Claims:We claim:

1. A method for conducting on-board diagnostics of emission control system, wherein said method comprises the step of coating a wall-flow substrate (sDPF) of Diesel Particulate Filter (DPF) with a selective catalyst reductant (SCR) to control both nitrous oxides (NOx) and particulate matter (PM) present in exhaust of said CI-engine.

2. Method as claimed in claim 1, wherein said method comprises meeting OBD threshold limit in case of total failure of sDPF.

3. Method as claimed in claim 1, wherein said method comprises determining the threshold limit of pressure based on exhaust flow and permissible across said sDPF.

4. Method as claimed in claim 3, wherein said method comprises checking the compliance with the mandatory exhaust mass flow to monitor said emission control system.

5. Method as claimed in claim 4, wherein said method comprises detecting/measuring the actual pressure-drop across said sDPF after positively confirming the compliance of said release conditions.

6. Method as claimed in claim 5, wherein said method comprises comparing said actual pressure-drop detected/measured across said sDPF with said threshold limit.

7. Method as claimed in claim 6, wherein said method comprises indicating the removal or absence of sDPF by turning on Malfunction Indication Lamp (MIL) on detecting/measuring the actual pressure-drop across said sDPF to be less than said threshold limit.
8. Method as claimed in claim 6, wherein said method comprises turning off Malfunction Indication Lamp (MIL) if on, when the actual pressure-drop detected/measured across said sDPF is not less than said threshold limit, for indicating a defective sDPF to be replaced/repaired.

9. Method for conducting on-board diagnostics of emission control system in CI engines as claimed in claim 1, said method comprising the steps of:

• coating a wall-flow substrate (sDPF) of Diesel Particulate Filter (DPF) with a selective catalyst reductant (SCR) to control both nitrous oxides (NOx) and particulate matter (PM) present in exhaust of said CI-engine;

• determining a threshold limit of the pressure based on exhaust flow and permissible across said sDPF;

• checking the compliance of mandatory exhaust mass flow to monitor said emission control system;

• detecting/measuring the actual pressure-drop across said sDPF after positively confirming the compliance of said release conditions;

• comparing said actual pressure-drop detected/measured across said sDPF with said threshold limit; and either

• turning on said Malfunction Indication Lamp (MIL), on finding said actual pressure-drop to be less than said threshold limit, to indicate the removal or absence of sDPF; or

• turning off said MIL (if on) on finding said actual pressure-drop being not less than said threshold limit, to indicate defective sDPF to be replaced/repaired.

Dated this 09th day of August 2019.

Digitally Signed.

(SANJAY KESHARWANI)
APPLICANT’S PATENT AGENT
REGN. NO. IN/PA-2043. , Description:FIELD OF INVENTION

The present invention concerns a method for conducting on-board diagnostics (OBD) of an active emission control system such as Selective Catalyst Reduction (SCR) system equipped in internal combustion engines. In particular, the present invention relates to a method for conducting on-board diagnostics of SCR system fitted in Compression Ignition (CI) engines. More particularly, the present invention relates to a method for conducting on-board diagnostics of SCR system fitted in CI engines only by determining the removal of selective catalyst reductant.

BACKGROUND OF THE INVENTION

Government of India has notified migration to Bharat Stage VI (BS VI) emission norms, which are based on European Emission Standards Euro 6 (2014) applicable for light passenger and commercial vehicles (LCVs).

Therefore, it is crucial for all Indian automobile (LCVs) manufacturers to meet these BS VI emission norms for 2, 3 and 4 wheeled vehicles with effect from 1st April 2020. Similarly, for agricultural tractors, construction equipment vehicles and combine harvesters (having power exceeding 37 kW), the next stage emission norms BS (CEV/TREM-IV) and BS (CEV/TREM-V) are notified to be implemented with effect from dates 1st April 2020 and 1st October 2020 respectively.

An important aspect of these BS VI emission norms is the requirement of meeting On-Board Diagnostics (OBD) norms as defined by the relevant Automotive Industry Standard AIS-137 (Part 4) under Chapter 8A titled: “On-board Diagnostic systems (OBD)”.

