Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:

Field of the invention:
[0001] The present invention relates to an assembly for an exhaust system of a straddle type vehicle.

Background of the invention:
[0002] In order to meet stringent emission norms (such as BS6, EU5, etc.) for single cylinder engines CO, HC, NMHC and NOx, an Engine Management System (EMS) requires operating the air/fuel ratio of the combustion near to 1 (i.e. lambda=1). At lambda =1, the three-way catalyst produces lowest tail pipe emissions. The air-fuel ratio is oscillated near lambda = 1 simultaneously in rich and lean states to convert all emission constituents. This limits the efficiency of the engine as the fueling should always be provided at lambda =1. The engine would be at highest efficiency around lambda = 1.05 and its Brake Specific Fuel Consumption (BSFC) can be reduced only when lambda >1. This is not possible with current exhaust systems. Operating at lambda>1 would result in High NOx emission as well.

[0003] A patent literature WO2011040365 discloses a saddle type vehicle. Disclosed is a saddle type vehicle which comprises: an internal combustion engine that is operated at an air/fuel ratio leaner than the stoichiometric air/fuel ratio; a first catalyst that is provided in an exhaust channel for discharging the combustion gas from the internal combustion engine; a second catalyst that is provided in the downstream of the first catalyst in the exhaust channel; and a secondary air introduction unit for introducing a secondary air to a portion of the exhaust channel, said portion lying between the first catalyst and the second catalyst. Each of the first catalyst and the second catalyst contains a noble metal component that contains at least one of platinum, rhodium, palladium, or gold. The second catalyst additionally contains an ammonia decomposition component that decomposes ammonia. The ammonia decomposition component contains iridium and barium. Consequently, the NOx removal ratio can be improved in the saddle type vehicle that comprises an internal combustion engine that is operated at an air/fuel ratio leaner than the stoichiometric air/fuel ratio.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0005] Fig. 1 illustrates a block diagram of an assembly for an exhaust system of a straddle type vehicle, according to an embodiment of the present invention;
[0006] Fig. 2 illustrates a graphs for the operation of the assembly, according to an embodiment of the present invention, and
[0007] Fig. 3 illustrates a method for operating an engine of the straddle type vehicle, according to the present invention.

Detailed description of the embodiments:
[0008] Fig. 1 illustrates a block diagram of an assembly for an exhaust system of a straddle type vehicle, according to an embodiment of the present invention. The exhaust system 100 comprises, an exhaust conduit 104 connected to an exhaust outlet (not shown) of an engine 102 of the vehicle, characterized in that, the assembly 110 positioned in the exhaust conduit 104 to treat emissions. The assembly 110 comprises, a binary lambda sensor 108, and a NOx trap 106 positioned downstream of the binary lambda sensor 108. The exhaust system 100 uses the binary lambda sensor 108 to detect whether the fueling provided to the engine 102 is rich (excess than required to maintain stoichiometric lambda) or lean (lower than required to maintain stoichiometric lambda). In other words, the binary lambda sensor 108 detects air/fuel ratio as any one of rich state and lean state. If a voltage of the binary lambda sensor 108 is greater than a threshold value, the exhaust system 100 is operating in rich condition. Similarly, if the voltage of the binary lambda sensor 108 is lesser than the threshold voltage, the exhaust system 100 is operating in lean condition. For example, if the detected voltage is > 0.55V, the exhaust system 100 is operating in rich condition, and if the detected voltage is <0.55V, the exhaust system 100 is operating in lean condition.

[0009] According to an embodiment of the present invention, the assembly 110 for an exhaust system 100 of the straddle type vehicle is disclosed. The exhaust system 100 comprises, the exhaust conduit 104 connected to the exhaust outlet of the engine 102 of the vehicle, characterized in that, the assembly 110 positioned in the exhaust conduit 104 to treat emissions. The assembly 110 comprises, the binary lambda sensor 108, a NOx trap 106 positioned downstream of the binary lambda sensor 108, and a Three-Way Catalyst (TWC) between the binary lambda sensor 108 and the NOx trap 106.

[0010] According to an embodiment of the present invention, the engine 102 comprises a single cylinder with capacity less than 200 Cubic Capacity (CC). In the Fig. 1, only a part of the engine 102 with fuel injector is shown, and the same must not be understood in limiting manner.

