JP2016049967A - Intake device of internal combustion engine for small-sized vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intake device of an internal combustion engine for a small-sized vehicle in which fuel supply means for mixing fuel with intake air is interposed in the middle of an intake passage with a downstream end communicating with an intake port of an engine body and an upstream end communicating with a clean chamber of an air cleaner, so as to prevent the fuel from stagnating in the air cleaner to dispense with maintenance work for discharging the fuel from the air cleaner.SOLUTION: Mounted on a vehicle, an air cleaner 31 is arranged spaced apart in the longitudinal direction from fuel supply means 30. A bottom wall 55 of a clean chamber 44 is formed in an air cleaner case 40 of the air cleaner 31 and is arranged inclined so as to be at a gradually lower position as it advances toward one side in the vehicle width direction. At the lowest portion of the bottom wall 55, a connection port 57 is provided for communication with an upstream end of an intake passage which is at a gradually higher position as it advances toward the air cleaner 31 side from an intake port.SELECTED DRAWING: Figure 3

Description

  The present invention provides a fuel supply means for mixing fuel with intake air in the middle of an intake passage where a downstream end communicates with an intake port of an engine body mounted on a vehicle body frame and an upstream end communicates with a clean chamber of an air cleaner. The present invention relates to an intake device for an internal combustion engine for a small vehicle.

  In an internal combustion engine mounted on a motorcycle, which is a small vehicle, a carburetor, which is a fuel supply means, is connected to a cylinder head, which is a part of the engine body, via an intake pipe that leads to the intake port, and is connected to the carburetor. An air cleaner connected via a tube is disclosed in Patent Document 1, in which a connecting portion of the connecting tube to the air cleaner is provided at an intermediate portion in the vertical direction of the air cleaner, and is connected from the intake port to the air cleaner. The intake passage to is generally horizontal.

JP 2000-53055 A

  By the way, in a small vehicle that cannot secure a long distance between the fuel supply means such as a carburetor and the air cleaner, the air-fuel mixture in the intake passage is returned to the air cleaner by the blowback gas in the intake passage. As a result, fuel may stay in the air cleaner. In this case, as disclosed in the above-mentioned Patent Document 1, when the intake passage extends substantially horizontally, the fuel accumulated in the air cleaner is difficult to be discharged, and a connection port connected to the intake passage is provided in the intermediate portion in the vertical direction of the air cleaner. As a result, fuel does not accumulate at the bottom of the air cleaner and is not discharged. Therefore, in order to discharge the fuel from the air cleaner, a drain hole for fuel is provided at the bottom of the cleaner case of the air cleaner, and the fuel discharged from the drain hole and accumulated in the fuel reservoir is periodically discharged or cleaned. However, if possible, it is desirable that the fuel accumulated in the air cleaner is not required to be discharged and cleaned, and that maintenance is free.

  The present invention has been made in view of such circumstances, and provides an intake device for an internal combustion engine for a small vehicle that prevents fuel from accumulating in the air cleaner and eliminates maintenance work for discharging the fuel from the air cleaner. The purpose is to do.

  In order to achieve the above object, the present invention provides an intake air in the middle of an intake passage in which a downstream end communicates with an intake port of an engine body mounted on a vehicle body frame and an upstream end communicates with a clean chamber of an air cleaner. In an intake device for an internal combustion engine for a small vehicle in which fuel supply means for mixing fuel is interposed, the air cleaner is disposed at a position spaced in the front-rear direction from the fuel supply means in a vehicle-mounted state, and a cleaner case for the air cleaner The bottom wall of the clean chamber formed inside is inclined so as to gradually become a lower position toward one side in the vehicle width direction, toward the air cleaner side from the intake port at the lowest part of the bottom wall As a first feature, there is provided a connection port through which the upstream end of the intake passage which gradually becomes an upper position is provided.

  According to the present invention, in addition to the configuration of the first feature, a connection cylinder that is connected to the connection port and protrudes outward from the cleaner case is integrally formed on the cleaner case, and an upstream end portion of the intake passage A second feature is that an upstream end portion of the intake pipe member that forms the pipe is connected to the connection tube.

