Claims:We Claim:

1. A NOx storage catalyst system (10) for a vehicle, the system (10) comprising:
a NOx storage catalyst module (105) for adsorbing exhaust gases from an engine (20) of the vehicle;
a temperature sensor (106) located at an inlet (107) of the NOx storage catalyst module (105);
characterized in that:
a flow path (110) from an outlet (115) of an EGR cooler (120) to the NOx storage catalyst module (105);
a valve (125) on the flow path (110) for regulating flow of a portion of exhaust gas from the EGR cooler (120) to the NOx storage catalyst module (105), the valve (125) adapted to be actuated by a control unit (127) based on a temperature measured by the temperature sensor (106).

2. An electronic control unit (127) for operating a NOx storage catalyst system (10), the electronic control unit (127) adapted to:
measure temperature of exhaust flowing into a NOx storage catalyst module (105) by a temperature sensor (106) located at an inlet (107) of the NOx storage catalyst module (105);
compare whether the measured temperature exceeds a temperature threshold for the NOx storage catalyst module (105); and
actuate a valve (125) on a flow path (110) from an outlet (115) of an EGR cooler (120) to the NOx storage catalyst module (105) to any one of open the valve (125) or increase flow through the valve (125) upon positive determination of the measured temperature exceeding the temperature threshold.

3. The electronic control unit (127) for operating the NOx storage catalyst system (10) as claimed in Claim 2, further adapted to:
measure temperature of exhaust flowing into the NOx storage catalyst module (105) by the temperature sensor (106);
compare whether the measured temperature is below the temperature threshold for the NOx storage catalyst module (105); and
actuate the valve (125) to any one of close the valve (125) and decrease flow through the valve (125) upon positive determination of the measured temperature below the temperature threshold.

4. A method (50) of operating a NOX storage catalyst system (10), the method (50) comprises:
measuring (502) temperature of exhaust flowing into a NOx storage catalyst module (105) by a temperature sensor (106) located at an inlet (107) of the NOx storage catalyst module (105);
comparing (503) whether the measured temperature exceeds a temperature threshold for the NOx storage catalyst module (105), by a control unit (127); and
actuating (510) the valve (125) on a flow path (110) from an outlet (115) of an EGR cooler (120) to the NOx storage catalyst module (105) to any one of open the valve (125) and increase flow through the valve (125) upon positive determination of the measured temperature exceeding the temperature threshold, by the control unit (127).

5. The method (50) of operating the NOx storage catalyst system (10) as claimed in Claim 4, the method further comprises:
measuring (512) temperature of exhaust flowing into the NOx storage catalyst module (105) by the temperature sensor (106);
comparing (513) whether the measured temperature is below the temperature threshold for the NOx storage catalyst module (105), by the control unit (127); and
actuating (520) the valve (125) in the flow path (110) to any one of close the valve (125) and decrease flow through the valve (125) upon positive determination of the measured temperature below the temperature threshold, by the control unit (127).
, Description:FIELD OF THE INVENTION
[0001] This invention relates to a NOx storage catalyst system, an electronic control unit and a method for operating the NOx storage catalyst system.

BACKGROUND OF THE INVENTION
[0002] Among the many exhaust gas treatment options for diesel vehicles is the NOx storage catalyst option.
[0003] 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. EP1031708 discloses an exhaust cooler integrated with a storage catalyst system.

BRIEF DESCRIPTION OF DRAWINGS
[0004] Embodiments of this disclosure is explained in principle below with reference to the drawings. The drawings are:
[0005] FIGURE 1 shows a schematic of a NOx storage catalyst system in relation to an engine and an exhaust system of the engine
[0006] FIGURE 2 shows steps of a method of operating a NOx storage catalyst system

