JP6544381B2 - Multi-cylinder engine intake system - Google Patents

Description

  The technology disclosed herein relates to a multi-cylinder engine intake system.

  Patent Document 1 discloses an example of a multi-cylinder engine. Specifically, this engine (a spark-ignition direct injection engine with a supercharger) has a plurality of cylinders provided in a row, two intake ports respectively communicating with each of the plurality of cylinders, and two intake ports And an intake passage connected to each of the intake valves, and in a predetermined operation region, the closing timing of the intake valve is set during the compression stroke (so-called "slow closing" of the intake valve) There is. According to this configuration, since the intake valve remains open immediately after the transition from the intake stroke to the compression stroke, a portion of the gas trapped in the cylinder is taken to the intake side (specifically, as the piston rises). Is designed to blow back to the intake port).

Japanese Patent Application Laid-Open No. 2003-027977

  In recent years, a negative overlap period in which both the intake valve and the exhaust valve close with the exhaust top dead center in an operation region where fuel efficiency is prioritized, for example, in view of securing in-cylinder temperature and reduction of pump loss. The internal EGR gas is confined in the cylinder by providing (hereinafter referred to as “NVO”), and a mirror cycle is realized using the late closing as described in Patent Document 1 along with the setting of NVO. It is being considered.

  However, when the setting of NVO and the mirror cycle of the late closing method are used in combination, the internal EGR gas trapped in the cylinder is blown to the intake side as in the case of Patent Document 1 immediately after the transition from the intake stroke to the compression stroke. I will be back. At that time, depending on the layout of the surge tank, the internal EGR gas blown back to the intake side may flow back to the surge tank.

  As a result of intensive studies, the inventors of the present invention have found that differences in cylinders can occur in the in-cylinder state due to the gas blown back to the surge tank.

  That is, for example, in the case of a four-cylinder engine, the gas blown back to the surge tank from the cylinder located inside in the cylinder row direction like the second and third cylinders can be diffused to both sides in the cylinder row direction. Although gas can be blown back from cylinders located at both ends in the cylinder row direction, such as No. 1 and No. 4 cylinders, it can be diffused sufficiently because there is only a place to go to one side in the cylinder row direction. I can not do it.

  Therefore, in the surge tank, in the space near the upstream end of the independent passage leading to the first cylinder and the fourth cylinder, the gas is compared with the space near the upstream end of the independent passage leading to the second cylinder and the third cylinder. Because the diffusivity of the cylinder is poor, the gas blown back from each cylinder tends to stay.

  Then, the inventors of the present invention realized that the distribution of the internal EGR gas becomes uneven between the inner side and the end side of the surge tank, and as a result, a difference between cylinders can occur in the in-cylinder state.

  The technique disclosed herein has been made in view of such a point, and an object thereof is to provide an intake system for a multi-cylinder engine, in which an inter-cylinder state caused by gas blown back to a surge tank is generated. It is to reduce the difference.

  The technology disclosed herein includes at least three or more cylinders arranged in a row, a plurality of intake ports communicating with each of the plurality of cylinders, and an intake connected to each of the plurality of intake ports. And an intake system for a multi-cylinder engine having a passage.

  The intake passages are connected to a plurality of independent passages respectively connected to each of the plurality of intake ports, and an upstream end of each of the plurality of independent passages is lined up in a row according to the order of arrangement of corresponding cylinders. And a surge tank.

Then, among the plurality of cylinders, the cylinder located on the end side in the cylinder row direction is referred to as an end-side cylinder, while the cylinder adjacent to the end-side cylinder inside in the cylinder row direction is referred to as a center-side cylinder Then, in the surge tank, a portion facing the section from the upstream end of the independent passage corresponding to the end-side cylinder among the plurality of independent passages to the upstream end portion of the independent passage corresponding to the center-side cylinder is the returned blown from the central side cylinder to the surge tank gas, guide surface for guiding a direction that does not close the upstream end portion of the independent passages corresponding to said end side cylinder is provided, in the surge tank, wherein A portion of the plurality of independent passages facing the upstream end of the independent passage corresponding to the end side cylinder is inclined toward the opposite side with respect to the plurality of cylinders as it goes inward in the cylinder row direction On the part where the guide surface is extended to the end side in the cylinder row direction, adjacent to the inner side in the cylinder row direction with respect to the inclined surface, and from the end side cylinder to the surge tank A second guide surface is formed to guide the blown-back gas toward the central cylinder .

  For example, in the low load operation range where fuel efficiency is prioritized (hereinafter referred to as "fuel efficiency range"), the confinement of the internal EGR gas may be used in combination with the late closing of the intake valve. In that case, the gas blown back in the compression stroke may flow back to the surge tank through the intake port and the independent passage. At that time, although the gas blown back to the surge tank from the center side cylinder can be diffused to both sides in the cylinder row direction, the gas blown back from the end side cylinder is on one side in the cylinder row direction. Because there is only a place to go, it can not be diffused enough.

  Therefore, in the surge tank, the space near the upstream end of the independent passage corresponding to the end-side cylinder is less diffusive than the space near the upstream end of the independent passage corresponding to the center-side cylinder. It becomes easy to retain the returned gas. As a result, the gas blown back from both the end-side cylinder and the center-side cylinder stagnates at the end of the surge tank, which may cause unevenness in the gas distribution.

  However, according to the above configuration, the guide surface disposed in the surge tank is a direction (for example, an end where the gas blown back from the central cylinder does not approach the upstream end of the independent passage corresponding to the end cylinder). It guides in the direction away from the side cylinder). As a result, the amount of gas staying at the end side of the surge tank (in particular, the gas staying due to the blowback from the center side cylinder) can be reduced, and the distribution of the gas can be equalized.

  Therefore, the difference between cylinders in the in-cylinder state can be reduced in an operation region where blowback of gas is assumed, such as a fuel consumption region.

Further, according to the above configuration, the gas blown back from the end-side cylinder flows toward the opposite side with respect to the plurality of cylinders and then collides with the inclined surface formed in the surge tank. In consideration of the flow direction of the gas and the inclination direction of the inclined surface, the gas that has collided with the inclined surface is guided inward in the cylinder row direction. The gas guided by the inclined surface is subsequently guided by the second guide surface towards the central cylinder. As a result, the amount of gas staying on the end side of the surge tank (in particular, the gas staying due to the blowback from the end cylinders) can be reduced, and the distribution of the gas can be equalized.

In this way, not only the gas blown back from the center side cylinder but also the gas blown back from the end side cylinder, by suppressing its retention, in the operation region where the blow back of gas is assumed, such as the fuel consumption region, It is advantageous in reducing the inter-cylinder difference in the in-cylinder state.

  In addition, the plurality of intake ports include SCV ports configured such that the flow rate of the passing gas is adjusted via a swirl control valve for each of the plurality of cylinders, and the guide surface is the surge tank In the independent passage corresponding to the central side cylinder, it may be disposed at a position facing the upstream end of the independent passage connected to the intake port configured as a non-SCV port.

  Here, the SCV port includes both a configuration in which a swirl control valve (hereinafter referred to as "SCV") is disposed on the intake port and a configuration in which the SCV is disposed on an independent passage leading to the intake port. . Also, "non-SCV port" refers to an intake port other than an SCV port.

  For example, in the above-described fuel consumption region, the SCV may be closed to promote gas mixing. In this case, when the SCV port is closed, when the gas blows back, a strong jet may be generated through the non-SCV port.

  Therefore, as described above, by disposing a guide surface at a portion facing the upstream end of the independent passage related to the non-SCV port, the gas blown back from the center side cylinder can be guided more reliably. Becomes possible. This is effective in reducing the inter-cylinder difference in the in-cylinder state.

  Further, the multi-cylinder engine is configured as an in-line four-cylinder engine in which the plurality of intake ports are provided two by two for each of the plurality of cylinders, and the plurality of intake ports are of the plurality of cylinders. Each of the plurality of cylinders comprises a first port and a second port adjacent to the first port in the cylinder row direction and configured as the SCV port, and the plurality of cylinders are viewed from one side in the cylinder row direction. The first port, the second port, the second port, the third port, and the fourth port can be referred to as No. 1, No. 2, No. 3, and No. 4, respectively. The ports are arranged side by side in the same order, and the guide surface is a portion of the surge tank facing the upstream end of the independent passage connected to the first port leading to the second cylinder, and the third Lead to the cylinder Serial is arranged in both the portion facing the upstream end of the connected independent passages to the first port may be.

  According to this configuration, in the so-called intake two-port four-cylinder engine, it is possible to reduce the difference between in-cylinder cylinders due to the blowback of gas.

Further, according to the above configuration, since the first port and the second port are arranged in the same order in each cylinder, for example, the mounting structure of parts such as the injection valve and the spark plug can be used in all four cylinders. It can be unified .

Also, the intake passage, the downstream end portion is connected to the surge tank has an upstream passage for introducing the gas to the surge tank, the second guide surface, the cylinder axis of the surge tank When viewed in the direction, it is inclined to protrude toward the plurality of cylinders as it goes inward in the cylinder row direction, and the downstream end of the upstream side passage is the second in the cylinder row direction. The gas may be directed to the side of the plurality of cylinders while being connected to a portion closer to the end side cylinder than the guide face of the above, and flowing through the downstream end portion of the upstream side passage.

  According to this configuration, the upstream passage directs the gas flowing in the upstream passage to the plurality of cylinders. Then, the gas introduced into the surge tank from the upstream passage flows away from both of the aforementioned inclined surface and the second guide surface. This makes it difficult for the gas introduced from the upstream passage to be guided toward the central cylinder.

  Moreover, the second guide surface is formed to protrude toward the plurality of cylinders. As a result, when viewed in the cylinder axial direction, the surge tank narrows a portion near the second guide surface. In consideration of the increase in flow path resistance at the narrowed portion and the fact that the upstream passage is connected to a portion closer to the end cylinder than the second guide surface, it is introduced into the surge tank from the upstream passage. Gas (for example, gas mainly composed of fresh air) tends to flow closer to the end side cylinder. The gas introduced toward the end side cylinder can flush out the gas (for example, the gas mainly composed of the internal EGR gas) accumulated at the end side of the surge tank.

