JP2005214029A - Exhaust pipe heat exchange structure of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchange structure capable of preventing heat stress from occurring and providing a high exchanging efficiency while suppressing manufacturing cost in the exhaust pipe heat exchange structure of the engine. <P>SOLUTION: This heat exchange structure comprises a cooling water pipe 6 fitted to surround at least a part of the exhaust manifold 2 of the engine 1 and allowing cooling water to flow therein and formed in a flat shape in cross section and an elastic metal body 9 interposed between the exhaust manifold 3 and the cooling water pipe 6, performing heat conduction between there both pipes, and having elasticity in the pipe radial direction of the exhaust manifold 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust pipe heat exchange structure for an engine.

  Conventionally, a structure for exchanging heat between exhaust gas and cooling water on the exhaust side of an engine is known. The exhaust temperature is lowered by heat exchange to improve the durability of the exhaust diameter member and the like. Further, when cold, there is an advantage that exhaust heat can be efficiently recovered by a heat exchange medium such as cooling water, and the oil temperature can be raised by the heat to accelerate engine warm-up.

  As an example of a conventional engine exhaust pipe heat exchange structure, there is an invention described in Patent Document 1. The invention described in Patent Document 1 includes an engine body, an exhaust manifold that extends from the engine body and discharges burned gas in the cylinder to the outside, and a groove is formed on the outer periphery of the exhaust manifold, and the groove is covered. And a plurality of water jackets covered with. Then, cooling water is circulated inside the water jacket. The cover and the exhaust manifold are sealed in a liquid-tight manner by a sealing member. In such a structure, heat is exchanged between the exhaust discharged to the outside through the exhaust manifold and the cooling water circulating around the outer periphery of the exhaust manifold to cool the exhaust temperature and recover the exhaust heat.

Furthermore, there exists invention of patent document 2 as another structure. In the invention described in Patent Document 2, each branch pipe of the exhaust manifold is formed as a double structure including an exhaust passage and a water jacket, and the water jacket is formed as in the invention described in Patent Document 1. No seal member is required.
JP 2002-256868 A JP 2002-364361 A

  However, as in the invention described in Patent Document 1, a structure in which another member is joined to the exhaust manifold via a seal member causes problems such as a decrease in sealing performance and generation of thermal stress. That is, the temperature of the exhaust system changes as the operating state of the engine changes, and each member such as the exhaust manifold repeatedly expands and contracts due to the temperature change. However, the temperature may differ depending on the linear expansion coefficient of each member and the distance from the heat source. As a result, the thermal strain due to the temperature change of the exhaust system is different for each member, and there arises a problem that the sealing performance of the sealing member is deteriorated or a thermal stress is generated at the joint portion of each member.

  On the other hand, since the invention described in Patent Document 2 does not have a structure in which another member is attached to the exhaust manifold via a seal member, there is no problem due to thermal expansion in the seal portion. However, in order to realize such a structure, it is necessary to produce a double-structure exhaust manifold by casting or the like, which increases the manufacturing cost.

  This invention is made | formed in view of this point, The place made into the objective is to provide a heat exchange structure with high heat exchange efficiency, generating a thermal stress, suppressing manufacturing cost. .

  The first invention is directed to an engine exhaust pipe heat exchange structure for exchanging heat between engine coolant and exhaust in an exhaust system of an in-line multi-cylinder engine having a plurality of exhaust ports.

  And a branch exhaust pipe curved downward from an engine connection flange portion fixed to the engine, including a plurality of manifolds communicating with the exhaust port independently and arranged in the cylinder row direction, A cooling manifold having a flat cross-sectional shape, the exhaust manifold comprising a collective exhaust pipe that joins the plurality of manifolds, and a pipe through which the cooling water circulates attached so as to hold at least a part of the exhaust manifold. It is assumed that a water pipe and an elastic metal body interposed between the exhaust manifold and the cooling water pipe to conduct heat between them and have elasticity in the pipe radial direction of the exhaust manifold are provided.

  In the case of the above configuration, the cooling water pipe formed as a separate part is attached so as to hold at least a part of the exhaust manifold. Since the cooling water pipe has a flat shape in the radial direction, the contact area between the cooling water pipe and the exhaust manifold is expanded.

  Further, by interposing an elastic metal body between the cooling water pipe and the exhaust manifold, heat conduction is performed to the cooling water side through the elastic metal body, and heat exchange is performed between the exhaust gas and the cooling water. . These exhaust manifolds, cooling water pipes, and elastic metal bodies thermally expand as the temperature rises, but the difference in linear expansion coefficient due to the difference in the material of each member, the exhaust manifold through which exhaust flows, and the cooling water pipe through which cooling water flows A large temperature difference causes a difference in thermal strain of each member. Here, when the elastic metal body is not interposed, the exhaust manifold and the cooling water pipe are arranged in direct contact with each other. In such a structure, even if both parts are in proper contact when the parts are attached, as described above, as the heat exchange with the exhaust proceeds and the temperature of each part rises, the contact between the exhaust manifold and the cooling water pipe The two parts are constrained by each other, and thermal stress is generated between the parts. Or conversely, there is a part where the distance between the two parts is locally opened and the contact is insufficient.

