Connection structure for exhaust muffler

Abstract

To provide a connection structure for an exhaust muffler, which can suppress vibration transmission to the exhaust muffler to prevent damage to the exhaust muffler formed of a heat-resistant resin.SOLUTION: In a connection structure 1 for an exhaust muffler, which is formed of a heat-resistant resin or the like, an upstream-side metal exhaust pipe 4 installed in an automobile and a connection pipe 3 formed of a soft polymer material having a copper damage resistance or the like are secured, the connection pipe 3 and an exhaust introduction pipe 21 of the exhaust muffler 2 are secured, and the exhaust pipe 4 and the exhaust introduction pipe 21 are disposed spaced apart at an interval of 35 mm or more in the pipe axis direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a connection structure of an exhaust muffler.

Background Art

[0002] An exhaust muffler that discharges exhaust gas generated by an internal combustion engine of an automobile to the outside is generally formed of a heat-resistant metal such as stainless steel because the flowing exhaust gas is at a high temperature. However, it is also possible to form an exhaust muffler with a heat-resistant resin as disclosed in Patent Document 1. The exhaust muffler of Patent Document 1 is configured by attaching a layered structure of a heat-resistant material to the inner surface of a muffler body formed of a heat-resistant resin or a mixture of a heat-resistant resin and an inorganic substance.

[0003] Furthermore, Patent Document 1 discloses that as the heat-resistant resin used for the exhaust muffler, at least one thermosetting resin selected from epoxy resin, phenol resin, silicone resin, unsaturated polyester resin, diallyl phthalate resin, melamine resin, and thermosetting polycarbodiimide resin, or at least one thermoplastic resin selected from polyamide resin, polyester resin, polyphenylene sulfide resin, thermoplastic fluororesin, polysulfone resin, and polyphenylene ether resin is used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the strength of exhaust mufflers made of heat-resistant resin is often lower than that of metal exhaust mufflers. If a heat-resistant resin exhaust muffler is directly connected to the upstream exhaust pipe, there is a concern that engine vibrations will be transmitted through the upstream exhaust pipe, and these vibrations may damage the heat-resistant resin exhaust muffler. The same problem occurs when an exhaust muffler is made from a metal material with lower strength than a normal metal exhaust muffler.

[0006] Furthermore, in the case of exhaust mufflers made of heat-resistant resin, resins such as polypropylene, ABS resin, and polyethylene, which have degradation characteristics due to metal ions, have another problem: contact with metal ions causes so-called copper damage, which accelerates oxidation. Oxidation of the resin due to copper damage is further accelerated at high temperatures, and the strength of the resin decreases significantly in a short time. Therefore, when using an exhaust muffler made of heat-resistant resin, copper damage occurs at the connection point with the upstream metal exhaust pipe, reducing the strength of the heat-resistant resin exhaust muffler.

[0007] The present invention is proposed in view of the above problems and aims to provide an exhaust muffler connection structure that can suppress the transmission of vibrations to the exhaust muffler and prevent damage to exhaust mufflers made of low-strength materials. Another object of the present invention is to provide an exhaust muffler connection structure that can prevent a decrease in strength due to copper damage in exhaust mufflers made of heat-resistant resin. [Means for solving the problem]

[0008] The exhaust muffler connection structure of the present invention is characterized in that an upstream metal exhaust pipe installed in an automobile is fixed to a connecting pipe made of a soft polymer material, the connecting pipe is fixed to an exhaust inlet pipe made of a material with lower strength than the exhaust pipe of the exhaust muffler, and the exhaust pipe and the exhaust inlet pipe are spaced apart at a distance of 35 mm or more in the direction of the pipe axis. According to this method, by connecting the exhaust pipe and the exhaust inlet pipe via a connecting pipe made of a soft polymer material, and by using a connecting pipe of a length such that the exhaust pipe and the exhaust inlet pipe are spaced apart by 35 mm or more, vibrations transmitted from the automobile engine to the exhaust pipe can be greatly absorbed and reduced by the connecting pipe, suppressing the transmission of vibrations to the exhaust muffler and preventing damage to the exhaust inlet pipe of the exhaust muffler, which is made of a material with lower strength than the exhaust pipe.

