JP2017180484A - Connection structure for exhaust gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection structure having a superior sealing characteristic for an exhaust gas recirculation device including a connecting part for connecting a pipe forming EGR passage.SOLUTION: This invention relates to a connecting structure for an exhaust gas recirculation device 1 including a first connecting part 30 and a second connecting part 40 for connecting pipes oppositely faced to each other to form an EGR passage at the EGR passage 3 communicating an exhaust passage with an intake passage of an internal combustion engine and an annular gasket 50 arranged between the first connecting part and the second connecting part. At least the first connecting part of the first connecting part and the second connecting part has an annular groove part 35 and a thermal expansion member 33 inserted into the groove part and expandable to an opening side of the groove part. The gasket has a first seal part 53 forming a protruded shape facing to the opposing surfaces of the first connecting part and the second connecting part while being oppositely faced against the thermal expansion member.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a connection structure for an exhaust gas recirculation device, and more particularly to a connection structure for an exhaust gas recirculation device having a connection portion for connecting a pipe forming an EGR passage and a gasket disposed in the connection portion.

  Conventionally, an exhaust passage (exhaust manifold) and an intake passage (intake manifold) are connected by an EGR passage (EGR pipe), and a part of exhaust gas is returned to the intake passage and mixed with combustion air (fresh air). Therefore, exhaust gas recirculation devices that control the combustion temperature and reduce pump loss and improve the thermal efficiency of the internal combustion engine have been widely put into practical use.

  In general, in an exhaust gas recirculation device, a gasket is interposed between the first and second connecting parts such as a flange to maintain the sealing performance against EGR gas when connecting the exhaust passage and the EGR passage to each other. Thus, leakage of EGR gas is prevented (for example, Patent Document 1).

JP 2005-083366 A

  In the exhaust gas recirculation device having the above-described connection structure, the temperature becomes low during cold start, but after the engine is driven, the exhaust gas recirculation device is exposed to high-temperature EGR gas in accordance with the change of the operation region from low rotation and low load to high rotation and high load. And the temperature frequently fluctuates greatly. By repeating such temperature fluctuations, so-called sag occurs in the gasket, and the repulsive force of the gasket decreases. If hot EGR gas flows through the EGR passage in a state where the gasket has sag, the required sealing performance cannot be maintained, and there is a concern that the EGR gas leaks.

  The present invention has been made in view of the above problems, and in the connection structure of the exhaust gas recirculation apparatus provided with a connection portion for connecting a pipe forming the EGR passage, the exhaust gas recirculation having excellent sealing performance at the connection portion. It is an object of the present invention to provide a connecting structure for an apparatus.

  In order to achieve the above object, the exhaust gas recirculation device connecting structure according to claim 1 is a piping that forms the EGR passage so as to face each other in an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine. In the connection structure of the exhaust gas recirculation device, the first connection portion and the second connection portion for connecting the first connection portion and the second connection portion, and the annular gasket disposed between the first connection portion and the second connection portion. And at least the first connecting portion has an annular groove portion and a thermal expansion member that is inserted into the groove portion and can be thermally expanded toward the opening side of the groove portion, And a first seal portion that is convex toward the opposing surfaces of the first connecting portion and the second connecting portion, facing the thermal expansion member.

  According to this configuration, when the high-temperature EGR gas flows through the EGR passage, the thermal expansion member inserted into the groove portion thermally expands toward the opening side of the groove portion and presses the first seal portion of the gasket. The sealing performance between the thermal expansion member and the first seal portion is improved. Thereby, even if it is a case where the repulsive force of a gasket falls, the sealing performance in a connection part can be kept favorable.

  According to a second aspect of the present invention, there is provided the exhaust gas recirculation device connecting structure according to the first aspect, wherein the gasket is located on the inner side or the outer side in the radial direction with respect to the first seal portion. A second seal portion having an annular shape projecting toward an opposing surface of the connecting portion and the second connecting portion, and the second seal portion is formed in a non-arranged region of the groove portion; And contacting each of the opposing surfaces of the second connecting part.