  Therefore, by adopting a structure in which an elastic metal body is interposed between the cooling water pipe and the exhaust manifold, even if the interval between the cooling water pipe and the exhaust manifold becomes narrow due to a difference in thermal strain between the two parts, The metal body is elastically deformed to absorb the thermal strain of both parts, and thermal stress is not generated in both parts. Also, even if the interval between the cooling water pipe and the exhaust manifold is increased due to the difference in thermal strain between the two parts, the elastic metal body is elastically deformed to cause the cooling water pipe, the elastic metal body, and the elastic metal body to Sufficient contact with the exhaust manifold can be ensured. Thus, by maintaining the contact state between the exhaust manifold and the cooling water pipe via the elastic metal body, a decrease in thermal conductivity is prevented.

  As another heat exchange structure, a heat exchange structure in which a double pipe structure spacer having an exhaust passage and a cooling water passage is interposed between the exhaust manifold and the engine is also conceivable. However, this structure increases the outer dimension of the engine in the engine width direction by the length of the spacer. In contrast, the present invention does not increase the outer dimension in the engine width direction.

  Therefore, according to the first invention, even if the temperatures of the cooling water pipe and the exhaust manifold change, thermal stress is not generated between the two parts, and the heat exchange efficiency is not impaired.

  And unlike the invention of the said patent document 1, since it is set as the structure which attaches a cooling water pipe to the outer periphery of an exhaust manifold, it is not necessary to consider the sealing performance of cooling water.

  Further, since a cooling water pipe as a separate part is attached to the outer periphery of the exhaust manifold, only a cooling water pipe corresponding to the shape of the existing exhaust manifold needs to be newly manufactured, leading to cost reduction.

  Further, the present invention requires fewer protrusions in the engine width direction than the spacer method described above, and there are fewer restrictions on the vehicle.

  According to a second invention, in the first invention, each of the manifolds is a circular pipe, and the cooling water pipe has an arc portion along an arc shape of an upper surface or a lower surface of each manifold near the engine connection flange portion. It has a wave shape that is continuously formed in the cylinder row direction by the number of the manifolds, and has a curved shape that follows the curved portion of the branch exhaust pipe. It is attached so that it can be held.

  In the case of the above configuration, the temperature of the exhaust discharged through the exhaust manifold is higher as it is closer to the engine. Therefore, in the exhaust manifold, the exhaust temperature is highest at a portion immediately downstream of the engine connection flange portion. . And the said cooling water pipe | tube is arrange | positioned in the part where this exhaust gas temperature becomes the highest. Since the amount of heat exchanged by heat transfer or conduction is proportional to the temperature difference between the two points, heat can be efficiently exchanged by arranging a cooling water pipe near the engine connection flange.

  The cooling water pipe is continuously formed in the cylinder row direction over the entire manifold, and has a shape along the outer peripheral arc of the upper surface or the lower surface of each manifold, and has a wave shape when viewed from the side of the engine. ing. Moreover, the cooling water pipe has a curved shape along the curve in the vicinity of the engine connecting flange portion. The cooling water pipe has a flat shape. This shape further increases the contact area with the exhaust manifold. .

  Further, the cooling water pipe is attached to the branch exhaust pipe so as to be held in a restrained relaxation state that is not completely restrained. This "restraint relaxation state" means that the cooling water pipe and the exhaust manifold are not completely restrained and attached by welding, bolt fastening, or the like, but kept attached to the exhaust manifold, It is in a state where it can move relatively. Therefore, in addition to the elastic deformation of the elastic metal body, the thermal expansion of the exhaust manifold can be absorbed by the relative movement of the cooling water pipe with respect to the exhaust manifold.

  Therefore, the efficiency of exhaust cooling can be improved by disposing the cooling water pipe in the vicinity of the engine connection flange having the highest exhaust temperature. At the same time, the heat recovery efficiency is improved. Further, by cooling the exhaust at the upstream portion of the branch exhaust pipe having the highest exhaust temperature, it is possible to prevent the branch exhaust pipe and the exhaust collecting pipe on the downstream side from being exposed to the high-temperature exhaust.

  Further, the contact area between the cooling water pipe and the exhaust manifold is expanded to further improve the exhaust cooling efficiency.

  Furthermore, by attaching the cooling water pipe so as not to be completely restrained but to be held in a restrained relaxation state, in addition to the effect of the first invention, the thermal expansion of the exhaust manifold can be absorbed more flexibly.

  According to a third invention, in the first or second invention, the cooling water pipe includes a first cooling water pipe disposed on an upper surface side of the branch exhaust pipe and a second cooling water pipe disposed on a lower surface side. In addition, the first cooling water pipe and the second cooling water pipe hold the branch exhaust pipe in the vertical direction.

  In the case of the above configuration, cooling water pipes are disposed on both the upper and lower surfaces of the branch exhaust pipe, and heat exchange is performed on both sides.

  Therefore, by disposing the two cooling water pipes, the contact area between the cooling water pipe and the exhaust manifold is expanded, and the heat exchange efficiency is improved.

  In a fourth aspect based on the third aspect, the first cooling water pipe and the second cooling water pipe are connected to each other at one opening end in the cylinder row direction by a connector.