It prescribes the OBD threshold limits under clause 3.2.2 thereof, which states:
The vehicles shall be equipped with an On-Board Diagnostic system for emission control which shall have the capability of identifying the likely area of the malfunctions by means of fault codes stored in computer memory and communicating that information off-board, as per procedure described in this part, when that failure results in an increase in emission above the limits given in Table 1 or Table 2 below (as applicable):

Accordingly, these BS VI emission norms require that-

1. Any component failure resulting in emission higher than above OBD threshold limit should be detected and Malfunction Indication Lamp (MIL) should be ON.
2. The manufacturers may demonstrate to the testing agency that certain components or systems need not be monitored, if in the event of their total failure or removal, emissions do not exceed above OBD emission limits.

3. The following devices should however be monitored for total failure or removal (if the removal thereof would cause the applicable emission limits to be exceeded):

(a) A particulate trap fitted to compression ignition engines as a separate unit or integrated into a combined emission control device;

(b) A NOx after-treatment system (AFS) fitted to compression ignition engines as a separate unit or integrated into a combined emission control device;

(c) A Diesel Oxidation Catalyst (DOC) fitted to compression ignition engines as a separate unit or integrated into a combined emission control device.

Presently, SCR systems for conversion of NOx emissions in diesel engines are used in two different configurations of SCR and DPF as given below:

Configuration 1:

Here, the diesel engine’s aftertreatment system includes a Diesel Oxidation Catalyst (DOC) for promoting the oxidation of exhaust gas components by ample amount of oxygen present in diesel exhaust, and followed by a Diesel Particulate Filter (cDPF) catalyst for controlling the amount of particulate matter (PM) and also a separate SCR catalyst for controlling nitrous oxides (NOX).

In Diesel Oxidation Catalyst (DOC), carbon monoxide (CO) and gas phase hydrocarbons (HC) are passed over the oxidation catalyst therein, whereby the organic fraction (OF) of diesel particulates and non-regulated emissions like aldehydes or PAHs are oxidized to harmless products.

In modern diesel aftertreatment systems (AFS), Diesel Oxidation Catalyst (DOC) also plays an important role of oxidizing nitric oxide (NO) by conversion into nitrogen dioxide (NO2) - a gas required to support the performance of diesel particulate filter (cDPF/DPF) catalyst as well as SCR catalysts used for NOx reduction, which are placed downstream this DOC. DPF/cDPF requires a pressure drop sensor to monitor the performance thereof and SCR requires a NOx sensor to monitor the efficiency thereof.

Configuration 2:

Here, SCR catalyst is coated on a wall-flow filter substrate, termed as sDPF, which controls nitrous oxides (NOX) and particulate matter (PM). Accordingly, there is a saving due to omission of a separate SCR used in Configuration 1. It is mandatory to monitor SCR for catalyst removal, even if emission with completely failed SCR are within the prescribed OBD limits.

DESCRIPTION OF THE INVENTION

In accordance with the present invention, this SCR catalyst removal can be detected through monitoring the pressure-drop across the catalyst.

Since Configuration 2 involves a wall-flow substrate coated with selective catalyst, i.e. a sDPF, which controls both nitrous oxides (NOx) and particulate matter (PM).

Therefore, the pressure-drop across sDPF is sufficient to detect whether sDPF is fitted or not. This can be achieved by means of a differential pressure sensor, e.g. delta (??) pressure sensor.

In accordance with the present invention, this method is successfully applied to diesel engine powered vehicles without a separate SCR and having emissions within prescribed OBD limits and having sDPF used as after-treatment system (AFS) of the engine.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a method for conducting on-board diagnostics (OBD) of Selective Catalyst Reduction (SCR) system equipped in compression ignition (CI) engines.

Another object of the present invention is to provide a method for conducting on-board diagnostics (OBD) of Selective Catalyst Reduction (SCR) system of CI engines by determining the removal of selective catalyst reductant.

