JPH0692778B2 - Intake device for motorcycles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an intake system for a motorcycle including an engine having a horizontally opposed type or a V type cylinder arrangement in which several cylinders are arranged in the front-rear direction, for example.

Generally, in a motorcycle equipped with this type of engine,
An intake expansion box is provided below the fuel tank, and intake pipes that rise upward from the front and rear cylinders are connected to the lower surface of the intake expansion box. In this case, since the intake pipe is usually composed of a down-draft type carburetor in order to reduce the ventilation resistance, the total length of the intake pipe is increased vertically in order to secure the carburetor arrangement space. That is, the intake pipe largely protrudes upward from the cylinder, so that the intake expansion box is positioned upward.

Moreover, when the intake expansion box and the air cleaner are provided below the fuel tank, the space between the lower surface of the fuel tank and the engine is occupied by these components, and the lower surface of the fuel tank must be largely recessed upward. Do not become (for example
56-148662). That is, the capacity of the fuel tank is reduced. This becomes more remarkable when the intake expansion box becomes large due to a request for reduction of engine noise.

The present invention has been made in order to solve this problem, and provides an intake device that has a sufficient fuel tank capacity, is excellent in noise reduction performance, has a high degree of freedom in design, and is highly adaptable to various vehicles. To do.

An intake system for a motorcycle according to the present invention is provided with a fuel tank provided on an upper front surface of a vehicle body frame, and an engine having at least one cylinder provided on the lower surface of the fuel tank in front of and behind the crank chamber with a crank chamber interposed therebetween. Then, an intake expansion box extending in the front-rear direction from above the front cylinder to above the rear cylinder is provided below the fuel tank, and the intake pipes rising upward from the front cylinder and the rear cylinder are connected to the lower surface of the intake expansion box. , An air cleaner is disposed laterally of the fuel tank to form a space between the inside of the air cleaner and the outside of the intake expansion box, and the intake outlet of the air cleaner and the intake inlet of the intake expansion box are It is characterized in that they are arranged so as to be displaced in the front-rear direction of the vehicle body, and are connected to each other by both end portions of a connecting pipe arranged in the space.

The present invention will be described below with reference to the illustrated embodiments. Reference numeral 1 in the figure is a motorcycle having a body frame 2 in which steel pipes are welded and assembled, a front fork 4 pivotally supporting a front wheel 3 is rotatably supported at the front end of the body frame 2, and a rear wheel is provided at the rear end. A rear arm 5 supporting 4 is pivotally supported by a pivot 6 so as to be vertically swingable. A buffer spring 7 is bridged between the body frame 2 and the rear arm 5. A fuel tank 8 and a passenger's seat 9 are supported on the upper side of the vehicle body frame 2, and an engine 10 is mounted below the fuel tank 8.

The engine 10 is a horizontally opposed four-cylinder engine having two front cylinders 12 extending forward from the crank chamber 11 and two rear cylinders 13 extending rearward. The engine 10 includes front and rear cylinders 12 and 13 and the vehicle body frame. An exhaust pipe 15 is connected between the exhaust silencer 14 and the exhaust silencer 14 mounted on the rear side of the vehicle.

The lower surface of the fuel tank 8 is slightly recessed, and the upper portion of the intake expansion box 16 having a planar shape of the outer shell that is substantially the same as that of the fuel tank 8 is housed therein.
The 16 and the front and rear cylinders 12, 13 are connected by an intake pipe constituted by a carburetor 17. That is, the intake expansion box 16 is formed so as to extend in the front-rear direction from above the front cylinder 12 to above the rear cylinder 13.
Intake pipes that rise upward from the front cylinder 12 and the rear cylinder 13 are connected to the lower surface of the. Reference numeral 18 is a drive chain spanned between the engine 10 and the rear wheel 4, and 19 is a radiator for cooling the engine.

The intake expansion box 16 has a hole through the center as shown in FIG.
21 is provided, and the bottom portion 8a of the fuel tank 8 projects downward, and the periphery of the bottom portion of the fuel tank 8 is covered with the intake expansion box 16. 22 are air cleaners which are located laterally of the fuel tank 8 and the intake expansion box 16 and are symmetrically provided one by one, and are projected below the intake expansion box 16 by connecting pipes 23 arranged along the sides of the vehicle body. It is connected to the outer surface. The air cleaner 22 is arranged laterally of the fuel tank 8 so that a space is formed between an inner side surface of the air cleaner 22 which is a vehicle width direction center side and an outer side surface of the intake expansion box 16. The connecting pipe 23 is arranged in the space. Also, the air cleaner 22
The intake outlet and the intake inlet of the intake expansion box 16 are arranged offset from each other in the front-rear direction of the vehicle body, and are connected by both ends of the connecting pipe 23 arranged in the space. twenty four
Is a filter paper of an air cleaner, and 25 is an intake port that opens to the atmosphere, and is displaced in the vehicle front-rear direction from the connection position of the connection pipe 23 to the intake expansion box 16. The intake expansion box 16 is not limited to this shape, and as shown in FIG. 4, two intake expansion boxes 16 are symmetrically connected to each other, and a pair of front and rear carburetors 17 is connected to each of the left and right sides. The hole 21 described above may also be open at the front and back.

