METHOD FOR OPERATING A DRIVE DEVICE AND CORRESPONDING DRIVE DEVICE

Abstract

A method for operating a drive device which has a drive unit that generates exhaust gas and an exhaust gas aftertreatment device for aftertreatment of the exhaust gas. A composition of a fuel-air mixture used for operating the drive unit is determined at least temporarily by a lambda control based on a first measured value of a first lambda sensor arranged upstream of the exhaust gas aftertreatment device and based on a second measured value of a second lambda sensor arranged downstream of the exhaust gas aftertreatment device.

Claims

1-10. (canceled)

11. A method for operating a drive device, which has an exhaust gas generating drive unit and an exhaust gas aftertreatment device for the aftertreatment of the exhaust gas, wherein a composition of a fuel-air mixture used to operate the drive unit is determined at least temporarily by a lambda control based on a first measured value of a first lambda sensor arranged upstream of the exhaust gas aftertreatment device and based on a second measured value of a second lambda sensor arranged downstream of the exhaust gas aftertreatment device, wherein in order to adjust an oxygen filling level of an oxygen storage of the exhaust gas aftertreatment device to a target filling level after an occurrence of a value of the second measured value, which corresponds to the boundary value of a fill level range that accommodates the target fill level, the composition is adjusted in such a way that the oxygen fill level changes by a pilot oxygen amount in the direction of the target fill level, then the composition is determined during a control period using the lambda control until the second measured value is at least within an unavoidable tolerance equal to a target value corresponding to the target filling level and finally the pilot oxygen amount is corrected by an oxygen balance value determined during the control period.

12. The method according to claim 11, wherein as part of the lambda control, the first measured value is regulated to a first target value, wherein the first measured value and/or the first target value are corrected with a trim value, which is determined by a trim control by means of the second measured value.

13. The method according to claim 11, wherein as part of the trim control, the second measured value is regulated by setting the trim value to a second target value corresponding to the target value.

14. The method according to claim 11, wherein the filling level range is delimited, on the one hand, by a first value corresponding to a completely empty oxygen storage and, on the other hand, by a second value corresponding to an oxygen storage tank completely filled with oxygen.

15. The method according to claim 11, wherein a fill level value is used as the target fill level, which lies between the first value and the second value and is spaced from both values.

16. The method according to claim 11, wherein a fill level value is used as the target fill level, which is closer to the first value than to the second value.

17. The method according to claim 11, wherein it is assumed that the second measured value is equal to the target value if a gradient of the trim value is equal to zero.

18. The method according to claim 11, wherein the second measured value during the control period is continuously held in a target value range corresponding to the fill level range at a distance from a further boundary value opposite the boundary value.

19. The method according to claim 11, wherein the second measured value is continuously and consistently adjusted in the direction of the target value during the control period.

20. A drive device, in particular for carrying out the method according to claim 11, with an exhaust gas generating drive unit and an exhaust gas aftertreatment device for aftertreatment of the exhaust gas, wherein the drive device is intended and designed to determine a composition of a fuel-air mixture used to operate the drive unit at least temporarily by means of a lambda control based on a first measured value of a first lambda sensor arranged upstream of the exhaust gas aftertreatment device and based on a second measured value of a second lambda sensor arranged downstream of the exhaust gas aftertreatment device, wherein the drive direction is further provided and designed, for adjusting an oxygen filling level of an oxygen storage of the exhaust gas aftertreatment device to a target fill level after an occurrence of a value of the second measured value, which corresponds to a boundary value of a fill level range that accommodates the target fill level, for adjusting the composition in such a way that the oxygen fill level changes by a pilot oxygen amount in the direction of the target fill level, then, during a regulation period, for determining a composition by means of lambda control until the second measured value is at least within an unavoidable tolerance equal to a target value corresponding to the target filling level and finally for correcting the pilot oxygen amount by an oxygen balance value determined during the control period.

21. The method according to claim 12, wherein as part of the trim control, the second measured value is regulated by setting the trim value to a second target value corresponding to the target value.

22. The method according to claim 12, wherein the filling level range is delimited, on the one hand, by a first value corresponding to a completely empty oxygen storage and, on the other hand, by a second value corresponding to an oxygen storage tank completely filled with oxygen.

23. The method according to claim 13, wherein the filling level range is delimited, on the one hand, by a first value corresponding to a completely empty oxygen storage and, on the other hand, by a second value corresponding to an oxygen storage tank completely filled with oxygen.

24. The method according to claim 12, wherein a fill level value is used as the target fill level, which lies between the first value and the second value and is spaced from both values.

25. The method according to claim 13, wherein a fill level value is used as the target fill level, which lies between the first value and the second value and is spaced from both values.

26. The method according to claim 14, wherein a fill level value is used as the target fill level, which lies between the first value and the second value and is spaced from both values.

27. The method according to claim 12, wherein a fill level value is used as the target fill level, which is closer to the first value than to the second value.

28. The method according to claim 13, wherein a fill level value is used as the target fill level, which is closer to the first value than to the second value.

29. The method according to claim 14, wherein a fill level value is used as the target fill level, which is closer to the first value than to the second value.

30. The method according to claim 15, wherein a fill level value is used as the target fill level, which is closer to the first value than to the second value.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0043] In the following, the invention will be explained in greater detail with reference to the exemplary embodiments depicted in the drawings, without this restricting the invention. In the figures:

[0044] FIG. 1 is a schematic representation of a drive device with a drive unit and an exhaust gas aftertreatment device,

[0045] FIG. 2 shows several diagrams in which different state variables of the drive device are plotted over time.

