensor) modulates thepressure in the pressure cylinder.
If input torque increases, the outlet boresare initially closed further by the controledge. The pressure in the pressure cylinderrises until a force equilibrium again exists.
If input torque decreases, the outlet boresare opened further. The pressure in thepressure cylinder decreases until the forceequilibrium is restored.
SSP 228/057
PressureCylinder
SSP 228/056
Torque SensorSpace 1
OutletBore
PressureCylinder
ControlEdge
OutletBore
100
75
50
25
02.4 1 0.4
36
Modules
At peak torque levels, the control edgecloses off the outlet bores. If the torquesensor moves any further, it acts as an oilpump. The displaced oil volume causes arapid rise in the pressure inside thepressure cylinder and immediately adjuststhe contact pressure.
Extremely high peak torques canoccur when the vehicle drivesover a pot-hole or if thecoefficient of friction of the roadsurface fluctuates considerably(transitions from black ice toasphalt for example).
Adaptation of contact pressure
depending on transmission ratio
The contact pressure exerted by the taperpulleys depends not only on the inputtorque but also on chain track radius and,therefore, on the actual reduction ratio ofthe Variator.
As the diagram shows, the starting torqueratio (clutch engagement) requires thegreatest contact pressure.
The radius of the chain is smallest in pulleyset 1. For power transmission, only a smallnumber of cradle type pressure pieces arein mesh despite the high input torque.
Therefore, a higher contact pressure isapplied by the taper pulleys until a definedreduction ratio of 1:1 is exceeded.
OutletBore
SSP 228/046
SSP 228/058
PressureCylinder
Con
tact
Pre
ssur
e in
%
Required Contact Pressurefor 25% Torque Requirement
VariatorRatio
Overdrive
Starting Torque Ratio
Overdrive
Starting Torque Ratio
Required Contact Pressurefor 100% Torque Requirement
Contact Pressure
37
Modules
Function and Mode of Operation
The ratio-dependent contact pressureis adapted in torque sensor space 2.The pressure level in the pressure cylinderis varied by increasing or decreasing thepressure in torque sensor space 2.The pressure in torque sensor space 2is controlled by two transverse holes inthe shaft of pulley set 1. These holes areopened or closed through axialdisplacement of the variable taper pulley.
The transverse holes are open when theVariator is in the starting torque ratio(torque sensor space 2 is depressurized).
When the Variator changes the ratioto end torque multipliction ratio (overdrive),the transverse holes are shut off initially. Ata defined reduction ratio, the left-handtransverse hole is opened to the pressurecylinder through corresponding holes in thevariable taper pulley.
This allows the oil pressure to betransferred from the pressure cylinder intotorque sensor space 2. This pressurecounteracts the axial force of the torquesensor and moves the torque sensor pistonto the left.
The control edge opens up the outlet boresfurther, reducing the oil pressure inside thepressure cylinder.
The main advantage of the two-stagepressure adaptation process is that a lowcontact pressure can be utilized in themid-ratio range which increases efficiency(refer to illustration SSP 228/046,previous page).
SSP 228/060
Torque Sensor Piston
SSP 228/059
Transverse HolesTorque Sensor Space 2
Variable Taper Pulley
Torque Sensor Space 2Bore
Bore
38
Modules
The Splash Oil Cover
Another special feature of the Variator isthe “splash oil cover” on pulley set 2 whichcounteracts the dynamic pressure buildupin the pressure cylinder.
At high engine speeds, the transmission oilin the pressure cylinder is subjected to highrotation-induced centrifugal forces, whichleads to a rise in pressure. This process isknown as “dynamic pressure buildup.”
A dynamic pressure buildup is undesirablebecause it unduly increases the contactpressure and has an adverse effect ontransmission control.
The oil confined in the splash oil cover issubjected to the same dynamic pressurebuildup as in the pressure cylinder. Thedynamic pressure buildup in the pressurecylinder is compensated by this.
The splash oil chamber receives its oilsupply directly from the hydraulic controlmodule through an oil injection hole. Oil iscontinuously injected into the splash oilchamber inlet through this hole.
A reduction in volume inside the splash oilchamber (when varying the transmissionratio) causes the oil to be dischargedthrough the supply inlet.
SSP 228/061
Oil Injection Hole
Splash Oil CoverPulley Set 2
Pressure Cylinder
Splash Oil Chamber
39
Modules
The Chain
The chain is a key component part of theVariator of the multitronic®.
