JP6477763B2 - Intake passage structure of multi-cylinder engine - Google Patents

Description

  The technology disclosed herein relates to an intake passage structure of a multi-cylinder engine.

  Patent Document 1 discloses an intake device for an in-line four-cylinder engine as an example of an intake passage structure of a multi-cylinder engine. This intake device includes an independent passage connected to each of the four cylinders (inner passage of the downstream branch pipe section) and a surge tank (downstream) common to each independent passage arranged along the outer surface of the engine body. A collecting portion of the branch pipe portion). The surge tank according to Patent Literature 1 is disposed so as to face the opposite end portion (inlet) of the intake port on the opposite side of the intake port so as to be close to the intake port. With such an arrangement, the flow path length (runner length) from the surge tank to the intake port can be shortened.

  Patent Document 1 also discloses that an upstream-side passage (internal passage of the intermediate intake pipe portion) for introducing gas into the surge tank is connected to the central portion in the cylinder row direction of the surge tank.

Japanese Unexamined Patent Publication No. 2013-147953

  By the way, in an engine with a high geometric compression ratio, there is a concern about an increase in pump loss. Therefore, in a specific operation region (for example, an operation region where fuel efficiency is prioritized), the intake valve is closed during the compression stroke. It is possible to do. When such late closing is performed, a so-called delayed closing type mirror cycle can be realized, so that throttling can be omitted or suppressed, and pump loss can be reduced.

  However, when the valve is closed late, the intake valve remains open immediately after the transition from the intake stroke to the compression stroke, so that the gas charged in the cylinder blows back to the intake side as the piston rises. It becomes like this.

  Here, if the runner length is shortened as in Patent Document 1, the gas blown back to the intake side may flow back to the surge tank via the intake port.

  On the other hand, for example, in a four-cylinder engine, when a predetermined cylinder (hereinafter also referred to as “starting cylinder”) is in the compression stroke, the cylinder that will enter the compression stroke next to that cylinder (hereinafter also referred to as “following cylinder”). ) Is during the intake stroke.

  Therefore, when the gas is blown back from the preceding cylinder in the compression stroke, the inside of the succeeding cylinder becomes negative pressure. Therefore, if the starting cylinder and the succeeding cylinder are adjacent in the cylinder row direction, the starting cylinder is transferred to the surge tank. The inventors of the present application have noticed that the backflowed gas may be sucked into the later cylinder.

  As a result of further investigation, the inventors of the present application have accelerated the suction of the gas blown back from the preceding cylinder into the succeeding cylinder depending on the connection location between the upstream passage and the surge tank. It has been found that there is a possibility of causing an ignition (hereinafter, also referred to as “plague”).

  For example, when the upstream side passage and the connection portion of the surge tank, the upstream end portion of the independent passage leading to the preceding cylinder, and the upstream end portion of the independent passage leading to the subsequent cylinder are arranged in this order in the cylinder row direction, The gas flowing into the surge tank from the upstream passage passes through the space near the upstream end corresponding to the preceding cylinder and the space near the upstream end corresponding to the succeeding cylinder in this order inside the surge tank. A flow like this is formed. As a result, the gas flowing into the surge tank from the upstream passage becomes “following wind”, and the gas blown back from the preceding cylinder is pushed away to the succeeding cylinder.

  As a result of the gas blown back from the starting cylinder being pushed away by the gas flowing in from the upstream passage, the inventors of the present application introduce more gas than necessary to the succeeding cylinder, and as a result, there is a risk of reaching the pre-ignition. I realized that there was.

  In order to suppress the plague, the upstream flow passage and the surge tank connecting portion, the upstream end portion of the independent passage leading to the succeeding cylinder, and the starting cylinder so that the gas flowing in from the upstream flow passage becomes a “head wind”. It is conceivable to arrange the upstream end portion of the independent passage leading to this in the order in the cylinder row direction. However, with this configuration, although the suction of the blown back gas is suppressed, the flow path length from the upstream passage to the preceding cylinder is different from the flow path length from the upstream passage to the subsequent cylinder. Therefore, the responsiveness may be deteriorated in the starting cylinder. Also, if the flow path length differs between cylinders, there is a possibility that the difference between cylinders may increase in the state quantity such as the charging efficiency.

  As another measure for suppressing the plague, for example, it is conceivable to increase the capacity of the surge tank, but in this case, since the volume of the entire intake passage is increased by the increase in the capacity of the surge tank, When configured in combination with a supercharger, it is not preferable in that there is a risk of a decrease in supercharging response. In addition, such a configuration is disadvantageous because it may interfere with the layout of peripheral components of the intake device.

  The technology disclosed herein has been made in view of such a point, and an object of the technology is to suppress the occurrence of pre-age caused by gas blowback in an intake structure of a multi-cylinder engine.

  The technology disclosed herein includes a plurality of cylinders arranged in a row, an engine body configured to perform combustion in a predetermined combustion order in each of the plurality of cylinders, and the engine body. A plurality of intake ports that communicate with each of the plurality of cylinders, a plurality of intake valves that open and close each of the intake ports, and a variable valve mechanism that changes opening and closing timings of the plurality of intake valves. And the variable valve mechanism is configured to set the closing timing of the plurality of intake valves during the compression stroke when the operating state of the engine body is in a predetermined operating range. It relates to the passage structure.

  The intake passage structure includes an intake passage connected to each of the plurality of intake ports, and the intake passage includes a plurality of independent passages connected to each of the plurality of intake ports, and the plurality of intake ports. The upstream end of each of the plurality of independent passages is arranged in a row according to the order in which the corresponding cylinders are arranged. And a upstream end passage connected to the surge tank and introducing gas into the surge tank.

  Of the plurality of cylinders, when two combustion cylinders whose combustion order is adjacent and adjacent in the cylinder row direction are referred to as a first cylinder and a second cylinder in the order in which combustion occurs, the downstream end portion of the upstream passage and the cylinder The connection location with the surge tank is in the section from the upstream end of the independent passage corresponding to the preceding cylinder to the upstream end of the independent passage corresponding to the succeeding cylinder in the cylinder row direction. The upstream passage is formed to direct the gas flowing through the upstream passage toward the succeeding cylinder of the preceding cylinder and the succeeding cylinder.

  According to this configuration, the multi-cylinder engine can close the intake valve during the compression stroke in a predetermined operation region. When such slow closing is performed, when the piston rises in the compression stroke, the gas side charged in the cylinder blows back to the intake side.

  Moreover, according to the said structure, the surge tank is arrange | positioned so as to oppose the intake port across each independent passage. With such an arrangement, the surge tank can be brought close to the intake port, and the flow path length (runner length) from the surge tank to the intake port can be shortened. By shortening the runner length, the entire engine can be laid out compactly, the volume of the intake passage can be reduced, and as a result, the response to intake can be improved.

  By the way, in an engine with a short runner length, if the above-described slow closing is executed, the gas blown back to the intake side may flow back to the surge tank via the intake port.

  In particular, in a four-cylinder engine, when the gas is blown back from the preceding cylinder during the compression stroke, the inside of the succeeding cylinder during the intake stroke becomes negative pressure, so the starting cylinder and the succeeding cylinder are adjacent in the cylinder row direction. In view of this, the gas that has flowed back from the preceding cylinder to the surge tank may be sucked into the subsequent function.

  In particular, depending on the connection point between the upstream passage and the surge tank, the gas blown back from the starting cylinder is swept away by the gas flowing in from the upstream passage, and as a result, more gas than necessary is introduced into the succeeding cylinder. This may cause pre-ignition (hereinafter, also referred to as “play”).

  On the other hand, according to the above configuration, the upstream passage and the surge tank are connected at the upstream end of the independent passage leading to the succeeding cylinder from the upstream end of the independent passage leading to the preceding cylinder in the cylinder row direction. It is set within the interval between. With this setting, when the succeeding cylinder is in the intake stroke (that is, when the vicinity of the upstream end corresponding to the succeeding cylinder has a negative pressure), the gas flowing from the upstream passage into the surge tank Coupled with the direction toward the later cylinder, a flow toward the later cylinder is formed without joining the gas blown back from the earlier cylinder.

