Engine intake system

Abstract

To provide an intake device of an engine capable of suppressing accumulation of deposits such as soot on an intake passage.SOLUTION: An intake passage comprises an upstream side passage (110), a downstream side passage (31Y), and a curve part 31X bending and connecting a downstream end 110 of the upstream side passage (110) and an upstream end of the downstream side passage (31Y). The downstream side passage (31Y) has a shape linearly extending in a predetermined first direction. An intake side connection part 152 of an EGR passage (51) has a shape extending in the first direction, and is connected to the curve part 31X at a posture that a downstream end 152b in a flow direction of EGR gas is opened toward a downstream side in a flow direction of intake air on the downstream side passage 31Y. When seen in the first direction, an aperture 152a of the downstream end 152b of the intake side connection part 152 is positioned inside the downstream side passage (31Y).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an intake device for an engine. [Background Art]

[0002] Conventionally, in engines installed in vehicles and the like, EGR is sometimes performed in which an exhaust passage through which exhaust gas flows and an intake passage through which intake air flows are connected via an EGR passage, so that EGR gas, which is a part of the exhaust gas, is recirculated to the intake passage.

[0003] For example, Patent Document 1 discloses an engine having an EGR passage, wherein a venturi portion and an annular chamber surrounding the venturi portion are provided in the middle of the intake passage, a slit communicating the annular chamber with the interior of the venturi portion is formed in the venturi portion, and the downstream end of the EGR passage is connected to the outer peripheral surface of the annular chamber in a posture facing the venturi portion. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2013-83209 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] In the configuration of the above Patent Document 1, the downstream end of the EGR passage is connected to the outer peripheral surface of the annular chamber in a posture facing the venturi portion, that is, in a posture facing the central axis of the annular chamber and the venturi portion. Therefore, the EGR gas flowing from the EGR passage into the annular chamber collides with the outer peripheral surface of the venturi portion and the inner peripheral surface of the annular chamber. Here, EGR gas contains soot, unburned fuel, and the like. Accordingly, in the configuration of Patent Document 1, deposits such as soot may adhere and accumulate on the outer peripheral surface of the venturi portion and the inner peripheral surface of the annular chamber, which may impede the flow of EGR gas and intake air.

[0006] This invention has been made in view of the above circumstances, and aims to provide an engine intake system that can suppress the accumulation of deposits such as soot in the intake passage. [Means for solving the problem]

[0007] To solve the aforementioned problems, the present invention provides an intake system for an engine comprising an engine body in which cylinders are formed, an intake passage through which intake air introduced into the engine body flows, and an exhaust passage through which exhaust gas discharged from the engine body flows, wherein the system includes an intake-side connection part connected to the intake passage, and an EGR passage that connects the intake passage and the exhaust passage and recirculates a portion of the exhaust gas as EGR gas to the intake passage, and the intake passage comprises an upstream passage and an exit passage located downstream of the upstream passage in the direction of intake air flow. The system comprises a downstream passage and a bent section that connects the downstream end of the upstream passage to the upstream end of the downstream passage while bending, wherein the downstream passage has a shape that extends linearly along a predetermined first direction, and the intake side connection section has a shape that extends along the first direction, and its downstream end in the direction of EGR gas flow is connected to the bent section in a position that opens toward the downstream side in the direction of intake air flow in the downstream passage, and when viewed along the first direction, the opening of the downstream end of the intake side connection section is located inside the downstream passage. Furthermore, the intake side connection portion has a projection that extends into the inner space of the bent portion, including the downstream end, and the projection extends to a position such that the EGR gas discharged from the opening at the downstream end merges with the intake air, which proceeds linearly along the first direction toward the downstream passage after passing through the bent portion, from one side of the first direction. , characterized by (Claim 1) .

[0008] According to the present invention, a bend is provided between the upstream and downstream passages in the intake passage, and the downstream end of the EGR passage is connected to the bend. In particular, the downstream of the intake passage The side passage is formed to extend linearly along a first direction, and the intake-side connection portion, which constitutes the downstream end of the EGR passage, is also shaped to extend along the first direction and is connected to the bent portion in a manner that opens toward the downstream side in the direction of intake air flow in the downstream passage. Therefore, after passing through the bent portion, EGR gas can be introduced along the flow of intake air as it travels linearly along the first direction in the downstream passage. As a result, it is possible to suppress the accumulation of EGR gas with a high concentration of soot and other deposit-causing substances, which is introduced into the intake passage from the intake-side connection portion, near the opening of the intake-side connection portion. Moreover, in this invention, since the opening of the intake-side connection portion is located inside the downstream passage when viewed along the first direction, it is possible to suppress the collision of EGR gas with a high concentration of soot and other deposits introduced into the downstream passage with the inner surface of the downstream passage. Accordingly, according to this invention, it is possible to suppress the adhesion and accumulation of deposits such as soot contained in the EGR gas on the inner surface of the intake passage. Furthermore, in this invention, since the protruding portion including the downstream end of the intake-side connection portion protrudes into the inner space of the bent portion, the downstream end of the intake-side connection portion of the EGR passage and the inner circumferential surface of the bent portion can be separated, and the adhesion of EGR gas with a high concentration of soot, etc., to the inner circumferential surface of the bent portion can be reliably suppressed.

[0009] In the above configuration, preferably, when viewed along the first direction, the central axis of the downstream passage is located inside the opening at the downstream end of the intake connection (Claim 2).

[0010] This configuration ensures that the EGR gas follows the intake airflow, and reliably prevents the accumulation of EGR gas with high concentrations of soot and other contaminants near the opening of the intake side connection.

[0013] In the above configuration, preferably, the protruding portion is positioned such that its outer peripheral surface is spaced apart from the inner peripheral surface of the bent portion over its entire circumference. Claim 3 ).

