Intake structure for multi-cylinder engine

Abstract

Provided is a technology that, in a multi-cylinder engine, uses a simple and reasonable structure and distributes substantially homogeneously diffused mixed gas of EGR gas to each intake port as fresh gas to be taken into each cylinder, to suppress deterioration of exhaust emission caused by a deviation in EGR rate. A fresh gas distribution chamber (20) and a gas collection chamber (30) are provided with a plurality of fresh gas distribution ports (25) that communicate with each intake port (12), the gas collection chamber (30) has a communication region (30B) provided with a first communication port (7a) that communicates with the fresh gas distribution chamber (20), a first mixing region (30A) provided with an air introduction port (31a) and an EGR gas introduction port (32a), and located at a position upstream of the communication region (30B) in a flow direction of mixed gas (M) of air (A) and EGR gas (R), and a second mixing region (30C) located at a position downstream of the communication region (30B) in the flow direction of the mixed gas (M).

Description

Technical Field

[0001] The present invention relates to an intake configuration for a multi-cylinder engine in which a portion of the exhaust gas is returned as EGR gas relative to the fresh air intake of multiple cylinders. Background Technology

[0002] In multi-cylinder engines that utilize EGR (Exhaust Gas Recirculation), when the EGR gas cannot diffuse sufficiently in the fresh air, the EGR rate, or the proportion of EGR gas returning to the fresh air, will deviate and vary between cylinders, resulting in increased NOx concentration in the exhaust gas and other deterioration of exhaust emissions.

[0003] As a conventional multi-cylinder engine, multi-cylinder engines equipped with mechanisms for promoting the diffusion of EGR gas in the fresh air are known (see, for example, Patent Document 1). For instance, in the multi-cylinder engine described in Patent Document 1, an exhaust gas dispersion chamber for introducing EGR gas is formed on the outer periphery of the connection portion connecting the air inlet pipe to the intake chamber. Furthermore, an outlet for the exhaust gas dispersion chamber is provided around the outlet of the air inlet pipe in the intake chamber. This structure prevents backflow of EGR gas caused by large pulsations in the fresh air and introduces EGR gas into the intake chamber in a manner that surrounds the introduced air, thereby promoting the mixing of air and EGR gas.

[0004] Patent Document 1: Japanese Patent Application Publication No. 10-131812

[0005] In the multi-cylinder engine described in Patent Document 1, air and EGR gas are introduced into an intake chamber with multiple fresh air distribution ports communicating with the intake ports of each of the multiple cylinders, and then merged to generate a gas mixture. Therefore, even if mixing is promoted, the gas mixture may still be drawn into each cylinder as fresh air during a stage of insufficient mixing. Furthermore, in this multi-cylinder engine, the intake chamber is formed as a space within an intake manifold installed in the cylinder head, and an exhaust gas dispersion chamber is formed around the connection between the air intake pipe and the intake chamber within this intake manifold. Therefore, the intake manifold has a complex structure, which is a significant factor contributing to increased cost. Summary of the Invention

[0006] In view of this actual situation, the main objective of the present invention is to provide a technology that, in a multi-cylinder engine with EGR, employs a simple and reasonable structure and distributes the mixture of EGR gas, which diffuses in a substantially homogeneous manner, as fresh gas to each intake port so that it enters each cylinder, thereby suppressing the deterioration of exhaust emissions caused by deviations in the EGR rate.

[0007] The first feature of the present invention is an intake structure for a multi-cylinder engine, wherein a portion of the exhaust gas is returned as EGR gas relative to the fresh air entering the multiple cylinders. The intake structure comprises: a fresh air distribution chamber having multiple fresh air distribution ports communicating with the intake ports of each of the multiple cylinders; and a gas collection chamber having an air inlet for introducing air, an EGR gas inlet for introducing EGR gas, and a first connecting port communicating with the fresh air distribution chamber. The gas collection chamber has: a connecting region having the first connecting port; a first mixing region having the air inlet and the EGR gas inlet, and located upstream of the connecting region along the flow direction of the air-EGR gas mixture; and a second mixing region located downstream of the connecting region along the flow direction of the mixed gas.

[0008] According to this structure, in a multi-cylinder engine that performs EGR, in addition to a fresh air distribution chamber for distributing fresh air to multiple fresh air distribution ports, a gas collection chamber is also provided, which is connected to the fresh air distribution chamber via a first connecting port and is used to introduce air and EGR gas. That is, in the gas collection chamber, by merging EGR gas with air, a mixture of air and EGR gas is generated. This mixture is introduced into the fresh air distribution chamber through the first connecting port and then distributed as fresh air to each fresh air distribution port, entering each cylinder from each intake port.

