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CN-114483277-B - Method for monitoring a reducing agent tank

CN114483277BCN 114483277 BCN114483277 BCN 114483277BCN-114483277-B

Abstract

The invention relates to a method for monitoring a reducing agent tank of a delivery module of an SCR catalyst system. The method comprises determining a first system pressure (p 1 ) of the delivery module when the return valve is activated, deactivating the return valve, and activating the return valve for a predefinable time period ) After deactivation, a second system pressure (p 2 ) of the delivery module is determined, and a determination is made from the first system pressure (p 1 ) and the second system pressure (p 2 ) as to whether the return line of the delivery module is immersed in the reducing agent solution in the reducing agent tank.

Inventors

  • QIAN RUI
  • LIU ZHONGZHENG

Assignees

  • 罗伯特·博世有限公司

Dates

Publication Date
20260505
Application Date
20211112
Priority Date
20201113

Claims (9)

  1. 1. Method for monitoring a reductant tank (10) of a delivery module (20) of an SCR catalyst system, the method comprising the steps of: when the return valve is activated, a first system pressure (p 1 ) of the delivery module (20) is determined (71), Deactivating (72) the return valve, -At the return valve for a predefinable period of time [ ] ) After deactivation, a second system pressure (p 2 ) of the delivery module (20) is determined (73), and -Determining (74) from the first system pressure (p 1 ) and the second system pressure (p 2 ) whether a return line (40) of the delivery module (20) is immersed in a reducing agent solution (11) located in the reducing agent tank (10).
  2. 2. The method according to claim 1, characterized in that the first system pressure (p 1 ) is determined immediately before the return valve is deactivated (72).
  3. 3. The method according to claim 1, characterized in that when the difference between the second system pressure (p 2 ) and the first system pressure (p 1 ) is [ ] ) When a threshold value is exceeded, the return line (40) is identified as immersed in the reducing agent solution (11).
  4. 4. A method according to any one of claims 1 to 3, characterized in that the immersion of the return line (40) into the reducing agent solution (11) is recognized when the first system pressure (p 1 ) is greater than the second system pressure (p 2 ) and furthermore the first system pressure (p 1 ) and/or the second system pressure (p 2 ) lie outside a predefinable pressure range.
  5. 5. A method according to any one of claims 1-3, characterized in that a motor indicator light is activated upon recognition of the immersion of the return line (40) into the reducing agent solution (11).
  6. 6. A method according to any one of claims 1-3, characterized in that upon recognition of the immersion of the return line (40) into the reducing agent solution (11), a fault record is generated in a cloud database.
  7. 7. Computer program configured to perform each step of the method according to any one of claims 1 to 6.
  8. 8. A machine readable storage medium having stored thereon a computer program according to claim 7.
  9. 9. Electronic controller (60) configured to monitor a reductant tank (10) of a delivery module (20) of an SCR catalyst system by means of a method according to any one of claims 1 to 6.

Description

Method for monitoring a reducing agent tank Technical Field The invention relates to a method for monitoring a reducing agent tank of a delivery module of an SCR catalyst system. Furthermore, the invention relates to a computer program for carrying out each step of the method and to a machine-readable storage medium for storing the computer program. Finally, the invention relates to an electronic controller which is configured to carry out the method. Background The reduction of nitrogen oxides in the exhaust gas of an internal combustion engine, in particular a diesel engine, can be carried out by means of ammonia by means of Selective Catalytic Reduction (SCR). Here, the nitric oxide molecules are reduced to elemental nitrogen on the surface of the catalyst by ammonia as a reducing agent. Urea is added as an ammonia decomposition reagent in the form of a reducing agent solution (Harnstoff-Wasserl, sung; HWL (aqueous urea solution)) into the exhaust tract of the internal combustion engine upstream of the SCR catalyst. For this purpose, the reducing agent solution is transported from the reducing agent tank to the metering valve by means of a transport module. The reducing agent solution is sucked up here by means of a delivery line. The transfer line is immersed in the reductant solution. When the internal combustion engine is switched off, the reducing agent solution still present in the metering valve and the delivery module is returned to the reducing agent tank via the return line. For this purpose, the conveying direction of the conveying pump arranged in the conveying module can be reversed by means of a return valve. The return line should not be immersed in the reducing agent solution. If the return line is immersed in the reducing agent solution due to an excessively high filling level of the reducing agent tank or due to an inclined parking position of the motor vehicle, there is the risk that the reducing agent solution will flow back into the delivery module via the return line as long as no check valve is installed at the delivery module. Disclosure of Invention The method for monitoring a reducing agent tank of a delivery module of an SCR catalyst system includes determining a first system pressure of the delivery module when a return valve is activated. Activation of the return valve (ON state) results in the transfer direction of the transfer pump of the transfer module being reversed, so that the reducing agent solution is returned from the transfer module into the reducing agent tank. In particular, the system pressure measured in the pressure line between the return pump and the metering valve of the SCR catalytic converter system can generally drop below ambient pressure when the return valve is activated, since a negative pressure is generated in the delivery module and its line system by evacuating it. The return valve deactivation (on state OFF) is then performed. The direction of conveyance of the conveying pump is thus switched back to conveying the reducing agent solution into the conveying module. This deactivation also occurs in the usual operating strategy of the delivery module for preparing the delivery module for shut-down, so that the delivery pump is already set to the correct delivery direction for the delivery of the reducing agent solution when operation is resumed. In order to prevent the reducing agent solution from being fed into the feed module again before closing when the return valve is deactivated, the feed pump is switched off before the return valve is deactivated. If the return line is not immersed in the reducing agent solution, a pressure equalization between the air volume in the reducing agent tank and the air volume below the negative pressure in the delivery module can now be achieved. After the return valve has been deactivated for a predefinable period of time, a second system pressure of the delivery module is determined after the return valve has been deactivated. A determination is then made as to whether the return line of the delivery module is immersed in the reductant solution in the reductant storage tank by analyzing the first and second system pressures. If the return line is actually immersed in the reducing agent solution, no pressure equalization takes place between the exhaust gas volumes, but instead the reducing agent solution is sucked into the delivery module via the return line. In this case, a further pressure profile is obtained in the delivery module, which can be evaluated to determine the immersion of the return line into the reducing agent solution. In this case, the first system pressure is preferably ascertained immediately before the return valve is deactivated, so that the difference between the two ascertained system pressures is based solely on a possible pressure equalization between the reducing agent tank and the delivery module. Preferably, the return line is identified as immersed in the reductant solution when a di