This is the first time that a chain has beenused as a driving means in a CVT.
The chain is a new development and hasthe following advantages over conventionaldriving means such as sliding link beltsor V-belts:
• Very small track radii make possible alarge “spread” despite the small size ofthe Variator.
• High transferable torque.
• High efficiency.
Pulley Set 1
SSP 228/026
The spread indicates the rangeof ratios which a transmissionprovides.
The spread is specified as a ratio.The starting torque ratio dividedby the spread equals to the endtorque multiplication ratio.In general a large spread is anadvantage because both a highstarting torque ratio (for goodperformance) and a low endtorque multiplication ratio (for lowfuel consumption) are available.This applies in particular to theCVT concept, since practicallyall intermediate steps areavailable and no ratio steps areout of place.
Pulley Set 2
Chain
40
Modules
Design and Function
On a conventional chain, the chain linkplates are interconnected by joint pins witha slip fit. For torque transmission, gearteeth move into engagement with the pinsbetween the chain link plates.
The CVT chain uses a
different technology.
The CVT chain has adjacent rows of chainlink plates linked continuously with cradletype pressure pieces (two per link).
On the CVT chain, the cradle type pressurepieces are “jammed” between the taperpulleys of the Variator as the taper pulleysare pressed toward one another.
The torque is transmitted only by thefrictional force between the ends of thecradle type pressure pieces and thecontact faces of the taper pulleys.
This is how it works:
Each of the cradle type pressure pieces ispermanently connected to a row of linkplates so that it cannot be twisted.Two cradle type pressure pieces form acradle type joint.
The cradle type pressure pieces now roll offone another with very little friction as they“drive” the chain within the track radius ofthe taper pulleys.
In this way, lost power and wear areminimized despite the high torque and thelarge angle of bend. The result is longservice life and optimal efficiency.
Cradle TypePressure Piece
SSP 228/027
Taper Pulley of the Variator
Cradle TypePressure Pieces
Top
View
Shackle
Side
View
CradleType Joint
41
Modules
Acoustic Measures
Two different lengths of link plate are usedto ensure that the chain runs as quietlyas possible.
When using a constant length oflink plate, the cradle type pressurepieces strike the taper pulleys at uniformintervals and induce vibrations which causea noise nuisance.
Using different lengths of link platecounteracts resonance and minimizesrunning noise.
SSP 228/028
Different Lengthsof Link Plate
42
Modules
The Oil Supply
In the multitronic®, power transmission isdependent on the electrical power supplyand also on the hydraulics.
In order to work, an electric current and
adequate oil supply are required.
The oil pump is the main power consumerin the transmission and its capacity isimportant for overall efficiency.
The transmission control and coolingsystems are designed to run on a minimumof oil, and an innovative oil supply systemhas been developed.
Intake Filter
The Oil Pump
The oil pump is mounted directly on thehydraulic control module to avoidunnecessary interfaces. The oil pumpand the control module form a compactunit, which reduces pressure losses andproduction costs.
The multitronic® is equipped with anefficient crescent pump. This pumpproduces the necessary pressures, butrequires only a relatively small quantity ofoil. A suction jet pump (entrainment pump)supplies the additional quantity of oilrequired for the clutch cooling at lowpressure. The compact crescent-vanepump is integrated in the hydraulic controlmodule and driven directly by the inputshaft by a spur gear and pump shaft.
SSP 228/034
HydraulicControl Module(Valve Body)
Pressure Tube Routedto Suction Jet Pump(Entrainment Pump)
Oil Pump
43
Modules
As a special feature, the oil pump has axialand radial clearance adjustment.
A pump with good “internal sealing” isrequired in order to produce high pressuresat low engine speeds.
“Internal sealing” refers to theability of the pump to minimizeleakage past the surfaces movingthe fluid through the pump.
SSP 228/035Axial Plates
Conventional oil pumps do not meetthese requirements due to componenttolerances.
The axial clearance between the gearsand the housing, as well as the radialclearance between the gears and thecrescent vane can vary depending on thetolerance zone position of the componentparts in a conventional pump.
The pressure generated can thus more orless escape “internally.”
The result will be a loss of pressure and adrop in efficiency.
Segmental SpringsSealing Roller
Stop PinInner Segment
Spring Rod
Oil Pump Housing
Outer Segment
Driver
44
Modules
Axial Clearance Adjustment
Two axial plates cover the pressure rangeof the crescent pump and form a separatedischarge casing inside the pump.They seal the pump pressure chamberlaterally (axially). These plates, fitted witha special seal, are supported by the oilpump housing or the pump plate of thehydraulic control module.
