Engine muffler

Abstract

To provide a silencer that effectively prevents the generation of reflected waves flowing back up the exhaust pipe. [Solution] The silencer has a muffler shell 1, an inlet pipe 2, and an outlet pipe 3, and a guide body 15 is provided on the downstream end plate 7, projecting toward the inlet pipe 2. The tip 15c of the guide body 15 is offset toward the upper end of the inlet pipe 2 and is close to the outlet 2a of the inlet pipe 2. The main guide surface 15a extends, for example, to the left and right outer sides of the inlet pipe 2. Therefore, the guide body 15 is wedge-shaped. The main guide surface 15a has a sufficient area to redirect the exhaust gas, so reflected waves are difficult to generate, and even if they are generated, their direction is toward the partition plate 9 and not toward the inlet pipe 2. Therefore, even if the overlap angle is large, scavenging is reliable and no exhaust gas remains in the cylinder, preventing a decrease in output.

Description

[Technical Field]

[0001] The present invention relates to a silencer for engines, and particularly suitably targets silencers for engines of four-wheeled motor vehicles. [Background Art]

[0002] A silencer for an automobile engine is arranged at the rear end of an exhaust system, and achieves noise reduction by combining expansion and throttling. The silencer includes a hollow muffler shell (case, housing), an inlet pipe and an outlet pipe arranged inside the muffler shell, and an atmospheric discharge pipe protruding outward from the muffler shell. The atmospheric discharge pipe is sometimes formed by extending the outlet pipe, and is sometimes formed independently of the outlet pipe.

[0003] As mentioned above, an engine silencer attenuates and eliminates exhaust noise by utilizing the expansion and throttling of exhaust gas. However, since the inlet pipe opens at the downstream end plate of the muffler shell, there is a phenomenon in which exhaust gas collides with the downstream end plate to generate reflected waves. Since the downstream end plate has a natural frequency (wavelength) depending on its shape, thickness and other factors, when the frequency of the reflected wave is tuned with the natural frequency of the downstream end plate, the energy of the reflected wave also increases.

[0004] On the other hand, a four-stroke engine generally has an overlap region where both the exhaust valve and the intake valve are open, and the pulsation frequency of the positive pressure wave of exhaust gas flowing through the exhaust pipe changes depending on the overlap angle. In an engine in which the opening / closing timing of the intake valve is adjusted by VVT, when the overlap angle increases in a rotation region where the intake valve is advanced (particularly in the medium rotation region), the frequency of the positive pressure wave is tuned with the frequency of the reflected wave, and a phenomenon occurs where the reflected wave acts to push back the exhaust gas, reducing the scavenging effect. As a result, exhaust gas remains in the cylinder, leading to problems such as reduced charging efficiency and excessive EGR, which deteriorates engine performance.

[0005] To address this problem, it is sufficient to prevent or suppress the generation of reflected waves inside the silencer, and the structure proposed by the present inventor in Patent Document 1 is considered beneficial as a means to achieve this. Specifically, Patent Document 1 discloses the provision of a guide portion for diffusing exhaust gas on the downstream end plate, and by adopting the configuration of Patent Document 1, it is possible to prevent the exhaust gas from violently colliding with the downstream end plate, thus being beneficial in reducing reflected waves. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-122453 [Overview of the project] [Problems that the invention aims to solve]

[0007] While providing a guide portion on the downstream end plate, as described in Patent Document 1, is beneficial for suppressing reflected waves, the inventors of this application have reconsidered and found that there is still room for improvement. Specifically, in Patent Document 1, the guide portion takes the form of a protrusion or inclined portion and is formed by pressurizing the downstream end plate. However, because the exhaust gas released from the inlet pipe has high straight-line propagation, it is expected that the exhaust gas will collide violently with the guide portion, generating reflected waves.

[0008] Furthermore, in Patent Document 1, the outlet of the inlet pipe and the inlet of the outlet pipe are far apart. While this structure is advantageous in terms of expanding the exhaust gas, it is considered disadvantageous in terms of changing the direction of the exhaust gas released from the inlet pipe because the exhaust gas tends to accumulate inside the muffler shell.

