JP5251220B2 - Piping joint structure - Google Patents

Description

  The present invention relates to a pipe joint structure, and more particularly to a pipe joint structure connected via a flange member.

  Generally, an exhaust system of an internal combustion engine mounted on a vehicle such as an automobile has an exhaust port, an exhaust manifold, a catalyst, a silencer, an exhaust pipe and the like communicating with a combustion chamber of the internal combustion engine. As for the connection of the exhaust pipe, various techniques have been proposed, and the one shown in FIG. 6 is known.

  In FIG. 6, a first exhaust pipe 1 that is one pipe is connected to an exhaust manifold of an internal combustion engine (not shown), and a first flange that is one flange member is connected to an end of the first exhaust pipe 1. The flange member 3 is provided.

  A second flange member 4 that is the other flange member is provided at an end of the second exhaust pipe 2 that is the other pipe, and the first flange member 3 and the second flange member 4 After the sealing member 5 is interposed therebetween, the first and second exhaust pipes 1 and 2 are fastened by fastening the first flange member 3 and the second flange member 4 with bolts and nuts (not shown). Are connected to each other (see, for example, Patent Document 1).

  On the other hand, an exhaust gas recirculation (hereinafter referred to as “EGR”) device is known as a technique for reducing the amount of nitrogen oxide (NOx) discharged from an internal combustion engine. This is a technique for reducing the amount of NOx generated by reflowing the gas discharged from the internal combustion engine into the combustion chamber.

  In this EGR device, an EGR pipe is connected to a side of an exhaust pipe immediately downstream of a catalyst disposed in an exhaust system of an internal combustion engine, and this EGR pipe is connected to an intake pipe (for example, Patent Document 2). reference). As described above, the EGR pipe has the same configuration as the first exhaust pipe and the second exhaust pipe, and is interposed between the exhaust pipe and the intake pipe.

  By the way, after the operation of the internal combustion engine of the vehicle equipped with such an exhaust pipe or EGR pipe (travel of the vehicle) is stopped, for example, when it is left at a very low outside temperature, such as at night, the exhaust pipe or Since the EGR pipe is rapidly cooled by outside air, the water vapor component contained in the exhaust gas is condensed due to the temperature difference between the exhaust pipe and the pipe wall of the EGR pipe and the exhaust gas remaining in the inside. become. Further, when the EGR cooler is provided in the EGR pipe, the high-temperature exhaust gas is cooled, so that the water vapor component contained in the exhaust gas is condensed.

  For this reason, this condensed water vapor component (condensed water) comes to adhere to the pipe wall of the exhaust pipe or the EGR pipe. Since this condensed water has strong acidity, SUS (stainless steel) material is usually used as the material having excellent acid resistance for the first exhaust pipe 1 and the second exhaust pipe 2, and corrosion caused by condensed water. Is supposed to suppress.

Further, the first exhaust pipe 1 and the second exhaust pipe 2 connected by the first flange member 3 and the second flange member 4 shown in FIG. Since the second flange member 4 is exposed to the exhaust gas exhaust passages formed on the inner peripheral surfaces of the first exhaust pipe 1 and the second exhaust pipe 2, respectively, the first flange member 3 and the second flange member 4 are exposed. The flange member 4 is exposed to condensed water. For this reason, in order to suppress the corrosion by condensed water, the 1st flange member 3 and the 2nd flange member 4 are also using SUS material.
JP-A-8-144453 Japanese Patent Laid-Open No. 2008-14210

  However, in such a conventional exhaust pipe joint structure, the first exhaust pipe 1, the second exhaust pipe 2, the first flange member 3 and the Since the 2nd flange member 4 was comprised from the expensive SUS material, there existed a problem that the manufacturing cost of an exhaust pipe will increase.

  The present invention was made to solve the above-described conventional problems, and the flange member can be made of an inexpensive material to prevent corrosion due to condensed water, thereby reducing the manufacturing cost. It aims at providing the joint structure of piping.

