JP3586740B2 - Engine intake structure of underbone type motorcycle - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an engine intake structure for an underbone type motorcycle.
[0002]
[Prior art]
In order to improve the performance of the engine in not only the underbone type motorcycle but also any other type of motorcycle, a branched intake chamber is provided in a communication passage between the air cleaner and the carburetor. Although this has already been done, the inventor tried various experiments for stabilizing the idling of the engine, and as a result, the air cleaner connected to the engine and the outside air inlet for introducing outside air to the air cleaner were found. It has been found that it is effective to provide a branched intake chamber in the outside air introduction passage therebetween.
[0003]
Thus, by providing the intake chamber in the outside air introduction passage as described above, intake pulsation due to engine rotation fluctuation during idling is eliminated, and large capacity intake air is retained in the intake chamber. The variation in the air-fuel ratio of the air-fuel mixture is eliminated, and the idling of the engine is stabilized. Since the intake chamber is provided at a position distant from the engine, the intake chamber has almost no effect on the engine performance. Therefore, the engine performance during the running of the motorcycle does not decrease due to the presence of the intake chamber.
[0004]
[Problems to be solved by the invention]
However, if the intake chamber is separately provided as an independent part as in a conventional motorcycle, the number of parts increases and the cost increases, and it is necessary to secure a separate installation space for the intake chamber. In addition to this, there is a possibility that the front gouge space of the underbone type motorcycle is reduced, and that the rider's getting on and off is deteriorated.
[0005]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object thereof is to use an existing part to intake air without increasing the number of parts, increasing the size of a vehicle body, and deteriorating rider getting on and off. It is an object of the present invention to provide an engine intake structure of an underbone type motorcycle that can exert an effect of stabilizing an engine idling by a chamber.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 includes a vehicle body frame including a head pipe rotatably supporting a handle, and a down tube extending diagonally downward toward the rear from the head pipe. An engine disposed below the down tube, and an underbone type motorcycle including an air cleaner connected to the engine ,
The inside of the down tube is a closed space and an opening is formed in the down tube, an outside air introduction port for introducing outside air, and an outside air introduction passage formed between the outside air introduction port and the air cleaner. , the outer air introduction passage, together occupy passed, communicating the closed space in the down tube via the opening, characterized in that the air cleaner is arranged downstream of the closed space in the down tube.
[0007]
According to a second aspect of the present invention, in the first aspect, over both welded to reinforce the connection portion between the down tube and the head pipe, having a suction port communicating with the outside air introduction port A gusset, wherein the suction port of the gusset is formed at the top of the gusset as a long hole extending in the vehicle body front-rear direction, and the opening of the down tube is an upper part of the down tube as a long hole extending in the vehicle body front-back direction, and The gusset is formed inside, and the opening of the down tube and the suction port of the gusset are arranged at substantially the same position in the vertical direction .
[0008]
According to a third aspect of the invention, in the invention according to claim 1 or 2, as well as connecting the the opening of the gusset air cleaner by an intake duct, the opening of the down tube, before the vehicle longitudinal direction Ki吸 It is provided between the opening of the air duct and the outside air introduction port.
[0009]
Therefore, according to the first aspect of the present invention, since the closed space formed in the existing down tube functions as an intake chamber, there is no need to separately provide an independent intake chamber, thereby reducing the number of parts and cost. In addition to reducing the size of the body and preventing the rider from getting on and off due to the decrease in the space for the front gouging, the closed space inside the down tube has the effect of stabilizing the engine's idling as an intake chamber. be able to. In particular, since the air cleaner is located downstream of the closed space in the down tube, a large amount of intake air, which is the sum of the volumes of the air cleaner and the closed space in the down tube, can be retained, and the air-fuel ratio of the air-fuel mixture can be kept. And the engine idling can be stabilized.
[0010]
According to the second aspect of the present invention, even if the opening of the down tube is a long hole elongated in the front-rear direction of the vehicle body in order to increase the opening area, this opening is provided inside the gusset as a reinforcing member. The opening does not significantly reduce the rigidity of the down tube, and the down tube has sufficient and necessary rigidity. In addition, since the opening of the down tube and the suction port of the gusset are arranged at substantially the same position in the vertical direction, the outside air introduced from the outside air introduction port passes through the opening of the down tube from the suction port of the gusset and enters the down tube. Is efficiently introduced into the closed space.