[0009] This invention was made in response to the current situation, and while following the concept of Patent Document 1, it aims to disclose a silencer that improves the effect of preventing the generation of reflected waves. [Means for solving the problem]

[0010] The engine silencer of the present invention is "It comprises a muffler shell whose body is closed by an upstream end plate and a downstream end plate, an inlet pipe that penetrates the upstream end plate and extends toward the downstream end plate, an outlet pipe whose inlet opens toward the downstream end plate so that exhaust gas released from the inlet pipe into the muffler shell flows in, and an atmospheric discharge pipe that protrudes outward from the downstream end plate." A guide body is provided, either integrally or separately, on the downstream end plate, which redirects the exhaust gas released from the inlet pipe so that it is mainly directed towards the front part of the outlet pipe inlet. This is the basic structure.

[0011] And in the above basic configuration, "The guide body protrudes from the downstream end plate toward the outlet of the inlet pipe and has a main guide surface facing the outlet of the inlet pipe, the main guide surface is inclined or curved toward the outlet pipe as its height decreases from the downstream end plate, and its tip is offset from the center of the inlet pipe toward the opposite side of the outlet pipe." It possesses the following characteristics.

[0012] In the present invention, it is preferable that the main guide surface of the guide body extends to the left and right outer sides of the inlet pipe when viewed from the axial direction of the inlet pipe. Furthermore, it is preferable that the protruding height of the guide body is approximately the outer diameter of the inlet pipe. The guide body can be formed by bending it into the downstream end plate, or it can be manufactured as a separate component and fixed to the downstream end plate. In the case of a separate component, both a block structure such as a die-cast part and a sheet metal part can be used. [Effects of the Invention]

[0013] In the present invention, the guide body protrudes from the flat surface of the downstream end plate, which is excellent at redirecting (bending) the exhaust gas released from the inlet pipe. However, because the tip of the main guide surface is offset to the opposite side of the outlet pipe, most of the exhaust gas released from the inlet pipe flows smoothly toward the outlet pipe without violently colliding with the downstream end plate.

[0014] Therefore, the generation of reflected waves in the inlet pipe can be prevented or significantly suppressed, and even if reflected waves are generated, their direction will not be towards the inlet pipe but away from it. Thus, a pushback effect on the exhaust gas can be prevented. As a result, even if the intake valve advance is controlled and the overlap angle increases, high scavenging performance can be maintained, preventing a decrease in charging efficiency and performance deterioration due to excessive EGR.

[0015] Furthermore, since the outlet pipe inlet also opens towards the downstream end plate, the exhaust gas released from the inlet pipe expands inside the muffler shell before quickly flowing into the inlet pipe. In other words, the exhaust gas does not tend to accumulate inside the muffler shell, and is smoothly guided to the outlet pipe. Therefore, the muffler shell can be made as compact as possible while maintaining high noise reduction performance. [Brief explanation of the drawing]

[0016] [Figure 1] This is a separated perspective view of the first embodiment. [Figure 2] The figure shows the first embodiment, where (A) is a longitudinal side view, (B) is a cross-sectional view of (A) at point BB, (C) is a cross-sectional view of (A) and (B) at point CC, and (D) and (E) show the machining process of the guide body. [Figure 3] This figure shows a second embodiment in which the guide body is a separate component. [Figure 4] This is a longitudinal cross-sectional front view of the third embodiment. [Figure 5] This is a partial longitudinal cross-sectional side view of the fourth embodiment. [Figure 6] It is a diagram showing the fifth embodiment, in which (A) is a vertical side view and (B) is a sectional view taken along line B-B of (A). [Figure 7] It is a diagram showing the sixth embodiment, in which (A) is a vertical side view and (B) is a sectional view taken along line B-B of (A). MODES FOR CARRYING OUT THE INVENTION

[0017] (1) Structure of the first embodiment Next, embodiments of the present invention will be described with reference to the drawings. First, the first embodiment shown in Fig. 1 will be described. The muffler comprises: a muffler shell (case) 1 which has an oval cross-section and a hollow structure; an inlet pipe 2 and an outlet pipe 3 arranged inside the muffler shell 1; and an atmosphere discharge pipe 4 exposed to the outside of the muffler shell 1.

