DESC:Field of invention
This invention is generally related to an exhaust system for an automotive vehicles, more particular for two wheeled, three wheeled or four wheeled vehicle with an internal combustion engine.
Background
Automotive vehicle with internal combustion engine generally equipped with exhaust system to exhaust combustion products to the atmosphere. Exhaust system carries exhaust gases from exhaust port of the engine and passes through the exhaust pipe and muffler. The exhaust pipe is connected to muffler through specific routing depending upon the vehicle or engine layout. For example in case of two wheeled vehicle having vertically mounted engine, exhaust pipe connected to exhaust port of the engine and the muffler. Generally in such type of vehicles exhaust pipe extends in front direction of the vehicle from the exhaust port and then it bend towards backward direction to connect muffler when vehicle viewed in side view.
Vehicular engine exhaust releases combustion products into the atmosphere. Combustion products contain volatile organic compounds such as oxides of nitrogen, hydrocarbons, carbon monoxide, particulate matter and other pollutants. Hence, regulatory bodies came up with emission standards for automobile which quantitatively limits the permissible amount of specific air pollutants that may be released into atmosphere. These emission standards can also be defined as threshold values of amount of any particular pollutant is allowed to be emitted, beyond which different emission control techniques might be needed. Use of catalyst is one of the technologies currently in use.
Catalyst are the materials which can react with exhaust gases like hydrocarbon, carbon monoxide and oxides of nitrogen to convert them in less harmful products. Catalytic convertor (here in after referred as CAT) can be defined as a device which comprising catalyst to converts harmful pollutants and carbon monoxide into carbon dioxide and water. Typically combination of platinum, palladium and rhodium are used as a catalyst.
Due demand of high speed and higher power, higher capacity engines came into existence. Simultaneously noise through exhaust gets increases as speed or power increase. Generally increase in performance is associated with increase in noise level which is undesirable and may also exceed statutory limits. To control this undesirable noise and vibrations, resonator may be used. Hence, vehicle with internal combustion engine are generally equipped with exhaust system comprising exhaust pipe, CAT, resonator box, muffler etc. Resonator is an acoustic chamber which helps to reduce noise level or change noise pattern of engine exhaust. It is also called as an echo chamber of the exhaust system of an automobile. Resonator can be a box designed with particular dimensions such that sound waves reflected from the resonator box walls cancel out certain frequencies and helps to reduce noise of the engine exhaust.
CAT is generally placed in an exhaust pipe such that exhaust gases from the exhaust port would pass through or over the CAT before release in to the atmosphere. While resonator box generally packaged in parallel with respect to the exhaust pipe. A resonator tube may be provided connecting resonator box and exhaust pipe. Both CAT and resonator box may be located anywhere between exhaust port and muffler. CAT works efficiently at higher temperatures (>400°C). At higher temperatures catalyst gets activated to react with exhaust gas to convert in to less harmful gas efficiently. The temperature of the exhaust gases reduces with the increase in distance from the exhaust port. Hence placement of the catalytic device closer to exhaust port plays significant role in performance of exhaust system and engine. However, too high temperature may affect durability of CAT.
For example in two wheeled vehicle, exhaust system comprises a catalytic converter or CAT which is typically placed in a straight portion between exhaust port and muffler. While resonator box may be packaged in exhaust system using bracket mounted on exhaust pipe and resonator box in cantilever manner.
One of the disadvantages of placing the catalyst in the above position, the temperature of the exhaust gas will be significantly lower than what is required for the activation of the CAT. To improve the efficiency of emission conversion, the catalysts needs to be moved closer to exhaust port. Another disadvantage is the uniformity index of the exhaust gas flow over the CAT surface will be only around 90% when CAT positioned in straight portion of the exhaust pipe. Superior uniformity index will result in better conversion efficiency as well as the durability of the catalyst. Hence, there is need to improve the performance of exhaust system.
In another example, exhaust pipe carries exhaust gases from the exhaust port and then forming a curved portion in the direction of the muffler. This curved portion is in the close vicinity of the exhaust port. Hence positioning CAT at this curved portion having limitation with respect to space and aesthetics. Due to very close proximity to the exhaust port, durability of the CAT may be affected. Further, positioning CAT at this location may generate back pressure towards exhaust port, which may affect the engine torque and ultimately performance of the engine
In case of resonator box positioned parallel to exhaust pipe as mentioned above, due to such arrangement the entire width of the exhaust system increases consuming more space. Conventionally bracket is used to mount resonator box to the exhaust pipe. Stiffness of resonator box assembly is a major concerned when it is bracket mounted since resonator box is in cantilever condition. This type of construction is a constraint for packaging other parts such as engine covers, belly pan.
Due to CAT and resonator box assembly, exhaust system may become bulky and hence compact packaging of such exhaust system components always be a challenge for automobile industry in view of performance and aesthetics.
Object of invention is to improve the performance of exhaust system such that emission of pollutants reduced. Another object of invention is to improve the efficiency of CAT. Yet another object of the invention is to provide convenient and compact packaging of the exhaust system components.
