US3645357A

US3645357A - Quarter-wave tuner structure

Info

Publication number: US3645357A
Application number: US65375A
Authority: US
Inventors: Thomas R Cassel
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-08-20
Filing date: 1970-08-20
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28

Abstract

A vehicle exhaust system is disclosed in which a soundattenuating device in the form of a quarter-wave tuner is incorporated within an exhaust gas pipe. A partition of sheetlike construction extends axially of the pipe over a predetermined length and extends transversely from wall to wall with its opposite edges in contact therewith to separate the space into first and second portions. In the tuner structure the length is approximately equal to one-fourth of the wavelength of the sound energy to be attenuated and the upstream end of the partition is located at a pressure point corresponding to the wavelength to be attenuated and the downstream end of the partition is closed. The pipe is formed with protuberances on the internal surface such as would result from indentations of the wall and the protuberances are arranged along the length of the pipe to retain the sheetlike partition in place in engagement with the wall of the pipe. This construction permits the location of the partition in an exhaust gas pipe to form a sound-attenuating structure in either a straight or curved section of the pipe so that the pipe and the attenuating structure may be fit into the available space under the vehicle body.

Description

United States Patent Cassel [54] QUARTER-WAVE TUNER STRUCTURE [72] lnventor: Thomas R. Cassel, 226 Shirley, Birmingham, Mich. 48009 [22] Filed: Aug. 20, 1970 [21] Appl. No.: 65,375

1 1 Feb. 29, 1972 Primary Examiner-Robert S. Ward, Jr. Attorney-McGlynn, Reising, Milton & Ethington [5 7] ABSTRACT A vehicle exhaust system is disclosed in which a sound-attenuating device in the form of a quarter-wave tuner is incorporated within an exhaust gas pipe. A partition of sheetlike construction extends axially of the pipe over a predetermined length and extends transversely from wall to wall with its opposite edges in contact therewith to separate the space into first and second portions. 1n the tuner structure the length is approximately equal to one-fourth of the wavelength of the sound energy to be attenuated and the upstream end of the partition is located at a pressure point corresponding to the wavelength to be attenuated and the downstream end of the partition is closed. The pipe is formed with protuberances on the internal surface such as would result from indentations of the wall and the protuberances are arranged along the length of the pipe to retain the sheetlike partition in place in engagement with the wall of the pipe. This construction permits the location of the partition in an exhaust gas pipe to form a sound-attenuating structure in either a straight or curved section of the pipe so that the pipe and the attenuating structure may be fit into the available space under the vehicle body.

14 Claims, 8 Drawing Figures PATENTED FEB 2 9 I972 SHEET 2 OF 2 IATTORN QUARTER-WAVE TUNER STRUCTURE This invention relates to sound-attenuating systems and, more particularly, vehicle exhaust systems provided with an acoustical quarter-wave tuner.

In certain automotive exhaust systems it has been a common practice to augment the sound attenuating properties of the conventional muffler or other silencing devices with acoustical quarter-wave tuners. As is well known, such tuners are typically constructed of a tube having one end closed and the other end open and in communication with the exhaust gas conduit or pipe, preferably at a pressure point for the wavelength of sound energy which is to be attenuated by the quarter-wave tuner. The tube of the tuner has a length which is approximately one-fourth the wavelength of the sound energy to be attenuated. A sound wave entering the open end of the tube from the exhaust gas pipe is reflected from the closed end and returns to the open end in phase opposition to the succeeding sound wave of the same frequency. Thus, the sound waves of the selected frequency are caused by the quarter-wave tuner to interfere with each other in a destructive sense which resultsin attenuation of the selected frequency. Such quarter-wave tuners produce a high degree of attenuation over a relatively narrow band of frequency and are especially useful for decreasing the sound level at the lower frequency range in the exhaust system of an automotive vehicle. It is also known that the attenuation bandwidth of an acoustical quarter wave tuner may be increased to produce a more desirable attenuation characteristic by providing a passage or opening of very limited extent in the closed end of the tube of the quarter-wave tuner.

