Vehicle exhaust pipe

Abstract

To provide a vehicular exhaust pipe capable of obtaining larger exhaust sound volume when an engine is operated at high speed.SOLUTION: A vehicular exhaust pipe 1 includes: first piping 10 in which exhaust gas from an engine flows; a muffler 40 provided in the first piping 10; and a first branch pipe 30 connected to the first piping 10 on the engine side of the muffler 40 and discharging at least part of the exhaust gas in the first piping 10 to outside. The first piping 10 includes a first bent pipe part 20 bent in one direction from the engine side toward the muffler 40 side. The first branch pipe 30 is connected to the first piping 10 between a bending start end part 21 in which bending of the first bent pipe part 20 starts and a bending terminal part 22 in which the bending ends.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust pipe for a vehicle. [Background technology]

[0002] The following Patent Document 1 discloses an exhaust silencer having an exhaust pipe with an exhaust passage through which exhaust gas from an internal combustion engine is discharged, and a container with a volume chamber connected to a branching portion of the exhaust pipe and communicating with the exhaust passage. The container has an opening that can open and close the volume chamber to the outside space, and is also equipped with an opening / closing means for switching the opening between an open state and a closed state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-190679 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vehicle exhaust pipe disclosed in Patent Document 1, the exhaust noise generated by the engine was easily transmitted to the exhaust pipe equipped with a silencer. Therefore, even when the engine was operated at high revolutions, the exhaust noise was reduced by the silencer, making it difficult to achieve a loud exhaust volume.

[0005] An object of the present invention is to provide an exhaust pipe for a vehicle that can produce a louder exhaust sound when the engine is operated at a high rotation speed. [Means for solving the problem]

[0006] A vehicle exhaust pipe according to one aspect of the present invention includes a first pipe, a silencer, and a first branch pipe. The first pipe includes a first bent pipe section that bends in one direction from the engine side to the silencer side, and the first branch pipe is connected to the first pipe between a bend start end where the bending of the first bent pipe section begins and a bend end end where the bending ends. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an exhaust pipe for a vehicle that can produce a louder exhaust sound when the engine is operated at a high rotation speed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a plan view showing a configuration of a vehicle exhaust pipe according to an embodiment of the present invention; [Figure 2] 1 is a partial perspective view showing a configuration of a vehicle exhaust pipe according to an embodiment of the present invention; [Figure 3] 4 is a diagram for explaining the arrangement relationship between a first curved pipe portion and a first branch pipe of the vehicle exhaust pipe according to the embodiment, and is a partial plan view showing the vicinity of the first curved pipe portion. FIG. [Figure 4] 10 is a diagram for explaining the arrangement relationship between the second curved pipe portion and the second branch pipe of the vehicle exhaust pipe according to the embodiment, and is a partial plan view showing the vicinity of the second curved pipe portion. FIG. [Figure 5] FIG. 2 is a diagram for explaining the behavior of exhaust sound waves traveling through the internal space of the first pipe of the vehicle exhaust pipe according to the embodiment, and is a schematic partial cross-sectional view taken along line VV in FIG. 1, showing one mode of sound wave propagation in a low rotation speed state. [Figure 6] FIG. 6 is a diagram for explaining the behavior of exhaust sound waves traveling through the internal space of the first pipe of the vehicle exhaust pipe according to the embodiment, and is a schematic partial cross-sectional view corresponding to FIG. 5, showing one mode of sound wave propagation in a high rotation speed state. [Figure 7] 1 is a diagram for explaining the propagation direction of sound waves of exhaust sound in a low rotation speed state of a vehicle exhaust pipe according to an embodiment, and is a schematic partial cross-sectional view showing the periphery of a first curved pipe portion. FIG. [Figure 8]1 is a diagram for explaining the propagation direction of sound waves of exhaust sound in a vehicle exhaust pipe according to an embodiment in a high rotation speed state, and is a schematic partial cross-sectional view showing the periphery of a first curved pipe portion. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a vehicle exhaust pipe 1 according to an embodiment will be described with reference to the drawings. In each drawing, FR and RR indicate the front and rear in the longitudinal direction of the vehicle exhaust pipe 1, LH and RH indicate the left and right in the width direction of the vehicle exhaust pipe 1, and UP and DN indicate the upper and lower sides of the vehicle exhaust pipe 1. Elements having the same function are given the same reference numerals, and duplicate explanations will be omitted.

[0010] In the examples shown in Figures 1 to 8, the front of the vehicle exhaust pipe 1 corresponds to the front in the vehicle's fore-and-aft direction, and the rear corresponds to the rear in the vehicle's fore-and-aft direction. The left side of the vehicle exhaust pipe 1 corresponds to the left in the vehicle width direction, and the right side corresponds to the right in the vehicle width direction. The center of the vehicle in the vehicle width direction is referred to as the inner side in the vehicle width direction, and the side opposite the inner side in the vehicle width direction is referred to as the outer side in the vehicle width direction. In each figure, the inner side in the vehicle width direction is indicated by IS, and the outer side in the vehicle width direction is indicated by OS. In the following explanation, the front and rear in the vehicle's fore-and-aft direction will be simply referred to as the "front of the vehicle" and the "rear of the vehicle," respectively.

[0011] The vehicle exhaust pipe 1 according to the embodiment can be used to discharge exhaust gas from a vehicle driven by an engine (not shown) to the outside. The engine may be a V-type engine having banks on one side and on the other side. An exhaust manifold (not shown) may be connected to each of the banks.

[0012] As shown in FIG. 1 or 2, a vehicle exhaust pipe 1 according to the embodiment includes a first pipe 10, a first branch pipe 30, and a silencer 40.