  Thus, while suppressing the retention of the gas blown back from each cylinder on the end side of the surge tank, by promoting the introduction of the gas introduced from the upstream passage, the inter-cylinder difference in the in-cylinder state can be reduced. It is advantageous to reduce.

  The multi-cylinder engine further includes a supercharger configured to supercharge the gas introduced to each of the plurality of cylinders in an operation region on a high load side of a predetermined load, and the multi-cylinder engine includes A downstream end is connected to the surge tank via an inlet, and a supercharging passage is provided in which the supercharger is interposed, and the inlet is a cylinder row central portion of the surge tank. The supercharger is open at a larger diameter than the intake port, and the upstream passage is in an operation area on a lower load side than the predetermined load when the operating condition of the multi-cylinder engine is lower than the predetermined load. It may be configured as a bypass passage that guides the gas to bypass the above and reach the surge tank.

  In the low load to medium load operation range such as the above-described fuel consumption range, the effect of the blowback of gas becomes relatively large because the amount of introduction of new air is small. In such an operation region, natural intake is realized by the bypass passage, and by configuring the bypass passage by the above-described upstream side passage, the inter-cylinder state of the cylinder due to the blowback of gas is obtained. The difference can be reduced.

  On the other hand, in the high load side operation region, the influence of the blowback of the gas becomes relatively small because the amount of introduction of fresh air is large. In such an operating range, supercharging using a supercharging passage is realized. Since the effect of blowback of gas is small, the supercharging passage can be laid out simply.

  As described above, according to the intake system of the multi-cylinder engine, the difference between cylinders in the in-cylinder state caused by the gas blown back to the surge tank can be reduced.

FIG. 1 is a schematic view illustrating the configuration of a multi-cylinder engine. FIG. 2 is a perspective view showing a configuration of a multi-cylinder engine with a part thereof omitted. FIG. 3 is a plan view schematically showing the configuration around four cylinders. FIG. 4 is a perspective view showing the entire configuration of the intake device as viewed from the front side. FIG. 5 is a perspective view showing the entire configuration of the intake device as viewed from the rear side. FIG. 6 is a cross-sectional view showing the passage structure on the turbocharger side. FIG. 7 is a longitudinal sectional view showing the passage structure on the turbocharger side. FIG. 8 is a perspective view showing a longitudinal cross section around the surge tank. FIG. 9 is a perspective view showing a vertical cross section different from FIG. FIG. 10 is a view showing a passage structure related to the bypass passage as viewed from the front side. FIG. 11 is a view showing a passage structure related to the bypass passage as viewed from the rear side. FIG. 12 is a view showing a passage structure related to the bypass passage from above. FIG. 13 is a longitudinal sectional view showing a connection structure of the surge tank and the bypass passage. FIG. 14 is a cross-sectional view showing a connection structure of a surge tank and a bypass passage. FIG. 15 is a view showing the flow passage structure around the surge tank as viewed from the upper side. FIG. 16 is a view showing a flow path structure around the surge tank as viewed from the front side. FIG. 17 is a cross-sectional view showing a structure related to the guide portion. FIG. 18 is a diagram comparing the cross-sectional area of the portion narrowed by the left guide portion with the cross-sectional area of the intake port inlet leading to the fourth cylinder.

  Hereinafter, an embodiment of a multi-cylinder engine intake system will be described in detail based on the drawings. The following description is an example. FIG. 1 is a diagram illustrating an engine 1 configured with an intake system of a multi-cylinder engine disclosed herein. Moreover, FIG. 2 is a perspective view which partially abbreviate | omits and shows the structure, and FIG. 3 is a top view which shows roughly the structure of four cylinders 11 periphery.

  The engine 1 is a gasoline engine (in particular, a four-stroke internal combustion engine) mounted on an FF type vehicle and, as shown in FIG. 1, has a mechanically driven supercharger (so-called supercharger) 34 It has composition.

  Further, as shown in FIG. 3, the engine 1 according to the present embodiment includes four cylinders (cylinders) 11 arranged in a row, and the four cylinders 11 are arranged in the vehicle width direction. It is configured as a so-called in-line four-cylinder horizontal engine mounted in a posture. Thus, in the present embodiment, the longitudinal direction of the engine, which is the arrangement direction (cylinder row direction) of the four cylinders 11, substantially coincides with the vehicle width direction, and the transverse direction of the engine substantially coincides with the longitudinal direction .

  Hereinafter, unless otherwise specified, the front side means one side in the engine width direction (the front side in the vehicle longitudinal direction), the rear side the other side in the engine width direction (the rear side in the vehicle longitudinal direction), and the left side One side (left side in the vehicle width direction and the engine front side) of the direction (cylinder row direction) is the right side is the other side (right side in the vehicle width direction) of the engine longitudinal direction (cylinder row direction) Point to the rear).

  Further, in the following description, the upper side refers to the upper side in a state where the engine 1 is mounted on a vehicle (hereinafter, also referred to as “vehicle mounted state”), and the lower side refers to the lower side in the vehicle mounted state.

(Schematic configuration of engine)
The engine 1 is configured to have a front intake air and a rear exhaust system. That is, as shown in FIG. 3, the engine 1 is disposed on the engine body 10 having four cylinders 11 (only one cylinder is shown in FIG. 1) and on the front side of the engine body 10 An intake passage 30 in communication with each cylinder 11 and an exhaust passage 50 disposed on the rear side of the engine body 10 and in communication with each cylinder 11 via an exhaust port 19 are provided.

  In the intake passage 30 according to the present embodiment, a plurality of passages for guiding gas, devices such as the turbocharger 34 and the intercooler 36, and a bypass passage 40 bypassing these devices are combined into a unitized intake Configure the device.

  The engine body 10 is configured to burn a mixture of gas and fuel supplied from the intake passage 30 in each cylinder 11 according to a predetermined combustion order. Specifically, the engine body 10 has a cylinder block 12 and a cylinder head 13 mounted thereon.

  Four cylinders 11 are formed in the cylinder block 12. The four cylinders 11 are arranged in a row along the central axis direction of the crankshaft 15 (that is, the cylinder row direction). The four cylinders 11 are each formed in a cylindrical shape, and central axes (hereinafter referred to as "cylinder axes") of the cylinders 11 extend parallel to one another and perpendicular to the cylinder row direction. Hereinafter, the four cylinders 11 shown in FIG. 3 may be referred to as No. 1 cylinder 11 A, No. 2 cylinder 11 B, No. 3 cylinder 11 C, and No. 4 cylinder 11 D sequentially from the right side along the cylinder row direction.

  A piston 14 is slidably inserted into each cylinder 11. The piston 14 is connected to the crankshaft 15 via a connecting rod 141. The piston 14 defines the combustion chamber 16 together with the cylinder 11 and the cylinder head 13.

  The ceiling surface of the combustion chamber 16 has a so-called pent roof shape, and is constituted by the lower surface of the cylinder head 13. The engine 1 is configured such that the ceiling surface of the combustion chamber 16 is lower than in the conventional case in order to increase the geometric compression ratio. The pent roof shape of the ceiling surface is almost flat.

  In the cylinder head 13, two intake ports 17 and 18 are formed for each cylinder 11. The two intake ports 17 and 18 communicate with the combustion chamber 16, and for each cylinder 11, a first port 17 and a second port 18 adjacent to the first port 17 in the cylinder row direction Have. In any of the first cylinder 11A to the fourth cylinder 11D, the first port 17 and the second port 18 are arranged in the same order. Specifically, as shown in FIG. 3, in each cylinder 11, the second port 18 and the first port 17 are arranged in order from the right side along the cylinder row direction.

  The upstream ends of the intake ports 17 and 18 respectively open to the outer surface (mounting surface) 10 a of the engine body 10, and the downstream end of the intake passage 30 is connected. On the other hand, the downstream end of each of the ports 17 and 18 respectively opens to the ceiling surface of the combustion chamber 16.

  In the following, the first port leading to the first cylinder 11A is given "17A" instead of "17" and the second port leading to the cylinder 11A is given "18A" instead of "18" There is. The same applies to the second cylinder 11B to the fourth cylinder 11D. For example, the second port leading to the third cylinder 11C may be given "18C" instead of "18".

  Also, the two intake ports 17, 18 include SCV ports configured such that, for each cylinder 11, the flow rate of the passing gas is throttled through a swirl control valve (SCV) 80. In the present embodiment, the second port 18 described above is configured as an SCV port.

  An intake valve 21 is disposed in each of the two intake ports 17 and 18. The intake valve 21 opens and closes between the combustion chamber 16 and each of the intake ports 17 and 18. The intake valve 21 is opened and closed at a predetermined timing by an intake valve mechanism.

  In this configuration example, as shown in FIG. 1, the intake valve operating mechanism has an intake electric motor VVT (Variable Valve Timing) 23 which is a variable valve operating mechanism. The intake electric motor VVT 23 is configured to continuously change the rotational phase of the intake camshaft within a predetermined angular range. As a result, the opening timing and closing timing of the intake valve 21 change continuously. The intake valve mechanism may have a hydraulic VVT instead of the electric VVT.

  The cylinder head 13 is also provided with two exhaust ports 19, 19 for each cylinder 11. The two exhaust ports 19 19 communicate with the combustion chamber 16 respectively.

  An exhaust valve 22 is disposed in each of the two exhaust ports 19, 19. The exhaust valve 22 opens and closes between the combustion chamber 16 and each of the exhaust ports 19, 19. The exhaust valve 22 is opened and closed at a predetermined timing by an exhaust valve mechanism.