The principle difficulties heretofore in the use of a quarterwave tuner, especially in automotive vehicle exhaust systems, arise from space requirements for accommodating the tube and the cost of incorporating the tube into the exhaust system. Generally, the quarter wave tuner has been attached as an appendage externally of the exhaust pipe or tailpipe and with the requirement for placement of the upstream end at a pressure point, there are sometimes difficulties in fitting the tube into the available space under the body of the vehicle. It has been proposed to place the tube of the quarter wave tuner inside the exhaust gas pipe, such as the tailpipe, but this also poses problems such as the reduction in the cross-sectional area of the exhaust gas pipe with resulting high back pressure in the exhaust system. Also, in many installations the exhaust gas pipes have several bends in them to fit into the available space under the vehicle body and a suitable placement of the upstream end of the quarter-wave tube is not available with a straight section long enough to accommodate the tube. In addition to these problems of space and location for a quarterwave tuner the cost of providing the additional tube and installation thereof has been a deterrent to widespread use. As mentioned above, the quarter-wave tuner has been heretofore constructed of a tube which is substantially closed at one end and connected, as by a suitable pipe fitting or welding, to the exhaust gas pipe at the other end and such construction produces a substantial cost factor.

In accordance with the present invention a sound-attenuating device such as a quarter-wave tuner for vehicle exhaust systems may be located at the appropriate pressure point in the exhaust gas pipe without requiring additional space under the vehicle body and is unusually economical in material and installation cost. This is accomplished by providing a partition in the exhaust gas pipe extending axially from one of the pressure points and having a length approximately equal to onefourth of the wavelength of the sound energy to be attenuated and producing the pressure point. The partition extends transversely from wall to wall of the exhaust gas pipe and has its opposite edges in contact therewith, thus separating the space Inside the pipe into first and second axially extending passages. The partition is formed so that it substantially closes the downstream end of the first passage and terminates adjacent the upstream end to form a mouth for the first passage thereby forming a quarter wave tuner. The second of the passages is open at both ends to accommodate the flow of the gas stream through the exhaust gas pipe. The partition is preferably of sheetlike construction such as a unitary sheet metal member extending from wall to wall thereby requiring a minimum of material and occupying a minimum of space in the exhaust gas pipe for a given cross section of the two passages. Further, the sheetlike partition may be disposed in the exhaust gas pipe in a configuration which provides an enlarged cross section at the mouth of the quarter-wave tuner and a reduced cross section downstream thereof so that a minimum impedance or obstruction is presented to the gas stream flowing through the adjacent passage in the exhaust gas pipe. Additionally, the sheetlike partition may be retained in position inside the exhaust gas pipe by deformations in the wall of the pipe thus avoiding the need for separate fasteners or welding to secure the partition in place. Such construction enables the insertion of the partition by sliding it in a frictional fit from either the upstream or the downstream end of the exhaust gas pipe. This construction affords the additional advantage of minimizing pop-down noises which occur upon cooling of the parts after operation. Furthermore, by reason of the sheetlike construction of the partition the quarter wave tuner may be located in either a straight section of exhaust gas pipe or a curved section thereof, the partition being inserted in the pipe either before or after bending of the pipe with the plane of the partition normal to the direction of the bend in the pipe.

A more complete understanding of the invention and the advantages thereof may be obtained from the detailed description that follows taken with the accompanying drawings in which:

FIG. 1 is a side elevation view of an automotive vehicle exhaust system including the inventive quarter-wave tuner;

FIG. 2 is an enlarged view of a portion of an exhaust gas pipe including the quarter-wave tuner;

FIG. 3 is a view taken on line 33 of FIG. 2;

FIG. 4 is a view taken on lines 44 of FIG. 2;

FIG. 5 shows a modification of the structure of the quarterwave tuner in an exhaust gas pipe;

FIG. 6 is a view taken on lines 6-6 of FIG. 5;

FIG. 7 is a view taken on lines 77 of FIG. 5; and

FIG. 8 shows an embodiment of the quarter-wave tuner in a curved section of an exhaust gas pipe.

