METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE, CONTROL DEVICE FOR AN INTERNAL COMBUSTION ENGINE AND INTERNAL COMBUSTION ENGINE WITH A CONTROL DEVICE OF THIS TYPE

Abstract

A method for operating an internal combustion engine includes: introducing a fuel gas with a fluctuating hydrogen content into an air path of the internal combustion engine; adjusting a combustion air ratio for a combustion chamber of the internal combustion engine via a predeterminable fuel gas mass flow into the air path; adjusting a power variable of the internal combustion engine by a throttle valve that is arranged in the air path; detecting a nitrogen oxide concentration in an exhaust gas path of the internal combustion engine; adjusting the combustion air ratio depending on the nitrogen oxide concentration that is detected; detecting a throttle valve reserve in the air path; and selecting an ignition timing in the combustion chamber of the internal combustion engine depending on the throttle valve reserve that is detected.

Claims

1. A method for operating an internal combustion engine, the method comprising the steps of: introducing a fuel gas with a fluctuating hydrogen content into an air path of the internal combustion engine; adjusting a combustion air ratio for a combustion chamber of the internal combustion engine via a predeterminable fuel gas mass flow into the air path; adjusting a power variable of the internal combustion engine by a throttle valve that is arranged in the air path; detecting a nitrogen oxide concentration in an exhaust gas path of the internal combustion engine; adjusting the combustion air ratio depending on the nitrogen oxide concentration that is detected; detecting a throttle valve reserve in the air path; and selecting an ignition timing in the combustion chamber of the internal combustion engine depending on the throttle valve reserve that is detected.

2. The method according to claim 1, wherein the power variable is regulated by way of the throttle valve to a setpoint.

3. The method according to claim 1, wherein the combustion air ratio is increased if the nitrogen oxide concentration that is detected is greater than a target nitrogen oxide concentration, and wherein the combustion air ratio is reduced if the nitrogen oxide concentration that is detected is less than the target nitrogen oxide concentration.

4. The method according to claim 1, wherein the ignition timing is retarded if the throttle valve reserve that is detected reaches or drops below a predetermined minimum reserve value, and wherein the ignition timing is advanced after a retard setting if the throttle valve reserve that is detected exceeds the predetermined minimum reserve value.

5. The method according to claim 4, wherein the ignition timing is advanced after the retard setting if the throttle valve reserve that is detected exceeds the predetermined minimum reserve value plus a predetermined hysteresis value.

6. The method according to claim 4, wherein the ignition timing is advanced as long as previous retard adjustments have not yet been compensated.

7. The method according to claim 1, wherein an alarm is issued if the throttle valve reserve that is detected reaches or drops below a predetermined minimum reserve value and at the same time the ignition timing reaches or exceeds a predetermined maximum ignition timing and at the same time the nitrogen oxide concentration that is detected is greater than a predetermined target nitrogen oxide concentration.

8. The method according to claim 1, wherein the throttle valve reserve is adjusted via a bypass path setting device arranged in a compressor bypass path bypassing a compressor arranged in the air path, wherein a flow cross-section of the compressor bypass path is changed by controlling the bypass path setting device.

9. The method according to claim 8, wherein the ignition timing is retarded only if a predetermined closing position in the bypass path setting device has been reached or exceeded.

10. A control device for an internal combustion engine, the control device comprising: the control device, which is configured for carrying out a method for operating the internal combustion engine, the method including the steps of: introducing a fuel gas with a fluctuating hydrogen content into an air path of the internal combustion engine; adjusting a combustion air ratio for a combustion chamber of the internal combustion engine via a predeterminable fuel gas mass flow into the air path; adjusting a power variable of the internal combustion engine by a throttle valve that is arranged in the air path; detecting a nitrogen oxide concentration in an exhaust gas path of the internal combustion engine; adjusting the combustion air ratio depending on the nitrogen oxide concentration that is detected; detecting a throttle valve reserve in the air path; and selecting an ignition timing in the combustion chamber of the internal combustion engine depending on the throttle valve reserve that is detected.

11. An internal combustion engine, comprising: an air path; a gas injection device configured for introducing a fuel gas into the air path of internal combustion engine; a throttle valve which is arranged in the air path; an exhaust path; a nitrogen oxide sensor arranged in the exhaust gas path; a combustion chamber; an ignition device arranged in the combustion chamber; a control device, which is operatively connected with the gas injection device, the throttle valve, and the nitrogen oxide sensor, the control device being configured for carrying out a method for operating the internal combustion engine, the method including the steps of: introducing the fuel gas with a fluctuating hydrogen content into the air path of the internal combustion engine; adjusting a combustion air ratio for the combustion chamber of the internal combustion engine via a predeterminable fuel gas mass flow into the air path; adjusting a power variable of the internal combustion engine by the throttle valve that is arranged in the air path; detecting a nitrogen oxide concentration in the exhaust gas path of the internal combustion engine; adjusting the combustion air ratio depending on the nitrogen oxide concentration that is detected; detecting a throttle valve reserve in the air path; and selecting an ignition timing in the combustion chamber of the internal combustion engine depending on the throttle valve reserve that is detected.

