Air cleaner

Abstract

To improve the output made from when an engine rotates at low speed to when the engine rotates at high speed even if an air cleaner is disposed behind the engine.SOLUTION: An air cleaner (50) is disposed at the inner side of a vehicle body frame behind an engine. The air cleaner includes: an air cleaner case (51) provided with a suction chamber (56); an air filter (57) which divides the suction chamber (56) into a dirty side (58) and a clean side (59); an inlet tube (62) which takes air into the dirty side from the vehicle rear; and an outlet tube (64) which sends air from the clean side to the engine. The inlet tube and the outlet tube are attached to the upper side of the air cleaner case, and an extension part (65) where the clean side is extended more downward than the dirty side is formed at the lower side of the air cleaner case.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an air cleaner. [Background technology]

[0002] A straddle-type vehicle having an air cleaner disposed behind the engine is known (see, for example, Patent Document 1). The air cleaner described in Patent Document 1 has an inlet tube attached to the rear surface of an air cleaner case, and an outlet tube attached to the front surface of the air cleaner case. Air is taken into the air cleaner case from the inlet tube, and is filtered by a filter disposed inside the air cleaner. Clean air then enters the outlet tube from the air cleaner, and is sent out to the throttle body through the outlet tube. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4121392 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the air cleaner described in Patent Document 1 is located in a small space inside the body frame under the seat. This makes it difficult to ensure an air cleaner volume that satisfies the required engine output. In particular, there is a problem of insufficient air volume when the throttle is suddenly opened.

[0005] The present invention has been made in consideration of these points, and aims to provide an air cleaner that can improve engine output from low to high revolutions, even when placed behind the engine. [Means for solving the problem]

[0006] An air cleaner of one embodiment of the present invention is an air cleaner positioned inside the body frame behind the engine, and comprises an air cleaner case in which an intake chamber is formed, an air filter that divides the intake chamber into a dirty side and a clean side, an inlet tube that takes in air from the rear of the vehicle to the dirty side, and an outlet tube that sends air from the clean side to the engine, wherein the inlet tube and the outlet tube are attached to the upper side of the air cleaner case, and an extension portion is formed on the lower side of the air cleaner case that extends the clean side downward further than the dirty side, thereby solving the above-mentioned problem. Effect of the Invention

[0007] According to an air cleaner of one aspect of the present invention, the inlet tube and the outlet tube are attached to the upper side of the air cleaner case, so that air can easily flow directly from the inlet tube to the outlet tube. Therefore, air flows smoothly toward the engine from low to high engine speeds, improving engine output. The air cleaner case has an extension portion formed by extending the clean side below the dirty side, so that the clean side has a sufficient volume even in the narrow space inside the body frame. Therefore, even when the throttle is suddenly opened, the air inside the extension portion is used to improve engine output. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a left side view of the saddle-ride type vehicle of the present embodiment. [Diagram 2] FIG. 2 is a left side view of the engine and its periphery according to the present embodiment. [Diagram 3] FIG. 2 is a top view of the periphery of the engine according to the embodiment. [Figure 4] FIG. 2 is a side view of the air cleaner of the present embodiment. [Diagram 5] 1 is a cross-sectional view of an air cleaner according to an embodiment of the present invention. [Figure 6]FIG. 2 is a top view of the air cleaner of the present embodiment. [Figure 7] FIG. 7 is a top view of the air cleaner in FIG. 6 with a filter cover removed. [Figure 8] 8 is a top view of the air cleaner in FIG. 7 with an upper case removed. [Figure 9] 4 is a diagram showing the flow of air in the air cleaner of the present embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An air cleaner according to one embodiment of the present invention is disposed behind the engine and inside the vehicle frame. An air cleaner case of the air cleaner has an intake chamber formed therein, which is divided into a dirty side and a clean side by an air filter. Air is taken in from the rear of the vehicle through an inlet tube into the dirty side, and air is sent from the clean side to the engine through an outlet tube. An inlet tube and an outlet tube are attached to the upper side of the air cleaner case, which facilitates direct air flow from the inlet tube to the outlet tube. As a result, air flows smoothly toward the engine from low to high engine speeds, improving engine output. An extension portion is formed on the lower side of the air cleaner case by extending the clean side downward more than the dirty side, and the volume of the clean side is sufficiently secured even in a narrow space inside the vehicle frame. As a result, even when the throttle is suddenly opened, the air inside the extension portion is utilized to improve engine output. EXAMPLES

[0010] The present embodiment will be described in detail below with reference to the accompanying drawings. Fig. 1 is a left side view of a saddle riding type vehicle according to the present embodiment. In the following drawings, the arrow FR indicates the front of the vehicle, the arrow RE indicates the rear of the vehicle, the arrow L indicates the left side of the vehicle, and the arrow R indicates the right side of the vehicle.

