Muffling device for engine

Abstract

In the present invention, a plurality of holes (61-68) are provided in a pipe (50) disposed in a chamber communicating with an engine (10), openings (51, 52) at the ends of the pipe are closed, and a space (A4) communicating with the chamber via the plurality of holes (61-68) is formed.

Description

Engine silencer

[0001] The present invention relates to an engine silencer.

[0002] A silencer is known that includes a main body sealed by end plates and divided into multiple chambers by partition plates, and a hollow pipe that penetrates the end plates and partition plates, has through holes formed in the side surfaces, and is sealed at both ends (see Patent Document 1). The hollow pipe functions as a resonator.

[0003] Japanese Utility Model Application Publication No. 62-176416

[0004] In the above-mentioned conventional technology, in order to increase the sound-deadening effect of the hollow pipe that serves as the resonator, it is necessary to enlarge the through-hole. However, when the through-hole is enlarged, the frequency of the exhaust noise to be silenced increases, resulting in the problem that relatively low-frequency exhaust noise cannot be silenced.

[0005] An object of the present invention is to provide an engine silencer that can suppress the sound pressure level of low-frequency exhaust noise.

[0006] The present invention solves the above problem by providing multiple holes in a pipe placed in a chamber connected to an engine, blocking the opening at the end, and forming a space connected to the chamber via the multiple holes.

[0007] According to the present invention, the sound pressure level of low frequency exhaust noise can be suppressed.

[0008] FIG. 1B is a plan view showing an example of a silencer according to an embodiment of the present invention. FIG. 1C is a left side view of the silencer of FIG. 1A. FIG. 1D is a cross-sectional view showing the inside of the muffler of FIG. 1A, taken along line A-A of FIG. 1B. FIG. 2A is a left side view of the partition plate of FIG. 2A. FIG. 2C is a perspective view of a main portion of the silencer pipe of FIG. 2A. FIG. 2D is a cross-sectional view showing another example of a muffler according to an embodiment of the present invention. FIG. 4C is a cross-sectional view showing a main portion of the silencer pipe of FIG. 4A. FIG. 4D is a cross-sectional view showing a still further example of a muffler according to an embodiment of the present invention. FIG. 4E is a cross-sectional view showing a still further example of a muffler according to an embodiment of the present invention. FIG. 4F is a cross-sectional view showing a still further example of a muffler according to an embodiment of the present invention. FIG. 4G is a cross-sectional view showing a still further example of a muffler according to an embodiment of the present invention.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the front side of a vehicle engine is defined as the front side. In addition, in the drawings, "front" refers to the front of the vehicle, "rear" refers to the rear of the vehicle, "right" refers to the right side of the vehicle, "left" refers to the left side of the vehicle, "up" refers to the top of the vehicle, and "down" refers to the bottom of the vehicle.

[0010] [Configuration of silencer] Fig. 1A is a plan view showing an example of a silencer according to an embodiment of the present invention, and Fig. 1B is a left side view of the silencer shown in Fig. 1A. The silencer is a device that reduces exhaust noise from an engine 10, and includes an exhaust pipe 20, a muffler 30, and a tail pipe 40. The engine 10 may be an internal combustion engine that obtains output by combusting a combustible air-fuel mixture, or may be a hybrid engine that combines an internal combustion engine with an electric motor.

[0011] The exhaust pipe 20 is a pipe that introduces exhaust gas (hereinafter simply referred to as "exhaust gas") from the engine 10 and sound waves (hereinafter simply referred to as "sound waves") from the exhaust sound of the engine 10 into the muffler 30, and is routed under the floor of the vehicle. For example, the exhaust pipe 20 is made by welding together multiple circular pipes made of corrosion-resistant stainless steel (such as SUS409), and is attached to the vehicle by stays that are fixed to the floor via rubber. The base end of the exhaust pipe 20 is attached to the exhaust manifold (not shown) of the engine 10, and the exhaust gas and sound waves are introduced from the engine 10. Meanwhile, the end of the exhaust pipe 20 is attached to the muffler 30 and communicates with the chamber of the muffler 30.

[0012] The muffler 30 is a device that reduces the temperature of exhaust gases introduced from the exhaust pipe 20 and the sound pressure level of exhaust noise, and has at least one chamber. For example, the muffler 30 is a cylindrical hollow molded product made of corrosion-resistant stainless steel, and its cross-sectional shape may be circular, elliptical, rectangular, or the like. A muffler 30 having a desired shape is manufactured, for example, by pressing and welding a stainless steel plate. The muffler 30 is suspended from the underside of the vehicle floor, for example, via stays provided at both ends in the longitudinal and / or lateral directions. The stays are fixed to the underside of the floor via rubber.

[0013] The tail pipe 40 is a pipe that discharges exhaust gas and sound waves outside the muffler 30 (for example, into the atmosphere). The tail pipe 40 is made of the same material as the exhaust pipe 20, and is attached to the muffler 30 using a joining method such as welding. The shape of the tail pipe 40 is not particularly limited. When the muffler 30 is connected to a different subsequent muffler, the tail pipe 40 discharges the exhaust gas and sound waves that are introduced into the different muffler outside the housing of the muffler 30.