[0009] The exhaust muffler connection structure of the present invention is characterized in that the exhaust muffler is made of a heat-resistant resin and the connecting pipe is made of a copper-resistant soft polymer material. According to this method, by connecting the upstream metal exhaust pipe and the exhaust inlet pipe of the heat-resistant resin exhaust muffler via a connecting pipe made of a copper-resistant soft polymer material, and by spacing the exhaust pipe and exhaust inlet pipe at a distance of 35 mm or more in the axial direction of the pipes, it is possible to prevent a decrease in strength of the heat-resistant resin exhaust muffler due to copper damage. Furthermore, by connecting the exhaust pipe and exhaust inlet pipe via a connecting pipe made of a soft polymer material, and by using a connecting pipe of a length that allows the exhaust pipe and exhaust inlet pipe to be spaced at a distance of 35 mm or more, vibrations transmitted from the automobile engine to the exhaust pipe can be greatly absorbed and reduced by the connecting pipe, suppressing the transmission of vibrations to the exhaust muffler and preventing damage to the heat-resistant resin exhaust muffler.

[0010] The exhaust muffler connection structure of the present invention is characterized in that the heat-resistant resin of the exhaust muffler is polypropylene. According to this, the manufacturing cost of exhaust mufflers can be reduced by using polypropylene, a general-purpose plastic frequently used in automotive parts, as a heat-resistant resin. Furthermore, it is possible to create an exhaust muffler that is resistant to acids and alkalis and does not easily absorb water, resulting in an exhaust muffler that is less susceptible to the effects of condensed water, etc. In addition, because polypropylene is resistant to cracking, damage to exhaust mufflers made of heat-resistant resin can be prevented.

[0011] The exhaust muffler connection structure of the present invention is characterized in that the soft polymer material is silicone rubber, fluororubber, EPDM, or alloy resin. According to this method, it is possible to reliably prevent copper damage and oxidative degradation from occurring in connecting pipes made of soft polymer materials.

[0012] The exhaust muffler connection structure of the present invention is characterized in that a bellows-shaped peripheral wall is formed on the connecting pipe. According to this design, the bellows-shaped perimeter wall of the connecting pipe can more effectively absorb and reduce vibrations transmitted from the automobile engine's exhaust pipe, thereby more reliably suppressing vibration transmission to the exhaust muffler. Furthermore, the bellows-shaped perimeter wall of the connecting pipe can create turbulence in the exhaust flow, allowing metal ions generated in the upstream metal exhaust pipe to diffuse turbulently. In the case of a heat-resistant resin exhaust muffler, this reliably prevents high concentrations of metal ions from adhering to specific localized areas within the heat-resistant resin exhaust muffler.

[0013] The exhaust muffler connection structure of the present invention is characterized in that the exhaust muffler is formed in a flat shape that spreads out substantially horizontally and is installed under the floor of an automobile, the exhaust inlet pipe is formed in a flat cylindrical shape, the upstream end of the connecting pipe is formed in a substantially cylindrical shape corresponding to the substantially cylindrical downstream end of the exhaust pipe, and the downstream end of the connecting pipe is formed in a substantially flat cylindrical shape corresponding to the substantially flat cylindrical upstream end of the exhaust inlet pipe. According to this design, by connecting a roughly cylindrical exhaust pipe and a roughly flattened exhaust inlet pipe via a connecting pipe, the exhaust muffler installed under the vehicle floor can be made into a roughly horizontally spreading, flattened shape. This reduces the height of the installation space for the exhaust muffler under the vehicle floor, promoting a lower vehicle floor. Consequently, it is possible to improve the ease of getting in and out of the vehicle, secure a larger interior space, and improve driving stability and ride comfort by lowering the vehicle's center of gravity. Furthermore, by reducing the height of the installation space for the exhaust muffler under the vehicle floor, air resistance can be reduced, improving the aerodynamic characteristics of the vehicle.

