JP3423352B2 - Engine intake system - Google Patents

Description

Description: 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. About. 2. Description of the Related Art In an intake device 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 provided in an air cleaner. An opening is common. The vaporizer includes an air main and a pilot jet for introducing outside air into the fuel main and the pilot jet. In this case, in order to avoid that the suction negative pressure affects the air introduced into the air jet, the air passage is constituted by a main passage and a sub passage surrounding the main passage. A structure in which the air jet is opened has been proposed. However, in the above-mentioned conventional apparatus, it is difficult to secure a necessary intake pipe length depending on the structure of the main air passage and the sub air passage, and further, from the carburetor side to the air cleaner side. There is also a problem that the returned fuel easily enters the air jet. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and it is easy to secure a necessary intake pipe length, and it is possible to suppress the penetration of fuel blown back from a carburetor side to an air cleaner side into an air jet. It is intended to provide an intake device. According to the present invention, a carburetor is connected to an external connection port of an intake port, and an air cleaner disposed above the carburetor is connected to the carburetor via an air passage. In the intake device of the engine, the air passage, the main pipe connected to the suction port of the venturi passage of the carburetor,
A secondary pipe formed separately from the main pipe and arranged so as to surround an air jet positioned outside the main pipe, wherein the main pipe is coaxial with the venturi passage from the suction port. A straight metal part extending in the direction and curved away from the air jet side following the straight part
Constituted by a rubber bend, the straight portion above the bench
The fitting is fitted to the suction port of the
The bent part is the upstream end of the straight part.
The sub-tube is attached to the straight section with respect to the straight section.
Inclined and arranged in a counter-air jet side Te, the downstream end of the secondary pipe as well as connected to the carburetor, and the upstream portion and characterized in that connected to the air cleaner. According to the intake device for an engine according to the present invention, since a bent portion is provided in the main pipe, it is easy to secure a necessary intake pipe length inside the air cleaner, and an intake pipe length corresponding to engine characteristics is obtained. be able to. Further, since the bent portion is provided in the main pipe, the blowback fuel from the carburetor is directed in the radial direction of the venturi passage by the bend and blows out, and falls outside the gap between the main pipe and the sub pipe. As a result, it is possible to prevent the returning fuel from entering the air jet. Further, in this case, since the bent portion is curved to the opposite side of the air jet, it is possible to prevent the fuel from entering the air jet from this point. An embodiment 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 where the engine of the embodiment is mounted on a vehicle body, and FIG. 2 is a sectional side view of the intake system. FIGS. 3 and 4 are views showing the assembled state of the main passage and the sub passage, respectively. In FIG. 1, reference numeral 1 denotes a motorcycle, and a vehicle body frame 2 has 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 cradles, and a seat rail 2d and a back stay 2 are provided at the rear of the main tube 2a.
e, so-called double cradle type. An engine unit 3 is mounted in the cradle of the body frame 2. The 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 stacked and fastened to a front part of a crankcase 4 containing a transmission, and a head cover 7 is put on the cylinder head 6. It is of a structure. Reference numeral 8 denotes an exhaust pipe, 9 denotes a drive shaft cover also serving as a rear arm, and 10 denotes a rear wheel suspension device disposed between the drive shaft cover 9 and a rear portion of the vehicle body frame 2. A carburetor 11 is connected to an external connection port 6b of an 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
Numeral 3 is disposed between the left and right main tubes 2a, 2a, and its upper portion is covered with a fuel tank 14. In the carburetor 11, a float chamber 17 is connected to a lower part of a carburetor body 16 having a substantially straight venturi passage 16a, and a diaphragm chamber 18 is connected to an upper part thereof, and acts on a diaphragm 18a in the diaphragm chamber 18. This is an automatic variable venturi type that controls the venturi passage area by moving the piston valve 19 forward and backward by negative pressure. Reference numeral 20 denotes a throttle valve that opens and closes the venturi passage 16a on the downstream side of the piston valve. Four air jets 21 of different sizes are provided radially outside the venturi passage 16a and on the float chamber 17 side, and each of the air jets 21 communicates with a fuel pilot jet, a main jet, and the like. are doing. An introduction hole 16b for introducing atmospheric pressure into the diaphragm chamber 18 is formed radially outside the venturi passage 16a and on the side of the diaphragm chamber 18. Further, a mounting flange portion 16c is formed on the upstream end surface of the vaporizer 11 so as to protrude upstream so as to surround the introduction hole 16b and each air jet 21. The air passage 12 includes a main pipe 22 and a sub pipe 23.
It is composed of The main pipe 22 is composed of a linear portion 24 having the same axis as the venturi passage 16a and a bent portion 25 curved 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 fixed to the suction port end face by bolting. The bent portion 25 is made of rubber,
