GB2449684A

GB2449684A - Flexible exhaust coupling with support between liner and bellows

Info

Publication number: GB2449684A
Application number: GB0710426A
Authority: GB
Inventors: Charles Penny; Antony Thole
Original assignee: Senior UK Ltd
Current assignee: Senior UK Ltd
Priority date: 2007-05-31
Filing date: 2007-05-31
Publication date: 2008-12-03
Anticipated expiration: 2027-05-31
Also published as: GB0710426D0; GB2449684B

Abstract

A flexible exhaust coupling 501 comprises a cylindrical inner liner 503 and a fluid tight conduit 505 extending circumferentially around said cylindrical inner liner 503. The conduit 505 comprises two bellows sections 517 and 519 and a central constricted section 521 which locates the liner 503. The constricted section has indents 527 which secure the liner within the conduit. The conduit may be enclosed within a steel mesh 507.

Description

FLEXIBLE EXHAUST COUPLING DEVICE

Field of the Invention

The present invention relates to flexible exhaust coupling devices comprising a cylindrical inner liner and a fluid tight conduit extending circumferentially around an external surface of the cylindrical inner liner, wherein the fluid tight conduit comprises at least one bellows section.

Background to the Invention

Car manufacturers fit flexible exhaust coupling devices to the primary exhaust systems of vehicles in order to decouple gross engine motions from the underbody part of the exhaust system, minimising motions of the exhaust system and therefore, reducing damage to the exhaust system. The flexible nature of the device minimises the transfer of energy from the portion of the exhaust system located on the engine of the vehicle to the underbody part of the exhaust system.

However, the flexible nature of the coupling device can give rise to unfavourable noise which resonates through the cabin of the vehicle, which is undesirable for the passengers within the cabin of the vehicle.

Arrangements of flexible exhaust coupling devices comprising cylindrical inner liners surrounded by fluid tight conduits are known in the art for example from US 5,456,291, EPI,576,263, US 2003/0024584, EPI,597,506 and US 6,612,342 in which flexible pipe elements are disclosed which attempt to solve the above problems.

One prior art solution is to provide a spacer element which is positioned between the fluid tight conduit and the cylindrical inner liner of the coupling device. This enables the fluid tight conduit and cylindrical inner liner to flex thereby decoupling the gross engine motions from the underbody part of the exhaust system. Furthermore, the spacer element attempts to prevent the bellows portion of the fluid tight conduit from contacting the cylindrical inner liner. Where the bellows contacts the inner liner, this can result in a noisy component and can cause severe bellows/cylindrical inner liner abrasion which ultimately results in bellows failure. The objective of the spacer elements are further significant when a relatively soft outer bellows having a high elongation capacity along its length, and the cylindrical inner liner are supported at either end of the arrangement, as these components will have a greater tendency to sag and therefore contact one another. However, although, the spacer element attempts to reduce the noise production of the coupling device the disadvantages are that such a spacer will increase the cost of the device and in general the known spacer solution has not effectively reduced the problem as the spacer may produce a noisy element in itself.

In general, an underbody exhaust system comprising the flexible exhaust coupling devices of the prior art require a loose form of mounting to the underbody of the vehicle in order to allow for movement of the exhaust system.

This is a consequence of the prior art devices not being fully effective in decoupling the gross engine motions and therefore allowing residual energy transfer between the exhaust portion from the engine of the vehicle and the underbody exhaust system. If the underbody exhaust system was rigidly maintained to the underbody of the vehicle, residual energy transfer could cause significant noise to be transferred to the cabin passenger space. Loosely mounting the exhaust system to the underbody of the vehicle is undesirable as it prevents the addition of heavy exhaust gas treatment devices or heat recovery canisters to the exhaust system which are required in order to meet ever more stringent EU legislation on exhaust emissions.

The use of very soft bellows within the fluid tight conduit of prior art devices results in the known bellows having a number of natural resonance frequencies (NRFs) within the high energy band of the vehicle, having a frequency within the range of 25 to 250Hz. These NRFs act to prevent the flexible exhaust coupling device from successfully decoupling the engine generated vibration energy from the underbody part of the exhaust system.

Further problems with the flexible exhaust coupling devices of the prior art arise from the cylindrical inner liner known within the prior art. Cylindrical inner liners of the prior art comprise interlocking components which when subjected to high temperature exhaust gases open up radially which substantially changes the frictional loading of the cylindrical inner liner, therefore, increasing the stiffness of the cylindrical inner liner. The consequence of the increased stiffness of the cylindrical inner liner is that even when a very soft bellows material is employed in a flexible exhaust coupling device, the overall flexibility and therefore the ability of the device to de-couple gross engine motions and engine generated vibrations is greatly reduced.

One prior art solution to the temperature depending of the inner stiffness has been to use a relatively soft material for the cylindrical inner liner. However, if the cylindrical inner liner is too soft, individual interlocking components rattle against one another therefore increasing the noise problem. Some prior art devices have sought to overcome this problem by fitting a mesh sock around the cylindrical inner liner. However, this does not successfully eliminate the noise problem.

Furthermore, known cylindrical inner liners have elongation limits of around 29%. This limitation decreases the flexibility of prior art devices, thus preventing the flexible exhaust coupling device from successfully decoupling the gross engine motions from the underbody part of the exhaust system within a vehicle.

The applicants have provided a novel solution to the above problems which is a cheaper, more effective means of decoupling sound vibrations and motions within an exhaust system of a vehicle.

Summary of the Invention

One object of the present invention is to provide an improved flexible exhaust coupling device that successfully decouples gross engine motions from the underbody part of the exhaust system and reduces noise level within the cabin of the vehicle.

A further object of the present invention is to provide a flexible coupling device which has a functional life exceeding the vehicle design life and is durable in terms of fatigue, wear and corrosion.

The invention achieves this object for a flexible exhaust coupling device of the above type by providing a fluid tight conduit comprising a first bellows section, a second bellows section and a centralised constricted section; the centralised constricted section comprising at least one indent protruding from an internal surface of the centralised constricted section and wherein the at least one indent is disposed adjacent to and abutting a central portion of the surface of the cylindrical inner liner.