The axial plates are designed to allow thepump pressure to act between the axialplates and the housing. The seal preventspressure from escaping. As pump pressure
SSP 228/051
increases, the axial plates are pressedmore firmly against the crescent seal andthe pump gears, which compensates foraxial clearance.
The axial and radial clearanceadjustment allows the pump togenerate the required highpressures and simultaneouslyachieve high efficiency despite itscompact design.
Seal
Axial Plate
Oil Pump Housing
Axial Plate
Axial Plate
45
Modules
Radial Clearance Adjustment
The radial clearance adjustment featurecompensates for the radial gap betweenthe crescent seal and the gears (pinion andring gear).
For this purpose, the crescent seal is splitin two segments, the inner segment andthe outer segment.
The inner segment seals the pressurechamber off from the pinion. It also holdsthe outer segment in a radial direction.The outer segment seals the pressurechamber off from the ring gear. The pumppressure flows between the two
SSP 228/049
Inner Segment
segments. The segments are pressedmore firmly against the pinion and ring gearas the pump pressure increases, whichcompensates for radial clearance.
When the pump is depressurized, thesegmental springs provide the basiccontact pressure for the segments and thesealing roller, and improve the suctioncharacteristics of the oil pump.
They also ensure that the pump pressurecan act between the segments and on thesealing roller.
Crescent SealOuter Segment
Pinion
Ring Gear
46
Modules
The Suction Jet Pump
(Entrainment Pump)
The quantity of oil required to ensuresufficient cooling of the two clutchesexceeds the capacity of the internal gearpump, particularly when pulling away(there is high heat buildup due to slip).
SSP 228/036
View of Suction Jet Pump
(Entrainment Pump)
Pressure Tube(Routed toforward clutch)
Inlet Pipe
Pressure Tube(Routed from hydrauliccontrol moduleto suction jet pump(entrainment pump))
ATF Overflow Pipe
A suction jet pump (entrainment pump) isintegrated in the clutch cooling system tosupply the quantity of oil required forcooling the clutch.The suction jet pump (entrainment pump) ismade of plastic and projects deep into theoil sump.
47
Modules
SSP 228/037
Suction Jet Pump (Entrainment Pump)
(Shown in Profile and Folded Out)
CheckValve
VenturiNozzle
This is how it works:
The suction jet pump (entrainment pump)operates according to the Venturi principle.When the clutch requires cooling, thecooling oil (pressurized oil) supplied by theoil pump is ducted through the suction jetpump (entrainment pump) in the formof a powerful jet. The oil flow through theentrainment pump nozzle results in a partialvacuum which “sucks” oil out of the oilsump and, together with the powerful jet,results in a large, almost depressurizedquantity of oil.
The quantity of cooling oil is almostdoubled as required without additionalpumping capacity.A check valve prevents the suction jetpump (entrainment pump) from running dryand facilitates a quick response of thecooling oil feed.
48
Modules
Electro-Hydraulic Control
A new feature is that theoil pump, hydraulic controlmodule (valve body) andTransmission Control ModuleJ217 are combined as acompact assembly.
Selector Shaft
The hydraulic control module containsthe manual selector valve, nine hydraulicvalves and three electromagnetic pressurecontrol valves.
The hydraulic control module and theTransmission Control Module J217 areconnected electrically by direct plug-incontacts.
SSP 228/063
Oil Pump
ManualSelectorValve
Transmission ControlModule J217
Direct Plug-In Contact
Hydraulic Control Module
49
Modules
The hydraulic control module executes thefollowing functions:
• Forward-reverse clutch control
• Clutch pressure regulation
• Clutch cooling
• Pressurized oil supply to the contactpressure control
• Transmission control
• Supplying the splash oil cover
The hydraulic control module isconnected directly to pulley set 1 andpulley set 2 by “screw inserts.”
The screw inserts are sealed by O-rings.
Screw Inserts for Pulley Set 1
SSP 228/085
Screw Inserts for Pulley Set 2
O-Ring
Oil Injection Hole forSplash Oil Cover
O-Ring
50
Modules
Sectional View of Valve Plate
SSP 228/047
The descriptions of the valves that followrefer to valves not included in the previousmodule/function descriptions:
To protect the component parts, pressure
limiting valve 1 limits the pump pressureto maximum 1189 psi (8 200 kPa).