Still another object of the present invention is to provide a device for conducting on-board diagnostics of Selective Catalyst Reduction system equipped in CI engines.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.

SUMMARY OF INVENTION

In accordance with the present invention, there is provided a method for conducting on-board diagnostics of emission control system, wherein the method comprises the step of coating a wall-flow substrate (sDPF) of Diesel Particulate Filter (DPF) with a selective catalyst reductant (SCR) to control both nitrous oxides (NOx) and particulate matter (PM) present in exhaust of the CI-engine.

Typically, the method comprises meeting OBD threshold limit in case of total failure of sDPF.

Typically, the method comprises determining the threshold limit of pressure based on exhaust flow and permissible across the sDPF.

Typically, the method comprises checking the compliance with the mandatory exhaust mass flow to monitor the emission control system.

Typically, the method comprises detecting/measuring the actual pressure-drop across the sDPF after positively confirming the compliance of the release conditions.

Typically, the method comprises comparing the actual pressure-drop detected/measured across the sDPF with the threshold limit.

Typically, the method comprises indicating the removal or absence of sDPF by turning on Malfunction Indication Lamp (MIL) on detecting/measuring the actual pressure-drop across the sDPF to be less than the threshold limit.

Typically, the method comprises turning off Malfunction Indication Lamp (MIL) if on, when the actual pressure-drop detected/measured across the sDPF is not less than the threshold limit, for indicating a defective sDPF to be replaced/repaired.

In accordance with the present invention, there is also provided a method comprising the steps of:

• coating a wall-flow substrate (sDPF) of Diesel Particulate Filter (DPF) with a selective catalyst reductant (SCR) to control both nitrous oxides (NOx) and particulate matter (PM) present in exhaust of the CI-engine;

• determining a threshold limit of the pressure based on exhaust flow and permissible across the sDPF;

• checking the compliance of mandatory exhaust mass flow to monitor the emission control system;

• detecting/measuring the actual pressure-drop across the sDPF after positively confirming the compliance of the release conditions;

• comparing the actual pressure-drop detected/measured across the sDPF with the threshold limit; and either

• turning on the Malfunction Indication Lamp (MIL), on finding the actual pressure-drop to be less than the threshold limit, to indicate the removal or absence of sDPF; or

• turning off the MIL (if on) on finding the actual pressure-drop being not less than the threshold limit, to indicate defective sDPF to be replaced/repaired.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described in the following with reference to the accompanying drawings.

Figure 1 shows the first configuration of the conventional device used in diesel engine powered vehicles.

Figure 2 shows the second configuration of the conventional device used in diesel engine powered vehicles.

Figure 3 shows the conventional SCR monitoring method for diesel engine powered vehicles uses NOx sensor.

Figure 4 shows a flow-chart of the method discussed with respect to Figure 3.

Figure 5 shows the method employed for alternative OBD monitoring of SCR system configured in accordance with the present invention simply by detecting pressure-drop across the wall-flow substrate of Diesel Particulate Filter (sDPF).

Figure 6 shows a flow-chart of the method shown in Figure 5 above.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, the method for alternative OBD monitoring of SCR system by detecting pressure-drop across sDPF using the device configured in accordance with the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention.

Figure 1 shows the first configuration of the conventional device used in diesel engine powered vehicles. Here, Diesel Oxidation Catalyst (DOC) is fitted to CI engine of diesel powered vehicle as an emission control device integrated downstream with a combined Diesel Particulate Filter (cDPF) connected to a Selective Catalytic Reduction (SCR) catalyst. cDPF controls the amount of particulate matter (PM) and SCR catalyst controls the amount of nitrous oxides present in the exhaust released to the atmosphere by the diesel (CI) engine.

Figure 2 shows the second configuration of the conventional device used in diesel engine powered vehicles. Here, Selective Catalytic Reduction (SCR) catalyst is coated on a wall-flow substrate (sDPF), which actually controls the amount of both nitrous oxides (NOx) and particulate matter (PM) present in the exhaust released to the atmosphere by the diesel (CI) engine.