In this way, it is possible in a very simple fashion to circumvent the previously existing need to dispose a spacer element within the flexible exhaust coupling device between the fluid tight conduit and the cylindrical inner liner in order to reduce noise production to a minimum. Furthermore, this arrangement reduces the contact and thus abrasion between the bellows of the fluid tight conduit and the cylindrical inner liner, thereby increasing the functional life of the flexible exhaust coupling device.

A further advantage of the present invention is that by employing at least one indent protruding from an internal surface of the centralised constricted section, the bellows of the fluid tight conduit can be made softer and more flexible than the bellows in the prior art. Therefore, the flexible exhaust coupling device of the present invention is more effective at minimising the energy transfer function between the exhaust components within the engine and the underbody part of the exhaust system, enabling the underbody exhaust system to be more rigidly mounted to the body of the vehicle. This further enhances the functional life of the flexible exhaust coupling device. The effective decoupling of the gross engine motions by the flexible exhaust coupling device allows the underbody exhaust system to be more rigidly mounted to the under side of a vehicle. This enables a lighter exhaust system to be used as it is possible to reduce the exhaust pipe material thickness due to the reduction in stress experienced by the underbody exhaust system. More rigidly mounting the exhaust system further allows addition of heavy exhaust gas treatment and/or heat recovery canisters to be used in the exhaust system which are important in meeting ever more stringent exhaust emissions EU legislation. Furthermore, due to effective attenuation of the engine generated vibration, the rigidly mounted underbody exhaust system does not transfer energy from the exhaust system into the cabin of the vehicle thus providing quieter cabin noise levels for the passengers of the vehicle.

In a preferred embodiment of the present invention the centralised constricted section comprises three indents protruding from the internal surface of the centralised constricted section, the three indents disposed equal distance from one another. In this way, the cylindrical inner liner is supported substantially concentric within the fluid tight conduit of the flexible exhaust coupling device of the present invention, therefore reducing bellows/cylindrical inner liner contact and hence abrasion.

As stated previously, a consequence of employing softer and more flexible bellows within the fluid tight conduit of the flexible exhaust coupling device is that the bellows will have a number of natural resonance frequencies (NRFs) within the high energy band of the vehicle, typically 25 to 250Hz, resulting in high peaks in the energy transfer function. Therefore, the bellow sections must be very effectively dampened. A preferred embodiment of the present invention overcomes this problem by providing a fluid tight conduit further comprising a first compressed end section located at a first end portion of the coupling device and a second compressed end section located at a second end portion of the coupling device, the first compressed end section, the centralised constricted section and the second compressed end section being connected to one another by the bellow sections. The first compressed end section and the second compressed end section are configured to abut the external surface of the cylindrical inner liner. The at least one indent protruding from the internal surface of the centralised constricted section and the first and second compressed end sections are secured to a substantial portion of the external surface of the cylindrical inner liner. By securing the fluid tight conduit to the cylindrical inner liner the flexible exhaust coupling device is given some additional damping, the inner liner acting as a frictional damper.

Furthermore, the compressed end sections further support the cylindrical inner liner substantially concentric within the centre of the fluid tight conduit. This further reduces contact between the bellow sections of the fluid tight conduit and the cylindrical inner liner therefore reducing wear and increasing the functional life of the flexible exhaust coupling device.

Preferably, the fluid type conduit is made of steel.

The flexible exhaust coupling device having a radially elastic mesh configured to extend circumferentially about and abutting the exterior of the fluid type conduit. Preferably, the radially elastic mesh comprises a network of interlocking radiussed loops. In order for the mesh to clamp positively onto the fluid tight conduit, the radially elastic mesh may have a smaller internal diameter than the external diameter of the bellows section of the fluid tight conduit. This elastic mesh, in conjunction with the inner liner dampens the bellow resonances effectively reducing all the peaks to levels that are not of concern.

Furthermore, the pitch of the radially elastic mesh, which is the distance between the centre points of the adjacent interlocking radiussed loops, may be greater than 60% of the pitch of the bellow sections of the fluid tight conduit, which is the distance between the crests of adjacent corrugations. In this way, the radially elastic mesh will not substantially dip between the crests of the bellow sections, which may lead to unnecessary wear of the bellow sections.

Preferably the radially elastic mesh is made of steel wire.

In a preferred embodiment of the present invention the flexible exhaust coupling device may further comprise a plurality of ancillaries configured to secure the cylindrical inner liner, the fluid tight conduit and the radially elastic mesh together. The plurality of ancillaries may comprise two end portions located adjacent to the end portions of the raidially elastic mesh and two liner adapters connected to the cylindrical inner liner and adjacent to the compressed end sections of the fluid tight conduit.

Preferably, the flexible exhaust coupling device of the invention has an axial motion envelope of 20% of its working length. By having an axial motion envelope of 20% the flexible exhaust coupling device can effectively undergo elongation and compression to eliminate gross engine motions from being transferred to the underbody part of the exhaust system.

In a further preferred embodiment of the present invention, the cylindrical inner liner isolates the fluid tight conduit from the exhaust gases flowing through the flexible exhaust coupling device. This feature is advantageous as it further eliminates noise production resulting from the exhaust gases flowing over the bellow sections of the fluid tight conduit, therefore providing a reduction in cabin noise levels, making for a more enjoyable travel experience for the passengers.

The flexible exhaust coupling device of the present invention may be situated between and fixed to an exhaust down pipe and a primary exhaust system within a vehicle.

It is a further object of the present invention to improve a cylindrical inner liner of the prior art such that the stiffness of the cylindrical inner liner does not substantially increase when the cylindrical inner liner is subjected to high temperatures, therefore increasing the energy transfer function of a flexible exhaust coupling device. Furthermore, it is an object of the present invention to produce a cylindrical inner liner which is as soft as possible without being a noisy component. A further object of the present invention is to reduce the wear experienced within the cylindrical inner liner when it is subjected to high temperatures. Therefore, the design of the cylindrical inner liner must effectively reduce the effect of exhaust gas temperature to a minimum. The present invention seeks to provide a cylindrical inner liner with increased elongation capabilities in order for it to accommodate the applied gross engine motions and therefore effectively decouple these motions from the underbody of the exhaust system.

The present invention acheives these objectives by providing a cylindrical inner liner comprising a plurality of helical windings wherein each of the plurality of windings comprise a body portion having a first substantially parallel portion, a substantially perpendicular portion and a second substantially parallel portion; and the body portion further comprising a first curved portion disposed at the end of the first substantially parallel portion and a second curved portion disposed at the end of the second substantially parallel portion: The invention is characterised in that each of the curved portions comprise an end portion extending perpendicularly to the substantially parallel portions of the body portion.

