Steering Column Switch (SZL) and Multifunction Steering Wheel (MFL) (SZL Steering Column Switch Center 2)

Steering Column Switch (SZL) And Multifunction Steering Wheel (MFL)

The functions of the steering column switch can be subdivided into two main blocks:
- Steering column switch cluster as switching center for the control functions at the steering column
- Steering column switch center as steering-angle sensor.

Furthermore, the signals are forwarded to the priming caps to activate the driver's airbag stages 1 and 2 by the steering column switch.

The multifunction steering wheel provides the means by which the driver can easily and ergonomically perform the following functions:
- audio, telephone, fanfare (horn) and a definable button -> via the function buttons of the multifunction steering wheel
- direction indicators / high beam headlights, windshield wiper, cruise control, -> via the control levers on the steering column

Brief description of components
The multifunction steering wheel consists of:
- Steering-column levers: All steering-column levers are one-touch levers and do not lock in the operated position
- Horn switch,
- 2 blocks with function keys.

Located below the multifunction steering wheel are
- a button for the steering column setting
- the steering column switch cluster control module with integral steering angle sensor

The signal transfer from the steering wheel to the steering column electronics (control module for steering column switch) is ensured by a coil spring conductor.

Steering column stalk, top left: Turn indicator-low beam switch
The turn indicator-low beam switch consists of
- a steering-column lever
- two one-touch buttons.

The turn signal/dip switch also incorporates two axial touch switches.
- The top button activates the Info display on the right of instrument cluster below the tachometer.
- The bottom button activates the Info Display on the left of instrument cluster below the speedometer.

Transfer concept: steering column stalks and axial touch buttons have differing signal transmission routes:

Steering column stalk signal transmission route: When the driver operates the steering column lever, a message is sent to the light module.

Signal path: steering column switch -> data bus CAN -> Body Gateway Module -> data bus K-CAN -> light module.

For safety reasons, there is an additional serial cable from the steering column switch cluster to the light module. An analog coded signal is applied to that cable and is analyzed by the light module. Each switch position is allocated a voltage range. The serial cable enables transmission of all positions of the turn signal/dip switch in the event of a bus fault, though with some limitations to the possible functions:
- High beam and headlamp flasher only function if the steering column stalk is held in position.
- The direction indicators only function while the steering column stalk is held in position, no continuous flashing, no automatic reset
- No hazard-warning lights in the event of a crash and when arming the antitheft alarm.

Touch button signal transmission path: When the driver operates one of the axial touch buttons, a message is sent to the instrument cluster.

Signal path: steering column switch -> data bus CAN -> Body Gateway Module -> data bus K-CAN -> instrument cluster.

Steering-column lever, bottom left: vehicle speed control
The lever for the cruise-control system consists of
- a steering-column lever
- a one-touch button
- a knurled wheel (only ACC).

Transfer concept: When the driver operates the steering-column lever or the axial one-touch button, a message is sent to the digital engine electronics.

Signal path: steering column switch -> data bus PT CAN -> Digital Engine Electronics.

Transfer concept: When the driver operates the knurled wheel, a message is sent to the Active Cruise Control (ACC) control module.

Signal path: steering column switch -> data bus PT CAN -> Active Cruise Control (ACC).

Steering column stalk, bottom right: Wiper switch
The wiper switch consists of:
- a steering-column lever
- a one-touch button
- a knurled wheel.

Transfer concept: When the driver operates the steering column lever, a message is sent to the body base module.

When the driver operates the axial button or the adjuster wheel,
- on a vehicle without rain/light sensor, a message is sent to the body base module.
- on a vehicle with rain/light sensor, a message is sent to the rain/light control module.

Signal path: steering column switch -> data bus PT CAN -> Body Gateway Module -> data bus K-CAN -> body base module and/or rain/driving light sensor.

Function button block on the left and right of the multifunction steering wheel
The function buttons enable selection of
- Voice input
- Free definition of function (e.g. recirculated air mode)
- Audio functions (radio, telephone, etc.)

Switch for steering column adjustment
The steering wheel position is adjusted electrically by means of a switch. The switch has four possible directions of movement. These enable the steering wheel to be moved up, down, forwards or backwards.

Transfer concept: When the driver operates the switch for steering column adjustment, a message is sent to the center console switching center.

Signal path: steering column switch -> data bus PT CAN -> Body-Gateway Module -> data bus K-CAN -> center console switching center

Fanfare (horn)
The fanfare horns serve both as a warning signal and as redundant-system audible alarms of the vehicle.

The directly read horn switch signal is sent as a valid status via the steering wheel module and the coil spring conductor to the steering column switch SZL. The steering column switching center can control the high-tone and low-tone horns separately.

Steering wheel heater
The steering wheel heating system consists of
- a button for switching the steering wheel heater on and off
- Function display in the steering-wheel-heating button: the LED in the button lights up when the steering wheel heating is switched on.
- Heating mat in the steering wheel rim: a heating mat heats up the steering wheel rim.
- Temperature sensor: a temperature sensor in the steering wheel rim sends the temperature signal back to the steering column switch.

The steering column switch activates the heater mat as required in order to ensure even heating of the steering wheel.