EGR pipe

Abstract

To enhance a temperature rise effect on the whole circumference to suppress generation of condensate water over the whole circumference of an inner wall, in an EGR pipe configured to provide a hot water passage provided along a length on a part of the whole circumference and heat it with hot water.SOLUTION: A resin-based EGR pipe 18 constitutes an EGR passage through which EGR gas flows. The EGR pipe 18 is formed by joining a first divided pipe material 21 and a second divided pipe material 22, which are divided into two in a radial direction, at joints 21b, 22b. The first divided pipe material 21 is provided with a hot water passage 23 through which hot water flows in order to heat the EGR pipe 18, and a thickness T1 of the second divided pipe material 22 is formed to be thinner than thicknesses T2, T3 of the first divided pipe material 21. The first divided pipe material 21 includes an outer pipe part 21aa and an inner pipe part 21ab, and the hot water passage 23 is formed between the outer pipe part 21aa and the inner pipe part 21ab.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an EGR pipe used in an EGR device of an engine for flowing EGR gas. [Background technology]

[0002] A known example of this type of technology is the "EGR pipe" described in Patent Document 1 below. This technology relates to an EGR pipe that flows a portion of exhaust gas discharged from an engine into an exhaust passage into an intake passage to be recirculated to the engine as EGR gas. This EGR pipe is characterized by the inclusion of a flexible mechanism that displaces radially to absorb axial displacement, with the aim of being flexible and not breaking in response to both axial expansion and pressure fluctuations caused by high-temperature EGR gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-29197 Summary of the Invention [Problem to be solved by the invention]

[0004] In the EGR pipe described in Patent Document 1, there is a risk of condensation of EGR gas on its inner wall. To prevent this, it is possible to heat the EGR pipe with hot water. However, due to issues with mounting the EGR pipe on a vehicle and manufacturing, it is difficult to provide a hot water passage around the entire circumference of the EGR pipe. Therefore, it may be necessary to integrally mold the hot water passage along the longitudinal direction over a range of less than half the circumference, or to insert-mold a metal pipe for the hot water passage over a portion of the half circumference. However, in this case, there is a risk that insufficient heating will occur in the portion of the EGR pipe where the hot water passage is not provided, making it impossible to sufficiently prevent the generation of condensation.

[0005] This disclosed technology has been made in consideration of the above circumstances, and its purpose is to increase the temperature rise effect over the entire circumference of an EGR pipe that is configured to be heated with hot water by providing a hot water passage along the longitudinal direction of part of the circumference, and to improve the effect of suppressing the generation of condensation water on the inner wall. [Means for solving the problem]

[0006] In order to achieve the above object, the technology described in claim 1 is a resin EGR pipe used in an EGR passage that flows a portion of exhaust gas discharged from an engine into an exhaust passage into the engine's intake passage as EGR gas. The EGR pipe is formed by joining a first divided pipe member and a second divided pipe member that are divided into two in the radial direction at a joint, and the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, and the second divided pipe member is formed to be thinner than the first divided pipe member. The first split pipe member includes an outer pipe section and an inner pipe section, and the hot water passage is formed between the outer pipe section and the inner pipe section. The first split pipe member includes a first pipe section having a substantially U-shaped cross section in the circumferential direction perpendicular to its longitudinal direction, and first joint sections formed at both ends of the first pipe section in the circumferential direction. The second split pipe member includes a second pipe section having a substantially U-shaped cross section in the circumferential direction perpendicular to its longitudinal direction, and second joint sections formed at both ends of the second pipe section in the circumferential direction. The first joint section and the second joint section joined to each other are positioned offset from the center of the EGR pipe toward the second split pipe member. The purpose of this is to

[0007] According to the configuration of the above technology, the resin EGR pipe is formed by a first and a second divided pipe material that are divided in two radially and joined at a joint. Here, when hot water is flowed through the hot water passage to heat the EGR pipe, the temperature of the inner wall of the first divided pipe material rises due to heat transfer from the hot water. On the other hand, the second divided pipe material is formed thinner than the first divided pipe material, so its inner wall is more likely to rise in temperature due to the heat of the EGR gas. Therefore, the entire inner wall of the resin EGR pipe is more likely to rise in temperature. In addition, the first divided pipe member including the hot water passage is integrally formed with the outer pipe portion and the inner pipe portion without providing a separate member. Furthermore, by positioning the first and second joint portions joined to each other offset toward the second split pipe material, the second pipe portion of the second split pipe material is shortened in the circumferential direction. Therefore, the wall thickness of the second pipe portion can be reduced by the amount of circumferential shortening, making it easier for the second split pipe material to be heated by the heat of the EGR gas.

[0012] In order to achieve the above object, claims 2 The technology described in A resin EGR pipe used in an EGR passage that directs a portion of exhaust gas discharged from an engine into an exhaust passage into an intake passage of the engine as EGR gas, the EGR pipe being formed by joining a first divided pipe member and a second divided pipe member that are radially divided into two at a joint, the first divided pipe member being provided with a hot water passage through which hot water flows to heat the EGR pipe, and the second divided pipe member being formed thinner than the first divided pipe member; The hot water passage is constituted by a metal pipe provided along the longitudinal direction of the first separate pipe member.

[0013] According to the configuration of the above technology , thSince the hot water passage of the one split pipe member is formed by the metal pipe provided in the first split pipe member, the metal pipe can be molded integrally by insert molding when molding the first split pipe member.

[0014] In order to achieve the above object, claims 3 The technology described in claim 2 In the technology described above, the first split pipe material includes a first pipe section having a substantially U-shaped circumferential cross section perpendicular to its longitudinal direction, and a first joint section formed at both circumferential ends of the first pipe section, and the second split pipe material includes a second pipe section having a substantially U-shaped circumferential cross section perpendicular to its longitudinal direction, and a second joint section formed at both circumferential ends of the second pipe section, and the first joint section and the second joint section joined to each other are positioned offset toward the first split pipe material from the center of the EGR pipe.

[0015] According to the configuration of the above technology, claims 2 In addition to the effect of the technology described in 2. above, the first joint portion and the second joint portion joined to each other are offset toward the first split pipe member, thereby shortening the first pipe portion of the first split pipe member in the circumferential direction. Therefore, the first split pipe member is more likely to be heated by the heat of the hot water flowing through the hot water passage of the metal pipe by the amount of circumferential shortening.

[0016] In order to achieve the above object, claims 4 The technology described in A resin EGR pipe used in an EGR passage that directs a portion of exhaust gas discharged from an engine into an exhaust passage into an intake passage of the engine as EGR gas, the EGR pipe being formed by joining a first divided pipe member and a second divided pipe member that are radially divided into two at a joint, the first divided pipe member being provided with a hot water passage through which hot water flows to heat the EGR pipe, and the second divided pipe member being formed thinner than the first divided pipe member; The joint is composed of a first joint of the first split pipe material and a second joint of the second split pipe material, and the thickness of the second joint and its vicinity is greater than the thickness of other parts of the second split pipe material.

[0017] According to the configuration of the above technology , th The second joint is joined to the first joint, which makes it easier for the first split pipe to transfer heat from the hot water in the hot water passage. Also, because the thickness of the second joint and its vicinity is greater than the thickness of the other parts of the second split pipe, the heat transfer passage area in this area is expanded, making it easier for the heat of the hot water to be transferred to the second pipe section.

[0018] In order to achieve the above object, claims 5 The technology described in A resin EGR pipe used in an EGR passage that directs a portion of exhaust gas discharged from an engine into an exhaust passage into an intake passage of the engine as EGR gas, the EGR pipe being formed by joining a first divided pipe member and a second divided pipe member that are radially divided into two at a joint, the first divided pipe member being provided with a hot water passage through which hot water flows to heat the EGR pipe, and the second divided pipe member being formed thinner than the first divided pipe member; The second separate pipe member is formed so that its thickness increases stepwise or gradually from the upstream side to the downstream side of the second separate pipe member.

[0019] According to the configuration of the above technology 、E The temperature of the GR gas decreases toward the downstream side of the EGR pipe, and the temperature-raising effect of the heat from the EGR gas on the inner wall of the EGR pipe decreases toward the downstream side. Here, the thickness of the second divided pipe member increases in stages or gradually from the upstream side to the downstream side of the second divided pipe member, so the heat transfer passage area of ​​the second divided pipe member increases toward the downstream side, and the amount of heat transferred from the EGR gas increases.

