Exhaust gas recirculation device

Abstract

The present invention provides an exhaust gas recirculation device (1) including a pipe body (4) that returns exhaust gas exhausted from an exhaust pipe (2) of an internal combustion engine to an intake pipe (3) and a cover (5) provided on the pipe body (4), said device being configured such that: the pipe body (4) has a first pipe section (7a), which extends along a first pipe axial direction (x1) and in which a bellows (6) is formed, and a second pipe section (7b), which is bent to extend in a second pipe axial direction (x2) different from the first pipe axial direction (x1) and which is connected to the first pipe section (7a); a first bracket (12) for securing one end of the cover (5) is provided on the side of the first pipe section (7a) opposite from the side that is in continuity with the second pipe section (7b); a second bracket (13) for securing the other end of the cover (5) and having a plane-normal component in the first pipe axial direction (x1) is provided to the second pipe section (7b); and the two ends of the cover (5) are each secured to the first bracket (12) and the second bracket (13), respectively, by means of a securing member (14).

Description

Exhaust Gas Recirculation System

[0001] The present invention relates to an exhaust gas recirculation system.

[0002] In vehicles that employ an exhaust gas recirculation system that recirculates exhaust gas discharged from an exhaust pipe of an internal combustion engine back into the intake pipe of the engine, a cover is often provided on the pipe to prevent thermal problems in surrounding components caused by the high-temperature exhaust gas flowing through the pipe of the system, as shown in, for example, Patent Document 1 below (see Figure 2 of Patent Document 1, etc.). This cover may be fixed to a flange on the pipe with fixing members such as bolts so as to cover a bellows formed on the pipe to absorb expansion and contraction.

[0003] JP 2009-68377 A

[0004] As described above, when the cover is fixed to the flange using fixing members such as bolts, stress is repeatedly applied to the fixed parts of the flange and cover due to vibrations caused by the expansion and contraction of the bellows formed in the piping, which may cause defects in the flange and cover due to fatigue.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent problems caused by stress acting on the fixing portion between the pipe body and the cover of an exhaust gas recirculation device.

[0006] In order to solve the above problems, the present invention provides an exhaust gas recirculation device having a pipe main body that recirculates exhaust gas discharged from an exhaust pipe of an internal combustion engine to an intake pipe of the internal combustion engine, and a cover that is provided on the pipe main body, wherein the pipe main body has a first pipe section that has a bellows formed thereon and extends along a first pipe axis direction, and a second pipe section that is connected to the first pipe section and bends and extends in a second pipe axis direction that is different from the first pipe axis direction, a first bracket is provided on the side of the first pipe section opposite to the side where it is connected to the second pipe section, for fixing one end of the cover, a second bracket having a surface normal component in the first pipe axis direction is provided on the second pipe section, for fixing the other end of the cover, and the one end of the cover is fixed to the first bracket, and the other end of the cover is fixed to the second bracket, each by a fixing member.

[0007] Furthermore, in the above configuration, it is preferable that the first pipe section side of the pipe body is connected to a cooling device that cools the exhaust gas sent to the intake pipe, and the second pipe section side of the pipe body is connected to the exhaust pipe, and that the one end side of the cover and the first bracket are rigidly connected by the fixing member, while the other end side of the cover and the second bracket are fixed by the fixing member via a cushioning material.

[0008] In all of the above configurations, it is preferable that the first bracket is provided on an outlet flange that fixes the pipe body to the cooling device.

[0009] In addition, in all of the above configurations, it is preferable that the fixing member is a bolt, and that the axial directions of the bolt fixing the one end side of the cover and the bolt fixing the other end side of the cover are different from each other.

[0010] In this invention, since the exhaust gas recirculation device is configured as described above, vibrations caused by expansion and contraction of the bellows formed on the pipe body can be absorbed by the flange (second bracket) having a surface normal component in the direction of expansion and contraction (first pipe axial direction). Therefore, when the bellows vibrates, shear force is less likely to act between the flange and the fixed portion of the cover, preventing defects caused by fatigue in the flange and the cover.