[0014] First Embodiment The configuration of a muffler 30 according to a first embodiment of the present invention will be described using Figures 2A to 2C. Figure 2A is a cross-sectional view showing the interior of the muffler 30 shown in Figure 1A, taken along line A-A in Figure 1B (a cross-sectional view perpendicular to the up-down direction). As shown in Figure 2A, the muffler 30 comprises a housing 31 that houses the devices that make up the muffler 30, and partition plates 32 and 33 that separate the interior of the housing 31. The shape of the housing 31 is not particularly limited, but may be, for example, a substantially rectangular parallelepiped.

[0015] The interior (chamber) of the housing 31 is divided into three compartments by partition plates 32 and 33. That is, the muffler 30 has a first compartment A1 divided by the partition plate 32, a second compartment A2 divided by the partition plates 32 and 33, and a third compartment A3 divided by the partition plate 33. The first compartment A1 is a chamber defined by the housing 31 and the partition plate 32, and is connected to the engine 10 via the exhaust pipe 20. The second compartment A2 is a chamber defined by the housing 31 and the partition plates 32 and 33, and is connected to the first compartment A1 via a hole 32a in the partition plate 32 and to the third compartment A3 via a hole 33a in the partition plate 33. The third compartment A3 is a chamber defined by the housing 31 and the partition plate 33, and is connected to the outside of the muffler 30 via a tailpipe 40.

[0016] 2B is a left side view of the partition plate 32 of FIG. 2A. The shape of the hole 32a of the partition plate 32 is not particularly limited, and may be, for example, circular as shown in FIG. 2B. The size (opening area) of the hole 32a can be set as appropriate within a range that allows the exhaust gas to move appropriately and the sound waves to propagate appropriately. The hole 32b is a hole through which the tail pipe 40 is inserted, and has a shape that corresponds to the outer side surface of the tail pipe 40. The partition plate 33 has a structure similar to that of the partition plate 32. The partition plates 32 and 33 shown in FIG. 2A may have the same structure or different structures.

[0017] In the muffler 30 shown in Fig. 2A, exhaust gas is introduced from the exhaust pipe 20 into the first section A1 (arrow B1), moves from the first section A1 to the second section A2 through the holes 32a, and moves from the second section A2 to the third section A3 through the holes 33a (arrow B2). The exhaust gas that moves to the third section A3 is then introduced into the tail pipe 40 and discharged to the outside of the muffler 30 (arrow B3). Similarly, sound waves introduced from the exhaust pipe 20 into the first section A1 propagate through the first section A1, the second section A2, and the third section A3, and are discharged to the outside of the muffler 30 via the tail pipe 40. The sound pressure level of the sound waves decreases as they pass through the holes 32a and 33a due to the expansion effect, etc.

[0018] The muffler 30 shown in FIG. 2A includes a pipe 50 (hereinafter also referred to as a "silencer pipe") disposed in a first section A1, which is a chamber communicating with the engine 10, to suppress the sound pressure level of sound waves (particularly to suppress the sound pressure level of low-frequency exhaust noise, such as muffled noise). The silencer pipe 50 has an end opening closed by a closing member. The closing member is not particularly limited as long as it is a member that closes the opening of the silencer pipe 50, and examples thereof include an end plate and a lid. In the silencer pipe 50 shown in FIG. 2A, an opening 51 at one end is closed by an end plate 53, and an opening 52 at the other end is closed by an end plate 54. The closing member has at least the same rigidity as the silencer pipe 50 to appropriately reflect sound waves inside the silencer pipe 50. For example, if the closing member is an end plate or a lid made of the same material as the silencer pipe 50, the thickness of the end plate or the lid is set to be 1.5 to 3 times the thickness of the silencer pipe 50.

[0019] Furthermore, the silencer tube 50 has a plurality of holes. FIG. 2C is a perspective view of the essential parts showing the holes provided in the silencer tube 50 of FIG. 2A, with the end plates 53 and 54 omitted. As shown in FIG. 2C, eight holes 61 to 68 are provided in the side surface of the silencer tube 50, and the silencer tube 50 forms a space A4 that communicates with the first section A1 via the plurality of holes 61 to 68, as shown in FIG. 2A. The number of holes can be set to an appropriate value of two or more depending on the shape of the holes, as long as sound waves are appropriately propagated inside the silencer tube 50. The shape of the holes can be set to an appropriate shape, such as a circle, as long as sound waves are appropriately propagated inside the silencer tube 50. As an example, the size of the holes is set to 5 to 50% of the inner diameter of the silencer tube 50.

[0020] When multiple holes are provided in the silencer tube 50, the holes may be spaced at a predetermined interval or less so that the multiple holes form a single group and function as a single hole. The predetermined interval can be set to an appropriate value within the range in which the multiple holes form a single group, and may be, for example, 1 to 2 times the diameter of the hole. For example, holes 61 to 68 shown in FIG. 2C are spaced at intervals less than the predetermined interval, and eight holes function as a single hole.