[0014] This configuration makes it possible to more reliably suppress the adhesion of EGR gas with high concentrations of soot and other contaminants to the inner surface of the intake passage.

[0015] In the above configuration, preferably, the bent portion has a U-shape that curves so as to bulge out to one side in the first direction. Claim 4 ).

[0016] This configuration allows the upstream and downstream passages of the intake passage to be brought close together in a direction perpendicular to the first direction, making the intake passage more compact in that direction.

[0017] The intake passage comprises a supercharger that supercharges the intake air and an intercooler that is positioned downstream of the supercharger in the direction of intake air flow and cools the intake air, and the bent portion may be provided downstream of the intercooler in the direction of intake air flow. Claim 5 ).

[0018] In engines equipped with a supercharger and an intercooler, where EGR gas is introduced into the intake passage downstream of the intercooler, the intake air is cooled by the intercooler, which lowers the temperature of the intake passage downstream of the intercooler. This makes it easier for soot contained in the EGR gas to mix with condensed water and oil contained in blow-by gas in the intake passage, causing it to accumulate as deposits. This configuration makes it possible to suppress the adhesion and accumulation of deposits on the inner surface of the intake passage, which is a concern in such engines.

[0019] The exhaust passage is provided with a filter for collecting particulate matter contained in the exhaust gas, and the EGR passage may be connected to the portion of the exhaust passage upstream of the filter in the direction of exhaust gas flow. Claim 6 ).

[0020] In engines where the EGR passage is connected to the exhaust passage upstream of the filter that collects particulate matter, the EGR gas that passes through the EGR passage and is returned to the intake passage will contain a relatively large amount of soot and other particles. This configuration makes it possible to suppress the adhesion and accumulation of deposits in the intake passage, which is a concern in such engines.

[0021] The engine body may be a diesel engine that uses light oil as fuel. Claim 7 ).

[0022] In a diesel engine, exhaust gas and EGR gas contain a relatively large amount of soot and the like. According to this configuration, the adhesion and deposition of deposits in the intake passage, which is a concern in such diesel engines, can be suppressed. Effects of the Invention

[0023] As described above, according to the engine intake device of the present invention, deposition of deposits such as soot in the intake passage can be suppressed. Brief Description of the Drawings

[0024] [Figure 1] It is a system diagram showing a schematic configuration of an engine according to an embodiment of the present invention. [Figure 2] It is a schematic plan view showing a part of the engine shown in Fig. 1. [Figure 3] It is a schematic side view showing a part of the engine shown in Fig. 1. [Figure 4] It is a schematic cross-sectional view showing a part of a cross-section taken along line IV-IV of Fig. 3. [Figure 5] It is a cross-sectional view showing a part of an intake system device taken along line V-V of Fig. 4. [Figure 6] It is a cross-sectional view taken along line VI-VI of Fig. 5. [Figure 7] It is a cross-sectional view showing a part of a cross-section taken along line VII-VII of Fig. 6. [Figure 8] It is a cross-sectional view showing a part of a cross-section taken along line VIII-VIII of Fig. 7. [Figure 9] It is a schematic diagram showing the distribution of EGR gas in the intake passage, wherein (a) is a view of a cross-section taken along line A-A of Fig. 6, (b) is a view of a cross-section taken along line B-B of Fig. 6, and (c) is a view of a cross-section taken along line C-C of Fig. 6. Mode for Carrying Out the Invention

[0025] (Overall Configuration of Engine) Hereinafter, an embodiment of the intake system according to the present invention will be described with reference to the drawings. First, the overall configuration of an embodiment of an engine E to which the intake system according to the present invention is applied will be described with reference to Figure 1. The engine E shown in Figure 1 is a four-cycle engine. The engine E is mounted on a vehicle, for example, as a power source for driving. The engine E comprises an engine body 1 in which cylinders are formed, an intake passage 30 through which intake air introduced into the engine body 1 flows, an exhaust passage 40 through which exhaust gas discharged from the engine body 1 flows, and HP-EGR device 50H and LP-EGR device 50L, which recirculate EGR gas, which is a part of the exhaust gas flowing through the exhaust passage 40, back into the intake passage 30. The engine body 1 is a diesel engine driven by a fuel mainly composed of light oil. The engine E is also a turbocharged engine and includes a turbocharger 60 which includes a compressor 61 located in the intake passage 30 and a turbine 62 located in the exhaust passage 40.

[0026] The engine body 1 is an inline multi-cylinder engine. Specifically, the engine body 1 is an inline 6-cylinder engine, having six cylinders 2 (only one of which is shown in Figure 1) arranged perpendicular to the plane of the paper in Figure 1. The engine body 1 has a cylinder block 3 in which the cylinders 2 are formed, and a cylinder head 4 attached to the upper surface of the cylinder block 3. A piston 5 is housed in the cylinder 2 so as to be able to reciprocate and slide in the vertical direction, and is connected to the crankshaft 7 via a connecting rod 8. In response to the reciprocating motion of the piston 5, the crankshaft 7 rotates around its central axis. A combustion chamber 6 is partitioned above the piston 5. Here, the direction in which the cylinder block 3 and cylinder head 4 are aligned and the direction of reciprocating motion of the piston 5 are referred to as the vertical direction, the side of the cylinder head 4 relative to the cylinder block 3 is referred to as the upper side, and the opposite side as the lower side.

[0027] The cylinder head 4 has intake ports 9 and exhaust ports 10 that communicate with each combustion chamber 6, and is equipped with intake valves 11 that open and close each intake port 9 and exhaust valves 12 that open and close each exhaust port 10. The intake valves 11 and exhaust valves 12 are driven to open and close by valve trains 13 and 14 provided on the cylinder head 4. The cylinder head 4 is fitted with one injector 15 for each cylinder 2 that injects fuel into the combustion chamber 6 from its tip. The injector 15 injects fuel supplied through a fuel supply pipe (not shown) into the combustion chamber 6. The fuel injected from the injector 15 mixes with air in the combustion chamber 6. The fuel-air mixture burns in the combustion chamber 6, and the piston 5 is pushed down by the expansion force caused by the combustion of the mixture and reciprocates in the vertical direction.

