Method for purging pressure lines of a pumping device - Patents.com

Abstract

The present invention relates to a method for operating an apparatus (1) for pumping a urea solution in a motor vehicle, the apparatus (1) comprising a pump (2) for pumping the urea solution, the pump (9) pumping the urea solution from a tank (3) through a suction line (7) and a pressure line (6) to injectors (4, 5) arranged outside the pump (9), the injectors (4, 5) being arranged in an exhaust gas line and configured to inject the urea solution into the exhaust gas line, a bypass (8) extending from a point in the pressure line (6) upstream of the injectors (4, 5) toward the tank (3), and the pump (2) pumping the urea solution toward the injectors (4, 5) in a first pumping process. the pump (2) operates in a first pumping direction to pump the fuel; after completion of a first pumping process in the first pumping direction of the pump (2), the injectors (4, 5) are closed; the pump (2) operates in a second pumping direction opposite to the first pumping direction in a second pumping process, the injectors (4, 5) are opened for a predetermined duration T1, air is sucked through the injectors (4, 5) into the pressure line (6), the air sucked through the injectors (4, 5) is sucked into the pumping device (9); then, in a third pumping process, the pump (2) operates again in the first pumping direction while the injectors (4, 5) are closed, and the air sucked into the pumping device (9) is forced along the bypass (8) towards the tank (3).

Description

[Technical Field]

[0001] The invention relates to a method for operating a device for pumping a urea-water solution in a motor vehicle, the device comprising a pump for pumping the urea-water solution, the urea-water solution being pumped by the pumping device via a suction line from a tank through a pressure line to an injector arranged outside the pumping device, the injector being arranged in an exhaust gas line and configured to inject the urea-water solution into the exhaust gas line, a bypass extending from a point in the pressure line upstream of the injector towards the tank, the pump operating in a first pumping process in a first pumping direction to pump the urea-water solution towards the injector, the injector being closed after completion of the first pumping process in the first pumping direction of the pump, the pump operating in a second pumping process in a second pumping direction opposite to the first pumping direction, the injector being opened for a predetermined duration T1 and air being sucked through the injector into the pressure line. Furthermore, the invention relates to an apparatus for performing the method. [Background technology]

[0002] Many countries around the world have legal restrictions that set upper limits on the content of certain substances in the exhaust gases of internal combustion engines. These restrictions usually concern substances whose release into the environment is undesirable. One such substance is nitrogen oxides (NOx), whose proportion in exhaust gases must not exceed legally established limits. However, due to framework conditions, such as the design of internal combustion engines for fuel economy, there are limits to how much nitrogen oxide emissions can be avoided within the engine itself to reduce the proportion of nitrogen oxides in exhaust gases. Therefore, exhaust gas aftertreatment is necessary to comply with the relatively low limit values.

[0003] In this context, selective catalytic reduction (SCR) of nitrogen oxides has proven advantageous. This SCR method requires a nitrogen-containing reducing agent. In particular, the use of ammonia (NH3) as a reducing agent has emerged as a viable option. Due to its chemical properties and legal regulations in many countries, ammonia is not typically available as pure ammonia, as this can cause problems, especially in automotive and other mobility applications. Instead of storing the reducing agent itself, a reducing agent precursor is often stored and transported. By reducing agent precursor, we mean a substance from which the reducing agent can be separated or chemically converted into the reducing agent. For example, urea is a reducing agent precursor for ammonia, which is a reducing agent.

[0004] The urea, an aqueous ammonia solution, is carried in a tank and pumped into the exhaust gas line in precisely metered amounts by a suitable pumping device, which for this purpose typically comprises a pump for pumping the fluid, one or more filters for cleaning the fluid, a heating device for optionally thawing the fluid, and a control device for processing internal and external data and controlling the pump, the heating device, and other controllable components, such as one or more injectors.

[0005] The pumping device used to pump the ammonia-water solution, and in particular the injector, must be designed to prevent the ammonia-water solution from freezing, particularly to prevent damage to the injector. For this purpose, a method is used to remove the urea-water solution from the injector after the pumping device is stopped. At the same time, this method must ensure that the ammonia-water solution continues to be supplied to the components of the pumping device to prevent crystallization of the ammonia-water solution in these components. For this purpose, a purge process is performed in which the pumping pump operates in the reverse direction while the injector is closed. Finally, the injector is opened for a specified period of time, so that air is sucked through the injector toward the pumping device and the ammonia-water solution is sucked out of the line and the injector.

