Exhaust Pipe Assembly for a Combustion Engine

TECHNICAL FIELD

The invention relates to an exhaust pipe assembly for a combustion engine, particularly for a vehicle such as a commercial vehicle, a passenger car, or a power generator. The invention relates also to a vehicle comprising such an exhaust pipe assembly.

BACKGROUND OF THE INVENTION It is known in the art that the exhaust pipe of a vehicle has to pass through the engine noise shield which encapsulates the engine. The encapsulation

arrangement has to provide an opening on the one hand since the pipe and the engine noise shield move relative to each other and on the other hand due to the high operation temperature of the exhaust pipe.

Future legislation sets new demands on the noise insulation of a combustion engine, particularly in a power train of a vehicle and more particularly of commercial vehicles. In parallel with increased absorption rate of the noise encapsulation package, the aperture rate of the shield must be minimized. One major opening in the engine noise shield is where the exhaust pipe passes from the combustion engine or turbocharger to a main muffler.

US 4,026,381 discloses a cover assembly for an exhaust muffler and tail pipe of a truck to reduce noise and eliminate corrosion. The cover assembly is formed from a pair of moulded rigid fibre glass shells that can be fastened together about both the exhaust pipe and the muffler. Layers of asbestos and spun glass are sandwiched about the muffler and exhaust pipe shells. The shell itself is a combination of a fire retardant resin and fibre glass. The insulation cover pipe is ^" formed from two identical half shells wherein asbestos and fibre glass layers are wrapped around the exhaust pipe.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an exhaust pipe assembly for a vehicle which improves noise reduction and which provides significant noise abatement efficiency.

Another object is to provide a vehicle comprising such an exhaust pipe assembly.

The objects are achieved by the features of the independent claims. The other claims, the drawings and the description disclose advantageous embodiments of the invention.

An exhaust pipe assembly is proposed for a combustion engine, comprising an exhaust pipe and an engine noise shield of the engine, wherein the engine noise shield has an opening for passing the exhaust pipe through the engine noise shield. The exhaust pipe is acoustically coupled to the engine noise shield via a shield section associated with the exhaust pipe.

The exhaust pipe is acoustically coupled to the engine noise shield in a way to reduce air borne as well as structural noise emission through the opening for passing the exhaust pipe.

The acoustical coupling of the exhaust pipe to the engine noise shield solves the noise problems related to the exhaust pipe between the engine and a main muffler of an exhaust gas aftertreatment system in an advantageous way and provides noise reduction and significant noise abatement efficiency. The invention still allows necessary movements between the exhaust pipe and the engine noise shield. Further the invention offers heat protection for the engine noise shield from the heat of the exhaust pipe. Favourably, the shield section associated with the exhaust pipe is reducing the effective noise emission of the opening for passing the exhaust pipe. Thus, the noise emission is reduced to provide an effective engine sound insulation that also will give an increased efficiency for the other noise shields on the vehicle. According to an expedient embodiment, the acoustic coupling can be performed by selecting at least one of a distance of the shield section from the exhaust pipe and/or a length of the shield section along the exhaust pipe and/or a width of the shield section crosswise to the exhaust pipe and/or a distance of the shield section from the opening of the engine noise shield in a way to reduce airborne and/or structural noise emission originating substantially from the engine and/or the exhaust pipe. The noise abatement can be achieved although the engine and exhaust pipe may need a certain space for vibrational movements caused during operation of a vehicle, particularly a truck.

Advantageously, by selecting a sufficiently large distance between the shield section and the exhaust pipe, sufficient free space can be provided for vibrational movements of the exhaust pipe during operation of e.g. the vehicle. Alternatively or additionally a proper length of the shield section along the exhaust pipe can be selected. Sound waves travelling along the exhaust pipe in the space between the exhaust pipe and the shield section can be reduced by multiple reflections and absorption. Expediently, at least those surfaces towards which the sound waves are reflected can be covered with a sound absorber to avoid that the sound energy will escape. Alternatively or additionally, the width of the shield section crosswise to the exhaust pipe can be adapted to a desired absorption of the sound waves travelling between the shield section and the engine noise shield. Alternatively or additionally, the distance of the shield section from the opening of the engine noise shield can also be adjusted to provide an advantageous noise abatement.

