Exhaust pipe muffler for internal combustion engine

Abstract

Provided is an exhaust pipe muffler for an internal combustion engine that enables the muffling capability of an expansion chamber to be sufficiently exhibited. The exhaust pipe muffler (100A) is used in an exhaust pipe of an internal combustion engine, and comprises: a muffler body (10) having an expansion chamber (11); and an inlet-side exhaust pipe (20) and outlet-side exhaust pipe (50) that protrude into the expansion chamber (11) of the muffler body (10). The inlet-side exhaust pipe (20) has a slit (30) that forms an opening in the side surface of the inlet-side exhaust pipe (20). The slit (30) is oriented toward the longitudinal direction of the expansion chamber (11) and is open along the protrusion direction of the inlet-side exhaust pipe (20) in the expansion chamber (11).

Description

Muffler for exhaust pipe of internal combustion engine

[0001] The present invention relates to a muffler for an exhaust pipe of an internal combustion engine.

[0002] In the technology described in Patent Document 1, an inlet-side exhaust pipe and an outlet-side exhaust pipe are protruded in parallel within a muffler main body. The open ends of the respective exhaust pipes are vertically spaced apart from each other in an expansion chamber inside the muffler main body, and an exhaust introduction plate is disposed opposite to the open end of each exhaust pipe in the expansion chamber. The open end of the inlet-side exhaust pipe is formed as an inclined surface, and the opposing surface of the exhaust introduction plate is disposed obliquely. Further, the open end of the outlet-side exhaust pipe is also formed as an inclined surface with respect to the opposing surface of the exhaust introduction plate. Accordingly, according to the technology described in said document, back pressure can be reduced by smoothly guiding exhaust gas from the upstream exhaust pipe toward the outlet-side exhaust pipe.

[0003] Japanese Unexamined Patent Publication No. 11-132023 (Figure 1)

[0004] However, in the technology described in Patent Document 1, the open end of each exhaust pipe is formed as an inclined surface in the expansion chamber of the muffler main body, and the opposing surface of the exhaust introduction plate is disposed obliquely with respect to said inclined surface. Therefore, there is formed a region in the expansion chamber where exhaust gas does not pass, such as in a region on the opposite side from the opposing surface of the exhaust introduction plate. For this reason, it is difficult to sufficiently spread sound waves throughout the entire expansion chamber, and there still remains room for study in sufficiently exerting the silencing capability of the expansion chamber.

[0005] Accordingly, the present invention has been made in view of such problems, and an object of the present invention is to provide a muffler for an exhaust pipe of an internal combustion engine that can sufficiently exert the silencing capability of an expansion chamber.

[0006] In order to solve the above problem, a muffler for an exhaust pipe of an internal combustion engine according to one aspect of the present invention is a muffler used for an exhaust pipe of an internal combustion engine, comprising: a muffler main body having an expansion chamber; and an inlet-side exhaust pipe and an outlet-side exhaust pipe protruded into the expansion chamber of the muffler main body, wherein the inlet-side exhaust pipe has a first slit opening in a side surface thereof in the expansion chamber, and the first slit opens toward the longitudinal direction of the expansion chamber and along the protruding direction of the inlet-side exhaust pipe in the expansion chamber.

[0007] According to the present invention, the sound-dampening capacity of the expansion chamber can be fully utilized.

[0008] This is a schematic diagram showing a first embodiment of a muffler for the exhaust pipe of an internal combustion engine according to one aspect of the present invention, where (a) shows a schematic cross-section in a plan view along the axis of the muffler body which has an elliptical cylindrical shape, and (b) shows a schematic cross-section in a front view (the same applies to other embodiments and comparative examples below). These are schematic diagrams ((a), (b)) showing a second embodiment of a muffler for the exhaust pipe of an internal combustion engine according to one aspect of the present invention. These are schematic diagrams ((a), (b)) showing a third embodiment of a muffler for the exhaust pipe of an internal combustion engine according to one aspect of the present invention. This is a schematic diagram illustrating a modified example of a slit in an embodiment of the present invention, where (a) is a view of the opening shape of a slit formed in the inlet exhaust pipe as seen from the front in the opening direction, and (b) is an enlarged view of the main part of (a). These are schematic diagrams ((a), (b)) of a muffler for the exhaust pipe of an internal combustion engine shown as a comparative example.

[0009] The following describes one embodiment of the present invention with reference to the drawings as appropriate. Note that the drawings are schematic. Therefore, the relationship and ratios between thickness and planar dimensions may differ from those in reality, and there may be differences in the dimensional relationships and ratios between drawings. Furthermore, the embodiments described below illustrate devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the material, shape, structure, arrangement, etc., of the components.

