Method for operating a feed module of an SCR catalytic converter system

Abstract

A method for operating a feed module of an SCR catalytic converter system which has a feed pump, a feedback pump and a hydraulic interface channel. The feed module is operated in a test state in which a feed operation of the feed pump takes place and a feed operation of the feedback pump does not take place. Owing to a time profile of an MSP current (I.sub.MSP) of the feed pump it is decided in the test state whether the feed module is to change into a thawing state.

Claims

1. A method for operating a feed module (10) of an SCR catalytic converter system which has a feed pump (11), a feedback pump (12) and a hydraulic interface channel (19), wherein the feed module (10) is operated in a test state in which a feed operation of the feed pump (11) takes place and a feed operation of the feedback pump (12) does not take place, wherein owing to a time profile of an MSP current (I.sub.MSP) of the feed pump (11) it is decided in the test state whether the feed module (10) is to change into a thawing state.

2. The method according to claim 1, characterized in that the feed module (10) is started in a test state in which the feed module (10) is operated in a first test phase (Z.sub.1) and in a second test phase (Z.sub.2), wherein the feedback pump (12) is opened in the first test phase (Z.sub.1) and closed in the second test phase (Z.sub.2), and wherein on the basis of a time profile of the MSP current (I.sub.MSP) in the first test phase (Z.sub.1) and on the basis of a time profile of the MSP current (I.sub.MSP) in the second test phase (Z.sub.2) it is decided whether the feed module (10) is to change into the thawing state.

3. The method according to claim 2, characterized in that it is decided that the feed module (10) is to change into the thawing state if, in the first test phase (Z.sub.1), at least one expected measured value of the MSP current (I.sub.MSP) cannot be detected, or at least one measured value of the MSP current (I.sub.MSP) differs at least by a first threshold value from the first measured value in the time profile of the MSP current (I.sub.MSP), or a rise in the MSP current (I.sub.MSP) over time exceeds a second threshold value, or at least one measured value of the MSP current (I.sub.MSP) exceeds a predefined maximum value, or a rise in the MSP current (I.sub.MSP) over time does not exceed the second threshold value but fluid is not detected in a working space (111) of the feed pump (11).

4. The method according to claim 3, characterized in that it is decided that the feed module (10) is to change into the thawing state, if in the second test phase (Z.sub.2) at least one expected measured value of the MSP current (I.sub.MSP) cannot be detected, or at least one measured value of the MSP current (I.sub.MSP) differs at least by a first threshold value from the measured value in the time profile of the MSP current (I.sub.MSP), or at least one measured value of the MSP current (I.sub.MSP) exceeds a predefined maximum value, or a rise in the MSP current (I.sub.MSP) over time exceeds a second threshold value.

5. The method according to claim 1, characterized in that the test state is a ventilation phase (Z.sub.3) of the feed module (10), in which phase the feedback pump (12) is opened, wherein it is decided that the feed module (10) is to change into the thawing state if at least one predefined number of expected measured values of the MSP current (I.sub.MSP) cannot be detected within a predefined time interval, or at least one measured value of the MSP current (I.sub.MSP) differs at least by a first threshold value from the measured value in the time profile of the MSP current (I.sub.MSP), or at least one measured value of the MSP current (I.sub.MSP) exceeds a predefined maximum value, or a rise in the MSP current (I.sub.MSP) over time exceeds a second threshold value, or a rise in the MSP current (I.sub.MSP) over time does not exceed a second threshold value but fluid is not detected in a working space (111) of the feed pump (11).

6. The method according to claim 1, characterized in that the test state is a pressure build-up phase (Z.sub.4) of the feed module (10), in which phase the feedback pump (12) is closed, wherein it is decided that the feed module (10) is to change into the thawing state if within a predefined time interval at least one predefined number of expected measured values of the MSP current (I.sub.MSP) cannot be detected, or at least one measured value of the MSP current (I.sub.MSP) differs at least by a first threshold value from the measured value in the time profile of the MSP current (I.sub.MSP), or at least one measured value of the MSP current (I.sub.MSP) exceeds a predefined maximum value, or a rise in the MSP current (I.sub.MSP) over time exceeds a second threshold value.

7. The method according to claim 6, characterized in that the pressure build-up phase (Z.sub.4) follows a heating assistance phase for the hydraulic interface channel (19), in which a heating operation and a feed operation of the feed pump (11) take place at the same time and in which the feedback pump (12) is opened.