[0020] In order to achieve the above object, claims 6 The technology described in In a resin EGR pipe used in an EGR passage that channels a portion of the exhaust gas discharged from an engine into an exhaust passage into the engine's intake passage as EGR gas, the EGR pipe is formed by joining a first divided pipe member and a second divided pipe member at a joint, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, the second divided pipe member is formed thinner than the first divided pipe member, the first divided pipe member includes an outer pipe portion and an inner pipe portion, and the hot water passage is formed between the outer pipe portion and the inner pipe portion, The inner pipe section has at least one first ridge formed along its longitudinal direction toward the outer pipe section.

[0021] According to the configuration of the above technology , within The side pipe section has a first ridge formed toward the outer pipe section, which increases the heat-receiving area of ​​the inner pipe section from the hot water. The first ridge also separates the hot water passage into two hot water passage sections along its length.

[0022] In order to achieve the above object, claims 7 The technology described in claim 6 In the technique described in the above, at least one second ridge is formed on the exterior pipe section along its longitudinal direction, adjacent to the first ridge, and facing the interior pipe section.

[0023] According to the configuration of the above technology , outside A second ridge is formed adjacent to the first ridge on the side pipe section, pointing toward the inner pipe section, forming a maze between the first ridge and the second ridge, making it difficult for hot water to leak between the two separated hot water passage sections.

[0024] In order to achieve the above object, claims 8 The technology described in claim 7 In the technique described in the above, the first convex ridges have a height in the convex direction greater than that of the second convex ridges.

[0025] According to the configuration of the above technology , 1st Since the height of the first ridge in the convex direction is greater than that of the second ridge, the area of ​​the first ridge that receives heat from the hot water is greater than that of the second ridge.

[0026] In order to achieve the above object, claims 9 The technology described in A resin EGR pipe used in an EGR passage that directs a portion of exhaust gas discharged from an engine into an exhaust passage into an intake passage of the engine as EGR gas, the EGR pipe being formed by joining a first divided pipe member and a second divided pipe member that are radially divided into two at a joint, the first divided pipe member being provided with a hot water passage through which hot water flows to heat the EGR pipe, and the second divided pipe member being formed thinner than the first divided pipe member; The second segment pipe member has a rib formed on at least one of its inner wall and outer wall.

[0027] According to the configuration of the above technology , thin Since ribs are formed on at least one of the inner wall and outer wall of the second separate pipe member, the second separate pipe member is reinforced by the ribs.

[0028] In order to achieve the above object, claims 10 The technology described in A resin EGR pipe used in an EGR passage that directs a portion of exhaust gas discharged from an engine into an exhaust passage into an intake passage of the engine as EGR gas, the EGR pipe being formed by joining a first divided pipe member and a second divided pipe member that are radially divided into two at a joint, the first divided pipe member being provided with a hot water passage through which hot water flows to heat the EGR pipe, and the second divided pipe member being formed thinner than the first divided pipe member; The second separate pipe member is intended to have a thick portion formed in part.

[0029] According to the configuration of the above technology , th Since the two-piece pipe member has a thick-walled portion formed in a part thereof, the second piece of pipe member, which is formed thin, is reinforced by the thick-walled portion.

[0030] In order to achieve the above object, claims 11 The technology described in claim 3 In the technique described in the above, the offset amount of the joint is set to decrease stepwise or gradually from the upstream side to the downstream side of the EGR pipe.

[0031] According to the configuration of the above technology 、EIn the EGR pipe, the EGR gas temperature decreases toward the downstream side, but the hot water temperature in the hot water passage remains almost the same regardless of whether it is upstream or downstream. The offset of the joint toward the first separate pipe member from the center of the EGR pipe decreases from the upstream side toward the downstream side of the EGR pipe. As a result, the first pipe section of the first separate pipe member, where the hot water passage is provided, becomes longer circumferentially toward the downstream side, while the second pipe section of the second separate pipe member, which has a thinner wall, becomes shorter circumferentially toward the downstream side. Therefore, the thermal mass of the second pipe section decreases toward the downstream side as the EGR gas temperature decreases, making it easier for the EGR gas to heat up the second pipe section. Meanwhile, the thermal mass of the first pipe section increases toward the downstream side, making it easier for the hot water heat to be transferred.

[0032] In order to achieve the above object, claims 12 The technology described in In a resin EGR pipe used in an EGR passage that channels a portion of the exhaust gas discharged from an engine into an exhaust passage into the engine's intake passage as EGR gas, the EGR pipe is formed by joining a first divided pipe member and a second divided pipe member at a joint, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, the second divided pipe member is formed thinner than the first divided pipe member, the first divided pipe member includes an outer pipe portion and an inner pipe portion, and the hot water passage is formed between the outer pipe portion and the inner pipe portion, The first split pipe material is formed by DSI molding an outer pipe portion and an inner pipe portion with a hot water passage between them.

[0033] According to the configuration of the above technology , th The one-piece pipe section is formed by DSI molding of an outer pipe section and an inner pipe section sandwiching the hot water passage, which increases the product reliability of the first-piece pipe section having the hot water passage.

[0034] In order to achieve the above object, claims 13 The technology described in In a resin EGR pipe used in an EGR passage that channels a portion of the exhaust gas discharged from an engine into an exhaust passage into the engine's intake passage as EGR gas, the EGR pipe is formed by joining a first divided pipe member and a second divided pipe member at a joint, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, the second divided pipe member is formed thinner than the first divided pipe member, the first divided pipe member includes an outer pipe portion and an inner pipe portion, and the hot water passage is formed between the outer pipe portion and the inner pipe portion, The first split pipe member includes a first pipe section having a substantially U-shaped cross section in the circumferential direction perpendicular to its longitudinal direction, and first joint sections formed in the shape of flanges along the longitudinal direction at both ends of the circumferential direction of the first pipe member, and a hot water passage having a substantially U-shaped cross section is disposed inside the first joint sections, and the second split pipe member includes a second pipe section having a substantially U-shaped cross section in the circumferential direction perpendicular to its longitudinal direction, and first joint sections formed in the shape of flanges along the longitudinal direction at both ends of the circumferential direction of the second pipe member. Condition to formationThe first joint and the second joint are joined by vibration welding in cooperation with a fixing jig and a vibrating jig, the first joint is arranged on the side of the fixing jig and the second joint is arranged on the side of the vibrating jig, the first joint includes a first joint surface joined to the second joint and a first contact surface opposite to the first joint surface with which the fixing jig contacts, and the second joint includes a second joint surface joined to the first joint and a second contact surface opposite to the second joint surface with which the vibrating jig contacts.

[0035] According to the configuration of the above technology , shaking To stabilize the weldability of the first and second joints by dynamic welding, the width of the second joint surface where the vibration jig contacts must be within the width of the second contact surface. This positions the circumferential ends of the second pipe section closer to the center of the second pipe section than the vibration jig. In contrast, to stabilize the weldability by vibration welding, the width of the first joint surface where the fixing jig contacts does not need to be strictly within the width of the first contact surface. The first joint surface may be offset outside the first contact surface. This allows the circumferential ends of the first pipe section to be positioned closer to the first joint. Therefore, if the positions of the inner walls of the circumferential ends of the first pipe section and the second pipe section are aligned, the thickness of the first pipe section can be made larger than the thickness of the second pipe section by the amount that the circumferential ends of the first pipe section are shifted closer to the first joint. This allows the width of the hot water passage to be increased accordingly.

[0036] In order to achieve the above object, claims 14 The technology described in claim 13 In the technique described in the above, the positions of both ends of the substantially U-shaped cross section of the hot water passage are arranged closer to the second separate pipe member than the first contact surface with the fixing jig.

[0037] According to the configuration of the above technology , thThe first joints located at both ends of the approximately U-shaped cross section of the first split pipe member include a first joint surface that joins to the second joint surface of the second split pipe member and a first contact surface that comes into contact with the fixing jig on the opposite side of the first joint surface, and the positions of both ends of the approximately U-shaped cross section of the hot water passage are positioned closer to the second split pipe member than the first contact surface with the fixing jig. Therefore, because the positions of both ends of the cross section of the hot water passage are closer to the second split pipe member than the first contact surface with the fixing jig, the heat of the hot water in the hot water passage is more easily transferred to the second split pipe member. [Effects of the Invention]

[0038] According to the technology described in claim 1, in an EGR pipe made of resin that is configured to be heated with hot water by providing a hot water passage along the longitudinal direction of part of the circumference, the temperature rise effect can be increased over the entire circumference, and the effect of suppressing the generation of condensation water on the inner wall can be improved. Furthermore, a resin EGR pipe including a hot water passage can be formed using only the first and second segment pipe members. Furthermore, for a resin EGR pipe, the temperature rise effect on the inner wall of the second segment pipe member can be further improved, and the effect of suppressing condensation in this area can be further improved.

