Claims:WE CLAIM:
1. An exhaust system (100) for a motor vehicle (10), comprising:
a first exhaust pipe (110) extending between a receiving end (112) and a releasing end (114), the receiving end (112) being coupled to an outlet port (12a) of an engine (12);
a second exhaust pipe (120) extending between an intake end (122) and an outlet end (124); and
at least one catalytic converter (200) for treating exhaust gas released from the engine (12), the at least one catalytic converter (200) being disposed between the releasing end (114) of the first exhaust pipe (110) and the intake end (122) of the second exhaust pipe (120) and anterior to the engine (12) in a vehicle front-rear direction (F-R) at a distance from the engine (12) such that heat generated by the engine (12) accentuates the exhaust gas treatment inside the at least one catalytic converter (200).

2. The exhaust system (100) as claimed in claim 1, wherein the at least one catalytic converter (200) is disposed at a distance from a foot peg (50) extending laterally from a vehicle frame such that rider’s foot when rested on the foot peg (50) is always away from the at least one catalytic converter (200).

3. The exhaust system (100) as claimed in claim 1, wherein the at least one catalytic converter (200) is substantially parallel to a longitudinal axis (X) of the engine (12).

4. The exhaust system (100) as claimed in claim 3, wherein the at least one catalytic converter (200) is disposed obliquely downwards from the releasing end (114) of the first exhaust pipe (110).

5. The exhaust system (100) as claimed in claim 1, wherein the first exhaust pipe (110) extends frontwards from the outlet port (12a) of the engine (12) in the vehicle front-rear direction (F-R).

6. The exhaust system (100) as claimed in claim 2, wherein the second exhaust pipe (120) extends rearwardly underneath the foot peg (50) and towards a rear wheel (16) along a longitudinal axis of the vehicle (10).

7. The exhaust system (100) as claimed in claim 1, wherein the at least one catalytic converter (200) comprises a first catalytic converter (300) extending between a first end (302) and a second end (304), the first end (302) configured to receive the exhaust gas from the releasing end (114) of the first exhaust pipe (110).

8. The exhaust system (100) as claimed in claim 7, wherein the at least one catalytic converter (200) comprises: a second catalytic converter (400) extending between an inlet end (402) coupled with the second end (304) of the first catalytic converter (300), and an egress end (404) coupled with the intake end (122) of the second exhaust pipe (120).

9. The exhaust system (100) as claimed in claim 7 or 8, comprises a housing (500) extending between an effluent inlet (502) and an effluent outlet (504), the housing (500) configured to receive the first catalytic converter (300) and the second catalytic converter (400) such that the first end (302) of the first catalytic converter (300) is adjacent to the effluent inlet (502) of the housing (500) and the egress end (404) of the second catalytic converter (400) is adjacent to the effluent outlet (504) of the housing (500).

10. The exhaust system (100) as claimed in claim 9, wherein the egress end (404) of the second catalytic converter (400) is welded to the effluent outlet (504) of the housing (500).

11. The exhaust system (100) as claimed in claim 9, wherein the releasing end (114) of the first exhaust pipe (110) is received through a wall of the housing (500) adjacent to the effluent inlet (502) of the housing (500).

12. The exhaust system (100) as claimed in claim 9, comprises a top cover (250) for covering the effluent inlet (502) of the housing (500) to prevent untreated exhaust gas released from the first exhaust pipe (110) into atmosphere.

13. The exhaust system (100) as claimed in claim 9, comprises an adaptor (450) being circumferentially mounted on the effluent outlet (504) of the housing (500) and connected to the intake end (122) of the second exhaust pipe (120).

14. The exhaust system (100) as claimed in claim 8, comprises a bridge member (350) disposed between the second end (304) of the first catalytic converter (300) and the inlet end (402) of the second catalytic converter (400).

15. The exhaust system (100) as claimed in claim 14, wherein the bridge member (350) comprises a hollow tubular body having one end welded to the second end (304) of the first catalytic converter (300) and another end welded to the inlet end (402) of the second catalytic converter (400).

16. The exhaust system (100) as claimed in claim 12, comprises an oxygen sensor (280) mounted on the top cover (250), the oxygen sensor (280) being coupled with an electronic control unit of the vehicle (10).
, Description:FIELD OF THE INVENTION
[001] The present invention generally relates to an exhaust system, more particularly it relates to an exhaust system for a saddle-type motor vehicle.