  According to this structure, between the 1st and 2nd connection parts can be sealed by the 2nd seal part with the 1st seal part, and sealability improves.

  The invention according to claim 3 is the exhaust gas recirculation device connection structure according to claim 1 or 2, wherein the thermal expansion member is made of a bimetal that protrudes toward the seal portion by thermal expansion. And

  According to this configuration, the thermal expansion member can be thermally expanded in a predetermined direction (that is, the opening side of the groove portion that is a direction in contact with the first seal portion) with a simple configuration.

According to a fourth aspect of the present invention, in the connecting structure for an exhaust gas recirculation device according to any one of the first to third aspects, the first connecting portion is provided in a cylinder head of an internal combustion engine, A 2nd connection part is provided in piping located in the upstream of an EGR cooler, It is characterized by the above-mentioned.
According to this configuration, excellent sealing performance can be achieved at the connecting portion with the cylinder head exposed to high temperature.

  According to the connection structure of the exhaust gas recirculation device according to the present invention, when high-temperature EGR gas flows in the connection portion that connects the pipes that form the EGR passage, the sealing performance can be improved. Are better.

It is a figure explaining the outline | summary of the connection structure of the exhaust gas recirculation apparatus which is 1st Embodiment of this invention, (a) is a front view which shows the state which attached the EGR cooler to the cylinder head, (b) is (a). The b arrow line view used as a side view. FIG. 2 is a schematic cross-sectional view taken along a line AA in FIG. 1A, which is a portion surrounded by II in FIG. Sectional drawing which follows the III-III line | wire of FIG. FIG. 4 is a schematic enlarged view of the IV part in FIG. 2, (a) shows a state at a low temperature, and (b) shows a state at a high temperature. The figure similar to FIG. 2 which shows the connection structure of the exhaust gas recirculation apparatus which is 2nd Embodiment of this invention. FIG. 6 is a schematic enlarged view of a VI part in FIG. 5, (a) shows a state at a low temperature, and (b) shows a state at a high temperature. The figure similar to FIG. 2 which shows the connection structure of the exhaust gas recirculation apparatus which is 3rd Embodiment of this invention.

(First embodiment)
FIG. 1 is a diagram for explaining an outline of a connection structure of an exhaust gas recirculation device 1 according to the first embodiment of the present invention. The exhaust gas recirculation device 1 is attached to a cylinder head 2 in an internal combustion engine (engine), and includes an EGR pipe 10, an EGR cooler 20, and an EGR valve 25.

  The cylinder head 2 constitutes an engine body, and has an attachment boss (first connection portion) 30 serving as a connection portion for attaching the exhaust gas recirculation device 1. The mounting boss 30 protrudes from the outer peripheral surface of the cylinder head 2 and has an exhaust gas branch passage 31 branched from the exhaust port of the cylinder head 2 inside.

  The exhaust gas branch passage 31 extends from the exhaust port to a flat top surface serving as a mounting surface (a surface facing the other connecting portion) 32 of the mounting boss 30, and constitutes a part of the EGR passage 3. A screw hole is formed in the mounting surface 32 of the mounting boss 30.

  The EGR pipe 10 connects the cylinder head 2 and the EGR cooler 20 to form an EGR passage 3 through which EGR gas flows. A flange (second connecting portion) 40 that is a connecting portion with the cylinder head 2 is integrally provided at the upstream end of the EGR pipe 10. Bolt holes are formed in the flange 40, and the flange 40 and the mounting boss 30 of the cylinder head 2 are connected by fastening the fastening bolts 12 with the gasket 50 interposed therebetween (see FIG. 2).

  The EGR cooler 20 includes a cooling unit 22, an inlet-side cap 23 positioned on the upstream side of the cooling unit 22, and an outlet-side cap 24 positioned on the downstream side of the cooling unit 22. In the present embodiment, the upstream end of the inlet side cap 23 is integrally connected to the downstream end of the EGR pipe 10 by welding or the like, and the airtightness between these is maintained.