In a favourable embodiment the shield section may comprise a tube segment which at least partially encloses a portion of a longitudinal extension of the exhaust pipe. Particularly, the tube segment can be arranged upstream of a flexible portion of the exhaust pipe arranged at a side of the exhaust pipe distant from the engine. The tube section facilitates an undisturbed vibrational movement of the exhaust pipe inside the tube section. With the tube segment closer to the engine than the flexible portion vibrational movements of the exhaust pipe requires a sufficient diameter of the opening in the engine noise shield for feeding through the exhaust pipe. Expediently, the space through which the sound waves can propagate from the engine to the outside is a long, preferably narrow channel. The narrower the channel can be the better, whereas the shape of the channel can be chosen as required so that the sound waves can be damped and/or absorbed while passing the clearance. Particularly, the tube segment should be provided with sound absorbing material to improve the noise reduction. Although the opening is a major source of noise emission the invention favourably allows improved noise abatement.

Advantageously, the tube segment may comprise a damping structure or layer facing the exhaust pipe. The damping structure or layer further improves the noise abatement and attenuates sound waves travelling in the space between the exhaust pipe and the tube segment.

According to another expedient embodiment, the tube segment can be made out of at least two shells separated in an axial direction. The tube segment can be easily mounted around the exhaust pipe. However, the tube segment may be also be made out of one shell.

According to another expedient embodiment, the shield section may comprise a collar with a main extension crosswise to a longitudinal extension of the exhaust pipe. Advantageously, the collar may be a plate arranged parallel to a surface of the engine noise shield in the vicinity of the opening in the engine noise shield. The collar can overlap the opening in the engine noise shield and damp the noise travelling between the collar and the engine noise shield. The noise abatement can be improved. The size of the collar and the distance from the opening can be chosen to provide sufficient noise abatement. By having a larger area than the opening and overlapping the opening with the collar, the effective noise emission size of the opening for passing the exhaust pipe is reduced even when the shield section is moving relative to the engine noise shield. Sound waves cannot leave the opening directly and can be effectively damped instead. This results in an advantageous reduction of noise emission, providing an effective engine sound insulation that also will give an increased efficiency for the other noise shields on the vehicle. Expediently, the space through which the sound waves can propagate from the engine to the outside is a long, flat channel so that the sound waves can be reflected back into the engine house (also called engine bay) and/or absorbed while passing the clearance. Particularly, the collar can or should be provided with sound absorbing material for further improvement of the noise reduction.

In a favourable embodiment, the shield section can form a continuous shield extending from the engine noise shield to the main muffler. It is of advantage when the shield section may comprise a heat insulating portion arranged in the opening of the engine noise shield. Favourably, in case of a damaged flexible portion or a damaged exhaust pipe exhaust gas may under certain circumstances be still encapsulated within the shield section and the engine noise shield and not released directly into the ambient without cleaning of the exhaust gas. By way of example the flexible portion can be covered and encapsulated completely by the shield section.

In a further embodiment, a flexible portion of the exhaust pipe may be arranged at a side of the exhaust pipe close to the engine. Vibrational movements of the exhaust pipe downstream of the flexible portion can be strongly reduced.

Expediently, when the location of the flexible part is close to the engine, the shield section can form a continuous shield around the exhaust pipe without disturbing vibrations of the exhaust pipe inside the shield section.

Advantageously, arranging the flexible part remote from the engine allows movement of the engine relative to the main muffler to which the exhaust pipe is attached. Arranging the flexible part close to the engine expediently allows movement of the engine relative to the exhaust pipe and eliminates a movement of the exhaust pipe relative to the opening of the engine noise shield.