  Thus, for example, a configuration in which the connection portion between the upstream passage and the surge tank, the upstream end portion of the independent passage leading to the preceding cylinder, and the upstream end portion of the independent passage leading to the succeeding cylinder are arranged in this order in the cylinder row direction. As compared with, for the gas blown back from the starting cylinder, the gas flowing in from the upstream passage is less likely to become “tailing wind”. As a result, it is possible to suppress the intake of the gas blown back from the preceding cylinder into the subsequent cylinder, thereby suppressing the occurrence of pre-ignition.

  Moreover, if the connection location between the upstream passage and the surge tank is set as described above, for example, the upstream end portion of the independent passage corresponding to the starting cylinder, the upstream end portion of the independent passage corresponding to the succeeding cylinder, and the upstream Compared with the configuration in which the side passage and the surge tank are connected in this order in the cylinder row direction, the difference between cylinders such as charging efficiency is reduced, and the response is comparable between the starting cylinder and the succeeding cylinder It becomes possible to ensure the sex.

  As described above, according to the above-described configuration, it is possible to suppress the occurrence of plague due to gas blowback while ensuring the responsiveness of each cylinder.

  In addition to the upstream passage, the intake passage is connected to the surge tank at a downstream end, and has a second upstream passage for introducing gas into the surge tank. The connection location between the downstream end of the upstream passage and the surge tank may be offset in the cylinder row direction with respect to the connection location between the downstream end of the upstream passage and the surge tank. .

  For example, in the case of an engine equipped with a supercharger, a plurality of passages to the surge tank such as a passage that passes through the supercharger and reaches the surge tank and a passage that bypasses the turbocharger and reaches the surge tank. There is a possibility that the passages are connected so that gas flows from each passage.

  According to the above configuration, the connection point between the second upstream passage and the surge tank is offset in the cylinder row direction from the connection point between the upstream passage and the surge tank. Both the gas flow flowing into the gas tank and the gas flow flowing into the surge tank from the second upstream passage can be made to flow smoothly without colliding with each other.

  Further, the second upstream passage is configured as a supercharging passage in which a supercharger and an intercooler are arranged in order from the upstream side along the gas flow direction, while the upstream passage is The second upstream passage is configured as a bypass passage that branches from the upstream side of the supercharger and that bypasses the supercharger and the intercooler and is connected to the surge tank. It is good.

  In an engine equipped with a supercharger, there is a concern about the occurrence of plague due to gas blowback compared to a naturally aspirated engine. Therefore, if it is configured so that the gas flows in from a plurality of passages, the configuration that suppresses the occurrence of the plague while smoothly flowing the gas into the surge tank, as described above, particularly includes a supercharger. It becomes effective in the engine.

  In addition, the engine body includes at least a first set of first cylinders, a first set of subsequent cylinders adjacent to the first cylinder in the cylinder row direction and having a subsequent combustion order, a second set of first cylinders, and the A second set of succeeding cylinders that are adjacent to the starting cylinder in the cylinder row direction and follow the combustion order, and the upstream passage is along a direction from one side to the other side in the cylinder row direction After extending, the first branch passage branches into a first branch passage and a second branch passage. The first branch passage extends along a direction from one side to the other side in the cylinder row direction, and then in the surge tank, 1 The second branch passage is connected to face the section from the upstream end of the independent passage corresponding to the first cylinder of the set to the upstream end of the independent passage corresponding to the first cylinder of the first set. , After extending along the direction from the other side of the cylinder row direction to one side, In the surge tank, connected in opposition to a section from the upstream end of the independent passage corresponding to the second set of the preceding cylinders to the upstream end of the independent passage corresponding to the second set of the subsequent cylinders, The connection location between the second branch passage and the surge tank may be set closer to the succeeding cylinder in the cylinder row direction than the connection location between the first branch passage and the surge tank.

  According to the above configuration, the upstream side passage extends from one side to the other side in the cylinder row direction, and then branches into the first branch passage and the second branch passage.

  Here, the first branch passage is connected to the surge tank after extending in the direction from one side of the cylinder row direction to the other side in the same manner as before branching, whereas the second branch passage is connected to the surge tank before branching. Is extended to the opposite side and then connected to the surge tank. Because of such “turnback”, the flow velocity of the gas flowing into the surge tank from the second branch passage becomes lower than the gas flowing into the surge tank from the first branch passage.

  On the other hand, depending on the connection point between the surge tank and the first and second branch passages, the gas flowing back from the first cylinder to the surge tank flows from the first and second branch passages, even if “tailing wind” does not occur. There is a possibility that the gas will be sucked into the succeeding cylinder in preference to the gas (first).

  In particular, the second set of succeeding cylinders is relatively easier to flow than the backflowed gas compared to the first set of succeeding cylinders because the flow velocity of the gas flowing in from the second branch passage is low.

  Therefore, according to the above configuration, the connection location between the second branch passage and the surge tank is set closer to the subsequent cylinder in the cylinder row direction than the connection location between the first branch passage and the surge tank. If it sets in this way, the gas which flows in from a 2nd branch passage will become easy to flow in into the 2nd set of succeeding cylinders. Thereby, the fall of the flow rate can be compensated.

  Further, each of the plurality of intake ports includes a first port and a second port arranged in a line along a cylinder row direction in each of the plurality of cylinders, and the plurality of independent passages includes the plurality of cylinders. Each of the first and second independent passages connected to the first port and the second independent passage connected to the second port, and the connection point between the upstream passage and the surge tank is Of the first and second independent passages corresponding to the starting cylinder, the first and second corresponding to the succeeding cylinder from one upstream end disposed on the succeeding cylinder side in the cylinder row direction. The two independent passages may be set so as to face each other in a section extending to one upstream end disposed on the side of the starting cylinder in the cylinder row direction.

  According to this configuration, in an engine in which two intake ports are provided for each cylinder, it is possible to suppress the occurrence of plague due to gas blowback while ensuring the responsiveness of each cylinder.

  As described above, according to the intake passage structure of the above-described multi-cylinder engine, it is possible to suppress the occurrence of plague due to gas blowback while ensuring the responsiveness of each cylinder.

FIG. 1 is a schematic view illustrating the configuration of a multi-cylinder engine. FIG. 2 is a perspective view showing the multi-cylinder engine with a part thereof omitted. FIG. 3 is a plan view schematically showing a configuration around four cylinders. FIG. 4 is a perspective view showing the overall configuration of the intake device as viewed from the front side. FIG. 5 is a perspective view showing the overall configuration of the intake device as seen from the rear side. FIG. 6 is a cross-sectional view showing a passage structure on the supercharger side. FIG. 7 is a longitudinal sectional view showing a passage structure on the supercharger side. FIG. 8 is a perspective view showing a longitudinal section around the surge tank. FIG. 9 is a perspective view showing a vertical section different from FIG. FIG. 10 is a view showing a passage structure related to the bypass passage as seen from the front side. FIG. 11 is a view showing the passage structure according to the bypass passage as seen from the rear side. FIG. 12 is a view showing a passage structure related to the bypass passage as viewed from above. FIG. 13 is a perspective view showing a pipeline of the bypass passage. FIG. 14 is a diagram showing a flow path around the surge tank. FIG. 15 is a longitudinal sectional view showing a connection structure between the surge tank and the bypass passage. FIG. 16 is a cross-sectional view showing a connection structure between the surge tank and the bypass passage.

  Hereinafter, an embodiment of an intake passage structure of a multi-cylinder engine will be described in detail with reference to the drawings. In addition, the following description is an illustration. FIG. 1 is a diagram illustrating an engine 1 to which an intake passage structure of a multi-cylinder engine disclosed herein is applied. FIG. 2 is a perspective view in which the configuration is partially omitted, and FIG. 3 is a plan view schematically showing the configuration around the four cylinders 11.

  The engine 1 is a gasoline engine (particularly a 4-stroke internal combustion engine) mounted on an FF vehicle, and includes a mechanically driven supercharger (so-called supercharger) 34 as shown in FIG. It is configured.

  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 along the vehicle width direction. It is configured as a so-called in-line 4-cylinder horizontal engine mounted in a posture. Thus, in the present embodiment, the engine longitudinal direction, which is the arrangement direction (cylinder row direction) of the four cylinders 11, substantially matches the vehicle width direction, and the engine width direction substantially matches the vehicle longitudinal direction. .