[0014] The exhaust muffler connection structure of the present invention is characterized in that a retaining projection that protrudes outward is formed circumferentially at the upstream end of the exhaust inlet pipe, and the upstream end of the exhaust inlet pipe is inserted into the downstream end of the connecting pipe, so that the retaining projection is covered and caught by the downstream end of the connecting pipe, thereby fixing the connecting pipe and the exhaust inlet pipe. According to this, when fixing a connecting pipe made of flexible polymer material to the exhaust inlet pipe of an exhaust muffler, there is a possibility that the connecting pipe made of flexible polymer material may come loose from the exhaust inlet pipe. In particular, when fixing a connecting pipe made of flexible polymer material to the exhaust inlet pipe of an exhaust muffler made of heat-resistant resin, there is a possibility that the exhaust inlet pipe may come loose due to expansion of the connecting pipe made of flexible polymer material. However, by covering the anti-loosening projection of the exhaust inlet pipe with the connecting pipe made of flexible polymer material and fixing it in a way that hooks onto it, it is possible to reliably prevent the exhaust inlet pipe from coming loose from the connecting pipe. Furthermore, since the anti-loosening projection is formed in a localized area in the axial direction of the exhaust inlet pipe, a gap for insertion can be secured on the outside of the outer surface of the exhaust inlet pipe other than the anti-loosening projection, and the upstream end of the exhaust inlet pipe can be smoothly inserted into the downstream end of the connecting pipe.

[0015] The exhaust muffler connection structure of the present invention is characterized in that the upstream end of the exhaust inlet pipe is inserted into the downstream end of the connecting pipe, and the connecting pipe and the exhaust inlet pipe are fastened and secured from the outside of the connecting pipe with a fastening band. According to this method, a connecting pipe made of a soft polymer material and an exhaust inlet pipe made of heat-resistant resin can be easily fixed together. Furthermore, by utilizing the softness of the connecting pipe made of the soft polymer material and the tightening of the clamping band, the sealing performance between the exhaust inlet pipe and the connecting pipe can be improved, and exhaust leakage from the gap between the exhaust inlet pipe and the connecting pipe can be reliably prevented. In addition, if there is a retaining projection on the exhaust inlet pipe at a position corresponding to the tightening point of the clamping band, the tightening allowance between the exhaust inlet pipe and the connecting pipe made of the soft polymer material can be locally increased, causing the retaining projection to bite into the connecting pipe made of the soft polymer material, further improving the retaining and sealing performance. Moreover, the connection structure can be simplified by tightening and fixing with a clamping band, improving ease of assembly and reducing the number of connecting parts.

[0016] The connection structure of the exhaust muffler of the present invention is characterized in that a strength-retaining collar is engaged inside the exhaust introduction pipe at a position corresponding to the tightening portion of the fastening band. According to this, when tightening with the fastening band, if the strength of the exhaust introduction pipe is insufficient, the exhaust introduction pipe may deform due to the tightening load, and there is a concern about exhaust leakage and damage to the exhaust introduction pipe. However, by engaging a strength-retaining collar inside the exhaust introduction pipe at a position corresponding to the tightening portion of the fastening band, deformation of the exhaust introduction pipe can be reliably prevented, and exhaust leakage and damage to the exhaust introduction pipe caused by the deformation of the exhaust introduction pipe can be prevented.

Effects of the Invention

[0017] According to the connection structure of the exhaust muffler of the present invention, vibration transmission to the exhaust muffler can be suppressed, and damage to an exhaust muffler formed of a material with low strength, such as a heat-resistant resin or a metal material that is lower in strength than a metal exhaust pipe, can be prevented. Further, when using an exhaust muffler made of a heat-resistant resin, a decrease in strength due to copper damage of the exhaust muffler formed of the heat-resistant resin can be prevented.

Brief Description of the Drawings

[0018] [Figure 1] Perspective view of the exhaust muffler connected by the connection structure of the exhaust muffler according to an embodiment of the present invention, viewed from below. [Figure 2] Perspective view of the connection structure of the exhaust muffler according to an embodiment of the present invention, viewed from below. [Figure 3] Plan view of the connection structure of the exhaust muffler according to the embodiment. [Figure 4] Side view of the connection structure of the exhaust muffler according to the embodiment. [Figure 5] Cross-sectional view taken along line A-A in FIG. 3. [Figure 6] Partial enlarged view of FIG. 5. [Figure 7] Perspective view of the connection structure of the exhaust muffler according to a modification of the embodiment, viewed from below.

Modes for Carrying Out the Invention

[0019] [Connection structure of the exhaust muffler in the embodiment] The exhaust muffler connection structure 1 of the embodiment according to the present invention connects the exhaust inlet pipe 21 of the exhaust muffler 2, which is made of heat-resistant resin, to the upstream metal exhaust pipe 4 through which the exhaust gas discharged from the engine of the automobile flows, via a connecting pipe 3 made of copper-resistant soft polymer material. The upstream exhaust pipe 4, the heat-resistant resin exhaust muffler 2, and the connecting pipe 3 made of soft polymer material are all installed under the floor of the automobile (see Figure 2).

