Claims:We Claim:

1. A NOx storage catalyst system (10) for a vehicle, said system comprising:
a NOx storage catalyst module (12) located downstream of an engine (14) in an exhaust path (16) for receiving exhaust gases from an outlet (14a) of said engine (14) through a primary flowpath (18);
characterized in that
a secondary flowpath (20) bypassing said primary flowpath (18) and comprising a cooler (22), said cooler (22) connected between said outlet (14a) of said engine (14) and said NOx storage catalyst module (12) for enabling cooling of said exhaust gases flowing in said secondary flowpath (20) into said NOx storage catalyst module (12); and
a valve (24) located in at least one of said primary flowpath (18) and said secondary flowpath (20), said valve (24) being operated based on temperature of said exhaust gases measured by a temperature sensor (11) located at an inlet of said NOx storage catalyst module (12).

2. The NOx storage catalyst system (10) as claimed in claim 1 further comprising:
a temperature sensor (11) located at an inlet of said NOx storage catalyst module (12) for measuring temperature of said exhaust gases flowing into said inlet of said NOx storage catalyst module (12).

3. An electronic control unit for operating a NOx storage catalyst system (10), said electronic control unit comprising:
a processor, said processor adapted to:
receive temperature value of exhaust gases flowing into said NOx storage catalyst module (12) using a temperature sensor (11) located at an inlet of said NOx storage catalyst module (12);
compare said temperature value with a pre-defined temperature value stored in a memory of said processor;
determine if said temperature value is above said pre-defined temperature value; and
actuate a valve (24) located in at least one of a primary flowpath (18) and a secondary flowpath (20) such that said exhaust gases are enabled to flow through a cooler (22) located in said secondary flowpath (20) when said temperature value is above said pre-defined temperature value.

4. An electronic control unit for operating a NOx storage catalyst system (10), said electronic control unit comprising:
a processor, said processor adapted to:
receive temperature value of exhaust gases flowing into said NOx storage catalyst module (12) using a temperature sensor (11) located at an inlet of said NOx storage catalyst module (12);
compare said temperature value with a pre-defined temperature value stored in a memory of said processor;
determine if said temperature value is below said pre-defined temperature value; and
actuate a valve (24) located in at least one of a primary flowpath (18) and a secondary flowpath (20) such that said exhaust gases are prevented to flow through a cooler (22) located in said secondary flowpath (20) when said temperature value is below said pre-defined temperature value.
, Description:Field of the invention:
[0001] The invention relates to a NOx storage catalyst system for a vehicle.

Background of the invention:
[0002] Among the many exhaust gas treatment options for diesel vehicles is the NOx storage catalyst option. The NOx storage catalyst (NSC) modules are coated with an adsorption catalyst, which adsorb NOx during lean exhaust conditions and are released during rich operation or increased temperatures. The adsorption and the holding capacity of the catalyst is optimal at lower temperatures and not at higher temperatures. At higher loads, the temperature of the exhaust increases and therefore the temperature prevailing in the NSC modules go up thereby heating up the catalyst. This makes the catalyst reduce their NOx holding capacity, thereby releasing NOx which is undesirable. Hence there is a need to reduce NOx. EP1031708 discloses an exhaust cooler integrated with a storage catalyst system.

Brief description of the accompanying drawings:
[0003] Figure 1 is a block diagram of a NOx storage catalyst system for a vehicle, in accordance with one embodiment of the present disclosure; and
[0004] Figure 2 is a flowchart illustrating a method performed by a processor for operating a NOx storage catalyst system, in accordance with one embodiment of the present disclosure.