  As shown in FIG. 1, the exhaust valve mechanism has an exhaust motor VVT (Variable Valve Timing) 24 which is a variable valve mechanism in this configuration example. The exhaust motor VVT 24 is configured to continuously change the rotational phase of the exhaust camshaft within a predetermined angular range. Thereby, the valve opening timing and the valve closing timing of the exhaust valve 22 change continuously. The exhaust valve mechanism may have a hydraulic VVT instead of the electric VVT.

  Although details will be omitted, the engine 1 adjusts the length of the overlap period related to the opening timing of the intake valve 21 and the closing timing of the exhaust valve 22 by the intake electric VVT 23 and the exhaust electric VVT 24. As a result, residual gas in the combustion chamber 16 is scavenged, hot burnt gas is confined in the combustion chamber 16 (that is, internal EGR (Exhaust Gas Recirculation) gas is introduced into the combustion chamber 16, ). In this configuration example, the intake motor VVT 23 and the exhaust motor VVT 24 constitute an internal EGR system. The internal EGR system is not necessarily configured by VVT.

  An injector 6 is attached to the cylinder head 13 for each cylinder 11. The injector 6 is a multi-injection-type fuel injection valve in this configuration example, and is configured to inject fuel directly into the combustion chamber 16.

  A fuel supply system 61 is connected to the injector 6. The fuel supply system 61 includes a fuel tank 63 configured to store fuel, and a fuel supply passage 62 connecting the fuel tank 63 and the injector 6 to each other. A fuel pump 65 and a common rail 64 are interposed in the fuel supply passage 62. The fuel pump 65 pumps fuel to the common rail 64. The fuel pump 65 is a plunger type pump driven by the crankshaft 15 in this configuration example. The common rail 64 is configured to store the fuel pumped by the fuel pump 65 at a high fuel pressure. When the injector 6 is opened, the fuel stored in the common rail 64 is injected from the injection port of the injector 6 into the combustion chamber 16.

  A spark plug 25 is attached to the cylinder head 13 for each cylinder 11. The spark plug 25 is attached in such a position that its tip is in the combustion chamber 16 and forcibly ignites the mixture in the combustion chamber 16.

  As shown in FIG. 2, the intake passage 30 is connected to a front side surface (hereinafter referred to as “mounting surface”) 10 a of the engine body 10 and communicates with the intake ports 17 and 18 of the cylinders 11. The intake passage 30 is a passage through which the gas introduced into the combustion chamber 16 flows. An air cleaner 31 for filtering fresh air is disposed at the upstream end of the intake passage 30. A surge tank 38 is disposed near the downstream end of the intake passage 30. As shown in FIG. 3, the intake passage 30 downstream of the surge tank 38 constitutes an independent passage 39 branched into two cylinders for each cylinder 11.

  Although details will be described later, one of the two independent paths 39 is connected to the first port 17 and the other is connected to the second port 18. Hereinafter, while the code “391” is given to the former independent passage 39, the code “392” may be given to the latter. Thus, the downstream end of the independent passage 39 is connected to the intake port 17, 18 of each cylinder 11.

  A throttle valve 32 is disposed between the air cleaner 31 and the surge tank 38 in the intake passage 30. The throttle valve 32 is configured to adjust the amount of fresh air introduced into the combustion chamber 16 by adjusting the degree of opening thereof.

  A supercharger 34 is also disposed downstream of the throttle valve 32 in the intake passage 30. The supercharger 34 is configured to supercharge the gas introduced into the combustion chamber 16. In this configuration example, the supercharger 34 is a mechanical supercharger driven by the engine 1. The supercharger 34 according to the present embodiment is configured as a Roots-type supercharger, but this configuration may be any. For example, a Lysholm type or a centrifugal type may be used.

  An electromagnetic clutch 34 a is interposed between the supercharger 34 and the engine 1. The electromagnetic clutch 34 a transmits the driving force between the supercharger 34 and the engine 1 and blocks the transmission of the driving force. When the control means (not shown) such as an ECU (Engine Control Unit) switches between disconnection and connection of the electromagnetic clutch 34a, the supercharger 34 is switched on and off. That is, the engine 1 switches between the operation of supercharging the gas introduced into the combustion chamber 16 and the operation of not supercharging the gas introduced into the combustion chamber 16 by switching the supercharger 34 on and off. It is configured to be able to

  An intercooler 36 is disposed downstream of the turbocharger 34 in the intake passage 30. The intercooler 36 is configured to cool the gas compressed in the turbocharger 34. The intercooler 36 in this configuration example is configured to be water-cooled.

  Further, as a passage connecting various devices incorporated in the intake passage 30, the intake passage 30 is disposed downstream of the air cleaner 31 and is a first passage for guiding the intake air cleaned by the air cleaner 31 to the turbocharger 34. 33, a second passage 35 for guiding the intake air compressed by the turbocharger 34 to the intercooler 36, and a third passage 37 for guiding the gas cooled by the intercooler 36 to the surge tank 38. The surge tank 38 is disposed in the vicinity of the inlets (upstream ends) of the intake ports 17 and 18 in order to shorten the flow path length (runner length) from the surge tank 38 to the intake ports 17 and 18. The second passage 35 and the third passage 37, together with the turbocharger 34 and the intercooler 36, constitute a "supercharging passage".

  Further, the intake passage 30 is provided with a bypass passage 40 that bypasses the turbocharger 34 and the intercooler 36. The bypass passage 40 connects the surge tank 38 to a portion of the intake passage 30 from the downstream portion of the throttle valve 32 to the upstream portion of the turbocharger 34. In the bypass passage 40, a bypass valve 41 configured to adjust the flow rate of the gas flowing through the bypass passage 40 is disposed. The bypass passage 40 is an example of the “upstream passage”.

  When the supercharger 34 is turned off (that is, when the electromagnetic clutch 34a is disconnected), the bypass valve 41 is fully opened. Thus, the gas flowing through the intake passage 30 bypasses the turbocharger 34 and flows into the surge tank 38, and is introduced into the combustion chamber 16 via the independent passage 39. The engine 1 operates in a non-supercharged state, that is, in a state of natural intake.

  When the supercharger 34 is turned on (that is, when the electromagnetic clutch 34a is connected), the opening degree of the bypass valve 41 is appropriately adjusted. As a result, part of the gas that has passed through the turbocharger 34 in the intake passage 30 flows back through the bypass passage 40 upstream of the turbocharger 34. Since the reverse flow rate can be adjusted by adjusting the opening degree of the bypass valve 41, the supercharging pressure of the gas introduced into the combustion chamber 16 can be adjusted. In this configuration example, a supercharging system is configured by the supercharger 34, the bypass passage 40, and the bypass valve 41.

  The exhaust passage 50 is connected to the rear side surface of the engine body 10 and communicates with the exhaust port 19 of each cylinder 11. The exhaust passage 50 is a passage through which the exhaust gas discharged from the combustion chamber 16 flows. The upstream portion of the exhaust passage 50 constitutes an independent passage which branches for each cylinder 11, although detailed illustration is omitted. The upstream end of the independent passage is connected to the exhaust port 19 of each cylinder 11. An exhaust gas purification system having one or more catalytic converters 51 is disposed in the exhaust passage 50. The catalytic converter 51 is configured to include a three-way catalyst. The exhaust gas purification system is not limited to one including only the three-way catalyst.

  An EGR passage 52 constituting an external EGR system is connected between the intake passage 30 and the exhaust passage 50. The EGR passage 52 is a passage for recirculating a part of the burned gas to the intake passage 30. The upstream end of the EGR passage 52 is connected to the downstream of the catalytic converter 51 in the exhaust passage 50. The downstream end of the EGR passage 52 is connected upstream of the turbocharger 34 in the intake passage 30 and upstream of the upstream end of the bypass passage 40.

  A water-cooled EGR cooler 53 is disposed in the EGR passage 52. The EGR cooler 53 is configured to cool the burned gas. An EGR valve 54 is also disposed in the EGR passage 52. The EGR valve 54 is configured to adjust the flow rate of the burnt gas flowing through the EGR passage 52. By adjusting the opening degree of the EGR valve 54, it is possible to adjust the reflux amount of the cooled burned gas, that is, the external EGR gas.

  In this configuration example, the EGR system 55 includes an external EGR system including the EGR passage 52 and the EGR valve 54 and an internal EGR system including the intake electric VVT 23 and the exhaust electric VVT 24 described above. It is configured.

(Configuration of intake passage)
Hereinafter, the configuration of the intake passage 30 will be described in detail.

  FIG. 4 is a perspective view showing the overall configuration of the unitized intake passage 30 as viewed from the front side, and FIG. 5 is a perspective view showing the overall configuration of the intake passage 30 as viewed from the rear side. 6 is a transverse sectional view showing a passage structure on the turbocharger side of the intake passage 30, and FIG. 7 is a longitudinal sectional view thereof. 8 is a perspective view showing a vertical cross section around the surge tank 38, and FIG. 9 is a perspective view showing another vertical cross section.

  Each component constituting the intake passage 30 is disposed on the front side of the engine body 10, specifically, on the front side of the mounting surface 10a described above. The mounting surface 10 a is configured by the outer surface on the front side of the cylinder head 13 and the cylinder block 12 as shown in FIGS. 6 to 7.

  First, the schematic arrangement of each part constituting the intake passage 30 will be described.