[0020] As shown in Figure 1, the exhaust muffler 2 in this embodiment consists of an exhaust inlet pipe 21, an exhaust pipe 22, and an exhaust pipe 23 arranged at intervals from the upstream side of the exhaust system, and a first silencer 24, a second silencer 25, and a third silencer 26 arranged at intervals from the upstream side of the exhaust system. The first silencer 24 is positioned between the exhaust inlet pipe 21 and the exhaust pipe 22, the second silencer 25 is positioned between the exhaust pipe 22 and the exhaust pipe 23, and the third silencer 26 is positioned behind the exhaust pipe 23 and provided at the rear end of the exhaust muffler 3. Inside each of the first silencer 24, the second silencer 25, and the third silencer 26, an expansion space that functions as an expansion chamber is provided.

[0021] The exhaust inlet pipe 21, exhaust pipe 22, exhaust pipe 23, and the first silencer 24, second silencer 25, and third silencer 26 are each formed in a substantially horizontally spreading, flattened cylindrical or flattened shape, and the exhaust muffler 2 as a whole is formed in a substantially horizontally spreading, flattened shape. Furthermore, the substantially flattened cylindrical upstream end 211 of the exhaust inlet pipe 21 has a retaining projection 212 that protrudes outward in the circumferential direction. In the illustrated example, the retaining projection 212 is formed so as to bend in a substantially mountain shape in a longitudinal cross-sectional view of the exhaust inlet pipe 21 and is arranged in a series in the circumferential direction of the exhaust inlet pipe 21 (see Figures 1, 5, and 6). In addition, although there is one retaining projection 212 circumferentially arranged in the circumferential direction of the exhaust inlet pipe 21 in the illustrated example, it is also possible to provide multiple retaining projections 212 with spacing in the axial direction of the exhaust inlet pipe 21.

[0022] Mounting plate portions 27, 27 are extended from the upper side of the first silencer 24, the upper side of the exhaust pipe 22, and the upper side of the third silencer 26, respectively, so as to protrude laterally on both sides in the width direction of the exhaust muffler 2. In this example, the mounting plate portions 27 are formed in the shape of elongated plates, and fasteners 101 made of separate components such as screws and bolts are inserted through mounting holes formed near the tip of each mounting plate portion 27, and the tips of the fasteners are fixed by embedding them in the mounting member installed under the floor of the automobile, thereby installing the exhaust muffler 2 under the floor of the automobile.

[0023] The entire exhaust muffler 2 is made of heat-resistant resin. While any heat-resistant resin suitable for the exhaust muffler 2 can be used, such as polypropylene, polyethylene, or ABS resin, polypropylene is preferred. When forming the exhaust muffler 2, it is preferable to integrally form each component of the whole using a heat-resistant synthetic resin of the same material, such as polypropylene, by injection molding, or to integrally form the required components using a heat-resistant synthetic resin of the same material, such as polypropylene, and then weld the other components together.

[0024] The upstream exhaust pipe 4 is formed in a generally cylindrical shape from a metal material such as stainless steel, and its downstream end 41 is also formed in a generally cylindrical shape. Preferably, an exhaust cooling device such as a heat exchanger or exhaust heat recovery device that exchanges heat with cooling water is installed in the exhaust path of the automobile upstream of the metal exhaust pipe 4, and exhaust gas with a reduced temperature is circulated through the exhaust pipe 4. This makes it possible to use materials with lower heat resistance, and increases the freedom of choice for the type of heat-resistant resin that can be used as the material for the exhaust muffler 2, and the type of copper-resistant soft polymer material that can be used as the material for the connecting pipe 4.

[0025] As shown in Figures 2 to 6, the copper-resistant soft polymer material connecting pipe 3 has an upstream end 31 that is roughly cylindrical, corresponding to the roughly cylindrical downstream end 41 of the upstream metal exhaust pipe 4, and a downstream end 32 that is roughly flattened, corresponding to the roughly flattened upstream end 211 of the exhaust inlet pipe 21. The connecting pipe 3 has a bellows-like circumferential wall 33 formed on it. In this example, the bellows-like circumferential wall 33, which is approximately half to two-thirds the length of the entire connecting pipe 3, is formed in the middle section near the downstream end 32 of the connecting pipe 4, forming a roughly flattened cylindrical bellows-like circumferential wall 33.