[0021] Although the silencer tube 50 shown in Fig. 2A is a circular tube, the silencer tube 50 may be an elliptical tube or a square tube. Although the silencer tube 50 shown in Fig. 2C is straight, the silencer tube 50 may be curved. Furthermore, the shape of the cross section perpendicular to the axial direction of the silencer tube 50 may differ depending on the position in the axial direction.

[0022] Next, the operation of the muffler 30 according to the first embodiment of the present invention will be described. When suppressing the sound pressure level of exhaust noise introduced into the first section A1, the silencer tube 50 shown in FIG. 2A generates reflected waves by reflecting sound waves (hereinafter also referred to as "first sound waves") introduced into the silencer tube 50 through the multiple holes 61-68 by the end plates 53 and 54. The generated reflected waves interfere with the first sound waves. In the silencer tube 50 shown in FIG. 2A, a reflected wave C1 travels leftward from the multiple holes 61-68 and is reflected by the end plate 53, and a reflected wave C2 travels rightward from the multiple holes 61-68 and is reflected by the end plate 54. These waves interfere with the first sound waves. If at least one of the reflected waves C1 and C2 has a waveform that is out of phase with the first sound wave, the first sound wave is canceled out.

[0023] Furthermore, the sound wave reflected by the end plate 53 propagates to the end plate 54 and is reflected again, forming a sound wave that travels back and forth between the end plates 53, 54. Similarly, the sound wave reflected by the end plate 54 propagates to the end plate 53 and is reflected again, forming a sound wave that travels back and forth between the end plates 53, 54. The two sound waves that travel back and forth between the end plates 53, 54 interfere with each other, and become a standing wave C3 whose antinodes are located at the positions of the end plates 53, 54, when the standing wave C3 has a waveform that is in opposite phase to the first sound wave.

[0024] 2A cancels three types of exhaust noise having frequencies corresponding to the reflected waves C1 and C2 and the standing wave C3. The waveforms of the reflected waves C1 and C2 depend on the distance from the multiple holes 61-68 to the end plates 53 and 54, and the waveform of the standing wave C3 depends on the distance between the end plates 53 and 54. Therefore, the frequency of the sound waves canceled by the silencer tube 50 shown in FIG. 2A depends on the distance from the multiple holes 61-68 to the end plate 53 and the distance from the multiple holes 61-68 to the end plate 54.

[0025] Second Embodiment The configuration of a muffler 30 according to a second embodiment of the present invention will be described using Figure 3. Figure 3 is a cross-sectional view showing the interior of the muffler 30 according to the second embodiment of the present invention. The muffler 30 shown in Figure 3 is similar to the muffler 30 shown in Figure 2A except for the positions of the holes 61 to 68 in the silencer tube 50. In the silencer tube 50 shown in Figure 3, the multiple holes 61 to 68 are provided in positions closer to the ends than the central portion X in the axial direction of the silencer tube 50. In this way, the multiple holes provided in the silencer tube 50 may be provided in positions closer to the ends than the central portion X in the axial direction of the silencer tube 50.

[0026] Next, the operation of the muffler 30 according to the second embodiment of the present invention will be described. In the silencer tube 50 shown in FIG. 3 , a reflected wave C4 travels leftward from the positions of the multiple holes 61-68 and is reflected by the end plate 53. A reflected wave C5 travels rightward from the positions of the multiple holes 61-68 and is reflected by the end plate 54. A standing wave C3, whose antinode is located at the positions of the end plates 53 and 54, is formed. In other words, the silencer tube 50 shown in FIG. 3 cancels three types of exhaust noise having frequencies corresponding to the reflected waves C4, C5, and the standing wave C3. By positioning the multiple holes in the silencer tube 50 from the central portion X of the silencer tube 50 toward the ends in the axial direction, it is possible to change the frequency of the exhaust noise canceled by the reflected waves C4 and C5.

[0027] Third Embodiment The configuration of a muffler 30 according to a third embodiment of the present invention will be described using Figures 4A and 4B. Figure 4A is a cross-sectional view showing the interior of muffler 30 according to the third embodiment of the present invention, and Figure 4B is a perspective view showing holes formed in silencer tube 50 of Figure 4A. Note that end plates 53 and 54 are not shown in Figure 4B.

[0028] The muffler 30 shown in FIG. 4A is similar to the muffler 30 shown in FIG. 2A except for the silencer tube 50. The silencer tube 50 shown in FIG. 4A extends across the first section A1 and the second section A2. Also, as shown in FIG. 4B , a first group of holes consisting of holes 61-68 is provided near the opening 51 of the silencer tube 50, and a second group of holes consisting of holes 71-78 is provided at a position axially away from the end opening 51 (i.e., a position closer to the opening 52 of the silencer tube 50). In this manner, the first group of holes 61-68 may be provided at a first position of the silencer tube 50, and the second group of holes 71-78 may be provided at a second position axially away from the first position of the silencer tube 50. For example, the first position and the second position are separated by a predetermined distance in the axial direction of the silencer tube 50, and this predetermined distance can be set appropriately depending on the frequency of the exhaust noise to be silenced by the silencer tube 50.