  Hereinafter, unless otherwise specified, the front side is one side in the engine width direction (the front side in the vehicle front-rear direction), the rear side is the other side in the engine width direction (the rear side in the vehicle front-rear direction), and the left side is the engine front-rear direction Direction (cylinder row direction) on one side (left side in the vehicle width direction and engine front side), and the right side is the other side in the engine longitudinal direction (cylinder row direction) (right side in the vehicle width direction and engine) Points to the rear).

  In the following description, the upper side refers to the upper side in a state where the engine 1 is mounted on the 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 the engine)
The engine 1 is configured as a front intake rear exhaust type. That is, the engine 1 is arranged on the front side of the engine body 10 having four cylinders 11 (only one cylinder is shown in FIG. 1) and the intake ports 17 and 18 as shown in FIG. And an exhaust passage 50 disposed on the rear side of the engine body 10 and communicating with each cylinder 11 via the exhaust port 19.

  The intake passage 30 according to the present embodiment is unitized by combining a plurality of passages for guiding gas, devices such as a supercharger 34 and an intercooler 36, and a bypass passage 40 that bypasses these devices. It is configured as an “intake device”.

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

  Four cylinders 11 are formed inside 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 the central axes (hereinafter referred to as “cylinder axes”) of the cylinders 11 extend parallel to each other and perpendicular to the cylinder row direction. Hereinafter, the four cylinders 11 shown in FIG. 3 may be referred to as the first cylinder 11A, the second cylinder 11B, the third cylinder 11C, and the fourth cylinder 11D in order 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 divides 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. This engine 1 is configured such that the ceiling surface of the combustion chamber 16 is lower than before in order to increase the geometric compression ratio. The pent roof shape of the ceiling surface is close to a flat shape.

  Two intake ports 17 and 18 are formed in the cylinder head 13 for each cylinder 11. The two intake ports 17, 18 communicate with the combustion chamber 16, and each cylinder 11 has 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 19 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 ports 17 and 18 are respectively open to the outer surface (mounting surface) 10a of the engine body 10, and the downstream end of the intake passage 30 is connected thereto. On the other hand, the downstream ends of the ports 17 and 18 are respectively open to the ceiling surface of the combustion chamber 16.

  Hereinafter, “17A” instead of “17” is attached to the first port leading to the first cylinder 11A, and “18A” is attached instead of “18” to the second port leading to the cylinder 11A. There is. The same applies to the second cylinder 11B to the fourth cylinder 11D. For example, “18C” may be attached to the second port leading to the third cylinder 11C instead of “18”.

  Further, the two intake ports 17 and 18 include SCV ports configured so that the flow rate of the gas passing through each cylinder 11 is throttled through a swirl control valve (SCV) 80. In the present embodiment, the aforementioned second port 18 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, the intake valve mechanism has an intake electric VVT (Variable Valve Timing) 23 which is a variable valve mechanism as shown in FIG. The intake electric VVT 23 is configured to continuously change the rotation phase of the intake camshaft within a predetermined angle range. Thereby, the valve opening timing and the valve 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 formed with two exhaust ports 19, 19 for each cylinder 11. The two exhaust ports 19, 19 communicate with the combustion chamber 16.

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

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

  Although details are 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 burned 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 electric VVT 23 and the exhaust electric VVT 24 constitute an internal EGR system. Note that the internal EGR system is not necessarily configured by VVT.

  An injector 6 is attached to the cylinder head 13 for each cylinder 11. In this configuration example, the injector 6 is a multi-injection type fuel injection valve, 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 path 62 that connects 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 path 62. The fuel pump 65 pumps fuel to the common rail 64. In this configuration example, the fuel pump 65 is a plunger-type pump driven by the crankshaft 15. The common rail 64 is configured to store the fuel pumped from 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 into the combustion chamber 16 from the injection port of the injector 6.

  A spark plug 25 is attached to the cylinder head 13 for each cylinder 11. The spark plug 25 is attached in such a posture that its tip faces the combustion chamber 16 and forcibly ignites the air-fuel 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 in the engine body 10 and communicates with the intake ports 17 and 18 of each cylinder 11. The intake passage 30 is a passage through which gas introduced into the combustion chamber 16 flows. An air cleaner 31 that filters 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 that branches into two for each cylinder 11. Although details will be described later, one of the two independent passages 39 is connected to the first port 17 and the other is connected to the second port 18. Hereinafter, the former independent passage 39 may be denoted by reference numeral “391” while the latter may be denoted by reference numeral “392”. In this way, the downstream end of the independent passage 39 is connected to the intake ports 17 and 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 opening thereof.

  A supercharger 34 is also disposed in the intake passage 30 downstream of the throttle valve 32. 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. Although the supercharger 34 according to the present embodiment is configured as a roots-type supercharger, this configuration may be anything. For example, a re-sholm 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 34a transmits driving force between the supercharger 34 and the engine 1 or interrupts transmission of driving force. An unillustrated control means such as an ECU (Engine Control Unit) switches between disconnection and connection of the electromagnetic clutch 34a, whereby the supercharger 34 is switched on and off. That is, the engine 1 switches between an operation of supercharging the gas introduced into the combustion chamber 16 and an 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 supercharger 34 in the intake passage 30. The intercooler 36 is configured to cool the gas compressed in the supercharger 34. The intercooler 36 in this configuration example is configured as a water-cooled type.

  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 a first passage that guides the intake air purified by the air cleaner 31 to the supercharger 34. 33, a second passage 35 that guides the intake air compressed by the supercharger 34 to the intercooler 36, and a third passage 37 that guides the gas cooled by the intercooler 36 to the surge tank 38. The surge tank 38 is disposed in the vicinity of the inlet (upstream end) 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 supercharger 34 and the intercooler 36 constitute a “supercharging passage”.

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

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

  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 supercharger 34 in the intake passage 30 flows back upstream of the supercharger 34 through the bypass passage 40. 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, the supercharger 34, the bypass passage 40, and the bypass valve 41 constitute a supercharging system.

  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 exhaust gas discharged from the combustion chamber 16 flows. Although the detailed illustration is omitted, the upstream portion of the exhaust passage 50 constitutes an independent passage branched for each cylinder 11. 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 includes a three-way catalyst. Note that the exhaust gas purification system is not limited to one including only a 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 returning a part of the burned gas to the intake passage 30. The upstream end of the EGR passage 52 is connected downstream of the catalytic converter 51 in the exhaust passage 50. The downstream end of the EGR passage 52 is connected upstream of the supercharger 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 burned gas flowing through the EGR passage 52. By adjusting the opening degree of the EGR valve 54, the recirculation amount of the cooled burned gas, that is, the external EGR gas can be adjusted.

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

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

  4 is a perspective view showing the entire configuration of the intake passage 30 unitized as an intake device as seen from the front side, and FIG. 5 is a perspective view showing the entire configuration of the intake passage 30 as seen from the rear side. FIG. 6 is a transverse sectional view showing a supercharger side passage structure in the intake passage 30, and FIG. 7 is a longitudinal sectional view thereof. FIG. 8 is a perspective view showing a vertical section around the surge tank 38, and FIG. 9 is a perspective view showing another vertical section.

  Each part constituting the intake passage 30 is arranged on the front side of the engine body 10, specifically, on the front side of the mounting surface 10a. Note that the mounting surface 10a is configured by a front outer surface of the cylinder head 13 and the cylinder block 12, as shown in FIGS.

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

  As shown in FIG. 2 and FIGS. 4 to 8, the supercharger 34 is disposed opposite to the four cylinders 11 across the surge tank 38. A gap (interval) corresponding to the dimension of the surge tank 38 is provided between the rear surface of the supercharger 34 and the mounting surface 10a. The first passage 33 extends along the cylinder row direction on the left side of the supercharger 34 and is connected to the left end of the supercharger 34. Further, the intercooler 36 is disposed below the supercharger 34, and is disposed at a predetermined interval with respect to the mounting surface 10 a, similarly to the supercharger 34. The supercharger 34 and the intercooler 36 are adjacent to each other in the vertical direction. The second passage 35 extends vertically so as to connect the front part of the supercharger 34 and the front part of the intercooler 36. The surge tank 38 is disposed in a gap between the supercharger 34 and the mounting surface 10a, and sandwiches a plurality of independent passages 39 with respect to the end portions (inlet) of the intake ports 17 and 18 on the non-cylinder side. Opposed 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 10a, so that the intercooler 36 is positioned below the surge tank 38. The rear part of the intercooler 36 and the bottom part of the surge tank 38 are connected. The bypass passage 40 is formed so as to extend upward from the middle of the first passage 33 and then extend inward (rightward) of the engine body 10 and is connected to the upper portion of the surge tank 38. Yes.