[0026] In the illustrated example, the length of the connecting pipe 3 is preferably 41 mm or more, from the viewpoint of preventing copper damage to the heat-resistant resin exhaust muffler 2 and suppressing vibration transmission. This is done in order to fix the upstream metal exhaust pipe 4 and the connecting pipe 3, and to fix the connecting pipe 3 and the exhaust inlet pipe 21 of the exhaust muffler 2, while ensuring that the upstream metal exhaust pipe 4 and the exhaust inlet pipe 21 of the exhaust muffler 2 are spaced apart at a distance of 35 mm or more in the pipe axis direction.

[0027] For the copper-resistant soft polymer material used in the connecting pipe 3, any suitable soft polymer material can be used within the applicable range. However, for example, using silicone rubber, fluororubber, EPDM (ethylene propylene diene rubber), or a copper-resistant alloy resin is preferable because it can reliably prevent copper damage and oxidative degradation from occurring in the connecting pipe 3 made of soft polymer material. Furthermore, the copper-resistant soft polymer material used for the connecting pipe 3 should preferably satisfy the following conditions (1) to (6): (1) Heat resistance: Since the exhaust temperature flowing through the exhaust pipe 4 will be close to 150°C even when a heat exchanger or exhaust heat recovery device is installed in the exhaust path, the heat resistance temperature should be 150°C or higher; (2) Acid resistance: Since highly acidic condensed water is generated in the exhaust path, it should not corrode or deteriorate even at pH 1.0; (3) Cold resistance: Since it is expected to be used in the outside air in cold regions, it should not deteriorate even at a temperature of -40°C; (4) Weather resistance: Since it will be used in the atmosphere, it should be resistant to ozone, water, and oils and fats without deterioration; (5) Airtightness: It should be airtight so as not to leak exhaust; (6) Flexural resistance: Since vibrations are transmitted to the exhaust muffler 2 from the heat-resistant resin and vibrations are applied, it should have the required flexural resistance to absorb axial misalignment caused by vibrations with an amplitude of, for example, 40 mm.

[0028] In fixing the upstream metal exhaust pipe 4 to the copper-resistant soft polymer connecting pipe 3, as shown in Figures 5 and 6, the downstream end 41 of the upstream metal exhaust pipe 4 is inserted into the upstream end 31 of the connecting pipe 3, or in other words, the upstream end 31 of the connecting pipe 3 is extrapositioned onto the downstream end 41 of the exhaust pipe 4. The substantially cylindrical downstream end 41 of the exhaust pipe 4 also has a circumferentially formed retaining projection 411 that protrudes outward. In the illustrated example, the retaining projection 411 is formed to bend in a substantially mountain shape in a longitudinal cross-section view of the exhaust pipe 4 and is arranged in a continuous manner in the circumferential direction of the exhaust pipe 4. In addition, although there is only one circumferentially formed retaining projection 411 on the exhaust pipe 4 in the illustrated example, it is also possible to provide multiple circumferentially formed retaining projections 411 spaced apart in the axial direction of the exhaust pipe 4.

[0029] The retaining projection 411 at the downstream end 41 of the exhaust pipe 4 is inserted into the upstream end 31 of the connecting pipe 3 and is covered and hooked by the upstream end 31 of the connecting pipe 3 made of soft polymer material. A tightening band 51 is positioned on the outside of the connecting pipe 4 so as to extend from the front end to the rear end in the axial direction of the retaining projection 411, and the connecting pipe 3 is fixed to the upstream metal exhaust pipe 4 and the connecting pipe 3 made of soft polymer material by being tightened from the outside by the tightening band 51. In other words, the retaining projection 411 at the downstream end 41 of the exhaust pipe 4 is covered and hooked by the upstream end 31 of the connecting pipe 3 made of soft polymer material, and the two are connected by being tightened and fixed with the tightening band 51.

[0030] In fixing the exhaust inlet pipe 21 of the exhaust muffler 2 to the connecting pipe 3 made of copper-resistant soft polymer material, the upstream end 211 of the exhaust inlet pipe 21 of the exhaust muffler 2 is inserted into the downstream end 32 of the connecting pipe 3, or in other words, the downstream end 32 of the connecting pipe 3 is extrapositioned onto the upstream end 211 of the exhaust inlet pipe 21. The upstream end 211 of the exhaust inlet pipe 21 is formed in a substantially flat cylindrical shape with a retaining projection 212 that protrudes outward in the circumferential direction, and the downstream end 32 of the connecting pipe 3 has a substantially flat cylindrical shape corresponding to the substantially flat cylindrical upstream end 211.

