Air intake device for motorcycle

In an air intake device for motorcycle, an air cleaner having a front end formed with a main intake port is disposed between a pair of left and right main frame pieces forming a main frame. An introducing passage is formed within the main frame for capturing an incoming wind. An intake air introducing port of the introducing passage is provided at a location rearwardly of the main intake port in the main frame piece. An intake air discharge port is defined in an intermediate portion of a front portion of the main frame with respect to a motorcycle widthwise direction so as to open rearwardly and to be fluid connected with the main intake port. A sub intake port is provided in communication with the main intake port so as to introduce an intake air into the main intake port.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an air intake device for a motorcycle in which an air intake sound is reduced and an engine performance is improved.

Description of Related Art

The patent document 1 listed below, for example, discloses a conventional air intake device for a motorcycle of a design in which air is introduced from an air intake port into a motorcycle frame structure and then, an air is introduced into an air cleaner main body through an intake port communicated with an intake air discharge port in the motorcycle frame structure.

PRIOR ART LITERATURE

It has, however, been found that, according to the above mentioned conventional technique, since the air intake port of the air cleaner has a limited open area, the conventional technique is unable to meet sufficiently the recent demands to increase the air intake efficiency and to increase the engine performance. Although it may be contemplated to increase the air intake efficiency by increasing the open area of the intake port of the air cleaner, the increase of the open area of the intake port of the air cleaner necessitates a concomitant increase of the open area of the intake air discharge port in the motorcycle frame structure that is in communication with the intake port of the air cleaner and, hence, the rigidity of the motorcycle frame structure is adversely affected.

SUMMARY OF THE INVENTION

In view of foregoing, the present invention has been devised to provide a motorcycle air intake device in which the air intake efficiency is increased to increase the engine performance and to improve the acoustic quality of sounds of air being introduced.

In order to accomplish the foregoing object, a motorcycle air intake device in accordance with the present invention includes: an air cleaner having an front end formed with a main intake port, the air cleaner being positioned between a pair of left and right main frame pieces forming a main frame; introducing passage defined within the main frame to capture an incoming wind as an engine intake air; an intake air introducing port of the introducing passage provided in a portion of the main frame piece at a location rearwardly of the main intake port in the air cleaner; an intake air discharge port defined in an intermediate portion of a front portion of the main frame with respect to a motorcycle widthwise direction, the intake air discharge port being opened rearwardly and fluid connected with the main intake port; and a sub intake port provided in communication with the main intake port to introduce an intake air from a location in the vicinity of the main intake port into the main intake port.

According to the present invention, the incoming air taken from the intake air introducing port in the main frame as an engine intake air is supplied from the main intake port in the air cleaner into the air cleaner that is fluid connected with the intake air discharge port in the main frame. At this time, the introducing port of the introducing passage referred to above is defined in a portion of the main frame piece, which is situated rearwardly of the main intake port of the air cleaner, and the intermediate portion of the front portion of the main frame with respect to the motorcycle widthwise direction is formed with the intake air discharge port that is opened rearwardly and fluid connected with the main intake port. Therefore, the introducing passage within the main frame is increased in length and, accordingly, intake air sounds are reduced. Also, since the intake air is also introduced from the sub intake port into the main intake port, the surface area of the intake port is substantially increased. Accordingly, the amount of air sucked into the air cleaner is increased to thereby increase the air intake efficiency, resulting in an increase of the engine performance. Furthermore, since the main frame itself can be used with the conventional parts in the form as they are, the manufacturing cost can be suppressed to a low cost.

In a preferred embodiment of the present invention, the sub intake port is preferably disposed on a lower side of the main intake port. This structural feature makes it possible to avoid an undesirable intrusion of rain into the sub intake port.

In another preferred embodiment of the present invention, the air cleaner preferably has a tip end having an intake duct in which the main intake port is formed, and the intake duct has a peripheral wall provided with a cutout portion, which is provided with the sub intake port. According to this structural feature, the sub intake port can be formed with a simplified structure merely by cutting out a peripheral wall of the intake duct.

In a further preferred embodiment of the present invention, the intake duct preferably has a tip end portion fluid connected with the intake air discharge port through a connecting ring made of an elastic material, in which case the connecting ring is provided with a guide portion that protrude downwardly and forwardly from the main intake port to introduce the intake air into the sub intake port. According to this structural feature, merely by mounting the connecting ring, which is made of the elastic material, on the intake duct, the sub intake port can be easily formed by a combination of the guide portion of the connecting ring and the cutout portion in the intake duct. The air cleaner and the main frame are connected together by means of the connecting ring made of the elastic material, and therefore, air tightness is secured, whereby upward and lateral leakage of intake sounds can be reduced.

