Claims:We Claim:
1. A method of detecting clogging of a filter in a supply module of a dosing system, said dosing system comprising at least a tank (200), a first flow path (202) connecting said tank 200 and said supply module (204) via said filter (206), and a second flow path (208) connecting said supply module (204) and said dosing module and return flow path, said method comprising:

detecting (100), by a control unit actual time taken by said dosing system to achieve a calibrated dosing pressure;

comparing (102), by said control unit, said actual time with a calibrated time stored in a data map for said dosing pressure;

checking (104), by said control if said actual time exceeds said calibrated time; and
detecting (106), the clogging of said filter based on difference between said actual time and said calibrated time.
2. The method of claim 1, further comprising actuating a control valve located along said inlet for enabling purging through said first flow path.
3. The method of claim 1, wherein said filter is a pre-filter.
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001]This invention relates to the field of dosing system.

Background of the invention
[0002]A dosing system is used for NOx reduction in the exhaust system. For reducing NOx an aqueous solution of urea is stored in a tank, from the tank this solution flows to the supply module via a filter. The supply module then supplies aqueous solution to the dosing module where aqueous solution of urea is injected into the exhaust stream. The filter that is located in inlet connector of supply module in DNOX dosing system is susceptible to clogging due to presence of impurities and the particles located in the flow paths of the dosing system. The clogging of filter reduces the ability of the dosing system to build pressure that is required for dosing of aqueous urea into the exhaust system.

Brief description of the accompanying drawing
[0003] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0004] FIG. 1 method of detecting clogging of a filter in a supply module of a dosing system.

Detailed description of the embodiments
[0005] FIG. 1 method of detecting clogging of a filter in a supply module of a dosing system. The method comprises detecting 100 by a control unit actual time taken by the dosing system to achieve a calibrated dosing pressure, and comparing 102 actual time with a calibrated time stored in a data map for calibrated dosing pressure. The control unit checks if the actual time exceeds the calibrated time and detects the clogging of filter based on the difference between the actual time and calibrated time. The method further comprises actuating a control valve located along the inlet for enabling purging through the first flow path 202. By actuating the control valve the fluid (mixture of aqueous urea and air) is forced back causing the impurities from the filter to reach the tank 200. The control valve may be a reverting valve.

[0006]The working of the above mentioned method will be explained in further detail. The dosing system disclosed herein is used to inject aqueous urea solution into the exhaust stream for reduction of NOx. Initially aqueous urea is stored in the tank 200, from the tank 200 during dosing requirement aqueous urea flows through the first flow path 202 reaches the supply module, the supply module comprises a pump that directs the aqueous urea towards the dosing module. The dosing system needs to build pressure within a stipulated time as defined during calibration for ensuring flow of aqueous urea to the dosing module, this is called calibrated dosing pressure. The control unit in the proposed method detects the time taken during actual working condition of the dosing system to build pressure. The time taken to build pressure during actual working of the dosing system will be affected due to presence of impurities in filter, higher the concentration of impurities in the filter, the dosing system has to overcome the resistance offered due to presence of impurities before the pressure is built. Based upon the difference in time, that is, between the actual time and calibrated time for the dosing pressure the clog will be detected. The clogging of filter will be detected based on the dosing system pressure build behaviour and the time taken for system to empty itself of the aqueous urea solution. System pressure and supply module pump behaviour will be used as inputs to release the pre-filter clog removal function following the normal purge cycle. The concept used for removal of the clog will be extended after run cycle in steps based on the reverting valve actuation limitation. With initial defined number of attempts the system would analyse the clog removal based on the emptying behaviour of system pressure.

[0007]The above mentioned method will be explained with respect to an example. For the purpose of understanding consider the case wherein the dosing system pressure of 9 bar has to be achieved in 15 seconds. Now the in the proposed method the control unit will detect the actual time taken by dosing system to achieve the dosing system pressure. It is assumed that the actual time taken to be 30 seconds. Now upon comparison by the control unit, this difference in time is arrived because of clogging of filter. A control valve that is located along the inlet path is actuated, the actuation of control valve will cause the first flow path 202 to function like a backflow path. The aqueous urea solution will now flow from the supply module and second flow path into the first flow path via the filter. The flow of the aqueous urea solution will now cause removal of particles trapped in the filter leading to unclogging of the filter. Based on the clogging of pre-filter, an attempt to remove the trapped dirt particles will be made by actuating the reverting valve in multiple steps to enable extended purge function. The system pressure during after run will be monitored then to ensure the removal of clog in pre-filter of supply module

[0008]It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of the type dosing system. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.