JP7404054B2 - vehicle ram duct - Google Patents

Description

The present invention relates to a ram duct for introducing air into an air cleaner of a vehicle engine.

Some vehicles, such as motorcycles, are equipped with a ram duct that introduces air in front of the engine into an air cleaner of the engine (for example, Patent Document 1).

Patent No. 5514639

In a vehicle such as that disclosed in Patent Document 1, intake noise may be emitted to the outside of the vehicle from the intake port of the ram duct.

An object of the present invention is to provide a ram duct for a vehicle that can suppress noise emitted from the ram duct.

In order to achieve the above object, a ram duct for a vehicle according to the present invention is a ram duct that introduces air into an air cleaner of a vehicle engine, and is provided with a constriction area that narrows an air passage at at least one of the front end and the rear end. It is being

According to this configuration, at least one of the front end portion and the rear end portion of the ram duct is provided with a constriction region that restricts the air passage. Thereby, the intake noise of the ram duct and the emission of intake noise from the air cleaner can be suppressed.

In the present invention, the throttle area is formed by an inclined piece that protrudes radially inward with respect to a peripheral wall forming a flow path space through which air flows, and the inclined piece extends radially inward toward the downstream; A retention space may be formed between the back surface of the inclined piece and the inner peripheral surface of the peripheral wall. According to this configuration, sound traveling from the downstream side to the upstream side tends to remain in the retention space of the inclined piece, and it is possible to prevent sound traveling from the downstream side to the upstream side from passing through the aperture space. In addition, the inclined piece can suppress intake resistance when air is drawn from the upstream side to the downstream side.

In the present invention, the throttle region has a first throttle part at the front end, and may further include a duct body and an inlet member attached to the duct body and forming the front end. According to this configuration, since the first constriction part is formed in the inlet member, by changing the inlet member, it is possible to switch between a specification with a constriction area and a specification without a constriction area.

When the aperture region has the first aperture, the opening of the first aperture may be offset downward from the center of the passage. According to this configuration, when the inlet of the ram duct is viewed from the outside, the opening of the first throttle section is deviated downward from the center of the passage, so that the throttle structure is difficult to see. Therefore, the appearance of the vehicle is improved.

When the throttle area includes the first throttle part, the first throttle part may have an inclined piece that slopes toward the downstream toward the center of the passage. According to this configuration, since the intake air is guided by the inclined piece, the air flow becomes smoother and the passage resistance is reduced compared to the case where the passage is narrowed without providing the inclined piece.

When the first constriction part has the inclined piece, a locking groove in which a dustproof net that prevents foreign matter from entering the air passage is locked is formed in the inlet member, and a locking groove in the locking groove in the inlet member is formed. A base portion of the inclined piece may be formed on the downstream side. According to this configuration, the periphery of the locking groove is reinforced by the base of the inclined piece, so that the net can be held stably.

In the present invention, the throttle area may include a second throttle section at the rear end, and the second throttle section may be entirely disposed inside the air cleaner. According to this configuration, the distance from the intake port of the ram duct to the air cleaner inlet, that is, the length of the portion of the ram duct excluding the portion included inside the air cleaner can be shortened. This improves the appearance of the vehicle.

When the throttle area includes the second throttle part, a fixing part fixed to the air cleaner may be provided in front of the second throttle part. Specifically, a large diameter part that is a part of the duct body may be provided in front (upstream side) of the second throttle part, and the fixing part may be provided in this large diameter part. According to this configuration, by sharing the fixed part, it is possible to switch between a specification with an aperture area and a specification without an aperture area. This improves the versatility of the ram duct.

When the throttle region has the second throttle part, the ram duct is curved so as to protrude outward from the vehicle body, and the second throttle part is eccentric outwardly with respect to the fixed part on the upstream side thereof. Good too. According to this configuration, the air in the ram duct that is biased due to centrifugal force smoothly passes through the second constriction portion.