[0029] Next, the operation of the muffler 30 according to the third embodiment of the present invention will be described. In the silencer tube 50 shown in Figure 4A, a sound wave (first sound wave) introduced into the silencer tube 50 through the multiple holes 61-68 travels leftward from the positions of the multiple holes 61-68 and is reflected by the end plate 53, forming a reflected wave C6. Another reflected wave C7 travels rightward from the positions of the multiple holes 61-68 and is reflected by the end plate 54. If the first sound wave has a waveform that is out of phase with the reflected wave C6, the first sound wave is canceled out by the reflected wave C6. If the sound wave (hereinafter also referred to as the "second sound wave") introduced into the silencer tube 50 through the multiple holes 71-78 has a waveform that is out of phase with the reflected wave C7, the second sound wave is canceled out by the reflected wave C7. Furthermore, since the reflected waves C6 and C7 propagate inside the silencer tube 50, if the first sound wave has a waveform that is out of phase with the reflected wave C7, the first sound wave is canceled out by the reflected wave C7, and if the second sound wave has a waveform that is out of phase with the reflected wave C6, the second sound wave is canceled out by the reflected wave C6.

[0030] Similarly, in the silencer tube 50 shown in Figure 4A, the second sound wave travels left from the positions of the multiple holes 71-78 and is reflected by the end plate 53, forming a reflected wave C8, and travels right from the positions of the multiple holes 71-78 and is reflected by the end plate 54. If the first sound wave has a waveform that is out of phase with the reflected wave C8 or C9, the first sound wave is canceled by the reflected wave C8 or C9, and if the second sound wave has a waveform that is out of phase with the reflected wave C8 or C9, the second sound wave is canceled by the reflected wave C8 or C9. Also, as in the case shown in Figure 2A, when a standing wave C10 is formed whose antinode is located at the positions of the end plates 53 and 54, if the first sound wave has a waveform that is out of phase with the standing wave C10, the first sound wave is canceled by the standing wave C10, and if the second sound wave has a waveform that is out of phase with the standing wave C10, the second sound wave is canceled by the standing wave C10. In this way, by providing holes at a plurality of positions spaced apart in the axial direction of the silencer pipe 50, it is possible to increase the frequency of the exhaust noise that the silencer pipe 50 cancels.

[0031] Fourth Embodiment The configuration of a muffler 30 according to a fourth embodiment of the present invention will be described using Figure 5. Figure 5 is a cross-sectional view showing the interior of the muffler 30 according to the fourth embodiment of the present invention. The muffler 30 shown in Figure 5 is similar to the muffler 30 shown in Figure 4A except for the positions of the holes 71-78 in the silencer tube 50. The silencer tube 50 shown in Figure 5 extends across a first section A1 and a second section adjacent to the first section A1, and the silencer tube 50 is provided with a first group of holes 61-68 that communicate with the first section A1 and a second group of holes 71-78 that communicate with the second section A2. In this way, when the chamber of the housing 31 is divided into multiple compartments by partition plates 32, 33, and the silencer tube 50 extends across the first compartment A1 and the second compartment A2 adjacent to the first compartment A1, the silencer tube 50 may be provided with a first group of multiple holes communicating with the first compartment A1 and a second group of multiple holes communicating with the second compartment A2.

[0032] Next, the operation of the muffler 30 according to the fourth embodiment of the present invention will be described. In the silencer tube 50 shown in FIG. 5, the exhaust noise is canceled by the first sound wave C11 and the second sound wave C12 in addition to the reflected waves C6 to C9 and the standing wave C10 shown in FIG. 4A. Specifically, because the holes 61 to 68 are provided in the first section A1 and the holes 71 to 78 are provided in the second section A2, the second sound wave has a different frequency from the first sound wave due to pressure loss when the sound wave propagates through the holes 32a. In this case, if the second sound wave C12 has a waveform that is out of phase with the first sound wave C11, the second sound wave C12 is canceled out by the first sound wave C11. Conversely, if the first sound wave C11 has a waveform that is out of phase with the second sound wave C12, the first sound wave C11 is canceled out by the second sound wave C12.

[0033] Fifth Embodiment The configuration of a muffler 30 according to a fifth embodiment of the present invention will be described using FIG. 6 . FIG. 6 is a cross-sectional view showing the interior of the muffler 30 according to the fifth embodiment of the present invention. The muffler 30 shown in FIG. 6 is similar to the muffler 30 shown in FIG. 2A , except that holes 53a and 54a are provided in the end plates 53 and 54 of the muffler tube 50. In this manner, when the openings 51 and 52 of the muffler tube 50 are closed by blocking members, at least one of the blocking members may be provided with a hole that connects the space A4 formed by the muffler tube 50 to the chamber. The size (opening area) of the holes 53a and 54a can be set to an appropriate value within a range that can suppress resonance inside the muffler tube 50 due to reflection by the end plates 53 and 54. The number and shape of the holes 53a and 54a are set according to the set opening area.

