Method for operating a dosing device and motor vehicle having a dosing device

Abstract

A method for operating a dosing device for metering an additive to an exhaust-gas treatment device includes determining a dosing amount of additive required by the exhaust-gas treatment device in step a). Subsequently, in step b), an operating mode for the dosing device is determined by carrying out at least steps b.1) and b.2). In step b.1), at least one characteristic operating value of at least one component of the dosing device is provided being definitive of a degree of aging of the dosing device. In step b.2), an operating mode for the dosing device is set in dependence on the characteristic operating value from step b.1). In step c), the dosing device is operated with the set operating mode so that the dosing amount required in step a) is supplied to the exhaust-gas treatment device. A motor vehicle having a dosing device is also provided.

Claims

1. A method for operating a doser for adding an additive to an exhaust-gas treatment device, the method comprising the following steps: a) determining a dosing amount of the additive required by the exhaust-gas treatment device; b) determining an operating mode for the doser by carrying out at least the following steps: b.1) determining, directly at the doser, at least one characteristic operating value of at least one component of the doser being definitive of a degree of aging of the doser, the at least one characteristic operating value referring to a property of the at least one component of the doser and the property not fluctuating over short timescales making the property a count variable; b.2) setting the operating mode for the doser in dependence on the at least one characteristic operating value from step b.1); c) operating the doser with the set operating mode to supply the dosing amount required in accordance with step a) to the exhaust-gas treatment device; and d) setting a number of repetitions in which the method is executed with the steps a) and c), increasing a counter in each case, until the counter has reached the number of repetitions, and then executing steps b.1) and b.2).

2. The method according to claim 1, which further comprises giving consideration, for determining the at least one characteristic operating value in step b.1), to at least one of the following parameters relevant to the aging of the doser: number of dosing processes having been previously performed, age of the doser, or past operating duration of the doser.

3. The method according to claim 1, which further comprises, giving consideration for determining the at least one characteristic operating value in step b.1), to at least one of the following operating conditions having prevailed during the operation of the doser in at least one prior time interval: load range in which the doser has been operated, or temperature that prevailed in the doser.

4. The method according to claim 1, which further comprises, in step b.1), reading out the at least one characteristic operating value from a memory, updating the at least one characteristic operating value in the memory at regular intervals, and giving consideration, for the update, to at least one relevant parameter, at least one relevant event or at least one relevant operating condition from at least one prior time interval.

5. The method according to claim 1, which further comprises, in step a) giving consideration, for determining the dosing amount, to at least one of the following operating parameters of the exhaust-gas treatment device: exhaust-gas temperature, exhaust-gas composition, exhaust-gas mass flow rate, activity of a catalytic converter in the exhaust-gas treatment device, or loading of a particle separator in the exhaust-gas treatment device.

6. The method according to claim 1, which further comprises, in step a) giving consideration, for determining the dosing amount, to at least one of the following operating parameters of an internal combustion engine connected to the exhaust-gas treatment device: torque, engine speed, power output, or lambda value.

7. The method according to claim 1, which further comprises, in step c), giving consideration to at least one operating parameter of the doser selected from the following group: pressure of the additive in the doser, fill level in a tank of the doser, temperature of the doser, or vibration of the doser.

8. The method according to claim 1, which further comprises including in the operating mode set in step b.2) at least one of the following operating functions defining an operation of a delivery pump or of an injector being influenced in a manner dependent on the at least one characteristic operating value: an activation current profile for the delivery pump; an activation current profile for the injector; an activation frequency for the delivery pump, or an activation frequency for the injector.

9. The method according to claim 1, which further comprises, in step b.2), comparing the at least one characteristic operating value with at least one reference value, and selecting at least one operating function of the operating mode from a plurality of predefined operating functions in dependence on the comparison.

10. The method according to claim 1, which further comprises setting the number of repetitions in dependence on a characteristic operating value.

11. The method according to claim 1, which further comprises providing the doser with a dosing pump and an injector, and, in step c), implementing the set dosing amount from step a) by using the dosing pump and by using the injector.