Referring now to the drawings, there is shown an illustrative embodiment of the invention in the exhaust system of an automotive vehicle. The vehicle is provided with an engine 10 which includes an exhaust manifold 12 from which the exhaust gases must be conveyed to the rear of the vehicle for discharge to the atmosphere. For this purpose the exhaust system includes an exhaust pipe 14 which extends downwardly to a point below the vehicle body and thence rearwardly of the body to a muffler I6 which attenuates the sound level of the exhaust gases. The downstream end of the mufiler 16 is connected to the tailpipe 18 which extends rearwardly through a configuration required to clear the underbody of the vehicle to a point at the rear thereof for discharge of the exhaust gases to the atmosphere. In order to augment the sound attenuation provided by the muffler 16 the exhaust system is also provided with a quarter-wave tuner 20 in accordance with the present invention.

As is well known, the flow of engine exhaust gas through the exhaust gas system just described is accompanied with sound energy which creates sound pressure points along the length of the exhaust gas pipes including the exhaust pipe 14 and the tailpipe 18. In order to provide for attenuation of a selected band of sound wave frequencies the quarter-wave tuner 20 is provided with a length properly related to the wavelength of the selected frequencies and a location properly related to one of the pressure points corresponding to the frequency of the sound energy that is to be attenuated, as will be described in more detail subsequently.

Referring now to FIG. 2 which shows the quarter-wave tuner in greater detail, it is noted that the tuner is incorporated in a straight section of the tailpipe 18. The tuner is formed by a partition 22 of sheetlike construction suitably of preformed sheet metal, such as a conventional cold rolled steel as is commonly used in the construction of exhaust system components such as mufflers and the like. The partition 22 extends axially of the tailpipe from an upstream end 24 which defines the open end or mouth of the tuner tube or passage 26. It is noted that the partition 22 extends transversely of the pipe 18 from wall to wall thereof throughout its length and is provided with depending

flanges

28 and 30 in engagement with the wall of the pipe 18. The partition terminates at the downstream end 32 in a transversely extending closure or tab 34 which is suitably an integral part of the partition 22. The length of the partition 22 from the mouth at the upstream end 24 to the closure 34 at the downstream end 32 is approximately equal to one-fourth of the wavelength of the sound wave energy which is to be attenuated by the tuner and the mouth of the passage 26 defined thereby is located at a pressure point corresponding to such wavelength. In order to retain the partition in place the wall of the pipe 18 is provided with a pair of oppositely disposed axially extending grooves or indentations 36 which protrude inwardly to form a radial shoulder extending axially of the pipe. As shown in FIGS. 3 and 4 the opposite edges of the partition 22 are disposed in engagement with the radial shoulders to retain the partition against lateral motion in the pipe. The indentations 36 and 38 are suitably formed by forming rolls during the bending and sizing operation performed on the tailpipe 18. The partition 22 is of such width that it may be inserted into the tailpipe 18 by axial sliding motion with frictional fit against the walls thereof by the

flanges

28 and 30 so that the partition is restrained by friction against axial motion. It is noted that the partition 22 divides the space in the pipe 18 into the closed-end tuner passage 26 and into a throughpassage 40 which is open at both ends and adapted to conduct the exhaust gases therethrough for discharge to the atmosphere.

In certain installations it may be desirable to minimize the back pressure effect resulting from the presence of the closedend tuner passage 26 and at the same time provide an adequate cross-sectional area at the mouth thereof for the intake of sound energy in the exhaust gas. For this purpose the indentations 36 extend somewhat obliquely of the axis of the pipe 18 and the partition 22 seated against the shoulders thereof also extends throughout its length obliquelyof the pipe axis. This relationship is illustrated in FIGS. 3 and 4 wherein it is noted at the partition 22 at the upstream end is located at the centerline of the pipe 18 whereas at the downstream end the partition 22 is located below the centerline of the pipe 18, thus providing a greater cross-sectional area of the tuner passage 26 at the mouth than at the closed end. This correspondingly provides an increasing cross-sectional area of the through-passage 40 in the direction of the flow of the'exhaust gases sothat the impedance or obstruction to gas flow presented by the partition 22 diminishes as the distance therealong increases.

