Saddle-riding type vehicle

Abstract

To provide a saddle-riding type vehicle which can make a structure of a peripheral portion of an intake path simple and compact and enables reduction of intake noise.SOLUTION: A motor cycle 1 100 includes an engine 30, an air cleaner 10, and an intake pipe 50. The intake pipe 50 forms a part of an intake path which guides air purified by the air cleaner 10 to the engine 30. Further, the intake pipe 50 has: an upstream part disposed at a clean side of an internal space of the air cleaner 10; a downstream part disposed outside the air cleaner 10; and an attached part located between the upstream part and the downstream part in the intake pipe 50 and attached to an outer wall of the air cleaner 10. The upstream part of the intake pipe 50 includes: a funnel part which is open in the internal space of the air cleaner 10; and a pipe part which connects the funnel part with the attached part. One or multiple through holes 59 are formed in a portion, which is located closer to the attached part than the funnel part, of the pipe part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a saddle-type vehicle having an engine and an air cleaner. [Background technology]

[0002] When a saddle-type vehicle equipped with an engine is traveling, intake noise is generated by air being drawn into the engine. The volume of the intake noise is determined by the air path that draws air from outside the vehicle to the engine and the operating state of the engine.

[0003] It is preferable that the extremely loud intake noise is reduced as much as possible. Various configurations have been proposed to reduce the intake noise. For example, the motorcycle described in Patent Document 1 has a resonator for reducing the intake noise. Specifically, the motorcycle described in Patent Document 1 has an engine and an air cleaner. The motorcycle also has a duct part at the front of the vehicle that guides air flowing from the front of the vehicle to the air cleaner. The resonator is attached to the duct part. The internal space of the duct part and the internal space of the resonator are connected by a connecting pipe. The intake noise is reduced by resonating the sound generated when air flows from the duct part into the resonator and the sound of air flowing from the duct part into the air cleaner. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-127076 A Summary of the Invention [Problem to be solved by the invention]

[0005] Due to the above mechanism, the resonator needs to have an internal space of a predetermined volume according to the intake noise to be reduced. Therefore, the resonator has a certain size. Therefore, the resonator described in Patent Document 1 is molded so as to have an internal space of a predetermined volume and to have a shape according to the positional relationship with other members (headlights, etc.) provided around the duct part. However, the configuration of the resonator manufactured in this way is likely to be complicated. On the other hand, when the resonator has a predetermined shape, the configuration of the peripheral part of the intake path is likely to be large in order to suppress interference between the resonator and the intake path of the engine and its peripheral members.

[0006] An object of the present invention is to provide a saddle-type vehicle capable of simplifying and compactly configuring the peripheral portion of the intake path and reducing intake noise. [Means for solving the problem]

[0007] A saddle-type vehicle according to one aspect of the present invention comprises an engine, an air cleaner that purifies air to be supplied to the engine, and an intake pipe that forms part of an intake path that guides the air purified by the air cleaner to the engine, the intake pipe having an upstream portion positioned on the clean side of the internal space of the air cleaner, a downstream portion positioned outside the air cleaner, and a mounting portion located between the upstream and downstream portions of the intake pipe and attached to an outer wall of the air cleaner, the upstream portion including a funnel portion that opens into the internal space of the air cleaner and a pipe portion that connects the funnel portion and the mounting portion, and one or more through holes are formed in a portion of the pipe portion that is closer to the mounting portion than the funnel portion. Effect of the Invention

[0008] According to the present invention, it is possible to simplify and compact the configuration of the peripheral portion of the intake path and reduce intake noise. [Brief description of the drawings]

[0009] [Figure 1] 1 is a side view of one side of a motorcycle according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged plan view of a front half of the motorcycle of FIG. [Diagram 3] 3 is a cross-sectional view of the motorcycle shown in FIG. 2 taken along line AA. [Figure 4] 3 is a view of the air cleaner in FIG. 2 as seen from the rear of the vehicle. [Diagram 5] 3 is a schematic side view of the left intake pipe of FIG. 2 as viewed from the left of the motorcycle. [Figure 6] 3 is a schematic side view of the right intake pipe of FIG. 2 as viewed from the right of the motorcycle. [Figure 7] 1 is a graph showing test results of an intake sound level measurement experiment. [Figure 8] FIG. 1 is a schematic diagram showing a list of first to ninth intake pipe configurations related to an intake pipe characteristic evaluation experiment. [Figure 9] FIG. 1 is a schematic diagram showing a list of first to ninth intake pipe configurations related to an intake pipe characteristic evaluation experiment. [Figure 10] 11 is a graph showing frequency response functions of sounds output from each of the first to ninth intake pipes in an intake pipe characteristic evaluation experiment. [Figure 11] 13 is a graph showing the relationship between the peak frequency of the first to ninth intake pipes in an intake pipe characteristic evaluation experiment and the total opening area of ​​one or more through holes in the first to ninth intake pipes. [Figure 12] 4 is a graph showing the relationship between crankshaft output and engine rotation speed measured in an engine intake performance confirmation experiment. [Figure 13] 4 is a graph showing the relationship between the torque of the crankshaft and the engine rotation speed measured in an engine intake performance confirmation experiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A saddle-ride type vehicle according to an embodiment of the present invention will now be described with reference to the drawings.

[0011] 1. Overall structure of motorcycle FIG. 1 is a side view of one side of a motorcycle according to an embodiment of the present invention. FIG. 1 shows a motorcycle 100 standing vertically to a road surface. In each of the figures following FIG. 1, the front-rear direction FB, the left-right direction LR, and the up-down direction UD of the motorcycle 100 are appropriately indicated by arrows. In the front-rear direction FB, the direction in which the arrow points is called the front, and the opposite direction is called the rear. In the left-right direction LR, the direction in which the arrow points is called the left, and the opposite direction is called the right. In the up-down direction UD, the direction in which the arrow points is called the up, and the opposite direction is called the down. In each of the figures following FIG. 1, the symbols F, B, L, R, U, and D shown together with directional arrows represent the front, rear, left, right, up, and down, respectively.

[0012] The motorcycle 100 in FIG. 1 includes a metal main frame 1 and a rear frame 5. The front end of the main frame 1 constitutes a head pipe 1H. The main frame 1 is formed so as to extend obliquely downward from the head pipe 1H while branching off to the left and right. In the following description, where necessary, the portion of the main frame 1 that extends to the left from the head pipe 1H will be referred to as the left frame 1A, and the portion that extends to the right from the head pipe 1H will be referred to as the right frame 1B (FIG. 2). The rear frame 5 is attached to the main frame 1 so as to extend rearward and slightly upward from the rear end of the main frame 1.

[0013] A front fork 2 is provided on the head pipe 1H so as to be rotatable about the central axis of the head pipe 1H. A front wheel 3 is rotatably supported on the lower end of the front fork 2. A handlebar 4 is provided on the upper end of the front fork 2.

[0014] The main frame 1 supports the engine 30 at a position below the head pipe 1H. The engine 30 according to this embodiment is a parallel twin-cylinder engine and has two combustion chambers 31A, 31B (FIG. 4) aligned in the left-right direction LR. An air cleaner 10 and a fuel tank 20 are provided so as to be located above the engine 30 and behind the head pipe 1H. The air cleaner 10 and the fuel tank 20 are aligned in this order from front to rear with a gap between them. The air cleaner 10 is supported by the main frame 1, and the fuel tank 20 is supported by the main frame 1 and the rear frame 5. A seat 6 is provided above the fuel tank 20. The seat 6 extends in the front-rear direction FB from a position above the fuel tank 20 to a position above the rear half of the rear frame 5.

[0015] A throttle body 40 and two intake pipes 50 are disposed between the air cleaner 10 and the fuel tank 20 in the front-rear direction FB. The throttle body 40 is attached to a portion of the engine 30 where an intake port is formed.

[0016] The two intake pipes 50 connect the air cleaner 10 and the throttle body 40, and form part of two intake paths VP (FIG. 4) that extend from the air cleaner 10 to the two combustion chambers 31A, 31B (FIG. 4) of the engine 30. The two intake pipes 50 are made of resin or rubber having a certain degree of flexibility, and are arranged side by side in the left-right direction LR. In FIG. 1, only one of the intake pipes 50 (the left intake pipe 50) is shown.