According to the vehicle ram duct of the present invention, it is possible to suppress the sound emitted from the ram duct.

1 is a side view showing the front portion of a motorcycle, which is a type of vehicle equipped with a ram duct according to a first embodiment of the present invention. FIG. 2 is a horizontal sectional view showing the front part of the motorcycle. FIG. 3 is a longitudinal sectional view of the front cowl of the motorcycle. It is a front view showing the entrance member of the same ram duct. It is a sectional view showing a connection part of the same ram duct and an air cleaner.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing the front part of a motorcycle, which is a type of vehicle equipped with a ram duct according to a first embodiment of the present invention. In this specification, "right" and "left" refer to "right" and "left" as seen from a driver riding in a vehicle. Furthermore, "upstream" and "downstream" refer to "upstream" and "downstream" in the flow direction of intake air.

The body frame FR of the motorcycle of this embodiment is a pipe frame in which steel pipe members are joined together by welding. The main frame 1 constituting the front half of the vehicle body frame FR extends rearward from a head pipe 4 at the front end, slanting downward. The main frame 1 of this embodiment has an upper frame 1a and a lower frame 1b. The upper frame 1a extends rearward from the upper part of the head pipe 4 in a downwardly inclined manner. The lower frame 1b extends rearward from the lower part of the head pipe 4 in a downwardly inclined manner.

As shown in FIG. 2, a pair of left and right main frames 1 are provided. Specifically, a pair of left and right upper frames 1a and lower frames 1b are provided. As shown in FIG. 1, two reinforcing pipes 12 are provided at the front of the main frame 1 in parallel in the front-rear direction. Each reinforcing pipe 12 extends in the vertical direction and connects the upper frame 1a and the lower frame 1b. A plate-shaped gusset 13 is joined between the upper frame 1a, the lower frame 1b, and the two reinforcing pipes 12, 12, and an opening 14 facing the vehicle width direction is formed in the gusset 13.

A pair of left and right front forks 16 are rotatably supported by a head pipe 4 at the front end of the main frame 1 via a steering shaft (not shown). A front wheel 18 is supported at the lower end of this front fork 16. A handle 20 is attached to an upper bracket 17 that supports the upper end of the front fork 16. A pair of left and right swing arms (not shown) are supported at the lower rear end of the main frame 1, and a rear wheel (not shown) is supported by the swing arms. An engine E is supported at the lower center of the main frame 1. Engine E drives the rear wheels.

The engine E of this embodiment is a water-cooled, four-cylinder, four-cycle engine in which cylinders are arranged in the vehicle width direction. However, the type of engine E is not limited to this. The engine E includes a crankcase 22 that supports a crankshaft (not shown), a cylinder 24 that projects upward from the front of the crankcase 22, and a cylinder head 26 above the cylinder 24. An intake port 26a through which intake air is introduced is formed on the rear surface of the cylinder head 26. An exhaust port 26b is formed on the front surface of the cylinder head 26, through which exhaust gas is led out. A radiator 28 is arranged in front of the engine E. The radiator 28 is supported by the main frame 1 and radiates heat from engine cooling water.

An air cleaner 25 is arranged above the cylinder head 26 of the engine E. Air cleaner 25 filters air supplied to engine E. As shown in FIG. 2, the air cleaner 25 is arranged between the left and right main frames 1 in plan view. The air cleaner 25 is supported by the main frame 1 via a bracket (not shown). A cleaner inlet 25a is formed at the front of the air cleaner 25, and a cleaner outlet 25b is formed at the rear. In this embodiment, the cleaner inlet 25a is formed at the boundary between the front wall and the side wall of the air cleaner 25.

Four cleaner outlets 25b are arranged in the vehicle width direction for each cylinder. The cleaner outlet 25b of this embodiment is configured with a funnel that passes through the bottom wall of the case of the air cleaner 25. A throttle body 27 is connected between the cleaner outlet 25b and the intake port 26a of the engine E. In this embodiment, the air cleaner 25 is arranged above the cylinder head 26. The intake system of this embodiment has a downdraft structure in which air flows downward from the air cleaner toward the engine.