  In order to achieve the object, the pipe joint structure according to the present invention has (1) a plurality of pipes into which exhaust gas discharged from the internal combustion engine is introduced, and one provided at the outer peripheral end of each pipe. In a pipe joint structure in which a plurality of pipes are connected by fastening one flange member and the other flange member, the end outer peripheral surface of the other pipe contacts the inner peripheral surface of the one pipe. An outer peripheral end portion of the one pipe is extended from the one flange member to an inner peripheral surface of the other pipe so as to contact the upstream side and the downstream side with respect to the one flange member and the other flange member. A concave bent portion protruding at least below the end of the one pipe and the end of the other pipe is provided in each of the end of the one pipe on the side and the vicinity of the end of the other pipe. From the stuff It is.

  With this configuration, the outer peripheral end of one pipe is extended from one flange member to the inner peripheral surface of the other pipe so that the outer peripheral face of the other pipe is in contact with the inner peripheral face of the other pipe. Since it was put out, the entire inner peripheral surface of one flange member and the other flange member can be covered with the outer peripheral surface of the end of one pipe and the other pipe, and when condensed water is generated inside the pipe, One flange member and the other flange member can be prevented from being exposed to condensed water.

In addition, at least one end of one pipe and the other end of the other pipe are located near the end of one pipe on the upstream side and the downstream side of the other flange member and the end of the other pipe, respectively. Since the concave bent portion projecting downward from the end portion is provided, the condensed water generated in the pipe can be accumulated in the concave bent portion, and this condensed water is supplied from the bent portion to one flange member and the other flange. It can prevent moving toward a member.
For this reason, it prevents the condensed water from entering the inner peripheral surface of one flange member and the other flange member from a minute gap between the inner peripheral surface of the end of one pipe and the outer peripheral surface of the end of the other pipe. It is possible to reliably prevent the one flange member and the other flange member from being exposed to condensed water.

Further, the condensed water accumulated in the bent portion is evaporated by the high-temperature exhaust gas during operation of the internal combustion engine, and can be easily removed from the bent portion.
As a result, in order to prevent corrosion due to condensed water, the pipe can be made of SUS, and one flange member and the other flange member can be made of an inexpensive metal such as steel or iron. Cost can be reduced.

Moreover, since one flange member and the other flange member which have thickness can be comprised from steel, iron, etc. whose hardness is lower than SUS, formation of one flange member and the other flange member can be performed easily. It is possible to improve the workability of the molding operation of one flange member and the other flange member.
In addition to this, in general, thick SUS such as a flange member is difficult to obtain in the market, but thick steel and iron are easy to obtain in the market, so it is easy to procure the flange member. it can.

  In the joint structure of the pipe of (1) above, (2) the plurality of pipes are configured to include a pipe for exhaust gas recirculation, and the pipe for exhaust gas recirculation is connected to any one of the plurality of pipes. It is comprised from what is provided with the cooler which cools the flowing exhaust gas.

  With this configuration, in order to prevent corrosion due to condensed water, the pipe for exhaust gas recirculation can be configured from SUS, and one flange member and the other flange member can be configured from an inexpensive metal such as steel or iron, The manufacturing cost of piping can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the flange member can be comprised from an inexpensive material, the corrosion by condensed water can be prevented, and the joint structure of piping which can reduce manufacturing cost can be provided.

Embodiments of a joint structure for piping according to the present invention will be described below with reference to the drawings.
[First Embodiment]
FIGS. 1-3 is a figure which shows 1st Embodiment of the joint structure of piping which concerns on this invention.
First, the configuration will be described.

In FIG. 1, an engine 11 as an internal combustion engine includes a plurality of cylinders # 1 to # 4, and an intake manifold 12 is connected to an unillustrated intake port of each cylinder # 1 to # 4 of the engine 11. ing.
The intake manifold 12 includes a number of intake branches corresponding to the number of the cylinders # 1 to # 4 and a collecting pipe in which the intake branches gather, and each cylinder # 1 to # 4 is provided at the end of the intake branch. Communicates with each of the intake ports.

  An exhaust manifold 13 is connected to an exhaust port (not shown) of each cylinder # 1 to # 4 of the engine 11, and a flange member 15 is provided at the downstream end of the exhaust manifold 13. 15 is fastened to a flange member 16 provided at the upstream end of the catalytic converter exhaust pipe 14 by bolts and nuts (not shown). For this reason, the exhaust manifold 13 and the catalytic converter exhaust pipe 14 are connected via the flange members 15 and 16.

