Sensotronic Brake Control (SBC) 327 HO 09 SBC (WJB) 03-05-04 R230 and W211: Starting MY2003 1
Objectives 1. 2. 3. 4. 5. 6. 7. 8. 9.
Contents Advantages of SBC Driving with SBC SBC components Brake operating unit (BOU) Traction system hydraulic unit Three pressure stages Temperature Compensation Deactivation System activation Bleeding the system 5 8 13 17 27 32 38 39 42 49 3
SBC Incorporates these Functions: ABS (Anti lock Brakes 1984) + ASR (Automatic Slip Regulation 1991) + ETS (Electronic Traction System 1995) + ESP (Electronic Stability Program 1996) + BAS (Brake Assist System 1998) 4
Advantages of SBC • Improves metering of required brake pressure – each wheel can be precisely controlled • Improved BAS function – monitors release of accelerator pedal and application of brake – maximum pressure available immediately – pre-filling of system (overcoming play) – when the BAS function is anticipated, slight pressure is applied 5
Advantages of SBC • Electronic Brake Proportioning: EBP – allows brake proportioning front to back and side to side • No pedal vibration during ABS operation – eliminates “distraction” to the driver during critical moments – indicator light in instrument cluster signals traction loss • Improved driving dynamics: ABS, ASR, and ESP – faster response to brake request inputs 6
Advantages of SBC • Pressure reduction at standstill – reduces stress on components • Dry braking function – wiper input via CAN – ~every 7 to 14 minutes – brake actuation changes time interval 7
Driving with SBC - Wake-Up SBC is functional as soon as it is “wakened” by: • opening a door (via CAN) • operating the central locking system (via CAN) • depressing the brake pedal • turning key to position 1 • operating parking brake •The Wake-Up may be followed by a Pre-Drive self Check performed by SBC 8
Driving with SBC – Pre-Drive Check (PDC) When SBC performs a PDC after a "wake-up", the following are checked: Warning! Pressure is applied to brake calipers (~60 bar) • reservoir pressure (if low, it will be corrected by running the high pressure charge pump in the hydraulic unit) • pressure sensors • control valves • leak tests • operational checks Note: self-tests are constantly conducted during driving (~ once every 16 brake applications) 9
Driving with SBC – Delayed Off Function Time that SBC remains operational after use: • with vehicle stationary and was locked = 20 seconds • with vehicle stationary and ignition in “0”, brake pedal not operated = 2 minutes • with vehicle stationary, ignition in “0”, brake pedal operated in delayed off phase and released again = 4 minutes 10
Warning Display Complete ESP control module failure Instrument cluster will scroll through failure displays 11
Warning Display SBC control module failure Certain faults will trigger audible signal 12
SBC Components • Brake Operating Unit (BOU) • Wheel speed sensors • Traction System Hydraulic Unit (A7/3) 13
W211 System Overview Circuit 30 Brake lights Rear SAM (N10/2) Circuit 87 SBC Circuit 31 Wheel speed sensors L6/1, L6/2, L6/3, L6/4 SBC control module (A7/3n1) CAN Wheel speeds Wake up Brake lights Stop lamp switch (S9/1) SBC pedal travel sensor (B37/1) Speed status Diagnostics ESP control module (N47/5) Front SAM (N10/1) Diagnostic connector (X11/4) 14
R230 System Overview Circuit 30 Brake lights Circuit 87 Circuit 31 Wheel speed sensors L6/1, L6/2, L6/3, L6/4 Stop lamp switch (S9/1) SBC pedal travel sensor (B37/1) SBC control module (A7/3n1) Rear SAM (N10/8) Diagnostic connector (X11/4) SBC CAN Wheel speeds Wake up Brake lights Speed status ESP control module (N47/5) Passenger side SAM (N10/11) 15
X11/4 Diagnosis Connection R230 W211 A7/3n1 SBC A7/3n1 SBC X11/4 N47/5 ESP X11/4 N10/1 L.F.
Brake Operating Unit - (BOU) 17
Brake Operating Unit The Brake Operating Unit (BOU) consists of the following: • Brake fluid reservoir (Do not overfill!) • SBC pedal value sensor • Tandem master cylinder • Brake pressure simulator (Note: no vacuum booster) 18
Master Cylinder • Fluid level sensor • Fluid return line • Do not overfill • Hydraulic lines to SBC • Supply hose to SBC 19
Fluid Reservoir Cover • Ultraviolet protection (211 only) 20
Pedal Value Sensor - (B37/1) • Contains two hall effect sensors • Converts pedal travel value to an electrical signal • Provides input to SBC control module A7/3 21
BOU Tandem Master Cylinder Fluid reservoir Fill valves Primary piston Floating piston y2 y1 A7/3 - Traction system hydraulic unit with separation valves y1 and y2 A7/3 Brake pressure simulator 22 GF42.
Normal Braking - Light Pressure • Driver applies pressure to the brake pedal • Fill valves close • Pedal travel sensor sends a signal to A7/3 • y1 and y2 energized, preventing fluid movement externally y2 y1 A7/3 • Floating piston allows fluid to enter simulator, compressing the light spring, providing pedal feel to the driver 23 GF42.
Normal Braking - Increased Pressure y2 y1 A7/3 • Increasing pedal travel causes the larger spring to compress, providing harder pedal feel 24
Normal Braking - Strongest Feedback • Further pedal travel y2 y1 A7/3 causes piston to compress rubber bumper, providing greatly increased pedal pressure 25
Emergency Operation • All electrical functions canceled • Hydraulic pressure created with NO power assist • Pressure directed through A7/3 y1 and y2 to .... Left Front and Right Front calipers only! y2 y1 Left front A7/3 Right front 26 GF42.46-P-4200-03SL GF42.
