Brief description of components DSC5.7 (E65)

The Main unit

Tandem master brake cylinder
The tandem brake master cylinder is fitted with an integral DSC back-pressure restrictor (pushrod/baffle design) and a brake fluid reservoir.

Single pre-charger pump
The single pre-charger pump ensures that adequate hydraulic pressure is available quickly enough under all operating conditions, specifically with regard to the increased viscosity of brake fluid at low temperatures.
The single pre-charger pump has a separate connection to the brake fluid reservoir, from which it draws in fluid, and a separate connection to the tandem master cylinder, to which it delivers fluid.

Hydraulic unit
The hydraulic control unit consists of the following components:
· Pump motor with self-priming return-flow pump
· Damper chambers
· Accumulators
· Integrated flow dampers
· Inlet/outlet valves
· High-pressure modulator/change-over valves
· Pressure sensor
· Add-on control unit

Pump motor with self-priming return-flow pump
The pump motor operates the pump elements (one for each brake circuit) of the self-priming return-flow pump. When brake pressure is released, the return-flow pump pumps the brake fluid returning from the brake calipers back to the tandem master cylinder via integral flow dampers, damper chambers and accumulator chambers.
When the DSC system is actively intervening in braking system operation, the return-flow pump generates the required brake pressure.

Damper chambers
The damper chambers (one for each brake circuit) reduce pump pressure fluctuation at the brake calipers.

Accumulators
The accumulators (one for each brake circuit) act as initial brake fluid collectors when pressure is released during active operation of the ABS/ASC/DSC.

Integrated flow dampers
The integrated flow dampers (one for each brake circuit) reduce pump pressure fluctuation at the tandem master cylinder. This reduces noise levels and feedback of vibration to the brake pedal.

Inlet/outlet valves
The inlet and outlet valves (one pair per brake caliper) control the flow of brake fluid to and from the brake calipers during the pressure modulation phase.

High-pressure modulator/change-over valves
The high-pressure modulator valves, which are closed when de-energized, and the change-over valves, which are open when de-energized (one pair per braking circuit), control braking system pressurization during active intervention by the DSC.

Pressure sensor
The pressure sensor measures the brake pressure in the front-wheel circuit. It has a detection range of 0...250 bar. Its zero point is continuously calibrated when the brake light switch is off and the ignition is on.

Add-on control unit
The add-on control unit is the ABS/ASC/DSC control centre. To secure the functions, the system is subject to permanent self-monitoring. Faults that occur are stored in a fault code memory and, if required, displayed to the driver.

Wheel speed sensors
The wheel speed sensors detect the speed of each wheel individually. On the E65, they also detect the direction of rotation.

Yaw rate/lateral acceleration sensor
The yaw rate sensor detects the speed of rotation around the vertical axis of the vehicle (yaw) and the lateral acceleration sensor the sideways acceleration. That data is used to determine whether the vehicle is following a course in keeping with the steering angle or whether it is starting to slide sideways. The two sensors are housed in a single unit.

Steering angle sensor
The steering angle sensor and road speed of the vehicle provide the information from which intended course of the vehicle is calculated. On the E65, the steering angle sensor is integrated in the steering column control centre.

Brake fluid level warning switch
The brake fluid warning switch monitors the brake-fluid level in the brake fluid reservoir of the tandem master cylinder. If the switch of brake fluid warning trips, the ASC/DSC function is deactivated to prevent air being drawn into the hydraulic system.

Brake light switch
The brake light switch informs the DSC system when the brake pedal is being operated by the driver. This triggers/disables calibration and plausibility checking procedures and cancels braking system intervention during active ASC operation.

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