  As shown in FIGS. 2 and 4 to 8, the supercharger 34 is disposed opposite to the four cylinders 11 with the surge tank 38 interposed therebetween. Between the rear surface of the turbocharger 34 and the mounting surface 10a, a gap (space) corresponding to the size of the surge tank 38 is open. The first passage 33 extends in the cylinder row direction on the left side of the turbocharger 34 and is connected to the left end of the turbocharger 34. Moreover, the intercooler 36 is arrange | positioned downward with respect to the supercharger 34, and the supercharger 34 is arrange | positioned at predetermined intervals with respect to the attachment surface 10a similarly to the supercharger 34. As shown in FIG. The turbocharger 34 and the intercooler 36 are vertically adjacent to each other. The second passage 35 extends up and down so as to connect the front of the turbocharger 34 and the front of the intercooler 36. The surge tank 38 is disposed in a gap between the turbocharger 34 and the mounting surface 10 a, and a plurality of independent passages 39 are interposed between the non-cylinder end portions (inlets) of the intake ports 17 and 18. It is disposed opposite to the opposite side. The third passage 37 is extended so as to sew a gap between the intercooler 36 and the supercharger 34 and the mounting surface 10 a, and the intercooler 36 is positioned below the surge tank 38, The rear of the intercooler 36 and the bottom of the surge tank 38 are connected. The bypass passage 40 is formed to extend upward from the middle of the first passage 33 and to extend inward (rightward) of the engine body 10 and is connected to the upper portion of the surge tank 38. There is.

  Next, the structure of each part constituting the intake passage 30 will be described.

  The first passage 33 is formed in a tubular shape extending substantially in the cylinder row direction (left and right direction), and an upstream side (left side) portion thereof is constituted by a throttle body 33a in which the throttle valve 32 is built. The throttle body 33a is formed in a short cylindrical shape made of metal, and as shown in FIGS. 4 to 6, in a posture in which the openings at both ends are directed to the left and right, it is positioned leftward and forward with respect to the mounting surface 10a. It is arranged to be. The air cleaner 31 is connected to the upstream end (left end) of the throttle body 33a via a passage (not shown), while the downstream end (right side) of the first passage 33 is connected to the downstream end (right end) of the throttle body 33a. A first passage main body 33b which is a portion is connected.

  The first passage main body 33b is configured to connect the throttle body 33a to the supercharger 34, as shown in FIG. Specifically, the first passage main body 33b is formed in a long cylindrical shape with the openings at both ends directed to the left and right. The first passage body 33b is disposed in front of the mounting surface 10a so as to be coaxial with the throttle body 33a. More specifically, the first passage body 33b is formed to gradually increase in diameter from the outside in the cylinder row direction toward the inside (from the left side to the right side). While the downstream end of the throttle body 33a is connected to the upstream end (left end) of the first passage main body 33b as described above, the suction port of the turbocharger 34 is connected to the downstream end (right end) thereof. ing.

  Further, in the first passage main body 33b, a merging portion 33c where the EGR passage 52 merges is opened. As shown in FIG. 6, the merging portion 33 c is formed on the rear surface of the upstream portion of the first passage body 33 b, and the downstream end of the EGR passage 52 is connected. The merging portion 33 c is formed at least downstream of the throttle valve 32.

  Further, in the first passage main body 33b, a branched portion 33d branched to the bypass passage 40 is also opened. In the first passage body 33b, the branch portion 33d is formed on the top surface near the junction portion 33c (substantially the same position in the gas flow direction), and is connected to the upstream end of the bypass passage 40 (see FIG. See also 10). The branch portion 33d is connected to the supercharger 34, the intercooler 36, the four pairs of intake ports 17 and 18, and the respective intake ports 17 and 18 through independent passages 39, as shown in FIG. 10 and the like. It is located on the outer side (left side) in the cylinder row direction than the surge tank 38.

  Thus, after the fresh air that has been purified by the air cleaner 31 and flows into the first passage 33 passes through the throttle valve 32, it merges with the external EGR gas that has flowed in from the merging portion 33c. Then, the gas in which the fresh air and the external EGR gas are combined flows into the bypass passage 40 via the branch portion 33d at the time of natural intake, while it is joined with the gas flowing back in the bypass passage 40 during supercharging. The supercharger 34 is sucked from the downstream end of the first passage body 33b (see an arrow A1 in FIG. 6).

  Hereinafter, the passage structure on the side of the turbocharger 34 and the passage structure on the side of the bypass passage 40 will be described in order.

-Passageway structure on the turbocharger side-
First, the passage structure on the suction side of the turbocharger 34 will be described in detail.

  As described above, the turbocharger 34 according to the present embodiment is configured as a roots-type supercharger. Specifically, the supercharger 34 includes a pair of rotors (not shown) provided with a rotating shaft extending along the cylinder row direction, a casing 34b accommodating the rotor, and a drive pulley 34d for rotationally driving the rotor. The drive pulley 34d is connected to the crankshaft 15 via a drive belt (not shown) wound around the drive pulley 34d. The aforementioned electromagnetic clutch 34a is interposed between the drive pulley 34d and the rotor, and the driving force is transmitted to the turbocharger 34 via the crankshaft 15 by switching the electromagnetic clutch 34a off and on. Transmit and block transmission of driving force.

  The casing 34 b is formed in a cylindrical shape extending in the cylinder row direction, and divides the housing space of the rotor and the flow path of the gas passing through the turbocharger 34. More specifically, the casing 34b is formed in a cylindrical shape in which the left end and the front face are opened in the cylinder direction, and as shown in FIG. 6 etc., a predetermined center portion of the mounting surface 10a in the cylinder row direction is provided. It is arranged to be spaced apart and coaxial with the first passage 33.

  At the left end in the longitudinal direction of the casing 34b, a suction port for taking in the gas compressed by the rotor is opened, and the downstream end (right end) of the first passage 33 is connected. On the other hand, as shown in FIGS. 6 to 7, a discharge port 34 c for discharging the gas compressed by the rotor is opened at the front of the casing 34 b (the side opposite to the engine body 10). The upstream end (upper end) of the second passage 35 is connected.

  The drive pulley 34d is configured to rotationally drive the rotor housed in the casing 34b. Specifically, the drive pulley 34d is formed in an axial shape that protrudes from the right end of the casing 34b and extends substantially coaxially with both the first passage 33 and the casing 34b. A drive belt (not shown) is wound around the tip of the drive pulley 34d, and as described above, the crankshaft 15 is drivingly connected to the supercharger 34 according to the switching state of the electromagnetic clutch 34a. It is configured.

  The second passage 35 is configured to connect the supercharger 34 to the intercooler 36 as shown in FIG. 4 and FIGS. In order to make the turbocharger 34 and the intercooler 36 vertically adjacent to each other, the second passage 35 according to the present embodiment is formed to extend along the vertical direction of the engine 1. Further, as shown in FIG. 7, the upper and lower ends of the second passage 35 are respectively opened rearward (toward the engine main body 10). Here, the upper opening 35a is connected to the front (specifically, the discharge port 34c) of the casing 34b, and the lower opening 35b is the front of the intercooler 36 (the front of the cooler housing 36c) )It is connected to the.

  Specifically, the second passage 35 extends in the vertical direction and is formed as a rectangular tube portion which is flat in the lateral direction, and the upper and lower end portions thereof are respectively bent rearward. That is, as shown in FIG. 7, the second passage 35 is configured to form a substantially U-shaped flow passage when viewed in the cylinder row direction (particularly when viewed from the right direction). .

  As described above, the intercooler 36 according to the present embodiment is configured to be water-cooled, and is attached to the core 36 a having a gas cooling function and the side of the core 36 a as shown in FIGS. 4 to 7. A core connection portion 36b and a cooler housing 36c for accommodating the core 36a are provided. Although details will be omitted, a water supply pipe for supplying cooling water to the core 36a and a drainage pipe for discharging the cooling water from the core 36a are connected to the core connection portion 36b.

  The core 36a is formed in a rectangular shape, and is supported in a posture in which one side surface (rear surface) and the mounting surface 10a face each other. The front surface of the core 36a constitutes the inflow surface of the gas, while the rear surface of the core 36a constitutes the outflow surface of the gas, which is the widest surface of the core 36a. Although not shown, a plurality of water tubes each having a flat cylindrical thin plate material are arranged in the core 36a, and corrugated corrugated fins are connected to the outer wall surfaces of the water tubes by brazing or the like. . With this configuration, the cooling water supplied from the water supply pipe is introduced into each water tube to cool the high-temperature gas. Cooling water warmed by cooling the gas is drained from each water tube through a drain. Further, by providing the corrugated fins, the surface area of each water tube is increased to improve the heat radiation effect.

  As shown in FIG. 4, the core connection portion 36b is a rectangular thin plate-like member, and is attached to the right side surface of the core 36a. The water supply pipe and the drainage pipe, and the water tube are mutually connected via the core connection portion 36b. The core connection portion 36 b constitutes a right side wall portion of the intercooler 36 and, together with the cooler housing 36 c, divides the housing space of the core 36 a.

  The cooler housing 36 c is disposed below the casing 34 b and defines a storage space of the core 36 a and is a flow interposed between the second passage 35 and the third passage 37 in the intake passage 30. It constitutes a road.

  Specifically, the cooler housing 36c is formed in the shape of a rectangular thin box in which the front surface and the rear surface are open, and is supported in a posture in which the rear surface and the mounting surface 10a face each other at the lower position of the casing 34b. There is. The rear surface is disposed at a predetermined distance (see FIG. 7) with respect to the mounting surface 10a of the engine body 10, similarly to the casing 34b.

  The downstream end of the second passage 35 is connected to the front opening 36d of the cooler housing 36c, while the upstream end of the third passage 37 is connected to the rear opening 36e. . Further, the cooler housing 36c is also open on the right side. The opening is configured as an insertion port when the core 36a is accommodated inside the cooler housing 36c, and is closed by the core connection portion 36b.

  The third passage 37 is a member integrally formed with the surge tank 38 and the independent passage 39 and configured to connect the intercooler 36 to the surge tank 38 as shown in FIGS. 7 and 8. There is. More specifically, the third passage 37 is fastened to the cooler housing 36c sequentially from the upstream side, and the introduction portion 37a for collecting the gas having passed through the intercooler 36 and the introduction for introducing the gas collected in the collection portion 37a to the surge tank 38 And a portion 37b. The third passage 37 is disposed below the surge tank 38 at least in a vehicle mounted state.