12. The internal combustion engine according to claim 11, wherein the internal combustion engine further includes a compressor, a compressor bypass path, and a bypass path setting device, the compressor being in the air path, the compressor bypass path being around the compressor, the bypass path setting device being arranged in the compressor bypass path and being configured for changing a flow cross-section of the compressor bypass path, the control device being operatively connected with the bypass path setting device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above-mentioned and other features and advantages of this invention, and the

[0038] manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0039] FIG. 1 is a schematic representation of one design example of an internal combustion engine with a design example of a control device;

[0040] FIG. 2 is a first schematic representation of a design example of the method in the form of a flow chart; and

[0041] FIG. 3 a second schematic representation of the method.

[0042] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0043] FIG. 1 is a schematic representation of a design example of an internal combustion engine 1 with a design example of a control device 3.

[0044] Internal combustion engine 1 has an air path 5 and a gas injection device 7, in particular a gas injection valve in air path 5, wherein gas injection device 7 is arranged and designed to introduce a fuel gas having a temporally fluctuating hydrogen component into air path 5. Internal combustion engine 1 moreover has a throttle valve 9 arranged in air path 5, and a nitrogen oxide sensor 13, arranged in an exhaust gas path 11 of internal combustion engine 1. Furthermore, internal combustion engine 1 has an ignition device 17 arranged in combustion chamber 15 of internal combustion engine 1. For the sake of clarity, only one combustion chamber 15 and only one ignition device 17 are identified with the corresponding reference symbol. Control device 3 is operatively connected with gas injection device 7, throttle valve 9 and nitrogen oxide sensor 13. It is designed, in particular, to carry out a process described in more detail below.

[0045] In particular, internal combustion engine 1 has a compressor 19 in air path 5, as well as a compressor bypass path 21 around compressor 19, wherein a bypass path setting device 23, in particular a bypass flap, is arranged in compressor bypass path 21. The latter is designed to change the flow cross section of compressor bypass path 21. Control device 3 is operatively connected with bypass path setting device 23.

[0046] In particular, internal combustion engine 1 also has a turbine 25 in exhaust gas path 11, which is drive-and operatively connected with compressor 19. Internal combustion engine 1 has, in particular, an exhaust gas turbocharger 27, which has on the one hand compressor 19 arranged in air path 5 and on the other hand turbine 25 which is arranged in exhaust gas path 11 and is drive-and operatively connected with compressor 19.

[0047] FIG. 2 is a first schematic representation of a design example of the process in the form of a flow chart.

[0048] Identical and functionally identical elements are provided with the same reference symbols in all drawings, so that reference is made respectively to the previous description.

[0049] In the herein illustrated design example, the process starts in a first step S1. In a second step S2, it is verified whether a nitrogen oxide concentration [NO.sub.x] in the exhaust gas detected by nitrogen oxide sensor 13in particular, an actual nitrogen oxide concentration-is greater than a predetermined target nitrogen oxide concentration [NO.sub.x].sub.s, wherein the predetermined target nitrogen oxide concentration [NO.sub.x].sub.s corresponds in particular to a legally mandated limit valueoptionally minus a safety margin. If this is the case, combustion air ratio is increased in a third step S3 starting from a current valuein particular by a predetermined lambda incrementin particular by suitably controlling gas injection device 7 in order to reducein particular incrementallya mass flow of combustion gas into air path 5. Subsequently it is verified in a fourth step S4 whether a throttle valve reserve DKRin particular, an actual throttle valve reserve-has reached or exceeded a predetermined minimum reserve value DKR.sub.min. If this is the case, the process is continued in second step S2.

[0050] If, on the other hand throttle valve reserve DKR drops below predetermined minimum reserve value DKR.sub.min, it is verified in a fifth step S5, whether an ignition timing ZP, in particular a current actual ignition timing reaches or exceeds a predetermined maximum ignition timing ZP.sub.max. If this is not the case, ignition timing ZP is retarded in a sixth step S6especially by a predetermined ignition timing incrementstarting from its current value. Optionally, however, ignition timing ZP is only retarded in sixth step S6 if bypass path setting device 23 has reached or exceeded a predetermined closing position. The process is then continued in second step S2.