[0006] The drawback of the prior art solutions is that it is extremely difficult to scale the negative pressure and the resulting return flow so that the injector and the lines leading to it are emptied, but the remaining components of the pumping system are not. This generally results in a relatively small negative pressure and therefore a small return flow. This can lead to residues of aqueous ammonia remaining in the injector or lines, where they can form deposits.

[0007] If the negative pressure and therefore the return flow are scaled too high, air may be sucked into the pumping device, which may then cause crystallization in the pump, filter, or other components of the pumping device. This is especially true because all installed components have some degree of component tolerance, which causes the actual pump discharge rate to vary unpredictably from pump to pump, resulting in an unknown amount of ammonia-water solution being sucked in. The unpredictability of the amount of ammonia-water solution sucked in leads to an unreliable purging process that cannot reliably prevent damage to the injector or the pumping device. Summary of the Invention [Problem to be solved by the invention]

[0008] Summary of the invention, problems, solutions, and effects It is therefore an object of the present invention to provide a method for operating a device for exhaust gas aftertreatment that ensures a reliable purging process of the lines to the injectors and the injectors themselves in order to prevent damage to the injectors and the pumping device themselves. [Means for solving the problem]

[0009] The method problem is solved by a method having the features of claim 1.

[0010] An embodiment of the present invention is a method for operating an apparatus for pumping urea-water solution in a motor vehicle, the apparatus comprising: a pumping device having a pump for pumping urea-water solution, the urea-water solution being pumped by the pumping device from a tank via a suction line and a pressure line to an injector arranged outside the pumping device, the injector being arranged in an exhaust gas line and configured to inject the urea-water solution into the exhaust gas line, a bypass extending from a point in the pressure line upstream of the injector towards the tank, and the pump pumping the urea-water solution towards the injector in a first pumping process. the pump operates in a first pumping direction, and after completion of a first pumping process in the first pumping direction, the injector is closed, the pump operates in a second pumping direction opposite to the first pumping direction in a second pumping process, the injector is opened for a predetermined duration T1, air is sucked through the injector into the pressure line, the air sucked through the injector is sucked into the pumping device, and then in a third pumping process, the pump operates again in the first pumping direction while the injector is closed, and the air sucked into the pumping device is forced along the bypass towards the tank.

[0011] The object of the method is to create a significantly greater negative pressure in the pressure line and in parts of the pumping device, particularly during the second pumping process, compared to methods known from the prior art, so that when the injector is opened, the urea-water solution present in the pressure line is sucked back into the pumping device to a much greater depth than would be the case without the method, thereby ensuring that the injector and preferably the entire pressure line are no longer filled with urea-water solution and, in particular, that no deposits form in the pressure line.

[0012] By providing a third pumping process in which a pump again pumps the urea-water solution from the tank toward the pressure line or toward the injector, any air present in the pumping device is pumped back into the tank through a bypass branching off from the pressure line. The air can then be removed from the system by a tank degassing device. During the third pumping process, the injector is completely closed, so the air is preferably pumped along the bypass. The section of the pressure line downstream of the bypass branch point and upstream of the injector is also filled with air before the third pumping process. During the third pumping process, this air is displaced by the urea-water solution pumped back toward the closed injector, where it is compressed by the incompressible urea-water solution. This compressed air volume ensures that no urea-water solution is supplied to the injector after the third pumping process is completed.

[0013] After the third pumping process is completed, the compressed air before the injector expands again somewhat because the pump pressure of the compressing pump disappears, and the length of the pressure line filled with air increases.

[0014] It is particularly advantageous if the part of the air remaining in the pressure line remains in the section of the pressure line that ends at the injector, thereby ensuring that no urea solution is supplied to the injector when the device is not in operation, thereby ensuring that the injector is not damaged.

[0015] It is advantageous if the air remaining in the pressure line adjacent to the injector expands in the pressure line after the pump is stopped, and the amount of air during expansion is sufficiently small so that the air does not reach the pumping device via the pressure line. This further ensures that the urea-water solution does not remain in the injector. Furthermore, expansion of the air volume remaining in the pressure line prevents air from entering the pumping device again, and thus possibly into the pump, filter, or other components to which the urea-water solution is supplied when the pump is not operating.