  The collecting portion 37a is formed in the front side, that is, in the form of a shallow box having a depth in the front and rear, in which the cooler housing 36c side is open. The opening is an opening on the rear side of the cooler housing 36c as shown in FIG. Connected to 36e. The collecting portion 37 a is positioned in a gap between the rear surface of the cooler housing 36 c and the mounting surface 10 a of the engine body 10. Further, the upstream end of the introducing unit 37b is connected to the rear surface of the collecting unit 37a.

  The introduction portion 37b is formed as a curved pipe portion extending substantially in the vertical direction, and the upstream end thereof is connected to the rear surface of the collective portion 37a, while the downstream end thereof is the central portion of the bottom surface of the surge tank (FIG. 9) are connected. As shown in FIG. 7 and the like, the introduction portion 37b sews a gap between a region from the rear surface of the collecting portion 37a to the rear surface of the casing 34b of the turbocharger 34 and the mounting surface 10a of the engine body 10. It is extended.

  More specifically, as shown in FIG. 8, the upstream portion of the introducing portion 37 b extends obliquely upward and to the right from the connecting portion with the collecting portion 37 a, while the downstream portion thereof extends from the connecting portion with the surge tank 38. It is formed to extend directly upward to the connection portion. As a result of this formation, the downstream end of the introducing portion 37b extends in a direction substantially orthogonal to the gas flow direction in the independent passage 39 when viewed from one side in the cylinder row direction (see FIG. 7).

  The surge tank 38 is formed in a substantially cylindrical shape extending in the cylinder row direction and closing both ends in the same direction. As described above, the surge tank 38 is disposed opposite to the opposite end of the intake ports 17 and 18 with the plurality of independent passages 39 interposed therebetween (see FIG. 7). As described later, when the plurality of independent passages 39 are respectively formed in a short cylindrical shape, the surge tank 38 is located in the vicinity of the inlets (upstream ends) of the intake ports 17 and 18 in combination with such an arrangement. It will be. This is effective in shortening the flow path length (runner length) from the surge tank 38 to the intake ports 17 and 18.

  Further, as shown in FIG. 9, the downstream end of the third passage 37 (introduction part 37 b) is connected to the bottom of the surge tank 38. An inlet 38b having a substantially circular cross section is opened at a central portion (specifically, a central portion in the cylinder row direction) of the inner bottom surface 38a of the surge tank 38, and a downstream end of the inlet 37b is Is connected to the surge tank 38 via the inlet 38b.

  The inlet 38 b is larger in diameter than the intake ports 17 and 18.

  Furthermore, in the surge tank 38, the dimension from the inlet 38b to one end (end on the first cylinder 11A side) in the cylinder row direction and the dimension from the other end (end on the fourth cylinder 11D) are substantially equal. It has become. With such a configuration, it is possible to secure the distribution performance of the intake air, which is advantageous in reducing the inter-cylinder difference in the filling efficiency.

  Further, as shown in FIG. 9, the upstream ends of the plurality of independent passages 39 are connected to the surge tank 38 in a row in the order in which the corresponding intake ports 17 and 18 are arranged.

  Specifically, on the side surface (rear surface) on the side of the engine body 10 in the surge tank 38, four sets (that is, a total of eight) of two independent passages 39 forming one set along the cylinder row direction It is formed. Each of the eight independent passages 39 is formed as a short cylindrical passage extending substantially straight toward the rear in a vehicle mounted state, and one end side (upstream side) communicates with the space in the surge tank 38 On the other hand, the other end side (downstream side) is opened at the engine body 10 side (rear side).

  Four sets of independent passages 39 are disposed to correspond to each of the four sets of intake ports 17 and 18, respectively, and integrally formed third passage 37, surge tank 38 and independent passages 39 are provided. When assembled in the engine body 10, each independent passage 39 and the corresponding intake ports 17, 18 constitute one passage.

  As described above, the independent passages 39 are composed of an independent passage 391 corresponding to the first port 17 and an independent passage 392 corresponding to the second port 18 in one set. When the third passage 37, the surge tank 38, and the independent passage 39 are assembled to the cylinder block 12, the first port 17 and the corresponding independent passage 391 constitute one independent passage, while the second The port 18 and the corresponding independent passage 392 constitute a single independent passage. In this way, eight independent paths are constructed.

  The SCV 80 described above is disposed in the independent passage 392 connected to the second port 18 (see FIGS. 7 and 11). Since the flow rate of the gas passing through the second port 18 is reduced by reducing the opening degree of the SCV 80, the flow rate passing through the other first port 17 can be relatively increased.

  By the way, as described later, the downstream side portion of the bypass passage 40 is bifurcated, and the downstream ends of the branched passages (hereinafter referred to as “branch passages” 44b and 44c) are both surge tank 38 Connected to the top of the.

  In order to realize such a structure, two first and second introductions are arranged on the upper surface of the surge tank 38 at intervals in the cylinder row direction and configured to communicate the inside and the outside of the surge tank 38. The parts 38c and 38d are provided.

  Then, one branch passage (hereinafter referred to as “first branch passage”) is provided to the first introduction portion 38c located on one side (right side) in the cylinder row direction of the two first and second introduction portions 38c and 38d. The second introduction portion 38d located on the other side (left side) is connected to the downstream end of the other branch passage (hereinafter also referred to as "second branch passage") 44c, while the downstream end of the other end 44b is connected. The ends are connected (see also FIG. 13).

  Specifically, both of the first and second introduction parts 38c and 38d are formed in a short cylindrical shape, and are perpendicular to the cylinder row direction from the upper surface of the surge tank 38, as shown in FIG. Extends diagonally upward and forward.

  As shown in FIG. 8, the first introduction portion 38c is disposed to face a portion near the independent passage 392 corresponding to the second port 18B of the second cylinder 11B. On the other hand, the second introduction portion 38d is disposed to face a portion near the independent passage 392 corresponding to the second port 18D of the fourth cylinder 11D.

  The gas sucked into the supercharger 34 reaches each cylinder 11 through the "supercharge passage" configured as described above.

  That is, at the time of supercharging, while the engine 1 is operating, the output from the crankshaft 15 is transmitted through the drive belt and the drive pulley 34d to rotate the rotor. As the rotor rotates, the supercharger 34 compresses the gas sucked from the first passage 33 and discharges it from the discharge port 34c. The exhaled gas flows into the second passage 35 disposed in front of the casing 34b.

  As shown by arrow A2 in FIG. 7, the gas discharged from the turbocharger 34 and flowing into the second passage 35 flows from the discharge port 34c of the turbocharger 34 toward the front, and then flows to the second passage 35. It flows downward along. The gas that has flowed downward flows downward toward the intercooler 36 after reaching the lower part of the second passage 35.

  Subsequently, as shown by arrow A3 in FIG. 7, the gas that has passed through the second passage 35 flows into the inside of the cooler housing 36c from the opening 36d on the front side, and flows from the front to the rear. The gas flowing into the cooler housing 36c is cooled by the cooling water supplied to the water tube when passing through the core 36a. The cooled gas flows out of the opening 36 e on the rear side of the cooler housing 36 c and flows into the third passage 37.

  Then, as shown by arrow A4 in FIG. 7, the gas flowing from the intercooler 36 into the third passage 37 flows obliquely upward to the right along the upstream portion of the introduction portion 37b after passing through the collecting portion 37a ( The section S1 in FIG. 8 is also referred to), and thereafter, the flow flows directly upward along the downstream side portion of the introducing portion 37b (also refer to section S2 in FIG. 8). As shown by the arrow A5 in the figure, the gas that has passed through the introduction portion 37b flows into the space substantially at the center in the cylinder row direction in the surge tank 38, is temporarily stored in the surge tank 38, and then becomes independent. It is supplied to each cylinder 11 through the passage 39.

-Passage structure on the bypass side-
Next, the configuration of the bypass passage 40 will be described in detail.

FIG. 10 is a view showing a passage structure related to the bypass passage 40 as viewed from the front side, FIG. 11 is a view showing it as viewed from the rear side, and FIG. 12 is a view showing it as viewed from the upper side is there. Also,
FIG. 13 is a longitudinal sectional view showing a connection structure of the surge tank 38 and the bypass passage 40, and FIG. 14 is a transverse sectional view thereof.

  The bypass passage 40 extends upward from the branch 33 d of the first passage 33 and then extends substantially straight rightward. The bypass passage 40 changes its direction so as to be directed obliquely downward to the rear, when the portion extending toward the right reaches near the center of the surge tank 38 (specifically, the center in the cylinder row direction). Branch to the crotch. Each branched branch is connected to the upper surface of the surge tank 38.

  Specifically, the bypass passage 40 includes, in order from the upstream side along the flow direction, a valve body 41a in which the bypass valve 41 is incorporated, a curved pipe portion 42 for adjusting the flow direction of the gas passing through the valve body 41a, and A straight pipe portion 43 for guiding the gas that has passed through the pipe portion 42 to the right and a gas that has passed through the straight pipe portion 43 are directed obliquely downward and to the rear, and then branched into two branches and connected to the surge tank 38 And a branched pipe portion 44.

  The valve body 41 a is formed in a short cylindrical shape, and as shown in FIGS. 10 to 11, the openings at both ends above the first passage 33 and at the left with respect to the turbocharger 34. It is arranged in the posture which turned up and down. Further, similarly to the first passage 33, the valve body 41a is located forward of the portion near the left end of the mounting surface 10a. The upstream end (lower end) of the valve body 41a is connected to the branched portion 33d of the first passage 33, while the downstream end (upper end) of the valve body 41a is connected to the upstream end of the curved pipe portion 42 There is.