  According to the present invention, in addition to the configuration of the second feature, the vehicle body frame includes a frame member that slopes rearwardly downward through the air cleaner, and at least a part of the bottom wall of the clean chamber A third feature is that an inclined wall portion disposed forward of the connection port is formed along the frame member, and the connection port is provided at the lowest portion of the inclined wall portion.

  In the present invention, in addition to any of the first to third features, a gas-liquid separation chamber that introduces a breather gas from the engine body and performs gas-liquid separation is disposed behind the connection port. The fourth feature is that it is formed in the clean chamber.

  According to the present invention, in addition to the configuration of the fourth feature, the air cleaner includes a clean side case that forms a part of the clean chamber, and a clean side case that forms a part of the dirty chamber. And a partition wall that partitions the clean chamber and the dirty chamber and is sandwiched between the clean side case and the dirty side case while holding a cleaner element, and comprising the bottom of the clean chamber An isolation wall that forms a recess that opens to the partition wall side is provided integrally with the clean side case, and the gas-liquid separation chamber includes the bottom wall and the isolation wall of the clean chamber, A fifth feature is that the partition wall is formed close to and opposite to the open end of the recess.

  In addition to the fifth feature, the sixth feature of the present invention is that the partition wall is integrally provided with a rib extending along the isolation wall in the gas-liquid separation chamber.

  According to the present invention, in addition to any of the first to sixth features, the cleaner case includes a clean side case forming a part of the clean chamber, and a part of the dirty chamber. A dirty side case coupled to the side case, and the bottom wall of the dirty side case forming the bottom of the dirty chamber is formed so as to be inclined downwardly as it approaches the clean side case, A drain hole that discharges moisture in the dirty chamber is provided in a portion of the bottom wall of the dirty side case near the clean side case, and a flange that covers the drain hole from above is integrated with the dirty side case. The seventh feature is that it is provided.

  Furthermore, in addition to the configuration of the seventh feature of the present invention, a partition wall that partitions the clean chamber and the dirty chamber while holding a cleaner element is sandwiched between the clean side case and the dirty side case, The eighth feature is that the collar is formed so that the tip of the collar contacts the partition wall.

  According to the first feature of the present invention, the bottom wall of the clean chamber in the air cleaner is inclined so as to gradually become a lower position toward one side in the vehicle width direction, and is provided at the lowest part of the bottom wall. Since the upstream end of the intake passage, which is located at an upper position, gradually leads to the connection port toward the air cleaner side, the fuel accumulated in the clean chamber by the blow-back gas in the intake passage returns to the connection port side through the bottom wall of the clean chamber. Therefore, fuel flows from the connection port to the intake passage, which is located at the lower position toward the intake port. This prevents fuel from accumulating in the air cleaner and eliminates the need for maintenance work for fuel discharge. Can do.

  Further, according to the second feature of the present invention, the connection tube connected to the connection port is integrally connected to the cleaner case and protrudes outward, and the intake tube member forming the upstream end portion of the intake passage is formed in the connection tube portion. Since the upstream end portion is connected, the intake pipe member does not enter the clean chamber of the air cleaner, and the fuel can be easily returned from the connection port to the intake passage side.

  According to the third feature of the present invention, at least a part of the bottom wall of the clean chamber is inclined forwardly from the connection port so as to be along the frame member inclined downwardly passing through the lower part of the air cleaner. Since the wall portion is formed and the connection port is provided at the lowest portion of the inclined wall portion, the fuel in the clean chamber can be actively guided to the connection port side along the inclined wall portion, and the air cleaner It is possible to secure the capacity of the air cleaner by forming a part of the air cleaner extending forward along the frame member.

  According to the fourth aspect of the present invention, the gas-liquid separation chamber that performs gas-liquid separation by introducing the breather gas is formed in the clean chamber behind the connection port, so that the flow of fuel to the connection port is inhibited. The gas-liquid separation chamber can be configured in the clean chamber at a position where no action is taken.