[0028] The intake passage 30 is connected to one side of the engine body 1 so as to communicate with each intake port 9. The intake passage 30 contains, in order from upstream, an air cleaner 31, a compressor 61, a throttle valve 32, an intercooler 33, a surge tank 34, and an intake manifold 35.

[0029] The air cleaner 31 cleans the intake air by removing foreign matter from it. The throttle valve 32 opens and closes the intake passage 30 to adjust the flow rate of intake air in the intake passage 30. The compressor 61 compresses the intake air and sends it downstream of the intake passage 30. The intercooler 33 cools the intake air compressed by the compressor 61. The intake manifold 35 has multiple passages that communicate with the intake ports 9 of each cylinder 2, and distributes the intake air to each cylinder 2 through these passages. The surge tank 34 is located directly upstream of the intake manifold 35 and is a tank that provides space for evenly distributing the intake air to each cylinder 2.

[0030] In this embodiment, a portion of the exhaust passage 40 is formed inside the cylinder head 4. The exhaust passage 40 comprises a cylinder head internal passage 41 formed inside the cylinder head 4 to communicate with the exhaust port 10 of each cylinder 2, and a main exhaust passage 42 connected to the other side of the cylinder head 4 while communicating with the cylinder head internal passage 41. As shown in Figure 4, which will be described later, in this embodiment, two cylinder head internal passages 41, each communicating with the exhaust port 10 of the three cylinders 2, are formed inside the cylinder head 4. The main exhaust passage 42 includes a portion that communicates with these two cylinder head internal passages 41 to collect the exhaust gases discharged from these cylinder head internal passages 41, and a portion that extends from this collection portion and divides a single flow path. The exhaust passage 40 (main exhaust passage 42) has, in order from upstream, a turbine 62, a DOC (diesel oxidation catalyst) 43, a DPF (diesel particulate filter) 44, and an exhaust shutter valve 45. DPF44 corresponds to the "filter" in the claim.

[0031] The turbine 62 is connected to the compressor 61 so as to be able to rotate together. The turbine 62 rotates by receiving energy from the exhaust gas flowing through the exhaust passage 40, and rotates the compressor 61. The DOC 43 is a catalytic converter that oxidizes and neutralizes harmful components (CO and HC) contained in the exhaust gas. The DPF 44 is a filter that captures particulate matter such as soot contained in the exhaust gas. The exhaust shutter valve 45 opens and closes the exhaust passage 40 to adjust the flow rate of the exhaust gas.

[0032] The exhaust passage 40 (main exhaust passage 42) is provided with a bypass passage 63 that bypasses the turbine 62 and a wastegate valve 64. The wastegate valve 64 opens and closes the bypass passage 63 to adjust the flow rate of exhaust gas passing through the bypass passage 63, that is, exhaust gas that goes to the DOC 41 without passing through the turbine 62. Note that the exhaust shutter valve 45, bypass passage 63, and wastegate valve 64 described above may be omitted.

[0033] The HP-EGR device 50H comprises an HP-EGR passage 51 connecting the exhaust passage 40 and the intake passage 30, and an HP-EGR valve 52 provided in the HP-EGR passage 51. The HP-EGR passage 51 connects the portion of the exhaust passage 40 upstream of the turbine 62 and the portion of the intake passage 30 between the intercooler 33 and the surge tank 34. The HP-EGR valve 52 adjusts the amount of EGR gas that flows back into the intake passage 30 through the HP-EGR passage 51 by opening and closing the HP-EGR passage 51. Hereinafter, the EGR gas that flows back into the intake passage 30 through the HP-EGR passage 51 will be referred to as HP-EGR gas. The HP-EGR passage 51 described above corresponds to the "EGR passage" in the claim.

[0034] The LP-EGR device 50L includes an LP-EGR passage 55 connecting the exhaust passage 40 and the intake passage 30, and an EGR cooler 56 and an LP-EGR valve 57 provided in the LP-EGR passage 55. The LP-EGR passage 55 connects the portion of the exhaust passage 40 downstream of the DPF 44 and the portion of the intake passage 30 between the air cleaner 31 and the compressor 61. The LP-EGR valve 57 adjusts the amount of EGR gas that flows through the LP-EGR passage 55 back into the intake passage 30 by opening and closing the LP-EGR passage 55. The EGR cooler 56 is a heat exchanger that cools the EGR gas flowing through the LP-EGR passage 55 by heat exchange.

[0035] As described above, the upstream end of the LP-EGR passage 55 is connected to the portion of the exhaust passage 40 downstream of the turbine 62 and DPF 44. On the other hand, the upstream end of the HP-EGR passage 51 is connected to the portion of the exhaust passage 40 upstream of the turbine 62 and DPF 44. As a result, high-temperature, high-pressure exhaust gas before passing through the turbine 62 and DPF 44 is recirculated into the intake passage 30 through the HP-EGR passage 51, while low-temperature, low-pressure exhaust gas after passing through the turbine 62 and DPF 44 is recirculated through the LP-EGR passage 55.