  The curved pipe portion 42 is configured as an elbow-shaped pipe joint, and is disposed in a posture in which the opening is directed downward and to the right at the upper position of the first passage 33 and thus the valve body 41a. Therefore, after flowing into the direction perpendicular to the main flow of gas in the first passage 33 (immediately upward), the gas flowing into the curved pipe portion 42 changes the flow direction according to the bending direction of the curved pipe portion 42 Be done. As a result, the gas flowing through the curved pipe portion 42 flows a little in the backward direction from the outside in the cylinder row direction toward the inside (from the left side to the right) when viewed in the cylinder axial direction (see FIG. 12). Flow. Further, the curved pipe portion 42 is located forward of the portion near the left end of the mounting surface 10a, as with the first passage 33 and the valve body 41a. As described above, the downstream end (upper end) of the valve body 41a is connected to the upstream end (lower end) of the curved pipe portion 42, while the downstream end (right end) of the curved pipe portion 42 is a straight pipe portion The upstream end of 43 is connected.

  The straight pipe portion 43 is formed in a long cylindrical shape (specifically, a cylindrical shape extending in a direction from one side (left side) to the other side (right side) in the cylinder row direction, as shown in FIGS. As can be seen from the back, at the upper position of the first passage 33 or the supercharger 34, the openings at both ends are disposed in a posture directed to the left and right. The upstream end (left end) of the straight pipe portion 43 is connected to the downstream end (right end) of the bent pipe portion 42 as described above, while the downstream end (right end) of the straight pipe portion 43 is a branch pipe The upstream end of the part 44 is connected.

  The branch pipe portion 44 is composed of a bent passage 44a bent in an elbow shape, and two branched passages 44b and 44c branched in a tournament shape from the downstream end of the bent passage 44a. At the upper position of the surge tank 38, the upstream end of the bending passage 44a is directed leftward, and the two branched branch passages 44b and 44c are both directed obliquely downward and backward.

  Specifically, the bending passage 44a is bent substantially at a right angle so as to be directed obliquely downward from the front to the rear as going from the left to the right. The rear end portion of the bent passage 44a branches into two branch passages 44b and 44c in a substantially T shape when viewed in the cylinder axial direction, as shown in FIG.

  The flow path lengths of the two branch passages 44b and 44c are substantially the same, and the first branch passage 44b which is one branched branch passage extends from the branch point to the right along the cylinder row direction. Later, it is bent diagonally to the lower back. On the other hand, the second branch passage 44c, which is the other branched branch passage, extends leftward along the cylinder row direction from the branch point and is then bent diagonally downward and rearward. The downstream end portions of the two branch passages 44b and 44c are connected to the first introducing portion 38c and the second introducing portion 38d formed on the upper surface of the surge tank 38 as described above.

  At the time of natural intake, the gas flowing into the bypass passage 40 passes through the portions 41 to 44 forming the passage 40 and reaches the cylinders 11.

  That is, the gas that has passed through the throttle valve 32 flows into the valve body 41 a of the bypass valve 41 from the middle of the first passage 33 according to the opening / closing condition of the bypass valve 41.

  As shown by arrow A6 in FIG. 12, the gas flowing through the valve body 41a and flowing into the bent pipe portion 42 flows toward the upper right, and then flows toward the right while slightly going backward.

  Subsequently, the gas having passed through the curved pipe portion 42 flows to the right along the straight pipe portion 43 as shown by arrow A7 in FIG. 12 and then flows into the branch pipe portion 44. Then, as shown by arrows A8 to A10 in the figure, the gas flowing into the branch pipe portion 44 is distributed to the first branch passage 44b and the second branch passage 44c after passing through the bending passage 44a, and is distributed. Each flows into the surge tank 38 (see also arrows A9 to A10 in FIGS. 13 to 14). The gas flowing into the surge tank 38 is drawn into each cylinder 11 via the independent passage 39.

  On the other hand, at the time of supercharging, the gas flowing backward from the surge tank 38 to the bypass passage 40 passes through the portions 41 to 44 of the bypass passage 40 in the opposite direction to the above and flows out to the first passage 33.

(Configuration related to gas blowback)
FIG. 15 is a plan view showing the flow channel structure around the surge tank 38 as viewed from the top, and FIG. 16 is a front view showing the flow channel structure as viewed from the front. 15 to 16 correspond to the shape of the core when casting the members around the surge tank 38, respectively.

  The engine 1 is provided with an ECU for operating the engine 1. The ECU determines the operating state of the engine 1 based on detection signals output from various sensors, and calculates control amounts of various actuators. Then, the ECU converts the control signal corresponding to the calculated control amount into the electromagnetic waves of the injector 6, the spark plug 25, the intake electric VVT 23, the exhaust electric VVT 24, the fuel supply system 61, the throttle valve 32, the EGR valve 54, and the turbocharger 34. The engine 1 is operated by outputting to the clutch 34 a and the bypass valve 41.

  The operating range of the engine 1 is divided, for example, by the engine speed and the load, and the ECU controls each actuator so as to realize an operating state suitable for each range.

  For example, in an operating area on a lower load side than the predetermined load (hereinafter referred to as “fuel efficiency area”), the engine 1 is operated by natural intake while an operating area on a higher load side than the predetermined load (hereinafter referred to as “supercharged In the region “), the gas introduced into each cylinder 11 is supercharged by driving the supercharger 34.

  In addition, the ECU closes the SCV 80 to promote the generation of swirl in the fuel consumption area. As a result, the flow rate of the gas passing through the first port 17 can be increased to facilitate the mixing of the gases. On the other hand, in the supercharging region, the ECU gradually opens the SCV 80 as the load on the engine 1 increases in order to secure the introduction amount of gas.

  By the way, in such an engine 1, it is considered to provide a negative overlap period (NVO) via the internal EGR system in the above-mentioned fuel consumption region from the viewpoint of securing the in-cylinder temperature, reducing the pump loss, etc. Be

  Specifically, exhaust electric motor VVT 24 sets the closing timing (hereinafter referred to as "EVC") of exhaust valve 22 to a predetermined crank angle before the exhaust top dead center according to the control signal received from the ECU in the fuel consumption region. Hold. Since the adjustment of the EVC is performed by the exhaust motorized VVT 24, when the EVC is kept substantially constant, the EVO is also kept substantially constant. Thus, the exhaust motor VVT 24 sets the EVC during the exhaust stroke.

  In contrast, in the case of fuel consumption region, intake electric motor VVT 23 sets the opening timing (hereinafter referred to as "IVO") of intake valve 21 to a predetermined crank angle after exhaust top dead center according to the control signal received from the ECU. Do. Therefore, in this fuel consumption area, a negative overlap period in which both the intake valve 21 and the exhaust valve 22 are closed is provided across the exhaust top dead center.

  In the engine 1, the intake electric motor VVT 23 sets IVC between the previous period and the middle period of the compression stroke. That is, in the engine 1, so-called “slow closing” of the intake valve 21 can be performed. By performing the late closing, the gas filling amount can be reduced.

  By providing the negative overlap period, the burnt gas is trapped in the combustion chamber 16 (in other words, the internal EGR gas is introduced). As a result, the temperature in the combustion chamber 16, especially the temperature before ignition increases. Thus, for example, when compression ignition combustion is performed instead of general spark ignition combustion to improve fuel efficiency, it is possible to stably perform the combustion. In addition, since the IVC is delayed, the gas filling amount is reduced. Although the filling amount is reduced in the fuel consumption region, the Miller cycle is realized along with the provision of the negative overlap period, so throttling can be omitted or suppressed. That reduces pump losses.

  However, when such control is executed, the intake valve 21 remains open immediately after the transition from the intake stroke to the compression stroke, so the internal EGR introduced into the cylinder 11 along with the rise of the piston 14 Gas will be blown back to the intake side.

  In particular, when the surge tank 38 is disposed in the vicinity of the inlets of the intake ports 17 and 18 as in the above embodiment, the gas blown back to the intake side passes through the intake ports 17 and 18 and the independent passages 391 and 392. Backflow to the surge tank 38.

  As a result of intensive studies, the inventors of the present invention have found that a difference between cylinders can occur in the in-cylinder state due to the gas blown back to the surge tank 38.

  That is, when the cylinder 11 located on the end side in the cylinder row direction is referred to as an end side cylinder, and the cylinder 11 adjacent to the end side cylinder 11 inward in the cylinder row direction is referred to as a center side cylinder, for example, 4 In the case of a cylinder engine, the gas blown back from the second cylinder 11B or the third cylinder 11C as the center side cylinder can be diffused to both left and right in the cylinder row direction, but the first cylinder as the end side cylinder The gas blown back from the 11A and the 4th cylinder 11D can not be sufficiently diffused because there is only a place to go to the left or right of the cylinder row direction.

  Therefore, in the space near the upstream end of the independent passage 39 communicating with the first cylinder 11A and the fourth cylinder 11D in the surge tank 38, the vicinity of the upstream end of the independent passage 39 communicating with the second cylinder 11B and the third cylinder 11C. Since the gas diffusibility is inferior to the space of the above, the gas blown back from each cylinder 11 tends to stay. As a result, at the end of the surge tank 38, the gas blown back from both the end cylinder and the center cylinder is retained, and there is a possibility that the distribution of the gas may be uneven.

  As described above, when the distribution of the internal EGR gas becomes uneven between the center side and the end side of the surge tank 38, the difference between the cylinders in the in-cylinder state may be caused due to the fact. Etc noticed.

  In the engine 1, in order to reduce the difference between the cylinders, the left and right guide portions 71 and 72 are disposed in the surge tank 38.

  FIG. 17 is a longitudinal sectional view showing a structure related to the guide portions 71 and 72. As shown in FIG.

  As shown in FIG. 17, the right guide portion 71 which is one of the pair of guide portions 71 and 72 is disposed on the right side of the surge tank 38 while the pair of guides is disposed on the left side of the surge tank 38. The left guide portion 72 which is the other of the portions 71 and 72 is disposed.

  Each of the guide portions 71, 72 is formed as a wall portion projecting rearward from the front surface of the surge tank 38, and each has a substantially triangular shape as shown in FIG. 17 when viewed in a cross section perpendicular to the cylinder axis. It has a cross section. In the present embodiment, each of the guide portions 71 and 72 is integrally formed with the surge tank 38, respectively.