[0034] Next, the operation of the muffler 30 according to the fifth embodiment of the present invention will be described. In the silencer tube 50 shown in FIG. 6 , similar to the silencer tube 50 shown in FIG. 2A , a reflected wave C1 travels leftward from the positions of the multiple holes 61-68 and is reflected by the end plate 53, a reflected wave C2 travels rightward from the positions of the multiple holes 61-68 and is reflected by the end plate 54, and a standing wave C3, whose antinode is located at the positions of the end plates 53 and 54, interfere with the first sound wave. If at least one of the reflected waves C1, C2 and the standing wave C3 has a waveform that is out of phase with the first sound wave, the first sound wave is canceled out. Furthermore, in the silencer tube 50 shown in FIG. 6 , sound waves Y1 and Y2 propagate from the holes 53a and 54a in the end plates 53 and 54 to the first section A1, thereby reducing the amplitude of the first sound wave reflected by the end plates 53 and 54 and suppressing the resonance phenomenon inside the silencer tube 50 caused by the reflected waves C1 and C2.

[0035] Sixth Embodiment The configuration of a muffler 30 according to a sixth embodiment of the present invention will be described using Figures 7A and 7B. Figure 7A is a cross-sectional view showing an example of the interior of a muffler 30 according to the sixth embodiment of the present invention. The muffler 30 shown in Figure 7A is similar to the muffler 30 shown in Figure 2A, except that the projected area E1 of the opening 52 on a plane Z perpendicular to the axial direction of the silencing tube 50 is larger than the cross-sectional area E2 of the transverse section of the silencing tube 50 at the positions where the holes 61 to 68 are provided. Figure 7B is a cross-sectional view showing another example of the interior of a muffler 30 according to the sixth embodiment of the present invention. The muffler 30 shown in Figure 7B is similar to the muffler 30 shown in Figure 7A, except that the projected area E3 of the opening 51 on a plane Za perpendicular to the axial direction of the silencing tube 50 is larger than the cross-sectional area E2 of the transverse section of the silencing tube 50 at the positions where the holes 61 to 68 are provided. In this way, the projected area of ​​at least one opening of the silencer tube 50 on a plane perpendicular to the axial direction of the silencer tube 50 may be larger than the cross-sectional area of ​​the silencer tube 50 perpendicular to the axial direction at the position where the hole is provided.

[0036] Next, the operation of the muffler 30 according to the sixth embodiment of the present invention will be described. In the silencer tube 50 shown in Figures 7A and 7B, similar to the silencer tube 50 shown in Figure 2A, the reflected wave C1 reflected by the end plate 53, the reflected wave C2 reflected by the end plate 54, and the standing wave C3 formed between the end plates 53 and 54 interfere with the first sound wave. If at least one of the reflected waves C1, C2, and the standing wave C3 has a waveform that is out of phase with the first sound wave, the first sound wave is canceled. However, in the silencer tube 50 shown in Figure 7A, the projected area E1 of the end plate 54 relative to the plane Z is larger than that of the end plate 54 shown in Figure 2A, so the sound pressure level of the sound wave reflected by the end plate 54 is higher, thereby enhancing the effect of canceling the exhaust noise. Similarly, in the silencer tube 50 shown in Figure 7B, the projected area E1 of the end plate 54 with respect to the plane Z is larger than that of the end plate 54 shown in Figure 2A, and the projected area E3 of the end plate 53 with respect to the plane Za is larger than that of the end plate 53 shown in Figure 2A, so the sound pressure level of the sound waves reflected at the end plates 53, 54 is larger, and the effect of canceling out the exhaust noise is greater.

[0037] Seventh Embodiment The configuration of a muffler 30 according to a seventh embodiment of the present invention will be described using Figures 8A to 8D. Figure 8A is a cross-sectional view showing an example of the interior of a muffler 30 according to the seventh embodiment of the present invention. The muffler 30 shown in Figure 8A is similar to the muffler 30 shown in Figure 2A, except that the muffler 30 is a double-walled pipe consisting of an inner pipe 80 and an outer pipe 90 disposed outside the inner pipe 80. In this manner, the muffler 50 may include a first side member and a second side member disposed inside or outside the first side member. The first side member and the second side member are elongated members with openings at both ends, and may be, for example, a circular pipe, an elliptical pipe, a rectangular pipe, or the like. In the muffler 30 shown in Figure 8A, the inner pipe 80 corresponds to the first side member, and the outer pipe 90 corresponds to the second side member. The outer pipe 90 shown in Figure 8A is longer than the inner pipe 80. The first and second side members may be straight or curved, and the cross-sectional shape perpendicular to the axial direction may vary depending on the axial position. Note that the inner tube 80 shown in Fig. 8A is supported by a stay (not shown).

