JP6551462B2 - Multi-cylinder engine intake structure - Google Patents

Description

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

  Patent Document 1 discloses an in-line 6-cylinder engine including six cylinders arranged in a row and an intake device connected to each cylinder via an intake port as an example of a multi-cylinder engine. Yes. Specifically, in the intake system according to Patent Document 1, six downstream passages (intake connection pipes) whose downstream ends are connected to the respective intake ports, and upstream ends of the respective downstream passages are, A surge tank connected in a line according to the order of corresponding cylinders, a first upstream passage (intake pipe) and a second upstream passage (bypass passage) each having one end connected to the surge tank; ,have.

  More specifically, the surge tank according to the patent document 1 is formed in a substantially tubular shape extending in the cylinder row direction, and a first upstream passage in which a supercharger is interposed is formed at the central portion in the cylinder row direction. It is connected. On the other hand, a second upstream passage that bypasses the supercharger is connected to one end portion in the cylinder row direction.

  When the multi-cylinder engine configured in this manner operates, for example, in the supercharging zone, the gas boosted by the turbocharger is introduced into the surge tank via the first upstream passage, while Part of the gas introduced into the surge tank returns to the turbocharger upstream side via the second upstream side passage. The circulation of the gas through the first and second upstream passages makes it possible to properly control the supercharging pressure.

  Patent Document 2 discloses another example of such a multi-cylinder engine. Specifically, in Patent Document 2, as in Patent Document 1, a first upstream side passage (intake passage) in which a supercharger (mechanical supercharger) is interposed with respect to the surge tank, It is disclosed that a second upstream passage (bypass passage) that bypasses the supercharger is connected.

Unexamined-Japanese-Patent No. 4-237826 Unexamined-Japanese-Patent No. 3-138419

  By the way, in the engine which provided the 2nd upstream path which bypasses a supercharger separately from the 1st upstream path where the supercharger was interposed like the said patent documents 1 and 2, a supercharger Non-supercharging operation (ie, operation by natural intake) by stopping the operation of the turbocharger (especially a mechanical supercharger) and introducing gas from the second upstream passage instead of the first upstream passage to the surge tank May be performed.

  In recent years, in order to improve the thermal efficiency of an engine having such a configuration, it is required to ensure combustion stability and reduce pump loss. As measures for satisfying such demands, it has been studied to reduce the pressure loss of gas in the intake system and the difference in pressure loss between cylinders by devising the configuration around the surge tank.

  Specifically, for example, when the surge tank described in Patent Document 1 is used, the gas flowing into the surge tank from the first upstream passage reaches the cylinder disposed on the end side in the cylinder row direction. Is diverted at the central portion in the cylinder row direction, and flows from the central portion toward the end. Then, with respect to the end side cylinders, the flow path length becomes relatively longer compared to the cylinders disposed on the center side in the cylinder row direction, and the influence of flow separation at the time of direction change (for example, In combination with this, a vortex is produced at a turning corner that changes direction, and the gas does not flow easily), and the pressure loss becomes relatively large. As a result, there is a difference between cylinders in pressure loss. In addition, due to the formation of the surge tank in a substantially tubular shape, pressure loss may also occur depending on the flow passage diameter.

  Therefore, for example, by changing the configuration around the surge tank, the shape of the flow path from the first upstream passage to each cylinder via the surge tank is improved, thereby reducing the pressure loss difference between cylinders, etc. It is possible to do.

  However, in this engine, as already described, gas may flow not only from the first upstream passage but also from the second upstream passage. In this case, depending on the connection structure between each passage and the surge tank, between the flow path related to the first upstream side passage and the flow path from the second upstream side passage to each cylinder via the surge tank. There is a possibility that the tendency of the difference between cylinders is different. Therefore, even if the difference between the cylinders is reduced with respect to the gas flowing in from the first upstream passage, the difference between the cylinders may not be sufficiently reduced with respect to the gas flowing in from the second upstream passage.

  Thus, if the tendency of the difference between the cylinders differs between the two flow paths, it is not desirable to reduce the gas pressure loss and the pressure loss difference between the cylinders at the same time.

  The technology disclosed herein has been made in view of such a point, and the purpose thereof is to reduce the pressure loss of gas flowing in from each passage when two passages are connected to the surge tank, And reducing the difference in pressure loss between cylinders.

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

The intake device includes a plurality of downstream passages each having a downstream end connected to each of the plurality of intake ports, and an upstream end of each of the plurality of downstream passages according to the order in which the corresponding cylinders are arranged. A surge tank connected side by side in a row , and first and second upstream passages, each downstream end portion of which is connected to an intermediate portion in the cylinder row direction of the surge tank and introduces gas into the surge tank; Have

The surge tank is disposed along the cylinder row direction, and the first and second vertices are set opposite to the inlets of both intake ports located at both ends of the plurality of intake ports in the cylinder row direction, The third apex set to face the opening to which the downstream end of the first upstream passage is connected, and the opening to which the downstream end of the second upstream passage is connected. A fourth apex, and the third and fourth apexes are arranged along a direction orthogonal to the cylinder row direction.

In the surge tank, a triangular pyramid space connecting the first and second vertices and the third and fourth vertices is partitioned, and an inner wall surface of the surge tank is The diameter is increased along a ridge line connecting the first vertex, the second vertex, and the third vertex, and the diameter is increased along a ridge line connecting the first vertex, the second vertex, and the fourth vertex. To do .

Hereinafter , the term “part near the third vertex” includes the part including the third vertex (for example, the top corresponding to the third vertex among the tops of the triangular pyramid ) and other vertices. the third part position in proximity to the vertices Te are included. The same applies to the fourth vertex.

  For example, as in Patent Document 1, when the surge tank is formed in a substantially tubular shape extending in the cylinder row direction and the first upstream passage is connected to the center portion in the cylinder row direction, the gas flowing into the surge tank is When reaching the cylinder disposed on the direction end side, the direction is changed at the center portion in the cylinder row direction, and the flow flows from the center portion to the end side. Then, with respect to the cylinders on the cylinder row direction end side, the flow path length becomes relatively longer compared to the cylinder disposed on the center side, and the influence of flow separation at the time of direction change (for example, direction Combined with the fact that vortices are produced at the turning corners to make the gas difficult to flow, the pressure loss becomes relatively large. As a result, there is a difference between cylinders in pressure loss. In addition, due to the formation of the surge tank in a substantially tubular shape, pressure loss may also occur depending on the flow passage diameter.