[0010] Figure 1 shows a first embodiment of a silencer for the exhaust pipe of an internal combustion engine according to one aspect of the present invention. As shown in the figure, the silencer 100A for the exhaust pipe of the first embodiment comprises a silencer body 10 having an elliptical cylindrical expansion chamber 11, and an inlet exhaust pipe 20 and an outlet exhaust pipe 50 protruding into the expansion chamber 11 of the silencer body 10.

[0011] The muffler body 10 is mounted on the vehicle, for example, with its elliptical cylindrical axis oriented towards the front and rear of the vehicle, and with the major axis of the ellipse positioned horizontally at the lower rear of the vehicle. The inlet exhaust pipe 20 is connected so as to protrude from the side of the cylindrical part of the muffler body 10 into the expansion chamber 11 of the muffler body 10. The connection point of the inlet exhaust pipe 20 is located on the opposite side from the connection point of the outlet exhaust pipe 50, and is connected to the side of the muffler body 10 from the vehicle width direction on the front side of the vehicle.

[0012] The exhaust outlet pipe 50 is connected to the rear end face of the vehicle so as to protrude into the muffler body 10 from the elliptical end face of the muffler body 10. The exhaust outlet pipe 50 has an inlet opening 51 that opens into the expansion chamber 11, and an outlet opening 52 that extends from the rear end face of the muffler body 10 toward the rear of the vehicle and opens toward the rear of the vehicle.

[0013] In this embodiment, the inlet exhaust pipe 20 has a slit 30 on its side that opens in the longitudinal direction of the expansion chamber 11. The slit 30 in the first embodiment opens in a rectangular shape, facing the rear of the vehicle in the direction of the cylindrical axis of the expansion chamber 11 and along the direction in which the inlet exhaust pipe 20 protrudes within the expansion chamber 11. As illustrated by the dashed line, the outlet end face 22 of the inlet exhaust pipe 20 may be provided with a cap 40 that covers the opening on the end face.

[0014] Next, the operation and effects of the exhaust pipe silencer 100A of the first embodiment will be described. In the exhaust pipe silencer 100A of the first embodiment, exhaust gas is supplied into the silencer body 10 from the inlet side in the vehicle width direction via the inlet exhaust pipe 20. The exhaust gas introduced into the silencer body 10 from the inlet exhaust pipe 20 is exhausted to the rear of the vehicle from the outlet opening end 52 of the outlet exhaust pipe 50.

[0015] Sound waves that have passed through the inlet exhaust pipe 20 are input to the expansion chamber 10 through the slit 30. The slit 30 faces the longitudinal direction of the expansion chamber 10 of the silencer body 10, in other words, the direction in which the width of the expansion chamber 10 is wider. Therefore, the sound waves A input to the expansion chamber 10 are expanded toward the rear of the vehicle in the longitudinal direction of the expansion chamber 10. As a result, with the exhaust pipe silencer 100A of the first embodiment, the expansion ratio (ELn / Dr) becomes large (see Figure 1(b)), and sound suppression can be achieved with high sound suppression capacity. Hereinafter, Dr is the inner diameter of the pipe, and ELn is the expansion distance.

[0016] Here, a comparative example of this type of exhaust pipe silencer is shown in Figure 5. As shown in the figure, the comparative exhaust pipe silencer 100P comprises a silencer body 10 having an expansion chamber 11 surrounded by it, and a cylindrical inlet exhaust pipe 20P and outlet exhaust pipe 50 protruding from the expansion chamber 11. The inlet exhaust pipe 20P is provided at a position near one end in the longitudinal direction of the long side surface of the expansion chamber 11, and the tip opening of the inlet exhaust pipe 20P protruding into the expansion chamber 11 is positioned opposite the inner surfaces of the opposing long side surfaces of the expansion chamber 11, spaced apart. As a result, in the comparative silencer 100P, sound waves Ap are expanded in all 360 degrees from the tip opening of the inlet exhaust pipe 20P.

[0017] However, when considering the vehicle mounting position, the dimensions of this type of exhaust pipe silencer are constrained by the vertical dimensions of the silencer body 10, resulting in the vertical dimensions of the expansion chamber 11 being smaller than in other directions (for example, becoming a vertically flattened elliptical cylinder). Therefore, the vertical expansion ratio (S / Dr) of the expansion chamber 10 becomes relatively smaller compared to the horizontal direction, which may result in insufficient expansion effect and reduced sound suppression performance. In other words, in the comparative example exhaust pipe silencer 100P, sound waves A are expanded in all 360 degrees from the tip opening of the inlet exhaust pipe 20P. Therefore, the expansion ratio (S / Dr) is determined in the direction where the width of the expansion chamber 10 is narrower, resulting in a smaller expansion ratio (S / Dr) and reduced sound suppression ability.