[0011] According to an embodiment of the present invention, a controller 112 configured to operate the engine 102 at an air/fuel ratio leaner than the stoichiometric air/fuel ratio. The engine 102 is operated leaner air/fuel ratio until the NOx trap 106 is full. Further, the NOx trap 106 is regenerated by operating the engine 102 at richer stoichiometric air/fuel ratio than the stoichiometric air/fuel ratio for a predetermined time duration or till the NOx trap 106 is regenerated to a desired state as detected by a model or suitable sensor.

[0012] The controller 112 refers to computing devices/units comprising components such as memory element such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC), Digital-to-Analog Convertor (DAC), clocks, timers, and a processor (such as Central Processing Unit (CPU)) (capable of implementing machine learning) connected with each other and to other components through communication bus channels. The components mentioned are just for understanding and may have more or less components as per requirement. The memory element of the controller 112 is prestored with logics or instructions or programs or applications or thresholds or values which is accessed by the processor as per the defined routines. The internal components of the controller 112 are not explained for being state of the art, and the same must not be understood in a limiting manner. The controller 112 is capable to communicate through wired and wireless means such as but not limited to Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, Universal Serial Bus (USB) cable, micro-USB, and the like.

[0013] Further, the straddle type vehicle is any one selected from a group comprising a two-wheeler such as scooter, motorcycle, a three-wheeler such as autorickshaw, and other low-end vehicles. The present invention is also applicable for machines with low engine 102 capacity apart from the vehicles.

[0014] According to an embodiment of the present invention, the assembly 110 is retrofit to existing vehicles by replacement of the TWC with the NOx trap 106. In another embodiment, a voltage output of the binary lambda sensor 108 is used to detect and maintain the lean air/fuel ratio.

[0015] Fig. 2 illustrates a graph for the operation of the assembly, according to an embodiment of the present invention. A first curve 202 represents output voltage of binary lambda sensor 108. A second curve 204 represents air/fuel ratio of the exhaust gases. A third curve 206 represents fuel timing. The three curves are shown with the common X-axis represented by time in suitable units, whereas the Y-axis is different as voltage, ratio, and time. The engine 102 is operated in lean air/fuel ratio, with 1.1 as the air/fuel ratio. At a first time instant 208, consider the NOx trap 106 is adsorbed completely and need to be regenerated. The controller 112 initiates regeneration of the NOx trap 106 by operating the engine 102 in rich air/fuel ratio. The rich air/fuel ratio is represented by the curve between the first time instant 208 and a second time instant 212. The rich air/fuel ratio is at 0.97 as can be seen in the second curve 204. Once the NOx trap 106 is regenerated, the controller 112 moves back the operation of the engine 102 to lean mode, i.e. in lean air/fuel ratio. It can be seen in the third curve 206, that the fueling is increased in the rich mode, i.e. rich air-fuel ratio. A time period 210 for which the engine 102 is operated in rich air/fuel ratio is either static or dynamic, i.e. a predetermined duration or duration which is determined based on the adsorption state or regeneration state.

[0016] Fig. 3 illustrates a method for operating an engine of the straddle type vehicle, according to the present invention. Specifically, the method for operating the engine 102 using the assembly 110 of the exhaust system 100 of the straddle type vehicle is provided. The method is characterized by plurality of steps, of which a step 302 comprises controlling combustion parameters and operating the engine 102 in the leaner stoichiometric air/fuel ratio than the stoichiometric air/fuel ratio. A step 304 comprises detecting adsorption of the NOx trap 106 positioned downstream of the binary lambda sensor 108. A step 306 comprises regenerating the NOx trap 106 by operating the engine 102 at rich stoichiometric air/fuel ratio than the stoichiometric air/fuel ratio. The binary lambda sensor 108 and the NOx trap 106 are components of the assembly 110. Further, the method is for the straddle type vehicle with single cylinder engine 102 with small capacity such as less than 200 CC. In another alternative, the TWC is another component of the assembly 110 which is positioned between the binary lambda sensor 108 and the NOx trap 106.

[0017] According to the present invention, an example of working is envisaged. The binary lambda sensor 108 detects the lambda (or air/fuel ratio) in the exhaust and provides the feedback to the controller 112. The fueling is provided based on the feedback from the binary lambda sensor 108. The lambda is operated greater than one. The produced NOx is then stored inside improved catalyst or the NOx trap 106. The reactions taking place in the NOx trap 106 are state of the art and the same is not mentioned here for simplicity. This method of operation allows operation of the single cylinder engine 102 at lambda greater than one. The lambda is brought lower than 1 for some time in order to replenish the NOx trap 106 sites for NOx storage.