Further, the catalytic converter exhaust pipe 14 is provided with a catalytic converter 14a. The catalytic converter 14a is provided in the middle of the catalytic converter exhaust pipe 14, and hydrocarbons in exhaust gas discharged from the engine 11, It has a catalyst that purifies harmful components such as carbon monoxide and nitrogen oxides.
The upstream end portion indicates the upstream side in the exhaust gas discharge direction, and the downstream end portion indicates the downstream side in the exhaust gas discharge direction.

  Further, as shown in FIG. 2, an exhaust pipe 31 including a front exhaust pipe 17, a center exhaust pipe 18, and a tail exhaust pipe 19 is connected to the downstream side of the catalytic converter exhaust pipe 14. In the present embodiment, the exhaust manifold 13, the catalytic converter exhaust pipe 14, the front exhaust pipe 17, the center exhaust pipe 18 and the tail exhaust pipe 19 constitute a pipe.

  A flange member 21 is provided at the upstream end portion of the front exhaust pipe 17, and this flange member 21 is attached to a flange member 20 provided at the downstream end portion of the exhaust pipe for catalytic converter 14 by bolts and nuts (not shown). It is concluded. Therefore, the front exhaust pipe 17 and the catalytic converter exhaust pipe 14 are connected via the flange members 20 and 21.

  Further, a flange member 22 is provided at the downstream end portion of the front exhaust pipe 17, and this flange member 22 is attached to a flange member 23 provided at the upstream end portion of the center exhaust pipe 18 by bolts and nuts (not shown). It is concluded. For this reason, the front exhaust pipe 17 and the center exhaust pipe 18 are connected via the flange members 22 and 23.

  Further, a flange member 24 is provided at the downstream end portion of the center exhaust pipe 18, and this flange member 24 is attached to a flange member 25 provided at the upstream end portion of the tail exhaust pipe 19 by bolts and nuts (not shown). It is concluded. For this reason, the center exhaust pipe 18 and the tail exhaust pipe 19 are connected via the flange members 24 and 25.

  The center exhaust pipe 18 is provided with a silencer 26, and the tail exhaust pipe 19 is provided with a silencer 27, and the exhaust noise caused by the exhaust gas introduced into the exhaust pipe 31 is reduced by the silencer 26. , 27.

  The center exhaust pipe 18 and the silencer 27 are provided with support brackets 28, 29, 30. The exhaust pipe 31 is suspended by the support brackets 28, 29, 30 below the floor of the vehicle. Yes.

  On the other hand, the present embodiment has a feature in the joint structure of the exhaust pipe 31, and the joint structure includes a connecting portion of the exhaust manifold 13 and the catalytic converter exhaust pipe 14, the catalytic converter exhaust pipe 14 and the front exhaust pipe. 17, a connection portion between the front exhaust pipe 17 and the center exhaust pipe 18, and a connection portion between the center exhaust pipe 18 and the tail exhaust pipe 19.

  Since the joint structures of the present embodiment all have the same structure, the connecting portion of the front exhaust pipe 17 and the center exhaust pipe 18 will be described as a representative.

  In FIG. 3, a flange member 22 is provided at the downstream end which is the outer peripheral end of the front exhaust pipe 17 as one pipe, and the upstream which is the outer peripheral end of the center exhaust pipe 18 as the other pipe. A flange member 23 is provided at the end.

  The flange member 22 as one flange member and the flange member 23 as the other flange member are fastened by a bolt 33 and a nut 34 with a seal member 32 interposed between the flange members 22 and 23. Thus, the downstream end of the front exhaust pipe 17 and the upstream end of the center exhaust pipe 18 are connected.

  Further, the upstream end portion of the center exhaust pipe 18 extends from the flange member 23 to the inner peripheral surface of the front exhaust pipe 17, and this extending portion constitutes an extending portion 18 a. For this reason, the outer peripheral surface of the upstream end portion of the center exhaust pipe 18 is in contact with the inner peripheral surface of the downstream end portion of the front exhaust pipe 17.