[0041] Claim 2 According to the technology described in , tree A hot water passage can be provided in a grease EGR pipe with few man-hours.

[0042] Claim 3 According to the technology described in claim 2 In addition to the effects of the technology described above, for a resin EGR pipe, the temperature rise effect on the inner wall of the first separate pipe member 21 can be further enhanced, and the effect of suppressing the generation of condensed water in this portion can be further enhanced.

[0043] Claim 4 According to the technology described in , tree In the case of an EGR pipe made of grease, the temperature rise effect can be increased particularly on the inner wall of the second divided pipe material, and the effect of suppressing the generation of condensed water in this portion can be further increased.

[0044] Claim 5 According to the technology described in 、EEven downstream of the EGR pipe where the temperature of the GR gas is low, the decrease in the temperature-raising effect of the second divided pipe material can be suppressed, and the decrease in the effect of suppressing the generation of condensation water on its inner wall can be suppressed.

[0045] Claim 6 According to the technology described in , warm The increased heat receiving area from the water further increases the temperature rise effect of the inner pipe section. Also, by connecting the two separated hot water passage sections downstream, the hot water passage section can be configured as a U-turn flow path, which eliminates the need for additional piping to return the hot water from the hot water passage.

[0046] Claim 7 According to the technology described in claim 6 In addition to the effect of the technology described above, it is possible to maintain a smooth flow of hot water in the hot water passage configured as a U-turn flow path.

[0047] Claim 8 According to the technology described in claim 7 In addition to the effects of the technology described above, the effect of increasing the temperature of the hot water due to the heat of the inner pipe section can be increased, and heat radiation of the hot water from the outer pipe section can be suppressed.

[0048] Claim 9 According to the technology described in , th The strength of the two-piece pipe material can be improved, and the temperature rise property of the inner wall can be improved.

[0049] Claim 10 According to the technology described in , thin This can reduce the lack of strength of the thick second divided pipe material.

[0050] Claim 11 According to the technology described in claim 3 In addition to the effects of the technology described above, the temperature rise characteristics of the resin EGR pipe as a whole due to hot water and EGR gas can be improved.

[0051] Claim 12 According to the technology described in , treeThis can improve the product reliability of oil EGR pipes.

[0052] Claim 13 According to the technology described in , th By placing one joint of one split pipe material on the side of the fixing jig and the second joint of the second split pipe material on the side of the vibrating jig, the cross-sectional area of ​​the hot water passage can be increased without increasing the outer diameter dimension of the EGR pipe, compared to the case where the two are placed in the opposite direction, thereby improving the temperature rise of the inner wall.

[0053] Claim 14 According to the technology described in claim 13 In addition to the effects of the technology described above, the temperature rise property of the second separate pipe member can be improved by receiving the heat of the hot water in the hot water passage provided in the first separate pipe member. [Brief explanation of the drawings]

[0054] [Figure 1] FIG. 1 is a schematic configuration diagram showing an engine system according to a first embodiment. [Figure 2] FIG. 2 is a side view showing a part of the EGR pipe in the first embodiment. [Figure 3] 3 is a cross-sectional view taken along line AA in FIG. 2 showing the EGR pipe according to the first embodiment. [Figure 4] 3 is a cross-sectional view taken along line BB in FIG. 2 showing the EGR pipe according to the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view equivalent to FIG. 3 showing an EGR pipe according to a second embodiment. [Figure 6] FIG. 10 is a cross-sectional view equivalent to FIG. 3 showing an EGR pipe according to a third embodiment. [Figure 7] FIG. 10 is an enlarged cross-sectional view showing a part of a first split pipe member of an EGR pipe according to a fourth embodiment. [Figure 8] FIG. 11 is an enlarged cross-sectional view showing a part of a first split pipe member of an EGR pipe according to a fifth embodiment. [Figure 9] FIG. 13 is a side view showing a part of an EGR pipe in the sixth embodiment. [Figure 10]FIG. 10 is a cross-sectional view taken along line CC in FIG. 9, showing an EGR pipe according to a sixth embodiment. [Figure 11] FIG. 13 is an exploded cross-sectional view of the EGR pipe for explaining a method for manufacturing the EGR pipe according to the seventh embodiment. [Figure 12] FIG. 13 is an exploded cross-sectional view of the first and second separate pipe members in order to explain a method of joining the first and second separate pipe members together according to the eighth embodiment. [Figure 13] FIG. 13 is a cross-sectional view showing a first separate pipe member and a second separate pipe member joined together to explain a method of joining the two separate pipe members according to the eighth embodiment. [Figure 14] FIG. 13 is a cross-sectional view showing a comparative example to FIG. 12 in the eighth embodiment. [Figure 15] FIG. 14 is a cross-sectional view showing a comparative example to FIG. 13 in the eighth embodiment. [Figure 16] FIG. 13 is a side view showing a part of an EGR pipe in the ninth embodiment. [Figure 17] FIG. 17 is a cross-sectional view taken along line DD in FIG. 16, showing an EGR pipe according to the ninth embodiment. [Figure 18] FIG. 23 is a side view showing a part of an EGR pipe in the tenth embodiment. [Figure 19] FIG. 19 is a cross-sectional view taken along line EE in FIG. 18, showing the EGR pipe according to the tenth embodiment. [Figure 20] FIG. 20 is a cross-sectional view taken along line FF in FIG. 18, showing an EGR pipe according to a tenth embodiment. [Figure 21] FIG. 22 is a cross-sectional view equivalent to FIG. 3 showing an EGR pipe according to the eleventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0055] Hereinafter, several embodiments in which the EGR pipe is embodied in an EGR device for a vehicle engine will be described.

[0056] First Embodiment First, the first embodiment will be described in detail with reference to FIGS.

[0057] [About the engine system] FIG. 1 is a schematic diagram showing a gasoline engine system (hereinafter simply referred to as "engine system") according to this embodiment. The engine system mounted on an automobile includes an engine 1 having multiple cylinders. The engine 1 is a four-cylinder, four-stroke reciprocating engine, and includes well-known components such as pistons and a crankshaft. The engine 1 is provided with an intake passage 2 for introducing intake air into each cylinder, and an exhaust passage 3 for leading exhaust gas from each cylinder of the engine 1.

[0058] An air cleaner 4, a throttle device 5, and an intake manifold 6 are provided in the intake passage 2. The intake manifold 6 forms part of the intake passage 2. An exhaust manifold 7 and a catalyst 8 are provided in the exhaust passage 3, in this order from the upstream side. The catalyst 8 may incorporate, for example, a three-way catalyst to purify the exhaust gas. In addition, a high-pressure loop type exhaust gas recirculation device (EGR device) 11 is provided between the exhaust passage 3 and the intake passage 2.

[0059] The throttle device 5 is disposed in the intake passage 2 upstream of the intake manifold 6, and adjusts the amount of intake air flowing through the intake passage 2 by driving a butterfly throttle valve 5a to open and close with a variable opening in response to accelerator operation by the driver. The intake manifold 6 is mainly made of a resin material, and is disposed in the intake passage 2 immediately upstream of the engine 1. The intake manifold 6 includes one surge tank 6a into which intake air is introduced, and multiple (four) branch pipes 6b branching off from the surge tank 6a to distribute the intake air introduced into the surge tank 6a to each cylinder of the engine 1.

[0060] The engine 1 is provided with a fuel injection device (not shown) for injecting fuel into each cylinder. The fuel injection device is configured to inject fuel supplied from a fuel supply device (not shown) into each cylinder of the engine 1. In each cylinder, a combustible mixture is formed by the fuel injected from the fuel injection device and the intake air introduced from the intake manifold 6.

[0061] The engine 1 is also provided with an ignition device (not shown) corresponding to each cylinder. The ignition device is configured to ignite a combustible air-fuel mixture in each cylinder. The combustible air-fuel mixture in each cylinder explodes and burns when ignited by the ignition device, and the exhaust gas after combustion is discharged from each cylinder to the outside via an exhaust manifold 7 and a catalyst 8. At this time, the pistons (not shown) in each cylinder move up and down, causing the crankshaft (not shown) to rotate, thereby generating power for the engine 1.