The motorcycle of this embodiment includes a cowling 29 that protects the rider from wind pressure while driving. The cowling 29 has a front cowl 30 and a pair of left and right side cowls 32. The front cowl 30 covers the front of the head pipe 4. The side cowl 32 is arranged behind the front cowl 30 and covers the front part of the vehicle body, specifically, the main frame 1, the radiator 28, and the engine E from the outside.

A headlamp 36 is attached to the front of the front cowl 30. A meter unit 38 is arranged in front of the head pipe 4 and above the front cowl 30. The front cowl 30 and the meter unit 38 are supported by the vehicle body frame FR via a meter stay 40.

As shown in FIG. 2, a ram duct 52 is provided that communicates the air intake port 50 and the air cleaner 25. The ram duct 52 extends rearward from the front of the head pipe 4 to the outside of the front fork 14 and the main frame 1 in the vehicle width direction, curves inward in the vehicle width direction, and is connected to the air cleaner 25 . The ram duct 52 of this embodiment is made of resin such as polyethylene and is formed by blow molding. However, the material and manufacturing method of the ram duct 52 are not limited to these.

The ram duct 52 is formed into a tubular shape extending in the longitudinal direction, and in this embodiment extends in the front-rear direction. The ram duct 52 forms a flow path that guides the running wind introduced into the air intake port 50 during the vehicle to the air cleaner 25. The ram duct 52 of this embodiment extends in the front-rear direction from the air intake port 50 of the front cowl 30 to the rear of the head pipe 4. Further, the ram duct 52 extends on a circular arc that generally bulges outward in the vehicle width direction when viewed from above. Specifically, when viewed from above, the ram duct extends from the air intake port 50 of the front cowl 30 in a curved manner outward in the vehicle width direction, avoiding the movable area of the head pipe 4 and the front fork 16.

Further, the ram duct 52 passes through the movable region of the front fork 16 in the longitudinal direction, curves inward in the vehicle width direction, passes through the main frame 1 in the vehicle width direction, and is connected to the air cleaner 25. The ram duct 52 includes, for example, a ram duct main body 53 formed in an elongated shape, and an inlet member 92 for connecting the ram duct main body 53 and the front cowl 30 (air intake port). Details of the inlet member 92 will be described later. The air intake port 50 is formed in a cylindrical shape extending in the front-rear direction.

An inlet 52a at the front end of the ram duct 52 is located on the vehicle widthwise center line C1 and faces the air intake port 50. That is, the ram duct 52 takes in the running wind from the inlet 52a and supplies it to the air cleaner 25.

As shown in FIG. 1, the inlet 52a of the ram duct 52 behind the air intake port 50 is also located above the headlamp 36 and between the left and right headlamps 36, 36. The entrance 52a of the ram duct 52 has an inverted triangular shape when viewed from the front. However, the shape of the entrance 52a is not limited to this. A dustproof net 54 is attached to the entrance 52a of the ram duct 52. The dustproof net 54 is, for example, a mesh screen provided on a frame forming the outer shell, and prevents foreign matter from entering the ram duct 52.

As shown in FIG. 3, the front cowl 30 is formed with an air introduction passage 55 that communicates the air intake port 50 with the inlet 52a of the ram duct 52. The air introduction passage 55 has a passage area that gradually decreases toward the rear from the air intake port 50. Thereby, the flow velocity of the air increases while flowing through the air introduction passage 55.

As shown in FIG. 2, the ram duct 52 extends rearward on the outside of the front fork 16 and the main frame 1 in the vehicle width direction. Further, as shown in FIG. 1, the ram duct 52 passes above the radiator 28 and below the handle 20 in a side view. In this embodiment, the ram duct 52 is covered from the outside by the front cowl 30 and the side cowls 32.