In addition, concave bent portions 35 and 36 are formed in the vicinity of the downstream end portion of the upstream and downstream front exhaust pipes 17 and the upstream end portion of the center exhaust pipe 18 with respect to the flange members 22 and 23, respectively. The bent portions 35 and 36 project in an annular shape outward in the radial direction of the front exhaust pipe 17 and the center exhaust pipe 18.
Further, the side surface of the flange member 22 is in contact with the bent portion 35, and the side surface of the flange portion 23 is in contact with the bent portion 36, and the flange portions 22, 23 are connected to the front exhaust pipe 17 and the center exhaust pipe. The movement of 18 in the axial direction is restricted.

  The bent portions 35, 36 are also formed at the downstream end of the catalytic converter exhaust pipe 14, the upstream end of the front exhaust pipe 17, the downstream end of the center exhaust pipe 18, and the upstream end of the tail exhaust pipe 19. Has been.

  In the exhaust pipe 31 having such a configuration, when the outside air temperature is left at a very low state such as at night, the exhaust pipe 31 is rapidly cooled by the outside air. The water vapor component contained in the exhaust gas is condensed due to the temperature difference between the exhaust pipe 14, the front exhaust pipe 17, the center exhaust pipe 18, and the tail exhaust pipe 19 and the exhaust gas remaining therein. become.

For this reason, the condensed water vapor component (condensed water) adheres to the pipe walls of the exhaust manifold 13, the catalytic converter exhaust pipe 14, the front exhaust pipe 17, the center exhaust pipe 18 and the tail exhaust pipe 19.
Since this condensed water has a strong acidity, it is usual to use SUS (stainless steel) material for the exhaust manifold 13, the catalytic converter exhaust pipe 14, the front exhaust pipe 17, the center exhaust pipe 18 and the tail exhaust pipe 19. In order to prevent corrosion caused by condensed water.

  Here, if the flange members 15, 16, 20 to 25 having a thickness are made of SUS, SUS is expensive and difficult to obtain from the market, and SUS is hard and difficult to manufacture. The flange members 15, 16, 20 to 25 according to the embodiment are made of metal such as steel or iron that is inexpensive and easy to form.

  However, steel and iron are easily oxidized and thus corrode early when exposed to condensed water. In the present embodiment, the upstream end of the center exhaust pipe 18 is moved from the flange member 23 to the front so that the outer peripheral surface of the downstream end of the front exhaust pipe 17 contacts the inner peripheral surface of the upstream end of the center exhaust pipe 18. Since it extends to the inner peripheral surface of the exhaust pipe 17, the entire inner peripheral surface of the flange members 22, 23 can be covered with the outer peripheral surface of the downstream end portion of the front exhaust pipe 17 and the upstream end portion of the center exhaust pipe 18. In addition, it is possible to prevent the flange members 22 and 23 from being exposed to the condensed water generated inside the front exhaust pipe 17 and the center exhaust pipe 18.

  Also, the downstream end of the front exhaust pipe 17 and the center exhaust are respectively located in the vicinity of the downstream end of the upstream exhaust pipe 17 and the upstream end of the center exhaust pipe 18 upstream and downstream of the flange members 22 and 23. Since the concave bent portions 35 and 36 projecting radially outward from the upstream end portion of the pipe 18 are formed, the condensed water generated in the front exhaust pipe 17 and the center exhaust pipe 18 is fed to the bent portions 35 and 36. The condensed water can be prevented from moving from the bent portions 35 and 36 toward the flange members 22 and 23.

  For this reason, the condensed water enters the inner peripheral surfaces of the flange members 22 and 23 through a minute gap between the inner peripheral surface of the upstream end portion of the front exhaust pipe 17 and the outer peripheral surface of the extending portion 18a of the center exhaust pipe 18. It is possible to prevent the flange members 22 and 23 from being exposed to condensed water.

  Further, since the condensed water accumulated in the bent portions 35 and 36 is evaporated by the high-temperature exhaust gas when the engine 11 is operated, it can be easily removed from the bent portions 35 and 36.

  As a result, the exhaust manifold 13, the catalytic converter exhaust pipe 14, the front exhaust pipe 17, the center exhaust pipe 18 and the tail exhaust pipe 19 are made of SUS to prevent corrosion due to condensed water, and the flange members 20 to 25 are inexpensive. Therefore, the manufacturing cost of the joint structure of the exhaust pipe 31 can be reduced.