BACKGROUND OF THE INVENTION
[002] Generally, exhaust systems of saddle-type motor vehicles have a catalytic converter disposed therein. The catalytic converter in general reduces toxicity of exhaust gases. Typically, the catalytic converters use catalysts to oxidize carbon monoxide and unburned hydrocarbons, and reduce oxides of nitrogen. Even though present day catalytic converters eliminate up to 97% of carbon monoxide (CO) and hydrocarbon (HC) emissions, and in spite of usage of catalytic converters being made compulsory by various governments, there is still an exponential increase in the CO, nitrous oxides, HC and other harmful compounds.
[003] One inherent property of the catalysts used in the catalytic converters is that the catalysts are not completely effective at low temperatures. Accordingly, it is of utmost importance that the catalyst reaches the required temperature range – termed as activation temperature or light off temperature – to facilitate the conversion for as long as the emissions are generated.
[004] Catalytic converters generally use noble precious metals such as platinum, palladium, or rhodium as catalyst. Light off temperature of such noble metals is generally in a range of 250 to 300 degree Celsius which is very high. As a result, if a catalytic converter is not supplied with adequate amount of heat, it will take very long time to reach light off temperature for the catalyst which will eventually lead to higher emission. Hence, there have been several approaches made by manufacturers to achieve quick activation temperatures and have an effective conversion as well.
[005] In one approach, more noble metals are used in the catalytic converters as catalyst. However, since noble metals are costly, such approach is not a feasible approach as it will directly impact the overall cost of the vehicle.
[006] In another approach, the catalytic converter is heated electrically or with a catalyzed fuel burner. In this regard, the electric energy is supplied by an alternator or battery. Electrically heated converters typically require 1 to 2 kW for 20 to 40 seconds to start conversions. However, issues with this approach arise because energy from the battery cannot be used to continuously supply energy for heat conversion. Further problems related to durability due to increased stress over the alternator or the battery, along with heating elements and connectors persist.
[007] In yet another approach, the converters are insulated by refractory materials like oxides of aluminum, silicon, magnesium etc. whereby heat loss is reduced and high temperatures can be maintained. However, such refractory insulation makes the catalytic converters extremely bulky and heavy causing problems in installation, serviceability, maintenance etc.
[008] Thus, there is a need in the art for an exhaust system for a motor vehicle which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[009] The present invention is directed to an exhaust system for a motor vehicle. The exhaust system has a first exhaust pipe extending between a receiving end and a releasing end, the receiving end being coupled to an outlet port of an engine. The exhaust system further has a second exhaust pipe extending between an intake end and an outlet end. Furthermore, the exhaust system has at least one catalytic converter for treating exhaust gas released from the engine, the at least one catalytic converter being disposed between the releasing end of the first exhaust pipe and the intake end of the second exhaust pipe and anterior to the engine in a vehicle front-rear direction at a distance from the engine such that heat generated by the engine accentuates the exhaust gas treatment inside the at least one catalytic converter.
[010] In an embodiment of the invention, at least one catalytic converter is disposed at a distance from a foot peg extending laterally from a vehicle frame such that rider’s foot when rested on the foot peg is always away from the at least one catalytic converter.
[011] In another embodiment of the invention, the at least one catalytic converter is substantially parallel to a longitudinal axis of the engine.
[012] In a further embodiment of the invention, the at least one catalytic converter is disposed obliquely downwards from the releasing end of the first exhaust pipe.
[013] In yet another embodiment of the invention, the first exhaust pipe extends frontwards from the outlet port of the engine in a vehicle front rear direction.
[014] In an embodiment, the second exhaust pipe extends rearwardly underneath the foot peg and towards a rear wheel along a longitudinal axis of the vehicle.
[015] In another embodiment, the at least one catalytic converter comprises a first catalytic converter extending between a first end and a second end, the first end configured to receive the exhaust gas from the releasing end of the first exhaust pipe.
