Exhaust muffler

Abstract

An exhaust muffler (100,fig.1) comprising a baffle 101 dividing an internal volume of the muffler. The muffler has an outer skin 104 and an inner skin 103. The inner skin at least partially surrounds

Description

TECHNICAL FIELD The present disclosure relates to an exhaust muffler. Aspects of the invention relate to an exhaust muffler, an exhaust system and a vehicle. BACKGROUND It is known that high temperatures in known exhaust systems can discolour and / or stain components of the exhaust system. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide an exhaust muffler, an exhaust system and a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided a muffler or an exhaust muffler for a vehicle, the muffler comprising: a baffle which divides an internal volume of the muffler; an outer skin or outer wall; and an inner skin orinnerwall located inside of the outer skin and at least partially surrounding the baffle, the inner skin at least partially defining the inner volume of the muffler. According to an aspect of the present invention there is provided a muffler or an exhaust muffler for a vehicle, the muffler comprising: a baffle which divides an internal volume of the muffler; an outer skin or outer wall; and an inner skin orinnerwall located inside of the outer skin and at least partially surrounding the baffle, the inner skin at least partially defining the inner volume of the muffler, the inner skin comprising: a contact surface portion on an inner surface of the inner skin, the contact surface portion being in contact with a peripheral portion of the baffle along a length of the peripheral portion of the baffle which is at least 3% of a total length of a periphery of the baffle; and an opposing contact surface portion located on an outer surface of the inner skin, the opposing contact surface portion being directly opposite to the contact surface portion; wherein the opposing contact surface portion of the inner skin is separated from the outer skin to provide an insulating gap. Advantageously, conduction between the baffle and the outer skin may be reduced or eliminated due to the separation of the contact surface portion from the outer skin. This may prevent material deterioration, unsightly staining and reduce the temperature of the outer skin. The periphery of the baffle may be provided by a baffle lip. The baffle may comprise a plate. The baffle lip may be a part of the baffle which is bent to be at an angle to, for example orthogonal to, a major part of the baffle. Advantageously, the baffle may be stamped or pressed into shape. Further advantageously, the baffle lip may stabilise the baffle in the correct position. The contact surface portion may have a length along the periphery of the baffle which is at least 10%, 20%, or 30% of a total length of the periphery of the baffle. The insulating gap may advantageously prevent conduction despite the contact surface portion having a significant length. The baffle may abut the inner skin. The baffle may abut the inner skin with no other fastening present. Advantageously, the baffle may be able to expand and contract due to heat. The outer surface of the inner skin may comprise a non-opposing contact surface portion being distinct from the opposing contact surface portion. The non-opposing contact surface portion may be spaced from the outer skin. Advantageously, this may prevent heat conduction between the non-opposing contact surface portion and the outer skin. In some embodiments, the contact surface portion of the inner skin may be separated from the outer skin by an air gap. Advantageously, an air gap may reduce or eliminate conduction to the outer skin. Connection between the inner skin and the remainder of the baffle may be at a periphery of the inner skin. The inner skin may be connected in the remainder of the muffler at a periphery of the inner skin. The inner skin may be connected in the remainder of the muffler only at a periphery of the inner skin. Advantageously, this may reduce conduction to the outer skin. The outer skin may be provided by two parts connected together at two seams which extend along an axial direction of the muffler. The inner skin may be only attached to the outer skin on the seams. The seam may be situated such that it is not visible from behind a vehicle when the muffler is installed on a vehicle. Advantageously the contact points may not be visible. The air gap may have a thickness of at least 5 mm. The air gap may have a thickness of less than 10 mm. Advantageously, this may provide sufficient distance to reduce the amount of heat transfer. In some embodiments, the opposing contact surface portion of the inner skin is separated from the outer skin by a layer having a thermal conductivity which is less than the thermal conductivity of the opposing contact surface portion of the inner skin. The layer may have a thermal conductivity which is less than the thermal conductivity of a portion of the outer skin nearest to the opposing contact surface portion. Advantageously, thermal conduction may be reduced. The layer may comprise polycrystalline fibres. The polycrystalline fibres may contain at least 95% alumina. The polycrystalline fibres may comprise 96% alumina and 4% silica. Advantageously, this may reduce the amount of heat transfer. The muffler or exhaust muffler may comprise a condensate passage extending in an axial direction of the muffler. The condensate passage may extend across the contact surface portion. The inner skin may be spaced from the outer skin at the condensate passage. Advantageously, condensate may pass the contact portion through the condensate passage. The condensate passage may have a length along a circumferential direction of the muffler which is less than or equal to a width along an axial direction of the muffler. Advantageously, this may provide a narrow passage for the flow of condensate, to direct the condensate to an outlet. The muffler or exhaust muffler may have a height direction corresponding to a vertical direction when in use on a vehicle and a width direction corresponding to a horizontal direction when in use on a vehicle, such that the height and width directions define a first lower quadrant and a second lower quadrant of the muffler, and a first upper quadrant and a second upper quadrant of the muffler, the first upper quadrant being adjacent the first lower quadrant, wherein the opposing contact surface portion extends across at least part of a circumferential direction of the first lower quadrant and / or the first upper quadrant. Advantageously, this may mean that any staining or discolouration is less visible from outside the vehicle. The vertical and horizontal directions may be defined as when vehicle is on a horizontal surface. Advantageously, visible staining due to heat conduction