Function requirements for transmission control
Circuit 15 ON
Transmission control
The transmission control system electronically actuates the control solenoid valves. The control solenoid valves are located in the hydraulic valve body assembly. This provides the hydraulic functionality and is part of the fully integrated transmission control (VGS) electric controller unit (N15/11).
The function of the fully integrated transmission control (VGS) control unit (N15/11n4) basically consists of the evaluation of various input signals relevant to the function of the transmission. Based on this, eight electromechanical control solenoid valves are actuated that then determine the gear selection, the working pressure and the torque converter lockup.
The fully integrated transmission control (VGS) control unit, the intelligent servo module (ISM) for DIRECT SELECT control unit (A80) and the CDI control unit (N3/33) (with engine 651) or the ME-SFI control unit (N3/34) (with engine 274) read in the status of circuit 15. This is transmitted by the electronic ignition lock (EZS) control unit (N73) via the chassis CAN, the CDI control unit or the ME-SFI control unit and the drive train CAN.
Using the DIRECT SELECT selector lever (S16/13), the status of which is sent by the steering column tube module control unit (N80) via the chassis CAN, the CDI control unit or ME-SFI control unit and the drive train CAN to the fully integrated transmission control (VGS) control unit and the intelligent servo module (ISM) for DIRECT SELECT control unit, the driver can engage the desired 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 torque converter and automatic transmission.
The intelligent servo module (ISM) for DIRECT SELECT control unit sends the status of the range selection position via the drive train CAN to the CDI control unit or the ME-SFI control unit and to the fully integrated transmission control (VGS) control unit.
The drive authorization system enable signal is sent by the electronic ignition lock (EZS) control unit via the chassis CAN, the CDI control unit or ME-SFI control unit and the drive train CAN to the fully integrated transmission control (VGS) control unit and to the intelligent servo module (ISM) for DIRECT SELECT control unit.
The following control solenoid valves are actuated by the fully integrated transmission control (VGS) control unit:
Working pressure control solenoid valve (N15/11y1)
K1 clutch control solenoid valve (N15/11y2)
K2 clutch control solenoid valve (N15/11y3)
K3 clutch control solenoid valve (N15/11y4)
B1 multidisk brake control solenoid valve (N15/11y5)
B2 multidisk brake control solenoid valve (N15/11y6)
B3 multidisk brake control solenoid valve (N15/11y7)
Torque converter lockup clutch control solenoid valve (N15/11y8)
The signals of the following components are processed by the fully integrated transmission control (VGS) control unit:
Turbine wheel rpm sensor (N15/11n1)
Rpm sensor for internal input speed (N15/11n2)
Output shaft rpm sensor (N15/11n3)
Selection range sensor (N15/11s1)
Transmission oil temperature sensor (N15/11s2)
Transmission control function sequence
The function sequence is described in the following steps:
Function sequence for transmission mode
Function sequence for electronic and hydraulic transmission control
Function sequence for kickdown
Function sequence for limp-home mode
Function sequence for transmission mode
The transmission mode includes upshift and downshift characteristics for all 7 gears, designed for:
Empty vehicle
Operating temperature
Smooth road
Sea level
Transmission 722.9 in model 447.6/7
The transmission mode can be influenced by the driver using the transmission mode button (N72/1s6), which is located in the upper control panel (UCP) control unit (N72/1). The status is sent via the upper control panel (UCP) control unit, the battery sensor LIN (LIN B15), the signal acquisition and actuation module (SAM) control unit (N10/1), the interior CAN (CAN B), the electronic ignition lock (EZS) control unit (N73) and the chassis CAN to the CDI control unit or ME-SFI control unit. The CDI control unit or ME-SFI control unit sends the status via the drive train CAN to the fully integrated transmission control (VGS) control unit.
Transmission 722.9 in model 447.8
The transmission mode can be influenced by the driver using the AGILITY SELECT switch (A40/1s1), which is located in the area of the center console. The status is sent via the left lower control panel (LCPL) control unit (A40/1), the telephone keypad LIN (LIN A2), the central operating unit (COU) control unit (A40), the telematics CAN (CAN A), the radio (Audio/COMAND) (N87/6), the user interface CAN (CAN HMI), the gateway for the user interface CAN (N93/4) and the chassis CAN to the CDI control unit. The CDI control unit transmits the status via the drive train CAN to the fully integrated transmission control (VGS) control unit.
