METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE, AND INTERNAL COMBUSTION ENGINE

Abstract

The invention relates to a method for operating an internal combustion engine (1), which comprises at least one combustion chamber (3) and an injector (5) which is assigned to the combustion chamber (3) and intended for introducing a first gaseous fuel into the combustion chamber (3), wherein a second liquid fuel is used for operation of the injector (5), wherein in a start-up operation of the internal combustion engine (1) the injector (5) is actuated in at least one operational cycle, avoiding complete combustion of the fuel introduced into the combustion chamber (3) via the injector (5).

Claims

1.-10. (canceled)

11. A method for operating an internal combustion engine, the method comprising: actuating, during at least one operational cycle of a start-up operation of the internal combustion engine, an injector to introduce a fuel into a combustion chamber of the internal combustion engine; and avoiding complete combustion of the fuel introduced into the combustion chamber of the internal combustion engine by the injector; wherein the internal combustion engine is configured to introduce a first gaseous fuel into the combustion chamber, and is configured to operate the injector based on a second liquid fuel.

12. The method of claim 11, further comprising actuating the injector at an actuation time within the at least one operational cycle, at which: (a) no ignition conditions for the second liquid fuel are present in the combustion chamber, or (b) it is ensured that the fuel introduced via the injector is at most partially converted.

13. The method of claim 11, wherein in the start-up operation the injector is actuated in a plurality of operational cycles while avoiding complete combustion of the fuel introduced into the combustion chamber via the injector.

14. The method of claim 11, wherein the injector in the start-up operation, is actuated: a) during a valve overlap phase, or b) after a top dead center assigned to an expansion cycle of a piston movable by performing a stroke in the combustion chamber in a range between about 15 crank angle (CA) about 50 C.A after the top dead center.

15. The method of claim 14, further comprising: predicting a maximum fuel quantity of the second liquid fuel introduced via the injector wherein an actuation time at which the injector is actuated after the top dead center, and determining the actuation time at which the injector is actuated after the top dead center, during start-up operation, based on the predicted maximum fuel quantity.

16. The method of claim 11, wherein the injector is actuated during start-up operation only after a predetermined limit speed has been reached or exceeded.

17. The method of claim 11, wherein the injector is only actuated during start-up operation when a pressure in a fuel supply system for the injector has reached or exceeded: a) a first fuel pressure limit value for the first gaseous fuel, and b) a second fuel pressure limit value for the second liquid fuel.

18. The method of claim 11, further comprising: determining that a predetermined number of actuations of the injector have occurred; and stepwise displacing an actuation time, at which the injector is actuated during start-up operation until combustion in the combustion chamber is detected.

19. The method of claim 11, further comprising: detecting a combustion in the combustion chamber during or after a stepwise advanced displacement of an actuation time; and setting the actuation time to a starting operating value based on the detecting.

20. An internal combustion engine comprising: at least one combustion chamber having an injector configured to introduce a first gaseous fuel into the combustion chamber, and the injector is configured to use a second liquid fuel for operation of the injector; and a control device operatively connected to the injector and configured to actuate the injector in at least one operational cycle in a start-up operation of the internal combustion engine while avoiding complete combustion of the first gaseous fuel, the second liquid fuel, or both introduced into the combustion chamber via the injector.

21. The internal combustion engine of claim 20, wherein the control device is configured to: actuate, during the at least one operational cycle of a start-up operation of the internal combustion engine, the injector to introduce the first, gaseous fuel into the combustion chamber of the internal combustion engine; and avoid complete combustion of the first gaseous fuel, the second liquid fuel, or both introduced into the combustion chamber of the internal combustion engine by the injector; wherein the internal combustion engine is configured to introduce a first gaseous fuel into the combustion chamber, and is configured to operate the injector based on the second liquid fuel.

22. The internal combustion engine of claim 21, further comprising actuating the injector at an actuation time within the at least one operational cycle, at which: (a) no ignition conditions for the second liquid fuel are present in the combustion chamber, or (b) it is ensured that the first gaseous fuel, the second liquid fuel, or both introduced via the injector is at most partially converted.

23. The internal combustion engine of claim 21, wherein in the start-up operation the injector is actuated in a plurality of operational cycles while avoiding complete combustion of the first gaseous fuel, the second liquid fuel, or both introduced into the combustion chamber via the injector.

24. The internal combustion engine of claim 21, wherein the injector in the start-up operation, is configured to be actuated: a) during a valve overlap phase, or b) after a top dead center assigned to an expansion cycle of a piston movable by performing a stroke in the combustion chamber in a range between about 15 crank angle (CA) and about 50 CA after the top dead center.

25. The internal combustion engine of claim 24, further comprising: predicting a maximum fuel quantity of the second liquid fuel introduced via the injector wherein an actuation time at which the injector is actuated after the top dead center, and determining the actuation time at which the injector is actuated after the top dead center, during start-up operation, based on the predicted maximum fuel quantity.