[0051] If it is determined in second step S2 that nitrogen oxide concentration [NO.sub.x] is not greater than target nitrogen oxide concentration [NO.sub.x].sub.s, it is verified in a seventh step S7 whether nitrogen oxide concentration [NO.sub.x] is less than the target nitrogen oxide concentration [NO.sub.x].sub.s. If this is the case, combustion air ratio A is reduced in an eighth step S8 starting from its current valuein particular by the predetermined lambda incrementin particular by suitably controlling gas injection device 7 in order to increase the mass flow of combustion gas into air path 5in particular incrementally. It is then verified in a ninth step S9, whether throttle valve reserve DKR reaches or exceeds the predetermined minimum reserve value DKR.sub.min plus a predetermined hysteresis value DKR.sub.Hyst. If this is not the case, the process is continued in second step S2.

[0052] If, however, throttle reserve DKR exceeds the predetermined minimum reserve value DKR.sub.min plus the predetermined hysteresis value DKR.sub.Hyst, it is verified in a tenth step S10 whether ignition timing ZP has already been changed to retard. If this is the case, and in particular if the retard adjustment has not already been compensated for by subsequent advance adjustments, ignition timing ZP is readjusted to an advance setting in an eleventh step S11, starting from its current valuein particular by the predetermined ignition timing increment. The process is then continued in step S2.

[0053] If, in contrast it is determined in tenth step S10, that previously no change to retard the ignition timing ZP has yet occurred, the process is continued in second step S2, directly following tenth step S10.

[0054] If it is determined in seventh step S7, that the nitrogen oxide concentration [No.sub.x] is not less than the target nitrogen oxide concentration [No.sub.x].sub.s, it is verified in a twelfth step S12 whether the nitrogen oxide concentration [No.sub.x] is equal to the target nitrogen oxide concentration [No.sub.x].sub.s. If this is the case, no further action will be taken andafter a predetermined optional waiting period-the process is restarted in first step S1. If this is not the casewhich based on the intrinsic logic of the process should actually not be the case but could possibly occur as an exception in the event of high-frequency fluctuations in the hydrogen contentthe process is continued in step S2.

[0055] If it is determined in fifth step S5 that ignition timing ZP reaches or exceeds the predetermined maximum ignition timing ZP.sub.max, it is verified again in a thirteenth step S13, whether the nitrogen oxide concentration [No.sub.x] is greater than the predetermined target nitrogen oxide concentration [No.sub.x].sub.s. If this is not the case, the process is continued in seventh step S7.

[0056] If, on the other hand, the nitrogen oxide concentration [NO.sub.x] in thirteenth step S13 exceeds the predetermined target nitrogen oxide concentration [NO.sub.x].sub.s, an alarm is issued in a fourteenth step S14. The process optionally ends herewith. Alternatively, the process can also be restarted in first step S1, especially following measures that have been implemented in response to the alarm.

[0057] FIG. 2 shows the process in a sequence of discrete steps that are implemented successively. While it is possible in one design example, to carry out the method in this way this illustration serves in particular to provide a better understanding of the structure of the method. In fact, the method is optionally carried out simultaneously by a plurality of control devices, in particular in another embodiment example, as explained below in connection with FIG. 3.

[0058] In this respect, FIG. 3 illustrates a second schematic representation of the method. In the design example shown here, the actual nitrogen oxide concentration [NO.sub.x] and the target nitrogen oxide concentration [NO.sub.x].sub.s are fed into a nitrogen oxide control device 29. Nitrogen oxide control device 29 calculates an offset combustion air ratio from a control deviation calculated from this, which is offset in a first calculation element 31 with a target combustion air ratio .sub.s read in particular from a characteristic map to form a combustion air ratio . Combustion air ratio is used to control gas injection device 7 in order to adjust combustion air ratio .

[0059] At the same time, the actual throttle valve reserve DKR and a target throttle valve reserve DKRs are entered into a bypass flap control device 33, which is provided for adjusting the position of bypass path setting device 23. Bypass flap control device 33 calculates a bypass flap position BKP from a control deviation calculated from this, which is used to control bypass path setting device 23.

[0060] Bypass flap position BKP is also transmitted to an ignition time control device 35, wherein bypass flap position BKP is used in particular, to activate or trigger ignition timing control device 35. In particular, ignition timing control device 35 is inactive, as long as bypass flap position BKP has not reached or exceeded a predetermined closing position. If bypass flap position BKP reaches or exceeds the predetermined closing position, ignition timing control device 35 is activated. Optionally, ignition timing control device 35 is again deactivated, when bypass flap position BKP drops again below the predetermined closing position.

[0061] If ignition timing control device 35 is active, it calculates an offset ignition timing AZP from the actual throttle valve reserve DKR and the reserve minimum value DKR.sub.min, which is offset in a second calculation element 37 with a target ignition timing ZPs read in particular from a characteristic map to form an ignition timing ZP, which is then used to control ignition device 17. In particular, predetermined hysteresis value DKR.sub.Hyst is still included in ignition timing control device 35 in order to reset ignition timing ZP to advance only if throttle valve reserve DKR exceeds the reserve minimum value DKR.sub.min plus the predetermined hysteresis value DKR.sub.Hyst.

[0062] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.