  In each of the guide portions 71 and 72, a first guide surface 71a and 72a and a second guide surface 71b and 72b are formed. The first guide surfaces 71a and 72a both illustrate the "guide surface", and the second guide surfaces 71b and 72b both illustrate the "second guide surface".

  First, the configuration related to the right guide portion 71 will be described.

  As shown in FIG. 17, in the surge tank 38, the first guide surface 71a is from the upstream end of the independent passages 391, 392 corresponding to the first cylinder 11A as the end side cylinder among the plurality of independent passages 391, 392. The gas which is blown back to the surge tank 38 from the second cylinder 11B is disposed at a position opposite to the section to the upstream end of the independent passages 391, 392 corresponding to the second cylinder 11B as the center side cylinder. Is guided in a direction not approaching the upstream end of the independent passage 39 corresponding to the No. 1 cylinder 11A (in this example, the direction away from the No. 1 cylinder 11A) (arrow A11 in FIG. 17). reference).

  Specifically, in the surge tank 38, the first guide surface 71a is upstream of the independent passage 391 connected to the first port (that is, non-SCV port) 17B among the independent passages 391 and 392 corresponding to the second cylinder 11B. It is arrange | positioned in the site | part which opposes an edge part. This portion extends from the upstream end of the independent passage 391 related to the first port 17B of the No. 2 cylinder 11B on the extension line L1 extending to the opposite side with respect to each cylinder 11 when the surge tank 38 is viewed in the cylinder axial direction. It is supposed to be located in

  The first guide surface 71 a is configured as an inclined surface corresponding to one oblique side of the right guide portion 71 when the surge tank 38 is viewed in the cylinder axial direction. That is, as the first guide surface 71a goes from the end side (right side) to the center side (left side or inside) in the cylinder row direction, the first guide surface 71a moves to the opposite side to each cylinder 11, particularly the second cylinder 11B as the center side cylinder. It is inclined towards. Therefore, when the gas flowing out from the first port 17B of the second cylinder 11B to the opposite side (front side) of the second cylinder 11B collides with the first guide surface 71a, the gas flows along the first guide surface 71a. It is guided to the center side in the cylinder row direction.

  On the other hand, the second guide surface 71b is formed at a portion where the first guide surface 71a extends to the end side (right side) in the cylinder row direction, and the gas blown back from the first cylinder 11A is the second cylinder 11B. It is configured to guide in a direction approaching (see arrow A12 in FIG. 17).

  Specifically, the second guide surface 71b is connected to the second port 18B of the second cylinder 11B from the upstream end of the independent passage 391 connected to the first port 17B of the second cylinder 11B in the surge tank 38. It is disposed at a position opposite to the section to the upstream end of the independent passage 392.

  In addition, the second guide surface 71b is configured as an inclined surface corresponding to one oblique side (an oblique side different from that corresponding to the first guide surface 71a) of the right guide portion 71 when the surge tank 38 is viewed in the cylinder axial direction. It is done. The inclination formed by the second guide surface 71b is different from the inclination formed by the first guide surface 71a. That is, the second guide surface 71b protrudes toward each cylinder 11, particularly the second cylinder 11B as the center side cylinder, as it goes from the end side (right side) to the center side (left side or inside) in the cylinder row direction. So it is inclined. Therefore, the gas which has flowed out from the first port 17A of the first cylinder 11A to the opposite side (front side) of the first cylinder 11A is guided by the right side inclined surface 38e described later, and then to the second guide surface 71b. It is guided along the center side in the cylinder row direction.

  In the surge tank 38, a right inclined surface 38e is disposed at a position adjacent to the end side (right side) in the cylinder row direction with respect to the second guide surface 71b. In the present embodiment, the right side inclined surface 38 e is also integrally formed with the surge tank 38 in the same manner as the right guide portion 71.

  Specifically, the right side inclined surface 38e is disposed in the surge tank 38 at a position facing the upstream end of the independent passages 391, 392 corresponding to the No. 1 cylinder 11A, and goes to the center side in the cylinder row direction. In accordance with this, each cylinder 11 is inclined to the opposite side with respect to the first cylinder 11A as the end side cylinder.

  The right inclined surface 38e, the second guide surface 71b, and the first guide surface 71a are continuous in this order from the end side in the cylinder row direction.

  By the way, as described above, the first branch passage 44b is connected to the surge tank 38 via the first introduction portion 38c. As shown in FIG. 15, the first branch passage 44b is connected to a portion closer to the first cylinder 11A than the second guide surface 71b in the cylinder row direction. Further, as shown in FIGS. 12 and 14 and the like, the first branch passage 44b generally extends from the front side to the rear side in the front-rear direction. Considering that each cylinder 11 is disposed behind the surge tank 38, this means that the first branch passage 44b directs the gas flowing through the downstream end of the passage to the cylinder 11 side. (See arrow A13 in FIG. 17).

  On the other hand, as shown in FIG. 17, the left guide portion 72 is configured to be symmetrical with respect to the right guide portion 71 except that the left guide portion 72 is generally disposed on the left side.

  Although the details will be omitted, the first guide surface 72a of the left guide portion 72 is provided to the first port (that is, non-SCV port) 17C of the independent passages 391, 392 corresponding to the third cylinder 11C in the surge tank 38. It is disposed at a position opposite to the upstream end of one of the independent passages 391 to be connected. The first guide surface 72 a brings the gas blown back to the surge tank 38 from the No. 3 cylinder 11 C as the center side cylinder close to the upstream end of the independent passage 39 corresponding to the No. 4 cylinder 11 D as the end side cylinder. It is configured to guide in a direction (in this example, a direction away from the fourth cylinder 11A) (see an arrow A14 in FIG. 17).

  The first guide surface 72a of the left guide portion 72 is also configured as an inclined surface corresponding to one oblique side of the left guide portion 72 when the surge tank 38 is viewed in the cylinder axis direction. From the left side) to the center side (right side or inside), each cylinder 11 is inclined toward the opposite side of the third cylinder 11C as the center side cylinder.

  On the other hand, the second guide surface 72b of the left guide portion 72 is formed at a portion where the first guide surface 72a extends to the end side (left side) in the cylinder row direction, and the gas blown back from the fourth cylinder 11D is The third cylinder 11C is configured to be guided in the direction approaching the third cylinder 11C (see the arrow A15 in FIG. 17).

  The second guide surface 72b of the left guide portion 72 also corresponds to one oblique side (an oblique side different from the one corresponding to the first guide surface 72a) of the left guide portion 72 when the surge tank 38 is viewed in the cylinder axial direction. It is configured as an inclined surface, and protrudes toward each cylinder 11, particularly the third cylinder 11C as a center side cylinder as it goes from the end side (left side) in the cylinder row direction to the center side (right side or inside) It is inclined to

  In the surge tank 38, a left inclined surface 38f is disposed at a position adjacent to the end side (left side) in the cylinder row direction with respect to the second guide surface 72b. The left inclined surface 38f is disposed in the surge tank 38 at a position opposed to the upstream end of the independent passages 391, 392 corresponding to the fourth cylinder 11D, and each left inclined surface 38f extends toward the center in the cylinder row direction. It inclines to the opposite side of the cylinder 11, particularly the fourth cylinder 11D as the end side cylinder.

  Further, as described above, the second branch passage 44c is connected to the surge tank 38 via the second introduction portion 38d. As shown in FIG. 15, the second branch passage 44c is connected to a portion closer to the fourth cylinder 11D than the second guide surface 72b of the left guide portion 72 in the cylinder row direction. Further, the second branch passage 44c, like the first branch passage 44b, directs the gas flowing through the downstream end of the passage 44b toward the cylinders 11 (see arrow A16 in FIG. 17). ).

  As described above, the first guide surfaces 71a and 72a disposed in the surge tank 38 are respectively the second cylinder 11B and the third cylinder as the center side cylinder as shown by the arrows A11 and A14 in FIG. The gas blown back from 11C is configured to be guided in a direction that does not approach the upstream end of the independent passage 39 corresponding to the first cylinder 11A and the fourth cylinder 11D as end-side cylinders. As a result, the amount of gas staying on the end side of the surge tank 38 (in particular, the gas staying due to the blowback from the center side cylinder) can be reduced, and in turn, the distribution of the gas can be equalized.

  Therefore, the difference between cylinders in the in-cylinder state can be reduced in an operation region where blowback of gas is assumed, such as a fuel consumption region.

  In the fuel consumption area, the SCV 80 is closed to promote gas mixing. In this case, when the second port 18 as the SCV port is closed, when the gas blows back, a strong jet may be generated through the first port 17 as the non-SCV port.

  Therefore, as shown in FIG. 17, by disposing the first guide surfaces 71a and 72a at the portion facing the upstream end of the independent passage 391 related to the non-SCV port, the gas blown back from the center side cylinder can be It becomes possible to guide more reliably. This is effective in reducing the inter-cylinder difference in the in-cylinder state.

  Further, as shown in FIG. 3 and FIGS. 15 to 17 etc., in each cylinder 11, the first port 17 and the second port 18 are arranged in the same order, so for example, the injector 6 and the spark plug 25 etc. The mounting structure of the parts can be unified in all four cylinders 11.

  Further, as shown by arrow A12 and arrow A15 in FIG. 17, the gas blown back from the first cylinder 11A and the fourth cylinder 11D as end side cylinders is directed to the opposite side (front side) of each cylinder 11 After flowing, it collides with the right side inclined surface 38 e or the left side inclined surface 38 f formed in the surge tank 38. Considering the gas flow direction and the inclination directions of the inclined surfaces 38e and 38f, the gas that has collided with the inclined surfaces 38e and 38f is guided inward in the cylinder row direction. The gas guided by the inclined surfaces 38e and 38f is subsequently guided by the second guide surfaces 71b and 72b toward the second cylinder 11B or the third cylinder 11C as the center side cylinder. . As a result, the amount of gas staying on the end side of the surge tank 38 (in particular, the gas staying due to the blowback from the end-side cylinder) can be reduced, and in turn, the distribution of the gas can be equalized.