[0009] Furthermore, within the gas collection chamber, along the flow direction of the mixed gas, a first mixing region with an air inlet and an EGR gas inlet is provided upstream. Downstream of this first mixing region, a connecting region with a first connecting port is provided, and downstream of this connecting region, a second mixing region is provided. In the first mixing region upstream of the gas collection chamber, the newly generated mixed gas flows towards the connecting region. Conversely, in the second mixing region downstream of the gas collection chamber, the mixed gas that did not flow out of the first connecting port but passed through the connecting region experiences a reversal, thus flowing towards the connecting region again. Furthermore, in the connecting region located in the middle of the gas collection chamber, collisions occur between the mixed gas arriving from the first mixing region and the mixed gas arriving from the second mixing region.

[0010] Based on the above, in the second mixing zone of the gas collection chamber, the simple and reasonable structure of reversing the flow of the mixed gas promotes the mixing of EGR gas with air. Furthermore, in the connecting zone of the gas collection chamber, the simple and reasonable structure of colliding the mixed gas further promotes the mixing of EGR gas with air. Therefore, in the connecting zone of the gas collection chamber, a well-mixed mixture of air and EGR gas exists. Moreover, the well-mixed gas can be introduced from the first connecting port into the fresh air distribution chamber, and distributed as fresh air to each intake port, allowing it to enter each cylinder.

[0011] Therefore, according to the present invention, it is possible to provide a technology as follows: in a multi-cylinder engine with EGR, a simple and reasonable structure is adopted, and a mixture of EGR gas with approximately homogeneous diffusion is distributed as fresh gas to each intake port so that it enters each cylinder, thereby suppressing the deterioration of exhaust emissions caused by deviations in the EGR rate.

[0012] The second feature of the present invention is that the new gas distribution chamber is a concave internal space formed on the side of the cylinder head, and the gas collection chamber is the internal space of a collector installed on the side of the cylinder head in a state that covers the open portion of the new gas distribution chamber. The gas collection chamber has a partition plate that is sandwiched between the side of the cylinder head and the mounting surface of the collector, separates the new gas distribution chamber and the gas collection chamber, and has the first communication port formed thereon.

[0013] According to this structure, since the fresh air distribution chamber is formed as a concave internal space on the side of the cylinder head, the intake manifold, which is separate from the cylinder head, can be omitted. Furthermore, by simply covering the fresh air distribution chamber, a collector with a simple shape, which does not require the complex branching flow paths of the aforementioned intake manifold, can be installed on the side of the cylinder head, and the internal space of this collector can be used as a gas collection chamber. Moreover, by using only a simple structure—a partition plate with a first connecting port sandwiched between the side of the cylinder head and the mounting surface of the collector—the fresh air distribution chamber on the cylinder head side and the gas collection chamber on the collector side can be appropriately separated, and they can be connected through the first connecting port. Furthermore, by adopting this structure, the size, shape, and position of the first connecting port formed in the partition plate can be easily changed, thereby easily adjusting the mixing state of air and EGR gas in the gas collection chamber to a suitable level.

[0014] The third structural feature of the present invention is that the new gas distribution chamber is a concave internal space formed on the side of the cylinder head, and the gas collection chamber is installed in the internal space of a collector on the side of the cylinder head in a state that covers the open portion of the new gas distribution chamber. The collector is provided with a plurality of protrusions for inserting mounting bolts on the mounting portion of the side of the cylinder head, and the outer periphery of the plurality of protrusions is configured as a convex portion formed on the inner wall surface of the gas collection chamber for promoting mixing.

[0015] According to this structure, since a protrusion for promoting mixing is formed on the inner wall surface of the gas collection chamber where the EGR gas and air are combined to generate a mixed gas, the mixing of air and EGR gas in the mixed gas can be further promoted by the turbulence generated by the flow of the mixed gas along the protrusion.

[0016] Furthermore, since the gas collection chamber is the internal space of the collector that is installed in a state that covers the opening of the new gas distribution chamber which is a concave internal space formed on the side of the cylinder head, multiple protrusions for inserting mounting bolts can be provided at the mounting part of the collector relative to the side of the cylinder head, and the outer periphery of the protrusions can be used as a convex part formed on the inner wall surface of the gas collection chamber to promote mixing.