According to an advantageous embodiment, efficient noise abatement can be achieved if a heat insulating material and/or a noise insulating material is arranged between the shield section and the exhaust pipe. In particular, the heat insulating material and/or a noise insulating material may comprise a flexible ceramics material. The heat insulating material and/or a noise insulating material can be compressed by the shield section, particularly by a tube segment arranged around the exhaust pipe. As result, the heat situation can be positively affected and, in case of a vehicle, vehicle parts, e.g. the cab air suspension, can be protected from the heat of the exhaust pipe. The heat insulating material and/or a noise insulating material can maintain a high exhaust gas temperature in the exhaust pipe so that hot exhaust gas streams into the main muffler. This is favourably for reducing exhaust emissions in the exhaust gas aftertreatment system used today for e.g. selective catalytic reduction systems. Particularly, the heat insulating material and/or a noise insulating material can comprise a flexible ceramics material which makes it easy to adapt to the form of the exhaust pipe. The flexible ceramics material may have a density of several tens of kg/m ³ , for instance between 60 and 70 kg/m ³ .

According to an advantageous embodiment, noise abatement can be further improved if a noise damping structure is arranged between a portion of the shield section and the noise shield. Generally, the exhaust pipe can be provided with material wrapped around the exhaust pipe, and/or a coating material can be deposited on the exhaust pipe e.g. by spray coating and the like. Advantageously, the shield section associated with the exhaust pipe may be made out of steel, particularly stainless steel, with a thickness of a few millimetres, for instance about 0.5-3 mm, particularly about 2 mm.

Embodiments of the exhaust pipe assembly according to the present invention can be applied to vehicles where one is desirous to fulfil noise reduction requirements and where the exhaust mufflers are mounted outside the engine encapsulation, i.e. passenger cars, commercial vehicles such as trucks, buses, construction equipment and the like.

Embodiments of the exhaust pipe assembly according to the present invention can be applied to power generators where one is desirous to fulfil noise reduction requirements and where the exhaust mufflers are mounted outside the engine encapsulation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention together with the above-mentioned and other objects and advantages may best be understood from the following detailed description of the embodiments, but not restricted to the embodiments, wherein is shown

schematically:

Fig. 1 a perspective partial view of a truck having an exhaust pipe

assembly according to prior art;

Fig. 2a, 2b a cross sectional view of an arrangement having an exhaust pipe assembly in accordance with a first embodiment of the present invention;

Fig. 3a, 3b a perspective partial view of an arrangement having an exhaust pipe assembly in accordance with a second embodiment of the present invention;

Fig. 4a-4c a partial cross sectional view of an arrangement having an exhaust pipe assembly in accordance with a third example embodiment of the present invention;

Fig. 5 a partial cross sectional view of an arrangement having an exhaust pipe assembly in accordance with a fourth example embodiment of the present invention; and

Fig. 6 an example embodiment of a vehicle according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.

Representing the state of the art, Fig. 1 depicts schematically a detail of a vehicle 10, for instance a truck 10, comprising an engine 60 coupled to an exhaust gas aftertreatment system with a main muffler 50 via an exhaust pipe assembly 20 comprising an exhaust pipe 12 with a flexible part 14 which is arranged at an exhaust pipe portion remote from the engine 60 and may be covered with an insulation device 16. The engine 60 is enclosed in an engine noise shield 30.

The engine noise shield 30 around the engine 60 is not completely closed due to movements between the cab and the chassis, air and heat evacuation from engine house (also called engine bay) and components going through the noise shield 30 such as the exhaust pipe 12.

The opening 34 is arranged between the exhaust pipe 12 and the engine noise shield 30 around the engine 60. The reason for this is to allow for movements between the exhaust pipe 12 and the engine noise shield 30. Additionally, the heat of the exhaust pipe 12 during operation of the engine 60 requires a certain distance between the engine noise shield 30 and the exhaust pipe 12. The opening 34 in the engine noise shield 30 results in a high emission of engine noise and makes it hard to achieve good noise abatement of the engine 60 and of the noise emitted by the exhaust pipe 12 itself. The noise radiation from the exhaust pipe 12 may be significant as it is directly connected to the engine 60 without some part that will provide a vibration insulation between the exhaust pipe 12 and the engine 60.

