[0001] The present disclosure relates to a system and method of
detecting successful regeneration of Diesel Particulate Filter (DPF) in a vehicle.
Background of the invention
[0002] Exhaust gas treatment systems in passenger vehicles with
compact packaging restraints comprise at least a NOx storage catalyst (NSC) and a diesel particulate filter (DPF). In the NSC, nitrous oxides are stored as they react with basic components forming nitrates. The first step of the storage mechanism is the oxidation of NO to NO2 on the precious metals of the catalyst, mainly Platinum (Pt). This NO2 is subsequently stored on the corresponding storage materials (e.g. Barium Carbonate BaC03) incorporated in the catalyst formulation until the desired storage capacity is reached. Besides this, the NSC is also an excellent oxidation catalyst that can reduce carbon monoxide (CO) and other hydrocarbons like fuel.
[0003] DPF is a filter designed to remove diesel particulate matter
or soot from the exhaust gas of a diesel engine. Collected carbon particulates are removed from the filter, continuously or periodically, through thermal regeneration. This regeneration of DPF is accomplished by programming engine to run (when the filter is full) in a manner that it elevates the exhaust temperature, in conjunction with an extra fuel

injected in the exhaust stream. The injected fuel reacts with a catalyst in the NSC to release thermal energy enough burn off accumulated soot in the DPF filter.
[0004] Like DPF, the NSC also needs regeneration from time to
time. Unfortunately, due to the presence of sulphur into the fuel, the NSC is also exposed to the sulphur poisoning, which heavily reduces the NOx storage capacity of the catalyst. In order to re-enable this capability of the, a desulphation also called DeSOx regeneration or simply DeSOx is needed. Hence the NSC needs to be regenerated periodically by means of rich exhaust gas in order to replenish the NSC. In conventional exhaust gas systems, a regeneration request from NSC is clubbed with a regeneration request from the DPF. However when regeneration request from the NSC is withdrawn, regeneration of the DPF is also terminated leading to an incomplete regeneration of the DPF. However in the vehicle this is incomplete regeneration is also counted as a successfully one. There is a need for a method of detection of successful DPF regeneration that fixes this anomaly.
Brief description of the accompanying drawings
[0005] An embodiment of the invention is described with
reference to the following accompanying drawings:
[0006] Figure 1 depicts a layout (100) for a portion of an exhaust gas
treatment system in a vehicle; and

[0007] Figure 2 is a flow-chart for methods steps regeneration of a
Diesel Particulate filter (DPF (101)) in a vehicle.
Detailed description of the drawings
[0008] Figure 1 depicts a layout of an exhaust gas treatment system
in a vehicle. The system comprises aNOx storage catalyst (NSC (102)), a diesel particulate filter (DPF (101)), a differential pressure sensor (106), temperature sensors (105) and at least an Electronic control unit (ECU (103)). The ECU (103) is in communication with the differential pressure sensor (106) and the temperature sensor (105). The Electronic Control Unit (ECU (103)) of vehicle is adapted to detect a successful regeneration of the Diesel Particulate filter (DPF (101)). The DPF (101) is mounted downstream from the NSC (102).
[0009] The ECU (103) is configured to receive a regeneration
request from the NSC (102). Due to the presence of sulphur into the fuel, the NSC is exposed to the sulphur poisoning, which heavily reduces the NOx storage capacity of the catalyst. In order to re-enable this capability of the, a desulphation also called DeSOx regeneration or simply DeSOx is needed. The regeneration request from NSC (102) is received is by the ECU (103) when the SOx load in the NSC (102) exceeds beyond a threshold level. This threshold is pre-defined and calculated for various vehicles based on their layout and fuel efficiency. The threshold level is defined for every vehicle as the level of SOx accumulation beyond which the NSC (102) can't function efficiently.