  However, according to the above configuration, a triangular pyramid-shaped space is defined in the surge tank. Specifically, the gas flowing into the surge tank from the first upstream passage is, in plan view, a third apex located near the connection with the first upstream passage, and the first apex located on one side in the cylinder row direction. Each cylinder is reached through a space corresponding to a triangle connecting the vertex and the second vertex positioned on the other side in the cylinder row direction.

  Here, the third vertex is located on the opposite side of the plurality of downstream side passages across the line segment connecting the first vertex and the second vertex. This means that the gas flowing into the surge tank from the vicinity of the third vertex passes through each downstream side through a flow path that is tapered toward the line segment connecting the first vertex and the second vertex. It means to reach the passage. In addition, with the triangular pyramid shaped space, the diameter is expanded not only in one plane, but is expanded in three dimensions in a plurality of directions such as the height direction.

  When the diameter of the flow passage is expanded as described above, unlike the configuration described in Patent Document 1, the cylinder located at the end in the cylinder row direction is directed toward the cylinder without changing the direction in the central portion in the cylinder row direction. It becomes possible to flow gas at an angle. As a result, it is possible to reduce the inter-cylinder difference in the flow path length as compared with the configuration involving the change in direction. Furthermore, it is also possible to suppress flow separation, since it does not involve turning.

  In addition, since the diameter of the flow path is increased in a tapered shape, the cross section of the flow path to each cylinder can be widened. This is effective in reducing the pressure loss according to the flow path diameter.

  Thus, the pressure loss of the gas flowing in from the first upstream passage is combined with the reduction in the difference between the cylinders in the flow path length, the suppression of the flow separation, and the reduction in the pressure loss according to the flow path diameter. And the difference in pressure loss between cylinders can be reduced.

  Moreover, according to the above configuration, the gas flowing into the surge tank from the second upstream passage is also the fourth vertex located in the vicinity of the connection with the second upstream passage, and the first and second vertices described above It reaches each cylinder through the space corresponding to the triangle connecting the two.

  Here, similarly to the third vertex, the fourth vertex is located on the opposite side of the plurality of downstream passages across the line segment connecting the first vertex and the second vertex. If it does so, the gas which flows in from a 2nd upstream channel | path will reach each downstream channel | path via the flow path similar to the gas which flows in from a 1st upstream channel | path.

  Therefore, it becomes possible to make the tendency of the difference between the cylinders the same between the flow passage related to the first upstream side passage and the flow passage related to the second upstream side passage. As a result, with respect to the gas flowing in from the second upstream passage, the pressure loss and the difference in pressure loss between the cylinders can be reduced in the same manner as the gas flowing in from the first upstream passage.

  Thus, according to the above configuration, the tendency of the difference between the cylinders is made the same between the first upstream passage and the second upstream passage, and thus the pressure loss of the gas flowing in from each passage, and the pressure loss between the cylinders of the pressure loss. The difference can be reduced simultaneously.

  The upstream end of each of the plurality of downstream passages may be connected side by side along a ridge line connecting the first and second vertices in the surge tank.

  According to this configuration, the gas can flow smoothly from each of the first and second upstream passages toward each downstream passage.

  In addition, the multi-cylinder engine is provided with an injector and an ignition plug for each cylinder, and the surge tank is positioned above the first apex, the second apex, and the third and fourth apexes. It is good also as having a tank upper surface corresponding to the plane which connected one side, and at least one of the injector and the spark plug is arranged along the tank upper surface.

  According to this structure, an injector and a spark plug can be arrange | positioned using the tank upper surface. That is, the upper surface of the tank is flat at least in the cylinder row direction. Therefore, when the injectors and the ignition plugs are arranged in the cylinder row direction, interference with the surge tank can be prevented, and the installation can be ensured.

  In addition, the first upstream passage is configured as a supercharging passage in which a supercharger is interposed, while the second upstream passage is upstream of the supercharger in the first upstream passage. It is good also as a bypass passage branched from the side and bypassing the supercharger and connected to the surge tank.

  According to this configuration, the tendency of the difference between the cylinders between the supercharging passage and the bypass passage can be made the same, and the pressure loss of the gas flowing in from each passage and the difference in pressure loss between the cylinders can be simultaneously reduced. . This is effective when using both supercharging and natural aspiration.

  The supercharger is positioned below the surge tank in a vehicle-mounted state, and is below the gas discharge port in the supercharger and the third and fourth vertices in the surge tank. The site near one apex located is connected to each other via the supercharging passage, and the site near the other apex located above the third apex of the third and fourth apexes in the surge tank The downstream end of the bypass passage may be connected.

  According to this configuration, the supercharger and the portion near the apex where the supercharging passage is connected in the surge tank are arranged in the vertical direction. Accordingly, the pressure loss of gas and the difference in pressure loss between cylinders can be reduced while the supercharger and the supercharging passage are laid out in a compact manner.

  As described above, according to the intake structure of the multi-cylinder engine described above, when two passages are connected to the surge tank, the tendency of the inter-cylinder difference between the passages is made the same, and hence the inflow from each passage The pressure loss of the gas and the cylinder-to-cylinder difference of the pressure loss can likewise be reduced.

FIG. 1 is a schematic view illustrating the configuration of a multi-cylinder engine. FIG. 2 is a plan view schematically showing the configuration around four cylinders. FIG. 3 is a perspective view showing the configuration of the multi-cylinder engine with a part thereof omitted. FIG. 4 is a front view showing the configuration of the multi-cylinder engine with parts thereof omitted. FIG. 5 is a side view showing the configuration of the multi-cylinder engine with a part thereof omitted. FIG. 6 is a perspective view showing the surge tank. FIG. 7 is a view for explaining a schematic shape of the surge tank. FIG. 8 is a side view showing the surge tank. FIG. 9 is a view of the surge tank as viewed from the arrow A. FIG. 10 is a B arrow view of the surge tank. FIG. 11 is a C arrow view of the surge tank. FIG. 12 is a view of the surge tank as viewed from the direction of arrow D. FIG. 13 is an aa cross-sectional view of the surge tank. FIG. 14 is a cross-sectional view taken along line bb of the surge tank. FIG. 15 is a cc cross-sectional view of the surge tank. FIG. 16 is a diagram showing the configuration around the surge tank in comparison with the conventional configuration. FIG. 17 is a diagram showing the configuration around the surge tank in comparison with the conventional configuration.