[0018] In contrast, in the exhaust pipe silencer 100A of the first embodiment, the slit 30 is formed to open in a rectangular shape toward the rear of the vehicle in the longitudinal direction, so as shown in Figure 1, the sound wave A can be effectively expanded toward the rear of the vehicle in the longitudinal direction where the width of the expansion chamber 10 is wider. As a result, the expansion ratio (ELn / Dr) is larger than that of the exhaust pipe silencer 100P of the comparative example, and a high sound-reducing capacity can be achieved [Invention 1]. Furthermore, if a cap 40 is provided to close the tip opening of the inlet exhaust pipe 20, the only place to expand the input sound wave A is the slit 30, so an even greater sound-reducing effect can be achieved [Invention 5].

[0019] Next, the exhaust pipe silencer 100B of the second embodiment will be described with reference to Figure 2. As shown in the figure, the exhaust pipe silencer 100B of the second embodiment differs from the exhaust pipe silencer 100A of the first embodiment in that a second slit 32 is added. In the exhaust pipe silencer 100B of the second embodiment, the other components are the same as or similar to those of the exhaust pipe silencer 100A of the first embodiment, so the differences will be described below, and other components and effects will be denoted by the same reference numerals and their descriptions will be omitted as appropriate (the same applies to other embodiments below). Also, the component referred to as slit 30 in the first embodiment will be read as the first slit 31.

[0020] As shown in Figure 2, in the exhaust pipe silencer 100B of the second embodiment, the inlet exhaust pipe 20 has a first slit 31 that opens rectangularly toward the rear of the vehicle in the longitudinal direction where the width of the expansion chamber 10 is wider, and a second slit 32 that opens rectangularly toward the opposite direction from the first slit 31. As with the first embodiment, the rear end of the inlet exhaust pipe 20 may be provided with a cap 40.

[0021] Next, the operation and effects of the exhaust pipe silencer 100B of the second embodiment will be described. In the exhaust pipe silencer 100B of the second embodiment, sound waves A that have passed through the inlet exhaust pipe 20 are input to the expansion chamber 11 through the first slit 31 and the second slit 32. According to the exhaust pipe silencer 100B of the second embodiment, as shown in Figure 2, the sound waves A input to the expansion chamber 11 are expanded from the first slit 31 toward the rear of the vehicle in the longitudinal direction where the width of the expansion chamber 11 is wider, and the sound waves A' are also expanded toward the opposite side in the longitudinal direction by the second slit 32. Therefore, it is possible to achieve an even greater sound-dampening effect compared to the exhaust pipe silencer 100A of the first embodiment [Invention 2].

[0022] Next, the exhaust pipe silencer 100C of the third embodiment will be described with reference to Figure 3. As shown in the figure, the exhaust pipe silencer 100C of the third embodiment differs from the exhaust pipe silencer 100B of the second embodiment in that the inlet exhaust pipe 20 further has a third slit 33 and a fourth slit 34. In the exhaust pipe silencer 100C of the third embodiment, the third slit 33 opens rectangularly along the inlet exhaust pipe 20 at a position rotated 90 degrees clockwise with respect to the first slit 31. The fourth slit 34 opens rectangularly along the inlet exhaust pipe 20, facing in the opposite direction from the third slit 33. As with the first embodiment, the rear end of the inlet exhaust pipe 20 may be provided with a cap 40.

[0023] Next, the operation and effects of the exhaust pipe silencer 100C of the third embodiment will be described. Sound waves A that have passed through the inlet exhaust pipe 20 are input into the expansion chamber 11 through the first to fourth slits 31, 32, 33, and 34 formed in the inlet exhaust pipe 20. The sound waves A that have been input into the expansion chamber 11 are expanded by the first slit 31 toward the rear of the vehicle in the longitudinal direction (length L in the longitudinal direction) where the width of the expansion chamber 11 is wide, and the sound waves A' are also expanded toward the opposite side by the second slit 32. Therefore, the same sound-dampening effect as the second embodiment can be achieved.

[0024] Furthermore, in the exhaust pipe silencer 100C of the third embodiment, in addition to the two slits 31 and 32 facing the longitudinal direction of the expansion chamber 11, as shown in Figure 3, there is a third slit 33 and a fourth slit 34. Therefore, in addition to the direction in which sound is expanded by the first and second slits 31 and 32, sound wave A' is also expanded in the vertical direction (length S in the short direction) rotated 90 degrees clockwise. As a result, it is possible to achieve an even higher sound-reducing function compared to the second embodiment [Invention 3]. Moreover, if a cap 40 is provided at the rear end of the inlet exhaust pipe 20, the locations where sound waves A and sound waves A' are expanded are limited to the first to fourth slits 31, 32, 33, and 34, thus achieving an even greater sound-reducing effect [Invention 5].