[0013] The first pipe 10 is a pipe through which exhaust gas from the engine flows. The first pipe 10 is a cylindrical pipe member and may be made of a metal such as stainless steel or iron. An internal space 13 having a substantially circular shape in a cross section perpendicular to the extension direction of the first pipe 10 is formed inside the first pipe 10.

[0014] The first pipe 10 is directly or indirectly connected to an exhaust manifold formed on one side of the engine. Therefore, engine exhaust gas flows into an internal space 13 of the first pipe 10, as shown by arrow A in Fig. 1. When the first pipe 10 and the exhaust manifold are indirectly connected, other pipe members (not shown) or a catalytic converter (not shown), which is a device for purifying exhaust gas, may be interposed, for example, forward of the end 11 of the first pipe 10.

[0015] As illustrated in the figure, the first pipe 10 has an end 11 and an end 12. The end 11 is an end that is connected directly or indirectly to an engine. The end 11 may be formed with a flange portion that extends radially outward of the first pipe 10. The end 12 is an end of the first pipe 10 opposite the end 11. A silencer 40 is connected to the end 12.

[0016] In the illustrated example, the first pipe 10 extends from the end 11 toward the rear of the vehicle, and then extends outward in the vehicle width direction and toward the rear of the vehicle. The first pipe 10 starts bending at the bending start end 21 and ends at the bending end 22, forming the first bent pipe section 20. The first pipe 10 then extends inward in the vehicle width direction from the bending end 22 and is connected to the silencer 40 at the end 12.

[0017] A silencer 40 is provided in the first pipe 10. The silencer 40 is a device that reduces the volume of exhaust noise from the engine. In the illustrated example, the silencer 40 extends in the vehicle width direction, and one end 41 of the silencer 40 is connected to the end 12 of the first pipe 10.

[0018] The muffler 40 may be a muffler that reduces exhaust noise using a known method. For example, the muffler 40 may be an expansion-type muffler that reduces exhaust noise by gradually expanding exhaust gas, an absorption-type muffler that reduces exhaust noise by absorbing exhaust noise with sound-absorbing material disposed inside, or a resonator-type muffler that uses Helmholtz resonance. In the illustrated example, the muffler 40 is connected to the first pipe 10, but this is not limiting. For example, the straight pipe portion 26 may be extended inward in the vehicle width direction so that the end portion 12 is positioned further inward in the vehicle width direction, and the muffler 40 that attenuates exhaust noise using a resonator may be provided on the side of the portion of the first pipe 10 between the end portion 12 and the bent end portion 22. Alternatively, the muffler 40 may be disposed in the space inside the pipe in that portion.

[0019] The first pipe 10 includes a first curved pipe portion 20 that curves in one direction from the engine side to the silencer 40 side. In the illustrated example, the first curved pipe portion 20 is disposed between the end 11 and the end 12.

[0020] In the example shown in FIG. 3, the pipe axis 23 of the first bent pipe section 20 is formed by a curve extending on a plane, and the curve does not include an inflection point. The pipe axis 23 does not include a straight line. In the example shown in the figure, the pipe axis 23 is an arc of a curvature circle O1 with a curvature radius R1. The center of curvature C1 of the curvature circle O1 is located inside the pipe axis 23 in the vehicle width direction. The pipe axis 23 may be, for example, a quadratic curve, or a curve whose curvature continuously increases and decreases from the end on the bend start end 21 side to the end on the bend end 22 side, and the pipes do not have to be on the same plane. The curvature radius R1 may be set to, for example, 10 mm or more. The inner diameter of the pipe at the first bent pipe section 20 may be set to, for example, 20 mm or more and 120 mm or less.

[0021] Because the first curved pipe section 20 has such a pipe axis 23, it curves in one direction from the bending start point 21 on the engine side to the bending end point 22 on the silencer 40 side. The bending start point 21 is the part where the curvature of the first curved pipe section 20 begins. The bending start point 21 constitutes the engine side end of the first curved pipe section 20. The bending end point 22 is the part where the curvature of the first curved pipe section 20 ends. The bending end point 22 constitutes the silencer 40 side end of the first curved pipe section 20.

[0022] In the illustrated example, the portion of the first piping 10 connected to the bend start end 21 is composed of a straight pipe section 24. The straight pipe section 24 is a cylindrical section extending linearly and has a pipe axis 25. The pipe axis 25 is composed of a straight line. Furthermore, the portion of the first piping 10 connected to the bend end 22 is composed of a straight pipe section 26. The straight pipe section 26 is a cylindrical section extending linearly and has a pipe axis 27. The pipe axis 27 is composed of a straight line. The pipe axis 25 and the pipe axis 23 are connected at the bend start end 21. The pipe axis 27 and the pipe axis 23 are connected at the bend end 22. Furthermore, the pipe axis 23, the pipe axis 25, and the pipe axis 27 may extend on the same plane.

[0023] The first curved pipe section 20 may be configured as an integral part of or separate from the first pipe 10. For example, the first curved pipe section 20 may be formed integrally with the first pipe 10 by bending the first pipe 10 at a predetermined curvature. Alternatively, the first pipe 10 may be formed by connecting pipe members to one end and the other end of the first curved pipe section 20 configured as a separate part.

[0024] 1 or 2, the first branch pipe 30 is connected to the first pipe 10 on the engine side of the silencer 40, and is a pipe that discharges at least a portion of the exhaust gas in the first pipe 10 to the outside. The first branch pipe 30 is connected to the first pipe 10 between a bending start end 21 where the bending of the first bent pipe section 20 begins and a bending end end 22 where the bending ends.

