JPH06330826A - Intake system of engine - Google Patents

Abstract

PURPOSE:To provide an intake system of an engine of which necessary length of an intake pipe is easily secured and invasion of fuel blown back from the carburetor side to the air cleaner side into air jets can be restrained. CONSTITUTION:In an intake system of an engine in which a carburetor 11 is connected to the outer connecting port 6b of an intake port, and an air cleaner 13 is connected to the carburetor 11 through an air passage 12, the air passage 12 is formed into a double construction constituted of a main pipe 22 connected to the suction port of the venturi passage 16a of the carburetor 11 and an auxiliary pipe 23 which is formed separately from the main pipe 22 and arranged so as to surround air jets 21 positioned outside the main pipe 22, the main pipe 22 is constituted of a straight part 24 extending in the same axial direction as a venturi passage 16a from the suction port and a curved part 25 continued to the straight part 24 and bending so as to part from the airjets 21 side, and the downstream end part of the auxiliary pipe 23 is connected to the carburetor 11 and the upstream part is connected to the air cleaner 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an engine in which an air cleaner is connected to a carburetor via an air passage, and more specifically to an improvement in the structure of the air passage.

[0002]

2. Description of the Related Art In an intake system for an engine, a carburetor is connected to an external connection port of an intake port formed in a cylinder head, an air passage is connected to the carburetor, and the air passage is opened in an air cleaner. Things are common. The carburetor includes an air main for introducing outside air into the fuel main and a pilot jet, and a pilot jet. In this case, in order to avoid the influence of the suction negative pressure on the air introduced into the air jet for air, the air passage is composed of a main passage and a sub passage surrounding the main passage, and the air passage is formed in a gap portion between the both passages. A structure in which the air jet is opened has been proposed.

[0003]

However, in the above-mentioned conventional apparatus, it is difficult to secure a required intake pipe length depending on the structure of the main air passage and the sub air passage, and the air is blown back from the carburetor side to the air cleaner side. There is also a problem that fuel easily enters the air jet.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is easy to secure a required intake pipe length, and it is possible to suppress the inflow of fuel blown back from the carburetor side to the air cleaner side into the air jet. It is intended to provide an intake device.

[0005]

SUMMARY OF THE INVENTION The present invention provides an intake system for an engine in which a carburetor is connected to an external connection port of an intake port, and an air cleaner is connected to the carburetor via an air passage. Double pipe structure consisting of a main pipe connected to a suction port of a venturi passage of a carburetor, and a sub pipe formed separately from the main pipe and arranged so as to surround an air jet located outside the main pipe The main pipe is composed of a straight portion extending from the suction port in the same axial direction as the Venturi passage, and a curved portion that follows the straight portion and is curved away from the air jet side, and the downstream end of the sub pipe. The part is connected to the carburetor, and the upstream part is connected to the air cleaner.

[0006]

According to the engine intake device of the present invention, since the main pipe is provided with the bent portion, it is easy to secure the required intake pipe length inside the air cleaner, and the intake pipe length according to the engine characteristics can be obtained. .

Further, since the main pipe is provided with a bend, the blowback fuel from the carburetor side is directed in the radial direction of the venturi passage by this bend and blows out, and falls outside the gap between the main pipe and the auxiliary pipe. This makes it possible to prevent blowback fuel from entering the air jet. Further, in this case, since the bent portion is curved on the opposite side of the air jet, the intrusion of fuel into the air jet can be prevented from this point as well.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views for explaining an intake system for an engine according to an embodiment of the present invention, FIG. 1 is a side view showing a state in which the engine of the embodiment is mounted on a vehicle body, and FIG. 2 is a sectional side view of the intake system. FIG. 3, FIG. 3 and FIG. 4 are views showing the assembled state of the main passage and the sub passage, respectively.

In the figure, reference numeral 1 is a motorcycle, whose body frame 2 is a pair of left and right main tubes 2a,
A head pipe 2c is fixed to the front end of the down tube 2b to form a pair of left and right cradle, and a seat rail 2d and a back stay 2 are provided at the rear of the main tube 2a.
It is a so-called double cradle type in which e is connected.

