Muffler for an exhaust system of an internal combustion engine

Abstract

A muffler for an exhaust system of an internal combustion engine, comprises a housing comprising a shell having an inner wall, an inlet pipe and an outlet pipe, the inlet pipe and the outlet pipe extending into an inner space of the housing, for conveying an exhaust gas stream into and out of the inner space of the housing, at least one baffle arranged in the inner space of the housing, the baffle comprising a baffle plate, the baffle plate having a circumference, and a baffle lip arranged at the circumference of the baffle plate, the baffle lip engaging the inner wall of the shell and having an end portion, wherein the end portion of the baffle lip is curved inwardly away from the inner wall of the shell.

Claims

1. A muffler for an exhaust system of an internal combustion engine, comprising: a housing comprising a shell having an inner wall, an inlet pipe and an outlet pipe, the inlet pipe and the outlet pipe extending into an inner space of the housing, for conveying an exhaust gas stream into and out of the inner space of the housing, at least one baffle arranged in the inner space of the housing and made of at least one metal sheet, the baffle comprising a baffle plate having a circumference, a curved connection portion and a baffle lip arranged at the circumference of the baffle plate and being connected to the baffle plate through the curved connection portion, the baffle lip engaging the inner wall of the shell and having an end portion, wherein the end portion of the baffle lip is curved inwardly away from the inner wall of the shell and the inwardly curved end portion of the baffle lip has a tip, the baffle lip having a contact portion which is in contact with the inner wall of the shell, the contact portion being arranged between the curved connection portion and the inwardly curved end portion of the baffle lip, and wherein the inwardly curved end portion has a curvature angle varying along the circumference of the baffle plate, the curvature angle being formed between a tangent to a metal sheet face of the contact portion engaging the inner wall of the shell and a tangent to the inwardly curved end portion of the baffle lip at the tip of the inwardly curved end portion on the same metal sheet face being in contact with the inner wall of the shell at the contact portion.

2. The muffler according to claim 1, wherein the contact portion has a contact portion length (L), and wherein the contact portion length (L) varies along the circumference of the baffle plate.

3. The muffler according to claim 1, wherein the baffle lip has a developed length ranging from the curved connection portion to the tip of the inwardly curved end portion of the baffle lip and the variation of the developed length is less than 10 mm, particularly less than 5 mm, very particularly less than 2 mm, around the circumference of the baffle plate.

4. The muffler according to claim 3, wherein the developed length of the baffle lip is constant around the circumference of the baffle plate.

5. The muffler according to claim 1, wherein the curvature angle of the inwardly curved end portion is reduced with decreasing contact portion bending radius along the circumference of the baffle plate.

6. The muffler according to claim 1, wherein the length of the contact portion of the baffle lip is reduced with increasing curvature angle of the inwardly curved end portion.

7. The muffler according to claim 1, wherein the inwardly curved end portion of the baffle lip can be described by at least one osculating circle having a radius of curvature corresponding to the curvature of the inwardly curved end portion at a location on the inwardly curved end portion and wherein the radius of curvature of the at least one osculating circle varies along the circumference of the baffle plate.

8. The muffler according to claim 1, wherein the curved connection portion can be described by at least one osculating circle having a radius of curvature corresponding to the curvature of the curved connection portion at a location on the curved connection portion wherein the radius of curvature of the at least one osculating circle varies along the circumference of the baffle plate.

9. The muffler according to claim 1, wherein the inwardly curved end portion of the baffle lip has a tip which is arranged at a distance (d) from the inner wall of the shell, the distance (d) being at least 0.5 times the total thickness (t) of the baffle.

10. The muffler according to claim 1, wherein the contact portion of the baffle lip has a length in the range of up to 10 mm, particularly of from 5 mm to 10 mm.

11. The muffler according to claim 1, wherein the baffle plate further comprises stiffening sections.

12. The muffler according to claim 1, wherein the baffle plate has perforations.

13. The muffler according to claim 1, wherein the baffle plate has at least one orifice, the at least one orifice receiving the inlet pipe or the outlet pipe.

