JP2019163718A - Intake air passage structure of engine - Google Patents

Abstract

To provide an intake air passage structure of an engine that more reliably restrains adherence of fuel to an inner wall surface of an intake air passage and stabilizes an air-fuel ratio of an air-fuel mixture.SOLUTION: An intake air passage structure 41 of an engine 17 comprises: a throttle body 46 for adjusting a flow rate of intake air; a fuel injection device 52 comprising a fuel injection port 75 for injecting fuel to the intake air; and a branch passage part 55 comprising a branch passage inlet 81 arranged upstream of the fuel injection port 75, and a branch passage outlet 82 arranged downstream of the fuel injection port 75 and provided in parallel with the fuel injection port 75, and passing a portion of the intake air.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an intake passage structure for an engine.

  2. Description of the Related Art An engine intake device is known that includes a main port, an intake port divided into a pair of subports on both the left and right sides of the main port, and an injector that injects fuel into the main port (for example, Patent Document 1). reference).

Japanese Utility Model Publication No. 7-38665

  Generally, the flow of intake air drawn into the combustion chamber of the engine changes direction so that it is curved at the intake port of the cylinder head.

  A conventional engine intake device branches to a subport and causes a portion of the intake air to flow out to the left and right sides of the outlet of the main port. Therefore, the conventional engine intake device prevents the fuel injected from the injector from adhering to the left and right sides of the outlet of the main port and to the inner wall surface downstream of the subport.

  However, the conventional engine intake device is difficult to prevent fuel from adhering to the upper and lower inner wall surfaces of the outlet of the main port, in particular, the upper inner wall surface corresponding to the outer peripheral side of the intake air flowing curvedly in the intake port. . The upper inner wall surface corresponding to the outer peripheral side of the intake air flowing in a curved manner in the intake port is directly behind the outlet of the injector that injects fuel into the intake passage (downstream immediately below), following the direction of the intake air flow. .

  When fuel adheres to the inner wall surface of the intake passage, the air-fuel ratio of the air-fuel mixture becomes thinner (lean) by the amount of fuel attached to the inner wall surface of the intake passage.

  Therefore, an object of the present invention is to provide an intake passage structure for an engine that stabilizes the air-fuel ratio of an air-fuel mixture by more reliably suppressing the adhesion of fuel to the inner wall surface of the intake passage.

  In order to solve the above problems, an intake passage structure for an engine according to the present invention is an intake passage structure for an engine having an intake passage that guides intake air to a combustion chamber of the engine, and the intake passage adjusts the flow rate of the intake air. A throttle body, a fuel injection device having a fuel injection port for injecting fuel into the intake air, a branch passage inlet disposed upstream of the fuel injection port, and a downstream of the fuel injection port. And a branch passage portion that has a branch passage outlet provided alongside the fuel injection port and distributes a part of the intake air.

  ADVANTAGE OF THE INVENTION According to this invention, the intake passage structure of the engine which suppresses adhesion of the fuel to the inner wall face of an intake passage more reliably, and stabilizes the air fuel ratio of air-fuel | gaseous mixture can be provided.

1 is a left side view showing an example of a motorcycle to which an intake passage structure according to an embodiment of the present invention is applied. Sectional drawing of the intake passage structure of the engine which concerns on embodiment of this invention. Sectional drawing of the intake passage structure of the engine which concerns on embodiment of this invention. Sectional drawing of the intake passage structure of the engine which concerns on embodiment of this invention. The figure which looked at the intake manifold of the intake passage structure which concerns on embodiment of this invention from the opening of the upstream. The perspective sectional view which passes along the center line of the downstream straight passage of the branch passage part of the intake passage structure concerning the embodiment of the present invention. The figure which looked at the intake manifold of the branch passage part of the intake passage structure which concerns on embodiment of this invention from the outer side of the curved part. The figure which looked at the intake manifold of the branch passage part of the intake passage structure concerning the embodiment of the present invention from the normal direction of the virtual plane which passes along the mainstream passage. Sectional drawing which passes along the centerline of the upstream linear passage of the branch passage part of the intake passage structure which concerns on embodiment of this invention.

  An embodiment of an intake passage structure for an engine according to the present invention will be described with reference to FIGS.

  FIG. 1 is a left side view showing an example of a motorcycle to which an intake passage structure according to an embodiment of the present invention is applied.

  In the present embodiment, front and rear, top and bottom, and left and right expressions are based on the passenger of the motorcycle 1.

  As shown in FIG. 1, a motorcycle 1 according to this embodiment is a scooter type vehicle.