[0025] In the illustrated example, the first branch pipe 30 is a tubular member having a substantially circular shape in a cross section perpendicular to its extension direction, and may be made of a metal such as stainless steel or iron. A silencer may be disposed in or connected to the first branch pipe 30. An end 31 of the first branch pipe 30 is connected to the first bent pipe section 20 between the bending start end 21 and the bending end 22. Therefore, the end 31 is connected to the first piping 10 closer to the engine than the silencer 40. The first branch pipe 30 extends outward in the vehicle width direction from the end 31.

[0026] The internal space 34 of the first branch pipe 30 and the internal space 13 of the first piping 10 are in communication with each other. Therefore, at least a portion of the exhaust gas introduced into the first piping 10 flows into the internal space 34. The first branch pipe 30 may be provided with a cylindrical tail pipe (not shown).

[0027] A first exhaust port 36 is formed at end 32 of first branch pipe 30. End 32 is the end opposite end 31 of first branch pipe 30. In the illustrated example, end 32 constitutes the end of first branch pipe 30 on the vehicle rear side. First exhaust port 36 is an outward opening formed at end 32, and first exhaust port 36 connects internal space 34 with the outside of vehicle exhaust pipe 1. Therefore, exhaust gas that has flowed into internal space 34 of first branch pipe 30 can be discharged to the outside.

[0028] As shown in FIG. 3 , the first branch pipe 30 is connected to the curved outer side of the first curved pipe section 20. The curved outer side refers to the direction in which the curve that forms the pipe axis of the curved pipe protrudes. In the illustrated example, the curved outer side of the first curved pipe section 20 is the direction in which the first curved pipe section 20 bulges when bending, and is on the outside of the curve formed by the first curved pipe section 20. The curved outer side of the first curved pipe section 20 corresponds to the outer side in the vehicle width direction. In addition, the first branch pipe 30 is connected to the pipe wall of the first curved pipe section 20 on the radially outer side of the curvature circle O1.

[0029] The pipe axis 33 of the end 31 of the first branch pipe 30 connected to the first piping 10 may extend on a plane including the pipe axis 23 of the first curved pipe section 20. The pipe axis 33 is the pipe axis at the end 31 of the first branch pipe 30 and is composed of a straight line. Note that this straight line also includes a half line extending toward the first curved pipe section 20. In the illustrated example, the pipe axis 33 extends on a plane in which the circle of curvature O1 extends. That is, the pipe axis 25, the pipe axis 27, and the pipe axis 33 may extend on the same plane.

[0030] The pipe axis 33 of the end 31 of the first branch pipe 30 connected to the first piping 10 may be perpendicular to the pipe axis 23 of the first curved pipe section 20. In the example shown, the pipe axis 23 and the pipe axis 33 are perpendicular to each other at the intersection P1. In other words, the pipe axis 33 is a normal to the pipe axis 23 at the intersection P1. Furthermore, since the pipe axis 23 is formed by the arc of the curvature circle O1, the straight line that forms the pipe axis 33 is perpendicular to the curvature circle O1. In other words, the first branch pipe 30 may be connected to the first curved pipe section 20 at a right angle.

[0031] As illustrated in the figure, the pipe axis 33 of the end 31 of the first branch pipe 30 connected to the first pipe 10 may pass through the center of curvature C1 of the pipe axis 23 of the first bent pipe section 20. This allows the sound waves of the exhaust sound propagating inside the first pipe 10 to be propagated inside the first branch pipe 30 more reliably in a high rotation speed state described below.

[0032] Furthermore, the smaller of the angles formed between the straight pipe portion 24 and the straight pipe portion 26 may be equal to or greater than 0 degrees and equal to or less than 90 degrees. That is, the smaller angle θ1 of the angles formed between the pipe axis 25 and the pipe axis 27 may be equal to or greater than 0 degrees and equal to or less than 90 degrees. This allows the sound waves of the exhaust sound that have propagated inside the first piping 10 to be propagated inside the first branch pipe 30 more reliably in a high rotation speed state described below.

[0033] As shown in FIG. 1 or 2, the vehicle exhaust pipe 1 may include a second pipe 50 and a second branch pipe 70.

[0034] The second pipe 50 is a pipe through which exhaust gas from the engine flows. The second pipe 50 is a cylindrical pipe member and may be made of a metal such as stainless steel or iron. An internal space 53 having a substantially circular shape in a cross section perpendicular to the extension direction of the second pipe 50 is formed inside the second pipe 50.

[0035] The second pipe 50 is directly or indirectly connected to an exhaust manifold formed on the other side of the engine. Therefore, engine exhaust gas flows into an internal space 53 of the second pipe 50, as shown by arrow B in Fig. 1. When the second pipe 50 and the exhaust manifold are indirectly connected, for example, other pipe members (not shown) or a catalytic converter (not shown) that purifies exhaust gas may be interposed further forward of the end 51 of the second pipe 50 on the vehicle.

[0036] As illustrated in the figure, the second pipe 50 has an end 51 and an end 52. The end 51 is an end that is connected directly or indirectly to the engine. The end 51 may be formed with a flange portion that extends radially outward of the second pipe 50. The end 52 is an end of the second pipe 50 opposite the end 51. The silencer 40 is connected to the end 52.

[0037] In the illustrated example, the second pipe 50 extends from the end 51 toward the rear of the vehicle, and then extends outward in the vehicle width direction and toward the rear of the vehicle. The bending starts at the bending start end 61 and ends at the bending end 62, forming the second curved pipe portion 60. The second pipe 50 then extends inward in the vehicle width direction from the bending end 62 and is connected to the silencer 40 at the end 52.

[0038] The second pipe 50 is a pipe that communicates with the first pipe 10 via the silencer 40 and allows exhaust gas from the engine to flow into the silencer 40. In the illustrated example, an end 52 of the second pipe 50 is connected to the other end 42 of the silencer 40. Therefore, the internal space 13 of the first pipe 10 and the internal space 53 of the second pipe 50 communicate with each other via the inside of the silencer 40. Furthermore, at least a portion of the exhaust gas from the engine that has flowed into the second pipe 50 flows into the silencer 40 from the end 42.