As shown in FIG. 2, the ram duct 52 is curved to one side in the vehicle width direction (to the left in this embodiment) toward the rear from the entrance 52a at the front end. Specifically, the inlet 52a at the front end of the ram duct 52 is located in front of the head pipe 4, and its axis coincides with the vehicle width direction center line C1 in a plan view. The ram duct 52 is curved so as to protrude rearward from the entrance 52a to one side in the vehicle width direction, that is, to the left in this embodiment, and passes behind the headlamp 36 and in front of the front fork 14. The ram duct 52 curves to a position outward in the vehicle width direction from the range in which the front fork 16 rotates.

The ram duct 52 extends rearward on the outside (left side) of the front fork 16 and the main frame 1. The passage area of the ram duct 52 gradually becomes narrower toward the downstream (backward). As a result, the flow velocity of the air gradually increases toward the downstream, so the amount of air flowing into the air cleaner 25 increases.

A rear portion of the ram duct 52 is curved inward in the vehicle width direction and is connected to the air cleaner 25. In this embodiment, the rear part of the ram duct 52 is connected to the air cleaner 25 by passing through an opening 14 formed in the gusset 13 of the main frame 1 shown in FIG. 1 from the outside in the vehicle width direction to the inside. Although the ram duct 52 of this embodiment is arranged on the left side of the vehicle body, the ram duct 52 may be arranged on either the left or right side, or on both sides. However, in this embodiment, since the reservoir tank of the radiator 28, the cam chain of the engine E, etc. are arranged on the right side, the ram duct 52 is arranged on the left side of the vehicle body.

A constriction area 84 is provided at the front end 80 and rear end 82 of the ram duct 52 . The constriction region 84 is formed to have a passage area sufficiently smaller than that on its upstream side, and constricts the air passage 85 inside the ram duct 52 . The aperture area 84 of this embodiment includes a first aperture section 86 at the front end 80 and a second aperture section 88 at the rear end 82 . The first constriction section 86 is provided mainly to suppress noise emitted from the ram duct 52 and the air cleaner 25, and the second constriction section 88 is provided mainly to suppress noise emitted from the air cleaner 25 and components downstream of the air cleaner 25. It is installed to suppress sound.

The air intake port 50 is formed to be exposed from the vehicle body. The intake noise generated by the air cleaner 25 becomes emission sound that is emitted to the outside of the vehicle body via the ram duct 52 and the air intake port 50. As the engine output increases, the sound emitted from the air cleaner 25 increases. In other words, the larger the intake air amount (engine speed), the louder the sound emitted. The ram duct 52 of this embodiment can reduce such emitted sound.

In this embodiment, the front end of the ram duct 52 constitutes an inlet portion connected to the front cowl 30. The front end portion is formed in a straight portion of the ram duct 52 that extends in the front-rear direction along the center line in the vehicle width direction. The front end portion is formed forward of a front fixed portion of the ram duct that is fixed to the vehicle body.

The first aperture section 86 will be explained. The ram duct 52 includes a duct body 90 and an inlet member 92 attached to the front end of the duct body 90. In this embodiment, the inlet member 92 constitutes the front end 80 of the ram duct 52. The inlet member 92 is made of an elastic member such as rubber, and is formed by molding.

In this embodiment, the inlet member 92 constitutes the front end of the ram duct 52. The front end portion is configured to be detachable from the ram duct main body 53. The front end is made of a stretchable elastic material, for example a rubber material, specifically ethylene propylene rubber. The inlet member 92 includes a front tightening portion 92a that covers and tightens the outlet portion of the air intake port 50, a rear tightening portion 92b that covers and tightens the inlet portion of the ram duct body 53, and a net holding portion that holds the dustproof net 54. 92c, and a diaphragm portion 92d that constitutes the first diaphragm portion 86.