  The inlet-side cap 23 is a cylindrical body whose inner diameter and outer diameter increase from the upstream side toward the downstream side so that the cross-sectional area increases toward the cooling unit 22. The outlet side cap 24 is a cylindrical body whose inner diameter and outer diameter are reduced from the upstream side toward the downstream side so that the cross-sectional area decreases from the cooling unit 22 side toward the discharge port side. At the downstream end of the outlet-side cap 24, a flange 21 serving as a connecting portion with the EGR valve is provided.

  The cooling unit 22 includes a cooling water passage and a plurality of EGR gas passages therein. The EGR gas passage extends from the upstream side to the downstream side, and the cooling water passage surrounds the periphery of the EGR gas passage. The cooling water channel is a water channel through which the engine cooling water branched from the engine cooling water circulation channel flows, and distributes the engine cooling water along the outer periphery of the EGR gas passage. When the engine cooling water passes through the cooling water passage, heat exchange is performed between the EGR gas flowing through the EGR gas passage and the engine cooling water. The engine coolant after the heat exchange is returned to the engine coolant circulation path from a coolant outlet (not shown) of the cooling unit 22.

  The EGR valve 25 includes a valve main body 26, a flange 27, and a mounting bracket 28. The valve body 26 has a valve body for controlling the flow rate of EGR gas and the like inside, and a discharge port 26 a for discharging EGR gas whose flow rate is controlled is provided on the downstream side of the valve body 26. A motor unit 29 that drives the valve body is installed above the valve body 26. The discharge port 26a is connected to an intake manifold which is an intake system of the engine via an EGR pipe or the like (not shown). The flange 27 of the EGR valve 25 and the flange 21 of the EGR cooler 20 are connected by fastening of fastening bolts with a gasket 60 interposed therebetween. The mounting bracket 28 is a connecting member for fixing the valve body 25 to the cylinder head 2, and is attached to the mounting boss 4 of the cylinder head 2 using a fastening bolt 61.

  Next, in the exhaust gas recirculation device 1 described above, a connection structure of piping constituting the EGR passage 3 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of a portion surrounded by II in FIG. 1B, and is a schematic cross-sectional view along the line AA in FIG. Note that the arrows in FIG. 2 indicate the flow direction of EGR gas flowing through the EGR passage 3.

  As described above, the cylinder head 2 is provided with the mounting boss (first connection portion) 30 that is a connection portion with the EGR pipe 10 of the exhaust gas recirculation device 1. Further, the EGR pipe 10 is provided with a flange (second connecting portion) 40 that is opposed to the top surface serving as the mounting surface 32 of the mounting boss 30 and serves as a connecting portion with the cylinder head 2. A gasket 50 is disposed between the mounting boss 30 and the flange 40 to maintain airtightness between them.

  The mounting boss 30 has a groove 35 on the surface facing the flange 40. As shown in FIG. 3, the groove portion 35 is formed in an annular shape surrounding the EGR passage 3, and in the present embodiment, is formed in an annular shape having a substantially rectangular cross section. A thermal expansion member 33 is inserted into the groove portion 35.

  The flange 40 has a groove 45 on the surface facing the mounting boss 30. The groove portion 45 is formed at a position facing the groove portion 35 of the mounting boss 30 in a connected state with the mounting boss 30. The groove portion 45 is formed in an annular shape surrounding the EGR passage 3, and in the present embodiment, is formed in an annular shape having a substantially square cross section, like the groove portion 35 of the mounting boss 30. A thermal expansion member 33 is inserted into the groove 45.

  As shown in FIG. 3, each of the thermal expansion members 33 and 43 is formed in an annular shape that can be inserted into each of the groove portions 35 and 45. The thermal expansion members 33 and 43 are volume-expanded by being heated to a predetermined temperature or higher, and press the gasket 50 disposed on the opening side of the groove portions 35 and 45. As such thermal expansion members 33 and 43, for example, in a state of being inserted into the groove portions 35 and 45, the heat expansion members 33 and 43 are unidirectional so as to protrude toward the gasket 50 side by being heated to a predetermined temperature or higher. A bimetal that thermally expands intensively can be used.

