Method and control device for operating a common-rail fuel supply system

1. A method for operating a common-rail fuel supply system of an internal combustion engine configured as a diesel internal combustion engine of a ship, the common-rail fuel supply system having a low-pressure region ( 4 ), a high-pressure region ( 6 ) and a high-pressure pumping device ( 3 ) having at least two high-pressure pumps ( 2 ), with the help of which fuel from the low-pressure region ( 4 ) of the fuel supply system is deliverable into the high-pressure region ( 6 ) of the fuel supply system, wherein in the high-pressure region ( 6 ) between the high-pressure pumping device ( 3 ) and injectors ( 1 ) assigned to cylinders, a pressure storage system ( 7 ) that is under high pressure is provided, and wherein a rate of delivery of the high-pressure pumping device ( 3 ) is adjustable by way of throttle valves ( 13 ) upstream of the high-pressure pumps ( 2 ), the method comprising:

determining, dependent on a requested operating point of the internal combustion engine, a set point rate of delivery of the high-pressure pumping device ( 3 ), and a set point pressure for the pressure storage system ( 7 ) under high pressure,

determining, dependent on the set point rate of delivery of the high-pressure pumping device ( 3 ) for all throttle valves ( 13 ), a control portion for the position of the respective throttle valve ( 13 ), and activating the respective throttle valve ( 13 ) with the determined control portion,

determining, dependent on a deviation between the set point pressure and an actual pressure in the pressure storage system ( 7 ) under high pressure, for a first part quantity of the throttle valves ( 13 ) a closed-loop control portion for the position of the respective throttle valve ( 13 ), and activating the first part quantity of the throttle valves ( 13 ) with the closed-loop control portion in addition to open-loop control for only the respective throttle valve ( 13 ) of the first part quantity of the throttle valves ( 13 ), whereas the, or each, throttle valve ( 13 ) of a second part quantity of the throttle valves ( 13 ) is exclusively activated with the open-loop control portion, and

exchanging or replacing, the, or each, throttle valve ( 13 ) of the first part quantity of the throttle valves ( 13 ), with a throttle valve of the second part quantity of the throttle valves ( 13 ).

2. The method according to claim 1 , wherein the first part quantity of the throttle valves ( 13 ), which are activated with the open-loop control portion and the closed-loop control portion, comprises a single throttle valve for each cylinder bank.

3. The method according to claim 2 , wherein the exchanging or replacing is performed in a time-controlled manner.

4. The method according to claim 3 , wherein the exchanging or replacing is performed after expiration of a defined period of time.

5. The method according to claim 1 , wherein the exchanging or replacing is performed in an event-controlled manner.

6. The method according to claim 5 , wherein the exchanging or replacing is performed during an engine start.

7. The method according to claim 1 , further comprising determining the set point rate of delivery and the set point pressure dependent on a requested load of the internal combustion engine.

8. A common-rail fuel supply system of an internal combustion engine configured as a diesel internal combustion engine of a ship, comprises:

a low-pressure region ( 4 );

a high-pressure region ( 6 );

a high-pressure pumping device ( 3 ) comprising at least two high-pressure pumps ( 2 ) configured to deliver fuel from the low-pressure region ( 4 ) of the fuel supply system into the high-pressure region ( 6 );

a pressure storage system ( 7 ) under high pressure arranged in the high-pressure region ( 6 ) between the high-pressure pumping device ( 3 ) and injectors ( 1 ) assigned to cylinders of the internal combustion engine;

a plurality of throttle valves arranged upstream of the high-pressure pumps ( 2 ), and configured to adjust a rate of delivery of the high-pressure pumping device ( 3 ); and

a controller,

wherein the controller, dependent on a requested operating point of the internal combustion engine on the one hand, determines a set point rate of delivery of the high-pressure pumping device ( 3 ) and a set point pressure for the pressure storage system ( 7 ) under high pressure,

wherein the controller, dependent on the set point rate of delivery of the high-pressure pumping device ( 3 ), determines a control portion for the position of the respective throttle valve ( 13 ) for each throttle valve ( 13 ), with which the controller activates each throttle valve ( 13 ),

wherein the controller, dependent on a deviation between the set point pressure and an actual pressure in the pressure storage system ( 7 ) under high pressure, is configured to determine a closed-loop control portion for the position of the respective throttle valve ( 13 ) for a first part quantity of the throttle valves ( 13 ), with which the controller, in addition to open-loop control, activates the respective throttle valve ( 13 ) of the first part quantity of the throttle valves ( 13 ), whereas the controller activates the, or each, throttle valve ( 13 ) of a second part quantity of the throttle valves ( 13 ) exclusively with the open-loop control portion, and

wherein the controller controls exchanging or replacing, of the, or each, throttle valve ( 13 ) of the first part quantity of the throttle valves ( 13 ), with a throttle valve of the second part quantity of the throttle valves ( 13 ).