[0011] As shown in Fig. 1, the saddle-type vehicle 1 is configured by mounting an engine 40, an electrical system, and various other parts on a diamond-shaped body frame 10 formed of pipes and sheet metal. The body frame 10 has a pair of main frames 12 that branch off to the left and right from a head pipe 11 and extend rearward, and a pair of down frames 13 that branch off to the left and right from the head pipe 11 and extend downward. The pair of main frames 12 support a rear portion of the engine 40, and the pair of down frames 13 support a front portion of the engine 40. Supporting the engine 40 on the body frame 10 ensures the rigidity of the entire vehicle.

[0012] The front portion of the main frame 12 forms a tank rail 14 located above the engine 40, and a fuel tank 31 is supported from below by the tank rail 14. The rear portion of the main frame 12 forms a body frame 15 located behind the engine 40, and a swing arm 25 is supported in a swingable manner in the lower half of the body frame 15. A seat rail 21 consisting of an upper rail 22 and a lower rail 23 is attached to the upper half of the body frame 15. A rider seat 32 and a pillion seat 33 are supported behind the fuel tank 31 on the upper portion of the upper rail 22.

[0013] A pair of front forks 34 are steerably supported on the head pipe 11 via a steering shaft (not shown). A front wheel 35 is rotatably supported on the lower part of the front forks 34, and an upper part of the front wheel 35 is covered by a front fender (not shown). The swing arm 25 extends rearward from the body frame 15. A rear wheel 36 is rotatably supported on the rear end of the swing arm 25, and an upper part of the rear wheel 36 is covered by a rear fender (not shown). An engine 40 is connected to the rear wheel 36 via a chain drive type transmission mechanism, and power from the engine 40 is transmitted to the rear wheel 36 via the transmission mechanism.

[0014] Meanwhile, there is a demand for an effective air cleaner for a vehicle equipped with a two-cylinder engine, which has a narrow width and requires output even at high revolutions. In the case of a vehicle in which the air cleaner is disposed behind the engine, the space available for disposing the air cleaner is limited by the frame width of the main frame and the rail width of the seat rail. This makes it difficult to ensure the volume of the air cleaner, and the amount of intake air is insufficient, particularly when the throttle is suddenly opened. Therefore, in the saddle-type vehicle 1 of this embodiment, the lower part of the air cleaner 50 is expanded downward to ensure the volume so that the air cleaner 50 does not interfere with the seat rail 21.

[0015] The peripheral configuration of the engine and the air cleaner will be described with reference to Figures 2 to 8. Figure 2 is a left side view of the engine periphery of this embodiment. Figure 3 is a top view of the engine periphery of this embodiment. Figure 4 is a side view of the air cleaner of this embodiment. Figure 5 is a cross-sectional view of the air cleaner of this embodiment. Figure 6 is a top view of the air cleaner of this embodiment. Figure 7 is a top view of the air cleaner of Figure 6 with the filter cover removed. Figure 8 is a top view of the air cleaner of Figure 7 with the upper case removed.

[0016] As shown in Figures 2 and 3, the engine 40 is a two-cylinder engine and has a crankcase 41 with an upper and lower split structure. A cylinder 42, a cylinder head 43, and a cylinder head cover 44 are attached to the upper part of the crankcase 41. A magneto cover 45 that covers a magneto (not shown) from the side is attached to the left side of the crankcase 41. A sprocket cover 46 that covers a drive sprocket (not shown) from the side is attached to the rear of the magneto cover 45. A clutch cover 47 that covers a clutch (not shown) from the side is attached to the right side of the crankcase 41.

[0017] A throttle body 48 is connected to the rear surface of the cylinder head 43, and an air cleaner 50 is connected upstream (rear side) of the throttle body 48. The air cleaner 50 is disposed rearward of the engine 40 and inside the pair of main frames 12 and the pair of seat rails 21. As described above, the rear portions of the pair of main frames 12 form the pair of body frames 15, and the front end portion of the air cleaner 50 is positioned inside the pair of body frames 15. The upper half of the body frame 15 is inclined obliquely downward toward the rear, and the air cleaner case 51 behind the body frame 15 is also inclined obliquely downward.