[0025] As described above, the exhaust pipe silencers 100A, 100B, and 100C of the above embodiments provide an exhaust pipe silencer that can fully utilize the sound-dampening capacity of the expansion chamber 11. However, the exhaust pipe silencer according to the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. For example, in the above embodiments, an example was shown in which the opening shape of each slit 30, 31, 32, 33, and 34 is rectangular, but this is not limited to this, and the opening shape of the slits can also be modified in various ways. Modifications are shown below. Note that the modifications shown below are applicable to any or all of the slits 30, 31, 32, 33, and 34, but here, slit 30 is shown as a representative reference numeral.

[0026] As shown in Figure 4, the slit 30 of this modified example differs from the rectangular opening shape of the slit 30 described above in the shape of the short side on the entry side. That is, as shown in the figure, the slit 30 of this modified example has a pointed tip 35 that forms an isosceles triangle with a convex radius on the side that is upstream of the airflow passing through the slit 30. The pointed tip 35 that forms an isosceles triangle with a convex radius can be provided in any of the slits labeled 30, 31, 32, 33, and 34, or in all of them, as described above.

[0027] In the exhaust pipe silencers 100A, 100B, and 100C of the above-described embodiments, the airflow (including other fluids) flows along the slope of the pointed tip 35, which forms an isosceles triangle shape with a convex radius, as illustrated in Figure 4(b). In this modified example, the pointed tip 35 is provided on the side that is upstream of the airflow passing through the slit 30. In other words, with the configuration of the slit 30 in this modified example, small vortices that have just been generated and are yet to grow in the vicinity of the side of the slit 30 that is upstream of the airflow collide with each other at the vertices of the two sides along the isosceles triangle shape of the pointed tip 35, causing the vortices to collapse while they are still small and before they grow. Therefore, with the configuration of the slit 30 in this modified example, the generation of large vortices that are formed when small vortices grow can be suppressed, thus preventing or suppressing airflow noise generated from large vortices and deterioration of airflow resistance due to the generation of large vortices [Invention 4].

[0028] 10 Silencer body 11 Expansion chamber 20 Inlet exhaust pipe 21 Inlet side 22 Outlet side 30 Slit (representative symbol) 31 First slit 32 Second slit 33 Third slit 34 Fourth slit 35 (Edge shape of base end) Pointed head 40 Cap 50 Outlet exhaust pipe 51 Inlet side 52 Outlet side 100A, 100B, 100C Silencer for exhaust pipe Dr Pipe inner diameter ELn Expansion distance L Length in longitudinal direction S Length in transverse direction A Sound wave C Airflow V Vortex

Claims

1. A silencer for use in the exhaust pipe of an internal combustion engine, comprising: a silencer body having an expansion chamber; and an inlet exhaust pipe and an outlet exhaust pipe protruding from the expansion chamber of the silencer body, wherein the inlet exhaust pipe has a first slit opening to its side within the expansion chamber, and the first slit is oriented in the longitudinal direction of the expansion chamber and opens along the direction in which the inlet exhaust pipe protrudes within the expansion chamber.

2. Furthermore, the inlet exhaust pipe has a second slit that opens to its side within the expansion chamber, the second slit is opened along the protruding direction of the inlet exhaust pipe at a position where the opening position in the axial direction of the inlet exhaust pipe is the same as the opening position in the axial direction of the inlet exhaust pipe with respect to the formation position of the first slit, but the opening position in the circumferential direction is different, and the opening position in the circumferential direction is oriented in the opposite direction to the first slit, the silencer for the exhaust pipe of an internal combustion engine according to claim 1.

3. Furthermore, the inlet exhaust pipe has a third slit and a fourth slit that open to its side within the expansion chamber, the third slit and the fourth slit are opened along the protruding direction of the inlet exhaust pipe at positions where the axial opening position of the inlet exhaust pipe is the same as the formation positions of the first slit and the second slit, but the circumferential opening position of the third slit is different, the circumferential opening position of the third slit is rotated 90 degrees clockwise with respect to the first slit, and the circumferential opening position of the fourth slit is facing in the opposite direction to the third slit, the silencer for the exhaust pipe of an internal combustion engine according to claim 2.

4. The exhaust pipe silencer for an internal combustion engine according to any one of claims 1 to 3, wherein any or all of the aforementioned slits have an isosceles triangular pointed end with a convex radius at the upstream end of the airflow passing through any or all of the slits.

5. The exhaust pipe silencer for an internal combustion engine according to any one of claims 1 to 3, wherein the inlet exhaust pipe has a cap that closes the opening at its own end that protrudes into the expansion chamber.

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