As shown in the Figures 2 to 6, an exhaust pipe assembly 122 for a combustion engine 60 is proposed according to the invention, comprising an exhaust pipe 1 12 and an engine noise shield 30 of the engine 60, wherein the engine noise shield 30, has an opening 34 for passing the exhaust pipe 12, 1 12 through the engine noise shield 30. The exhaust pipe 1 12 is acoustically coupled to the engine noise shield 30 via a shield section 120 associated with the exhaust pipe 112. Favourably, the shield section 120 has a geometrical relationship to the opening 34 of the engine noise shield 30 so that a distance to a noise emitting portion of the engine noise shield 30 and/or the exhaust pipe 112, which may emit airborne noise and/or noise due to structural vibrations is just big enough so the noise insulating shield section 120 can manage the movements of the exhaust pipe 112 and can withstand the heat from the exhaust pipe 112. Typically, the engine 60, including the exhaust pipe 112 that is stiffly connected to the engine 60, moves about 30 mm in all directions during operation relative to the chassis, where engine noise shield 30 is mounted.

A first embodiment of the exhaust pipe arrangement 122 is shown in Figs. 2a and 2b. Depicted is an engine noise shield 30 enclosing the engine 60 and having an opening 34 for passing the exhaust pipe 112 which is attached to a muffler 50 of an exhaust gas after treatment system. At its inside, the engine noise shield 30 has a sound absorbing structure 32 for reducing noise emission from the engine 60. The opening 34 has a diameter D34 providing sufficient room for movement of the exhaust pipe 112 during operation of the engine 60, but small enough to trap the noise. A shield section 120 is arranged at the opening 34, wherein the shield section 120 is formed as a tube segment 130 protruding from the opening 34. The tube segment 130 encloses partially a portion of a longitudinal extension L 12 of the exhaust pipe 112. The tube segment 130 is arranged upstream of a flexible portion 114 of the exhaust pipe 12 arranged at a side of the exhaust pipe 112 distant from the engine 60 and adjacent to the muffler 50.

The tube segment 130 extends with a length L130 along the exhaust pipe 112 and has a distance (clearance D130) between the outside of the exhaust pipe 112 and an inner surface of the tube segment 130 which is formed by a sound absorbing structure 132.

This arrangement is efficient for reducing air-borne noise from the engine 60 in the engine house formed by the inner volume of the engine noise shield 30. Expediently, the clearance D130 is just big enough so the shield section 120 can manage the movements of the exhaust pipe 112 and can withstand the heat from the exhaust pipe 112. It is expedient when the length L130 of the tube segment 130 is just big enough so the shield section 120 creates a noise trap for air-borne noise from the engine 60 in the engine house.

Fig. 2b shows an improved arrangement where, additionally to the reduction of the air-borne noise from engine 60 room structural noise from the shell of the exhaust pipe 112 is also improved by increasing the length L130 of the tube segment 130.

Expediently, the clearance D130 is just big enough so the shield section 120 can manage the movements of the exhaust pipe 112 and can withstand the heat from the exhaust pipe 112, and the length L130 is just big enough so the shield section 120 can create a noise trap for air-borne noise from the engine 60 in the engine house and can suppress the structural noise from the exhaust pipe 112.

A second embodiment of the exhaust pipe arrangement 122 is shown in Figs. 3a and 3b. Depicted is an engine noise shield 30 enclosing the engine 60 and having an opening 34 for passing the exhaust pipe 112 which is attached to a muffler 50 of an exhaust gas after treatment system. At its inside, the engine noise shield 30 has a sound absorbing structure 32 for reducing noise emission from the engine 60. The opening 34 has a diameter D34 providing sufficient room for movement of the exhaust pipe 112 during operation of the engine 60. A shield section 120 is arranged about the exhaust pipe 112, wherein the shield section 120 is formed as a disc like collar 140 surrounding the exhaust pipe 112 with a distance D140 from the opening 34 and a radial width WHO. The collar 140 is mounted to the exhaust pipe 112 via a package comprising a heat insulating material 116 connected to the exhaust pipe 112 and a noise insulating material 118 arranged between the heat insulating material 16 and the collar 140.