The transmission mode is adapted by offsetting the characteristics depending on the following factors:
Load condition of vehicle
Change in driving resistance
Accelerator pedal movement
Trailer detected
With code Q22 (Trailer hitch, non-removable ball head) or with code Q50 (Trailer hitch, removable ball head)
The status of the trailer recognition is transmitted by the trailer recognition (AAG) control unit (N28/1) via the interior CAN (CAN B), the electronic ignition lock (EZS) control unit, the chassis CAN, the CDI control unit or ME-SFI control unit and the drive train CAN to the fully integrated transmission control (VGS) control unit.
The fully integrated transmission control (VGS) control unit shifts depending on the following factors:
Vehicle speed
Selector lever position
Accelerator pedal position
Transmission mode selection
The Electronic Stability Program (ESP) control unit (N30/4) receives the signals from the left front rpm sensor (L6/1), the right front rpm sensor (L6/2), the left rear rpm sensor (L6/3) and the right rear rpm sensor (L6/4) and forwards these via the chassis CAN, the CDI control unit or ME-SFI control unit and the drive train CAN to the fully integrated transmission control (VGS) control unit.
The signals for the selector lever position and the transmission mode selection are sent by the fully integrated transmission control (VGS) control unit via the drive train CAN to the CDI control unit or ME-SFI control unit. This generates the request and transmits it via the chassis CAN to the instrument cluster (IC) control unit (A1/1); in model 447.8 with the interface between the gateway for the user interface CAN and the user interface CAN.
The instrument cluster (IC) control unit implements the request and actuates the multifunction display (A1/1p13).
The accelerator pedal position is transmitted by the accelerator pedal module (B37/4) to the CDI control unit or ME-SFI control unit. This transmits the status via the drive train CAN to the fully integrated transmission control (VGS) control unit.
Function sequence for electronic and hydraulic transmission control
Whilst the electronic transmission control is responsible for gear selection and for adjusting the pressures, the power is controlled via the hydraulic elements. The oil supply for the hydraulic elements, such as the hydrodynamic torque converter, the shift elements and the hydraulic transmission control, is provided by an oil pump (primary pump) connected to the torque converter and through the electric auxiliary oil pump (M42). 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 transmission control system prevents any impermissible high engine speeds with a downshift lockout device. Furthermore, the transmission control system offers the advantage of a flexible adaptation to various vehicle and engine versions.
The electrical auxiliary oil pump ensures oil supply to the hydraulic system when the engine is switched off. It also supports the primary pump during coast down shifting in hot idling. It is actuated via the transmission oil auxiliary oil pump control unit (N89), which receives the signal from the CDI control unit or ME-SFI control unit via the drive train CAN from the fully integrated transmission control (VGS) control unit. The transmission oil auxiliary pump control unit sends the status of the electric auxiliary oil pump to the fully integrated transmission control (VGS) control unit via the drive train CAN. This routes the signal for the electric auxiliary oil pump and the status of the transmission control to the CDI control unit or to the ME-SFI control unit .
Function sequence for kickdown
The kickdown function is activated as of a pedal travel > 90 %.
The "kickdown" signal is transmitted from the accelerator pedal module (B37/4) to the CDI control unit or ME-SFI control unit. This transmits the status via the drive train CAN to the fully integrated transmission control (VGS) control unit.
Based on this information, the fully integrated transmission control (VGS) control unit actuates the control solenoid valves so that the gearchanges occur at a higher engine speed.
Function sequence for limp-home mode
If the signals are implausible, the transmission control system is only partially operational and switches to the emergency performance map.
Up to 16 faults can be stored simultaneously in the fault memory. These can be read out using Xentry Diagnostics. The diagnostic connector (X11) receives the status of the transmission control diagnosis from the fully integrated transmission control (VGS) control unit via the drive train CAN, the CDI control unit or ME-SFI control unit, the chassis CAN, the electronic ignition lock (EZS) control unit and the diagnostic CAN (CAN D).
Referenced documents
- gf2710s9992tra Overview of system components of automatic transmission (AT)