  According to the fifth feature of the present invention, the cleaner element is held by the partition wall sandwiched between the clean side case and the dirty side case that cooperate to form the cleaner case, and is partitioned between the bottom wall of the clean chamber. An isolation wall that forms a recess that opens to the wall side is provided integrally with the clean case, and the gas-liquid separation chamber is close to and faces the bottom wall of the clean chamber, the isolation wall, and the open end of the recess. Since the gas-liquid separation chamber is formed with walls, the gas-liquid separation chamber is configured without using other members other than the clean case and the partition wall, and the increase in the number of parts for forming the gas-liquid separation chamber is avoided. be able to.

  According to the sixth aspect of the present invention, the rib extending along the separating wall is integrally provided in the partition wall in the gas-liquid separation chamber, so that a labyrinth passage is formed in the gas-liquid separation chamber to form the inside of the gas-liquid separation chamber. Effective gas-liquid separation can be performed, and only gas can flow into the clean chamber.

  According to the seventh feature of the present invention, the bottom wall of the dirty side case that constitutes the cleaner case in cooperation with the clean side case is inclined so as to become a lower position as it approaches the clean side case. Since the drain hole for draining moisture in the dirty chamber is provided in the part of the bottom wall of the dirty side case near the clean side case, the drain hole is covered from above with a flange part integrated with the dirty side case. Moisture that has entered the dirty chamber of the air cleaner can be discharged well from the drain hole, and even if water or dust enters the dirty chamber from the drain hole, it is recommended that the moisture and dust adhere directly to the cleaner element. Can be suppressed.

  Further, according to the eighth feature of the present invention, since the tip of the collar portion comes into contact with the partition wall, water or dust that has entered the dirty chamber from the drain hole rises along the partition wall by the intake air, and the cleaner element Heading to the side can be prevented by the buttocks.

1 is a left side view of a motorcycle. FIG. 2 is an enlarged view of a portion indicated by an arrow 2 in FIG. 1. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. FIG. 5 is an enlarged view of a part indicated by an arrow 5 in FIG. 3. It is a partially cutaway rear view of the dirty side case seen from the direction of arrow 6 in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, front and rear, left and right, and top and bottom refer to directions as viewed from the occupant riding the motorcycle.

  First, in FIG. 1, a body frame F of the motorcycle includes a head pipe 13 that supports a front fork 11 for pivotally supporting a front wheel WF at a lower end portion and a steering bar handle 12 for steering, and the head pipe 13 A main frame 14 extending downwardly from the rear, an upper frame 15 disposed above the main frame 14 and extending rearward from the head pipe 12, and a pair of left and right extending downward from the rear end of the main frame 14 A pivot frame 16, a pair of left and right seat frames 17 connected to the rear end portion of the upper frame 15 and extending rearward, and extending rearward from the upper end portions of the pair of left and right pivot frames 16, and the rear end portion of the pair. And a pair of left and right rear frames 18 connected to the rear portion of the seat frame 17.

  The pivot frame 16 supports a front end portion of a swing arm 19 around which a rear wheel WR is suspended so as to swing up and down via a support shaft 20. A rear cushion unit 21 is provided between the rear portion of the swing arm 19 and the seat frame 17.

  The engine body 22 of the internal combustion engine E that exerts power for driving the rear wheels WR is supported by the main frame 14 and the pivot frame 16 of the vehicle body frame F with the cylinder axis C tilted forward until it becomes substantially horizontal. Rotational power from the internal combustion engine E is transmitted to the rear wheel WR via a power transmission mechanism 24 having an endless drive chain 23.

  A fuel tank 25 disposed above the engine main body 22 is supported on the upper frame 15 of the vehicle body frame F, and a tandem type riding seat 26 disposed behind the fuel tank 25 includes the fuel tank 25. It is supported by the seat frame 17.