  In the case of the above configuration, the cooling water introduction port and the discharge port can be collectively arranged on the other end side in the cylinder row direction, so that the cooling water channel can be easily arranged up to or from the cooling water tube. It becomes easy. Moreover, the structure which clamps the said branch exhaust pipe is easily realizable by connecting one end side with a connector.

  According to a fifth invention, in the fourth invention, the second cooling water pipe is located inward of the curved portion of the branch exhaust pipe and extends substantially linearly along the cylinder row direction. To do.

  In the case of the above configuration, the cooling water pipe can be easily manufactured because the second cooling water pipe has a substantially linear shape.

  In addition, since the substantially straight second cooling water pipe is located inward of the curved portion of each branch, the curved surface inside the curved portion of the branch and the outer peripheral part of the second cooling water pipe are elastic. The contact is made through the metal body, and the contact area between the branch exhaust pipe and the second cooling water pipe is increased.

  Therefore, the manufacture of the second cooling water pipe is facilitated, and the contact area between the second cooling water pipe and the branch exhaust pipe is increased to improve the heat exchange efficiency.

  According to a sixth invention, in any one of the first to fifth inventions, the elastic metal body is formed of a wire mesh of a heat-resistant metal.

  In the case of the above-described configuration, the cooling water pipe can be attached to the branch exhaust pipe with elasticity easily by using the elastic metal body as a wire mesh. Further, since the wire mesh can be easily processed or deformed, it can be easily mounted between the cooling water pipe and the branch exhaust pipe.

  In a seventh aspect based on the first aspect, the collective exhaust pipe has a cylindrical shape, a catalytic converter is disposed downstream thereof, and the cooling water pipe is an outer peripheral surface of the collective exhaust pipe. It is assumed that it is attached so as to hold the collective exhaust pipe while being wound around.

  In the case of the above configuration, the exhaust temperature is highest in the vicinity of the engine connection flange immediately after exhaust port discharge. However, since the exhaust stroke is intermittently performed for each cylinder, the exhaust manifold temperature is the highest on average. It is the collective exhaust pipe in which exhaust from each cylinder always collects that becomes high temperature. Therefore, in the seventh invention, heat exchange is performed at a portion where the temperature becomes the highest on average. Furthermore, the contact area between the cooling water pipe and the collecting exhaust pipe is increased by attaching the cooling water pipe so as to hold the entire circumference of the cylindrical collecting exhaust pipe.

  A catalytic converter is disposed downstream of the collective exhaust pipe. Since the collective exhaust pipe is cooled, the downstream catalytic converter is also cooled through the pipe wall. Furthermore, the temperature of the exhaust gas sent to the catalytic converter is also lowered. For this reason, the temperature rise of the catalytic converter can be suppressed.

  Therefore, by disposing the cooling water pipe in the collective exhaust pipe having the highest temperature on average in the exhaust manifold, the exhaust can be cooled with high heat exchange efficiency and the heat recovery efficiency can be increased. At the same time, the temperature of the catalytic converter is suppressed and the life of the catalyst is improved.

  The collective exhaust pipe is a double pipe composed of an outer cylindrical body and an inner cylindrical body, and the inner cylindrical body is expanded and deformed into a barrel shape as the exhaust temperature rises so as to come into contact with the outer cylindrical body. It may be.

  As a result, in the cold state, an air layer is interposed between the cooling water pipe and the exhaust gas, so that the heat exchange efficiency is low. It is used to make it. On the other hand, during the warm time, the inner cylindrical body becomes a barrel shape due to thermal expansion and comes into contact with the outer cylindrical body, so that the heat exchange efficiency between the cooling water and the exhaust is increased, and the temperature rise of the catalytic converter is suppressed. Life shortening can be prevented.

  According to an eighth invention, in any one of the first to seventh inventions, the cooling water pipe is formed by hydroforming.

  In the case of said structure, formation of the said cooling water pipe becomes easy. In particular, it is effective in forming a cooling water pipe having a flat shape or a complicated shape such as a three-dimensional shape, and the cooling water pipe can be formed in a desired shape without clogging the inside of the pipe at the time of formation.

  According to the exhaust pipe heat exchange structure of the present invention, since an elastic metal body is interposed between the exhaust manifold and the cooling water pipe, even if the exhaust manifold and the cooling water pipe cause thermal strain due to temperature change, Since the elastic metal body absorbs the thermal strain, the generation of thermal stress between the two parts can be prevented, and the heat exchange efficiency is lowered because the elastic metal body ensures the contact state between the two parts. This can be prevented.

  Further, since a cooling water pipe as a separate part is attached to the outer periphery of the exhaust manifold, it is only necessary to newly manufacture a cooling water pipe corresponding to the shape of the existing exhaust manifold, leading to cost reduction.

  Furthermore, since the cooling water pipe is attached to the outer periphery of the exhaust manifold, it is not necessary to consider the sealing property of the cooling water.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
FIG. 1 is a plan view of an exhaust manifold according to Embodiment 1 of the present invention attached to one side of an engine. 1 is an in-line four-cylinder engine in which four cylinders 11, 11,... Are arranged in series at a predetermined interval, and 2 is an exhaust manifold attached to one side of the engine 1. Here, in the following description, for convenience of explanation, in FIGS. 1, 2, 7 and 8, the right side of the figure is the engine front side and the left side is the engine rear side.