  The thermal expansion members 33 and 43 are preferably set so as to protrude from the openings of the groove portions 35 and 45 by heating at a predetermined temperature or higher (see FIG. 4B). In the present embodiment, the expansion members 33 and 43 are set to be substantially flush with the mounting surface 32 of the mounting boss 30 and the mounting surface 42 of the flange 40 at a low temperature that is lower than a predetermined temperature. ing. Further, in the present embodiment, the thermal expansion member 33 on the mounting boss 30 side and the thermal expansion member 43 on the flange 40 side are formed in substantially the same shape by the same metal material, and have the same thermal expansion coefficient. Is set.

  The gasket 50 is substantially plate-shaped, and has an annular shape in which an opening serving as the EGR passage 3 is formed in the center in a plan view. In this embodiment, a metal gasket formed of a metal material is used as the gasket 50. ing. The gasket 50 is formed with a convex and annular seal portion (first seal portion) 53 protruding from both plate-like surfaces. The seal portion 53 is formed at a position corresponding to the groove portion 35 of the mounting boss 30 and the groove portion 45 of the flange 40. In a state where the gasket 50 is mounted, the seal portion 53 faces the thermal expansion members 33 and 43 inserted into the respective groove portions 35 and 45 and is in contact with each other.

  In the exhaust gas recirculation device 1 described above, hot EGR gas is introduced into the EGR passage 3 from the exhaust port of the cylinder head 2 when the engine is driven. Hereinafter, a seal structure between the mounting boss 30 through which the high-temperature EGR gas flows and the flange 40 will be described with reference to FIG. FIG. 4 is a schematic enlarged view of the IV part of FIG. 2, in which (a) shows a state at a low temperature, and (b) shows a state at a high temperature.

  When the engine temperature is low, such as immediately after the engine is started, that is, when the temperature of the thermal expansion members 33 and 43 is lower than a predetermined temperature for thermal expansion, the seal portion 53 of the gasket 50 comes into contact with the thermal expansion member 33 of the mounting boss 30. A repulsive force is generated by contact with the thermal expansion member 43 of the flange 40. Thereby, the sealing performance of the EGR passage 3 can be ensured.

  On the other hand, when the engine is driven at a high temperature, that is, when the temperature of the thermal expansion members 33 and 43 is equal to or higher than a predetermined temperature for thermal expansion, the thermal expansion inserted into the grooves 35 and 45 in the mounting boss 30 and the flange 40 is performed. The members 33 and 43 expand in volume so as to protrude toward the opening side of the groove portions 35 and 45, respectively. Thereby, the thermal expansion members 33 and 43 will be in the state which pressed the seal part 53 of the gasket 50 rather than the time of low temperature, and a sealing performance will improve.

  As described above, in the connection structure of this embodiment, the thermal expansion members 33 and 43 are thermally expanded by the high-temperature EGR gas, whereby the sealing performance between the mounting boss 30 and the flange 40 is improved. Thereby, even if it is a case where the repulsive force of the gasket 50 falls by repeating a temperature fluctuation | variation, at the time of distribution | circulation of EGR gas, a sealing performance can be ensured and leakage of EGR gas can be prevented.

  Note that, in the exhaust gas recirculation device 1, on the downstream side of the EGR cooler 20, the high-temperature EGR gas is cooled by exchanging heat with the engine coolant. Therefore, the downstream side of the EGR cooler 20 is kept at a relatively low temperature even when the engine is driven, and the sag of the gasket 29 due to temperature fluctuations hardly occurs, and the sealing performance between the flanges 26 and 31 connected to each other is maintained. can do.

  In this embodiment, the connection structure using the thermal expansion members 33 and 43 is used only on the upstream side of the EGR cooler 20, but a similar connection structure may be used on the downstream side of the EGR cooler 20. . In this case, on the downstream side of the EGR cooler 20, it is preferable to configure the connection structure using a thermal expansion member whose predetermined temperature for thermal expansion is lower than that of the upstream side.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a view similar to FIG. 2 showing the connection structure of the exhaust gas recirculation apparatus according to the second embodiment of the present invention, and FIG. 6 is a schematic enlarged view of the VI part of FIG. ) Shows a state at a low temperature, and (b) shows a state at a high temperature. In FIGS. 5 and 6, parts corresponding to those in the first embodiment are denoted by the same reference numerals. In the second embodiment described below, detailed description of the same configuration as that of the first embodiment is omitted.