8. The method according to claim 7, characterized in that the heating assistance phase is a thawing operation into which the feed module (10) is changed after it has been decided in the second test phase (Z.sub.4) that the feed module (10) is to change into a thawing operation, wherein it is decided that the feed module (10) is to change into the thawing state, if in the second test phase (Z.sub.2) at least one expected measured value of the MSP current (I.sub.MSP) cannot be detected, or at least one measured value of the MSP current (I.sub.MSP) differs at least by a first threshold value from the measured value in the time profile of the MSP current (I.sub.MSP), or at least one measured value of the MSP current (I.sub.MSP) exceeds a predefined maximum value, or a rise in the MSP current (I.sub.MSP) over time exceeds a second threshold value.

9. The method according to claim 3, characterized in that it is decided that the feed module (10) is to change into the thawing state, if in the second test phase (Z.sub.2) at least one expected measured value of the MSP current (I.sub.MSP) cannot be detected.

10. The method according to claim 3, characterized in that it is decided that the feed module (10) is to change into the thawing state, if in the second test phase (Z.sub.2) at least one measured value of the MSP current (I.sub.MSP) differs at least by a first threshold value from the measured value in the time profile of the MSP current (I.sub.MSP).

11. The method according to claim 3, characterized in that it is decided that the feed module (10) is to change into the thawing state, if in the second test phase (Z.sub.2) at least one measured value of the MSP current (I.sub.MSP) exceeds a predefined maximum value.

12. The method according to claim 3, characterized in that it is decided that the feed module (10) is to change into the thawing state, if in the second test phase (Z.sub.2) a rise in the MSP current (I.sub.MSP) over time exceeds a second threshold value.

13. The method according to claim 1, characterized in that the test state is a ventilation phase (Z.sub.3) of the feed module (10), in which phase the feedback pump (12) is opened, wherein it is decided that the feed module (10) is to change into the thawing state if at least one predefined number of expected measured values of the MSP current (I.sub.MSP) cannot be detected within a predefined time interval.

14. The method according to claim 1, characterized in that the test state is a ventilation phase (Z.sub.3) of the feed module (10), in which phase the feedback pump (12) is opened, wherein it is decided that the feed module (10) is to change into the thawing state if at least one measured value of the MSP current (I.sub.MSP) differs at least by a first threshold value from the measured value in the time profile of the MSP current (I.sub.MSP).

15. The method according to claim 1, characterized in that the test state is a ventilation phase (Z.sub.3) of the feed module (10), in which phase the feedback pump (12) is opened, wherein it is decided that the feed module (10) is to change into the thawing state if at least one measured value of the MSP current (I.sub.MSP) exceeds a predefined maximum value.

16. The method according to claim 1, characterized in that the test state is a ventilation phase (Z.sub.3) of the feed module (10), in which phase the feedback pump (12) is opened, wherein it is decided that the feed module (10) is to change into the thawing state if a rise in the MSP current (I.sub.MSP) over time exceeds a second threshold value.

17. The method according to claim 1, characterized in that the test state is a ventilation phase (Z.sub.3) of the feed module (10), in which phase the feedback pump (12) is opened, wherein it is decided that the feed module (10) is to change into the thawing state if a rise in the MSP current (I.sub.MSP) over time does not exceed a second threshold value but fluid is not detected in a working space (111) of the feed pump (11).

18. A non-transitory computer-readable storage medium, storing instructions that when executed by a computer cause the computer to carry out the method of claim 1.

19. An electronic control device (40) configured to operate a feed module (10) of an SCR catalytic converter system by means of the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.

(2) FIG. 1 shows a schematic view of a feed module which can be operated by means of embodiments of the method according to the invention.

(3) FIG. 2 shows current profiles over time in a plurality of diagrams in an exemplary embodiment of the method according to the invention.

(4) FIG. 3 shows current profiles over time in diagrams in another exemplary embodiment of the method according to the invention.

(5) FIG. 4 shows current profiles over time in diagrams in yet another exemplary embodiment of the method according to the invention.

(6) FIG. 5 shows a schematic view of a hydraulic interface channel of a feed module, which channel is blocked by frozen AUS.

DETAILED DESCRIPTION

(7) A feed module 10 which is illustrated in FIG. 1 serves to feed AUS from a tank 20 to a metering valve 30. It is controlled by an electronic control device 40. A feed pump 11 and a feedback pump 12 are arranged in the feed module 10. The two pumps 11, 12 are each embodied as reciprocating piston diaphragm pumps. A feed line leads from the tank 20 through a first non-return valve 13 into a working space 111 of the feed pump 11. From there it leads on through a first restrictor 14 and a second non-return valve 15 to a branching point via which it is connected to a feedback line. The feedback line leads through a third non-return valve 16 into a working space 121 of the feedback pump 12. From there it leads through a fourth non-return valve 17 back into the tank 20. A bypass in which a second restrictor 18 is arranged bypasses the fourth non-return valve 17. Beyond the branching point, the feed line leads through a hydraulic interface channel 19 to the metering valve 30.