[0017] In a side view of the motorcycle 100, most of the two intake pipes 50 overlap with the main frame 1. A through hole 59 is formed in each intake pipe 50 to reduce intake noise generated when the engine 30 is operating. Details of the through holes 59 will be described later. In the following description, the left of the two intake pipes 50 will be referred to as the left intake pipe 50A, and the right intake pipe will be referred to as the right intake pipe 50B (FIG. 2), as necessary.

[0018] Fig. 2 is an enlarged plan view of the front half of the motorcycle 100 of Fig. 1. In Fig. 2, the outline of the motorcycle 100 of Fig. 1 is indicated by a dashed line. In Fig. 2, components other than the main frame 1, the air cleaner 10, the fuel tank 20, the throttle body 40, and the two intake pipes 50 are omitted so as to make it easier to understand the positional relationship between the two intake paths VP (Fig. 4) and their peripheral members.

[0019] 2, in a plan view of the motorcycle 100, the air cleaner 10, the two intake pipes 50, and the throttle body 40 are disposed between the left frame 1A and the right frame 1B in the left-right direction LR. In addition, in a plan view of the motorcycle 100, the fuel tank 20 is disposed behind the air cleaner 10 such that both left and right sides overlap the rear part of the left frame 1A and the rear part of the right frame 1B.

[0020] With this configuration, the two intake pipes 50 connect the air cleaner 10 and the throttle body 40 through a space surrounded by the air cleaner 10, the fuel tank 20, the left frame 1A, and the right frame 1B. In other words, the two intake pipes 50 are provided to pass through a space restricted by a predetermined layout of the air cleaner 10, the fuel tank 20, the left frame 1A, and the right frame 1B.

[0021] 1, a rear arm 7 is provided below the rear frame 5 so as to extend rearward from the rear end of the engine 30. A rear wheel 8 is rotatably supported at the rear end of the rear arm 7. The rear wheel 8 serves as a drive wheel and is rotated by power generated by the engine 30.

[0022] 2. Details of the intake path and surrounding components Fig. 3 is a cross-sectional view of the motorcycle 100 in Fig. 2 taken along line AA, and Fig. 4 is a view of the air cleaner 10 in Fig. 2 as seen from the rear of the vehicle. The main frame 1 is omitted in Fig. 3. Meanwhile, Fig. 4 shows the air cleaner 10 as well as two intake pipes 50 (50A, 50B) connected to the air cleaner 10. Furthermore, Fig. 4 shows the engine 30 in a block diagram, and also shows, by dashed dotted lines, a portion of the intake path VP extending from the left intake pipe 50A to the combustion chamber 31A, and a portion of the intake path VP extending from the right intake pipe 50B to the combustion chamber 31B.

[0023] 3, the air cleaner 10 includes an air cleaner case 11 and a filter element 12. The air cleaner case 11 has an internal space and houses the filter element 12 in the internal space. The filter element 12 divides the internal space of the air cleaner case 11 into two spaces: a dirty side space DS and a clean side space CS.

[0024] Two air introduction parts 13 (FIG. 4) that guide air outside the air cleaner 10 to the dirty side space DS are formed in the upper part of the air cleaner case 11. In addition, two air outlet parts 14 (FIG. 4) that connect the clean side space CS to the space outside the air cleaner 10 are formed in the rear part of the air cleaner case 11. The two air outlet parts 14 are circular openings formed in part of the air cleaner case 11 (the outer wall of the air cleaner 10).

[0025] As shown in Fig. 4, the two air outlet portions 14 are arranged side by side in the left-right direction LR with a gap between them. A portion of the left intake pipe 50A is inserted into and fixed to the left air outlet portion 14. A portion of the right intake pipe 50B is inserted into and fixed to the right air outlet portion 14. The other portions of the left intake pipe 50A and the right intake pipe 50B extend obliquely downward outside the air cleaner 10 while curving.

[0026] As shown in Fig. 3, engine 30 according to this embodiment has a cylinder head SH. The cylinder head SH is located at the front end of engine 30 when engine 30 is supported by main frame 1. Two intake ports 32 are formed in cylinder head SH so as to open upward. The two intake ports 32 correspond to two combustion chambers 31A, 31B (Fig. 4), respectively, and are aligned in the left-right direction LR.

[0027] The throttle body 40 is attached to a portion of the cylinder head SH where the two intake ports 32 are formed. The throttle body 40 includes two flow passage forming pipes 41 respectively corresponding to the two intake ports 32 of the engine 30. The two flow passage forming pipes 41 are aligned in the left-right direction LR, similar to the two intake ports 32.

[0028] The throttle body 40 also includes two throttle valves 42, two injectors 43, and two valve actuators 44, which are respectively attached to the two flow passage forming pipes 41. In the throttle body 40, the valve actuator 44 operates in response to the operation of an accelerator grip (not shown), thereby adjusting the opening of the throttle valve 42. Also, the state of fuel injection by the injector 43 is adjusted under the control of an ECU (Engine control Unit) (not shown).

[0029] As described above, the two intake pipes 50 connect the air cleaner 10 and the throttle body 40. As a result, in this embodiment, as shown by the light dot pattern in Fig. 3, a right intake path VP is formed by the right intake pipe 50B, the right flow passage forming pipe 41 of the throttle body 40, and the internal space of the right intake port 32 of the engine 30. Also, a left intake path VP is formed by the left intake pipe 50A, the left flow passage forming pipe 41 of the throttle body 40, and the internal space of the left intake port 32 of the engine 30.

[0030] When the engine 30 is operating, air outside the motorcycle 100 is introduced into the dirty side space DS of the air cleaner 10. The introduced air flows into the clean side space CS while being purified by the filter element 12. In the clean side space CS, the purified air flows into the two intake pipes 50 through a funnel portion 511 and a through hole 59 (described later) and is supplied to the combustion chambers 31A, 31B of the engine 30.

[0031] The length of each intake path VP (the length in the axial direction of each intake path VP), together with the size of the cross-sectional area (flow path cross-sectional area) of the opening perpendicular to the axial direction of the intake path VP, is highly related to the performance of supplying air to the engine 30 (hereinafter referred to as engine intake performance). When the engine intake performance is high, the output of the engine 30 is high, and when the engine intake performance is low, the output of the engine 30 is low. Therefore, the output of the engine 30 when the rotation speed of the engine 30 is within a predetermined rotation speed range depends on the length of each intake path VP. Therefore, in this embodiment, the length of each intake path VP is set so that the output of the engine 30 in the predetermined rotation speed range is maintained at a relatively high level.

[0032] On the other hand, the length of each intake path VP is highly related to the natural frequency of the intake path VP. Therefore, when the natural frequency of the intake path VP corresponding to the length set in consideration of the output of the engine 30 overlaps with the frequency band of a specific intake sound generated from the intake path VP, the level (sound pressure level) of the intake sound becomes significantly high. Therefore, in the motorcycle 100 according to this embodiment, a through hole 59 is formed in the intake pipe 50 in order to shift the natural frequency of each intake path VP from the frequency band of the specific intake sound.

[0033] The left intake pipe 50A will be described in detail. Fig. 5 is a schematic side view of the left intake pipe 50A in Fig. 2 as viewed from the left side of the motorcycle 100. In Fig. 5, the pattern and irregularities formed on the outer surface of the left intake pipe 50A are omitted. In Fig. 5, a part of the air cleaner case 11 (the outer wall of the air cleaner 10) is indicated by a dashed line.

[0034] 5, the left intake pipe 50A is a cylindrical member curved from one end to the other end, and is composed of an upstream portion 51, a downstream portion 52, and a mounting portion 53. The upstream portion 51 is a portion that is disposed in the clean side space CS of the air cleaner 10 when the left intake pipe 50A is connected to the air cleaner 10. The downstream portion 52 is a portion that is disposed in the external space ES of the air cleaner 10 when the left intake pipe 50A is connected to the air cleaner 10. In the axial direction of the left intake pipe 50A according to this embodiment, the length of the upstream portion 51 of the left intake pipe 50A is greater than ⅓ and less than ½ of the entire length of the left intake pipe 50A.