14. The muffler according to claim 1, wherein the baffle comprises a first and a second baffle element, each of the first and second baffle elements comprising a baffle plate element having a respective circumference and the baffle plate element of the first baffle element abutting the baffle plate element of the second baffle element, and each baffle plate element having a baffle lip element arranged at the circumference of each respective baffle plate element, each of the baffle lip element engaging the inner wall of the shell and having an end portion element, wherein the end portion element of each baffle lip element is curved inwardly away from the inner wall of the shell and wherein the baffle lip element of the baffle plate element of the first baffle element is arranged in opposite direction to the baffle lip element of the baffle plate element of the second baffle element with respect to the plane formed by the baffle plate elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a vertical sectional view of one embodiment of a muffler according to the present invention.

(2) FIG. 2 is a vertical sectional view of a muffler showing pushing/pulling and friction forces.

(3) FIG. 3 is a vertical sectional view of a standard baffle illustrating the baffle deformation due to the friction forces.

(4) FIG. 4 is a sectional view of a part of a baffle of a muffler according to the present invention;

(5) FIG. 5 is a sectional view of a part of a baffle of a muffler according to the present invention showing a baffle lip end with a minimal curvature;

(6) FIG. 6 is a sectional view of a part of a baffle of a muffler according to the present invention showing a baffle lip end with a curvature angle of 90;

(7) FIG. 7 is a sectional view of a part of a baffle of a muffler according to the present invention showing a baffle lip end with a curvature angle of 180,

(8) FIG. 8 is a sectional view of a part of a baffle of a muffler according to the present invention showing a baffle lip end with a maximal curvature;

(9) FIG. 9 is a vertical sectional view of part of a baffle according to one embodiment of the present invention without stiffening bead.

(10) FIG. 10 is a vertical sectional view of part of a baffle according to another embodiment of the present invention with a stiffening bead.

(11) FIG. 11 is a vertical sectional view of part of two baffle elements forming a baffle according to a further embodiment of the present invention.

(12) FIG. 12 is view of a perforated baffle of a muffler according to the present invention;

(13) FIG. 13 is a schematic view of a baffle of a muffler according to the present invention showing a baffle lip end with variable curvature angles;

(14) FIG. 14 is a view of a baffle according of a muffler according to another embodiment of the present invention;

(15) FIG. 15 is a sectional view of the baffle according to FIG. 14;

(16) FIG. 16 is another sectional view of the baffle according to FIG. 14.

DETAILED DESCRIPTION OF EMBODIMENTS

(17) As shown in FIG. 1, a muffler includes a housing 1 comprising a shell 11 having an inner wall 12 and receiving an inlet pipe 2 and an outlet pipe 3 both extending into an inner space formed by the housing 1. An inner space 13 is delimited by the shell 11 and by end-caps 7 of the housing. The end-caps 7 seal the housing 1 and generally comprise an orifice for receiving the inlet pipe 2 and/or the outlet pipe 3.

(18) The inlet pipe 2 conveys exhaust gas stream from an exhaust of an internal combustion engine into the inner space 13 of the housing 1 and the outlet pipe 3 conveys the exhaust gas stream out of the inner space 13 of the housing 1.

(19) As shown in FIG. 1, the muffler has three baffles 4, 5, 6 arranged at a defined distance from each other inside the housing 1 in the inner space 13 of the muffler. The baffle plates 4, 5, 6 each comprise a baffle plate and a baffle lip arranged at the circumference of the respective baffle plate, which will be explained in the following for baffle 4 comprising baffle plate 41 and baffle lip 42. The baffle lip 42 has an end portion 43 which is curved inwardly away from the inner wall 12 of the shell 11. Due to the scale of FIG. 1, the inwardly curved end portion 43 according to the present invention is not visible on the figure.

(20) Each of the baffle 4, 5 receives the inlet pipe 2 as well as the outlet pipe 3 extending through the respective baffles 4, 5 while baffle 6 only receives the inlet pipe 2. In another embodiment, the inlet and outlet pipes may not extend between the baffle plates 4 and 5, or 5 and 6, respectively.