[0036] (Configuration of intake passage and HP-EGR passage) Next, the main parts of the intake passage 30 and the HP-EGR passage 51 will be described. Figure 2 is a schematic plan view showing a part of the engine E. Figure 3 is a schematic side view showing a part of the engine E. Figure 4 is a schematic cross-sectional view showing a part of the cross section along line IV-IV in Figure 3. Hereafter, the left-right direction in Figure 2, which is the direction of arrangement of the cylinders 2, will be referred to as the front-rear direction, with the left side of Figure 2 being the front and the opposite side being the rear. Also, the direction perpendicular to the up-down direction and the front-rear direction will be referred to as the left-right direction. In this case, left and right refer to the left and right when facing forward. As shown in Figure 4, the intake port 9 opens on the left side of the cylinder head 4, and the exhaust port 10 opens on the right side of the cylinder head 4. In other words, hereafter, the intake side where the intake port 9 is provided will be referred to as the left side, and the exhaust side where the exhaust port 10 is provided will be referred to as the right side.

[0037] The turbocharger 60 is positioned along the right side of the engine body 1. The turbocharger 60 is fixed approximately in the center of the right side of the engine body 1 in the front-to-back direction, with the turbine 62 and compressor 61 aligned in this order in the front-to-back direction.

[0038] The throttle valve body 32B, which includes the throttle valve 32, is located on the left side of the rear of the engine body 1. The throttle valve body 32B includes the throttle valve 32, a passage surrounding it, and a device for opening and closing the throttle valve 32.

[0039] The intercooler 33 is located to the left of the engine body 1 and in front of the throttle valve body 32B. The intercooler 33 has a roughly rectangular shape and is positioned to the left of the approximate center of the engine body 1 in the front-to-back direction, extending in the front-to-back direction.

[0040] The surge tank 34 is located to the left of the engine body 1 and below the intercooler 33. The surge tank 34 has a shape that extends in the front-to-back direction and is located to the left of the cylinder head 4, extending over substantially the entire front-to-back length of the left side of the cylinder head 4. Furthermore, when viewed from above, the surge tank 34 is located in a position where its left side portion, approximately in the center of its front-to-back length, overlaps with a portion of the intercooler 33.

[0041] The intake manifold 35 is positioned between the surge tank 34 and the left side of the cylinder head 4. More specifically, the intake manifold 35 has a shape that extends in the front-rear direction and, like the surge tank 34, is fixed to the left side of the cylinder head 4 in a position that extends over substantially the entire front-rear length of the left side of the cylinder head 4. In this embodiment, the intake manifold 35 and the surge tank 34 are made of resin and are molded integrally with each other.

[0042] The HP-EGR valve body 52B, which includes the HP-EGR valve 52, is located to the left of the front end of the engine body 1. The HP-EGR valve body 52B includes the HP-EGR valve 52, a passage surrounding it, and a device for opening and closing the HP-EGR valve 52.

[0043] The intake passage 30 includes a first intake passage 31A connecting the compressor 61 and the throttle valve body 32B, a second intake passage 31B connecting the throttle valve body 32B and the intercooler 33, and a third intake passage 31C connecting the intercooler 33 and the surge tank 34.

[0044] The first intake passage 31A is positioned above the engine body 1 and extends horizontally across the compressor 61 and the throttle valve body 32B. The first intake passage 31A is curved to bulge rearward and is connected to the rear surface of the throttle valve body 32B.

[0045] The second intake passage 31B extends forward from the front of the throttle valve body 32B and is connected to the rear of the intercooler 33.

[0046] The third intake passage 31C has a roughly U-shape that bulges forward when viewed along the left-right direction, and has a portion that extends forward from the front of the intercooler 33, a portion that curves forward from this portion, and a portion that extends rearward from this portion. The rear end of the portion of the third intake passage 31C that extends rearward from the curved portion is connected to the surge tank 34. The detailed structure of the third intake passage 31C will be described later.

[0047] The HP-EGR passage 51 is connected to and communicates with the third intake passage 31C. In this embodiment, a portion of the HP-EGR passage 51 is formed inside the cylinder head 4, and the HP-EGR passage 51 comprises a first HP-EGR passage 51A formed inside the cylinder head 4, a second HP-EGR passage 51B connecting the first HP-EGR passage 51A and the HP-EGR valve body 52B, and a third HP-EGR passage 51C connecting the HP-EGR valve 52 and the third intake passage 31C.

[0048] The first HP-EGR passage 51A is connected to the cylinder head internal passage 41, which is located at the front of the cylinder head 4. The first HP-EGR passage 51A extends forward from the cylinder head internal passage 41, then extends to the left at the front end of the cylinder head 4, and opens at the front end of the left side of the cylinder head 4. The HP-EGR valve body 52B is located to the left of the opening of the first HP-EGR passage 51A. The second HP-EGR passage 51B extends to the left from the opening of the first HP-EGR passage 51A and is connected to the HP-EGR valve body 52B. The third intake passage 31C is located diagonally to the left and rear of the HP-EGR valve body 52B. The third HP-EGR passage 51C has a shape that curves diagonally to the left and rear from the HP-EGR valve body 52B and is connected to the front end of the third intake passage 31C.

[0049] (Detailed configuration) Next, the connection portion between the intake passage 30 (third intake passage 31C) and the HP-EGR passage 51 (third HP-EGR passage 51C), which are characteristic features of the present invention, and the surrounding configuration will be described in detail. Figure 5 is a cross-sectional view showing a part of the intake system along line VV in Figure 4. Figure 6 is a cross-sectional view along line VI-VI in Figure 5. Figure 7 is a cross-sectional view showing a part of the cross section along line VII-VII in Figure 6. Figure 8 is a cross-sectional view showing a part of the cross section along line VIII-VIII in Figure 7.

[0050] The third intake passage 31C is composed of multiple intake pipes. In this embodiment, the third intake passage 31C is composed of four intake pipes: the first intake pipe 110, the second intake pipe 120, the third intake pipe 130, and the fourth intake pipe 140. The details of each intake pipe (110, 120, 130, 140) will be described below, but in that description, upstream and downstream in each intake pipe refer to the upstream and downstream in the direction of the intake air flowing through each intake pipe.