[0018] According to the present invention, the exhaust system 100 uses the conventional system design with improvements on binary lambda sensor 108 and the NOx trap 106. In general a fuel efficient electronic fuel injection system is enabled. The binary lambda sensor 108 is improvised such that the exact operating exhaust lambda is retrieved/determined by the controller 112. The three-way-catalyst is replaced with the NOx trap 106 adsorption of NOx takes place at lambda greater than one. With the above alterations/replacements, the exhaust system 100 is made to operate at lambda greater than one leading to an efficient engine 102 performance and low fuel consumption/BSFC. With the present invention, the stringent emission requirement is met for small capacity single cylinder engines 102 at lower cost. Both the binary lambda sensor 108 and the NOx trap 106 reduces the cost of the vehicle and achieves better emission treatment. In addition, the temperature of the exhaust gases in the small size single cylinder engine 102 is suits the assembly 110.

[0019] According to the present invention, the use of binary sensor, which gives output indicating only rich and lean state of the exhaust gas, in combination with maintaining lean air/fuel ratio for low capacity engine 102 is unique. In contrary, use of non-binary lambda sensor is possible because the exact air/fuel ratio is received as output but increases the cost and maintenance. Hence, the assembly 110 makes use of the low cost binary lambda sensor 108 to efficiently control the emission. Further, the present invention provides embodiment of the assembly 110 with and without the TWC. The exhaust system 100 is operated at lambda leaner than one, whereas the conventional exhaust system 100 operate at lambda =1 to meet emission norms. The fuel efficiency is increased by at least 10% over the existing vehicle. The current vehicles mainly produce low CO, HC, and NOx. The present invention reduces CO2 as well as the mentioned constituents. Also, considering the fuel price rises, the present invention enables vehicles to be fuel efficient in the field and makes vehicle affordable to run.

[0020] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. 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. An assembly (110) for an exhaust system (100) of a straddle type vehicle, said exhaust system (100) comprises,
an exhaust conduit (104) connected to an exhaust outlet of an engine (102) of said vehicle, characterized in that, said assembly (110) positioned in said exhaust conduit (104) to treat emissions, said assembly (110) comprises,
a binary lambda sensor (108), and
a NOx trap (106) positioned downstream of said binary lambda sensor (108).

2. The assembly (110) as claimed in claim 1 comprises a Three-Way Catalyst (TWC) between said binary lambda sensor (108) and said NOx trap (106).

3. The assembly (110) as claimed in claim 1, wherein said engine (102) comprises a single cylinder with capacity less than 200 Cubic Capacity (CC).

4. The assembly (110) as claimed in claim 1, wherein a controller (112) configured to operate said engine (102) at an air/fuel ratio leaner than the stoichiometric air/fuel ratio.

5. The assembly (110) as claimed in claim 4, wherein said engine (102) is operated leaner air/fuel ratio until said NOx trap (106) is full.

6. The assembly (110) as claimed in claim 5, wherein said NOx trap (106) is regenerated by operating said engine (102) at richer stoichiometric air/fuel ratio than the stoichiometric air/fuel ratio.

7. The assembly (110) as claimed in claim 1 is retrofit to existing vehicles by replacement of a TWC with said NOx trap (106).

8. The assembly (110) as claimed in claim 1, wherein a voltage output of said binary lambda sensor (108) is used to detect and maintain lean air/fuel ratio.

9. A method for operating an engine (102) using an assembly (110) of an exhaust system (100) of a straddle type vehicle, characterized by, said method comprises the steps of:
controlling combustion parameters and operating said engine (102) in a leaner stoichiometric air/fuel ratio than a stoichiometric air/fuel ratio;
detecting adsorption of a NOx trap (106) positioned downstream of a binary lambda sensor (108), and
regenerating said NOx trap (106) by operating said engine (102) at rich stoichiometric air/fuel ratio than said stoichiometric air/fuel ratio, wherein said binary lambda sensor (108) and said NOx trap (106) are components of said assembly (110).

10. The method as claimed in claim 9 is for a straddle type vehicle with a single cylinder with small capacity.