[016] In a further embodiment of the invention, the at least one catalytic converter comprises: a second catalytic converter extending between an inlet end coupled with the second end of the first catalytic converter, and an egress end coupled with the intake end of the second exhaust pipe.
[017] In an embodiment of the invention, the exhaust system has a housing extending between an effluent inlet and an effluent outlet, the housing configured to receive the first catalytic converter and the second catalytic converter such that the first end of the first catalytic converter is adjacent to the effluent inlet of the housing and the egress end of the second catalytic converter is adjacent to the effluent outlet of the housing.
[018] In another embodiment, the egress end of the second catalytic converter is welded to the effluent outlet of the housing.
[019] In a further embodiment, the releasing end of the first exhaust pipe is received through a wall of the housing adjacent to the effluent inlet of the housing.
[020] In another embodiment of the invention, the exhaust system has a top cover for covering the effluent inlet of the housing to prevent untreated exhaust gas released from the first exhaust pipe into atmosphere.
[021] In a further embodiment, the exhaust system has an adaptor being circumferentially mounted on the effluent outlet of the housing and connected to the intake end of the second exhaust pipe.
[022] In another embodiment of the invention, the exhaust system has a bridge member disposed between the second end of the first catalytic converter and the inlet end of the second catalytic converter.
[023] In another embodiment, the bridge member comprises a hollow tubular body having one end welded to the second end of the first catalytic converter and another end welded to the inlet end of the second catalytic converter.
[024] In yet another embodiment of the invention, the exhaust system has an oxygen sensor mounted on the top cover, the oxygen sensor being coupled with an electronic control unit of the vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[025] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows a right-side view of a saddle-type motor vehicle in accordance with an embodiment of the invention.
Figure 2 shows a front view of the saddle-type motor vehicle in accordance with an embodiment of the invention.
Figure 3 shows an exhaust system in accordance with an embodiment of the invention.
Figure 4 shows the exhaust system in accordance with an embodiment of the invention.
Figure 5 shows a housing of the exhaust system with catalytic converters disposed therein in accordance with an embodiment of the invention.
Figure 6 is a graph of relation between length from outlet port of the engine and activation temperature of the catalytic converter in accordance with an embodiment of the invention.
Figure 7 is a graph of emission value of the present invention with respect to conventional exhaust systems in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[026] The present invention relates to an exhaust system for a saddle-type motor vehicle.
[027] Figure 1 illustrates an exemplary motor vehicle, in accordance with an embodiment of the invention. The saddle-type motor vehicle 10 has an IC engine 12 that is vertically disposed. Preferably, the IC engine 12 is a single-cylinder type IC engine. The motor vehicle 10 has a front wheel 14, a rear wheel 16, a frame member, a seat assembly 18 and a fuel tank 20. The frame member includes a head pipe 22, a main tube 24, a down tube 40 (shown in Figure 2), and a pair of seat rails (not shown). The head pipe 22 supports a steering shaft (not shown) and two telescopic front suspensions 26 (only one shown). The two telescopic front suspensions 26 support the front wheel 14. The upper portion of the front wheel 14 is covered by a front fender 28 mounted to the lower portion of the telescopic front suspension 26 at the end of the steering shaft. A handlebar 30 is fixed to upper bracket (not shown) and can rotate to both sides.
[028] The down tube 40 of the frame member is located in front of the IC engine 12 in a vehicle front-rear F-R direction and extends slantingly downward from head pipe 22. The main tube 24 of the frame member is located above the IC engine 12 and extends rearward from head pipe 22 in the vehicle front-rear direction F-R. The IC engine 12 is mounted at the front to the down tube 40 and a rear of the IC engine 12 is mounted at the rear portion of the main tube 24. In an embodiment, the IC engine 12 is mounted vertically, with a cylinder block extending vertically above a crankcase.