(21) In the particular embodiment, wherein the pipe 3 extends through two baffles 4 and 5, baffle 4 has one orifice for receiving the outlet pipe 3 and baffle 5 has two orifices for receiving both the inlet pipe 2 and the outlet pipe 3.

(22) As can be seen in FIG. 1, the inlet pipe 2 and outlet pipe 3 may be perforated over defined sections 21 and 31 for specific tuning of the sound attenuation effect of the muffler.

(23) Particularly, the perforated section 21 in the inlet pipe 2 opens into a chamber formed by one end-cap 7 receiving the inlet pipe 2 and one baffle 6 also receiving the inlet pipe 2. The chamber 14 is filled with glass wool fibers.

(24) The baffles 4, 5 and 6 may be made of at least one metal sheet, in particular of steel, particularly of stainless steel. The baffles 4, 5, 6 may also be obtained by using two or more metal sheets, for example by superposing two or more metal sheets and stamping the superposed metal sheets to form the desired baffle 4, 5, 6. The friction between several metal sheets additionally increase the damping of vibrations in the muffler.

(25) In preferred embodiments, the inlet and outlet tubes 2 and 3 may have a diameter of from 30 mm to 130 mm and may be made of steel, particularly stainless steel.

(26) FIG. 2 depicts a schematic representation of the forces exerted on the baffle 4 caused by thermal expansion during heat-up of the muffler. The friction force 401 at the circumference of the baffle plate 41 results from the sliding contact of the baffle 4 and the housing 11 and plays a role in the deformation of the baffle 4 and/or in a possible damage to the baffle 4 and/or the muffler housing 11. The deformation of the baffle 4 is caused by the force pair 401 and 402 occurring during thermal expansion or thermal contraction during or after operation. In FIG. 2, the baffle 4 further has indentations 49 stiffening the baffle for further enhancement of the stiffness of the baffle 4.

(27) FIG. 3 illustrates the direct impact of the force pair 401 and 402 onto the deformation of a baffle according to the prior art. As the forces 401 and 402 increase due to various phenomena occurring, the baffle plate tends to bend (deform) under the influence of the force pair 401 and 402. One way to reduce deformation of the baffle and ultimately to avoid irreversible damage to the baffle and to the muffler is to increase the stiffness of the baffle by using a metal sheet having an increased thickness t and hence resulting in higher total weight of the muffler. Another way to reduce deformation of the baffle and irreversible damage to the baffle is by diminishing the frictional force exerted on the baffle by increasing the circumference of the housing and thus the baffles are more loosely fitted in the housing. However this procedure does not guarantee the contact between the baffle and the housing at all times, increasing the risk of noise radiation by the housing, more particularly rattling noise and ultimately irreversible damage of the muffler.

(28) On the contrary to the baffle according to the prior art, the baffle 4 according to the present invention reduces the forces exerted on the baffle 4. Ideally, the friction force 401 exerted on the baffle 4 is very low and the baffle plate 41 does not bend or deform even with a low total thickness t of the baffle 4.

(29) The friction force 401 is strongly affected by the geometry of the baffle lip 42 and the potential gripping of the tip 44 of the baffle lip 42 into the inner wall 12 of the shell 11 of the muffler housing 1. The geometry of the end portion 43 of the baffle lip 42 which will be discussed drastically reduces the friction force 401 along the circumference of the baffle plate 41 and hence has a direct impact on reduction of the deformation of the baffle 4 and the damage to the baffle and/or to the muffler . Similarly, the pushing and pulling force 402 exerted by the inlet pipe 2 and/or of the outlet pipe 3 may additionally affect the deformation of the baffle 4 and may also be reduced accordingly by using similar geometries at the orifices of the baffles through which the inlet pipe and/or the outlet pipe extend. Further increasing the stiffness of the baffle additionally reduces the risk of deformation of the baffle and hence the risk of damaging the baffle or the muffler housing.

