GB2572645A

GB2572645A - An attenuator for a fluid duct

Info

Publication number: GB2572645A
Application number: GB1805787.7A
Authority: GB
Inventors: Reucroft Laurence; John Mitchley Stephen
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2018-04-06
Filing date: 2018-04-06
Publication date: 2019-10-09
Anticipated expiration: 2038-04-06
Also published as: GB201805787D0; GB2572645B

Abstract

An attenuator 100 comprises a fluid duct 110, surrounded by an enclosure 120 with end walls 126 to form a chamber 140. A plurality of walls 132, 134 extend between the fluid duct and the enclosure to form a plurality of channels (142, 144, fig 3a). The fluid duct has a perforation 130 providing fluid communication between the fluid duct and a first channel (142, fig 3a). One of the plurality of walls has a port providing fluid communication between the first channel and a second channel (144, fig 3a). The port and the perforation are at substantially opposite ends of the attenuator. A motor vehicle exhaust system and a motor vehicle comprise the attenuator. A method of manufacturing an attenuator comprises stamping a sheet to produce a slot, folding the sheet to define walls, bending the sheet about a mandrel, joining edges of the sheet to form a fluid duct where a plurality of axially extending walls are provided on an outer surface of the fluid duct, providing an enclosure and end walls, and arranging the enclosure to surround at least a portion of the fluid duct to define a plurality of axially extending channels.

Description

The present invention relates to an attenuator for a fluid duct and particularly, but not exclusively, the air exhaust duct of an internal combustion engine of a vehicle. Aspects of the invention relate to an attenuator, to a method of manufacturing an attenuator, to a motor vehicle exhaust system and to a motor vehicle.

BACKGROUND

Vehicle engines require an exhaust duct to remove combustion gases from the engine. The size, shape and routing of this duct is determined by the maximum engine air flow requirement, and by space and packaging requirements for other vehicle equipment.

Air flow confined in the exhaust duct tends to generate noise and may also generate vibration of the vehicle structure via mountings of the duct. The frequency range of such noise and vibration tends to be restricted to relatively low frequencies, and at certain frequencies the air in the duct and/or the duct itself may resonate so as to amplify noise and vibration.

Noise and vibration associated with the exhaust duct can be noticeable to occupants of the vehicle, and it would be desirable to provide attenuation. Insulation and muffling provide one possible solution, but the increase in overall duct size may be difficult to accommodate in a congested vehicle architecture. Furthermore it may be impossible to insulate the duct over the entire length thereof.

Attenuators are used on fluid ducts so as to reduce or cancel unwanted noises. One such example are exhaust resonators. Exhaust resonators are used for reducing the amount of noise emitted by the exhaust system of an internal combustion engine (see W02004029561 for an example).

What is required is a compact device for attenuating noise and vibration over a targeted frequency band, which is economical to manufacture, and which can fit with the vehicle architecture. Furthermore this compact device should be able to be tuned without substantial change of overall size and position within the engine bay.

The present invention aims to address one or more of the above problems.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an attenuator, a method of manufacturing an attenuator, a motor vehicle exhaust system and a motor vehicle as claimed in the appended claims.

According to an aspect of the invention, there is provided an attenuator for a fluid comprising a fluid duct having an outer surface, an enclosure having an inner surface and which surrounds at least a portion of the fluid duct, a plurality of walls extending between the outer surface of the fluid duct and the inner surface of the enclosure, and respective end walls at either end of the enclosure. The outer surface of the fluid duct, the inner surface of the enclosure, the plurality of walls and the respective end walls define a chamber comprising a plurality of channels. The fluid duct has at least one perforation and one of the plurality of walls has a port. The at least one perforation provides direct fluid communication between the fluid duct and a first channel of the chamber and the port provides direct fluid communication between the first channel and a second channel of the chamber. The port and the perforation are arranged at substantially opposite ends of the attenuator.

The channels preferably extend linearly along the outside of the fluid duct, in a direction parallel to the longitudinal axis of the fluid duct. However, it will be appreciated that the channels could be angled with respect to the longitudinal axis of the fluid duct, and/or could follow a curved path to spiral or part-spiral around the fluid duct.

An acoustic transmission line is essentially a duct which acts as a guide for sound waves and is used to transmit sound from one end of the duct to the other. The length of an acoustic transmission line is tuned according to the wavelength of the sound to be transmitted. In use, the air contained in the chamber resonates at its natural frequency. The chamber is tuned, i.e. its length, volume etc. is selected, so that the natural frequency of the air contained in the chamber is such that is cancels out the frequency of the noise in the exhaust gas which is required to be cancelled.