[0018] An upper bracket 16 and a lower bracket 17 are formed on the rear edge of the upper half of the body frame 15. An upper rail 22 of a seat rail 21 is connected to the upper bracket 16, and a lower rail 23 of the seat rail 21 is connected to the lower bracket 17. The upper rail 22 extends rearward across the side of the upper half of the air cleaner case 51, and the lower rail 23 extends diagonally rearward across the side of the lower half of the air cleaner case 51. The front sides of the upper rail 22 and the lower rail 23 are connected via a bridge 24, and the rear sides of the upper rail 22 and the lower rail 23 are connected at the rear of the vehicle.

[0019] The front part of the air cleaner case 51 protrudes upward from the upper rail 22, and the protruding part at the front is contained in the space inside the rider's seat 32 (see FIG. 1). The rear part of the air cleaner case 51 protrudes downward from the lower rail 23, and the protruding part at the rear serves as an extension part 65 that expands the intake chamber inside the air cleaner case 51. The extension part 65 of the air cleaner case 51 is positioned above the swing arm 25 (see FIG. 1), and the extension part 65 extends rearward so as to avoid the swing range of the swing arm 25. In this way, the volume of the air cleaner case 51 is expanded by utilizing the space below the seat rail 21.

[0020] 4 and 5, an air cleaner case 51 of the air cleaner 50 has an upper case 52 and a lower case 53 which are divided vertically, and a filter cover 54 attached to the rear surface of the upper case 52. The upper case 52 and the lower case 53 spread out diagonally downward from the front to the rear, and the filter cover 54 bulges out in a dome shape at the rear side of the upper case 52. The internal spaces of the upper case 52 and the lower case 53 and the internal space of the filter cover 54 are connected through an opening 55 formed in the rear surface of the upper case 52, forming an intake chamber 56 inside the air cleaner 50.

[0021] An air filter 57 is disposed in an opening 55 on the rear surface of the upper case 52, and the air filter 57 is covered from the rear by the filter cover 54. The air filter 57 is tilted along the upper surface of the upper case 52 so that the upper part of the air filter 57 is closer to the front of the vehicle than the lower part. The air filter 57 purifies the air, dividing the intake chamber 56 into a dirty side 58 and a clean side 59. In other words, the dirty side 58 is formed by the filter cover 54 upstream of the air filter 57, and the clean side 59 is formed by the upper case 52 and the lower case 53 downstream of the air filter 57.

[0022] A pair of inlet tubes 62 are attached to the left and right side surfaces 61 of the filter cover 54. The pair of inlet tubes 62 extend from the left and right side surfaces 61 of the filter cover 54 toward the rear of the vehicle, and air is taken in from the rear of the vehicle to the dirty side 58 by the pair of inlet tubes 62. A pair of outlet tubes 64 are attached to the front surface 63 of the lower case 53. The pair of outlet tubes 64 extend forward and backward, penetrating the front surface 63 of the lower case 53, and the pair of outlet tubes 64 send air from the clean side 59 to the engine 40 (see FIG. 1 ).

[0023] The inlet tube 62 and the outlet tube 64 are attached to the upper side of the air cleaner case 51. As described above, the inlet tube 62 is attached to the filter cover 54, and the outlet tube 64 is attached to the front surface 63 of the lower case 53, so that the filter cover 54 and the front surface 63 of the lower case 53 face each other in the front-rear direction via the air filter 57 in a side view. Since the downstream end of the inlet tube 62 and the upstream end of the outlet tube 64 are located at approximately the same height, air easily flows directly from the inlet tube 62 to the outlet tube 64.

[0024] The upper case 52 and the lower case 53 protrude downward beyond the filter cover 54, and an extension portion 65 is formed on the lower side of the air cleaner case 51. The extension portion 65 also extends further rearward than the inlet tube 62. The extension portion 65 extends the clean side 59 downward and rearward beyond the dirty side 58, ensuring a sufficient volume of the clean side 59 so that there is no shortage of air when the throttle is suddenly opened. The extension portion 65 also has a volume that suppresses noise caused by intake pulsation. Since the extension portion 65 is positioned below the inlet tube 62, the extension portion 65 acts as a wall to prevent the inlet tube 62 from suctioning sand and dust.

[0025] The upstream end (rear end) of the outlet tube 64 is positioned at approximately the same height as the upper part of the air filter 57. In addition, the upstream end of the outlet tube 64 faces the extension portion 65. This makes it easier for air to enter the outlet tube 64 from the dirty side via the air filter 57, and also makes it easier for air to enter the outlet tube 64 from the extension portion 65 of the clean side 59.

