Claims:We Claim:

1. An exhaust pipe (12) in an exhaust unit (10) of a vehicle, said exhaust pipe (12) comprising :
- a first set of metal fins (14) positioned on an inner surface (15) said exhaust pipe (12) dividing an interior portion of said exhaust pipe (12);
- a second set of metal fins (16) positioned radially around on an outer surface (17) of said exhaust pipe (12);
said first set and said second set of metal fins (14,16) adapted to dissipate heat of an exhaust gas passing through said exhaust pipe (12).
2. The exhaust pipe (12) as claimed in claim 1, wherein said first set and said second set of metal fins (14,16) are welded onto said interior surface (15) and onto said outer surface (17) of said exhaust pipe (12) respectively by anyone of the welding technique.
3. The exhaust pipe (12) as claimed in claim 1, wherein said first set of metal fins (14) are interconnected in said interior portion of said exhaust pipe (12).

4. The exhaust pipe (12) as claimed in claim 1, wherein said first set of metal fins (14) are different in size and shape than said second set of metal fins (16).
5. The exhaust pipe (12) as claimed in claim 1, wherein said first set of metal fins (14) and said second set of metal fins (16) are of equal size and shape.
6. The exhaust pipe (12) as claimed in claim 1, further comprises a coolant tube (20) wound around on an area of said outer surface (17) that is present in between two ends of said exhaust pipe (12).
7. The exhaust pipe (12) as claimed in claim 5, wherein said coolant tube (20) is positioned above said second set of metal fins (16) such that, said coolant tube (20) is in connection with said second set of metal fins (16) welded on said outer surface (17) of said exhaust pipe (12).
, 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] This invention relates to an exhaust pipe in an exhaust unit of a vehicle.
Background of the invention
[0002] Diesel engines typically run on excess air. This leads to higher nitrogen oxide (NOx) levels since, availability of nitrogen and temperature are two important precursors for NOx formation and hence, its emission. With stringent emission norms in place (BS6), it becomes very important to arrive at methods to reduce NOx emissions. Implementing exhaust gas recirculation (EGR) in all its varied forms (low pressure, high pressure and internal) is a proven technique for reducing NOx emissions. Further, an EGR cooler can be used to reduce the temperature of the recirculated exhaust gas and hence improve its mass flow rate. The improvement in mass flow rate is felt through an increase in density of recirculated exhaust, since it is at a lower temperature. This also brings down the mixing temperature of fresh air and EGR and thereby reduces particulate emissions slightly. The cooler is essentially a heat exchanger, which can be of shell-tube, shell-plate or tube-fin type. These constructions improve the heat transfer co-efficient between the coolant and the recirculated exhaust. A typical EGR cooler uses engine coolant, which is comparatively at a lower temperature, to cool the recirculated exhaust gases.
[0003] Prior art patent application US6609590 discloses an in-line exhaust systems comprising an exhaust pipe, and a sound-attenuating baffle in the exhaust pipe. The baffle has one or more baffle plates extending across the gas flow channel, at least one at an oblique angle. Each plate has an array of apertures therethrough. The plates are joined to each other, preferably in edge-to-edge relationship, preferably forming included angles with each other and forming preferably different, oblique angles to the longitudinal axis. In preferred embodiments, plate aperture area increases, plate-to-plate, along the direction of advance of gases in the exhaust system.

Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[0005] FIG. 1 illustrates an exhaust pipe in an exhaust unit of a vehicle in accordance with one embodiment of the invention; and
[0006] FIG.2 illustrates an exhaust pipe in an exhaust unit of a vehicle in accordance with one embodiment of the invention.

Detailed description of the embodiments
[0007] FIG. 1 illustrates an exhaust pipe 12 in an exhaust unit 10 of a vehicle according to one embodiment of the invention. The exhaust pipe 12 comprises a first set of metal fins 14 positioned on an inner surface 15 of the exhaust pipe 12 dividing an interior portion of the exhaust pipe 12 and a second set of metal fins 16 positioned radially around on an outer surface 17 of the exhaust pipe 12. The first set and the second set of metal fins (14,16) adapted to dissipate heat of an exhaust gas passing through the exhaust pipe 12.