[0035] The mounting portion 53 is located between the upstream portion 51 and the downstream portion 52, and has a first annular protrusion 53a and a second annular protrusion 53b. Each of the first annular protrusion 53a and the second annular protrusion 53b is formed in an annular shape so as to surround the outer circumferential surface of the left intake pipe 50A. The first annular protrusion 53a and the second annular protrusion 53b are arranged so as to be aligned at a small interval in the direction of the central axis ca of the left intake pipe 50A (axial direction). The interval between the first annular protrusion 53a and the second annular protrusion 53b is set to match or nearly match the thickness of the air cleaner case 11. In addition, the outer diameter of the portion of the left intake pipe 50A located between the first annular protrusion 53a and the second annular protrusion 53b is set to match or nearly equal the inner diameter of each air outlet portion 14 of the air cleaner case 11.

[0036] As a result, when assembling the motorcycle 100, the upstream portion 51 of the left intake pipe 50A is inserted into the left air outlet portion 14 (opening) of the air cleaner case 11. Also, the forming portion of the left air outlet portion 14 of the air cleaner case 11 (the inner edge of the opening) is fitted between the first annular protrusion 53a and the second annular protrusion 53b of the left intake pipe 50A. As a result, the left intake pipe 50A is attached to the air cleaner case 11. In this state, the downstream portion 52 is further connected to the left flow passage forming pipe 41 of the throttle body 40.

[0037] Here, the upstream section 51 of the left intake pipe 50A includes a funnel section 511 and a pipe section 512. The funnel section 511 is an upstream end of the intake path VP of the left intake pipe 50A that opens into the clean side space CS of the air cleaner 10. The funnel section 511 is formed so that the inner diameter continuously increases from the inside of the left intake pipe 50A toward the clean side space CS. On the other hand, the pipe section 512 is formed so that the inner diameter is constant or approximately constant in the axial direction of the left intake pipe 50A.

[0038] A through hole 59 is formed in a portion of pipe portion 512 that is closer to attached portion 53 than funnel portion 511. In left intake pipe 50A, a through hole 59 is formed in the left side portion of pipe portion 512 so as to open toward the left of motorcycle 100.

[0039] The right intake pipe 50B will be described in detail. Fig. 6 is a schematic side view of the right intake pipe 50B in Fig. 2 as seen from the right side of the motorcycle 100. In Fig. 6, similar to the example in Fig. 5, the pattern and unevenness formed on the outer surface of the right intake pipe 50B are omitted. Also, in Fig. 6, a part of the air cleaner case 11 is indicated by a dashed line.

[0040] The right intake pipe 50B is basically formed symmetrically to the left intake pipe 50A with respect to a vertical plane that passes between the left intake pipe 50A and the right intake pipe 50B and extends in the front-rear direction FB. Therefore, like the left intake pipe 50A, the right intake pipe 50B is a cylindrical member that is curved from one end to the other end, and is composed of an upstream portion 51, a downstream portion 52, and a mounting portion 53. In the axial direction of the right intake pipe 50B, the length of the upstream portion 51 of the right intake pipe 50B is greater than 1 / 3 and less than 1 / 2 of the entire length of the right intake pipe 50B.

[0041] Therefore, when assembling the motorcycle 100, the upstream portion 51 of the right intake pipe 50B is inserted into the right air outlet portion 14 (opening) of the air cleaner case 11. Also, the forming portion of the right air outlet portion 14 of the air cleaner case 11 (the inner edge of the opening) is fitted between the first annular protrusion 53a and the second annular protrusion 53b of the right intake pipe 50B. In this state, the right intake pipe 50B is attached to the air cleaner case 11. In this state, the downstream portion 52 is further connected to the right flow passage forming pipe 41 of the throttle body 40.

[0042] Like the left intake pipe 50A, the upstream section 51 of the right intake pipe 50B also includes a funnel section 511 and a pipe section 512. A through hole 59 is formed in a portion of the pipe section 512 that is closer to the attached section 53 than the funnel section 511. However, unlike the through hole 59 of the left intake pipe 50A, the through hole 59 formed in the right intake pipe 50B is formed to open toward the right of the motorcycle 100 on the right side of the pipe section 512.

[0043] Therefore, in this embodiment, the through hole 59 of the left intake pipe 50A and the through hole 59 of the right intake pipe 50B face in directions that do not face each other in the left-right direction LR, as shown by black dots in Fig. 2. More specifically, the through hole 59 of the left intake pipe 50A and the through hole 59 of the right intake pipe 50B face in opposite directions to each other in the left-right direction LR.

[0044] 3. Intake sound level measurement experiment and intake sound listening experiment <1> Intake sound level measurement experiment For the motorcycle 100 described above, the inventors conducted an experiment (intake sound level measurement experiment) to confirm the level of the intake sound generated when the engine 30 operates in a specific vehicle speed range.

[0045] Specifically, the inventors prepared a motorcycle 100 equipped with two intake pipes 50 as shown in Fig. 5 and Fig. 6 as the motorcycle 100 of the embodiment. The axial length of each intake pipe 50 was approximately 180 mm, and the axial length of the upstream portion 51 was approximately 90 mm. The through hole 59 was formed at a position approximately 80 mm away from the funnel portion 511. Furthermore, the cross-sectional area (flow path cross-sectional area) of the opening perpendicular to the axial direction of the intake pipe 50 was approximately 962 mm 2 The opening area of ​​the through hole 59 is about 79 mm 2 In this embodiment, the flow passage cross-sectional area of ​​the intake pipe 50 is, for example, the area of ​​a region surrounded by the inner circumferential surface of the portion of the intake pipe 50 that has the smallest inner diameter.

[0046] The inventors also prepared a motorcycle as a comparative example, which was equipped with two intake pipes having the same configuration as the two intake pipes 50 of the embodiment, except that no through hole 59 was formed.

[0047] For the motorcycle 100 of the embodiment, the sound pressure level of the intake sound generated from the motorcycle 100 was measured while the vehicle speed reached from a "first speed v1" to a "second speed v2 higher than the first speed v1" with the throttle valve 42 at the maximum opening. Similarly to the motorcycle 100 of the embodiment, for the motorcycle of the comparative example, the sound pressure level of the intake sound generated from the motorcycle was measured while the vehicle speed reached from a "first speed v1" to a "second speed v2" with the throttle valve 42 at the maximum opening.

[0048] Fig. 7 is a graph showing the test results of the intake sound level measurement experiment. In the graph of Fig. 7, the vertical axis represents sound pressure level, and the horizontal axis represents vehicle speed. In addition, in the graph of Fig. 7, the measurement results of the intake sound when the motorcycle 100 of the embodiment is accelerating are shown by a thick solid line, and the measurement results of the intake sound when the motorcycle of the comparative example is accelerating are shown by a dotted line.

[0049] 7, the sound pressure levels of the intake noise generated by the motorcycle 100 of the embodiment and the motorcycle of the comparative example increase while the vehicle speed increases from the "first speed v1" to the "second speed v2." However, the amount of change in sound pressure level accompanying the increase in vehicle speed differs between the motorcycle 100 of the embodiment and the motorcycle of the comparative example.

[0050] In most of the range of vehicle speeds from "first speed v1" to "second speed v2" except for the vicinity of "first speed v1", the sound pressure level of the intake sound generated from motorcycle 100 of the example is lower than the sound pressure level of the intake sound generated from motorcycle 100 of the comparative example. Furthermore, the difference in sound pressure level between the example and the comparative example basically increases with increasing vehicle speed. As a result, the sound pressure level of the intake sound generated from motorcycle 100 of the example is lower by a maximum of about -2 dB(A) than the sound pressure level of the intake sound generated from motorcycle 100 of the comparative example.