[0011]
Further, according to the third aspect of the present invention, since the opening is provided between the opening of the intake duct of the air cleaner and the outside air introduction port in the longitudinal direction of the vehicle body, the outside air introduced from the outside air introduction port flows from the opening. Efficiently flows into the closed space in the down tube.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0013]
1 is a side view of an underbone type motorcycle having an engine intake structure according to the present invention, FIG. 2 is a partial front view of the motorcycle, and FIG. 3 is a partial side view of the motorcycle showing an engine intake structure according to the present invention. FIG. 4 is a cutaway front view of the engine intake structure of the motorcycle.
[0014]
In the underbone-type motorcycle 1 shown in FIG. 1, reference numeral 2 denotes a head pipe 2 located at an upper front part of a vehicle body, and a large-diameter down tube 3 extends rearward (to the right in FIG. 1) from the head pipe 2. It extends diagonally downward. A pair of left and right seat rail frames 4 extend obliquely upward rearward from the rear end of the down tube 3, and the head pipe 2, the down tube 3 and the seat rail frame 4 constitute a body frame. I have.
[0015]
A steering shaft 5 is rotatably inserted into the head pipe 2, and a steering wheel 6 is attached to an upper end of the steering shaft 5. An upper end of a front fork 7 is connected to a lower end of the steering shaft 5, and a front wheel 8 is rotatably supported at a lower end of the front fork 7. The upper part of the front fork 7 is covered by a mudguard 9, and the upper half of the front wheel 8 is covered by a front fender 10.
[0016]
A rear arm bracket 11 curved in a substantially L shape is welded to the rear end of the down tube 3, and a four-cycle engine 12 is mounted and supported on the rear arm bracket 11 and the down tube 3. The four-cycle engine 12 has a cylinder 12a extending substantially horizontally toward the front of the vehicle below the down tube 3, and a plurality of cooling fins 12a-1 extending in the front-rear direction of the vehicle are formed in the cylinder 12a. . An oil pan is formed at the bottom of the crankcase 12b of the engine 12, and the bottom of the engine 12 is protected by an engine guard 13. In FIG. 1, 14 and 15 are steps, 16 is a main stand, and 17 is a side stand.
[0017]
Here, the engine intake structure according to the present invention will be described.
[0018]
In the motorcycle 1 according to the present embodiment, the rear end of the down tube 3 is closed by a lid member 36, and a closed space S (see FIG. 4) is formed in the down tube 3.
[0019]
A gusset 18 for reinforcing the connection between the head pipe 2 and the down tube 3 is welded over the head pipe 2 and the down tube 3, and the gusset 18 constitutes an intake box. A circular opening 18a (see FIG. 3) is formed on both sides of the gusset 18, and a pair of left and right intake ducts 19 of the air cleaner 20 are connected to these openings 18a.
[0020]
Thus, as shown in FIGS. 3 and 4, an opening 3a formed of a narrow hole long in the longitudinal direction of the vehicle body is formed in a portion of the down tube 3 located in the gusset 18. In addition, a suction port 18b is formed in the upper portion of the gusset 18 and is also formed by a narrow hole long in the longitudinal direction of the vehicle body. A resin cover 37 is detachably attached to the upper surface of the gusset 18 with a screw (not shown) so as to cover the air inlet 18b. A rear end of the cover 37 has an outside air inlet 37a opening to the atmosphere. Is composed. Therefore, the opening 3a of the down tube 3 is disposed between the opening 19a (see FIG. 4) of the intake duct 19 of the air cleaner 20 and the outside air inlet 37a in the vehicle longitudinal direction.
[0021]
On the other hand, a carburetor 21 is connected to a lower portion of the air cleaner 20 by an intake pipe 22. The carburetor 21 is connected to an intake passage (not shown) of the cylinder 12a by an intake pipe 23. An exhaust pipe 24 extends from below the cylinder 12a. As shown in FIG. 3, an element 20a is accommodated in the air cleaner 20.
[0022]
Therefore, in the engine intake structure according to the present invention, the air intake passage between the air cleaner 20 communicating with the engine 12 and the outside air introduction port 37a for introducing outside air to the air cleaner 20 is lowered through the opening 3a. The closed space S in the tube 3 is communicated.