[0010] The ECU (103) is further configured to enable chemical
reactions by the injection of fuel in the NSC (102) to raise the temperature downstream of the NSC (102) to a pre-defined threshold. The temperature in the DPF (101) is raised to a pre-defined threshold which is enough to burn soot in the DPF (101). The injection of fuel in NSC (102) is achieved by injecting an additional quantity of fuel either in the engine cylinder, or in the exhaust system, upstream of the DPF (101).
[0011] In an embodiment of the present system, the fuel is
introduced through late cycle injection (post-injection) using the fuel injection system of the diesel engine. In another embodiment of the present system, the fuel is introduced to and combusted in the exhaust system using specialized hardware (104) such as an injector as shown in figure 1. Injection of fuel in the NSC (102) leads combustion of hydrocarbons in the fuel which is a highly exothermic reaction. The thermal energy released by this reaction raises the temperature downstream of the NSC (102) to approximately 600 degree Celsius. This is enough to burn the soot in the DPF (101) and also enables the DeSOx regeneration of NSC (102).
[0012] The ECU (103) is further configured to maintain the raised
temperature for a pre-determined amount of time and till a sufficient soot load is decreased in the DPF (101). The temperature is maintained downstream of the NSC (102) by injection of fuel in sufficient quantity

and for a suitable duration through the specialized hardware (104). The pre-determined amount of time is calculated based on the soot load in the DPF (101). Maintaining such high temperatures downstream of NSC (102) is pertinent for the DPF (101) regeneration i.e. burning of the soot.
[0013] Figure 2 is a flow-chart for methods steps (200) regeneration
of a Diesel Particulate filter (DPF (101)) in a vehicle. The vehicle comprises a NOx storage catalyst (NSC (101)), a diesel particulate filter (DPF (101)), a differential pressure sensor (106), temperature sensors ) (105) and at least an Electronic control unit (ECU (103)). The ECU (103) is in communication with the differential pressure sensor (106) and the temperature sensors (105). The DPF (101) is mounted downstream from the NSC (102).
> [0014] In step 201, the ECU (103) receives a regeneration request
from the NSC (102). Due to the presence of Sulphur into the fuel, the NSC is exposed to the Sulphur poisoning, which heavily reduces the NOx storage capacity of the catalyst. In order to re-enable this capability of the, a desulphation also called DeSOx regeneration or simply DeSOx is
) needed. The regeneration request from NSC (102) is received is by the ECU (103) when the SOx load in the NSC (102) exceeds beyond a threshold level. This threshold is pre-defined and calculated for various vehicles based on their layout and fuel efficiency. The threshold level is defined for every vehicle as the level of SOx accumulation beyond which

the NSC (102) can't function efficiently. Hence a regeneration request is automatically triggered by the NSC (102) when such threshold is reached.
[0015] In step 202, ECU (103) enables chemical reactions by the
injection of fuel in the NSC (102) to raise the temperature downstream of the NSC (102) to a pre-defined threshold. The temperature in the DPF (101) is raised to a pre-defined threshold which is enough to burn soot in the DPF (101). The injection of fuel in NSC (102) is achieved by injecting an additional quantity of fuel either in the engine cylinder, or in the exhaust system, upstream of the DPF (101). In the first approach, the fuel is introduced through late cycle injection (post-injection) using the fuel injection system of the diesel engine. In the second approach, fuel is introduced to and combusted in the exhaust system using specialized hardware (104) such as an injector. In both these methods the ECU (103) sends a signal to either the specialized hardware (104) of the engine to inject an additional quantity of fuel.
[0016] Injection of fuel in the NSC (102) leads combustion of
hydrocarbons in the fuel which is a highly exothermic reaction. The thermal energy released by this reaction raises the temperature downstream of the NSC (102) to approximately 600 degree Celsius. This is enough to burn the soot in the DPF (101) and also enable the DeSOx regeneration of NSC (102) by mean of a series of rich pulses.