[0017] The fourth feature of the present invention is that it includes a second connection port that connects the second mixing region of the gas collection chamber to the new gas distribution chamber and is formed with a diameter smaller than that of the first connection port.

[0018] According to this structure, since a second connection port is provided that connects the second mixing region of the gas collection chamber to the fresh gas distribution chamber, gas exchange can be appropriately carried out between the second mixing region and the fresh gas distribution chamber through the second connection port. Therefore, it is possible to suppress the accumulation of EGR gas in the second mixing region in the gas collection chamber, which causes the flow of mixed gas arriving from the first mixing region through the connection region to be reversed. Furthermore, since the size of the second connection port connecting the second mixing region and the fresh gas distribution chamber is formed to have a smaller diameter than the size of the first connection port connecting the connection region and the fresh gas distribution chamber, it is possible for mixed gas with sufficient mixing in the connection region to flow into the fresh gas distribution chamber from the first connection port, and to suppress the inflow of insufficiently mixed mixed gas in the second mixing region into the fresh gas distribution chamber from the second connection port.

[0019] The fifth structural feature of the present invention is that the first mixing region is the region in which the mixed gas flows in a direction intersecting the central axis direction of the first communication port, and the second mixing region is the region located inside the communication region along the flow direction of the mixed gas in the first mixing region.

[0020] According to this structure, since the mixed gas flows from the first mixing region into the connecting region with the first connecting port in a direction intersecting the central axis of the first connecting port in the gas collection chamber, most of the mixed gas flowing from the first mixing region into the connecting region can flow smoothly into the second mixing region, located further inside the connecting region along the flow direction of the mixed gas, without changing its flow direction. This further promotes the mixing of air and EGR gas in the mixed gas. Furthermore, since the mixed gas flowing from the first connecting port into the fresh gas distribution chamber changes its flow direction through the first connecting port in the connecting region of the gas collection chamber, mixing is also promoted when its flow direction changes.

[0021] The sixth structural feature of the present invention is that the first mixing region is a region in which the EGR gas introduced from the EGR gas inlet flows along the flow direction of the mixed gas, and the fresh gas introduced from the air inlet merges with the flowing EGR gas in a direction that intersects with the flow direction of the mixed gas.

[0022] According to this structure, in the first mixing zone of the gas collection chamber, air can be made to merge with EGR gas flowing toward the connecting area with the first connecting port in a direction intersecting the flow direction of the EGR gas. That is, since the air and EGR gas merge in mutually intersecting directions, their mixing can be promoted. Furthermore, since the air with a flow rate greater than that of the EGR gas flows into the gas collection chamber from the air inlet in a direction intersecting the flow direction of the EGR gas toward the connecting area, the incoming air collides with the inner wall of the gas collection chamber immediately after merging with the EGR gas. The turbulence generated by this collision further promotes the mixing of the air and the EGR gas. Attached Figure Description

[0023] Figure 1 It is a 3D view of the cylinder head of a multi-cylinder engine.

[0024] Figure 2 This is a top sectional view of the cylinder head section of a multi-cylinder engine.

[0025] Figure 3 This is a side view of the intake structure of a multi-cylinder engine.

[0026] Figure 4 It is an exploded 3D view of the intake structure of a multi-cylinder engine.

[0027] Figure 5 It is a three-dimensional diagram showing the disassembled state of the collector and the separator.

[0028] Figure 6It is a three-dimensional diagram showing the assembled state of the collector and the separator.

[0029] Figure 7 This is a side view of the open section of the collector. Detailed Implementation

[0030] based on Figures 1 to 7 This invention describes an embodiment of the intake structure of a multi-cylinder engine.

[0031] like Figure 1 as well as Figure 2 As shown, the multi-cylinder engine of this embodiment (hereinafter referred to simply as "this engine") is configured as an inline four-cylinder diesel engine, comprising an engine body 1 having four cylinders 10 arranged in a straight line. Furthermore, this engine is configured to perform EGR, in which a portion of the exhaust gas E is returned as EGR gas R relative to the fresh air entering each cylinder 10.