[0031] The retaining projection 212 at the upstream end 211 of the exhaust inlet pipe 21 is inserted into the downstream end 31 of the connecting pipe 3 and is covered and caught by the downstream end 32 of the connecting pipe 3 made of soft polymer material. A tightening band 52 is positioned on the outside of the connecting pipe 4 so as to extend from the front end to the rear end in the axial direction of the retaining projection 212, and the exhaust inlet pipe 21 and the connecting pipe 3 made of soft polymer material are fixed together by tightening the connecting pipe 3 from the outside with the tightening band 52. In other words, the retaining projection 212 at the upstream end 211 of the exhaust inlet pipe 21 is covered and caught by the downstream end 32 of the connecting pipe 3 made of soft polymer material, and the two are connected by tightening and fixing with the tightening band 52.

[0032] Furthermore, in this embodiment, a strength-retaining collar 6 is positioned inside the exhaust inlet pipe 21 at a location corresponding to the tightening point of the fastening band 52, in order to reinforce the strength of the exhaust inlet pipe 21 made of heat-resistant resin. The strength-retaining collar 6 has circumferentially formed circumferential or point-shaped engaging portions 61 that protrude outward, and the engaging portions 61 engage with the recesses inside the retaining projections 212, thereby positioning the strength-retaining collar 6 at a predetermined position on the upstream end 211 of the exhaust inlet pipe 21, and in this position the strength-retaining collar 6 is locked to the inside of the exhaust inlet pipe 21. The strength-retaining collar 6 is made of a material that has sufficient compression strength to withstand the tightening force of the fastening band 52.

[0033] According to the exhaust muffler connection structure of this embodiment, the upstream metal exhaust pipe 4 and the exhaust inlet pipe 21 of the heat-resistant resin exhaust muffler 2 are connected via a connecting pipe 3 made of a copper-resistant soft polymer material, and the exhaust pipe 4 and the exhaust inlet pipe 21 are spaced apart at a distance of 35 mm or more in the axial direction of the pipes, thereby preventing a decrease in strength of the heat-resistant resin exhaust muffler 2 due to copper damage. Furthermore, by connecting the exhaust pipe 4 and the exhaust inlet pipe 21 via a connecting pipe 3 made of a soft polymer material, and by using a connecting pipe 3 of a length such that the exhaust pipe 4 and the exhaust inlet pipe 21 are spaced apart at a distance of 35 mm or more, vibrations transmitted from the automobile engine through the exhaust pipe 4 can be greatly absorbed and reduced by the connecting pipe 3, suppressing the transmission of vibrations to the exhaust muffler 2 and preventing damage to the heat-resistant resin exhaust muffler 2.

[0034] Furthermore, the bellows-shaped peripheral wall 33 of the connecting pipe 3 can more effectively absorb and reduce vibrations transmitted from the automobile engine to the exhaust pipe 4, thereby more reliably suppressing vibration transmission to the exhaust muffler 2. In addition, the bellows-shaped peripheral wall 33 of the connecting pipe 3 creates turbulence in the exhaust, allowing metal ions generated in the upstream metal exhaust pipe 4 to diffuse turbulently, thereby reliably preventing high concentrations of metal ions from adhering to specific local areas such as the exhaust inlet pipe 21 in the heat-resistant resin exhaust muffler 2.

[0035] Furthermore, by connecting the roughly cylindrical exhaust pipe 4 and the roughly flattened exhaust inlet pipe 21 via the connecting pipe 3, the exhaust muffler 2 installed under the floor of the vehicle can be made into a roughly horizontally spreading, flattened shape, thereby suppressing the height of the installation space for the exhaust muffler 2 under the vehicle floor and promoting a lower vehicle floor. Consequently, improvements can be made to the ease of getting in and out of the vehicle, securing a larger interior space, and improving driving stability and ride comfort by lowering the vehicle's center of gravity. Moreover, since the height of the installation space for the exhaust muffler 2 under the vehicle floor can be suppressed, air resistance can be reduced and the aerodynamic characteristics of the vehicle can be improved.

