A Detailed Overview
System Overview
^ Transmission range switch (245)
^ Main instrument unit (540)
^ Engine control module (655/589/595)
^ SID (541)
^ Control module, TCM (502)
^ Switch, WINTER (506)
^ Switch, SPORT (537)
^ Output shaft speed sensor (533)
^ Input shaft speed sensor (532)
^ Transmission fluid temperature sensor (535)
^ Control module, TWICE (632)
^ Solenoid for Lock-up SLU (531)
^ Solenoid for gear changing S1 (531)
^ Solenoid for gear changing S2 (531)
^ Solenoid for gear changing S3 (531)
^ Solenoid for gear changing S4 (531)
^ Solenoid for gear changing S5 (531)
^ Solenoid for system pressure SLT (531)
^ Solenoid for clutch pressure SLS (531)
^ Buttons for manual gear selection (633)
Sentronic
Function Chain
SID feeds the steering wheel controls with +5V via pin 22 and grounds though pin 9. The 9 steering wheel control switches comprise 9 resistors connected in series. Pressing the button will ground the associated contact. Depending on which switch is pressed the aggregate resistance in the circuit is changed and thereby the voltage which SID senses. SID receives information from SWC on the gear selected by the driver in position M. This information is forwarded from SID pin 10 to TCM pin 8 (A) by means of SID sending out specific voltage values as per below:
1. Hold Gear, Voltage between 0.5V - 1.4V
2. Shift Gear -UP, (+) Voltage between 1.4V - 1.79V
3. Shift Gear -Down, (-) Voltage between 2.7V - 3.5V
When the ignition is on SID continuously sends a voltage between 0.5 - 1.4V corresponding to Hold Gear. If the driver presses Shift Gear-Up (+) or Shift Gear -Down (-) the voltage is raised to between 1.4V - 1.79V (+) or 2.7V - 3.5V (-) during the time the button is pressed down. When the driver releases the button SID returns to sending out between 0.5V - 1.4V i.e. the Hold Gear function. The driver must press the + or - buttons for more than 20 msec before shifting can take place. TCM ignores the signals if position M is not selected with the selector lever.
Gearbox
The automatic transmission has 4 planetary gears with accompanying clutches, brakes, and freewheel. It has two shafts (primary and secondary shafts). Two of the 4 planetary gears, PI and P2, are located on the primary shaft.
The P3 and P4 planetary gears are located on the secondary shaft.
The power from the primary shaft is transmitted to the secondary shaft via two intermediate gears. From the secondary shaft the power is then transmitted to the final drive via two final drive pinions, one driving and one driven.
The transmission has 5 forward gears and one reverse.
A certain amount of slipping normally occurs in the torque converter. The amount of slip is proportional to the torque amplification which it produces. In order to reduce fuel consumption a Lock-up clutch is used in the 3rd, 4th, and 5th gears (on the V6 petrol only in the 4th and 5th gears). This clutch is located in the torque converter and when it is engaged there is a direct drive through the torque converter.
In order to effectively use the engine torque a certain amount of slipping is allowed in the Lock-up clutch. This function has the purpose of saving fuel and operates in the manner that when the torque demand is moderate (small throttle opening), the Lock-up clutch slips within a certain speed range (50 - 200 rpm). This means that a change down to a lower gear is avoided.
Neutral Control
In vehicles fitted with the 2.2L diesel engine and an automatic transmission there is a transmission function called Neutral Control (NC).
On condition that the Footbrake is depressed and the vehicle is stationary, clutch C1 is disengaged. This means that the drive to the transmission is disconnected so that the car is not driven forward, even though the Drive position is selected. This function reduces fuel consumption, by reducing the torque demand on the engine, and also reduces vibrations and noise.
Planetary Gear, Animation
Function
To obtain the different gear ratios, the component parts of the planetary gears, such as the sun wheel, planet wheel, ring wheel and planet carrier are locked or released respectively. The friction elements for this are all disc type except for brake B4 which is band type. As there are four different planetary gears, it is possible to obtain a wide range of different ratios.
Planetary Gear
Animation
Press "P" to brake the planet carrier, "S" to brake the sun gear and "R" the ring gear. "S+P" will stop the sun gear and the planet gear. Observe the power flow. Pay attention to the direction of rotation with the help of the markings.