[0062] [About the EGR device] The EGR device 11 of this embodiment is configured to cause a portion of the exhaust gas discharged from each cylinder of the engine 1 to flow into the exhaust passage 3 as exhaust gas recirculation gas (EGR gas) into the intake passage 2 and recirculate it to each cylinder of the engine 1. That is, the EGR device 11 includes an exhaust gas recirculation passage (EGR passage) 12 that causes the EGR gas to flow from the exhaust passage 3 to the intake passage 2, an exhaust gas recirculation cooler (EGR cooler) 13 that is provided in the EGR passage 12 and that cools the EGR gas that has flowed into the EGR passage 12, an exhaust gas recirculation valve (EGR valve) 14 that controls (adjusts) the flow rate of the EGR gas flowing through the EGR passage 12, and an exhaust gas recirculation gas distributor (EGR gas distributor) 15 that distributes the EGR gas to each branch pipe 6b of the intake manifold 6 in order to distribute the EGR gas flowing through the EGR passage 12 to each cylinder of the engine 1.

[0063] The EGR passage 12 includes an inlet 12a and an outlet 12b. The inlet 12a is connected to the exhaust passage 3 downstream of the catalyst 8, and the outlet 12b is connected to an EGR gas distributor 15. In addition to an EGR cooler 13 and an EGR valve 14, the EGR passage 12 is also composed of an EGR pipe 17 upstream of the EGR cooler 13 and an EGR pipe 18 made of resin downstream of the EGR valve 14. The EGR gas distributor 15 constitutes the final stage of the EGR passage 12. In the EGR passage 12, the EGR valve 14 is provided downstream of the EGR cooler 13, and the EGR gas distributor 15 is provided downstream of the EGR valve 14.

[0064] The EGR gas distributor 15 is mainly made of a resin material, has an elongated shape overall, and is disposed so that its longitudinal direction crosses the multiple branch pipes 6b of the intake manifold 6. In this embodiment, the EGR gas distributor 15 includes a gas chamber 15a in which introduced EGR gas collects, and multiple (four) gas distribution passages 15b that distribute the EGR gas from the gas chamber 15a to each branch pipe 6b.

[0065] In this EGR device 11, when the EGR valve 14 opens, a portion of the exhaust gas flowing through the exhaust passage 3 flows as EGR gas through the EGR passage 12, is cooled by the EGR cooler 13, has its flow rate controlled by the EGR valve 14, is distributed to each branch pipe 6b of the intake manifold 6 via the EGR gas distributor 15, and is further distributed and recirculated to each cylinder of the engine 1.

[0066] [EGR pipe configuration] Here, there is a risk of condensation occurring on the inner wall of the resin EGR pipe 18 due to the EGR gas flowing in from the EGR valve 14, and to prevent this, the EGR pipe 18 is configured to be heated with hot water. In this embodiment, from the viewpoint of vehicle mountability and ease of manufacture of the EGR pipe 18, a hot water passage 23 is provided along the longitudinal direction of the EGR pipe 18 over an area of ​​less than half of the circumference of the EGR pipe 18, and the EGR pipe 18 is configured to be able to be sufficiently heated even in areas where no hot water passage is provided.

[0067] Fig. 2 shows a side view of a portion of the EGR pipe 18 of this embodiment. Fig. 3 shows a cross-sectional view of the EGR pipe 18 of this embodiment taken along line AA in Fig. 2. Fig. 4 shows a cross-sectional view of the EGR pipe 18 of this embodiment taken along line BB in Fig. 2. As shown in Figs. 2 to 4, the EGR pipe 18 of this embodiment is formed by joining a lower first divided pipe member 21 and an upper second divided pipe member 22, which are divided in two radially, at their joints 21b, 22b.

[0068] As shown in Figures 3 and 4, the first separate pipe material 21 includes a first pipe section 21a having a substantially U-shaped cross section in the circumferential direction perpendicular to the longitudinal direction X (see Figure 2), and flange-shaped first joint sections 21b formed along the longitudinal direction X at both circumferential ends of the first pipe section 21a. A hot water passage 23 having a substantially U-shaped cross section is provided in the pipe section 21a located inside the joint sections 21b. The second separate pipe material includes a second pipe section 22a having a substantially U-shaped cross section in the circumferential direction perpendicular to the longitudinal direction X, and flange-shaped second joint sections 22b formed along the longitudinal direction X at both circumferential ends of the second pipe section 22a.

[0069] Hot water flows through the hot water passage 23 of the first separate pipe member 21 to heat the EGR pipe 18. The hot water passage 23 is arranged along the longitudinal direction X of the first separate pipe member 21. As shown in FIG. 3 , the first separate pipe member 21 includes an exterior pipe portion 21aa and an interior pipe portion 21ab, and the hot water passage 23 is formed between the exterior pipe portion 21aa and the interior pipe portion 21ab. The thickness T1 of the pipe portion 22a of the second separate pipe member 22, which does not include the hot water passage 23, is thinner than the thickness T2 of the exterior pipe portion 21aa and the thickness T3 of the interior pipe portion 21ab of the first separate pipe member 21. That is, the second separate pipe member 22 is thinner than the first separate pipe member 21 to facilitate the temperature rise of its inner wall by the heat of EGR gas. Here, the thickness T2 of the exterior pipe portion 21aa is set larger than the thickness T3 of the interior pipe portion 21ab. The first and second joint portions 21b and 22b, which are joined together, are offset from the center P1 of the EGR pipe 18 toward the second divided pipe member 22. In this embodiment, the first and second joint portions 21b and 22b are joined by vibration welding BW.

[0070] In Fig. 2, the left side of the EGR pipe 18 indicates the upstream side of the EGR gas flow, and the right side indicates the downstream side of the EGR gas flow. As shown in Fig. 3 and Fig. 4, the thickness T1 of the second separate pipe member 22 in this embodiment is formed so that it increases stepwise or gradually from the upstream side to the downstream side of the second separate pipe member 22. That is, the thickness T1 of the second pipe portion 22a of the upstream second separate pipe member 22 shown in Fig. 3 is thin, and as shown in Fig. 4, the thickness T1 of the second pipe portion 22a of the downstream second separate pipe member 22 is thicker than that of the upstream side.

[0071] [About the function and effect of EGR pipes] According to the configuration of the EGR pipe 18 of this embodiment described above, the resin EGR pipe 18 is formed by the first and second separate pipe members 21 and 22, which are radially divided into two and joined at the joints 21b and 22b. Here, when hot water is passed through the hot water passage 23 to heat the EGR pipe 18, the temperature of the inner wall of the first separate pipe member 21 rises due to heat transfer from the hot water. Meanwhile, the second separate pipe member 22 is formed thinner than the first separate pipe member 21, so its inner wall is more likely to rise in temperature due to the heat of the EGR gas. Therefore, the entire inner wall of the EGR pipe 18 is more likely to rise in temperature. Therefore, in a resin EGR pipe 18 configured to have the hot water passage 23 along the longitudinal direction along a portion of its circumference and to be heated by hot water, the temperature rise effect can be enhanced throughout the entire circumference, thereby improving the effectiveness of suppressing condensation on the inner wall.

[0072] According to the configuration of this embodiment, the first split pipe member 21 including the hot water passage 23 is integrally formed by the outer pipe portion 21aa and the inner pipe portion 21ab without providing a separate member. Therefore, the EGR pipe 18 including the hot water passage 23 can be formed only by the first split pipe member 21 and the second split pipe member 22.

[0073] According to the configuration of this embodiment, the first joint portion 21b and the second joint portion 22b, which are joined together, are offset toward the second split pipe member 22, thereby shortening the second pipe portion 22a of the second split pipe member 22 in the circumferential direction. Therefore, the wall thickness of the second pipe portion 22a can be reduced by the shortened circumferential length, making it easier for the second split pipe member 22 to be heated by the heat of the EGR gas. Therefore, for the resin EGR pipe 18, the temperature rise effect on the inner wall of the second split pipe member 22 can be further improved, and the effect of suppressing the generation of condensed water in this portion can be further improved.

[0074] According to the configuration of this embodiment, the second joint portion 22b is joined to the first joint portion 21b, which facilitates the transfer of heat received by the first separate pipe member 21 from the hot water in the hot water passage 23. Furthermore, the thickness of the second joint portion 22b and its vicinity is greater than the thickness of other portions of the second separate pipe member 22, which increases the heat transfer passage area in this portion and facilitates the transfer of heat from the hot water to the second pipe portion 22a. Therefore, for the resin EGR pipe 18, the temperature rise effect on the inner wall of the second separate pipe member 22 can be further enhanced, further improving the effect of suppressing the generation of condensation water in this portion.