[0051] As a result, it was confirmed that the motorcycle 100 of the embodiment can reduce the intake noise generated when the vehicle speed is in a relatively wide range from a speed slightly higher than the "first speed v1" (a speed about 5 km / h higher than the first speed v1) to the "second speed v2" compared to the motorcycle of the comparative example having an intake pipe without the through hole 59. This is considered to be due to the fact that the natural frequency of each intake path VP in the motorcycle 100 of the embodiment is significantly shifted from the frequency of a specific intake sound by the through holes 59 formed in the two intake pipes 50.

[0052] <2> Intake sound listening experiment The inventors conducted an experiment (intake sound audibility experiment) to confirm how a person feels when hearing the intake sound generated when the engine 30 operates in a specific vehicle speed range for the motorcycle 100 of the above embodiment and the motorcycle of the comparative example.

[0053] Specifically, the inventors ran the motorcycle 100 of the embodiment at a vehicle speed of about 40 km / h while maintaining the throttle valve 42 at half the maximum opening. The inventors also ran the motorcycle of the comparative example at a vehicle speed of about 40 km / h while maintaining the throttle valve 42 at half the maximum opening. Then, it was determined whether the intake sound generated from the motorcycle 100 of the embodiment and the intake sound generated from the motorcycle of the comparative example differed in how they were heard. As a result, it was determined that the intake sound generated from the motorcycle 100 of the embodiment was heard lower than the intake sound generated from the motorcycle of the comparative example.

[0054] Furthermore, the inventors ran the motorcycle 100 of the embodiment at a vehicle speed of about 80 km / h while maintaining the throttle valve 42 at the maximum opening. The inventors also ran the motorcycle of the comparative example at a vehicle speed of about 80 km / h while maintaining the throttle valve 42 at the maximum opening. Then, it was determined whether the intake sound generated from the motorcycle 100 of the embodiment and the intake sound generated from the motorcycle of the comparative example differed in how they were heard. As a result, it was determined that the intake sound generated from the motorcycle 100 of the embodiment was heard lower than the intake sound generated from the motorcycle of the comparative example.

[0055] It was thus confirmed that the motorcycle 100 of the embodiment reduces the level of intake sound audible to humans compared to the motorcycle of the comparative example, regardless of the opening degree of the throttle valve 42 and the vehicle speed. In other words, it was confirmed that the motorcycle 100 of the embodiment can reduce noise caused by intake sound compared to the motorcycle of the comparative example.

[0056] 4. Effects of the embodiment (a) In motorcycle 100 according to this embodiment, upstream portions 51 of two intake pipes 50 are inserted into two air outlet portions 14 of air cleaner case 11. Also, mounting portions 53 of each intake pipe 50 are mounted to the corresponding air outlet portions 14 of air cleaner case 11. Upstream portions 51 of intake pipes 50 are located in clean side space CS of air cleaner 10. On the other hand, downstream portions 52 are located in external space ES of air cleaner 10.

[0057] A through hole 59 is formed in the upstream portion 51 of the intake pipe 50. The through hole 59 is located in the clean side space CS of the internal space of the air cleaner 10. Therefore, unpurified air and droplets of rainwater, etc. do not flow into the intake pipe 50 through the through hole 59.

[0058] The natural frequency of each intake path VP from the air cleaner 10 to the combustion chambers 31A, 31B of the engine 30 is determined depending on the length of the intake path VP and the flow path cross-sectional area of ​​the intake path VP. Furthermore, the natural frequency of each intake path VP is determined depending on the position of the through hole 59 formed in the intake pipe 50 and the opening area of ​​the through hole 59. In the relationship between the natural frequency of the intake path VP and the position of the through hole 59, the natural frequency of the intake path VP changes more significantly as the position of the through hole 59 is farther away from the funnel portion 511 and closer to the air cleaner case 11 (the outer wall of the air cleaner 10). Therefore, according to the above configuration, the natural frequency of the intake path VP can be changed significantly. Therefore, by shifting the natural frequency of the intake path VP from the frequency band of a specific intake sound, it is possible to reduce the specific intake sound.

[0059] Furthermore, with the above configuration, in order to reduce intake noise, there is no need to provide an additional configuration such as a resonator around the air cleaner 10 and the two intake pipes 50. Therefore, the configuration of the surrounding areas of the air cleaner 10 and the two intake pipes 50 can be made simple and compact.

[0060] As a result, the configuration of the surrounding area of ​​the intake path VP can be made simple and compact, and intake noise can be reduced.

[0061] (b) As described above, in motorcycle 100, there is no need to provide two intake pipes 50 with additional components for reducing intake noise, such as resonators. Therefore, in throttle body 40, a valve actuator can be provided near flow passage forming pipe 41 without considering interference with additional components for reducing intake noise. This allows the air cleaner 10, two intake pipes 50, throttle body 40, and their peripheral members to be compact in configuration. In addition, the freedom of layout of air cleaner 10, two intake pipes 50, throttle body 40, and their peripheral members is improved.

[0062] (c) As described above, the natural frequency of each intake path VP is determined depending on the position of the through hole 59 formed in each intake pipe 50 and the opening area of ​​the through hole 59. In the above example, one intake pipe 50 has one through hole 59. When there is one through hole 59, the opening area of ​​the through hole 59 can be easily calculated. Therefore, the design of one through hole 59 to be formed in the intake pipe 50 becomes easy. Furthermore, when there is one through hole 59 formed in the intake pipe 50, the decrease in strength of the intake pipe 50 is suppressed compared to when a large number of through holes 59 are formed in the intake pipe 50. Furthermore, the increase in the number of steps required to form the through hole 59 during the manufacture of the intake pipe 50 is suppressed.

[0063] (d) The length of the upstream portion 51 in the axial direction of each intake pipe 50 is greater than 1 / 3 of the entire length of the intake pipe 50. In this case, since the upstream portion 51 is disposed in the internal space of the air cleaner 10, the space occupied by the intake pipe 50 around the air cleaner 10 can be significantly reduced compared to the case where the entire intake pipe 50 is provided in the external space ES of the air cleaner 10. In addition, since the length of the upstream portion 51 is greater than 1 / 3 of the entire length of the intake pipe 50, the through hole 59 can be formed at a position farther away from the funnel portion 511. That is, the through hole 59 can be formed at a position where the natural frequency of the intake path VP can be shifted more significantly. As a result, it becomes easy to form the through hole 59 at a position suitable for reducing intake noise while setting the length of the intake pipe 50 to a length that takes into account the intake performance of the engine.

[0064] (e) The length of the upstream portion 51 of each intake pipe 50 in the axial direction is shorter than half the entire length of the intake pipe 50. In this case, in order to arrange a part of the intake pipe 50 (the upstream portion 51) in the internal space of the air cleaner 10, it is not necessary to make the air cleaner 10 excessively large.

[0065] (f) When the two intake pipes 50 are attached to the air cleaner 10, the through hole 59 of the left intake pipe 50A and the through hole 59 of the right intake pipe 50B face in opposite directions in the left-right direction LR. In this case, the air inflow state into the through hole 59 of one of the left intake pipe 50A and the right intake pipe 50B is not easily affected by the airflow generated near the through hole 59 of the other intake pipe. Therefore, the natural frequencies of the two intake paths VP formed by the left intake pipe 50A and the right intake pipe 50B can be appropriately adjusted. In addition, the deterioration of the engine intake performance caused by the inflow state of air into the two intake pipes 50 becoming unstable is suppressed.

[0066] 5. Preferred conditions for forming the through hole 59 in the intake pipe 50 <1> Regarding the opening area of ​​the through hole 59 formed in one intake pipe 50 The number, positions and shapes of the through holes 59 formed in each of the two intake pipes 50 are not limited to the above example, so long as the natural frequency of the corresponding intake path VP can be set outside a specific frequency range (adjusted to a desired natural frequency). Two or more through holes 59 may be formed in one intake pipe 50.

[0067] When a plurality of through holes 59 are formed in one intake pipe 50, the natural frequency of the corresponding intake path VP is determined depending on the positions of the plurality of through holes 59 formed in the intake pipe 50 and the total opening area of ​​the plurality of through holes 59. Here, the total opening area of ​​the one or more through holes 59 formed in one intake pipe 50 is preferably 8% or more and 16% or less of the flow passage cross-sectional area of ​​the one intake pipe 50. This range was derived based on experiments conducted by the present inventors. Below, a description is given of a plurality of experiments for deriving a preferable range of the total opening area of ​​the one or more through holes 59 and the results of those experiments.