[0032] A cylinder head 2 is provided on the upper surface of the engine body 1. For example... Figure 2 As shown, a concave internal space, namely a fresh air distribution chamber 20, is mainly formed on one side surface 2a of the cylinder head 2, extending along the arrangement direction of the plurality of cylinders 10 as viewed from above (hereinafter referred to as the "cylinder arrangement direction"). Furthermore, in this fresh air distribution chamber 20, four fresh air distribution ports 25, communicating with the air intake ports 12 of each of the four cylinders 10, are arranged to open outwards. Thus, since the fresh air distribution chamber 20 is formed as an internal space of the cylinder head 2, the separate intake manifold relative to the cylinder head 2 is omitted.

[0033] A collector 3 is installed on the side portion 2a of the cylinder head 2 on the side where the new air distribution chamber 20 is formed, covering the open portion of the new air distribution chamber 20. A gas collection chamber 30 is formed inside the collector 3. That is, the collector 3 is not configured with a complex branch flow path inside like the intake manifold, but is configured with a simple shape as a concave space with the gas collection chamber 30 formed on the side of the cylinder head 2.

[0034] On the other hand, four exhaust outlets 27 are formed on the side portion 2b of the cylinder head 2, communicating with the exhaust ports 14 of each of the plurality of cylinders 10. An exhaust manifold 8 is installed on the side portion 2b of the cylinder head 2 on the side where the exhaust outlets 27 are formed, in a state of connection with the exhaust outlets 27. An exhaust gas collection chamber 80 extending along the cylinder arrangement direction is formed inside the exhaust manifold 8.

[0035] Moreover, in such multi-cylinder engines, such as Figure 2As shown, air A and EGR gas R are introduced into the gas collection chamber 30 inside the collector 3 and merge, generating a mixture M of air A and EGR gas R in the gas collection chamber 30. This mixture M flows into the fresh air distribution chamber 20 inside the cylinder head 2, and is distributed as fresh air to each fresh air distribution port 25, and enters each cylinder 10 through each air intake port 12.

[0036] On the other hand, the exhaust gas E discharged from each cylinder 10 through each exhaust port 14 is introduced into the exhaust gas collection chamber 80 inside the exhaust manifold 8 through each exhaust outlet 27. Most of the exhaust gas E introduced into the exhaust gas collection chamber 80 is sent to the exhaust gas treatment section (not shown) through the exhaust gas outlet 81 opened in the exhaust gas collection chamber 80, and is released into the atmosphere after appropriate harmless treatment.

[0037] Additionally, a portion of the exhaust gas E introduced into the exhaust gas collection chamber 80 is extracted as EGR gas R through the EGR gas extraction pipe 82 provided in the exhaust manifold 8 and then into the EGR gas line 29. This extracted EGR gas R passes through the EGR gas inlet pipe 5 and the EGR control valve 6 (see reference). Figure 1 as well as Figure 3 The gas is introduced into the gas collection chamber 30 inside the collector 3.

[0038] This engine employs a simple and rational air supply structure. By using this structure, the mixture M, from which the EGR gas R diffuses approximately homogeneously, can be distributed as fresh air to each intake port 12 and enter each cylinder 10, thereby suppressing the deterioration of exhaust emissions caused by deviations in the EGR rate. The details of this intake structure are explained below.

[0039] like Figure 4 as well as Figure 5 As shown, a steel plate partition 7 is sandwiched between the side portion 2a of the cylinder head 2 where the new gas distribution chamber 20 is formed and the mounting portion 3a of the collector 3. The partition 7 has a first connecting port 7a and a second connecting port 7b with a diameter smaller than the first connecting port 7a. That is, the new gas distribution chamber 20, which forms part of the internal space of the cylinder head 2, and the gas collection chamber 30, which forms part of the internal space of the collector 3, are interconnected through the first connecting port 7a and the second connecting port 7b, and are separated from each other by the partition 7.

[0040] Furthermore, the size, shape, number, or location of the first connecting port 7a and the second connecting port 7b in the partition plate 7 can be appropriately changed. By changing them, the mixing state of air A and EGR gas R in the gas collection chamber 30 can be easily adjusted to a suitable state.

[0041] Additionally, a gasket 72 is sandwiched between the outer periphery of the partition plate 7 and the side portion 2a of the cylinder head 2 and the mounting portion 3a of the collector 3. Furthermore, if the partition plate 7 is made of a material that functions as a gasket, the additional gasket 72 can be omitted.

[0042] like Figure 2 As shown, the new gas distribution chamber 20, which forms the internal space of the cylinder head 2, is a space that extends along the cylinder arrangement direction. Therefore, the mixed gas M introduced from the first communication port 7a formed in the partition plate 7 in a direction orthogonal to the cylinder arrangement direction is distributed to each new gas distribution port 25 after the flow direction is changed in the direction along the cylinder arrangement direction.