[0051] The first intake pipe 110 is cylindrical in shape. The first intake pipe 110 extends forward from the front end 33E of the intercooler 33, and its front end constitutes the downstream end 111 of the first intake pipe 110, which opens forward.

[0052] The second intake pipe 120 is a tubular member with a roughly L-shape, and when viewed along the left-right direction, the central axis X1 (Figure 5) of the second intake pipe 120 exhibits a roughly quarter-circle arc shape. The second intake pipe 120 curves diagonally downward and forward from the downstream end (front end) 111 of the first intake pipe 110, and the downstream end 122 of the second intake pipe 120 opens downward. In other words, the rear end of the second intake pipe 120 forms an upstream end 121 that opens rearward and communicates with the downstream end 111 of the first intake pipe 110, and its lower end forms a downstream end 122 that opens downward. Each cross-section of the second intake pipe 120 (cross-section perpendicular to the central axis X1) is roughly circular, and its area is approximately constant. The opening shape of the upstream end 121 of the second intake pipe 120 and the opening shape of the downstream end 111 of the first intake pipe 110 are almost the same, and the first intake pipe 110 and the second intake pipe 120 are connected so that their inner surfaces are continuous without any steps.

[0053] The third intake pipe 130 is a hollow member whose central axis X2 extends along a straight line L. The straight line L extends approximately horizontally and in the front-rear direction. In other words, the third intake pipe 130 is positioned such that its central axis X2 extends approximately horizontally and in the front-rear direction. More specifically, the central axis X2 is slightly inclined diagonally to the rear and left with respect to a straight line extending in the front-rear direction. As a result, the rear side of the third intake pipe 130 is further away from the engine body 1 in the lateral direction than the front side.

[0054] The third intake pipe 130 has a main body portion 131 that has a flattened cross-section overall and extends along a straight line L, and a substantially cylindrical EGR mounting portion 132 that protrudes forward from the main body portion 131 along the straight line L. The main body portion 131 and the EGR mounting portion 132 are coaxial. Hereafter, the central axes of both the main body portion 131 and the EGR mounting portion 132 will be described as the central axis X2. The outer and inner diameters of the EGR mounting portion 132 are smaller than the outer and inner diameters of the main body portion 131, and the front end of the third intake pipe 130 tapers towards the front.

[0055] Each cross-section of the main body 131 has a roughly elliptical shape, with the horizontal dimension being longer than the vertical dimension. A first opening 131a that opens upward is formed on the upper surface of the front end of the main body 131, and a second opening 131d that opens rearward (to the rear and slightly to the left) is formed on the rear end of the main body 131. More specifically, a cylindrical projection 131b that protrudes slightly upward is formed on the front end of the main body 131, and the circular opening at the upper end surface of the projection 131b constitutes the first opening 131a.

[0056] The third intake pipe 130 is connected to the second intake pipe 120 so that intake air is introduced from the second intake pipe 120 toward the first opening 131a. In other words, the upper end of the projection 131b where the first opening 131a is formed constitutes the upstream end 131c of the third intake pipe 130. The rear end of the third intake pipe 130 where the second opening 131d is formed constitutes the downstream end 131e of the third intake pipe 130. The shape of the first opening 131a, that is, the opening shape of the upstream end 131c of the third intake pipe 130, is almost the same as the opening shape of the downstream end 122 of the second intake pipe 120, and the second intake pipe 120 and the third intake pipe 130 are connected so that their inner circumferential surfaces are continuous without any steps.

[0057] The longitudinal dimension of the third intake pipe 130 is longer than the combined longitudinal dimension from the front end of the second intake pipe 120 to the rear end of the first intake pipe 110. Thus, the third intake pipe 130 extends beneath the intercooler 33, from the front end position of the second intake pipe 120 to a position behind the front end of the intercooler 33 in the longitudinal direction. As shown in Figure 4, in this embodiment, the longitudinal dimension of the main body 131 of the third intake pipe 130 is set to be approximately the same as the dimension from the front end position of the engine body 1 to the midpoint between the second cylinder 2 and the third cylinder 2 from the front.

[0058] The fourth intake pipe 140 is a roughly L-shaped tubular member, and when viewed along the vertical direction, the central axis X3 (Figure 6) of the fourth intake pipe 140 exhibits a quarter-circular arc shape. The fourth intake pipe 140 curves diagonally to the right and rear from the downstream end (rear end) 131e of the third intake pipe 130, and the downstream end 142 of the fourth intake pipe 140 opens to the right. In other words, the front end of the fourth intake pipe 140 forms an upstream end 141 that opens forward and communicates with the downstream end 131e of the third intake pipe 130, and its right end forms a downstream end 142 that opens to the right. Each cross-section of the fourth intake pipe 140 is approximately the same as the cross-sectional shape of the main body 131 of the third intake pipe 130, and the third intake pipe 130 and the fourth intake pipe 140 are connected such that their inner circumferential surfaces are continuous without any steps.

[0059] An opening 34a is formed approximately in the center of the surge tank 34 in the front-to-back direction, opening to the left. The fourth intake pipe 140 is connected to the surge tank 34 such that its downstream end 142 is in communication with this opening 34a of the surge tank 34. The fourth intake pipe 140 is located below the intercooler 33.

[0060] As is clear from the above configuration, the front part of the third intake passage 31C is sharply bent. That is, the third intake passage 31C (intake passage 30) has a bent section 31X formed from the front parts of the second intake pipe 120 and the third intake pipe 130. When viewed along the left-right direction, this bent section 31X has a U-shape that is convex to one side, that is, in the direction along the straight line L. Note that the term "U-shape" here does not only mean that it has the exact shape of a U, but also that it deviates from a U shape but generally has the shape of a U overall.

