Method for operating a device for conveying a liquid

Abstract

A method for operating a device configured to deliver a liquid includes: a) back-suctioning a liquid situated in a pressure line section counter to a usual delivery direction by at least one pump; b) monitoring at least one operating parameter of the at least one pump during the back-suctioning, the at least one operating parameter being representative of a counterpressure that the at least one pump operates against during the back-suctioning; and c) detecting an increase in the counterpressure, and stopping the back-suctioning.

Claims

1. A method for operating a device configured to deliver a liquid, the device having a delivery line dividable into a suction line section, from a filter space in a tank to at least one pump, and into a pressure line section, from the at least one pump to at least one injector, wherein the filter space is separated from an interior of the tank by at least one filter layer, the method comprising: a) back-suctioning a liquid situated in the pressure line section counter to a delivery direction by the at least one pump; b) monitoring at least one operating parameter of the at least one pump during the back-suctioning, wherein the at least one operating parameter is representative of a counterpressure that the at least one pump operates against during the back-suctioning; and c) detecting an increase in the counterpressure, and stopping the back-suctioning.

2. The method as claimed in claim 1, the method further comprising, after step c): d) delivering liquid in the delivery direction until the filter space has been fully filled with liquid again.

3. The method as claimed in claim 1, wherein the at least one filter layer extends at least over a portion of a height of the tank such that the liquid can flow from the interior into the filter space at different heights.

4. The method as claimed in claim 1, wherein the suction line section of the delivery line extends from an upper region of the filter space.

5. The method as claimed in claim 1, wherein the filter space forms a jacket delimiting a housing with the at least one pump with respect to the interior of the tank, wherein, at least one heater for heating the liquid is arranged in the housing.

6. The method as claimed in claim 1, wherein the operating parameter of the pump monitored in step b) is at least one of the following parameters: an electrical power consumed by a drive of the pump; an electrical current consumed by a drive of the pump; an operating voltage consumed by a drive of the pump; a movement speed of a drive of the pump; a pressure or a pressure gradient built up by the pump in the suction line section during the back-suctioning process.

7. A motor vehicle, having at least an internal combustion engine, an exhaust-gas treatment device configured to purify the exhaust gases of the internal combustion engine, and a device configured to deliver a liquid to the exhaust-gas treatment device, wherein the device is configured to be operated in accordance with a method for operating the device configured to deliver the liquid, the device having a delivery line dividable into a suction line section, from a filter space in a tank to at least one pump, and into a pressure line section, from the at least one pump to at least one injector, wherein the filter space is separated from an interior of the tank by at least one filter layer, the method including: a) back-suctioning a liquid situated in the pressure line section counter to a delivery direction by the at least one pump; b) monitoring at least one operating parameter of the at least one pump during the back-suctioning, wherein the at least one operating parameter is representative of a counterpressure that the at least one pump operates against during the back-suctioning; and c) detecting an increase in the counterpressure, and stopping the back-suctioning.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and the technical field will be explained in more detail below on the basis of the figures. The figures show particularly preferred exemplary embodiments, to which the invention is however not restricted. In particular, it should be noted that the figures and in particular the illustrated proportions are merely schematic. In the figures:

(2) FIG. 1: shows a first design variant of a device for the described method;

(3) FIG. 2: shows a motor vehicle having a device for the described method;

(4) FIG. 3: shows a second design variant of a device for the described method; and

(5) FIG. 4: shows a profile of the pressure in the suction line section during the execution of the described method.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(6) FIG. 1 illustrates a first design variant of a device 1 which can be evacuated in accordance with the described method. The device 1 comprises a tank 7, in the interior 10 of that the liquid (in particular an aqueous urea-water solution) is stored. In the tank 7 there is arranged a housing 16 which extends into the interior 10 of the tank 7 from the tank base 33. The tank 7 has a height 13. The housing 16 extends over a portion 12 of the height 13 of the tank 7. The filter space 6 is formed as an encircling jacket 15 around the housing 16. The filter space 6 is separated from the interior 10 of the tank 7 by a filter layer 9. A heater 17 is arranged in the housing 16. The heater 17 is designed to supply heat through the filter space 6 and the filter layer 9 to liquid stored in the interior 10 of the tank 7. For this purpose, it is provided that the filter space 6 is filled with liquid in order to realize good thermal conductivity through the filter space 6.

(7) In the housing 16 there are situated functional components of the device 1 which serve to deliver the liquid from the tank 7 to an injector 8. The functional components comprise, in particular, a pump 3 which performs the delivery of the liquid and which has a drive 18 that is preferably an electric motor.

(8) Proceeding from the filter space 6, a delivery line 2 extends from the filter space 6 to the injector 8. The pump 3 is also arranged on the delivery line 2. The delivery line 2 is divided by the pump 3 into a suction line section 4, from the filter space 6 to the pump 3, and a pressure line section 5, from the pump to the injector 8. Proceeding from the filter space 6 toward the injector 8, the pump 3 delivers the liquid in a usual delivery direction 11. The delivery line 2 or the suction line section 4 of the delivery line 2 issues into an upper region 14 of the filter space 6 at an intake point 34.

(9) The motor vehicle 19 shown in FIG. 2 has an internal combustion engine 20 and has an exhaust-gas treatment device 21 for the purification of the exhaust gases of the internal combustion engine 20. A liquid for exhaust-gas purification purposes can be fed to the exhaust-gas treatment device 21 by way of a device 1. The liquid is preferably a reducing agent precursor solution. In the exhaust-gas treatment device 21 there is provided an SCR catalytic converter 23 by which nitrogen oxide compounds in the exhaust gas of the internal combustion engine 20 can be reduced. The device 1 delivers the liquid out of a tank 7 in which the liquid is stored. For the provision of the liquid at the exhaust-gas treatment device 21, an injector 8 is provided, which permits dosed dispensing of the liquid. The motor vehicle 19 preferably has a control unit 22, which is connected at least to the pump (not illustrated here) and to the injector 8 of the device 1 in order to control the operation of the device 1. In particular, executable routines for carrying out the described method are also stored, for example in a non-transitory computer-readable medium, in the control unit.

(10) FIG. 3 shows a modification of the device 1 as per FIG. 1, wherein, in the suction line section 4, there is arranged a pressure sensor 24 by which the pressure in the suction line section 4 during the back-suctioning process can be actively monitored.

(11) An exemplary pressure profile 27 in the suction line section, such as arises immediately before the back-suctioning process and during the back-suctioning process, is illustrated in FIG. 4 on the time axis 26 versus the pressure axis 25. Along the time axis 26, there is firstly illustrated a suction phase 28, during which usual operation (dosing) of the device is still performed, and during which a negative pressure 31 prevails in the suction line section. At the time when the pressure profile 27 intersects the time axis 26, the evacuation phase 29 begins, during which back-suctioning of the liquid is performed. The pressure in the suction line section is now positive, because the liquid is now forced out of the pressure line section through the suction line section and back into the filter space and into the interior of the tank. At the end of the evacuation phase 29, a significant pressure increase 30 occurs, which is detected (method step c)). It is thus possible, when a threshold value 35 is reached, for the evacuation phase 29 to be stopped.

(12) The described method is particularly advantageous for targetedly evacuating the device for the provision of liquid and, in so doing, expending the least possible energy for the back-suctioning process, and at the same time ensuring that the device is evacuated only to the extent necessary, so as to prevent damage being caused to components of the device by freezing liquid in the delivery line of the device.

(13) Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.