SBC normal braking, function - GF42.46-P-1000T

MODEL 211 up to 31.5.06 except CODE (494) USA version except CODE (498) Japan version 

MODEL 211 up to 30.6.06 with CODE (494) USA version with CODE (498) Japan version 

Fig 1: SBC Normal Braking Function Diagram - Pressure Buildup

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Function display of pressure buildup 

Normal braking, pressure build-up 

Each brake application begins when the driver presses the brake pedal.

The ESP control unit (N47-5) computes the brake pressure. The specified data is passed on to the SBC control unit (A7/3n1) and this starts with the control in the traction system hydraulic unit (A7/3).

At the beginning of the brake application, the left and right front separation valves A7/3y1A7/3y2are closed. They remain closed only during the control phase (except for during temperature compensation or activation via the brake pedal) and are otherwise open (de-energized).

The left front outlet control valve (A7/3y7), right front outlet control valve (A7/3y9), left rear outlet control valve (A7/3y11) and right rear outlet control valve (A7/3y13) are likewise closed. The left front inlet control valve (A7/3y6), right front inlet control valve (A7/3y8), left rear inlet control valve (A7/3y10) and right rear inlet control valve (A7/3y12) are open.

The front axle balance valve (A7/3y3) and rear axle balance valve (A7/3y4) remain open.

The pressure from the pressure reservoir (3) can now be built up at the left front brake caliper (5b) and right front brake caliper (5a) of the front axle via the left front dividing piston (7) and right front dividing piston (8). The pressure is increased directly at the rear axle.

Fig 2: SBC Normal Braking Function Diagram - Pressure Holding

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Function display of pressure holding 

Normal braking hold pressure 

The control procedure described in the example and the corresponding valve positions relate to the complete brake system. They can, however, be used individually at each wheel.

Function 

As soon as the computed brake pressure is reached, the left front inlet control valve (A7/3y6), right front inlet control valve (A7/3y8), left rear inlet control valve (A7/3y10) and right rear inlet control valve close A7/3y12).

The left front outlet control valve (A7/3y7), right front outlet control valve (A7/3y9), left rear outlet control valve (A7/3y11) and right rear outlet control valve (A7/3y13) remain closed.

The front axle balance valve (A7/3y3) and rear axle balance valve (A7/3y4) remain open.

Fig 3: SBC Normal Braking Function Diagram - Pressure Reduction

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Function display of depressurization 

Normal braking, pressure reduction 

The control procedure described in the example and the corresponding valve positions relate to the complete brake system. They can, however, be used individually at each wheel.

If the brake pressure required for braking is too high, the pressure-reduction phase of the control mode begins.

Function 

The left front outlet control valve (A7/3y7), right front outlet control valve (A7/3y9), left rear outlet control valve (A7/3y11) and right rear control valve (A7/3y13) are opened.

The left front inlet control valve (A7/3y6), right front inlet control valve (A7/3y8), left rear (A7/3y10)inlet control valve and right rear inlet control valve (A7/3y12) remain closed.

The front axle balance valve (A7/3y3) and rear axle balance valve (A7/3y4) remain open.

The brake fluid flowing back flows back to the expansion reservoir via the return line (R).