  In the present embodiment, the gasket 50 includes a first seal portion 53 provided at a position corresponding to the groove portions 35 and 45, and a second seal portion 54 located on the radially outer side of the first seal portion 53. The second seal portion 54 is formed in a convex and annular shape protruding from both surfaces of the plate-like gasket 50, and is formed so as to be positioned in a non-arrangement region of the groove portions 35 and 45 when the gasket 50 is mounted. The The second seal portion 54 is in contact with each of the mounting surface 32 of the mounting boss 30 and the mounting surface 42 of the flange 40 at a low temperature and a high temperature, and seals between the mounting boss 30 and the flange 40. .

  As shown in FIG. 6A, the first seal portion 53 is in a non-contact state with the thermal expansion members 33 and 43 at a low temperature. On the other hand, as shown in FIG. , 43 are brought into contact with the thermal expansion members 33, 43 by volume expansion. Such adjustment of the contact state and the non-contact state is performed by appropriately setting the convex height of the first seal portion 53 of the gasket 50, the volume expansion coefficient of the thermal expansion members 33 and 43, and the like. Can do.

  In the connection structure of the present embodiment, when the temperature of the thermal expansion members 33 and 43 is lower than a predetermined temperature at which the thermal expansion members 33 and 43 are below a predetermined temperature, such as when cold, the second seal portion 54 of the gasket 50 is connected to the EGR passage. By contacting the mounting boss 30 and the flange 40 so as to surround 3, sealing performance can be ensured. At this time, the first seal portion 53 is in a non-contact state with the thermal expansion members 33 and 43 arranged to face each other, and is in a non-seal state.

  On the other hand, at the time of high temperature, the thermal expansion members 33 and 43 are thermally expanded, and the first seal portion 53 is in contact with the mounting boss 30 and the thermal expansion members 33 and 43 of the flange 40 so as to surround the EGR passage 3, Become. Further, the gap between the mounting boss 30 and the flange 40 can be sealed by the second seal portion 54 located on the radially outer side of the first seal portion 53.

  As described above, by providing a double seal structure with the first seal portion 53 and the second seal portion 54 at a high temperature, the effect of preventing leakage of EGR gas can be enhanced. In addition, since the sealing can be performed mainly by the first seal portion 53 located radially inside the second seal portion 54 at a high temperature, the second seal portion 54 is prevented from being exposed to the high temperature EGR gas. it can. Thereby, the fall of the repulsive force of the 2nd seal part 54 by the repetition of a temperature fluctuation can be suppressed, and durability of the 2nd seal part 54 can be improved. Furthermore, the load applied to the first seal portion 53 can be reduced because the first seal portion 53 is not in contact with the thermal expansion members 33 and 43 at a low temperature. Thereby, the durability of the first seal portion 53 can be improved.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a view similar to FIG. 2 showing the connection structure of the exhaust gas recirculation apparatus according to the second embodiment of the present invention. In FIG. 7, parts corresponding to those in the first embodiment are denoted by the same reference numerals. In the third embodiment described below, detailed description of the same configuration as that of the first embodiment is omitted.

  In the present embodiment, the gasket 50 includes a first seal portion 53 provided at a position corresponding to the groove portions 35 and 45, and a second seal portion 54 positioned on the radially inner side of the first seal portion 53. The second seal portion 54 is formed in a convex and annular shape protruding from both surfaces of the plate-like gasket 50, and is formed so as to be positioned in a non-arrangement region of the groove portions 35 and 45 when the gasket 50 is mounted. The The second seal portion 54 is in contact with each of the mounting surface 32 of the mounting boss 30 and the mounting surface 42 of the flange 40 at a low temperature and a high temperature, and seals between the mounting boss 30 and the flange 40. .