[0011] 1 is a perspective view of an exhaust gas recirculation device according to the present invention; FIG. 2 is a perspective view of the exhaust gas recirculation device shown in FIG. 1 with the cover removed; FIG. 3 is a perspective view of the pipe body constituting the exhaust gas recirculation device shown in FIG. 1; and FIG. 4 is a perspective view of the pipe body shown in FIG. 3 from a different direction.

[0012] An embodiment of an exhaust gas recirculation system 1 according to the present invention will be described with reference to Figures 1 to 5. As shown in Figure 1, the exhaust gas recirculation system 1 has a pipe body 4 that recirculates exhaust gas discharged from an exhaust pipe 2 of an internal combustion engine (hereinafter referred to as the engine) to an intake pipe 3 of the engine, and a cover 5 that is provided on the pipe body 4.

[0013] As shown in FIGS. 2 to 4 , the tube main body 4 is a tubular member made of stainless steel and includes a first tube section 7a extending along a first tube axis direction x1 and having a bellows 6 formed therein, and a second tube section 7b connected to the first tube section 7a and bending in a second tube axis direction x2 different from the first tube axis direction x1 (see FIG. 4 for the tube axes x1 and x2). Both the first tube section 7a and the second tube section 7b have a straight tube shape. A first bent section 8a is formed between the first tube section 7a and the second tube section 7b, bending at a predetermined angle (approximately 50 degrees in this embodiment (the angle between the first tube axis direction x1 and the second tube axis direction x2)). The bellows 6 allows the first tube section 7a to expand and contract in the first tube axis direction x1.

[0014] A second bent portion 8b, bent at a predetermined angle (approximately 110 degrees in this embodiment), is connected to the first pipe portion 7a on the side opposite to the side where the first pipe portion 7a is connected to the second pipe portion 7b. A third bent portion 8c is connected to the second pipe portion 7b, and the fourth bent portion 8d is connected to the second pipe portion 7b. A fifth bent portion 8e is connected to the second pipe portion 7b. The exhaust gas introduced from the exhaust pipe 2 into the pipe body 4 passes through the fifth bent portion 8e, the fourth bent portion 7d, the fourth bent portion 8d, the third pipe portion 7c, the third bent portion 8c, the second pipe portion 7b, the first bent portion 8a, the first pipe portion 7a, and the second bent portion 8b in this order before being sent to the intake pipe 3.

[0015] An outlet-side flange 10 is provided at the open end of the second bent portion 8b for connecting the pipe body 4 to a cooling device 9 that cools the exhaust gas sent to the intake pipe 3. An inlet-side flange 11 is provided at the open end of the fifth bent portion 8e for connecting the pipe body 4 to the exhaust pipe 2. The outlet-side flange 10 and the inlet-side flange 11 both have a surface normal that is parallel to the pipe axial direction at the open end of the second bent portion 8b or the fifth bent portion 8e.

[0016] The outlet-side flange 10 is provided with a first bracket 12 having an attachment surface perpendicular to the flange surface of the outlet-side flange 10. The second pipe section 7b is provided with a second bracket 13 extending tangentially from the second pipe section 7b and having a surface normal component in the first pipe axis direction x1. That is, the extension of the first pipe axis direction x1 intersects the same plane as the surface extending tangentially of the second bracket 13 and is parallel to the second pipe axis direction x2. Preferably, the second bracket 13 is provided at a position outside the first bent section 8a so that the angle of intersection is deep. This allows the bracket 13 to bear a large amount of stress in the first pipe axis direction x1. Furthermore, the surface normals of the first bracket 12 and the second bracket 13 face in different directions. The first bracket 12 and the second bracket 13 each have a through hole 15 for passing a fixing member 14 (a bolt in this embodiment; hereinafter, the same reference numeral as the fixing member 14 will be used). A nut 16 is welded coaxially to each through hole 15.