Summary of Invention
To overcome above problems and to achieve above objectives, an exhaust system for an automotive vehicle comprising a CAT may be placed in inclined position with respect to a vertical or horizontal portion of an exhaust pipe.
The exhaust pipe is connected to an exhaust port of an engine. Exhaust port and the muffler are connected via exhaust pipe through a specific routing. Exhaust pipe may have several straight and curved portions. Some part of it is substantially vertical straight portion and some part of it is substantially horizontal straight portion. Exhaust gases exhausted from the exhaust port of an engine, follows the exhaust pipe routing and are released to the atmosphere from a muffler. In between exhaust gases reacts with the CAT positioned in exhaust pipe. To achieve an above objective, CAT may be placed in inclined position such that it connects substantially vertical straight portion of an exhaust pipe and substantially horizontal straight portion of an exhaust pipe.
Hence exhaust pipe routine can be made such that another curved portion is formed after first curved portion. The first curved portion is closer to the exhaust port as compared to second curved portion. CAT may be positioned at second curved portion which is placed optimally closed to exhaust port. Further CAT is positioned such that the angle of incidence of exhaust gas at the axis of the CAT should be 110 to 160 degrees, which increases uniformity index of gas flow thus providing highest conversion efficiency.
The said second curved portion may be created between exhaust port and muffler. Due to optimum closeness of second curved portion position to the exhaust port, temperature of the exhaust gases may be enough to activate CAT to work with higher efficiencies and also not too high temperature that affecting durability of CAT.
In another embodiment, two CATs may be used to further improve the performance of the exhaust system. More specifically, first CAT may be positioned at the second curved portion as disclosed in previous embodiment and second CAT may be positioned in tandem with first CAT. Alternatively the second CAT may be positioned in the second curve along with the first CAT or it may be positioned in substantially horizontal or vertical portion.
In such type of double CAT arrangement, resonator box may be positioned around a CAT and a tube connecting resonator box to an exhaust pipe is provided. Alternatively, resonator box can be positioned around on CAT and also surrounds another CAT at least partially.
By creating second curved portion closer to the exhaust port to position CAT in inclined with respect to horizontal and vertical plane, which enables to take the CAT closer to exhaust port. Hence sufficiently high temperature of exhaust gas may be obtained to activate CAT and convert gases with improved efficiently. Also, by maintaining the angle of the CAT such that the angle of incidence of the exhaust gases is around 110~160°, the uniformity index of the exhaust gases over the catalysts face increases from 90% to minimum 95%.
Advantageously, the said second curved portion created such that CAT position on second curved portion lies in the close vicinity of oil pan of the engine. Also CAT lies in front and downward direction of an engine when vehicle seen in the side view.
As an another embodiment , the Resonator box is positioned around the exhaust pipe away from the said CAT/s. Gases are supplied to a resonator box through the tube connecting exhaust pipe and resonator box. Resonator box surrounds exhaust pipe circumferentially and advantageously it is in the form of two halves.
Further, due to positioning of resonator box around exhaust pipe circumferentially there is no need of any bracket and hence problems related to the bracket are eliminated. This packaging position and method causing symmetric and compact arrangement of resonator box around exhaust pipe. Further, present invention advantageously provides improved, stiffness in comparison with bracket mounted resonator box arrangement. It causes easy assembly of the resonator box to the exhaust system. Also, this arrangement leads to reduction in bulkiness of exhaust system. This invention provides compact arrangement of components of exhaust system.
Brief description of drawings
Fig. 1 is a perspective view of a typical two wheeled vehicle illustrating exhaust system according to present invention
Fig. 2 is a detailed view of exhaust system according present invention
Fig. 3 is a perspective view of another embodiment of the present invention
Fig. 4 illustrates resonator box arrangement according to present invention
Fig. 5 illustrates resonator box arrangement according to another embodiment of the present invention
Detailed description of the preferred embodiments
Fig. 1 is a perspective view of a two wheeled vehicle 101 having a vehicle body frame structure 102, vertically mounted engine 103 with a cylinder head 104, exhaust port 105, oil pan 114, and an exhaust system 106. Exhaust system 106 comprises exhaust pipe 107 carries exhaust gases from the exhaust port to the muffler 108. In between exhaust pipe forming a curved portion 109 immediately after the exhaust port towards muffler. Further, exhaust pipe may have substantially vertical straight portion 110 and substantially horizontal straight portion 111.
According to the present invention, CAT 113 may be placed in inclined position such that it connects substantially vertical straight portion 110 of an exhaust pipe and substantially horizontal straight portion 111 of an exhaust pipe. The said exhaust pipe 107 forming another curved portion 112 after first curved portion 109 and closer to the exhaust port 105. It also lies in the vicinity of oil pan and in the front and downward direction of an engine when vehicle seen in the side view. Second curved portion 112 is formed in a way that a CAT 113 may be positioned on a curved portion such that said CAT makes certain angle with horizontal and vertical plane.