  The motorcycle 1 includes a body frame 3 extending in the front and rear direction of the motorcycle 1, a power unit 5 supported by the body frame 3 and swingable in the vertical direction of the motorcycle 1, and a motorcycle 1 supported by the body frame 3. A steering mechanism 6 that can be steered in the left-right direction, a rotatable front wheel 7 that is supported by the steering mechanism 6, a rotatable rear wheel 8 that is supported by the power unit 5, and a vehicle body cover 9 that covers the vehicle body frame 3. I have.

  The steering mechanism 6 includes a pair of left and right front forks 11 that sandwich and support a front wheel 7, a suspension mechanism (not shown) provided in the left and right front forks 11, and a front fender 12 that covers the front wheel 7. And a handle bar 13 provided on the top of the front fork 11.

  The front wheel 7 is rotatably supported by a front wheel shaft (not shown) that spans the lower ends of the left and right front forks 11.

  The handle bar 13 includes grips 15 at the left and right ends. The grip 15 on the right side of the vehicle functions as a throttle for the engine 17. A brake lever (not shown) is provided in front of the left and right grips 15. The right brake lever is connected to a brake (not shown) of the front wheel 7. The left brake lever is connected to a brake (not shown) of the rear wheel 8.

  The power unit 5 is swingably supported on the lower end portion of the vehicle body frame 3 via the link mechanism 18. The power unit 5 includes an engine 17 and a power transmission device 23 integrally. The power unit 5 is a unit swing type that integrally swings the engine 17, the power transmission device 23, and the rear wheel 8.

  The power unit 5 is elastically supported on the vehicle body frame 3 via the rear cushion unit 27. The rear cushion unit 27 buffers the force transmitted from the rear wheel 8 to the vehicle body frame 3.

  The engine 17 generates a driving force for the rear wheel 8. The engine 17 generates electric power consumed by each part of the motorcycle 1. The power transmission device 23 changes the output of the engine 17 and transmits it to the rear wheels 8 as drive wheels.

  The engine 17 lays the cylinder 31 toward the front of the motorcycle 1. In other words, the center line of the cylinder bore 31 a of the engine 17 faces the front-rear direction of the motorcycle 1. That is, the engine 17 includes a cylinder 31 provided on the front side of the crankcase 32, a cylinder head 33 provided on the front side of the cylinder 31, and a head cover 35 provided on the front side of the cylinder head 33.

  The engine 17 may be erected with the cylinder 31 facing upward of the motorcycle 1. In other words, the center line of the cylinder bore 31a of the engine 17 may face the vertical direction of the motorcycle 1. The cylinder 31 and the cylinder head 33 of the engine 17 are disposed directly below the seat 37 or directly below a storage box 38 provided below the seat 37.

  An intake passage structure 41 that supplies intake air to the engine 17 is provided between the engine 17 and the seat 37 and inside the vehicle body cover 9. The intake passage structure 41 includes an air cleaner 42 that filters outside air to clean intake air, and an intake passage 43 that guides the intake air purified by the air cleaner 42 to the engine 17.

  The intake passage 43 connects the air cleaner 42 and the engine 17. The intake passage 43 guides intake air from the air cleaner 42 to the engine 17. The intake passage 43 includes an inlet tube 45 connected to the air cleaner 42, a throttle body 46 connected to the downstream end of the inlet tube 45 to adjust the flow rate of intake air supplied to the engine 17, and a downstream end of the throttle body 46. And an intake manifold 47 connected to the.

  The air cleaner 42 is disposed behind the cylinder head 33 of the engine 17. That is, the air cleaner 42 causes the intake air to flow forward. The intake passage 43 guides the intake air that has flowed out forward by the air cleaner 42 to the cylinder head 33 of the engine 17.

  The throttle body 46 is disposed between the inlet tube 45 and the intake manifold 47. The throttle body 46 includes a linear intake passage (not shown) and a throttle valve (butterfly valve, not shown) disposed in the intake passage.

  The vehicle body cover 9 adjusts the appearance of the motorcycle 1 and protects internal devices. The vehicle body cover 9 includes a plurality of synthetic resin molded products connected to each other.

  Next, the intake passage structure 41 of the engine 17 will be described in detail.

  FIG. 2 is a cross-sectional view of the intake passage structure of the engine according to the embodiment of the present invention.

  FIG. 2 is a cross-sectional view passing through the center of the main flow passage 68 in the intake manifold 47.

  As shown in FIG. 2, the intake passage 43 of the intake passage structure 41 according to the present embodiment connects the air cleaner 42 and the combustion chamber 51 of the engine 17. The intake passage 43 guides intake air from the air cleaner 42 to the combustion chamber 51 of the engine 17.

  In addition to the inlet tube 45, the throttle body 46, and the intake manifold 47, the intake passage 43 includes a fuel injection device 52 that is provided in the intake manifold 47 and injects fuel into the intake air, and an intake port 53 of the cylinder head 33. A branch passage portion 55 that bypasses a part of the intake air from the upstream side to the downstream side of the position where the fuel is injected into the intake air.