The first constriction portion 86 is formed in the inlet member 92 . Specifically, as shown in FIG. 5, the first constriction section 86 has an inclined piece 94 that projects toward the center of the passage. The inclined piece 94 is inclined so as to approach the center of the passage toward the downstream side. In this embodiment, since the inlet member 92 is formed by molding, it is easy to form the inclined piece 94. A locking groove 96 into which the dustproof net 54 is locked is formed in the entrance member 92 . A base 94a of the inclined piece 94 is formed on the downstream side of the locking groove 96 in the entrance member 92. The opening direction of the first constriction portion 86 is offset downward from the center of the passage. Specifically, the protrusion length d1 of the upper inclined piece 94 toward the center of the passage is larger than the protrusion length d2 of the lower inclined piece 94 toward the passage center.

In this embodiment, the passage area S1 of the first restricting portion 86 is set to approximately 1/3 of the passage area S2 of the inlet member 92. The passage area S2 of the inlet member 92 is the passage area that is minimum on the upstream side of the first constriction part 86 in the inlet member 92. In this embodiment, the minimum passage area S2 is the area of the opening 93 surrounded by the protrusion 95 on the upstream side of the locking groove 96 in the inlet member 92. In this way, as a result of narrowing the passage area S1 of the first constriction section 86 to be smaller than the passage area S2 of the opening of the inlet member 92, the maximum output of the engine is almost maintained and the maximum sound volume is approximately It dropped by 2 decibels.

The passage area S1 of the first throttle portion 86 is preferably 30 to 50% of the passage area S2 of the opening of the inlet member 92. As a result of verification tests, when the throttle amount (S1/S2) exceeds 65%, there is almost no effect in reducing intake noise, and when the throttle amount (S1/S2) is less than 50%, the intake noise reduction effect begins to appear. Ta. Furthermore, when the throttle amount (S1/S2) was less than 20%, the engine output began to decrease.

The throttle portion 84 is formed by an inclined wall that is inclined radially inward toward the downstream side from the peripheral wall that forms the air passage. The inclined wall is formed over the entire circumferential direction. In this embodiment, an inclined wall is formed by the inclined piece 94. A retention space SP is formed between the back surface of the inclined piece 94 and the inner peripheral surface of the peripheral wall. The retention space SP is closed on the upstream side and open on the downstream side. That is, sound (flow) from the downstream side to the upstream side tends to stay in the retention space SP. Therefore, it is possible to suppress sound traveling from the downstream side to the upstream side from passing through the constriction part 84 and being emitted as emitted sound from the air intake port 50.

The inclined piece 94 is arranged on the downstream side of the dustproof net 54. This can prevent collisions with pebbles and the like. The inclined piece 94 is arranged on the upstream side of the ram duct main body 53. As a result, the inclined piece 94 reduces the sound after energy is consumed by propagating through the ram duct body 53 from the downstream side to the upstream side. Therefore, emitted sound can be effectively reduced. In particular, in this embodiment, since the ram duct 52 is curved, it is possible to suppress the sound that reaches the inclined piece 94 while moving from the downstream side to the upstream side.

When a resonator (not shown) is provided in the ram duct 52, by arranging the inclined piece 94 upstream of the resonator, the inclined piece 94 prevents the sound muffled by the resonator from being emitted to the inlet side. be able to. Therefore, the emitted sound can be further suppressed.

Since the inclined piece 94 is made of rubber with a high damping coefficient, the vibration of the inclined piece 94 is suppressed compared to a case where the inclined piece 94 is made of resin. Thereby, it is possible to suppress the generation of sound caused by the vibration of the inclined piece 94. While the vehicle is traveling, a force directed toward the downstream side is generated on the inclined piece 94 due to the traveling wind. This also prevents vibration and deformation due to sound moving from the downstream side to the upstream side.

As described above, the intake passage has a passage area that gradually decreases toward the downstream side. In other words, the passage area gradually increases toward the upstream side. Thereby, the density of sound can be suppressed when going from the downstream side to the upstream side, and the sound reduction effect of the inclined piece 94 can be further enhanced. Further, the passage area of the portion where the inclined piece 94 is formed is sufficiently larger than the passage area of the longitudinally intermediate portion of the ram duct 52, for example, 1.5 times or more larger. Thereby, the density of sound at the portion where the inclined piece 94 is formed can be suppressed to a sufficiently high level.