[0039] The second piping 50 includes a second curved pipe portion 60 that curves in one direction from the engine side to the silencer 40 side. In the illustrated example, the second curved pipe portion 60 is disposed between the end portion 51 and the end portion 52.

[0040] In the example shown in FIG. 4, the pipe axis 63 of the second bent pipe section 60 is formed by a curve extending on a plane, and the curve does not include an inflection point. The pipe axis 63 does not include a straight line. In the example shown in the figure, the pipe axis 63 is an arc of a curvature circle O2 with a curvature radius R2. The center of curvature C2 of the curvature circle O2 is located inside the pipe axis 63 in the vehicle width direction. The pipe axis 63 may be, for example, a quadratic curve, or a curve whose curvature continuously increases and decreases from the end on the bend start end 61 side to the end on the bend end end 62 side, and the pipes do not have to be on the same plane. The curvature radius R2 may be set to, for example, 10 mm or more. The inner diameter of the pipe in the second bent pipe section 60 may be set to, for example, 20 mm or more and 120 mm or less.

[0041] Because the second curved pipe section 60 has such a pipe axis 63, it curves in one direction from the bending start end 61 on the engine side to the bending end 62 on the silencer 40 side. The bending start end 61 is the part where the curvature of the second curved pipe section 60 begins. The bending start end 61 constitutes the engine side end of the second curved pipe section 60. The bending end 62 is the part where the curvature of the second curved pipe section 60 ends. The bending end 62 constitutes the silencer 40 side end of the second curved pipe section 60.

[0042] In the illustrated example, the portion of the second piping 50 connected to the bend start end 61 is composed of a straight pipe section 64. The straight pipe section 64 is a cylindrical section extending linearly and has a pipe axis 65. The pipe axis 65 is composed of a straight line. Furthermore, the portion of the second piping 50 connected to the bend end end 62 is composed of a straight pipe section 66. The straight pipe section 66 is a cylindrical section extending linearly and has a pipe axis 67. The pipe axis 67 is composed of a straight line. The pipe axis 65 and the pipe axis 63 are connected at the bend start end 61. The pipe axis 67 and the pipe axis 63 are connected at the bend end end 62. Furthermore, the pipe axis 63, the pipe axis 65, and the pipe axis 67 may extend on the same plane.

[0043] The second curved pipe portion 60 may be configured as an integral part or a separate part from the second piping 50. For example, the second curved pipe portion 60 may be formed integrally with the second piping 50 by bending the second piping 50 at a predetermined curvature. Alternatively, the second piping 50 may be formed by connecting piping members to one end and the other end of the second curved pipe portion 60 configured as a separate part.

[0044] 1 or 2, the second branch pipe 70 is connected to the second pipe 50 on the engine side of the silencer 40, and is a pipe that discharges at least a portion of the exhaust gas in the second pipe 50 to the outside. The second branch pipe 70 is also connected to the second pipe between a bending start end 61 where the bending of the second bent pipe section 60 begins and a bending end end 62 where the bending ends.

[0045] In the illustrated example, the second branch pipe 70 is a tubular member having a substantially circular shape in a cross section perpendicular to its extension direction, and may be made of a metal such as stainless steel or iron. A silencer may be disposed in or connected to the second branch pipe 70. An end 71 of the second branch pipe 70 is connected to the second bent pipe section 60 between the bending start end 61 and the bending end 62. Therefore, the end 71 is connected to the second piping 50 closer to the engine than the silencer 40. The second branch pipe 70 extends outward in the vehicle width direction from the end 71.

[0046] The internal space 74 of the second branch pipe 70 and the internal space 53 of the second piping 50 are in communication with each other. Therefore, at least a portion of the exhaust gas introduced into the second piping 50 flows into the internal space 74. The second branch pipe 70 may be provided with a cylindrical tail pipe (not shown).

[0047] A second exhaust port 76 is formed at end 72 of second branch pipe 70. End 72 is the end opposite end 71 of second branch pipe 70. In the illustrated example, end 72 constitutes the end of second branch pipe 70 on the vehicle rear side. Second exhaust port 76 is an outward opening formed at end 72, and second exhaust port 76 connects internal space 74 to the outside of vehicle exhaust pipe 1. Therefore, exhaust gas that flows into internal space 74 of second branch pipe 70 can be discharged to the outside.

[0048] As shown in Fig. 4, the second branch pipe 70 is connected to the curved outer side of the second curved pipe section 60. In the illustrated example, the curved outer side of the second curved pipe section 60 is the side in the direction in which the second curved pipe section 60 bulges when curved, and is on the outside of the curve formed by the second curved pipe section 60. The curved outer side of the second curved pipe section 60 corresponds to the outer side in the vehicle width direction. In addition, the second branch pipe 70 is connected to the pipe wall of the second curved pipe section 60 on the radially outer side of the curvature circle O2.

[0049] The pipe axis 73 of the end 71 of the second branch pipe 70 connected to the second piping 50 may extend on a plane including the pipe axis 63 of the second curved pipe section 60. The pipe axis 73 is the pipe axis at the end 71 of the second branch pipe 70 and is composed of a straight line. Note that this straight line also includes a half line extending toward the second curved pipe section 60. In the illustrated example, the pipe axis 73 extends on a plane in which the circle of curvature O2 extends. That is, the pipe axis 65, the pipe axis 67, and the pipe axis 73 may extend on the same plane.

