GF42.46-P-5130TX Operating Unit, Component Description

GF42.46-P-5130TX Operating unit, component description

MODEL 219.3 up to 31.5.06
except CODE (494) USA version
MODEL 219.3 up to 30.6.06
with CODE (494) USA version

Component Identification:

Task
The operating unit (1) simulates the brake pedal counterforce. It conveys the position of the brake pedal and the speed with which the brake pedal is actuated by the SBC pedal value sensor to the SBC control unit (A7/3n1).

In the event of a system failure of the Sensotronic Brake Control (SBC) function, the operating unit (1) serves as a master brake cylinder.

Component Identification:

Body
A tandem brake master cylinder (1a) with a brake fluid reservoir (1b) forms the basis of the operating unit (1).

The brake pressure simulator (2) and the SBC pedal value sensor are attached to the operating unit (1).

Component Identification:

Function during normal braking
During a normal brake application the operating unit (1) is isolated from the wheel brakes by the closed left front separation valve (A7/3y1) and right front separation valve (A7/3y2) in the traction system hydraulic unit (A7/3).

Simulation of the brake pedal counterforce in the brake pressure simulator (2):
^ The brake fluid is pressed against the force of the spring (soft) (2a) via the piston A (2d).
^ If the brake pedal is actuated further, the spring (hard, progressive) (2b) is compressed via the piston B (2e). This spring has a progressive characteristic.
^ The back pressure of the rubber buffer (2c) also acts in the case of very heavy brake applications.

Function in the event of a system failure of the Sensotronic Brake Control (SBC)
If a fault occurs in the system, the operating unit functions like a normal tandem brake master cylinder without additional brake power assistance at the front axle circuit of the brake system. In the process the floating piston (S) acts on the left front brake and the primary piston (D) acts on the right front brake. The inflow to the brake pressure simulator (2) is shut off by moving the floating piston (S).