JP6230098B2 - EGR introduction pipeline - Google Patents

Description

  The present invention relates to an EGR introduction conduit for an internal combustion engine.

  In an internal combustion engine for a vehicle, exhaust gas is recirculated to an intake system in order to improve fuel efficiency. In this case, if the high-temperature exhaust gas is directly recirculated, there is a problem such as a decrease in filling efficiency. Therefore, cooling the EGR gas with an EGR cooler is also widely performed.

  The EGR gas of the EGR device is often taken from the exhaust system via the EGR introduction pipe (or EGR gas introduction pipe), and in Patent Document 1, as one of its piping structure, one end of the EGR introduction pipe is exhausted. It is described that the manifold is connected to the manifold and the other end is connected to the cylinder head. Patent Document 2 describes that one end of the EGR introduction pipe is connected to the tapered end of the catalyst case, and the like. Fixing the end to the flange of the exhaust manifold is disclosed. In any case, the EGR introduction pipeline is composed of one pipe and is welded to the exhaust system.

Japanese Patent Laid-Open No. 10-122201 JP 2004-278342 A

  Now, the EGR introduction pipe line is exposed to the exhaust gas and becomes high temperature, but the degree of the temperature rise becomes higher as it is closer to the exhaust system. For this reason, the thermal stress generated in the EGR pipe is also likely to be non-uniform. In particular, if an EGR cooler is provided in the EGR introduction pipe, the temperature difference between the start end and the end of the EGR cooler becomes larger, and the temperature difference in the EGR introduction pipe also increases. It can be said that it concentrates on the part near the beginning of the pipeline.

  For this reason, in the configuration in which the EGR introduction pipe line is simply constituted by pipes as in both patent documents, since the thickness is constant and the heat load cannot be concentrated on a specific portion, measures can be taken. There is a problem that the start side portion is easily damaged. Further, since the portion of the exhaust system to which the EGR introduction pipe is connected is a curved surface, there is also a problem that it is troublesome to process the start end of the EGR introduction pipe so as to exactly overlap the exhaust system.

  When providing an EGR cooler in the EGR introduction pipe, it is normal that a part of the EGR introduction pipe is built in the EGR introduction pipe, so that there is a gap between the exhaust system and the EGR cooler. The joint pipe must be interposed, but in this case as well, there are still problems that cannot take effective measures against heat load and troublesome processing, and the burden is further increased because the EGR cooler acts as a load. Become.

  Further, when the catalyst case and the EGR introduction pipe are arranged side by side in a vertically long posture as in Patent Document 2, the EGR introduction pipe is pulled downward by the thermal expansion of the catalyst case, and is restored to its original state by stopping the engine. As a result, the load is repeatedly applied, and thus the load acting on the EGR introduction pipe line is further increased.

  The present invention has been made in view of such a current situation, and intends to provide an EGR introduction pipe having excellent heat resistance without incurring an increase in cost.

The EGR introduction pipeline of the present invention is
“The start end where EGR gas flows is fixed to the exhaust system member, and the end point where the EGR gas is discharged is fixed to the cylinder head or other intake side member, and the EGR cooler is between the start end and the end point. It is the structure which has provided,
A starting end portion fixed to the exhaust system member is formed of a cast product , and a stainless steel main pipe covered with the EGR cooler is connected to the cast product, and at the end of the main pipe, Similarly, a joint pipe made of stainless steel pipe is connected, and the end of the joint pipe is fixed to the cylinder head or other intake side member,
In addition, by making the main pipe and the joint pipe intersect, the main pipe is allowed to move in the axial direction due to its own thermal deformation or thermal deformation of the exhaust system member due to the bending deformation of the joint pipe. Has been
Furthermore, the main pipe and the joint pipe are made of stainless steel pipes that become ductile over time by repeated heating. ''
Is.