from the baffle may be reduced or prevented because the insulated gap is in the first lower quadrant and / or first upper quadrant. The opposing contact surface portion may extend across at least part of a circumferential direction of the first lower quadrant. The opposing contact surface portion may extend across all of the circumferential direction of the first lower quadrant. Advantageously, this may mean that any staining or discolouration is less visible from outside the vehicle. When installed in a vehicle each of the at least one coupling portion and each of the spaced portions may correspond to a visible portion of the outer skin. The visible portion may be visible when viewed from a rear of the vehicle. In this case, the visible portion is defined as being visible by a user standing in the vicinity of the vehicle when the vehicle is in a state of normal repair. Advantageously, this may mean that any staining or discolouration is less visible from outside the vehicle. The at least one baffle may be two baffles located either side of a chamber. The muffler may comprise a perforated pipe which is attached to each baffle and which extends through the chamber. The opposing contact surface portion may extend around a central axis of the muffler from at least 70° up to 270°, where 0° corresponds to a vertical direction when the muffler is in use on a vehicle and where the central axis extends along the axial direction of the muffler. The opposing contact surface portion may extend around a central axis of the muffler from around one quarterto around three quarters. Advantageously, this may mean that any staining or discolouration is less visible from outside the vehicle. According to an aspect of the present invention there is provided an exhaust system comprising the aforementioned muffler or exhaust muffler. According to an aspect of the present invention there is provided a vehicle comprising the aforementioned muffler or exhaust muffler, or the aforementioned exhaust system. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a section view of a first example of an exhaust muffler according to an embodiment of the invention; Figure 2 shows another view of the exhaust muffler of Figure 1; Figure 3 shows another view of the exhaust muffler of Figure 1; Figure 4 shows a section view of a second example of an exhaust muffler according to an embodiment of the invention; Figure 5 shows another view of the exhaust muffler of Figure 4; Figure 6 shows another view of the exhaust muffler of Figure 4; and Figure 7 shows a vehicle comprising an exhaust system and exhaust muffler according to an embodiment of the invention. DETAILED DESCRIPTION Exhaust mufflers 100, 200 in accordance with embodiments of the present invention are described herein with reference to the accompanying Figures 1 to 6. As shown in Figure 7, an exhaust muffler 100, 200 is installed in an exhaust system 300 in a vehicle 400. Referring to Figure 1, there is shown a section view along a vertical plane of a first example of a muffler, which is an exhaust muffler 100. The exhaust muffler 100 has a series of pipes P passing therethrough, some of which have perforations therethrough. The exhaust muffler 100 has a plurality of baffles 101 dividing an internal volume of the exhaust muffler 100. In this example each side of the muffler 100 has two baffles 101 located either side of a chamber, and a perforated pipe which is attached to each baffle and which extends through the chamber. As is usual in the art, the exhaust muffler 100 operates by receiving flow of exhaust gas through the pipes P, where gas and sound waves pass through the perforations and are reflected by walls of the internal volume and by the baffles 101, thereby attenuating sound waves. The exhaust gases then leave the muffler through an outlet pipe. Due to the high temperature of the exhaust gases, this can stain or discolour components of the exhaust muffler 100. The exhaust muffler 100 is a part of a larger exhaust system 300 of a vehicle 400, as shown in Figure 7. The exhaust muffler 100 is mounted to an underside of the vehicle 400, for example via mounting brackets 102, which are shown in Figure 1. In Figure 1 there are arrows showing a vertical direction V and an axial direction A of the exhaust muffler 100. A horizontal direction H is orthogonal to the vertical direction V and axial direction A, and the horizontal direction H is shown by an arrow in Figures 5 and 6. The vertical direction V and horizontal direction H correspond to vertical and horizontal directions when the vehicle 400 is located on a horizontal surface (not shown). Referring now to Figures 2 and 3, detailed views of parts of the exhaust muffler 100 are provided. The exhaust muffler 100 has an outer skin 104, which provides a majority of an outer surface of the muffler 100, and an inner skin 103 located inside of the outer skin 104 and partially surrounding the baffles 101. The inner skin 103 is directly connected to the outer skin 104 around edges of the inner skin 103, for example by welding or by a mechanical interference fit around the periphery of the inner skin 103. In this example, the inner skin 103 extends, in a circumferential direction of the muffler 100, across most of each of a first and second lower quadrant of the muffler 100, the lower quadrants being defined by intersections of vertical and horizontal planes intersecting at a centre line of a cross-section of the muffler 100. The inner skin 103 may, in examples, also extend into upper quadrants. As is best shown in the example muffler 200 shown in Figures 5 and 6 (see the seams 209 in these Figures), but which is the same as in the muffler 100 of this example, the outer skin 104 is provided by two parts connected together at seams which extend along an axial direction of the muffler 100, in what may be referred to as a ‘clam shell’ construction. The inner skin 103 is fixed to the outer skin 104 along the seams and at axial ends of the inner skin 103. Each baffle 101 has a peripheral portion which, in this example, is a baffle lip 105 provided by bending a part of the baffle 101, which is a plate, to be at an angle to, for example orthogonal to, a major part of the baffle 101. The baffle lip 105 extends around an entire periphery of the baffle 101. A part of the baffle lip 105 is in contact with the inner skin 103 and a part of the baffle lip 105 is in contact with the outer skin 104. In this example, each baffle lip 105 is in contact with the inner skin 103 or outer skin 104 without any additional fixing means, but it will be appreciated that further fixing means could be used, for example welding, adhesive or fasteners. The inner skin 103 comprises a contact surface portion 106 on an inner surface of the inner skin 103. The contact surface portion 106 is the part of the inner