[0061] The rear portion 31Y of the third intake pipe 130, which extends downstream from the bent portion 31X in the direction of intake air flow, extends linearly along the straight line L. The first intake pipe 110, located upstream of the bent portion 31X, extends approximately parallel to the rear portion 31Y of the third intake pipe 130. In other words, the bent portion 31X connects the downstream end 111 of the first intake pipe 110 and the upstream end of the rear portion 31Y of the third intake pipe 130 by bending approximately 180°. In this case, the first intake pipe 110 corresponds to the "upstream passage" in the claim, and the rear portion 31Y of the third intake pipe 130 corresponds to the "downstream passage" in the claim. The direction along the straight line L corresponds to the "first direction" in the claim. That is, in this embodiment, the direction along the straight line L, which is horizontal and inclined diagonally to the rear left, corresponds to the first direction.

[0062] The downstream end of the HP-EGR passage 51 (third HP-EGR passage 51C) is connected to the bent section 31X. The details of this connection structure will be explained below, in which the upstream and downstream of the third HP-EGR passage 51C refer to the upstream and downstream in the flow direction of the HP-EGR gas flowing through the third HP-EGR passage 51C.

[0063] The third HP-EGR passage 51C has an intake-side connection portion 152 at its downstream end that is connected to the EGR mounting portion 132 of the third intake pipe 130. The EGR mounting portion 132 is located at the front end of the third intake pipe 130 and is included in the bend 31X. In other words, the intake-side connection portion 152 of the third HP-EGR passage 51C is connected to the bend 31X of the third intake passage 31C.

[0064] As described above, the third HP-EGR passage 51C has a shape that curves diagonally to the left and rearward from the HP-EGR valve body 52B. However, the intake side connection portion 152 has a cylindrical shape that extends along a straight line L, and the intake side connection portion 152 is connected to the EGR mounting portion 132 in a position that extends parallel to the third intake pipe 130. The rear end of the intake side connection portion 152 constitutes the downstream end 152b of the third HP-EGR passage 51C, and this downstream end (rear end) 152b has an opening 152a that opens to the rear.

[0065] The intake-side connection portion 152 is fixed to the EGR mounting portion 132 by being inserted into the front end face of the EGR mounting portion 132 from front to rear, and the rear part of the intake-side connection portion 152 protrudes inward into the EGR mounting portion 132 and the third intake pipe 130. In other words, the rear part of the intake-side connection portion 152 constitutes a protruding portion 152f that protrudes inward into the third intake pipe 130. The protruding portion 152f includes the downstream end 152b of the third HP-EGR passage 51C (intake-side connection portion 152).

[0066] As shown in Figure 6, the intake-side connection portion 152 is inserted to a position behind the front end of the main body portion 131 of the third intake pipe 130. In other words, the downstream end 152b of the intake-side connection portion 152 is located behind the front end of the main body portion 131. In this embodiment, the position of the downstream end 152b of the intake-side connection portion 152 in the front-rear direction is slightly behind the front end of the first opening 131a provided in the main body portion 131 of the third intake pipe 130, and in front of the center of the first opening 131a in the front-rear direction.

[0067] As shown in Figure 8, when viewed along the straight line L, the opening 152a at the downstream end 152b of the intake side connection 152 is located inside the third intake pipe 130. More specifically, when viewed along the straight line L, the opening 152a at the downstream end 152b of the intake side connection 152 is located inside both the EGR mounting portion 132 and the main body portion 131 of the third intake pipe 130. In this embodiment, the straight line L passes inside the opening 152a at the downstream end 152b of the intake side connection 152, and when viewed along the straight line L, the central axis X2 of the third intake pipe 130 (Figures 4 to 7) is located inside the opening 152a at the downstream end 152b of the intake side connection 152.

[0068] Furthermore, the protruding portion 152f, including the downstream end 152b of the intake-side connection portion 152, is positioned so that its outer circumferential surface is spaced radially inward from the inner circumferential surface of the third intake pipe 130 (EGR mounting portion 132 and main body portion 131) along its entire circumference, and a gap is formed around the entire circumference between the outer circumferential surface of the intake-side connection portion 152 and the inner circumferential surface of the third intake pipe 130.

[0069] (effect, etc.) As described above, in the above embodiment, a U-shaped bent portion 31X is formed by the second intake pipe 120 and the front portion of the third intake pipe 130 in the intake passage 30, and the rear portion 31Y of the third intake pipe 130, which extends downstream from this bent portion 31X in the direction of intake air flow, extends linearly along the straight line L. The intake-side connection portion 152 of the HP-EGR passage 51, which is connected to the intake passage 30, is shaped to extend along the straight line L and is connected to the bent portion 31X in a position that opens towards the rear, that is, downstream of the third intake pipe 130.

[0070] As shown by arrow Y1 in Figure 7, for intake air that flows and proceeds linearly along the straight line L in the third intake pipe 130 after passing through the bend 31X, the HP-EGR gas that recirculates to the intake passage 30 through the HP-EGR passage 51 can be introduced into the intake passage 30 from the intake-side connection part 152 in line with the intake air flow, as shown by arrow Y2 in Figure 7. Therefore, the HP-EGR gas immediately after being introduced into the intake passage 30 from the intake-side connection part 152 can be flowed downstream of the intake passage 30 together with the intake air, and the accumulation of the HP-EGR gas immediately after introduction, i.e., EGR gas with a high concentration of soot and other deposit-causing substances, near the downstream end 152b of the intake-side connection part 152 can be suppressed. Also, when viewed along the straight line L, the opening 152a at the downstream end 152b of the intake-side connection part 152 is located inside the third intake pipe 130. Therefore, it is possible to suppress the collision of HP-EGR gas with a high concentration of soot, etc., which is led from the intake side connection part 152 to the third intake pipe 130 with the inner surface of the third intake pipe 130. Accordingly, according to the above embodiment, it is possible to suppress the adhesion and accumulation of deposits such as soot contained in the HP-EGR gas on the inner surface of the intake passage of the third intake pipe 130.