Detailed description of the embodiments:
[0005] The present disclosure discloses a NOx storage catalyst system (10) for a vehicle. The system comprises a NOx storage catalyst module (12) located downstream of an engine (14) in an exhaust path (16) for receiving exhaust gases from an outlet (14a) of the engine (14) through a primary flowpath (18). The NOx storage catalyst system (10) is characterized by a secondary flowpath (20) bypassing the primary flowpath (18) and comprising a cooler (22), the cooler (22) is connected between the outlet (14a) of the engine (14) and the NOx storage catalyst module (12) for enabling cooling of the exhaust gases flowing into the NOx storage catalyst module (12) and a valve (24) located in at least one of the primary flowpath (18) and the secondary flowpath (20), the valve (24) being operated based on temperature of the exhaust gases measured by a temperature sensor (11) located at an inlet of said NOx storage catalyst module (12).
[0006] The present disclosure also discloses an electronic control unit for operating a NOx storage catalyst system (10). The electronic control unit comprises a processor, the processor is adapted to receive temperature value of exhaust gases flowing into the NOx storage catalyst module (12) using a temperature sensor (11) located at an inlet of the NOx storage catalyst module (12), compare the temperature value with a pre-stored temperature value stored in a memory of the processor, determine if the temperature value is above the pre-stored temperature value and actuate a valve (24) located in at least one of a primary flowpath (18) and a secondary flowpath (20) such that the exhaust gases are enabled to flow through a cooler (22) located in the secondary flowpath (20) when the temperature value is above the pre-stored temperature value.
[0007] The present disclosure also discloses an electronic control unit for operating a NOx storage catalyst system (10). The electronic control unit comprising a processor, the processor adapted to receive temperature value of exhaust gases flowing into the NOx storage catalyst module (12) using a temperature sensor located at an inlet of the NOx storage catalyst module (12), compare the temperature value with a pre-stored temperature value stored in a memory of the processor, determine if the temperature value is below the pre-stored temperature value and actuate a valve (24) located in at least one of a primary flowpath (18) and a secondary flowpath (20) such that the exhaust gases are prevented to flow through a cooler (22) located in the secondary flowpath (20) when the temperature value is below the pre-stored temperature value.
[0008] The NOx storage catalyst system (10) is explained in conjunction with Figure 1.
[0009] Figure 1 is a block diagram of a NOx storage catalyst system (10) for a vehicle, in accordance with one embodiment of the present disclosure.
[0010] The NOx storage catalyst system (10) comprises a NOx storage catalyst module (12). The NOx storage catalyst module (12) is a standalone module that traps NOx molecules within it by means of adsorption. The NOx storage catalyst module (12) is located downstream of an engine (14) in an exhaust path (16) of the vehicle.
[0011] Exhaust gases discharged from an outlet (14a) of the engine (14) flows into an inlet of the NOx storage catalyst module (12) through a primary flowpath (18). The NOx storage catalyst module (12) is located downstream of the primary flowpath (18). The primary flowpath (18) is a flow channel in the exhaust path (16) that directly connects the outlet (14a) of the engine (14) to the inlet of the NOx storage catalyst module (12) thus enabling flow of exhaust gases into the inlet of the NOx storage catalyst module (12). In case of a turbocharged engine (14), a turbocharger (26) is located in the primary flowpath (18) and the exhaust gases discharged from the outlet (14a) of the engine (14) flows into the inlet of the NOx storage catalyst module (12) through an outlet of the turbocharger (26).
[0012] The NOx storage catalyst system (10) is characterized by a secondary flowpath (20) bypassing the primary flowpath (18). The secondary flowpath (20) is an auxiliary flowpath that forms diversion path from the primary flowpath (18) such that secondary flowpath (20) establishes fluid connection between the outlet (14a) of the engine (14) and the inlet of the NOx storage catalyst module (12).
[0013] For the purpose of illustration the valve (24) as show in FIG. 1 is located in primary flow path 18. However the valve (24) may also be located in secondary flow path (20). The location of the valve (24) in the secondary flow path (20) is not shown in FIG. 1.
[0014] The secondary flowpath (20) comprises a cooler (22) such that the cooler (22) is connected between the outlet (14a) of the engine (14) and the inlet of the NOx storage catalyst module (12). The cooler (22) enables cooling of the exhaust gases flowing in the secondary flowpath (20) into the NOx storage catalyst module (12).
[0015] The secondary flowpath (20) functions as a bypass path with respect to the primary flowpath when temperature of the exhaust gases measured by the temperature sensor (11) is above a pre-defined temperature value so that the cooler (22) present in the secondary path can be used for cooling the exhaust gases.
[0016] The NOx storage catalyst system (10) is also characterized by a valve (24) located in at least one of the primary flowpath (18) and the secondary flowpath (20). The valve (24) is operated such that at least one of the primary flowpath (18) or the secondary flowpath (20) is partially or fully opened or closed. The valve (24) is being operated based on temperature of the measured by the temperature sensor (11) located at an inlet of the NOx storage catalyst module (12).
[0017] In an embodiment, the valve (24) may be a three way valve and may be located at junction of the primary flowpath (18) and the secondary flowpath (20).
[0018] When the valve (24) is located in the primary flowpath (18) and the temperature of the exhaust gases measured by the temperature sensor (11) is above a pre-defined temperature value, then the valve (24) is operated to a close position or partially open position such that large volume of exhaust gases flow through the secondary flowpath (20) through the cooler located in the secondary flowpath (20).
[0019] When the valve (24) is located in the secondary flowpath (20) and the temperature of the exhaust gases measured by the temperature sensor (11) is above a pre-defined temperature value, then the valve (24) is operated to an open position or partially close position such that large volume of exhaust gases flow through the secondary flowpath (20) through the cooler located in the secondary flowpath (20).