  The engine 1 is formed with four exhaust ports 12, 12,... That open from one of the four cylinders 11, 11,... To one side surface. Discharged. The exhaust port 12 is formed at a predetermined interval like the cylinders 11, 11,.

  As shown in FIGS. 1 to 3, the exhaust manifold 2 is branched by four upstream exhaust manifolds 31, 31,... Communicating with the exhaust ports 12, 12,. The exhaust pipe 3 and the downstream exhaust pipe 4 where the exhaust manifolds 31, 31,. Further, as shown in FIG. 1, the exhaust manifold 2 is attached to one side of the engine 1 by the engine connection flange portion 5.

  The engine connection flange portion 5 is formed integrally with the exhaust manifolds 31, 31,... At the upstream end portion of the exhaust manifold 2. Then, bolts are fastened to one side of the engine 1. Further, as shown in FIG. 4, the opening 32 of each exhaust manifold is formed on the joint surface of the engine connecting flange portion 5 with the engine. When the exhaust manifold 2 is attached to the engine 1, the openings 32 of the exhaust manifolds 31, 31,... Communicate with the exhaust ports 12 of the engine 1.

  As shown in FIG. 3, the exhaust manifolds 31, 31,... Are projected downward after projecting outward from the engine connection flange portion 5 to one side of the engine 1. On the other hand, as shown in FIG. 2, when viewed from the side of the engine, the upstream end is parallel to the cylinder row direction at the same interval as the exhaust ports 12, 12,. The intervals between the manifolds 31 are narrowed, and the exhaust manifolds 31 are gathered at the downstream end. Each exhaust manifold 31 has a substantially circular cross section.

  The collective exhaust pipe 4 is a common pipe in which exhaust manifolds 31, 31,... Are gathered as shown in FIGS. A catalytic converter or a muffler (not shown) is disposed downstream of the collective exhaust pipe 4.

  The exhaust is very hot, and if the exhaust manifold 2 continues to be exposed to high temperature exhaust, its durability will be adversely affected.

  Therefore, as shown in FIGS. 1 to 3, a cooling water pipe 6 including a first cooling water pipe 7 and a second cooling water pipe 8 is disposed in the vicinity of the engine connection flange portion 5 of the branch exhaust pipe 3.

  The first cooling water pipe 7 includes a main body portion 71 and connecting portions 72 a and 72 a located at both ends of the main body portion 71. The first cooling water pipe 7 is disposed on the upper part of the branch exhaust pipe 3 in the vicinity of the engine connection flange portion 5. The exhaust manifolds 31, 31,... In the vicinity of the engine connection flange portion 5 are portions curved downward. As shown in FIGS. 1 and 2, the main body 71 has a wave shape in which four arc portions 71 a along the outer peripheral arc of the upper surface of each exhaust manifold 31 are continuously formed in the cylinder row direction. . Further, as shown in FIG. 3, in the engine front view, each arc portion 71 a is curved along the shape of the corresponding exhaust manifold 31 in the tube axis direction, and the main body portion 71 has a flat cross section. It has a shape. The connecting portions 72a and 72a are formed so as to protrude from both end portions of the main body 71 in the longitudinal direction of the main body (cylinder row direction).

  The second cooling water pipe 8 includes a main body part 81 and connection parts 82 a and 82 a located at both ends of the main body part 81. The said 2nd cooling water pipe 8 is arrange | positioned under the curved part of the branch exhaust pipe 3 of the said engine connection flange part 5 vicinity, as shown in FIGS. The main body 81 has a substantially linear shape extending in the cylinder row direction. The main body 81 bulges 81 a, 81 a bulges toward the exhaust manifold 31 at a side position of the exhaust manifold 31 so as to partially surround the sides of the exhaust manifolds 31. ,…have. A portion of the main body 81 located below each exhaust manifold 31 has a flat shape in the radial direction, and the contact area with each exhaust manifold 31 is increased.

  The first cooling water pipe 7 and the second cooling water pipe 8 have a complicated shape as described above. In particular, the first cooling water pipe 7 is curved downward when viewed from the front of the engine, is wave-shaped in the direction of the cylinder row when viewed from the side of the engine, and is hollow inside so that cooling water flows therethrough. Yes. Such a tubular material is easily clogged and difficult to manufacture. Therefore, the main body portions 71 and 81 of the first cooling water pipe 7 and the second cooling water pipe 8 are formed by hydroforming. And after forming the main-body parts 71 and 81, the connection parts 72a and 72a and 82a and 82a are joined to the both ends by means, such as welding, respectively. By forming such a hydroform, even the above-described flat and three-dimensionally complex pipe can be formed without clogging.

  Further, as shown in FIG. 2, the first cooling water pipe 7 and the second cooling water pipe 8 are formed by extrapolating the U-shaped connecting pipe 6a to the respective connection portions 72a and 82a on one end side in the cylinder row direction. Are connected in series. On the other hand, on the other end side in the cylinder row direction, the outlet pipe 63a is extrapolated to the connection part 72a of the first cooling water pipe 7, and the introduction pipe 62a is extrapolated to the connection part 82a of the second cooling water pipe 8. The first cooling water pipe 7 and the second cooling water pipe 8 are attached to the exhaust manifold 2 so as to sandwich the branch exhaust pipe 3.