[0017] In this embodiment, the first pipe section 7a is disposed downstream, closer to the outlet flange 10 than the center of the entire length of the pipe body 4. The second pipe section 7b is disposed approximately in the center of the entire length of the pipe body 4. Note that the shape of the pipe body 4 shown in Figures 1 to 4 is merely an example, and the length and number of pipe sections 7a, 7b, 7c, and 7d, the number and magnitude of bending angles of bent sections 8a, 8b, 8c, 8d, and 8e, and the like are designed as appropriate in accordance with the arrangement of each component provided in the engine compartment.

[0018] As shown in Fig. 5, the cover 5 is a heat shield plate made of a long aluminum-plated steel plate that extends along the shape of the pipe body 4. The cover 5 covers the area from the second bent portion 8b to the third bent portion 8c of the pipe body 4. At both longitudinal ends of the cover 5, through holes 17 are formed for passing bolts 14 that secure the cover 5 to the first bracket 12 and the second bracket 13, respectively. The cover 5 is secured to the pipe body 4 by passing the bolts 14 through the through holes 17 formed in the cover 5 and tightening the bolts 14 into nuts 16 welded to the first bracket 12 and the second bracket 13, respectively.

[0019] 1, the first bracket 12, which is closer to the cooling device 9, and the cover 5 are rigidly connected by bolts 14. The term "rigidly connected" here means that the first bracket 12 and the cover 5 are firmly fixed together so that rattle caused by vibrations is minimized.

[0020] On the other hand, a grommet (hereinafter, designated by the same reference numeral as the cushion material 18) that acts as a cushion material 18 is provided in a through hole 17 formed on the second bracket 13 side of the cover 5, which is relatively closer to the exhaust pipe 2. The cover 5 and the second bracket 13 are fixed with bolts 14 via the grommet 18. In this embodiment, the grommet 18 is made of a circular cold-rolled steel plate on the surface of which a mesh-like steel wire made of stainless steel is laminated.

[0021] The first bracket 12 and the second bracket 13 have mutually different surface normals, and accordingly, the axial directions of the bolts 14 provided on the brackets 12, 13 are also mutually different. The pipe main body 4 (second bent portion 8b) is located on an extension of the axis of the bolt 14 provided on the first bracket 12. On the other hand, the pipe main body 4 is not located on an extension of the axis of the bolt 14 provided on the second bracket 13, and this axis and the pipe axis of the pipe main body 4 (second pipe portion 7b) are in a twisted positional relationship with each other.

[0022] In the exhaust gas recirculation device 1, the pipe main body 4 includes a first pipe section 7a extending along a first pipe axis direction x1 and having a bellows 6 formed thereon, and a second pipe section 7b extending and bending in a second pipe axis direction x2 different from the first pipe axis direction x1. A first bracket 12 is provided on the first pipe section 7a, and a second bracket 13 is provided on the second pipe section 7b. The cover 5 is fixed by both brackets 12 and 13. Therefore, vibrations caused by expansion and contraction of the bellows 6 formed on the pipe main body 4 can be absorbed by the flange (second bracket 13) having a surface normal component in the expansion and contraction direction (first pipe axis direction x1). Furthermore, because the bellows also expands and contracts due to heat, thermal expansion and contraction can also be absorbed by the flange (second bracket 13) having a surface normal component in the expansion and contraction direction (first pipe axis direction x1). Therefore, when the bellows 6 expands and contracts, shear forces are less likely to act between the flange (second bracket 13) and the fixed portion of the cover 5, preventing fatigue-related defects in the flange (second bracket 13) and the cover 5.