Provision within the plurality of windings extending axially along the length of the flexible exhaust coupling device of radially formed contact legs rather than axially contacting legs, as in the prior art, enables the cylindrical inner liner to cope with the effects of high temperature usage whilst controlling the friction within the cylindrical inner liner to the lowest extent. This is due to the design accurately controlling the frictional surfaces as the end portion of the plurality of windings has a smaller but a very defined point of contact with the adjacent windings. Furthermore, only a small increase in stiffness of the cylindrical inner liner is experienced when high temperature exhaust gases are flowing through the flexible exhaust coupling device of the present invention.

In a preferred embodiment of the present invention the end portion comprises a first substantially perpendicular portion, a second curved portion and a second substantially perpendicular portion; the first substantially perpendicular portion being connected to the second substantially perpendicular portion via the second curved portion.

Preferably when the flexible exhaust coupling device of the present invention has not been subjected to high temperatures, the first substantially perpendicular portion and the second substantially perpendicular portion of the end portions are adjacent to one another such that the angle between them is nominally 00 i.e. they are parallel.

Preferably when the flexible exhaust coupling device of the present invention is subjected to high temperatures, the end portions relax' due to material memory such that the angle between the first substantially perpendicular portion and the second substantially perpendicular portion is not greater than 15 . Furthermore, the first substantially perpendicular portion may be disposed at an angle of from 90 to 105 to the substantially parallel portion of the body portion of the plurality of windings.

Therefore, when the cylindrical inner liner is subjected to high temperatures the windings expand in the axial direction, along the length of the flexible exhaust coupling device, therefore the frictional load does not change substantially as the radial force between conjoined windings substantially does not change.

Furthermore, the stiffness of the cylindrical inner liner does not increase at high temperatures as the windings of the present invention are no longer interlocking and so elongation of the cylindrical inner liner can occur more freely.

Preferably the cylindrical inner liner has an elongation of at least 45%.

In a further preferred embodiment of the present invention, the flexible exhaust coupling device upon heat conditioning, nominally 850 C for 60 minutes in practical terms at a temperature greater than 500 C for a period of greater than minutes has an axial and shear dynamic stiffness of between 1 N/mm to 100 N/mm when excited at +1-0.1 mm in the frequency range of 5 to 250Hz.

Preferably, the cylindrical inner liner isolates the fluid tight conduit from the exhaust gases flowing through the flexible exhaust coupling device, thereby reducing the gas over bellows noise production.

In a preferred embodiment of the present invention the plurality of windings are clamped at a first and second end of the flexible exhaust coupling device.

The plurality of wind ings may be clamped by the ancillary members, namingly the liner adapters. Alternatively the cylindrical inner liner may be directly attached to the first and second end of the flexible coupling device.

Furthermore, the present embodiments relate to cylindrical inner liners comprising a plurality of windings wherein each of the plurality of windings comprise a body portion having a first substantially parallel portion, a substantially perpendicular portion and a second substantially parallel portion; and the body portion further comprises a first curved portion end of the first substantially parallel portion and a second curved portion disposed at the end of the second substantially parallel portion. In particular, this invention relates to a flexible exhaust coupling device for use in the exhaust system of a vehicle.

According to a third aspect there is provided a tubular exhaust liner comprising: a cylindrical inner liner having a wall comprising a plurality of latched turns, each turn comprising: a first substantially cylindrical portion, of a first relatively larger diameter; a second substantially cylindrical portion, of a second relatively smaller diameter; a connecting portion extending in a direction transverse to a main axial length of said liner and connecting said first and second substantially cylindrical portions; a first substantially radially extending portion, extending from one end of said first substantially cylindrical portion; and a second substantially radially extending portion extending from one end of second substantially cylindrical portion.

Preferably, a said turn comprises a helical winding. However, in other embodiments a turn may comprise an annular ring.

Preferably said first substantially radially extending portion comprises a distal end, which, in use contacts a surface of said second substantially cylindrical portion of an adjacent turn, and as the inner liner extends and contracts in an axial direction, said distal end slides over said second substantially cylindrical portion. The substantially radially extending portion may operate to maintain the rigidity of the inner liner in a radial direction, and to latch one turn with its neighbouring turns.

Said first radially extending portion may comprise a fold of material, connected at said distal end.

Preferably, said second substantially radially extending portion comprises a distal end which, in use contacts a surface of said first substantially cylindrical portion, as the inner liner extends and contracts in an axial direction. The second substantially radially extending portion may serve to maintain the radial rigidity of the component in use.

Said second radially extending portion may comprise a fold of material, connected at said distal end, which in use contacts a surface of said second substantially cylindrical portion of an adjacent winding, as the inner liner extends and contracts in an axial direction.

Said first and / or substantially radially extending portion may comprise a fold of material, which may expand predominantly in a direction substantially axially of the inner liner when raised to an operational temperature of said exhaust coupling.

Other aspects of the invention are as recited in the claims herein.

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: Figure 1 shows a prior art arrangement of a flexible exhaust coupling device in situ within an exhaust system; Figure 2 shows a prior art arrangement of a cylindrical inner liner prior to being subjected to high temperatures; Figure 3 shows a prior art arrangement of a cylindrical inner liner when and after it is subjected to high temperatures; Figure 4 illustrates schematically a plot of phase angle and stiffness against frequency for a flexible exhaust coupling device of the prior art having an axial excitation of 0.2 mm; Figure 5 shows in cut-away view a flexible exhaust coupling device in accordance with a first embodiment of the present invention; Figure 6 shows an arrangement of the fluid tight conduit and the circumferentially elastic mesh of a flexible exhaust coupling device in accordance with an embodiment of the present invention at an intermediate stage of manufacture; Figure 7 shows a cut-away view of the fluid tight conduit in accordance with an embodiment of the present invention after extended durability; Figure 8 shows a cross sectional view of a portion of the cylindrical inner liner in accordance with a second embodiment of the present invention prior to being subjected to high temperatures; Figure 9 shows a cross sectional view of a portion of the cylindrical inner liner of figure 8 when or after it is subjected to high temperatures; Figure 10 shows a cross sectional view of a portion of the cylindrical inner liner of figure 8 when or after it is subjected to high temperatures and compression; Figure 11 illustrates schematically a plot of phase angle and stiffness against frequency for a flexible exhaust coupling device in accordance with an embodiment of the present invention having an axial excitation of 0.2 mm peak to peak; and Figure 12 illustrates schematically a plot of phase angle and stiffness against frequency for a flexible exhaust coupling device in accordance with an embodiment of the present invention having a shear excitation of 0.2 mm peak to peak.