  By connecting one end side with the U-shaped connecting pipe 6a, the first cooling water pipe 7 and the second cooling water pipe 8 are sandwiched and can be easily attached to the branch exhaust pipe 3. Furthermore, an error in the shape of the part or an attachment error can be absorbed by the U-shaped portion of the U-shaped connecting pipe 6a. In addition, since the cooling water inlet and outlet are gathered at the other end, which is one side of the first cooling water pipe 7 and the cooling water pipe 8, the cooling water hose and the like can be easily arranged.

  At this time, the first cooling water pipe 7 and the second cooling water pipe 8 are not directly attached to the branch exhaust pipe 3, but are attached via a heat-resistant metal wire mesh 9 as an elastic metal body. Accordingly, the first cooling water pipe 7 and the second cooling water pipe 8 and the branch exhaust pipe 3 are substantially in contact with each other via the wire mesh 9, and the wire mesh 9 is elastically deformed. Contact area is increased. Further, the first cooling water pipe 7 and the second cooling water pipe 8 are not completely restrained by the structure sandwiched via the wire mesh 9, and are attached to the branch exhaust pipe 3 in a restrained relaxation state. . That is, since the cooling water pipe 6 is not completely restrained, the cooling water pipe 6 can move relatively in a range where the branch exhaust pipe 3 is sandwiched.

  In the case of the above configuration, as shown in FIG. 2, cooling water is introduced into the second cooling water pipe 8 from the introduction pipe 62a in the direction of the arrow. Then, the cooling water flows into the first cooling water pipe 7 through the U-shaped connecting pipe 6a, and is led out from the outlet pipe 63a in the direction of the arrow. In this way, heat exchange is performed with the exhaust gas while the cooling water flows through the cooling water pipe 6. That is, the exhaust heat of the exhaust flowing through the exhaust manifold 2 is obtained from the pipe wall of each exhaust manifold 31, the wire mesh 9, the pipe wall of the first cooling water pipe 7, the pipe wall of the second cooling water pipe 8, and the cooling water pipe. Heat transfer or heat conduction is carried out in the order of the cooling water flowing through the inside.

  The temperature of the exhaust gas flowing through the exhaust manifold 2 is the highest in the vicinity of the engine connection flange portion 5 to which the cooling water pipe 6 is attached. Therefore, the cooling water pipe 6 is disposed in the vicinity of the engine connection flange portion 5 having the highest exhaust temperature, and cooling the exhaust in this portion has very good heat exchange efficiency, and high exhaust cooling efficiency and exhaust heat recovery. Efficiency can be realized. Further, if cooling is performed on the upstream side of the exhaust, it is advantageous for the exhaust pipe on the downstream side in terms of thermal environment.

  The first cooling water pipe 7 has an arc portion 71a along the outer circumferential direction while being curved along the pipe axis direction of each exhaust manifold 31. By adopting a shape corresponding to each exhaust manifold 31 in this way, the first cooling water pipe 7 can increase the substantial contact area with each exhaust manifold 31.

  Further, the second cooling water pipe 8 has a substantially straight shape, but has bulging portions 81a, 81a,... Projecting toward the exhaust manifold 31 so as to partially surround each exhaust manifold 31 from the side. Have. With this shape, the second cooling water pipe 8 can increase the substantial contact area with each exhaust manifold 31.

  Furthermore, the shape of the portion of the first cooling water pipe 7 or the second cooling water pipe 8 that contacts the exhaust manifold 31 is completely the shape of the contact portion of the exhaust manifold 31 due to, for example, manufacturing error or thermal strain. Even if the wire mesh 9 does not match, the wire mesh 9 that is elastically deformed is in contact with the cooling water pipe 6. It can be placed in contact with the exhaust manifold 31.

  Further, in the heat exchange, when the temperatures of the exhaust manifolds 31 and the cooling water pipe 6 are increased, the respective components are thermally expanded. At this time, the wire mesh 9 is interposed between the exhaust manifold 31 and the cooling water pipe 6, and the thermal expansion of both parts can be absorbed within the elastic range of the wire mesh 9. Here, assuming that the cooling water pipe 6 and each exhaust manifold 31 are in direct contact with each other without the wire mesh 9 interposed therebetween, the cooling water pipe 6 and each exhaust manifold 31 that should be thermally expanded are The contact surfaces are constrained to each other, and thermal stress is generated, which adversely affects the durability of the exhaust manifold 2.

  Therefore, by interposing the wire mesh 9, the wire mesh 9 elastically deforms and absorbs the thermal strain of each component described above, and as a result, thermal stress is generated in the branch exhaust pipe 3, the cooling water pipe 6, and the like. There is nothing to do.

  The wire mesh 9 does not only absorb thermal strain. Even if the distance between the branch exhaust pipe 3 and the cooling water pipe 6 is locally expanded due to thermal strain, the contact state between each exhaust manifold 31 and the cooling water pipe 6 can be maintained by interposing the wire mesh 9. The exhaust heat conduction efficiency is not impaired.

  Further, the cooling water pipe 6 is supported so as to sandwich the branch exhaust pipe 3 via a wire mesh 9. Therefore, the cooling water pipe 6 is not completely restrained and can relatively move within the range where the branch exhaust pipe 3 is sandwiched. That is, even within this movable range, heat strain can be absorbed and heat conduction efficiency can be maintained. And the structure attached in the state clamped can be implement | achieved easily by connecting the said 1st cooling water pipe 7 and the 2nd cooling water pipe 8 by the U-shaped connection pipe 6a.