  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-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 metal short cylinder shape, and as shown in FIGS. 4 to 6, the throttle body 33a is positioned leftward and forward with respect to the mounting surface 10a in a posture in which the openings at both ends are directed left and right. Are arranged to be. An 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 end) of the throttle body 33a is connected to the downstream side (right side) of the first passage 33. The first passage body 33b, which is a part, is connected.

  As shown in FIG. 6, the first passage body 33 b is configured to connect the throttle body 33 a to the supercharger 34. Specifically, the first passage body 33b is formed in a long cylindrical shape with 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 so as to gradually increase in diameter from the outside in the cylinder row direction toward the inside (from the left side to the right side). As described above, the downstream end of the throttle body 33a is connected to the upstream end (left end) of the first passage body 33b, while the suction port of the supercharger 34 is connected to the downstream end (right end) thereof. ing.

  Further, the first passage body 33b has a junction 33c where the EGR passage 52 joins. 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 thereto. The junction 33c is formed at least downstream of the throttle valve 32.

  In addition, a branch portion 33d that branches to the bypass passage 40 is also opened in the first passage body 33b. The branch portion 33d is formed on the upper surface of the first passage body 33b in the vicinity of the junction portion 33c (substantially the same position with respect to the gas flow direction) and is connected to the upstream end of the bypass passage 40 (see FIG. 10). As shown in FIG. 10 and the like, the branch portion 33d is connected to the supercharger 34, the intercooler 36, the four sets of intake ports 17 and 18, and the intake ports 17 and 18 through an independent passage 39. It is located on the outer side (left side) in the cylinder row direction than the surge tank 38.

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

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

-Passage structure on the turbocharger side-
First, the passage structure on the side sucked into the supercharger 34 will be described in detail.

  As described above, the supercharger 34 according to this embodiment is configured as a roots-type supercharger. Specifically, the supercharger 34 includes a pair of rotors (not shown) provided with a rotation shaft extending along the cylinder row direction, a casing 34b that houses the rotor, and a drive pulley 34d that rotationally drives the rotor. The drive shaft 34d is connected to the crankshaft 15 via a drive belt (not shown) wound around the drive pulley 34d. The above-described electromagnetic clutch 34a is interposed between the drive pulley 34d and the rotor, and the driving force is supplied to the supercharger 34 via the crankshaft 15 by switching the cutoff and connection of the electromagnetic clutch 34a. Transmits or interrupts transmission of driving force.

  The casing 34b is formed in a cylindrical shape extending in the cylinder row direction, and divides the housing space of the rotor and the gas flow path passing through the supercharger 34. Specifically, the casing 34b is formed in a metal cylindrical shape having an opening at the left end and the front surface in the cylinder direction. As shown in FIG. 6 and the like, the casing 34b is substantially at the center of the mounting surface 10a in the cylinder row direction. The first passage 33 and the first passage 33 are arranged so as to leave a predetermined interval.

  A suction port for sucking gas compressed by the rotor is opened at the left end of the casing 34b in the longitudinal direction, 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 34c for discharging the gas compressed by the rotor is opened at the front portion (side portion opposite to the engine body 10) of the casing 34b. The upstream end (upper end) of the second passage 35 is connected.

  The drive pulley 34d is configured to rotationally drive the rotor accommodated in the casing 34b. Specifically, the drive pulley 34d is formed in a shaft shape that protrudes from the right end of the casing 34b and extends substantially coaxially with respect to 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 connected to the supercharger 34 in accordance with 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. The second passage 35 according to this embodiment is formed so as to extend along the vertical direction of the engine 1 so that the supercharger 34 and the intercooler 36 are vertically adjacent. Further, as shown in FIG. 7, the upper and lower ends of the second passage 35 are each open toward the rear (the engine body 10 side). Here, the upper opening 35a is connected to the front part of the casing 34b (specifically, the discharge port 34c), and the lower opening 35b is the front part of the intercooler 36 (the front surface of the cooler housing 36c). )It is connected to the.

  Specifically, the second passage 35 is formed as a square tube portion made of a resin that extends in the vertical direction and is flat in the horizontal direction, and both upper and lower end portions are bent toward the rear. That is, as shown in FIG. 7, the second passage 35 is configured to form a substantially U-shaped flow path 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 36a having a gas cooling function and the side portion of the core 36a as shown in FIGS. A core connecting portion 36b and a cooler housing 36c that accommodates the core 36a are provided. Although details are omitted, a water supply pipe for supplying cooling water to the core 36a and a drain pipe for discharging cooling water from the core 36a are connected to the core connecting portion 36b. As shown in FIG. 4 and the like, the dimension in the width direction (left-right direction) of the intercooler 36 is shorter than the dimension in the width direction of the supercharger 34, and the second passage 35 in the same direction It is almost the same as the dimensions.

  The core 36a is formed in a rectangular shape, and is supported in such a posture that one side surface (rear surface) thereof faces the mounting surface 10a. The front surface of the core 36a constitutes a gas inflow surface, while the rear surface of the core 36a constitutes a gas outflow surface, each being the widest surface of the core 36a. Although not shown, the core 36a has a plurality of water tubes in which a thin plate material is formed into a flat cylindrical shape, and a corrugated fin corrugated fin is connected to the outer wall surface of each water tube by brazing or the like. . By comprising in this way, the cooling water supplied from the water supply pipe is introduce | transduced into each water tube, and cools high temperature gas. The cooling water warmed by cooling the gas is discharged from each water tube through the drain pipe. Further, by providing the corrugated fins, the surface area of each water tube is increased and the heat dissipation effect is improved.

  As shown in FIG. 4, the core connecting 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, the drain pipe, and the water tube are connected to each other through the core connection portion 36b. The core connecting part 36b constitutes the right side wall part of the intercooler 36, and partitions the accommodation space for the core 36a together with the cooler housing 36c.

  The cooler housing 36 c is disposed below the casing 34 b, defines a housing space for the core 36 a, and flows between the second passage 35 and the third passage 37 in the intake passage 30. Constitutes the road.

  Specifically, the cooler housing 36c is formed in a rectangular thin box shape in which a front surface and a rear surface are opened, and is supported in a posture where the rear surface and the mounting surface 10a face each other at a position below the casing 34b. Yes. Similar to the casing 34b, the rear surface is disposed at a predetermined interval (see FIG. 7) with respect to the mounting surface 10a of the engine body 10.

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

  The third passage 37 is a resin member formed integrally with the surge tank 38 and the independent passage 39, and connects the intercooler 36 to the surge tank 38 as shown in FIGS. It is configured. Specifically, the third passage 37 is fastened to the cooler housing 36c in order from the upstream side, and a collecting portion 37a where the gas that has passed through the intercooler 36 gathers, and an introduction that guides the gas gathered in the collecting portion 37a to the surge tank 38. Part 37b. The third passage 37 is disposed below the surge tank 38 at least in a vehicle-mounted state.

  The collective portion 37a is formed in a shallow box shape with front and rear depths opened on the front side, that is, the cooler housing 36c side, and the open portion is an opening on the rear side of the cooler housing 36c as shown in FIG. 36e. The collective portion 37a is positioned in the gap between the rear surface of the cooler housing 36c and the mounting surface 10a of the engine body 10. Moreover, the upstream end of the introduction part 37b is further connected to the rear surface of the gathering part 37a.

  The introduction portion 37b is formed as a curved pipe portion extending substantially in the vertical direction, and its upstream end is connected to the rear surface of the collecting portion 37a, while its downstream end is the central portion of the bottom surface of the surge tank (FIGS. 8 to 8). 9). As shown in FIG. 7 and the like, the introducing portion 37b sews a gap between the region from the rear surface of the collecting portion 37a to the rear surface of the casing 34b of the supercharger 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 introduction portion 37b extends obliquely upward to the right from the connecting portion with the collecting portion 37a, while the downstream portion thereof is connected to the surge tank 38. It is formed to extend directly upward toward the connecting portion. As a result of this formation, the downstream end portion of the introduction 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 (FIG. 7).