Detailed Description

There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to

unnecessarily obscure the description.

With reference to figure 1 herein there is provided a primary vehicle exhaust system 101 comprising a cylindrical flexible exhaust coupling device 103 as known in the prior art. The primary exhaust system 101 further comprises a heat shield 105, a catalytic converter 107, an exhaust hanger 109 and an exhaust down pipe 111.

The exhaust down pipe 111 is attached at a first end to the exhaust manifold (not shown) within the engine bay of a vehicle and is attached at a second end to a first end portion of the cylindrical flexible exhaust coupling device 103. A second end of the cylindrical flexible exhaust coupling device 103 is connected to a first end of the catalytic converter 107 via a first intermediate pipe portion 113. A second end of the catalytic converter 107 is connected to a secondary exhaust system (not shown) via a second intermediate pipe portion 115.

The heat shield 105 partially surrounds the catalytic converter 107, the second intermediate pipe portion 115 and the secondary exhaust system (not shown) at a position between the primary exhaust system 101 and the underside of the vehicle 117.

Exhaust hanger 109 is located adjacent to the first intermediate pipe portion 113 at a position close to the second end portion of the first intermediate pipe portion 113.

When the vehicle comprising the primary exhaust system 101 is in use, the exhaust manifold (not shown) collects exhaust gases from the engine and transfers them to the exhaust down pipe 111. The exhaust gases are then transferred into the cylindrical flexible exhaust coupling device 103. The exhaust gases then flow through the first intermediate pipe portion 113 to the catalytic converter 107. The catalytic converter 107 reduces the toxicity of the exhaust gases and converts unused fuel into completely spent fuel. The exhaust gases then flow through the second intermediate pipe portion 115 and into the secondary exhaust system (not shown) where they are ejected into the atmosphere.

During use of the vehicle, the cylindrical flexible exhaust coupling device flexes in order to decouple the gross engine motions from the primary exhaust system 101 in an attempt to reduce damage to the primary exhaust system 101.

The exhaust hanger 109 comprises a metal strap and two brackets connected to the underside of the engine. The purpose of the exhaust hanger 109 is to connect the primary exhaust system 101 to the underside of the vehicle, allowing the primary exhaust system 101 a degree of movement independent of the underside of the vehicle. The exhaust hanger 109 may also comprise a rubber insulator who's function is to attenuate vibration energy from the exhaust pipe to the under body of the body, thus helping to reduce noise.

The components of the exhaust system 101 are made of stainless steel in order to enhance the functional life of the primary exhaust system 101.

Referring to figure 2 herein there is provided a cross sectional viewof a known cylindrical inner liner 201 disposed in a flexible exhaust coupling device of the prior art. The cylindrical inner liner as shown in figure 2 comprises one complete winding 203 and two halves of a winding 205 and 207.

Known prior art helically wound inner liners of the type shown in figure 2 are capable of extending in an axial direction to the order of 29% of their fully compressed length.

The complete winding 203 comprises a body portion 209 having a first substantially parallel portion, a substantially perpendicular portion and a second substantially parallel portion. The complete winding 203 further comprising two curved sections 211 and 213 and two end sections 215 and 217.

The first substantially parallel portion is connected to the substantially perpendicular portion which is connected to the second substantially parallel portion to form an S-shape. The two curved portions 211 and 213 are disposed at opposite ends of the body portion 209. End portions 215 and 217 extend parallel to said substantially parallel portions of said body 209.

Winding 205 has an identical configuration to that of the central complete winding 203. The curved portion 219 and parallel end portion 221 of winding 205 interlocks with the curved portion 211 and parallel end portion 215 of complete central winding 203.

Winding 207 also has an identical configuration to central complete winding 203 and the curved portion 223 and parallel end portion 225 of winding 207 interlocks with the curved portion 213 and parallel end portion 217 of central complete winding 203.

The known cylindrical inner liner 201 of figure 2 shows the configuration of the windings 205, 203 and 207 prior to the flow of hot gases through the component temperatures, i.e. when the vehicle comprising the flexible exhaust coupling device having the known cylindrical inner liner 201 of figure 2 incorporated therein, is not in use.

With reference to figure 3 herein, there is provided the configuration of known cylindrical inner liner 201 of figure 2 when or after it is subjected to high temperatures as it is during use as part of an exhaust system.

Upon application of heat to the cylindrical inner liner 201, the end portion 215, 217, 221 and 225 of the windings 203, 205 and 207 expand in a radial direction about the curved portions 211, 213, 219 and 223 towards the substantially parallel portions 301, 303, 305 and 307 of the body portions of the winding 203, 205 and 207. When fully expanded, the end portions 215, 217, 221 and 223 will contact the substantially parallel portions 301, 305, 303 and 307 as shown in figure 3. In this configuration, the fictional loading of the cylindrical inner liner 201 inéreases due to increased contact force between the portions of the cylindrical inner liner 201 and so the stiffness of the cylindrical inner liner 201 is greatly increased. Therefore, it is very difficult to control the stiffness of the cylindrical inner liner 201 at high temperatures.

Furthermore, elongation of the cylindrical inner liner 201 is restricted due to increased stiffness resulting from the radial expansion and interlocking nature of the windings 203, 205 and 207.

Figure 4 illustrates schematically a plot of phase angle and stiffness against frequency for a flexible exhaust coupling device of the prior art having an axial dynamic stiffness of 0.2 mm peak to peak.

After heat conditioning (nominally at 850 C for 60 minutes, but in practical terms at greater than 500 C for more than 5 minutes) the flexible exhaust coupling device of the prior art has a varying dynamic stiffness of between 10 to 875 N/mm when excited at +1-0.1 mm in the frequency range of 5Hz to 250Hz.