An engine unit 3 is mounted in the cradle of the vehicle body frame 2. This engine unit 3 is an air-cooled four-cycle parallel four-cylinder engine, in which a cylinder block 5 and a cylinder head 6 are laminated and fastened to the front portion of a crankcase 4 having a built-in transmission, and the cylinder head 6 is covered with a head cover 7. It has a different structure. Reference numeral 8 is an exhaust pipe, 9 is a drive shaft cover that also serves as a rear arm, and 10 is a rear wheel suspension device disposed between the drive shaft cover 9 and the rear portion of the vehicle body frame 2.

A carburetor 11 is connected to the external connection port 6b of the intake port 6a formed in the cylinder head 6, and an air cleaner 13 is connected to the carburetor 11 via an air passage 12. . This air cleaner 1
3 is disposed between the left and right main tubes 2a, 2a, and an upper portion thereof is covered with a fuel tank 14.

In the carburetor 11, the float chamber 17 is connected to the lower part of the carburetor body 16 having a substantially straight venturi passage 16a, and the diaphragm chamber 18 is connected to the upper part thereof, and acts on the diaphragm 18a in the diaphragm chamber 18. It is an automatic variable venturi type that controls the venturi passage area by advancing and retracting the piston valve 19 by negative pressure. Reference numeral 20 is a throttle valve that opens and closes the piston valve downstream side of the venturi passage 16a.

Four air jets 21 of different sizes are provided on the outside of the venturi passage 16a in the radial direction and on the side of the float chamber 17, and each air jet 21 communicates with a fuel pilot jet, a main jet, and the like. is doing. An introduction hole 16b for introducing atmospheric pressure into the diaphragm chamber 18 is formed radially outside of the venturi passage 16a and on the diaphragm chamber 18 side. Further, on the upstream end surface of the carburetor 11, a mounting flange portion 16c is formed in a cylindrical shape so as to surround the introduction hole 16b and each air jet 21, and projects toward the upstream side.

The air passage 12 has a main pipe 22 and a sub pipe 23.
It consists of and. The main pipe 22 is composed of a straight line portion 24 having the same axis as the venturi passage 16 a and a curved portion 25 that curves in a direction away from the air jet 21. The straight portion 24 is made of metal, is fitted and attached to the suction port of the venturi passage 16a, and the flange portion 24a is bolted to the end face of the suction port. The bent portion 25 is made of rubber,
It is fitted and attached to the upstream end of the straight portion 24 and is fixed by a spring ring 26.

The auxiliary pipe 23 is made of rubber, and is formed in an elliptical shape with its major axis increasing toward the upstream side. In addition, the sub-pipe 23 is opposed to the straight portion 24, that is, the venturi passage 16a so that the air jet side gap d1 between the upstream end portion and the bent portion 25 is narrower than the anti-air jet side gap d2. It is arranged to incline toward the air jet side. The downstream end 23a of the auxiliary pipe 23 is fitted and attached to the mounting flange portion 16c of the carburetor 11,
It is fixed by a metal band 29, and a mounting flange portion 23b formed in the middle thereof is fitted and mounted in a mounting opening 26d of the air cleaner 13.

The air cleaner 13 is a two-part cleaner case 26 consisting of upper and lower cases 26a and 26b.
A cylindrical element 27 is provided in the interior of the upper case 26a, and the recess 2 is provided at the center of the upper case 26a in the vehicle width direction.
6c includes a suction pipe 2 for introducing outside air into the element 27.
8 are provided. In addition, the bent portion 25 of the main pipe 22
Is disposed close to the inner surface of the vertical wall of the lower case 26b.

Next, the function and effect of this embodiment will be described. In order to assemble the intake device of this embodiment to the cylinder head 6, first, the downstream end of the carburetor 11 is connected to the external connection port 6b of the intake port 6a of the cylinder head 6, and the intake port of the carburetor 11 is straightened. The downstream end of the main pipe 22, which is an assembly of the portion 24 and the bent portion 25, is fitted and mounted, and the flange portion 2
4a is bolted and fixed. The main pipe 22 may be attached to the carburetor 11 in advance and then connected to the engine side.