In the embodiment described above, when the engine 10 is started, the outside air that has been sucked in through the intake port 25 and filtered by the air cleaner 22 is introduced into the intake expansion box 16, where it becomes a stable airflow and is distributed to the front and rear carburetors 17. Are led to cylinders 12 and 13 separately.

Since the intake expansion box 16 is provided in the recessed portion on the lower surface of the fuel tank 8, not only a large intake expansion box can be installed and a large intake silencing effect can be expected, but also the pressure change of intake air introduced into the engine is reduced. Stable engine output is obtained.

In addition, the connecting portion of the connecting pipe 23 to the intake expansion box 16 and the intake port 25
And are displaced in the front-rear direction of the vehicle body by the connecting pipe 23, and
By arranging the connecting pipe 23 along the side portion of the vehicle body, the relatively high vehicle body side, which does not come into contact with parts such as the fuel tank 8, the vehicle body frame 2, and the crankcase 11 as shown in FIG. The optimum position of the part is selected and the intake port 25 is opened. Then, the cold outside air flowing on the side of the vehicle body is sucked in through the intake port 25, and passes through the air cleaner 22, etc., as described above, and then the cylinder 1
Guided by 2 and 13.

As described above, the intake system for a motorcycle according to the present invention is a motorcycle equipped with an engine having at least one cylinder in the front-rear direction, and in the front-rear direction from above the front cylinder to above the rear cylinder below the fuel tank. An intake expansion box that extends to is provided, and the intake pipes that rise upward from the front cylinder and the rear cylinder are connected to the lower surface of the intake expansion box,
An air cleaner is arranged on the side of the fuel tank to form a space between the inside of the air cleaner and the outside of the intake expansion box, and the intake outlet of the air cleaner and the intake inlet of the intake expansion box are displaced in the front-rear direction of the vehicle body. In addition, since the connecting pipes arranged in the space are connected to each other by both ends thereof, only the intake expansion box exists below the fuel tank, and the pace occupied by the intake device is reduced.

Therefore, even if the intake expansion box is positioned above in order to secure the space for disposing the intake pipes that rise upward from the front and rear cylinders respectively, the bottom surface of the fuel tank does not have to be largely recessed upwards. The capacity of the tank never decreases. Then, the intake pipe can be configured by a down-draft type carburetor to reduce the ventilation resistance and improve the output of the engine.

In addition, a space is formed between the inside of the air cleaner arranged on the side of the fuel tank and the outside of the intake expansion box, and the intake outlet of the air cleaner and the intake inlet of the intake expansion box are arranged so as to be offset in the vehicle front-rear direction. At the same time, since the connecting pipes are connected by both ends of the connecting pipe arranged in the space, the connecting pipe has a shape extending in the front-rear direction of the vehicle body.

Since not only the volume of the intake expansion box and the volume of the air cleaner but also the volume of the connecting pipe are added to the volume of the intake device, according to the present invention, the volume of the entire intake device is increased and the pulsation of intake air is suppressed. The action to be performed is increased and the noise is reduced.

The distance between the intake outlet of the air cleaner and the intake inlet of the intake expansion box in the longitudinal direction of the vehicle body can be adjusted by changing the length of the connecting pipe, so that the air cleaner does not contact the engine on the side of the fuel tank. It can be placed in the optimum position, increasing the degree of freedom in design.

Furthermore, it is easy to manufacture only the connecting pipe part separately from the intake expansion box and the air cleaner, and to make it a structure that can be removed, so even for vehicles where the relative positions of the body frame and the engine are different. If the connecting pipes with different distances are prepared, this intake device can be easily applied to various vehicles.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a side view of a motorcycle, FIG. 2 is an enlarged side view of the essential parts thereof,
FIG. 3 is a sectional view taken along the line III-III, and FIG. 4 is a sectional view corresponding to FIG. 3 showing another embodiment. 2 ... Body frame, 8 ... Fuel tank, 9 ... Engine, 16 ... Intake expansion box, 23 ... Connecting pipe, 25 ... Intake port.

Claims (1)

[Claims] 1. A fuel tank is provided on an upper front surface of a vehicle body frame, and an engine having at least one cylinder is provided on the lower surface of the fuel tank with a crank chamber sandwiched therebetween. An intake expansion box that extends in the front-rear direction from above the front cylinder to above the rear cylinder is provided below, and the intake pipes that rise upward from the front cylinder and the rear cylinder are connected to the lower surface of this intake expansion box, and the side of the fuel tank. An air cleaner is disposed on one side to form a space between the inside of the air cleaner and the outside of the intake expansion box, and the intake outlet of the air cleaner and the intake inlet of the intake expansion box are shifted in the vehicle longitudinal direction. An intake device for a motorcycle, wherein the intake pipes are arranged and connected by both ends of a connecting pipe arranged in the space.