Compressed air system for a motor vehicle

A compressed air system for a motor vehicle with an air supply system, an internal combustion engine and a passive parking brake, which is activated by decreasing pressure in parking spring brake cylinders and is released by increasing pressure in the parking brake cylinders to a parking brake release pressure, comprising:

• an electric drive motor, which is controllable for variable speed;
• an air compressor coupled to be driven by the electric drive motor;
• an electric power supply for supplying electric power to the electric drive motor;
• at least one air reservoir connected with said air compressor to receive air from the air compressor;
• an air utilization system connected to said at least one air reservoir to receive air from said at least one air reservoir;
• and
• a controller to control the speed of the electric drive motor,
• wherein
• the controller is configured to control the electric drive motor to determine the speed of the electric drive motor based upon a signal representing a status of the electric power supply and upon a signal representing a pressure in the at least one air reservoir, and
• when starting the vehicle or when the internal combustion engine of the vehicle is in a stopped status, a setup filling mode is activated, where the speed of the electric drive motor is controlled by the controller such that
• if the pressure in the at least one air reservoir is equal to or higher than the parking brake release pressure of the passive parking brake of the vehicle, the set up filling mode is stopped,
• if the pressure in the at least one air reservoir is lower than the parking brake release pressure, and if a power level of the electric power supply reaches or exceeds a predetermined power level limit, the electric drive motor is operated at a maximum electric drive motor speed until the pressure in the at least one air reservoir reaches a predetermined cut off pressure, and the set up filling mode is stopped, or
• if the pressure in the at least one air reservoir is below the parking brake release pressure of the passive parking brake of the vehicle, and if the power level of the electric power supply is below the predetermined power level limit, the electric drive motor is operated with a speed between zero speed and the maximum electric drive motor speed until the pressure level in the at least one air reservoir reaches the cut off pressure, and the set up filling mode is stopped.