[0043] like Figure 1 as well as Figure 3 As shown, the upper surface of the collector 3 is provided with a connection part 31 that connects to the air inlet pipe 4 and a connection part 32 that connects to the EGR control valve 6. Furthermore, mainly as shown... Figure 5 as well as Figure 7 As shown, on the top surface of the gas collection chamber 30, which forms the internal space of the collector 3, there are an air inlet 31a for introducing air A through the air inlet pipe 4 and an EGR gas inlet 32a for introducing EGR gas R through the air inlet pipe 4. Both the air inlet 31a and the EGR gas inlet 32a are formed as openings that introduce air A and EGR gas R downwards along a plumb line.

[0044] like Figure 2 As shown, the gas collection chamber 30, which forms the internal space of the collector 3, is configured to be adjacent to the outer side of the new gas distribution chamber 20 inside the cylinder head 2 and extend along the cylinder arrangement direction in the same way as the new gas distribution chamber 20. That is, in the gas collection chamber 30, air A and EGR gas R are respectively introduced vertically downwards from the air inlet 31a and the EGR gas inlet 32a. Furthermore, the introduced air A and EGR gas R collide with the bottom surface of the gas collection chamber 30 and move in the direction along the cylinder arrangement direction (in... Figure 2 After the direction of flow (represented by FM in the attached diagram) is changed, the gas flows in the gas collection chamber 30.

[0045] like Figure 7 As shown, in the collector 3, the EGR gas inlet 32a is adjacent to and open at one end of the gas collection chamber 30 along the cylinder arrangement direction. Additionally, in the collector 3, the air inlet 31a is adjacent to and open at the central portion side relative to the EGR gas inlet 32a along the cylinder arrangement direction. That is, in the gas collection chamber 30, the EGR gas R, which is vertically introduced from the EGR gas inlet 32a, flows in the direction along the cylinder arrangement direction (in... Figure 7The direction of flow is changed (indicated by the reference numeral FR in the attached diagram). Furthermore, relative to the EGR gas R flowing along the cylinder arrangement direction, the introduced air A flows downwards from the air inlet 31a in a vertical direction (in...). Figure 7 The gas flows in the direction indicated by the reference numeral FA in the attached diagram, and then the gas flows together to generate a mixed gas M. This mixed gas M then flows along the cylinder arrangement direction (in the direction indicated by the reference numeral FA in the attached diagram). Figure 7 (The direction indicated by FM in the attached diagram) circulates.

[0046] like Figure 2 As shown, a first connection port 7a, which connects the gas collection chamber 30 inside the collector 3 with the fresh gas distribution chamber 20 inside the cylinder head 2, is provided on a partition plate 7 parallel to the cylinder arrangement direction when viewed from above. Therefore, the flow direction of the mixed gas M in the gas collection chamber 30 is orthogonal to the central axis A7a of the first connection port 7a and along the cylinder arrangement direction.

[0047] like Figure 2 as well as Figure 7 As shown, the gas collection chamber 30 inside the collector 3 has a connecting region 30B, a first mixing region 30A, and a second mixing region 30C. The connecting region 30B has a first connecting port 7a provided by the partition plate 7. The first mixing region 30A has an air inlet 31a and an EGR gas inlet 32a, and is located upstream of the connecting region 30B along the flow direction FM of the mixed gas M. Furthermore, the second mixing region 30C is located downstream of the connecting region 30B along the flow direction FM of the mixed gas M. That is, in the gas collection chamber 30, the first mixing region 30A, the connecting region 30B, and the second mixing region 30C are sequentially arranged from the upstream side along the flow direction FM of the mixed gas M.

[0048] In the first mixing region 30A located at the upstream side of the gas collection chamber 30, EGR gas R introduced from the EGR gas inlet 32a flows along the flow direction FM of the mixed gas M, i.e., the cylinder arrangement direction. Meanwhile, air A introduced from the air inlet 31a merges with the flowing EGR gas R in a downward plumb line FA, intersecting the flow direction FM of the mixed gas M, i.e., the cylinder arrangement direction, to generate the mixed gas M. Then, the newly generated mixed gas M flows towards the connecting region 30B along the cylinder arrangement direction FM, which is approximately orthogonal to the direction of the central axis A7a of the first connecting port 7a.