For a given wavelength to be cancelled, an overall shorter resonator is required compared with a conventional single resonator chamber. This means that the resonator can be packaged within a smaller space within a vehicle. For example, in use, the exhaust gas pulse enters the chamber via the perforation only on one side, the pulse travels down one side of the fluid duct (i.e. in the first channel), and transfers across to the second channel via the first port, travels along the other side of the fluid duct (i.e. in the second channel), hits the end wall and bounces back. This allows the available packing space to be halved.

The fluid duct may have n walls to define n channels, where n is greater than 2.

N-1 of the n walls may be provided with a port.

The walls may extend axially so as to define a plurality of axially extending channels.

Adjacent walls provided with a port may be provided with a port at opposite ends of the attenuator.

The port may be provided adjacent to one of the respective end walls.

In embodiments of the invention in which n-1 of the n walls are provided with a port, the ports may be provided adjacent to one of the respective end walls.

At least a first port of the ports may comprise a slot in an end of one of the plurality of extending walls.

N may be an integer between 3 and 15. N may be an integer between 3 and 5.

The at least one perforation may comprises a single perforation. The single perforation may comprise an elongate slot.

The at least one perforation may comprise a group of perforations aligned with the first channel.

The enclosure may fully encircle the fluid duct or the enclosure may only partially encircle the fluid duct.

The plurality of walls may be provided on or formed from the outer surface of the fluid duct, and the inner surface of the enclosure may abut the plurality of walls.

According to another aspect of the invention, there is provided a method of manufacturing an attenuator for a fluid duct comprising: providing a sheet having a first edge, and an opposite, second edge; stamping the sheet along the first edge and second edge to produce a plurality of slots; folding the sheet three times in the region of the slot along lines extending between the first edge and the second edge so as to define a wall extending between the first edge and the second edge, the slot defining a port in the wall; forming a further wall, not having a port, extending between the first edge and the second edge; bending the sheet about a mandrel; joining the edges extending perpendicularly to the first edge and the second edge to form a fluid duct wherein the plurality of axially extending walls are provided on an outer surface of the fluid duct;

providing an enclosure having an inner surface and providing respective end walls; and arranging the enclosure to surround at least a portion of the pipe so that inner surface of the enclosure abuts the plurality of axially extending walls thereby defining, along with the respective end walls, a plurality of axially extending channels between the enclosure and the pipe.

The pipe may be perforated to provide at least one perforation, and the pipe and the enclosure may be rotationally aligned so that at least one perforation is in direct fluid communication with a single axially extending channel.

The first edge may be joined to second edge by a spot weld.

According to yet another aspect of the invention, there is provided a motor vehicle exhaust system comprising: an attenuator as hereinbefore described, wherein the fluid duct is an exhaust pipe.

According to another aspect of the invention, there is provided a motor vehicle comprising the attenuator as hereinbefore described.

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 4 features of any embodiment can be combined in any way 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 is a side elevation of a motor vehicle;

Figure 2 is a schematic cross sectional view of the attenuator of the present invention;

Figure 3a is a schematic section view of the attenuator of Figure 2 taken at line A-A;

Figure 3b is a schematic section view of an alternative attenuator of the present invention; and

Figure 4 is a flow diagram of the method steps for manufacturing an attenuator for a fluid duct.

DETAILED DESCRIPTION

A motor vehicle 50 is provided with a bonnet 60 arranged at a front end of the motor vehicle 50, and an underside 70 extending between the front end and a rear end of the motor vehicle 50. An engine (not shown in Figure 1) is housed under the bonnet 60. An exhaust system 80 connects the engine to an exhaust outlet 90 adjacent the rear end of the motor vehicle 50. The exhaust system 80 extends in part along the underside 70.

Referring to Figures 2 and 3a, the attenuator 100 comprises a fluid duct 110 and an enclosure 120.

The fluid duct 110 is cylindrical pipe 111. The pipe 111 has an inner surface 112 and an outer surface 113, an inlet 114 and an outlet 116. The pipe 111 has longitudinal axis 118 which extends between the inlet 114 and the outlet 116.

A plurality of walls are provided on, and extend outwardly from, the outer surface 113 of the fluid duct 110. A first wall 132 extends radially, and for a portion of the axial length of the pipe 111. A second wall 134 also extends radially, and for the same portion of the axial length of the pipe 111. The second wall 134 is provided with a port 150. The port 150 is located at an end of the second wall 134 proximate the inlet 114.