[0023]
As shown in FIG. 1, a tandem-type seat 25 is supported above the engine 12 and supported by the seat rail frame 4, and a fuel tank 26 and a battery 27 are provided below the seat 25. Is established.
[0024]
A front end of a rear arm 28 is pivotally supported on the rear arm bracket 11 by a pivot shaft 29 so as to be vertically rotatable. A rear wheel 30 is rotatably supported on a rear end of the rear arm bracket 28. ing. The rear arm 28 and the rear wheel 30 are suspended from the vehicle body by a rear cushion 31 interposed between the seat rail frame 4 and the rear arm 28. The upper half of the rear wheel 30 is covered with a rear fender 32. In FIG. 1, reference numeral 33 denotes a chain case that covers a chain (not shown) for transmitting the rotational power of the engine 12 to the rear wheel 30.
[0025]
The motorcycle 1 having the above configuration is covered with a resin body cover 34. The body cover 34 is a leg shield 34a that covers a portion extending from the down tube 3 to both sides of the engine 12. And a rear cover 34b that covers the rear half of the vehicle body.
[0026]
Further, in the motorcycle 1 according to the present embodiment, the traveling wind is efficiently guided to the cylinder 12a below the down tube 3 and above the cylinder 12a of the engine 12 so that the engine 12 A wind guide plate 35 for improving the cooling performance is arranged obliquely downward along the down tube 3 toward the rear of the vehicle body.
[0027]
In the underbone type motorcycle 1 configured as described above, when the engine 12 is driven, the outside air is pulled by the negative pressure generated in the intake stroke of the engine 12 and the outside air is drawn as indicated by an arrow in FIG. The air is sucked into the cover 37 from the outside air inlet 37 a of the cover 37. The outside air sucked into the cover 37 flows into the gusset 18 through the suction port 18b, flows into the closed space S in the down tube 3 through the opening 3a, and temporarily stays there. The air flows into the left and right intake ducts 19 through the portions 18 a and 19 a and is guided to the air cleaner 20. The outside air guided to the air cleaner 20 is purified by passing through the element 20 a of the air cleaner 20, then guided to the carburetor 21 through the intake pipe 22, mixed with the fuel in the carburetor 21 in the carburetor 21, and subjected to a predetermined process. An air-fuel mixture is formed.
[0028]
Thus, the air-fuel mixture formed in the carburetor 21 is supplied to the combustion chamber of the engine 12 through the intake pipe 23 for combustion, and the exhaust gas generated by the combustion of the air-fuel mixture passes through the exhaust pipe 24. Released into the atmosphere.
[0029]
As described above, in the engine intake structure according to the present embodiment, the inside of the branched down tube 3 is closed in the outside air introduction passage between the air cleaner 20 and the outside air introduction port 37a for introducing outside air to the air cleaner 20. Since the space S is communicated, the closed space S functions as an intake chamber, and outside air flows into the closed space S and temporarily stays therein, so that intake pulsation due to rotation fluctuation of the engine 12 during idling is eliminated. Further, since a large amount of outside air (intake air) is retained in the closed space S, the variation in the air-fuel ratio of the air-fuel mixture is eliminated, and the idling of the engine 12 is stabilized. Since the closed space S as the intake chamber is provided at a position distant from the engine 12, the closed space S has little effect on the performance of the engine 12, and therefore, the performance of the engine 12 when the motorcycle 1 travels. Is not reduced by the existence of the closed space S.
[0030]
As described above, in the present embodiment, since the closed space S formed in the existing down tube 3 functions as an intake chamber, there is no need to separately provide an independent intake chamber as in the related art, and the number of parts is reduced. , Cost reduction and downsizing of the vehicle body can be achieved, and in particular, in the underbone type motorcycle 1, there is no accompanying reduction in the space for the front gouge, and the rider's getting on and off is not deteriorated. In addition, while achieving these, the effect as an intake chamber of stabilizing the idling of the engine 12 in the closed space S in the down tube 3 can be exhibited. In addition, since the down tube 3 is thick and long, the capacity, length, and shape of the closed space S formed therein can be freely set.
[0031]
In addition, according to the present embodiment, the opening 3a formed in the down tube 3 is a narrow hole that is long and narrow in the longitudinal direction of the vehicle body and is provided inside the gusset 18 that is a reinforcing member. The rigidity of the down tube 3 is not significantly reduced by 3a, and the down tube 3 has sufficient and necessary rigidity.