In a still further referred embodiment of the present invention, the connecting ring is preferably mounted on an outer periphery of the tip end portion of the intake duct and has a pawl portion engageable with an outer wall surface in the vicinity of the intake air discharge port in the main frame. According to this structural feature, when the front portion of the main frame and the tip end of the intake duct are connected together through the connecting ring, the connecting ring is connected with the main frame in a stable fashion by means of the pawls in the connecting ring.

DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will be described in detail with particular reference to the accompanying drawings.FIG. 1illustrates a schematic side view of a motorcycle equipped with an air intake device designed in accordance with a preferred embodiment of the present invention. The illustrated motorcycle has a motorcycle frame structure FR which includes a main frame1, forming a front half unit thereof, and a rear frame2connected with a rear portion of the main frame1and forming a rear half unit thereof. A head pipe3is fitted to a front end portion of the main frame1; an upper bracket4and an under bracket5are fitted to a steering shaft (not shown) that is rotatably inserted in the head pipe3. A front fork8is supported by the upper bracket4and the under bracket5, and a front wheel9is supported by a lower end portion of the front fork8. A handlebar10is fitted to the upper bracket4at an upper end portion of the front fork8.

A swingarm bracket11is provided in a rear end portion of the main frame1, and a swingarm12is supported by the swingarm bracket11through a pivot pin13, inserted in a front end portion of the swingarm12, for swinging movement up and down. A rear wheel14is supported by a rear end portion of the swingarm12. A combustion engine E is supported by a lower portion of the main frame1, and the combustion engine E drives the rear wheel14through a power transmission mechanism16such as, for example, a drive chain. The combustion engine E employed in the practice of this embodiment is, for example, a four cylinder, four cycle water-cooling engine.

A rider's seat22is supported by the rear frame2, and a fuel tank18is fitted to an upper portion of the main frame1, that is, to an upper portion of a motorcycle body and between the handlebar10and the rider's seat22. A region beneath the rider's seat22is laterally covered by a side covering17. A large sized front fairing30enough to cover a large region ranging from a front end portion of the motorcycle body to a location laterally of the combustion engine E is mounted on a motorcycle front portion, and a headlamp unit23is mounted on the front fairing30. An air cleaner36is disposed in the vicinity of the rear portion of the head pipe3.

As shown inFIG. 2, the main frame1includes a pair of left and right main frame pieces1aand1b. The air cleaner36is positioned between the frame pieces1aand1band in the vicinity of the rear portion of the head pipe3. A front portion of the air cleaner36is supported by the main frame1by means of a connecting member60such as, for example, a bolt through a tank bracket59as will be detained later. A rear portion of the air cleaner36is supported by a throttle body44of the combustion engine E shown inFIG. 1.

FIG. 3illustrates a schematic side view showing an air intake device and its neighborhood. As shown inFIG. 3, at an intermediate portion of the front portion of the main frame1, which intermediate portion lies with respect to a motorcycle widthwise direction, an intake air discharge port39opens rearwardly. Intake air introducing ports40are opened in opposite side faces of the main frame1. The main frame1has a hollow in which an introducing passage43is formed for introducing an incoming wind, which is captured as an engine intake air A through the intake air introducing ports40shown inFIG. 2, forwardly to the intake air discharge port39.

The air cleaner36has a main intake port41, best shown inFIG. 3, which is fluid connected with the intake air discharge port39in the main frame1via a connecting ring50. In continuation to a lower portion of the main intake port41, a sub intake port42for capturing an additional air protrudes downwardly from the air cleaner36and is exposed to the outside of the main intake port41. The air cleaner36includes a lower casing37and a covering38for covering an upper portion of the lower casing37. Each of the lower casing37and the covering38is made of a resinous material.

FIG. 4illustrates a condition in which the connecting ring50is removed from a tip end of an intake duct51of the air cleaner36. As shown inFIG. 4, the main intake port41of the air cleaner36is formed in a tip end of the intake duct51, and the connecting ring50is mounted on the intake duct51by inserting the former in a direction shown by the arrow P. The connecting ring50can be separated from the intake duct51, during the maintenance, by pulling the connecting ring50in a direction shown by the arrow Q. The shape of the main intake port41of the intake duct51substantially coincides with the shape of the intake air discharge port39defined in the intermediate portion of the front portion of the main frame1, shown inFIG. 6, with respect to the motorcycle widthwise direction. The intake duct51, shown inFIG. 4, has a peripheral wall in which a lower portion of the tip end is cut out to form a cutout portion53.