  The wire mesh 9 may be an elastic metal body having elasticity. However, the wire mesh 9 is easy to process or deform, so that it is easy to attach and has moderate elasticity.

  In addition, the above configuration has a structure in which a separate cooling water pipe 6 is attached to the outer periphery of the exhaust manifold 2. For this reason, only the cooling water pipe 6 corresponding to the shape of the existing exhaust manifold 2 may be newly manufactured, which leads to cost reduction.

<< Embodiment 2 of the Invention >>
5 and 6 show an exhaust manifold according to Embodiment 2 of the present invention. The second embodiment is different from the first embodiment in that the cooling water pipe 6 is disposed in the collective exhaust pipe 4 of the exhaust manifold 2. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 5 and 6, the exhaust manifold 2 has a shape corresponding to an in-line four-cylinder engine. The first exhaust manifold 31a, the second exhaust manifold 31b, A third exhaust manifold 31c and a fourth exhaust manifold 31d are arranged in parallel in the cylinder row direction. These exhaust manifolds 31a, 31b,... Constitute the branch exhaust pipe 3.

  The exhaust manifolds 31a, 31b,... Become the first merge pipe 4a where the first exhaust manifold 31a and the fourth exhaust manifold 31d merge at the downstream end thereof, and the second exhaust manifold 31b and the second exhaust manifold 31b. It becomes the 2nd merge pipe 4b where 3 exhaust manifold 31c merges. The first joining pipe 4a and the second joining pipe 4b constitute a cylindrical collective exhaust pipe 4. The downstream end of the collective exhaust pipe 4 communicates with the catalytic converter 10.

  The exhaust manifold 2 according to the second embodiment is a so-called 4-2-1 exhaust manifold. The exhaust manifold 2 which is this 4-2-1 exhaust manifold is effective for preventing exhaust interference. In the case of a four-cylinder engine, the exhaust gas from the first and second exhaust manifolds 31a and 31b and the third and fourth exhaust manifolds 31c and 31d is likely to collide with each other. , 31d and the second and third exhaust manifolds 31b, 31c are merged first.

  The exhaust manifolds 31a, 31b,... Are intermittently exhausted, and the exhaust gas always flows through the collective exhaust pipe 4. Therefore, the exhaust gas having the highest temperature is circulated in the exhaust manifolds 31a, 31b,... In the vicinity of the engine connection flange portion 5, but the temperature of the exhaust pipe is on average the highest in the collective exhaust pipe 4. It is. Therefore, cooling the exhaust with the collective exhaust pipe 4 having the highest average exhaust pipe temperature has very good heat exchange efficiency.

  Therefore, in the second embodiment, the cooling water pipe 6 is disposed in the collective exhaust pipe 4. As shown in FIG. 6, the cooling water pipe 6 includes a main body 61 that is flat in the radial direction and formed by hydroforming, and connecting portions 64 and 64 connected to both ends. The cooling water pipe 6 is attached so as to be held so as to surround the entire circumference of the collective exhaust pipe 4. At this time, the wire mesh 9 is interposed between the cooling water pipe 6 and the collective exhaust pipe.

  Further, a lead-out pipe 63c is extrapolated to the upstream side (upper side in FIG. 6) of the collective exhaust pipe 4, and an introduction pipe 62c is extrapolated to the downstream side (lower side of FIG. 6). Yes. Then, the cooling water flows from the introduction pipe 62c, flows through the cooling water pipe 6, and flows out from the outlet pipe 63c. At this time, heat is exchanged with the exhaust, and the exhaust and the collective exhaust pipe 4 are cooled.

  The catalytic converter 10 is a device that purifies exhaust gas. The catalytic converter 10 is a component that needs to be raised to an appropriate temperature at an early stage in order to activate the function of the catalyst, and whose life is shortened when exposed to high temperatures. By disposing the cooling water pipe 6 on the upstream side of the catalytic converter 10, the life of the catalytic converter 10 is prevented from being shortened.

  In order to activate the catalyst at an early stage, the exhaust collecting pipe 4 has a double barrel structure. Specifically, a coaxial inner peripheral pipe 41 is inserted inside the exhaust collecting pipe 4. The inner peripheral pipe 41 includes a main body 41a, an upstream end 41b, and a downstream end 41c. As shown in FIG. 6, the main body 41a has a barrel shape in which the tube diameter at the center in the longitudinal direction is increased. For ease of understanding, FIG. 6 exaggerates the barrel shape, but the outer peripheral diameter of the central portion is smaller than the inner peripheral diameter of the exhaust collecting pipe 4 and is expanded at low temperatures. The inner peripheral pipe 41 and the exhaust collecting pipe 4 are not in contact with each other even in the longitudinal center. The upstream end 41b continuously expands from the main body 41a, and its outer diameter is the same as the inner diameter of the exhaust collecting pipe 4. Then, it is loosely fitted in a mounting groove 42 provided inside the exhaust collecting pipe 4 so as to contact the inner wall of the exhaust collecting pipe 4. On the other hand, the downstream end portion 41 c is folded outward with a curvature, and the outermost periphery thereof is in contact with the inner wall of the exhaust collecting pipe 4. The downstream end 41c is in contact with the support 10a located at the upstream end of the catalytic converter 10 when the exhaust collecting pipe 4 is attached to the catalytic converter 10, and the inner peripheral pipe 41 is The tube is simply supported from the downstream side in the longitudinal direction of the tube.

