Method for controlling a boost pressure of an engine

A method for controlling a boost pressure of an engine, the engine including a charging device including a compressor and a compressor bypass, the compressor bypass including a blow off valve configured to open and close the compressor bypass, a boost pressure control using an actual boost pressure and a setpoint boost pressure as input parameters, the method comprising the following steps:

• ascertaining a first compressor pressure ratio as a function of a limit line from a compressor characteristic map and an engine absorption characteristic for the engine;
• ascertaining a second compressor pressure ratio as a function of the limit line from the compressor characteristic map, a mass flow through the engine, and a throttle characteristic curve for the blow off valve;
• ascertaining a maximum permissible compressor pressure ratio for the compressor from the first compressor pressure ratio and the second compressor pressure ratio;
• determining a maximum permissible boost pressure as a function of the maximum permissible compression ratio;
• limiting the boost pressure control to the maximum boost pressure.

A non-transitory electronic memory medium on which is stored a computer program for controlling a boost pressure of an engine, the engine including a charging device including a compressor and a compressor bypass, the compressor bypass including a blow off valve configured to open and close the compressor bypass, a boost pressure control using an actual boost pressure and a setpoint boost pressure as input parameters, the computer program, when executed by computer, causing the computer to perform the following steps:

• ascertaining a first compressor pressure ratio as a function of a limit line from a compressor characteristic map and an engine absorption characteristic for the engine;
• ascertaining a second compressor pressure ratio as a function of the limit line from the compressor characteristic map, a mass flow through the engine, and a throttle characteristic curve for the blow off valve;
• ascertaining a maximum permissible compressor pressure ratio for the compressor from the first compressor pressure ratio and the second compressor pressure ratio;
• determining a maximum permissible boost pressure as a function of the maximum permissible compression ratio;
• limiting the boost pressure control to the maximum boost pressure.

A device, comprising:

• a control device configured to control a boost pressure of an engine, the engine including a charging device including a compressor and a compressor bypass, the compressor bypass including a blow off valve configured to open and close the compressor bypass, a boost pressure control using an actual boost pressure and a setpoint boost pressure as input parameters, the control device configured to:
• ascertain a first compressor pressure ratio as a function of a limit line from a compressor characteristic map and an engine absorption characteristic for the engine;
• ascertain a second compressor pressure ratio as a function of the limit line from the compressor characteristic map, a mass flow through the engine, and a throttle characteristic curve for the blow off valve;
• ascertain a maximum permissible compressor pressure ratio for the compressor from the first compressor pressure ratio and the second compressor pressure ratio;
• determine a maximum permissible boost pressure as a function of the maximum permissible compression ratio;
• limit the boost pressure control to the maximum boost pressure.