[029] The fuel tank 20 is mounted on the horizontal portion of the main tube 24. A rear swing arm 34 is connected to the frame member to swing vertically, and a rear wheel 16 is connected to rear end of the rear swing arm 34. Generally, the rear swing arm 34 is supported by a mono rear suspension 36 (as illustrated in the present embodiment) or through two suspensions on either side of the motor vehicle 10. A taillight unit (not shown) is disposed at the end of the motor vehicle 10 and at the rear of the seat assembly 18. A grab rail (not shown) is also provided on the rear of the seat rails. The rear wheel 16 arranged below seat 18 rotates by the driving force of the IC engine 12 transmitted through a chain drive (not shown) from the IC engine 12. Further, a rear fender 38 is disposed above the rear wheel 16. Furthermore, a headlamp assembly 44, and a speedometer unit 46 are arranged on an upper portion of the head pipe 22.
[030] The motor vehicle 10 has an exhaust system 100. Referring to Figure 1, the exhaust system 100 has an exhaust pipe extending out of an outlet port 12a of the engine 12. The exhaust pipe extends vertically downward from the IC engine 12 up to a point and then extends below the IC engine 12, longitudinally along the vehicle length before terminating in a muffler 42. The muffler 42 is typically disposed adjacent to the rear wheel 16.
[031] Referring to Figures 3 and 4, the exhaust system 100 has a first exhaust pipe 110. The first exhaust pipe 110 extends between a receiving end 112 and a releasing end 114. The receiving end 112 of the first exhaust pipe 110 is connected to the outlet port 12a of the engine 12. In an embodiment of the invention, the first exhaust pipe 110 extends frontwards from the outlet port 12a of the engine 12 in the vehicle front-rear direction F-R. According to the invention, all exhaust gas emitted from the engine 12 travels out of the outlet port 12a of the engine 12 into the first exhaust pipe 110.
[032] As seen in the Figures 3 and 4, the exhaust system 100 of the present invention has a second exhaust pipe 120. The second exhaust pipe 120 extends between an intake end 122 and an outlet end 124. In an embodiment of the invention, the second exhaust pipe 120 extends rearwardly in the vehicle front-rear direction F-R towards the rear wheel 16 along a longitudinal axis of the vehicle 10. As seen in Figure 2, in an embodiment, the second exhaust pipe 120 extends underneath a front foot peg 50 towards the rear wheel 16.
[033] According to the present invention, the exhaust system 100 has at least one catalytic converter 200 for treating the exhaust gas released from the outlet port 12a of the engine 12. As seen in Figures 3 and 4, the at least one catalytic converter 200 is disposed between the releasing end 114 of the first exhaust pipe 110 and the intake end 122 of the second exhaust pipe 120. Further, according to the invention, the at least one catalytic converter 200 is disposed anterior to the engine 12 in a vehicle front-rear direction F-R. According to the invention, the at least one catalytic converter 200 is disposed at a distance from the engine 12. The distance of the at least one catalytic converter 200 from the engine 12 is optimized such that heat generated by the engine 12 is adequately received by the at least one catalytic converter 200 in order to accentuate exhaust gas treatment inside the at least one catalytic converter 200.
[034] In an embodiment of the invention, an as seen in Figure 2, even though the at least one catalytic converter 200 is optimally disposed anterior to the engine 12 for receiving the heat generated by the engine 12, the at least one catalytic converter 200 is however disposed at a distance from the front foot peg 50 which extends laterally from the vehicle frame. Due to this, when a rider’s foot is rested on the foot peg 50, the foot is always away from the at least one catalytic converter 200.
[035] Referring to Figure 3, in an embodiment of the invention, the at least one catalytic converter 200 is substantially parallel to a longitudinal axis X of the engine 12. In yet another embodiment, and referring to Figure 3, the at least one catalytic converter 200 is disposed obliquely downwards from the releasing end 114 of the first exhaust pipe.
[036] Referring now to Figure 5, in an embodiment of the invention, the exhaust system 100 has a first catalytic converter 300. The first catalytic converter 300 extends between a first end 302 and a second end 304. In the present embodiment, the first end 304 is configured to receive the exhaust gas from the releasing end 114 of the first exhaust pipe 110.
[037] Referring yet to Figure 5, in an embodiment of the invention, the exhaust system 100 has a second catalytic converter 400. The second catalytic converter 400 extends between an inlet end 402 and an egress end 404. In the present embodiment, the inlet end 402 of the second catalytic converter 400 is coupled with the second end 304 of the first catalytic converter 300 to receive the treated exhaust gas from the first catalytic converter 300.