The side of the collar 140 facing the engine noise shield 30 is covered with a sound absorbing structure 142. The portion of the engine noise shield 30 facing the collar 140 may also be provided with a sound absorbing structure 36. This arrangement allows for a good reduction of air-borne noise from the engine 60 in the engine house. The clearance D130 between the exhaust pipe 1 12 and the opening 34 and the distance D140 expediently are just big enough so shield section 120 can manage the movements of the exhaust pipe 1 12 and can withstand the heat from the exhaust pipe 1 12. The radial extension (width W140) of the collar 140 is expediently big enough so the shield section 120 creates a noise trap for air-borne noise from the engine 60 in the engine house. Generally, the larger the width WHO, the better from a noise damping point of view, whereas the smaller the distance DHO, the better from a noise damping point of view.

Heat and/or vibration isolation are not needed if the shield section 120 is heat resistant and/or well damped. Fig. 3b shows a variant in which additional to the improved reduction of air-borne noise from engine 60 noise emission from the shell of the exhaust pipe 1 12 is also reduced by adding a tube segment 130 to the collar 140.

The shield section 120 comprises the collar 140 and the tube segment 130 attached to the collar 140. The tube section 130 extending with a length L130 along the exhaust pipe 1 12 and being spaced with a distance (clearance D130) to the exhaust pipe 1 12 is attached to the collar 140 at the side pointing away from the opening 34 of the engine noise shield 30. The tube segment 130 encloses partially a portion of a longitudinal extension L1 12 of the exhaust pipe 1 12. The tube segment 130 is arranged upstream of a flexible portion 1 14 of the exhaust pipe 1 12 arranged at a side of the exhaust pipe 1 12 distant from the engine 60 and adjacent to the muffler 50.

The clearance D130 and the distance DHO of the collar 140 from the engine noise shield 30 and its opening 34 expediently are just big enough so the shield segment 120 can manage the movements of the exhaust pipe 1 12 and can withstand the heat from the exhaust pipe 1 12. The radial extension of the collar 140 is expediently big enough so the shield section 120 creates a noise trap for air-borne noise from the engine 60 in the engine house, and the length L130 of the tube segment 130 is big enough so the shield section 120 suppresses the noise from the exhaust pipe 1 12.

Heat and/or vibration isolation are not needed if the shield section 120 is heat resistant and/or well damped.

At the inner surface of the tube segment 130 a sound absorbing structure 132 is provided. Between the noise damping structure 132 and the exhaust pipe 1 12 a package of a heat insulating material 1 16 and a noise insulating material 1 18 is arranged, wherein the heat insulating material 1 16 contacts the exhaust pipe 1 12 and the noise insulating material 1 18 is arranged between the noise damping structure 132 and the heat insulating material 1 16. Alternatively, it is also possible to replace the several different layers 1 16, 1 18 and 132 for 130 by one layer of a sound and heat insulating material.

A third embodiment of the exhaust pipe arrangement 122 is shown in Figs. 4a, 4b and 4c. Depicted is an engine noise shield 30 enclosing the engine 60 and having an opening 34 for passing the exhaust pipe 1 12 which is attached to a muffler 50 of an exhaust gas after treatment system. At its inside, the engine noise shield 30 has a sound absorbing structure 32 for reducing noise emission from the engine 60. The opening 34 has a diameter D34 providing sufficient room for movement of the exhaust pipe 1 12 during operation of the engine 60.

Other than in the other embodiments described so far, the exhaust pipe 1 12 is connected to the engine 60 by a flexible part 1 14 inside the engine noise shield 30 whereas there may be no flexible part at the side of the exhaust pipe 1 12 attached to the muffler 50.