The second aperture section 88 will be explained. As shown in FIG. 2, the second constriction portion 88 of the rear end portion 82 is constricted inside the air cleaner 25. As shown in FIG. That is, the entire second constriction portion 88 is disposed inside the air cleaner 25. A fixing portion 98 fixed to the air cleaner 25 is provided in the ram duct 52 on the front side (upstream side) of the second throttle portion 88 . That is, a large-diameter portion 90a that is a part of the duct main body 90 on the front side (upstream side) of the second throttle portion 88 is provided, and a large-diameter fixing portion 98 is provided on this large-diameter portion 90a. The second constricted portion 88 and the fixed portion 98 are integrally formed by blow molding.

In this embodiment, the passage area S3 of the second throttle part 88 shown in FIG. 5 is set to about 1/2 of the passage area S4 of the fixing part 98 on the upstream side thereof. The passage area S3 of the second throttle part 88 is preferably 40 to 70% of the passage area S4 of the fixing part 98. Thereby, intake noise from inside the air cleaner 25 can be reduced while suppressing an increase in air resistance. However, the ratio (S3/S4) between the passage area S3 of the second throttle part 88 and the passage area S4 of the fixed part 98 is not limited to this.

As is clear from FIG. 2, the ram duct 52 is curved at the front so as to protrude outward (to the left) of the vehicle body, and at the rear of the ram duct 52 is curved toward the inside (right side) of the vehicle body. In this embodiment, the second throttle part 88 is eccentric toward the outside (to the left) with respect to the fixed part 98 on the upstream side thereof. Specifically, the axis A1 of the second throttle part 88 is eccentric to the outside (left side) with respect to the axis A2 of the fixed part 98.

In other words, the second constricted portion 88 is largely constricted on the inside, and not so constricted on the outside. In other words, the first concave portion 88a on the inside of the second constricted portion 88 is greatly concave, and the second concave portion 88b on the outside is concave by a small amount. As a result, the second throttle section 88 is eccentrically outward (to the left) with respect to the fixed section 98 on the upstream side thereof.

As described above, the entire second constriction section 88 is disposed inside the air cleaner 25. In other words, a space is formed on the radially outer side of the second constricted portion 88. Further, by arranging the entire second constriction portion 88 inside the air cleaner 25, all of the sound transmitted inside the air cleaner 25 is prevented from reaching the ram duct 52. That is, with respect to the opening (outlet 52b) of the ram duct 52, sounds that proceed in the axial direction A1 of the opening 52b enter the ram duct 52, but other sounds are suppressed from entering the ram duct 52. Further, by forming the constriction portion 84 at the rear end, it is possible to further suppress the sound entering the ram duct 52 from the air cleaner 25. In this manner, by providing the throttle portions 84 at both the front end and the rear end of the ram duct 52, the effect of suppressing emitted sound can be further enhanced.

Next, the support structure of the ram duct 52 of this embodiment will be explained. The rear part of the ram duct 52 passes through the opening 14 of the main frame 1 shown in FIG. 3 and is connected to the cleaner inlet 25a of the air cleaner 25. Specifically, as shown in FIG. 10, a cylindrical connecting member 72 is attached to the opening of the cleaner inlet 25a, and the rear part 82 of the ram duct 52 is fitted into the inner peripheral surface of the connecting member 72. In this state, the ram duct 52 and the connecting member 72 are gripped/fixed from the outer periphery by the clamp 74. The clamp 74 is attached and detached using a fastening member 75 such as a screw body. Thereby, the rear end portion 82 of the ram duct 52 is supported by the vehicle body frame FR of FIG. 2 via the air cleaner 25. A front portion and a longitudinally intermediate portion of the ram duct 52 are fixed to the vehicle body frame FR via a meter stay (not shown).