[0049] That is, since air A and EGR gas R merge in mutually intersecting directions, their mixing is promoted. Furthermore, air A, with a flow rate greater than that of EGR gas R, flows into the gas collection chamber 30 from the air inlet 31a in a direction FA intersecting the flow direction FM of EGR gas R towards the connecting region 30B, and merges with EGR gas R. Therefore, immediately after merging with EGR gas R, the incoming air A collides with the inner wall of the gas collection chamber 30, and the turbulence generated by this collision further promotes the mixing of air A and EGR gas R.

[0050] Furthermore, in the first mixing region 30A, since the amount of air A introduced is greater than the amount of EGR gas R introduced, the EGR gas R is entrained near the top. Consequently, in the mixed gas M facing the connecting region 30B, the concentration of EGR gas R increases towards the top.

[0051] In the connecting region 30B located in the middle of the gas collection chamber 30, a first connecting port 7a is provided on a partition plate 7 parallel to the cylinder arrangement direction as viewed from above. Accordingly, a portion of the mixed gas M arrives from the first mixing region 30A along the cylinder arrangement direction, i.e., the flow direction FM. This arriving portion of the mixed gas M does not flow out from the first connecting port 7a, which has a central axis A7a orthogonal to its flow direction, toward the new gas distribution chamber 20, but instead flows through the connecting region 30B toward the second mixing region 30C.

[0052] Furthermore, as described above, in the mixed gas M flowing from the first mixing region 30A to the connecting region 30B, the concentration of EGR gas R increases towards the top. Therefore, in order to actively feed the EGR gas R from the mixed gas M into the second mixing region 30C, the aforementioned first connecting port 7a can be positioned at the bottom. Additionally, by positioning the first connecting port 7a at the bottom, the formation of deposits caused by the retention of EGR gas R near the bottom can be appropriately suppressed.

[0053] The mixed gas M passing through the connecting region 30B reaches the second mixing region 30C located at the downstream end of the gas collection chamber 30. The mixed gas M is deflected and re-forms a flow toward the connecting region 30B. Therefore, in the connecting region 30B, a collision occurs between the mixed gas M arriving from the first mixing region 30A and the mixed gas M arriving from the second mixing region 30C. The mixed gas M after the collision flows out from the first connecting port 7a into the fresh gas distribution chamber 20.

[0054] By forming a flow of mixed gas M as described above in the gas collection chamber 30, the mixing of EGR gas R with air A can be promoted in the second mixing region 30C of the gas collection chamber 30 using a simple and reasonable structure that reverses the flow of mixed gas M. Furthermore, in the connecting region 30B of the gas collection chamber 30, the mixing of EGR gas R with air A can be further promoted using a simple and reasonable structure that causes the mixed gas M to collide. Therefore, in the connecting region 30B of the gas collection chamber 30, there exists a well-mixed mixture of air A and EGR gas R, gas M. Moreover, the well-mixed gas M flows from the first connecting port 7a of the partition plate 7 into the fresh air distribution chamber 20, where it is distributed as fresh air to each air inlet 12 and enters each cylinder 10.

[0055] The second mixing region 30C is located further inside the connecting region 30B than the first mixing region 30A, along the flow direction FM of the mixed gas M in the first mixing region 30A, i.e., the cylinder arrangement direction. Accordingly, in the gas collection chamber 30, the mixed gas M flowing from the first mixing region 30A to the connecting region 30B along the cylinder arrangement direction (flow direction FM) can effectively flow towards the second mixing region 30C without changing its flow direction. Thus, as much mixed gas M as possible flows into the second mixing region 30C, thereby further promoting the mixing of air A and EGR gas R in the mixed gas M.

[0056] Furthermore, in the connecting region 30B, the mixed gas M flows out from the first connecting port 7a towards the fresh gas distribution chamber 20 after its flow direction is changed at approximately a right angle. Even with this change in flow direction, mixing in the mixed gas M is still promoted.

[0057] Furthermore, although the shape of the first connecting port 7a can be appropriately set to be circular, elliptical, rectangular, etc., in this embodiment, in order to maximize the flow path area and generate homogeneous flow, the shape of the first connecting port 7a is formed as an elongated orifice. Accordingly, the flow velocity of the mixed gas M flowing from the first connecting port 7a into the fresh gas distribution chamber 20 is reduced as much as possible and made homogeneous, thereby preventing deflection of the flow to each fresh gas distribution port 25 in the fresh gas distribution chamber 20.