[038] As seen in Figure 5, in an embodiment of the invention, the exhaust system 100 has a housing 500 extending between an effluent inlet 502 and an effluent outlet 504. The housing 500 is configured to receive the first catalytic converter 300 and the second catalytic converter 400. Thus, when the first catalytic converter 300 and the second catalytic converter 400 are received inside the housing, the first end 302 of the fist catalytic converter 300 is disposed adjacent to the effluent inlet 502 of the housing 500. Similarly, the egress end 404 of the second catalytic converter 400 is adjacent to the effluent outlet 504 of the housing 500.
[039] In this regard, in the present embodiment, the first catalytic converter 300 and the second catalytic converter 400 are serially disposed. In an embodiment, and as seen in Figure 5, the exhaust system 100 has a bridge member 350 disposed between the first catalytic converter 300 and the second catalytic converter 400. In an embodiment, the bridge member 350 has a hollow tubular body whereby, on one end the bridge member 350 is welded to the second end 304 of the first catalytic converter 300, while on the other end the bridge member 350 is welded to the inlet end 402 of the second catalytic converter 400.
[040] As seen in Figure 5, the housing 500 along with the serially disposed first catalytic converter 300 and the second catalytic converter 400 is disposed between the releasing end 114 of the first exhaust pipe 110 and the intake end 122 of the second exhaust pipe 120. At the effluent inlet 502 of the housing 500, the releasing end 114 of the first exhaust pipe 110 is received. In this regard, the releasing end 114 of the first exhaust pipe 110 is received inside a wall of the housing as shown in Figure 5. Accordingly, the releasing end 114 of the first exhaust pipe 110 is disposed adjacent to the first end 302 of the first catalytic converter 300.
[041] Further, for the serially disposed first catalytic converter 300 and the second catalytic converter 400 to be affixed in the housing, in an embodiment of the invention, the egress end 404 of the second catalytic converter 400 is affixed to the effluent outlet 504 of the housing 500. In another embodiment, the egress end 404 of the second catalytic converter 400 is welded to the effluent outlet 504 of the housing 500.
[042] In an embodiment of the invention, and as seen in Figure 4, the exhaust system 100 has a top cover 250. The top cover 250 covers the effluent inlet 502 of the housing 500. Accordingly, the top cover 250 prevents any untreated exhaust gas released from the first exhaust pipe 110 into atmosphere. In an embodiment of the invention, an oxygen sensor 280 is mounted on the top over 250. The oxygen sensor 280 is further coupled with an Electronic Control Unit (ECU) of the vehicle 10. Thus, the oxygen sensor 280 monitors the amount of oxygen present in the exhaust gas and signals the ECU. The ECU further alters functioning of the engine 12.
[043] In another embodiment of the invention, the exhaust system 100 has an adaptor 450. As seen in Figure 5, on one end, the adaptor 450 is circumferentially mounted on the effluent outlet 504 of the housing 500. While on the other end, the adaptor is connected to the intake end 122 of the second exhaust pipe 120. The adaptor 450 accordingly channelizes all treated exhaust gas released from the egress end 404 of the second catalytic converter 400 into the second exhaust pipe 120, below the foot of the rider towards the outlet end 124 of the second exhaust pipe 120, into the atmosphere.
[044] Advantageously, the catalytic converter being disposed anterior to the engine at an optimum distance greatly accentuates exhaust gas treatment in the catalytic converter. Referring to Figure 6, whereby a relation between length from outlet port of the engine and activation temperature of the catalytic converter has been plotted. As it can be seen, as distance between the outlet port of the engine and the catalytic converter increases, the activation temperature of the catalytic converter decreases which results in poor treatment of the exhaust gas. Referring now to Figure 7, due to the presence of serially disposed catalytic converters, there is a substantial decease in Carbon Monoxide (CO), Total Hydrocarbons (THS), Non-Methane Hydrocarbons (NMHC), and Nitrogen Oxide (NOx) emissions. Further, although the catalytic converter is disposed at a distance such that it achieves activation temperatures quickly, the distance is kept such that the rider’s foot when rested on the foot peg is always away from the catalytic converter, saving the rider’s foot from discomfort and burns. In various embodiments, lengths of the catalytic converters are miniaturized or maximized in order to fit into emission norms and/ or aesthetic requirements.
[045] Further, since catalytic converter of the present invention is placed closed to the engine, catalysts like platinum, palladium, or rhodium takes lesser time to reach the light off temperature thereby treating the exhaust gases more effectively. As a result, requirement of more noble metals is avoided by the present invention.
[046] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.