  The engine 17 according to the present embodiment has the center line C of the cylinder bore 31a directed in the front-rear direction of the motorcycle 1. The inlet 53 a of the intake port 53 of the engine 17 is open on the upper surface of the cylinder head 33. An outlet 53 b of the intake port 53 is connected to the combustion chamber 51. An outlet 53 b of the intake port 53 is opened and closed by an intake valve 56.

  The cylinder head 33 is provided with an exhaust port 57. An inlet 57 a of the exhaust port 57 is connected to the combustion chamber 51. An inlet 57 a of the exhaust port 57 is opened and closed by an exhaust valve 58. An outlet 57 b of the exhaust port 57 opens on the lower surface of the cylinder head 33. An exhaust pipe (not shown) and a muffler (silencer) are sequentially connected to the exhaust port 57.

  An insulator 61 is provided between the throttle body 46 and the intake manifold 47.

  The intake manifold 47 is connected to the intake port 53 of the cylinder head 33. The intake manifold 47 guides the intake air purified by the air cleaner 42 and adjusted in flow rate by the throttle body 46 to the intake port 53. The intake manifold 47 is a so-called elbow that is a tube curved or bent in an arc shape. The intake manifold 47 includes a flange portion 62 that is fixed to the intake port 53 of the engine 17. A gasket 63 is sandwiched between the intake port 53 and the flange portion 62.

  The intake manifold 47 is connected to the throttle body 46 and extends in a straight line, an upstream straight part 65, connected to the intake port 53 of the cylinder head 33, and extends in a straight line, and an upstream straight part 65. And a curved portion 67 which is provided between the downstream straight portion 66 and is curved in an arc shape.

  The upstream linear portion 65, the curved portion 67, and the downstream linear portion 66 circulate most of the intake air that passes through the intake manifold 47. The flow paths in the upstream linear portion 65, the curved portion 67, and the downstream linear portion 66 are referred to as a main flow passage 68 of the intake manifold 47.

  The upstream linear portion 65 is connected to the intake passage of the throttle body 46 substantially linearly. The upstream linear portion 65 extends toward the front of the motorcycle 1.

  The downstream straight portion 66 is connected to the intake port 53 of the engine 17. The upstream linear portion 65 extends downward of the motorcycle 1.

  A portion close to the center of curvature of the bending portion 67 is referred to as “inside of the bending portion 67”, and a portion far from the center of curvature of the bending portion 67 is referred to as “outside of the bending portion 67”.

  Further, the intake manifold 47 has a recessed portion 69 that allows a part of the wall surface of the intake passage 43 to be recessed in a direction crossing the intake flow direction.

  The recessed portion 69 straddles the curved portion 67 and the downstream straight portion 66. The recessed portion 69 bulges the intake manifold 47 toward the outside of the curved portion 67. The recessed space 71 defined by the recessed portion 69 is recessed toward the outside of the curved portion 67 and reaches (is crossed) the downstream linear portion 66. The hollow space 71 extends the main flow passage 68 of the intake manifold 47 toward the outside of the curved portion 67.

  The recessed portion 69 includes a bottom wall portion 72 to which the fuel injection device 52 is fixed, and a side wall portion 73 interposed between the bottom wall portion 72, the curved portion 67, and the downstream straight portion 66. . The bottom wall 72 is provided with a fuel injection device insertion hole 76 for inserting the fuel injection port 75 of the fuel injection device 52 into the intake manifold 47.

  The inner surface of the bottom wall portion 72, that is, the bottom surface portion 72 a of the recessed portion 69 faces the intake port 53 disposed below the intake manifold 47. That is, the bottom surface portion 72a according to the present embodiment faces downward.

  The inner surface, that is, the side surface portion 73a of the side wall portion 73 extends toward the intake port 53 substantially perpendicular to the edge of the bottom surface portion 72a.

  The fuel injection device 52 injects fuel into the intake air, that is, the air flowing through the intake passage 43. The fuel injected from the fuel injection device 52 and the intake air mix to become an air-fuel mixture. The fuel injection device 52 is provided in the intake manifold 47. The fuel injection device 52 is provided on the outside of the curved portion 67 of the intake manifold 47 or on the downstream straight portion 66 close to the outside of the curved portion 67 of the intake manifold 47.

  The fuel injection device 52 has a fuel injection port 75 that injects fuel into the intake air. The fuel injection port 75 is exposed in the intake manifold 47 in the middle of the main flow passage 68 and faces the main flow passage 68. The fuel injection port 75 is disposed below the intake manifold 47 from the fuel injection device 52 provided on the outside of the curved portion 67 of the intake manifold 47 or the downstream straight portion 66 close to the outside of the curved portion 67 of the intake manifold 47. The intake port 53 is directed to. That is, the fuel injection port 75 according to the present embodiment is directed downward. The fuel injection port 75 faces the valve fillet 77 of the intake valve 56.

