A NOVEL SOLUTION FOR ABSORBING EXHAUST PIPE VIBRATIONS FROM ENGINE

Technical field: The present invention relates to a flexible line element, particularly for exhaust pipes of internal combustion engines of motor vehicles.

Background and prior art: Exhaust system transfer the by-products of combustion to the environment via suitable sound and emissions control components such as mufflers, resonators, catalytic converters and the like. Exhaust systems in general are subjected to relatively harsh operating conditions. For example, high temperature exhaust gases tend to induce thermal stress, the effects of which are increased by expansion and contraction as the system undergoes temperature change cycles not to mention the corrosive environmental factors and dynamic stress loading. The dynamic stresses including axial, lateral and diagonal forces, originate from vibrations associated with the engine and movement of the vehicle. In the past, such dynamic stresses have been attenuated and controlled by flexible metal hose with corrugations and/or edge interlocking. It is known that corrugated metal hose is adapted to dissipate heat and dampen vibration-induced dynamic stress, and is further adapted to accommodate expansion and retraction associated with conveying high temperature exhaust gases under conditions which involve significant vibration from combustion engines and from on-the-road operating conditions. For example, US 5,882,046 claim a flexible hose section which includes a body with a corrugated medial portion and first and second ends with first and second mouths. The body mouths receive the ends of the upstream and downstream exhaust pipe sections and are secured therein by suitable connectors such as weldments, clamps, gaskets and the like. The hose section, through the arrangements of its corrugations and/or its end connections, permits relative rotational displacement between the exhaust pipe sections whereby dynamic torsional stress is attenuated in and controlled by the hose section.

Another prior art US 5,924,282 discloses an exhaust system for a vehicle which includes an exhaust pipe and a flexible metal hose joined in the vicinities of their respective ends by a clamp assembly. The clamp assembly includes a gasket with sections confirming to the configurations of the exhaust pipe and the flexible hose. A band subassembly generally encircles the gasket and securely retains same in place on the exhaust pipe and the flexible hose.

Yet another prior art, US 6,893,053 discloses a flexible bellows tube connecting pipes in a system such as a vehicle exhaust system. Various embodiments are disclosed with each including two conduit sections having mating corrugations that overlap to provide a seal while allowing the two sections to rotate in response to torsion loading.

Whereas US 6,315,332 discloses at least two interconnected metal bellows for exhaust pipes of an internal combustion engine wherein the metal bellows is provided with cylindrical joining ends and at least one of the bellows may be helically corrugated. The bellows may be either in line or telescoped, are connected at only one of their joining ends.

In case of metal bellows such as helically or annularly corrugated bellows, a strip wound metal hose is placed co-axially with the bellows. This strip-wound metal hose is responsible for damping of movements by converting the movements into friction, the so-called lost work of deformation, between the adjacent strip edges or layers with interlocked profile for an angular, axial, lateral or torsional deflection. The strip winding rate is predetermined for optimum damping of movements. Even then, there are still applications in which the damping properties can be diminished at certain operating temperatures of the strip-wound metal hose i.e. at high temperatures of the hose due to a longer operating period of the exhaust system. One reason for this effect is the so-called thermal stiffening occurring especially in the bending zones of the strip-wound hose due to the different material tensions induced during the winding process trying to relax and expand at different rates in this process. As a result, there is an increase in friction between the adjacent strip edges or layers with interlocked profile, which will cause a restriction of mobility of the hose or an increase in wear and tear of the hose areas which are in contact with each other and finally, a deterioration of the damping properties may occur.

In other cases, torsional forces caused by differential rotation of the exhaust system components connected by flexible metal hose section can inflict significant damage, particularly when the flexible section design is rigid with respect to rotational forces. Such dynamic torsional forces can lead to premature metal fatigue cracking and failure of the exhaust system components, including previous designs of flexible metal hoses. More so, the production cost involved in manufacturing of such existing flex pipe designs being extremely high renders no economic benefit to the automobile manufacturer.

The present invention addresses all these concerns in connection with the application of flexible metal hose to applications involving dynamic stresses. Therefore, there has not been available a dynamic stress controlling flexible hose section with the advantage and features of the present invention.

Accordingly, it is the principal object of the present invention to provide for a flex pipe adapted to control dynamic stresses including axial, lateral and diagonal and rotational stresses. It is further object of the present invention to provide for flex pipe which can be operate effectively in relatively severe operating conditions, such as those associated with vehicle exhaust system. Last but not the least, it is another object of the present invention to provide a flex pipe which is inexpensive to manufacture thereby imparting economical benefit to the manufacturer, efficient in operation, capable of long operating life and particularly well adapted for the purposed usage thereof.