26. The internal combustion engine of claim 20, wherein the control device is configured to actuate the injector during start-up operation only after a predetermined limit speed has been reached or exceeded.

27. The internal combustion engine of claim 20, wherein the control device is configured to actuate the injector only during start-up operation when a pressure in a fuel supply system for the injector has reached or exceeded: a) a first fuel pressure limit value for the first gaseous fuel, and b) a second fuel pressure limit value for the second liquid fuel.

28. The internal combustion engine of claim 20, wherein the control device is further configured to: determine that a predetermined number of actuations of the injector have occurred; and stepwise displace an actuation time, at which the injector is actuated during start-up operation until combustion in the combustion chamber is detected.

29. The internal combustion engine of claim 20, wherein the control device is further configured to: detect a combustion in the combustion chamber during or after a stepwise advanced displacement of an actuation time; and set the actuation time to a starting operating value based on the detecting a combustion in the combustion chamber.

Description

[0053] The invention is explained in more detail below with reference to the drawing. In particular:

[0054] FIG. 1 shows a schematic representation of an exemplary embodiment of an internal combustion engine, and

[0055] FIG. 2 shows a schematic representation of an embodiment of a method for operating the internal combustion engine in the manner of a flow chart.

[0056] FIG. 1 shows a schematic representation of an exemplary embodiment of an internal combustion engine 1. This has at least one combustion chamber 3, preferably a plurality of combustion chambers 3. An injector 5 is assigned to the combustion chamber 3, which injector is configured to introduce a first gaseous fuel into the combustion chamber 3. The injector 5 is also configured to use a second, liquid fuel for its operation, in particular a control oil, a sealing oil and/or a a pilot fuel.

[0057] In a preferred embodiment, the internal combustion engine 1 is configured for a two-component operation, wherein the first gaseous fuel is introduced as a main fuel into the combustion chamber 3, wherein the first gaseous fuel is ignited by introducing an ignition quantity of the second liquid fuel as a pilot fuel into the combustion chamber 3. The pilot fuel can be introduced via an additional, separate injector, or via the injector 5 into the combustion chamber 3. In a preferred embodiment, the second liquid fuel is also introduced via the injector 5 into the combustion chamber 3. The injector 5 is preferably designed as a two-component injector.

[0058] The internal combustion engine 1 also has a control device 7, which is operatively connected to the injector 5 and is configured to control the injector 5 in at least one operational cycle in a start-up operation of the internal combustion engine 1 while avoiding complete combustion of the fuel introduced into the combustion chamber 3 via the injector 5. In this way, undesirably present quantities of the second, liquid fuel can be discharged into the combustion chamber 3 without the risk of damaging the chamber or any other parts of the internal combustion engine 1 due to excessively high combustion end pressures due to an excessively large amount of second liquid fuel in the combustion chamber 3.

[0059] The control device 7 is configured in particular to control the injector 5 in the start-up operation in the at least one operational cycle at an actuation time within the operational cycle at which no ignition conditions for the second fuel are present in the combustion chamber 3, or it is additionally ensured that the fuel introduced via the injector 5 is at most partially converted.

[0060] In particular, the control device 7 is preferably configured to control the injector 5 in the start-up operation in a plurality of operational cycles while avoiding complete combustion of the fuel introduced into the combustion chamber 3 via the injector 5.

[0061] A piston 9 is preferably displaceable in the combustion chamber 3 by performing a stroke. The internal combustion engine 1 is preferably designed as a reciprocating piston engine.

[0062] An inlet valve 11 for introducing fresh mass into the combustion chamber 3 is preferably assigned to the combustion chamber 3. Furthermore, an outlet valve 13 for discharging exhaust gas from the combustion chamber 3 is preferably assigned to the combustion chamber 3.

[0063] The control device 7 is preferably configured to actuate the injector 5 in the start-up operation during a valve overlap phase of the inlet valve 11 and of the outlet valve 13, in particular from 50 C.A before intake TDC of the piston 9 to 50 C.A after intake TDC, preferably from 45 C.A before intake TDC to 45 CA after intake TDC, preferably from 40 C.A before intake TDC to 40 C.A after intake TDC, preferably from 46 C.A before intake TDC to 43 C.A after intake TDC.

[0064] The control device 7 is preferably configured to actuate the injector 5 in the start-up operation after a top dead center assigned to an expansion stroke, the expansion TDC of the piston 9, in particular at least 15 C.A to at most 50 CA after expansion TDC, preferably at least 20 C.A to 40 C.A after expansion TDC, preferably at least 25 C.A up to at most 35 C.A after expansion TDC, preferably 30 C.A after expansion TDC.

[0065] The control device 7 is preferably configured to select the actuation time at which the injector 5 is actuated during start-up operation after the expansion TDC as a function of a prediction regarding a maximum fuel quantity of the second liquid fuel introduced via the injector 5, in particular in relation to a predetermined maximum mechanical load of the combustion chamber 3.