  Hereinafter, an embodiment of an intake structure of a multi-cylinder engine will be described in detail based on the drawings. The following description is an example. FIG. 1 is a schematic view illustrating a multi-cylinder engine (hereinafter simply referred to as “engine”) 1 to which the intake structure of a multi-cylinder engine disclosed herein is applied. FIG. 2 is a plan view schematically showing the configuration around the four cylinders 11. 3 is a perspective view showing the configuration of the engine 1 with a part omitted, FIG. 4 is a front view showing the configuration of the engine 1 with a part omitted, and FIG. Is a side view showing a part of the

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

  In addition, as shown in FIG. 2, 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. Thereby, in this embodiment, the engine front-rear direction, which is the arrangement direction (cylinder row direction) of the four cylinders 11, substantially coincides with the vehicle width direction, and the engine width direction substantially coincides with the vehicle front-rear direction. .

  Hereinafter, unless otherwise specified, the front side refers to one side in the engine width direction (front side in the vehicle longitudinal direction), the rear side refers to the other side in the engine width direction (rear side in the vehicle longitudinal direction), and the left side It points to one side (left side in the vehicle width direction and the engine front side) of the engine longitudinal direction (cylinder row direction), and the right side is the other side (right side in the vehicle width direction) of the engine longitudinal direction (cylinder row direction) And, it points to the engine rear side).

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

(Schematic configuration of the engine)
The engine 1 is configured to have a front intake air and a rear exhaust system. 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), as shown in FIG. An intake passage 30 that communicates with each cylinder 11 via the exhaust passage 50 and an exhaust passage 50 that is disposed on the rear side of the engine body 10 and communicates with each cylinder 11 via exhaust ports 19 and 19.

  The intake passage 30 according to the present embodiment includes a plurality of passages that guide gas, devices such as a supercharger 34 and an intercooler 36, and a bypass passage 40 that bypasses these devices in a unitized intake air. Configure the device. Hereinafter, the intake system is simply referred to as "intake passage".

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

  Four cylinders 11 are formed in the cylinder block 12. The four cylinders 11 are arranged in a row along the central axis direction of the crankshaft 15 (that is, the cylinder row direction). The four cylinders 11 are each formed in a cylindrical shape, and 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. 2 may be referred to as No. 1 cylinder 11 A, No. 2 cylinder 11 B, No. 3 cylinder 11 C, and No. 4 cylinder 11 D in this 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 defines the combustion chamber 16 together with the cylinder 11 and the cylinder head 13.

  The cylinder head 13 is provided with two intake ports 17 and 18 per 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 18 are arranged in the same order. Specifically, as shown in FIG. 2, in each cylinder 11, the second port 18 and the first port 17 are arranged in order from the right side along the cylinder row direction.

  The upstream ends of the intake ports 17 and 18 are respectively open to the outer surface 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.

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

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

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

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

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

  As shown in FIG. 1, the exhaust valve mechanism has an exhaust motor VVT (Variable Valve Timing) 24 which is a variable valve mechanism in this configuration example. The exhaust 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 change continuously. The exhaust valve mechanism may have a hydraulic VVT instead of the electric VVT.

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

  An injector 6 is attached to the cylinder head 13 for each cylinder 11. 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 passage 62 connecting the fuel tank 63 and the injector 6 to each other. A fuel pump 65 and a common rail 64 are interposed in the fuel supply passage 62. The fuel pump 65 pumps fuel to the common rail 64. 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 by the fuel pump 65 at a high fuel pressure. When the injector 6 is opened, the fuel stored in the common rail 64 is injected from the injection port of the injector 6 into the combustion chamber 16.

  A spark plug 25 is attached to the cylinder head 13 for each cylinder 11. The spark plug 25 is attached in such a position that its tip is in the combustion chamber 16 and forcibly ignites the mixture in the combustion chamber 16. On the other hand, the base end portion of the spark plug 25 is exposed to the outside of the engine body 10, and as shown in FIGS. 3 to 5, the upper surface of the surge tank 38 constituting the intake passage 30 (hereinafter referred to as “tank upper surface”). (Also referred to as 38) c.

  As shown in FIGS. 3 to 5, the intake passage 30 is connected to the side surface on the front side of the engine body 10 and communicates with the intake ports 17 and 18 of the cylinders 11. The intake passage 30 is a passage through which the gas introduced into the combustion chamber 16 flows. An air cleaner 31 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. The intake passage 30 downstream of the surge tank 38 constitutes an independent passage 39 that branches into two for each cylinder 11. Note that the plurality of independent passages 39 exemplifies the “downstream passage”.

  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. When the control means (not shown) such as an ECU (Engine Control Unit) switches between disconnection and connection of the electromagnetic clutch 34a, the supercharger 34 is switched on and off. That is, the engine 1 switches between 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 to be water-cooled.

  Further, as a passage connecting various devices incorporated in the intake passage 30, the intake passage 30 is disposed downstream of the air cleaner 31, and a first passage that guides the intake air purified by the air cleaner 31 to the supercharger 34. 33, a second passage 35 for guiding the intake air compressed by the turbocharger 34 to the intercooler 36, and a third passage 37 for guiding the gas cooled by the intercooler 36 to the surge tank 38. The surge tank 38 is disposed in the vicinity of the inlets (upstream ends) of the intake ports 17 and 18 in order to shorten the flow path length from the surge tank 38 to the intake ports 17 and 18. The second passage 35 and the third passage 37, together with the turbocharger 34 and the intercooler 36, constitute a "first upstream passage" and 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 surge tank 38 to a portion of the intake passage 30 from the downstream portion of the throttle valve 32 to the upstream portion of the turbocharger 34. 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. This bypass passage 40 is an example of a “second upstream passage”.

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

  When the supercharger 34 is turned on (that is, when the electromagnetic clutch 34a is connected), the opening degree of the bypass valve 41 is appropriately adjusted. As a result, part of the gas that has passed through the 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, a supercharging system is configured by the supercharger 34, the bypass passage 40, and the bypass valve 41.

  The exhaust passage 50 is connected to the rear side surface of the engine body 10 and communicates with the exhaust port 19 of each cylinder 11. The exhaust passage 50 is a passage through which the exhaust gas discharged from the combustion chamber 16 flows. The upstream portion of the exhaust passage 50 constitutes an independent passage which branches for each cylinder 11, although detailed illustration is omitted. The upstream ends of the independent passages are 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. The exhaust gas purification system is not limited to one including only the three-way catalyst.

  An EGR passage 52 constituting an external EGR system is connected between the intake passage 30 and the exhaust passage 50. The EGR passage 52 is a passage for 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 turbocharger 34 in the intake passage 30 and upstream of the upstream end of the bypass passage 40.

  A water-cooled EGR cooler 53 is disposed in the EGR passage 52. The EGR cooler 53 is configured to cool the burned gas. An EGR valve 54 is also disposed in the EGR passage 52. The EGR valve 54 is configured to adjust the flow rate of 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.