  The intake device 28 of the internal combustion engine E is connected to an intake pipe 29 having a downstream end connected to an upper side wall of a cylinder head 27 constituting a part of the engine body 22, and to an upstream end of the intake pipe 29. A carburetor 30 as a fuel supply means; an air cleaner 31 disposed behind the carburetor 30; and a connecting tube 32 connecting the carburetor 30 and the air cleaner 31.

  The exhaust device 33 of the internal combustion engine E is connected to an exhaust pipe 34 connected to the lower side wall of the cylinder head 27, an exhaust muffler 35 disposed below the engine body 22, and the exhaust pipe 34. Thus, a catalytic converter 36 accommodated in the exhaust muffler 35 is provided.

  With reference to FIGS. 2 to 4, in the intake device 28, the intake air whose downstream end communicates with the intake port 38 of the cylinder head 27 in the engine body 22 and whose upstream end communicates with the clean chamber of the air cleaner 31. A carburetor 30 that mixes fuel with intake air is provided in the middle of the passage 39, and the air cleaner 31 is rearward in the front-rear direction from the carburetor 30 when mounted on the motorcycle of the internal combustion engine E. It is arranged at a separated position.

  The intake passage 39 is formed in the intake pipe 29, the carburetor 30, and the connecting tube 32 so as to gradually move upward from the intake port 38 toward the air cleaner 31 side.

  The air cleaner 31 includes a clean side case 41 that forms part of the clean chamber 44, a dirty side case 42 that forms part of the dirty chamber 45 and forms the cleaner case 40 together with the clean side case 41, and a cleaner element. A partition wall 43 that partitions the clean chamber 44 and the dirty chamber 45 and is sandwiched between the clean side case 41 and the dirty side case 42.

  The clean side case 41 and the dirty side case 42 are formed in a box shape with the partition wall 43 side open, and the fitting recess 47 provided on the entire circumference of the open end of the clean side case 41 Projections 43a provided on the outer periphery of the partition wall 43 are fitted so as to sandwich the seal member 48 between the clean side case 41 and the outer periphery of the partition wall 43 is formed between the clean side case 41 and the dirty side case 42. The clean side case 41 and the dirty side case 42 are fastened to each other by a plurality of bolts 49 arranged at intervals in the circumferential direction while being sandwiched between the open ends.

  A rectangular holding cylinder 43b is integrally provided at a substantially central portion of the partition wall 43, and the cleaner element 46 is accommodated and held in the holding cylinder 43b.

  The air cleaner 31 includes a frame member that constitutes a part of the vehicle body frame F while disposing the clean chamber 44 on the left side of the partition wall 43 and the dirty chamber 45 on the right side of the partition wall 43. It is arranged above the rear part of the main frame 14. In the cleaner case 40, upper mounting plate portions 41a are respectively provided at two positions spaced in front and rear of the upper portion of the clean case 41, and are fixed to the right seat frame 17 of the pair of left and right seat frames 17. The upper mounting plate portion 41a is fastened to the pair of front and rear upper stays 50 with bolts 51, respectively. A lower mounting plate portion 41b provided at the lower rear portion of the clean side case 41 is fastened by a bolt 53 to a lower stay 52 that is fixed to the rear end portion of the main frame 14 and extends upward.

  Thus, the bottom wall 55 of the clean chamber 44 formed in the cleaner case 40 in a state supported by the seat frame 17 and the main frame 14 of the vehicle body frame F is one in the vehicle width direction (this embodiment). Then, it is arranged to be inclined so as to gradually become a lower position as it goes to the left.

  In the dirty side case 42, a suction cylinder 56 is integrally projected so as to open rearward from the rear of the air cleaner 31 into the dirty chamber 45 so as to suck air from the outside. Further, the connection port 57 through which the clean air from the clean chamber 44 is led to the intake passage 39 and through the upstream end of the intake passage 39 becomes the bottom wall 55 of the clean chamber 44 in the clean side case 41. Provided in the part. Moreover, the bottom wall 55 is inclined so as to gradually become a lower position toward the left in the vehicle width direction, and the connection port 57 is provided at the lowest part of the bottom wall 55.