(30) In FIG. 4, a schematic sectional view of a baffle 4 according to a particular embodiment of the invention is depicted. The baffle 4 has a baffle plate 41 and a baffle lip 42 comprising a contact portion 45 in contact with the inner wall 12 of the shell 11 of the housing when being arranged in the shell 11, an inwardly curved end portion 43 of the lip 42 as well as a tip 44 of the inwardly curved end portion. The contact portion has a contact portion length L which is the length between the curved connection portion 46 and the inwardly curved end portion 43 of the baffle lip 42.

(31) The baffle as well as its portions are made of at least one metal sheet having a total thickness t. The baffle lip 42 is connected to the baffle plate 41 through a curved connection portion 46 which has the shape of an arc of a circle having a radius R, and preferably subtends an angle of 90 with the center of the arc of the circle of the curved connection portion 46.

(32) The end portion 43 of the baffle lip 42 is curved to have the shape of an arc of a circle having a radius R and subtending an angle .sub.max of up to 322 with the center of the arc of the circle.

(33) FIGS. 5 to 8 show several particular embodiments according to the present invention in which the end portion 43 of the baffle lip 42 which is curved inwardly away from the inner wall 12 of the shell 11 when being arranged in the shell 11 has different geometries. In FIG. 5, the tip 44 of the inwardly curved end portion 43 of the baffle lip 42 has a minimal curvature only so as not to contact the inner wall 12 of the shell.

(34) The curvature results in that the tip 44 of the baffle lip is arranged a distance d away from the inner wall 12 of the shell 11 in the muffler and hence avoids gripping of the tip 44 of the baffle lip 42 into the inner wall 12 of the shell 11. FIGS. 6 and 7 depict specific curvatures of the end portion 43 of the baffle lip 42 describing an arc of a circle subtending an angle of 90 and 180 with the center of the arc of the circle. FIG. 8 shows a specific embodiment, wherein the end portion 43 of the lip 42 describes an arc of the circle wherein the subtended angle is such that the tip 44 of the end portion 43 of the baffle lip 42 contacts the baffle lip 42. This angle .sub.max is the maximum subtended angle wherein the tip 44 of the curved end portion 43 of the baffle lip 42 contacts the baffle lip 42.

(35) FIG. 9 and FIG. 10 depict sectional view of a baffle 4 according to a particular embodiment of the invention. In FIG. 9 and FIG. 10, the baffle 4 has a baffle plate 41 and a baffle lip 42 comprising a contact portion 45 in contact with the inner wall 12 of the shell 11 of the housing when being arranged in the shell 11, an inwardly curved end portion 43 of the lip 42. The baffle in FIG. 9 does not have stiffening sections such as a bead, an indentation or a rib, whereas the baffle in FIG. 10 has a stiffening section in shape of a bead 49 protruding in the same direction as the baffle lip 42. The bead 49 may alternatively also protrude in the opposite direction of the baffle lip 42. The geometry (shape and size) of the stiffening sections and their number and position may be designed such to improve the structural stiffness of the baffle. The stiffening sections 49 may have a linear shape or a cross shape in form of a rib or may be irregularly shaped indentations or dents.

(36) In FIG. 11 a further embodiment according to the invention is shown. In this embodiment two baffle elements 80 and 81 are abutting along their respective baffle plate elements 801 and 811. The baffle elements 80 and 81 together form the baffle 4. The baffle plate elements 801 and 811 contact each other over at least part of the surface of the baffle plate elements 801 and 811. Both baffles have a baffle lip element 821 and 822 arranged at the circumference of each respective baffle plate element 801 and 811. The baffle lip elements 821 and 822 both have inwardly curved end portions 831 and 832, respectively. The baffle elements 80 and 81 further comprise stiffening sections 891 and 892 in shape of a bead and protruding in the same direction as the baffle lip element 821 and 822 respectively. These stiffening sections 891 and 892 may have various geometries (shape and size) and positions, and may be formed as mirrored pairs wherein the stiffening sections 891 and 892 have same position and geometries on the baffle element pairs 80 and 81, respectively, the protruding parts being in opposite directions relative to the baffle plates 801 and 811. Alternatively, the stiffening sections 892 on the second baffle element 81 may have positions and geometries differing from the position and geometries of the stiffening sections 891 of the first baffle element 80. In the latter case, the geometry and position of the stiffening sections 891 and 892 may be designed such to improve the structural vibrations over a broad frequency range when the resonance frequencies of both baffles are non-identical. The friction between the two baffles 80 and 81 additionally increase the damping of vibrations in the muffler.