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

  Each part constituting the intake passage 30 is arranged on the front side of the engine body 10 as shown in FIGS. For example, the supercharger 34, the intercooler 36, and the surge tank 38 are attached to the front surface of the engine body 10 in order from the bottom in the vehicle mounted state. That is, the supercharger 34, the intercooler 36, and the surge tank 38 are arranged along the vertical direction. The first passage 33 is connected to the left end of the supercharger 34, and the second passage 35 is provided so as to connect the upper surface of the supercharger 34 and the lower surface of the intercooler 36 (second passage). 35 is shown only in FIG. 1). The third passage 37 is connected to the bottom of the surge tank 38 after extending from the top surface of the intercooler 36. On the other hand, the bypass passage 40 branches from the middle of the first passage 33 and extends substantially upward, and is then connected to the front of the surge tank 38. The plurality of independent passages 39 are disposed between the engine body 10 and the surge tank 38, and are connected to the non-cylinder end (inlet) of the intake ports 17 and 18.

  Subsequently, the structure of each part constituting the intake passage 30 will be described in the order of a passage structure near the throttle valve 32, a passage structure on the supercharger 34 side, a bypass side passage structure, and a passage structure near the surge tank 38. .

-Passage structure near the throttle valve-
The first passage 33 is formed in a substantially tubular shape, and an upstream portion thereof is constituted by a throttle body 33a in which a throttle valve 32 is built. The throttle body 33a is formed in a metal short cylinder shape, and is disposed in front of the left end of the cylinder block 12 in a posture in which openings at both ends are directed substantially front and rear. The height position of the throttle body 33 a is closer to the turbocharger 34 than the surge tank 38. An air cleaner 31 is connected to an upstream end (front end) of the throttle body 33a via a duct (not shown), while a downstream portion of the first passage 33 is connected to a downstream end (rear end) of the throttle body 33a. The first passage main body 33b is connected.

  As shown in FIGS. 3 to 5, 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, and is disposed forward of the left end of the cylinder block 12 and rearward of the throttle body 33a. As described above, the downstream end of the throttle body 33a is connected to the upstream end (front end) of the first passage body 33b, while the intake port of the turbocharger 34 is connected to the downstream end (rear end) thereof. Has been.

  In addition, a merging portion where the EGR passage 52 merges opens in the first passage body 33b. As shown in FIG. 4, the downstream end of the EGR passage 52 is connected to the junction. The merging portion is formed at least downstream of the throttle valve 32.

  The first passage body 33b also has a branch (not shown) that branches to the bypass passage 40. This branch portion is formed in the first passage main body 33b in the vicinity of the merging portion (substantially the same position with respect to the gas flow direction), and the upstream end of the bypass passage 40 is connected thereto.

  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 merge portion. And the gas which the fresh air and the external EGR gas merged flows into the bypass passage 40 via the aforementioned branching part at the time of natural intake, while at the time of supercharging, it merges with the gas which flows back through the bypass passage 40, The turbocharger 34 is sucked from the downstream end of the first passage main body 33b.

-Passageway structure on the turbocharger side-
As described above, the turbocharger 34 according to the present embodiment is configured as a roots-type supercharger. Specifically, the supercharger 34 includes a pair of rotors (not shown) having a rotation shaft extending along the cylinder row direction, a casing 34b that houses the rotor, and a drive pulley (not shown) that rotationally drives the rotor. And is connected to the crankshaft 15 via a drive belt (not shown) wound around the drive pulley. The above-described electromagnetic clutch 34a is interposed between the drive pulley and the rotor, and the driving force is transmitted to the supercharger 34 via the crankshaft 15 by switching between disconnection and connection of the electromagnetic clutch 34a. Or interrupt the transmission of driving force.

  The casing 34 b is formed in a cylindrical shape extending in the cylinder row direction, and divides the housing space of the rotor and the flow path of the gas passing through the turbocharger 34. Specifically, 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 of the first passage 33 is connected. On the other hand, a discharge port for discharging the gas compressed by the rotor is opened at the top of the casing 34b, and the upstream end of the second passage 35 is connected.

  The drive pulley is configured to rotationally drive the rotor accommodated in the casing 34b. Specifically, the drive pulley is formed in an axial shape that protrudes from the right end of the casing 34 b and extends substantially coaxially with the casing 34 b. The above-mentioned drive belt is wound around the tip of the drive pulley.

  The second passage 35 is formed in a substantially rectangular tube shape that extends short in the vertical direction, and is configured to connect the supercharger 34 to the intercooler 36. As described above, the discharge port of the supercharger 34 is connected to the upstream end of the second passage 35, while the introduction port of the intercooler 36 is connected to the downstream end thereof.

  As described above, the intercooler 36 according to the present embodiment is configured in a water-cooled manner, and includes a core (not shown) having a gas cooling function and a cooler housing 36c that houses the core.

  The cooler housing 36 c is disposed above the casing 34 b of the turbocharger 34 to define a storage space of the core and to be interposed between the second passage 35 and the third passage 37 in the intake passage 30. Constitute a flow path.

  Specifically, the cooler housing 36c is formed in a rectangular thin box shape in which the lower surface and the upper surface are opened, and the opening (introduction port for gas) at the lower surface side is downstream of the second passage 35 as described above. The ends are connected. On the other hand, the upstream end of the third passage 37 is connected to the opening (the gas outlet) on the upper surface side of the cooler housing 36 c.

  The third passage 37 is disposed above the cooler housing 36 c of the intercooler 36 and below the surge tank 38, and is configured to connect the intercooler 36 to the surge tank 38. Specifically, the third passage 37 is formed in a short cylindrical shape extending in the vertical direction, and the opening on the upper surface side of the cooler housing 36c is connected to the upstream end (lower end) thereof as described above, A first opening 38 a provided at the bottom of the surge tank 38 is connected to the downstream end (upper end).

  The gas sucked into the supercharger 34 from the first passage 33 reaches the surge tank 38 through the supercharging passage configured in this way.

  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 to rotate the rotor. As the rotor rotates, the turbocharger 34 compresses the gas sucked from the first passage 33 and discharges it from the discharge port. The discharged gas flows upward toward the intercooler 36 through the second passage 35.

  The gas flowing into the intercooler 36 is cooled as it passes through the core. The cooled gas flows out of the intercooler 36 and then flows into the surge tank 38 through the third passage 37.

-Passage structure on the bypass side-
The bypass passage 40 changes the direction so as to extend upward after extending from the branch portion of the first passage 33 substantially to the right. The bypass passage 40 extends upward and then changes direction again toward the rear, and is connected to the front portion of the surge tank 38.