[0068] <2> Intake pipe characteristic evaluation experiment (a) The inventors conducted an experiment (intake pipe characteristic evaluation experiment) to confirm the relationship between the position and total opening area of ​​one or more through holes formed in an intake pipe 50 and the natural frequency of the intake path VP corresponding to the intake pipe 50.

[0069] Specifically, the inventors first prepared nine intake pipes having the same configuration as the intake pipe 50 in Fig. 5 except that the through hole 59 is not formed. The length of each of the nine intake pipes in the axial direction is about 180 mm. The inner diameter of each intake pipe is 35 mm excluding the funnel portion 511.

[0070] Next, the inventors took out one of the nine intake pipes and determined that it was a first intake pipe. The first intake pipe is an intake pipe in which no through hole 59 is formed. Here, a circular portion that is considered appropriate for forming a through hole 59 for reducing intake noise in the axial direction of the intake pipe is called a hole formation target portion. The hole formation target portion is a portion of the intake pipe that is disposed in the clean side space CS and is close to the inner surface of the air cleaner case 11. In this intake pipe characteristic evaluation experiment, the hole formation target portion was a portion that was separated from the funnel portion 511 by about 80 mm in the axial direction.

[0071] Next, the inventors took one of the remaining eight intake pipes, and while the intake pipe was maintained in a predetermined experimental position, they formed two circular through holes 59 with an inner diameter of 5 mm in the downward-facing portion of the hole formation target portion. The intake pipe thus produced was designated as the second intake pipe.

[0072] Next, the inventors took one of the remaining seven intake pipes, and while the intake pipe was maintained in a predetermined experimental position, they formed two 8 mm x 6 mm rectangular through holes 59 in the downward-facing portion of the hole formation target portion. The intake pipe thus produced was designated as the third intake pipe.

[0073] Next, the inventors took one of the remaining six intake pipes, and while the intake pipe was maintained in a predetermined experimental position, they formed two circular through holes 59 with an inner diameter of 5 mm in the upward-facing portion of the hole formation target portion. The intake pipe thus produced was designated as the fourth intake pipe.

[0074] Next, the inventors took one of the remaining five intake pipes, and while the intake pipe was maintained in a predetermined experimental position, they formed two circular through holes 59 with an inner diameter of 5 mm in each of the portions facing one side and the other side of the hole formation target portion. The intake pipe produced in this way was designated as the fifth intake pipe.

[0075] Next, the inventors took one of the remaining four intake pipes, and while the intake pipe was maintained in a predetermined experimental position, they formed two circular through holes 59 with an inner diameter of 10 mm in each of the portions facing one side and the other side of the hole formation target portion. The intake pipe produced in this way was designated as the sixth intake pipe.

[0076] Next, the inventors took one of the remaining three intake pipes, and while the intake pipe was maintained in a predetermined experimental position, formed one circular through hole 59 with an inner diameter of 10 mm in the portion facing one side of the hole formation target portion. The intake pipe thus produced was designated as the seventh intake pipe.

[0077] Next, the inventors took one of the remaining two intake pipes, and while the intake pipe was maintained in a predetermined experimental position, formed a circular through hole 59 with an inner diameter of 10 mm in the portion of the hole formation target portion facing the other side. The intake pipe produced in this way was designated as the eighth intake pipe.

[0078] Next, the inventors took out the remaining intake pipe, and while the intake pipe was maintained in a predetermined experimental position, formed a circular through hole 59 with an inner diameter of 12 mm in the portion of the hole formation target portion facing the other side. The intake pipe thus produced was designated as the ninth intake pipe.

[0079] 8 and 9 are schematic diagrams showing a list of the configurations of the first to ninth intake pipes related to the intake pipe characteristic evaluation experiment. In each of the first to ninth intake pipes, a side view of the intake pipe maintained in a predetermined experimental position and an end view of the hole formation target portion are shown. In each of the side views of Fig. 8 and Fig. 9, the part surrounded by a dotted line frame represents the hole formation target portion 54 in the intake pipe. In each of the side views of Fig. 8 and Fig. 9, the cut surface corresponding to the end view of the hole formation target portion 54 shown to the right of the side view is indicated by line QQ.

[0080] After producing the first to ninth intake pipes, the inventors input sound to the end of the downstream portion 52 of each of the first to ninth intake pipes, and continuously changed (sweep) the frequency of the input sound. In addition, the inventors measured the frequency response function of the sound output from the funnel portion 511 of each intake pipe when the sound was input to the intake pipe.

[0081] FIG. 10 is a graph showing the frequency response functions of the sounds output from each of the first to ninth intake pipes in the intake pipe characteristic evaluation experiment. In the graph of FIG. 10, the vertical axis represents the frequency response function, and the horizontal axis represents the frequency of the sound. In the graph of FIG. 10, the solid line represents the frequency response function corresponding to the first intake pipe, the dotted line represents the frequency response function corresponding to the second intake pipe, and the dashed line represents the frequency response function corresponding to the third intake pipe. Furthermore, the thick dashed line represents the frequency response function corresponding to the fourth intake pipe, the thick dotted line represents the frequency response function corresponding to the fifth intake pipe, and the two-dot chain line represents the frequency response function corresponding to the sixth intake pipe. Furthermore, the thick dashed line represents the frequency response function corresponding to the seventh intake pipe, the thick solid line represents the frequency response function corresponding to the eighth intake pipe, and the dashed line represents the frequency response function corresponding to the ninth intake pipe.

[0082] In the graph of FIG. 10, the frequency (peak frequency) corresponding to the peak of the frequency response function of each of the first to ninth intake pipes represents the natural frequency (resonance frequency) of the intake pipe. In the frequency band from the "first frequency f1" to the "second frequency f2 higher than the first frequency f1" of the intake sound predicted to be generated as noise from the above-mentioned multiple intake pipes, the peak frequencies of the second to ninth intake pipes are shifted from the peak frequency fp1 of the first intake pipe. The peak frequencies of the second to ninth intake pipes are higher than the peak frequency fp1 of the first intake pipe by about 10 Hz to 30 Hz. From this result, it can be seen that when the through hole 59 is formed in the intake pipe 50, the natural frequency of the intake pipe 50 can be shifted (increased) from the natural frequency of an intake pipe without the through hole 59.

[0083] FIG. 11 is a graph showing the relationship between the peak frequency of the first to ninth intake pipes in the intake pipe characteristic evaluation experiment and the total opening area of ​​one or more through holes 59 in the first to ninth intake pipes. In the graph of FIG. 11, the vertical axis represents the peak frequency, and the horizontal axis represents the total opening area of ​​one or more through holes 59 in each intake pipe. In addition, as for the indices in the graph of FIG. 11, a hollow inverted triangle represents the peak frequency of the first intake pipe, a hollow circle represents the peak frequency of the second intake pipe, and a hollow square represents the peak frequency of the third intake pipe. In addition, an X represents the peak frequency of the fourth intake pipe, a double circle represents the peak frequency of the fifth intake pipe, and a hollow triangle represents the peak frequency of the sixth intake pipe. Furthermore, a filled circle represents the peak frequency of the seventh intake pipe, a filled square represents the peak frequency of the eighth intake pipe, and a filled triangle represents the peak frequency of the ninth intake pipe.

[0084] As shown in FIG. 11, the first intake pipe does not have a through hole 59, so the total opening area is 0 mm 2 On the other hand, the total opening area of ​​the second intake pipe, the fourth intake pipe and the fifth intake pipe is about 39 mm 2 The total opening area of ​​the seventh and eighth intake pipes is approximately 79 mm 2 On the other hand, the total opening area of ​​the third intake pipe is 96 mm 2 The total opening area of ​​the ninth intake pipe is approximately 113 mm 2 The total opening area of ​​the sixth intake pipe is approximately 157 mm 2 It is.