[0050] The pipe axis 73 of the end 71 of the second branch pipe 70 connected to the second piping 50 may be perpendicular to the pipe axis 63 of the second curved pipe section 60. In the example shown, the pipe axis 73 and the pipe axis 73 are perpendicular to each other at intersection P2. In other words, the pipe axis 73 is a normal to the pipe axis 63 at intersection P2. Furthermore, since the pipe axis 63 is formed by the arc of the circle of curvature O2, the straight line that forms the pipe axis 73 is perpendicular to the circle of curvature O2. In other words, the second branch pipe 70 may be connected to the second curved pipe section 60 at a right angle.

[0051] As illustrated in the figure, the pipe axis 73 of the end 71 of the second branch pipe 70 connected to the second piping 50 may pass through the center of curvature C2 of the pipe axis 63 of the second curved pipe portion 60. This allows the sound waves of the exhaust sound propagating inside the second piping 50 to be propagated inside the second branch pipe 70 more reliably in a high rotation speed state described below.

[0052] Furthermore, the smaller of the angles formed between the straight pipe portion 64 and the straight pipe portion 66 may be greater than or equal to 0 degrees and less than or equal to 90 degrees. That is, the smaller angle θ2 of the angles formed between the pipe axis 65 and the pipe axis 67 may be greater than or equal to 0 degrees and less than or equal to 90 degrees. This allows the sound waves of the exhaust sound that have propagated inside the second piping 50 to be propagated inside the second branch pipe 70 more reliably in a high rotation speed state, which will be described later.

[0053] 1 and 2, the first branch pipe 30 or the second branch pipe 70 extends from the end 31 or the end 71 outward in the vehicle width direction and toward the rear of the vehicle, and then curves and extends toward the rear of the vehicle, but this is not limited to this. The shape of the first branch pipe 30 or the second branch pipe 70 can be set appropriately depending on the shape and dimensions of the vehicle exhaust pipe 1, its installation position on the vehicle, etc.

[0054] Hereinafter, the functions and effects of the vehicle exhaust pipe 1 according to the embodiment will be described with reference to FIGS.

[0055] First, we will explain the relationship between the engine rotation speed and the wavefront of the sound waves propagating through the pipe, taking the exhaust sound flowing from the engine into the first pipe 10 as an example. When the engine is running, the sound waves of the exhaust sound generated by the engine travel through the internal space 13 of the first pipe 10 toward the opposite side of the engine. Note that these sound waves are longitudinal waves in which the displacement of the medium is parallel to the direction of wave propagation. Furthermore, these sound waves propagate mainly through the engine exhaust gas as a medium.

[0056] In the following description, a state in which the engine is operating at a speed equal to or higher than the transition speed is referred to as a high speed state. A state in which the engine is operating at a speed lower than the transition speed is referred to as a low speed state. The transition speed is the speed at which the wavefront shape of the exhaust sound wave begins to change from a flat surface to a curved surface when the engine speed is increased. In one embodiment, the transition speed may be set to a value between 1000 revolutions per minute (rpm) and 6500 rpm, for example.

[0057] 5 and 6 are diagrams showing an example of an exhaust sound wave traveling through the internal space 13 of the first pipe 10. FIG. 5 shows the example of the sound wave in a low rotation speed state. FIG. 6 shows the example of the sound wave in a high rotation speed state. The propagation of the sound wave is generally represented by the vibration of gas particles connected to each other by elastic lines. In the example shown, multiple gas particles 80, 80a, and 80b are connected to each other by an elastic line 81.

[0058] At low rotation speeds, the wavefront formed by the vibration of gas particles has a substantially planar shape. Since the sound wave propagates in a direction perpendicular to the wavefront, the sound wave propagates through the internal space 13 as a plane wave, as shown by arrow C in FIG. 5.

[0059] Here, when the exhaust pressure increases with an increase in engine speed, the vibration velocity of the gas particles 80 increases. Furthermore, among the gas particles 80, gas particles 80a located near the pipe wall of the first piping 10 are subjected to a frictional force from the pipe wall. As a result, the vibration velocity of gas particles 80b located farther from the pipe wall than gas particle 80a becomes higher than the vibration velocity of gas particle 80a. Note that the frictional force from the pipe wall increases as the vibration velocity of the gas particles increases.

[0060] Therefore, the wavefront of the sound wave at high rotation speeds forms a curved surface that is located closer to the center than the ends in the width direction perpendicular to the direction of sound wave propagation. Since the sound wave propagates in a direction perpendicular to the wavefront, the exhaust sound wave propagates through the internal space 13 as a curved wave, as shown by arrow D in Figure 6. Note that a curved wave is a wave whose wavefront is formed by a curve in a cross section parallel to the direction of sound wave propagation. The curved surface that forms the wavefront of a curved wave may be, for example, a parabolic or spherical surface.

[0061] Next, the propagation direction of exhaust sound waves in a low rotation speed state and a high rotation speed state will be described with reference to Figures 7 and 8. Figure 7 is a schematic diagram showing one mode of propagation of the sound waves in a low rotation speed state. Figure 8 is a schematic diagram showing one mode of propagation of the sound waves in a high rotation speed state.

[0062] At low engine speeds, the sound waves of the exhaust sound are plane waves. Therefore, sound waves propagating through the internal space 13 of the first pipe 10 tend to travel in the direction indicated by arrow E in Figure 7. That is, the sound waves travel inside the first bent pipe section 20 along the curvature of the first bent pipe section 20 and are likely to be guided to the silencer 40. Therefore, the volume of the exhaust sound generated at low engine speeds is reduced by the silencer 40. In the vehicle exhaust pipe 1 shown in Figures 1 and 2, the sound waves pass through the silencer 40, then pass through the second bent pipe section 60 and the second branch pipe 70, and are released from the second exhaust port 76.