  Moreover, since the flange members 20-25 can be comprised from metals, such as steel and iron whose hardness is lower than SUS, the shaping | molding of the flange members 20-25 can be performed easily, and shaping | molding of the flange members 20-25. The workability of the work can be improved.

  In addition to this, a thick SUS like a flange member is difficult to obtain on the market, but a thick metal such as steel or iron like the flange members 20 to 25 is easily available on the market. ˜25 can be easily procured.

  Further, the catalyst component may elute into the condensed water immersed in the catalyst of the catalytic converter 14a and flow out of the catalyst. Even when the catalyst component has strong acidity, Since it can be stored in the bent parts 35 and 36 provided in the downstream end part of the exhaust pipe for catalytic converters, it can prevent reliably that the flange members 20 and 21 are exposed to the component of a catalyst.

  Further, in the present embodiment, the bent portions 35, 36 are formed in an annular shape so as to protrude radially outward from the downstream end portion of the front exhaust pipe 17 and the upstream end portion of the center exhaust pipe 18, You may form in the concave shape which protrudes from the downstream end part of the front exhaust pipe 17 and the upstream end part of the center exhaust pipe 18, ie, the gravity direction.

  In the present embodiment, the exhaust pipe 31 is constituted by a plurality of exhaust pipes including the exhaust manifold 13, the catalytic converter exhaust pipe 14, the front exhaust pipe 17, the center exhaust pipe 18, and the tail exhaust pipe 19. When the manifold 13 is one pipe, the catalytic converter exhaust pipe 14 is the other pipe, the front exhaust pipe 17 is one pipe, the center exhaust pipe 18 is the other pipe, and the tail exhaust pipe 19 is one pipe. For this reason, when the number of exhaust pipes is large, one pipe and the other pipe are alternately installed from the upstream side toward the downstream side.

When the exhaust manifold 13 is the other pipe, the catalytic converter exhaust pipe 14 is one pipe, the front exhaust pipe 17 is the other pipe, the center exhaust pipe 18 is one pipe, and the tail exhaust pipe 19 is the other pipe. Become. For this reason, when the number of exhaust pipes is large, the other pipe and the one pipe are alternately installed from the upstream side toward the downstream side.
Therefore, the exhaust manifold 13 and the catalytic converter exhaust pipe 14 will be described. The portion corresponding to the extending portion 18a may be provided in either the exhaust manifold 13 or the catalytic converter exhaust pipe 14.

[Second Embodiment]
4 and 5 are views showing a second embodiment of the pipe joint structure according to the present invention. The pipe joint structure of the present embodiment is used for exhaust gas recirculation, that is, for the pipe of the EGR device. An applied example is shown.

In FIG. 4, a diesel engine 41 as an internal combustion engine includes a fuel injection valve 42 that directly injects fuel into each cylinder # 1 to # 4, and an intake pipe 43 that guides air into each cylinder # 1 to # 4. I have.
In the middle of the intake pipe 43, a compressor housing 44a and an intercooler 46 of the turbocharger 44 are arranged, and a compressor impeller is accommodated in the compressor housing 44a.

  The intake air supercharged by the compressor housing 44a is cooled by the intercooler 46 and then guided into the cylinders # 1 to # 4 via the intake manifold 47. The intake air led to is ignited and burned in the cylinders # 1 to # 4 together with the fuel injected from the fuel injection valve.

  The diesel engine 41 includes an exhaust manifold 48, and the exhaust gas burned in the cylinders # 1 to # 4 is discharged to the exhaust manifold 48. The exhaust gas discharged to the exhaust manifold 48 is discharged into the atmosphere through the turbine housing 44b of the turbocharger 44 and the catalytic converter 50a disposed in the middle of the exhaust manifold 48.

  The catalytic converter 50a is provided in the middle of the exhaust pipe 50 for catalytic converter, and has a catalyst for purifying harmful components such as hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas discharged from the diesel engine 41. doing.

  The downstream configuration of the catalytic converter exhaust pipe 50 is the same as that of the first embodiment, and the flange member 21 of the center exhaust pipe 18 is fastened to the flange member 20 of the catalytic converter 50a.