[0085] The peak frequencies of multiple intake pipes with the same total opening area are consistent to the extent that they vary within a range of a few Hz. For example, as shown in the thick dashed line in Figure 11, the total opening area of ​​the intake pipes is about 39 mm 2 The peak frequencies of the second, fourth and fifth intake pipes are concentrated within a range of about 5 Hz. As shown in FIG. 11 by the thick dashed double-dashed line, the total opening area is about 79 mm 2The peak frequencies of the seventh and eighth intake pipes are concentrated within a range of about 5 Hz. This shows that the peak frequency of the intake pipe is determined mainly by the total opening area, regardless of the number of through holes 59 and the position of the through holes 59 in the circumferential direction of the intake pipe.

[0086] 11, the peak frequency of the intake pipe tends to be higher as the total opening area of ​​one or more through holes 59 formed in the intake pipe increases. 2 The peak frequency fp1 of the first intake pipe, which is the largest among the nine intake pipes, and the total opening area is 157 mm 2 A straight line LL is drawn connecting the peak frequency fp6 of the sixth intake pipe, which is the sixth intake pipe (see the thick dotted line in FIG. 11). In this case, the total opening area is 0 mm 2 ~157mm 2 The peak frequencies of the second intake pipe, the third intake pipe, the fourth intake pipe, the fifth intake pipe, the seventh intake pipe, the eighth intake pipe and the ninth intake pipe located between the first and second intake pipes show values ​​that correspond to the sum of the opening areas of each intake pipe, roughly along the straight line LL.

[0087] As a result, it was found that when the through holes 59 are formed in the intake pipe 50, the larger the total opening area is, the greater the change in the natural frequency of the intake pipe 50 can be, regardless of the number of the through holes 59 and the positions of the through holes 59 in the circumferential direction of the intake pipe. In other words, it was found that by increasing the total opening area of ​​one or more through holes 59 formed in the intake pipe 50, the natural frequency of the two intake paths VP can be significantly changed, and a specific intake sound can be significantly reduced.

[0088] <3> Engine intake performance verification experiment Considering the results of the intake pipe characteristic evaluation experiment, it is considered preferable to form one or more through holes 59 in the intake pipe 50 so that the total opening area is larger. However, if the total opening area of ​​the through holes 59 becomes excessively large, air may not be appropriately supplied to each of the combustion chambers 31A, 31B during operation of the engine 30. In other words, the engine intake performance may be degraded.

[0089] The present inventors conducted an experiment (engine intake performance determination experiment) to grasp the relationship between the total opening area of ​​one or more through holes 59 formed in the intake pipe 50 and the engine intake performance.

[0090] Specifically, the inventors first prepared a first intake pipe, a sixth intake pipe, and a seventh intake pipe that were fabricated in an intake pipe characteristic evaluation experiment. The first intake pipe is an intake pipe without a through hole 59. The sixth intake pipe is an intake pipe with two circular through holes 59 with an inner diameter of 10 mm. The seventh intake pipe is an intake pipe with one circular through hole 59 with an inner diameter of 10 mm.

[0091] Next, the inventors operated a given engine with the first intake pipe installed in its intake path. The inventors also measured the output and torque of the crankshaft using a dynamometer when the engine speed was within a predetermined range (hereinafter referred to as the experimental speed range). Furthermore, the inventors also performed the same measurements as for the first intake pipe for the sixth and seventh intake pipes.

[0092] FIG. 12 is a graph showing the relationship between the output of the crankshaft and the engine rotation speed measured in an engine intake performance confirmation experiment. In the graph of FIG. 12, the vertical axis represents the engine output (output of the crankshaft), and the horizontal axis represents the engine rotation speed. In addition, as for the indices in the graph of FIG. 12, a hollow inverted triangle represents the engine output corresponding to the first intake pipe, a hollow triangle represents the engine output corresponding to the sixth intake pipe, and a filled circle represents the engine output corresponding to the seventh intake pipe. Furthermore, in the graph of FIG. 12, the measurement results of multiple engine outputs corresponding to the first intake pipe are connected by a solid line, the measurement results of multiple engine outputs corresponding to the sixth intake pipe are connected by a dashed line, and the measurement results of multiple engine outputs corresponding to the seventh intake pipe are connected by a dotted line.

[0093] As shown in Fig. 12, according to the results of the engine intake performance verification experiment, the relationship between the engine output and the engine rotation speed varies slightly when the engine rotation speed is within a certain range of the experimental speed range. Specifically, as shown by the double-dashed line frame in Fig. 12, when the engine rotation speed is within a certain range of the experimental speed range, the engine output corresponding to the sixth and seventh intake pipes is lower than the engine output corresponding to the first intake pipe.

[0094] FIG. 13 is a graph showing the relationship between the torque of the crankshaft and the engine speed measured in an engine intake performance confirmation experiment. In the graph of FIG. 13, the vertical axis represents the engine torque (torque of the crankshaft), and the horizontal axis represents the engine speed. As for the indices in the graph of FIG. 13, a hollow inverted triangle represents the engine torque corresponding to the first intake pipe, a hollow triangle represents the engine torque corresponding to the sixth intake pipe, and a filled circle represents the engine torque corresponding to the seventh intake pipe. Furthermore, in the graph of FIG. 13, the measurement results of multiple engine torques corresponding to the first intake pipe are connected by a solid line, the measurement results of multiple engine torques corresponding to the sixth intake pipe are connected by a dashed line, and the measurement results of multiple engine torques corresponding to the seventh intake pipe are connected by a dotted line.

[0095] As shown in Fig. 13, the results of the engine intake performance verification experiment show that the relationship between engine torque and engine speed varies over a relatively wide range of engine speeds. Specifically, as shown by the dashed double-dashed line in Fig. 13, the engine torques corresponding to the sixth and seventh intake pipes are lower than the engine torque corresponding to the first intake pipe over almost the entire experimental speed range.

[0096] As a result of these, it was found that the total opening area of ​​the one or more through holes 59 formed in the intake pipe 50 should be determined taking into consideration the engine intake performance in addition to reducing the intake noise.

[0097] <4> Experiment to determine optimal conditions Based on the results of the intake pipe characteristic evaluation experiment and the engine intake performance confirmation experiment, the inventors conducted an experiment (optimum condition determination experiment) to determine a preferable range for the total opening area of ​​one or more through holes 59.

[0098] Specifically, the inventors first prepared a first intake pipe, a second intake pipe, a sixth intake pipe, and a seventh intake pipe that were created in an intake pipe characteristic evaluation experiment. The first intake pipe is an intake pipe without a through hole 59. The second intake pipe is an intake pipe with two circular through holes 59 with an inner diameter of 5 mm. The sixth intake pipe is an intake pipe with two circular through holes 59 with an inner diameter of 10 mm. The seventh intake pipe is an intake pipe with one circular through hole 59 with an inner diameter of 10 mm.

[0099] Next, the inventors incorporated the first intake pipe into a motorcycle corresponding to the motorcycle 100 in FIG. 1. The inventors also ran the motorcycle into which the first intake pipe was incorporated under predetermined conditions, and determined the degree of discomfort felt when listening to the intake sound generated by the motorcycle. The degree of discomfort felt by the intake sound determined at this time is called the reference discomfort. The inventors also ran the motorcycle into which the first intake pipe was incorporated under predetermined conditions, and confirmed the riding feel (power feeling) of the rider. The riding feel confirmed at this time is called the reference riding feel.

[0100] Next, the inventors incorporated the second intake pipe into a motorcycle corresponding to the motorcycle 100 in FIG. 1. The inventors also ran the motorcycle into which the second intake pipe was incorporated under predetermined conditions, and determined whether the degree of discomfort felt when hearing the intake sound generated from the motorcycle was reduced below the reference discomfort. The inventors also ran the motorcycle into which the second intake pipe was incorporated under predetermined conditions, and determined whether the riding sensation of the driver changed significantly from the reference riding sensation. Furthermore, the inventors also performed the same measurements as for the second intake pipe on the sixth and seventh intake pipes.