[0026] A breather nipple 67 is formed in the front of the upper case 52, and a breather hose (not shown) extending from the engine 40 is connected to the breather nipple 67. A secondary air nipple 69 is formed in the front of the lower case 53, and a secondary air hose (not shown) extending to the exhaust system is connected to the secondary air nipple 69. A drain plug 71 is provided in the bottom of the lower case 53, and water inside the air cleaner case 51 is drained from the drain plug 71.

[0027] 6 and 7, the air filter 57 is entirely covered from above by the filter cover 54. As described above, the pair of inlet tubes 62 are attached to the filter cover 54, and the pair of inlet tubes 62 are located outboard of the upper case 52 in the left-right direction in a top view. The upstream sides (rear sides) of the pair of inlet tubes 62 extend toward the rear of the vehicle along the seat rails 21 (see FIG. 3), and the downstream sides (front sides) of the pair of inlet tubes 62 are directed toward the center of the air filter 57. Air easily flows from the pair of inlet tubes 62 toward the center of the air filter 57.

[0028] As shown in Figures 7 and 8, a pair of outlet tubes 64 are attached to the front surface of the lower case 53, spaced apart from each other on the left and right sides. The upstream sides (rear sides) of the pair of outlet tubes 64 extend toward the air filter 57, and the downstream sides (front sides) of the pair of outlet tubes 64 are connected to the throttle body 48 (see Figure 3). The pair of outlet tubes 64 have different lengths, with the left outlet tube 64 being longer than the right outlet tube 64. The difference in length between the pair of outlet tubes 64 adjusts the output characteristics of the engine 40.

[0029] The upstream sides of the pair of outlet tubes 64 face the center of the air filter 57, so that air easily flows from the pair of inlet tubes 62 through the center of the air filter 57 to the pair of outlet tubes 64. The pair of outlet tubes 64 are formed with umbrella portions 72 that widen toward the upstream ends, and the umbrella portions 72 make it easier for air to flow into the outlet tubes 64. The pair of outlet tubes 64 are of different lengths, and the umbrella portions 72 of the pair of outlet tubes 64 are offset forward and backward, so that the pair of umbrella portions 72 do not interfere with each other in the center of the air filter 57.

[0030] The positional relationship between the air cleaner and the body frame and the air flow in the air cleaner will be described with reference to Fig. 9. Fig. 9 is a diagram showing the air flow in the air cleaner of this embodiment.

[0031] As shown in Fig. 9, the rear side of the air cleaner case 51 is supported by the seat rails 21, and the front side of the air cleaner case 51 is supported by the throttle body 48 (see Fig. 2) via a pair of outlet tubes 64. The pair of outlet tubes 64 are positioned between the pair of body frames 15, and the pair of inlet tubes 62 are positioned between the pair of seat rails 21. The front part of the air cleaner case 51 protrudes obliquely upward and forward from the upper rails 22 of each seat rail 21, and an extension part 65 at the bottom of the air cleaner case 51 protrudes obliquely downward and rear from the lower rails 23 of each seat rail 21.

[0032] As described above, the air filter 57 is inclined so that the upper part is closer to the front of the vehicle than the lower part in a side view. The upper part of the air filter 57 is located above the upper rail 22, and the air filter 57 is located above the lower rail 23. The downstream end (front end) of the inlet tube 62 faces the center of the front surface of the air filter 57, and the upstream end (rear end) of the outlet tube 64 faces the upper part of the back surface of the air filter 57. Since the center of the front surface and the upper part of the back surface of the inclined air filter 57 are at approximately the same height, the downstream end of the inlet tube 62 and the upstream end of the outlet tube 64 face each other with the air filter 57 in between.

[0033] An extension portion 65 that extends the clean side 59 is located below the air filter 57. The extension portion 65 extends further rearward than the air filter 57 below the lower rail 23, and extends the clean side 59 downward and rearward than the dirty side 58. Since the extension portion 65 extends the clean side 59 downward and rearward, a sufficient volume of the clean side 59 is ensured even in a model equipped with a two-cylinder engine and having a narrow vehicle width. Since the extension portion 65 is located below the air filter 57, the flow of air from the inlet tube 62 to the outlet tube 64 is not obstructed by the extension portion 65.