[0038] When the silencer tube 50 includes a first side member and a second side member, the first side member and the second side member close at least two of one opening of the first side member, the other opening of the first side member, one opening of the second side member, and the other opening of the second side member so as to form a space that communicates with the chamber via a plurality of holes. Which openings of the first side member and the second side member are closed depends on the arrangement of the first side member and the second side member. As an example, in the silencer tube 50 shown in Fig. 8A, openings 81 and 82 of the inner tube 80 are closed with end plates 83 and 84, and openings 91 and 92 of the outer tube 90 are closed with end plates 93 and 94, so that all four openings are closed. As shown in Fig. 8A , four holes 85 to 88 are provided in the side surface of the inner pipe 80, and two holes 95, 96 are provided in the side surface of the outer pipe 90, so that the silencer pipe 50, consisting of the inner pipe 80, the outer pipe 90, and the end plates 83, 84, 93, 94, forms a space A4 that communicates with the first section A1 via the plurality of holes 85 to 88, 95, 96. As another example, in the silencer pipe 50 shown in Fig. 8A , the openings 81, 82 of the inner pipe 80 may not be closed, and only the openings 91, 92 of the outer pipe 90 may be closed by the end plates 93, 94. In this case, the outer pipe 90 and the end plates 93, 94 form a space A4 that communicates with the first section A1 via the plurality of holes 95, 96.

[0039] FIG. 8B is a cross-sectional view showing another example of the interior of a muffler 30 according to the seventh embodiment of the present invention. The muffler 30 shown in FIG. 8B is similar to the muffler 30 shown in FIG. 2A , except that the silencing pipe 50 is a double pipe consisting of an inner pipe 80 and an outer pipe 90. The outer pipe 90 shown in FIG. 8B is shorter than the inner pipe 80, and therefore, in the arrangement shown in FIG. 8B , the openings 91 and 92 of the outer pipe 90 are annular. In the silencing pipe 50 shown in FIG. 8B , the openings 81 and 82 of the inner pipe 80 are not blocked, and the openings 91 and 92 of the outer pipe 90 are blocked by annular end plates 93 and 94. In addition, four holes 85 to 88 are formed in the side surface of the inner pipe 80. As a result, the silencing pipe 50 shown in FIG. 8B forms a space A4 that communicates with the first section A1 via the openings 81 and 82 and the multiple holes 85 to 88.

[0040] FIG. 8C is a cross-sectional view showing another example of the interior of a muffler 30 according to the seventh embodiment of the present invention. The muffler 30 shown in FIG. 8C is similar to the muffler 30 shown in FIG. 2A , except that the silencing pipe 50 is a double pipe consisting of an inner pipe 80 and an outer pipe 90. The outer pipe 90 shown in FIG. 8C is shorter than the inner pipe 80, and therefore the opening 91 of the outer pipe 90 has a circular shape in the arrangement shown in FIG. 8C . In the silencing pipe 50 shown in FIG. 8C , the opening 82 of the inner pipe 80 is closed by an end plate 84, and the openings 91 and 92 of the outer pipe 90 are closed by end plates 93 and 94. Four holes 85 to 88 are provided on the side surface of the inner pipe 80. As a result, the silencing pipe 50 shown in FIG. 8C forms a space A4 that communicates with the first section A1 via the opening 81 and the multiple holes 85 to 88.

[0041] FIG. 8D is a cross-sectional view showing yet another example of the interior of the muffler 30 according to the seventh embodiment of the present invention. The muffler 30 shown in FIG. 8D is similar to the muffler 30 shown in FIG. 8C except for the positions of the holes 85-88 in the inner pipe 80, the closed state of the openings 81 and 82, and the position of the inner pipe 80 relative to the outer pipe 90. In the silencer tube 50 shown in FIG. 8D, the opening 81 in the inner pipe 80 is closed by an end plate 83, and the openings 91 and 92 in the outer pipe 90 are closed by end plates 93 and 94. Furthermore, four holes 85-88 are provided on the side surface of the inner pipe 80 at positions in the radial direction of the inner pipe 80 where the outer pipe 90 is not present. As a result, the silencer tube 50 shown in FIG. 8D forms a space A4 that communicates with the first section A1 via the opening 82 and the multiple holes 85-88.

[0042] Next, the operation of the muffler 30 according to the seventh embodiment of the present invention will be described. In the silencer tube 50 shown in FIG. 8A , a reflected wave D1 is introduced into the silencer tube 50 through the holes 95 and 96 and reflected by the left end plate 93. A reflected wave D2 is introduced into the silencer tube 50 through the holes 95 and 96 and reflected by the right end plate 94. A standing wave D3, whose antinode is located at the end plates 93 and 94, is formed. If the sound waves introduced through the holes 95 and 96 have a waveform that is out of phase with at least one of the reflected waves D1 and D2 and the standing wave D3, the sound waves introduced through the holes 95 and 96 are canceled out. Furthermore, the sound waves introduced into the silencer tube 50 through the holes 85-88 propagate into the inner tube 80, forming a reflected wave D4 reflected by the left end plate 83 and a reflected wave D5 reflected by the right end plate 84. The reflected waves D4 and D5 reach holes 85 to 88, are introduced between the inner pipe 80 and the outer pipe 90, and reach holes 95 and 96. If the sound waves that reach holes 95 and 96 have waveforms that are out of phase with the sound waves introduced from holes 95 and 96, the sound waves introduced from holes 95 and 96 are canceled out. In this way, by making the silencer pipe 50 a double pipe, it is possible to lower the frequency of the exhaust noise that is canceled out by the silencer pipe 50 while preventing the silencer pipe 50 from becoming too long.