[0036] Furthermore, when fixing the connecting pipe 3 made of soft polymer material to the exhaust inlet pipe 21 of the exhaust muffler 2 made of heat-resistant resin, there is a possibility that the exhaust inlet pipe 21 may come loose due to expansion of the connecting pipe 3 made of soft polymer material. However, by covering the retaining projection 212 of the exhaust inlet pipe 21 with the connecting pipe 3 made of soft polymer material and fixing it in a way that hooks onto it, it is possible to reliably prevent the exhaust inlet pipe 21 from coming loose from the connecting pipe 3. Moreover, since the retaining projection 212 is formed in a localized area in the axial direction of the exhaust inlet pipe 21, a gap for insertion can be secured outside the outer surface of the outer circumferential surface of the exhaust inlet pipe 21 other than the retaining projection 212, and the upstream end 211 of the exhaust inlet pipe 21 can be smoothly inserted into the downstream end 32 of the connecting pipe 3. In addition, the retaining projection 411 of the exhaust pipe 4 can also be used to obtain a similar effect for the connecting pipe 3 made of soft polymer material and the upstream metal exhaust pipe 4.

[0037] Furthermore, the clamping band 52 allows for easy fixing of the soft polymer material connecting pipe 3 to the heat-resistant resin exhaust inlet pipe 21. Additionally, the flexibility of the polymer material connecting pipe 4 and the tightening of the clamping bands 52 and 51 improve the sealing performance between the exhaust inlet pipe 21 and the connecting pipe 3, and between the exhaust pipe 4 and the connecting pipe 3, reliably preventing exhaust leakage from gaps between the exhaust inlet pipe 21 and the connecting pipe 3, and between the exhaust pipe 4 and the connecting pipe 3. Moreover, by providing the anti-loosening projections 212 on the exhaust inlet pipe 21 and 411 on the exhaust pipe 4 at positions corresponding to the clamping points of the clamping bands 52 and 51, the amount of tension between the exhaust inlet pipe 21, the exhaust pipe 4 and the polymer material connecting pipe 3 is locally increased, causing the anti-loosening projections 212 and 411 to bite into the polymer material connecting pipe 3, further improving anti-loosening and sealing performance. Furthermore, the connection structure can be simplified by tightening and securing the fastening bands 52 and 51, improving ease of assembly and reducing the number of connecting parts.

[0038] Furthermore, when tightening with the fastening band 52, if the strength of the heat-resistant resin exhaust inlet pipe 21 is insufficient, the fastening load may cause the exhaust inlet pipe 21 to deform, raising concerns about exhaust leakage or damage to the exhaust inlet pipe 21. However, by attaching the strength-retaining collar 6 to the inside of the exhaust inlet pipe 21 at a position corresponding to the fastening point of the fastening band 52, deformation of the exhaust inlet pipe 21 can be reliably prevented, thereby preventing exhaust leakage or damage to the exhaust inlet pipe 21 caused by deformation.

[0039] Furthermore, if polypropylene is used as the heat-resistant resin constituting the exhaust muffler 2, the manufacturing cost of the exhaust muffler 2 can be reduced by using polypropylene, a general-purpose plastic frequently used as an automotive part. In addition, the exhaust muffler 2 can be made acid-resistant, alkali-resistant, and less susceptible to water absorption, thus providing an exhaust muffler 2 that is less affected by condensed water, etc. Moreover, because polypropylene is less prone to cracking, damage to the heat-resistant resin exhaust muffler 2 can be prevented.

[0040] [Scope of the invention disclosed herein] The inventions disclosed herein include, in addition to the inventions and embodiments listed herein, those specified by modifying some of these to the extent applicable, or by adding other to these, or by deleting some of these to the extent that some effects are obtained and defining them as broader concepts. Furthermore, the inventions disclosed herein also include the modifications and additions listed below.

[0041] For example, in the exhaust muffler connection structure 1 of the above embodiment, a bellows-shaped peripheral wall 33 is formed in the middle of the connecting pipe 3. However, as in the connecting pipe 3a of the copper-resistant soft polymer material in the modified exhaust muffler connection structure 1a shown in Figure 7, it is also possible to form the portion corresponding to the bellows-shaped peripheral wall 33 with a flat peripheral wall 34a without irregularities.