[0032]
Further, according to the present embodiment, the opening 3a is provided between the opening 19a of the intake duct 19 of the air cleaner 20 and the outside air inlet 37a in the front-rear direction of the vehicle body. The opening 19a is open in a direction orthogonal to the flow direction of the outside air (the front-rear direction of the vehicle body) leading to the outside air, so that the outside air introduced from the outside air introduction port 37a is efficiently transmitted from the opening 3a to the closed space S in the down tube 3. It flows well and stays.
[0033]
【The invention's effect】
As apparent from the above description, according to the first aspect of the present invention, since the closed space formed in the existing down tube functions as an intake chamber, there is no need to separately provide an independent intake chamber. In addition to reducing the number of parts and cost, miniaturizing the body, and preventing the rider from getting on and off due to the reduction of the front gouge space, the intake of the engine stabilizes in the closed space inside the down tube. The effect that the effect as a chamber can be exhibited is obtained. In particular, since the air cleaner is located downstream of the closed space in the down tube, a large amount of intake air, which is the sum of the volumes of the air cleaner and the closed space in the down tube, can be retained, and the air-fuel ratio of the air-fuel mixture can be kept. And the engine idling can be stabilized.
[0034]
According to the second aspect of the present invention, even if the opening of the down tube is a long hole elongated in the front-rear direction of the vehicle body in order to increase the opening area, this opening is provided inside the gusset as a reinforcing member. Further, the rigidity of the down tube is not significantly reduced by the opening, and the effect that the necessary and sufficient rigidity is secured in the down tube is obtained. In addition, since the opening of the down tube and the suction port of the gusset are arranged at substantially the same position in the vertical direction, the outside air introduced from the outside air introduction port passes through the opening of the down tube from the suction port of the gusset and enters the down tube. Is efficiently introduced into the closed space.
[0035]
Further, according to the third aspect of the present invention, since the opening is provided between the opening of the intake duct of the air cleaner and the outside air introduction port in the longitudinal direction of the vehicle body, the outside air introduced from the outside air introduction port flows from the opening. The effect of efficiently flowing into the closed space in the down tube is obtained.
[Brief description of the drawings]
FIG. 1 is a side view of an underbone type motorcycle including an engine intake structure according to the present invention.
FIG. 2 is a partial front view of an underbone type motorcycle including an engine intake structure according to the present invention.
FIG. 3 is a partial side view of an underbone type motorcycle showing an engine intake structure according to the present invention.
FIG. 4 is a cutaway front view of an engine intake structure of the underbone type motorcycle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Anta bone type motorcycle 2 Head pipe 3 Down tube 3a Opening 6 Handle 12 Engine 18 Gusset 18a Opening 18b Inlet 19 Intake duct 19a Opening 20 Air cleaner 37 Cover 37a Outside air inlet S Closed space

Claims (3)

A vehicle body frame including a head pipe rotatably supporting a handle and a down tube extending obliquely downward toward the rear from the head pipe; an engine disposed below the down tube ; and the engine In an underbone type motorcycle equipped with an air cleaner communicating with
The inside of the down tube is a closed space and an opening is formed in the down tube, an outside air introduction port for introducing outside air, and an outside air introduction passage formed between the outside air introduction port and the air cleaner. Wherein the closed space in the down tube is communicated with the outside air introduction passage through an opening, and the air cleaner is disposed downstream of the closed space in the down tube. Engine intake structure for motorcycles. Over both welded to reinforce the connection portion between the down tube and the head pipe comprises a gusset having an inlet communicating with the external air inlet port, long the inlet of the gusset in the vehicle longitudinal direction The opening of the down tube is formed in the upper part of the gusset as an elongated hole, and the opening of the down tube is formed in the upper part of the down tube and inside the gusset as an elongated hole in the vehicle longitudinal direction. 2. The engine intake structure for an underbone type motorcycle according to claim 1 , wherein the intake port of the gusset is arranged at substantially the same position in the vertical direction . Thereby connecting the air cleaner and the opening of the gusset by the intake duct, that the opening of the down tube, provided between the air introduction port and the opening of the front Ki吸 duct in the longitudinal direction of the vehicle body The engine intake structure for an underbone-type motorcycle according to claim 1 or 2, wherein:

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