Field of the invention
[0001]This invention relates to the field of a diesel particulate filter.
Background of the invention
[0002] Accumulation of ash in diesel particulate filter (DPF) is one the factor that hinders regeneration of DPF. Ash accumulation is mainly in part due to aging of components of engine, use of improper grade oil. For a diesel particulate filter over accumulation of ash due to factors mentioned above may lead to a reduction in efficiency of DPF during regeneration.
[0003]Prior art patent application US6405528B discloses method for determining the load on an internal combustion engine exhaust particulate filter optimizes filter regeneration by determining the portion of the filter load constituted by accumulated ash. In one technique, the ash load is determined by recording the lowest value of DPF load over a time or distance interval. In another technique, an estimate is made of the amount of load remaining at each of a plurality of DPF regeneration events; the amount of remaining load immediately following the regeneration event corresponds to the amount of accumulated ash in the DPF. DPF load estimation is performed using equations for laminar or turbulent flow in pipes. These equations establish a linear or quadratic relationship between the flow through the DPF and the pressure drop measured across it.
Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description
and illustrated in the accompanying drawing:
[0005] FIG. 1 illustrates a method of detecting ash in a diesel particulate filter.

Detailed description of the embodiments
[0006] FIG. 1 illustrates a method of detecting ash concentration in a diesel particulate filter. The method comprises measuring (100) by a differential pressure sensor the pressure difference across the diesel particulate filter (DPF) during flow of exhaust through DPF. Comparing (102), by a control unit, the measured pressure difference with the pressure difference for the flow of exhaust as obtained from a data map. The date map is stored in the control unit and contains the pressure difference for flow of exhaust on an empty diesel particulate filter. The control unit determines (104), the deviation between the measured pressure with the pressure difference as obtained from the data map (for the flow of exhaust) for detecting ash concentration in the diesel particulate filter. Since the empty diesel particulate filter is devoid of ash, for different flow rates of exhaust the pressure difference is calculated and stored in a data map. This data map is then used as reference, when the differential pressure sensor measures pressure difference with ash accumulation during real time conditions.
[0007]The above mentioned method is used for determining the concentration of ash that is accumulated in the DPF. Ash accumulation in DPF happens due to aging of fuel injection components also improper use of lubricating oil. That is every vehicle has a recommended grade of lubricating oil. Use of lubricating oil other than the recommended grade may result in formation of ash at an interval that is earlier than the formation of ash with the recommended grade of lubricating oil. For example, if the ash formation with recommended grade of lubricating oil happens at an interval of 30000Km, then in case of use of a non-recommended lubricating oil the ash formation may happen at an interval

that is less than 30000Km. This formation of ash needs to be detected. The detection of ash will now be explained in further detail.
[0008]The method comprises the following steps. The pressure difference across the diesel particulate filter (DPF) is measured 100 by a pair of pressure sensor during flow of exhaust through the DPF, the pressure sensor may be a differential pressure sensor. The differential pressure sensor may comprise a first and a second pressure sensor. The first pressure sensor is located on the inlet side of the DPF and a second pressure sensor is located on the outlet side of the DPF. The measured difference of pressure against the flow of exhaust is compared 102 with the DPF pressure difference by the control unit based on the data map. The control unit determines 104 the deviation between the pressure as measured by the differential pressure sensor and the pressure as obtained from a data map for detecting ash concentration in the diesel particulate filter. The determined concentration of ash is then compared with threshold limit defined in the control unit. The threshold limit here indicates the maximum ash concentration permissible for the flow of exhaust. If the detected ash concentration is greater than the defined threshold limit, it is indicated on a display device of the vehicle.
[0009] For the purpose of better understanding, the above mentioned method will be explained by considering the example of flow rate of exhaust to be X mg/sec. For the flow rate of X mg/ sec let us assume the pressure difference as measured by the differential pressure sensor to be 4 bar. This pressure difference is taken as an input by the control unit and this is compared by the control unit for the pressure difference for X mg/sec as stored in data map. Let us assume that for X mg/sec from the pressure difference from the data map to be 2 bar. This difference between the pressure measured by the differential

pressure sensor and that stored in the data map is an indication of accumulation of ash in the diesel fuel filter. Now, the control unit checks if the ash concentration is within the threshold limit for X mg/sec. If the determined ash concentration is greater than the defined threshold limit of ash, it is indicated on a display device of the vehicle. By using the above mentioned method it is now possible to predict the ash concentration in DPF.
[0010] 'Adapted' or 'arranged', in the context of the instant disclosure, refers to the technical capability or the technical capacity of a component, in relation to which the term 'adapted' or 'arranged' is used, to carry out or executed a specified action or actions, upon the requirement of the specified action or actions to be carried out or executed. Moreover, the usage of the term 'adapted' or 'arranged' here, is in reference with the normal technical capability or technical capacity of the component, imparted by the design or the structure or the composition of the component, and not in reference with any special or extraneous capability or capacity, beyond the scope of the normal technical capability or technical capacity. Therefore there is a need to address this problem.
[0011]lt 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 of diesel particulate filter used. 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.

CLAIMS
We Claim:
1. A method of detecting ash concentration in a diesel particulate filter
(DPF), said method comprising:
measuring (100), by a differential pressure sensor the pressure difference across the diesel particulate filter (DPF) during flow of exhaust through said DPF;
comparing (102), by a control unit, said measured pressure difference with pressure difference for said flow of exhaust as obtained from a data map; and
determining (104), by said control unit deviation between said measured pressure with said actual pressure for detecting ash concentration in said diesel particulate filter.
2. The method of claim 1, further comprising checking said determined
ash concentration with respect to a threshold limit of ash for said flow
of exhaust.