DETAILED DESCRIPTION

[0046] FIG. 1 shows a schematic representation of a drive device 1, which is used, for example, to drive a motor vehicle. In general, the drive device 1 serves to provide a drive torque, namely by means of a drive unit 2. During its operation, the drive unit 2 is supplied with a fuel-air mixture with a specific composition. The composition is determined using a device 3 for carrying out lambda control. During operation of the drive unit 2 exhaust gas is generated, which is removed from the drive unit 2 and fed to an exhaust gas aftertreatment device 4. With respect to a main flow direction of the exhaust gas, the first lambda sensor 5 is located upstream of the exhaust gas aftertreatment device 4 and the second lambda sensor 6 is located downstream of the exhaust gas aftertreatment device 4.

[0047] The two lambda sensors 5 and 6 are used to detect a residual oxygen concentration in the exhaust gas. A measured value delivered by the first lambda sensor 5 is used as the first measured value and a measured value delivered by the second lambda sensor 6 is used as the second measured value. The first measured value serves as the input variable of a first sub-device 7 of the device 3. The actual lambda control of the composition of the fuel-air mixture is carried out in this. In the first sub-device 7, the composition is determined based on the first measured value and a setting value is determined according to the arrow 8. In addition, a trim value is transmitted to the first sub-device 7 according to the arrow 9, which trim value is also used to determine the composition. In particular, the first measured value and/or a first target value determined from the setting value is corrected with the trim value.

[0048] The trim value is determined using a second sub-device 10 of the device 3, which is used to carry out a trim control. The trim control is carried out using the second measured value of the second lambda sensor 6 by setting the second measured value to a second target value. value is regulated, which is also determined, for example, from the default value.

[0049] FIG. 2 shows several diagrams in which different courses are plotted over time t. The top first diagram shows the first measured value of the first lambda sensor 5 in courses 11, 12 and 13. These courses 11, 12 and 13 are identical for and between times t.sub.1, t.sub.2 and t.sub.3 and only differ starting from time t.sub.3. The central second diagram shows courses 14, 15 and 16 for an oxygen level of an oxygen storage of the exhaust gas aftertreatment device 4. The courses 14, 15 and 16 are identical for and between the periods t.sub.1 and t.sub.2, but differ starting from time t.sub.2. The lower third diagram shows courses 17, 18 and 19 for the second measured value of the second lambda sensor 6. The courses 17, 18 and 19 are identical for and between times t.sub.1 and t.sub.2, but differ starting from time t.sub.2.

[0050] The diagram above shows that the first measured value was before time t.sub.1 corresponds to a stoichiometric composition of the fuel air mixture that is supplied to the drive unit 2. From time t.sub.1, a thrust operation of the drive device 1 or the drive unit 2 is carried out, the drive unit 2 is therefore towed by an externally provided torque and the fuel supply to the drive unit 2 is interrupted. This means that through the drive unit 2 exhaust gases with a high proportion of air or oxygen excess enters the exhaust gas aftertreatment device 4.

[0051] This can be seen in the oxygen level of courses 14, 15 and 16, which increases from time t.sub.1 up to time t.sub.2 to 100%. The oxygen storage at time t.sub.2 is therefore completely filled with oxygen. This circumstance can also be recognized from courses 17, 18 and 19: The second measured value decreases between time t.sub.1 and time t.sub.2 starting from an initial value of, for example, approximately 0.65 V. The value to which the second measured value falls corresponds, for example, to a boundary value of a level range containing a target filling level of the oxygen storage.

[0052] After such a value of the second measured value occurs, the oxygen level should be set to a target level, which in the exemplary embodiment shown here is 50%. Tho this end, initially, starting from time t.sub.2 to time t.sub.3 the oxygen level is changed by a pilot oxygen amount in the direction of the target level by appropriate operation of the drive unit 2. This measure is completed at time t.sub.3. In the case of courses 11, 14 and 17, the pilot control oxygen amount is sufficient to adjust the oxygen level up to the target level. This can be seen in courses 14 and 17.

[0053] From time t.sub.3 the composition of the fuel-air mixture is determined using the lambda control. In this context, the trim control is also carried out, as part of which the second measured value is regulated to a target value which corresponds to the target filling level. Courses 12 and 13 show the influence of the trim control on the first measured value. For course 12, the pilot oxygen amount was too small, so that more oxygen has to be subsequently added to the oxygen storage. Course 12 corresponds to courses 15 and 18.

[0054] For course 13, however, the amount of pilot control oxygen was too large. Accordingly, oxygen must be discharged from the oxygen storage as part of the lambda control or trim control. The course 13 corresponds to the courses 16 and 19. It can be seen that at the time t.sub.4 the second measured value has reached the target value. Correspondingly, courses 15 and 16 have also reached the target level and according to courses 12 and 13, the intervention of the trim control has also decreased. The latter means in particular that a gradient of the trim value, which results from the trim control and is used to correct the lambda control, is equal to zero or at least almost equal to zero.

[0055] The procedure described enables particularly quick adjustment of the oxygen level to the target level, in particular without running through the entire level range. This achieves a reduction in fuel consumption of the drive device 1 and a reduction in pollutant emissions.

LIST OF REFERENCE NUMERALS

[0056] 1 drive device [0057] 2 drive unit [0058] 3 device [0059] 4 exhaust gas aftertreatment device [0060] 5 first lambda sensor [0061] 6 second lambda sensor [0062] 7 first sub-device [0063] 8 arrow [0064] 9 arrow [0065] 10 second sub-device [0066] 11 course [0067] 12 course [0068] 13 course [0069] 14 course [0070] 15 course [0071] 16 course [0072] 17 course [0073] 18 course [0074] 19 course