  Further, the fuel injection port 75 is exposed in the intake manifold 47 through the fuel injection device insertion hole 76 in the bottom wall portion 72 of the recessed portion 69.

  By the way, since the intake manifold 47 has the curved portion 67, the flow rate of the intake air in the main flow passage 68 is increased outside the curved portion 67 than inside the curved portion 67. Then, the fuel injected from the fuel injection port 75 into the intake air in the main flow passage 68 is pushed to the outside of the curved portion 67 where the flow velocity is further increased. And it approaches the outside of the downstream linear portion 66 continuous to the outside of the curved portion 67. Therefore, the intake passage structure 41 according to the present embodiment includes a branch passage portion 55 that prevents the fuel approaching the inner wall surface of the main flow passage 68 from adhering to the inner wall surface of the main flow passage 68 in the intake manifold 47.

  FIG. 3 is a cross-sectional view of the intake passage structure of the engine according to the embodiment of the present invention.

  FIG. 3 is a cross-sectional view passing through the center of the passage in the branch passage portion 55.

  As shown in FIG. 3 in addition to FIG. 2, the branch passage portion 55 of the intake passage structure 41 according to the present embodiment is integrally formed with the intake manifold 47. The branch passage portion 55 branches a part of the intake air flowing through the intake manifold 47. That is, the branch passage portion 55 diverts a part of the intake air flowing through the main flow passage 68. The branch passage portion 55 diverts a part of the intake air from the main flow passage 68 and returns a part of the intake air diverted by bypassing the fuel injection port 75 to the downstream side of the fuel injection port 75.

  The branch passage section 55 has a branch passage inlet 81 disposed on the upstream side of the fuel injection port 75 and a branch passage outlet 82 disposed on the downstream side of the fuel injection port 75 and provided to the fuel injection port 75. is doing. In other words, the fuel injection port 75 is located between the branch passage inlet 81 and the branch passage outlet 82 in the direction of the intake air flow in the main flow passage 68 (that is, the intake air flow of the intake manifold 47 passing through other than the branch passage portion 55). Has been placed.

  The branch passage inlet 81 is provided in the vicinity of the upstream end of the curved portion 67 of the intake manifold 47. The branch passage outlet 82 is provided in the vicinity of the downstream end of the curved portion 67 of the intake manifold 47.

  Further, the branch passage inlet 81 is provided outside the curved portion 67 of the intake manifold 47. The branch passage outlet 82 is provided outside the curved portion 67 of the intake manifold 47. The branch passage inlet 81 and the branch passage outlet 82 are substantially open in the tangential direction of the intake manifold 47. The branch passage inlet 81 and the branch passage outlet 82 are substantially open in the tangential direction outside the curved portion 67.

  The branch passage inlet 81 is open in the upstream direction of the flow of intake air toward the fuel injection port 75.

  4 is a cross-sectional view of the intake passage structure of the engine according to the embodiment of the present invention, taken along line IV-IV in FIG.

  In addition to FIGS. 2 and 3, as shown in FIG. 4, the branch passage outlet 82 of the intake passage structure 41 according to the present embodiment opens in the downstream direction of the flow of the intake air away from the fuel injection port 75. Yes. The branch passage outlet 82 is provided on the bottom surface portion 72 a of the recessed portion 69. That is, the recessed portion 69 has a bottom surface portion 72a where the fuel injection port 75 and the branch passage outlet 82 are disposed, and a side surface portion 73a including a portion 69a disposed on the downstream side of the branch passage outlet 82. ing.

  The branch passage outlet 82 is provided at the fuel injection port 75 of the fuel injection device 52. Here, “adjacent to the fuel injection port 75” means the fuel injection device insertion hole 76 of the intake manifold 47 and the wall (the wall of the recessed portion 69 and the wall of the branch passage portion 55) attached thereto. As long as a suitable strength is ensured or as long as processing is possible, the closer it is, the better. For example, when viewed from the opening direction of the fuel injection port 75, the opening direction of the fuel injection device insertion hole 76, or the opening direction of the branch passage outlet 82, the branch passage outlet 82 has an opening diameter from the center of the fuel injection port 75. It is preferable to penetrate from the center of the circular area A having a diameter twice that of the opening diameter of the fuel injection device insertion hole 76 to the inside of the circular area A having a diameter twice that of the opening diameter.

