SECONDARY BRAKE SYSTEM OF A VEHICLE, AND METHOD FOR CONTROLLING IT

The invention relates to an electronically controllable secondary brake system (), operated by pressure medium, useable as both as a parking brake system and an auxiliary brake system, with spring brake cylinders (, ) arranged on wheel brakes of at least one vehicle axle (), with a directly or indirectly electronically controllable brake control valve (). The brake force of the spring brake cylinder () can be reduced by a feed of pressure medium and can be increased by a discharge of pressure medium, and with an electronic brake control unit () for controlling the brake control valve () dependent on the current value of a brake value signal (SBW). The brake control valve () is configured as a -way proportional valve with a pressure medium inlet, a pressure medium outlet, and a working connector, which is connected via a working line () to the spring brake cylinders.