Summary of invention: The present invention describes a plain flex pipe assembly comprising of one or more tube assemblies comprising of medial body and first and second ends and first and second mouths of differential diameters. The plain flex pipe assembly being positioned in the vehicular exhaust system is suitably connected to the upstream and downstream exhaust pipe sections. The plain flex pipe assembly and its end connections thereof, permit relative rotational displacement between the exhaust pipe sections whereby dynamic stresses are attenuated and controlled. It also takes care of the misalignment between the upstream and the downstream pipe sections both in axial and lateral direction.

Brief description of drawings: A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

FIG. I is a 3D image of the plain flex pipe of present invention.

FIG. II is an exploded view of the flex pipe.

FIG. Ill is an exploded view of the piston ring assembly.

FIG. IV is a 3D image of the body of the plain flex pipe.

FIG. Va and Vb are the exploded views of the end flange portions of the tube.

FIG. VIa, VIb, VIc, VId shows the results of simulation studies for pipe assembly having ends with differential diameters.

Detailed Description: The present invention describes a plain flex pipe assembly comprising of one or more tube assemblies comprising of medial body and first and second ends with first and second mouths of differential diameters. The plain flex pipe assembly is positioned as an intermediate part in an automotive exhaust system and is suitably connected to the upstream and downstream exhaust pipe sections thereby forming upstream and downstream conduit pipe sections respectively. The main purpose of the plain flex pipe assembly of the present invention is to absorb such movements and vibrations as are caused by the rubber mounted supported engine, by engine vibration owing to dynamic forces acting on the engine during running condition, by shock, by changes of length due to thermal effects, etc, and of insulating adjacent components from such movements and vibrations. The flex pipe being plain in nature does not lead to premature metal fatigue cracking as in corrugated pipes and bellows thereby providing a long lasting product. Being less expensive and simple to manufacture with conventional tools/machines without requiring special purpose machines as in case of exiting designs of flex bellow / pipe, it imparts significant economic advantage to the manufacturer. The plain flex pipe assembly is manufactured using suitable metals with characteristics appropriate to the desired applications such as corrosion resistance, flexibility, strength, malleability etc. for example, stainless steel, aluminum and other corrosion resistant metals have been found to be appropriate for applications such as automotive exhaust systems. The plain tube can be suitably connected to its first and second end sections as well as to the upstream and downstream pipe sections of the exhaust systems with suitable weldments, clamps, gaskets, bolted flanges, etc.

Exemplary Embodiment:

As required, a preferred embodiment of the present invention is disclosed herein in detail; however, it is to be understood that the disclosed embodiment is merely an exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and the representative basis one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

FIG I show the plain flex pipe element 10 of the present invention comprising of plain tube assembly 11 in which the length of the pipe is 2 to 3 times its diameter for achieving better flexibility and also isolation of vibrations from the main source. The tube 11 is constructed of suitable material such as IS 3074 Gr.ERW1 and Stainless steel / aluminized steel tube in applications requiring high corrosion resistance. The tube 11 has the first and second end sections being the male end connector 13 and female end connector 12 suitably connected by weldments thereto. The male end connector 13 is in turn connected to a pipe 17 which extends to the turbo outlet 23 (not shown); the male connector end 13 being telescopically received within the pipe 17 with the help of a female end connector 19 fitted thereon with a flange 20. As seen in FIG IV, the male end connector 13 further has a groove 22 on its outer surface to accommodate a ring 24 similar to a piston ring present on the female end connector 19 of the pipe 17 extending to the turbo outlet 23. The ring 24 ensures that the exhaust gases are not leaked through the clearance provided between the ends 13 and 19 in the assembled condition and to provide flexibility to absorb vibrations in the lateral directions. Similarly the female end connector 12 is further connected to the pipe 14 extending to the silencer 18 (not shown) of the exhaust system of internal combustion engine. The pipe 14 has a male end connector 15 corresponding to the female end connector 12 of the tube section 11 and is connected thereto with the help of a flange 16 (as seen in FIG Va and Vb). The female end connector 12 has a ring 25 similar to a piston ring on its inner surface to slide over the groove 21 present on outer surface of the male end connector 15 to provide exhaust gas leak proof arrangement. The end connection of the tube 11 of the plain flex pipe element 10 is welded with pipes 17 and 18 to form a conduit for exhaust gases. The flanges 16 and 20 are bolted to the end connectors 12 and 13 through bores 29, 30 and 31 (as seen in FIG Va and Vb) with the help of bolts and nuts thread ably mounted on bolts.

The material of construction for first and second end section as well as the flanges is suitably selected from steel to EN-1A.

As seen, the tube 11 of the plain flex pipe of the present invention has ends 12 and 13 having differential diameters. The main advantage of having different diameters is improved flexibility while compared with same diameters. FIG VIa, VIb VIe and VId show simulation studies using software for checking actual deflection.