[0066] A pressure sensor 15 is assigned to the combustion chamber 3 and is arranged and configured to detect a combustion chamber pressure in the combustion chamber 3. The control device 7 is operatively connected to the pressure sensor 15 and is preferably configured to detect a temporal combustion chamber pressure profile of the combustion chamber pressure in the combustion chamber 3 by means of the pressure sensor 15. The control device 7 is preferably configured to detect combustion in the combustion chamber 3 on the basis of the detected temporal combustion chamber pressure profile.

[0067] The internal combustion engine 1 has a starter 17, in particular an electric starter motor, which is configured to drag the internal combustion engine 1 in start-up operation. For this purpose, the starter 17 is preferably mechanically operatively connectable, in particular drivingly connectable, preferably drivingly connected to a crankshaft 19 of the internal combustion engine 1. In a preferred embodiment, the starter 17 can be mechanically separated from the crankshaft 19 and/or deactivated after start-up operation or for terminating the start-up operation.

[0068] FIG. 2 shows a schematic representation of an embodiment of a method for operating the internal combustion engine 1.

[0069] The method is started in a first step S1. At this time, the internal combustion engine 1 is at a standstill, its rotational speed n is 0.

[0070] In a second step S2, the starter 17, also referred to as starter in FIG. 2, is started. In a third step S3, it is checked whether the rotational speed of the internal combustion engine 1 has reached or exceeded a predetermined initial rotational speed, preferably of 150 rpm. Furthermore, it is checked in step S3 whether the control device 7, or ECU, is ready. If one of these conditions is not fulfilled, the third step S3 is carried out until both conditions are fulfilled.

[0071] The method is then continued in a fourth step S4, in that a pressure build-up for the first, gaseous fuel and for the second liquid fuel takes place, preferably in a predetermined sequence. In particular, a sealing oil pressure is preferably initially built up, then a control oil pressure, and finally the pressure for the first, gaseous fuel, which is also referred to as fuel gas for short.

[0072] In a fifth step S5, the pressure buildup is monitored, in particular with respect to the time profile of the pressure build-up, wherein it is preferably evaluated whether the pressure build-up is too slowpreferably also with respect to the sequence of the pressure buildup. In a sixth step S6, it is checked whether the pressure buildup is correct. If the pressure buildup is found to be correct, an OK signal SIG is output.

[0073] The OK signal SIG is preferably only output when a fuel pressure in a fuel supply system, shown schematically in FIG. 1 and denoted by the reference numeral 21, has reached or exceeded a first fuel pressure limit value for the injector 5 for the first, gaseous fuel, and has reached or exceeded a second fuel pressure limit value for the second liquid fuel. The fuel supply system 21 serves, in particular, for providing the fuels, in particular for providing the control oil, the sealing oil and the fuel gas.

[0074] If, also with reference to FIG. 2, the pressure buildup in the sixth step S6 is evaluated as not being OK, the pressure build-up is stopped in a seventh step S7. In an eighth step S8, pressure relief takes place. In a ninth step S9, the start parameters are adapted, for example a longer time interval is provided for the pressure build-up between the individual fuel circuits, and the method is then continued in the fourth step S4 with a renewed pressure buildup.

[0075] In a tenth step S10, it is checked whether the OK signal SIG is present, i.e., the pressure buildup is OK, and whether the rotational speed of the internal combustion engine 1 has at the same time reached or exceeded a predetermined limit speed, in particular a starter speed, in particular 180 rpm.

[0076] Only if both conditions are met is the method continued in an eleventh step S11. Otherwise, the check is repeated in the tenth step S10 until both conditions are fulfilled.

[0077] In the eleventh step S11, the injector 5 is then actuated in at least one operational cycle, preferably in a plurality of operational cycles, preferably in a clocked manner, while avoiding complete combustion of the fuel introduced into the combustion chamber 3 via the injector 5, that is to say it is in particular purged. The fuel is preferably introduced into the combustion chamber 3 at 30 CA after the expansion TDC.

[0078] After a predetermined number of actuations of the injector 5 and/or a predetermined number of operational cycles in which the injector 5 has been actuated accordingly, the actuation time is then shifted stepwise so as to be advanced in a twelfth step S12. At the same time, in a thirteenth step S13, it is checked whether a combustion is detected in the combustion chamber 3. The advanced displacement in the twelfth step S12 takes place in particular until combustion is detected in the thirteenth step S13. If this is the case, in a fourteenth step S14 the actuation time is set to a starting operating value, and the internal combustion engine 1 is started or operated in a fifteenth step S15.

[0079] Preferably, after an idle speed or nominal rotational speed of the internal combustion engine 1 has been reached, the actuation time for the injector 5 is set to a continuous operating value. This can vary depending on an instantaneous operating point of the internal combustion engine 1.