  The bypass passage 40 is provided with a valve body 41a in which a bypass valve 41 is incorporated. The valve body 41 a is formed in a short cylindrical shape, and is disposed in front of the third passage 37 in a posture in which the openings at both ends are directed vertically.

  A portion of the bypass passage 40 downstream of the valve body 41a is configured as an elbow-shaped pipe joint as shown in FIG. 5 and the like, and below the valve body 41a and in front of the surge tank 38, It is arranged in a posture with the opening facing backwards. The upper end of the valve body 41a is connected to the upstream end (lower end) of the pipe joint, while the downstream end (rear end) of the valve body 41a has a second opening 38b provided at the front of the surge tank 38. It is connected.

  During natural intake, the gas that has flowed into the bypass passage 40 passes through each part of the bypass passage 40 and reaches the surge tank 38.

  That is, the gas that has passed through the throttle valve 32 flows into the bypass passage 40 from the middle of the first passage 33 according to the opening / closing condition of the bypass valve 41. The gas that has flowed into the bypass passage 40 flows into the surge tank 38 via the valve body 41a and the like.

  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 each part of the bypass passage 40 in the reverse direction and flows out to the first passage 33.

-Passage structure near the surge tank-
6 is a perspective view showing the surge tank 38, FIG. 7 is a view for explaining a schematic shape of the surge tank 38, and FIG. 8 is a side view of the surge tank 38. As shown in FIG.

  9 is a view as viewed from the arrow A of the surge tank 38 (see arrow A in FIG. 8), and FIG. 10 is a view as viewed from the arrow B of the surge tank 38 (see arrow B in FIG. 8). Is a C arrow view of the surge tank 38 (see arrow C in FIG. 8), and FIG. 12 is a D arrow view of the surge tank 38 (see arrow D in FIG. 8).

  13 is an aa cross-sectional view of the surge tank 38 (see the aa cross-section of FIG. 8), and FIG. 14 is a bb cross-sectional view of the surge tank 38 (see the bb cross-section of FIG. 8). FIG. 15 is a cross-sectional view of the surge tank 38 taken along the line c-c (see the cross-section c-c in FIG. 9).

  As shown in FIGS. 6 to 8, at the downstream end of the intake passage 30, four sets of independent passages 391 and 392, each downstream end portion of which is connected to each of the four sets of intake ports 17 and 18, A surge tank 38 in which the upstream end portions of each of the independent passages 391 and 392 are connected in a line according to the order in which the corresponding cylinders 11 are arranged is integrally formed. As described above, the surge tank 38 is disposed opposite to the opposite end of the intake ports 17 and 18 on the opposite side of the four independent passages 391 and 392. As will be described later, when each of the independent passages 391 and 392 is formed in a short cylindrical shape, the surge tank 38 is located near the inlet (upstream end) of the intake ports 17 and 18 in combination with such an arrangement. Will do. This is effective in shortening the flow path length from the surge tank 38 to the intake ports 17 and 18.

  And as shown in FIG. 9, the surge tank 38 is comprised by the triangular pyramid shape which followed one ridgeline in the cylinder row direction. Specifically, the surge tank 38 includes four sets of first and second vertices V1 and V2 arranged along the cylinder row direction and a line segment connecting the first and second vertices V1 and V2. A third vertex V3 and a fourth vertex V4 which are located on the opposite side of the independent passages 391 and 392 and are disposed along a direction (specifically, the top and bottom or front and back direction) orthogonal to the cylinder row direction It is configured to define a triangular pyramid-shaped space.

  In the present embodiment, as shown in FIGS. 13 to 15, etc., the first vertex V1 is on the right side in the cylinder row direction and in the vicinity of the inlets of the intake ports 17 and 18 in the vertical direction (specifically, 1 (The vicinity of the second port 18A related to the cylinder 11A). In addition, the second vertex V2 is disposed on the left side in the cylinder row direction and at substantially the same height as the first vertex V1 in the vertical direction (specifically, near the first port 17D related to the fourth cylinder 11D) ing.

  That is, the surge tank 38 has a posture such that a ridge line corresponding to a line segment connecting the first vertex V1 and the second vertex V1 is along the cylinder row direction and faces the inlets of the intake ports 17 and 18. It has become. By setting it as such an attitude | position, the top part corresponding to the 1st vertex V1 protrudes toward the right side, and the top part corresponding to the 2nd vertex V2 comes to protrude toward the direction.

  On the other hand, as shown in FIGS. 13 to 15 and the like, the third vertex V3 is intermediate between the first vertex V1 and the second vertex V2 in the cylinder row direction (that is, between the second cylinder 11B and the third cylinder 11C). In addition, the first vertex V1 and the second vertex V2 are arranged obliquely downward and forward in the vertical and front-back directions. Further, the fourth vertex V4 is disposed at the same position as the third vertex V3 in the cylinder row direction, and is disposed obliquely above and forward of the first vertex V1 and the second vertex V2 in the vertical and front-back directions. .

  That is, the surge tank 38 causes the ridge corresponding to the line connecting the third vertex V3 and the fourth vertex V4 to run along the vertical or front-rear direction, and the top corresponding to the third vertex V3 is obliquely downward and forward. On the other hand, the top portion corresponding to the fourth vertex V4 protrudes obliquely upward and forward while projecting. The relative positional relationship between the third vertex V3 and the fourth vertex V4 is not limited to the one disclosed herein. For example, the third vertex V3 and the fourth vertex V4 may be at the same position in the front-rear direction, or one of them may be protruded forward.

  As described above, the third vertex V3 and the fourth vertex V4 are both arranged between the first vertex V1 and the second vertex V2 in the cylinder row direction. Such an arrangement is equivalent to that the space defined in the surge tank 38 is mirror-symmetric with respect to the plane including the third vertex V3 and the fourth vertex V4. Thereby, the space defined in the surge tank 38 is bilaterally symmetrical in the cylinder row direction.

  As shown in FIGS. 6 to 15, the first opening 38 a is opened at the bottom of the surge tank 38, specifically, the portion near the third vertex V <b> 3 in the surge tank 38, as described above. The downstream end of the third passage 37 is connected.

  As shown in FIGS. 13 to 15, the central axis of the first opening 38 a extends straight upward along a plane including the third vertex V 3 and the fourth vertex V 4, and then upwards from below. It is bent from the front to the rear as it goes to With such a configuration, it is advantageous in directing the gas flowing into the surge tank 38 through the first opening 38a obliquely upward and backward, and thus evenly distributing it to the right and left sides in the cylinder row direction. become.