[0063] At high engine speeds, exhaust sound waves are curved waves. Therefore, a portion of the wavefront of the sound waves propagating through the internal space 13 of the first piping 10 is likely to propagate toward the first branch pipe 30 near the connection between the first bent pipe portion 20 and the first branch pipe 30. In the example shown in FIG. 8, a portion of the sound waves travels toward the first branch pipe 30 as indicated by arrow F in the figure and is guided to the internal space 34, while a portion travels inside the first bent pipe portion 20 along the curve of the first bent pipe portion 20 as indicated by arrow G and is guided to the silencer 40. The sound waves that have propagated into the internal space 34 are released to the outside of the vehicle exhaust pipe 1 through the first exhaust port 36 (see FIG. 1) without passing through the silencer 40. This allows for a louder exhaust sound.

[0064] Due to a similar effect, at low engine speeds, sound waves of the exhaust noise propagating through the second pipe 50 travel inside the second bent pipe section 60 and are likely to be guided to the silencer 40. Therefore, the volume of the exhaust noise generated at low engine speeds is reduced by the silencer 40. In the vehicle exhaust pipe 1 shown in Figures 1 and 2, the sound waves pass through the silencer 40, then travel through the first bent pipe section 20 and the first branch pipe 30, and are released from the first exhaust port 36.

[0065] Furthermore, in a high rotation speed state, part of the wavefront of the sound waves propagating through the internal space 53 of the second piping 50 is likely to propagate toward the second branch pipe 70 near the connection between the second bent pipe portion 60 and the second branch pipe 70. As a result, part of the sound waves travel toward the second branch pipe 70 and are guided to the internal space 74, and part of the sound waves travel inside the second bent pipe portion 60 along the curve of the second bent pipe portion 60 and are guided to the silencer 40. The sound waves that have propagated into the internal space 74 are released to the outside of the vehicle exhaust pipe 1 through the second exhaust port 76 without passing through the silencer 40. As a result, a louder exhaust sound can be obtained.

[0066] 1 and 2, the vehicle exhaust pipe 1 includes a first pipe 10, a first branch pipe 30, a silencer 40, a second pipe 50, and a second branch pipe 70, but is not limited to this. When the vehicle exhaust pipe 1 is composed of the first pipe 10, the first branch pipe 30, and the silencer 40, for example, the first pipe 10 may be directly or indirectly connected to exhaust manifolds on one side and the other side of the engine. In this case, the sound waves of the exhaust sound that have passed through the silencer 40 may be configured to be able to be released from an exhaust port formed at an end 42 of the silencer 40.

[0067] In the illustrated example, the vehicle exhaust pipe 1 has a bilaterally symmetrical shape, but this is not limiting. For example, the inner diameters of the first pipe 10, the first bent pipe portion 20, and the first branch pipe 30 may be different from the inner diameters of the second pipe 50, the second bent pipe portion 60, and the second branch pipe 70. The first bent pipe portion 20 and the second bent pipe portion do not have to be curved in a bilaterally symmetrical shape. For example, the radius of curvature R1 of the circle of curvature O1 and the radius of curvature R2 of the circle of curvature O2 may be set to different values. The pipe axis 23 of the first bent pipe portion 20 and the pipe axis 63 of the second bent pipe portion 60 do not have to extend on the same plane.

[0068] The transition rotation speed of the sound wave propagating inside the first pipe 10 can be set appropriately by adjusting the pipe inner diameter of the first pipe 10. For example, by increasing the pipe inner diameter of the first bent pipe section 20 of the first pipe 10, the flow velocity of the exhaust gas inside the first bent pipe section 20 decreases and the static pressure increases. This reduces the vibration velocity of the gas particles. This increases the engine rotation speed when the sound wave changes from a plane wave to a curved wave. In other words, the transition rotation speed increases.

[0069] Furthermore, by adjusting the curvature of the first bent pipe portion 20, it is possible to adjust the exhaust noise volume at high rotation speeds. For example, by curving the first bent pipe portion 20 more gently, it is possible to suppress the exhaust noise volume. In the example shown in FIG. 3, by increasing the curvature radius R1 of the pipe axis 23, sound waves can more easily travel toward the silencer 40, thereby reducing the exhaust noise volume. On the other hand, by curving the first bent pipe portion 20 more sharply, it is possible to increase the exhaust noise volume. For example, by reducing the curvature radius R1 of the pipe axis 23, it is more easy for sound waves to travel toward the first branch pipe 30, thereby increasing the exhaust noise volume.

[0070] Similarly, the transition rotation speed of the sound waves propagating inside the second piping 50 can be appropriately set by adjusting the inner diameter of the second piping 50. For example, by increasing the inner diameter of the second curved pipe section 60 of the second piping 50, the engine rotation speed at which the sound waves change from plane waves to curved waves increases. In other words, the transition rotation speed increases.

[0071] Furthermore, the exhaust sound volume at high rotation speeds can be adjusted by adjusting the curvature of the second curved pipe portion 60. In the example shown in Fig. 4, by increasing the curvature radius R2 of the pipe axis 63, sound waves can more easily travel toward the silencer 40, thereby reducing the exhaust sound volume. On the other hand, by decreasing the curvature radius R2 of the pipe axis 63, sound waves can more easily travel toward the second branch pipe 70, thereby increasing the exhaust sound volume.

[0072] Next, the flow direction of exhaust gas in a low rotation speed state or a high rotation speed state will be described with reference to FIG.

[0073] At low engine speeds, the flow velocity of exhaust gas is relatively small. Therefore, when exhaust gas flows into the first pipe 10 and passes through the first bent pipe section 20 as indicated by arrow A in FIG. 1, the centrifugal force acting on the exhaust gas is relatively small, and the exhaust gas tends to flow toward the silencer 40. Here, the silencer 40 has an exhaust resistance. Therefore, the exhaust resistance of the vehicle exhaust pipe 1 includes the exhaust resistance caused by the silencer 40.