  In addition, a partition wall 43 that separates the first joining pipe 4 a and the second joining pipe 4 b is disposed in the inner peripheral pipe 41 so as to pass through the central axis of the inner peripheral pipe 41. As a result, the exhaust gas can be guided to just before the catalytic converter 10 without causing exhaust interference.

  The exhaust collecting pipe 4 and the catalytic converter 10 are fixed by fastening the flange portions 44 and 101 with bolts or the like.

  If the collective exhaust pipe 4 has the above-mentioned double barrel structure, the exhaust gas flows through the inner peripheral pipe 41 and does not contact the wall of the collective exhaust pipe 4. And since the said inner peripheral pipe 41 is not high temperature at the time of cold, such as immediately after an engine start, the said collective exhaust pipe 4 and the main-body part 41a of the inner peripheral pipe 41 have a state with a space | interval. . On the other hand, at the time of high speed operation or the like, the inner peripheral pipe 41 becomes high temperature and thermally expands. At this time, since the upstream end 41b of the inner peripheral pipe 41 is loosely fitted in the mounting groove 42 of the exhaust collecting pipe 4, and the downstream end 41c is simply supported by the support 10a of the catalytic converter 10, The peripheral tube 41 cannot expand in the longitudinal direction. Here, the central portion of the body portion 41a of the inner peripheral tube 41 has a barrel shape that is expanded outwardly, and the tube wall of the inner peripheral tube 41 that cannot expand in the longitudinal direction is outward on the periphery of the central portion. The shape is easy to expand. For this reason, the periphery of the central portion of the main body portion 41a further expands outward due to thermal expansion, and comes into contact with the inner wall of the collective exhaust pipe 4. And as the temperature of the inner peripheral pipe 41 rises, its contact area increases.

  This means that the heat exchange efficiency between the cooling water pipe 6 and the exhaust gas is low during the cold state and increases as the temperature increases. That is, in the cold state, the heat of the exhaust gas flowing through the inner peripheral pipe 41 is the tube wall of the inner peripheral pipe 41, the air layer between the inner peripheral pipe 41 and the collective exhaust pipe 4, and the collective exhaust pipe. Heat transfer or heat conduction is performed in the order of the pipe wall 4, the wire mesh 9, the pipe wall of the cooling water pipe 6, and the cooling water flowing through the inside of the cooling water pipe 6. On the other hand, when the main body portion 41a of the inner peripheral pipe 41 is in contact with the collective exhaust pipe 4 when warm, the above-described heat transfer / conduction path is formed between the inner peripheral pipe 41 and the collective exhaust pipe 4. Heat is directly conducted from the tube wall of the inner peripheral pipe 41 to the tube wall of the collective exhaust pipe 4 without passing through an air layer therebetween. By not interposing the air layer, the heat exchange efficiency is dramatically improved.

  Therefore, the heat exchange efficiency can be suppressed during cold and exhaust heat can be used for early activation of the catalytic converter 10, and the heat exchange efficiency can be increased during warm to suppress the temperature rise of the catalytic converter 10 and prevent the life from being shortened. .

  In the second embodiment, the cooling water pipe 6 has a flat shape in the radial direction, and is attached so as to hold the cooling water pipe 6 over the entire circumference of the collective exhaust pipe 4, so that the contact area is large. , Improving heat exchange efficiency.

  In addition, the wire mesh 9 increases the substantial contact area between the collective exhaust pipe 4 and the cooling water pipe 6 as in the first embodiment, and absorbs the thermal strain between the two parts to both parts. No thermal stress is generated, and further, the thermal contact efficiency is not impaired without changing the substantial contact state between the two parts even after thermal expansion.

<< Other Embodiments >>
The present invention may be configured as follows with respect to the above embodiment. That is, in the first embodiment, the main body portions 71 and 81 of the first cooling water pipe 7 and the second cooling water pipe 8 are formed by hydroforming, and the connection portions 72a and 82a are coupled to both ends thereof by welding or the like. However, as shown in FIGS. 7 to 9, the connecting portions 72 b and 82 b may be hydroformed integrally with the main body portions 71 and 81, respectively. In the case of such a configuration, the U-shaped connecting pipe 6b, the introducing pipe 62b, and the outlet pipe 63b have large diameters in accordance with the outer diameters of the connecting portions 72b and 82b. In the present embodiment, since the radius of curvature of the U-shaped connecting pipe 6b decreases as the diameter increases, the rigidity of the U-shaped connecting pipe 6b increases, and the mounting accuracy improves. Other effects are the same as those of the first embodiment.

  Further, in order to improve the mounting accuracy, a connector 6c having a U-shaped path inside may be employed as shown in FIG. In such a configuration, since it is not a U-shaped tube shape such as 6a and 6b, the effect of absorbing attachment errors and the like is lost, but the rigidity of the connector 6c is high, and the attachment accuracy is further improved.