12. A method for operating a doser for adding an additive to an exhaust-gas treatment device, the method comprising the following steps: a) determining a dosing amount of the additive required by the exhaust-gas treatment device; b) determining an operating mode for the doser by carrying out at least the following steps: b.1) determining, directly at the doser, at least one characteristic operating value of at least one component of the doser being definitive of a degree of aging of the doser, the at least one characteristic operating value referring to a property of the at least one component of the doser and the property not fluctuating over short timescales making the property a count variable, and giving consideration, for determining the at least one characteristic operating value in step b.1), to at least a number of occurrences of the following events relevant to the aging of the doser: number of freezing processes to which the doser has been exposed, number of emergency deactivations of the doser, number of hot shutdown processes of an internal combustion engine connected to the exhaust-gas treatment device, number of instances of misfueling of a tank from which the doser extracts the additive, or number of phases in which the doser has been deactivated for longer than a predefined time interval; b.2) setting the operating mode for the doser in dependence on the at least one characteristic operating value from step b.1); and c) operating the doser with the set operating mode to supply the dosing amount required in accordance with step a) to the exhaust-gas treatment device.

13. A motor vehicle, comprising: an internal combustion engine; an exhaust-gas treatment device configured to purify exhaust gases of said internal combustion engine; a doser configured to supply reducing agent to said exhaust-gas treatment device; and a control unit constructed and configured to operate said doser for adding the reducing agent to said exhaust-gas treatment device by carrying out the following steps: a) determining a dosing amount of the reducing agent required by said exhaust-gas treatment device; b) determining an operating mode for said doser by carrying out at least the following steps: b.1) determining, directly at said doser, at least one characteristic operating value of at least one component of said doser being definitive of a degree of aging of said doser, said at least one characteristic operating value referring to a property of said at least one component of said doser, said property not fluctuating over short timescales making said property a count variable; b.2) setting said operating mode for said doser in dependence on said at least one characteristic operating value from step b.1); c) operating said doser with said set operating mode to supply said dosing amount required in accordance with step a) to said exhaust-gas treatment device; and d) setting a number of repetitions in which the method is executed with the steps a) and c), increasing a counter in each case, until the counter has reached the number of repetitions, and then executing steps b.1) and b.2).

14. A method for operating a doser for adding an additive to an exhaust-gas treatment device, the method comprising the following steps: a) determining a dosing amount of the additive required by the exhaust-gas treatment device; b) determining an operating mode for the doser by carrying out at least the following steps: b.1) determining, directly at the doser, at least one characteristic operating value of at least one component of the doser being definitive of a degree of aging of the doser; b.2) setting the operating mode for the doser in dependence on the at least one characteristic operating value from step b.1): and c) operating the doser with the set operating mode to supply the dosing amount required in accordance with step a) to the exhaust-gas treatment device: giving consideration for determining the at least one characteristic operating value in step b.1) to at least one of the following parameters relevant to the aging of the doser: number of dosing processes having been previously performed, or past operating duration of the doser.

15. A method for operating a doser for adding an additive to an exhaust-gas treatment device, the method comprising the following steps: a) determining a dosing amount of the additive required by the exhaust-gas treatment device; b) determining an operating mode for the doser by carrying out at least the following steps: b.1) determining, directly at the doser, at least one characteristic operating value of at least one component of the doser being definitive of a degree of aging of the doser: b2) setting the operating mode for the doser in dependence on the at least one characteristic operating value from step b.1); and c) operating the doser with the set operating mode to supply the dosing amount required in accordance with step a) to the exhaust-gas treatment device; giving consideration for determining the at least one characteristic operating value in step b.1) to at least a number of occurrences of the following events relevant to the aging of the doser: number of freezing processes to which the doser has been exposed, number of emergency deactivations of the doser, number of hot shutdown processes of an internal combustion engine connected to the exhaust-gas treatment device, number of instances of misfueling of a tank from which the doser extracts the additive, or number of phases in which the doser has been deactivated for longer than a predefined time interval.

16. A method for operating a doser for adding an additive to an exhaust-gas treatment device, the method comprising the following steps: a) determining a dosing amount of the additive required by the exhaust-gas treatment device; b) determining an operating mode for the doser by carrying out at least the following steps: b.1) determining, directly at the doser, at least one characteristic operating value of at least one component of the doser being definitive of a degree of aging of the doser; b.2) setting the operating mode for the doser in dependence on the at least one characteristic operating value from step b.1); and c) operating the doser with the set operating mode to supply the dosing amount required in accordance with step a) to the exhaust-gas treatment device; giving consideration for determining the at least one characteristic operating value in step b.1) to the following operating condition having prevailed during the operation of the doser in at least one prior time interval: load range in which the doser has been operated.