  Further, the clean side case 41 of the cleaner case 40 is integrally formed with a connection cylinder 58 that is connected to the connection port 57 and protrudes outward from the clean side case 41, and an upstream end portion of the intake passage 39 is formed at the clean side case 41. An upstream end portion of the connecting tube 32 that is an intake pipe member to be formed is connected to the connection tube 58.

  By the way, the main frame 14 is inclined downward and passes below the air cleaner 31, and the main frame 14 is disposed on at least a part (a part in this embodiment) of the bottom wall 55 of the clean chamber 44. An inclined wall portion 55a disposed in front of the connection port 57 is formed along the frame 14, and the connection port 57 is provided at the lowest portion of the inclined wall portion 55a.

  Referring also to FIG. 5, the crankcase 59 of the engine body 22 is connected to one end of a hose 60 for leading out the breather gas from the crankcase 59. The breather gas guided by the hose 60 is connected to the crankcase 59. It is introduced into the gas-liquid separation chamber 61 formed in the clean chamber 44 so as to be arranged behind the port 57, and the gas-liquid separation is performed in the gas-liquid separation chamber 61.

  An isolation wall 63 that forms a recess 62 that opens to the partition wall 43 side between the clean wall 44 and the bottom wall 55 is provided integrally with the clean case 41, and the gas-liquid separation chamber 61 is The bottom wall 55 and the isolation wall 63 of the clean chamber 44 and the partition wall 43 close to and opposite to the open end of the recess 63 are formed.

  Moreover, since the bottom wall 55 of the clean chamber 44 is inclined so as to gradually become a lower position toward the left in the vehicle width direction, the gas-liquid separation chamber 61 is also inclined in the same direction as the bottom wall 55. The other end of the hose 60 is connected to a breather gas introduction cylinder 64 that is formed integrally with the bottom wall 55 so as to communicate with the lowest part of the gas-liquid separation chamber 61.

  In addition, the partition wall 43 is integrally provided with a rib 65 extending along the isolation wall 63 in the gas-liquid separation chamber 61.

  In FIG. 6, the bottom wall 42 a of the dirty side case 42 that forms the bottom of the dirty chamber 45 is formed to be inclined so as to become a lower position as it approaches the clean side case 41, and the dirty side case 42. A drain hole 66 that discharges moisture in the dirty chamber 45 is provided in a portion of the bottom wall 42a near the clean side case 41, and a flange 67 that covers the drain hole 66 from above is provided in the dirty side case. 42 is integrally provided.

  Moreover, the flange portion 67 is formed so that the tip of the flange portion 67 abuts on the partition wall 43.

  Next, the operation of this embodiment will be described. An air cleaner 31 is disposed at a position separated rearward from the vaporizer 30 in the front-rear direction in a vehicle-mounted state, and a clean chamber 44 formed in the cleaner case 40 of the air cleaner 31. The bottom wall 55 of the bottom wall 55 is inclined so as to gradually become a lower position toward one side in the vehicle width direction (to the left in this embodiment). Since the connection port 57 is provided through the upstream end of the intake passage 39 which gradually becomes an upper position toward the side 31, the fuel accumulated in the clean chamber 44 by the blow-back gas in the intake passage 39 is the bottom wall 55 of the clean chamber 44. And is returned to the connection port 57 side, and the intake air that is positioned downward from the connection port 57 toward the intake port 38 side. Since fuel flows to the road 39, to prevent the fuel accumulated in the cleaner 31, the maintenance work for the fuel discharge can be eliminated.

  The cleaner case 40 is integrally formed with a connecting tube 58 that is connected to the connection port 57 and protrudes outward from the cleaner case 40, and the upstream end of the connecting tube 32 that forms the upstream end of the intake passage 39. Since the connecting portion is connected to the connecting cylinder 58, the connecting tube 32 does not enter the clean chamber 44 of the air cleaner 31, and the fuel can be easily returned from the connecting port 57 to the intake passage 39 side.

