Method for operating a hybrid motor vehicle

Abstract

A method for operating a hybrid motor vehicle. In one example, the vehicle comprises an internal combustion engine (10) and at least one electric motor (20). As long as at least one parameter of an exhaust gas aftertreatment system (12) of the internal combustion engine (10) lies outside a given range, the starting of the internal combustion engine (10) is delayed and the internal combustion engine (10) is dragged by the electric motor (20). At the same time at least one measure is carried out which changes the parameter.

Claims

1. A method for operating a hybrid motor vehicle that includes an internal combustion engine (10) and at least one electric motor (20), the method comprising: as long as at least one parameter of an exhaust gas aftertreatment system (12) of the internal combustion engine (10) lies outside a given range, delaying starting of the internal combustion engine (10), dragging the internal combustion engine (10) by the electric motor (20); determining a temperature (T.sub.12) of the exhaust gas aftertreatment system as one parameter; when the temperature (T.sub.12) lies below a temperature threshold value, heating the exhaust gas aftertreatment system with a burner (16) arranged in an exhaust gas line (11) between a nitrogen storage (NSC) catalyst (13) and a selective catalytic reduction (SCR) catalyst (14); determining a nitrogen oxide load (B.sub.NOx) of the nitrogen oxide storage catalyst (13) of the exhaust gas aftertreatment system (12) as another parameter; and when the nitrogen oxide load (B.sub.NOx) exceeds a nitrogen oxide load threshold value, dispensing fuel into an exhaust gas line of the internal combustion engine (10).

2. The method according to claim 1, including determining an ammonia load (B.sub.NH3) of an SCR catalyst (14) of the exhaust gas aftertreatment system (12) as another parameter.

3. The method according to claim 2, when the ammonia load (B.sub.NH3) is below an ammonia load threshold value, dispensing (63) ammonia or an ammonia-cleaving reagent into an exhaust gas line (11) of the internal combustion engine (10).

4. The method according to claim 3, including checking whether the exhaust gas aftertreatment system (12) is ready to operate, and starting the internal combustion engine when the temperature (T.sub.12) lies at or above a temperature threshold value, the nitrogen oxide load (B.sub.NOx) is at or below a nitrogen oxide load threshold value, and the ammonia load (B.sub.NH3) is at or above an ammonia load threshold value.

5. A non-transitory computer-readable storage medium comprising instructions that when executed by a computer cause the computer to control a hybrid motor vehicle that includes an internal combustion engine (10) and at least one electric motor (20), by: as long as at least one parameter of an exhaust gas aftertreatment system (12) of the internal combustion engine (10) lies outside a given range, delaying starting of the internal combustion engine (10), dragging the internal combustion engine (10) by the electric motor (20), and, at the same time, carrying out at least one measure which changes the parameter; determining a temperature (T.sub.12) of the exhaust gas aftertreatment system as one parameter; when the temperature (T.sub.12) lies below a temperature threshold value, controlling a heating of the exhaust gas aftertreatment system by a burner (16) arranged in an exhaust gas line (11) between a nitrogen storage (NSC) catalyst (13) and a selective catalytic reduction (SCR) catalyst (14); determining a nitrogen oxide load (BNOx) of the nitrogen oxide storage catalyst (13) of the exhaust gas aftertreatment system (12) as another parameter; and when the nitrogen oxide load (BNOx) exceeds a nitrogen oxide load threshold value, controlling a dispensing of fuel into an exhaust gas line of the internal combustion engine (10).

6. The non-transitory computer-readable storage medium according to claim 5, wherein the instructions executed by the computer cause the computer to: determine an ammonia load (B.sub.NH3) of an SCR catalyst (14) of the exhaust gas aftertreatment system (12) as another parameter.

7. The non-transitory computer-readable storage medium according to claim 6, wherein the instructions executed by the computer cause the computer to: when the ammonia load (B.sub.NH3) is below an ammonia load threshold value, control dispensing (63) of ammonia or an ammonia-cleaving reagent into an exhaust gas line (11) of the internal combustion engine (10).

8. The non-transitory computer-readable storage medium according to claim 7, wherein the instructions executed by the computer cause the computer to check whether the exhaust gas aftertreatment system (12) is ready to operate, and start the internal combustion engine when the temperature (T.sub.12) lies at or above a temperature threshold value, the nitrogen oxide load (B.sub.NOx) is at or below a nitrogen oxide load threshold value, and the ammonia load (B.sub.NH3) is at or above an ammonia load threshold value.

9. An electronic controller (40) for operating a hybrid motor vehicle that includes an internal combustion engine (10) and at least one electric motor (20), wherein the electronic controller is configured to: as long as at least one parameter of an exhaust gas aftertreatment system (12) of the internal combustion engine (10) lies outside a given range, delay starting of the internal combustion engine (10), while dragging the internal combustion engine (10) by the electric motor (20); determine a temperature (T.sub.12) of the exhaust gas aftertreatment system as one parameter; when the temperature (T.sub.12) lies below a temperature threshold value, control heating of the exhaust gas aftertreatment system by a burner (16) arranged in an exhaust gas line (11) between a nitrogen storage (NSC) catalyst (13) and a selective catalytic reduction (SCR) catalyst (14); determine a nitrogen oxide load (B.sub.NOx) of the nitrogen oxide storage catalyst (13) of the exhaust gas aftertreatment system (12) as another parameter; and when the nitrogen oxide load (B.sub.NOx) exceeds a nitrogen oxide load threshold value, control dispensing of fuel into an exhaust gas line of the internal combustion engine (10).

10. The electronic controller according to claim 9, wherein the electronic controller is configured to: determine an ammonia load (B.sub.NH3) of an SCR catalyst (14) of the exhaust gas aftertreatment system (12) as another parameter.