As the material of the cast product, it is preferable to use a stainless steel casting in view of rust prevention performance and strength, ease of joining with a stainless steel pipe portion, and the like. The starting end portion made of a cast product may have a single structure or may be composed of a plurality of members. Further, the downstream portion of the cast product may be composed of only one piece, or may have a structure in which a plurality of pieces are connected. It is also possible to provide a flow control valve (EGR valve) on the downstream side of the EGR cooler in the EGR introduction pipe line made of stainless steel pipe .

In the present invention, the start end portion of the cast product of the EGR pipe line functions as a joint to the exhaust system member . However, since the cast product can easily correspond to a complicated shape, it is exactly overlapped with the curved surface of the exhaust system member. In addition to being able to manufacture, it is easy to change the wall thickness according to the degree of stress. Therefore, high sealing performance and strength can be ensured, and the support function of the EGR cooler is excellent. It is also resistant to vibration.

  When the exhaust system member and the EGR cooler are arranged in parallel, the thermal expansion / contraction of the exhaust system member accompanying the operation / stop of the engine repeatedly acts as an external force on the EGR introduction pipe line. Since the starting end of the introduction pipe is a cast product and hardly deforms, the external force accompanying the thermal expansion of the exhaust system member acts exclusively to deform the stainless pipe part. Therefore, it is possible to prevent cracks from being easily generated due to repeated thermal expansion and contraction at the start end portion where the temperature is highest. As a result, deterioration can be suppressed and high reliability can be maintained.

Moreover, as the scan Ten-less pipes, with repeated heating due to the use over time ductility increases material can suppress an improved allowed by the stress itself deformation followability of stainless steel pipes to thermal expansion and contraction of the exhaust system member Therefore, it is possible to increase the reliability by suppressing the influence of the thermal expansion of the exhaust system member , the main pipe itself, and the EGR cooler without cost.

(A) is a front view of an embodiment, (B) is a BB view sectional view of (A) in the state where a stay was displayed. It is a side view. (A) is a plan view, (B) is a partial side view, and (C) is a sectional view taken along line IIIC-IIIC in FIG. FIG. 4 is a separation view of a main part when viewed from the IV-IV viewing direction of FIG. (A) is the principal part front view in the middle of an assembly | attachment process, (B) is the partially broken view seen from the IV-IV view direction of FIG.

  Next, an embodiment of the present invention will be described with reference to the drawings. The present embodiment is applied to a vehicle internal combustion engine. In the following description, the terms “up”, “left”, “right”, “front” and “front” are used to specify the direction, but “up” and “down” are directions of a vertical line, “front” and “down” are directions perpendicular to the crankshaft and It is the longitudinal direction.

(1). Overview The internal combustion engine of the present embodiment includes an engine body having a cylinder block 1 and a cylinder head 2 fixed to the upper surface of the cylinder block 1, and the engine body has a crankshaft (not shown) extending in the longitudinal direction. It is mounted on the vehicle in the sideways orientation. The internal combustion engine of the present embodiment has three cylinders, and three exhaust ports 3 are opened side by side on the front surface 2a of the cylinder head 2 and an exhaust manifold 4 communicating with the exhaust port 3 is fixed. . Although it is not necessary to mention, the intake port is opened on the rear surface of the cylinder head 2 and the intake manifold is fixed.

Since the internal combustion engine has three cylinders, the exhaust manifold 4 has three branch pipes 5 and a collecting pipe 6 communicating with them. The collecting pipe 6 is opened downward, and a catalyst case 7 having a circular cross section is welded thereto. Further, the exhaust manifold 4 includes a flange 8 connected to the inlet portion of each branch pipe 5, and the flange 8 is fixed to the cylinder head 2 with a bolt (not shown). Reference numeral 9 shown in FIG. 1 is a mounting hole through which a bolt is inserted. In FIG. 1, the collecting pipe 6 is shifted to the right side from the left and right intermediate position of the exhaust manifold 4, but may be shifted to the left side or provided in the left and right intermediate part.