  The surge tank 38 has an intake port 17 corresponding to the fourth cylinder 11D from the position of the intake ports 17 and 18 (specifically, the second port 18A) corresponding to the first cylinder 11A in the cylinder row direction. 18 (specifically, the first port 17D) is formed in a substantially cylindrical shape that extends to the position where it is disposed and is closed at both ends in the same direction.

  As described above, the surge tank 38 is disposed opposite the opposite ends of the intake ports 17 and 18 on the opposite cylinder side with the plurality of independent passages 39 interposed therebetween (see FIG. 7). As will be described later, when each of the plurality of independent passages 39 is formed in a short cylindrical shape, the surge tank 38 is positioned near the inlets (upstream end portions) 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 portion 37 b) is connected to the bottom of the surge tank 38. An introduction port 38b having a substantially circular cross section is opened at the center portion of the inner bottom surface 38a of the surge tank 38 (specifically, the center portion in the cylinder row direction), and the downstream end portion of the introduction portion 37b is And, it is connected to the surge tank 38 through the introduction port 38b.

  The introduction port 38b is formed to have a larger diameter than the intake ports 17 and 18.

  In the surge tank 38, the dimension from the introduction port 38b to one end (the end on the first cylinder 11A side) in the cylinder row direction is substantially equal to the dimension from the other end (the end on the fourth cylinder 11D side). It has become. By adopting such a configuration, it becomes possible to ensure the distribution performance of intake air, which is advantageous in reducing the difference in charging efficiency between cylinders.

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

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

  The four sets of independent passages 39 are arranged so as to correspond to the four sets of intake ports 17, 18, respectively, and include the integrally formed third passage 37, surge tank 38, and independent passage 39. When assembled to the engine body 10, each independent passage 39 and the corresponding intake ports 17 and 18 constitute a single passage.

  As described above, the independent passage 39 is composed of the independent passage 391 corresponding to the first port 17 and the independent passage 392 corresponding to the second port 18 for each 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, The port 18 and the independent passage 392 corresponding to the port 18 constitute an independent passage. In this way, eight independent passages are configured. The independent passage 391 corresponding to the first port 17 is an example of “first independent passage”, and the independent passage 392 corresponding to the second port 18 is an example of “second independent passage”.

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

  Incidentally, as will be described later, the downstream 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 tanks 38. It is connected to the top surface.

  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 outside of the surge tank 38. Portions 38c and 38d are provided.

  The two first and second introduction portions 38c and 38d are both set at positions offset in the cylinder row direction with respect to the introduction port 38b of the surge tank 38. Of the two first and second introduction portions 38c and 38d, the first introduction portion 38c located on one side (right side) in the cylinder row direction has one branch passage (hereinafter referred to as "first branch passage"). The downstream end of 44b is connected to the second introduction portion 38d located on the other side (left side), and downstream of the other branch passage (hereinafter also referred to as “second branch passage”) 44c. The ends are connected (see also FIG. 12).

  Specifically, the first and second introduction portions 38c and 38d are both formed in a short cylinder shape, and as shown in FIG. 8, are perpendicular to the cylinder row direction from the upper surface of the surge tank 38 and , Extending obliquely upward and forward.

  As shown in FIG. 8, the first introduction portion 38c extends from the upstream end of the independent passage 392 corresponding to the second port 18A of the first cylinder 11A to the first port 17B of the second cylinder 11B in the cylinder row direction. Corresponding to the second port 18B of the second cylinder 11B from the upstream end of the independent passage 391 corresponding to the first port 17A of the first cylinder 11A, specifically in the section from the corresponding upstream end of the independent passage 391. In the section from the upstream end of the independent passage 392, more specifically, it is disposed so as to face a portion near the upstream end of the independent passage 392 corresponding to the second port 18B of the second cylinder 11B. (See also FIG. 14).

  On the other hand, as shown in FIG. 8, the second introduction part 38d is connected to the first port of the fourth cylinder 11D from the upstream end of the independent passage 392 related to the second port 18C of the third cylinder 11C in the cylinder row direction. In the section from the upstream end of the independent passage 391 related to 17D, specifically, from the upstream end of the independent passage 391 related to the first port 17C of the third cylinder 11C to the second port 18D of the fourth cylinder 11D. In the section from the upstream end of the passage 392, more specifically, it is disposed so as to face a portion near the upstream end of the independent passage 392 related to the second port 18D of the fourth cylinder 11D (see FIG. 14).

  That is, the second introduction portion 38d is offset in the cylinder row direction to the left of the first introduction portion 38c, that is, in the direction from the first cylinder 11A to the fourth cylinder 11D. As a result of such offset, in the cylinder row direction, the independent passages 391 and 392 corresponding to the second introduction portion 38d and the fourth cylinder 11D are independent passages 391 corresponding to the first introduction portion 38c and the first cylinder 11A, 392 and relatively closer.

  As shown in FIGS. 8 to 9, the inner bottom surface 38 a of the surge tank 38 is formed lower than the lower surface 39 a at the upstream end of each of the eight independent passages 39 in the vehicle-mounted state. Each inner bottom surface 38a is formed so as to be positioned relatively upward when it is away from the introduction port 38b in the cylinder row direction than when it is approaching.

  That is, the height of the inner bottom surface 38a is such that the lower surface 39a at the upstream end of each independent passage 39 increases as the distance from the introduction port 38b corresponding to the connection portion with the downstream end of the third passage 37 increases in the cylinder row direction. It is configured to be close to the height (see also FIG. 15).

  Specifically, the inner bottom surface 38a of the surge tank 38 is inclined so as to gradually increase as the distance from the introduction port 38b increases. Therefore, the inner bottom surface 38a is higher in the vicinity of the first cylinder 11A and the fourth cylinder 11D on both ends than in the vicinity of the second cylinder 11B and the third cylinder 11C on the center side.

  As shown in FIGS. 8 to 9, a pair of left and right wall portions 71 and 72 are erected on both sides of the introduction port 38b (on the left and right sides in the cylinder row direction). Each of the wall portions 71 and 72 rises from the inner bottom surface 38a of the surge tank 38 along the gas flow direction at both edges of the introduction port 38b formed as a connection portion between the third passage 37 and the surge tank 38. It is erected. The dimensions of the walls 71 and 72 in the height direction are the same.

  The gas sucked into the supercharger 34 reaches each cylinder 11 through the “supercharge passage” thus configured.

  That is, during supercharging, while the engine 1 is operating, the output from the crankshaft 15 is transmitted via 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 then discharges it from the discharge port 34c. The discharged gas flows into the second passage 35 disposed in front of the casing 34b.

  As indicated by an arrow A2 in FIG. 7, the gas discharged from the supercharger 34 and flowing into the second passage 35 flows forward from the discharge port 34c of the supercharger 34 and then flows into the second passage 35. It flows down along. The gas flowing downward reaches the lower portion of the second passage 35 and then flows backward toward the intercooler 36.

  Subsequently, as shown by an 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 surface side, and flows backward from the front side thereof. 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 from the opening 36e on the rear surface side in the cooler housing 36c and flows into the third passage 37.

  As shown by an arrow A4 in FIG. 7, the gas flowing into the third passage 37 from the intercooler 36 passes through the collecting portion 37a and then flows obliquely upward to the right along the upstream portion of the introducing portion 37b ( 8 (see also section S1 in FIG. 8), and then flows directly upward along the downstream portion of the introduction portion 37b (see also section S2 in FIG. 8). As shown by an arrow A5 in the figure, the gas that has passed through the introduction portion 37b flows into a substantially central space in the surge tank 38 in the cylinder row direction, and is temporarily stored in the surge tank 38, and then independently. It is supplied to each cylinder 11 through a passage 39.

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

  10 is a view showing the passage structure according to the bypass passage 40 as seen from the front side, FIG. 11 is a view showing it from the rear side, and FIG. 12 is a view showing it from the upper side. is there. FIG. 13 is a perspective view showing a conduit of the bypass passage 40.