It is fitted and mounted on the upstream end of the linear portion 24 and is fixed by a spring ring 26. The sub-tube 23 is made of rubber, and is formed in an elliptical shape such that the longer the upstream side, the longer its diameter. The sub-tube 23 is opposite 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 smaller than the counter air jet side gap d2. It is arranged inclined to the air jet side. The downstream end 23a of the auxiliary pipe 23 is fitted and mounted on the mounting flange 16c of the vaporizer 11,
It is fixed by a metal band 29, and a mounting flange portion 23 b formed in the middle thereof is fitted and mounted in a mounting opening 26 d of the air cleaner 13. The air cleaner 13 is a two-part cleaner case 26 composed of upper and lower cases 26a and 26b.
A cylindrical element 27 is provided in the upper case 26a.
6c is a suction pipe 2 for introducing outside air into the element 27.
8 are provided. The bent portion 25 of the main pipe 22
Are arranged close to the inner surface of the vertical wall of the lower case 26b. Next, the operation 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 a straight line is connected to the suction port of the carburetor 11. The downstream end of the main pipe 22, which is an assembly of the part 24 and the bent part 25, is fitted and mounted, and the flange part 2
4a is fixed by bolting. The main pipe 22 may be attached to the carburetor 11 in advance and connected to the engine. Next, the air cleaner 13 in which the mounting flange portion 23b of the sub 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,
The downstream end 23a is connected to the connection flange 16 of the carburetor 11.
Then, the air cleaner 13 is moved so as to be fitted to c, and both connection ports are fixed by the metal band 29. In this embodiment, since the main pipe 22 has the bent portion 25 which curves toward 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 mounted. However, in the present embodiment, the sub-tube 23 is inclined toward the side opposite to the air jet, that is, in the same direction as the bent portion 25, so that the interference can be avoided, and the work for attaching and detaching the vaporizer 11 and the cleaner 13 is hindered. Never. When the engine is tuned to, for example, a high-speed type or a low-speed type, the length of the intake pipe is adjusted to be longer for the lower-speed type. In this embodiment, the main pipe 22 is constituted by a straight portion 24 and a bent portion 25. So the bend 25
The required length of the intake pipe can be easily ensured by installing different lengths, and tuning according to engine characteristics is possible. 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. However, in this embodiment, the fuel is blown back because the main pipe 22 is provided with a bent portion 25 which curves inward of the air cleaner. As shown by a broken line in FIG. 2, the fuel is blown out in a radial direction of the venturi passage, and falls outside the gap between the main pipe 22 and the sub pipe 23. Therefore, it is possible to prevent the above-mentioned blown back fuel from entering the air jet 21. Further, in this embodiment, 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, so that the fuel can be prevented from entering the air jet 21 also from this point. In this embodiment, the straight portion 24 of the main pipe 22 is provided.
Since the connection point between the air jet 21 and the bent 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. As described above, according to the engine intake device of the present invention, since the main pipe is formed by the straight portion and the bent portion, the length of the bent portion is adjusted. There is an effect that a necessary intake pipe length can be secured. Also, since a bent portion is provided in the main pipe, the blown back fuel flow can be directed in the radial direction, the fuel can be prevented from dropping between the main and sub pipes, and the fuel can be prevented from entering the air jet. There is an effect that can be done.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing a mounted state of an engine having 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 embodiment. FIG. 3 is a view taken along line III-III of FIG. 2; FIG. 4 is an IV in a state where the air passage of the apparatus of the embodiment is removed.
FIG. [Description of Signs] 3 Engine 6a Intake port 11 Carburetor 12 Air passage 13 Air cleaner 16a Venturi passage 21 Air jet 22 Main pipe 23 Sub pipe 24 Straight section 25 Curved section

Claims (1)

(57) [Claims 1] A carburetor is connected to an external connection port of an intake port, and the carburetor is disposed above the carburetor via an air passage.
In the intake device of the engine to which the air cleaner is connected, the air passage is formed separately from the main pipe connected to the suction port of the venturi passage of the carburetor,
A double pipe structure consisting of a sub pipe arranged so as to surround the air jet located outside the main pipe, wherein the main pipe is formed of a metal linear portion extending in the same axial direction as the venturi passage from the suction port. Following the straight portion , a rubber bent portion that curves away from the air jet side is formed, and the straight portion fits into the suction port of the Venturi passage.
It is attached and bolted and fixed to the suction port end face.
The barbed portion is fitted and mounted on the upstream end of the linear portion,
The sub pipe is inclined toward the anti-air jet side with respect to the straight section
And by arranging the downstream end of the secondary pipe as well as connected to the carburetor, an intake device for an engine upstream portion, characterized in that connected to the air cleaner.