  The catalyst case 7 constitutes a part of the exhaust system, and a three-way catalyst is disposed inside the catalyst case 7. Further, the catalyst case 7 has a cylindrical shape in which the upper end portion is formed as a stepped reduced diameter portion 7a and the lower end portion is formed as a lower tapered portion 7b. The joint pipe 10 faces downward to the lower tapered portion 7b. , And a support bracket 11 made of a metal plate is fixed to the joint pipe 10 by welding. An exhaust pipe 12 is connected to the joint pipe 10 from below. The exhaust pipe 12 also constitutes an exhaust system. A sensor mounting seat 13 is provided in the collecting pipe 6 of the exhaust manifold 4.

  The support bracket 11 extends across the joint pipe 10 in a state of being almost horizontal, and is inclined at one end (the left end in FIG. 1) to the side opposite to the catalyst case 7 in a front view and rearward in a side view. The raised portion 11a is bent. The rising portion 11a is fixed to a stay 14 fixed to the cylinder block 1 with a bolt.

  Therefore, the catalyst case 7 is supported by the cylinder block 1 via the support bracket 11 and the stay 14. As a fixing means for the support bracket 11, a nut 16 is screwed into a stud bolt 15 projecting forward from the stay 14, but a headed bolt and a nut may be used, or a bolt may be screwed into the stay 14. .

  The catalyst case 7 is an example of an exhaust system member described in the claims, and an EGR main pipe 18 is built in an outer peripheral surface of the lower taper portion 7b of the catalyst case 7 opposite to the rising portion 11a of the support bracket 11. An EGR cooler 17 is connected via an L-shaped pipe 19 and a boss body 20. The boss body 20, the L-shaped pipe 19 and the EGR main pipe 18 have a circular cross section to form an EGR introduction conduit, and the boss body 20 and the L-shaped pipe 19 serve as a start end portion of the EGR introduction conduit. The boss body 20 constitutes a joint portion at the start of the EGR introduction conduit.

A joint pipe 21 having a circular cross section that is long in the front-rear direction is connected to the upper end of the EGR main pipe 18 in the direction of the cylinder head 2. The joint pipe 21 is connected to the cylinder head 2 via a flange plate 22. It is fixed to the front surface 2a of this with bolts (not shown). Joint pipe 21 is also a part of the EGR inlet conduit, terminating der the termination EGR inlet conduit of the joint tube 21 is, the flange plate 22 constitute the joining portion of the end of the EGR inlet conduit. The flange plate 22 has a shape that is long in the vertical direction, and an upper end portion and a lower end portion are fixed to the cylinder head 2 with bolts (not shown).

  A tip portion of the joint pipe 21 fixed to the flange plate 22 is pressed and held from above by a pressing member 23 fixed to the flange plate 22 by brazing. Although not shown, an EGR passage communicating with the joint pipe 21 is formed at the right end portion of the cylinder head 2, and exhaust gas flowing into the EGR passage is passed to the intake system via an EGR valve (not shown). Reflux.

(2). Overall configuration of EGR device related elements As described above, the EGR cooler 17 and the EGR main pipe 18 are located to the right of the catalyst case 7 in the state of FIG. In the side view, the posture is slightly tilted backward. As shown in FIG. 3, the attachment position with respect to the catalyst case 7 is located in front of a line X passing through the axis of the catalyst case 7 and parallel to the front surface 2 a of the cylinder head 2. That is, it is joined to a position slightly ahead of the portion directly beside the catalyst case 7.

  The exhaust manifold 4 and the catalyst case 7 are covered from the front side by an insulator (not shown). Therefore, attachment pieces 25 for fixing the insulator are fixed by welding to two locations at the upper end of the exhaust manifold 4, one location on the catalyst case 7, and two locations on the rear surface of the EGR cooler 17. The right end of the insulator extends toward the space between the catalyst case 7 and the EGR cooler 17.