(8) If the feed module 10 is activated, in one exemplary embodiment of the method, it starts in a first test phase Z.sub.1. In the latter the feedback pump 12 is energized by means of a feedback pump current I.sub.12 in such a way that its working space 121 is open and the throughflow of AUS is permitted. The feed pump 11 is energized by means of a feed pump current I.sub.11 in such a way that it carries out feed strokes. An MSP current I.sub.MSP of the feed pump 11 is read out in the first test phase Z.sub.1.

(9) In a first example, B1, the MSP current I.sub.MSP rises with each feed stroke of the feed pump 11. It is inferred from this that the hydraulic connection from the tank 20 through the feed pump 11, the feedback pump 12 and back into the tank 20 is not free of ice and the electronic control device 40 does not bring about a change of the feed module 10 into a thawing state. However, in one example B2 the MSP current I.sub.MSP is essentially constant, which means that its rise is below a predefined threshold value. The feed module 10 then changes into a second test phase Z.sub.2 in that the energization of the feedback pump 12 is broken off, so that its working space 121 closes. The energization of the feed pump 11 is, in contrast, continued in the same way as in the first test phase Z.sub.1. In one example B3, a rise of the MSP current I.sub.MSP occurs in the second test phase Z.sub.2. It is inferred from this that the hydraulic interface channel 19 is frozen and the electronic control device 40 in turn initiates a thawing state. However, in one example B4, the MSP current I.sub.MSP in the second test phase Z.sub.2 is essentially constant, in response to which the feed module 10 is detected as ready for metering and changes into a metering mode.

(10) If a thawing state is already initiated in the first test phase Z.sub.1, this occurs in the way illustrated in FIG. 3. Firstly, the feed pump 11 and the feedback pump 12 are energized with a constant feed pump current I.sub.11 and constant feedback pump current I.sub.12, in order to generate heat in the actuators of the pumps 11, 12, which heats the components of the feed module 10. Then, in a venting phase Z.sub.3 the feedback pump current I.sub.12 is increased even further in order to completely open the working space 121 of the feedback pump 12. The feed pump 11 is energized in such a way that it executes feed strokes in order to vent the feed module 10. In this context, the MSP current I.sub.MSP is monitored. If the latter rises, a return into the thawing state occurs. If, on the other hand, it remains essentially constant, a change into the second test phase Z.sub.2 occurs.

(11) If a change into the thawing state occurs as a result of the evaluation of the MSP current I.sub.MSP in the second test phase Z.sub.2, said thawing state is firstly implemented in the form of a heating assistance phase in the way illustrated in FIG. 4. In this context, the feedback pump 12 is energized constantly, so that its workspace 121 is open. The feed pump 11 carries out pump strokes. In this context, warm AUS is generated. Subsequently, in a pressure build-up phase Z.sub.4 the energization of the feedback pump 12 is ended, and in this way the working space 121 of the feedback pump 12 is closed. The feed pump 11 subsequently carries out the pump strokes. As illustrated in FIG. 5, in this context warm AUS is forced into the hydraulic interface channel 19. If the latter is blocked by a frozen region 50 in the feed line, which region is bounded by partially thawed regions 51, 52, accelerated thawing of this region occurs. In the pressure build-up phase Z.sub.4 monitoring of the MSP current I.sub.MSP occurs in turn. If said MSP current I.sub.MSP rises, the hydraulic interface channel 19 and its feed line are not yet free of ice and a renewed change into the heating assistance phase occurs in that the feedback pump 12 is energized again. However, if the MSP current I.sub.MSP essentially no longer rises, it is detected that the feed module 10 is then ready for metering.

(12) A change into a thawing state occurs in each of the embodiments of the method described above even instead of a rise in the MSP current I.sub.MSP it is detected that an expected measured value of the MSP current I.sub.MSP could not be detected, that is to say a pump stroke of the feed pump 11 cannot be assigned a measured value, or at least one measured value of the MSP current I.sub.MSP differs by a threshold value from the respective first measured value in the time profile of the MSP current I.sub.MSP in the first test phase Z.sub.1, of the second test phase Z.sub.2, of the venting phase Z.sub.3 or of the pressure build-up phase Z.sub.4, or if at least one measured value of the MSP current I.sub.MSP exceeds a predefined maximum value of, for example, 1800 mA.

(13) In the first test phase Z.sub.1 or in the venting phase Z.sub.3 a change occurs into the thawing state even if none of the conditions described above is satisfied, and the MSP current I.sub.MSP also remains essentially constant but it is detected by means of a software function of the electronic control device 40 that no fluid is located in the working space 111 of the feed pump 11.

(14) In the thawing state and in the phases Z.sub.1 to Z.sub.4, the electronic control device 40 activates a component protection function of the feed pump 11 and of the feedback pump 12, in order to avoid damage to the pumps 11, 12.