[0075] According to the configuration of this embodiment, the temperature of the EGR gas decreases toward the downstream side of the EGR pipe 18, and the temperature-raising effect of the heat of the EGR gas on the inner wall of the EGR pipe 18 decreases toward the downstream side. Here, the thickness of the second separate pipe member 22 increases stepwise or gradually from the upstream side to the downstream side of the second separate pipe member 22, so that the heat transfer passage area of ​​the second separate pipe member 22 increases toward the downstream side, and the amount of heat transferred from the hot water increases. Therefore, even at the downstream side of the EGR pipe 18 where the temperature of the EGR gas is low, the temperature-raising effect of the second separate pipe member 22 can be prevented from decreasing, and the effect of suppressing the generation of condensation water on the inner wall can be prevented from decreasing.

[0076] Second Embodiment Next, the second embodiment will be described in detail with reference to Fig. 5. In the following description, the same components as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted, and differences will be mainly described.

[0077] [EGR pipe configuration] This embodiment differs from the first embodiment in the configuration of the second split pipe member 22. Fig. 5 shows the EGR pipe 18 in a cross-sectional view similar to Fig. 3. As shown in Fig. 5, in the EGR pipe 18 of this embodiment, a thick-walled portion 22aa is partially formed in the second split pipe member 22. That is, in this embodiment, the thick-walled portion 22aa is formed so that the center of the second pipe portion 22a bulges inward and outward and extends along the longitudinal direction X.

[0078] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above provides the following advantages in addition to those of the first embodiment. That is, the thick-walled portions 22aa are formed in parts of the second separate pipe member 22, so that the thin second separate pipe member 22 is reinforced by the thick-walled portions 22aa. This makes it possible to prevent the thin second separate pipe member 22 from being insufficiently strong.

[0079] In this embodiment, the thick portion 22aa of the second pipe portion 22a also functions as a reinforcing rib for the second pipe portion 22a.

[0080] <Third embodiment> Next, a third embodiment will be described in detail with reference to FIG.

[0081] [EGR pipe configuration] This embodiment differs from the first embodiment in the configuration of the first split pipe member 21. Fig. 6 shows the EGR pipe 18 in a cross-sectional view similar to Fig. 3. As shown in Fig. 6, in the EGR pipe 18 of this embodiment, a single first protrusion 21aba is formed in the inner pipe portion 21ab of the first split pipe member 21 along the longitudinal direction X toward the outer pipe portion 21aa. That is, in this embodiment, the center of the inner pipe portion 21ab is formed to protrude outward within the hot water passage 23 and extend along the longitudinal direction X.

[0082] In this embodiment, by forming the first protruding strip 21aba in the center of the hot water passage 23 in this manner, the hot water passage 23 is divided into two parts along the longitudinal direction X, and the two parts of the hot water passage 23 communicate with each other downstream of the EGR pipe 18. In the EGR pipe 18, the hot water passage 23 has a U-turn configuration.

[0083] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above provides the following advantages in addition to those of the first embodiment. Specifically, the first ridge 21aba is formed on the inner pipe portion 21ab toward the outer pipe portion 21aa, increasing the heat-receiving area of ​​the inner pipe portion 21ab from the hot water by the amount of the first ridge 21aba. Furthermore, the hot water passage 23 is separated into two hot water passage portions along the longitudinal direction X by the first ridge 21aba. This increases the heat-receiving area from the hot water, further enhancing the temperature rise effect of the inner pipe portion 21ab. Furthermore, by connecting the two separated hot water passage portions downstream, the hot water passage portion can be configured as a U-turn flow path, eliminating the need for additional piping to return hot water from the hot water passage 23.

[0084] In this embodiment, one first ridge 21aba is formed on the interior pipe portion 21ab, but as a modification, two or more first ridges can be formed in parallel on the interior pipe portion.

[0085] <Fourth embodiment> Next, a fourth embodiment will be described in detail with reference to FIG.

[0086] [EGR pipe configuration] This embodiment differs from the third embodiment in the configuration of the first split pipe member 21. FIG. 7 shows an enlarged cross-sectional view of a portion of the first split pipe member 21 of the EGR pipe 18. As shown in FIG. 7, in the EGR pipe 18 of this embodiment, a single first ridge 21aba is formed in the center of the inner pipe portion 21ab of the first split pipe member 21, extending in the hot water passage 23 along the longitudinal direction X toward the outer pipe portion 21aa. In addition, in this embodiment, two second ridges 21aaa are formed in the center of the outer pipe portion 21aa, extending in the hot water passage 23 along the longitudinal direction and adjacent to the first ridge 21aba, toward the inner pipe portion 21ab, in parallel with each other and sandwiching the first ridge 21aba. That is, in this embodiment, the center of the outer pipe portion 21aa is formed to protrude inward across the first ridge 21aba and extend in the longitudinal direction X. Moreover, in this embodiment, the first ridge 22aba is formed to have a greater height in the convex direction and a greater width than the second ridge 21aaa.

[0087] In this way, the first convex rib 21aba and the second convex rib 21aaa are adjacent to each other in the center of the hot water passage 23 and are arranged in alternating directions, so that a small maze-like gap is formed between the two convex ribs 21aba, 21aaa, which is small enough that the hot water is not blocked, allowing the hot water to flow.

[0088] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above provides the following advantages in addition to those of the third embodiment. Specifically, the outer pipe portion 21aa of the first split pipe member 21 has a second ridge 21aaa formed adjacent to the first ridge 21aba toward the inner pipe portion 21ab. This creates a labyrinth between the first ridge 21aba and the second ridge 21aaa, making it difficult for hot water to leak between the two separated hot water passage portions. This maintains a smooth flow of hot water in the hot water passage 23, which is configured as a U-turn flow path.

[0089] According to the configuration of this embodiment, the first ridges 21aba are taller in the convex direction than the second ridges 21aaa, and therefore the first ridges 21aba have a larger heat-receiving area from the hot water than the second ridges 21aaa, which increases the temperature rise effect of the hot water in the inner pipe portion 21ab and reduces heat radiation from the hot water from the outer pipe portion 21aa.

[0090] Fifth Embodiment Next, the fifth embodiment will be described in detail with reference to FIG.

[0091] [EGR pipe configuration] This embodiment differs from the fourth embodiment in the configuration of the first split pipe member 21. FIG. 8 is an enlarged cross-sectional view of a portion of the first split pipe member 21 of the EGR pipe 18. As shown in FIG. 8, in the EGR pipe 18 of this embodiment, two first ridges 21aba are formed adjacent to each other in the center of the hot water passage 23, sandwiching one second ridge 21aaa. Unlike the fourth embodiment, this embodiment has the first ridge 21aba and the second ridge 21aaa set to have approximately the same height and width in the convex direction. As a result, the maze of gaps between the first ridge 21aba and the second ridge 21aaa is deeper than in the fourth embodiment.

[0092] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above provides the same functions and effects as those of the fifth embodiment. Additionally, in this embodiment, the labyrinth of gaps between the first ridge 21aba and the second ridge 21aaa is deeper than that of the fourth embodiment, making it even more difficult for hot water to leak between the two separated hot water passage sections. In this sense, the hot water flow can be made smoother in the hot water passage 23 configured as a U-turn flow path.

[0093] Sixth Embodiment Next, a sixth embodiment will be described in detail with reference to FIGS.

[0094] [EGR pipe configuration] This embodiment differs from the first embodiment in the configuration of the second split pipe member 22. Fig. 9 shows a side view of a portion of the EGR pipe 18 of this embodiment. Fig. 10 shows a cross-sectional view of the EGR pipe 18 of this embodiment taken along line CC in Fig. 9. As shown in Figs. 9 and 10, in the EGR pipe 18 of this embodiment, a plurality of ribs 22c are formed on the outer wall of the second split pipe member 22. In this embodiment, the ribs 22c are formed along the circumferential direction on the outer wall of the second split pipe member 22, and the plurality of ribs 22c are arranged at equal intervals in the longitudinal direction of the EGR pipe 18.

[0095] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above provides the following advantages in addition to those of the first embodiment. That is, the ribs 22c are formed on the outer wall of the thin second separate pipe member 22, reinforcing the second separate pipe member 22. This improves the strength of the second separate pipe member 22 and also improves the temperature rise property of its inner wall.

[0096] [About modified examples] In this embodiment, ribs 22c are formed only on the outer wall of the second split pipe material 22, but it is also possible to form ribs only on the inner wall of the second split pipe material, or to form ribs on both the outer wall and inner wall of the second split pipe material.

[0097] Seventh Embodiment Next, the seventh embodiment will be described in detail with reference to FIG.