  The EGR main pipe 18 is built in the EGR cooler 17. Therefore, formally, the EGR main pipe 18 has an appearance like a part of the EGR cooler 17. As shown in FIG. 3C, the EGR main pipe 18 has a shape in which a fin-shaped pipe 18a having a cross-sectional petal shape is covered with a sheath pipe 18b, and a space between the sheath pipe 18b and the EGR cooler 17 is formed. Cooling water passes through.

  The EGR cooler 17 is a water-cooling system, and for example, as shown in FIG. 1, a cooling water introduction pipe 26 and a cooling water discharge pipe 27 are connected to the EGR cooler 17. In the present embodiment, the cooling water introduction pipe 26 is connected to the rear surface of the lower end portion of the EGR cooler 17, and the cooling water discharge pipe 27 is connected to the front surface of the upper end portion of the EGR cooler 17. The inflow / outflow of the cooling water may be reversed, and the mounting positions of the pipes 26 and 17 in the circumferential direction with respect to the EGR cooler 17 can be changed without changing the height of the pipes 26 and 27. (For example, both are turned sideways.)

  A soft material tube (hose) 28 is fitted from the outside to the distal ends of the cooling water introduction pipe 26 and the cooling water discharge pipe 27. Since the cooling water introduction pipe 26 is long, the fixing piece 29 is fixed to the upward inclined portion 26 a on the tip side by welding or brazing, and the fixing piece 29 is fixed to the rising portion 11 a of the support bracket 11 with the bolt 30. ing. As shown in FIG. 2, the base portion of the cooling water introduction pipe 26 is supported from below by a suspension bracket 31 fixed to the EGR cooler 17 by welding.

(3). L-shaped pipe and boss body As clearly shown in FIG. 4, the L-shaped pipe 19 includes a horizontal portion 19 a connected to the boss body 20 by welding and an upright portion (vertical portion connected to the EGR main pipe 18. ) 19b. The horizontal portion 19b has a straight shape, and its end portion enters the boss body 20.

  Since the boss body 20 overlaps the lower taper portion 7b of the catalyst case 7, the tip of the boss body 20 is an inclined surface that is cut obliquely in front view. Therefore, when viewed from the side, the flange portion 20a is not a perfect circle but an ellipse. Further, the end surface of the flange 20 a is gently curved so as to exactly overlap the curved surface of the outer periphery of the tapered portion 7 b in the catalyst case 7.

  The standing portion 19b of the L-shaped pipe 19 is provided with a small-diameter fitting portion 19c connected to the EGR main pipe 18. As described above, the EGR main pipe 18 surrounds the fin tube 18a with the sheath tube 18b. The sheath pipe 18 b of the EGR main pipe 18 has a larger diameter than the fitting part 19 c of the L-shaped pipe 19.

  Therefore, connection end portions 18b 'are formed by narrowing at the upper and lower ends of the sheath pipe 18b in the EGR main pipe 18, and the fitting portion 19c of the L-shaped pipe 19 is inserted into the lower connection end portion 18b'. It is fixed. Brazing is performed seamlessly over the entire circumference. The upper connection end 18 b ′ of the upper end of the sheath pipe 18 b is also brazed to the joint pipe 21.

  For the EGR cooler 17, the EGR main pipe 18 (18a, 18b), and the joint pipe 21, for example, a stainless steel pipe such as a pipe made of SUS304 in JIS is used. On the other hand, the boss body 20 and the L-shaped pipe 19 constituting the upstream portion of the EGR introduction pipe line are castings (stainless steel castings) made of stainless steel such as SUS430 in JIS.

Although not shown, L-shaped pipe 19 and the boss 20 is manufactured using a sand mold having a mold outer obtained by superimposing and between them a pinching retained core type, as a standard method of casting, hot water The end of the road is a large volume gate . The trace of the gate is generally excised, but the gate mark 41 is left as it is in this embodiment. The pouring gate 41 of the boss body 20 is located on the lower surface, and the pouring gate 41 of the L-shaped pipe 19 is arranged on the outer surface of the upstanding portion 19b opposite to the catalyst case 7.