  In addition, the vehicle body frame F includes a main frame 14 that is inclined downward and passes below the air cleaner 31, and is connected to at least a part of the bottom wall 55 of the clean chamber 44 along the main frame. An inclined wall portion 55a disposed in front of the opening 57 is formed, and the connection port 57 is provided at the lowest portion of the inclined wall portion 55a. Therefore, the fuel in the clean chamber 44 is caused to follow the inclined wall portion 55a. Thus, the capacity of the air cleaner 31 can be secured by forming the air cleaner 31 so as to extend forward along the main frame 14.

  A gas-liquid separation chamber 61 that performs gas-liquid separation by introducing a breather gas from the crankcase 59 of the engine body 22 is formed in the clean chamber 44 so as to be disposed behind the connection port 57. Therefore, the gas-liquid separation chamber 61 can be configured in the clean chamber 44 at a position where the flow of fuel to the connection port 57 is not hindered.

  The air cleaner 31 includes a clean side case 41 that forms a part of the clean chamber 44, a dirty side case 42 that forms a part of the dirty chamber 45 and forms the cleaner case 40 together with the clean side case 41, A partition wall 43 that partitions the clean chamber 44 and the dirty chamber 45 and is sandwiched between the clean side case 41 and the dirty side case 42 while holding the cleaner element 46, and the bottom of the clean chamber 44 An isolation wall 63 that forms a recess 62 that opens to the partition wall 43 side is provided integrally with the clean case 41, and the gas-liquid separation chamber 61 is connected to the bottom wall 55 of the clean chamber 44. And the separation wall 64 and the partition wall 43 which is close to and faces the open end of the recess 62, so that a gas-liquid separation chamber is formed. 1, can be configured without using members other than the clean side case 41 and the partition wall 43, to prevent the number of parts is increased in order to constitute a gas-liquid separation chamber 61.

  Further, the partition wall 43 is integrally provided with a rib 65 extending along the isolation wall 63 in the gas-liquid separation chamber 61. Therefore, a labyrinth passage is formed in the gas-liquid separation chamber 61 to form the gas-liquid separation chamber 61. In this way, effective gas-liquid separation can be performed, and only gas can flow into the clean chamber 44.

  In addition, the bottom wall 42a of the dirty side case 42 that forms the bottom of the dirty chamber 45 is formed so as to be inclined downward as it approaches the clean side case 41, and the bottom wall 42a of the dirty side case 42 is Since a drain hole 66 for discharging moisture in the dirty chamber 45 is provided in a portion near the clean side case 41, a flange 67 that covers the drain hole 66 from above is provided integrally with the dirty side case 42. The water that has entered the dirty chamber 45 of the air cleaner 31 can be discharged well from the drain hole 66, and even if water or dust enters the dirty chamber 45 from the drain hole 66, the water or dust is removed from the cleaner element. Direct attachment to 46 can be suppressed by the flange 67.

  Further, since the flange 67 is formed so that the tip of the flange 67 abuts on the partition wall 43, water and dust that have entered the dirty chamber 45 from the drain hole 66 are separated by the intake air. It is possible to prevent the flange 67 from going up through 43 and heading toward the cleaner element 46 side.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

  For example, in the above-described embodiment, the case where the present invention is applied to a motorcycle has been described. However, the present invention can be widely implemented in connection with a small vehicle including a motor tricycle.

  The present invention can also be applied to an intake device in which a throttle body is used instead of the carburetor 30 of the above-described embodiment, and a fuel injection valve as a fuel supply means is attached to the throttle body or the intake pipe. it can.

14 ... main frame 22 as frame member ... engine body 30 ... carburetor 31 as fuel supply means ... air cleaner 32 ... connecting tube 38 as intake pipe member ... intake port 39 ... Intake passage 40 ... Cleaner case 41 ... Clean side case 42 ... Dirty side case 42a ... Bottom wall 43 of the dirty side case ... Division wall 44 ... Clean chamber 45 ... Dirty chamber 46 ... Cleaner element 55 ... Clean chamber bottom wall 55a ... Inclined wall 57 ... Connection port 58 ... Connection cylinder 61 ... Gas-liquid separation chamber 62 ... Recess 63 ... Isolation wall 65 ... Rib 66 ... Drain hole 67 ... Ridge F ... Body frame