Next, the air cleaner 13 in which the mounting flange portion 23b of the auxiliary pipe 23 is fitted and mounted in the mounting hole 26d of the lower case 26b in advance is connected to the carburetor 11. At this time, the bent portion 25 of the main pipe 22 is inserted into the sub pipe 23,
And the downstream end portion 23a is the connection flange portion 16 of the carburetor 11.
The air cleaner 13 is moved so as to be fitted in c, and the connection ports of both are fixed by the metal band 29.

In this embodiment, since the main pipe 22 has the bent portion 25 which is curved on the side opposite to the air jet, there is a concern that this may interfere with the sub pipe 23 when the air cleaner is attached. However, in this embodiment, since the auxiliary pipe 23 is inclined toward the side opposite to the air jet, that is, in the same direction as the curved portion 25, the above interference can be avoided and the work of attaching and removing the carburetor 11 and the acrina 13 is hindered. There is no such thing.

When the engine is tuned to, for example, a high speed type or a low speed type, the intake pipe length is adjusted to be longer for the lower speed type. In this embodiment, the main pipe 22 is composed of the straight line portion 24 and the bent portion 25. So the bend 25
As a result, it is possible to easily secure the required intake pipe length by installing different lengths, and it is possible to tune according to the engine characteristics.

On the other hand, depending on the operating condition of the engine, the fuel may be blown back to the upstream side of the carburetor. In this embodiment, however, the main pipe 22 was provided with the bent portion 25 curved inwardly of the air cleaner, so that the blowback was made. As shown by the broken line in FIG. 2, the fuel is directed in the radial direction of the Venturi passage, blows out, and exceeds the gap between the main pipe 22 and the auxiliary pipe 23 to fall outside thereof. Therefore, it is possible to prevent the blown-back fuel from entering the air jet 21. Further, in the present embodiment, since the air jet side portion of the gap between the main and sub pipes is narrowed to d1 due to the inclined arrangement of the sub pipe 23, fuel intrusion into the air jet 21 can be prevented from this point as well.

In this embodiment, the straight portion 24 of the main pipe 22 is also used.
Since the connection point between the curved portion 25 and the curved portion 25 is located at a point away from the air jet 21, even if the sealing property at the connection point is reduced, the influence of the pressure fluctuation in the main pipe affects the air jet 21. Can be suppressed.

In the above embodiment, the main pipe 22 has the two-part structure of the straight part 24 and the bent part 25. However, the main pipe of the present invention does not necessarily have the two-part structure and both are integrally formed. Good. In this case, since it is necessary to form the curved portion, it is preferable in terms of manufacturing that the whole be made of rubber.

[0024]

As described above, according to the intake system for an engine of the present invention, since the main pipe is composed of the straight portion and the bent portion, the required intake pipe length is secured by adjusting the length of the bent portion. There is an effect that can be done.

Further, since the main pipe is provided with the bent portion, the blowback fuel flow can be directed in the radial direction, the fuel can be prevented from dropping between the main pipe and the auxiliary pipe, and the fuel can be prevented from entering the air jet. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a side view showing a mounted state of an engine including an intake device according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional side view of the apparatus of the above embodiment.

FIG. 3 is a view taken along the line III-III in FIG.

FIG. 4 is an IV of the apparatus of the above embodiment with the air passage removed.
It is a line IV-arrow line view.

[Explanation of symbols]

 3 Engine 6a Intake port 11 Vaporizer 12 Air passage 13 Air cleaner 16a Venturi passage 21 Air jet 22 Main pipe 23 Sub-pipe 24 Straight part 25 Bent part

Claims (1)

[Claims] 1. In an intake system of an engine, wherein a carburetor is connected to an external connection port of an intake port, and an air cleaner is connected to the carburetor via an air passage, the air passage is sucked into a venturi passage of the carburetor. A main pipe connected to the mouth,
The main pipe has a double pipe structure formed separately from the main pipe and an auxiliary pipe arranged so as to surround an air jet located outside the main pipe, and the main pipe has the same axis line as the venturi passage from the suction port. A straight portion extending in the direction, and a curved portion that follows the straight portion and curves away from the air jet side. The downstream end of the auxiliary pipe is connected to the carburetor, and the upstream portion is connected to the air cleaner. The intake system of the engine, which is characterized by being connected to.