[0098] [EGR pipe configuration] In this embodiment, an example of a manufacturing method for the EGR pipe of each of the above embodiments will be outlined. Fig. 11 shows an exploded cross-sectional view of the EGR pipe 18 to explain the manufacturing method for the EGR pipe 18. As shown in Fig. 11, the first split pipe member 21 constituting the EGR pipe of this embodiment is formed by "DSI molding" an outer pipe portion 21aa and an inner pipe portion 21ab with a hot water passage 23 sandwiched therebetween.

[0099] DSI molding (Die Slide Injection Molding) is a technology developed by The Japan Steel Works, Ltd. for injection molding hollow bodies and laminated structures, and is an injection molding method that can accurately and quickly mold hollow bodies with complex internal structures. The principle is to slide the primary molded part of a half-split hollow body inside a mold, and after the mold is opened, a secondary resin is injected and joined to the joining surface to obtain a hollow body. The molding machine has a mold structure that slides using hydraulic equipment, and it is possible to mold a combination of two types of raw materials.

[0100] That is, the same fixed and movable molds are used for the exterior pipe section 21aa and interior pipe section 21ab shown in FIG. 11. First, in the primary injection process, the hollow exterior pipe section 21aa and interior pipe section 21ab are molded simultaneously. Next, in the die slide process, the mold is opened, and the exterior pipe section 21aa or interior pipe section 21ab, which is the primary molded product, is slid within the mold. Next, in the secondary injection process, secondary resin is injected to join the exterior pipe section 21aa and interior pipe section 21ab shown in FIG. 11 together (B1). After cooling, the mold is opened to obtain the first segmented pipe member 21, which includes the hot water passage 23, exterior pipe section 21aa, interior pipe section 21ab, and first joint section 21b. (Reference: Commentary by Yoshiyama Plastic Industry Co., Ltd.)

[0101] In this embodiment, the joining B2 between the first joint portion 21b of the first separate pipe member 21 and the second joint portion 22b of the second separate pipe member 22 shown in Figure 11 is performed by "vibration welding." Here, vibration welding is performed by sandwiching the first joint portion 21b and the second joint portion 22b between a fixed jig and a vibrating jig and applying vibrations with the vibrating jig. Specific examples of vibration welding will be described later.

[0102] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above provides the following advantages in addition to the advantages of the previous embodiments. That is, the first separate pipe member 21 is formed by DSI molding so that the outer pipe portion 21aa and the inner pipe portion 21ab sandwich the hot water passage 23 therebetween, thereby improving the product reliability of the first separate pipe member 21 having the hot water passage 23. This improves the product reliability of the resin EGR pipe 18.

[0103] Eighth Embodiment Next, the eighth embodiment will be described in detail with reference to FIGS.

[0104] [EGR pipe configuration] In this embodiment, an example of a manufacturing method for the EGR pipe of each of the above embodiments will be described. Fig. 12 shows an exploded cross-sectional view of the first and second separate pipe members 21 and 22 to explain how they are joined. Fig. 13 shows a cross-sectional view of the first and second separate pipe members 21 and 22 joined together to explain how they are joined. As shown in Figs. 12 and 13, the first joint portion 21b of the first separate pipe member 21 and the second joint portion 22b of the second separate pipe member 22 are joined by vibration welding using a lower fixing jig 31 and an upper vibrating jig 32 in cooperation. Here, the first separate pipe member 21 is positioned on the side (lower side) of the fixing jig 31, and the second separate pipe member 22 is positioned on the side (upper side) of the vibrating jig 32.

[0105] 12 and 13, the first separate pipe member 21 includes a first pipe section 21a having a substantially U-shaped cross section in the circumferential direction perpendicular to the longitudinal direction X, and first joint sections 21b formed in a flange shape along the longitudinal direction X at both ends of the circumferential direction of the first pipe section 21a. A hot water passage 23 having a substantially U-shaped cross section is disposed inside the first joint sections 21b. The second separate pipe member 22 includes a second pipe section 22a having a substantially U-shaped cross section in the circumferential direction perpendicular to the longitudinal direction X, and second joint sections 22b formed in a flange shape along the longitudinal direction X at both ends of the circumferential direction of the second pipe section 22a. The first joint section 21b and the second joint section 22b are joined by vibration welding using a fixing jig 31 and a vibrating jig 32 in cooperation with each other. Here, the first joint portion 21b is disposed on the side of the fixing jig 31, and the second joint portion 22b is disposed on the side of the vibration jig 32. The first joint portion 21b includes a first joint surface 21ba that is joined to the second joint portion 22b, and a first contact surface 21bb that comes into contact with the fixing jig 31 on the side opposite the first joint surface 21ba. The second joint portion 22b includes a second joint surface 22ba that is joined to the first joint portion 21b, and a second contact surface 22bb that comes into contact with the vibration jig 32 on the side opposite the second joint surface 22ba. The positions of both ends 23a of the approximately U-shaped cross section of the hot water passage 23 are disposed closer to the second segment pipe member 22 than the first contact surface 21bb with the fixing jig 31.

[0106] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above provides the following advantages in addition to the advantages of the previous embodiments. That is, to stabilize the weldability of the first joint portion 21b and the second joint portion 22b by vibration welding, the width W1 of the second joint surface 22ba with which the vibrating jig 32 contacts must be within the width W2 of the second contact surface 22bb in FIG. 12 . As a result, positions P2 of both circumferential ends of the second pipe portion 22a are positioned closer to the center of the second pipe portion 22a (to the right in FIG. 12 ) than the vibrating jig 32. On the other hand, to stabilize the weldability by vibration welding, the width W3 of the first joint surface 21ba with which the fixing jig 31 contacts does not need to be strictly within the width W4 of the first contact surface 21bb, and the first joint surface 21ba may be shifted outside the first contact surface 21bb. This allows the positions P3 of both circumferential ends of the first pipe section 21a to be positioned closer to the first joint portion 21b. In Fig. 12, the position P3 of the first pipe section 21a is shifted to the left of the position P2 of the second pipe section 22a. Therefore, in Fig. 12, if the positions P4 of the inner walls of both circumferential ends of the first pipe section 21a and the second pipe section 22a are aligned, the thickness T5 of the first pipe section 21a can be made larger than the thickness T6 of the second pipe section 22a by the amount that the positions P3 of both circumferential ends of the first pipe section 21a are shifted closer to the first joint portion 21b, and the width W5 of the hot water passage 23 can be increased accordingly. Therefore, by arranging the first joint 21b of the first split pipe material 21 on the side of the fixing jig 31 and the second joint 22b of the second split pipe material 22 on the side of the vibrating jig 32, the cross-sectional area of ​​the hot water passage 23 can be increased without increasing the outer diameter dimension of the EGR pipe 18, compared to the case of the opposite arrangement, and the temperature rise property of the inner wall can be improved.

[0107] 14 and 15 show comparative examples to the cases shown in Figures 12 and 13. This comparative example is the opposite of the above case, and shows a case where the hot water passage 23 is arranged on the side of the second segment pipe member 22, which vibrates the second joint portion 22b with the vibration jig 32. In this comparative example, it can be seen that, in Figure 14, the width W1 of the second joint surface 22ba, which comes into contact with the vibration jig 32, needs to be within the width W2 of the second contact surface 22bb, and therefore the positions P2 of both circumferential ends of the second pipe portion 22a cannot be arranged closer to the second joint portion 22b, and the thickness of the second pipe portion 22a cannot be increased.

[0108] According to the configuration of this embodiment, the first joint portions 21b located at both ends of the substantially U-shaped cross section of the first split pipe member 21 include a joint surface 21ba that is joined to the second split pipe member 22 and a first contact surface 21bb that is in contact with the fixing jig 31 on the opposite side of the joint surface 21ba. The positions of both ends of the substantially U-shaped cross section of the hot water passage 23 are closer to the second split pipe member 22 than the first contact surface 21bb with the fixing jig 31. Therefore, as shown in FIGS. 12 and 13 , the positions of both ends 23a of the cross section of the hot water passage 23 are closer to the second split pipe member 22 than the first contact surface 21bb with the fixing jig 31. This makes it easier for the heat of the hot water in the hot water passage 23 to be transferred to the second split pipe member 22. This improves the temperature rise of the second split pipe member 22 by receiving the heat of the hot water in the hot water passage 23 provided in the first split pipe member 21.

[0109] Ninth Embodiment Next, the ninth embodiment will be described in detail with reference to FIGS.

[0110] [EGR pipe configuration] This embodiment differs from the above-described embodiments in the configuration of the EGR pipe 18. Fig. 16 shows a side view of a portion of the EGR pipe 18 of this embodiment. Fig. 17 shows a cross-sectional view of the EGR pipe 18 of this embodiment taken along line DD in Fig. 16. As shown in Figs. 16 and 17, the EGR pipe 18 of this embodiment is also formed by joining a lower first divided pipe member 21 and an upper second divided pipe member 22, which are divided in two radial directions, at their joints 21b, 22b.