There are three prominent peaks within this plot; the first providing a stiffness of slightly less than 300N/mmmm at a frequency of around 70Hz, the second providing a dynamic stiffness of 665N/mm at a frequency of slightly greater than 125Hz and the third heat providing a stiffness of 875N/mm at a frequency of around 190Hz. These peaks are caused by self resonance (NRFs) of the bellows sections.

The wide range of dynamic stiffness (0 to 875N/mm) clearly shows that it is impossible to control the stiffness of a flexible exhaust coupling device of the prior art, in particular the stiffness of the cylindrical inner liner of the flexible exhaust coupling device at high temperatures and the NRFs of the bellows.

With reference to figure 5 herein, there is provided a cross sectional view of a flexible exhaust coupling device 501 in accordance with an embodiment of the invention.

Flexible exhaust coupling device 501 comprises a cylindrical inner liner 503, a fluid tight conduit 505, an outer mesh 507, two end caps 509 and 511 and liner adapter 513 and 515.

The internal surface of the flexible exhaust coupling device 501 comprises cylindrical inner liner 503 which comprises a plurality of windings (shown in more detail at figure 9). Liner adapters 513 and 515 clamp the cylindrical inner liner 503 at either end of the flexible exhaust coupling device 501. The cylindrical inner liner 503 is clamped in place to prevent the plurality of windings unwinding once the cylindrical inner liner 503 has been incorporated into the flexible exhaust coupling device 501 as the plurality of windings tend to revert back to their cylindrical/circular form, moving apart in the radial direction.

Fluid tight conduit 505 extends circumferentially about the external surface of the cylindrical inner liner 505. Fluid tight conduit 505 comprises two bellow sections 517 and 519, a centralised constricted section 521 which has localised areas, generated by the indents, at an inner diameter of less than an inner diameter of either bellows section, and two compressed end sections 52 and 525.

The bellows sections each comprise a plurality of annular corrugations or rings spaced apart from each other, with valleys in between and formed in the wall of the fluid tight metal conduit. In alternative embodiments, the bellows may comprise an helically formed spiral ridge in the wall of the fluid tight conduit.

Centralised compressed section 521 comprises three indents 527 (of which 2 are shown protruding from the internal surface of the centralised compressed section 521) which are equally spaced from one another. The internal surface of centralised compressed section 521 is aligned with the external surface of cylindrical inner liner 503 and the internal surface of the centralised compressed section 521 is secured to the external surface of cylindrical inner liner 505 via the internally protruding indents 527. Compressed end sections 523 and 525 are secured between liner adapters 513 and 515, mesh 507 and end caps 509 and 511. By securing the compressed sections 521, 523 and 525 of the fluid tight conduit 505 at these points along the flexible exhaust coupling device 501, the cylindrical inner liner 503 is supported substantially concentric to the fluid tight conduit 505. Therefore, the cylindrical inner liner 503 will not contact the internal surfaces of the valleys 529 of the bellow sections 517 and 519 of fluid tight conduits and so fluid tight conduit 505 is not subjected to wear and corrosion.

The overall effect of these features is that the flexible exhaust coupling device 501 has a longer functional life, and produces lower noise emissions than

comparable prior art devices.

Mesh 507 extends circumferentially about the exterior surface of fluid tight conduit 505 such that it contacts the external surface of crests 531 of the bellow sections 517 and 519 of fluid tight conduit 505. The end portions of mesh 507 are secured in place by end caps 509 and 511 and are adjacent to compressed end sections 523 and 525 of the fluid tight conduit 505.

At either end of the flexible exhaust coupling device 501, the layers between end caps 509 and 511 and the internal surface of the device 501 (including mesh 507, compressed end sections 523 and 525 of the fluid tight conduit 505 and liner adapters 513 and 515) are configured to be flush or positively stacked.

Fluid tight conduit 505 is made from two ply stainless steel having a thickness of 0.2 mm. Mesh 507 is made from stainless steel wire having a diameter of 0.15 mm. Liner adapters 513 and 515 and end caps 509 and 511 are also made from steel having a thickness of 1.0 mm.

Flexible exhaust coupling device 501 has an outer diameter of 80.7 mm and an internal diameter of 47.0 mm. The length of the flexible exhaust coupling device 501 is 230 mm and the length of the region comprising the flexible sections of the fluid tight conduit 505 is 196 mm +1-3 mm.

In use, the flexible exhaust coupling device 501 is located within the primary exhaust system of a vehicle connecting the exhaust down pipe to the rest of the primary exhaust system located on the underside of the vehicle. The exhaust head pipe is connected to the exhaust manifold which collects exhaust gases from the engine. Exhaust gases flow from the exhaust manifold through the exhaust down pipe and into the primary exhaust system at the flexible exhaust coupling device 501. Cylindrical inner liner 503 directs exhaust gas flow directly through the cylindrical inner liner thus minimizing the amount of gas entering the region comprising the fluid tight conduit 505, in order to eliminate the noise produced if high volumes of exhaust gas flowed over bellow sections 517 and 519.

During use, flexible exhaust coupling device 501 is subjected to gross engine motions transferred to the flexible exhaust coupling device 501 by the exhaust down pipe. These motions can be damaging to the primary exhausts system and so the flexible exhaust coupling device 501 decouples the motions between the engine and the underbody of the car. This is achieved by the soft pseudo static stiffness and the large motion capabilities of the flexible exhaust coupling device 501. Mesh 507, fluid tight conduit 505 and cylindrical inner liner 503 maybe stretched and compressed when the flexible exhaust coupling device 501 is subjected to the gross engine motions, therefore decoupling the gross engine motions from the primary exhaust system. Flexible exhaust coupling device 501 has an elongation of minimum 20%, therefore, the particular embodiment flexible exhaust coupling device 501 as shown may be extended and compressed 39.2mm.

It will be appreciated by the skilled person that in other embodiments, having other length and diameter dimensions, due to the novel form of helical winding of inner liner, the inner liner may provide extension from a fully compressed state in the axial direction, taken as 100%, up to a minimum of 140% in a fully extended axial condition, thus to enable the exhaust flexible to both extend and compress the cylindrical inner liner is installed in it's mid length between fully compressed and fully extended.

With reference to figure 6 herein, there is provided a side view of an end portion of an arrangement 601 of a mesh 603 and fluid tight conduit 605 according to the present invention.

Fluid tight conduit 605 comprises a compressed end section 607 which is substantially smooth and a bellow section 609. Bellows section 609 comprises a plurality of equally spaced crests 611 and a plurality of corresponding valleys (not visible).