  The branch passage outlet 82 is farther from the center of the main flow passage 68 than the fuel injection port 75. In other words, the branch passage outlet 82 is closer to the portion 69 a farthest from the center of the main flow passage 68 in the side wall portion 73 of the recessed portion 69 than the fuel injection port 75. This leads a part of the intake air flowing out from the branch passage outlet 82 to the portion 69 a farther from the center of the main flow passage 68 than the fuel injection port 75 in the side wall portion 73 of the recessed portion 69, and toward the intake port 53. Create an air wall. Even if the fuel injected from the fuel injection port 75 is pushed toward the outside of the curved portion 67 by the intake air flowing through the main flow passage 68, the air wall causes the fuel to flow into the inner surface of the intake manifold 47 (the fuel injection port 75. Diffuses before reaching the inner surface). At this time, the air wall is generated from the inside of the hollow space 71 of the recessed portion 69. The air wall prevents the fuel injected from the fuel injection port 75 from entering the hollow space 71, and the fuel injected from the fuel injection port 75 includes the side wall portion 73 of the recessed portion 69. Prevents from adhering to the inner surface.

  The branch passage section 55 includes an upstream straight passage 83 that extends linearly from the branch passage inlet 81, and a downstream straight passage 84 that is connected to the upstream straight passage 83 and extends linearly toward the branch passage outlet 82. Have.

  FIG. 5 is a view of the intake manifold of the intake passage structure according to the embodiment of the present invention as seen from the opening on the upstream side.

  As shown in FIG. 5 in addition to FIGS. 2 and 3, the upstream straight passage 83 of the intake passage structure 41 according to the present embodiment extends in the tangential direction of the intake manifold 47 at the branch passage inlet 81. The upstream linear passage 83 opens in the tangential direction outside the curved portion 67 at the branch passage entrance 81. The upstream linear passage 83 can be seen from the opening on the upstream side of the intake manifold 47. Therefore, the upstream linear passage 83 can be easily processed by inserting a tool such as a drill from the upstream opening of the intake manifold 47.

  FIG. 6 is a perspective cross-sectional view passing through the center line of the downstream straight passage of the branch passage portion of the intake passage structure according to the embodiment of the present invention.

  As shown in FIG. 6 in addition to FIGS. 2 and 3, the downstream straight passage 84 of the intake passage structure 41 according to the present embodiment extends in the tangential direction of the intake manifold 47 at the branch passage outlet 82. The downstream straight passage 84 opens in a tangential direction outside the curved portion 67 at the branch passage outlet 82. The downstream straight passage 84 can be seen from the downstream opening of the intake manifold 47 or the downstream edge (end) of the recessed space 71 of the recessed portion 69. Therefore, the downstream straight passage 84 can be easily processed by inserting a tool such as a drill from the downstream opening of the intake manifold 47.

  FIG. 7 is a view of the intake manifold of the branch passage portion of the intake passage structure according to the embodiment of the present invention as seen from the outside of the curved portion.

  FIG. 8 is a view of the intake manifold of the branch passage portion of the intake passage structure according to the embodiment of the present invention as seen from the normal direction of a virtual plane passing through the main flow passage.

  In addition to FIGS. 2 and 3, as shown in FIGS. 7 and 8, the fuel injection device 52 of the intake passage structure 41 according to the present embodiment is based on a virtual plane P passing through the center of the intake passage 43. Is arranged on one side of the plane P or on one side of the plane P across the plane P. The branch passage portion 55 is disposed on the other side of the plane P.

  The upstream straight passage 83 of the branch passage portion 55 is biased to the left of a virtual plane P that passes through the center of the intake passage 43 in a plan view of the motorcycle 1. The upstream straight passage 83 passes forward on the left side of the fuel injection device 52 in a plan view of the motorcycle 1. The downstream straight passage 84 of the branch passage portion 55 extends toward the lower right so as to go around the front of the fuel injection device 52.

  When viewed from the normal direction of the plane P passing through the center line of the intake passage 43 (FIG. 8), the branch passage portion 55 overlaps the fuel injection device 52.

  Further, when viewed from the normal direction of the plane P passing through the center line of the intake passage 43 (FIG. 8), the direction perpendicular to the coupling surface 62a of the flange portion 62 on the downstream side of the intake manifold 47 and away from the flange portion 62 In (the solid line arrow in the figure), the portion 55a farthest from the engine 17 of the branch passage portion 55 is closer to the engine 17 than the portion 52a farthest from the engine 17 of the fuel injection device 52. In other words, a portion 55 a farthest from the engine 17 of the branch passage portion 55 in the direction perpendicular to the coupling surface 62 a of the flange portion 62 on the downstream side of the intake manifold 47 and away from the flange portion 62 is the engine of the fuel injection device 52. 17 is closer to the flange portion 62 on the downstream side of the intake manifold 47 than the portion 52 a farthest from the portion 17. In FIG. 8, a one-dot chain line L1 that is parallel to the mounting surface of the engine 17 and passes through the portion 52a farthest from the engine 17 of the fuel injection device 52 is shown.