[0018] Hereinafter, the terms front-rear, left-right, and up-down are used to specify directions. The front-rear direction corresponds to the longitudinal direction of the inlet pipe 2, the left-right direction is the horizontal direction when viewed from the axial direction of the inlet pipe 2, and the up-down direction is the vertical direction. For avoidance of doubt, the directions are clearly shown in Fig. 1.

[0019] The muffler shell 1 is formed as a hollow body by: a vertically elongated body (body cylinder, cylindrical body) 5 having an oval cross-section; an upstream end plate 6 that closes the upstream end of the body 5; and a downstream end plate 7 that closes the downstream end of the body 5. Although the downstream end plate 7 is provided with a cylindrical portion 7a that tightly fits the body 5 from the outside, a configuration in which the downstream end plate is fitted into the body 5 is also possible.

[0020] The inlet pipe 2 is straight and passes through the upstream end plate 6, with its outlet 2a opening toward the downstream end plate 7. The outlet pipe 3 is positioned below the inlet pipe 2 and has a U-shape when viewed from the side, with its inlet 3a and outlet 3b opening toward the downstream end plate 7. Inside the muffler shell 1, the inlet pipe 2 and outlet pipe 3 pass through, and two vertical partition plates 8 and 9 are positioned front and rear. Furthermore, a horizontal partition plate 10 is connected to the downstream vertical partition plate 9 at an intermediate height position of the outlet pipe 3 and to the downstream end plate 7.

[0021] Therefore, the inside of the muffler shell 1 is divided into a first space 11 located upstream of the upstream vertical partition plate 8, a second space 12 located between the front and rear vertical partition plates 8 and 9, a third space 13 located above the horizontal partition plate 10, and a fourth space 14 located below the horizontal partition plate 10. The atmospheric discharge pipe 4 is connected to the downstream end plate 7, but the outlet pipe 3 can also be extended to form the atmospheric discharge pipe 4, in which case the horizontal partition plate 10 is not necessary. The vertical partition plates 8 and 9 and the horizontal partition plate 10 are made of perforated plates with numerous small holes.

[0022] On the downstream end plate 7, a guide body 15 with a V-shape in side view is formed by pressing and bending (pressing) at the portion facing the inlet pipe 2. The guide body 15 has a main guide surface 15a facing downward and a secondary guide surface 15b facing upward. As clearly shown in Figure 2(B), both guide surfaces 15a and 15b extend laterally with a width greater than the outer diameter of the inlet pipe 2. Therefore, the guide body 15 is wedge-shaped.

[0023] Therefore, the tip of the guide body 15 is a ridge line 15c formed by the connection of both guide surfaces 15a and 15b, and the ridge line 15c is offset above the centerline of the inlet pipe 2 so that it is located near the upper end of the inlet pipe 2. In other words, when viewed in the axial direction of the inlet pipe 2, the ridge line 15c of the guide body 15 overlaps with the inlet pipe 2 and is located near the upper end of the inlet pipe 2.

[0024] The bases of both guide surfaces 15a and 15b are curved in side view, but it is also possible to form one or both of them as flat surfaces. In other words, it is also possible to form the guide body 15 as a triangular mountain shape in side view. The protruding height H of the guide body 15 is approximately the same as the outer diameter D of the inlet pipe 2, but it is preferable that the protruding height H is more than half the outer diameter D of the inlet pipe 2, as shown in the drawing. The ridge (tip) 15c of the guide body 15 is close to the inlet pipe 2 with a small gap between them.

[0025] As can be seen from Figure 2(B), the widths of both guide surfaces 15a and 15b decrease towards the ridge line 15c. Therefore, the guide body 15 is trapezoidal in plan view (and bottom view). This shape is mainly based on requirements for press working, and the widths of both guide surfaces 15a and 15b may be constant throughout the entire height.

[0026] It goes without saying that each component of the silencer is made of a metal such as stainless steel, and the components are joined together by welding or brazing. As clearly shown in Figure 2(C), it is possible to form multiple longitudinal ribs 16 on the portion of the downstream end plate 7 that is exposed to the third space 13.

[0027] As shown in Figure 2(D), the guide body 15 is formed by press working using a die 17 and a punch 18. However, since the punch 18 needs to have a certain thickness T at its tip to ensure durability, the tip of the guide body 15 is formed in a bulging state. On the other hand, in order to improve the exhaust gas flow separation function, it is preferable that the ridge line 15c of the guide body 15 be as acute as possible when viewed from the side.