  On the other hand, as shown in FIGS. 6 to 15, the second opening 38 b is opened at the front portion of the surge tank 38, specifically, at a portion near the fourth vertex V <b> 4 in the surge tank 38. Thus, the downstream end of the bypass passage 40 is connected.

  The central axis of the second opening 38b is the upper inner wall surface of the surge tank 38 (specifically, the first vertex V1, the second vertex V2, and the fourth vertex V4, as shown in FIGS. 13 to 15). (Inner wall surface corresponding to the plane connecting the two). With such a configuration, the gas flowing into the surge tank 38 through the second opening 38 b can be guided along the upper inner wall surface.

  As described above, the plurality of independent passages 39 have the independent passage 391 connected to the first port 17 and the independent passage 392 connected to the second port 18 for each cylinder 11. The upstream end of each of the independent passages 391, 392 is connected to the surge tank 38 in a row in the order in which the corresponding cylinders 11 are lined up.

  Specifically, in the rear portion of the surge tank 38, as shown in FIGS. 9 to 12, four sets of independent passages 391 and 392 that form a pair of two are arranged in the cylinder row direction (that is, 8) in total. These independent passages 391, 392 are each formed as a short cylindrical passage extending substantially straight toward the rear in the vehicle mounted state, and one end side (upstream side) communicates with the space in the surge tank 38. On the other hand, the other end side (downstream side) is open to the engine body 10 side (rear side).

  Further, as shown in FIGS. 13 to 15, the upstream end of each of the four sets of independent passages 391, 392 is arranged in the surge tank 38 along a ridge line connecting the first vertex V1 and the second vertex V2. Connected by Thereby, as shown in FIG. 15, the upstream end of each independent passage 391, 392 has a plane connecting the first vertex V1, the second vertex V2, and the fourth vertex V4, and the first vertex V1. The second vertex V2 and the plane connecting the third vertex V3 are arranged at the corners where they intersect.

  The four sets of independent passages 391 and 392 are arranged so as to correspond to the four sets of intake ports 17 and 18, respectively. As described above, the four independent passages 391, 392 are respectively constituted by the independent passage 391 corresponding to the first port 17 and the independent passage 392 corresponding to the second port 18; Is assembled to the engine body 10, the first port 17 and the corresponding independent passage 391 constitute one independent passage, while the second port 18 and the corresponding independent passage 392 are independent. It constitutes one passage. In this way, eight independent paths are constructed.

  Further, as can be seen from FIGS. 13 and 14, in the space partitioned in the surge tank 38, both left and right ends are bulged with respect to the triangular pyramid connecting the four apexes V1 to V4.

  Specifically, as shown in FIG. 14, in the surge tank 38, the inner wall surface 38d facing the downstream end of the independent passages 391, 392 related to the first cylinder 11A is curved so as to form a convex rightward forward It swells diagonally right forward with respect to the line segment connecting the first vertex V1 and the fourth vertex V4. Such a tendency also applies to the left side in the cylinder row direction. That is, in the surge tank 38, the inner wall surface 38d facing the downstream end of the independent passages 391, 392 related to the fourth cylinder 11D is diagonally left with respect to the line segment connecting the first vertex V1 and the fourth vertex V4. It bulges forward.

  Further, the independent passage 391 related to the first port 17A of the first cylinder 11A and the independent passage 392 related to the second port 18B of the second cylinder 11B are adjacent to each other on the right side in the cylinder row direction. As shown, they are connected via an inner wall surface 38 e having an arc-shaped cross section that is convex toward the front. Further, the independent passage 391 related to the first port 17B of the second cylinder 11B and the independent passage 392 related to the second port 18C of the third cylinder 11C are adjacent to each other in the vicinity of the center in the cylinder direction, and toward the front. It is connected via an inner wall surface 38 e having an arc-like cross section that forms a convex. The same applies to the independent passage 391 related to the first port 17C of the third cylinder 11C and the independent passage 392 related to the second port 18D of the fourth cylinder 11D.

  Also, as described above, the spark plug 25 is disposed along the tank upper surface 38c. As shown in FIGS. 6 to 15, the tank upper surface 38c corresponds to a plane connecting the first vertex V1, the second vertex V2, and the fourth vertex V4.

(About pressure loss of gas flowing into surge tank)
16 to 17 are diagrams showing the configuration around the surge tank 38 in comparison with the conventional configuration.

  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 converts the control signal corresponding to the calculated control amount into the electromagnetic waves of the injector 6, the spark plug 25, the intake electric VVT 23, the exhaust electric VVT 24, the fuel supply system 61, the throttle valve 32, the EGR valve 54, and the turbocharger 34. The power is output to the clutch 34a, the bypass valve 41, etc., and the engine 1 is operated.

  The operation region of the engine 1 is divided, for example, by the engine speed and the load, and the ECU controls each actuator so as to realize an operation state corresponding to 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 (that is, the electromagnetic clutch 34a is shut off and the bypass valve 41 is fully opened). In the operating region on the higher load side than the predetermined load (hereinafter referred to as “supercharging region”), the turbocharger 34 is driven to supercharge the gas introduced into each cylinder 11 (that is, electromagnetic The clutch 34a is connected to adjust the opening degree of the bypass valve 41).

  Therefore, in the supercharging region, gas flows into the surge tank 38 through the third passage 37 constituting the first upstream passage, while in the fuel consumption region, the gas passes through the bypass passage 40 as the second upstream passage. As a result, gas flows into the surge tank 38.

  In recent years, in order to improve the thermal efficiency of an engine having such a configuration, securing of combustion stability, reduction of pump loss and the like are provided. As measures for satisfying such demands, it has been studied to reduce the pressure loss of gas in the intake system and the difference in pressure loss between cylinders by devising the configuration around the surge tank.

  First, a case where the conventional configuration shown in FIGS. 16 to 17 is applied will be described. Here, the surge tank 1038 shown in the upper part of FIGS. 16 to 17 has a conventional configuration and is formed in a substantially tubular shape extending in the cylinder row direction. A first upstream side passage 1037 having a supercharger is connected to the central portion in the cylinder row direction, whereas an excessive portion from the passage on the upstream side of the supercharger is connected to one end portion in the cylinder row direction. A second upstream passage 1040 extending around the feeder is connected. Similarly to the present embodiment, gas flows from one of the first upstream side passage 1037 and the second upstream side passage 1040 in accordance with the operating region of the engine. About another structure, it is the same as that of the surge tank 38 which concerns on this embodiment.