  Further, in the present embodiment, the exhaust manifold 48, the turbine housing 44b, and the catalytic converter exhaust pipe 50 are integrally formed. The exhaust manifold 48, the turbine housing 44b, and the catalytic converter exhaust pipe 50 may be formed separately and connected via flange members, respectively.

  On the other hand, a portion of the intake pipe 43 downstream from the intercooler 46 and a portion of the exhaust manifold 48 upstream of the turbine housing 44b are connected by an EGR pipe 52 as a pipe for exhaust gas recirculation.

  The EGR pipe 52 includes a branch EGR pipe 53 branched from the exhaust manifold 48, a first EGR pipe 54, a second EGR pipe 55, a third EGR pipe 56, and a branch EGR pipe 57 branched from the intake manifold 47. It consists of and. In the present embodiment, the branch EGR pipe 53, the first EGR pipe 54, the second EGR pipe 55, the third EGR pipe 56, and the branch EGR pipe 57 constitute a pipe.

  A flange member 58 is provided at the downstream end portion of the branch EGR pipe 53, and this flange member 58 is connected to a flange member 59 provided at the upstream end portion of the first EGR pipe 54 with bolts and nuts (not shown). It is concluded by Therefore, the branch EGR pipe 53 and the first EGR pipe 54 are connected via the flange members 58 and 59.

  A flange member 60 is provided at the downstream end of the first EGR pipe 54, and this flange member 60 is not shown in the flange member 61 provided at the upstream end of the second EGR pipe 55. Fastened with bolts and nuts. For this reason, the first EGR pipe 54 and the second EGR pipe 55 are connected via the flange members 60 and 61.

  Further, a flange member 62 is provided at the downstream end portion of the second EGR pipe 55, and this flange member 62 is not shown in the flange member 63 provided at the upstream end portion of the third EGR pipe 56. Fastened with bolts and nuts. For this reason, the second EGR pipe 55 and the third EGR pipe 56 are connected via the flange members 62 and 63.

  Further, a flange member 64 is provided at the downstream end of the third EGR pipe 56, and this flange member 64 is connected to a bolt (not shown) and a flange member 65 provided at the upstream end of the branch EGR pipe 57. Fastened with a nut or the like. For this reason, the third EGR pipe 56 and the branch EGR pipe 57 are connected via the flange members 64 and 65.

  The branch EGR pipe 57 is provided with an EGR valve 66, and this EGR valve 66 adjusts the flow rate of exhaust gas (hereinafter referred to as “EGR gas”) flowing through the EGR pipe 52.

  Further, an EGR cooler 67 as a cooler is provided in the middle of the second EGR pipe 55. The EGR cooler 67 includes an introduction pipe (not shown) into which cooling water supplied to the cylinder block of the diesel engine 41 is introduced. The EGR cooler 67 covers the periphery of the second EGR pipe 55 and flows through the EGR pipe 52. The gas is cooled.

  On the other hand, the present embodiment has a feature in the joint structure of the EGR pipe 52, and the joint structure includes a connecting portion of the branch EGR pipe 53 and the first EGR pipe 54, the first EGR pipe 54, and the second EGR pipe 52. This corresponds to a connecting portion of the EGR pipe 55, a connecting portion of the second EGR pipe 55 and the third EGR pipe 56, a connecting portion of the third EGR pipe 56 and the branch EGR pipe 57.

Since all the joint structures of the present embodiment have the same structure, the connecting portion of the first EGR pipe 54 and the second EGR pipe 55 will be described as a representative.
In FIG. 5, a flange member 60 is provided at the downstream end which is the outer peripheral end of the first EGR pipe 54 as one pipe, and the outer peripheral end of the second EGR pipe 55 as the other pipe. A flange member 61 is provided at the upstream end which is the portion.

  The flange member 60 as one flange member and the flange member 61 as the other flange member are fastened by a bolt 69 and a nut 70 with a seal member 68 interposed between the flange members 61 and 62. Thus, the downstream end of the first EGR pipe 54 and the upstream end of the second EGR pipe 55 are connected.