The pipe 111 is provided with a perforation 130. The perforation is located adjacent the end of the first wall 132 proximate the outlet 116. In an alternate embodiment, a plurality of perforations are provided. In yet a further alternate embodiment, the perforation 130 comprises an elongate slot.

The enclosure 120 has a cylindrical wall 121 having an inner surface 122 and an outer surface 123. The enclosure 120 further has a first annular end wall 126 and a second annular end wall 128.

The first annular end wall 126 is arranged proximate the inlet 114 and the second annular end wall 128 is arranged proximate the outlet 116. The enclosure 120 is arranged to surround at least a portion of the fluid duct 110 so that the inner surface 122 of the enclosure abuts the plurality of walls 132, 134 and the respective end walls 126, 128 thereby defining a chamber 140 between the enclosure 120 and the fluid duct 110. The enclosure 120 is fluidly sealed relative to the pipe 111.

The chamber 140 comprises a plurality of channels 142, 144. Namely a first channel 142 and a second channel 144.

The perforation 130 provides fluid communication between the pipe 111 and the chamber 140. The perforation 130 is provided adjacent the second annular end wall 128 and provides direct fluid communication into the first channel 142. The first channel 142 has direct fluid communication with the second channel 144 via the port 150 which is provided adjacent the first annular end wall 126. The port 150 and the perforation 130 are thereby arranged at substantially opposite ends of the attenuator 100. Therefore, a transmission line is set up in the chamber 140 which extends from the perforation 130, towards the first annular end wall 126, through the port 150 and back towards the second annular end wall 128.

The distance between the perforation 130 and first annular end wall 126 of the enclosure 120 is L. The distance between the first annular end wall 126 and the second annular end wall 128 is M. This arrangement provides an acoustic transmission line of length L+M within the chamber 140.

The enclosure 120 is arranged co-axially with the pipe 111 and surrounds the pipe 111. The enclosure 120 thus fully encircles the fluid duct 110. In an alternate embodiment, as shown in figure 3b, the enclosure 120 only partially encircles the fluid duct 110. In such an arrangement, a third wall 136 is provided on the outer surface 113 of the fluid duct 110 so as to define the chamber 140.

The fluid duct 110 is arranged to receive exhaust gases from an engine of a vehicle 50 as part of a vehicle exhaust system 80. The attenuator 100 is positioned, for example on the underside 70 of the vehicle so that the fluid duct 110 is the exhaust pipe 111 of the exhaust system 80.

In a further embodiment, the fluid duct 110 is provided with n walls to on the outer surface 113 of the fluid duct 110. The n walls define n channels, where n is greater than 2. N may be an integer between 3 and 15. N may be an integer between 3 and 5. N-1 of the n walls are provided with a port. The n walls extend axially so as to form n axially extending channels. Adjacent walls provided with a port 150 are provided with a port 150 at opposite ends of the attenuator 100. The ports are provided adjacent to the respective end walls. The perforation 130 may comprise a group of perforations aligned with the first channel 142.

Referring to Figure 4, a method of manufacturing an attenuator for a fluid duct is described. The attenuator may be the same as the attenuator described with respect to Figures 2 and 3, but equally may include the further features described in the immediately preceding paragraph.

The method has the following steps:

Providing a sheet having a first edge, and an opposite, second edge; (S1)

Stamping the sheet along the first edge and second edge to produce a plurality of slots; (S2) Folding the sheet three times in the region of each slot along lines extending between the first edge and the second edge so as to form a sheet with a plurality of axially extending walls, each wall defining a port 150; (S3)

Forming a further axially extending wall in the sheet in a further region not having a slot; (S4) Bending the sheet about a mandrel; (S5)

Joining the edges extending perpendicularly to the first edge and the second edge to form a pipe wherein the plurality of axially extending walls are provided on an outer surface of the pipe; (S6)

Providing an enclosure having an inner surface and respective end walls; and (S7)

Arranging the enclosure to surround at least a portion of the pipe so that inner surface of the enclosure abuts the plurality of axially extending walls thereby defining a plurality of axially extending channels between the enclosure and the pipe. (S8)

The sheet may be made of metal.

The method may include the further steps:

The pipe 111 may be perforated to provide at least one perforation 130, and the pipe 111 and the enclosure 120 are rotationally aligned so that at least one perforation 130 is in direct fluid communication with a single axially extending channel.

The edges extending perpendicularly to the first edge and the second edge are joined by a spot weld.