[0028] In this regard, as shown in Figure 2(D), the tip is bulged to give it a rounded shape, and then, as shown in Figure 2(E), the guide body 15 is crushed from the side of the guide surfaces 15a and 15b using a pair of clamping molds 19, thereby forming a pointed tip on the ridge line 15c. When crushing with the clamping molds 19, it is preferable to hold the guide body 15 from the inside with the holding mold 20.

[0029] (2) Summary of the first embodiment In the above configuration, exhaust gas released in a straight line from the inlet pipe 2 into the third space 13 expands in the third space 13, then flows into the outlet pipe 3 where it is narrowed, is released from the outlet pipe 3 into the fourth space 14 where it expands further, and then flows into the atmospheric discharge pipe 4 in a narrowed state and is released into the atmosphere.

[0030] Due to the effects of this expansion and throttling, the pulsation of the exhaust gas is eliminated and the exhaust noise is almost completely eliminated. Since partition plates 8-10 have many small holes, some of the exhaust gas passes through partition plates 8-10 and flows from the third space 13 to the fourth space 14 and the second space 12, and finally reaches the fourth space 14. However, as the exhaust gas passes through the small holes in partition plates 8-10, it is subjected to the effects of throttling and expansion, which also attenuates the exhaust noise.

[0031] As the exhaust gas is released from the inlet pipe 2 into the third space 13, most of the exhaust gas is redirected downward by the main guide surface 15a to become the main flow that heads toward the outlet of the outlet pipe 3, while only a small portion of the exhaust gas is guided by the secondary guide surface 15b of the guide body 15 to become a sideflow that redirects upward. This upward-directed sideflow makes a U-turn and heads toward the bottom of the third space 13, where it merges with the main flow and flows into the outlet pipe 3.

[0032] In this embodiment, the guide body 15 protrudes significantly from the base of the downstream end plate 7, the main guide surface 15a is offset near the upper end of the inlet pipe 2, and the main guide surface 15a and the sub-guide surface 15b extend to the left and right with a width dimension larger than the outer diameter D of the inlet pipe 2. As a result, the exhaust gas travels straight into the third space 13 without violently colliding with the downstream end plate 7, and its direction is smoothly changed by the guide surfaces 15a and 15b so that it is directed downwards.

[0033] Therefore, no reflected waves are generated due to the exhaust gas violently colliding with the downstream end plate 7. Even if reflected waves are generated, the direction of reflection is toward the vertically elongated partition plate 9 downstream and not toward the inlet pipe 2. As a result, the reflected waves do not tend to flow back into the cylinder from the inlet pipe 2 and push back the exhaust gas. Consequently, even if the opening timing of the intake valve is controlled so that the overlap angle between the intake valve and the exhaust valve is large in a specific rotation range, the discharge of exhaust gas from the cylinder (scavenging) is performed without hindrance. Therefore, a decrease in charging efficiency and internal EGR phenomena do not occur, and high output can be maintained.

[0034] Furthermore, since the outlet 2a of the inlet pipe 2 and the inlet 3a of the outlet pipe 3 open in the same direction, the exhaust gas expanded in the third space 13 can be quickly flowed into the outlet pipe 3. Therefore, the muffler shell 1 can be made more compact while enjoying a high level of noise reduction.

[0035] As in the embodiment, when the guide body 15 is formed as a bulge on the downstream end plate 7, the thickness of the downstream end plate 7 cannot be made very thick. However, since the guide body 15 has a width greater than the outer diameter of the inlet pipe 2, the guide body 15 functions as a rigidity-enhancing rib that prevents elastic deformation of the downstream end plate 7. Therefore, membrane vibration of the downstream end plate 7 can be suppressed, and even if membrane vibration occurs, it can be set to a natural frequency that does not resonate with the positive pressure wave of the exhaust gas. Consequently, even with a simple structure in which the guide body 15 is formed by press working, high scavenging performance can be maintained. Forming a group of ribs 16 on the downstream end plate 7 as in the embodiment is particularly beneficial because it can improve the membrane vibration suppression effect.