[0016] A preferred embodiment is characterized in that the pressure generated during the third pumping process is sufficiently low to prevent the pumping of the urea-water solution towards the injector, thus preventing any possible pumping of the urea-water solution towards the injector.

[0017] It is also preferred if two injectors are provided, which are fluidly connected to one another in parallel and are arranged in the pressure line downstream of the bypass.

[0018] Furthermore, it is advantageous if the negative pressure generated by the pump during the second pumping process is selected so that the entire aqueous urea solution present in the pressure line is sucked back into the pumping device, which is advantageous in order to ensure that the pressure line is completely emptied, that no aqueous urea solution remains in the injector, and that no deposits or residues of the aqueous urea solution remain in the pressure line.

[0019] Furthermore, during the third pumping process, it is advantageous if the air present in the pumping device and the pressure line is forced into the tank via a bypass, with a portion of the air remaining compressed in front of the closed injector, forming a cushion between the urea-water solution and the injector. The air forced into the tank can be easily removed from the tank using a tank degassing device, as is known in the prior art. Because the injector is completely closed during the third pumping process, the air that was present immediately in front of the injector before the third pumping process cannot escape. This air, acting as a compressible medium, is compressed by the incompressible urea-water solution in front of the closed injector.

[0020] The problem with the device is solved by a device having the features of claim 8.

[0021] One embodiment of the present invention relates to an apparatus for pumping a urea-water solution in a motor vehicle, the apparatus including a pumping device configured to pump the urea-water solution from a tank towards at least one injector arranged outside the pumping device, the at least one injector configured to inject the urea-water solution into an exhaust gas line, the pumping device having a pump configured to draw the urea-water solution from the tank along a suction line and to pump the urea-water solution along a pressure line to the injectors, a bypass extending from the pressure line to the tank upstream of the injectors, the pump configured to operate in a first pumping direction and a second pumping direction opposite to the first pumping direction.

[0022] Such an invention may advantageously be operated in accordance with the method described above.

[0023] It is also advantageous if two injectors arranged fluidly in parallel are provided outside the pumping device and are connected to the pressure line downstream of the branch point of the bypass.

[0024] Advantageous refinements of the invention are set forth in the dependent claims and in the following description of the drawings.

[0025] The present invention will be described in detail below based on an embodiment with reference to the drawings. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing an apparatus according to the invention operated by a method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0027] Figure 1 shows three views of the device 1. From left to right, the three views show the device 1 in different operating states.

[0028] The left-hand diagram shows the device 1 in a state where the pump 2 has finished its normal operation of pumping the urea-water solution from the tank 3 along the pressure line 6 towards both injectors 4, 5. It can be seen that the suction line 7 from the tank 3 to the pump 2, the bypass 8 leading from the pressure line 6 towards the tank 3, and the pressure line 6 to the injectors 4, 5 are completely filled with the urea-water solution.

[0029] The actual pumping device 9 comprises, inter alia, the pump 2, the bypass 8 and, if necessary, a filter for the urea-water solution. The pumping device is preferably arranged in a separate housing, which has a connection for the suction line from the tank 3 and a connection for the pressure line 6 leading to the pumping device.

[0030] The middle diagram shows the second pumping process. Pump 2 operates in the opposite direction to the normal pumping operation, forcing the urea / water solution from the injectors 4 and 5 along pressure line 6 toward tank 3. Since the injectors 4 and 5 are open, negative pressure is generated in pressure line 6 by the back pumping. Air is pumped through the open injectors 4 and 5 into pressure line 6 and ultimately into pump 2 and bypass 8, while the urea / water solution previously present there is displaced toward tank 3. At the end of the second pumping process, the injectors 4 and 5 are closed and pump 2 is stopped.

[0031] The right-hand diagram shows a third pumping process following the second pumping process, in which the injectors 4, 5 remain closed and the pump 2 is again operated in the pumping direction 9 defined for normal pumping operation, so that the urea-water solution is again pumped from the tank 3 into the pressure line 6. The bypass 8, which is fluidly connected to the tank 3, is also filled with the urea-water solution by the third pumping process.

[0032] As can be seen in the diagram on the right, a certain portion of the air remains just before the closed injectors 4, 5, where it is compressed by the subsequently pumped urea-water solution, thus ensuring that the injectors 4, 5 are not in direct contact with the urea-water solution, and at the same time that the pumping device 9 or the individual components of the pumping device 9 are completely supplied with the urea-water solution.

