GF27.60-P-2002AHV Transmission Control, Function
GF27.60-P-2002AHV Transmission Control, Function
- TRANSMISSION 722.930 in MODEL 204.0 /2 /3
Function requirements for transmission control, general
^ Status "Circuit 87 ON"
^ Function test of fully integrated transmission control unit (Y3/8n4) carried out
Transmission control, general
The transmission control actuates the following actuators electronically:
- Working pressure control solenoid valve (Y3/8y1)
- Clutch control solenoid valve K1 (Y3/8y2)
- Clutch control solenoid valve K2 (Y3/8y3)
- Clutch control solenoid valve K3 (Y3/8y4)
- Multidisk brake control solenoid valve B1 (Y3/8y5)
- Multidisk brake control solenoid valve B2 (Y3/8y6)
- Multidisk brake control solenoid valve B3 (Y3/8y7)
- Wet clutch control solenoid valve (Y3/8y9)
The solenoid valves are positioned on the fully integrated transmission control controller unit. This then realizes the hydraulic functionality.
The function of the fully integrated transmission control unit consists of the evaluation of various input signals (relevant for the transmission function). Based on this, 8 electromechanical hydraulic valves are actuated which determine the gear ratio of the transmission (gear selection), the working pressure and the wet clutch.
Transmission control function sequence
The function sequence is subdivided into the following steps:
^ Function sequence for basic shift program
^ Function sequence for electronic and hydraulic transmission control
^ Function sequence for kickdown
^ Function sequence for limp-home mode
Function sequence for basic shift program
The basic shift program includes upshift and downshift characteristics for all 7 gears, designed for:
- Empty vehicle
- Warm operating condition
- Smooth road
- Sea level
The basic shift program can be influenced by the driver using the transmission mode rotary switch (S192). The information from the transmission mode rotary switch is recorded by the transmission mode control unit (N145) over the AMG DRIVE UNIT-LIN (LIN B11).
The transmission mode control unit routes the signal over the drive train CAN (CAN C) and on to the fully integrated transmission control unit (Y3/8n4).
The shift programs are adapted by offsetting the characteristics depending on:
- Load condition of vehicle
- Change in driving resistance
- Accelerator pedal movement
The fully integrated transmission control unit monitors and shifts depending on:
- Vehicle speed
- Drive position
- Accelerator pedal position
- Transmission mode selection
- Engaged gear, with Manual "M" transmission mode
- Signals on the drive train CAN or forwarded signals from the chassis CAN (CAN E)
Slow accelerator release
- Undesired downshifts in the upper vehicle speed range are prevented
Rapid accelerator release:
- Upshifting to next gear is prevented and only permitted again when the vehicle accelerates more slowly
Function sequence for electronic and hydraulic transmission control
While the electronic transmission control is responsible for gear selection and for matching pressures to the torque to be transmitted, the power supply control of the transmission occurs via hydraulic elements of the fully integrated transmission control controller unit.
Oil is supplied to the hydraulic elements (wet clutch, actuators, hydraulic transmission control) via an oil pump connected to the wet clutch.
The transmission control system makes possible a precise adaptation of pressures to the respective operating states and to the engine output during the gearshift phase, resulting in a significant improvement in shift quality. It is possible to reach the engine rpm limit in the individual gears using full throttle and kickdown. The shift range can be changed while driving in the forward gears. The transmission control system prevents impermissibly high engine speeds with a downshift lockout device.
Furthermore, the transmission control offers the advantage of flexible adaptation to various vehicle versions.
A lubricating oil volume flows through the housing of the wet clutch
The lubrication oil volume flow and a special geometry of the clutch linings ensure optimum cooling of the wet clutch.
Function sequence for kickdown
The driver's wish for maximum acceleration is met by the kickdown function.
The kickdown function is activated as of a pedal travel > 90 %.
The "Kick-down" signal is sent to the fully integrated transmission control control unit by the ME-SFI [ME] control unit (N3/10) over the drive CAN.
Based on this information the fully integrated transmission control unit actuates the control solenoid valves so that upshifts and downshifts take place at an increased engine speed in order to achieve maximum performance
The forced downshift into the next lower gear is performed when transmission temperatures are too high and lower Vehicle speed.
Function sequence for limp-home mode
If the signals are implausible, the transmission control system is only partially operational and switches to the programmed emergency performance map.
The fault is stored with the assigned fault code in the fault memory. A fault signal is sent over the drive train CAN to the ME-SFI [ME] control unit and forwarded over the chassis CAN to the instrument cluster (A1). The instrument cluster actuates the engine diagnosis indicator lamp (A1e58).
The electronic selector lever module control unit (N15/5) can be used by the driver to engage the required gear ranges "P, R, N, D".
The driver can choose been forward and reverse travel, engage the park pawl or, when in neutral, interrupt the power flow between the wet clutch and the transmission.