  As described above, not only the gas blown back from the center side cylinder but also the gas blown back from the end side cylinder is suppressed in the operation area where the blowback of gas is assumed, such as the fuel consumption area, by suppressing its retention. This is advantageous in reducing the inter-cylinder difference in the in-cylinder state.

  Further, as shown by arrow A13 and arrow A16 in FIG. 17, the first and second branch passages 44b and 44c direct the gas flowing through the branch passages 44b and 44c to the cylinders 11. Then, the gas introduced from each branch passage 44b, 44c to the surge tank 38 flows away from both the inclined surfaces 38e, 38f and the second guide surfaces 71b, 72b. Become. As a result, the gas introduced from each of the branch passages 44b and 44c is not easily guided toward the central cylinder.

  Moreover, the second guide surfaces 71 b and 72 b are formed to project toward the cylinders 11 respectively. As a result, in the surge tank 38, the portion in the vicinity of the second guide surfaces 71b and 72b is narrowed when viewed in the cylinder axial direction. In consideration of the increase in the flow passage resistance at the narrowed portion and the fact that each branch passage 44b, 44c is connected to a portion closer to the end cylinder than the second guide surfaces 71b, 72b, each branch passage 44b The gas introduced into the surge tank 38 from 44c (for example, the gas mainly composed of fresh air) tends to flow closer to the end side cylinder. The gas introduced closer to the end-side cylinder can flush the gas (for example, the gas mainly composed of the internal EGR gas) accumulated at the end side of the surge tank 38.

  As described above, at the end of the surge tank 38, the stagnation of the gas blown back from each cylinder 11 is suppressed, while the introduction of the gas introduced from each of the branch passages 44b and 44c is promoted to thereby achieve the in-cylinder state. It is advantageous in reducing the inter-cylinder difference of

  However, when the left and right guide portions 71, 72 such as the second guide surfaces 71b, 72b protrude more than necessary, the flow path resistance increases excessively, and the gas introduced from the third path 37 at the time of supercharging However, it may become difficult to flow to the end side of the surge tank 38 (specifically, the pressure loss when passing through the narrowed portion becomes excessively large).

  As a result of intensive studies, the inventors of the present invention have found that the cross-sectional area of the portion narrowed by the left and right guide portions 71 and 72 (particularly, the most narrowed portion) is the first port 17 and the second port 18 in each cylinder 11. It has been found that pressure loss is not a problem for the gas introduced from the third passage 37 if the sum of the opening cross-sectional areas of the upstream end (inlet) of

  FIG. 18 shows a cross-sectional area (A) of a portion narrowed by the left guide portion 72 (specifically, corresponding to the B-B cross section in FIG. 16) and the inlets of the intake ports 17D and 18D leading to the fourth cylinder 11D. It is a figure which compares and shows a cross-sectional area (B). The cross-sectional area of the portion narrowed by the left guide portion 72 is C3, the cross-sectional area of the inlet of the first port 17D leading to the fourth cylinder 11D is C1, and the cross-sectional area of the inlet of the second port 18D leading to the cylinder 11D is C2. Then, if the relationship of C3> C1 + C2 is established, the pressure loss does not matter as described above.

  Further, in the low load to medium load operation range such as the above-described fuel consumption range, the effect of the blowback of gas becomes relatively large because the amount of introduction of new air is small. In such an operation area, natural intake is realized by the bypass passage 40. Therefore, by forming the bypass passage 40 by the first and second branch passages 44c and 44d described above, the gas is blown back. In the in-cylinder state caused by the difference between the cylinders can be reduced.

  On the other hand, in the high load side operation region, the influence of the blowback of the gas becomes relatively small because the amount of introduction of fresh air is large. In such an operating range, supercharging via the second passage 35, the third passage 37, etc. is realized. The second passage 35 and the third passage 37 can be laid out simply because the influence of the blowback of gas is small.

Other Embodiments
In the said embodiment, although illustrated about the in-line 4-cylinder engine, it is not restricted to this structure. For example, it may be an engine having at least three or more cylinders, such as an in-line three-cylinder engine or an in-line six-cylinder engine. For example, in the case of an in-line three-cylinder engine, the first and third cylinders are end-side cylinders, and the second cylinder is a center-side cylinder corresponding to both the first and third cylinders. On the other hand, in the case of the in-line six-cylinder engine, the first and sixth cylinders become end-side cylinders, while the second and fifth cylinders become central-side cylinders. Further, the number of passages branched in the bypass passage as the upstream passage may be increased according to the number of cylinders.

  Moreover, although the said embodiment illustrated about the structure which integrally formed the surge tank 38 and the guide parts 71 and 72 on either side, it is not restricted to this structure. The guide portions 71 and 72 may be separated. The same applies to the right side inclined surface 38e and the left side inclined surface 38f.

1 Engine (multi-cylinder engine)
11 cylinders
11A 1st cylinder (end side cylinder)
11B second cylinder (center side cylinder)
11C 3rd cylinder (center side cylinder)
11D 4th cylinder (end side cylinder)
17 First port (intake port)
18 2nd port (intake port, SCV port)
30 intake passage 34 supercharger (supercharged passage)
35 second passage (supercharged passage)
36 Intercooler (supercharged aisle)
37 third aisle (supercharged aisle)
38 Surge tank 38b Inlet 38e Right inclined surface (inclined surface)
38f Left inclined surface (inclined surface)
39 Independent passage 40 Bypass passage (upstream passage)
44b first branch passage 44c second branch passage 71 right guide portion 71a first guide surface (guide surface)
71b Second guide surface (second guide surface)
72 left guide portion 72a first guide surface (guide surface)
72b Second guide surface (second guide surface)
80 swirl control valve

Claims (5)

A plurality of cylinders including at least three or more cylinders arranged in a row, a plurality of intake ports respectively communicating with each of the plurality of cylinders, and an intake passage connected to each of the plurality of intake ports An intake system for a cylinder engine,
The intake passage is
A plurality of independent passages each connected to each of the plurality of intake ports;
The upstream end of each of the plurality of independent passages has a surge tank connected in a row according to the alignment order of the corresponding cylinders;
Among the plurality of cylinders, a cylinder located on the end side in the cylinder row direction is referred to as an end-side cylinder, and a cylinder adjacent to the end-side cylinder inside in the cylinder row direction is referred to as a center-side cylinder, Of the plurality of independent passages, a portion of the surge tank facing the section from the upstream end of the independent passage corresponding to the end-side cylinder to the upstream end of the independent passage corresponding to the central-side cylinder A guide surface for guiding the gas blown back to the surge tank from the central side cylinder in a direction not approaching the upstream end of the independent passage corresponding to the end side cylinder ;
In the surge tank, at a portion of the plurality of independent passages facing the upstream end of the independent passage corresponding to the end-side cylinder, the opposite side to the plurality of cylinders as it goes inward in the cylinder row direction An inclined surface inclined toward the
At a portion where the guide surface extends to the end side in the cylinder row direction, the gas blown back to the surge tank from the end side cylinder adjacent to the inner side in the cylinder row direction with respect to the inclined surface is An intake system of a multi-cylinder engine having a second guide surface for guiding toward a central cylinder . In the multi-cylinder engine intake system according to claim 1,
The plurality of intake ports include, for each of the plurality of cylinders, an SCV port configured to adjust a flow rate of passing gas through a swirl control valve;
The guide surface is disposed in the surge tank at a portion of the independent passage corresponding to the central side cylinder that faces the upstream end of the independent passage connected to the intake port configured as a non-SCV port. Multi-cylinder engine intake system. In the multi-cylinder engine intake system according to claim 2,
The multi-cylinder engine is configured as an in-line four-cylinder engine provided with two each of the plurality of intake ports for each of the plurality of cylinders.
Each of the plurality of intake ports includes a first port and a second port adjacent to the first port in the cylinder row direction and configured as the SCV port, for each of the plurality of cylinders.
When the plurality of cylinders are referred to as No. 1, No. 2, No. 3, No. 4 and No. 4 cylinders sequentially from one side in the cylinder row direction, No. 1, No. 2, No. 3, No. 3 and No. 4 cylinders. In any of the above, the first port and the second port are arranged in the same order,
The guide surface is connected to a portion of the surge tank facing the upstream end of the independent passage connected to the first port communicating with the second cylinder, and the first port communicating with the third cylinder An intake system for a multi-cylinder engine, which is disposed on both the upstream end of the independent passage and the portion facing the upstream end. The intake system for a multi-cylinder engine according to any one of claims 1 to 3 .
The intake passage has an upstream passage whose downstream end is connected to the surge tank and introduces gas to the surge tank,
The second guide surface is inclined so as to protrude toward the plurality of cylinders as it extends inward in the cylinder row direction when the surge tank is viewed in the cylinder axial direction.
The downstream end of the upstream passage is connected to a portion closer to the end-side cylinder than the second guide surface in the cylinder row direction, and gas flowing through the downstream end of the upstream passage is An intake system of a multi-cylinder engine which is directed toward the plurality of cylinders. In the multi-cylinder engine intake system according to claim 4 ,
The multi-cylinder engine is
And a supercharger configured to supercharge the gas introduced to each of the plurality of cylinders in an operation region on a load side higher than a predetermined load,
The intake passage is provided with a supercharge passage having a downstream end connected to the surge tank via an inlet and having the supercharger interposed therein.
The inlet is opened at a central portion in the column direction of the surge tank and has a diameter larger than that of the intake port.
The upstream passage is a bypass that guides gas so as to bypass the supercharger and reach the surge tank when the operating state of the multi-cylinder engine is in an operating area on a lower load side than the predetermined load. The intake system of a multi-cylinder engine configured as a passage.

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