[0017] In step 203, ECU (103) maintains the raised temperature for
a pre-determined amount of time and till a sufficient soot load is decreased in the DPF (101). The pre-determined amount of time is calculated based on the soot load in the DPF (101). The temperature is maintained downstream of the NSC (102) by injection of fuel in sufficient quantity and for a suitable duration. The temperature sensors (105) give value of temperature downstream of NSC (102) to the ECU (103) on a real-time basis. The differential pressure sensor (106) senses differential pressure across the DPF (101), which is an indication of the soot load in the DPF (101). Information from these sensors helps ECU (103) decide if regeneration in DPF (101) is complete (i.e. sufficient soot is burnt in the DPF (101)) and if temperature exists for such regeneration. The ECU (103) withdraws the additional fuel injection signal to the engine or the specialized hardware (104) only when regeneration in complete both in the NSC (102) and the DPF (101).
[0018] Maintaining such high temperatures downstream of NSC
(102) and for pre-determined amount of time is pertinent for the DPF (101) regeneration i.e. burning of the soot. Hence the regeneration request that was initiated by the NSC (102) is not recorded as successful until the DPF (101) is also completely regenerated.
[0019] This idea is to develop a method of detection of successful
DPF regeneration in a vehicle takes into the account the misdetection of an incomplete DPF (101) regeneration as successful when the

regeneration request is raised by the NSC (102). Often DPF (101) regeneration is incomplete when the regeneration request was initiated by the NSC (102), however in the ECU (103) this is recorded as complete. The above mentioned method and ECU (103) ensure that when regeneration request is received from the NSC (102), until the DPF (101) is regenerated (i.e. sufficient soot is burnt) it is not deemed to be complete. Hence the method ensures that conditions favorable to DPF (101) regeneration also exist when regeneration request is initiated by the NSC (102). In other words both NSC (102) are DPF (101) are regenerated by this method. Further there is no need for a separate logics for DPF (101) regeneration and NSC (102) regeneration.
[0020] It must be understood that the embodiments explained in the
above detailed description are only illustrative and do not limit the scope of this invention. Any modification to the method of regeneration of a Diesel Particulate filter (DPF (101)) in a vehicle are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.

1. A method of detecting successful regeneration of Diesel Particulate
Filter (DPF) in a vehicle, the DPF (101) mounted downstream from a
NOx storage catalyst (NSC (102)), the vehicle comprising at least an
Electronic Control Unit (ECU (103)), the method comprising:
receiving a regeneration request from the NSC (102) by the
ECU (103);
enabling chemical reactions by the injection of fuel in the
NSC (102) to raise the temperature downstream of the NSC
(102) to a pre-defined threshold;
maintaining the raised temperature in the NSC (102) for a
pre-determined amount of time and till a sufficient soot load
is decreased in the DPF (101).
2. The method of detecting successful regeneration of DPF (101) as claimed in claim 1, where the regeneration request from NSC (102) is received when the SOx load in the NSC (102) exceeds beyond a threshold level.
3. The method of detecting successful regeneration of DPF (101) as claimed in claim 1, where the temperature is raised to a pre-defined threshold which is enough to burn soot in the DPF (101).
4. The method of detecting successful regeneration of DPF (101) as claimed in claim 1, where the temperature is maintained in the NSC

(102) by injection of fuel in sufficient quantity and for a suitable
duration.
5. The method of detecting successful regeneration of DPF (101) as claimed in claim 1, where the temperature is maintained for a pre¬determined amount of time, the pre-determined amount of time is calculated based on the soot load in the DPF (101).
6. An Electronic Control Unit (ECU (103)) of a vehicle adapted to detect a successful regeneration of the Diesel Particulate filter (DPF (101)) mounted downstream from a NOx storage catalyst (NSC (102)), the ECU (103) configured to:
receive a regeneration request from the NSC (102);
enable chemical reactions by the injection of fuel in the NSC
(102) to raise the temperature downstream of the NSC (102)
to a pre-defined threshold;
maintain the raised temperature for a pre-determined amount
of time and till a sufficient soot load is decreased in the DPF
(101).
7. The ECU (103) of a vehicle as claimed in claim 6, where the
regeneration request from NSC (102) is received is by the ECU
(103) when the SOx load in the NSC (102) exceeds beyond a
threshold level.

. The ECU (103) of a vehicle as claimed in claim 6, where the temperature in the DPF (101) is raised to a threshold which is enough to burn soot in the DPF (101).
. The ECU (103) of a vehicle as claimed in claim 6, where the temperature is maintained in the NSC (102) by injection of fuel in sufficient quantity and for a suitable duration.
O.The ECU (103) of a vehicle as claimed in claim 6, where the temperature is maintained for a pre-determined amount of time, the pre-determined amount of time is calculated based on the soot load in the DPF (101).