Figure 3 shows the conventional SCR monitoring method for diesel engine powered vehicles uses NOx sensor for both the configurations depicted in Figures 1 and 2. Here, SCR NOx conversion efficiency is calculated based NOx emission value detected by NOx sensor, both captured before SCR and after SCR. The failure of SCR system is confirmed, if NOx conversion efficiency is detected to be less than the threshold value and then Malfunction Indication Lamp (MIL) is turned on.

Figure 4 shows a flow-chart of method 100 discussed with respect to Figure 3. The method starts at step 110 and it is checked at step 120, whether the release condition for SCR monitoring are fulfilled. If the release conditions are fulfilled, the efficiency of SCR system is evaluated at step 130 based on whether the NOx conversion rate is less than the minimum threshold efficiency of SCR system. However, if the release conditions are not fulfilled, the method evaluation process return via path 122 to restart SCR monitoring method 100 from step 110, until the release conditions are fulfilled at step 120 to proceed ahead. Further, once NOx conversion rate is detected at step 130 to be less than the minimum threshold efficiency of SCR system, i.e. there are issues with SCR system and the method follows path 134. Accordingly, the fault is set or SCR system failure is confirmed at step 136, and Malfunction Indication Lamp (MIL) is turned on at step 138. However, if NOx conversion rate detected at step 130 is not less than the minimum threshold efficiency of SCR system, i.e. there are certain issues with SCR system, the method follows path 132 to proceed to next method step 140 involving correcting the detected fault. Finally, once this fault detected in the SCR system is corrected, the method ends with turning Malfunction Indication Lamp (MIL) off at step 150.

Figure 5 shows the method employed for alternative OBD monitoring of SCR system by detecting pressure-drop across wall-flow substrate of Diesel Particulate Filter (sDPF) by the device configured in accordance with the present invention.

Figure 6 shows a flow-chart of the method shown in Figure 5 above. The method starts at step 210 and it is checked at step 220, whether the release condition for SCR monitoring are fulfilled. If the release conditions are fulfilled, the efficiency of SCR system is evaluated at step 230 based on whether the actual pressure-drop across sDPF is less than the minimum pressure based on exhaust flow rate. However, if the release conditions are not fulfilled, the method evaluation process return via path 222 to restart SCR monitoring method 200 from step 210, until the release conditions are fulfilled at step 220 to proceed ahead. Further, once the actual pressure-drop across sDPF is found at step 130 to be less than the minimum pressure based on exhaust flow rate, i.e. there are issues with actual pressure-drop across sDPF and the method follows path 234.

Accordingly, the fault is confirmed or absence or removal of sDPF is confirmed at step 236, and Malfunction Indication Lamp (MIL) is turned on at step 238.

However, if the actual pressure-drop across sDPF found at step 230 is not less than the minimum pressure based on exhaust flow rate, i.e. there are certain issues with sDPF, the method follows path 232 to proceed to next method step 240 involving correcting the detected fault.

Finally, once this fault detected in the sDPF is corrected, the method ends with turning Malfunction Indication Lamp (MIL) off at step 250.
TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The method and device for OBD monitoring of SCR system configured in accordance with the present invention offers the following advantages:

• Does not require NOx sensors.

• Brings NOx emissions within OBD limit without sDPF.

• Dispenses with NOx sensors required until now for monitoring NOx emissions.

• Provided a substantially simpler and more economic diesel exhaust aftertreatment system thanks to fewer components (by dispensing SCR)

• Applicable to diesel engines without SCR and with sDPF.

• Satisfies the current legislative requirement of AIS 137.

• Successfully detects completely removed SCR for an sDPF system.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.

Although, the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification.

Accordingly, the skilled person can make innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to imply including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.

The description of the exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower”, “upper”, “horizontal”, “vertical”, “above”, “below”, “up”, “down”, “top”, and “bottom” as well as derivatives thereof (e.g. “horizontally”, “downwardly”, “upwardly” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion.

These relative terms are for convenience of description and do not require that the corresponding apparatus or device be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected”, refer to a relationship, wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.