[0074] At high engine speeds, the flow velocity of exhaust gas is high. Therefore, when the exhaust gas that has flowed into the first piping 10 passes through the first bent pipe portion 20, a large centrifugal force acts on the exhaust gas, and the exhaust gas tends to flow toward the first branch pipe 30. The exhaust resistance of the first branch pipe 30 is smaller than the exhaust resistance of the silencer 40. Therefore, the exhaust resistance of the vehicle exhaust pipe 1 at high engine speeds can be reduced.

[0075] Similarly, with respect to exhaust gas that has flowed into the second pipe 50 as indicated by arrow B, in a low rotation speed state, the exhaust gas tends to flow toward the silencer 40. On the other hand, in a high rotation speed state, the exhaust gas tends to flow toward the second branch pipe 70. The exhaust resistance of the second branch pipe 70 is smaller than the exhaust resistance of the silencer 40. Therefore, the exhaust resistance of the vehicle exhaust pipe 1 in a high rotation speed state can be reduced.

[0076] By adjusting the inner diameter of the first pipe 10 and the curvature of the first bent pipe portion 20, the flow direction of the exhaust gas at the first bent pipe portion 20 at a predetermined engine speed can be adjusted.

[0077] By setting the inner diameter of the first piping 10 to be larger, the flow velocity of the exhaust gas passing through the first bent pipe section 20 decreases, and the centrifugal force acting on the exhaust gas decreases. This makes it easier for the exhaust gas to flow toward the silencer 40 in the first bent pipe section 20. On the other hand, by setting the inner diameter of the first piping 10 to be smaller, the flow velocity of the exhaust gas passing through the first bent pipe section 20 increases, and the centrifugal force acting on the exhaust gas increases. This makes it easier for the exhaust gas to flow toward the first branch pipe 30 in the first bent pipe section 20.

[0078] Furthermore, for example, if the radius of curvature R1 (see FIG. 3 ) of the pipe axis 23 of the first bent pipe section 20 is set larger and the first bent pipe section 20 is curved more gently, the centrifugal force acting on the exhaust gas passing through the first bent pipe section 20 becomes smaller. Therefore, the exhaust gas is more likely to flow toward the muffler 40 in the first bent pipe section 20. On the other hand, if the radius of curvature R1 is set smaller and the first bent pipe section 20 is curved more sharply, the centrifugal force acting on the exhaust gas passing through the first bent pipe section 20 becomes larger. Therefore, the exhaust gas is more likely to flow toward the first branch pipe 30 in the first bent pipe section 20.

[0079] Similarly, for the exhaust gas in the second curved pipe section 60, the flow direction of the exhaust gas in the second curved pipe section 60 at a specified engine speed can be adjusted by adjusting the inner diameter of the second piping 50 and the curvature of the second curved pipe section 60.

[0080] By setting the inner diameter of the second piping 50 to a larger value, the exhaust gas can more easily flow toward the silencer 40 at the first bent pipe section 20. On the other hand, by setting the inner diameter of the second piping 50 to a smaller value, the exhaust gas can more easily flow toward the second branch pipe 70 at the second bent pipe section 60. Furthermore, for example, if the radius of curvature R2 (see FIG. 4 ) of the pipe axis 63 of the second bent pipe section 60 is set to a larger value and the second bent pipe section 60 is curved more gently, the exhaust gas can more easily flow toward the silencer 40 at the second bent pipe section 60. On the other hand, if the radius of curvature R2 is set to a smaller value and the second bent pipe section 60 is curved more sharply, the exhaust gas can more easily flow toward the second branch pipe 70 at the second bent pipe section 60.

[0081] (1) The vehicle exhaust pipe 1 according to the embodiment comprises a first pipe 10 through which exhaust gas from the engine flows, a silencer 40 provided on the first pipe 10, and a first branch pipe 30 connected to the first pipe 10 on the engine side of the silencer 40 and discharging at least a portion of the exhaust gas in the first pipe 10 to the outside, the first pipe 10 including a first curved pipe section 20 that curves in one direction from the engine side to the silencer 40 side, and the first branch pipe 30 is connected to the first pipe 10 between a bending start end 21 where the bending of the first curved pipe section 20 begins and a bending end end 22 where the bending ends.

[0082] In the vehicle exhaust pipe 1 according to this embodiment, when the engine is operating at a low rotation speed, sound waves of the exhaust sound generated by the engine propagate from the first bent pipe portion 20 in the direction to which the silencer 40 is connected, thereby reducing the exhaust volume. Furthermore, when the engine is operating at a high rotation speed, part of the sound waves propagate into the first branch pipe 30 and are released to the outside of the vehicle exhaust pipe 1 without passing through the silencer 40. This makes it possible to suppress a decrease in the exhaust volume. Therefore, a louder exhaust volume can be obtained when the engine is operating at a high rotation speed.

[0083] (2) In the vehicle exhaust pipe 1 according to the embodiment, the first branch pipe 30 may be connected to the outer curved side of the first curved pipe portion 20 .

[0084] As the engine speed increases, the flow velocity of the exhaust gas increases, and the centrifugal force acting on the exhaust gas flowing through the first bent pipe section 20 also increases. In the vehicle exhaust pipe 1 according to this embodiment, the first branch pipe 30 is connected to the outer curved side of the first bent pipe section 20. As a result, as the centrifugal force acting on the exhaust gas increases, the proportion of exhaust gas guided to the first branch pipe 30 increases and the proportion of exhaust gas guided to the silencer 40 decreases. This allows more of the exhaust gas introduced into the first piping 10 to be discharged from the first branch pipe 30. Here, the exhaust resistance of the first branch pipe 30 is smaller than the exhaust resistance of the silencer. Therefore, when the engine operates at high speeds, the exhaust gas can be discharged more efficiently. This ultimately improves engine output.