skin 103 which is in contact with the baffle lip 105. In this example, around 50% of a total length of the periphery of the baffle 101 is in contact with the contact surface portion 106. This means that the inner skin 103 extends from around 90° to around 270° around a central axis of the muffler 100 which extends along the axial direction of the muffler 100, where 0° aligns with the vertical direction V. However, it will be appreciated that this is dependent upon the size of the inner skin 103, which is dependent upon the specific design of the exhaust muffler 100, and so this may be any value from around 3%, for example if the inner skin 103 is fixed to the outer skin 104 has a small size because not much of the muffler 100 is visible, in use, to around 97%, for example if the inner skin 103 is fixed to the outer skin 104 at just one position at the axial position of the baffle 101. In this example, the contact surface portion 106 is a surface of a channel in which the baffle lip 105 sits. Either side of the channel are located non-contact portions 110 of the inner skin 103, which are spaced from the outer skin 104 to provide an air gap therebetween. The inner skin 103 comprises an opposing contact surface portion 107 located on an outer surface of the inner skin 103, the opposing contact surface portion 107 being directly opposite to the contact surface portion 106. In this example, the opposing contact surface portion 107 is an outer skin of the channel of the inner skin 103, in which the baffle lip 105 sits. In this example, the opposing contact surface portion 107 of the inner skin 103 is separated from the outer skin 104 to provide an insulating gap. The insulating gap of this example is provided by a layer 108 having a thermal conductivity which is less than a thermal conductivity of the opposing contact surface portion 106 of the inner skin 103 and which is less than a thermal conductivity of a portion of the outer skin 104 nearest to the opposing contact surface portion 106. In this example the layer 108 comprises polycrystalline fibres which contain 96% alumina and 4% silica. The layer 108 reduces an amount of thermal conduction from the baffle 101 to the outer skin 104. In this example the exhaust muffler 100 comprises a condensate passage 109 extending along the axial direction A of the muffler 100. The condensate passage 109 extends across the contact surface portion 106. The inner skin 103 is spaced from the outer skin 104 at the condensate passage 109. The condensate passage 109 is narrow compared to a width of the contact surface portion 106 and provides a flow path for liquid condensate to flow past the contact surface portion 106 to condensate evacuation features (not shown) located at various positions along the axial direction A of the muffler 10. When the exhaust muffler 100 is designed for a specific vehicle, the inner skin 103 is located at a position corresponding to a visible portion of the outer skin 104 when the muffler 100 is installed in the vehicle, and the baffle 101 conducts heat directly to the inner skin 103. In use, the air gaps between the non-contact portions 110 and the outer skin 104 act to prevent or reduce discolouration or staining of the corresponding parts of the outer skin 104. However, each baffle 101 conducts heat directly to the inner skin 103 and, if the inner skin 103 was in direct contact with the outer skin 104 (e.g., without the layer 108 being present), this heat would be conducted to the outer skin 104. By providing the layer 108 between the opposing contact surface portion 107 and the outer skin 104, heat conduction is reduced and so this reduces or eliminates discolouration or staining of the outer skin 104 in the vicinity of the baffle 101, whilst still maintaining indirect contact between the opposing contact surface portion 107 of the inner skin 103 and the outer skin 104, thereby providing stability of the inner skin 103 in the vicinity of the baffle 101. Whilst this example has been described with reference to one baffle 101, it will be appreciated that the same construction could apply to any number of baffles in the muffler 100. Referring now to Figures 4-6, there is shown another example of an exhaust muffler 200. The exhaust muffler 200 of this example is similar to the exhaust muffler 100 of the previous example, and similar feature are denoted with a leading ‘2’ instead of a leading ‘1 ’. The exhaust muffler 200 of this example differs from that of the previous example in that the insulating gap is provided by an airgap 208 instead of a layer 108. In this example the airgap has a thickness of greater than 5 mm and less than 10 mm. However, it will be appreciated that the air gap 208 thickness may be designed for specific heat transfer properties. In this example the airgap 208 has a substantially consistent gap around the perimeter of the muffler 200, but it will be appreciated that the air gap 208 may vary in thickness in other examples. As in the previous example, the outer skin 204 is provided by two parts connected together at seams 209 which extend along an axial direction of the muffler 200, in what may be referred to as a ‘clam shell’ construction. The inner skin 203 is fixed to the outer skin 204 along the seams and at axial ends of the inner skin 203. In this example, heat conduction may be eliminated due to the air gap, to reduce or eliminate discolouration or staining of the outer skin 204 in the vicinity of the baffle 201. This solution is usable where indirect contact between the opposing contact surface portion 207 of the inner skin 203 and the outer skin 204 may be omitted, for example because the inner skin 203 has sufficient stability in the vicinity of the baffle 201. Referring now to Figure 7, the vehicle 400 is shown, comprising the exhaust system 300 which comprises one of the exhaust mufflers 100, 200 described above. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. An exhaust muffler for a vehicle, the muffler comprising:a baffle which divides an internal volume of the muffler;an outer skin; andan inner skin located inside of the outer skin and at least partially surrounding the baffle, the inner skin at least partially defining the inner volume of the muffler, the inner skin comprising:a contact surface portion on an inner surface of the inner skin, the contact surface portion being in contact with a peripheral portion of the baffle along a length of the peripheral portion of the baffle which is at least 3% of a total length of a periphery of the baffle; andan opposing contact surface portion located on an outer surface of the inner skin, the opposing contact surface portion being directly opposite to the contact surface portion;wherein the opposing contact surface portion of the inner skin is separated from the outer skin to provide an insulating gap.