[0023] Furthermore, in the above-described exhaust gas recirculation device 1, the first pipe section 7a side of the pipe body 4 is connected to a cooling device 9 that cools the exhaust gas sent to the intake pipe 3, and the second pipe section 7b side of the pipe body 4 is connected to the exhaust pipe 2, and one end side of the cover 5 and the first bracket 12 are rigidly connected by bolts 14, while the other end side of the cover 5 and the second bracket 13 are fixed by bolts 14 via grommets 18. Therefore, vibrations caused by misalignment of the cover 5 are suppressed by the rigid connection to the cooling device 9 side, which vibrates less, and vibrations transmitted from the exhaust pipe 2 to the pipe body 4 are absorbed by the grommets 18, preventing the vibrations from being transmitted to the cover 5.

[0024] Furthermore, the above-mentioned exhaust gas recirculation device 1 is configured such that the first bracket 12 is provided on the outlet side flange 10 that fixes the pipe body 4 to the cooling device 9, thereby further suppressing vibration of the cover 5 that is rigidly connected to the first bracket 12 by the bolts 14.

[0025] Furthermore, in the above-described exhaust gas recirculation device 1, the fixing members 14 are bolts 14, and the bolts 14 that fix one end of the cover 5 and the bolts 14 that fix the other end of the cover 5 have different axial directions, so that vibrations of the cover 5 in any direction can be effectively suppressed by at least one of the bolts 14. Furthermore, if the axial directions of the bolts 14 are different, variations in the assembly of the cover 5 can also be absorbed.

[0026] Furthermore, by positioning the pipe body 4 (second bend portion 8b) on the extension of the axis of the bolt 14 provided on the first bracket 12, while not positioning the pipe body 4 on the extension of the axis of the bolt 14 provided on the second bracket 13, it may be possible to suppress resonance between the pipe body 4 and the cover 5.

[0027] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, the scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

[0028] REFERENCE SIGNS LIST 1 exhaust gas recirculation device 2 exhaust pipe 3 intake pipe 4 pipe body 5 cover 6 bellows 7a first pipe section 7b second pipe section 7c third pipe section 7d fourth pipe section 8a first bent section 8b second bent section 8c third bent section 8d fourth bent section 8e fifth bent section 9 cooling device 10 outlet side flange 11 inlet side flange 12 first bracket 13 second bracket 14 fixing member (bolt) 15 through hole (of first and second brackets) 16 nut 17 through hole (of cover) 18 cushion material (grommet) x1 first pipe axial direction x2 second pipe axial direction

Claims

1. An exhaust gas recirculation device having a pipe main body that recirculates exhaust gas discharged from an exhaust pipe of an internal combustion engine to an intake pipe of the internal combustion engine, and a cover provided on the pipe main body, wherein the pipe main body has a first pipe section having a bellows formed thereon and extending along a first pipe axis direction, and a second pipe section that is connected to the first pipe section and bends and extends in a second pipe axis direction different from the first pipe axis direction, a first bracket is provided on the side of the first pipe section opposite to the side where it is connected to the second pipe section, for fixing one end of the cover, a second bracket having a surface normal component in the first pipe axis direction is provided on the second pipe section, for fixing the other end of the cover, and the one end of the cover is fixed to the first bracket and the other end of the cover to the second bracket, each by a fixing member.

2. An exhaust gas recirculation device as described in claim 1, wherein the first pipe section of the pipe body is connected to a cooling device that cools the exhaust gas sent to the intake pipe, and the second pipe section of the pipe body is connected to the exhaust pipe, and the one end of the cover and the first bracket are rigidly connected by the fixing member, while the other end of the cover and the second bracket are fixed by the fixing member via a cushioning material.

3. An exhaust gas recirculation system according to claim 2, wherein the first bracket is provided on an outlet flange that fixes the pipe body to the cooling device.

4. An exhaust gas recirculation device as described in any one of claims 1 to 3, wherein the fixing members are bolts, and the axial directions of the bolts fixing the one end side of the cover and the bolts fixing the other end side of the cover are different from each other.

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