One also describes it as electromechanical brake booster. In the picture it reaches from the expansion tank right up to the piston rod left, which extends into the tandem brake master cylinder. The connection to the brake pedal on the right is covered. Is not difficult to guess that this connection forms a unit with the piston rod, which also allows the purely mechanical operation of the brake at a pinch.

In the picture immediately front of the compensation tank, the electric motor is arranged with a relatively large diameter. If one follows the shapings in the housing, its shaft with worm and two therewith meshing wheels are to imagine right and left of it. The electric motor drives so with a large transmission two shafts with two straight-toothed gears, which grip into the teeth of a reinforcing sleeve around the piston rod.

In normal operation, this sleeve is fixedly connected to the piston rod and thus allows to transmit the movement of the electric motor on this. It can be unlatched when the electronic control fails. It is important that the electrics can work both with and against the pedal pressure, so it can also simulate a counter-pressure.

The volume compensation is ensured by a pressure accumulator. This is a cylinder filled with brake fluid with an at the end movable piston by e-drive and spindle. The volume is directly connected with the main brake cylinder. So brake fluid can be supplied or removed. The former strengthens the braking force, the latter weakens. Therefore, together with the mechanical intervention brake pressure can be generated or reduced without affecting the pedal counterforce. Both components described so far are to regard as a unit.

The braking torque of the generator is present at each braking, but goes at speeds below 10 km/h to zero. If thus at higher speeds the brake pedal will pressed and the car slows down, case of evenly delay and decreasing speed the recuperation increases rapidly, while the engagement of the service brake decreases about the same rate. In partial braking it will be even zero sometime and the generator solely is responsible for the braking until both alternate from 10 km/h.

By the laterally arranged control unit, the interaction between the two types of brakes is controlled in such a manner that the driver notices neither in the pedal pressure still during delaying a difference to the previous brake. In emergency braking an even faster pressure build-up shall be possible, which manifests itself in measurable braking distance difference. And of course brake pressure can be built up also without pressing the pedal by this system. 09/15