  14 is a view showing a flow path around the surge tank 38, FIG. 15 is a longitudinal sectional view showing a connection structure between the surge tank 38 and the bypass passage 40, and FIG. 16 is a transverse sectional view thereof. It is. Of these figures, FIG. 14 corresponds to the shape of the core when the members around the surge tank 38 are cast.

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

  Specifically, the bypass passage 40 includes, in order from the upstream side in the flow direction, a valve body 41a in which a bypass valve 41 is incorporated, a bent pipe portion 42 that adjusts the flow direction of the gas that has passed through the valve body 41a, A straight pipe part 43 that guides the gas that has passed through the pipe part 42 to the right, and a gas that has passed through the straight pipe part 43 are directed obliquely downward and rearward, and then branched into two branches and connected to the surge tank 38. And a branch pipe portion 44 to be formed.

  The valve body 41a is formed in a metal short cylinder shape, and as shown in FIGS. 10 to 11, at a position above the first passage 33 and on the left side with respect to the supercharger 34, It is arranged with the opening at both ends facing up and down. Further, like the first passage 33, the valve body 41a is located in front of the portion near the left end of the mounting surface 10a. The branch end 33d of the first passage 33 is connected to the upstream end (lower end) of the valve body 41a, while the upstream end of the curved pipe portion 42 is connected to the downstream end (upper end) of the valve body 41a. Yes.

  The bent pipe portion 42 is made of a resin and is configured as an elbow-shaped pipe joint, and is arranged in a posture in which the opening is directed downward and to the right in the upper position of the first passage 33 and eventually the valve body 41a. . Therefore, after the gas flowing into the curved pipe portion 42 flows in a direction (directly above) perpendicular to the main flow of gas in the first passage 33, the flow direction is changed according to the bending direction of the curved pipe portion 42. Is done. As a result, the gas flowing through the curved pipe portion 42 flows slightly rearward from the outside in the cylinder row direction (from the left side to the right side) when viewed in the cylinder axial direction (see FIG. 12). Flowing. Further, similarly to the first passage 33 and the valve body 41a, the curved pipe portion 42 is located in front of the portion near the left end of the mounting surface 10a. 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 part 42, while the straight pipe part is connected to the downstream end (right end) of the curved pipe part 42. The upstream end of 43 is connected.

  The straight pipe portion 43 is formed in a resin 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 can be seen when returning to FIG. 5, the openings at both ends are arranged in the posture toward the left and right at the position above the first passage 33 or the supercharger 34. As described above, the downstream end (right end) of the curved pipe portion 42 is connected to the upstream end (left end) of the straight pipe portion 43, while the branch pipe is connected to the downstream end (right end) of the straight pipe portion 43. The upstream end of the portion 44 is connected.

  The branch pipe portion 44 includes a bent passage 44a bent in an elbow shape, and two branch passages 44b and 44c branched in a tournament form from the downstream end of the bent passage 44a. At a position above the surge tank 38, the bent passage 44a is disposed in such a posture that the upstream end of the bent passage 44a is directed leftward, and the two branched passages 44b, 44c are both directed obliquely downward and rearward.

  Specifically, the bent passage 44a is bent at a substantially right angle so as to go obliquely downward and rearward from the front as it goes from the left to the right. As shown in FIG. 12, 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.

  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 of the branched branch passages, extends rightward from the branch location along the cylinder row direction. After that, it is bent so as to go diagonally downward and rearward. On the other hand, the second branch passage 44c, which is the other branch passage branched, is bent so as to extend to the left (in the direction of the cylinder row from the branch point, and then obliquely downward and rearward. As described above, the downstream end portions of the branch passages 44b and 44c are connected to the first introduction portion 38c and the second introduction portion 38d formed on the upper surface of the surge tank 38.

  During natural intake, the gas flowing into the bypass passage 40 passes through the respective parts 41 to 44 constituting 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 open / close state of the bypass valve 41.

  As shown by an arrow A6 in FIG. 12, the gas that has passed through the valve body 41a and has flowed into the curved pipe portion 42 flows rightward, and then flows to the right while slightly moving backward.

  Subsequently, the gas that has passed through the curved pipe portion 42 flows to the right along the straight pipe portion 43 as shown by an arrow A <b> 7 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 passes through the bending passage 44a and is then distributed to the first branch passage 44b and the second branch passage 44c. Each of these flows into the surge tank 38 (see also arrows A9 to A10 in FIGS. 15 to 16). The gas that has flowed into the surge tank 38 is supplied to each cylinder 11 via the independent passage 39 while merging with the gas that has flowed through the introduction portion 37b. Of the gas flowing into the branch pipe portion 44, the gas passing through the first branch passage 44b is directed toward the right side in the cylinder row direction according to the extending direction of the first branch passage 44b. On the other hand, the gas passing through the second branch passage 44c is directed toward the left side in the cylinder row direction in accordance with the extending direction of the second branch passage 44c.

  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 respective portions 41 to 44 of the bypass passage 40 in the opposite direction and flows out to the first passage 33.

(Configuration related to gas blowback)
The engine 1 includes 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 sends a control signal corresponding to the calculated control amount to the injector 6, spark plug 25, intake electric VVT 23, exhaust electric VVT 24, fuel supply system 61, throttle valve 32, EGR valve 54, and supercharger 34 electromagnetic. The power is output to the clutch 34a and the bypass valve 41, and the engine 1 is operated.

  Specifically, when the engine 1 is operated, it burns in the order of the first cylinder 11A, the third cylinder 11C, the fourth cylinder 11D, and the second cylinder 11B.

  Hereinafter, the two cylinders 11 that are in the order of combustion and are adjacent to each other in the cylinder row direction may be referred to as a first cylinder and a second cylinder in the order in which combustion occurs. In other words, in the case of the engine 1, the second cylinder 11B is the first set of the first cylinder, the first cylinder 11A is the first set of the subsequent cylinder, and the third cylinder 11C is the second set of the first cylinder. In addition, a pair in which the fourth cylinder 11D is a second set of subsequent cylinders is configured. Hereinafter, unless otherwise specified, the first set of the first and second cylinders will be described. In this case, the same reference numeral “11B” as that of the second cylinder 11B is assigned to the first cylinder, while the same reference numeral “11A” as that of the first cylinder 11A is assigned to the subsequent cylinder.

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

  For example, in an operation region on the lower load side than a predetermined load (hereinafter referred to as “fuel consumption region”), the engine 1 is operated by natural intake, while an operation region on the higher load side than the predetermined load (hereinafter referred to as “supercharging”). In the “zone”), the supercharger 34 is driven to supercharge the gas introduced into each cylinder 11.

  By the way, in the engine 1 in which the geometric compression ratio is increased as in this configuration example, there is a concern about an increase in pump loss. Therefore, in the above-described fuel consumption region, in order to give priority to fuel consumption performance, an internal EGR system is used. It is conceivable to provide a negative overlap period (NVO).

  Specifically, the exhaust electric VVT 24 maintains the closing timing of the exhaust valve 22 (hereinafter referred to as “EVC”) at a predetermined crank angle before the exhaust top dead center in accordance with a control signal received from the ECU in the fuel consumption range. To do. Since the EVC is adjusted by the exhaust electric VVT 24, when the EVC is kept substantially constant, the EVO is also kept substantially constant. In this way, the exhaust electric VVT 24 sets EVC during the exhaust stroke.

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

  In this engine 1, the intake electric VVT 23 sets the IVC between the first half and the middle half 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 slow closing, the gas filling amount can be reduced.

  By providing the negative overlap period, the burned gas is confined in the combustion chamber 16 (in other words, the internal EGR gas is introduced). As a result, the temperature in the combustion chamber 16, particularly the temperature before ignition, increases. Thereby, for example, when compression ignition combustion is performed instead of general spark ignition combustion in order to improve fuel efficiency, the combustion can be stably performed. Moreover, since IVC is delayed, the filling amount of gas is reduced. Although the filling amount is reduced in the fuel consumption region, the mirror cycle is realized with the provision of the negative overlap period, so that throttling can be omitted or suppressed. As a result, pump loss is reduced.

  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 that the internal EGR introduced into the cylinder 11 as the piston 14 moves up. Gas comes 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. Therefore, there is a possibility that the surge tank 38 flows backward.