Mesh 603 comprises a plurality of interlocking radiussed loops 613 and extends circumferentially about fluid tight conduit 605 such that mesh 603 abuts the plurality of crests 611 of bellows section 609 and the compressed end section 607 of fluid tight conduit 605.

The plurality of interlocking radiussed loops 613 of mesh 603 allow for circumferential extension and compression of the mesh 603 when the flexible exhaust coupling device of the invention is used within the primary exhaust system of a vehicle. Mesh 603 loops are shaped such that they can move relatively to each other the relative axial motion allows extension and compression whilst the friction of one loop on another gives damping.

The internal diameter of mesh 603 is less than the external diameter of fluid tight conduit 605. Therefore, when the mesh 603 is fitted over the fluid tight conduit 605, the mesh 603 is stretched such that when the mesh 603 returns to its relaxed state it is held securely in place over the fluid tight conduit 605.

The pitch of mesh 603, which is measured as the distance between the centres of two adjacent interlocking radiussed loops 613 (as shown at A), is less than the pitch of the bellows section 609 of fluid tight conduit 605, which is the distance between adjacent crests 611 (as indicated at B). The difference between the pitch of mesh 603 and the pitch of the bellows section 609 of the fluid tight conduit 605 prevents the mesh 603 from substantially dipping between the crests 611 of the bellows section 609 during elongation and compression of the flexible exhaust coupling device.

The arrangement 601 forms part of the flexible exhaust coupling device according to the present invention which is positioned within a primary exhaust system. When the arrangement 601 is subjected to gross engine motions, the fluid tight conduit 605 and mesh 603 elongate such that the pitch of the bellows section 609 of the fluid tight conduit 609 and the pitch of the mesh 603 increases.

With reference to figure 7 herein there is provided a cut away view of a portions section 609 of the fluid tight conduit 701 according to an embodiment of the present invention which has been subjected to extended durability.

Fluid tight conduit 701 comprises two bellow sections 703 and 705 and a centralised compressed section 707. Bellow sections 703 and 705 comprises a plurality of equally spaced crests 709 and a plurality of corresponding equally spaced troughs 711 Centralised compressed section 707 Ic currounded by tho two comprises an indent 713 protruding from the internal surface of the centralised compressed section 707.

In use, fluid tight conduit 701 surrounds a cylindrical inner liner of a flexible exhaust coupling device and the internal surface of centralised compressed section 707 is adjacent to the external surface of a central section of the cyfindrical inner liner. In this arrangement indent 713 is in contact with the external surface of the cylindrical inner liner.

As shown in figure 7, after extended use of fluid tight conduit 701 within a flexible exhaust coupling device of the present invention, the internal surface of the plurality of valleys 711 of bellow sections 703 and 705 do not display any wear as they are supported at a distance from the cylindrical inner liner and so do not come into direct contact with the cylindrical inner liner. Furthermore, minimal wear is experienced by the indent 713 of the centralised compressed section 707 as a consequence of its intimate contact with the cylindrical inner liner of the flexible exhaust coupling device.

With reference to figure8 herein there is shown a cylindrical inner liner 801 of a flexible exhaust coupling device according to an embodiment of the present invention.

Cylindrical inner liner 801 comprises a first winding 803 and a second winding 805. Only two complete windings 803 and 805 are shown for the sake of simplicity and it should be apparent to those skilled in the art that these windings may form part of a greater network windings.

Windings 803 and 805 comprise a body portion having a first substantially parallel portion 807 and 809, a substantially perpendicular portion 811 and 813 and a second substantially parallel portion 815 and 817. Windings 803 and 805 further comprise curved portions 819, 821, 839 and 841 and end portions 823, 825, 835 and 841.

First substantially parallel portions 807 and 809 are connected to the substantially perpendicular portions 811 and 813 which are then connected to the second substantially parallel portions 815 and 817 forming the body portion of windings 803 and 805. A first curved portion 819 and 821 is disposed at the end of the first substantially parallel portions 807 and 809 and a second curved portion 839 and 841 is disposed at the end of the second substantially parallel portions 815 and 817. End portions 823, 825, 835 and 841 extend from curved portions 819, 821, 839 and 841 substantially perpendicular to the first and second substantially parallel portions 807, 809, 815 and 817.

End portions 823, 825, 835 and 841 comprise a first substantially perpendicular portion 827, 829, 843 and 845 a curved portion and a second substantially perpendicular portion 831, 833,847 and 849.

Prior to the cylindrical inner liner 801 being subjected to high temperatures, i.e. when the flexible exhaust coupling device of the present invention is in its new condition prior to the engine being started, the windings 803 and 805 are in a tense state as in figure 8. When the windings 803 and 805 are in this state the second substantially perpendicular portions 831, 833, 847 and 849 of the end portions 823, 825, 835 and 837 are adjacent to the first substantially perpendicular portions 827, 829, 843 and 845 of the end portion 823, 825, 835 and 837. The angle between the first substantially perpendicular portion 827, 829, 843 and 845 and the second substantially perpendicular portion 831, 833, 847 and 849 is 00 In the pre heat conditioning state the windings 803 and 805 of the cylindrical inner liner 801 have a wide degree of movement along the parallel plane such that the flexible exhaust coupling device, in which the cylindrical inner liner 801 is incorporated can undergo elongation and compression. This degree of movement is primarily determined by the distance between the substantially perpendicular portions 811 and 813 of the body portion of winding 803 and 805 and the end portions 825 and 835 (further factors may influence the degree of movement as discussed below). Therefore, the end portion 825 of second winding 805 can be moved from a position in which it is adjacent to the substantially perpendicular portion 811 of the first winding 803 to a position in which it is adjacent to the end portion 835 of the first winding 803 and vice versa.

As is apparent in figure 8, when the cylindrical inner liner 801 is in its new condition prior to the application of high temperatures the only contact between the first winding 803 and the second winding 805 occurs between the curved portion of end portions 825 and 835 and the substantially parallel portions 815 and 809. As this is an area of contact that is formed with precision and has a radiused contact area, the windings 803 and 805 move with a smooth motion during elongation and compression of the cylindrical inner liner 801.

