Operating method for operating a fuel injection system and fuel injection system

1. An operating method for operating a fuel injection system of an internal combustion engine, the method comprising:

providing a fuel injection system, having a high-pressure fuel pump with a pump piston which is movable in translational fashion in a pressure chamber during operation and which serves for highly pressurizing a fuel, having a high-pressure region for storing the highly pressurized fuel, and having at least one injector valve which is connected to the high-pressure region and which serves for injecting highly pressurized fuel into a combustion chamber of the internal combustion engine;

providing at least two operating states of the internal combustion engine, wherein, in an overrun mode, no injection of fuel through the at least one injector valve into the combustion chamber takes place, wherein, in an injection mode, at least one injection of fuel through the at least one injector valve into the combustion chamber takes place;

providing a pressure-limiting valve which, when a predefined opening pressure is reached in the high-pressure region, discharges fuel from the high-pressure region into the pressure chamber of the high-pressure fuel pump;

detecting a fault situation in the fuel injection system, wherein the predefined opening pressure is overshot in the high-pressure region;

deactivating the overrun mode of the internal combustion engine in the fault situation, such that the internal combustion engine is operated exclusively in the injection mode;

determining a period duration with four evenly distributed quadrants between a first top dead center time, at which the pump piston is at a top dead center, and a second top dead center time, at which the pump piston is at the top dead center; and

actuating the at least one injector valve such that an opening time of the at least one injector valve lies in an opening duration which extends in at least one of a second quadrant of the four evenly distributed quadrants of the period duration and a third quadrant of the four evenly distributed quadrants of the period duration.

2. The operating method as claimed in claim 1 , wherein the fuel injection system includes a high-pressure sensor and the fault situation is detected by the high-pressure sensor.

3. The operating method as claimed in claim 1 , further comprising setting the predefined opening pressure of the pressure-limiting valve to be lower than a maximum admissible maximum pressure in the high-pressure region, wherein the maximum admissible pressure is defined in a range above 500 bar.

4. The operating method as claimed in claim 3 , further comprising injecting a quantity of fuel through the at least one injector valve so that a pressure lower than the maximum pressure takes effect in the high-pressure region.

5. The operating method as claimed in claim 1 , further comprising injecting a quantity of fuel through the at least one injector valve so that a pressure that corresponds to the opening pressure of the pressure-limiting valve is set in the high-pressure region.

6. The operating method as claimed in claim 1 , further comprising, following deactivating the overrun mode, detecting re-entry in a normal mode of the fuel injection system in which the predefined opening pressure is undershot in the high-pressure region, and reactivating the overrun mode.

7. The operating method as claimed in claim 1 , further comprising, detecting the first and second top dead center times at which the pump piston is situated at the top dead center, and performing at least one of storing a characteristic map which assigns a predetermined crank angle of the internal combustion engine to the top dead center, and acquiring a crank angle of the internal combustion engine.

8. The operating method as claimed in claim 1 , wherein pressure in the high-pressure region has cyclic pressure peaks and pressure troughs, and the second and third quadrants correspond to at least one trough of the pressure troughs.

9. An operating method for operating a fuel injection system of an internal combustion engine, the method comprising:

providing a fuel injection system, having a high-pressure fuel pump with a pump piston which is movable in translational fashion in a pressure chamber during operation and which serves for highly pressurizing a fuel, having a high-pressure region for storing the highly pressurized fuel, and having at least one injector valve which is connected to the high-pressure region and which serves for injecting highly pressurized fuel into a combustion chamber of the internal combustion engine;

providing at least two operating states of the internal combustion engine, wherein, in an overrun mode, no injection of fuel through the at least one injector valve into the combustion chamber takes place, wherein, in an injection mode, at least one injection of fuel through the at least one injector valve into the combustion chamber takes place;

providing a pressure-limiting valve which, when a predefined opening pressure is reached in the high-pressure region, discharges fuel from the high-pressure region into the pressure chamber of the high-pressure fuel pump;

detecting a fault situation in the fuel injection system, wherein the predefined opening pressure is overshot in the high-pressure region;

deactivating the overrun mode of the internal combustion engine in the fault situation, such that the internal combustion engine is operated exclusively in the injection mode;

determining a period duration with four evenly distributed quadrants between a first top dead center time, at which the pump piston is at the top dead center, and a second top dead center time, at which the pump piston is at the top dead center, defining an injection time at which the at least one injector valve begins to inject fuel, and

adjusting a camshaft angle of the camshaft relative to the pump piston such that the injection time lies in a duration which extends in at least one of a second quadrant of the period duration and a third quadrant of the period duration.