[0058] Multiple protrusions 22 and 36 are provided on the outer periphery of the opening portion of the fresh air distribution chamber 20 at the side surface 2a of the cylinder head 2 and on the outer periphery of the opening portion of the gas collection chamber 30 at the mounting surface 3a of the collector 3. The cylinder head 2 and the collector 3 are joined together by these multiple protrusions 22 and 36. Furthermore, the outer periphery of these protrusions 22 and 36 are formed as inwardly projecting protrusions 21 and 35 on the respective inner wall surfaces (bottom and top surfaces) of the fresh air distribution chamber 20 and the gas collection chamber 30 to promote mixing. That is, in the gas collection chamber 30 and the fresh air distribution chamber 20, the mixed gas M flows along the cylinder arrangement direction between the bottom and top surfaces where the multiple protrusions 21 and 35 are formed. Accordingly, by the mixed gas M flowing near the protrusions 21 and 35, turbulence is generated, and this turbulence promotes the mixing of air A and EGR gas R in the mixed gas M.

[0059] Because the flow of mixed gas M from the first mixing region 30A through the connecting region 30B is reversed in the second mixing region 30C of the gas collection chamber 30, if the original state is maintained, for example, EGR gas R will stagnate near the bottom, thus easily forming a buildup. Therefore, a second connecting port 7b with a smaller diameter than the first connecting port 7a is opened on the lower side of the portion of the partition plate 7 adjacent to the second mixing region 30C, and the second mixing region 30C is connected to the fresh gas distribution chamber 20 through this second connecting port 7b. That is, since the second mixing region 30C and the fresh gas distribution chamber 20 are connected through the small-diameter second connecting port 7b, gas exchange is appropriately carried out between the second mixing region 30C and the fresh gas distribution chamber 20 through the second connecting port 7b. Accordingly, the stagnation of EGR gas R in the second mixing region 30C is suppressed, and the formation of a buildup can be appropriately prevented. In addition, because the diameter of the second connection port 7b is smaller than that of the first connection port 7a, it is possible to appropriately suppress the inflow of insufficiently mixed gas M present in the second mixing region 30C from the second connection port 7b into the fresh gas distribution chamber 20.

[0060] [Other Implementation Methods]

[0061] Other embodiments of the present invention will be described below. Furthermore, the structures of the embodiments described below are not limited to individual application, but can also be combined with the structures of other embodiments.

[0062] (1) In the above embodiment, although the engine is configured as an inline four-cylinder diesel engine, the number of cylinders, configuration and type of fuel can be appropriately changed.

[0063] (2) In the above embodiment, by forming the fresh air distribution chamber 20 as the internal space of the cylinder head 2, and providing a plurality of fresh air distribution ports 25 communicating with each air intake port 12 in the fresh air distribution chamber 20, the provision of the intake manifold is omitted. However, it is also possible to form a plurality of fresh air distribution ports on the side portion 2a of the cylinder head 2, and install the intake manifold in a state of being connected to these fresh air distribution ports.

[0064] (3) In the above embodiment, a collector 3 is mounted on a side portion 2a of the cylinder head 2 on the side where the fresh air distribution chamber 20 is formed, with a partition plate 7 having a first communication port 7a, etc., and a gas collection chamber 30 is formed inside the collector 3, which communicates with the fresh air distribution chamber 20 via the first communication port 7a. However, the structure of the first communication port 7a and the gas collection chamber 30 can be appropriately modified. For example, the gas collection chamber can be arranged separately from the fresh air distribution chamber, and they can be connected by a connecting pipe, with the connection port of the connecting pipe relative to the gas collection chamber serving as the first communication port.

[0065] (4) In the above embodiment, the outer periphery of the plurality of protrusions 36 provided at the outer periphery of the opening of the gas collection chamber 30 is formed as protrusions 21, 35 protruding inward in each bottom and top surface of the gas collection chamber 30 to promote mixing. However, such protrusions for promoting mixing can be omitted or changed appropriately. For example, the protrusions can be arranged at positions suitable for promoting mixing, independent of the protrusions 36.

[0066] (5) In the above embodiment, in the first mixing region 30A, the mixed gas M is arranged along the cylinder arrangement direction, i.e., the flow direction FM, which is orthogonal to the direction of the central axis A7a of the first connecting port 7a, and the second mixing region is set to be a region located inside the connecting region 30B along the flow direction FM of the mixed gas M in the first mixing region 30A. However, the intersection angle of the flow direction FM of the mixed gas M in the first mixing region 30A with the direction of the central axis A7a of the first connecting port 7a can be appropriately changed within a range that can appropriately suppress most of the mixed gas M from the first mixing region 30A to the connecting region 30B from flowing directly out of the first connecting port 7a.