The presence of piston ring 24 and 25 on the end grooves 21 and 22 imparts flexibility to tube 11. Thus the plain flex pipe assembly 10 moves on the end connectors with the help of flanges 16 and 20 and piston rings 24 and 25 and hence absorbs the axial vibration and thermal expansion. The same is demonstrated with the help of virtual Experiment using computer aided engineering tools.

Experiment: A plain flex pipe assembly having tube diameter 100 mm was taken for this study. The assembly was modeled in ADAMS with careful selection of a) pipe length, b) tolerance between male and female end connectors. ADAMS is software used for CAE analysis/simulation of various components. Here, the boundary conditions are provided by fixing the assembly at one end and loading at the other end. By adjusting the axial distance, various lateral deflection readings are noted. The results are tabulated in table I.

Table I: shows the change in lateral deflection by changing the allowable axial deflection.

It was concluded that the pipe was capable of taking 10mm axial vibration and ± 40mm lateral vibration.

As seen, the tube 11 of the plain flex pipe of the present invention has ends 12 and 13 having differential diameters. The main advantage of having different diameters is improved flexibility while compared with same diameters. FIG VIa,VIb VIc and VId show simulation studies using software for checking actual deflection.

It is to be noted that the invention is explained above with the help of an exemplary embodiment which is presented for the purpose of illustration and description in order to explain the various principles of the invention and their practical application. This is not intended to exhaust or limit the invention to a precise form that is disclosed and obviously many modifications and variations are possible in the light of the above teachings.

WE CLAIM :

1. A plain flex pipe assembly positioned in the exhaust system of an internal combustion engine of a vehicle comprising of one or more tube assemblies which are plain and do not contain any corrugations or bellows.

2. The plain flex pipe assembly as claimed in claim 1, wherein the tube assembly comprises of a medial body portion which is plain and connected to first and second end sections with first and second mouths for receiving the upstream and downstream pipe sections of the exhaust system.

3. The plain flex pipe assembly as claimed in claim 2, wherein the first and second end sections with the first and second mouths have differential diameters for achieving better flexibility of the flex pipe assembly.

4. The plain flex pipe assembly as claimed in claims 2 and 3, wherein the first mouth section has a male end connector which slips into the female end connector of upstream connecting pipe section to form an upstream conduit pipe section for the exhaust gases in the exhaust pipe assembly.

5. The plain flex pipe assembly as claimed in claims 2 and 3, wherein the second mouth section has a female end connector which telescopically receives the male end connector of downstream connecting pipe section to form a downstream conduit pipe section for exhaust gases in the exhaust pipe assembly.

6. The plain flex pipe assembly as claimed in any of the preceding claims, wherein the first mouth has a groove on its outer surface to accommodate a piston ring which acts as a barrier to leakage of exhaust gases from the clearance between the said male end connector of the first mouth section and the female end connector of the upstream connecting pipe section in an assembled condition and provide flexibility to absorb vibrations in the lateral direction.

7. The plain flex pipe assembly as claimed in any of the preceding claims, wherein the male end connector of the downstream connecting pipe section has a groove on its outer surface to accommodate a piston ring which acts as a barrier to leakage of exhaust gases from the clearance between the said female end connector of the tube assembly and the male end connector of the downstream connecting pipe section in an assembled condition and provide a flexibility to absorb vibrations in the lateral direction.

8. The plain flex pipe assembly as claimed in any of the preceding claims, wherein the said pipe sections are connected to the corresponding upstream and downstream connecting pipe sections with a suitable connector such as elements, gaskets, clamps or flanges.

9. The plain flex pipe assembly as claimed in claim 8, wherein first and second end pipe sections are connected to the corresponding upstream and downstream connecting pipe sections with the help of flange secured with nuts and bolts.

10. The plain flex pipe assembly as claimed in any of the preceding claims, wherein the tube assembly is constructed of CEW1/ERW1 tubes, stainless steel, aluminized steel and other corrosion resistant metals appropriate for applications such as in automotive exhaust systems and Genset applications based on operating and environmental conditions.

11. The plain flex pipe assembly as claimed in any of the preceding claims, wherein the length of the tube is at least two to three times its diameter for achieving better flexibility and also isolation of vibrations from the main source.

12. The plain flex pipe assembly as claimed in any of the preceding claims, wherein the tube along its end connectors permit relative rotational displacement between the exhaust pipe sections thereby attenuating and controlling dynamic stresses there within and prevents misalignment between the upstream and the downstream pipe sections both in axial and lateral direction.

13. An exhaust system of an internal combustion engine of a vehicle comprising the plain flex pipe assembly as claimed in any of the preceding claims.