Next, the flow of intake air in the motorcycle of this embodiment will be explained. When the motorcycle runs, running wind A shown in FIG. 2 is introduced into the ram duct 52 from the air intake port 50. At this time, the traveling wind A is throttled by the first throttle section 86. Air A introduced into the ram duct 52 is guided to the outside (left side) in the vehicle width direction, and flows toward the rear on the outside of the main frame 1. At this time, since the passage area gradually decreases toward the downstream, the flow velocity gradually increases.

Further, the air A is guided inward in the vehicle width direction and introduced into the air cleaner 25. At this time, the traveling wind A is throttled by the second throttle section 88. Air A introduced into the air cleaner 25 is filtered by an element 79 inside the air cleaner 25 to become clean air CA. The clean air CA is supplied to the engine E from the cleaner outlet 25b via the throttle body 27 in FIG.

According to the above configuration, the first constriction part 86 and the second constriction part 88 are provided at the front end part 80 and the rear end part 82 of the ram duct 52 in FIG. 2, respectively. Thereby, intake noise from the air cleaner 25 can be suppressed. Therefore, even in the ram duct 52 having a large inlet area, the intake noise of the ram duct 52 and the intake noise from the air cleaner 25 can be suppressed from increasing. Thereby, by utilizing the ram duct 52, it is possible to achieve both an improvement in engine output and a reduction in intake noise.

It is known to narrow down the air passage as a noise countermeasure, but conventionally this has been done with a funnel at the air cleaner outlet. The idea of constricting the air passage of the ram duct 52, which has a large intake port, in order to take in a large amount of air and improve engine output is a new idea that breaks conventional wisdom. Additionally, as a sound countermeasure, some vehicles are equipped with a resonator, but the resonator is intended to suppress the volume of a specific frequency, and it is difficult to eliminate intake noise from the air cleaner and its upstream side.

A first constriction portion 86 shown in FIG. 3 is formed in an inlet member 92 attached to a duct body 90. Noise regulation values may differ depending on the country. According to this configuration, by changing the inlet member 92, it is possible to switch between a specification with the first constriction part 86 and a specification without the first constriction part 86. This improves the degree of freedom of the ram duct 52.

The first constriction portion 86 is formed by a sloped piece 94 that slopes toward the downstream toward the center of the passage. According to this configuration, since the intake air is guided by the inclined piece 94, the airflow becomes smooth and the passage resistance is reduced. Further, when the inlet member 94 is formed by molding, since the inlet member 92 is constricted by the inclined piece 94 formed on the inlet member 92, switching to a specification without the constricted area 84 can be done by replacing the core. Therefore, only one mold is required.

Further, the opening of the first restrictor 86 is offset downward from the center of the passage. As a result, when the inlet portion of the ram duct 52 is viewed diagonally from above and in front, the inclined piece 94 of the first throttle portion 86 is hidden behind the cowling and is difficult to see. Therefore, the appearance of the vehicle is improved.

A locking groove 96 into which the dustproof net 54 is locked is formed in the entrance member 92, and a base 94a of the inclined piece 94 is formed on the downstream side of the locking groove 96 in the entrance member 92. As a result, the periphery of the locking groove 96 is reinforced by the base 94a of the inclined piece 94, so that the dustproof net 54 can be held stably.

The entire second throttle portion 88 of the rear end portion 82 shown in FIG. 2 is disposed inside the air cleaner 25. Thereby, the distance from the inlet of the ram duct 52 to the inlet of the air cleaner 25, that is, the length of the exposed portion of the ram duct 52 excluding the portion included inside the air cleaner 25 can be shortened. This improves the appearance of the vehicle.