[0067] (6) In the above embodiment, the configuration is such that, in the first mixing region 30a, while the EGR gas R introduced from the EGR gas inlet 32a flows along the flow direction FM of the mixed gas M, the fresh air introduced from the air inlet 31a merges with the EGR gas R in a direction FA orthogonal to the flow direction FM of the mixed gas M. However, the merging state of the EGR gas R and the air A in the first mixing region 30a can also be appropriately changed.

[0068] Industrial availability

[0069] This invention can be applied to multi-cylinder engines in which a portion of the exhaust gas is returned as EGR gas relative to the fresh air entering multiple cylinders.

[0070] Explanation of reference numerals in the attached figures:

[0071] 2…Cylinder head; 2a…Side section; 2b…Side section; 3…Collector; 3a…Mounting surface; 7…Divider; 7a…First connecting port; 7b…Second connecting port; 10…Cylinder; 12…Inlet; 20…Fresh air distribution chamber; 21…Protrusion; 25…Fresh air distribution port; 30…Gas collection chamber; 30A…First mixing zone; 30B…Connecting zone; 30C…Second mixing zone; 30a…First mixing zone; 31a…Air inlet; 32a…EGR gas inlet; A…Air; E…Exhaust gas; M…Mixed gas; R…EGR gas.

Claims

1. An intake configuration of a multi-cylinder engine that causes a portion of exhaust gas to flow back as EGR gas with respect to fresh air that enters a plurality of cylinders, wherein the intake configuration is provided with: a fresh air distribution chamber that is provided with a plurality of fresh air distribution ports that communicate with respective intake ports of the plurality of cylinders; and a gas collection chamber that is provided with an air introduction port through which air is introduced, an EGR gas introduction port through which the EGR gas is introduced, and a first communication port that communicates with the fresh air distribution chamber, the first communication port being disposed at a position that is on a downstream side from any one of the air introduction port and the EGR gas introduction port in a flow direction of a mixture gas of the air and the EGR gas and at a position that is at a middle of the gas collection chamber.

2. The intake configuration of the multi-cylinder engine according to claim 1, wherein the fresh air distribution chamber is provided at a side surface portion of a cylinder head, and the gas collection chamber is provided at a collector that is attached to a position of the side surface portion of the cylinder head that corresponds to the fresh air distribution chamber.

3. The intake configuration of the multi-cylinder engine according to claim 2, wherein a partition plate that is formed with the first communication port is further provided between the fresh air distribution chamber and the gas collection chamber.

4. The intake configuration of the multi-cylinder engine according to any one of claims 1 to 3, wherein the intake configuration is further provided with a second communication port that is disposed at a position that is on a downstream side from the first communication port in the flow direction of the mixture gas and that is formed to have a smaller diameter than the first communication port.

5. The intake configuration of the multi-cylinder engine according to any one of claims 1 to 3, wherein the first communication port is a long hole.

6. The intake configuration of the multi-cylinder engine according to claim 4, wherein the first communication port is a long hole.

7. The intake configuration of the multi-cylinder engine according to any one of claims 1 to 3, wherein the gas collection chamber extends along a cylinder arrangement direction in which the plurality of cylinders are arranged, and the first communication port is disposed at a position that is at a middle of the gas collection chamber in the cylinder arrangement direction.

8. The intake configuration of the multi-cylinder engine according to claim 4, wherein the gas collection chamber extends along a cylinder arrangement direction in which the plurality of cylinders are arranged, and the first communication port is disposed at a position that is at a middle of the gas collection chamber in the cylinder arrangement direction.

9. The intake configuration of the multi-cylinder engine according to claim 5, wherein the gas collection chamber extends along a cylinder arrangement direction in which the plurality of cylinders are arranged, and the first communication port is disposed at a position that is at a middle of the gas collection chamber in the cylinder arrangement direction.

10. The intake configuration of the multi-cylinder engine according to claim 6, wherein the gas collection chamber extends along a cylinder arrangement direction in which the plurality of cylinders are arranged, and the first communication port is disposed at a position that is at a middle of the gas collection chamber in the cylinder arrangement direction. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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