10. A fuel injection system for injecting fuel into combustion chambers of an internal combustion engine, the fuel injection system comprising:

a high-pressure fuel pump with a pump piston which moves in translational fashion in a pressure chamber during operation and which serves for highly pressurizing a fuel;

a high-pressure region for storing the highly pressurized fuel;

at least one injector valve which is connected to the high-pressure region and which serves for injecting highly pressurized fuel into a combustion chamber of the internal combustion engine;

a pressure-limiting valve which, when a predefined opening pressure is reached in the high-pressure region, discharges fuel from the high-pressure region into the pressure chamber of the high-pressure fuel pump; and

a control device which is configured to

provide at least two operating state of the internal combustion engine, wherein, in an overrun mode, no injection of fuel through the at least one injector valve into the combustion chamber takes place, wherein, in an injection mode, at least one injection of fuel through the at least one injector valve into the combustion chamber takes place;

detect a fault situation in the fuel injection system, wherein pressure in the high-pressure region exceeds the predefined opening pressure; and

deactivate the overrun mode of the internal combustion engine in the fault situation, such that the internal combustion engine is operated exclusively in the injection mode,

wherein pressure in the high-pressure region has cyclic pressure peaks and pressure troughs,

wherein a period duration with four evenly distributed quadrants is determined between a first top dead center time at which the pump piston is at a top dead center, and a second top dead center time at which the pump piston is at the top dead center, and

wherein the at least one injector valve is actuated such that an opening time of the at least one injector valve lies in an opening duration which extends in at least one of a second quadrant of the four evenly distributed quadrants of the period duration and a third quadrant of the four evenly distributed quadrants of the period duration, the second and third quadrants corresponding to a trough of the pressure troughs.

11. The fuel injection system of claim 10 , wherein the predefined opening pressure of the pressure-limiting valve is set to be lower than a maximum admissible maximum pressure in the high-pressure region, and wherein a quantity of fuel is injected through the at least one injector valve so that a pressure lower than the maximum pressure takes effect in the high-pressure region.

12. The fuel injection system of claim 10 , wherein a quantity of fuel is injected through the at least one injector valve so that a pressure that corresponds to the opening pressure of the pressure-limiting valve is set in the high-pressure region.

13. The fuel injection system of claim 10 , wherein a quantity of fuel is injected through the at least one injector valve so that a pressure that corresponds to the opening pressure of the pressure-limiting valve is set in the high-pressure region.

14. The fuel injection system of claim 10 , wherein, upon a detection of re-entry into a normal mode of the fuel injection system in which pressure in the high-pressure region is below the predefined opening pressure, the overrun mode is reactivated.

15. The fuel injection system of claim 10 , wherein, for detection of the top dead center times at which the pump piston is situated at the top dead center, at least one of a characteristic map is stored which assigns a predetermined crank angle of the internal combustion engine to the top dead center, and a crank angle of the internal combustion engine is acquired.

16. A fuel injection system for injecting fuel into combustion chambers of an internal combustion engine, the fuel injection system comprising:

a high-pressure fuel pump with a pump piston which moves in translational fashion in a pressure chamber during operation and which serves for highly pressurizing a fuel;

a high-pressure region for storing the highly pressurized fuel;

at least one injector valve which is connected to the high-pressure region and which serves for injecting highly pressurized fuel into a combustion chamber of the internal combustion engine;

a pressure-limiting valve which, when a predefined opening pressure is reached in the high-pressure region, discharges fuel from the high-pressure region into the pressure chamber of the high-pressure fuel pump; and

a control device which is configured to

provide at least two operating state of the internal combustion engine, wherein, in an overrun mode, no injection of fuel through the at least one injector valve into the combustion chamber takes place, wherein, in an injection mode, at least one injection of fuel through the at least one injector valve into the combustion chamber takes place;

detect a fault situation in the fuel injection system, wherein pressure in the high-pressure region exceeds the predefined opening pressure; and

deactivate the overrun mode of the internal combustion engine in the fault situation, such that the internal combustion engine is operated exclusively in the injection mode,

wherein pressure in the high-pressure region has cyclic pressure peaks and pressure troughs, and wherein the control device is further configured to determine a period duration with four evenly distributed quadrants between a first top dead center time, at which the pump piston is at the top dead center, a second top dead center time, at which the pump piston is at the top dead center, define an injection time at which the at least one injector valve begins to inject fuel, and adjust at least one of the injection time and a camshaft angle of the camshaft relative to the pump piston such that the injection time lies in a duration which extends in at least one of a second quadrant of the period duration and a third quadrant of the period duration, the second and third quadrants corresponding to at least one of the pressure troughs.

17. The fuel injection system of claim 16 , wherein the at least one of the injection time and the camshaft angle comprises the camshaft angle.

18. The fuel injection system of claim 16 , wherein the at least one of the injection time and the camshaft angle includes the injection time.