The pressure control valves aresupplied with a constant pilot controlpressure of 73 psi (500 kPa) by thepilot pressure value.
SSP 228/044
Hydraulic Control Module
(Transmission Control Module J217 Removed)
Connection toAutomaticTransmissionSender -1-for HydraulicPressure G193
ElectricalConnectorfor N88
ElectricalConnectorfor N216
ElectricalConnectorfor N215
PressureLimitingValve 1
Connection toAutomaticTransmissionSender -2-for HydraulicPressure G194
Pressure ControlValve -2- forAutomaticTransmissionN216
SolenoidValve 1N88
PilotPressureValve
PressureControl Valve-1- forAutomaticTransmissionN215
ClutchControlValve
MinimumPressureValve
PressureLimitingValve 1Clutch
CoolingValve
The minimum pressure valve preventsthe oil pump drawing in engine air whenthe engine is started. When pump output ishigh, the minimum pressure valve opensand allows oil to flow from the oil returnpipe to the suction side of the oil pump;this improves efficiency.
51
Modules
The pressurizing valve controls thesystem pressure so that sufficient oilpressure is always available for a particularfunction (application of contact pressureor adjustment).
Solenoid Valve 1 N88, Pressure ControlValve -1- for Automatic Transmission N215,and Pressure Control Valve -2- forAutomatic Transmission N216 are designedas “pressure control valves.”
They convert an electric control current to aproportional, hydraulic control pressure.
The Solenoid Valve 1 N88 controls theclutch cooling valve and the safety valve.Pressure Control Valve -1- for AutomaticTransmission N215 actuates the clutchcontrol valve. Pressure Control Valve -2- forAutomatic Transmission N216 actuates thereduction valve.
Sectional View of Pump Plate
ReductionValve
SSP 228/048
SafetyValve
ManualSelectorValve
VolumetricFlow RateLimiting Valve
PressurizingValve
SSP 228/100
Current in mA
SSP 228/101
Diagram of Pressure Control Valve
Con
trol
Pre
ssur
e in
psi
(kP
a)
Pressure Control Valve
(Proportional Valve)
0 (0)0 1000
73 (500)
52
Modules
Selector Shaft and Parking Lock
A mechanical connection (cable pull) fortransmission of selector lever positions P,R, N and D still exists between the gateselector lever and the transmission.
The following functions are executed viaselector shaft:
• Actuation of the manual selector valve inthe hydraulic control module, i.e.hydromechanical control of vehicleoperating state (forward/reverse/neutral).
• Operating the parking lock.
• Actuation of the multi-functional switchfor electronic recognition of the selectorlever position.
SSP 228/065
Actuation ofthe Outer SelectorMechanism
In selector lever position P, the linkagewith locking teeth is displaced axially sothat the parking lock ratchet is pressedagainst the parking lock gear and theparking lock is engaged.
The parking lock gear is permanentlyconnected to the drive pinion.
Parking Lock Ratchet
Linkage with Locking Teeth
Pulley Set 2
Detent Gate
Drive Pinion
Magnetic Gate
Parking Lock Gear
Manual Selector Valve
Selector Shaft
53
Modules
Transmission Housing Ducting
and Sealing Systems
Sheathed Sealing Ring System
The multitronic® is equipped with a newsheathed sealing ring system.
The sheathed sealing rings seal thepressure cylinder and the variable-displacement cylinder of pulley set 1,the pulley set 2, and the piston forthe forward clutch.
The O-ring presses down and seals thesheathed sealing ring.
The oil pressure present assists thesheathed sealing rings with contactpressure application.
Advantages of the sheathed sealing ringsystem:
• Good anti-friction properties
• Low displacement forces
• Wear is minimized
• Stable at high pressures
SSP 228?062
Double-Corrugated Sealing Ring
O-Ring
SheathedSealing Ring
54
Modules
To save weight, the three-piecetransmission housing is manufacturedfrom the AZ91 HP magnesium alloy.This alloy is highly corrosion resistant,easy to process and has a 17.6 lb (8 kg)weight advantage over a conventionalaluminum alloy. As a special feature,the ATF pressurized oil is not distributedthrough housing ducts as is usual onautomatic transmissions, but almostexclusively by pipes.