  In the first embodiment, the introduction pipe 62a is attached to the second cooling water pipe 8, and the outlet pipe 63a is attached to the first cooling water pipe 7. However, as shown in FIGS. The flow of the cooling water may be reversed by attaching the pipe 62b to the first cooling water pipe 7 and the outlet pipe 63b to the second cooling water pipe 8.

  In the first embodiment, the first cooling water pipe 7 and the second cooling water pipe 8 are connected in series by the U-shaped connecting pipe 6a. However, the first cooling water pipe is not connected by the U-shaped connecting pipe 6a. It is good also as a structure which distribute | circulates a cooling water in parallel with 7 and the 2nd cooling water pipe 8. FIG. Alternatively, a structure in which any one of the first cooling water pipe 7 and the second cooling water pipe 8 is disposed may be employed.

It is a top view which shows the exhaust pipe heat exchange structure of the engine which concerns on Embodiment 1 of this invention. It is a front view which shows the exhaust manifold which concerns on Embodiment 1 of this invention. It is a side view which shows the exhaust manifold which concerns on Embodiment 1 of this invention. FIG. 3 is a cross-sectional explanatory view taken along line AA in FIG. 2. It is a top view which shows the exhaust pipe heat exchange structure of the engine which concerns on Embodiment 2 of this invention. It is a front partially cutaway sectional view showing an exhaust manifold according to Embodiment 2 of the present invention. It is a top view which shows the exhaust pipe heat exchange structure of the engine which concerns on other embodiment of this invention. It is a front view which shows the exhaust manifold which concerns on other embodiment of this invention. It is a side view which shows the exhaust manifold which concerns on other embodiment of this invention. It is a front view which shows the connector of the cooling water pipe which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 11 Cylinder 12 Exhaust port 2 Exhaust manifold 3 Branch exhaust pipe 31 Exhaust manifold 4 Collective exhaust pipe 5 Engine connection flange part 6 Cooling water pipe 6a U-shaped connection pipe (connector)
6b U-shaped connecting pipe (connector)
7 1st cooling water pipe 71a Arc part 72a Connection part (opening edge part)
8 2nd cooling water pipe 82a connection part (opening edge part)
9 Wire mesh (elastic metal body)
10 Catalytic converter

Claims (8)

An exhaust pipe heat exchange structure for an engine that performs heat exchange between engine coolant and exhaust in an exhaust system of an in-line multi-cylinder engine having a plurality of exhaust ports,
A branch exhaust pipe that includes a plurality of manifolds that communicate with the exhaust port independently and are aligned in the cylinder row direction, curved downward from an engine connection flange fixed to the engine, and the plurality of pipes on the downstream side An exhaust manifold composed of a collective exhaust pipe that joins
A pipe through which the cooling water is attached so as to hold at least a part of the exhaust manifold, and a cooling water pipe having a flat cross-sectional shape;
An exhaust pipe heat characterized by comprising an elastic metal body interposed between the exhaust manifold and the cooling water pipe to conduct heat between them and having elasticity in the pipe radial direction of the exhaust manifold. Exchange structure. The exhaust pipe heat exchange structure for an engine according to claim 1,
Each of the above branches is a circular tube,
The cooling water pipe has a wave shape in which arc portions along the arc shape of the upper surface or the lower surface of each manifold near the engine connection flange portion are continuously formed in the cylinder row direction by the number of the manifolds, and the branched exhaust pipe An exhaust pipe heat exchange structure characterized in that the exhaust pipe heat exchange structure has a curved shape along the curved portion of the branch exhaust pipe, and is attached so as to hold the vicinity of the engine connection flange portion of the branch exhaust pipe in a restrained relaxation state. The exhaust pipe heat exchange structure for an engine according to claim 1 or 2,
The cooling water pipe includes a first cooling water pipe disposed on the upper surface side of the branch exhaust pipe, and a second cooling water pipe disposed on the lower surface side,
The exhaust pipe heat exchange structure, wherein the first cooling water pipe and the second cooling water pipe sandwich the branch exhaust pipe in the vertical direction. The engine exhaust pipe heat exchange structure according to claim 3,
The exhaust pipe heat exchanging structure, wherein the first cooling water pipe and the second cooling water pipe are connected to each other by a connector at one opening end in the cylinder row direction. The engine exhaust pipe heat exchange structure according to claim 4,
2. The exhaust pipe heat exchange structure according to claim 1, wherein the second cooling water pipe is positioned inward of the curved portion of the branch exhaust pipe and extends substantially linearly along the cylinder row direction. The engine exhaust pipe heat exchange structure according to any one of claims 1 to 5,
The exhaust pipe heat exchange structure according to claim 1, wherein the elastic metal body is made of a heat-resistant metal wire mesh. The exhaust pipe heat exchange structure for an engine according to claim 1,
The collective exhaust pipe has a cylindrical shape, and a catalytic converter is disposed on the downstream side thereof,
The exhaust pipe heat exchanging structure, wherein the cooling water pipe is attached so as to hold the collective exhaust pipe while being wound around the outer peripheral surface of the collective exhaust pipe. The exhaust pipe heat exchange structure for an engine according to any one of claims 1 to 7,
The exhaust pipe heat exchange structure, wherein the cooling water pipe is formed by hydroforming.

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