  On the other hand, in the case of a four-cylinder engine, when the preceding cylinder 11B defined as described above is in the compression stroke, the subsequent cylinder 11A is in the middle of the intake stroke. Therefore, when the gas is blown back from the preceding cylinder 11B, the interior of the succeeding cylinder 11A becomes negative pressure. Therefore, considering that the leading cylinder 11B and the succeeding cylinder 11A are adjacent to each other in the cylinder row direction, the runner length is increased. The inventors of the present application have noticed that the gas blown back from the starting cylinder 11B may be sucked into the succeeding cylinder 11A during the intake stroke via the surge tank 38 because of the short configuration.

  As a result of further studies, the inventors of the present application have determined that the gas blown back from the preceding cylinder 11B is sucked into the succeeding cylinder 11A, depending on the connection location between the bypass passage 40 as the upstream passage and the surge tank 38. As a result, it has been found that there is a risk of reaching so-called pre-ignition (hereinafter, also referred to as “pre-ignition”).

  For example, as in the intermediate intake pipe portion described in Patent Document 1, the bypass passage 40 has a central portion in the cylinder row direction of the surge tank 38 (between the second cylinder 11B and the third cylinder 11C in this configuration example). It is possible to connect to.

  In this case, the connection portion of the bypass passage 40 and the surge tank 38, the upstream end portion of the independent passage 39 that communicates with the starting cylinder 11B, and the upstream end portion of the independent passage 39 that communicates with the succeeding cylinder 11A are arranged in the cylinder row direction. They will be arranged in order. As a result, the gas flowing into the surge tank 38 from the bypass passage 40 is located inside the surge tank 38 in the space near the upstream end of the independent passage 39 corresponding to the preceding cylinder 11B and the independent passage 39 corresponding to the succeeding cylinder 11A. A flow is formed so as to pass through the space near the upstream end in this order. As a result, the gas flowing into the surge tank 38 from the bypass passage 40 becomes “trailing wind”, and the gas blown back from the preceding cylinder is pushed away to the succeeding cylinder. Specifically, when such a tailwind is generated, the gas blown back from the starting cylinder 11B is pushed away toward the succeeding cylinder 11A.

  As a result of the gas blown back from the starting cylinder 11B being pushed away by the gas flowing in from the bypass passage 40, the inventors of the present application may inhale the gas excessively in the succeeding cylinder 11A, and as a result, there is a risk of reaching the pre-ignition. I noticed that there is.

  In order to suppress the plague, the bypass passage 40 is connected to the end of the surge tank 38 in the cylinder row direction (in this configuration example, from the first cylinder 11A so that the gas flowing in from the bypass passage 40 becomes a “heading wind”. Can also be connected to the right side or the left side of the fourth cylinder 11D.

  In this case, the connecting portion of the bypass passage 40 and the surge tank 38, the upstream end portion of the independent passage 39 communicating with the succeeding cylinder 11A, and the upstream end portion of the independent passage 39 communicating with the starting cylinder 11B are arranged in this order in the cylinder row direction. Will be lined up. However, with such a configuration, although the suction of the blown-back gas is suppressed, the flow from the bypass passage 40 to the preceding cylinder 11B with respect to the passage length from the bypass passage 40 to the succeeding cylinder 11A. Since the road length becomes long, the responsiveness may be deteriorated in the starting cylinder 11B. Also, if the flow path length differs between cylinders, there is a possibility that the difference between cylinders may increase in the state quantity such as the charging efficiency.

  As another measure for suppressing the plague, for example, it is conceivable to increase the capacity of the surge tank 38. In this case, however, the volume of the entire intake passage 30 is increased by the increase in the capacity of the surge tank 38. For this reason, it is not preferable in that it may cause a decrease in the supercharging response particularly when configured in combination with the supercharger 34. In addition, such a configuration is inconvenient because the layout of peripheral parts of the intake passage 30 may be hindered.

  However, in this configuration example, as described above, the first introduction portion 38c to which the surge tank 38 and the bypass passage 40 are connected corresponds to the second port 18B of the second cylinder 11B as shown in FIG. It is disposed at a location near the independent passage 392. As a result, the connection location between the bypass passage 40 and the surge tank 38 is independent from the upstream end of the independent passage 392 corresponding to the starting cylinder 11B among the plurality of independent passages 39 in the cylinder row direction. It is set so as to face the section extending to the upstream end of the passage 391.

  Moreover, the gas passing through the first branch passage 44b connected to the first introduction portion 38c is directed to the right in the cylinder row direction in accordance with the extending direction of the first branch passage 44b. Considering that the first cylinder 11A as the next cylinder is adjacent to the right side with respect to the second cylinder 11B as the first cylinder, the first branch passage 44b allows the gas flowing through the first branch passage 44b to flow. It is equivalent to being formed so as to be directed toward the succeeding cylinder 11A out of the starting cylinder 11B and the succeeding cylinder 11A.

  With this configuration, when the succeeding cylinder 11A is in the intake stroke (that is, when the vicinity of the upstream end corresponding to the succeeding cylinder 11A is negative in the surge tank 38), the surge tank 38 is connected to the bypass passage 40. The gas flowing into the cylinder is coupled with the gas blown back from the preceding cylinder 11B (see arrow A11 in FIG. 14) in combination with the fact that the gas is directed toward the succeeding cylinder 11A. A flow toward the 11A side (see arrow A9 in FIG. 14) is formed.

  Therefore, for the gas blown back from the starting cylinder 11B, the gas flowing in from the bypass passage 40 is less likely to become “trailing wind”. As a result, it is possible to suppress the suction of the gas blown back from the preceding cylinder 11B into the succeeding cylinder 11A, and thus suppress the occurrence of pre-ignition.

  Moreover, as compared with the configuration in which the bypass passage 40 is connected to the right end of the surge tank 38, the difference between the cylinders such as the charging efficiency is reduced, and the same level of responsiveness is secured in the starting cylinder 11B and the starting cylinder 11A. Is possible.

  As described above, according to the above configuration, in the first cylinder 11A and the second cylinder 11B, it is possible to suppress the occurrence of pre-age caused by the gas blowback while ensuring the responsiveness of each cylinder 11.

  The same applies to the second set of the first cylinder (third cylinder 11C) and the second cylinder (fourth cylinder 11D). In this case, the bypass passage 40 and the surge tank 38 are connected to the succeeding cylinder from the upstream end of the independent passage 39 corresponding to the starting cylinder (third cylinder) 11C among the plurality of independent passages 39 in the cylinder row direction. (4th cylinder) It is set to oppose in the section to the upstream end part of independent passage 39 corresponding to 11D. In addition, the second branch passage 44c connected to the second introduction portion 38d directs the gas flowing through the second branch passage 44c toward the succeeding cylinder 11D out of the preceding cylinder 11C and the succeeding cylinder 11D (that is, Equal to the left side).

  By configuring in this way, also in the third cylinder 11C and the fourth cylinder 11D, it is possible to suppress the occurrence of pre-age due to gas blowback while ensuring the responsiveness of each cylinder 11.

  The bypass passage 44 extends from the left side to the right side in the cylinder row direction, and then branches into the first branch passage 44b and the second branch passage 44c.

  Here, the first branch passage 44b is connected to the surge tank 38 after extending in the direction from the left side to the right side in the cylinder row direction in the same manner as before branching, while the second branch passage 44c is connected to the surge tank 38 before branching. After extending toward the opposite side, the surge tank 38 is connected. The amount of gas flowing into the surge tank 38 from the second branch passage 44c is lower than the gas flowing into the surge tank 38 from the first branch passage 44b by the amount of such “turnback”.

  On the other hand, depending on the location where the surge tank 38 and the bypass passage 40 are connected, the gas that has flowed back to the surge tank 38 from the first cylinder flows in from the first and second branch passages 44b and 44c, even if “following wind” does not occur. There is a possibility that the gas will be sucked into the succeeding cylinder in preference to the gas to be performed (first).

  Therefore, as shown in FIG. 15, the connection location between the second branch passage 44 c and the surge tank 38 is compared with the connection location between the first branch passage 44 b and the surge tank 38, and is closer to the succeeding cylinder ( Set to (Outward). With this setting, the gas flowing in from the second branch passage 44c is likely to flow into the second set of subsequent cylinders 11D. Thereby, the fall of the flow rate can be compensated.