Referring to figure 9 herein there is provided the cylindrical inner liner 901 of figure 9 having an identical arrangement of windings as in figure 8. However, the cylindrical inner liner 901 has now been subjected to higher temperatures, similar, to those experienced within the flexible exhaust coupling device of the present invention when the vehicle for which it is fitted is in use.

When the windings 903 and 905 are subjected to high temperatures the end portions 923, 925 and 935 begin to relax and open. The second substantially perpendicular portion 933 of the end portion 925 moves away from the first substantially perpendicular portion 929 of the end portion 925 such that the angle between the first substantially perpendicular portion 929 and the second substantially perpendicular portion 933 increases in the order of around 0 to 150.

Referring to figure 10 herein this is provided the cylindrical inner liner 901 of figure 8 being subjected to high temperatures and compression/elongation when the vehicle, to which the flexible exhaust coupling device at the present invention is attached, is in use. The end portion 925 of winding 905 is in its most expanded and relaxed state due to the high temperature and the cylindrical inner liner 901 is being subject to compression as the flexible exhaust coupling device flexes to decouple the gross engine motions from the primary exhaust system.

As in figure 9, the second substantially perpendicular portion 933 of the end portion 925 has moved away from the first substantially perpendicular portion 929 of the end portion 925 creating an angle between the two substantially perpendicular portions 929 and 933 of between 0 and 150. Furthermore, the first substantially perpendicular portion 929 of the end portion 925 has moved away from the first substantially parallel portion 909 of the body portion of the winding 905, increasing the angle there between. When the cylindrical inner liner 901 is in a cold state as in figure 9, the first substantially perpendicular portion 929 of the end portion 925 is at right angles to the first substantially parallel portion 909 of the winding 905. In figure 11, the angle between the first substantially perpendicular portion 929 of the end portion 925 and the first substantially parallel portion 909 of the winding 905 has increased in the order of 0 to 100 such that the angle is now 90 to 1000.

When the cylindrical inner liner 901 is compressed at a high temperature the tip 1101 of the second substantially perpendicular portion 933 of the end portion 925 of the second winding 905 is forced into contact with the substantially perpendicular portion 911 of the first winding 903. Therefore, in a heated state, there is a further point of contact between the first winding 903 and the second winding 905 occurring between tip 1101 of the second substantially perpendicular portion 933 of the end portion 925 of the second winding 905 and the substantially perpendicular portion 911 of the first winding 903. Therefore, the windings 903 and 905 may experience further wear during elongation or compression of the cylindrical inner liner 901 at high temperatures, however, this wear is once again kept to a minimum by reducing the area of contact between the first winding 903 and second winding 905.

When the cylindrical inner liner 901 is subjected to high temperatures, as in figure 10, and expansion of the end portion 925 takes place, the degree of movement of the windings 903 and 905 is reduced by a percentage of the distance between the substantially perpendicular portion 911 and the end portion of 935 of winding 903 equal to the distance between the tip 1101 of the second substantially perpendicular portion 933 of the end portion 925 of winding 905 and the curved portion 921 disposed at the end of the first substantially parallel portion 909 of the winding 905. The reduction in the degree of movement of the windings 903 and 905 results in a slight increase in the stiffness of the cylindrical inner liner 901 however, this is not as great as with the prior art cylindrical inner liner.

Figure 11 illustrates schematically a plot of phase angle and stiffness against frequency for a flexible exhaust coupling device according to an embodiment of the present invention having an axial dynamic stiffness of 0.2 mm peak to peak.

A flexible exhaust coupling device according to an embodiment of the present invention was heat conditioned (nominally at 850 C for 60 minutes but in practical terms at greater than 500 C for more than 5 minutes) and the stiffness of the flexible exhaust coupling device was measured asit was excited at +1-0.1 mm in the frequency range or 5 to 250Hz. The stiffness of the flexible exhaust coupling device varied between 14N/mm up to 70N/mm however, the dynamic stiffness did not exceed I OON/mm within this range of frequencies. The line representing dynamic stiffness did not comprise any sharp peaks, therefore, illustrating that the stiffness of a flexible exhaust coupling device according to an embodiment of the present invention can be controlled within the frequency range of 5 to 250Hz. Furthermore, as the dynamic stiffness did not exceed lOON/mm, this illustrates that the dynamic stiffness of the flexible exhaust coupling device according to an embodiment of the present invention did not increase to a point in which it was detrimental to the elongation and compression of the flexible exhaust coupling device.

Figure 12 illustrates schematically a plot of phase angle and stiffness against frequency for a flexible exhaust coupling device according to an embodiment of the present invention having a shear dynamic stiffness of 0.2 mm peak to peak.