  In such a configuration, for example, in the supercharging region, as shown in the upper part of FIG. 16, when the gas flowing into the surge tank 1038 reaches the cylinder disposed at the cylinder row direction end side, the cylinder row direction It changes direction in the central part and flows from the central part toward the end (see arrow fc). Then, with respect to the cylinder at the cylinder row direction end side, the flow path length becomes relatively longer than the cylinder arranged at the center side thereof, and the influence of flow separation when changing the direction (for example, the direction) The pressure loss becomes relatively large due to the combination of swirling at the turning corner and making the gas difficult to flow. As a result, there is a difference between cylinders in pressure loss. Further, due to the formation of the surge tank 1038 in a substantially tubular shape, pressure loss may also occur depending on the flow passage diameter.

  Therefore, for example, by changing the configuration around the surge tank 1038, the configuration of the flow path from the first upstream passage 1037 to each cylinder via the surge tank 1038 is improved, and thereby, the difference in pressure loss between the cylinders is improved. Etc. can be reduced.

  However, in this engine, as already described, gas may flow not only from the first upstream passage 1037 but also from the second upstream passage 1040. In this case, depending on the connection structure between the passages 1037 and 1040 and the surge tank 1038, the flow path related to the first upstream passage 1037 and the cylinders from the second upstream passage 1040 to the cylinders via the surge tank 1038. The tendency of the inter-cylinder difference is different between the flow passage and the passage. For example, in the case of the conventional configuration, an increase in pressure loss is a concern in cylinders located at both ends in the cylinder row direction in the supercharging region. However, in the fuel efficiency region, as shown in the upper part of FIG. 17, the flow path length differs between one end and the other end in the cylinder row direction, and the pressure loss is sufficiently suppressed at one end side, while the other end On the side there is a concern for increased pressure loss (see arrow fn). Therefore, even if the difference between the cylinders is reduced with respect to the gas flowing in from the first upstream passage 1037, the difference between the cylinders may not be sufficiently reduced with respect to the gas flowing in from the second upstream passage 1040. .

  On the other hand, according to the present embodiment, as shown in the lower part of FIG. Specifically, the gas that has flowed into the surge tank 38 from the third passage 37 that forms the first upstream passage, and the third vertex V3 located near the first opening 38a and the cylinder in the cross-sectional view shown in the lower part of FIG. Each cylinder 11 is reached through a space corresponding to a triangle connecting a first vertex V1 located on the right side in the column direction and a second vertex V2 located on the left side in the cylinder direction (see arrow Fc) .

  Here, as can be seen from the lower part of FIG. 16, the third vertex V3 is located on the opposite side of the plurality of independent paths 39 across the line segment connecting the first vertex V1 and the second vertex V2. This is because the gas that has flowed into the surge tank 38 from a portion near the third vertex V3 passes through a flow path that tapers in diameter toward the line segment connecting the first vertex V1 and the second vertex V2. This means that each independent passage 39 is reached. In addition, by forming a triangular pyramid-shaped space, the diameter does not increase only in one plane shown in the lower part of FIG. 16, but three-dimensionally in a plurality of directions such as a height direction as shown in FIG. 14, for example. The diameter increases.

  When the diameter of the flow path is increased in this way, unlike the surge tank 1038 shown in the upper part of FIG. 16, the direction toward the cylinder 11 positioned on the cylinder row direction end side is not required without changing the direction in the center of the cylinder row direction. It is possible to flow gas at an angle. This makes it possible to reduce the inter-cylinder difference in flow path length as compared with the conventional configuration that involves a change in direction. Furthermore, it is also possible to suppress flow separation, since it does not involve turning.

  In addition, the cross section of the flow path leading to each cylinder 11 can be widened by increasing the diameter of the flow path in a tapered shape. This is effective in reducing the pressure loss according to the flow path diameter.

  As described above, the reduction in the difference between the flow path lengths between the cylinders, the suppression of the flow separation, and the reduction in the pressure loss according to the flow path diameter are combined with each other from the third passage 37 through the first opening 38a. The pressure loss of the inflowing gas and the inter-cylinder difference in pressure loss can be reduced.

  Moreover, according to the present embodiment, as can be seen from the lower stage of FIG. 17, the gas flowing into the surge tank 38 from the bypass passage 40 as the second upstream passage is also the second opening to which the bypass passage 40 is connected. Each cylinder 11 is reached through a space corresponding to a triangle connecting the fourth vertex V4 located near 38b and the aforementioned first vertex V1 and second vertex V2 (see arrow Fn).

  Here, like the third vertex V3, the fourth vertex V4 is located on the opposite side of the plurality of independent passages 39 across the line segment connecting the first vertex V1 and the second vertex V2. Then, the gas flowing in from the bypass passage 40 via the second opening 38b reaches each independent passage 39 via the flow path having the same shape as the gas flowing in from the third passage 37.

  Therefore, it is possible to make the tendency of the difference between the cylinders similar between the flow path related to the third passage 37 and the flow path related to the bypass passage 40. As a result, with respect to the gas flowing in from the bypass passage 40 as well as the gas flowing in from the third passage 37, the pressure loss and the difference in pressure loss between the cylinders can be reduced.

  Thus, according to the present embodiment, the tendency of the difference between the cylinders between the third passage 37 and the bypass passage 40 is made the same, and as a result, the pressure loss of the gas flowing in from each passage and the difference in pressure loss between the cylinders are made simultaneously. Can be reduced.

  Further, according to the present embodiment, the upstream ends of the independent passages 391 and 392 are ridge lines connecting the first vertex V1 and the second vertex V2 in the surge tank 38, as shown in FIGS. Connected side by side along. By setting it as such a structure, gas can be smoothly flowed from each of the 3rd channel | path 37 and the bypass channel | path 40 toward each independent channel | path 391,392.

  Further, according to the present embodiment, as shown in FIG. 4 and the like, the spark plug 25 can be disposed using the tank upper surface 38c. That is, for example, as shown in FIG. 6, the tank upper surface 38c is flat at least in the cylinder row direction. For this reason, when the spark plugs 25 are arranged in the cylinder row direction, it is possible to prevent interference with the surge tank 38 and to ensure installation.

  Further, according to the present embodiment, the third passage 37 constitutes a supercharging passage in which the supercharger 34 is interposed in the intake passage 30. On the other hand, as described above, the bypass passage 40 bypasses the turbocharger 34 and is connected to the surge tank 38. Such a configuration is effective in using the supercharging area and the fuel consumption area in combination.