[0042] Furthermore, in the above embodiment, the retaining projection 212 of the exhaust inlet pipe 21 and the retaining projection 411 of the metal exhaust pipe 4 are arranged around the perimeter in a shape that is roughly bent in a mountain shape when viewed in a vertical cross-section. However, the shape of the retaining projection of the exhaust inlet pipe 21 and the shape of the retaining projection of the metal exhaust pipe 4 can be any shape within the scope of the present invention. For example, in addition to a roughly mountain shape that slopes on both sides of the top, it is possible to have a shape that is bent in a roughly mountain shape that slopes on one side of the central part of the pipe or on one side of the end of the pipe when viewed in a vertical cross-section, a shape in which there is no recess on the inside of each roughly mountain shape, or a shape in which each roughly mountain shape is arranged in a row in the direction of the pipe axis.

[0043] Furthermore, the exhaust muffler in the exhaust muffler connection structure of the present invention is not limited to an exhaust muffler made of heat-resistant resin, but can also be an exhaust muffler made of a metal material, and can be an appropriate exhaust muffler or exhaust inlet pipe for an exhaust muffler made of a material with lower strength than a metal exhaust pipe. [Industrial applicability]

[0044] This invention can be used as a connection structure for an exhaust muffler that discharges exhaust gases from an internal combustion engine of an automobile. [Explanation of Symbols]

[0045] 1, 1a…Exhaust muffler connection structure 2…Exhaust muffler 21…Exhaust inlet pipe 211…Upstream end 212…Retaining projection 22, 23…Exhaust pipe 24…First silencer 25…Second silencer 26…Third silencer 27…Mounting plate 3, 3a…Connecting pipe 31…Upstream end 32…Downstream end 33…Bellows-shaped peripheral wall 34a…Peripheral wall 4…Exhaust pipe 41…Downstream end 411…Retaining projection 51, 52…Tightening band 6…Strength-retaining collar 61…Engaging part 101…Retaining

Claims

1. The upstream metallic exhaust pipe installed in the automobile and the connecting pipe made of a soft polymeric material are fixed to each other, The connecting pipe and an exhaust introduction pipe formed of a material having a lower strength than the exhaust pipe of the exhaust muffler are fixed to each other, the exhaust pipe, the exhaust muffler having the exhaust introduction pipe, and the connecting pipe are all installed under a floor of the automobile; 13. A connection structure for an exhaust muffler, wherein the exhaust pipe and the exhaust introduction pipe are spaced apart from each other by a distance of 35 mm or more in an axial direction of the pipes.

2. The exhaust muffler is formed of a heat-resistant resin, 2. The exhaust muffler connection structure according to claim 1, wherein the connection pipe is made of a soft polymeric material that is resistant to copper damage.

3. 3. The exhaust muffler connection structure according to claim 2, wherein the heat-resistant resin of the exhaust muffler is polypropylene.

4. 4. The exhaust muffler connection structure according to claim 1, wherein the soft polymer material is silicone rubber, fluororubber, EPDM, or alloy resin.

5. 5. The connection structure of an exhaust muffler according to claim 1, wherein the connecting pipe is formed with a bellows-shaped peripheral wall.

6. The exhaust muffler is formed in a flat shape that spreads substantially horizontally and is installed under the floor of the automobile, The exhaust gas introduction pipe is formed in a flat cylindrical shape, an upstream end of the connecting pipe is formed in a substantially cylindrical shape corresponding to a substantially cylindrical downstream end of the exhaust pipe; The exhaust muffler connection structure according to any one of claims 1 to 5, characterized in that the downstream end of the connecting pipe is formed in an approximately flattened cylindrical shape corresponding to the approximately flattened cylindrical upstream end of the exhaust inlet pipe.

7. a stopper protrusion protruding outward is formed in a circumferential direction at an upstream end of the exhaust introduction pipe, A connection structure for an exhaust muffler as described in any one of claims 1 to 6, characterized in that the upstream end of the exhaust inlet pipe is inserted into the downstream end of the connecting pipe so that the anti-pullout protrusion is covered and hooked by the downstream end of the connecting pipe.

8. The exhaust muffler connection structure according to any one of claims 1 to 7, characterized in that the upstream end of the exhaust inlet pipe is inserted into the downstream end of the connecting pipe, and the connecting pipe and the exhaust inlet pipe are fastened and fixed from the outside of the connecting pipe with a fastening band.

9. 9. The exhaust muffler connection structure according to claim 8, wherein a strength retaining collar is attached to the inside of the exhaust introduction pipe at a position corresponding to the fastening point of the fastening band.

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