Traction System Hydraulic Unit (A7/3) Consists of: • SBC control module (A7/3n1) • High pressure charge pump (A7/3m1) • Pressure reservoir 27
Traction System Hydraulic Unit A7/3 28 GF42.
Legend 1 2 3 7 8 A7/3 A7/3b1 A7/3b2 A7/3b3 A7/3b4 A7/3b5 A7/3b6 A7/3m1 Brake Operating Unit Brake pressure simulator Pressure reservoir Left front media separator (dividing piston) Right front media separators (dividing piston) Traction system hydraulic unit Front axle pre-pressure sensor Reservoir pressure sensor Left front pressure sensor Right front pressure sensor Left rear pressure sensor Right rear pressure sensor High-pressure charge pump A7/3y1 A7/3y2 A7/3y3 A7/3y4 A7/3y6 A7/3y7 A7/3y8 A7/3y9 A7/3
Emergency Operation Circuit • Pressure applied directly to front calipers • y1 and y2 not energized • b1, b3, and b4 pressure sensors may provide information to SBC control module • Media separator/Dividing piston 7 and 8 isolate emergency circuit from normal circuit 30 GF42.
Brake Pressure Supply • pressure reservoir charged to 160 bar • the high pressure charge pump runs as needed • pressure blocked by y6, y8, y10, y12 31 GF 42.50-P-4000-04S GF42.
Three Pressure Stages Same pressure stages as used with ABS functions: • Pressure apply • Pressure hold • Pressure release 32
Pressure Apply - Rear Wheels Brake pedal pressure Reservoir pressure • Brake pedal depressed • B37/1 and b1 report brake application to control module • y1 and y2 energized • y10 and y12 intake control valves energized • Pressure at each rear wheel monitored by b5 and b6 • Balance valve y4 not energized GF42.50-P-4000-04S33 GF42.46-P-1000SL GF42.
Pressure Apply - Front Wheels Brake pedal pressure Reservoir pressure • y6 and y8 energized • pressure applied to left and right dividing pistons 7 and 8 • 7 and 8 apply pressure to caliper • pressure at each wheel monitored by b3 and b4 • Balance valve y3 not energized 34 GF42.50-P-4000-04S GF42.
Pressure Apply - All Wheels • Outlet control valves y7, y9, y11, y13 energized 35 GF42.50-P-4000-04S GF42.
Pressure Hold - All Wheels • y6, y8, y10, y12 de-energized 36 GF42.50-P-4000-04S GF42.
Pressure Reduction - All Wheels • y7, y9, y11, y13 de-energized 37 GF42.50-P-4000-04S GF42.
Temperature Compensation During continuous brake use the fluid in the calipers expand, this: • creates high pressure • prevents valves 7 & 8 from moving To reduce this pressure, y1 and y2 are pulsed 38
Deactivation SBC must be deactivated with SDS before any work is performed on the system. This will prevent the pre-drive check from being automatically performed which could cause injury. Deactivating the system will: • empty the pressure reservoir (a lower pressure with no volume may be retained) • prevent the charge pump from operating •Note: the warning buzzer is deactivated when accessing SBC with the SDS.
Deactivation SBC must be deactivated PRIOR to: • working on the hydraulic system • removing or installing brake pads • replacing rotors • replacing the pressure reservoir • replacing the BOU • replacing the SBC hydraulic unit (A7/3) 40
Deactivation Charge pump disabled and accumulator fluid returned to the reservoir! 41 Pressure at A7/3b2
System Activation Activation must be performed anytime the system has been deactivated, BEFORE the engine is started! Failure to activate will prevent proper operation and create fault codes! Activating SBC with SDS will: • charge the accumulator • perform a Predrive Check • move the pads towards the rotors with ~60 bar pressure • erase the fault memory (Note: may have to activate several times to position the brake pads) 42
System Activation 43
Activation - Left Front Caliper held with ~60 bar 44
Activation - Right Front Caliper held with ~60 bar 45
Activation - Right Rear Caliper held with ~60 bar 46
Activation - Left Rear Caliper held with ~60 bar 47
Activation - Recharge 48
Bleeding the Brake System Proper system bleeding is critical! Follow directions in SDS • Bleeding must be performed using the SDS • Pressure at bleeder valves will exceed 100 bar (Hold the bleeder hose securely) • Bleeding may require ~1.5 hours • Bleeding may use ~ 1.5 liters of brake fluid 49 AR42.
Equipment Required • Pressure bleeder • Adapters • Fluid receptacle • SDS - follow instructions carefully 211 589 01 91 00 CAUTION: Extremely high pressure at bleeder! AR42.10-P-0010-02R AR42.10-P-0012R WS42.
Bleeding the Brake System Connect equipment and follow steps in SDS 51 AR42.
Acronym List (Used in This Handout.
Appendix AR42.10-P-0010I AR42.10-P-0012R GF42.45-P-0001-04SL GF42.45-P-0001SL GF42.45-P-2000SL GF42.45-P-3500SL GF42.46-P-0001SL GF42.46-P-1000SL GF42.46-P-2000SL GF42.46-P-3000SL GF42.46-P-4200-03SL GF42.46-P-4210SL GF42.46-P-4500-02SL GF42.50-P-4000-03S GF42.50-P-4000-04S GF42.50-P-4000S WS42.