11. The electronic controller according to claim 10, wherein the electronic controller is configured to: when the ammonia load (B.sub.NH3) is below an ammonia load threshold value, control dispensing (63) of ammonia or an ammonia-cleaving reagent into an exhaust gas line (11) of the internal combustion engine (10).

12. The electronic controller according to claim 11, wherein the electronic controller is configured to: check whether the exhaust gas aftertreatment system (12) is ready to operate, and start the internal combustion engine when the temperature (T.sub.12) lies at or above a temperature threshold value, the nitrogen oxide load (B.sub.NOx) is at or below a nitrogen oxide load threshold value, and the ammonia load (B.sub.NH3) is at or above an ammonia load threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention is represented in the drawings and will be explained more closely in the following description.

(2) FIG. 1 shows schematically components of a hybrid motor vehicle, which can be operated by means of an exemplary embodiment of the method according to the invention.

(3) FIG. 2 shows a flow chart of an exemplary embodiment of the method according to the invention.

DETAILED DESCRIPTION

(4) A hybrid motor vehicle comprises in one exemplary embodiment of the invention an internal combustion engine 10, which is designed as a diesel engine, and an electric motor 20. The two motors 10, 20 are arranged in series on a drive train and can be separated from each other by means of a coupling 30. The internal combustion engine 10 comprises an exhaust gas line 11 with an exhaust gas aftertreatment system 12. The exhaust gas aftertreatment system 12 comprises an NSC catalyst 13 and, downstream from the NSC catalyst 13, a SCR catalyst 14. The catalyst material of the SCR catalyst 14 is arranged on a diesel particulate filter (SCR on filter; SCRF). A dispensing valve 15 is arranged between the two catalysts 13, 14 in the exhaust gas line 11. It is designed to dispense HWL from a reducing agent tank, not shown, into the exhaust gas line 11. Between the NSC catalyst 13 and the dispensing valve 15 there is arranged a burner 16 in the exhaust gas line 11. When the burner 16 is turned on, it heats up the exhaust gas in the exhaust gas line 11 and thereby heats the SCR catalyst 14 situated downstream from the burner 16. Soot particles emitted by the burner 16 are bound in the diesel particulate filter of the SCR catalyst 14.

(5) An electronic controller 40 controls the internal combustion engine 10, the electric motor 20 and the coupling 30. Moreover, it controls the dispensing valve 15 and the burner 16. By means of sensors, not represented, and models stored in the controller 40, it can ascertain the temperature T.sub.12 of the exhaust gas aftertreatment system 12, the nitrogen oxide load B.sub.NOx of the NSC catalyst 13 and the ammonia load B.sub.NH3 of the SCR catalyst 14.

(6) An exemplary embodiment of the method according to the invention begins with a start request 50 arriving at the internal combustion engine 10. As a result of the start request 50, the coupling 30 is closed, in order to drag the internal combustion engine 10 by means of the electric motor 20. The fuel injection and ignition of the internal combustion engine 10 are for now not yet activated. In the controller 40, the current temperature T.sub.12 of the exhaust gas aftertreatment system 12 is determined 51. If a following first check 52 reveals that the temperature T.sub.12 lies below a temperature threshold value, a heating 61 of the exhaust gas aftertreatment system 12 will be started by activating the burner 16. Moreover, an entry will be generated in the controller 40 that the exhaust gas aftertreatment system 12 is not yet ready to operate. Regardless of the outcome of the first check 52, the current nitrogen oxide load B.sub.NOx of the NSC catalyst 13 is now determined 53. In a second check 54, it is checked whether this exceeds a nitrogen oxide load threshold value. If this is the case, a dispensing 62 of diesel fuel into the exhaust gas line 11 occurs, in that a fuel injection is initiated in the internal combustion engine 10 with the ignition switched off. This fuel may react on the surface of the NSC catalyst 13 with the nitrogen oxides stored there. Moreover, an entry will be generated in the controller 40 that the exhaust gas aftertreatment system 12 is not yet ready to operate. Regardless of the outcome of the second check 54, the ammonia load B.sub.NH3 of the SCR catalyst 14 is determined 55. If a third check 56 reveals that this is below an ammonia load threshold value, a dispensing 63 of HWL into the exhaust gas line 11 will be carried out by initiating an injection by means of the dispensing valve 15. The HWL is decomposed in the exhaust gas line 11 to form ammonia, which is stored in the SCR catalyst 14. In this case as well, an entry is generated in the controller 40 that the exhaust gas aftertreatment system 12 is not yet ready to operate. Regardless of the outcome of the third check 56, a fourth check 57 will now be carried out. This will check whether an entry has been generated in the electronic controller 40 that the exhaust gas aftertreatment system 12 is not yet ready for dispensing. If no such entry is present, a starting 58 of the internal combustion engine 10 will occur. The coupling 30 can then be opened and the electric motor 20 switched off.

(7) However, if such an entry is present, the entry will be reset and steps 51 to 57 will be performed once more. The measures 61, 62, 63 will be repeated as often as it takes until the first three checks 52, 54, 56 reveal that all parameters T.sub.12, B.sub.NOx, B.sub.NH3 lie within their given ranges. The dragging of the internal combustion engine 10 by the electric motor 20 while waiting for the operational readiness of the exhaust gas aftertreatment system 12 will support the measures 61, 62, 63 by generating an air stream through the exhaust gas line 11. This transports the hot exhaust gases of the burner 16 and the HWL of the dispensing valve 15 to the SCR catalyst 14. Furthermore, it transports fuel injected into the internal combustion engine 10 to the NSC catalyst 13. In this way, a starting of the internal combustion engine 10 in an optimal operating range for the exhaust gas aftertreatment is made possible.