  Further, when viewed from the normal direction of the plane P passing through the center line of the intake passage 43 (FIG. 8), the portion 55 b farthest from the intake manifold 47 of the branch passage portion 55 is the farthest from the intake manifold 47 of the fuel injection device 52. It is closer to the intake manifold 47 than the distant portion 52b. In FIG. 8, an alternate long and short dash line L2 that passes through a portion 52b that is perpendicular to the mounting surface of the engine 17 and is farthest from the intake manifold 47 of the fuel injection device 52 is shown.

  Further, when viewed from the normal direction of the plane P passing through the center line of the intake passage 43, the branch passage is perpendicular to the coupling surface 62 a of the flange portion 62 on the downstream side of the intake manifold 47 and away from the flange portion 62. A portion 55 a farthest from the engine 17 of the portion 55 is closer to the engine 17 than a portion 47 a farthest from the engine 17 of the intake manifold 47. In other words, a portion 55 a of the branch passage portion 55 farthest from the engine 17 in the direction perpendicular to the coupling surface 62 a of the flange portion 62 on the downstream side of the intake manifold 47 and away from the flange portion 62 is the engine 17 of the intake manifold 47. Is closer to the flange portion 62 on the downstream side of the intake manifold 47 than the portion 47a farthest from the center. In FIG. 8, an alternate long and short dash line L <b> 3 that is parallel to the mounting surface of the engine 17 and passes through a portion 47 a farthest from the engine 17 of the intake manifold 47 is shown.

  In other words, the branch passage portion 55 extends along the intake passage 43 through a route that does not protrude from the fuel injection device 52 attached so as to protrude from the intake passage 43.

  FIG. 9 is a cross-sectional view passing through the center line of the upstream straight passage of the branch passage portion of the intake passage structure according to the embodiment of the present invention.

  As shown in FIG. 9, the upstream straight passage 83 of the intake passage structure 41 according to the present embodiment has a substantially uniform flow path breakage along its entire length until it reaches the downstream straight passage 84 from the branch passage inlet 81. It has an area.

  Further, as shown by a two-dot chain line in FIG. 9, the upstream linear passage 83 may have a tapered portion 86 whose flow passage cross-sectional area decreases from the branch passage inlet 81 toward the downstream. Further, the upstream straight passage 83 is continuous with the branch passage inlet 81 and has a counter-sink that the flow passage cross-sectional area becomes sharply narrow from a large diameter portion (not shown) having a flow passage cross-sectional area equivalent to that of the branch passage inlet 81. May have a stepped portion (not shown). In these cases, the opening area of the branch passage inlet 81 is larger than the channel cross-sectional area in the middle of the branch passage portion 55.

  The intake manifold 47 may be formed integrally with the cylinder head 33 of the engine 17. That is, the intake manifold 47 and the intake port 53 of the cylinder head 33 may be integrally formed. In this case, the intake manifold 47 and the intake port 53 of the cylinder head 33 according to the present embodiment are simply referred to as an intake port. A fuel injection device 52 is provided at the intake port, and the branch passage portion 55 is integrally formed.

  Further, the intake manifold 47 may be a straight pipe. For example, in the motorcycle 1 that supplies the intake air in a straight line from the air cleaner 42 to the intake port 53 of the engine 17 as in the super sports type motorcycle 1, the branch passage to the straight intake manifold 47 is provided. A portion 55 may be provided. In this case, the opening direction of the branch passage inlet 81, the opening direction of the branch passage outlet 82, the extending direction of the upstream linear passage 83, and the extending direction of the downstream straight passage 84 depend on the center line of the main flow passage 68 of the intake manifold 47 ( It is preferable that the angle formed with a substantially straight line extending in the vertical direction is shallow (small).

  The intake passage structure 41 of the engine 17 according to the present embodiment is disposed at the upstream side of the fuel injection port 75, and at the downstream side of the fuel injection port 75, and is provided side by side with the fuel injection port 75. A branch passage portion 55 that has a branch passage outlet 82 and distributes a part of the intake air is provided. Therefore, even if the fuel injected from the fuel injection device 52 is likely to be pushed to the wall surface of the main flow passage 68 by the intake air flowing through the main flow passage 68, the intake passage structure 41 moves from the branch passage portion 55 to the main flow passage 68. By the intake air flowing in, the fuel is forced to flow downstream before reaching the wall surface of the main flow passage 68. That is, the intake passage structure 41 makes it difficult for the fuel injected from the fuel injection device 52 to adhere to the wall surface of the main flow passage 68. Therefore, the intake passage structure 41 can stabilize the air-fuel ratio of the air-fuel mixture.