2. An exhaust muffler according to claim 1, wherein the contact surface portion has a length along the periphery of the baffle which is at least 10% of a total length of the periphery of the baffle.

3. An exhaust muffler according to claim 1 or claim 2, wherein the contact surface portion of the inner skin is separated from the outer skin by an air gap.

4. An exhaust muffler according to claim 3, wherein a connection between the inner skin and the remainder of the muffler is at a periphery of the inner skin.

5. An exhaust muffler according to either of claim 3 or claim 4, wherein the air gap has a thickness of at least 5 mm.

6. An exhaust muffler according to claim 1 or claim 2, wherein the opposing contact surface portion of the inner skin is separated from the outer skin by a layer having a thermal conductivity which is less than the thermal conductivity of the opposing contact surface portion of the inner skin and less than the thermal conductivity of a portion of the outer skin nearest to the opposing contact surface portion.

7. An exhaust muffler according to claim 6, wherein the layer comprises polycrystalline fibres.

8. An exhaust muffler according to either of claim 6 or 7, comprising a condensate passage extendingin an axial direction of the muffler, across the contact surface portion, the inner skin being spaced from the outer skin at the condensate passage.

9. An exhaust muffler according to any preceding claim, wherein the muffler has a height direction corresponding to a vertical direction when in use on a vehicle and a width direction corresponding to a horizontal direction when in use on a vehicle, such that the height and width directions define a firstlower quadrant and a second lower quadrant of the muffler, and a first upper quadrant and a second upper quadrant of the muffler, the first upper quadrant being adjacent the first lower quadrant, wherein the opposing contact surface portion extends across at least part of a circumferential direction of the first lower quadrant and / or the first upper quadrant.

10. An exhaust muffler according to claim 9, wherein the opposing contact surface portion extends across at least part of a circumferential direction of the first lower quadrant.

11. An exhaust muffler according to either of claim 9 or claim 10, wherein the opposing contact surface portion extends across all of the circumferential direction of the first lower quadrant.

12. An exhaust muffler according to any preceding claim, wherein the opposing contact surface portion extends around a central axis of the muffler from at least 70° up to 270°, where 0° corresponds to a vertical direction when the muffler is in use on a vehicle and where the central axis extends along the axial direction of the muffler.

13. An exhaust system comprising the exhaust muffler of any preceding claim.

14. A vehicle comprising the exhaust system of claim 13 or an exhaust muffler according to any of claims 1 to 12.