  The first seal portion 53 is in contact with the thermal expansion members 33 and 43 at a low temperature and a high temperature, and the thermal expansion members 33 and 43 are volume-expanded at a high temperature, so that the thermal expansion member 33 is higher than at a low temperature. , 43 is pressed. (See FIGS. 4A and 4B).

  In the connection structure of the present embodiment, the first seal portion 53 surrounds the EGR passage 3 when the temperature is low, such as when it is cold, that is, when the temperature of the thermal expansion members 33 and 43 is lower than a predetermined temperature for thermal expansion. Thus, the sealing performance can be ensured by contacting the thermal expansion members 33 and 43 of the mounting boss 30 and the flange 40. Further, a double seal structure can be obtained by bringing the second seal portion 54 into contact with the mounting boss 30 and the flange 40 so as to surround the EGR passage 3 on the radially inner side of the first seal portion 53. Further, at the time of high temperature, the double seal structure is maintained, and the thermal expansion members 33 and 43 are thermally expanded, whereby the sealing performance of the first seal portion 53 can be improved.

  As described above, by providing a double seal structure with the first seal portion 53 and the second seal portion 54 at a low temperature and a high temperature, the EGR gas leakage prevention effect can be enhanced. Further, since the sealing can be performed mainly by the second seal portion 54 located radially inside the first seal portion 53 at a high temperature, the exposure of the first seal portion 53 to the high temperature EGR gas is suppressed. it can. Thereby, the fall of the repulsive force of the 1st seal | sticker part 53 by the repetition of a temperature fluctuation can be suppressed, and durability of the 1st seal | sticker part 53 can be improved. Further, at the time of low temperature, the pressing force by the thermal expansion members 33 and 43 becomes smaller than that at the time of high temperature, and the load applied to the first seal portion 53 is reduced, so that the durability of the first seal portion 53 can be improved. .

  The present invention is not limited to the first to third embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, in each of the above-described embodiments, the groove portions 35 and 45 are formed in both the mounting boss 30 and the flange 40 and the thermal expansion members 33 and 43 are inserted. It is good also as a structure which forms a groove part and inserts a thermal expansion member only in any one.

DESCRIPTION OF SYMBOLS 1 Exhaust gas recirculation apparatus 2 Cylinder head 3 EGR passage 10 EGR piping 30 Mounting boss (1st connection part)
33 Thermal expansion member 35 Groove part 40 Flange (2nd connection part)
43 Thermal expansion member 45 Groove 50 Gasket 53 Seal (first seal)
54 Second seal part

Claims (4)

A first connecting portion and a second connecting portion that connect pipes that form the EGR passage so as to face each other in an EGR passage that communicates an exhaust passage and an intake passage of the internal combustion engine;
An exhaust gas recirculation device connection structure comprising: an annular gasket disposed between the first connection portion and the second connection portion;
At least the first connecting portion of the first connecting portion and the second connecting portion includes an annular groove portion and a thermal expansion member that is inserted into the groove portion and can be thermally expanded toward the opening side of the groove portion. ,
The exhaust gas recirculation device connection characterized in that the gasket has a first seal portion that faces the thermal expansion member and is convex toward the opposing surfaces of the first connection portion and the second connection portion. Construction. The gasket has an annular second seal portion that is located on the inner side or the outer side in the radial direction with respect to the first seal portion and has a convex shape toward the opposing surfaces of the first connection portion and the second connection portion. And
2. The exhaust gas recirculation according to claim 1, wherein the second seal part is formed in a non-arranged region of the groove part and contacts each of the opposing surfaces of the first connection part and the second connection part. Device linkage structure.   The exhaust gas recirculation device connection structure according to claim 1, wherein the thermal expansion member is made of a bimetal that protrudes toward the seal portion by thermal expansion.   The said 1st connection part is provided in the cylinder head of an internal combustion engine, and the said 2nd connection part is provided in piping located in the upstream of an EGR cooler, The any one of Claims 1-3 characterized by the above-mentioned. The connection structure of the exhaust gas recirculation apparatus described in 1.

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