[0034] When the engine 40 is rotating at low to high speeds, air is taken in from the inlet tube 62 into the dirty side 58, and as shown by arrow A1, the air flows from the center of the front surface of the air filter 57 toward the upper part of the back surface toward the front of the vehicle. Air flows from the upper part of the back surface of the air filter 57 into the outlet tube 64 of the clean side 59, and is sent out through the outlet tube 64 to the engine 40. In this way, air mainly flows forward above the air cleaner 50, and it becomes easier for air to flow from the inlet tube 62 to the outlet tube 64 across the air filter 57, improving engine output.

[0035] When the throttle is suddenly opened, air flows from the inlet tube 62 into the dirty side 58 as indicated by arrow A1, and also flows from the extension portion 65 into the outlet tube 64 as indicated by arrow A2. Because the upstream end (rear end) of the outlet tube 64 faces diagonally downward and rearward, air easily flows from the extension portion 65 toward the outlet tube 64. In this way, in addition to the direct air flow from the inlet tube 62 to the outlet tube 64, air is sucked from the air reservoir inside the extension portion 65 into the outlet tube 64, enhancing the intake pulsation effect and improving engine output.

[0036] As described above, according to this embodiment, since the inlet tube 62 and the outlet tube 64 are attached to the upper side of the air cleaner case 51, air easily flows directly from the inlet tube 62 to the outlet tube 64. Therefore, air flows smoothly toward the engine 40 from low rotation to high rotation of the engine 40, improving engine output. Since the air cleaner case 51 has the extension portion 65 formed by extending the clean side 59 diagonally downward and rearward from the dirty side 58, the clean side 59 has a sufficient volume even in the narrow space inside the body frame 10. Therefore, even when the throttle is suddenly opened, the air inside the extension portion 65 is utilized to improve engine output.

[0037] In this embodiment, the extension portion extends the clean side diagonally downward and rearward further than the dirty side, but it is sufficient that the extension portion extends at least the clean side downward further than the dirty side.

[0038] In addition, in this embodiment, a two-cylinder engine is exemplified as the engine, but the type of engine is not particularly limited.

[0039] In this embodiment, the downstream end of the inlet tube and the upstream end of the outlet tube are positioned at approximately the same height, but it is sufficient that the inlet tube and the outlet tube are attached at least to the upper side of the air cleaner case. As long as a direct air flow is created from the inlet tube to the outlet tube, the inlet tube and the outlet tube may be misaligned in the vertical direction.

[0040] In addition, in this embodiment, the upstream end of the outlet tube faces the expanded portion, but the orientation of the upstream end of the outlet tube is not particularly limited as long as air can enter the outlet tube from the expanded portion.

[0041] In addition, although the air filter is arranged at an angle in this embodiment, the air filter does not have to be arranged at an angle. For example, the air filter may be arranged vertically.

[0042] In addition, in this embodiment, the pair of outlet tubes are formed to have different lengths, but the pair of outlet tubes may be formed to have the same length.

[0043] Furthermore, the air cleaner is not limited to the illustrated saddle-ride type vehicle, and may be used in other types of saddle-ride type vehicles. A saddle-ride type vehicle is not limited to all vehicles on which a rider sits astride a seat, but also includes small scooter-type vehicles on which a rider does not sit astride a seat.

[0044] As described above, the air cleaner (50) of this embodiment is an air cleaner disposed inside the vehicle body frame (10) behind the engine (40), and includes an air cleaner case (51) in which an intake chamber (56) is formed, an air filter (57) that divides the intake chamber into a dirty side (58) and a clean side (59), an inlet tube (62) that takes in air from the rear of the vehicle to the dirty side, and an outlet tube (64) that sends air from the clean side to the engine, and the inlet tube and outlet tube are attached to the upper side of the air cleaner case, and an extension part (65) that extends the clean side downward more than the dirty side is formed on the lower side of the air cleaner case. According to this configuration, since the inlet tube and outlet tube are attached to the upper side of the air cleaner case, air easily flows directly from the inlet tube to the outlet tube. Therefore, air flows smoothly toward the engine from low to high revolutions of the engine, improving engine output. The air cleaner case has an extension section that extends the clean side below the dirty side, ensuring sufficient volume for the clean side even in the narrow space inside the body frame. Therefore, even when the throttle is suddenly opened, the air inside the extension section is utilized to improve engine output.

[0045] In the air cleaner of this embodiment, the downstream end of the inlet tube and the upstream end of the outlet tube are located at approximately the same height. With this configuration, air can more easily flow from the inlet tube to the outlet tube.