(37) FIG. 12 shows a particular embodiment of the present invention. The baffle depicted is perforated and the perforations also allow for tuning of the acoustic attenuation of the muffler. To this end, the number of perforations 47 as well as their diameter may be varied to obtain a customized sound attenuation. The perforations may also be in the sub-millimeter range (micro-perforated baffle plate 41). The baffle shown in FIG. 12 also has two orifices 48 for receiving, for example, the inlet pipe 2 and the outlet pipe 3. In other embodiments, the baffle may be designed with more or less orifices. The orifices 48 are usually formed in the baffle plate by stamping and may also have lips with geometries similar to the geometry of the baffle lip 42.

(38) As shown in FIG. 13, in another embodiment of the present invention the curved end portion 43 of the baffle lip 42 has the shape of an arc of a circle subtending an angle with the center of the arc of the circle which varies along the circumference of the baffle. This is illustrated in FIG. 13 by various subtended angles .sub.1 to .sub.n around the circumference of the baffle plate 41 and the subtended angles may vary in a continuous manner. As the subtended angle has an influence on the stiffness of the baffle 4, the subtended angle may be tuned along the circumference of the baffle plate 42 according to requirements with regard to stiffness.

(39) FIGS. 14 to 16 show another particular embodiment according to the present invention in which the geometries, in particular the curvature angle and the curvature radius of the baffle lip 42 and the length of the contact portion 45 vary. However these geometric parameters may vary independently from one another, while other geometric parameters may be kept constant. It becomes obvious from the figures, that the curvature angle of the inwardly curved end portion 43 in this particular embodiment is smaller at the corners 401 of the baffle 4, where the contact portion bending radius is smaller than at the intermediate portions 402 between the corners 401, when compared to the curvature angle of the inwardly curved end portion 43 at the intermediate portions 402 of the baffle lip between the corners 401 of the baffle 4, where the contact portion bending radius is larger than at the corners 401.

(40) Thus, the curvature angle of the inwardly curved end portion 43 is reduced with decreasing contact portion bending radius.

(41) At the same time, the length of the contact portion 45 of the baffle lip 42 is reduced with increasing curvature angle of the inwardly curved end portion 43. Actually, in the present embodiment, the length of the contact portion 45 is larger at the corners 401 of the baffle 4 than at the intermediate portions 402 of the baffle 4 between the corners 401.

(42) Additionally, from the sectional views of FIGS. 15 and 16, it becomes apparent that the inwardly curved end portion 43 of the baffle lip 42 does not describe an arc of a circle around the complete circumference of the baffle plate in this embodiment.

(43) In this embodiment, the developed length of the baffle lip only varies in a small range of less than 10 mm around the circumference of the baffle plate.

(44) The previously described embodiments do equally apply to half shell mufflers. The housing 1 is then composed of two half shells forming the shell 11 of the housing 1 when assembled rather than using one single shell 11. Usually, the two half shells are turned by 180 with respect to each other and assembled in an overlapped way; the two half shells may have identical or dissimilar form and structure.

(45) While the invention has been described with the aid of embodiments, it is evident for the person skilled in the art that various changes and alterations can be made without departing from the technical teaching underlying the invention. In particular, combinations of individual features of different variants as well as of aspects thereof are also part of the invention disclosed herein. Therefore, the invention is not intended to be limited to the described embodiments, but rather the scope of protection is defined by the appended claims.