  The upstream end portion of the second EGR pipe 55 extends from the flange member 61 to the inner peripheral surface of the first EGR pipe 54, and this extended portion constitutes an extended portion 55a. . For this reason, the outer peripheral surface of the upstream end portion of the second EGR pipe 55 is in contact with the inner peripheral surface of the downstream end portion of the first EGR pipe 54.

  In addition, a concave bent portion 71, respectively, in the vicinity of the downstream end portion of the first EGR pipe 54 on the upstream side and the downstream side of the flange members 60, 61 and the upstream end portion of the second EGR pipe 55, 72 is formed, and the bent portions 71 and 72 project annularly outward in the radial direction of the first EGR pipe 54 and the second EGR pipe 55.

  The bent portions 71 and 72 are the downstream end of the branch EGR pipe 53, the upstream end of the first EGR pipe 54, the downstream end of the second EGR pipe 55, and the upstream and downstream of the third EGR pipe 56. An end portion is also formed at the upstream end portion of the branch EGR pipe 57.

  In the EGR pipe 52 having such a configuration, the high-temperature exhaust gas flowing through the EGR pipe 52 is cooled by the EGR cooler 67, so that the water vapor component contained in the exhaust gas is condensed.

  Further, if the outside air temperature is left at a very low state such as at night, the EGR pipe 52 and the exhaust pipe 31 are rapidly cooled by the outside air, so that the EGR pipe 52, the exhaust manifold 13, the catalytic converter exhaust pipe 14, Due to the temperature difference between the front exhaust pipe 17, the center exhaust pipe 18 and the tail exhaust pipe 19 and the exhaust gas remaining therein, the water vapor component contained in the exhaust gas is condensed.

  Due to these factors, the condensed water vapor component (condensed water) adheres to the pipe walls of the branch EGR pipe 53, the first EGR pipe 54, the second EGR pipe 55, the third EGR pipe 56, and the branch EGR pipe 57. To come. Since this condensed water has strong acidity, the branch EGR pipe 53, the first EGR pipe 54, the second EGR pipe 55, the third EGR pipe 56, and the branch EGR pipe 57 are made of SUS (stainless steel). By using the material, corrosion caused by condensed water is suppressed.

  Since the intake manifold 47 is made of resin, the downstream end portion of the branch EGR pipe 57 is attached to the intake manifold 47 having a double structure or a heat insulating structure so that the intake manifold 47 is not deformed by high-temperature EGR gas. It has been.

  In the present embodiment, the second EGR pipe 55 is arranged such that the outer peripheral surface of the downstream end portion of the second EGR pipe 55 is in contact with the inner peripheral face of the upstream end portion of the first EGR pipe 54. Since the upstream end portion extends from the flange member 61 to the inner peripheral surface of the first EGR pipe 54, the entire inner peripheral surface of the flange members 60 and 61 extends over the downstream end portion of the first EGR pipe 54 and the second end portion. It can be covered with the outer peripheral surface of the upstream end portion of the EGR pipe 55, and the flange members 60 and 61 are prevented from being exposed to the condensed water generated in the first EGR pipe 54 and the second EGR pipe 55. can do.

  Further, the first EGR pipe 54 and the upstream end part of the first EGR pipe 54 on the upstream side and the downstream side with respect to the flange members 60 and 61 and the vicinity of the upstream end part of the second EGR pipe 55 respectively. Since the concave bent portions 71 and 72 projecting downward from the second EGR pipe 55 are formed, the condensed water generated in the first EGR pipe 54 and the second EGR pipe 55 is accumulated in the bent portions 71 and 72. The condensed water can be prevented from moving from the bent portions 71 and 72 toward the flange members 60 and 61.

  For this reason, condensed water is formed on the inner peripheral surfaces of the flange members 60 and 61 from a minute gap between the inner peripheral surface of the upstream end portion of the first EGR pipe 54 and the outer peripheral surface of the extended portion 55a of the second EGR pipe 55. Can be prevented and the flange members 60 and 61 can be reliably prevented from being exposed to condensed water.