DETAILED DESCRIPTION
[0007] FIGURE 1 shows a schematic of a NOx storage catalyst system 10 in relation to an engine 20 and an exhaust system 30 of the engine.
[0008] The NOx storage catalyst system 10 for a vehicle comprises a NOx storage catalyst module 105 for adsorbing exhaust gases from an engine 20 of the vehicle. The NOx storage catalyst system 10 further comprises a temperature sensor 106 located at an inlet 107 of the NOx storage catalyst module 105, a flow path 110 from an outlet 115 of an EGR cooler 120 to the NOx storage catalyst module 105 and a valve 125 on the flow path 110 for regulating flow of a portion of exhaust gas from the EGR cooler 120 to the NOx storage catalyst module 105, the valve 125 adapted to be actuated by a control unit 127 based on a temperature measured by the temperature sensor 106.
[0009] The NOx storage catalyst module 105 and the working of the same is understood by a person of ordinary skill in the art. The NOx storage catalyst module 105 refers to the component or unit attached to a vehicle exhaust system that is capable of adsorbing NOx gases in the engine exhaust. The arrangement of the NOx storage catalyst module 105 in relation to the engine 20 and the exhaust system 30 of the engine 20 is also understood by the person of ordinary skill in the art. The EGR cooler 120 is the exhaust gas recirculation cooler and the working of the same is also understood by the person of ordinary skill in the art.
[0010] The flow path 110 is composed of standard tubing and materials adapted to carry hot exhaust gases in an engine system. The valve 125 on the flow path 110 can be a variable flow valve which can vary the quantity of exhaust gases from the EGR cooler 120 flowing to the NOx storage catalyst module 105. Some examples of the variable flow valve can be a progressive pneumatic or an electric valve. The valve 125 can also be an ON-OFF valve or open-close valve, which allows a fixed quantity of gas to flow through when the valve 125 is open or does not allow any gas to flow through when the valve 125 is closed. The valve 125 is adapted to be controlled by the control unit 127 which will be described hereinafter. The temperature sensor 106 is connected to the control unit 127 and is adapted to receive signals from the temperature sensor 106. The control unit 127 can be an electronic control unit (ECU) of the vehicle or can be any other electronic based control unit in the vehicle specifically suited for the control of the NOx storage catalyst system 10. The flow path 110 can be a tubing or conduit that can carry hot gases. The working of the NOx storage catalyst system 10 is described hereinafter.
[0011] An electronic control unit 127 for operating a NOx storage catalyst system 10 is adapted to measure temperature of exhaust flowing into the NOx storage catalyst module 105 by the temperature sensor 106 located at the inlet 107 of the NOx storage catalyst module 105, compare whether the measured temperature exceeds a temperature threshold for the NOx storage catalyst module 105 and actuate the valve 125 on the flow path 110 from the outlet 115 of the EGR cooler 120 to the NOx storage catalyst module 105 to any one of open the valve 125 or increase flow through the valve 125 upon positive determination of the measured temperature exceeding the temperature threshold.
[0012] The electronic control unit 127 is further adapted to measure temperature of exhaust flowing into the NOx storage catalyst module 105 by the temperature sensor 106, compare whether the measured temperature is below the temperature threshold for the NOx storage catalyst module 105 and actuate the valve 125 to any one of close the valve 125 to stop gas flow and decrease flow through the valve 125 upon positive determination of the measured temperature below the temperature threshold.
[0013] FIGURE 2 shows steps of a method 50 of operating a NOx storage catalyst system 10. The method 50 of operating a NOx storage catalyst system 10 comprises a first step 502 of measuring temperature of exhaust flowing into the NOx storage catalyst module 105 by the temperature sensor 106 located at the inlet 107 of the NOx storage catalyst module 105, a second step 503 of comparing whether the measured temperature exceeds a temperature threshold for the NOx storage catalyst module 105 by the control unit 127 and a third step 510 of actuating the valve 125 on the flow path 110 from the outlet 115 of the EGR cooler 120 to the NOx storage catalyst module 105 to any one of open the valve 125 and increase flow through the valve 125 upon positive determination of the measured temperature exceeding the temperature threshold by the control unit 127. The working of the system 10 will be described hereinafter.