In Fig. 4a, a shield section 120 is arranged about the exhaust pipe 1 12, wherein the shield section 120 is formed as a ring 150 comprising heat insulating material 1 16 surrounding the exhaust pipe 1 12 at the opening 34. This arrangement can efficiently reduce air-borne noise from engine 60 and noise from the shell of the exhaust pipe 1 12 when the flexible part 1 14 is a soft flexible part 1 14 such as a soft hose or soft bellows portion and not a stiff flexible part such as a bellows. Heat isolation is not needed if the shield section 120 is heat resistant.

The variant in Fig. 4b shows, similar to Fig. 2a, the shield section 120 associated with the exhaust pipe 120 embodied as a tube segment 130 which extends with a length L130 along the exhaust pipe 1 12 and is spaced to the exhaust pipe with a clearance D130. The tube segment 130 may have a sound absorbing structure 132 at its inside facing the exhaust pipe 1 12.

As in Fig. 4a, the variant in Fig. 4b reduced the air-borne noise from engine 60 in the engine house and, in case the flexible part 1 14 is a soft flexible part 1 14 such as a hose portion, the noise from the shell of the exhaust pipe 112 can also be well reduced.

The clearance D130 is expediently just big enough so the shield section 120 can withstand the heat from the exhaust pipe 1 12. The length L130 of the tube segment 130 is expediently big enough so the shield section 120 creates a noise trap for air-borne noise from the engine 60 in the engine house.

Fig. 4c shows an improved version of the version shown in Fig. 4b where the noise from the shell of the exhaust pipe 1 12 is well reduced as the length L130 is increased and the tube segment 130 coming close to the muffler 50.

The clearance D130 is expediently just big enough so the shield section 120 can withstand the heat from the exhaust pipe 1 12.

The length L130 of the tube segment 130 is expediently big enough so the shield section 120 can creates a noise trap for air-borne noise from the engine house and can suppress the noise from the exhaust pipe 12.

Fig. 5 shows a variant of the embodiment of Fig. 4c where the air-borne noise from engine house as well as the noise from the shell of the exhaust pipe 1 12 can be well reduced by connecting the tube segment 130 to the muffler 50 so that the exhaust pipe 1 12 may be completely enclosed by the shield segment 120 formed by the tube segment 130 and the engine noise shield 30. However, the enclosure of the exhaust pipe 1 12 does not need to be complete. As there is a soft connection to the engine 60 it may be sufficient to cover only a part of the exhaust pipe 1 12 to get a good integration with the main engine encapsulation 30.

The length L130 of the tube segment 130 is expediently just big enough so the shield section 120 can suppress the noise from the exhaust pipe 1 12.

Heat isolation is not needed if the shield section 120 is heat resistant. However, the exhaust pipe 1 12 can be surrounded by a noise insulating material 1 18 and/or a heat insulating material 16. Whereas the materials 1 18, 1 16 and the sound absorbing structure 132 are shown in the Figure as three separate layers, the noise insulating material 1 18 and the sound absorbing structure 132 can be replaced by one sound absorbing layer 132. The heat insulating material 1 16 needs only be provided in case the sound absorbing layer 132 is not heat resistant. Generally, in all embodiments where a tube segment 130 is provided as a part of the shield section 120, a noise absorbent or damping layer can be wrapped around the exhaust pipe 1 12 to improve the noise trap performance and give possibility to reduce the length L130 of the tube segment 130. Fig. 6 depicts an example embodiment of a vehicle 10 employing an exhaust pipe assembly 122 described above.

Embodiments of the exhaust pipe assembly 122 according to the present invention can be applied to all vehicles 10 where one is desirous to fulfil the external noise legislation and where the exhaust mufflers are mounted outside the engine encapsulation, e.g. in passenger cars, commercial vehicles such as trucks and certain buses, construction equipment and the like. Of course, such exhaust pipe assemblies 122 as described for a vehicle 10 can also be employed with a power generator (not displayed) powered by a combustion engine, where the combustion engine produces power for driving an electric machine (not shown).