  The intake passage structure 41 of the engine 17 according to the present embodiment has a branch passage inlet 81 that opens in the upstream direction of the flow of intake air toward the fuel injection port 75. Therefore, the intake passage structure 41 can smoothly guide the intake air flowing along the wall surface of the intake passage 43 to the branch passage portion 55.

  Furthermore, the intake passage structure 41 of the engine 17 according to the present embodiment has an opening area of the branch passage inlet 81 that is larger than the middle channel cross-sectional area of the branch passage portion 55. Therefore, the intake passage structure 41 can supply more intake air to the branch passage outlet 82 as compared with the case where the flow path cross-sectional area is constant or the opening area of the branch passage inlet 81 is smaller. That is, the intake passage structure 41 makes it difficult for the fuel injected from the fuel injection device 52 to adhere to the wall surface of the main flow passage 68.

  Further, the intake passage structure 41 of the engine 17 according to the present embodiment has a tapered portion 86 whose flow passage cross-sectional area decreases from the branch passage inlet 81 toward the downstream. Therefore, the intake passage structure 41 can supply more intake air to the branch passage outlet 82 more smoothly. That is, the intake passage structure 41 makes it difficult for the fuel injected from the fuel injection device 52 to adhere more reliably to the wall surface of the main flow passage 68.

  Furthermore, the intake passage structure 41 of the engine 17 according to the present embodiment has a branch passage outlet 82 that opens in the downstream direction of the flow of intake air leaving the fuel injection port 75. Therefore, the intake passage structure 41 can smoothly send the intake air flowing through the branch passage portion 55 toward the wall surface of the intake passage 43. Therefore, the intake passage structure 41 can more reliably push the fuel directed toward the wall surface of the main flow passage 68 in the downstream direction of the intake air flowing through the main flow passage 68.

  In addition, the intake passage structure 41 of the engine 17 according to the present embodiment includes a recessed portion 69 that allows a part of the wall surface of the intake passage 43 to be recessed in a direction that intersects the flow direction of intake air. Therefore, the intake passage structure 41 makes it difficult for the fuel injected from the fuel injection device 52 to reach the outer wall surface of the main flow passage 68, and can easily prevent the fuel from adhering to the wall surface.

  Furthermore, the intake passage structure 41 of the engine 17 according to the present embodiment includes a branch passage portion 55 that overlaps the fuel injection device 52 when viewed from the normal direction of the plane P. In other words, the branch passage portion 55 does not protrude around the fuel injection device 52 (a direction away from the intake manifold 47). For this reason, the intake passage structure 41 is less likely to cause an influence of the installation space on the surrounding structures and electric components (contention of the installation space).

  Further, when the intake passage structure 41 of the engine 17 according to the present embodiment is viewed from the normal direction of the plane P passing through the center of the intake passage 43, the portion 55a farthest from the engine 17 of the branch passage portion 55 is the fuel injection. The device 52 is closer to the engine 17 than the portion 52 a farthest from the engine 17. Therefore, the intake passage structure 41 can suppress the branch passage portion 55 from projecting around the fuel injection device 52, particularly in a direction away from the intake passage 43.

  Furthermore, when the intake passage structure 41 of the engine 17 according to the present embodiment is viewed from the normal direction of the plane P passing through the center of the intake passage 43, a portion 55a farthest from the engine 17 of the branch passage portion 55 is an intake manifold. It is closer to the engine 17 than a portion 47 a farthest from the 47 engine 17. Therefore, the intake passage structure 41 can suppress the branch passage portion 55 from projecting around the intake manifold 47, particularly in the direction in which the intake passage 43 extends.

  The intake passage structure 41 of the engine 17 according to the present embodiment has a branch passage inlet 81 and a branch passage outlet 82 that open in the tangential direction of the intake manifold 47. Therefore, when the intake manifold 47 is curved, the intake passage structure 41 can smoothly guide the intake air flowing along the wall surface of the intake passage 43 to the branch passage portion 55, while moving to the wall surface of the main flow passage 68. It is possible to more surely push the fuel that flows toward the downstream side of the intake air flowing through the main flow passage 68.

  Further, the intake passage structure 41 of the engine 17 according to the present embodiment includes an upstream straight passage 83 and a downstream straight passage 84 connected to the upstream straight passage 83. The branch passage portion 55 is a single road that does not have a branch in addition to the upstream straight passage 83 and the downstream straight passage 84. Therefore, the intake passage structure 41 can merge with the intake air flowing through the main flow passage 68 without reducing the momentum of the intake air flowing through the branch passage portion 55. In addition, the intake passage structure 41 can easily form the branch passage portion 55.

  Therefore, according to the intake passage structure 41 of the engine 17 according to the present embodiment, the adhesion of fuel to the inner wall surface of the intake passage 43 is more reliably suppressed and the air-fuel ratio of the air-fuel mixture is stabilized.