Another embodiment which tends to minimize the back pressure created by the quarter wave tuner structure is illustrated in FIGS. 5, 6 and 7. In this embodiment it is noted that the indentations 44 extend parallel to the axis of the pipe 18 and thus the partition 22', which is seated on the shoulders of the indentations, also extends parallel to the pipe axis throughout substantially all of its length. However, the partition 22' is provided with an upstream end 24 which is bent out of the plane of the partition 22' and provided with arcuate cross section so that the mouth of the tuner passage 26' is of enlarged cross-sectional area. A corresponding reduction in the cross-sectional area of the through-passage 40' extends over only'a small axial length and hence the increased back pressure to the gas fiow is minimized.

In certain installations it may be necessary or desirable to locate the quarter-wave tuner in a section of the exhaust gas pipe which is bent in order to conform to the available space of the underbody of the vehicle. Such an installation is illustrated in FIG. 8 wherein the tailpipe 18 is 'provide with a bend in the vertical plane to provide clearance for the rear axle of the vehicle. In this embodiment the tailpipe 18 is provided with axial grooves or indentations 50 which extend parallel to the centerline or axis of the pipe although it will be apparent that the indentation may extend obliquely as described with reference to FIG. 2. The partition 22 is of the same construction as described with reference to FIG. 2 except that the flanges thereof are preferably provided with a plurality of notches 52 at spaced intervals so that the partition may be more readily bent in a direction normal to the plane thereof. Although the bending of the pipe 18 may be accomplished prior to the insertion of the partition 22", it will be appreciated that the partition may be first positioned in the pipe 18 and then the bending operation may be performed on both members at once, it being noted that in either case the bend of the pipe and the partition is in a direction perpendicular to the plane of the partition. It will also be noted that the plane of the partition in the embodiment of FIG. 8 as well as in the embodiments of FIGS. 2 and 5 may be disposed in a vertical plane or in any plane intermediate the vertical and horizontal directions.

It is noted that the tab or closure 34 of the partition 22 which forms the closed end of the tuner passage 26 may not closely engage the wall of the pipe and hence an opening or space may exist which will leak exhaust gases therethrough. If the fit of the closure 34 is such that the area of the opening in relation to the cross-sectional area of the passage 26 is small, for example less than 10 percent, the lack of sealing engagement is quite acceptable. In fact, in many installations such an opening in the closed end of the tuner passage is desirable because it has the effect of broadening the bandwidth of the frequencies which are attenuated by the quarter wave tuner.

Although the description of this invention has been given with reference to a particular embodiment thereof, it is not to be construed in a limiting sense. Many variations and modifications will now occur to those skilled in the art. For a definition of the invention reference is made to the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. For use in a sound attenuating system, a pipe adapted to be connected with a gas stream and a source of sound energy producing a plurality of pressure points therein, an edgebounded sheetlike partition extending axially of said pipe from one of said pressure points and having a length approximately equal to one-fourth the wavelength of the sound energy producing the pressure point, said partition extending transversely from wall to wall of said pipe and having its opposite edges in contact therewith and separating the space inside said pipe into first and second axially extending passages, said partition defining a terminal end portion substantially closing the first of said passages at one end and defining an inlet portion of the first of said passages at the other end thereby forming a quarter-wave tuner, said partition being of planar configuration between said portions and the other of said passages being open at both ends for the flow of said gas stream therethrough.

2. The invention as defined in claim 1 wherein said partition is a unitary sheet of metal with the edges thereof in slidable frictional engagement with said pipe.

3. The invention as defined in claim 2 wherein the wall of said pipe is provided with indentations adjacent the edges of said partition to retain it in place.

4. The invention as defined in claim 1 wherein the mouth of said first passage opens in the upstream direction of said gas fiow, said pipe is of unifonn cross section and said partition has a laterally offset portion adjacent the mouth of the first passage so that the cross-sectional area of said mouth is greater than the downstream portion of said first passage.