[0071] In particular, in the above embodiment, when viewed along the straight line L, the central axis X2 of the third intake pipe 130 is located inside the opening 152a at the downstream end 152b of the intake side connection 152. Therefore, HP-EGR gas can be discharged from the intake side connection 152 to the main intake air flowing near the central axis X2 of the third intake pipe 130, which has a high flow velocity, and the accumulation of HP-EGR gas with a high concentration of soot, etc., near the downstream end 152b of the intake side connection 152 can be reliably suppressed.

[0072] Furthermore, in the above embodiment, the protruding portion 152f, including the downstream end 152b of the intake-side connection portion 152, is inserted into the inside of the third intake pipe 130, and the downstream end 152b of the intake-side connection portion 152 is spaced apart from the inner circumferential surface of the front end of the third intake pipe 130, that is, from the inner circumferential surface of the bent portion 31X. Therefore, it is possible to more reliably suppress the collision of HP-EGR gas with a high concentration of soot, etc., which is led from the downstream end 152b of the intake-side connection portion 152 to the third intake pipe 130, with the inner circumferential surface of the front end of the third intake pipe 130.

[0073] Furthermore, in the above embodiment, the protrusion 152f is arranged such that its outer peripheral surface is spaced apart from the inner peripheral surface of the third intake pipe 130 (EGR mounting portion 132 and main body portion 131) over its entire circumference, and a gap is defined over its entire circumference between the outer peripheral surface of the protrusion 152f and the inner peripheral surface of the third intake pipe 130.

[0074] Therefore, it is possible to reliably suppress the collision of HP-EGR gas with a high concentration of soot, etc., which is led to the third intake pipe 130 from the rear end of the protrusion 152f, i.e., the downstream end 152b of the intake-side connection part 152, with the inner surface of the third intake pipe 130. In detail, as shown by arrow Y10 in Figure 8, a portion of the intake air going from the second intake pipe 120 to the third intake pipe 130 branches out in the left-right direction at the protrusion 152f, as shown by arrow Y11, and enters the gap between the outer surface of the protrusion 152f and the inner surface of the third intake pipe 130. In other words, the HP-EGR gas led to the third intake pipe 130 from the downstream end 152b of the intake-side connection part 152 (protrusion 152f) is surrounded by intake air around its entire circumference. As a result, the HP-EGR gas, which has a high concentration of soot and other deposits before diffusion, comes into contact with the inner surface of the third intake pipe 130, and the adhesion of soot and other deposits to the inner surface is suppressed.

[0075] Figure 9 schematically shows the results of a simulation of the distribution of HP-EGR gas in the third intake pipe 130. In Figure 9, points with a high concentration of HP-EGR gas (the concentration of components introduced by HP-EGR gas in the gas flowing through the third intake pipe 130), i.e., points with a high concentration of soot and other deposit-causing substances, are indicated by darker colors. Furthermore, Figure 9(a) shows the distribution of HP-EGR gas in the cross-section of line AA in Figure 6, (b) shows the distribution of HP-EGR gas in the cross-section of line BB in Figure 6, and (c) shows the distribution of HP-EGR gas in the cross-section of line CC in Figure 6.

[0076] As shown in Figure 9(a), in the cross-section along line AA in Figure 6, that is, near the downstream end 152b of the intake-side connection portion 152 of the third intake pipe 130, the HP-EGR gas is concentrated almost in the center of the third intake pipe 130. This suppresses contact between the HP-EGR gas with a high concentration of soot, etc., which is led from the HP-EGR passage 51 to the intake passage 30 and the inner surface of the third intake pipe 130.

[0077] Furthermore, as shown in Figures 9(b) and (c), the HP-EGR gas diffuses from the center of the third intake pipe 130 outwards. Therefore, even at a relatively downstream position of the third intake pipe 130, the concentration of HP-EGR gas near the inner surface of the third intake pipe 130 is kept low. As a result, the adhesion of soot and other deposits is suppressed throughout the third intake pipe 130. Thus, according to the above embodiment, it is possible to diffuse the HP-EGR gas into the intake air before it is introduced into the engine body 1, while suppressing the adhesion of deposits such as soot contained in the HP-EGR gas to the third intake pipe 130 and the intake passage 30.

[0078] (modified version) In the above embodiment, the case was described in which the intake-side connection portion 152 of the HP-EGR passage 51 has a protruding portion 152f, that is, the portion including the downstream end 152b of the intake-side connection portion 152 (protruding portion 152f) protrudes into the third intake pipe 130. However, the intake-side connection portion 152 may be connected to the third intake pipe 130 in a manner that does not protrude into the third intake pipe 130.

[0079] However, if the portion of the intake-side connection portion 152 including the downstream end 152b protrudes inward into the third intake pipe 130, then, as described above, it is possible to more reliably suppress the collision of HP-EGR gas with a high concentration of soot, etc., which is led from the downstream end 152b of the intake-side connection portion 152 to the third intake pipe 130, with the inner circumferential surface of the front end of the third intake pipe 130.

[0080] Furthermore, the projection 152f does not necessarily have to be configured such that its outer circumferential surface is spaced apart from the inner circumferential surface of the third intake pipe 130 over its entire circumference. In other words, a portion of the outer circumferential surface of the projection 152f may be connected to the inner circumferential surface of the third intake pipe 130.

[0081] However, if the protrusion 152f is configured such that its outer surface is spaced apart from the inner surface of the third intake pipe 130 over its entire circumference, then, as described above, it is possible to reliably suppress the collision of HP-EGR gas with high concentrations of soot, etc., with the inner surface of the third intake pipe 130.