  The entire circumference of the boss body 20 is welded to the catalyst case 7, and the entire circumference of the horizontal portion 19 a of the L-shaped pipe 19 is also welded to the boss body 20. The standing part 19b of the L-shaped pipe 19 and the lower connection end part 18b 'of the EGR main pipe 18 are joined by brazing. Of course, you may weld. As a processing procedure, the L-shaped pipe 19 is first brazed to the lower connection end 18 b ′ of the EGR main pipe 18, while the boss body 20 is first welded to the catalyst case 7. Is attached to the boss body 20 so that the EGR cooler 17 of the catalyst case 7 is attached.

(4) Advantages / Others of Embodiment Now, the catalyst case 7, the EGR cooler 17, and the EGR main pipe 18 are long in the vertical direction, and thus thermally expand in the vertical direction. In this case, if the three are thermally expanded at the same rate, distortion due to the thermal expansion can be suppressed. However, since the catalyst case 7 has the highest temperature, the amount of thermal expansion of the catalyst case 7 is the largest. The EGR main pipe 18 and the EGR cooler 17 tend to be pulled downward due to thermal expansion.

  On the other hand, the joint pipe 21 that connects the EGR cooler 17 (EGR main pipe 18) and the cylinder head 2 extends in a horizontal posture and is bent in a plan view, and has a structure that bends greatly in the vertical direction. . For this reason, downward movement of the EGR cooler 17 and the EGR main pipe 18 is allowed by bending deformation of the joint pipe 21.

  The coefficient of thermal expansion has a specific value depending on the individual material, but the ease of deformation due to thermal expansion depends on the ductility of the material. In this regard, SUS304 constituting the EGR main pipe 18, EGR cooler 17, and joint pipe 21 has a property that the structure becomes dense and ductility increases when thermal expansion and thermal contraction are repeated by repeated heating and natural cooling. While using the internal combustion engine, the deformation followability of the joint pipe 21 against the pulling of the EGR cooler 18 accompanying the thermal expansion of the catalyst case 7 is improved, and the stress itself can be reduced over time. Thereby, the malfunction that strain (stress) concentrates on a specific part and fractures can be prevented.

  The present invention can be embodied in various ways other than the above-described embodiment. For example, the joining target of the EGR introduction pipe line of the present invention is not necessarily a catalyst case, and can be connected to a simple exhaust pipe or an exhaust manifold. It is also possible to connect to an exhaust turbocharger.

  The present invention can be actually embodied in an internal combustion engine. Therefore, it can be used industrially.

2 Cylinder head 4 Exhaust manifold 7 Catalyst case as an example of exhaust system member 7a Lower taper portion of catalyst case 17 EGR cooler 18 EGR main pipe constituting EGR introduction pipe 19 Cast product constituting start end of EGR introduction pipe joint tube constituting the boss portion 21 EGR inlet pipe as casting that constitutes the starting end of the L-shaped pipe 20 EGR inlet pipe as

Claims (1)

The starting end where the EGR gas flows is fixed to the exhaust system member, and the end where the EGR gas is discharged is fixed to the cylinder head or other intake side member. An EGR cooler is installed between the starting end and the end. It is the composition which is provided,
A starting end portion fixed to the exhaust system member is formed of a cast product , and a stainless steel main pipe covered with the EGR cooler is connected to the cast product, and at the end of the main pipe, Similarly, a joint pipe made of stainless steel pipe is connected, and the end of the joint pipe is fixed to the cylinder head or other intake side member,
In addition, by making the main pipe and the joint pipe intersect, the main pipe is allowed to move in the axial direction due to its own thermal deformation or thermal deformation of the exhaust system member due to the bending deformation of the joint pipe. Has been
Furthermore, the main pipe and the joint pipe are composed of stainless steel pipes that become ductile over time by repeated heating.
EGR introduction pipeline.

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