Axial sealing elements are used to sealthe pipe connections. The axial sealingelements of the pressure pipes have twosealing lips which apply a higher contactpressure as a result of the oil pressure, andtherefore seal the pipes reliably. Diagonalpipe connections can also be sealedwithout difficulty using this technology (e.g.pressure tube connected to reverse clutch).The oil pump intake fitting axial sealingelement has sealing beads which seal thefitting by contact pressure.
The double-corrugated sealing ring (seepage 53) separates the ATF reservoirfrom the final drive oil reservoir. It preventsthe ATF from entering the final drive andoil from the final drive entering theATF reservoir.
Leaks in the double-corrugated sealing ringbecome visible at the oil return hole.
Groove forDouble-CorrugatedSealing Ring
Inner Section
Pressure Tube Routedto Reverse Clutch
Differential PressureValve 1 withATF Strainer 1
Oil Return Hole
55
Modules
Pressure Tube Routed toSuction Jet Pump (Entrainment Pump)
SSP 228/041
Oil Drain Screw
Suction Jet Pump (Entrainment Pump)
ATF Inspection Plug
Axial Sealing Element
Pressure Tube Routed toForward Clutch
ATF Level
Intake Filter
Return Pipe from ATF Coolerwith Spray Nozzles for Chainand Pulley Sets
56
Modules
Hydraulic Circuit Diagram
23
Pulley Set 1
2 Pulley Set 2
7
3
4 5 19
22
2011
26
28
15
18 6
27
24 9
8 30
1410
13
25
31
1
29
12P R N D
21
16
SSP 228/039
32
17
57
Modules
Hydraulic Circuit Diagram Legend
(Selector Lever Position P
and Engine “OFF”)
1 Pressure Limiting Valve 12 Pressure Limiting Valve 23 Differential Pressure Valve 14 Differential Pressure Valve 25 ATF Filter6 Manual Selector Valve7 ATF Cooler8 Clutch Cooling Valve9 Clutch Control Valve
10 Minimum Pressure Valve11 Measuring Point for Contact
Pressure (Registered by G194)12 Measuring Point for Clutch Pressure
(Registered by G193)13 Solenoid Valve 1 N88
(Clutch Cooling/Safety Shut-Off)14 Pressure Control Valve -1- for
Automatic Transmission N215 (Clutch)15 Pressure Control Valve -2- for
Automatic Transmission N216 (Ratio)16 Oil Pump17 Selector Lever Position PRND18 Reverse Clutch19 ATF Strainer 120 ATF Strainer 221 ATF Strainer 322 Four Spray Holes for Pulley Set
Lubrication/Cooling23 ATF Intake Filter24 Safety Valve25 Suction Jet Pump (Entrainment Pump)26 Reduction Valve27 Forward Clutch28 Volumetric Flow Rate Limiting Valve29 Pressurizing Valve30 Pilot Pressure Value31 To Splash Oil Cover32 To the Clutches
Differential Pressure Valve 1and ATF Strainer 1
SSP 228/071
Pressure Limiting Valve 2 inthe Transmission Housing
Return Pipe fromATF Cooler
In the Oil Sump
Hydraulic Control Module
Peripheral Components inthe Vehicle
58
Modules
ATF Cooling
The ATF coming from pulley set 1 initiallypasses through the ATF cooler. The ATFflows through the ATF filter before it isreturned to the hydraulic control module.
The ATF cooler is integrated in the radiator.Heat is exchanged with the coolant inthe engine cooling circuit (oil-coolantheat exchanger).
The differential pressure valve 1 protectsthe ATF cooler against excessively highpressures (ATF cold). When the ATFis cold, a large pressure differencedevelops between the supply line and thereturn line. When a specific pressuredifferential is reached, the differentialpressure valve 1 opens and the supply line
is short-circuited with the return line tobypass the ATF cooler. This also causesthe temperature of the ATF to rise tonormal operating temperature rapidly.
The differential pressure valve 2 openswhen the flow resistance of the ATF filter istoo high (e.g. filter blockage). This preventsthe differential pressure valve 1 fromopening and the ATF cooling system frombeing disabled by the backpressure.
If the ATF cooler is leaky, coolantcan enter the ATF. Even smallquantities of coolant in the ATFcan have an adverse effect onclutch control.
SSP 228/090
Peripheral Components in the Vehicle
To HydraulicControl Module
ATF Filter
multitronic®
PressureLimitingValve 2
Supply Line
ATF Cooler
ATF FilterReturn LineDifferential
PressureValve 2
ATF Strainer 1
DifferentialPressureValve 1
FromPulleySet 1
Supply Line
Return Line
Recommended