Fig. 2 shows exhaust system 106 according to present invention in detail and enlarged. The said CAT 113 connecting substantially vertical portion 110 and substantially horizontal portion 111. Also, it may be positioned on a second curved portion 112 of exhaust pipe 107 such that the path of exhaust gas in vertical straight portion 110 makes an angle between 110 and 160 degrees with axis of the CAT 113. This angle can be defined as incidence angle of an exhaust gas in a CAT. It can also be define as an angle between axis 213 of CAT 113 and an axis 210 of straight portion 110 of exhaust pipe in vertical direction. This advantageous arrangement improves uniformity index of the exhaust gases over the catalysts face increases from 90% to minimum 95%. Such arrangement enables to move CAT closer to the exhaust port than the conventional arrangement of CAT in second straight portion. Temperature of the exhaust gas getting incident on CAT face is enough for CAT to get activated and work efficiently in comparison with conventional arrangement.
Fig. 3 represents another embodiment of the present invention, exhaust system with two CATs where first CAT 301 positioned on second curved portion 112 and second CAT 302 in tandem with the first CAT 301. An axis 311 of CAT 301 makes angle between 110 to 160 degrees with an axis 310 of first straight portion 210. Due to double CAT arrangement performance of the exhaust system improves further.
Fig. 4 is a representation of resonator box arrangement according to the present invention. Resonator box 401 packaged around exhaust pipe 107 with resonator tube 402 connecting resonator box 401 to the exhaust pipe 107. In this way the stream 403 of exhaust gas enters into the resonator box through resonator tube and cancel out certain frequencies and hence reduces noise and vibrations. Resonator box may be formed in two halves 401A and 401B. It facilitates easy installation or assembly of the resonator box in exhaust system.
Fig.5 shows resonator box according to another embodiment of the present invention, having resonator box 501 may be packaged around CAT 302. Alternatively, in case of double CAT arrangement as shown in Fig. 3, resonator box 501 may be positioned around on CAT 301 and also surrounds another CAT 301 partially. Resonator tube 502 connecting resonator box 501 to the exhaust pipe 107.
Due to arrangement of the resonator box around exhaust pipe, resonator box gets support over circumference of exhaust pipe or CAT according to one of the embodiments disclosed above. Such arrangement do not require any bracket to mount resonator box and hence cantilever arrangement is eliminated. It enhances the stiffness of the arrangement leads to reduction in vibration. Hence over all symmetricity and compactness can be achieved.
Modifications and variations to the exhaust system described in the present specification may be apparent to skilled readers of this disclosure. Such modifications and variations are deemed within the scope of the present invention.
,CLAIMS:1. The exhaust system (106) for an automotive vehicle (101) having internal combustion engine (103) comprised of: an exhaust pipe (107) connected to the said engine; wherein exhaust port of the said engine (103) and the muffler (108) are connected via exhaust pipe (107) through a routing of exhaust pipe; wherein the said exhaust pipe may comprised of plurality of straight and curved portions; characterized in that the said exhaust pipe comprised of a substantially vertical straight portion (110) and a substantially horizontal straight portion (111); the said exhaust system comprised of atleast a CAT (113) wherein the said CAT is placed in inclined position to connect said substantially vertical straight portion (110) of the said exhaust pipe and said substantially horizontal straight portion (111) of the said exhaust pipe.
2. The exhaust system for an automotive vehicle as claimed in claim 1 wherein the said exhaust pipe comprises a first curved portion (109) and second curved portion (112) and the said CAT (113) is positioned at second curved portion (112).
3. The exhaust system for an automotive vehicle as claimed in claim 1 wherein CAT is positioned proximate to the exhaust port.
4. The exhaust system for an automotive vehicle as claimed in claim 2 wherein the said second curved portion (112) lies in the close vicinity of oil pan (114) of the said engine.
5. The exhaust system for an automotive vehicle as claimed in claim 2 wherein the said second curved portion lies in front and downward direction of an engine when vehicle seen in the side view.
6. The exhaust system for an automotive vehicle as claimed in claim 1 wherein the CAT (113) in positioned such that the angle of incidence of exhaust gas at the axis of the CAT (213) is between 110 to 160 degrees.
7. The exhaust system for an automotive vehicle as claimed in claim 1 comprised of two CATs.
8. The exhaust system for an automotive vehicle as claimed in claim 7 wherein first CAT (301) is positioned on the said second curved portion and second CAT is positioned in tandem with the said first CAT.
9. The exhaust system for an automotive vehicle as claimed in claim 8 wherein the said second CAT (302) lies in said substantially vertical portion or substantially horizontal portion or in said second curved portion.
10. The exhaust system for an automotive vehicle as claimed in claim 1 wherein the said exhaust system may comprised of a resonator box (401) said resonator box (401) packaged around said exhaust pipe circumferentially and positioned away from said CAT/s .
11. The exhaust system for an automotive vehicle as claimed in claim 10 wherein the said resonator box (401) is packaged around atleast one CAT circumferentially fully or partially.
12. The exhaust system for an automotive vehicle as claimed in claim 8 and 10 wherein the said resonator box (401) may be packaged around both first CAT and second CAT circumferentially fully or partially.
13. The exhaust system for an automotive vehicle as claimed in claim 8 wherein the said resonator box (401) packaged with a resonator tube 402 connecting resonator box (401) to the exhaust pipe (107).