As shown in FIG. 5 , a large-diameter fixing portion 98 fixed to the air cleaner 25 is provided in front (upstream) of the second constriction portion 88 in the ram duct 52 . As mentioned above, there are cases where noise regulation values differ depending on the country. According to this configuration, by making the fixing part 98 common, it is possible to switch between a specification with the second aperture part 88 and a specification without the second aperture part 88. Specifically, by changing the cutting location of the rear end portion 82 of the ram duct 52 after blow molding, it is possible to switch between a specification with the second constricted portion 88 and a specification without the second constricted portion 88. In this way, since the ram duct 52 having a plurality of specifications can be formed with one mold, the degree of freedom of the ram duct 52 is improved. As a result, the ram duct 52 can be formed to meet various noise regulation values.

As shown in FIG. 6, the ram duct 52 is curved so as to protrude outward (to the left) of the vehicle body. In this embodiment, a downdraft structure in which an air cleaner 25 is disposed above the cylinder head 26 is employed to improve engine output. If the vehicle body frame is cast aluminum, it is possible to provide a head block in the head pipe 4 at the center of the steering wheel, and to arrange the ram duct 52 from the head block toward the air cleaner in the center of the vehicle body, but in this embodiment, an iron pipe is used. Since it is a frame, using an iron head block will increase the weight. Therefore, the ram duct 52 is curved in the vehicle width direction (left side) and connected to the air cleaner 25. Furthermore, the second constriction part 88 is eccentric to the outside (to the left) with respect to the fixed part 98. As a result, air biased by centrifugal force passes through the second constriction section 88 smoothly.

In this way, in the above embodiment, the steel pipe frame provides a sharp appearance, and the downdraft structure is used to improve engine output, while smoothing uneven air flow and increasing air filling efficiency. be able to.

The present invention is not limited to the above-described embodiments, and various additions, changes, or deletions can be made without departing from the gist of the present invention. For example, in the above embodiment, the aperture region 84 is provided at both the front end portion 80 and the rear end portion 82, but the aperture region 84 may be provided at at least one of the front end portion 80 or the rear end portion 82. . The ram duct 52 of the present invention can be suitably used in a high-speed engine, that is, an engine with a small displacement per cylinder, and can improve charging efficiency. Furthermore, the ram duct of the present invention is also applicable to vehicles other than motorcycles. Therefore, such materials are also included within the scope of the present invention.

25 Air cleaner 52 Ram duct 54 Dustproof net 80 Front end of ram duct 82 Rear end of ram duct 84 Throttle area 85 Air passage 86 First throttle section 88 Second throttle section 90 Duct body 92 Inlet member (elastic member)
94 Inclined piece 94a Base of inclined piece 96 Locking groove 98 Fixing part E Engine

Claims (5)

A ram duct that introduces air into an air cleaner of a vehicle engine,
At least one of the front end or the rear end is provided with a constriction area for constricting the air passage;
The constriction region has a first constriction portion at the front end,
Further, it includes a duct body and an inlet member attached to the duct body and forming the front end portion,
The first constriction part has a sloped piece that slopes toward the downstream toward the center of the passage,
A locking groove is formed in the inlet member to lock a dustproof net that prevents foreign matter from entering the air passage,
A ram duct for a vehicle, wherein a base portion of the inclined piece is formed on a downstream side of the locking groove in the inlet member. The ram duct for a vehicle according to claim 1, wherein the throttle area is formed by an inclined piece that projects inward in a radial direction with respect to a peripheral wall portion forming a flow path space through which air flows;
the inclined piece extends radially inward toward the downstream;
A ram duct for a vehicle, wherein a retention space is formed between a back surface of the inclined piece and an inner peripheral surface of the peripheral wall. The ram duct for a vehicle according to claim 1 or 2, wherein the opening of the first constriction portion is offset downward from the center of the passage. The ram duct for a vehicle according to any one of claims 1 to 3, wherein the constriction area has a second constriction portion at the rear end portion;
A ram duct for a vehicle, wherein the second throttle portion is entirely disposed inside the air cleaner. 5. The ram duct for a vehicle according to claim 4, further comprising a fixing portion fixed to the air cleaner on the front side of the second throttle portion.

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