[0036] (3) Other embodiments The second embodiment shown in Figure 3 is a modification of the first embodiment, in which the guide body 15 is made as a separate block from the downstream end plate 7 and fixed to the downstream end plate 7 by welding or the like. In the third embodiment shown in Figure 4, the guide body 15 is formed in a shape that curves downward when viewed from the front (view in the axial direction of the inlet pipe 2). In this embodiment, the main guide surface 15a is particularly curved downward, which can be said to be excellent in its function of directing exhaust gas toward the outlet pipe 3.

[0037] In the fourth embodiment shown in Figure 5, the guide body 15 is made of a metal plate and is fixed to the downstream end plate 7 by welding or the like. In this embodiment, curled portions 15d and 15e are provided above and below the guide body 15 to direct the exhaust gas toward the third space 13. The outlet 2a of the inlet pipe 2 is inclined downward.

[0038] In the fifth embodiment shown in Figure 6, the downstream end plate 7 is also made of a metal plate, and its features include the fact that the tip of the guide body 15 is located above the inlet pipe 2, the main guide surface 15a has a greatly curved curled portion 15f, and there is a gap 21 between the main guide surface 15a of the guide body 15 and the downstream end plate 7. In this embodiment, because the main guide surface 15a is greatly curved, the exhaust gas released from the inlet pipe 2 tends to flow into the outlet pipe 3 from the left and right sides while swirling in a side view.

[0039] In the sixth embodiment shown in Figure 7, the guide body 15 is made of a metal plate, and the main guide surface 15a is tilted forward toward the inlet pipe 2, while in plan view it is curved to surround the outlet 2a of the inlet pipe 2. The upper end of the guide body 15 is located slightly below the upper end of the inlet pipe 2. Therefore, a small portion of the exhaust gas released from the inlet pipe 2 is released into the third space 13 from above the guide body 15, but because the opening area above the guide body 15 is small, the exhaust gas does not violently collide with the downstream end plate 7 and generate reflected waves.

[0040] One of the features of this embodiment is that there is a large space 22 between the guide body 15 and the downstream end plate 7. Some of the exhaust gas that escapes above the guide body 15 flows downward from this space 22 towards the outlet pipe 3. Therefore, it can be said that it has excellent exhaust gas diffusion capabilities. In addition, because the main guide surface 15a is curved to surround the outlet 2a of the inlet pipe 2, the exhaust gas is also directed toward the left and right sides of the outlet pipe 3. Therefore, the volume of the third space 13 can be kept as small as possible while improving the exhaust gas diffusion function. As a result, it can be said that it can be made compact while exhibiting a high noise reduction effect.

[0041] Although embodiments of the present invention have been described above, the present invention can be implemented in various other ways. For example, the cross-sectional shape of the muffler shell does not necessarily have to be oval; circular, elliptical, or rectangular shapes can also be adopted. It is also possible to arrange the inlet pipe and outlet pipe horizontally. [Industrial applicability]

[0042] The present invention can be implemented in an engine silencer. Therefore, it has industrial merit. [Explanation of symbols]

[0043] 1 Muffler Shell 2 Inlet pipes 2a exit 3 Outlet pipes 3a Entrance 4. Atmospheric discharge pipe 5 Torso 6 Upstream end plate 7 Downstream end plate 8,9 Vertical partition plate 10 Horizontal partition plates 11~14 space 15 Guide Body 15a Main guide surface 15b Sub-guide surface 15c Ridge (Tip)

Claims

[Claim 1] The muffler shell comprises a body closed by an upstream end plate and a downstream end plate, an inlet pipe extending through the upstream end plate toward the downstream end plate, an outlet pipe whose inlet opens toward the downstream end plate so that exhaust gas released from the inlet pipe into the muffler shell flows in, and an atmospheric discharge pipe protruding outward from the downstream end plate. An engine silencer having a guide body, either integrally or separately, provided on the downstream end plate, which redirects the exhaust gas discharged from the inlet pipe so that it is mainly directed towards the front part of the outlet pipe inlet, The guide body protrudes from the downstream end plate toward the outlet of the inlet pipe and has a main guide surface facing the outlet of the inlet pipe, the main guide surface is inclined or curved toward the outlet pipe as its height decreases from the downstream end plate, and its tip is offset from the center of the inlet pipe toward the opposite side of the outlet pipe. Engine muffler.

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