When folding the sheet three times in the region of each slot along lines extending between the first edge and the second edge so as to form a sheet with a plurality of axially extending walls, each wall defining a port 150; (S3), the three folds 200 may be made with each fold line extending between the first edge and the second edge of the sheet, with one fold line extending along a central axis of the slot and the other two fold lines extending along the periphery of the slot. This is shown in Figure 5.

The wall not defining a port can be formed by folding one or both of the edges of the sheet extending perpendicularly to the first edge and the second edge, and then bonding the surfaces provided by these folds, or by folding the sheet along three further fold lines extending between the first edge and second edge.

It will be appreciated that although Figure 4 illustrates a particular order to the steps of a method, this does not necessarily imply that there is a required or preferred order for the steps and the order and arrangement of the steps may be varied.

In an alternate arrangement, the fluid duct 110 is arranged to receive gases on an engine air intake path of a vehicle 50.

Claims

1. An attenuator for a fluid comprising:

a fluid duct having an outer surface;

an enclosure having an inner surface and which surrounds at least a portion of the fluid duct;

a plurality of walls extending between the outer surface of the fluid duct and the inner surface of the enclosure; and respective end walls at either end of the enclosure; wherein the outer surface of the fluid duct, the inner surface of the enclosure, the plurality of walls and the respective end walls define a chamber comprising a plurality of channels; wherein the fluid duct has at least one perforation and one of the plurality of walls has a port; wherein the at least one perforation provides direct fluid communication between the fluid duct and a first channel of the chamber and the port provides direct fluid communication between the first channel and a second channel of the chamber; and wherein the port and the perforation are arranged at substantially opposite ends of the attenuator.

2. The attenuator according to claim 1, wherein the port comprises a slot in the corresponding one of the plurality of walls.

3. The attenuator according to claim 1 or claim 2, wherein the plurality of walls is n walls which define n channels, where n is greater than 2.

4. The attenuator according to claim 3, wherein n-1 of the n walls are provided with a port.

5. The attenuator according to any of claims 1 to 4, wherein the walls extend axially so as to define a plurality of axially extending channels.

6. The attenuator according to claim 4 or claim 5 when dependent on claim 4, wherein adjacent walls provided with a port are provided with a port at opposite ends of the attenuator.

7. The attenuator according to any preceding claim, wherein a port is provided adjacent to one of the respective end walls.

8. The attenuator according to claim 4, wherein each port is provided adjacent to one of the respective end walls.

9. The attenuator according to claim 3, claim 4 or claim 8, wherein n is an integer between 3 and 15.

10. The attenuator according to claim 3, claim 4 or claim 8, wherein n is an integer between 3 and 5.

11. The attenuator according to any preceding claim, wherein the at least one perforation comprises a single perforation.

12. The attenuator according to claim 11, wherein the single perforation comprises an elongate slot.

13. The attenuator according to any of claims 1 to 10, wherein the at least one perforation comprises a group of perforations aligned with the first channel.

14. The attenuator according to any preceding claim, wherein the enclosure fully encircles the fluid duct.

15. The attenuator according to any of claims 1 to 13, wherein the enclosure only partially encircles the fluid duct.

16. The attenuator according to any preceding claim, wherein the plurality of walls are provided on or formed from the outer surface of the fluid duct, and the inner surface of the enclosure abuts the plurality of walls.

17. A method of manufacturing an attenuator for a fluid duct comprising:

providing a sheet having a first edge, and an opposite, second edge; stamping the sheet along the first edge or second edge to produce a slot;

folding the sheet three times in the region of the slot along lines extending between the first edge and the second edge so as to define a wall extending between the first edge and the second edge, the slot defining a port in the wall;

forming a further wall, not having a port, extending between the first edge and the second edge;

bending the sheet about a mandrel;

joining the edges extending perpendicularly to the first edge and the second edge to form a fluid duct wherein the plurality of axially extending walls are provided on an outer surface of the fluid duct;

providing an enclosure having an inner surface;

providing respective end walls; and arranging the enclosure to surround at least a portion of the pipe so that inner surface of the enclosure abuts the plurality of axially extending walls thereby defining, along with the respective end walls, a plurality of axially extending channels between the enclosure and the pipe.

18. The method of claim 17, wherein the pipe is perforated to provide at least one perforation, and the pipe and the enclosure are rotationally aligned so that at least one perforation is in direct fluid communication with a single axially extending channel.

19. The method of any of claims 17 or 18, wherein the edges extending perpendicularly to the first edge and the second edge are joined by a spot weld.

20. A motor vehicle exhaust system comprising the attenuator according to any of claims 1 to 16.

21. A motor vehicle comprising the attenuator according to any of claims 1 to 16.