[0020] When the valve (24) is located in the primary flowpath (18) and the temperature of the exhaust gases measured by the temperature sensor (11) is below a pre-defined temperature value, then the valve (24) is operated to an open position such that large volume of exhaust gases flow through the primary flowpath (18) since the temperature of the exhaust gases is already below the pre-defined temperature value and thus no cooling is required.
[0021] When the valve (24) is located in the secondary flowpath (20) and the temperature of the exhaust gases measured by the temperature sensor (11) is below a pre-defined temperature value, then the valve (24) is operated to an closed position such that large volume of exhaust gases flow continue to flow through the primary flowpath (18) since the temperature of the exhaust gases is already below the pre-defined temperature value and thus no cooling is required.
[0022] Figure 1 also illustrates an EGR system comprising an intercooler (30), an EGR valve (32) and an EGR cooler (34).
[0023] Working of the NOx storage catalyst system (10) is explained in detail in the below paragraphs. The working of the NOx storage catalyst system (10) is explained with the help of a method performed by the processor which is illustrated using a flowchart in conjunction with Figure 2.
[0024] The electronic control unit of the vehicle is adapted to operate the NOx storage catalyst system (10). The electronic control unit comprises a processor that performs a method of operating NOx storage catalyst system (10). The valve (24) present in the NOx storage catalyst system (10) is connected to the electronic control unit and is operated by the processor.
[0025] At step 205, the processor receives temperature value of the exhaust gases flowing into the NOx storage catalyst module (12) from a temperature sensor (11) located at an inlet of the NOx storage catalyst module (12).
[0026] The temperature sensor (11) is connected to the electronic control unit and provides the temperature value of the exhaust gases present at the inlet of the NOx storage catalyst module (12). The temperature value provided by the temperature sensor (11) is thus received by the processor.
[0027] At step 210, the temperature value is compared with a pre-defined temperature value stored in the memory of the processor. A comparator which may be standalone unit connected to the processor or a comparator circuit within the processor may be used for such comparison.
[0028] At step 215, the processor determines if the temperature value is above a pre-defined temperature value.
[0029] At step 220, the processor actuates the valve (24) located in at least one of a primary flowpath (18) and a secondary flowpath (20) such that the exhaust gases are enabled to flow through a cooler (22) located in the secondary flowpath (20) when the temperature value is above said pre-defined temperature value.
[0030] If the temperature value is above the pre-defined temperature value, then the exhaust gases are considered to be above optimal temperature at which the NOx storage catalyst module (12) operates. Hence, the exhaust gases are required to be cooled by enabling the exhaust gases to flow through the cooler (22) located in the secondary flowpath (20).
[0031] If the valve (24) is located in the primary flowpath (18), then the valve (24) may be fully closed or partially opened in a manner such that large volume of exhaust gases are allowed to flow through the secondary flowpath (20) into the cooler (22) so that the exhaust gases may be cooled. The cooling of the exhaust gases occurs such that the temperature of the exhaust gases at the inlet of the NOx storage catalyst module (12) is optimal for its operation.
[0032] If the valve (24) is located in the secondary flowpath (20), then the valve (24) may be fully opened or partially closed in a manner such that large volume of exhaust gases are allowed to flow through the secondary flowpath (20) into the cooler (22) so that the exhaust gases may be cooled. The cooling of the exhaust gases occurs such that the temperature of the exhaust gases at the inlet of the NOx storage catalyst module (12) is optimal for its operation.
[0033] In one embodiment, the processor determines if the temperature value is below the pre-defined temperature value. The temperature value being below the pre-defined value means that the temperature of the exhaust gases measured by the temperature sensor (11) is sufficient for optimal functioning of the NOx storage catalyst module (12) without need for cooling of the exhaust gases.
[0034] If the temperature value is below the pre-defined temperature value, then the processor actuates the valve (24) located in at least one of a primary flowpath (18) and a secondary flowpath (20) such that the exhaust gases are prevented to flow through a cooler (22) located in the secondary flowpath (20).
[0035] If the valve (24) is located in the primary flowpath (18), then the valve (24) may be fully opened such that large volume of exhaust gases are allowed to flow through the primary flowpath (18) since no cooling of the exhaust gases are required since the temperature of the exhaust gases measured by the temperature sensor (11) is already at an optimal temperature for operation of the NOx storage catalyst module (12).
[0036] If the valve (24) is located in the secondary flowpath (20), then the valve (24) may be fully closed in a manner such that exhaust gases are prevented from flowing in the secondary flowpath (20) through the cooler (22) since the exhaust gases measured by the temperature sensor (11) is already at an optimal temperature for operation of the NOx storage catalyst module (12) and hence no cooling is required. In this case, large volume of exhaust gases are allowed to flow through the primary flowpath (18) into the inlet of the NOx storage catalyst module (12).
[0037] Therefore the present disclosure discloses NOx storage catalyst system (10) with a secondary flowpath (20) that bypasses primary flowpath (18) for enabling the temperature of the exhaust gases to maintain optimal temperature for operating the NOx storage catalyst module (12). By introducing the secondary flowpath (20) comprising a cooler (22) enables cooling of the exhaust gases for optimal functioning of the NOx storage catalyst module (12). Thereby enabling efficient NOx conversion into elemental nitrogen hence meeting emission norms.
[0038] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. The scope of the invention is only limited by the scope of the claims.