17. A motor vehicle, comprising: an internal combustion engine; an exhaust-gas treatment device configured to purify exhaust gases of said internal combustion engine; a doser configured to supply reducing agent to said exhaust-gas treatment device; and a control unit constructed and configured to operate said doser for adding the reducing agent to said exhaust-gas treatment device by carrying out the following steps: a) determining a dosing amount of the reducing agent required by said exhaust-gas treatment device; b) determining an operating mode for said doser by carrying out at least the following steps: b.1) determining, directly at said doser, at least one characteristic operating value of at least one component of said doser being definitive of a degree of aging of said doser, said at least one characteristic operating value referring to a property of said at least one component of said doser, said property not fluctuating over short timescales making said property a count variable, and giving consideration, for determining the at least one characteristic operating value in step b.1), to at least a number of occurrences of the following events relevant to the aging of the doser: number of freezing processes to which the doser has been exposed, number of emergency deactivations of the doser, number of hot shutdown processes of an internal combustion engine connected to the exhaust-gas treatment device, number of instances of misfueling of a tank from which the doser extracts the additive, or number of phases in which the doser has been deactivated for longer than a predefined time interval; b.2) setting said operating mode for said doser in dependence on said at least one characteristic operating value from step b.1); and c) operating said doser with said set operating mode to supply said dosing amount required in accordance with step a) to said exhaust-gas treatment device.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a block diagram of a motor vehicle having a dosing device and a control unit which are configured for operating the dosing device; and

(2) FIG. 2 is a flow diagram of a structural variant of the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) Referring now in detail to the figures of the drawing for explaining the invention and the technical field in more detail by showing particularly preferred structural variants to which the invention is not restricted and in which dimensional relationships are diagrammatic, and first, particularly, to FIG. 1 thereof, there is seen a motor vehicle 7 which has an internal combustion engine 8 and an exhaust-gas treatment device 2 for the purification of exhaust gases of the internal combustion engine 8. A catalytic converter 3 and a particle separator 4 for the purification of the exhaust gases are illustrated in the exhaust-gas treatment device 2. It is not imperative for precisely one catalytic converter 3 and one particle separator 4 to be provided in the exhaust-gas treatment device. Any desired configurations with at least one particle separator 4 and/or at least one catalytic converter 3 are possible. An additive (in particular a urea-water solution) can be supplied to the exhaust-gas treatment device 2 by using a dosing device 1. The dosing or metering device 1 is connected to a tank 10 and withdraws the additive from the tank 10. In this case, the tank 10 is, for example, filled with additive up to a fill level 11. The dosing device 1 has a dosing pump 5 and an injector 6. A dosing device 1 which has both a dosing pump 5 and an injector 6 is merely one structural variant. The dosing device may optionally have a passive injection device, such as, for example, a self-opening valve and/or a nozzle, instead of the injector 6. Furthermore, purely a delivery pump without a dosing function may be provided instead of the dosing pump 5. The dosing device 1 is controlled by a control unit 9, wherein the latter may be formed separately or may be formed as part of an engine controller of the motor vehicle.

(4) FIG. 2 shows a flow diagram of an exemplary embodiment of the method according to the invention. The figure shows method steps a), b) and c), which are performed repeatedly at regular intervals in the manner of a loop. The method step b) breaks down into method steps b.1), b.2) and b.3). The method step b.3) is performed during every execution of the method. As part of the method step b.3), a counter is increased. The method steps b.1) and b.2) are carried out every time the counter in step b.3) reaches a number of repetitions. In the method step a), arrows indicate operating parameters of an exhaust-gas treatment device and of an internal combustion engine that may be used for setting of the dosing or metering amount. In the method step c), arrows indicate operating parameters of the dosing device that may be taken into consideration in the implementation, in step c), of the dosing amount set in step a). In the method step b.1), arrows indicate characteristic operating values that may be taken into consideration for the setting of the operating mode of the dosing device in the step b.2). Reference is made to the general description given further above for a more detailed explanation of the actions within the steps.

(5) The present invention has the effect that the technical problems highlighted in conjunction with the prior art can be alleviated. In particular, with the method according to the invention, the operation of a dosing device is possible with a particularly high level of dosing accuracy. In this case, the susceptibility to failure and the complexity have been further reduced in relation to known dosing methods. It has likewise been achieved that the method is usable on different embodiments of the dosing device and, if appropriate, also takes into consideration, and is adaptable in a simple manner, to changes that arise with progressive operating duration.