[0111] As shown in Figures 16 and 17, the first separate pipe member 21 of this embodiment also has a substantially U-shaped cross section perpendicular to its longitudinal direction, and includes flange-shaped first joint portions 21b formed along the longitudinal direction at both widthwise ends of the cross section, and a first pipe portion 21a formed along the longitudinal direction between the joint portions 21b. A metal pipe 36 is provided in the center of the first pipe portion 21a along the longitudinal direction by insert molding. In this embodiment, the hot water passage 23 is formed by the metal pipe 36. The second separate pipe member 22 also has a substantially U-shaped cross section perpendicular to its longitudinal direction, and includes flange-shaped second joint portions 22b formed along the longitudinal direction at both widthwise ends of the cross section, and a second pipe portion 22a formed along the longitudinal direction between the second joint portions 22b.

[0112] As shown in FIG. 17 , in this embodiment, the thickness T1 of the second pipe section 22a of the second split pipe section 22, which does not have the hot water passage 23, is thinner than the thickness T2 of the first pipe section 21a of the first split pipe section 21. The first and second joint sections 21b and 22b are offset toward the first split pipe section 21 relative to the center P1 of the EGR pipe 18. The second pipe section 22a between the second joint sections 22b is thin-walled, but the thickness T4 of the second pipe section 22a at and near the second joint section 22b (the area surrounded by the chain circle S1) is greater than the thickness T1 of the remaining portions of the second pipe section 22a. In the EGR pipe 18 of this embodiment, multiple ribs 22c are formed on the outer wall of the second split pipe section 22. In this embodiment, ribs 22d are also formed on the inner wall of the second split pipe section 22. This rib 22d is formed at the center of the inner wall so as to extend along the longitudinal direction of the EGR pipe 18. In this embodiment as well, the first joint portion 21b and the second joint portion 22b are joined by vibration welding BW.

[0113] In Fig. 17, the left side of the EGR pipe 18 indicates the upstream side of the EGR gas flow, and the right side indicates the downstream side of the EGR gas flow. As shown in Fig. 17, the thickness T1 of the second separate pipe member 22 in this embodiment is formed so that it increases stepwise or gradually from the upstream side to the downstream side of the second separate pipe member 22. That is, as shown in Fig. 17, the thickness T1 of the second pipe portion 22a of the upstream second separate pipe member 22 is thin, and the thickness T2 of the first pipe portion 21a of the downstream first separate pipe member 21 is thicker than the upstream side.

[0114] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above has functions and effects that differ from those of the previous embodiments in the following respects: In this embodiment, the hot water passage 23 of the first split pipe member 21 is formed by the metal pipe 36 provided in the first split pipe member 21, so the metal pipe 36 can be molded integrally by insert molding when molding the first split pipe member 21. This allows the hot water passage 23 to be provided in the resin EGR pipe 18 with fewer steps.

[0115] According to the configuration of this embodiment, the first joint portion 21b and the second joint portion 22b, which are joined together, are offset toward the first split pipe member 21, thereby shortening the first pipe portion 21a of the first split pipe member 21 in the circumferential direction. Therefore, the first split pipe member 21 is more likely to be heated by the heat of the hot water flowing through the hot water passage 23 of the metal pipe 36 due to the shortened circumferential length. Meanwhile, the second split pipe member 22, which is not provided with the metal pipe 36, is heated by the heat of the EGR gas due to its thinner wall. Therefore, the temperature rise effect on the inner wall of the first split pipe member 21 can be further enhanced for the resin EGR pipe 18, further improving the suppression of condensation in this area.

[0116] Tenth Embodiment Next, the tenth embodiment will be described in detail with reference to FIGS.

[0117] [EGR pipe configuration] This embodiment differs from the ninth embodiment in the configurations of the first joint 21b and the second joint 22b of the EGR pipe 18. Fig. 18 shows a side view of a portion of the EGR pipe 18 of this embodiment. Fig. 19 shows a cross-sectional view of the EGR pipe 18 of this embodiment taken along line EE in Fig. 18. Fig. 20 shows a cross-sectional view of the EGR pipe 18 of this embodiment taken along line FF in Fig. 18.

[0118] In Fig. 18, the left side of the EGR pipe 18 indicates the upstream side of the EGR gas flow, and the right side indicates the downstream side of the EGR gas flow. As shown in Figs. 18 to 20, the offset amounts OF1, OF2 (indicated by arrows) of the two joints 21b, 22b in this embodiment are set so as to gradually decrease from the upstream side to the downstream side of the EGR pipe 18. That is, on the upstream side of the EGR pipe 18, as shown in Fig. 19, the first joint 21b and the second joint 22b are positioned offset toward the first separate pipe member 21 with respect to the center P1 of the EGR pipe 18. On the other hand, on the downstream side of the EGR pipe 18, as shown in Fig. 20, the first joint 21b and the second joint 22b are positioned offset toward the second separate pipe member 22 with respect to the center P1 of the EGR pipe 18. Between the upstream and downstream sides of the EGR pipe 18, the forward offset amount OF1 toward the first divided pipe material 21 gradually becomes shorter, and further, as shown in Figure 20, the offset direction is reversed and the reverse offset amount OF2 gradually becomes larger.

[0119] [About the function and effect of EGR pipes] The configuration of the EGR pipe 18 of this embodiment described above differs in operation and effect from the ninth embodiment in the following respects. In other words, in the EGR pipe 18 of this embodiment, the EGR gas temperature decreases toward the downstream side, but the hot water temperature in the hot water passage 23 remains almost constant regardless of whether it is upstream or downstream. The offset OF, by which the first joint portion 21b and the second joint portion 22b are offset toward the first separate pipe member 21 from the center of the EGR pipe 18, decreases from the upstream side to the downstream side of the EGR pipe 18. As a result, the first pipe portion 21a of the first separate pipe member 21, in which the hot water passage 23 is provided, becomes longer in the circumferential direction toward the downstream side, and the second pipe portion 22a of the second separate pipe member 22, which is formed with a thin wall, becomes shorter in the circumferential direction toward the downstream side. Therefore, the thermal mass of the second pipe portion 22a decreases toward the downstream side as the EGR gas temperature decreases, making it easier for the second pipe portion 22a to be heated by the EGR gas. Meanwhile, the thermal mass of the first pipe portion 21a increases toward the downstream side, making it easier for the hot water to be transferred. Therefore, the temperature rise characteristics of the resin EGR pipe 18 as a whole due to hot water and EGR gas can be improved.

[0120] [About modified examples] In this embodiment, the offset amount OF of the two joints 21b, 22b gradually decreases from the upstream side to the downstream side of the EGR pipe 18, but the offset amount OF can also be set to decrease in stages from the upstream side to the downstream side of the EGR pipe 18.

[0121] Eleventh Embodiment Next, the tenth embodiment will be described in detail with reference to FIG.

[0122] [EGR pipe configuration] This embodiment differs from the previous embodiments in the configuration of the EGR pipe 18, particularly the first split pipe member 21. FIG. 21 shows the EGR pipe 18 of this embodiment in a cross-sectional view similar to FIG. 3. As shown in FIG. 21, this embodiment also uses a resin EGR pipe 18 to form the EGR passage 12, which channels a portion of the exhaust gas discharged from the engine 1 into the exhaust passage 3 as EGR gas into the intake passage 2 of the engine 1. The EGR pipe 18 is formed by joining a first split pipe member 21 and a second split pipe member 22, which are radially split into two, at joints 21b, 22b by vibration welding. The first split pipe member 21 and the second split pipe member 22 are formed so that the first pipe portion 21a and the second pipe portion 22a are as thin as possible to reduce thermal mass. That is, in this embodiment, the second split pipe member 22 is formed to have a thin wall, as in the previous embodiments, but the first split pipe member 21 is not provided with a hot water passage 23, unlike the previous embodiments, and the first pipe section 21a is formed to have the same thin wall as the second pipe section 22a. Also, as shown in Fig. 21, ribs 21c, 21d, 22c, and 22d are formed on the outer and inner walls of the first pipe section 21a and the second pipe section 22a. Furthermore, the two joints 21b and 22b are not positioned offset from the center P1 of the EGR pipe 18, but are positioned at positions that coincide with the center P1.