[0033] After the third pumping process is completed, the air previously compressed by the urea solution before the injectors 4, 5 expands and pushes the urea solution slightly back into the pressure line 6.

[0034] The state shown in the diagram on the right is the final state of the device 1 after the end of normal operation: in this state, the injectors 4, 5 are protected from freezing, and the pumping device 9 is fully supplied with urea-water solution, so that no crystallization can occur in the components of the pumping device 9, which could cause damage to the components.

[0035] The embodiment of FIG. 1 is not particularly limiting and serves to clarify the idea of ​​the invention. [Explanation of symbols]

[0036] 1 device 2 pumps 3 Tank 4 injectors 5 injectors 6 Pressure Pipeline 7 Suction pipe 8. Bypass 9. Pressure feeding device

Claims

1. A method for operating a device (1) for pumping a urea solution in a motor vehicle, the device (1) comprising a pump (2) for pumping the urea solution, the pump (9) pumping the urea solution from a tank (3) through a suction line (7) and a pressure line (6) to an injector (4, 5) arranged outside the pump (9), the injector (4, 5) being arranged in an exhaust gas line and configured to inject the urea solution into the exhaust gas line, and the pressure line (6) pumping the urea solution from a point upstream of the injector (4, 5) to a point upstream of the injector (4, 5) in the pressure line (6). a bypass (8) extending towards the tank (3), the pump (2) operating in a first pumping process in a first pumping direction to pump the urea-water solution towards the injectors (4, 5), after completion of the first pumping process in the first pumping direction of the pump (2), the injectors (4, 5) are closed, the pump (2) operating in a second pumping process in a second pumping direction opposite to the first pumping direction, the injectors (4, 5) being opened for a predetermined duration T1, and air being sucked into the pressure line (6) through the injectors (4, 5), the air sucked through the injectors (4, 5) is sucked into the pumping device (9), and then, in a third pumping process, the pump (2) operates again in the first pumping direction while the injectors (4, 5) are closed, and the air sucked into the pumping device (9) is forced along the bypass (8) towards the tank (3).

2. 2. The method according to claim 1, wherein the part of the air remaining in the pressure line (6) remains in the section of the pressure line (6) that ends in the injector (4, 5).

3. 3. The method according to claim 2, characterized in that the air remaining in the pressure line (6) adjacent to the injectors (4, 5) expands in the pressure line (6) after the pump (2) is stopped, and during expansion, the amount of air is sufficiently small so that air does not reach the pumping device via the pressure line (6).

4. 4. The method according to claim 1, wherein the pressure generated during the third pumping process is sufficiently low to preclude pumping of the urea-water solution towards the injectors (4, 5).

5. 5. The method according to claim 1, wherein two injectors (4, 5) are provided, which are fluidly connected to one another in parallel and are arranged in the pressure line (6) downstream of the bypass (8).

6. 6. The method according to claim 1, wherein the negative pressure generated by the pump (2) during the second pumping process is selected so that the entire urea-water solution present in the pressure line (6) is sucked back into the pumping device (9).

7. 7. The method according to claim 1, wherein during the third pumping process, the air present in the pumping device (9) and in the pressure line (6) is forced into the tank (3) via the bypass (8), and part of the air remains compressed before the closed injectors (4, 5), forming a cushion between the urea-water solution and the injectors (4, 5).

8. 1. An apparatus for pumping a urea-water solution in a motor vehicle, the apparatus comprising: a pumping device (9) configured to pump the urea-water solution from a tank (3) towards at least one injector (4, 5) arranged outside the pumping device (9), the at least one injector (4, 5) configured to inject the urea-water solution into an exhaust gas line; the pumping device (9) having a pump (2) configured to draw the urea-water solution from the tank (3) along a suction line (7) and pump the urea-water solution along a pressure line (6) to the injectors (4, 5); a bypass (8) extending from the pressure line (6) to the tank (3) upstream of the injectors (4, 5); and the pump (2) configured to operate in a first pumping direction and a second pumping direction opposite to the first pumping direction.

9. 9. The device (1) according to claim 8, characterized in that two injectors (4, 5) arranged fluidically in parallel are provided outside the pumping device (9), and the two injectors (4, 5) are connected to the pressure line (6) downstream of the branching point of the bypass (8).

Images