Claims

Claims 1. A flexible exhaust coupling device comprising a cylindrical

inner liner and a fluid tight conduit extending circumferentially around said cylindrical inner liner, characterised in that: said fluid tight conduit comprises a first bellows section, a second bellows section and a constricted section between said first and second bellows sections, wherein said constricted section acts to locate said inner liner at a position between first and second ends of said fluid tight conduit, such that as said coupling device flexes, said inner liner locates in said fluid tight conduit by contact at said first and second ends of said conduit, and at said constricted section.
2. A flexible exhaust coupling device according to claim 1, wherein said constricted section comprises at least one indent protruding from an internal surface of said constricted section, said at least one indent being disposed adjacent to and abuthng a central portion of said cylindrical inner liner.
3. A flexible exhaust coupling device as claimed in claim 1 or 2, wherein said constricted section is positioned approximately mid way along a length of said fluid tight conduit.
4. A flexible exhaust coupling device as claimed in any one of the preceding claims, wherein said constricted section acts to locate said inner liner substantially co-axially with a main axis of said fluid tight conduit.
5. A flexible exhaust coupling device according to any one of the preceding claims wherein said constricted section comprises three indents protruding from said internal surface of said constricted section.
6. A flexible exhaust coupling device according to any of the preceding claims wherein said fluid tight conduit further comprises a first compressed end section located at a first end portion of said coupling device and a second compressed end section located at a second end portion of said coupling device; wherein said first compressed end section and said second compressed end section are each configured to abut said surface of said cylindrical inner liner.
7. A flexible exhaust coupling device according to any one of claims I to 3, wherein said fluid tight conduit is made of steel.
8. A flexible exhaust coupling device according to any one of the preceding claims wherein said coupling device further comprises a circumferentially elastic mesh configured to extend circumferentially about and abutting the exterior of said fluid tight conduit.
9. A flexible exhaust coupling device according to claim 8, wherein said circumferentially elastic mesh comprises a network of interlocking loops.
10. A flexible exhaust coupling device according to claim 8 or9 wherein said circumferentially elastic mesh has a smaller internal diameter than an external diameter of said fluid tight conduit.
11. A flexible exhaust coupling device according to any one of claims 8 to 10 wherein the pitch of said circumferentially elastic mesh is greater than 60% of the pitch of said bellow section of said fluid tight conduit.
12. A flexible exhaust coupling device according to any one of claims 8 to 11 wherein said circumferentially elastic mesh is made of steel wire.
13. A flexible exhaust coupling device according to any one of claims 8 to 12 wherein said coupling device further comprises a plurality of ancillaries configured to secure said cylindrical inner liner, said fluid tight conduit and said circumferentially elastic mesh together.
14. A flexible exhaust coupling device according to any one of the preceding claims wherein said at least one indent protruding from said internal surface of said constricted section is secured to a substantial portion of the external surface of said cylindrical inner liner.
15. A flexible exhaust coupling device according to any one of the preceding claims wherein said flexible exhaust coupling device has a minimum elongation of 35% of its fully compressed length.
16. A flexible exhaust coupling device according to any one of the preceding claims wherein said cylindrical inner liner isolates said fluid tight conduit from the exhaust gases flowing through said flexible exhaust coupling device.
17. A flexible exhaust coupling device according to any one of the preceding claims wherein the functional life of said flexible exhaust coupling device exceeds the design life of the exhaust system to which it is attached.
18. A flexible exhaust coupling device according to any one of the preceding claims wherein when said flexible exhaust coupling is heate4 conditioned at a temperature greater than 500 C for a time period greater than 5 minutes, said flexible exhaust coupling device has an axial and shear dynamic stiffness within the range of from 1 N/mm to I OON/mm when excited at 0.1 mm in the frequency range of from 5Hz to 250Hz.
19. A flexible exhaust coupling device according to any preceding claim configured for use between and affixed to an exhaust manifold and a primary exhaust system within a vehicle.
20. A flexible exhaust coupling device comprising a cylindrical inner liner and a fluid tight conduit extending circumferentially around said cylindrical inner liner; said fluid tight conduit comprising at least one bellows section; said cylindrical inner liner comprising at least one winding comprising a body portion having a first portion which is substantially parallel to a main axial direction of the inner liner; a first transverse portion which extends in a direction transverse to said axial direction; and a second substantially parallel portion which extends substantially parallel to said axial direction; and said body portion further comprising a first curved portion disposed at the end of said first substantially parallel portion and a second curved portion disposed at the end of said second substantially parallel portion; characterised in that each said curved portion comprises a respective end portion extending perpendicularly to said substantially parallel portions of said body portion.
21. A flexible exhaust coupling device according to claim 20 wherein said end portion comprises a first substantially perpendicular portion, a second curved portion and a second substantiafly perpendicular portion, said first substantially perpendicular portion being connected to said second substantially perpendicular portion via said second curved portion.
22. A flexible exhaust coupling device according to any one of claims 20 or 21 wherein said first substantially perpendicular portion and said second substantially perpendicular portion of said end portions are adjacent to one another in its new pre heat conditioning state such that the angle between said first substantially perpendicular portion and said second substantially perpendicular portion is 00.
23. A flexible exhaust coupling device according to any one of claims or 21 wherein said end portions expand at high temperatures such that the angle between said first substantially perpendicular portion and said second substantially perpendicular portion is from 00 to 150; and said first substantially perpendicular portion is disposed at an angle of from to 105 0 to said substantially parallel portions of said body portion of said plurality of windings.
24. A flexible exhaust coupling device according to any one of claims 17 to 20 wherein said cylindrical inner liner has an elongation of at least 35%.
25. A flexible exhaust coupling device according to any one of claims to 24 wherein when said flexible exhaust coupling has been heated at a temperature greater than 500 C for a time period greater than 5 minutes, said flexible exhaust coupling device has an axial and shear dynamic stiffness within the range of from 1 N/mm to I OON/mm when excited at 0.1 mm in the frequency range of from 5Hz to 250Hz.
26. A flexible exhaust coupling device according to any one of claims to 25 wherein said cylindrical inner liner isolates said fluid tight conduit from the exhaust gases flowing through said flexible exhaust coupling device.
27. A flexible exhaust coupling device according to any one of claims to 26 wherein said plurality of windings are clamped at a first and second end of said flexible exhaust coupling device.
28. A tubular exhaust liner comprising: a cylindrical inner liner having a wall comprising a plurality of latching turns, each turn comprising: a first substantially cylindrical portion, of a first relatively larger diameter; a second substantially cylindrical portion, of a second relatively smaller diameter; a connecting portion extending in a direction transverse to a main axial length of said liner and connecting said first and second substantially cylindrical portions; a first substantially radially extending portion, extending from one end of said first substantially cylindrical portion; and a second substantially radially extending portion extending from one end of second substantially cylindrical portion.
29. A tubular exhaust liner as claimed in daim 28, wherein a said turn comprises a helical winding.
30. A tubular exhaust liner as claimed in claim 28, wherein a said turn comprises a substantially annular ring.
31. A tubular exhaust liner as claimed in any one of claims 28 to 30, wherein said first substantially radially extending portion comprises a distal end, which, in use contacts a surface of said second substantially cylindrical portion, and as the inner liner extends and contracts in an axial direction, said distal end slides over said second substantially cylindrical portion.
32. A tubular exhaust liner as claimed in claim 31, wherein said first radially extending portion comprises a fold of material, connected at said distal end.
33. A tubular exhaust liner as claimed in any one of claims 28 to 32, wherein said second substantially radially extending portion comprises a distal end which, in use contacts a surface of said first substantially cylindrical portion, as the inner liner extends and contracts in an axial direction.
34. A tubular exhaust liner as claimed in claim 33, wherein said first radially extending portion comprises a fold of material, connected at said distal end, which in use contacts a surface of said second substantially cylindrical portion, as the inner liner extends and contracts in an axial direction.
35. A tubular exhaust liner as claimed in claim 34, wherein said first and / or second radially extending portion comprises a fold of material, which expands predominantly in a direction substantially axially of the inner liner when raised to an operational temperature of said exhaust coupling.