[0046] In the air cleaner of this embodiment, the upstream end of the outlet tube faces the expanded portion. With this configuration, air can easily enter the outlet tube from the expanded portion when the throttle is suddenly opened, improving engine output.

[0047] In the air cleaner of this embodiment, the upper part of the air filter is tilted forward more than the lower part in a side view, the downstream end of the inlet tube faces the center of the front surface of the air filter in a side view, and the upstream end of the outlet tube faces the upper part of the back surface of the air filter in a side view. With this configuration, air easily flows from the inlet tube to the outlet tube across the air filter, improving engine output.

[0048] In the air cleaner of this embodiment, the engine is a two-cylinder engine, and the pair of outlet tubes are different in length, and the pair of outlet tubes are formed with umbrella portions (72) that widen toward their upstream ends, and the upstream ends of the pair of outlet tubes are directed toward the center of the air filter. With this configuration, since the two outlet tubes are different in length, even if the two outlet tubes are formed with umbrella portions, the umbrella portions of the two outlet tubes do not interfere with each other at the center of the air filter. In addition, the output characteristics of the engine can be adjusted by changing the lengths of the two outlet tubes.

[0049] In the air cleaner of this embodiment, the inlet tube extends from the air cleaner case toward the rear of the vehicle, and the extension portion extends toward the rear of the vehicle below the inlet tube. With this configuration, the extension portion extends the clean side of the air cleaner case downward and rearward from the dirty side, ensuring sufficient volume for the clean side. In addition, because the extension portion is positioned below the inlet tube, the extension portion acts as a wall to prevent the inlet tube from suctioning sand and dust.

[0050] In the air cleaner of this embodiment, the vehicle body frame has a seat rail that supports the seat from below, the air filter is located above the lower end of the seat rail, and the extension part extends below the seat rail and toward the rear of the vehicle beyond the air filter. With this configuration, even in the narrow space inside the seat rail, the extension part ensures a sufficient volume for the clean side of the air cleaner case. In addition, the direct flow of air from the inlet tube to the outlet tube is not obstructed.

[0051] Although the present embodiment has been described, other embodiments may be made by combining the above-described embodiments and modifications in whole or in part.

[0052] In addition, the technology of the present invention is not limited to the above examples, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to the progress of technology or a different technology derived therefrom, the invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea. [Explanation of symbols]

[0053] 10: Body frame 21: Seat rail 40: Engine 50: Air cleaner 51: Air cleaner case 56: Intake chamber 57: Air filter 58: Dirty Side 59: Clean Side 62: Inlet tube 64: Outlet tube 65: Extension 72: Umbrella part

Claims

1. An air cleaner disposed inside the vehicle frame behind the engine, an air cleaner case in which an intake chamber is formed; an air filter that divides the intake chamber into a dirty side and a clean side; an inlet tube that takes in air from the rear of the vehicle to the dirty side; an outlet tube for delivering air from the clean side to the engine; An air cleaner characterized in that the inlet tube and the outlet tube are attached to the upper side of the air cleaner case, and an extension portion is formed on the lower side of the air cleaner case by extending the clean side downward more than the dirty side.

2. 2. The air cleaner according to claim 1, wherein the downstream end of said inlet tube and the upstream end of said outlet tube are positioned at substantially the same height.

3. 3. The air cleaner according to claim 1, wherein an upstream end of the outlet tube is directed toward the expansion portion.

4. The air filter is inclined so that an upper portion of the air filter is forward of a lower portion in a side view, A downstream end of the inlet tube faces a center of a surface of the air filter in a side view, 4. The air cleaner according to claim 1, wherein an upstream end of the outlet tube faces an upper portion of a rear surface of the air filter in a side view.

5. The engine is a two-cylinder engine, and the outlet tube is a pair of outlet tubes having different lengths, The pair of outlet tubes are formed with umbrella portions that expand toward the upstream ends, 5. The air cleaner according to claim 1, wherein upstream ends of the pair of outlet tubes are directed toward a center of the air filter.

6. The inlet tube extends from the air cleaner case toward the rear of the vehicle, 6. The air cleaner according to claim 1, wherein the extension portion extends rearward of the vehicle below the inlet tube.

7. the vehicle body frame has a seat rail that supports a seat from below, 7. The air cleaner according to claim 1, wherein the air filter is located above a lower end of the seat rail, and the extension portion extends below the seat rail and toward the rear of the vehicle beyond the air filter.

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