  Further, according to the present embodiment, the supercharger 34 is disposed below the surge tank 38, and the passage (specifically, the cooler housing 36c and the third tank) extends from the supercharger 34 toward the surge tank 38. By connecting the passage 37 including the passage 37 to the vicinity of the third vertex V3 located below the third vertex V3 and the fourth vertex V4, the passage connecting the supercharger 34 and each part can be compactly laid out. At the same time, the pressure loss of the gas and the inter-cylinder difference in pressure loss can be reduced.

  As shown in FIG. 14, in the space defined in the surge tank 38, the inner wall surfaces 38d and 38d at the left and right ends bulge with respect to the triangular pyramid connecting the four vertices V1 to V4. If comprised in this way, it will become possible to enlarge the capacity | capacitance (volume of the surge tank 38) of both right-and-left both ends by the amount which bulged each inner wall surface 38d and 38d. This is advantageous in suppressing pressure loss at the end side in the cylinder row direction.

  Further, as shown in FIG. 14, the independent passage 391 related to the first port 17A of the first cylinder 11A and the independent passage 392 related to the second port 18B of the second cylinder 11B are projected forward. They are connected via an inner wall surface 38e having a circular arc shape.

  When the surge tank 38 according to the present embodiment is applied, for example, gas flowing into the surge tank 38 from the bypass passage 40 generally flows backward. Such gas also includes the gas flowing toward the inner wall 38e described above. According to the above configuration, the gas colliding with the inner wall surface 38e is smoothly distributed to the gas flowing into the independent passage 39 related to the first cylinder 11A and the gas flowing into the independent passage 39 related to the second cylinder 11B. It becomes possible. This is advantageous in reducing the pressure loss difference between cylinders. The same applies to the other inner wall surface 38e.

  As shown in FIGS. 3 to 5, the height position of the throttle body 33 a in which the throttle valve 32 is built is closer to the supercharger 34 than the surge tank 38. With such a configuration, the volume of the flow passage from the throttle valve 32 to the turbocharger 34 can be reduced. This is advantageous in securing the response of the supercharger 34 in combination with the supercharger 34, the intercooler 36, and the surge tank 38 being arranged in a line in the vertical direction.

  Further, since the merge portion of the EGR passage 52 is disposed between the throttle valve 32 and the supercharger 34, the volume of the flow path from the EGR passage 52 to the supercharger 34 can be reduced. Such a configuration is also advantageous from the viewpoint of the response of the external EGR.

<< Other embodiments >>
In the embodiment described above, the configuration in which the spark plug 25 is disposed along the tank upper surface 38c of the surge tank 38 has been described, but the configuration is not limited thereto. For example, instead of the spark plug 25, the injector 6 may be disposed along the tank upper surface 38c, or both the spark plug 25 and the injector 6 may be disposed along the tank upper surface 38c.

  Moreover, although the said embodiment demonstrated the structure which arrange | positions the supercharger 34 below the surge tank 38, it is not restricted to this structure. For example, the supercharger 34 may be disposed above the surge tank 38. Further, regardless of the relative positional relationship between the surge tank 38 and the supercharger 34, the positional relationship between the third vertex V3 and the fourth vertex V4 may be changed. For example, the surge tank 38 may be turned upside down.

  Moreover, although the said embodiment illustrated about the in-line 4 cylinder engine, it is not restricted to this structure. For example, it may be an engine having at least three or more cylinders, such as an in-line three-cylinder engine or an in-line six-cylinder engine.

1 engine (multi-cylinder engine)
6 injector 10 engine body 11 cylinder (cylinder)
17 First port (intake port)
18 2nd port (intake port)
25 spark plug 30 intake passage (intake device)
34 Turbocharger 37 third passage (first upstream passage)
38 Surge tank 38a First opening 38b Second opening 38c Tank upper surface 39 Independent passage (downstream passage)
391 Independent passage (downstream passage)
392 Independent passage (downstream passage)
40 bypass passage (second upstream passage)
V1 1st vertex V2 2nd vertex V3 3rd vertex V4 4th vertex

Claims (5)

A plurality of cylinders arranged in a row, a plurality of intake ports each communicating with each of the plurality of cylinders, and an intake device connected to each of the plurality of intake ports Intake structure of multi-cylinder engine,
The intake device is
A plurality of downstream passages, each downstream end of which is connected to each of the plurality of intake ports;
A surge tank in which the upstream ends of each of the plurality of downstream passages are connected in a line according to the order in which the corresponding cylinders are arranged;
Each downstream end is connected to an intermediate portion of the surge tank in the cylinder row direction , and has first and second upstream passages for introducing gas into the surge tank,
The surge tank is disposed along the cylinder row direction, and the first and second vertices are set opposite to the inlets of both intake ports located at both ends of the plurality of intake ports in the cylinder row direction, The third apex set to face the opening to which the downstream end of the first upstream passage is connected, and the opening to which the downstream end of the second upstream passage is connected. A fourth apex, and the third and fourth apexes are arranged along a direction orthogonal to the cylinder row direction,
In the surge tank, a triangular pyramid-shaped space connecting the first and second vertices and the third and fourth vertices is defined, and an inner wall surface of the surge tank includes the first A diameter that increases in a taper shape along a ridge line connecting the vertex, the second vertex, and the third vertex, and a diameter that increases in a taper shape along a ridge line that connects the first vertex, the second vertex, and the fourth vertex. The intake structure of the cylinder engine. In the intake structure of a multi-cylinder engine according to claim 1,
The upstream end portion of each of the plurality of downstream passages is an intake structure of a multi-cylinder engine that is connected side by side along a ridge line connecting the first and second vertices in the surge tank. In the intake structure of a multi-cylinder engine according to claim 1 or 2,
The multi-cylinder engine is provided with an injector and a spark plug for each cylinder,
The surge tank has a tank upper surface corresponding to a plane connecting the first apex, the second apex, and one apex located above the third and fourth apexes,
An intake structure for a multi-cylinder engine, wherein at least one of the injector and the spark plug is disposed along the upper surface of the tank. In the multi-cylinder engine intake structure according to any one of claims 1 to 3,
The first upstream passage is configured as a supercharging passage in which a supercharger is interposed,
The second upstream-side passage is configured as a bypass passage that branches from the upstream side of the supercharger in the first upstream-side passage and that bypasses the supercharger and is connected to the surge tank. Multi-cylinder engine intake structure. In the intake structure of a multi-cylinder engine according to claim 4,
The supercharger is located below the surge tank in a vehicle mounted state,
A gas discharge port in the supercharger and a portion near one apex located below the third and fourth apexes in the surge tank are connected to each other via the supercharging passage.
An intake structure for a multi-cylinder engine, wherein a downstream end portion of the bypass passage is connected to a portion near the other vertex located above the third and fourth vertices in the surge tank.

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