[0085] (3) In the vehicle exhaust pipe 1 according to the embodiment, the pipe axis 33 of the end 31 of the first branch pipe 30 connected to the first piping 10 may extend on a plane including the pipe axis 23 of the first curved pipe section 20.

[0086] According to the vehicle exhaust pipe 1 according to this embodiment, the pipe axis 23 and the pipe axis 33 extend on the same plane. Therefore, in a high rotation speed state, the sound waves of the exhaust sound can be more reliably propagated inside the first branch pipe 30. Therefore, it is possible to more reliably suppress a decrease in the exhaust sound volume in a high rotation speed state, and to obtain a louder exhaust sound volume when the engine is operated at a high rotation speed.

[0087] (4) In the vehicle exhaust pipe 1 according to the embodiment, the pipe axis 33 of the end 31 of the first branch pipe 30 connected to the first pipe 10 may be perpendicular to the pipe axis 23 of the first bent pipe portion 20.

[0088] According to the vehicle exhaust pipe 1 according to this embodiment, the pipe axis 23 and the pipe axis 33 are perpendicular to each other. Therefore, in a high rotation speed state, the sound waves of the exhaust sound can be more reliably propagated inside the first branch pipe 30. Therefore, it is possible to more reliably suppress a decrease in the exhaust sound volume in a high rotation speed state, and to obtain a louder exhaust sound volume when the engine is operated at a high rotation speed.

[0089] (5) The vehicle exhaust pipe 1 according to the embodiment includes a second pipe 50 that communicates with the first pipe 10 via the silencer 40 and allows exhaust gas from the engine to flow into the silencer 40, and a second branch pipe 70 that is connected to the second pipe 50 on the engine side of the silencer 40 and discharges at least a portion of the exhaust gas in the second pipe 50 to the outside, and the second pipe 50 includes a second curved pipe section 60 that curves in one direction from the engine side to the silencer 40 side, and the second branch pipe 70 may be connected to the second pipe 50 between a bending start end 61 where the bending of the second curved pipe section 60 begins and a bending end end 62 where the bending ends.

[0090] In the vehicle exhaust pipe 1 according to this embodiment, the first pipe 10 and the second pipe 50 are connected to the same silencer 40. Therefore, when the engine is operating at a low rotation speed, exhaust noise propagating through the first pipe 10 passes through the silencer 40 and is emitted from the second exhaust port 76 of the second branch pipe 70. Then, exhaust noise propagating through the second pipe 50 passes through the silencer 40 and is emitted from the first exhaust port 36 of the first branch pipe 30. Furthermore, when the engine is operating at a high rotation speed, exhaust noise propagating through the first pipe 10 is emitted from the first exhaust port 36 and the second exhaust port 76. Then, exhaust noise propagating through the second pipe 50 is emitted from the first exhaust port 36 and the second exhaust port 76. Thus, according to the vehicle exhaust pipe 1 according to this embodiment, the silencer 40 can be shared between the first pipe 10 and the second pipe 50, and even when a loud exhaust sound volume is desired, an increase in the number of exhaust ports can be suppressed. Therefore, the vehicle exhaust pipe 1 can be configured with a simpler structure.

[0091] In the above embodiment, a vehicle equipped with an engine having exhaust manifolds on both sides has been described as an example, but the present invention is not limited to this. Of course, the vehicle exhaust pipe 1 according to the embodiment can also be applied to a vehicle equipped with an in-line engine having an exhaust manifold on only one side, for example. [Explanation of symbols]

[0092] 1. Vehicle exhaust pipe 10 First piping 20 1st curved pipe section 21 Bending start point 22 Bending end 23 Tube shaft 30 First branch pipe 31 End 33 Tube shaft 40 Silencer 50 Second piping 60 2nd curved pipe section 61 Bending start point 62 Bend end 70 Second branch pipe

Claims

1. a first pipe through which exhaust gas from the engine flows; a silencer provided in the first pipe; a first branch pipe connected to the first pipe on the engine side of the silencer and configured to discharge at least a portion of the exhaust gas in the first pipe to the outside; Equipped with the first pipe includes a first curved pipe portion that curves in one direction from the engine side to the silencer side, the first branch pipe is connected to the first pipe between a bend start end where the bending of the first bent pipe section starts and a bend end end where the bending ends, The first bent pipe portion has straight pipe portions that are cylindrical portions extending linearly at the bend start end and the bend end end, and the smaller angle between the straight pipe portions is equal to or smaller than a right angle. Vehicle exhaust pipe.

2. The vehicle exhaust pipe according to claim 1 , wherein the first branch pipe is connected to an outer curved side of the first curved pipe portion.

3. The vehicle exhaust pipe according to claim 2 , wherein a pipe axis of the end of the first branch pipe connected to the first pipe extends on a plane including a pipe axis of the first bent pipe portion.

4. The vehicle exhaust pipe according to claim 3 , wherein an axis of the end of the first branch pipe connected to the first pipe is perpendicular to an axis of the first bent pipe portion.

5. a second pipe that communicates with the first pipe via the silencer and allows exhaust gas from the engine to flow into the silencer; a second branch pipe connected to the second pipe on the engine side of the silencer and configured to discharge at least a portion of the exhaust gas in the second pipe to the outside; Equipped with the second pipe includes a second curved pipe portion that curves in one direction from the engine side to the muffler side, The second branch pipe is connected to the second pipe between a bending start end where the bending of the second bent pipe section starts and a bending end end where the bending ends. The exhaust pipe for a vehicle according to any one of claims 1 to 4.

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