  As shown in FIG. 14, the plurality of independent passages 39 have an independent passage 391 connected to the first port 17 and an independent passage 392 connected to the second port 18 in each cylinder 11. Here, the independent passage 391 and the independent passage 392 are arranged in a row along the cylinder row direction.

  The bypass passage 40 and the surge tank 38 are connected to an independent passage 392 disposed on the side of the succeeding cylinder 11A in the cylinder row direction among the independent passages 391 and 392 corresponding to the starting cylinder 11B in the cylinder row direction. Of the independent passages 391 and 392 corresponding to the succeeding cylinder 11A to the upstream end of the independent passage 391 provided on the preceding cylinder 11B side.

  With this configuration, in the engine 1 in which two intake ports 17 and 18 are provided for each cylinder 11, the occurrence of pre-age due to gas blowback is ensured while ensuring the responsiveness of each cylinder 11. Can be suppressed.

<< Other embodiments >>
In the said embodiment, although the inline 4 cylinder engine was illustrated, it is not restricted to this structure. For example, an engine having a plurality of cylinders such as an in-line 3-cylinder engine or an in-line 6-cylinder engine may be used. Further, the number of passages branched from the bypass passage 40 as the upstream passage may be changed according to the number of cylinders.

  In the above-described embodiment, the configuration in which the gas flows from the third passage 37 and the gas flows backward from the bypass passage 40 at the time of supercharging is illustrated, but the configuration is not limited thereto. For example, by changing the layout of the entire engine, the third passage 37 (more precisely, the passage corresponding to the third passage 37 is changed when the configuration of the entire engine is changed, even during supercharging. In order to simplify the description, the other elements may be configured so that gas flows in from both the bypass passage 40 and the same name and reference numerals as in the above embodiment. In such a configuration, the supercharger 34, the second passage 35, the intercooler 36, and the third passage 37 exemplify the “second upstream side passage”. That is, the second upstream passage is configured as the above-described supercharging passage.

  In this case, as shown in FIG. 15, the connection portion between the third passage 37 and the surge tank 38 is offset to the left side in the cylinder row direction with respect to the connection portion between the bypass passage 40 and the surge tank 38. Both of the gas flow flowing into the surge tank 38 from the bypass passage 40 and the gas flow flowing into the surge tank 38 from the third passage 37 can smoothly flow into each other without colliding with each other.

  Further, in the engine 1 provided with the supercharger 34, there is a concern about the occurrence of pre-age due to gas blowback compared to a naturally aspirated engine. Therefore, if the gas is configured to flow from both the third passage 37 and the bypass passage 40, as described above, the gas is smoothly flowed into the surge tank 38 and the occurrence of pre-ignition is suppressed. The configuration is particularly effective in the engine 1 including the supercharger 34.

1 Engine 10 Engine body 11 Cylinder
11A No. 1 cylinder (the first set of subsequent cylinders)
11B No. 2 cylinder (first cylinder of the first set)
11C 3rd cylinder (2nd set starting cylinder)
11D 4th cylinder (2nd set of succeeding cylinders)
17 First port (intake port)
18 Second port (intake port)
21 Intake Valve 23 Intake Electric VVT (Variable Valve Mechanism)
30 Intake passage 32 Throttle valve 34 Supercharger (supercharging passage, second upstream passage)
35 Second passage (supercharging passage, second upstream passage)
36 Intercooler (supercharged passage, second upstream passage)
37 third passage (supercharging passage, second upstream passage)
38 Surge tank 39 Independent passage 391 Independent passage (first independent passage)
392 Independent passage (second independent passage)
40 Bypass passage (upstream passage)
41 Bypass valve 44b First branch passage 44c Second branch passage

Claims (5)

An engine body having a plurality of cylinders arranged in a row and configured to perform combustion in a predetermined combustion order in each of the plurality of cylinders;
A plurality of intake ports provided in the engine body, each communicating with each of the plurality of cylinders;
A plurality of intake valves each for opening and closing each of the intake ports;
A variable valve mechanism that changes the opening and closing timing of the plurality of intake valves,
The variable valve mechanism includes an intake passage structure for a multi-cylinder engine configured to set closing timings of the plurality of intake valves during a compression stroke when an operating state of the engine body is in a predetermined operating region. Because
An intake passage connected to each of the plurality of intake ports;
The intake passage is
A plurality of independent passages each connected to each of the plurality of intake ports;
The plurality of intake ports are disposed opposite to the opposite ends of the plurality of intake passages with the plurality of independent passages interposed therebetween, and the upstream ends of the plurality of independent passages are arranged on the corresponding cylinders. Surge tanks connected in line according to the order in which they are arranged,
A downstream end connected to the surge tank, and an upstream passage for introducing gas to the surge tank,
Of the plurality of cylinders, two cylinders whose combustion order is adjacent and adjacent in the cylinder row direction are referred to as a first cylinder and a second cylinder in the order in which combustion occurs. Is connected in the cylinder row direction in the section from the upstream end of the independent passage corresponding to the preceding cylinder to the upstream end of the independent passage corresponding to the succeeding cylinder in the plurality of independent passages. Is set as
The upstream-side passage is formed so as to direct the gas flowing through the upstream-side passage toward the succeeding cylinder of the preceding cylinder and the succeeding cylinder, and an intake passage for a multi-cylinder engine Construction. In the multi-cylinder engine intake passage structure according to claim 1,
The intake passage, apart from the upstream passage, has a second upstream passage where a downstream end is connected to the surge tank and gas is introduced into the surge tank,
The connection location between the downstream end of the second upstream passage and the surge tank is offset in the cylinder row direction with respect to the connection location between the downstream end of the upstream passage and the surge tank. An intake passage structure for a multi-cylinder engine. In the multi-cylinder engine intake passage structure according to claim 2,
While the second upstream passage is configured as a supercharging passage in which a supercharger and an intercooler are arranged in order from the upstream side along the gas flow direction,
The upstream passage is a bypass passage that branches from the upstream side of the supercharger in the second upstream passage, and that bypasses the supercharger and the intercooler and is connected to the surge tank. An intake passage structure for a multi-cylinder engine, characterized by being configured. The intake passage structure of the multi-cylinder engine according to any one of claims 1 to 3,
The engine body includes at least a first set of first cylinders, a first set of subsequent cylinders adjacent to the first cylinder in a cylinder row direction and having a subsequent combustion order, a second set of first cylinders, and the first cylinder A second set of subsequent cylinders adjacent to each other in the cylinder row direction and followed by the combustion order,
The upstream passage extends along a direction from one side to the other side in the cylinder row direction, and then branches into a first branch passage and a second branch passage,
The first branch passage extends along a direction from one side to the other side in the cylinder row direction, and then, from the upstream end portion of the independent passage corresponding to the first set of the first cylinders in the surge tank, 1 It is connected oppositely in the section to the upstream end of the independent passage corresponding to the subsequent cylinder of the set,
The second branch passage extends in a direction from the other side to the one side in the cylinder row direction, and then, in the surge tank, 2nd from the upstream end of the independent passage corresponding to the second set of the starting cylinders. Connected oppositely in the section to the upstream end of the independent passage corresponding to the subsequent cylinder of the set,
The connection location between the second branch passage and the surge tank is set closer to the succeeding cylinder in the cylinder row direction than the connection location between the first branch passage and the surge tank. Intake passage structure for a multi-cylinder engine. In the intake passage structure of the multi-cylinder engine according to any one of claims 1 to 4,
The plurality of intake ports each have a first port and a second port arranged in a row along the cylinder row direction in each of the plurality of cylinders;
The plurality of independent passages include a first independent passage connected to the first port and a second independent passage connected to the second port in each of the plurality of cylinders,
The upstream passage and the surge tank are connected at one upstream end of the first and second independent passages corresponding to the preceding cylinder, which is disposed on the subsequent cylinder side in the cylinder row direction. From among the first and second independent passages corresponding to the succeeding cylinder, they are set to face each other in a section extending from one upstream end disposed on the preceding cylinder side in the cylinder row direction. An intake passage structure for a multi-cylinder engine.

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