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Transmission description
w5 speed automated manual transmission (AMT 2)
T he new smart fortwo is fitted with the newly devel oped 2nd generation 5 speed automated manual transmission (AMT 2). This transmission is derived from the 5 speed manual transmission of the smart forfour. Advantages of the automated transmission: • Greater comfort • Reduced fuel consumption • Less noise New features compared with the 6 speed manual transmission (AMT 1) of model series 450 with single drum control are: • 5 speed transmission • Two drum control • Potentiometer free position sensor system The standard AMT 2 is shifted manually by means of the softip operating mode. A second variant with softouch automatic function is available as special equipment.
P26.10-2157-00
5 speed manual transmission (AMT 2)
Introduction of the smart fortwo, Model Series 451
– This printout will not be recorded by the update service. Status: 03 / 2007 –
53
Automated manual transmission
Automated manual transmission
Transmission data and operation
ATM 2 in model 451
Unit Transmission model Number of forward/reverse gears Max. torque Clutch Overall length (including 75 mm for clutch) Housing material Weight (without oil charge) Oil charge (permanent charge) Housing kg l mm Nm G
33 kW diesel
Gasoline natu rally aspirated 717.48 5/1 120 Single plate dry clutch 364 Aluminum alloy approx. 34 1.7
Gasoline turbocharged
Two piece with bell housing
Control possibilities
The selector lever module on the center console is pressed forward to shift up and pulled back to shift down. When the lever is pushed to the right, the transmission is in neutral. Pulling the selector lever back from the neutral position engages reverse gear. softip The driver indicates that he wishes to change gear by operating the electronic selector lever module control unit. The sensor system in the gear selector lever is designed to detect the failure of a Hall sensor and therefore prevent any uncommanded shift operation from being initiated. softouch The driver operates a button on the electronic selector lever module control unit (Sedrive unit). The automated manual transmission control unit then evaluates the current vehicle speed, taking into account the current accelerator pedal position, and initiates the upshift, downshift or kickdown function with no further action on the part of the driver. Steering wheel gearshift In addition to the softip and softouch control options, it is possible to order a steering wheel with paddle shifts as special equipment for the passion (standard on the pulse).
54
Introduction of the smart fortwo, Model Series 451
– This printout will not be recorded by the update service. Status: 03 / 2007 –
Mechanical components
Shift mechanism
The central components of the gearshift system are two selector drums for moving the shift forks. Each selector drum is driven by a separate electric motor via two sintered spur gear sets. One selector drum shifts the odd gears, while the other shifts the even gears and reverse gear. The position of the selector drum, and thus the current shift position, is determined by two incre mental sensors in each electric motor. Both electric motors and the spur gears are located in a common aluminum housing, the actuator unit, which is mounted on the transmission. The two selector drums are arranged to allow over lapping shift operations to minimize shift times. It is possible to skip gears (e.g. double downshifts).
P26.10-2158-00
1 Housing 2 Selector drum 3 Shift fork
4 M18
Shift actuator Clutch motor
Introduction of the smart fortwo, Model Series 451
– This printout will not be recorded by the update service. Status: 03 / 2007 –
55
Automated manual transmission
Automated manual transmission
Transmission control
P26.19-2123-00
Data flow chart of transmission control
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 A1
Circuit status Shift request Transmission speed Clutch request Clutch motor status Gearchange request Transmission motor status Engine speed Backup light actuation Vehicle speed Shift program selection Accelerator pedal position Brake pedal status Door status Engaged gear Gear indicator actuation Instrument cluster
A45 E4e3 L2 M17/3 M17/4 M18 N3/9 N3/10 N10/10 N15/5 N15/6 N47 5 S112s1 S112s2 CAN
Fanfare horns and airbag clock spring contact Right backup light Transmission rpm sensor Transmission motor 1 Transmission motor 2 Clutch motor CDI control unit (diesel engine) ME SFI [ME] control unit (gasoline engine) SAM control unit Electronic selector lever module control unit Automated manual transmission control unit ESP control unit Steering wheel gear shifter PLUS Steering wheel gear shifter MINUS Controller Area Network (data bus/CAN bus)
56
Introduction of the smart fortwo, Model Series 451
– This printout will not be recorded by the update service. Status: 03 / 2007 –
Transmission control
Task and function
The transmission control converts the driver's shift requests into corresponding control signals to the clutch and the automated transmission. This is done by relaying the shift signal about the shift request at the electronic selector lever module control unit over a direct line to the automated manual transmission control unit. The automated manual transmission control unit checks the plausibility of the shift request in rela tion to the vehicle speed, the load (accelerator pedal position) and the engine speed. i Note When reverse gear is requested, the backup light is actuated directly by the electronic selector lever module control unit. If the plausibility check is passed, the automated manual transmission control unit sends the signal to initiate the selected shift operation to the two actu ator motors for the two selector drums and to the clutch motor to open or close the clutch.
Introduction of the smart fortwo, Model Series 451
– This printout will not be recorded by the update service. Status: 03 / 2007 –
57
Automated manual transmission
Automated manual transmission
Clutch
Single plate dry clutch
Model 451 is equipped with a single plate dry clutch for gasoline engines as well as diesel engines. In contrast to the modular clutch in the predecessor model 450, which consisted of a flywheel and clutch, these components are now installed separately. An internal computer in the automated manual trans mission control unit evaluates the clutch load. If a threshold value is exceeded, the clutch starts to pulse as an overload warning to the driver. If the overloading continues, e.g. if the car is being held with the clutch on a gradient, the clutch is closed in order to provoke a stall.
P25.00-2010-00
Single plate dry clutch
58
Introduction of the smart fortwo, Model Series 451
– This printout will not be recorded by the update service. Status: 03 / 2007 –
Clutch
Clutch motor General
All versions of model 451 are fitted with an auto mated manual transmission. This means that a single plate dry clutch is installed instead of the torque converter that is usual with conventional automatic transmissions. The single plate dry clutch is actuated by the clutch motor.
Function
When the automated manual transmission control unit issues a request for a gearchange, the clutch motor is actuated at the same time. The electric motor integrated in the clutch motor operates the clutch via the actuating plunger. The power flow is interrupted and the shift operation can be performed.
P25.19-2010-00
1 Electric motor 2 Electric motor connector 3 Actuating plunger
M18
Clutch motor
Introduction of the smart fortwo, Model Series 451
– This printout will not be recorded by the update service. Status: 03 / 2007 –
59
Automated manual transmission