The connecting ring50is made of an elastic material such as, for example, rubber material and has an exterior shape sufficient to cover a tip end portion of the peripheral wall of the intake duct51. The connecting ring50is somewhat undersized as compared with a peripheral wall dimension of the intake duct51so that, when the connecting ring50is inserted into the peripheral wall of the intake duct51in the direction of the arrow P, the connecting ring50can be elastically supported with no gap formed between the connecting ring50and the intake duct51. In this way, by the connecting ring50, the main intake port41of the intake duct51and the cutout portion53are covered from an outer peripheral side. A pair of left and right pawls55and55are formed in an upper side of the connecting ring50. Also, the connecting ring50has a lower portion formed with a guide portion56so as to protrude downwardly. The connecting ring50has a front face50awhich serves as a sealing face.

FIG. 5is a longitudinal sectional view showing a condition of connection between the intake duct51of the air cleaner36and the main frame1. The front face50aof the connecting ring50is brought into contact under pressure with a peripheral edge portion of the intake air discharge port39in the main frame1to thereby seal a gap between the main intake port41and the intake air discharge port39. While in this condition, the pawls55are elastically pressed against and are hence engaged with an outer wall surface1dof an upper side of the main frame1. The cutout portion53in the intake duct51of the air cleaner36and the guide portion56of the connecting ring50cooperate with each other to form the sub intake port42referred to previously.

As shown inFIG. 6, the intake discharge port39has a pair of left and right oval openings57and57with a partition wall58formed between those openings57and57. The partition wall58is formed with a communicating port61best shown inFIG. 5. The intake air A having passed through the left and right introducing passages43within the main frame1is guided rearwardly by the partition wall58and at this time sufficiently mixed through the communicating port61. The intake air A is then guided into the air cleaner36through the intake air discharge port39by way of the main intake port41in the air cleaner36.

The air intake device of the construction as hereinbefore fully described is of such a design that, as shown inFIG. 3, the incoming air taken from the intake air introducing port40in the main frame1as an engine intake air A is introduced from the main intake port41of the air cleaner36into the air cleaner36that is fluid connected with the intake air discharge port39in the main frame1. At this time, as shown inFIG. 2, the introducing port40of the introducing passage43referred to previously is defined in a portion of each of the main frame pieces1aand1b, which is situated rearwardly of the main intake port41of the air cleaner36, and the intermediate portion of the front portion of the main frame with respect to the motorcycle widthwise direction is formed with the intake air discharge port39that is opened rearwardly and fluid connected with the main intake port41. Therefore, the introducing passage43within the main frame1is increased in length, whereby intake air sounds are reduced.

Also, as shown inFIG. 5, since the intake air A is also introduced from the sub intake port42into the main intake port41and an in-duct air intake passage45, the surface area of the intake port is substantially increased. Accordingly, the amount of air sucked into the air cleaner36is increased to thereby increase the air intake efficiency, resulting in an increase of the engine performance. Also, since the intake air A introduced from the sub intake port42does not flow through the introducing passage43within the main frame1, the air intake resistance or pipe loss is reduced. Furthermore, since the sub intake port42is provided in the intake duct51of the air cleaner36, the main frame1itself can be used with the conventional parts in the form as they are. Accordingly, the manufacturing cost can be suppressed to a low level.

Since the sub intake port42is disposed on a lower side of the main intake port41, an undesirable intrusion of rain into the sub intake port42can be avoided. Also, with a simplified structure in which the cutout portion53is formed in the peripheral wall of the intake duct51by merely cutting, the sub intake port42can be formed.

In addition, merely by mounting the connecting ring50, which is made of the elastic material, on the intake duct51, the sub intake port42can be easily formed by a combination of the guide portion56of the connecting ring50and the cutout portion53in the intake duct51. The air cleaner36and the main frame1are connected together by means of the connecting ring50made of the elastic material, and therefore, air tightness is secured, whereby upward and lateral leakage of intake sounds can be reduced.

Yet, when the front portion of the main frame1and the tip end of the intake duct51are connected together through the connecting ring50, the connecting ring50is connected with the main frame1in a stable fashion by means of the pawls55in the connecting ring50.

REFERENCE NUMERALS