[0101] As a result, for the second intake pipe, the degree of discomfort caused by the intake noise hardly changed from the standard discomfort. In other words, the effect of reducing the intake noise was hardly observed for the second intake pipe. Also, for the second intake pipe, the driver's riding comfort did not change significantly from the standard riding comfort. In other words, it was not observed that the engine intake performance changed (decreased) significantly when the second intake pipe was used.

[0102] On the other hand, for the sixth intake pipe, the degree of discomfort caused by the intake noise was reduced from the standard discomfort. In other words, the sixth intake pipe was found to be effective in reducing the intake noise. Also, for the sixth intake pipe, although the driver's riding comfort changed from the standard riding comfort, the change was within the range that the driver could tolerate. In other words, it was not found that the engine intake performance changed (decreased) significantly when the sixth intake pipe was used.

[0103] On the other hand, for the seventh intake pipe, the degree of discomfort caused by the intake noise was reduced from the standard discomfort. In other words, the seventh intake pipe was found to be effective in reducing the intake noise. Also, for the seventh intake pipe, although the driver's riding comfort changed from the standard riding comfort, the change was within the range that the driver could tolerate. In other words, it was not found that the engine intake performance changed (decreased) significantly when the seventh intake pipe was used.

[0104] <5> Summary of preferable conditions for forming the intake pipe 50 From the above results, it was found that in order to obtain the effect of reducing intake noise for an intake pipe having a length and inner diameter corresponding to the first intake pipe, it is desirable to ensure an opening area at least equal to or larger than the opening area of ​​the through hole 59 formed in the seventh intake pipe. Also, in order not to significantly reduce the engine intake performance for an intake pipe having a length and inner diameter corresponding to the first intake pipe, it is desirable to ensure an opening area at least equal to or smaller than the sum of the opening areas of the two through holes 59 formed in the sixth intake pipe.

[0105] It is believed that the relationship between the total opening area of ​​one or more through holes 59 formed in one intake pipe and the effect of reducing intake noise can be determined based on the relationship between the total opening area and the flow path cross-sectional area of ​​the intake pipe.

[0106] Specifically, according to the above experimental results, the seventh intake pipe has the minimum total opening area required to achieve the effect of reducing the intake noise. Therefore, the inventors calculated the ratio of the opening area of ​​one through hole 59 formed in the seventh intake pipe to the flow passage cross-sectional area of ​​the seventh intake pipe. The calculated result was 8%.

[0107] According to the above experimental results, the intake pipe having the maximum total opening area without deteriorating the engine intake performance is the sixth intake pipe. Therefore, the inventors calculated the ratio of the total opening area of ​​the two through holes 59 formed in the sixth intake pipe to the flow passage cross-sectional area of ​​the sixth intake pipe. The calculated result was 16%.

[0108] From the above calculation results, it is preferable to design the intake pipe 50 so that the ratio of the total opening area of ​​the one or more through holes 59 to the flow passage cross-sectional area of ​​the intake pipe 50 is 8% or more and 16% or less. In this case, it is possible to obtain a sufficient effect of reducing intake noise while preventing a large decrease in the engine intake performance.

[0109] 6. Other embodiments (a) The engine 30 of the motorcycle 100 according to the above embodiment is a parallel two-cylinder engine, but the present invention is not limited to this. The engine 30 may be a single cylinder engine, or an engine having three or more cylinders. In this case, an intake path VP is formed according to the number of cylinders. Therefore, the motorcycle 100 is provided with intake pipes 50 in a number corresponding to the number of cylinders.

[0110] (b) Although the motorcycle 100 according to the above embodiment includes an intake pipe 50 having one through hole 59, the present invention is not limited to this. The motorcycle 100 may include an intake pipe 50 having two through holes 59, or an intake pipe 50 having three through holes 59, or an intake pipe 50 having four through holes 59.

[0111] (c) The above embodiment is an example in which the present invention is applied to a motorcycle. However, the present invention is not limited to this and may be applied to other saddle-type vehicles such as four-wheeled motor vehicles, three-wheeled motor vehicles, or ATVs (All Terrain Vehicles).

[0112] 7. Correspondence between each part of the embodiment and each component of the claims Below, examples of the correspondence between each component of the claims and each element of the embodiment will be described, but the present invention is not limited to the following examples. Various other elements having the configuration or function described in the claims can also be used as each component of the claims.

[0113] In the above embodiment, engine 30 is an example of an engine, air cleaner 10 is an example of an air cleaner, intake pipe 50, left intake pipe 50A and right intake pipe 50B are examples of intake pipes, intake path VP is an example of an intake path, upstream portion 51 is an example of an upstream portion, downstream portion 52 is an example of a downstream portion, and mounting portion 53 is an example of a mounting portion.

[0114] In addition, funnel portion 511 is an example of a funnel portion, tube portion 512 is an example of a tube portion, one or more through holes 59 are an example of one or more through holes, motorcycle 100 is an example of a saddle-type vehicle, air cleaner case 11 is an example of an outer wall and an air cleaner case, filter element 12 is an example of a filter element, and air outlet portion 14 is an example of an opening.

[0115] In addition, the intake port 32 is an example of an intake port, the throttle body 40 is an example of a throttle body, the two intake paths VP are examples of a first intake path and a second intake path, the left intake pipe 50A is an example of a first intake pipe, the right intake pipe 50B is an example of a second intake pipe, and the left-right direction LR is an example of one direction.

[0116] 8. Summary of the embodiment (1) The saddle-type vehicle pertaining to paragraph 1 is The engine, an air cleaner for purifying air to be supplied to the engine; an intake pipe constituting a part of an intake path that guides the air purified by the air cleaner to the engine, The intake pipe is an upstream portion disposed on a clean side of an internal space of the air cleaner; a downstream portion disposed outside the air cleaner; a mounting portion located between the upstream portion and the downstream portion of the intake pipe and mounted to an outer wall of the air cleaner, The upstream portion is a funnel portion that opens into the internal space of the air cleaner; a pipe portion connecting the funnel portion and the attached portion, The pipe portion has one or more through holes formed in a portion closer to the mounting portion than the funnel portion.

[0117] In the saddle-type vehicle, the mounting portion of the intake pipe is mounted to the outer wall of the air cleaner, the upstream portion of the intake pipe is located on the clean side of the internal space of the air cleaner, and the downstream portion of the intake pipe is located outside the air cleaner from the outer wall of the air cleaner.

[0118] One or more through holes are formed in the upstream portion of the intake pipe. The one or more through holes are located on the clean side of the internal space of the air cleaner. Therefore, unpurified air and liquid droplets such as rainwater do not flow into the intake pipe through the one or more through holes.

[0119] The natural frequency of the intake path is determined depending on the length of the intake path and the flow path cross-sectional area of ​​the intake path. Furthermore, the natural frequency of the intake path is determined depending on the position and the total opening area of ​​one or more through holes formed in the intake pipe. In the relationship between the natural frequency of the intake path and the position of one or more through holes, the natural frequency of the intake path changes more significantly as the position of the one or more through holes is farther away from the funnel portion and closer to the outer wall of the air cleaner. Therefore, according to the above configuration, the natural frequency of the intake path can be changed significantly. Therefore, by shifting the natural frequency of the intake path from the frequency band of a specific intake sound, it is possible to reduce the intake sound.

[0120] Furthermore, with the above configuration, there is no need to provide an additional configuration such as a resonator around the air cleaner and the intake pipe in order to reduce intake noise, and therefore the configuration of the air cleaner and the surrounding area of ​​the intake pipe can be made simple and compact.

[0121] As a result, the configuration of the peripheral portion of the intake path can be made simple and compact, and intake noise can be reduced.

[0122] (2) In the saddle-type vehicle according to paragraph 1, The one or more through holes may be a single through hole.

[0123] As described above, the natural frequency of the intake path varies depending on the position of one or more through holes formed in the intake pipe, as well as the total opening area of ​​the one or more through holes. When there is one through hole, it is easy to adjust the total opening area of ​​the one or more through holes. Therefore, it is easy to design one through hole to be formed in the intake pipe. Furthermore, according to the above configuration, a decrease in the strength of the intake pipe caused by forming a large number of through holes in the intake pipe is suppressed. Furthermore, an increase in the number of processes required to form the through hole is suppressed.