[0082] In the above embodiment, a U-shaped bent portion 31X that bends approximately 180° is used, but the specific shape of the bent portion 31X is not limited to this. For example, an L-shaped bent portion that bends approximately 90° may also be used. However, if a U-shaped bent portion 31X that is convex on one side in the direction along the straight line L is used, the first intake pipe 110 and the third intake pipe 130 can be brought closer together in the direction perpendicular to the straight line L, and the third intake passage 31C (intake passage 30) can be made more compact. Specifically, in the above embodiment, the third intake passage 31C can be made compact in the left-right and up-down directions.

[0083] In the above embodiment, the case was described in which the EGR passage connected to the bent portion 31X is an HP-EGR passage 51, that is, the case in which the HP-EGR passage 51, which connects the intake passage 30 downstream in the direction of intake air flow of the intercooler 33 and the exhaust passage 40 upstream in the direction of exhaust gas flow of the DPF 44, is connected to the bent portion 31X. However, the EGR passage connected to the bent portion 31X may be an LP-EGR passage 55.

[0084] However, the intake passage 30 downstream of the intercooler 33 to which the HP-EGR passage 51 is connected becomes cooler as the intake air is cooled by the intercooler 33. Therefore, near the downstream end 152b of the HP-EGR passage 51, soot contained in the HP-EGR gas mixes with condensed water and oil in the blow-by gas, making it more likely to accumulate as a deposit. Accordingly, by making the EGR passage connected to the bent section 31X the HP-EGR passage 51, as in the above embodiment, the accumulation of soot and other deposits that tend to occur near the downstream end 152b of the HP-EGR passage 51 can be effectively suppressed.

[0085] Furthermore, EGR gas is introduced into the HP-EGR passage 51 before any fine particles such as soot are collected by the DPF 44. As a result, a relatively large amount of soot and other particles are introduced from the HP-EGR passage 51 to the intake passage 30, and these tend to accumulate. Therefore, as in the above embodiment, if the EGR passage connected to the bent section 31X is the HP-EGR passage 51, the accumulation of soot and other particles that tends to occur near the downstream end 152b of the HP-EGR passage 51 can be effectively suppressed.

[0086] Furthermore, the engine is not limited to a diesel engine. However, diesel engines have a higher content of soot and other contaminants in their exhaust gas and EGR gas compared to gasoline engines, making it easier for soot and other contaminants to accumulate in the intake passage 30. Therefore, by applying the above-described configuration of the intake passage 30 and HP-EGR passage 51 to a diesel engine, the accumulation of soot and other contaminants in the intake passage 30 can be effectively suppressed.

[0087] Furthermore, the specific configuration of other engines is not limited to those described above. For example, the number of cylinders in an engine is not limited to those described above. Also, the supercharger provided in engine E may be an electric supercharger. Also, engine E may be an engine that does not have a turbocharger 60 and an intercooler 33. Also, engine E may be an engine that has only one of the HP-EGR passage 51 and the LP-EGR passage 55. [Explanation of Symbols]

[0088] 1. Engine body 30 Intake passage 31X bent part 31Y (Rear (downstream passage) of the third intake pipe) 33 Intercooler 40 Exhaust passage 44 DPF (filter) 51 HP-EGR passage (EGR passage) 60 Supercharger 61 Compressor 62 Turbine 110 First intake manifold (upstream passage) 152 Intake side connection 152a opening 152b Downstream end (of intake side connection) 152f Projection E-engine

Claims

1. In an engine intake system comprising an engine body in which cylinders are formed, an intake passage through which intake air introduced into the engine body flows, and an exhaust passage through which exhaust gas discharged from the engine body flows, It includes an intake-side connection part connected to the intake passage, and an EGR passage that connects the intake passage and the exhaust passage and recirculates a portion of the exhaust gas to the intake passage as EGR gas. The intake passage comprises an upstream passage, a downstream passage located downstream of the upstream passage in the direction of intake air flow, and a bent portion that connects the downstream end of the upstream passage and the upstream end of the downstream passage while bending. The downstream passage has a shape that extends linearly along a predetermined first direction, The intake-side connection portion has a shape that extends along the first direction, and its downstream end in the direction of EGR gas flow is connected to the bent portion in a manner that opens toward the downstream side in the direction of intake gas flow in the downstream passage. When viewed along the first direction, the opening at the downstream end of the intake side connection is located inside the downstream side passage. The intake side connection portion has a projection that extends into the inner space of the bent portion, including the downstream end. The intake system for an engine is characterized in that the protruding portion protrudes to a position such that, with respect to the intake air that proceeds linearly along the first direction toward the downstream passage after passing through the bent portion, the EGR gas discharged from the opening at the downstream end merges with it from one side of the first direction.

2. In the intake system for the engine according to claim 1, An engine intake system characterized in that, when viewed along the first direction, the central axis of the downstream passage is located inside the opening at the downstream end of the intake connection.

3. In the intake system for the engine according to Claim 1, The intake device for an engine is characterized in that the protruding portion is positioned such that its outer circumferential surface is spaced apart from the inner circumferential surface of the bent portion over its entire circumference.

4. In the intake system for the engine according to claim 1, The intake device for an engine is characterized in that the bent portion has a U-shape that curves so as to bulge out to one side in the first direction.

5. In the intake system for the engine according to claim 1, The intake passage comprises a supercharger that supercharges the intake air, and an intercooler that is positioned downstream of the supercharger in the direction of intake air flow and cools the intake air. An engine intake system characterized in that the bent portion is provided downstream of the intercooler in the direction of intake airflow.

6. In the intake system for the engine according to claim 1, The exhaust passage is equipped with a filter for capturing particulate matter contained in the exhaust gas. An engine intake system characterized in that the EGR passage is connected to the portion of the exhaust passage upstream of the filter in the direction of exhaust gas flow.

7. In the intake system for the engine according to claim 1, An engine intake system characterized in that the engine body is a diesel engine that uses light oil as fuel.

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