[0014] The method 50 further comprises a step 512 of measuring temperature of exhaust flowing into the NOx storage catalyst module 105 by the temperature sensor 106, a step 513 of comparing whether the measured temperature is below the temperature threshold for the NOx storage catalyst module 105 by the control unit 127 and a step 520 of actuating the valve 125 in the flow path 110 to any one of close the valve 125 and decrease flow through the valve 125 upon positive determination of the measured temperature below the temperature threshold by the control unit 127.
[0015] The actuation of the valve 125 by the control unit 127, which is also recited in the step 510 of the method 50 enables the flow of cooled exhaust gases from the EGR cooler 120 through the flow path 110 to the NOx storage catalyst module 105 to reduce the temperature of the exhaust gases entering the NOx storage catalyst module 105. The gases coming through the flow path 110 mixes with the exhaust gases coming directly from the engine 20 through a flow path 140 and reduces the temperature of the gases entering the NOx storage catalyst module 105. The flow path 110 is adapted to only carry a portion of the cooled exhaust gases from the EGR cooler 120. The remaining cooled exhaust gases from the EGR cooler 120 is forced to the engine 20 for the recirculation of exhaust gases for reducing NOx generation as in a conventional exhaust gas recirculation system. In other words, the NOx storage catalyst system 10 is an addition or increment to the exhaust gas recirculation system with the EGR cooler 120. In the context of the instant disclosure, the control unit and the electronic control unit refer to the same entity, which applies to the functions carried out also. The control unit 127 or the electronic control unit 127 can also process information, receive information in the form of signals and transmit control signals for control or actuation. The actuation in step 510 can either comprise opening the valve 125 from a closed state which can be achieved by an ON-OFF valve or open-close valve or increasing the valve opening to increase the flow of gases through the valve 125 from the EGR cooler 120 which can be achieved by a variable flow valve. Both the above results in a decrease in temperature of the gases entering the module 105. The actuation in step 520 can either comprise closing the valve 125 from an open state which can be achieved by the ON-OFF valve or open-close valve or decreasing the valve opening to decrease flow through the valve 125 which can be achieved by the variable flow valve.
[0016] The signals from the temperature sensor 106 indicates the temperature of the exhaust gases flowing into the module 105 and hence is indicative of the temperature of the catalyst inside the module 105 used for adsorption of the NOx gases. The temperature of the NOx gases flowing or forced into the module 105 is thus determined by the control unit 127. The control unit 127 then compares whether the measured or determined temperature exceeds a temperature threshold or threshold temperature for the NOx storage catalyst module 105. For example, if the threshold temperature for the module 105 is 450°C or the threshold range is 400°C - 450°C and if the temperature measured through the temperature sensor 106 is 500°C, then the control unit 127 actuates the valve 125 to release an amount of cooled exhaust gases from the EGR cooler 120. This cooled gases mixes with the exhaust directly coming from the engine 20 and therefore reduces the temperature of the exhaust flowing or forced into the module 105. For example, with a variable flow valve, depending on the temperature measured by the sensor 106, the quantity of gases flowing through the valve 125 can be varied. For example, if the temperature threshold is 450°C and if the measured temperature is 800°C, then the valve 125 is opened relatively more than if the measured temperature is 500°C. The objective of the control unit 127 in such cases can be to maintain the temperature of the gases flowing or forced into the module 105 to be kept at an optimal working temperature of the catalyst in the module 105. If the measured temperature is less than 450°C, then the valve 125 is not opened or actuated by the control unit 127.
[0017] If after the cooling of the module 105 mentioned above, the measure temperature shows a temperature below the temperature threshold, then the valve 125 is either closed or the gas flow through the valve 125 is reduced to maintain the temperature of the module 105.
[0018] Moreover, there is a continuous reading of signals from the temperature sensor 106 and correspondingly the valve 125 is actuated by the control unit 127.
[0019] The advantage of the above two methods and the system 10 is to maintain the temperature of the catalyst in the module 105 at an optimal working temperature range of the catalyst for effective adsorption of the NOx gases from the exhaust.
[0020] This can be applied in commercial diesel engines.
[0021] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. Any modification in the embodiments are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.