[0124] (3) In a saddle-type vehicle according to paragraph 1 or 2, In the axial direction of the intake pipe, the length of the upstream portion may be greater than ⅓ of the entire length of the intake pipe.

[0125] In this case, since the upstream portion is disposed within the internal space of the air cleaner, the space occupied by the intake pipe around the air cleaner can be significantly reduced compared to when the entire intake pipe is provided outside the air cleaner. Also, since the length of the upstream portion is greater than 1 / 3 of the entire length of the intake pipe, one or more through holes can be formed at a position farther away from the funnel portion. As a result, it becomes easy to form one or more through holes at a position suitable for reducing intake noise while setting the length of the intake pipe in consideration of the performance of supplying air to the engine.

[0126] (4) In the saddle-type vehicle according to any one of paragraphs 1 to 3, A ratio of a total opening area of ​​the one or more through holes to a flow passage cross-sectional area of ​​the intake pipe may be equal to or greater than 8% and equal to or less than 16%.

[0127] The flow passage cross-sectional area of ​​the intake pipe is called the pipe area, and the total opening area of ​​one or more through holes is called the hole opening area. If the ratio of the hole opening area to the pipe area is less than 8%, it is difficult to keep the natural frequency of the intake path out of the frequency band of a specific intake sound. On the other hand, if the ratio of the hole opening area to the pipe area is greater than 16%, the performance of the intake path in supplying air to the engine may decrease. Therefore, according to the above configuration, it is possible to change the natural frequency of the intake path to a degree that makes it possible to keep it out of the frequency band of the intake sound while suppressing the decrease in the performance of supplying air to the engine.

[0128] (5) In the saddle-type vehicle according to any one of the first to fourth paragraphs, The air cleaner includes: an air cleaner case that constitutes the outer wall and defines the internal space of the air cleaner; a filter element that divides the internal space into a dirty side and a clean side, an opening is formed in the outer wall to connect the clean side of the inner space to an outer space of the air cleaner case; The mounting portion of the intake pipe may be mounted to the outer wall by being fitted into the opening of the outer wall.

[0129] In this case, air introduced into the dirty side of the air cleaner is purified by the filter element and flows to the clean side. On the clean side, the purified air flows into the intake pipe through a funnel portion of the intake pipe and one or more through holes. The purified air is then supplied to the engine through the intake pipe.

[0130] (6) In the saddle-type vehicle according to any one of paragraphs 1 to 5, The saddle type vehicle includes: The engine may further include a throttle body that is connected to the downstream portion of the intake pipe and is connected to an intake port of the engine, forming another portion of the intake path.

[0131] The throttle body includes, for example, a flow passage forming pipe, a throttle valve, and a valve actuator. The flow passage forming pipe is a member that forms a flow passage that guides air purified by the air cleaner to the engine. The throttle valve is a valve configured to be able to open and close the flow passage formed by the flow passage forming pipe. The valve actuator is a device that adjusts the opening degree of the throttle valve. According to the above configuration, the downstream portion of the intake pipe is connected to the flow passage forming pipe.

[0132] In this case, there is no need to provide an additional structure for reducing intake noise, such as a resonator, in the intake pipe. Therefore, the valve actuator can be provided near the flow passage forming pipe without considering interference with the additional structure for reducing intake noise. This allows the air cleaner, intake pipe, throttle body, and surrounding members to be compact in configuration. In addition, the freedom of layout of the air cleaner, intake pipe, throttle body, and surrounding members is improved.

[0133] (7) In the saddle-type vehicle according to any one of the first to sixth paragraphs, the intake passage includes a first intake passage and a second intake passage, each of which guides the air purified by the air cleaner to the engine; The intake pipe is a first intake pipe constituting a part of the first intake path; a second intake pipe arranged in one direction relative to the first intake pipe and constituting a part of the second intake path, each of the first intake pipe and the second intake pipe has the upstream portion, the downstream portion, and the attached portion, and the one or more through holes are formed in a portion of the pipe portion of the upstream portion that is closer to the attached portion than the funnel portion; The one or more through holes formed in the first intake pipe and the one or more through holes formed in the second intake pipe may be arranged so as not to face each other in the one direction.

[0134] In this case, the air inflow state into one or more through holes in one of the first and second intake pipes is less affected by the airflow occurring near one or more through holes in the other intake pipe. Therefore, the natural frequencies of the first and second intake paths can be appropriately adjusted. Also, the performance of supplying air to the engine is prevented from being degraded due to the instability of the air inflow state into the two intake pipes. [Explanation of symbols]

[0135] 1...main frame, 1A...left frame, 1B...right frame, 1H...head pipe, 2...front fork, 3...front wheel, 4...handlebar, 5...rear frame, 6...seat, 7...rear arm, 8...rear wheel, 10...air cleaner, 11...air cleaner case, 12...filter element, 13...air inlet, 14...air outlet, 20...fuel tank, 30...engine, 31A, 31B...combustion chamber, 32...intake port, 40...throttle body, 41...flow passage forming pipe, 42...throttle Inlet valve, 43... injector, 44... valve actuator, 50... intake pipe, 50A... left intake pipe, 50B... right intake pipe, 51... upstream portion, 52... downstream portion, 53... mounting portion, 53a... first annular convex portion, 53b... second annular convex portion, 54... hole formation target portion, 59... through hole, 100... motorcycle, 511... funnel portion, 512... pipe portion, CS... clean side space, DS... dirty side space, ES... external space, SH... cylinder head, VP... intake path, ca... central axis

Claims

1. The engine, an air cleaner for purifying air to be supplied to the engine; an intake pipe constituting a part of an intake path that guides the air purified by the air cleaner to the engine, The intake pipe is an upstream portion disposed on a clean side of an internal space of the air cleaner; a downstream portion disposed outside the air cleaner; a mounting portion located between the upstream portion and the downstream portion of the intake pipe and mounted to an outer wall of the air cleaner, The upstream portion is a funnel portion that opens into the internal space of the air cleaner; a pipe portion connecting the funnel portion and the attached portion, A saddle-type vehicle, wherein one or a plurality of through holes are formed in a portion of the pipe portion that is closer to the mounting portion than the funnel portion.

2. The saddle-type vehicle according to claim 1 , wherein the one or more through holes are one through hole.

3. 3. The saddle-type vehicle according to claim 1, wherein the length of the upstream portion in the axial direction of the intake pipe is greater than one-third of the entire length of the intake pipe.

4. 3. The saddle-type vehicle according to claim 1, wherein a ratio of a total opening area of ​​the one or more through holes to a flow passage cross-sectional area of ​​the intake pipe is equal to or greater than 8% and equal to or less than 16%.

5. The air cleaner includes: an air cleaner case that constitutes the outer wall and defines the internal space of the air cleaner; a filter element that divides the internal space into a dirty side and a clean side, an opening is formed in the outer wall to connect the clean side of the inner space to an outer space of the air cleaner case; 3. The saddle-type vehicle according to claim 1, wherein the mounting portion of the intake pipe is mounted to the outer wall by being fitted into the opening of the outer wall.

6. 3. The straddle-type vehicle according to claim 1, further comprising a throttle body connected to the downstream portion of the intake pipe and to an intake port of the engine, the throttle body forming another portion of the intake path.

7. the intake passage includes a first intake passage and a second intake passage, each of which guides the air purified by the air cleaner to the engine; The intake pipe is a first intake pipe constituting a part of the first intake path; a second intake pipe arranged in one direction relative to the first intake pipe and constituting a part of the second intake path, each of the first intake pipe and the second intake pipe has the upstream portion, the downstream portion, and the attached portion, and the one or more through holes are formed in a portion of the pipe portion of the upstream portion that is closer to the attached portion than the funnel portion; 2. The saddle-type vehicle according to claim 1, wherein the one or more through holes formed in the first intake pipe and the one or more through holes formed in the second intake pipe are arranged so as not to face each other in the one direction.

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