Electronically controlled valve for vehicle braking force booster

摘要

The invention relates to an electronically controllable brake booster comprising a vacuum chamber and a pressure chamber which are separated from one another by a movable wall (2). The invention also comprises a control valve assembly (6, 7, 9) which can be actuated by an electromagnetic actuating device (3, 4) and can be adjusted by a pressure differential between the pressure and vacuum chambers. According to a current flowing through the electromagnetic actuating device (3, 4), the control valve assembly (6, 7, 9) occupies a stopping position in which the current (I) lies in a region between a higher value and a lower value such that the control valve assembly does not abandon the stopping position. Said control valve assembly also occupies a build-up position in which the current is greater than the higher value, and a reduction position in which the current is less than the lower value. A characteristic value for the pressure differential between the vacuum chamber and pressure chamber is detected at two varying pressure levels in the pressure chamber. The control valve assembly is respectively located in the stopping position. Starting from the stopping position, the respective current flowing through the electromagnetic actuating device is changed such that the control valve assembly reaches the pressure build-up position and the pressure reduction position. The current values are evaluated for the transition from the stopping position to the pressure build-up position at a high pressure level, for the transition from the stopping position to the pressure build-up position at a low pressure level, and/or for the transition from the stopping position to the pressure reduction position at a high pressure level, and for the transition from the stopping position to the pressure reduction position at a low pressure level. In addition, the current values are changed according to the current values for the upper and lower limits of the control valve assembly stopping position at varying pressure levels in order to detect a characteristic line for operating the brake booster.