Claims (8)

  An intake passage (39) whose downstream end communicates with the intake port (38) of the engine body (22) mounted on the vehicle body frame (F) and whose upstream end communicates with the clean chamber (44) of the air cleaner (31). In the intake device of the small vehicle internal combustion engine in which the fuel supply means (30) for mixing the fuel with the intake air is provided in the middle of the engine, the position separated from the fuel supply means (30) in the front-rear direction in the vehicle mounted state And the bottom wall (55) of the clean chamber (44) formed in the cleaner case (40) of the air cleaner (31) is gradually lowered toward the one side in the vehicle width direction. The lower wall of the bottom wall (55) is gradually placed at an upper position as it goes from the intake port (38) toward the air cleaner (31). The intake system for a small vehicle internal combustion engine upstream end of the through make connection port (57) and which are located in the intake passage (39).   The cleaner case (40) is integrally formed with a connection tube (58) that is connected to the connection port (57) and protrudes outward from the cleaner case (40), and an upstream end of the intake passage (39). 2. The intake device for an internal combustion engine for a small vehicle according to claim 1, wherein an upstream end portion of an intake pipe member (32) that forms a valve is connected to the connection cylinder (38).   The vehicle body frame (F) includes a frame member (14) that is inclined downwardly and passes below the air cleaner (31), and at least a part of the bottom wall (55) of the clean chamber (44), An inclined wall portion (55a) disposed forward of the connection port (57) is formed along the frame member (14), and the connection port (57) is the lowest of the inclined wall portion (55a). The intake device for an internal combustion engine for a small vehicle according to claim 2, wherein the intake device is provided in a portion.   A gas-liquid separation chamber (61) that performs gas-liquid separation by introducing a breather gas from the engine body (22) is arranged behind the connection port (57) so as to be disposed in the clean chamber (44). The intake device for an internal combustion engine for a small vehicle according to any one of claims 1 to 3, wherein the intake device is formed as follows.   The air cleaner (31) includes a clean side case (41) that forms part of the clean chamber (44), and a part of the dirty chamber (45) that forms the cleaner case together with the clean side case (41). The clean side case (41) and the dirty side case (42) constituting the (40) and the clean side case (41) and the clean room (45) are partitioned by holding the cleaner element (46). A partition wall (43) sandwiched between dirty side cases (42), and a recess (62) that opens to the partition wall (43) side between the bottom wall (55) of the clean chamber (44) Is formed integrally with the clean case (41), and the gas-liquid separation chamber (61) is connected to the bottom wall (55) of the clean chamber (44) and the isolation wall. 63), the proximity to the open end of the recess (62), an intake apparatus of a small vehicle internal combustion engine according to claim 4, characterized in that it is formed out with the partition wall facing (43).   The small vehicle according to claim 5, wherein a rib (65) extending along the isolation wall (63) is integrally provided in the partition wall (43) in the gas-liquid separation chamber (61). Intake device for internal combustion engine.   The cleaner case (40) is coupled to the clean side case (41) forming a part of the clean chamber (44) and the clean side case (41) forming a part of the dirty chamber (45). The bottom wall (42a) of the dirty side case (42) that forms the bottom of the dirty chamber (45) is positioned lower as it approaches the clean side case (41). A drain that discharges moisture in the dirty chamber (45) to a portion of the bottom wall (42a) of the dirty side case (42) close to the clean side case (41). A hole (66) is provided, and a flange (67) covering the drain hole (66) from above is integrally provided in the dirty side case (42). Or intake system for a small vehicle internal combustion engine according to (1).   A partition wall (43) that partitions the clean chamber (44) and the dirty chamber (45) while holding the cleaner element (46) is disposed between the clean side case (41) and the dirty side case (42). 8. The internal combustion engine for a small vehicle according to claim 7, wherein the flange portion (67) is sandwiched and formed so that a tip end of the flange portion (67) abuts on the partition wall (43). Engine intake system.

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