In addition, it is possible to prevent the condensed water from being introduced into the cylinders # 1 to # 4 of the diesel engine 41 through the intake manifold, and to prevent the inner peripheral surface of the cylinder from being corroded. In addition, it is possible to prevent deterioration of combustion due to mixing of condensed water with fuel.
As a result, in order to prevent corrosion due to condensed water, the branch EGR pipe 53, the first EGR pipe 54, the second EGR pipe 55, the third EGR pipe 56, and the branch EGR pipe 57 are made of SUS, and the flange member 58-65 can be comprised from cheap steel and iron, and the manufacturing cost of the joint structure of the EGR piping 52 can be reduced.

  Further, since the flange members 58 to 65 can be made of metal such as steel or iron having a hardness lower than that of SUS, the flange members 58 to 65 can be easily formed, and the flange members 58 to 65 can be formed. The workability of the work can be improved.

  In addition, a thick SUS such as a flange member is difficult to obtain in the market, but a thick metal such as steel or iron such as the flange members 58 to 65 is easily available in the market. ~ 65 can be easily procured.

  The joint structure of the exhaust pipe (not shown) on the downstream side from the catalytic converter 50a is the same as that in the first embodiment. Therefore, even in the exhaust system on the downstream side from the catalytic converter 50a, the same as in the first embodiment. The effect of can be obtained.

  The embodiment disclosed this time is illustrative in all respects and is not limited to this embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  As described above, the joint structure for piping according to the present invention has an effect that the flange member can be made of an inexpensive material to prevent corrosion due to condensed water, and the manufacturing cost can be reduced. This is useful as a joint structure for piping connected via a flange member.

It is a figure which shows 1st Embodiment of the joint structure of the exhaust pipe which concerns on this invention, and is a figure which shows an engine and an exhaust manifold. It is a figure which shows 1st Embodiment of the joint structure of the exhaust pipe which concerns on this invention, and is a figure which shows the exhaust system of the downstream of an engine. It is a figure which shows 1st Embodiment of the joint structure of the exhaust pipe which concerns on this invention, and is sectional drawing of the connection part of a front exhaust pipe and a center exhaust pipe. It is a figure which shows 2nd Embodiment of the joint structure of the exhaust pipe which concerns on this invention, and is a block diagram of an engine and an intake / exhaust system. It is a figure which shows 2nd Embodiment of the joint structure of the exhaust pipe which concerns on this invention, and is sectional drawing of the connection part of 1st EGR piping and 2nd EGR piping. It is sectional drawing of the connection part of the conventional 1st exhaust pipe and 2nd exhaust pipe.

Explanation of symbols

11 Engine (Internal combustion engine)
13 Exhaust manifold (piping)
14 Exhaust pipe (piping) for catalytic converter
15, 16, 20-25 Flange member 17 Front exhaust pipe (pipe)
18 Center exhaust pipe (pipe)
19 Tail exhaust pipe (pipe)
35, 36 Bent part 41 Diesel engine (internal combustion engine)
48 Exhaust manifold (piping)
50 Exhaust pipe (piping) for catalytic converter
53 Branch EGR piping (Piping)
54 First EGR piping (piping)
55 Second EGR piping (piping)
56 Third EGR piping (piping)
57 Branch EGR piping (Piping)
58-65 Flange member 71, 72 Bent part

Claims (3)

It has a plurality of pipes into which exhaust gas discharged from the internal combustion engine is introduced, and connects the plurality of pipes by fastening one flange member and the other flange member provided at the outer peripheral end of each pipe In the pipe joint structure
The outer peripheral end of the one pipe is moved from the one flange member to the inner peripheral surface of the other pipe so that the outer peripheral surface of the end of the other pipe contacts the inner peripheral surface of the end of the one pipe. Extension,
At least one end of the one pipe and the end of the one pipe on the upstream side and the downstream side in the vicinity of the end of the other pipe and the one flange member and the other flange member, joint structure of a pipe projecting downwardly of the end of the other pipe, characterized in that the side opposite to the surface of said flange member is provided with a bent portion of concave side surfaces abutting said flange member.   The plurality of pipes are configured to include a pipe for exhaust gas recirculation, and any one of the plurality of pipes is provided with a cooler for cooling the exhaust gas flowing through the pipe for exhaust gas recirculation. The piping joint structure according to claim 1. The plurality of pipes are made of stainless steel,
The said flange member is formed with steel or iron, The joint structure of piping of Claim 1 or Claim 2 characterized by the above-mentioned.

Images