[0043] 8B, a reflected wave D1 is introduced into the silencer tube 50 from the holes 85 to 88 and reflected by the left end plate 93, a reflected wave D2 is introduced into the silencer tube 50 from the holes 85 to 88 and reflected by the right end plate 94, and a standing wave D3 whose antinode is located at the positions of the end plates 93 and 94. If the sound waves introduced from the holes 85 to 88 have a waveform that is out of phase with at least one of the reflected waves D1 and D2 and the standing wave D3, the sound waves introduced from the holes 85 to 88 are canceled out. Furthermore, when sound waves introduced from at least one of the openings 81, 82 are introduced between the inner pipe 80 and the outer pipe 90 through the holes 85-88, reflected by the end plates 93, 94 to reach the holes 85-88, introduced into the inner pipe 80 and then to the openings 81, 82, if the sound waves have a waveform that is out of phase with the sound waves introduced from the openings 81, 82, the sound waves introduced from the openings 81, 82 are canceled out. In this way, by making the silencer pipe 50 a double pipe, the path of the reflected waves can be lengthened even with a short pipe, and the frequency of the exhaust noise canceled out by the silencer pipe 50 can be lowered while preventing the silencer pipe 50 from becoming too long.

[0044] In the silencer tube 50 shown in FIG. 8C , a reflected wave D1 is introduced into the silencer tube 50 through the holes 85-88 and reflected by the left-hand end plate 93, a reflected wave D2 is introduced into the silencer tube 50 through the holes 85-88 and reflected by the right-hand end plate 94, and a standing wave D3 whose antinode is located at the end plates 93 and 94 is formed. If the sound waves introduced through the holes 85-88 have a waveform that is out of phase with at least one of the reflected waves D1 and D2 and the standing wave D3, the sound waves introduced through the holes 85-88 are canceled out. Also, in the silencer tube 50 shown in FIG. 8C , a reflected wave D6 is also formed that is introduced into the inner tube 80 through the opening 81 of the inner tube 80 and reflected by the right-hand end plate 84. If the sound waves introduced through the holes 85-88 have a waveform that is out of phase with the reflected wave D6, the sound waves introduced through the holes 85-88 are canceled out.

[0045] In the silencer tube 50 shown in FIG. 8D , a reflected wave D7 is introduced into the silencer tube 50 through holes 85-88 and reflected by the left end plate 83, a reflected wave D8 is introduced into the silencer tube 50 through holes 85-88 and reflected by the right end plate 94, and a standing wave D9 whose antinode is located at the end plates 83 and 94 is formed. If the sound waves introduced through holes 85-88 have a waveform that is out of phase with at least one of the reflected waves D7 and D8 and the standing wave D9, the sound waves introduced through holes 85-88 are canceled out. Also, in the silencer tube 50 shown in FIG. 8D , a reflected wave D10 is formed when the sound waves reflected by end plate 94 are reflected by end plate 93. If the sound waves introduced through holes 85-88 have a waveform that is out of phase with the reflected wave D10, the sound waves introduced through holes 85-88 are canceled out. Furthermore, sound waves introduced through any of the holes 85 to 88 reach the opening 82, are introduced into the outer pipe 90, reach the end plate 93 of the outer pipe 90 and are reflected, reach the opening 82 again, are introduced into the inner pipe 80, and reach the holes 85 to 88. If the sound waves that reach the holes 85 to 88 have waveforms that are out of phase with the sound waves introduced through the holes 85 to 88, the sound waves introduced through the holes 85 to 88 are canceled out. In this way, in the silencer tube 50 shown in Figures 8B to 8D, as in the silencer tube 50 shown in Figure 8A, by making the silencer tube 50 a double pipe, it is possible to lengthen the path of the reflected waves even in a short pipe, and it is possible to lower the frequency of the exhaust noise that is canceled out by the silencer tube 50 while preventing the silencer tube 50 from becoming too long.

[0046] Up to this point, each embodiment of the muffler 30 has been described. Each of the first to seventh embodiments described above may be combined with other embodiments. For example, the first embodiment may be combined with at least one of the second to seventh embodiments. The same applies to the second to seventh embodiments.