[0008] Further the construction of the exhaust pipe 12 and the components of the exhaust pipe 12 is explained as follows. The first set and the second set of metal fins (14,16) are welded to the interior surface 15 and to the outer surface 17 of the exhaust pipe respectively by anyone of the welding technique as known to the person skilled in the art. The first set of metal fins 14 divides the inside area of the exhaust pipe 12 into plurality of portions based on the number of metal fins used. The exhaust pipe 12 comprises a minimum of one metal fin to multiple metal fins. For example, if the exhaust pipe 12 comprises multiple metal fins 14, then the fins 14 welded onto the inner surface 15 of the exhaust pipe 12 forms a wheel spoke kind of structure for the dissipation of the heat from the exhaust gas. According to one embodiment of the invention, the first set of metal fins 14 are interconnected in the interior region of the exhaust pipe 12.

[0009] The first set of metal fins 14 are different in size and shape from the second set of metal fins 16. The second set of metal fins 16 that are radially welded on the outer surface 17 of the exhaust pipe 12 forms a shape of a circle. The position of the fins 16 helps in dissipating the heat of the exhaust gas into the atmosphere rapidly. According to one embodiment of the invention, the first set of metal fins 14 and the second set of metal fins 16 are of equal size and shape. According to another embodiment of the invention, the first and second of metal fins (14,16) are of different size and shape. The first and second set of metal fins (14,16) are not restricted to the fin kind of structure, but can be of any structure like a baffle plate or heat exchanger plate or the like.

[0010] Figure 2 illustrates an exhaust pipe 12 of an exhaust unit in a vehicle according to one embodiment of the invention. The exhaust pipe 12 comprises a coolant tube 20 wound around on an area of the outer surface 17 that is present in between two ends of the exhaust pipe 12. The coolant tube 20 is positioned above the second set of metal fins 16 such that, the coolant tube 20 is in connection with the second set of metal fins 16 welded on the outer surface 17 of the exhaust pipe 12. The ends of the coolant tube 20 is directed into a coolant tank 22, where a pump 24 is positioned inside the tank 22. The pump 24 is adapted to pump the coolant 22 into the coolant tube 20 and the circulated coolant is directed back to the tank 22 where it is cooled and again it is sent into the coolant tube 20. The coolant is chosen from a group of coolants like water, ethylene glycol or the like. The heat of the exhaust pipe 12 dissipated from the second set of metal fins 16 is further cooled down by the coolant tube 20 for a faster dissipation process.

[0011] A method of working of the exhaust pipe 12 with multiple metal fins (14 & 16) and the coolant tube 20 is explained as follows. The first set of the metal fins 14 that are diving the inside area of the exhaust pipe 12, distributes the concentrated hot exhaust gas coming from the engine 18 , such that, the exhaust gas flows out onto the second set of the metal fins 16. Due to the shape and size of the multiple fins 14 in the exhaust pipe 12, the heat from the exhaust gas gets dissipates into the atmosphere with a low temperature. In another embodiment, the temperature of the exhaust gas is much more reduced due to the presence of the coolant tube 20 wound around the exhaust pipe 12. The pump 24 pumps the coolant into the coolant tube 20 at the end of every stroke cycle, such that, the exhaust gas coming from the engine 18 at the end of the exhaust stroke. The exhaust gas comes into contact with the coolant in the coolant tube 20 after flowing through the second set of metal fins 16 and the heat of the exhaust gas is reduced due to the movement of the coolant in the tube 20.

[0012] Due to the multiple metal fins (14 & 16) in the exhaust pipe 12 as disclosed in the invention, the usage of the exhaust cooler is eliminated. The invention provides a cost-effective solution as maintenance cost of the metal fins (14 & 16) is less than the maintenance cost of the exhaust cooler. The cost of adding the first set of fins 14 inside the exhaust pipe 12, can be kept at a minimum by tack-welding the fins in the exhaust pipe 12, after ensuring that the fins touch the wall of the exhaust pipe 12 all along their length. The exhaust pipe 12 is split into smaller streams with the least manufacturing effort possible for a faster heat dissipation.

[0013] 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.