[0123] [About the function and effect of EGR pipes] According to the configuration of the EGR pipe 18 of this embodiment described above, the first and second separate pipe members 21 and 22 constituting the resin EGR pipe 18 are formed as thin as possible to reduce thermal mass, making the first and second separate pipe members 21 and 22 more likely to be heated by the heat of the EGR gas flowing through the EGR pipe 18. Furthermore, the first and second separate pipe members 21 and 22 are reinforced by the ribs 21c and 22c formed on their outer walls, and their heat-receiving areas are increased by the amount of the ribs 21c and 22c. Therefore, the resin EGR pipe 18 can be heated more effectively around its entire circumference, and condensation on its inner walls can be more effectively suppressed.

[0124] [About modified examples] In this embodiment, ribs 21c, 22c are formed only on the outer walls of the first split pipe material 21 and the second split pipe material 22, but it is also possible to form ribs only on the inner walls of the first split pipe material and the second split pipe material, or to form ribs on both the outer and inner walls of the first split pipe material and the second split pipe material.

[0125] <Another embodiment> The disclosed technology is not limited to the above-described embodiment, and part of the configuration can be appropriately modified within the scope of the disclosed technology.

[0126] (1) In the above-described embodiments, the disclosed technology is embodied in the downstream EGR pipe 18 that constitutes the EGR passage 12, but it can also be embodied in the upstream EGR pipe 17.

[0127] (2) In each of the above embodiments, the EGR gas distributor 15 includes the gas chamber 15a and a plurality of gas distribution passages 15b branching from the gas chamber 15a to each branch pipe 6b. However, an EGR gas distributor without a gas chamber and having gas distribution passages branching in a tournament shape may also be used.

[0128] <Additional notes> In addition to the technology described in the claims, the above specification also includes the following disclosed technology, which will be described below in an additional note.

[0129] [Appendix 1] A resin EGR pipe is used to form an EGR passage that directs a portion of exhaust gas discharged from an engine into an exhaust passage into an intake passage of the engine as EGR gas, The EGR pipe is formed by joining a first divided pipe member and a second divided pipe member, which are divided into two in the radial direction, at a joint portion, the first and second divided pipe members are formed as thin as possible in order to reduce thermal mass; The first and second divided pipe members have ribs formed on at least one of their inner and outer walls. An EGR pipe characterized by:

[0130] According to the above configuration, the first and second split pipe members constituting the EGR pipe are formed as thin as possible to reduce thermal mass, making them more susceptible to heating by the heat of the EGR gas flowing through the EGR pipe. Furthermore, the first and second split pipe members are reinforced by ribs formed on at least one of their inner and outer walls, and their heat-receiving area is increased by the amount of the ribs. This increases the temperature rise effect over the entire circumference of the EGR pipe, improving the effectiveness of suppressing condensation on the inner wall. [Industrial Applicability]

[0131] The disclosed technology can be used in an EGR device provided in an engine. [Explanation of symbols]

[0132] 1 engine 2 Intake passage 3 Exhaust passage 11 EGR device 12 EGR passage 18 EGR pipe (downstream) 21 First divided pipe material 21a First pipe section 21aa Outer pipe section 21aaa 2nd protrusion 21ab Inner pipe section 21aba 1st convex strip 21b 1st joint 21ba 1st joint surface 21bb 1st contact surface 22 Second split pipe material 22a Second pipe section 22b 2nd joint 22ba 2nd joint surface 22bb 2nd contact surface 22aa thick part 22c Rib 22d Rib 23 Hot water passage 23a edge 31 Fixture 32 Vibration jig 36 Metal Pipe X Longitudinal direction T1 Thickness (of the second divided pipe) T2 Thickness (outer pipe part) T3 Thickness (inner pipe) T4 Thickness (near the second joint) P1 center OF offset amount

Claims

1. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, the first divided pipe member includes an outer pipe portion and an inner pipe portion, and the hot water passage is formed between the outer pipe portion and the inner pipe portion; The first split pipe member includes a first pipe portion having a substantially U-shaped cross section in a circumferential direction perpendicular to its longitudinal direction, and first joint portions formed on both ends of the first pipe portion in the circumferential direction, The second split pipe member includes a second pipe portion having a substantially U-shaped cross section in a circumferential direction perpendicular to its longitudinal direction, and second joint portions formed on both ends of the second pipe portion in the circumferential direction, The first joint portion and the second joint portion joined to each other are disposed offset from the center of the EGR pipe toward the second divided pipe member. An EGR pipe characterized by:

2. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, The hot water passage is formed of a metal pipe provided along the longitudinal direction of the first split pipe member. An EGR pipe characterized by:

3. In the EGR pipe described in claim 2, The first split pipe member includes a first pipe portion having a substantially U-shaped cross section in a circumferential direction perpendicular to its longitudinal direction, and first joint portions formed on both ends of the first pipe portion in the circumferential direction, The second split pipe member includes a second pipe portion having a substantially U-shaped cross section in a circumferential direction perpendicular to its longitudinal direction, and second joint portions formed on both ends of the second pipe portion in the circumferential direction, The first joint portion and the second joint portion joined to each other are disposed offset from the center of the EGR pipe toward the first divided pipe member. An EGR pipe characterized by:

4. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, the joint portion is constituted by a first joint portion of the first split pipe member and a second joint portion of the second split pipe member, The thickness of the second joint and its vicinity is greater than the thickness of other portions of the second split pipe member. An EGR pipe characterized by:

5. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, The thickness of the second divided pipe member is formed to increase stepwise or gradually from the upstream side to the downstream side of the second divided pipe member. An EGR pipe characterized by:

6. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, the first divided pipe member includes an outer pipe portion and an inner pipe portion, and the hot water passage is formed between the outer pipe portion and the inner pipe portion; The inner pipe section has at least one first ridge formed along its longitudinal direction toward the outer pipe section. An EGR pipe characterized by:

7. In the EGR pipe described in claim 6, The exterior pipe section has at least one second ridge formed along its longitudinal direction and adjacent to the first ridge toward the interior pipe section. An EGR pipe characterized by:

8. In the EGR pipe according to claim 7, The first convex streak has a height in a convex direction greater than that of the second convex streak. An EGR pipe characterized by:

9. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, A rib is formed on at least one of the inner wall and the outer wall of the second divided pipe member. An EGR pipe characterized by:

10. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, The second divided pipe member has a thick portion formed in part. An EGR pipe characterized by:

11. In the EGR pipe described in claim 3, The offset amount of the joint is set to decrease stepwise or gradually from the upstream side to the downstream side of the EGR pipe. An EGR pipe characterized by:

12. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, the first divided pipe member includes an outer pipe portion and an inner pipe portion, and the hot water passage is formed between the outer pipe portion and the inner pipe portion; The first split pipe member is formed by DSI molding the outer pipe portion and the inner pipe portion with the hot water passage therebetween. An EGR pipe characterized by:

13. A resin EGR pipe is used in an EGR passage that allows a portion of exhaust gas discharged from an engine into an exhaust passage to flow as EGR gas into an intake passage of the engine, The EGR pipe is formed by joining a first divided pipe material and a second divided pipe material, which are divided into two in the radial direction, at a joint portion, the first divided pipe member is provided with a hot water passage through which hot water flows to heat the EGR pipe, The thickness of the second divided pipe material is formed to be thinner than the thickness of the first divided pipe material, the first divided pipe member includes an outer pipe portion and an inner pipe portion, and the hot water passage is formed between the outer pipe portion and the inner pipe portion; The first split pipe member includes a first pipe portion having a substantially U-shaped cross section in a circumferential direction perpendicular to the longitudinal direction thereof, and first joint portions formed in a flange shape along the longitudinal direction at both ends of the circumferential direction of the first pipe portion, and the hot water passage having a substantially U-shaped cross section is disposed inside both first joint portions, The second split pipe material includes a second pipe section having a substantially U-shaped cross section in a circumferential direction perpendicular to the longitudinal direction thereof, and second joint sections formed in a flange shape along the longitudinal direction at both ends of the circumferential direction of the second pipe section, the first joint portion and the second joint portion are joined by vibration welding using a fixed jig and a vibration jig in cooperation with each other, the first joint portion being disposed on the side of the fixed jig, and the second joint portion being disposed on the side of the vibration jig; the first joint portion includes a first joint surface joined to the second joint portion and a first contact surface opposite to the first joint surface with which the fixing jig comes into contact, The second joint portion includes a second joint surface joined to the first joint portion and a second contact surface opposite to the second joint surface with which the vibration jig comes into contact. An EGR pipe characterized by:

14. In the EGR pipe described in claim 13, The hot water passage is disposed so that both ends of the substantially U-shaped cross section are closer to the second split pipe member than the first contact surface with the fixing jig. An EGR pipe characterized by:

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