[0047] According to this embodiment, there is provided an engine silencer including a chamber communicating with an engine 10 and a pipe 50 disposed in the chamber, the pipe 50 having a plurality of holes and a closed end opening to form a space A4 communicating with the chamber via the plurality of holes. This makes it possible to suppress the sound pressure level of low-frequency exhaust noise.

[0048] In the engine silencer of this embodiment, the holes are provided at positions closer to the ends than to the central portion X in the axial direction of the pipe 50. This makes it possible to change the frequency of the exhaust noise that is canceled by the reflected waves.

[0049] In the engine silencer of this embodiment, a first group of the holes is provided at a first position on the pipe 50, and a second group of the holes is provided at a second position that is spaced apart from the first position in the axial direction of the pipe 50. This makes it possible to increase the frequency of exhaust noise that is canceled by the silencer pipe 50.

[0050] In the engine silencer of this embodiment, the chamber is divided into a plurality of sections, the pipe 50 extends across a first section A1 and a second section A2 adjacent to the first section A1, and the pipe 50 is provided with a first group of holes communicating with the first section A1 and a second group of holes communicating with the second section A2. This makes it possible to further increase the frequencies of exhaust noise that the silencer pipe 50 cancels.

[0051] In the engine silencer of this embodiment, the opening of the pipe 50 is closed by a closing member, and at least one of the closing members is provided with the hole that connects the space A4 to the chamber, thereby suppressing the resonance phenomenon inside the silencer pipe 50 caused by the reflected waves C1 and C2.

[0052] In the engine silencer of this embodiment, the projected areas E1, E3 of at least one of the openings on planes Z, Za perpendicular to the axial direction of the pipe 50 are larger than the cross-sectional area E2 of the pipe 50 perpendicular to the axial direction at the position where the hole is provided, thereby increasing the effect of canceling out exhaust noise.

[0053] In the engine silencer of this embodiment, the pipe 50 includes a first side member and a second side member disposed inside or outside the first side member, and at least two of the openings on one side of the first side member, the openings on the other side of the first side member, the openings on one side of the second side member, and the openings on the other side of the second side member are closed so that the first side member and the second side member form the space A4 that communicates with the chamber via the plurality of holes. This makes it possible to increase the frequency of exhaust noise that is canceled by the silencer pipe 50 while preventing the silencer pipe 50 from becoming large.

[0054] DESCRIPTION OF SYMBOLS 10... Engine 20... Exhaust pipe 30... Muffler 31... Housing 32, 33... Partition plate 32a, 32b, 33a... Holes 40... Tail pipe 50... Pipe (silencer pipe) 51, 52... Openings 53, 54... End plate 53a, 54a... Holes 61, 62, 63, 64, 65, 66, 67, 68, 71, 72, 73, 74, 75, 76, 77, 78... Holes 80... Inner pipe 81, 82... Openings 83, 84... End plate 85, 86, 87, 88... Holes 90... Outer pipe 91, 92... Openings 93, 94... End plate 95, 96... Holes A1... First compartment A2... Second compartment A3... Third compartment A4... Space B1, B2, B3... Arrows C1, C2, C4, C5, C6, C7...Reflected wave, C3, C10...Standing wave, C8, C9...Sound wave, C11...First sound wave, C12...Second sound wave D1, D2, D4, D5, D6, D7, D8, D10...Reflected wave, D3, D9...Standing wave X...Central part, Y1, Y2...Sound wave, Z, Za...plane

Claims

1. A silencer for an engine comprising: a chamber communicating with an engine; and a pipe disposed in said chamber, said pipe having a plurality of holes and an opening at one end which is closed, forming a space communicating with said chamber via said plurality of holes.

2. The engine silencer according to claim 1, wherein the plurality of holes are provided at positions closer to the end portions than to the central portion in the axial direction of the pipe.

3. An engine silencer as described in claim 1 or 2, wherein a first group of the holes is provided at a first position of the tube, and a second group of the holes is provided at a second position axially away from the first position of the tube.

4. A silencer for an engine as described in any one of claims 1 to 3, wherein the chamber is divided into a plurality of compartments, the pipe extends across a first compartment and a second compartment adjacent to the first compartment, and the pipe is provided with a first group of a plurality of the holes communicating with the first compartment, and a second group of a plurality of the holes communicating with the second compartment.

5. A silencer for an engine as claimed in any one of claims 1 to 4, wherein the opening of the pipe is closed by a closing member, and at least one of the multiple closing members is provided with the hole through which the space communicates with the chamber.

6. An engine silencer as claimed in any one of claims 1 to 5, wherein the projected area of ​​at least one of the openings on a plane perpendicular to the axial direction of the pipe is greater than the cross-sectional area of ​​the pipe perpendicular to the axial direction at the position where the hole is provided.

7. A silencer for an engine as claimed in any one of claims 1 to 6, wherein the pipe comprises a first side member and a second side member arranged inside or outside the first side member, and at least two of the opening on one side of the first side member, the opening on the other side of the first side member, the opening on one side of the second side member, and the opening on the other side of the second side member are closed so that the first side member and the second side member form the space communicating with the chamber via a plurality of the holes.

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