  DESCRIPTION OF SYMBOLS 1 ... Motorcycle, 3 ... Body frame, 5 ... Power unit, 6 ... Steering mechanism, 7 ... Front wheel, 8 ... Rear wheel, 9 ... Body cover, 11 ... Front fork, 12 ... Front fender, 13 ... Handlebar, 15 ... Grip, 17 ... Engine, 18 ... Link mechanism, 23 ... Power transmission device, 27 ... Rear cushion unit, 31 ... Cylinder, 31a ... Cylinder bore, 32 ... Crankcase, 33 ... Cylinder head, 35 ... Head cover, 37 ... Seat, 38 ... Storage box, 41 ... Intake passage structure, 42 ... Air cleaner, 43 ... Intake passage, 45 ... Inlet tube, 46 ... Throttle body, 47 ... Intake manifold, 47a ... Farthest part from engine, 51 ... Combustion chamber, 52 ... fuel injection device, 52a ... the part farthest from the engine, 52b ... The farthest part from the intake manifold, 53 ... intake port, 53a ... inlet, 53b ... outlet, 55 ... branch passage, 55a ... part, 56 ... intake valve, 57 ... exhaust port, 57a ... inlet, 57b ... outlet, 58 ... Exhaust valve, 61 ... Insulator, 62 ... Flange part, 62a ... Coupling surface, 63 ... Gasket, 65 ... Upstream straight part, 66 ... Downstream straight part, 67 ... Curved part, 68 ... Mainstream passage, 69 ... Depressed Part, 69a ... part located downstream from the branch passage outlet in the recessed part, 71 ... hollow space, 72 ... bottom wall part, 72a ... bottom part, 73 ... side wall part, 73a ... side part, 75 ... Fuel injection port 76 ... Fuel injection device insertion hole, 77 ... Valve fillet, 81 ... Branch passage inlet, 82 ... Branch passage outlet, 83 ... Upstream straight passage, 84 ... Downstream straight passage, 86 ... Taper .

Claims (11)

An intake passage structure for an engine including an intake passage for guiding intake air to a combustion chamber of the engine,
The intake passage is
A throttle body for adjusting the flow rate of the intake air;
A fuel injection device having a fuel injection port for injecting fuel into the intake air;
A branch passage inlet disposed upstream of the fuel injection port, and a branch passage outlet disposed downstream of the fuel injection port and provided side by side with the fuel injection port to circulate a part of the intake air An intake passage structure for an engine having a branch passage portion. 2. The intake passage structure for an engine according to claim 1, wherein the branch passage inlet opens in an upstream direction of the intake air flow toward the fuel injection port. 3. The intake passage structure for an engine according to claim 1 or 2, wherein an opening area of the branch passage inlet is larger than a flow path cross-sectional area in the middle of the branch passage. The engine intake passage structure according to claim 3, wherein the branch passage portion has a tapered portion in which a flow passage cross-sectional area decreases from the branch passage inlet toward the downstream. The engine intake passage structure according to any one of claims 1 to 4, wherein the branch passage outlet opens toward a downstream direction of the intake air flow away from the fuel injection port. The intake passage has a recessed portion that dents a part of the wall surface of the intake passage in a direction intersecting the flow direction of the intake air,
The recessed portion has a bottom surface portion on which the fuel injection port and the branch passage outlet are disposed, and a side surface portion including a portion disposed on the downstream side of the branch passage outlet. The engine intake passage structure according to any one of claims 1 to 5. With reference to a plane passing through the center of the intake passage,
The fuel injection device is disposed on one side of the plane,
The engine intake according to any one of claims 1 to 6, wherein the branch passage portion is disposed on the other side of the plane and overlaps the fuel injection device when viewed from the normal direction of the plane. Passage structure. 2. The portion of the branch passage portion that is farthest from the engine when viewed from the normal direction of a plane that passes through the center of the intake passage is closer to the engine than the portion of the fuel injection device that is farthest from the engine. The engine intake passage structure according to any one of claims 1 to 7. The intake passage has an intake manifold provided with the fuel injection port and having the branch passage portion,
The portion of the branch passage portion farthest from the engine when viewed from the normal direction of the plane passing through the center of the intake passage is closer to the engine than the portion of the intake manifold farthest from the engine. 9. An intake passage structure for an engine according to any one of 8 above. The intake passage is provided with the fuel injection port and has an intake manifold that has the branch passage and is curved in an arc shape;
The engine intake passage structure according to any one of claims 1 to 9, wherein the branch passage inlet and the branch passage outlet are opened in a tangential direction of the intake manifold. The branch passage section includes an upstream straight passage that extends linearly from the branch passage inlet, and a downstream straight passage that extends to the upstream straight passage and extends straight toward the branch passage outlet. The intake passage structure for an engine according to any one of claims 1 to 10.

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