5. For use in a vehicle exhaust system for attenuating selected sound frequencies, a pipe of circular cross section adapted to be connected with the exhaust manifold of the vehicle engine whereby the sound energy produced thereby produces a plurality of pressure points in said pipe, a sheetlike partition extending axially of said pipe from one of said pressure points and having a length approximately equal to onefourth the wavelength of the sound energy producing the pressure point, said partition extending transversely from wall to wall of said pipe having its opposite edges in contact therewith and separating the space inside said pipe into first and second axially extending passages, said partition having a terminal end portion extending laterally of said pipe and substantially closing the downstream end of said first passage and having an inlet portion at the other end of said first passage thereby forming a quarter-wave tuner, said partition being substantially flat between said portions, and said second passage being open at both ends to accommodate the flow of said gas stream therethrough.

6. The invention as defined in claim 5 wherein said pipe is formed with oppositely disposed, axially extending indentations to retain said sheetlike partition in place.

7. The invention as defined in claim 6 wherein said partition is slidable engaged with the wall of said pipe and is restrained against axial motion by frictional engagement therewith.

8. The invention as defined in claim 6 wherein said sheetlike partition includes a flange at each edge.

9. The invention as defined in claim 5 wherein said pipe and said partition are curved in a plane perpendicular to the plane of said partition.

10. The invention as defined in claim 5 wherein said platelike partition extends obliquely of the axis of said pipe over a portion thereof so that the mouth of said first passage is of larger cross-sectional area than the remainder of said portion.

11. The invention as defined in claim 5 wherein the edges of said platelike partition extend parallel to the axis of said pipe, the partition being formed adjacent the mouth of said first passage to provide a greater cross-sectional area at the mouth than at the remainder of said first passage.

12. For use in a vehicle exhaust system, a pipe adapted to be connected with the exhaust manifold of the vehicle engine for conducting exhaust gases to a discharge point, sound attenuating means including a sheetlike partition extending axially of said pipe over a predetermined length and extending transversely from wall to wall of said pipe, said partition terminating in side edges in contact with the wall of said pipe and separating the space inside said pipe into first and second portions, said partition closing the first of said portions at least at one end thereof, said pipe being provided with protuberances being arranged along the length of said pipe to retain said sheetlike partition in place.

13. The invention as defined in claim 12 wherein said partition is slidable engaged with the wall of said pipe with each edge disposed in the concave portion of said wall adjacent the respective protuberance whereby the partition is restrained thereby against transverse motion is restrained against axial motion by frictional engagement with said wall.

14. The invention as defined in claim 13 wherein said pipe and said partition are curved in a plane substantially perpendicular to the plane of said partition.

Claims

1. For use in a sound attenuating system, a pipe adapted to be connected with a gas stream and a source of sound energy producing a plurality of pressure points therein, an edge-bounded sheetlike partition extending axially of said pipe from one of said pressure points and having a length approximately equal to one-fourth the wavelength of the sound energy producing the pressure point, said partition extending transversely from wall to wall of said pipe and having its opposite edges in contact therewith and separating the space inside said pipe into first and second axially extending passages, said partition defining a terminal end portion substantially closing the first of said passages at one end and defining an inlet portion of the first of said passages at the other end thereby forming a quarter-wave tuner, said partition being of planar configuration between said portions and the other of said passages being open at both ends for the flow of said gas stream therethrough.

4. The invention as defined in claim 1 wherein the mouth of said first passage opens in the upstream direction of said gas flow, said pipe is of uniform cross section and said partition has a laterally offset portion adjacent the mouth of the first passage so that the cross-sectional area of said mouth is greater than the downstream portion of said first passage.

5. For use in a vehicle exhaust system for attenuating selected sound frequencies, a pipe of circular cross section adapted to be connected with the exhaust manifold of the vehicle engine whereby the sound energy produced thereby produces a plurality of pressure points in said pipe, a sheetlike partition extending axially of said pipe from one of said pressure points and having a length approximately equal to one-fourth the wavelength of the sound energy producing the pressure point, said partition extending transversely from wall to wall of said pipe having its opposite edges in contact therewith and separating the space inside said pipe into first and second axially extending passages, said partition having a terminal end portion extending laterally of said pipe and substantially closing the downstream end of said first passage and having an inlet portion at the other end of said first passage thereby forming a quarter-wave tuner, said partition being substantially flat between said portions, and said second passage being open at both ends to accommodate the flow of said gas stream therethrough.