BRAKE ASSIST DEVICE, AND MOTOR VEHICLE COMPRISING SUCH A DEVICE

摘要

A brake-assist device for a motor vehicle having a servomotor is described. A servomotor has a plunger piston, a moving part, and an arrangement to move the moving part into position with respect to the plunger piston. The servomotor is actuated by a control rod. The control rod has a first end that presses upon the plunger piston and a second end to receive a force exerted by a brake pedal intended to be moved by a driver of the vehicle. The servomotor includes a sensor interposed in a contact space between the plunger piston and the moving part. A spring is compressed between the plunger piston and the moving part. The servomotor includes an arrangement for displacing the plunger piston in the contact space based on the driving mode. A stiffness of the spring is sufficiently high for an onset of braking to occur only with a striking force that is significantly higher during a reactive driving mode than it is during a calm driving mode.