An actuating device for a brake-by-wire brake apparatus of a motor vehicle, comprising:
- a housing body having a cavity and an opening into the cavity;
- an actuating element which is actuatable by muscle power and which is transferable by the muscle power from a non-actuated rest position to a working position;
- a control unit which comprises at least one sensor, said sensor being able to be used to indirectly or directly detect a position of the actuating element, wherein the control unit is configured to set a braking force of a brake, which is actuatable by the control unit, in dependence on the working position of the actuating element, the working position being detected by the sensor;
- a restoring unit which is usable to preload the actuating element with a restoring force into the non-actuated rest position, wherein the restoring force of the restoring unit and the braking force set at the brake by the control unit increase as a deviation of the working position from the rest position of the actuating element increases;
- a piston which is arranged in the cavity between the restoring unit and the opening, said piston having a cross section which corresponds to a cross section of a hollow-cylindrical portion of the cavity, wherein the piston is supported by one end on the restoring unit and is connected to the actuating element by another end facing away from the restoring unit, kinematics of said piston being coupled to the actuating element;
- wherein the restoring unit comprises a plunger element, a bar-shaped projection of which engages into and is moveable relative to a cutout in the piston, said cutout being of corresponding form to a cross section of the projection,
- the restoring unit comprises at least one spring which is supported on a plate portion of the plunger element and also on the piston and which surrounds the bar-shaped projection of the plunger element;
- the restoring unit comprises at least one elastomeric compression body, which is arranged on a side of the plunger element which faces away from the piston, and which is supported on the plunger element and also on a housing boundary;
- and
- the bar-shaped projection of the plunger element is arrangeable entirely in the cutout in the piston during which only a spring rate of the compression body acts during movement of the piston until the compression body completely fills its respective cross-section of the cavity.